A Multifunctional Organic Salt for Synergistic Crystallization Control and Defect Management in Efficient and Stable Perovskite Solar Cells

Achieving simultaneously high efficiency and long‐term operational stability remains a fundamental challenge for perovskite solar cells (PSCs), primarily limited by defect‐mediated nonradiative recombination and uncontrolled crystallization. To address this, we introduce a multifunctional organic salt based on a rigid bicyclic cage, 1‐amino‐1,4‐diazabicyclo[2.2.2]octan‐1‐ium dichloride (DzA·2Cl), which in inverted‐architecture PSCs concurrently modulates crystallization kinetics and synergistically passivates multiple charged defects. DzA·2Cl forms stable coordination complexes with PbI 2 , promoting homogeneous nucleation and retarding crystal growth, thereby producing perovskite films with enlarged grains and reduced defect densities. Furthermore, DzA·2Cl exhibits a unique synergistic passivation effect. The nitrogen atoms in the –NH 2 groups and NH + moieties coordinate with undercoordinated Pb 2+ and anchor FA + cations to suppress FA + vacancies, while Cl − ions compensate iodide vacancies, collectively enabling synergistic passivation of both shallow and deep‐level defects. As a result, PSCs incorporating DzA·2Cl deliver an impressive power conversion efficiency of 26.51% and outstanding operational stability, retaining 92.3% of the initial efficiency after 1000 h of continuous 1‐sun illumination. This study provides an effective cation–anion strategy for the synergistic regulation of defects and crystallization, offering a pathway toward high‐efficiency and operationally stable perovskite solar cells.