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 the 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 short 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 fibre optic communications,"
he says.
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 Program; and the Ontario Graduate
Scholarship.
CONTACT:
Sonnet L'Abbé
U of T Public Affairs
416-978-0260
sonnet.labbe@utoronto.ca
Professor
Ted Sargent
Deptartment of Electrical and Computer Engineering
416-946-5051 ted.sargent@utoronto.ca |
