Web Release Date: February 26,
Nanostructured TiO2 Films with Controlled Morphology Synthesized in a Single Step Process: Performance of Dye-Sensitized Solar Cells and Photo Watersplitting
Aerosol and Air Quality Research Laboratory, Department of Energy, Environmental and Chemical Engineering, Washington University in Saint Louis, Saint Louis, Missouri 63130
Received: October 29, 2007
In Final Form: December 14, 2007
Abstract:
Nanostructured titanium dioxide (TiO2) films were synthesized with controlled morphology and thickness in
an ambient pressure single-step flame aerosol reactor (FLAR) for use in water splitting photocells and dye-sensitized solar cells. Two different morphologies were studied: a granular morphology and a highly crystalline
columnar morphology. The granular morphology consisted of nanoparticles, approximately 10 nm in diameter,
aggregated into fractal structures on the substrate. The granular morphology contained a large number of
grain boundaries and other interfacial defects. The columnar morphology consisted of single-crystal structures,
approximately 85 nm in width, oriented normal to the substrate. The well controlled deposition process was
used to deposit films with thicknesses in the range from 98 nm to 12 
m to establish the relationship to water
splitting and dye-sensitized solar cell performance. It was found that for watersplitting there was an optimum
thickness (~1.5 m), which was a tradeoff between light absorption and electron transport losses, where the
conversion efficiency was maximized. Due to differences in electron transport and lifetime in the TiO2 film,
for both applications the columnar morphology outperformed the granular morphology, achieving a uv-light
to hydrogen conversion efficiency of 11% for water splitting and a visible light to electricity conversion
efficiency of 6.0% for the dye-sensitized solar cell.
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