Dual center luminescence properties of LiGaAl4O8:Cr3+ near infrared phosphors for LED applications

Near-infrared (NIR) phosphor-converted light emitting diodes (NIR pc-LEDs) hold great promise for applications in night vision imaging, nondestructive analysis, and plant growth. Although some NIR phosphors have been developed in recent years, there are fewer studies on Cr³⁺-doped multisite luminescent phosphors. Here, we report a novel LiGaAl₄O₈:xCr³⁺ (LGAO:Cr³⁺) phosphors with double Cr³⁺ luminescence centers. At low doping concentration, LGAO:Cr³⁺ is dominated by the emission of Cr1. With the increase of doping concentration x, the Cr2 portion of emission intensity increases due to the increased probability of the energy transfer from Cr1 to Cr2. Finally, using the LGAO:0.02Cr³⁺ NIR phosphor and a commercial 410 nm chip, a NIR pc-LED prototype with a NIR output power of 43.7 mW at 100 mA drive current and a photovoltaic conversion efficiency of 19.2 % at 10 mA was fabricated and its application in visual inspection of precise devices and angiography was demonstrated. This work provides an in-depth and careful study of the luminescent mechanism of the dual-centerd NIR phosphor and serves as a good paradigm for the development of NIR pc-LEDs.