Photos: Left: National Renewable Energy Laboratory; Right: Plextronics

UP CLOSE: A technician [left] at the National Renewable Energy Laboratory measures the spectral response of a photovoltaic device, which indicates how sensitive it is to different hues of light. Industry leader Plextronics subjects its organic PV cells [right] to such independent evaluation, but others contend that the practice is expensive and time-consuming and that it stifles innovation.

Inorganic PV experts avoid such bickering through a culture of independent verification: prior to publishing, scientists and companies submit potentially record-breaking cells to international reference labs, including NREL, Germany's Fraunhofer Institute for Solar Energy Systems, and Japan's National Institute of Advanced Industrial Science and Technology, which offer such services at no cost to the researchers. The Materials Today editorial urged the organic PV community to adopt the same practice.

Easier said than done. The testing may be free, but preserving the fragile cells while they're en route and awaiting testing (a two- to eight-week queue at NREL) can cost several thousand dollars. At a minimum, the cells must be vacuum-packed. Better still is encapsulating the cells in glass or protective polymers—a sophisticated process that is beyond the expertise and resources of most academic labs.

Verification advocates recognize the added challenge but say that the interests of the community must prevail. “We have sympathy, up to a point,” says Shawn Williams, vice president of technology for Plextronics, which does adhere to prepublication verification. Especially with the industry approaching commercialization, Williams says, record claims must be “tempered” with certified results: “It's about credibility. If people go out there and publish results that are not substantiated, then we or anyone else who's out there with real results get lost in the noise.”

Some influential academics agree. One is Niyazi Serdar Sariciftci, a physicist at Austria's Johannes Kepler University Linz who collaborated with Heeger on his early PV research and whose work since then has helped Konarka raise more than US $100 million to commercialize organic PV. “In my opinion, every scientist has to go to an accredited lab and certify the claimed efficiency, particularly if the claim is for a world-record efficiency,” Sariciftci says. “If it has never been reproduced objectively, it does not exist for science.”

That kind of talk strikes others as elitist and counterproductive. “It took years to reproduce the Millikan oil-drop experiment. Therefore it didn't exist to scientists?” Carroll asks, referring to physicist Robert Millikan's famous 1910 experiment measuring the electron's charge and the resulting acrimonious debate that delayed Millikan's Nobel Prize by several years. Carroll says that a verify-then-publish system would thwart young researchers and other newcomers short on funds and influence. “That's going to begin to narrow down the number of people who are allowed to work and publish,” he says. “Is that really what you want happening at a time when we need to be exploring all options in solar energy?”

Heeger echoes Carroll's last sentiment. He and others who favor the publish-first, verify-later approach could even point to one of Heeger's own early reports on organic PV technology: a 1995 paper in Science reporting a cell that, according to the authors, delivered a conversion efficiency of 2.9 percent, seemingly shattering the 1 percent ceiling that had defined organic PV for a decade. Competitors quickly recognized that a calculation error had more than doubled the reported power output. Despite the mistake, the paper continues to be heavily cited as a seminal advance that pointed a path to the organic PV devices now edging toward commercial readiness.

Heeger never issued a retraction and still makes no apologies for the error. “Numbers are indeed important,” he says. “But scientific advances that demonstrate and enable quantum-step improvements are perhaps even more important.”