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Flexible Thermoelectric Polymers and Systems. Группа авторовЧитать онлайн книгу.

Flexible Thermoelectric Polymers and Systems - Группа авторов


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of thermoelectric generators. They can be used in thermoelectric cooling systems in terms of the Peltier effect as well.

      Polymers emerge as the next‐generation thermoelectric materials mainly due to their high mechanical flexibility. Flexible thermoelectric materials can enable the realization of flexible or even portable/wearable thermoelectric generators or coolers. They are significant because of the ubiquitous heat on earth and the convenient heat collection related to the mechanical flexibility. For example, a wearable thermoelectric generator can harvest heat from human body and provide electricity to other wearable or implanted devices that are used for communication or healthcare. Polymers have much lower thermal conductivity than their inorganic counterparts, but their Seebeck coefficient is remarkably inferior to the latter. Therefore, the research focus on developing high‐performance thermoelectric polymers is very different from developing high‐performance inorganic thermoelectric materials.

      I am grateful to all the authors for their contributions to this book particularly in this special time of the COVID‐19 pandemic. I also would like to thank my wife and my two sons for their support.

      Jianyong Ouyang

       Jianyong Ouyang and Hanlin Cheng

       Department of Materials Science and Engineering, National University of Singapore, Singapore, Singapore

Schematic illustration of band structures of (a) conductors, (b) semiconductors, and (c) insulators.

      In terms of the energy band structure, the conventional conductors are metals or heavily doped semiconductors that can have the Fermi level higher than the minimum of the conduction band or lower than the maximum of the valence band. Some charge‐transfer organic salts, intrinsically conducting polymers, multi‐walled carbon nanotubes (MWCNTs), single‐walled carbon nanotubes (SWCNTs) with certain chirality, graphene, and MXenes can have partially filled band structure, and they are thus conductors. The conventional semiconductors include Si, Ge, and compound semiconductors. Conjugated organic compounds and conjugated polymers in neutral state are considered as organic semiconductors. Single‐walled carbon nanotubes can be semiconductive or metallic depending on the chirality.

      Apart from the electrical conductivity, the Seebeck coefficient and thermal conductivity are important parameters for thermoelectric materials. The thermoelectric performance of a material is usually characterized by the dimensionless figure of merit (ZT),

upper Z upper T equals StartFraction upper S squared sigma upper T Over kappa EndFraction comma

      where S is the Seebeck coefficient, σ is the electrical conductivity, T is the absolute temperature, and κ is the thermal conductivity. S2 σ is called the power factor. To have a high ZT value, the thermoelectric material should have a high power factor and a low thermal conductivity. Because thermoelectric polymers or organic molecules usually have very low thermal conductivity, the power factor is the important parameter for their thermoelectric performance.


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