Multi‐Self‐Trapped‐Exciton Engineering in Sb‐Doped Zr‐Hybrid‐Halides Towards Near‐Unity Quantum Efficiency and Excitation‐Tunable Luminescence

Luminescent materials with simultaneously high quantum efficiency and excitation‐tunable emission are highly desirable for advanced optoelectronic and information‐security applications, yet remain challenging to realize within a single, lead‐free material system. Here, we report a multi‐self‐trapped‐exciton (STE) engineering strategy in Zr‐based hybrid halides, where the deliberate introduction of Sb 3+ ions reconstructs the excitonic energy landscape of a zero‐dimensional host. Beyond the intrinsic Zr‐centered STE emission, Sb doping activates multiple Sb‐related STE states that efficiently capture organic triplet excitons, effectively suppressing room‐temperature phosphorescence while dramatically enhancing radiative recombination. As a result, the obtained phosphors simultaneously achieve nearly perfect photoluminescence efficiency and pronounced excitation‐dependent luminescence, with emission color continuously tunable from warm white to orange‐red. A 4×8 dot matrix system for ASCII encoding was designed using these materials, demonstrating a dynamic, time‐sequential decoding process that enhances information concealment and encryption. Finally, the materials were also incorporated into a digital display model for optical information encryption, where a deceptive message transforms into true information under different excitation wavelengths. This work emphasizes the attractiveness of Sb: ETPP 2 ZrCl 6 materials for high‐security applications, offering a new approach for developing advanced optoelectronic devices and smart labels.