Shiny Quantum Dots Brighten Future of Solar Cells



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Shiny Quantum Dots Brighten Future of Solar Cells

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.

"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 thatcontainshighly

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

-0- 04/14/2014

/CONTACT: Nancy Ambrosiano, 505.667.0471, nwa@lanl.gov

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

PRN Photo Desk, photodesk@prnewswire.com

CO: Los Alamos National Laboratory

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0000 04/14/2014 18:27:00 EDT http://www.prnewswire.com

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The Associated Press

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