Materials Science

Wiry Approaches to Solar Harvesting

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Science  12 Oct 2007:
Vol. 318, Issue 5848, pp. 173
DOI: 10.1126/science.318.5848.173a

Silicon wire arrays could in principle provide a cost-effective alternative to high-performance single-crystal Si wafers. Wires grown via vapor-liquid-solid methods are also single crystals and avoid problems of recombination at grain boundaries. Moreover, the wire geometry facilitates carrier collection and fosters carrier generation in the space charge region deep within the array. Two studies have explored the use of Si wire arrays in photoelectrochemical cells. Goodey et al. grew p-type Si nanowire (NW) arrays either from a base of gold-capped cobalt NWs in anodic aluminum oxide membranes, or from a gold-coated p-type Si (111) substrate. On array immersion in dry acetonitrile solutions of Ru(2,2′-bipyridyl)3 2+ and Hg/Xe arc lamp illumination, cyclic voltammetry showed a shift in reduction wave peaks to more positive voltages relative to a Pt disk electrode. Photocurrent densities were about twice that of planar p-type Si. Maiolo et al. grew single-crystalline Si wires with diameters of ∼1 μm using a gold catalyst on an n-type Si(111) substrate with a silicon oxide buffer layer. In a 1,1′-dimethylferrocene redox system in methanol, illumination with simulated sunlight produced a shortcircuit photocurrent density of 2.2 mA/cm2. In both systems, better protection of the wire surfaces may improve performance. — PDS

J. Am. Chem. Soc. 129, 10.1021/ja073125d; 10.1021/ja074897c (2007).

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