Exploratory study of dopedpolymers as potential high thermopower materials

X. Gao¹,I. Levesque¹, J.S. Tse¹, D.D. Klug¹, C.I.Ratcliffe¹, M. Leclerc², T. Tritt³

¹SteacieInstitute for Molecular Sciences, National Research Council of Canada, Ottawa,Ontario, Canada

²Departmentof Chemistry, Laval University, Quebec, PQ, Canada

³Departmentof Physics, Clemson University, Clemson, SC 29634, U.S.A.

An efficient thermoelectric material must possess a large Seebeckcoefficient, moderate electrical conductivity and a low thermal conductivity.In the search for advanced high thermopower materials, low band-gap polymersappear to have all these characteristics. It is possible that high electronicdensity of states near the Fermi level can be manipulate by careful adjustmentof the concentration of valence electron of such polymers via n- or p-doping. In this way, a favourable balancebetween electrical conductivity and large Seebeck coefficient may be achieved.In this study, we combined theoretical and experimental approaches toinvestigate this possibility. The accuracy of a recently developed method forthe prediction of Seebeck coefficients is tested on NaCoO4 and its analogs - apromising series of high efficiency thermoelectric materials. Theoreticalcalculations have also performed on several representative polymers and theirderivatives. It is shown that their electron band structures are adequate forthermoelectric materials. We will describe the synthesis of several lowband-gap polymers, as well as some physical and electrical properties of thepure and doped samples. Thermoelectric measurements on selected conjugatedpolymers will be compared to theoretical calculations.