Surface treatment of Mixed-Halide CsPb(BrxI1-x)(3) perovskite quantum dots for thermal stability enhancement

Abstract

In this study, the thermal stability of mixed-halide CsPb(BrxI1-x)(3) perovskite quantum dots was investigated by monitoring its absorption, photoluminescence spectra, and X-ray diffraction. CsPb(Br0.8I0.2)(3) was found to be the most stable composition at a constant temperature of 100 degrees C for up to 96 h, although some agglomeration was observed. In contrast, CsPb(Br0.2I0.8)(3) revealed the most unstable composition under the same conditions as the aggregated iodide-rich domain easily transformed into the yellow-colored, non-luminescent delta-phase. CsPb(Br0.5I0.5)(3) also showed phase segregation, where its original phase separated into bromide-rich and iodide-rich domains. By passivating the surface of mixed-halide perovskite, the particle agglomeration of CsPb(Br0.8I0.2)(3) and phase segregation of CsPb(Br0.5I0.5)(3) were significantly suppressed; however, the prevention of CsPb(Br0.2I0.8)(3) phase transformation was less successful.