Thermally Robust Broadband Near-Infrared Luminescence in the NaGaP2O7:Cr3+ Phosphor

The near-infrared (NIR) phosphor-converted light-emitting diode (pc-LED) is an emerging portable light source and has multifunctional applications based on spectroscopic technology. Nevertheless, it is still difficult to develop broadband NIR materials with strong resistance toward thermal quenching. In this work, a thermally robust broadband NIR phosphor NaGaP2O7:Cr3+ was reported, which has an emission peak located at 793 nm, and the emission spectrum covers 650–1100 nm with a full width at half-maximum (fwhm) of 115 nm. The emission intensity at 150 °C was surprisingly maintained as 85.45% of that at 25 °C, indicating an outstanding ability to resist thermal quenching. A systematic investigation of aspects such as structural rigidity, the band gap of the host, and the electron phonon coupling effect was carried out to understand the mechanism of thermally robust luminescence in this material. Finally, the NaGa0.94Cr0.06P2O7 NIR phosphor and 450 nm InGaN LED chip were combined to produce a prototype NIR light source. This device generates a NIR output power of 44.43 mW and a photoelectric conversion efficiency of 10.4% when driven at 150 mA, demonstrating a good performance of this material for practical applications.