Sticky thermoelectric materials for flexible thermoelectric modules to capture low–temperature waste heat

Abstract

We examined a working hypothesis of sticky thermoelectric (TE) materials, which is inversely designed to mass-produce flexible TE sheets with lamination or roll-to-roll processes without electric conductive adhesives. Herein, we prepared p-type and n-type sticky TE materials via mixing antimony and bismuth powders with low-volatilizable organic solvents to achieve a low thermal conductivity. Since the sticky TE materials are additionally injected into punched polymer sheets to contact with the upper and bottom electrodes in the fabrication process, the sticky TE modules of ca. 2.4 mm in thickness maintained temperature differences of ca. 10°C and 40°C on a hot plate of 40 °C and 120°C under a natural-air cooling condition with a fin. In the single-cell resistance analysis, we found that 75∼150-µm bismuth powder shows lower resistance than the smaller-sized one due to the fewer number of particle-particle interfaces in the electric pass between the upper and bottom electrodes. After adjusting the printed wiring pattern for the upper and bottom electrodes, we achieved 42 mV on a hot plate (120°C) with the 6 x 6 module having 212 Ω in the total resistance. In addition to the possibility of mass production at a reasonable cost, the sticky TE materials provide a low thermal conductivity for flexible TE modules to capture low-temperature waste heat under natural-air cooling conditions with fins for the purpose of energy harvesting.

Keynote Review of Latest Advances in Thermoelectric Generation Materials, Devices, and Technologies 2022

“…Additionally, the temperature difference which can be obtained from wearable application is relatively small, so the output power is small, and highest performance from the materials themselves is desirable. Another issue is that it has been pointed out that many of the polymer-based modules ultimately use expensive metal (e.g., silver, gold) pastes as contacts, so are actually not inexpensive and different approaches may also be necessary to consider [105,106]. In the case of Ag 2 S or Ag 2 Se-based materials, they have relatively high performance, however, the materials with silver as the major component are quite costly, and inexpensive module fabrication methods also need to be developed.…”

A hierarchical design for thermoelectric hybrid materials: Bi2Te3 particles covered by partial Au skins enhance thermoelectric performance in sticky thermoelectric materials

“…One target value for energy harvesting is 250 µW, which can be used to drive various electric devices using commercially available voltage boosters. However, when progressing to applications, there is a general difficulty in making electrical contacts between the soft TE materials and electrodes because we cannot simply apply the traditional method for solid-state TEs, i.e., soldering, to soft TEs due to the low thermostability of organics [4] .…”

“…As a possible solution to making electrical contacts based on materials design, we presented a working hypothesis of sticky TE materials to contact with the electrodes by themselves and enable the mass production of flexible TE sheets through lamination or roll-to-roll processes without using electrically conductive adhesives [Figure 1] [4] . The concept of sticky TE materials has been demonstrated using inorganic/organic hybrid materials of TE particles with low-volatilizable organic solvents, which exhibit Seebeck coefficients based on the TE particles and low thermal conductivities based on the organic matrix [5] .…”