Dependence of emitting light for LEDs fabricated by YAG:Ce crystal wafer on wafer thickness

Abstract

Influence of YAG:Ce crystal wafer thickness on their optical properties were investigated. The crystal wafers were cut from the YAG:Ce single crystal grown by the Czochralski technique. XRD patterns suggest the cubic phase of the grown single crystal. The transmittance spectra of YAG:Ce crystal wafers with different thicknesses show that they have strong absorption of Ce3+ ions in a wide wavelength range of 420–500 nm. Under the excitation at 465 nm, YAG:Ce crystal wafer shows emission band peaking at about 535 nm, which originates from the 5d1 → 4 f1 transition of Ce3+. The thickness of crystal wafer has obvious influence on Ce3+ emission intensity, which increases with the increasing wafer thickness and reach a maximum value at a thickness of 1.5 mm. Moreover, YAG:Ce crystal wafer shows excellently thermal stability. The emission intensity of Ce3+ emission at 510 K is about 68.3% of its initial intensity at 300 K. The fabricated WLED by the crystal chip with the thickness of 1.5 mm reaches a maximum luminous efficacy of 112.33 lm/W and a CCT value of 4458.