Towards Improvement of Photovoltaic Performance of Aqueous Dye-sensitized Solar Cells by Tungsten-doped Mesoporous Nanobeads TiO_2 Working Electrode

Tungsten doped(W-doped) TiO_2 mesoporous nanobeads, possessing high surface area and superior scattering effect, were used for photoanode preparation. The W-doping would induce a positive shift of the TiO_2 conduction band, and enhance the driving force for electron injection and collection efficiencies. The electrochemical impedance spectra indicated a retarded charge recombination and increased electron diffusion length after W-doping. By fine-tuning the W-doping concentration to 0.25%, aqueous DSCs produced a significant improved the open circuit voltage of 712 mV and a short circuit current of 7.05 mA·cm^(-2), leading to an overall increased power conversion efficiency of 3.40% at 1 000 W·m^(-2) simulated irradiation, which is roughly 25% enhancement compared to that without W-doping photoanode.

Structural and optical properties of tungsten-doped vanadium dioxide films

Thin films of tungsten （W）-doped thermochromic vanadium dioxide （VO2） were deposited onto soda-lime glass and fused silica by radio frequency magnetron sputtering. The doped VO2 films were characterized by X-ray diffraction, optical transmittance measurement, and near field optical microscopy with Raman spectroscopy. X-ray diffraction patterns show that the （011） peak of W-doped thermochromic VO2 film shifts to a lower diffraction angle with the increase of W concentration. The optical measurements indicated that the transmittance change （AT） at wavelength of 2500 nm drops from 65% （AT at 35 ℃ and 80 ℃ for undoped VO2 film） to 38% （AT at 30 ℃ and 42 ℃ for the doped VO2 film）. At the same time, phase transition temperature drops from 65 ℃ to room temperature or lower with the increase of W concentration. Near field optical microscopy image shows that the surface of W-doped VO2 film is smooth. Raman results show that the main Raman modes of W-doped VO2 are centered at 614 cm 1, the same as that of undoped VO2, suggesting no Raman mode changes for lightly W-doped VO2 at room temperature, due to no phase transition appearing under this condition.

Preparation and characterization of transparent conducting ZnO:W films by DC magnetron sputtering

Tungsten-doped zinc oxide（ZnO：W） films with low resistivity and high transmittance were successfully deposited on glass substrates by direct current magnetron sputtering at low temperature.The deposition pressure is varied from 12 to 21 Pa.The X-ray diffraction results show that all of the deposited films are polycrystalline and have a hexagonal structure with a preferred c-axis orientation.The crystallinity,morphologies and resistivity of ZnO：W films greatly depend on deposition pressure while the optical properties including optical transmittance, optical band gap as well as refractive index are not sensitive to deposition pressure.The deposited films with an electrical resistivity as low as 1.5×10^（-4）Ω·cm,sheet resistance of 6.8Ω/□and an average transmittance of 91.3% in the visible range were obtained at a deposition pressure of 21 Pa and sputtering power of 130 W.