Counter-ion and dopant effects on the electronic structure and thermoelectric properties of intrinsically conductive polymers

Conductive organic polymers have seen increased interest in the field of thermoelectrics, in part due to their high electrical conductivity (≈ 10³ S cm^-1) and intrinsically low thermal conductivity (<1 W m^-1K^-1). These properties are highly tunable through optimization of their chemical structure and polymerization methods. It is well documented that modifications to the counter-ion present in conductive polymers as well as any alteration done to the polymerization process will change their thermoelectric properties significantly. Such variations yield an extremely broad range of reported thermoelectric figure of merit (ZT) values (0.1-0.42) for conductive polymers. While charge carriers at lower conductivities have been identified as polarons, an understanding of the electronic structure of conductive polymers as their conductivity increases is not well understood. We have investigated the electronic and thermoelectric properties of conductive polymers to provide insight into how their electronic structure and the type of charge carriers present change with different counter-ions as well as different polymerization processes. We believe the fundamental insights developed in this study might be beneficial in the development of emerging polymers for thermoelectric applications.