Evaluation of TiO₂ nanotubes decorated with Ag nanoparticles and photosensitized with grape skin extracts as a potential photoanode for dye-sensitized solar cells

The ITO/TiO₂NTs/AgNPs–dye photoanode, with potential applicability for dye-sensitized solar cells (DSSCs), was characterized by X-ray diffraction (XRD), Raman spectroscopy, field emission gun scanning electron microscopy (FEG-SEM), and diffuse reflectance spectroscopy (DRS). XRD analysis and Raman spectra confirmed the presence of the anatase phase of TiO₂NTs, while Raman also identified the presence of the grape skin extract (“dye”) on the surface of the film. FEG-SEM images revealed TiO₂NTs the presence of tubes with lengths of 1263.33 ± 58.59 nm and diameters of 92.7 ± 21 nm. DRS spectra and Tauc plots allowed to estimate the bandgap values of TiO₂NTs films between 3.00 and 3.20 eV. The electrochemical characteristics of the ITO/TiO₂NTs films, decorated or not with AgNPs and dye, were evaluated by transient photocurrent (TP) and electrochemical impedance spectroscopy (EIS) on different compositions. The TP analysis showed that the photoanode did not respond without a light source, but when UV light was applied it showed significant photocurrent responses. The best result was obtained with the ITO/TiO₂NTs-dye composition, due to the reduction in bandgap value and the higher visible radiation absorption. EIS analysis showed a significant reduction in the charge transfer resistance in the TiO₂NTs films when exposed to UV radiation, and the dye deposition onto ITO/TiO₂NTs surface caused significant changes in the electrode’s properties. Finally, the films presented in this study can potentially contribute to the capture of solar radiation and conversion into electricity in DSSCs, being a sustainable and highly attractive alternative for energy production.