Self-Passivation of CsPbBr₃ Nanocrystals through Introducing Bromide Vacancies and Ultraviolet Irradiation

Abstract

Lead halide perovskites (LHP) nanocrystals (NCs) are promising materials for a variety of optoelectronic applications, especially for light-emitting diodes (LEDs), due to their high photoluminescence quantum yield (PLQY) and optically tunable bandgap. However, poor photostability is one of the major obstacles to their practical use. In this work, surface stoichiometry was modulated by lead oleate modification, and the effects of variation in surface stoichiometry on photostabiltiy of CsPbBr3 NCs were investigated. The experimental results show that the Br-rich surface is detrimental for their photostability, while the Br-deficient (in certain degrees) surface is favorable for photoactivation and following light-induced self-passivation. We reveal that coalescence will be dominant on an illuminated Br-rich surface, while defects annihilation and self-passivation due to light-induced bromide ion migration predominant on an illuminated Br-deficient surface. We provide evidence for the key role of surface stoichiometry in the photostabilty of LHP materials and demonstrate the possibility for taking advantage of photoinduced ion migration to improve the photostability of LHP materials.