This is an interesting article from June of this year. Here is a snippet.
"OLEDs fall into two categories: passive matrix and active matrix. Active matrix means that every pixel is individually switched, as opposed to a passive matrix arrangement, where row and column electrodes are used to control the pixel at a given intersection.
Unfortunately for manufacturers, OLED driving schemes tend to be more complicated than LCD devices. The reason behind this is that OLEDs are current-driven and are sensitive to slight fluctuations in current. LCDs on the other hand are voltage-driven. Instead of needing one thin film transistor (TFT) per pixel in an active matrix scheme, OLEDs need between two to five, arranged in a compensation circuit.
However, the biggest hurdle facing OLED developers is short lifetime. Although OLED materials and device structures have improved greatly over the past few years, manufacturers can still only guarantee between 5000 and 15,000 h of operation before the brightness of the panel is reduced to half of its initial value. This performance is sufficient for mobile phones and other consumer electronics, but inadequate for television and more sophisticated products. The organic materials simply do not hold up well under the driving current or the exposure to other materials within the device. What's more, the cathode material is highly sensitive to air and even when sealed, the OLED performance degrades slowly over time.
Device lifetime is shortened not only by declining brightness, but also by colour drift. For example, if the red, green and blue emitters degrade at different rates, the display shifts in hue over time. Typically, colour OLEDs are made by patterning red, green and blue emitters into subpixels, although it is also possible to mix multiple emitters together to form a single "white" material and use a colour filter.
With a commercial history of just seven years, OLED manufacturing remains at an early stage, both in terms of technique and equipment. Small-molecule OLEDs are made using vapour deposition techniques, such as evaporation through a shadow mask. OLED materials are too delicate for photolithography. Polymer OLEDs are made by solution processing, either spin-on techniques (for monochrome) or inkjet printing (for colour), although the latter has not yet been commercialized. Yields are quite high for simple panels, but established processes have not been put in place for most types of colour panels. This means that OLEDs are still priced higher than equivalent LCDs."
Thanks for the informative post. Even if this article was archived previously, it is not really "old" news, and hence nice to get a refresher that's not buried. OLED seems very far away from any sort of credible development for average size flat panel displays, much less the larger variety gaining popularity in the Home Theater market. SED however DOES have working prototypes w/critical but limited reviews, as well as building production facilities as I type, and even this seems not enough to break into the competitive CE market. OLED appears to be at least a decade behind SED in these respects.
EDIT 1/17/2007 : Due to recent developments between now and when I first posted, SED seems to be headed in the wrong direction. There were no SED's at CES 2007 due to US litigation, Canon has since become the sole owner of SED Inc., and has since put the brakes on the proposed production plant in Japan. What does that spell for SED?...doom.