Post-treatment of Perovskite Films toward Efficient Solar Cells via Mixed Solvent Annealing

Post-treatment of perovskite films plays a crucial role in obtaining high-performance perovskite solar cells (PSCs). Solvent annealing (SA), as a universal post-treatment strategy, is profoundly beneficial for enhancing the quality of perovskite films. Here, a mixed-solvent vapor (MSA)-assisted gradient thermal annealing strategy is developed for the post-treatment of perovskite films. It is found that the synergistic effect of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) is significant for obtaining high-quality perovskite films with large grain size and low trap state density, which shows much better effects in comparison with single-solvent annealing. MSA-treated planar PSCs with a regular n–i–p structure achieve a maximum power conversion efficiency (PCE) of 19.76% with an average PCE of 19.29% under a reverse scan at a rate of 0.1 V/s, compared with an average PCE of 15.85% of the counterparts (TTA) with thermal annealing only. Such facile, effective, and low-cost annealing strategy exhibits commendable utilization potentiality to obtain high-quality perovskite films and efficient PSCs.