Traditional solar cell production techniques are usually time consuming and require expensive vacuum systems or toxic chemicals. Depositing chemical compounds such as CIGS on a substrate using vapor phase deposition also wastes most of the expensive material in the process. For the first time, engineers at Oregon State University (OSU) have now developed a process to create "CIGS" solar cells with inkjet printing technology that allows for precise patterning to reduce raw material waste by 90 percent and significantly lower the cost of producing solar cells with promising, yet expensive compounds.
The researchers focused on chalcopyrite, or "CIGS" - so named for the copper, indium, gallium and selenium elements of which it's composed - due to its high solar efficiency. A layer of chalcopyrite one or two microns thick has the ability to capture the energy from photons about as efficiently as a 50-micron-thick layer made of silicon.
The researchers were able to create an ink that could print chalcopyrite onto substrates with an inkjet approach, with a power conversion efficiency of about five percent. While this isn't yet high enough to create a commercially viable solar cell, the researchers say they expect to be able to achieve an efficiency of about 12 percent with continued research.
"This is very promising and could be an important new technology to add to the solar energy field," said Chih-hung Chang, an OSU professor in the School of Chemical, Biological and Environmental Engineering. "Until now no one had been able to create working CIGS solar devices with inkjet technology."
One of the major advantages of the new approach is the dramatic reduction in wasted material, which makes it feasible to rapidly produce ultra-low cost, thin film solar cells with promising yet expensive compounds.
"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."
The engineers are also studying other compounds that could be used with the inkjet technology that could cost even less. If they are able to reduce costs enough, the researchers say it also offers the prospect of creating solar cells that could be built directly into roofing materials.
The OSU team's findings have been published in Solar Energy Materials and Solar Cells and they have applied for a patent for the technology.