Search

Among the structurally diverse NNRTIs, pyridinone scaffolds demonstrate high potency against HIV-1 wild type and drug-resistant strains. During the optimization of our pyridinone compound 1 (LAM-trans), we found that the introduction of the N atoms in the C-4 position could dramatically improve the water solubility (7b), whereas protonation of the piperidine N atom resulted in a decrease in its hydrophobic interaction with the binding pocket. In particular, protonation altered the orientation of the alicyclic rings in the hydrophobic pocket, thus impeding the formation of key halogen bond and eventually leading to a huge change in anti-HIV-1 RT activity. These results provided theoretical and experimental basis for the subsequent structural modification of pyridinone compounds. [ABSTRACT FROM AUTHOR]

The article presents a review of the study which describes the techniques in fabrication and characterization of organic thin films for field-effect transistors. It categorizes the experimental techniques such as characterization, patterning and printing, and deposition in the microelectronics industry. The authors think that the study of organic electronics using the modern techniques is a growing area of science which requires additional work to understand its principles and applications.

One-dimensional (1D) nanostructures of the wide band gap semiconductors are promising building blocks for photoelectric nanodevices. However, some problems like strong 1D confinement largely hamper their applications. To avoid these problems, here, we provide another 1D configuration, in which an inner-wire coaxial Schottky junction exists, thus effectively avoiding the recombination of the photoexcited carriers. As an example, we produce ZnS/carbon nanotube nanocables with uniform morphologies by a two-step vapor deposition method and find that they have good conductance, obvious light response, and ohmic contacts with electrodes, avoiding the limitations of both the pristine nanomaterials. We believe that this configuration would be valuable for applying the 1D nanomaterials in photoelectronics. [ABSTRACT FROM AUTHOR]

Controllable and scalable production is of great importance for the application of graphene; however, to date, it is still a great challenge and a major obstacle which hampers its practical applications. Here, we develop a template chemical vapor deposition method for scalable synthesis of few-layer graphene ribbons (FLGRs) with controlled morphologies. The FLGRs have a good conductivity and are ideal for use in nanoelectromechanics (NEM). As an application, we fabricate a reversible NEM switch and a logic gate by using the FLGRs. This work realizes both controllable and scalable synthesis of graphene, provides an application of graphene in NEM switches, and would be valuable for both the scientific studies and the practical applications of graphene. [ABSTRACT FROM AUTHOR]

Two novel wide-energy-gap molecules, 1,3-bis(9-phenyl-9H-fluoren-9-yl)benzene (mDPFB) and 1,4-bis(9-phenyl-9H-fluoren-9-yl)benzene (pDPFB), suitable for blue phosphorescent host materials, were designed and prepared. The thermal, photophysical, and electrochemical properties as well as electroluminescence characteristics were fully investigated. Both mDPFB and pDPFB possess high singlet (4.0 eV) and triplet (2.8 eV) energies, well energy-matched with the deep-blue phosphorescent dopant, iridium(III) bis(4′,6′-difluorophenylpyridinato)tetrakis(1-pyrazolyl)borate (FIr6). The single crystals of the newly synthesized compounds mDPFB and pDPFB were grown, and their crystal structures were determined by X-ray diffraction. Both molecules adopt a rigid twisted tetrahedral crystallographic conformation, and no facial to facial π−π stacking exists in the solid state. The substituents at the 1,4-positions of benzene enhance the twisted degree of the fluorenyl rings and have predominant influence on the thermal and morphological properties. Both molecules possess excellent thermal stability with decomposition temperatures (Td) of 354 and 386 °C in nitrogen, respectively. Blue phosphorescent organic light-emitting diodes (OLEDs) were fabricated using pDPFB or mDPFB as host materials and FIr6 as a blue phosphorescent dopant with the configuration of ITO/NPB/mCP/host:FIr6/BCP/Ca:Ag. Devices based on the pDPFB host showed a maximum luminous power efficiency of 18.9 lm/W, with CIE coordinates (x, y) of (0.18, 0.33), improved by a factor of over 10 compared with the reference devices based on N,N′-dicarbazolyl-3,5-benzene (mCP) host. We discussed the mechanism and demonstrated that highly efficient blue phosphorescent OLEDs can be achieved in designing host materials which possess matched energy levels with the phosphorescent dopant, with high miscibility to the dopant, and with excellent film-forming ability and thermal and morphological stability. [ABSTRACT FROM AUTHOR]

In this work the equation of circular loops of cosmic string possessing time-dependent tension is studied in the de Sitter spacetime. We find that the cosmic string loops with initial radius r( t0)>0.707 L, L de Sitter radius, should not collapse to form a black hole. It is also found that in the case of r( t0)<0.707 L a loop of cosmic string whose tension depends on some power of cosmic time can not become a black hole if the power is lower than a critical value which is associated with the initial size of the loop. Our research gives rise to some important corrections to the conclusion in the case of loops of cosmic string with constant tension in the same background. [ABSTRACT FROM AUTHOR]

The equation of circular loops of cosmic string with time-dependent tension is studied in the Minkowski spacetime and Robertson–Walker universe. We found that, in the case where the tension depends on some power of the cosmic time, cosmic string loops with time-varying tension should not collapse to form a black hole if the power is lower than a critical value. [ABSTRACT FROM AUTHOR]

A magnetism-assisted chemical vapor deposition method was developed to synthesize branched or iron-encapsulated carbon nanotubes. In the process, the external magnetic field can promote the coalescence or division of the catalyst particles, causing the formation of branched or encapsulated nanostructures. This finding will extend the understanding of the chemical vapor deposition method in a magnetic field and promote the applications of branched or encapsulated nanostructures. [ABSTRACT FROM AUTHOR]

Here we develop a simple method by using flow fluctuation to synthesize arrays of multibranched carbon nanotubes (CNTs) that are far more complex than those previously reported. The architectures and compositions can be well controlled, thus avoiding any template or additive. A branching mechanism of fluctuation-promoted coalescence of catalyst particles is proposed. This finding will provide a hopeful approach to the goal of CNT-based integrated circuits and be valuable for applying branched junctions in nanoelectronics and producing branched junctions of other materials. [ABSTRACT FROM AUTHOR]

We present the synthesis and characterization of a fused-ring compound, dithieno[2,3-d:2',3'-d']thieno[3,2-b:4,5-b']dithiophene (pentathienoacene, PTA). In contrast to pentacene, PTA has a larger band gap than most semiconductors used in organic field-effect transistors (OFETs) and therefore is expected to be stable in air. The large π-conjugated and planar molecular structure of PTA would also form higher molecular orders that are conductive for carrier transport. X-ray diffraction and atomic force microscopy experiments on its films show that the molecules stack in layers with their long axis upright from the surface. X-ray photoelectron spectroscopy suggests that there are no chemical bonds at the PTA/Au interlace. OFETs based on the PTA have been constructed, and their performances as p-type semiconductors are also presented. A high mobility of 0.045 cm²/V s and an on/off ratio of 10³ for a PTA OFET have been achieved, demonstrating the potential of PTA for application in future organic electronics. [ABSTRACT FROM AUTHOR]

We report on the fabrication and characterization of field-effect transistor based on an individual multiwalled nitrogen-doped carbon nanotube. Our measurements show that the N-doped carbon nanotubes have n-type properties. The contact properties of the tube and Pt electrodes are also studied in detail. Temperature dependence of two-terminal transport experiments suggests that transport is dominated by thermionic emission and tunneling through a 0.2 eV Schottky contact barrier. [ABSTRACT FROM AUTHOR]

A new rigid cyclic thiophene molecule was synthesized and its unusual and interesting single-crystal tubular products on a millimeter scale were obtained unexpectedly by a simple self-assemble technique in a solution process under ambient conditions. [ABSTRACT FROM AUTHOR]

The authors report on the organic field-effect transistors based on copper phthalocyanine with a inserted layer of molybdenum oxide (MoO3). After applying a positive gate voltage of 100 V, the threshold voltage had a large shift from -11.8 to +66.2 V and the device operating model was changed from the enhancement model into the depletion one. A possible mechanism is believed to be originated from the stored charges in the interface between the thin MoO3 layer and the active layer. Largely reversible shift in the threshold voltage and retention time were also obtained in the devices by the programs used. [ABSTRACT FROM AUTHOR]

Employing 5,5′-bis-biphenyl-dithieno[3,2-b:2′,3′-d]thiophene (BPDTT) as semiconducting layer and poly(vinyl alcohol) (PVA) as gate dielectric layer, we have fabricated organic thin-film transistors. These devices exhibit excellent field-effect performances with a high mobility of up to 0.6 cm2/V s and a very low operating voltage (<1 V) at room temperature. The single crystal of BPDTT was grown and analyzed. The high performances are mainly attributed to the close herringbone packing of BPDTT molecules and the high homogeneity between PVA and BPDTT molecules. [ABSTRACT FROM AUTHOR]

We fabricate single-walled carbon nanotube field-effect transistors (SWNT FETs) with a simple, low-cost, high-efficiency, and solution-based orientational self-assembly method. The SWNT was first functionalized with thiol groups, then suspended in an N,N-dimethylformamide solution, and finally self-assembled on predefined gold contact pads by an orientational N2 blow. A relatively high mobility of 9.2×102 cm2/V s and an on/off ratio greater than 105 at a bias voltage of -1 V have been achieved as a result of directly covalent interaction between end-thiolated SWNT and gold contacts, which favors the fabrication of SWNT FETs as compared to the SWNT FETs bearing the similar geometry but relies on random deposition. Therefore, this orientational self-assembly approach should be a valuable tool in the mass fabrication of high-performance SWNT FETs and SWNT-based molecular-scale electronic devices. [ABSTRACT FROM AUTHOR]

Field-effect transistors (FETs) based on an individual CN[sub x]/C nanotube (NT) were fabricated by focus ion-beam technology. The nanotube transistors exhibited n-type semiconductor characteristics, and the conductance of nanotube FETs can be modulated more than four orders of magnitude at room temperature. The electron mobility of a CN[sub x]/C NT FET estimated from its transconductance was as high as 3.84×10[sup 3] cm[sup 2]/V s. The n-type gate modulation could be explained as due the effect of bending of the valence band in the Schottky-barrier junction. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Features an efficient light-emitting diodes using a binaphthalene polymer as the emissive layer and a fluorinated copper phthalocyanine as the electron injecting/transporting layer. Twisted, nonplanar backbone with two hexyloxy side groups; Energy levels; Brightness, luminous efficiency and quantum efficiency of a light-emitting diode with aluminum electrode.

The article focuses on the development of a closed-loop catalytic nanoreactor system, which enables precise control and monitoring of chemical reactions at the molecular level. Topics include the use of Deoxyribonucleic Acid (DNA) frameworks and enzymes for precise reaction control, the application of this technology in sensitive molecular diagnostics, and the intelligent nano-systems for precision chemistry.

With the help of hydrogen bonding and π⋯π stacking, the small molecular clusters in the impregnating solution was induced to self-assemble and form a new Ni–Mo polyoxometalate based on octamolybdate with a molecular formula of [Ni(pyz)6] [Mo8O26(pyz)2]⋅10H2O (pyz = pyrazole). The polyoxometalate was structurally characterized detailed by various technologies, and its sulfide was also characterized to make a preliminary study to explore the use of it as a potential NiMoS active phase precursor. Much more NiMoS active phase and higher catalytic activity of the Ni–Mo sulfided catalyst was found, and the structure-directing effects can account for the phenomenon. The results show the Ni–Mo polyoxometalate [Ni(pyz)6] [Mo8O26(pyz)2]⋅10H2O can make a superior precursor to prepare the hydrodesulfurization catalyst, and it provides a new preparation methodology to the rational design and controllable preparation of superior hydrodesulfurization catalysts. [ABSTRACT FROM AUTHOR]

In the present study, subcutaneous fat was obtained from adult women that had undergone conventional liposuction surgery. A comparative study was performed to investigate the effect of transparent and white poly-β-hydroxyethyl methacrylate (PHEMA) stents, which have different surface and cross-sectional morphological characteristics, on the differentiation of adipose-derived stem cells (ASCs) into myocardial cells. The cell counting kit-8 assay revealed that cell growth increased at varying rates among the different treatment groups. The absorbance of the experimental transparent PHEMA treated group increased in a time-dependent manner with the duration of incubation. The highest levels of proliferation were observed in the transparent PHEMA group. In addition, the transparent PHEMA treated group exhibited the strongest cell adhesion ability, which was significantly different to that of the white PHEMA group (P<0.01 and P<0.05 for Matrigel and fibronectin assay, respectively). Comparisons between the two stent materials with the inducer control group revealed statistically significant differences in the rate of ASC differentiation (P<0.05). The level of differentiation was the greatest in the transparent PHEMA group, and was significantly different to the white PHEMA group (P<0.05) and the blank control group (P<0.01). The results suggest that the inducers 5-aza-2-deoxycytidin and laminin, and material microstructure stents effectively promote the proliferation, growth and adhesion of ASCs. However, the transparent material microstructure may be a more suitable candidate for ASC-associated injections. The present study provides further evidence that a PHEMA stent structure, comprised of a high number of matrixes and a low water content, induces a high level of ASC differentiation to myocardial cells. [ABSTRACT FROM AUTHOR]

The use of an 'internal' oxidant contained within a directing group has emerged as a practical strategy in metal-catalyzed direct C-H activations in recent years, owing to its being highly sustainable. This review presents the rapid advances of this novel strategy through analyzing and comparing the different types of internal oxidant in transition-metal-catalyzed C-H activation reactions. [ABSTRACT FROM AUTHOR]

In this article, four “A3ݯ”-type hyperbranched conjugated polymers (P1−P4) containing hexaphenylbenzene as the core were synthesized successfully for the first time with high yields through one-pot Suzuki polymerization reaction. The copolymerization percent of 1,3,4-oxadiazole units was adjusted to investigate the effect of polymer composition on the physical, optical, and EL properties. All polymers were well-characterized and exhibited good solubility, film-forming ability, and thermal stability. Both the solution and the films of these hyperbranched polymers emitted pure and stable deep-blue light emission, and their PL spectra did not change after annealing at 150 °C for 0.5 h in air, indicating that the hyperbranched structure, coupled to the introduced hexaphenylbenzene moieties, effectively suppressed the formation of aggregation excimer and keto defects. Two-layer PLED devices were fabricated to investigate the electroluminescence properties of these hyperbranched polymers, and P3demonstrated a maximum luminance efficiency of 0.72 cd/A and a maximum brightness of 549 cd/m2at 16.5 V. [ABSTRACT FROM AUTHOR]

Ni-promoted tetramethylammonium tetrathiomolybdate precursor was prepared by the aqueous solution precipitation method using (NH4)2MoS4, (CH3)4NBr and NiCl2.6H2O as raw materials. Carbon-containing Ni–Mo sulfide nanospheres, namely Ni/C1–MoS2, were obtained by ex situ thermal decomposition of the precursor under N2 atmosphere. Energy dispersive X-ray spectroscopy (EDS), low temperature N2 adsorption (BET method), X-ray diffraction (XRD), scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM) techniques were employed to characterize these as–synthesized sulfide particles. The results showed that the average size of solid Ni–Mo sulfide nanospheres, with surface composition MoNi0.40S0.73C1.43, is 75 nm and the solid structure leads to low surface area of Ni/C1–MoS2. In addition, the introduction of methyl chain improved the dispersion of nickel phases and resulted in C/Mo ratio, 1.4. By comparison with catalytic performance of the Ni/MoS2 catalyst counterpart, Ni/C1–MoS2 revealed lower HDS activity but higher direct desulfurization (DDS) selectivity. Lower stacking number of MoS2 slabs (5 layers) and shorter slabs length of MoS2 slabs (6 nm) explained higher DDS selectivity satisfactorily. The formation of carbon-containing Ni–Mo sulfide nanospheres was possibly due to surfactant effect of tetramethylammonium cations and the potential measure to increase their surface area was discussed as well in this work. [ABSTRACT FROM AUTHOR]

Two new dendronized nonlinear optical (NLO) polyfluorenes were synthesized with high azo-chromophore loading density by the introduction of high generation chromophore dendrons on the side chains. Thanks to the advantages of Sharpless’ click chemistry reaction, the dendrons were conveniently bonded to the backbone of polyfluorene with the conversion of 100%, although they were really very bulky. The new-formed triazole rings in the dendrons acted as suitable isolation groups to minimize the strong dipole−dipole interactions among the polar chromophore moieties to improve NLO effects, according to the results obtained from UV−vis spectra and order parameters. All the polymers were well characterized and exhibited good solubility, high thermal ability, wide optical window, and large NLO effects (up to 106.0 pm/V). In addition, the tested NLO results of these dendronzied polymers demonstrated a deviation from the dipolar frustration that typically limits the NLO effect in conventional chromophore/polymer composite materials, indicating that the frequently observed asymptotic dependence of electro-optic activity on chromophore density may be overcome through rational design. [ABSTRACT FROM AUTHOR]

In recent years, tetrathiafulvalene (TTF) and its derivatives have been used as semiconducting materials for organic field-effect transistors (OFETs). In this review, we summarize the recent progress in the field of TTF-based OFETs. We introduce the structure and operation of OFETs, and focus on TTF derivatives used in OFETs. TTF derivatives used in OFETs can be divided into three parts by the semiconductor's morphology and the device fabrication technique: (1) TTF derivatives used for single-crystal OFETs, (2) TTF derivatives used for vacuum-deposited thin-film OFETs, and (3) TTF derivatives used for solutionprocessed thin-film OFETs. The single-crystal OFETs based on TTF derivatives were fabricated by drop-casting method and showed high performance, with the mobility up to 1.4 cm2/Vs. The vacuum-deposited thin-film OFETs based on TTF derivatives were well developed, some of which have shown high performance comparable to that of amorphous silicon, with good air-stability. Although the mobilities of most solution-processed OFETs based on TTF derivatives are limited at 10-2 cm2/Vs, the study on solution-processable TTF derivatives and their devices are promising, because of their low-cost, large-area-coverage virtues. The use of organic charge-transfer (OCT) compounds containing TTF or its derivatives in OFETs is also included in this review. [ABSTRACT FROM AUTHOR]

In the past decade, tremendous progress has been made in organic field-effect transistors (OFETs). Their real applications require further development of device performance. OFETs consist of organic semiconductors, dielectric layers, and electrodes. Organic semiconductors play a key role in determining the device characteristics. The properties of the organic semiconductors, such as molecular structure and packing, as well as molecular energy levels, can be properly controlled by molecular design. Therefore, we designed and synthesized a series of organic molecules. The synthesized organic semiconductors exhibit excellent field-effect properties due to strong intermolecular interactions and proper molecular energy levels. Meanwhile, the influence of the device fabrication process, organic semiconductor/dielectric layer interface, and organic layer/electrode contact on the device performance was investigated. A deep understanding of these factors is helpful to improve field-effect properties. Furthermore, single-crystal field-effect transistors are highlighted because the single-crystal-based FETs can provide an accurate conducting mechanism of organic semiconductors and higher device performance as compared with thin film FETs. [ABSTRACT FROM AUTHOR]

The excellent electroluminescent (EL) properties of 1 ,1-disubstituted 2,3,4,5-tetraphenylsiloles, 1-methyl-1,2,3,4,5-pentaphenylsilole (MPPS), and 1,1,2,3,4,5-hexaphenylsilole (HPS) have been found. Despite some studies devoted to these materials, very little is known about the real origin of their unique EL properties. Therefore, we investigated the structures, photoluminescence (PL), and charge carrier transport properties of 1,1 -disubstituted 2,3,4,5-tetraphenylsiloles as well as the effect of substituents on these characteristics. The single crystals of the three siloles involving 1,1 -dimethyl-2,3,4,5-tetraphenylsilole (DMTPS), MPPS, and HPS were grown and their crystal structures were determined by X-ray diffraction. Three siloles have nonplanar molecular structures. The substituents at 1,1-positions enhance the steric hindrance and have predominant influence on the twisted degree of phenyl groups at ring carbons. This nonplanar structure reduces the intermolecular interaction and the likelihood of excimer formation, and increases PL efficiency in the solid state. The silole films show high fluorescence quantum yields (75- 85%), whereas their dilute solutions exhibit a faint emission. The electronic structures of the three siloles were investigated using quantum chemical calculations. The highest occupied molecular orbitals (HOMOs) and the lowest unoccupied molecular orbitals (LUMOs) are mainly localized on the silole ring and two phenyl groups at 2,5-positions in all cases, while the LUMOs have a significant orbital density at two exocyclic Si-C bonds. The extremely theoretical studies of luminescent properties were carried out. We calculated the nonradiative decay rate of the first excited state as well as the radiative one. It is found that the faint emission of DMTPS in solutions mainly results from the huge nonradiative decay rate. In solid states, molecular packing can remarkably restrict the intramolecular rotation of the peripheral side phenyl ring, which has a large contribution to the nonradiative transition process. This explains why the 1,1 -disubstituted 2,3,4,5-tetraphenylsiloles in the thin films exhibit high fluorescence quantum yields. The charge carrier mobilities of the MPPS and HPS films were measured using a transient EL technique. We obtained a mobility of 2.1 × 10-6 cm2/V-s in the MPPS film at an electric field of 1.2 × 106 V/cm. This mobility is comparable to that of A1q3, which is one of the most extensively used electron transport materials in organic light-emitting diodes (LEDs), at the same electric field. The electron mobility of the HPS film is about ∼1.5 times higher than that of the MPPS film. To the best of our knowledge, this kind of material is one of the most excellent emissive materials that possess both high charge carrier mobility and high PL efficiency in the solid states simultaneously. The excellent EL performances of MPPS and HPS are presumably ascribed to these characteristics. [ABSTRACT FROM AUTHOR]

A flexible continuous optical beamformer with time delay for a phased-array antenna is proposed and demonstrated. It is constructed using a novel tunable chirped fiber grating achieved by bending a uniform grating, and a multi-wavelength fiber laser based on a novel Sagnac interferemetric filter that consists of a polarization-maintaining directional coupler and polarization-maintaining fibers. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 187–190, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10716 [ABSTRACT FROM AUTHOR]

Focuses on a study which explored the electron structures and non-linear optical properties of tertbutyl-nitro-phthalocyanines. Methodology; Results and discussion; Conclusion.

A fused-seven-ring anthracene derivative with two sulfur bridges, benzobisthioxanthene (BTA), was synthesized, facilely. OLEDs employing BTA as the emitter exhibited bright (maximum 40 752 cd m-2) and efficient red emission (CIE, x = 0.64, y = 0.36) with a luminous efficiency of 4.4 cd A-1. [ABSTRACT FROM AUTHOR]

A novel type of antiand synisomers of a pentacyclic compound consisting of two thiophene rings and one pyrrole ring were efficiently synthesized from benzo[b]thiophene, and the antiisomer exhibits better charge transport and OFET properties compared with the synisomer and its N-hexyl substitution. [ABSTRACT FROM AUTHOR]

A new series of ladder-type heteroacenes containing both pyrrole and furan rings, 5,6-disubstituted diindolo[3,2-b:4,5-b′]thiophenes (DITs), were effectively synthesized from N-functionalized 3,3′-dibromo- 2,2′-biindoles undergoing intramolecular cyclization with bis(phenylsulfonyl) sulfide and organolithium. Single-crystal X-ray results demonstrate that 5,6-dipropyldiindolo[3,2-b:4,5-b′]thiophene (4b) forms a herringbone-type of packing motif and 5,6-di(p-tolyl)diindolo[3,2-b:4,5-b′]thiophene (4d) forms a parallel packing motif. Both of them have S-S contacts, enhancing the electronic transport between molecules. Their photophysical properties suggest that the skeleton of diindolo[3,2-b:4,5-b′]thiophene is more favorable to aggregate in solid than that of indolo[3,2-b]carbazole. The large band gaps and low-lying HOMO energy levels could result in much better stability. [ABSTRACT FROM AUTHOR]

We demonstrate modification of the indium tin oxide (ITO) surface with an ultrathin layer of hexadecafluorocopper phthalocyanine (F16CuPc) can significantly enhance hole injection as a result of the formation of an interfacial dipole layer. The dipole layer produces a surface potential shift, which reduces the hole injection energy barriers and thus improves the hole injection efficiency. The devices with anode modification exhibit significantly enhanced luminance efficiencies and dramatically decreased operation voltages, compared to devices with the bare ITO anode. The minimum turn-on voltage of 2.6 V and the maximum efficiency of 5.1 cd/A are achieved. [ABSTRACT FROM AUTHOR]

We present a method of fabricating noncoplanar channel organic field-effect transistors (OFETs) by a conventional photolithographic technique. Using this method, OFETs with micrometer critical features in slanting configurations and submicrometer critical features in vertical configurations were fabricated. The critical channel length over 1 μm was controlled by the patterning technique, while the one of 0.5 μm was defined by the thickness of an insulating layer between the drain and source electrodes. Also, we demonstrate that the OFETs containing two different metals as source and drain electrodes, respectively, are easily realized. All the OFETs based on copper phthalocyanine exhibit a high performance. [ABSTRACT FROM AUTHOR]

We report an efficient blue light-emitting diode (LED) using N, N′-bis(1-naphthyl)-N, N′-diphenylbenzidine as an emitting layer and tetra(β-naphthyl)silane (TNS) as a hole-blocking layer (HBL). We find that the hole-blocking performance, thermal stability, and film-forming ability of TNS are improved over those of the prototypical hole-blocking material 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP). The device that used TNS as the HBL exhibits a narrower light emission and higher current efficiency (2.5 cd/A) as compared with the device containing BCP as the HBL. TNS should be promising as an excellent hole-blocking layer in LEDs. [ABSTRACT FROM AUTHOR]

We report the effects of a metal chelate, bis[2-(2-hydroxyphenyl)benzothiazolate]zinc [Zn(BTZ)2] and 8-tris-hydroxyquinoline aluminum (Alq3) used as electron-transporting layers, and various cathodes on electroluminescent and current-voltage characteristics of a polymer light-emitting diode with phenyl-substituted poly(phenylene vinylene) as an emissive layer. We find that the metal chelate layers also play a role in hole blocking. For a double-layer device with the structure of indium-tin oxide (ITO)/polymer/Zn(BTZ)2 or Alq3/Al, the metal chelate layer lowers the hole current and improves the electroluminescent properties. Inserting a LiF layer between the metal chelate layer and the Al cathode enhances the electron injection and improves the elctroluminescent efficiency. The device with the structure of ITO/polymer/Zn(BTZ)2/Alq3/LiF/Al can reach the highest luminous efficiency of 5.0 cd/A. [ABSTRACT FROM AUTHOR]