Transparent Conductive Coatings Research Articles

The system of automatic control of the substrate temperature in the installation for the production of film material spray pyrolysis method

A system of automatic control of the substrate temperature is proposed, which ensures the required accuracy of temperature maintenance and its minimum gradient over the surface when obtaining transparent conductive coatings by spray pyrolysis. During pyrolysis, aerosol droplets are transferred to a heated substrate; at the right temperature, they decompose, and then synthesize or melt on a hot substrate. The ideal temperature regime for evaporation of aerosol droplets will be the mode when a drop appears at the substrate immediately after evaporation of the solvent from it. Precise control of the substrate temperature and temperature gradient ensures this mode. The functional scheme of the proposed automatic control system consists of an automatic temperature controller, a power regulator, an infrared heater on halogen lamps, and a temperature sensor. The variational problem of minimizing power consumption when the infrared heater is turned on has been solved. This activation eliminates current emissions and thereby increases the service life of the heater. It is proposed to connect the heater to a current source in order to eliminate current emissions, thereby ensuring the optimal switching mode. The synthesis and analysis of the specified automatic control system has been performed, its time and frequency parameters have been calculated. Acceptable performance, zero static control error and zero overshoot, a significant margin of stability in phase and amplitude have been confirmed. The use of such an automatic temperature control system contributes to the creation of an optimal mode of evaporation of aerosol droplets, allows you to stabilize the substrate temperature and temperature gradient, thereby ensuring the stability of the characteristics of the resulting films. The investigated transparent conductive coatings are part of glasses with adjustable transparency, and are also used as layers of solar cells.

Fabrication of Functional Coating Layer for Emerging Transparent Electrodes using Antimony Tin Oxide Nano-colloid

This study fabricated a functional coating layer for transparent electrodes using antimony tin oxide nanopowder. The wet grinding method was employed to create a stable dispersion solution of antimony tin oxide nanopowder with aminopropyl tri-methoxysilane and acetyl acetone as primary dispersing agents. Various concentrations of these dispersing agents were used to determine optimal conditions, followed by a gel reaction to form a stable solution. The primary objective was to provide a viable alternative to indium-based transparent electrodes, specifically indium tin oxide, by incorporating antimony oxide. This approach not only addresses limitations associated with indium, but also enhances mechanical properties. The methodology involves the utilization of antimony tin oxide nanopowder and various solvents including ethanol and aforementioned dispersing agents to create a stable antimony tin oxide sol through wet grinding. Effects of dispersant concentration and milling time on the secondary particle size of the antimony tin oxide sol were thoroughly evaluated. Furthermore, this study examined sheet resistance of resulting coating layers by conducting a comparative analysis between antimony tin oxide and indium tin oxide under similar conditions. Findings of this study meticulously detailed in subsequent sections of the manuscript provide valuable insights into optimizing the entire process, encompassing synthesis, coating, heat treatment, and the production of high-quality transparent conductive coatings. These techniques and outcomes can significantly contribute to the development of more sustainable and cost-effective alternatives to traditional indium-based transparent electrodes.

Sb-doped tin oxide nanonets for improved conductivity in transparent conductive coatings

In light of the three primary challenges faced by transparent conductive coatings, namely poor conductivity, elevated the active substance content, and insufficient visible light transmittance, net-like conductive agents due to the unique morphology and structure have been developed to address these concerns simultaneously. A straightforward synthesis of antimony-doped tin oxide (ATO) nanonets was accomplished through a simple two-step coprecipitation and hydrothermal methods. Firstly, an antimony-doped stannic hydroxide hydrogel precursor was generated through coprecipitation. Secondly, by adjusting the pH value in the hydrothermal reaction, ATO nanocrystals network were obtained without the need for additional materials. The synthesized ATO, with a net-like morphology, comprises particles of approximately 3–5 nm in diameter. Throughout the reaction, ammonium hydroxide, used as a pH regulator, played a vital role as a reducing agent in forming ATO nanonets without the need for further post-treatment. Moreover, net-like ATO compounded with SiO2 transparent conductive coatings exhibited exceptional transparent conductive properties, with a visible-light transmittance of approximately 84.7 % at the wavelength of 550 nm and a square resistance of 0.5 kΩ/sq upon spin-coating deposition on glass. This remarkable performance can be attributed to the generation of a continuous conductive network. In comparison to granular ATO, the network structure ATO nanocrystal showcases a significant improvement in resistivity, demonstrating its exemplary transparent conductivity. The approach for the preparation of ATO nanonets was simple and easy to scale up to provide an enormous potential and broad prospect for the application of net-like ATO in transparent conductive coating.

Methods for detecting and counting nodes in images of crack networks

The article discusses a technique for segmenting a network of cracks in micrographs and identifying the main elements such as a node, the junction of several cracks, and an edge, the body of the crack itself, to build a model of the network as an undirected graph. Crack segmentation was carried out using two methods: using threshold binarization and applying masks that separate nodes from edges based on morphological characteristics, and a combined method using a convolutional neural network to detect nodes. Such methods make it possible to detect nodes and edges automatically, facilitating the construction of a model and opening up new possibilities in theoretical calculations of the resistance of a network of conductors in transparent conductive coatings.

Automated system for measuring electrophysical parameters of semiconductor structures

сThe article is devoted to the development of an automated information and measurement system for measuring the voltfarad characteristics of semiconductor structures, including structures based on transparent conductive coatings. The structure of the information-measuring system is proposed, the results of functional and metrological analysis of the measurement channel of complex conductivity are presented. In particular, as a result of functional analysis, the functions of converting complex conductivity into a digital code proportional to the capacitive component and the active component of conductivity are obtained. In the process of metrological analysis, a metrological structural model of the complex conductivity measurement channel has been compiled, which, unlike the functional model, takes into account additive, multiplicative errors of the links, as well as the quantization error of the analog-to-digital converter. Expressions are obtained for the real functions of converting complex conductivity into a digital code proportional to the capacitive and active component of conductivity, taking into account the instrumental errors of the links that make up the measuring channel. Metrological analysis makes it possible to solve both the direct problem of calculating the instrumental error of the measuring channel according to the known nominal parameters and errors of its constituent links, and the inverse problem, which consists in assigning requirements to the metrological characteristics of the links in the measuring channels to ensure the required value of the maximum measurement error. In particular, based on the metrological analysis performed, it was found that the limits of the permissible relative error of capacitance and conductivity measurements do not exceed ±3 %, which is confi rmed experimentally. The developed automated information and measurement system allows not only to measure the volt-farad characteristics of the studied semiconductor structures, but also to process measurements in order to determine the electrophysical parameters by an indirect method.

Analysis of the Effect of Technological Parameters on the Properties of Transparent Conductive Oxides

It is shown that a promising method for obtaining transparent conductive oxides is spray pyrolysis, which allows to obtain films of proper quality without the use of vacuum. For the effective use of the spray pyrolysis method in order to obtain reproducible films with specified properties, it is necessary to take into account a variety of heterogeneous technological parameters that affect the quality of transparent conductive coatings. To this end, the authors have developed a model in the form of an oriented graph that displays the relationship of technological modes and quality parameters of transparent conductive coatings. The model displays parameters in the form of graph vertices, which are divided into technological and parameters characterizing the quality of transparent conductive coatings. The arcs connecting the vertices represent the properties of the coatings, and the arrows of the arcs indicate the direction from the action property to the reaction property. This model made it possible to systematize the influencing factors and offer an analytical description of the influencing parameters, reactions to them and properties of the synthesized coatings in the form of a system of differential equations. Based on the specified mathematical model of the relationship between technological modes and coating properties, a method for selecting optimal technological parameters has been developed in order to obtain transparent conductive coatings with specified properties. The technique has been tested on the example of the synthesis of a transparent conductive film of tin dioxide doped with antimony. Analysis of the factors affecting the surface resistance of coatings showed that the concentration of charge carriers significantly depends on the volume and concentration of impurities. The results of the analysis of experimental studies of the dependences of the concentration of charge carriers on the concentration of the impurity, the volume of the solution, on the thickness, the dependence of the surface resistance of the film on the thickness are presented

Enhanced conductivity of infrared transparent Bi2Se3 thin films as anti-interference coatings for infrared detectors

Infrared transparent conductive coatings are extensively utilized in both military and civilian infrared detectors due to their superior infrared transmission and electromagnetic shielding properties. It is a major scientific challenge to find a solution to the contradiction between high transmittance and low conductivity in the area of wide-band infrared transparent conductive film research. This study utilized new material systems and film preparation technologies to clarify the problem. A higher c-axis preferred orientation infrared transparent conducting Bi2Se3 thin film on a p-Si (111) substrate was developed using plasma-enhanced chemical vapor deposition (PECVD) technology. At room temperature, the film exhibited n-type conductivity, with high surface mobility of 2565 cm2/V·s and low surface resistivity of 2.6 × 10−5 Ω cm. In the mid-IR and far-IR regions, the produced Bi2Se3 thin film displayed transparency of 90% and 80%, respectively. To the best of our knowledge, this n-type conductive thin film created using chemical vapor deposition is the best IR-transparent thin film to date. Using this film, a Bi2Se3/p-Si heterojunction diode with a maximum voltage of 0.7 V was created. Young's modulus and hardness were determined to be 80 ± 5.5 GPa and 15 ± 2.2 GPa, respectively, for the film. It demonstrates the film's resistance to wear and deformation. The findings imply that Bi2Se3 film may be used as an anti-interference coating for infrared detectors and other optoelectronic devices throughout a wide wavelength range, from the mid-IR to the far-IR, due to its good optical transparency and electrical conductivity.

Transparent Silver Coatings with Copper Addition for Improved Conductivity by Combined DCMS and HiPIMS Process

The demand for transparent conductive coatings has increased over recent years, leading to the development of various technical solutions. One of the approaches is to use metallic coatings very close to their coalescence thickness, so that a good compromise between transparency and conductivity is obtained. In this contribution, a combination of two elements with high potential in this field is used, namely silver and copper. The continuity of silver films on a dielectric transparent substrate is significantly improved by the addition of a copper seed layer that promotes the formation of a continuous layer at smaller effective thicknesses. Two distinct deposition processes are used for the deposition of the two materials, namely HiPIMS (High Power Impulse magnetron sputtering) for copper and DC sputtering for silver. The use of HiPIMS enables a better control of the structure and quantity of deposited material, allowing us to deposit a very small amount of material. The mono-element coatings are characterized from the optical and electrical point of view, and then mixed to form a structure with better transparency, up to 80% in the visible spectrum, good electrical properties, resistivity of ~2 × 10−5 (Ω × cm), and significantly lower surface roughness, down to 0.2 nm.

Transparent conductive stannic oxide coatings employing an ultrasonic spray pyrolysis technique: The relevance of the molarity content in the aerosol solution for improvement the electrical properties

Highly transparent conductive stoichiometric nanocrystalline stannic oxide coatings were deposited onto Corning® EAGLE XG® slim glass substrates. Including each coating, it was deposited for various concentrations in the aerosol solution with the substrate temperature maintained at 623.15 K by an ultrasonic spray pyrolysis (USP) technique. Nitrogen was employed both as the solution carrier in addition to aerosol directing gas, maintaining its flow rates at 3500.0 and 500.0 mL/min, respectively. The coatings were polycrystalline, with preferential growth along the stannic oxide (112) plane, irrespective of the molarity content in the spray solution. The coating prepared at 0.2 M, a concentration in the aerosol solution, showed an average transmission of 60% in the visible light region spectrum with a maximum conductivity of 24.86 S/cm. The coatings deposited exhibited in the general photoluminescence spectrum emission colors of green, greenish white, and bluish white calculated on the intensities of the excitonic and oxygen vacancy defect level emissions.

Design of highly transparent conductive optical coatings optimized for oblique angle light incidence

Design of highly transparent conductive optical coatings optimized for oblique angle light incidence

Ultra-Fast, Chemical-Free, Mass Production of High Quality Exfoliated Graphene

As graphene penetrates into industries, it is essential to mass produce high quality graphene sheets. New discoveries face formidable challenges in the marketplace due to the lack of proficient protocols to produce graphene on a commercial scale while maintaining its quality. Here, we present a conspicuous protocol for ultrafast exfoliation of graphite into high quality graphene on the sub-kilogram scale without the use of any intercalants, chemicals, or solvent. We show that graphite can be exfoliated using a plasma spray technique with high single-layer selectivity (∼85%) at a very high production rate (48 g/h). This is possible because of the inherent characteristics of the protocol which provides sudden thermal shock followed by two-stage shear. The exfoliated graphene shows almost no basal defect (Id/Ig: 0) and possesses high quality (C/O ratio: 21.2, sp2 %: ∼95%), an indication of negligible structural deterioration. The results were reproducible indicating the adeptness of the protocol. We provided several proofs-of-concept of plasma spray exfoliated graphene to demonstrate its utility in applications such as mechanical reinforcements; frictionless, transparent conductive coatings; and energy storage devices.

Electrical Response of Silicon Heterojunction Solar Cells with Transparent Conductive Oxide Antireflective Coating

Electrical Response of Silicon Heterojunction Solar Cells with Transparent Conductive Oxide Antireflective Coating

Special Issue: “Optical Thin Films and Structures: Design and Advanced Applications”

This Special Issue is devoted on design and application of thin films and structures with special emphasis on optical applications. It comprises ten papers, five featured and five regular papers, authored by respective scientists all over the world. Diverse materials are studied and their possible applications are demonstrated and discussed: transparent conductive coatings and structures from ZnO doped with Al and Ga and Ti-doped SnO2, polymer and nanosized zeolite thin films for optical sensing, TiO2 with linear and non-linear optical properties, organic diamagnetic materials, broadband optical coatings, CrWN glass molding coatings and silicon on insulator waveguides.

Modification of Silver Nanowire Coatings with Intense Pulsed Ion Beam for Transparent Heaters.

In this report, an improvement of the electrical performance and stability of a silver nanowire (AgNW) transparent conductive coating (TCC) is presented. The TCC stability against oxidation is achieved by coating the AgNWs with a polyvinyl alcohol (PVA) layer. As a result, a UV/ozone treatment has not affected the morphology of the AgNWs network and the PVA protection layer, unlike non-passivated TCC, which showed severe degradation. The irradiation with an intense pulsed ion beam (IPIB) of 200 ns duration and a current density of 30 A/cm2 is used to increase the conductivity of the AgNWs network without degradation of the temperature-resistant PVA coating and decrease in the TCC transparency. Simulations have shown that, although the sample temperature reaches high values, the ultra-high heating and cooling rates, together with local annealing, enable the delicate thermal processing. The developed coatings and irradiation strategies are used to prepare and enhance the performance of AgNW-based transparent heaters. A single irradiation pulse increases the operating temperature of the transparent heater from 92 to 160 °C at a technologically relevant voltage of 12 V. The proposed technique shows a great promise in super-fast, low-temperature annealing of devices with temperature-sensitive components.

Ultrasonic Spray Pyrolysis of Antimony‐Doped Tin Oxide Transparent Conductive Coatings

AbstractTransparent conducting oxides are fundamental for the fabrication of optoelectronic devices including touchscreen displays, solar cells, and light emitting diodes. However, they mostly rely on rare elements and expensive vacuum‐based deposition methods that negatively affect the overall cost of optoelectronics. Here, a detailed investigation on the synthesis of antimony‐doped tin oxide films using an ultrasonic spray coating system is presented. High‐quality, crystalline SnO2 films are deposited via decomposition of metal precursors sprayed directly onto hot (>400 °C) substrates. Doping is easily achieved by adding the dopant salt to the spray solution, and the presence of the dopant atoms heavily influences the optical, electrical, and structural properties of SnO2. These coatings are characterized using a comprehensive suite of techniques including X‐ray diffraction, electron microscopy, X‐ray and ultraviolet photoelectron spectroscopies, Hall effect measurements, optical spectroscopy in the visible and near infrared, and atomic force microscopy, in order to elucidate the relationship between the synthetic conditions and functional properties. Through a careful optimization process, Sb‐doped SnO2 coatings showing transmittance values in the visible spectrum between 80% and 90%, and sheet resistances of 10–20 Ω/sq−1 are achieved. Such values are suitable for immediate applications of these Sb‐doped SnO2 films as high‐performance transparent conductors.

Optically and radio frequency (RF) transparent meta-glass

Abstract We propose a radio frequency (RF) and visibly transparent composite metasurface design comprising newly developed transparent multilayer conductive coatings. Detailed experimental and theoretical analysis of the RF/visible transparency of the proposed meta-glass is provided. The proposed nature-inspired symmetrical honeycomb-shaped meta-glass design, alters the electromagnetic properties of the glass substrate in the RF spectrum by utilizing visibly transparent Ag-based conductive coatings on each side. Furthermore, the competing effect of the Ag thickness on optical and RF transparency is discussed. We show that using multilayer dielectric-metal coatings, specifically 5-layered spectrally selective coatings, RF transparency of the meta-glass can be enhanced while preserving visible transparency. Herein we demonstrate high transparency meta-glass with 83% and 78% peak RF and optical transmission at 28 GHz and 550 nm, respectively. The meta-glass yields enhanced RF transmission by 80% and 10% when compared to low-emissivity glass and bare glass, respectively. The meta-glass design presented here is amenable to a variety of 5G applications including automobile radar systems. This work provides a superior alternative to the standard indium-tin-oxide (ITO) transparent material which is becoming scarce. Moreover, this study paves the way for the design of new visibly transparent metamaterials and artificial dielectrics.

Copper-Plating Metallization With Alternative Seed Layers for c-Si Solar Cells Embedding Carrier-Selective Passivating Contacts

In this article, we develop in parallel two fabrication methods for copper (Cu) electroplated contacts suitable for either silicon nitride or transparent conductive oxide antireflective coatings. We employ alternative seed layers, such as evaporated Ag or Ti, and optimize the Ti–Cu or Ag–Cu contacts with respect to uniformity of plating and aspect ratio of the final plated grid. Moreover, we test plating/deplating sequence instead of a direct current plating or the SiO2 layer approach to solve undesired plating outside the designed contact openings. The main objective of this paper is to explore the physical limit of this contact formation technology keeping the process compatible with industrial needs. In addition, we employ the optimized Cu-plating contacts in three different front/back-contacted crystalline silicon solar cells architectures: 1) silicon heterojunction solar cell with hydrogenated nanocrystalline silicon oxide as doped layers, 2) thin SiO2/doped poly-Si-poly-Si solar cell, and 3) hybrid solar cell endowed with rear thin SiO2/poly-Si contact and front heterojunction contact. To investigate the metallization quality, we compare fabricated devices to reference ones obtained with standard front metallization (Ag screen printing and Al evaporation). We observe a relatively small drop in V OC by 5 to 10 mV by using Cu-plating front grid, whereas fill factor was improved for solar cells with Cu-plated front contact if compared with evaporated Al.

The study of the optical properties of transparent conductive oxides SnO2:Sb, obtained by spray pyrolysis

The study results of the dependences of the refractive index and samples transmittance of transparent conductive films of tin dioxide depending on wavelength are presented. Films with different doping levels, with different solutions volumes were synthesized on an automated installation by spray pyrolysis. It is shown that the transmittance practically does not depend on the amount of substance sprayed onto the substrate; the transmittance practically does not depend on the solution volume, but depends on the impurity concentration. The chemical composition and temperature of film deposition influence on its refractive index is established. The research results can be used in the development of technologies for the manufacture of optoelectronic structures containing transparent conductive coatings.

Electrochemical Coprecipitation of Zinc and Aluminum in Aqueous Electrolytes for ZnO and AZO Coverage Deposition

The aim of this study is to examine the technological challenge of the electrochemical formation of zinc oxide and Al-doped ZnO films (ZnO:Al, AZO) as transparent conductive oxide coatings with complex architectures for solar cell photoanode materials. A cathodic electrodeposition of AZO was performed using aqueous nitrate electrolytes at 25°C. A significant positive deviation in aluminum percentage in the films was demonstrated by the LAES, EDX, and XPS methods, which originates from aluminum hydroxide sedimentation. The photoluminescent characteristics of the ZnO films reveal low band intensities related to intrinsic defects, while the samples with 1 at.% of aluminum show a strong and wide PL band at 600±80 nm and increase in conductivity.

Transparent Conductive Dielectric-Metal-Dielectric Structures for Electrochromic Applications Fabricated by High-Power Impulse Magnetron Sputtering.

The growing applications of electrochromic (EC) devices have generated great interest in bifunctional materials that can serve as both transparent conductive (TC) and EC coatings. WO3/Ag/WO3 (WAW) heterostructures, in principle, facilitate this extension of EC technology without reliance on an indium tin oxide (ITO) substrate. However, these structures synthesized using traditional methods have shown significant performance deficiencies. Thermally evaporated WAW structures show weak adhesion to the substrate with rapid degradation of coloration efficiency. Improved EC durability can be obtained using magnetron sputtering deposition, but this requires the insertion of an extra tungsten (W) sacrificial layer beneath the external WO3 layer to prevent oxidation and associated loss of conductivity of the silver film. Here, we demonstrate for the first time that a new method, known as high-power impulse magnetron sputtering (HiPIMS), can produce trilayer bifunctional EC and TC devices, eliminating the need for the additional protective layer. X-ray photoelectron spectroscopy and X-ray diffraction data provided evidence that oxidation of the silver layer can be avoided, whilst stoichiometric WO3 structures are achieved. To achieve optimum WAW structures, we tuned the partial pressure of oxygen in the HiPIMS atmosphere applied for the deposition of WO3 layers. Our optimized WO3 (30 nm)/Ag (10 nm)/WO3 (50 nm) structure had a sheet resistance of 23.0 ± 0.4 Ω/□ and a luminous transmittance of 80.33 ± 0.07%. The HiPIMS coatings exhibited excellent long-term cycling stability for at least 2500 cycles, decent switching times (bleaching: 22.4 s, coloring: 15 s), and luminescence transmittance modulation (Δ T) of 34.5%. The HiPIMS strategy for the fabrication of ITO-free EC coatings for smart windows holds great promise to be extended to producing other metal-dielectric composite coatings for modern applications such as organic light-emitting diodes (OLEDs), liquid crystals, and wearable displays.