Aggregation‐Enhanced‐Emission Polymer Donor Improves the Efficiency of Organic Solar Cells by Suppressing Nonradiative Recombination

Abstract Nonradiative voltage loss (Δ V nr ) is a critical factor that limits the efficiency of organic solar cells (OSCs). Introducing highly luminescent materials is a promising approach to reduce Δ V nr . The majority of prior works have focused on enhancing luminescence of low‐bandgap nonfullerene acceptors, whereas highly luminescent donors have received far less attention. Herein, we designed and synthesized a highly luminescent polymer donor with aggregation‐enhanced emission property, namely PiNTSO‐F, and incorporated it into PM6:BTP‐eC9‐based system. Interestingly, PiNTSO‐F was found to locate at the donor–acceptor interface, where it optimizes the interfacial morphology, energetic landscape, and charge dynamics of the active layer. Consequently, the nonradiative recombination rate in the ternary system is significantly reduced, while the interfacial charge generation efficiency is simultaneously improved to nearly unity, effectively minimizing Δ V nr of the device. As a result, the ternary devices achieve a low Δ V nr of 0.192 V and a high efficiency of 20.36%. This work demonstrates an effective strategy for suppressing Δ V nr through developing the highly luminescent polymer donors as a third component, providing mechanistic insights that enable high‐performance OSCs with minimized voltage loss.