Multicolor luminescence of Cs₂KLuCl₆ for anti-counterfeiting and information encryption applications

Sb³⁺-doped inorganic perovskites have attracted great attention for anti-counterfeiting and information encryption applications due to their excellent optical properties. We have synthesized a novel perovskite, Cs₂KLuCl₆, which exhibits weak cyan emission originating from the self-trapped excitons (STEs) of the host. Its photoluminescence quantum yield is enhanced from 2% to 68% by Sb³⁺ doping. The energy transfer channel from the STEs to Ho³⁺ was constructed, and the luminescent color was modulated from cyan to white with increasing Ho³⁺ doping concentration. The Sb³⁺/Ho³⁺ co-doped sample has two-color luminescence performance due to the introduction of new emission centers. Up-conversion green emission was obtained by introducing Yb³⁺/Er³⁺. Finally, the optical properties of the obtained samples were utilized to design an anti-counterfeit label and information encryption strategy.