Nanotechnology Now

Our NanoNews Digest Sponsors

Heifer International

Wikipedia Affiliate Button

Home > Press > Cause of LED Efficiency Droop Finally Revealed: Researchers at UC Santa Barbara and École Polytechnique confirm that Auger recombination theory is responsible for LED droop phenomenon

LED emitting light under forward bias in an ultra high vacuum chamber allowing simultaneous electron emission energy. Credit: Ecole Polytechnique, Ph. Lavialle
LED emitting light under forward bias in an ultra high vacuum chamber allowing simultaneous electron emission energy.

Credit: Ecole Polytechnique, Ph. Lavialle

Abstract:
Researchers at University of California, Santa Barbara, in collaboration with colleagues at the École Polytechnique in France, have conclusively identified Auger recombination as the mechanism that causes light emitting diodes (LEDs) to be less efficient at high drive currents.

Cause of LED Efficiency Droop Finally Revealed: Researchers at UC Santa Barbara and École Polytechnique confirm that Auger recombination theory is responsible for LED droop phenomenon

Santa Barbara, CA | Posted on April 23rd, 2013

Until now, scientists had only theorized the cause behind the phenomenon known as LED "droop"—a mysterious drop in the light produced when a higher current is applied. The cost per lumen of LEDs has held the technology back as a viable replacement for incandescent bulbs for all-purpose commercial and residential lighting.

This could all change now that the cause of LED efficiency droop has been explained, according to researchers James Speck and Claude Weisbuch of the Center for Energy Efficient Materials at UCSB, an Energy Frontier Research Center sponsored by the U.S. Department of Energy.

Knowledge gained from this study is expected to result in new ways to design LEDs that will have significantly higher light emission efficiencies. LEDs have enormous potential for providing long-lived high quality efficient sources of lighting for residential and commercial applications. The U.S. Department of Energy recently estimated that the widespread replacement of incandescent and fluorescent lights by LEDs in the U.S. could save electricity equal to the total output of fifty 1GW power plants.

"Rising to this potential has been contingent upon solving the puzzle of LED efficiency droop," commented Speck, professor of Materials and the Seoul Optodevice Chair in Solid State Lighting at UCSB. "These findings will enable us to design LEDs that minimize the non-radiative recombination and produce higher light output."

"This was a very complex experiment—one that illustrates the benefits of teamwork through both an international collaboration and a DOE Energy Frontier Research Center," commented Weisbuch, distinguished professor of Materials at UCSB. Weisbuch, who is also a faculty member at the École Polytechnique in Paris, enlisted the support of his colleagues Lucio Martinelli and Jacques Peretti. UCSB graduate student Justin Iveland was a key member of the team working both at UCSB and École Polytechnique.

In 2011, UCSB professor Chris van de Walle and colleagues theorized that a complex non-radiative process known as Auger recombination was behind nitride semiconductor LED droop, whereby injected electrons lose energy to heat by collisions with other electrons rather than emitting light.

A definitive measurement of Auger recombination in LEDs has now been accomplished by Speck, Weisbuch, and their research team.

The experiment used an LED with a specially prepared surface that permitted the researchers to directly measure the energy spectrum of electrons emitted from the LED. The results unambiguously showed a signature of energetic electrons produced by the Auger process.

The results of their work are to be published in the journal Physical Review Letters. A similar version of the accepted manuscript can be found at http://arxiv.org/abs/1304.5469.

This work was funded by the UCSB Center for Energy Efficient Materials, an Energy Frontier Research Center of the US Department of Energy, Office of Science. Additional support for the work at École Polytechnique was provided by the French government.

####

About University of California - Santa Barbara
The Center for Energy Efficient Materials at UCSB is a research program within the Institute for Energy Efficiency, a cross-campus institute dedicated to science and engineering research for a more efficient sustainable energy future.

The College of Engineering at University of California, Santa Barbara is recognized globally as a leader among the top tier of engineering education and research programs, and is renowned for a successful interdisciplinary approach to engineering research.

For more information, please click here

Contacts:
Melissa Van De Werfhorst

(805) 893-4301

Copyright © University of California - Santa Barbara

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

News and information

ANU invention to inspire new night-vision specs December 7th, 2016

Arrowhead Pharmaceuticals to Webcast Fiscal 2016 Year End Results December 7th, 2016

Journal Nanotechnology Progress International (JONPI), newest edition out December 7th, 2016

In IEDM 2016 Keynote, Leti CEO Says ‘Hyperconnectivity’, Human-focused Research and the IOT Promise Profound, Positive Changes December 7th, 2016

Display technology/LEDs/SS Lighting/OLEDs

Trace metal recombination centers kill LED efficiency: UCSB researchers warn that trace amounts of transition metal impurities act as recombination centers in gallium nitride semiconductors November 3rd, 2016

Diamond nanothread: Versatile new material could prove priceless for manufacturing: Would you dress in diamond nanothreads? It's not as far-fetched as you might think November 3rd, 2016

Researchers surprised at the unexpected hardness of gallium nitride: A Lehigh University team discovers that the widely used semiconducting material is almost as wear-resistant as diamonds October 31st, 2016

Inspiration from the ocean: An interdisciplinary team of researchers at UC Santa Barbara has developed a non-toxic, high-quality surface treatment for organic field-effect transistors October 18th, 2016

Govt.-Legislation/Regulation/Funding/Policy

Physicists decipher electronic properties of materials in work that may change transistors December 6th, 2016

Construction of practical quantum computers radically simplified: Scientists invent ground-breaking new method that puts quantum computers within reach December 5th, 2016

Shape matters when light meets atom: Mapping the interaction of a single atom with a single photon may inform design of quantum devices December 4th, 2016

Research Study: MetaSOLTM Shatters Solar Panel Efficiency Forecasts with Innovative New Coating: Coating Provides 1.2 Percent Absolute Enhancement to Triple Junction Solar Cells December 2nd, 2016

Discoveries

ANU invention to inspire new night-vision specs December 7th, 2016

Leti IEDM 2016 Paper Clarifies Correlation between Endurance, Window Margin and Retention in RRAM for First Time: Paper Presented at IEDM 2016 Offers Ways to Reconcile High-cycling Requirements and Instability at High Temperatures in Resistive RAM December 6th, 2016

Tokyo Institute of Technology research: 3D solutions to energy savings in silicon power transistors December 6th, 2016

Physicists decipher electronic properties of materials in work that may change transistors December 6th, 2016

Announcements

ANU invention to inspire new night-vision specs December 7th, 2016

Arrowhead Pharmaceuticals to Webcast Fiscal 2016 Year End Results December 7th, 2016

Journal Nanotechnology Progress International (JONPI), newest edition out December 7th, 2016

In IEDM 2016 Keynote, Leti CEO Says ‘Hyperconnectivity’, Human-focused Research and the IOT Promise Profound, Positive Changes December 7th, 2016

Research partnerships

Deep insights from surface reactions: Researchers use Stampede supercomputer to study new chemical sensing methods, desalination and bacterial energy production December 2nd, 2016

Quantum obstacle course changes material from superconductor to insulator December 1st, 2016

Novel silicon etching technique crafts 3-D gradient refractive index micro-optics November 28th, 2016

Single photon converter -- a key component of quantum internet November 28th, 2016

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