Effects of side groups on the thermoelectric properties of composites based on conjugated poly(3,4‐ethylenedioxythiophene methine)s with low bandgaps

Abstract

A series of conjugated poly(3,4-ethylenedioxythiophene methine)s (PEDOT-Ms) with different side groups (e.g., electron-withdrawing, electron-donating, and electronneutralizing groups) containing 3,4-ethylenedioxythiophene (EDOT) units was synthesized and characterized, showing low optical bandgaps. Then, the PEDOT-M polymers were blended with graphite (G) to prepare polymer-inorganic composites to compare their thermoelectric (TE) properties. The optical absorption study indicated direct bandgaps ranging from 1.72 to 1.79 eV. The results showed that PEDOT-M polymers with strongly electron-withdrawing and electron-donating groups exhibited lower bandgap values and higher Seebeck coefficients, and their composites exhibited better TE properties than PEDOT-M with an electronneutralizing side group. The highest figure of merit (ZT) value for the (poly[{3,4-ethylenedioxythiophene-2,5-diyl} {p-nitrobenzylidene}{3,4-ethylenedioxythiophenequinodimethane-2,5-diyl}])(PEDOT-NBQ)/80 wt% G composite was 6.75 3 10 23 at 1208C, which was higher than the ZT value of the other PEDOT-M/G composites. These results reveal a novel approach using the structural modifications of polymers to improve the understanding of TE performance and confirm that the conjugated PEDOT-M samples studied are low-bandgap conducting polymers that can be used as TE materials. POLYM. COMPOS.,

Thermoelectric properties of polyvinylpyrrolidone/polyaniline‐mixed Bi2Te3 composites prepared by electrospinning

“…( σ T = σ Bi2Te3 + σ PANI ) is sum of both (Bi 2 Te 3 and PANI). [ 13,46,47 ] In this case, conductivity can be written as. …”

Preparation and Characterization of Bi2Te3/Graphite/Polythiophene Thermoelectric Composites

“…The cuboid specimen with dimensions of 16.0 mm 9 5.10 mm 9 3.0 mm was prepared under a pressure of 15 MPa for the electrical properties measurement, and the disk specimen with a diameter of 15.0 mm and a height of 3.0-4.0 mm was prepared under a pressure of 20 Mpa for the thermal conductivity measurement. 19 The measurement was done in in-plane for disk specimens. All the prepared samples had close densities with the range from 1.56 g/cm 3 to 1.96 g/ cm 3 , as shown in Table SII (Supporting Information).…”

Preparation of high‐performance bismuthene thermoelectric composites doped with graphene using UV‐curing 3D printing technology

“…S 2 σ is defined as the power factor, which is commonly used to assess the characteristics of thin-film thermoelectric materials. [1][2][3][4] An excellent thermoelectric material should have a high ZT value, which is achieved through high electrical conductivity, high Seebeck coefficient and low thermal conductivity. 5,6 Conventional thermoelectric materials often take the form of block-like alloys such as PbTe and SiGe etc., 7 which exhibit low ZT values due to their inherent structural and size limitations.…”

“…The performance of thermoelectric materials is typically evaluated by the dimensionless quality factor ZT = S 2 σT/к, where S represents the Seebeck coefficient, σ is the electrical conductivity, к is the thermal conductivity, and T is the absolute temperature. S 2 σ is defined as the power factor, which is commonly used to assess the characteristics of thin‐film thermoelectric materials 1–4 . An excellent thermoelectric material should have a high ZT value, which is achieved through high electrical conductivity, high Seebeck coefficient and low thermal conductivity 5,6 .…”