Gd₃B(W,Mo)O₉: Eu³⁺ red phosphor: From structure design to photoluminescence behavior and near-UV white-LEDs performance

Highlights: • Red phosphor Gd₃B(W,Mo)O₉:Eu³⁺ designed according to structure was synthesized. • The substitution of W⁶⁺ by Mo⁶⁺ makes the absorption band edge of this phosphor extend to 440 nm. • The energy transfer from MoO₆ to Eu³⁺ improves the temperature quenching property of photoluminescence in this system. • Red emission of the optimized phosphor is almost 10 times stronger than that of Y₂O₂S:Eu³⁺. • The performance of NUV w-LEDs device fabricated with this phosphor verified the potential application. - Abstract: The photoluminescence behavior of a high efficient red phosphor Gd₃B(W,Mo)O₉:Eu³⁺ designed according to crystal structure and electronic structure is presented in detail. The substitution of isolated WO₆ group by MoO₆ 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 (C₁) of Eu³⁺(Gd³⁺) site enables Eu³⁺ ion to show dominant electronic dipole transition ⁵D₀ → ⁷F₂ (∼616 nm) with five apparent splitting peaks according to group theory, which is almost 10 times stronger than that of commercial Y₂O₂S:Eu³⁺ 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 MoO₆ groups to the well-dispersed Eu³⁺ ion separated by BO₃ 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 6031K, 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