Apparent dependence of conductivity of a conducting polymer on an electric field in a field effect transistor configuration

A curious effect is reported whereby an electric field apparently greatly affects the conductivity of an organic polymer, poly-3,4-ethylenedioxythiophene (PEDOT), doped to the "metallic" conducting regime when it is used in an all-organic polymer field effect transistor configuration. The response time for change in current in the source/drain PEDOT polymer with a change of gate voltage is slow (less than or equal tosimilar to2 s), suggesting that ionic diffusion is involved in the phenomenon. It is suggested that the electric field changes only the conductivity of the lowly conducting polymer matrix, which contains highly conducting islands of PEDOT, thus changing the extent of percolation of electric charge between metallic islands, and thereby affecting the bulk conductivity of the PEDOT source/drain material. (C) 2002 American Institute of Physics.