Cu+@Sb3+-Codoped All-Inorganic Metal Halide of Cs2ZnCl4 with Tunable Dual Emission for Fluorescence Anticounterfeiting and Information Encryption

In recent years, low-dimensional lead-free metal halides have captured wide interest in the application of fluorescence anticounterfeiting due to their unique optical properties, low toxicity, and excellent environmental stability. Herein, we report an effective multimode photoluminescent material of Cu+@Sb3+-codoped Cs2ZnCl4 microcrystals via a facile solution synthesis method. Upon a 365 nm ultraviolet (UV) excitation, Cu+@Sb3+-codoped Cs2ZnCl4 shines a highly efficient broad red emission band at 714 nm. Under a 254 nm UV irradiation, this codoped compound exhibits a dual-band emission with an additional high-intensity emission band at 492 nm, enabling a bright sky-blue emission to be observed. The study of the photophysical mechanism reveals that the observed dual-emission bands at 492 and 714 nm in this compound stem from the self-trapped exciton emission of [CuCl4]3– and [SbCl4]− clusters, respectively. In addition, inspired by the obvious excitation-wavelength-dependent emission characteristics and excellent stabilities of Cu+@Sb3+-codoped Cs2ZnCl4, we successfully applied this compound to fluorescent anticounterfeiting and information encryption–decryption applications.