Is Organic PV the Future of Solar?
When Dr. Alan Heeger and his colleagues began experimenting with newly-found semiconducting polymers in the 1970s, they just wanted to understand the basic physics of how electrons were set free in the materials. But they ended up making a discovery that has helped advance a new generation of solar plastics and inks.
By oxidizing polyacetylene, a long-chain molecule which acts like a pigment, the researchers found the polymer to have extraordinarily high conductive properties.
“We realized it in a classic ‘ah ha moment,’” says Heeger. “But then over and over again, we saw additional properties that we had not foreseen.”
Eventually, Heeger and his colleagues, Alan MacDiarmind and Hideki Shirakawa, figured out that the material was not just a novelty. It had the potential to change the way we manufacture electronic devices, transistors, diodes and solar cells. These semiconducting polymers could be put in a solution and printed on a substrate - potentially creating a revolution in electronics that rivals what Gutenberg’s printing press did for books 600 years earlier.
“Printing is a low-cost, high speed manufacturing process…I doubt that there’s a lower-cost manufacturing for any solar technology,” says Heeger.
The science community agreed. In 2000, the three researchers received the Nobel Prize in chemistry for their work.
A year later Heeger co-founded Konarka, a Massachussets-based company working to commercialize organic solar PV technologies. The company has since racked up tens of millions of dollars in financing and has built a GW-scale manufacturing facility that produces “power plastic,” a flexible material that can be integrated into bags, electronics, and building materials.
With all this promising sounding news, one might think that the revolution in printed organic PV is underway. But that’s definitely not the case. A number of technical challenges and changing market conditions have made it difficult for third-generation solar companies to ramp up production and sell products.
“Clearly the industry had a good story to tell,” says technology journalist Peter Fairley. “But that story has since changed and I think things look very different today for these companies.”
During the height of the silicon shortage between 2005 and 2007, interest in emerging third-generation solar technologies was strong. The high price of silicon made printable, non-silicon based solar products look very attractive. Never mind that they were only 4 to 5 percent efficient and lasted for only a few years - roll-to-roll printing below a dollar per watt was an attractive selling point.
Then came Cadmium Telluride thin-film producer First Solar, which said it was manufacturing 11-percent efficient products below a dollar per watt. It quickly steamrolled its way to the top of global module producers.
The eventual easing of the silicon shortage and the global oversupply of PV caused a roughly 30% drop in prices, making traditional PV technologies more attractive than they’ve ever been. This has taken some of the spotlight off the third-gen PV industry as well.
Konarka may have a GW-scale manufacturing facility, but they don’t appear to be shipping anywhere close to that amount of product.
“I don’t believe that Konarka is producing a GW of material a year,” says Fairley. “They have to find buyers and people who want a GW of their material. And that’s still the number one challenge.”
With such low efficiencies and short product lifetimes, third-generation PV companies are trying to find a unique niche rather than taking traditional PV head-on. Applications like portable chargers, solar clothing, solar umbrellas and roll-out awnings are the most obvious. And after that, windows and building facades are a potentially promising area. Companies are already installing small building integrated systems, but organic solar technologies need to get much more efficient in order to achieve real scale.
“In the laboratory today, people are making these organic solar cells with peak power efficiencies in the range of 6 to 8 percent. We should be able to get twice that - and that’s our challenge,” says Konarka’s Heeger.
Success in the lab does not necessarily mean success in the market. However, these technologies have moved fairly quickly from research to reality. And if the progress continues, organic PV may someday be competitive with more traditional solar products - someday being the key word.
“It seems premature to call the technology commercialized,” says Fairley. “Many of the products that we’ve heard about have failed to materialize.”