Beneficial roles of Al back reflectors in optical absorption of Si nanowire array solar cells

We investigate the influence of Al back reflectors on the optical absorption spectra of Si nanowire (NW) arrays by using the finite-difference time-domain simulation method. A flat Al layer enhances the absorption in the NW array due to not only the reflection-induced optical path length enlargement but also reflection of light between NWs and localized surface plasmon induced optical field confinement. An Al underlayer with a grating structure allows grating-coupled surface plasmon polariton excitation and raise the optical absorption in the Si NWs. Interplay among all these factors on the optical absorption and expected solar cell performance of the NW arrays is discussed. (C) 2013 AIP Publishing LLC.This work was supported by the Pioneer Research Center Program (2010-0002231) and the Quantum Metamaterials Research Center (2008-0061893) through the National Research Foundation of Korea Grant. This work was also supported by the New & Renewable Energy Technology Development Program of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) Grant (20123010010160)