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  • Pushing the envelope: Trends in green research and technology

Photonics Spectra
Jan 2010
Anne L. Fischer, Senior Editor,

Raising efficiency while lowering costs is the trend in solar as well as solid-state lighting. Researchers have been working toward this end in both areas for decades, and there are many advances to report.

Researchers at the University of Texas at Austin are working on sunlight-absorbing nanoparticle inks.

In the solar research arena, scientists are looking at new materials, such as cadmium telluride (CdTe) thin film, nanoparticles, optical fibers and more. First Solar of Tempe, Ariz., hit the milestone of $1 per watt in October 2009 with its CdTe technology, but, like others, the company continues pushing the envelope of research to try to meet grid parity without subsidies and has set 2012 as a target. And the quest goes on. A group in Jerusalem, for example, is working on glass plates coated with silver nanoparticles and dyes with just a thin strip of silicon along the edges. The method is expected to result in solar panels with 20 percent efficiency that can be manufactured at lower costs than traditional silicon-based panels. Developed by Renata Reisfeld’s group at Hebrew University, the technology is being commercialized by GreenSun Energy, where Reisfeld was formerly chief technology officer.

In June of last year, Photonics Spectra reported the use of zinc by a team at Northwestern University in Chicago to develop low-cost photodetectors (“Not just for your nose,” p. 35). Georgia Institute of Technology researchers are now using zinc oxide nanostructures on optical fibers in a 3-D photovoltaic system.

Old materials, new ways

Others in solar research are using established materials in a new way. Brian Korgel’s group at the University of Texas at Austin is using CIGS (copper indium gallium selenide), a material that he said is known to work well, to reinvent how the devices are made. Korgel noted, “In a sense, all of these research groups and companies are competing to find the solution. In terms of society, it’s not a competition – it’s people trying to solve the energy problem.”

RoseStreet Labs Energy tests hybrid photovoltaic cells on its pilot line.

Another trend is the pairing of solid-state lighting with solar, whether in shared technologies or in the final application. For example, drawing on work with nitride materials used in solid-state lighting and blue lasers, Phoenix-based RoseStreet Labs Energy is developing a photovoltaic cell that combines traditional silicon with a nitride thin film. According to Bob Forcier, chairman and CEO, the company initially was developing a triple-junction cell but decided to focus its research first on a “simpler, more elegant first product.” Forcier indicated that the company is currently testing a hybrid device that could achieve 25 to 30 percent efficiency.

Solar Roadways is a group that’s testing LEDs embedded in a road paved with solar cells. The brainchild of Scott Brusaw, chief executive officer of the Sagle, Idaho-based company, the idea is to generate electricity on the road, with road lines and signage “painted” under the surface with LEDs. A prototype is currently under development for the US Department of Transportation.

thin film
A thin layer of a substance deposited on an insulating base in a vacuum by a microelectronic process. Thin films are most commonly used for antireflection, achromatic beamsplitters, color filters, narrow passband filters, semitransparent mirrors, heat control filters, high reflectivity mirrors, polarizers and reflection filters.
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