Recent Progress in Thermoelectric Materials Based on Conjugated Polymers

Abstract

Organic thermoelectric (TE) materials can directly convert heat to electricity, and they are emerging as new materials for energy harvesting and cooling technologies. The performance of TE materials mainly depends on the properties of materials, including the Seebeck coefficient, electrical conductivity, thermal conductivity, and thermal stability. Traditional TE materials are mostly based on low-bandgap inorganic compounds, such as bismuth chalcogenide, lead telluride, and tin selenide, while organic materials as promising TE materials are attracting more and more attention because of their intrinsic advantages, including cost-effectiveness, easy processing, low density, low thermal conductivity, and high flexibility. However, to meet the requirements of practical applications, the performance of organic TE materials needs much improvement. A variety of efforts have been made to enhance the performance of organic TE materials, including the modification of molecular structure, and chemical or electrochemical doping. In this review, we summarize recent progress in organic TE materials, and discuss the feasible strategies for enhancing the properties of organic TE materials for future energy-harvesting applications.

Thermal Transport in Conductive Polymer–Based Materials

“…In contrast, heat conduction parallel to the substrate becomes dominant when the width of the heater shrinks. The ratio between reduced temperature of the narrow and wide heater, together with the ratio between width and thickness of heater are used to extract the ratio κ ∥ /κ ⊥ = 1.11 for PEDOT:PSS (inset of Figure g) and κ ∥ /κ ⊥ = 1.73 for PEDOT:PSS . κ ∥ can be obtained after κ ⊥ is measured using differential 3ω method (Figure e).…”

“…Nowadays, there are many other conductive polymers, such as PA, PPY, PANI, and their composites, which have been experimentally and theoretically studied as promising organic thermoelectric materials. [18,20,94,[158][159][160][161] Since the conductive polymers combine the mechanical flexibility with good thermoelectric properties, it is natural to consider using conductive polymers to fabricate flexible thermoelectric generators (TEG). Recently, Du et al [162] have fabricated the flexible TEG using PEDOT:PSS coated cotton fabric.…”

“…Conductive polymer blends with improved biodegradability, such as polycaprolactone (PCL)/polypyrrole (PPY), have been synthesized and exploited for the fabrication of bioelectronic devices such as electrical resonator circuit . Hence, conductive polymer–based materials have been demonstrated to have wide applications, ranging from the flexible electronics, biomedical applications, smart textiles, to thermoelectric materials …”

“…[12,13] Hence, conductive polymer-based materials have been demonstrated to have wide applications, ranging from the flexible electronics, [14] biomedical applications, [15,16] smart textiles, [17] to thermoelectric materials. [18][19][20] However, thermal conductivity of most polymers is very low, which might lead to serious problems for device applications such as heat dissipation failure, especially for the organic electronic devices. Previous studies have shown that the low thermal conductivity in polymers mainly comes from the amorphous structures and weak interchain interactions.…”

Poly(3,4-Ethylenedioxythiophene) Nanoparticles as Building Blocks for Hybrid Thermoelectric Flexible Films

“…When using inorganic materials, high power factor were obtained, for instance, for n-type and p-type Sb 2 Te 3 by electrochemical deposition (−80 and 100 µW m −1 K −2 , respectively) [20,21]. However, conducting polymers are much more flexible than inorganic materials and offer the possibility to produce highly flexible films for thermoelectric applications [22] in different substrates, such as paper with PEDOT:PSS [23,24] or polyimide with poly(3-hexylthiophene-2,5-diyl) (P3HT)/CNT nanocomposites [25].In this work, we have prepared films from PEDOT nanoparticles, which embed single-wall (SWCNT), double-wall (DWCNT), and multiwall (MWCNT) carbon nanotubes. We analyze the effect of different types of CNTs on the thermoelectric properties.…”