09 Jun 2006
As competition intensifies in the small-to-medium display market, OLED manufacturers are working to introduce lower cost fabrication techniques.
While displays based on organic light-emitting diodes (OLEDs) continue to dominate technical discussions at this year's Society of Information Display (SID) conference, analysts at iSuppli warn that OLED manufacturers must reduce prices to compete in the small to medium display market.
"Currently the battle is in active matrix devices," Paul Semenza, vice-president for display and consumer research at the US-based analyst firm, told optics.org. "Active matrix OLEDs carry a significant [a factor of two] premium over comparable TFT-LCDs."
Semenza concedes that OLED makers have made real progress in increasing production volumes, with unit shipments forecast to increase from 88 m in 2006 to 364 m in 2012. Revenues over the same time frame are predicted to increase from about $0.7 bn to $3.5 bn.
However, almost all OLED devices produced today are based on small-molecule technology and a passive-matrix design, which limits their use to simple displays in car dashboards and portable devices. The focus for OLED manufacturers now is to produce more sophisticated active-matrix devices, and to introduce polymer-based technology and new fabrication techniques to lower manufacturing costs.
For example, Cambridge Display Technology of the UK and Toppan Printing of Japan announced at the SID conference that they have exploited a novel roll-printing technique developed by Toppan to produce full-color active-matrix displays based on polymer OLEDs. Inkjet printing is currently the favored approach for OLED manufacture, but the two companies believe that roll printing offers a cheaper alternative that still achieves good uniformity and resolution.
Toppan's technique is based on relief printing, an established method for transferring soluble materials onto a range of substrates. But the Japanese firm has improved the precision of the technology to enable small-area pixels to be patterned with highly uniform distribution. The demonstrator displays measure 5.5 inches, but CDT and Toppan claim that the process could be scaled to larger substrate sizes and a resolution of 200 pixels per inch (ppi). In future, the process could also be suitable for producing flexible OLED displays.
DuPont has also developed a printing process for small-molecule OLED materials that it claims is cheaper and more scalable to large display sizes than techniques such as vapor deposition. Using this technique, DuPont has achieved lifetimes exceeding 10 000 hours for the three primary colors at the brightnesses required for a 200 nit display.
Craig Naylor, group vice president for electronic and communication technologies at DuPont, says that these early results demonstrate that OLEDs can be manufactured at high yields and low cost. "Our model shows that the total cost of OLEDs can be 30% less than LCDs. With this development, we expect OLEDs to become the next-generation flat-panel technology."
• A joint research effort between Philips Lighting, Philips Research and Novaled has produced a white OLED with an efficacy of 32 lm/W at a brightness of 1000 cd/m2. The lifetime of the device was more than 20 000 hours, and had a colour-rendering index of 88. The companies claim that the device sets a record combination for lifetime and efficiency for a high-brightness white LED, and the researchers are now targeting 50 lm/W as the next benchmark.