Design, luminescence and energy transfer of single-phased color-tunable YNbO4: Bi3+, Eu3+ phosphor for UV pumped white light-emitting diodes

Single-phased white light-emitting YNbO4: Bi3+, Eu3+ phosphors were synthesized by conventional solid-state reaction. YNbO4: Bi3+ phosphor exhibits a broad excitation band ranging from 220 to 360 nm and a blue light emission band peaking at 457 nm, originating from the P-3(1)-S-1(0) transition of Bi3+, whereas YNbO4: Eu3+ phosphor exhibits the typical red emission aroused from the D-5(1) -> F-7(1), D-5(1) -> F-7(2), D-5(0) -> F-7(1), D-5(0) -> F-7(2) transitions of Eu3+. Under the excitation at 330 nm, the YNbO4: Bi3+, Eu3+ exhibits both the blue emission band of Bi3+ and the red emission of Eu3+ due to the energy transfer from Bi3+ to Eu3+ ions. By tuning the Bi3+/Eu3+ ratio via the energy transfer, the emission hue of YNbO4: Bi3+, Eu3+ varied from blue (0.16, 0.18) to white (0.33, 0.24) and eventually to red (0.62, 0.33). The mechanism of energy transfer from a sensitizer Bi3+ to an activator Eu3+ in YNbO4: Bi3+, Eu3+ phosphors was demonstrated to be an exchange interaction.