Ultrabroadband and Temperature-Responsive Emission Achieved in All-Inorganic Metal Halide Single Crystal K ₂ Cu _0.95 Ag _0.05 Br ₃

Luminescent metal halide single crystal materials have attracted widespread attention in recent years due to their high luminescence efficiency and tunable spectral characteristics. However, the currently reported materials are limited in multifunctional lighting applications because of their relatively narrow emission spectra. In this study, by introducing Ag+ into K2CuBr3 to induce an isomorphic phase transition and generate a new lattice structure, we regulated the defect states and energy levels of the crystal, thereby achieving an ultrabroadband emission spectrum in the K2Cu0.95Ag0.05Br3 single crystal material. This material exhibits a high photoluminescence quantum yield of 38.52% and excellent environmental stability of 180 days, along with additional temperature-responsive luminescence properties. Through temperature-dependent spectroscopy and other experimental techniques, we systematically elucidated the luminescence characteristics and photophysical mechanisms of the crystal. Owing to its ultrabroadband emission and temperature-responsive luminescence behavior, this material shows great potential for applications in broadband solid-state lighting and advanced anticounterfeiting technologies, providing new insights and perspectives for the development of metal halide materials.