Potential Applications of Tb3+/Ho3+-Codoped Cs2AgInCl6 Nanocrystals in Color Codes and Encryption

Up until now, the applications of lanthanide ion-doped lead-free double perovskite Cs2AgInCl6 nanocrystals (NCs) have been rarely reported, especially in fluorescence anticounterfeiting and coding. Here, we successfully incorporated Tb3+/Ho3+ ions into Cs2AgInCl6 NCs by the hot-injection method. Benefiting from the energy transfer process, Tb3+- and Ho3+-codoped Cs2AgInCl6 NCs showed tunable emission color in a green-blue-orange triangle region. Combining our NCs with transparent ink for printing, we put forward the applications of color bar codes and color QR codes (3D codes) as well as information encryption. Compared with traditional codes, color bar codes and 3D codes conquer the shortcomings of low information density, weak information security, and poor aesthetics. Furthermore, through double-mode excitation, we list an encoding table corresponding to 26 letters and 10 numbers. The encoding table embodies the application value of information encryption and coding.