Temperature-induced localized exciton dynamics in inorganic CsPbX3 (X=I, Br, Cl) perovskite nanocrystals

Abstract

The exceptional luminescent properties of inorganic halide perovskites have recently garnered significant attention. This study comprehensively investigates the temperature dependence of the anomalous behavior of localized excitons in inorganic CsPbX₃ (X = I, Br, and Cl) perovskite nanocrystals (NCs). A quantitative model has been developed to determine the photoluminescence (PL) peak energy and PL linewidth through a broad temperature range (from 10 K to 300 K) using Monte Carlo simulation of exciton relaxation and hopping processes. Incorporating temperature-induced bandgap expansion allows for a quantitative fit of our computational model to the experimental findings. The PL peak energies of all CsPbX₃ NCs exhibit a blue shift due to the localization of excitons in higher energy states at elevated temperatures. On moving from X = I to Br to Cl, the rate of bandgap expansion decreases with temperature, which indicates that the ionic bond between cation and anion becomes stronger, resulting in less shifting in PL peak energy. The PL linewidth is significantly influenced by thermal disorder, resulting in a noticeable increase in the full-width half maximum (FWHM) as the temperature rises. Additionally, it has been observed that excitons in deeper localized states are minimal in CsPbBr₃ and CsPbCl₃. This study is important in understanding and optimizing the performance, tuning the emission characteristics, and improving the reliability of cesium halide perovskite-based devices.