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.