(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
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
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:
Effectiveness and cost-effectiveness of automated external defibrillators in private homes
University of Phoenix College of Social and Behavioral Sciences leadership publishes white paper on trauma-informed education
Microbial iron mining: turning polluted soils into self-cleaning reactors
Molecular snapshots reveal how the body knows it’s too hot
Analysis finds alarming rise in severe diverticulitis among younger Americans
Mitochondria and lysosomes reprogram immune cells that dampen inflammation
Cockroach infestation linked to home allergen, endotoxin levels
New biochar-powered microbial systems offer sustainable solution for toxic pollutants
Identifying the best high-biomass sorghum hybrids based on biomass yield potential and feedstock quality affected by nitrogen fertility management under various environments
How HIV’s shape-shifting protein reveals clues for smarter drug design
Study identifies viral combinations that heighten risk of severe respiratory illnesses in infants
Aboveground rather than belowground productivity drives variability in miscanthus × giganteus net primary productivity
Making yeast more efficient 'cell factories' for producing valuable plant compounds
Aging in plain sight: What new research says the eyes reveal about aging and cardiovascular risk
Child welfare system involvement may improve diagnosis of developmental delays
Heavier electric trucks could strain New York City’s roads and bridges, study warns
From womb to world: scientists reveal how maternal stress programs infant development
Bezos Earth Fund grants $2M to UC Davis and American Heart Association to advance AI-designed foods
Data Protection is transforming humanitarian action in the digital age, new book shows
AI unlocks the microscopic world to transform future manufacturing
Virtual reality helps people understand and care about distant communities
Optica Publishing Group announces subscribe to open pilot for the Journal of the Optical Society of America B (JOSA B)
UNF partners with Korey Stringer Institute and Perry Weather to open heat exercise laboratory on campus
DNA from Napoleon’s 1812 army identifies the pathogens likely responsible for the army’s demise during their retreat from Russia
Study suggests two unsuspected pathogens struck Napoleon's army during the retreat from Russia in 1812
The 25-year incidence and progression of hearing loss in the Framingham offspring study
AI-driven nanomedicine breakthrough paves way for personalized breast cancer therapy
Fight or flight—and grow a new limb
Augmenting electroencephalogram transformer for steady-state visually evoked potential-based brain–computer interfaces
Coaches can boost athletes’ mental toughness with this leadership style
[Press-News.org] Novel LEDs pave the way to cheaper displaysApplications in smart phones or luminescent bathroom tiles conceivable / Collaboration of Bonn University, Regensburg University, the University of Utah and MIT