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We successfully prepared a surfactant-assisted carbon nanotube (CNT) liquid crystal (LC) dispersion with double-walled CNTs (DWCNTs) having a high aspect ratio (≈1378). Compared to dispersions of single-walled CNTs (SWCNTs) with lower aspect ratio, the transition concentrations from isotropic phase to biphasic state, and from biphasic state to nematic phase are lowered, which is consistent with the predictions of the Onsager theory. An aligned DWCNT film was prepared from the DWCNT dispersion by a simple bar-coating method. Regardless of the higher aspect ratio, the order parameter obtained from the film is comparable to that from SWCNTs with lower aspect ratios. This finding implies that precise control of the film formation process, including a proper selection of substrate and deposition/drying steps, is crucial to maximize the CNT-LC utilization.

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 (CH3NH3)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%. [ABSTRACT FROM AUTHOR]

Here, the utilization of a highly uniform water‐borne polyimide (W‐PI) thin film as a gate dielectric layer for large‐scale organic thin film transistors (OTFTs) exceeding 100 cm2 is presented, employing the bar‐coating technique. The W‐PI thin films are obtained uniformly over a large area by systematically manipulating the surface tension of the water‐soluble poly(amic acid) salts (W‐PAAS) solution using alcohol as a co‐solvent in a "Green" process. The thickness of the W‐PI thin film is precisely controlled within the range of tens to hundreds of nanometers by adjusting key parameters, including the concentration of the W‐PAAS solution, wire diameter, and bar‐coating speed. As a result, 500 pentacene‐based OTFTs are successfully fabricated on a 10 × 10 cm2 substrate, utilizing a 280 nm thick W‐PI gate dielectric film. These devices exhibit excellent uniformity, with field‐effect mobility of 0.20 ± 0.02 cm2 V−1 s−1. Furthermore, the fabrication of electronic devices using an environmental‐friendly bar‐coating method on large‐area flexible substrates is demonstrated. This study highlights the considerable potential of eco‐friendly W‐PI thin films as dielectric materials, offering advantages such as cost‐effectiveness and high efficiency for reliable industrial applications. [ABSTRACT FROM AUTHOR]

Abstract Here, the utilization of a highly uniform water‐borne polyimide (W‐PI) thin film as a gate dielectric layer for large‐scale organic thin film transistors (OTFTs) exceeding 100 cm2 is presented, employing the bar‐coating technique. The W‐PI thin films are obtained uniformly over a large area by systematically manipulating the surface tension of the water‐soluble poly(amic acid) salts (W‐PAAS) solution using alcohol as a co‐solvent in a “Green” process. The thickness of the W‐PI thin film is precisely controlled within the range of tens to hundreds of nanometers by adjusting key parameters, including the concentration of the W‐PAAS solution, wire diameter, and bar‐coating speed. As a result, 500 pentacene‐based OTFTs are successfully fabricated on a 10 × 10 cm2 substrate, utilizing a 280 nm thick W‐PI gate dielectric film. These devices exhibit excellent uniformity, with field‐effect mobility of 0.20 ± 0.02 cm2 V−1 s−1. Furthermore, the fabrication of electronic devices using an environmental‐friendly bar‐coating method on large‐area flexible substrates is demonstrated. This study highlights the considerable potential of eco‐friendly W‐PI thin films as dielectric materials, offering advantages such as cost‐effectiveness and high efficiency for reliable industrial applications.

In recent years, exciting advances have been achieved in pursuing organic thin film transistors (OTFTs) with high mobility. Whereas, the economical infeasibility of Au source/drain (S/D) electrodes that are widely used in OTFTs hinders the further development of OTFTs in industry. In this study, the modified indium tin oxide (ITO) as S/D electrodes is adopted. The ITO is modified by HCl aqueous solutions, its surface work function is improved from 4.8 to 5.5 eV. By first‐principle calculations and experiments, the charge analysis shows that the Cl atom traps 0.475 electrons, which indicates that In–Cl dipoles are responsible for the increase of the surface work function, besides the HCl modification leads to In+‐Cl− bonds instead of In3+‐Cl− bonds on the ITO surface compared with the reported InCl3 modification. More encouragingly, In+‐Cl− surface is found to have higher Cl density, higher work function and higher conductivity. TIPS‐pentacene, with suitable HOMO level of 5.2 eV, is adopted as organic semiconductor, and the bar‐coating process is optimized to realize oriented films. OTFTs with maximum field‐effect mobility of 0.77 cm2 V−1 s−1 are achieved. The ITO electrodes modified by HCl can be promising in the industry. [ABSTRACT FROM AUTHOR]

The radical proliferation of pathogenic bacteria and their infections causes significant issues for human health and the environment. Today, biopolymers are used to produce different nanoparticles. In the present investigation, the fabricated chitosan/agar-silver nanoparticles (Cht/Ar-AgNPs)-coated papers were tested for antibacterial applications. Agar was used as a reducing agent for the synthesis of AgNPs. Synthesized Ar-AgNPs were examined through optical, phase crystallinity and topological analysis. Cht and Ar-AgNPs solution was mixed with various ratios of 9:1, 8:2, 7:3, 6:4, and 5:5 by weight. In addition to that, the conformity of Cht/Ar-AgNPs-coated papers was characterized by structural, spectral, and morphological analysis. However, Cht/Ar-AgNPs-coated papers were subjected to antibacterial properties. The ratio of (6:4) Cht/Ar-AgNPs-coated paper showed excellent antibacterial agent, and it can be used as extending the food product shelf life.

Advancements in cell coculture systems with porous membranes have facilitated the simulation of human-like in vitro microenvironments for diverse biomedical applications. However, conventional Transwell membranes face limitations in low porosity (ca. 6%) and optical opacity due to their large thickness (ca. 10 μm). In this study, we demonstrated a one-step, large-scale fabrication of freestanding polymer ultrathin porous (PUP) membranes with thicknesses of hundreds of nanometers. PUP membranes were produced by using a gap-controlled bar-coating process combined with polymer blend phase separation. They are 20 times thinner than Transwell membranes, possessing 3-fold higher porosity and exhibiting high transparency. These membranes demonstrate outstanding molecular permeability and significantly reduce the cell-cell distance, thereby facilitating efficient signal exchange pathways between cells. This research enables the establishment of a cutting-edge in vitro cell coculture system, enhancing optical transparency, and streamlining the large-scale manufacturing of porous membranes.

Abstract Molecularly oriented thin films of non-peripherally pentyl-substituted phthalocyanine (C5PcH 2), which exhibits α-type and β-type crystal polymorphs, were fabricated by the bar-coating method. By setting an α-type or β-type seed crystal around the initial position of the coating bar on a substrate, oriented thin films with either an α-type or β-type crystal structure were selectively fabricated, respectively. This was confirmed by grazing-incidence wide-angle X-ray scattering studies of the thin films. Without the seed crystal in the same bar-coating condition, an unidentified crystal polymorph of C5PcH 2 appeared in the film state, which was discussed by taking the peak intensities in the X-ray diffraction pattern into consideration. Graphical abstract Image 1 Highlights • Selective crystal growth of phthalocyanine in bar-coating film was demonstrated. • Introduction of seed crystal was effective for selectivity of crystal structure. • Crystal structures in films were determined by using a GIWAX technique. • An unidentified crystal polymorph appeared in bar-coating without seed crystal. [ABSTRACT FROM AUTHOR]

We report efficient, planar heterojunction perovskite solar cells prepared via bar coating that are compatible with large-scale fabrication on flexible substrates. Our MAPbI 3 perovskite devices by bar coating method achieved a maximum power conversion efficiency (PCE) of 13.0% using a ITO/PEDOT: PSS/CH 3 NH 3 PbI 3 (MAPbI 3) /PCBM/Ag structure, and there is very weak hysteresis in these devices. After formulation of the precursor solution and optimization of the coating process, planar perovskite thin films containing large-size grains with low surface roughness were obtained. We found that anti-solvent plays an important role in determining the uniformity, size of grains and width of grain boundaries in perovskite films. The addition of 5 vol% isopropanol into the precursor solution leads to the formation of large aspect ratio grains with a length ca. 200 µm and width of a few hundred nanometers, together with narrow grain boundaries. However, the absence or excessive of isopropanol result in perovskite films with high surface roughness and broad grain boundaries due to inefficient crystal growth or the formation of ridges between crystal grains. These grain boundaries have high PL intensity due to charge recombination and consequently deteriorate device efficiency. When bar-coating the perovskite films in air, best devices with PCE over 11% can be achieved with a relatively high humidity around 50%, eliminating the low humidity requirement during air processing. [ABSTRACT FROM AUTHOR]

We report high-performance organic thin-film transistors (OTFTs) with an ultrathin active layer of difluorobenzothiadiazole-dithienosilole copolymer (PDFDT) form by using the wire bar-coating process. The top-gate/bottom contact (TG/BC) OTFTs based on bar-coated PDFDT polymer as channel material and poly(methyl methacrylate) (PMMA) as gate dielectric show a hole mobility of up to 2.2 cm 2 V −1 s −1 with a current ON/OFF ratio ( I on / I off ) of 10 4 ∼10 5 , with the mobility being two times larger than that of the spin-coated PDFDT based OTFTs. The higher mobility of the bar-coated PDFDT polymer films can be attributed to the well-organized fibril structures of the polymer chains. Importantly, two different molecular weight polymers ( M n = 23 and 34 kDa) were employed to conduct these experiments and both batches showed about the same performance, which mitigates the typical batch-to-batch variation in OTFT performance. Furthermore, we explored the operational stability of the bar-coated OTFTs in ambient air and nitrogen environments. The bias-stress and cycling tests between the ON/OFF states of the bar-coated devices showed high stability in both nitrogen and air. Conclusively, here we demonstrate that (i) a simple bar-coating process is a better method to control and obtain good polymer morphology in comparison to spin-coating, and (ii) the PDFDT polymer has great potential to provide good reproducibility and stability in large-area OTFT devices. [ABSTRACT FROM AUTHOR]

A fast meniscus-guided coating for ultrahighly oriented thin films of a typical donor-acceptor π-conjugated polymer, poly[2,5-(2-octyldodecyl)-3,6-diketopyrrolopyrrole- alt -5,5-(2,5-di(thien-2-yl)thieno[3,2- b ]thiophene)](PDPP-DTT) was realized. A coating speed higher than 100 mm/s, which was regarded as a Landau-Levich regime, was applicable. The 2D order parameter ( S 2 ) of the thin films changed by selecting the solvent and adjusting the initial concentration of the solution, and the large elongated rodlike preaggregates formed particularly in chlorobenzene contributed to the high orientation in the solid film state, resulting in the highest value of S 2 = 0.87. Focused on the PDPP-DTT preaggregate formation in the solution, the SAXS analysis was carried out to investigate the shape and size of the preaggregates. The mechanism of the molecular orientation was discussed by taking the preaggregates and the solution flow under the coating process into account.

The SiOx thin film with a thickness of about 1 mum was formed on a GaAs substrate by bar-coating with the organic solution of the SiOx nanoparticles (~40 nm). The as-formed SiOx thin film consists of the SiOx nanoparticles; thus the thin film is macroscopically discontinuous and is referred to as a nanoparticle thin film. Although there were no silicon (Si) nanocrystals in the as-formed SiOx nanoparticle thin film, Si nanocrystals were observed by Raman scattering measurement after the thin film was exposed to the laser beam. The growth of Si nanocrystals by laser irradiation is referred to as photosynthesis. The photosynthesis of Si nanocrystals is found to be a self-limiting process. After the average size reaches a certain value, further increase of irradiation time or laser power does not increase the average size. The photosynthesis is similar to the thermal synthesis of Si nanocrystals from SiOx but much faster and low-temperature growth of Si nanocrystals from SiO x. Furthermore, the laser irradiation makes nanoparticles larger by merging. This suggests a possibility of low-temperature formation of a Si-nanocrystal array embedded in a SiO2 thin film. Such a structure has many potential device applications [ABSTRACT FROM PUBLISHER]

CH 3 NH 3 PbI 3 (MAPbI 3) thin films were fabricated via a bar-coating process, which is appropriate for large-scale and mass production. By using the bar-coating process, the plane orientation [100] of MAPbI 3 was vertically aligned in the thin film on the substrate. Blending NH 4 Cl to the precursor solution before the bar-coating, the film quality markedly changed depending on the amount of NH 4 Cl, resulting in the suppression of the grain boundary and the improvement of the surface morphology. Thus, the highly (100)-oriented and uniform thin film of MAPbI 3 with the large grains could be obtained. Typical inverted-type solar cells were fabricated using such an excellent MAPbI 3 thin film, and the high device performance was demonstrated. Image 1 • Bar-coating process was adopted for thin film fabrication of MAPbI 3. • Fabrication of highly (100)-oriented MAPbI 3 thin films was demonstrated. • Additive effects of NH 4 Cl for film morphology were revealed. • Growth of large-size grain in MAPbI 3 thin films was realized. • High performance of solar cells fabricated via bar-coating were exhibited. [ABSTRACT FROM AUTHOR]

The development of a scalable fabrication technology for halide perovskite solar cells (HPSCs) is an important challenge to realize their commercialization. In particular, continuous solution-coating processes are needed to produce scalable large-area HPSCs. Herein, we report a single-solution bar-coating process that introduces an intermediate phase stage for large-area CH 3 NH 3 PbI 3 films with full coverage and smooth morphology using N-cyclohexyl-2-pyrrolidone (CHP) as a mediator. In contrast to the conventional double-solution coating methods that use antisolvent treatments, the preformed uniform intermediate phase in the single-solution bar-coating process enables the formation of highly uniform perovskite films with a 10 cm × 10 cm area even without antisolvent treatment. The HPSCs fabricated using the resultant single-solution bar-coated perovskite films exhibit superior photovoltaic performance, narrower distribution, and smaller loss with a larger active area than devices fabricated using single-solution spin-coated perovskite films.

Silver nanowire (AgNW) networks are considered to be promising structures for use as flexible transparent electrodes for various optoelectronic devices. One important application of AgNW transparent electrodes is the flexible touch screens. However, the performances of flexible touch screens are still limited by the large surface roughness and low electrical to optical conductivity ratio of random network AgNW electrodes. In addition, although the perception of writing force on the touch screen enables a variety of different functions, the current technology still relies on the complicated capacitive force touch sensors. This paper demonstrates a simple and high-throughput bar-coating assembly technique for the fabrication of large-area (>20 × 20 cm 2 ), highly cross-aligned AgNW networks for transparent electrodes with the sheet resistance of 21.0 Ω sq -1 at 95.0% of optical transmittance, which compares favorably with that of random AgNW networks (sheet resistance of 21.0 Ω sq -1 at 90.4% of optical transmittance). As a proof of concept demonstration, we fabricate flexible, transparent, and force-sensitive touch screens using cross-aligned AgNW electrodes integrated with mechanochromic spiropyran-polydimethylsiloxane composite film. Our force-sensitive touch screens enable the precise monitoring of dynamic writings, tracing and drawing of underneath pictures, and perception of handwriting patterns with locally different writing forces. The suggested technique provides a robust and powerful platform for the controllable assembly of nanowires beyond the scale of conventional fabrication techniques, which can find diverse applications in multifunctional flexible electronic and optoelectronic devices.

The influence of processing conditions, such as ink concentration and coating method, on the thermoelectric properties of SWCNT/P3HT nanocomposite films was investigated systematically. Using simple wire-bar-coating, SWCNT/P3HT nanocomposite films with high thermoelectric performance could be obtained without additional P3HT doping. The wire-bar-coated SWCNT/P3HT nanocomposite films exhibited power factors of up to 105 μW m(-1) K(-2) at room temperature. The SWCNT bundles with diameters in the range of 6-23 nm formed an interconnected network in the wire-bar-coated nanocomposite films. Network formation in these nanocomposite films was expected to be strongly related to the development of electrical pathways due to inter-SWCNT bundle connections. This study suggests that the thermoelectric performance of SWCNT/P3HT nanocomposite films could be optimized by controlling their processing conditions and morphology.

Large-area polymer FET arrays and integrated circuits (ICs) are successfully demonstrated via a simple wire-bar-coating process. Both a highly crystalline conjugated polymer layer and very smooth insulating polymer layer are formed by a consecutive wire-bar-coating process on a 4-inch plastic substrate with a short processing time for application as the active and dielectric layers of OFET arrays and ICs., (Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)