A Nonfused Ring Electron Acceptor with Aggregation‐Induced Emission Assistance Achieving Over 20% Efficiency in Organic Solar Cells

Abstract

Abstract The development of nonfused ring electron acceptors (NFREAs) with high electroluminescence quantum efficiency (EQE EL ) is essential for advancing the commercialization of organic solar cells (OSCs), due to their low‐cost and minimal energy losses ( E loss ). However, designing such NFREAs remains a significant challenge. Herein, we present a medium‐bandgap NFREA, TT‐TCBr, which exhibits a high EQE EL of 1.0 × 10 −3 and an excellent electron mobility of 1.5 × 10 −4  cm 2  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 EQE EL in the L8‐BO: TT‐TCBr blend. When TT‐TCBr is introduced as a guest molecule into the D18:L8‐BO‐based OSC, E loss 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.