Electronic Configuration Tuning of Centrally Extended Non‐Fullerene Acceptors Enabling Organic Solar Cells with Efficiency Approaching 19 %

Abstract In the molecular optimizations of non‐fullerene acceptors (NFAs), extending the central core can tune the energy levels, reduce nonradiative energy loss, enhance the intramolecular (donor‐acceptor and acceptor‐acceptor) packing, facilitate the charge transport, and improve device performance. In this study, a new strategy was employed to synthesize acceptors featuring conjugation‐extended electron‐deficient cores. Among these, the acceptor CH‐BBQ, embedded with benzobisthiadiazole, exhibited an optimal fibrillar network morphology, enhanced crystallinity, and improved charge generation/transport in blend films, leading to a power conversion efficiency of 18.94 % for CH‐BBQ‐based ternary organic solar cells (OSCs; 18.19 % for binary OSCs) owing to its delicate structure design and electronic configuration tuning. Both experimental and theoretical approaches were used to systematically investigate the influence of the central electron‐deficient core on the properties of the acceptor and device performance. The electron‐deficient core modulation paves a new pathway in the molecular engineering of NFAs, propelling relevant research forward.