Ternary Strategy Enabling High‐Performance Organic Solar Cells with Optimized Film Morphology and Reduced Nonradiative Energy Loss

Ternary strategy has been demonstrated to be an effective way to improve power conversion efficiency (PCE) of single‐junction organic solar cells (OSCs). Herein, high‐efficiency ternary OSCs are fabricated based on the PBDB‐T:DO‐2F binary system and acceptor IDTT‐OB with asymmetric side chains as the third component. The introduction of nonfullerene acceptors (NFAs) IDTT‐OB as a third component can efficiently increase the compatibility of the ternary system, reduce the crystallinity of DO‐2F, optimize the blend film morphology, improve the charge transport and collection, suppress the bimolecular recombination, and reduce the nonradiative energy loss (Δ E nonrad ). Finally, the PBDB‐T:DO‐2F:IDTT‐OB‐based ternary device exhibits a high PCE of 14.09% with V oc of 0.87 V, J sc of 21.47 mA cm −2 , and fill factor of 75.70%, which is about 30% higher than the corresponding PBDB‐T:DO‐2F‐ and PBDB‐T:IDTT‐OB‐based binary devices. Meanwhile, the ternary device also achieves a very low Δ E nonrad of 0.22 eV. This work indicates that the ternary strategy can effectively optimize morphology of active layer, reduce nonradiative energy loss, and further improve photovoltaic performance of OSCs.