Figure 4: Absorption spectra of nanostructured silicon thin films.

(a) Absorption spectra of a 1 μm silicon thin film patterned by a quasi-random supercell (in black) and un-patterned (in red). The thin film is coated with a 70 nm AR coating and has a perfect conductor as the back electrode. The broad-band thin film absorption approaches the Lambertian limit across the entire spectrum of interest. (b) Comparison between a quasi-random structure (in black) and an optimized photonic crystal (in red). (c) Comparison between a quasi-random structure (in black) and a perturbed photonic crystal (in red). (d) Comparison between a quasi-random structure (in black) and an amorphous structure (in red). All spectra were calculated assuming un-polarized light.