We analyze photoluminescence (PL) and electroluminescence (EL) using a hyperspectral imager that records spectrally resolved luminescence images of solar cell absorbers. The system is calibrated to yield the luminescence flux in absolute values. This system enables to quantitatively image physical parameters such as the photovoltage with an uncertainty of less than 30mV. The wide field illumination, low power excitation and fast acquisition brings new insights compared to classical setups such as confocal microscope. Several types of absorbers have been analyzed. For instance, we can investigate spatial fluctuations of the Quasi Fermi Levels splitting in CIGS polycristalline absorbers and link those fluctuations to transport properties. The method is general to the point that third generation PV cells absorbers can also be evaluated. We illustrate the great potential of our setup by imaging carrier temperature in Hot Carriers Solar cells absorbers and quasi Fermi levels splitting in Intermediate Band Solar cells.

The effect of strain rate on hydrogen embrittlement of low alloy 4340 steel was studied using double-notched tensile samples electrochemically charged in-situ with hydrogen in 1N H2SO4 + 5 mg/l As2O3 solution. The mechanical response of samples with prior austenitic grain sizes of 10 and 40 μm and martensitic hardness of 43-52 HRC were examined after hydrogen charging times of 0-20 min. Increasing the strain rate for hydrogen charged samples resulted in decreased failure strains and increased evidence of brittle fracture. Brittle fracture surfaces for the harder samples showed primarily intergranular fracture while softer samples exhibited predominantly quasi-cleavage.

Recently, Fickenscher et al. [1] have shown that, in a core-multi-shell structure where a GaAs quantum well is embedded into an AlGaAs shell wrapped around a [111] oriented GaAs nanowire, the electron and hole ground states are strongly confined to the corners of the hexagonally symmetric quantum well. Thus this confinement defines quantum wires which run along the length of the nanowires along its corners. Here we review single nanowire photoluminescence measurements which show the significant confinement energy of the excitons. For well widths larger than 5 nm, optical transitions between electron and hole excited states can be seen in excitation spectra, while for widths less than 5 nm only the ground state optical transitions are observed. For well widths smaller than 5 nm, high resolution spatially resolved photoluminescence measurements show directly the appearance of localized states. Single nanowire spectra from the 4 nm QWT sample display ultranarrow emission lines on the high energy side of the luminescence band. Spatially-resolved PL images show that these quantum dots are localized randomly along the length of the wire.

In this paper, high temperature (>1400°C) thermal oxidation has been applied, for the first time, to 4H-SiC PiN diodes with thick (110 μm) drift regions, for the purpose of increasing the carrier lifetime in the semiconductor. PiN diodes were fabricated using 4H-SiC material that had undergone thermal oxidation performed at 1400°C, 1500°C and 1600°C, then were electrically characterized. Forward current-voltage (I-V) measurements showed that thermally oxidized PiN diodes exhibited considerably improved electrical characteristics, with devices oxidized at 1500°C having a forward voltage drop (V F ) of 4.15 V and a differential on-resistance (R on,diff ) of 8.9 mΩ-cm2 at 100 A/cm2 and 25°C. Compared to typical control sample PiN diode characteristics, this equated to an improvement of 8% and 23% for V F and R on,diff , respectively. From analysis of the reverse recovery characteristics, the carrier lifetime of the PiN diodes oxidized at 1500°C was found to be 1.05 μs, which was an improvement of around 30% compared to the control sample PiN diodes.

We show evidence that the competition between the antiferromagnetic metallic phase and the charge- and orbital-ordered insulating phase at the reentrant phase boundary of a layered manganite, LaSr2Mn2O7, can be manipulated using ultrafast optical excitation. The time-dependent evolution of the Jahn-Teller superlattice reflection, the indicator of the formation of charge and orbital order, was measured at different laser fluences. The laser-induced change in the Jahn-Teller reflection intensity shows a reversal of sign between earlier (∼10 ns) and later (∼150 ns) times during the relaxation of the sample. This is consistent with a physics picture whereby the laser excitation modulates the local competition between the metallic and the insulating phases.

A novel method for introducing quaternary ammonium-bearing side chains has been developed and applied to a polybenzimidazole backbone to generate new anionic-exchange polymers, TMHA-m-FPBI where m = the degree of substitution of available sites (values ranging from 74 to 100%). These polymers have been shown to exhibit hydroxide ion conductivities up to 34 mS cm-1 in hydrated membranes at ambient temperature and 13 mS cm-1 at 60 °C, RH = 95%. Immersion of these polymers in 2 M KOH at 60 °C has shown they remain stable with no sign of chemical structure degradation to a period of at least 15 days.

A chemical decomposition and related phase transformation have been observed in 2.2 GeV 197Au irradiated SnO2 nanopowder. X-ray diffraction (XRD), Raman spectroscopy, and transmission electron microscopy (TEM) were used to characterize the transformation from tetragonal SnO2 (P4 2 /mnm) into tetragonal SnO (P4/nmm). Rietveld refinement of the XRD data determined the structures and proportion of these phases up to a fluence of 2.4×1013 ions/cm2. The initially intense diffraction maxima corresponding to SnO2 gradually decrease in intensity with an increase in fluence. At a fluence of approximately 3.9×1012 ions/cm2, diffraction maxima corresponding to SnO become clearly evident and increase in intensity as fluence increases. Both Raman and TEM analyses confirm the transformation from tetragonal SnO2 to SnO. The XRD refinement results are consistent with a multiple-impact model of transformation, confirmed by TEM as no single tracks were observed. Previous swift heavy ion irradiations of SnO2 have led only to changes in grain size, degrees of crystallinity, and the formation of “holes”. The inconsistency in results is discussed in depth. The proposed mechanism for the currently observed transformation is the interrelation of defect accumulation and thermal-spike mechanisms. The formation of SnO, apparent O loss from the transformation regions, and associated Sn reduction are discussed in terms of thermodynamic, kinetic, and thermal-spike model considerations.

Magnetic nanoparticles have drawn much attention due to their potential in magnetic recording as well as many biological and medical applications such as magnetic separation, hyperthermia treatment, magnetic resonance contrast enhancement and drug delivery. The magnetic fields generated by these nanoparticles can be used for diagnostics in Magnetic Resonance Imaging (MRI) etc. Manganese doped tin dioxide (SnO2:Mn) possess interesting physical and chemical properties. The physical and chemical properties of the particles themselves like the size, shape, crystallinity and composition, will control the magnetic properties and response of the particles to magnetic fields. Our work is rooted to control the properties of the particles as well as tailor their magnetic properties for specific applications. In this study, SnO2: Mn films with different Mn doping concentrations (0-3 mol%) were deposited on the glass substrates by sol-gel dip coating technique. XRD patterns shows tetragonal structure for all the SnO2:Mn films and crystallite size decreased as Mn doping concentration increased from 0 - 3 mol%. The magnetic property shows that pure SnO2 film is diamagnetic and 1- 3 mol% SnO2:Mn films posses room temperature ferromagnetism. The optical properties of the films revealed that transmittance of the films decreased with increase in Mn doping concentration. The optical energy band gap values (3.55 eV-3.71 eV) increased with the increase in Mn doping concentrations. Such SnO2:Mn films with structural, optical and magnetic properties can be used as dilute magnetic semiconductors.

In this paper, we report on a new micropillar sensor array that is stretchable, flexible, and has high sensitivity in the tactile sensing regime (<10 kPa). The sensor array is capable of detecting deformation modes other than pressure such as shear and planar extension. The capacitance-type sensor is fabricated using soft nanolithography whereby the micropillars are individually electroded using a sputtering technique. Buckled gold electrodes are used in this study to enable large sensor stretches up to 55%. Three micropillar aspect ratios were considered in this work (1:1, 1:2, 1:3). Here we present the highest reported sensitivity [0.8 kPa-1] of a capacitance type flexible/stretchable sensor. Our results show that this sensor is also able to detect very low pressures down to 5.4 Pa, which is in the range of ultra-low detection pressures recently reported. Finally, the microstructured sensor array naturally lends itself to the development of pixel-type pressure sensors. We present preliminary results for a 25 pixel array.

More than 50% of total input energy is wasted as heat in various industrial processes. If we could harness a small fraction of the waste heat while satisfying the economic demands of cost versus performance, then thermoelectric (TE) power generation could bring substantial positive impacts. To meet these demands single-crystal semiconductor nanowire networks have been investigated as a method to achieve advanced TE devices because of their predicted large reduction in thermal conductivity and increase in power factor.

To further our goal of developing practical and economical TE devices, we designed and developed a material platform that combined a semiconductor nanowire network and a semiconductor thin film integrated directly on a mechanically flexible metallic substrate. We assessed the potential of this platform by using indium phosphide (InP) nanowire networks and a doped poly-silicon (poly-Si) thin film combined on copper sheets. InP nanowires were grown by metal organic chemical vapor deposition (MOCVD). In the nanowire network, InP nanowires were grown in three-dimensional networks in which electrical charges and heat travel under the influence of their characteristic scattering mechanisms over a distance much longer than the mean length of the constituent nanowires. Subsequently, plasma-assisted CVD was utilized to form a poly-Si thin film to prevent electrical shorting when an ohmic copper top contact was made. An additional facet to this design is the utilization of multiple materials to address the various temperature ranges at which each material is most efficient at heat-to-energy conversion. The utilization of multiple materials could enable the enhancement of total power generation for a given temperature gradient. We investigated the use of poly-Si thin films combined with InP nanowires to enhance TE properties. TE power production and challenges of a large area nanowire device on a flexible metallic substrate were presented.

Colloidal dispersion of nanocarbon (NC) materials in dilute solutions or pastes is prerequisite for applications of NC-based electrodes from flexible electronics and flexible conducting fibers to electrochemical devices. Here, we show a straightforward method for fabricating NC suspensions with >10% weight concentrations in absence of organic dispersants. The method involves introducing supramolecular quadruple hydrogen bonding motifs into the NC materials without sacrificing the electrical conductivity.

A cross-linked copolymer was designed and synthesized bythe imidation of poly(oxyethylene)-diamine and 4,4’-oxydiphthalic anhydride, and followed by a late-stage curing to generate the cross-linked gels. The copolymers consisting of crosslinking sites and multiple functionalities such aspoly(oxyethylene)-segments, amido-acids, imides, and amine termini, characterized by Fourier Transform Infrared Spectroscopy. After the self-curing at 80 °C, the gel-like material enabled to absorb liquid form of electrolytesin the medium of propylene carbonate(PC), dimethylformamide(DMF),and N-methyl-2-pyrrolidone(NMP).By using a field emission scanning electronic microscope, we observed a 3D interconnected nanochannel microstructure, within which, the liquid electrolytes were absorbed. When the novel polymer gel electrolyte (PGE) was fabricated into a dye-sensitized solar cell (DSSC), an extremely high photovoltaic performance was demonstrated. The PGE, absorbed 76.7 wt% of the liquid electrolyte (soaking in the PC solution) based on the polymer’s weight gave rise to a power conversion efficiency of 8.31%, superior to that (7.89%) of the DSSC with liquid electrolytes. It was further demonstrated that the cell had a long-term stabilityduring the test of 1000hat-rest at room temperature or only slightly decreasing in efficiency of 5%.This is the first time demonstration for a PGE exhibiting a higher performance than its liquid counterpart cell. The observation is ascribed to the suppression of the back electron transfer through the unique morphology of the polymer microstructures.

Results are presented of a study of {113}-defect formation in Si nanowires withdiameters ranging from 50 to 500 nm. The Si nanowires, used for the processingof tunnel-FET's, are etched into a moderately doped epitaxial Si layeron a heavily doped n-type Si substrate. {113}- defects are created in situ by 2MeV e-irradiation at temperatures between room temperature and 375 °Cin an ultra high voltage electron microscope. The observations are discussed inthe frame of intrinsic point defect out-diffusion and interaction with dopantatoms.

The formation of native point defects in layered multicomponent InAMO4 oxides with A 3+=Al or Ga, and M 2+=Ca, Mg, or Zn, is investigated using first-principles density functional calculations. We calculated the formation energy of acceptor (cation vacancies, acceptor antisites) and donor (oxygen vacancy, donor antisites) defects within the structurally and chemically distinct layers of InAMO4 oxides. We find that the antisite donor defect, in particular, the A atom substituted on the M atom site (A M ) in InAMO4 oxides, have lower formation energies, hence, higher concentrations, as compared to those of the oxygen vacancy which is know to be the major donor defect in binary constituent oxides. The major acceptor (electron “killer”) defects are cation vacancies except for InAlCaO4 where the antisite CaAl is the most abundant acceptor defect. The results of the defect formation analysis help explain the changes in the observed carrier concentrations as a function of chemical composition in InAMO4, and also why the InAlZnO4 samples are unstable under a wide range of growing conditions.

Magnetic nanoparticle-vesicle aggregates (MNPVs), a controlled release nanostructure, have been enhanced with the inclusion of a novel galactose terminated lipid for cell targeting. Quartz crystal microgravimetry with dissipation (QCM-D) demonstrated that the galactose headgroup was available to bind Erythrina Crista-galli lectin (ECL) when the lipid was incorporated into a lipid bilayer. Similarly, UV-visible spectrophotometry indicated that ECL recognized the galactose headgroup in vesicles, leading to vesicle adhesion and aggregation. Finally, confocal fluorescence microscopy was used to assess the galactose-mediated interaction of both vesicles and MNPVs with HepG2 human hepatocellular carcinoma cells expressing the asialoglycoprotein (ASGPR) galactose receptor.

This article reports on a new composite gypsum binder (CGB) with nanostructured silica-based admixture (NSS). NSS is obtained by a wet ultrafine milling of quartz sand resulting in the formation of an inorganic polydisperse binding system, which has a high concentration of active nanoscale phase (about 10%). Developed CGB contains hemihydrate gypsum and nano-component based on quartz sand. It is observed that the addition of 15–20 % of NSS improves the rheological properties of gypsum systems through the formation of solvate shells hindering the access of water to gypsum particles; this process also retards the setting of binder.

The experimental program used infrared IR spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM) to reveal the contribution of NSS. The porosity of CGB is analyzed by the kinetics of water adsorption and BET. The XRD and IR investigations determined the formation of a new sulfosilicate phase, hydroxyellestadite during the hydration of CGB. With the addition of NSS an overall reduction in pore volume, as well as the shifts in macro-, meso- and nano- porosity values are observed.

Analysis of CGB microstructure reveals that in the presence of the NSS the size and morphology of crystals are changed contributing to the formation of dense fine-grained structure. Experimental studies have demonstrated that the composite gypsum binders with NSS are characterized by reduced water absorption and increased density, as well as improved mechanical performance especially, higher compressive strength.

It has been found that the hybrid materials are a compatible matrix for numerous organic compounds, such as organic dyes, laser dyes, and compounds that exhibit photo-chromic behavior and many more The epoxy-silica system seems to be an excellent matrix for organic dyes and a hybrid material suitable for to be used as coating on glass substrates with good adhesion properties. This work presents a systematic study of the effects of the different amount of using rhodamine 6G as dye on the structure and properties of epoxy–silica hybrids coatings synthesized by the sol-gel process. We have taken advantage on the high solubility of organic dyes in a hybrid organic–inorganic epoxy resin–silica (epoxy–SiO2) matrix to obtain homogeneous, hard and high optical quality red color films on glass substrates. The effects of the content of rhodamine 6 G on the optical and thermal properties of epoxy-silica hybrid films were also examined. Epoxy resin DER 332 cured with an amine (4,4 diamino diphenyl methane) was used as organic component and tetraethyl orthosilicate (TEOS) was used as precursor of the inorganic component. The results showed that at a concentration of rhodamine 0.05% coatings retain adhesion properties similar to coatings without colorant and the coatings are uniform and free of defects. These coatings have the potential to be used as filters and ornamental coatings.

Chondroitin sulfate (CS) is one of the major glycosaminoglycans (GAGs) present in the connective tissue extracellular matrix (ECM) and is responsible for the regulation of cellular activities as well as providing mechanical support for the surrounding tissue. Due to presence of CS in the natural tissues including cartilage, hydrogels of CS and other GAGs have been widely used in cartilage regeneration. Due to their polyelectrolyte nature, GAG-based hydrogels are brittle and require modifications to overcome the weak mechanical properties. In this work, we showed copolymerization of methacrylated chondroitin sulfate with oligo(ethylene glycol)s improved the crosslink density of the gels from 2 to 20 times depending on the methacrylation degree of CS and length of the crosslinking monomer. Copolymerization of CS with oligo(ethylene glycol) acrylates is a method to design hydrogels with tunable swelling and mechanical properties.

The improvement of concrete workability can provide a considerable reduction of production expenses and also leads to significant improvement of construction quality. This paper reports on the development of self-consolidating concrete (SCC) based on local materials, such as metakaolin (MK) and aggregate fines. The use of metakaolin in SCC is found to be very promising, due to its ability to increase the flowability and segregation resistance of concrete mixtures. Furthermore, due to pozzolanic properties, the application of MK provides an improvement of concrete microstructure, strength and durability. The proposed SCC design includes the optimization of aggregates and combined aggregate-binder powders to target 0.45- and 0.3- power particle size distributions, respectively.