Thermally stable fluoride phosphor Na₃Sc₂Li₃F₁₂:Cr³⁺ with broadband emission for NIR pc-LED applications

Near-infrared (NIR) phosphors face numerous challenges due to the diverse application needs of NIR light. In order to obtain a small-sized and efficient NIR light device, NIR phosphors must be suitable for practical applications while achieving excellent thermal stability and efficiency. In this paper, the garnet-type fluoride phosphor Na₃Sc₂Li₃F₁₂:Cr³⁺ was successfully obtained using hydrothermal method. And the wide luminescence of 650–1000 nm with an internal quantum yield of 41% could be observed after effective absorption of 420 nm light. Particularly, profiting from a large band gap value and the small Huang-Rhys factor, the NIR emission intensity of Na₃Sc₂Li₃F₁₂:7%Cr³⁺ sample maintains 84% at 423 K compared to room temperature (RT), presenting outstanding thermal stability. In addition, the commercial blue chip was assembled with Na₃Sc₂Li₃F₁₂:7%Cr³⁺ phosphor to integrate the NIR phosphor-converted light-emitting diode (pc-LED). At 300 mW driving current, a NIR radiation flux of 131 mW was obtained, indicating broad application prospects in NIR pc-LEDs.