Thermoelectric Properties of Highly Conductive Poly(3,4-ethylenedioxythiophene) Polystyrene Sulfonate Printed Thin Films

Organic conductors are being evaluated for potential use in waste heat recovery through lightweight and flexible thermoelectric generators manufactured using cost-effective printing processes. Assessment of the potentiality of organic materials in real devices still requires a deeper understanding of the physics behind their thermoelectric properties, which can pave the way toward further development of the field. This, article reports a detailed,thermo electric Study of a set of highly conducting inkjet-printed films of Commercially available poly(3,4-ethylenedioxythiopliene) ystyrene sulfonate formulations characterized by in -plane electrical conductivity, spanning the interval 10-500 S/cm. The power factor is maximized-for the formulation showing an intermediate,electrical conductivity. The Seebeck coefficient is studied in the framework of Mott's relation, assuming a (semi-classical) definition of the transport fuliction. Ultraviolet photoelectron spectroscopy at the Fermi level clearly indicates that the shape of the density of states alone is riot sufficient to explain the observed Seebeck coefficient, suggesting that carrier mobility is important in determining both the electrical conductivity and thermopower. Finally, the cross-plane thermal conductivity is reliably extracted thanks to a scaling approach that can be easily performed using typical pump-probe spectroscopy.