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New connection between stacked solar cells can handle energy of 70,000 suns

Date:
September 6, 2013
Source:
North Carolina State University
Summary:
Researchers have come up with a new technique for improving the connections between stacked solar cells, which should improve the overall efficiency of solar energy devices and reduce the cost of solar energy production. The new connections can allow these cells to operate at solar concentrations of 70,000 suns' worth of energy without losing much voltage as 'wasted energy' or heat.

The discovery means solar cell manufacturers can create stacked solar cells that can handle high-intensity solar energies without losing voltage at the connecting junctions, potentially improving conversion efficiency.
Credit: NC State University

North Carolina State University researchers have come up with a new technique for improving the connections between stacked solar cells, which should improve the overall efficiency of solar energy devices and reduce the cost of solar energy production. The new connections can allow these cells to operate at solar concentrations of 70,000 suns' worth of energy without losing much voltage as "wasted energy" or heat.

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Stacked solar cells consist of several solar cells that are stacked on top of one another. Stacked cells are currently the most efficient cells on the market, converting up to 45 percent of the solar energy they absorb into electricity.

But to be effective, solar cell designers need to ensure the connecting junctions between these stacked cells do not absorb any of the solar energy and do not siphon off the voltage the cells produce -- effectively wasting that energy as heat.

"We have discovered that by inserting a very thin film of gallium arsenide into the connecting junction of stacked cells we can virtually eliminate voltage loss without blocking any of the solar energy," says Dr. Salah Bedair, a professor of electrical engineering at NC State and senior author of a paper describing the work.

This work is important because photovoltaic energy companies are interested in using lenses to concentrate solar energy, from one sun (no lens) to 4,000 suns or more. But if the solar energy is significantly intensified -- to 700 suns or more -- the connecting junctions used in existing stacked cells begin losing voltage. And the more intense the solar energy, the more voltage those junctions lose -- thereby reducing the conversion efficiency.

"Now we have created a connecting junction that loses almost no voltage, even when the stacked solar cell is exposed to 70,000 suns of solar energy," Bedair says. "And that is more than sufficient for practical purposes, since concentrating lenses are unlikely to create more than 4,000 or 5,000 suns worth of energy. This discovery means that solar cell manufacturers can now create stacked cells that can handle these high-intensity solar energies without losing voltage at the connecting junctions, thus potentially improving conversion efficiency.

"This should reduce overall costs for the energy industry because, rather than creating large, expensive solar cells, you can use much smaller cells that produce just as much electricity by absorbing intensified solar energy from concentrating lenses. And concentrating lenses are relatively inexpensive," Bedair says.


Story Source:

The above story is based on materials provided by North Carolina State University. Note: Materials may be edited for content and length.


Journal Reference:

  1. Joshua P. Samberg, C. Zachary Carlin, Geoff K. Bradshaw, Peter C. Colter, Jeffrey L. Harmon, J. B. Allen, John R. Hauser, S. M. Bedair. Effect of GaAs interfacial layer on the performance of high bandgap tunnel junctions for multijunction solar cells. Applied Physics Letters, 2013; 103 (10): 103503 DOI: 10.1063/1.4819917

Cite This Page:

North Carolina State University. "New connection between stacked solar cells can handle energy of 70,000 suns." ScienceDaily. ScienceDaily, 6 September 2013. <www.sciencedaily.com/releases/2013/09/130906102651.htm>.
North Carolina State University. (2013, September 6). New connection between stacked solar cells can handle energy of 70,000 suns. ScienceDaily. Retrieved November 22, 2014 from www.sciencedaily.com/releases/2013/09/130906102651.htm
North Carolina State University. "New connection between stacked solar cells can handle energy of 70,000 suns." ScienceDaily. www.sciencedaily.com/releases/2013/09/130906102651.htm (accessed November 22, 2014).

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