Remarkable quality improvement of CsPbIBr2 perovskite film by cellulose acetate addition for efficient and stable carbon-based inorganic perovskite solar cells

All-inorganic CsPbIBr2 perovskite has been regarded as a promising candidate for perovskite solar cells (PSCs) considering its suitable bandgap and high stability. However, the poor quality of CsPbIBr2 film greatly impedes the performance improvement of CsPbIBr2-based PSCs. Herein, we report a facile strategy to improve the quality of CsPbIBr2 perovskite film by introducing cellulose acetate (CA) into the perovskite precursor solution. The interaction between the oxygen functional groups of CA and Pb2+ and the increase of the precursor viscosity induced by CA addition can slow down the crystallization rate of CsPbIBr2 perovskite, which allows the perovskite films have enough time to form high-quality crystal structure. By optimizing the amount of CA (the optimal amount of CA is 2.5 wt%), a high-quality CsPbIBr2 perovskite film with high crystallinity, large grain size, and smooth surface is obtained. As consequence, the carbon-based PSC with a structure of FTO/TiO2/perovskite/carbon using the CsPbIBr2 perovskite film with 2.5 wt% CA achieves a champion efficiency of 7.52%, which is increased by 40.8% compared with the cell based on pure CsPbIBr2 perovskite film. In addition, the PSC based on CsPbIBr2 film with CA exhibits an excellent long-term stability under both ambient condition and highhumidity environment.