Technical / Research - Page 27

OLEDs are nowadays facing the same issues they had since the beginning: basically, OLED materials are extremely sensitive to oxidizing agents and, especially, to moisture. This requires encapsulation materials with exceptionally high barrier properties and active fillers or getters, capable of absorbing water on a single molecule basis. The optimization of many functional properties in single encapsulating materials is a very complex materials science problem. The fact that OLED materials can also be very sensitive to heat or radiations, generates many process constraints as well.

It turns out that encapsulation materials must be specifically engineered taking into account the OLED structure, the device architecture, the chemical and physical nature of the materials and, nevertheless, the specific processes to be applied.

Researchers from ETRI (Korea's Electronics and Telecommunications Research Institute) developed transparent graphene based electrodes specifically for OLED displays.

The researchers say that current metal (mostly silver) based electrodes have a limited viewing angle because of their internal light reflection, and the external light reflection affects the image quality. Graphene electrodes are more transparent and reduce the reflectance by 40-60 percent.

Taiwan's ITRI research institute developed a long-lasting OLED blue emitter. The researchers used a green phosphorescent emitter with a new double metal structure - that emits a blue light. The so-called Plasmon-Coupled Organic Light Emitting Diode (PCOLED) structure's lasts 27 times as long as a blue fluorescent emitter.

The researchers explain that a regular green phosphorescent emitter always emits a very weak emission. By using the double-metal structure, more plasmons are generated which means a larger blue emission. This is not an up-conversion process - but merely a change in conditions within the green material. This condition was actually discovered by accident.

Researchers from Oxford University developed a new technology based on phase-change materials (similar to ones used in re-writable DVDs) that can be used to create non-volatile highly-efficient displays - similar to E Ink displays. The University established a new company called Bodle Technologies to commercialize this new technology.

The phase-change materials can manipulate light and can be used to filter, steer or dim light using very little power. Bodle already demonstrated a sub-100 nm pixel size and a very rich color gamut - they say it exceeds "other display technologies", although it's not clear what they mean by that...

Taiwan's National Tsing-Hua University has been pursuing blue-light free OLED panels for a long time, developing orange-colored (1,914K) OLED panels which they claim is much healthier than regular OLEDs or LED devices.

In November 2014, we reported that Taiwan's PMOLED maker WiseChip Semiconductors licensed technology Tsing-Hua's technology, with an aim to produce such panels by early 2015. This did not happen, but today we hear that the Taiwanese government decided to fund WiseChip development - awarding the company with 10 million NTD (about $300,000 USD) each year for two years - and the Wisechip will be able to start mass producing those 1900K OLEDs.

The US PTO published a new patent application from Apple that describes an OLED display with a built-in fingerprint reader. The idea is that integrating Near Infrared (NIR) emitters and detectors between the OLED subpixels will enable a much thinner design compared to separate display and detector layers. This also means that there is no need to have a separate reader in the home button as in current iPhones.

The Fraunhofer Institute has demonstrated bi-directional OLED microdisplays back in 2012 that are based on a similar idea - embedding photo detectors (in the visible light range, in that case) within the OLED sub pixels. The latest prototype unveiled in 2015 supports SVGA resolution and a hi-res image sensor. The bi-directional displays are available for sampling.

Idemitsu Kosan and Doosan Corporation announced a new OLED business arrangement and cross-patent agreement. The two companies will cooperate in OLED manufacturing and each company will be allowed to develop, manufacture and sell OLED materials using the other company's patents.

Idemitsu and Doosan hope that the new agreement (which will hopefully be concluded by the end of 2015) will enable the acceleration of OLED material development, lower production costs and an increase in OLED supply deals.

Update: It turns out that these are actually LEDs and not OLEDs in this video - and PolyPhotonix indeed developed both LED and OLED prototypes.

UK-based PolyPhotonix, in collaboration with the Centre for Process Innovation (CPI), developed a wearable electronic blanket that uses printed OLED lighting to administer a phototherapy for the possible treatment of a number of skin conditions such as acne, psoriasis, eczema and jaundice. The blanket could also be used for wound healing and anti inflammatory treatments.

The blanket uses small flexible OLED devices. The treatment schedule and dosage of the light are programmable - so the treatment can be optimized and also be used for different conditions. The prototype blanket that was demonstrated also includes sensors and can log and record the usage.

Researchers at the University of Michigan developed a new deep-blue energy-efficient phosphorescent OLED (PHOLED) emitter. The researchers say that this is the brightest deep-blue PHOLED ever reported - in fact it is about 10 times brighter than previous deep-blue PHOLEDs. The lifetime of this material is still very low, and future research will attempt to stabilize the molecule.

The new emitter is based on a N-heterocyclic carbene iridium-III complex molecule. This is an efficient compound because its design reduces the chances that light-emitting excitons will either get lost as heat or destroy the compound itself. This research is sponsored by Universal Display Corporation and the U.S. Air Force.

Researchers from Arizona State University (ASU) are developing high-qualify OLED lighting devices that emit no UV light. Such OLEDs will be particularly useful in museums, art galleries and similar places, since UV light inhibits the human eye in clearly discerning color variations and the texture of objects.

The researchers recently received a $875,000 grant from the US DoE to expand the research. The team is collaborating with Universal Display to develop OLEDs that use a single emissive material to create white light - and not a white OLED device that uses a combination of red, green and blue emissive materials (or yellow and blue).