2006
DOI: 10.1021/ma052505l
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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

Abstract: 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 c… Show more

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Cited by 66 publications
(61 citation statements)
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“…The two faster lifetime components of 48 and 135 ps for the blend at 1.0% are interpreted as the result of intramolecular and/or intermolecular redistribution energy mechanisms due to exciton migration and energy traps before the final PFO radiative state recombination corresponding to the longer decay at 380 ps. 10 Faster decays τ l1 and τ l2 , however, are observed for the bilayer and for the blends at 5.4% and 11.5% MEH PPV concentrations, which is a consequence of the effective energy transfer rate to the MEH PPV sites. The consecutive increase of τ r 1 for the blends is interpreted as a more complex MEH PPV recombination probably due to intermediary intermolecular MEH PPV/PFO complexation states (steric interactions) that would take place with increasing MEH PPV concentration in the blend.…”
Section: Resultsmentioning
confidence: 86%
“…The two faster lifetime components of 48 and 135 ps for the blend at 1.0% are interpreted as the result of intramolecular and/or intermolecular redistribution energy mechanisms due to exciton migration and energy traps before the final PFO radiative state recombination corresponding to the longer decay at 380 ps. 10 Faster decays τ l1 and τ l2 , however, are observed for the bilayer and for the blends at 5.4% and 11.5% MEH PPV concentrations, which is a consequence of the effective energy transfer rate to the MEH PPV sites. The consecutive increase of τ r 1 for the blends is interpreted as a more complex MEH PPV recombination probably due to intermediary intermolecular MEH PPV/PFO complexation states (steric interactions) that would take place with increasing MEH PPV concentration in the blend.…”
Section: Resultsmentioning
confidence: 86%
“…The increase in the emission intensity from trap sites looks similar to the effects of keto defects in polyfluorene, 24 where one sees large increases in a LE, broad peak in solid state in comparison to solution and where longer wavelength peaks act as luminescence quencher sites via energy transfer mechanisms. 25 The quenching is so effective that very large changes in emission color of the material may be observed as in CBP. Castex 26 observed the photodegradation under UV light illumination of the carbazole derivative N , N-diethyl-3,3-bicarbazyl, causing the emergence of a new emission band between 400 and 500 nm.…”
Section: -5mentioning
confidence: 99%
“…Recently, fluorenone-fluorene statistical co-polymers were synthesized. Their solutions exhibited a featureless emission band centred at 535 nm, even at low concentrations, consequently excluding the formation of excimers or aggregates and confirming that keto defects are responsible for the green emission band (24,25). However, the presence of on-chain defects does not completely explain the intensity of green bands in degraded PFs; for this reason, interchain interactions and the formation of fluorenonebased excimers has been proposed by Sims et al (26).…”
Section: Introductionmentioning
confidence: 64%