Perovskite is a material with excellent photovoltaic properties, and the efficiency of perovskite solar cells has increased rapidly in recent years. By utilizing the adjustable bandgap characteristics of perovskite materials, wide-bandgap perovskite solar cells can be combined with narrow-bandgap solar cells to make tandem solar cells. Tandem devices can improve the utilization of the solar spectra and achieve higher power conversion efficiency. An important prerequisite for preparing efficient photovoltaic devices is to fabricate high-quality perovskite active layers. Antisolvent-assisted spin-coating is currently a commonly used method for preparing high-quality perovskite films in the laboratory. However, the low solubility of inorganic cesium and bromine salts in the preparation of wide-bandgap perovskite thin films leads to a fast crystallization rate, poor crystallization quality and a large number of defects, seriously reducing the photovoltaic performance of the devices. In addition, the antisolvent has a narrow working window, which is not conducive to the preparation of large-area perovskite films. In this work, a mild gas quenching process is used to assist the spin-coating method in preparing wide-bandgap perovskite films, and propylamine hydrochloride is introduced as an additive to improve the crystallization quality and uniformity of large-area preparation of perovskite film. The interaction between the propylamine cation and the perovskite component produces a two-dimensional perovskite phase. Two-dimensional phase is used as the growth template for perovskite composition in order to reduce the formation energy of α-phase perovskite, which is beneficial to uniform nucleation and preferential orientation growth of perovskite, the increase of grain size and the decrease of grain boundaries within the film. The improvement of the crystalline quality of the perovskite film can reduce the defect density inside the film and suppress the non-radiative recombination of the photogenerated carriers. The perovskite solar cell with a bandgap of 1.68 eV, prepared by using this strategy, achieves a power conversion efficiency of 21.48%. In addition, the 8 cm×8 cm wide-bandgap perovskite films prepared by this method exhibit good uniformity. This work provides a strategy for developing the process of efficient and large-area perovskite photovoltaic devices.