Scientists Study How To Stack The Deck For Organic Solar Power

A new class of economically viable solar power cells—cheap, flexible and easy to make—has come a step closer to reality as a result of recent work at the National Institute of Standards and Technology (NIST), where scientists have deepened their understanding of the complex organic films at the heart of the devices.

Organic photovoltaics, which rely on organic molecules to capture sunlight and convert it into electricity, are a hot research area because in principle they have significant advantages over traditional rigid silicon cells. Organic photovoltaics start out as a kind of ink that can be applied to flexible surfaces to create solar cell modules that can be spread over large areas as easily as unrolling a carpet. They'd be much cheaper to make and easier to adapt to a wide variety of power applications, but their market share will be limited until the technology improves.

Even the best organic photovoltaics convert less than 6 percent of light into electricity and last only a few thousand hours. "The industry believes that if these cells can exceed 10 percent efficiency and 10,000 hours of life, technology adoption will really accelerate," says NIST's David Germack. "But to improve them, there is critical need to identify what's happening in the material, and at this point, we're only at the beginning."

The NIST team has advanced that understanding with their latest effort, which provides a powerful new measurement strategy for organic photovoltaics that reveals ways to control how they form. In the most common class of organic photovoltaics, the "ink" is a blend of a polymer that absorbs sunlight, enabling it to give up its electrons, and ball-shaped carbon molecules called fullerenes that collect electrons. When the ink is applied to a surface, the blend hardens into a film that contains a haphazard network of polymers intermixed with fullerene channels. In conventional devices, the polymer network should ideally all reach the bottom of the film while the fullerene channels should ideally all reach the top, so that electricity can flow in the correct direction out of the device. However, if barriers of fullerenes form between the polymers and the bottom edge of the film, the cell's efficiency will be reduced.

By applying X-ray absorption measurements to the film interfaces, the team discovered that by changing the nature of the electrode surface, it will repulse fullerenes (like oil repulses water) while attracting the polymer. The electrical properties of the interface also change dramatically. The resultant structure gives the light-generated photocurrent more opportunities to reach the proper electrodes and reduces the accumulation of fullerenes at the film bottom, both of which could improve the photovoltaic's efficiency or lifetime.

"We've identified some key parameters needed to optimize what happens at both edges of the film, which means the industry will have a strategy to optimize the cell's overall performance," Germack says. "Right now, we're building on what we've learned about the edges to identify what happens throughout the film. This knowledge is really important to help industry figure out how organic cells perform and age so that their life spans will be extended."

Source: National Institute of Standards and Technology (NIST)

Intersolar North America 2009 Supports US Market Growth

Conference and exhibition attendance records surpass expectations

Intersolar North America, the most diverse global business-to-business exhibition in the United States dedicated to the transformation of the solar marketplace, showed continued growth with 2009's exhibition and conference. The co-located Intersolar North America and SEMICON West events, which took place last week in San Francisco, presented more than 560 solar exhibitors to approximately 17,000 trade visitors, exceeding organizers expectations for the second straight year. Intersolar North America alone featured 444 exhibitors, up from 210 exhibitors a year before - a 111 percent increase.

Further reinforcing the importance of Intersolar North America's international platform for exchange, trade visitors came from circa 90 countries with companies exhibiting from 23 countries, reflecting the incredible internationality of the solar market

"We are extremely excited about the growth of Intersolar North America," said Markus Elsaesser, CEO of Solar Promotion International GmbH, exhibition and conference organizer. "The US solar market has incredible potential, and with the support of industry associations, including the SEMI PV Group, ASES and CALSEIA, we are creating an opportunity for solar professionals to come together and discuss continued development for the US market."

While the exhibition alone was a draw for many, the conference and accompanying programs of Intersolar North America were heavily attended attracting more than 2,000 visitors. The conference portion featured more than 170 speakers presented at 25 conference tracks like the "Solar Start-ups Forum," "The Role of Public Policy in U.S. PV Market Development," and "Solar Gigawatts Symposium - Learning from European Success and American Ambition."

The "Solar Gigawatts Symposium" demonstrated the international roots of the Intersolar show, bringing together leaders from the European and American solar markets. Highlights included a high-level debate between policy and industry leaders on the appropriate policy tools for sparking market growth. An additional panel discussed the financing and residential installation trends in the US, as well as perspectives on European and US market growth.

In the extensive session "The Role of Public Policy in U.S. Market Development" a high-end range of speakers, from organizations and institutions such as the U.S. Department of Energy, CALSEIA, National Renewable Energy Laboratory (NREL), and the Fraunhofer Institute of Solar Energy Systems (ISE), came together to discuss the current challenges in creating a growth climate for solar technology in the United States. Discussions centered on how to optimize and carry forward the current programs in existence. During this track traditional incentives such as tax credits were discussed and compared with the highly debated topic of Feed-in-Tariffs (FiT) which was proposed as a crucial mean to support the continued development of solar technology and further stimulate solar energy growth in the US.

Intersolar North America 2010 will take place from July 13-15 in San Francisco.

For video highlights of Intersolar North America 2009, Intersolar TV can be found at: http://intersolar.us/index.php?id=441&L=1

www.intersolar.us >> Intersolar TV

Photos from the exhibition and conference can be downloaded at: http://intersolar.us/index.php?id=108&L=1&tx_ttnews[pointer]=0&cHash=fa2006870b

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About Intersolar North America

Intersolar North America is the most diverse international business-to-business trade show in the United States for the global solar industry. As the only solar trade show in North America dedicated to recruiting companies across the solar supply chain from around the world, Intersolar helps the industry improve global supply, distribution, training, regulation and business issues in order to accelerate market transformation and advance solar as a significant part of the global energy supply. Intersolar North America 2009 and SEMICON West featured more than 560 exhibitors and approximately 17,000 attendees in San Francisco on July 14-16. Intersolar North America was created in 2008 as a sister event to Intersolar in Munich, the world's largest and longest-running solar technology trade show. Intersolar North America is organized by Solar Promotion International GmbH and Freiburg Management and Marketing International (FMMI) GmbH and is co-organized with PV Group - the global photovoltaic initiative of SEMI. www.intersolar.us

Source: PRNewswire