Acene Ring Size Optimization in Fused Lactam Polymers Enabling High n-Type Organic Thermoelectric Performance

Area of Science:

• Materials Science
• Organic Electronics
• Energy Conversion

Background:

• Development of n-type organic semiconductors is crucial for advancing thermoelectric devices and organic field-effect transistors (OFETs).
• Efficient solution doping and high charge carrier mobility are key performance metrics for these materials.

Purpose of the Study:

• Synthesize novel n-type fused lactam semiconducting polymers.
• Investigate the impact of central acene core size on electronic properties and thermoelectric performance.
• Establish molecular design guidelines for high-performance n-type conjugated polymers.

Main Methods:

• Transition-metal-free aldol polycondensation for polymer synthesis.
• Energy level analysis to determine electron affinities.
• OFET device fabrication and mobility measurements.
• Thermoelectric power factor (PF) characterization.

Main Results:

• Three n-type polymers (A-A, A-N, N-N) were synthesized with varying acene core sizes.
• Smaller acene cores (N-N, A-N) exhibited increased electron affinity, facilitating efficient solution doping with N-DMBI.
• N-N and A-N polymers showed high charge carrier mobilities.
• N-N and A-N polymers achieved high power factors (3.2 and 1.6 μW m⁻² K⁻²), among the best reported for n-type polymers.

Conclusions:

• Modulating central acene ring size is an effective strategy for optimizing thermoelectric performance in conjugated polymers.
• The study provides valuable insights for designing next-generation high-performance n-type thermoelectric materials.
• The synthesized polymers demonstrate significant potential for thermoelectric and transistor applications.