Intrinsic optical properties and structural transition of CsPbCl3 revealed by temperature dependent studies of a single microplatelet

Abstract

A deep understanding of the luminescence mechanism of CsPbX₃ (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 CsPbCl₃ perovskite. Here, CsPbCl₃ 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 CsPbCl₃ 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.