Exploring seebeck-coefficient fluctuations in endohedral-fullerene, single-molecule junctions

Area of Science:

• Molecular Nanotechnology
• Condensed Matter Physics
• Materials Science

Background:

• Single-molecule junctions are key for converting temperature differences into voltage via the Seebeck effect.
• Screening molecules for high Seebeck coefficients is crucial for developing efficient thermoelectric devices.
• Understanding molecular-scale thermoelectricity requires examining Seebeck coefficient distributions.

Purpose of the Study:

• To investigate the Seebeck coefficient and electrical conductance of endohedral metallofullerenes (EMFs) in single-molecule junctions.
• To correlate molecular properties like charge inhomogeneity and geometric disorder with thermoelectric performance.
• To identify potential high-performance molecular thermoelectric materials.

Main Methods:

• Utilized scanning tunneling microscopy (STM) for experimental transport measurements.
• Employed density-functional theory (DFT) for theoretical transport calculations.
• Analyzed Seebeck histograms, focusing on widths and extreme values for Sc3N@C80, Sc3C2@C80, and Er3N@C80 EMFs, benchmarked against C60.

Main Results:

• Standard deviations in Seebeck coefficients (σS) of EMF junctions correlate with geometric standard deviation (σ) and charge inhomogeneity (σq).
• Sc3C2@C80 exhibited the largest σ and σq, while C60 showed the smallest.
• EMFs demonstrated a range of Seebeck coefficients, including positive and negative values, indicating bi-thermoelectric behavior.

Conclusions:

• The width of the Seebeck coefficient distribution (σS) is a key indicator of a molecule's thermoelectric potential.
• EMFs, particularly Sc3C2@C80, show promise for high-performance thermoelectricity due to significant charge inhomogeneity and geometric disorder.
• All studied EMFs function as bi-thermoelectric materials, capable of generating voltage from temperature gradients in either direction.