Thermoelectric films and periodic structures and spin Seebeck effect systems: facets of performance optimization

The growing market for sensors, Internet of Things, and wearable devices is fueling the development of low-cost energy-harvesting materials and systems. Film based thermoelectric (TE) devices offer the ability to address the energy requirements by using ubiquitously available waste-heat. This review narrates recent advancements in fabricating high-performance TE films and superlattice structures, from the aspects of microstructure control, doping, defects, composition, surface roughness, substrate effect, interface control, nanocompositing, and crystal preferred orientation realized by regulating various deposition parameters and subsequent heat treatment. The review begins with a brief account of heat conduction mechanism, quantum confinement effect in periodic layers, film deposition processes, thin film configurations and design consideration for TE in-plane devices. It then proceeds to analyzing the latest findings on the TE properties of Bi-2(Te,Se)(3) and (Bi,Sb)(2)Te-3, PbTe, GeTe, SnSe, SnTe, Cu2-xSe, skutterudite, and other TE material films, including superlattices and the performance of TE generators, sensors, and cooling devices. Thickness dependent microstructure evolution and TE characteristics of films in relation to temperature are also analyzed. In the context of spin Seebeck effect (SSE) based systems, SSE mechanism analysis, recent developments in enhancing the spin Seebeck signal are covered from the facets of new spin generating and collecting elements, new system design, interface effect on spin pumping, thickness-dependent longitudinal spin Seebeck signal, and length scale of phonon and magnon transport in longitudinal SSE (LSSE) in different bi-layer systems. At the end, possible strategies for further enhancing zT of TE films and spin Seebeck signals of many systems are addressed. (C) 2022 Elsevier Ltd. All rights reserved.

Automated summary

The growing market for sensors, Internet of Things, and wearable devices has led to the development of low-cost energy-harvesting materials and systems. This review discusses the recent advancements in fabricating high-performance thermoelectric films and superlattice structures, including microstructure control, doping, defects, composition, surface roughness, and interface control. The review also analyzes the properties and performance of various thermoelectric material films, as well as the spin Seebeck effect in different systems.