Red-emitting LiEuMo2−xSixO8 phosphors for white light-emitting diodes

Abstract

Si4+ was introduced to the lattice of LiEuMo2O8 by solid-state reaction to prepare a new kind of red-emitting LiEuMo2−xSixO8 (0<x≤0.5) phosphors. The introduction of Si4+ ion caused the distortion and slight shrinking of the unit cell of LiEuMo2O8 material, and the blue-shift of the charge-transfer-absorption (CTA) band of LiEuMo2O8. Photoluminescence excitation (PLE) and photoluminescence measurements showed that the introduction of Si4+ was able to enhance the excitation efficiency of LiEuMo2O8 in NUV spectral region (360–400nm). Consequently the red emission of LiEuMo2O8 phosphor was improved by 30% at x=0.2 under 395nm light excitation, without loss of color purity. The enhanced red emission of LiEuMo2−xSixO8 was discussed in terms of the blue-shift of CTA band and the relaxation of parity-forbidden selection rules for trivalent europium luminescent centers.