Luminescence of Tb3Al5O12 phosphors co-doped with Ce3+/Gd3+ for white light-emitting diodes

Tb2.96−xCe0.04GdxAl5O12 phosphors were synthesized through solid-state reactions. The influence of Gd3+ on the luminescence was investigated. Under the excitation at 460 nm, Tb2.96Ce0.04Al5O12 shows the characteristic emission band of Ce3+ with a peak wavelength at about 554 nm. After co-doping Gd3+ into Tb2.96Ce0.04Al5O12, the peak wavelength of the Ce3+ emission band shifts to longer wavelengths, which is induced by the increasing crystal field splitting. However, the Ce3+ emission intensity also decreases because the substitution of Tb3+ with Gd3+ causes lattice deformation and generates numerous structural and chemical defects. By comparing the light parameters of white light-emitting diodes (WLEDs) containing Y2.96Ce0.04Al5O12, Tb2.96Ce0.04Al5O12 and Tb2.81Ce0.04Gd0.15Al5O12 phosphors, we can find that the WLED containing the Tb2.81Ce0.04Gd0.15Al5O12 phosphor generates warmer light than the WLEDs containing Y2.96Ce0.04Al5O12 and Tb2.96Ce0.04Al5O12 phosphors. Moreover, the WLEDs fabricated by integrating a blue LED chip and Ce3+/Gd3+-co-doped Tb3Al5O12 phosphors show outstanding colour stability when driven under different currents.