Vertically Oriented TiO₂ Nanotube Arrays Grown on Ti Meshes for Flexible Dye-Sensitized Solar Cells

We describe here the growth of vertically oriented TiO 2 nanotube arrays on Ti meshes by electrochemical anodization and their application as flexible electrodes for dye-sensitized solar cells (DSC). The dependence of physical features (i.e., diameter, wall thickness, and length) of TiO 2 nanotube arrays on the anodization duration is systematically studied. Our results indicate that this type of flexible electrodes features transparency and high bend ability when subjected to external force. Varying the length of nanotube arrays has been demonstrated to critically influence the solar-to-electric conversion efficiency of DSCs. In combination with a low-volatility organic electrolyte and a rigid platinized conductive glass counter electrode, TiO 2 nanotube arrays with an optimized length of 40 μm on a 50-mesh substrate achieve a conversion efficiency of 1.47% (calculated from the geometric area of Ti mesh) at 97.4 mW/cm 2 AM 1.5 simulated full light. A lightweight flexible DSC is also fabricated using the same nanotube arrays combined with a flexible Pt/ITO/PET counter electrode, which generates a conversion efficiency of 1.23%.