White-Light-Emitting Diodes Using Red-Emitting LiEu(WO[sub 4])[sub 2−x](MoO[sub 4])[sub x] Phosphors

The fundamental luminescence and chromaticity properties of a class of red-emitting phosphors under near-UV excitation have been investigated. The photoluminescence (PL) and photoluminescence excitation (PLE) spectra reveal that the absorption is mainly attributed to charge transfer at and the transitions in near-UV and visible regions, and red emissions are assigned to intraconfigurational 4f-4f transitions of . Both PL and PLE intensity were found to increase with increasing doped Mo content. The intensity of the emission of activated at was found to reach a maximum when the relative ratio of was 2:0. The CIE chromaticity coordinates were found to be (0.66, 0.33) for and it reached the same level as the commodity phosphor . A white-light-emitting diode fabricated using the composition-optimized and the matching green- and blue-emitting phosphors shows that the quality of red color reproduction based on was found to be much higher and improved than that using .