title: Hopping transport and the Hall effect near the insulator-metal transition in electrochemically gated poly(3-hexylthiophene) transistors.
abstract: Despite 35 years of investigation, much remains to be understood regarding charge transport in semiconducting polymers, including the ultimate limits on their conductivity. Recently developed ion gel gating techniques provide a unique opportunity to study such issues at very high charge carrier density. Here we have probed the benchmark polymer semiconductor poly(3-hexylthiophene) at electrochemically induced three-dimensional hole densities approaching 10(21) cm(-3) (up to 0.2 holes per monomer). Analysis of the hopping conduction reveals a remarkable phenomenon where wavefunction delocalization and Coulomb gap collapse are disrupted by doping-induced disorder, suppressing the insulator-metal transition, even at these extreme charge densities. Nevertheless, at the highest dopings, we observe, for the first time in a polymer transistor, a clear Hall effect with the expected field, temperature and gate voltage dependencies. The data indicate that at such mobilities (~0.8 cm(2)V(-1) s(-1)), despite the extensive disorder, these polymers lie close to a regime of truly diffusive band-like transport.
authors.affiliation: Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, USA.
authors.forename: Shun
authors.initials: S
authors.lastname: Wang
authors.forename: Mingjing
authors.initials: M
authors.lastname: Ha
authors.forename: Michael
authors.initials: M
authors.lastname: Manno
authors.forename: C
authors.initials: C
authors.lastname: Daniel Frisbie
authors.forename: C
authors.initials: C
authors.lastname: Leighton