A novel germanate based red-emitting phosphor with high efficiency, high color purity and thermal stability for white light-emitting diodes and field emission displays

Abstract

White light-emitting diodes (WLEDs) and field-emission displays (FEDs) have attracted much attention in the field of lighting and displays. The key to improving the performances of WLEDs and FEDs is to explore and develop red-emitting phosphors with high quality. In this work, a novel red K₂SrGe₈O₁₈:Eu³⁺ (KSGO:Eu³⁺) phosphor has been developed by a solid-state method under mild conditions. Its crystal structure was examined by X-ray diffraction and Rietveld refinements for the first time. The luminescence property measurements suggested that the phosphor can emit intense red light peaking at 617 nm under near-ultraviolet (n-UV) light excitation. Also, the phosphor exhibited an outstanding quantum efficiency of 57.6% and excellent thermal stability (retains 80.9% of the initial value at 150 °C). Besides, its CIE coordinates were calculated to be (0.670, 0.329) with a high color purity of 95.5%. Furthermore, by employing the KSGO:0.08Eu³⁺ phosphor as a red component, a warm WLED was obtained with the color coordinates, CRI and CCT being (0.344, 0.333), 84.7 and 4963 K, respectively. Moreover, under low voltage electron bombardment, the phosphor can also yield similar red emission with high efficiency, high current saturation, and excellent resistance. Its degradation property is much better than that of the commercial Y₂O₃:Eu³⁺ and Y₂O₂S:Eu³⁺ phosphors. Therefore, the investigated results indicated that the KSGO:Eu³⁺ phosphor could be a suitable candidate as a red phosphor for both WLEDs and FEDs. Besides, our obtained phosphor also shows much potential for application in other fields like LED professional lighting, pilot lamps and micro LEDs.