Low-Temperature Discrimination of Defect States by Exciton Dynamics in Thin-Film MAPbBr₃ Perovskite

Exciton dynamics significantly influences the performance of the optoelectronic devices, which is intensively studied in the light-emitting perovskite of CH₃NH₃PbBr₃ (MAPbBr₃). However, most of the existing investigations have focused on the free excitons. In this study, we investigate the emissive recombination from defect states in MAPbBr₃ using temperature- and excitation-dependent photoluminescence measurements. It is revealed that two emission peaks centered at about 550 and 590 nm are presented at temperatures as low as 10 K, instead of one peak at 535 nm for the observation at room temperature. These two peaks are attributed to the emission of bound excitons after self-absorption and bulk defects, respectively. It is found that the distribution of the bound and trapped excitons is strongly influenced by the morphology of the MAPbBr₃ films. These results provide deep insights into the exciton dynamics in MAPbBr₃, facilitating new physics for the design of related optoelectronic materials and devices.