Free Newsletters - Space News - Defense Alert - Environment Report - Energy Monitor
. Solar Energy News .




SOLAR DAILY
Solar cells made from black silicon
by Staff Writers
Berlin, Germany (SPX) Oct 10, 2012


illustration only

Solar cells convert three-quarters of the energy contained in the Sun's spectrum into electricity - yet the infrared spectrum is entirely lost in standard solar cells. In contrast, black silicon solar cells are specifi cally designed to absorb this part of the Sun's spectrum - and researchers have recently succeeded in doubling their overall efficiency.

The Sun blazes down from a deep blue sky - and rooftop solar cells convert this solar energy into electricity. Not all of it, however: Around a quarter of the Sun's spectrum is made up of infrared radiation which cannot be converted by standard solar cells - so this heat radiation is lost. One way to overcome this is to use black silicon, a material that absorbs nearly all of the sunlight that hits it, including infrared radiation, and converts it into electricity. But how is this material produced?

"Black silicon is produced by irradiating standard silicon with femtosecond laser pulses under a sulfur containing atmosphere," explains Dr. Stefan Kontermann, who heads the Research group "Nanomaterials for Energy Conversion" within the Fraunhofer Project Group for Fiber Optical Sensor Systems at the Fraunhofer Institute for Telecommunications, Heinrich-Hertz-Institut, HHI.

"This structures the surface and integrates sulfur atoms into the silicon lattice, making the treated material appear black." If manufacturers were to equip their solar cells with this black silicon, it would significantly boost the cells' efficiency by enabling them to utilize the full Sun spectrum.

Researchers at HHI have now managed to double the efficiency of black silicon solar cells - in other words, they have created cells that can produce more electricity from the infrared spectrum. "We achieved that by modifying the shape of the laser pulse we use to irradiate the silicon," says Kontermann.

This enabled the scientists to solve a key problem of black silicon: In normal silicon, infrared light does not have enough energy to excite the electrons into the conduction band and convert them into electricity, but the sulfur incorporated in black silicon forms a kind of intermediate level. You can compare this to climbing a wall: The first time you fail because the wall is too high, but the second time you succeed in two steps by using an intermediate level.

However, in sulfur this intermediate level not only enables electrons to climb the 'wall', it also works in reverse, enabling electrons from the conduction band to jump back via this intermediate level, which causes electricity to be lost once again.

By modifying the laser pulse that drives the sulfur atoms into the atomic lattice, researchers can change the positions that these atoms adopt in the lattice and change the height of their 'levels', in other words their energy level. "We used the laser pulses to alter the embedded sulfur in order to maximize the number of electrons that can climb up while minimizing the number that can go back down," Kontermann sums up.

Prize-winning project
In the first stage of the project, the scientists modified the laser pulses and investigated how this changed the properties of black silicon and the efficiency of solar cells made from this material. Now they are working on using different shapes of laser pulses and analyzing how this changes the energy level of the sulfur.

In the future, they hope that a system of algorithms will automatically identify how the laser pulse should be modified in order to achieve optimum efficiency. The 'Customized light pulses' project was one of this year's winners in the '365 Places in the Land of Ideas' competition; the awards ceremony is due to be held in Goslar on October 11, 2012.

The researchers have already successfully built prototypes of black silicon solar cells and their next step will be to try and merge these cells with commercial technology. "We hope to be able to increase the efficiency of commercial solar cells - which currently stands at approximately 17 percent - by one percent by combining them with black silicon," Kontermann says. Their starting point is a standard commercial solar cell: The experts simply remove the back cover and incorporate black silicon in part of the cell, thereby creating a tandem solar cell that contains both normal and black silicon.

The researchers are also planning a spin-off: This will be used to market the laser system that manufacturers will be able to acquire to expand their existing solar cell production lines. Manufacturers would then be able to produce the black silicon themselves and include it in the cells as standard.

Research News October 2012 [ PDF 0,38 MB ]

.


Related Links
Fraunhofer Institute for Telecommunications, Heinrich Hertz Institute HHI
All About Solar Energy at SolarDaily.com






Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle




Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News





SOLAR DAILY
PSEG Queen Creek Solar Farm in Arizona Begins Commercial Operation
Newark NJ (SPX) Oct 10, 2012
PSEG Solar Source has announced the commercial operation of the 25.2 megawatt DC (19 megawatt AC) Queen Creek Solar Farm in Queen Creek, Arizona. Salt River Project (SRP) has a 20-year agreement to acquire all of the solar energy generated by the project and has begun accepting power from the plant. The solar plant, located on148 acres of land approximately 30 miles southeast of Phoenix, c ... read more


SOLAR DAILY
Computational Model IDs Potential Pathways to Improve Plant Oil Production

Biorefining: The new green wave

Turd-eating worms clear air around Canadian toilets

Napiergrass: A Potential Biofuel Crop for the Sunny Southeast

SOLAR DAILY
Worldwide patent for a Spanish stroke rehabilitation robot

Robot artist learns masters' brush strokes

Toyota unveils robot helping hand

Researchers Examine How Characteristics of Automated Voice Systems Affect Users' Experience

SOLAR DAILY
Sandia Labs benchmark helps wind industry measure success

Bigger wind turbines make greener electricity

EU wind power capacity reaches 100GW

Lawsuit fights Obama ban on wind farm sale to Chinese

SOLAR DAILY
China's September auto sales fall on Japan row

Japan's Toyota to recall 7.43 mn vehicles globally

GM says China auto sales hit record in September

Plans to cut urban motorway through Bucharest stir outcry

SOLAR DAILY
Researchers Develop New Way to Determine Amount of Charge Remaining in Battery

What Impact does Oil have on the Syrian Civil War?

Chevron decries court refusal to block Ecuador fine

Topological Superconductors

SOLAR DAILY
Japan's Toshiba to boost Westinghouse stake

S. Korea denies entry to Greenpeace activists

Japan forum to discuss nuclear-free energy future

Japan PM tours troubled Fukushima nuclear plant

SOLAR DAILY
Regulator: Britain faces power shortages

Money: A New (Decentralized) Shade of Green

Energy New Front in Economic Warfare

Ireland Unlikely To Meet EU Energy Targets

SOLAR DAILY
Study finds nearly 50% of retail firewood infested with insects

Northern conifers youngest of the species

Climate change cripples forests

Semi-dwarf trees may enable a green revolution for some forest crop




The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA Portal Reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement