The Multi‐Functional Third Acceptor Realizes the Synergistic Improvement in Photovoltaic Parameters and the High‐Ratio Tolerance of Ternary Organic Photovoltaics

The ternary strategy proves effective for breakthroughs in organic photovoltaics (OPVs). Elevating three photovoltaic parameters synergistically, especially the proportion-insensitive third component, is crucial for efficient ternary devices. This work introduces a molecular design strategy by comprehensively analyzing asymmetric end groups, side-chain engineering, and halogenation to explore the outstanding optoelectronic properties of the proportion-insensitive third component in efficient ternary systems. Three asymmetric non-fullerene acceptors (BTP-SA1, BTP-SA2, and BTP-SA3) are synthesized based on the Y6 framework and incorporated as the third component into the D18:Y6 binary system. BTP-SA3, featuring asymmetric terminal (difluoro-indone and dichloride-cyanoindone terminal), with branched alkyl side chains, exhibited high open-circuit voltage (V_OC), balanced crystallinity and compatibility, achieving synergistic enhancements in V_OC (0.862 V), short circuit-current density (J_SC, 27.52 mA cm^-2), fill fact (FF, 81.01%), and power convert efficiency (PCE, 19.19%). Device based on D18/Y6:BTP-SA3 (layer-by-layer processed) reached a high efficiency of 19.36%, demonstrating a high tolerance for BTP-SA3 (10-50%). This work provides novel insights into optimizing OPVs performances in multi-component systems and designing components with enhanced tolerance.