摘要
Thermoelectricity is a therrnorelated property that is of great importance in single-molecule junctions. The electrical conductance (σ), electron-derived thermal conductance(kel) and Seebeck coefficient (S) of Bgo-based single-molecule junctions are investigated by using density functional theory in combination with non-equilibrium Green's function. When the dist ance bet ween the left/right elec trodes is 11.4 A, the relationship between σ and kel obeys the Wiedemann-Franz law very well because of the strong hybridization between B80 molecular orbitals and the surface states of Au electrodes. Furthermore, the calculated Lorenz number is close to the famous value in metal or degenerate semiconductors. In addition, S is only —19.09 μV/K at 300 K, thus leading to the smaller electron's thermoelec trie figure of merit (ZeiT = S^2 σT / Kel). Interestingly, the st rain and chemical pot ential can modulate B80-based single-molecule junctions from n-type to p-type when the compressive strain reaches —0.6 A or the chemical potential shifts to —0.16 eV. This might be attributed that S reflects the asymmetry in the electrical conductance with respect to the chemical potential and is proportional to the slopes of the transmission spectrum.
基金
the National Natural Science Foundation of China under Grant Nos. 61704044, 11547170, 51772297, and 11464052
the Natural Science Foundation of Hebei Province under Grant No. A2017201219
the Educational Commission of Hebei Province under Grant No. ZD2018030.
