Displays with more brilliant colors through a fundamental physical concept
A research team from the University of Cologne (Germany) and the University of St Andrews (Scotland) has shown in a new study how a fundamental physical concept can be used to boost the colour brilliance of smartphone, computer or TV screens without cutbacks in energy efficiency. The results have been published in Nature Photonics.
Organic light-emitting diodes (OLEDs) have conquered the market for displays in recent years – from high-resolution smartphone to wall-sized television screens. However, industry and science face several challenges in creating the next generation of devices with even higher colour saturation, brightness and efficiency. The organic molecules from which OLEDs are made have intrinsically broad emission spectra – a property that limits the available colour space and saturation for high-end displays. Colour filters or optical resonators can be used to artificially narrow the emission spectra of OLEDs to circumvent this issue. However, this either comes at the expense of efficiency or leads to a strong dependence of the perceived colour on the viewing angle.
Researchers at the two universities have now shown that a fundamental scientific principle – the strong coupling of light and matter – can be used to change the emission spectra of OLEDs while avoiding the change of colour at oblique viewing angles. When photons (light) and excitons (matter) exhibit sufficiently large interaction with each other, they can strongly couple, creating so-called exciton polaritons. The principle can be compared to energy transferred between two coupled pendulums, except here it is both light and matter that are coupling with each other and continuously exchanging energy. These polaritons eventually emit light again. By embedding the entire layer stack of the OLED between thin mirrors made of metallic materials, which are already widely used in the display industry, the coupling between light and organic material can be significantly improved. Until now, however, strong coupling in OLEDs has inevitably led to low electrical efficiency. To avoid this, the researchers added a separate thin film of strongly light-absorbing molecules similar to those already used in organic solar cells, but not in OLEDs. The additional layer maximized the effect of strong coupling, but without significantly reducing the efficiency of the light-emitting molecules in the OLED.
“By generating polaritons, we can transfer some of the advantageous properties of matter to our OLEDs – including their significantly lower angular dependence, so that the colour impression of a display remains brilliant and stable from any perspective,” said Dr Andreas Mischok, first author of the study.
Although polariton-based OLEDs have been reported on in the past, their energy efficiency and brightness have been low. This has prevented practical applications and kept them mainly confined to basic research. With the new strategy, the team has now successfully realized polariton-based OLEDs at efficiency and brightness levels suitable for practical application for the first time.
Professor Malte Gather, who led the study, believes: “With efficiency and brightness comparable to OLEDs that are used in commercial displays, but with significantly improved colour saturation and colour stability, our polariton-based OLEDs are of great interest to the display industry.”
The on-demand and efficient production of a large number of polaritons is not only relevant for the next generation of displays, but can also be used for a wide range of other applications – from lasers to quantum computing.
ELSE PRESS RELEASES FROM THIS DATE:
Hot topic – how heat flow affects the Earth’s magnetic field
Compass readings that do not show the direction of true north and interference with the operations of satellites are a few of the problems caused by peculiarities of the Earth’s magnetic field.
The magnetic field radiates around the world and far into space, but it is set by processes that happen deep within the Earth’s core, where temperatures exceed 5,000-degress C.
New research from geophysicists at the University of Leeds suggests that ...
A new method to cure HIV—by transplanting HIV-resistant stem cells from umbilical cord blood—has yielded long-term successful results, say scientists. The approach was successfully used to treat the “New York patient,” a middle-aged woman with leukemia and HIV who self-identifies as mixed race, who has been without HIV since 2017. Using stem cells from cord blood rather than from compatible adult donors, as has been done previously, increases the potential to cure HIV via stem cell transplantation ...
The Ashaninka are the most numerous Indigenous people living in the rainforests of Peru and Brazil where they inhabit a crucial area between the Andes and sources of the Amazon River. And yet, despite the size of the population and their importance in the past and present, their genetic history has remained understudied.
Now a team of researchers reporting in the journal Current Biology on March 16 has analyzed the genomes of more than 50 individuals to clarify the group’s interactions with nearby South American regions, including Central America and the Caribbean. ...
Geneticists have written new chapters in the reconstruction of pre-colonial Americas history after using DNA from the indigenous Ashaninka people from Amazonian Peru. They have discovered previously unexpected levels of genetic variation in this group and uncovered a strong hint that these people were involved in a South-to-North migration that led to the transition from an archaic to ceramic culture in the Caribbean islands.
The dramatic impact of European colonisation during the second half of the last millennium has strongly influenced the genetic history of the Americas, making the reconstruction ...
About The Study: This survey study found that people with disabilities were more likely to report household employment loss and financial hardship during the initial COVID-19 pandemic, which are especially pronounced among racial and ethnic minority respondents. These findings suggest people with disabilities may be disproportionately affected by the initial pandemic and may require additional resources and policy strategies (e.g., training programs, workplace accommodations) as several labor markets adapt to the pandemic (e.g., shifting to remote working).
Authors: Kea Turner, Ph.D., M.P.H., M.A., of the H. Lee Moffitt Cancer Center ...
About The Study: In this study of 722,000 hospitalization episodes, patients with Alzheimer disease and related dementias (ADRD) had higher readmission rates and overall readmission and episode costs than their counterparts without ADRD. Hospitals may need to be better equipped to care for patients with ADRD, especially in the post-discharge period. Considering that any type of hospitalization may put patients with ADRD at a high risk of 30-day readmission, judicious preoperative assessment, postoperative discharge, and ...
Preterm infants do not get used to repeated pain in the way that full-term infants, children and adults do habituate to pain, finds a study led by UCL (University College London) researchers.
The authors of the new Current Biology paper say that if preterm infants have not yet developed the mechanism that enables people to get used to moderate pain, medical procedures in their first few weeks of life could potentially impact their development.
Lead author Dr Lorenzo Fabrizi (UCL Neuroscience, Physiology & Pharmacology) said: “The way that we can get used to things can be seen as the simplest example of behavioural and brain plasticity, and it is ...
Ikoma, Japan – The generation and maintenance of tissue boundaries are fundamental to the development of functional organs in both plants and animals. In general, tissue boundaries are initially set among primordial cells, and their shapes and arrangements are refined during subsequent organ growth. In this process, cell migration plays a curtail role for boundary refinement in animal systems, however, plant tissue lacks such cell fluidity due to its cell walls. Despite significant progress in understanding the initial patterning of tissue boundaries in several ...
A recent study makes it clear: Countries like Sweden that can link data from different areas - such as the labor market and health care - have a decisive advantage when it comes to setting targeted actions.
A research team from the Complexity Science Hub, together with scientists from Sweden, Denmark and the Netherlands, investigated the extent to which mental and somatic illnesses influence integration into the labor market and whether there is a difference here between refugee and Swedish-born young adults. "In total, we analyzed ...
Coal-fired power plants have been in place for a long time to meet the global demands for power generation. Needless to say, there are environmental and human health concerns to be addressed on this front. While there are ongoing efforts to transition to renewable energy resources, coal-fired power plants may not become obsolete just yet. Against this backdrop, it is pertinent to explore how the efficiency of these coal-fired boilers can be improved while mitigating their harmful effects on the environment, namely greenhouse gas emissions, acid rain, and photochemical smog generation, and the human health.
To this end, various ...
LAST 30 PRESS RELEASES:
[Press-News.org] Displays with more brilliant colors through a fundamental physical concept