Near-unity near-infrared emission from Mo6 cluster doped hybrid halide glasses via halide-ligand and matrix engineering.

Efficient and air-stable near-infrared emitters are needed for compact optical systems, but translating highly emissive molecular triplet emitters into processable bulk solids remains challenging because aggregation, molecular motion and oxygen deactivate long-lived excited states. Here we show that a molecular hybrid halide glass can serve as a protective and regulating host for the triplet emission of molybdenum cluster. By comparing isostructural cluster salts with chloride, bromide and iodide terminal ligands, we establish how apical halide chemistry controls electronic structure and near-infrared radiative dynamics. The chloride-terminated cluster shows the highest efficiency among the molecular salts. When incorporated into a cadmium chloride-based molecular hybrid glass, the clusters become molecularly dispersed, while matrix-dictated halide redistribution and amorphous confinement suppress aggregation, vibrational deactivation and oxygen accessibility. The optimized glass achieves 96.95% internal quantum efficiency and 91.43% external quantum efficiency in air, enabling compact near-infrared illumination for imaging applications.