Titanium flexible photoanode consisting of an array of TiO2 nanotubes filled with a nanocomposite of TiO2 and graphite for dye-sensitized solar cells

A flexible dye-sensitized solar cell (DSSC) was fabricated using a photoanode consisting of an array of TiO₂ nanotubes (TNT) filled with a nanocomposite of TiO₂ (P90) and nanographite. The array of TNT was obtained by anodic oxidation of Ti foil, and this Ti foil with TNT was used as the photoanode of the DSSC. Each tube in the array has an average diameter of 100 nm. The morphologies of the array of TNT were obtained both after and before filling them with the TiO₂/graphite nanocomposite, using a field-emission scanning electron microscopy (FE-SEM). DSSC with photoanode consisting of the nanocomposite (photoanode designated as Graphite/P90-TNT) rendered a light-to-electricity conversion efficiency (η) of 5.75%. In contrast, the cells with photoanodes consisting of only TNT (photoanode designated as TNT) and TNT filled with P90-TiO₂ (photoanode designated as P90-TNT) exhibited efficiencies (η) of 4.44% and 5.14%, respectively. The enhancements in the η’s in favor of the cells with P90-TNT and Graphite/P90-TNT were attributed to the filled P90 and nanocomposite, respectively. The filled particles were assumed to provide more conductive pathways for electron transfer and prolonged lifetime for electrons in the film of TNT. The results were substantiated by light-absorption values, incident-photo-to-current efficiency (IPCE) curves, Nyquist and Bode plots of electrochemical impedance spectroscopy (EIS), and photopotential transient curves.