title: Broad Band Light Absorption and High Photocurrent of (In,Ga)N Nanowire Photoanodes Resulting from a Radial Stark Effect.
abstract: The photoelectrochemical properties of (In,Ga)N nanowire photoanodes are investigated using H2O2as a hole scavenger to prevent photocorrosion. Under simulated solar illumination, In0.16Ga0.84N nanowires grown by plasma-assisted molecular beam epitaxy show a high photocurrent of 2.7 mA/cm2at 1.2 V vs reversible hydrogen electrode. This value is almost the theoretical maximum expected from the corresponding band gap (2.8 eV) for homogeneous bulk material without taking into account surface effects. These nanowires exhibit a higher incident photon-to-current conversion efficiency over a broader wavelength range and a higher photocurrent than a compact layer with higher In content of 28%. These results are explained by the combination of built-in electric fields at the nanowire sidewall surfaces and compositional fluctuations in (In,Ga)N, which gives rise to a radial Stark effect. This effect enables spatially indirect transitions at energies much lower than the band gap. The resulting broad band light absorption leads to high photocurrents. This benefit of the radial Stark effect in (In,Ga)N nanowires for solar harvesting applications opens up the perspective to break the theoretical limit for photocurrents.
authors.affiliation: Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5-7, 10117 Berlin, Germany.
authors.forename: Jumpei
authors.identifier: http://orcid.org/0000-0003-3465-9869
authors.initials: J
authors.lastname: Kamimura
authors.affiliation: Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Institute for Solar Fuels , Hahn-Meitner-Platz 1, 14109 Berlin, Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: Bogdanoff
authors.affiliation: Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5-7, 10117 Berlin, Germany.
authors.forename: Pierre
authors.initials: P
authors.lastname: Corfdir
authors.affiliation: Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5-7, 10117 Berlin, Germany.
authors.forename: Oliver
authors.initials: O
authors.lastname: Brandt
authors.affiliation: Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5-7, 10117 Berlin, Germany.
authors.forename: Henning
authors.initials: H
authors.lastname: Riechert
authors.affiliation: Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5-7, 10117 Berlin, Germany.
authors.forename: Lutz
authors.initials: L
authors.lastname: Geelhaar
keywords: H2O2; molecular beam epitaxy; nanowire; photoelectrode; water splitting