Abnormal Anti-Quenching and Controllable Multi-Transitions of Bi3+ Luminescence by Temperature in a Yellow-Emitting LuVO4:Bi3+ Phosphor for UV-Converted White LEDs

Phosphors with an efficient yellow-emitting color play a crucial role in phosphor-converted white LEDs (pc-WLEDs), but popular yellow phosphors such as YAG: Ce or Eu2+-doped (oxy)nitrides cannot smoothly meet this seemingly simple requirement due to their strong absorptions in the visible range. Herein, we report a novel yellow-emitting LuVO4:Bi3+ phosphor that can solve this shortcoming. The emission from LuVO4:Bi3+ shows a peak at 576 nm with a quantum efficiency (QE) of up to 68%, good resistance to thermal quenching (T-50% = 573 K), and no severe thermal degradation after heating-cooling cycles upon UV excitation. The yellow emission, as verified by X-ray photoelectron spectra (XPS), originates from the (P-3(0),P-3(1))-> S-1(0) transitions of Bi3+. Increasing the temperature from 10 to 300 K produces a temperature-dependent energy-transfer process between VO43- groups and Bi3+, and further heating of the samples to 573 K intensifies the emission. However, it subsequently weakens, accompanied by blueshifts of the emission peaks. This abnormal anti-thermal quenching can be ascribed to temperature-dependent energy transfer from VO43- groups to Bi3+, a population redistribution between the excited states of P-3(0) and P-3(1) upon thermal stimulation, and discharge of electrons trapped in defects with a trap depth of 359 K. Device fabrication with the as-prepared phosphor LuVO4:Bi3+ has proved that it can act as a good yellow phosphor for pc-WLEDs.