Intermediate Film Research Articles

Synchrotron Radiation-Based In Situ GIWAXS for Metal Halide Perovskite Solution Spin-Coating Fabrication.

Solution-processable perovskite-based devices are potentially very interesting because of their relatively cheap fabrication cost but outstanding optoelectronic performance. However, the solution spin-coating process involves complicated processes, including perovskite solution droplets, nucleation of perovskite, and formation of intermediate perovskite films, resulting in complicated crystallization pathways for perovskite films under annealing. Understanding and therefore controlling the fabrication process of perovskites is difficult. Recently, synchrotron radiation-based in situ grazing-incidence wide-angle X-ray scattering (GIWAXS) techniques, which possess the advantages of high collimation, high resolution, and high brightness, have enabled to bridge complicated perovskite structure information with device performance by revealing the real-time crystallization pathways of perovskites during the spin-coating process. Herein, the developments of synchrotron radiation-based in situ GIWAXS are discussed in the study of the crystallization process of perovskites, especially revealing the important crystallization mechanisms of state-of-the-art perovskite optoelectronic devices with high performance. At the end, several potential applications and challenges associated with in situ GIWAXS techniques for perovskite-based devices are highlighted.

Multiscale Mixed Elastohydrodynamics in Inclined Fixed Pad Thrust Bearing Involving Surface Roughness and Low Clearance

The film pressures, surface separation profiles and carried loads of the hydrodynamic inclined fixed pad thrust bearing with the sandwich films were calculated by the multiscale approach when the bearing clearance was low and the combined effects of the adsorbed layer, the surface roughness and the surface elastic deformation were incorporated; The sandwich film consists of two physically adsorbed layers respectively on the coupled bearing surfaces and the intermediate continuum fluid film. The results show that the surface roughness intrinsically generates the film pressure ripples, but the rough surface is somewhat flattened and the film pressure ripples are a bit reduced by the surface elastic deformation. For a given sliding speed and a given original bearing clearance, the surface elastic deformation results in the significant reductions of both the maximum film pressure and the carried load of the bearing especially for a strong fluid-bearing surface interaction. In spite of this, the slope of the increase of the bearing load with the magnitude () of the surface roughness is nearly the same for the elastic surfaces with that for the rigid surfaces. The presence of the surface roughness does not qualitatively alter the influence of the surface elastic deformation on the performance of the bearing.

Efficient and stable perovskite mini-module via high-quality homogeneous perovskite crystallization and improved interconnect

The efficiency and stability of perovskite module devices are mainly limited by the quality of scalable perovskite films and sub-cells’ lateral contact. Here, firstly, we report constant low temperature substrate to regulate the growth of perovskite intermediate films to slow down the crystallization for obtaining high-quality homogeneous perovskite films in large scale size, which avoid the effect of the ambient temperature on the film quality. Secondly, a scribing step named P1.5 was added before the top function layers deposition, the diffusion barrier layer can be formed “naturally” at the interconnection interface without introducing any additional materials, which well alleviates the diffusion degradation process. As a result, our inverted perovskite devices exhibit a very small efficiency loss with area expansion comparable to other photovoltaic devices (for example, Cadmium Telluride), the perovskite module (aperture area 14.61 cm2) shows a certified quasi-steady-state power conversion efficiency of 22.73%, and the module maintaining over 90% of its initial efficiency after 1000 hours of continuous operation under illumination.

Characterization of the Physical, Mechanical, and Morphological Properties of Films Generated from Cassava Pomace

The pollution of the environment caused by conventional packing materials such as plastic has driven the need for biodegradable alternatives. Although starch is an important component in the development of such materials, starch is not suited for use as a biodegradable packaging material due to global hunger challenges. The current study successfully utilized the major industrial waste of the cassava starch processing industry to develop biodegradable films. Three packaging materials were developed using the casting procedure, which involved combining various quantities of cassava pomace (CP) and plasticizer combinations. The developed films were analyzed to evaluate their characteristics, such as color, thickness, density, moisture content, solubility, swelling index, mechanical properties, microscopic, and FT-IR characteristics. In contrast, concerning multiple aspects, each of the films demonstrated unique characteristics. The film with the lowest CP (C1) appeared to be thinner and lighter in color; however, it tended to contain a greater amount of moisture. The C1 film exhibited an adhesive property that was wellsuited for use as cling film. The intermediate CP film (C2) stands out because of its excellent mechanical characteristics, including high tensile strength and elongation at break. These attributes make it particularly well-suited for packaging applications, such as the production of biodegradable bags. Conversely, the swelling index and thickness of the highest CP film (C3) outperform both other films, suggesting that it may have the capacity to absorb higher moisture content. The scanning electron microscopic images revealed a uniform surface for all three samples. However, the cross-sectional images of C3 indicated internal cracks that were consistent with the lowest mechanical characteristics and flexibility. Therefore, the C3 film is more suitable for packaging items like plates. These films can serve as a viable, environmentally friendly, and biodegradable alternative to conventional packaging materials. Keywords: Mechanical properties, cassava pomace, physical properties, biodegradable films, micro-structure properties

Methylammonium‐Free Ink for Low‐Temperature Crystallization of α‐FAPbI3 Perovskite

AbstractFormamidinium lead triiodide (FAPbI3) perovskite without methylammonium and/or Cs cations is considered the most promising candidate for perovskite photovoltaics. However, the crystallization of photoactive α‐FAPbI3 requires high‐temperature annealing (≥150 °C) and a controlled humidity environment when methylammonium‐containing additives are absent. A methylammonium‐free ink is reported that enables low‐temperature (≤80 °C) crystallization of photoactive α‐FAPbI3 films, while also demonstrating compatibility with blade‐coating large‐area films in ambient air. The synergistical effects of methylphenyl sulfoxide and PbCl2 facilitate the formation of an intermediate phase of nanoscale‐disordered δ‐FAPbI3, which dramatically reduces the crystallization temperature of α‐FAPbI3 down to 80 °C and even below. The 80 °C crystalized α‐FAPbI3 exhibits reduced strain and improved uniformity compared to high‐temperature annealed counterparts. The synthesized ink and the corresponding intermediate precursor film are also found remarkably stable, allowing open‐air processing without the need for humidity control. Highly efficient n–i–p structured α‐FAPbI3 minimodules can be fabricated under an ambient environment RH 50% with the ink at 80 °C, achieving a power conversion efficiency of up to 22.4%. The discovery of the low‐temperature FAPbI3 ink paves a new avenue for printing perovskite solar cells and associated optoelectronic applications, accelerating the commercialization progress of perovskite materials.

Effect of β-Mg17Al12 phase on the surface interactions and morphology of hydroxyapatite coating deposited on AZ91 alloy

Coating morphology is one of the challenging parameters that significantly control the surface properties of magnesium alloys. The surface reactions on the AZ91 Mg alloy substrate and the formation of an intermediate film significantly affect the morphology of electrodeposited hydroxyapatite coating. Hence, this study aims to provide a comprehensive investigation of the effect of heat treatment times on the morphology, volume fraction, and distribution of secondary phases present in the AZ91 Mg alloy, and then the effect of these changes on the morphology of the subsequent hydroxyapatite coating. In this regard, different morphologies of hydroxyapatite coating were developed by changing the ratio of the cathode (β-phase) to anode (α-phase) area in AZ91 alloy as a controlling factor in the intensity of micro-galvanic reactions on the substrate surface as well as the formation of the next intermediate film by performing processes such as heat treatment at different times. Scanning electron microscope images of the coatings and cross-sectional regions have shown considerable changes in the morphology of coatings as a result of the change in the uniformity and thickness of Mg(OH)2 intermediate film. The homogeneity of the coatings changes as well as the substrate-coating interactions by changing the heating time. After 8 h heat treatment, the formation of a thin and uniform Mg(OH)2 intermediate film leads to a homogeneous and fine microstructure of hydroxyapatite coating by controlling the current density and release of Mg2 + ions. In addition, the thermally stable Al8Mn5 intermetallic compound can provide conditions to form a thick film of Mg(OH)2 after the complete dissolution of β-phase which leads to the formation of a coarse morphology of coating. Overall, there is a meaningful relationship between the nucleation and growth of the coating and surface reactions of the substrates.

Magnetron-Sputtered Long-Term Superhydrophilic Thin Films for Use in Solid-State Cooling Devices

Pulse-magnetron-sputtered long-term superhydrophilic coatings have been synthesized to functionalize the surfaces of solid-state cooling devices, e.g., electrocaloric heat pumps, where not only a complete wetting of the surface by a fluid is intended, but also fast wetting and dewetting processes are required. The coatings consist of a (Ti,Si)O2 outer layer that provides lasting hydrophilicity thanks to the mesoporous structure, followed by an intermediate WO3 film that enables the reactivation of the wettability through visible light irradiation, and a W underlayer which can work as a top electrode of the electrocaloric components thanks to its suitable electrical and thermal conductivity properties. Process parameter optimization for each layer of the stack as well as the influence of the microstructure and composition on the wetting properties are presented. Finally, water contact angle measurements, surface energy evaluations, and a contact line dynamics assessment of evaporating drops on the coatings demonstrate that their enhanced wetting performance is attributed not only to their intrinsic hydrophilic nature but also to their porous microstructure, which promotes wicking and spreading at the nanometric scale.

Redox-Sensitive NiOx Stabilizing Perovskite Films for High-Performance Photovoltaics.

Metal halide perovskite materials inherently possess imperfections, particularly under nonequilibrium conditions, such as exposure to light or heat. To tackle this challenge, we introduced stearate ligand-capped nickel oxide (NiOx), a redox-sensitive metal oxide with variable valence, into perovskite intermediate films. The integration of NiOx improved the efficiency and stability of perovskite solar cells (PSCs) by offering multifunctional roles: (1) chemical passivation for ongoing defect repair, (2) energetic passivation to bolster defect tolerance, and (3) field-effect passivation to mitigate charge accumulation. Employing a synergistic approach that tailored these three passivation mechanisms led to a substantial increase in the devices' efficiencies. The target cell (0.12 cm2) and module (18 cm2) exhibited efficiencies of 24.0 and 22.9%, respectively. Notably, the encapsulated modules maintained almost 100 and 87% of the initial efficiencies after operating for 1100 h at the maximum power point (60 °C, 50% RH) and 2000 h of damp-heat testing (85 °C, 85% RH), respectively. Outdoor real-time tests further validated the commercial viability of the NiOx-assisted PSMs. The proposed passivation strategy provides a practical and uncomplicated approach for fabricating high-efficiency and stable photovoltaics.

Rupture of thin nematic walls between isotropic droplets of the same mesogenic material

ABSTRACT We prepared isotropic droplets surrounded by nematic fringes in smectic A freely suspended films. During their coalescence, a thin nematic film is formed that acts as a barrier and separates the isotropic cores of these droplets. This film ruptures in the course of the droplet merging process. The observation of the film dynamics provides an exceptional opportunity to study the rupture of a thin liquid barrier embedded in a surrounding viscous liquid. A detailed dynamic characterisation of the nematic walls is performed. Qualitatively similar observations have been reported in 3D for oil drops coalescing in water and vice versa, where the rupture of an intermediate thin fluid film retards the merging process. The peculiarity of the system reported here is that the material of the droplets and the membrane is identical.

Solution-processed CsPbBr3 perovskite films via CsBr intercalated PbBr2 intermediate for high-performance photodetectors towards underwater wireless optical communication

All inorganic CsPbBr3 perovskite is regarded as a promising candidate of halide perovskites and has attracted great attention due to its superior optoelectronic properties and stability. However, the low and unbalanced solubility of precursors and uncontrollable crystallization result in poor coverage and impurity phases in CsPbBr3 polycrystalline films, hindering the application in optoelectronic devices. In this work, a facile CsBr intercalated nanostructured intermediate based two-step method is reported for simultaneously achieving good morphology and pure phase of CsPbBr3 films. With the CsBr intercalation, the intermediate films deposited in the first step exhibit porous nanostructure and CsxPb2Br4+x crystal phase. This unique porous morphology and crystal structure favor CsBr solution penetration and Cs+ ion diffusion. First-principles calculations are conducted to investigate the phase diagram of intermediates and the diffusion kinetics of Cs+ ions in the various polymorphs. The key role of CsBr intercalation is confirmed for achieving high-quality CsPbBr3 perovskite films with features of pinhole free, pure phase, large grains, and high crystallinity. Photodetectors based on optimized CsPbBr3 films exhibit excellent performance with a peak EQE of 83%, responsivity of 0.35 A/W, and specific detectivity of 1.25×1013 Jones. Fast response speed is also achieved with rise/fall time of 1.41 μs and 2.06 μs and −3 dB bandwidth up to 800 kHz. Moreover, CsPbBr3 PD shows great potential in the application of underwater wireless optical communication due to its low background noise current under ambient light illumination. Overall, this work paves the way for further research on optoelectronic devices and their applications based on CsPbBr3 films.

Antibubble formation through single drop impact: Effect of density difference

The antibubble has emerged as a promising tool for the microdroplet manipulation since the intermediate air film can protect the inner globule from external contaminants. Moreover, the antibubble structure allows the convenient package and release of microdroplets since the intermediate air film would not hinder the separation between the inner globule and the liquid surface. Despite the development of various methods for antibubble formation, the initial approach involving single drop impact on a free liquid surface has received limited attention in subsequent studies, partly due to the challenges in replicating this phenomenon in practical applications. This paper presents an experimental investigation into antibubble formation via single drop impact on a liquid surface. Experimental results imply that antibubble formation requires the droplet to penetrate deeply into the liquid bath before the intermediate air film collapses or the deformed liquid surface contracts. A theoretical analysis is introduced to emphasize the crucial role of the density difference between the droplet and the liquid bath. A higher density of the droplet results in an increased penetration speed into the liquid bath, facilitating the formation of antibubbles. Notably, this study repeats the experimental results reported by Hughes and Hughes in 1932. Moreover, the method provides a means to control antibubble parameters such as diameter and air film thickness. This control offers valuable insight for subsequent investigations on antibubbles, establishing a foundation for further exploration and application of this intriguing phenomenon.

Sound insulation enhancement of polyvinyl butyral film by blending polyurethane and its laminated safety glass

Laminated glass based on PVB film is widely used in military industry and life depending on its excellent safety performance. However, the insufficient sound insulation performance of PVB film restricts its practical application and has gained much more attention. In this work, a PVB-TPU composites with high strength and excellent sound insulation acoustic performance was designed by melt blending method which is attributed to their molecular entanglement and hydrogen bonding interactions between PVB and TPU molecule chains. It has been showed that the maximum tensile strength and elongation at break of the PVB-TPU blending film reached 34 MPa and 235 % respectively when 10 wt% content of TPU in the system. In addition, 20–41 dB of the sound transmission loss (TL) for the composite film with 1 mm thickness in the range of 2000–6000 Hz was achieved, which was obvious enhanced compared with the existing laminated glass intermediate film. The high impact resistance of the laminated glass based on the PVB-TPU film was confirmed by the falling ball impact test. The high sound insulation and safety laminated glass prepared here will be widely used in more fields.

Physicochemical properties of AH plus bioceramic sealer, Bio-C Sealer, and ADseal root canal sealer

BackgroundThe aim of this study was to evaluate the physicochemical properties of two newly introduced premixed calcium silicate-based root canal sealers (AH Plus Bioceramic Sealer and Bio-C Sealer) compared to a resin-based root canal sealer (ADseal root canal sealer).MethodsSolubility, pH analysis, calcium ion release, and film thickness of each sealer were evaluated following ISO guidelines. The data were examined using the two-way ANOVA test. Furthermore, X-ray diffraction (XRD) examination was performed to investigate the crystalline phase of each type of sealer. X-ray fluorescence (XRF) analysis was done for the chemical elemental analysis of each sealer.ResultsThe least film thickness, highest alkalinity, and highest calcium ion release were all displayed by AH Plus Bioceramic Sealer. High solubility, high alkalinity, intermediate calcium ion release, and intermediate film thickness were all displayed by Bio-C Sealer. While ADseal root canal sealer displayed the greatest film thickness, least solubility, alkalinity, and calcium ion release.ConclusionsBoth AH Plus Bioceramic Sealer and Bio-C Sealer represented adequate properties to be considered a good sealer that could be used as a potential alternative to resin-based root canal sealers.

MULTISCALE SIMULATION OF HYDRODYNAMIC STEP BEARING WITH ULTRA-LOW CLEARANCE INVOLVING SURFACE ROUGHNESS

The numerical calculation was carried out for the multiscale hydrodynamic step bearing with ultra-low clearance and nanoscale surface roughness based on the newly developed multiscale approach. The moving surface was assumed as perfectly smooth and the stationary surface was imposed with the sinusoidal surface roughness. Due to the surface roughness, locally the physically adsorbed boundary layer may be only present, while in other areas, the sandwich films consisting of both the adsorbed boundary layers and the intermediate continuum fluid film may be present. In this bearing, the fluid film may be locally severely squeezed so that the local film pressure is very high. In this circumstance, the influences of the film pressure on both the film viscosity and density were considered. The results show that with the increase of the surface roughness, the hydrodynamic pressure and carried load of the bearing are very significantly increased especially for a stronger fluid-bearing surface interaction; the fluid piezo-viscous effect becomes stronger with the increases of both the surface roughness and the fluid-bearing surface interaction strength.

Interfacing poly(p-anisidine) with photosystem I for the fabrication of photoactive composite films.

Photosystem I (PSI) is an intrinsically photoactive multi-subunit protein that is found in higher order photosynthetic organisms. PSI is a promising candidate for renewable biohybrid energy applications due to its abundance in nature and its high quantum yield. To utilize PSI's light-responsive properties and to overcome its innate electrically insulating nature, the protein can be paired with a biologically compatible conducting polymer that carries charge at appropriate energy levels, allowing excited PSI electrons to travel within a composite network upon light excitation. Here, a substituted aniline, 4-methoxy-aniline (para-anisidine), is chemically oxidized to synthesize poly(p-anisidine) (PPA) and is interfaced with PSI for the fabrication of PSI-PPA composite films by drop casting. The resulting PPA polymer is characterized in terms of its structure, composition, thermal decomposition, spectroscopic response, morphology, and conductivity. Combining PPA with PSI yields composite films that exhibit photocurrent densities on the order of several μA cm-2 when tested with appropriate mediators in a 3-electrode setup. The composite films also display increased photocurrent output when compared to single-component films of the protein or PPA alone to reveal a synergistic combination of the film components. Tuning film thickness and PSI loading within the PSI-PPA films yields optimal photocurrents for the described system, with ∼2 wt% PSI and intermediate film thicknesses generating the highest photocurrents. More broadly, dilute PSI concentrations show significant importance in achieving high photocurrents in PSI-polymer films.

Preparation and application of high sound insulation polyurethane composite film through glass fiber reinforcement

AbstractLaminated glasses have been widely used in buildings, physical protections, and vehicles because of their safety, sound insulation, thermal insulation, and other performance. In recent years, the high sound insulation performance of laminated glass intermediate films in the frequency range of low or high frequencies has attracted more and more attentions. In this work, a glass fiber/polyurethane elastomer composite (PU‐MGF) film with high transparency and impact resistance has been successfully synthesized, 5 dB of the transmission loss increased at 1600–6000 Hz, and 3.6 dB increased at 63–1600 Hz compared with the control polyurethane film. This is a significant progress in the laminated glass industry. In addition, the transmittance of the composite reaches over 75%. The excellent impact resistance of the laminated glass, based on PU‐MGF film, has been confirmed through falling ball impact test, demonstrating its ability to withstand multiple impacts without spattering. The PU‐MGF film prepared in this work exhibits great potential for applications in building windows, transportation, and soundproof devices.

Optical and structural changes in intermediate phase Ge22Se78 thin film under 100 MeV Ag swift-heavy ion irradiation

Optical and structural changes in intermediate phase Ge22Se78 thin film under 100 MeV Ag swift-heavy ion irradiation

Effect of Chloride Incorporation on the Intermediate Phase and Film Morphology of Methylammonium Lead Halide Perovskites.

The influence of chloride integration on perovskite film deposition, encompassing both the structures of intermediate phases and the properties of the final films, was explored. Our methodology involved the fabrication of perovskite intermediate-phase films with varying concentrations of methylammonium chloride (MACl). Subsequently, we conducted an analysis employing X-ray diffraction and Rietveld refinement, incorporating the March-Dollase correction, to gain insights into how chloride-induced intermediate phases impact film morphology. Remarkably, a distinct preferred orientation was observed in the (020) lattice plane perpendicular to the substrate surface, and this orientation was found to be directly correlated to the MACl concentration. This distinctive arrangement of chloride-induced intermediate-phase complexes facilitated controlled crystallization, leading to highly oriented crystals and an improved film morphology. As a consequence, perovskite solar cell devices incorporating chloride-containing methylammonium lead iodide achieved a power conversion efficiency exceeding 20%. These findings suggest a crucial link between the preferred orientation observed in the final chlorine-derived perovskite films and the intermediate-phase structure formed during the initial stages of perovskite formation. These results suggest a profound impact of intermediate phase compositions and crystal structures on perovskite formation, emphasizing the importance of a comprehensive understanding of these factors to enable precise control over ideal structures and the subsequent transformation into high-quality perovskite films.

The effect of Cr atoms: From non-stoichiometric Ge-Te to Cr2Ge2Te6

The traditional phase change material Ge-Te presents a large difference with Cr2Ge2Te6 (CrGT) in the phase change properties. Compared with Ge-Te, the two-dimensional van der Waals material CrGT presents a reversed resistance state, in which the crystalline phase is in a high-resistance state and the amorphous phase is in a low-resistance state. Nevertheless, there are some structural similarities between the two materials. CrGT may be regarded as the Cr doping of Ge-Te. It is necessary to investigate the evolution of the structure and phase change properties of Ge-Te to CrGT through Cr doping. In this study, phase change materials Ge40Te60 (GT) and CrGT were fabricated. Subsequently, a series of intermediate state films were fabricated by changing the Ge/Te/Cr cation-to-anion ratio. Surprisingly, the coexistence of the CrGT and GT phases was observed in all intermediate films. As a result, a gradual reversal in the resistance between the amorphous and crystalline states can be observed. Transmission electron microscopy experiments were also performed to characterize the grain growth and the phase separation. Unlike GT, CrGT island-like crystal grains usually have boundaries with regular shapes. The pure CrGT-based device exhibited an excellent device performance. This work may provide a useful guide for further application of the CrGT phase change material.

Solvent racing crystallization: Low-solvation dispersion cosolvents for high-quality halide perovskites in photovoltaics

•Designing dispersion cosolvents with reduced solvation capacity •Utilizing solvent polarity and hydrogen-bonding property to their advantage •Promoting the growth of perovskite films with preferred orientation •Attaining solar module (18 cm2 active area) with an efficiency exceeding 22% The solvation capacity of dispersion solvents plays a crucial role in the solution processing of metal halide perovskites. For instance, N,N-dimethylformamide (DMF), a widely used dispersion solvent, possesses high solvation capacity but often generates suboptimal film quality due to slow crystallization kinetics. We propose using low-solvation binary cosolvents (nitrile- and ether-type solvents) to achieve a balance between solvation (i.e., sufficient solubility of precursors) and desolvation (i.e., rapid crystallization of films) processes during perovskite synthesis. The polarity and hydrogen-bonding property of these cosolvents synergistically enhance their solvation capacity, facilitating perovskite precursor dissolution. Moreover, the low-solvation cosolvents accelerate the crystallization of well-defined intermediate films, yielding higher-quality perovskites than those synthesized with DMF. The optimized modules achieved an active-area efficiency of 22.27%, with a certified aperture-area efficiency of 16.10% and corresponding active-area efficiency of 20.75%. This research on solvation regulation provides universal guidelines for innovatively preparing high-quality halide perovskites. The solvation capacity of dispersion solvents plays a crucial role in the solution processing of metal halide perovskites. For instance, N,N-dimethylformamide (DMF), a widely used dispersion solvent, possesses high solvation capacity but often generates suboptimal film quality due to slow crystallization kinetics. We propose using low-solvation binary cosolvents (nitrile- and ether-type solvents) to achieve a balance between solvation (i.e., sufficient solubility of precursors) and desolvation (i.e., rapid crystallization of films) processes during perovskite synthesis. The polarity and hydrogen-bonding property of these cosolvents synergistically enhance their solvation capacity, facilitating perovskite precursor dissolution. Moreover, the low-solvation cosolvents accelerate the crystallization of well-defined intermediate films, yielding higher-quality perovskites than those synthesized with DMF. The optimized modules achieved an active-area efficiency of 22.27%, with a certified aperture-area efficiency of 16.10% and corresponding active-area efficiency of 20.75%. This research on solvation regulation provides universal guidelines for innovatively preparing high-quality halide perovskites.