Recently, metal-halide perovskites have demonstrated an extraordinarily rapid advance in single junction cell efficiency to over 20%, while still offering potentially low costs. Since the bandgap is larger than the ideal single-junction value, perovskite-based tandem cells can theoretically offer even higher efficiencies. Instead, however, the record tandem cell performance in experiments to date has come in slightly below that of record single junctions, although slightly higher than the same single junctions. In this work, we consider both how this disconnect can be explained quantitatively, and then devise experimentally feasible, variance-aware approaches to address them. The first stage of our approach is based on reconfiguring dielectric front coatings to help reduce net reflected power and balance junction currents by reshaping the reflection peaks. This method could be applied to post-fabrication stage of perovskite/c-Si tandem cells, and also applicable to cell and module level structures. In the second stage of our approach, we can almost entirely eliminate Fresnel reflection by applying a conformal periodic light trapping structure. In the best case, a short circuit current (Jsc) of 18.0 mA/cm2 was achieved, after accounting for 4.8 mA/cm2 of parasitic loss and 1.6 mA/cm2 reflection loss. Further improvements may require a change in the baseline materials used in perovskite cells.

The Supercontainer is the reference concept for the post-conditioning of vitrified high-level radioactive waste and spent fuel in Belgium. It consists of a prefabricated concrete buffer that completely surrounds a carbon steel overpack. In this highly alkaline environment (pH ∼ 13.6) and under normal conditions (i.e. without the ingress of aggressive species), the carbon steel overpack will be protected by a passive oxide film, which is believed to result in very low uniform corrosion rates.

This paper gives an overview of the status of the uniform corrosion, pitting corrosion and stress corrosion cracking behaviour of carbon steel expected during the waste disposal period.

We demonstrated the fabrication of 10 emitters InGaN laser diode array of themaximum output power of 9 W at 420 nm. The device as a whole has thedifferential efficiency of above 1 W/A. The maximum output power is limited to 9W (pulse operation) by catastrophic mirror damage or to around 5 W in CWoperation by thermal roll-over. Larger arrays with stripes width of around 15µm and numbers of emitters up to 20 should enable reaching 20 W, whichis suitable for light engine of desktop projectors and a building block ofcinema theater projectors.

A number of thin silicon films are prepared through ultra-high-vacuum evaporation on optical quality fused quartz substrates with different growth temperatures. Through an analysis of grazing incidence X-ray diffraction results, a phase transition, from amorphous-to-crystalline, is found corresponding to increases in the growth temperature. The corresponding Raman spectra are also observed to change their form as the films go through this phase transition. Using a Raman peak decomposition process, this phase transition is then quantitatively characterized through the determination of the amount of intermediate-range order and the crystalline volume fraction for the various growth temperatures considered in this analysis. The possible device consequences of these results are then commented upon.

We present a new concept applicable to the epitaxial growth of dislocation-free semiconductor structures on a mismatched substrate with a thickness far exceeding the conventional critical thickness for plastic strain relaxation. This innovative concept is based on the out-of-equilibrium growth of compositionally graded alloys on deeply patterned substrates. We obtain space-filling arrays of individual crystals several micrometers wide in which the mechanism of strain relaxation is fundamentally changed from plastic to elastic. The complete absence of dislocations at and near the heterointerface may pave the way to realize CMOS integrated SiGe X-ray detectors.

We report a simple approach to fabricate high performance energy storage devices based on aqueous inorganic ink comprised of hexagonal MnO2 nanosheets. The MnO2 ink exhibits long term stability. Continuous thin films can be formed on various substrates without using any binder. To obtain a flexible electrode for capacitive energy storage, we printed the MnO2 ink on commercially available A4 paper pre-treated by multi-walled carbon nanotubes. The electrode exhibited a maximum specific capacitance of 90.8 mF/cm2. The electrode could maintain 98.7% capacitance retention for 1,000 cycles at 10 mV/s. The MnO2 ink could be a potential candidate for large-scale production of flexible and printable electronic devices for energy storage and conversion.

Defect formation in the samples of graphene, graphene oxide and silicon irradiated with Ar cluster and highly-charged ion irradiations were studied. Ar cluster ions, with acceleration energy E = 30 kV (Exogenesis nAccel00, Boston, USA) and total Ar cluster ion fluences ranged from 1x109 cm-2 to 1x1013 cm-2 were directed toward various surfaces. Highly-charged ions (HCI) bombardment on surfaces with highly charged Xeq+ (q = 22) was employed at Eurasian National University, Kazakhstan, using a DC-60 cyclotron accelerator. Multi-layer graphene oxide, single-layer graphene- (SLG), few-layer of graphene (FLG) and polished Si are used for irradiation experiments. The study of irradiated samples was conducted by Raman spectroscopy, atomic force microscopy (AFM). Uniformly distributed defects and craters were observed on the surfaces of graphene, graphene oxide and silicon irradiated with cluster and HCI beams in our experiments. Ab-initio density-functional theory (DFT) was used to study point defects and molecular-dynamics (MD) simulations were used for studying formation of craters due to gas cluster ion impacts in graphene. The results of simulations were compared with experimental craters and surface shape.

We report in this study the dissociation conditions for the carbon dioxide hydrate in the presence of additive materials. We measured the hydrate-water-vapor (H-Lw-V) three-phase equilibrium data using the isochoric method. Examples of these phase equilibrium data for the additive materials of 1,3,5-trioxane, 2,5-dihydrofuran, 1,3-dioxolane, and 3,4-dihydro-2H-pyran are presented. The experimental pressure range is from 1.6 to 3.3 MPa, and the concentration of each additive is at 10 wt%. The experimental results indicate that cyclic ethers of 1,3,5-trioxane, 2,5-dihydrofuran, and 1,3-dioxolane promote the formation of carbon dioxide hydrate. Their promotion effects at a given pressure are up to 5 K, 6.9 K, and 4.2 K, respectively, The additive material of 3,4-dihydro-2H-pyran, however, shows the inhibitor behavior. The average inhibition effect is about 1.3 K at a given pressure.

Thin films of organic semiconductor PEDOT:PSS deposited onto silicon and fusedsilica substrates. These films were then treated with sulfuric acid(H2SO4) for various amounts of time (i.e., 10, 20, 40,60, and 80 minutes). Preliminary results obtained with FT-IR, UV-VIS, and VanDerPauw conductivity methods suggest that the H2SO4removes the PSS isonomer from the PEDOT:PSS system. This PSS removal alsoinduces a decrease in film thickness.

Decorin is a small leucine-rich repeat proteoglycan supporting collagen fibril formation by controlling the rate of collagen fibrillogenesis and fibril dimensions. Peptides derived from the inner surface of decorin have been shown to bind to collagen, while peptides derived from the outer surface do not display such binding affinity. As typical secondary structural elements such as β-sheets and α-helical regions were found in the decorin X-ray crystal structure, here it was investigated by Circular Dichroism (CD) spectroscopy in solution, whether the same structural elements can be found in the derived peptides. Here it is shown that the peptide derived from decorin’s outer surface has the propensity to adopt helical conformation, as it was found in the crystal structure. The results were more pronounced in 80 vol% TFE solution, which led to an increase in the number as well as the length of helices. In contrast, peptides derived from the inner surface had a higher tendency to adopt β-sheet conformation, also in TFE, which corresponds to the conformation of the original sequence in the crystal structure of decorin. This suggests that the peptides derived from decorin adopt the structures present in the native protein.

GaSb/GaAs and InSb/GaAs material systems can create type-II quantum nanostructures which provide interesting electronic and optical properties such as having long carrier life time, low carriers-recombination rate, and emitting/absorbing low photon energy. These characteristics of type-II nanostructures can be applied for infrared or gas detection devices, for memory devices and even for novel intermediate band solar cells. In contrast, lattice mismatches of GaSb/GaAs and InSb/GaAs material system are 7.8% and 14.6%, respectively, which need some specific molecular beam epitaxial (MBE) growth conditions for quantum nanostructure formation via Stranski–Krastanov growth mode.

In this paper, the growth of self-assembled GaSb and InSb quantum nanostructures on (001) GaAs substrate by using MBE was reported. The surface morphology of these two quantum nanostructures and their optical properties were characterized by atomic force microscopy and photoluminescence (PL). The experimental results were compared between these two quantum nanostructures. Due to the lattice mismatch in each material system and the difference in sticking coefficient of Ga- and In-atoms during epitaxial growth, we obtain GaSb/GaAs quantum dots (QDs) with a density ∼1010 dots/cm2 and InSb/GaAs QDs with a density of ∼108 dots/cm2. The facet analysis of individual quantum nanostructure in each material system reveals that GaSb/GaAs QD has a dome-like shape with nearly isotropic property while InSb QDs form a rectangular-like shape with elongation along [110]-direction showing a strong anisotropic property.

Low temperature PL spectra from capped GaSb and InSb quantum nanostructures show the energy peaks at 1.08-1.11 and 1.16-1.17 eV, respectively. The variations of PL peaks as a function of both temperature and excitation power are investigated. PL peak shows clear blue shift when excitation power is increased. This work manifests a possibility to use both GaSb and InSb quantum nanostructures for nanoelectronic and nanophotonic applications.

Nanoparticle system with the compositionxEu2O3-(1-x)α-Fe2O3 (x= 0.1 and 0.5) was successfully synthesized by mechanochemicalactivation of Eu2O3 andα-Fe2O3 mixtures for 0-12 hours of ball millingtime. The study is of relevance to catalysis, biomedical, sensing andenergy-related applications. 57Fe and 151EuMössbauer spectroscopy were used to investigate the phase evolution,solid solution formation and hyperfine parameters ofxEu2O3-(1-x)α-Fe2O3nanoparticle system under the mechanochemical activation process. The57Fe Mössbauer studies showed that the spectrum of the ballmilled samples evolved from a sextet for hematite to sextets and a doublet uponduration of the milling process with europium oxide. This indicated theformation of the EuFeO3 perovskite for large x values and longmilling times. The 151Eu Mössbauer investigations showedthat the isomer shift decreased with increasing milling time for all molarconcentrations employed.

Antiviral activity of metallic Ag nanoparticles immobilized on textile fabrics were investigated. The Ag nanoparticles synthesized by radiochemical process are firmly immobilized on the surface of support textile fabrics of cotton. Small Ag particles of about 2–4 nm were observed together with relatively large particles of more than 10 nm. The Ag nanoparticles showed antiviral activity against Influenza A and Feline Calicivirus. The antiviral activity significantly depended on the concentration of the Eagle’s minimal essential medium. It was implied that the surface passivation by inhibitory agent lead to the deactivation of metallic Ag nanoparticles.

Seebeck effect is widely used for the energy harvesting from wasted heat. In the Seebeck effect, the electric power can be generated by the temperature difference between both ends of the thermoelectric materials. However, low conversion efficiency is caused by heat flux from hot side to cold side of sample. In this paper, we have proposed a new thermal power generation mechanism with no temperature difference. We investigated the band structure of Ba8AuxSi46-x clathrate single crystal synthesized by Czochralski method. The single crystal has a gradient of the gold contents along the growth direction. According to the results of Seebeck coefficient, the electrical properties of the Ba8AuxSi46-x clathrate dramatically changed depending on the gold contents. In the case of gold content of lower than 5.33, the Ba8AuxSi46-x clathrate showed a n-type semiconductor. In the case of gold content of higher than 5.33, the Ba8AuxSi46-x clathrate showed a p-type semiconductor. The band gap of the n-type and p-type Ba8AuxSi46-x clathrate were wider than the intrinsic semiconductor. We can successfully synthesize a n-p junction single crystal, which obtaining energy band curve generated from the difference of Fermi level between p- and n- type semiconductors. The single crystal was heated under the uniform temperature and able to obtain generated electric voltage of around 0.6 mV at 400°C. These results suggested that the obtained electric voltage can be generated from the separation of hole-electron pair excited by heating at the intrinsic part with a narrow band gap along to the energy band curve formed by p-n junction.

InP membranes have been bonded oxide mediated onto a patterned and unpatterned Si substrate. Indentation is shown to allow local testing on patterned areas. Both responses on patterned and unpatterned are compared and placed in reference to oxide free bonded membranes. Delamination of the membrane was observed to depend on the presence of patterns in the Silicon substrate. It occurs when the indenting load reached 55 mN for an oxide mediated bonded unpatterned structure and 42 mN for an oxide mediated bonded patterned one. This is in both cases below the value of 80 mN obtained for an oxide free bonded membrane (unpatterned). Weibull analysis of these events yielded a modulus m of magnitude 6 to 10, indicating that delamination fracture is relatively predictable with a weaker resistance obtained in patterned oxide mediated bonding. Delamination of the membrane is the result of constraint of plastic flow by the InP/Si interface. Membrane rotation is induced and increases with the indentation load, until it is sufficient to initiate and propagate an interfacial crack.

Ge-Si alloy nanoparticles (NPs) covering the full range of compositions were studied in regard to their suitability as semiconducting channel layer in thin-film transistors (TFTs). Special focus is given to the influence of annealing and encapsulation techniques on the contact and channel properties. Therefore, electrical characterization methods separating contact from channel characteristics are highlighted and applied. It is demonstrated that appropriate passivation of the nanoparticle surfaces can improve the Ion/Ioff ratios by modulation of the density of free charge carriers and also can suppress hysteresis effects. Ge-rich NP alloys can generally be passivated more effectively regardless if passivation is done with solution-processed poly(methyl methacrylate) (PMMA) or by aluminum oxide (Al2O3) from Atomic Layer Deposition (ALD). Sufficient annealing improves the contact formation between aluminum electrodes and Ge-Si particles by modification of charge injection. The presented analysis leads to a better understanding interface and surface effects in porous nanoparticle semiconductors for application in TFT devices.

The paper presents the research results of formation features of nanoporous titanium oxide structure under electrochemical anodizing by AC-DC current. It is shown that addition of current AC-component (at the frequency of 100 Hz – 10 kHz) leads to increase of the coating formation rate and to structure quality changes of nanoporous TiO2 coatings: open intertubular space appears, intertubular bridges are formed and the nanotubes section form becomes round.

In this paper, hydrothermal method has been employed to synthesize oxygen-modified carbon dots (O-CDs) from citric acid and nitrogen and sulfur modified carbon dots (N,S-CDs) from citric acid and cysteine. Both as-prepared carbon dots achieve naked-eye observable blue-green luminescence. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) are used to exhibit the chemical composition of carbon dots. The structure and size of both carbon dots are similar via transmission electron microscopy (TEM) and dynamic light scattering (DLS), which indicates that the function of size effect can be neglected in this study. Fluorescence properties, UV-vis absorption and solubility are systemically studied to investigate the influence of surface modification. The N,S-CDs show high quantum yield and excitation independent photoluminescence, however, the O-CDs present low quantum yield and excitation dependent photoluminescence, and both carbon dots achieve strong photo-stability. The cytotoxicity of carbon dots is also performed on U87-MG brain tumor cells, which shows that both carbon dots process good biocompatibility and low toxicity in live cell. The bright cellular imaging photos indicate that both carbon dots have great potential to serve as high quality optical imaging probes.

The present work demonstrates a novel technique for dispersing nanofillers in a thermoplastic polymer, where polymerization and dispersion of the nanofillers occur simultaneously via dynamic emulsion polycondensation at ambient temperature. The composite is manufactured in the form of a uniform powder, which can then be molded into desired shape by melting or sintering. The technique is demonstrated for Ag nanowire / Nylon 66 composites. In this demonstration, Ag nanowires are synthesized by the polyol process. Polyvinylprrolidone (PVP) is used to functionalize the Ag nanowires. Nanocomposites with varying Ag content are prepared and investigated. The nanowires are found to be monodispersed and hydrogen-bonded to the Nylon 66 matrix through PVP. Glass transition temperature of the composites decreases from 61 to 48 °C with Ag weight fraction increasing from 0 to 6.47%. The depression of the glass transition temperature is owed to the plasticizer effect as well as heterogeneous nucleation effect of the nanowires for polymerization leading to shorter chain length.

In this study, mode I debonding of the interface between silica and nylon-6 is examined using molecular dynamics, to predict the mechanical behavior of the interface between the polymer and silica. The effect of two types of surface treatment to the silica– Aminopropyltriethoxysilane and Hexamethyldisilazane (APTES and HMDZ) – on debonding is studied. Comparing the results for debonding between untreated, APTES and HMDZ modified surfaces suggests that the APTES treated surface provides a higher strength and toughness for surface debonding. The strength and toughness of the treated interfaces are higher than that of those of bare silica. The simulation results also show the formation of nano-sized voids in the polymer prior to separation with silica.