Showing papers on "Thermoelectric effect published in 2021"
TL;DR: In this paper, an n-type PbSe-based high-entropy material formed by entropy-driven structural stabilization was used to improve the performance of thermoelectric materials.
Abstract: Thermoelectric technology generates electricity from waste heat, but one bottleneck for wider use is the performance of thermoelectric materials. Manipulating the configurational entropy of a material by introducing different atomic species can tune phase composition and extend the performance optimization space. We enhanced the figure of merit (zT) value to 1.8 at 900 kelvin in an n-type PbSe-based high-entropy material formed by entropy-driven structural stabilization. The largely distorted lattices in this high-entropy system caused unusual shear strains, which provided strong phonon scattering to largely lower lattice thermal conductivity. The thermoelectric conversion efficiency was 12.3% at temperature difference ΔT = 507 kelvin, for the fabricated segmented module based on this n-type high-entropy material. Our demonstration provides a paradigm to improve thermoelectric performance for high-entropy thermoelectric materials through entropy engineering.
384 citations
TL;DR: The current status of, and future outlook for, thermoelectric cooling materials are reviewed, coefficients of performance for these systems and the state-of-the-art for materials are discussed, and strategies for the discovery of improved thermoeLECTric materials are suggested.
Abstract: Solid-state thermoelectric devices can directly convert electricity into cooling or enable heat pumping through the Peltier effect. The commercialization of thermoelectric cooling technology has been built on the Bi2Te3 alloys, which have had no rival for the past six decades around room temperature. With the discovery and development of more promising materials, it is possible to reshape thermoelectric cooling technology. Here we review the current status of, and future outlook for, thermoelectric cooling materials. Thermoelectric materials can generate electricity from waste heat but can also use electricity for cooling. This Perspective discusses coefficients of performance for these systems and the state-of-the-art for materials, and suggests strategies for the discovery of improved thermoelectric materials.
275 citations
TL;DR: In this paper, hole-doped SnSe polycrystalline samples with reagents carefully purified and tin oxides removed exhibit an ZT of roughly 3.1 at 783 K.
Abstract: Thermoelectric materials generate electric energy from waste heat, with conversion efficiency governed by the dimensionless figure of merit, ZT. Single-crystal tin selenide (SnSe) was discovered to exhibit a high ZT of roughly 2.2–2.6 at 913 K, but more practical and deployable polycrystal versions of the same compound suffer from much poorer overall ZT, thereby thwarting prospects for cost-effective lead-free thermoelectrics. The poor polycrystal bulk performance is attributed to traces of tin oxides covering the surface of SnSe powders, which increases thermal conductivity, reduces electrical conductivity and thereby reduces ZT. Here, we report that hole-doped SnSe polycrystalline samples with reagents carefully purified and tin oxides removed exhibit an ZT of roughly 3.1 at 783 K. Its lattice thermal conductivity is ultralow at roughly 0.07 W m–1 K–1 at 783 K, lower than the single crystals. The path to ultrahigh thermoelectric performance in polycrystalline samples is the proper removal of the deleterious thermally conductive oxides from the surface of SnSe grains. These results could open an era of high-performance practical thermoelectrics from this high-performance material. SnSe has a very high thermoelectric figure of merit ZT, but uncommonly polycrystalline samples have higher lattice thermal conductivity than single crystals. Here, by controlling Sn reagent purity and removing SnOx impurities, a lower thermal conductivity is achieved, enabling ZT of 3.1 at 783 K.
236 citations
TL;DR: In this paper, the atomic disorder in cadmium-doped polycrystalline silver antimony telluride (AgSbTe2) was optimized to improve electronic properties by tuning disorder-induced localization of electronic states.
Abstract: High thermoelectric performance is generally achieved through either electronic structure modulations or phonon scattering enhancements, which often counteract each other. A leap in performance requires innovative strategies that simultaneously optimize electronic and phonon transports. We demonstrate high thermoelectric performance with a near room-temperature figure of merit, ZT ~ 1.5, and a maximum ZT ~ 2.6 at 573 kelvin, by optimizing atomic disorder in cadmium-doped polycrystalline silver antimony telluride (AgSbTe2). Cadmium doping in AgSbTe2 enhances cationic ordering, which simultaneously improves electronic properties by tuning disorder-induced localization of electronic states and reduces lattice thermal conductivity through spontaneous formation of nanoscale (~2 to 4 nanometers) superstructures and coupling of soft vibrations localized within ~1 nanometer around cadmium sites with local strain modulation. The strategy is applicable to most other thermoelectric materials that exhibit inherent atomic disorder.
223 citations
TL;DR: In this article, the authors developed SnSe crystals with a wide bandgap of 33 kBT with attractive thermoelectric properties through Pb alloying, which achieved an ultra-high power factor of 75 μWcm-1K-2 at 300 K and a ZTave of 1.90.
Abstract: Thermoelectric materials transfer heat and electrical energy, being useful for power generation or cooling applications. Many of these materials have narrow bandgaps, especially for cooling applications where this property has been seen as particularly important for enhancing the thermoelectric properties. We developed SnSe crystals with a wide bandgap Eg ~ 33 kBT with attractive thermoelectric properties through Pb alloying. The momentum and energy multiband alignment promoted by Pb alloying resulted in an ultra-high power factor ~75 μWcm–1K–2 at 300 K, and a ZTave ~ 1.90. We show that a 31-pair thermoelectric device can produce a power generation efficiency ~4.4% and a cooling ΔTmax ~ 45.7 K. These results demonstrate that wide bandgap compounds can be used for thermoelectric cooling applications.
192 citations
TL;DR: In this article, the n-type Mg3Sb1.5Bi0.5 system by minor Cu additions was reported, which significantly modified phonon modes via filling in the phonon gap and increased anharmonic phonon scattering, thereby leading to the anomalously low thermal conductivity.
152 citations
147 citations
TL;DR: In this article, the authors summarize the recent progress of flexible thermoelectric materials, including conducting polymers, organic/inorganic hybrid composites, and fully inorganic materials.
142 citations
01 Feb 2021
TL;DR: In-depth analysis of TEGs is presented, beginning with a comprehensive overview of their working principles such as the Seebeck effect, the Peltier effect,The Thomson effect and Joule heating with their applications, materials used, Figure of Merit, improvement techniques including different thermoelectric material arrangements and technologies used and substrate types.
Abstract: Nowadays humans are facing difficult issues, such as increasing power costs, environmental pollution and global warming. In order to reduce their consequences, scientists are concentrating on improving power generators focused on energy harvesting. Thermoelectric generators (TEGs) have demonstrated their capacity to transform thermal energy directly into electric power through the Seebeck effect. Due to the unique advantages they present, thermoelectric systems have emerged during the last decade as a promising alternative among other technologies for green power production. In this regard, thermoelectric device output prediction is important both for determining the future use of this new technology and for specifying the key design parameters of thermoelectric generators and systems. Moreover, TEGs are environmentally safe, work quietly as they do not include mechanical mechanisms or rotating elements and can be manufactured on a broad variety of substrates such as silicon, polymers and ceramics. In addition, TEGs are position-independent, have a long working life and are ideal for bulk and compact applications. Furthermore, Thermoelectric generators have been found as a viable solution for direct generation of electricity from waste heat in industrial processes. This paper presents in-depth analysis of TEGs, beginning with a comprehensive overview of their working principles such as the Seebeck effect, the Peltier effect, the Thomson effect and Joule heating with their applications, materials used, Figure of Merit, improvement techniques including different thermoelectric material arrangements and technologies used and substrate types. Moreover, performance simulation examples such as COMSOL Multiphysics and ANSYS-Computational Fluid Dynamics are investigated.
131 citations
01 Aug 2021
TL;DR: The use of colloidal quantum dots in the development of next-generation electronics, including luminescent, optoelectronic, memory and thermoelectric devices, is discussed in this article.
Abstract: The development of electronics is increasingly dependent on low-cost, flexible, solution-processed semiconductors. Colloidal quantum dots are solution-processed semiconducting nanocrystals that have a size-tunable bandgap and can be fabricated on a range of substrates. Here we review developments in colloidal quantum dot electronics, focusing on luminescent, optoelectronic, memory and thermoelectric devices. We examine the role of surface chemistry in the suppression of non-radiative processes, the control of light–matter interactions and the regulation of carrier transport properties. We also highlight the prospects of perovskite quantum dots as single-photon sources, the design of new classes of colloidal quantum dots and superlattices for emerging applications and the role of hybrid device architectures in compensating for the limited carrier mobility in colloidal quantum dot solids while maintaining their tunable spectral response. This Review examines the use of colloidal quantum dots in the development of next-generation electronics, including luminescent, optoelectronic, memory and thermoelectric devices.
128 citations
TL;DR: The basic principle of the thermoelectric effects when the particles transporting the electric charge are electrons, ions, and redox molecules is presented and the conceptual differences between the three thermodiffusion phenomena are described.
Abstract: Heat is an abundant but often wasted source of energy. Thus, harvesting just a portion of this tremendous amount of energy holds significant promise for a more sustainable society. While traditional solid-state inorganic semiconductors have dominated the research stage on thermal-to-electrical energy conversion, carbon-based semiconductors have recently attracted a great deal of attention as potential thermoelectric materials for lowtemperature energy harvesting, primarily driven by the high abundance of their atomic elements, ease of processing/manufacturing, and intrinsically low thermal conductivity. This quest for new materials has resulted in the discovery of several new kinds of thermoelectric materials and concepts capable of converting a heat flux into an electrical current by means of various types of particles transporting the electric charge: (i) electrons, (ii) ions, and (iii) redox molecules. This has contributed to expanding the applications envisaged for thermoelectric materials far beyond simple conversion of heat into electricity. This is the motivation behind this review. This work is divided in three sections. In the first section, we present the basic principle of the thermoelectric effects when the particles transporting the electric charge are electrons, ions, and redox molecules and describe the conceptual differences between the three thermodiffusion phenomena. In the second section, we review the efforts made on developing devices exploiting these three effects and give a thorough understanding of what limits their performance. In the third section, we review the state-of-the-art thermoelectric materials investigated so far and provide a comprehensive understanding of what limits charge and energy transport in each of these classes of materials.
TL;DR: In this article, a review of the state-of-the-art on conducting polymers and their thermoelectric devices is presented, starting with the summary of the fundamentals as well as several well-accepted theoretical models.
TL;DR: In this article, a general overview of the thermoelectric principles and conductive polymer characteristics is provided, followed by the recent progress in their application in flexible and wearable devices.
TL;DR: In this article, the authors proposed n-type polymers with deep-positioned lowest unoccupied molecular orbital (LUMO) energy levels are essential for enabling OFTs with high stability.
Abstract: n-Type polymers with deep-positioned lowest unoccupied molecular orbital (LUMO) energy levels are essential for enabling n-type organic thin-film transistors (OTFTs) with high stability and n-type ...
TL;DR: In this article, the reduced lattice thermal conductivity due to the formation of carbon allotrope hybrid is derived from various additional phonon scattering features, which can potentially further widen the variety of applications of these materials.
Abstract: As an emission-free energy conversion technology, thermoelectric technology has been considered an essential component in solving the global energy crisis. Carbon allotrope hybrids, with relatively low cost, high performance and engineerable mechanical strength and flexibility, are attracting increasing research interest. The key challenge of developing carbon allotrope hybrid thermoelectric applications lies in material performance enhancement, which is further restricted by enhancing the electrical performance, refraining the lattice thermal conductivity and engineering the mechanical properties. Compositing carbon allotropes to enhance electrical transport properties should be mainly attributed to the material orientation effect which increases the carrier mobility or to the energy filtering effect which increases the Seebeck coefficient. The reduced lattice thermal conductivity due to the formation of carbon allotrope hybrid is derived from various additional phonon scattering features. Furthermore, carbon allotrope-compositing is also effective in enhancing the mechanical properties of thermoelectric materials, which can potentially further widen the variety of applications of these materials. A key opportunity in better utilizing the flexibility of carbon materials is deploying them as stents. Carbon allotrope hybrids can provide a pathway such that rigid thermoelectric materials can be designed into flexible thermoelectric materials. Finally, we point out future research directions for carbon-hybrid thermoelectric materials.
TL;DR: In this article, the performance of thermoelectric modules assembled from Bi2Te3-substitute compounds, including p-type MgAgSb and n-type mg3(Sb,Bi)2, was reported.
Abstract: Thermoelectric technology converts heat into electricity directly and is a promising source of clean electricity. Commercial thermoelectric modules have relied on Bi2Te3-based compounds because of their unparalleled thermoelectric properties at temperatures associated with low-grade heat (<550 K). However, the scarcity of elemental Te greatly limits the applicability of such modules. Here we report the performance of thermoelectric modules assembled from Bi2Te3-substitute compounds, including p-type MgAgSb and n-type Mg3(Sb,Bi)2, by using a simple, versatile, and thus scalable processing routine. For a temperature difference of ~250 K, whereas a single-stage module displayed a conversion efficiency of ~6.5%, a module using segmented n-type legs displayed a record efficiency of ~7.0% that is comparable to the state-of-the-art Bi2Te3-based thermoelectric modules. Our work demonstrates the feasibility and scalability of high-performance thermoelectric modules based on sustainable elements for recovering low-grade heat. Though earth abundant magnesium-based materials are attractive for thermoelectrics (TEs) due to their device-level performance, realizing efficient modules remains a challenge. Here, the authors report a scalable route to realizing Mg-based compounds for high performance TE modules.
TL;DR: In this article, several approaches were reviewed, including increasing Seebeck coefficient, electrical conductivity, power factor, and decreasing thermal conductivity to improve thermoelectric performances, and the current challenges hindering the further improvement of zT value were pointed out.
TL;DR: In this paper, a single-leg thermoelectric device with a conversion efficiency as high as 14% under a temperature gradient of 440 K was fabricated on the basis of GeTe-Cu2Te-PbSe alloys, which show a peak thermoelection figure of merit (zT) > 2.5 and an average zT of 1.8 within working temperatures.
Abstract: GeTe alloys have recently attracted wide attention as efficient thermoelectrics. In this work, a single-leg thermoelectric device with a conversion efficiency as high as 14% under a temperature gradient of 440 K was fabricated on the basis of GeTe-Cu2Te-PbSe alloys, which show a peak thermoelectric figure of merit (zT) > 2.5 and an average zT of 1.8 within working temperatures. The high performance of the material is electronically attributed to the carrier concentration optimization and thermally due to the strengthened phonon scattering, the effects of which all originate from the defects in the alloys. A design of Ag/SnTe/GeTe contact successfully enables both a prevention of chemical diffusion and an interfacial contact resistivity of 8 microhm·cm2 for the realization of highly efficient devices with a good service stability/durability. Not only the material’s high performance but also the device’s high efficiency demonstrated the extraordinariness of GeTe alloys for efficient thermoelectric waste-heat recovery.
TL;DR: In this article, the authors reported significantly suppressed thermal conductivity in SrTiO3-based thermoelectric ceramics via high-entropy strategy for the first time, and optimized electrical conductivity by defect engineering.
Abstract: Oxide-based ceramics could be promising thermoelectric materials because of their thermal and chemical stability at high temperature However, their mediocre electrical conductivity or high thermal conductivity is still a challenge for the use in commercial devices Here, we report significantly suppressed thermal conductivity in SrTiO3-based thermoelectric ceramics via high-entropy strategy for the first time, and optimized electrical conductivity by defect engineering In high-entropy (Ca02Sr02Ba02Pb02La02)TiO3 bulks, the minimum thermal conductivity can be 117 W/(m·K) at 923 K, which should be ascribed to the large lattice distortion and the huge mass fluctuation effect The power factor can reach about 295 μW/(m·K2) by inducing oxygen vacancies Finally, the ZT value of 02 can be realized at 873 K in this bulk sample This approach proposed a new concept of high entropy into thermoelectric oxides, which could be generalized for designing high-performance thermoelectric oxides with low thermal conductivity
TL;DR: In this paper, the authors reported a record high ZT of ~0.65 at 623 K in the n-type Ag/In co-doped CoSb3 thin films, fabricated by a facile magnetron sputtering technique.
TL;DR: In this paper, the authors demonstrate that the thermoelectric properties of p-type chalcogenides can be effectively improved by band convergence and hierarchical structure based on a high-entropy-stabilized matrix.
Abstract: We demonstrate that the thermoelectric properties of p-type chalcogenides can be effectively improved by band convergence and hierarchical structure based on a high-entropy-stabilized matrix. The band convergence is due to the decreased light and heavy band energy offsets by alloying Cd for an enhanced Seebeck coefficient and electric transport property. Moreover, the hierarchical structure manipulated by entropy engineering introduces all-scale scattering sources for heat-carrying phonons resulting in a very low lattice thermal conductivity. Consequently, a peak zT of 2.0 at 900 K for p-type chalcogenides and a high experimental conversion efficiency of 12% at ΔT = 506 K for the fabricated segmented modules are achieved. This work provides an entropy strategy to form all-scale hierarchical structures employing high-entropy-stabilized matrix. This work will promote real applications of low-cost thermoelectric materials. The synergism of entropy engineering and the typical optimization mechanisms in high-entropy-stabilized chalcogenide is unknown. Here, the authors find high-entropy-stabilized composition works as a promising matrix of applying synergistic effect to realize high thermoelectric performance.
TL;DR: In this article, an Sb-, Bi-, and Se-doped GeTe-based material, with a chemical composition of Ge0.92Sb0.95Se0.04Bi0.4Sb12 TE module is fabricated and evaluated, which shows a comparable energy conversion efficiency with those of skutterudite and half-Heusler-based modules in a similar temperature range.
Abstract: GeTe-Based materials have great potential to be used in thermoelectric generators for waste heat recovery due to their excellent thermoelectric performance, but their module research is greatly lagging behind material research. In this work, we successfully fabricate a GeTe-based thermoelectric module and report a high energy conversion efficiency of 7.8% under a temperature gradient of 500 K. An Sb-, Bi-, and Se-doped GeTe-based material, with a chemical composition of Ge0.92Sb0.04Bi0.04Te0.95Se0.05 and a peak ZT of 2.0 at 700 K, is used to make the p-type legs in the module. By using a high-throughput strategy, Mo is screened from 12 pure metals as an effective diffusion barrier material between the GeTe-based material and the electrode. Based on the optimal geometry predicted by three-dimensional numerical analysis, one eight-couple Ge0.92Sb0.04Bi0.04Te0.95Se0.05/Yb0.3Co4Sb12 TE module is fabricated and evaluated, which shows a comparable energy conversion efficiency with those of skutterudite- and half-Heusler-based modules in a similar temperature range. This study opens the door for the development of GeTe-based modules.
TL;DR: In this paper, the Seebeck-effect-induced charge current was used to drive transverse thermoelectric generation, which has great potential for energy harvesting and heat sensing applications owing to the orthogonal geometry of the heat-to-charge current conversion.
Abstract: When a temperature gradient is applied to a closed circuit comprising two different conductors, a charge current is generated via the Seebeck effect1. Here, we utilize the Seebeck-effect-induced charge current to drive 'transverse' thermoelectric generation, which has great potential for energy harvesting and heat sensing applications owing to the orthogonal geometry of the heat-to-charge-current conversion2-9. We found that, in a closed circuit comprising thermoelectric and magnetic materials, artificial hybridization of the Seebeck effect into the anomalous Hall effect10 enables transverse thermoelectric generation with a similar symmetry to the anomalous Nernst effect11-27. Surprisingly, the Seebeck-effect-driven transverse thermopower can be several orders of magnitude larger than the anomalous-Nernst-effect-driven thermopower, which is clearly demonstrated by our experiments using Co2MnGa/Si hybrid materials. The unconventional approach could be a breakthrough in developing applications of transverse thermoelectric generation.
TL;DR: In this paper, a three-dimensional spring-like thermoelectric device (S-TED) with fundamantal dual elastomer layers and air gaps is proposed.
TL;DR: In this paper, the authors designed and built a thermoelectric power generation system for cold energy, taking liquid nitrogen as the cryogenic liquid, and the temperature difference between the hot and cold module ends was small, being only 7.2-28.1°C.
04 Jan 2021
TL;DR: In this paper, a mass-producible potentially low-cost fully screen printed flexible origami TEG is presented, where a mechanically stable 3D cuboidal device from a 2D layout printed on a thin flexible substrate using thermoelectric inks based on PEDOT nanowires and a TiS2:Hexylamine-complex material.
Abstract: Energy-harvesting from low-temperature environmental heat via thermoelectric generators (TEG) is a versatile and maintenance-free solution for large-scale waste heat recovery and supplying renewable energy to a growing number of devices in the Internet of Things (IoT) that require an independent wireless power supply. A prerequisite for market competitiveness, however, is the cost-effective and scalable manufacturing of these TEGs. Our approach is to print the devices using printable thermoelectric polymers and composite materials. We present a mass-producible potentially low-cost fully screen printed flexible origami TEG. Through a unique two-step folding technique, we produce a mechanically stable 3D cuboidal device from a 2D layout printed on a thin flexible substrate using thermoelectric inks based on PEDOT nanowires and a TiS2:Hexylamine-complex material. We realize a device architecture with a high thermocouple density of 190 per cm² by using the thin substrate as electrical insulation between the thermoelectric elements resulting in a high-power output of 47.8 µWcm−² from a 30 K temperature difference. The device properties are adjustable via the print layout, specifically, the thermal impedance of the TEGs can be tuned over several orders of magnitudes allowing thermal impedance matching to any given heat source. We demonstrate a wireless energy-harvesting application by powering an autonomous weather sensor comprising a Bluetooth module and a power management system.
TL;DR: In this article, a polyvinylpyrrolidone (PVP)/Ag2Se composite film on nylon membrane is presented for powering wearable electronics and node sensor of internet-of-things.
TL;DR: In this paper, 2D WSe2 nanoinclusions were introduced in n-type Pb/I co-doped SnSe matrix to form p-n junctions, which act as energy barriers and effective phonon scattering sources.
TL;DR: In this article, a novel solar driven hybrid system composed of a concentrated solar collector, thermionic generator and thermoelectric device is proposed, and the design parameters affecting proposed hybrid system performance such as solar irradiance density, anode work function, heat conductivity, ratio of resistances and cooled space temperature sensitivity analysis is discussed.