Polysilane-Based Polymer Diodes Emitting Ultraviolet Light

Ebihara, Keikichi; Koshihara, Shin‐ya; Miyazawa, Takashi; Kira, Mitsuo

doi:10.1143/jjap.35.l1278

Cited by 31 publications

(10 citation statements)

References 12 publications

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“…Polysilanes have received considerable attention of researchers because of their unique electric and optical properties, − such as electron conductivity, photoconductivity, thermochromism, photoresists, and electroluminescence. As the electronic properties originate from the delocalization of σ-electrons along the main chain, most of the properties are anisotropic with respect to the silicon chain axis.…”

Section: Introductionmentioning

confidence: 99%

Orientation Behavior in a Comblike Polysilane Having Long Alkyl Side Chains

Kaito¹,

Yatabe²,

Ohnishi³

et al. 1999

Macromolecules

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The orientation behavior of poly(methyloctadecylsilylene) (PMOdS), a comblike polysilane having long alkyl side chains, was studied by the measurements of polarized ultraviolet (UV) and polarized Fourier transform infrared (FTIR) spectra. The oriented films were prepared by drawing on supporting polymer substrates, mechanical deposition, and crystallization on highly oriented polymer substrates. The main chains of PMOdS are oriented parallel to the drawing direction in the film drawn on polypropylene (PP) films and in the mechanically deposited film. Stretching PMOdS on polyethylene (PE) films however induces side-chain orientation along the drawing direction. The orientation behavior of PMOdS on the polymer substrates is discussed in relation to the surface morphology of the PP and PE substrates. When PMOdS is crystallized on highly oriented poly(dimethylsilylene) and poly(tetrafluoroethylene) films, the side chains tend to align in the orientation direction of the substrate polymer. Thus, the side-chain orientation competes with the main-chain orientation, depending upon the processing technique used. It is also shown that the silicon chains of PMOdS consist of various conformations and that the extended conformation orients more highly to the mechanical direction than the disordered conformation. The result of the polarized fluorescence measurement suggests that the electronic energy is transferred from the disordered conformation to the extended conformation with higher trans content.

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Section: Introductionmentioning

confidence: 99%

Orientation Behavior in a Comblike Polysilane Having Long Alkyl Side Chains

Kaito¹,

Yatabe²,

Ohnishi³

et al. 1999

Macromolecules

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“…The σ-conjugated system of polysilanes also exhibits an efficient emission in the UV and near UV regions, which lets us use them as the lightemitting device (LED). [7][8][9][10][11][12] Polysilanes are not only used as a hole-transporting layer in the multilayered LED device 7,8 but also applied to a single-layered LED device owing to their lightemissive and hole-transporting functions. [9][10][11][12] The electronic structures of polysilanes depend on both substitutents and the conformation of molecular chains.…”

Section: Introductionmentioning

confidence: 99%

“…[7][8][9][10][11][12] Polysilanes are not only used as a hole-transporting layer in the multilayered LED device 7,8 but also applied to a single-layered LED device owing to their lightemissive and hole-transporting functions. [9][10][11][12] The electronic structures of polysilanes depend on both substitutents and the conformation of molecular chains. The electronic spectroscopy of polysilanes was discussed on the basis of the segment model.…”

Section: Introductionmentioning

confidence: 99%

“…Polysilanes are chainlike polymers composed of the silicon backbones and having organic substituents. Considerable attention has been given to the fundamental properties of polysilanes, such as electron conductivity, photoconductivity, thermochromism, photoresists, luminescence, and nonlinear optical properties, owing to their potential applications. − The electronic properties of polysilanes originate from the conjugation of σ-electrons in the silicon−silicon linkages, which gives rise to light absorption in the UV region. The σ-conjugated system of polysilanes also exhibits an efficient emission in the UV and near UV regions, which lets us use them as the light-emitting device (LED). − Polysilanes are not only used as a hole-transporting layer in the multilayered LED device 7,8 but also applied to a single-layered LED device owing to their light-emissive and hole-transporting functions. − …”

Section: Introductionmentioning

confidence: 99%

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Electronic Energy Transfer in Oriented Bilayer Films of Polysilanes

et al. 1999

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The intermolecular energy transfer was studied in a bilayer film of polysilanes. The highly oriented films of poly(diethylsilylene) (PDES) were prepared by the mechanical deposition technique, which had been originally developed by Wittmann and co-workers. The poorly oriented layer was formed on the highly oriented PDES layer by spin-casting a solution of poly(methyloctadecylsilylene) (PMOdS). The bilayer films were characterized with polarized UV absorption and polarized fluorescence spectroscopy. It was shown that the light absorption in the PMOdS layer contributed to the fluorescence intensity of the PDES layer and that the electronic energy was transferred from the PMOdS layer to the PDES layer. Although the poorly oriented PMOdS layer absorbs both parallel-polarized light and perpendicular-polarized light, the highly oriented PDES layer emits only light polarized parallel to the orientation direction of the silicon main chains. Thus, the bilayer film has a function of rotating the polarization direction and of the isotropic-to-polarized light conversion. The fluorescence intensity of PDES was shown to increase with an increase in the thickness of the PMOdS layer, but the increase in the fluorescence intensity saturates above 500 nm. The saturation is caused by the limitation of the migration distance of excitons. The polarization of the excitation light influenced the emission intensity when the thickness of the PMOdS layer was thinner than 100 nm, suggesting that the excitons move between the sites having similar orientations of transition dipole moments. The possible mechanism of exciton migration was discussed in terms of the segment models, in which the molecular chains are separated into the ordered segments with various lengths.

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“…Electroluminescence from a polysilane was first observed with poly͑methylphenylsilane͒ ͑PMPS͒-based singlelayer LEDs, 6,7 and there have been several EL studies on polysilanes with diverse substituents. [8][9][10][11][12][13][14][15][16] However, the UV or NUV EL from those LEDs is usually observed at low temperature, or is very weak and inefficient at room temperature.…”

Section: Introductionmentioning

confidence: 99%

Near-ultraviolet electroluminescent performance of polysilane-based light-emitting diodes with a double-layer structure

Hoshino

Ebata

Furukawa

2000

Journal of Applied Physics

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We fabricated double-layer light-emitting diodes (LEDs) by utilizing poly[bis(p-nbutylphenyl)silane] (PBPS) and oxadiazole derivatives, and investigated their basic LED characteristics. The near-ultraviolet electroluminescence (EL) performance, such as the EL threshold electric field and the current density, depended on the oxadiazole derivatives used as the electron transport materials as well as the components of the EL emission. We observed better EL performance where the EL external quantum efficiency in a double-layer LED with a 2-(4′-tert-butylphenyl)-5-(4″-biphenyl)-1,3,4-oxadiazole based electron transport layer was twice that of a PBPS single-layer LED. By contrast, we observed a worse EL threshold electric field and current density when we used 2,5-bis(1-naphthyl)-1,3,4-oxadiazole as an electron transport material. The reason for the difference in the EL performance was revealed by investigating the charge carrier injection and transport dynamics of the two LEDs.

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Polysilane-Based Polymer Diodes Emitting Ultraviolet Light

Cited by 31 publications

References 12 publications

Orientation Behavior in a Comblike Polysilane Having Long Alkyl Side Chains

Orientation Behavior in a Comblike Polysilane Having Long Alkyl Side Chains

Electronic Energy Transfer in Oriented Bilayer Films of Polysilanes

Near-ultraviolet electroluminescent performance of polysilane-based light-emitting diodes with a double-layer structure

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