  Doped organic semiconductors are critical to emerging device applications,
including thermoelectrics, bioelectronics, and neuromorphic computing devices.
It is commonly assumed that low conductivities in these materials result
primarily from charge trapping by the Coulomb potentials of the dopant
counter-ions. Here, we present a combined experimental and theoretical study
rebutting this belief. Using a newly developed doping technique, we find the
conductivity of several classes of high-mobility conjugated polymers to be
strongly correlated with paracrystalline disorder but poorly correlated with
ionic size, suggesting that Coulomb traps do not limit transport. A general
model for interacting electrons in highly doped polymers is proposed and
carefully parameterized against atomistic calculations, enabling the
calculation of electrical conductivity within the framework of transient
localisation theory. Theoretical calculations are in excellent agreement with
experimental data, providing insights into the disordered-limited nature of
charge transport and suggesting new strategies to further improve
conductivities.

Materials Science