Ambient Air Fabrication of Highly Efficient and Stable Perovskite Solar Cells via Local Spontaneous Gas‐Mediated Crystallization

Ambient air fabrication of perovskite solar cells (PSCs) is highly desirable for industrial scalability, yet the realization of high efficiency and long‐term stability still typically relies on nitrogen‐filled gloveboxes, a costly and space‐limited strategy that impedes large‐scale deployment. This study introduces di‐tert‐butyl dicarbonate (BOC) as a multifunctional additive that enables the fabrication of high‐performance n‐i‐p PSCs entirely in ambient air. BOC begins to thermal decomposition at 70°C, releasing gases that induce an open porous PbI 2 structure to enhance FAI infiltration. During subsequent perovskite crystallization, residual BOC slowly decomposes, forming a dynamic gas barrier that aligns with the crystallization window. This mechanism suppresses moisture and oxygen induced Pb 2+ reduction and perovskite decomposition, effectively minimizing harmful Pb 0 and unreacted PbI 2 , thereby resulting in high‐quality films with enhanced crystallinity and reduced defects. The champion device achieves a remarkable power conversion efficiency of 26.02%. Furthermore, these devices demonstrate outstanding stability under both environmental storage and operational conditions. After 1800 h of dark storage, they retain over 97% of their initial PCE, and after 1000 h of continuous illumination, they maintain more than 85% of their initial PCE.