Multiscale Thermoelectric Transport: Bridging Quantum Mechanics to Macroscopic Systems Through the Landauer-Boltzmann Paradigm

Abstract

Thermoelectric energy conversion is a promising pathway toward sustainable energy technologies, enabling the direct conversion of temperature gradients into electrical power as well as solid-state cooling without moving parts. Despite decades of intensive research, however, the efficiency of practical thermoelectric devices remains limited to approximately 5-10%. This persistent bottleneck arises primarily from the intrinsic coupling between electrical and thermal transport, governed by carrier concentration, scattering mechanisms, and energy transport across multiple length scales. This review presents a holistic, multiscale perspective on thermoelectric transport phenomena, spanning atomic-scale quantum transport, nanoscale materials engineering, and macroscopic device design. The theoretical framework is based on the Landauer-Boltzmann formalism, which provides a unified and physically consistent description of transport without invoking the conventional dichotomy between ballistic and diffusive regimes, while treating electronic and phononic excitations on equal footing. Within this framework, we examine microscopic mechanisms responsible for enhanced thermoelectric coefficients, including electrical conductivity, Seebeck and Peltier coefficients, and thermal conductivity, as well as macroscopic strategies for optimizing overall device performance. Emerging paradigms such as topological materials, quantum confinement, ionic thermoelectrics, and organic-inorganic hybrid systems challenge traditional optimization rules and open new avenues toward substantially improved thermoelectric performance. Finally, we discuss pathways for accelerating the development of commercially viable thermoelectric technologies for waste-heat recovery, automotive thermal management, and distributed energy generation, emphasizing the roles of high-throughput computational screening, advanced nanoscale characterization, and machine-learning-assisted materials discovery. This review serves both as a pedagogical introduction to the fundamental physics of thermoelectricity and as a critical assessment of the field's current achievements and unresolved challenges, outlining directions needed to achieve transformative advances in thermoelectric technology..