Side-Chain-Engineered Guest Acceptor Synchronously Optimizes Vertical Phase Separation and Non-radiative Loss in Organic Solar Cells
Ternary organic solar cells (OSCs) incorporating a structurally compatible guest acceptor (C7-Cl) into the PM6:BTP-eC9 host system are demonstrated. The low Flory-Huggins interaction parameter between host and guest acceptors facilitates intimate mixing, optimizing molecular packing and energy-level alignment. High-sensitivity sEQE and EQEEL analyses reveal a reduced non-radiative energy loss (KE3) of 0.216 eV in the ternary device. Consequently, the optimized ternary OSC achieves a champion power conversion efficiency (PCE) of 20.02% and an improved T80 operational lifetime of 1065 h. This work establishes a feasible strategy via structurally compatible guest doping to simultaneously optimize vertical phase separation and suppress non-radiative loss, providing a facile and effective route toward high-performance and stable OSCs.