Technology.am (Aug. 6, 2009) — University of Washington researchers are striving to develop organic solar cells that can be produced easily and inexpensively as thin films that could be widely used to generate electricity.
They have found a way to measure exactly how much electrical current is carried by tiny bubbles and channels that form inside nanoscale solar cells, paving the way for development of more efficient materials.
They aims to develop cells made from low-cost plastics that will transform at least 10 percent of the sunlight that they absorb into usable electricity and can be easily manufactured.
David Ginger, a UW associate professor of chemistry, displays the tiny probe for a conductive atomic force microscope, used to record photocurrents on scales of millionths of an inch in carbon-based solar cells.
He has found a way to make images of tiny bubbles and channels, roughly 10,000 times smaller than a human hair, inside plastic solar cells.
They are able to measure directly how much current each tiny bubble and channel carries, thus developing an understanding of exactly how a solar cell converts light into electricity.
As researchers approach that threshold, nanostructured plastic solar cells could be put into use on a broad scale, he said. As a start, they could be incorporated into purses or backpacks to charge cellular phones or mp3 players, but eventually they could make in important contribution to the electrical power supply.
For the current research, the scientists worked with a blend of polythiophene and fullerene, model materials considered basic to organic solar cell research because their response to forces such as heating can be readily extrapolated to other materials.
Ginger noted that the polymer tested is not likely to reach the 10 percent efficiency threshold. But the results, he said, will be a useful guide to show which new combinations of materials and at what baking time and temperature could form bubbles and channels in a way that the resulting polymer might meet the standard.
Such testing can be accomplished using a very small tool called an atomic force microscope, which uses a needle similar to the one that plays records on an old-style phonograph to make a nanoscale image of the solar cell.
As the microscope traces back and forth over a solar cell, it records the channels and bubbles that were created as the material was formed.
If costs can be brought low enough, then solar cells could offset the need for more coal-generated electricity in years to come.