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Katherine Mazzio1 2 Monika Raja Thulasimani1 2 3 Britta Ryll4 Danny Kojda4 Klaus Habicht4 5 Simone Raoux1 2 3

1, Helmholtz-Zentrum Berlin für Materialien und Energie, Berlin, , Germany
2, Helmholtz-Zentrum Berlin für Materialien und Energie, Berlin, , Germany
3, Humboldt Universität zu Berlin, Berlin, , Germany
4, Helmholtz-Zentrum Berlin für Materialien und Energie, Berlin, , Germany
5, Universität Potsdam, Potsdam, , Germany

Hybrid materials consisting of conducting polymers in conjunction with inorganic nanostructures have been proposed for thermoelectric applications near room temperature. The performance of thermoelectric materials are typically discussed in terms of the dimensionless figure of merit ZT = S2σκ-1T, where S is the Seebeck coefficient, σ is the electrical conductivity, κ is the thermal conductivity, and T is the temperature. Improvements in the figure of merit can be realized by having a large Seebeck coefficient and electrical conductivity, while simultaneously limiting the thermal conductivity. In practice, this can be challenging because each of these variables are interrelated by the carrier concentration. Hybrid composites are attractive because they can enhance the thermoelectric performance via the intrinsic low thermal conductivity of the polymer, utilizing nanostructuring to improve phonon scattering, and through energy filtering effects. In addition, these hybrid materials systems also offer advantages related to their solubility characteristics, whereby they can be utilized in high-throughput, solution processable manufacturing routes. Most of the hybrid thermoelectric materials that have been reported in the literature have been p-type, owing to difficulties in n-type doping of conducting polymers in conjunction with the nature of the applied nanocrystals. As a result, there is a strong drive to compliment the advances in hybrid p-type materials with new n-type materials, since both types are required for module development. In this contribution, we explore our recent developments in the synthesis of new hybrid materials, where chalcogenide nanowires encapsulated in poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) are utilized as templates for the growth of a variety of compounds, such as silver-, bismuth-, and lead-based chalcogenides. We have found that we are able to directly control the stoichiometry of our materials during synthesis, such that we can effectively tune our composites from p-type to n-type. We utilize X-Ray diffraction (XRD), X-Ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and photoemission electron microscopy (PEEM) to detail the development in the structural and morphological properties of our materials and relate these modifications to the overall thermoelectric performance. Ultimately, we aim to develop high-performance composites for low-cost room temperature thermoelectric applications.

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