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We investigate the kinetics of elemental segregation during the synthesis of Cu(In1−x,Gax)Se2 (CIGS) thin films via a rapid thermal growth process. Changes in elemental concentration are mapped rapidly via in situ X-ray fluorescence (XRF) microscopy. In situ XRF enables the quantification of Cu, In, Ga, and Se concentrations with 200 nm spatial resolution over a region of 7 μm × 7 μm, large enough to map multiple CIGS grains. Reacting elemental precursor stacks at 500, 550, and 600 °C, we find that copper is the driving force for α-CIGS phase formation at a rate of 17 nmol/cm2/min at 500 °C. Because of the thermal expansion of the substrate, cluster analysis and classification algorithms were employed to track compositionally similar regions over time and across samples measured at different temperatures. Beyond the direct application of these results for the optimization of CIGS manufacturing, these in situ experiments demonstrate the feasibility of quantitative compositional evaluation at the nanoscale ...

Unveiling the correlation among electrical performance, elemental distribution, and defects at the microscale is crucial for the understanding and improvement of the overall solar cell performance. While this is true in general for solar cells with polycrystalline absorber layers, it is particularly critical for defect engineering of the complex quaternary CuIn $_x$ Ga $_{1-x}$ Se $_2$ (CIGS) material system. Studying these relationships under standard ambient conditions can provide important insights but does not provide input on the behavior of the cell under real operating conditions. In this contribution, we take a close look at the complex temperature dependence of defects and voltage in CIGS at the microscale. We have developed correlative X-ray microscopy methods and adapted them for temperature-dependent measurements of the locally generated voltage and elemental compositions at the microscale. We have applied these techniques to industrial CIGS solar cells covering temperatures from room temperature up to 100 $^\circ \text{C}$ . We find underperforming areas spanning multiple grains that do not correlate with the elemental distribution of major absorber constituents. However, we demonstrate that low-performing areas perform better at higher temperatures relative to the high-performing areas.

The lamination process of photovoltaic modules relies on the application of high temperatures and pressures, which inherently introduces different amounts of expansion and shrinkage of the individual layers including glass, solar cells, polymeric encapsulants, and backsheet. There is no doubt that these effects translate into the cell in the form of deflection and stresses. Thus far though, only the consequences of this have been tracked in terms of failure modes—microcracks, delamination, stress points, etc. The general approaches have been applied to optimize processes with a focus on encapsulant properties, such as degree of cross-linking, moisture permeability, and their long-term lifetime, overlooking their effect on the solar cells. Module reliability is a major driver to lower the levelized cost of electricity and the bankability of projects, and more effort needs to be placed in predictive failure analysis and the optimization of the module components from the point of view of the active components—the cells. In this paper, we propose an in-house X-ray based technique as a novel approach to assess the state of the solar cell under polymeric encapsulation inside a fully assembled module. This gives access for the first time not only to the evaluation of cracks and microdefects, but also to the cell deflection and stress distribution inside the encapsulation.

Background:. The recovery for patients after tendon repair is frequently limited by development of tendon adhesions. This scar tissue formation is dependent on immune system activation. Tacrolimus has unique properties that may contribute to the prevention of overactive scarring by inhibition of inflammatory cytokines. Methods:. Herein, we present a case using systemic immunosuppression to prevent recurrent adhesion accumulation in a patient with a prior spaghetti wrist injury. Tacrolimus began 1 week before repeat-secondary tenolysis surgery, and it continued for 3 months postoperative. Dosing was tapered to a serum level between 5 and 8 µg/L. Results:. The 27-year-old male patient suffered a volar wrist laceration transecting all flexor tendons and volar wrist nerves. He underwent immediate repair but had a poor outcome despite early range of motion therapy. A primary tenolysis only improved his average arc of finger motion from 72 to 95 degrees. Secondary tenolysis augmented with systemic tacrolimus improved his arc of finger motion from 95 to 202 degrees. Mechanistically, tacrolimus prevents proper function of activated T and B cells. This results in decreased proliferation, angiogenesis, and cytoskeletal organization of fibroblasts on inflammation and integrin adhesions, and it potentially explains the reduced tendon molecule adhesions seen in this patient. Conclusions:. Tacrolimus may be effective in reducing motion, limiting tendon adhesions. The novel use of this medication resulted in the return of near-normal hand function in a patient placed on low-dose tacrolimus after primary tenolysis had failed.

In situ and operando measurement techniques combined with nanoscale resolution have proven invaluable in multiple fields of study. We argue that evaluating device performance as well as material behavior by correlative X-ray microscopy with

Statistical and correlative analysis are increasingly important in the design and study of new materials, from semiconductors to metals. Non-destructive measurement techniques, with high spatial resolution, capable of correlating composition and/or structure with device properties, are few and far between. For the case of polycrystalline and inhomogeneous materials, the added challenge is that nanoscale resolution is in general not compatible with the large sampling areas necessary to have a statistical representation of the specimen under study. For the study of grain cores and grain boundaries in polycrystalline solar absorbers this is of particular importance since their dissimilar behavior and variability throughout the samples makes it difficult to draw conclusions and ultimately optimize the material. In this study, we present a nanoscale in-operando approach based on the multimodal utilization of synchrotron nano x-ray fluorescence and x-ray beam induced current collected for grain core and grain boundary areas and correlated pixel-by-pixel in fully operational Cu ( In ( 1 − x ) Ga x ) Se 2 solar cells. We observe that low gallium cells have grain boundaries that over perform compared to the grain cores and high gallium cells have boundaries that under perform. These results demonstrate how nanoscale correlative X-ray microscopy can guide research pathways towards grain engineering low cost, high efficiency solar cells.

Metal impurities are known to hinder the performance of commercial Si-based solar cells by inducing bulk recombination, increasing leakage current, and causing direct shunting. Recently, a set of photoluminescence (PL) images of neighboring multicrystalline silicon wafers taken from a cell production line at different processing stages has been acquired. Both band-to-band PL and sub-bandgap PL (subPL) images showed various regions with different PL signal intensity. Interestingly, in several of these regions a reversal of the subPL intensity was observed right after the deposition of the antireflective coating. In this paper, we present the results of the synchrotron-based nano-X-ray fluorescence imaging performed in areas characterized by the subPL reversal to evaluate the possible role of metal decoration in this uncommon behavior. Furthermore, the acquisition of a statistically meaningful set of data for samples taken at different stages of the solar cell manufacturing allows us to shine a light on the precipitation and rediffusion mechanisms of metal impurities at these grain boundaries.

Nano-X-ray fluorescence microscopy is used to correlate elemental inhomogeneity to device performance measured through X-ray beam induced current (XBIC). Unsupervised machine learning techniques can be useful in the processing and correlation of XRF/XBIC data. A case study using CuInSe 2 solar cells treated with Ag-alloying and KF-post- deposition treatment (PDT) is presented. The implementation of K-means clustering is studied for its ability to identify statistically meaningful results from XRF/XBIC data. The procedure described may be applied to datasets of a similar nature.

Diverse sociocultural influences in rapidly growing dense urban areas may induce strain on civil services and reduce the resilience of those areas to exogenous and endogenous shocks. We present a novel approach with foundations in computer and social sciences, to estimate the resilience of dense urban areas at finer spatiotemporal scales compared to the state-of-the-art. We fuse multi-modal data sources to estimate resilience indicators from social science theory and leverage a structured ontology for factor combinations to enhance explainability. Estimates of destabilizing areas can improve the decision-making capabilities of civil governments by identifying critical areas needing increased social services.

JPhys energy 2(2), 025001 (Tbd). doi:10.1088/2515-7655/ab5fa6, The efficiency of thin-film solar cells with a CuIn1-xGaxSe2 absorber is limited by nanoscopic inhomogeneities and defects. Traditional characterization methods are challenged by the multi-scale evaluation of the performance at defects that are buried in the device structures. Multi-modal X-ray microscopy offers a unique tool-set to probe the performance in fully assembled solar cells, and to correlate the performance with composition down to the micro- and nanoscale. We applied this approach to the mapping of temperature-dependent recombination for CuIn1-xGaxSe2 solar cells with different absorber grain sizes, evaluating the same areas from room temperature to 100 C. It was found that poor performing areas in the large-grain sample are correlated with a Cu-deficient phase, whereas defects in the small-grain sample are not correlated with the distribution of Cu. In both samples, classes of recombination sites were identified, where defects were activated or annihilated by temperature. More generally, the methodology of combined operando and in-situ X-ray microscopy was established at the physical limit of spatial resolution given by the device itself. As proof-of-principle, the measurement of nanoscopic current generation in a solar cell is demonstrated with applied bias voltage and bias light., Published by IOP Publishing, Bristol

The quantification of X-ray fluorescence (XRF) microscopy maps by fitting the raw spectra to a known standard is crucial for evaluating chemical composition and elemental distribution within a material. Synchrotron-based XRF has become an integral characterization technique for a variety of research topics, particularly due to its non-destructive nature and its high sensitivity. Today, synchrotrons can acquire fluorescence data at spatial resolutions well below a micron, allowing for the evaluation of compositional variations at the nanoscale. Through proper quantification, it is then possible to obtain an in-depth, high-resolution understanding of elemental segregation, stoichiometric relationships, and clustering behavior. This article explains how to use the MAPS fitting software developed by Argonne National Laboratory for the quantification of full 2-D XRF maps. We use as an example results from a Cu(In,Ga)Se(2) solar cell, taken at the Advanced Photon Source beamline 2-ID-D at Argonne National Laboratory. We show the standard procedure for fitting raw data, demonstrate how to evaluate the quality of a fit and present the typical outputs generated by the program. In addition, we discuss in this manuscript certain software limitations and offer suggestions for how to further correct the data to be numerically accurate and representative of spatially resolved, elemental concentrations.

X-Ray Microscopy 2018, Saskatoon, Canada, 19 Aug 2018 - 24 Aug 2018; Microscopy and microanalysis 24(S2), 434 - 435 (2018). doi:10.1017/S1431927618014423, Published by Cambridge University Press

The efficiency of solar cells with a polycrystalline absorber is typically limited by grain boundaries. Many questions need to be answered such as: which roles do elemental and structural inhomogeneities play with respect to electrical performance? By which mechanisms does degradation occur and how can it be mitigated? The answers to these questions lie at the nanoscale. Ideally, we would measure performance, composition, and structure in-situ and operando all at once. Correlative, synchrotron-based X-ray microscopy offers a step in this direction. Here, we present a novel technique, X-ray beam induced voltage (XBIV) measurements, which complements the set of X-ray microscopy techniques. Combining the penetration depth of visible-light microscopy with the spatial resolution of electron-beam methods, XBIV measurements shine light on recombination and absorber-layer bandgap variations at nanoscale resolution. We give experimental details and discuss the use of lock-in amplification based on first applications of XBIV measurements to $\text{CuIn}_{x} \text{Ga}_{1}-x\text{Se}_{2}$ solar cells.

Correlative microscopy techniques have improved tremendously in the last 5 years and enabled simultaneous high spatial resolution mapping of a variety of material parameters. As acquisition speeds and resolution increase giving us a greater density of data points and the functionality of the measurements add more dimensions to be analyzed; the handling, management and analysis of data sets becomes more and more complicated. Operando measurements as well as in-situ studies pose a new challenge. Finding correlations in the 3+ dimensional data sets that result from many of these measurements is not straight forward, and the possibility of missing correlations and trends is increasingly concerning. In the following, we evaluate the potential of two machine-learning methods, an unsupervised Gaussian-Mixture-Model and a supervised Naive Bayes model, to identify two groups of pixels in a micro-X-ray fluorescence map, given varied Innnt data sizes.

It is well known that the addition of alkali elements such as Na and K during and after growth of Cu(In, Ga)Se 2 (CIGS) has beneficial effects on the electronic properties of bulk material, improving device performance significantly. While the device level effects have been measured and reported, a direct observations of the localization of Na including its chemical nature are missing, and the impact of Na on elemental and phase segregation during CIGS growth is not fully understood. We investigate these aspects to shine light on the role of Na in CIGS solar cells with the ultimate goal of increasing their conversion efficiency. Utilizing a suite of synchrotron based x-ray characterization techniques, we discuss the challenges and advantages of these techniques for investigating segregation of main constituents of CIGS, Na distribution, chemical bonding of Na, and collection efficiency in CIGS as well as their correlations.

Solar panel's reliability studies focus mainly on the properties of the encapsulating such as gel content and transmittance, while ignoring the impact of encapsulation process on the solar cells themselves. The harsh lamination conditions apply high temperature and pressure on the wafers, which can induce increased stress, deformation and defects. The investigation of solar cells sealed inside modules calls for a non-destructive method. In this paper, we demonstrate that transmission X-ray topography (XRT) can be used as an accurate method to evaluate bending feature of encapsulated wafers and present in detail the experimental methods from capturing diffraction data to the data analysis.

In-situ investigations of Cu(In, Ga)(S, Se) 2 (CIGS) absorber layers during growth have the potential to provide insight into the origin behind elemental segregation and defect formation at grain boundaries and in grain cores. Our study focuses on CIGS films grown by an industrially relevant precursor reaction process. An in-situ stage developed for these synchrotron studies is used to image the growth of CIGS layers with nanoscale resolution. Utilizing synchrotron based x-ray fluorescence, we are able to rapidly monitor changes in elemental distribution and particle diffusion, with better than 200 nm spatial resolution throughout the 25 minute process. In this work, we highlight some challenges associated with this type of measurements and discuss solutions identified to overcome them.

Unveiling the correlation between elemental composition, fermi-level splitting, and charge collection in perovskite solar cells (PSCs) exposed to different environments is crucial to understanding the origin of defects. This will enable defect engineering to achieve high performing and long lasting perovskite solar cells. In this contribution we measured for the first time the spatial distribution and charge collection efficiency at the nano-scale by synchrotron-based x-ray fluorescence (XRF) and x-ray beam induced current (XBIC) with sub-grain resolution, and we observe a correlation between Pb/I ratio and charge collection efficiency. In contrast to other thin-film solar cells, perovskite solar cells are highly sensitive to ambient conditions (atmosphere and illumination). As the XRF and XBIC measurements were conducted in vacuum under an x-ray source illumination, the impact of measurement conditions on the measurements need to be taken into account. Furthermore, necessary conditions for quantification of XRF/XBIC measurements are not fulfilled for perovskite solar cells. Therefore, we will discuss fundamentals of XRF/XBIC measurements of perovskite solar cells that will enable reliable quantitative, high-resolution measurements of elemental distribution and charge collection.

Hydrogen-doped indium oxide (IO:H) has recently garnered attention as a high-performance transparent conducting oxide (TCO) and has been incorporated into a wide array of photovoltaic devices due to its high electron mobility (>100 cm2/V s) and transparency (>90% in the visible range). Here, we demonstrate IO:H thin-films deposited by sputtering with mobilities in the wide range of 10–100 cm2/V s and carrier densities of 4 × 1018 cm–3–4.5 × 1020 cm–3 with a large range of hydrogen incorporation. We use the temperature-dependent Hall mobility from 5 to 300 K to determine the limiting electron scattering mechanisms for each film and identify the temperature ranges over which these remain significant. We find that at high hydrogen concentrations, the grain size is reduced, causing the onset of grain boundary scattering. At lower hydrogen concentrations, a combination of ionized impurity and polar optical phonon scattering limits mobility. We find that the influence of ionized impurity scattering is reduced with the increasing hydrogen content, allowing a maximization of mobility >100 cm2/V s at moderate hydrogen incorporation amounts prior to the onset of grain boundary scattering. By investigating the parameter space of the hydrogen content, temperature, and grain size, we define the three distinct regions in which the grain boundary, ionized impurity, and polar optical phonon scattering operate in this high mobility TCO. Published version

In situ characterization of micro- and nanoscale defects in polycrystalline thin-film materials is required to elucidate the physics governing defect formation and evolution during photovoltaic device fabrication and operation. X-ray fluorescence spectromicroscopy is particularly well-suited to study defects in compound semiconductors, as it has a large information depth appropriate to study thick and complex materials, is sensitive to trace amounts of atomic species, and provides quantitative elemental information, non-destructively. Current in situ methods using this technique typically require extensive sample preparation. In this work, we design and build an in situ temperature stage to study defect kinetics in thin-film solar cells under actual processing conditions, requiring minimal sample preparation. Careful selection of construction materials also enables controlled non-oxidizing atmospheres inside the sample chamber such as H2Se and H2S. Temperature ramp rates of up to 300 °C/min are achieved, with a maximum sample temperature of 600 °C. As a case study, we use the stage for synchrotron X-ray fluorescence spectromicroscopy of CuIn(x)Ga(1-x)Se2 (CIGS) thin-films and demonstrate predictable sample thermal drift for temperatures 25-400 °C, allowing features on the order of the resolution of the measurement technique (125 nm) to be tracked while heating. The stage enables previously unattainable in situ studies of nanoscale defect kinetics under industrially relevant processing conditions, allowing a deeper understanding of the relationship between material processing parameters, materials properties, and device performance.

The study of a multilayered and multicomponent system by spatially resolved X-ray fluorescence microscopy poses unique challenges in achieving accurate quantification of elemental distributions. This is particularly true for the quantification of materials with high X-ray attenuation coefficients, depth-dependent composition variations and thickness variations. A widely applicable procedure for use after spectrum fitting and quantification is described. This procedure corrects the elemental distribution from the measured fluorescence signal, taking into account attenuation of the incident beam and generated fluorescence from multiple layers, and accounts for sample thickness variations. Deriving from Beer–Lambert's law, formulae are presented in a general integral form and numerically applicable framework. The procedure is applied using experimental data from a solar cell with a Cu(In,Ga)Se2 absorber layer, measured at two separate synchrotron beamlines with varied measurement geometries. This example shows the importance of these corrections in real material systems, which can change the interpretation of the measured distributions dramatically.

We present the latest developments in the characterization of thin-film solar cells based on the combination of elemental mapping from fluorescence measurements using synchrotron x-rays, with beam induced current from electron and x-ray beams. This is a powerful method to directly correlate compositional variations with charge collection efficiency. We compare different approaches for mapping solar cells both in cross-section and in plan view on CIGS and CdTe solar cells. Based on examples from our latest research, we discuss the experimental approaches and highlight the advantages and limitations of each technique. Finally, we present an outlook to experiments that will allow x-ray based characterization to enter new fields of research that were not accessible before.

Cu(In,Ga)Se 2 (CIGS) solar cells were characterized in cross section using electron beam induced current (EBIC) and synchrotron based x-ray fluorescence (XRF) measurements. Samples with varying gallium ratios and growth methods were compared. A correlation was observed between the compositional gallium grading profile from XRF and carrier activity seen in EBIC through the thickness of the CIGS layer. Samples with steep back grading showed carrier activity isolated near the CIGS/CdS interface, whereas a more uniform grading resulted in carrier activity seen throughout the absorber layer. ‘Notch’ grading showed only slight variation in EBIC profile compared to a back graded sample with similar gallium ratios.

The purpose of this study was to determine if ondansetron is more effective in the prevention of PONV when administered prior to induction versus prior to emergence from general endotracheal anesthesia. This was a prospective, randomized, double-blind study of ASA I-Ill patients. Group I received ondansetron at induction (n = 75) and Group II received ondansetron at emergence (n = 75). A general anesthesia protocol was followed and data was collected in the recovery room and at 24 hours. Group I had a 28.1 % incidence of nausea in the PACU and 1.2 hours of nausea for the 24 hours post emergence, while Group II had a 23.4% incidence in the PACU and 1.5 hours respectively. Vomiting in the PACU for the Group I was 4.8 % and 25% at 24 hours post emergence. Group II had a 1.6% incidence of vomiting in the PACU and 14 % at 24 hours. No significant difference was found between these two groups of mostly of female patients. When ondansetron 4 mg IV is administered at induction or emergence from general endotracheal anesthesia, patients experience a similar incidence of PONV in the recovery room and up to 24 hours post emergence.

Entry-level characteristics of teacher candidates who satisfied higher program admission standards were compared with those of candidates who did not. The authors found that those who met the standards scored higher on most, but not all, measures of achievement. The two groups expressed similar educational beliefs and levels of commitment to teaching.

The journal of physical chemistry / C 124(33), 17949 - 17956 (2020). doi:10.1021/acs.jpcc.0c04645, Synchrotron micro- and nanoprobe beamlines have demonstrated great potential to advance photovoltaic devices. Most importantly, their small X-ray spot size has enabled the direct correlation of electrical performance with elemental composition at subgrain resolution for a variety of polycrystalline solar cells. Whereas the bulk of most inorganic semiconductors is stable under the high X-ray flux of focused X-ray beams, semiconductors with organic components are prone to a variety of degradation mechanisms. This is particularly critical to evaluate for the emerging organometal halide perovskite solar cells. Here, we investigate the effects of hard X-rays on the nanoscale performance and elemental distribution of these solar cells. We show that their composition does not change during common operando and in situ measurements at synchrotron nanoprobes. However, we found a significant X-ray-induced electronic degradation of solar cells with methylammonium lead iodide absorbers. Time- and dose-dependent measurements unveiled two characteristic degradation time constants on the order of 12 and 200 s that are independent of the X-ray flux. On the basis of heat and dose simulations, we attribute the fast decay to the dose-driven creation of recombination centers, while the slow decay is compatible with the observation of compositional changes. Finally, we detail how degradation-induced measurement artifacts can be outrun and showcase the high correlation of the X-ray-beam-induced current with the iodine and lead distribution., Published by Soc., Washington, DC

Unveiling the correlation between elemental composition, Fermi-level splitting, and charge collection in perovskite solar cells (PSCs) when exposed to different environments is crucial to understanding the origin of defects. This will enable defect engineering to achieve high-performance and long-lasting PSCs. In this paper, we measured, for the first time, the spatial distribution and charge-collection efficiency at the nanoscale by synchrotron-based X-ray fluorescence (XRF) and X-ray beam-induced current (XBIC) with subgrain resolution, and we observe a correlation between Pb/I ratio and charge-collection efficiency. In contrast with other thin-film solar cells, PSCs are highly sensitive to ambient conditions (atmosphere and illumination). As the XRF and XBIC measurements were conducted in vacuum under an X-ray source illumination, the impact of measurement conditions on the cells needs to be taken into account. Furthermore, necessary conditions for quantification of XRF/XBIC measurements, such as film homogeneity, are not fulfilled in the case of PSCs. Therefore, we will discuss fundamentals of XRF/XBIC measurements of PSCs that will enable reliable, quantitative, high-resolution measurements of elemental distribution and charge collection.

Understanding the electron scattering mechanisms dominating transport in high and low mobility transparent conducting oxides can provide insight into improving the properties of this crucial photovoltaic device layer. Contributions from ionized impurity scattering, phonon scattering, and grain boundary scattering were measured and quantified in hydrogenated indium oxide thin films, which had varying composition and grain size, resulting in a wide range of carrier densities $(\sim 10^{1S}\mathrm {c}\mathrm {m}^{-3}-\sim 10^{20}\mathrm {c}\mathrm {m}^{-3})$ and carrier mobilities $(\sim 10 \mathrm {c}\mathrm {m}^{2}/\mathrm {V}\mathrm {s} - \gt100 \mathrm {c}\mathrm {m}^{2}/\mathrm {V}\mathrm {s})$. We used temperature-dependent Hall measurements from 5–300 Kelvin to characterize electrical properties of the sputtered films. Grain boundary scattering dominated films with the lowest mobility, whereas films with $\gt100 \mathrm {c}\mathrm {m}^{2}/\mathrm {V}\mathrm {s}$ mobilities were dominated by contributions from ionized impurity scattering and polar optical phonon scattering.