More Efficient, and Cheaper, Solar Cells

New manufacturing techniques could cut solar power costs by 20 percent.

Improvements to conventional solar cell manufacturing that could significantly increase the efficiency of multicrystalline silicon cells and bring down the cost of solar power by about 20 percent have been announced by startup 1366 Technologies of Lexington, MA.

Light trap: Incoming light reflects off grooves in a silver band and is redirected along a glass cover. This light, which is usually lost, can then be absorbed by the solar cell. The grooved band is one of three improvements that could significantly lower the cost of making solar power. Credit: Technology Review

Multimedia   Take a tour of the labs and pilot manufacturing line at 1366 Technologies.   Watch a detailed demonstration of how to make solar cells more efficient.   See how solar has changed in the last 30 years, and where it's headed.

Such cost reduction would make solar power more competitive with conventional sources of electricity. In sunny environments, this could bring the cost of solar down to about 15 or 16 cents per kilowatt hour, says Craig Lund, 1366 Technologies's director of business development. That's cheaper than some conventional sources of electricity, especially those used during times of peak electricity demand.

1366 Technologies has developed three processes that can be incorporated into existing solar cell manufacturing lines to improve cell efficiency. It has shown that these technologies can be used to produce multicrystalline solar cells that are 18 percent efficient at converting sunlight into electricity. The current industry standard for such solar cells is 15 percent to 16 percent, according to Joonki Song, a partner with Photon Consulting, based in Boston, MA, although higher efficiencies have been reported. The company has demonstrated the new technologies before, but only with very small, experimental solar cells in a laboratory. Now it's made full-size solar cells using the type of equipment used in large-scale manufacturing.

The key to the startup's technologies, however, isn't the efficiency that it's achieved, but how little that efficiency costs. Lund says that the new processes add only a few cents per watt to the cost of fabricating solar cells, but this investment leads to much greater cost savings in the final product. Improving the amount of power each solar cell generates lowers materials costs, solar module manufacturing costs (in which cells are assembled into solar panels), and installation costs. In the end, Lund says, the cost of an installed solar panel will be reduced by 50 cents to 80 cents per watt.

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The new processes, which were invented by Emanuel Sachs, the company's chief technology officer and a professor of mechanical engineering at MIT, all increase the amount of light that solar cells can absorb.

In a normal silicon solar cell, electrons generated in the silicon must make their way out of the material to produce an electrical current, traveling first to the top layer of the silicon and then along this layer to narrow silver lines called "fingers." The fingers then conduct the electrons to the busbars, two or three prominent silver bands seen on the surface of most silicon solar cells. These bands shade the silicon under them, reducing the amount of light the cells can absorb.