Semiconducting polymers are promising materials for thermoelectric devices. The thermoelectric effect allows for the conversion of a thermal gradient into an electrical potential or an applied electrical potential into a thermal gradient. The efficiency of a thermoelectric material is related to its electrical and thermal conductivity as well as the thermopower (Seebeck coefficient). Optimization of the thermopower of a material requires control over its carrier concentration. We have studied p-type and n-type doping of a series of high performance polymers to uncover the connection between morphology and their thermoelectric performance. We have examined how tetrafluorotetracyanoquinodimethane (F4TCNQ) changes the ordering of several highly crystalline semiconducting polymers and find substantial reduction in the p-spacing of the polymer chains. The Seebeck coefficient is found to be correlated to the electrical conductivity independent of the chemical structure of the semiconducting polymer suggesting similar transport mechanisms between systems. We have also examined the thermopower in n-type semiconductors and find that their performance is limited by the compatibility of the dopant molecule rather than the intrinsic electrical properties of the polymer. An outlook for the future performance of organic thermoelectrics will be presented based on recent results.

Semiconducting polymers for thermoelectrics

247th National Meeting (2014)

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