A display of huge versatility

Cheaper, longer-lasting and more versatile materials for high-performance flat panel displays claim to have been perfected by DuPont, which will use them to improve the manufacture of organic light emitting diodes (OLEDs).

These need less power and are thinner than current LCDs, but until now it has not been possible to combine high performance and long lifetime of the materials with a printing process that costs substantially less and is more scalable to larger display sizes.

The class of OLED materials, known as 'small molecular', has long been the highest performing material technology on the market, but they can only be used with expensive manufacturing techniques in which they are evaporated in high-vacuum equipment.

Also, evaporation has proved to be very difficult to scale to the large motherglass used in flat panel displays. To overcome this problem, DuPont's development allows it to capture the advantages of small molecular materials, but use them in solution form. It has a material, DB, which is termed a 'hole injection material' and used in a layer next to the OLED's anode. It is an aqueous semi-conducting material, enabling holes to enter the diode. Several advantages are promised because the DB material is in solution form.

Solution OLEDs open the possibility of using printing and coating processes which can be much cheaper to use than semiconductor processes like evaporation. Solution processes are easily scalable to large-size motherglass, and solution equipment requires less maintenance and lower capital investment than high vacuum evaporation equipment.

'Our model shows that the total cost of OLEDs can be 30 per cent less than LCDs,' said Craig Naylor of DuPont. 'Our proprietary materials are also designed to use less power than LCDs. And OLEDs can be very thin, less than 1mm.' They are starting to penetrate key applications in small displays, such as mobiles and MP3 players. DuPont hopes that eventually it will use derivatives of its DB material to use OLEDs for large-screen TVs.

DuPont expects the displays to be on sale within three years.