Nanosinusoidal Surface Zinc Oxide for Optical Out-coupling of Inverted Organic Light-Emitting Diodes

A zinc oxide (ZnO) layer having a random nanosinusoidal surface on one side is reported. Our new ZnO nanostructure is fabricated in a few minutes at room temperature by simplified one-step nanoparticle lithography utilizing spin-coated SiO2 nanoparticles as a temporal mask. Inverted organic light-emitting diodes adopting the nanosinusoidal surface ZnO in the bottom cathode exhibit better angular characteristics and 35% enhancement of efficiency in both phosphorescent and fluorescent emission through the liberation of waveguide and surface plasmon modes while maintaining good electrical characteristics and lifetime. The fabrication recipe can be freely modified and expanded to create various or more complicated nanoshapes of ZnO films, which can inspire other possible applications of the ZnO nanostructures.