Temperature effect on spectral properties of cesium lead bromide perovskite nanocrystals in borogermanate glass

This work is devoted to the study of phase transitions in CsPbBr₃ perovskite nanocrystals nucleated in borogermanate glass. Perovskite nanocrystals are obtained by bulk crystallization in a glass matrix. A series of glass samples with nanocrystals of different sizes is investigated. Upon heating, the temperature dependence of the 1S exciton intensity for the entire series of samples shows the presence of three phase transitions: in the range 130-150, 440-450, and 510-515°C. The first phase transition refers to the transition from a tetragonal to a cubic structure. The last phase transition is associated with the melting of the crystalline phase. The phase transition at 440°С is declared for the first time. Upon cooling, the temperature curve shows the presence of only one phase transition in the region of 330°C, which is associated with the crystallization onset of CsPbBr₃ perovskite nanocrystals in glass matrix.