Ultra‐Broadband and Anti‐Thermal Quenching NIR Emission in ZnMgAl 10 O 17 :Cr 3+ via Cr 3+ Concentration Engineering

Broadband near‐infrared (NIR) phosphors that simultaneously deliver high efficiency and good thermal stability are highly desired for NIR phosphor‐converted light‐emitting diodes (pc‐LEDs), yet remain difficult to achieve. Here, blue‐light‐excitable ZnMgAl 10 O 17 :Cr 3+ (ZMAO:Cr) phosphors are reported with pronounced NIR spectral broadening of full width at half maximum from 32 to 214 nm and red‐shifts from 690 to 782 nm as the Cr 3+ concentration increases, which is directly linked to the transition of the emitting center from isolated Cr 3+ to exchange‐coupled Cr 3+ ‐Cr 3+ pairs. Enabled by thermally accessible oxygen‐defect states, the optimized ZMAO:0.07Cr phosphor maintains 95% of its room‐temperature intensity at 425 K, with an IQE of 73.8%. The as‐fabricated high‐power NIR pc‐LED further demonstrates the promise of ZMAO:Cr for night‐vision‐related applications. This work establishes concentration engineering as a viable strategy to improve both the emission features and applications of Cr 3+ ‐activated NIR phosphors.