Pm-Si:H PIN and NIP solar cells structures grown using plasma enhanced chemical vapor deposition (PECVD) technique were analyzed during 400 hrs of light-soaking exposition. The evolution of the structural and optical properties was observed and characterized by Raman spectroscopy, spectroscopic ellipsometry. The effect observed is related to defects creation due to induced hydrogen diffusion, break of Si-H bonds and the generation of dangling bonds that causes less passivated films. The film microstructure, and therefore the optical properties varied with the exposition time. The crystalline fraction of these structures presents a slight decrease and it is observed to be between 15 to 24% for the PIN and 5 to 10% for the NIP. The optical gap increases from 1.66 to 1.68 eV for the PIN structure while for the NIP no significant change is observed during light-soaking. Hydrogen diffusion during lights soaking generates a decrease on the absorption properties of the films which in turn is expected to reduce the device efficiency during operation. In this work we show that long range motion of hydrogen during light-soaking causes a hydrogen rearrangement on the film and microstructure changes. We determined that there is not an pronounced change on the film structure during prolonged light exposition related to the stability of the pm-Si:H films. The PIN structure properties are more affected during light soaking in comparison to the NIP structure which is expected to cause less degradation of its optoelectronic properties under illumination, and a more stable device during operation.

A facile, high-yield synthesis of edge gold-coated silver nanoprisms (GSNPs) with a gold nanoframe as thin as 1.7 nm and their comprehensive characterizations by using various spectroscopic and microscopic techniques is introduced. The GSNPs exhibit remarkably higher stability than silver nanoprisms (SNPs) and are therefore explored as effective optical antennae for light-harvesting applications. When embedded into a bulk heterojunctions film of P3HT:PCBM, plasmonic GSNPs with a localized surface plasmon resonance (LSPR) around 500 nm can effectively act as optical antennae to enhance light harvesting in the active layer. As a result, we measured up to 7-fold enhancement in the polaron generation yield through photoinduced absorption spectroscopy. Owing to the high stability and strong field enhancement, the presented GSNPs feature great potential as plasmonic probes for photovoltaic applications and LSPR sensing.

For safety assessment analyses of the disposal of spent nuclear fuel (SNF) in deep geological repositories it is indispensable to evaluate the contribution of fission products to the instant release fraction (IRF). During the last three years the EURATOM FP7 Collaborative Project, “Fast / Instant Release of Safety Relevant Radionuclides from Spent Nuclear Fuel (CP FIRST-Nuclides)” was carried out to get a better understanding of the IRF.

Within CP FIRST-Nuclides, a leaching experiment with a cladded SNF pellet was performed in bicarbonate water (19 mM NaCl + 1 mM NaHCO3) under Ar /H2 atmosphere over 333 days. The cladded SNF pellet was obtained from a fuel rod segment which was irradiated in the Gösgen pressurized water reactor; the average burn-up of the segment was 50.4 MWd/kgUO2. In the multi-sampling experiment, gaseous and liquid samples were taken periodically. The moles of the fission gases Kr and Xe released in the gas phase and those of 129I and 137Cs released in solution were measured. Cumulative release fractions of (1.6 ± 0.2)·10-1 fission gases, (1.6 ± 0.1)·10-1129I and (3.9 ± 0.2)·10-2 137Cs, respectively, were achieved after 333 days of leaching. Accordingly the release ratio of fission gases to 129I was 1:1 and the release ratio of fission gases to 137Cs was 4:1, respectively.

Due to the potential applications to high-efficiency and light-weight solar cells, the growth of CuInGaSe2 (CIGS) nanoparticles is a recent research focus. We have developed a relatively simple solvothermal route to grow high quality CIGS nanoparticles in an autoclave under different temperatures (170 – 280°C). The effect of reaction temperature on the shape of CIGS nanoparticles has been investigated. At lower temperatures, the CIGS particles show plate-like shape. Whereas at higher temperatures, most of them exhibit rod-like feature. The nanoparticle products have been also characterized by field emission scanning electron microscopy and X-ray diffraction techniques.

2D nanomaterials, when assembled into an ordered macrostructure, will present many great opportunities, including for Li-ion batteries (LIBs). We report densely-packed vertically-aligned VO2(B) nanobelts (NBs)-based forest structure synthesized on edge-oriented graphene (EOG) network. Using a EOG/Ni foam as a 3D scaffold, aligned VO2(B) NBs can be further synthesized into a folded 3D forest structure to construct a freestanding electrode for LIBs. Electrochemical studies found that such a freestanding VO2(B)/EOG electrode, which combines the unique merits of 2D VO2(B) NBs and 2D graphene sheets, has excellent charge-discharge rate performance. A discharge capacity of 178 mAh g-1 at a rate of 59 C and 100 mAh g-1 at 300 C was measured. A good charge-discharge cycling stability under a high current density was also demonstrated. The results indicate VO2(B)/EOG forest based freestanding electrode is very promising for developing high-rate LIBs.

The effects of WO3 doping in 4,4’-bis-9-carbozyl biphenyl (CBP) were studied through detailed electrical device characterization. A series of hole-only devices have been fabricated, where the doping level was varied from 10-40mol% and the doped CBP thickness was varied from 5-40 nm. It was found that, to achieve effective doping for improved hole injection and transport, the doping level should be greater than 20mol% and the doped layer should be at least 10 nm thick. It was also found that an energy barrier exists at the doped and undoped CBP interface, resulting in an additional voltage drop. This finding was explained by a large downward shift of the Fermi level in WO3-doped CBP, which causes band bending and depletion at the interface. Finally, simplified green phosphorescent organic light-emitting diodes (OLEDs) with CBP as the hole transport and host material were fabricated. With a WO3-doped hole transport layer, the OLEDs attained brightness above 105 cd/m2 at 20 mA/cm2, and exhibited an improved reliability under constant-current stressing as compared to undoped OLEDs.

Chemical Vapor Deposited (CVD) diamond growth on (111)-diamond surfaces has received increased attention lately because of the use of N-V related centers in quantum computing as well as application of these defect centers in sensing nano-Tesla strength magnetic fields. We have carried out a detailed study of homoepitaxial diamond deposition on (111)-single crystal diamond (SCD) surfaces using a 1.2 kW microwave plasma CVD (MPCVD) system employing methane/hydrogen/nitrogen/oxygen gas phase chemistry. We have utilized Type Ib (111)-oriented single crystal diamonds as seed crystals in our study. The homoepitaxially grown diamond films were analyzed by Raman spectroscopy, Photoluminescence Spectroscopy (PL), X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). The nitrogen concentration in the plasma was carefully varied between 0 and 1500 ppm while a ppm level of silicon impurity is present in the plasma from the quartz bell jar. The concentration of N-V defect centers with PL zero phonon lines (ZPL) at 575nm and 637nm and the Si-defect center with a ZPL at 737nm were experimentally detected from a variation in CVD growth conditions and were quantitatively studied. Altering nitrogen and oxygen concentration in the plasma was observed to directly affect N-V and Si-defect incorporation into the (111)-oriented diamond lattice and these findings are presented.

Since 1994, the KHNP has developed a vitrification technology to treat the LILW generated from Korean nuclear power plant. To vitrify the LILW including combustible Dry Active Waste (DAW) and Ion Exchange Resin (IER) containing Zeolite, two borosilicate glasses are formulated. One of the formulated glass, DG2, is for the DAW vitrification solely and the other one, AG8W1, is for the blended wastes (DAW & IER) vitrification in a commercial vitrification facility in HanUl (former Ulchin) nuclear power plant. The physicochemical properties of the two glasses have been evaluated. To evaluate the processability of the glasses, the viscosities and electrical conductivities of the glass melts were measured in the laboratory within a temperature range between 950 and 1,350 degrees C, respectively. The liquidus temperatures of the glasses were evaluated using a gradient furnace for DG2 and data from heat treatment for AG8W1. The Mössbauer spectroscopy for AG8W1 was employed to evaluate the relations between the redox equilibria of iron. In addition, to verify the waste acceptance criteria for the final disposal of the vitrified forms, the compressive strengths of the vitrified forms were tested after an immersion test, a thermal cycling test, and an irradiation test. To verify the chemical durability of the glasses, several tests such as PCT, ISO, VHT, Soxhlet, MCC-1, and ANS16.1 were carried out. The PCT showed leach rates of B, Na, Li and Si were much less than those of the benchmark glass. The ISO test was performed at 90 degrees C for 1,022 days and Cumulative Fraction Leached of all elements in the glasses were analyzed. According to the VHT, the glasses had an outstanding chemical resistance under humid environment at 200 degrees C for 7 days. The Soxhlet leaching was performed on rectangular glass samples at 98 degrees C for 30 days. To analyze the forward dissolution rates of major glass elements, the MCC-1 was conducted at temperatures of 40, 70, and 90 degrees C for three weeks in pH buffer solutions ranging from pH 4 to 11. The processability of the glasses was in the desired ranges. And the product quality of the glasses met all regulatory guidelines. Using two glasses, the CCIM commissioning tests in the UVF were successfully performed and they showed good workability.

Today’s conversion of solar energy into electricity is based on silicon, which is pure, eventually crystalline, and its most efficient transitions are away from solar radiation maximum. The continuous search of efficient photovoltaic materials has recently focused on lead-halide organic-inorganic perovskite materials due to the very flexible, sustainable, and forgiving procedure of their fabrication, which is successful even if the concentrations of precursors, and temperature regimes deviate from optimal values. In addition to simple fabrication, this class of materials provides impressively high efficiency of photovoltaic (PV) cells. Attention to these materials helps to understand the mechanisms of their high efficiencies and to identify other materials with same type of properties. This work presents computational analysis of photo-induced processes in perovskite materials at ambient temperatures.

Transitioning to low-carbon energy systems depends on fundamental changes in technologies, policies, and institutions. In Western democracies, public perceptions and engagement with energy have encouraged innovation while also slowing deployment of low-carbon energy technologies (LCETs).

Transitioning to low-carbon energy systems requires re-engineering technologies and changing the ways people interact with energy. This shift involves both technological and social changes including modifications in policies and institutional configurations. In Western democracies, public perceptions and engagement with energy have encouraged innovation while also slowing deployment of low-carbon energy technologies (LCETs). To aid understanding of how energy systems are evolving toward lower-carbon technologies in Western democracies, this study reviews the literature on public perception of and engagement with emerging LCETs. Focusing primarily on electricity generating technologies, we explore how multiple factors related to place and process shape public perceptions of and engagement with LCETs, thereby influencing their development and deployment. This study first reviews literature related to how place and process influence emerging LCETs and then provides a comparative example of differential development of wind energy in Texas and Massachusetts (USA) to demonstrate how place and process may interact to influence the patterns of LCET deployment.

We present a nano-patterning process for semiconducting polymeric composites that could potentially be utilized for the development of polymer-based data storage devices. Nano-patterning (writing) operates on the basis of the mechanical interaction between the electrically unbiased tip of an atomic force microscope and the surface of polymeric composite films. Via friction forces, the tip/sample interaction produces a local increase of molecular disorder in the polymer matrix, inducing a localized lowering in the conductivity of the organic semiconductor. Herein we suggest a figure of merit for quantifying the efficiency of pattern formation and we address the dependence of the writing process on the thermal annealing temperature of the composite film. Control experiments on composite films deposited on substrates with different roughness suggest that the writing effect is invariant to the roughness of the substrate. The potential storage density of the writing process depends on the tip curvature.

Geological disposal of HLW and spent nuclear fuel (SNF) in very deep boreholes is a concept whose time has come. The alternative – disposal in a mined, engineered repository is beset with difficulties not least of which are the constraints placed upon the engineered barriers by the high thermal loading. The deep borehole concept offers a potentially safer, faster and more cost-effective solution. Despite this, international interest has been slow to materialize, largely due to perceived problems with retrievability and uncertainty about the ability to drill accurate vertical holes with diameters greater than 0.5 m to a depth of 4-5 km. The closure of Yucca Mountain and the subsequent recommendations of the Blue Ribbon Commission have lead to a renewed interest in deep borehole disposal (DBD) and the US DoE has commissioned Sandia National Labs, working with industrial and academic partners (including the University of Sheffield), to undertake a program of R&D leading to a demonstration borehole being drilled somewhere in the continental USA by 2016.

In this paper, we focus on some of the key safety and engineering features of DBD including methods of sealing the boreholes, sealing and support matrices for the waste packages. Numerical modeling has, and continues to play, a significant role in expanding and validating the DBD concept. We report on progress in the use of modeling in the above contexts, paying particular attention to constraints on the engineering materials resulting from high heat loading.

Using the density functional theory (DFT) and time dependent DFT, within the generalized gradient approximation (GGA), the electronic and optical properties of stoichiometric (ZnS)n nanoparticles (NP) were calculated. The dependence of the gap on the size (n) of the nanoparticle will be presented. The effect of replacing S atoms with P, Se or Te atoms in the (ZnS)n nanoparticles and its influence in the gap will be also shown.

Resistive switching, a reversible change in electrical resistance of a dielectric layer through the application of a voltage bias, has propelled a field of research to form improved non-volatile memory device. Tantalum oxide has been investigated as the dielectric component of resistive switching devices as a leading candidate for a few years. Presented here is a structural and chemical investigation of TaOx devices with 55nm in diameter in the virgin, forming on, and switched off (reset) states for comparison using cross sectional TEM techniques including HRTEM, and EELS to gain further understanding of this material system. The nanodevices imaged in this study were switched below 100µA. Unique features found in this study are in agreement with previous hypotheses made by various researchers based on X-ray fluorescence microscopy of micron-scale devices, indicating a variation in oxygen concentration around the switching area.

We study W | Ta | CoFeB | MgO stacks for spin-orbit torque MRAM applications. A strong perpendicular magnetic anisotropy is obtained after annealing for CoFeB layer thickness of 0.9 nm or 1.2 nm and for specific W/Ta ratios, were the Ta layer thickness is between 0.3 nm and 1 nm. Furthermore, the desired high-spin orbit coupling β-phase of W is preserved even after annealing at 350°C. We argue that an efficient B getter, like Ta, is necessary for the coherent crystallization of the CoFeB | MgO interface that allows for the establishment of perpendicular magnetic anisotropy.

Nafion α-relaxation has been the subject of intense investigations as it regulates the performance of electric actuators and polymer electrolyte fuel cells (PEMFC). Dielectric spectroscopy and atomic force microscopy (AFM) measurements of Nafion membranes allowed identifying the conformation transition of the polymeric aggregates as the process underlying the α-transition. The dielectric permittivity curves of Nafion showed that for temperatures T > 120 °C, the α-relaxation displaces to lower frequencies. Such unusual behavior was attributed to an elongation of Nafion polymeric aggregates occurring at T ∼ 120 °C and is in agreement with both water uptake measurements and morphological changes inferred from AFM analyses.

The cooling dynamics of hot charge carriers in colloidal lead chalcogenide nanocrystals is studied by white light transient absorption spectroscopy. We demonstrate a transient accumulation of charge carriers at a high-energy critical point in the Brillouin zone. Using a theoretical study of the cooling rate in lead chalcogenides, we attribute this slowing down of charge carrier cooling to a phonon scattering bottleneck around this critical point. Our approach allows for the first ever determination of hot carrier cooling rates, relevant in e.g. modeling of multiple exciton generation.

Hyperbranched structures containing pyrrole units were obtained from ortho-, meta- and para-diaminodiphenyldiacetylenes as AB2 type monomers by one-step polymerization.

The para-hyperbranched compound was observed by optical microscopy and scanning electron microscopy.

Microscopy studies identify two phases. The first is the insoluble one which gives origin to flake type structures. The second is acetone soluble phase, which generated crystalline structure manifesting in optic anisotropy and rhomboids and triangles dendrimeric structures.