Doped conducting polymer-based field effect devices

Field effect devices (FEDs) prepared completely from conducting polymers PEDOT/PSS (poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) and polypyrrole doped with Cl- (PPy/Cl-) are reported. In the "on" (conductive) state when the gate voltage V-G is applied, these FEDs have threshold turn-off positive V-g's of similar to15 V (varying with polymer, geometry, and preparation conditions). The current ratio I-on/I-off can exceed 10(+4) at room temperature. We have found this field effect is strongly temperature dependent and nearly entirely disappears with decrease of temperature by as little as ten degrees. The conductance of the active channel has stronger temperature dependence when V-G exceeds the threshold voltage. Time dynamics of drain current with gate voltage modulation and its temperature dependence supports that this transition is coupled with ion motion. We suggest that the conducting polymer is near the insulator-metal transition (IMT) and this field effect caused by positive V-g in the FED may be related with this IMT in the region underneath the gate.