PRESS-NEWS.org - Press Release Distribution
PRESS RELEASES DISTRIBUTION

Novel LEDs pave the way to cheaper displays

Applications in smart phones or luminescent bathroom tiles conceivable / Collaboration of Bonn University, Regensburg University, the University of Utah and MIT

2013-11-08
(Press-News.org) Contact information: Dr. Sigurd Höger
hoeger@uni-bonn.de
49-228-736-127
University of Bonn
Novel LEDs pave the way to cheaper displays Applications in smart phones or luminescent bathroom tiles conceivable / Collaboration of Bonn University, Regensburg University, the University of Utah and MIT

OLEDs are already used in the displays of smart phones or digital cameras today. They offer an especially bright image with high contrast, but come with a serious drawback: typically, only one quarter of the electrical energy invested in running the device is actually converted into light. This ratio can be raised by adding traces of noble metals such as platinum or iridium to the active material, but these elements are rare and very expensive. Making high-quality OLEDs is therefore a rather costly business.

This could change in the near future. The scientists from Bonn, Regensburg and the US have demonstrated a novel type of OLED, which shows potential for high conversion efficiencies without having to resort to noble metals. OLED displays could well get quite a bit cheaper soon.

OLEDs aren't really "organic"

OLEDs are called so because, ideally, they are made up of organic molecules, which consist solely of carbon and hydrogen. The operating principle of an OLED is rather simple: a thin film of the molecules is contacted by electrodes, which are connected to a battery so that an electrical current can flow. This current is made up of positive and negative charges. When the charges meet, they annihilate, destroying each other in a flash of light.

Since positive and negative charges attract each other, generating light from electricity should be a pretty efficient business. The problem lies in the intricate quantum-mechanical nature of charges, which also posses a magnetic moment – scientists call this the "spin". Charges with like spin repel each other, much as the north poles of two bar magnets do. This repulsion outweighs the attraction between positive and negative charges, so that different charges with like spin cannot generate light. Instead, they convert electrical energy into heat – a rather exotic and not overly useful way of electrical heating.

In conventional OLEDs this loss of energy occurs frequently: three quarters of all charges carry the same spin. Much like the needle of a compass, they point in the same direction but cannot touch each other, effectively lowering the yield of useful light. OLED manufacturers have come up with a clever trick to raise the yield: they twirl the compass needles around with an even stronger magnet, allowing the charges to generate light after all. To do this requires heavy metals such as platinum or iridium, which allow virtually all of the electrical energy to be converted into light. Strictly speaking, conventional materials in OLEDs are not organic compounds at all, but metal-organic substances. This distinction is more than semantic in nature, since noble metals are extremely expensive.

Useful spin flip flops

"We can also raise the efficiency using a different mechanism", Dr. John Lupton, Professor of Physics at the University of Regensburg, explains. "Charges can flip the orientation of their spins spontaneously – you just have to wait for long enough for this to occur." In conventional OLEDs, however, there is not enough time to do this since the electrical energy is not stored for long enough in the molecular architecture. Instead, the molecules give up and simply convert the energy to heat.

"It appears that, in our OLEDs, the molecules can store electrical energy for significantly longer than is conventionally assumed", notes chemists Professor Sigurd Höger of the University of Bonn. "Our molecules can therefore exploit the spontaneous jumps in spin orientation in order to generate light." The new compounds therefore hold potential to minimize electrical generation of heat in OLEDs without having to resort to any "metal-organic tricks", thereby converting the electrical energy very effectively into light.



INFORMATION:

The study was supported by the Volkswagen Foundation and the German Science Foundation (DFG), with collaborators based at the University of Utah and the Massachusetts Institute of Technology (M.I.T.).

Publication: Metal-free OLED triplet emitters by side-stepping Kasha's rule; D. Chaudhuri, E. Sigmund, A. Meyer, L. Röck, P. Klemm, S. Lautenschlager, A. Schmid, S. R. Yost, T. Van Voorhis, S. Bange, S. Höger und J. M. Lupton; Angewandte Chemie (DOI: 10.1002/anie.201307601)

Contact:

Prof. Dr. Sigurd Höger
Universität Bonn
Kekulé-Institut für Organische Chemie und Biochemie
Tel.: 0228 73-6127
hoeger@uni-bonn.de

Prof. Dr. John Lupton
Universität Regensburg
Institut für Experimentelle und Angewandte Physik
Tel.: 0941 943-2081
John.Lupton@ur.de



ELSE PRESS RELEASES FROM THIS DATE:

New test for patients with sore throats cuts antibiotic use by nearly a third

2013-11-08
New test for patients with sore throats cuts antibiotic use by nearly a third A new 'clinical score' test for patients with sore throats could reduce the amount of antibiotics prescribed and result in patients feeling better more quickly, research in the British ...

Mother's immunosuppressive medications not likely to put fetus at risk

2013-11-08
Mother's immunosuppressive medications not likely to put fetus at risk Women with chronic autoimmune diseases who take immunosuppressive medications during their first trimester of pregnancy are not putting their babies at significantly increased ...

Study shows veterans psychologically impacted by Boston Marathon Bombing

2013-11-08
Study shows veterans psychologically impacted by Boston Marathon Bombing (Boston) - According to a new study, many Boston-area military veterans diagnosed with post-traumatic stress disorder (PTSD) experienced flashbacks, unwanted memories and other psychological ...

Safe long term storage of CO2 is possible

2013-11-08
Safe long term storage of CO2 is possible Conclusion of an international project for the geological storage of carbon dioxide Potsdam, 07.11.2013 | At the final conference of the EU project CO2CARE - CO2 Site Closure Assessment Research ...

In animal study, 'cold turkey' withdrawal from drugs triggers mental decline

2013-11-08
In animal study, 'cold turkey' withdrawal from drugs triggers mental decline SAN DIEGO – Can quitting drugs without treatment trigger a decline in mental health? That appears to be the case in an animal model of morphine addiction. Georgetown University Medical ...

NASA sees Super-Typhoon Haiyan maintain strength crossing Philippines

2013-11-08
NASA sees Super-Typhoon Haiyan maintain strength crossing Philippines Super-Typhoon Haiyan slammed into the eastern Philippines as the strongest tropical cyclone of the year, and today, Nov. 8, is exiting the country and moving into the South China Sea. NASA's Aqua ...

Drug may guard against periodontitis, and related chronic diseases

2013-11-08
Drug may guard against periodontitis, and related chronic diseases WASHINGTON, DC – November 7, 2013 – A drug currently used to treat intestinal worms could protect people from periodontitis, an advanced gum disease, which untreated can erode the structures—including ...

A new scorpion species from ancient Lycia

2013-11-08
A new scorpion species from ancient Lycia Scientists discover and describe a new species of scorpion, Euscorpius lycius, coming from the area of ancient Lycia, nowadays the regions of the Muğla and Antalya Provinces in Southwestern Turkey. With the new discovery, ...

Next-generation semiconductors synthesis

2013-11-08
Next-generation semiconductors synthesis Aluminum nitride semiconductors synthesized at significantly reduced temperatures -- Described in the journal 'Applied Physics Letters' WASHINGTON, D.C. Nov. 8, 2013 -- Although silicon semiconductors are nearly universal ...

Penn study identifies new trigger for breast cancer metastasis

2013-11-08
Penn study identifies new trigger for breast cancer metastasis For years, scientists have observed that tumor cells from certain breast cancer patients with aggressive forms of the disease contained low levels of mitochondrial DNA. But, until recently, ...

LAST 30 PRESS RELEASES:

A third of licensed GPs in England not working in NHS general practice

ChatGPT “thought on the fly” when put through Ancient Greek maths puzzle

Engineers uncover why tiny particles form clusters in turbulent air

GLP-1RA drugs dramatically reduce death and cardiovascular risk in psoriasis patients

Psoriasis linked to increased risk of vision-threatening eye disease, study finds

Reprogramming obesity: New drug from Italian biotech aims to treat the underlying causes of obesity

Type 2 diabetes may accelerate development of multiple chronic diseases, particularly in the early stages, UK Biobank study suggests

Resistance training may improve nerve health, slow aging process, study shows

Common and inexpensive medicine halves the risk of recurrence in patients with colorectal cancer

SwRI-built instruments to monitor, provide advanced warning of space weather events

Breakthrough advances sodium-based battery design

New targeted radiation therapy shows near-complete response in rare sarcoma patients

Does physical frailty contribute to dementia?

Soccer headers and brain health: Study finds changes within folds of the brain

Decoding plants’ language of light

UNC Greensboro study finds ticks carrying Lyme disease moving into western NC

New implant restores blood pressure balance after spinal cord injury

New York City's medical specialist advantage may be an illusion, new NYU Tandon research shows

Could a local anesthetic that doesn’t impair motor function be within reach?

1 in 8 Italian cetacean strandings show evidence of fishery interactions, with bottlenose and striped dolphins most commonly affected, according to analysis across four decades of data and more than 5

In the wild, chimpanzees likely ingest the equivalent of several alcoholic drinks every day

Warming of 2°C intensifies Arctic carbon sink but weakens Alpine sink, study finds

Bronze and Iron Age cultures in the Middle East were committed to wine production

Indian adolescents are mostly starting their periods at an earlier age than 25 years ago

Temporary medical centers in Gaza known as "Medical Points" (MPs) treat an average of 117 people daily with only about 7 staff per MP

Rates of alcohol-induced deaths among the general population nearly doubled from 1999 to 2024

PLOS One study: In adolescent lab animals exposed to cocaine, High-Intensity Interval Training boosts aversion to the drug

Scientists identify four ways our bodies respond to COVID-19 vaccines

Stronger together: A new fusion protein boosts cancer immunotherapy

Hidden brain waves as triggers for post-seizure wandering

[Press-News.org] Novel LEDs pave the way to cheaper displays
Applications in smart phones or luminescent bathroom tiles conceivable / Collaboration of Bonn University, Regensburg University, the University of Utah and MIT