Luminescent properties of crystalline YAG:Ce for white LED applications
Performed is a comparative study of the characteristics of YAG:Ce luminescent converters with single-crystalline, cellular and polycrystalline structure obtained by the method of directed crystallization of the melt. Peculiarities of the structure and surface morphology of the converters are found to essentially influence their spectral characteristics and luminescence efficiency. It is shown that polycrystalline converters based on YAG:Ce are promising for application in white light emitting diodes.
Growth and characterization of air annealing Mn-doped YAG:Ce single crystal for LED
Abstract The growth of Mn-doped YAG:Ce (yttrium aluminum garnet doped cerium) single crystal by the Czochralski (CZ) method and the characterization of its spectroscopy and color-electric parameters are presented. The absorption spectra indicate that the crystal absorbed highly in the 300–500 nm wavelength range. The emission spectrum of the crystal consists of a peak around 538 nm when excited by 460 nm blue light, which prove the YAG:Ce,Mn single crystal could be used in the white light emitting doides (LED). The different charges of Mn ions have different luminescence properties, and the air annealing process for the single crystal would change the concentration of Mn ions with different charges, which could influence the emission intensity of the single crystal.
Energy transfer-based spectral properties of Tb-, Pr-, or Sm-codoped YAG:Ce nanocrystalline phosphors
Abstract Tb3+-, Pr3+-, or Sm3+-codoped YAG:Ce nanocrystalline phosphors were prepared using a modified polyol process. Possible tunability of Ce3+-related yellow emission in codoped YAG:Ce nanocrystalline systems was investigated. Dual emission of yellow and red spectral component with a single excitation wavelength was observed from YAG:Ce, Pr or YAG:Ce,Sm codoped systems via an energy transfer from Ce3+ and Pr3+ or Sm3+ ion. It was also observed that the energy transfer event in YAG:Ce, Pr nanocrystalline phosphor occurs mutually between Ce3+↔Pr3+, while in YAG:Ce, Sm and YAG:Ce, Tb the energy transfer progresses one way. The detailed pathways for transferring an excitation energy are explained based on the energy level diagrams of respective Ce3+, Pr3+, Sm3+, Tb3+ ion.