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Zirconium (Zr) is doped up to 5 at. % in anatase TiO2 nanowires by electrospinning and used as working electrode in dye-sensitized solar cells. Variations observed in the photovoltaic parameters were correlated by electrochemical impedance spectroscopy, open circuit voltage decay, and X-ray diffraction measurements. Results show that homovalent substitution of Zr in TiO2 increased the chemical capacitance and electron diffusion coefficient which in turn decreased charge transport resistance and charge transit time. However, lattice strain due to size mismatch between the Zr4+ and Ti4+ ions decreased open circuit voltage and fill factor thereby setting a trade-off between doping concentration and photovoltaic properties. [ABSTRACT FROM AUTHOR]

Dye-sensitized solar cell (DSC) modules are generally made by interconnecting large photoelectrode strips with optimized thickness (∼14 μm) and show lower current density (JSC) compared with their single cells. We found out that the key to achieving higher JSC in large area devices is optimized photoelectrode volume (VD), viz., thickness and area which facilitate the electron channeling towards working electrode. By imposing constraints on electronic path in a DSC stack, we achieved >50% increased JSC and ∼60% increment in photoelectric conversion efficiency in photoelectrodes of similar VD (∼3.36×10-4 cm³) without using any metallic grid or a special interconnections. [ABSTRACT FROM AUTHOR]

One-dimensional nanostructures of niobium-doped anatase TiO2 (Nb:TiO2) up to 5 at.% Nb were synthesized by electrospinning a polymeric solution containing titanium and niobium precursors and subsequent annealing. Thus obtained fibers had diameter ∼150 nm. The undoped TiO2 fibers were constituted by larger single crystalline grains of size ∼50 nm, whereas the doped ones had decreased grain sizes (∼30 nm) under similar processing conditions. The Nb doping decreased the BET surface area of TiO2. A strain-induced lattice contraction was observed in Nb:TiO2. The continuous nanofibers were shortened to nanowires (NW) of aspect ratio 10:1 by ultrasonically dispersing them in acetic acid, which were developed as films of thickness ∼8-13 μm onto conducting glass substrates. The TiO2 and Nb:TiO2 nanowire films were further sensitized by a dye; the amount of dye anchored was found to decrease with increase in the dopant concentration. The dye-sensitized solar cells fabricated using the doped fibers, although with a nominally increased current density (JSC), have reduced efficiency due to lower fill factor and open circuit voltage (VOC). The electron diffusion coefficient (Dn) and mobility (μn) of the TiO2 and Nb:TiO2 NW in the presence of iodide/triiodide ions were an order of magnitude higher compared with the undoped samples. [ABSTRACT FROM AUTHOR]