Z Xu, Wen-Jie Qiu, Guan-Wu Wang
The Y-series acceptor mix-X4 was synthesized and separated into meso -X4 and rac -X4, whose configurations were assigned by single-crystal X-ray diffraction. The isolated isomers exhibited distinct packing, solubility, film organization and photovoltaic performance. The best photovoltaic performance was obtained with rac -X4, affording 17.35% PCE with 1.01 V V OC . These results highlight configurational composition as an underappreciated structural variable in Y-series acceptors.