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Thermoelectric degrees of freedom determining thermoelectric efficiency.

ABSTRACT: For over half a century, the development of thermoelectric materials has based on the dimensionless figure of merit zT , assuming that the efficiency is mainly determined by this single parameter. Here, we show that the thermoelectric conversion efficiency is determined by three independent parameters, Zgen , τ, and β, which we call the three thermoelectric degrees of freedom (DoFs). Zgen is the well-defined mean of the traditional zT under nonzero temperature differences. The two additional parameters τ and β are gradients of material properties and crucial to evaluating the heat current altered by nonzero Thomson heat and asymmetric Joule heat escape. Each parameter is a figure of merit. Therefore, increasing one of the three DoFs leads to higher efficiency. Our finding explains why the single-parameter theory is inaccurate. Further, it suggests an alternative direction in material discovery and device design in thermoelectrics, such as high τ and β, beyond zT .

SUBMITTER: Ryu B

PROVIDER: S-EPMC8382987 | biostudies-literature | 2021 Sep

REPOSITORIES: biostudies-literature

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Thermoelectric degrees of freedom determining thermoelectric efficiency.

Ryu Byungki B Chung Jaywan J Park SuDong S

iScience 20210805 9

For over half a century, the development of thermoelectric materials has based on the dimensionless figure of merit z T , assuming that the efficiency is mainly determined by this single parameter. Here, we show that the thermoelectric conversion efficiency is determined by three independent parameters, Z gen , τ, and β, which we call the three thermoelectric degrees of freedom (DoFs). Z gen is the well-defined mean of the traditional z T under nonzero tempera ...[more]

PMID: 34466781

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