Fabrication Of Layers Research Articles

Microstructural and surface analysis of NiTi TPMS lattice sections fabricated by laser powder bed fusion

Due to their high ductility and superior strength, the machining of NiTi shape memory alloys using conventional subtractive manufacturing technologies poses significant challenges. However, additive manufacturing (AM) offers a viable solution by circumventing the limitations of machinability through the elimination of tooling, thereby enabling the production of NiTi structures with previously unachievable intricacy. This study focuses on the fabrication of base layers of architected triply periodic minimal surface (TPMS) lattices using laser powder bed fusion (LPBF) and explores primitive and gyroid topologies. The investigation involves a comprehensive analysis and discussion of the influence of geometric properties and process parameters on the microstructural characteristics and the distribution of solid phases within the samples. Notably, the study reveals a substantial impact of process parameters and structural topology on the microstructural features. Additionally, notable observations are made concerning nickel evaporation, as well as the formation of oxide- and titanium-rich phases in relation to their distance from the base plate. Investigating intricate TPMS geometries in NiTi alloys in conjunction with varying laser process parameters represents a relatively new and unexplored area of research. These geometries may offer unique structural and functional properties that can potentially lead to innovative applications and advancements in various fields.

Enhanced electron extraction using neodymium ions doped TiO2 for all-inorganic CsPbBr3 perovskite solar cells

The high-quality electron-transport layer (ETL) plays a vital role in boosting the power conversion efficient (PCE) of perovskite solar cells (PSCs). Herein, the lanthanide neodymium (Nd) is used as a dopant to incorporate into the lattice of TiO2 to reduce the trap states and form a n-doping effect, resulting in an increase in electron mobility and conductivity of TiO2, an energy level of TiO2 matching well with that of the perovskite layer. Moreover, the improved wettability of the Nd-TiO2 film enables a fabrication of perovskite light-absorbing layer with high-quality. As a result, the all-inorganic CsPbBr3 PSCs based on Nd-TiO2 ETL achieve a champion PCE of 10.06% owing to the promotion of charge extraction and the inhibition of charge recombination, which is a significantly improved efficiency in comparison with the 6.57% value of the reference cell. Additionally, the target device without encapsulation displays an effectively enhanced stability with over 90% and 80% retention of the original efficiency after aging in ambient air with high humidity (80% RH, 25 °C) for 30 days and under AM 1.5 G illumination at 85 °C for 100 h, respectively.

Green Solvent Ethanol-Based Inks for Industrially Applicable Deposition of High-Quality Perovskite Films for Optoelectronic Device Applications.

Incontrovertibly there is an increasing demand for the development of benign inks suitable for fabrication of high-performing perovskite-based thin film functional layers. Nevertheless, most reported perovskite precursors rely on the use of highly toxic solvents such as acetonitrile, 2-methoxyethanol, dimethylformamide, and many others. Hence, there is a strong imperative for the development of novel and greener inks, which will facilitate smoother commercialization of technologies based on functional perovskite films. Therefore, four perovskite precursors are studied, some of which consist of up to 90% ethanol. All inks are developed to fulfill the requirements of a high-throughput deposition compatible with roll-to-roll techniques at room temperature, assisted by an air knife for instant solvent removal. Two of the inks are particularly suitable for the fabrication of high-quality and densely packed multi-crystalline (CH3 NH3 )PbI3 layers, as confirmed by numerous nanoscale spectroscopic and material characterization techniques. Additionally, large-area photoluminescence (PL) imaging is demonstrated to improve the quality of the deposited perovskite films, with a route to enhance deposition uniformity when upscaling for manufacture. The genuine potential of the developed greener perovskite inks is demonstrated with the fabrication of solar cells with power conversion efficiencies above 19.5%.

Hot Gas‐Blowing Assisted Crystallinity Management of Bar‐Coated Perovskite Solar Cells and Modules

The bar‐coating technique for perovskite solar cells has been studied as a scalable process in relation to solar cell commercialization. In large‐area bar coating, solvents with the high boiling points like dimethylformamide or γ‐butyrolactone have difficulty in obtaining uniform and planar film at room temperature as they have slow evaporation rate. As an alternative, 2‐methoxyethanol is a volatile and polar solvent, which is useful on a bar coating if applied using an air‐blowing method with an air knife. Herein, a hot gas‐blowing method for the fabrication of a perovskite layer to achieve both proper solvent evaporation and high crystallinity is developed. With 75 °C of N2 blowing on the bar‐coated perovskite solution, highly crystalline perovskite films with large grains without voids are fabricated, showing excellent optical and electrical characteristics, such as long carrier lifetime, few carrier recombinations, and low trap density. Both small‐area solar cells and large‐area modules show good performance, 20.85% for the solar cell and 15.4% for the solar module. The results indicate that the newly proposed method can equally be applied to the fabrication of large‐area solar cells toward commercialization.

Molecular Tailoring of Pyridine Core-Based Hole Selective Layer for Lead Free Double Perovskite Solar Cells Fabrication.

To solve the toxicity issues related to lead-based halide perovskite solar cells, the lead-free double halide perovskite Cs2AgBiBr6 is proposed. However, reduced rate of charge transfer in double perovskites affects optoelectronic performance. We designed a series of pyridine-based small molecules with four different arms attached to the pyridine core as hole-selective materials by using interface engineering. We quantified how arm modulation affects the structure-property-device performance relationship. Electrical, structural, and spectroscopic investigations show that the N3,N3,N6,N6-tetrakis(4-methoxyphenyl)-9H-carbazole-3,6-diamine arm's robust association with the pyridine core results in an efficient hole extraction for PyDAnCBZ due to higher spin density close to the pyridine core. The solar cells fabricated using Cs2AgBiBr6 as a light harvester and PyDAnCBZ as the hole selective layer measured an unprecedented 2.9% power conversion efficiency. Our computed road map suggests achieving ∼5% efficiency through fine-tuning of Cs2AgBiBr6. Our findings reveal the principles for designing small molecules for electro-optical applications as well as a synergistic route to develop inorganic lead-free perovskite materials for solar applications.

Improved Device Performance and Stability in Organic Solar Cells by Morphology Control via Size‐Controlled Chevron‐Shaped Blades

Organic solar cells (OSCs) have been studied widely as renewable energy resources for a few decades owing to their technological advantages, including low cost, light weight, flexibility, and the potential of large area printing. To upgrade the active layers of OSCs into an optimized form, a simple and straightforward strategy is demonstrated by introducing two types of size‐controlled chevron (V)‐shaped blades to delicately control PM6:Y6‐based bulk heterojunction (BHJ) films under ambient conditions. A power conversion efficiency of 15.97% is achieved from the blade‐coating methods using a small‐sized V‐shaped blade (V1), compared with 14.31% using a conventional flat blade (F). Using blade coating based on V1 improves the phase separation and molecular crystallinity in the active layer, which lead to decreased trap‐assisted recombination and leakage current, finally increasing the short circuit current and fill factor. In addition, following these morphological changes in the optimal BHJ structure, the devices printed with V1 exhibit higher stability in the long‐term shelf‐life test (320 h storage in ambient conditions). Notably, strategy is a facile layer fabrication method that adopts V‐shaped blades to achieve high device performance and stability for the practical use of large‐area OSCs.

Replaceable Dielectric Film for Low-Voltage and High-Performance Electrowetting-Based Digital Microfluidics.

Electrowetting-on-dielectric (EWOD) technology has been considered as a promising candidate for digital microfluidic (DMF) applications due to its outstanding flexibility and integrability. The dielectric layer with a hydrophobic surface is the key element of an EWOD device, determining its driving voltage, reliability, and lifetime. Hereby, inspired by the ionic-liquid-filled structuring polymer with high capacitance independent on thickness, namely ion gel (IG), we develop a polymer (P)-ion gel-amorphous fluoropolymer, namely, PIGAF, composite film as a replaceable hydrophobic dielectric layer for fabrication of a high-efficiency and stable EWOD-DMF device at relatively low voltage. The results show that the proposed EWOD devices using the PIGAF-based dielectric layer can achieve a large contact angle (θ) change of ∼50° and excellent reversibility with a contact angle hysteresis of ≤5° at a relatively low voltage of 30 Vrms. More importantly, the EWOD actuation voltage did not change obviously with the PIGAF film thickness in the range of several to tens of microns, enabling the thickness of the film to be adjusted according to the demand within a certain range while keeping the actuation voltage low. An EWOD-DMF device can be prepared by simply stacking a PIGAF film onto a PCB board, demonstrating stable droplet actuation (motion) at 30 Vrms and 1 kHz as well as a maximum moving velocity of 69 mm/s at 140 Vrms and 1 kHz. The PIGAF film was highly stable and reliable, maintaining excellent EWOD performance after multiple droplet manipulations (≥50 cycles) or long-term storage of 1 year. The proposed EWOD-DMF device has been demonstrated for digital chemical reactions and biomedical sensing applications.

Fabrication of biofunctional oxide layer with potential self-antibacterial performance for biomedical applications

Fabrication of biofunctional oxide layer with potential self-antibacterial performance for biomedical applications

Nanoscale paraffin layer fabricated using spin coating technique for on-demand removable passivation

Passivation is an essential process in the research and application of reactive and air-sensitive materials, and there has been an increasing demand to develop materials for stable but readily removable temporary passivation layers. Paraffin coating has been suggested as a possible candidate for such applications, which, however, further requires the demonstration of thin paraffin coating with complete surface coverage as well as effective depassivation performance. In this study, we demonstrate on-demand removable passivation using nanoscale paraffin layers fabricated using a spin-coating technique. Based on the Emslie Bonner and Peck's and Mark-Houwink-Sakurada (MHS) equations, eicosane and hexane were selected as the solute and solvent, respectively, to ensure low viscosity for the fabrication of nanoscale paraffin layers, facilitating depassivation process under a vacuum. Optimizing the solution concentration and spin speed generates nanoscale paraffin layers with complete surface coverage, which is confirmed through optical microscopic images and subsequent image processing using Python. The simple removal of the nanoscale paraffin layer through vacuum treatment allows us to revisit a passivated surface underneath, and subsequent contact resistance and x-ray photoelectron spectroscopy measurements evince the suppressed surface oxidation of paraffin-coated silicon samples. These results further attest to the applicability of paraffin coating as an on-demand removable passivation technique.

Tin(IV) Oxide Electron Transport Layer via Industrial-Scale Pulsed Laser Deposition for Planar Perovskite Solar Cells.

Electron transport layers (ETL) based on tin(IV) oxide (SnO2) are recurrently employed in perovskite solar cells (PSCs) by many deposition techniques. Pulsed laser deposition (PLD) offers a few advantages for the fabrication of such layers, such as being compatible with large scale, patternable, and allowing deposition at fast rates. However, a precise understanding of how the deposition parameters can affect the SnO2 film, and as a consequence the solar cell performance, is needed. Herein, we use a PLD tool equipped with a droplet trap to minimize the number of excess particles (originated from debris) reaching the substrate, and we show how to control the PLD chamber pressure to obtain surfaces with very low roughness and how the concentration of oxygen in the background gas can affect the number of oxygen vacancies in the film. Using optimized deposition conditions, we obtained solar cells in the n-i-p configuration employing methylammonium lead iodide perovskite as the absorber layer with power conversion efficiencies exceeding 18% and identical performance to devices having the more typical atomic layer deposited SnO2 ETL.

Research of the Pre-Processing Strategy Influence on the Tribological Properties of PEI Processed by Fused Filament Fabrication Technology

The aim of this study was to investigate the effect of Fused Filament Fabrication (FFF) layer generation strategies on abrasive wear resistance and compare the material loss of PEI (polyetherimide) plastic specimens based on different specimen building strategies. The study also compares a newly proposed path generation strategy (parallel paths in layers with 0.25 mm displacement of alternate layers) with samples from a previous study where samples were printed without displacement of alternate layers, i.e., layers stacked perpendicularly to each other. The primary focus was on the weight loss due to abrasive wear before and after the test. The tests were conducted on a tribometer constructed according to ASTM G65/16 standards using dry sand. Two printing directions were examined: X (longitudinal) and Z (portrait) orientations. For X construction, three orientations of deposition path generation were utilized, resulting in three samples for each orientation (nine samples in total for X construction). The same approach was applied to Z construction, resulting in another nine samples. In total, 18 samples were produced and tested. The deposited infill path width was 0.5 mm, and the layer thickness used in printing was 0.254 mm. Garnet abrasive Fe3Al2(SiO4)3 was employed in this test. Analysis of the experimental data revealed a relationship between the construction method (X and Z orientations) and the variation in different orientations (1X–3X and 1Z–3Z). The research results can be categorized as overall and partial. The overall results indicate poorer wear resistance for 1X–3X and 1Z–3Z specimens, while the partial results illustrate the findings within each individual specimen.

Construction of high-performance thin-film composite membrane for CO2 separation via interface engineering

High-efficiency CO2 capture has become increasingly vital for alleviating the ongoing global temperature which leads to severe impacts on virtually every aspect of human life. Thin-film composite membranes (TFCM) have attracted growing attention for conducting CO2 capture, owning to their energy-efficient and environment-friendly merits. However, the nonideal interface between the gutter layer and the separation layer hampers the fabrication of defect-free and thin separation layer, which renders low separation performance. In this work, we developed a strategy, i.e., coupling the oxygen-plasma modification with spin-coating, for engineering the interface between the gutter layer and separation layer of TFCM. Leveraging this idea, the TFC membrane, consisting polydimethylsiloxane (PDMS) served as the gutter layer and poly (ether-block-amide) (PEBA) as the thin separation layer, was manufactured by conveniently spin-coating PEBA solution on the oxygen-plasma-treated PDMS layer. The optimized PEBA-based TFCM membrane realized superior separation performance, e.g., a CO2 permeance of 2011 GPU, a CO2/N2 selectivity of 24, and 100-hour stably running, which outperformed most of the reported PEBA-based TFCM. Thus, the interface engineering strategy proposed in this study opens a new door for rational fabrication of high-performance TFCM.

Isolate Utilization of Plasmonic Hot Holes in Optoelectronic Enhancement for Copper Iodide (CuI): A Cross‐Investigation by Confocal Kelvin Probe Force Microscopy

AbstractNonradiative decays of surface plasmon (SP) can generate photocarriers in femtosecond, and it therefore has been attracting widespread research attention in ultrafast optoelectronics. Taking advantage of the probe technique, Kelvin probe force microscopy (KPFM) can characterize the spatial distribution of hot carriers in nanoscale and thereby provide necessary analysis for device investigation and engineering. In this work, the behavior of plasmonic hot holes is demonstrated for Ag nanoparticles (NPs) based on the fabrication of CuI hole transport layers. The morphological, optical, and electronic properties of Ag NPs and CuI films are systematically investigated. With the confocal lasers of over‐ and sub‐bandgap wavelength, reversed evolution trends of surface potentials are observed by KPFM, indicating the effective injection of hot holes into CuI valence band (VB). Cross‐verification is also performed based on the fabrication of metal–semiconductor–metal (MSM) photodetectors, and the photoelectrical tests highly dovetail with the surface potential evolution. This research provides an important reference for the plasmonic photoelectronics in both device design and research methods.

Room-temperature electrochemical deposition of nanostructured ZnO films on FTO substrate and their photoelectrochemical activity

The possibility of fabrication of nanostructured ZnO layers on conductive glass substrates via simple room-temperature electrodeposition was studied in detail. The process was carried out in zinc nitrate electrolyte at different potentials for various durations. The morphology, composition, and semiconducting properties of the deposits were examined by various techniques. As-synthesized materials were found to be amorphous and co-deposition of the metallic Zn at more negative potentials was confirmed. Nevertheless, thermal treatment in air results in the successful conversion of the as-deposited precipitate to the wurtzite ZnO. The potential of −1.5 V vs. SCE was identified as optimal to achieve both full coverage of the glass substrate, as well as uniform morphology of the deposits. In general, the photoelectrochemical performance of such kind of ZnO photoanodes was found to be significantly dependent on the electrodeposition duration since this parameter strongly affected the thickness, surface morphology, as well as semiconducting properties of the obtained material. In consequence, the photoanode deposited at −1.5 V vs. SCE for 40 min exhibited the most promising photoelectrochemical activity under studied conditions.

Twisted Bilayer Graphene Induced by Intercalation.

Twisted bilayer graphene (tBLG) has gained significant attention due to its unique physical and electronic properties. However, efficient fabrication of high-quality tBLG with diverse twist angles is crucial to expedite research on angle-dependent physics and potential applications. In this study, an intercalation strategy utilizing organic molecules, such as 1,2-dichloroethane, is developed to weaken the interlayer interaction and induce slide or rotation of the topmost graphene layer for tBLG fabrication. The proportion of tBLGs in the resulting 1,2-dichloroethane-treated BLG (dtBLG) reaches up to 84.4% for twist angles ranging from 0° to 30°, surpassing previously reported methods using chemical vapor deposition (CVD). Moreover, the twist angle distribution is not uniform and tends to concentrate in the ranges of 0-10° and 20-30°. This facile and rapid intercalation-based methodology provides a practical solution for studying angle-dependent physics and advancing the utilization of twisted two-dimensional materials.

Biodegradable elastomeric circuit boards from citric acid-based polyesters

Recyclable and biodegradable microelectronics, i.e., “green” electronics, are emerging as a viable solution to the global challenge of electronic waste. Specifically, flexible circuit boards represent a prime target for materials development and increasing the utility of green electronics in biomedical applications. Circuit board substrates and packaging are good dielectrics, mechanically and thermally robust, and are compatible with microfabrication processes. Poly(octamethylene maleate (anhydride) citrate) (POMaC) – a citric acid-based elastomer with tunable degradation and mechanical properties – presents a promising alternative for circuit board substrates and packaging. Here, we report the characterization of Elastomeric Circuit Boards (ECBs). Synthesis and processing conditions were optimized to achieve desired degradation and mechanical properties for production of stretchable circuits. ECB traces were characterized and exhibited sheet resistance of 0.599 Ω cm−2, crosstalk distance of <0.6 mm, and exhibited stable 0% strain resistances after 1000 strain cycles to 20%. Fabrication of single layer and encapsulated ECBs was demonstrated.

Efficient Charge Transfer in Narrowband Organic Photodiodes Based on Self‐Assembled Heterojunction for Spectrally Selective Photodetection and Imaging

AbstractSpectrally selective photodetection has been used in many areas where only band‐specific optical signals are aimed to be detected. Organic photodiodes (OPDs) based on internal light depletion mechanisms have been utilized to realize narrowband photodetection. However, the fabrication of the photoactive layers by conventional solution methods can result in the deterioration of the underneath organic depletion layers and cause high‐density defect states at their interface. Herein, a new approach is presented to realize efficient charge transfer by adopting a self‐assembly strategy to prepare donor/acceptor bulk heterojunctions as the photoactive layers for narrowband OPDs. This method is able to prepare highly smooth, phase‐uniform, and low‐defect‐density thin films with controlled thickness. With this strategy, a narrowband near‐infrared OPD centered at 760 nm with a full‐width‐at‐half‐maximum of around 60 nm, peak external quantum efficiency of 49%, and peak specific detectivity of over 1013 Jones under −5 V is achieved. Multiple material combinations for the depletion and photoactive layers are examined, and the results show the effectiveness to realize the spectrally selective photodetection (from 740 to 900 nm) in general. More importantly, the narrowband OPDs can be integrated into a matrix for imaging, which demonstrates the mass‐scale fabrication feasibility of these OPDs.

Decoration of β-Cyclodextrin and Tuning Active Layer Chemistry Leading to Nanofiltration Membranes for Desalination and Wastewater Decontamination.

Given the huge potential of thin film composite (TFC) nanofiltration (NF) membranes for desalination and micro-pollutant removal, two different sets of six NF membranes were synthesized. The molecular structure of the polyamide active layer was tuned by using two different cross-linkers, terephthaloyl chloride (TPC) and trimesoyl chloride (TMC), reacted with tetra-amine solution containing β-Cyclodextrin (BCD). To further tune the structure of the active layers, the time duration of interfacial polymerization (IP) was varied from 1 to 3 min. The membranes were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), water contact angle (WCA), attenuated total reflectance Fourier transform infra-red (ATR-FTIR) spectroscopy, elemental mapping and energy dispersive (EDX) analysis. The six fabricated membranes were tested for their ability to reject divalent and monovalent ions followed by rejection of micro-pollutants (pharmaceuticals). Consequently, terephthaloyl chloride turned out to be the most effective crosslinker for the fabrication of membrane active layer with tetra-amine in the presence of β-Cyclodextrin using interfacial polymerization reaction for 1 min. The membrane fabricated using TPC crosslinker (BCD-TA-TPC@PSf) showed higher % rejection for divalent ions (Na2SO4 = 93%; MgSO4 = 92%; MgCl2 = 91%; CaCl2 = 84%) and micro-pollutants (Caffeine = 88%; Sulfamethoxazole = 90%; Amitriptyline HCl = 92%; Loperamide HCl = 94%) compared to the membrane fabricated using TMC crosslinker (BCD-TA-TMC@PSf). For the BCD-TA-TPC@PSf membrane, the flux was increased from 8 LMH (L/m2.h) to 36 LMH as the transmembrane pressure was increased from 5 bar to 25 bar.

(Digital Presentation) Prolonged Operation Strategies For Solid Oxide Fuel Cell Through Barrier Layer-Based Interface Engineering

In order to clarify the relationship between area specific resistance degradation and barrier layer, three symmetrical cathode cells with varied GDC barrier layer fabrication methods are investigated, i.e. (1) screen printed GDC, (2) screen printed GDC with Cobalt Nitrate sintering aid (GDC-Co), and (3) hydrothermal modified cell (GDC-Co-HY). Stable LSCF@GDC cathode is used for the electrode. The results show largely decreased of ~20% when sintering aid is used. Furthermore, both and values of GDC-Co-HY are extremely stable after hydrothermal modification, with degradation rate of 0.014 and 0.03 Ω·cm2/kh, respectively. Comparatively, the pristine GDC-Co shows and increase of 0.22Ω·cm2/kh and 0.248Ω·cm2/kh. Current study suggests that interface engineering is an effective method to enable smaller ASR and improved long-term operation durability.

Variation of Charge Carrier Dynamics for Polycrystalline Perovskite Films by One-Step Solution and Vapor-Deposition Methods.

To date, solution-processing and vapor-deposition fabrication methods have achieved huge successes in high-efficiency perovskite solar cells (PSCs) and satisfy special demanding requirements for diverse application purposes, respectively. Although people realize that the fabrication procedure is crucial in device performance, insightful studies of charge carrier dynamics in perovskite films by different methods still lack. In this work, we compare the carrier behaviors in one-step spin-coated and dual-source coevaporated MAPbI3 perovskite films by combining time-resolved photoluminescence spectroscopy and carrier dynamics simulation. We suggest that strains, lattice orientations, and defects at buried side of perovskite films, which are associated with different preparation processes, lead to variations in carrier behaviors. Hence fabrication of perovskite layers should be elaborately designed in order to satisfy the needs of different carrier behaviors in specified device configurations of PSCs such as smooth planar or textured monolithic tandem structures.