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Published June 2013 | Supplemental Material
Journal Article Open

Optical, electrical, and solar energy-conversion properties of gallium arsenide nanowire-array photoanodes


Periodic arrays of n-GaAs nanowires have been grown by selective-area metal–organic chemical-vapor deposition on Si and GaAs substrates. The optical absorption characteristics of the nanowire-arrays were investigated experimentally and theoretically, and the photoelectrochemical energy-conversion properties of GaAs nanowire arrays were evaluated in contact with one-electron, reversible, redox species in non-aqueous solvents. The radial semiconductor/liquid junction in the nanowires produced near-unity external carrier-collection efficiencies for nanowire-array photoanodes in contact with non-aqueous electrolytes. These anodes exhibited overall inherent photoelectrode energy-conversion efficiencies of [similar]8.1% under 100 mW cm^−2 simulated Air Mass 1.5 illumination, with open-circuit photovoltages of 590 ± 15 mV and short-circuit current densities of 24.6 ± 2.0 mA cm^−2. The high optical absorption, and minimal reflection, at both normal and off-normal incidence of the GaAs nanowire arrays that occupy <5% of the fractional area of the electrode can be attributed to efficient incoupling into radial nanowire guided and leaky waveguide modes.

Additional Information

© 2013 The Royal Society of Chemistry. Received 23rd January 2013; Accepted 14th March 2013. First published online 17 Apr 2013. The non-aqueous photoelectrochemistry and optical simulation was supported by the Office of Science of the U.S. Department of Energy under Award no. DE-SC0004993 to the Joint Center for Artificial Photosynthesis, a DOE Energy Innovation Hub; and the MOCVD growth was supported by the Center for Energy Nanoscience, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Basic Energy Sciences under Award Number DE-SC0001013. The authors acknowledge Professor Hans-Joachim Lewerenz, Professor Michelle Povinelli and Stanley Burgos for helpful discussions, and Dr Ron Grimm for assistance with the photoelectrochemical studies. Optical data were collected at the Molecular Materials Research Center of the Beckman Institute of the California Institute of Technology. M.Y. acknowledges a USC Provost's Ph.D. Fellowship and K. T. F. acknowledges the National Science Foundation for Graduate Research Fellowship under Grant no. DGE-1144469.

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