General Efficiency Theory of Thermoelectric Conversion

Abstract

In this Letter, we show thermoelectric conversion efficiency is \emph{exactly} determined by \emph{three} independent material parameters $Z_{\mathrm{gen}}$, $\tau$, and $\beta$. Each parameter is a figure of merit hence improving $\tau$ or $\beta$ is an additional way to increase the efficiency. The $Z_{\mathrm{gen}}$ generalizes the traditional figure of merit \emph{zT}. Two degrees of freedom $\tau$ and $\beta$ reflect the temperature gradients of the material properties and are crucial to evaluate the heat current altered by non-zero Thomson heat and asymmetric Joule heat escape. Physical insights on high $\tau$ or $\beta$ materials explain why the single parameter approaches can be inaccurate for efficiency prediction.

arXiv comment9 pages, 4 figures, 19 references for main manuscript. Total 31 pages including Supporting Material. 263 references for thermoelectric property data. arXiv admin note: substantial text overlap with arXiv:1810.11148

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