Hydrothermal growth of perpendicularly oriented ZnO nanorod array film and its photoelectrochemical properties

By using a low cost, low-temperature hydrothermal approach, well-aligned ZnO nanorods with high aspect ratio have been successfully prepared on ITO substrates that were pre-modified with ZnO nanoparticles. The obtained ZnO nanostructure was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), and Raman spectroscopy. The results of characterization indicate that the nanorods are high-quality single crystals, grow along [0 0 1] direction and for 2 h growth time 90% of them have diameters of 120–190 nm. The thin films consisting of ZnO nanorods with controlled orientation onto ITO substrates allow a more efficient transport and collection of photogenerated electrons through a designed path. For a sandwich-type cell, with 0.3 mol/L LiI and 0.03 mol/L I2 in propylene carbonate electrolyte, the overall solar energy conversion efficiency reaches 2.1%.