January 1, 2016.
Thermoelectric (TE) materials are used to convert waste heat into electrical power. Semiconducting single-walled carbon nanotubes (s-SWCNT) have great potential to be used in thermoelectric devices, either on their own or in composites with conducting polymers. Certain polymers can selectively extract s-SWCNT from raw carbon nanotube soot (containing impurities such as metallic SWCNT, amorphous carbon, metal catalysts particles), but most of these polymers (e.g. polyfluorenes) are electrical insulators, rendering them inefficient in TE nanocomposites. On the other hand, conducting polymers, such as poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), have been used in efficient TE nanocomposites, but have never been rationally designed with s-SWCNT. Furthermore, the electrical conductivity and thermopower of PEDOT:PSS can also be tuned via chemical treatments, such as treatments with dimethyl sulfoxide. The hypothesis of our research is that each component (s-SWCNT and PEDOT) can be tuned independently to achieve optimal TE efficiency and our aim is to produce porous, polymer-free s-SWCNT networks, which could subsequently be filled with an electrically active PEDOT:PSS matrix. To achieve this, films were fabricated directly from dispersions of plasma-torch carbon nanotubes by NanoIntegris and poly[(9,9-di-n-dodecyl-2,7-flourendiyl-dimethine)-(1,4-phenylenedinitrilomethine)] (PFPD), a highly selective and removable polymer that extracts exclusively s-SWCNT. PFPD was easily removed from the films by depolymerization using triflouroacetic acid (TFA). After deposition, we investigated p-type doping of the s-SWCNT PT networks, using triethyloxonium hexachloroantimonate (OA), to discover the doping conditions required to optimize the thermoelectric power factor of these films. We subsequently demonstrated the effect of filling the s-SWCNT PT network with PEDOT:PSS on the thermoelectric performance. These results will help to inform future rational designs of thermoelectric composites composed of s-SWCNT and conducting polymers.
Environmental Chemistry | Materials Chemistry
National Renewable Energy Laboratory (NREL)
This material is based upon work supported by the National Science Foundation through the Robert Noyce Teacher Scholarship Program under grant 1546150. Any opinions, finding, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation. The research was made possible by the California State University STEM Teacher Researcher Program in partnership with the National Renewable Energy Laboratory .