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Integrating a Triplet-triplet Annihilation Up-conversion System to Enhance Dye-sensitized Solar Cell Response to Sub-bandgap Light
Published on: September 12, 2014
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Spin Statistics for Triplet-Triplet Annihilation Upconversion: Exchange Coupling, Intermolecular Orientation, and
David G Bossanyi1, Yoichi Sasaki2, Shuangqing Wang1
1Department of Physics and Astronomy, The University of Sheffield, Hicks Building, Hounsfield Road, Sheffield S3 7RH, U.K.
JACS Au
|January 3, 2022
Summary
Triplet-triplet annihilation upconversion (TTA-UC) efficiency is governed by spin statistics. Weakly coupled triplet pairs, not strongly coupled ones, influence this, impacting TTA-UC applications in photovoltaics and biomedicine.
Area of Science:
- Photochemistry
- Materials Science
- Organic Electronics
Background:
- Triplet-triplet annihilation upconversion (TTA-UC) enhances light harvesting in photovoltaics and has biomedical uses.
- The spin statistical factor (η) is crucial for TTA-UC efficiency, determining singlet state formation from triplet pairs.
Purpose of the Study:
- To investigate the spin statistics of TTA-UC using rubrene as a model system.
- To challenge the conventional assumption of strong exchange coupling in TTA-UC.
- To develop an updated model for understanding TTA-UC spin statistics.
Main Methods:
- Experimental magnetic field effects on solid rubrene.
- Pump-push-probe spectroscopy.
- Theoretical modeling of spin statistics.
Main Results:
- Experimentally measured magnetic field effects confirm weakly exchange-coupled triplet-pair states in TTA-UC.
- Intermolecular orientation significantly tunes the spin statistical factor (η).
- Evidence for a high-level reverse intersystem crossing channel was found, impacting spin-1 triplet-pair state dynamics.
Conclusions:
- The spin statistics of TTA-UC are governed by weakly coupled triplet pairs and influenced by factors like intermolecular orientation and reverse intersystem crossing.
- An updated model framework rationalizes reported η values across different annihilator systems.
- Harnessing high-level reverse intersystem crossing channels offers a promising strategy to surpass spin statistical limits in TTA-UC.
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