Technical / Research - Page 101

Novaled is showing their Defect Tolerant white OLEDs. Those displays maintain the appearance of a
homogeneously lighted-up surface even in the case of electrical shorts,
thanks to the use of its proprietary electrode design. One OLED element
consists of two comb-shaped interlocked electrodes, which give a uniform
light emission. If a short in one of the stripes appears, the resistance
of the stripe will limit the current flow and prevent a further rise of
current and temperature, which would otherwise destroy the OLED.

Novaled Ultra Stable OLED prototype

UDC reported data for a series of white PHOLEDs that span a range of white colors that were designed to satisfy the requirements of differing lighting applications. These research results range from warm to cool white with varied power efficacies of 54 to 102 lumens per watt (lm/W). Depending on the specific designs employed, the color rendering indices (CRI’s) varied from 70 to 88, and lifetimes varied from 4,000 to 17,000 hours (to 70% of initial luminance at 1,000 nits*).

UDC white light OLED prototype

White OLED performance characteristics can be tuned by manipulating the OLED materials and structures that are used. To show this effect, a series of white OLEDs, from approximately 2,700 to 4,000 Kelvin, were developed that exceed the Energy Star Category A Color Specification of color rendering index (CRI) of > 75 and the Efficiency Specification of > 35 lm/W. The Energy Star lifetime specification is ? 25,000 hours (to 70% of initial luminance at 1000 nits*), however, the lifetime results for this series may be sufficient for a variety of niche products while the Company continues to develop white OLEDs that meet the requirements for more demanding applications.

UDC says that they are moving closer to meeting the U.S. Department of Energy’s solid-state lighting targets and the requirements of Energy Star, a joint specification between DOE and U.S. Environmental Protection Agency.

Agfa, Philips and the Holst Center are showing a large-area (12x12cm2) flexible OLED - without ITO as transparent electrode, and with printed shunting lines. This means that costly materials and lithography processes are not needed, and the OLEDs are much cheaper.

Flexible OLED lighting prototype with no ITO

Up till now, ITO was needed as supporting layer for the PEDOT/PSS* anode layer with lower conductivity. Thanks to Agfa’s high-conductive transparent polymer OrgaconTM, a PEDOT/PSS-based solution with six orders better conductivity than its predecessor, the use of ITO can now be avoided. Proof is the latest OLED lighting demonstrator of Holst Centre’s shared programs: a homogeneous white OLED tile of 12x12cm2 without the use of ITO.

A research group from the Kanazawa
Institute of Technology in Japan succeeded in making an green phospor-based OLED achieving a very high
light-emitting efficiency of 210lm/W (56.9% more efficient than existing OLEDs).

The OLED is a bottom-emission type on a 0.7mm-thick glass plate. 

The material for the device's light-emitting layer is a host material called "CBP" added with an iridium complex, "Ir(ppy)₃." Its light emission peak lies in the range of wavelengths between 500 and 550nm, which corresponds to green color.

When emitting light at a luminance of 10cd/m², it has a
light-emitting efficiency of 210lm/W and a light-extraction efficiency
of 56.9%. On the other hand, when emitting light without the
high-refractive glass plate, its light-emitting efficiency is only
94.3lm/W. This means the glass plate boosted the light-extraction
efficiency by 2.3 times.

Novaled and Holst Centre have decided to collaborate under a joint development agreement. They will work on using the Holst centre's Organic TFT tech and Novaled's OLED dopants:

Novaled's doping technology contributes to very high power efficiencies and long lifetimes in OLEDs by improving charge carrier injection and transport in the organic layers. Novaled has shown that these effects are also relevant for organic TFT as the carrier injection from drain and source into the organic material has a major influence on the device performance. Novaled currently develops dopant and host materials which can be processed both in vacuum and in solution.

Scientists at the Pacific
Northwest National Laboratory scientist have designed, synthesized and tested new blue OLED materials. They claim that these new materials have an improved efficiency - by at least 25 percent.

Blue OLED prototype

The new materials are phosphorescent OLEDs.

Dongbu said they developed a driver for AMOLED displays, supporting resolutions up to 1024x768. They will start shipping the drivers in a few months.

Dongbu also said that they are in advanced talks with Panasonic and NEC to supply the chips.

Britain has officially opened their printable electronics technology centre (or PETEC). The center offers space and resources for companies to build mini production lines, and a place to develop and prototype applications.

Petec has 20 employees, and there are plans to grow to 40 by 2011.

The nice chaps at the OLED100.eu project sent me this nice EuroNews video, explaining OLED lighting and the OLED100.eu project. It includes some nice ideas on flexible or transparent OLED lighting.

I really liked the OLED chess set featured in this film. Also the futuristic OLED kitchen has some nice ideas.

Panasonic is working on OLED lighting panels, using printing methods. They prototypes a high efficiency panel at Printable Electronics 2009.

The OLED lighting panel features a luminance efficiency of 40lm/W and a CRI (color rendering index) value of 95. The external quantum efficiency is 36.1%, and the half-life of the luminance exceeds 20,000 hours when the initial luminance is 1,000cd/m^2.

Read more at TechOn