Core-shell Au–TiO2 nanoarchitectures formed by pulsed laser deposition for enhanced efficiency in dye sensitized solar cells

Abstract

Vertically aligned Au–TiO₂ core–shell nanowires were synthesized by using a two step method. Au nanowires were first synthesized using a galvanostatic constant current electrodeposition technique. A shell of anatase TiO₂ was subsequently grown on the Au nanowires using pulsed laser deposition. The core–shell nanostructures were then characterized using electron microscopy, electron diffraction, and X-ray diffraction techniques. The results showed that the wires were highly aligned and well separated. Dye sensitized solar cells were then fabricated using the core–shell nanowire arrays as photoanode, N535 dye as the sensitizer and I₃⁻/I⁻ as the redox electrolyte. The Au nanowires inside the highly crystalline TiO₂ anatase nanoshell provided a direct conduction path and improved transport for electrons between the TiO₂ and the conducting substrate. This efficient electron conduction out of the oxide semiconductor enhanced the current generation as well as the power conversion efficiency of the cell. The influence of the TiCl₄ post-treatment on Au–TiO₂ core–shell nanowire electrodes is investigated and compared to nontreated films. Cell efficiencies are improved, due to higher photocurrents as a result of this post-treatment. Optical effects of the metal nanowire may have also contributed to improved performance.