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-FAPbI₃ 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.