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Title: Exciton Correlations in Intramolecular Singlet Fission

Journal Article · · Journal of the American Chemical Society

We have synthesized a series of asymmetric pentacene-tetracene heterodimers with a variable-length conjugated bridge that undergo fast and efficient intramolecular singlet fission (iSF). These compounds have distinct singlet and triplet energies, which allow us to study the spatial dynamics of excitons during the iSF process, including the significant role of exciton correlations in promoting triplet pair generation and recombination. We demonstrate that the primary photoexcitations in conjugated dimers are delocalized singlets that enable fast and efficient iSF. However, in these asymmetric dimers, the singlet becomes more localized on the lower energy unit as the length of the bridge is increased, slowing down iSF relative to analogous symmetric dimers. We resolve the recombination kinetics of the inequivalent triplets produced via iSF, and find that they primarily decay via concerted processes. By identifying different decay channels, including delayed fluorescence via triplet-triplet annihilation, we can separate transient species corresponding to both correlated triplet pairs and uncorrelated triplets. Recombination of the triplet pair proceeds rapidly despite our experimental and theoretical demonstration that individual triplets are highly localized and unable to be transported across the conjugated linker. In this class of compounds, the rate of formation and yield of uncorrelated triplets increases with bridge length. Overall, these constrained, asymmetric systems provide a unique platform to isolate and study transient species essential for singlet fission, which are otherwise difficult to observe in symmetric dimers or condensed phases.

Research Organization:
Brookhaven National Laboratory (BNL), Upton, NY (United States). Center for Functional Nanomaterials
Sponsoring Organization:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI ID:
1329780
Report Number(s):
BNL--112603-2016-JA; KC0403020
Journal Information:
Journal of the American Chemical Society, Journal Name: Journal of the American Chemical Society Journal Issue: 23 Vol. 138; ISSN 0002-7863
Publisher:
American Chemical Society (ACS)Copyright Statement
Country of Publication:
United States
Language:
English

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Cited By (39)

Effect of Off-Diagonal Exciton–Phonon Coupling on Intramolecular Singlet Fission journal July 2017
The entangled triplet pair state in acene and heteroacene materials journal July 2017
New insights into the design of conjugated polymers for intramolecular singlet fission journal July 2018
Spin density encodes intramolecular singlet exciton fission in pentacene dimers journal January 2019
Elaborately Tuning Intramolecular Electron Transfer Through Varying Oligoacene Linkers in the Bis(diarylamino) Systems journal November 2016
Striking the right balance of intermolecular coupling for high-efficiency singlet fission journal January 2018
The butterfly effect in bisfluorenylidene-based dihydroacenes: aggregation induced emission and spin switching journal January 2019
Triplet Transfer Mediates Triplet Pair Separation during Singlet Fission in 6,13-Bis(triisopropylsilylethynyl)-Pentacene journal October 2017
Triplet Harvesting from Intramolecular Singlet Fission in Polytetracene journal September 2017
Intramolecular Singlet Fission in an Antiaromatic Polycyclic Hydrocarbon journal July 2017
Intramolecular Singlet Fission in an Antiaromatic Polycyclic Hydrocarbon journal July 2017
High‐Yield Generation of Triplet Excited States by an Efficient Sequential Photoinduced Process from Energy Transfer to Singlet Fission in Pentacene‐Modified CdSe/ZnS Quantum Dots journal July 2018
Theoretical Studies of Singlet Fission: Searching for Materials and Exploring Mechanisms journal February 2018
Charge-Transfer Character in a Covalent Diketopyrrolopyrrole Dimer: Implications for Singlet Fission journal October 2017
Efficient triplet pair separation from intramolecular singlet fission in dibenzopentalene derivatives journal May 2019
Harnessing singlet exciton fission to break the Shockley–Queisser limit journal October 2017
The entangled triplet pair state in acene and heteroacene materials journal July 2017
Quintet multiexciton dynamics in singlet fission journal October 2016
New insights into the design of conjugated polymers for intramolecular singlet fission journal July 2018
Spin density encodes intramolecular singlet exciton fission in pentacene dimers journal January 2019
Ultra-fast intramolecular singlet fission to persistent multiexcitons by molecular design journal August 2019
Elaborately Tuning Intramolecular Electron Transfer Through Varying Oligoacene Linkers in the Bis(diarylamino) Systems journal November 2016
Azaacenes as active elements for sensing and bio applications journal January 2016
Photophysical characterization and time-resolved spectroscopy of a anthradithiophene dimer: exploring the role of conformation in singlet fission journal January 2017
Effect of a heavy heteroatom on triplet formation and interactions in single conjugated polymer molecules and aggregates journal January 2017
6,6′,11,11′-Tetra((triisopropylsilyl)ethynyl)-anti-[2.2](1,4)tetracenophane: a covalently coupled tetracene dimer and its structural, electrochemical, and photophysical characterization journal January 2017
Singlet exciton fission in a linear tetracene tetramer journal January 2018
Striking the right balance of intermolecular coupling for high-efficiency singlet fission journal January 2018
Annihilator dimers enhance triplet fusion upconversion journal January 2019
The butterfly effect in bisfluorenylidene-based dihydroacenes: aggregation induced emission and spin switching journal January 2019
Singlet fission in a hexacene dimer: energetics dictate dynamics journal January 2020
Morphology independent triplet formation in pentalene films: Singlet fission as the triplet formation mechanism journal September 2019
Design of singlet fission chromophores with cyclic (alkyl)(amino) carbene building blocks journal June 2019
Heavy-atom effects on intramolecular singlet fission in a conjugated polymer journal July 2019
Vibrational probe of the origin of singlet exciton fission in TIPS-pentacene solutions journal October 2019
Time dependent correlations of entangled states with nondegenerate branches and possible experimental realization using singlet fission journal September 2019
Lessons from intramolecular singlet fission with covalently bound chromophores journal January 2020
Superintermolecular orbitals in the C 60 -pentacene complex journal December 2016
The entangled triplet pair state in acene and heteroacene materials text January 2017

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