High-resolution inkjet-printed organic thin film transistor array with commercially applicable source-drain electrode process

Abstract

High-resolution inkjet printing of an organic thin film transistor (OTFT) array for mass-production is still regarded as an immature technology due to the difficulty in controlling the dimension of pattern and registry with other layers in commercial large-scale substrates. Especially, in the case of on organic gate insulator (OGI) in an inkjet-printed OTFT array, it is impossible to use plasma pre-treatment of the OGI for the hydrophobicity required for high-resolution inkjet printing of an organic semiconductor (OSC) due to its non-selectivity between organic layers, both inside and outside the channel area. A novel and commercially applicable process of the source-drain (SD) electrode prior to inkjet printing of the OSC in the bottom contact structure not only allowed a selective plasma treatment for high-resolution inkjet printing of OSC on OGI without the extra photolithographic process, but also protected the channel interface from the harmful outcomes of wet or plasma processes. This method enabled uniform electrical characteristics of more than 300 thousand pixels of an OTFT array for a backplane. Based on these results, a 5.7 inch electrophoretic display (EPD), with a high resolution of 140 dots per inch (DPI), on a plastic substrate was successfully demonstrated.