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Morphological Stability (morphological + stability)
Selected AbstractsIn situ observation experiment for semiconductor solution growth under reduced convection condition , a reviewCRYSTAL RESEARCH AND TECHNOLOGY, Issue 7-8 2003Yuko Inatomi Abstract Morphological stability of solid/liquid interface in semiconductor crystal growth from solution has been investigated using a near-infrared microscopic interferometer under a reduced convection condition by authors and Prof. Benz's group. In the result, step kinetic coefficient of the interface of GaP/GaP(111)B in liquid phase epitaxy growth was obtained and the estimated value of macrostep wavelength agreed well with the measured one. [source] Highly Efficient Red Phosphorescent OLEDs based on Non-Conjugated Silicon-Cored Spirobifluorene Derivative Doped with Ir-ComplexesADVANCED FUNCTIONAL MATERIALS, Issue 3 2009Yi-Yeol Lyu Abstract A novel host material containing silicon-cored spirobifluorene derivative (SBP-TS-PSB), is designed, synthesized, and characterized for red phosphorescent organic light-emitting diodes (OLEDs). The SBP-TS-PSB has excellent thermal and morphological stabilities and exhibits high electroluminescence (EL) efficiency as a host for the red phosphorescent OLEDs. The electrophosphorescence properties of the devices using SBP-TS-PSB as the host and red phosphorescent iridium (III) complexes as the emitter are investigated and these devices exhibit higher EL performances compared with the reference devices with 4,4,- N,N,-dicarbazole-biphenyl (CBP) as a host material; for example, a (piq)2Ir(acac)-doped SBP-TS-PSB device shows maximum external quantum efficiency of ,ext,=,14.6%, power efficiency of 10.3 lm W,1 and Commission International de L'Eclairage color coordinates (0.68, 0.32) at J,=,1.5,mA cm,2, while the device with the CBP host shows maximum ,ext,=,12.1%. These high performances can be mainly explained by efficient triplet energy transfer from the host to the guests and improved charge balance attributable to the bipolar characteristics of the spirobifluorene group. [source] Tuning the Optoelectronic Properties of Carbazole/Oxadiazole Hybrids through Linkage Modes: Hosts for Highly Efficient Green ElectrophosphorescenceADVANCED FUNCTIONAL MATERIALS, Issue 2 2010Youtian Tao Abstract A series of bipolar transport host materials: 2,5-bis(2-(9H -carbazol-9-yl)phenyl)-1,3,4-oxadiazole (o -CzOXD) (1), 2,5-bis(4-(9H -carbazol-9-yl)phenyl)-1,3,4-oxadiazole (p -CzOXD) (2), 2,5-bis(3-(9H -carbazol-9-yl)phenyl)-1,3,4-oxadiazole (m -CzOXD) (3) and 2-(2-(9H -carbazol-9-yl)phenyl)-5-(4-(9H-carbazol-9-yl)phenyl)-1,3,4-oxadiazole (op -CzOXD) (4) are synthesized through simple aromatic nucleophilic substitution reactions. The incorporation of the oxadiazole moiety greatly improves their morphological stability, with Td and Tg in the range of 428,464,°C and 97,133,°C, respectively. The ortho and meta positions of the 2,5-diphenyl-1,3,4-oxadiazole linked hybrids (1 and 3) show less intramolecular charge transfer and a higher triplet energy compared to the para-position linked analogue (2). The four compounds exhibit similar LUMO levels (2.55,2.59,eV) to other oxadiazole derivatives, whereas the HOMO levels vary in a range from 5.55,eV to 5.69,eV, depending on the linkage modes. DFT-calculation results indicate that 1, 3, and 4 have almost complete separation of their HOMO and LUMO levels at the hole- and electron-transporting moieties, while 2 exhibits only partial separation of the HOMO and LUMO levels possibly due to intramolecular charge transfer. Phosphorescent organic light-emitting devices fabricated using 1,4 as hosts and a green emitter, Ir(ppy)3 or (ppy)2Ir(acac), as the guest exhibit good to excellent performance. Devices hosted by o -CzOXD (1) achieve maximum current efficiencies (,c) as high as 77.9,cd A,1 for Ir(ppy)3 and 64.2,cd A,1 for (ppy)2Ir(acac). The excellent device performance may be attributed to the well-matched energy levels between the host and hole-transport layers, the high triplet energy of the host and the complete spatial separation of HOMO and LUMO energy levels. [source] Multifunctional Fluorene-Based Oligomers with Novel Spiro-Annulated Triarylamine: Efficient, Stable Deep-Blue Electroluminescence, Good Hole Injection, and Transporting Materials with Very High TgADVANCED FUNCTIONAL MATERIALS, Issue 24 2009Zuoquan Jiang Abstract A series of fluorene-based oligomers with novel spiro-annulated triarylamine structures, namely DFSTPA, TFSTPA, and TFSDTC, are synthesized by a Suzuki cross-coupling reaction. The spiro-configuration molecular structures lead to very high glass transition temperatures (197,253,°C) and weak intermolecular interactions, and consequently the structures retain good morphological stability and high fluorescence quantum efficiencies(0.69,0.98). This molecular design simultaneously solves the spectral stability problems and hole-injection and transport issues for fluorene-based blue-light-emitting materials. Simple double-layer electroluminescence (EL) devices with a configuration of ITO/TFSTPA (device A) or TFSDTC (device B)/ TPBI/LiF/Al, where TFSTPA and TFSDTC serve as hole-transporting blue-light-emitting materials, show a deep-blue emission with a peak around 432,nm, and CIE coordinates of (0.17, 0.12) for TFSTPA and (0.16, 0.07) for TFSDTC, respectively, which are very close to the National Television System Committee (NTSC) standard for blue (0.15, 0.07). The maximum current efficiency/external quantum efficiencies are 1.63,cd A,1/1.6% for device A and 1.91,cd A,1/2.7% for device B, respectively. In addition, a device with the structure ITO/DFSTPA/Alq3/LiF/Al, where DFSTPA acts as both the hole-injection and -transporting material, is shown to achieve a good performance, with a maximum luminance of 14,047,cd m,2, and a maximum current efficiency of 5.56,cd A,1. These values are significantly higher than those of devices based on commonly usedN,N,-di(1-naphthyl)- N,N,-diphenyl-[1,1,-biphenyl]-4,4,-diamine (NPB) as the hole-transporting layer (11,738,cd m,2 and 3.97,cd A,1) under identical device conditions. [source] Versatile, Benzimidazole/Amine-Based Ambipolar Compounds for Electroluminescent Applications: Single-Layer, Blue, Fluorescent OLEDs, Hosts for Single-Layer, Phosphorescent OLEDsADVANCED FUNCTIONAL MATERIALS, Issue 16 2009Chih-Hsin Chen Abstract A series of compounds containing arylamine and 1,2-diphenyl-1H -benz[d]imidazole moieties are developed as ambipolar, blue-emitting materials with tunable blue-emitting wavelengths, tunable ambipolar carrier-transport properties and tunable triplet energy gaps. These compounds possess several novel properties: (1) they emit in the blue region with high quantum yields; (2) they have high morphological stability and thermal stability; (3) they are capable of ambipolar carrier transport; (4) they possess tunable triplet energy gaps, suitable as hosts for yellow-orange to green phosphors. The electron and hole mobilities of these compounds lie in the range of 0.68,144,×,10,6 and 0.34,147,×,10,6,cm2 V,1 s,1, respectively. High-performance, single-layer, blue-emitting, fluorescent organic light-emitting diodes (OLEDs) are achieved with these ambipolar materials. High-performance, single-layer, phosphorescent OLEDs with yellow-orange to green emission are also been demonstrated using these ambipolar materials, which have different triplet energy gaps as the host for yellow-orange-emitting to green-emitting iridium complexes. When these ambipolar, blue-emitting materials are lightly doped with a yellow-orange-emitting iridium complex, white organic light-emitting diodes (WOLEDs) can be achieved, as well by the use of the incomplete energy transfer between the host and the dopant. [source] Doping of the Metal Oxide Nanostructure and its Influence in Organic ElectronicsADVANCED FUNCTIONAL MATERIALS, Issue 8 2009Mi-Hyae Park Abstract Synthesizing metal oxides through the sol,gel process provides a convenient way for forming a nanostructured layer in wide band gap semiconductors. In this paper, a unique method of introducing dopants into the metal oxide semiconductor is presented. The doped TiO2 is prepared by adding a Cs2CO3 solution to a nanocrystalline TiO2 solution that is synthesized via a non-hydrolytic sol,gel process. The properties of the TiO2:Cs layer are investigated and the results show stable nanostructure morphology. In addition to providing morphological stability, Cs in TiO2 also gives rise to a more desirable work function for charge transport in organic electronics. Polymer solar cells based on the poly(3-hexylthiophene) (P3HT): methanofullerene (PC70BM) system with the addition of a TiO2:Cs interfacial layer exhibit excellent characteristics with a power conversion efficiency of up to 4.2%. The improved device performance is attributed to an improved polymer/metal contact, more efficient electron extraction, and better hole blocking properties. The effectiveness of this unique functionality also extends to polymer light emitting devices, where a lower driving voltage, improved efficiency, and extended lifetime are demonstrated. [source] Multifunctional Deep-Blue Emitter Comprising an Anthracene Core and Terminal Triphenylphosphine Oxide GroupsADVANCED FUNCTIONAL MATERIALS, Issue 4 2009Chen-Han Chien Abstract A highly efficient blue-light emitter, 2- tert -butyl-9,10-bis[4,-(diphenyl-phosphoryl)phenyl]anthracene (POAn) is synthesized, and comprises electron-deficient triphenylphosphine oxide side groups appended to the 9- and 10-positions of a 2- tert -butylanthracene core. This sophisticated anthracene compound possesses a non-coplanar configuration that results in a decreased tendency to crystallize and weaker intermolecular interactions in the solid state, leading to its pronounced morphological stability and high quantum efficiency. In addition to serving as an electron-transporting blue-light-emitting material, POAn also facilitates electron injection from the Al cathode to itself. Consequently, simple double-layer devices incorporating POAn as the emitting, electron-transporting, and -injecting material produce bright deep-blue lights having Commission Internationale de L'Eclairage coordinates of (0.15,0.07). The peak electroluminescence performance was 4.3% (2.9 cd A,1). For a device lacking an electron-transport layer or alkali fluoride, this device displays the best performance of any such the deep-blue organic light-emitting diodes reported to date. [source] Solution-Processed Solid Solution of a Novel Carbazole Derivative for High-Performance Blue Phosphorescent Organic Light-Emitting DiodesADVANCED MATERIALS, Issue 37 2010Shanghui Ye Blue light: Incorporation of two fluorenyl rings into a phenyl group at the C9 position of fluorene builds a bulky and rigidly tetrahedral framework, which is functionalized by two carbazole groups. This molecule possesses excellent thermal and morphological stability, miscibility to the phosphorescent dopant, and high triplet energy, leading to narrow blue phosphorescent emission. [source] Developments in Oxide Fiber CompositesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 11 2006Frank W. Zok Prospects for revolutionary design of future power generation systems are contingent on the development of durable high-performance ceramic composites. With recent discoveries in materials and manufacturing concepts, composites with all-oxide constituents have emerged as leading candidates, especially for components requiring a long service life in oxidizing environments. Their insertion into engineering systems is imminent. The intent of this article is to present a synopsis of the current understanding of oxide composites as well as to identify outstanding issues that require resolution for successful implementation. Emphasis is directed toward material systems and microstructural concepts that lead to high toughness and long-term durability. These include: the emergence of La monazite and related compounds as fiber-coating materials, the introduction of the porous-matrix concept as an alternative to fiber coatings, and novel strategies for enabling damage tolerance while retaining long-term morphological stability. Additionally, materials and mechanics models that provide insights into material design, morphology evolution, and composite properties are reviewed. [source] Migration of human and mouse primordial germ cells and colonization of the developing ovary: An ultrastructural and cytochemical study ,MICROSCOPY RESEARCH AND TECHNIQUE, Issue 6 2006Jaime Pereda Abstract This review is an account of the origin and migratory events of primordial germ cells until their settlement in the gonad before sexual differentiation in the human as well as mice. In this context, the morphodynamic characteristics of the migration of the primordial germ cells, the macromolecular characteristics of the extracellular matrix of the migratory pathway, and the factors involved in the germ cell guidance have been analyzed and discussed in the light of recent advances in this field, by means of immunocytochemical procedures. The events prior to gonadal morphogenesis and the origin of the somatic cell content of the human gonadal primordium have been also analyzed. In particular, evidences are presented showing that cells derived from the coelomic epithelium and mesenchyme are at the origin of the somatic components of the gonadal primordium, and that a mesonephric cell contribution to the generation of somatic cell components of the genital ridge in humans should be discarded due to the morphological stability of the different nephric structures during the period preceding the sexual differentiation of the gonad. Microsc. Res. Tech., 2006. © 2006 Wiley-Liss, Inc. [source] Diphenylamino End-Capped Oligofluorenes with Enhanced Functional Properties for Blue Light Emission: Synthesis and Structure,Property RelationshipsCHEMISTRY - A EUROPEAN JOURNAL, Issue 11 2005Zhong Hui Li Abstract A novel series of monodisperse asymmetrically and symmetrically substituted diphenylamino end-capped oligofluorenes, OF(2)-NPhR, R = H or An (An = 9-anthryl) and OF(n)-NPh, n = 2,4, has been synthesized by a convergent approach using palladium-catalyzed Suzuki cross-coupling. End-capping of oligofluorenes with diphenylamino group(s) has been shown to offer advantages in terms of lowering their first ionization potentials, enhancing thermal stability, and inducing good amorphous morphological stability. By tuning the number of diphenylamino end-caps and the chain length, the optimal conjugated length for optical and luminescence properties has been determined. Of all the hitherto reported oligofluorenes capable of serving as non-doped blue emitters, OF(3)-NPh, with an optimal conjugated length, exhibits some of the best hole-transport and blue-emitting properties. A maximum luminance of 7500 cd,m,2 and a luminance efficiency up to 1.8 cd,A,1 have been achieved. [source] | ||||||||||