The next generation of high-performing, rapidly produced and cheaper thin-film solar devices could come courtesy of the common inkjet printer. "This is very promising and could be an important new technology to add to the solar energy field," said Chih-hung Chang, a professor in the School of Chemical, Biological and Environmental Engineering at Oregon State University. "Until now no one had been able to create working CIGS (copper indium gallium selenide) solar devices with inkjet technology." Part of the advantage of this approach, Chang said, is a dramatic 90 percent reduction in wasted material. Instead of depositing chemical compounds on a substrate with expensive vapor phase deposition — wasting most of the material in the process — inkjet technology could be used to create precise patterning with very low waste. This scanning electron microscope cross-sectional image shows the various compounds of a new chalcopyrite solar cell only a few microns thick, which can be created much less expensively with inkjet printing. (Image: Oregon State University) "Some of the materials we want to work with for the most advanced solar cells, such as indium, are relatively expensive," Chang said. "If that's what you're using, you can't really afford to waste it, and the inkjet approach almost eliminates the waste." One of the most promising compounds and the focus of the current study is called CIGS chalcopyrite. CIGS has extraordinary solar efficiency: Alayer of chalcopyrite one or two microns thick can capture the energy from photons about as efficiently as a 50-micron-thick layer made with silicon. In the new findings, published in the journal Solar Energy Materials and Solar Cells, researchers created an ink that could print chalcopyrite onto substrates with an inkjet approach with a power conversion efficiency of about 5 percent. The OSU researchers say that with continued research, they should be able to achieve an efficiency of about 12 percent, which would make a commercially viable solar cell. In related work, which is being done in collaboration with Greg Herman, an OSU associate professor of chemical engineering, the engineers are studying other compounds that might be used with inkjet technology and that might cost even less. Some approaches to producing solar cells are time-consuming, or require expensive vacuum systems or toxic chemicals. OSU experts are working to eliminate some of those roadblocks and to create much less costly solar technology that is also more environmentally friendly. New jobs and industries in the Pacific Northwest could evolve from such initiatives, they said. If costs can be reduced enough and other hurdles breached, it might even be possible to create solar cells that could be built directly into roofing materials, scientists say, opening a huge new potential for solar energy. "In summary, a simple, fast and direct-write, solution-based deposition process is developed for the fabrication of high-quality CIGS solar cells," said the researchers. "Safe, cheap and air-stable inks can be prepared easily by controlling the composition of low-cost metal salt precursors at a molecular level." This work was supported by the Daegu Gyeongbuk Institute of Science and Technology, the US Department of Energy and OSU's University Venture Development Fund. For more information, visit: www.oregonstate.edu