Published online by Cambridge University Press: 01 May 2014
Using first-principles full-field electromagnetic simulations, we demonstrate that near-perfect above-band-gap solar absorption can be achieved in nanostructured, ultra-thin-film iron oxide photoanodes for photoelectrochemical (PEC) water splitting. In our designed core-shell nanocone structures, all regions of hematite (α-iron oxide) are away from the interface between hematite and water by a minimum distance of less than the hole diffusion length in hematite, which is assumed to be no greater than 20nm. The optical absorption in our structure corresponds to a photocurrent density of 12.5mA/cm2 if one assumes an air mass 1.5 solar spectrum and a unity absorbed photon-to-current efficiency (APCE) for all wavelengths in that spectrum. Our photon management strategy eliminates the trade-off between optical absorption and carrier collection as commonly found in conventional designs of PEC cells, and variants of the strategy are generally applicable to other material systems.