Fluence-Dependent Photoinduced Charge Transfer Dynamics in Polymer-Wrapped Semiconducting Single-Walled Carbon...

Area of Science:

• Materials Science
• Physical Chemistry
• Nanotechnology

Background:

• Single-walled carbon nanotubes (SWNTs) can absorb multiple photons, leading to variable exciton densities.
• Excitons in SWNTs interact with charges, enabling diverse charge transfer reactions crucial for energy conversion.

Purpose of the Study:

• To investigate how excitation fluence affects ultrafast charge separation (CS) and charge recombination (CR) dynamics.
• To elucidate the role of exciton-charge interactions in SWNT-based hybrid systems.

Main Methods:

• Utilized a SWNT-molecular donor-acceptor hybrid system (R-PBN(b)-Ph6-PDI-\[(6,5) SWNT]) with fixed spatial organization.
• Employed pump-probe spectroscopy to analyze photoinduced CS and thermal CR reactions across a range of excitation fluences.

Main Results:

• Observed CS states with both geminate and nongeminate spatial relationships between perylene diimide (PDI) radical anions and SWNT hole polarons.
• Found that increasing excitation fluence leads to the formation of lower-energy CS states involving SWNT electron and hole polarons.
• Demonstrated that SWNT excitons can drive additional charge transfer reactions under high excitation conditions.

Conclusions:

• Excitation fluence critically controls charge separation and recombination pathways in SWNT hybrid systems.
• The energy conversion efficiency is influenced by the interplay between excitons, charge carriers, and their spatial organization.
• SWNTs exhibit tunable electronic properties for advanced energy applications based on controlled excitation.