Enhanced Luminescence and Stability of Cesium Lead Halide Perovskite CsPbX₃ Nanocrystals by Cu²⁺-Assisted Anion Exchange Reactions

Abstract

Inorganic CsPbX3 perovskite nanocrystals (NCs) have exhibited great optical properties, such as tunable emission wavelength, narrow emission line-widths, and high photoluminescent quantum yields. However, the unstable crystal structure of perovskite CsPbX3 NCs lead to a deterioration in optical performance. In this work, it is demonstrated that inorganic perovskite NCs, including CsPbCl3 and CsPbBr3-xClx NCs with excellent photoluminescence quantum yield and optical stability can be improved via anion exchange reaction treated with a new halide precursor consisting of copper halide– (CuX2−) oleylamine (OLA) complexes. Unlike traditional perovskite synthesized processes for better crystalline structures operated at high temperatures, this work offers an economical method operable at the room temperatures. The treated CsPbX3 perovskite nanocrystals were characterized by in situ photoluminescence (PL) spectra and in situ X-ray diffraction (XRD). Cu2+ ions were only absorbed on the surface of perovskite NCs confirmed by the X-ray absorption spectroscopy (XAS) analysis. Density functional theory calculation explained that the origin of high stability and good crystallinity for treated perovskite NCs stemmed from adsorption of CuCl2 on perovskite’s surface to passivate defect sites during the recrystallization process.