Singlet Fission, Polaron Generation and Intersystem Crossing in Hexaphenyl Film

Area of Science:

• Organic electronics
• Photophysics
• Materials science

Background:

• Hexaphenyl films are promising for organic electronic devices.
• Understanding exciton and polaron dynamics is key to improving device efficiency.

Purpose of the Study:

• To investigate the ultrafast dynamics of triplet excitons and polarons in hexaphenyl films.
• To elucidate the mechanisms and timescales of triplet formation pathways.
• To explore the potential of hexaphenyl films for singlet fission-based solar cells.

Main Methods:

• Time-resolved fluorescence spectroscopy
• Femtosecond transient absorption spectroscopy
• Variable excitation photon energies

Main Results:

• Two distinct triplet formation pathways were identified: singlet fission-intersystem crossing (4.5 ps) and singlet fission from vibrational electronic states (1.5 ns).
• Polarons formed from hot excitons on a <30 fs timescale and recombined with an ultrafast lifetime of 0.37 ps.
• Hexaphenyl film characterization revealed crystal and aggregate morphologies suitable for organic electronics.

Conclusions:

• The findings provide insights into the fundamental photophysical processes in hexaphenyl systems.
• A universally applicable film fabrication method is proposed for hexaphenyl systems.
• This research paves the way for advanced singlet fission solar cells and other organic electronic devices.