Tuning Singlet Fission in π-Bridge-π Chromophores
- Columbia Univ., New York, NY (United States). Department of Chemistry
- University of New South Wales, Sydney (Australia). School of Photovoltaic and Renewable Energy Engineering; University of Cambridge (United Kingdom). Cavendish Laboratory
- University of New South Wales, Sydney (Australia). ARC Centre of Excellence in Exciton Science, School of Physics
- Cornell Univ., Ithaca, NY (United States). Department of Chemistry and Chemical Biology; Cambridge University (United Kingdom). Jesus College
- Cornell Univ., Ithaca, NY (United States). Department of Chemistry and Chemical Biology
- Princeton Univ., NJ (United States). Department of Chemistry
- Brookhaven National Lab. (BNL), Upton, NY (United States). Center for Functional Nanomaterials
For this study, we have designed a series of pentacene dimers separated by homoconjugated or nonconjugated bridges that exhibit fast and efficient intramolecular singlet exciton fission (iSF). These materials are distinctive among reported iSF compounds because they exist in the unexplored regime of close spatial proximity but weak electronic coupling between the singlet exciton and triplet pair states. Using transient absorption spectroscopy to investigate photophysics in these molecules, we find that homoconjugated dimers display desirable excited-state dynamics, with significantly reduced recombination rates as compared to conjugated dimers with similar singlet fission rates. In addition, unlike conjugated dimers, the time constants for singlet fission are relatively insensitive to the interplanar angle between chromophores, since rotation about σ bonds negligibly affects the orbital overlap within the π-bonding network. In the nonconjugated dimer, where the iSF occurs with a time constant >10 ns, comparable to the fluorescence lifetime, we used electron spin resonance spectroscopy to unequivocally establish the formation of triplet–triplet multiexcitons and uncoupled triplet excitons through singlet fission. Together, these studies enable us to articulate the role of the conjugation motif in iSF.
- Research Organization:
- Brookhaven National Laboratory (BNL), Upton, NY (United States). Center for Functional Nanomaterials (CFN)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES)
- Grant/Contract Number:
- SC0012704; SC0015429
- OSTI ID:
- 1413948
- Report Number(s):
- BNL-114743-2017-JA; KC0403020; TRN: US1800601
- Journal Information:
- Journal of the American Chemical Society, Vol. 139, Issue 36; ISSN 0002-7863
- Publisher:
- American Chemical Society (ACS)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
Web of Science
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