High-Field-Effect Mobility of Low-Crystallinity Conjugated Polymers with Localized Aggregates

Area of Science:

• Materials Science
• Organic Electronics
• Polymer Chemistry

Background:

• Charge carrier mobility in conjugated polymers is limited by the balance between crystalline and amorphous regions.
• High crystallinity enhances charge transport but compromises mechanical flexibility, crucial for soft electronics.
• Existing methods to boost crystallinity face inherent limitations and may not be suitable for flexible applications.

Purpose of the Study:

• To develop a novel strategy for enhancing charge carrier transport in conjugated polymers.
• To improve charge carrier delocalization and connectivity within amorphous regions.
• To achieve high charge carrier mobility without compromising the mechanical properties of conjugated polymers for soft electronics.

Main Methods:

• A new strategy was developed by modulating the density of random copolymer alkyl side chains.
• Steric hindrance from side chains was controlled to generate localized aggregates via π-orbital overlap in amorphous regions.
• Field-effect mobility measurements were performed to evaluate charge transport efficiency.

Main Results:

• A random polymer with low alkyl side chain density and low crystallinity exhibited significantly enhanced field-effect mobility (1.37 cm²/ (V·s)).
• This mobility surpasses that of highly crystalline poly(3-hexylthiophene).
• The strategy successfully formed localized aggregates in amorphous regions, improving charge carrier connectivity.

Conclusions:

• Increasing polymer chain connectivity through localized aggregates in amorphous regions is a more effective approach for efficient charge transport than solely increasing crystallinity.
• Modulating side chain density offers a simple and effective method to engineer charge transport in conjugated polymers.
• This approach holds promise for developing high-performance conjugated polymers for soft electronics applications.