You walk into a clothing store. You buy a T-shirt, walk out into the sunny Texas weather, and later in the day notice that your phone battery is dying. On a cord poking out of your shirt is a tiny battery pack disguised as a button. You plug your phone in and charge it with the energy harnessed in the shirt. This is the not-so-distant future UT professor Brian Korgel’s research group is working toward.
For the past decade, Korgel’s team has been developing a photovoltaic solar ink that can be sprayed or printed as semiconductors on unusual surfaces like paper or plastic for use as solar panels. These nanoscopic solar cells are thousands of times smaller than a human hair, and are much smaller than the traditional method of wiring small electronics. The team is experimenting with creating a fabric from these semiconductors, in essence making solar panels with the flexibility and thickness of fabric.
“What we do is come up with ways of making materials that have never been made before and have interesting properties,” says Korgel, who also directs the Center for Next Generation Photovoltaics, a research group focused on the future of solar power.
Korgel first arrived at the idea of photovoltaic ink when he was working on his PhD in nanomaterials, finishing at UCLA. While he was there, he began to think about applications for the materials he was making. He got the idea for making conductors into paints from the structural similarity of solar cells and paint pigment.
“A lot of the materials we make in my research group are like paints, so it’s like peanut butter and chocolate—one day we thought, ‘Oh, that’ll be cool,’” Korgel says.
The next step for Korgel and his group was determining which materials to work with. “We targeted a material called CIGS, and that material had never been synthesized in this ink form before, so the second ‘aha’ moment was being able to make that,” he says.
Korgel’s group currently produces small solar cells an inch in diameter that can be painted onto paper, plastic, or rocks. A visited artist even worked with the group, creating art by painting solar cells onto rocks. The process and materials are very cheap, making commercialization a realistic goal. Another goal is to produce disposable solar cells—for example, painting the conductors onto a plastic coffee cup, charging something, and then throwing the cup away.
Korgel’s former student Taylor Harvey, PhD ’14, is working toward commercializing solar cells, but in a different application: rollable solar panels. Harvey started a company called Lucelo right before graduating, and collaborates with a larger company to work toward disposable plastic solar cells that can be spread around.
However, the research is still a work in progress. The solar cells function on a small scale and prove the concept, but Korgel hopes to make them better and larger. Currently they are able to charge at a 3 percent efficiency level, which is about one-sixth of a commercial solar panel. For Harvey’s rollable chargers, 3 percent can work, but for a T-shirt, there needs to be around 10 percent charging efficiency. In order for the cells to be painted onto fabric, Korgel’s group is experimenting with stretchable solar cells.
“With research you never really know if everything’s going to work, or where things are going to go,” Korgel says. Still, he remains hopeful that the product might be commercially viable within the next decade.
“I hope 10 years from now we’ll get there and make fabric you can wear and charge your phone with,” he says.
Solar rock photo courtesy James Sham.