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 x 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 O-2 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. (C) 2011 Elsevier B.V. All rights reserved.