Plasmonic photovoltaics: near-field of a metal nanowire array on the interface for solar cell efficiency enhancement

Abstract

The analysis of the main principles of plasmonic photovoltaics relative to the enhancement of the efficiency of solar cells (SCs) by means of light trapping in a thin film SC is considered in this paper. Theoretical analysis and corresponding numerical calculations of the transmittance into a semiconductor base enhancement due to light trapping via the excitation of local (surface) plasmons and surface plasmon polaritons in a periodic metal nanowire array have been performed. The calculations have been performed for rectangular cross-section metal nanowires by the differential formalism method using the covariant form of Maxwell’s equations in a curvilinear coordinate system. Local distributions of the electric field in plasmonic nanostructures are calculated for metal nanowires in both s- and p-polarization of incident light. Then both the light transmittance in the near- and far-field (wave) zones and the local generation rate of electron–hole pairs have been calculated using the spatial distribution of the Poynting vector. Angular/spectral distributions of transmittance and position/spectral distributions of the generation rate in the near-field zone have complicated the non-homogeneous character due to the excitation of surface plasmons and surface plasmon polaritons. It has been shown that the main highly enhanced near-field generation is localized in the so-called hot points on the nanoparticles/nanowires surface. The planar-averaged generation rate for the p-polarization of light has a near-field component, which is always more for a Si base (indirect bandgap semiconductor) than for GaAs (direct bandgap one). This plasmonic effect can be used for the base thicknesses down up to 100–150 nm due to light scattering and the surface plasmon enhancement of near-fields. These plasmon-carrying metal nanowires can be used as a current grid in an SC too.