Electrode, method for manufacturing same, and structure

Abstract

Provided are: a novel electrode with relaxed and reduced restrictions on a use environment; a method for manufacturing the same; and a structure.　The electrode according to the present invention contains: a metal nanowire; and a composite polymer of polyethylenedioxythiophene and an anionic fluorine-based polymer. The electrode has a single-layer structure or a layered structure. The composite polymer is contained at least in an outermost surface layer on the side opposite to a supported side. This method for manufacturing an electrode according to the present invention involves: a step for applying a first liquid containing the metal nanowire onto a surface to form a coating layer; and a step for applying a second liquid containing a solution of the composite polymer onto a surface of the coating layer to form the outermost surface layer.

Description

Electrode, manufacturing method thereof and structure thereof

[0001] The present invention relates to an electrode, a method for manufacturing the same, and a structure thereof.

[0002] Organic electronics have the potential to lead to a new generation of consumer electronics that are stable in a wide range of environments.

[0003] Organic semiconductors and biomaterials generally have low operating temperatures. Therefore, it is not easy to deposit transparent electrodes, such as ITO, on them by high-temperature or vacuum thermal evaporation. Liquid metals, conductive polymers, and metal nanowires have been used to directly deposit top electrodes on organic semiconductors or substrates at low temperatures. Organic electronic devices, particularly transparent electrodes, have been fabricated from a variety of materials using solution processing. Organic thin-film solar cells, in which all organic layers are fabricated using solution processing, offer lightweight, flexibility, and scalable production.

[0004] However, thin films such as solution-processed transparent electrodes face challenges, particularly in terms of material instability, particularly long-term stability in real-world environments. Top electrodes, which are directly exposed to the environment, are exposed to water sources such as air, rain, seawater, and biological tissue fluids, causing reactions under prolonged exposure to light and ambient air. Changes in sunlight intensity and climate, particularly outdoor temperatures such as hot weather and heavy rain, hinder the long-term stability of low-temperature solution-processed electrodes. These aqueous environments not only lead to the dissolution of conductive polymers and the oxidation-reduction of metals, but also to different pH levels that promote corrosion of metal nanowires and alter the permeation behavior of liquid metals. For example, in the real atmosphere, ambient air contains moisture, and oxygen, sulfur, and ultraviolet rays can rapidly deteriorate solution-processed electrodes, such as silver nanowires. Solution-processed electrodes that can withstand a wide range of aqueous environments, such as those with pHs ranging from 1 to 12, and thus improve the environmental operational stability of organic electronics are highly desirable. In particular, for applications in organic thin-film solar cells, skin electronics, and implantable devices that are exposed to wind and rain outdoors, electrodes that can be processed using solution methods and achieve high levels of conductivity, transparency, and stability against water are desired.

[0005] Among organic electronic devices, in the case of organic thin-film solar cells, PEDOT:PSS, a composite polymer of poly(3,4-ethylenedioxythiophene) and polystyrene sulfonic acid, is known as a water-dispersible hole transport material commonly used in printed electronics. However, its instability due to its acidity and hygroscopicity, as well as its poor processability due to poor wettability, affect device performance. Non-Patent Document 1 reports an alcohol-dispersible composite polymer (PEDOT:F) of poly(3,4-ethylenedioxythiophene) and a perfluorosulfonic acid polymer as a solution to these problems.

[0006] Nature Energy, VOL 7, April 2022, 310-311

[0007] In Non-Patent Document 1, an alcohol dispersion of PEDOT:F is applied to the surface of the active layer of an organic thin-film solar cell with a doctor blade to form a hole transport layer, and silver nanowires are sprayed onto the surface to form an upper electrode as the outermost surface layer. However, there is no report on its broad stability against water, and there are also issues with conductivity and durability due to current flow, i.e., heat resistance.

[0008] An object of the present invention is to provide a novel electrode that is less subject to environmental restrictions, a method for producing the same, and a structure thereof. For example, an object of the present invention is to provide an electrode that is excellent in conductivity and transparency, and that has excellent environmental durability and long-term stability, and a method for producing the same and a structure thereof.

[0009] In view of the above problems, the present disclosure provides the following inventions. [1] An electrode containing metal nanowires and a composite polymer of polyethylenedioxythiophene and an anionic fluorine-based polymer, the electrode having a single-layer structure or a laminate structure, and the composite polymer being contained in at least the outermost surface layer opposite to the supported side. [2] The electrode according to [1], wherein the anionic fluorine-based polymer is a perfluorosulfonic acid polymer. [3] The electrode according to [1] or [2], wherein the metal nanowires are silver nanowires. [4] The electrode according to any one of [1] to [3], wherein the electrode has a thickness of 100 nm or less. [5] The electrode according to any one of [1] to [4], wherein the electrode has a light transmittance of 90% or more in the wavelength range of 400 to 1000 nm. [6] A structure comprising the electrode according to any one of [1] to [5] and a support on which the electrode is supported. [7] The structure according to [6], wherein the support has a functional layer. [8] The structure according to [7], wherein the functional layer is a photoelectric conversion layer. [9] A sensor having the electrode according to any one of [1] to [5] and a detection unit for detecting an electrical signal from the electrode.

[10] A method for producing the electrode according to any one of [1] to [5], comprising the steps of: applying a first liquid containing the metal nanowires to a surface to form a coating layer; and applying a second liquid containing the composite polymer to the surface of the coating layer to form the outermost layer.

[11] The method according to

[10] , in which the first and second liquids are applied by spray coating.

[0010] According to the present invention, it is possible to provide a novel electrode that is less subject to environmental restrictions, a method for producing the electrode, and a structure thereof. According to one example of the present invention, it is possible to provide an electrode that is excellent in electrical conductivity and transparency, and that simultaneously satisfies high levels of water repellency on the electrode surface, adhesion to the support, and suppression of deterioration due to pH and heat generation during electrical conduction, and that has excellent durability in a wide range of environmental conditions and long-term stability, as well as a method for producing the electrode and a structure thereof.

[0011] Figure 1A shows a photograph of an example of contact angle evaluation using rainwater, phosphate buffer solution (PBS), and seawater dropped onto various solution-processed thin films. Figure 1B shows the results of measuring the surface tension in Figure 1A. The results show the optical transmittance in the visible to near-infrared range of spray-coated MWCNTs, PEDOT:PSS, AgNWs, and AgNWs-PEDOT-PFSA. HCl or NaOH solution was dropped onto the center of the electrode, and the change in series resistance due to the difference in solution-processed electrodes (AgNWs electrode and AgNWs / PEDOT:F electrode) was measured. The photograph (top) and schematic diagram (bottom) show the device used to measure resistance using a gold-deposited electrode and perform contact measurements with a multimeter. Figure 3 shows the results when a diluted HCl solution (pH = 2) was dropped. The results of the measurements shown in Figure 3, when a diluted NaOH solution (pH = 13) was dropped, are shown. The initial current-voltage characteristics of the AgNWs electrode and the AgNWs / PEDOT:F electrode are shown. A voltage of +2 V was applied from left to right to the AgNWs electrode (top) and the AgNWs / PEDOT:F electrode (bottom). The change in the surface temperature profile obtained using thermography after voltage application is shown. The results of measuring the interfacial adhesion strength of the AgNWs electrode and the AgNWs / PEDOT:F electrode are shown. The inset shows a schematic diagram of the peeling experiment. The solution-treated electrode was applied to human skin. Figure 9A is a photograph showing an example of an electrode attached to a finger, Figure 9B is a microscopic image showing an example of an electrode attached to a finger, and Figure 9C shows the frequency-impedance characteristics of a commercially available gel Ag / AgCl electrode, an AgNWs electrode, and an AgNWs-PEDOT-PFSA electrode. Figure 10A shows the appearance of a commercially available electrode, an AgNWs electrode, and an AgNWs-PEDOT-PFSA electrode attached to the surface of the arm when the electrode was repeatedly gripped and opened, and Figures 10B, 10C, and 10D show the results of measuring the potential response. Figure 11A shows the appearance of a commercially available electrode, an AgNWs electrode, and an AgNWs-PEDOT-PFSA electrode attached to the surface of the chest, and Figures 11B, 11C, and 11D show the results of measuring EMG.Figure 12A shows the results of recording EMG signals using photographs of hand gestures in various positions underwater (top) and wrist bending at five angles (bottom) when AgNWs-PEDOT-PFSA electrodes were formed on the surface of the hand and the response to underwater scratching movements (IV) was measured. Figure 12B visualizes the t-SNE for EMG classification. Figure 12C shows the confusion matrix of the five action recognition results. Figure 13A shows the semipermeable membrane (top) and PEDOT:PFSA polymer film (bottom) for an underwater ion blocking device. Figure 13B shows the D-SIMS depth profiles of the PEDOT:PSS and PEDOT-PFSA polymer films after immersion in an ionic solution. Figure 14A shows a photograph of the glass-sealed all-solution-processed OPV and electrode, and Figure 14B shows a microscope image of the electrode in Figure 14A. Figure 15A shows a cross-sectional SEM image of the electrode interface of the all-solution-processed OPV in Figure 14A, for AgNWs, and Figure 15B shows the AgNWs-PEDOT-PFSA case. Cross-sectional SEM images of the electrode interface of the all-solution-processed OPV are shown. Previously reported light-air stability data for all-solution-processed and vacuum-deposited OPVs are summarized. Figure 18A shows a photograph of the sealed all-solution-processed OPV under actual outdoor conditions. Figure 18B shows a plot of the power conversion efficiency (PCE) of the all-solution-processed OPV at actual outdoor irradiance (from May 25 to July 12, 2023), corresponding precipitation, and maximum and minimum outdoor temperatures, along with precipitation. Figure 19A is a photograph showing an example of a film electrode fabricated by patterning AgNWs-PEDOT:F electrode arrays in parallel lines on the surface of a resin film and connecting them to terminals. Figure 19B is an optical microscope image of the electrode site on the film electrode shown in Figure 19A. Figures 20A to 20D are photographs of an electrode attached to the biceps brachii muscle; the scale bar indicates 1 cm. Figures 21A to 21D are images of blood vessels of an electrode attached to the radial flexor muscle, taken using a venography device; the scale bar indicates 6 mm.

[0012] The present invention will be described in detail below. (Electrode) The electrode of the present invention contains metal nanowires and a composite polymer of polyethylenedioxythiophene and an anionic fluorine-based polymer.

[0013] The metal nanowire is composed of multiple metal nanowires, and adjacent metal nanowires are in contact with each other. Adjacent metal nanowires may be arranged so as to be stacked on top of each other. When two adjacent metal nanowires contact each other, a conductive network is formed, which serves as a path for current to flow. The metal nanowire network has voids between them, making it porous. Such porosity provides optical transparency, flexibility, and the like. The electrode of the present invention further contains a composite polymer, which is a conductive polymer, in addition to such a metal nanowire network, thereby enhancing the conductivity of the metal nanowires.

[0014] The metal nanowires are not particularly limited, but examples thereof include silver nanowires, gold nanowires, and platinum nanowires. Of these, silver nanowires are preferred. The metal nanowires may be used alone or in combination of two or more types.

[0015] The diameter and length of the metal nanowires are not particularly limited, but as an example, silver nanowires may have a diameter of 10 to 100 nm and a length of 1 to 100 μm.

[0016] The composite polymer is a conductive polymer composed of cationic polyethylenedioxythiophene and an anionic fluorine-based polymer as components. The composite polymer exhibits conductivity by doping the anionic fluorine-based polymer into polyethylenedioxythiophene. The composite polymer may be used alone or in combination of two or more types.

[0017] Examples of polyethylenedioxythiophene include poly(3,4-ethylenedioxythiophene) and those having this as a basic skeleton and having a substituent on a carbon atom, and particularly poly(3,4-ethylenedioxythiophene). The substituent is not particularly limited as long as it does not impair the effects of the present invention and exhibits conductivity when doped with an anionic fluorine-based polymer. The molecular weight of polyethylenedioxythiophene is not particularly limited, but a range of 500 to 200,000 in weight average molecular weight is considered, for example.

[0018] The anionic fluorine-based polymer is not particularly limited, but examples thereof include polymers having a perfluoroalkylene or polyfluoroalkylene skeleton, particularly a perfluoroalkylene skeleton, and an anionic group. Among these, perfluorosulfonic acid polymers are preferred.

[0019] The perfluorosulfonic acid polymer has a main chain with a perfluoroalkylene skeleton. The main chain has a polytetrafluoroethylene (PTFE) skeleton -(CF ２ CF ２ ) ｍ - is preferred.

[0020] The perfluorosulfonic acid polymer has a sulfonic acid group, and in particular, the sulfonic acid group is bonded to the end of a side chain. The side chain preferably has an ether bond as its base end and is a linear or branched perfluoroalkylene group that may be interrupted by an ether bond, to which the sulfonic acid group is bonded. The perfluoroalkylene group preferably has 2 to 5 carbon atoms.

[0021] Commercially available perfluorosulfonic acid polymers can be used, for example, Nafion, a long side chain type polymer having perfluoroether side chains with sulfonic acid groups at the terminals. ＴＭ (For example, DuPont has an equivalent mass of 1100 to 900 g / mol, an ion exchange capacity of 0.91 to 1.11 mmol / g, and a repeat number of perfluoroethylene units between perfluoroethylene units having side chains of about 6.6). ２ Aquivion is a short side chain type consisting only of fluoroether groups and does not contain fluoroether groups. ＴＭ(Dow Chemical Company equivalent mass 830 g / mol, number of repeating perfluoroethylene units between perfluoroethylene units having side chains 5.5), four CF ２ 3M is a short side chain type consisting only of fluoroether groups and does not contain fluoroether groups. ＴＭ The ionomer (3M equivalent mass: 850 g / mol, number of repeating perfluoroethylene units between perfluoroethylene units having side chains: 4.7) is known as a perfluorosulfonic acid ionomer.

[0022] The electrode of the present invention has a single-layer structure or a laminate structure. Furthermore, the electrode of the present invention contains a composite polymer at least in the outermost surface layer opposite the supported side. By including a fluorine-containing component in the outermost surface layer in a state complexed with the conductive polymer polyethylenedioxythiophene, durability such as water resistance can be imparted to the surface without impairing the conductivity of the polyethylenedioxythiophene, and the electrode properties can be maintained in various environments. In particular, when the anionic fluorine-based polymer constituting the composite polymer is a polymer having a perfluoro group (e.g., a perfluorosulfonic acid polymer), the outermost surface layer becomes highly hydrophobic, allowing the electrode properties to be maintained even in environments such as exposure to acidic or basic aqueous liquids or aqueous liquids with high salt concentrations. For example, the electrode properties can be maintained even in environments exposed to rainwater, seawater, or physiological fluids in the bodies of living organisms (humans and animals). Furthermore, as shown in the Reference Examples described below, an electrode can be obtained that has excellent conductivity and transparency, and simultaneously satisfies high levels of water repellency on the electrode surface, adhesion to the support, and suppression of deterioration due to pH and heat generation by electrical conduction, resulting in an electrode with durability that can withstand a wide range of environmental conditions and excellent long-term stability.

[0023] The electrode of the present invention may have a single-layer structure or a laminated structure. In the present invention, the distinction between single-layer and laminated is not based on the manufacturing method. More specifically, even if the layer formation process is performed multiple times, if the electrode has a single-layer structure when used, it is a single-layer electrode. On the other hand, even if the layer formation process is performed only once, if phase separation or the like occurs thereafter and the electrode has a laminated structure when used, it is a laminated electrode. The distinction between single-layer and laminated is determined by whether an interface can be recognized when the cross section is observed using an SEM. Furthermore, whether or not the layers constituting the electrode of the present invention "contain" a predetermined component is not determined by the manufacturing method. The presence of a predetermined component in a raw material composition such as a coating liquid used in a process for forming each layer does not necessarily mean that the layer "contains" the predetermined component. A layer that contains a predetermined component in a raw material composition such as a coating liquid used in a process for forming another layer, and that comes to contain part or all of the predetermined component through diffusion or the like during or after the process for forming the other layer, is a layer that "contains" the predetermined component. Whether or not a given layer contains a given component can be determined by performing SEM-EDX mapping analysis of the cross section or the like.

[0024] A preferred example of the present invention is an example in which the fluorine-containing component of the composite polymer is distributed more on the surface side of the outermost layer than on the support side. This example can be obtained by using a raw material composition containing the composite polymer to form the outermost layer. For example, it can be produced by a method including steps (A) and (B) described below.

[0025] When the electrode of the present invention has a single layer structure, the electrode of the present invention consists of one layer (layer A) containing metal nanowires and a composite polymer.

[0026] An example of an electrode of the present invention having a laminated structure is an example including the following layer A and layer B. Layer A: a layer containing metal nanowires and a composite polymer Layer B: a layer containing a composite polymer Another example of an electrode of the present invention having a laminated structure is an example in which layer A is disposed between layers B.

[0027] Here, Layer A is a layer that essentially contains metal nanowires. Layer A is a layer obtained by applying a liquid containing a composite polymer to the surface of a layer to which a liquid containing metal nanowires has been applied during the production of the electrode of the present invention, so that the composite polymer has permeated into the metal nanowires. Alternatively, Layer A is a layer obtained by further applying a liquid containing metal nanowires to the surface of a layer to which a liquid containing a composite polymer has been applied, so that the composite polymer has permeated into the metal nanowires.

[0028] Layer B is a layer containing a composite polymer and substantially no metal nanowires. Layer B is a layer consisting of the remaining composite polymer present in a significant thickness above Layer A in which the composite polymer has partially impregnated with the metal nanowires, when a liquid containing a composite polymer is applied to the surface of a layer to which a liquid containing metal nanowires has been applied in producing the electrode of the present invention. Alternatively, Layer B is a layer consisting of the remaining composite polymer present in a significant thickness below Layer A in which the composite polymer has partially impregnated with the metal nanowires, when a liquid containing a composite polymer is applied to the surface of a layer to which a liquid containing a composite polymer has been applied.

[0029] The outermost layer in the electrode of the present invention is either layer A, in which a liquid containing a composite polymer is applied to the surface of a layer to which a liquid containing metal nanowires has been applied during the production of the electrode of the present invention, and the composite polymer has infiltrated into the metal nanowires, or layer B, in which a liquid containing a composite polymer is applied to the surface of a layer to which a liquid containing metal nanowires has been applied during the production of the electrode of the present invention, and the composite polymer has partially infiltrated into the metal nanowires, and which is composed of the remaining composite polymer present in a significant thickness on top of layer A.

[0030] When the electrode of the present invention has a laminated structure, the number of layers in the laminated structure is not particularly limited, but is preferably 2 or 3. Examples of the order in which Layer A and Layer B are laminated, in order from the outermost layer to the supported side, include an embodiment in which they are Layer B, Layer A, Layer B, and Layer A, and an embodiment in which they are Layer A, Layer B.

[0031] The electrode of the present invention is in the form of a thin film. The shape of the electrode is not particularly limited, and may be planar or have any pattern such as a linear shape. The thickness of the electrode of the present invention is not particularly limited, but is preferably 100 nm or less, more preferably 80 nm or less. Here, the thickness of the electrode is the average value measured at 10 arbitrary points by cross-sectional observation using a means for obtaining an enlarged cross-sectional image such as an electron microscope.

[0032] The surface resistance of the electrode of the present invention is not particularly limited, but is preferably 100 Ω / Sq. or less, and more preferably 50 Ω / Sq. or less.

[0033] The light transmittance of the electrode of the present invention is not particularly limited, but the light transmittance at wavelengths of 400 to 1000 nm is preferably 85% or more, more preferably 90% or more.

[0034] (Method for manufacturing an electrode) The method for manufacturing an electrode of the present invention is a method for manufacturing the electrode of the present invention described above, and includes the following steps (A) and (B): step (A): applying a first liquid containing metal nanowires to a surface to form a coating layer; and step (B): applying a second liquid containing a composite polymer to the surface of the coating layer to form an outermost layer.

[0035] The means for applying the first liquid in step (A) and the means for applying the second liquid in step (B) are not particularly limited, but examples thereof include spray coating, spin coating, and blade coating.

[0036] In step (A), the first liquid is a solution or dispersion of metal nanowires in a solvent. A commercially available metal nanowire ink or the like can be used as the first liquid. The solvent is not particularly limited, but examples thereof include water, lower alcohols (ethanol, propanol, etc.), and mixtures thereof. The first liquid may contain other components such as a dispersant, a surfactant, and an antioxidant, as long as the effects of the present invention are not impaired. The concentration of the metal nanowires in the first liquid is not particularly limited, but is, for example, 0.2 to 1.0% by mass.

[0037] In step (B), the second liquid is prepared by dissolving or dispersing a composite polymer in a solvent. The polyethylene dioxythiophene and the anionic fluorine-based polymer that constitute the composite polymer may be separately prepared and then composited in the process of dissolving or dispersing them in a solvent. That is, the second liquid can be prepared by dissolving or dispersing polyethylene dioxythiophene and the fluorine-based polymer in a solvent. The solvent is not particularly limited, but examples include lower alcohols such as ethanol. The concentration of the composite polymer in the second liquid is not particularly limited as long as a liquid can be prepared that does not cause problems in layer formation, such as aggregation, but is, for example, 0.1 to 10% by mass, 0.1 to 5% by mass, or 0.1 to 3% by mass in terms of solids content.

[0038] In a liquid in which metal nanowires and a composite polymer are simultaneously dissolved or dispersed, aggregation occurs. In the electrode manufacturing method of the present invention, an electrode is manufactured by separately applying a first liquid containing metal nanowires and a second liquid containing a composite polymer.

[0039] When applying the first liquid and the second liquid, it is preferable to heat the surface to be applied, preferably at a heating temperature of 80 to 120°C, more preferably 90 to 110°C.

[0040] Here, when the outermost layer is the aforementioned Layer A, it is a layer in which the composite polymer has permeated into the metal nanowires, obtained by applying a liquid containing a composite polymer to the surface of a layer to which a liquid containing metal nanowires has been applied in step (A) during the production of the electrode of the present invention. When the outermost layer is the aforementioned Layer B, it is a layer in which the composite polymer has permeated into the metal nanowires, obtained by applying a liquid containing a composite polymer to the surface of a layer to which a liquid containing metal nanowires has been applied in step (A) during the production of the electrode of the present invention, and it is a layer consisting of the residual composite polymer present in a significant thickness on Layer A in which the composite polymer has partially permeated into the metal nanowires.

[0041] (Structure) The structure of the present invention has the electrode of the present invention described above and a support on which the electrode is supported. The support is not particularly limited, but examples thereof include an insulating substrate, a semiconductor substrate, a rubber substrate, etc. The configuration of the support is not limited, and may be either a single layer or a multi-layer, and the shape may be a sheet, a substrate, human skin, etc., and may be any shape.

[0042] In a preferred example, the support has a functional layer, which mainly has functions of detecting, emitting, converting, transferring, etc., energy related to light or electricity.

[0043] In a preferred example, the functional layer is a photoelectric conversion layer. Examples of devices having a photoelectric conversion layer as a functional layer include organic thin-film solar cells, organic electronic devices such as photodetectors, and sensors.

[0044] For example, an organic thin-film solar cell has a lower electrode (anode), an electron transport layer, a photoactive layer, a hole transport layer, and an upper electrode (cathode) on a substrate in this order. Photoactive layers using fullerene acceptors and non-fullerene acceptors are known. Holes generated from the photoactive layer upon receiving light move to the cathode through the hole transport layer, and electrons from the photoactive layer pass from the anode through the electron transport layer and an external circuit to recombine with holes in the cathode, thereby causing a current to flow. The functional layer may be a hole transport layer or an electron transport layer.

[0045] In a preferred example, the functional layer is a light-emitting layer. Examples of devices in which the functional layer is a light-emitting layer include display devices such as organic EL devices.

[0046] (Applications) The electrode of the present invention has excellent conductivity and transparency, and simultaneously satisfies high levels of water repellency on the electrode surface, adhesion to the support, and inhibition of degradation due to pH and heat generation caused by electrical current. It also has excellent durability under a wide range of environmental conditions and excellent long-term stability, and is therefore expected to be applied to fields such as the manufacture of organic electronic devices such as organic thin-film solar cells and photodetectors, the synthesis of new materials possessing specific physical properties during the manufacture of organic electronic devices, and thin-film formation by solution processing methods. As final products, the electrode is expected to be applied to organic electronic devices such as organic solar cells and photodetectors, transparent electrodes, sensors, etc. Other expected applications include wearable devices applied to human skin, implantable devices implanted in the body, and optogenetics, which involves expressing light-activated substances in cells and controlling cellular function using light.

[0047] The present invention also relates to a sensor comprising at least the electrode of the present invention and a detection unit that detects electrical signals from the electrode of the present invention. The sensor of the present invention may further comprise a display unit that displays the electrical signals detected by the detection unit, and may be configured to be connectable to the display unit. Because the electrode of the present invention has good environmental resistance, it can be placed outdoors where it is exposed to rainwater, in seawater with high salt concentrations, or inside a living body and / or on the epidermis (e.g., the surface of a part of the human body, hand, foot, or torso) that comes into contact with body fluids. The detection unit can have any known configuration as long as it is capable of detecting electrical signals from the electrode of the present invention. The electrode of the present invention and the detection unit can transmit and receive electrical signals via wired and / or wireless connections. An implantable device that is implanted in a living body can acquire bioelectrical and optical signals from the surface of a living body using a transparent, thin, conductive, and waterproof nanomembrane. Such a film-like electrode can be implanted and used in a living body. Transparent implantable devices enable the integration of neural recording and optical technologies, and are expected to contribute to neuroscience and biomedical engineering. For example, they can be used as ultrathin transparent electrode arrays to form an interface with the surface of the brain cortex of a living body. This implantable ECoG electrode device can be comfortably attached to the cerebral cortex in vivo and is highly conformable. The electrode array provides high-resolution, stable recording of electrophysiological signals, making it suitable for precision neural interfacing applications. The transparency of the electrodes improves visualization and monitoring during implantation, thereby reducing the risk of displacement and potential damage to cortical tissue.

[0048] The following examples illustrate specific embodiments of the present disclosure, but the present invention is not limited thereto.

[0049] (Fabrication of Solution-Processed Electrodes) In the following examples, solution-processed electrodes (thin films) were fabricated using the following procedure. A silver nanowire-containing solution (commercially available, 1 wt %, solvent: ethanol) was spray-coated onto a substrate in the atmosphere. A mixed solution of poly(3,4-ethylenedioxythiophene) (PEDOT) and perfluorosulfonic acid polymer (PFSA) (prepared similarly to Non-Patent Document 1 so that the solids content of the composite polymer was in the range of 1.3-2.0 wt %, using ethanol as the solvent) was then spray-coated onto the substrate in the atmosphere. The spray coating was completed within 1 minute, and each spray coating was performed while the substrate was heated to 85°C. SEM observation of the cross-section of the resulting electrode revealed unclear layer interfaces. SEM-EDX mapping analysis revealed that fluorine atoms in the PFSA were unevenly distributed at the surface of the layer, but were also present at the depth where the silver atoms of the nanowires were present.

[0050] Example 1: The contact angle of a solution-treated electrode was evaluated (Figures 1A and 1B). Solution-treated thin films of multiwalled carbon nanotubes (MWCNTs), poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) (PEDOT:PSS), silver nanowires (AgNWs), and silver nanowire-poly(3,4-ethylenedioxythiophene)-perfluorosulfonic acid polymer (AgNWs-PEDOT-PFSA, hereafter also referred to as PEDOT:F) were used. Rainwater, phosphate buffer solution (PBS solution), and seawater were dropped onto the solution-treated thin films, and the surface tension (mN / m) was measured using a simple contact angle meter DMe-211Plus (Kyowa Interface Science Co., Ltd.). The results are shown in Figure 1B. The solution-processed thin film of AgNWs-PEDOT-PFSA exhibited the highest hydrophobicity in rainwater, phosphate buffer solution, and seawater.

[0051] Example 2: The transparency of solution-processed electrodes was evaluated. Figure 2 shows the results of measuring the optical transmittance in the visible to near-infrared region of spray-coated MWCNTs, PEDOT:PSS, AgNWs, and AgNWs-PEDOT-PFSA. Measurements were performed while maintaining a sheet resistance of approximately 20 Ω / sq. AgNWs-PEDOT-PFSA exhibited the highest optical transmittance (94% @ 550 nm at 21 Ω / sq.).

[0052] Example 3: The pH stability of solution-treated electrodes was evaluated. AgNWs electrodes or AgNWs / PEDOT:F electrodes were fabricated by spray coating on glass substrates. The AgNWs / PEDOT:F electrode was fabricated by spray coating AgNWs on a glass substrate and then spray coating PEDOT:F on the AgNWs electrode. Figure 3 shows a photograph and schematic diagram of the device used to measure resistance using a gold-deposited electrode and perform contact measurements with a multimeter. HCl or NaOH solution was dropped onto the center of the electrode to measure the change in series resistance due to the difference in solution-treated electrodes. Figure 4 shows the results when a diluted HCl solution (pH = 2) was dropped, and Figure 5 shows the results when a diluted NaOH solution (pH = 13) was dropped. The resistance of the AgNWs electrode increased over time, while the increase in resistance of the AgNWs / PEDOT:F electrode was gradual and stable. In Figure 5, the resistance of the AgNWs electrode increased rapidly after several tens of seconds. The initial current-voltage characteristics of these electrodes are shown in Figure 6. The AgNWs / PEDOT:F electrode also had improved initial resistance compared to the AgNWs electrode.

[0053] Example 4: The stability of the solution-treated electrode during application of current was evaluated. An AgNWs electrode or an AgNWs / PEDOT:F electrode was fabricated on a glass substrate in the same manner as in Example 3, and the electrode surface temperature during continuous voltage application was confirmed. ２ The figure shows the change in the surface temperature profile (infrared spectrum) obtained by thermography after applying a voltage of +2 V from left to right for an AgNWs electrode and an AgNWs / PEDOT:F electrode with a resistance of approximately 20 Ω / sq. The AgNWs electrode showed localized excessive temperatures after approximately 60 seconds of voltage application, while the surface temperature of the AgNWs / PEDOT:F electrode stabilized and showed a more uniform temperature distribution. The temperature increase can cause degradation of the AgNWs electrode, reducing its conductivity and resulting in an increase in the series resistance of the device.

[0054] Example 5: The peel strength of solution-treated electrodes was evaluated. As shown in Figure 8, an AgNWs electrode or an AgNWs / PEDOT:F electrode (24 mm x 24 mm) was fabricated on a glass substrate in the same manner as in Example 3, and tape (Kapton (registered trademark) tape) was attached to it. The tape was then peeled off from the long end, and the peel strength was measured. The results are shown in Figure 8. During the peeling process, the AgNWs / PEDOT:F electrode exhibited a maximum peel force of 2.5 N, while the AgNWs electrode only reached approximately 1.0 N. Thus, the AgNWs / PEDOT:F electrode exhibited a higher peel strength than the AgNWs electrode.

[0055] Example 6: Solution-processed electrodes were applied to human skin. The electrodes were deposited by direct coating onto the skin. Figures 9A and 9B are photographs and microscope images showing an example of an electrode attached to a finger. The electrodes form a conductive path to light up an LED. Figure 9C shows the frequency-impedance characteristics of a commercially available Ag / AgCl gel electrode, an AgNWs electrode, and an AgNWs-PEDOT-PFSA electrode. The AgNWs-PEDOT-PFSA electrode exhibited lower impedance at 100 Hz than the commercially available Ag / AgCl gel electrode and the AgNWs electrode, and the AgNWs-PEDOT-PFSA electrode exhibited the highest conductivity. Figures 10A-10D show the results of measuring the potential response (Figures 10B-10D) during repeated gripping and unclenching movements (Figure 10A) when a commercially available gel electrode, an AgNWs electrode, and an AgNWs-PEDOT-PFSA electrode were attached to the surface of the arm. The commercially available gel was attached to the brachioradialis muscle of one arm as an electrode, and an ultrathin hydrogel was attached to the back of the hand as a ground electrode. EMG signals recorded with different electrodes were compared by consistently placing the electrodes in the same size and position on the skin of the arm. The AgNWs-PEDOT-PFSA electrode achieved a signal-to-noise ratio (SNR) similar to that of the commercially available gel electrode and showed the highest potential amplitude. Figures 11A to 11D show the results of EMG measurements (Figures 11B to 11D) of commercially available electrodes, AgNWs electrodes, and AgNWs-PEDOT-PFSA electrodes attached to the chest (Figure 11A). Before indicates before water droplets were applied, and after indicates after water droplets were applied. After water droplets were applied, the commercially available gel electrodes and AgNWs electrodes generated irregular signals, while the AgNWs-PEDOT-PFSA electrodes maintained their initial signal quality. Figures 12A to 12C show the responses of AgNWs-PEDOT-PFSA electrodes attached to the hand during a scratching motion (IV) in water. Figure 12A shows the results of recording EMG signals using wrist flexion at five angles as photographed hand gestures in various positions underwater (top), and the real-time high-pass filtered ECG output signal with STFT during electrode action (bottom). Figure 12B visualizes the t-SNE for EMG classification.Each cluster group corresponds to a specific swimming gesture action, and the supervised learning (SL) algorithm can easily achieve high classification accuracy for EMG signals due to the clear division of signals for different actions. Figure 12C shows the confusion matrix for the five action recognition results. To evaluate the reliability of the AgNWs-PEDOT-PFSA electrode for motion analysis and prediction, we used a machine learning (ML) framework to recognize gestures. Data augmentation was employed for training and cross-validation, and the highest accuracy of 99.4% was achieved using the random forest algorithm. The application of the ML scheme to swimming gesture prediction is promising, and the ability of the AgNWs-PEDOT-PFSA electrode to acquire ECG and EMG signals underwater will be beneficial for future applications in swimming and rescue operations.

[0056] Reference Example 1: Cl of solution-treated electrode － Ion permeability was evaluated. Figure 13A shows the semipermeable membrane (top) and PEDOT:PFSA polymer film (bottom) for the ion blocking device in water. The reaction was performed using 1 mol / L HCl solution and 0.1 mg / ml AgNO. ３ A solution was used. When 10 mg / ml purple litmus solution was added to a hydrochloric acid solution for color development, white silver chloride (AgCl) precipitated in the semipermeable membrane. Chloride ions can easily pass through the semipermeable membrane, but cannot penetrate the fluorinated polymer film. The hydrophobic surface of the PEDOT:PFSA polymer film can inhibit the penetration of hydrated ions. Figure 13B shows the D-SIMS depth profiles of the PEDOT:PSS and PEDOT-PFSA polymer films after immersion in the ionic solution. The Cl incorporation into the films by D-SIMS was confirmed. － Permeation characterization was used to evaluate the ion diffusion ability. Compared to the PEDOT:PSS polymer film, the PEDOT-PFSA polymer film exhibited Cl － Transmission is 10 ３ The PEDOT:PSS polymer film showed an increasing intensity up to 10 ５ From the above results, it can be seen that the AgNWs-PEDOT-PFSA electrode exhibits a high strength up to Cl even in seawater with a high salt concentration as in Example 6 or in body fluids.－ This suggests that electrical signals can be detected by suppressing transmission.

[0057] Example 7: A fully solution-processed organic thin-film solar cell (OPV) was fabricated. AgNPs, PEI-Zn, PEI, PM6:BTP-eC9, PEDOT:F, AgNWs, and PEDOT:F were solution-processed onto a substrate in this order. In this structure, PM6:BTP-eC9 was used as the organic active layer. Due to its excellent solution-processing properties, it can be dissolved in various organic solvents (chloroform, chlorobenzene, and toluene) while maintaining high efficiency. The morphological stability of BTP-eC9 can mitigate performance degradation of the active layer itself under long-term light irradiation, which contributes to optimizing interfacial stability. A silver nanoparticle (AgNPs) ink and a solution-processed silver (S-Ag) electrode derived from PEI-Zn / PEI constituted the bottom reflective electrode and electron transport layer (ETL), respectively. PEDOT:F / AgNWs / PEDOT:F was used as the hole transport layer (HTL) and top transparent electrode. The fully solution-processed OPV was fabricated using the following procedure. A glass substrate was cleaned, and a patterned AgNPs bottom electrode was deposited by lift-off. An electron transport layer (PEI-Zn and PEI) was spin-coated, followed by an organic active layer (PM6:BTP-eC9) and annealed. A hole transport layer (PEDOT:F) was spin-coated and annealed. The top electrode was fabricated by spray-coating AgNWs using a shadow mask, followed by spray-coating PEDOT:F. A control top electrode consisting of only AgNWs and no PEDOT:F was also fabricated. Figure 14A shows a photograph of the fully solution-processed OPV and electrodes sealed with glass, Figure 14B shows a microscope image, and Figures 15A and 15B show cross-sectional SEM images of the electrode interface. Cross-sectional SEM images of the electrode interface show that the electrode is covered with PEDOT-PFSA, presenting a smoother surface.

[0058] The efficiency and stability of all solution-processed OPVs were evaluated. Figure 16 shows the J-V curves of all solution-processed OPVs. For the AgNWs-PEDOT-PFSA electrode, Jsc = 24.3 mA cm －２The results showed superior performance compared to the AgNWs electrode (12.80%), with Voc = 0.81 V, FF = 0.69, and PCE = 13.58%. Figure 17 summarizes the light-air stability of all solution-processed and vacuum-deposited OPVs previously reported (see below for the previous report). Summarizing the stability results of vacuum-deposited and all solution-processed OPVs tested in air using standard sunlight (AM 1.5G) as an aging light source, the all solution-processed OPVs showed the most durable stability in air testing and also had the highest initial efficiency. [S2] P. Cheng, H. Bai, NK Zawacka, TR Andersen, W. Liu, E. Bundgaard, M. Jorgensen, H. Chen, FC Krebs, X. Zhan, Adv. Sci. 2015, 2, 1500096. PET / Ag gird / PEDOT:PSS / ZnO / PBDTTT-CT:DC-IDT2T / PEDOT:PSS / Ag gird [S3] GA dos Reis Benatto, B. Roth, MV Madsen, M. Hosel, RR Sondergaard, M. Jorgensen, FC Krebs, Adv. Energy Mater. 2014, 4, 1400732. PEDOT:PSS / ZnO / P3HT:PCBM / PEDOT:PSS / Carbon [S4] NK Zawacka, TR Andersen, JW Andreasen, LH Rossander, HF Dam, M. Jorgensen, FC Krebs, J. Mater. Chem. A 2014, 2, 18644. PET / Ag gird / PEDOT:PSS / ZnO / P3HT:PCBM / PEDOT:PSS / Ag gird [S5] TR Andersen, HF Dam, M. Hosel, M. Helgesen, JE Carle, TT Larsen-Olsen, SA Gevorgyan, JW Andreasen, J. Adams, N. Li, F. Machui, GD Spyropoulos, T. Ameri, N.Lemaitre, M. Legros, A. Scheel, D. Gaiser, K. Kreul, S. Berny, OR Lozman, S. Nordman, M. Valimaki, M. Vilkman, RR Sondergaard, M. Jorgensen, CJ Brabec, FC Krebs, Energy Environ. Sci. 2014, 7, 2925. PET / Ag grid / PEDOT:PSS / ZnO / tandem cells / HTL / PEDOT:PSS / Ag grid [S6] H. Xu, J. Han, S. Chen, Y. Liu, L. Huerta Hernandez, J. Bertrandie, M. Babics, Villva, S. K. Alamva, DR. Paleti, J. Gorenflot, C. Herok, N. Ramos, J. Troughton, A. Sharma, TB Marder, B. Engels, J. Martin, S. De Wolf, F. Laquai, D. Baran, Joule 2023, DOI: https: / / doi.org / 10.1016 / j.joule.20207.03.03. Glass / ITO / PEDOT:PSS / PM6:BTP-eC9 / PDINO / Ag [S7] C.-N. Weng, H.-C. Yang, C.-Y. Tsai, S.-H. Chen, Y.-S. Switch. Chen, K.-M. Huang, H.-F. Meng, Y.-J. Chao, C.-Y. Chang, H.-W. John, S.-F. Horng, P.-C. Yu, K.-W. Su, Sol. Energy 2020, 199, 308. Glass / ITO / PEDOT:PSS / PBDTTT-EFT:PC71BM / ZrOXAl / Ag [S8] Q. An, F. Zhang, W. Gao, Q. Sun, M. Zhang, C. Yang, J. Zhang, Nano Energy 2018, 177.Glass / ITO / ZnO / PBDB-T:ITIC:N2200 / MoO3 / Ag [S9] G. Williams, H. Aziz, Org. Electron. 2014, 15, 47. Glass / ITO / CF4 / P3HT:PC61BM / BCP / Al [S10] H. Lee, S. Oh, CE Song, HK Lee, SK Lee, WS Shin, W.-W. So, S.-J. Moon, J.-C. Lee, RSC Adv. 2019, 9, 20733. Glass / ITO / ZnO / PEIE / P3HT:SF-HR / MoO3 / Ag [S11] CL Chochos, N. Leclerc, N. Gasparini, N. Zimmerman, E. Tatsi, A. Katsouras, D. Moschovas, E. Serzopet, I. Kongloidakis, P. Fallou, S. Leveque, T. Heiser, M. Spanos, VG Gregoriou, E. Stratakis, T. Ameri, CJ Brabec, A. Avgeropoulos, J. Mater. Chem. A 2017, 5, 25064. ITO / PEDOT:PSS / CTL3: :PC71BM / Ca / Al.

[0059] Figure 18A shows a photograph of the sealed, all-solution-processed OPV placed under actual outdoor conditions. After sealing with a single pane of glass, the OPV was installed at a 35° angle relative to the ground to maximize solar irradiance. The OPV was installed in Saitama Prefecture, at 35°46'36.7"N, 139°36'40.2"E, from May 25 to July 12, 2023, and exposed to actual outdoor conditions, including day-night cycles, sunny days, rainy days, cloudy days, and strong winds. The device's efficiency was recorded every few days and then returned to the outdoor environment to continue the aging test. During this time, the device was maintained in an open-circuit state. Figure 18B shows a plot of the power conversion efficiency (PCE) of the all-solution-processed OPV at actual outdoor irradiance (from May 25 to July 12, 2023), corresponding precipitation, and maximum and minimum outdoor temperatures, along with precipitation. After 48 days of outdoor exposure, all solution-processed OPVs with AgNWs-PEDOT-PFSA as the top electrode maintained 80.7% of the initial efficiency.

[0060] Example 8: Figure 19A is a photograph showing an example of fabricating a film-like electrode in which an AgNWs-PEDOT:F electrode array was patterned in parallel lines on the surface of a resin film and connected to a terminal, and Figure 19B is an optical microscope image of the electrode site. The array has nine electrode channels, and each channel site is 300 × 300 μm in size. ２ The substrate is a 5 μm-thick parylene film, and the AgNWs-PEDOT-PFSA portion is exposed through patterned SU-8 on the top layer, resulting in a total electrode thickness of 5.5 μm. Such a film electrode can be used, for example, by implanting it in a living body.

[0061] Example 9 In Examples 8 and 9, a transparent, conductive, and waterproof nanomembrane was obtained using a solution-processed biphasic percolation network (BIPIN), which enabled simultaneous acquisition of bioelectrical and optical signals from a biological surface. Figures 20A–20D show photographs of an electrode attached to the biceps brachii muscle; the scale bar indicates 1 cm. Figures 21A–21D show vascular images of an electrode attached to the flexor radialis muscle, taken using a venography device; the scale bar indicates 6 mm. To compare different electrodes during gripping movements for EMG monitoring, different electrodes were placed on the biceps brachii muscle (Figures 20A–20D). Although electrodes such as AgNWs@PDMS and PVA gel are transparent to the naked eye, they still produce strong imaging artifacts under near-infrared venous visualization, hindering clear vascular imaging (Figures 21A–21D). In contrast, BIPIN maintained clear vascular imaging during gripping movements. This is primarily due to direct optical interference caused by the opacity of commercially available electrodes. AgNWs@PDMS electrodes are relatively thick (over 1 mm) and have poor adhesion to the skin, resulting in refraction of infrared light and image artifacts. PVA hydrogel electrodes are characterized by high water content and a smooth surface, but they absorb excessive infrared light and exhibit a surface morphology significantly different from that of skin tissue. However, the excellent optical transparency and ultrathin structure of BIPIN, which is deposited directly on the skin, effectively prevent optical signal distortion. Furthermore, BIPIN's waterproofing capability ensures reliable, high-quality biosignal acquisition even under wet or aqueous conditions. Such film-like electrodes can be implanted in vivo, for example. Transparent implantable devices for BIPIN in vivo applications have attracted great interest in neuroscience and biomedical engineering, as they enable the integration of neural recording and optical technologies. BIPIN's outstanding performance has motivated the pursuit of implantable bioelectronic applications, such as ultrathin transparent electrode arrays for interfacing with the cortical surface of rats. For example, this array has nine electrode channels, each with a size of 300 × 300 μm ２The substrate is a 5 μm-thick 45 Parylene / SU-8 film, with the BIPIN components exposed through the patterned SU-8 on the top layer, resulting in a total electrode thickness of 5.5 μm. The fabricated electrodes can be peeled off from the substrate and become self-standing. The electrical performance of the ECoG electrodes demonstrates high conformality, with BIPIN's excellent stability allowing comfortable adhesion to the mouse cerebral cortex before and after detachment. When used for in vivo ECoG measurements, electrodes fabricated with BIPIN and gold (Au) remain transparent in the measurement area when implanted into the somatosensory cortex, allowing electrophysiological signals recorded from a 9-channel BIPIN electrode array to be obtained. BIPIN electrodes provide high-resolution, stable recording, making them suitable for precision neural interfacing applications. The transparency of BIPIN electrodes improves visualization and monitoring during implantation, thereby reducing the risk of misalignment and potential damage to cortical tissue.

Claims

1. An electrode comprising metal nanowires and a composite polymer of polyethylenedioxythiophene and an anionic fluorine-based polymer, having a single-layer structure or a multilayer structure, wherein the composite polymer is contained in at least the outermost surface layer opposite to the supported side.

2. The electrode according to claim 1, wherein the anionic fluorine-based polymer is a perfluorosulfonic acid polymer.

3. The electrode according to claim 1, wherein the metal nanowires are silver nanowires.

4. The electrode according to claim 1, having a thickness of 100 nm or less.

5. The electrode according to claim 1, which has a light transmittance of 90% or more in the wavelength range of 400 to 1000 nm.

6. A structure comprising the electrode according to any one of claims 1 to 5 and a support on which the electrode is supported.

7. The structure according to claim 6, wherein the support has a functional layer.

8. The structure according to claim 7, wherein the functional layer is a photoelectric conversion layer.

9. A sensor comprising the electrode according to any one of claims 1 to 5 and a detection unit for detecting an electrical signal from the electrode.

10. A method for producing the electrode according to any one of claims 1 to 5, comprising the following steps: applying a first liquid containing the metal nanowires to a surface to form a coating layer; and applying a second liquid containing the composite polymer to the surface of the coating layer to form the outermost layer.

11. The method of claim 10, wherein the first and second liquids are applied by spray application.

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