Present Status of Roll-to-Roll OLED Fabrication and Encapsulation

Within Fraunhofer COMEDD a roll-to-roll line for research and development for OLED lighting on metal and barrier films has been brought into operation. The roll-to-roll line consists of a vacuum coater for small molecule depositions; a roll-to-roll encapsulation unit for lamination under inert atmosphere and an optical inspection system for defect characterization. White emitting OLEDs on meter long substrates have been demonstrated. Beside the challenging deposition technology a proper encapsulation is the key issue for further development. In general, the performance of a barrier film will be mainly benchmarked with the water vapor transmission rate, but on the other hand adhesion compatibility, mechanical stability, defect level and residual water left in the barrier stack or adhesive a re also of interest. In particular particle contamination on barrier film substrates may negatively affect the OLED lifetime. This is caused by local elevated leakage current which could result in cumulative dark spot growths on active OLED areas. Novel R2R inspection concepts have been developed within the roll-to-roll line to determine defect densities for different defect types. Additionally, the detected defects can be visualized in bin size distributions to allow a better understanding of the OLED device performance and degradation mechanisms.