Synthesis and characterisation of a carbazole-based bipolar exciplex-forming compound for efficient and color-tunable OLEDs

In solution processed single layer white organic light emitting diode (WOLED) applications, the choice of host matrix and optimization of dopant levels represent two crucial parameters to consider. In this work, poly(N-vinylcarbazole) (PVK): 2-(4-Biphenylyl)-5-phenyl-1,3,4-oxadiazole (PBD) and PVK:1,3-bis[(4-tert-butylphenyl)-1,3,4-oxadiazolyl] phenylene (OXD-7) matrices are used as hosts for perylene based devices. PVK:PBD presented better compatibility and lower turn-on voltages compared to PVK:OXD-7. Benefiting from the exciplex emission observed at 630 nm, a color rendering index (CRI) value of 90 is reached with the device containing PVK:PBD as the host and 0.1 wt.% of an orange emitting perylene derivative, i.e., PDI. Introduction of the perylene based green emitter, i.e., PTE, in this emitting layer not only caused a fading in the exciplex emission, but also resulted in disappearance of the electroplex peak at 535 nm, which is detected between PVK:PBD and PTE in bare PTE containing devices. Full visible range coverage is achieved by optimizing the PDI:PTE ratio. WOLED containing PVK:PBD:0.06 wt.% PDI:0.03 wt.% PTE presented high CRI (≥95) and adjustable correlated color temperatures (CCT, 3800 K-5100 K).

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Balanced Charge Injection and Singlet Exciton Quenching in Bilayer Organic Electroluminescent Devices

MRS Proceedings ◽

10.1557/proc-771-l4.37 ◽

2003 ◽

Vol 771 ◽

Cited By ~ 3

Author(s):

Chimed Ganzorig ◽

Masamichi Fujihira

Keyword(s):

Light Emission ◽

Single Layer ◽

Electron Injection ◽

Singlet Exciton ◽

Chemically Modified ◽

Single Carrier ◽

Current Voltage ◽

Organic Electroluminescent ◽

Uv Ozone ◽

Bilayer Devices

AbstractWe demonstrate here balancing between hole and electron injection in bilayer organic tris(8-hydroxyquinoline)aluminum (Alq3) based electroluminescent (EL) devices by measuring current-voltage (I-V) characteristics of single-carrier devices with different thickness and by comparing the device performance with various chemically modified ITO. We measure I-V characteristics due to holes in hole-only bilayer devices with various modified ITO anodes and those due to electrons in electron-only single-layer devices with C6H5COOLi(2 nm)/Al cathode. Here, hole-only devices are those, in which only holes are carriers and the current due to electrons is negligible. We found that the I-V characteristics observed for the hole-only bilayer devices with UV-ozone and ClC6H4COCl treated ITO were comparable to the I-V characteristics for the electron-only single-layer device of ITO(as-cleaned)/Alq3(150 nm)/C6H5COOLi(2 nm)/Al. In other words, hole and electron injections are well balanced when we use UV-ozone and ClC6H4COCl treated ITO anodes. EL characteristics have shown that luminance decreased clearly for bilayer organic EL devices with an Al cathode where electron injection was not enhanced significantly. The decrease in EL efficiency can be attributed to unbalanced hole and electron injection. The unbalanced injection results in excess of one carrier type that does not contribute to light emission, and results in deactivation of 1Alq3 at high currents due to quenching 1Alq3 by large excess of Alq3+. in the emission zone.

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Highly Fluorescent and Color-Tunable Exciplex Emission from Poly(N-vinylcarbazole) Film Containing Nanostructured Supramolecular Acceptors

Advanced Functional Materials ◽

10.1002/adfm.201302924 ◽

2014 ◽

Vol 24 (19) ◽

pp. 2746-2753 ◽

Cited By ~ 23

Author(s):

Jong H. Kim ◽

Byeong-Kwan An ◽

Seong-Jun Yoon ◽

Sang Kyu Park ◽

Ji Eon Kwon ◽

...

Keyword(s):

Color Tunable ◽

Exciplex Emission

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Crystalline order to a resolution of 4.7 A in the sheath of Methanospirilium hungatii: A cross-beta structure

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100111185 ◽

1984 ◽

Vol 42 ◽

pp. 214-215

Author(s):

Murray Stewart ◽

T.J. Beveridge ◽

D. Sprott

Keyword(s):

Cell Wall ◽

Single Layer ◽

Uranyl Acetate ◽

Optical Diffraction ◽

Tube Axis ◽

Basic Subunit ◽

Beta Structure ◽

Diffraction Patterns ◽

Protein Treatment ◽

General Appearance

The archaebacterium Methanospirillum hungatii has a sheath as part of its cell wall which is composed mainly of protein. Treatment with dithiothreitol or NaOH released the intact sheaths and electron micrographs of this material negatively stained with uranyl acetate showed flattened hollow tubes, about 0.5 μm diameter and several microns long, in which the patterns from the top and bottom were superimposed. Single layers, derived from broken tubes, were also seen and were more simply analysed. Figure 1 shows the general appearance of a single layer. There was a faint axial periodicity at 28.5 A, which was stronger at irregular multiples of 28.5 A (3 and 4 times were most common), and fine striations were also seen at about 3° to the tube axis. Low angle electron diffraction patterns (not shown) and optical diffraction patterns (Fig. 2) from these layers showed a complex meridian (as a result of the irregular nature of the repeat along the tube axis) which showed a clear maximum at 28.5 A, consistent with the basic subunit spacing.

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Differentiation Processes of the Ocellar Retina of the Honeybee (Apis Mellifera L.)

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100159692 ◽

1990 ◽

Vol 48 (3) ◽

pp. 430-431

Author(s):

Maria Anna Pabst

Keyword(s):

Apis Mellifera ◽

Distal Part ◽

Cell Layer ◽

Single Layer ◽

Photoreceptor Cells ◽

Distal Segment ◽

Compound Eyes ◽

Thin Sections ◽

Ultrastructural Studies ◽

Adult Worker

In addition to the compound eyes, honeybees have three dorsal ocelli on the vertex of the head. Each ocellus has about 800 elongated photoreceptor cells. They are paired and the distal segment of each pair bears densely packed microvilli forming together a platelike fused rhabdom. Beneath a common cuticular lens a single layer of corneagenous cells is present.Ultrastructural studies were made of the retina of praepupae, different pupal stages and adult worker bees by thin sections and freeze-etch preparations. In praepupae the ocellar anlage consists of a conical group of epidermal cells that differentiate to photoreceptor cells, glial cells and corneagenous cells. Some photoreceptor cells are already paired and show disarrayed microvilli with circularly ordered filaments inside. In ocelli of 2-day-old pupae, when a retinogenous and a lentinogenous cell layer can be clearly distinguished, cell membranes of the distal part of two photoreceptor cells begin to interdigitate with each other and so start to form the definitive microvilli. At the beginning the microvilli often occupy the whole width of the developing rhabdom (Fig. 1).

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Characterization of a monolayer graphitic structure

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100171535 ◽

1994 ◽

Vol 52 ◽

pp. 760-761

Author(s):

X. Lin ◽

X. K. Wang ◽

V. P. Dravid ◽

J. B. Ketterson ◽

R. P. H. Chang

Keyword(s):

Three Dimensional ◽

Single Layer ◽

Synthesis Process ◽

Graphitic Structure ◽

Positive Gaussian Curvature ◽

Graphitic Sheet ◽

Structural And Electronic Properties ◽

New Material ◽

Hexagonal Network

For small curvatures of a graphitic sheet, carbon atoms can maintain their preferred sp2 bonding while allowing the sheet to have various three-dimensional geometries, which may have exotic structural and electronic properties. In addition the fivefold rings will lead to a positive Gaussian curvature in the hexagonal network, and the sevenfold rings cause a negative one. By combining these sevenfold and fivefold rings with sixfold rings, it is possible to construct complicated carbon sp2 networks. Because it is much easier to introduce pentagons and heptagons into the single-layer hexagonal network than into the multilayer network, the complicated morphologies would be more common in the single-layer graphite structures. In this contribution, we report the observation and characterization of a new material of monolayer graphitic structure by electron diffraction, HREM, EELS.The synthesis process used in this study is reported early. We utilized a composite anode of graphite and copper for arc evaporation in helium.

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The Continuous Single-Layer Anastomosis in the Gastrointestinal Tract

Swiss Surgery ◽

10.1024/1023-9332.9.3.114 ◽

2003 ◽

Vol 9 (3) ◽

pp. 114-120 ◽

Cited By ~ 1

Author(s):

Steinke ◽

Leippold ◽

Schweizer

Keyword(s):

Gastrointestinal Tract ◽

Single Layer

Über die Frage der besten oder "richtigen" Technik bei gastrointestinalen Anastomosen wird seit je diskutiert. Die Ansprüche an eine gute Anastomosentechnik sind: Gute Durchblutung, Wasserdichtigkeit, Spannungsfreiheit, Sicherheit, leichte Durchführbarkeit, wenig Unruhe und Verschmutzung im Operationsgebiet und geringe Kosten. Die Operationstechnik der extramukösen, fortlaufenden Anastomosentechnik im Gastrointestinaltrakt wird in Wort und Bild erläutert. Anhand einer Pilotstudie, einer randomisierten Vergleichsstudie, einer Schweizer Multizenterstudie und schliesslich einer 5-jährigen Qualitätskontrollstudie wird gezeigt, dass diese "Schweizer"-Technik allen Anforderungen zur Durchführung einer "idealen" Anastomose gerecht wird und an fast allen intestinalen Lokalisationen verwendet werden kann.

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