Luminescence properties of CsPbBr3 single crystals and CsPbBr3 crystalline phases dispersed in a KBr matrix

Spectra of steady-state X-ray excited luminescence (XEL) and thermally stimulated luminescence (TSL) of CsPbBr3 single crystals in the temperature range of 80–294 K were studied. Each of the measured XEL spectra of CsPbBr3 single crystal contain only one elementary band peaking at 535 nm, which can be attributed to the radiative decay of the matrix exciton. The activation energy of exponential luminescence thermal quenching in this range, as determined by Mott's formula, is equal to 75 meV, close to the hole trap depth of 110 meV obtained for the main TSL peak of this crystal at 125 K. This value of the XEL quenching activation energy is associated with the thermal deactivation of the exciton hole component in the CsPbBr3 matrix. Doping of KBr crystals with CsPbBr3 perovskite impurities (0.05–1 mol. %) leads to the formation of CsPbBr3 micro- and nanocrystals in a KBr matrix with characteristic spectra of exciton photo- and XEL luminescence. A five-fold increase in the intensity of XEL was registered in KBr: CsPbBr3 (0.05 mol. %) samples at 294 K compared to that of CsPbBr3 single crystal. The temperature dependence of the XEL intensity of KBr: CsPbBr3 crystals and the analysis of their TSL integral curves allow us to make a conclusion about the hole mechanism of high-energy excitation energy transfer from the matrix to the activator resulting in the appearance of typical exciton luminescence in CsPbBr3 nanoparticles.