Perpendicular crossing chains enable high mobility in a noncrystalline conjugated polymer

Area of Science:

• Materials Science
• Organic Electronics
• Polymer Chemistry

Background:

• High-mobility conjugated polymers are crucial for organic electronic devices.
• Understanding the relationship between polymer microstructure and charge transport is essential for device optimization.

Purpose of the Study:

• To elucidate the nature of interchain π-system contacts in C16-IDTBT.
• To correlate these contacts with the observed high hole transport mobility.
• To explain the microstructural basis for efficient charge transport in noncrystalline polymers.

Main Methods:

• Scanning tunneling microscopy (STM) for nanoscale imaging.
• Molecular dynamics (MD) simulations, including coarse-grained MD.
• Quantum chemical calculations for electronic structure analysis.
• Charge transport simulations.

Main Results:

• Identified an unusual packing motif in C16-IDTBT with paired chains crossing at near-perpendicular angles.
• Linked nanoscale packing to mesoscale microstructural features.
• Demonstrated that perpendicular contacts promote a highly interconnected charge transport network.
• Showed that fast intrachain transport complements the intermolecular network for high mobility.

Conclusions:

• The high hole mobility of C16-IDTBT arises from a combination of fast intrachain transport and an interconnected intermolecular transport network.
• This network is facilitated by a unique nanoscale packing motif favoring perpendicular interchain π-system contacts.
• The findings provide critical insights into structure-property relationships for high-performance noncrystalline conjugated polymers.