Colour evolution of dynamic persistent luminescence of Zn3Ga2Ge2O10:Cr3+,Mn2+ phosphors for advanced anti-counterfeiting

Abstract

Persistent luminescent anti-counterfeiting materials and techniques are highly required to protect products and the rights and interests of consumers. However, traditional persistent materials maintain almost unchanged persistent luminescence (PersL) color after cessation of excitation and a characteristic that can be easily imitated using sophisticated forgery techniques. Herein, Zn₃Ga₂Ge₂O₁₀ (ZGGO):Cr,Mn phosphors with “chameleon” PersL behavior are developed. Strong red and green PersL can be obtained simultaneously after the cessation of UV excitation. In addition to the color changes observed in photoluminescence (PL), these phosphors exhibit a dynamic shift in PersL color from green to yellow/red within a single phosphor with a time delay or in response to an environment temperature increase. The mechanism of the temperature-dependent changeable color in PersL is proposed based on different carrier paths for different traps via temperature management. Persistent materials easily integrate the advantages of changeable PL color by excitation wavelength management and PersL colors via temperature management into the same phosphor. Especially, these phosphors are simultaneously used in information storage and multi-level encryption, promising enormous potential for next-generation anti-counterfeiting applications.