A New Flexibility With Thin Solar Cells
By Henry Fountain, October 6, 2008
Source: New York Times
http://www.nytimes.com/2008/10/07/science/07obsola.html?ref=environment
Photovoltaic cells, the basic building blocks of solar panels, are more efficient and less costly than ever. But manipulating cells (which are usually made of semiconductor materials) and incorporating them into different panel designs is not necessarily easy. John A. Rogers of the University of Illinois, Urbana-Champaign, and colleagues have come up with a novel method for creating extremely thin solar cells that can be combined in flexible, even partially transparent, arrays. Described in Nature Materials, it could be called the rubber-stamp approach.
The technique involves creating a series of precisely spaced “microbars” on a block of single-crystal silicon. These bars, which have a thickness of a few micrometers, have doped regions that create p-n junctions, the main feature of most photovoltaic cells.
Through an etching process, the bars are undercut so they can be lifted off the remaining silicon using a block of rubbery material. They can be transferred to a substrate of another material, and this transfer-printing process can be repeated many times to build a cell. A metal grid is overlaid to create electrical connections.
The technique may allow the fabrication of solar arrays with a variety of characteristics. For example, the researchers say it would be possible to print the cells on rollable plastic sheets that would be easy to transport and install. Or by printing the cells on glass in different densities, solar arrays could be incorporated into windows that have a specific level of transparency.