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The poly(3,4-ethylenedioxythiophene)/single walled carbon nanotube (PEDOT/SWCNT) composite films with various SWCNT contents (0–50 wt.%) have been prepared by a vapor phase polymerization technique for the first time. The Seebeck coefficients of the composite films increase with the SWCNT contents. The maximum power factor is 37.8 μW mK −2 for a composite film with 35 wt% SWCNT, which is 1.7 times as high as that of the film without SWCNTs. The composite film with 35 wt% SWCNT has then been treated with a 0.04 wt% NaBH 4 /DMSO solution and the power factor increases to 44.1 μW mK −2 after the treatment. The PEDOT chains are more orderly arranged and with decreased doping level by forming composites with SWCNT and may be de-doped further after further treated with NaBH 4 /DMSO. Therefore, the Seebeck coefficient of the composite film has been further enhanced. [ABSTRACT FROM AUTHOR]

MoS 2 nanosheets with size of several-hundred nanometers were prepared by a hydrothermal intercalation/exfoliation method, then MoS 2 /Bi 2 Te 3 composite nanopowders were prepared by a microwave-assisted wet chemical method using the MoS 2 nanosheets, TeO 2 , Bi(NO 3 ) 3 ·5H 2 O, KOH and ethylene glycol as raw materials. Bulk MoS 2 /Bi 2 Te 3 nanocomposites were prepared by hot pressing the MoS 2 /Bi 2 Te 3 composite nanopowders with MoS 2 nanosheet content ranging from 0 to 17 wt% at 80 MPa and 648 K in vacuum. X-ray photoelectron spectroscopy and X-ray diffraction analyses indicate that MoS 2 and Bi 2 Te 3 did not react each other during the hot pressing. FESEM observation reveals that the MoS 2 /Bi 2 Te 3 composite samples had a more compact microstructure than the pristine Bi 2 Te 3 bulk sample. The MoS 2 phase was relatively randomly dispersed in the composite. At a given temperature, the electrical conductivity of the composites increases first then decreases as the MoS 2 content increases, whereas the Seebeck coefficient of the bulk nanocomposites does not change much. A highest power factor, ~18.3 μW cm −1 K −2 which is about 30% higher than that of pristine Bi 2 Te 3 sample, at 319 K has been achieved from a nanocomposite sample containing 6 wt% MoS 2 . [ABSTRACT FROM AUTHOR]

Poly(3,4-ethylenedioxythiophene)-tosylate-polyethylene glycol- polypropylene glycol-polyethylene glycol (PEDOT-Tos-PPP) films were prepared via a vapor phase polymerization (VPP) method. The thermoelectric (TE) properties of the films before and after treated with various concentrations of HI acid have been studied. The electrical conductivity and Seebeck coefficient of the films simultaneously increased after treated with dilute HI acid solutions (<5 wt%). The electrical conductivity of the film treated with 5 wt% HI acid increased from 1532 to 1690 S cm −1 and the Seebeck coefficient increased slightly from 14.9 to 20.3 μV K −1 . The maximum power factor value of the treated film is 69.6 μW m −1 K −2 at 304 K, which is about twice as high as that of the pristine film (33.8 μW m −1 K −2 ). Field emission scanning electron microscopy (FESEM), Raman spectroscopy analyses and the thickness measurement of the films indicate that the tri-block copolymer PPP have been removed by the HI acid treatment. The UV–vis-NIR absorption spectroscopy and X-ray photoelectron spectroscopy (XPS) analyses reveal that iodine anions (I − , I 3 − and I 5 − ) exist as dopants in the film after the treatment. The TE properties enhancement are, therefore, attributed to the combined effects of the removal of the insulating PPP and Tos − and iodine ions doping by the HI acid treatment. [ABSTRACT FROM AUTHOR]

ZnO flower/poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) composite films were prepared by spin-coating dimethyl sulfoxide doped PEDOT:PSS on the ZnO flowers grown on glass substrate. The thermoelectric properties of the ZnO flower/PEDOT:PSS composite films were measured at room temperature. As the number of spin coated PEDOT:PSS layer increased, the electrical conductivity of the ZnO flower/PEDOT:PSS composite films increases dramatically from 1-layer (177.3 S/m) to 4-layer (910.4 S/m), however, all the composite films have almost the same Seebeck coefficient (~20-22 μV/K). A maximum power factor of ~0.4 μWm K at room temperature was obtained from the composite film with 4-layer PEDOT:PSS. [ABSTRACT FROM AUTHOR]

Poly(3,4-ethylenedioxythiophene)–tosylate–polyethylene glycol–polypropylene glycol–polyethylene glycol (PEDOT–Tos–PPP) films were prepared via a vapor phase polymerization (VPP) method. The films possess good electrical conductivity (1550 S cm −1 ), low Seebeck coefficient (14.9 μV K −1 ) and thermal conductivity (0.501 W m −1 K −1 ), and ZT ∼ 0.02 at room temperature (RT, 295 K). Then, the films were treated with NaBH 4 /DMSO solutions of different NaBH 4 concentrations to adjust the redox level. After the NaBH 4 /DMSO treatment (dedoping), the electrical conductivity of the films continuously decreased from 1550 to 5.7 S cm −1 , whereas the Seebeck coefficient steeply increased from 14.9 to 143.5 μV K −1 . A maximum power factor of 98.1 μW m −1 K −2 has been achieved at an optimum redox level. In addition, the thermal conductivity of the PEDOT–Tos–PPP films decrease from 0.501 to 0.451 W m −1 K −1 after treated with 0.04% NaBH 4 /DMSO solution. A maximum ZT value of 0.064 has been achieved at RT. The electrical conductivity and thermal conductivity (Seebeck coefficient) of the untreated and 0.04% NaBH 4 /DMSO treated PEDOT–Tos–PPP films decrease (increases) with increasing temperature from 295 to 385 K. And the power factor of the films monotonically increases with temperature. The ZT at 385 K of the 0.04% NaBH 4 /DMSO treated film is 0.155. [ABSTRACT FROM AUTHOR]

Poly(3,4-ethylenedioxythiophene)–tosylate–polyethylene glycol–polypropylene glycol–polyethylene glycol (PEDOT–Tos–PPP) films were prepared via a vapor phase polymerization (VPP) method. The thermoelectric (TE) properties of the films before and after treated with H 2 SO 4 at different concentrations were measured at 295 K. The TE properties of the films have been significantly improved by the H 2 SO 4 treatment. For example, after treated with H 2 SO 4 at 1 M, the electrical conductivity of the film has increased remarkably from 944 to 1750 S cm −1 , the Seebeck coefficient of the film reduced slightly from 16.5 to 14.6 μV K −1 , and the thermal conductivity decreased from 0.495 to 0.474 W/mK. Hence, the ZT value at 295 K has increased from 0.016 to 0.024. The electrical conductivity (Seebeck coefficient) of the untreated and 1 M H 2 SO 4 treated PEDOT-Tos-PPP films decreases (increases) with increasing temperature from 295 to 375 K. And the power factor of the films monotonically increases with temperature. The power factor at 375 K of the 1 M H 2 SO 4 treated film is almost twice as high as that at 295 K. Atomic force microscope (AFM) and X-ray photoelectron spectroscopy (XPS) analyses, and the thickness measurement of the films indicate that the tri-block copolymer PPP have been removed from the PEDOT-Tos-PPP films after the H 2 SO 4 treatment, and the UV–Vis-NIR absorption spectroscopy and Raman spectroscopy analyses reveal an increasing in the doping level in the PEDOT chains after the H 2 SO 4 treatment. Therefore, the TE properties enhancement may be attributed to the combined effects of the removal of the insulating PPP from the PEDOT-Tos-PPP film, increase the doping level and conformational change of the PEDOT chains resulted from the H 2 SO 4 treatment. [ABSTRACT FROM AUTHOR]

Ag-poly(3,4-ethylenedioxythiophene) (PEDOT) and Cu-PEDOT nanocomposites have been synthesized by an interfacial polymerization method, using 3,4-ethylenedioxythiophene (EDOT) and AgNO or Cu(NO) as starting materials. Ag-PEDOT or Cu-PEDOT nanocomposites prepared at an interface of n-hexane and acetonitrile are spherical Ag- or Cu- nanoparticle (0D)-modified PEDOT nanostructures, while a Cu-PEDOT nanocomposite prepared at an interface of n-hexane and a mixture of acetonitrile and glycol exhibits a different morphology: Cu nanostructures are needle-like (1D) and embedded in a PEDOT matrix. Ag- or Cu-nanoparticle contents in the composites can be tuned by changing oxidant (AgNO or Cu(NO))/EDOT molar ratios, and thermoelectric properties of the pellets cold pressed from composite powders with different Ag or Cu contents have been measured at room temperature. When the oxidant/EDOT molar ratio is 2, both Ag-PEDOT and Cu-PEDOT nanocomposites with spherical Cu nanoparticles reach their largest power factors of 1.49 and 7.07 μW mK, respectively, while Cu-PEDOT nanocomposite with needle-like Cu nanoparticles has consistently higher power factor than the above composites. When the oxidant/EDOT molar ratio is 1, it reaches its largest power factor of 12.47 μW mK and the highest ZT value of 0.01 at room temperature. [ABSTRACT FROM AUTHOR]

Abstract: SnSe1−x Te x (x=0, 0.0625) bulk materials were fabricated by melting Sn, Se and Te powders and then hot pressing them at various temperatures. The phase compositions of the materials were determined by X-ray diffraction (XRD) and the crystal lattice parameters were refined by the Rietveld method performed with DBWS. XRD analysis revealed that the grains in the materials preferentially grew along the (l00) directions. The structural behavior of SnSe1−x Te x (x=0, 0.0625) was calculated using CASTEP package provided by Materials Studio. We found that the band gap of SnSe reduced from 0.643 to 0.608eV after Te doping. The calculated results were in good agreement with experimental results. The electrical conductivity and the Seebeck coefficient of the as-prepared materials were measured from room temperature to 673K. The maximum power factor of SnSe is ∼0.7μWcm−1K−2 at 673K. [Copyright &y& Elsevier]

BiTe/Polythiophene (PTH) thermoelectric bulk composite materials were prepared by a two-step method. Firstly, BiTe and PTH nanopowders were prepared by hydrothermal synthesis and chemical oxidative polymerization, respectively. Secondly, the mixture of the BiTe and PTH nanopowders (50:50 wt) was pressed under vacuum at 80 MPa and 298, 473, or 623 K. For comparison, BiTe powders were hot pressed at 623 K. The bulk materials were analyzed by conventional methods, such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy, thermogravimetric analysis (TGA) and field emission scanning electron microscopy equipped with electron dispersive X-ray spectroscopy. The XRD and TGA results showed that the PTH decomposed when the hot pressing temperature exceeded 473 K, and BiTeS phase was formed. The thermoelectric properties of the bulk composite materials were investigated. The composite pressed at 623 K showed a higher power factor, ~2.54 μ Wm K at 473 K, which is as ~20 times as that of the composite pressed at 473 K, although, it is still much lower than that of the pressed BiTe material (~1,266 μ Wm K at 348 K). [ABSTRACT FROM AUTHOR]

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: A thermoelectric (TE) material is a material where a potential difference is generated as a result of a temperature difference or the corollary of this where a temperature difference is generated when a voltage is applied. These phenomena can be used to generate electricity and/or control temperature. Traditionally, thermoelectric materials are inorganic semiconductors which have been limited in their application by low efficiency and high cost. Since the 1990s, both theoretical and experimental studies have shown that low-dimensional TE materials, such as superlattices and nanowires, can enhance the value of the TE figure of merit (ZT) which is an indicator of TE thermodynamic efficiency. To date it has not been feasible to apply these materials in large-scale energy-conversion processes because of limitations in both their heat transfer efficiency and cost. When compared to inorganic materials, organic conducting polymers possess some unique features, such as low density, low cost, low thermal conductivity, easy synthesis and versatile processability and their use in preparing polymer-inorganic TE nanocomposites appears to have great potential for producing relatively low cost and high-performance TE materials. Recently, an increasing number of studies have reported on polymeric and polymer-inorganic TE nanocomposite materials. The purpose of this paper is to review the research progress on the conducting polymers and their corresponding TE nanocomposites. Its main focus is the TE nanocomposites based on conducting polymers such as polyaniline (PANI), polythiophene (PTH), poly (3, 4-ethylenedioxythiophene): poly (styrenesulfonate) (PEDOT:PSS), as well as other polymers such as polyacetylene (PA), polypyrrole (PPY), polycarbazoles (PC) and polyphenylenevinylene (PPV). Typically, polymer-inorganic TE nanocomposites are produced by physical mixing, solution mixing and in situ polymerization. The key factors that limit the use of these polymers and their polymer-inorganic TE nanocomposites as TE materials are their low ZT values. More recent developments designed to overcome the limitation including, for example, the use of carbon nanotubes and graphenes and the use of computational modelling to accelerate the selection of suitable pairs of conductive polymer and inorganic TE materials to achieve best possible nanocomposites are reviewed. [Copyright &y& Elsevier]

Nowadays, thermoelectric (TE) materials have gained considerable attention due to their unique ability to directly convert waste heat to electricity and vice versa . For a long time, researchers have mainly focused on developing high-performance inorganic TE materials, e.g., Bi-Te, Pb-Te, and Si-Ge based alloys, etc. However, inorganic TE materials have various disadvantages, such as high-cost, heavy metal contamination, as well as relatively poor processability, etc. Compared to inorganic TE materials, poly(3,4-ethylenedioxythiophene) (PEDOT) has great potential to be used for TE materials, due to its low thermal conductivity, low-cost, and low-density, etc. Therefore, more and more attention has been focused on the preparation and TE properties of PEDOT and PEDOT based nanocomposites, especially one-dimensional (1-D) PEDOT and 1-D PEDOT based nanocomposites, due to 1-D nanostructures always have enhanced TE properties. This article presents an overview of the synthesis of PEDOT nanoparticles, 1-D PEDOT nanostructures and their corresponding nanocomposites, as well as TE properties. [ABSTRACT FROM AUTHOR]