Inkjet printing of polymer thin film transistors

All-polymer thin film transistors, inverters and active-matrix backplanes have been fabricated by inkjet printing technique. Source, drain and gate electrodes were printed with an aqueous dispersion of conducting polymer, poly(ethylenedioxythiophene) (PEDOT). The semiconductor and the gate dielectric were spin-coated from solutions of conjugated polymer and insulator polymer, respectively. In order to overcome the resolution limit of inkjet printing, PEDOT aqueous dispersion has been deposited onto a pre-patterned substrate which involves wettability contrast to define a channel, and polymer transistors with a channel length of 5 μm have been achieved. These transistors were applied to inverter circuits and active-matrix backplanes. Active-matrix operation of an electrophoretic display device has been demonstrated with the printed polymer active-matrix backplane.