You probably won't find it in the Guinness Book of World Records. But researchers working on an early stage technology called organic solar cells are fighting to prove who holds the goods that can convert the most light into electricity.
Such a claim doesn't just come with bragging rights. Showing higher energy conversion rates also could open the door to private and public investment.
But some scientists are concerned that when it comes to reporting record efficiencies for organic solar cells, a slew of published research papers are coming up with unrealistic and questionable results.
Their fear, made public in the October issue of the magazine Materials Today, is that sloppy outcomes could damage the burgeoning field. But just how realistic are such qualms?
Organic solar cells are made from carbon-based materials. They can come in the form of high-tech plastics that conduct electricity. In comparison, most solar cells are made from conventional inorganic (non-carbon-based) materials, like silicon.
These organic cells are part of the so-called "thin-film" solar category, which is made up of technologies that use little or no silicon -- an attractive characteristic in a worldwide shortage of solar-grade silicon.
Thin-film advocates say the technologies can be made using a simpler and cheaper manufacturing process, leading to lower costs. The cells also can be printed onto a flexible and lightweight substrate and other surfaces, which could lead to new applications for solar, such as textiles.
Investors are taking note.
Investors Go Organic
This month, startup Konarka bagged $45 million in private equity for its "power plastic" technology from the likes of Mackenzie Financial Corporation, Good Energies, Pegasus Capital and Draper Fisher Jurvetson.
And the Carbon Trust, a private company set up by the British government in response to climate change, is also getting in on the action. In October, it unveiled a £5 million, or $10.24 million, organic solar cell R&D program. The University of Cambridge and The Technology Partnership will spearhead the project.
But the technology still has hurdles to overcome before researchers and companies can bring it to the masses. Currently the cells hold relatively low efficiency rates ranging from about 3 to 5 percent. Traditional solar electric cells offer about a 15- to 20-percent efficiency.
Analysts say higher efficiencies will be needed to bring organic cells into the mass market.
"World-record efficiencies are popping up almost every month, leading the (organic solar cell) community into an endless and dangerous tendency to outbid the last report," said Gilles Dennler, author of the opinion piece and researcher for solar startup Konarka, in a statement.
A group of more than 15 scientists signed the opinion piece. Among them were eight scientists from Konarka, a Lowell, Mass.-based company working on organic solar-cell technology. The article noted opinions expressed are those of the author and the signatories, not the company's.
Dennler explained that the outbidding phenomenon damages the reputation of organic solar cells, which already face enough difficulties when it comes to convincing people of their benefits over other energy sources.
Dennler said part of the solution lies in researchers seeking independent verification of solar-cell efficiencies from the likes of the U.S. National Renewable Energy Laboratory, Germany's Fraunhofer Institute for Solar Energy Systems and other high-level international institutions.
But Mike McGehee, an associate professor at Stanford University and fellow signator, wants readers to keep things in perspective.
"They are being exaggerated by about 10, maybe 20, percent," he said of some researchers. But mostly the problem is graduate students making slight measurement mistakes, which shouldn't detract from the excitement around the industry, he said.
However, when it comes to reporting a world record, "there is a lot at stake," McGehee said. "I think the reason some of us are upset about this is that we could be penalized by funding agencies or investors because the numbers we are reporting aren't as high."
Why is it so hard to measure an organic solar cell's efficiency? McGehee said some of the challenges lie in the fact that researchers can't measure efficiency using the sun, since it emits light at different wavelengths. As a result, researchers measure using lab lights, which are not identical.
So who does hold the world record for the organic solar cell with the highest energy conversion rate? According to the independent verifiers, that honor belongs to Plextronics.
The Pittsburgh-based company said in August the National Renewable Energy Laboratory certified a 5.4 conversion rate.
In August, Plextronics also closed its second round of funding, raking in $20.6 million Investors included Solvay North America Investments, Firelake Capital Management and Draper Triangle Ventures. Plextronics also is a Top 10 Greentech Media company (see Top Ten Startups in Greentech).
Since the company first started working in the area more than two years ago, it has called for a standardized way of measuring the conversion rate, said Jim Dietz, Plextronics' vice president of business and development.
The company also has been concerned about the impact of questionable efficiency claims. Dietz worries about the negative impact of researchers who publish results that the industry can't deliver.
But, with the emergence of new technologies, performance-measurement inconsistencies often come along with them.
"It's an early stage market," Dietz said. He anticipates that in the next year or two, a standard for measuring efficiencies in organic solar cell will become a staple in the industry.
Until then, he says, look for that verification.