Bi and Sb Codoped Cs₂Ag_0.1Na_0.9InCl₆ Double Perovskite with Excitation-Wavelength-Dependent Dual-Emission for Anti-Counterfeiting Application

The growing demands for optical anti-counterfeiting technology require the development of new environmentally friendly materials with single component, multimodal fluorescence and high stability. Herein, the Bi/Sb codoped Cs₂Ag_0.1Na_0.9InCl₆ lead-free double perovskite material is reported as an efficient multimodal luminescence material with excitation-wavelength-dependent emission. When excited by 360 nm UV light, dual-emission is observed at 455 and 560 nm, which comes from the ³P₁-¹S₀ transition of Sb³⁺ ions and self-trapped excitons (STEs), respectively. Under the 320 nm UV lamp, the microcrystals show only a blue emission centered at 455 nm. Therefore, the Bi/Sb codoped Cs₂Ag_0.1Na_0.9InCl₆ double perovskite emits blue and yellow lights under the 320 and 360 nm UV lamp, respectively. Moreover, the obtained double perovskite shows a high PLQY up to 41% and excellent stability against both air and high temperature, which make it a promising anti-counterfeiting material.