Tuning Linker Rigidity in Dimeric Acceptors Enables Efficient Organic Solar Cells

초록

Organic solar cells (OSCs) based on nonfullerene acceptors have achieved remarkable efficiency improvements, yet the structure-property relationships of oligomeric acceptors, particularly the role of pi-bridge rigidity in governing molecular packing and device physics, remain insufficiently understood. Here, we report two dimeric acceptors, DY-TT and DY-T-T, constructed from an identical monomeric backbone but featuring distinct pi-bridge linkers to elucidate the impact of linker rigidity on photovoltaic performance. Compared with the more rigid DY-TT containing a fused bithiophene linker, the DY-T-T acceptor with a more flexible bithiophene linker exhibits a slightly narrower optical bandgap and more favorable energy-level alignment. In the corresponding PM6-based blends, DY-T-T enables enhanced charge generation and a more optimized phase-separated morphology. Moreover, the PM6:DY-T-T blend shows more coherent molecular packing and reduced trap-assisted recombination, which are attributed to its moderate conformational flexibility. As a result, the DY-T-T-based device delivers an improved power conversion efficiency of 18.92%, outperforming the DY-TT counterpart (17.90%) with simultaneously improved short-circuit current density and fill factor. These findings demonstrate that rational modulation of linker rigidity represents an effective molecular design strategy for advancing high-performance oligomeric acceptors in OSCs.

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