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Keywords:

  • conjugated polymers;
  • ionic liquid;
  • transport properties;
  • gate dielectric;
  • pressure

An effective way of using ionic liquid as a gate dielectric as well as a pressure medium to tune the transport of an exemplary polymer semiconductor, poly(2,5-bis(3-tetradecyl-thiophene-2-yl)thieno[3,2-b]thiophene) (pBTTT-C14) is presented. Working as gate dielectrics, the ionic liquids exhibit the well-known ability to induce dense carriers (>1020 cm−3) in the polymer film contributing to the high conductivity (≈102 S cm−1). In addition, it is found that the ionic liquid works as a pressure medium at the highly charged state, leading to significant enhancement of conductivity. By combining both gating and pressuring, a crossover of transport properties is observed from one-dimensional to three-dimensional hopping, as the clear indication that the polymer film has accessed the regime adjacent to the transition region between insulator and metal. These results show an effective way of utilizing pressure effect of ionic liquid as a new degree of freedom in controlling transport of polymers, a method having strong potential to be generalized for even broader range of materials.