A plasma sputtering decoration route to producing thickness-tunable ZnO/TiO(2) core/shell nanorod arrays

We report a radio frequency magnetron sputtering method for producing TiO(2) shell coatings directly on the surface of ZnO nanorod arrays. ZnO nanorod arrays were firstly fabricated on transparent conducting oxide substrates by a hydrothermal route, and subsequently decorated with TiO(2) by a plasma sputtering deposition process. The core/shell nanorods have single-crystal ZnO cores and anatase TiO(2) shells. The shells are homogeneously coated onto the whole ZnO nanorods without thickness change. This approach enables us to tailor the thickness of the TiO(2) shell for desired photovoltaic applications on a one-nanometer scale. The function of the TiO(2) shell as a blocking layer for increasing charge separation and suppression of the surface recombination was tested in dye-sensitized solar cells. The enhanced photocurrent and open-circuit voltage gave rise to increased photovoltaic efficiency and decreased dark current, indicating successful functioning of the TiO(2) shell.