High-Efficiency and High-Operational-Stability Top-Emitting Organic Light-Emitting Diodes Using Antioxidant Buffer Layer

Abstract

We have succeeded in developing top-emitting organic light-emitting diodes (OLEDs) with high efficiency and high operational stability using an antioxidant buffer layer. V 2 O 5 was selected as the antioxidant buffer layer to suppress the degradation of the organic materials of OLEDs caused by active oxygen during buffer layer deposition and the damage caused by the bombardment of high-energy particles during transparent electrode sputtering. The top-emitting device with a V 2 O 5 buffer layer had the same current density-voltage (J-V ) characteristics as the bottom-emitting device with the same material system. The quantum efficiency of the top-emitting device was about 5%, the same as that of the bottom-emitting device. The time required for luminance to drop to 90% of the initial value of the top-emitting device was over 700 h, which is longer than that of the bottom-emitting device (300 h). From X-ray photoelectron spectroscopy (XPS) analysis of the interface between organic materials and V 2 O 5 , it was determined that there was no degradation of organic materials under V 2 O 5 .