Delocalized exciton formation in C60 linear molecular aggregates

Area of Science:

• Materials Science
• Physical Chemistry
• Organic Electronics

Background:

• Organic semiconductors, particularly those with C60 molecules, are crucial as acceptors in planar perovskite solar cells.
• Understanding exciton properties in C60 aggregates is key to optimizing solar cell performance.

Purpose of the Study:

• To theoretically investigate the optical and excitonic properties of C60 linear molecular aggregates.
• To explore exciton formation mechanisms in varying sizes of C60 aggregates (1-7 molecules).

Main Methods:

• Utilized the real-time-propagation real-time time-dependent density functional theory (rt-TDDFT) technique.
• Analyzed photoabsorption spectra and exciton characteristics.

Main Results:

• Single C60 molecules exhibit photoabsorption peaks dominated by localized molecular excitons.
• C60 linear molecular aggregates show photoabsorption peaks arising from localized molecular excitons, charge transfer excitons, and delocalized excitons.
• This contradicts the established theory that only localized or charge transfer excitons form in such organic materials.

Conclusions:

• The formation of delocalized excitons in C60 aggregates provides novel insights into exciton dynamics.
• These findings can guide the rational design of more efficient organic and perovskite solar cells.