Best thermoelectric efficiency of ever-explored materials.

A thermoelectric device is a heat engine that directly converts heat into electricity. Many materials with a high figure of merit have been discovered in the anticipation of a high thermoelectric efficiency. However, there has been a lack of investigations on efficiency-based material evaluation, and little is known about the achievable limit of thermoelectric efficiency.

Thermoelectric degrees of freedom determining thermoelectric efficiency.

For over half a century, the development of thermoelectric materials has based on the dimensionless figure of merit , assuming that the efficiency is mainly determined by this single parameter. Here, we show that the thermoelectric conversion efficiency is determined by independent parameters, , , and , which we call the three thermoelectric degrees of freedom (DoFs). is the well-defined of the traditional under nonzero temperature differences.

Dimension reduction of thermoelectric properties using barycentric polynomial interpolation at Chebyshev nodes.

The thermoelectric properties (TEPs), consisting of Seebeck coefficient, electrical resistivity and thermal conductivity, are infinite-dimensional vectors because they depend on temperature. Accordingly, a projection of them into a finite-dimensional space is inevitable for use in computers. In this paper, as a dimension reduction method, we validate the use of high-order polynomial interpolation of TEPs at Chebyshev nodes of the second kind.