Ultraviolet Light-Induced Degradation of Luminescence in Mn-Doped CsPbCl3 Nanocrystals

Improving the photostability of highly luminescent Mn2+ doped all-inorganic halide perovskite nanocrystals (NCs) is challenging because their excellent optical performances are determined by the stable structure and low defect/trap states. The optical properties of Mn2+ doped CsPbCl3 (Mn2+:CsPbCl3) NCs with various Mn2+ doping concentrations under ultraviolet (UV) illumination were studied to unravel their photodegradation by using photoluminescence (PL) spectroscopy at room temperature. The PL intensities of band-edge excitons and Mn2+ ions in the Mn2+:CsPbCl3 NC films significantly decreased due to formation of nonradiative defects/traps in NCs with increasing illumination times. It was surprisingly found that the single- and multiexponential decay times (1.81-1.15 ms) of Mn2+ emissions ranging from 595 to 640 nm observed in the doped NC films with low and high Mn/Pb ratios were almost not varied with increasing UV illumination times. However, the blue-shift of Mn2+ emission was observed in high Mn2+ doping concentration NCs under illumination, which might result from the diffusion of Mn2+ ions to the surface of doped NCs. Further, the surface passivation of Mn2+ :CsPbCl3 NCs by using a Cs4PbCl6 shell was found to effectively suppress the photodegradation of Mn2+:CsPbCl3 NCs and enhance the PL stability of Mn2+.