A High-Performance Non-Fullerene Acceptor Compatible with Polymers with Different Bandgaps for Efficient Organic Solar Cells

Owing to their good polymer compatibility, fullerene derivatives, such as PC₆₁BM and PC₇₁BM, have been the dominant electron acceptors to pair with various polymer donors in polymer solar cells (PSCs). The recent surge of non-fullerene materials leads to several high-performance molecular acceptors. Despite their high performance in a given polymer/acceptor system, the generality of these acceptors, i.e., their compatibility with different donor polymers remains uncertain. Here, a high-performance small molecule acceptor (SMA), BTTIC, is designed and synthesized to combine with three polymers with different bandgaps, namely J71 (1.92 eV), PBDB-T (1.80 eV), and PTB7-Th (1.58 eV). Complementary absorption, compatible energy levels, and particularly the favorable morphologies between BTTIC and the three polymers enable high power conversion efficiencies (PCEs), which are 12.8%, 13.2%, and 10.4% for J71:BTTIC-, PBDB-T:BTTIC-, and PTB7-Th:BTTIC-based PSCs, respectively, significantly higher than the PCEs of the fullerene- or other non-fullerene-based counterparts. Moreover, another famous p-type polymer donor PffBT4T-2OD, which shows poor solubility in chloroform and has not yet been studied in non-fullerene PSCs, is also investigated. Processing by dissolving PffBT4T-2OD and BTTIC in boiling chloroform enables PffBT4T-2OD:BTTIC-based PSCs with a PCE of 10.18%, which is significantly higher than that of PSCs (4.78%) before using boiling chloroform processing. The good compatibility of BTTIC with polymers that have either large, moderate, or small bandgaps makes it a promising non-fullerene acceptor for next-generation non-fullerene PSCs.