In the process of preparing perovskite polycrystalline films by solution method, toxic solvents are used, and heat treatment is still the main way to induce perovskite grain growth, which not only increases energy consumption, but also hinders the development of flexible solar cells. In order to avoid the use of toxic solvents and high-temperature process, CsPbBr₃ nanocrystal films are treated with low temperature solution to obtain corresponding polycrystalline thin films, which are applied to solar cells. Firstly, CsPbBr₃ nanocrystalline (nanocrystalline NC) ink precursor is prepared by hot injection method, and nanocrystalline film is prepared by spinning coating method. In atmospheric environment, CsPbBr₃ nanocrystalline films are prepared by saturated solution of Pb(SCN)₂ and NH₄Br methyl acetate. Using the CsPbBr₃ nanocrystalline film as an absorbing layer, the perovskite solar cell is prepared and the performance of the cell is effectively improved, and the efficiency of the cell reaches 8.43%. The results show that the saturated solution of Pb(SCN)₂ and NH₄Br methyl acetate (MA) can not only continue the nanocrystalline crystallization, but also effectively passivate the defects in the perovskite films. In the process of preparing CsPbBr₃ polycrystalline films, neither high temperature treatment nor the high boiling point toxic solvent is used, which is suitable for the preparation rigid and flexible solar cells.

The inorganic halide perovskite nanocrystals are developed and used as “ink” to fabricate fully air-processed, electrically stable solar cells. Although the prepared film is composed of mosaic nanocrystals capped with a large number of organic ligands and surface traps, this method provides a new approach for single-step, large-scale fabrication of inorganic perovskite devices. Moreover, the flexible control of the material composition provides a platform for uncovering the optimal conditions for optoelectronics and photonics.