Cryogenic photoluminescence study on perovskite MAPbBr3 single crystals

We investigated the cryogenic photoluminescence process of MAPbBr3 single crystal from 10 K to 120 K. The PL spectra can be fitted by Gauss functions perfectly, and the free excitons as well as bound excitons emission coexist. During the cryogenic recombination process, the exciton localization effect and the thermal effect both react on the MAPbBr3 single crystal. From 10 K to 55 K, the localization effect is dominant due to the lower temperature, the excitons are inclined to migrate toward lower energy sites and cause the red-shift with narrow widths. Simultaneously, the localization effect tends to weaken with the temperature increasing, and the intensities gradually enhance. From 55 K to 120 K, the thermal effect becomes stronger than the localization effect, and becomes the dominant factor. Due to the thermal quenching effect and multi-broadening mechanism, all emissions present lower intensities and wider profile. Meanwhile, the thermal expansion of crystal lattice contributes to the emission blueshift. The competition between exciton localization effect and thermal effect determines the PL non-monotonic variation of the MAPbBr3 single crystal in the cryogenic process.