Singlet fission in a hexacene dimer: energetics dictate dynamics
Samuel N Sanders1, Elango Kumarasamy1, Kealan J Fallon1
1Department of Chemistry, Columbia University New York NY 10027 USA lc2730@columbia.edu.
Chemical Science
|June 4, 2021
Summary
Singlet fission in hexacene dimers reveals design rules for efficient solar cells. Controlling energy gaps is key to optimizing this exciton multiplication process for higher solar energy conversion.
Area of Science:
- Photochemistry
- Materials Science
- Renewable Energy
Background:
- Singlet fission (SF) enhances solar cell efficiency by creating two triplet excitons from one singlet exciton.
- SF typically occurs in solid-state crystals, but molecular dimers offer insights into fundamental photophysics.
- Hexacene dimers serve as model systems to study SF dynamics.
Purpose of the Study:
- To synthesize and characterize the singlet fission properties of a hexacene dimer.
- To compare SF dynamics in hexacene dimers with tetracene and pentacene dimers.
- To establish design principles for future singlet fission chromophores.
Main Methods:
- Covalent coupling of hexacene molecules to form dimers.
- Photophysical characterization techniques to study exciton dynamics.
- Comparative analysis of SF rates and triplet pair recombination in different acene dimers.
Main Results:
- Excess exoergicity in hexacene dimers was found to slow down singlet fission.
- Lower triplet energy in hexacene dimers increased triplet pair recombination rates, consistent with the energy gap law.
- The study identified key energy gap parameters influencing SF efficiency.
Conclusions:
- Minimal energy gap between singlet and triplet pair states is crucial for efficient SF.
- A large energy gap between the triplet pair and ground state minimizes recombination losses.
- These findings provide critical design rules for developing advanced singlet fission materials for solar cells.
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