The optical properties of Cs4PbBr6–CsPbBr3 perovskite composites

Although the optoelectronic applications of metal halide perovskites have been intensively investigated in recent years, the fundamental carrier dynamics of zero-dimensional (0D) Cs4PbBr6 perovskites has been relatively underexplored; in particular, the nature of the green fluorescence is highly debated. Nevertheless, the unique photophysical properties are of immense interest for a variety of potential applications. In this work, the green emission of the CsPbBr3–Cs4PbBr6 perovskite composites is studied using temperature dependent photoluminescence (PL). The PL spectra at different temperatures simultaneously contain two sub-peaks (520 nm and 550 nm), which are ascribed to the emissions of the band-edge and the defect trapped exciton of CsPbBr3. This finding will help to understand the controversial photoluminescence currently observed in different 0D Cs4PbBr6 perovskites.