Amazing OLEDs

 - April 17, 2008, 11:17 AM

“This is the future,” announced Rogelio Sobers, a tall, soft-spoken Eastman Kodak salesman, as he stooped over a simple-looking color video display tucked in a corner of the Kodak exhibit at a recent technology trade show. “Maybe,” he added a moment later, a wry smile curling his lips.

Sobers, who works at Eastman Kodak’s display products division in Walnut Creek, Calif., east of San Francisco, made his uncertain proclamation while waving a hand over and behind the miniature display, the way a magician might reveal a chosen card to his delighted audience. But this was no magic act. Sobers was showing off a revolutionary new display technology pioneered by Eastman Kodak that uses organic light-emitting diodes (OLED) to create brighter, sharper and thinner flat-panel video displays than previously thought possible.

The Kodak screen–a prototype Nintendo GameBoy terminal with an enticingly vivid picture–measured no more than three inches wide by two inches high and, intriguingly, was about the thickness of a credit card. On it, bright, brilliant full-color video images danced and swayed in time to high-energy music. One could imagine the display right at home in the next generation of personal digital assistants, cellphones, handheld GPS receivers or, as shown here, video-gaming devices. Light-emitting polymer OLEDs hold such high promise, in fact, they are shaking the very foundations of the flat-panel LCD industry–to the point that many display industry executives are predicting the emerging technology will topple LCDs in the next decade and assume the throne as the new reigning king of the consumer display market.


The success of OLEDs will depend chiefly on whether display makers are successful in solving the technological shortcomings of the thin-film screens, namely the fact that prototypes built to date have had extremely short useful lives and are difficult to produce. But with more than 50 display companies around the world spending serious money on OLED research and development, experts are predicting engineers will soon solve the puzzles that have so far kept color active-matrix OLED displays from entering the consumer marketplace.

Once they do, experts predict buyers of consumer electronics will start tossing away their LCD-based portable electronics in favor of OLEDs, a technology that is unquestionably superior to LCDs in some fundamental ways. Eventually, OLEDs could be used for everything from handheld electronics to computers screens and even ultra-thin TVs. The possibilities are helping to stimulate interest and fuel a palpable excitement.

So what exactly are OLEDs? The simple answer is that they are electronic display devices produced by placing organic thin films (as opposed to silicone) between a pair of conductors. When electrical current is applied to the conductors, a bright light is emitted. By placing diodes on the film patterned in clusters of red, blue and green, OLEDs can create full-color images that are far more vivid than the view provided by LCDs, which are backlit and voltage-driven.

Unlike displays in which light reflects off of or passes through liquid crystals, OLED devices use organic elements that actually emit light. The result is a brighter display with higher resolution, improved contrast, and wider viewing angles.

In fact, viewing angles with OLEDs really aren’t an issue because the diodes lie on top of the film and emit their light, as opposed to being lit from behind. OLEDs are also lightweight, durable and power-efficient. Several companies are even attempting to produce flexible, full-color OLED displays that can be bent and twisted without affecting picture quality.

OLEDs have been called the first example of molecular electronics, a reference to the displays’ organic molecule structure. Not since Kodak developed the technique in the early 1990s has so small and bright a light source been applied successfully in the design of displays. The first OLEDs were monochrome and had useful lives that could be measured in microseconds. A decade later, the technology is poised to make its market debut, possibly in full-color GameBoy consoles, digital cameras and cellphones as early as this Christmas.

The major advantages of OLEDs over LCDs are greater brightness, faster response time for sharper full-motion video, fuller viewing angles, lighter weight, greater durability and better power efficiency. OLED displays are also self-luminous, or “emissive,” and therefore do not require backlighting or the layers of polarizing filters, diffusers, glass plates and transparent electronics that add to the weight and thickness of LCDs. And research has shown that the human eye prefers emissive type displays to LCDs.

Impressive Newcomer
There seems to be little debate that OLED-based displays are potentially superior to LCDs. Whether it’s contrast, brightness, resolution, power consumption, response times or color quality, OLEDs win the battle, or at least match the venerable LCD. Where LCDs outshine OLEDs, however, is in their long lifetimes, currently in the realm of about 20,000 hr or more of continuous use before failure. OLEDs, on the other hand, currently last only about 1,000 hr at most.

Almost from the time they are switched on, OLED screens begin losing pixels as the individual diodes on the film start to fail. At the trade show, held in Boston in late May and hosted by the Society for Information Display (SID), Toshiba unveiled a 17-in. flat-panel OLED display, the largest full-color organic screen ever shown in public. The image on the display was good, but a closer look revealed the flaws of this industry newcomer.

Tiny black dots blanketed the display. These were pixels that had failed during use. Blue pixels fail first, so that over time the display begins to lose overall sharpness of blue color. When asked how long the monitor on the show floor would last before it completely failed, a Toshiba spokesman responded seriously, “We’re hoping to make it through the week.”

Indeed, all of the full-color OLED displays shown at SID 2002 had bad pixels, although Kodak’s display seemed to be suffering the least from the effects of age. Sony’s 13-in. full-color, 800- by 600-pixel resolution OLED intrigued showgoers with its brightness, vivid colors and super-wide viewing angle–yet perhaps 5 percent of the organic diodes making up the display image had already failed early in the show, leaving behind scores of tiny black dots on the screen.

When asked about the life of the display, a Sony spokesman answered that the company does not disclose any technical details of the screen. He gave this answer in reply to questions posed by dozens of passersby, who seemed completely mesmerized by the paper-thin display. “It’s like magic,” said one attendee. “It is magic,” added another. A third chimed in, “I’m definitely holding onto my Sony stock.” His colleague replied, “I’m going to log in tonight from the hotel and buy some more.”

Probably not a bad idea, assuming Sony’s progress to date serves as a prescient indication of the company’s future success in the OLED arena. Of all the displays on exhibit at SID 2002, Sony’s was by far the most impressive. Its light output is said to be greater than 300 candelas per square meter. Pixel pitch is 0.35- by 0.33 mm, and the 264- by 198-mm panel itself is a thin 1.4 mm. Except for the failed diodes, the display could have gone on the market tomorrow and easily outsold any similar-size active-matrix LCD–the image quality was that good. Obviously, however, Sony must come up with a way to increase the life of the diodes.

Toshiba’s display was the largest, but image quality suffered in the tradeoff between large size and image sharpness. Kodak’s small OLED display had the fewest failed pixels of any display at the show, and the company is said to be close to bringing a product to market. Kodak and Sanyo recently formed a joint venture, SK Display Corp., to manufacture consumer OLED displays starting next year.

Adding credence to speculation that OLEDs are about to go mainstream was the announcement at the show that Kodak is now offering an “evaluation kit” for companies seeking to do their own appraisals of the active-matrix OLED display. The Kodak kit, designated the AM550L, gives manufacturers their first opportunity to design new-generation devices that take advantage of OLEDs’ bright, crisp image quality, wide viewing angle, thin profile and low power consumption. The $5,200 kit includes an AM500L panel, an interface board, software drivers, cables and instructions for use.

OLEDs in the Cockpit?
Avionics makers have been keeping close tabs on the progress of OLEDs over the past few years. With news of recent advances, some are now predicting the super-thin-polymer displays could one day replace LCDs in the cockpit and cabin, just as LCDs replaced the CRT. Engineers at Rockwell Collins dream of curved, panoramic instrument panels spanning the entire cockpit, and perhaps the evolution of super-thin handheld displays for viewing electronic approach plates, checklists, weight-and-balance figures and other flight-related information.

Marty Steffensmeier, engineering manager for advanced displays and graphics technologies at Rockwell Collins, said in an interview earlier this year that the company is bullish about the long-term prospects for thin monolithic displays, and is particularly interested in OLEDs.

“This looks to be a real technology, not just something that is always on the drawing board but never makes it to the cockpit,” said Steffensmeier of OLEDs. “They’re the next big thing in displays.”

In cooperation with several defense industry partners, Collins later this summer will demonstrate a handheld GPS receiver for the Defense Department that uses a curved, green monochrome OLED display.

Most observers agree that OLEDs will make their mark initially in portable devices, but a number of industry experts interviewed for this article said LCDs may soon be relegated to dinosaur status if OLEDs begin to make market inroads. Once this happens, look for larger OLED devices, including ultra-thin cabin video displays, to begin popping up at aviation trade shows.

Of course, as is the case with most emerging technologies, makers of OLEDs have some high hurdles to clear before large OLED displays can be declared market ready. For one thing, no one is quite sure how best to mass-produce OLEDs.

Color OLED screens consist of hundreds or thousands of tiny diodes laid in precise patterns. Because OLEDs can be made using a roll-to-roll process not unlike a printing press, serious thought is being given to using special laser printers to apply the diodes. Japan’s Seiko-Epson is using ink-jet technology for OLED fabrication in the hopes of making small low-cost displays in the near term, and economical large displays in the future.

A Watershed Year
Considering all the excitement now being generated in OLED camps, it came as no small surprise that a major topic of conversation during SID 2002 was whether OLEDs have a chance to give LCDs a serious run for their money. A spirited panel discussion on this topic sparked rancorous debate among research executives as they sparred over technical issues such as lifetime differential aging, color purity, temperature sensitivity, manufacturing and price. All agreed, however, that this year will be a telling one for OLEDs.

“OLED manufactur-ability still needs improvements, but power efficiency is expected to be greatly improved and material costs are expected to be reduced with volume production,” said panel moderator Paul Drzaic, vice president of display technology at Alien Technology of Morgan Hill, Calif. He pointed to tremendous improvements in reliability in the last three or four years as a positive sign that OLEDs are more than just “a Chihuahua nipping at the heels of the LCD Doberman.”

“Do OLEDs have a chance [against LCDs]? The answer is, absolutely.” So said Michael Hack, vice president of strategic market development at Universal Display Corp. of Mine Hill, N.J., who recalled the LCD’s replacement of CRTs in the last decade, and targeted that shift as a main reason OLEDs will be successful in supplanting LCDs in five to 10 years.

“OLEDs are emissive, meaning we put power only to the pixels we want to illuminate,” he said. “It’s a well known fact that the human eye prefers emissive-type displays. Also, OLEDs can be transparent and flexible, and they are lighter and more durable. The technology has tremendous promise and is making tremendous progress. There are a lot of smart and hungry people in the display industry who are betting their careers on OLEDs, and that’s not by accident.”

Hack went on to quip that the active-matrix LCD will soon be relegated to a “historical footnote,” with a good but short market run, a comment that raised the hackles of skeptical panelists. Fang-Chen Luo, vice president of Taiwan-based AU Optronics Corp., cautioned that the flat-panel display industry ought not place too much faith in an as yet unproven technology. Luo reminded his colleagues and the roomful of several hundred audience members that previous promising technologies, such as field emission displays (FED) and plasma devices, had gone after LCDs’ turf but failed to prove themselves worthy challengers. He argued that such stalled research sapped needed resources from LCD development.

“There are 50 companies working on OLEDs. So what? Anyone can make a prototype,” he said. “So is it really serious? Is it just an exaggerated R&D project, or is it for real? The fact is there’s not a single [flat-panel display] company that has not announced an OLED-related initiative. But just because a company is looking into something doesn’t mean much will necessarily come of it. It could just be that the company’s CEO is getting excited by the hype because he’s read some articles in magazines.”

Detractors point to a laundry list of issues and problems with OLEDs that they say threaten to derail the technology before it enters the market. “How do you fabricate OLEDs?” asked panel member and IBM researcher Kai Schleupen. “It scares me to death to think about fabricating a 17-inch or 20-inch OLED panel. In my mind manufacturability is still the biggest question.”

Other discussions followed more esoteric lines, with panelists arguing about potential market niches, where OLEDs might gain much needed footholds to be nurtured.

“OLEDs cannot compete with AMLCDs in the notebook and desktop market,” declared Schleupen. “There is no niche where OLEDs can grow.” To this, Universal’s Hack waved a cellphone with an LCD and crooned, “Here’s your niche!” This sparked back-and-forth sparring over whether the cellphone market is large enough to sustain OLEDs, and whether there is the “urgency” in the portable consumer electronics market to replace LCDs.

The argument was rendered more or less moot by an audience member, who stood up and said, “The market will decide whether OLEDs are successful or not. And I can tell you that when my kid gets hold of that GameBoy with the OLED display from Kodak this Christmas, the old one with the LCD is going to end up at the bottom of the toy box!”

While it may be premature to call 2002 the year of the OLED, from walking the halls of SID 2002 it was clear this was at least the year of the OLED exhibitor. Everywhere one turned OLED technology featured prominently. Philips impressed with a number of consumer products with monochrome OLED displays, from electric shavers to miniature cellphones, while Du Pont’s exhibit was dominated by OLED-based displays, both monochrome and full-color versions.

Market analyst Display Search of Austin, Texas, predicts the worldwide OLED market will top $100 million this year, and rise to $2.8 billion by 2007, assuming the supporting manufacturing infrastructure is established and display driver circuits are developed. Philips and Du Pont are both working to accelerate the development of drivers to power OLED displays.