Rb₂HfCl₆:Sb³⁺phosphors with tunable energy transfer for advanced information encryption and high-CRI WLEDS

The realization of controllable multi-excitonic emission within a single-phase system remains a formidable challenge, yet it holds the key to advancing next-generation smart optoelectronics. Herein, we strategically engineer a dynamic energy transfer landscape in the zero-dimensional (0D) vacancy ordered double perovskite Rb₂HfCl₆by introducing Sb³⁺dopants. In this 0D framework, the spatial isolation of [HfCl₆]^2-octahedron by Rb induces strong exciton localization, which provides a robust platform for efficient self-trapped exciton (STE) emission. By precisely tailoring the Sb³⁺impurity levels, we established an excitation wavelength driven equilibrium between the host and dopant STEs. This synergistic modulation not only relaxes the Sb parity forbidden transitions, elevating the photoluminescence quantum yield to 59%, but also enables a seamless switching of emission colors from green to orange-red under 254-365 nm excitation. Leveraging these unique optical signatures, we further demonstrate the material's potential in multilevel anticounterfeiting smart locks and high color rendering white LEDs (CRI = 90.2). This work underscores the power of excitonic state engineering in low dimensional metal halides for the rational design of smart-responsive photonic materials.