Asymmetric Isomer Effects in Benzo[c][1,2,5]thiadiazole-Fused Nonacyclic Acceptors: Dielectric Constant and Molecular Crystallinity Control for Significantly Photovoltaic Performance Enhancement

Asymmetric isomerization from BP6T‐4F to ABP6T‐4F not only lowers the exciton bonding energy but also optimizes the crystallization performance, achieving a pronounced isomer effect with 9.4% power conversion efficiency enhancement. Moreover, ternary devices are also fabricated, considering good compatibility between ABP6T‐4F and CH1007, to deliver a power conversion efficiency over 17%.