An efficient rare-earth free deep red-emitting GdGeSbO 6 :Mn 4+ 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 Mn 4+ -activated deep red phosphor GdGeSbO 6 : x %Mn 4+ and analyze its crystal structure, composition and luminescence behavior in detail. Its optimal doping concentration of Mn 4+ is 0.3%. Under ultraviolet (UV) excitation, GdGeSbO 6 :0.3%Mn 4+ 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 2 E g → 4 A 2g transition of Mn 4+ ions. Notably, the optimal phosphor GdGeSbO 6 :0.3%Mn 4+ has a high internal quantum efficiency (IQE ≈ 65%) and excellent thermal stability performance ( I 423 K / I 303 K ≈ 62%). The synthesis of high-performance warm WLEDs and full-spectrum WLEDs was achieved by combining and coating GdGeSbO 6 :0.3%Mn 4+ phosphors with commercial phosphors on the surface of a 365 nm UV chip.