Defects at the surface and grain boundary of the three-dimensional (3D) organic-inorganic metal halide perovskite film incline to cause non-radiative recombination of charge carriers and accelerate decomposition of 3D perovskite, in turn deteriorating the power conversion efficiency (PCE) and stability of the perovskite solar cells (PSCs). In this study, the organic 4-chlorobenzylamine cation was applied to react with 3D perovskite and the residual PbI₂ to in-situ form a two-dimensional (2D) perovskite top layer, which can passivate the surface and grain boundary defects of the 3D perovskite film, and improve the surface hydrophobicity. Based on this strategy, 2D/3D-PSCs with higher PCE and better stability were successfully obtained. Their structure, morphology photoelectric propery and stability of PSCs were systematically studied. All results show that 2D/3D-PSCs achieve PCEs up to 20.88%, much higher than that of 18.70% for the 3D-PSCs. In addition, 2D/3D-PSCs can maintain 82% of the initial PCE after 200 h continuous operation under 1-sun illumination in N₂ atmosphere, exhibiting excellent stability.