Preparation And Characteristics Of Newly Developed Rare Earth RE (RE=Pr, Sm, Eu, Gd) Co-doped Ce:YAG Single Crystal Phosphors For White-led

White Light Emitting Diodes (W-LED) are widely used in common lighting and backlighting areas with many advantages of solidification, small size, low heat, low power consumption, long life, fast response, and environmental friendly, etc. At present, The commercial W-LEDs are mainly assembled by a blue chip and phosphor with yellow, Blue chip emit blue light and phosphor emit yellow light , these light mix and generate white light. Commercial phosphor has gotten huge successful, but the phosphor of white LED also has many shortages of low efficiency, poor uniformity, large light decline, short life, and poor physical and chemical characteristics, etc. These influence the W-LED performance seriously.In order to improve the shortage of phosphor used for white LED,single crystals phosphor is studied as a substitute. Rare earth ions Pr, Sm, Eu, Gd have been co-doped with Ce ion in YAG single crystal respectively, want to gain red light component and improve the optical performance of the W-LED.High quality Ce:YAG and Pr, Sm, Eu or Gd co-doped Ce:YAG single crystals were grown by Czochralski(CZ) method, and the luminescence properties of the crystals and the W-LEDs were studied by means of absorption, emission and excitation spectra, electroluminescence spectra , color rendering index(CRI), correlated color temperature(Tc), luminous efficiency, etc.The results are as follows: the XRD spectrums of the 5 crystals are consistent with the JCPDS No. 33-0040. They all absorb blue light with center emission wavelength of 460 nm; it matches with GaN blue chip with center emission wavelength of 460±15 nm. The broad emission band of the 5 crystal chips range from 480-650nm, were produced with blue light excitation. The reason of the fluorescence emission is investigated. It has been found that red light component of Ce: YAG crystal phosphor, which is important to improve the color rendering index, could be efficiently compensated by Pr³⁺, or Sm³⁺ co-doping. There is no red light component emission and fluorescent quenching was happed with Eu³⁺ co-doping, which reduce the luminous efficiency greatly. Gd³⁺ ions co-doped as matrix ions could make the emission of the Ce³⁺ ions red shift; these could gain more red light component. Pr³⁺, Sm³⁺, Eu³⁺, Gd³⁺ ions co-doping influence the emission of Ce³⁺ ions, the reason are investigated, too.We have tested the light color electricity performance, the chip thickness, and the influence of operating current size to the illumination of the white light LED which consist of five crystal sample. The result showed that five kinds of white light LED can produce the white light. The bigger of chip thickness, the stronger of luminous efficiency of LED, the lower of related color temperature, but the colored index is reduce; The bigger of operating current, the lower of luminous efficiency of blue light chip, but the corresponding luminous efficiency of white light LED is reduce. The co-doping of Pr³⁺ or Sm³⁺ ion can sensitization the illumination of Ce³⁺, enhance the luminous efficiency of white light LED; The co-doping of Eu³⁺ can reduce the luminous efficiency of white light LED obviously; The co-doping of Eu³⁺ can induce the red shift of Ce³⁺, but it have not influence to the luminous efficiency.The chip of blue light have been absorbed massively, the surplus blue light is insufficient, the proportion of blue light and the chip of yellow light is unbalanced, and the white light colored performance is not very ideal due to the density of doping Ce³⁺ ion is high. Further work to better improve that parameter is still under way.