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Published January 8, 2010 | Supplemental Material
Journal Article Open

Energy-Conversion Properties of Vapor-Liquid-Solid–Grown Silicon Wire-Array Photocathodes


Silicon wire arrays, though attractive materials for use in photovoltaics and as photocathodes for hydrogen generation, have to date exhibited poor performance. Using a copper-catalyzed, vapor-liquid-solid–growth process, SiCl_4 and BCl_3 were used to grow ordered arrays of crystalline p-type silicon (p-Si) microwires on p^+-Si(111) substrates. When these wire arrays were used as photocathodes in contact with an aqueous methyl viologen^(2+/+) electrolyte, energy-conversion efficiencies of up to 3% were observed for monochromatic 808-nanometer light at fluxes comparable to solar illumination, despite an external quantum yield at short circuit of only 0.2. Internal quantum yields were at least 0.7, demonstrating that the measured photocurrents were limited by light absorption in the wire arrays, which filled only 4% of the incident optical plane in our test devices. The inherent performance of these wires thus conceptually allows the development of efficient photovoltaic and photoelectrochemical energy-conversion devices based on a radial junction platform.

Additional Information

© 2010 American Association for the Advancement of Science. Submitted 19 August 2009; accepted 10 November 2009. We acknowledge the Stanford Global Climate and Energy Project and the U.S. Department of Energy (grant DE-FG02-05ER15754) for financial support. S.W.B. thanks the Kavli Nanoscience Institute for a postdoctoral fellowship. L. O'Leary is thanked for her contributions. The authors have filed U.S. patent applications (20090020150 and 20090020853) related to this work.

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October 19, 2023