Powerful Ideas: Spray-On Solar Cells

Jeanna Bryner

Date: 24 August 2009 Time: 10:27 AM ET

Sunlight-absorbing nano-inks could be spray painted onto solar cells.
CREDIT: Beverly Barrett.

Editor's Note: This occasional series looks at powerful ideas — some existing, some futuristic — for fueling and electrifying modern life.

Solar cells soon could be painted onto the sides of buildings or rooftops with nanoparticle inks, according to one chemical engineer.

The new nano-ink process could replace the standard method of manufacturing solar cells, which requires high temperatures and is relatively expensive, said Brian Korgel of the University of Texas at Austin.

"The sun provides a nearly unlimited energy resource, but existing solar energy harvesting technologies are prohibitively expensive and cannot compete with fossil fuels," Korgel said.

Also called photovoltaic cells, solar cells convert sunlight directly into electricity and are typically made from silicon, although other materials that are flexible are gaining steam. Solar panels used to power homes and businesses each consist of 40 or so of these cells, according to the National Renewable Energy Laboratory.

Rather than silicon, the inks developed by Korgel's team are made up of copper indium gallium selenide (CIGS) — sunlight-absorbing nanoparticles that are 10,000 times thinner than a strand of hair.

"We make a solution of these nanocrystals, and we spray paint them onto a substrate," said Matthew Panthani, a doctoral student and graduate research assistant in Korgel's lab.

The team envisions printing such inks in a newspaper-like process. "We'd have some sort of flexible substrate, maybe plastic or metal foil, and it would be on a spool and be unrolled. And the nanocrystals would be sprayed on," Panthani told LiveScience.

So far, they have developed solar-cell prototypes that can convert 1 percent of the sunlight that hits the cell into electricity.

"If we get to 10 percent, then there's real potential for commercialization," said Korgel, who co-founded the Calif.-based company Innovalight, which is currently producing silicon-based inks. "If it works, I think you could see it being used in three to five years."

But there's still a lot of work ahead. "It shows that there is potential but there's still a lot of research that needs to be done to figure out how to get 10 percent," Panthani said.

The prospect of painting these inks onto a rooftop or building is not far-fetched, the researchers say. In addition, the inks are semi-transparent, and so could some day be used to develop windows that double as solar cells, the researchers say.

The research, which was published in a recent issue of the Journal of the American Chemical Society, was funded by the National Science Foundation, the Welch Foundation and the Air Force Research Laboratory.