Exciton diffusion and charge transfer dynamics in nano phase-separated P3HT/PCBM blend films

Area of Science:

• Materials Science
• Organic Electronics
• Photophysics

Background:

• Efficient exciton dissociation is crucial for organic photovoltaic devices.
• Understanding exciton dynamics in polymer:fullerene blends is key to improving device performance.

Purpose of the Study:

• To systematically investigate exciton quenching dynamics in pristine P3HT and P3HT/PCBM blend films.
• To elucidate the mechanism of exciton transport to the interface.

Main Methods:

• Femtosecond fluorescence up-conversion spectroscopy was employed.
• Measurements were conducted under various excitation intensities.
• Data was analyzed using a three-dimensional diffusion model.

Main Results:

• Exciton behavior in both pristine and blend films was accurately described by a 3D diffusion model.
• A small diffusion length and large charge transfer radius were observed.
• Excitons primarily reach the interface through delocalization within P3HT fibrils (4.8-9 nm).

Conclusions:

• Exciton delocalization in P3HT fibrils is the dominant pathway for reaching the interface.
• This rapid delocalization facilitates efficient exciton dissociation and charge transfer.
• Findings provide insights for designing high-performance organic electronic materials.