CsPbBr3 Nanoplatelets: Synthesis and Understanding of Ultraviolet Light-Induced Structural Phase Change and Luminescence Degradation

Abstract

CsPbBr3 perovskite nanocrystals (mainly nanoplatelet morphology) have attracted attention due to their promising applications in optoelectronic devices. However, ultraviolet (UV) light exposure to these materials is one of the major factors for the degradation of halide perovskite nanocrystals, which needs to be studied to improve stability and boost performance. In this study, we synthesized CsPbBr3 perovskite nanoplatelets utilizing a hot injection method. The UV illumination effect on luminescence and structural properties of perovskite CsPbBr3 nanoplatelets were studied in detail. Under UV light illumination, less-emissive phases like CsPb2Br5 were observed within 10 h. However, long-term (i.e., 48 h) illumination of UV light resulted in the formation of some trace of PbCO3 and PbO phases that causes further degradation of perovskite CsPbBr3 nanoplatelets. This was verified by a significant decrease in photoluminescence (PL) intensity. Interestingly, UV light treated samples exhibited a stable CsPb2Br5 phase, which was observed after aging for a long period (∼9 months) of time that showed no further degradation. Furthermore, X-ray diffraction and full-width half maxima results confirmed an increase in crystalline size with illumination time increase. Obtained results strongly indicate that the UV light-induced PL degradation and trap state formation causes a synergistic effect of photo annealing in the presence of oxygen and moisture.