Design Strategies in the Pen-Printing Technique toward Elaborated Organic Electronics

Abstract

Printing techniques suitable for the commercial production of organic electronics, especially organic field-effect transistors, have been a topic of intense research interest. In the current work, we carried out systematic studies aimed at improving the printing performance of a facile pen-printing technique. To achieve this goal, two strategies were deployed. In the first strategy, the capillary pen of the pen-printing system was specifically engineered so that the nib angle could be controlled, and the angles 20°, 25°, 30°, and 40° were tested; the aim here was to influence the properties of discharging of the ink solution from the pen to the substrate, such as the amount of ink transferred and the area of contact between the nib and substrate surface. The other strategy involved precisely controlling the surface energy of the target substrate by treating the substrate with hexamethyldisilazane (HMDS)-, octadecyltrichlorosilane (ODTS)-, or HMDS:ODTS-mixed self-assembled monolayers, with the aim of affecting the wetting of the transferred ink. By combining these two strategies, we substantially improved the printing resolution of the pen-printing method; specifically, we were able to reduce the diameters of the patterned deposits from 205 to 31 μm for the water-soluble poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) ink and from 369 to 84 μm for the organic solvent-soluble poly(dimethyl-triarylamine) (PTAA) ink. We also tested the utility of the new pen-printing system by assessing the performances of PTAA transistors made using this system. The highest field-effect mobility (μFET) value we obtained was 0.009 cm2 V–1 s–1, which is among the highest reported for any PTAA transistor; this value was obtained using the pen-printing apparatus with a nib angle of 20° on a substrate treated with HMDS(1):ODTS(2). We expect these results to promote the use of the pen-printing technique in the commercial fabrication of highly integrated electronic devices in low-cost large-area printed fields.