Colloidal Synthesis and Optical Properties of All-Inorganic Low-Dimensional Cesium Copper Halide Nanocrystals

Low-dimensional metal halides have recently attracted extensive attention owing to their unique structure and photoelectric properties. Herein, we report the colloidal synthesis of all-inorganic low-dimensional cesium copper halide nanocrystals (NCs) by adopting a hot-injection approach. Using the same reactants and ligands, but different reaction temperatures, both 1D CsCu₂ I₃ nanorods and 0D Cs₃ Cu₂ I₅ NCs can be prepared. Density functional theory indicates that the reduced dimensionality in 1D CsCu₂ I₃ compared to 0D Cs₃ Cu₂ I₅ makes the excitons more localized, which accounts for the strong emission of 0D Cs₃ Cu₂ I₅ NCs. Subsequent optical characterization reveals that the highly luminescent, strongly Stokes-shifted broadband emission of 0D Cs₃ Cu₂ I₅ NCs arises from the self-trapped excitons. Our findings not only present a method to control the synthesis of low-dimensional cesium copper halide nanocrystals but also highlight the potential of 0D Cs₃ Cu₂ I₅ NCs in optoelectronics.