Thermoelectric Polymer Research Articles

Thermoelectric Polymers and their Elastic Aerogels.

Electronically conducting polymers constitute an emerging class of materials for novel electronics, such as printed electronics and flexible electronics. Their properties have been further diversified to introduce elasticity, which has opened new possibility for "stretchable" electronics. Recent discoveries demonstrate that conducting polymers have thermoelectric properties with a low thermal conductivity, as well as tunable Seebeck coefficients - which is achieved by modulating their electrical conductivity via simple redox reactions. Using these thermoelectric properties, all-organic flexible thermoelectric devices, such as temperature sensors, heat flux sensors, and thermoelectric generators, are being developed. In this article we discuss the combination of the two emerging fields: stretchable electronics and polymer thermoelectrics. The combination of elastic and thermoelectric properties seems to be unique for conducting polymers, and difficult to achieve with inorganic thermoelectric materials. We introduce the basic concepts, and state of the art knowledge, about the thermoelectric properties of conducting polymers, and illustrate the use of elastic thermoelectric conducting polymer aerogels that could be employed as temperature and pressure sensors in an electronic-skin.

Organic Electronics: Bulk Interpenetration Network of Thermoelectric Polymer in Insulating Supporting Matrix (Adv. Mater. 15/2014)

Organic Electronics: Bulk Interpenetration Network of Thermoelectric Polymer in Insulating Supporting Matrix (Adv. Mater. 15/2014)

Bulk Interpenetration Network of Thermoelectric Polymer in Insulating Supporting Matrix

Thermoelectric properties of conjugated polymers are found to improve upon homogeneously distributing conjugated polymer into an insulating supporting matrix. The local one-dimensional charge transport along the interpenetration conductive network simultaneously leads to lower thermal conductivity, higher electrical conductivity without sacrifice of Seebeck coefficient, and thus a higher figure of merit ZT, as compared with neat conjugated polymer.

Significant improvement in the thermoelectric properties of zwitterionic polysquaraine composite films

In this study, the polysquaraine SQI0.1, a zwitterionic π-conjugated polymer, was adopted as the matrix for the preparation of flexible and freestanding films; the low band gap of this semiconducting polymer made it a natural choice for use as a thermoelectric (TE) polymer. To enhance their TE applications, both single-walled carbon nanotubes (SWNTs) and mesoporous carbon (i.e., CMK-3) were integrated into the SQI0.1-based films and the effects of doping with iodine were also investigated. Using scanning electron microscopy, the variations in morphology of these SQI0.1-based films were examined. Raman spectroscopy was used to study the π–π interactions between iodine and the carbon materials (i.e., SWNT, CMK-3); X-ray diffraction and Raman spectroscopy to investigate the intercalation of the doped iodine in the composite films; and X-ray photoelectron spectroscopy to determine the valence state of the doped iodine. The TE properties of these materials were characterized in terms of the electrical conductivity (σ), thermal conductivity (κ), and Seebeck coefficient (S). The TE properties of the iodine-doped composite film prepared from SWNTs, CMK-3, and SQI0.1 included a notable value of ZT (Figure of Merit) of 4.563 × 10−3, which was 143% of that of the corresponding iodine-doped SQI0.1 film.

Practical evaluation of organic polymer thermoelectrics by large‐area R2R processing on flexible substrates

AbstractHere, we present a process based on roll‐to‐roll (R2R) technology which allows for very fast processing of polymer thermoelectric (TE) devices and we furthermore demonstrate a simplified but more efficient way of serially connecting these devices by means of R2R thin‐film processing. The new device architecture makes it possible to use only one TE material (opposed to two materials which are employed in well‐known Peltier elements), and a total of 18,000 serially connected junctions were prepared by flexoprinting of silver electrodes and by rotary screen printing of poly(3,4‐ethylenedioxythiophene) (PEDOT):polystyrene sulfonate (PSS) as the TE material. Testing of devices revealed that the new architecture clearly showed to be functioning as expected, but also pointed toward challenges for thin‐film TE development which is the influence of the substrate thickness on the thermal gradient over a device and the currently low performance available. A life‐cycle assessment (LCA) was carried out in order to evaluate the sustainability of the new architecture and to estimate the requirements for development of a successful technology.

A Review on the Fabrication of Polymer-Based Thermoelectric Materials and Fabrication Methods

Thermoelectricity, by converting heat energy directly into useable electricity, offers a promising technology to convert heat from solar energy and to recover waste heat from industrial sectors and automobile exhausts. In recent years, most of the efforts have been done on improving the thermoelectric efficiency using different approaches, that is, nanostructuring, doping, molecular rattling, and nanocomposite formation. The applications of thermoelectric polymers at low temperatures, especially conducting polymers, have shown various advantages such as easy and low cost of fabrication, light weight, and flexibility. In this review, we will focus on exploring new types of polymers and the effects of different structures, concentrations, and molecular weight on thermoelectric properties. Various strategies to improve the performance of thermoelectric materials will be discussed. In addition, a discussion on the fabrication of thermoelectric devices, especially suited to polymers, will also be given. Finally, we provide the challenge and the future of thermoelectric polymers, especially thermoelectric hybrid model.

Tuning the Thermoelectric Properties of Conducting Polymers in an Electrochemical Transistor

While organic field-effect transistors allow the investigation of interfacial charge transport at the semiconductor-dielectric interface, an electrochemical transistor truly modifies the oxidation level and conductivity throughout the bulk of an organic semiconductor. In this work, the thermoelectric properties of the bulk of the conducting polymer poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) were controlled electrically by varying the gate voltage. In light of the growing interest in conducting polymers as thermoelectric generators, this method provides an easy tool to study the physics behind the thermoelectric properties and to optimize polymer thermoelectrics.

Prospects for polymer-based thermoelectrics: state of the art and theoretical analysis

This perspective discusses theories of polymer thermoelectrics, identifying combinations of electronic charge carrier energies and thermal conductivity mechanisms that could lead to the highest efficiencies. Structures, electrical conductivities, Seebeck coefficients, and figures of merit are summarized for some recently devised polymer-based thermoelectric materials. Foundational equations that define these quantities are presented, and are related to thermal conductivities as well. Finally, approaches to polymer composite design that optimize thermoelectric performance in light of the theoretical models are proposed.

Electrical and Thermoelectric Properties of Poly(2,7-Carbazole) Derivatives

A series of alternating poly(2,7-carbazole) derivatives have been synthesized. The evaluation of their thermoelectric properties in doped films revealed high electrical conductivity (up to 500 S/cm) and a relatively high Seebeck coefficient (up to 70 μV/K). The best compromise between these two thermoelectric parameters led to a maximum value of 19 μW m−1 K−2 as the power factor. As observed from X-ray analyses, it has been observed that the high electrical conductivity was obtained with structured polymers. Good air stability was also observed with these thermoelectric polymers.