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Abstract PEDOT:PSS coated Te (PC Te) nanorod/PEDOT:PSS composite films were prepared by a drop-casting technique. H 2 SO 4 treatment was employed to enhance thermoelectric (TE) properties of the composite films. The addition of PC Te nanorods increased both the electrical conductivity and the Seebeck coefficient of the composite films. An optimized power factor of 141.9 μW/mK2 was obtained for the film containing 90 wt% PC Te nanorods treated with 12 M H 2 SO 4 at room temperature, which was 2.75 times as high as that of the untreated composite film, corresponding to the electrical conductivity and Seebeck coefficient of 204.6 S/cm and 83.27 μV/K, respectively. XPS and GIWAXS analysis revealed the removal of insulating PSS units and the rearrangement of PEDOT chains after the H 2 SO 4 treatment. Finally, a 9-leg TE generator prototype was fabricated using the optimized composite film. The maximum output power and area output power density produced from the prototype were 47.7 nW and 57.2 μW/cm2, respectively, at the temperature difference of 40 K. Graphical abstract Image 1 Highlights • PEDOT:PSS coated Te (PC Te) nanorods were synthesized. • PC Te/PEDOT:PSS composite films were prepared by a drop-casting method. • H 2 SO 4 treatment was used to enhance TE properties of the composite films. • An optimized power factor of 141.9 μW/mK2 was obtained. • A flexible thermoelectric generator prototype was fabricated using the optimized film. [ABSTRACT FROM AUTHOR]

Abstract Herein, we demonstrate a concept of making flexible thermoelectric (TE) generators by applying cotton thread as the platforms for poly(3-hexylthiophene) (P3HT) and Argentum (Ag) paste through selectable coating method. The coated thermoelectric cotton thread can be sewed on the flexible fabrics with different knitting pictures and form thermoelectric devices. The most important is that the temperature gradient of the device was in the direction of cross-plane of the flexible fabrics, that is, between the inner and outer surfaces of clothing, therefore the flexible device can be easily wore on the body since the temperature gradient between the human body and surrounding environment is in the cross-plane direction. The maximum output power of the device with thirteen P N type legs reached 1.15 μW at a temperature gradient of 50 K when the load resistance matched the resistance of the module. Cotton-based TE device coated with P3HT may be useful for the development of self-powered wearable electronics. Highlights • Thermoelectric (TE) cotton thread was obtained through selectable coating method. • Poly(3-hexylthiophene) and Argentum paste was sequentially spaced as p-type leg and n-type leg. • Temperature gradient (ΔT) of the TE device was in the cross-plane direction. • Output power of the flexible TE device reached 1.15 μW at ΔT = 50 K. [ABSTRACT FROM AUTHOR]

The intrinsic ultra-low lattice thermal conductivity ( κ L ) of high performance thermoelectric Cu 2 S may arise from its multiform complex crystal structures while the further sharp drop of κ L observed at elevating temperatures close to the phase transition to hexagonal high-chalcocite is of considerable interest. In this work, in-depth in-situ transmission electron microscopy investigations have been performed by either heating or electron irradiation to analyze the structural evolution of Cu 2 S. Multiple including new phase structures have been observed in Cu 2 S. Upon increasing the temperature, drastic structural changes took place including phase transition among different phases, formation of an intermediate phase, switching of crystal orientation and inverse phase transitions, which indicate multiple forms of Cu ordering with high temperature-sensitivity. Such tremendous structural evolution along with formation and movement of phase boundaries are believed to strongly scatter the phonons. [ABSTRACT FROM AUTHOR]

Polymer/carbon nanotube composites have gained great progress in the past decade. However, the lack of scalability of production due to the relatively high volatility and strong toxicity of the dispersion solvent have created a great need for environmental friendly process for expanding TE applications. In this work, organic-inorganic composite films composed of a novel hydrophilic pyridinium salt polymer (noted as P2 ) and SWCNTs were prepared for thermoelectric application. The novel hydrophilic pyridinium salt polymer was designed and synthesized containing the pyridinium salt for aqueous dissolution and thiophenes as the conjugation group to make the polymer/CNT composite film electrical connecting, therefore improving the thermoelectric performance. Another pyridinium salt polymer (noted as P1 ) without thiophene group was also synthesized for the purpose of comparison. The polymers attach on the surface of CNTs through π-π conjugation interaction between conjugation groups and π-electrons of CNTs. The P2/CNT composites were homogeneously dispersed in the aqueous solution, revealing better dispersion behavior than P1/CNT , which is probably because of the stronger contact interaction between P2 /CNT than P1 /CNT due to the higher electron delocalization of polymer P2 than P1 . The electrical conductivity of P2 /CNT composite film reached the maximum value of 159 S/cm with 50% CNT content. Consequently, a high power factor of 46.4 μW/mK 2 was obtained for the P2 /50%CNT composite film. [ABSTRACT FROM AUTHOR]

The anisotropy in thermoelectric properties of three-dimensional carbon nanotubes (CNTs) and CNT/polyaniline (PANI) composites have been studied by utilizing an orderly aligned CNT arrays with a self-sustained construction. In the length direction of CNT, the electrical conductivity of the CNT array is ∼5 times larger as compared to the direction vertical to the alignment of CNTs, while the difference in thermal conductivity between these two directions is ∼25 times. As a result, strong anisotropic thermoelectric transportation has been also observed in the composites composed of PANI and CNT arrays. An enhanced thermopower in the composites, as compared to the pure PANI or CNTs, is only observed in the direction along the CNTs. This study helps the fundamental understanding on the un-conventional improved thermopower, which is more likely to be realized via adjusting the carrier transportation within the interface between CNTs and PANI rather than across it. [ABSTRACT FROM AUTHOR]

The interfacial stability of thermoelectric (TE) joints is among the key issues determining the durability of thermoelectric generators (TEGs) in practical operation. For skutterudite (SKD) based TEGs, the inter-diffusion between the metal electrode and the SKD material at high temperature plays a vital role on the interfacial stability of the joints. In this work, we report the evolution of the interfacial microstructure and the interfacial contact resistivity for a series of p-type SKD TE joints (Ti/Ce y Fe x Co 4 -x Sb 12 , x = 1.5–4, y = 0.35–1) at high temperature. The growth of the intermetallic compound (IMC) layers at the interface of all the joints was found to be controlled by the diffusion process. In contrast to the binary Ti/CoSb 3 joints, the growth of the interfacial IMC layers in the p-type Ti/Ce y Fe x Co 4 -x Sb 12 joints was considerably depressed. Moreover, no brittle TiCoSb phase was formed at the interface of the p-type joints, which resulted in good stability of the interfacial contact resistivity at high temperature. Related mechanisms were discussed. [ABSTRACT FROM AUTHOR]

Highly (001)-oriented Cu 2- y Se thin films with tunable thermoelectric performances have been grown by pulsed laser deposition. By using targets with different Cu/Se ratios that further determines the copper deficiency of as-grown films, the carrier concentrations of as-grown films are tuned within a broad range from 10 18 to 10 21 cm −3 . The optimum performance is observed at carrier concentration ~1.58×10 20 cm −3 . The distinct properties of Cu 2- y Se thin films with nearly ideal chemical stoichiometric ratio are observed. In addition, a weak change in the electrical transport during the second-order phase transition was observed in the thin films due to the anisotropic structure of the Cu 2- y Se. [ABSTRACT FROM AUTHOR]

Short carbon fiber-reinforced p-type skutterudite CeFe 4 Sb 12 composites were fabricated by a melting-annealing process combined with spark plasma sintering, the effect of carbon fibers on the thermoelectric and mechanical properties were investigated, and the relationship between the microstructure and the mechanical properties of the composites were elucidated. The results indicate that the carbon fibers were well distributed throughout the matrix and were in intimate contact with the CeFe 4 Sb 12 grains without interlayers. Both the flexural strength and the fracture toughness of CeFe 4 Sb 12 were enhanced with the addition of the carbon fibers. Considering the tradeoff between the thermoelectric and mechanical properties, the optimal carbon fiber content was found to be 1 vol.%. The flexural strength of the composite containing 1 vol.% fiber was improved by 53%, whereas the fracture toughness and ZT value remained nearly unchanged. [ABSTRACT FROM AUTHOR]