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Br Induced Suppression of Low Temperature Phase Transitions in Mixed Cation Mixed Halide Perovskites
Get PDFMixed cation mixed halide lead perovskites have been shown to be excellent candidates for solar energy conversion. However, understanding the structural phases of these mixed ion perovskites across a wide range of operating temperatures, including very low temperatures for space applications, is crucial. In this study, we investigated the structure of formamidinium based CsyFA1 yPb BrxI1 x 3 using low temperature in situ synchrotron powder X ray diffraction. Our findings revealed that substituting the I anion with Br in mixed cation Cs,FA perovskites suppressed the phase transformation from tetragonal to orthorhombic at low temperatures. The addition of Br also prevented the formation of nonperovskite secondary phases. We gained fundamental insights into the structural behavior of these materials by creating a low temperature phase diagram for the compositional set of mixed cation mixed halides. understanding of the structural properties lays the groundwork for designing more robust and efficient energy materials capable of functioning under extreme temperature conditions, including space based solar energy conversio
Integration of multi junction absorbers and catalysts for efficient solar driven artificial leaf structures a physical and materials science perspective
Get PDFArtificial leaves could be the breakthrough technology to overcome the limitations of storage and mobility through the synthesis of chemical fuels from sunlight, which will be an essential component of a sustainable future energy system. However, the realization of efficient solar driven artificial leaf structures requires integrated specialized materials such as semiconductor absorbers, catalysts, interfacial passivation, and contact layers. To date, no competitive system has emerged due to a lack of scientific understanding, knowledge based design rules, and scalable engineering strategies. Herein, competitive artificial leaf devices for water splitting, focusing on multiabsorber structures to achieve solar to hydrogen conversion efficiencies exceeding 15 , are discussed. A key challenge is integrating photovoltaic and electrochemical functionalities in a single device. Additionally, optimal electrocatalysts for intermittent operation at photocurrent densities of 10 20 mA cm2 must be immobilized on the absorbers with specifically designed interfacial passivation and contact layers, so called buried junctions. This minimizes voltage and current losses and prevents corrosive side reactions. Key challenges include understanding elementary steps, identifying suitable materials, and developing synthesis and processing techniques for all integrated components. This is crucial for efficient, robust, and scalable devices. Herein, corresponding research efforts to produce green hydrogen with unassisted solar driven photo electrochemical devices are discussed and reporte
Reactivity of graphene supported Co clusters
No full textGraphene supported Co clusters were investigated by high resolution XPS, TPD and IRRAS using CO as a probe molecule. CO adsorption was observed at edge, on top and bridge hollow sites on the as prepared clusters. Temperature programmed XPS showed CO dissociation at T gt; 300 K. The CO desorption temperatures were determined by TPD measurements to be 260, 320 and 400 K for CObridge hollow, COedge and COtop, respectively. The CO dissociation products were used to investigate the adsorption of CO on carbon and oxygen precovered Co clusters. Site blocking by these adatoms was found resulting in the absence of COedge XPS and TPD and a decrease of the CO adsorption capacity XPS, TPD and IRRAS . Additionally, no CO dissociation was found on the precovered clusters concluding a blocking of the catalytically active sites which are the edge sites of the cluster
Traceable characterization of hollow organosilica beads as potential reference materials for extracellular vesicle measurements with optical techniques
No full textThe concentration of cell type specific extracellular vesicles EVs is a promising biomarker for various diseases. However, concentrations of EVs measured by optical techniques such as flow cytometry FCM or particle tracking analysis PTA in clinical practice are incomparable. To allow reliable and comparable concentration measurements suitable reference materials RMs and SI traceable SI International system of units methods are required. Hollow organosilica beads HOBs are promising RM candidates for concentration measurements of EVs based on light scattering, as the shape, low refractive index, and number concentration of HOBs are comparable to EVs of the respective size range that can be detected with current optical instrumentation. Here, we present traceable methods for measuring the particle size distribution of four HOB types in the size range between 200 and 500 nm by small angle X ray scattering SAXS and atomic force microscopy AFM , as well as the number concentration by single particle inductively coupled plasma mass spectrometry spICP MS . Based on the size and shape results, traceable reference values were obtained to additionally determine the refractive index of the shell of the HOB samples by FCM. Furthermore, the estimated refractive indexes of the HOBs plausibly agree with the refractive indexes of EVs of corresponding size. Due to their narrow size distribution and their similar shape, and low refractive index, all HOB samples studied are suitable RM candidates for calibration of the measured sample volume by optical methods within the photon wavelength range used, and thus for calibration of number concentration measurements of EVs in the size range indicated. This was confirmed as the number concentration values obtained by PTA and two independent flow cytometric measurements agreed with the concentration reference values obtained by two independent spICP MS measurements within the calculated uncertainty limit
Characterization of silicon pore optics for the NewAthena X ray observatory in the PTB laboratory at BESSY II
No full textThe New Advanced Telescope for High ENergy Astrophysics NewAthena will be the largest space based X ray observatory ever built. It will have an effective area above 1.1 amp; 8197;m2 at 1 amp; 8197;keV, which corresponds to a polished mirror surface of about 300 amp; 8197;m2 due to the grazing incidence. As such a mirror area is not achievable with an acceptable mass even with nested shells, silicon pore optics SPO technology will be utilized. In the PTB laboratory at BESSY II, two dedicated beamlines are in use for their characterization with monochromatic radiation at 1 amp; 8197;keV and a low divergence well below 2 amp; 8197;arcsec the X ray Pencil Beam Facility XPBF 1 and the X ray Parallel Beam Facility XPBF 2.0 , where beam sizes up to 8 amp; 8197;mm 8 amp; 8197;mm are available while maintaining low beam divergence. This beamline is used for characterizing mirror stacks and controlling the focusing properties of mirror modules MMs consisting of four mirror stacks during their assembly at the beamline. A movable CCD based camera system 12 amp; 8197;m from the MM registers the direct and the reflected beams. The positioning of the detector is verified by a laser tracker. The energy dependent reflectance in double reflection through the pores of an MM with an Ir coating was measured at the PTB four crystal monochromator beamline in the photon energy range 1.75 amp; 8197;keV to 10 amp; 8197;keV, revealing the effects of the Ir M edges. The measured reflectance properties are in agreement with the design values to achieve the envisaged effective are
Ion induced field screening as a dominant factor in perovskite solar cell operational stability
Get PDFThe presence of mobile ions in metal halide perovskites has been shown to adversely affect the intrinsic stability of perovskite solar cells PSCs . However, the actual contribution of mobile ions to the total degradation loss compared with other factors such as trap assisted recombination remains poorly understood. Here we reveal that mobile ion induced internal field screening is the dominant factor in the degradation of PSCs under operational conditions. The increased field screening leads to a decrease in the steady state efficiency, often owing to a large reduction in the current density. Instead, the efficiency at high scan speeds gt;1,000 amp; 8201;V amp; 8201;s amp; 8722;1 , where the ions are immobilized, is much less affected. We also show that the bulk and interface quality do not degrade upon ageing, yet the open circuit voltage decreases owing to an increase in the mobile ion density. This work reveals the importance of ionic losses for intrinsic PSC degradation before chemical or extrinsic mechanical effects manifes
Rational designing and prospecting iron based compounds as efficient host materials for lithium sulfur batteries
Get PDFKnown for its high theoretical capacity and low cost, the commercialization of Li S batteries is hindered by the notorious shuttle behavior of the intermediate lithium polysulfides in liquid electrolyte and the sluggish kinetics of the liquid to solid reaction. Recently, to improve the electrochemical performance, iron based compounds with well designed nano structures have been developed and applied as host material for sulfur because they have strong chemisorption of polar polysulfide molecules and could reduce the nucleation energy of solid Li2S. 2 S. Here, we have reviewed the latest research progresses in the last three years of various iron based compounds as sulfur host materials and prospected the designing principles of efficient host materials with multiple functionalities to address the issues in sulfur cathod
Automated screening of precipitation polymerizations and evaluation using image recognition for divinylbenzene and methacrylic acid
Get PDFBy applying automated high throughput experimentation, 63 precipitation polymerizations of divinylbenzene and methacrylic acid were performed with a total of 1638 samples analyzed by gas chromatography GC , nuclear magnetic resonance NMR spectroscopy, and scanning electron microscopy SEM . The conversion of each reaction was investigated revealing the best substrate concentrations within the current setup. The GC evaluation was performed automatically via a new custom made Python script significantly reducing the time to evaluate the results. Furthermore, the particle growth was monitored by utilizing an innovative image recognition tool to identify particles and their respective sizes using SEM images. Furthermore, a statistical particle size distribution analysis was performed, which is hardly achievable in reasonable time by classical evaluation methods. Using this new procedure, the highest conversion 70 as well as the largest particles 3700 nm have been obtained utilizing a high initial monomer 5 vol and initiator 5 mol concentration. Accordingly, the smallest particles 245 nm yielded from the lowest starting concentration 1 vol monomer and 1 mol initiato
A Review Application of Doped Hydrogenated Nanocrystalline Silicon Oxide in High Efficiency Solar Cell Devices
Get PDFDue to the unique microstructure of hydrogenated nanocrystalline silicon oxide nc SiOx H , the optoelectronic properties of this material can be tuned over a wide range, which makes it adaptable to di amp; 64256;erent solar cell applications. In this work, the authors review the material properties of nc SiO x H and the versatility of its applications in di amp; 64256;erent types of solar cells. The review starts by introducing the growth principle of doped nc SiO x H layers, the e amp; 64256;ect of oxygen content on the material properties, and the relationship between optoelectronic properties and its microstructure. A theoretical analysis of charge carrier transport mechanisms in silicon heterojunction SHJ solar cells with wide band gap layers is then presented. Afterwards, the authors focus on the recent developments in the implementation of nc SiOx H and hydrogenated amorphous silicon oxide a SiO x H amp; 64257;lms for SHJ, passivating contacts, and perovskite silicon tandem device
Optimizing ionic transport in argyrodites a unified view on the role of sulfur halide distribution and local environments
Get PDFUnderstanding diffusion mechanisms in solid electrolytes is crucial for advancing solid state battery technologies. This study investigates the role of structural disorder in Li7 amp; 8722;xPS6 amp; 8722;xBrx argyrodites using ab initio molecular dynamics, focusing on the correlation between key structural descriptors and Li ion conductivity. Commonly suggested parameters, such as configurational entropy, bromide site occupancy, and bromine content, correlate with Li ion diffusivity but do not consistently explain conductivity trends. We find that a uniform distribution of bromine and sulfur ions across the 4a and 4d sublattices is critical for achieving high conductivity by facilitating optimal lithium jump activation energies, anion lithium distances, and charge distribution. Additionally, we introduce the ionic potential as a simple descriptor that predicts argyrodite conductivity by assessing the interaction strength between cations and anions. By analyzing the correlation between ionic potential and conductivity for a range of argyrodite compositions published over the past decade, we demonstrate its broad applicability. Minimizing and equalizing ionic potentials across both sublattices enhances conductivity by reducing the strength of anion lithium interactions. Our analysis of local environments coordinating Li jumps reveals that balancing high and low energy pathways is crucial for enabling macroscopic diffusion, supported by investigating percolating pathways. This study highlights the significance of the anionic framework in lithium mobility and informs the design of solid electrolytes for improved energy storage systems