Imagine a home with “smart” walls responsive to the environment in the room, a digital camera sensitive enough to work in the dark, or clothing with the capacity to turn the sun’s power into electrical energy. Researchers at University of Toronto have invented an infrared-sensitive material that could shortly turn these possibilities into realities.
In a paper to be published on the Nature Materials website Jan. 9, senior author Professor Ted Sargent, Nortel Networks – Canada Research Chair in Emerging Technologies at U of T’s Department of Electrical and Computer Engineering, and his team report on their achievement in tailoring matter to harvest the sun’s invisible rays.
“We made particles from semiconductor crystals which were exactly two, three or four nanometres in size. The nanoparticles were so small they remained dispersed in everyday solvents just like the particles in paint,” explains Sargent. Then, they tuned the tiny nanocrystals to catch light at very long wavelengths. The result – a sprayable infrared detector.
Existing technology has given us solution-processible, light-sensitive materials that have made large, low-cost solar cells, displays, and sensors possible, but these materials have so far only worked in the visible light spectrum, says Sargent. “These same functions are needed in the infrared for many imaging applications in the medical field and for fiber optic communications,” he said.
The discovery may also help in the quest for renewable energy sources. Flexible, roller-processed solar cells have the potential to harness the sun’s power, but efficiency, flexibility and cost are going to determine how that potential becomes practice, says Josh Wolfe, Managing Partner and nanotechnology venture capital investor at Lux Capital in Manhattan. Wolfe, who was not part of the research team, says the findings in the paper are significant: “These flexible photovoltaics could harness half of the sun’s spectrum not previously accessed.”
Professor Peter Peumans of Stanford University, who has reviewed the U of T team’s research, also acknowledges the groundbreaking nature of the work. “Our calculations show that, with further improvements in efficiency, combining infrared and visible photovoltaics could allow up to 30 per cent of the sun’s radiant energy to be harnessed, compared to six per cent in today’s best plastic solar cells.”
U of T electrical and computer engineering graduate student Steve MacDonald carried out many of the experiments that produced the world’s first solution-processed photovoltaic in the infrared. “The key was finding the right molecules to wrap around our nanoparticles,” he explains. “Too long and the particles couldn’t deliver their electrical energy to our circuit; too short, and they clumped up, losing their nanoscale properties. It turned out that one nanometer – eight carbon atoms strung together in a chain – was ‘just right’.”
Other members of the U of T research team are Gerasimos Konstantatos, Shiguo Zhang, Paul W. Cyr, Ethan J.D. Klem, and Larissa Lavina of electrical and computer engineering; Cyr is also with the Department of Chemistry. The research was supported in part by the Government of Ontario through Materials and Manufacturing Ontario, a division of the Ontario Centres of Excellence; the Natural Sciences and Engineering Research Council of Canada through its Collaborative Research and Development Program; Nortel Networks; the Canada Foundation for Innovation; the Ontario Innovation Trust; the Canada Research Chairs Programme; and the Ontario Graduate Scholarship.
Contact: Professor Edward H. Sargent, Nortel Networks – Canada Research Chair in Emerging Technologies, (416) 946-5051; e-mail: ted.sargent@utoronto.ca
source: http://www.news.utoronto.ca/bin6/print/050110-832.htm 10jan05
TORONTO — Researchers at the University of Toronto have invented an infrared-sensitive material that's five times more efficient at turning the sun's power into electrical energy than current methods.
The discovery could lead to shirts and sweaters capable of recharging our cellphones and other wireless devices, said Ted Sargent, professor of electrical and computer engineering at the university.
Sargent and other researchers combined specially-designed minute particles called quantum dots, three to four nanometres across, with a polymer to make a plastic that can detect energy in the infrared.
Infrared light is not visible to the naked eye but it is what most remote controls emit, in small amounts, to control devices such as TVs and DVD players.
It also contains a huge untapped resource — despite the surge in popularity of solar cells in the 1990s, we still miss half of the sun's power, Sargent said.
"In fact, there's enough power from the sun hitting the Earth every day to supply all the world's needs for energy 10,000 times over," Sargent said in a phone interview Sunday from Boston. He is currently a visiting professor of nanotechnology at the Massachusetts Institute of Technology.
Sargent said the new plastic composite is, in layman's terms, a layer of film that "catches" solar energy. He said the film can be applied to any device, much like paint is coated on a wall.
"We've done the same thing, but not with something that just sit there on the wall the way paint does," said the Ottawa native.
"We've done it to make a device which actually harnesses the power in the room in the infrared."
The film can convert up to 30 per cent of the sun's power into usable, electrical energy. Today's best plastic solar cells capture only about six per cent.
Sargent said the advance would not only wipe away that inefficiency, but also resolve the hassle of recharging our countless gadgets and pave the way to a true wireless world.
"We now have our cellphones and our BlackBerries and we're walking around without the need to plug in, in order to get our data," he said.
"But we seem trapped at the moment in needing to plug in to get our power. That's because we charge these things up electrically, from the outlet. But there's actually huge amounts of power all around us coming from the sun."
The film has the ability to be sprayed or woven into shirts so that our cuffs or collars could recharge our IPods, Sargent said.
While that may sound like a Star Trek dream, venture capitalists are keen to Sargent's invention.
Josh Wolfe, managing partner at Lux Capital, a New York City-based venture capital firm, said while such a luxury may be five years away, the technology knows no bounds.
"When you have a material advance which literally materially changes the way that energy is absorbed and transmitted to our devices... somebody out there tinkering away in a bedroom or in a government lab is going to come up with a great idea for a new device that will shock us all," he said in a phone interview.
"When the Internet was created nobody envisioned that the killer app (application) would be e-mail or instant messaging."
Sargent's work was published in the online edition of Nature Materials on Sunday and will appear in its February issue.
source: http://www.commondreams.org/cgi-bin/print.cgi?file=/headlines05/0110-07.htm 10jan05
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