Broadband Ca₃MgZrGe₃O₁₂:Cr³⁺ garnet phosphor for high-performance NIR pc-LED application

The near-infrared (NIR) phosphor-converted light-emitting diode (pc-LED) is heavily reliant upon the performance of NIR phosphors. However, the current NIR pc-LEDs suffer from low photoelectric efficiency and insufficient near-infrared output power. In this study, Cr³⁺-doped Ca₃MgZrGe₃O₁₂ phosphors leading to high-performance NIR pc-LEDs were developed for the first time. They feature robust and wide NIR emission that extends over the spectrum from 650 to 1100 nm with a full width at half maximum of 120 nm, a high quantum yield of 82% and excellent thermal stability of T_50% = 250 °C and I_{150 °C} = 80% when excited at 460 nm. The NIR pc-LED was constructed by combining the Ca₃MgZrGe₃O₁₂:0.04Cr³⁺ phosphor with a blue LED chip, resulting in a device that exhibits a photoelectric conversion efficiency of 20% and a near-infrared output power of 54.19 mW when operated at a current of 100 mA. The obtained luminous efficacy is superior to that of the vast majority of current broadband near-infrared pc-LEDs. In addition, this NIR pc-LED exhibits strong penetration and its applications in bio-imaging are demonstrated. The results indicate that Ca₃MgZrGe₃O₁₂:Cr³⁺ NIR broadband phosphors are efficient for NIR pc-LEDs.