Boosting the Film Quality by Simultaneously Pre‐wetting the PbI2 Film and Ostwald Ripening the MAPbI3 Film with DMSO Addition into MAI Solution

Generally, the typical two‐step sequential spin‐coating deposition (TSSD) method is not compatible with the preparation of the high‐efficiency perovskite solar cells due to the low film quality. Herein, we introduced trace amounts of DMSO into the MAI/isopropanol solution aiming at improving the quality of perovskite film fabricated with TSSD method. Based on this strategy, the perovskite film formed with an optimal DSMO addition ratio of 0.5 v% exhibits a significant higher film quality with improved optical properties than that of the pristine one, which can be attributed to an optimized crystallization process including pre‐wetting the PbI2 film and simultaneously Ostward ripening the formed perovskite crystals induced by the DMSO addition. Thus the corresponding perovskite solar cells yielded a higher power conversion efficiency as high as 15.39% comapred with the pristine counterpart, finally achieving a 14.42% enhancement of the PCE. In conclusion, this work provides a facile and effective strategy to fabricate high‐quality perovskite films with TSSD method by introducing some polar solvents. A trace amounts DMSO addition into the MAI/isopropanol can induce a synergistically optimized crystallization process including pre‐wetting the PbI2 film and simultaneously Osward ripening the formed perovskite crystals