Conducting polymers are of great interest for a variety of applications within the emergent field of flexible, low-cost organic electronics. Doping of polymers to obtain high conductivities via chemical, electrochemical, and electrostatic processes have been widely investigated. A fundamental question remains, however, of exactly how high polymer conductivity levels can reach. Poly(styrene sulfonate)-doped poly(3,4-ethylenedioxythiophene) (PEDOT:PSS), a commonly employed electrode material in organic electronic devices, typically exhibits a conductivity of only ~0.1 S/cm; conductivities of typical metals are closer to ~10⁵ S/cm. Using a solid electrolyte dielectric in a field-effect device platform, room-temperature conductivities of ~10³ S/cm can be achieved in regioregular poly(3-hexylthiophene) (P3HT) thin films. Experimental evidence suggests that these large conductivities are a product of nearly trap-free carrier mobilities and large two-dimensional charge densities obtained by electrostatic injection. Four-probe measurements at low temperatures reveal that in spite of the low polymer channel resistance, contact resistances at the metal-organic interfaces are even lower (~1 kW•cm), and are on par with some of the best observed in organic field-effect transistors (OFETs). At very large 2D carrier densities (exceeding 10¹⁴ charges/cm²), a maximum in polymer transconductance is observed in several polymeric thin films. Further investigation into the origins of this phenomenon may provide insight into the ultimate limits of polymer conductivity and how these values might be improved.

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