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

Gold nanocrystal vibration captured on billion-frames-per-second film May 23rd, 2013

Whirlpools on the Nanoscale Could Multiply Magnetic Memory: At the Advanced Light Source, Berkeley Lab scientists join an international team to control spin orientation in magnetic nanodisks May 22nd, 2013

Bacterial spare parts filter antibiotic residue from groundwater May 22nd, 2013

UofL scientists uncover how grapefruits provide a secret weapon in medical drug delivery May 22nd, 2013

Announcements

Conference Scheduled June 5-7 on Safe Use of Nanotechnology in Environmental Remediation May 23rd, 2013

Heinrich Rohrer dies at 79; a father of nanotechnology: With IBM colleague Gerd Binnig, Rohrer invented the scanning tunneling microscope, which can show individual atoms on a surface and move them around May 23rd, 2013

Gold nanocrystal vibration captured on billion-frames-per-second film May 23rd, 2013

Glowing Plant Releases Maker Kit, Enabling Anyone to Make a Glowing Plant at Home: Glowing Plant seeks funds via crowdfunding and raises almost $400,000 May 23rd, 2013

Energy

IDTechEx launches online Market Intelligence Portal May 23rd, 2013

Innovation could bring flexible solar cells, transistors, displays May 22nd, 2013

Researchers Stitch Defects into the World’s Thinnest Semiconductor May 22nd, 2013

Atomic-Scale Investigations Solve Key Puzzle of LED Efficiency: MIT and Brookhaven Lab scientists use electron microscopy imaging techniques to settle a solid-state controversy and raise new experimental possibilities May 22nd, 2013

Quantum Dots/Rods

Perfectly doped quantum dots yield colors to dye for May 11th, 2013

Researchers use graphene quantum dots to detect humidity and pressure May 8th, 2013

Hamburger nano specialist enlarges the CANdots® product Series by fluorescent nanocrystals Series A plus May 8th, 2013

A step toward optical transistors? McGill researchers demonstrate new way to control light in semiconductor nanocrystals April 9th, 2013

Solar/Photovoltaic

IDTechEx launches online Market Intelligence Portal May 23rd, 2013

Innovation could bring flexible solar cells, transistors, displays May 22nd, 2013

Researchers Stitch Defects into the World’s Thinnest Semiconductor May 22nd, 2013

Atomic-Scale Investigations Solve Key Puzzle of LED Efficiency: MIT and Brookhaven Lab scientists use electron microscopy imaging techniques to settle a solid-state controversy and raise new experimental possibilities May 22nd, 2013

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





  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoTech-Transfer
University Technology Transfer & Patents
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More












ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project








abbigliamento uomo
Computer Accessories
© Copyright 1999-2013 7th Wave, Inc. All Rights Reserved PRIVACY POLICY :: CONTACT US :: STATS :: SITE MAP :: ADVERTISE