Efficient Near‐Infrared Luminescence in Cr ³⁺ Activated <i>β</i> ‐Alumina Structure Phosphor via Multiple‐Sites Occupancy

Abstract Broadband near‐infrared (NIR) phosphors play vital roles in the research and development of compact NIR light sources. Herein, improved NIR luminescence properties have been achieved in β ‐alumina structure Ba 0.2 La 0.55 Mg 0.55 Al 2.45 Ga 8 O 17.25 (BLMAG):Cr 3+ phosphor by cation co‐substitution strategy, which controls the local crystal environment for site‐selective occupancy of Cr 3+ emitters. With the increase of La 3+ ‐Mg 2+ couples in host lattice, the NIR emission peak can be tuned from 712 to 746 nm under 405 nm excitation with a high internal (external) quantum efficiency of 97% (42.6%) and superior thermal stability of 90% @150 °C. The structural refinement and spectral analysis indicate that the broadband NIR emission drives from the Cr 3+ occupying multiple luminescence centers in the lattice. Moreover, the as‐prepared phosphor‐converted light‐emitting diode (pc‐LED), using the optimized BLMAG:0.10Cr 3+ phosphor, achieves an NIR output power of 72.9 mW at 150 mA with photoelectric conversion efficiency of 15.4%. The spectra well matched to the absorption of photosensitive pigment P FR appear promising in plant growth, the captured doll as well as the penetration experiments also illustrate the application in night vision and biosensing.