Plasmonics induced absorption enhancement in silicon nanowires coated with metallic nanoparticles

The optical properties of silicon nanowires (Si NWs) coated with metallic nanoparticles (NPs) were theoretically investigated. A three dimensional (3D) model of a solar cell has been proposed, in which the Si NWs were geometrically modeled to be periodically aligned nano-pillars in a square lattice. Hemispherical metallic NPs were coated onto a sidewall of Si NWs. We numerically studied the optical properties of the structure with the finite element method (FEM) by using the commercial software COMSOL Multiphysics. It is demonstrated that the electromagnetic field is strongly localized around the metallic NPs as well as between the metallic NPs and Si NWs. Localized surface plasmons (LSPs) are generated around the metallic NPs, coupling and scattering a large amount of light into the Si NWs. A significant enhancement of the light absorption is observed, especially in the long wavelength range of the solar spectrum. These theoretical investigations agree well with our experimental data while providing a fundamental background for improving the efficiency of Si NWs solar cells.