IR Solar Cell Record Set
EWING, New Jersey, Jan. 12, 2006 -- Global Photonic Energy Corp. (GPEC), a developer of organic photovoltaic technology for high-power solar cells, announced that its research partners at Princeton University and the University of Southern California have achieved a record in an organic solar cell that is responsive to light in the near-infrared range of the solar spectrum.
The achievement is the highest level of conversion performance yet achieved for an organic solar cell in the IR portion of the solar spectrum, GPEC said.
GPEC sponsors research by Professor Stephen R. Forrest at Princeton and Professor Mark E. Thompson at the University of Southern California. They reported their results in a recent issue of Applied Physics Letters.
Forrest's research team has focused on organic "small-molecule" devices that are assembled literally a molecule at a time in highly efficient nanostructures. These devices have layers or structural elements that can be extremely small -- only half a billionth of a meter thick -- and can be applied to low-cost, flexible plastic surfaces.
"This latest device demonstrates that significant power can be harvested from the IR and near-IR portion of the solar spectrum," said Forrest. "In fact, this novel approach has the potential to double the power output of organic solar devices with power harvested from the near-IR and IR portion of the solar spectrum.
"With this approach, we are well on our way to power levels exceeding 100 watts per meter," he said.
Near-infrared (NIR) radiation is invisible to the human eye. Many night-vision devices operate by sensing IR light emitted by warm objects. Under only NIR radiation, the Princeton solar cell would appear to be generating power in the dark, since the human eye is only sensitive to visible light.
Traditionally, photovoltaic, or solar, cells have been constructed of an inorganic semiconductor like silicon. Efficient silicon-based devices, especially those with large surface areas, are difficult and expensive to produce. Although the cost of silicon solar cells has dropped dramatically since the 1950s, further reductions and new capabilities are needed for additional market penetration and broader adoption, GPEC said.
Recent efforts have focused on the use of "organic" materials. Organic semiconductors contain carbon and are capable of achieving ultralow-cost solar power generation that is competitive with traditional fossil-fuel sources. Organic materials have the potential to achieve ultralow cost production costs and high-power output, GMAC said. They can be applied to virtually any surface using a method akin to spray painting and can also be used in flexible applications.
One challenge for organic solar cells has been the efficient capture and conversion of sunlight. Sunlight is comprised of photons (particles of light) that are delivered across a spectrum that includes invisible ultraviolet (UV) light, the visible spectrum of colors -- violet, indigo, blue, green, yellow, orange and red -- and the invisible IR spectrum. The amount of incoming photons across the UV, visible and IR spectrums is about 4, 5 and 45 percent, respectively. The photons absorbed by a solar cell directly impacts the power output. The best organic solar cells absorb and convert only about a third of the total available light utilizing primarily the visible portion of the spectrum.
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