The authors numerically investigate the absorption enhancement of an amorphous Si solar cell, in which a periodical one-dimensional nanowall or two-dimensional nanopillar structure of the Ag back-reflector is fabricated such that a dome-shaped grating geometry is formed after Si deposition and indium-tin-oxide coating. Electrical field amplitude distributions (in log scale) at the wavelengths of 500 (a), 600 (b), 695 (c), and 745 (d) nm in the solar cell with a 1-D grating of h = 110 nm when TEpolarized sunlight is normally incident (Ã?Â¸ = 0). See Y.-W. Kiang et al. Fig. 6 for details.