Thermoelectric properties of fullerene-based junctions: a first-principles study

Area of Science:

• Condensed Matter Physics
• Materials Science
• Nanotechnology

Background:

• Molecular electronics offers potential for novel electronic devices.
• Understanding thermoelectric properties at the nanoscale is crucial for energy harvesting applications.
• Fullerene (C60) molecules are promising candidates for molecular junctions due to their unique electronic structure.

Purpose of the Study:

• To investigate thermoelectric transport mechanisms in C60 molecules interfaced with Aluminum nano-electrodes.
• To analyze the influence of different anchoring configurations (planar, pyramidal, asymmetric) on thermoelectric properties.
• To explore the effects of temperature and strain on the performance of C60-based molecular junctions.

Main Methods:

• Density Functional Theory (DFT) calculations.
• Non-equilibrium Green's function (NEGF) formalism.
• Simulations of C60 molecules contacted to Al nano-electrodes in various geometries.

Main Results:

• Electrical and thermal conductance decreased significantly with reduced molecule-electrode coupling in planar and pyramidal junctions.
• Seebeck coefficients were reduced by approximately 55% when switching from planar/pyramidal configurations.
• A maximum thermoelectric figure of merit (ZelT) of 0.12 was achieved in the asymmetric junction.
• Thermoelectric properties showed a slight increase with temperature, except in the pyramidal junction where the Fermi level was distant from frontier orbitals.
• Strain significantly affected the Seebeck coefficient, with optimal values found at specific compressive and tensile strains for different junction types.

Conclusions:

• The anchoring configuration of C60 molecules to electrodes critically influences thermoelectric transport.
• Asymmetric junctions demonstrate superior thermoelectric performance.
• Fermi level engineering is an effective strategy to maximize the thermoelectric figure of merit in molecular junctions.