Molecular Thermoelectricity in EGaIn-Based Molecular Junctions

Area of Science:

• Nanoscience and nanotechnology
• Condensed matter physics
• Materials science

Background:

• Miniaturization of electronic devices necessitates efficient thermoregulation.
• Molecular thermoelectricity offers insights beyond conventional electrical measurements.
• Understanding structure-thermopower relationships is crucial for nanoscale energy conversion.

Purpose of the Study:

• Introduce a reliable junction technique for measuring thermovoltage in self-assembled monolayers (SAMs).
• Establish atomic-detailed structure-thermopower correlations.
• Investigate quantum-chemical mechanisms governing thermoelectric functions in molecular junctions.

Main Methods:

• Utilized a novel microelectrode technique with eutectic gallium-indium (EGaIn) liquid metal.
• Formed noninvasive thermoelectric contacts with SAMs.
• Enabled efficient, reproducible thermovoltage data collection and statistical analysis.

Main Results:

• Successfully measured thermovoltage of one-molecule-thick SAMs.
• Unraveled quantum-chemical mechanisms (Mott formula) influencing thermoelectricity.
• Demonstrated that reducing energy offset and tuning orbital broadening enhance thermopower.
• Identified structural modifications in anchoring groups, molecular backbone, and electrodes to tune thermoelectric properties.
• Highlighted thermal instability issues with thiol anchor groups and proposed solutions.

Conclusions:

• The EGaIn technique provides reliable structure-thermopower relations for molecular thermoelectricity.
• Molecular thermoelectricity offers a platform for fundamental understanding of charge transport at the nanoscale.
• Future work should address practical challenges like molecular degradation and optimize power factor for efficient energy conversion.