ABSTRACT Relative positioning of functional groups in molecular additives and its impact on defect passivation in perovskite solar cells remains insufficiently understood. Here, we systematically investigate three diaminobenzenesulfonic acid (DABSA) isomers (2,4‐DABSA, 2,5‐DABSA, and 3,4‐DABSA) as model additives and reveal the critical role of the spatial arrangement between amino and sulfonic acid groups in enabling synergistic passivation. Among them, the ortho‐para‐substituted 2,4‐DABSA exhibits the strongest interaction with the perovskite precursor, inducing a distinct “fast nucleation followed by slow crystallization” kinetics. This dynamic control suppresses the formation of vacancies and grain boundaries by allowing ordered lattice arrangement, yielding 1.68 eV (FA₀.₇₇MA₀.₂₃)₀.₉₅Cs₀.₀₅Pb(I₀.₇₇Br₀.₂₃)₃ perovskite films, which exhibit a significantly reduced defect density. Notably, in‐situ photoluminescence measurements confirm that 2,4‐DABSA effectively suppresses light‐induced phase segregation under combined light and thermal stress (1‐sun at 65°C). Consequently, the 2,4‐DABSA‐modified device achieved a champion PCE of 23.48% and significantly enhanced operational stability. The unencapsulated devices retain 93.00%, 90.12%, and 80.23% of their initial efficiency after 1000 h of aging at 85°C/35% RH, 20°C/80% RH, and 85°C/80% RH, respectively. This work demonstrates that isomer selection adds a crucial dimension beyond functional group engineering, providing new insights for overcoming the stability bottlenecks in wide‐bandgap perovskite photovoltaics.
Chu et al. (Tue,) studied this question.