Singlet fission in a hexacene dimer: energetics dictate dynamics

Sanders, Samuel N.; Kumarasamy, Elango; Fallon, Kealan J.; Sfeir, Matthew Y.; Campos, Luis M.

doi:10.1039/c9sc05066c

Cited by 39 publications

(65 citation statements)

References 63 publications

(97 reference statements)

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“…dynamics have widely been studied using the transient absorption spectroscopic methods together with theoretical modeling taking into account the vibronic effects in the ultrafast regimes. [9][10][11][12][13][14][15] The correlated intermolecular triplet pair 1 (TT) generated with the singlet character is known to be converted to the quintet (Q) state as 5 (TT). [16][17][18][19][20][21][22][23][24][25] These TT pairs separate into individual triplets as the T+T state.…”

Section: Toc Graphicsmentioning

confidence: 99%

Geometries and Terahertz Motions Driving Quintet Multiexcitons and Ultimate Triplet–Triplet Dissociations via the Intramolecular Singlet Fissions

et al. 2020

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Importance of vibronic effects has been highlighted for the singlet-fission (SF) that convert one high-energy singlet exciton into doubled triplet excitons, as strongly correlated multiexcitons. However, molecular mechanisms of spin conversion processes and ultimate de-couplings in the multiexcitons are poorly understood. We have analyzed geometries and exchange couplings of the photoinduced multiexcitons in the pentacene dimers bridged by a phenylene at ortho and meta positions [denoted as o-(Pc) 2 and m-(Pc) 2 ] by simulations of the time-resolved electron paramagnetic resonance spectra. We clarified that terahertz molecular conformation dynamics plays a role on the spin conversion from the singlet strongly coupled multiexcitons 1 (TT) to the quintet state 5 (TT). The strongly coupled 5 (TT) multiexcitons are revealed to possess entirely planar conformations stabilized by mutually delocalized spin distributions, while the intramolecular de-coupled spin-correlated triplet pairs generated at 1 microsecond are also stabilized by distorted conformations resulting in two separately localized biradical characters. File list (2) download file view on ChemRxiv JPCL_SI_PcD-2020_0801.docx (143.92 KiB) download file view on ChemRxiv JPCL_PcD-2020_0804.docx (1.17 MiB)

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Section: Toc Graphicsmentioning

confidence: 99%

Geometries and Terahertz Motions Driving Quintet Multiexcitons and Ultimate Triplet–Triplet Dissociations via the Intramolecular Singlet Fissions

et al. 2020

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“…In the meantime, incoherent SF processes have been mostly examined in molecular dimers by changing linkage types between two chromophores to control relative orientations [42–53] . Feng et al.…”

Section: Introductionmentioning

confidence: 99%

Multiexcitonic Triplet Pair Generation in Oligoacene Dendrimers as Amorphous Solid‐State Miniatures

et al. 2020

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Singlet fission in organic semiconducting materials has attracted great attention for the potential application in photovoltaic devices. Research interests have been concentrated on identifying working mechanisms of coherent SF processes in crystalline solids as ultrafast SF is hailed for efficient multiexciton generation. However, as long lifetime of multiexcitonic triplet pair in amorphous solids facilitates the decorrelation process for triplet exciton extractions, a precise examination of incoherent SF processes is demanded in delicate model systems to represent heterogeneous structures. Heterogeneous coupling and energetics for SF were developed in our oligoacene dendrimers, which mimic complicated SF dynamics in amorphous solids. SF dynamics in dendritic structures was thoroughly investigated by time‐resolved spectroscopic techniques and quantum chemical calculations in respect of the relative orientation/distance between chromophores and though‐bond/‐space interactions.

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“…44,45 The triplet pairs, exhibiting as a singlet state as a whole and makes the fission process spin allowed, play a critical role in the SF process. 29,39,40,[46][47][48][49][50] However, it still remains controversial about the formation and evolution of the triplet pairs during the fission process. [15][16][17][18][19][20][21][22]31,41,[51][52][53][54][55][56] Keeping these in mind, we systematically investigate the excited state dynamics in triisopropylsilylethynyl (TIPS)pentacene thin films by femtosecond (fs) time-resolved transient absorption (TA) spectroscopy.…”

Section: Introductionmentioning

confidence: 99%

“…However, more information related to the properties and dynamics of triplet pairs is still limited, 42,43 which mainly due to their elusiveness in detection 44,45 . The triplet pairs, exhibiting as a singlet state as a whole and makes the fission process spin allowed, play a critical role in the SF process 29,39,40,46‐50 . However, it still remains controversial about the formation and evolution of the triplet pairs during the fission process 15‐22,31,41,51‐56 …”

Section: Introductionmentioning

confidence: 99%

Multiexciton state of singlet fission in triisopropylsilylethynyl‐pentacene

Cui

Jiang

Zhang

et al. 2021

Micro & Optical Tech Letters

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Singlet fission (SF) is a spin-allowed conversion process, in which one singlet exciton is replaced by a pair of triplet excitons resided on adjacent molecules. To rationalize this phenomenon, a multiexcitonic spin-zero triplet-pair state is generally hypothesized as an intermediate state for SF. However, the details of its formation during the fission process, and its subsequent evolution over time are still remain unclear. Thus, this work provides a model of the SF system for triisopropylsilylethynyl-pentacene by using femtosecond time-resolved transient absorption spectroscopy. A mixed state of singlet and multiexciton, which mediates the ultrafast SF process is directly observed. This work represents a new viewpoint for the research on SF intermediates.

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Singlet fission in a hexacene dimer: energetics dictate dynamics

Abstract: We report the synthesis and photophysical characterization of highly exoergic singlet fission in a hexacene dimer revealing exciton dynamics that follow the energy gap law.

Cited by 39 publications

References 63 publications

Geometries and Terahertz Motions Driving Quintet Multiexcitons and Ultimate Triplet–Triplet Dissociations via the Intramolecular Singlet Fissions

Geometries and Terahertz Motions Driving Quintet Multiexcitons and Ultimate Triplet–Triplet Dissociations via the Intramolecular Singlet Fissions

Multiexcitonic Triplet Pair Generation in Oligoacene Dendrimers as Amorphous Solid‐State Miniatures

Multiexciton state of singlet fission in triisopropylsilylethynyl‐pentacene

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