Films of two-dimensional (2D) perovskite (PEA)(2)(MA)(n-1)PbnI3n+1 (PEA = phenylethylammonium, MA = methylammonium) series (n = 1, 2, 3) show high stability in contrast to their three-dimensional counterparts. Development of an effective means to fabricate 2D perovskite solar cells which can achieve a better power conversion efficiency (PCE) and have less current density-voltage (J-V) hysteresis, is crucial to boost their applications. We present a one-step solution process to fabricate the 2D perovskite (PEA)(2)(MA)(2)Pb3I10 as light absorbers in solar cells by adding methylammonium acetate (MAAc) in a precursor solution. With an appropriate molar ratio of MAAc, the 2D perovskite films show a smoother surface, higher coverage, and better crystallinity, resulting in an optimal PCE of 5.7%, and importantly, no J-V hysteresis.