Showing papers on "Thermoelectric effect published in 2009"
TL;DR: The most promising bulk materials with emphasis on results from the last decade are described and the new opportunities for enhanced performance bulk nanostructured composite materials are examined and a look into the not so distant future is attempted.
Abstract: Herein we cover the key concepts in the field of thermoelectric materials research, present the current understanding, and show the latest developments. Current research is aimed at increasing the thermoelectric figure of merit (ZT) by maximizing the power factor and/or minimizing the thermal conductivity. Attempts at maximizing the power factor include the development of new materials, optimization of existing materials by doping, and the exploration of nanoscale materials. The minimization of the thermal conductivity can come through solid-solution alloying, use of materials with intrinsically low thermal conductivity, and nanostructuring. Herein we describe the most promising bulk materials with emphasis on results from the last decade. Single-phase bulk materials are discussed in terms of chemistry, crystal structure, physical properties, and optimization of thermoelectric performance. The new opportunities for enhanced performance bulk nanostructured composite materials are examined and a look into the not so distant future is attempted.
1,951 citations
TL;DR: This is the first demonstration of viable chip-scale refrigeration technology and has the potential to enable a wide range of currently thermally limited applications.
Abstract: There is a significant need for site-specific and on-demand cooling in electronic, optoelectronic and bioanalytical devices, where cooling is currently achieved by the use of bulky and/or over-designed system-level solutions. Thermoelectric devices can address these limitations while also enabling energy-efficient solutions, and significant progress has been made in the development of nanostructured thermoelectric materials with enhanced figures-of-merit. However, fully functional practical thermoelectric coolers have not been made from these nanomaterials due to the enormous difficulties in integrating nanoscale materials into microscale devices and packaged macroscale systems. Here, we show the integration of thermoelectric coolers fabricated from nanostructured Bi2Te3-based thin-film superlattices into state-of-the-art electronic packages. We report cooling of as much as 15 degrees C at the targeted region on a silicon chip with a high ( approximately 1,300 W cm-2) heat flux. This is the first demonstration of viable chip-scale refrigeration technology and has the potential to enable a wide range of currently thermally limited applications.
678 citations
TL;DR: In the quantum Hall regime at a high magnetic field, quantized thermopower and Nernst signals are observed and are also in agreement with the generalized Mott relation, except for strong deviations near the charge neutrality point.
Abstract: The conductance and thermoelectric power (TEP) of graphene is simultaneously measured using a microfabricated heater and thermometer electrodes. The sign of the TEP changes across the charge neutrality point as the majority carrier density switches from electron to hole. The gate dependent conductance and TEP exhibit a quantitative agreement with the semiclassical Mott relation. In the quantum Hall regime at a high magnetic field, quantized thermopower and Nernst signals are observed and are also in agreement with the generalized Mott relation, except for strong deviations near the charge neutrality point.
663 citations
TL;DR: In this paper, a melt spinning technique followed by a quick spark plasma sintering procedure was used to fabricate high performance p-type Bi0.52Sb1.48Te3 bulk material with unique microstructures.
Abstract: We report a melt spinning technique followed by a quick spark plasma sintering procedure to fabricate high-performance p-type Bi0.52Sb1.48Te3 bulk material with unique microstructures. The microstructures consist of nanocrystalline domains embedded in amorphous matrix and 5–15 nm nanocrystals with coherent grain boundary. The significantly reduced thermal conductivity leads to a state-of-the-art dimensionless figure of merit ZT∼1.56 at 300 K, more than 50% improvement of that of the commercial Bi2Te3 ingot materials.
539 citations
TL;DR: A binary crystalline n-type material, In4Se3-δ, is reported, which achieves the ZT value of 1.48 at 705 K—very high for a bulk material and suggests a new direction in the search for high-performance thermoelectric materials, exploiting intrinsic nanostructural bulk properties induced by charge density waves.
Abstract: Thermoelectric materials, which convert heat into electricity, are much studied for their potential in energy-saving applications — for example as a way of recovering waste heat in cars. At present, though, these materials are inefficient, with very few of them achieving a thermoelectric figure of merit (ZT) above one in the mid-temperature range (500–900 K). Now a figure of merit of 1.48, notably high for a bulk material, is reported for indium selenide crystals (In4Se3–δ) at 705 K. The high thermoelectric performance of this material is related to a Peierls distortion of the crystal lattice at 710 K. This work suggests a new direction in the search for high-performance thermoelectric materials, exploiting intrinsic nanostructural bulk properties induced by charge density waves. Thermoelectric materials, which can convert heat into electricity, are of great interest for energy sustainability. The problem is the low efficiency of these materials, quantified by a coefficient, ZT, which for mid-temperature materials is usually around 1. The realization of a material, In4Se3–δ, which achieves the ZT value of 1.48 at 705 K, could open up a new avenue in the research to generate high ZT materials. Thermoelectric energy harvesting—the transformation of waste heat into useful electricity—is of great interest for energy sustainability. The main obstacle is the low thermoelectric efficiency of materials for converting heat to electricity, quantified by the thermoelectric figure of merit, ZT. The best available n-type materials for use in mid-temperature (500–900 K) thermoelectric generators have a relatively low ZT of 1 or less, and so there is much interest in finding avenues for increasing this figure of merit1. Here we report a binary crystalline n-type material, In4Se3-δ, which achieves the ZT value of 1.48 at 705 K—very high for a bulk material. Using high-resolution transmission electron microscopy, electron diffraction, and first-principles calculations, we demonstrate that this material supports a charge density wave instability which is responsible for the large anisotropy observed in the electric and thermal transport. The high ZT value is the result of the high Seebeck coefficient and the low thermal conductivity in the plane of the charge density wave. Our results suggest a new direction in the search for high-performance thermoelectric materials, exploiting intrinsic nanostructural bulk properties induced by charge density waves.
497 citations
TL;DR: The inferred graphene thermal conductivity from temperature dependent measurements has a T(1.5) dependence below approximately 100 K, which agrees with recent theoretical predictions.
Abstract: We investigate the optoelectronic response of a graphene interface junction, formed with bilayer and single-layer graphene, by photocurrent (PC) microscopy. We measure the polarity and amplitude of the PC while varying the Fermi level by tuning a gate voltage. These measurements show that the generation of PC is by a photo-thermoelectric effect. The PC displays a factor of ~10 increase at the cryogenic temperature as compared to room temperature. Assuming the thermoelectric power has a linear dependence on the temperature, the inferred graphene thermal conductivity from temperature dependent measurements has a T^{1.5} dependence below ~100 K, which agrees with recent theoretical predictions.
453 citations
TL;DR: In this article, a thermoelectric study of graphene in both zero and applied magnetic fields was conducted and it was shown that the Seebeck coefficient Sxx diverges with 1/sqrt[n 2D] where n 2D is the carrier density.
Abstract: We report a thermoelectric study of graphene in both zero and applied magnetic fields. As a direct consequence of the linear dispersion of massless particles, we find that the Seebeck coefficient Sxx diverges with 1/sqrt[|n_{2D}|], where n_{2D} is the carrier density. We observe a very large Nernst signal S_{xy} ( approximately 50 microV/K at 8 T) at the Dirac point, and an oscillatory dependence of both Sxx and S_{xy} on n_{2D} at low temperatures. Our results underscore the anomalous thermoelectric transport in graphene, which may be used as a highly sensitive probe for impurity bands near the Dirac point.
396 citations
TL;DR: In this article, a state-of-the-art ZT of 1.0 has been achieved for the levitation-melted and spark-plasma-sintered half-Heusler thermoelectric alloys.
371 citations
02 Jun 2009
TL;DR: In this paper, a third element was added to the co-dopant with Al to achieve a significant improvement in the thermoelectric performance of dense ZnO ceramics.
Abstract: A marked improvement in the thermoelectric performance of dense ZnO ceramics is achieved by employing a third element as a co-dopant with Al. Dual doping of ZnO with Al and Ga results in a drastic decrease in the thermal conductivity of the oxide, while the decrease in the electrical conductivity is relatively small. With the aid of a significant enhancement in the thermopower, the dually doped oxide shows thermoelectric figure of merit values, ZT, values of 0.47 at 1000 K and 0.65 at 1247 K at the composition Zn 0.96 Al 0.02 Ga 0.02 O. These results appear to be the highest ZT values so far reported for bulk n-type oxides. Microscopic observation of the samples reveals a granular texture in the densely sintered oxide matrix, suggesting that considerable reduction of the thermal conductivity while maintaining high electrical conductivity could be achieved by such a bulk nanocomposite structure in the samples.
368 citations
TL;DR: In this article, the authors review current progress in the understanding of interfaces in bulk thermoelectric materials and focus on emerging routes to engineer the nanoscale grain and interfacial structures.
Abstract: We review current progress in the understanding of interfaces in bulk thermoelectric materials. Following a brief discussion of the mechanisms by which embedded interfaces can enhance the electronic and thermal transport properties, we focus on emerging routes to engineer the nanoscale grain and interfacial structures in bulk thermoelectric materials. We address in particular (i) control of crystallographic texture, (ii) reduction of grain size to nanocrystalline dimensions, and (iii) formation of nanocomposite structures. While these approaches are beginning to yield promising improvements in performance, continued progress will require an improved fundamental understanding of the mechanisms governing the formation, stability, and properties of thermoelectric interfaces.
367 citations
TL;DR: In this paper, the thermoelectric transport properties of polycrystalline, Ba_(8)Ga_(16−x)Ge_(30+x) were characterized from 300 to 1000 K.
Abstract: The thermoelectric transport properties of polycrystalline, Ba_(8)Ga_(16−x)Ge_(30+x) were characterized from 300 to 1000 K. The carrier density was found to vary precisely with the experimental x as expected from simple electron counting. The experimental data are analyzed within the framework of a single parabolic band model, which is found to accurately describe transport for the compositions of interest for thermoelectric application. The lattice thermal conductivity, calculated with a degeneracy adjusted Lorenz number, does not show a trend with composition and a value of ~1 Wm^(−1) K^(−1) is observed at 300 K. A maximum figure of merit zT = 0.86 is obtained at 950 K, and the optimal doping level for thermoelectric application is predicted to be ~2 × 10^(20) cm^(−3), which corresponds to Ba_(8)Ga_(15.75)Ge_(30.25_ by electron counting. An unexpected transition event is observed near 650 K, which results in a significant increase in the heat capacity.
13 Feb 2009
TL;DR: In this paper, a review of existing and potential automotive applications of thermoelectric technology is presented, where both material and device issues related to automotive applications are discussed and several challenges for automotive thermolectric applications are highlighted.
Abstract: This report reviews several existing and potential automotive applications of thermoelectric technology. Material and device issues related to automotive applications are discussed. Challenges for automotive thermoelectric applications are highlighted.
TL;DR: In this paper, the authors used a melt-quench-anneal-spark plasma sintering method to obtain high performance skutterudite materials with high thermoelectric performance.
Abstract: n-Type skutterudites InxCeyCo4Sb12 with in situ forming nanostructured InSb phase have been prepared by a melt-quench-anneal-spark plasma sintering method. Doping of In results in a nanostructured InSb phase with the grain size of 10–80 nm that is evenly distributed on the boundaries of the skutterudite matrix. The nanostructured InSb phase has a strong influence on phonon scattering and leads to a notable suppression of the lattice thermal conductivity of InxCeyCo4Sb12. The combined effect of In and Ce doping results in high performance skutterudite materials. The highest thermoelectric figure of merit ZT=1.43 is achieved at 800 K in the In0.2Ce0.15Co4Sb12 compound.
TL;DR: In this article, a thermoelectric waste heat energy recovery system for internal combustion engine automobiles, including gasoline vehicles and hybrid electric vehicles, is proposed and implemented, which directly converts the heat energy from automotive waste heat to electrical energy.
TL;DR: In this paper, a new reduction route to bismuth nanoparticles is described, which are then applied as starting materials in the formation of rhombohedral Bi2Te3 nanoparticles.
Abstract: Here, a novel synthesis for near monodisperse, sub-10 nm Bi2Te3 nanoparticles is reported. A new reduction route to bismuth nanoparticles is described, which are then applied as starting materials in the formation of rhombohedral Bi2Te3 nanoparticles. After ligand removal by a novel hydrazine hydrate etching procedure, the nanoparticle powder is spark plasma sintered to a pellet with preserved crystal grain sizes. Unlike previous works on the properties of Bi2Te3 nanoparticles, the full thermoelectric characterization of such sintered pellets shows a highly reduced thermal conductivity and the same electric conductivity as bulk n-type Bi2Te3.
TL;DR: Chalcopyritelike quaternary chalcogenides, Cu2ZnSnQ4 (Q=S,Se), were investigated as an alternative class of wideband-gap p-type thermoelectric materials as mentioned in this paper.
Abstract: Chalcopyritelike quaternary chalcogenides, Cu2ZnSnQ4 (Q=S,Se), were investigated as an alternative class of wide-band-gap p-type thermoelectric materials. Their distorted diamondlike structure and quaternary compositions are beneficial to lowering lattice thermal conductivities. Meanwhile, partial substitution of Cu for Zn creates more charge carriers and conducting pathways via the CuQ4 network, enhancing electrical conductivity. The power factor and the figure of merit (ZT) increase with the temperature, making these materials suitable for high temperature applications. For Cu2.1Zn0.9SnQ4, ZT reaches about 0.4 at 700 K, rising to 0.9 at 860 K.
TL;DR: In this paper, it was shown that pyroelectric energy harvesting can achieve an efficiency of up to 50% of the Carnot efficiency with a limited temperature gradient due to the limited heat exchange.
Abstract: This paper deals with small-power energy harvesting from heat. It can be achieved using both thermoelectric and pyroelectric effects. In the first case, temperature gradients are necessary. The main difficulty of thermoelectric energy harvesting is imposing a large temperature gradient. This requires huge heat flows because of the limited surface heat exchanges and the large heat conductivity of thermoelectric materials. This results in a drastic decrease of power and the efficiency of conversion. In case of pyroelectric energy harvesting, a time varying temperature is necessary. Although such a temperature time profile is hard to find, the overall optimization is easier than the thermoelectric strategy. Indeed, it depends much less on heat exchange between the sample and the outer medium, than on heat capacity that dimensions optimization may easily compensate. As a consequence, it is shown that the efficiency and output power may be much larger using pyroelectric energy harvesting than thermoelectric methods. For instance, using a limited temperature gradient due to the limited heat exchange, a maximum efficiency of 1.7% of Carnot efficiency can be expected using a thermoelectric module. On the contrary, a pyroelectric device may reach an efficiency up to 50% of Carnot efficiency. Finally, an illustration shows an estimation of the output power that could be expected from natural time variations of temperature of a wearable device. Power peaks up to 0. 2m W cm −3 were found and a mean power of 1 μ Wc m −3 on average was determined within 24 h testing.
TL;DR: The microstructures of bulk nanograined p-type bismuth antimony telluride with a thermoelectric dimensionless figure-of-merit ZT = 1.4 are investigated using transmission electron microscopy and it is found that the bulk material contains both nano- and microsized grains.
Abstract: The microstructures of bulk nanograined p-type bismuth antimony telluride with a thermoelectric dimensionless figure-of-merit ZT = 1.4 are investigated using transmission electron microscopy. It is found that the bulk material contains both nano- and microsized grains. Between the nanograins, bismuth-rich interface regions with a 4 nm thickness were detected. In addition, nanoprecipitates as well as other defects are also found to be embedded in the nanograins. The high ZT is attributed to the slight increase in the electrical conductivity, and to the large decrease of the thermal conductivity.
TL;DR: In this paper, the thermoelectric properties of graphene nanoribbons were investigated by solving atomistic electron and phonon transport equations in the nonequilibrium Green's function formalism.
Abstract: We investigate the thermoelectric properties of graphene nanoribbons (GNRs) by solving atomistic electron and phonon transport equations in the nonequilibrium Green’s function formalism. The dependence of thermopower on temperature and chemical potential is compared to that of graphene, which shows the important role of quasi-one-dimensional geometry in determining the thermoelectric properties of a GNR. The edge roughness and lattice vacancy are found to increase the thermopower but decrease the thermoelectric ZT factor because the decrease in the electronic conductance outweighs the decrease in the thermal conductance and the increase in the thermopower.
TL;DR: In this paper, the tetrahedrally bonded stannite compound Cu2ZnSnSe4 with a band gap of 1.44 eV can also exhibit a high figure of merit at intermediate temperature.
Abstract: It is usually accepted that good thermoelectric (TE) materials should be narrow-gap semiconductors. Here we show an example that the tetrahedrally bonded stannite compound Cu2ZnSnSe4 with a band gap of 1.44 eV can also exhibit a high figure of merit at intermediate temperature. The highly distorted structure strives for the relatively low thermal conductivity, and the tunability of the electrical properties were demonstrated through doping. The maximum ZT of Cu2ZnSn0.90In0.10Se4 reaches 0.95 at 850 K. This work may open a way for exploring high-performance TE materials with the family of widely existing tetrahedrally bonded semiconductors.
TL;DR: It was found that the In filler caused the [Sb(4)](4-) rings to get smaller and squarer because of a reverse electron transition from Ba to Sb induced by a large difference in electronegativities between Ba and Sb.
Abstract: Maximizing the thermoelectric figure-of-merit (ZT) is a challenge owing to the conflicting combination of material properties. We explored simultaneously enhancing the power factor and reducing the thermal conductivity through filling In in Ba-filled skutterudite (Ba(0.3)Co(4)Sb(12)). Two large ZT values of 1.33 and 1.34 have been achieved for Ba(0.15)In(0.16)Co(4)Sb(11.83) and Ba(0.14)In(0.23)Co(4)Sb(11.84) at 850 K, respectively. The excellent thermoelectric transport properties for Ba(r)In(s)Co(4)Sb(12) are supposed to be due to the orbital hybridizations induced by In filler. It was found that the In filler made the [Sb(4)](4-) rings become bigger and squarer because of an electron transition from Sb to In brought out by the orbital hybridization between In and Sb and that the Ba filler caused the [Sb(4)](4-) rings to get smaller and squarer because of a reverse electron transition from Ba to Sb induced by a large difference in electronegativities between Ba and Sb. A model of how to form the rectangular [Sb(4)](4-) ring is presented, and the five chemical states of Sb in CoSb(3) are reasonably assigned to different chemical bonds in the model.
TL;DR: In this article, the performance of fully integrated and flexible micro thermoelectric generators (muTEGs) is discussed, and the authors demonstrate and discuss their performance with a low-cost microfabrication process based on electrochemical deposition.
Abstract: We demonstrate and discuss the performance of fully integrated and flexible micro thermoelectric generators (muTEGs). The devices are fabricated with a low-cost microfabrication process based on electrochemical deposition of a thermoelectric material into a polymer mold. Overall system optimization is demonstrated by means of NiCu and p- and n-type Bi2Te3-based muTEGs . Influences of design, material, fabrication, and performance parameters on device performance are explained by means of measurements and model calculations. The fabricated devices generate up to 2.6*10-3muWldrcm-2ldrK-2 for devices with NiCu thermocouples and up to 0.29 muWldrcm-2ldrK-2 for Bi2Te3-based generators in planar state. Mechanical testing on NiCu muTEGs demonstrated functionality of the generator when bent to curvatures down to 7.5 mm. This allows for enhanced thermal contact to nonplanar surfaces.
TL;DR: In this paper, the role of dimensionality on the electronic performance of thermoelectric devices is clarified using the Landauer formalism, which shows that the thermodelectric coefficients are related to the transmission, T(E), and how the conducting channels, M(E) are distributed in energy.
Abstract: The role of dimensionality on the electronic performance of thermoelectric devices is clarified using the Landauer formalism, which shows that the thermoelectric coefficients are related to the transmission, T(E), and how the conducting channels, M(E), are distributed in energy. The Landauer formalism applies from the ballistic to diffusive limits and provides a clear way to compare performance in different dimensions. It also provides a physical interpretation of the “transport distribution,” a quantity that arises in the Boltzmann transport equation approach. Quantitative comparison of thermoelectric coefficients in one, two, and three dimensions shows that the channels are utilized more effectively in lower dimensions. To realize the advantage of lower dimensionality, however, the packing density must be very high, so the thicknesses of the quantum wells or wires must be small. The potential benefits of engineering M(E) into a delta function are also investigated. When compared with a bulk semiconducto...
TL;DR: In this article, a model describing the carrier conductivity and Seebeck coefficient of thermoelectric nanocomposite materials consisting of granular regions is presented to explain relevant experimental data.
Abstract: We present a model describing the carrier conductivity and Seebeck coefficient of thermoelectric nanocomposite materials consisting of granular regions. The model is successfully applied to explain relevant experimental data for PbTe nanocomposites. A key factor is the grain potential boundary scattering mechanism. Other mechanisms, such as carrier-acoustic phonon, carrier-nonpolar optical phonon, and carrier-ionized impurities scattering are also included. Our calculations reveal that by changing the physical characteristics of the grains, such as potential barrier height, width, and distance between the grains, one can increase the mean energy per carrier in order to obtain an optimum power factor for improved thermoelectric performance. The model can be applied to other nanocomposites by incorporating the appropriate electronic structure parameters.
TL;DR: In this paper, the Boltzmann transport equation under the relaxation-time approximation was used to calculate the thermoelectric properties of $n$-type and $p$ -type SiGe nanocomposites.
Abstract: Nanocomposite thermoelectric materials have attracted much attention recently due to experimental demonstrations of improved thermoelectric properties over those of the corresponding bulk material. In order to better understand the reported data and to gain insight into transport in nanocomposites, we use the Boltzmann transport equation under the relaxation-time approximation to calculate the thermoelectric properties of $n$-type and $p$-type SiGe nanocomposites. We account for the strong grain-boundary scattering mechanism in nanocomposites using phonon and electron grain-boundary scattering models. The results from this analysis are in excellent agreement with recently reported measurements for the $n$-type nanocomposite but the experimental Seebeck coefficient for the $p$-type nanocomposite is approximately 25% higher than the model's prediction. The reason for this discrepancy is not clear at the present time and warrants further investigation. Using new mobility measurements and the model, we find that dopant precipitation is an important process in both $n$-type and $p$-type nanocomposites, in contrast to bulk SiGe, where dopant precipitation is most significant only in $n$-type materials. The model also shows that the potential barrier at the grain boundary required to explain the data is several times larger than the value estimated using the Poisson equation, indicating the presence of crystal defects in the material. This suggests that an improvement in mobility is possible by reducing the number of defects or reducing the number of trapping states at the grain boundaries.
TL;DR: In this article, a detailed description of an innovative route of a melt spinning (MS) technique combined with a subsequent spark plasma sintering process in order to obtain high performance p-type Bi0.52Sb1.48Te3 bulk material, which possesses a unique low-dimensional structure.
Abstract: We report a detailed description of an innovative route of a melt spinning (MS) technique combined with a subsequent spark plasma sintering process in order to obtain high performance p-type Bi0.52Sb1.48Te3 bulk material, which possesses a unique low-dimensional structure. The unique structure consists of an amorphous structure, 5–15 nm fine nanocrystalline regions, and coherent interfaces between the resulting nanocrystalline regions. Measurements of the thermopower, electrical conductivity, and thermal conductivity have been performed over a range of temperature of 300–400 K. We found that MS technique can give us considerable control over the resulting nanostructure with good thermal stability during the temperature range of 300–400 K and this unique structure can effectively adjust the transport of phonons and electrons, in a manner such that it is beneficial to the overall thermoelectric performance of the material, primarily a reduction in the lattice thermal conductivity. Subsequently, this results...
TL;DR: The surface (interface) state density and the radial dopant profile of individual silicon nanowire field-effect transistors with the capacitance-voltage technique is measured.
Abstract: Silicon nanowires could be central components in electronic and thermoelectric devices, but understanding nanowire surface properties and dopant distribution will be essential for making reproducible high-performance devices. Present methods for determining these parameters are problematic. Now, by using capacitance-voltage analysis, the radial profile and interface state density of silicon-nanowire field-effect transistors have been measured.
TL;DR: In this paper, the average phonon and electron transmissions through long SiNWs containing many vacancies can be accurately estimated from the scattering properties of the isolated vacancies using a recently proposed averaging method.
Abstract: We compute both electron- and phonon transmissions in thin disordered silicon nanowires. Our atomistic approach is based on tight-binding and empirical potential descriptions of the electronic and phononic systems, respectively. Surface disorder is modeled by including surface silicon vacancies. It is shown that the average phonon- and electron transmissions through long SiNWs containing many vacancies can be accurately estimated from the scattering properties of the isolated vacancies using a recently proposed averaging method [Phys. Rev. Lett. 99, 076803 (2007)]. We apply this averaging method to surface disordered SiNWs in the diameter range 1 − 3 nm to compute the thermoelectric figure of merit, ZT. It is found that the phonon transmission is affected more by the vacancies than the electronic transmission leading to an increased thermoelectric performance of disordered wires, in qualitative agreement with recent experiments. The largest ZT > 3 is found in strongly disordered h 111i oriented wires with a diameter of 2 nm.
TL;DR: In this paper, a series of alternating poly(2,7-carbazole) derivatives have been synthesized and the evaluation of their thermoelectric properties in doped films revealed high electrical conductivity and a relatively high Seebeck coefficient (up to 70 μV/K).
Abstract: A series of alternating poly(2,7-carbazole) derivatives have been synthesized. The evaluation of their thermoelectric properties in doped films revealed high electrical conductivity (up to 500 S/cm) and a relatively high Seebeck coefficient (up to 70 μV/K). The best compromise between these two thermoelectric parameters led to a maximum value of 19 μW m−1 K−2 as the power factor. As observed from X-ray analyses, it has been observed that the high electrical conductivity was obtained with structured polymers. Good air stability was also observed with these thermoelectric polymers.