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Optoelectronics/Displays  

OLEDs fail to meet expectations

Posted: 03 Mar 2008     Print Version  Bookmark and Share

Keywords:OLED display  active-matrix OLED  AMOLEDs  active-matrix LCDs  organic LED 

First appearing in 1999, the OLED display was expected to be the wunderkind of the flat-panel display world, the LCD killer that would quickly take over across a range of applications. Pundits cautioned, however, that it might take OLED technology until 2002 or even 2003 to scale up to 10 inches.

Flash forward nine years to 2008, and only one 10-inch-plus OLED has made it to production?and that only in relatively small quantities, with the manufacturer reportedly losing money on every one. Otherwise, the OLED has yet to progress beyond a few small-screen applications. What happened? And now that Sony Corp. has started testing the market with an 11-inch OLED TV, what's next?

Two reasons are most often cited for the OLED's failure to meet expectations. The first is that the LCD, ever a moving target, continued its relentless drive to better performance for lower cost, and passive OLEDs became less attractive. The second is that active-matrix OLEDs (AMOLEDs) present manufacturing challenges in the active-matrix circuitry, in the display materials and structures, and in the interaction between the circuitry and display. Given the advances in active-matrix LCDs, the investment required to iron out the wrinkles in AMOLEDs and achieve reasonable manufacturing yield just didn't seem worth it.

Survivors
Only about a handful of passive OLED manufacturers remain out of the 15 or so that existed "before the bottom dropped out in 2004/2005," said Barry Young, vice president at research firm DisplaySearch. The survivors include RITDisplay, TDK, Pioneer, Univision, Samsung SDI and a few others. It wasn't until Q4 07 that the first manufacturer went into high-volume production of AMOLEDs, with Samsung SDI shipping hundreds of thousands of 2-inch equivalents per month. Two others started manufacturing in low volume in 2007: Chi Mei EL Corp. (CMEL), about tens of thousands, and Sony, about thousands.

According to DisplaySearch, almost 90 per cent of OLEDs shipping are for just two applications: personal media players and cellphones; in the latter, AMOLEDs are commonly the main cellphone display, while passive OLEDs provide the less-demanding subdisplay.

Today's cellphone-class AMOLEDs, such as this 2.2-incher from Samsung SDI, deliver 262,000 colours and a 10,000:1 contrast ratio.

The most common OLED is 2.2- 2.4-inch, with a QVGA (320 x 240pixel) format, although some movement into the 2.8-inch to 3.2-inch realm is evident. CMEL, for example, recently expanded beyond 2.4 inches to release a 262,000-colour, 2.8-inch AMOLED. The module shows off the advantages of OLED over LCD: a tiny 2mm profile, an essentially unlimited ?90? viewing angle, and a wide -40?C to 85?C operating temperature range.

The latest-generation 2.2-inch AMOLEDs are very capable devices with upward of 10,000:1 in contrast ratio, a brightness of 200 nits and power draw of only about 0.25W (with 40 per cent of pixels on). Display lifetime (to half brightness) is now about 50,000hrs.

The demand for small OLEDs is running way ahead of supply, according to Young, but there are indications that supply will increase this year. CMEL and Samsung SDI have both announced plans to build new lines to double their OLED capacity, for example, and yield improvements on current lines will increase supply further. In the midrange for various kinds of handheld equipment, both Samsung SDI and CMEL are targeting AMOLEDs in the 3-inch to 8-inch realm this year.

In turn, LG Electronics Inc, a former manufacturer of passive OLEDs, went into production of AMOLEDs during 2007, and companies such as Canon Inc. may join the club.

Market stir
There are also indications that large OLEDs could come to market within a few years. Several companies have demonstrated larger AMOLEDs: Sony, 11-incher and 27-inchers; Samsung SDI, a 15.1-inch display; and CMEL, a 25-inch display, for example. The stir created by demonstrations of OLED TVs in the 2006 time frame revitalised large-screen OLED projects that had been dormant, according to Young, leading to Sony's late-2007 introduction of an 11-inch OLED TV.

To date, Samsung SDI has announced that it expects to have 14-, 15- and 21-inch AMOLED monitors available by 2009, as well as 42-inch AMOLED TVs by the following year. Meanwhile, Samsung Electronics has demonstrated a 40-inch AMOLED TV. For its part, CMEL has a goal of delivering 32-inch AMOLEDs for TVs by 2010. LG.Philips LCD, in turn, is developing AMOLEDs, and has demonstrated the technology for building flexible versions. Matsushita is reportedly in pursuit of TV-size AMOLEDs, and Casio is sometimes mentioned as a possible new player. DisplaySearch expects 30-inch AMOLED TVs to appear in 2009.

This in-dash audio system from Pioneer supports customisable graphics on its 65,000-colour OLED.

But, of course, there is no guarantee that OLED makers won't back off again. Toshiba, in fact, announced its own 30-inch AMOLED TVs for 2009, only to reverse itself this last December. The company's new AMOLED focus will be on small displays for cellphones and such.

Meanwhile, the SonyDrive XEL-1 TV, with a 960 x 540pixel AMOLED screen, is said to be a real stunner, reportedly selling out in Japan in its first day of availability, despite its hefty price tag. The TV is a mere 3mm thick and weighs just 3.3lbs. Sony said the TV will soon be headed to the United States.

- David Lieberman
EE Times




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