Molecular Aggregation Engineering of Indacenodithiophene-Based Non-Fullerene Acceptors for High-Performance Vacuum-Deposited Organic Photodiodes

Organic photodiodes (OPDs) have attracted significant attention for optical sensing applications owing to their tunable photoresponse and excellent compatibility with flexible substrates. However, most OPDs reported to date have been fabricated through solution-based processes, which often suffer from limited film uniformity, reproducibility, and scalability for large-area manufacturing. Vacuum deposition has emerged as a promising alternative because of its compatibility with complementary metal–oxide–semiconductor (CMOS) technology, precise thickness control, and highly reproducible thin-film formation. Nevertheless, vacuum-deposited OPDs have largely relied on fullerene-based acceptors, which are hindered by high material cost, limited absorption tunability, and insufficient operational stability.

Herein, we report a series of indacenodithiophene (IT)-based small-molecule acceptors with systematically modulated electron-withdrawing groups (EWGs) for high-performance vacuum-deposited OPDs. The enhanced electron-withdrawing ability strengthens intramolecular charge transfer (ICT), leading to increased molecular dipole moments and pronounced changes in molecular aggregation during vacuum deposition. In particular, the optimized molecular design promotes J-aggregation in the deposited films, thereby improving light absorption, charge transport, responsivity, and detectivity. The controlled aggregation also suppresses trap-assisted noise and enhances thermal stability, resulting in superior device performance compared with conventional C60-based OPDs. These results demonstrate that molecular-level aggregation control through EWG engineering is an effective strategy for developing non-fullerene acceptors for vacuum-deposited OPDs and provide useful design guidelines for next-generation organic photodetectors.