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A graphene/NPB structure with Re2O7 as an interfacial layer in the context of its potential use in the design of an organic light-emitting diode (OLED) is investigated. The X-ray photoelectron spectroscopy (XPS) study shows the formation of the Re2O7 phase on a monolayer graphene on quartz during thermal deposition in ultra-high vacuum (UHV). The ultraviolet photoelectron spectroscopy (UPS) study shows an enhancement of the work function of the graphene heterostructure after deposition of the Re2O7 layer up to 5.4 eV. The hole injection barrier between the Re2O7/graphene heterostructure and the N-bis-(1-naphthyl)-N,N-diphenyl-(1,1-biphenyl)-4,4-diamine (NPB) layer was estimated to be 0.35 eV, which is very promising for a good OLED performance. [ABSTRACT FROM AUTHOR]

Compiled low-level languages, such as C/C++ and Fortran, have been employed as programming tools to implement applications to explore GPU devices. As a counterpoint to that trend, this paper presents a performance and programming effort analysis with Python, an interpreted and high-level language, which was applied to develop the kernels and applications of NAS Parallel Benchmarks targeting GPUs. We used Numba environment to enable CUDA support in Python, a tool that allows us to implement the GPU programs with pure Python code. Our experimental results showed that Python applications reached a performance similar to C++ programs employing CUDA and better than C++ using OpenACC for most NPB benchmarks. Furthermore, Python codes demanded less operations related to the GPU framework than CUDA, mainly because Python needs a lower number of statements to manage memory allocations and data transfers. Despite that, our Python implementations required more operations than OpenACC ones. [ABSTRACT FROM AUTHOR]

NAS Parallel Benchmarks (NPB) is a standard benchmark suite used in the evaluation of parallel hardware and software. Several research efforts from academia have made these benchmarks available with different parallel programming models beyond the original versions with OpenMP and MPI. This work joins these research efforts by providing a new CUDA implementation for NPB. Our contribution covers different aspects beyond the implementation. First, we define design principles based on the best programming practices for GPUs and apply them to each benchmark using CUDA. Second, we provide ease of use parametrization support for configuring the number of threads per block in our version. Third, we conduct a broad study on the impact of the number of threads per block in the benchmarks. Fourth, we propose and evaluate five strategies for helping to find a better number of threads per block configuration. The results have revealed relevant performance improvement solely by changing the number of threads per block, showing performance improvements from 8% up to 717% among the benchmarks. Fifth, we conduct a comparative analysis with the literature, evaluating performance, memory consumption, code refactoring required, and parallelism implementations. The performance results have shown up to 267% improvements over the best benchmarks versions available. We also observe the best and worst design choices, concerning code size and the performance trade‐off. Lastly, we highlight the challenges of implementing parallel CFD applications for GPUs and how the computations impact the GPU's behavior. [ABSTRACT FROM AUTHOR]

A π-conjugated small molecule N, N'-bis(naphthalen-1-yl)-N, N'-bis(phenyl)benzidine (NPB) was introduced into poly(9-vinylcarbazole) (PVK) as a hole transport layer (HTL) in inverted perovskite solar cells (PSCs). The NPB doping induces a better perovskite crystal growth, resulting in perovskite with a larger grain size and less defect density. Thus, the VOC, JSC, and FF of the PSC were all enhanced. Experimental results show that it can be ascribed to the reduction of surface roughness and improved hydrophilicity of the HTL. The effect of NPB on the aggregation of PVK was also discussed. This work demonstrates the great potential of PVK as the HTL of PSCs and provides an attractive alternative for HTL to realize high-efficiency PSCs. [ABSTRACT FROM AUTHOR]

A π-conjugated small molecule N, N’-bis(naphthalen-1-yl)-N, N’-bis(phenyl)benzidine (NPB) was introduced into poly(9-vinylcarbazole) (PVK) as a hole transport layer (HTL) in inverted perovskite solar cells (PSCs). The NPB doping induces a better perovskite crystal growth, resulting in perovskite with a larger grain size and less defect density. Thus, the VOC, JSC, and FF of the PSC were all enhanced. Experimental results show that it can be ascribed to the reduction of surface roughness and improved hydrophilicity of the HTL. The effect of NPB on the aggregation of PVK was also discussed. This work demonstrates the great potential of PVK as the HTL of PSCs and provides an attractive alternative for HTL to realize high-efficiency PSCs.

The methylammonium lead halide solar cell has attracted a great deal of attention due to its lightweight, low cost, and simple fabrication and processing. Despite these advantages, these cells are still far from commercialization because of their lead-based toxicity. Among lead-free perovskites, cesium-titanium (IV) bromide (Cs2TiBr6) is considered one of the best alternatives, but it faces a lack of higher PCE (power conversion efficiency) due to the unavailability of the matched hole and electron transport layers. Therefore, in this study, the ideal hole and electron transport layer parameters for the Cs2TiBr6-based solar cell were determined and discussed based on a simulation through SCAPS-1D software. It was observed that the maximum PCE of 20.4% could be achieved by using the proper hole and electron transport layers with optimized parameters such as energy bandgap, electron affinity, doping density, and thickness. Unfortunately, no hole and electron transport material with the required electronic structure was found. Then, polymer NPB and CeOx were selected as hole and electron transport layers, respectively, based on their closed electronic structure compared to the simulation results, and, hence, the maximum PCE was found as ~17.94% for the proposed CeOx/Cs2TiBr6/NPB solar cell.

Charge-carrier mobilities in organic diodes based on an anthracene-containing poly(arylene-ethynylene)-alt-poly(p-phenylene-vinylene) generally known as AnE-PVstat, stacked with an electron blocking thin layer of NPB(N, N′-bis (1-naphythyl)-N, N-diphenyl-1,1′-biphenyl-4,4′-diamin) of various thicknesses are investigated through current density-voltage (J-V), capacitance-frequency (C-w), conductance-frequency (G-w) and impedance-frequency (Z-w) experiments in conventional structures of ITO/AnE-PVstat/NPB/Al. Analysis of J-V, C-w and G-w results show that current-density, capacitance and conductance of the active layer decrease with increasing NPB thickness and permit determination separately of a hole mobility of the polymer of the order of ∼ 10 - 4 cm 2 V - 1 s - 1 . This value is less than the global mobility (7 × 10−4 cm 2 V - 1 s - 1 ) obtained without the blocking layer, which probably includes electrons and holes mobilities and indicates that NPB absorbs the majority of electrons. Analysis of impedance spectroscopy results shows that the impedance (Z) and parallel capacitor (Cp) decrease and parallel resistance (Rp) increases with increasing NPB thickness layer. All these results clearly confirm the role of NPB as a blocking layer for the electrons. [ABSTRACT FROM AUTHOR]

Neuropeptide W (NPW) and neuropeptide B (NPB) are two structurally and functionally related regulatory peptides, which are highly expressed in several brain regions and, additionally, in some peripheral tissues. Nevertheless, their distributions in the tissues are not similar. They act on target tissues via two subtypes of G protein-coupled receptors which are designated as NPBWR1 (GPR7) and NPBWR2 (GPR8), respectively, and possess different binding affinities. NPB activates NPBWR1, whereas NPW stimulates both the receptors with similar potency. Both of these peptides takes a part in the central regulation of neuroendocrine axes, feeding behavior, energy homeostasis, cardiovascular functions, circadian rhythm, pain sensation, modulation of inflammatory pain, and emotions. Over the past few years, studies have shown that NPB is also involved in sleep regulation. On the contrary, NPW participates in regulation of vascular myogenic tone, inhibits gastric tension sensitive vagal afferents and insulin secretion. Also, expression of NPW in the stomach is regulated by feeding. Abovementioned findings clearly demonstrate the functional diversity among NPW versus NPB signaling systems. In this review, signal transduction pathways of NPW/NPB are critically evaluated and observed together with mapping of expression of their signaling systems.

Human BCL-2-associated death promoter (hBAD) is an apoptosisregulatory protein mediating survival signals to carcinoma cells upon phosphorylation of Ser99, among other residues. Herein, we screened multiple small-molecule databases queried in a Laplacianmodified naive Bayesian-based cheminformatics platform and identified a Petasis reaction product as a site-specific inhibitor for hBAD phosphorylation. Based on apoptotic efficacy against mammary carcinoma cells, N-cyclopentyl-3-((4-(2,3-dichlorophenyl) piperazin-1-yl) (2-hydroxyphenyl) methyl) benzamide (NPB) was identified as a potential lead compound. In vitro biochemical analyses demonstrated that NPB inhibited the phosphorylation of hBAD specifically on Ser99. NPB was observed to exert this effect independently of AKT and other kinase activities despite the demonstration of AKTmediated BAD-Ser99 phosphorylation. Using a structure-based bioinformatics platform, we observed that NPB exhibited predicted interactions with hBAD in silico and verified the same by direct binding kinetics. NPB reduced phosphorylation of BAD-Ser99 and enhanced caspase 3/7 activity with associated loss of cell viability in various human cancer cell lines derived from mammary, endometrial, ovarian, hepatocellular, colon, prostatic, and pancreatic carcinoma. Furthermore, by use of a xenograft model, it was observed that NPB, as a single agent, markedly diminished BAD phosphorylation in tumor tissue and significantly inhibited tumor growth. Similar doses of NPB utilized in acute toxicity studies in mice did not exhibit significant effects. Hence, we report a site-specific inhibitor of BAD phosphorylation with efficacy in tumor models. [ABSTRACT FROM AUTHOR]

Efficient polymer solar cells were fabricated with regioregular poly 3-hexylthiophene (P3HT):(6,6)-phenyl C61 butyric acid methyl ester (PCBM)) as active layer and molybdenum trioxide (MoO 3 ) and (N,N′-diphenyl)-N,N′-bis(1-naphthyl)-1,1′-biphenyl-4,4′-diamine (NPB) as buffer layers. The results of transient photocurrent and electrochemical impedance spectrometry of device indicate that the insertion of NPB layer between the active layer and MoO 3 layer is critical to the enhanced performance. It can effectively prevent charge recombination at the interface of MoO 3 hole extraction layer, reduce interfacial resistance due to the formation of Ohmic contact and enhance the exciton dissociation because of the newly formed NPB/PCBM dissociation interface. The optimized thickness of NPB layer is 5 nm, resulting in maximized power conversion efficiency (PCE) of 3.94% under AM1.5G 100 mW cm −2 illumination. [ABSTRACT FROM AUTHOR]

Neuropeptide W (NPW) and neuropeptide B (NPB) are two structurally and functionally related regulatory peptides, which are highly expressed in several brain regions and, additionally, in some peripheral tissues. Nevertheless, their distributions in the tissues are not similar. They act on target tissues via two subtypes of G protein-coupled receptors which are designated as NPBWR1 (GPR7) and NPBWR2 (GPR8), respectively, and possess different binding affinities. NPB activates NPBWR1, whereas NPW stimulates both the receptors with similar potency. Both of these peptides takes a part in the central regulation of neuroendocrine axes, feeding behavior, energy homeostasis, cardiovascular functions, circadian rhythm, pain sensation, modulation of inflammatory pain, and emotions. Over the past few years, studies have shown that NPB is also involved in sleep regulation. On the contrary, NPW participates in regulation of vascular myogenic tone, inhibits gastric tension sensitive vagal afferents and insulin secretion. Also, expression of NPW in the stomach is regulated by feeding. Abovementioned findings clearly demonstrate the functional diversity among NPW versus NPB signaling systems. In this review, signal transduction pathways of NPW/NPB are critically evaluated and observed together with mapping of expression of their signaling systems. [ABSTRACT FROM AUTHOR]

Neuropeptide B (NPB) is an endogenous ligand for the orphan G protein-coupled receptors NPBWR1 (GPR7) and NPBWR2 (GPR8). Some reports have investigated the role of NPB in the regulation of feeding, energy metabolism and hormone secretion in many species. However, few papers reported the physiological function of NPB in the pig. In this study, we cloned and sequenced the NPB mRNA from a pig, which was found to consist of 123 bases. NPB mRNA expression was detected in central and peripheral tissues by the quantitative fluorescence method. The results showed that NPB mRNA expression was higher in hippocampus, cerebellum, spinal cord, thymus, tonsil, duodenum, cecum, colon, ovary and testis. The distribution of NPB suggested that it may be involved in the regulation of reproductive functions in the pig. Subsequently, the expression and distribution of NPBWR1 and NPBWR2 were found in Leydig cells and ovarian granular cells. We then investigated the direct effect of NPB on pig reproductive cells in vitro. The results showed that different concentrations of NPB (10 −12 , 10 −10 , 10 −8 and 10 −6 M) promoted the secretion of testosterone in Leydig cells in concentration-dependent manner. Different doses of NPB could promote the secretion of progesterone in ovarian granulosa cells in dose-dependent manner. Low concentrations of NPB (10 −8 and 10 −10 M) promoted estradiol secretion, but high concentrations of NPB (10 −6 M) inhibited its secretion. All the results suggested that the NPB/NPBWR1 or NPBWR2 system may play a role in modulating the reproductive activity in the pig. [ABSTRACT FROM AUTHOR]

In this study, we investigated the multi-jet mode modified electrospray deposition (ESD) production of NPB/Alq3 small-molecule multilayer structures with suppressed interface mixing, using common solvents. Observations of the initial deposition stage and analysis of the photoluminescence spectra of the multilayer structure were conducted. It was demonstrated that, by optimizing the deposition conditions, surface erosion of the NPB layer and the initiation of interface mixing between the NPB and Alq3 layers could be suppressed. A 55-nm NPB/60-nm Alq3 multilayer structure with suppressed intermixing and smooth surface morphology (RMS roughness of 3.9 nm) was obtained at the lowest levels of under-layer erosion. Schematic of a modified electrospray (nanomist deposition: NMD) system and an NPB/Alq3 multilayer structure deposited by NMD. [ABSTRACT FROM AUTHOR]

Graphene is highly promising as an electrode for flexible optoelectronic devices due to its excellent conductivity and transparency. However, it is necessary to tailor its work function with a charge injection layer in order to obtain favorable energy level alignment for efficient charge injection. An adequate charge injection layer can only be chosen with the understanding of the interfacial electronic structure between a charge transport layer and an electrode. In this study, we investigated the energy level alignment of N , N ′-diphenyl-1,1′-biphenyl-4,4′-diamine (NPB)/hexaazatriphenylene hexacarbonitrile (HAT-CN)/graphene using in situ ultraviolet and X-ray photoelectron spectroscopy measurements. The effective work function of graphene was significantly increased by 0.94 eV by the HAT-CN hole injection layer (HIL) due to the interface dipole formation. In addition, the charge generation barrier (CGB) between NPB and HAT-CN, which plays a decisive role in charge injection efficiency with a charge generation HIL, was measured to be 0.66 eV. This CGB on graphene is the same as the CGBs on other electrodes, and smaller than that of the widely-used MoO 3 HIL. Therefore, HAT-CN could be a promising HIL for efficient flexible organic light-emitting diodes with a graphene anode. [ABSTRACT FROM AUTHOR]

Poly(9-vinylcarbazole) (PVK) is an attractive hole transport layer (HTL) for high efficiency perovskite solar cells (PSCs). But there is still some room for improvement in energy level alignment between the highest occupied molecular orbital (HOMO) of PVK and the perovskite layer. In this work, the solvent of PVK-based HTL was optimized to adjust the energy level of HTLs by changing the volume ratio of chlorobenzene (CB) in dimethylformamide (DMF). Experimental results shows that 20% is the optimal ratio of CB in DMF, based on which the HOMO level of HTL was lifted from −5.62 eV to −5.44 eV. Meanwhile, the morphology of perovskite layer with larger grain size and lower trap density was obtained. As a result, the V OC and J SC of PSCs was enhanced, leading to the increase of PCE from 15.41% to 18.27%. This work paves the way to realize high-efficiency PSCs based on PVK HTL. [Display omitted] • The solvent of PVK-based HTL was optimized to adjust the energy level of HTLs. • The HOMO level of HTL was lifted from −5.62 eV to −5.44 eV. • The V OC and J SC of PSCs was enhanced, leading to the increase of PCE from 15.41% to 18.27%. [ABSTRACT FROM AUTHOR]

The electronic structures of Ag-doped In 2 O 3 (IAgO) and its energy level alignments with a N,N' -bis-(1-naphthyl)- N,N' -diphenyl-1,1′-biphenyl-4,4′-diamine (NPB) hole transport layer (HTL) were investigated using in situ ultraviolet and X-ray photoelectron spectroscopies (UPS and XPS). As compared to the conventional Sn-doped In 2 O 3 (ITO), IAgO has less oxygen vacancies leading to a higher work function (WF). The lower hole injection barrier (Φ h ) from IAgO to a NPB HTL is observed, which is attributed mainly to its higher WF and interface dipoles. The UPS measurements reveal that the Φ h is 0.87 eV at NPB/IAgO while 1.11 eV is at NPB/ITO. Therefore, IAgO could be an alternative transparent anode in organic optoelectronics. [ABSTRACT FROM AUTHOR]

A study is presented of the effects of sample temperature on the sputter depth profiling of two organic materials, NPB ( N,N′-Di(1-naphthyl)- N,N′-diphenyl-(1,1′-biphenyl)-4,4′-diamine) and Irganox 1010, using a 5 keV Ar cluster ion beam and analysis by secondary ion mass spectrometry. It is shown that at low temperatures, the yields increase slowly with temperature in accordance with the Universal Sputtering Yield equation where the energy term is now modified by Trouton's rule. This occurs up to a transition temperature, T , which is, in turn, approximately 0.8 T , where T is the sample melting temperature in Kelvin. For NPB and Irganox 1010, these transition temperatures are close to 15 °C and 0 °C, respectively. Above this temperature, the rate of increase of the sputtering yield rises by an order of magnitude. During sputtering, the depth resolution also changes with temperature with a very small change occurring below T . At higher temperatures, the depth resolution improves but then rapidly degrades, possibly as a result first of local crater surface diffusion and then of bulk inter-diffusion. The secondary ion spectra also change with temperature with the intensities of the molecular entities increasing least. This agrees with a model in which the molecular entities arise near the crater rim. It is recommended that for consistent results, measurements for organic materials are always made at temperatures significantly below T or 0.8 T , and this is generally below room temperature. [ABSTRACT FROM AUTHOR]

Parallel computation model is an abstraction for the performance characteristics of parallel computers, and should evolve with the development of computational infrastructure. The heterogeneous CPU/Graphics Processing Unit (GPU) systems have been and will be important platforms for scientific computing, which introduces an urgent demand for new parallel computation models targeting this kind of supercomputers. In this research, we propose a parallel computation model called HLognGP to abstract the computation and communication features of heterogeneous platforms like TH-1A. All the substantial parameters of HLognGP are in vector form and deal with the new features in GPU clusters. A simplified version HLog3GP of the proposed model is mapped to a specific GPU cluster and verified with two typical benchmarks. Experimental results show that HLog3GP outperforms the other two evaluated models and can well model the new particularities of GPU clusters. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

We report fully vacuum–processed perovskite solar cells with high open circuit voltage. All the layers in the solar cells including the perovskite active layer, hole extraction layers and electron extraction layers were deposited in the vacuum process. Use of molybdenum oxide (MoO 3 ) as an interfacial layer and N,N′-Di(1-naphthyl)-N,N′-diphenyl-(1,1′-biphenyl)-4,4′-diamine (NPB) as a hole transport material (HTM) for hole extraction resulted in a high open circuit voltage ( V OC ) of 1.12 V. Due to the effective hole extraction and high V OC , the devices showed a maximum power conversion efficiency (PCE) of 13.7%. The vacuum processed perovskite solar cells showed relatively high reproducibility showing the average value of PCE of 11.1%. [ABSTRACT FROM AUTHOR]

The performance of three color single emissive layer white phosphorescent organic light-emitting diodes (PHOLEDs), with different hole transporting materials of N,N′-diphenyl-N,N′-bis(l-naphthyl-phenyl)-(l,l′-biphenyl)-4,4′-diamine (NPB), 4,4_,4_-tris_N-carbazolyl_tri-Phenylamine (TCTA) and 1,1-bis[(di-4-tolylamino)phenyl]cyclohexane (TAPC), was analyzed. It is found that the luminous efficiency of white PHOLEDs is closely related to the triplet exciton energy level in the hole transporting layer (HTL). White PHOLEDs with a TAPC as HTL, having the highest triplet exciton energy level amongst the three different hole transporting materials, yielded external quantum efficiency of 25.5% at 4.5 V and a high luminous efficiency of 51 cd/A at 4.5 V with CIE color coordinates of (0.34, 0.39) at 10 V. The results reveal that the effective confinement of triplet excitons in white PHOLEDs with a high triplet exciton energy level HTL (TAPC) allows improving the luminous efficiency, as compared to the devices made with NPB and TCTA. Additionally, we demonstrated possibility for the loss of intensity in EL spectra of the white PHOLED devices with NPB and TCTA as HTL compared to that of the device with TAPC as HTL. [ABSTRACT FROM AUTHOR]

Modern systems present complex memory hierarchies and heterogeneity among cores and processors. As a consequence, efficient programming is challenging. An easy-to-understand performance model, offering guidelines and information about the behaviour of a code, may be useful to alleviate these issues. In this paper, we present two extensions of the well-known Berkeley Roofline Model. The first of these extensions, the Dynamic Roofline Model (DyRM), takes into consideration the complexities of multicore and heterogeneous systems, offering a more detailed view of the evolution of the execution of a code. The second, the 3DyRM, also adds information about the latency of memory accesses to better represent the behaviour on systems with complex memory hierarchies. A set of tools to obtain and represent the models has been implemented. These tools obtain the needed data from hardware counters, with low overhead. Different views are displayed by the tool that can be used to extract the main features of the code. Results of studying, with these tools, the NAS Parallel Benchmarks for OpenMP on two different systems are presented. [ABSTRACT FROM AUTHOR]

Electronic structures with the copper iodide (CuI) interlayer in organic electronic devices were measured and its strong electron-withdrawing properties were revealed. In situ ultraviolet and X-ray photoelectron spectroscopy showed the interfacial electronic structures of N,N′ -diphenyl- N,N′ -bis(1-naphthyl)-1,1′-biphenyl-4,4′-diamine (NPB)/CuI/indium–tin-oxide (ITO) and tris-(8-hydroxyquinolinato)aluminum (Alq 3 )/CuI/ITO as a representative hole- and electron-transport material. The large work function of the CuI interlayer induces electron transfer from both molecules and ITO to CuI. As a result, CuI dramatically reduces the hole injection barrier (HIB) from ITO to NPB and Alq 3 layers. Notably, CuI assists molecular ordering of the NPB layer, which would increase the intermolecular interaction, so would enhance the charge transport properties. Simultaneous enhancement in HIB and molecular ordering with the CuI interlayer would improve the device performance. [ABSTRACT FROM AUTHOR]

Nucleoli in mammalian oocytes and zygotes, sometimes referred to as nucleolus precursor bodies (NPBs), are compact and morphologically different from nucleoli in somatic cells. We applied a unique NPB analyzing method “enucleolation” technique to zygotes to remove the NPBs. It has been reported that oocyte NPBs are essential for embryonic development; in their absence, the oocytes complete maturation and can be fertilized, but no nucleoli are formed in the zygotes and embryos, leading to developmental failure. However, we found that when NPBs were removed from zygotes, the zygotes developed successfully to live-born pups. These results indicated that oocyte NPBs are essential for embryonic development, but zygote NPBs are not. In addition, the enucleolated zygotes formed somatic-type nucleoli during early embryonic development, demonstrating that somatic-type nucleoli do not originate from zygote NPBs. We summarize our recent investigation on NPBs, and provide additional comments and findings. [ABSTRACT FROM PUBLISHER]

We fabricated white phosphorescent organic light-emitting diodes (PHOLEDs) with the primary color(Red, Green and Blue) in single emissive layer using NPB, TCTA and TAPC as hole transporting layer (HTL) having different triplet energy level to observe triplet exciton's behavior. White PHOLED with TAPC having higher triplet energy level shows 51cd/A of luminous efficiency, and CIEXY color coordinate of (0.35, 0.40) at 10V. [ABSTRACT FROM AUTHOR]

Determination of hole drift mobility of 4,4′-bis[N-(1-naphthyl)-N-phenyl-amino]-biphenyl (NPB)/ tris(8-hydroxy-quinolinato) aluminium (Alq3) double-layer diodes has been examined from the simulation of impedance spectra. The theoretical basis for the determination of carrier drift mobility rests on a theory for single-injection space-charge limited current. The simulation for NPB/Alq3 double-layer hole-only devices shows that the transit-time effect seen in the impedance spectra is due to hole transit in Alq3 layer of NPB/Alq3 double-layer hole-only devices. The experimentally obtained hole drift mobilities of the NPB/Alq3 double-layer hole-only devices are in good agreement with those of Alq3 in literature, consistent with the simulation results. The results are useful for determination of charge-carrier drift mobility in multilayer organic light-emitting diodes. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Abstract: The hole mobility of tris(8-hydroxy-quinolinato) aluminum (Alq3) thin films and double layer films of a 4,4′-bis[N-(1-naphthyl)-N-phenyl-amino]-biphenyl (NPB) and Alq3, have been determined using impedance spectroscopy (IS) measurements. The theoretical basis of mobility measurement with IS rests on a theory for single-injection space-charge limited current. The NPB thin film operates as an injection layer to reduce the hole injection barrier between an injection electrode and the Alq3 thin film. The hole mobilities of Alq3 thin films measured with IS are identical to those measured by a time-of-flight (TOF) transient photocurrent technique. The hole drift mobility determined using IS measurements in NPB/Alq3 double layer hole-only devices where the thickness of NPB is comparable to that of Alq3 are also identical to the hole drift mobility of Alq3 layer. The origin of the observation is discussed using a device simulation and the results are useful for the determination of charge carrier mobility in multilayer devices. [Copyright &y& Elsevier]

Abstract: The current–voltage (I–V) characteristics of the Al/NPB/p-Si contact shows rectifying behavior with a potential barrier formed at the contact interface. The barrier height and ideality factor values of 0.65eV and 1.33 are measured at the forward bias of the diode. The barrier height of the Al/NPB/p-Si diode at room temperature is larger that (∼0.58eV) of conventional Al/p-Si diode. It reveals the NPB organic film control the carrier transport of the diode at the contact interface. The temperature effect on the I–V measurement is also performed to reveal the junction characteristics. The ideality factor of the Al/NPB/p-Si contact increases with decreasing temperature. And the barrier height decreases with decreasing temperature. The effects are due to the existence of the interface states and the inhomogeneous of the barrier at the junction. [Copyright &y& Elsevier]

The structure of N,N′-diphenyl- N,N′-bis(1-naphthyl)-1,1′-biphenyl-4,4′-diamine (NPB) with two molecules in the asymmetric unit, was solved and refined to a final R factor of 0.0434. The compound crystallized in the triclinic crystal system, space group P − 1, Z = 2, V = 1597.0(3) Å3 with unit cell parameters a = 10.3077(10) Å, b = 11.3545(11) Å, c = 14.4778(14) Å, α = 82.339(2)°, β = 77.657(2)°, and γ = 75.526(2)°. The two molecules in the asymmetric unit differed in the orientation of their triarylamino groups. The biphenyl group in the central structure is coplanar, and the angle between the least-square planes of the two six-carbon rings of the biphenyl moiety is zero degree. The packing of the molecules in the lattice is mainly due to the naphthyl-to-naphthyl π–π interaction with a distance of 3.861 Å. The title compound, C44H32N2, crystallizes in the triclinic space group P − 1. The two molecules in the asymmetric unit differed in the orientation of their triarylamino groups. The biphenyl group in the central structure was nearly coplanar and the packing of the molecules in the lattice was mainly due to the naphthyl-to-naphthyl π–π interaction.[Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Abstract: Two of the commonly-used Organic Light Emitting Diode (OLED) materials tris-(8-hydroxyquinoline) aluminum (Alq3) and N,N′-bis(naphthalen-1-yl)-N,N′-bis(phenyl)benzidine (NPB) are thermally evaporated as thin-films on two kinds of substrates with different hardness. By using nano-indentation techniques, the reduced elastic modulus of each of the coatings is measured. The data are carefully analysed through the standard Oliver and Pharr method, and the recently developed critical indentation depth method which takes the effect of the substrate more into account. [Copyright &y& Elsevier]

The transition from sequential computing to parallel computing represents the next turning point in the way software engineers design and write software. This paradigm shift leads the integration of parallel programming standards for high-end shared-memory machine architectures into desktop programming environments. In this paper we present a performance study of these new systems. We evaluate the performance of an OpenMP shared-memory programming model that is integrated into Microsoft Visual Studio C++ 2005 and Intel C++ compilers on a multicore processor. We benchmarked using the NAS OpenMP high-level applications benchmarks and the EPCC OpenMP low-level benchmarks. We report the basic timings and runtime profiles of each benchmark and analyze the running results. [ABSTRACT FROM AUTHOR]

Abstract: The high temperature limit of hole mobility (μ ∞) in N,N′-diphenyl-N,N′-bis(1-naphthyl)(1,1′-biphenyl)-4,4′diamine (NPB) has been studied by time-of-flight technique. The effect of dopants on μ ∞ was also investigated. It was found that the μ ∞ is independent of the nature of dopants. The common μ ∞ can be applied to estimate the full temperature dependence of zero-field mobility (μ0 ), if μ 0 at one temperature is known. We demonstrate this concept by predicting the room temperature μ 0 of NPB-doped with copper phthalocyanine (CuPc). The mobility prediction of CuPc-doped-NPB was then verified by the classic work of Hoesterey and Letson [D.C. Hoesterey, G.M. Letson, J. Phys. Chem. Solids 24 (1963) 1609]. [Copyright &y& Elsevier]

The methylammonium lead halide solar cell has attracted a great deal of attention due to its lightweight, low cost, and simple fabrication and processing. Despite these advantages, these cells are still far from commercialization because of their lead-based toxicity. Among lead-free perovskites, cesium-titanium (IV) bromide (Cs2TiBr6) is considered one of the best alternatives, but it faces a lack of higher PCE (power conversion efficiency) due to the unavailability of the matched hole and electron transport layers. Therefore, in this study, the ideal hole and electron transport layer parameters for the Cs2TiBr6-based solar cell were determined and discussed based on a simulation through SCAPS-1D software. It was observed that the maximum PCE of 20.4% could be achieved by using the proper hole and electron transport layers with optimized parameters such as energy bandgap, electron affinity, doping density, and thickness. Unfortunately, no hole and electron transport material with the required electronic structure was found. Then, polymer NPB and CeOx were selected as hole and electron transport layers, respectively, based on their closed electronic structure compared to the simulation results, and, hence, the maximum PCE was found as ~17.94% for the proposed CeOx/Cs2TiBr6/NPB solar cell. [ABSTRACT FROM AUTHOR]

Abstract: LaCuOSe:Mg is a wide-gap p-type semiconductor with a high conductivity and a large work function. Potential of LaCuOSe:Mg as a transparent hole-injection electrode of organic light-emitting diodes (OLEDs) was examined by employing N,N′-diphenyl-N,N′-bis (1,1′-biphenyl)-4,4′-diamine (NPB) for a hole transport layer. Photoemission spectroscopy revealed that an oxygen plasma treated surface of LaCuOSe:Mg formed a hole-injection barrier as low as 0.3eV, which is approximately a half of a conventional ITO/NPB interface. Hole-only devices composed of a LaCuOSe:Mg/NPB/Al structure showed a low threshold voltage ∼0.2V and high-density current drivability of 250mAcm−2 at 2V, which is larger by two orders of magnitude than that of ITO/NPB/Al devices. These results demonstrate that LaCuOSe:Mg has great potential as an efficient transparent anode for OLEDs and other organic electronic devices. [Copyright &y& Elsevier]

Abstract: The interfacial electronic structures of N,N′-bis(1-naphthyl)-N,N′-diphenyl-1,1′-biphenyl-4,4′-diamine (NPB)/hexadecafluoro copper phthalocyanine (F16CuPc)/Au and NPB/copper phthalocyanine (CuPc)/Au were investigated by in situ X-ray and ultraviolet photoelectron spectroscopy to study the hole-injection barrier depending on the ionization energy of hole-injection layer materials. Although the measured ionization energy of F16CuPc (6.30eV) was much higher than that of CuPc (5.15eV), the difference in the barrier heights of the two different films was relatively marginal (0.27eV) due to the formation of interface dipole caused by the charge redistribution. We confirmed that the interface dipole of the buffer layer (CuPc and F16CuPc) pushed down the core levels as well as the valence levels of the top organic layer (NPB) in the NPB/F16CuPc/Au and NPB/CuPc/Au heterojunction. [Copyright &y& Elsevier]

Abstract: Recently, triphenylamine (TPA), 4,4′-bis(phenyl-m-tolylamino)biphenyl (TPD), 4,4′-bis(1-naphthylphenylamino)biphenyl (NPB) and their derivatives are widely used in the organic light-emitting diode (OLED) devices as a hole-transporting material (HTM) layer. We have optimized twenty different structures of HTM materials by using density functional theory (DFT), B3LYP/6-31G method. All these different structures contain mono-amine and diamine TPA derivatives. The energies of highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) along with molecular orbitals for these HTMs are also determined. We have found that the central amine nitrogen atom and the phenyl ring, which is next to the central amine nitrogen atom, show significant contribution to the HOMO and LUMO, respectively. The sum of the calculated bond angles (α+β+γ) of the central amine nitrogen atom has been applied to describe the bonding and the energy difference for HOMO and LUMO in these TPA derivatives. Electronic structure calculations have been performed for these TPA derivatives. Again, the LCAO-MO patterns of HOMO and LUMO levels of these derivatives are used to investigate their electron density. A series of electron-transporting steps are predicted for these compounds employing these calculated results. [Copyright &y& Elsevier]