Extremely efficient exciton fission and fusion and its dominant contribution to the photoluminescence yield in rubrene single crystals

Biaggio, Ivan; Irkhin, Pavel

doi:10.1063/1.4857095

Cited by 34 publications

(58 citation statements)

References 17 publications

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“…This was consistent with some previous reports that non-geminate triplets did not play an important role in the fission/fusion dynamics in amorphous organic solids [16,19]. This differs considerably from previous observation of triplet dynamics in rubrene crystals [24][25][26], where triplet excitons can freely diffuse in crystal and collide with each other to form intermediate 1 (TT) i states. In that case, the intensity of delayed fluorescence is proportional to n(t) 2 , where n(t) is triplet exciton density.…”

Section: Resultssupporting

confidence: 68%

Temperature-dependent singlet exciton fission observed in amorphous rubrene films

Chen

Zhang

et al. 2015

Organic Electronics

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Section: Resultssupporting

confidence: 68%

Temperature-dependent singlet exciton fission observed in amorphous rubrene films

Chen

Zhang

et al. 2015

Organic Electronics

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“…This value is determined only by the observed decay dynamics and measured pulse fluences, and it agrees well with previous estimates. 2,3 Put another way, the measurements in Fig. 3 imply that quadratic recombination leads to the destruction of 50% of the original excitation after $3 ns at an average excitation density at the surface of the crystal corresponding to q 0 $ 0.5 Â 10 20 .…”

Section: à3mentioning

confidence: 99%

“…2,3 Singlet fission in rubrene single crystals has not been consistently described yet. Tao et al 4 have observed a $100 ps fast decay of a photoinduced infrared absorption band which they assigned to singlet excitons, but they interpreted the decay as caused by exciton dissociation, not fission.…”

Section: à3mentioning

confidence: 99%

“…Investigating triplet dynamics in rubrene is particularly interesting because of its large triplet diffusion length of 4 lm, 17 long triplet lifetime of 100 ls, 2,14 large hole mobility, [19][20][21][22] large delayed photocurrent 23,24 due to triplet dissociation, and large triplet fusion probabilities. 2,3 Transient grating experiments are based on the photoexcitation of a spatial excited state distribution using the interference pattern between two optical pulses, followed by the detection of the resulting absorption or polarizability changes by diffraction of a time-delayed probe pulse from the resulting grating. Compared to the straight detection of a photoinduced absorption, transient grating experiments are characterized by a backgroundless signal that allows the detection of both absorption and refractive index changes with a higher sensitivity.…”

Section: à3mentioning

confidence: 99%

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Nanosecond pump and probe observation of bimolecular exciton effects in rubrene single crystals

Ward

Richman

Biaggio

2015

Applied Physics Letters

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Transient grating pump and probe experiments are used to investigate excitonic processes on the nanosecond time scale in rubrene single crystals. We find that bimolecular interactions cause a photoinduced excited state density on the order of 0.5 × 1020 cm−3—corresponding to an average distance of ∼3 nm between individual states—to decrease by a factor of 2 after 2 ns, following a typical power-law decay. We assign the observed power-law decays to high-density interactions between excited states. Because of the high efficiency singlet exciton fission observed in rubrene, these bimolecular interactions are likely those between triplet excitons or between coherent quantum superpositions of a singlet and a pair of triplet-excitons.

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“…Moreover, rubrene shows high singlet fission efficiencies in both, single crystals 22,23 and amorphous thin films 24 . Rubrene became thus a model system to study intermolecular interactions and charge transport properties of molecular solid states 10,20,21,[25][26][27][28][29][30][31] .…”

Section: Introductionmentioning

confidence: 99%

Transient Monolayer Structure of Rubrene on Graphite: Impact on Hole–Phonon Coupling

Bussolotti

Xin

et al. 2016

J. Phys. Chem. C

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Charge transport in molecular thin films is often dominated by incoherent hopping processes and charge-carrier phonon coupling plays a major role in defining mobilities. Our high resolution angle-resolved ultraviolet photoelectron spectroscopy (ARUPS) study reveals the influence of molecular configuration and packing on the hole-phonon coupling in vacuum-sublimed thin films of rubrene on graphite and allows determining charge reorganization energies. In the contact layer to the substrate rubrene is well-ordered with, for low coverages, the tetracene backbone being almost parallel to the graphite surface forming a loose-packed monolayer. Increasing the coverage leads to an orientational transition and a more tilted orientation of rubrene in a close-packed monolayer. This transition results in dramatic changes of spectral features in ARUPS including the photoelectron angular distribution of the highest occupied molecular orbital derived intensity. The charge reorganization energy, however, only changes slightly. The transient monolayer structure of rubrene on graphite allows thus to demonstrate that hole-phonon coupling in organic thin films does not depend very critically on the packing structure. IntroductionLow charge-carrier mobilities are often limiting the performance of organic (opto-)electronic devices as charge transport in organic semiconductor thin films is often dominated by incoherent hopping processes 1-4 . Hopping mobilities depend critically on the charge-carrier phonon coupling 5-8 , which determines the charge reorganization energy λ. In most molecular thin films intermolecular interactions are weak and λ is consequently dominated by intramolecular vibrations and is often taken from gas-phase calculations 5,9-11 or gas-phase ultraviolet photoelectron spectroscopy (UPS) data 9,12-14 . However, the relevant quantities for device application are the solid state values, which depend on the molecular surrounding, i.e. the interaction with neighboring molecules and/or a substrate 7,15 . Due to the similarities of ionization (followed by neutralization) during localized hopping transport and photoionization, UPS is the method of choice to measure charge reorganization energies of organic thin films by an analysis of the vibrational fine structure of the highest occupied molecular orbital (HOMO)-derived peak 7,8,[15][16][17][18] . The relevant vibrational energies (hν i ) of a molecule are often centered closely and in good approximation the analysis can be done by a single mode fit with one main vibrational energy (hν) 19 . Moreover, in most molecular thin films the relaxation energies for ionization and neutralization of a molecule are rather similar and the charge reorganization energy is thus simply given by λ=2Shν with S being the Huang-Rhys factor, which is determined by the relative intensity contribution to the vibrational progressions 7,13 .

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Extremely efficient exciton fission and fusion and its dominant contribution to the photoluminescence yield in rubrene single crystals

Cited by 34 publications

References 17 publications

Temperature-dependent singlet exciton fission observed in amorphous rubrene films

Temperature-dependent singlet exciton fission observed in amorphous rubrene films

Nanosecond pump and probe observation of bimolecular exciton effects in rubrene single crystals

Transient Monolayer Structure of Rubrene on Graphite: Impact on Hole–Phonon Coupling

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