An easy approach for the fabrication of TiO2 nanotube-based transparent photoanodes for Dye-sensitized Solar Cells

The fabrication and characterization of TiO2 nanotube (NT) arrays and their integration in front-side illuminated Dye-sensitized Solar Cells (DSCs) are reported. Vertically oriented TiO2 NTs were obtained by anodic oxidation of titanium foil and not-curling free-standing NT membranes were easily separated from the metal without the formation of cracks. Stoichiometry, crystalline phase and morphology of the films were investigated, evidencing the formation of a highly ordered 1D NT array, with a pure anatase crystalline structure. Transparent photoanodes were fabricated transferring the membranes on FTO/glass sheet with an adhesion layer made of TiO2 nanoparticle (NP). What makes this work different from others reported in literature is the easiness of the technological approach: no mechanical or chemical etchings are required for NT membrane detachment and only one thermal step is needed for NT crystallization and TiO2 NPs/NTs interface formation. TiO2 NT-based DSCs were fabricated using a reversible microfluidic architecture and the cells were characterized by I–V electrical measurements, incident-photon-to-electron conversion efficiency, open circuit voltage decay and impedance spectroscopy. Compared to the standard NP-based DSC, the TiO2 NT-based one shows a huge increase of the transport properties and a consequent improvement in cell performances.