Dopant-Catalyzed Singlet Exciton Fission

Area of Science:

• Solid-state photophysics
• Molecular crystal dynamics
• Organic electronics

Background:

• Singlet exciton fission (SEF) in acene-based molecular crystals is a key process for organic electronics.
• SEF occurs via superexchange, mediated by virtual charge-transfer states, making it sensitive to the local molecular environment.

Purpose of the Study:

• To investigate the influence of local environmental factors on singlet exciton fission.
• To explore the potential of using dopant molecules to catalyze and enhance SEF rates.

Main Methods:

• Model calculations of superexchange coupling in acene-based molecular crystals.
• Analysis of charge-quadrupole interactions and their balance with surrounding matrix interactions.
• Inclusion of effects from vacancies, impurities, polarization, and dipolar contributions.

Main Results:

• Superexchange coupling is highly sensitive to local symmetry and environmental perturbations.
• Breaking local symmetry, e.g., near vacancies or impurities, affects SEF.
• Model calculations demonstrate that dopant molecules can effectively catalyze SEF.

Conclusions:

• The local environment critically controls singlet exciton fission rates in molecular crystals.
• Carefully designed dopant molecules can significantly enhance SEF, with dipolar dopants showing potential for order-of-magnitude increases.
• This finding opens avenues for optimizing organic electronic devices through targeted molecular design.