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Generation and Coherent Control of Pulsed Quantum Frequency Combs
Published on: June 8, 2018
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Coherent singlet fission activated by symmetry breaking
Kiyoshi Miyata1, Yuki Kurashige1,2,3, Kazuya Watanabe1
1Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan.
Nature Chemistry
|September 23, 2017
Summary
Singlet fission in rubrene crystals exhibits a novel coherent pathway alongside the known thermal pathway. This ultrafast process enhances potential photovoltaic applications by efficiently generating triplet excitons.
Area of Science:
- Photovoltaics
- Materials Science
- Quantum Chemistry
Background:
- Singlet fission converts one singlet exciton into two triplet excitons, a process with significant potential for enhancing solar cell efficiency.
- Understanding the dynamics of singlet fission requires detailed knowledge of potential energy surfaces and their conical intersections, which is challenging for molecular aggregates.
Purpose of the Study:
- To investigate the dynamics of singlet fission in rubrene crystals.
- To elucidate the mechanisms and conditions enabling efficient singlet fission for photovoltaic applications.
Main Methods:
- Utilized transient absorption spectroscopy to probe ultrafast dynamics.
- Employed state-of-the-art quantum chemical calculations to model potential energy surfaces and electronic couplings.
Main Results:
- Observed both a coherent, ultrafast singlet fission channel and the conventional thermally assisted incoherent channel in rubrene crystals.
- Identified that the proximity of the conical intersection to the ground-state equilibrium position facilitates the coherent pathway.
- Demonstrated that excitation of an intermolecular symmetry-breaking mode activates the electronic coupling essential for singlet fission.
Conclusions:
- Rubrene crystals exhibit a dual mechanism for singlet fission, including a previously uncharacterized coherent pathway.
- The findings provide critical insights into the fundamental photophysics governing singlet fission, paving the way for advanced photovoltaic materials.
- This study highlights the importance of molecular geometry and intermolecular interactions in controlling exciton dynamics for energy conversion.
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