Elevating Thermoelectric Performance by Compositing Dibromo-Substituted Thienoacene with SWCNTs.

Area of Science:

• Materials Science
• Nanotechnology
• Solid State Physics

Background:

• Flexible thermoelectric (TE) materials are crucial for energy harvesting.
• Organic small molecules (OSMs) combined with single-walled carbon nanotubes (SWCNTs) are emerging TE materials.

Purpose of the Study:

• To synthesize and characterize novel thieno[2',3':4,5]thieno[3,2-b]thieno[2,3-d]thiophene (TTA) and its brominated derivative (TTA-2Br) for TE applications.
• To investigate the effect of bromination on the electronic structure and TE properties of OSM/SWCNT composites.
• To optimize the composition for enhanced thermoelectric performance and device fabrication.

Main Methods:

• Synthesis of TTA and TTA-2Br.
• Compounding TTA and TTA-2Br with SWCNTs to form composite films.
• Characterization of material properties, including electronic structure, Seebeck coefficient (S), and power factor (PF).
• Fabrication and testing of a thermoelectric generator (TEG) device.

Main Results:

• TTA-2Br exhibited a reduced highest molecular orbital energy level and bandgap compared to TTA.
• OSM/SWCNT composite films showed significantly improved Seebeck coefficient and power factor.
• The 40 wt % TTA-2Br/SWCNT composite achieved an optimal power factor of 242.59 ± 9.42 μW m⁻¹ K⁻² at room temperature.
• A TEG device demonstrated an output power of 102.8 ± 7.4 nW at a 20 °C temperature difference.

Conclusions:

• Bromination of TTA effectively enhances the thermoelectric properties of OSM/SWCNT composites.
• The optimized TTA-2Br/SWCNT composite exhibits excellent thermoelectric performance, thermal stability, and mechanical flexibility.
• This study offers a pathway for developing high-performance flexible thermoelectric materials and devices.