Thermal Quenching and Antiquenching of Photoluminescence in Solution-Grown Cs4PbBr6 Perovskite Single Crystals

Cs4PbBr6 perovskites have attracted much attention recently due to their outstanding optical properties including efficient and narrowband green emission and unexpected high exciton binding energy. In this work, the exciton recombination behaviors in solutio-grown Cs4PbBr6 single crystals were investigated via temperaturedependent photoluminescence (PL) spectroscopy in the temperature range of 83-293 K. X-ray diffraction as well as room-temperature PL and absorption investigations suggested that the efficient green emission was attributed to the parasitic CsPbBr3 nanocrystals embedded in the Cs4PbBr6 host matrix. With increasing temperature, the PL spectrum blueshifted and broadened monotonously. In addition, thermal quenching and antiquenching behaviors of PL emission were observed, which involves exciton trapping by CsPbBr3 nanocrystal surface defect states, exciton dissociation, and delocalization of excitons localized at CsPbBr3/Cs4PbBr6 interface states. Accordingly, a schematic model was finally proposed. The results reported in this paper will provide valuable insights into the origination of efficient green emission observed in Cs4PbBr6 perovskites.