David Kirkpatrick

May 12, 2010

Doubling organic solar cell efficiency …

Filed under: et.al. — Tags: , , , , , — David Kirkpatrick @ 12:39 pm

… with “light pipes.” If this research bears fruit it will be a major solar breakthrough — drastically increased efficiency coupled with lower cost manufacturing. A win-win.

From the link:

Researchers in North Carolina have developed a way to more than double the performance of organic solar cells by adding a layer of upright optical fibers that act as sunlight traps.

David Carroll, a professor of physics at Wake Forest University, led the development of a prototype solar cell incorporating the fibers. He is the chief scientist at a spinoff company called FiberCell that is developing a reel-to-reel manufacturing process to produce the cells. “We’re on the cusp of having working demonstrators that would convince someone to go into production with this,” said Carroll.

The best organic solar cells today are nearly 8 percent efficient, although efforts are ongoing to develop organic chemistries that would push the efficiency of such cells above 10 percent. But Carroll says improved chemistries alone won’t be enough to catch up to the performance of silicon cells. “The answer doesn’t lie in chemistry–it lies in the architecture of the cell itself,” he says. Carroll adds that the dollar-per-watt cost of manufacturing fiber-based organic cells should be about the same cost as for flat organic cells. “But they can be produced in a factory costing one-tenth that of a silicon foundry,” he says. This would make them much cheaper to produce than silicon cells.

Fiber forest: This prototype solar panel is covered with optical fibers. Photons bounce around inside the fibers before being absorbed, and this doubles the panel’s efficiency compared to regular organic cells.
Credit: Wake Forest University

August 5, 2009

Solar cells, nanotech and plastics

This release involves using nanotechnology to help create that efficiently turn light into electricity, improving solar cells in the process.

The release:

Plastics that convert light to electricity could have a big impact

IMAGE: David Ginger, a University of Washington associate professor of chemistry, displays the tiny probe for a conductive atomic force microscope, used to record photocurrents on scales of millionths of an…

Click here for more information. 

Researchers the world over are striving to develop organic solar cells that can be produced easily and inexpensively as thin films that could be widely used to generate electricity.

But a major obstacle is coaxing these carbon-based materials to reliably form the proper structure at the nanoscale (tinier than 2-millionths of an inch) to be highly efficient in converting light to electricity. The goal is to develop cells made from low-cost plastics that will transform at least 10 percent of the sunlight that they absorb into usable electricity and can be easily manufactured.

A research team headed by David Ginger, a University of Washington associate professor of chemistry, has found a way to make images of tiny bubbles and channels, roughly 10,000 times smaller than a human hair, inside plastic solar cells. These bubbles and channels form within the polymers as they are being created in a baking process, called annealing, that is used to improve the materials’ performance.

The researchers are able to measure directly how much current each tiny bubble and channel carries, thus developing an understanding of exactly how a solar cell converts light into electricity. Ginger believes that will lead to a better understanding of which materials created under which conditions are most likely to meet the 10 percent efficiency goal.

As researchers approach that threshold, nanostructured plastic solar cells could be put into use on a broad scale, he said. As a start, they could be incorporated into purses or backpacks to charge cellular phones or mp3 players, but eventually they could make in important contribution to the electrical power supply.

Most researchers make plastic solar cells by blending two materials together in a thin film, then baking them to improve their performance. In the process, bubbles and channels form much as they would in a cake batter. The bubbles and channels affect how well the cell converts light into electricity and how much of the electric current actually gets to the wires leading out of the cell. The number of bubbles and channels and their configuration can be altered by how much heat is applied and for how long.

The exact structure of the bubbles and channels is critical to the solar cell’s performance, but the relationship between baking time, bubble size, channel connectivity and efficiency has been difficult to understand. Some models used to guide development of plastic solar cells even ignore the structure issues and assume that blending the two materials into a film for solar cells will produce a smooth and uniform substance. That assumption can make it difficult to understand just how much efficiency can be engineered into a polymer, Ginger said.

For the current research, the scientists worked with a blend of polythiophene and fullerene, model materials considered basic to organic solar cell research because their response to forces such as heating can be readily extrapolated to other materials. The materials were baked together at different temperatures and for different lengths of time.

Ginger is the lead author of a paper documenting the work, published online last month by the American Chemical Society journal Nano Letters and scheduled for a future print edition. Coauthors are Liam Pingree and Obadiah Reid of the UW. The research was funded by the National Science Foundation and the U.S. Department of Energy.

Ginger noted that the polymer tested is not likely to reach the 10 percent efficiency threshold. But the results, he said, will be a useful guide to show which new combinations of materials and at what baking time and temperature could form bubbles and channels in a way that the resulting polymer might meet the standard.

Such testing can be accomplished using a very small tool called an atomic force microscope, which uses a needle similar to the one that plays records on an old-style phonograph to make a nanoscale image of the solar cell. The microscope, developed in Ginger’s lab to record photocurrent, comes to a point just 10 to 20 nanometers across (a human hair is about 60,000 nanometers wide). The tip is coated with platinum or gold to conduct electrical current, and it traces back and forth across the solar cell to record the properties.

As the microscope traces back and forth over a solar cell, it records the channels and bubbles that were created as the material was formed. Using the microscope in conjunction with the knowledge gained from the current research, Ginger said, can help scientists determine quickly whether polymers they are working with are ever likely to reach the 10 percent efficiency threshold.

Making solar cells more efficient is crucial to making them cost effective, he said. And if costs can be brought low enough, solar cells could offset the need for more coal-generated electricity in years to come.

“The solution to the energy problem is going to be a mix, but in the long term solar power is going to be the biggest part of that mix,” he said.

 

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March 9, 2009

NanoMarkets report on organic photovoltaics sector

News from the inbox today.

The release:

NanoMarkets Issues New Report on Materials for Organic Photovoltaics Sector

GLEN ALLEN, Va., March 9 /PRNewswire/ — NanoMarkets, a leading industry analyst firm based here, today announced the release of its newest report, “Organic Photovoltaic Materials Markets: 2009 – 2016”.  The report projects that sales of materials for both “pure” organic solar cells (OPV) and hybrid organic/inorganic dye-sensitized solar cells (DSC), are expected to reach almost $600 million ($US) by 2016. The report goes on to note that the willingness of materials firms to meet the small demands from organic PV manufacturers today stands a good chance of being rewarded with substantial orders today. Details about the report are available at www.nanomarkets.net.

The firm will also be holding a webinar to present findings from the report on Tuesday, March 17th at 10:00 EDT.  See the NanoMarkets website for details.

Other Findings from the Report:

As there are no settled architectures or materials structures for organic PV there is considerable potential for materials firms of all sizes to set industry standards. According to NanoMarkets’ new report, three areas of special opportunity are (1) more efficient organic absorber materials, (2) improved electrode materials, (3) new layers for OPV cells that enable these cells to leap to greater energy conversion efficiencies. With regard to new materials, the new NanoMarkets report discusses in depth the role of nanomaterials and new dye types for DSCs. It notes in the latter case that today’s DSCs use ruthenium, one of the rarest metals on the planet.

New materials and architectures will similarly spell opportunities for equipment makers. Today, OPV/DSC cell manufacturers require production equipment that is good enough for prototype production. The next step will be to create production equipment that is optimized for production runs of working devices.  NanoMarkets believes that OPV may eventually be helped from the development of large scale manufacturing of OLED lighting applications, which are likely to be very similar to those required for OPV and DSC fabrication, so there may be some synergistic opportunities in providing R2R production equipment for both applications.

About the Report:

Organic Photovoltaic Materials Markets: 2009 – 2016 analyzes and quantifies the markets for OPV/DSC materials of all kinds. Coverage includes the latest R&D and commercialization efforts in the area of the core absorber layers for pure OPV and DSC solar cells, as well as the materials used for electrodes, encapsulation and substrates. The report discusses the materials products and strategies of the key players and companies, including both firms that are specifically focused on OPV materials (e.g., Plextronics) and those that develop materials for their own solar panels (e.g., Konarka). The new NanoMarkets study also provides a roadmap for improvements in OPV lifetimes, materials prices, efficiencies and other factors, along with a detailed eight-year forecast of OPV/DSC materials in both volume and value terms.

This report focuses on developments at the materials level that are impacting the commercialization of OPV/DSC and will be invaluable to strategic planners and marketing managers at materials and solar panel firms of all kinds, as well as electronics companies and investors.

About NanoMarkets:

NanoMarkets tracks and analyzes emerging market opportunities in electronics created by developments in advanced materials. The firm has published numerous reports related to organic, thin film and printable electronics materials and applications and maintains a blog at www.nanotopblog.com that comments on industry trends and events. NanoMarkets research database is the industry’s most extensive source of information on thin film, organic and printable (TOP) electronics. Visit www.nanomarkets.net for a full listing of NanoMarkets’ reports and other services.

Source: NanoMarkets

Web Site:  http://www.nanomarkets.net/

January 16, 2009

The latest in organic solar cells

Another subject I haven’t had the opportunity to cover in a while. I really get the impression that basic research into advanced solar cell technology has passed a critical point where it’s when, and not how — and more importantly, the when part is now sooner than later.

The release:

U of T chemistry discovery brings organic solar cells a step closer

Inexpensive solar cells, vastly improved medical imaging techniques and lighter and more flexible television screens are among the potential applications envisioned for organic electronics.

Recent experiments conducted by Greg Scholes and Elisabetta Collini of University of Toronto’s Department of Chemistry may bring these within closer reach thanks to new insights into the way molecules absorb and move energy. Their findings will be published in the prestigious international journal Science on January 16.

The U of T team — whose work is devoted to investigating how light initiates physical processes at the molecular level and how humans might take better advantage of that fact — looked specifically at conjugated polymers which are believed to be one of the most promising candidates for building efficient organic solar cells.

Conjugated polymers are very long organic molecules that possess properties like those of semiconductors and so can be used to make transistors and LEDs. When these conductive polymers absorb light, the energy moves along and among the polymer chains before it is converted to electrical charges.

“One of the biggest obstacles to organic solar cells is that it is difficult to control what happens after light is absorbed: whether the desired property is transmitting energy, storing information or emitting light,” explains Collini. “Our experiment suggests it is possible to achieve control using quantum effects, even under relatively normal conditions.”

“We found that the ultrafast movement of energy through and between molecules happens by a quantum-mechanical mechanism rather than through random hopping, even at room temperature,” explains Scholes. “This is extraordinary and will greatly influence future work in the field because everyone thought that these kinds of quantum effects could only operate in complex systems at very low temperatures,” he says.

Scholes and Collini’s discovery opens the way to designing organic solar cells or sensors that capture light and transfer its energy much more effectively. It also has significant implications for quantum computing because it suggests that quantum information may survive significantly longer than previously believed.

In their experiment, the scientists used ultrashort laser pulses to put the conjugated polymer into a quantum-mechanical state, whereby it is simultaneously in the ground (normal) state and a state where light has been absorbed. This is called a superposition state or quantum coherence. Then they used a sophisticated method involving more ultrashort laser pulses to observe whether this quantum state can migrate along or between polymer chains. “It turns out that it only moves along polymer chains,” says Scholes. “The chemical framework that makes up the chain is a crucial ingredient for enabling quantum coherent energy transfer. In the absence of the chemical framework, energy is funneled by chance, rather than design.”

This means that a chemical property – structure — can be used to steer the ultrafast migration of energy using quantum coherence. The unique properties of conjugated polymers continue to surprise us,” he says.

 

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Greg Scholes and Elisabetta Collini are with the Department of Chemistry, the Institute for Optical Sciences and the Centre for Quantum Information and Quantum Control at the University of Toronto. The research was funded by the Natural Sciences and Engineering Research Council of Canada.

October 17, 2008

Organic solar cells go into mass production

Filed under: Business, Science, Technology — Tags: , , , — David Kirkpatrick @ 1:14 am

One step closer to my rooftop.

From the link:

In a significant milestone in the deployment of flexible, printed photovoltaics, Konarka, a solar-cell startup based in Lowell, MA, has opened a commercial-scale factory, with the capacity to produce enough organic solar cells every year to generate one gigawatt of electricity, the equivalent of a large nuclear reactor.

Organic solar cells could cut the cost of solar power by making use of inexpensive organic polymers rather than the expensive crystalline silicon used in most solar cells. What’s more, the polymers can be processed using low-cost equipment such as ink-jet printers or coating equipment employed to make photographic film, which reduces both capital and manufacturing costs compared with conventional solar-cell manufacturing.

The company has produced its cells in a relatively small pilot plant with the capacity of creating about one megawatt of solar cells a year. The large gigawatt capacity of the plant was made possible by the fact that Konarka does not require specialized equipment to make its solar cells. Indeed, the factory and equipment were formerly owned by Polaroid and used to make film for medical imaging. With minor modifications, the same equipment can now be used to make solar cells. Richard Hess, Konarka’s president and CEO, says that the company’s ability to use existing equipment allows it to scale up production at one-tenth the cost compared with conventional technologies.