Display Week 2009 Review: OLEDs

OLEDs seem poised to wrest some market share from dominant display technologies.

by Paul Drzaic

AT LEAST FOR ME, the last couple of SID meetings have reinforced the notion that the major display manufacturers are taking organic light-emitting diode (OLED) displays quite seriously and bravely taking the plunge to compete against liquid-crystal displays (LCDs). Obviously, OLED-display manufacturers are not students of history or they would have given up long ago. LCD technology has clearly been hard to beat. Through history, it has conquered almost every rival, regardless of investment and entrenchment – one has only to look at cathode-ray tubes and field-emission displays as examples of technologies that have been beaten down by LCDs. Nevertheless, this SID symposium showed that not only are OLEDs appearing in unconventional guises, but they are also taking on LCDs directly in applications such as televisions and monitors.

So what was different this time around? Well, for one, there was simply "more" – more sizes, more applications, and more areas of innovation. OLED displays are still being viewed as a premium alternative to LCDs, but the quality of the displays, and some novel form factors, showed why these displays are attractive to early adopters of new technologies.

The most extensive set of OLED-based products was shown by Samsung Mobile Display. SMD exhibited OLED displays in a number of form factors and application areas. An impressive 31-in. 1920 x 1080 HDTV display capable of rendering the broad color gamut that is so attractive in OLED units was the first display most people saw when approaching the Samsung booth, and many lingered for a long, long look. Inside the Samsung pavilion, many more surprises awaited. OLED displays with over 300-ppi resolution for mobile devices, 3-D OLED displays, and super-thin OLED displays only 50 μm thick were all being shown. One example that showed the unique potential of OLEDs was the incorporation of a color video display into a smart-card format. The display drew its power wirelessly from a nearby radio-frequency antenna (Fig. 1).

eMagin took OLED displays in a different direction, with its latest head-mounted units. The images were shown at SXGA resolution (1280 x 1024 triad pixel array), with each individual pixel only 12 μm on a side. When Itested the display myself, I found that the colors were saturated, the image quality was high, and the videos rendered seamlessly. eMagin is aiming these displays at applications in commercial, consumer, and military markets.

Fig. 1: Samsung Mobile Display showed this smart card with an integrated color OLED display, driven by a wireless power source.

Other impressive demonstrations appeared in various places around the exhibit floor. LG Display showed ruggedized 15- and 3-in. AMOLED panels in its booth. TMD showed its line of long-life OLED displays, with a 4.15-in. display rated for 60,000 hours (almost 7 years!) at 200 cd/m². Following an alternative path, Ignis Innovation, an intellectual property creator and technology development company out of Quebec, demonstrated a number of OLED units driven using amorphous-silicon backplanes, the same backplane technology that has been perfected by the LCD industry. Ignis has taken the practical approach of using clever sensing and compensation circuitry to overcome the image artifacts that appear over time when a-Si backplanes are used to drive OLED displays. Ignis claims that with the compensation running, any image artifacts that arise are erased by modifying the local drive voltage, overcoming the major hurdle that has prevented a-Si backplanes from being used in OLEDs

Innovation continued in the form of a number of materials and fabrication methods necessary to build long-lived attractive OLED displays. Corning was honored with a Display Component of the Year Award for its Jade glass, specially designed to provide stability, uniformity, and high yields for the fabrication of LTPS backplanes. Add-Vision demonstrated its screen-printable OLED technology, showing a credit card with an emissive logo powered by a radio-frequency powersource. Universal Display Corp. demonstrated its latest white-OLED emitters, built using thecompany's phosphorescent molecular technology. It also showed a wearable, curved OLED display, built in collaboration with LG Display and L3 Corp. (a photograph appears in the Flexible Display review in this issue.)

Kodak showed white-light panels built using both internal and external light extraction technology, more than doubling the light output from a standard OLED stack not using these designs. Novaled continues to lead in the development of its PIN-type OLED displays, claiming an encapsulation regime that enables lifetimes up to 110,000 hours and efficiencies up to 50 lm/W. It's important to note that general lighting applications are also driving OLED development, and SID will be supporting the connection between OLED lighting and displays in future meetings.

So why OLEDs? For many people, greater contrast, wider color gamut, and superior response time provide a more satisfying viewing experience than that of LCDs. For applications and designs for which a super-thin format is required, an LCD might be hard-pressed to match a 50-μm display stack, or provide full-motion video in a highly flexible format, or beat OLEDs in power consumption when showing many types of images. In all cases, the lifetimes and quality of OLED displays – definite drawbacks in the past – have reached a level that is acceptable to consumers. Will LCDs disappear? Unlikely! Will OLED displays start encroaching into LCD territory or enabling new display applications? That seems like a safe bet. •