Fabrication and characterization of front-illuminated dye-sensitized solar cells with anodic titanium oxide nanotubes

We have fabricated front-side illuminated dye-sensitized solar cells (DSSCs) with a thin film of vertically oriented TiO₂ nanotubes used as the negative electrode. The TiO₂ nanotube film was formed by anodizing a metallic titanium thin film that was deposited on a transparent conductive oxide (TCO) layer with an intermediate, protective TiO₂ layer. We characterized the structural and electronic properties of the formed TiO₂ nanotube films. Titanium tetrachloride (TiCl4) treatment was applied on the TiO₂ nanotube film to improve the performance of the DSSCs. We have investigated effects of TiCl₄ treatment on the solar cell parameters of the DSSCs: short-circuit current density (I_SC), open-circuit voltage (V_oc), ideal factor (n), series resistance (R_s) and shunt resistance (R_sh). The parameters have been derived by analyzing measured I-V characteristic of the DSSCs on the basis of the method we have previously proposed. We demonstrate that the performance of the DSSCs is improved by TiCl₄ treatment. We discuss the effects of TiCl₄ treatment on the performance on the basis of the derived cell parameters.