p-Type PVA/MWCNT-Sb2Te3 Composites for Application in Different Types of Flexible Thermoelectric Generators in Combination with n-Type PVA/MWCNT-Bi2Se3 Composites

Abstract

This work is devoted to the fabrication of p-type polyvinyl alcohol (PVA)-based flexible thermoelectric composites using multiwall carbon nanotubes-antimony telluride (MWCNT-Sb2Te3) hybrid filler, the study of the thermoelectrical and mechanical properties of these composites, and the application of these composites in two types (planar and radial) of thermoelectric generators (TEG) in combination with the previously reported PVA/MWCNT-Bi2Se3 flexible thermoelectric composites. While the power factors of PVA/MWCNT-Sb2Te3 and PVA/MWCNT-Bi2Se3 composites with 15 wt.% filler were found to be similar, the PVA/MWCNT-Sb2Te3 composite with 25 wt.% filler showed a ~2 times higher power factor in comparison with the PVA/MWCNT-Bi2Se3 composites with 30 wt.% filler, which is attributed to its reduced electrical resistivity. In addition, developed PVA/MWCNT-Sb2Te3 composites showed a superior mechanical, electrical, and thermoelectric stability during 100 consequent bending cycles down to a 3 mm radius, with insignificant fluctuations of the resistance within 0.01% of the initial resistance value of the not bent sample. Demonstrated for the first time, 2-leg TEGs composed from p-type PVA/MWCNT-Sb2Te3 and n-type PVA/MWCNT-Bi2Se3 composites showed a stable performance under different external loads and showed their potential for applications involving low temperature gradients and power requirements in the range of nW.

Positive and Negative Changes in the Electrical Conductance Related to Hybrid Filler Distribution Gradient in Composite Flexible Thermoelectric Films Subjected to Bending

“…In addition, low-intensity diffraction peaks related to Sb 2 O 3 ( Figure 1 d, blue curve) and Te ( Figure 1 d, green curve) were observed, indicating the presence of native oxide layer on the Sb 2 Te 3 nanostructures, as well as possible inclusion of clusters of Te in the Sb 2 Te 3 -MWCNT heterostructures. These results are consistent with the previously reported for the MWCNT-Sb 2 Te 3 heterostructures [ 13 ].…”

“…For the fabrication of flexible films containing encapsulated Sb 2 Te 3 -MWCNT or bare MWCNTs, the heterostructures were deposited on polyimide substrates, then coated with PDMS (Sigma-Aldrich, Inc., St. Louis, MI, USA), cured for 10 min in 150 °C, and then the resulting elastic film was lifted off the glass using tweezers. For the fabrication of mixed composite, the Sb 2 Te 3 -MWCNT heterostructures were deposited on glass substrates, then scrapped off the substrates and mixed in PVA (Sigma-Aldrich, Inc., St. Louis, MI, USA) as described elsewhere [ 13 ].…”

“…Recently, it was shown that using CNTs as a scaffold for the deposition of inorganic thermoelectric nanostructures as Bi 2 Te 3 , Bi 2 Se 3 or Sb 2 Te 3 allows to obtain effective flexible thermoelectric material [ 10 , 11 , 12 ]. Such networks of Bi 2 Se 3 -CNT and Sb 2 Te 3 -CNT heterostructures can also be used for the fabrication of effective flexible thermoelectric composites based on polyvinyl alcohol (PVA) matrix [ 6 , 7 , 13 ]. For the fabrication of these composites, the TE fillers were prepared by direct deposition of inorganic Bi 2 Se 3 or Sb 2 Te 3 nanostructures on a multiwalled CNT network [ 12 ], and further mixed-in or encapsulated-by a polymer [ 6 , 7 , 13 ].…”

“…Such networks of Bi 2 Se 3 -CNT and Sb 2 Te 3 -CNT heterostructures can also be used for the fabrication of effective flexible thermoelectric composites based on polyvinyl alcohol (PVA) matrix [ 6 , 7 , 13 ]. For the fabrication of these composites, the TE fillers were prepared by direct deposition of inorganic Bi 2 Se 3 or Sb 2 Te 3 nanostructures on a multiwalled CNT network [ 12 ], and further mixed-in or encapsulated-by a polymer [ 6 , 7 , 13 ]. Both mixing and encapsulation approaches resulted in a gradient distribution of the TE filler across the polymer matrix due to the fabrication issues.…”

Fabrication and Characterization of Encapsulated CNT-Sb2Te3 Thermoelectrical Hybrid Structures

“…Previously, it has been shown that direct deposition of bismuth or antimony chalcogenides on pre-fabricated CNT scaffolds results in a formation of flexible n-type CNT-Bi2Se3 or p-type CNT-Sb2Te3 hybrid networks, exhibiting Seebeck coefficients comparable with the values reported for bulk Bi2Se3 or Sb2Te3 [3]. Recently, an approach of the application of CNT-Bi2Se3 and CNT-Sb2Te3 hybrid networks for the fabrication of n-type and p-type PVA-based TE composites and the development of flexible TEG has been demonstrated [4]. However, the thermoelectric efficiency of these composites was low due to the high resistance of the nanocomposites.…”