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Molecular Design of Interfacial Modifiers for Polymer‐Inorganic Hybrid Solar Cells

Molecular Design of Interfacial Modifiers for Polymer‐Inorganic Hybrid Solar Cells The heterojunction of poly(3‐hexylthiophene) (P3HT) and TiO2 in hybrid solar cells is systematically engineered with four cyanoacrylic acid‐containing conjugated molecules with various lowest unoccupied molecular orbital (LUMO) levels, WL‐1 to WL‐4, which are prepared by the formylation of thiophene derivatives in a Vilsmeier–Haack reaction, followed by treatment with cyanoacetic acid. The optical characteristics, redox properties, and intrinsic dipole moments of these interfacial modifiers (IMs) are examined using UV‐vis spectrophotometry, cyclic voltammetry, and density functional theory calculations. Using cyanoacrylic acid as a terminal anchoring group in IMs increases the electron affinity in regions close to the titania surface and forms a molecular dipole that is orientated away from the TiO2 surface, enabling both open‐circuit voltage (VOC) and short‐circuit current density to be increased simultaneously. Photovoltaic measurements demonstrate that VOC increases with the dipole moment of IMs along the molecular backbone. Moreover, the external quantum efficiency (EQE) spectra display a bimodal distribution, revealing that both IMs and P3HT contribute to the photocurrent. The EQE at 570 nm is identified as characteristic of P3HT. More importantly, the LUMO of the IMs decisively determines the dissociation efficiency of P3HT excitons. The device based on P3HT/WL‐4/TiO2 exhibits the highest power conversion efficiency of 2.87%. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Advanced Energy Materials Wiley

Molecular Design of Interfacial Modifiers for Polymer‐Inorganic Hybrid Solar Cells

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References (46)

Publisher
Wiley
Copyright
Copyright © 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim
ISSN
1614-6832
eISSN
1614-6840
DOI
10.1002/aenm.201100581
Publisher site
See Article on Publisher Site

Abstract

The heterojunction of poly(3‐hexylthiophene) (P3HT) and TiO2 in hybrid solar cells is systematically engineered with four cyanoacrylic acid‐containing conjugated molecules with various lowest unoccupied molecular orbital (LUMO) levels, WL‐1 to WL‐4, which are prepared by the formylation of thiophene derivatives in a Vilsmeier–Haack reaction, followed by treatment with cyanoacetic acid. The optical characteristics, redox properties, and intrinsic dipole moments of these interfacial modifiers (IMs) are examined using UV‐vis spectrophotometry, cyclic voltammetry, and density functional theory calculations. Using cyanoacrylic acid as a terminal anchoring group in IMs increases the electron affinity in regions close to the titania surface and forms a molecular dipole that is orientated away from the TiO2 surface, enabling both open‐circuit voltage (VOC) and short‐circuit current density to be increased simultaneously. Photovoltaic measurements demonstrate that VOC increases with the dipole moment of IMs along the molecular backbone. Moreover, the external quantum efficiency (EQE) spectra display a bimodal distribution, revealing that both IMs and P3HT contribute to the photocurrent. The EQE at 570 nm is identified as characteristic of P3HT. More importantly, the LUMO of the IMs decisively determines the dissociation efficiency of P3HT excitons. The device based on P3HT/WL‐4/TiO2 exhibits the highest power conversion efficiency of 2.87%.

Journal

Advanced Energy Materials – Wiley

Published: Feb 1, 2012

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