CsPbBr <sub>3</sub> Nanoplatelets: Synthesis and Understanding of Ultraviolet Light-Induced Structural Phase Change and Luminescence Degradation
Vandana Nagal, Virendra Kumar, Rahul Kumar, Kedar Singh, Ajit Khosla, Rafiq Ahmad, Aurangzeb Khurram Hafiz
Abstract
CsPbBr 3 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 CsPbBr 3 perovskite nanoplatelets utilizing a hot injection method. The UV illumination effect on luminescence and structural properties of perovskite CsPbBr 3 nanoplatelets were studied in detail. Under UV light illumination, less-emissive phases like CsPb 2 Br 5 were observed within 10 h. However, long-term (i.e., 48 h) illumination of UV light resulted in the formation of some trace of PbCO 3 and PbO phases that causes further degradation of perovskite CsPbBr 3 nanoplatelets. This was verified by a significant decrease in photoluminescence (PL) intensity. Interestingly, UV light treated samples exhibited a stable CsPb 2 Br 5 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.