Facile and controllable chemical doping of conducting polymers with an ionic liquid dopant

A facile method for chemical doping of conducting polymers is demonstrated with an ionic liquid containing FeCl4 - anions as the oxidizing agents. A drop of the ionic liquid on the film of a typical semicrystalline polymer immediately changed the room temperature conductivity to 500 S/cm. The highly conductive state originated from both the high doping level and the high crystallinity of the doped film, as confirmed by optical absorption and X-ray diffraction measurements, respectively. Furthermore, the doping level was continuously controlled by the gate voltage of the ionic-liquid-gated transistor structure through an electrochemical dedoping process.