Surface hopping simulations on charge separation in an organic donor-acceptor system

Area of Science:

• Organic electronics
• Photovoltaics
• Computational chemistry

Background:

• Charge separation is crucial for organic solar cell efficiency.
• Understanding exciton dissociation mechanisms is key.
• Simulations offer insights into complex molecular processes.

Purpose of the Study:

• To simulate charge separation in a model organic donor-acceptor system.
• To investigate factors influencing charge separation yield.
• To explore the role of external electric fields.

Main Methods:

• Surface hopping method.
• Pariser-Parr-Pople (PPP) Hamiltonian.
• Configuration Interaction Singles (CIS) approximation.

Main Results:

• Simulated electron transfer from donor to acceptor chains, forming polaron pairs.
• Full charge separation observed before system relaxation to the lowest excited state.
• Charge separation yield strongly depends on donor-acceptor band offset, less on photoexcitation energy.

Conclusions:

• Band offset is the primary driver for charge separation in this system.
• External electric fields significantly impact free charge generation.
• The simulation methodology provides a valuable tool for studying organic photovoltaic processes.