摘要： To date, extensive research has been carried out, with considerable success, on the development of high-performance perovskite solar cells (PSCs). Owing to its wide absorption range and remarkable thermal stability, the mixed-cation perovskite FAxMA1?xPbI3 (formamidinium/methylammonium lead iodide) promises high performance. However, the ratio of the mixed cations in the perovskite film has proved difficult to control with precursor solution. In addition, the FAxMA1?xPbI3 films contain a high percentage of MA+ and suffer from serious phase separation and high trap states, resulting in inferior photovoltaic performance. In this study, to suppress phase separation, a post-processing method was developed to partially nucleate before annealing, by treating the as-prepared intermediate phase FAI-PbI2-DMSO (DMSO: dimethylsulfoxide) with mixed FAI/MAI solution. It was found that in the final perovskite, FA0.92MA0.08PbI3, defects were substantially reduced because the analogous molecular structure initiated ion exchange in the post-processed thin perovskite films, which advanced partial nucleation. As a result, the increased light harvesting and reduced trap states contributed to the enhancement of open-circuit voltage and short-circuit current. The PSCs produced by the post-processing method presented reliable reproducibility, with a maximum power conversion efficiency of 20.80% and a degradation of ~30% for 80 days in standard atmospheric conditions.