Advances in thermoelectrics

Abstract

Thermoelectric generators, capable of directly converting heat into electricity, hold great promise for tackling the ever-increasing energy sustainability issue. The thermoelectric energy conversion efficiency is heavily dependent upon the materials’ performance that is quantified by the dimensionless figure-of-merit (ZT). Therefore, the central issue in the research of thermoelectric materials lies in continuously boosting the ZT value. Although thermoelectric effects were discovered in the nineteenth century, it was only until the 1950s when classic materials like Bi₂Te₃ and PbTe were developed and basic science of thermoelectrics was established. However, the research of thermoelectrics did not take a smooth path but a rather tortuous one with ups and downs. After hiatus in the 1970s and 1980s, relentless efforts starting from the 1990s were devoted to understanding the transport and coupling of electrons and phonons, identifying strategies for improving the thermoelectric performance of existing materials, and discovering new promising compounds. Rewardingly, substantial improvements in materials’ performance have been achieved that broke the ZT limit of unity. Meanwhile, advancements in fundamental understanding related to thermoelectrics have also been made. In this Review, recent advances in the research of thermoelectric materials are overviewed. Herein, strategies for improving and decoupling the individual thermoelectric parameters are first reviewed, together with a discussion on open questions and distinctly different opinions. Recent advancements on a number of good thermoelectric materials are highlighted and several newly discovered promising compounds are discussed. Existing challenges in the research of thermoelectric materials are outlined and an outlook for the future thermoelectrics research is presented. The paper concludes with a discussion of topics in other fields but related to thermoelectricity.

PACS:

• 72.20.Pa Thermoelectric effects
• 84.60.Rb Thermoelectric energy conversion
• 66.70.Df Thermal conduction
• 72.20.Jv Charge carriers
• 72.20.-i Electrical conductivity
• 63.22.-m Phonons
• 63.20.kp Phonon-defect interactions

Keywords:

• thermoelectric
• efficiency
• power factor enhancement
• phonon scattering
• electron-phonon coupling
• defects

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Acknowledgements

Authors are thankful for Prof. Bolin Liao, Dr Chenguang Fu for sharing the data, Dr Chen Chen for the Hall measurement, Tian Tong for the bandgap measurement. Authors also want to thank Prof. Jiming Bao for the insightful discussions.

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

Jun Mao http://orcid.org/0000-0001-5275-8954

Zihang Liu http://orcid.org/0000-0002-2040-1632

Additional information

Funding

This work is partially funded by the Solid-State Solar-Thermal Energy Conversion Center (S³TEC), an Energy Frontier Research Center funded by the US Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number: DE-SC0001299, and also under Contract DE-SC0010831 (Z.R.). Q.Z. acknowledges the support by Shenzhen fundamental research project (JCYJ20160427184825558), the National Natural Science Foundation of China (11674078), Startup Foundation for Advanced Talents from Shenzhen and Startup Foundation from Harbin Institute of Technology (Shenzhen).