%0 Journal Article
%T Plasmonic Nanostructure for Enhanced Light Absorption in Ultrathin Silicon Solar Cells
%A Jinna He
%A Chunzhen Fan
%A Junqiao Wang
%A Yongguang Cheng
%A Pei Ding
%A Erjun Liang
%J Advances in OptoElectronics
%D 2012
%I Hindawi Publishing Corporation
%R 10.1155/2012/592754
%X 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. 1. Introduction The low conversion efficiencies and high production costs have been the major difficulties facing photovoltaic technology. For solar cells based on bulk crystalline silicon, around 40% of a solar cell module¡¯s price comes from the silicon (Si) materials and its processing costs. To reduce the costs, thin film solar cells with an active layer thickness of about 1 to 2£¿¦̀m are desired. Thin film solar cells with the thickness of material film smaller than the carrier diffusion length can also reduce carrier recombination and improve carrier collection efficiency in bulk recombination-dominated semiconductors. In addition, a significant reduction of the active materials enables some scare semiconductor materials such as Te and In to be used in a large scale. However, the performance of all thin film solar cells is limited by the poor light absorption due to the reduced absorber thickness. For example, the indirect band gap semiconductor Si material has poor absorption to near-band gap light, where the absorption length is larger than 300£¿¦̀m. Therefore, light trapping schemes are essential for the design of ultrathin solar cells with improved absorption. In the past years, many light trapping techniques have been investigated for solar cell applications. A typical example is the use of micron-size pyramidal surface textures [1]. However, such textures are not suitable for thin film solar cells due to large texturing size with respect to the film thickness. Recently, the concept of
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