Revealing the Nature of Singlet Fission under the Veil of Internal Conversion

Singlet fission (SF) holds the potential to boost the maximum power conversion efficiency of photovoltaic devices. Internal conversion (IC) has been considered as one of the major competitive deactivation pathways to transform excitation energy into heat. Now, using time‐resolved spectroscopy and th...

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Bibliographic Details
Published in:Angewandte Chemie International Edition 2020-01, Vol.59 (5), p.2003-2007
Main Authors: Wang, Long, Bai, Shuming, Wu, Yishi, Liu, Yanping, Yao, Jiannian, Fu, Hongbing
Format: Article
Language:English
Subjects:
Deactivation
Energy conversion efficiency
Fission
Internal conversion
intramolecular singlet fission
isoindigo
Maximum power
photophysics
Photovoltaic cells
Photovoltaics
Spectroscopy
transient absorption spectroscopy
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Summary:Singlet fission (SF) holds the potential to boost the maximum power conversion efficiency of photovoltaic devices. Internal conversion (IC) has been considered as one of the major competitive deactivation pathways to transform excitation energy into heat. Now, using time‐resolved spectroscopy and theoretical calculation, it is demonstrated that, instead of a conventional IC pathway, an unexpected intramolecular singlet fission (iSF) process is responsible for excited state deactivation in isoindigo derivatives. The 1TT state could form at ultrafast rate and nearly quantitatively in solution. In solid films, the slipped stacked intermolecular packing of a thiophene‐functionalized derivative leads to efficient triplet pair separation, giving rise to an overall triplet yield of 181 %. This work not only enriches the pool of iSF‐capable materials, but also contributes to a better understanding of the iSF mechanism, which could be relevant for designing new SF sensitizers. Deactivate by fission: An efficient intramolecular singlet fission (iSF) process, rather than detrimental internal conversion, is shown to be responsible for excited‐state deactivation in isoindigo derivatives. The 1(TT) states are generated nearly quantitatively in solution and can further split into two independent free triplets with a yield of about 180 % in solid thin films.
ISSN:1433-7851
1521-3773
DOI:10.1002/anie.201912202