Jack Kenny, Editor06.03.09
A typical OLED consists of organic thin films placed between thin-film conductive electrodes. The application of electricity causes the emission of light and/or heat (simply stated). According to Universal Display Corporation (UDC), a major developer of OLED products, conventional fluorescent emission results in only about 25 percent of the excitonic energy producing light. The remaining 75 percent is lost as heat.
UDC is actively working on improving the production of light in OLEDs, and has been working for years with several university partners on the development of PHOLEDs: phosphorescent light emitting diodes. Through the use of certain phosphorescent materials, UDC’s partners at Princeton University and the University of Southern California discovered in the late 1990s that up to 100 percent of the excitonic energy could be converted into light. Therefore, a PHOLED has up to four times higher efficiency than that of a conventional fluorescent OLED.
This week, UDC and the Flexible Display Center (FDC) at Arizona State University introduced the first a-Si:H active matrix flexible OLED display to be manufactured directly on DuPont Teijin’s polyethylene naphthalate (PEN) substrate. The 4.1” monochrome quarter video graphics array (QVGA) display implements UDC’s PHOLED technology and materials, and the FDC’s proprietary bond-debond manufacturing technology. The introduction is viewed by its creators as a milestone toward achieving a manufacturing solution for flexible OLEDs.
Universal Display and the FDC will present a paper discussing the active matrix flexible OLED on June 5 at SID 2009 in San Antonio, as well as demonstrate the device and other flexible display technologies. The SID International Symposium, Seminar and Exhibition, now in its 47th year, is a major international gathering of scientists, engineers, manufacturers, and users in the electronic display industry.
“Being a founding member of the Flexible Display Center, Universal Display is pleased to see the significant progress enabled by our cooperation,” says Mike Hack, vice president of strategic product development at UDC. “Together we have demonstrated technology paths which will accelerate the introduction of exciting new flexible OLED displays on plastic substrates.”
Flexible OLEDs today are targeted at military and commercial applications that require more rugged displays. UDC’s PHOLED technology and materials, Hack says, can achieve the same brightness as traditional displays with extremely low power consumption. Additional advantages include lower operating temperature due to less heat being generated, easier to drive, longer battery life, and more stable transistors.
“This development of flexible AMOLED technology gives the industry a solid starting point towards manufacturing, mass production and commercialization of flexible OLEDs,” says Shawn O’Rourke, director of engineering for the FDC. (AMOLED is active-matrix OLED.) “The fact that we have achieved a functional flexible OLED manufactured directly on plastic using the center’s manufacturing process represents a significant achievement, and continued developments over the next few years will lead to full color, full motion video flexible displays.”
The flexible backplane display was manufactured at the Flexible Display Center utilizing a 180° C thin film transistor process. The FDC’s plant uses traditional flat panel and semiconductor tools and processes to achieve flexible displays, enabled by its bond-debond technology to secure the plastic substrate to a rigid carrier during manufacture. In the creation of the new phosphorescent OLED, UDC’s PHOLED frontplane was married to the backplane designed and manufactured by the FDC.
One of the challenges that PHOLED development encountered in years past is that blue PHOLEDs did not last anywhere near as long as those that are red and green in color. In 2005 UDC announced a breakthrough – what it described as “a fundamental technical achievement” – in the development of its blue PHOLED technology: a sky blue PHOLED with more than 15,000 hours of operating lifetime. It was the first blue PHOLED to break, by an order of magnitude, the 1,000 hour lifetime barrier – a challenge that some thought might be insurmountable. Over the past few years, Universal Display has announced a series of performance milestones for its red, green and blue PHOLED systems, as well as its white PHOLED technology for lighting applications. The company’s technology can be found in a variety of cell phone, multi-media players and other display devices already on the market, and the technology has been useful in the development of OLED lighting and display applications for the US government.
“In the past year, we have made tremendous progress in the performance of our PHOLED materials and technologies for display and lighting applications,” says Steven Abramson, Universal Display’s president and CEO. “As manufacturers increase OLED production, they are increasingly looking at PHOLED technology as a critical element to making energy efficient, environmentally friendly and cost-effective OLED products.”
Last month, UDC announced the signing of an agreement extending its sponsored research program with the University of Southern California and the University of Michigan. Universal Display will provide up to approximately $7.5 million for the next four years to support research in the growing field of organic electronics under the direction of Professors Stephen R. Forrest and Mark E. Thompson at their respective institutions. The company has funded more than $8.8 million in sponsored research at these institutions, as well as at Princeton University since 1994. Patents derived from the research program will continue to be licensed exclusively to Universal Display. Princeton University will continue to manage the patent portfolio on behalf of all three universities.
“Stephen Forrest and Mark Thompson not only pioneered today’s commercial phosphorescent OLED technology, they are at the forefront of tomorrow’s PHOLED technology, including flexible, transparent and white PHOLED technology for lighting,” says Abramson. “Our commercialization of PHOLED technology based on their academic research will continue to be crucial in driving innovation for the growing organic electronics industry.”
Universal Display Corporation (NASDAQ: PANL) is headquartered in Ewing, NJ, USA. It has established numerous commercial relationships with companies such as Chi Mei EL, DuPont Displays, Konica Minolta Technology Center, LG Display, Samsung, Seiko Epson, Sony, Tohoku Pioneer, and Toyota Industries. The company currently owns or has exclusive, co-exclusive or sole license rights with respect to more than 940 issued and pending patents worldwide.