Charge-transfer electronic states in organic solar cells: a TDDFT study

Area of Science:

• Materials Science
• Computational Chemistry
• Renewable Energy

Background:

• Organic solar cells (OSCs) efficiency depends on charge-transfer (CT) states governing electron transfer.
• Current computational methods struggle to integrate morphology effects with electron-transfer calculations.
• Existing formalisms for electron transfer lack connection to phase morphologies.

Purpose of the Study:

• To develop a simple, fast method for characterizing electron-transfer processes in organic solar cells.
• To determine electron-transfer rate constants by analyzing excitation energy distributions.
• To enable the rational design of novel organic photovoltaic materials.

Main Methods:

• Utilized time-dependent density-functional theory (TD-DFT) calculations.
• Analyzed vertical excitation energies of local excitation (LE) and charge-transfer (CT) states.
• Extracted donor-acceptor pair structures from molecular dynamics simulations (MDS).

Main Results:

• Proposed a method based on the distribution of vertical excitation energies.
• Tested various density functionals and dielectric models.
• Found a strong correlation between the proposed method and experimental data for electron-transfer events.

Conclusions:

• The developed method offers a simple and fast characterization of electron-transfer processes.
• The approach successfully links computational analysis with experimental observations.
• This method holds promise for the rational design of advanced organic photovoltaic materials.