White Organic Light-Emitting Devices Fabricated Utilizing a Down-Conversion CaAl12O19:Mn Phosphor Layer

Abstract

White organic light-emitting devices (OLEDs) were fabricated utilizing a CaAl12O19:Mn phosphor layer. X-ray diffraction patterns for CaAl12O19:Mn phosphors showed that Mn ions in the CaAl12O19:Mn phosphors were completely substituted into Ga ions. Field-emission-scanning electron microscopy images showed that the sizes of the CaAl12O19:Mn phosphor crystals were approximately between 0.1 and 3 mu m. Although a broad band approximately between 250 and 550 nm of an excitation spectrum for CaAl12O19:Mn appeared, peaks were observed at 639, 654, and 665 nm of the fluorescence emission spectrum. The color coordinates of the electroluminescence spectra for white OLEDs 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 light converted by the CaAl12O19:Mn phosphor down-conversion layer. The color conversion efficiency of white OLEDs was significantly affected by the excitation source and the thickness of the phosphor layer.