Solid-State Order and Charge Mobility in [5]- to [12]Cycloparaphenylenes

Area of Science:

• Computational chemistry
• Materials science
• Organic electronics

Background:

• Cycloparaphenylenes ([n]CPPs) are structural components of fullerenes and carbon nanotubes.
• Understanding their mesoscale morphology and charge transport is key for advanced materials.

Purpose of the Study:

• To computationally investigate the relationship between ring size, morphology, and charge transport in [n]CPPs.
• To determine how structural properties influence charge carrier mobility and reorganization energy.

Main Methods:

• Molecular dynamics simulations for mesoscale morphology.
• Density functional theory for electronic properties.
• Kinetic Monte Carlo simulations for charge-carrier mobilities.

Main Results:

• Intramolecular stability increases, while intermolecular stability decreases with larger [n]CPP ring sizes.
• Reorganization energy decreases with increasing n, while charge-transfer couplings remain weak.
• Hole mobility increases with system size, scaling as ~n^4, reaching up to 2 cm^2/(V·s) in disordered [n]CPPs.

Conclusions:

• A strong inverse correlation exists between reorganization energy and hole mobility (μ ~ λ^-4).
• Orbital delocalization in larger [n]CPPs drives decreased reorganization energies and electronic couplings.
• [n]CPPs show promise for high-performance organic electronic applications.