A monolithically integrated high‐efficiency Cu(In,Ga)Se2 mini‐module structured solely by laser

Monolithically integrated Cu(In,Ga)Se₂ mini‐modules were fabricated in order to reduce the width of patterning related dead area. The Cu(In,Ga)Se₂ layers were prepared on soda‐lime glasses using the multistage process at low substrate temperature below 500 °C. A picosecond laser with a wavelength of 532 nm was used for all of the structuring processes (P1, P2, and P3) for the monolithic integration. A “lift‐off” type structuring was applied for P1 and P3, and an “ablation” type was for P2. The laser structuring was optimized to be minimizing the dead area width, and the width of about 70 µm was successfully achieved. A mini‐module, in which the optimized structuring processes were applied for the integration, demonstrated a certified efficiency of 16.6%. Copyright © 2015 John Wiley & Sons, Ltd.     

Solvent‐Induced Morphology in Polymer‐Based Systems for Organic Photovoltaics

Studies on the influence of four different solvents on the morphology and photovoltaic performance of bulk‐heterojunction films made of poly(3‐hexylthiophene) (P3HT) and [6,6]‐phenyl‐C₆₁ butyric acid methyl ester (PCBM) via spin‐coating for photovoltaic applications are reported. Solvent‐dependent PCBM cluster formation and P3HT crystallization during thermal annealing are investigated with optical microscopy and grazing‐incidence wide‐angle X‐ray scattering (GIWAXS) and are found to be insufficient to explain the differences in device performance. A combination of atomic force microscopy (AFM), X‐ray reflectivity (XRR), and grazing‐incidence small‐angle X‐ray scattering (GISAXS) investigations results in detailed knowledge of the inner film morphology of P3HT:PCBM films. Vertical and lateral phase separation occurs during spin‐coating and annealing, depending on the solvent used. The findings are summarized in schematics and compared with the IV characteristics. The main influence on the photovoltaic performance arises from the vertical material composition and the existence of lateral phase separation fitting to the exciton diffusion length. Absorption and photoluminescence measurements complement the structural analysis.     

The photoinduced charge transfer mechanism in aligned and unaligned carbon nanotubes

Using time-resolved reflectivity measurements on unaligned and aligned bundled single-wall carbon nanotubes with a pump energy of 1.55 eV, quasi-resonant with the second Van Hove singularity of semiconducting tubes, a positive sign of the transient reflectivity is detected in unaligned nanotubes. In contrast a negative sign is detected in aligned nanotubes. This discovery addresses a long-standing question showing that in unaligned nanotubes the stronger intertube interactions favor the formation of short-lived free charge carriers in semiconducting tubes. A detailed analysis of the transient reflectivity spectral response shows that the free carriers in the photo-excited state of semiconducting tubes move towards metallic tubes in about 400 fs.     

A Highly Active and Selective Manganese Oxide Promoted Cobalt-on-Silica Fischer�CTropsch Catalyst

A highly active and selective manganese oxide-promoted silica-supported cobalt catalyst for the Fischer?CTropsch reaction is reported. Co/MnO/SiO₂ catalysts were prepared via impregnation of a cobalt nitrate and manganese nitrate precursor, followed by drying and calcination in an NO/He flow. The catalysts were studied with STEM?CEELS, infrared spectroscopy measurements of adsorbed CO and Steady-State Isotopic Transient Kinetic Analysis experiments. Based on those experiments, a relation between C₅₊-selectivity and surface-coverages of CH _x -intermediates on cobalt was found.     

Acidity and porosity modulation of MWW type zeolites for Nopol production by Prins condensation

Prins condensation of β-pinene with paraformaldehyde was carried out over MCM-22, delaminated ITQ-2 and silica pillared MCM-36. The mesopore-containing MCM-36 and ITQ-2 catalysts exhibit higher conversion of β-pinene due to more exposed acid sites. Lewis acid sites are responsible for Prins condensation while Brønsted acid sites favor the isomerization of pinene. The Brønsted acid sites can be removed mostly by ion-exchanging the zeolites with sodium cations. Thus, NaMWW zeolites had a higher selectivity towards Nopol. Of these, NaITQ-2 showed the highest activity and selectivity, and is a stable and reusable catalyst for production of Nopol.     

In situ Characterization of SiO2 Nanoparticle Biointeractions Using BrightSilica

By adding a gold core to silica nanoparticles (BrightSilica), silica‐like nanoparticles are generated that, unlike unmodified silica nanoparticles, provide three types of complementary information to investigate the silica nano‐biointeraction inside eukaryotic cells in situ. Firstly, organic molecules in proximity of and penetrating into the silica shell in live cells are monitored by surface‐enhanced Raman scattering (SERS). The SERS data show interaction of the hybrid silica particles with tyrosine, cysteine and phenylalanine side chains of adsorbed proteins. Composition of the biomolecular corona of BrightSilica nanoparticles differs in fibroblast and macrophage cells. Secondly, quantification of the BrightSilica nanoparticles using laser ablation inductively coupled plasma mass spectrometry (LA‐ICP‐MS) micromapping indicates a different interaction of silica nanoparticles compared to gold nanoparticles under the same experimental conditions. Thirdly, the metal cores allow the investigation of particle distribution and interaction in the cellular ultrastructure by cryo nanoscale X‐ray tomography (cryo‐XT). In 3D reconstructions the assumption is confirmed that BrightSilica nanoparticles enter cells by an endocytotic mechanism. The high SERS intensities are explained by the beneficial plasmonic properties due to agglomeration of BrightSilica. The results have implications for the development of multi‐modal qualitative and quantitative characterization in comparative nanotoxicology and bionanotechnology.     

Enhanced Electron Mobility Due to Dopant‐Defect Pairing in Conductive ZnMgO

The increase of the band gap in Zn_1‐xMg_xO alloys with added Mg facilitates tunable control of the conduction band alignment and the Fermi‐level position in oxide‐heterostructures. However, the maximal conductivity achievable by doping decreases considerably at higher Mg compositions, which limits practical application as a wide‐gap transparent conductive oxide. In this work, first‐principles calculations and material synthesis and characterization are combined to show that the leading cause of the conductivity decrease is the increased formation of acceptor‐like compensating intrinsic defects, such as zinc vacancies (V_Zn), which reduce the free electron concentration and decrease the mobility through ionized impurity scattering. Following the expectation that non‐equilibrium deposition techniques should create a more random distribution of oppositely charged dopants and defects compared to the thermodynamic limit, the paring between dopant Ga_Zn and intrinsic defects V_Zn is studied as a means to reduce the ionized impurity scattering. Indeed, the post‐deposition annealing of Ga‐doped Zn_0.7Mg_0.3O films grown by pulsed laser deposition increases the mobility by 50% resulting in a conductivity as high as σ = 475 S cm^‐1.     

Gyroid‐Structured 3D ZnO Networks Made by Atomic Layer Deposition

3D continuous ZnO morphologies with characteristic feature sizes on the 10 nm length scale are attractive for electronic device manufacture. However, their synthesis remains a challenge because of the low crystallization temperature of ZnO. Here, we report a method for the robust and reliable synthesis of fully crystalline 3D mesoporous ZnO networks by means of atomic layer deposition (ALD) of ZnO into a self‐assembled block copolymer template. By carefully optimizing the processing conditions we are able to synthesize several‐micrometer‐thick layers of mesoporous ZnO networks with a strut width of 30 nm. Two 3D mesoporous morphologies are manufactured: a periodic gyroid structure and a random worm‐like morphology. Exploiting the ALD property to conformally coat complex surfaces of high aspect ratio, the channel network of a 3D continuous channel network of a self‐assembled block copolymer is replicated into ZnO. X‐ray photoemission spectroscopy and x‐ray diffraction measurements reveal that the chemical composition of the mesoporous structures is uniform and consists of wurtzite‐ZnO throughout the film. Scanning electron microscopy reveals an average pore dimension of 30 nm. The potential of this material for a hybrid photovoltaic application is demonstrated by the manufacture of a poly(3‐hexylthiophene)/ZnO solar cell.     

HIAWSC： An Immune Algorithm Based Heuristic Web Service Composition Framework

The introduction of of web services has led to web service composition being a focus of many researchers. Composing web services using workflows is seen as the most realistic method from an industrial viewpoint. Amongst other method, the use of natural computing methods has been proposed previously to automate web service composition. The need for a fast response when computing the most suitable sequence of services is addressed in this paper. In particular, we propose a novel heuristic immune algorithm with an efficient encoding and mutation method. The algorithm involves two steps： an immune selection operation, which is maintaining antibody population diversity and the clonal selection. The use of a vaccine during the evolution provides heuristic information that accelerates the convergence. Our experimental results illustrate that the proposed heuristic immune algorithm is very effective in improving the convergence speed. We also provide a schema analysis for this method.     

Evaluation of a press-fit osteochondral poly(ester-urethane) scaffold in a rabbit defect model

The purpose of this study was to evaluate the impact on osteochondral healing of press-fitted multiphasic osteochondral scaffolds consisting of poly(ester-urethane) (PUR) and hydroxyapatite into a cylindric osteochondral defect in the distal non-weight bearing femoral trochlear ridge of the rabbit. Two scaffolds were investigated, one with and one without an intermediate microporous membrane between the cartilage and the bone compartment of the scaffold. A control group without a scaffold placed into the defect was included. After 12 weeks macroscopic and histomorphological analyses were performed. The scaffold was easily press-fitted and provided a stable matrix for tissue repair. The membrane did not demonstrate a detrimental effect on tissue healing compared with the scaffold without membrane. However, the control group had statistically superior healing as reflected by histological differences in the cartilage and subchondral bone compartment between control group and each scaffold group. A more detailed analysis revealed that the difference was localized in the bone compartment healing. The present study demonstrates that an elastomeric PUR scaffold can easily be press-fitted into an osteochondral defect and provides a stable matrix for tissue repair. However, the multi-phasic scaffold did not provide a clear advantage for tissue healing. Future investigations should refine especially the bone phase of the implant to increase its stiffness, biocompatibility and osteoconductive activity. A more precise fabrication technique would be necessary for the matching of tissue organisation.