ZnO/CdSe nanowires and nanotubes: formation, properties and applications

Arrays of vertically aligned ZnO nanotubes were obtained in two steps by combining the electrochemical deposition and chemical dissolution of the nanowire core. In the first step arrays of nanowires (diameter ∼ 200 nm, length ∼ 1.5 μm) were electrodeposited from O2 reduction in aqueous zinc chloride solutions. In the second step, the chemical dissolution of the nanowire core in a neutral pH chloride solution led to the formation of arrays of ZnO nanotubes with the same external dimensions and a wall thickness of ∼ 35 nm. Nanowires and nanotubes exhibited single-crystalline nature and no spurious phases were detected. The light scattering in both types of arrays was studied, emphasizing its influence on the sensitization of ZnO to solar light, by using a CdSe nanocrystalline coating as a light absorber. For a constant amount of CdSe deposited, the ZnO/CdSe nanowire arrays had a slightly higher effective absorption of the solar light (86% in the 400–725 nm range of (AM1.5) solar spectrum) than the ZnO/CdSe nanotubes (84%). However, ZnO/CdSe nanotubes exhibit a more attractive morphology for the transfer of electrical charge carriers and arrays of ZnO nanotubes appear to be very promising building blocks for nanostructured solar cells. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)