Cu(InGa)Se2 solar cells modeling is challenging due to their complex electronic structure, to the presence of interface states between layer and grains and to the microcrystalline structure of the absorber. Here we present a ISE-TCAD based realistic absorber 3D model, with the specific objective to take into account, among several effects, these challenging aspects. The CdS/Cu(InGa)Se2 solar cell is modeled as an array of columnar microcells, connected in parallel, mimicking the polycrystalline nature of the absorber. The model optical and electrical parameters are optimized based on a review of available experimental material characterization and realization results. Simulation outcomes are compared with experimental data in order to validate the model.

In this work we present a detailed theoretical investigation of the thermal conductivities of n-type 0.1 wt.% CuBr doped 85% Bi2Te3 - 15% Bi2Se3 and p-type 3 wt% Te doped 20% Bi2Te3 - %80 Sb2Te3 single crystals. The thermal conductivity contributions arising from carriers, electron-hole pairs and phonons are computed rigorously in the temperature range $300\,{\rm{K}}\, \le \,T\, \le \,500\,{\rm{K}}$ . In agreement with available experimental measurements we theoretically find that the lowest total thermal conductivity is 3.15 W K−1 m−1 at 380 K for the n-type alloy and 1.145 W K−1 m−1 at 400 K for the p-type alloy. Stronger mass-defect scattering is found to be responsible for the lower thermal conductivity of the p-type alloy throughout the temperature range of the study.

Atomistic lattice-gas models for thermodynamically and kinetically directed assembly are applied to Ru nanocluster formation on a monolayer of graphene supported on Ru(0001) at 309 K. Nanocluster density, mean size, height distribution, and spatial ordering are analyzed by kinetic Monte Carlo simulations. Both models can reproduce the experimental data, but additional density functional theory analysis favors the former.

Highly transparent and conducting Fluorine doped zinc oxide thin films were deposited using spray pyrolysis method on glass substrates held at 450 °C. The X-ray diffraction study revealed that as the dopant concentration increases in ZnO films, the intensity of the preferential orientation of (002) reflection decreased and (101) was found to increase up to 5 at. % F. The crystallite size was varied from 40 to 50 nm with dopant concentration. The optical band gap of the un-doped films was 3.30 eV and it increased to 3.34 eV for 3 at. % F. The refractive index of the films was increased from 2.05 to 2.18 with the increase of dopant concentration from 0 to 5 at. %. The scanning electron microscopy results depicted that the microstructure of ZnO: F films highly influenced by the fluorine doping. After annealing the films in hydrogen atmosphere, the resistivity of the films decreased as increase the dopant concentration and it is 4×10−3 Ω cm for 3at. % F beyond which it increased. The mobility of the charge carriers was 14 cm2/ V sec and the carrier concentration was 7.8×1019 cm3 obtained for the films doped with 3 at. % of fluorine concentration in the starting solution.

Carbon-based nanostructures have been the center of intense research and development for more than two decades now. Of these materials, graphene, a two-dimensional (2D) layered material system, has had a significant impact on science and technology in recent years after it was experimentally isolated in single layers in 2004. The recent emergence of other classes of 2D layered systems beyond graphene has added yet more exciting and new dimensions for research and exploration given their diverse and rich spectrum of properties. For example, h-BN a layered material closest in structure to graphene, is an insulator, while NbSe, a transition metal dichalcogenide is metallic and monolayers of other transition metal di-chalcogenides such as MoS2 are direct band-gap semiconductors. The rich variety of properties that 2D layered material systems offer can potentially be engineered on-demand, and creates exciting prospects for their device and technological applications ranging from electronics, sensing, photonics, energy harvesting and flexible electronics in the near future.

Papers in the Appendix were published in electronic format as Volume 1534

Semiconductor heterostructures as quantum dots demonstrate discrete atom-like energy level structure based on several hundred of electron confinement states. In the case of double QD (DQD) or double QR (DQR), there is a single electron spectrum composed of a set of quasi-doublets. We study these specific spectrum properties with their relation to the electron tunneling in DQD (DCQR) when the wave function of electron localized initially in one of the double quantum object is spread into whole system. The double InAs/GaAs quantum dots are considered within the effective approach. Tunneling in DQD is studied in connection with change of inter-dot distance and QD geometry. There are two types of such tunneling in DQD. The first is related to tunneling in the system of two identical QDs; the second one occurs in the system of non-identical QDs. The tunneling in the DQR is a tunneling in the system with non-identical quantum objects. The quasi-doublets of the DQD spectrum play an important role in the tunneling. We study effect of violation of symmetry of DQD geometry on the tunneling and show that the violation of symmetry makes difficulties for such tunneling.

The traditional CdCl2 passivation of CdTe is expanded by adding other chlorides such as MgCl2, NaCl, and MnCl2 into the process through a two-step passivation procedure that combines closed space sublimation step with a vapor process. This allows the possibility of forming a highly doped field at the back of the device that could act as an electron reflector that could boost device performance by directing electrons back into the absorber layer and increasing the voltage while limiting recombination at the back of the device. The effects the two-step passivation process on device performance are characterized by current-voltage measurements, and by electroluminescence and laser-beam induced current images to show the degree of device uniformity. Additionally, capacitance voltage measurements are used to study doping density, depletion width, and possible formation of a field at the back of the device.

The present work investigates the UV stability of the dye-sensitized solar cell (DSC) by parametrical investigation of the material influence on UV stability. UV illumination has been observed to cause degradation by slow photocatalysis in the DSC. Photooxidized impurities represent an unwanted side reaction with the redox pair of the electrolyte as the released electron will deplete the triiodide concentration. A study on the DSC cell was carried out with intermediate electrical characterization by cyclic voltammetry (CV) and electrical impedance spectroscopy (EIS) to map the influence of UV illumination as a function of the H2O concentration in the electrolyte, the plate distance and the triiodide concentration. The results show that the H2O content has a detrimental influence on the DSC stability during UV illumination. A higher concentration of triiodide can buffer the reaction with impurities, so that a longer-term stability is achieved. A recovery of triiodide in UV aged cells with either no remaining triiodide or with such a low concentration that the cell current has been diffusionlimited, was seen during CV to -0.75 V under illumination. The reappearance of triiodide was accompanied with a production of hydrogen bubbles, which was related to the H2O content in the electrolyte and the exposure to UV. Our approach can be used to test the purity and the UV stability of various electrolytes.

A study on light absorption enhancement of an InAs quantum dots embedded into InxGa1-xAs quantum well with GaAs as a barrier solar cells was carried out. Solar cell devices were fabricated from different structures, which were grown by using molecular beam epitaxy, with the In mole fraction (x) varied between 0 – 25 %. Poly-L-Lysine ligands and ZnO sol-gel was used to modify the surface of the solar cells and act as anti-reflection coatings. The anti-reflection characteristic of the ligands and the sol-gel were investigated by measuring the solar cell characteristics before and after the solar cells surface modifications. The current-voltage characteristics were measured of the fabricated solar cells before and after Poly-L-Lysine and ZnO coatings. A significant enhancement on the order of 40 % of the solar cells performance was observed. This type of enhancement was observed in the power conversion efficiency, spectral response measurements, and external quantum efficiency.

Polymer network formation is an important tool for tailoring mechanical properties of polymeric materials. One option to synthesize a network is the addition of bivalent crosslinkers reacting with functional groups present in a polymer. In case of polymer network syntheses based on biopolymers, performing such a crosslinking reaction in water is sometimes necessary in view of the solubility of the biopolymer, such as gelatin, and can be beneficial to avoid potential contamination of the formed material with organic solvents in view of applications in biomedicine. In the case of applying diisocyanates for the crosslinking in water, it is necessary to show that the low molecular weight bifunctional crosslinker has fully reacted, while tailoring of the mechanical properties of the resulting hydrogels is possible despite the complex reaction mechanism. Here, the formation of gelatin-based hydrogel networks with the diisocyanates 2,4-toluene diisocyanate, 1,4-butane diisocyanate, and isophorone diisocyanate is presented. It is shown that extensive washing of materials is required to ensure full conversion of the diisocyanates. The use of different diisocyanates gives hydrogels covering a large range of Young’s moduli (12-450 kPa). The elongations at break (up to 83%) as well as the maximum tensile strengths (up to 410 kPa) of the hydrogels described here are much higher than for lysine diisocyanate ethyl ester crosslinked gelatin reported before. Rheological investigations suggest that the network formation in some cases is due to physical interactions and entanglements rather than covalent crosslink formation.

Following the release of radionuclides into the environment as a result of the accident at Fukushima Daiichi nuclear power plant, Japan Atomic Energy Agency (JAEA) had to develop an immediate and effective method of reducing the dose rate received by students in school facilities. A demonstration of a reducing method was carried out by JAEA at a junior high school ground and kindergarten yard in the center of Fukushima-city. Dose rates of the released radionuclides are largely controlled by the ground level contamination and accumulation of mainly Cesium137 (Cs-137) and Cesium 134 (Cs-134) in populated areas. An effective means of reducing dose rate was to remove the surface soil and to bury it on-site under fresh uncontaminated soil or soil collected under deep depth at the site for shielding. The dose rate at1 m above ground level was reduced from 2.5 µSv/h to 0.15 µSv/h.

The effect of bio-conjugation of CdSe/ZnS core-shell quantum dots (QDs) with Interleukin 10 (IL-10) antibodies on the aging of photoluminescence (PL) spectra of the QDs was investigated. The aging occurred upon storage of QDs for about 2 years or thermal annealing at 190 oC for up to 12 hours at atmospheric ambience and consisted in “blue” shifting the PL band position, increasing a PL band half-width and decreasing the PL intensity. The bio-conjugation is found to promote PL aging. The aging upon storage is attributed to the oxidation that decreases the QD core dimension, while the aging upon thermal annealing can be due to both oxidation and alloying of CdSe core and ZnS shell.

Nowadays, the nature of the non radiative recombination centres in ZnO is a matter of controversy; they have been related to extended defects, zinc vacancy complexes, and surface defects, among other possible candidates. We present herein the optical characterization of catalyst free ZnO nanorods grown by atmospheric MOCVD by microRaman and cathodoluminescence spectroscopies. The correlation between the defect related Raman modes and the cathodoluminescence emission along the nanorods permits to establish a relation between the non radiative recombination centers and the defects responsible for the local Raman modes, which have been related to Zn interstitial complexes.

Polymer-based, degradable microparticles (MP) are attractive delivery vehicles for vaccines as the polymer properties can be specifically tailored and the carrier can be loaded with adjuvant. For all newly developed carrier systems it is important to analyze cellular uptake efficiency and the specific effects mediated by the encapsulated agent when phagocytosed by the cells, which is barely reported so far. By the encapsulation of N-acetylmuramyl-L-alanyl-D-isoglutamine (MDP) labeled with fluoresceinisothiocyanat (FITC) in poly[(rac-lactide)-co-glycolide] (PLGA) MP, the MP was fluorescent and used to visualize the phagocytic uptake. Since encapsulated MDP can activate dendritic cells (DC) via the cytosolic nucleotide-binding oligomerization domain receptors (NOD), it can be investigated whether only cells that have phagocytosed the MP are activated or whether bystander effects occur, resulting in activation of cells, which did not take up MDP-FITC loaded MP. Here, it is demonstrated that increasing MP concentrations in the culture medium had no impact on the viability of DC and that the MP uptake efficiency was dose dependent. Interestingly, it could be shown by the CD86 expression, that only DC, which had engulfed MP, were significantly stronger activated than DC, which had not phagocytosed MDP-FITC loaded MP. On the one hand these results indicate that sufficient amounts of MDP were released from the PLGA carriers into the cytosol of the DC. On the other hand, based on the correlation of uptake and activation on the single cell level, minimal MP induced bystander effects may be expected for in vivo applications.

Noise and electrical conductivity measurements were made at temperatures ranging from approximately 270°K to 320°K on devices fabricated on as grown Boron doped p-type a-Si:H films. The room temperature 1/f noise was found to be proportional to the bias voltage and inversely proportional to the square root of the device area. As a result, the 1/f noise can be described by Hooge’s empirical expression [1]. The 1/f noise was found to be independent of temperature in the range investigated even though the device conductivity changed by a factor of approximately 4 over this range. Conductivity temperature measurements exhibit a T-0.25 dependence, indicative of conduction via localized states in the valence band tail [2,3]. In addition, multiple authors have analyzed hole mobility in a-Si:H and find that the hole mobility depends on the scattering of mobile holes by localized states in the valence band tail [4-7]. We conclude that the a-Si:H carrier concentration does not change appreciably with temperature, and thus, the resistance change in this temperature range is due to the temperature dependence of the hole mobility. Our results are applicable to a basic understanding of noise and conductivity requirements for a-Si:H materials used for microbolometer ambient temperature infrared detection.

The purpose of this study was to achieve a descellularized scaffold from cartilage tissue, which can be used as xenograft for cartilage tissue regeneration.

This work presents the results obtained using one method to wash porcine trachea in order to remove cellular material from the extracellular matrix and to avoid the immune reaction using enzymatic detergent and partial enzymatic degradation with Deoxyribonuclease I (DNase-I), Ethylenediaminetetraacetic Acid (EDTA) and Trypsin. This treatment was qualitatively evaluated by Scanning Electron Microscopy (SEM), and H&E Stain (Histology), and quantitatively evaluated by DNA quantification. The thermal characterization of the descellularized scaffold was carried out using Termogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC). The type of collagen obtained from the scaffold was determined through SDS-PAGE electrophoresis. When using Enzymatic Treatment (ET) to wash trachea tissue, it is possible to obtain an acellular xenograft; this procedure has the potential to avoid rejection reactions of the xenograft.