High-Performance n-Type Organic Thermoelectrics Enabled by Synergistically Achieving High Electron Mobility and...

Area of Science:

• Materials Science
• Organic Electronics
• Thermoelectrics

Background:

• High electrical conductivity (σ) in n-doped polymers is crucial for efficient organic thermoelectric generators (OTEs).
• The scarcity of such materials hinders OTE development.

Purpose of the Study:

• To synthesize and characterize novel fused bithiophene imide dimer-based polymers.
• To investigate the effect of oligo(ethylene glycol) side-chain length on electrical conductivity and thermoelectric performance.
• To optimize polymer structure for enhanced organic thermoelectric applications.

Main Methods:

• Synthesis of a polymer series (PO8, PO12, PO16) with varying side-chain lengths.
• Fabrication of organic thermoelectric devices.
• Measurement of electrical conductivity and power factor.
• Morphological studies using X-ray diffraction and other techniques.

Main Results:

• Electrical conductivity decreased monotonically with increasing side-chain length due to reduced crystallinity and altered backbone orientation.
• Polymer PO12, with a moderate side-chain, achieved a champion conductivity of 92.0 S cm⁻¹ and a power factor of 94.3 µW m⁻² K⁻².
• PO12 exhibited high doping efficiency and charge carrier mobility attributed to moderate crystallinity and a 3D conduction channel from bimodal orientation.

Conclusions:

• Simple side-chain tuning is a powerful strategy for developing high-performance n-doped polymers for OTEs.
• The PO12 polymer demonstrates significant potential for solution-processed organic thermoelectric applications.
• Optimized morphology, including crystallinity and charge transport pathways, is key to achieving high thermoelectric performance.