Bright Idea

The future of solar energy could be on your desk — the inkjet printer

In the beginning, there was silicon, and it was really good.

Silicon is one of the most abundant elements on Earth. It gave us golden, sandy beaches and sunlit kitchen windows. Beer mugs and home insulation. Silicon Valley in California and Silicon Forest in the Pacific Northwest. Personal computers and the Information Age.

And solar energy — in its infancy. But for this critically important energy source, which is one of the most promising of all the alternative energy forms, silicon may not be the only source.

Illustration by Gavin Potenza

Illustration by Gavin Potenza

“Solar energy has enormous potential, but to reach that potential with large-scale electrical generation we’re probably going to need something besides current silicon technology,” says Chih-hung Chang, professor of chemical engineering at Oregon State University and director of the Oregon Process Innovation Center for Sustainable Solar Cell Manufacturing, or OPIC.

“We need huge improvements in solar cell manufacturing, to lower costs and reduce environmental impacts at the same time,” he adds. “Silicon will probably always be a significant player, but for mass commercial power production we will need additional solutions.”

Those solutions, OSU researchers say, may be with thin-film compounds that have an ability to outperform silicon by capturing more energy from photons at a lower cost, such as one called chalcopyrite that’s made from copper, indium, gallium and selenium. Or a less expensive but also promising compound made from copper, zinc, tin and sulfide.

There is one problem. Chalcopyrite doesn’t offer the crisp name recognition of Silicon Valley. So that’s bad. The wordsmiths may have to think of a catchy or colorful name.

But that aside, it could work better and usher in an era of high performing, rapidly produced, ultra-low-cost thin-film solar electronics. And it’s happening right now in Oregon.

Bay Area Partners

“We have five private companies already working with OPIC, including some Bay Area companies, and we’ve had discussions with several others,” says Greg Herman, an OSU associate professor of chemical engineering and associate director of the center. “So far this has attracted around $3 million in support, and Oregon is continuing to evolve as a focus of the solar energy industry.”

Earlier this summer, OSU researchers took an important step in that direction with a publication and patent application on a new technology that, for the first time, has created successful solar devices with inkjet printing. This rather pedestrian technology that decades ago revolutionized home and small office printing may now have unanticipated benefits for solar energy.

This novel approach reduces raw material waste by 90 percent. Instead of depositing chemical compounds on a substrate with more expensive vapor phase deposition — wasting most of the material in the process — inkjet technology creates precise patterning with a very low waste.

“Some of the materials we want to work with for the most advanced solar cells, such as indium, are relatively expensive,” Chang says. “If that’s what you’re using you can’t really afford to waste it, and the inkjet approach almost eliminates the waste.”

Power Conversion

So far, researchers have created an ink that can print chalcopyrite onto substrates with a power conversion efficiency of about 5 percent. With continued research they hope to achieve an efficiency of about 12 percent, which would make a commercially viable solar cell. In related work, Herman is continuing research with other compounds that might also be used with inkjet technology and cost even less.

Others are helping. OPIC is a collaboration of OSU, the University of Oregon, Portland State University, Oregon Institute of Technology, the Pacific Northwest National Laboratory, private industry and the Oregon Built Environment and Sustainable Technologies Center (Oregon BEST). Support is being sought from the U.S. Department of Energy, National Science Foundation, and Department of Defense. Collaborators are coming from Germany, Taiwan and South Korea.

In another advance reported last year, researchers used a “microreactor-assisted nanomaterial deposition” process to rapidly deposit thin films for solar cells, sidestepping more expensive processes such as sputtering and evaporation.

There may even be spinoffs that go beyond solar energy. Another application of these deposition processes is use of nanostructure films as coatings for eyeglasses, which could capture more light, reduce glare and cost less than existing coatings.

But solar energy is the primary target, and making Oregon a focus of that industry is a significant goal.

“We think with improved manufacturing processes and new materials, we can cut the materials cost of solar cells and produce these materials with low-cost, Earth-abundant materials in an environmentally sustainable way,” Herman says.

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