Asymmetric B←N Functionalized Benzothiadiazoles for High-Performance n-Type Semiconducting Polymers

Area of Science:

• Organic electronics
• Materials science
• Polymer chemistry

Background:

• Boron-nitrogen (B←N) containing polymers show promise in organic electronics.
• Developing effective B←N acceptor units for n-type polymers is challenging.
• High-performance organic transistors require advanced n-type semiconducting materials.

Purpose of the Study:

• To design and synthesize novel B←N functionalized acceptor units.
• To develop new n-type semiconducting polymers for organic transistors.
• To investigate the impact of B←N incorporation on polymer electronic properties and device performance.

Main Methods:

• Rational design and synthesis of asymmetric half-fused B←N functionalized benzothiadiazole derivatives (BTBN and FBTBN).
• Polymerization to create two new n-type polymers, PBTBN and PFBTBN.
• Characterization of polymer electronic properties, including lowest unoccupied molecular orbital (LUMO) levels.
• Fabrication and testing of organic field-effect transistors (OFETs) to evaluate electron mobility (µe).
• Assessment of device stability under mechanical stress (bending cycles).

Main Results:

• Synthesized BTBN and FBTBN derivatives incorporating the B←N motif.
• Developed PBTBN and PFBTBN polymers exhibiting significantly lowered LUMO levels (∼ -4.0 eV for PFBTBN).
• Achieved high unipolar n-type transistor performance with PFBTBN, demonstrating an electron mobility (µe) of 3.85 cm² V⁻¹ s⁻¹.
• The asymmetric B←N backbone stabilized the electronic structure and promoted a near-amorphous morphology.
• PFBTBN-based flexible transistors maintained high electron mobility (3.16 cm² V⁻¹ s⁻¹) after 1000 bending cycles.

Conclusions:

• Asymmetric B←N functionalized acceptors are effective for developing high-performance n-type semiconducting polymers.
• The developed polymers exhibit excellent electron mobility and stability, suitable for advanced organic electronics.
• This work highlights the potential of B←N chemistry in advancing organic transistor technology.