The development of non-fused ring electron acceptors (NFREAs) with high electroluminescence quantum efficiency (EQEEL) is essential for advancing the commercialization of organic solar cells (OSCs), due to their low-cost and minimal energy losses (Eloss). However, designing such NFREAs remains a significant challenge. Herein, we present a medium-bandgap NFREA, TT-TCBr, which exhibits a high EQEEL of 1.0×10-3 and an excellent electron mobility of 1.5×10-4 cm2 V-1 s-1. Interestingly, TT-TCBr shows enhanced photoluminescence quantum yield from solution (9.24%) to film (20.7%). In OSCs, the D18:TT-TCBr-based OSC achieves a good power conversion efficiency (PCE) of 13.20% with a high open-circuit voltage of 1.09 V and a low nonradiative energy loss of 0.177 eV. Importantly, TT-TCBr shows good miscibility with L8-BO, leading to an increased exciton diffusion length and EQEEL in the L8-BO: TT-TCBr blend. When TT-TCBr is introduced as a guest molecule into the D18:L8-BO-based OSC, Eloss is reduced from 0.543 to 0.530 eV, resulting in a significantly increased PCE from 19.16% to 20.10%, which represents one of the highest PCEs reported for OSCs. This research will significantly contribute to the advancement of high-performance guest materials for the rapid development of single-junction OSCs.
Keywords: non-fused ring electron acceptor , high Electroluminescence, organic solar cells, power conversion efficiency, aggregation-induced emission.
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