The poor internal quantum efficiency (IQE) in hematite photoelectrodes arising from high recombination and insufficient absorption is one of the critical challenges towards achieving high efficiency water splitting. By combining the nanowire  geometry with the localized surface plasmon resonance  in semiconductor-metal-metal oxide core-multishell nanowires, we theoretically demonstrate an effective route to strongly improve absorption within ultrathin (sub-50 nm) hematite layers. The integrated photon flux absorbed within the hematite layer and the ideal corresponding photocurrent density computed are used as the basis to compare between various core-shell  and core-multishell NW structures. We show that Al based core-multishell nanowires exhibit photocurrent densities comparable to Ag based coremultishell nanowires. Specifically; Al based nanowires reach photocurrent densities of ~11.81 mA/cm2 (solar to hydrogen efficiency of 14.5%) within a 40 nm thick hematite shell. This corresponds to about 93% of the theoretical maximum for bulk hematite. Therefore, we establish Al as an excellent alternative plasmonic material to precious metals. Further, the absorbed photon flux is high close to the nanowire surface which ensures the charges generated can reach the reaction site without recombining. Although the nanowire geometry is anisotropic, the core-multishell NWs exhibit polarization independent absorption over large angles of incidence. These theoretical results strongly establish the effectiveness of the Al based core-multishell NWs for achieving scalable and cost-effective photoelectrodes with improved IQE enabling a novel route towards high efficiency water splitting.

Aluminum plasmonics in core-multishell nanowire photoelectrodes for high efficiency water splitting

248th National Meeting (2014)

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