Abstract: In recent years, CH(NH₂)₂PbI₃ (FAPbI₃) has received extensive attention due to the suitable band gap, becoming the most attractive photoelectric functional material in perovskite solar cells. However, the traditional perovskite layer prepared by formamidine iodide (FAI) and lead iodide (PbI₂) has inaccurate stoichiometric ratio, high defect density, low stability, and low crystallinity, which makes it challenging to improve the performance of perovskite solar cells further. In this paper, the perovskite film prepared by FAPbI₃ single crystal has high crystallinity, high stability, accurate stoichiometric ratio and low defect density. The single crystal derived perovskite film has a large grain size and few grain boundaries, resulting in fewer defects in the grain boundaries, which improves the short-circuit current density (J_SC) and open-circuit voltage (V_OC) of perovskite solar cells, and greatly improves the photoelectric conversion efficiency. This work provides an efficient strategy for fabricating perovskite solar cells with high stability, high crystallinity, and low defect density.