Tunable Emission Properties of Sb/Pb Co-Doped CsCdBr for Optical Anti-Counterfeiting Application.

Cd-based perovskite materials have the advantages of high emission efficiency and tunable emission, as well as broad application prospects in the field of optoelectronics. However, achieving multimode dynamic luminescence under UV light excitation in a single system is a great challenge. Here, we successfully prepared Sb/Pb co-doped CsCdBr crystals by a simple hydrothermal method. Tunable emission from orange to white and then to blue, covering the wavelength range between 370 and 800 nm, was achieved by varying the doping concentration of Pb ions in CsCdBr:0.5%Sb. Temperature-dependent photoluminescence (PL) spectra and density functional theory (DFT) calculations confirm that the wide-band white-light emission of CsCdBr: Sb/Pb crystal comes from the first self-trapped exciton (STE1) of undoped CsCdBr intrinsic capture state and the emission of free excitons (FEs) and STE2 induced by the confining effect and the Jahn-Teller effect by Pb incorporation, as well as the Sb triplet self-trapped exciton (STE3). More specifically, the samples with the best co-doped ratio exhibit significant excitation-wavelength-dependent luminescence characteristics and can realize the conversion of the emission color from white and blue to orange. Based on the tunable emission characteristics of three emission colors, the material has good prospects in encryption and anti-counterfeiting applications. This work provides a new strategy for the application of Cd-based halides in the field of anti-counterfeiting.