Due to their high specific surface area and advanced properties, TiO2 nanotubes (TiO2 NTs) have a great significance for production and storage of energy. In this paper, TiO2 NTs were synthesized from anodization of Ti-6Al-4V alloy at 60 V for 3 h in fluoride ethylene glycol electrolyte by varying the water content and further annealing treatment. The morphological, structural, optical and electrochemical performances of TiO2 NTs were investigated by scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), UV-Visible spectroscopy and electrochemical characterization techniques. By varying the water content in the solution, a honeycomb and porous structure was obtained at low water content and the presence of (α + β) phase in Ti-6Al-4V alloy caused not uniform etching. With an additional increase in water content, a nanotubular structure is formed in the (α + β) phases with different morphological parameters. The anatase TiO2 NTs synthesized with 20 wt% H2O shows an improvement in absorption band that extends into the visible region due the presence of vanadium oxide in the structure and the effective band gap energy (Eg) value of 2.25 eV. The TiO2 NTs electrode also shows a good cycling performance, delivering a reversible capacity of 82 mAh.g−1 (34 μAh.cm−2.μm−1) at 1C rate over 50 cycles.

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The interfacial layer in a Schottky barrier solar cell plays an important role in determining the short circuit current, open circuit voltage, fill factor and efficiency of the cell. In this paper, we studied the effects of interfacial oxide layer thickness, interface state density and Ф0 (the level above the valence band to which surface states are filled in isolated semiconductor) on the open circuit voltage and efficiency of the SnO2/SiO2/Si (N) solar cells. From our analysis, we have found that the efficiency of the cell increases at first with the interfacial oxide layer thickness δ, and after acquiring a maximum value falls with a further increase of δ. We have optimized the interfacial layer thickness for maximum efficiency. The solar cell current–voltage characteristics under illumination are also computed for different values of insulator thickness δ. The results obtained by numerical simulation using Matlab programs are presented and discussed. The SnO2/SiO2/Si (N) solar cells, in which the interfacial oxide layer thickness is optimized to 21 A°, have an average open circuit voltage of 0.62 V and a short circuit current of 36 mA/cm². The calculated conversion efficiency of the cells can be as high as 17.5 %.