Morphology Controlling of All-Inorganic Perovskite at Low Temperature for Efficient Rigid and Flexible Solar Cells

All-inorganic cesium lead halide (CsPbX3) perovskites have emerged as promising photovoltaic materials owing to their superior thermal stability compared to traditional organic-inorganic hybrid counterparts. However, the CsPbX3 perovskites generally need to be prepared at high-temperature, which restricts their application in multilayer or flexible solar cells. Herein, the formation of CsPbX3 perovskites at room-temperature (RT) induced by dimethylsulphoxide (DMSO) coordination is reported. It is further found that a RT solvent (DMSO) annealing (RTSA) treatment is valid to control the perovskite crystallization dynamics, leading to uniform and void-free films, and consequently a maximum power conversion efficiency (PCE) of 6.4% in the device indium tin oxide (ITO)/NiOx/RT-CsPbI2Br/C-60/Bathocuproine (BCP)/Ag, which is, as far as it is known, the first report of RT solution-processed CsPbX3-based perovskite solar cells (PSCs). Moreover, the efficiency can be boosted up to 10.4% by postannealing the RTSA-treated perovskite film at an optimal temperature of 120 degrees C. Profiting from the moderate temperature, flexible PSCs are also demonstrated with a maximum PCE of 7.3% for the first time. These results may stimulate further development of all-inorganic CsPbX3 perovskites and their application in flexible electronics.