Effect of doping on the phase stability and photophysical properties of CsPbI(2)Br perovskite thin films

In this study, we demonstrate that the crystallization process of CsPbI(2)Br films can be modulated when small amounts of additives are added to the precursor solution, leading to the formation of the bright brownish α-phase perovskite films with high orientation along the [100] crystallographic direction. Doped CsPbI(2)Br films exhibit improved crystallinity, with high coverage, large grain size and pinhole-free surface morphology, suitable for making high performance optoelectronic devices. We also explored the role of Cl in the photophysical properties of CsPbI(2)Br perovskite films using the temperature dependent photoluminescence technique. We found that the Cl ions enhance the photoluminescence emission by reducing the density of trap states, and also decrease the exciton binding energy from (22 ± 3) meV to (11 ± 2) meV. We believe this work contributes to understanding the effect of doping on the crystallization process with an in-depth insight into the photophysical properties of the cesium-based perovskite materials.