Synergistic Crystallization Regulation and Defect Suppression via Dual‐Site Molecular Coordination for Efficient Inverted Perovskite Solar Cells

ABSTRACT Defects in polycrystalline perovskite films induce carrier ion migration and recombination, restricting the efficiency and durability of inverted perovskite solar cells (PSCs). Conventional additive strategies based on ammonium salts often provide insufficient defect passivation and poor long‐term stability. Herein, (1H‐benzo[d]imidazol‐2‐yl)methanamine hydrochloride (BMHCl) serves as a multifunctional molecule regulator to cooperatively regulate defect evolution and crystallization kinetics through dual‐site molecular interactions in inverted PSCs. Benefiting from the coordinated interactions of the protonated amino group (─NH 3 + ) and electron‐rich nitrogen atoms with defective [PbI 6 ] 4− octahedra, BMHCl effectively regulates crystallization kinetics, suppresses defect formation, and alleviates residual lattice strain. Consequently, the BMHCl‐modified perovskite films exhibit enhanced crystallinity, enlarged grain sizes, optimized vertical orientation, and reduced trap density. These combined microstructural improvements facilitate charge carrier transport while suppressing non‐radiative recombination. BMHCl also produces more favorable energy‐level alignment and faster interfacial charge extraction. Consequently, the champion PSC achieves the conversion efficiency of 26.50% while demonstrating excellent operational and damp‐heat stability, retaining 87.49% and 80.52% of its initial efficiency after 1000 h at 85°C and 800 h at 85°C, 85% relative humidity, respectively. This work demonstrates a practical molecular‐interaction strategy for efficient and durable inverted PSCs based on multifunctional, dual‐site passivation and crystallization regulation.