In a paper published in Nature Photonics,
University of Toronto Engineering researchers report a new solar cell
that may pave the way to inexpensive coatings that efficiently convert
the sun’s rays to electricity.
The
Univ. of Toronto researchers, led by Professor Ted Sargent, report the first
efficient tandem solar cell based on colloidal quantum dots (CQD).
“The
U of T device is a stack of two light-absorbing layers – one tuned to
capture the sun’s visible rays, the other engineered to harvest the half
of the sun’s power that lies in the infrared,” said lead author Dr.
Xihua Wang.
“We
needed a breakthrough in architecting the interface between the visible
and infrared junction,” said Sargent, a Professor of Electrical and
Computer Engineering at the University of Toronto, who is also the
Canada Research Chair in Nanotechnology. “The team engineered a cascade –
really a waterfall – of nanometers-thick materials to shuttle electrons
between the visible and infrared layers.”
According
to doctoral student Ghada Koleilat, “We needed a new strategy – which
we call the Graded Recombination Layer – so that our visible and
infrared light-harvesters could be linked together efficiently, without
any compromise to either layer.”
The
team pioneered solar cells made using CQD, nanoscale materials that can
readily be tuned to respond to specific wavelengths of the visible and
invisible spectrum. By capturing such a broad range of light waves –
wider than normal solar cells – tandem CQD solar cells can in principle
reach up to 42 per cent efficiencies. The best single-junction solar
cells are constrained to a maximum of 31 per cent efficiency. In
reality, solar cells that are on the roofs of houses and in consumer
products have 14 to 18 per cent efficiency. The work expands the Toronto
team’s world-leading 5.6 per cent efficient colloidal quantum dot solar
cells.
“Building
efficient, cost-effective solar cells is a grand global challenge. The
University of Toronto is extremely proud of its world-class leadership
in the field,” said Professor Farid Najm, Chair of The Edward S. Rogers
Sr. Department of Electrical & Computer Engineering.
Sargent
is hopeful that in five years solar cells using the graded
recombination layer published in today’s Nature Photonics paper will be
integrated into building materials, mobile devices, and automobile
parts.
“The
solar community – and the world – needs a solar cell that is over 10%
efficient, and that dramatically improves on today’s photovoltaic module
price points,” said Sargent. “This advance lights up a practical path
to engineering high-efficiency solar cells that make the best use of the
diverse photons making up the sun’s broad palette.”
SOURCE: http://www.utoronto.ca/
