Absorption enhancement in silicon nanowire-optical nanoantenna system for photovoltaic applications

• We designed a system made of silicon nanowire and so called bowtie nanoantenna.
• We investigate the effect of bowtie on absorption of visible and near infrared light by nanowire.
• The absorption enhancement in the nanowire caused by gold nanoprism was observed.
• The absorption enhancement occurs mostly in the near infrared part of solar spectrum.
• The absorption enhancement is dependent on the size of the nanoprisms.

The rapidly growing green energy sector has prompted the search for new solutions to increase the performance of solar cells. In this area there is still room for the silicon-based photovoltaic, although the main problem is to find a way to increase the efficiency of the silicon solar cells, at the lowest possible cost. In this work we investigate the influence of a gold bowtie nanoantenna on the absorption profile of silicon nanowire. Because of the energy band gap and low effective absorption cross section, bulk silicon absorbs rather poorly in longer wavelengths of visible light and near-infrared range. Our calculations with frequency domain solver show the absorption boost in nanowire at long-wavelengths due to the coupling of the large local near-field of metallic bowtie nanoantenna to the semiconductor layer. The enhancement was observed at various levels although it was correlated with the shift of localized surface plasmon resonance thus making it dependent on the bowtie geometry. The results suggest that by incorporating metallic nanostructures as well as nanoparticles to the nanowire system, the performance of photovoltaic device can be improved thanks to greater generation of a electron–hole pairs.

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