Developing a Near-Infrared Garnet Phosphor with Near-Unity Internal Quantum Efficiency and Wide-Range Spectral Tunability

Near-infrared phosphor-converted light-emitting diodes (NIR pc-LEDs) embedded in portable smart devices emerge as a new generation of NIR light sources for multifunctional applications. However, developing a NIR phosphor with ultrahigh efficiency, robust thermal stability, and wide-range spectral tunability remains a great challenge. Herein, a series of garnet-type Ca₂GdM_AM_BGe₃O₁₂:Cr³⁺ (M_A = Zn, Mg; M_B = Sc, In) phosphors were designed and synthesized. Among them, the Ca₂GdZnScGe₃O₁₂:Cr³⁺ phosphor was screened with a superior performance. Upon 465 nm excitation, this material exhibits a broadband emission with a peak centered at 795 nm and a near-unity internal quantum efficiency (IQE = 97%). The integrated emission intensity at 423 K can retain 83.4% of that at room temperature. Moreover, the emission peak can be tuned from 795 to 870 nm via varying the ratio of the [Na⁺–Gd³⁺] unit cosubstituting the [Ca²⁺–Ca²⁺] unit, and the IQE still maintains over 90% when the emission peak gradually shifts to 830 nm. Finally, the applications of the developed materials in nondestructive testing, information encryption, and organic matter analysis were demonstrated, which confirmed the feasibility of these materials in multifunctional spectroscopy applications.