Achieving an efficient La3Si8N11O4: Eu2+ phosphor via chemical reduction of nano-scale carbon film: Toward white light-emitting diodes

In this work, Eu-doped La3Si8N11O4 phosphors with different doping concentrations are fabricated by solid state reaction method. A broad and asymmetric emission band that covers the wavelength range of 425–550 nm is observed. X-ray diffraction Rietveld refinement and X-ray absorption near edge structure (XANES) analyses reveal the co-existence of both trivalent and divalent states of Eu. By coating the phosphor particles with an ultrathin carbon layer using CVD technique, followed by an annealing in N2 at 1600 °C, the trivalent ions Eu3+ are reduced to Eu2+, resulting in a significant enhancement of quantum efficiency, both internal and external, and absorption efficiency. The application of the La3Si8N11O4:Eu in white light-emitting diodes is tested by coating the phosphor onto a near-UV LED chip in combination with the red-, green- and blue-emitting phosphors ([Ca, Sr]AlSiN3:Eu, ®-Sialon:Eu and BaMgAl10O17:Eu, respectively). It is demonstrated that the presence of the La3Si8N11O4:Eu phosphor significantly enhances the color rendering index of the device, showing its great potential for wLEDs applications.