Lanthanide doped Cs2Ag1-xNaxBiCl6 as an efficient anti-counterfeiting and information encryption material

Luminescent anti-counterfeiting materials based on double perovskite has attracted people's attention due to its low cost, high stability, easy preparation, and environmental friendliness. However, advanced anti-counterfeiting and information encryption call for materials with multi-color emission and multimode excitation to avoid being imitated and replaced. In this study, upconversion luminescence of lanthanide Cs2Ag1-xNaxBiCl6 were investigated through adjusting the feed ratio of Ag + to Na+ and controlling the types and concentrations of the lanthanide ions. Cs2Ag0.4Na0.6BiCl6-Yb-Er emits green light under excitation at 980 and 1540 nm. Cs2Ag0.4Na0.6BiCl6-Yb-Tm and Cs2Ag0.4Na0.6BiCl6-Yb-Ho show purple and white light under excitation at 980 nm, respectively. Under excitation at 365 nm, the Cs2Ag0.4Na0.6BiCl6-Yb-Er presents yellow light, while both Cs2Ag0.4Na0.6BiCl6-Yb-Tm and Cs2Ag0.4Na0.6BiCl6-Yb-Ho exhibit orange-red light. Additionally, Yb ions doping make three samples present good near-infrared luminescent properties. At last, the high level anti-counterfeiting and information encryption applications based on lanthanide doped Cs2Ag1-xNaxBiCl6 were designed and implemented, using the characteristics of the material's luminescence properties that differ with the type of doping, excitation wavelength, and excitation power. This work indicates that lanthanide doped double perovskite has the potential to obtain more efficient anti-counterfeiting materials and information encryption materials.