Regulating Molecular Structure of S,N‐Heteroacene Non‐fullerene Acceptors to Achieve Efficient Photoelectric Properties^†

Comprehensive Summary The ternary strategy has demonstrated its efficacy in improving charge transport in organic solar cells (OSCs). Here, three novel non‐fullerene acceptors, SN6C9‐4F, SN6C9‐4Cl and SN6C10‐4F, based on S,N‐heteroacene linear backbone were designed and synthesized. The three acceptors exhibit excellent molecular coplanarity, high crystallinity and possess a deep‐lying lowest unoccupied molecular orbital energy level, which is beneficial for charge transport and injection in organic field‐effect transistors (OFETs). Notably, the OFET devices based on all three acceptors achieved impressive electron mobilities, with SN6C10‐4F achieving up to 0.73 cm 2 ·V –1 ·s –1 , which is one of the highest values among A‐D‐A type small molecules. In addition, the OSCs device based on PBDB‐T:SN6C9‐4F exhibited the best power conversion efficiency of 12.07% owing to its optimal morphology and enhanced charge transport. Moreover, the incorporation of SN6C9‐4F into the efficient PM6:L8‐BO binary system to form ternary OSCs resulted in extended absorption range, enhanced donor crystallization, improved and more balanced charge transport, ultimately leading to an improvement of PCE from 17.78% to 18.32%. This study highlights the potential of developing acceptors with distinct structures from Y‐series acceptors to broaden absorption and regulate donor crystallization, providing a novel approach to enhance the PCE of OSCs.