Fabrication of polymer-based transistors with source–drain electrodes made of carbon nanotubes and silver nanoparticles by soft lithography techniques

• Carbon nanotube and silver nanoparticle composites for source–drain electrodes
• All printed polymer transistors fabricated by soft lithography
• Reduced contact resistance by carbon nanotube electrodes
• Very low sheet resistance of Ag and Ag/carbon nanotube composite electrodes

In this study, we have developed multilayer deposition and patterning processes with a resolution of 1 μm that can be used to fabricate all-printed, polymer-based organic field-effect transistors (p-OFETs) on the basis of vacuum-free, solution-processable soft lithography techniques. We have used regioregular poly(3-hexylthiophene) (P3HT) as a soluble polymer semiconductor and poly(methylmethacrylate) as soluble polymer gate insulators. We have compared the electrical properties of p-OFETs with multi-walled carbon nanotubes (MWNTs), silver nanoparticles (NPs), and their composites as printed source–drain (S–D) electrodes in order to fabricate vacuum-free, all-printed p-OFETs. The p-OFETs with MWNT S–D electrodes exhibited higher hole mobility and on/off ratios than the devices with Ag NP S–D electrodes owing to better contact at the MWNT/P3HT interface. The high sheet resistance of MWNT electrodes was considerably reduced by mixing with Ag NPs. Both the contact resistance and channel resistance were maintained at low values, resulting in improved electrical properties of p-OFETs.