Characterization of light absorption in thin-film silicon with periodic nanohole arrays

Light absorption in thin-film nanostructured monocrystalline silicon (c-Si) in a glass/Ag(0.2 µm)/c-Si(1 µm) stack is characterized using simulations and measurements. Nanohole (NH) arrays designed for a practical thin-film solar cell configuration experimentally exhibit a significant improvement of the light absorption in the 1-µm ultrathin c-Si layer that exceeds the theoretical Yablonovitch limit in the long wavelength range. Fabricated square-lattice and hexagonal NH arrays give relative improvements of 65 and 70%, respectively, in the total absorption compared to a nonpatterned stack. The effect of an indium-tin-oxide (ITO) coating is also simulated, and an empty NH configuration gives the lowest ITO parasitic absorption.