Photo-induced PL colour change and anion migration of CsPb(Br,I)3 perovskite nanocrystals in glass-ceramics

Mixed halide perovskites have attracted significant attention due to their potential in solar energy applications. However, owing to their inherent structural instability, these materials may exhibit fluorescence color changes when exposed to light through phase segregation and lattice distortions(1,2) which can lead to degradation in device performance. This phenomenon has been studied both in thin film and single crystals, but very limited in glass-ceramics. We report a glass-ceramics containing CsPb(Br,I)3 perovskite nanocrystals, which exhibits a fluorescence color change from yellow to red upon UV illumination (Figure 1(a). This transition suggests that the luminescent component undergoes a transformation from a bromide-rich phase to an iodide-rich phase. In a dark environment, the sample gradually recovers to pre-illumination state. The changes in fluorescence intensity under continuous illumination suggest that ion exchange and defect migration occur between the nanocrystals and the surrounding amorphous matrix (Figure 1(b).