Different Rates of Singlet Fission in Monoclinic versus Orthorhombic Crystal Forms of Diphenylhexatriene

Dillon, Robert J.; Piland, Geoffrey B.; Bardeen, Christopher J.

doi:10.1021/ja409266s

Cited by 139 publications

(192 citation statements)

References 34 publications

(32 reference statements)

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“…The localization of these triplet pairs (coupling to vibrations) may lead to efficient intramolecular singlet fission, as suggested previously for carotenoids (76)(77)(78). Singlet fission has been reported for solid films/aggregates of carotenoids (79) or diphenylhexatriene (80). The addition of the two cyano (−CN) groups may introduce CT characteristics to the singlet excited state, facilitating coupling to the multiexciton state.…”

Section: Figurementioning

confidence: 56%

Charge Transfer–Mediated Singlet Fission

Monahan

Zhu

2015

Annu. Rev. Phys. Chem.

264

403

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Singlet fission, the splitting of a singlet exciton into two triplet excitons in molecular materials, is interesting not only as a model many-electron problem, but also as a process with potential applications in solar energy conversion. Here we discuss limitations of the conventional four-electron and molecular dimer model in describing singlet fission in crystalline organic semiconductors, such as pentacene and tetracene. We emphasize the need to consider electronic delocalization, which is responsible for the decisive role played by the Mott-Wannier exciton, also called the charge transfer (CT) exciton, in mediating singlet fission. At the strong electronic coupling limit, the initial excitation creates a quantum superposition of singlet, CT, and triplet-pair states, and we present experimental evidence for this interpretation. We also discuss the most recent attempts at translating this mechanistic understanding into design principles for CT state-mediated intramolecular singlet fission in oligomers and polymers.

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Section: Figurementioning

confidence: 56%

Charge Transfer–Mediated Singlet Fission

Monahan

Zhu

2015

Annu. Rev. Phys. Chem.

264

403

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“…We have reported and correlated several experimental observables in the present work supporting this interpretation, which is consistent with the general consensus emerging from contemporary theoretical models of singlet fission. 24,30,135 We suggest that incorporating aspects of exciton delocalization 43,45 into theoretical models investigating the effect of various molecular packing arrangements on singlet fission dynamics 32,33 represents a necessary challenge. 33 Journal of the American Chemical Society Article ■ ASSOCIATED CONTENT * S Supporting Information Additional synthetic, experimental, and theoretical details as well as data, including laser pulse characterization, dynamic light scattering measurements, steady-state absorption and fluorescence measurements, fluorescence quantum yield measurements, transient absorption and anisotropy measurements, analysis of crystallographic data, X-ray diffractograms, and molecular orbitals for a pair of functionalized pentacenes.…”

Section: ■ Conclusionmentioning

confidence: 99%

Exciton Delocalization Drives Rapid Singlet Fission in Nanoparticles of Acene Derivatives

et al. 2015

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We compare the singlet fission dynamics of five pentacene derivatives precipitated to form nanoparticles. Two nanoparticle types were distinguished by differences in their solid-state order and kinetics of triplet formation. Nanoparticles that comprise primarily weakly coupled chromophores lack the bulk structural order of the single crystal and exhibit nonexponential triplet formation kinetics (Type I), while nanoparticles that comprise primarily more strongly coupled chromophores exhibit order resembling that of the bulk crystal and triplet formation kinetics associated with the intrinsic singlet fission rates (Type II). In the highly ordered nanoparticles, singlet fission occurs most rapidly. We relate the molecular packing arrangement derived from the crystal structure of the pentacene derivatives to their singlet fission dynamics and find that slip stacking leads to rapid, subpicosecond singlet fission. We present evidence that exciton delocalization, coincident with an increased relative admixture of charge-transfer configurations in the description of the exciton wave function, facilitates rapid triplet pair formation in the case of single-step singlet fission. We extend the study to include two hexacene derivatives and find that these conclusions are generally applicable. This work highlights acene derivatives as versatile singlet fission chromophores and shows how chemical functionalization affects both solid-state order and exciton interactions and how these attributes in turn affect the rate of singlet fission.

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“…1, 2 Decades after its first observation in anthracene crystals, SF has been recently experimented in a wide variety of crystalline organic materials, [3][4][5][6][7][8][9][10] polymers, 11 quantum dots, 12 and in solution. 13 One of the reasons behind a renewed interest on this physical phenomenon is given by the opportunity to exploit it, in order to overcome the Shockley-Queisser theoretical limit of conversion efficiency for single junction solar cells, 14 a possibility that has been verified in few instances 4,15 but it is still under debate.…”

Section: Introductionmentioning

confidence: 99%

Singlet fission in linear chains of molecules

Ambrosio

Troisi

2014

The Journal of Chemical Physics

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We develop a model configuration interaction Hamiltonian to study the electronic structure of a chain of molecules undergoing singlet fission. We first consider models for dimer and trimers and then we use a matrix partitioning technique to build models of arbitrary size able to describe the relevant electronic structure for singlet fission in linear aggregates. We find that the multi-excitonic state (ME) is stabilized at short inter-monomer distance and the extent of this stabilization depends upon the size of orbital coupling between neighboring monomers. We also find that the coupling between ME states located on different molecules is extremely small leading to bandwidths in the order of ~10meV. This observation suggests that multi-exciton states are extremely localized by electron-phonon coupling and that singlet fission involves the transition between a relatively delocalized Frenkel exciton and a strongly localized multi-exciton state. We adopt the methodology commonly used to study non-radiative transitions to describe the singlet fission dynamics in these aggregates and we discuss the limit of validity of the approach. The results indicate that the phenomenology of singlet fission in molecular crystals is different in many important ways from what is observed in isolated dimers.

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Different Rates of Singlet Fission in Monoclinic versus Orthorhombic Crystal Forms of Diphenylhexatriene

Cited by 139 publications

References 34 publications

Charge Transfer–Mediated Singlet Fission

Charge Transfer–Mediated Singlet Fission

Exciton Delocalization Drives Rapid Singlet Fission in Nanoparticles of Acene Derivatives

Singlet fission in linear chains of molecules

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