The SiO 2 -Fe 3 O 4 core-shell nanostructures were synthesized by sol-gel chemistry. The morphological features of the nanostructures were examined by field emission scanning electron microscopy which revealed the core-shell nature of the nanoparticles. X-ray diffraction studies evidenced the formation of SiO 2 -Fe 3 O 4 core-shell nanostructures with high degree of homogeneity. The elemental composition of the SiO 2 -Fe 3 O 4 core-shell nanostructures was determined by energy-dispersive X-ray spectroscopy analysis. Fourier transform infrared spectroscopy showed the Si-O-Fe stretching vibrations. On analysis of the optical properties with UV-Vis spectra and Tauc's plot, it was found that the band gap of SiO 2 -Fe 3 O 4 core-shell nanostructures diminished to 1.5 eV. Investigation of the electrical properties of the core-shell nanostructures using field-dependent conductivity measurements presented a significant increase in photoconductivity as compared to those of its single components, thereby rendering them as promising candidates for application as photoelectrodes in dye-sensitized solar cells.
The main objective of this study is to show the effect of TiO 2 nanotube length, diameter and intertubular lateral spacings on the performance of back illuminated dye sensitized solar cells (DSSCs). The present study shows that processing short TiO 2 nanotubes with good lateral spacings could significantly improve the performance of back illuminated DSSCs. Vertically aligned, uniform sized diameter TiO 2 nanotube arrays of different tube lengths have been fabricated on Ti plates by a controlled anodization technique at different times of 24, 36, 48 and 72 h using ethylene glycol and ammonium fluoride as an electrolyte medium. Scanning electron microscopy (SEM) showed formation of nanotube arrays spread uniformly over a large area. X-ray diffraction (XRD) of TiO 2 nanotube layer revealed the presence of crystalline anatase phases. By employing the TiO 2 nanotube array anodized at 24 h showing a diameter ∼80 nm and length ∼1•5 μm as the photo-anode for back illuminated DSSCs, a full-sun conversion efficiency (η) of 3•5 % was achieved, the highest value reported for this length of nanotubes.
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