New Materials Boost Organic Solar Cell's Performance
EWING, N.J., July 27, 2006 -- New materials have been integrated into an organic solar cell that double its open-circuit voltage and demonstrate the potential to make highly efficient photovoltaic cells much less expensively than with silicon, those involved in the project said.
The research, conducted by organic photovoltaic technology developer Global Photonic Energy Corp. of Ewing, N.J., and its research partners at the University of Southern California (USC), Princeton University and the University of Michigan, boosted the power output of photovoltaic cells, which in turn reduces their cost per kilowatt-hour. The researchers achieved an open-circuit voltage of 0.97 V, while surpassing the power output of a control organic solar cell by over 50 percent. A high-efficiency organic solar cell typically has a open-circuit voltage of 0.54 V. Silicon solar cells can have an open-circuit voltage as high as approximately 0.71 V.
"This latest research demonstrates that we can achieve high open-circuit voltages in small-molecular organic solar cells while also making gains in power output," said Stephen R. Forrest, Michigan's vice president for research and the William Gould Dow Collegiate Professor in Electrical Engineering, Materials Science and Engineering and Physics.
Traditionally, photovoltaic or "solar" cells have been constructed of an inorganic semiconductor like silicon. Efficient silicon-based devices, especially of large surface area, are difficult and expensive to produce. Silicon cells are fragile, heavy and opaque, limiting applications and potential uses. Cost is a critical factor in the solar cell industry as solar generated power is still four to six times more expensive to consumers than coal-generated power.
According to the US Department of Energy's International Energy Outlook 2005, electricity demand will nearly double by 2025, requiring an additional 11.7 trillion kilowatt-hours of capacity, and solar energy must play a major role in meeting this demand to mitigate greenhouse gas effects and meet global emission standards. Global solar cell production has grown 25 percent annually for the last 20 years, reaching sales of $9 billion in 2005. This accelerating growth has resulted in a worldwide shortage of semiconductor silicon, driving solar cell prices higher.
Recent efforts have focused on the use of "organic" semiconductor materials. Organic semiconductors contain the ubiquitous element carbon and have the potential to achieve ultralow production costs and high power output. Organic materials are ultrathin, flexible and can be applied to large areas, including curved or spherical surfaces. Because the organic layers are so thin, transparent solar cells can be fabricated creating power-generating windows that retain their basic function.
The researchers at USC, Princeton and Michigan, led by Forrest at Michigan and professor Mark E. Thompson at USC, have focused on organic "small-molecule" devices that are assembled literally a molecule at a time in highly efficient nanostructures.
Organic materials can be applied to virtually any surface using a low-temperature method akin to spray painting. These kind of production methods are easily adaptable to continuous and so-called "roll-to-roll" manufacturing processes and hold the promise of dramatically reduced production costs. Organic materials also can be used in flexible applications, or even be used to create photovoltaic cells that act as window tinting in buildings.
The researchers detailed their work in the June 2 issue of The Journal of the American Chemical Society. For more information, visit: www.globalphotonicenergy.com/research.html
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