Temperature induces the change of CsPbBr1.5I1.5 perovskite nanocrystals and affects luminescence properties

Colloidal CsPbBr3−x I x QDs have been investigated that possess a two-phase region for some ranges of intermediate compositions, and CsPbBr1.5I1.5 happens to be in this range. We focus on the structural changes of CsPbBr1.5I1.5 after heat treatment and the correlation between the structural changes and luminescence properties. The results show that with the increase in heat treatment temperature, iodine is partially precipitated to form PbI2, and the decrease of the iodine element content leads to the transformation from the orthorhombic δ-phase to cubic or nearly cubic orthorhombic γ-phase. At the same time, the blue shift followed by red shift occurred in the standard photoluminescence (PL) spectrum, and the PL intensity decreases.