Synergistic Modulation of Interfacial Energetics and Crystallization Kinetics for Efficient Perovskite Solar Cells

ABSTRACT The power conversion efficiency (PCE) and long‐term stability of polycrystalline perovskite solar cells (PSCs) are fundamentally limited by bulk non‐radiative recombination and mismatched interfacial energy levels. To address these bottlenecks, we introduced 4,4’‐(2,1,3‐benzothiadiazole‐4,7‐diyl)dibenzoic acid (BTBA) as a twisted molecular additive for regulating crystallization kinetics and interfacial energetics. With dual carboxylic acid groups and a rigid, non‐coplanar benzothiadiazole‐based backbone, BTBA coordinates with Pb‐based precursor during film formation, which retards the crystallization kinetics and yields films with enlarged grains. In addition, residual BTBA at the perovskite surface passivates undercoordinated Pb 2+ defects and regulates the surface work function, which improves the energy‐level alignment with C 60 and facilitates charge extraction. The resulting PSCs achieved a champion PCE of 27.16% (certified 27.14%) with a fill factor (FF) of 86.73%. Furthermore, the unencapsulated devices exhibited improved stability, retaining over 90% of their initial PCEs after 1200 h of maximum‐power‐point tracking (MPPT) under continuous 1‐sun illumination and after 500 h of thermal aging at 85°C.