Cambridge Display Technology has announced that several new patents have been allowed in the United States, Europe and Canada, further expanding its portfolio of intellectual property in the field of organic light emitting diodes (OLEDs) used for display and lighting applications.

Among the patents now allowed in the US is a patent relating to OLEDs which comprise hole transport, electron transport and emissive components, using type II interfaces, contained in the same molecule. This is believed to be of considerable importance in the context of the printing of OLED devices. Molecules containing 'type II' interfaces are believed to be important in achieving high efficiency display devices.

Other new US patents include a patent relating to the use of a dielectric barrier layer over the key emissive layer to protect it from damage due to sputtering of a conductive layer. This is expected to have important application in top emitting devices in which the light does not have to pass between the transistors but, more efficiently, through a transparent cathode structure, the company reports.

Another patent is jointly owned with Seiko Epson Corporation and covers certain solvents used in ink formulations for ink jet printing of polymer OLEDs.

These patents are the result of work carried out over the last few years by CDT into all areas of P-OLEDs, including materials development, device optimisation and manufacturing process development.

The ability of manufacturers to print displays is seen as key to the ability to produce lower cost, ever-larger display sizes e.g. for OLED televisions. The use of ink jet printing is seen by many companies as the best current approach to the challenges of manufacture of OLED displays.