We report the new application of electrospun TiO2 fibres as an electrode for dye-sensitized solar cells (DSSCs). TiO2 fibre electrode was electrospun directly onto a conducting glass substrate from a mixture of titanium(IV) propoxide and poly(vinyl acetate) (PVAc) in dimethyl formamide. The TiO2 fibres are composed of one-dimensionally aligned nanofibrils about 20 nm thick with an islands-in-a-sea morphology, which was obtained from the phase separation of TiO2 gel and PVAc during the solidification process. The porous structure of the electrospun TiO2 electrode was found to be efficiently penetrated by a viscous polymer gel electrolyte. In order to improve the photocurrent generation, we treated the electrospun TiO2 electrode with TiCl4 aqueous solution. The rutile crystal was grown on the surface of anatase TiO2 fibres. An additional TiO2 layer increased the volume fraction of active materials, resulting in an increase of sensitizer adsorption. The energy conversion efficiency obtained from electrospun TiO2 electrodes with a PVDF-HFP gel electrolyte was over 90% of that from a liquid electrolyte system.

In this report, dye-sensitized solar cells (DSSCs) with high energy conversion efficiencies were fabricated using TiO2 nanorods electrospun from a solution mixture of titanium n-propoxide and poly(vinyl acetate) in dimethyl formamide. Investigation of the charge transport characteristics of this unique type of DSSC disclosed that the efficiency of the DSSCs was enhanced by optimizing the nanorod morphology to facilitate charge transport. Our TiO2 nanorods have an intrinsically higher sensitizer loading capability than conventional TiO2 nanoparticles and have much slower recombination lifetimes compared to conventional nanoparticles. Long electron lifetime in nanorod electrode contributes to the enhanced effective photocarrier collection as well as the conversion efficiency. The electron transport behavior of nanorod photoelectrodes was further improved by TiCl4 post-treatment. The post-treatment reduces the pore volume of nanorod photoelectrodes while improving inter-rod connectivity and enhancing electron diffusion. The electron diffusion coefficient of post-treated nanorod was ∼51% higher than that of an untreated one, leading to a charge collection efficiency that was 19% higher at a incident photonflux of 8.1 × 1016 cm−2 s−1. Finally, the efficiency of nanorod-based DSSCs was optimized at a photoelectrode thickness of 14 μm to achieve 9.52% under masked illumination of simulated solar light, AM 1.5 Global (V oc = 761 mV, J sc = 17.6 mA cm−2, fill factor = 70.0%).

Ti O 2 single-crystalline nanorods are prepared from electrospun fibers which are composed of nanofibrils with an islands-in-a-sea morphology. The mechanical pressure produces each fibril into nanorods which are converted to anatase single crystals after calcination. High-resolution transmission electron microscopy shows that the (001) plane is growing along the longitudinal direction of the rod. In this work, the nanorod electrode provides the efficient photocurrent generation in a quasi-solid-state dye-sensitized solar cell using highly viscous poly(vinylidenefluoride-co-hexafluoropropylene)-based gel electrolytes. The overall conversion efficiency of the TiO2 nanorods shows 6.2% under 100mW∕cm2 (AM 1.5G) illumination.

URL: https://www.clinicaltrials.gov. Unique identifier: NCT02555319.