Backbone Structure Effect on the Thermoelectric Properties of IDT-Based p-Type Conjugated Polymers

Area of Science:

• Materials Science
• Organic Electronics
• Polymer Chemistry

Background:

• Conjugated polymers are crucial for organic electronics.
• Indacenodithiohene (IDT) is a promising building block for high-performance polymers.
• Optimizing polymer structure and doping is key to enhancing charge transport and thermoelectric properties.

Purpose of the Study:

• To synthesize and characterize four novel conjugated polymers incorporating the indacenodithiohene (IDT) unit.
• To investigate the impact of different comonomers on charge transport and thermoelectric performance.
• To explore synergistic doping strategies for improving electrical conductivity.

Main Methods:

• Copolymerization of indacenodithiohene (IDT) with thiophene and its derivatives.
• Measurement of charge transport mobilities and thermoelectric properties.
• Theoretical calculations (e.g., DFT) to assess polymer coplanarity.
• X-ray Photoelectron Spectroscopy (XPS) to analyze doping mechanisms.

Main Results:

• Indacenodithiohene-co-thieno[3,2-b]thiophene (IDT-TT) and indacenodithiohene-co-trans-1,2-di(2-thienyl)ethylene (IDT-TVT) exhibited superior charge transport mobilities compared to IDT-T and IDT-EDOT.
• IDT-TT and IDT-TVT demonstrated enhanced thermoelectric properties post-doping.
• Theoretical studies indicated better coplanarity for IDT-EDOT and IDT-TVT, with low molecular weight potentially limiting IDT-EDOT performance.
• Synergistic doping using CN6CP and CuTFSI significantly improved electrical conductivities.
• XPS analysis confirmed that copper ions from CuTFSI coordinate with CN6CP, increasing the doping ratio and conductivity.

Conclusions:

• Copolymer structure significantly influences charge transport and thermoelectric performance in IDT-based polymers.
• Synergistic doping offers an effective route to enhance electrical conductivity in conjugated polymers.
• The coordination interaction between dopants plays a vital role in achieving higher doping levels.