Organic conductors, in particular conducting polymers, continue to attract intense research efforts, motivated by emerging applications in organic electrochemical transistors for bioelectronics and neuromorphic computing, energy storage and thermoelectric devices. These materials are typically doped in their bulk to very high carrier densities on the order of 1020-1021 cm-3 and exhibit fascinating non-linear, many-body and non-equilibrium transport phenomena in this regime, that are being exploited in these applications, but whose scientific origin remains poorly understood. Here we focus on the underpinning charge transport physics and review how the complex microstructure, interactions between the electrons as well as interactions between electrons and the dopant counterions govern the transport physics, including the evolution of the density of states with carrier density. We include a discussion of reliable experimental methods for determining carrier concentrations and measuring transport coefficients. An in-depth understanding of the charge transport physics in this regime of high carrier density is a pre-requisite for harnessing these transport phenomena in device applications.
Sirringhaus et al. (Tue,) studied this question.