Organic photovoltaic cells, including dye-sensitized cells (DSCs) – may be the ultimate when it comes to offering off-grid, micro-power generation. Initial small-scale technology and market tests – solar chargers for mobile phones in Africa, for example – are under way as researchers continue to try to find ways to boost solar energy conversion efficiencies – which now surpass 5% for small organic PV cells and up to 11% for DSCs – minimize production costs and develop markets for both small- and large-scale applications.
Pioneering industry leaders such as Pittsburgh-based Plextronics envisage wide-ranging uses for its Plexcore line of organic, nano-engineered PV and conductive polymers and inks, from applying printed PV and electronic circuits on plastics, fabrics, glass, concrete and other construction materials, to printing, rolling out and applying them over much larger areas, such as walls and rooftops. They are also being used to create organic light-emitting diodes (OLED) for displays and lighting.
Materials for use in thin-film and organic photovoltaics (PV) will reach $3.8 billion by 2015, according to a recently released study by NanoMarkets. “The three main areas where OPV is expected to eventually outperform more traditional approaches to PV are (1) very low-costs, (2) enhanced ability to operate in dim light, (3) integration of PV capabilities in building materials and fabrics, and (4) the ability to be printed on flexible substrates,” according to the report.
Pushing the Organic PV Envelope
A commercial spin-off founded in 2002 as a result of research originally conducted at Carnegie- Mellon University, Plextronics in August 2007 announced that its organic solar PV cells, made of plastic-like polymers, had set a conversion efficiency record of 5.4% independently confirmed by the US DoE’s National Renewable Energy Labs.
“Solar power holds the promise of delivering clean, renewable energy, but the cost of today’s silicon-based technology often limits use mainly to large, on-grid installations. However, printed solar power – where printed inks replace silicon – enables new uses of solar power in portable and off-grid products, as well as the ultimate goal of low-cost, on-grid energy,” Plextronics notes on its web site.
The company in June announced it was introducing, and was already filling orders for, its Plexcore ink systems for organic solar cell fabrication for use in research applications. “What makes this particularly exciting is that these initial products will allow us to work closely with researchers and commercial partners around the world to push development of organic photovoltaics even further,” vice president of products Troy Hammond stated in a press release.
Significantly lower cost, low weight, and the ability to quickly scale-up production are the chief advantages of organic PV inks, DSCs and printed circuitry. Their ability to capture solar energy and convert it to electricity in low light conditions is another plus.
Lower conversion efficiency, as well as durability, are the main drawbacks at this point, something researchers at Plextronics and other industry leaders, such as Konarka Technologies, are striving to address.
Konarka on June 24 announced that the durability of its Power Plastic flexible organic PV material had been tested and verified by the Energy Research Centre of the Netherlands. According to Konarka, the PowerPlastic solar cells demonstrated “outstanding high lifetime after comprehensive environmental testing under accelerated conditions, including high temperature storage and prolonged illumination.”
In its latest published research, Nanomarkets emphasizes its use of the word “eventually” when discussing OPV’s market potential. “The advantages of OPV set out above are goals rather than current achievements. For example, the ‚Äòvery low-costs’ potentially achievable by OPV are predicated on the assumptions of high volume demand for the underlying materials and on manufacturability using low-cost processes such as printing. Neither of these assumptions reflects current realities. Still, the goals of OPV do seem fairly realistic in the long run; there are certainly reasons for optimism,” the authors conclude.