Enhancing the Contact Area of Ti Wire as Photoanode Substrate of Flexible Fiber-Type Dye-Sensitized Solar Cells Using the TiO₂ Nanotube Growth and Removal Technique

The fiber-type dye-sensitized solar cell (FDSSC) with flexible and dim-light workable features is one of the promising energy generation devices for soft electronics. A novel TiO₂ nanotube (TNT) growth and removal technique is proposed in this study to enhance the contact area of the Ti wire substrate using anodization and ultrasonication processes. Smaller and denser imprints of TNT on the surface of Ti wire are obtained when a smaller voltage was applied for anodization. The thickness of the TiO₂ nanoparticle layer coated on the Ti wire is also optimized by varying the dip-coating layers. With the smallest diameter and densest distribution of TNT imprints on the Ti wire, the FDSSC with the TiO₂/TNT-printed Ti wire photoanode, prepared using 30 V as the anodization voltage, shows the highest photon-to-electricity efficiency of 2.37% as a result of the rough surface of Ti wire substrate, which provides more contact, as well as the suitable thickness of the TiO₂ nanoparticle layer, which promotes charge generation and transportation. The smallest charge-transfer resistance and the highest electron collection efficiency are also obtained in this case, as examined using the electrochemical impedance spectroscopy and intensity modulated photocurrent spectroscopy/intensity modulated photovoltage spectroscopy. This facile TNT growth and removal technique is expected to be able to be applied to other fields for enhancing the contact area of the titanium substrate and promoting the generation of electrochemical reactions.