Improvement of the External Quantum Efficiency of Lithium Europium Tung-state and its Application to White Light Emitting Diodes

摘要

In order to improve the quantum efficiency of the red phosphor LiEu_(0.96)Sm_(0.04)W_2O_8 under 395 nm excitation, we synthesized samples having various particle sizes. We investigated the emission properties of near UV-pumped white LEDs containing this red phosphor. At room temperature, the external quantum efficiency improved to 49.4 % as the particle size increased, a value comparable to that of commercialized green and blue phosphors used in n-UV LEDs.rnIn a white LED fabricated by combining an n-UV LED with RGB phosphors, including our synthesized LiEu_(0.96)Sm_(0.04)W_2O_8, the luminance of an LED with a red phosphor particle size of 183 μm was 1.6 times higher than that with a particle size of 21.7 μm. The color rendering properties showed excellent uniformity: there was no observable correlation between color rendering properties and particle size. We consider that an emission peak at 614 nm had a beneficial effect on the luminance and color rendering properties of a white light LED.