摘要： Quasi-2D halide perovskites have emerged as one of the most promising photovoltaic materials owing to their excellent stability, yet the device power conversion efficiency (PCE) is far from satisfactory. Beside of crystal orientation related carrier transport, defects in absorbers also play a crucial role in device performance, which receives limited attention in the 2D perovskite field. Herein we systematically profiled the defects states in 2D perovskite film by the temperature-dependent admittance spectroscopy (AS), light-intensity-dependent VOC, space-charge-limited-circuit (SCLC), and photoluminescence measurements. It is revealed that the Quasi-2D perovskite films suffer from severe defects as compared to the 3D counterparts in terms of both trap energy levels and trap densities. Consequently, nonradiative recombination of photogenerated carriers is much greater in the corresponding devices, wherein the monomolecular recombination is dominant. These findings substantially benefit a deeper understanding of the nature of 2D perovskite materials, which promotes the further design of 2D perovskite solar cells.