Optimised power harvesting by controlling the pressure applied to molecular junctions

Area of Science:

• Materials Science
• Nanotechnology
• Condensed Matter Physics

Background:

• Self-assembled monolayers (SAMs) offer mechanical flexibility for thermoelectric devices.
• Previous work highlighted flexibility for skin attachment and deformation avoidance.
• Controlling thermoelectric properties through mechanical manipulation of SAMs remains underexplored.

Purpose of the Study:

• To demonstrate control over thermoelectric properties by exploiting the mechanical flexibility of molecular devices.
• To investigate the relationship between molecular conformation and thermoelectric performance in SAMs.
• To optimize the power factor of SAM-based thermoelectric devices through applied mechanical force.

Main Methods:

• Fabrication of SAMs using thiol-terminated molecules.
• Measurement of thermoelectric properties using a modified Atomic Force Microscopy (AFM) system.
• Control of SAM conformation by regulating loading force, altering the metal-molecule interface tilt angle.

Main Results:

• A correlation was observed between the thermopower shift and the SAM's tilt angle.
• Both electrical conductivity and Seebeck coefficient were found to change with tilt angle.
• An optimized power factor was achieved at a specific molecular tilt angle, confirmed by theoretical calculations.

Conclusions:

• Thermoelectric performance of SAMs can be optimized by controlling molecular conformation through applied pressure.
• This method provides a general strategy for enhancing the power factor of molecular thermoelectric devices.
• Mechanical flexibility is a key parameter for tuning and optimizing thermoelectric properties in SAMs.