Patterning quality control of inkjet printed PEDOT:PSS films by wetting properties

In this contribution, we describe the development of inkjet printable PEDOT:PSS polymer-based inks for fabrication of polymeric organic light-emitting devices (OLEDs). By using a 10 × 10 array of SU8 wells on ITO/glass substrates, guided deposition of PEDOT in a simulated OLED pixel structure was possible. The quality of the printed patterns was controlled by fine tuning of the surface wetting properties using self-assembled monolayers (SAMs) and/or oxygen reactive plasma. All the investigated surface treatments improved the quality of the printed pattern. However, the O2 plasma treated surfaces, which had the highest free energy, resulted in smoother and more uniform PEDOT films than did the SAM-coated surfaces. Rainbow-like features and non-uniformities observed at the edges of the film were attributed mostly to the well-known coffee stain effect and the drying environment. A good reduction of such features was achieved by decreasing the PEDOT content in the inks.