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Orientation dependent molecular electrostatics drives efficient charge generation in homojunction organic solar cells

Yifan Dong, Vasileios C. Nikolis, Felix Talnack, Yi-Chun Chin, Johannes Benduhn, Giacomo Londi, Jonas Kublitski, Xijia Zheng, Stefan C. B. Mannsfeld, Donato Spoltore, Luca Muccioli, Jing Li, Xavier Blase, David Beljonne, Ji-Seon Kim, Artem A. Bakulin, Gabriele D’Avino, James Durrant Orcid Logo, Koen Vandewal

Nature Communications, Volume: 11, Issue: 1

Swansea University Author: James Durrant Orcid Logo

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DOI (Published version): 10.1038/s41467-020-18439-z

Abstract

Organic solar cells usually utilise a heterojunction between electron-donating (D) and electron-accepting (A) materials to split excitons into charges. However, the use of D-A blends intrinsically limits the photovoltage and introduces morphological instability. Here, we demonstrate that polycrystal...

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Published in: Nature Communications
ISSN: 2041-1723
Published: Springer Science and Business Media LLC 2020
Online Access: Check full text

URI: https://cronfa.swan.ac.uk/Record/cronfa55253
Abstract: Organic solar cells usually utilise a heterojunction between electron-donating (D) and electron-accepting (A) materials to split excitons into charges. However, the use of D-A blends intrinsically limits the photovoltage and introduces morphological instability. Here, we demonstrate that polycrystalline films of chemically identical molecules offer a promising alternative and show that photoexcitation of α-sexithiophene (α-6T) films results in efficient charge generation. This leads to α-6T based homojunction organic solar cells with an external quantum efficiency reaching up to 44% and an open-circuit voltage of 1.61 V. Morphological, photoemission, and modelling studies show that boundaries between α-6T crystalline domains with different orientations generate an electrostatic landscape with an interfacial energy offset of 0.4 eV, which promotes the formation of hybridised exciton/charge-transfer states at the interface, dissociating efficiently into free charges. Our findings open new avenues for organic solar cell design where material energetics are tuned through molecular electrostatic engineering and mesoscale structural control.
College: Faculty of Science and Engineering
Funders: EPSRC
Issue: 1

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