Hydrothermal synthesis of ZnGa2O4 nanophosphors with high internal quantum efficiency for near-infrared pc-LEDs

Abstract

NIR luminescent materials have garnered widespread attention because of their exceptional properties, with high tissue penetration, low absorption and high signal-to-noise ratio in the field of optical imaging. However, producing nanophosphors with high quantum yields of emitting infrared light with wavelengths above 1000 nm remains a significant challenge. Here, we prepared a nanoscale ZnGa₂O₄:xCr³⁺,yNi²⁺ phosphor with good luminescence performance in near-infrared emission, which was synthesized via a hydrothermal method and subsequent calcination process. By co-doping with Cr³⁺ and Ni²⁺, the ZnGa₂O₄ phosphor shows a strong broadband emission of 1100–1600 nm in the second near-infrared (NIR-II) region, owing to the energy transfer from Cr³⁺ to Ni²⁺ with an efficiency up to 90%. Meanwhile, a near-infrared phosphor-conversion LED (NIR pc-LED) device is fabricated based on the ZnGa₂O₄:0.8%Cr³⁺,0.4%Ni²⁺ nanophosphor, which has under 100 mA input current, an output power of 23.99 mW, and a photoelectric conversion efficiency of 7.53%, and can be effectively applied in imaging and non-destructive testing. Additionally, the intensity ratio of I_Ni/I_Cr of ZnGa₂O₄:0.8% Cr³⁺,0.4%Ni²⁺ with its high sensitivity value of 4.21% K⁻¹ at 453 K under 410 nm excitation, indicates its potential for thermometry application.