In the process of preparing CsPbBr₃ films by two-step or multi-step methods, due to the low solubility of CsBr in organic solvents, the prepared perovskite films often have a large number of holes, which is definitely not conducive to the performance of CsPbBr₃ perovskite solar cells (PSCs). In response to this problem, this article proposed a method of introducing InBr₃ into the PbBr₂ precursor to prepare a porous PbBr₂ film to increase the reaction efficiency between CsBr and PbBr₂ and achieve the purpose of In (Ⅲ) incorporation, which not only optimized the morphology of the produced CsPbBr₃ film but also enhanced the charge extraction and transport capabilities, which was ascribed to the reduction of the trap state density and impurity phases in the perovskite films, improving the performance of CsPbBr₃ PSCs. At the optimal InBr₃ concentration of 0.21 M, the InBr₃:CsPbBr₃ perovskite solar cell exhibited a power conversion efficiency of 6.48%, which was significantly higher than that of the pristine device.

Due to the low solubility of CsBr in organic solvents, the CsPbBr₃ film prepared by the multi-step method has holes and insufficient thickness, and the light absorption capacity and current density of the perovskite film hinder the further improvement in the power conversion efficiency (PCE) of CsPbBr₃ solar cells. In this study, we introduced InBr₃ into the PbBr₂ precursor solution and adjusted the concentration of PbBr₂, successfully prepared PbBr₂ with a porous structure on the compact TiO₂ (c-TiO₂) substrate to ensure that it fully reacted with CsBr, and obtained the planar carbon-based CsPbBr₃ solar cells with high-quality perovskite film. The results reveal that the porous PbBr₂ structure and the increasing PbBr₂ concentration are beneficial to increase the thickness of the CsPbBr₃ films, optimize the surface morphology, and significantly enhance the light absorption capacity. Finally, the PCE of the CsPbBr₃ solar cells obtained after conditions optimization was 5.76%.