Evidence for Charge-Transfer Mediation in the Primary Events of Singlet Fission in a Weakly Coupled Pentacene Dimer
| Autor: | Michel Volland, Michael R. Wasielewski, Constantin Hetzer, Rik R. Tykwinski, Matthew D. Krzyaniak, Ryan M. Young, Dirk M. Guldi, Bettina S. Basel, Timothy Clark, S. Rajagopala Reddy, Pedro B. Coto, Brian T. Phelan, Michael Thoss, Johannes Zirzlmeier |
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| Rok vydání: | 2018 |
| Předmět: |
Materials science
General Chemical Engineering Exciton Dimer 02 engineering and technology 010402 general chemistry 01 natural sciences Biochemistry law.invention Pentacene chemistry.chemical_compound law Ultrafast laser spectroscopy Materials Chemistry Environmental Chemistry Singlet state Electron paramagnetic resonance Biochemistry (medical) General Chemistry 021001 nanoscience & nanotechnology 0104 chemical sciences chemistry Chemical physics Excited state Singlet fission 0210 nano-technology |
| Zdroj: | ResearcherID |
| ISSN: | 2451-9294 |
| Popis: | Summary Singlet fission (SF) is a process that converts one singlet excited state into two triplet states. The mechanism of SF is still not well understood. Here, we report on the use of a combination of transient absorption and electron paramagnetic resonance spectroscopies in conjunction with theoretical calculations to probe SF in a pentacene dimer linked by a non-conjugated, 1,4-diethynylbicyclo[2.2.2]octane spacer. Next to observing the key intermediates in solution-based SF, including the formation and decay of a quintet state that precedes formation of the pentacene triplet excitons, we demonstrate that the coupling is sufficiently weak that SF is essentially inoperative in non-polar media. Transitioning to a polar medium, however, amplifies the coupling strength such that SF becomes operative and supports long triplet lifetimes. Our results offer strong evidence for a charge-transfer mediation and, in turn, provide a solid framework for decoding the complete mechanism of SF in systems beyond pentacene. |
| Databáze: | OpenAIRE |
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