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Published on: December 27, 2018
9.2K
Using temperature dependent fluorescence to evaluate singlet fission pathways in tetracene single crystals.
Chad D Cruz1, Eric L Chronister2, Christopher J Bardeen1
1Department of Chemistry, University of California Riverside, Riverside, California 92521, USA.
The Journal of Chemical Physics
|December 23, 2020
Summary
Singlet fission in tetracene crystals shows temperature-dependent mechanisms. Above 250 K, direct triplet production is thermally activated, while below 250 K, it
Area of Science:
- Photophysics
- Materials Science
- Quantum Mechanics
Background:
- Singlet fission is a key process for enhancing solar cell efficiency.
- Understanding the mechanism of singlet fission in organic semiconductors is crucial.
- Tetracene is a model system for studying singlet fission due to its favorable properties.
Purpose of the Study:
- To elucidate the temperature-dependent mechanism of singlet fission in single tetracene crystals.
- To investigate the role of exciton localization and structural defects in triplet pair formation.
Main Methods:
- Temperature-dependent measurements of fluorescence spectrum, decay rate, and spin quantum beats.
- Analysis of vibronic lineshape to determine exciton localization.
- Kinetic analysis of delayed fluorescence components.
Main Results:
- Exciton localization observed at 400 K, but singlet fission remains Arrhenius-like.
- Direct, thermally activated production of triplet pairs above 250 K.
- Complex, defect-sensitive triplet production below 250 K, with distinct emission pathways.
Conclusions:
- Singlet fission in tetracene involves distinct mechanisms at different temperature regimes.
- Above 250 K, a direct, thermally activated process dominates triplet generation.
- Below 250 K, triplet production is complex and influenced by structural defects.
