Unraveling All?Inorganic CsPbI ₃ and CsPbI ₂ Br Perovskite Thin Films Formation – Black Phase Stabilization by Cs ₂ PbCl ₂ I ₂ Addition and Flash?Annealing

Phase formation and transformation of 3D inorganic halide perovskites CsPbI3 CsPbI2Br were investigated by in-situ X-ray diffraction (XRD) in nitrogen or air from 30 °C up to 320 °C. Thin films obtained spin-coating a liquid solution salt precursors dissolved DMSO under normal conditions. XRD data analysis, using the Le Bail method, evidenced for first time, our knowledge, spontaneous crystallization black orthorhombic ? phase at ambient temperature, both perovskite phases. For once, this could be studied upon heating. It transforms tetragonal ? cubic ? The reverse transitions also cooling. influence all-inorganic 2D Cs2PbI2Cl2 material addition over stability was unprecedently analyzed XRD. mixture phases, mix [3D+2D], exhibits an improved compared single phase, tends induce highly oriented thin increased compactness, probably due chemical insertion anchoring. Finally, flash-annealed various temperatures (RT<T<325 °C) air, alone presence studied. A more textured layer is [3D+2D] film, showing larger grains compact above 200 film 300 remained four days after exposure 50 % relative humidity.