Excitation wavelength-dependent emission of Mn2+/Sn2+ co-doped Cs3ZnI5 for optical fluorescence anti-counterfeiting applications

Abstract

Conventional fluorescent anti-counterfeiting techniques are monolithic, however, most of them involve single-mode emission and are easily forged. Thus, it is especially important to develop efficient multimodal fluorescent anti-counterfeiting materials. Herein, we report a fluorescent material with double multicolor emission, Cs₃ZnI₅:Mn²⁺/Sn²⁺, that exhibits yellow-red emission at 555 nm and 690 nm under 405 nm laser excitation. Its temperature-dependent spectroscopic characteristics are used to investigate the effect of the thermal property and stability on the photoluminescence (PL) and structure of Cs₃ZnI₅:Mn²⁺/Sn²⁺, whose PL is mainly attributed to the ³P₁–¹S₀ transition of the self-trapped exciton and ⁴T₁–⁶A₁ transitions of Mn²⁺. Under 360 nm laser excitation, the single crystals (SCs) show only red emission centered at 670 nm, which has excitation wavelength-dependent properties and excellent thermal stability. The obtained materials are excitation wavelength-dependent, and this co-doping strategy promotes the application of novel metal halide materials in the fields of fluorescent anti-counterfeiting and information encryption/decryption.