Multiscale modeling of charge transfer in polymers with flexible backbones

Area of Science:

• Materials Science
• Computational Chemistry
• Polymer Physics

Background:

• Understanding charge transport in polymers is crucial for organic electronics.
• Polymers with flexible backbones present unique challenges due to conformational disorder.
• Existing models may not accurately capture carrier dynamics in amorphous polymer systems.

Purpose of the Study:

• To develop and validate a simplified multi-scale modeling approach for evaluating carrier transfer properties in flexible polymers.
• To investigate hole transfer mechanisms in amorphous polyethylene (PE) as a model system.
• To elucidate the impact of conformational disorder on charge carrier mobility.

Main Methods:

• Combined molecular dynamics (MD) simulations, first-principles calculations, and kinetic Monte Carlo (KMC) simulations.
• Utilized polyethylene (PE) oligomers (e.g., C12H26) as model systems for amorphous PE.
• Analyzed hole localization and site energy variations.

Main Results:

• The characteristic length scale of hole localization in PE is comparable to its Kuhn length.
• Polyethylene oligomers of Kuhn length exhibit electronic structures similar to amorphous PE.
• Computed hole mobility in amorphous PE oligomers is significantly lower (several orders of magnitude) than in crystalline PE.
• This reduction is attributed to strong hole localization and energy variations caused by conformational disorder.

Conclusions:

• The proposed multi-scale modeling approach accurately predicts carrier mobilities in polymers with flexible backbones.
• Conformational disorder in amorphous polymers is a primary factor limiting charge carrier mobility.
• The modeling strategy offers a computationally efficient method for predicting polymer electronic properties.