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Effect of Ga Variation on the Bulk and Grain Boundary Properties of Cu In,Ga Se2 Absorbers in Thin Film Solar Cells and Their Impacts on Open Circuit Voltage Losses
Full text linkPolycrystalline widegap Cu In,Ga Se2 CIGSe absorbers for top cells in photovoltaic tandem devices can be synthesized via [Ga] [Ga] [In] GGI ratios of gt; 0.5. However, the power conversion efficiencies of such high GGI devices are smaller than those of the record cells with GGI lt; 0.5. In the present work, the effects of the GGI ratio on various CIGSe material properties were studied and correlated with the radiative and nonradiative open circuit voltage VOC deficits of the thin film solar cells. Average grain sizes, grain boundary GB recombination velocities, fluctuations in luminescence energy distribution, barrier heights at GBs, effective electron lifetimes, and Urbach energies were investigated in five solar cells with GGI ratios from 0.13 to 0.83. It was found that the GGI variation affects GB recombination velocities, fluctuations in spatial luminescence distributions, the average grain size, the electron lifetime, and the Urbach energy. In contrast, the detected ranges of barrier heights at GBs are independent of the GGI ratio. Mainly Ga In gradients give rise to substantial radiative VOC losses in all solar cells. Nonradiative VOC deficits are dominant especially for solar cells with GGI gt; 0.5, which can be attributed to low bulk lifetimes and enhanced recombination at GBs in CIGSe absorbers in this compositional rang
3D Printable Polymer Filters for the Selective Complexation of Silver Ions
Full text linkThis study presents the fabrication of polymeric filters, which are able to selectively bind silver ions from aqueous solution. Those filters are fabricated within an easy approach via 3D digital light processing DLP printing enabling a tailor made design. In first order, an acrylamide containing a benzo trithiacrown ether BTCE functionality is synthesized. This monomer is further 3D printed via layer by layer photo polymerization together with commercially available comonomers, resulting in polymer networks containing the BTCE groups in their side chains as selective binding moiety for silver ions. Within isothermal titration calorimetry ITC measurements, the complexation abilities of the BTCE to bind the Ag ions are determined. Furthermore, the resulting 3D printed filters are investigated regarding their complexation behavior, in a detailed fashion applying inductively coupled plasma optical emission spectroscopy ICP OE
Biobased Self Healing Thin Film Coatings Based on Poly Itaconic Acid Esters
Full text linkPaper used for packaging applications is often coated with thin polymer coatings to improve the properties, like printability and barrier properties, respectively. Today, these coatings are still often based on petroleum based polymers. In this study, the fabrication of biobased thin film coatings is described. Poly itaconic acid ester s, which are prepared by emulsion polymerization, are used as water based coatings for paper. The thermal properties of the polymers are tuned by the side chain of the monomers diethyl itaconate vs. dibutyl itaconate . Different formulations based on the polymer emulsion and additives, like rheology modifiers, are prepared and their film formation is studied. The usage of a rheology modifier results in excellent film formation. These polymer coatings feature an additional function they are capable of self healing. The healing ability is studied in scratch healing tests, in which almost complete recovery can be observed after healing at 100 degrees C. Moreover, the restoration of optical properties aesthetics is studied. In gloss measurements before and after damage as well as after a healing time the complete recovery of the gloss can be observed. Furthermore, the barrier properties against fat are studie
Pore nucleation and growth in aluminium alloy foams analysed by X ray tomoscopy
Full text linkNucleation and growth of pores in AlSi6Mg4Cu4, AlSi6Cu4, AlCu10, AlSi7 alloys were examined in situ using Xray tomoscopy. The pore evolution in the foaming precursors was visualized in three dimensions as a function of time. The phases in the alloys were characterised using microscopy. The evolution of the phases with temperature was studied using X ray tomoscopy. The pore formation was correlated with the temperatures at which different phases formed or evolved. From these studies, the preferred locations for pore initiation were identified. Also, variation in pore size and shape with temperature was studied in detai
Investigating skyrmion stability and core polarity reversal in NdMn2Ge2
Full text linkWe present a study on nanoscale skyrmionic spin textures in NdMn2Ge2, a rare earth complex noncollinear ferromagnet. We confirm, using X ray microscopy, that NdMn2Ge2 can host lattices of metastable skyrmion bubbles at room temperature in the absence of a magnetic field, after applying a suitable field cooling protocol. The skyrmion bubbles are robust against temperature changes from room temperature to 330 K. Furthermore, the skyrmion bubbles can be distorted, deformed, and recovered by varying strength and orientation of the applied magnetic field. We have used nitrogen vacancy nanoscale magnetic imaging to estimate and map the magnetic stray fields originating from our NdMn2Ge2 lamella samples and find stray field magnitudes on the order of a few mT near the sample surface. Micromagnetic simulations show an overall agreement with the observed behaviour of the sample under different magnetic field protocols. We also find that the presence of the Dzyaloshinskii Moriya interaction is not required to reproduce our experimental results. Its inclusion in the simulation leads to a reversal of the skyrmionic object core polarity, which is not experimentally observed. Our results further corroborate the stability and robustness of the skyrmion bubbles formed in NdMn2Ge2 and their potential for future spintronic application
The O SE endstation at BESSY II operando X ray absorption spectroscopy for energy materials
Full text linkThe investigation of a wide range of energy materials under relevant operation conditions, allowing for real time investigations of the electro chemical mechanisms governing the performance of related applications, is enabled by the new Operando Absorption and Emission Spectroscopy at EMIL O SE endstation in the Energy Materials In situ Laboratory Berlin EMIL at the BESSY II synchrotron facility in Berlin, Germany. Currently primarily used for X ray absorption spectroscopy XAS studies, the O SE endstation utilizes the undulator based two colour EMIL beamline covering an energy range between 80 and 10000 amp; 8197;eV to enable soft, tender, and hard XAS. In this work, the setup, along with operando sample environments tailored to address specific questions, is described, emphasizing its modularity and adaptability, and detailing specific strategies to minimize undesired radiation induced effects caused by the high brilliance of the EMIL beamline. The in situ growth of electrodeposited copper monitored by soft and hard XAS, at the Cu L3 edge sXAS and Cu K edge hXAS , respectively, is used as a proof of concept experiment, showcasing the capabilities of the O SE endstation as a versatile tool for comprehensive in situ operando studies of energy materials under relevant condition
Optical refractive properties and phonon spectra of Na2SO4 single crystal
Full text linkNa2SO4 crystal was grown by slow evaporation method from an aqueous solution. Using the PXRD method, the crystal structure of Na2SO4 was investigated at room temperature, and it was found that the crystal belongs to the orthorhombic symmetry of the space group Fddd no. 70 with the following unit cell parameters a 5.8568 4 , b 12.2957 7 , c 9.809 1 , and V 706.52 8 3. The dispersion of the refractive indices of Na2SO4 crystal in the visible and ultraviolet ranges was measured at room temperature and the principle refractive indices of optical indicatrix were determined to be nX 1.4703, nY 1.4847, and nZ 1.47669 for the wavelength amp; 955; 500 nm. The first principle calculations of the phonon properties of the crystal were performed using the lattice dynamics method and DFPT approach. The polarized normal incidence reflection spectra of Na2SO4 crystal were measured in the infrared range 50 1300 cm amp; 8722;1 by using FTIR spectrometer and synchrotron radiation. The calculated reflection spectra of Na2SO4 crystal are in very good agreement with the experimental ones. In Na2SO4 crystal, the Reststrahlen band in the spectral range of 1120 1200 cm amp; 8722;1 is confirmed experimentally and theoreticall
Pyridinium Benzoxazole Based Anode Material for Sustainable All Organic Polymer Based Batteries
Full text linkIn search of anode materials for organic batteries, we propose benzoxazole based redox active polymers. We report theoretically calculated redox properties of the monomer and polymer based on small polymer chain models using density functional theory DFT . Subsequently, a straightforward synthesis of poly 4 benzoxazol 2 yl 1 4 vinyl benzyl pyridinium chloride PBO via radical polymerization is presented. To our knowledge, PBO is the first representative of this class of redox active polymers applied in batteries, and it has a theoretical specific capacity of 76.8 mA h g 1 first redox process . PBO was utilized as an anode and capacity limiting electrode in an all organic radical battery using aqueous and organic based electrolytes as well as 2,2,6,6 tetramethylpiperidinyl N oxy TEMPO derivatives as cathodes, providing a cell voltage of 1.3 and 1.4 V in aqueous and organic based electrolytes, respectively. The material revealed 99 capacity utilization at 1 C in the first cycle using an organic electrolyte 1 M LiClO4 in CH3CN and more than 75 capacity utilization in an aqueous electrolyte 1 M LiClO4 in H2O . In both systems, after rate capability tests from 0.2 to 50 C , the cells were cycled again at 1 C, where 50 of the initial capacity was retained after 100 cycles. Even though, due to the linearity and the molar mass of PBO, a capacity decay is observed during cycling tests, this study opens a promising class of molecules for the development of anode material
Combined X Ray Emission Spectroscopy at Phosphorus and Nickel Detecting Subtle Changes in Catalyst Electronic Structure at High Resolution
Full text linkValence to core X ray emission spectroscopy VtC XES is widely used to characterize valence electronic structure, especially of transition metal systems in homogeneous and bioinorganic catalysis. Although metal K edge VtC XES has proved useful, its observable information content is limited by the large lifetime broadening of the metal 1s core hole, and its practical application is limited by small VtC emission probability and thus low count rates. Ligand VtC XES in transition metal complexes, though largely unexplored, offers a higher resolution and potential for broad applications in catalysis research. Here, P VtC XES is introduced for catalysts with phosphine ligands, perhaps the most important class of spectator ligands in homogeneous catalysis. P VtC XES is sensitive to subtle changes in electronic structure, with difference spectra that are well reproduced by density functional theory DFT calculations, indicating that DFT can not only provide insight into the physical origins of spectral features but can also facilitate the identification of unknown species. Comparison to Ni VtC XES, as well as previously published X ray absorption data, establishes the high resolution and complementary benefits of the technique. The potential of P VtC XES as a metal and spin agnostic tool for experimentally assessing electronic structure and mechanisms in phosphine coordinated catalysts is highlighte
Nanoscale domain wall dynamics in micromagnetic structures with weak perpendicular anisotropy
No full textTime resolved pump probe soft x ray ptychography and scanning transmission x ray microscopy were employed to study the magnetic domain wall dynamics in microstructures of permalloy Ni81 amp; 8290;Fe19; Py with a weak growth induced perpendicular magnetic anisotropy. The x ray magnetic circular dichroism images of a micrometer sized Py square 160 nm thickness and an elliptical disk 80 nm thickness show flux closure patterns with domain walls that fall into alternating out of plane OOP magnetization states precipitated by the perpendicular anisotropy, which is a precursor of the nucleation of stripe domains at higher thicknesses. An oscillating magnetic field at frequencies from tens of MHz to GHz and up to 4 mT magnitude excited dynamic modes in the domain walls along with the vortex core gyration. The domain wall dynamics include the translation of inversion points of the OOP magnetization and nucleation of one dimensional spin wave