Textured Layer Research Articles

3D Branched Nanowire‐Coated Macroporous Titania Thin Films for Efficient Perovskite Solar Cells

AbstractMicroscopic design and morphological engineering of the semiconducting metal oxide as electron‐transporting layers (ETLs) is of vital importance for optical enhancement, photonic structuring, and charge collection optimization within optoelectronic devices. Herein, nanowire‐coated, branched macroporous titania (BMT) thin films are reported as a new type of ETL prepared by using silica spheres as a sacrificial template, followed by a sol–gel and subsequent alkaline‐assisted etching process. The BMT films feature 3D hierarchical structures and interconnected networks with tunable pore sizes, branch densities, and film thicknesses. The titania films are employed as ETLs in perovskite solar cells (PSCs), resulting in remarkable power conversion efficiencies (PCEs) of 20.1%; a noticeable 16% increase compared with titania nanowire (TNW) ETL‐based counterparts (PCE = 17.3%). The superior device performance of the BMT‐based PSCs can be attributed to the maximized light harvesting and charge collection capabilities. These beneficial properties are derived from the effective infiltration of the perovskite precursor into the titania macropores, efficient light confinement within the macropore structure, and the textured perovskite capping layer, as well as enhanced charge transport and reduced charge recombination through the BMT architecture. This work demonstrates a simple and effective approach for constructing branched macroporous metal‐oxide photoelectrodes toward high‐performance photovoltaic devices.

Crystallographic and magnetic investigations of textured bismuth ferrite lead titanate layers

— In present work we demonstrate the synthesis of textured 60BiFeO3–40PbTiO3 (60:40 BFPT) by using the templated grain growth technique with platelets of BaTiO3. Synthesised 60:40 BFPT has been examined by High-energy x-ray diffraction utilizing a synchrotron x-ray source. The crystallographic structure refinement results revealed the co-existence of monoclinic and tetragonal phases. By employing an external electric field, the mixed monoclinic/tetragonal phases transformed to the predominantly tetragonal phase. In addition, a crystallographic texture refinement was completed on unpoled state of 60:40 BFPT which showed the sample had 1.3 multiples of random distribution (MRD) crystallographic textured in tetragonal phase. However, magnetic measurements showed isotropic ferromagnetism for the sample which is not in agreement with the crystallographic texture properties of the sample. Low temperature magnetic transition has been found in zero field cooled—field cooled (ZFC-FC) measurements. This could be due to the possible existence of a secondary magnetic phase, which dominated the magnetic result.

14.1% efficiency hybrid planar-Si/organic heterojunction solar cells with SnO2 insertion layer

Hybrid planar-Si/organic heterojunction solar cells have gained considerable interest in the fabrication of cost-effective and high-efficiency devices. However, most of high power conversion efficiency (PCE) performances have been obtained with particular structures, front surface texture or rear surface field layer. In this paper, we provide a simple method without complex structures, and demonstrate the superiority and the mechanism of using stannic oxide (SnO2) as an insertion layer. The SnO2 insertion layer takes the place of the Schottky barrier, which reduces barrier height of rear Si to enhance charge transfer. And the effect of the insertion layer reduces contact resistance and enhances contact quality of rear Si side. Meanwhile, it has been indicated that the Si-O-Sn bonds were formed by SnO2 and Si dangling bond (Si-), which have a passivation effect on the Si surface to effectively suppress the recombination losses. Furthermore, simulations using density functional theory (DFT) confirm that the electrostatic potential can improve electronic transmission from Si to Sn between Si-O-Sn bonds. Finally, for the hybrid planar-Si/PEDOT:PSS heterojunction solar cells without any special structures, the highest PCE of 14.1% was achieved, up 10.8% compared with that without SnO2 insertion layer. These findings provide an effective way of improving Si/metal contact via a simple, room temperature process for other photovoltaic devices.

Dynamic variations in profile soil water on karst hillslopes in Southwest China

Precipitation in the karst regions of southwest China is plentiful, however, soils are shallow and highly permeable, which results in rapid transportation of surface water through a soil profile. Therefore, the presence and amount of water stress in a soil layer can be unpredictable. This study will investigate the soil water conditions on karst hillslopes in southwest China through dynamic in situ observations of profile soil moisture (θ). Three profiles at two slope positions on two shrub-grasslands (S1 and S2) were selected, respectively. At each profile, TDR 100 probes were set at 10, 20, 30, 50, and 70 cm and for 100 cm, only on downslopes. Soil samples (undisturbed and disturbed) were collected to measure basic physical and chemical properties. Precipitation and θ were monitored manually each week between July 15, 2012 and November 25, 2014. Results show that soil properties, which have an important effect on θ, varied among slope positions and between the two hisllslopes. A higher clay content, which led to greater water holding capacity, explained a higher θ in downslopes and on S2. Shallow soil layers (0–30 cm), especially in the coarse textured soil layers of S1, were susceptible to water stress due to the limited availability of soil water. Water stress was low during water supplying (December through April) and relatively stable periods (May to June). However, during water consuming periods (July to November), profile θ decreased greatly which resulted in severe water stress for the whole profile. Although precipitation was seasonally uneven, based on weekly observations, profile θ on both hillslopes was not temporally active (coefficients of variation of θ was smaller than 20%) and the variance of each depth was similar. Generally, the effects of precipitation on θ can last two (0–50 cm) to five (70–100 cm) weeks. Nevertheless, θ of downslope deep soil, which was (or near) saturated all year round, was barely affected by precipitation. These results can provide valuable information for hydrological models and rational strategies for ecological restoration designing in karst regions.

V. Telychko’s “Children’s Album” as an example of the modern tonal image of the world: peculiarities of the musical vocabulary and melodic ideas.

V. Telychko’s “Children’s Album” as an example of the modern tonal image of the world: peculiarities of the musical vocabulary and melodic ideas.

V. Telychko’s “Children’s Album” as an example of the modern tonal image of the world: peculiarities of the musical vocabulary and melodic ideas.

V. Telychko’s “Children’s Album” as an example of the modern tonal image of the world: peculiarities of the musical vocabulary and melodic ideas.

Superhydrophobic corrosion resistant coatings for copper via IR nanosecond laser processing

A series of superhydrophobic coatings with contact angles, exceeding 170° and roll-off angles less than 1.6° on copper alloy was designed using nanosecond IR laser processing, followed by vapor deposition of fluorooxysilane molecules. The experimental data show that for all samples, the surface layer consisted of cupric and cuprous oxide and demonstrated multimodal roughness. The morphology and composition of a textured surface layer for four fabricated samples varied depending on the laser processing parameters. It was found that the variation of parameters of laser processing leads to variation in chemical and corrosion resistance of fabricated coatings. Coatings with higher ratio of cupric to cuprous oxide show notably better barrier properties of the oxide layer, better chemical resistance in contact with an aqueous medium, and lower corrosion rate in chloride-containing electrolytes. It was demonstrated that in agreement with the previously reported analysis of mechanisms of corrosion protection by the superhydrophobic coatings, the higher is the chemical resistance of the layer of hydrophobic molecules with respect to desorption from the surface the better is the protective potential. The variation of laser processing parameters allowed selecting a regime for obtaining the superhydrophobic coating, for which the prolonged contact with the saline solution is accompanied by a significant decrease in the corrosion rate and the prolonged preservation of the superhydrophobic state.

Performance analysis of rigorous coupled-wave analysis and its integration in a coupled modeling approach for optical simulation of complete heterojunction silicon solar cells.

A variety of light management structures have been introduced in solar cells to improve light harvesting and further boost their conversion efficiency. Reliable and accurate simulation tools are required to design and optimize the individual structures and complete devices. In the first part of this paper, we analyze the performance of rigorous coupled-wave analysis (RCWA) for accurate three-dimensional optical simulation of solar cells, in particular heterojunction silicon (HJ Si) solar cells. The structure of HJ Si solar cells consists of thin and thick layers, and additionally, micro- and nano-textures are also introduced to further exploit the potential of light trapping. The RCWA was tested on the front substructure of the solar cell, including the texture, thin passivation and contact layers. Inverted pyramidal textures of different sizes were included in the simulations. The simulations rapidly converge as long as the textures are small (in the (sub)micrometer range), while for larger microscale textures (feature sizes of a few micrometers), this is not the case. Small textures were optimized to decrease the reflectance, and consequently, increase the absorption in the active layers of the solar cell. Decreasing the flat parts of the texture was shown to improve performance. For simulations of structures with microtextures, and for simulations of complete HJ Si cells, we propose a coupled modeling approach (CMA), where the RCWA is coupled with raytracing and the transfer matrix method. By means of CMA and nanotexture optimization, we show the possible benefits of nanotextures at the front interface of HJ Si solar cells, demonstrating a 13.4% improvement in the short-circuit current density with respect to the flat cell and 1.4% with respect to the cell with double-sided random micropyramids. We additionally demonstrate the ability to simulate a combination of nano- and microtextures at a single interface, although the considered structure did not show an improvement over the pyramidal textures.

Nighttime image enhancement based on image decomposition

Nighttime image captured in low- or non-uniform illumination scene always suffers from the loss of visibility and contains various noise and objectionable artifact. When we enlarge the amplitude of the brightness, the noise and artifact will be amplified as well. Hence, we propose a nighttime image enhancement approach based on image decomposition. We decompose the input image into two components: Structure layer contains main information of the image, and texture layer contains details, noise, and artifacts. We implement an improved retinex image enhancement algorithm to enhance the structure layer. To remain details and suppress noise and artifact in the texture layer, we use mask-weighted least squares method. In the final, we fuse these two components to obtain the result. The experimental results demonstrate that the proposed approach can improve the perceptual quality of nighttime images and suppress noise and artifact without excessive reinforcement.

Microstructural characteristics of naturally formed hardpan capping sulfidic copper-lead-zinc tailings

A massive and dense textured layer (ca. 35–50 cm thick) of hardpan was uncovered at the top layer, which capped the unweathered sulfidic Cu-Pb-Zn tailings in depth and physically supported gravelly soil root zones sustaining native vegetation for more than a decade. For the purpose of understanding functional roles of the hardpan layer in the cover profile, the present study has characterized the microstructures of the hardpan profile at different depth compared with the tailings underneath the hardpans. A suit of microspectroscopic technologies was deployed to examine the hardpan samples, including field emission-scanning electron microscopy coupled with energy dispersive spectroscopy (FE-SEM-EDS), X-ray diffraction (XRD) and synchrotron-based X-ray absorption fine structure spectroscopy (XAFS). The XRD and Fe K-edge XAFS analysis revealed that pyrite in the tailings had been largely oxidised, while goethite and ferrihydrite had extensively accumulated in the hardpan. The percentage of Fe-phyllosilicates (e.g., biotite and illite) decreased within the hardpan profile compared to the unweathered tailings beneath the hardpan. The FE-SEM-EDS analysis showed that the fine-grained Ca-sulfate (possibly gypsum) evaporites appeared as platelet-shaped that deposited around pyrite, dolomite, and crystalline gypsum particles, while Fe-Si gels exhibited a needle-like texture that aggregated minerals together and produced contiguous coating on pyrite surfaces. These microstructural findings suggest that the weathering of pyrite and Fe-phyllosilicates coupled with dolomite dissolution may have contributed to the formation of Ca-sulfate/gypsum evaporites and Fe-Si gels. These findings have among the first to uncover the microstructure of hardpan formed at the top layer of sulfidic Cu-Pb-Zn tailings, which physically capped the unweathered tailings in depth and supported root zones and native vegetation under semi-arid climatic conditions.

Adaptive decomposition method for multi‐modal medical image fusion

In traditional image fusion, source images are separated into a fixed space. The low-frequency part and the high-frequency part are not discriminated according to the nature of the image. Traditional fusion rules often use a fixed proportion, causing colour distortion. In this study, a new adaptive decomposition algorithm is proposed to distinguish high frequency and low frequency of structure image to obtain smoothing layer and texture layer. The smoothing layer of the structural image and the colour information of the function image are fused according to dynamic rules, and then the texture layer is added. On the basis of the objective evaluation metrics, the spectral information evaluation metrics are introduced to evaluate the retention of colour. In the experiments, the proposed method is compared with other six classical image fusion methods. The experiment results show that the proposed method can retain the colour information and structure information very well at the same time. Concerning subjective and objective evaluation, the proposed algorithm is superior to other algorithms.

Efficient rendering of layered materials using an atomic decomposition with statistical operators

We derive a novel framework for the efficient analysis and computation of light transport within layered materials. Our derivation consists in two steps. First, we decompose light transport into a set of atomic operators that act on its directional statistics. Specifically, our operators consist of reflection, refraction, scattering, and absorption, whose combinations are sufficient to describe the statistics of light scattering multiple times within layered structures. We show that the first three directional moments (energy, mean and variance) already provide an accurate summary. Second, we extend the adding-doubling method to support arbitrary combinations of such operators efficiently. During shading, we map the directional moments to BSDF lobes. We validate that the resulting BSDF closely matches the ground truth in a lightweight and efficient form. Unlike previous methods we support an arbitrary number of textured layers, and demonstrate a practical and accurate rendering of layered materials with both an offline and real-time implementation that are free from per-material precomputation.

Characterisation of the heterojunction microstructure for electrodeposited vertical ZnO nanorods on CVD-graphene

A low-cost heterostructure of a wide-bandgap nanostructured semiconductor on top of a transparent conductor (TC) fabricated from abundant sustainable materials is of great interest for optoelectronic devices, such as heterojunction photovoltaic cells. Due to its high optical transparency and electron mobility, graphene is an attractive carbon-based material to replace the costly traditional TCs (i.e. ITO), which pose health hazards and destructive environmental impact thorough their life cycle. However, for the industrial application of graphene as TC it is necessary to interface it with other materials, like oxides, while maintaining the sp2 network that provides its excellent electronic properties. We report the optimized electrodeposition of ZnO on graphene to obtain a textured layer of vertically aligned crystalline semiconducting nanorods (ZVNRs) evenly coating the graphene surface. Lattice distortions and mosaicity in the crystals indicate that the ZVNRs grow under out-of-plane compressive strain. The stability of the sp2 network of graphene during in situ growth of ZnO is demonstrated using Raman spectroscopy from the front and backside of the heterostructure, in a novel approach to investigate junctions of 2D–3D nanomaterials. Despite the structural stability of graphene, its R□ is found to increase by ∼100% with ZVNRs electrodeposition, which is attributed to reduction of mobility due to charge carrier scattering, reduction of carrier concentration due to doping, and/or interfacial strain. The cathodic electrodeposition is demonstrated to be an effective and versatile method to grow crystalline nanostructures in the surface of single layer-graphene while protecting its sp2 hybridization, and it provides relative fast deposition rates, affordability, and low processing temperatures that would allow using polymeric flexible substrates and. These findings on interfacial properties are important to advance the functionality of graphene as TC material and develop nano-heterostructures for myriad technological applications.

Tillage effects on the soil water balance and the use of water by oats and wheat in a Mediterranean climate

In the drylands of the Cordillera de la costa of central Chile, the water balance variables are governed by a typical Mediterranean precipitation pattern. In this environment, agronomic management practices are mainly aimed at improving the availability of water in the soil, creating optimal conditions for the crops to effectively use the available water. The aim of this study was to determine the soil water balance and water use efficiency in an oat-wheat crop rotation grown in a duplex soil with two contrasting textural layers. An experiment was conducted during the years 2007–2009 at the Experimental Center Cauquenes located in the inner dryland of the coastal range of central Chile. Conventional tillage (Ct), no tillage (Nt) and no tillage with subsoiling (Nt + Sb) systems were established. The water balance for each year of study and the total biomass, grain yield, harvest index (HI), 13C discrimination (Δ13C), crop evapotranspiration (ETc) and water use efficiency (WUE) were determined. The crop evapotranspiration (ETc) varied between 273 and 360 mm, with an overall seasonal average of 300 mm. The conservation tillage systems have a positive effect on SWC; however, the results are related to the annual rainfall. In a dry year, Nt + Sb improved the water use efficiency to 8.10 kg ha−1 mm−1, higher than that of Ct and Nt by 40% and 55%, respectively. We have demonstrated how understanding the impact of soil tillage systems on compacted soils with an abrupt contrasting soil texture can improve water use efficiency and consequently reduce water loss.

Hybrid design-based modelling and multi-objective optimization of hybrid machining of hybrid metal matrix composites

Electrical discharge diamond face surface grinding (EDDFSG) is a hybrid machining technique consisting of face surface electrical discharge grinding and diamond face surface grinding. The machining of hybrid metal matrix composites (HMMCs) is still facing challenges for better machining performance. In the present article, an effort was made for hybrid design-based experimental modelling, performance prediction and multi-objective optimization of EDDFSG of Al/Al2O3p/B4Cp and Al/SiCp/B4Cp HMMCs. Gap current, on-time, off-time, abrasive grit number, revolutions per minute (RPM) of wheel and table speed are the process parameters whose effects on material removal rate and surface roughness ( Ra) were analysed. The machining characteristics of HMMCs were investigated using performance predictions. Binary coded modified distance-based Pareto genetic algorithm was integrated with hybrid design-based RSM models for multi-objective optimization of EDDFSG process. The surface texture and re-solidified layers were also analysed using scanning electron microscopy. The selected optimized results were found to have better material removal rate and surface finish along with negligible presence of re-solidified layers during verification experiments.

Influence of pre-machining on post-machining deformation of thin-walled elements made of aluminium alloy EN AW-2024

The paper presents analysis of influence of pre-machining, consisting of removing the textured surface layer of the semi-finished product formed after plastic working, on deformation of thin-walled elements made of EN AW-2024 alloy after milling. The textured layer was removed from surface opposite to the machined surface. During tests, the influence on thin-walled elements deformation of the following machining strategies was analysed: High Speed Cutting (HSC), High Performance Cutting (HPC), and hybrid strategies HPC + HSC, HPC + CM, and HPC + CM (CM – Conventional Machining). On the basis of received results it was determined that residual stresses stored in subsurface, rolled, and unmachined surface layer have significant influence on value and character of deformations of thin-walled elements. Removing the textured surface layer formed after rolling changes character and value of the deformations of thin-walled elements. The largest difference between samples with initially removed textured layer and samples without such machining was determined for HPC + CM milling strategy. For this strategy, deformations without pre-machining were much larger than in the case of samples with removed textured surface layer.

Progress of REBCO Coated Conductor Program at SJTU and SSTC

At Shanghai Jiao Tong University (SJTU), REBa2Cu3O7‐σ (REBCO) coated conductor (CC) research program started in 2007. With the support of China's First National Key Project on CC Program, SJTU successfully developed hundred meters long class CC tapes with over 300 A/cm (at 77 K, self-field) based on PLD (pulsed laser deposition)/RABiTS processes in 2011. To develop high-performance CC tapes, in 2012, we switched from RABiTS to ion beam-assisted deposition (IBAD)-MgO tape and a pilot PLD/IBAD process CC fabrication line was set up at Shanghai Superconductor Technology Corporation in 2013, and deposition processes were successfully transferred from lab to fabrication line. Under optimized conditions, the IBAD-MgO layers showed pure (001) orientation and excellent in-plane texture. Atomic force microscopy observation showed MgO layer had very smooth surface. The rms is less than 1 nm. On the textured MgO layer, single CeO2 layer showed pure (001) orientation and excellent in-plane texture of ${\text{4}}^{\circ}$ – ${\text{5}}^\circ$ . Reel-to-reel PLD process was already scaled up to >100 m/h tape speed. Kilometer (Km) long CC tapes with over 300 A/cm have been routinely fabricated. Recently, our research work focused on introducing high-density nanoscale artificial flux pinning centers into REBCO superconducting layer to improve in-field superconducting properties and further expand application areas of REBCO tapes.

Black Silicon IR Photodiode Supersaturated With Nitrogen by Femtosecond Laser Irradiation

Micro-ripple and micro-bead structures are formed on a silicon (Si) surface after irradiation with femtosecond laser pulses in nitrogen (N2) atmosphere. Simultaneously, supersaturated nitrogen (N) atoms, with a concentration above 1020 cm−3, are doped into the textured black Si layer via laser ablation. The N-doped Si exhibits strong below-bandgap infrared absorption from 1.1 to $2.5~\mu \text{m}$ , which remains nearly unchanged after annealing for 30 min at 873 K. The mechanism of this thermally stable infrared absorption is analyzed by first-principles calculations. According to the transmission electron microscopy results, multiple phases (including single crystalline, nanocrystalline, and amorphous phases) are observed in the laser-irradiated layer. Hall Effect measurements prove that N-dopants induce a low background free-carrier concentration ( $\sim 1.67\times 10^{16}\,\,\text {cm}^{-3}$ ). Finally, a Schottky-based bulk structure photodiode is made. This broadband photodiode exhibits good thermal stability and a photo-responsivity of 5.3 mA/W for $1.31~\mu \text{m}$ at a reverse bias of 10 V.

Orientation of archive images on 3D digital models of painted vaults: an interesting tool for restorers

Over the last years, the area of conservation and enhancement of cultural heritage has benefited from new surveying methodologies. In particular, laser scanners and the latest evolutions in digital photogrammetry and processing software based on structure from motion and multi-view stereo algorithms allowed to achieve 3D models of the status quo whose features include precision suitable for restoration scales and high-quality textures. Besides methodological and technical issues, another key requirement for any intervention on this kind of buildings is their full, in-depth knowledge, which includes building design, modifications’ timeline, current conditions, present-day and historical causes of degradation etc. In this view, surveys are a valuable asset for the investigation of historical sources. The present work investigates historical photographic sources, focusing on the possibility of orientation by means of photogrammetry techniques, which provides an additional texture layer as a support tool for historical analysis. The paper displays a case study featuring the availability of a reference survey, which allows validation of the results, and two other cases highlighting the importance of this kind of documents to restoring teams.

Universal Texturing Layer for High-Current HTSC Tapes

The inclined substrate deposition method is used to grow MgO layers applicable to set textures incorporated in high-temperature superconductor (HTSCs) tapes with high critical current density. The method makes it possible to obtain polycrystalline sublayers with pronounced textures independently of the substrate crystal structure. Simultaneously, MgO has good adhesion to substrates made of a wide spectrum of materials. This makes the method a universal means for growing texturing buffer layers incorporated in high-current HTSC tapes.