Abstract
The performances of thin film solar cells are considerably limited by the low light absorption. Plasmonic nanostructures have been introduced in the thin film solar cells as a possible solution around this issue in recent years. Here, we propose a solar cell design, in which an ultrathin Si film covered by a periodic array of Ag strips is placed on a metallic nanograting substrate. The simulation results demonstrate that the designed structure gives rise to 170% light absorption enhancement over the full solar spectrum with respect to the bared Si thin film. The excited multiple resonant modes, including optical waveguide modes within the Si layer, localized surface plasmon resonance (LSPR) of Ag stripes, and surface plasmon polaritons (SPP) arising from the bottom grating, and the coupling effect between LSPR and SPP modes through an optimization of the array periods are considered to contribute to the significant absorption enhancement. This plasmonic solar cell design paves a promising way to increase light absorption for thin film solar cell applications.
Highlights
The low conversion efficiencies and high production costs have been the major difficulties facing photovoltaic technology
The simulation results demonstrate that the designed structure gives rise to 170% light absorption enhancement over the full solar spectrum with respect to the bared Si thin film
The excited multiple resonant modes, including optical waveguide modes within the Si layer, localized surface plasmon resonance (LSPR) of Ag stripes, and surface plasmon polaritons (SPP) arising from the bottom grating, and the coupling effect between LSPR and SPP modes through an optimization of the array periods are considered to contribute to the significant absorption enhancement
Summary
The low conversion efficiencies and high production costs have been the major difficulties facing photovoltaic technology. A kind of novel thin film solar cell design of introducing several metallic patterned back contacts has been investigated widely [11,12,13,14,15] These patterned back contacts can couple the sunlight into SPP mode propagating along the metal/semiconductor interface and waveguide mode within the absorber layer, leading to about 30% broadband absorption enhancement over the solar spectrum when compared to the bared thin film cells [11]. This design takes advantage of LSPR excited in metal strips on the top, and can couple sunlight to multiple SPP modes at metal/semiconductor interface by the coupling of the bottom nanograting. The fabrication of such metal-semiconductor-metal nanograting structures is technically feasible by using some advance nanofabrication methods [21, 22]
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