A short review on the advancements in electroplating of CuInGaSe2 thin films

Ramkumar Chandran; Subhendu Panda; Archana Mallik

doi:10.1007/s40243-018-0112-1

A short review on the advancements in electroplating of CuInGaSe2 thin films

Chandran, Ramkumar; Panda, Subhendu; Mallik, Archana 2018-03-27 00:00:00 Thin-film solar cell devices based on copper indium gallium diselenide (CIGSe) chalcogenide materials fabricated by vac - uum-based deposition techniques have already achieved lab scale efficiency beyond 21%. For industrial-scale applications, non-vacuum deposition technique such as electrodeposition and screen printing is considered to be suitable approaches for reducing the device fabrication cost. Moreover, electrodeposition has the potential to prepare large area thin l fi ms as it requires cheap raw material sources and equipment capital. Hence, it is imperative to understand the current status and advancements in the electroplating techniques of the CIGSe thin films. This article reviews on the experimental advances in electroplating of ternary CuInSe and quaternary CIGSe. Various approaches in electrodeposition, influential experimental parameters, and the deposition mechanisms which are related to the final cell efficiency are discussed in detail. Keywords Solar cells · Chalcopyrite · Thin films · Electrodeposition Introduction market share of about 90%, silicon wafer-based solar cells are the first generation solar cells which started with single Increasing demand for energy has spurred academic and crystalline (mono-Si) and later developed to polycrystal- technological interest to research into new resources, among line silicon (poly-Si or multi-crystalline Si). They exhibit a which solar energy seems to be the most ideal to meet the power conversion efficiency ranging between 12 and 16%, target as it is abundant, clean, and inexhaustible. Gradually, based on the variation of fabrication procedure and the wafer solar energy is getting attention as an important source of quality [1]. Though mono-Si devices exhibit high efficiency renewable energy, since the other renewable technologies and a dominant place in commercial market, setbacks such like solar heating, photovoltaics, solar thermal energy, solar as expensive purification process, poor defect tolerance, architectures, and artificial photosynthesis are emerging to indirect band-gap nature (less absorption coefficient) have harness the radiant light and heat from sun. Furthermore, made researchers seek for a better alternative. active solar techniques which convert solar energy from sun- The second generation or thin-film-based devices utiliz - light into electricity are primarily done using semiconduct- ing semiconducting materials like CISe/CIGSe, cadmium ing materials that exhibit the photovoltaic effect (generat - telluride (CdTe), and Si (a-Si) are then emerged as the alter- ing photocurrent upon illumination). A typical photovoltaic natives to the first generation devices. Solar devices based system employs solar panels, each comprising a number of on dye-sensitized solar cells (DSSC), organic photovoltaics solar cells, which generate electrical power. With a global (OPV), quantum dots, perovskite, tandem cells, hot carrier cells, impurity photovoltaics, and thermo-photovoltaics fall in the third generation solar cells. In specific, tandem con - * Archana Mallik figurations are designed to evade the power-loss mechanisms archananitrkl@gmail.com which take place in the conventional single band-gap (E ) cells due to the inability to absorb photons beyond their E Electrometallurgy and Corrosion Laboratory, Department of Metallurgical and Materials Engineering, National and thermalization of photons exceeding their E . By imple- Institute of Technology, Rourkela, Odisha 769 008, India menting semiconductor stacks exhibiting different bandgap, Electroplating and Metal Finishing Technology Division, tandem configurations are realized with efficiencies exceed - CSIR-Central Electrochemical Research Institute, Karaikudi, ing the Shockley–Queisser limit [2]. Tamilnadu 630 003, India Vol.:(0123456789) 1 3 6 Page 2 of 20 Materials for Renewable and Sustainable Energy (2018) 7:6 Among the second generation photovoltaic (PV) cells, this section which deals with copper chalcopyrite group CIGSe-based devices are considered to be the most effi- material being explored as the second generation solar cells; cient solar energy converter of any single band-gap thin- (2) experimental concerns in electrodeposition explaining film device. They can be easily fabricated on flexible sub- about the electrodeposition process of CIGSe and strategies strates which make them light weight, and thus, they have to improve the quality of the electrodeposited final CIGSe the potential to reduce the device fabrication as well as the thin films; (3) electrocrystallization mechanism of CIGSe; installation cost [3]. Recently, Chirilă et al. reported an this section elaborates about the deposition mechanism of efficiency of 20.4% for potassium fluoride post-deposition- the four elements to form the alloy (4) advancements in treated (KF-PDT) CIGSe devices fabricated over flexible CISe/CIGSe electrodeposition routes; recent advancements polyimide substrates. This efficiency is considered to be the in the electroplating procedures and the reported power con- highest until date for flexible CIGSe solar cells [4 ]. After version efficiency has been briefed in this section; and (5) discovering the beneficial effects of heavy alkali doping CdS-free buffer layers; the attempts that are being made and [potassium fluoride (KF), rubidium fluoride (RbF), and explored to replace this layer to avoid the involvement of caesium fluoride (CsF) PDT treatment] [5], the CIGSe hazardous chemicals have been cited in this section. solar cell performance was boosted beyond 20%. A record device efficiency of 22.6% (0.4092 cm ) was also reported by Jackson et al. for RbF-PDT-treated CIGSe/CdS device CISe/CIGSe material properties and device [6]. Friedlmeier et al. reported an efficiency of 21% [7 ] using structure Zn(O,S) buffer as a replacement for the conventional CdS/ CIGSe devices. Similarly, a record efficiency of 22.3% [8 ] The intermixing of ternary CuInSe (CISe) and CuGaSe 2 2 was achieved for Cd-free device by SoloPower, utilizing (CGSe) of I–III–VI group (I = Cu, III = In, Ga and VI = Se) (Zn,Mg)O/Zn(O,S,OH) as the window/buffer layer. Impres- crystallizes to form a quaternary CuInGaSe tetragonal chal- sive efficiencies (~ 15.7 ± 0.5%) are also reported for CIGSe copyrite structure, where the In and Ga atoms share the same modules of 9703 cm aperture area [9]. These efficiency atomic sites. The crystal structure of CIGSe chalcopyrite percentages motivate researchers to explore chalcogenide material is shown in Fig. 1a [13]. The crystal structure can materials for industrial-scale production. be realized as a doubled unit cell of zinc blend structure with The above-reported CIGSe device record efficiency evo- alternating Cu and In atoms [15]. Each of the Cu or In atoms lutions have been fabricated by vacuum deposition tech- are bonded tetragonally with four Se anion atom, whereas niques, which are being challenged due to the expensive each of the Se atoms are coordinated with 2 Cu and 2 In vacuum systems, target materials, and percentage of mate- atoms. As the bond strength existing between the I–VI and rials wastage. Hence, an alternative cost-effective deposi- III–VI is different, the lattice constants (c , a, where ‘a’ is tion technique with competitive efficiency of the fabricated base dimension and ‘c’ is cell height) are not always of the devices is sought for. Electrodeposition is a major tech- desired value 2:1 (c/a ratio), which may lead to lattice distor- nique which can respond to the challenges of reducing the tion [16]. The magnitude of distortion can be realized from PV device production cost due to cost-effective equipment the deviation of (c/a) value from 2:1. For a pure CuInSe , the capital, less material wastage, and its compatibility towards ratio is close to 2. However, due to the substitution of In by industrial-scale production. Electrochemically fabricated Ga atoms, the c/a ratio deviates towards lower values along commercial solar cell devices with a reported efficiency of with grain refinement, as shown in Fig. 1b [14]. 14.2% have been obtained by SoloPower [10]. NEXCIS has Now, concentrating on the band structure, the val- achieved a record efficiency of 17.3% (0.484 cm ) and 14% ance band of the CIGSe is derived from the weak Cu–Se for CIGSe module of aperture area 60 × 120 cm . Excel- bond group (I–VI) due to the hybridization of Cu-d and lent review on electrodeposition of semiconductors [11] Se-p orbitals. The bottom of the conduction band (CB) and CIGSe electrodeposition [12] can be found. However, is mainly contributed from the In and Ga atoms (group the technique has not yet been optimized for a single-step III—S orbital) [17]. Chalcopyrite-based absorber mate- co-deposition of the quaternary alloy, and hence, it needs rials are direct band-gap semiconductor with an opti- 5 −1 further research attention. cal absorption coefficient of α = 10 cm which makes Hence, this review would be a complimentary addition them a suitable candidate as p-type ‘absorber’ layers in to the research pool emphasizing on the recent technologi- thin-film solar cells. The Cu-poor CIGSe chalcopyrite cal advancements in the field of electrodeposition of CISe/ absorber (with a composition of [Cu/In + Ga] or CGI CIGSe thin films. The review has been classified into five ratio is < 1 and [Ga/In + Ga] or GGI ratio ≈ 0.25–0.35]) sections which provides some of the important aspects of the contains a large number of defects, most likely the Cu research area on electroplating of CISe/CIGSe thin films: (1) vacancies (V ) and In or Ga anti-sites [18, 19]. In Cu Cu Cu 2+ material properties of CISe/CIGSe: the review starts with the Cu-poor CIGSe, the In anti-sites pair easily with Cu 1 3 Materials for Renewable and Sustainable Energy (2018) 7:6 Page 3 of 20 6 Fig. 1 a CIGSe crystal structure (adapted from Ghorbani et al. [13]. Copyright©2015, American Chemical Society, permission granted), b lat- tice constant ratio (c/a) deviation as a function of Ga content (x) [14] (Copyright© John Wiley and Sons, 2008, permission granted) − − 2+ formation of excess Cu-deficiency-related defects such as 2V in the Cu-poor CIGSe to form ( 2V + In ) Cu Cu Cu Ga on Cu (In or Ga ) anti-sites [23]. These deep elec- neutral defect complex [20]. However, the presence Cu Cu tron traps (In, Ga and its complex-DX centers) limits of small excess of shallow acceptor like V vacancies Cu Cu, Cu V of the devices through fermi level pinning [24–26]. (energy position close to the valance band) contributes OC Other defects such as copper interstitial (C ), selenium to the intrinsic p-type doping of the CIGSe absorbers. i − 2+ vacancies (V ), and (V –In ) di-vacancy defect com- The ( 2V + In ) neutral defects complex with an Se Se Cu Cu Cu plex are considered as origin of metastable-related effects average composition of Cu In Se ,CuIn Se ,CuIn Se , 2 4 7 3 5 5 8 such as persistent photoconductivity (PPC) and red–blue etc., is known as the ordered vacancy compounds (OVC) illuminations. During electrical bias or illumination, this [21]. The existence of the OVCs in the CIGSe absorber di-vacancy complex (V –V ) can shift from a donor into is anticipated at the interface of CdS/CISe thin films. Se Cu an acceptor configuration in p-type CIGS, increasing the The structure of the OVC layers can be derived as the hole concentration and thus acts as a recombination chan- chalcopyrite structure with randomly introduced copper − 2+ nel for the minority charge carriers (electrons) [27, 28]. vacancies or ( 2V + In ) defect pairs and is assumed Cu Cu The prevalence of these intrinsic defects and compensa- to be beneficial for the device performance [ 22]. How- tions is considered to be the origin of potential fluctuations ever, increased OVC content in CIGSe may deteriorate in the material. the open-circuit voltage (V ) of the device due to the OC Fig. 2 a Device structure and its corresponding energy-band diagram at equilibrium and b straight line—no grading, dotted—double grading, inset— schematic of the “notch-type’ gallium distribution in CIGSe device, axis scale—CIGSe layer thickness vs. bandgap 1 3 6 Page 4 of 20 Materials for Renewable and Sustainable Energy (2018) 7:6 The schematic of the state-of-the-art CIGSe device struc- diagram of CIGSe device with (dotted), without double ture as Mo/CIGSe/CdS/i-ZnO/Al–ZnO with the correspond- grading (continuous line) and the energy-band-gap profile ing band diagram of the device is shown in Fig. 2a. These of the CIGS absorber layer used in simulation is given in devices have reported maximum reported efficiency ( η) of Fig. 2b, inset. The experimental and simulation studies have 21% [29]. The working principle of the device is followed shown that double grading in the CIGS absorber layer has after a brief introduction of the structure and properties of greatly improved the performance of single-junction CIGS the individual layers along with advancements. cells [40, 41]. For detailed information on grading schemes Owing to the high bandgap and optical transparency, alu- and their benefits in device performance, the readers can minum doped ZnO, as the front contact TCO layer, ensures refer the cited literatures [42–44]. maximum light incoming to the device. The sputtered i-ZnO/ Until date, all high-efficiency devices reported so far are ZnO:Al layers are classically used as the window/front TCO of low band-gap (1.15 eV—CuIn Ga Se ) values with 0.7 0.3 2 layers in high-ec ffi iency devices. With an optical bandgap of Cu-poor composition in the final device stage having a E = 3.3 eV, ZnO is considered to be the promising TCO, as GGI ratio of 0.3–0.35 and CGI ratio of 0.8–0.9. A slight- it is cheap, earth-abundant, and non-toxic [30]. It has been est increase in the Cu content is considered to be Cu-rich reported that the devices with i-ZnO window layers exhibit (≥ 25% of at wt%) as the excess Cu content reacts to form good stability towards the damp-heat stress. In addition, the Cu–Se secondary phase, which are detrimental to the device buffer/window i-ZnO/CdS combination mitigates electrical performance [46]. Hence, Cu-rich stoichiometry refers to the shunt paths in the devices by covering the local inhomogene- overall Cu content including Cu–Se secondary phase in the ity in the CIGSe absorber [31, 32]. Until date, most of the absorber. Though Cu-rich absorbers exhibits better crystal- widely reported high-efficiency CIGSe devices have utilized linity, low defect concentrations, less bulk recombination, cadmium sulfide (CdS) as the buffer layer component [9 ]. and high mobility, they exhibited poor efficiency than Cu- The CdS (E = 2.4 eV) buffer material transmits the light up poor devices [47]. For improving the Cu-rich device perfor- to the wavelength of 2.4 eV to the P-CIGSe absorber. mance, the excess Cu Se phase can be removed by selective According to Nakada [33], the Cu-poor surface at CIGSe etching using potassium cyanide (KCN) [48]. The interface is favorable for the substitution of Cd ions on Cu vacan- recombination problems which is prevalent in Cu-rich CISe cies (Cd donor defects) [34] due to the closest match- devices can be eliminated by controlling the doping level. Cu+ + + ing atomic radii of Cu (0.96 Å) and Cd (0.97 Å) [35]. Through simulation studies (Fig. 3), it has been realized that 16 3 The infiltrated Cd in the absorber inhomogeneity acts as low doping levels (N = 10 cm ) can increase the recom- a buried CIGSe/CdS homo-junction [36]. Thus, Cd dop- bination barrier existing between the fermi level (E ) and ing at the CIGSe/CdS grain boundaries and conductivity valance band edge reduces the tunnel assisted recombination inversion of the absorber from p- to n-types is inevitable. at the interface. The doping level of Cu-rich devices can be Other significant observations such as Se–S exchange within controlled by the Se flux. In contrast to the Cu-poor CISe CdS–CIGSe, Cd diffusion in CIGSe, Cu–Cd interdiffusion at CdS/CIGSe interface, alkali–oxygen (Na–O) impurity accumulations at the interface, Cu Se secondary phase, 2−x and Cd–Se formations are also reported [36–39]. However, the CdS/CIGSe junction interface study is still a debatable research topic which needs further clarifications. For substrate configuration CIGSe devices (Fig. 2a), the light entering through the metal grid spacing and TCO (Al:ZnO/i-ZnO) may suffer reflection loss due to difference in the refractive index (n). These reflection losses can be minimized by employing anti-reflective coating such as MgF [30]. The operation of the devices can be explained on the principle that upon illumination, the generated elec- tron–hole pair is swept away by the built-in electric field at the CdS/CIGSe heterojunction interface towards the respec- tive contacts to produce photocurrent. Some of the electrons can also move towards the wrong contact (back contact) and Fig. 3 Simulated energy-band model of a Cu-poor (red) and a Cu- rich (blue) CuInSe solar cell (higher doping of the Cu-rich absorber recombine. This can be avoided by introducing a back sur- 2 is assumed). The horizontal arrow indicates the tunnel recombination face field, an additional energy barrier for preventing the process due to high doping levels. Permission granted by the authors electron back flow. The band-gap gradient can be achieved to reuse the figure, Copyright© 2013 Society of Photo-optical Instru- by varying the GGI ratio. Figure 2b shows the energy-band mentation Engineers (SPIE) [45] 1 3 Materials for Renewable and Sustainable Energy (2018) 7:6 Page 5 of 20 6 device, Cu-rich device exhibited better efficiency of η = 8.6% for film inhomogeneity and pin holes formation. This makes under low Se flux conditions, whereas η = 6.2% at very high electrodeposition of stoichiometric and pinhole free CIGSe Se flux conditions [49]. Furthermore, by depositing a thin thin films even more challenging. This shortfall arised as an In–Se layer, the device efficiency of 13.1% was achieved. attempt for the controlled inclusion of In(III) and Ga(III) Such treatment recovers the open-circuit voltage loss by ions can be taken care by adding complexing agents. Com- reducing the interface recombination [50]. These results plexing agents can play a major role in shifting the reduc- are promising in the context that compositionally altered tion potential of noble ions (Cu) towards active ions (In, Cu-rich devices have the potential to compete in terms of Ga), hence making the co-deposition easier. These agents efficiency to the Cu-poor ones. diminish hydrogen generation avoid pinholes and improve In the future, compositionally altered Cu-rich absorb- the compactness of the as-deposited film. Other additives ers may be a major theme of study in the development of such as supporting electrolytes, surfactants, and brighten- CIGSe absorbers. Moreover, mimicking such studies in ers are often used for improving the bath chemistry and film electrochemical route is much easier when compared to quality. However, most complexing agents have no effect on vacuum deposition techniques. A detailed recent review on In (III) and Ga (III) ions and forms strong complex only with the progress in CIGSe solar cells defects mechanisms and copper and selenium ions [10]. the state-of-the-art CIGSe devices have been discussed in Hence, in the following sections, attention has been given the cited literature [51, 52]. towards significant recent advancements in the electrolyte 3+ 3+ chemistry for the controlled inclusion of In and Ga ions in CISe/CIGSe thin films both in aqueous- and non-aqueous- Experimental concerns in CIGSe based electrolytic deposition conditions. electrodeposition CISe/CIGSe electrodeposition using aqueous Irrespective of synthesis route, generally, the CIGSe/CISe electrolytes and complexing agents absorber deposition is carried out by two ways (1) simul- taneous deposition and selenization/sulfurization and (2) Bhattacharya et al. group was the first to report single-step precursor deposition followed by sequential selenization/sul- electrodeposition of CISe thin films using triethanol amine furization. The vacuum-based deposition techniques mostly (TEA) as complexing agents [56]. Since then, several works follow the simultaneous selenization and other processes on electrodeposition of CISe/CIGSe using TEA have been 2+ like electrodeposition, roll-to-roll printing, Ink/paste precur- reported as it can form strong complexes with Cu and 3+ sor coating follow the sequential selenization. Regardless HSeO ions and weak complexing with the In ions [57]. 2– of deposition techniques employed in thin film CIGSe/CISe Calixto et al. reported the electrodeposition of pinhole free fabrication, the ultimate goal of every route is to prepare a stoichiometric CIGSe using low concentrations of 2.56 mM 2+ 3+ 3+ 4+ compositional film exhibiting good crystallinity leading to Cu , 2.40 mM In , 5.7 mM Ga , and 4.5 mM Se ions in a material with good photovoltaic characteristics. the bath at a pH of 2.5. The electrolyte was stabilized using Electrodeposition is a non-vacuum technique in which a buffer of pH 3 (pHydrion mixture of sulphamic acid and the electro-reduction of ions at particular reduction potential potassium biphthalate) along with LiCl as supporting elec- takes place over a conductive substrate to form thin films trolyte [55]. Recent works by Liu et al. have suggested that by the influence of applied electric field. The equilibrium by increasing the sodium sulfamate concentration, (Cu + Se)/ reduction potential (in Fig. 5) of Cu, In, Ga, and Se ions in (In + Ga) decreases, while gallium content increases and the the EMF series is + 0.337/SHE, − 0.342/SHE, − 0.529/SHE, film composition transforms from Cu rich to Cu poor [58]. and + 0.741/SHE, respectively. The difficultness arises dur -Using KCN as the complexing agent, the reduction poten- 2+ 3+ ing electrodeposition of CIGSe is due to the active standard tial difference between of Cu and Ga was only 80 mV, reduction potential of In and Ga ions. Though increasing whereas 870 mV difference for un-complexed (Cu,Ga) spe- the concentrations of In(III) and Ga(III) shifts the potential cies [59]. At high thiocyanate complex concentrations, the closer to Cu(II) [53], excessive currents generated due to predominant species is Cu (I) in soluble form. Furthermore, high bath concentrations may cause significant pitting and the reduction of Ga can get catalyzed in the presence of corrosion of Mo/glass substrates [54]. Recent impedance thiocyanate (CNS ) ions. This makes thiocyanate a suitable studies by Saji et al. also verified that excessive In ions can complexing agent in CIGSe/CGSe electroplating [60]. interact or complex with Mo/surface oxides and that in effect Using potassium sodium tartrate as complexing agent for can cause a certain extent of Mo dissolution [55]. Electro- In and trisodium citrate for Ga ions, Aksu et al. were able to deposition at high cathodic potential conditions affects the electroplate In–Se and Ga–Se thin films even at high alka- In and Ga plating efficiency due to the parallel occurrence line conditions. For In–Se, the plating efficiency of 68% was of hydrogen evolution, which is considered to be the origin obtained at a pH of 13. For Ga–Se complexed with trisodium 1 3 6 Page 6 of 20 Materials for Renewable and Sustainable Energy (2018) 7:6 citrate, below the pH of 5, the Se percentage was dominated, During the process, the reduction of indium and gallium and at high pH of 13.5, Ga was dominant. They were able to takes place as two simultaneous steps involving nitrate co-deposit Ga–Se films within the pH window of 7–8.5 [61]. reduction and oxides precipitation. During the nitrate reduc- The same group could co-deposit Cu–In–Ga alloy at alkaline tion, the consumption of proton will induce a local change conditions (9–13.5) using blends of complexing agents for in pH at the vicinity of the cathode followed by In and Ga solubilizing and preventing hydroxide formation of ions at depositions in the form of precipitated oxides or hydrox- such high alkaline conditions. Though the processing con- ide. As shown in the standard deposition potential diagram ditions were not disclosed, common chelating agents such (Fig. 4), deposition of In and Ga in the form of oxides/ as TEA, EDTA, citric acid or trisodium citrate, potassium hydroxides takes place at very low cathodic potential com- sodium tartrate, and tartaric acid can be used as they have pared to the Cu–In–Ga electrodeposition using conventional the tendency to form complexes with Cu, In, and Ga ions. chloride/sulfate electrolytes. The crystalline CIGSe absorber The grading of Ga is also possible by modulating the current deposited and after subsequent H reduction and selenization density during electroplating [62]. pre-treatment (in Fig. 5a–c) revealed a power conversion An interesting alternative route for the inclusion of In efficiency of η = 9.4% [64]. (III) and Ga (III) is in the form of oxides/hydroxides using Yang et al. reported on the controlled Ga(III) inclusion respective nitrate salts as reported by Duchatelet et al. [63]. using hydrogen peroxide (H O ) as the oxygen precursor 2 2 facilitating the Ga incorporation in the form of Ga(OH) [65]. The reduction starts with the cupric ion followed by the reduction of H O which facilitates the inclusion of In 2 2 and Ga in the form of oxides/hydroxides. Precipitations of In and Ga were observed for higher concentration of H O 2 2 (20 mM) for which the deposition takes place by a controlled mass transfer of the hydroxide species [66]. Without any complexing agents and supporting electro- lytes, Chaure et al. reported the possibility to electrodeposit + + CISe (p, i, and n-type) [67] and CIGSe (p , p, i, n, and n ) [68] by varying the deposition potential from the same bath. The major hindrance in using the aqueous electrolytes is the abrupt changes in the (Ga/III) ratio, as even for a slight change in the deposition, potential can alter the composition and thus the deposition mechanism [69]. Hence, the mor- phology of the as-deposited film is strongly dependent on the applied deposition potential. As shown in Fig. 4, the narrow deposition potential window is often difficult to balance the film composition and quality. Moreover, tuning the (Ga/III) Fig. 4 Comparative diagram of the standard deposition potentials of ratio is possible up to a certain extent beyond which the copper, indium and gallium in the form of metals or hydroxide/oxide parallel occurrence of hydrogen evolution reaction (HER) during nitrate reduction. Reprinted with permission from Duchatelet takes place and has negative impact on the film quality such et al. [63]. Copyright 2014, The Electrochemical Society Fig. 5 SEM cross-sectional pictures of as-electrodeposited Cu–In–Ga osition (c). Reprinted from Duchatelet et al. [64], with the permission mixed oxide precursor films (a), after reduction under Ar-5% H into of AIP Publishing, Copyright©2013 AIP metallic alloy (b), and after selenization and front contact layers dep- 1 3 Materials for Renewable and Sustainable Energy (2018) 7:6 Page 7 of 20 6 as formation of pinholes and dendritic morphology [70]. concentrations can be achieved in water-free ionic liquids. However, the metal-oxide/hydroxide depositions are more Moreover, the high ligand concentrations ensure greater promising, where the problem of hydroxide formation dur- control on the metal speciation in the electrolyte [76, 77]. ing the conventional CuInGa electrodeposition is taken as an Therefore, reline forms strong metal complexes with the advantage. The difficultness of Ga inclusion in conventional ions, and hence, the necessity of using complexing agents CuInGa plating can be easily overcome by metal-oxide/ is eliminated. Reline is highly stable and does not decom- hydroxide depositions. pose even after prolonged heating conditions. By lowering The recent advancements in electrolyte chemistry in the the viscosity (η) of the reline, better mass transport proper- CIGSe depositions such as (1) complexing agent blends, ties of the ions can be achieved. For this reason, the optimal (2) nitrate precursor, and (3) hydrogen peroxide source are bath temperature during electroplating is usually maintained promising as the problem of Ga inclusion can be avoided within 60–70 °C. easily when compared to conventional deposition schemes. Harati et al. was the first to report the one-step electrodep- Further studies pertaining to the electrolyte stability and osition of quaternary CIGSe thin film using reline. The dep- replenishment of ions or reusing the electrolytes may con- osition temperature was fixed to 65 °C [71]. Steichen et al. tribute towards the cost-effective industrial-scale deposition. reported the electrodeposition of Cu–Ga thin films using reline at 60 °C. The selenized CuGaSe PV devices (pro- CISe/CIGSe electrodeposition in non‑aqueous cessed at 550 °C in Se atmosphere) achieved 4.1% total-area electrolytes power conversion efficiency. When only Ga or In–Ga thin films were electrodeposited on Mo substrates, no alloying The HER interference can be overcome using non-aqueous phenomena are observed and the obtained films were found electrolytes without complexing agents such as ionic liquids to be physical mixtures of In–Ga in the form of droplets [71], ethylene glycol [72], and alcohol or alcohol/ionic liquid (Fig. 6a). However, for Mo/Cu substrates, an improvement combinations [73]. Long et al. reported electrodeposition of in the Cu–Ga films film adhesion (Fig. 6b) was observed compact and quality CIGSe thin films at − 1.6 V/SCE using due to the CuGa alloy formation [75]. Zhang et al. reported alcohol and LiCl electrolyte (pH 1.9–2.2) [74]. Availability CIGSe device ec ffi iency of 10.1% for pulse electrodeposited of such wide electrochemical deposition window in non- CIG alloy. The selenization (using Se powder) was carried aqueous electrolytes allows electrodeposition of In (III) and by rapid thermal annealing (RTA) at 550 °C for 1 h. in the Ga(III) ions conveniently. Ar atmosphere [78]. Malaquias et al. showed the possibility Electrodeposition using ionic liquids has gained atten- to alter the [Ga/In] ratio from 0 to 1 by adjusting the elec- 3+ 3+ tion due to their advantages like biocompatibility, non-toxic, trolyte flux ratio of [Ga /In ] ions [79]. The same group cost-effectiveness, and wide electrochemical potential win- reported an efficiency of 9.8% for CIGSSe thin films. The dow that make them a suitable electrolyte to electrodeposit electrodeposition of In–Ga thin film was performed over the elements which are difficult to plate in conventional aqueous Mo/Cu thin films followed by a three-step annealing process bath conditions. Especially, choline chloride (ChCl)-based (H Se, Argon, and H S) [80]. 2 2 ionic liquids and aprotic deep eutectic solvents (DES) have emerged as an efficient replacement for conventional ionic Electrodeposition of CuGaSe thin films liquids and volatile organic solvents. A mixture of choline chloride/urea (ChCl/U—1/2) termed reline is one of the pop- We have also reviewed the approaches for electrodeposition ular DES used in CIGSe electrodeposition. Unlike aqueous of wide band-gap absorber CGSe thin films. Electroplat- electrolytes (where the metal ions solubility is limited by ing of CGSe is more difficult due to the standard poten- oxides/hydroxides precipitation), high solubility, and ligand tial (− 0.53 V SHE) of gallium. The parallel occurrence of Fig. 6 a Cross-sectional images of metallic Ga droplets electrodeposited on Mo from Reline–GaCl 50 mM at 1.1 V/ Ag for 30 min at 60 °C, b SEM top-view of a Ga deposit on Mo/ Cu from Reline–GaCl 50 mM at 0.9 V for 15 min at 60 °C. Adapted from Steichen et al. [75] with permission of The Royal Society of Chemistry 1 3 6 Page 8 of 20 Materials for Renewable and Sustainable Energy (2018) 7:6 Table 1 CGSe electrodeposition conditions and their compositions Bath composition Cu– Complexing agents and supporting electrolyte Deposition potential and pH CGS film composition (at.wt%) Ga–Se (mM) *Etching Cu Ga Se Cu Ga Se 2 10 4 [81] LiCl (300 mM), NH Cl (100 mM), KCN (50 mM) − 0.6 V/Ag/AgCl 26 24 50 pH 2.3 3 10 8 [82] LiSO (0.15 M) and gelatin (100 mg), *KCN etched − 0.6 V/Ag/AgCl 25 26 49 pH 2.6 4.6 25 9.2 [83] 2.0 M KSCN − 0.55 V/Ag/AgCl 23.91 23.53 52.53 pH 2.5 5 5.68 20 [59] 2.0 M NaSCN − 0.3 V/SCE Cu/Ga = 1; Se close to 50% pH 2.75 HER hinders the electrodeposition process hence resulting For CISe without PT, the surface nonuniformties, cracks in films with poor morphology and pin holes. Table 1 gives and pinholes were present, as shown in Fig. 7c, which was the deposition parameters for one-step deposition technique reduced after PT (Fig. 7d). In addition to this, the surface of CGSe thin films. without PT was found to have In nano-islands which may Until date, thiocyanate (KCN ) is reported to be a suit- affect the efficiency of the devices. Whereas the micro-struc- able complexing agent for single-step electrodeposition of tural studies revealed the presence of uniform particle mor- CuGaSe films. The shift in the reduction potential of Cu phology with reduced In-nano-islands for PT–CISe. Hence, towards the lower cathodic potential makes assimilation this would help in maintaining the composition throughout 3+ of Ga ions easier in the form of Ga Se to the growing the film. Though the exact role of pre-treatment have not 2 3 of CuGaSe film. Oda et al. reported crack free CGS thin been studied extensively, it has certain influence in altering films with lithium sulfate (Li SO ) and gelatin [82]. Using the deposition mechanism during the single-step deposition 2 4 DES such as reline, successful electrodeposition of CGSe and hence the film quality. The pre-treatment process seems has been reported [75]. Electrodeposition of Cu–Ga alloy to be applicable to all baths; however, further investigation using copper–gallium nitrate salts is also a good approach, is required to understand its role and mechanism in mor- where the inclusion of Ga takes place in the form of oxides/ phological and compositional changes. The homogenized hydroxides [63]. distribution of In and Ga seems to be possible by this pre- treatment process. Strategies for improving the quality of electrodeposited CIGSe thin films Compositional tuning to avoid micro‑cracks For an industrial-scale production of electrodeposited The studies related to the interdependence of CIGSe film CIGSe, the thin films should be free from voids, cracks, quality and stoichiometry with respect to the bath composi- surface, and compositional inhomogeneities. In this sec- tion was reported by Bhattacharya et al., as shown in Fig. 8 tion, we have discussed some of the reported experimental [84]. For a diffusion controlled deposition process, CIGSe 2+ 3+ approaches for improving the quality of the CIGSe absorbers films deposited using low Cu and In bath concentration for the high-performance devices. exhibited micro-cracks. Micro-crack-free CIGSe precursor 4+ films were obtained when electrodeposited at low Se and 2+ 3+ 3+ Pre‑treatment (PT) processhigh Cu, In , and Ga bath concentrations. Moreover, the composition of CIGSe can also be controlled by tuning Calixto et al. reported the significance of the pre-treatment the specific ion concentration. 2+ process in CIGSe electrodeposition [54]. In their observa- For increased Cu concentration, Cu content was found 3+ tion, for CIGSe thin films deposited without PT exhibited to be increasing and Se decreased. With the increase in In (Fig. 7a) pinholes, micro-cracks, and secondary Cu–Se concentration, In content increases steadily and Ga was phase which were avoided by carrying out pre-treatment found to be decreased. Cu and Se contents were found to be 3+ before deposition (Fig. 7b). Similar process was adopted unaffected by In concentration. All the ions are found to 2+ 3+ 3+ for CISe electrodeposition (4 mM—Cu , 9.75 mM—In , be unaffected towards the Ga ions at lower concentration. 4+ 3+ 6 mM—Se , 0.4 M citric acid and 0.35 g sodium dodecyl At high Ga , a steady increase in Cu and In, and decrease in 4+ sulfate, − 0.6 V/SCE for 20 min, and PT at − 0.5 V/SCE for Ga, Se content was observed. For Se , Cu and In contents 1 min over FTO substrates) to understand the effect of PT. decrease steeply, while Ga and Se contents increase. 1 3 Materials for Renewable and Sustainable Energy (2018) 7:6 Page 9 of 20 6 Fig. 7 a SEM cross section of CIGSe electrodeposition without (a) and with PT (b), FE-SEM of CISe electrodepos- ited without pre-treatment, photographic image (c, e) and (d, f) with pre-treatment (original work). Reprinted with permission from Calixto et al. [54]. Copyright 2006, The Electrochemical Society 400 °C. The CISe absorber of a bandgap 1.2 eV exhibited Selenization/sulfurization of electrodeposited CISe/CIGSe absorbers a rectifying behavior for the FTO/CISe/Al device structure [87]. Bamiduro et al. reported an Se loss of 1 at.wt % for Apart from electrodeposition parameters, the final device the CIGSe films annealed at 300 °C in argon atmosphere [88]. For a pulse electrodeposited CIGSe films, Mandati efficiencies are highly influenced by the post-processing annealing steps such as selenization and sulfurization. The et al. reported a stoichiometric CIGSe films after annealing at 550 °C for 30 min in Ar atmosphere [89]. As the device post-processing annealing schemes follow either a conven- tional furnace annealing (slow or fast heating rate/prolonged performance has not been studied for the N or Ar annealed CISe/CIGSe absorbers, it will be too early to conclude its annealing time) and rapid thermal processing (fast heating rate for a short annealing time) in H Se/selenium/sulfur/ benefits. A systematical study in this regard is required as it has the potential to reduce the device fabrication cost by Ar/N /vacuum atmospheres. The simplest post-processing annealing scheme is annealing the CIGSe absorber in vac- eliminating the sulfurization/selenization steps. The most common annealing treatment is selenization uum or Ar or N atmosphere. However, the major draw- back encountered during Ar and N annealing is the Se loss. using either H Se gas or Se powder in a controlled atmos- phere. However, due to the toxic nature of the H Se gas, the Some of the literatures have reported the retainment of Se in CISe successfully even after annealing at 400 °C in argon selenization using elemental Se powder is more preferable. During the annealing of CuInGaSe , the binary selenides atmosphere for 30 min [85]. Frontini et al. reported the diode characteristics behavior of electrodeposited CISe annealed of Cu and In are formed initially followed by the forma- tion of Cu InSe phase between the temperature ranges of at 350 °C for 15 min in Ar atmosphere [86]. Hamrouni et al. reported vacuum annealing of electrodeposited CuInSe at 370–380 °C. The formation of CuGaSe phase is induced 1 3 6 Page 10 of 20 Materials for Renewable and Sustainable Energy (2018) 7:6 Fig. 8 Composition variation of CIGSe as a function of Cu, In, Ga and Se ions concentration. Reprinted from Fernandez et al. [84]. Copyright (2003) with permission from Elsevier only around 425 °C. A complete single-phase CIGSe is stacks by Oliva et al., suggested that better incorporation/ formed by the slow interdiffusion between CISe and CGSe distribution of gallium in electrodeposited CIGSe pre- at high temperature along with the Ga accumulation towards cursor can be achieved through longer annealing time or the back contact. The problem of Ga segregation towards a higher annealing temperature [94]. Ribeaucourt et al. the back contact in the CIGSe absorbers during seleniza- reported an efficiency of 9.3% for an electrodeposited tion process is widely reported [90]. They tend to create an CuInGa alloy selenized at 450 °C. However, for CIGSe insufficient energy bandgap at the SCR, which leads to poor selenized at 600 °C, the obtained efficiency was only 4%. V . Studies by Mardudachalam et al. revealed that the accu-The MoSe layer thickness was found to be 1 µm and OC 2 mulation of more Ga towards the back contact (Mo) takes 500 nm thick for CIGSe selenized at 600 °C and 450 °C place as a consequence of preferential reaction between In for 45 min. In both the conditions, the Ga accumulation with H Se than Ga [91]. During high-temperature seleniza- towards the back contact was inevitable [70]. The same tion, the CIGSe/Mo heterocontact inverts from Schottky to group reported an efficiency of 12.4% for CuInGa oxide a favorable Ohmic-type contact due to the formation of thin precursor layer alloys after subsequent reduction (H MoSe layer. Moreover, the formation of thin M oSe layer atmosphere at 500-550 °C) and selenization at 550–600 °C 2 2 contributes towards the improvement of the adhesion at the for 45 min [95]. Bhattacharya et al. reported an efficiency CIGSe/Mo interface [92]. Yet, a high series resistance (R ) of 11.7 and 10.9% for a stacked Cu/In/Ga and CIGSe/Cu/ is induced when the MoSe layer is too thick which can dete- In precursor layers selenized at 550 °C for 45 min [96, 97]. riorate the fill factor (FF) and V of the CIGSe devices [93]. Başol et al. reported a total-area efficiency of 13.76% for OC 2 2 An extensive studies on the interdiffusion and phase a 0.48 cm device, 12.5% for cells with area of 120 cm , formation of electrodeposited Cu/In, Cu/Ga, Cu/(In + Ga) and 10% for a 1.07 m module exhibiting a total output of 1 3 Materials for Renewable and Sustainable Energy (2018) 7:6 Page 11 of 20 6 107.5 W (V = 38.2 V and I = 2.8 A) on flexible stain - Furthermore, the third selenization step avoids the forma- m m less steel (SS) substrates [98]. They also have reported tion of secondary phase at the surface. a certified efficiency of 14% for 12 cm and 15.36% for 5.4 cm over flexible SS substrates. A record efficiency of 13.4% for flexible CIGS module for a device dimen- Electrochemical formation mechanism sion of 147.1 × 26 cm by roll-to-roll electrodeposition of CISe/CIGSe was also reported [99]. Though the details of post-pro- cessing were not disclosed, they have mentioned that The formation mechanism of CIGSe is complex due to the devices were prepared from the electroplated metal the involvement of multiple electrochemical and chemical stacked layers of Mo/Cu–In–Ga/In–Se or Ga–Se followed reactions that takes place simultaneously during the qua- by rapid thermal annealing (RTA) at 500 °C. Similarly, ternary CIGSe deposition. In the recent years, the deposi- NEXCIS also reported a record efficiency of 14% for a tion mechanism of CIGSe has been explained satisfactorily of 60 × 120 cm modules for Cu(In,Ga)(S,Se) solar cells. by several research groups. Here, we have summarized the The electrodeposited Cu–In–Ga stacks were successively significant results which complete the understanding of the selenized and sulfurized between 500 and 550 °C [100]. deposition mechanism. Duchatelet et al. reported an efficiency of 8.7% for a According to Mishra and Rajeshwar, the formation of 370 nm-thick CIGSe thin films by electrodeposition of Cu/ CuSe binary phase occurs at the first place through under - In/Ga stacks. The as-deposited CuInGa precursor thick- potential deposition onto the previously reduced Cu from 2+ ness was around 120 nm. Upon selenization at 550 °C for Cu ions. Though Se is nobler than Cu, the formation of 15 min, they observed an increased V of 865 mV which Se (IV) to Se (0) is sluggish, and hence, the initial forma- OC was higher than the standard CIGSe (2100 nm) exhibit- tion of Cu is highly necessary for the direct reduction of ing V of 605 mV (η = 12.6%). The accumulated Ga in Se(IV) [104]. During the initial stage of deposition, the OC ultra-thin CIGSe devices played the role of back surface formation of Cu nano-nuclei over the Mo substrates allows field and inhibited the electron recombination at the back the incorporation of Se (0) to form Cu Se binary phase. contact [101]. Moreover, the growth of Cu Se phase can easily take place Malaquias et al. reported an efficiency of 9.8% for elec- over molybdenum even at open-circuit potential. trodeposited CuInGa alloys with reduced Ga accumula- Figure 10a shows the Raman spectra of Cu–Se films tion by employing a three-step annealing process [80]. immersed for different periods at OCP conditions. Irre - To explain the impact of three-step annealing process, spective of the immersion time, no peak correspond- −1 the work by Kim et al. has been explained below [102]. ing to Se (254 cm ) was observed. Only characteristic The three-step annealing process of vacuum-deposited Raman peaks corresponding to Cu Se (106, 141, 197, 3 2 −1 −1 CuInGa metal precursor involves (1) selenization in H Se and 216 cm ) and Cu Se (261 cm ) were observed [105]. 2 2 at 400 °C for 60 min, (2) annealing in Ar at 550 °C for Hence, at lower cathodic potential, Cu–Se binary co-exists 20 min, and (3) sulfization in H S at 550 °C for 10 min. as mixtures of Cu Se, Cu Se, CuSe, and Se(0) [107, 108]. 2 3 2 2 From the AES studies (in Fig. 9a–c), the sputter deposited For increased over potential, the direct reduction of Se(IV) CIGSe selenized samples were stoichiometric at the sur- to elemental Se(0) takes place over CuSe platelets, as face and Ga/Cu–Ga intermetallic rich at the back contact. shown in Fig. 10b. However, after selective dissolution of However, the homogenization of In and Ga was observed elemental Se, the atomic ratio of CuSe platelets [Se/Cu] after the Ar and H S post-heat treatments. As shown in was found to be close to unity (Fig. 10c) [106]. Increased Fig. 9a–c (SEM cross-sectional images), an improvement Se concentration (over CuSe platelets) contributes to the in the CIGSe micro-structure (vacuum-based deposition) formation of CuSe phase. CuSe can further reduce to 2 2 2+ was observed followed by the disappearance of flat voids form Cu and H Se at higher cathodic potentials which only after the Ar and H S treatment. Bi et al. reported chemically react with H Se to form a non-adherent Cu Se 2 2 2 an efficiency of 11.04% of CIGSe thin films for the elec- particles dispersing back to the electrolyte [85]. This reac- 3+ 3+ trodeposited metal stacks of Cu/In/Ga annealed in three tion is the key for the In and Ga incorporations as the steps: (1) selenization at 400 °C for 10 min; (2) N for In and Ga ions can react chemically with H2Se to form 30 min at 580 °C; and (3) selenization at 580 °C for 15 min their respective selenides. [103]. The Indium incorporation at low cathodic potential has Apart from rapid thermal annealing schemes, three- already been reported in several literatures. Kemell et al. 3+ step annealing is beneficial as during the N annealing, reported that CuSe phase enables the incorporation of In a slow interdiffusion step between CuInSe and CuGaSe ions by induced co-deposition process [110]. Chassaing 2 2 3+ is possible which ensures the homogenization In and Ga. and co-workers reported that In inclusion takes place when the [Se/Cu] ratio is greater than 1 to form CuInSe . 1 3 6 Page 12 of 20 Materials for Renewable and Sustainable Energy (2018) 7:6 Fig. 9 Compositional depth profiles determined by AES of the reacted CIGSe (or CIGSeS) films after a H Se (400 °C for 60 min), b Ar (550 °C for 20 min) and c H S (550 °C for 10 min) and corresponding cross-sectional SEM images of reacted CIGSe or CIGSeS films after a 1st step, b 2nd step, and c 3rd step. Reprinted from Kim et al. [102] with the permission of AIP Publishing −1 Excess selenium over CuSe phase is a perquisite of the can be observed. The peak at 260 cm corresponds to the indium incorporation at lower cathodic potential [106]. conductive Cu Se phase [107]. However, the inclusion of In through such surface-induced For CuGaSe or CuInGaSe , the Ga inclusion in the as- 2 2 reactions (at lower cathodic potential) is often limited deposited CIGSe films mainly depends on the applied poten- which is ascribed to the increased electrical resistance of tial. Unlike indium, such surface-induced reactions of In(III) the surface due to poor reacting nature of Se(0) species ions with Cu Se phase are not found for Ga species. The inclu- [111]. At higher cathodic potential conditions, the formed sion of Ga takes place either in the form of Ga(OH) (due to 3+ Se(–II) species chemically reacts with In to form indium the local change in pH) [112] and Ga Se (reaction with H Se) 2 3 2 selenides (In Se ) and assimilates to the growing CuInSe at lower or higher cathodic potential, respectively. Further 2 3 2 3+ film. In can also reduce directly to form In(0) at high increase in deposition potential usually may lead to formation precursor concentrations and deposition potential condi- of gallium oxides and hydroxide due to the parallel occurrence tions. Figure 11a shows Raman spectra of as-electrodepos- of HER [81]. So far, there is no direct evidence for the assimi- ited CISe of thickness 2 µm. The presence of Cu-deficient lation of CuGaSe or Ga Se species with CuInSe or In Se 2 2 3 2 2 3 −1 CISe phase (160 cm ) commonly known as OVC, A1 forming CIGSe thin film. For as-deposited CGSe films, Liu −1 −1 mode of CISe (177 cm ), and elemental Se(0) (260 cm ) et al. reported the absence of Raman peaks (Fig. 11b) corre- −1 −1 sponding to CuGaSe (184 cm ) or Ga Se (155 cm ) peaks, 2 2 3 1 3 Materials for Renewable and Sustainable Energy (2018) 7:6 Page 13 of 20 6 Fig. 10 a Raman spectra of CuSe films obtained after immersion at Cu] = 1.9, [In/Cu] = 0 and c SEM of Cu–Se after stripping in Na S, OCP in Cu(II)–Se(IV) solutions (pH 2.2) (reprinted with permis- [Se/Cu] = 0.95 (reprinted with permission from Chassaing et al. sion from Ramdani et al. [105] Copyright 2007, The Electrochemical [106], Copyright© 2008 John Wiley and Sons) Society), b SEM of as-deposited Cu–Se at V = − 0.55 V/MSE, [Se/ Fig. 11 a Raman spectra of electrodeposited CuInSe thin film (2 µm) mission from Elsevier), c Raman spectra of CuInGaSe (as-deposited 2 2 (reprinted with permission, Roussel [107], Copyright 2007, The Elec- and annealed) (reprinted with permission, Lai et al. [109], Copyright trochemical Society), b Raman spectra of CuGaSe (as-deposited and 2011, The Electrochemical Society) annealed) (reprinted from Liu et al. [81], Copyright (2012), with per- −1 instead only peaks corresponding to CuSe (255 and 263 cm ) The assimilation of In and Ga to the growing CIGSe is only −1 and elemental Se (238 cm ) were observed. Lai et al. also stronger at higher cathodic potential. A judicious bath prepara- −1 reported the appearance of CIGSe A1 mode (174 cm ) tion and deposition potential are necessary to have controlled (Fig. 11c) for as-deposited and for annealed CIGSe thin films inclusion of Ga with minimal oxygen content. −1 at 174 and 176 cm , suggesting that the Ga Se phase must 2 3 be in the dispersed nano-crystalline form which involves in the phase formation only during annealing [109]. 1 3 6 Page 14 of 20 Materials for Renewable and Sustainable Energy (2018) 7:6 Fig. 12 CIGSe electrodeposi- tion schemes and their power conversion efficiency Recently, Duchatelet et al. reported (Fig. 12c) an effi- CIGSe electrodeposition schemes and device ciency of 12.4% (0.1 cm ), where Cu–In–Ga are depos- performance ited in hydroxide form followed by H reduction and selenization [95]. The approaches followed to electrodeposit CIGSe absorber In Fig. 12d, for a three-stage electrodeposition of layers can be classified into two routes: (1) by one-step CIGSe/Cu/In metal stacks (selenization at 550 °C), deposition, where co-deposition of all the elements takes Bhattacharya et al. reported an efficiency of 10.9% for place at a single potential followed by post-treatments the device area of each cell is ~ 0.42 cm . They were or (2) by two steps to multi-step depositions to deposit able to fabricate these devices reproducibly and all nine either via binary phase deposition or element by element. cells had comparable efficiencies indicating uniform The deposition schemes which are already in practice and deposition over 12.5 cm area [97]. promising for large area CIGSe thin-film electrodeposition • For an electrodeposited stacked Cu/In/Ga layers as are presented Fig. 11. Irrespective of deposition schemes, mentioned in Fig. 12e (selenized at 550 °C), Bhattacha- a high-temperature annealing between 500 and 600 °C rya et al. reported an efficiency of 11.7% [96]. (under sulfur, selenium, or inert atmosphere) is required to enhance crystallinity and alloy formation process. Recently, an efficiency of 11.04% was also reported by Biet al. using the deposition scheme-e. However, the • The fabrication route mentioned in Fig. 12a deals with Cu/In/Ga metal stacks were formed by employing a pulse deposition of one-step electrodeposition of Cu–In–Ga electroplating technique and instead of conventional sele- layers followed by selenization/sulfurization. Using nization. They carried out three-step annealing processes: such scheme, a record efficiency of 17.30% (0.5 cm ) and (1) selenization at 400 °C for 10 min; (2) N for 30 min at 14% (60 × 120 cm ) in industrial scale were achieved for 580 °C; and (3) selenization at 580 °C for 15 min [103]. CIGSSe devices by NEXCIS [100]. In the above-mentioned schemes in Fig. 12, the direct • Using complexing agents, Başol et al. were able to elec- current (DC) was employed to deposit CIGSe thin films. trodeposit Cu–In–Ga/In–Se or Ga–Se stacks (Fig. 12b) The rate determining step in one-step direct current is in alkaline conditions. The reported efficiency for the the charge transfer process. The increased supersatu- devices fabricated through this route is of 14.17% 2 2 2 rated growth takes place over the same nucleation sites (11.8 cm ), 15.36% (5.4 cm ), and 13.4% (1.5 m ). The and hence results in the fine particles in porous/powdery above-mentioned routes are presently the most efficient deposits. Apart from DC depositions, there are other dif- regarding the final efficiencies of CIGSe devices [62, 98]. ferent plating techniques which includes pulse plating, pulse reverse plating and cyclic voltammetry techniques 1 3 Materials for Renewable and Sustainable Energy (2018) 7:6 Page 15 of 20 6 Fig. 13 a CIGSe device struc- ture with CdS as buffer layer (η = 21.7%) [29]. b Record efficiency CIGSe device struc- ture of η = 21% with Zn(O,S) as buffer layer [7] by which the secondary phase formation can be minimized (η = 13%) [118]. Furthermore, the thermal diffusion of Cd [71, 113, 114]. Compared to conventional constant poten- or Zn adatoms at the absorber surface creates donor anti- tial deposition techniques, electron charge transfer step is sites, thus can enhance inversion layer (more n-type). Recent prevented in pulse plating as the deposition diffusion con- results also indicated that Zn(O,S) with CIGSe functions to trolled process may lead thin films of large grain size mor - be a better substitution for CdS, exhibiting valence (VBO) phology. Such deposition techniques are advantageous as and conduction band off-set (CBO) of 1.15 ± 0.15 and we can have good control over the material composition. 0.09 ± 0.20 eV, respectively. The CBO of the hetero inter- face is sufficiently flat (with a small spike) providing better electron flow and a good blocking layer for the majority CdS‑free buffer layer in CIGSe devices carriers and hence reduces the interface recombination. Fur- thermore, the band-gap tuning is possible in Zn(O,S) buffer Until date, most of the reported record efficiency (η > 19%) layers by varying the [S/S + O] ratio [119, 120]. Even a mini- CIGSe devices employ CdS buffer layer which comprises of mal bandgap of 2.6 eV can be achieved with S/S + O = 45% the device, as shown in Fig. 13a [29]. which is 0.2 eV larger than CdS, thus avoiding the absorp- The buffer layers play major role in the formation of a tion losses. An increased device performance was observed favorable heterojunction band alignment (ΔE = 0–0.4 eV) when CIGSe/Zn(O,S) devices are annealed or HLS (heat and with CIGSe to provide an unimpeded electron flow. A thin light soaked) treatments are performed. These treatments CdS of thickness ≈ 50 nm is so far the most successful and decrease the [S/S + O] composition at the CIGSe/Zn(O,S) widely buffer layer employed in CIGSe solar cells. This interface and helps in the rearrangement of the CBO to be thin layer is deposited by chemical bath deposition (CBD), more favorable than the as-deposited Zn(O,S) [121, 122]. which incurs huge environmental issues with the toxic These results are encouraging which would pave the way chemicals involved in. Hence, on the aspect of mitigating to reduce the toxicity levels in the current CIGSe fabrication environmental hazards, replacement of hazardous CdS is techniques. highly essential. Various alternative buffer layers with higher bandgap than CdS (2.4 eV) [ZnS (3.8 eV), ZnSe (2.7 eV), ZnMgO, In Se (2.7 eV), In S (2.45 eV)] have been synthe- Conclusion 2 3 2 3 sized using various wet and dry deposition techniques [115, 116]. The advantageous part is that these materials exhibit Electrodeposition is probably one of the mature and scal- larger bandgap than CdS, thus minimizes the absorption loss able non-vacuum-based deposition techniques for CISe/ between the wavelength regions of 350–550 nm. Yet, these CIGSe absorber layers. This review has provided some of materials lack in terms of stability and final efficiency when the progresses in electrodeposition of these ternary and qua- compared to CdS. Remarkably, CBD grown Zn(O,S)/CIGSe ternary films which essentially covers formation mechanism devices exhibited better stability even when subjected to of the alloys, experimental practices, deposition routes, and 1000 h damp-heat testing and suffered no severe efficiency alternatives to replace the CdS buffer layer. The significant losses [117]. CBD is the most successful Zn(O,S) buffer observations can be listed as mentioned below: layer deposition technique used in the CIGSe device fabrica- tion. A comparison study by Ramanathan et al. revealed that • Until date, the reported highest efficiency of elec- Zn(O,S) buffer layers deposited by CBD exhibited highest trodeposited CIGSe devices is 17.30% in lab scale 2 2 power conversion efficiency (η = 18%) than the sputtered one (0.5 cm ) and 14% in industrial modules (60 × 120 cm ). 1 3 6 Page 16 of 20 Materials for Renewable and Sustainable Energy (2018) 7:6 distribution, and reproduction in any medium, provided you give appro- Though the reported efficiency is comparably less to vac- priate credit to the original author(s) and the source, provide a link to uum-based techniques, electroplating technique is still the Creative Commons license, and indicate if changes were made. a very promising technique for a simplified large scale solar cell manufacturing process. The primary concern in electrodeposition is to gain References control over the film stoichiometry and compactness. In addition, the current practice adopted by solar industries 1. Badawy Waheed, A.: A review on solar cells from Si-single to fabricate efficient CIGSe modules is by electroplat- crystals to porous materials and quantum dots. J. Adv. Res. 6, ing of single Cu–In–Ga or Cu–In–Ga/In–Se or Ga–Se 123–132 (2015) bi-layer stack deposition followed by selenization/sul- 2. Brown, G.F., Wu, J.: Third generation photovoltaics. Laser Pho- ton. Rev. 3, 394–405 (2009) furization in acidic baths. Formation of Cu–In–Ga/Cu– 3. Pagliaro, M., Ciriminna, R., Palmisano, G.: Flexible solar cells. Ga/In–Ga metal stacks in alkaline pH using complexing Chemsuschem 1, 880–891 (2008) agents can be an alternative promising route too. 4. Chirilă, A., Reinhard, P., Pianezzi, F., Bloesch, P., Uhl, A.R., Electrodeposition of Cu–In–Ga in the mixed oxide Fella, C., Kranz, L., Keller, D., Gretener, C., Hagendorfer, H., Jaeger, D., Erni, R., Nishiwaki, S., Buecheler, S., Tiwari, N.: form using nitrate precursors (of Cu, In, and Ga salts) Potassium-induced surface modification of Cu(In, Ga)Se thin or hydrogen peroxide (as the supporting electrolyte) is films for high-efficiency solar cells. Nat. Mater. 12, 1107 (2013) promising electrolyte recipes, as the oxides of Ga and 5. Reinhard, P., Bissig, B., Pianezzi, F., Avancini, E., Hagendor- In depositions take place at less cathodic potential. The fer, H., Keller, D., Fuchs, P., Döbeli, M., Vigo, C., Crivelli, P., Nishiwaki, S., Buecheler, S., Tiwari, A.N.: Features of KF and complexity of Ga inclusion is reduced when compared NaF postdeposition treatments of Cu(In, Ga)Se absorbers for to conventional electrodeposition routes. high efficiency thin film solar cells. Chem. Mater. 27, 5755–5764 Rapid thermal annealing (RTA) and successive seleniza- (2015) tion/sulfurization using elemental sulfur and selenium 6. Jackson, P., Wuerz, R., Hariskos, D., Lotter, E., Witte, W., Pow- alla, M.: Effects of heavy alkali elements in Cu(In, Ga)Se solar are the most preferred post-processing routes followed cells with efficiencies up to 22.6%. Phys. Status Solidi RRL 10, in the industrial scale. Other annealing schemes such as 583–586 (2016) triple step annealing in H Se/Ar/H S or H Se/Ar/H Se 2 2 2 2 7. Friedlmeier, T.M., Jackson, P., Bauer, A., Hariskos, D., Kiowski, were also reported to be effective towards minimizing O., Wuerz, R., Powalla, M.: Improved photocurrent in Cu(In, Ga) Se solar cells: from 20.8% to 21.7% efficiency with CdS buffer the Ga accumulation problems and in terms of device and 21.0% Cd-free. IEEE J. Photovolt. 5, 1487–1491 (2015) efficiency. However, for reducing the fabrication cost, 8. Kamada, R., Yagioka, T., Adachi, S., Handa, A., Tai, K. F., Kato, alternative routes for evading the Se loss during Argon/ T., Sugimoto, H.: New world record Cu(In,Ga)(Se,S) thin film N annealing and its effect on the device performance are solar cell efficiency beyond 22%. In: IEEE 43rd Photovoltaic Specialists Conference (PVSC), Portland, 2016. https ://doi. to be explored extensively. org/10.1109/pvsc.2016.77498 22 Regarding buffer layers, Zn(O,S) grown by chemical bath 9. Green, M.A., Emery, K., Hishikawa, Y., Warta, W., Dunlop, E.D., deposition technique is found to be a more promising Levi, D.H., Ho-Baillie, A.W.Y.: Solar cell efficiency tables (ver - alternative to CdS in terms of its performance and stabil- sion 49). Prog. Photovolt. Res. Appl. 25, 3–13 (2017) 10. Aksu, S., Pinarbasi, M.: Electrodeposition methods and chemis- ity. A record efficiency beyond 22% has been achieved tries for deposition of CIGS precursor thin films. In: 37th IEEE utilizing CBD grown Zn(O,S) buffer layers. Employing Photovoltaic Specialists Conference, Seattle, 2011. https ://doi. alkali-PDT treatments can help in improving the CIGSe org/10.1109/pvsc.2011.61859 07 devices. 11. Lincot, D.: Electrodeposition of semiconductors. Thin Solid Films 487, 40–48 (2005) 12. Saji, V.S., Choi, I.H., Lee, C.W.: Progress in electrodeposited A full-fledged industrialization of the devices fabricated absorber layer for CuIn Ga Se (CIGS) solar cells. Sol. (1−x) x 2 through electroplating routes requires further in-depth exten- Energy 85, 2666–2678 (2011) sive and explorative studies on electronic characteristics of 13. Ghorbani, E., Kiss, J., Mirhosseini, H., Roma, G., Schmidt, M., Windeln, J., Kühne, T.D., Felser, C.: Hybrid-functional calcu- the CIS/CGS/CIGSe absorber layers. For avoiding H Se or lations on the incorporation of Na and K impurities into the selenization steps, the annealing effects of the surface modi- CuInSe and CuIn Se solar-cell materials. J. Phys. Chem. C 2 5 8 fied CIGSe (CIGSe/In–Se or Se or Ga–Se) stacks and its role 119, 25197–25203 (2015) in Se retainment are to be explored for a competitive and 14. Abou-Ras, D., Caballero, R., Kaufmann, C.A., Nichterwitz, M., Sakurai, K., Schorr, S., Unold, T., Schock, H.W.: Impact of the cost-effective deposition scheme. Ga concentration on the microstructure of CuIn Ga Se . Phys. 1−x x 2 Status Solidi RRL 2, 135–137 (2008) Acknowledgements The authors would like to thank NIT-Rourkela for 15. Continenza, A., Massidda, S., Freeman, A.J., De Pascale, T.M., providing infrastructure and experimental facilities. Meloni, F., Serra, M.: Structural and electronic properties of narrow-gap ABC chalcopyrite semiconductors. Phys. Rev. B. Open Access This article is distributed under the terms of the Crea- 46, 10070–10077 (1992) tive Commons Attribution 4.0 International License (http://creat iveco mmons .org/licen ses/by/4.0/), which permits unrestricted use, 1 3 Materials for Renewable and Sustainable Energy (2018) 7:6 Page 17 of 20 6 16. Shafarman, W.N., Stolt, L.: Cu (InGa)Se Solar Cells. In: Luque, 36. Lei, C., Duch, M., Robertson, I.M., Rockett, A.: Effects of solu- A., Hegedus, S. (eds.) Handbook of photovoltaic science and tion-grown CdS on Cu(InGa)Se grain boundaries. J. Appl. Phys. engineering, pp. 567–616. Wiley, Chichester (2005) 108, 114908 (2010) 17. Jaffe, J.E., Zunger, A.: Theory of the band-gap anomaly in ABC 37. Liao, D., Rockett, A.: Cu depletion at the CuInSe surface. Appl. 2 2 chalcopyrite semiconductors. Phys. Rev. B. 29, 1882–1906 Phys. Lett. 82, 2829 (2003) (1984) 38. He, X., Paulauskas, T., Ercius, P., Varley, J., Bailey, J., Zapalac, 18. Zunger, A.: New insights on chalcopyrites from solid-state the- G., Poplavskyy, D., Mackie, N., Bayman, A., Spaulding, D., Klie, ory. Thin Solid Films 515, 6160–6162 (2007) R., Lordi, V., Rockett, A.: Cd doping at PVD–CdS/CuInGaSe 19. Zhao, Y.J., Persson, C., Lany, S., Zunger, A.: Why can CuInSe heterojunctions. Sol. Energy Mater. Sol. Cells 164, 128–134 be readily equilibrium-doped n -type but the wider-gap CuGaSe (2017) cannot? Appl. Phys. Lett. 85, 5860–5862 (2004) 39. Salome, P.M.P., Ribeiro-Andrade, R., Teixeira, J.P., Keller, J., 20. Guillemoles, J.F., Kronik, L., Cahen, D., Rau, U., Jasenek, A., Torndahl, T., Nicoara, N., Edoff, M., Gonzalez, J.C., Leitao, J.P., Schock, H.W.: Stability issues of Cu(In, Ga)Se -based solar cells. Sadewasser, S.: Cd and Cu interdiffusion in Cu(In, Ga)Se /CdS 2 2 J. Phys. Chem. B. 104, 4849–4862 (2000) hetero-interfaces. IEEE J. Photovolt. 7, 858–863 (2017) 21. Zhang, S.B., Wei, S.-H., Zunger, A., Katayama-Yoshida, H.: 40. Sozzi, G., Di Napoli, S., Menozzi, R., Carron, R., Avancini, E., Defect physics of the CuInSe chalcopyrite semiconductor. Phys. Bissig, B., Buecheler, S., Tiwari, A.N.: Analysis of Ga grading Rev. B. 57, 9642–9656 (1998) in CIGS absorbers with different Cu content. In: 2016 IEEE 43rd 22. Siebentritt, S., Gütay, L., Regesch, D., Aida, Y., Deprédurand, V.: Photovoltaic Specialists Conference (PVSC), Portland, 2016. Why do we make Cu(In, Ga)Se solar cells non-stoichiometric? https ://doi.org/10.1109/pvsc.2016.77500 42 Sol. Energy Mater. Sol. Cells 119, 18–25 (2013) 41. Song, J., Li, S.S., Huang, C.H., Crisalle, O.D., Anderson, T.J.: 23. Insignares-Cuello, C., Broussillou, C., Bermúdez, V., Saucedo, Device modeling and simulation of the performance of Cu(In , 1 − x E., Pérez-Rodríguez, A., V, Izquierdo-Roca: Raman scattering Ga )Se solar cells. Solid State Electron 48, 73–79 (2004) x 2 analysis of electrodeposited Cu(In, Ga)Se solar cells: Impact of 42. Lundberg, O., Bodegård, M., Malmstro̊m, J., Stolt, L.: Influence ordered vacancy compounds on cell efficiency. Appl. Phys. Lett. of the Cu(In, Ga)Se thickness and Ga grading on solar cell per- 105, 021905 (2014) formance. Prog. Photovolt. Res. Appl. 11, 77–88 (2003) 24. Siebentritt, S., Igalson, M., Persson, C., Lany, S.: The electronic 43. Richter, M., Schubbert, C., Eraerds, P., Parisi, J., Riedel, I., Dali- structure of chalcopyrites-bands, point defects and grain bounda- bor, T., Palm, J.: Comprehensive simulation model for Cu(In, Ga) ries. Prog. Photovolt. Res. Appl. 18, 390–410 (2010) (Se, S) solar cells. Sol. Energy Mater. Sol. Cells 132, 162–171 25. Turcu, M., Rau, U.: Fermi level pinning at CdS/Cu(In, Ga)(Se, (2015) S)2 interfaces: effect of chalcopyrite alloy composition. J. Phys. 44. Avancini, E., Carron, R., Bissig, B., Reinhard, P., Menozzi, R., Chem. Solids 64, 1591–1595 (2003) Sozzi, G., Di Napoli, S., Feurer, T., Nishiwaki, S., Buecheler, S., 26. Dharmadasa, I.M., Chaure, N.B., Samantilleke, A.P., Hassan, A.: Tiwari, A.N.: Impact of compositional grading and overall Cu Multi Fermi level pinning at metal/Cu(InGa)(SeS) interfaces. deficiency on the near-infrared response in Cu(In, Ga)Se solar 2 2 Sol. Energy Mater. Sol. Cells 92, 923–928 (2008) cells. Prog. Photovolt. Res. Appl. 25, 233–241 (2017) 27. Lany, S., Zunger, A.: Light- and bias-induced metastabilities 45. Deprédurand, V., Bertram, T., Siebentritt, S.: How does the sele- in Cu(In, Ga)Se based solar cells caused by the (V –V ]) nium activity influence CuInSe devices grown under Cu-excess? 2 Se Cu 2 vacancy complex. J. Appl. Phys. 100, 113725 (2006) In : Proceedings of SPIE 8823, Thin Film Solar Technology V, 28. Jensen, S.A., Kanevce, A., Mansfield, L.M., Glynn, S., Lany, S., 882304, 2013 Kuciauskas, D.: Optically induced metastability in Cu(In, Ga) 46. Gtay, L., Regesch, D., Larsen, J.K., Aida, Y., Depredurand, V., Se . Sci. Rep. 7, 13788 (2017) Siebentritt, S.: Influence of copper excess on the absorber quality 29. Jackson, P., Hariskos, D., Wuerz, R., Kiowski, O., Bauer, A., of CuInSe . Appl. Phys. Lett. 99, 151912 (2011) Friedlmeier, T.M., Powalla, M.: Properties of Cu(In, Ga)Se 47. Deprédurand, V., Tanaka, D., Aida, Y., Carlberg, M., Fèvre, N., solar cells with new record efficiencies up to 21.7%. Phys. Status Siebentritt, S.: Current loss due to recombination in Cu-rich Solidi RRL 9, 28–31 (2015) CuInSe solar cells. J. Appl. Phys. 115, 44503–44508 (2014) 30. Repins, I., Glynn, S., Duenow, J., Coutts, T.J., Metzger, W.K., 48. Kemell, M., Ritala, M., Leskelä, M.: Effects of post-deposition Contreras, M.A.: Required material properties for high-efficiency treatments on the photoactivity of CuInSe thin films deposited CIGS modules. Proc. SPIE 7409, 74090M (2009) by the induced co-deposition mechanism. J. Mater. Chem. 11, 31. Misic, B., Pieters, B.E., Theisen, J.P., Gerber, A., Rau, U.: Shunt 668–672 (2001) mitigation in ZnO:Al/i-ZnO/CdS/Cu(In, Ga)Se solar modules 49. Deprédurand, V., Bertram, T., Siebentritt, S.: Influence of the by the i-ZnO/CdS buffer combination. Phys. Status Solidi A 212, Se environment on Cu-rich CIS devices. Phys. B 439, 101–104 541–546 (2015) (2014) 32. Scheer, R., Messmann-Vera, L., Klenk, R., Schock, H.-W.: On 50. Aida, Y., Depredurand, V., Larsen, J.K., Arai, H., Tanaka, D., the role of non-doped ZnO in CIGSe solar cells. Prog. Photovolt. Kurihara, M., Siebentritt, S.: Cu-rich CuInSe solar cells with a Res. Appl. 20, 619–624 (2012) Cu-poor surface. Prog. Photovolt. Res. Appl. 23, 754–764 (2015) 33. Nakada, T.: Nano-structural investigations on Cd-doping into 51. Ramanujam, J., Singh, U.P.: Copper indium gallium selenide Cu(In, Ga)Se thin films by chemical bath deposition process. based solar cells—a review. Energy Environ. Sci. 10, 1306–1319 Thin Solid Films 361–362, 346–352 (2000) (2017) 34. Cojocaru-Mirédin, O., Choi, P., Wuerz, R., Raabe, D.: Exploring 52. Abou-Ras, D., Schmidt, S.S., Schäfer, N., Kavalakkatt, J., Ris- the p–n junction region in Cu(In, Ga)Se thin-film solar cells at som, T., Unold, T., Mainz, R., Weber, A., Kirchartz, T., Simsek the nanometer-scale. Appl. Phys. Lett. 101, 181603 (2012) Sanli, E., van Aken, P.A., Ramasse, Q.M., Kleebe, H.-J., Azu- 35. Abou-Ras, D., Kostorz, G., Romeo, A., Rudmann, D., Tiwari, lay, D., Balberg, I., Millo, O., Cojocaru-Mirédin, O., Barragan- A.N.: Structural and chemical investigations of CBD- and PVD– Yani, D., Albe, K., Haarstrich, J., Ronning, C.: Compositional CdS buffer layers and interfaces in Cu(In, Ga)Se -based thin film and electrical properties of line and planar defects in Cu(In, Ga) solar cells. Thin Solid Films 480–481, 118–123 (2005) Se thin films for solar cells—a review. Phys. Status Solidi RRL 10, 363–375 (2016) 1 3 6 Page 18 of 20 Materials for Renewable and Sustainable Energy (2018) 7:6 53. Savadogo, O.: Chemically and electrochemically deposited thin 71. Harati, M., Jia, J., Giffard, K., Pellarin, K., Hewson, C., Love, films for solar energy materials. Sol. Energy Mater. Sol. Cells D.A., Lau, W.M., Ding, Z.: One-pot electrodeposition, charac- 52, 361–388 (1998) terization and photoactivity of stoichiometric copper indium gal- 54. Calixto, M.E., Dobson, K.D., McCandless, B.E., Birkmire, R.W.: lium diselenide (CIGS) thin films for solar cells. Phys. Chem. Controlling growth chemistry and morphology of single-bath Chem. Phys. 12, 15282–15290 (2010) electrodeposited Cu(In, Ga)Se thin films for photovoltaic appli- 72. Wellings, J.S., Samantilleke, A.P., Heavens, S.N., Warren, P., cation. J. Electrochem. Soc. 153, G521 (2006) Dharmadasa, I.M.: Electrodeposition of CuInSe from ethylene 55. Saji, V.S., Jung, C.-Y., Lee, C.-W.: Electrodeposition of copper, glycol at 150 °C. Sol. Energy Mater. Sol. Cells 93, 1518–1523 selenium, indium, and gallium on molybdenum/surface oxides: (2009) unary, binary, ternary and quaternary compositions. J. Electro- 73. Lian, Y., Ji, S., Zhao, L., Zhang, J., Yang, P., Zhang, J., An, M.: chem. Soc. 162, D465–D479 (2015) One-step electrodeposition of CuIn Ga Se thin films from x 1−x 2 56. Bhattacharya, R.N., Rajeshwar, K.: Electrodeposition of CuIn a mixture system of ionic liquid and ethanol. New J. Chem. 39, (X = Se, Te) thin films. Solar Cells. 16, 237–243 (1986) 7742–7745 (2015) 57. Chiu, Y.-S., Hsieh, M.-T., Chang, C.-M., Chen, C.-S., Whang, 74. Long, F., Wang, W., Du, J., Zou, Z.: CIS(CIGS) thin films pre- T.-J.: Single-step electrodeposition of CIS thin films with the pared for solar cells by one-step electrodeposition in alcohol complexing agent triethanolamine. Appl. Surf. Sci. 299, 52–57 solution. J. Phys. Conf. Ser. 152, 012074 (2009) (2014) 75. Steichen, M., Thomassey, M., Siebentritt, S., Dale, P.: Controlled 58. Liu, J., Liu, F., Lai, Y., Zhang, Z., Li, J., Liu, Y.: Effects of electrodeposition of Cu–Ga from a deep eutectic solvent for low sodium sulfamate on electrodeposition of Cu(In, Ga)Se thin cost fabrication of CuGaSe thin film solar cells. Phys. Chem. 2 2 film. J. Electroanal. Chem. 651, 191–196 (2011) Chem. Phys. 13, 4292–4302 (2011) 59. Muthuraj, J.J.J., Rasmussen, D.H., Suni, I.I.: Electrodeposition 76. Simka, W., Puszczyk, D., Nawrat, G.: Electrodeposition of metals of CuGaSe from thiocyanate-containing electrolytes. J. Electro- from non-aqueous solutions. Electrochim. Acta 54, 5307–5319 chem. Soc. 158, D54 (2011) (2009) 60. Stratieva, N., Tzvetkova, E., Ganchev, M., Kochev, K., Tomov, 77. Gadilohar, B.L., Shankarling, G.S.: Choline based ionic liquids I.: Structural and optical properties of electrodeposited and their applications in organic transformation. J. Mol. Liq. 227, CuInSe layers. Sol. Energy Mater. Sol. Cells 45, 87–96 (1997) 234–261 (2017) 61. Aksu, S., Wang, J., Basol, B.M.: Electrodeposition of In–Se 78. Zhang, Y., Han, J., Liao, C.: Insights into the properties of deep and Ga–Se thin films for preparation of CIGS Solar Cells. eutectic solvent based on reline for Ga-controllable CIGS solar Electrochem. Solid State Lett. 12, D33 (2009) cell in one-step electrodeposition. J. Electrochem. Soc. 163, 62. Aksu, S., Pinarbasi, M.: Electrodeposition of Cu–In–Ga films D689–D693 (2016) for the preparation of CIGS solar cells. In: 35th IEEE Pho- 79. Malaquias, J.C., Regesch, D., Dale, P.J., Steichen, M.: Tuning tovoltaic Specialists Conference. Honolulu, 2010. https ://doi. the gallium content of metal precursors for Cu(In, Ga)Se thin org/10.1109/pvsc.2010.56171 15 film solar cells by electrodeposition from a deep eutectic solvent. 63. Duchatelet, A., Savidand, G., Loones, N., Chassaing, E., Lin- Phys. Chem. Chem. Phys. 16, 2561–2567 (2014) cot, D.: Mechanism of electrochemical deposition of Cu–In–Ga 80. Malaquias, J.C., Berg, D.M., Sendler, J., Steichen, M., Valle, mixed oxide/hydroxide thin films for Cu(In, Ga)Se solar cells. N., Dale, P.J.: Controlled bandgap CuIn Ga (S Se ) 2 1−x x 0.1 0.9 2 J. Electrochem. Soc. 161, D3120–D3129 (2014) (0.10 ≤ x≤0.72) solar cells from electrodeposited precursors. 64. Duchatelet, A., Savidand, G., Vannier, R.N., Chassaing, E., Thin Solid Films 582, 2–6 (2015) Lincot, D.: A new deposition process for Cu(In, Ga)(S, Se) 81. Liu, F., Yang, J., Zhou, J., Lai, Y., Jia, M., Li, J., Liu, Y.: One-step solar cells by one-step electrodeposition of mixed oxide pre- electrodeposition of CuGaSe thin films. Thin Solid Films 520, cursor films and thermochemical reduction. J. Renew. Sustain. 2781–2784 (2012) Energy. 5, 11203 (2013) 82. Oda, Y., Minemoto, T., Takakura, H.: Electrodeposition of crack- 65. Yang, J., Huang, C., Jiang, L.X., Liu, F.Y., Lai, Y.Q., Li, J., free CuGaSe thin films from single bath. J. Electrochem. Soc. Liu, Y.X.: Effects of hydrogen peroxide on electrodeposition 155, H292 (2008) of Cu(In, Ga)Se thin films and band gap controlling. Electro- 83. Manfredy, L., Marquez, O.P., Lopez-Rivera, S.A., Marquez, J., chim. Acta 142, 208–214 (2014) Martínez, Y., Miranda, D.A.: Electrochemical preparation and 66. Chassaing, E., Duchatelet, A., Lincot, D.: Mechanistic study of structural characterization of CuGaSe thin films. J. Phys. Conf. one-step cathodic electrodeposition of mixed Cu–In–Ga oxide/ Ser. 687, 12038 (2016) hydroxide films with hydrogen peroxide oxygen precursor. J. 84. Fernandez, A.M., Bhattacharya, R.N.: Electrodeposition of Electrochem. Soc. 164, D852–D860 (2017) CuIn Ga Se precursor films: optimization of film composi- 1−x x 2 67. Chaure, N.B., Young, J., Samantilleke, A.P., Dharmadasa, I.M.: tion and morphology. Thin Solid Films 474, 10–13 (2005) Electrodeposition of p–i–n type CuInSe multilayers for photo- 85. Thouin, L., Massaccesi, S., Sanchez, S., Vedel, J.: Formation of voltaic applications. Sol. Energy Mater. Sol. Cells 81, 125–133 copper indium diselenide by electrodeposition. J. Electroanal. (2004) Chem. 374, 81–88 (1994) 68. Chaure, N.B., Samantilleke, A.P., Burton, R.P., Young, J., 86. Frontini, M.A., Vázquez, M.: Electrodeposition of CuInSe in Dharmadasa, I.M.: Electrodeposition of p+, p, i, n and n+- citrate-containing electrolytes. J. Mater. Sci. 45, 2995–3000 type copper indium gallium diselenide for development of mul- (2010) tilayer thin film solar cells. Thin Solid Films 472, 212–216 87. Hamrouni, S., AlKhalifah, M.S., Boujmil, M.F., Saad, K.B.: (2005) Preparation and characterization of CuInSe electrodeposited 69. Li, Y., Shaikh, S.S., Menezes, S.: Film growth mechanism for thin films annealed in vacuum. Appl. Surf. Sci. 292, 231–236 electrodeposited copper indium selenide compounds. Thin (2014) Solid Films 524, 20–25 (2012) 88. Bamiduro, O., Chennamadhava, G., Mundle, R., Konda, R., 70. Ribeaucourt, L., Chassaing, E., Savidand, G., Lincot, D.: Syn- Robinson, B., Bahoura, M., Pradhan, A.K.: Synthesis and char- thesis of Cu(In, Ga)Se absorber using one-step electrodeposi- acterization of one-step electrodeposited CuIn Ga Se /Mo/ 2 (1−x) x 2 tion of Cu–In–Ga precursor. Thin Solid Films 519, 7241–7244 glass films at atmospheric conditions. Sol. Energy 85, 545–552 (2011) (2011) 1 3 Materials for Renewable and Sustainable Energy (2018) 7:6 Page 19 of 20 6 89. Mandati, S., Sarada, B.V., Dey, S.R., Joshi, S.V.: CuIn Ga Se Lincot, D., Kerrec, O.: Electrochemical cementation phenomena 1−x x 2 thin-film absorber layers for solar photovoltaics fabricated by on polycrystalline molybdenum thin films from Cu(II)–In(III)– two-stage pulsed current electrodeposition. Mater. Lett. 118, Se(IV) acidic solutions. J. Electrochem. Soc. 154, D383 (2007) 158–160 (2014) 106. Chassaing, E., Ramdani, O., Grand, P.P., Guillemoles, J.F., Lin- 90. Ganchev, M., Kois, J., Kaelin, M., Bereznev, S., Tzvetkova, E., cot, D.: New insights in the electrodeposition mechanism of Volobujeva, O., Stratieva, N., Tiwari, A.: Preparation of Cu(In, CuInSe thin films for solar cell applications. Phys. Stat. Sol. C. Ga)Se layers by selenization of electrodeposited Cu–In–Ga pre- 5, 3445–3448 (2008) cursors. Thin Solid Films 511–512, 325–327 (2006) 107. Roussel, O., Ramdani, O., Chassaing, E., Grand, P.P., Lamirand, 91. Marudachalam, M., Birkmire, R.W., Hichri, H.: Phases, morphol- M., Etcheberry, A., Kerrec, O., Guillemoles, J.F., Lincot, D.: ogy, and diffusion in CuIn Ga Se thin films. J. Appl. Phys. 82, First stages of CuInSe electrodeposition from Cu(II)–In(III)– x 1−x 2 2 2896 (1997) Se(IV) acidic solutions on polycrystalline Mo films. J. Electro- 92. Kohara, N., Nishiwaki, S., Hashimoto, Y., Negami, T., Wada, T.: chem. Soc. 155, D141–D147 (2008) Electrical properties of the Cu(In, Ga)Se /MoSe /Mo structure. 108. Chassaing, E., Grand, P.-P., Ramdani, O., Vigneron, J., Etch- 2 2 Sol. Energy Mater. Sol. Cells 67, 209–215 (2001) eberry, A., Lincot, D.: Electrocrystallization mechanism of Cu– 93. Hsiao, K.J., Liu, J.D., Hsieh, H.H., Jiang, T.-S.: Electrical impact In–Se compounds for solar cell applications. J. Electrochem. Soc. of MoSe on CIGS thin-film solar cells. Phys. Chem. Chem. 157, D387 (2010) Phys. 15, 18174–18178 (2013) 109. Lai, Y., Liu, J., Yang, J., Wang, B., Liu, F., Zhang, Z., Li, J., 94. Oliva, F., Broussillou, C., Annibaliano, M., Frederich, N., Grand, Liu, Y.: Incorporation mechanism of indium and gallium during P.P., Roussy, A., Collot, P., Bodnar, S.: Formation mechanisms of electrodeposition of Cu (In, Ga) Se thin film. J. Electrochem. Cu(In, Ga)Se solar cells prepared from electrodeposited precur- Soc. 158, D704–D709 (2011) sors. Thin Solid Films 535, 127–132 (2013) 110. Kemell, M., Ritala, M., Saloniemi, H., Leskelä, M., Sajavaara, 95. Duchatelet, A., Sidali, T., Loones, N., Savidand, G., Chassaing, T., Eero Rauhala, E.: One-step electrodeposition of Cu Se and 2 − x E., Lincot, D.: 12.4% Efficient Cu(In, Ga)Se solar cell prepared CuInSe thin films by the induced co-deposition mechanism. J. 2 2 from one step electrodeposited Cu–In–Ga oxide precursor layer. Electrochem. Soc. 147, 1080–1087 (2000) Sol. Energy Mater. Sol. Cells 119, 241–245 (2013) 111. Izquierdo-Roca, V., Saucedo, E., Jaime-Ferrer, J.S., Fontané, 96. Bhattacharya, R.N.: CIGS-based solar cells prepared from elec- X., Pérez-Rodríguez, A., Bermúdez, V., Morante, J.R.: Real- trodeposited stacked Cu/In/Ga layers. Sol. Energy Mater. Sol. time raman scattering analysis of the electrochemical growth of Cells 113, 96–99 (2013) CuInSe precursors for CuIn(S, Se) solar cells. J. Electrochem. 2 2 97. Bhattacharya, R.N., Oh, M.-K.K., Kim, Y.: CIGS-based solar Soc. 158, H521–H524 (2011) cells prepared from electrodeposited precursor films. Sol. Energy 112. Calixto, M.E., Dobson, K.D., McCandless, B.E., Birkmire, R.W.: Mater. Sol. Cells 98, 198–202 (2012) Growth mechanisms of electrodeposited C uInSe and Cu(In,Ga) 98. Başol, M., Pinarbaşi, M., Aksu, S., Freitag, J., Gonzalez, P., Se determined by cyclic voltammetry. In: MRS Proceedings. Johnson, T., Matus, Y., Metin, B., Narasimhan, M., Nayak, D., 865, F14.17 (2005). https ://doi.org/10.1557/proc-865-f14.17 Norsworthy, G., Soltz, D., Wang, J., Wang, T., Zolla, H.: Sta- 113. Caballero-Briones, F., Palacios-Padrós, A., Sanz, F.: C uInSe tus of electroplating bases CIGS technology development. In: films prepared by three step pulsed electrodeposition. Deposition Proceedings of the 34th IEEE PVSC. https ://doi.org/10.1109/ mechanisms, optical and photoelectrochemical studies. Electro- pvsc.2009.54113 42 chim. Acta 56, 9556–9567 (2011) 99. Aksu, S., Pethe, S., Shwarsctein, A.K., Kundu, S., Pinarbasi, 114. Fu, Y.-P., You, R.-W., Lew, K.K.: CuIn Ga Se absorber layer 1−x x 2 M.: Recent advances in electroplating-based CIGS solar cell fabricated by pulse-reverse electrodeposition technique for thin fabrication, In: Proceedings of the 38th IEEE Photovoltaics films solar cell. J. Electrochem. Soc. 156, D553–D577 (2009) Specialists Conference. Texas, 2012. h t t p s : / / d o i . o rg /1 0 . 1 1 0 9 / 115. Siebentritt, S.: Alternative buffers for chalcopyrite solar cells. pvsc.2012.63182 35 Sol. Energy 77, 767–775 (2004) 100. Broussillou, C., Viscogliosi, C., Rogee, A., Angle, S., Grand, P.P., 116. Naghavi, N., Abou-Ras, D., Allsop, N., Barreau, N., Bücheler, Bodnar, S., et al.: Statistical process control for Cu(In,Ga)(S,Se) S., Ennaoui, A., Fischer, C.-H., Guillen, C., Hariskos, D., Her- electrodeposition-based manufacturing process 60 × 120 cm rero, J., Klenk, R., Kushiya, K., Lincot, D., Menner, R., Nakada, modules up to 14.0% efficiency. In: 42nd IEEE Photovoltaic T., Platzer-Björkman, C., Spiering, S., Tiwari, A.N., Törndahl, Specialist Conference (PVSC), New Orleans, 2015. https ://doi. T.: Buffer layers and transparent conducting oxides for chalco- org/10.1109/pvsc.2015.73562 24 pyrite Cu(In, Ga)(S, Se) based thin film photovoltaics: present 101. Duchatelet, A., Letty, E., Ferrer, J.S., Grand, P.P., Mollica, F., status and current developments. Prog. Photovolt. Res. Appl. 18, Naghavi, N.: The impact of reducing the thickness of elec- 411–433 (2010) trodeposited stacked Cu/In/Ga layers on the performance of 117. Hariskos, D., Menner, R., Jackson, P., Paetel, S., Witte, W., CIGS solar cells. Sol. Energy Mater. Sol. Cells 162, 114–119 Wischmann, W., Powalla, M., Bürkert, L., Kolb, T., Oertel, M., (2017) Dimmler, B., Fuchs, B.: New reaction kinetics for a high-rate 102. Kim, K., Hanket, G.M., Huynh, T., Shafarman, W.N.: Three-step chemical bath deposition of the Zn(S, O) buffer layer for Cu(In, H Se/Ar/H S reaction of Cu–In–Ga precursors for controlled Ga)Se -based solar cells. Prog. Photovolt. Res. Appl. 20, 534– 2 2 2 composition and adhesion of Cu(In, Ga)(Se, S) thin films. J. 542 (2012) Appl. Phys. 111, 83710 (2012) 118. Ramanathan, K., Mann, J., Glynn, S., Christensen, S., Pankow, 103. Bi, J., Ao, J., Gao, Q., Zhang, Z., Sun, G., He, Q., Zhou, Z., Sun, J., Li, J., Scharf, J., Mansfield, L., Contreras, M., Noufi, R.,:A Y., Zhang, Y.: Controllable growth of Ga film electrodeposited comparative study of Zn(O, S) buffer layers and CIGS solar cells from aqueous solution and Cu(In, Ga)Se solar cells. ACS Appl. fabricated by CBD, ALD, and sputtering, In: Proceedings of the Mater. Interfaces 9, 18682–18690 (2017) IEEE Photovoltaic Specialists Conference, Texas, 2012. https :// 104. Mishra, K.K., Rajeshwar, K.: A voltammetric study of the elec-doi.org/10.1109/pvsc.2012.63179 18 trodeposition chemistry in the Cu + In + Se system. J. Electroa- 119. Mezher, M., Garris, R., Mansfield, L.M., Horsley, K., Weinhardt, nal. Chem. 271, 279–294 (1989) L., Duncan, D.A., Blum, M., Rosenberg, S.G., Bär, M., Ramana- 105. Ramdani, O., Chassaing, E., Canava, B., Grand, P.-P., Roussel, than, K., Heske, C.: Electronic structure of the Zn(O, S)/Cu(In, O., Lamirand, M., Rzepka, E., Etcheberry, A., Guillemoles, J.F., 1 3 6 Page 20 of 20 Materials for Renewable and Sustainable Energy (2018) 7:6 Ga)Se thin-film solar cell interface. Prog. Photovolt. Res. Appl. 122. Witte, W., Hariskos, D., Eicke, A., Menner, R., Kiowski, O., 24, 1142–1148 (2016) Powalla, M.: Impact of annealing on Cu(In, Ga)Se solar cells 120. Meyer, B.K., Polity, A., Farangis, B., He, Y., Hasselkamp, D., with Zn(O, S)/(Zn, Mg)O buffers. Thin Solid Films 535, 180–183 Krämer, T., Wang, C.: Structural properties and bandgap bowing (2013) of ZnO S thin films deposited by reactive sputtering. Appl. 1−x x Phys. Lett. 85, 4929 (2004) Publisher’s Note Springer Nature remains neutral with regard to 121. Kobayashi, T., Yamaguchi, H., Nakada, T.: Effects of combined jurisdictional claims in published maps and institutional affiliations. heat and light soaking on device performance of Cu(In, Ga)Se solar cells with ZnS(O, OH) buffer layer. Prog. Photovolt. Res. Appl. 22, 115–121 (2014) 1 3 http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Materials for Renewable and Sustainable Energy Springer Journals http://www.deepdyve.com/lp/springer-journals/a-short-review-on-the-advancements-in-electroplating-of-cuingase2-thin-zGARXgqVfA

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References (141)

T. Nakada (2000)
Nano-structural investigations on Cd-doping into Cu(In,Ga)Se2 thin films by chemical bath deposition process
Thin Solid Films, 361
C. Insignares-Cuello, C. Broussillou, V. Bermudez, E. Saucedo, A. Pérez‐Rodríguez, V. Izquierdo‐Roca (2014)
Raman scattering analysis of electrodeposited Cu(In,Ga)Se2 solar cells: Impact of ordered vacancy compounds on cell efficiency
Applied Physics Letters, 105
Fang-yang Liu, Jia Yang, Jiao-lian Zhou, Y. Lai, Ming Jia, Jie Li, Ye-xiang Liu (2012)
One-step electrodeposition of CuGaSe2 thin films
Thin Solid Films, 520
Shengbai Zhang, S. Wei, A. Zunger, H. Katayama‐Yoshida (1998)
Defect physics of the CuInSe 2 chalcopyrite semiconductor
Physical Review B, 57
N. Chaure, A. Samantilleke, R. Burton, J. Young, I. Dharmadasa (2005)
Electrodeposition of p+, p, i, n and n+-type copper indium gallium diselenide for development of multilayer thin film solar cells
Thin Solid Films, 472
I. Repins, Stephen Glynn, J. Duenow, T. Coutts, W. Metzger, M. Contreras (2009)
Required material properties for high-efficiency CIGS modules
, 7409
O. Ramdani, E. Chassaing, B. Canava, P. Grand, Olivier Roussel, M. Lamirand, E. Rzepka, A. Etcheberry, J. Guillemoles, D. Lincot, O. Kerrec (2007)
Electrochemical Cementation Phenomena on Polycrystalline Molybdenum Thin Films from Cu ( II ) –In ( III ) –Se ( IV ) Acidic Solutions
Journal of The Electrochemical Society, 154
O Bamiduro, G Chennamadhava, R Mundle, R Konda, B Robinson, M Bahoura, AK Pradhan (2011)
Synthesis and characterization of one-step electrodeposited CuIn(1−x)Ga x Se2/Mo/glass films at atmospheric conditions
Sol. Energy, 85
VS Saji, IH Choi, CW Lee (2011)
Progress in electrodeposited absorber layer for CuIn(1−x)Ga x Se2 (CIGS) solar cells
Sol. Energy, 85
M. Harati, J. Jia, K. Giffard, Kyle Pellarin, C. Hewson, David Love, W. Lau, Z. Ding (2010)
One-pot electrodeposition, characterization and photoactivity of stoichiometric copper indium gallium diselenide (CIGS) thin films for solar cells.
Physical chemistry chemical physics : PCCP, 12 46
B. Meyer, A. Polity, Baker Farangis, Yunbin He, D. Hasselkamp, T. Krämer, Changzhong Wang (2004)
Structural properties and bandgap bowing of ZnO1−xSx thin films deposited by reactive sputtering
Applied Physics Letters, 85
N. Chaure, J. Young, A. Samantilleke, I. Dharmadasa (2004)
Electrodeposition of p–i–n type CuInSe2 multilayers for photovoltaic applications
Solar Energy Materials and Solar Cells, 81
Y. Oda, T. Minemoto, H. Takakura (2008)
Electrodeposition of Crack-Free CuGaSe2 Thin Films from Single Bath
Journal of The Electrochemical Society, 155
M. Calixto, K. Dobson, B. McCandless, R. Birkmire (2006)
Controlling Growth Chemistry and Morphology of Single-Bath Electrodeposited Cu ( In , Ga ) Se2 Thin Films for Photovoltaic Application
Journal of The Electrochemical Society, 153
M Kemell, M Ritala, H Saloniemi, M Leskelä, T Sajavaara, E Eero Rauhala (2000)
One-step electrodeposition of Cu2 − x Se and CuInSe2 thin films by the induced co-deposition mechanism
J. Electrochem. Soc., 147
S. Siebentritt (2004)
Alternative buffers for chalcopyrite solar cells
Solar Energy, 77
Yongzheng Zhang, Junfeng Han, Cheng Liao (2016)
Insights into the Properties of Deep Eutectic Solvent Based on Reline for Ga-Controllable CIGS Solar Cell in One-Step Electrodeposition
Journal of The Electrochemical Society, 163
A. Duchatelet, T. Sidali, N. Loones, G. Savidand, E. Chassaing, D. Lincot (2013)
12.4% Efficient Cu(In,Ga)Se2 solar cell prepared from one step electrodeposited Cu–In–Ga oxide precursor layer
Solar Energy Materials and Solar Cells, 119
M. Calixto, K. Dobson, B. McCandless, R. Birkmire (2005)
Growth Mechanisms of Electrodeposited CuInSe2 and Cu(In,Ga)Se2 Determined by Cyclic Voltammetry
MRS Proceedings, 865
Y. Aida, V. Deprédurand, J. Larsen, H. Arai, D. Tanaka, M. Kurihara, S. Siebentritt (2015)
Cu‐rich CuInSe2 solar cells with a Cu‐poor surface
Progress in Photovoltaics: Research and Applications, 23
TM Friedlmeier, P Jackson, A Bauer, D Hariskos, O Kiowski, R Wuerz, M Powalla (2015)
Improved photocurrent in Cu(In, Ga)Se2 solar cells: from 20.8% to 21.7% efficiency with CdS buffer and 21.0% Cd-free
IEEE J. Photovolt., 5
JC Malaquias, DM Berg, J Sendler, M Steichen, N Valle, PJ Dale (2015)
Controlled bandgap CuIn1−x Ga x (S0.1Se0.9)2 (0.10 ≤ x≤0.72) solar cells from electrodeposited precursors
Thin Solid Films, 582
E. Ghorbani, J. Kiss, H. Mirhosseini, G. Roma, M. Schmidt, J. Windeln, T. Kühne, C. Felser (2015)
Hybrid-Functional Calculations on the Incorporation of Na and K Impurities into the CuInSe2 and CuIn5Se8 Solar-Cell Materials
Journal of Physical Chemistry C, 119
(2005)
Cu ( InGa ) Se 2 Solar Cells
M. Richter, C. Schubbert, P. Eraerds, J. Parisi, I. Riedel, T. Dalibor, J. Palm (2015)
Comprehensive simulation model for Cu(In,Ga)(Se,S)2 solar cells
Solar Energy Materials and Solar Cells, 132
M Marudachalam, RW Birkmire, H Hichri (1997)
Phases, morphology, and diffusion in CuIn x Ga1−x Se2 thin films
J. Appl. Phys., 82
S. Mandati, B. Sarada, S. Dey, S. Joshi (2014)
CuIn1−xGaxSe2 thin-film absorber layers for solar photovoltaics fabricated by two-stage pulsed current electrodeposition
Materials Letters, 118
M. Steichen, Matthieu Thomassey, S. Siebentritt, P. Dale (2011)
Controlled electrodeposition of Cu-Ga from a deep eutectic solvent for low cost fabrication of CuGaSe2 thin film solar cells.
Physical chemistry chemical physics : PCCP, 13 10
L. Thouin, S. Massaccesi, S. Sanchez, J. Vedel (1994)
Formation of Copper Indium Diselenide by Electrodeposition.
ChemInform, 25
A. Zunger (2007)
New insights on chalcopyrites from solid-state theory
Thin Solid Films, 515
V. Saji, Chan-Yong Jung, Chi-Woo Lee (2015)
Electrodeposition of Copper, Selenium, Indium, and Gallium on Molybdenum/Surface Oxides: Unary, Binary, Ternary and Quaternary Compositions
Journal of The Electrochemical Society, 162
E. Avancini, R. Carron, B. Bissig, P. Reinhard, R. Menozzi, G. Sozzi, S. Napoli, T. Feurer, S. Nishiwaki, S. Buecheler, A. Tiwari (2017)
Impact of compositional grading and overall Cu deficiency on the near‐infrared response in Cu(In, Ga)Se2 solar cells
Progress in Photovoltaics: Research and Applications, 25
O. Savadogo (1998)
Chemically and electrochemically deposited thin films for solar energy materials
Solar Energy Materials and Solar Cells, 52
Y-P Fu, R-W You, KK Lew (2009)
CuIn1−x Ga x Se2 absorber layer fabricated by pulse-reverse electrodeposition technique for thin films solar cell
J. Electrochem. Soc., 156
V. Saji, Ikho Choi, Chi-Woo Lee (2011)
Progress in electrodeposited absorber layer for CuIn(1−x)GaxSe2 (CIGS) solar cells
Solar Energy, 85
Jun Liu, Fang-yang Liu, Y. Lai, Zhian Zhang, Jie Li, Ye-xiang Liu (2011)
Effects of sodium sulfamate on electrodeposition of Cu(In,Ga)Se2 thin film
Journal of Electroanalytical Chemistry, 651
L. Manfredy, O. Márquez, S. López-Rivera, J. Márquez, Y. Martínez, D. Miranda (2016)
Electrochemical preparation and structural characterization of CuGaSe2 thin films
Journal of Physics: Conference Series, 687
M. Marudachalam, R. Birkmire, H. Hichri, J. Schultz, A. Swartzlander, M. Al‐Jassim (1997)
Phases, morphology, and diffusion in CuInxGa1−xSe2 thin films
Journal of Applied Physics, 82
R. Scheer, L. Messmann‐Vera, R. Klenk, H. Schock (2012)
On the role of non‐doped ZnO in CIGSe solar cells
Progress in Photovoltaics: Research and Applications, 20
J. Malaquias, D. Berg, Jan Sendler, M. Steichen, N. Valle, P. Dale (2015)
Controlled bandgap CuIn1 − xGax(S0.1Se0.9)2 (0.10 ≤ x ≤ 0.72) solar cells from electrodeposited precursors
Thin Solid Films, 582
M. Ganchev, J. Kois, M. Kaelin, S. Bereznev, E. Tzvetkova, O. Volobujeva, N. Stratieva, A. Tiwari (2006)
Preparation of Cu(In,Ga)Se2 layers by selenization of electrodeposited Cu–In–Ga precursors
Thin Solid Films, 511
J. Guillemoles, L. Kronik, D. Cahen, U. Rau, A. Jasenek, H. Schock (2000)
Stability Issues of Cu(In,Ga)Se2-Based Solar Cells
ChemInform, 31
M. Kemell, M. Ritala, M. Leskelä (2001)
Effects of post-deposition treatments on the photoactivity of CuInSe2 thin films deposited by the induced co-deposition mechanism
Journal of Materials Chemistry, 11
J. Jaffe, A. Zunger (1984)
Theory of the band-gap anomaly in AB C 2 chalcopyrite semiconductors
Physical Review B, 29
A. Chirilă, P. Reinhard, F. Pianezzi, P. Bloesch, A. Uhl, C. Fella, L. Kranz, D. Keller, C. Gretener, H. Hagendorfer, D. Jaeger, R. Erni, S. Nishiwaki, S. Buecheler, A. Tiwari (2013)
Potassium-induced surface modification of Cu(In,Ga)Se2 thin films for high-efficiency solar cells.
Nature materials, 12 12
E. Chassaing, O. Ramdani, P. Grand, J. Guillemoles, D. Lincot (2008)
New insights in the electrodeposition mechanism of CuInSe2thin films for solar cell applications
Physica Status Solidi (c), 5
R. Bhattacharya, Minju Oh, Young Kim (2012)
CIGS-based solar cells prepared from electrodeposited precursor films
Solar Energy Materials and Solar Cells, 98
M. Green, K. Emery, Y. Hishikawa, W. Warta, E. Dunlop, D. Levi, A. Ho-baillie (2017)
Solar cell efficiency tables (version 49)
Progress in Photovoltaics: Research and Applications, 25
A. Fernández, R. Bhattacharya (2004)
Electrodeposition of CuIn1−xGaxSe2 precursor films: optimization of film composition and morphology
Thin Solid Films, 474
L. Ribeaucourt, E. Chassaing, G. Savidand, D. Lincot (2011)
Synthesis of Cu(In,Ga)Se2 absorber using one-step electrodeposition of Cu–In–Ga precursor
Thin Solid Films, 519
Yan Li, Shahid Shaikh, S. Menezes (2012)
Film growth mechanism for electrodeposited copper indium selenide compounds
Thin Solid Films, 524
N. Naghavi, D. Abou‐Ras, N. Allsop, N. Barreau, S. Bucheler, A. Ennaoui, C. Fischer, C. Guillén, D. Hariskos, J. Herrero, R. Klenk, K. Kushiya, D. Lincot, R. Menner, T. Nakada, C. Platzer‐Björkman, S. Spiering, A. Tiwari, T. Törndahl (2010)
Buffer layers and transparent conducting oxides for chalcopyrite Cu(In,Ga)(S,Se)2 based thin film photovoltaics: present status and current developments
Progress in Photovoltaics: Research and Applications, 18
J Song, SS Li, CH Huang, OD Crisalle, TJ Anderson (2004)
Device modeling and simulation of the performance of Cu(In1 − x , Ga x )Se2 solar cells
Solid State Electron, 48
D. Abou-Rasa, G. Kostorza, A. Romeob, D. Rudmannb, A. Tiwarib (2005)
Structural and chemical investigations of CBD-and PVD-CdS buffer layers and interfaces in Cu ( In , Ga ) Se 2-based thin film solar cells
E. Chassaing, A. Duchatelet, D. Lincot (2017)
Mechanistic Study of One-Step Cathodic Electrodeposition of Mixed Cu-In-Ga Oxide/Hydroxide Films with Hydrogen Peroxide Oxygen Precursor
Journal of The Electrochemical Society, 164
A. Duchatelet, E. Letty, S. Jaime-Ferrer, P. Grand, F. Mollica, N. Naghavi (2017)
The impact of reducing the thickness of electrodeposited stacked Cu/In/Ga layers on the performance of CIGS solar cells
Solar Energy Materials and Solar Cells, 162
J. Ramanujam, U. Singh (2017)
Copper indium gallium selenide based solar cells – a review
Energy and Environmental Science, 10
Continenza, Massidda, Freeman, de TM, Meloni, Serra (1992)
Structural and electronic properties of narrow-gap ABC2 chalcopyrite semiconductors.
Physical review. B, Condensed matter, 46 16
Jinlian Bi, J. Ao, Qing Gao, Zhaojing Zhang, Guozhong Sun, Q. He, Zhi-qiang Zhou, Yun Sun, Yi Zhang (2017)
Controllable Growth of Ga Film Electrodeposited from Aqueous Solution and Cu(In,Ga)Se2 Solar Cells.
ACS applied materials & interfaces, 9 22
R. Bhattacharya (2013)
CIGS-based solar cells prepared from electrodeposited stacked Cu/In/Ga layers
Solar Energy Materials and Solar Cells, 113
P. Salomé, R. Ribeiro-Andrade, J. Teixeira, J. Keller, T. Törndahl, N. Nicoara, M. Edoff, J. González, J. Leitão, S. Sadewasser (2017)
Cd and Cu Interdiffusion in Cu(In, Ga)Se2/CdS Hetero-Interfaces
IEEE Journal of Photovoltaics, 7
R. Kamada, T. Yagioka, S. Adachi, A. Handa, Kong Tai, T. Kato, H. Sugimoto (2016)
New world record Cu(In, Ga)(Se, S)2 thin film solar cell efficiency beyond 22%
2016 IEEE 43rd Photovoltaic Specialists Conference (PVSC)
S. Hamrouni, M. Alkhalifah, M. Boujmil, K. Saad (2014)
Preparation and characterization of CuInSe2 electrodeposited thin films annealed in vacuum
Applied Surface Science, 292
Y. Chiu, M. Hsieh, Chih Chang, C. Chen, T. Whang (2014)
Single-step electrodeposition of CIS thin films with the complexing agent triethanolamine
Applied Surface Science, 299
O. Cojocaru-Mirédin, P. Choi, R. Wuerz, D. Raabe (2012)
Exploring the p-n junction region in Cu(In,Ga)Se2 thin-film solar cells at the nanometer-scale
Applied Physics Letters, 101
Balu Gadilohar, G. Shankarling (2017)
Choline based ionic liquids and their applications in organic transformation
Journal of Molecular Liquids, 227
I. Dharmadasa, N. Chaure, A. Samantilleke, A. Hassan (2008)
Multi Fermi level pinning at metal/Cu(InGa)(SeS)(2) interfaces
Solar Energy Materials and Solar Cells, 92
E. Chassaing, P. Grand, O. Ramdani, J. Vigneron, A. Etcheberry, D. Lincot (2010)
Electrocrystallization Mechanism of Cu–In–Se Compounds for Solar Cell Applications
Journal of The Electrochemical Society, 157
Jia Yang, Chun Huang, Liangxing Jiang, Fang-yang Liu, Y. Lai, Jie Li, Ye-xiang Liu (2014)
Effects of hydrogen peroxide on electrodeposition of Cu(In,Ga)Se2 thin films and band gap controlling
Electrochimica Acta, 142
M. Pagliaro, R. Ciriminna, G. Palmisano (2008)
Flexible solar cells.
ChemSusChem, 1 11
D Abou-Ras, R Caballero, CA Kaufmann, M Nichterwitz, K Sakurai, S Schorr, T Unold, HW Schock (2008)
Impact of the Ga concentration on the microstructure of CuIn1−x Ga x Se2
Phys. Status Solidi RRL, 2
Yen‐Pei Fu, Rui You, K. Lew (2009)
CuIn1 − x Ga x Se2 Absorber Layer Fabricated by Pulse-Reverse Electrodeposition Technique for Thin Films Solar Cell
Journal of The Electrochemical Society, 156
Jiyon Song, S. Li, C. Huang, O. Crisalle, T. Anderson (2004)
Device modeling and simulation of the performance of Cu(In1−x,Gax)Se2 solar cells
Solid-state Electronics, 48
E. Chassaing, P. Grand, A. Etcheberry, D. Lincot (2009)
Electrocrystallization Mechanism of Cu-In-Se Compounds for Solar Cell Applications Investigated by Impedance Spectroscopy
, 19
A. Duchatelet, G. Savidand, R. Vannier, E. Chassaing, D. Lincot (2013)
A new deposition process for Cu(In,Ga)(S,Se)2 solar cells by one-step electrodeposition of mixed oxide precursor films and thermochemical reduction
Journal of Renewable and Sustainable Energy, 5
S. Siebentritt, M. Igalson, C. Persson, S. Lany (2010)
The electronic structure of chalcopyrites—bands, point defects and grain boundaries
Progress in Photovoltaics: Research and Applications, 18
W. Witte, D. Hariskos, A. Eicke, R. Menner, O. Kiowski, M. Powalla (2013)
Impact of annealing on Cu(In,Ga)Se2 solar cells with Zn(O,S)/(Zn,Mg)O buffers
Thin Solid Films, 535
S. Aksu, M. Pinarbasi (2010)
Electrodeposition of Cu-In-Ga films for the preparation of CIGS solar cells
2010 35th IEEE Photovoltaic Specialists Conference
N. Kohara, S. Nishiwaki, Y. Hashimoto, T. Negami, T. Wada (2001)
Electrical properties of the Cu(In,Ga)Se2/ MoSe2/Mo structure
Solar Energy Materials and Solar Cells, 67
D. Abou‐Ras, S. Schmidt, N. Schäfer, J. Kavalakkatt, T. Rissom, T. Unold, R. Mainz, A. Weber, T. Kirchartz, Ekin Sanli, P. Aken, Q. Ramasse, H. Kleebe, D. Azulay, I. Balberg, O. Millo, O. Cojocaru-Mirédin, D. Barragan-Yani, K. Albe, J. Haarstrich, C. Ronning (2016)
Compositional and electrical properties of line and planar defects in Cu(In,Ga)Se2 thin films for solar cells – a review
physica status solidi (RRL) – Rapid Research Letters, 10
P. Reinhard, B. Bissig, F. Pianezzi, E. Avancini, H. Hagendorfer, D. Keller, P. Fuchs, M. Döbeli, C. Vigo, P. Crivelli, S. Nishiwaki, S. Buecheler, A. Tiwari (2015)
Features of KF and NaF Postdeposition Treatments of Cu(In,Ga)Se2 Absorbers for High Efficiency Thin Film Solar Cells
Chemistry of Materials, 27
P. Jackson, R. Wuerz, D. Hariskos, E. Lotter, W. Witte, M. Powalla (2016)
Effects of heavy alkali elements in Cu(In,Ga)Se2 solar cells with efficiencies up to 22.6%
physica status solidi (RRL) – Rapid Research Letters, 10
AM Fernandez, RN Bhattacharya (2005)
Electrodeposition of CuIn1−x Ga x Se2 precursor films: optimization of film composition and morphology
Thin Solid Films, 474
K. Ramanathan, J. Mann, Stephen Glynn, S. Christensen, J. Pankow, Jian Li, J. Scharf, L. Mansfield, M. Contreras, R. Noufi (2012)
A comparative study of Zn(O,S) buffer layers and CIGS solar cells fabricated by CBD, ALD, and sputtering
2012 38th IEEE Photovoltaic Specialists Conference
J. Wellings, A. Samantilleke, S. Heavens, P. Warren, I. Dharmadasa (2009)
Electrodeposition of CuInSe2 from ethylene glycol at 150 °C
Solar Energy Materials and Solar Cells, 93
D. Hariskos, R. Menner, P. Jackson, S. Paetel, W. Witte, W. Wischmann, M. Powalla, Linda Bürkert, T. Kolb, M. Oertel, B. Dimmler, B. Fuchs (2012)
New reaction kinetics for a high‐rate chemical bath deposition of the Zn(S,O) buffer layer for Cu(In,Ga)Se2‐based solar cells
Progress in Photovoltaics: Research and Applications, 20
D. Liao, A. Rockett (2003)
Cu depletion at the CuInSe2 surface
Applied Physics Letters, 82
Michelle Mezher, Rebekah Garris, L. Mansfield, K. Horsley, L. Weinhardt, Douglas Duncan, M. Blum, S. Rosenberg, M. Bär, K. Ramanathan, C. Heske (2016)
Electronic structure of the Zn(O,S)/Cu(In,Ga)Se2 thin‐film solar cell interface
Progress in Photovoltaics: Research and Applications, 24
S. Aksu, S. Pethe, A. Kleiman-Shwarsctein, S. Kundu, M. Pinarbasi (2012)
Recent advances in electroplating based CIGS solar cell fabrication
2012 38th IEEE Photovoltaic Specialists Conference
M. Turcu, U. Rau (2003)
Fermi level pinning at CdS/Cu(In,Ga)(Se,S)2 interfaces: effect of chalcopyrite alloy composition
Journal of Physics and Chemistry of Solids, 64
K. Mishra, K. Rajeshwar (1990)
A Voltammetric Study of the Electrodeposition Chemistry in the Cu + In + Se System.
ChemInform, 21
S. Aksu, Jiaxiong Wang, B. Basol (2009)
Electrodeposition of In–Se and Ga–Se Thin Films for Preparation of CIGS Solar Cells
Electrochemical and Solid State Letters, 12
WN Shafarman, L Stolt (2005)
Handbook of photovoltaic science and engineering
S. Lany, A. Zunger (2017)
Light-and bias-induced metastabilities in based solar cells caused by the vacancy complex
S Lany, A Zunger (2006)
Light- and bias-induced metastabilities in Cu(In, Ga)Se2 based solar cells caused by the (VSe–VCu]) vacancy complex
J. Appl. Phys., 100
M. Green (2017)
Corrigendum to ‘Solar cell efficiency tables (version 49)’[Prog. Photovolt: Res. Appl. 2017; 25:3–13]
Progress in Photovoltaics: Research and Applications, 25
P. Jackson, D. Hariskos, R. Wuerz, O. Kiowski, A. Bauer, T. Friedlmeier, M. Powalla (2015)
Properties of Cu(In,Ga)Se2 solar cells with new record efficiencies up to 21.7%
physica status solidi (RRL) – Rapid Research Letters, 9
D. Lincot (2005)
Electrodeposition of semiconductors
Thin Solid Films, 487
S. Aksu, M. Pinarbasi (2011)
Electrodeposition methods and chemistries for deposition of CIGS precursor thin films
2011 37th IEEE Photovoltaic Specialists Conference
F. Caballero-Briones, A. Palacios-Padrós, F. Sanz (2011)
CuInSe2 films prepared by three step pulsed electrodeposition. Deposition mechanisms, optical and photoelectrochemical studies
Electrochimica Acta, 56
W. Simka, Dagmara Puszczyk, G. Nawrat (2009)
Electrodeposition of metals from non-aqueous solutions
Electrochimica Acta, 54
N. Stratieva, E. Tzvetkova, M. Ganchev, K. Kochev, I. Tomov (1997)
Structural and optical properties of electrodeposited CuInSe2 layers
Solar Energy Materials and Solar Cells, 45
K. Hsiao, Jing-Da Liu, H. Hsieh, Ting-Shiuan Jiang (2013)
Electrical impact of MoSe2 on CIGS thin-film solar cells.
Physical chemistry chemical physics : PCCP, 15 41
S Mandati, BV Sarada, SR Dey, SV Joshi (2014)
CuIn1−x Ga x Se2 thin-film absorber layers for solar photovoltaics fabricated by two-stage pulsed current electrodeposition
Mater. Lett., 118
J. Malaquias, D. Regesch, P. Dale, M. Steichen (2014)
Tuning the gallium content of metal precursors for Cu(In,Ga)Se2 thin film solar cells by electrodeposition from a deep eutectic solvent.
Physical chemistry chemical physics : PCCP, 16 6
W. Badawy (2013)
A review on solar cells from Si-single crystals to porous materials and quantum dots
Journal of Advanced Research, 6
T. Friedlmeier, P. Jackson, A. Bauer, D. Hariskos, O. Kiowski, R. Wuerz, M. Powalla (2015)
Improved photocurrent in Cu(In,Ga)Se2 solar cells: From 20.8% to 21.7% efficiency
2015 IEEE 42nd Photovoltaic Specialist Conference (PVSC)
V. Deprédurand, D. Tanaka, Y. Aida, Miriam Carlberg, N. Fevre, S. Siebentritt (2014)
Current loss due to recombination in Cu-rich CuInSe2 solar cells
Journal of Applied Physics, 115
C. Lei, M. Duch, I. Robertson, A. Rockett (2010)
Effects of solution-grown CdS on Cu(InGa)Se2 grain boundaries
Journal of Applied Physics, 108
V. Deprédurand, T. Bertram, S. Siebentritt (2014)
Influence of the Se environment on Cu-rich CIS devices
Physica B-condensed Matter, 439
D. Abou‐Ras, R. Caballero, C. Kaufmann, M. Nichterwitz, K. Sakurai, S. Schorr, T. Unold, H. Schock (2008)
Impact of the Ga concentration on the microstructure of CuIn1–x Gax Se2
physica status solidi (RRL) – Rapid Research Letters, 2
Olivier Roussel, O. Ramdani, E. Chassaing, P. Grand, M. Lamirand, A. Etcheberry, O. Kerrec, J. Guillemoles, D. Lincot (2008)
First Stages of CuInSe2 Electrodeposition from Cu(II)-In(III)-Se(IV) Acidic Solutions on Polycrystalline Mo Films
Journal of The Electrochemical Society, 155
B. Basol, M. Pinarbasi, S. Aksu, J. Freitag, P. González, T. Johnson, Y. Matus, B. Metin, M. Narasimhan, D. Nayak, G. Norsworthy, D. Soltz, J. Wang, T. Wang, H. Zolla (2009)
Status of electroplating based CIGS technology development
2009 34th IEEE Photovoltaic Specialists Conference (PVSC)
L. Gütay, D. Regesch, J. Larsen, Y. Aida, V. Deprédurand, S. Siebentritt (2011)
Influence of copper excess on the absorber quality of CuInSe2
Applied Physics Letters, 99
Yu-Jun Zhao, C. Persson, S. Lany, A. Zunger (2004)
Why can CuInSe2 be readily equilibrium-doped n-type but the wider-gap CuGaSe2 cannot?
Applied Physics Letters, 85
R. Bhattacharya, K. Rajeshwar (1986)
Electrodeposition of CuInX (X = Se, Te) thin films
Solar Cells, 16
L. Thouin, Sylvie Rouquette-Sanchez, J. Vedel (1991)
One Step Electrodeposition of CuInSe 2
B. Misic, B. Pieters, J. Theisen, A. Gerber, Uwe Rau (2015)
Shunt mitigation in ZnO:Al/i‐ZnO/CdS/Cu(In,Ga)Se2 solar modules by the i‐ZnO/CdS buffer combination
physica status solidi (a), 212
G. Sozzi, S. Napoli, R. Menozzi, R. Carron, E. Avancini, B. Bissig, S. Buecheler, A. Tiwari (2016)
Analysis of Ga grading in CIGS absorbers with different Cu content
2016 IEEE 43rd Photovoltaic Specialists Conference (PVSC)
(1997)
Structural and optical properties of electrodeposited CuInSe 2 layers
Xiaoqing He, T. Paulauskas, P. Ercius, J. Varley, J. Bailey, G. Zapalac, D. Poplavskyy, N. Mackie, A. Bayman, D. Spaulding, R. Klie, V. Lordi, A. Rockett (2017)
Cd doping at PVD-CdS/CuInGaSe2 heterojunctions
Solar Energy Materials and Solar Cells, 164
Taizou Kobayashi, H. Yamaguchi, T. Nakada (2014)
Effects of combined heat and light soaking on device performance of Cu(In,Ga)Se2 solar cells with ZnS(O,OH) buffer layer
Progress in Photovoltaics: Research and Applications, 22
Y. Lai, Jun Liu, Jia Yang, Bo Wang, Fang-yang Liu, Zhian Zhang, Jie Li, Ye-xiang Liu (2011)
Incorporation Mechanism of Indium and Gallium during Electrodeposition of Cu(In,Ga)Se2 Thin Film
Journal of The Electrochemical Society, 158
BK Meyer, A Polity, B Farangis, Y He, D Hasselkamp, T Krämer, C Wang (2004)
Structural properties and bandgap bowing of ZnO1−x S x thin films deposited by reactive sputtering
Appl. Phys. Lett., 85
F. Oliva, C. Broussillou, M. Annibaliano, N. Frédérich, P. Grand, A. Roussy, P. Collot, S. Bodnar (2013)
Formation mechanisms of Cu(In,Ga)Se2 solar cells prepared from electrodeposited precursors
Thin Solid Films, 535
Kihwan Kim, G. Hanket, T. Huynh, W. Shafarman (2012)
Three-step H2Se/Ar/H2S reaction of Cu-In-Ga precursors for controlled composition and adhesion of Cu(In,Ga)(Se,S)2 thin films
Journal of Applied Physics, 111
S. Siebentritt, L. Gütay, D. Regesch, Y. Aida, V. Deprédurand (2013)
Why do we make Cu(In,Ga)Se2 solar cells non-stoichiometric?
Solar Energy Materials and Solar Cells, 119
O. Lundberg, M. Bodegård, J. Malmström, L. Stolt (2003)
Influence of the Cu(In,Ga)Se2 thickness and Ga grading on solar cell performance
Progress in Photovoltaics: Research and Applications, 11
J. Muthuraj, D. Rasmussen, I. Suni (2011)
Electrodeposition of CuGaSe2 from Thiocyanate-Containing Electrolytes
Journal of The Electrochemical Society, 158
(2003)
Cu depletion at the CuInSe 2 surface
A. Duchatelet, G. Savidand, N. Loones, E. Chassaing, D. Lincot (2014)
Mechanism of Electrochemical Deposition of Cu-In-Ga Mixed Oxide/Hydroxide Thin Films for Cu(In,Ga)Se2 Solar Cells
Journal of The Electrochemical Society, 161
M. Frontini, M. Vázquez (2010)
Electrodeposition of CuInSe2 in citrate-containing electrolytes
Journal of Materials Science, 45
F. Long, Weimin Wang, Jingjing Du, Z. Zou (2009)
CIS(CIGS) thin films prepared for solar cells by one-step electrodeposition in alcohol solution
, 152
V. Deprédurand, T. Bertram, S. Siebentritt (2013)
How does the selenium activity influence CuInSe2 devices grown under Cu-excess?
, 8823
D. Abou‐Ras, G. Kostorz, A. Romeo, D. Rudmann, A. Tiwari (2005)
Structural and chemical investigations of CBD- and PVD-CdS buffer layers and interfaces in Cu(In,Ga)Se2-based thin film solar cells
Thin Solid Films, 480
S. Jensen, A. Kanevce, L. Mansfield, Stephen Glynn, S. Lany, D. Kuciauskas (2017)
Optically induced metastability in Cu(In,Ga)Se2
Scientific Reports, 7
Gregory Brown, Junqiao Wu (2009)
Third generation photovoltaics
Laser & Photonics Reviews, 3
Ye Lian, Shanshan Ji, Lei Zhao, Jie Zhang, P. Yang, Jin-qiu Zhang, M. An (2015)
One-step electrodeposition of CuInxGa1−xSe2 thin films from a mixture system of ionic liquid and ethanol
New Journal of Chemistry, 39
O. Bamiduro, G. Chennamadhava, R. Mundle, R. Konda, B. Robinson, M. Bahoura, A. Pradhan (2011)
Synthesis and characterization of one-step electrodeposited CuIn(1−x)GaxSe2/Mo/glass films at atmospheric conditions
Solar Energy, 85
C. Broussillou, C. Viscogliosi, A. Rogee, S. Angle, P. Grand, S. Bodnar, C. Debauche, J. Allary, B. Bertrand, C. Guillou, L. Parissi, S. Coletti (2015)
Statistical Process Control for Cu(In,Ga)(S,Se)2 electrodeposition-based manufacturing process of 60×120cm2 modules up to 14,0% efficiency
2015 IEEE 42nd Photovoltaic Specialist Conference (PVSC)
V. Izquierdo‐Roca, E. Saucedo, J. Jaime-Ferrer, X. Fontané, A. Pérez‐Rodríguez, V. Bermudez, J. Morante (2011)
Real-Time Raman Scattering Analysis of the Electrochemical Growth of CuInSe2 Precursors for CuIn(S,Se)2 Solar Cells
Journal of The Electrochemical Society, 158

Publisher: Springer Journals
Copyright: Copyright © 2018 by The Author(s)
Subject: Materials Science; Materials Science, general; Renewable and Green Energy; Renewable and Green Energy
ISSN: 2194-1459
eISSN: 2194-1467
DOI: 10.1007/s40243-018-0112-1
Publisher site: See Article on Publisher Site

Abstract

Thin-film solar cell devices based on copper indium gallium diselenide (CIGSe) chalcogenide materials fabricated by vac - uum-based deposition techniques have already achieved lab scale efficiency beyond 21%. For industrial-scale applications, non-vacuum deposition technique such as electrodeposition and screen printing is considered to be suitable approaches for reducing the device fabrication cost. Moreover, electrodeposition has the potential to prepare large area thin l fi ms as it requires cheap raw material sources and equipment capital. Hence, it is imperative to understand the current status and advancements in the electroplating techniques of the CIGSe thin films. This article reviews on the experimental advances in electroplating of ternary CuInSe and quaternary CIGSe. Various approaches in electrodeposition, influential experimental parameters, and the deposition mechanisms which are related to the final cell efficiency are discussed in detail. Keywords Solar cells · Chalcopyrite · Thin films · Electrodeposition Introduction market share of about 90%, silicon wafer-based solar cells are the first generation solar cells which started with single Increasing demand for energy has spurred academic and crystalline (mono-Si) and later developed to polycrystal- technological interest to research into new resources, among line silicon (poly-Si or multi-crystalline Si). They exhibit a which solar energy seems to be the most ideal to meet the power conversion efficiency ranging between 12 and 16%, target as it is abundant, clean, and inexhaustible. Gradually, based on the variation of fabrication procedure and the wafer solar energy is getting attention as an important source of quality [1]. Though mono-Si devices exhibit high efficiency renewable energy, since the other renewable technologies and a dominant place in commercial market, setbacks such like solar heating, photovoltaics, solar thermal energy, solar as expensive purification process, poor defect tolerance, architectures, and artificial photosynthesis are emerging to indirect band-gap nature (less absorption coefficient) have harness the radiant light and heat from sun. Furthermore, made researchers seek for a better alternative. active solar techniques which convert solar energy from sun- The second generation or thin-film-based devices utiliz - light into electricity are primarily done using semiconduct- ing semiconducting materials like CISe/CIGSe, cadmium ing materials that exhibit the photovoltaic effect (generat - telluride (CdTe), and Si (a-Si) are then emerged as the alter- ing photocurrent upon illumination). A typical photovoltaic natives to the first generation devices. Solar devices based system employs solar panels, each comprising a number of on dye-sensitized solar cells (DSSC), organic photovoltaics solar cells, which generate electrical power. With a global (OPV), quantum dots, perovskite, tandem cells, hot carrier cells, impurity photovoltaics, and thermo-photovoltaics fall in the third generation solar cells. In specific, tandem con - * Archana Mallik figurations are designed to evade the power-loss mechanisms archananitrkl@gmail.com which take place in the conventional single band-gap (E ) cells due to the inability to absorb photons beyond their E Electrometallurgy and Corrosion Laboratory, Department of Metallurgical and Materials Engineering, National and thermalization of photons exceeding their E . By imple- Institute of Technology, Rourkela, Odisha 769 008, India menting semiconductor stacks exhibiting different bandgap, Electroplating and Metal Finishing Technology Division, tandem configurations are realized with efficiencies exceed - CSIR-Central Electrochemical Research Institute, Karaikudi, ing the Shockley–Queisser limit [2]. Tamilnadu 630 003, India Vol.:(0123456789) 1 3 6 Page 2 of 20 Materials for Renewable and Sustainable Energy (2018) 7:6 Among the second generation photovoltaic (PV) cells, this section which deals with copper chalcopyrite group CIGSe-based devices are considered to be the most effi- material being explored as the second generation solar cells; cient solar energy converter of any single band-gap thin- (2) experimental concerns in electrodeposition explaining film device. They can be easily fabricated on flexible sub- about the electrodeposition process of CIGSe and strategies strates which make them light weight, and thus, they have to improve the quality of the electrodeposited final CIGSe the potential to reduce the device fabrication as well as the thin films; (3) electrocrystallization mechanism of CIGSe; installation cost [3]. Recently, Chirilă et al. reported an this section elaborates about the deposition mechanism of efficiency of 20.4% for potassium fluoride post-deposition- the four elements to form the alloy (4) advancements in treated (KF-PDT) CIGSe devices fabricated over flexible CISe/CIGSe electrodeposition routes; recent advancements polyimide substrates. This efficiency is considered to be the in the electroplating procedures and the reported power con- highest until date for flexible CIGSe solar cells [4 ]. After version efficiency has been briefed in this section; and (5) discovering the beneficial effects of heavy alkali doping CdS-free buffer layers; the attempts that are being made and [potassium fluoride (KF), rubidium fluoride (RbF), and explored to replace this layer to avoid the involvement of caesium fluoride (CsF) PDT treatment] [5], the CIGSe hazardous chemicals have been cited in this section. solar cell performance was boosted beyond 20%. A record device efficiency of 22.6% (0.4092 cm ) was also reported by Jackson et al. for RbF-PDT-treated CIGSe/CdS device CISe/CIGSe material properties and device [6]. Friedlmeier et al. reported an efficiency of 21% [7 ] using structure Zn(O,S) buffer as a replacement for the conventional CdS/ CIGSe devices. Similarly, a record efficiency of 22.3% [8 ] The intermixing of ternary CuInSe (CISe) and CuGaSe 2 2 was achieved for Cd-free device by SoloPower, utilizing (CGSe) of I–III–VI group (I = Cu, III = In, Ga and VI = Se) (Zn,Mg)O/Zn(O,S,OH) as the window/buffer layer. Impres- crystallizes to form a quaternary CuInGaSe tetragonal chal- sive efficiencies (~ 15.7 ± 0.5%) are also reported for CIGSe copyrite structure, where the In and Ga atoms share the same modules of 9703 cm aperture area [9]. These efficiency atomic sites. The crystal structure of CIGSe chalcopyrite percentages motivate researchers to explore chalcogenide material is shown in Fig. 1a [13]. The crystal structure can materials for industrial-scale production. be realized as a doubled unit cell of zinc blend structure with The above-reported CIGSe device record efficiency evo- alternating Cu and In atoms [15]. Each of the Cu or In atoms lutions have been fabricated by vacuum deposition tech- are bonded tetragonally with four Se anion atom, whereas niques, which are being challenged due to the expensive each of the Se atoms are coordinated with 2 Cu and 2 In vacuum systems, target materials, and percentage of mate- atoms. As the bond strength existing between the I–VI and rials wastage. Hence, an alternative cost-effective deposi- III–VI is different, the lattice constants (c , a, where ‘a’ is tion technique with competitive efficiency of the fabricated base dimension and ‘c’ is cell height) are not always of the devices is sought for. Electrodeposition is a major tech- desired value 2:1 (c/a ratio), which may lead to lattice distor- nique which can respond to the challenges of reducing the tion [16]. The magnitude of distortion can be realized from PV device production cost due to cost-effective equipment the deviation of (c/a) value from 2:1. For a pure CuInSe , the capital, less material wastage, and its compatibility towards ratio is close to 2. However, due to the substitution of In by industrial-scale production. Electrochemically fabricated Ga atoms, the c/a ratio deviates towards lower values along commercial solar cell devices with a reported efficiency of with grain refinement, as shown in Fig. 1b [14]. 14.2% have been obtained by SoloPower [10]. NEXCIS has Now, concentrating on the band structure, the val- achieved a record efficiency of 17.3% (0.484 cm ) and 14% ance band of the CIGSe is derived from the weak Cu–Se for CIGSe module of aperture area 60 × 120 cm . Excel- bond group (I–VI) due to the hybridization of Cu-d and lent review on electrodeposition of semiconductors [11] Se-p orbitals. The bottom of the conduction band (CB) and CIGSe electrodeposition [12] can be found. However, is mainly contributed from the In and Ga atoms (group the technique has not yet been optimized for a single-step III—S orbital) [17]. Chalcopyrite-based absorber mate- co-deposition of the quaternary alloy, and hence, it needs rials are direct band-gap semiconductor with an opti- 5 −1 further research attention. cal absorption coefficient of α = 10 cm which makes Hence, this review would be a complimentary addition them a suitable candidate as p-type ‘absorber’ layers in to the research pool emphasizing on the recent technologi- thin-film solar cells. The Cu-poor CIGSe chalcopyrite cal advancements in the field of electrodeposition of CISe/ absorber (with a composition of [Cu/In + Ga] or CGI CIGSe thin films. The review has been classified into five ratio is < 1 and [Ga/In + Ga] or GGI ratio ≈ 0.25–0.35]) sections which provides some of the important aspects of the contains a large number of defects, most likely the Cu research area on electroplating of CISe/CIGSe thin films: (1) vacancies (V ) and In or Ga anti-sites [18, 19]. In Cu Cu Cu 2+ material properties of CISe/CIGSe: the review starts with the Cu-poor CIGSe, the In anti-sites pair easily with Cu 1 3 Materials for Renewable and Sustainable Energy (2018) 7:6 Page 3 of 20 6 Fig. 1 a CIGSe crystal structure (adapted from Ghorbani et al. [13]. Copyright©2015, American Chemical Society, permission granted), b lat- tice constant ratio (c/a) deviation as a function of Ga content (x) [14] (Copyright© John Wiley and Sons, 2008, permission granted) − − 2+ formation of excess Cu-deficiency-related defects such as 2V in the Cu-poor CIGSe to form ( 2V + In ) Cu Cu Cu Ga on Cu (In or Ga ) anti-sites [23]. These deep elec- neutral defect complex [20]. However, the presence Cu Cu tron traps (In, Ga and its complex-DX centers) limits of small excess of shallow acceptor like V vacancies Cu Cu, Cu V of the devices through fermi level pinning [24–26]. (energy position close to the valance band) contributes OC Other defects such as copper interstitial (C ), selenium to the intrinsic p-type doping of the CIGSe absorbers. i − 2+ vacancies (V ), and (V –In ) di-vacancy defect com- The ( 2V + In ) neutral defects complex with an Se Se Cu Cu Cu plex are considered as origin of metastable-related effects average composition of Cu In Se ,CuIn Se ,CuIn Se , 2 4 7 3 5 5 8 such as persistent photoconductivity (PPC) and red–blue etc., is known as the ordered vacancy compounds (OVC) illuminations. During electrical bias or illumination, this [21]. The existence of the OVCs in the CIGSe absorber di-vacancy complex (V –V ) can shift from a donor into is anticipated at the interface of CdS/CISe thin films. Se Cu an acceptor configuration in p-type CIGS, increasing the The structure of the OVC layers can be derived as the hole concentration and thus acts as a recombination chan- chalcopyrite structure with randomly introduced copper − 2+ nel for the minority charge carriers (electrons) [27, 28]. vacancies or ( 2V + In ) defect pairs and is assumed Cu Cu The prevalence of these intrinsic defects and compensa- to be beneficial for the device performance [ 22]. How- tions is considered to be the origin of potential fluctuations ever, increased OVC content in CIGSe may deteriorate in the material. the open-circuit voltage (V ) of the device due to the OC Fig. 2 a Device structure and its corresponding energy-band diagram at equilibrium and b straight line—no grading, dotted—double grading, inset— schematic of the “notch-type’ gallium distribution in CIGSe device, axis scale—CIGSe layer thickness vs. bandgap 1 3 6 Page 4 of 20 Materials for Renewable and Sustainable Energy (2018) 7:6 The schematic of the state-of-the-art CIGSe device struc- diagram of CIGSe device with (dotted), without double ture as Mo/CIGSe/CdS/i-ZnO/Al–ZnO with the correspond- grading (continuous line) and the energy-band-gap profile ing band diagram of the device is shown in Fig. 2a. These of the CIGS absorber layer used in simulation is given in devices have reported maximum reported efficiency ( η) of Fig. 2b, inset. The experimental and simulation studies have 21% [29]. The working principle of the device is followed shown that double grading in the CIGS absorber layer has after a brief introduction of the structure and properties of greatly improved the performance of single-junction CIGS the individual layers along with advancements. cells [40, 41]. For detailed information on grading schemes Owing to the high bandgap and optical transparency, alu- and their benefits in device performance, the readers can minum doped ZnO, as the front contact TCO layer, ensures refer the cited literatures [42–44]. maximum light incoming to the device. The sputtered i-ZnO/ Until date, all high-efficiency devices reported so far are ZnO:Al layers are classically used as the window/front TCO of low band-gap (1.15 eV—CuIn Ga Se ) values with 0.7 0.3 2 layers in high-ec ffi iency devices. With an optical bandgap of Cu-poor composition in the final device stage having a E = 3.3 eV, ZnO is considered to be the promising TCO, as GGI ratio of 0.3–0.35 and CGI ratio of 0.8–0.9. A slight- it is cheap, earth-abundant, and non-toxic [30]. It has been est increase in the Cu content is considered to be Cu-rich reported that the devices with i-ZnO window layers exhibit (≥ 25% of at wt%) as the excess Cu content reacts to form good stability towards the damp-heat stress. In addition, the Cu–Se secondary phase, which are detrimental to the device buffer/window i-ZnO/CdS combination mitigates electrical performance [46]. Hence, Cu-rich stoichiometry refers to the shunt paths in the devices by covering the local inhomogene- overall Cu content including Cu–Se secondary phase in the ity in the CIGSe absorber [31, 32]. Until date, most of the absorber. Though Cu-rich absorbers exhibits better crystal- widely reported high-efficiency CIGSe devices have utilized linity, low defect concentrations, less bulk recombination, cadmium sulfide (CdS) as the buffer layer component [9 ]. and high mobility, they exhibited poor efficiency than Cu- The CdS (E = 2.4 eV) buffer material transmits the light up poor devices [47]. For improving the Cu-rich device perfor- to the wavelength of 2.4 eV to the P-CIGSe absorber. mance, the excess Cu Se phase can be removed by selective According to Nakada [33], the Cu-poor surface at CIGSe etching using potassium cyanide (KCN) [48]. The interface is favorable for the substitution of Cd ions on Cu vacan- recombination problems which is prevalent in Cu-rich CISe cies (Cd donor defects) [34] due to the closest match- devices can be eliminated by controlling the doping level. Cu+ + + ing atomic radii of Cu (0.96 Å) and Cd (0.97 Å) [35]. Through simulation studies (Fig. 3), it has been realized that 16 3 The infiltrated Cd in the absorber inhomogeneity acts as low doping levels (N = 10 cm ) can increase the recom- a buried CIGSe/CdS homo-junction [36]. Thus, Cd dop- bination barrier existing between the fermi level (E ) and ing at the CIGSe/CdS grain boundaries and conductivity valance band edge reduces the tunnel assisted recombination inversion of the absorber from p- to n-types is inevitable. at the interface. The doping level of Cu-rich devices can be Other significant observations such as Se–S exchange within controlled by the Se flux. In contrast to the Cu-poor CISe CdS–CIGSe, Cd diffusion in CIGSe, Cu–Cd interdiffusion at CdS/CIGSe interface, alkali–oxygen (Na–O) impurity accumulations at the interface, Cu Se secondary phase, 2−x and Cd–Se formations are also reported [36–39]. However, the CdS/CIGSe junction interface study is still a debatable research topic which needs further clarifications. For substrate configuration CIGSe devices (Fig. 2a), the light entering through the metal grid spacing and TCO (Al:ZnO/i-ZnO) may suffer reflection loss due to difference in the refractive index (n). These reflection losses can be minimized by employing anti-reflective coating such as MgF [30]. The operation of the devices can be explained on the principle that upon illumination, the generated elec- tron–hole pair is swept away by the built-in electric field at the CdS/CIGSe heterojunction interface towards the respec- tive contacts to produce photocurrent. Some of the electrons can also move towards the wrong contact (back contact) and Fig. 3 Simulated energy-band model of a Cu-poor (red) and a Cu- rich (blue) CuInSe solar cell (higher doping of the Cu-rich absorber recombine. This can be avoided by introducing a back sur- 2 is assumed). The horizontal arrow indicates the tunnel recombination face field, an additional energy barrier for preventing the process due to high doping levels. Permission granted by the authors electron back flow. The band-gap gradient can be achieved to reuse the figure, Copyright© 2013 Society of Photo-optical Instru- by varying the GGI ratio. Figure 2b shows the energy-band mentation Engineers (SPIE) [45] 1 3 Materials for Renewable and Sustainable Energy (2018) 7:6 Page 5 of 20 6 device, Cu-rich device exhibited better efficiency of η = 8.6% for film inhomogeneity and pin holes formation. This makes under low Se flux conditions, whereas η = 6.2% at very high electrodeposition of stoichiometric and pinhole free CIGSe Se flux conditions [49]. Furthermore, by depositing a thin thin films even more challenging. This shortfall arised as an In–Se layer, the device efficiency of 13.1% was achieved. attempt for the controlled inclusion of In(III) and Ga(III) Such treatment recovers the open-circuit voltage loss by ions can be taken care by adding complexing agents. Com- reducing the interface recombination [50]. These results plexing agents can play a major role in shifting the reduc- are promising in the context that compositionally altered tion potential of noble ions (Cu) towards active ions (In, Cu-rich devices have the potential to compete in terms of Ga), hence making the co-deposition easier. These agents efficiency to the Cu-poor ones. diminish hydrogen generation avoid pinholes and improve In the future, compositionally altered Cu-rich absorb- the compactness of the as-deposited film. Other additives ers may be a major theme of study in the development of such as supporting electrolytes, surfactants, and brighten- CIGSe absorbers. Moreover, mimicking such studies in ers are often used for improving the bath chemistry and film electrochemical route is much easier when compared to quality. However, most complexing agents have no effect on vacuum deposition techniques. A detailed recent review on In (III) and Ga (III) ions and forms strong complex only with the progress in CIGSe solar cells defects mechanisms and copper and selenium ions [10]. the state-of-the-art CIGSe devices have been discussed in Hence, in the following sections, attention has been given the cited literature [51, 52]. towards significant recent advancements in the electrolyte 3+ 3+ chemistry for the controlled inclusion of In and Ga ions in CISe/CIGSe thin films both in aqueous- and non-aqueous- Experimental concerns in CIGSe based electrolytic deposition conditions. electrodeposition CISe/CIGSe electrodeposition using aqueous Irrespective of synthesis route, generally, the CIGSe/CISe electrolytes and complexing agents absorber deposition is carried out by two ways (1) simul- taneous deposition and selenization/sulfurization and (2) Bhattacharya et al. group was the first to report single-step precursor deposition followed by sequential selenization/sul- electrodeposition of CISe thin films using triethanol amine furization. The vacuum-based deposition techniques mostly (TEA) as complexing agents [56]. Since then, several works follow the simultaneous selenization and other processes on electrodeposition of CISe/CIGSe using TEA have been 2+ like electrodeposition, roll-to-roll printing, Ink/paste precur- reported as it can form strong complexes with Cu and 3+ sor coating follow the sequential selenization. Regardless HSeO ions and weak complexing with the In ions [57]. 2– of deposition techniques employed in thin film CIGSe/CISe Calixto et al. reported the electrodeposition of pinhole free fabrication, the ultimate goal of every route is to prepare a stoichiometric CIGSe using low concentrations of 2.56 mM 2+ 3+ 3+ 4+ compositional film exhibiting good crystallinity leading to Cu , 2.40 mM In , 5.7 mM Ga , and 4.5 mM Se ions in a material with good photovoltaic characteristics. the bath at a pH of 2.5. The electrolyte was stabilized using Electrodeposition is a non-vacuum technique in which a buffer of pH 3 (pHydrion mixture of sulphamic acid and the electro-reduction of ions at particular reduction potential potassium biphthalate) along with LiCl as supporting elec- takes place over a conductive substrate to form thin films trolyte [55]. Recent works by Liu et al. have suggested that by the influence of applied electric field. The equilibrium by increasing the sodium sulfamate concentration, (Cu + Se)/ reduction potential (in Fig. 5) of Cu, In, Ga, and Se ions in (In + Ga) decreases, while gallium content increases and the the EMF series is + 0.337/SHE, − 0.342/SHE, − 0.529/SHE, film composition transforms from Cu rich to Cu poor [58]. and + 0.741/SHE, respectively. The difficultness arises dur -Using KCN as the complexing agent, the reduction poten- 2+ 3+ ing electrodeposition of CIGSe is due to the active standard tial difference between of Cu and Ga was only 80 mV, reduction potential of In and Ga ions. Though increasing whereas 870 mV difference for un-complexed (Cu,Ga) spe- the concentrations of In(III) and Ga(III) shifts the potential cies [59]. At high thiocyanate complex concentrations, the closer to Cu(II) [53], excessive currents generated due to predominant species is Cu (I) in soluble form. Furthermore, high bath concentrations may cause significant pitting and the reduction of Ga can get catalyzed in the presence of corrosion of Mo/glass substrates [54]. Recent impedance thiocyanate (CNS ) ions. This makes thiocyanate a suitable studies by Saji et al. also verified that excessive In ions can complexing agent in CIGSe/CGSe electroplating [60]. interact or complex with Mo/surface oxides and that in effect Using potassium sodium tartrate as complexing agent for can cause a certain extent of Mo dissolution [55]. Electro- In and trisodium citrate for Ga ions, Aksu et al. were able to deposition at high cathodic potential conditions affects the electroplate In–Se and Ga–Se thin films even at high alka- In and Ga plating efficiency due to the parallel occurrence line conditions. For In–Se, the plating efficiency of 68% was of hydrogen evolution, which is considered to be the origin obtained at a pH of 13. For Ga–Se complexed with trisodium 1 3 6 Page 6 of 20 Materials for Renewable and Sustainable Energy (2018) 7:6 citrate, below the pH of 5, the Se percentage was dominated, During the process, the reduction of indium and gallium and at high pH of 13.5, Ga was dominant. They were able to takes place as two simultaneous steps involving nitrate co-deposit Ga–Se films within the pH window of 7–8.5 [61]. reduction and oxides precipitation. During the nitrate reduc- The same group could co-deposit Cu–In–Ga alloy at alkaline tion, the consumption of proton will induce a local change conditions (9–13.5) using blends of complexing agents for in pH at the vicinity of the cathode followed by In and Ga solubilizing and preventing hydroxide formation of ions at depositions in the form of precipitated oxides or hydrox- such high alkaline conditions. Though the processing con- ide. As shown in the standard deposition potential diagram ditions were not disclosed, common chelating agents such (Fig. 4), deposition of In and Ga in the form of oxides/ as TEA, EDTA, citric acid or trisodium citrate, potassium hydroxides takes place at very low cathodic potential com- sodium tartrate, and tartaric acid can be used as they have pared to the Cu–In–Ga electrodeposition using conventional the tendency to form complexes with Cu, In, and Ga ions. chloride/sulfate electrolytes. The crystalline CIGSe absorber The grading of Ga is also possible by modulating the current deposited and after subsequent H reduction and selenization density during electroplating [62]. pre-treatment (in Fig. 5a–c) revealed a power conversion An interesting alternative route for the inclusion of In efficiency of η = 9.4% [64]. (III) and Ga (III) is in the form of oxides/hydroxides using Yang et al. reported on the controlled Ga(III) inclusion respective nitrate salts as reported by Duchatelet et al. [63]. using hydrogen peroxide (H O ) as the oxygen precursor 2 2 facilitating the Ga incorporation in the form of Ga(OH) [65]. The reduction starts with the cupric ion followed by the reduction of H O which facilitates the inclusion of In 2 2 and Ga in the form of oxides/hydroxides. Precipitations of In and Ga were observed for higher concentration of H O 2 2 (20 mM) for which the deposition takes place by a controlled mass transfer of the hydroxide species [66]. Without any complexing agents and supporting electro- lytes, Chaure et al. reported the possibility to electrodeposit + + CISe (p, i, and n-type) [67] and CIGSe (p , p, i, n, and n ) [68] by varying the deposition potential from the same bath. The major hindrance in using the aqueous electrolytes is the abrupt changes in the (Ga/III) ratio, as even for a slight change in the deposition, potential can alter the composition and thus the deposition mechanism [69]. Hence, the mor- phology of the as-deposited film is strongly dependent on the applied deposition potential. As shown in Fig. 4, the narrow deposition potential window is often difficult to balance the film composition and quality. Moreover, tuning the (Ga/III) Fig. 4 Comparative diagram of the standard deposition potentials of ratio is possible up to a certain extent beyond which the copper, indium and gallium in the form of metals or hydroxide/oxide parallel occurrence of hydrogen evolution reaction (HER) during nitrate reduction. Reprinted with permission from Duchatelet takes place and has negative impact on the film quality such et al. [63]. Copyright 2014, The Electrochemical Society Fig. 5 SEM cross-sectional pictures of as-electrodeposited Cu–In–Ga osition (c). Reprinted from Duchatelet et al. [64], with the permission mixed oxide precursor films (a), after reduction under Ar-5% H into of AIP Publishing, Copyright©2013 AIP metallic alloy (b), and after selenization and front contact layers dep- 1 3 Materials for Renewable and Sustainable Energy (2018) 7:6 Page 7 of 20 6 as formation of pinholes and dendritic morphology [70]. concentrations can be achieved in water-free ionic liquids. However, the metal-oxide/hydroxide depositions are more Moreover, the high ligand concentrations ensure greater promising, where the problem of hydroxide formation dur- control on the metal speciation in the electrolyte [76, 77]. ing the conventional CuInGa electrodeposition is taken as an Therefore, reline forms strong metal complexes with the advantage. The difficultness of Ga inclusion in conventional ions, and hence, the necessity of using complexing agents CuInGa plating can be easily overcome by metal-oxide/ is eliminated. Reline is highly stable and does not decom- hydroxide depositions. pose even after prolonged heating conditions. By lowering The recent advancements in electrolyte chemistry in the the viscosity (η) of the reline, better mass transport proper- CIGSe depositions such as (1) complexing agent blends, ties of the ions can be achieved. For this reason, the optimal (2) nitrate precursor, and (3) hydrogen peroxide source are bath temperature during electroplating is usually maintained promising as the problem of Ga inclusion can be avoided within 60–70 °C. easily when compared to conventional deposition schemes. Harati et al. was the first to report the one-step electrodep- Further studies pertaining to the electrolyte stability and osition of quaternary CIGSe thin film using reline. The dep- replenishment of ions or reusing the electrolytes may con- osition temperature was fixed to 65 °C [71]. Steichen et al. tribute towards the cost-effective industrial-scale deposition. reported the electrodeposition of Cu–Ga thin films using reline at 60 °C. The selenized CuGaSe PV devices (pro- CISe/CIGSe electrodeposition in non‑aqueous cessed at 550 °C in Se atmosphere) achieved 4.1% total-area electrolytes power conversion efficiency. When only Ga or In–Ga thin films were electrodeposited on Mo substrates, no alloying The HER interference can be overcome using non-aqueous phenomena are observed and the obtained films were found electrolytes without complexing agents such as ionic liquids to be physical mixtures of In–Ga in the form of droplets [71], ethylene glycol [72], and alcohol or alcohol/ionic liquid (Fig. 6a). However, for Mo/Cu substrates, an improvement combinations [73]. Long et al. reported electrodeposition of in the Cu–Ga films film adhesion (Fig. 6b) was observed compact and quality CIGSe thin films at − 1.6 V/SCE using due to the CuGa alloy formation [75]. Zhang et al. reported alcohol and LiCl electrolyte (pH 1.9–2.2) [74]. Availability CIGSe device ec ffi iency of 10.1% for pulse electrodeposited of such wide electrochemical deposition window in non- CIG alloy. The selenization (using Se powder) was carried aqueous electrolytes allows electrodeposition of In (III) and by rapid thermal annealing (RTA) at 550 °C for 1 h. in the Ga(III) ions conveniently. Ar atmosphere [78]. Malaquias et al. showed the possibility Electrodeposition using ionic liquids has gained atten- to alter the [Ga/In] ratio from 0 to 1 by adjusting the elec- 3+ 3+ tion due to their advantages like biocompatibility, non-toxic, trolyte flux ratio of [Ga /In ] ions [79]. The same group cost-effectiveness, and wide electrochemical potential win- reported an efficiency of 9.8% for CIGSSe thin films. The dow that make them a suitable electrolyte to electrodeposit electrodeposition of In–Ga thin film was performed over the elements which are difficult to plate in conventional aqueous Mo/Cu thin films followed by a three-step annealing process bath conditions. Especially, choline chloride (ChCl)-based (H Se, Argon, and H S) [80]. 2 2 ionic liquids and aprotic deep eutectic solvents (DES) have emerged as an efficient replacement for conventional ionic Electrodeposition of CuGaSe thin films liquids and volatile organic solvents. A mixture of choline chloride/urea (ChCl/U—1/2) termed reline is one of the pop- We have also reviewed the approaches for electrodeposition ular DES used in CIGSe electrodeposition. Unlike aqueous of wide band-gap absorber CGSe thin films. Electroplat- electrolytes (where the metal ions solubility is limited by ing of CGSe is more difficult due to the standard poten- oxides/hydroxides precipitation), high solubility, and ligand tial (− 0.53 V SHE) of gallium. The parallel occurrence of Fig. 6 a Cross-sectional images of metallic Ga droplets electrodeposited on Mo from Reline–GaCl 50 mM at 1.1 V/ Ag for 30 min at 60 °C, b SEM top-view of a Ga deposit on Mo/ Cu from Reline–GaCl 50 mM at 0.9 V for 15 min at 60 °C. Adapted from Steichen et al. [75] with permission of The Royal Society of Chemistry 1 3 6 Page 8 of 20 Materials for Renewable and Sustainable Energy (2018) 7:6 Table 1 CGSe electrodeposition conditions and their compositions Bath composition Cu– Complexing agents and supporting electrolyte Deposition potential and pH CGS film composition (at.wt%) Ga–Se (mM) *Etching Cu Ga Se Cu Ga Se 2 10 4 [81] LiCl (300 mM), NH Cl (100 mM), KCN (50 mM) − 0.6 V/Ag/AgCl 26 24 50 pH 2.3 3 10 8 [82] LiSO (0.15 M) and gelatin (100 mg), *KCN etched − 0.6 V/Ag/AgCl 25 26 49 pH 2.6 4.6 25 9.2 [83] 2.0 M KSCN − 0.55 V/Ag/AgCl 23.91 23.53 52.53 pH 2.5 5 5.68 20 [59] 2.0 M NaSCN − 0.3 V/SCE Cu/Ga = 1; Se close to 50% pH 2.75 HER hinders the electrodeposition process hence resulting For CISe without PT, the surface nonuniformties, cracks in films with poor morphology and pin holes. Table 1 gives and pinholes were present, as shown in Fig. 7c, which was the deposition parameters for one-step deposition technique reduced after PT (Fig. 7d). In addition to this, the surface of CGSe thin films. without PT was found to have In nano-islands which may Until date, thiocyanate (KCN ) is reported to be a suit- affect the efficiency of the devices. Whereas the micro-struc- able complexing agent for single-step electrodeposition of tural studies revealed the presence of uniform particle mor- CuGaSe films. The shift in the reduction potential of Cu phology with reduced In-nano-islands for PT–CISe. Hence, towards the lower cathodic potential makes assimilation this would help in maintaining the composition throughout 3+ of Ga ions easier in the form of Ga Se to the growing the film. Though the exact role of pre-treatment have not 2 3 of CuGaSe film. Oda et al. reported crack free CGS thin been studied extensively, it has certain influence in altering films with lithium sulfate (Li SO ) and gelatin [82]. Using the deposition mechanism during the single-step deposition 2 4 DES such as reline, successful electrodeposition of CGSe and hence the film quality. The pre-treatment process seems has been reported [75]. Electrodeposition of Cu–Ga alloy to be applicable to all baths; however, further investigation using copper–gallium nitrate salts is also a good approach, is required to understand its role and mechanism in mor- where the inclusion of Ga takes place in the form of oxides/ phological and compositional changes. The homogenized hydroxides [63]. distribution of In and Ga seems to be possible by this pre- treatment process. Strategies for improving the quality of electrodeposited CIGSe thin films Compositional tuning to avoid micro‑cracks For an industrial-scale production of electrodeposited The studies related to the interdependence of CIGSe film CIGSe, the thin films should be free from voids, cracks, quality and stoichiometry with respect to the bath composi- surface, and compositional inhomogeneities. In this sec- tion was reported by Bhattacharya et al., as shown in Fig. 8 tion, we have discussed some of the reported experimental [84]. For a diffusion controlled deposition process, CIGSe 2+ 3+ approaches for improving the quality of the CIGSe absorbers films deposited using low Cu and In bath concentration for the high-performance devices. exhibited micro-cracks. Micro-crack-free CIGSe precursor 4+ films were obtained when electrodeposited at low Se and 2+ 3+ 3+ Pre‑treatment (PT) processhigh Cu, In , and Ga bath concentrations. Moreover, the composition of CIGSe can also be controlled by tuning Calixto et al. reported the significance of the pre-treatment the specific ion concentration. 2+ process in CIGSe electrodeposition [54]. In their observa- For increased Cu concentration, Cu content was found 3+ tion, for CIGSe thin films deposited without PT exhibited to be increasing and Se decreased. With the increase in In (Fig. 7a) pinholes, micro-cracks, and secondary Cu–Se concentration, In content increases steadily and Ga was phase which were avoided by carrying out pre-treatment found to be decreased. Cu and Se contents were found to be 3+ before deposition (Fig. 7b). Similar process was adopted unaffected by In concentration. All the ions are found to 2+ 3+ 3+ for CISe electrodeposition (4 mM—Cu , 9.75 mM—In , be unaffected towards the Ga ions at lower concentration. 4+ 3+ 6 mM—Se , 0.4 M citric acid and 0.35 g sodium dodecyl At high Ga , a steady increase in Cu and In, and decrease in 4+ sulfate, − 0.6 V/SCE for 20 min, and PT at − 0.5 V/SCE for Ga, Se content was observed. For Se , Cu and In contents 1 min over FTO substrates) to understand the effect of PT. decrease steeply, while Ga and Se contents increase. 1 3 Materials for Renewable and Sustainable Energy (2018) 7:6 Page 9 of 20 6 Fig. 7 a SEM cross section of CIGSe electrodeposition without (a) and with PT (b), FE-SEM of CISe electrodepos- ited without pre-treatment, photographic image (c, e) and (d, f) with pre-treatment (original work). Reprinted with permission from Calixto et al. [54]. Copyright 2006, The Electrochemical Society 400 °C. The CISe absorber of a bandgap 1.2 eV exhibited Selenization/sulfurization of electrodeposited CISe/CIGSe absorbers a rectifying behavior for the FTO/CISe/Al device structure [87]. Bamiduro et al. reported an Se loss of 1 at.wt % for Apart from electrodeposition parameters, the final device the CIGSe films annealed at 300 °C in argon atmosphere [88]. For a pulse electrodeposited CIGSe films, Mandati efficiencies are highly influenced by the post-processing annealing steps such as selenization and sulfurization. The et al. reported a stoichiometric CIGSe films after annealing at 550 °C for 30 min in Ar atmosphere [89]. As the device post-processing annealing schemes follow either a conven- tional furnace annealing (slow or fast heating rate/prolonged performance has not been studied for the N or Ar annealed CISe/CIGSe absorbers, it will be too early to conclude its annealing time) and rapid thermal processing (fast heating rate for a short annealing time) in H Se/selenium/sulfur/ benefits. A systematical study in this regard is required as it has the potential to reduce the device fabrication cost by Ar/N /vacuum atmospheres. The simplest post-processing annealing scheme is annealing the CIGSe absorber in vac- eliminating the sulfurization/selenization steps. The most common annealing treatment is selenization uum or Ar or N atmosphere. However, the major draw- back encountered during Ar and N annealing is the Se loss. using either H Se gas or Se powder in a controlled atmos- phere. However, due to the toxic nature of the H Se gas, the Some of the literatures have reported the retainment of Se in CISe successfully even after annealing at 400 °C in argon selenization using elemental Se powder is more preferable. During the annealing of CuInGaSe , the binary selenides atmosphere for 30 min [85]. Frontini et al. reported the diode characteristics behavior of electrodeposited CISe annealed of Cu and In are formed initially followed by the forma- tion of Cu InSe phase between the temperature ranges of at 350 °C for 15 min in Ar atmosphere [86]. Hamrouni et al. reported vacuum annealing of electrodeposited CuInSe at 370–380 °C. The formation of CuGaSe phase is induced 1 3 6 Page 10 of 20 Materials for Renewable and Sustainable Energy (2018) 7:6 Fig. 8 Composition variation of CIGSe as a function of Cu, In, Ga and Se ions concentration. Reprinted from Fernandez et al. [84]. Copyright (2003) with permission from Elsevier only around 425 °C. A complete single-phase CIGSe is stacks by Oliva et al., suggested that better incorporation/ formed by the slow interdiffusion between CISe and CGSe distribution of gallium in electrodeposited CIGSe pre- at high temperature along with the Ga accumulation towards cursor can be achieved through longer annealing time or the back contact. The problem of Ga segregation towards a higher annealing temperature [94]. Ribeaucourt et al. the back contact in the CIGSe absorbers during seleniza- reported an efficiency of 9.3% for an electrodeposited tion process is widely reported [90]. They tend to create an CuInGa alloy selenized at 450 °C. However, for CIGSe insufficient energy bandgap at the SCR, which leads to poor selenized at 600 °C, the obtained efficiency was only 4%. V . Studies by Mardudachalam et al. revealed that the accu-The MoSe layer thickness was found to be 1 µm and OC 2 mulation of more Ga towards the back contact (Mo) takes 500 nm thick for CIGSe selenized at 600 °C and 450 °C place as a consequence of preferential reaction between In for 45 min. In both the conditions, the Ga accumulation with H Se than Ga [91]. During high-temperature seleniza- towards the back contact was inevitable [70]. The same tion, the CIGSe/Mo heterocontact inverts from Schottky to group reported an efficiency of 12.4% for CuInGa oxide a favorable Ohmic-type contact due to the formation of thin precursor layer alloys after subsequent reduction (H MoSe layer. Moreover, the formation of thin M oSe layer atmosphere at 500-550 °C) and selenization at 550–600 °C 2 2 contributes towards the improvement of the adhesion at the for 45 min [95]. Bhattacharya et al. reported an efficiency CIGSe/Mo interface [92]. Yet, a high series resistance (R ) of 11.7 and 10.9% for a stacked Cu/In/Ga and CIGSe/Cu/ is induced when the MoSe layer is too thick which can dete- In precursor layers selenized at 550 °C for 45 min [96, 97]. riorate the fill factor (FF) and V of the CIGSe devices [93]. Başol et al. reported a total-area efficiency of 13.76% for OC 2 2 An extensive studies on the interdiffusion and phase a 0.48 cm device, 12.5% for cells with area of 120 cm , formation of electrodeposited Cu/In, Cu/Ga, Cu/(In + Ga) and 10% for a 1.07 m module exhibiting a total output of 1 3 Materials for Renewable and Sustainable Energy (2018) 7:6 Page 11 of 20 6 107.5 W (V = 38.2 V and I = 2.8 A) on flexible stain - Furthermore, the third selenization step avoids the forma- m m less steel (SS) substrates [98]. They also have reported tion of secondary phase at the surface. a certified efficiency of 14% for 12 cm and 15.36% for 5.4 cm over flexible SS substrates. A record efficiency of 13.4% for flexible CIGS module for a device dimen- Electrochemical formation mechanism sion of 147.1 × 26 cm by roll-to-roll electrodeposition of CISe/CIGSe was also reported [99]. Though the details of post-pro- cessing were not disclosed, they have mentioned that The formation mechanism of CIGSe is complex due to the devices were prepared from the electroplated metal the involvement of multiple electrochemical and chemical stacked layers of Mo/Cu–In–Ga/In–Se or Ga–Se followed reactions that takes place simultaneously during the qua- by rapid thermal annealing (RTA) at 500 °C. Similarly, ternary CIGSe deposition. In the recent years, the deposi- NEXCIS also reported a record efficiency of 14% for a tion mechanism of CIGSe has been explained satisfactorily of 60 × 120 cm modules for Cu(In,Ga)(S,Se) solar cells. by several research groups. Here, we have summarized the The electrodeposited Cu–In–Ga stacks were successively significant results which complete the understanding of the selenized and sulfurized between 500 and 550 °C [100]. deposition mechanism. Duchatelet et al. reported an efficiency of 8.7% for a According to Mishra and Rajeshwar, the formation of 370 nm-thick CIGSe thin films by electrodeposition of Cu/ CuSe binary phase occurs at the first place through under - In/Ga stacks. The as-deposited CuInGa precursor thick- potential deposition onto the previously reduced Cu from 2+ ness was around 120 nm. Upon selenization at 550 °C for Cu ions. Though Se is nobler than Cu, the formation of 15 min, they observed an increased V of 865 mV which Se (IV) to Se (0) is sluggish, and hence, the initial forma- OC was higher than the standard CIGSe (2100 nm) exhibit- tion of Cu is highly necessary for the direct reduction of ing V of 605 mV (η = 12.6%). The accumulated Ga in Se(IV) [104]. During the initial stage of deposition, the OC ultra-thin CIGSe devices played the role of back surface formation of Cu nano-nuclei over the Mo substrates allows field and inhibited the electron recombination at the back the incorporation of Se (0) to form Cu Se binary phase. contact [101]. Moreover, the growth of Cu Se phase can easily take place Malaquias et al. reported an efficiency of 9.8% for elec- over molybdenum even at open-circuit potential. trodeposited CuInGa alloys with reduced Ga accumula- Figure 10a shows the Raman spectra of Cu–Se films tion by employing a three-step annealing process [80]. immersed for different periods at OCP conditions. Irre - To explain the impact of three-step annealing process, spective of the immersion time, no peak correspond- −1 the work by Kim et al. has been explained below [102]. ing to Se (254 cm ) was observed. Only characteristic The three-step annealing process of vacuum-deposited Raman peaks corresponding to Cu Se (106, 141, 197, 3 2 −1 −1 CuInGa metal precursor involves (1) selenization in H Se and 216 cm ) and Cu Se (261 cm ) were observed [105]. 2 2 at 400 °C for 60 min, (2) annealing in Ar at 550 °C for Hence, at lower cathodic potential, Cu–Se binary co-exists 20 min, and (3) sulfization in H S at 550 °C for 10 min. as mixtures of Cu Se, Cu Se, CuSe, and Se(0) [107, 108]. 2 3 2 2 From the AES studies (in Fig. 9a–c), the sputter deposited For increased over potential, the direct reduction of Se(IV) CIGSe selenized samples were stoichiometric at the sur- to elemental Se(0) takes place over CuSe platelets, as face and Ga/Cu–Ga intermetallic rich at the back contact. shown in Fig. 10b. However, after selective dissolution of However, the homogenization of In and Ga was observed elemental Se, the atomic ratio of CuSe platelets [Se/Cu] after the Ar and H S post-heat treatments. As shown in was found to be close to unity (Fig. 10c) [106]. Increased Fig. 9a–c (SEM cross-sectional images), an improvement Se concentration (over CuSe platelets) contributes to the in the CIGSe micro-structure (vacuum-based deposition) formation of CuSe phase. CuSe can further reduce to 2 2 2+ was observed followed by the disappearance of flat voids form Cu and H Se at higher cathodic potentials which only after the Ar and H S treatment. Bi et al. reported chemically react with H Se to form a non-adherent Cu Se 2 2 2 an efficiency of 11.04% of CIGSe thin films for the elec- particles dispersing back to the electrolyte [85]. This reac- 3+ 3+ trodeposited metal stacks of Cu/In/Ga annealed in three tion is the key for the In and Ga incorporations as the steps: (1) selenization at 400 °C for 10 min; (2) N for In and Ga ions can react chemically with H2Se to form 30 min at 580 °C; and (3) selenization at 580 °C for 15 min their respective selenides. [103]. The Indium incorporation at low cathodic potential has Apart from rapid thermal annealing schemes, three- already been reported in several literatures. Kemell et al. 3+ step annealing is beneficial as during the N annealing, reported that CuSe phase enables the incorporation of In a slow interdiffusion step between CuInSe and CuGaSe ions by induced co-deposition process [110]. Chassaing 2 2 3+ is possible which ensures the homogenization In and Ga. and co-workers reported that In inclusion takes place when the [Se/Cu] ratio is greater than 1 to form CuInSe . 1 3 6 Page 12 of 20 Materials for Renewable and Sustainable Energy (2018) 7:6 Fig. 9 Compositional depth profiles determined by AES of the reacted CIGSe (or CIGSeS) films after a H Se (400 °C for 60 min), b Ar (550 °C for 20 min) and c H S (550 °C for 10 min) and corresponding cross-sectional SEM images of reacted CIGSe or CIGSeS films after a 1st step, b 2nd step, and c 3rd step. Reprinted from Kim et al. [102] with the permission of AIP Publishing −1 Excess selenium over CuSe phase is a perquisite of the can be observed. The peak at 260 cm corresponds to the indium incorporation at lower cathodic potential [106]. conductive Cu Se phase [107]. However, the inclusion of In through such surface-induced For CuGaSe or CuInGaSe , the Ga inclusion in the as- 2 2 reactions (at lower cathodic potential) is often limited deposited CIGSe films mainly depends on the applied poten- which is ascribed to the increased electrical resistance of tial. Unlike indium, such surface-induced reactions of In(III) the surface due to poor reacting nature of Se(0) species ions with Cu Se phase are not found for Ga species. The inclu- [111]. At higher cathodic potential conditions, the formed sion of Ga takes place either in the form of Ga(OH) (due to 3+ Se(–II) species chemically reacts with In to form indium the local change in pH) [112] and Ga Se (reaction with H Se) 2 3 2 selenides (In Se ) and assimilates to the growing CuInSe at lower or higher cathodic potential, respectively. Further 2 3 2 3+ film. In can also reduce directly to form In(0) at high increase in deposition potential usually may lead to formation precursor concentrations and deposition potential condi- of gallium oxides and hydroxide due to the parallel occurrence tions. Figure 11a shows Raman spectra of as-electrodepos- of HER [81]. So far, there is no direct evidence for the assimi- ited CISe of thickness 2 µm. The presence of Cu-deficient lation of CuGaSe or Ga Se species with CuInSe or In Se 2 2 3 2 2 3 −1 CISe phase (160 cm ) commonly known as OVC, A1 forming CIGSe thin film. For as-deposited CGSe films, Liu −1 −1 mode of CISe (177 cm ), and elemental Se(0) (260 cm ) et al. reported the absence of Raman peaks (Fig. 11b) corre- −1 −1 sponding to CuGaSe (184 cm ) or Ga Se (155 cm ) peaks, 2 2 3 1 3 Materials for Renewable and Sustainable Energy (2018) 7:6 Page 13 of 20 6 Fig. 10 a Raman spectra of CuSe films obtained after immersion at Cu] = 1.9, [In/Cu] = 0 and c SEM of Cu–Se after stripping in Na S, OCP in Cu(II)–Se(IV) solutions (pH 2.2) (reprinted with permis- [Se/Cu] = 0.95 (reprinted with permission from Chassaing et al. sion from Ramdani et al. [105] Copyright 2007, The Electrochemical [106], Copyright© 2008 John Wiley and Sons) Society), b SEM of as-deposited Cu–Se at V = − 0.55 V/MSE, [Se/ Fig. 11 a Raman spectra of electrodeposited CuInSe thin film (2 µm) mission from Elsevier), c Raman spectra of CuInGaSe (as-deposited 2 2 (reprinted with permission, Roussel [107], Copyright 2007, The Elec- and annealed) (reprinted with permission, Lai et al. [109], Copyright trochemical Society), b Raman spectra of CuGaSe (as-deposited and 2011, The Electrochemical Society) annealed) (reprinted from Liu et al. [81], Copyright (2012), with per- −1 instead only peaks corresponding to CuSe (255 and 263 cm ) The assimilation of In and Ga to the growing CIGSe is only −1 and elemental Se (238 cm ) were observed. Lai et al. also stronger at higher cathodic potential. A judicious bath prepara- −1 reported the appearance of CIGSe A1 mode (174 cm ) tion and deposition potential are necessary to have controlled (Fig. 11c) for as-deposited and for annealed CIGSe thin films inclusion of Ga with minimal oxygen content. −1 at 174 and 176 cm , suggesting that the Ga Se phase must 2 3 be in the dispersed nano-crystalline form which involves in the phase formation only during annealing [109]. 1 3 6 Page 14 of 20 Materials for Renewable and Sustainable Energy (2018) 7:6 Fig. 12 CIGSe electrodeposi- tion schemes and their power conversion efficiency Recently, Duchatelet et al. reported (Fig. 12c) an effi- CIGSe electrodeposition schemes and device ciency of 12.4% (0.1 cm ), where Cu–In–Ga are depos- performance ited in hydroxide form followed by H reduction and selenization [95]. The approaches followed to electrodeposit CIGSe absorber In Fig. 12d, for a three-stage electrodeposition of layers can be classified into two routes: (1) by one-step CIGSe/Cu/In metal stacks (selenization at 550 °C), deposition, where co-deposition of all the elements takes Bhattacharya et al. reported an efficiency of 10.9% for place at a single potential followed by post-treatments the device area of each cell is ~ 0.42 cm . They were or (2) by two steps to multi-step depositions to deposit able to fabricate these devices reproducibly and all nine either via binary phase deposition or element by element. cells had comparable efficiencies indicating uniform The deposition schemes which are already in practice and deposition over 12.5 cm area [97]. promising for large area CIGSe thin-film electrodeposition • For an electrodeposited stacked Cu/In/Ga layers as are presented Fig. 11. Irrespective of deposition schemes, mentioned in Fig. 12e (selenized at 550 °C), Bhattacha- a high-temperature annealing between 500 and 600 °C rya et al. reported an efficiency of 11.7% [96]. (under sulfur, selenium, or inert atmosphere) is required to enhance crystallinity and alloy formation process. Recently, an efficiency of 11.04% was also reported by Biet al. using the deposition scheme-e. However, the • The fabrication route mentioned in Fig. 12a deals with Cu/In/Ga metal stacks were formed by employing a pulse deposition of one-step electrodeposition of Cu–In–Ga electroplating technique and instead of conventional sele- layers followed by selenization/sulfurization. Using nization. They carried out three-step annealing processes: such scheme, a record efficiency of 17.30% (0.5 cm ) and (1) selenization at 400 °C for 10 min; (2) N for 30 min at 14% (60 × 120 cm ) in industrial scale were achieved for 580 °C; and (3) selenization at 580 °C for 15 min [103]. CIGSSe devices by NEXCIS [100]. In the above-mentioned schemes in Fig. 12, the direct • Using complexing agents, Başol et al. were able to elec- current (DC) was employed to deposit CIGSe thin films. trodeposit Cu–In–Ga/In–Se or Ga–Se stacks (Fig. 12b) The rate determining step in one-step direct current is in alkaline conditions. The reported efficiency for the the charge transfer process. The increased supersatu- devices fabricated through this route is of 14.17% 2 2 2 rated growth takes place over the same nucleation sites (11.8 cm ), 15.36% (5.4 cm ), and 13.4% (1.5 m ). The and hence results in the fine particles in porous/powdery above-mentioned routes are presently the most efficient deposits. Apart from DC depositions, there are other dif- regarding the final efficiencies of CIGSe devices [62, 98]. ferent plating techniques which includes pulse plating, pulse reverse plating and cyclic voltammetry techniques 1 3 Materials for Renewable and Sustainable Energy (2018) 7:6 Page 15 of 20 6 Fig. 13 a CIGSe device struc- ture with CdS as buffer layer (η = 21.7%) [29]. b Record efficiency CIGSe device struc- ture of η = 21% with Zn(O,S) as buffer layer [7] by which the secondary phase formation can be minimized (η = 13%) [118]. Furthermore, the thermal diffusion of Cd [71, 113, 114]. Compared to conventional constant poten- or Zn adatoms at the absorber surface creates donor anti- tial deposition techniques, electron charge transfer step is sites, thus can enhance inversion layer (more n-type). Recent prevented in pulse plating as the deposition diffusion con- results also indicated that Zn(O,S) with CIGSe functions to trolled process may lead thin films of large grain size mor - be a better substitution for CdS, exhibiting valence (VBO) phology. Such deposition techniques are advantageous as and conduction band off-set (CBO) of 1.15 ± 0.15 and we can have good control over the material composition. 0.09 ± 0.20 eV, respectively. The CBO of the hetero inter- face is sufficiently flat (with a small spike) providing better electron flow and a good blocking layer for the majority CdS‑free buffer layer in CIGSe devices carriers and hence reduces the interface recombination. Fur- thermore, the band-gap tuning is possible in Zn(O,S) buffer Until date, most of the reported record efficiency (η > 19%) layers by varying the [S/S + O] ratio [119, 120]. Even a mini- CIGSe devices employ CdS buffer layer which comprises of mal bandgap of 2.6 eV can be achieved with S/S + O = 45% the device, as shown in Fig. 13a [29]. which is 0.2 eV larger than CdS, thus avoiding the absorp- The buffer layers play major role in the formation of a tion losses. An increased device performance was observed favorable heterojunction band alignment (ΔE = 0–0.4 eV) when CIGSe/Zn(O,S) devices are annealed or HLS (heat and with CIGSe to provide an unimpeded electron flow. A thin light soaked) treatments are performed. These treatments CdS of thickness ≈ 50 nm is so far the most successful and decrease the [S/S + O] composition at the CIGSe/Zn(O,S) widely buffer layer employed in CIGSe solar cells. This interface and helps in the rearrangement of the CBO to be thin layer is deposited by chemical bath deposition (CBD), more favorable than the as-deposited Zn(O,S) [121, 122]. which incurs huge environmental issues with the toxic These results are encouraging which would pave the way chemicals involved in. Hence, on the aspect of mitigating to reduce the toxicity levels in the current CIGSe fabrication environmental hazards, replacement of hazardous CdS is techniques. highly essential. Various alternative buffer layers with higher bandgap than CdS (2.4 eV) [ZnS (3.8 eV), ZnSe (2.7 eV), ZnMgO, In Se (2.7 eV), In S (2.45 eV)] have been synthe- Conclusion 2 3 2 3 sized using various wet and dry deposition techniques [115, 116]. The advantageous part is that these materials exhibit Electrodeposition is probably one of the mature and scal- larger bandgap than CdS, thus minimizes the absorption loss able non-vacuum-based deposition techniques for CISe/ between the wavelength regions of 350–550 nm. Yet, these CIGSe absorber layers. This review has provided some of materials lack in terms of stability and final efficiency when the progresses in electrodeposition of these ternary and qua- compared to CdS. Remarkably, CBD grown Zn(O,S)/CIGSe ternary films which essentially covers formation mechanism devices exhibited better stability even when subjected to of the alloys, experimental practices, deposition routes, and 1000 h damp-heat testing and suffered no severe efficiency alternatives to replace the CdS buffer layer. The significant losses [117]. CBD is the most successful Zn(O,S) buffer observations can be listed as mentioned below: layer deposition technique used in the CIGSe device fabrica- tion. A comparison study by Ramanathan et al. revealed that • Until date, the reported highest efficiency of elec- Zn(O,S) buffer layers deposited by CBD exhibited highest trodeposited CIGSe devices is 17.30% in lab scale 2 2 power conversion efficiency (η = 18%) than the sputtered one (0.5 cm ) and 14% in industrial modules (60 × 120 cm ). 1 3 6 Page 16 of 20 Materials for Renewable and Sustainable Energy (2018) 7:6 distribution, and reproduction in any medium, provided you give appro- Though the reported efficiency is comparably less to vac- priate credit to the original author(s) and the source, provide a link to uum-based techniques, electroplating technique is still the Creative Commons license, and indicate if changes were made. a very promising technique for a simplified large scale solar cell manufacturing process. The primary concern in electrodeposition is to gain References control over the film stoichiometry and compactness. In addition, the current practice adopted by solar industries 1. Badawy Waheed, A.: A review on solar cells from Si-single to fabricate efficient CIGSe modules is by electroplat- crystals to porous materials and quantum dots. J. Adv. Res. 6, ing of single Cu–In–Ga or Cu–In–Ga/In–Se or Ga–Se 123–132 (2015) bi-layer stack deposition followed by selenization/sul- 2. Brown, G.F., Wu, J.: Third generation photovoltaics. Laser Pho- ton. Rev. 3, 394–405 (2009) furization in acidic baths. Formation of Cu–In–Ga/Cu– 3. Pagliaro, M., Ciriminna, R., Palmisano, G.: Flexible solar cells. Ga/In–Ga metal stacks in alkaline pH using complexing Chemsuschem 1, 880–891 (2008) agents can be an alternative promising route too. 4. Chirilă, A., Reinhard, P., Pianezzi, F., Bloesch, P., Uhl, A.R., Electrodeposition of Cu–In–Ga in the mixed oxide Fella, C., Kranz, L., Keller, D., Gretener, C., Hagendorfer, H., Jaeger, D., Erni, R., Nishiwaki, S., Buecheler, S., Tiwari, N.: form using nitrate precursors (of Cu, In, and Ga salts) Potassium-induced surface modification of Cu(In, Ga)Se thin or hydrogen peroxide (as the supporting electrolyte) is films for high-efficiency solar cells. Nat. Mater. 12, 1107 (2013) promising electrolyte recipes, as the oxides of Ga and 5. Reinhard, P., Bissig, B., Pianezzi, F., Avancini, E., Hagendor- In depositions take place at less cathodic potential. The fer, H., Keller, D., Fuchs, P., Döbeli, M., Vigo, C., Crivelli, P., Nishiwaki, S., Buecheler, S., Tiwari, A.N.: Features of KF and complexity of Ga inclusion is reduced when compared NaF postdeposition treatments of Cu(In, Ga)Se absorbers for to conventional electrodeposition routes. high efficiency thin film solar cells. Chem. Mater. 27, 5755–5764 Rapid thermal annealing (RTA) and successive seleniza- (2015) tion/sulfurization using elemental sulfur and selenium 6. Jackson, P., Wuerz, R., Hariskos, D., Lotter, E., Witte, W., Pow- alla, M.: Effects of heavy alkali elements in Cu(In, Ga)Se solar are the most preferred post-processing routes followed cells with efficiencies up to 22.6%. Phys. Status Solidi RRL 10, in the industrial scale. Other annealing schemes such as 583–586 (2016) triple step annealing in H Se/Ar/H S or H Se/Ar/H Se 2 2 2 2 7. Friedlmeier, T.M., Jackson, P., Bauer, A., Hariskos, D., Kiowski, were also reported to be effective towards minimizing O., Wuerz, R., Powalla, M.: Improved photocurrent in Cu(In, Ga) Se solar cells: from 20.8% to 21.7% efficiency with CdS buffer the Ga accumulation problems and in terms of device and 21.0% Cd-free. IEEE J. Photovolt. 5, 1487–1491 (2015) efficiency. However, for reducing the fabrication cost, 8. Kamada, R., Yagioka, T., Adachi, S., Handa, A., Tai, K. F., Kato, alternative routes for evading the Se loss during Argon/ T., Sugimoto, H.: New world record Cu(In,Ga)(Se,S) thin film N annealing and its effect on the device performance are solar cell efficiency beyond 22%. In: IEEE 43rd Photovoltaic Specialists Conference (PVSC), Portland, 2016. https ://doi. to be explored extensively. org/10.1109/pvsc.2016.77498 22 Regarding buffer layers, Zn(O,S) grown by chemical bath 9. Green, M.A., Emery, K., Hishikawa, Y., Warta, W., Dunlop, E.D., deposition technique is found to be a more promising Levi, D.H., Ho-Baillie, A.W.Y.: Solar cell efficiency tables (ver - alternative to CdS in terms of its performance and stabil- sion 49). Prog. Photovolt. Res. Appl. 25, 3–13 (2017) 10. Aksu, S., Pinarbasi, M.: Electrodeposition methods and chemis- ity. A record efficiency beyond 22% has been achieved tries for deposition of CIGS precursor thin films. In: 37th IEEE utilizing CBD grown Zn(O,S) buffer layers. Employing Photovoltaic Specialists Conference, Seattle, 2011. https ://doi. alkali-PDT treatments can help in improving the CIGSe org/10.1109/pvsc.2011.61859 07 devices. 11. Lincot, D.: Electrodeposition of semiconductors. Thin Solid Films 487, 40–48 (2005) 12. Saji, V.S., Choi, I.H., Lee, C.W.: Progress in electrodeposited A full-fledged industrialization of the devices fabricated absorber layer for CuIn Ga Se (CIGS) solar cells. Sol. (1−x) x 2 through electroplating routes requires further in-depth exten- Energy 85, 2666–2678 (2011) sive and explorative studies on electronic characteristics of 13. Ghorbani, E., Kiss, J., Mirhosseini, H., Roma, G., Schmidt, M., Windeln, J., Kühne, T.D., Felser, C.: Hybrid-functional calcu- the CIS/CGS/CIGSe absorber layers. For avoiding H Se or lations on the incorporation of Na and K impurities into the selenization steps, the annealing effects of the surface modi- CuInSe and CuIn Se solar-cell materials. J. Phys. Chem. C 2 5 8 fied CIGSe (CIGSe/In–Se or Se or Ga–Se) stacks and its role 119, 25197–25203 (2015) in Se retainment are to be explored for a competitive and 14. Abou-Ras, D., Caballero, R., Kaufmann, C.A., Nichterwitz, M., Sakurai, K., Schorr, S., Unold, T., Schock, H.W.: Impact of the cost-effective deposition scheme. Ga concentration on the microstructure of CuIn Ga Se . Phys. 1−x x 2 Status Solidi RRL 2, 135–137 (2008) Acknowledgements The authors would like to thank NIT-Rourkela for 15. Continenza, A., Massidda, S., Freeman, A.J., De Pascale, T.M., providing infrastructure and experimental facilities. Meloni, F., Serra, M.: Structural and electronic properties of narrow-gap ABC chalcopyrite semiconductors. Phys. Rev. B. Open Access This article is distributed under the terms of the Crea- 46, 10070–10077 (1992) tive Commons Attribution 4.0 International License (http://creat iveco mmons .org/licen ses/by/4.0/), which permits unrestricted use, 1 3 Materials for Renewable and Sustainable Energy (2018) 7:6 Page 17 of 20 6 16. Shafarman, W.N., Stolt, L.: Cu (InGa)Se Solar Cells. In: Luque, 36. Lei, C., Duch, M., Robertson, I.M., Rockett, A.: Effects of solu- A., Hegedus, S. (eds.) Handbook of photovoltaic science and tion-grown CdS on Cu(InGa)Se grain boundaries. J. Appl. Phys. engineering, pp. 567–616. Wiley, Chichester (2005) 108, 114908 (2010) 17. Jaffe, J.E., Zunger, A.: Theory of the band-gap anomaly in ABC 37. Liao, D., Rockett, A.: Cu depletion at the CuInSe surface. Appl. 2 2 chalcopyrite semiconductors. Phys. Rev. B. 29, 1882–1906 Phys. Lett. 82, 2829 (2003) (1984) 38. He, X., Paulauskas, T., Ercius, P., Varley, J., Bailey, J., Zapalac, 18. Zunger, A.: New insights on chalcopyrites from solid-state the- G., Poplavskyy, D., Mackie, N., Bayman, A., Spaulding, D., Klie, ory. Thin Solid Films 515, 6160–6162 (2007) R., Lordi, V., Rockett, A.: Cd doping at PVD–CdS/CuInGaSe 19. Zhao, Y.J., Persson, C., Lany, S., Zunger, A.: Why can CuInSe heterojunctions. Sol. Energy Mater. Sol. Cells 164, 128–134 be readily equilibrium-doped n -type but the wider-gap CuGaSe (2017) cannot? Appl. Phys. Lett. 85, 5860–5862 (2004) 39. Salome, P.M.P., Ribeiro-Andrade, R., Teixeira, J.P., Keller, J., 20. Guillemoles, J.F., Kronik, L., Cahen, D., Rau, U., Jasenek, A., Torndahl, T., Nicoara, N., Edoff, M., Gonzalez, J.C., Leitao, J.P., Schock, H.W.: Stability issues of Cu(In, Ga)Se -based solar cells. Sadewasser, S.: Cd and Cu interdiffusion in Cu(In, Ga)Se /CdS 2 2 J. Phys. Chem. B. 104, 4849–4862 (2000) hetero-interfaces. IEEE J. Photovolt. 7, 858–863 (2017) 21. Zhang, S.B., Wei, S.-H., Zunger, A., Katayama-Yoshida, H.: 40. Sozzi, G., Di Napoli, S., Menozzi, R., Carron, R., Avancini, E., Defect physics of the CuInSe chalcopyrite semiconductor. Phys. Bissig, B., Buecheler, S., Tiwari, A.N.: Analysis of Ga grading Rev. B. 57, 9642–9656 (1998) in CIGS absorbers with different Cu content. In: 2016 IEEE 43rd 22. Siebentritt, S., Gütay, L., Regesch, D., Aida, Y., Deprédurand, V.: Photovoltaic Specialists Conference (PVSC), Portland, 2016. Why do we make Cu(In, Ga)Se solar cells non-stoichiometric? https ://doi.org/10.1109/pvsc.2016.77500 42 Sol. Energy Mater. Sol. Cells 119, 18–25 (2013) 41. Song, J., Li, S.S., Huang, C.H., Crisalle, O.D., Anderson, T.J.: 23. Insignares-Cuello, C., Broussillou, C., Bermúdez, V., Saucedo, Device modeling and simulation of the performance of Cu(In , 1 − x E., Pérez-Rodríguez, A., V, Izquierdo-Roca: Raman scattering Ga )Se solar cells. Solid State Electron 48, 73–79 (2004) x 2 analysis of electrodeposited Cu(In, Ga)Se solar cells: Impact of 42. Lundberg, O., Bodegård, M., Malmstro̊m, J., Stolt, L.: Influence ordered vacancy compounds on cell efficiency. Appl. Phys. Lett. of the Cu(In, Ga)Se thickness and Ga grading on solar cell per- 105, 021905 (2014) formance. Prog. Photovolt. Res. Appl. 11, 77–88 (2003) 24. Siebentritt, S., Igalson, M., Persson, C., Lany, S.: The electronic 43. Richter, M., Schubbert, C., Eraerds, P., Parisi, J., Riedel, I., Dali- structure of chalcopyrites-bands, point defects and grain bounda- bor, T., Palm, J.: Comprehensive simulation model for Cu(In, Ga) ries. Prog. Photovolt. Res. Appl. 18, 390–410 (2010) (Se, S) solar cells. Sol. Energy Mater. Sol. Cells 132, 162–171 25. Turcu, M., Rau, U.: Fermi level pinning at CdS/Cu(In, Ga)(Se, (2015) S)2 interfaces: effect of chalcopyrite alloy composition. J. Phys. 44. Avancini, E., Carron, R., Bissig, B., Reinhard, P., Menozzi, R., Chem. Solids 64, 1591–1595 (2003) Sozzi, G., Di Napoli, S., Feurer, T., Nishiwaki, S., Buecheler, S., 26. Dharmadasa, I.M., Chaure, N.B., Samantilleke, A.P., Hassan, A.: Tiwari, A.N.: Impact of compositional grading and overall Cu Multi Fermi level pinning at metal/Cu(InGa)(SeS) interfaces. deficiency on the near-infrared response in Cu(In, Ga)Se solar 2 2 Sol. Energy Mater. Sol. Cells 92, 923–928 (2008) cells. Prog. Photovolt. Res. Appl. 25, 233–241 (2017) 27. Lany, S., Zunger, A.: Light- and bias-induced metastabilities 45. Deprédurand, V., Bertram, T., Siebentritt, S.: How does the sele- in Cu(In, Ga)Se based solar cells caused by the (V –V ]) nium activity influence CuInSe devices grown under Cu-excess? 2 Se Cu 2 vacancy complex. J. Appl. Phys. 100, 113725 (2006) In : Proceedings of SPIE 8823, Thin Film Solar Technology V, 28. Jensen, S.A., Kanevce, A., Mansfield, L.M., Glynn, S., Lany, S., 882304, 2013 Kuciauskas, D.: Optically induced metastability in Cu(In, Ga) 46. Gtay, L., Regesch, D., Larsen, J.K., Aida, Y., Depredurand, V., Se . Sci. Rep. 7, 13788 (2017) Siebentritt, S.: Influence of copper excess on the absorber quality 29. Jackson, P., Hariskos, D., Wuerz, R., Kiowski, O., Bauer, A., of CuInSe . Appl. Phys. Lett. 99, 151912 (2011) Friedlmeier, T.M., Powalla, M.: Properties of Cu(In, Ga)Se 47. Deprédurand, V., Tanaka, D., Aida, Y., Carlberg, M., Fèvre, N., solar cells with new record efficiencies up to 21.7%. Phys. Status Siebentritt, S.: Current loss due to recombination in Cu-rich Solidi RRL 9, 28–31 (2015) CuInSe solar cells. J. Appl. Phys. 115, 44503–44508 (2014) 30. Repins, I., Glynn, S., Duenow, J., Coutts, T.J., Metzger, W.K., 48. Kemell, M., Ritala, M., Leskelä, M.: Effects of post-deposition Contreras, M.A.: Required material properties for high-efficiency treatments on the photoactivity of CuInSe thin films deposited CIGS modules. Proc. SPIE 7409, 74090M (2009) by the induced co-deposition mechanism. J. Mater. Chem. 11, 31. Misic, B., Pieters, B.E., Theisen, J.P., Gerber, A., Rau, U.: Shunt 668–672 (2001) mitigation in ZnO:Al/i-ZnO/CdS/Cu(In, Ga)Se solar modules 49. Deprédurand, V., Bertram, T., Siebentritt, S.: Influence of the by the i-ZnO/CdS buffer combination. Phys. Status Solidi A 212, Se environment on Cu-rich CIS devices. Phys. B 439, 101–104 541–546 (2015) (2014) 32. Scheer, R., Messmann-Vera, L., Klenk, R., Schock, H.-W.: On 50. Aida, Y., Depredurand, V., Larsen, J.K., Arai, H., Tanaka, D., the role of non-doped ZnO in CIGSe solar cells. Prog. Photovolt. Kurihara, M., Siebentritt, S.: Cu-rich CuInSe solar cells with a Res. Appl. 20, 619–624 (2012) Cu-poor surface. Prog. Photovolt. Res. Appl. 23, 754–764 (2015) 33. Nakada, T.: Nano-structural investigations on Cd-doping into 51. Ramanujam, J., Singh, U.P.: Copper indium gallium selenide Cu(In, Ga)Se thin films by chemical bath deposition process. based solar cells—a review. Energy Environ. Sci. 10, 1306–1319 Thin Solid Films 361–362, 346–352 (2000) (2017) 34. Cojocaru-Mirédin, O., Choi, P., Wuerz, R., Raabe, D.: Exploring 52. Abou-Ras, D., Schmidt, S.S., Schäfer, N., Kavalakkatt, J., Ris- the p–n junction region in Cu(In, Ga)Se thin-film solar cells at som, T., Unold, T., Mainz, R., Weber, A., Kirchartz, T., Simsek the nanometer-scale. Appl. Phys. Lett. 101, 181603 (2012) Sanli, E., van Aken, P.A., Ramasse, Q.M., Kleebe, H.-J., Azu- 35. Abou-Ras, D., Kostorz, G., Romeo, A., Rudmann, D., Tiwari, lay, D., Balberg, I., Millo, O., Cojocaru-Mirédin, O., Barragan- A.N.: Structural and chemical investigations of CBD- and PVD– Yani, D., Albe, K., Haarstrich, J., Ronning, C.: Compositional CdS buffer layers and interfaces in Cu(In, Ga)Se -based thin film and electrical properties of line and planar defects in Cu(In, Ga) solar cells. Thin Solid Films 480–481, 118–123 (2005) Se thin films for solar cells—a review. Phys. Status Solidi RRL 10, 363–375 (2016) 1 3 6 Page 18 of 20 Materials for Renewable and Sustainable Energy (2018) 7:6 53. Savadogo, O.: Chemically and electrochemically deposited thin 71. Harati, M., Jia, J., Giffard, K., Pellarin, K., Hewson, C., Love, films for solar energy materials. Sol. Energy Mater. Sol. Cells D.A., Lau, W.M., Ding, Z.: One-pot electrodeposition, charac- 52, 361–388 (1998) terization and photoactivity of stoichiometric copper indium gal- 54. Calixto, M.E., Dobson, K.D., McCandless, B.E., Birkmire, R.W.: lium diselenide (CIGS) thin films for solar cells. Phys. Chem. Controlling growth chemistry and morphology of single-bath Chem. Phys. 12, 15282–15290 (2010) electrodeposited Cu(In, Ga)Se thin films for photovoltaic appli- 72. Wellings, J.S., Samantilleke, A.P., Heavens, S.N., Warren, P., cation. J. Electrochem. Soc. 153, G521 (2006) Dharmadasa, I.M.: Electrodeposition of CuInSe from ethylene 55. Saji, V.S., Jung, C.-Y., Lee, C.-W.: Electrodeposition of copper, glycol at 150 °C. Sol. Energy Mater. Sol. Cells 93, 1518–1523 selenium, indium, and gallium on molybdenum/surface oxides: (2009) unary, binary, ternary and quaternary compositions. J. Electro- 73. Lian, Y., Ji, S., Zhao, L., Zhang, J., Yang, P., Zhang, J., An, M.: chem. Soc. 162, D465–D479 (2015) One-step electrodeposition of CuIn Ga Se thin films from x 1−x 2 56. Bhattacharya, R.N., Rajeshwar, K.: Electrodeposition of CuIn a mixture system of ionic liquid and ethanol. New J. Chem. 39, (X = Se, Te) thin films. Solar Cells. 16, 237–243 (1986) 7742–7745 (2015) 57. Chiu, Y.-S., Hsieh, M.-T., Chang, C.-M., Chen, C.-S., Whang, 74. Long, F., Wang, W., Du, J., Zou, Z.: CIS(CIGS) thin films pre- T.-J.: Single-step electrodeposition of CIS thin films with the pared for solar cells by one-step electrodeposition in alcohol complexing agent triethanolamine. Appl. Surf. Sci. 299, 52–57 solution. J. Phys. Conf. Ser. 152, 012074 (2009) (2014) 75. Steichen, M., Thomassey, M., Siebentritt, S., Dale, P.: Controlled 58. Liu, J., Liu, F., Lai, Y., Zhang, Z., Li, J., Liu, Y.: Effects of electrodeposition of Cu–Ga from a deep eutectic solvent for low sodium sulfamate on electrodeposition of Cu(In, Ga)Se thin cost fabrication of CuGaSe thin film solar cells. Phys. Chem. 2 2 film. J. Electroanal. Chem. 651, 191–196 (2011) Chem. Phys. 13, 4292–4302 (2011) 59. Muthuraj, J.J.J., Rasmussen, D.H., Suni, I.I.: Electrodeposition 76. Simka, W., Puszczyk, D., Nawrat, G.: Electrodeposition of metals of CuGaSe from thiocyanate-containing electrolytes. J. Electro- from non-aqueous solutions. Electrochim. Acta 54, 5307–5319 chem. Soc. 158, D54 (2011) (2009) 60. Stratieva, N., Tzvetkova, E., Ganchev, M., Kochev, K., Tomov, 77. Gadilohar, B.L., Shankarling, G.S.: Choline based ionic liquids I.: Structural and optical properties of electrodeposited and their applications in organic transformation. J. Mol. Liq. 227, CuInSe layers. Sol. Energy Mater. Sol. Cells 45, 87–96 (1997) 234–261 (2017) 61. Aksu, S., Wang, J., Basol, B.M.: Electrodeposition of In–Se 78. Zhang, Y., Han, J., Liao, C.: Insights into the properties of deep and Ga–Se thin films for preparation of CIGS Solar Cells. eutectic solvent based on reline for Ga-controllable CIGS solar Electrochem. Solid State Lett. 12, D33 (2009) cell in one-step electrodeposition. J. Electrochem. Soc. 163, 62. Aksu, S., Pinarbasi, M.: Electrodeposition of Cu–In–Ga films D689–D693 (2016) for the preparation of CIGS solar cells. In: 35th IEEE Pho- 79. Malaquias, J.C., Regesch, D., Dale, P.J., Steichen, M.: Tuning tovoltaic Specialists Conference. Honolulu, 2010. https ://doi. the gallium content of metal precursors for Cu(In, Ga)Se thin org/10.1109/pvsc.2010.56171 15 film solar cells by electrodeposition from a deep eutectic solvent. 63. Duchatelet, A., Savidand, G., Loones, N., Chassaing, E., Lin- Phys. Chem. Chem. Phys. 16, 2561–2567 (2014) cot, D.: Mechanism of electrochemical deposition of Cu–In–Ga 80. Malaquias, J.C., Berg, D.M., Sendler, J., Steichen, M., Valle, mixed oxide/hydroxide thin films for Cu(In, Ga)Se solar cells. N., Dale, P.J.: Controlled bandgap CuIn Ga (S Se ) 2 1−x x 0.1 0.9 2 J. Electrochem. Soc. 161, D3120–D3129 (2014) (0.10 ≤ x≤0.72) solar cells from electrodeposited precursors. 64. Duchatelet, A., Savidand, G., Vannier, R.N., Chassaing, E., Thin Solid Films 582, 2–6 (2015) Lincot, D.: A new deposition process for Cu(In, Ga)(S, Se) 81. Liu, F., Yang, J., Zhou, J., Lai, Y., Jia, M., Li, J., Liu, Y.: One-step solar cells by one-step electrodeposition of mixed oxide pre- electrodeposition of CuGaSe thin films. Thin Solid Films 520, cursor films and thermochemical reduction. J. Renew. Sustain. 2781–2784 (2012) Energy. 5, 11203 (2013) 82. Oda, Y., Minemoto, T., Takakura, H.: Electrodeposition of crack- 65. Yang, J., Huang, C., Jiang, L.X., Liu, F.Y., Lai, Y.Q., Li, J., free CuGaSe thin films from single bath. J. Electrochem. Soc. Liu, Y.X.: Effects of hydrogen peroxide on electrodeposition 155, H292 (2008) of Cu(In, Ga)Se thin films and band gap controlling. Electro- 83. Manfredy, L., Marquez, O.P., Lopez-Rivera, S.A., Marquez, J., chim. Acta 142, 208–214 (2014) Martínez, Y., Miranda, D.A.: Electrochemical preparation and 66. Chassaing, E., Duchatelet, A., Lincot, D.: Mechanistic study of structural characterization of CuGaSe thin films. J. Phys. Conf. one-step cathodic electrodeposition of mixed Cu–In–Ga oxide/ Ser. 687, 12038 (2016) hydroxide films with hydrogen peroxide oxygen precursor. J. 84. Fernandez, A.M., Bhattacharya, R.N.: Electrodeposition of Electrochem. Soc. 164, D852–D860 (2017) CuIn Ga Se precursor films: optimization of film composi- 1−x x 2 67. Chaure, N.B., Young, J., Samantilleke, A.P., Dharmadasa, I.M.: tion and morphology. Thin Solid Films 474, 10–13 (2005) Electrodeposition of p–i–n type CuInSe multilayers for photo- 85. Thouin, L., Massaccesi, S., Sanchez, S., Vedel, J.: Formation of voltaic applications. Sol. Energy Mater. Sol. Cells 81, 125–133 copper indium diselenide by electrodeposition. J. Electroanal. (2004) Chem. 374, 81–88 (1994) 68. Chaure, N.B., Samantilleke, A.P., Burton, R.P., Young, J., 86. Frontini, M.A., Vázquez, M.: Electrodeposition of CuInSe in Dharmadasa, I.M.: Electrodeposition of p+, p, i, n and n+- citrate-containing electrolytes. J. Mater. Sci. 45, 2995–3000 type copper indium gallium diselenide for development of mul- (2010) tilayer thin film solar cells. Thin Solid Films 472, 212–216 87. Hamrouni, S., AlKhalifah, M.S., Boujmil, M.F., Saad, K.B.: (2005) Preparation and characterization of CuInSe electrodeposited 69. Li, Y., Shaikh, S.S., Menezes, S.: Film growth mechanism for thin films annealed in vacuum. Appl. Surf. Sci. 292, 231–236 electrodeposited copper indium selenide compounds. Thin (2014) Solid Films 524, 20–25 (2012) 88. Bamiduro, O., Chennamadhava, G., Mundle, R., Konda, R., 70. Ribeaucourt, L., Chassaing, E., Savidand, G., Lincot, D.: Syn- Robinson, B., Bahoura, M., Pradhan, A.K.: Synthesis and char- thesis of Cu(In, Ga)Se absorber using one-step electrodeposi- acterization of one-step electrodeposited CuIn Ga Se /Mo/ 2 (1−x) x 2 tion of Cu–In–Ga precursor. Thin Solid Films 519, 7241–7244 glass films at atmospheric conditions. Sol. Energy 85, 545–552 (2011) (2011) 1 3 Materials for Renewable and Sustainable Energy (2018) 7:6 Page 19 of 20 6 89. Mandati, S., Sarada, B.V., Dey, S.R., Joshi, S.V.: CuIn Ga Se Lincot, D., Kerrec, O.: Electrochemical cementation phenomena 1−x x 2 thin-film absorber layers for solar photovoltaics fabricated by on polycrystalline molybdenum thin films from Cu(II)–In(III)– two-stage pulsed current electrodeposition. Mater. Lett. 118, Se(IV) acidic solutions. J. Electrochem. Soc. 154, D383 (2007) 158–160 (2014) 106. Chassaing, E., Ramdani, O., Grand, P.P., Guillemoles, J.F., Lin- 90. Ganchev, M., Kois, J., Kaelin, M., Bereznev, S., Tzvetkova, E., cot, D.: New insights in the electrodeposition mechanism of Volobujeva, O., Stratieva, N., Tiwari, A.: Preparation of Cu(In, CuInSe thin films for solar cell applications. Phys. Stat. Sol. C. Ga)Se layers by selenization of electrodeposited Cu–In–Ga pre- 5, 3445–3448 (2008) cursors. Thin Solid Films 511–512, 325–327 (2006) 107. Roussel, O., Ramdani, O., Chassaing, E., Grand, P.P., Lamirand, 91. Marudachalam, M., Birkmire, R.W., Hichri, H.: Phases, morphol- M., Etcheberry, A., Kerrec, O., Guillemoles, J.F., Lincot, D.: ogy, and diffusion in CuIn Ga Se thin films. J. Appl. Phys. 82, First stages of CuInSe electrodeposition from Cu(II)–In(III)– x 1−x 2 2 2896 (1997) Se(IV) acidic solutions on polycrystalline Mo films. J. Electro- 92. Kohara, N., Nishiwaki, S., Hashimoto, Y., Negami, T., Wada, T.: chem. Soc. 155, D141–D147 (2008) Electrical properties of the Cu(In, Ga)Se /MoSe /Mo structure. 108. Chassaing, E., Grand, P.-P., Ramdani, O., Vigneron, J., Etch- 2 2 Sol. Energy Mater. Sol. Cells 67, 209–215 (2001) eberry, A., Lincot, D.: Electrocrystallization mechanism of Cu– 93. Hsiao, K.J., Liu, J.D., Hsieh, H.H., Jiang, T.-S.: Electrical impact In–Se compounds for solar cell applications. J. Electrochem. Soc. of MoSe on CIGS thin-film solar cells. Phys. Chem. Chem. 157, D387 (2010) Phys. 15, 18174–18178 (2013) 109. Lai, Y., Liu, J., Yang, J., Wang, B., Liu, F., Zhang, Z., Li, J., 94. Oliva, F., Broussillou, C., Annibaliano, M., Frederich, N., Grand, Liu, Y.: Incorporation mechanism of indium and gallium during P.P., Roussy, A., Collot, P., Bodnar, S.: Formation mechanisms of electrodeposition of Cu (In, Ga) Se thin film. J. Electrochem. Cu(In, Ga)Se solar cells prepared from electrodeposited precur- Soc. 158, D704–D709 (2011) sors. Thin Solid Films 535, 127–132 (2013) 110. Kemell, M., Ritala, M., Saloniemi, H., Leskelä, M., Sajavaara, 95. Duchatelet, A., Sidali, T., Loones, N., Savidand, G., Chassaing, T., Eero Rauhala, E.: One-step electrodeposition of Cu Se and 2 − x E., Lincot, D.: 12.4% Efficient Cu(In, Ga)Se solar cell prepared CuInSe thin films by the induced co-deposition mechanism. J. 2 2 from one step electrodeposited Cu–In–Ga oxide precursor layer. Electrochem. Soc. 147, 1080–1087 (2000) Sol. Energy Mater. Sol. Cells 119, 241–245 (2013) 111. Izquierdo-Roca, V., Saucedo, E., Jaime-Ferrer, J.S., Fontané, 96. Bhattacharya, R.N.: CIGS-based solar cells prepared from elec- X., Pérez-Rodríguez, A., Bermúdez, V., Morante, J.R.: Real- trodeposited stacked Cu/In/Ga layers. Sol. Energy Mater. Sol. time raman scattering analysis of the electrochemical growth of Cells 113, 96–99 (2013) CuInSe precursors for CuIn(S, Se) solar cells. J. Electrochem. 2 2 97. Bhattacharya, R.N., Oh, M.-K.K., Kim, Y.: CIGS-based solar Soc. 158, H521–H524 (2011) cells prepared from electrodeposited precursor films. Sol. Energy 112. Calixto, M.E., Dobson, K.D., McCandless, B.E., Birkmire, R.W.: Mater. Sol. Cells 98, 198–202 (2012) Growth mechanisms of electrodeposited C uInSe and Cu(In,Ga) 98. Başol, M., Pinarbaşi, M., Aksu, S., Freitag, J., Gonzalez, P., Se determined by cyclic voltammetry. In: MRS Proceedings. Johnson, T., Matus, Y., Metin, B., Narasimhan, M., Nayak, D., 865, F14.17 (2005). https ://doi.org/10.1557/proc-865-f14.17 Norsworthy, G., Soltz, D., Wang, J., Wang, T., Zolla, H.: Sta- 113. Caballero-Briones, F., Palacios-Padrós, A., Sanz, F.: C uInSe tus of electroplating bases CIGS technology development. In: films prepared by three step pulsed electrodeposition. Deposition Proceedings of the 34th IEEE PVSC. https ://doi.org/10.1109/ mechanisms, optical and photoelectrochemical studies. Electro- pvsc.2009.54113 42 chim. Acta 56, 9556–9567 (2011) 99. Aksu, S., Pethe, S., Shwarsctein, A.K., Kundu, S., Pinarbasi, 114. Fu, Y.-P., You, R.-W., Lew, K.K.: CuIn Ga Se absorber layer 1−x x 2 M.: Recent advances in electroplating-based CIGS solar cell fabricated by pulse-reverse electrodeposition technique for thin fabrication, In: Proceedings of the 38th IEEE Photovoltaics films solar cell. J. Electrochem. Soc. 156, D553–D577 (2009) Specialists Conference. Texas, 2012. h t t p s : / / d o i . o rg /1 0 . 1 1 0 9 / 115. Siebentritt, S.: Alternative buffers for chalcopyrite solar cells. pvsc.2012.63182 35 Sol. Energy 77, 767–775 (2004) 100. Broussillou, C., Viscogliosi, C., Rogee, A., Angle, S., Grand, P.P., 116. Naghavi, N., Abou-Ras, D., Allsop, N., Barreau, N., Bücheler, Bodnar, S., et al.: Statistical process control for Cu(In,Ga)(S,Se) S., Ennaoui, A., Fischer, C.-H., Guillen, C., Hariskos, D., Her- electrodeposition-based manufacturing process 60 × 120 cm rero, J., Klenk, R., Kushiya, K., Lincot, D., Menner, R., Nakada, modules up to 14.0% efficiency. In: 42nd IEEE Photovoltaic T., Platzer-Björkman, C., Spiering, S., Tiwari, A.N., Törndahl, Specialist Conference (PVSC), New Orleans, 2015. https ://doi. T.: Buffer layers and transparent conducting oxides for chalco- org/10.1109/pvsc.2015.73562 24 pyrite Cu(In, Ga)(S, Se) based thin film photovoltaics: present 101. Duchatelet, A., Letty, E., Ferrer, J.S., Grand, P.P., Mollica, F., status and current developments. Prog. Photovolt. Res. Appl. 18, Naghavi, N.: The impact of reducing the thickness of elec- 411–433 (2010) trodeposited stacked Cu/In/Ga layers on the performance of 117. Hariskos, D., Menner, R., Jackson, P., Paetel, S., Witte, W., CIGS solar cells. Sol. Energy Mater. Sol. Cells 162, 114–119 Wischmann, W., Powalla, M., Bürkert, L., Kolb, T., Oertel, M., (2017) Dimmler, B., Fuchs, B.: New reaction kinetics for a high-rate 102. Kim, K., Hanket, G.M., Huynh, T., Shafarman, W.N.: Three-step chemical bath deposition of the Zn(S, O) buffer layer for Cu(In, H Se/Ar/H S reaction of Cu–In–Ga precursors for controlled Ga)Se -based solar cells. Prog. Photovolt. Res. Appl. 20, 534– 2 2 2 composition and adhesion of Cu(In, Ga)(Se, S) thin films. J. 542 (2012) Appl. Phys. 111, 83710 (2012) 118. Ramanathan, K., Mann, J., Glynn, S., Christensen, S., Pankow, 103. Bi, J., Ao, J., Gao, Q., Zhang, Z., Sun, G., He, Q., Zhou, Z., Sun, J., Li, J., Scharf, J., Mansfield, L., Contreras, M., Noufi, R.,:A Y., Zhang, Y.: Controllable growth of Ga film electrodeposited comparative study of Zn(O, S) buffer layers and CIGS solar cells from aqueous solution and Cu(In, Ga)Se solar cells. ACS Appl. fabricated by CBD, ALD, and sputtering, In: Proceedings of the Mater. Interfaces 9, 18682–18690 (2017) IEEE Photovoltaic Specialists Conference, Texas, 2012. https :// 104. Mishra, K.K., Rajeshwar, K.: A voltammetric study of the elec-doi.org/10.1109/pvsc.2012.63179 18 trodeposition chemistry in the Cu + In + Se system. J. Electroa- 119. Mezher, M., Garris, R., Mansfield, L.M., Horsley, K., Weinhardt, nal. Chem. 271, 279–294 (1989) L., Duncan, D.A., Blum, M., Rosenberg, S.G., Bär, M., Ramana- 105. Ramdani, O., Chassaing, E., Canava, B., Grand, P.-P., Roussel, than, K., Heske, C.: Electronic structure of the Zn(O, S)/Cu(In, O., Lamirand, M., Rzepka, E., Etcheberry, A., Guillemoles, J.F., 1 3 6 Page 20 of 20 Materials for Renewable and Sustainable Energy (2018) 7:6 Ga)Se thin-film solar cell interface. Prog. Photovolt. Res. Appl. 122. Witte, W., Hariskos, D., Eicke, A., Menner, R., Kiowski, O., 24, 1142–1148 (2016) Powalla, M.: Impact of annealing on Cu(In, Ga)Se solar cells 120. Meyer, B.K., Polity, A., Farangis, B., He, Y., Hasselkamp, D., with Zn(O, S)/(Zn, Mg)O buffers. Thin Solid Films 535, 180–183 Krämer, T., Wang, C.: Structural properties and bandgap bowing (2013) of ZnO S thin films deposited by reactive sputtering. Appl. 1−x x Phys. Lett. 85, 4929 (2004) Publisher’s Note Springer Nature remains neutral with regard to 121. Kobayashi, T., Yamaguchi, H., Nakada, T.: Effects of combined jurisdictional claims in published maps and institutional affiliations. heat and light soaking on device performance of Cu(In, Ga)Se solar cells with ZnS(O, OH) buffer layer. Prog. Photovolt. Res. Appl. 22, 115–121 (2014) 1 3

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A short review on the advancements in electroplating of CuInGaSe2 thin films

A short review on the advancements in electroplating of CuInGaSe2 thin films

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A short review on the advancements in electroplating of CuInGaSe2 thin films

A short review on the advancements in electroplating of CuInGaSe2 thin films

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