White LED based on nano-YAG:Ce3+/YAG:Ce3+,Gd3+ hybrid phosphors

Nano-YAG:Ce3+ and YAG:Ce3+,Gd3+ 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 F-2(7/2), F-2(5/2) states of the Ce3+ ion. Red-shift of emission peak wavelength from 532 nm to 568 nm has been achieved as doping Gd3+ ions into the YAG:Ce3+ to substitute some Y3+ ions. White LEDs were fabricated by combining GaN (460 nm) chip with the YAG:Ce3+ and YAG:Ce3+,Gd3+. 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:Ce3+,Gd3+ phosphor increased, the color rendering index of the LED improved significantly under the forward bias of 20 mA. As the ratio of YAG:Ce3+ and YAG:Ce3+,Gd3+ 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. (C) 2011 Elsevier GmbH. All rights reserved.