Plasmonic Photovoltaics: Near-Field of Metal Nanowire Assemblies for Solar Cell Efficiency Enhancement

Abstract

Analysis of main principles of plasmonic photovoltaics relatively the enhancement of efficiency of solar cells (SC) by means of light trapping in thin film SC is considered in this report. Theoretical analysis and corresponding calculations of light transmittance enhancement into semiconductor due to light trapping via excitation of local (surface) plasmons and surface plasmon polaritons in periodic metal nanoparticles and nanowires array has been performed. The calculations have been performed for hexagonal lattice of nanoparticles or for rectangular cross section metal wires. The differential formalism method using the covariant form of Maxwell’s equations in curvilinear coordinate system has been used. Local distributions of electric field in plasmonic nanostructures are calculated for metal nanoparticles & nanowires in both s- and p-polarizaion of incident light. Then the light transmittance in far-field (wave) zone and the local generation rate of electron-hole pairs in near-field zone have been calculated using the spatial distribution of Poynting vector. Angular/spectral distributions of transmittance and position/spectral distributions of generation rates in nearfield zone have complicate non-homogeneous character due to excitation of surface plasmons and surface plasmon polaritons. It was shown that the main high near-field generation is localized in so-called hot points on the nanoparticles/nanowires surface. Averaged perpendicular to interface generation rate for p-polarization of light has near-field component, which phenomenologically can be considered as some additional term in boundary conditions for differential equations describing the photocurrent formation in solar cells.