Abstract
Abstract Hybrid organic–inorganic perovskite solar cells (PSCs) are among the most promising photovoltaic technologies, yet their performance is critically constrained by uncontrolled crystallization, which generates suboptimal film morphologies and abundant defects. In this study, diphenyl carbonate (DPC) is introduced as a dual‐functional molecular regulator that simultaneously governs nucleation and growth in FAPbI 3 films. Through synergistic covalent carbonyl‐Pb 2+ coordination and non‐covalent aromatic π‐Pb 2+ interactions, DPC promotes controlled PbI 2 pre‐aggregation to lower the nucleation barrier, while its strong precursor binding retards subsequent crystal growth. This cooperative regulation yields uniform, large‐grain perovskite films with markedly reduced defect densities. Consequently, DPC‐enabled PSCs achieve a champion power conversion efficiency (PCE) of 26.61% (certified 26.21%), outperforming the control devices (23.65%). Scalable mini‐module (14.0 cm 2 active area) with DPC achieves a PCE of 21.24%. Furthermore, DPC‐modified devices exhibit outstanding stability, retaining over 90% of their initial PCE after 1200 h storage under ISOS‐D‐3 accelerated aging conditions and after 1100 h of maximum power point tracking following ISOS‐L‐2 protocols. These findings establish a generalizable molecular strategy for overcoming intrinsic crystallization bottlenecks, advancing perovskite photovoltaics toward efficient, stable, and scalable deployment.