Modular slot-die coater for in situ grazing-incidence x-ray scattering experiments on thin films.

Multimodal in situ experiments during slot-die coating of thin films pioneer the way to kinetic studies on thin-film formation. They establish a powerful tool to understand and optimize the formation and properties of thin-film devices, e.g., solar cells, sensors, or LED films. Thin-film research benefits from time-resolved grazing-incidence wide- and small-angle x-ray scattering (GIWAXS/GISAXS) with a sub-second resolution to reveal the evolution of crystal structure, texture, and morphology during the deposition process. Simultaneously investigating optical properties by in situ photoluminescence measurements complements in-depth kinetic studies focusing on a comprehensive understanding of the triangular interdependency of processing, structure, and function for a roll-to-roll compatible, scalable thin-film deposition process. Here, we introduce a modular slot-die coater specially designed for in situ GIWAXS/GISAXS measurements and applicable to various ink systems. With a design for quick assembly, the slot-die coater permits the reproducible and comparable fabrication of thin films in the lab and at the synchrotron using the very same hardware components, as demonstrated in this work by experiments performed at Deutsches Elektronen-Synchrotron (DESY). Simultaneous to GIWAXS/GISAXS, photoluminescence measurements probe optoelectronic properties in situ during thin-film formation. An environmental chamber allows to control the atmosphere inside the coater. Modular construction and lightweight design make the coater mobile, easy to transport, quickly extendable, and adaptable to new beamline environments.

INSIGHT: in situ heuristic tool for the efficient reduction of grazing-incidence X-ray scattering data.

INSIGHT is a Python-based software tool for processing and reducing 2D grazing-incidence wide- and small-angle X-ray scattering (GIWAXS/GISAXS) data. It offers the geometric transformation of the 2D GIWAXS/GISAXS detector image to reciprocal space, including vectorized and parallelized pixel-wise intensity correction calculations. An explicit focus on efficient data management and batch processing enables full control of large time-resolved synchrotron and laboratory data sets for a detailed analysis of kinetic GIWAXS/GISAXS studies of thin films. It processes data acquired with arbitrarily rotated detectors and performs vertical, horizontal, azimuthal and radial cuts in reciprocal space. It further allows crystallographic indexing and GIWAXS pattern simulation, and provides various plotting and export functionalities. Customized scripting offers a one-step solution to reduce, process, analyze and export findings of large in situ and operando data sets.

A Practical Approach Toward Highly Reproducible and High-Quality Perovskite Films Based on an Aging Treatment.

Solution processing of hybrid perovskite semiconductors is a highly promising approach for the fabrication of cost-effective electronic and optoelectronic devices. However, challenges with this approach lie in overcoming the controllability of the perovskite film morphology and the reproducibility of device efficiencies. Here, a facile and practical aging treatment (AT) strategy is reported to modulate the perovskite crystal growth to produce sufficiently high-quality perovskite thin films with improved homogeneity and full-coverage morphology. The resulting AT-films exhibit fewer defects, faster charge carrier transfer/extraction, and suppressed non-radiative recombination compared with reference. The AT-devices achieve a noticeable improvement in the reproducibility, operational stability, and photovoltaic performance of devices, with the average efficiency increased by 16%. It also demonstrates the feasibility and scalability of AT strategy in optimizing the film morphology and device performance for other perovskite components including MAPbI3 , (MAPbBr3 )15 (FAPbI3 )85 , and Cs0.05 (MAPbBr3 )0.17 (FAPbI3 )0.83 . This method opens an effective avenue to improve the quality of perovskite films and photovoltaic devices in a scalable and reproducible manner.

Trace Water in Lead Iodide Affecting Perovskite Crystal Nucleation Limits the Performance of Perovskite Solar Cells.

The experimental replicability of highly efficient perovskite solar cells (PSCs) is a persistent challenge faced by laboratories worldwide. Although trace impurities in raw materials can impact the experimental reproducibility of high-performance PSCs, the in situ study of how trace impurities affect perovskite film growth is never investigated. Here, light is shed on the impact of inevitable water contamination in lead iodide (PbI2 ) on the replicability of device performance, mainly depending on the synthesis methods of PbI2 . Through synchrotron-based structure characterization, it is uncovered that even slight additions of water to PbI2 accelerate the crystallization process in the perovskite layer during annealing. However, this accelerated crystallization also results in an imbalance of charge-carrier mobilities, leading to a degradation in device performance and reduced longevity of the solar cells. It is also found that anhydrous PbI2 promotes a homogenous nucleation process and improves perovskite film growth. Finally, the PSCs achieve a remarkable certified power conversion efficiency of 24.3%. This breakthrough demonstrates the significance of understanding and precisely managing the water content in PbI2 to ensure the experimental replicability of high-efficiency PSCs.

Decoding the Self-Assembly Plasmonic Interface Structure in a PbS Colloidal Quantum Dot Solid for a Photodetector.

Hybrid plasmonic nanostructures have gained enormous attention in a variety of optoelectronic devices due to their surface plasmon resonance properties. Self-assembled hybrid metal/quantum dot (QD) architectures offer a means of coupling the properties of plasmonics and QDs to photodetectors, thereby modifying their functionality. The arrangement and localization of hybrid nanostructures have an impact on exciton trapping and light harvesting. Here, we present a hybrid structure consisting of self-assembled gold nanospheres (Au NSs) embedded in a solid matrix of PbS QDs for mapping the interface structures and the motion of charge carriers. Grazing-incidence small-angle X-ray scattering is utilized to analyze the localization and spacing of the Au NSs within the hybrid structure. Furthermore, by correlating the morphology of the Au NSs in the hybrid structure with the corresponding differences observed in the performance of photodetectors, we are able to determine the impact of interface charge carrier dynamics in the coupling structure. From the perspective of architecture, our study provides insights into the performance improvement of optoelectronic devices.

Diblock copolymer pattern protection by silver cluster reinforcement.

Pattern fabrication by self-assembly of diblock copolymers is of significant interest due to the simplicity in fabricating complex structures. In particular, polystyrene-block-poly-4-vinylpyridine (PS-b-P4VP) is a fascinating base material as it forms an ordered micellar structure on silicon surfaces. In this work, silver (Ag) is applied using direct current magnetron sputter deposition and high-power impulse magnetron sputter deposition on an ordered micellar PS-b-P4VP layer. The fabricated hybrid materials are structurally analyzed by field emission scanning electron microscopy, atomic force microscopy, and grazing incidence small angle X-ray scattering. When applying simple aqueous posttreatment, the pattern is stable and reinforced by Ag clusters, making micellar PS-b-P4VP ordered layers ideal candidates for lithography.

Investigating the thermal stability of ultra-small Ag, Au and AuAg alloy nanoparticles embedded in a silica matrix.

Thermal growth kinetics of embedded bimetallic (AuAg/SiO2) nanoparticles are explored and compared with their monometallic (Au/SiO2 and Ag/SiO2) counterparts, as their practical applicability demands stability and uniformity. The plasmonic properties of these nanoparticles (NPs) significantly improve when their size falls in the ultra-small region (diameter < 10 nm), owing to their large active surface area. Interestingly, the bimetallic NPs exhibit better optical properties and structural stability as compared to their monometallic counterparts. This calls for a thorough understanding of the nucleation and temperature-dependent growth to ensure size stability against thermal coarsening that most bimetallic NPs completely lack. Herein, the atom beam sputtered AuAg NPs are systematically analysed over a wide range of annealing temperatures (ATs), and the results are compared with those of Au and Ag NPs. The X-ray photoelectron spectroscopy spectra and other experimental results confirm the formation of AuAg alloy NPs inside the silica matrix. Furthermore, techniques like transmission electron microscopy and grazing-incidence small-/wide-angle X-ray scattering were used to explore the temperature-dependent structural and morphological stability of the NPs. Our results show that the deposited AuAg NPs retain their spherical shape and remain as an alloy for the entire range of ATs. When the AT increases from 25 °C to 800 °C, the size of the NPs also increases from 3.5 to 4.8 nm; beyond that, their size grows substantially to 13.6 nm at 900 °C. We observed that the NPs remain in the ultra-small size range (∼5 nm) until an AT of 800 °C. Beyond that Ostwald ripening is ascribed to be the major cause of particle growth, resulting in an active surface area loss. Based on the outcomes, a three-step nucleation and growth mechanism is proposed.

Effect of Molecular Organization on the Properties of Fractionated Lignin-Based Thiol-Ene Thermoset Materials.

In this study, the combination of sequential solvent fractionation of technical Kraft lignin was followed by allylation of most OH functionalities to give highly functional thermoset resins. All lignin fractions were highly functionalized on the phenolic (≥95%) and carboxylic acid OH (≥85%) and to a significant extent on the aliphatic OH moieties (between 43 and 75%). The resins were subsequently cross-linked using thiol-ene chemistry. The high amount of allyl functionalities resulted in a high cross-link density. Dynamic mechanical analysis measurements showed that the thioether content, directly related to the allyl content, strongly affects the performance of these thermosets with a glass transition temperature (Tg) between 81 and 95 °C and with a storage modulus between 1.9 and 3.8 GPa for all thermosets. The lignin fractions and lignin-based thermosets' morphology, at the nanoscale, was studied by wide-angle X-ray scattering measurements. Two π-π stacking interactions were observed: sandwich (≈4.1-4.7 Å) and T-shaped (≈5.5-7.2 Å). The introduction of allyl functionalities weakens the T-shaped π-π stacking interactions. A new signal corresponding to a distance of ≈3.5 Å was observed in lignin-based thermosets, which was attributed to a thioether organized structure. At the same time, a lignin superstructure was observed with a distance/size corresponding to 7.9-17.5 Å in all samples.

In Situ Study of Structure Formation under Stress in Stretchable Conducting Nanocomposites.

One of the major limitations of flexible sensors is the loss of conductivity upon multiple stretching and bending cycles. Conducting fillers with two different geometries, carbon black and carbon nanotubes, were introduced in polydimethylsiloxane (PDMS) for physical insights into the structure formation of nanofillers by the application of periodic tensile stress. The loading of the nanofillers was selected beyond the percolation threshold to determine the cyclic stability of the resulting network channels. The surface chemistry of carbon nanotubes has been varied to understand the interfacial interactions at the molecular length scale. The combination of in situ stretching, annealing, and vis-à-vis conductometry of nanocomposite films with synchrotron-based ultra-small angle X-ray scattering experiments enables us to highlight the importance of the fractal dimensions of nanofillers for the molecular level interactions. The irreversible formation of nanofiller network geometries under cyclic stress and annealing was found to be responsible for the electrical properties of a flexible conducting film.

Superlattice deformation in quantum dot films on flexible substrates via uniaxial strain.

The superlattice in a quantum dot (QD) film on a flexible substrate deformed by uniaxial strain shows a phase transition in unit cell symmetry. With increasing uniaxial strain, the QD superlattice unit cell changes from tetragonal to cubic to tetragonal phase as measured with in situ grazing-incidence small-angle X-ray scattering (GISAXS). The respective changes in the optoelectronic coupling are probed with photoluminescence (PL) measurements. The PL emission intensity follows the phase transition due to the resulting changing inter-dot distances. The changes in PL intensity accompany a redshift in the emission spectrum, which agrees with the Förster resonance energy transfer (FRET) theory. The results are essential for a fundamental understanding of the impact of strain on the performance of flexible devices based on QD films, such as wearable electronics and next-generation solar cells on flexible substrates.

3D Printable Hybrid Gel Made of Polymer Surface-Modified Cellulose Nanofibrils Prepared by Surface-Initiated Controlled Radical Polymerization (SI-SET-LRP) and Upconversion Luminescent Nanoparticles.

A cellulose nanofibril-based hybrid gel material was developed by grafting the polymerized stearyl acrylate (PSA) and upconversion nanoparticles (UCNPs) onto cellulose nanofibrils (CNFs) via Cu0-mediated radical polymerization (SET-LRP) to create a highly cross-linked CNF system. A two-step strategy was exploited to surface-exchange the ligand of the UCNPs from a hydrophobic ligand (oleic acid) to a hydrophilic small-molecule ligand (2-acrylamido-2-methyl-1-propanesulfonic acid, AMPS) and therefore be suitable for SET-LRP. The characteristics and properties of the hybrid material (UCNP-PSA-CNF) were monitored by Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), rheology, X-ray diffraction (XRD), and microscopic analysis. Those characterization techniques prove the efficient modification of the CNF, with the presence of 1.8% UCNPs. The luminescence measurement was carried out using a homebuilt confocal microscope with a 980 nm laser source. The nanostructure of UCNPs and their incorporated CNF species were measured by small-angle X-ray scattering (SAXS). In addition, this CNF-based hybrid gel has decisive rheological properties, such as good viscoelasticity (loss tangent was below 0.35 for the UCNP-PSA-CNF gel, while the PSA-CNF gel reached the highest value of 0.42), shear-thinning behavior, and shape retention, and was successfully applied to three-dimensional (3D) gel printing throughout various 3D print models.

Use of the National Early Warning Score for predicting deterioration of patients with acute pulmonary embolism: a post-hoc analysis of the YEARS Study.

BACKGROUND: The Pulmonary Embolism Severity Index (PESI) and the simplified PESI (sPESI) are validated scores for mortality prediction in patients with pulmonary embolism (PE). National Early Warning Score (NEWS) is a general prognostic risk score for multiple clinical settings. We investigated whether the NEWS had a comparable performance with the PESI and sPESI, for predicting intensive care unit (ICU) admission and death in patients with acute PE. METHODS: In haemodynamically stable patients with confirmed PE from the YEARS Study (2013-2015), we evaluated the performance of the NEWS, PESI and sPESI for predicting 7-day ICU admission and 30-day mortality. Receiver operating characteristic curves were plotted and the area under the curve (AUC) was calculated. RESULTS: Of 352 patients, 12 (3.4%) were admitted to the ICU and 5 (1.4%) died. The AUC of the NEWS for ICU admission was 0.80 (95% CI 0.66 to 0.94) and 0.92 (95% CI 0.82 to 1.00) for 30-day mortality. At a threshold of 3 points, NEWS yielded a sensitivity and specificity of 92% and 53% for ICU admission and 100% and 52% for 30-day mortality. The AUC of the PESI was 0.64 (95% CI 0.48 to 0.79) for ICU admission and 0.94 (95% CI 0.87 to 1.00) for mortality. At a threshold of 66 points, PESI yielded a sensitivity of 75% and a specificity of 38% for ICU admission. For mortality, these were 100% and 37%, respectively. The performance of the sPESI was similar to that of PESI. CONCLUSION: In comparison with PESI and sPESI, NEWS adequately predicted 7-day ICU admission as well as 30-day mortality, supporting its potential relevance for clinical practice.

Evolution of Structure and Optoelectronic Properties During Halide Perovskite Vapor Deposition.

The efficiency of perovskite-based solar cells has increased dramatically over the past decade to as high as 25%, making them very attractive for commercial use. Vapor deposition is a promising technique that potentially enables fabrication of perovskite solar cells on large areas. However, to implement a large-scale deposition method, understanding and controlling the specific growth mechanisms are essential for the reproducible fabrication of high-quality layers. Here, we study the structural and optoelectronic kinetics of MAPbI3, employing in-situ photoluminescence (PL) spectroscopy and grazing-incidence small/wide-angle X-ray scattering (GI-SAXS/WAXS) simultaneously during perovskite vapor deposition. Such a unique combination of techniques reveals MAPbI3 formation from the early stages and uncovers the morphology, crystallographic structure, and defect density evolution. Furthermore, we show that the nonmonotonous character of PL intensity contrasts with the increasing volume of the perovskite phase during the growth, although bringing valuable information about the presence of defect states.

Scalable Paper Supercapacitors for Printed Wearable Electronics.

Printed paper-based electronics offers solutions to rising energy concerns by supplying flexible, environmentally friendly, low-cost infrastructure for portable and wearable electronics. Herein, we demonstrate a scalable spray-coating approach to fabricate tailored paper poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS)/cellulose nanofibril (CNF) electrodes for all-printed supercapacitors. Layer-by-layer spray deposition was used to achieve high-quality electrodes with optimized electrode thickness. The morphology of these electrodes was analyzed using advanced X-ray scattering methods, revealing that spray-coated electrodes have smaller agglomerations, resulting in a homogeneous film, ultimately suggesting a better electrode manufacturing method than drop-casting. The printed paper-based supercapacitors exhibit an areal capacitance of 9.1 mF/cm2, which provides enough energy to power electrochromic indicators. The measured equivalent series resistance (ESR) is as low as 0.3 Ω, due to improved contact and homogeneous electrodes. In addition, a demonstrator in the form of a self-powered wearable wristband is shown, where a large-area (90 cm2) supercapacitor is integrated with a flexible solar cell and charged by ambient indoor light. This demonstration shows the tremendous potential for sequential coating/printing methods in the scaling up of printed wearables and self-sustaining systems.

State of the art of ultra-thin gold layers: formation fundamentals and applications.

Fabrication of ultra-thin gold (Au) layers (UTGLs) has been regarded as the key technique to achieve applications with tunable optical response, flexible sensors and electronic devices. Various strategies have been developed to optimize the wetting process of Au, resulting in the formation of UTGLs at a minimum thickness. The related studies on UTGLs attracted huge attention in recent years. On the one hand, the growth processes of UTGLs on different substrates were in-depth probed by advanced in situ characterization techniques and the effects of optimization strategies on the growth of UTGLs were also revealed. On the other hand, based on the understanding of the growth behavior and the assistance of optimization strategies, various applications of UTGLs were realized based on optical/plasmon responses, surface-enhanced Raman scattering and as electrodes for various sensors and electronic devices, as well as being seed layers for thin film growth. In this focused review, both the fundamental and practical studies on UTGLs in the most recent years are elaborated in detail. The growth processes of UTGLs revealed by in situ characterization techniques, such as grazing-incidence small-angle X-ray scattering (GISAXS), as well as the state of the art of UTGL-based applications, are reviewed.

A Combinatorial Study Investigating the Growth of Ultrasmall Embedded Silver Nanoparticles upon Thermal Annealing.

Ultrasmall nanoparticles (NPs) with a high active surface area are essential for optoelectronic and photovoltaic applications. However, the structural stability and sustainability of these ultrasmall NPs at higher temperatures remain a critical problem. Here, we have synthesized the nanocomposites (NCs) of Ag NPs inside the silica matrix using the atom beam co-sputtering technique. The post-deposition growth of the embedded Ag NPs is systematically investigated at a wide range of annealing temperatures (ATs). A novel, fast, and effective procedure, correlating the experimental (UV-vis absorption results) and theoretical (quantum mechanical modeling, QMM) results, is used to estimate the size of NPs. The QMM-based simulation, employed for this work, is found to be more accurate in reproducing the absorption spectra over the classical/modified Drude model, which fails to predict the expected shift in the LSPR for ultrasmall NPs. Unlike the classical Drude model, the QMM incorporates the intraband transition of the conduction band electrons to calculate the effective dielectric function of metallic NCs, which is the major contribution of LSPR shifts for ultrasmall NPs. In this framework, a direct comparison is made between experimentally and theoretically observed LSPR peak positions, and it is observed that the size of NPs grows from 3 to 18 nm as AT increases from room temperature to 900 °C. Further, in situ grazing-incidence small- & wide-angle X-ray scattering and transmission electron microscopy measurements are employed to comprehend the growth of Ag NPs and validate the UV + QMM results. We demonstrate that, unlike chemically grown NPs, the embedded Ag NPs ensure greater stability in size and remain in an ultrasmall regime up to 800 °C, and beyond this temperature, the size of NPs increases exponentially due to dominant Ostwald ripening. Finally, a three-stage mechanism is discussed to understand the process of nucleation and growth of the silica-embedded Ag NPs.

Robust Assembly of Cross-Linked Protein Nanofibrils into Hierarchically Structured Microfibers.

Natural, high-performance fibers generally have hierarchically organized nanosized building blocks. Inspired by this, whey protein nanofibrils (PNFs) are assembled into microfibers, using flow-focusing. By adding genipin as a nontoxic cross-linker to the PNF suspension before spinning, significantly improved mechanical properties of the final fiber are obtained. For curved PNFs, with a low content of cross-linker (2%) the fiber is almost 3 times stronger and 4 times stiffer than the fiber without a cross-linker. At higher content of genipin (10%), the elongation at break increases by a factor of 2 and the energy at break increases by a factor of 5. The cross-linking also enables the spinning of microfibers from long straight PNFs, which has not been achieved before. These microfibers have higher stiffness and strength but lower ductility and toughness than those made from curved PNFs. The fibers spun from the two classes of nanofibrils show clear morphological differences. The study demonstrates the production of protein-based microfibers with mechanical properties similar to natural protein-based fibers and provides insights about the role of the nanostructure in the assembly process.

Real-Time Observation of Temperature-Induced Surface Nanofaceting in M-Plane α-Al2O3.

The spontaneous crystal surface reconstruction of M-plane α-Al2O3 is employed for nanopatterning and nanofabrication in various fields of research including, among others, magnetism, superconductivity, and optoelectronics. In this reconstruction process the crystalline surface transforms from a planar morphology to one with a nanoscale ripple patterning. However, the high sample temperature required to induce surface reconstruction made in situ studies of the process seem unfeasible. The kinetics of ripple pattern formation therefore remained uncertain, and thus production of templates for nanofabrication could not advance beyond a trial-and-error stage. We present an approach combining in situ real-time grazing incidence small-angle X-ray scattering experiments (GISAXS) with model-based analysis and with ex situ atomic force microscopy (AFM) to observe this morphological transition in great detail. Our approach provides time-resolved information about all relevant morphological parameters required to trace the surface topography on the nanometer scale during reconstruction, i.e., the time dependence of the pattern wavelength, the ripple length, width, and height, and thus their facet angles. It offers a comprehensive picture of this process exemplified by a M-plane α-Al2O3 surface annealed at 1325 °C for 930 min. Fitting the model parameters to the experimental GISAXS data revealed a Johnson-Mehl-Avrami-Kolmogorov type of behavior for the pattern wavelength and a predominantly linear time dependence of the other parameters. In this case the reconstruction resulted in a crystalline surface fully patterned with asymmetric ripple-shaped nanostructures of 75 nm periodicity, 15 nm in height, and 630 nm in length. By elucidating the time dependence of these morphological parameters, this study shows a powerful way to significantly advance the predictability of annealing outcome and thus to efficiently customize nanopatterned α-Al2O3 templates for improved nanofabrication routines.

Process-Aid Solid Engineering Triggers Delicately Modulation of Y-Series Non-Fullerene Acceptor for Efficient Organic Solar Cells.

Volatile solids with symmetric π-backbone are intensively implemented on manipulating the nanomorphology for improving the operability and stability of organic solar cells. However, due to the isotropic stacking, the announced solids with symmetric geometry cannot modify the microscopic phase separation and component distribution collaboratively, which will constrain the promotion of exciton splitting and charge collection efficiency. Inspired by the superiorities of asymmetric configuration, a novel process-aid solid (PAS) engineering is proposed. By coupling with BTP core unit in Y-series molecule, an asymmetric, volatile 1,3-dibromo-5-chlorobenzene solid can induce the anisotropic dipole direction, elevated dipole moment, and interlaminar interaction spontaneously. Due to the synergetic effects on the favorable phase separation and desired component distribution, the PAS-treated devices feature the evident improvement of exciton splitting, charge transport, and collection, accompanied by the suppressed trap-assisted recombination. Consequently, an impressive fill factor of 80.2% with maximum power conversion efficiency (PCE) of 18.5% in the PAS-treated device is achieved. More strikingly, the PAS-treated devices demonstrate a promising thickness-tolerance character, where a record PCE of 17.0% is yielded in PAS devices with a 300 nm thickness photoactive layer, which represents the highest PCE for thick-film organic solar cells.