Tandem organic solar cells with two stacked cells were fabricated using semiconducting polymers and fullerene derivatives. A thin intermediate multilayer of calcium, silver, and molybdenum oxide connects the front and the back cells. Bulk heterojunction (BHJ) films of the low band gap (BG) polymer, poly[N-9″-heptadecanyl-2,7-carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)] (PCDTBT), and [6,6]-phenyl C71-butyric acid methyl ester (PC71BM) are used for the front cell. As for the back cell of the tandem structure, the same PCDTBT:PC71BM BHJ (T1) or the high BG polymer poly(3-hexylthiophene) (P3HT) blended with [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) BHJ (T2) are used. The critical role of interlayer properties on the photovoltaic performance of devices are investigated. The observed open-circuit potential for the tandem cell approaches the sum of the potentials of the two respective subcells, demonstrating the potential for increasing the voltage of the solar cell using the tandem structure even with same or lower band gap polymer in the front.

The effect of off-stoichiometry on the microstructures and tensile properties of Ni3Al–Ni3V pseudo-binary alloys was investigated by a scanning electron microscope, a transmission electron microscope, Vickers hardness test, and high-temperature tensile test. As the alloy deviates from a just-stoichiometric composition toward Ni-rich one, the microstructures constituted by two ordered phases, Ni3Al and Ni3V changed to those constituted by two ordered phases, Ni3Al and Ni3V, and one disordered phase, Ni solid solution. Also, the deviation from the stoichiometric composition resulted in a decrease in flow strength as well as Vickers hardness and conversely increase in tensile elongation. Higher tensile elongation in the off-stoichiometric alloys was induced by the transition from intergranular fracturing to transgranular fracturing. The trade-off relation in the yield strength (or hardness) versus tensile elongation curve, which was drawn plotting the data obtained from the alloys with different off-stoichiometric compositions, was most excellent at 600 °C but rapidly became worse at high temperatures beyond 600 °C. It was demonstrated that the deviation to the off-stoichiometric composition in the two-phase Ni3Al–Ni3V pseudo-binary alloy system was a useful alloying parameter to improve the balance of the flow strength and tensile ductility.

Under electrochemical cycling, stress intensification and relaxation within small volumes at the lithium/solid-state electrolyte (SSE) interface are thought to be critical factors contributing to mechanical failure of the SSE and subsequent short-circuiting of the device. Nanoindentation has been used to examine the diffusion-limited pressure lithium can support in the absence of active dislocation sources at high homologous temperatures. Based on the underlying physics of this deformation mechanism, a simple perturbation model coupling local current density, elastic stress, and diffusional creep relaxation is introduced. Combining this analysis with the indentation results, it is possible to describe a defect length scale which is too large for effective diffusional creep relaxation, but too small for efficient dislocation multiplication. In this instance, the properties of the SSE may become critical, and relevant indentation results of the SSE are described. The final outcome of the proposed analysis is a newly developed deformation mechanism map.

A fracture analysis is developed for crack initiation sequences occurring during sharp indentation of brittle materials. Such indentations, generated by pyramidal or conical loading, generate elastic and plastic deformation. The analysis uses a nonlinear elements-in-series model to describe indentation load–displacement responses, onto which lateral, radial, cone, and median crack initiation points are located. The crack initiation points are determined by extension and application of a contact stress-field model coupled to the indentation load, originally developed by Yoffe, in combination with crack nuclei coupled to the indentation displacement to arrive at an explicit fracture model. Parameters in the analysis are adapted directly from experimental fracture and deformation measurements, and the analysis outputs are directly comparable to experimental observations. After adaptation, crack initiation loads and sequences during indentation loading and unloading of glasses and crystals are predicted by the model from material modulus, hardness, and toughness values to within about 25% of peak contact load. This work is dedicated to George M. Pharr IV on the occasion of his 65th birthday in recognition of his contributions to indentation mechanics.

Chitosan is an important cationic biopolymer widely used in various biomedical applications such as wound care, drug delivery, biomaterial scaffolds, and tissue engineering. In this work, hollow silica sphere (HSS) nanoparticles with an average size of 400–450 nm (via TEM) were synthesized by sol–gel process and were epoxidized using epichlorohydrin. Then, chitosan was chemically bound to the epoxidized HSS to form a bionanocomposite, HSS-epoxy-CHI-X where X represents the percentage of chitosan in the sample. BET analysis showed that pure HSS has a specific surface area (Ass) of around 4.8 m2/g and adsorption average pore diameter of 10.18 nm. Bionanocomposites were characterized by FT-IR spectroscopy to confirm the bonding of chitosan on HSS nanoparticles. X-ray diffraction studies demonstrated that the amorphous character of the materials improved with the HSS content. Thermogravimetric analysis illustrated that at low temperatures, the thermal stability of bionanocomposites was higher than that of the sample with no chitosan in it. Scanning electron microscopic analysis results confirmed the homogenous distribution of HSS in the bionanocomposites. Considering the biological activity of chitosan and absorption characteristics of HSS, newly developed HSS-epoxy-CHI-X bionanocomposites were tested for wound healing by in vitro scratch assay using NIH 3T3 fibroblast cells. Among the bionanocomposites analyzed, HSS-epoxy-CHI-60 exhibited better performance where about 90% wound closure was observed for this sample after 21 h of exposure.

The phase evolution of reactive radio frequency (RF) magnetron sputtered Cr0.28Zr0.10O0.61 coatings has been studied by in situ synchrotron X-ray diffraction during annealing under air atmosphere and vacuum. The annealing in vacuum shows t-ZrO2 formation starting at ∼750–800 °C, followed by decomposition of the α-Cr2O3 structure in conjunction with bcc-Cr formation, starting at ∼950 °C. The resulting coating after annealing to 1140 °C is a mixture of t-ZrO2, m-ZrO2, and bcc-Cr. The air-annealed sample shows t-ZrO2 formation starting at ∼750 °C. The resulting coating after annealing to 975 °C is a mixture of t-ZrO2 and α-Cr2O3 (with dissolved Zr). The microstructure coarsened slightly during annealing, but the mechanical properties are maintained, with no detectable bcc-Cr formation. A larger t-ZrO2 fraction compared with α-Cr2O3 is observed in the vacuum-annealed coating compared with the air-annealed coating at 975 °C. The results indicate that the studied pseudo-binary oxide is more stable in air atmosphere than in vacuum.

Increasing the number of quantum bits while preserving precise control of their quantum electronic properties is a significant challenge in materials design for the development of semiconductor quantum computing devices. Semiconductor heterostructures can host multiple quantum dots that are electrostatically defined by voltages applied to an array of metallic nanoelectrodes. The structural distortion of multiple-quantum-dot devices due to elastic stress associated with the electrodes has been difficult to predict because of the large micrometer-scale overall sizes of the devices, the complex spatial arrangement of the electrodes, and the sensitive dependence of the magnitude and spatial variation of the stress on processing conditions. Synchrotron X-ray nanobeam Bragg diffraction studies of a GaAs/AlGaAs heterostructure reveal the magnitude and nanoscale variation of these distortions. Investigations of individual linear electrodes reveal lattice tilts consistent with a 28-MPa compressive residual stress in the electrodes. The angular magnitude of the tilts varies by up to 20% over distances of less than 200 nm along the length of the electrodes, consistent with heterogeneity in the metal residual stress. A similar variation of the crystal tilt is observed in multiple-quantum-dot devices, due to a combination of the variation of the stress and the complex electrode arrangement. The heterogeneity in particular can lead to significant challenges in the scaling of multiple-quantum-dot devices due to differences between the charging energies of dots and uncertainty in the potential energy landscape. Alternatively, if incorporated in design, stress presents a new degree of freedom in device fabrication.

Superparamagnetic iron oxide nanoparticles are well known for biomedical applications. The particle size, morphology, surface area, and functionalization are the key parameters that affect their bioactivity properties. Inline to this, the superparamagnetic Fe3O4 nanoparticles were prepared via chemical coprecipitation method with an average particle size of 6 ± 3 nm. The particles were surface-functionalized with chitosan and in-house prepared reduced graphene oxide (rGO) to obtain chitosan-coated Fe3O4 nanoparticles (C-Fe3O4) and rGO-Fe3O4 nanocomposites (G-Fe3O4), respectively. Upon functionalization, the physicochemical properties of the materials were characterized thoroughly using X-ray diffraction, transmission electron microscopy, vibrating sample magnetometer, Raman Spectroscopy, and thermal gravimetric analysis. Furthermore, they have subjected to cytotoxicity assay, agar two-fold broth dilution test, and disc diffusion assay experiments for the determination of cytotoxicity and antibacterial activities. The effect of surface functionalization on their bioactivity was investigated thoroughly. The surface functionalization with chitosan and rGO has enhanced the bioactivity of the Fe3O4 nanoparticles.

A series of ${\left\hbox[ {{{\left\hbox( {{\rm{SnSe}}} \right\hbox)}_{1 \hbox+ \delta }}} \right\hbox]_m}{\left\hbox[ {{\rm{TiS}}{{\rm{e}}_2}} \right\hbox]_2}$ heterostructure thin films built up from repeating units of m bilayers of SnSe and two layers of TiSe2 were synthesized from designed precursors. The electronic structure of the films was investigated using X-ray photoelectron spectroscopy for samples with m = 1, 2, 3, and 7 and compared to binary samples of TiSe2 and SnSe. The observed binding energies of core levels and valence bands of the heterostructures are largely independent of m. For the SnSe layers, we can observe a rigid band shift in the heterostructures compared to the binary, which can be explained by electron transfer from SnSe to TiSe2. The electronic structure of the TiSe2 layers shows a more complicated behavior, as a small shift can be observed in the valence band and Se3d spectra, but the Ti2p core level remains at a constant energy. Complementary UV photoemission spectroscopy measurements confirm a charge transfer mechanism where the SnSe layers donate electrons into empty Ti3d states at the Fermi energy.

Partial shading of Cu(In,Ga)(Se,S)2 (CIGS) photovoltaic (PV) modules is getting more attention, as is witnessed by the increase in publications on this topic in recent years. This review will give an overview of shading tests executed on CIGS modules and focuses on the more fundamental aspects that are often studied on cells. Generally, CIGS modules display very attractive performance under predictable row-to-row shading. However, potential damage could occur under nonoptimal shading orientations: module output after shading tests could reduce due to the formation of local shunts, often called wormlike defects. The influence of many factors on the formation of these defects, including the internal currents and voltages and the shape and intensity of the shade, will be discussed. This review allows an increased insight in the degradation mechanisms caused by partial shading, which would ultimately lead to the introduction of more shade-tolerant CIGS PV products in the future.

Energy density and safety are the main factors that govern the development of the rechargeable battery technology. Currently, batteries beyond typical Li-ion batteries such as those based on solid-state electrolytes (SSEs) or other active elements (e.g., Na or Mg) are being examined as alternatives. For example, SSEs that would enable stable and reliable operation of all-solid-state Li-, Na-, and Mg-based batteries, with preferably improved capacity, are considered to be one of the most desired inventions. Lightweight complex metal hydrides are a family of solid compounds that were recently discovered to have extraordinary ionic conductivities and, in some cases, electrochemical properties that enabled battery reversibility. Consequently, they have become one of the promising electrolyte materials for future development of electrochemical storage devices. In this work, we present an overview of a wide range of lightweight hydride-based materials that could be used as electrolytes and/or anodes for mono-/divalent batteries and have a pivotal role in the implementation of new technological solutions in the field of electrochemistry.

The authors summarize the results of selective-area growth of vertical MnAs/InAs heterojunction nanowire (NW) arrays and present a preliminary characterization of the transport properties of a single MnAs/InAs heterojunction NW and a single InAs host NW for MnAs inclusions. During the endotaxy of MnAs after the selective-area growth of host InAs nanowires (NWs) on partially SiO2-masked GaAs(111)B substrates, hexagonal NiAs-type MnAs nanoclusters (NCs), which exhibit spontaneous magnetization at room temperature, are formed with the 〈0001〉 direction oriented parallel to the 〈111〉B direction of the zinc-blende-type InAs host NWs. For InAs host NWs, a large positive ordinary magnetoresistance (MR) effect up to 165% is observed at temperatures between 7 and 280 K. In addition, magnetotransport measurements reveal universal conductance fluctuations and a weak Anderson localization at temperatures up to 20 K due to a charge-accumulation layer formed at the surface. Single MnAs/InAs heterojunction NWs, however, exhibit only a negative MR effect, which is independent of temperature T < 10 K and linearly decreases up to −10% at 10 T with increasing magnetic field. These results reveal the tremendous influence of ferromagnetic NCs on the transport behavior inside the InAs host NWs.

Microstructural analysis and bulk dielectric property analysis (real and imaginary permittivity at 95 GHz) were performed at temperatures ranging from 25 to 550 °C for ceramic composites comprising a hot-pressed aluminum nitride matrix (containing yttria and trace carbon as sintering additives) with molybdenum powder as a millimeter-wave radiation-absorbing additive. Loading percentages in the range of 0.25 vol% to 4.0 vol% Mo were characterized. For the temperature regime evaluated, the temperature-related changes in real and imaginary components of permittivity were found to be relatively modest compared with those driven by Mo loading. Energy-dispersive X-ray spectroscopic analysis of Mo grains and surrounding regions showed the presence of a mixed-phase layer, containing Mo2C, at the AlN–Mo interface. The Mo2C-containing mixed-phase layer, typically a few micrometers thick, surrounded the Mo grains. Further characterization of this mixed-phase layer is required to determine its contribution to the dielectric properties of the composite.