Towards printable organic field-effect transistors based on poly(3, 3’’’-didodecyl quarter thiophene) utilizing a crosslinkable gate dielectric layer

The choice of materials and geometry are of primary concern in the fabrication of polymer field-effect transistors, since the consequent layers interact with each other especially when strong or slowly evaporating solvents are used [1,2]. In this work we report on research towards roll-to-roll printable materials and methods for the fabrication of organic transistors. Organic field-effect transistors (OFETs) have been made using the air stable conjugated polymer poly(3,3’’’-didodecyl quarter thiophene) (PQT) (ADS12PQT purchased from American Dye Source Inc. and used as received) dissolved in toluene or dichlorobenzene (concentration typically 2 mg/ml). Two types of roll-to-roll printing compatible dielectric layer solutions have been tested and deposited by spin coating : 1) solvent-based PVPh/pMF blend (PVPh = polyvinyl phenol, pMF = poly(melamine-co-formaldehyde) crosslinker) and 2) water-based PVA/Kymene solution (PVA = polyvinyl alcohol, Kymene is a trademark for a crosslinking agent based on polyamide-epichlorohydrine chemistry). The curing temperature of these dielectric layers is 150-180 ºC and 100-130 ºC, respectively. Both bottom-gate and top-gate geometry were used in the fabrication, and it was noted that top-gate configuration gave the best results. This solution processed polymer bi-layer demonstrates the viability of printable transistors.