Functional layers of OLEDs are damaged by water and oxygen. Therefore to insure reliable functioning of components based on OLEDs a hermetic seal is necessary to prevent exposure to these substances. On rigid carriers this encapsulation is carried out using glass substrates, which are bonded to the substrate using suitable adhesives. For flexible OLEDs barrier substrates are used.
OLEDs are seen as a key technology for future displays. Their advantages over conventional display systems are especially their lower thickness and due to this, lower weight. Newly developed highly efficient OLEDs require a lower actuation voltage and use less electricity. Application is mainly in mobile telecommunications. Cell Phones and MP3-players already frequently contain OLEDs.
A comprehensive screen of commercially available adhesives was carried out and technology for encapsulation of OLEDs was developed. For this a quantitative calcium test was developed for the the characterization of barrier characteristics of polymers. This is designed to assess transmission rates in a geometry corresponding to the later encapsulation of OLEDs. Accordingly prepared samples, as well as identically prepared OLED are tested for various reliability factors (cycle tests, high temperatures and moisture).
The work was funded by the BMBF (Förderkennzeichen: 01BK916 – 919, 01BI158 ) and carried out in close cooperation with the institutes of Fraunhofer-Gesellschaft (Fraunhofer IPMS), Applied Films, Optrex Europe GmbH and TU Braunschweig.