Thermoelectric Performance Enhancement of Film by Pulse Electric Field and Multi‐Nanocomposite Strategy

Abstract

Thermoelectric (TE) film has wide potential application in low‐grade waste heat recovery and TE generation due to its quick response and multifunctional integration. Multi‐nanocomposite is a promising method to solve the difficulty of maintaining temperature difference and achieving a high figure of merit ZT. However, the depletion layer induced by the multi‐nanocomposite typically degrades performance. This study presents a simple and convenient method to solve this problem by pulse electric field (PEF). Prototypical TE Bi2Te3 is selected as the objective film. The strong current density effect of PEF removes the depletion layer among carbon nanotubes (CNT) and Bi2Te3 grains. Thus, the CNT nanocomposite with PEF treatment breaks the trade‐off between electrical conductivity and Seebeck coefficient, achieving a power factor of 4400 µW m−1 K−2 which stabilizes after annealing effect to 2920 µW m−1 K−2, a record for Bi2Te3 films. Simultaneously, the self‐assembled porosity decreases thermal conductivity via phonon scattering while still maintaining a high electrical conductivity of 3130 S cm−1. Thus, the porosity helps maintain the temperature difference and thereby enables a sharp increase in output power. These results indicate that the combination of PEF and multi‐nanocomposite is a new method to enhance TE performance, which would have a potential application in the commercial field.

Densification Induced Decoupling of Electrical and Thermal Properties in Free‐Standing MWCNT Films for Ultrahigh p‐ and n‐Type Power Factors and Enhanced ZT

“…[25] High power factor (PF) organic free-standing films with high electrical conductivity are still highly desired for making flexible OTEGs, especially for ntype materials. [23,24,[26][27][28][29] In this work, we reported that the PFs of MWCNT films could be further improved to 7.25 mW m −1 K −2 for p-type and 4.34 mW m −1 K −2 for n-type with high electrical conductivity over 10 000 S cm −1 through densifying the MWCNT films. The achieved PFs, to the best of our knowledge, are respectively the top values for both p-and n-type organic flexible TE films.…”

“…[ 25 ] High power factor (PF) organic free‐standing films with high electrical conductivity are still highly desired for making flexible OTEGs, especially for n‐type materials. [ 23,24,26–29 ]…”

“…reported that high power factors of ≈1.8 and ≈1 mW m −1 K −2 for p‐type and n‐type multi‐walled carbon nanotube (MWCNT) films, [ 16 ] respectively. However, the values are still far behind that of state‐of‐the‐art inorganic TE materials (≈4 mW m −1 K −2 for n‐type Bi 2 Te 3 /CNT film) [ 24 ] and carbon nanotube fibers (14 mW m −1 K −2 ). [ 25 ] High power factor (PF) organic free‐standing films with high electrical conductivity are still highly desired for making flexible OTEGs, especially for n‐type materials.…”

Carbon Nanotube/Biomolecule Composite Yarn for Wearable Thermoelectric Applications

“…Considering that method C does not have a centrifugation process, higher D/G + and 2D/G + ratios can stem from short CNT fibers after the mortar agate process. However, the results of Raman spectra cannot explain the change in the thermoelectric performance of CNT yarns because it is known that the Seebeck coefficient decreases by increasing the carrier density, which is related to the increase of defect density. , Therefore, the defect density of CNTs is not the major contributor to the difference in thermoelectric performance with different dispersion methods.…”

Micro TEC Manufacture: the Importance and Challenges

“…There are the familiar characteristics such as no moving parts, no emissions, long operating lifetime, and low maintenance costs; Micro TEC also delivers quick-response and the high-precision tem-perature control by regulation of the input current, making it suitable for spot cooling. The small size and light weight make it the most preferred temperature control solution in electronic components and in other size-critical applications [7,8] .…”