Performance of Functionally Graded Thermoelectric Materials and Devices: A Review

Cramer, Corson L.; Wang, Hsin; Ma, Kun

doi:10.1007/s11664-018-6402-7

Cited by 44 publications

(29 citation statements)

References 94 publications

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“…In recent years, thermoelectric modules (TEMs) have attracted much attention because of their stability, direct energy conversion, and having no moving parts in terms of energy management, temperature control, etc. [1][2][3]. Thermoelectric devices are divided into thermoelectric generators (TEGs), thermoelectric coolers (TECs), etc.…”

Section: Introductionmentioning

confidence: 99%

Modeling of an Integrated Thermoelectric Generation–Cooling System for Thermoelectric Cooler Waste Heat Recovery

Zhu

Kong

et al. 2020

Energies

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This paper focuses on the problem of thermoelectric cooler waste heat recovery and utilization, and proposes taking the waste heat together with the original heat source as the input heat source of the integrated thermoelectric generation–cooling system. By establishing an analytic model of this integrated thermoelectric generation–cooling system, the steady-state and transient thermal effects of this system are analyzed. The steady-state analysis results show that the thermoelectric generator’s actual heat source is about 20% larger than the intrinsic heat source. The transient analysis results prove that the current of thermoelectric power generation and the cold end temperature of the system show a nonlinear change rate with time. The cold end temperature of the system has a maximum value. Under different intrinsic heat sources, this maximum value can be reached between 1 s and 2.5 s.

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Section: Introductionmentioning

confidence: 99%

Modeling of an Integrated Thermoelectric Generation–Cooling System for Thermoelectric Cooler Waste Heat Recovery

Zhu

Kong

et al. 2020

Energies

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“…[2,12,13] Therefore, PEDOT:PSS has been selected as the organic polymer matrix in this work, as it can be readily processed with very low intrinsic κ. [14] Additionally, nanocomposite structuring methods can also be an effective approach to split the interdependence of electrical charge carriers and thermal carriers (electrons and phonons, respectively), thus significantly reducing κ without adversely affecting S and σ via selective phonon scattering at interfaces, thereby leading to greater ZT as a whole. [15][16][17][18][19] Numerous studies have been conducted on the enhancement of single-phase TE materials, with relatively fewer studies on the development of organic-inorganic hybrids, which have been shown to overcome some of the difficulties associated with single-phase materials.…”

Section: Introductionmentioning

confidence: 99%

“…[15][16][17][18][19] Numerous studies have been conducted on the enhancement of single-phase TE materials, with relatively fewer studies on the development of organic-inorganic hybrids, which have been shown to overcome some of the difficulties associated with single-phase materials. 2,14,[20][21][22][23] Nevertheless, all TE materials suffer from a problem that their ZT or PF values often have a strong dependence on temperature. Accordingly, even where it is possible to provide alternative TE materials which overcome some known problems of traditional TE materials, there is still the issue that TE materials can only ever be efficient within a small temperature range due to the variation of PF with temperature.…”

Section: Introductionmentioning

confidence: 99%

“…This problem was first considered in the context of inorganic TE materials in work by Ioffe et al, [23] where the concept of functionally graded thermoelectric material (FG-TEM) design was proposed, that could lead to 50-100% improvement in device efficiency with the use of existing inorganic TE materials. [14,[24][25][26] FG-TEMs are inhomogeneous materials with a spatial gradation in the composition and/or structure of materials, resulting in a corresponding variation in their thermoelectric, electrical, thermal, and/or mechanical properties. [14,27] As reported in the literature, FG-TEMs can be designed as continuous-graded structures or segmented-graded structures, depending on the material characteristics, processing methods, and/or their applications.…”

Section: Introductionmentioning

confidence: 99%

“…[14,[24][25][26] FG-TEMs are inhomogeneous materials with a spatial gradation in the composition and/or structure of materials, resulting in a corresponding variation in their thermoelectric, electrical, thermal, and/or mechanical properties. [14,27] As reported in the literature, FG-TEMs can be designed as continuous-graded structures or segmented-graded structures, depending on the material characteristics, processing methods, and/or their applications. The key challenge is to replace the sharp interfaces within the traditional composite structure with graded interfaces that may be achieved by tuning chemical composition, microstructure, or porosity.…”

Section: Introductionmentioning

confidence: 99%

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Compositionally Graded Organic–Inorganic Nanocomposites for Enhanced Thermoelectric Performance

Zhang

Jing

et al. 2019

Adv Elect Materials

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batteries that need frequent recharging and/or replacing. [1-3] Harvesting thermal energy is particularly attractive as there are abundant environmental heat sources and most of them, such as the heat released by exhausts, industrial processes, and radiators, or even that arising from human body heat, are mostly unexploited. [4] Thermoelectric generators (TEGs) based on thermoelectric (TE) materials are prime candidates for thermal energy harvesting due to their ability to convert ambient and ever-present waste heat into electrical energy by utilizing the Seebeck effect. [5] TEGs have the potential to be scaled down in size and integrated into self-powered electronic devices with minimal maintenance. [6] However, a problem faced in this field is that existing inorganic TE materials often suffer from scarcity and/or toxicity. Furthermore, it is difficult to scale up the production of many of these materials, which are often not suitable for flexible and/or conformable applications due to their rigid nature. Accordingly, it is important for the future of this technology that new classes of TE materials are developed and evaluated. In order to evaluate the performance of TE materials, the dimensionless figure of merit (ZT) is usually used to describe their potential energy conversion efficiency. For a given operating temperature, ZT is defined as ZT = S 2 σT / κ, where T is the temperature, κ is the thermal conductivity (W (m K) −1), σ is the electrical conductivity (S m −1), and S is the Seebeck coefficient (V K −1). [7,8] A good TE material therefore needs to possess a high S and σ to ensure a high-voltage output at a given temperature difference. The power factor (PF = S 2 σ) can also be used as an alternative way to evaluate TE materials, and increasing PF has been recognized as a key strategy in optimizing ZT, [8] particularly in the case of polymer-based TE materials where κ values are relatively low and similar in magnitude. TE materials with a higher PF value can convert more heat into electricity. One of the most pressing issues that researchers in this field are facing is the development of high-performance TE materials, which has proven to be difficult. Binary bulk chalcogenides such as bismuth telluride (Bi 2 Te 3) and antimony telluride (Sb 2 Te 3) are well-known to exhibit a maximum ZT value of more than 1.4 at room temperature, and are thus well-suited for near-room-temperature applications, such as refrigeration and waste heat recovery up to 200 °C. [10-12] However, using expensive inorganic TE modules to harvest thermal energy is

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Electrically Programmed Doping Gradients Optimize the Thermoelectric Power Factor of a Conjugated Polymer

Liu,

Craighero,

Gupta

et al. 2024

Adv Funct Materials

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Functionally graded materials (FGMs) are widely explored in the context of inorganic thermoelectrics, but not yet in organic thermoelectrics. Here, the impact of doping gradients on the thermoelectric properties of a chemically doped conjugated polymer is studied. The in‐plane drift of counterions in moderate electric fields is used to create lateral doping gradients in films composed of a polythiophene with oligoether side chains, doped with 2,3,5,6‐tetrafluoro‐tetracyanoquinodimethane (F4TCNQ). Raman microscopy reveals that a bias voltage of as little as 5 V across a 50 µm wide channel is sufficient to trigger counterion drift, resulting in doping gradients. The effective electrical conductivity of the graded channel decreases with bias voltage, while an overall increase in Seebeck coefficient is observed, yielding an up to eight‐fold enhancement in power factor. Kinetic Monte Carlo simulations of graded films explain the increase in power factor in terms of a roll‐off of the Seebeck coefficient at high electrical conductivities in combination with a mobility decay due to increased Coulomb scattering at high dopant concentrations. Therefore, the FGM concept is found to be a way to improve the thermoelectric performance of not yet optimally doped organic semiconductors, which may ease the screening of new materials as well as the fabrication of devices.

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Performance of Functionally Graded Thermoelectric Materials and Devices: A Review

Cited by 44 publications

References 94 publications

Modeling of an Integrated Thermoelectric Generation–Cooling System for Thermoelectric Cooler Waste Heat Recovery

Modeling of an Integrated Thermoelectric Generation–Cooling System for Thermoelectric Cooler Waste Heat Recovery

Compositionally Graded Organic–Inorganic Nanocomposites for Enhanced Thermoelectric Performance

Electrically Programmed Doping Gradients Optimize the Thermoelectric Power Factor of a Conjugated Polymer

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