“In the field of perovskite solar cells, researchers have found through Huck's theory calculations that carbonyl oxygen in N-ethyl-2-pyrrolidone (NEP) has stronger electronegativity than N-methylpyrrolidone (NMP), predicting its stronger interaction with PbI2. The use of solvent controlled assisted crystallization strategy, replacing NMP in the solvent with NEP, effectively improved the crystallization quality of perovskite films. The highest photoelectric conversion efficiency of the prepared FAPbI3 perovskite solar cell increased from 20.25% to 21.05%, and the average efficiency increased from 18.43% to 19.50%. Unpackaged devices can maintain 82.1% of their initial efficiency even after 1200 hours in environments with relative humidity ranging from 10% to 20% and room temperature. This strategy is also applicable in the solution system of perovskite precursor with dual cation components, and has universality, which is helpful for the preparation research of perovskite solar cells in air environment.”