Synthesis, Isomer Separation, and Photovoltaic Application of a Y-Series Acceptor

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 VOC. These results highlight configurational composition as an underappreciated structural variable in Y-series acceptors.