Dimethyl sulfoxide: a promising solvent for inorganic CsPbI3 perovskite

Inorganic CsPbI3 perovskite is an important photovoltaic material due to its suitable band gap and high chemical stability. However, it is a challenge to grow high-quality CsPbI3 perovskite because the stability of perovskite phase is low and is sensitive to solvent. So far, most of CsPbI3 perovskites in high-performance perovskite solar cells (PSCs) were prepared from N,N-dimethylformamide, a highly toxic solvent, and no successful case has been reported for dimethyl sulfoxide (DMSO), which is environmentally-friendly with considerably higher complexation capability. Herein, we reveal that forming DMSO-based adduct is the main cause for limiting the quality of CsPbI3 perovskite from DMSO-based solutions, which would inhibit the formation of DMAPbI3 (DMA = dimethylammonium, (CH3)2NH2+) intermediate. Then, by introducing a vacuum treatment, DMSO molecules could be efficiently extracted from the adduct to induce the formation of DMAPbI3 intermediate. After annealing, the intermediate is transitioned to the CsPbI3 perovskite with enhanced crystallinity, high orientation, low defect density, and high uniformity. By using the CsPbI3 perovskite as a light absorber, the PSCs based on carbon electrode (C-PSCs) achieve an efficiency of 16.7%, a new record for inorganic C-PSCs.