David Menzies

Nonlinear size dependence of anatase TiO2 lattice parameters

We characterized the size dependence of anatase TiO2 lattice parameters using Rietveld analysis of angle-dispersive synchrotron x-ray diffraction data obtained on a suite of nanocrystalline samples. The refined crystal structure and microstructure data suggest that for crystallites with size less than ∼10nm, the lattice parameters vary nonlinearly. Small lattice expansion, associated with possible increased Ti vacancy and lattice strain, at reduced crystallite size observed in our samples is in contrast to the lattice contraction behavior reported for “pure” anatase nanocrystals. The nonlinear, composition-dependent variation of anatase unit cell volume contrasts with the linear expansion behavior of rutile lattice at finite sizes.

Modification of mesoporous TiO2 electrodes by surface treatment with titanium(IV), indium(III) and zirconium(IV) oxide precursors: preparation, characterization and photovoltaic performance in dye-sensitized nanocrystalline solar cells

Post-treatment of titanium dioxide (TiO2) films for use in dye-sensitized solar cells has been carried out with titanium(IV), indium(III) and zirconium(IV) oxide precursor solutions. The nanostructured electrodes were characterized using nitrogen gas sorption (NGS), x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), energy dispersive x-ray spectroscopy (EDX), field emission scanning electron microscopy (FEGSEM) and high resolution transmission electron microscopy (HRTEM). The change in the nanostructure was quantified and the thicknesses of the core?shell coatings determined. An evaluation of the dependence of thickness by HRTEM concluded that one coating step of either the indium or zirconium precursor gave thicknesses of 0.5?nm, with EDX and XPS confirming the presence of either In or Zr at the TiO2 electrode surface, respectively. These working electrodes were then used to fabricate dye-sensitized nanocrystalline solar cells (DSSCs) whose performance was tested under AM1.5G 100?mW?cm?2 illumination. TiCl4 post-treatment was found to improve the photovoltaic efficiencies from 3.6% to 5.3%. Single coatings of either In2O3 or ZrO2 on the TiO2 working electrode resulted in an increased efficiency from 3.6% up to 5.0%. Thinner coatings gave the highest solar cell efficiency. The drop in performance was mainly due to a decrease in short circuit current density (Jsc) with the greater shell thicknesses. ZrO2-coated TiO2 electrodes subjected to microwave heat treatment using a 2.45?GHz microwave produced the highest efficiencies (5.6%) largely due to an increase in short circuit current from 11.4 to 13.3?mA?cm?2.

Sol-gel synthesis of TiO/sub 2/ nanocrystals for application in dye-sensitized solar cells

TiO/sub 2/ nanocrystals have been synthesized from Titanium(IV) butoxide without the use of an autoclave. It was found that using heat treatment temperatures below 600/spl deg/C pure anatase phase was retained in the nanocrystals. In addition, with increasing heat treatment temperature the nanocrystals became larger in size and the homogeneity was dramatically reduced.

Monitoring the Synthesis and Composition Analysis of Microsilica Encapsulated Acetylacetonatocarbonyl Triphenylphosphinerhodium Catalyst by Inductively Coupled Plasma (ICP) Techniques

A novel technique to monitor the synthesis process of encapsulated acetylacetonatocarbonyl triphenylphosphinerhodium within a microsilica nanoshell has been studied using inductively coupled plasma (ICP) techniques. Nanospheres sized around 50-100 nm were obtained and ICP was used to quantify the exact composition of rhodium, phosphorous, and silicon with differing digestion solvents. In addition, ICP was used to detect rhodium and phosphorous in the nano core-shell catalysts as a quality control procedure

NANOSTRUCTURED TiO2 FILMS IN DYE-SENSITIZED SOLAR CELLS

The need for cost-effective renewable energy technology is of ever-increasing importance with the diminishing stock of raw materials for traditional non-renewable energy production. The dye-sensitized solar cell (DSSC) is a relatively new device that offers the potential of economically feasible conversion of solar energy to electricity. This approach to photovoltaic technology is a promising development in that it offers reasonable efficiencies, while using cheap materials and relatively simple manufacturing techniques. The aim of this paper is to provide a general background to DSSCs, an understanding of the components that make up the cell and an overview of the current research objectives.