Backbone Engineering of Polythiophenes via Quinoid and Cyano Dual Functionalization for n-Type Polymers

Area of Science:

• Materials Science
• Organic Electronics
• Polymer Chemistry

Background:

• Developing high-performance n-type polymer semiconductors is challenging due to a lack of suitable electron-deficient building blocks.
• There is a continuous need for novel materials in organic electronics to improve device performance.

Purpose of the Study:

• To design and synthesize novel n-type polymers by integrating quinoid and cyano groups into polythiophene backbones.
• To investigate the electronic and thermoelectric properties of the newly synthesized polymers for organic electronic applications.

Main Methods:

• Stille copolymerization was employed to synthesize two new polymers, PQTTCN and PQTVTCN.
• Electrochemical analysis, computational studies, organic field-effect transistor (OFET) fabrication, and thermoelectric measurements were conducted.
• Atomic Force Microscopy (AFM) and Grazing Incidence Wide-Angle X-ray Scattering (GIWAXS) were used to analyze morphology and crystallinity.

Main Results:

• The synthesized polymers, PQTTCN and PQTVTCN, exhibit low-lying LUMO levels (-4.07 eV) and planar conformations.
• Both polymers demonstrated unipolar n-type charge transport in OFETs, with PQTTCN showing higher electron mobility (0.036 cm² V⁻¹ s⁻¹).
• Doped polymers displayed n-type thermoelectric performance, with PQTTCN achieving a power factor of 0.75 μW m⁻² K⁻².

Conclusions:

• The dual-functionalization strategy integrating quinoid and cyano units is effective for creating high-performance n-type polymer semiconductors.
• PQTTCN demonstrates superior performance due to better dopant compatibility and higher crystallinity compared to PQTVTCN.
• These findings offer a promising route for advancing n-type polymer semiconductors in organic electronics.