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

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.