Preparation of CsPbBr₃ Films for Efficient Perovskite Solar Cells from Aqueous Solutions

Toxic organic solvents are widely used in fabricating perovskite solar cells, which pose a potential threat to human health and the environment. Here, we try to prepare high-quality all-inorganic perovskite films from all aqueous solutions using a traditional two-step method. A continuous PbBr2 precursor film is first prepared from a HBr/H2O solution added with a certain amount of poly(ethylene glycol) (PEG). The PEG plays important roles in adjusting the viscosity of the aqueous solution and affecting the growth of the PbBr2 precursor crystals. A high concentration of the CsBr/H2O solution is then spin-coated on the PbBr2 precursor film followed by annealing to form a high-quality CsPbBr3 film. The CsPbBr3 perovskite solar cells prepared from the aqueous solutions show an efficiency of 7.19%, which is higher than those prepared from the organic solvents in the same conditions. It is a facile and green method to eliminate the solvent toxicity derived from organic solvents in fabricating perovskite solar cells.