Fig. 1. Schematic diagram of preparing Li₃Na₃Ga_2-xF₁₂∶xCr³⁺ phosphor

Fig. 2. Crystal structure and morphology analysis of Li₃Na₃Ga₂F₁₂∶Cr³⁺. (a) XRD pattern of Li₃Na₃Ga_1.90F₁₂∶0.10Cr³⁺ synthesized at different holding temperatures; (b) XRD pattern of Li₃Na₃Ga_1.90F₁₂∶0.10Cr³⁺ synthesized at different holding times; (c) XRD pattern of Li₃Na₃Ga_2-xF₁₂∶xCr³⁺(0.05<x<0.20) synthesized at different concentrations of Cr³⁺ doping; (d) crystal structure of Li₃Na₃Ga₂F₁₂∶Cr³⁺; (e) schematic diagram of the morphology evolution of Li₃Na₃Ga_1.90F₁₂∶0.10Cr³⁺ synthesized at different holding times; (f)‒(j) SEM images of Li₃Na₃Ga_1.90F₁₂∶0.10Cr³⁺ synthesized at 1 h, 3 h, 5 h, 7 h, and 10 h, respectively

Fig. 3. Electronic structure analysis of Li₃Na₃Ga₂F₁₂. (a) The Band structure diagram of Li₃Na₃Ga₂F₁₂; (b) the total electronic DOS diagram of Li₃Na₃Ga₂F₁₂; (c)‒(f) the partial DOS diagram of Li₃Na₃Ga₂F₁₂

Fig. 4. Element composition and valence analysis of Li₃Na₃Ga_1.90F₁₂∶0.10Cr³⁺. (a) XPS of Li₃Na₃Ga_1.90F₁₂:0.10Cr³⁺; (b) Cr 2p spectra of Li₃Na₃Ga_1.90F₁₂∶0.10Cr³⁺ (top) and Cr₂O₃ (bottom), with their crystal structures shown in the upper left corner respectively; (c) Li 1s spectra of Li₃Na₃Ga_1.90F₁₂∶0.10Cr³⁺; (d) Ga 3d and Ga 2p spectra of Li₃Na₃Ga_1.90F₁₂∶0.10Cr³⁺; (e) Na 1s spectra of Li₃Na₃Ga_1.90F₁₂∶0.10Cr³⁺; (f) F 1s spectra of Li₃Na₃Ga_1.90F₁₂∶0.10Cr³⁺

Fig. 5. Luminescence analysis of Li₃Na₃Ga_2-xF₁₂∶xCr³⁺. (a) The PL spectra of Li₃Na₃Ga_1.90F₁₂∶0.10Cr³⁺ at different holding temperatures; (b) the PL spectra of Li₃Na₃Ga_1.90F₁₂∶0.10Cr³⁺ at different holding times; (c) the PLE spectra of Li₃Na₃Ga_2-xF₁₂∶xCr³⁺(0<x<0.20) at different concentrations of Cr³⁺ doping; (d) PL spectra of Li₃Na₃Ga_2-xF₁₂∶xCr³⁺(0<x<0.20) at different concentrations of Cr³⁺ doping; (e) the emission intensity integration area of Li₃Na₃Ga_2-xF₁₂∶xCr³⁺ (0<x<0.20) at different concentrations of Cr³⁺ doping; (f) Tanabe-Sugano energy level curve of Cr³⁺ in regular octahedron

Fig. 6. Display and performance test of packaged Pc-LED devices. (a) The electroluminescence spectra of the assembled NIR pc-LED, the illustration shows the Li₃Na₃Ga_1.9F₁₂∶0.10Cr³⁺ green powder under natural light; (b) (c) the working states of NIR pc-LED without 650 nm filter and with 650 nm filter when energized, respectively; (d) NIR imaging photos of syringe needles placed under different thicknesses of chicken breasts under NIR pc-LED lighting

Fig. 7. Night vision applications of NIR Pc-LED device. (a) Image of water and milk illuminated by fluorescent lamps; (b) image of water and milk illuminated by NIR pc-LED