Giant Seebeck Effect in PEDOT Materials with Molecular Strain

TL;DR

This study demonstrates a giant Seebeck effect in PEDOT materials achieved by inducing molecular strain, significantly enhancing thermoelectric power and revealing potential for practical thermoelectric applications.

Contribution

Introduces a novel molecular strain technique to significantly increase the Seebeck coefficient in PEDOT, a promising thermoelectric material.

Findings

Seebeck coefficient increased by two orders of magnitude

Strain in specific bonds correlates with Seebeck variation

Molecular strain shifts the density of states near the Fermi level

Abstract

Poly 3,4-ethylenedioxythiophene (PEDOT) has been attracting attention as a thermoelectric material for room-temperature use due to its flexibility and non-toxicity. However, PEDOT reportedly generates insufficient thermoelectric power for practical use. This work tried to improve the Seebeck coefficient by introducing molecular strain to PEDOT molecules by loading a Polystyrene sulfonate (PSS)-free PEDOT on a Polyethyleneterephthalate (PET) fiber. Raman spectroscopy revealed the PEDOT materials with significant compression in the C{\alpha}-C{\alpha} bond and extension in the C{\alpha}=C\b{eta} bond exhibit Seebeck coefficients two orders of magnitude larger than usual. Furthermore, strain in the C\b{eta}-C\b{eta} bond strongly correlated with the Seebeck coefficient that varied in a broad range from -2100 to 3100 {\mu}V K-1. This variation indicated that the molecular strain formed a sharp peak or valley around the Fermi level in the density of state (DOS) function, which gradually shifts along with the C\b{eta}-C\b{eta} strain. This molecular strain-induced giant Seebeck effect is expected to be an applicable technique for other polythiophene molecules.