Fabrication of Polystyrene/ZnO Micronano Hierarchical Structure Applied for Light Extraction of Light-Emitting Devices.

Polystyrene(PS)/ZnO micronano hierarchical structures were fabricated on a flat surface by depositing ZnO nanoparticles from a cluster beam at oblique incidence on the surface predeposited with PS microspheres. The hierarchical structure was composed of submicron-sized PS particle layers covered with dense films of columnar ZnO nanoparticle piles separated with nanoscale pores. It was demonstrated that the cooperative effect that combines the microlens function of the PS microspheres and the enhanced Rayleigh scattering of the ZnO nanoparticle porous layers can be used to greatly reduce the total internal reflection at the medium-air interface. The PS/ZnO hierarchical structures were fabricated on the surface of GaN-based light-emitting diode (LED) chips to enhance the light-extraction efficiency. A 77.7% improvement on the light-output power was realized, which was much greater than that obtained with the PS microstructures alone.