Geometrical Structure Optimization Design of High-Performance Bi 2 Te 3 -Based Artificially Tilted Multilayer Thermoelec
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https://doi.org/10.1007/s11664-020-08324-2 Ó 2020 The Minerals, Metals & Materials Society
Geometrical Structure Optimization Design of High-Performance Bi2Te3-Based Artificially Tilted Multilayer Thermoelectric Devices YUZHENG LI,1 PING WEI,1,2 HONGYU ZHOU,1 XIN MU,1 WANTING ZHU,1 XIAOLEI NIE,1 XIAHAN SANG,1 and WENYU ZHAO1,3 1.—State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070, China. 2.—e-mail: [email protected]. 3.—e-mail: [email protected]
Artificially tilted multilayer thermoelectric devices (ATMTDs) are a kind of thermoelectric device that can directly convert heat into electricity based on transverse thermoelectric effect. Although the devices have a simplified multilayer structure, their geometrical optimization is a complicated task. In this work, n-type Bi2Te2.7Se0.3 and p-type Bi0.1Sb1.9Te3 materials, which have the most important commercial applications in conventional thermoelectric devices, were selected as the component materials to assemble a promising high-performance Bi2Te3-based ATMTD. A numerical analysis method was employed to optimize the device length, device width, and thickness of the component materials. The results revealed that a large device width/length ratio, a small device aspect ratio, and a small thickness of component materials are favorable for achieving a high conversion efficiency. The temperature and charge distributions inside the ATMTD are studied based on finite element simulation. The nonuniform distribution of temperature field inside the device strongly depends on the thermal conductivity of component materials. The accumulation of a transverse electric field, accompanied with the cancellation of longitudinal electric field, is a consequence of different electric field distributions in the two component materials. This work provides a better understanding on the anisotropic electrical and thermal transport behaviors in transverse thermoelectric devices. Key words: Artificially tilted multilayer thermoelectric device, transverse thermoelectric effect, geometrical structure optimization, anisotropic transport
INTRODUCTION Thermoelectric (TE) materials are able to realize direct interconversion between heat and electricity based on the Seebeck effect or Peltier effect,1–3 which have been used as power generators or coolers in the field of aerospace industry, vehicular exhaust recovery, industrial waste-heat power generation, portable refrigerators, and microchip
(Received March 11, 2020; accepted July 8, 2020)
coolers.4–7 Commercial TE devices are made in a p-type sandwich structure (Fig. 1a), where electricity flows in series and heat flows in parallel. However, due to the low figure of merit (ZT) of the TE materials and consequently low conversion efficiency of the devices, large-scale application of TE technology is still limited. The ZT values of commercial Bi2Te3 alloys have retained around 1.0 for several decades, although, in theory, the ZT of a TE material has no upper limit. In
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