Inkjet technology for large-area OLED and OPV applications

The roll-to-roll manufacturing process is believed to significantly reduce the cost-price of flexible electronics. Inkjet printing of organic-based inks is a major research topic for flexible electronic applications because of its advantage of non- contact deposition and the ease for patterning for various industrial processes. We herein present a study on inkjet printing of homogeneous layers of Orgacon™ (Agfa-Gevaert, Belgium). Orgacon™ is a water-based dispersion of poly (3,4- ethylenedioxythiophene): poly(styrenesulphonic acid (PEDOT:PSS). This printed layer can be used as a transparent electrode for the Organic Light Emitting Diodes (OLEDs) and for Organic Photovoltaic (OPV). For OLED lighting applications, uniform light emission of large areas is required; the main challenge of using inkjet technology is the deposition of highly homogenous layers onto flexible non-porous foil substrates. In this contribution, some of the fundamental aspects of inkjet ink and substrate interaction, and the resulting layer homogeneity of the active layer in relation to OLED and OPV-device performance are investigated. Combining both theoretical and experimental approaches, we studied the inkjet ink rheology and homogenous layer formation on a moisture barrier. We have enabled to deposit homogenous PEDOT and LEP using commercially available inkjet heads. Furthermore, we would like to demonstrate the ability of using inkjet printing for fabrication of 1 "by 1 "OLED devices, with Agfa high conductive PEDOT.PSS and Merck light emitting polymers dissolved in solution. The inkjet ink properties and the substrate pretreatment have been optimized in order to ensure a stable and robust printing and drying process. Moreover, inkjet printed OLEDs will be demonstrated and the resulting light emission uniformity, device performance and reliability on flexible substrates will be discussed.