Luminescence of Tb(3)Al(5)O(12) phosphors co-doped with Ce(3+)/Gd(3+) for white light-emitting diodes

Tb(2.96−)(x)Ce(0.04)Gd(x)Al(5)O(12) phosphors were synthesized through solid-state reactions. The influence of Gd(3+) on the luminescence was investigated. Under the excitation at 460 nm, Tb(2.96)Ce(0.04)Al(5)O(12) shows the characteristic emission band of Ce(3+) with a peak wavelength at about 554 nm. After co-doping Gd(3+) into Tb(2.96)Ce(0.04)Al(5)O(12), the peak wavelength of the Ce(3+) emission band shifts to longer wavelengths, which is induced by the increasing crystal field splitting. However, the Ce(3+) emission intensity also decreases because the substitution of Tb(3+) with Gd(3+) causes lattice deformation and generates numerous structural and chemical defects. By comparing the light parameters of white light-emitting diodes (WLEDs) containing Y(2.96)Ce(0.04)Al(5)O(12), Tb(2.96)Ce(0.04)Al(5)O(12) and Tb(2.81)Ce(0.04)Gd(0.15)Al(5)O(12) phosphors, we can find that the WLED containing the Tb(2.81)Ce(0.04)Gd(0.15)Al(5)O(12) phosphor generates warmer light than the WLEDs containing Y(2.96)Ce(0.04)Al(5)O(12) and Tb(2.96)Ce(0.04)Al(5)O(12) phosphors. Moreover, the WLEDs fabricated by integrating a blue LED chip and Ce(3+)/Gd(3+)-co-doped Tb(3)Al(5)O(12) phosphors show outstanding colour stability when driven under different currents.