On the tuning of electrical and thermal transport in thermoelectrics: an integrated theory–experiment perspective

TLDR

Thermoelectric research has advanced markedly over the past two decades, focusing on both fundamental understanding of electrical and thermal transport and on enhancing material performance through coordinated optimization of interrelated transport parameters. This review surveys successful strategies for tuning electrical and thermal transport, summarizing recent achievements and outlining future challenges. The authors discuss band‑degeneracy tuning, carrier‑scattering engineering, and conductive‑network design for electrical transport, and phonon‑phonon interactions, nanostructuring, and chemical‑bond‑hierarchy effects for thermal transport. The integrated theory–experiment approaches reviewed have led to measurable improvements in thermoelectric performance, while highlighting remaining challenges and directions for further progress.

Abstract

Abstract During the last two decades, we have witnessed great progress in research on thermoelectrics. There are two primary focuses. One is the fundamental understanding of electrical and thermal transport, enabled by the interplay of theory and experiment; the other is the substantial enhancement of the performance of various thermoelectric materials, through synergistic optimisation of those intercorrelated transport parameters. Here we review some of the successful strategies for tuning electrical and thermal transport. For electrical transport, we start from the classical but still very active strategy of tuning band degeneracy (or band convergence), then discuss the engineering of carrier scattering, and finally address the concept of conduction channels and conductive networks that emerge in complex thermoelectric materials. For thermal transport, we summarise the approaches for studying thermal transport based on phonon–phonon interactions valid for conventional solids, as well as some quantitative efforts for nanostructures. We also discuss the thermal transport in complex materials with chemical-bond hierarchy, in which a portion of the atoms (or subunits) are weakly bonded to the rest of the structure, leading to an intrinsic manifestation of part-crystalline part-liquid state at elevated temperatures. In this review, we provide a summary of achievements made in recent studies of thermoelectric transport properties, and demonstrate how they have led to improvements in thermoelectric performance by the integration of modern theory and experiment, and point out some challenges and possible directions.