Subscribe free to our newsletters via your
. Space Industry and Business News .




SOLAR DAILY
Shiny quantum dots brighten future of solar cells
by Staff Writers
Los Alamos NM (SPX) Apr 16, 2014


Quantum dot LSC devices under ultraviolet illumination.

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. Their emission color can be tuned by simply varying their dimensions. Color tunability is combined with high emission efficiencies approaching 100 percent. These properties have recently become the basis of a new technology - quantum dot displays - employed, for example, in the newest generation of the Kindle Fire e-reader.

Light-harvesting antennas
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, who worked at Los Alamos until 2012 and is now 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. One challenge, however, is an overlap between emission and absorption bands in the dots, which leads to significant light losses due to the dots re-absorbing some of the light they produce.

"Giant" but still tiny, engineered dots
To overcome this problem the Los Alamos and UNIMIB researchers have 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.

The separation of light-absorption and light-emission functions between the two different parts of the nanostructure results in a large spectral shift of emission with respect to absorption, which greatly reduces losses to re-absorption.

To implement this concept, 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 key to the success of this project was the use of a modified industrial method of cell-casting, we developed at UNIMIB Materials Science Department" said Francesco Meinardi, professor of Physics at UNIMIB.

Spectroscopic measurements indicated virtually no losses to re-absorption on distances of tens of centimeters. Further, tests using simulated solar radiation demonstrated high photon harvesting efficiencies of approximately 10% per absorbed photon achievable in nearly transparent samples, perfectly suited for utilization as photovoltaic windows.

Despite their high transparency, the fabricated structures showed significant enhancement of solar flux with the concentration factor of more than four.

These exciting results indicate that "Stokes-shift-engineered" quantum dots represent a promising materials platform. It may enable the creation of solution processable large-area LSCs with independently tunable emission and absorption spectra.

Publication: A research paper, "Large-area luminescent solar concentrators based on 'Stokes-shift-engineered' nanocrystals in a mass-polymerized PMMA matrix," is published online this week in Nature Photonics.

.


Related Links
Los Alamos National Laboratory
All About Solar Energy at SolarDaily.com






Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle




Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News





SOLAR DAILY
Microgrid Solar Completes Largest Single-Building Solar Installation on any Missouri School
St. Louis MO (SPX) Apr 14, 2014
Placing 386 solar panels on the science building at MICDS was no small feat for Microgrid Solar. This is the largest solar array installation on one building for any Missouri school. Due to the synthetic shingles on the new LEED certified McDonnell Hall, a group of engineers pioneered a system to allow the microinverters to be installed so that the students can carefully monitor how the we ... read more


SOLAR DAILY
Refreshingly cool, potentially toxic

Vanguard Space Technologies Antenna Reflectors on Amazonas Satellite Launch

Headwall Extends Global Reach in Asia/Pac and Israel

A new twist for better steel

SOLAR DAILY
Intelsat and L-3 Test Protected Air Force Tactical Technology on Ku-band

Spectrum Challenge Paves Way For More Reliable Radio Communications

Testing Begins on Third AEHF Satellite

Northrop Grumman Flies First Production Smart Node Pod

SOLAR DAILY
NASA Ames Launches Nanosatellites, Science Experiments on SpaceX Rocket

On-board camera provides a unique perspective on Arianespace Flight VS07

The DZZ-HR satellite is fueled for Arianespace's upcoming Vega launch

EUTELSAT 3B Mission Status Update

SOLAR DAILY
Fifth Boeing GPS IIF Satellite Joins Global Positioning System

Satellite Navigation Failure Confirms Urgent Need for Backup

USAF Awards Lockheed Martin Full Production Contracts For Next Two GPS 3 Satellites

PSLV-C24 Launches India's Second Dedicated Navigation Satellite IRNSS-1B

SOLAR DAILY
Gulfstream announces 60-plane deal for China

Boeing Phantom Badger Certified for V-22 Transport

Hunt for black box signals zeroes in on 'final resting place'

Kelly Aviation Center is Now Lockheed Martin Commercial Engine Solutions

SOLAR DAILY
Catching the Invisible Wave

To bridge LEDs' green gap, scientists think really small

Future computers that are 'normally off'

Intel lays off of 1,500 employees in Costa Rica

SOLAR DAILY
DMCii help Dutch company eLEAF provide much needed crop information to African farmers

China preps satellite to help detect quakes

NASA Radar Watches Over California's Aging Levees

Sentinel-1 performs opening dance routine

SOLAR DAILY
Snowstorms and power outages present elevated risk for carbon monoxide poisoning

Strong winds won't solve British pollution, advocacy says

China detains 18 over 'violent' chemical protests in Maoming

England issues health warnings over air pollution




The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement All images and articles appearing on Space Media Network have been edited or digitally altered in some way. Any requests to remove copyright material will be acted upon in a timely and appropriate manner. Any attempt to extort money from Space Media Network will be ignored and reported to Australian Law Enforcement Agencies as a potential case of financial fraud involving the use of a telephonic carriage device or postal service.