Geometric Complementarity and Electrostatic Fluctuation Control in Dual‐Asymmetric Acceptors for Efficient Organic Solar Cells

ABSTRACT Asymmetric molecular design has emerged as an effective strategy for developing high‐performance acceptors for organic solar cells (OSCs). Here, we introduce a dual‐asymmetric topology strategy, in which the stereochemical configurations of both the central core and terminal groups are co‐engineered. Using this approach, we synthesized an isomeric pair, Th2Cl‐a‐2Cl and Th2Cl‐b‐2Cl and benchmarked them against the singly asymmetric a‐CH‐Th2Cl and Th2Cl‐4Cl. We find that the distinctive steric conformation of Th2Cl‐a‐2Cl promotes a geometrically complementary, interlocked packing motif within the crystal lattice. This not only reinforces the three‐dimensional network connectivity but, more importantly, gives rise to a more uniform local electrostatic environment at the molecular‐skeleton scale. As a result, Th2Cl‐a‐2Cl exhibits weaker and more balanced environment‐induced electrostatic fluctuations along the backbone, which helps reduce local electrostatic perturbations during charge transport. Consequently, PM6:Th2Cl‐a‐2Cl devices deliver a champion PCE of 20.18% with a high fill factor (FF) of 80.88%, while significantly suppressing the non‐radiative recombination loss (Δ E 3 ) to 0.190 eV. These results establish geometric complementarity and electrostatic homogeneity, achieved through topological engineering, as an effective route to improve the efficiency of OSCs.