The study of light waveguide effects on ZnO nanorod arrays

Two different types of ZnO nanorods (hexagonal pyramid-shaped nanorod and hexagonal prism-shaped nanorod) were integrated on light emitting diodes (LEDs) for the investigation of light waveguide effects, which were evaluated using electroluminescence (EL) and current-voltage ( I – V ) characteristics. EL intensity in LEDs with hexagonal prism-shaped ZnO nanorod arrays were improved by 18% while EL intensity in LEDs with hexagonal pyramid-shaped ZnO nanorods were reduced by 25% compared to bare LEDs. 3D-finite dimension time domain (3D-FDTD) programs were used to simulate the light waveguide effect on the two different shapes of ZnO nanorods. In addition, photonic crystals (PCs) effects in ZnO nanorod arrays were simulated to verify the light waveguide effect. It was found that light in a hexagonal prism-shaped ZnO nanorod propagated from the bottom to the top end. However, the light in a hexagonal pyramid-shaped ZnO nanorod was dissipated on the lateral face. The light extraction efficiency in ZnO nanorod arrays was dominated by the top end shape and planar density of ZnO nanorods.