OLED fabrication uses direct-photolithography process

Researchers from Germany's University of Cologne have achieved what they say is the first high-resolution, full-color OLED display based on a direct photolithographic process.

The team reported on the OLED at the Society for Information Display (SID) symposium in San Francisco, California.

The direct photolithography technique was developed in collaboration with Merck OLED Materials GmbH. Unlike other approaches such as inkjet printing, the technique does not require development of an entirely new process technology; rather, it relies chemical modification of the organic material.

"By adding oxetane side groups, our emissive polymers gain the properties of photoresists. Thin films of these smart resists can be patterned simply by exposure to ultraviolet light," said team leader Klaus Meerholz, a Cologne professor.

The group has used the method to fabricate fully operational true-color matrix displays that can display simple pictures and support video while reportedly consuming less power than most conventional displays.

During the fabrication process, spin coating is used to deposit the first polymer onto a transparent substrate. The polymer film is then irradiated with ultraviolet light through a shadow mask, causing the polymer to cross-link and to form an insoluble material. Material in the nonilluminated areas of the film is washed away with solvent.

Two other polymers are subsequently deposited in the same way to fabricate a pixelated device with three individually addressable colors.

Meerholz emphasized that the work is preliminary and that research is required before commercialization can be contemplated.

- Nicolas Mokhoff
EE Times