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

Abstract

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 cm²·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.