|In the effort to convert sunlight into electricity, photovoltaic solar cells that use conductive organic polymers for light absorption and conversion have shown great potential. Organic polymers can be produced in high volumes at low cost, resulting in photovoltaic devices that are cheap, lightweight and flexible. In the last few years, much work has been done to improve the efficiency with which these devices convert sunlight into power, including the development of new materials, device structures and processing techniques. The year 2012 has seen several developments enhancing performance in the spectrum of solar cell technologies: thin-film (including CIGS, CdTe, and other), c-Si, some unknown combination, and even some with some nanoscale assistance, as per RenewableEnergyWorld.com. Another development has been organic (polymer/plastic) solar cells, approaching and exceeding 10% conversion efficiency. This is an improvement from the high-teens of crystalline silicon or even low-teens for other thin-film options. This is significant for a technology which promises more simplified manufacturability, and widened applications beyond the reach of rigid modules
• Researchers at the UCLA Henry Samueli School of Engineering and Applied Science and UCLA's California Nanosystems Institute (CNSI) report that they have significantly enhanced polymer solar cells' performance by building a device with a new "tandem" structure that combines multiple cells with different absorption bands. The device had a certified power-conversion efficiency of 8.62% and set a world record in July 2011. Further, after the researchers incorporated a new infrared-absorbing polymer material provided by Sumitomo Chemical of Japan into the device, the device's architecture proved to be widely applicable and the power-conversion efficiency jumped to 10.6% - a new record - as certified by the U.S. Department of Energy's National Renewable Energy Laboratory. By using cells with different absorption bands, tandem solar cells provide an effective way to harvest a broader spectrum of solar radiation. However, the efficiency doesn't automatically increase by simply combining two cells. The materials for the tandem cells have to be compatible with each other for efficient light harvesting. Until now, the performance of tandem devices lagged behind single-layer solar cells, mainly due to this lack of suitable polymer materials. The researchers have demonstrated highly efficient single-layer and tandem polymer solar cells featuring a low-band-gap�conjugated polymer specially designed for the tandem structure. The band gap determines the portion of the solar spectrum a polymer absorbs. "Envision a double-decker bus," said Yang Yang, a principal investigator on the research. "The bus can carry a certain number of passengers on one deck, but if you were to add a second deck, you could hold many more people for the same amount of space. That's what we've done here with the tandem polymer solar cell." To use solar radiation more effectively, the team stacked, in series, multiple photoactive layers with complementary absorption spectra to construct a tandem polymer solar cell. Their tandem structure consists of a front cell with a larger (or high) band gap material and a rear cell with a smaller (or low) band gap polymer, connected by a designed interlayer. When compared to a single-layer device, the tandem device is more efficient in utilizing solar energy, particularly by minimizing other energy losses. By using more than one absorption material, each capturing a different part of the solar spectrum, the tandem cell is able to maintain the current and increase the output voltage. These factors enable the increase in efficiency, as per the researchers.
• Konarka, long a pusher of organic PV, says Newport Corp. has certified its next-generation solar cells with 9% single-junction efficiency. These recent advances continue to be based upon it�s inverted cell architecture, the company�s intellectual property protected under issued patents. As per Howard Berke, chairman, CEO and co-founder of Konarka. "For architects, design engineers and builders integrating solar technology into curtain walls, windows, transit structures, automobiles with energy-harvesting rooftops, consumer electronics and more. Thin, lightweight, transparent and flexible, Konarka�s Power Plastic solar films are ideally suited for integration into various building materials, including glass, steel, plastics, composites and fabrics, offering creative architects and product designers superior, widespread latitude with several color and transparency options across a wide range of sizes enabled by Konarka's roll-to-roll continuous manufacturing process."
• Europe has recently launched a four-year, Euro 14.2 mln effort to develop advanced flexible plastic solar panels designed to be integrated into new consumer mobile applications and buildings. The launch of SUNFLOWER ("SUstainable Novel FLexible Organic Watts Efficiently Reliable") - a project created to generate solar energy with highly efficient and recyclable printed plastic solar cells, brings us a step closer to the dream of environmentally friendly and efficient power for everyone. Printed plastic solar cells are the most recent generation of solar panels and are currently limited by their relatively low efficiency and lifetime. However, they can be mass produced using large scale printing machines on rolls of flexible materials, unlike the rigid, silicon-based panels in use today. Flexibility, low weight, and low cost are the key advantages of printed plastic solar panels. They will enable the development of consumer applications like roll-up solar panels or panels integrated three-dimensionally into architectural structures and eventually make possible more economical and robust solar-panel fields for energy production farms. This is a key opportunity for the EU to further expand its innovation base in alternative energies - to develop a technology that is ideally suited to manufacturing in the EU due to its high level of automation, need for highly trained personnel, low energy consumption, and close proximity to suppliers and markets.
• New Energy Technologies and the National Renewable Energy Laboratory (NREL) has created a working organic photovoltaic (OPV) module 170 sq cm in size-14 times larger than previous NREL-made OPV devices - using the company's Solar Window technology that generates electricity on see-through glass. The heart of the development is New Energy's room-temperature "spray-on" coating to spread tiny polymer-based solar cells (composed primarily of hydrogen and carbon), a quarter the size of a grain of sand, onto a substrate (glass in this case), with just a tenth the thickness of other "thin" films and without high-temperature or high-vacuum methods. A lab-scale prototype device was built in August 2011. Recently, the researchers had "made use of" a high-speed/large-area solution-coating process, which the company says allows for more uniform and faster coating, thus enabling more rapid scale-up to larger glass surface areas.