MgO nano-facet embedded silver-based dielectric/metal/dielectric transparent electrode

Abstract

We replace Indium Tin Oxide (ITO) with an MgO nano-facet Embedded WO3/Ag/WO3(WAW) multilayer for electrodes of high efficiency OLEDs. WAW shows higher values for transmittance (93%) and conductivity (1.3x10(5) S/cm) than those of ITO. Moreover, WAW shows higher transmittance (92.5%) than that of ITO (86.4%) in the blue region (<500 nm). However, due to the large difference in refractive indices (n) of glass (n=1.55) and WO3 (n=1.95), the incident light has a small critical angle (52 degrees). Thus, the generated light is confined by the glass/WAW interface, resulting in low light outcoupling efficiency (similar to 20%). This can be enhanced by using a nano-facet structured MgO (n=1.73) layer and a ZrO2 (n=1.84) layer as a graded index layer. Using these optimized electrodes, ITO-free, OLEDs with various emission wavelengths have been produced. The luminance of OLEDs using MgO/ZrO2/WAW layers is enhanced by 24% compared to that of devices with ITO. (C)2012 Optical Society of America