Low voltage electrolyte-gated organic transistors making use of high surface area activated carbon gate electrodes†
In electrolyte-gated transistors, the exceptionally high capacitance of the electrical double layer forming at the electrolyte/transistor channel interface permits current modulations of several orders of magnitude, at relatively low gate voltages. The effect of the nature of the gate electrode on the performance of electrolyte-gated transistors is still largely unclear, despite recent intensive efforts. Here we demonstrate that the use of high surface area, low cost, activated carbon gate electrode enables low voltage (sub-1 V) operation in ionic liquid-gated organic transistors and renders unnecessary the presence of an external reference electrode to monitor the channel potential, thus dramatically simplifying the device structure. We used the organic electronic polymer MEH-PPV (poly[2-methoxy-5-(2′-ethylhexyloxy)-p-phenylene vinylene), as the channel material, and the high ionic conductivity, low viscosity ionic liquid [EMIM][TFSI] (1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide), as the electrolyte gating material. We believe that this will prove to be the first of a new generation of low voltage electrolyte-gated transistors for applications in organic printable electronics.