Challenges and Progress in Contact Development for PbTe‐based Thermoelectrics

Self Cite

Nanostructured lead telluride PbTe is among the best-performing thermoelectric materials, for both p-and n-types, for intermediate temperature applications. However, the fabrication of power-generating modules based on nanostructured PbTe still faces challenges related to the stability of the materials, especially nanoprecipitates, and the bonding of electric contacts. In this study, in situ high-temperature transmission electron microscopy observation confirmed the stability of nanoprecipitates in p-type Pb 0.973 Na 0.02 Ge 0.007 Te up to at least ∼786 K. Then, a new architecture for a packaged module was developed for improving durability, preventing unwanted interaction between thermoelectric materials and electrodes, and for reducing thermal stressinduced crack formation. Finite element method simulations of thermal stresses and power generation characteristics were utilized to optimize the new module architecture. Legs of nanostructured p-type Pb 0.973 Na 0.02 Ge 0.007 Te (maximum zT ∼ 2.2 at 795 K) and nanostructured n-type Pb 0.98 Ga 0.02 Te (maximum zT ∼ 1.5 at 748 K) were stacked with flexible Fe-foil diffusion barrier layers and Ag-foil-interconnecting electrodes forming stable interfaces between electrodes and PbTe in the packaged module. For the bare module, a maximum conversion efficiency of ∼6.8% was obtained for a temperature difference of ∼480 K. Only ∼3% reduction in output power and efficiency was found after long-term operation of the bare module for ∼740 h (∼31 days) at a hot-side temperature of ∼673 K, demonstrating good long-term stability.

Section: Introductionmentioning

confidence: 98%

Improving the Long-Term Stability of PbTe-Based Thermoelectric Modules: From Nanostructures to Packaged Module Architecture

Sauerschnig,

Saitou,

Koshino

et al. 2024

Self Cite

“…Data exchange through embedded terminals realizes innovative technologies, such as improved work efficiency through cooperation, automated driving systems, and real-time biological monitoring, for practical use. − To overcome power supply problems for embedded terminals, such as infrastructure sensors and smart watches, energy-harvesting technologies that generate power from ambient is essential for realizing IoT. − Energy-harvesting technologies that convert various ambient energies, such as light, heat, vibration, and static electricity, into power have been extensively explored. − Among these, thermoelectric generators (TEGs), which convert heat into electricity, have stable power generation regardless of weather conditions or mechanical drive mechanisms. Various types of TEGs have been developed, such as metal alloys with high thermoelectric conversion capabilities and flexible soft materials suitable for clothing applications. − Recently, single-walled carbon nanotubes (CNTs) have gained increasing attention as a potential thermoelectric material. − Theoretical and experimental studies have proven that controlling specific parameters, such as chirality, length, and carrier concentration, can lead to high thermoelectric conversion ability, as demonstrated by the power factor PF and figure of merit ZT . Various studies on the synthesis, purification, doping, processing, and applications of CNTs have been conducted. − …”

Section: Introductionmentioning

confidence: 99%

“…Various types of TEGs have been developed, such as metal alloys with high thermoelectric conversion capabilities and flexible soft materials suitable for clothing applications. 15 − 18 Recently, single-walled carbon nanotubes (CNTs) have gained increasing attention as a potential thermoelectric material. 19 − 23 Theoretical and experimental studies have proven that controlling specific parameters, such as chirality, length, and carrier concentration, can lead to high thermoelectric conversion ability, as demonstrated by the power factor PF and figure of merit ZT .…”

Section: Introductionmentioning

confidence: 99%

Aerosol Doping System for Microscale Seamless p–n Patterning of Carbon Nanotube Films

Suzuki,

Terasaki

2024

Carbon nanotube (CNT) films are extensively researched as a promising material for wearable thermoelectric generators (TEGs) owing to their good flexibility and high thermoelectric conversion ability. Miniaturizing a pair of p- and n-type thermocouples and increasing the number of repeating elements can effectively increase the power of TEGs. However, conventional p–n patterning methods, such as dipping and printing, have a coarse resolution at the submillimeter level, thereby limiting the miniaturization rate. This study developed an aerosol doping system as a fine n-doping method. A dopant aerosol with a <3 μm diameter was formed through ultrasonic nebulization and air separation, while n-doping was achieved by exposing the CNT film to the dopant aerosol. Microscale p–n patterning of 1 μm was achieved through exposure using small-sized aerosols at an exceptionally slow rate of 3 Å/min. This resolution is 100 times higher than those of conventional p–n patterning methods. The developed aerosol doping system for CNTs can also be used on organic semiconductor materials, such as PEDOT/PSS and perovskite materials. Therefore, it has the potential to significantly impact the realization of Internet of Things (IoT) terminals, such as flexible TEGs, transistors, and solar cells.

“…Thermoelectric (TE) materials have attracted worldwide attention for their ability to convert waste heat into useful electricity. − The figure of merit, which evaluates the conversion efficiency, is defined as zT = S 2 σ T /κ, where S , σ, κ, and T are the Seebeck coefficient, electrical conductivity, thermal conductivity, and absolute temperature, respectively. Thermal conductivity κ usually includes the electrical and lattice contributions, κ e and κ l . − As the electrical thermal conductivity is coupled with electrical conductivity, lattice thermal conductivity is the only independent transport parameter, and therefore many strategies for thermoelectric optimization have been established based on the increase of phonon scattering, such as defect engineering, all-scale phonon scattering, and entropy engineering. − …”

Section: Introductionmentioning

confidence: 99%

Improved Thermoelectric Performance of p-Type PbTe by Entropy Engineering and Temperature-Dependent Precipitates

Zhang,

Cai,

Gao

et al. 2023

Entropy engineering is aneffective scheme to reduce the thermal conductivity of thermoelectric materials, but it inevitably deteriorates the carrier mobility. Here, we report the optimization of thermoelectric performance of PbTe by combining entropy engineering and nanoprecipitates. In the continuously tuned compounds of Pb 0.98 Na 0.02 Te (1−2x) S x Se x , we show that the x = 0.05 sample exhibits an exceptionally low thermal conductivity relative to its configuration entropy. By introducing Mn doping, the produced temperature-dependent nanoprecipitates of MnSe cause the high-temperature thermal conductivity to be further reduced. A very low lattice thermal conductivity of 0.38 W m −1 K −1 is achieved at 825 K. Meanwhile, the carrier mobility of the samples is only slightly influenced, owing to the well-controlled configuration entropy and the size of nanoprecipitates. Finally, a high peak zT of ∼2.1 at 825 K is obtained in the Pb 0.9 Na 0.04 Mn 0.06 Te 0.9 S 0.05 Se 0.05 alloy.