Combinatorial screening of functional polymers for organic electronics via inkjet printing
Inkjet printing represents a solution deposition technique that is characterized by its non-contact, material-efficient and reproducible processing. It is, however, a long way to gain a full understanding of the complete drying process, since the process conditions as well as the ink properties correlate in a complex relation with the final device properties. For inkjet printing, all solute parameters have a significant influence on the preparation of the printed patterns, which makes the ink development crucial. Important factors include the contact angle, ink viscosity and surface tension as well as the nozzle diameter. By using multiple print heads, a high speed production of thin films can be performed. Therefore, inkjet printing can be used as a R2R coating technique. However, for the application of inkjet printing in a commercial available device, there are many challenges to overcome, which is the reason why inkjet printing is up to now mainly used in scientific research environment. For a detailed understanding of the preparation techniques as well as to evaluate whether inkjet printing has the potential for producing efficient devices, the drying processes and resulting film morphologies need to be well understood. This thesis provides an overview of methodical investigations of ink characteristics, printing conditions and final film properties. In particular, the possibility to integrate inkjet printing into a combinatorial screening workflow evolves inkjet printing to a notable method for an efficient screening of new materials for organic electronics applications like organic photovoltaics (OPVs), organic light emitting diodes (OLEDs) and organic radical batteries (ORBs).