Long-Lived Triplets from Singlet Fission in Pentacene-Decorated Helical Supramolecular Polymers

Area of Science:

• Materials Science
• Photovoltaics
• Supramolecular Chemistry

Background:

• Singlet fission (SF) converts one high-energy singlet exciton into two lower-energy triplet excitons, a process with potential for enhancing solar cell efficiency.
• Triplet-triplet annihilation and rapid decay of triplet excitons limit the practical application of SF in solar energy conversion.
• Understanding structure-property relationships is key to designing efficient SF materials, but this remains a challenge.

Purpose of the Study:

• To investigate intermolecular singlet fission dynamics in solution using helical supramolecular polymers.
• To promote the formation of long-lived, mobile triplet excitons for improved solar energy conversion.
• To establish design principles for advanced SF materials based on self-assembled structures.

Main Methods:

• Utilized helical supramolecular polymers with pentacene side groups, assembled via hydrogen bonding of benzene-1,3,5-tricarboxamide (BTA) cores.
• Investigated singlet fission dynamics and triplet exciton behavior in solution.
• Employed Monte Carlo simulations to analyze triplet diffusion and annihilation processes.

Main Results:

• Achieved singlet fission with triplet quantum yields exceeding 100% within hundreds of picoseconds.
• Demonstrated that triplet diffusion along supramolecular fibers is favored over annihilation, leading to slow triplet decay (tens of microseconds).
• Maintained triplet quantum yields over 100% for at least 100 ns by tuning molecular packing.

Conclusions:

• Helical supramolecular polymers serve as effective templates for achieving long-lived SF-generated triplets.
• The developed materials overcome limitations of triplet-triplet annihilation, paving the way for efficient solar energy conversion.
• This approach offers new strategies for designing advanced materials for photophysical applications.