University of Washington has claimed that its popcorn-ball design for
dye-sensitized solar cells (DSCs) yields more than double the
efficiency levels of previous DSCs. The findings were presented at the
American Chemical Society’s national meeting in New Orleans recently.
The novel method uses a thin light-absorbing zinc oxide film approximately 10 micrometers thick and composed of tiny clusters of grains, with each grain about 15 nanometers across. The cluster format scatters and manipulates the incoming light rays, causing the light to travel longer distances within the cell.
Each cluster measures about 300 nanometers across, addressing both schools of thought in the technology which propose that while smaller grains have a greater overall surface area, and as a result absorb more light rays, larger grains are closer to the wavelength of light and are thus more efficient at scattering the light. The popcorn-ball design incorporates both of these facets of DSC technology, using small grains to form the larger clusters.
Efficiency rates of 2.4 percent are yielded using small particles alone, but researchers at the University of Washington claim an efficiency rate of 6.2 percent for their popcorn-ball design. While the material used, zinc oxide, is chemically less stable than the commonly used titanium oxide, it is, claims lead author Guozhong Cao, easier to use.
“We first wanted to prove the concept in an easier material. Now we are working on transferring this concept to titanium oxide,” Cao said. Titanium oxide-based DSCs currently yield 11 percent maximum efficiency, and, if the new design is compatible with titanium oxide, rates of efficiency could be pushed well over this rate.
Further information is available on the University of Washington’s website.
By Síle Mc Mahon
Large image shows a 300-nanometer sphere consisting of 15-nanometer grains.
Smaller image shows a close-up of the thin zinc oxide film made up of 300-nanometer spheres.