by Steve Sechrist
At the recent SID 2006 Symposium, Seminar, and Exhibition in San Francisco, chemical giant DuPont made the startling announcement that it has developed a new set of technologies that enables solution processing of small-molecule organic-light-emitting-diode (OLED) materials. DuPont went on to say that its manufacturing process is "material agnostic," meaning polymer OLEDs (P-OLEDs) and small-molecule OLEDs (SM-OLEDs) can co-exist on the same OLED panel.
This is a significant manufacturing breakthrough, combining the display performance of SM-OLEDs with the cost advantages of solution processing. The company claims delivering an estimated 15–30% overall manufacturing cost advantage over current LCD manufacturing by requiring fewer manufacturing steps and reducing the bill of materials. DuPont backed up its claim on the SID exhibit floor by showing a 6-in.-diagonal OLED display that looked like it was ready for primetime.
The company explained that the solution process was enabled by a combination of processes, device architecture changes, and materials innovations including a blanket-coated (non-patterned) first layer over the thin-film-transistor (TFT) backplane using standard coating processes that cover up any non-uniformities. This eliminates defects from printing; special materials are used to prevent pixel crosstalk.
Next, DuPont employs a unique striped emitter approach using a wetting area for the emissive solution (active-area TFT) alternated by a non-wetting (inactive) area to control the spreading of emitters. The company said these stripes are much easier to print than the traditional cell approach. The cathode deposition does require evaporation but eliminates the need for a pixel mask, making the job simple and inexpensive.
A pre-manufactured DuPont Drylox cover glass is then used to encapsulate the OLED stack, offering cost, performance, and thickness advantages over existing cavity-glass methods. Additional cost savings can be realized here because the process is available today without further R&D.
The company emphasized that its solution process offers significant cost advantages over liquid-crystal-display (LCD) manufacturing and offered up two charts in its SID presentation showing a side-by-side manufacturing cost comparison with both 2.2-in. LCD (Gen 4) and 15.4-in. LCD (Gen 5) manufacturing. Even when assumptions included significantly higher OLED TFT and drivers costs over that for LCDs, the small display was forecast to be 15% less to produce, and the larger 15.4-in. OLED display was up to 30% cheaper to manufacture than the Gen 5 LCD. This gives the DuPont solution process what the company likes to call "OLED Headroom" or margin to compete with LCDs.
Suffice it to say, DuPont is ushering in a whole new era in OLED display manufacturing. With this announcement of material-agnostic solution processing, the company has rendered the P-OLED vs. SM-OLED debate moot and, in one fell swoop, shifted the discussion from the academic issues and nebulous future prospects of OLED technology to the concrete issues of process manufacturing, yield improvements, and product development to compete in the real world dominated by LCDs.