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!
Electrical fields drive nano-machines a 100,000 times faster than previous methods
19.01.2018 | Technische Universität München
ISFH-CalTeC is “designated test centre” for the confirmation of solar cell world records
16.01.2018 | Institut für Solarenergieforschung GmbH
On the way to an intelligent laboratory, physicists from Innsbruck and Vienna present an artificial agent that autonomously designs quantum experiments. In initial experiments, the system has independently (re)discovered experimental techniques that are nowadays standard in modern quantum optical laboratories. This shows how machines could play a more creative role in research in the future.
We carry smartphones in our pockets, the streets are dotted with semi-autonomous cars, but in the research laboratory experiments are still being designed by...
What enables electrons to be transferred swiftly, for example during photosynthesis? An interdisciplinary team of researchers has worked out the details of how...
For the first time, scientists have precisely measured the effective electrical charge of a single molecule in solution. This fundamental insight of an SNSF Professor could also pave the way for future medical diagnostics.
Electrical charge is one of the key properties that allows molecules to interact. Life itself depends on this phenomenon: many biological processes involve...
At the JEC World Composite Show in Paris in March 2018, the Fraunhofer Institute for Laser Technology ILT will be focusing on the latest trends and innovations in laser machining of composites. Among other things, researchers at the booth shared with the Aachen Center for Integrative Lightweight Production (AZL) will demonstrate how lasers can be used for joining, structuring, cutting and drilling composite materials.
No other industry has attracted as much public attention to composite materials as the automotive industry, which along with the aerospace industry is a driver...
Scientists at Tokyo Institute of Technology (Tokyo Tech) and Tohoku University have developed high-quality GFO epitaxial films and systematically investigated their ferroelectric and ferromagnetic properties. They also demonstrated the room-temperature magnetocapacitance effects of these GFO thin films.
Multiferroic materials show magnetically driven ferroelectricity. They are attracting increasing attention because of their fascinating properties such as...
08.01.2018 | Event News
11.12.2017 | Event News
08.12.2017 | Event News
19.01.2018 | Materials Sciences
19.01.2018 | Health and Medicine
19.01.2018 | Physics and Astronomy