Controlling Nuclei Growth and Phase Transition of CsFA‐Based Perovskite During Slot‐Die Coating via Solvent Engineering for High‐Performance Solar Cells and Modules

Abstract Slot‐die coating has become essential for the large‐scale production of perovskite solar cells (pero‐SCs) and solar modules (pero‐SMs). However, the power conversion efficiencies (PCEs) of pero‐SCs and pero‐SMs produced by slot‐die coating still significantly lag behind those of spin‐coated devices owing to the uncontrollable crystallization kinetics and complex phase evolution of perovskites during film formation. In this study, a perovskite precursor solution is engineered by adding volatile 2‐methoxyethanol (2‐ME) and combining it with DMF as the main solvent. Its high vapor pressure and Kamlet−Taft β value enabled rapid nucleation and hydrogen bonding with formamidinium iodide, promoting the formation of high‐density nuclei that template uniform growth and directly trigger α ‐phase perovskite formation. Consequently, a high‐quality, large‐area (25 cm 2 ) perovskite film, with uniform, pinhole‐free, and phase‐pure characteristics, is successfully deposited using the slot‐die coating method. Ultimately, the pero‐SCs (0.062 cm 2 ) and pero‐SMs (15.64 cm 2 ) fabricated by slot‐die coating achieved impressive PCEs of 24.20% and 21.84%, respectively. Notably, the unencapsulated pero‐SCs demonstrated superior operational stability, with T 90 > 1150 h.