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

• High performance red phosphors for near UV light excited white LEDs.
• Lithium lanthanide molybdate red phosphors.
• Bi and Si substitution.
• Considerable enhancement of luminescence intensity and excitation efficiency.
• CIE chromaticity coordinates very close to the NTSC standard values.

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 (395 nm) light and emit bright red light at 614 nm, 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 614 nm) 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 395 nm 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.

Doping of Bi and Si into the lattice leads to an considerable increase of the excitation efficiency and luminous intensity, and obvious movement of the CIE chromaticity coordinates to the NTSC standard values of the LiEu(MoO4)2, a promising red phosphors suitable for near UV excited white-light emitting diodes.Figure optionsDownload as PowerPoint slide