Novel green-emitting copper-doped Cs₂ZnCl₄ synthesized via low-temperature solid-state reaction using a small amount of water

All-inorganic halides exhibit excellent optical as well as luminescence properties. Among them, non-toxic copper-doped halide Cs₂ZnCl₄ with high stability is a promising material. However, the conventional method for preparing these materials, using the hot injection technique, is unsuitable for mass production. Therefore, herein, we suggest a simple and low-temperature (below 100 °C) method without using special equipment, regents, and treatments. Cu-doped Cs₂ZnCl₄ was successfully synthesized using the water-assisted solid-state reaction (WASSR) method, and the oxidation state of Cu in the samples was estimated through the iodometric titration technique. The optical and luminescence properties were investigated using the absorption and photoluminescence excitation/emission spectra. Significantly, Cu-doped Cs₂ZnCl₄ exhibited unique green emission centered at ³520 nm under ultraviolet irradiation. Moreover, the oxidation of Cu in the Cs₂ZnCl₄ lattice was suppressed owing to the low-temperature conditions in the WASSR.