Gd_3B(W,Mo)O_9: Eu~(3+) red phosphor: From structure design to photoluminescence behavior and near-UV white-LEDs performance

摘要

The photoluminescence behavior of a high efficient red phosphor Gd_3B(W,Mo)O_9:Eu~(3+) designed according to crystal structure and electronic structure is presented in detail. The substitution of isolated WO_6 group by MoO_6 makes the absorption band edge extend from 360 nm to 440 nm, as designed to fit the excitation of near ultraviolet (NUV) LED chip, which could be interpreted by the density functional theory calculations. The extreme low symmetry (Q) of Eu~(3+)(Gd~(3+)) site enables Eu~(3+) ion to show dominant electronic dipole transition ~5D_0→ ~7F_2 (~616 nm) with five apparent splitting peaks according to group theory, which is almost 10 times stronger than that of commercial Y_2O_2S:Eu~(3+) upon ~385 nm excitation. The outstanding thermal stability of photoluminescence of this phosphor up to 523 K may probably be owed to the energy transfer from isolated MoO_6 groups to the well-dispersed Eu~(3+) ion separated by BO_3 groups. The performance of NUV white-LEDs package fabricated with a blue, green and this red phosphor is also demonstrated. It shows high color stability of the white light (CIE coordinate (0.320, 0.349), CCT 603IK, at 20 mA) under the DC drive current varied from 20 mA to 350 mA, verifying the potential application of the red phosphor in tri-color phosphors coated white-LEDs.