Thermoelectric Properties Of PEDOT Research Articles

Raman Spectroscopy and Thermoelectric Characterization of Composite Thin Films of Cu2ZnSnS4 Nanocrystals Embedded in a Conductive Polymer PEDOT:PSS

Cu2ZnSnS4 (CZTS) is an intensively studied potential solar cell absorber and a promising thermoelectric (TE) material. In the form of colloidal nanocrystals (NCs), it is very convenient to form thin films on various substrates. Here, we investigate composites of CZTS NCs with PEDOT:PSS, a widely used photovoltaics polymer. We focus on the investigation of the structural stability of both NCs and polymers in composite thin films with different NC-to-polymer ratios. We studied both pristine films and those subjected to flash lamp annealing (FLA) or laser irradiation with various power densities. Raman spectroscopy was used as the main characterization technique because the vibrational modes of CZTS NCs and the polymer can be acquired in one spectrum and thus allow the properties of both parts of the composite to be monitored simultaneously. We found that CZTS NCs and PEDOT:PSS mutually influence each other in the composite. The thermoelectric properties of PEDOT:PSS/CZTS composite films were found to be higher compared to the films consisting of bare materials, and they can be further improved by adding DMSO. However, the presence of NCs in the polymer deteriorates its structural stability when subjected to FLA or laser treatment.

Thermoelectric Properties of PEDOT:PSS Containing Connected Copper Selenide Nanowires Synthesized by the Photoreduction Method.

Organic materials have attracted attention for thermoelectric materials reusing low-temperature waste heat. For the thermoelectric performance enhancement of organic materials, the introduction of inorganic nanowires is effective due to the percolation effect. In this study, we synthesized Cu2Se NWs by the photoreduction method and prepared poly(3,4-ethylenedioxythiophene):poly (styrene sulfonate) (PEDOT:PSS) thin films containing Cu2Se NWs by spin-coating PEDOT:PSS and Cu2Se NWs alternatively. The composite films exhibited a drastic increase in electrical conductivity at more than 40 wt % Cu2Se, and the Cu2Se amount threshold was in good agreement with surface structures as observed by a scanning electron microscope. This indicates that the percolation effect of connected Cu2Se NWs brought high electrical conductivity. As a result, the composite thin films exhibited a higher power factor than the PEDOT:PSS film. This power factor enhancement by the percolation effect would be expected to contribute to the development of thermoelectric performance enhancement for organic materials.

Enhanced thermoelectric performance of PEDOT: PSS films via ionic liquid post-treatment

Thermoelectric (TE) energy harvesting can effectively convert waste heat into electricity, which is a crucial technology to solve energy concerns. As a promising candidate for energy conversion, poly(3,4-ethylenedioxythiophene): poly (styrene sulfonate) (PEDOT:PSS) has gained significant attention owing to its easy doping, high transparency, and solution processability. However, the TE performance of PEDOT:PSS still needs to be further enhanced. Herein, different approaches have been applied for tuning the TE properties: (i) direct dipping PEDOT:PSS thin films in ionic liquid; (ii) post-treatment of the films with concentrated sulfuric acid (H2SO4), and then dipping in ionic liquid. Besides, the same bis(trifluoromethanesulfonyl)amide (TFSI) anion and different cation salts, including 1-ethyl-3-methylimidazolium (EMIM+) and lithium (Li+), are selected to study the influence of varying cation types on the TE properties of PEDOT:PSS. The Seebeck coefficient and electrical conductivity of the PEDOT:PSS film treated with H2SO4EMIM:TFSI increase simultaneously, and the resulting maximum power factor is 46.7 μW⋅m−1⋅K–2, which may be attributed to the ionic liquid facilitating the rearrangement of the molecular chain of PEDOT. The work provides a reference for the development of organic films with high TE properties.

Thermoelectric properties of PEDOT:PSS/SWCNT composite films with controlled carrier density

Previously, we developed a simple method to fabricate a composite film of a conducting polymer (PEDOT:PSS) and single-walled carbon nanotubes (SWCNTs) that exhibited high thermoelectric performance. In the present work, the carrier density of the composite film was controlled using an electrochemical method. The thermoelectric performances of the obtained composite films were analyzed in terms of their carrier densities. The electrical conductivities of the composite films were affected by the change in the carrier species of PEDOT:PSS, but overall the values were relatively high owing to the SWCNTs. The Seebeck effect showed a unique behavior reflecting the van Hove singularity in response to variations in the carrier density.

Tunable thermoelectric properties of free-standing PEDOT nanofiber film through adjusting its nanostructure

Recently, organic thermoelectric (TE) materials have attracted increasing attention in green energy conversion. However, researches on polymer nanostructured TE materials are still scarce, especially for the 1 D nanostructured polymer materials. In this work, 1D poly(3,4-ethylenedioxythiophene) (PEDOT) nanofiber was synthesized by a self-assembled micellar soft-template approach using anionic surfactant sodium dodecyl sulfate (SDS). Then, a flexible and free-standing PEDOT nanofiber film was prepared through a simple vacuum-assisted filtration method. FE-SEM and TEM characteristics real 1D configuration for all the PEDOT nanostructures. Through adjusting the molar ratio of SDS, oxidizing agent FeCl3 and EDOT monomer (nSDS: nFeCl3: nEDOT), nanofiber with different diameter (10–200 nm) and microtopography can be obtained. Electrical conductivity and Seebeck coefficient measurement indicates that the TE properties of PEDOT can be effectively tuned by adjusting its nanostructure, and a variation range as high as three orders of magnitude for the power factors (10-2–101 μW/mK2) can be realized. Due to a more ordered structure caused by the edge-on packing mode of PEDOT chain, the sample prepared with nSDS: nFeCl3: nEDOT = 30:15:7 shows the highest power factor of 7.2 μW/mK2. This value can be further enhanced to 14.4 μW/mK2 by constructing PEDOT nanofiber/SWCNTs composite.

Enhancements in the Mechanical Stretchability and Thermoelectric Properties of PEDOT:PSS for Flexible Electronics Applications

ConspectusIntrinsically conducting polymers can have important application in flexible electronic devices and systems owing to their high mechanical flexibility. Among them, poly(3,4-ethylenedioxyt...

Thermoelectric properties of PEDOT:PSS aerogel secondary-doped in supercritical CO2 atmosphere with low thermal conductivity

A poly (3,4-ethylenedioxythiophene):poly (styrene sulfonate) (PEDOT:PSS) aerogel was fabricated simply by freeze-drying as a thermoelectric (TE) material with low thermal conductivity. Conventional methods used to enhance the electrical conductivity of PEDOT:PSS, such as the addition of a secondary dopant to the dispersion and dipping in a secondary dopant, caused shrinkage and a reduction of the advantageous low thermal conductivity in the case of aerogel. Therefore, we have applied secondary doping in supercritical CO2 (ScCO2) atmosphere to maintain the porous structure of the aerogel so that a temperature gradient can be maintained. The structure and TE performance of PEDOT:PSS aerogels treated with secondary doping by the dipping and ScCO2 methods were investigated. The ScCO2 method caused little shrinkage of PEDOT:PSS aerogel with conductivity improvement by four orders of magnitude. The secondary doping with ScCO2 could be promising method for PEDOT-based TE devices with porous structure.

Thermoelectric properties of PEDOT: PSS and acid-treated SWCNT composite films

We investigated the thermoelectric properties of composite films that consist of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) and single-walled carbon nanotubes (SWCNTs). Thin films with 5−10 μm thickness of PEDOT:PSS/SWCNT and PEDOT:PSS/acid-treated SWCNT (AC-SWCNT) were prepared by varying the CNT content to determine their power factor. Both PEDOT:PSS/SWCNT and PEDOT:PSS/AC-SWCNT films showed an increase in their power factors with CNT content. The power factor values of PEDOT:PSS/AC-SWCNT films were higher than those of PEDOT:PSS/SWCNT films over the entire experimental range, which was mainly attributed to the significantly increased electrical conductivity. Thus, a series of PEDOT:PSS/AC-SWCNT freestanding films with 100−250 μm thickness were synthesized, and the same sample was used to measure electrical conductivity, Seebeck coefficient, and thermal conductivity to calculate the in-plane figure-of-merit ZT values. The composite films exhibited lower ZT values than those of PEDOT:PSS and AC-SWCNT films because of the high in-plane thermal conductivity caused by the dimensional anisotropy of AC-SWCNTs.

Influence of pressure of nitrogen gas on structure and thermoelectric properties of acid-treated PEDOT:PSS films

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is the most commonly investigated conductive polymer due to its unique thermoelectric properties. Several post treatments using various acids have been reported to improve the thermoelectric properties of PEDOT:PSS. In most articles, however, only the role of acids on the structure and thermoelectric properties of PEDOT:PSS were reported. In this article, we report the major role of the pressure of nitrogen gas (N2) on the structure and thermoelectric properties of PEDOT:PSS after treatment with various acids at optimized temperatures. After treatment with acids followed by N2 gas-passing, electrical conductivity enhances significantly. Therefore, N2 gas-passing after acid treatments results in higher thermoelectric properties than other traditional acid treatment methods. The enhancement in electrical conductivity is attributed to the removal of insulating PSS and the conformational change of the PEDOT chain. Furthermore, the pressure of N2 is responsible for the additional conformation of PEDOT chain, favoring the linear orientation of the PEDOT structure and resulting in an improvement of the electrical conductivity.

Preparation and thermoelectric properties of PEDOT:PSS coated Te nanorod/PEDOT:PSS composite films

Abstract PEDOT:PSS coated Te (PC Te) nanorod/PEDOT:PSS composite films were prepared by a drop-casting technique. H2SO4 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 H2SO4 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 H2SO4 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.

Facile preparation and thermoelectric properties of PEDOT nanowires/Bi2Te3 nanocomposites

Poly (3,4-ethylenedioxythiophene) nanowires (PEDOT NWs) with high electric conductivity were synthesized by a facile self-assembled micellar soft-template method. And then, Bi2Te3 powders and Bi2Te3 nanowires (Bi2Te3 NWs) were added as inorganic filler to form the PEDOT NWs/inorganic nanocomposite films by a simple and convenient vacuum filtration method. The thermoelectric (TE) properties of the flexible films were characterized. PEDOT NWs film exhibited the high σ value of 249.5 S cm−1 and does not require any treatment at room temperature. By incorporating both Bi2Te3 powders and Bi2Te3 NWs into these PEDOT NWs, the power factor of the polymer/inorganic composite materials is enhanced. The resulting PEDOT NWs/Bi2Te3 powders nanocomposite film exhibited a high power factor of 7.49 µW m−1 K−2 compared to that of 2.54 µW m−1 K−2 in PEDOT NWs. A maximum power factor of 9.06 µW m−1 K−2 is obtained from the PEDOT NWs/Bi2Te3 NWs composite film containing 10 wt% Bi2Te3 NWs at room temperature, which is about 3 of times that of the pure PEDOT NWs film. These composites provide a promising route to flexible and high-performance thermoelectric materials.

Higher PEDOT Molecular Weight Giving Rise to Higher Thermoelectric Property of PEDOT:PSS: A Comparative Study of Clevios P and Clevios PH1000.

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is a promising candidate as the next-generation thermoelectric (TE) material. Its TE properties are strongly dependent on its chemical and electronic structures. In this paper, we investigated the effect of PEDOT molecular weight on the TE properties of PEDOT:PSS films by a comparative study on two commercial grades of PEDOT:PSS, Clevios P, and Clevios PH1000. Dynamic light scattering (DLS) and Raman spectra imply that the PEDOT of Clevios PH1000 possesses longer conjugated chains than that of Clevios P. The TE properties of both the Clevios P and Clevios PH1000 films can be significantly enhanced through various post treatments, including solvent treatment, germinal diol treatment, organic solution treatment, and acid treatment. After these treatments, the treated Clevios PH1000 films constantly show both superior Seebeck coefficients and electrical conductivities over the treated Clevios P films. It is attributed to the higher molecular weight of PEDOT for the former than the latter. For the treated Clevios PH1000, longer PEDOT chains result in large PEDOT domains, facilitating the charge conduction a semimetallic behavior. Tuning the oxidation level of PEDOT:PSS is a facile way to enhance their TE property. A base treatment with sodium hydroxide was subsequently performed on both the treated Clevios P and Clevios PH1000 films. The power factors of both grades of PEDOT:PSS films were remarkably increased by a factor of 1.2-3.6. Still, both the conductivity and the Seebeck coefficient of a based-treated Clevios PH1000 film are superior over those of a control Clevios P film. The highest power factor the former is 334 μW/(m K2) for the former while only 11.4 μW/(m K2) for the latter. They are different by a factor of about 30 times.

Synergistic effect of graphene oxide and wet-chemical hydrazine/deionized water solution treatment on the thermoelectric properties of PEDOT:PSS sprayed films

The study of thermoelectric materials based on conductive polymers has been reinvigorated because of the hope of improving the thermoelectric properties and, therefore, the thermoelectric efficiency of these materials using nanostructures and nanoengineering. This work, shows the results of flexible thin film composites of graphene oxide and poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS), processed by simple and industrially scalable spray coating on polyethylene terephthalate substrates and subsequently treated with hydrazine (Hz) water solution. The power factor of PEDOT:PSS pristine films was found to be 14.3μWm−1K−2. On one hand, this power factor was increased to 21.3μWm−1K−2 (1.49 times higher) when 3wt.% of graphene oxide (GO) was present in the PEDOT:PSS film. On the other hand, the power factor (PF) was increased to 35.7μWm−1K−2 (2.59 times higher) when a very simple Hz water solution treatment was performed to the neat PEDOT:PSS pristine film. Nevertheless, the best power factor is attained when both, addition of GO and treatment with Hz are performed, obtaining a PF of 47.4μWm−1K−2 (3.31 times higher). Furthermore the optimum Hz water solution concentration is reduced by 10 times when GO is present. We report a ZT of 0.084 at 300K if a thermal conductivity of 0.17Wm−1K−1 is assumed. These results remark the importance of studying nanomaterials addition and reduction treatments at the same time when trying to enhance the thermoelectric performance of conductive polymers.

Significant Enhancement in the Thermoelectric Properties of PEDOT:PSS Films through a Treatment with Organic Solutions of Inorganic Salts.

PSS) films through a treatment with organic solutions of inorganic salts. N,N-Dimethylformamide (DMF) and a common inorganic salt like zinc chloride (ZnCl2) are used as the solvent and solute of the solutions, respectively. The treatments can significantly increase both the Seebeck coefficient and electrical conductivity of the PSS films. The thermoelectric properties of the PSS films are sensitive to the experimental conditions, such as the salt concentration, treatment temperature, and the cation of the salts. After treatment at the optimal experimental conditions, the PSS films can exhibit a Seebeck coefficient of 26.1 μV/K and an electrical conductivity of over 1400 S/cm at room temperature. The corresponding power factor is 98.2 μW/(m·K(2)). The mechanism for the enhancement in the thermoelectric properties is attributed to the segregation of some PSSH chains from PSS and the conformation change of PEDOT chains as a result of the synergetic effects of inorganic salts and DMF.

Sulfuric acid vapor treatment for enhancing the thermoelectric properties of PEDOT:PSS thin-films

We introduce a sulfuric acid vapor treatment method to enhance the thermoelectric (TE) performance of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) thin-films. The H2SO4 vapor treatment brought about the reduction of Coulomb interaction between PEDOT and PSS chains and structural rearrangement of PEDOT:PSS as expanded coil-like nanostructure. We studied the effects of the H2SO4 vapor treatment on the electrical conductivity and TE properties of PEDOT:PSS thin-films at various treatment temperatures. By the H2SO4 vapor treatment at 140 °C, both electrical conductivity and Seebeck coefficient of the PEDOT:PSS thin-film were improved from 1.1 to 1167 S/cm, and from 7.3 to 12.1 μV/K, respectively. At this condition, the maximum power factor of 17.0 μW/mK2 was obtained, which is higher than that of the pristine PEDOT:PSS film (0.006 μW/mK2) by the factor of 2833. Because the H2SO4 vapor treatment method introduced here has advantages in the large-area process and the film uniformity, we believe that the method can be applicable to various organic electronic devices using PEDOT:PSS as well as TE devices.

Thermoelectric properties of PEDOT nanowire/PEDOT hybrids.

PSS mixed with 5 vol% dimethyl sulfoxide while the low thermal conductivity was still maintained. Such a significant improvement could be attributed to the synergistic effects of interfacial energy filtering, component contributions, and changes of carrier concentrations in the host materials. Upon addition of 0.2 wt% PEDOT nanowires, the resultant composites demonstrated a power factor as high as 446.6 μW m(-1) K(-2) and the thermoelectric figure of merit could reach 0.44 at room temperature. The thermoelectric devices were investigated by using the PEDOT nanowire/PEDOT hybrid as a p-type leg and nitrogen-doped graphene as an n-type leg. The normalized power output was as high as ∼0.5 mW m(-2) for a temperature gradient of ΔT = 10.1 °C, indicating great potential for practical applications. These findings open up a new route towards high-performance organic thermoelectric materials and devices.

Improved Thermoelectric Properties of PEDOT:PSS Nanofilms Treated with Oxalic Acid

Poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) nanofilms were prepared by a simple spin-coating method. The thermoelectric properties of PEDOT:PSS nanofilms were improved by treatment with different concentrations of oxalic acid at 140°C. The electrical conductivity of PEDOT:PSS nanofilms can be improved from 0.48 to over 800 S cm−1, that is, by a factor of more than 1600 higher than for untreated PEDOT:PSS films. The Seebeck coefficient of the PEDOT:PSS nanofilms decreases slightly and the electrical conductivity increases. The maximum power factor of PEDOT:PSS nanofilms is up to 6.96 μW m−1 K−2. Atomic force microscopy and x-ray photoelectron spectroscopy were conducted to characterize the PEDOT:PSS nanofilms.

Effect of bismuth telluride concentration on the thermoelectric properties of PEDOT:PSS–glycerol organic films

In this work, the effect of bismuth-telluride concentration on the thermoelectric properties of PEDOT:PSS–Glycerol thin films is investigated. A thermoelectric device was fabricated by depositing the n-type and the p-type Bi2Te3 (BT) doped-PEDOT:PSS–Glycerol on a glass substrate via a spin coating method at 500rpm. Room-temperature electrical properties characterization shows that the electrical conductivity of both type thin film increases with increasing of BT doping concentration and optimum at concentration of 0.8wt% for both p-type and n-type thin films, i.e. 17.9S/cm and 7.78S/cm, respectively. However, the study of the temperature effect on the thin films electrical conductivity suggested that the thermoelectric properties of both types' samples improved with increasing of BT concentration and optimum at 0.8 and 0.6wt% for p-type and n-type thin films, respectively. It then decreased if the BT concentration further increased. The Sebeeck coefficient for these samples is as high as −11.9 and −15.7uV/K, which is equivalent to a power factors of 0.26 and 0.19μSV2/ (mK2), respectively. A thermoelectric device resembling a thermocouple system that was fabricated using the optimum p-type and n-type thin films can generate a voltage as high as 1.1V at a temperature difference as low as 55K, which is equivalent to a maximum power of 6.026μW at Vmax.power of 0.5489V (for an estimated matched-load of 50Ω). The present materials system is potential for powering low power consumption electronic devices.

6PM3-PMN-016 ポリチオフェン系導電性高分子の熱電特性に及ぼす還元剤の添加効果(OS5 マイクロ・ナノと熱電変換,ポスターセッション)

Conducting polymers, such as polyaniline, polypyrrole, and polythiophene, have attracted the attention of researchers investigating suitable materials for use in thermoelectric applications involving environmental energy conversion, because conducting polymers are inexpensive, lightweight, and relatively harmless materials. Moreover, conducting polymers have several attractive features for use as thermoelectric materials because of the thermal conductivity much lower than that for inorganic thermoelectric materials as well as the relatively high electrical conductivity. We investigated the thermoelectric properties for poly (3,4-ethylenedioxythiophene)(PEDOT):polystyrene sulphonic acid (PSS) films and the effect of addition of tetrakis(dimethylamino)ethylene(TDAE) on thermoelectric properties of PEDOT:PSS films. We found that the dimensionless thermoelectric figure of merit ZT of PEDOT:PSS film was enhanced by TDAE addition.