Optimization of the Luminescence Efficiencies in Solution-Processed Phosphorescent Dendrimers

Ribierre, Jean Charles; Stevenson, Stuart G.; Samuel, Ifor D. W.; Staton, S.V.; Burn, Paul L.

doi:10.1109/jdt.2007.896744

Cited by 16 publications

(18 citation statements)

References 18 publications

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“…30 From these PLQY values, the temperature dependence of the integrated phosphorescence intensities, and the PL lifetimes, we could determine the temperature dependence of the radiative and nonradiative decay rates, noted k R and k NR , respectively, in both the neat film and the blend using PLQY= k R / ͑k R + k NR ͒ and 1 / = k R + k NR . We verified that the radiative decay rates in the neat film and in the blend were the same ͑within the 5% error in the measurements͒.…”

Section: Resultsmentioning

confidence: 99%

“…4, k q decreases from 3.5ϫ 10 5 s −1 at 300 K to 1.6ϫ 10 5 s −1 at 77 K. These low values are due to the recent improvement in the film preparation procedure which enables the optimization of the PL efficiency by decreasing the quencher concentration. 30 The temperature dependence of k q can be described by the Arrhenius law: k ϰ exp͑−E a / kT͒, where E a is the activation energy, k is the Boltzmann constant, and T is the temperature. The best fits were obtained with E a =7Ϯ 1 meV.…”

Section: Resultsmentioning

confidence: 99%

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Temperature dependence of the triplet diffusion and quenching rates in films of anIr(ppy)3-cored dendrimer

et al. 2008

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We study photoluminescence and triplet-triplet exciton annihilation in a neat film of a fac-tris͑2-phenylpyridyl͒iridium͑III͒ ͓Ir͑ppy͒ 3 ͔-cored dendrimer and in its blend with a 4 , 4Ј-bis͑N-carbazolyl͒biphenyl host for the temperature range of 77-300 K. The nearest neighbor hopping rate of triplet excitons is found to increase by a factor of 2 with temperature between 150 and 300 K and is temperature independent at lower temperature. The intermolecular quenching rate follows the Arrhenius law with an activation energy of 7 meV, which can be explained by stronger dipole-dipole interactions with the donor molecule in the higher triplet substate. The results indicate that energy disorder has no significant effect on triplet transport and quenching in these materials.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Temperature dependence of the triplet diffusion and quenching rates in films of anIr(ppy)3-cored dendrimer

et al. 2008

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“…In solution each of the protonated forms of the dendrimers have a PLQY of around 80%. However, in the solid state the PLQYs of the materials are different with the protonated forms of 1, 2, and 3 having PLQYs of 65%, 16 74%, and 81% 16 respectively. The core of each dendrimer is emissive and hence the increase in PLQY across the series is due to the cores being less able to interact in the film.…”

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confidence: 96%

“…14 The deuterated surface groups provided contrast for the NR experiments but did not change their photoluminescence properties. For example, the film photoluminescence quantum yields ͑PLQYs͒ of the protonated and deuterated first generation dendrimer 1 measured using an integrating sphere 15 were 65% 16 and 63%, respectively, while the double dendrimer 2 had a PLQY of 82% which is within the error of the material with the protonated surface groups ͑81%͒. 16 Hydrodynamic diameters were calculated from the viscosity molecular weight obtained by gel permeation chromatography ͑GPC͒.…”

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confidence: 99%

“…For example, the film photoluminescence quantum yields ͑PLQYs͒ of the protonated and deuterated first generation dendrimer 1 measured using an integrating sphere 15 were 65% 16 and 63%, respectively, while the double dendrimer 2 had a PLQY of 82% which is within the error of the material with the protonated surface groups ͑81%͒. 16 Hydrodynamic diameters were calculated from the viscosity molecular weight obtained by gel permeation chromatography ͑GPC͒. 17 GPC was carried out using PLgel Mixed-A columns ͑600 mm + 300 mm lengths, 7.5 mm diameter͒ from Polymer Laboratories calibrated with polystyrene narrow standards ͑Mp = 580 to 3.2ϫ 10 6 ͒ in tetrahydrofuran.…”

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Light-emitting dendrimer film morphology: A neutron reflectivity study

Vickers

Barcena

Knights

et al. 2010

Applied Physics Letters

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We have used neutron reflectivity (NR) measurements to probe the physical structure of phosphorescent dendrimer films. The dendrimers consisted of fac-tris(2-phenylpyridyl)iridium(III) cores, biphenyl-based dendrons (first or second generation), and perdeuterated 2-ethylhexyloxy surface groups. We found that the shape and hydrodynamic radius of the dendrimer were both important factors in determining the packing density of the dendrimers. “Cone” shaped dendrimers were found to pack more effectively than “spherical” dendrimers even when the latter had a smaller radius. The morphology of the films determined by NR was consistent with the measured photoluminescence and charge transporting properties of the materials.

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Charge Transport in a Highly Phosphorescent Iridium(III) Complex‐Cored Dendrimer with Double Dendrons

Gambino

Liu

et al. 2011

Adv Funct Materials

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The charge transporting properties of a phosphorescent iridium(III) complexcored dendrimer, with two dendrons attached to each ligand of the core are reported. The results show that the high photoluminescence quantum yield of this material is obtained without compromising charge transport. The hole mobility values are reported over a wide range of temperatures and electric fields using the charge-generation layer time-of-flight technique. The results are analysed using the Gaussian disorder model (GDM), the correlated disorder model, the polaronic correlated disorder model, and the short-range correlated Gaussian disorder model. It is found that the GDM model gives the most comprehensive description of hole transport in this material. In spite of its larger size, the hole mobility of the doubly dendronised material compares favourably with that of a smaller singly dendronised material, and its spherical shape leads to low energetic disorder and clearly non-dispersive charge transport. This shows how molecular shape can be used to combine favourable photoluminescence and charge-transporting properties.

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Optimization of the Luminescence Efficiencies in Solution-Processed Phosphorescent Dendrimers

Cited by 16 publications

References 18 publications

Temperature dependence of the triplet diffusion and quenching rates in films of anIr(ppy)3-cored dendrimer

Temperature dependence of the triplet diffusion and quenching rates in films of anIr(ppy)3-cored dendrimer

Light-emitting dendrimer film morphology: A neutron reflectivity study

Charge Transport in a Highly Phosphorescent Iridium(III) Complex‐Cored Dendrimer with Double Dendrons

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