Press Release 07-020
New Coating Is Virtual Black Hole for Reflections

Non-reflecting material may help solar cells catch more of the Sun's rays

Layers of silica nanorods look like shag carpet when viewed with a scanning electron microscope. Credit and Larger Version

March 1, 2007

Researchers have created an anti-reflective coating that allows light to travel through it, but lets almost none bounce off its surface. At least 10 times more effective than the coating on sunglasses or computer monitors, the material, which is made of silica nanorods, may be used to channel light into solar cells or allow more photons to surge through the surface of a light-emitting diode (LED).

Publishing in the March 1, 2007, Nature Photonics, lead author Jong Kyu Kim and a team from Rensselaer Polytechnic Institute in Troy, N.Y., reveal how they crafted the coating, which reflects almost as little light as do molecules of air.

Guided by National Science Foundation-supported electrical engineer Fred Schubert, the researchers developed a process based on an already common method for depositing layers of silica, the building block of quartz, onto computer chips and other surfaces.

The method grows ranks of nanoscale rods that lie at the same angle. That degree of the angle is determined by temperature. Under a microscope, the films look like tiny slices of shag carpet.

By laying down multiple layers, each at a different angle, the researchers created thin films that are uniquely capable of controlling light. With the right layers in the right configuration, the researchers believe they can even create a film that will reflect no light at all.

One critical application for the material is in the development of next-generation solar cells. By preventing reflections, the coating would allow more light, and more wavelengths of light, to transmit through the protective finish on a solar cell surface and into the cell itself. Engineers may be able to use such a technique to boost the amount of energy a cell can collect, bypassing current efficiency limits.

Another application would involve coating LEDs to eliminate reflections that cut down the amount of light the LED can emit. The researchers hope the efficiency gains could allow the light sources to compete more effectively with fluorescent and incandescent bulbs. So, they will next focus their attention on solid state lighting.

-NSF-

Media Contacts
Joshua A. Chamot, NSF (703) 292-7730 jchamot@nsf.gov
Jason Gorss, Rensselaer Polytechnic Institute (518) 276-6098 gorssj@rpi.edu

Program Contacts
Rongqing Hui, NSF (703) 292-8339 rhui@nsf.gov

Principal Investigators
Fred Schubert, Rensselaer Polytechnic Institute (518) 276-8775 EFSchubert@rpi.edu

Related Websites
Fred Schubert's homepage: http://www.rpi.edu/~schubert/
Rensselaer Polytechnic Institute press release: http://news.rpi.edu:80/update.do?artcenterkey=1956
NSF award supporting this research: http://www.nsf.gov/awardsearch/showAward.do?AwardNumber=0401075

The National Science Foundation (NSF) is an independent federal agency that supports fundamental research and education across all fields of science and engineering, with an annual budget of $6.06 billion. NSF funds reach all 50 states through grants to over 1,900 universities and institutions. Each year, NSF receives about 45,000 competitive requests for funding, and makes over 11,500 new funding awards. NSF also awards over $400 million in professional and service contracts yearly.

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