An efficient rare-earth free deep red emitting phosphor for improving the color rendering of white light-emitting diodes

Abstract

In order to improve the quality of lighting and display devices based on InGaN blue chips, blue light excitable red phosphor is an essential component. Here, we prepared a series of efficient red emitting phosphors of Mg₁₄Ge₅O₂₄ doped with different concentrations of Mn⁴⁺ based on a conventional solid-state reaction. Crystal structure, composition, morphology, and luminescence properties of samples were characterized by utilizing Rietveld refinement, X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), photoluminescence (PL), and PL quantum yields (QYs). Moreover, reflectance spectra, temperature-dependent photoluminescence behavior, and the fabricated WLEDs performances were studied in detail. An absolute photoluminescence quantum yield as high as 81% was obtained for the Mg₁₄Ge_5(1–0.2%)O₂₄:0.2%Mn⁴⁺ phosphor with good thermal stability. The fabricated WLED with CCT = 2864 K and R_a = 80.6 was attained by combining the prepared red phosphor and YAG yellow phosphor with a blue LED chip, which was superior to the conventional YAG-type WLED. All the results indicate that Mg₁₄Ge₅O₂₄:Mn⁴⁺ is a promising phosphor and widens the horizon for materials in WLED applications.