Phase transition behavior enabling reversible luminescence in the novel Sb3+ doped double perovskite Cs2KInCl6 for advanced anti-counterfeiting applications

With the continuous advancement of counterfeiting technologies, traditional static anti-counterfeiting systems have exhibited inherent security vulnerabilities, urgently necessitating the development of novel intelligent anti-counterfeiting materials with multi-stimulus responsive mechanisms. This study developed a solvent evaporation crystallization method to successfully synthesize a novel lead-free halide double perovskite (LHDPs) Cs 2 KInCl 6 : Sb 3+ , which exhibits multi-color intelligent luminescence. By precisely controlling humidity and temperature, Cs 2 KInCl 6 : Sb 3+ can undergo reversible luminescence transitions from "green → yellow (Cs 2 InCl 5 (H 2 O): Sb 3+ ) → green". The unique stimulus-responsive behavior originates from the material's high sensitivity to water molecule adsorption/desorption, making it applicable for information encryption systems. Density functional theory calculations reveal that Sb 3+ -doped introduces intermediate energy levels, reducing the bandgaps of Cs 2 InCl 5 (H 2 O), Cs 3 In 2 Cl 9 , and Cs 2 KInCl 6 , which enhances their light absorption and emission properties. Moreover, LHDPs Cs 2 KInCl 6 : Sb 3+ maintain 93 % of their initial luminescence intensity at high temperatures (403 K), demonstrating excellent thermal stability. This study elucidates the luminescence regulation mechanism of Sb 3+ -doped LHDPs and establishes a dynamic color switching model ("structural phase transition-optical response"), providing theoretical support for design next-generation smart anti-counterfeiting materials and developing of high-temperature stable luminescent devices.