More-Efficient Solar Cells

A new solar panel could lower costs and improve efficiency.

By changing the way that conventional silicon solar panels are made, Day4 Energy, a startup based in Burnaby, British Columbia, has found a way to cut the cost of solar power by 25 percent, says George Rubin, the company's president.

Better cells: A new design for solar panels (top) improves their efficiency. Each panel is made of arrays of square solar cells. A conventional solar cell (bottom) requires thick silver contacts that block light and reduce cell performance. The new design uses a novel electrode that eliminates these silver contacts. Credit: Day4 Energy

The company has developed a new electrode that, together with a redesigned solar-cell structure, allows solar panels to absorb more light and operate at a higher voltage. This increases the efficiency of multicrystalline silicon solar panels from an industry standard of about 14 percent to nearly 17 percent. Because of this higher efficiency, Day4's solar panels generate more power than conventional panels do, yet they will cost the same, Rubin says. He estimates the cost per watt of solar power would be about $3, compared with $4 for conventional solar cells. That will translate into electricity prices of about 20 cents per kilowatt-hour in sunny areas, down from about 25 cents per kilowatt-hour, he says.

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Other experimental solar technologies could lead to much lower prices--indeed, they promise to compete with the average cost of electricity in the United States, which is about 10 cents per kilowatt-hour. But such technologies, including advanced solar concentrators and some thin-film semiconductor solar cells, probably won't be available for years. Day4's technology could be for sale within 18 months, the company says.

In conventional solar panels, the silicon that converts light into electricity is covered with a network of silver lines that conduct electrons and serve as connection points for soldering together the individual solar cells that make up a panel. The network consists of rows of thin silver lines that feed into thicker wires called bus bars. Day4 replaces these bus bars with a new electrode that consists of rows of fine copper wires coated with an alloy material. The wires are embedded in an adhesive and aligned on a plastic film. The coated copper wires run on top of and perpendicular to the thin silver lines, connecting them to neighboring cells. The new electrode conducts electricity better than the silver lines, resulting in less power loss. It also covers up less of the silicon than the bus bars, leaving more area for absorbing light.