Intrinsic optical properties and structural transition of CsPbCl revealed by temperature dependent studies of a single microplatelet

A deep understanding of the luminescence mechanism of CsPbX 3 (X = Cl, Br, I) perovskite materials is crucial for enhancing their performance in optoelectronic devices. Nonetheless, uncertainties persist regarding the correlation between luminescence properties and structure. Taking an individual microplatelet (MP) as a research object allows for a more accurate reflection of the intrinsic characteristics of the CsPbCl 3 perovskite. Here, CsPbCl 3 MPs with an average size of 56 μm and a single crystalline structure have been prepared via the chemical vapor deposition (CVD) method and characterized systematically by temperature-dependent (T-D) photoluminescence (PL), Raman and XRD techniques. It has been found that multiple PL features attributed to free excitons, bound excitons, stimulated emission, phonon-assisted transition and defect-related emission could be deconvoluted for a single CsPbCl 3 MP. The variation of PL emission features and the evolution of TO phonon modes in Raman as a function of temperature are strongly correlated with a strong structural phase transition at about 200 K from the tetragonal to orthorhombic phase which was solidly confirmed by the T-D powder XRD results as well a weak phase transition at about 320 K. In addition, the T-D XRD results clearly indicated that the tetragonal phase exhibits negative thermal expansion (NTE), while positive thermal expansion (PTE) is observed for the orthorhombic phase. This study may provide guidelines for further exploring the fundamental photoluminescence properties across a broad temperature range and improving device performance rationally. Based on CsPbCl 3 single crystal microplatelets, intrinsic optical properties and structural phase transitions are revealed through temperature-dependent photoluminescence, Raman spectroscopy, and XRD techniques.