Solution processing of organic light emitting diodes

Organic light emitting diodes (OLEDs) are often classified as a new generation of displays and lighting elements and have been the focus of research of development for over 20 years. The first products have been introduced into the market in applications such as displays for smart phones or TVs as well as solid state lighting. Typcially, most commercial products are produced via vacuum evaporation technologies. However, solution processing techniques for the production of OLEDs have a high potential due to several advantages over vacuum processing. The benefits of solution processing include less material waste, the potential for up-scaling with R2R-technologies as well as fast custom design changes by using digital printing techniques. This talk will provide an overview on up-scaling of O LED device fabrication from the lab scale (5 cm x 5 cm) to the pilot scale (15 cm x 15 cm) using inkjet printing and slot die coating. The influence of the replacement of indium tin oxide (ITO) through silver and copper grid structures will be discussed. Device degradation was hindered by conventional glass encapsulation as well as by thin film encapsulation using atomic layer deposition. With this method a dense inorganic layer can be deposited directly on the active stack with low defect density providing an efficient barrier for such devices. The influence of the processing conditions, layer thickness and composition on the device stability will be shown. Futhermore, an outlook on future developments such as quantum dot based QLEDs will be shown.