Investigation of the appropriateness of sensitized luminescence to determine exciton motion parameters in pure molecular crystals

Kenkre, V. M.; Parris, Paul Ernest; Schmid, Dirk

doi:10.1103/physrevb.32.4946

Cited by 40 publications

(43 citation statements)

References 61 publications

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“…This corrects our previous findings 20 and establishes a lower limit 39,40 for the magnitude of the energy migration rate constant in these systems of 0.12 ps -1 (1.2 × 10 -11 s -1 ). This value is in excellent agreement with recent reports [7][8][9] where the intramolecular energy migrations rate constant is computed for oligoindenofluorenes to be in the range of 0.06-0.25 ps -1 .…”

Section: Discussionsupporting

confidence: 75%

Fast and Slow Time Regimes of Fluorescence Quenching in Conjugated Polyfluorene−Fluorenone Random Copolymers: The Role of Exciton Hopping and Dexter Transfer along the Polymer Backbone

et al. 2006

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The luminescence decay kinetics of polyfluorene copolymers containing fluorenone units randomly distributed along the polymer chain have been studied by steady-state and time-resolved fluorescence techniques in toluene solution. The typical green emission from polyfluorenes containing 9-fluorenone moieties is only observed if the 9-fluorenone group is covalently attached to the polymer. Small-angle neutron scattering (SANS) measurements indicate that, independent of the 9-fluorenone fraction, all the studied copolymers adopt an open wormlike conformation. This prevalent 1-dimensional arrangement confirms that the green emission observed with polyfluorenes is not the result of excimer formation in the typical sandwich-like conformation. Analysis of time-resolved fluorescence decays by the maximum entropy method (MEM) collected at the polyfluorene emission (415 nm) and by global analysis of decays collected at 415 and 580 nm (the 9-fluorenone defect emission wavelength) clearly indicates two different time regimes in the population of the fluorenone defect: one occurring in the time interval of 10 to 30 ps and a second one occurring in the time range from 70 to 200 ps. While the slower process shows a linear dependence with the 9-fluorenone fraction, compatible with a hopping migration process along the polymer chain, the faster process does not show such a dependence and instead suggests a short-range Dexter mechanism. These findings are in agreement with our previous work where the presence of a faster component was suggested.

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Section: Discussionsupporting

confidence: 75%

Fast and Slow Time Regimes of Fluorescence Quenching in Conjugated Polyfluorene−Fluorenone Random Copolymers: The Role of Exciton Hopping and Dexter Transfer along the Polymer Backbone

et al. 2006

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“…As a helpful method to discriminate between capture and motion effects, surface-quenched time-resolved luminescence experiments have been also suggested. 17,23 Recent time-resolved luminescence decay measurements in conjugated polymer/fullerene heterostructures confirmed the dominance of diffusion-limited exciton quenching. 24 Consequently, eq 1 can be simplified by assuming an infinite exciton quenching rate at the polymer/fullerene interface, without any x dependence.…”

Section: Resultsmentioning

confidence: 99%

“…Two decades ago, it had been extensively demonstrated that a similar model, applied in molecular crystals with exciton traps, can cause a dramatic underestimation of the characteristic diffusion parameters: diffusion constant D and diffusion length L D . 17 This originates from the fact that two distinct rates govern the total exciton quenching process: the rate at which excitons migrate into the regions occupied by trap molecules, quantified by the diffusion term in eq 1, and second, the rate at which an excitation decays to the trap states from neighboring host molecules once it approaches a trap, described by the dissociation (capture) term in eq 1 given by -S(x)n(x, t). Thus, luminescence quenching by exciton traps introduced into organic crystals has been proven to be capture-but not motion-limited, which results from the fact that the exciton motion is faster then the exciton capture by traps.…”

Section: Resultsmentioning

confidence: 99%

Accurate Measurement of the Exciton Diffusion Length in a Conjugated Polymer Using a Heterostructure with a Side-Chain Cross-Linked Fullerene Layer

et al. 2005

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Accurate measurement of the exciton diffusion length in a conjugated polymer using a heterostructure with a side-chain cross-linked fullerene layer Markov, Denis E.; Amsterdam, Emiel; Blom, Paul W.M.; Sieval, Alexander B.; Hummelen, Jan C. Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands, and Biomade Technology Foundation, Nijenborgh 4, 9747 AG Groningen, The Netherlands ReceiVed: February 24, 2005; In Final Form: April 22, 2005 Exciton diffusion and photoluminescence quenching in conjugated polymer/fullerene heterostructures are studied by time-resolved photoluminescence. It is observed that heterostructures consisting of a spin-coated poly(pphenylene vinylene) (PPV)-based derivative and evaporated C 60 are ill-defined because of diffusion of C 60 into the polymer, leading to an overestimation of the exciton diffusion length. This artifact is resolved by the use of a novel, thermally side-chain polymerizing and cross-linking fullerene derivative (F2D) containing two diacetylene moieties, forming a completely immobilized electron acceptor layer. With this heterostructure test system, an exciton diffusion length of 5 ( 1 nm is derived for this PPV derivative from time-integrated luminescence quenching data.

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“…Thus, different research groups report different values of exciton diffusion length even for the same material largely due to the differences in the experimental methods they employ and the modeling of the data collected from these experiments. [6,8,[12][13][14][15] Most of these techniques are based on the quenching of photoluminescence (PL) in a bilayer donor/acceptor heterostructure where the population of photogenerated excitons is observed in the donor layer. After photoexcitation of the donor phase, the excitons migrate to the donor/acceptor interface and the excitons split into charges by transferring electrons to the acceptor phase.…”

Section: Introductionmentioning

confidence: 99%

Exciton Migration in Conjugated Dendrimers: A Joint Experimental and Theoretical Study

Köse¹,

Gräf²,

Kopidakis³

et al. 2009

ChemPhysChem

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We report a joint experimental and theoretical investigation of exciton diffusion in phenyl-cored thiophene dendrimers. Experimental exciton diffusion lengths of the dendrimers vary between 8 and 17 nm, increasing with the size of the dendrimer. A theoretical methodology is developed to estimate exciton diffusion lengths for conjugated small molecules in a simulated amorphous film. The theoretical approach exploits Fermi's Golden Rule to estimate the energy transfer rates for a large ensemble of bimolecular complexes in random relative orientations. Utilization of Poisson's equation in the evaluation of the Coulomb integral leads to very efficient calculation of excitonic couplings between the donor and the acceptor chromophores. Electronic coupling calculations with delocalized transition densities revealed efficient coupling pathways in the bulk of the material, but do not result in strong couplings between the chromophores which are calculated for more localized transition densities. The molecular structures of dendrimers seem to be playing a significant role in the magnitude of electronic coupling between chromophores. Simulated diffusion lengths correlate well with the experimental data. The chemical structure of the chromophore, the shape of the transition densities and the exciton lifetime are found to be the most important factors in determining the size of the exciton diffusion length in amorphous films of conjugated materials.

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Investigation of the appropriateness of sensitized luminescence to determine exciton motion parameters in pure molecular crystals

Cited by 40 publications

References 61 publications

Fast and Slow Time Regimes of Fluorescence Quenching in Conjugated Polyfluorene−Fluorenone Random Copolymers: The Role of Exciton Hopping and Dexter Transfer along the Polymer Backbone

Fast and Slow Time Regimes of Fluorescence Quenching in Conjugated Polyfluorene−Fluorenone Random Copolymers: The Role of Exciton Hopping and Dexter Transfer along the Polymer Backbone

Accurate Measurement of the Exciton Diffusion Length in a Conjugated Polymer Using a Heterostructure with a Side-Chain Cross-Linked Fullerene Layer

Exciton Migration in Conjugated Dendrimers: A Joint Experimental and Theoretical Study

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