Last night I went to the SID Mid-Atlantic Chapter meeting. The speaker was Dr. Kalluri R. Sarma, a Senior Research Fellow in the Honeywell Displays and Graphics Systems group. His topic was "Flexible Active Matrix Organic Light Emitting Diode (AM OLED) Displays." While there was little hard news in the presentation, it was good to get a full hour’s briefing, plus unlimited time for questions and answers, from one of the acknowledged experts in this field. My key take away: the main value proposition for flexible displays is their ruggedness which makes them best suited for military and specialized commercial needs, not consumer markets where they will probably need to compete on price.

Honeywell R&D is generally aimed at military and aerospace products, not consumer products. According to Dr. Kalluri, Honeywell had been a pioneer in AM-LCD displays for these applications, and was looking at AM-OLED for the same applications. The R&D at Honeywell had been partially funded by DARPA, through Dupont.

Apparently there are three enabling technologies that need significant improvement before flexible AM-OLEDs can become a product: The flexible substrate itself Barrier layers TFT technology.

Test panels from Honeywell had used Dupont Teonex Q65 PEN substrates. Permeability to water vapor and oxygen of the substrate is a major issue for OLEDs. While PEN is a factor of 5 better than PET, it is still not good enough: a barrier layer is required. Honeywell uses a multilayer organic/inorganic barrier layer from Vitex Systems.

Several types of TFTs can be used, including ULTPS (Ultra-low temperature polysilicon), amorphous silicon or organic TFTs. Honeywell chose amorphous silicon because of its well known properties and its low process temperatures. Even so, they needed to adjust the process to accommodate the even lower temperatures that can be tolerated by the substrate.

Honeywell used these materials and processes to make prototype flexible AM-OLED displays. It started with a 64 x 64 monochrome display that could be made 3-up on a 4" wafer and later moved to a 160 x 160 x 3 full color display in a 2"x2" format. According to Dr. Kalluri, R&D at Honeywell on these devices continues but has been given a lower priority.

At the end of the session, there was a blunt question from the audience: Is there room for another display technology? Dr. Kalluri admitted flexible AM-OLEDs would need to compete in the consumer market with small LCDs mostly on price, which is very tough to do. The biggest advantage an OLED would bring to the consumer would be low power for longer battery life in mobile applications, but you can get that from OLEDs on glass as well as from flexible systems. Potentially AM-OLEDs, whether flexible or rigid, are less expensive than LCDs because they eliminate the backlight and the color filter array. Competition in the consumer marketplace is conceivable, but flexible AM-OLEDs aren’t ready today.

In the military and aerospace arena, Dr. Kalluri was a little more encouraging. OLEDs will bring a wider temperature range to military displays, as well as a wider field of view. In most military applications, flexibility translates into ruggedness: the display won’t break if bumped by a hard object. The military is also less sensitive to cost than the consumer, which makes for easier entry for a new technology with technical advantages but higher costs.

In summary, flexible AM-OLEDs are a significant subject for research, and their advantages make it certain that the research will continue. Most of us already knew that, but it is just good to hear from an expert, and in detail. –MB