Surface energy patterning for ink-independent process optimization of inkjet-printed electronics

Abstract The applicability of inkjet-printed (opto-)electrical devices are hindered by their low lateral resolution, when compared to conventional techniques. The low lateral resolution is mainly caused by the flow and spreading of the functional ink on the substrate, which is determined by the substrate-ink-interaction. Recent approaches, that confine and control the spreading, have been developed. However, they suffer from low lateral resolution or the usage of physical barriers. The later needs an adjustment of the ink or may contain an overlaid height information. Both cases are not always applicable when fabricating functional devices. Herein, we report the utilization of a surface energy patterning approach based on siloxane self-assembled monolayers. The obtained energetic differences control the flow and suppress the spreading of the ink, without creating the necessity to alter the ink composition. Furthermore this approach leads to an improved structural fidelity and printing resolution of arbitrary shapes. With that, we were able to print silver- and gold-electrodes for organic filed-effect transistors with a channel length of <25 µ m, fabricating feature sizes below the footprint of a single drop. The electrical characterization of these transistors revealed that the utilization of this surface energy patterning has no negative influence on the device performance. The introduced approach facilitates the process development and improves the quality and resolution of printed features. This will facilitate the fabrication of high-quality and high resolution printed electronic devices.