Nanotechnology Now

Our NanoNews Digest Sponsors

Heifer International

Wikipedia Affiliate Button

Home > Press > Unique Quantum Effect Found in Silicon Nanocrystals

Abstract:
Quantum Dot Materials May Improve Efficiency of Silicon Solar Cells

Unique Quantum Effect Found in Silicon Nanocrystals

Golden, CO | Posted on July 25th, 2007

Researchers at the U.S. Department of Energy's National Renewable Energy Laboratory (NREL), collaborating with Innovalight, Inc., have shown that a new and important effect called Multiple Exciton Generation (MEG) occurs efficiently in silicon nanocrystals. MEG results in the formation of more than one electron per absorbed photon.

Silicon is the dominant semiconductor material used in present day solar cells, representing more than 93% of the photovoltaic cell market. Until this discovery, MEG had been reported over the past two years to occur only in nanocrystals (also called quantum dots) of semiconductor materials that are not presently used in commercial solar cells, and which contained environmentally harmful materials (such as lead). The new result opens the door to the potential application of MEG for greatly enhancing the conversion efficiency of solar cells based on silicon because more of the sun's energy is converted to electricity. This is a key step toward making solar energy more cost-competitive with conventional power sources.

In a paper published on July 24 in the initial on-line version of the American Chemical Society's Nano Letters Journal
(see http://pubs3.acs.org/acs/journals/doilookup?in_doi=10.1021/nl071486l ), an NREL team reported that silicon nanocrystals, or quantum dots, obtained from Innovalight can produce more than one electron from single photons of sunlight that have wavelengths less than 420 nm. When today's photovoltaic solar cells absorb a photon of sunlight, about 50% of the incident energy is lost as heat. MEG provides a way to convert some of this energy lost as heat into additional electricity.

The silicon nanocrystals produced by Innovalight, Inc., a thin-film solar cell developer based in Santa Clara, California, were studied at NREL as part of a collaboration between NREL and Innovalight scientists. The NREL team consisted of Matthew C. Beard, Kelly P. Knutsen, Joseph M. Luther, Qing Song, Wyatt Metzger, Randy J. Ellingson and Arthur J. Nozik.

The findings represent an important extension of the range of semiconductor materials that exhibit MEG and are a further confirmation of pioneering work by Nozik, who in 1997 predicted that semiconductor quantum dots could exhibit efficient electron multiplication and hence increase the efficiency of solar cells.

To date, all experiments showing the production of more than one electron per absorbed photon have been based on various types of optical spectroscopy. In a solar cell device it is necessary to extract the electrons produced in the quantum dots and pass them through an external circuit to generate electrical power. Such experiments are currently underway at NREL, Innovalight and other laboratories to demonstrate that MEG can indeed lead to enhanced solar cell efficiencies.

Calculations at NREL by Mark Hanna and Nozik have shown that the maximum theoretical efficiency of quantum dot solar cells exhibiting optimal MEG is about 44% with normal unconcentrated sunlight and 68% with sunlight concentrated by a factor of 500 with special lenses or mirrors. Today's conventional solar cells that produce one electron per photon have maximum efficiencies of 33% and 40%, respectively, under the same solar conditions.

In addition to efficiently extracting the electrons from the quantum dots in solar cells, future research is directed toward producing MEG at wavelengths that have a greater overlap with the solar spectrum, as well as producing a much sharper onset of the MEG processes with decreasing wavelength of the photons.

NREL is the U.S. Department of Energy's primary national laboratory for renewable energy and energy efficiency research and development. The NREL research was funded by DOE's Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences. NREL is operated for DOE by Midwest Research Institute and Battelle.

####

About Innovalight, Inc.
Innovalight is focused on bringing ultra low-cost solar power modules to the marketplace. Innovalight is harnessing a proprietary silicon-ink process, developed by the company to print thin-film solar power modules. Leveraging the advantages of solvent-based processing, Innovalight will help accelerate the promise of more affordable solar power solutions for residential and commercial applications.

The Company was recognized as a 2006 Technology Pioneer winner at the 2006 Annual Meeting of the World Economic Forum held in Davos, Switzerland. The Company has been extensively profiled in Time Magazine, The Economist, Red Herring and other major news organizations as a technology leader crusading for new cleaner energy solutions.

For more information, please click here

Contacts:
Innovalight, Inc.
3303 Octavius Drive
Suite 104
Santa Clara
California 95054
t: 408-987-9400
f: 408-987-9494

Copyright © Innovalight, Inc.

If you have a comment, please Contact us.

Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Bookmark:
Delicious Digg Newsvine Google Yahoo Reddit Magnoliacom Furl Facebook

Related News Press

Discoveries

Alzheimer's breakthrough: Brain metals that may drive disease progression revealed: In brains affected by Alzheimer's, researchers identify chemically reduced iron species, with mineral forms including a magnetic iron oxide June 22nd, 2018

Collaboration yields discovery of 12-sided silica cages June 20th, 2018

Carbon nanotube optics poised to provide pathway to optical-based quantum cryptography and quantum computing: Researchers are exploring enhanced potential of carbon nanotubes for unique applications June 18th, 2018

Camouflaged nanoparticles used to deliver killer protein to cancer June 17th, 2018

Announcements

Northwestern researchers achieve unprecedented control of polymer grids: Materials could find applications in water purification, solar energy storage, body armor June 22nd, 2018

Nanobiotix Publishes Positive Phase 2/3 Data For Nanomedicine in Soft Tissue Cancer (Webcast June 22) June 22nd, 2018

Alzheimer's breakthrough: Brain metals that may drive disease progression revealed: In brains affected by Alzheimer's, researchers identify chemically reduced iron species, with mineral forms including a magnetic iron oxide June 22nd, 2018

Collaboration yields discovery of 12-sided silica cages June 20th, 2018

Energy

Northwestern researchers achieve unprecedented control of polymer grids: Materials could find applications in water purification, solar energy storage, body armor June 22nd, 2018

Physicists devise method to reveal how light affects materials: The new method adds to the understanding of the fundamental laws governing the interaction of electrons and light June 15th, 2018

Tripling the Energy Storage of Lithium-Ion Batteries: Scientists have synthesized a new cathode material from iron fluoride that surpasses the capacity limits of traditional lithium-ion batteries June 14th, 2018

Remote control of transport through nanopores: New study outlines key factors affecting the transfer of molecules through biological channels May 24th, 2018

Quantum Dots/Rods

Individual quantum dots imaged in 3-D for first time February 28th, 2018

Moving nanoparticles using light and magnetic fields January 25th, 2018

Tweaking quantum dots powers-up double-pane solar windows: Engineered quantum dots could bring down the cost of solar electricity January 2nd, 2018

Quantum communications bend to our needs: By changing the wavelengths of entangled photons to those used in telecommunications, researchers see quantum technology take a major leap forward September 28th, 2017

Solar/Photovoltaic

Northwestern researchers achieve unprecedented control of polymer grids: Materials could find applications in water purification, solar energy storage, body armor June 22nd, 2018

Team achieves two-electron chemical reactions using light energy, gold May 15th, 2018

Hematene joins parade of new 2D materials: Rice University-led team extracts 3-atom-thick sheets from common iron oxide May 8th, 2018

Harvesting clean hydrogen fuel through artificial photosynthesis May 3rd, 2018

NanoNews-Digest
The latest news from around the world, FREE



  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More











ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project