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 beta-alumina structure Ba0.2La0.55Mg0.55Al2.45Ga8O17.25 (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 degrees 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:0.10Cr(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.