The Preparation And Luminescence Properties Of High-efficiency Phosphors For Light Emitting Diode

As the most important part for white lighting-emitting-diode (LED), phosphors play an important role in fabricating white LED with high-efficiency and low energy consumption. Because excellent red phosphors, which could be excitated by UV/blue LED chip and improve significantly the related color rendering index and color temperature, are rare, Na5La(WO4)4 tungstate host red phosphors were investigated systematically. In addition, novel BaSi3O4N2:Eu2+ oxynitride green phosphor was synthesized and characterised.Na5La(WO4)4:Eu3+, Na5Eu(WO4)4:Bi3+ and Na5Eu(WO4)4:Sm3+ red phosphors were synthesized by solid state reaction method under 700℃. Crystal structure and phase purity were studied by XRD, indicating that the samples were phase-pure with good crystallinity. Morphology and microstructure were observed by SEM and TEM images. This series of phosphors show characteristic excitation and emission spectra of Eu3+ ions, with the strongest emission at 616 nm originated from the 5D0â†'7F2 transition. The mechanism of Bi3+ and Sm3+ as the sensitizer was also proposed, and the optimal doping concentrations of Bi3+ and Sm3+ were found to be 20 mol% and 4 mol%, respectively.In addition, the oxynitride green phosphor BaSi3O4N2:Eu2+ was synthesized under a reducing atmosphere at 1350℃. XRD confirmed high purity and good crystallinity. SEM images indicated that the particle shape was flake with size ranging from 1μm to 5μm. The phosphors exhibited wide excitation and emission spectra, with the strongest emission at 525 nm. Concentration quenching was observed with the optimal Eu2+ concentration of 6 mol%. White LED, assembled by mentioned green phosphor, red phosphor, and blue chip, was found with color rendering index of 94 and color temperature of 3585 K.