Efficient Near-Infrared Luminescence in Cr3+ Activated β-Alumina Structure Phosphor via Multiple-Sites Occupancy

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_0.2La_0.55Mg_0.55Al_2.45Ga₈O_17.25 (BLMAG):Cr³⁺ phosphor by cation co-substitution strategy, which controls the local crystal environment for site-selective occupancy of Cr³⁺ emitters. With the increase of La³⁺-Mg²⁺ 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 Cr³⁺ occupying multiple luminescence centers in the lattice. Moreover, the as-prepared phosphor-converted light-emitting diode (pc-LED), using the optimized BLMAG:0.10Cr³⁺ 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.