The optical properties of white organic light-emitting devices (WOLEDs) fabricated utilizing a CaAl12O19:Mn and Zn2SiO4:Mn phosphor layer were investigated. X-ray diffraction patterns for CaAl12O19:Mn and Zn2SiO4:Mn phosphors showed that Mn ions in the CaAl12O19:Mn phosphors were completely substituted into Ca ions and that Mn ions in the Zn2SiO4:Mn phosphors were completely substituted into Zn ions. Field emission scanning electron microscopy images showed that the size of the CaAl12O19:Mn phosphor was approximately between 0.1 and 3 microm, and that the size of the Zn2SiO4:Mn phosphor was smaller than 7 microm. 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 CaAl12O19:Mn and the Zn2SiO4:Mn phosphor down-conversion layers.

Electrical and optical properties of blue organic light-emitting devices (OLEDs) with doped or undoped emitting layers (EMLs) consisting of a heterostructure layer or a single layer were investigated. The driving voltage of the OLEDs with an undoped heterostructure multiple EML was lower than those of both OLEDs with a single EML and a doped heterostructure multiple EML. The electroluminescence spectra of the OLEDs with an undoped and a doped heterostructure EMLs showed dominant peaks related to two heterostructure layers.