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.

中文翻译：

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在电极耦合和电化学浇铸的弱耦合分子结中具有出色的热电性能

分子结中的出色热电性能要求高功率因数，低热导率以及在费米能级附近的最大品质因数（ZT）。在当前的工作中，我们结合了密度泛函理论和非平衡格林函数来研究碳链-石墨烯结在电极与分子之间具有强耦合和弱耦合接触的热电性能。结果显示，室温ZT对于弱耦合分子结，可得到4的四分之一，比强耦合结所达到的大约高1个数量级。其原因是，强界面散射会抑制弱耦合系统中的大多数声子模，从而产生超低声子热导率。还研究了电极宽度，电极掺杂和电化学门控对弱耦合系统热电性能的影响，结果表明，在费米能级附近可以获得优异的热电性能。