Precise Modulation of Reorganization Energy through Methyl Substitution for High Performance Organic Solar Cells

) and improved charge transport. Among the synthesized materials, BQx-MeCl exhibited the lowest energy loss and the most balanced electron and hole mobilities, resulting in a superior power conversion efficiency (PCE) of 19.2% in a binary device. In optimized ternary OSCs, BQx-MeCl further reached a remarkable PCE of 19.6%. This enhancement is attributed to optimized molecular stacking, improved film morphology, and reduced trap-assisted recombination. These findings highlight the pivotal role of molecular design in lowering reorganization energy to minimize energy losses and maximize charge collection, offering an effective strategy for the development of high-efficiency OSCs.