Encapsulation issues in organic light-emitting diodes

Abstract

OLED is a new type of display technology based on electroluminescence of conjugated organic polymers or small organic molecules. It is widely believed that OLED technology will displace the position of LCD technology since it has many advantages over LCD. However the critical challenge now is to further improve the lifetime of OLED devices, particularly for flexible devices. Proper encapsulation is the key to this. Commonly, glass-epoxy encapsulation is used for OLED devices. This encapsulation layer is too thick and rigid to make flexible and/or thinner displays. Hence, thin film encapsulation of OLED is the subject of this thesis. Some issues examined here are the surface topography of the device wafer, ITO surface and the permeability of the barrier film. The fabrication process of OLED passive matrix displays and the development of thin film encapsulation are described. Subsequently we developed a multi-layer barrier stack as a potential encapsulation film structure. The barrier properties of this multi-layer barrier stack using organic and inorganiclayers were studied with the help of calcium corrosion test and device lifetime.