Highly Conducting Polythiophene Thin Films with Less Ordered Microstructure Displaying Excellent Thermoelectric...

Area of Science:

• Materials Science
• Polymer Chemistry
• Condensed Matter Physics

Background:

• Developing efficient organic thermoelectric materials is crucial for waste heat recovery.
• Polythiophene (PTh) offers potential due to its tunable electronic properties.
• Controlling molecular structure and morphology is key to optimizing thermoelectric performance.

Purpose of the Study:

• To synthesize highly regular polythiophene thin films using electrochemical methods.
• To investigate the relationship between synthesis parameters, structural regularity, and thermoelectric properties.
• To evaluate the potential of less ordered PTh for organic thermoelectric applications.

Main Methods:

• Electrochemical synthesis of polythiophene in a BFEE/DTBP mixed medium.
• Modulation of doping level and film morphology via current density control.
• Characterization using solid-state NMR, FT-IR, and Raman spectroscopy.
• Measurement of in-plane thermal conductivity using the self-heating 3ω-method.
• Analysis of electrical and thermal conductivities via the Wiedemann-Franz Law.

Main Results:

• Achieved highly regular, nearly amorphous polythiophene films.
• Optimized current density of 1 mA cm^-2 yielded maximum electrical conductivity of 700 S cm^-1.
• Extracted a low lattice thermal conductivity of 0.21 W m^-1 K^-1 and a reduced Lorenz number (6.49 × 10^-9 W Ω K^-2).
• Maximized thermoelectric figure of merit (ZT) reached 0.10 at room temperature.

Conclusions:

• Highly conducting polymers with less ordered structures represent a practical direction for organic thermoelectric materials.
• Electrochemical synthesis offers a viable route to tune PTh properties for thermoelectric applications.
• The achieved low lattice thermal conductivity contributes significantly to the thermoelectric performance.