Studies on Optical Properties and Ce Concentration of Ce : YAG Single Crystal for WLEDs

Ce : YAG single crystal for white light emitting diode(WLED) was grown by Czochralski method. The structure and optical properties of samples were characterized by X-ray diffraction(XRD) and photoluminescence spectra. Ce : YAG single crystal shows a 500-650 nm broad emission band around 526 nm (5d(1 2)E(g)Gamma(8g)-> 4f(1 2)F(7/2)Gamma(8u)) under blue light of 455 nm. The excitation spectrum of Ce : YAG single crystal is made up of 343 nm(5f(1 2)F(5/2)Gamma(7u)-> 5d(1 2)E(g)Gamma(7g)) and 466 nm (4f(1 2)F(5/2)Gamma(7u)-> 5d(1 2)E(g)Gamma(8g)) excitation peaks. The Stokes shift is 2448 cm(-1). The Huang-Rhys parameter is 6. 12. The Ce concentration of Ce YAG single crystal is related with colour coordinate of WLEDs made by Ce YAG single crystal with the red phosphor (650 nm), a best concentration range of Ce in Ce : YAG single crystal is 0. 034-0. 066.