Crystal Growth Regulation of 2D/3D Perovskite Films for Solar Cells with Both High Efficiency and Stability

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)2PbI4 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)2PbI4 modulated perovskite film shows a significantly improved film quality with enlarged grain size from ≈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.