An efficient rare-earth free deep red-emitting GdGeSbO6:Mn4+ phosphor for white light-emitting diodes

Red phosphors play an important role in improving the light quality and color rendering index of white light-emitting diodes (WLEDs) for lighting. In this paper, we report the transition ion Mn4+-activated deep red phosphor GdGeSbO6:x%Mn4+ and analyze its crystal structure, composition and luminescence behavior in detail. Its optimal doping concentration of Mn4+ is 0.3%. Under ultraviolet (UV) excitation, GdGeSbO6:0.3%Mn4+ produces a narrow emission peak centred at 682 nm in the range of 650-800 nm with a full width at half maximum (FWHM) of 25 nm, which is attributed to the spin-prohibited E-2(g) -> (4)A(2g) transition of Mn4+ ions. Notably, the optimal phosphor GdGeSbO6:0.3%Mn4+ has a high internal quantum efficiency (IQE approximate to 65%) and excellent thermal stability performance (I-423 K/I-303 K approximate to 62%). The synthesis of high-performance warm WLEDs and full-spectrum WLEDs was achieved by combining and coating GdGeSbO6:0.3%Mn4+ phosphors with commercial phosphors on the surface of a 365 nm UV chip.