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 solution-grown Cs₄PbBr₆ single crystals were investigated via temperature-dependent 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.