Excellent thermoelectric performance in weak-coupling molecular junctions with electrode doping and electrochemical gati
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ly 2020 Vol. 63 No. 7: 276811 https://doi.org/10.1007/s11433-019-1528-y
Excellent thermoelectric performance in weak-coupling molecular junctions with electrode doping and electrochemical gating 1
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Dan Wu , Xuan-Hao Cao , Pin-Zhen Jia , Yu-Jia Zeng , Ye-Xin Feng , Li-Ming Tang , 2* 1* Wu-Xing Zhou , and Ke-Qiu Chen 1
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Department of Applied Physics, School of Physics and Electronics, Hunan University, Changsha 410082, China; School of Materials Science and Engineering, Hunan University of Science and Technology & Hunan Provincial Key Laboratory of Advanced Materials for New Energy Storage and Conversion, XiangTan 411201, China Received December 21, 2019; accepted February 17, 2020; published online March 18, 2020
Excellent thermoelectric performance in molecular junctions requires a high power factor, a low thermal conductance, and a maximum figure of merit (ZT) near the Fermi level. In the present work, we used density functional theory in combination with a nonequilibrium Green’s function to investigate the thermoelectric performance of carbon chain-graphene junctions with both strong-coupling and weak-coupling contact between the electrodes and the molecules. The results revealed that a room temperature ZT of 4 could be obtained for the weak-coupling molecular junction, approximately one order of magnitude higher than that reached by the strong-coupling junction. The reason for this is that strong interfacial scattering suppresses most of the phonon modes in weak-coupling systems, resulting in ultralow phonon thermal conductance. The influence of electrode width, electrode doping, and electrochemical gating on the thermoelectric performance of the weak-coupling system was also investigated, and the results revealed that an excellent thermoelectric performance can be obtained near the Fermi level. thermoelectric, molecular junctions, weak-coupling, electrochemical gating, density functional theory PACS number(s): 72.20.Pa, 73.40.-c, 73.63.-b Citation:
D. Wu, X.-H. Cao, P.-Z. Jia, Y.-J. Zeng, Y.-X. Feng, L.-M. Tang, W.-X. Zhou, and K.-Q. Chen, Excellent thermoelectric performance in weakcoupling molecular junctions with electrode doping and electrochemical gating, Sci. China-Phys. Mech. Astron. 63, 276811 (2020), https://doi.org/ 10.1007/s11433-019-1528-y
1 Introduction The creation of technology that is able to generate clean electrical energy is currently a topic of great importance. Existing technologies, such as piezoelectricity [1,2], photoelectricity [3], and thermoelectricity [4-9], made considerable progress. Under temperature differences, thermoelectric technology can directly convert waste heat into electrical energy by driving carries of material. The dimensionless
*Corresponding authors (Ke-Qiu Chen, email: [email protected]; Wu-Xing Zhou, email: [email protected])
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figure of merit ZT, defined as ZT=S σT/κ, is generally adopted to characterize the performance of thermoelectric devices [6,7]. The parameters S and σ represent the Seebeck coefficient and electrical conductanc
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