Subscribe free to our newsletters via your
. 24/7 Space News .




ENERGY TECH
Breakthrough in OLED technology
by Staff Writers
Washington DC (SPX) Mar 03, 2015


This image shows charge diffusion in the transport region of an OLED. Image courtesy Thuc-Quyen Nguyen/UCSB. For a larger version of this image please go here.

Organic light emitting diodes (OLEDs), which are made from carbon-containing materials, have the potential to revolutionize future display technologies, making low-power displays so thin they'll wrap or fold around other structures, for instance.

Conventional LCD displays must be backlit by either fluorescent light bulbs or conventional LEDs whereas OLEDs don't require back lighting. An even greater technological breakthrough will be OLED-based laser diodes, and researchers have long dreamed of building organic lasers, but they have been hindered by the organic materials' tendency to operate inefficiently at the high currents required for lasing.

Now a new study from a team of researchers in California and Japan shows that OLEDs made with finely patterned structures can produce bright, low-power light sources, a key step toward making organic lasers. The results are reported in a paper appearing this week on the cover of the journal Applied Physics Letters, from AIP Publishing.

The key finding, the researchers say, is to confine charge transport and recombination to nanoscale areas, which extends electroluminescent efficiency roll off the current density at which the efficiency of the OLEDs dramatically decreases -- by almost two orders of magnitude. The new device structures do this by suppressing heating and preventing charge recombination.

"An important effect of suppressing roll-off is an increase in the efficiency of devices at high brightness," said Chihaya Adachi of Kyushu University, who is a co-author of the paper. "This results in lower power to obtain the same brightness."

"For years scientists working in organic semiconductors have dreamed of making electrically-driven organic lasers," said Thuc-Quyen Nguyen of the University of California, Santa Barbara, another co-author. "Lasers operate in extreme conditions with electric currents that are significantly higher than those used in common displays and lighting. At these high currents, energy loss processes become stronger and make lasing difficult.

"We see this work, which reduces some loss processes, as one step on the road toward realizing organic lasers," Nguyen added.

How OLEDs Work
OLEDs operate through the interaction of electrons and holes.

"As a simple visualization," Adachi said, "one can think of an organic semiconductor as a subway train with someone sitting in every seat. The seats represent molecules and the people represent energetic particles, i.e., electrons. When people board the train from one end, they have extra energy and want to go to the relaxed state of sitting. As people board, some of the seated people rise and exit the train at the other end leaving empty seats, or 'holes,' for the standing people to fill. When a standing person sits, the person goes to a relaxed state and releases energy. In the case of OLEDs, the person releases the energy as light."

Production of OLED-based lasers requires current densities of thousands of amperes per square centimeter (kA/cm2), but until now, current densities have been limited by heating. "At high current densities, brightness is limited by annihilation processes," Adachi said. "Think of large numbers of people on the train colliding into each other and losing energy in ways other than by sitting and releasing light."

In previous work, Adachi and colleagues showed OLED performance at current densities over 1 kA/cm2 but without the necessary efficiency required for lasers and bright lighting.

In their current paper, they show that the efficiency problem can be solved by using electron-beam lithography to produce finely-patterned OLED structures. The small device area supports charge density injection of 2.8 kA/cm2 while maintaining 100 times higher luminescent efficiency than previously observed.

"In our device structure, we have effectively confined the entrance and exit to the middle of the train. People diffuse to the two less crowded ends of the train and reduce collisions and annihilation."


Thanks for being here;
We need your help. The SpaceDaily news network continues to grow but revenues have never been harder to maintain.

With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords.

Our news coverage takes time and effort to publish 365 days a year.

If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution.
SpaceDaily Contributor
$5 Billed Once


credit card or paypal
SpaceDaily Monthly Supporter
$5 Billed Monthly


paypal only


.


Related Links
American Institute of Physics
Powering The World in the 21st Century at Energy-Daily.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





ENERGY TECH
Renewable energy obtained from wastewater
Barcelona, Spain (SPX) Feb 25, 2015
Currently, there are treatments in which wastewater can flow out to the river or sea without causing any environmental problems. These technologies however entail high energy costs, mainly in aeration and pumping, and an elevated economic cost in treating the sludge left over from the treatment process. Wastewater contains an elevated amount of chemical energy in the form of organic contam ... read more


ENERGY TECH
Application of laser microprobe technology to Apollo samples refines lunar impact history

NASA releases video of the far side of the Moon

US Issuing Licenses for Mineral Mining on Moon

LRO finds lunar hydrogen more abundant on Moon's pole-facing slopes

ENERGY TECH
How Can We Protect Mars From Earth, While Searching For Life

The Search For Volcanic Eruptions On Mars Reaches The Next Level

Using Curiosity to Search for Life

Curiosity Self-Portrait at 'Mojave' Site on Mount Sharp

ENERGY TECH
Water pools in US astronaut's helmet after spacewalk

Korean tech start-ups offer life beyond Samsung

Fast visas and dim sum: Spain seeks to attract Chinese tourists

Industry: Risk aversion costs more than 'fast failure'

ENERGY TECH
More Astronauts for China

China launches the FY-2 08 meteorological satellite successfully

China's Long March puts satellite in orbit on 200th launch

Countdown to China's new space programs begins

ENERGY TECH
Russia to use International Space Station till 2024

NASA preparing to reassemble International Space Station

Spacewalking 'cable guys' wrap up work outside station

Space Station 3-D Printed Items, Seedlings Return in the Belly of a Dragon

ENERGY TECH
Soyuz Installed at Baikonur, Expected to Launch Wednesday

Leaders share messages, priorities at AFA Symposium

Moog offers "SoftRide" for enhanced spacecraft protection during launch

Russian-Ukrainian Satan Rocket to Launch South Korean Satellite as Planned

ENERGY TECH
The mystery of cosmic oceans and dunes

Laser 'ruler' holds promise for hunting exoplanets

Scientists predict earth-like planets around most stars

"Vulcan Planets" - Inside-Out Formation of Super-Earths

ENERGY TECH
Japan's NTT to buy German data centre operator: report

Moving molecule writes letters

New filter could advance terahertz data transmission

A simple way to make and reconfigure complex emulsions




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.