White light-emitting diodes using blue and yellow–orange-emitting phosphors

A blue-emitting phosphor, BaMgAl10O17:Eu2+ (BAM) and a yellow–orange phosphor, Ba2+-codoped Sr3SiO5:Eu2+ were prepared by the solid-state reaction. Excitation and emission spectra results showed that BAM and Ba2+-codoped Sr3SiO5:Eu2+ can be efficiently excited by near-ultraviolet (n-UV)–visible light from 250 to 440 nm. The effects of the doped-Eu2+ concentration in BAM and Ba2+-codoped Sr3SiO5:Eu2+ on the photoluminescence were investigated in detail. White light-emitting diodes (LED) was obtained by combining n-UV LED chip (GaN-based 380 nm emitting) with BaMgAl10O17:0.09Eu2+ and 0.1Ba2+-codoped Sr3SiO5: 0.2Eu2+ phosphors with the characteristic of color-rendering index of 86, CIE chromaticity coordinates (x,y) of (0.3216,0.3096), and color temperature Tc of 5700 K. As the current increases, the relative intensity simultaneously increases. The CIE chromaticity coordinates (x,y) of the white LED tends to decrease. The correlated color temperature Tc increases from 4100 to 7500 K and the color-rendering index Ra increases from 82 to 87 simultaneously.