Probing free and bound excitons in Eu-doped CsPbBr3 by temperature-dependent photoluminescence and time-resolved photoluminescence

This report presents the recombination mechanisms of free and bound excitons in Eu-doped CsPbBr3. Through temperature-dependent photoluminescence (PL), the emission intensity of free excitons decreased as the temperature decreased from 300 to 10 K. The emission intensity of bound excitons appeared at T = 100 K and increased rapidly as the temperature decreased to 10 K. These observations are attributable to the dynamic migration of thermal energy between free and bound excitons, which is caused by the richer Eu3+ ion. The exciton-like emission can be demonstrated through power-dependent PL. Furthermore, the radiative and nonradiative recombinations of the bound exciton were determined through temperature-dependent time resolved photoluminescence (TR-PL). As a function of emission energies, the PL lifetimes of the bound exciton were investigated to corroborate that the bound exciton has a larger localization depth with decreasing temperature, which is another reason for the increased emission intensity of the bound exciton.