Blue Electroluminescent Diodes Utilizing Poly(alkylfluorene)

Ohmori, Yutaka; Uchida, Masao; Muro, K.; Yoshino, Katsumi

doi:10.1143/jjap.30.l1941

Cited by 674 publications

(314 citation statements)

References 9 publications

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“…1,2 Especially important, with respect to the use of conjugated polymers for lighting and display applications, are the dynamics in the solid state and with the potential for high brightness devices and polymer lasers, the behavior of excitons at high excitation densities is becoming of interest. [3][4][5] Most relevant are the mechanisms that can quench the excitons and represent a channel for the loss of efficiency of light emission.…”

Section: Introductionmentioning

confidence: 99%

Exciton annihilation in a polyfluorene: Low threshold for singlet-singlet annihilation and the absence of singlet-triplet annihilation

et al. 2007

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(2007) 'Exciton annihilation in a polyuorene : low threshold for singlet-singlet annihilation and the absence of singlet-triplet annihilation. ', Physical review B., 76 (8) Additional information: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. Ultrafast photoinduced absorption measurements have been used to directly investigate singlet-singlet annihilation in polyfluorene. The pump fluence threshold for annihilation to dominate the decay was measured to be ϳ1 J cm −2 corresponding to an excitation density of 1.5ϫ 10 17 cm −3 . The annihilation rate was found to be faster than that expected from a simple dipole-dipole interaction. This is ascribed to the additional influence of diffusion which, because of the dispersive nature of the exciton migration, has strong time dependence as the singlet excitons thermalize in the density of states as well as the expected intrinsic time dependence from a diffusion controlled process. Also, a comparable background level of triplets was created in the film to study the effect of singlet-triplet annihilation, which surprisingly, given the low threshold for singlet-singlet annihilation, was found to be negligible.

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Section: Introductionmentioning

confidence: 99%

Exciton annihilation in a polyfluorene: Low threshold for singlet-singlet annihilation and the absence of singlet-triplet annihilation

et al. 2007

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“…2 Polymer-based organic LED's were discovered by Burroughes et al some years later and have stimulated a new wave of interest in this field. 3 Polymer devices have now been demonstrated with internal quantum efficiencies of up to 4%, 4 operating voltages below 5 V, emission wavelengths throughout the visible spectrum, [3][4][5][6][7] and operating lifetimes beyond 1200 h. 8 The simplest organic LED's consist of a thin, light-emitting organic film sandwiched between two metal electrodes. Even in these structures there is a need for a better understanding of the mechanisms of operation and methods to control the electrical and optical properties of the organic film to optimize charge injection, charge transport, charge recombination, and light-emission processes.…”

Section: Introductionmentioning

confidence: 99%

Solid-state-concentration effects on the optical absorption and emission of poly(p-phenylene vinylene)-related materials

et al. 1996

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We present measurements of the optical absorption and emission properties of poly(p-phenylene vinylene͒ ͑PPV͒ -related materials focusing on the differences between molecules isolated by dispersion in an inert host and concentrated molecular films. Optical absorption spectra, photoluminescence ͑PL͒ spectra, PL efficiency, and time-resolved PL spectra of dilute blends of PPV oligomers with 2-5 phenylene-phenyl rings are compared with those of dense oligomer and polymer films. In dilute oligomer-poly͑methyl methacrylate͒ ͑PMMA͒ blends with high PL efficiency, the PL decay is exponential, independent of both temperature and oligomer length. This implies that the fundamental radiative lifetime of PPV oligomers is essentially independent of oligomer length. Concentrated spin-cast oligomer films and polymers have a faster and strongly temperaturedependent PL decay that approaches that of the dilute oligomer results at low temperature. The differences in PL decay correspond to changes in PL efficiency. The efficiency of the oligomer-PMMA blend is high and only weakly temperature dependent, whereas that of concentrated films is lower and strongly temperature dependent, decreasing by more than a factor of 3 from 10 to 350 K. The quenching of the PL efficiency in concentrated films is due to migration to extrinsic, impurity related centers as opposed to an intrinsic intermolecular recombination process. The PL spectrum of a dilute oligomer blend redshifts substantially, both as the excitation energy is decreased and as the emission time increases. This spectral redshift is due to disorderinduced site-to-site variation and not to diffusion to lower-energy sites. In contrast, no spectral shift with excitation energy or emission time was observed for dense oligomer films. ͓S0163-1829͑96͒03132-3͔

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“…It was developed by Yoshino and coworkers [27,28], to synthesize poly(9, 9-dialkylflourene)s (PAFs) and poly(3-alkylthiophene)s (PATs). In this work, the copolymer (PVK-PHT) is dissolved and oxidatively polymerized with FeCl 3 .…”

Section: Experimental Methodsmentioning

confidence: 99%

Chemical Synthesis, Electronic Study, and Vibrational Analysis of a New Organic Copolymer Based on PVK and 3-nhexylthiophene

et al. 2010

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Conjugated polymers containing carbazole moieties either in the main or in the side chains have attracted much attention because of their unique electronic properties, to their high photoluminescence quantum efficiency, and thermal stability. The aim of this work is to study a new organic copolymer which combines the PVK properties and those of PHT. We will describe in this study the protocol synthesis, the chemical structure, and the electronic and vibrational properties of the resulting copolymer. The experimental and theoretical studies are combined in order to describe the properties of this material. These properties suggest this compound (PVK-PHT) to be a good candidate for optoelectronic application.

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Blue Electroluminescent Diodes Utilizing Poly(alkylfluorene)

Abstract: Blue electroluminescent diodes utilizing poly(alkylfluorene) have been demonstrated for the first time. A Schottky-type electroluminescent diode of poly(9,9-dihexylfluorene) is driven at ∼10 V and has a peak emission wavelength of 470 nm at room temperature.

Cited by 674 publications

References 9 publications

Exciton annihilation in a polyfluorene: Low threshold for singlet-singlet annihilation and the absence of singlet-triplet annihilation

Exciton annihilation in a polyfluorene: Low threshold for singlet-singlet annihilation and the absence of singlet-triplet annihilation

Solid-state-concentration effects on the optical absorption and emission of poly(p-phenylene vinylene)-related materials

Chemical Synthesis, Electronic Study, and Vibrational Analysis of a New Organic Copolymer Based on PVK and 3-nhexylthiophene

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