All‐Solution‐Processed Micro/Nanowires with Electroplate Welding as Transparent Conducting Electrodes

An all‐solution‐processed transparent conductive electrode with sheet resistance one order of magnitude smaller than conventional nanowire‐based transparent conductors has been developed. This is achieved by integrating all‐solution produced microwires with a nanowire solution and electroplating and electrowelding. Advantages of the resulting transparent conductor are indium‐free, vacuum‐free, and lithographic‐facility‐free, and metallic‐mask‐free, with small domain size (≈10 μm2), low sheet resistance (Rs < 1 Ω □−1), high optical transmittance (T > 80%), mechanical flexibility, and scalability, thus making it an excellent replacement for ITO.

High-performance flexible Sn-doped In2O3 (indium tin oxide, ITO) electrodes were fabricated using a multicoating process on colorless polyimide (CPI) substrates for flexible perovskite solar cells (FPSCs). The effects of different coating sequences on the electrical, optical, and mechanical properties of the flexible ITO electrodes were thoroughly investigated after preparing them with direct-current magnetron sputtering (DMS) and arc plasma ion plating (APIP). Although both the sputtered ITO (SITO)/arc ion-plated ITO (AITO) film and the AITO/SITO film showed similarly low sheet resistance (18.69-25.29 Ω/sq) and high optical transmittance (94.96-96.85%), the coating sequence significantly affected the mechanical flexibility of the multicoated ITO films. The 120 nm-thick SITO/AITO electrode exhibited small outer and inner critical bending radii (3 mm and 3 mm, respectively) compared to the AITO/SITO electrode (4 and 5 mm, respectively). Owing to better adhesion of the arc-ion-plated ITO bottom layer and the amorphous structure of the top SITO layer, the SITO/AITO electrode exhibited excellent mechanical flexibility and durability. In addition, an FPSC using the SITO/AITO electrode achieved a higher power conversion efficiency (15.09%) than that with the AITO/SITO electrode (13.22%). This improvement was attributed to its high transmittance, low sheet resistance, smooth surface morphology, and enhanced hole collection efficiency. These findings highlight the efficacy of the combined DMS and APIP multicoating process for fabricating high-quality flexible ITO electrodes for high-performance FPSCs.

As an alternative to the brittle and expensive indium tin oxide (ITO) transparent conductor, a very simple, room‐temperature nanosoldering method of Ag nanowire percolation network is developed with conducting polymer to demonstrate highly flexible and even stretchable transparent conductors. The drying conducting polymer on Ag nanowire percolation network is used as a nanosoldering material inducing strong capillary‐force‐assisted stiction of the nanowires to other nanowires or to the substrate to enhance the electrical conductivity, mechanical stability, and adhesion to the substrate of the nanowire percolation network without the conventional high‐temperature annealing step. Highly bendable Ag nanowire/conducting polymer hybrid films with low sheet resistance and high transmittance are demonstrated on a plastic substrate. The fabricated flexible transparent electrode maintains its conductivity over 20 000 cyclic bends and 5 to 10% stretching. Finally, a large area (A4‐size) transparent conductor and a flexible touch panel on a non‐flat surface are fabricated to demonstrate the possibility of cost‐effective mass production as well as the applicability to the unconventional arbitrary soft surfaces. These results suggest that this is an important step toward producing intelligent and multifunctional soft electric devices as friendly human/electronics interface, and it may ultimately contribute to the applications in wearable computers.

The importance of transparent electrode technology for solar cells and perovskite solar cells will be introduced. First, we introduce the roll-to-roll sputtering technique and multilayer electrode for flexible solar cells. We fabricated flexible inverted solar cell (IOSC) modules (10 cm× 10 cm) on roll-to-roll (RTR) sputtered ITO/Ag/ITO multilayer cathodes. By using a pilot-scale RTR sputtering system equipped with mid-range frequency power for dual ITO targets and direct current power for the Ag target, we were able to continuously deposit a high-quality ITO/Ag/ITO multilayer on PET substrate with a width of 700 mm and length of 20,000 mm as a function of Ag thickness. To optimize the electrical and optical properties of the ITO/Ag/ITO multilayer, the thickness of Ag layer was varied by controlling of the DC power applied on Ag targets during the RTR sputtering process. At the Ag thickness of 12 nm, the ITO/Ag/ITO multilayer had a very low sheet resistance of 3.03 Ohm/square and high transmittance of 88.17%, which are better values than those of amorphous ITO film. Various bending test results showed that the high failure strain of the Ag inter layer led to good flexibility of the multilayer films. A strip-type ITO/Ag/ITO cathode was successfully patterned using a RTR wet etching process. Successful operation of flexible IOSC modules on RTR sputtered ITO/Ag/ITO cathodes indicate that the RTR sputtering technique is a promising coating process for fabrication of high-quality transparent and flexible cathodes and can advance the commercialization of cost-efficient flexible IOSCs. Second, we fabricated high-performance flexible CH3NH3PbI3 (MAPbI3) perovskite solar cells with a power conversion efficiency of 16.8% on transparent and flexible ITO electrode prepared by specially designed ion plating system. The ion plated ITO films on PET substrate showed a lower sheet resistance and higher optical transmittance than conventional sputtered ITO films because the high-energy input into a growing ITO film led to densification of the growing film during ion plating process. At optimal coating condition, the ion-plated ITO film with a thickness of 100 nm showed a sheet resistance of 15.75 Ohm/square and an optical transmittance of 84%, which are better than those of sputtered ITO film. Outer and inner bending tests demonstrated that the mechanical flexibility of the ion plated ITO film was superior to that of the conventional sputtered ITO film due to better adhesion between ion plated ITO and PET substrate. Flexible perovskite solar cells with the structure of Au/PTAA/MAPbI3/ZnO/ITO/PET showed a higher power conversion efficiency of 16.8% than sputtered ITO-based flexible perovskite solar cells (15.4%) due to lower sheet resistance and higher optical transmittance. Finally, we introduce a linear facing target sputtering technique to realize semi-transparent perovskite solar cells. By effective confinement of high density plasma between ITO targets, we can deposit plasma damage free IZTO electrode on layer. This indicates that linear facing target sputtering is a promising plasma damage free sputtering technique to deposit transparent electrode on perovskite active layer for high efficient semi-transparent perovskite solar cells.

Summary: A series of novel poly(amine‐amide‐imide)s with pendent N‐carbazolylphenyl units that have inherent viscosities of 0.45–0.66 dL · g−1 are prepared from various aromatic bis(trimellitimide)s and the new carbazole‐based aromatic diamine, 4,4′‐diamino‐4″‐N‐carbazolyltriphenylamine, by direct polycondensation. All the polymers are readily soluble in polar organic solvents. Flexible, amorphous, and deep reddish films of poly(amine‐amide‐imide)s can be obtained by solution casting, and have useful levels of thermal stability associated with high glass transition temperatures (307–343 °C), 10% weight‐loss temperatures in excess of 500 °C, and char yields at 800 °C in nitrogen higher than 65%. These polymers exhibit a maximum UV‐vis absorption at 300 nm with a fluorescence emission maxima around 449–454 nm in N‐methyl‐2‐pyrrolidinone solution. The hole‐transporting and electrochromic properties are examined by electrochemical and spectroelectrochemical methods. Cyclic voltammograms of the poly(amine‐amide‐imide) films cast onto an indium tin oxide‐coated glass substrate exhibit a reversible oxidation at 0.84 V and irreversible oxidation redox couples at 1.27 V versus Ag/AgCl in acetonitrile solution, and reveal good stability of electrochromic characteristics, with a color change from yellowish to green at applied potentials ranging from 0.00 to 0.95 V.Structure and properties of PAI‐2M (bottom left: cyclic voltammetry; bottom right: potential‐step absorptometry).imageStructure and properties of PAI‐2M (bottom left: cyclic voltammetry; bottom right: potential‐step absorptometry).

In order to perform nano-manipulation more accurately, it is necessary to study the relationship between the scanning electron microscope (SEM) image and the actual length. In this paper, based on the secondary electron image, the displacement of 1.81nm in SEM was measured the actual displacement was obtained according to the change of the pixels, so as to realize the nanometer displacement calibration and real-time measurement of the nano robot manipulator in SEM. According to the magnification, resolution and scale bar of SEM image, the mapping relationship between pixels and actual length was established. The obvious feature point and area in the SEM image were selected to be marked. The driving signal was applied to the manipulator of the nano robot, and the template matching algorithm was used to track the feature point and area in real time. The change of the feature point in the SEM image was obtained, and the actual displacement of the manipulator was calculated according to the mapping relationship between the pixel points and the actual displacement. We calibrated the displacement of the nanorobots and measured the actual displacement in real time, which laid a foundation for the precise control of the nanorobots in the future.

Image noise is an important factor that influences the accuracy of strain field measurements by means of digital image correlation and scanning electron microscope (SEM) imaging. We propose a new model to quantify the SEM image noise, which extends the classical photon noise model by taking into account the brightness setup in SEM imaging. Furthermore, we apply this model to investigate the impact of different SEM setting parameters on image noise, such as detector, dwell time, spot size, and pressure in the SEM chamber in the context of low vacuum imaging.

Transparent conductive films (TCFs) with low sheet resistance and high optical transmittance in the visible and infrared regions are essential components of a wide range of optoelectronic devices. Silver nanowires (AgNWs) have attracted significant attention due to their superior flexibility, conductivity, and transparency. However, TCFs prepared by commonly used film-forming methods such as spin coating suffer from a trade-off between conductivity and transmittance, which results in diminished device performance. Here, we report a layer-by-layer agitation-assisted alignment technique to fabricate highly aligned AgNWs films for transparent electrodes. The effects of solution concentration, rotation speed, and treatment time on the morphology, transmittance, and sheet resistance of the aligned AgNWs films were investigated systematically. Compared with randomly distributed AgNWs, optoelectronic performance was greatly improved, and the final film had a transmittance of 91.07% at 550 nm and a sheet resistance of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$27.5~\Omega $ </tex-math></inline-formula>/sq. Research findings indicate that optimized AgNW electrodes can be successfully utilized to fabricate high-performance silicon-based photodetectors. Compared with previous designs, these detectors exhibit a 13.3% increase in the external quantum efficiency (EQE) at a wavelength of 850 nm. This study offers a low-cost and simple method for aligned AgNWs films, which has great potential for use in optoelectronic devices.

Effects of substrate temperature on the Ga-doped ZnO films as an anode material of organic light emitting diodes

The MeX™ software is a useful tool for tridimensional data collection for surface evaluation and could be relevant to evaluate the same specimen in different phases of the study, assuming repeated measures of dental enamel roughness. The aim of this study was to evaluate the influence of sample metallization for dental enamel roughness analysis with 3D images reconstructed using MeX™ software from Scanning Electron Microscopy (SEM) images. The influence of 74.98% (%mol/mol) argon-oxygen plasma for carbon layer removal on surface roughness of the metallized specimen was also evaluated. Dental enamel specimens were prepared for SEM analysis with and without carbon metallization using conventional or environmental modes. Argon-oxygen plasma for carbon layer removal was used and surface roughness was re-evaluated. Roughness obtained by SEM and MeX™ reconstructed images, with or without metallization, did not differ. No significant alteration on surface roughness after carbon layer removal using plasma was found. SEM baseline evaluation using conventional mode without sample preparation and in environmental mode were not comparable. Roughness of enamel 3D images reconstructed with MeX™ software from SEM images, with or without metallization was similar. The 74.98% (%mol/mol) argon-oxygen plasma removed the carbon layer with no effect on enamel roughness.

Accurate identification and classification of atmospheric particulates can provide the basis for their source apportionment. Most current research studies mainly focus on the classification of atmospheric particles based on the energy spectrum of particles, which has the problems of low accuracy and being time-consuming. It is necessary to study the classification method of atmospheric particles with higher accuracy. In this paper, a convolutional neural network (CNN) model with attention mechanism is proposed to identify and classify the scanning electron microscopy (SEM) images of atmospheric particles. First, this work established a database, Qingdao 2016–2018, for atmospheric particles classification research. This database consists of 3469 SEM images of single particulates. Secondly, by analyzing the morphological characteristics of single particle SEM images, it can be divided into four categories: fibrous particles, flocculent particles, spherical particles, and mineral particles. Thirdly, by introducing attention mechanism into convolutional neural network, an Attention-CNN model for the identification and classification of the four types of atmospheric particles based on the SEM images is established. Finally, the Attention-CNN model is trained and tested based on the SEM images database, and the results of identification and classification for four types of particles are obtained. Under the same SEM images database, the classification results from Attention-CNN are compared with those of CNN and SVM. It is found that Attention-CNN has higher classification accuracy and reduces significantly the misclassification number of particles, which shows the focusing effect of attention mechanism.

A methodology for the automated analysis of metal powder scanning electron microscope (SEM) images towards material characterization is developed and presented. This software-based tool takes advantage of a combination of recent artificial intelligence advances (mask R-CNN), conventional image processing techniques, and SEM characterization domain knowledge to assess metal powder quality for additive manufacturing applications. SEM is being used for characterizing metal powder alloys, specifically by quantifying the diameter and number of spherical particles, which are key characteristics for assessing the quality of the analyzed powder. Usually, SEM images are manually analyzed using third-party analysis software, which can be time-consuming and often introduces user bias into the measurements. In addition, only a few non-statistically significant samples are taken into consideration for the material characterization. Thus, a method that can overcome the above challenges utilizing state-of-the-art instance segmentation models is introduced. The final proposed model achieved a total mask average precision (mAP50) 67.2 at an intersection over union of 0.5 and with prediction confidence threshold of 0.4. Finally, the predicted instance masks are further used to provide a statistical analysis that includes important metrics such as the particle size distinction.

HighlightsGraphene possesses high electronic mobility, minimal light absorbance, large surface area and exclusive mechanical properties.Graphene’s unique characteristics make it the perfect material for use in batteries, touch screens, transparent memory, and integrated circuits.The development of high-quality homogenous graphene, simple transfer processes, a lack of effective characterization methods, and high production costs prevent graphene from being widely used in the electronic industry.The production of large-area, nearly defect-free graphene using contemporary synthesis techniques, such CVD, holds great potential for the development of nanoelectronic devices.Graphene achieved a peerless level among nanomaterials in terms of its application in electronic devices, owing to its fascinating and novel properties. Its large surface area and high electrical conductivity combine to create high-power batteries. In addition, because of its high optical transmittance, low sheet resistance, and the possibility of transferring it onto plastic substrates, graphene is also employed as a replacement for indium tin oxide (ITO) in making electrodes for touch screens. Moreover, it was observed that graphene enhances the performance of transparent flexible electronic modules due to its higher mobility, minimal light absorbance, and superior mechanical properties. Graphene is even considered a potential substitute for the post-Si electronics era, where a high-performance graphene-based field-effect transistor (GFET) can be fabricated to detect the lethal SARS-CoV-2. Hence, graphene incorporation in electronic devices can facilitate immense device structure/performance advancements. In the light of the aforementioned facts, this review critically debates graphene as a prime candidate for the fabrication and performance enhancement of electronic devices, and its future applicability in various potential applications.

We introduce a new concept for transparent electrodes via the self-assembly of a silver nanowire (Ag NW) network with a cell shape. A transparent conductive network was achieved by forming an array of Ag NWs around droplets of a solvent with higher vapor pressure in Ag NWs ink. The difference in vapor pressure and viscosity of the solvent causes an Ag NWs network with a cell shape, and the cell size can be easily controlled from 10 to 100 μm using the solvent ratio. The cell network of Ag NWs with a high optical transmittance (>92%) and low sheet resistance (40 Ω/sq) was simply fabricated on flexible polymer films of large scale using a Meyer rod coating. In addition, we also studied and demonstrated the figure of merit of the transparent electrode between our method and a random Ag NWs network from the general method. The performance of the transparent electrode may be applied to a wide array of optoelectronic devices and can replace transparent conductive oxides such as Al-doped ZnO and indium tin oxide.

A flexible and transparent amorphous-indium tin oxide/silver/crystalline-indium tin oxide (a-ITO/Ag/c-ITO) triple-layer structure was prepared as an electrode for capacitive-type touch screen panels (TSPs). A very thin metal film of silver (Ag) was inserted between two ITO layers, and the triple-layer structures were deposited on a colorless polyimide (CPI) substrate by a sputtering method. It was found that the tunable electrical and optical properties of the a-ITO/Ag/c-ITO triple-layer structures were critically affected by the thickness of the inserted Ag layer. The optimized flexible a-ITO/Ag/c-ITO triple-layer structure has low sheet resistance, high optical transmittance, and low surface roughness. In addition, during the 30 000 bending cycles, the resistance change (ΔR) of the flexible a-ITO/Ag/c-ITO triple-layer structure was 4.12%. For environmental reliability, the ΔR values of the flexible a-ITO/Ag/c-ITO triple-layer structure were 2.86% and 0.96% at the environmental temperature of 80 °C-50% and −40 °C, respectively. The above results indicate that the a-ITO/Ag/c-ITO triple-layer structure can be utilized to construct a promising TCO electrode. Finally, flexible and foldable capacitive-type TSPs were fabricated with multiple touch points using the a-ITO/Ag/c-ITO triple-layer electrode.