Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Optoelectronic materials: Optimum solution

09.08.2011
Highly efficient organic light-emitting diodes are created by optimizing the molecular structure and device configuration

Organic light-emitting diodes (OLEDs) are seen as a promising replacement for the liquid-crystal displays (LCDs) used in many flat-screen televisions because they are cheaper to mass-produce. Zhikuan Chen at the A*STAR Institute of Materials Research and Engineering and co-workers have now shown how meticulous engineering of fluorescent molecules can dramatically increase OLED efficiency.

Conventional light-emitting diodes are made of inorganic crystals such as gallium arsenide. OLEDS, on the other hand, utilize carbon-based materials that can be made flexible. Today, OLED technology is commonly used to make large-area outdoor displays and wearable displays. However, further improvements in operation efficiency are required if OLEDs are to become truly competitive against the alternative options.

Chen and his co-workers have now reported blue light-emitting devices that reach an external quantum efficiency (EQE) of as high as 9.4%—almost double the classical upper limit of 5% for fluorescence-based OLEDs. “This improvement is important because higher efficiency means a lower driving voltage and thus lower power consumption and increased device lifetime,” explains Chen.

EQE is an important measure of LED operation as it determines what fraction of the charge carriers injected into the device are converted into photons that can be emitted. EQE takes into account the chance that the two types of charge carriers—negatively charged electrons and positively charged holes—recombine with each other, as well as the intrinsic probability that this results in the creation of a photon and the chance that this photon will escape from the device. Chen and his team have now used computer models to optimize these various processes.

Simulations enabled the researchers to find a structure for their active molecule—an oligofluorene—that best balanced charge carrier injection into the material and charge transport through it to enhance device emission efficiency. Further improvements were made by selecting the best emitting-layer thickness and by doping the emitter in an appropriate organic host material to minimize efficiency loss.

The OLEDs emitted blue light centered at a wavelength of 450 nanometers. Chen and his co-workers found that the high EQE was possible because the fraction of charge carriers that recombine without emitting light was negligible. Importantly, the light output was stable during operation, making it more amenable to use in practical situations. “Soon we hope to develop these materials further for lighting and displays applications,” says Chen.

The A*STAR-affiliated researchers contributing to this research are from the Institute of Materials Research and Engineering

References
Zhen, C. G. et al. Achieving highly efficient fluorescent blue organic light-emitting diodes through optimizing molecular structures and device configuration. Advanced Functional Materials 21, 699–707 (2011).

Lee Swee Heng | Research asia research news
Further information:
http://www.imre.a-star.edu.sg/
http://www.researchsea.com

More articles from Materials Sciences:

nachricht An innovative high-performance material: biofibers made from green lacewing silk
20.01.2017 | Fraunhofer-Institut für Angewandte Polymerforschung IAP

nachricht Treated carbon pulls radioactive elements from water
20.01.2017 | Rice University

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Traffic jam in empty space

New success for Konstanz physicists in studying the quantum vacuum

An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Sustainable Water use in Agriculture in Eastern Europe and Central Asia

19.01.2017 | Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

 
Latest News

Helmholtz International Fellow Award for Sarah Amalia Teichmann

20.01.2017 | Awards Funding

An innovative high-performance material: biofibers made from green lacewing silk

20.01.2017 | Materials Sciences

Ion treatments for cardiac arrhythmia — Non-invasive alternative to catheter-based surgery

20.01.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>