Impact of iodide substitution on the physical properties and stability of cesium lead halide perovskite thin films CsPbBr3−xIx (0 ≤ x ≤ 1)

This study sheds light on the effect of iodide substitution on the structural and optical properties of solution processed mixed cesium lead perovskite thin films CsPbBr3−xIx (0 ≤ x ≤ 1) as well as their atmospheric and thermal stability. Pawley fit indicated that the mixed lead halide CsPbBr3−xIx perovskite crystallizes in the orthorhombic (Pnma) space group. X-ray diffraction analyses showed a shift to lower angles when the average fraction of iodide incorporated increased indicating the expansion of the lattice. Absorbance measurements show that the CsPbBr3−xIx films exhibit a very high absorbance in the visible and short infrared region. The band gap of CsPbBr3−xIx is tuned from 2.38 (CsPbBr3) to 2.17 eV (CsPbBr2I1) following the Vegard's law. CsPbBr3 films showed a bright photoluminescence with emission maximum at 530 nm CsPbBr3−xIx films demonstrate excellent stability after aging for two days in a humid environment (relative humidity of ∼60%) and under thermal annealing at relatively high temperature.