Challenges and strategies to optimize the figure of merit: Keeping eyes on thermoelectric metamaterials

Wearable Thermoelectric Generators: Materials, Structures, Fabrications, and Applications

“…Many recent reviews have thoroughly summarized the recent developments of TE materials whose charge carriers are electrons/holes and found out these materials are mainly metallic alloys, metal oxides, metal chalcogenides, and some semiconductors, including Bi-Te alloys, skutterudites compounds, tetrahedrites compounds, Half-Heusler (HH) compounds, and other oxides. [31][32][33] As a large group of TE materials, metal oxides have attracted many research interests. [34][35][36][37] Although the crystal structure of the oxides are different from each other, many oxides can function well as TE materials thanks to their high stability at high temperature and low cost.…”

Review of Si-Based Thin Films and Materials for Thermoelectric Energy Harvesting and Their Integration into Electronic Devices for Energy Management Systems

“…Theories and experiments have demonstrated that low-dimensional nanometer-sized structures and bulk materials with nanograins can significantly reduce κ through inter-face and boundary phonon scattering mechanisms [112][113][114]. Recent advances in onedimensional nanotubes and nanowires and two-dimensional superstructures, such as Si, SiGe, SiGe/Si, and nanocomposites, have demonstrated an increase in interface phonon scattering, leading to a reduction in κ l [114][115][116].…”

“…Furthermore, µTEGs offer the possibility of exploring alternative applications beyond energy harvesting for which these devices are the optimal solution. Therefore, technological challenges related to the microelectronic integration of low-dimensional materials, such as thin films, must be addressed to further advance this area of research [28,30,112]. Finally, it is worth mentioning that power density, a commonly used metric for comparing the efficiency of macroscopic commercial modules, may not be suitable for accurately assessing the performance of microdevices in real-world operating environments, particularly when temperature gradients are imposed [30].…”

Thermoelectric and Magnetic Properties of Biphasic ZrFe0.5Ni0.5Sb Double Half-Heusler and ZrNiSb Half-Heusler Induced by Co Doping

“…However, these strategies have reached their zenith in optimizing the zT in the majority of the common TE materials, primarily due to the contrasting correlation of zT parameters to the charge carrier concentration (n) and the limited solubility of the suitable dopants on the target host sites. 11,12 Consequently, special techniques that decouple the intertwined interdependence of zT parameters to surpass these limitations are increasingly being sought after. Examples of such techniques are modulation doping, 13−16 the energy filtering effect, 17−19 phase separation, 20,21 in situ evolution of inclusions, 22,23 compositional/elemental optimization, 24,25 codoping, 26,27 and nanostructuring.…”

“…zT is directly proportional to the power factor (PF), which is a function of the square of the Seebeck coefficient ( S ) and the electrical conductivity (σ), and inversely proportional to the thermal conductivity (κ), which is the sum of the electronic (κ ele ) and lattice thermal conductivity (κ latt ) of the material. , The conventional paradigm to increasing the zT has been to tune the carrier concentration or engineer the band structure to optimize the power factor and introduce lattice defects to lower the thermal conductivity through doping with appropriate dopants. However, these strategies have reached their zenith in optimizing the zT in the majority of the common TE materials, primarily due to the contrasting correlation of zT parameters to the charge carrier concentration ( n ) and the limited solubility of the suitable dopants on the target host sites. , Consequently, special techniques that decouple the intertwined interdependence of zT parameters to surpass these limitations are increasingly being sought after. Examples of such techniques are modulation doping, − the energy filtering effect, − phase separation, , in situ evolution of inclusions, , compositional/elemental optimization, , codoping, , and nanostructuring. ,, …”