Boosting NIR Emissions and Thermal Resistance in Cr3+-Doped MgGa2O4 Semiconductor Microcrystals by Energy Transfer for Smart Detection.

High-radiant-intensity broadband near-infrared (NIR) emitters are highly desirable for nondestructive testing, night-vision imaging, and information encryption. However, the exploration of phosphors that possess both high luminous efficiency and outstanding thermal stability continues to pose significant difficulties. Among various NIR phosphor systems, Cr3+-doped MgGa2O4 (MGO:Cr3+) exhibits characteristic broadband emission. Herein, Bi3+ ions were incorporated as sensitizers into the MGO:Cr3+ phosphor system, resulting in substantial enhancements in photoluminescence (PL), mechanoluminescence (ML), and thermal stability. The Bi3+ co-doping enhanced the NIR PL intensity to 4.0 times and the ML output to 1.45 times those of the Cr3+ singly doped reference, indicating a pronounced sensitization effect and improved energy transfer efficiency. Furthermore, the emission-intensity retention at 423 K improved from 49.29 to 82.88%, confirming a significant enhancement in the thermal stability of the NIR emission. A broadband NIR phosphor-converted light-emitting diode (pc-LED) assembled by coupling the Bi3+, Cr3+-co-doped MGO with a blue LED further demonstrated the material's potential for nondestructive testing, night-vision imaging, and anti-counterfeiting.