New ORNL solar cell technology cranks up efficiency

[OKIsItJustMe]

http://www.ornl.gov/info/press_releases/get_press_release.cfm?ReleaseNumber=mr20110429-00

News Release

Media Contact: Ron Walli
Communications and External Relations
865.576.0226

New ORNL solar cell technology cranks up efficiency

OAK RIDGE, Tenn., April 29, 2011 — With the creation of a 3-D nanocone-based solar cell platform, a team led by Oak Ridge National Laboratory's Jun Xu has boosted the light-to-power conversion efficiency of photovoltaics by nearly 80 percent.

The technology substantially overcomes the problem of poor transport of charges generated by solar photons. These charges -- negative electrons and positive holes -- typically become trapped by defects in bulk materials and their interfaces and degrade performance.

"To solve the entrapment problems that reduce solar cell efficiency, we created a nanocone-based solar cell, invented methods to synthesize these cells and demonstrated improved charge collection efficiency," said Xu, a member of ORNL's Chemical Sciences Division.

The new solar structure consists of n-type nanocones surrounded by a p-type semiconductor. The n-type nanoncones are made of zinc oxide and serve as the junction framework and the electron conductor. The p-type matrix is made of polycrystalline cadmium telluride and serves as the primary photon absorber medium and hole conductor.

With this approach at the laboratory scale, Xu and colleagues were able to obtain a light-to-power conversion efficiency of 3.2 percent compared to 1.8 percent efficiency of conventional planar structure of the same materials.

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Research that forms the foundation of this technology was accepted by this year's Institute of Electrical and Electronics Engineers photovoltaic specialist conference and will be published in the IEEE Proceedings. The papers are titled "Efficient Charge Transport in Nanocone Tip-Film Solar Cells" and "Nanojunction solar cells based on polycrystalline CdTe films grown on ZnO nanocones."

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[wtmusic]

1. Sounds big.

I'll wait until it's duplicated to get really excited.

[OKIsItJustMe]

2. This certainly isn’t the first team to produce promising results using 3D surfaces

http://gtresearchnews.gatech.edu/nano-manhattan/

12/9/2009 in Energy

Nano-Manhattan: 3-D Solar Cell That Uses “Towers” to Boost Efficiency Wins International Patents

A three dimensional solar cell design that uses micron-scale “towers” to capture nearly three times as much light as flat solar cells made from the same materials has been awarded broad patent protection in both China and Australia. Modeling suggests that the 3-D cell could boost power production by as much as 300 percent compared to conventional solar cells.

Because it can capture more power from a given area, the 3-D design could be useful for powering satellites, cell phones, military equipment and other applications that have a limited surface area. Developed at the http://www.gtri.gatech.edu/">Georgia Tech Research Institute (GTRI), the ”three dimensional multi-junction photovoltaic device” uses its 3-D surface structure to increase the likelihood that every photon striking it will produce energy.


Image shows the three dimensional structures used by the GTRI photovoltaic cells to increase the amount of light captured. The additional light increases the power output of the cells. (Click image for high-resolution version. Credit: Georgia Tech)

“One problem with conventional flat solar cells is that the sunlight hits a flat surface and can bounce off, so the light only has one chance to be absorbed and turned into electricity,” explained John Bacon, president of IP2Biz , an Atlanta company that has licensed the technology from GTRI. “In the GTRI 3-D solar cell, we build a nanometer-scale version of Manhattan, with streets and avenues of tiny light-capturing structures similar to tall buildings. The sunlight bounces from building to building and produces more electricity.”

The arrays of towers on the 3-D solar cell can increase the surface area by several thousand percent, depending on the size and density of the structures.

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http://gtresearchnews.gatech.edu/superhydrophobic-cells/

3/24/2009 in Energy, Materials

Superhydrophobic: Self-Cleaning, Low-Reflectivity 3-D Surface Treatment Could Boost Efficiency for Photovoltaic Cells

Using two different types of chemical etching to create features at both the micron and nanometer size scales, researchers at the Georgia Institute of Technology have developed a surface treatment that could boost the light absorption of silicon photovoltaic cells in two complementary ways.

The surface treatment increases absorption both by trapping light in three-dimensional structures and by making the surfaces self-cleaning – allowing rain or dew to wash away the dust and dirt that can accumulate on photovoltaic arrays. Because of its ability to make water bead up and roll off, the surface is classified as superhydrophobic.

Image shows silicon pyramid structures etched for one minute using a hydrogen fluoride/hydrogen peroxide/water solution. The resulting structure has roughness at the micron and nanometer scales. (Click image for high-resolution version. Credit: C.P. Wong)

“The more sunlight that goes into the photovoltaic cells and the less that reflects back, the higher the efficiency can be,” said C.P. Wong, Regents’ professor in Georgia Tech’s School of Materials Science and Engineering. “Our simulations show that we can potentially increase the final efficiency of the cells by as much as two percent with this surface structure.”

Supported by the National Science Foundation (NSF) and the National Electric Energy Testing Research and Applications Center (NEETRAC) at Georgia Tech, the research was described March 24th at the Spring 2009 National Meeting of the American Chemical Society in Salt Lake City.

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[buddysmellgood]

3. We keep making it better. In 10 years, solar will solve the oil/coal problem

[OKIsItJustMe]

4. It could have already

The “Bell Solar Battery” unveiled over 50 years ago was about 6% efficient. The great problem was the cost of producing silicon.

http://www.time.com/time/magazine/article/0,9171,807289,00.html

Science: Sun Electricity

Monday, July 04, 1955

When Bell Telephone Laboratories announced its silicon solar battery (TIME, May 3, 1954), it fired the imaginations of the science fictionists, and the solar system was soon abuzz with solar-powered space ships. Trimming their silicon sails to catch the sunlight, spacemen used the electricity generated by the batteries to push themselves from planet to planet.

More practical imaginations were fired too. Last week National Fabricated Products Inc., a Chicago electronics manufacturer, announced that it has had more than 500 inquiries about the silicon batteries which it has just started making commercially under license from Bell Lab's parent company. Western Electric. Inquiries have come from industrial laboratories all over the world, including India.

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Large-scale uses are unlikely until the price comes down. The batteries are expensive because they are made of highly purified silicon ($280 per lb.), which must be "grown" by a tricky process into a single crystal about the size of a fat banana. The wafers are cross sections one-fiftieth of an inch thick, and they must go through a subtle chemical treatment before they will work as batteries.

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President Maurice E. Paradise, of National Fabricated Products, is sure that the solar batteries can be made much more cheaply. He hopes that eventually the magic silicon can be sprayed on a surface as a crystalline metallic varnish. Then really big batteries will be cheap. They are rugged and last practically forever. A house roofed with sun-absorbing silicon could generate all the current it needs whenever the sun is shining.