Asymmetric Molecule and Thermal Condition Enable Green Solvent‐Processed Organic Solar Cells Achieve 17.89% Efficiency

Using green solvents to fabricate high‐efficiency organic solar cells (OSCs) is the ultimate choice for realizing commercial application of OSCs. However, the low solubility of conventional materials in green solvents and unfavorable phase separation limit the development of green solvent‐processed organic solar cells (GSP‐OSCs). To solve the above problems, a new strategy in which asymmetric acceptor and thermal processing jointly optimize the device performance is proposed. PM6 with temperature‐dependent aggregation property is chosen as the donor, and thermal treatment can improve its solubility. The asymmetric small molecule acceptor BTP‐2F2Cl is chosen as the third material due to its strong crystallinity and good miscibility with the main system materials. Meanwhile, BTP‐2F2Cl can induce the formation of well‐ordered crystallization and molecular stacking in the active layer material, which promotes charge transport and inhibits recombination. Therefore, the PM6: L8‐BO: BTP‐2F2Cl‐based ternary GSP‐OSCs achieve a champion power conversion efficiency of 17.89% compared with the binary devices (16.99%). The results indicate that the introduction of asymmetric acceptor and thermal treatment are an effective strategy to regulate the active layer morphology and enhance the performance of GSP‐OSCs.