Reducing the electronic defects in perovskite films has become a substantial challenge to further boost the photovoltaic performance of perovskite solar cells. Here, 2D (NpMA)(2)PbI4 perovskite and 1-naphthalenemethylammonium iodide (NpMAI) are separately introduced into the PbI2 precursor solutions to regulate the crystal growth in a 2D/3D perovskite film using a two-step deposition method. The (NpMA)(2)PbI4 modulated perovskite film shows a significantly improved film quality with enlarged grain size from approximate to 500 nm to over 1000 nm, which greatly reduces the grain-boundary defects, improves the charge carrier lifetime, and hinders ionic diffusion. As a result, the best-performing device shows a high power conversion efficiency (PCE) of 24.37% for a small-area (0.10 cm(-2)) device and a superior PCE of 22.26% for a large-area (1.01 cm(-2)) device. Importantly, the unencapsulated device shows a dramatically improved operational stability with maintains over 98% of its initial efficiency after 1500 h by maximum power point (MPP) tracking under continuous light irradiation.