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

• Published in: Chemistry : a European journal 2014-09, Vol.20 (36), p.11522-11530
• Main Authors: Kang, Fengwen, Peng, Mingying, Zhang, Qinyuan, Qiu, Jianrong
• Format: Article
• Language: English
• Subjects: bismuth; Chemistry; energy transfer; light-emitting diodes; lutetium vanadate; phosphors; quantum yield; Temperature; thermal stimulation
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201402081

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 (T50 %=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 (3P0,3P1)→1S0 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 3P0 and 3P1 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. Yellow phosphor for WLEDs: A novel yellow phosphor, LuVO4:Bi3+, showing abnormal anti‐quenching and controllable multi‐transitions ((3P0,3P1)→1S0) of Bi3+ luminescence, has been prepared at 1373 K in air. It shows no excitation at wavelengths longer than 410 nm, a quantum efficiency of up to 68 %, and no severe degradation upon thermal cycling. These attributes make it suitable for use in UV‐converted white LEDs.