Technical / Research - Page 111

The new material called E255a has a high colour saturation making it ideal for a broad range of product applications in single colour and full colour displays. The material also has a very high efficiency delivering high brightness at low power making it ideal for mobile product applications with either passive matrix or active matrix driving.

The University of Hong Kong has manufactured OLED demonstrators using E255a and has reported a device efficiency of 40 cd/A at 1000 cdm-2 with a very saturated green colour coordinate of (0.28, 0.64) which is wider than commercially available LCD products.

E225a will be available for customer sampling from January 2008 and can be deposited onto any desired substrate by vacuum coating methods.

Oak Ridge National Laboratory (ORNL) claims it can make OLEDs 30 percent more efficient by doping them with magnetic nanoparticles. As a bonus, the introduction of magnetism into the OLED material enables brightness to be controlled without the addition of electrical contacts.

"What we did was to enhance the lighting efficiency of an OLED by doping the organic polymers with a very low concentration of magnetic nanoparticles," said ORNL senior researcher Jian Shen. "Doping also allows us to control the OLED-s intensity with a magnetic field, whereas conventional OLED intensity is tuned by an electric field, which needs [electrical] contacts."

The achievement of a green PIN PHOLED(TM) phosphorescent OLED device in bottom-emission geometry with a CIE of (0.36, 0.61) of above 200,000 hours were attained by combining Universal Display's high-efficiency phosphorescent OLED materials with low-voltage Novaled PIN-OLED(TM) technology and doped transport materials.

"We expect that very low driving voltages below 2.6 V which we already achieved for Ir(ppy)3 can also be obtained for other phosphorescent green emitters" adds Jan Birnstock, VP Technology Transfer.

The cooperative agreement between ARL and Plextronics establishes the Flexible Electronics Research Initiative (FERI). FERI will focus on the advancement of material and device technology for flexible electronics, which offers benefits particularly relevant to military applications. The resiliency of these devices, for example, could increase the lifetime and reliability of current display applications in harsh environments.

Some of the technologies and products that this research could lead to also include:

• Real-time maps and displays that continually receive electronic data and information, yet are durable and flexible enough to be rolled up and stored in soldiers' backpacks.
• Displays that are directly contoured onto a soldier's uniform, offering the ability to turn a shirt or jacket cuff into an information displaying device.

CMEL showcased a 4.3" AMOLED display. Sample shipments are slated for September 2007, and volume production and shipments are expected to start around December 2007. A life extends to "20,000 hours when lit at 50% luminance and 10,000 hours at 100%," a booth attendant said.

The materials and glass cover are made by DuPont.

Read more here (TechOn Asia)

Guo, an associate professor of Electrical Engineering & Computer Science at the University of Michigan, has come up with semitransparent metal electrodes, fabricated by nanoimprint lithography (NIL), that, with further optimization, could replace today's use of conventional ITO electrodes in OLEDs. The core findings of this research is that a nanowire metal grid can provide sufficient optical transparency and electrical conductivity for it to be used as a transparent electrode for organic optoelectronic applications. These metal electrodes contain no expensive metallic elements and do not suffer from atomic diffusion but are nevertheless very efficient.

Guo and his team based their new electrodes on a densely perforated thin film of metal supported on a glass layer. The perforations make the metal layer almost transparent, which means it can be the top electrode in an OLED. Moreover, they can fine-tune the fabrication process to make the perforations smaller or larger and to change their spacing. This allows them to adjust the transparency at different wavelengths of light allowing different colors to predominate. Most importantly though, NIL can be used to make an electrode with an enormous area, far bigger than a cellphone display, and so open up OLED technology to a much wider range of applications, including windows and giant screen TVs.

Read more here (Nanowerk)

Vitex Systems today announced its proprietary moisture and oxygen barrier solution demonstrated impressive reliability results when used for high-temperature applications. The company's revolutionary Barix(TM) thin-film barrier was continuously tested at 100 degrees C, 120 degrees C and as high as 140 degrees C for more than 500 hours without losing its barrier integrity. Moreover, results indicated that the barrier can maintain its integrity for more than 1,000 hours in this severe environment.

Vitex's Barix thin-film barrier uses an organic and inorganic multi-layer structure. To demonstrate product compatibility, it was used to create the world's first high-resolution AMOLED, which leverages an amorphous silicon backplane on a flexible metal foil. This flexible display -- jointly developed by Universal Display Corp. and LG. Philips LCD -- was showcased at last month's Society for Information Display (SID) conference in Long Beach, Calif. Similar encapsulation was shown by Samsung SDI on the world's first, and thinnest, full-color top emission AMOLED on a metal foil during last year's show.

Researchers at Purdue University and Northwest University have developed a flexible and transparent transistor using a combination of zinc-oxide and indium-oxide nanowires. These invisible and bendable transistors actually preform better than conventional transistors, and can be easily built onto sheets of flexible plastic.

Their work also revealed a promising new development in the control of OLED's. They found that when conformist nontransparent transistor circuitry is placed around the OLED, it could be inadvertently be emitting its own light. But these transparent transistors can actually be placed beneath the crest of the OLED. This would help to obscure the already invisible transistor, but making its light source a part of the OLED's light source. The transistor would control the OLED  as well. There is also the added benefit of less space used, bringing the hope of a higher resolution display with a small dot pitch.

The new set of materials rely on DuPont hole-injection layer (HIL) material and include those essential in the construction of an OLED display, such as light-emitting and charge-transport materials.

DuPont Displays said it has also exceeded the reported performance of other solution-based OLED materials and has measured accelerated lifetimes of the three primary colors that could translate in a display to 20,000 hours of white lifetime (which is extended by as much as five times when showing video) at a normal viewing brightness (200 cd/m2). At 1000 cd/m2 -- the standard test luminance used in the industry -- the DuPont materials have lifetimes (T50) of 14,000 hours for blue with CIE 1931 color coordinates of (0.14, 0.16), 230,000 hours for green with color coordinates of (0.29, 0.65), and 46,000 hours for red with color coordinates of (0.66, 0.34).