Processing Window Expansion Enables Uniform Crystallization in Scalable Ambient‐Fabricated Perovskite Photovoltaics

Slot‐die coating is a promising scalable deposition technique for perovskite devices due to its high material utilization and inherent compatibility with continuous manufacturing. However, a narrow deposition‐to‐annealing time window and inhomogeneous ink distribution limit the device performance. Herein, we report a combined additive (CA) strategy that simultaneously regulates nucleation kinetics and phase evolution, broadening the processing window for slot‐die coating in the ambient. By synergistically introducing rubidium thiocyanate (RbSCN) and formamidinium thiocyanate (FASCN), an in situ coordination mechanism is established that lowers the energy barrier for the δ‐to‐α phase transition while suppressing non‐photoactive phase formation. This leads to uniform crystallization over an extended time window exceeding 100 s, yielding dense large‐grained α‐FAPbI 3 films with minimized vertical compositional gradient and reduced residual strain. The resulting films exhibit suppressed defects, prolonged carrier lifetime, and optimized energy‐level alignment, enabling efficient charge extraction and reduced nonradiative recombination. The CA strategy enables highly uniform large‐area deposition to deliver an efficiency of 22.70% for perovskite solar modules. Meanwhile, the unencapsulated devices maintain 97.76% of the initial efficiency under ISOS‐L‐3 for 1300 h. This CA strategy establishes a generalizable pathway for decoupling crystallization kinetics from processing constraints, providing a robust method for scalable high‐performance perovskite photovoltaics.