Abstract  We have systematically investigated the influence of UV ozone and acid (HCl) treatments (separate and combined) of the surface of indium tin oxide (ITO) on the ITO parameters and the performance of organic light-emitting diodes (OLEDs) fabricated on the treated substrates. The ITO substrates were characterized by Hall measurements, Seebeck coefficient measurements and surface-probe microscopy. After ITO characterization, two types of devices (ITO/NPB/rubrene/Alq(3)/LiF/Al and ITO/TPD/rubrene/Alq(3)/LiF/Al) were fabricated on the differently treated substrates. It was found that in both cases the optimal treatment was HCl followed by UV ozone, which resulted in the lowest turn-on voltage and the highest luminous efficiency. The maximum luminous efficiency in the ITO/NPB/rubrene/Alq(3)/LiF/Al OLED with HCl followed by UV ozone treatment was 2.15 lm/W compared to 1.46 lm/W with UV ozone treatment only.

Abstract  A phosphorescent iridium(III) complex Ir(PBQ)(2)(acac) (PBQ: 4-phenylbenzoquinoline, acac: acetylacetone) was designed and synthesized, and the single crystal of this complex was obtained. This complex shows well optoelectronic properties. The organic light emitting devices (OLEDs) based on this complex were successfully fabricated with the device configuration of ITO/NPB or TCTA (40 nm)/Ir-complex: CBP (7%, 30 nm)/BCP (15 nm)/Alq (30 nm)/LiF (1 nm)/Al (100 nm). Using TCTA as the hole-transporting material, the device gives an extremely high external quantum efficiency of 14.6% at 5.0V, a brightness of 61,693 cd/m(2) at 16.0V, and a power efficiency of 37.0 Im/W at 3.5 V. (c) 2009 Elsevier B.V. All rights reserved.

Abstract  The measurement of charge mobility is of great importance to optimize the performance of organic semiconductor materials and understand the charge transport behaviors. In this Article, we present a new and in situ method to measure the carrier mobilities in organic semiconductor materials by testing the frequency characteristics of organic optoelectronic coupler (OOC), devices. In this method, a square-wave voltage was applied as the input signal and the mobilities of the related organic semiconductors in the device can be obtained from the falling-edge transient of the output current signal. On the basis of our sample OOC devices of ITO/PEDOT:PSS/C60/(NPB or m-MTDATA)/LiF/Al)/OLED, we successfully achieved the hole mobilities of N,N'-diphenyl-N, N'-bis(1,1'-biphenyl)-4,4'-diamine (NPB) and 4,4',4 ''-tris{N,-(3-methylphenyl)-N-phenylamino}triphenylamine (m-MTDATA) to be (1.21 to 2.38) x 10(-4) and 4.55 x 10(-5) cm(2) V-1 s(-1), respectively. These results verified the reliability of this new method. Compared with the traditional mobility measurement methods, the new method has advantages of showing the real mobilities in the operating devices and saving materials by decreasing the thickness of semiconductor thin films from micrometers to nanometers.

Abstract  In this paper, we investigate secure device-to-device (D2D) communication in energy harvesting large-scale cognitive cellular networks. The energy constrained D2D transmitter harvests energy from multiantenna equipped power beacons (PBs), and communicates with the corresponding receiver using the spectrum of the primary base stations (BSs). We introduce a power transfer model and an information signal model to enable wireless energy harvesting and secure information transmission. In the power transfer model, three wireless power transfer (WPT) policies are proposed: 1) co-operative power beacons (CPB) power transfer, 2) best power beacon (BPB) power transfer, and 3) nearest power beacon (NPB) power transfer. To characterize the power transfer reliability of the proposed three policies, we derive new expressions for the exact power outage probability. Moreover, the analysis of the power outage probability is extended to the case when PBs are equipped with large antenna arrays. In the information signal model, we present a new comparative framework with two receiver selection schemes: 1) best receiver selection (BRS), where the receiver with the strongest channel is selected; and 2) nearest receiver selection (NRS), where the nearest receiver is selected. To assess the secrecy performance, we derive new analytical expressions for the secrecy outage probability and the secrecy throughput considering the two receiver selection schemes using the proposed WPT policies. We presented Monte carlo simulation results to corroborate our analysis and show: 1) secrecy performance improves with increasing densities of PBs and D2D receivers due to larger multiuser diversity gain; 2) CPB achieves better secrecy performance than BPB and NPB but consumes more power; and 3) BRS achieves better secrecy performance than NRS but demands more instantaneous feedback and overhead. A pivotal conclusion is reached that with increasing number of antennas at PBs, NPB offers a comparable secrecy performance to that of BPB but with a lower complexity.

Abstract  Effects of doping molybdenum oxide (MoO3) in copper phthalocyanine (CuPc) as hole injection layer in OLEDs are studied. A green OLED with structure of ITO/MoO3-doped CuPc/NPB/10-(2-benzothiazolyl)-2,3,6,7-tetrahydro-1,1,7,7-tetramethyl-1H,5H, 11H-(1)-benzopyropyrano(6,7,8-ij) quinolizin-11-one (C545T): tris(8-hydroxyquinoline) aluminum (Alq(3))/Alq(3)/LiF/Al shows the driving voltage of 4.4 V. and power efficiency of 4.3 Im/W at luminance of 100 cd/m(2). The charge transfer complex between CuPc and MoO3 plays a decisive role in improving the performance of OLEDs. The AFM characterization shows that the doped film owns a better smooth surface, which is also in good agreement with the electrical performance of OLEDs. (C) 2011 Elsevier B.V. All rights reserved.

Abstract  Two series of n-type triphenylpyridine derivatives with good thermal properties and efficient deep-blue emissions were designed, synthesized and systematically characterized. Most of them show high glass transition temperatures (T-g > 100 degrees C), relatively high electron mobilities, large ionization potentials (IP > 6.31 eV) and suitable electron affinities (EA > 2.93 eV) for facilitating efficient electron-injection. These attributes of the n-type triphenylpyridine derivatives favours their applications in organic light-emitting devices (OLEDs) as electron-transporting and hole-blocking materials (ETMs and HBMs). With these new materials, deep-blue OLEDs with a configuration of indium-tin oxide (ITO)/alpha-napthylphenylbiphenyl diamine (NPB)/9,10-di(2-naphthyl) anthracene (ADN)/triphenylpyridine derivative/LiF/MgAg were fabricated to investigate the properties of these triphenylpyridine derivatives as ETMs and HBMs. The devices show higher efficiency (2.54 cd A(-1)), and better color purity (0.15, 0.10) compared to those of similarly-structured blue OLEDs using state-of-the-art ETMs. The large IP and deep-blue emission of the triphenylpyridine derivatives are considered to be key factors for the higher efficiencies and better color purity. Optical and other properties of the compounds are discussed in terms of their molecular structures.

Abstract  Conventional fluorescent dyes, i.e., 4-(dicyanomethylene)-2-t-butyl-6(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB), 5,12-dihydro-5,12-dimethylquino [2,3-b]acridine-7,14-dione (DMQA) and 5,6,11,12-tetraphenylnaphthacene (Rubrene), were used to investigate the performance of organic light-emitting diodes (OLEDs) based on indium tin oxide (ITO)/N,N'-bis-(1-naphthyl)-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine (NPB)/tris-(8-hydroxyquinolate)-aluminum(Alq(3))/MgAg. The dyes were either inserted into devices as an ultra-thin film at the NPB/Alq(3) interface by sequential evaporation, or doped into the Alq3 emission layer by co-evaporation with the doping ratio about 2%. Electroluminescence (EL) spectra of devices indicated that concentration quenching effect (CQE) of the dye-dopant was slightly bigger in the former than in the latter, while the degrees of CQE for three dopants are in the order of DMQA > DCJTB > Rubrene suggested by the difference in EL spectra and performances of devices. In addition, EL process of device with an ultra-thin layer of dopant is dominated by direct carrier trapping (DCT) process due to almost no holes recombine with electrons in Alq(3)-host layer. (C) 2007 Elsevier B.V. All rights reserved.

Abstract  The reorganization energy is one important parameter regarding the charge transfer in organic semiconductors. In the past, the influence of the molecular packing on the intramolecular reorganization energy was commonly neglected in theoretical estimations. Here, the quantum mechanic/molecular mechanic (qm/mm) method is used to study this influence for four small molecules: N,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine (TPD), N,N'-diphenyl-N,N'-bis(1-naphthyl)-1,1'-biphenyl-4,4'-diamine (NPB), 4,4'-bis(N-carbazolyl)-1,1'-biphenyl (CBP), and 4,7-diphenyl-1,10-phenanthroline (Bphen). An approximate linear relationship between the intramolecular reorganization energy and the change of the torsion angle during the molecular relaxation which causes the most steric hindrance is found. Furthermore, reorganization energies from qm/mm calculations are smaller depending on the degree of reduced conformational change.

Abstract  A thin layer of samarium (Sm) was introduced in the cathode fabrication of the organic light-emitting devices (OLEDs). An efficient cathode Sm/LiF/Al used to improve the performance of OLEDs was reported. Standard N,N'-bis(1-naphthyl)-N,N'-diphenyl-1,1'-biphenyl 4,4'-diamine (NPB)/tris-(8-hydroxyquinoline) aluminum (AlQ) devices with Sm/LiF/Al cathode showed dramatically enhanced electroluminescent (EL) brightness and efficiency. The optimized device with the 0.5 nm layer of Sm with the cathode structure of Sm/LiF/Al showed the improved power efficiency of 40% than the control device of the conventional LiF/Al cathode at 100 mA/cim(2). The drive voltage of the device with the Sm/LiF/Al cathode was decreased about 2 V at 500 mA/cm(2) compared with the conventional LiF/Al cathode device. The enhanced properties of the device with such a multilayer cathode are considered to the improved balance of electron/hole injection in the emitting layer. (C) 2007 Elsevier B.V. All rights reserved.

Abstract  Most of the Organic Light-Emitting Diodes (OLEDs) have a multilayered structure composed of functional organic layers sandwiched between two electrodes. Thin films of small molecules are generally deposited by thermal evaporation onto glass or other rigid or flexible substrates. The interface state between two organic layers in OLED device depends on the surface morphology of the layers and affects deeply the OLED performance. The morphology of organic thin films depends mostly on substrate temperature and deposition rate. Generally, the control of the substrate temperature allows improving the quality of the deposited films. For organic compounds substrate temperature cannot be increased too much due to their poor thermal stability. However, studies in inorganic thin films indicate that it is possible to modify the morphology of a film by using substrate vibration without increasing the substrate temperature. In this work, the effect of the resonance vibration of glass and silicon substrates during thermal deposition in high vacuum environment of tris (8-quinolinolate) aluminum(III) (Alq(3)) and N,N'-Bis(naphthalene-2-yl)-N,N'-bis(phenyl)-benzidine (beta-NPB) organic thin films with different deposition rates was investigated. The vibration used was in the range of hundreds of Hz and the substrates were kept at room temperature during the process. The nucleation and subsequent growth of the organic films on the substrates have been studied by atomic force microscopy technique. For Alq(3) and beta-NPB films grown with 0.1 nm/s as deposition rate and using a frequency of 100 Hz with oscillation amplitude of some micrometers, the results indicate a reduction of cluster density and a roughness decreasing. Moreover, OLEDs fabricated with organic films deposited under these conditions improved their power efficiency, driven at 4 mA/cm(2), passing from 0.11 lm/W to 0.24 lm/W with an increase in their luminance of about 352 cd/m(2) corresponding to an increase of about 250% in the luminance with respect to the same OLEDs fabricated in the same way and with the same conditions without substrate vibration. (C) 2011 Elsevier B.V. All rights reserved.

Abstract  In this study, the efficiency of organic light-emitting diodes (OLEDs) was enhanced by depositing a Li2CO3-doped NiO (LNO) film as a buffer layer between the indium tin oxide (ITO) electrode and alpha-naphthylphenylbiphenyl diamine (NPB) hole transport layer, with the structure configuration ITO/NiO:Li2CO3 (X wt%, Y nm) (X = 0, 5 and 10 wt%; Y = 0.5, 1, and 1.5 nm)/NPB (40 nm)/tris(8-hydroxyquinoline) aluminum (Alq(3)) (60 nm)/lithium fluoride (LiF) (1 nm)/Al (150 nm). The enhancement mechanism was systematically investigated the X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy results revealed the formation of the UV-ozone treated Li2CO3-doped NiO film. The work function increased from 4.8 eV (standard ITO electrode) to 5.45 eV (1-nm-thick UV-ozone treated Li2CO3-doped NiO film deposited on the ITO electrode with 5 wt%). The surface roughness of the UV-ozone treated Li2CO3-doped NiO film was smoother than that of the standard ITO electrode. Further, the UV-ozone treated Li2CO3-doped NiO film increased both the surface energy and polarity as determined from contact angle measurement and admittance spectroscopy measurement showed that increased capacitance and conductance of the OLEDs. In addition, the carrier injection increased in the space-charge region when the UV-ozone treated Li2CO3-doped NiO buffer layer was inserted. Moreover, the turn-on voltage decreased from 4.2 V to 3.5 V at 1 mA/cm(2), the luminance increased from 7588 cd/m(2) to 23240 cd/m(2), and the current efficiency increased from 3.2 cd/A to 3.4 cd/A when the 1-nm-thick UV-ozone treated Li2CO3-doped NiO film with 5 wt% was inserted of the OLEDs. (C) 2016 Published by Elsevier B.V.

Abstract  We demonstrate highly efficient Alq3-based p-i-n organic light-emitting diodes by using cesium carbonate (Cs2CO3)-doped 4'7-diphyenyl-1, 10-phenanthroline (Bphen) as an electron transport layer, and by using molybdenum trioxide (MoO3)-doped N, N'-diphenyl-N, N'-bis(1,1'-biphenyl)-4,4'-diamine (NPB) as a hole transport layer, which could significantly enhance the electron injection and transport, resulting in a large increase in luminance and efficiency. The maximum luminance, current efficiency and power efficiency reach 23 420 cd cm(-2), 6.4 cd A(-1) and 5.3 lm W-1, respectively, which are much higher than those of the referenced device (without doping). This improvement is attributed to the improved conductivity of the transport layers and the efficient charge balance in the emission zone.

Abstract  Hydroxyurea (HU) is an antineoplastic drug widely used in the clinical management of patients with sickle cell disease (SCD), and many questions related with its use remain unresolved. Given the severity of SCD, HU benefits, although not thoroughly confirmed, seem to outweigh its potential carcinogenicity. This study aimed to assess the genotoxicity associated with HU dose and treatment length by evaluating mutagenicity in patients with SCD treated with HU (SCHU) using the cytokinesis-block micronucleus assay (CBMN) in white cells. The study was conducted with 35 individuals in the SCHU group and 34 controls matched according to age, sex and smoking habit. CBMN results showed an increase (p=0.032) in the number of micronuclei (MN), but not of nucleoplasmic bridges (NPB) or nuclear buds (NBUD) in the SCHU group. The increased frequency of MN in the SCHU group was significantly correlated with treatment length and final HU dose, which confirms that patients with SCD treated with HU should be carefully monitored to reduce the risk of carcinogenicity.

Abstract  MCM-22, having MWW topology, Is a zeolite which has unique and unusual pore structure and acidic property on its external surface. In this paper, the total acid sites of MCM-22 (n(Si)/n(Al) = 15) were measured by means of TG and FT-IR. The B and L acid sites were 375 and 450 mumol/g respectively, and the external surface acid sites were 45 mumol/g. The ratio of initial reaction rate of benzene alkylation over beta zeolite ( n (Si) /n (Al) = 15) to that over MCM-22 was better consistent with the ratio of B acid sites on beta zeolite to that on the MCM-22 external surface. It was showed that the benzene alkylation took place on the external surface of MCM-22 and in the 12 MR pore channels of beta zeolite, respectively. The distribution of products, including isopropyl benzene(IPB), diisopropyl benzene(DIPB), tri-isopropyl benzene(TIPB), oligomers(Olig) and n-propyl benzene(NPB), was studied under the conditions of n(C6H6)/n(C3H6) = 2similar to10, WHSV(C3H6) = 2.5similar to30 h(-1), p = 3.0 MPa and theta = 140similar to210 degreesC. On the basis of the diffusion coefficients of the reactants and the energy barriers of the products in MCM-22 and beta zeolites, it was found that: (1) owing to that the benzene alkylation took place on the MCM-22 external surface, the selectivity for IPB was lower by 2%similar to4%, and the amount of DIPB and TIPB was higher over MCM-22 than over beta zeolite; (2) the B acid sites located in the 10 MR sinusoidal channels of MCM-22 may not take part in the benzene alkylation owing to the steric effect, but it may take part in oligomerization of propylene, so the oligomers formed over MCM-22 were higher than those over beta zeolite;.

Abstract  A series of new PPV oligomers containing 8-substituted quinoline, 2,2'-(arylenedivinylene) bis-8-quinoline derivatives, were designed and synthesized via a Knoevenagel condensation reaction of quinaldine, 8-hydroxy-or 8-methoxy-quinaldine with aromatic dialdehydes. These PPV oligomers were characterized by H-1 and C-13-NMR, X-ray diffraction, elemental analysis, UV-visible and fluorescence spectroscopies. The X-ray diffraction investigation showed that there are intermolecular pi...pi interactions in the solid state in 1 and 3. The optical and photoluminescent properties study demonstrated that the emission color of the resulting materials varies from blue to yellow and is dependent on the substituents (pi-donor and pi-acceptor groups) on both sides of the conjugated molecules and the aromatic core in the middle of the conjugated backbones. The electroluminescent devices using compounds 1-4 as the emitters and electron-transporting layers were fabricated with the structure ITO/NPB/emitter/LiF/Al. The best device performance with the maximum brightness of 5530 cd m(-2) and the luminous efficiency of 2.4 cd A(-1) is achieved by using compound 4, with intramolecular charge transfer character, as the emitter; these values represent a more than 5-fold improvement in brightness and efficiency compared to compound 3 without methoxy groups on the phenyl rings.

Abstract  We synthesized a hydroxyphenyloxadiazole lithium complex (LiOXD) as a blue light-emitting and electron injection/transport material to be used in double-layer organic electroluminescent devices. Devices with the concise configuration of ITO/TPD/LiOXD/Al showed bright blue EL emission centered at 468 nm with a maximum luminance of 2900 cd m(-2). A current efficiency of 3.9 cd A(-1) and power efficiency of 1.1 lm W-1 were obtained. LiOXD was also examined as an interface material. The efficiency of an ITO/NPB/Alq(3)/Al device increased considerably when LiOXD was inserted between Alq(3) and aluminium. The improvement of the device characteristics with LiOXD approached that observed with the dielectric LiF salt.

Abstract  Indium tin oxide (ITO) ultrathin films were prepared on glass substrate by DC (direct current) magnetron sputtering technique with the assistance of H2O vapor to avoid potential surface damage. The film properties were characterized by X-ray diffraction (XRD) technique, four-point probe method and spectrophotometer. The results show that the deposited ITO film with introduced H2O during sputtering process was almost amorphous. The average visible light transmission of 100 nm ITO film was around 85% and square resistivity was below 80 Omega/square. The film was used as the transparent anode to fabricate an inverted top-emitting organic light-emitting diodes (IT-OLEDs) with the structure of glass substrate/Alq(3) (40 nm)/NPB (15 nm)/CuPc (x nm)/ITO anode (100 nm), where the film thickness of CuPc was optimized. It was found that the luminance of this IT-OLEDs was improved from 25 cd/m(2) to more than 527 cd/m(2) by increasing the thickness of CuPc, and luminance efficiency of 0.24 lm/W at 100 cd/m(2) was obtained, which indicated that the optimized thickness of CuPc layer was around 15 nm.

Abstract  A series of bisindolylmaleimide dyes (1-3) were synthesized and they exhibited intensive orange to red color luminance deriving from charge transfer transitions. Highly efficient light-emitting devices were fabricated using these materials as emitters by doping 1% in a tris(8-hydroxyquinolinato)aluminium (Alq(3)) host, which performed in a quantum efficiency of similar to 4% with a maximal intensity >40 000 cd/m(2). Broad band white emission can be produced by combining their reddish color with another blue emitter. While doped in 4,4'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB) in suitable concentrations, dual emission was obtained from a single layer. The device with configuration ITO/PEDOT: PSS/dye 1 (1%): NPB/TPBI/LiF/Al yielded white light with maximum luminance efficiency of 6.6 cd/A, power efficiency of 6.4 lm/W and quantum efficiency of 2.6%, where PEDOT: PSS is poly(ethylenedioxythiophene): poly(styrenesulfonic acid), and TPBI is 2,2',2 ''-(1,3,5-benzentriyl)tris(1-phenyl-1H-benzimidazole). This device can be turned on at a low voltage (< 3 V) and emits a white color with CIE coordinate (0.32, 0.34), which stays invariant over a wide range of applied voltage.

Abstract  A novel hole injecting and transporting material, NN-di(9-ethylcarbaz-3-yl)-3-methylaniline (DECMA), was prepared by one-step reaction for use in organic electroluminescent (EL) devices. Organic EL device with configuration of ITO/DECMA (60 nm)/NPB (10 nm)/Alq(3) (60 nm)/Mg:Ag/Ag turned on at 3.7 V and displayed a brightness of 1150 cd m(-2) and a current efficiency of 5.5 cd A(-1) at the current density of 20 mA cm(-2), while a reference device with configuration of ITO/NPB (70 nm)/Alq3 (60 nm)/Mg:Ag/Ag turned on at 3.9 V and exhibited a brightness of 500 cd m(-2) and a current efficiency of 2.4 cd A(-1) at the same current density. The lower turn on voltage and higher brightness and efficiency obtained in DECMA-containing device can be ascribed to the improved hole injection at anode/organic interface due to the low ionization potential of DECMA and the better balanced hole-electron recombination in emitting layer due to the moderate hole drift mobility of DECMA. (C) 2004 Elsevier B.V. All rights reserved.

Abstract  New hole injection materials for organic light emitting diodes (OLEDs) based on phenothiazine and phenoxazine were synthesized, and the electro-optical properties of synthesized materials were examined by through UV-visible (UV-vis), photoluminescence (PL) spectrum and cyclic voltammetry (CV). 1-BPNA-t-BPBP and 1-BPNA-t-BPBPOX showed T-g of 127 and 200 degrees C, which are higher than that (110 degrees C) of 2-TNATA, a commercial hole injection layer (HIL) material. The highest occupied molecular orbital (HOMO) level of the synthesized materials of 1-BPNA-t-BPBP and 1-BPNA-t-BPBPOX were 4.97 and 4.91 eV, indicating values well-matched between HOMO (4.8 eV) of ITO and HOMO (5.4 eV) of NPB, hole transporting layer (HTL) material. As a result of using the synthesized materials in OLED device as HIL, 1-BPNA-t-BPBPOX of 2.43 Im/W was higher than 2-TNATA of 1.98 Im/W and 1-BPNA-t-BPBP of 1.39 Im/W in power efficiency. These results indicated that 1-BPNA-t-BPBPOX shows higher excellent power efficiency which is about 18% improved over 2-TNATA a commercial HIL material.

Abstract  Plasma-etched nanostructures are useful to provide antireflective properties to glass and plastic substrates. Organic compounds were deposited on glass substrates by thermal evaporation and etched by plasma emitted from an ion plasma source. A self-organized formation of surface structures takes place during etching of a layer of 1,3,5-Triazine-2,4,6triamine (melamine). On the other hand, the surface of N, N' -di(1-naphthyl)N, N' -diphenyl benzidine (NPB) remained smooth after etching. In this case, the structure formation was initiated by depositing a thin oxide layer on to the organic layer prior to the etching step. For both materials the etching process can be tailored to achieve antireflective properties over a desired wavelength range. (C) 2011 Optical Society of America

Abstract  We report the photo-(PL) and electro-luminescence (EL) properties of conjugated compounds based on carbazolyl vinylene moiety, 3,3-(1,4-phenylene di-2,1-ethenediyl)bis[9-ethyl-(E,E)-9H-carbazole] (PEEC) and 3,3'-([1,1'-biphenyl]-4,4'-diyldi-2,1-ethenediyl)bis[9-ethyl-9H-carbazole] (BPEEC), as emitting materials. The ITO/m-MTDATA/NPB/BPEEC/AlQ3/LiF/Al device shows bluish-green EL spectrum at 490 nm and turn-on voltage at 8 V. PEEC also shows bluish-green EL spectrum at 496 nm and turn-on voltage at 6 V and 2.4 cd/A efficiency in ITO/m-MTDATA/NPB/PEEC/AlQ3/LiF/Al device. ITO/m-MTDATA/NPB/ DPVBi + PEEC (3%)/AlQ3/LiF/Al device shows EL spectrum at 462 nm and EL efficiency was increased to 4.5 cd/A (1.7 lm/W) from 3.5 cd/A (the device without doping agent). (C) 2004 Elsevier B.V. All rights reserved.

Abstract  Novel distyrylarylene-based blue host materials, 4,4-bis(1,2-diphenylvinyl)-p-terphenyl (2), 4,4'-bis[1-phenyl-2-(p-tolyl)vinyl]-p-terphenyl (3) and 4,4'-bis[1-phenyl-2-(4,4'-biphenyl)vinyl]-p-terphenyl (4) were successfully synthesized using 4,4'-bisbenzoyl-p-terphenyl (1) through Wittig-Hornor reaction and a blue organic light-emitting diode (OLED) was made from them. The structure of the blue device is ITO/DNTPD/NPB/Host:DSA-Ph/Alq(3)/Al-LiF. Here, NPB is used as a hole transport layer, DNTPD as the hole injection layer, DSA-Ph as the blue dopant, Alq(3) as the electron transport layer and Alq(3) as the cathode. The blue device doped with 5%-DSA-Ph shows a blue EL spectrum at 463 nm and a high efficiency of 4.14-5.13 cd/A. (c) 2007 Elsevier B.V. All rights reserved.

Abstract  A series of blue-emitting materials with sp(3) Si cores were synthesized by Suzuki Coupling reaction and characterized by spectroscopy. Their usages as blue emitters in organic light-emitting diodes (OLEDs) were preliminary investigated. Blue emission with comparable brightness and efficiency were obtained with structure of ITO/NPB/tetraaryisilane/TPBi/LiF/Al. Moreover, these tetraarylsilane compounds exhibited high thermal decomposition temperatures (T(d)s) which indicated that these compounds might be explored for potential application in flat panel display. (C) 2008 Elsevier B.V. All rights reserved.

Abstract  Beef traders' and consumers' perceptions on the development of a natural pasture-fed beef (NPB) brand by smallholder cattle producers were investigated. In total, 18 meat traders (five abattoirs and 13 beef retailers) and 155 beef consumers were interviewed using structured questionnaires. All meat traders had the potential but were not willing to support the development of a NPB brand citing smallholder farmers' limited ability to supply sufficient volumes of high-quality cattle. Consumers (81%) were prepared to purchase NPB upon availability on the market but were not willing (80%) to pay a brand premium. Logistic regression model results showed that consumers' willingness to buy NPB and pay a premium were influenced (P < 0.05) by gender, household size, income source, meat preference, meat consumption frequency, money spent on beef, frequency of beef purchases and consumption. Overall, beef traders and consumers held positive impressions regarding the development of a NPB brand by smallholder cattle producers but were not willing to support its development. Positive impressions held by value chain partners on the development of a NPB brand provide a basis for advancing development of a NPB brand. Initial efforts should enhance farmers' capacity to supply sufficient volumes of high-quality cattle.