Ultrafast charge generation in a homogenous polymer domain

Area of Science:

• Materials Science
• Physical Chemistry
• Organic Electronics

Background:

• Efficient charge generation is crucial for high-performance organic photovoltaic devices.
• Charge separation mechanisms in heterojunctions are understood, but generation in homogenous polymer domains is unclear.

Purpose of the Study:

• To explore the mechanism of free charge carrier generation in homogenous polymer domains.
• To provide a theoretical explanation for ultrafast charge generation in pure polymer phases.

Main Methods:

• Utilized the extended tight-binding Su-Schrieffer-Heeger (SSH) model.
• Employed non-adiabatic molecular dynamics simulations to model polymer arrays in an electric field.

Main Results:

• Under a weak electric field (5.0 × 10⁻³ V/Å), excited states evolve into free charges within femtoseconds with 97% efficiency.
• Intermolecular coupling in stacked polymers delocalizes excited states, competing with electron-phonon coupling.
• Homogenous domains exhibit lower exciton binding energy, reduced energy dissipation, and faster charge separation.

Conclusions:

• Provides a mechanism for ultrafast charge generation in pure polymer phases, linked to exciton delocalization.
• Suggests devices based on homogenous domains are stress-sensitive and anisotropic due to competing interactions.
• Offers insights for designing advanced organic functional materials and devices.