Luminescent Properties of SrGa2S4 :Eu2+ and Its Application in Green-LEDs

Phosphor SrGa2S4:Eu2+ was synthesized with a high temperature solid state reaction. Its absorption spectrum, photoluminescence spectra, and fluorescence lifetime were studied in details. The excitation spectrum extended from UV to visible light region, and matched the emission of GaN chip. (Sr1-xEux)Ga2S4 emits strong green light and the concentration quenching did not occur; while the thermal quenching was evident. The emission peak shifted to long wavelength with increasing Eu2+ concentration because of the changing of the crystal field strength. The lifetime of Eu2+ ion was in the order of microsecond, which was reasonable for d→f transition. The electroluminescence spectrum of as-fabricated PC-LED at IF = 20 mA was measured and most of the blue light of blue-LED chip at 460 nm was absorbed by the phosphor and simultaneously down-converted into an intensive green light at 540 nm. The color coordinate was (0.32, 0.63). SrGa2S4:Eu2+ was a promising phosphor for GaN-based green LEDs.