Thermally stable NIR broad emission of Cr3+ doping phosphor with a high output power†

The development of high-performance near-infrared (NIR) luminescent materials remains a significant challenge, particularly in enhancing thermal stability. Herein, we observed an anti-thermal quenching effect in the YGa_1.5Al_1.5(BO₃)₄:Cr³⁺ phosphor, with its emission intensity reaching 104% at 423 K and 101% at 483 K compared to room temperature. This anti-thermal quenching is mainly attributed to thermal-induced emission compensation resulting from excited electrons trapped at crystal defects, as confirmed by density functional theory computation. Additionally, YGa_1.5Al_1.5(BO₃)₄:Cr³⁺ exhibits a broad NIR emission peaking at 760 nm with a full width at half maximum of 135 nm and a high photoluminescence quantum yield (86%). As a proof-of-concept, we fabricated an NIR phosphor-converted light-emitting diode device that achieves an NIR output power of 59.67 mW with an input working current of 150 mA, demonstrating a photoelectric conversion efficiency of 13.6%. The utilization of this high-power NIR light-emitting diode device as a lighting source enables a penetration depth of up to 15 mm, demonstrating the potential applications of Cr³⁺-doped YGa_1.5Al_1.5(BO₃)₄:Cr³⁺ phosphors for non-invasive detection of biological tissue.