Considerable photoluminescence enhancement of LiEu(MoO4)2 red phosphors via Bi and/or Si doping for white LEDs

Abstract

Novel Bi and/or Si substituted LiEu(MoO4)2 phosphors, where Bi was used as sensitizer to enhance the emission intensity and Si was used as substitution to improve the excitation efficiency, were prepared using the sol–gel method, and the photoluminescent properties of the resulting phosphors were intensively investigated. All samples can be excited efficiently by UV (395nm) light and emit bright red light at 614nm, which are coupled well with the characteristic emission from a UV-LED. In the Bi3+-doped samples, the intensities of the main emission line (5D0–7F2 transition at 614nm) are strengthened because of the energy transition from Bi3+ to Eu3+. With the substitution of Mo4+ by Si4+, there are no significant changes in the emission peak positions, but the emission intensity was significantly enhanced under 395nm excitation. Particularly, the LiEu0.9Bi0.1(Mo0.97Si0.03O4)2 phosphor doped with both Bi and Si demonstrates superior comprehensive photoluminescence properties with an excellent combination of easy excitation in the near UV range, bright emission intensity, high PL quantum efficiency as well as suitable decay time, which are very suitable for application as red phosphor for near UV type LEDs.