White LED based on nano-YAG:Ce ~(3+)/YAG:Ce ~(3+),Gd ~(3+) hybrid phosphors

摘要

Nano-YAG:Ce ~(3+) and YAG:Ce ~(3+),Gd ~(3+) phosphors were synthesized by glycothermal method. The X-ray diffraction (XRD) measurements showed that the samples can be well-crystallized at 600 °C. The transition electron microscope (TEM) showed that the particles have sizes mostly in the range between 35 and 100 nm. The YAG:Ce nano-phosphor had a wide emission band ranging from blue to yellow peaking at 532 nm, due to the transition from the lowest 5d band to ~2F _(7/2), ~2F _(5/2) states of the Ce ~(3+) ion. Red-shift of emission peak wavelength from 532 nm to 568 nm has been achieved as doping Gd ~(3+) ions into the YAG:Ce ~(3+) to substitute some Y ~(3+) ions. White LEDs were fabricated by combining GaN (460 nm) chip with the YAG:Ce ~(3+) and YAG:Ce ~(3+),Gd ~(3+). Color rendering index of the white LED as a function of the ratios of theses two kinds of phosphors was studied. As the ratio of YAG:Ce ~(3+),Gd ~(3+) phosphor increased, the color rendering index of the LED improved significantly under the forward bias of 20 mA. As the ratio of YAG:Ce ~(3+) and YAG:Ce ~(3+),Gd ~(3+) was 11:9, the white LED had a color rendering index, CIE chromaticity coordinates and color temperature T _c of 85, (0.3116, 0.3202) and 6564 K, respectively.