(468d) Electrochemical Effects in Thermoelectric Polymers

Solution processible, scalable polymers have the potential to have high electrical conductivity (Ï?), high Seebeck coefficient (also called thermopower, S), and low thermal conductivity (κ), all necessary attributes for good thermoelectric performance. Organic materials also offer new opportunities to design materials with complex transport properties. In comparison to inorganic materials, ionic conductivities can be relatively high in organic materials near room temperature, e.g. as high as 1 S/cm. These high ionic conductivities can be obtained alongside electronic conduction leading to organic mixed ion-electron conductors. We suggest that this ability to simultaneously carry significant electronic and ionic charge can lead to unique thermoelectric properties, but the way that these transport properties influence each other within a single material is poorly understood. Conductive polymers such as PEDOT:PSS hold great promise as flexible thermoelectric devices, where solution processing techniques can lead to flexible devices in novel geometries. The thermoelectric power factor of PEDOT:PSS is small relative to inorganic materials because the Seebeck coefficient is small. Ion conducting materials have previously been demonstrated to have very large Seebeck coefficients, and a major advantage of polymers over inorganics is the high room temperature ionic conductivity. Notably, PEDOT:PSS demonstrates a significant but short-term increase in Seebeck coefficient which is attributed to a large ionic Seebeck contribution. In this talk, I will discuss how electrochemistry can be utilized to stabilize the Seebeck enhancement leading to stable improvements to power factor in mixed conductor thermoelectrics.