Advanced Optical Information Encryption Enabled by Polychromatic and Stimuli‐Responsive Luminescence of Sb‐Doped Double Perovskites

Abstract The smart materials with multi‐color and stimuli‐responsive luminescence are very promising for next generation of optical information encryption and anti‐counterfeiting, but these materials are still scarce. Herein, a multi‐level information encryption strategy is developed based on the polychromatic emission of Sb‐doped double perovskite powders (SDPPs). Cs 2 NaInCl 6 :Sb, Cs 2 KInCl 6 :Sb, and Cs 2 AgInCl 6 :Sb synthesized through coprecipitation methods exhibit broadband emissions with bright blue, cyan, and orange colors, respectively. The information transmitted by specific SDPP is encrypted when different SDPPs are mixed. The confidential information can be decrypted by selecting the corresponding narrowband filter. Then, an encrypted quick response (QR) code with improved security is demonstrated based on this multi‐channel selection strategy. Moreover, the three types of SDPPs exhibit three different water‐triggered luminescence switching behaviors. The confidential information represented by Cs 2 NaInCl 6 :Sb can be erased/recovered through a simple water spray/drying. Whereas, the information collected from the green channel is permanently erased by moisture, which fundamentally avoids information leakage. Therefore, different encryption schemes can be designed to meet a variety of encryption requirements. The multicolor and stimuli‐responsive luminescence greatly enrich the flexibility of optical information encryption, which leaps the level of security and confidentiality.