Electrolyte-gated organic field-effect transistors for sensing applications

We report on the electrolytic gating of α-sexithiophene thin film transistors, in which the organic semiconductor is in direct contact with an electrolyte. Due to the large capacitance of the electrical double layer at the electrolyte/semiconductor interface, modulation of the channel conductivity via an electrical field effect is achieved at low voltages. The transistors are stable for several hours and are sensitive to variations in the pH resulting from a pH-dependent surface charge, which modulates the threshold voltage. The response to different ion concentrations is described by the influence of the ions on the mobility and an electrostatic screening effect.