Excitation Wavelength Regulated Dynamic Luminescence in Bi/Sb co‐Doped Tin Halide for Encrypted Information Transmission and High‐Sensitivity Wavelength Sensor

Abstract The coordination structure of Sb³⁺ within the host lattice critically influences its photophysical properties, sparking interest in luminescent metal halides with multiexciton emissions. Furthermore, the multi‐coordination lattice structure of Sb³⁺ dynamically emits light with excitation wavelength, highlighting the potential of Sb³⁺ ions in tuning luminescence and developing advanced optoelectronic materials. Herein, Sb³⁺ ions are successfully doped into Cs₂SnCl₆, and the obvious excitation wavelength‐dependent emission of Cs₂SnCl₆: Sb at room temperature is observed. To explain this phenomenon, density functional theory (DFT) calculations and time‐resolved spectra are conducted to confirm that the emission originated from two luminescence centers associated with the [SbCl₆]³⁻ and [SbCl₅]²⁻ coordination. Based on the tunable emission of Cs₂SnCl₆: Sb and the effective electron transfer between two triplet self‐trapped exciton states induced by Bi³⁺ and Sb³⁺, a pixelated code for information encryption is designed. The encoded patterns exhibit color changes under different UV wavelengths, enabling secure and straightforward information encryption. Furthermore, a sensitive UV wavelength sensor is prepared based on Cs₂SnCl₆: Bi/Sb, exploiting the monotonic relationship between chromaticity coordinates and wavelength, achieving a resolution superior to previously reported wavelength sensors. This study marks a substantial step toward advancing the multifunctional application of lead‐free metal halides.