Thermoelectric Transport from First-Principles—Biphenyl-Based Single-Molecule Junctions
Using first-principles electronic structure methods in conjunction with nonequilibrium Green function (NEGF) techniques, we study the thermoelectric transport through biphenyl-based single-molecule junctions. We show, based on our recently published works and their present extension to include also the electron energy current, that the single-molecule conductance, junction thermopower, and electron thermal conductance strongly depend on the choice of the molecular anchor group and on the geometry of the investigated gold-biphenyl-gold contacts. We compare two different anchor groups, sulfur and cyano. The electron-donating S anchor group gives rise to a positive thermopower, while the electron-withdrawing cyano anchor results in a negative thermopower. For the S-terminated biphenyl a strong variation of the transport coefficients with respect to the binding motif is observed, for CN-terminated biphenyl such variations remain small.
KeywordsHigh Occupied Molecular Orbital Lower Unoccupied Molecular Orbital Transport Coefficient Molecular Junction Electron Thermal Conductance
This work was partly supported by a FY2012 (P12501) Postdoctoral Fellowship for Foreign Researchers from the Japan Society for Promotion of Science (JSPS) and by a JSPS KAKENHI, i.e. ‘Grant-in-Aid for JSPS Fellows’, grant no. 24·02501.
F.P. gratefully acknowledges financial support from the Carl Zeiss Foundation as well as the collaborative research center of the German science foundation, SFB 767, through project C13.
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