Electrophoretic deposition of titanate nanotubes from commercial titania nanoparticles: Application to dye-sensitized solar cells

The titanate nanotubes were synthesized by hydrothermal process using commercial titania nanoparticles. Subsequently, the titanate nanotubes film was fabricated at room temperature on FTO (F-SnO₂ coated glass) substrates using electrophoretic deposition (EPD) method at 40 V. The titanate nanotubes and the films were characterized with field-emission scanning electron microscope (FESEM), energy dispersive X-ray analysis (EDX), and X-ray diffraction (XRD). The average lengths of these nanotubes are few hundreds of nanometers and diameters ∼10-20 nm, with reasonably dense and uniform film. It was found that during EPD, the intercalated sodium (Na) from the titanate nanotubes was removed, as confirmed by XRD and EDX studies. Finally, dye-sensitized solar cells (DSSC) were prepared, after annealing the film from 450 °C to 550 °C, on using the two types of the films fabricated by electrophoretic deposition and doctor-blade method. It was observed that the open circuit voltage (V_oc) in all the cases was ∼0.8 V, with incident radiation intensity adjusted to AM-1.5. The solar cell corresponding to electrodeposited titanate nanotubes annealed at 500 °C showed a photocurrent density (I_sc) of ∼15.67 mA/cm² (η = 6.71%). The solar cell fabricated with doctor-blade method using titanate nanotubes, annealed at 450 °C shows much lower photocurrent density ∼1.31 mA/cm² (η = 0.65%), due to non-conversion of titanate nanotubes to titania, intercalated sodium and poor interfacial adhesion between titanate nanotubes and FTO substrate.