Fabrication and characterization of all-inorganic halide perovskite CsPbBr3 films via the two–step sol–gel process: Impact of annealing temperature

Organic–inorganic hybrid perovskite solar cells (PSCs) have realized a 23.2% power conversion efficiency (PCE), thereby making the PSC application promising. However, the compositional instability of perovskites and PSCs in high-temperature and/or –humidity ambient air condition has restricted the PSC application. All–inorganic CsPbBr3-based PSCs can deal with the problem due to the high stability in heat and humidity of CsPbBr3. Perovskite CsPbBr3 is highly crystallized with micronscale crystallites by Pb2+ strongly coordinating with organic molecules in the one–step sol–gel process. By contrast, CsPbBr3 crystalizes in nanoscale crystallites in the two-step sol-gel process using nonpolar or weakly coordinating organic solvent. The related study is rarely reported so far. Herein, we reported the fabrication of all–inorganic perovskite CsPbBr3 films via the two–step sol–gel process using weakly coordinating methanol solvent. The impact of annealing temperature (Tanneal) was in particular studied on the film's microstructure and optical properties. The Increased Tanneal restricts the production of byproduct Cs4PbBr6 and greatly improves the film crystallization, thereby increasing the film's photoluminescence intensity and lifetime. A transition from the compressive stress to tensile stress in the films is observed at 250 °C Tanneal. The red shift in optical absorption edge with increased Tanneal is mainly due to the increased compressive stress and reduced tensile stress in the films.