This is an excerpt from EERE Network News, a weekly electronic newsletter.

April 03, 2002

New Solar Cell Design Combines Plastics, "Nanorods"

Researchers at DOE's Lawrence Berkeley National Laboratory (LBNL) have developed a new recipe for producing solar cells: combine nanometer-sized rods ("nanorods") of semiconducting material with a conductive plastic called P3HT, and spin-cast the mixture onto glass. The result: an inexpensive device that can convert about 6.9 percent of indoor light into electricity. The results in sunlight are less promising — converting only 1.7 percent of sunlight into electricity — but the researchers expect to be able to improve on that number. The research, conducted in collaboration with the University of California at Berkeley, was published in the March 29th edition of the journal Science.

The researchers used cadmium selenide rods measuring just 7 nanometers — that's one billionth of a meter — in diameter and 60 nanometers in length. They found that modifying the diameter of the nanorods allowed them to "tune" the solar cells to respond to light of varying frequencies. This intriguing result suggests that the cells could possibly be built in several layers, each of which would respond to different frequencies of sunlight. Such "tandem" solar cell designs have achieved high efficiencies in the past using more traditional semiconducting materials. The use of plastic to form the solar cells suggests that they could be cast into a variety of flexible or rigid shapes, opening up a wide range of potential applications. See the LBL press release.

While plastics and nanotubes may one day be the basis of a new solar cell industry, for now the industry continues to rely heavily on the same material that fuels computer chips: silicon. And although the solar cell industry has often played the neglected stepsister to the semiconductor industry, that may be changing. In late March, Advanced Silicon Materials LLC (ASiMI), a producer of high-purity silicon for the semiconductor industry, announced a joint venture with Renewable Energy Corporation of Norway to produce polycrystalline silicon for solar cells at its plant in Moses Lake, Washington. The plant, which accounts for 40 percent of the company's production capability, was largely shut down in early March due to a slowdown in the semiconductor industry. Converting the plant to produce solar-grade silicon will provide a stable supply of the material for the solar cell industry while providing new growth potential for ASiMI. See the ASiMI press releases

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