Yb3+/Eu3+/Ho3+ Tridoped Cs2Ag0.3Na0.7InCl6 Double Perovskite with Excitation-Wavelength-Dependent Triple Emission for Anti-Counterfeiting Application

Developing a secure anti-counterfeiting technology with more dimensional encryptions is urgently demanded. The lead-free double perovskite (DP) family represented by A2BIBIIIX6 hold great potential for applications in advanced fluorescence anti-counterfeiting owing to of large-bandgap engineering via BI/BIII site transmutation or exotic dopants. Herein, Ln3+ (Ln3+ = Eu3+, Ho3+, and Yb3+)-doped Cs2Ag0.3Na0.7InCl6 DP microcrystals (MCs) were firstly successfully synthesized by a hydrothermal method. By selective excitation of different luminescence centrals through precise control of excitation wavelength, we demonstrate dynamic color tuning in the Ln3+-doped Cs2Ag0.3Na0.7InCl6 DPMCs. Specifically, under various excitations of UV 300, 394, and NIR 980 nm, the as-synthesized DPMCs display triple emissions of warm yellow, red, and green, respectively. The warm yellow light stems from the self-trapped exciton (STE) downconversion (DC) luminescence of the DP matrix, while the red and green lights can be attributed to the strong Eu3+ 5D0→7FJ (J = 1, 2, 3, 4) DC luminescence and Ho3+ (5F4→5I8) upconversion (UC) luminescence sensitized by Yb3+. Thus, the as-synthesized Ln3+-doped Cs2Ag0.3Na0.7InCl6 DPMCs, which possess tunable combined DC/UC luminescence, show great potential to be an anti-counterfeiting material with a high security level.