Nature Communications 2015-01-01

A molecular nematic liquid crystalline material for high-performance organic photovoltaics.

Kuan Sun, Zeyun Xiao, Shirong Lu, Wojciech Zajaczkowski, Wojciech Pisula, Eric Hanssen, Jonathan M White, Rachel M Williamson, Jegadesan Subbiah, Jianyong Ouyang, Andrew B Holmes, Wallace W H Wong, David J Jones

Index: Nat. Commun. 6 , 6013, (2015)

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Abstract

Solution-processed organic photovoltaic cells (OPVs) hold great promise to enable roll-to-roll printing of environmentally friendly, mechanically flexible and cost-effective photovoltaic devices. Nevertheless, many high-performing systems show best power conversion efficiencies (PCEs) with a thin active layer (thickness is ~100 nm) that is difficult to translate to roll-to-roll processing with high reproducibility. Here we report a new molecular donor, benzodithiophene terthiophene rhodanine (BTR), which exhibits good processability, nematic liquid crystalline behaviour and excellent optoelectronic properties. A maximum PCE of 9.3% is achieved under AM 1.5G solar irradiation, with fill factor reaching 77%, rarely achieved in solution-processed OPVs. Particularly promising is the fact that BTR-based devices with active layer thicknesses up to 400 nm can still afford high fill factor of ~70% and high PCE of ~8%. Together, the results suggest, with better device architectures for longer device lifetime, BTR is an ideal candidate for mass production of OPVs.