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Shiny Quantum Dots Brighten Future of Solar Cells

              Shiny Quantum Dots Brighten Future of Solar Cells

Photovoltaic solar-panel windows could be next for your house

PR Newswire

LOS ALAMOS, N.M., April 14, 2014

LOS ALAMOS, N.M., April 14, 2014 /PRNewswire-USNewswire/ -- A house window
that doubles as a solar panel could be on the horizon, thanks to recent
quantum-dot work by Los Alamos National Laboratory researchers in
collaboration with scientists from University of Milano-Bicocca (UNIMIB),
Italy. Their project demonstrates that superior light-emitting properties of
quantum dots can be applied in solar energy by helping more efficiently
harvest sunlight.

Quantum dot luminescent solar concentrator devices (embedded in the glowing
pink bar) under ultraviolet illumination.

"The key accomplishment is the demonstration of large-area luminescent solar
concentrators that use a new generation of specially engineered quantum dots,"
said lead researcher Victor Klimov of the Center for Advanced Solar
Photophysics (CASP) at Los Alamos.

Quantum dots are ultra-small bits of semiconductor matter that can be
synthesized with nearly atomic precision via modern methods of colloidal
chemistry.

A luminescent solar concentrator (LSC) is a photon management device,
representing a slab of transparent material that  contains  highly efficient
emitters such as dye molecules or quantum dots. Sunlight absorbed in the slab
is re-radiated at longer wavelengths and guided towards the slab edge equipped
with a solar cell.

Klimov explained, "The LSC serves as a light-harvesting antenna which
concentrates solar radiation collected from a large area onto a much smaller
solar cell, and this increases its power output."

"LSCs are especially attractive because in addition to gains in efficiency,
they can enable new interesting concepts such as photovoltaic windows that can
transform house facades into large-area energy generation units," said Sergio
Brovelli, a faculty member at UNIMIB.

Because of highly efficient, color-tunable emission and solution
processability, quantum dots are attractive materials for use in inexpensive,
large-area LSCs. To overcome a nagging problem of light reabsorption, the Los
Alamos and UNIMIB researchers developed LSCs based on quantum dots with
artificially induced large separation between emission and absorption bands
(called a large Stokes shift).

These "Stokes-shift" engineered quantum dots represent cadmium
selenide/cadmium sulfide (CdSe/CdS) structures in which light absorption is
dominated by an ultra-thick outer shell of CdS, while emission occurs from the
inner core of a narrower-gap CdSe.

Los Alamos researchers created a series of thick-shell (so-called "giant")
CdSe/CdS quantum dots, which were incorporated by their Italian partners into
large slabs (sized in tens of centimeters) of polymethylmethacrylate (PMMA).
While being large by quantum dot standards, the active particles are still
tiny - only about hundred angstroms across. For comparison, a human hair is
about 500,000 angstroms wide.

A journal article is in Nature Photonics at
http://dx.doi.org/10.1038/NPHOTON.2014.54

About Los Alamos National Laboratory (www.lanl.gov)
Los Alamos National Laboratory, a multidisciplinary research institution
engaged in strategic science on behalf of national security, is operated by
Los Alamos National Security, LLC, a team composed of Bechtel National, the
University of California, The Babcock & Wilcox Company and URS Corporation for
the Department of Energy's National Nuclear Security Administration.

Los Alamos enhances national security by ensuring the safety and reliability
of the U.S. nuclear stockpile, developing technologies to reduce threats from
weapons of mass destruction, and solving problems related to energy,
environment, infrastructure, health and global security concerns.

Photo - http://photos.prnewswire.com/prnh/20140414/73007

SOURCE Los Alamos National Laboratory

Contact: Nancy Ambrosiano, 505.667.0471, nwa@lanl.gov
 
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