Cluster Stabilization: Breaking Heat Barrier in NIR Glass‐In‐Phosphors

The increasing demand for thermally robust near‐infrared (NIR) light sources has spurred the development of advanced phosphor designs beyond conventional host matrix engineering. Here, we propose a glass‐enabled stabilization strategy that integrates Mg 0.98 Ga 1.94 O 4 :0.06Cr 3+ ,0.02Ni 2+ (MGO) with a 3CaO–Ga 2 O 3 –3GeO 2 glass to form a series of glass‐in‐phosphor (GIP) composites. The introduction of the glass phase does not alter the local coordination environment of the luminescent centers, but it markedly enhances lattice stability and suppresses nonradiative losses at elevated temperatures. Temperature‐dependent measurements consistently reveal markedly improved thermal robustness for all GIP composites compared with pristine MGO. By suppressing the thermally induced fragmentation of Cr 3+ cluster emitters, this thermal mechanism‐guided glass‐stabilization strategy establishes a robust platform for thermally stable NIR photonic materials, which enables reliable, high‐power operation of NIR pc‐LED light sources under harsh thermal conditions.