Vertical Compositional Heterogeneity Induces Instability in All-Inorganic CsPbIBr₂ Perovskites

High Resolution Image Download MS PowerPoint Slide Understanding the vertical compositional homogeneity and defect distribution is of paramount importance in elucidating and maximizing the performance of halide-perovskite-based optoelectronic devices. This work reports the depth-dependent study of the chemical composition and metallic Pb 0 content of all-inorganic CsPbIBr 2 perovskite films undertaken using lab-based hard X-ray photoelectron spectroscopy and soft X-ray photoelectron spectroscopy. The presence of elemental or metallic Pb (Pb 0 ), in the bulk and at the surface of the perovskite films highlights the formation of defect or recombination centers throughout the analyzed depth. The Pb 0 content was found to be of higher concentration in the bulk of the CsPbIBr 2 films compared to that at the surface. Engineering the CsPbIBr 2 film growth using appropriate antisolvents resulted in the overall reduction and/or complete elimination of Pb 0 at the surface and at the bulk of the perovskite films. However, the effect of antisolvent treatment was significantly pronounced in the bulk-like region as compared to that at the surface. Pb 0 is synonymous with defect states/recombination centers in perovskite films and this reduction in defect density due to the antisolvent treatment corroborates the enhanced phase stability and improved solar cell performance of the corresponding CsPbIBr 2 devices.