Luminescence Characteristics of Ba2+ Co-Doped Sr2SiO4:Eu Yellow Phosphor for Light Emitting Diodes

Abstract

We have synthesized a Eu2+-activated (Sr,Ba)₂SiO₄ yellow phosphor and investigated the development of blue LEDs by combining the phosphor with a InGaN blue LED chip (λem=405 nm). The InGaN-based (Sr,Ba)₂SiO₄:Eu LED lamp shows two bands at 405 nm and 550 nm. The 405 nm emission band is due to a radiative recombination from a InGaN active layer. This 405 nm emission was used as an optical transition of the (Sr,Ba)₂SiO₄:Eu phosphor. The 550 nm emission band is ascribed to a radiative recombination of Eu2+ impurity ions in the (Sr,Ba)₂SiO₄ host matrix. In the preparation of UV Yellow LED Lamp with (Sr,Ba)₂SiO₄:Eu yellow phosphor, the highest luminescence efficiency was obtained at the epoxy-to-yellow phosphor ratio of 1:0.45. At this ratio, the CIE chromaticity was x=0.4097 and y=0.5488.