TOPICAL REVIEW — Progress in thermoelectric materials and devices

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    Electron delocalization enhances the thermoelectric performance of misfit layer compound (Sn1-xBixS)1.2(TiS2)2
    Xin Zhao(赵昕), Xuanwei Zhao(赵轩为), Liwei Lin(林黎蔚), Ding Ren(任丁), Bo Liu(刘波), and Ran Ang(昂然)
    Chin. Phys. B, 2022, 31 (11): 117202.   DOI: 10.1088/1674-1056/ac6493
    Abstract282)   HTML2)    PDF (2000KB)(113)      
    The misfit layer compound (SnS)1.2(TiS2)2 is a promising low-cost thermoelectric material because of its low thermal conductivity derived from the superlattice-like structure. However, the strong covalent bonds within each constituent layer highly localize the electrons thereby it is highly challenging to optimize the power factor by doping or alloying. Here, we show that Bi doping at the Sn site markedly breaks the covalent bonds networks and highly delocalizes the electrons. This results in a high charge carrier concentration and enhanced power factor throughout the whole temperature range. It is highly remarkable that Bi doping also significantly reduces the thermal conductivity by suppressing the heat conduction carried by phonons, indicating that it independently modulates phonon and charge transport properties. These effects collectively give rise to a maximum ZT of 0.3 at 720 K. In addition, we apply the single Kane band model and the Debye-Callaway model to clarify the electron and phonon transport mechanisms in the misfit layer compound (SnS)1.2(TiS2)2.
    Micro thermoelectric devices: From principles to innovative applications
    Qiulin Liu(刘求林), Guodong Li(李国栋), Hangtian Zhu(朱航天), and Huaizhou Zhao(赵怀周)
    Chin. Phys. B, 2022, 31 (4): 047204.   DOI: 10.1088/1674-1056/ac5609
    Abstract492)   HTML2)    PDF (4976KB)(303)      
    Thermoelectric devices (TEDs), including thermoelectric generators (TEGs) and thermoelectric coolers (TECs) based on the Seebeck and Peltier effects, respectively, are capable of converting heat directly into electricity and vice versa. Tough suffering from low energy conversion efficiency and relatively high capital cost, TEDs have found niche applications, such as the remote power source for spacecraft, solid-state refrigerators, waste heat recycling, and so on. In particular, on-chip integrable micro thermoelectric devices (μ-TEDs), which can realize local thermal management, on-site temperature sensing, and energy harvesting under minor temperature gradient, could play an important role in biological sensing and cell cultivation, self-powered Internet of Things (IoT), and wearable electronics. In this review, starting from the basic principles of thermoelectric devices, we summarize the most critical parameters for μ-TEDs, design guidelines, and most recent advances in the fabrication process. In addition, some innovative applications of μ-TEDs, such as in combination with microfluidics and photonics, are demonstrated in detail.
    Research status and performance optimization of medium-temperature thermoelectric material SnTe
    Pan-Pan Peng(彭盼盼), Chao Wang(王超), Lan-Wei Li(李岚伟), Shu-Yao Li(李淑瑶), and Yan-Qun Chen(陈艳群)
    Chin. Phys. B, 2022, 31 (4): 047307.   DOI: 10.1088/1674-1056/ac20c9
    Abstract405)   HTML6)    PDF (1636KB)(147)      
    Thermoelectric materials have the ability to directly convert heat into electricity, which have been extensively studied for decades to solve global energy shortages and environmental problems. As a medium temperature (400-800 K) thermoelectric material, SnTe has attracted extensive attention as a promising substitute for PbTe due to its non-toxic characteristics. In this paper, the research status of SnTe thermoelectric materials is reviewed, and the strategies to improve its performance are summarized and discussed in terms of electrical and thermal transport properties. This comprehensive discussion will provides guidance and inspiration for the research on SnTe.
    Advances in thermoelectric (GeTe)x(AgSbTe2)100-x
    Hongxia Liu(刘虹霞), Xinyue Zhang(张馨月), Wen Li(李文), and Yanzhong Pei(裴艳中)
    Chin. Phys. B, 2022, 31 (4): 047401.   DOI: 10.1088/1674-1056/ac3cae
    Abstract377)   HTML1)    PDF (5258KB)(281)      
    The (GeTe)x(AgSbTe2)100-x alloys, also called TAGS-x in short, have long been demonstrated as a promising candidate for thermoelectric applications with successful services as the p-type leg in radioisotope thermoelectric generators for space missions. This largely stems from the complex band structure for a superior electronic performance and strong anharmonicity for a low lattice thermal conductivity. Utilization of the proven strategies including carrier concentration optimization, band and defects engineering, an extraordinary thermoelectric figure of merit, zT, has been achieved in TAGS-based alloys. Here, crystal structure, band structure, microstructure, synthesis techniques and thermoelectric transport properties of TAGS-based alloys, as well as successful strategies for manipulating the thermoelectric performance, are surveyed with opportunities for further advancements. These strategies involved are believed to be in principle applicable for advancing many other thermoelectrics.
    Module-level design and characterization of thermoelectric power generator
    Kang Zhu(朱康), Shengqiang Bai(柏胜强), Hee Seok Kim, and Weishu Liu(刘玮书)
    Chin. Phys. B, 2022, 31 (4): 048502.   DOI: 10.1088/1674-1056/ac1b8f
    Abstract349)   HTML0)    PDF (564KB)(171)      
    Thermoelectric power generation provides us the unique capability to explore the deep space and holds promise for harvesting the waste heat and providing a battery-free power supply for IoTs. The past years have witnessed massive progress in thermoelectric materials, while the module-level development is still lagged behind. We would like to shine some light on the module-level design and characterization of thermoelectric power generators (TEGs). In the module-level design, we review material selection, thermal management, and the determination of structural parameters. We also look into the module-level characterization, with particular attention on the heat flux measurement. Finally, the challenge in the optimal design and reliable characterization of thermoelectric power generators is discussed, together with a calling to establish a standard test procedure.