IEEE Spectrum April, 2008 - 33

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.
Photos: leFt: NatioNal reNewable eNergy laboratory;
right: PlextroNics

Emery insists that he simply calibrated test equipment for
the researcher in question. "We had absolutely nothing to do
with designing the cells," Emery says. "I won't let anyone in
my lab get involved in fabricating PV technology." He adds that
doing so would violate his lab's certification.

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 quantumstep improvements are perhaps even more important." o

norganic 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 TO PROBE FURTHER The home page for the National Renewable
Sariciftci, a physicist at Austria's Johannes Kepler University Energy Laboratory's device-performance group (http://www.nrel.
Linz who collaborated with Heeger on his early PV research gov/pv/measurements/device_performance.html) has useful inforand whose work since then has helped Konarka raise more mation about how it measures photovoltaic cells.
than US $100 million to commercialize organic PV. "In my
Materials Today's November editorial on organic PV testing,
opinion, every scientist has to go to an accredited lab and cer- "The Value of Values," is available at http://dx.doi.org/10.1016/
tify the claimed efficiency, particularly if the claim is for a S1369-7021(07)70290-0.
40

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www.spectrum.ieee.org

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Table of Contents for the Digital Edition of IEEE Spectrum April, 2008