The search for innovative, cost-effective and energy-efficient solutions for display and lighting applications are the focus of ongoing intense worldwide photonics research and development activities.
Organic light-emitting diodes (OLEDs)—lightweight, potentially flexible, cheap-to-fabricate and highly energy-efficient lighting and display devices—offer one solution in alternative energy lighting and display applications. To highlight breakthroughs in this area, the Optical Society (OSA (http://www.osa.org)) today published a special Focus Issue on OLEDs (http://www.opticsinfobase.org/oe/issue.cfm?volume=19&issue=106) in Energy Express (http://www.opticsinfobase.org/ee), a bi-monthly supplement to its open access journal Optics Express (http://www.opticsinfobase.org/oe/home.cfm). The issue is organized and edited by Guest Editors Emil J.W. List of the NanoTecCenter Weiz GmbH and Graz University of Technology in Austria, and Norbert Koch of the Institute of Physics, Humbolt University in Germany.
"OLEDs are amongst the most promising candidates for alternative display and lighting solutions," said List. "The exciting findings presented in this focus issue will ultimately translate into real-world applications, providing consumers with cost-effective technology while reducing electricity consumption."
More than 20 percent of the world's total electricity consumption is used for lighting applications. That number increases to an estimated 25 percent when including display and TV applications. OLEDs, along with inorganic solid-state lighting technologies, are considered to be on the forefront of 21st century display and lighting technologies. The widespread use of this technology could save hundreds of gigawatt hours (GWh) of power or millions of tons of coal per year.
"OLEDs can be found in a variety of everyday products such as television screens, computer monitors and smartphones," said Koch. "As use of these products becomes more widespread, the need for research and development also grows. The latest advances reflected in this focus issue are truly exceptional and will prove to be invaluable to advancements in lighting and display technology."
Key Findings and Select Papers
The following papers are some of the highlights of the Energy Express Focus Issue on OLEDs. All are included in Volume 19, issue S6 and can be accessed online at http://www.opticsinfobase.org/ee.
The outcoupling of light from an OLED may be tackled by different means, including optical feedback structures in the active layer, by high index-media in top-emitting OLED, by lens or microlens-like arrays, or by using microcavity effects in the active device. As reviewed and discussed by Simone Hofmann, Karl Leo and their colleagues from the Institute for Applied for Photophysics, TU Dresden in Germany, in particular top-emitting OLEDs seem to be beneficial for lighting and display applications. Here, non-transparent substrates are used. The authors review and discuss different optical effects of the microcavity structure and identify important loss mechanisms due to waveguiding and surface plasmons, and show that further improvement in light extraction is required to reach the targeted high outcoupling efficiencies.
Paper: "Top-Emitting Organic Light-Emitting Diodes (http://www.opticsinfobase.org/oe/abstract.cfm?uri=oe-19-106-A1250)," Optics Express, Vol. 19, Issue S6, pp. A1250-A1264 (2011).
A very practical approach to improve the outcoupling efficiency in OLEDs up to 60 percent is demonstrated by Ruth Shinar and Joseph Shinar from the U.S. Department of Energy's Ames Laboratory and Iowa State University, and coworkers, using index-matching microporous phase-separated films of polymer blends acting as random microlens-like arrays. They demonstrate that the use of such blended thin films provides an economical method independent of the OLED fabrication technique, for improving outcoupling.
Paper: "Microporous phase-separated films of polymer blends for enhanced outcoupling of light from OLEDs (http://www.opticsinfobase.org/oe/abstract.cfm?uri=oe-19-106-A1272)," Optics Express, Vol. 19, Issue S6, pp. A1272-A1280 (2011).
To overcome the losses at the organic layer/cathode interface and to optimize the optical path in the devices, Lian Duan, Yong Qiu and their colleagues from the Key Lab of Organic Optoelectronics and Molecular Engineering of Ministry of Education, Tsinghua University, and the R&D Center, Visionox Tech. Ltd, Beijing, introduce an approach by using a novel, rather thick, n-doped layer. Using a combination of a low-temperature-evaporable n-dopant KBH4 and a high charge carrier mobility electron transport material they show excellent performance of their devices due to reduced losses at the organic layer/cathode interface.
Paper: "Improving the performance of OLEDs by using a low-temperature-evaporable n-dopant and a high-mobility electron transport host (http://www.opticsinfobase.org/oe/abstract.cfm?uri=oe-19-106-A1265)," Optics Express, Vol. 19, Issue S6, pp. A1265-A1271 (2011).
About Energy Express
As a special bi-monthly supplement to Optics Express, Energy Express is dedicated to rapidly communicating new developments in optics for sustainable energy. Energy Express will have original research side-by-side with review articles written by the world's leading experts in the science and engineering of light and its impact on sustainable energy development, the environment, and green technologies. For more information, see: http://www.OpticsInfoBase.org/EE.
About Optics Express
Optics Express reports on new developments in all fields of optical science and technology every two weeks. The journal provides rapid publication of original, peer-reviewed papers. It is published by the Optical Society and edited by C. Martijn de Sterke of the University of Sydney. Optics Express is an open-access journal and is available at no cost to readers online at http://www.OpticsInfoBase.org/OE.
Uniting more than 130,000 professionals from 175 countries, the Optical Society (OSA) brings together the global optics community through its programs and initiatives. Since 1916 OSA has worked to advance the common interests of the field, providing educational resources to the scientists, engineers and business leaders who work in the field by promoting the science of light and the advanced technologies made possible by optics and photonics. OSA publications, events, technical groups and programs foster optics knowledge and scientific collaboration among all those with an interest in optics and photonics.
Angela Stark | EurekAlert!
Researchers produce synthetic Hall Effect to achieve one-way radio transmission
13.09.2019 | University of Illinois College of Engineering
Penn engineers' new topological insulator reroutes photonic 'traffic' on the fly
13.09.2019 | University of Pennsylvania
Researchers from the Department of Atomically Resolved Dynamics of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg, the University of Hamburg and the European Molecular Biology Laboratory (EMBL) outstation in the city have developed a new method to watch biomolecules at work. This method dramatically simplifies starting enzymatic reactions by mixing a cocktail of small amounts of liquids with protein crystals. Determination of the protein structures at different times after mixing can be assembled into a time-lapse sequence that shows the molecular foundations of biology.
The functions of biomolecules are determined by their motions and structural changes. Yet it is a formidable challenge to understand these dynamic motions.
At the International Symposium on Automotive Lighting 2019 (ISAL) in Darmstadt from September 23 to 25, 2019, the Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP, a provider of research and development services in the field of organic electronics, will present OLED light strips of any length with additional functionalities for the first time at booth no. 37.
Almost everyone is familiar with light strips for interior design. LED strips are available by the metre in DIY stores around the corner and are just as often...
Later during this century, around 2060, a paradigm shift in global energy consumption is expected: we will spend more energy for cooling than for heating....
Researchers from the Department of Atomically Resolved Dynamics of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg, the University of Potsdam (both in Germany) and the University of Toronto (Canada) have pieced together a detailed time-lapse movie revealing all the major steps during the catalytic cycle of an enzyme. Surprisingly, the communication between the protein units is accomplished via a water-network akin to a string telephone. This communication is aligned with a ‘breathing’ motion, that is the expansion and contraction of the protein.
This time-lapse sequence of structures reveals dynamic motions as a fundamental element in the molecular foundations of biology.
Two research teams have succeeded simultaneously in measuring the long-sought Thorium nuclear transition, which enables extremely precise nuclear clocks. TU Wien (Vienna) is part of both teams.
If you want to build the most accurate clock in the world, you need something that "ticks" very fast and extremely precise. In an atomic clock, electrons are...
10.09.2019 | Event News
04.09.2019 | Event News
29.08.2019 | Event News
18.09.2019 | Innovative Products
18.09.2019 | Physics and Astronomy
18.09.2019 | Materials Sciences