High thermopower of mechanically stretched single-molecule junctions

Area of Science:

• Nanotechnology
• Materials Science
• Quantum Chemistry

Background:

• Metal-molecule-metal junctions offer potential for thermoelectric applications.
• Quantum confinement in zero-dimensional atomic structures can enhance thermoelectric figure of merit (ZT).
• Understanding the influence of molecular junction configuration on thermoelectricity is critical.

Purpose of the Study:

• To investigate the sensitivity of thermoelectric properties to molecular junction configurations.
• To measure single-molecule conductance and thermopower in mechanically-stretched junctions.
• To elucidate the charge transport mechanisms in molecular thermoelectric devices.

Main Methods:

• Simultaneous measurement of thermoelectric voltage and conductance.
• In-situ mechanical stretching of gold-1,4-benzenedithiol (BDT)-gold junctions at the sub-nanoscale.
• Analysis of single-molecule transport properties.

Main Results:

• Achieved average single-molecule conductance of 0.01 G0 and thermopower of 15 μV/K.
• Indicated charge transport primarily through the highest occupied molecular orbital.
• Demonstrated extreme sensitivity of thermoelectric transport to BDT bridge configurations.

Conclusions:

• Molecular junction configuration significantly impacts thermoelectric performance.
• Designing specific electrode-molecule contact motifs is essential for optimizing molecular junction thermoelectrics.
• This work highlights the importance of precise structural control in molecular thermoelectric devices.