Mechanisms of Enhanced Efficiency and Stability in Perovskite Luminescence via Rb Interstitial Doping

Metal halide perovskites have garnered significant attention due to their exceptional photoelectric properties. The alkali metal doping strategy has been demonstrated to effectively modulate grain size, control crystallization kinetics, and adjust band gap characteristics in perovskite. This study employs the first-principles calculations to reveal that the selection of alkali metal species and their corresponding doping methodologies exert markedly distinct influences on both the electronic properties and ion migration kinetics of CsPbBr₃ perovskites. There is an increase in the effective mass of electrons and holes in most alkali-metal substitutions and in all interstitial occupancy systems, which increases the exciton binding energy and radiation rate. Meanwhile, calculations demonstrate that alkali metal interstitial occupancy suppresses halide ion migration by simultaneously extending diffusion pathways and strengthening Br^- interactions, significantly increasing the migration barrier from 0.113 to 0.902 eV in the perovskite lattice. The Rb interstitial doped system exhibits high photoluminescence quantum yield (PLQY) and stability, retaining 87% of the original PLQY after heating at 300 °C for 30 min. This work offers a new method to optimize the performance of devices.