High color rendering index and directional emission of white OLEDs using nanorod waveguide channels

This paper presents the enhancement of light extraction and luminance efficiency by embedding nanorod waveguide channels on the external structure of organic light emitting diodes (OLEDs). In accordance with Rayleigh scattering and the Fresnel equations, much of the incident light will be propagated via multiple reflections and then extracted when a ZnO nanorod layer is prepared between the air and the glass backside of the OLED. For a blue OLED with a nanorod layer, the current efficiency and external quantum efficiency (EQE) were enhanced 16.1% and 48.9%, respectively. A nanorod-embedded white OLED (rod-WOLED), fabricated with a photoresist spacer coated between the nanorod layer and the color convention layer, showed a 98.5% enhancement in EQE. Highly stable and directional emission of the white OLED with a color rendering index of 77.5 was obtained, making it suitable for directional illumination applications.