Tailoring Crystallization Dynamics of CsPbI3 for Scalable Production of Efficient Inorganic Perovskite Solar Cells

All‐inorganic perovskite cesium lead triiodide (CsPbI3) with inorganic nature, low‐temperature synthesis, and a suitable bandgap is desirable for high‐performance photovoltaics. However, the scalable production of CsPbI3 photovoltaics is still challenging due to a large nucleation energy barrier and slow phase transition during unassisted natural crystallization. Here, the crystallization dynamics of CsPbI3 thin films is tailored via lead acetate (PbAc2) substitution in the perovskite precursor ink, allowing the scalable fabrication of efficient all‐inorganic perovskite solar cells and minimodules. Introducing PbAc2 enlarges CsPbI3 colloid size in the precursor and reduces the nucleation energy barrier. Additionally, reactions between acetate and dimethylammonium in the wet film accelerate the removal of dimethylammonium additives and generate solvent vapors for self‐regulate internal solvent annealing, resulting in densely packed, uniform, and pinhole‐free CsPbI3 perovskite films over large areas. This strategy demonstrates inverted CsPbI3 solar cells with 20.17% efficiency and good operational stability (retaining 95.5% of initial efficiency after continuous operation for 1800 h) and 15.1%‐efficient CsPbI3 minimodules with an active area of 26.8 cm2.