IBM boosts solar cell made of abundant materials

Researchers achieve efficiency gains with cell that uses "earth-abundant" materials. Cheaper thin-film cells rely on comparatively rare or costly metals.

IBM researchers are developing a solar cell with an eye towards what's in the ground.

Researchers on Wednesday published a technical paper in the journal Advanced Materials that describes a solar cell made of abundant materials with relatively high efficiency. The cell can convert 9.6 percent of solar energy into electrical energy, a 40 percent boost over current methods.

That level of efficiency is already far exceeded in commercial silicon-based cells and even beat by thin-film solar cells, which are cheaper to make than silicon cells but are less efficient. But IBM researchers set out to make a cell that uses materials that are relatively abundant elements--copper, zinc, tin, and sulfur, or selenium (CZTS). The availability of materials for existing solar technologies limits their long-term potential, according to IBM.

Solar cells made of copper, tin, zinc, and sulfur. IBM

First Solar, which claims to have the lowest cost per watt, makes its thin-film cells from cadmium and tellurium. GE, too, plans to sell solar panels with cadmium telluride cells as early as next year as well. There are also several start-up companies, including Nanosolar, Miasole, and HelioVolt, which make cells using a combination of copper, indium, gallium, and selenide, or CIGS.

The problem with these is the scarcity of materials or the environmental impact, according to IBM researchers Teodor Todorov, Kathleen Reuter, and David Mitz, who authored the paper. That means that other solar cell materials are needed to meet anticipated renewable energy demands, they said.

"Other solar cells which perform at similar efficiency levels are comprised of materials that have been either too costly to produce or contain elements that could limit production capacity, or have poor prospects for further improvements in efficiency, making commercialization and wide usage less likely," said Thomas Theis, director of physical sciences at IBM's T.J. Watson Research Lab, in a blog post.

One of the advantages of thin-film technologies is that that not much material is needed to make a cell, compared to traditional cell manufacturing. CIGS cells can be made using high-speed fabrication techniques, such as roll-to-roll manufacturing. The technique developed by IBM uses a similar "ink-based" method.

Matthew Beard, a researcher at the National Renewable Energy Laboratories not involved in the work, called the IBM research a "breakthrough."

The researchers estimate that if the technology can be taken beyond its basic state right now and achieve 12 percent efficiency, it could be an economically viable alternative to current products.

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