Effects of the Mixing Ratio of the CaAl ₁₂O ₁₉:Mn and Zn ₂SiO ₄:Mn color-conversion layer on the color tunable emissions of white organic light-emitting devices

The optical properties of white organic light-emitting devices (WOLEDs) fabricated utilizing a CaAl ₁₂O ₁₉:Mn and Zn ₂SiO ₄:Mn phosphor layer were investigated. X-ray diffraction patterns for CaAl ₁₂O ₁₉:Mn and Zn ₂SiO ₄:Mn phosphors showed that Mn ions in the CaAl ₁₂O ₁₉:Mn phosphors were completely substituted into Ca ions and that Mn ions in the Zn ₂SiO ₄:Mn phosphors were completely substituted into Zn ions. Field emission scanning electron microscopy images showed that the size of the CaAl ₁₂O ₁₉:Mn phosphor was approximately between 0.1 and 3 μm, and that the size of the Zn ₂SiO ₄:Mn phosphor was smaller than 7 μm. The color coordinates of the electroluminescence spectra for WOLEDs with phosphor thicknesses of 0.25 and 0.35 mm shifted to the white emission side because the generated blue light from the blue OLEDs combined with the red and green lights was converted by the CaAl ₁₂O ₁₉:Mn and the Zn ₂SiO ₄:Mn phosphor down-conversion layers.