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Non invasive characterization of the manufacturing process of a Nuragic bronze statuette a Neutron Imaging study
Get PDFThe Nuragic civilization Sardinia, Italy, XVIII VIII Cen. B.C developed a flourishing bronze metallurgy. The production of Nuragic bronze figurines from Sardinia represents a rich historical archive that provides key information about the iconography, the metal production and casting techniques, and on the development of metallurgy in the Mediterranean basin. Since the question about their manufacturing method remains without definitive answer, the understanding of the Sardinian bronze metallurgy is essential to determine which manufacturing techniques were employed to produce complex bronze artefacts. In the frame of a wider research project relating to Nuragic bronzes, four artefacts, three anthropomorphic statuettes a warrior, a priestess, and an offering figure , and one miniature of a basket, were made available by Museo Nazionale Preistorico L. Pigorini Roma, IT . In this work we present the results of the analyses conducted on a bronze figurine depicting an iconic type of Nuragic figure the Priestess. The analysis was performed using White Beam Neutron Tomography NT and Bragg Edge Neutron Transmission BENT at the Paul Scherrer Institut PSI Villigen, CH . Neutron techniques are nowadays the only available approach for revealing, non destructively and with good spatial resolution, the morphological and microstructural properties within the whole volume of solid cast metallic artefacts such as this bronze statuette. This work presents the result of a non invasive analytical investigation on an archaeological bronze artefact, providing outstanding results from a quantitative analysis of the composition to an in depth morphological and microstructural analysis capable of unveiling details on the ancient casting methods of the statuett
Switchable topological polar states in epitaxial BaTiO3 nanoislands on silicon
Get PDFA fascinating aspect of nanoscale ferroelectric materials is the emergence of topological polar textures, which include various complex and stable polarization configurations. The manipulation of such topological textures through external stimuli like electric fields holds promise for advanced nanoelectronics applications. There are, however, several challenges to reach potential applications, among which reliably creating and controlling these textures at the nanoscale on silicon, and with lead free compounds. We report the realization of epitaxial BaTiO3 nanoislands on silicon, with a lateral size as small as 30 60 amp; 8201;nm, and demonstrate stable center down convergent polarization domains that can be reversibly switched by an electric field to center up divergent domains. Piezoresponse force microscopy data reconstruction and phase field modeling give insight into the 3D patterns. The trapezoidal shape nanoislands give rise to center down convergent lateral swirling polarization component with respect to the nanoisland axis, which prevents the formation of bound charges on the side walls, therefore minimizing depolarization fields. The texture resembles a swirling vortex of liquid flowing into a narrowing funnel. Chirality emerges from the whirling polarization configurations. The ability to create and electrically manipulate chiral whirling polar textures in BaTiO3 nanostructures grown monolithically on silicon holds promise for applications in future topological nanoelectronic
Plasmonics Meets Perovskite Photovoltaics Innovations and Challenges in Boosting Efficiency
Get PDFPerovskite solar cells PSCs have garnered immense attention in recent years due to their outstanding optoelectronic properties and cost effective fabrication methods, establishing them as promising candidates for next generation photovoltaic technologies. Among the diverse strategies aimed at enhancing the power conversion efficiency PCE of PSCs, the incorporation of plasmonic nanoparticles has emerged as a pioneering approach. This review summarizes the latest research advancements in the utilization of plasmonic nanoparticles to enhance the performance of PSCs. We delve into the fundamental principles of plasmonic resonance and its interaction with perovskite materials, highlighting how localized surface plasmons can effectively broaden light absorption, facilitate hot electron transfer HET , and optimize charge separation dynamics. Recent strategies, including the design of tailored metal nanoparticles MNPs , gratings, and hybrid plasmonic photonic architectures, are critically evaluated for their efficacy in enhancing light trapping, increasing photocurrent, and mitigating charge recombination. Additionally, this review addresses the challenges associated with the integration of plasmonic elements into PSCs, including issues of scalability, compatibility, and cost effectiveness. Finally, the review provides insights into future research directions aimed at advancing the field, thereby paving the way for next generation, high performance perovskite based photovoltaic technologie
Probing Crystallinity and Grain Structure of 2D Materials and 2D Like Van der Waals Heterostructures by Low Voltage Electron Diffraction
Get PDF4D scanning transmission electron microscopy 4D STEM is a powerful method for characterizing electron transparent samples with down to sub ngstrom spatial resolution. 4D STEM can reveal local crystallinity, orientation, grain size, strain, and many more sample properties by rastering a convergent electron beam over a sample area and acquiring a transmission diffraction pattern DP at each scan position. These patterns are rich in information about the atomic structure of the probed volume, making this technique a potent tool to characterize even inhomogeneous samples. 4D STEM can also be used in scanning electron microscopes SEMs by placing an electron sensitive camera below the sample. 4D STEM in SEMs is ideally suited to characterize 2D materials and 2D like van der Waals heterostructures vdWH due to their inherent thickness of a few nanometers. The lower accelerating voltage of SEMs leads to strong scattering even from monolayers. The large field of view and down to sub nm spatial resolution of SEMs are ideal to map properties of the different constituents of 2D like vdWH by probing their combined sample volume. A unique 4D STEM in SEM system is applied to reveal the single crystallinity of MoS2 exfoliated with gold mediation as well as the crystal orientation and coverage of both components of a C60 MoS2 vdWH are determine
Optimization of Printed Large Area Perovskite Silicon Tandem Solar Cells by Understanding Its Loss Mechanisms
No full textOrganic inorganic hybrid perovskites with adjustable bandgap show promising potential as tandem top cells to pair with silicon bottom cells as they achieve power conversion efficiencies PCEs over 33 , while the fabrication costs are likely to stay low. To date, the most efficient perovskite layers are fabricated by spin coating, which is difficult to scale up to industrial wafer size, and the crystallization process remains difficult to control. In this work, Cs0.22FA0.78 Pb I0.85Br0.15 3 5 mol MAPbCl3 was reported on slot die coating for an efficient 1.68 eV wide bandgap triple halide 3halide absorber. A suitable solvent system was designed and optimized specifically for the slot die coating technique. This thesis demonstrated that with this recipe, our fabrication route enabled a bandgap of 1.68 eV, which was suitable for tandem solar cells, and without phase segregation typically observed into iodine rich and bromide rich phases. The slot die coated wet perovskite film was dried using a stream of nitrogen N2 from an N2 knife with high reproducibility, which avoided the need to use antisolvents. This thesis explored varying drying and annealing conditions from 100 C to 170 C and measured absolute as well as transient photoluminescence PL to extract information about the perovskite bandgap, quasi Fermi level splitting QFLS , and charge carrier lifetimes. This thesis found parameters allowing to crystallize the perovskite film into large grains reducing charge collection losses and thus enabling higher current density in solar cells. With annealing at 150 C, an optimized tradeoff was found between crystallization and the detrimental formation of PbI2 platelets on the film s top surface. In situ Grazing Incidence Wide Angle X ray Scattering GIWAXS investigation of the solution intermediate and film annealing at various stages unveiled the perovskite crystallization and PbI2 formation processes in comparison of two coating recipes spin coating recipe and slot die coating recipe and two quenching methods antisolvent and N2 quenching with the influence of annealing temperature. With the optimized annealing conditions, this work improved perovskite single junction cells cell stability and performance towards a stabilized power output of up to 19.4 0.16 cm2 . By integrating the optimized perovskite fabrication with commercial saw damage etched Czochralski silicon bottom cells, a two terminal monolithic tandem solar cell with a PCE of 25.2 on 1 cm2 active area was demonstrated with fully scalable processes fabricated on a 120 amp; 956;m thin wafer. The time resolved and wavelength resolved surface photovoltage SPV was utilized to understand the high fill factor and the charge extraction dynamics for perovskite interplaying with two types of silicon bottom cell concepts. Furthermore, a fully scalable 4 cm2 tandem solar cell was developed with screen printed silver front grids, yielding PCE up to 24 . For the solar cells, the loss mechanisms as well as guidelines are presented for further improving the printed films. Several strategies were attempted to control the PbI2 excess and improve the perovskite C60 interface with more suitable band alignment. Overall, this thesis emphasized the significant promise of slot die coating as a viable method for producing scalable and industrially relevant perovskite silicon tandem solar cell
Low Ti Additions to Stabilize Ru Ir Electrocatalysts for the Oxygen Evolution Reaction
Get PDFAnodic oxygen evolution reaction OER challenges large scale application of proton exchange membrane water electrolyzers PEMWE due to sluggish kinetics, high overpotential and extremely corrosive environment. While Ir oxides currently provide the best balance between activity and stability, the scarcity of Ir and corresponding high market price lead to poor cost benefit factors. Mixing Ir with more stable non precious Ti reduces the noble metal loading and may implicate stabilization, while addition of more catalytically active Ru ensures a high reaction rate. Here, we examine the activity stability behavior of Ru Ir Ti thin film material libraries with low Ti content under the OER conditions. The high sensitivity to the dissolution of the individual alloy components was achieved by using online and off line inductively coupled plasma mass spectrometry ICP MS analysis. Our data reveal that even low Ti additions improve the stability of Ru Ir catalysts without sacrificing activity. In particular, 5 amp; 8197;at. amp; 8201; of Ti enable stability increase of Ir in the Ru Ir catalyst by a factor of 3. Moreover, this catalyst exhibits higher activity compared to the Ti free Ru Ir alloys with similar Ir content. Observed activity stability trends are discussed in light of X ray photoelectron spectroscopy dat
Ground and excited state charge transfer at aqueous nanodiamonds
Get PDFNanodiamonds NDs are unique carbonaceous materials with exceptionally high stability, hardness, and notable electronic properties. Their applications in photocatalysis, biomedicine, and energy materials are usually carried out in aqueous environments, where they interact with aqueous adsorbates. Especially, electron density may rearrange from the diamond material toward oxidative adsorbates such as oxygen, which is known as charge transfer doping. In this article, we quantify the charge transfer doping for NDs with inhomogeneous surface coverings hydroxyl, fluorine, and amorphous carbon , as well as NDs doped with heteroatoms B, Si, N using hybrid density functional theory DFT calculations. The transfer doping magnitude is largely determined by the NDs highest occupied molecular orbital energies, which can in turn be modified by the surface covering and doping. However, local modifications of the ND structures do not have any local effects on the magnitude of the charge transfer. We furthermore analyze the impact of aqueous adsorbates on the excited states of an aqueous ND in the context of photocatalysis via time dependent DFT. Here, we find that the excited electrons are biased to move in the direction of the respective oxidative adsorbate. Surprisingly, we find that also unreactive species such as nitrous oxide may attract the excited electrons, which is probably due to the positive partial charge that is induced by the local N O solvation geometr
Biotoxicity of Halide Perovskites in Mice
Get PDFHalide perovskites are crystalline semiconductors with exceptional optoelectronic properties, rapidly developing toward large scale applications. Lead II Pb2 is the core element used to prepare halide perovskites. Pb2 can displace key 2 elements, including calcium, zinc and iron, that regulate vital physiological functions. Sn2 can replace Pb2 within the perovskite structure and, if accidentally dispersed in the environment, it readily oxidizes to Sn4 , which is compatible with physiological functions and thus potentially safe. The 3 salt bismuth III Bi3 is also potentially safe for the same reason and useful to prepare double perovskites. Here, this work studies the biotoxicity of Pb, Sn, and Bi perovskites in mice for the first time. This work analyses histopathology and growth of mice directly exposed to perovskites and investigate the development of their offspring generation. This study provides the screening of organs and key physiological functions targeted by perovskite exposure to design specific studies in mammalian
Charge Carrier Dynamics at Carbon Perovskite Interface Implications on Carbon Based HTM Free Solar Cell Stability
No full textCarbon based hole transport material HTM free perovskite solar cells CPSCs are an innovative device architecture that mitigates inherent challenges associated with record breaking perovskite solar cells PSCs , which rely on metal HTMs, including instability, manufacturing intricacy, and elevated costs. The photovoltaic efficiency and stability of CPSCs are profoundly influenced by the charge carrier dynamics at the interfaces. Herein, the charge carrier dynamics at the carbon C perovskite interface in CPSCs and its implications on photovoltaic performances and stability, an aspect that has received limited exploration thus far are probed, are investigated using transient surface photovoltage Tr SPV and transient photoluminescence measurements. The study reveals that the C electrode effectively acts as a selective barrier, impeding electrons while facilitating the extraction of holes at the C perovskite interface. This selective blocking mechanism holds significant implications for improving the performance and stability of CPSCs over HTM free PSCs with gold Au electrodes. The stability of CPSCs is evaluated by measuring shelf life, maximum power point tracking, Tr SPV, and X Ray diffraction measurements. By delving into these pivotal aspects, this work aims to contribute to the advancement and understanding of CPSCs for sustainable and efficient energy conversio
Springback effect of ambient pressure dried silica aerogels nanoscopic effects of silylation revealed by in situ synchrotron X ray scattering
No full textAmbient pressure drying APD allows for synthesizing aerogels without expensive and sophisticated equipment for achieving supercritical conditions. Since APD does not eliminate the capillary stress that is induced by the liquid vapour phase boundary, the shrinkage during drying needs to be prevented or reversed. The re expansion of the silylated silica gels during drying is commonly referred to as the springback effect SBE . The SBE is not only important for producing aerogels via APD, but is also a fascinating phenomenon, since it is accompanied by a significant volume change unusual for rigid ceramics. Synchrotron X ray scattering has proven to be especially effective for the investigation of the volume change of these fractal silica structures on different length scales. In this work, we follow the drying, shrinkage, and partial re expansion of various monolithic samples in situ to explore the occurrence of the SBE. For this purpose, various silylation agents, i.e., hexamethyldisilazane, trimethylchlorosilane, and triethylchlorosilane were used to investigate different shrinkage and re expansion behavior. A scattering model was used to extract additional information of the evolving primary particle size, correlation length, fractal dimension, and other intensity contributions of the silica network and the hexane. While the primary particles pointed towards a relaxation at near molecular size, they were likely not involved in the SBE. However, structures near the size of the correlation length could be essential for the occurrence of this phenomenon. These findings may lead to the origin of this interesting phenomenon, as well as a better understanding of the production of APD aerogel