Method for producing a transparent conductive film

Abstract

The application provides a preparation method of a transparent conductive film. The method comprises the following steps: laying a raw carbon nanotube film with a set area on a substrate surface and placing the substrate in a growth cavity; the substrate and the gas in the growth cavity are subjected to surface reconstruction, accompanied by transportation of facet atoms constituting a facet, so that a facet is formed, and the facet is in the form of a regular step on the substrate surface in a mesoscopic scale; and the facet and the raw carbon nanotube film are allowed to interact, so that impurities in the raw carbon nanotube film are removed, at least part of carbon nanotubes in the raw carbon nanotube film are driven to move by the facet, adjacent carbon nanotubes or bundles of carbon nanotubes tend to be close to each other, and a carbon nanotube network in the raw carbon nanotube film is recombined to obtain a recombined carbon nanotube film. The recombined carbon nanotube film obtained by the method has a more efficient conductive network inside, can be self-supported, and can also realize large-area preparation of the transparent conductive film.

Description

Technical Field

[0001] This invention relates to the field of materials technology, and in particular to a method for preparing a transparent conductive film. Background Technology

[0002] In today's world, the application of transparent conductors is widespread. Transparent conductive films (TCFs) are widely used in modern electronic devices. Currently, the main material for manufacturing TCFs is indium tin oxide (ITO), which possesses excellent transparent conductivity. ITO has developed a complete industrial chain over nearly a century of research. However, due to indium being a non-renewable resource, the cost of ITO has risen sharply in recent years as demand has continued to grow. Furthermore, the inherent brittleness and high areal density of ITO make it difficult to apply in increasingly flexible wearable devices and aerospace fields. In addition, ITO is fabricated on substrates using methods such as magnetron sputtering, which cannot achieve self-support (limiting its application in some cutting-edge applications, such as radiation thermophotodetectors and thermoacoustic speakers), and the fabrication area is limited by the target size. This indicates that the fabrication technology of large-area TCFs for high-end products is one of the key technologies.

[0003] With the development of next-generation flexible electronics / devices, flexible optoelectronics / devices, and wearable devices / systems, increasingly higher demands are being placed on TCFs. These demands require TCFs to not only possess excellent transparency and conductivity, but also flexibility, high strength, and even self-support, while simultaneously being able to be fabricated on a large scale and in large areas. This would truly solve the problem of fabricating carbon nanotube transparent conductive films that meet industrial standards, thus providing an effective solution to the key technical challenge of large-area TCFs. Therefore, the development of a large-area flexible TCF and its fabrication method is crucial to meeting the requirements of future electronic devices. This method aims to simultaneously enable TCFs to be lightweight, high-strength, flexible, with excellent transparency and conductivity, and capable of large-area production. Such a method has significant scientific and practical value for large-area flexible TCF applications, allowing for direct transfer at room temperature, unlike ITO which requires high-temperature sputtering. Summary of the Invention

[0004] In view of the above problems, the present invention proposes a method for preparing a transparent conductive film that overcomes or at least partially solves the above problems.

[0005] One objective of this invention is to achieve large-area fabrication of transparent conductive films.

[0006] A further objective of this invention is to improve the performance of transparent conductive films.

[0007] A further objective of this invention is to incorporate graphene into a transparent conductive film to obtain a recombinant carbon nanotube-graphene composite film, thereby greatly improving the performance of the transparent conductive film.

[0008] In particular, the present invention provides a method for preparing a transparent conductive film, comprising:

[0009] A raw carbon nanotube film of a predetermined area is laid on the substrate surface and placed in the growth chamber;

[0010] The substrate and the gas in the growth chamber undergo surface reconstruction, which, along with the transport of facet atoms that constitute the facets, forms facets. At the mesoscale, the facets appear as regular steps on the substrate surface.

[0011] The facets interact with the original carbon nanotube film, thereby removing impurities from the original carbon nanotube film. At least some of the carbon nanotubes in the original carbon nanotube film move under the drive of the facets, and adjacent carbon nanotubes or bundles tend to come closer together, so that the carbon nanotube network in the original carbon nanotube film is reorganized to obtain a reorganized carbon nanotube film.

[0012] Optionally, the step of surface reconstruction between the substrate and the gas in the growth chamber to form facets includes:

[0013] The growth chamber is purged to control the partial pressure of the gas in the growth chamber that undergoes surface reconstruction with the substrate within a set range.

[0014] The growth chamber is heated to control the surface reconstruction of the substrate surface with the gas, thus forming facets.

[0015] Optionally, the gas is a gas in the growth chamber that can undergo surface reconstruction with the substrate, including a mixture of one or more of the same type of oxidizing or reducing gas;

[0016] The sources of gas include: any one or more of the following forms: gas, liquid, and solid.

[0017] Optionally, the steps of causing the facets to interact with the original carbon nanotube film include:

[0018] Continue heating to gradually grow the facets on the substrate, thereby controlling the carbon nanotube network to gradually adhere to the facets and the impurities in the original carbon nanotube film to gradually dissolve.

[0019] As the facets grow, the carbon nanotubes in the carbon nanotube network move and approach each other, thereby reorganizing the carbon nanotube network into a Y-shaped interconnected network with long common segments, resulting in a reorganized carbon nanotube film.

[0020] Optionally, the temperature range for forming the facets is configured to be greater than or equal to 400°C;

[0021] The temperature range at which the carbon nanotube network gradually adheres to the facet is configured to be greater than or equal to 600°C.

[0022] The temperature range for the gradual dissolution of impurities is set to be greater than or equal to 500℃.

[0023] The steps to enable the facets to interact with the original carbon nanotube film also include: continuing to heat the film to gradually eliminate the morphological features of the facets, wherein the temperature range at which the morphological features of the facets gradually disappear is configured to be greater than or equal to 800°C.

[0024] Optionally, after the step of causing the facets to interact with the original carbon nanotube film, the method further includes: introducing a carbon source and an auxiliary gas into the growth chamber to grow graphene and obtain a recombinant carbon nanotube-graphene composite film.

[0025] Optionally, the step of causing the facets to interact with the original carbon nanotube film further includes:

[0026] The recombinant carbon nanotube film or the recombinant carbon nanotube-graphene composite film is cooled at a preset cooling rate.

[0027] The cooled reconstituted carbon nanotube film or reconstituted carbon nanotube-graphene composite film is etched away from the substrate in a substrate etchant, floats on the surface of the substrate etchant, and is then rinsed with a rinsing solution.

[0028] Optionally, the step of depositing a raw carbon nanotube film of a predetermined area onto the substrate surface includes:

[0029] Multiple original carbon nanotube films are spliced ​​and laid on the substrate surface, so that the original carbon nanotube films cover the substrate surface, and there is at least one layer of original carbon nanotube films on the substrate surface.

[0030] Optionally, after the step of depositing a raw carbon nanotube film of a predetermined area onto the substrate surface, the method further includes:

[0031] A volatile organic solvent was added dropwise to the original carbon nanotube film to wet the original carbon nanotube film, thereby increasing the contact between the original carbon nanotube film and the substrate surface.

[0032] After the organic solvent has evaporated, the original carbon nanotube film and the substrate are placed in the growth chamber.

[0033] Optionally, the organic solvent includes any one or a mixture of any number of organic solvents selected from ethanol, propanol, butanol, ethylene glycol, isopropanol, acetone, n-hexane, cyclohexane, anisole, and chlorobenzene.

[0034] The carbon nanotubes in the original carbon nanotube film include at least one or a mixture of more than one of single-walled carbon nanotubes, double-walled carbon nanotubes, few-walled carbon nanotubes, and multi-walled carbon nanotubes.

[0035] The original carbon nanotube film had a thickness greater than 0.1 nm;

[0036] The substrate material includes any one of the following metals: copper, platinum, gold, nickel, titanium, iron, lead, palladium, silver, tungsten, aluminum, zinc, chromium, gold, or an alloy of any combination of these metals.

[0037] The present invention discloses a method for preparing a transparent conductive film. A raw carbon nanotube film of a predetermined area is deposited on a substrate surface and placed in a growth chamber. Subsequently, surface reconstruction occurs on the substrate surface with the gas, forming facets. Accompanied by the transport of numerous facet-forming atoms, the facets exhibit a regular step-like structure on the substrate surface at the mesoscopic scale. Next, the facets interact with the raw carbon nanotube film, thereby removing impurities from the raw film. At least some carbon nanotubes in the raw film shift position under the drive of the facets, and the carbon nanotube network in the raw film is reorganized to obtain a reconstituted carbon nanotube film. The reconstituted carbon nanotube film obtained by this method, as a transparent conductive film, forms a more efficient conductive network internally compared to the raw carbon nanotube film, improving the performance of the transparent conductive film. Furthermore, the method of the present invention can achieve large-area preparation of transparent conductive films and also achieve self-support for such large-area transparent conductive films.

[0038] Furthermore, in the method for preparing the transparent conductive film of the present invention, after the facets interact with the original carbon nanotube film, a carbon source and an auxiliary gas are continuously introduced into the growth chamber to grow graphene, thereby obtaining a recombinant carbon nanotube-graphene composite film. This method allows graphene to fill the pores of the carbon nanotube network in the recombinant carbon nanotube film, resulting in a recombinant carbon nanotube-graphene composite film. This structure combines the advantages of graphene and carbon nanotubes, thereby greatly improving the performance of the transparent conductive film. Moreover, the method of the present invention can also achieve large-area preparation of the recombinant carbon nanotube-graphene composite transparent conductive film, and simultaneously achieve self-support for such large-area transparent conductive films.

[0039] The above and other objects, advantages and features of the present invention will become more apparent to those skilled in the art from the following detailed description of specific embodiments of the invention in conjunction with the accompanying drawings. Attached Figure Description

[0040] The following sections will describe some specific embodiments of the invention in a detailed manner, by way of example and not limitation, with reference to the accompanying drawings. The same reference numerals in the drawings denote the same or similar parts or portions. Those skilled in the art will understand that these drawings are not necessarily drawn to scale. In the drawings:

[0041] Figure 1 This is a schematic flowchart of a method for preparing a transparent conductive film according to an embodiment of the present invention;

[0042] Figure 2 This is a schematic flowchart of a method for preparing a transparent conductive film according to another embodiment of the present invention;

[0043] Figure 3 This is a schematic flowchart of a method for preparing a transparent conductive film according to yet another embodiment of the present invention;

[0044] Figure 4 This is a schematic diagram of the substrate cross-section of a method for preparing a transparent conductive thin film according to an embodiment of the present invention;

[0045] Figure 5A This is a schematic diagram of the substrate facet-driven carbon nanotube network prior to the recombination in a method for preparing a transparent conductive thin film according to an embodiment of the present invention.

[0046] Figure 5B This is a schematic diagram of the substrate facet-driven carbon nanotube network recombination process in a method for preparing a transparent conductive thin film according to an embodiment of the present invention.

[0047] Figure 6A This is a schematic diagram of the substrate faceting driven splicing of multilayer carbon nanotube network before the reorganization of a transparent conductive thin film preparation method according to an embodiment of the present invention.

[0048] Figure 6B This is a schematic diagram of the substrate facet-driven splicing and reorganization process of a multilayer carbon nanotube network in a method for preparing a transparent conductive thin film according to an embodiment of the present invention.

[0049] Figure 7 The mechanical strength test results of the original carbon nanotube film and the recombinant carbon nanotube-graphene composite film of the method for preparing a transparent conductive film according to an embodiment of the present invention are shown.

[0050] Figure 8A This is a typical high-resolution transmission electron microscope (HRTEM) image of pristine carbon nanotubes with a scale bar of 500 nm, prepared by a method for preparing a transparent conductive film according to an embodiment of the present invention.

[0051] Figure 8BThis is a typical high-resolution transmission electron microscope (HRTEM) image of pristine carbon nanotubes with a scale bar of 50 nm, produced by a method for preparing a transparent conductive thin film according to an embodiment of the present invention.

[0052] Figure 8C This is a typical high-resolution transmission electron microscope (HRTEM) image of pristine carbon nanotubes with a scale bar of 10 nm, produced by a method for preparing a transparent conductive film according to an embodiment of the present invention.

[0053] Figure 8D Energy dispersive spectroscopy (EDS) results of a method for preparing a transparent conductive thin film according to an embodiment of the present invention are shown.

[0054] Figure 9A This is a typical HRTEM image of recombinant carbon nanotubes with a scale bar of 500 nm, obtained by a method for preparing a transparent conductive film according to an embodiment of the present invention.

[0055] Figure 9B This is a typical HRTEM image of recombinant carbon nanotubes with a scale bar of 50 nm, obtained by a method for preparing a transparent conductive film according to an embodiment of the present invention.

[0056] Figure 9C Energy dispersive spectroscopy (EDS) results of a method for preparing a transparent conductive thin film according to an embodiment of the present invention are shown.

[0057] Figure 10 This is a copper-faceted SEM image of a method for preparing a transparent conductive thin film according to an embodiment of the present invention;

[0058] Figure 11A These are SEM images of the original carbon nanotube film and copper foil prepared by a method for preparing a transparent conductive film according to an embodiment of the present invention.

[0059] Figure 11B This is a SEM image of a reconstituted carbon nanotube film and a copper foil prepared by a method for preparing a transparent conductive film according to an embodiment of the present invention.

[0060] Figure 12A This is a SEM image of the original spliced ​​carbon nanotube film and copper foil prepared by a method for preparing a transparent conductive film according to an embodiment of the present invention.

[0061] Figure 12B This is a SEM image of a reconstituted carbon nanotube film and a copper foil prepared by a method for preparing a transparent conductive film according to an embodiment of the present invention.

[0062] Figure 13A This is a SEM image of the original two-layer carbon nanotube film and copper foil prepared by a method for preparing a transparent conductive film according to an embodiment of the present invention.

[0063] Figure 13B This is a SEM image of a reconstituted carbon nanotube film and a copper foil prepared by a method for preparing a transparent conductive film according to an embodiment of the present invention.

[0064] Figure 14A This is a raw carbon nanotube film SEM image of a method for preparing a transparent conductive film according to an embodiment of the present invention.

[0065] Figure 14B This is a SEM image of a recombinant carbon nanotube-graphene composite film prepared by a method for preparing a transparent conductive film according to an embodiment of the present invention.

[0066] Figure 15A This is an AFM image of the original carbon nanotube film prepared by a method for preparing a transparent conductive film according to an embodiment of the present invention.

[0067] Figure 15B This is an AFM image of a recombinant carbon nanotube-graphene composite film prepared by a method for preparing a transparent conductive film according to an embodiment of the present invention.

[0068] Figure 15C This is an AFM image cross-sectional analysis of the original carbon nanotube thin film prepared by a method for preparing a transparent conductive thin film according to an embodiment of the present invention;

[0069] Figure 15D This is an AFM image cross-sectional analysis of a recombinant carbon nanotube-graphene composite film prepared by a method for preparing a transparent conductive film according to an embodiment of the present invention.

[0070] Figure 16 These are transparent conductivity test diagrams of various transparent conductive films prepared according to an embodiment of the present invention.

[0071] Figure 17 This is a SEM image of a recombinant carbon nanotube-graphene composite film prepared according to a method for preparing a transparent conductive film according to one embodiment.

[0072] Figure 18 The invention illustrates a method for preparing a transparent conductive film, specifically a self-supporting large-area recombinant carbon nanotube film floating on the surface of deionized water.

[0073] Figure 19 A method for preparing a transparent conductive film according to an embodiment of the present invention is shown, which is a large-area recombinant carbon nanotube-graphene composite film that is self-supporting in air.

[0074] Figure 20 This invention illustrates a method for preparing a transparent conductive thin film according to an embodiment of the present invention, showing a self-supporting large-area reconstituted carbon nanotube-graphene composite film floating on the surface of a substrate etchant liquid; and

[0075] Figure 21 The invention illustrates a method for preparing a transparent conductive film, specifically a self-supporting large-area recombinant carbon nanotube-graphene composite film floating on the surface of deionized water, according to another embodiment of the present invention. Detailed Implementation

[0076] Those skilled in the art should understand that the embodiments described below are merely a part of the embodiments of the present invention, and not all of the embodiments of the present invention. These partial embodiments are intended to explain the technical principles of the present invention and are not intended to limit the scope of protection of the present invention. Based on the embodiments provided by the present invention, all other embodiments obtained by those skilled in the art without creative effort should still fall within the scope of protection of the present invention.

[0077] Currently, finding new TCFs to replace ITO films has been a primary goal for those skilled in the art. Industry generally believes that TCFs used in smart windows, displays, touchscreens, wearable products, etc., should maintain a transmittance of over 85%, and for most electronic devices (such as touchscreens), a sheet resistance of less than 300 Ω / sq is required, while for some electronic devices (such as liquid crystal displays), a sheet resistance even lower than 100 Ω / sq is required. In particular, future displays require flexible transparent electrodes that can be fabricated over large areas at low temperatures and low costs. To date, ITO TCFs and current potential alternatives (such as alternative metal oxides, metal films, or metal meshes) cannot meet all these requirements. However, the high transmittance and high conductivity of TCFs are mutually restrictive. This leads to the primary challenge in finding new flexible TCFs: how to ensure that flexible TCFs achieve sufficiently high transmittance while maintaining a suitable sheet resistance range. A key challenge is how to enable large-area fabrication of flexible TCFs at lower temperatures. The latter involves properties such as the areal density and mechanical strength of the TCF, which also determine its applicability in future flexible electronics and cutting-edge fields such as aerospace.

[0078] Among the various novel TCF materials, carbon nanofilms, metal nanowires, and conductive polymers are the main types. Carbon nanofilms were once considered the most competitive and ideal material to replace the widely used ITO TCF in industry due to their excellent electrical and optical properties, flexibility, outstanding stability, and the lightweight, radiation-resistant, and fatigue-resistant properties urgently needed for future military and aerospace applications. However, the prerequisite for the widespread application of TCFs is not only excellent transparency and conductivity, but also the ability to fabricate them on a large scale or even on a large scale. To date, most research on carbon nanofilms remains in the small-area experimental stage, with only a few studies proposing several large-area fabrication methods, but these methods still have some problems. Therefore, this invention proposes a method for preparing transparent conductive films to achieve large-area fabrication of transparent conductive films.

[0079] Figure 1 This is a schematic flowchart of a method for preparing a transparent conductive film according to an embodiment of the present invention.

[0080] In this embodiment, the process generally includes:

[0081] Step S101: A raw carbon nanotube film of a predetermined area is deposited on the substrate surface and placed in the growth chamber. The carbon nanotube film is a novel material composed of single or multiple layers of repeating carbon nanotubes. It is formed by filling freely arranged carbon nanotube arrays with physical or chemical methods to create a two-dimensional carbon nanotube network structure. This film possesses excellent properties, including lightweight, high strength, high corrosion resistance, high electromagnetic interference resistance, excellent thermal insulation properties, and good electrical insulation properties.

[0082] Optionally, the carbon nanotubes in the virgin carbon nanotube film include at least one or a mixture of multiple types of carbon nanotubes selected from single-walled carbon nanotubes, double-walled carbon nanotubes, few-walled carbon nanotubes, and multi-walled carbon nanotubes; and the thickness of the virgin carbon nanotube film needs to be greater than 0.1 nm. Preferably, the visible light transmittance of the virgin carbon nanotube film is ≥20%. It should be noted that this method does not limit the preparation method of the virgin carbon nanotube film. Those skilled in the art can determine the preparation method of the virgin carbon nanotube film according to the actual situation. One optional virgin carbon nanotube film can be a directly grown carbon nanotube film, and an optional growth method is, for example, chemical vapor deposition (CVD). Furthermore, during the laying process, the characteristic dimensions (e.g., length, width, diameter, etc.) of the virgin carbon nanotube film are not limited. Those skilled in the art can select according to the actual production situation. For example, the characteristic dimensions of the virgin carbon nanotube film can be divided into three ranges: ≤10 cm, 10 cm-1 m, and ≥1 m, and the corresponding characteristic dimensions of the virgin carbon nanotube film can be selected according to actual needs.

[0083] Optionally, the substrate material can generally include, but is not limited to, metals, semiconductors, and other compounds. Metals generally include: copper, platinum, gold, nickel, titanium, iron, lead, palladium, silver, tungsten, aluminum, zinc, chromium gold, and alloys of several metals. Semiconductors generally include: silicon, germanium, gallium arsenide, gallium nitride, indium phosphide, titanium oxide, aluminum oxide, iron sulfide, nickel sulfide, cadmium selenide, etc. Other compounds generally include vanadium oxide, manganese oxide, silicon oxide, etc. Preferably, the substrate material can be any one of copper, platinum, gold, nickel, titanium, iron, lead, palladium, silver, tungsten, aluminum, zinc, chromium gold, or an alloy of any combination of these metals. Those skilled in the art can select a suitable substrate material according to actual production needs.

[0084] In some optional embodiments, the substrate needs to be pretreated to make its surface smooth before laying the original carbon nanotube film. It should be noted that this method does not limit the pretreatment method; some preferred pretreatment methods may include mechanical polishing, electrochemical polishing, high-temperature annealing, and combinations of these methods. Those skilled in the art can determine the substrate pretreatment method according to the actual situation. Furthermore, this method does not limit the area of ​​the substrate; those skilled in the art can determine the substrate area for each preparation (for ease of explanation, the area of ​​the substrate will be denoted by M, and the area of ​​the original carbon nanotube film is M0). i The area of ​​the transparent conductive film to be grown is M. h The pretreated substrate area M needs to be slightly larger than or equal to the area M0 of the transparent conductive film to be grown. h That is, M≥M h Optionally, the substrate may extend more than 1 mm beyond each side of the transparent conductive film to be grown. Preferably, the substrate may extend more than 10 mm beyond each side of the transparent conductive film to be grown.

[0085] Optionally, this method does not limit the area and shape of the original carbon nanotube film. Therefore, during the laying process, a single original carbon nanotube film may not reach the set area. To address this, the step of laying an original carbon nanotube film of a set area on the substrate surface generally includes: taking multiple original carbon nanotube films and splicing them onto the substrate surface, thereby covering the entire substrate surface with the original carbon nanotube film, ensuring that at least one layer of original carbon nanotube film exists on the substrate surface. Specifically, N (N≥1, N is a positive integer) original carbon nanotube films are taken and laid on the substrate surface. Among the N carbon nanotube films, any one of N... i (i≤N) The area M of the carbon nanotube film i ≤M hThen, N sheets of raw carbon nanotube film are laid on the substrate surface, completely covering the substrate surface, with appropriate margins left on each side. It should be noted that this method does not limit the laying method of the raw carbon nanotube film on the substrate surface. Optional laying methods include: flat laying, interlaced laying, etc. Preferably, the final laying effect is such that, when viewed from above, there are no gaps exposing the substrate between the carbon nanotube films, and the upper and lower layers can overlap. Ultimately, it is necessary to ensure that after laying N sheets of raw carbon nanotube film on the substrate surface, the resulting multilayer carbon nanotube film has a uniform thickness and an intact and flat overall surface. Those skilled in the art can choose the laying method according to the actual situation of the raw carbon nanotube film and the substrate.

[0086] Optionally, after the step of laying the original carbon nanotube film of a predetermined area on the substrate surface, the method may further include: adding a volatile organic solvent dropwise to the original carbon nanotube film to wet it, thereby increasing the contact between the original carbon nanotube film and the substrate surface; after the organic solvent has evaporated, placing the original carbon nanotube film and the substrate in a growth chamber. This method is not limited to the type of organic solvent; a preferred example is any one or a mixture of more than one of the following organic solvents: ethanol, propanol, butanol, ethylene glycol, isopropanol, acetone, n-hexane, cyclohexane, anisole, and chlorobenzene. Those skilled in the art can select the appropriate organic solvent according to the actual situation.

[0087] Optionally, the growth chamber refers to the region that helps the original carbon nanotube film complete the growth process on the substrate surface, also known as the "growth region". The growth region typically refers to a specific area or device whose internal conditions are optimized to support the growth or synthesis of carbon nanotube films. Parameters such as temperature, pressure, gas composition, and flow rate are precisely controlled to provide the optimal environment for carbon nanotube growth. Those skilled in the art can select the appropriate growth region to implement this method based on the actual situation.

[0088] In step S102, the substrate and the gas in the growth chamber undergo surface reconstruction, accompanied by the transport of facet atoms that constitute the facets, thus forming facets. The facets appear as regular steps on the substrate surface at the mesoscale.

[0089] It should be noted that the substrate material is not limited in the method of the present invention. Depending on the substrate material, a corresponding reaction gas can be selected to reconstruct the substrate surface and form facets.

[0090] Optionally, the gas is a gas in the growth chamber capable of surface reconstruction with the substrate, including a mixture of one or more of the same type of oxidizing or reducing gas; where the same type of gas refers to gases with similar chemical properties. For example, multiple oxidizing gases of the same type can be selected, such as oxygen, chlorine, bromine, etc. Those skilled in the art can select the specific type and quantity of the reacting gas according to the actual situation. The source of the gas can generally include: a mixture of any one or more forms of gas, liquid, or solid. Those skilled in the art can select the corresponding gas capable of surface reconstruction with the substrate according to the actual situation of the substrate material and structure. Optionally, the step of surface reconstruction between the substrate and the gas in the growth chamber to form a facet generally includes: purging the growth chamber to control the partial pressure of the gas in the growth chamber that is undergoing surface reconstruction with the substrate within a set range; heating the growth chamber to control surface reconstruction between the substrate and the gas to form a facet. The gas scrubbing process involves removing impurities from the mixed gas while simultaneously controlling the partial pressure of the gas undergoing surface reconstruction with the substrate within a set range in the growth chamber. The gases used in the scrubbing process typically include any one or a mixture of nitrogen, argon, and hydrogen. Those skilled in the art can determine the specific type of gas used for scrubbing based on the actual situation.

[0091] In some optional embodiments of the present invention, when the substrate material is selected as a metal or alloy (e.g., copper), the oxidizing gas is generally chosen as the gas that remodels with the substrate surface; an optional example is oxygen. Oxygen partial pressure refers to the partial pressure of oxygen in a gas mixture, and is an indicator of oxygen concentration. It reflects the pressure of oxygen in the gas mixture and is usually expressed in millimeters of mercury (Torr) or pascals (Pa). Different substrate materials require different oxygen partial pressures to react with oxygen to form facets. Optionally, the oxygen partial pressure setting range for different substrates can generally be ≤1 Torr, 1-10 Torr, or ≥10 Torr. Those skilled in the art can select a substrate that forms facets under certain conditions and interacts with the reactants according to the specific target product, and determine the corresponding oxygen partial pressure setting range for this substrate. Meanwhile, the thickness of the substrate is not limited in principle, nor are its rigidity and flexibility. However, considering that the substrate usually needs to be flexible in the limited growth space of the growth region, a preferred substrate example is a foil substrate.

[0092] Once the substrate is selected and the partial pressure of the gas in the growth chamber is controlled within a set range, the growth chamber needs to be heated to control the gas on the substrate surface to undergo surface reconstruction, forming facets. The specific temperature value will vary depending on the substrate material. Optionally, for most substrates, the temperature range for facet formation is configured to be greater than or equal to 400°C.

[0093] Figure 4 This is a schematic diagram of the substrate cross-section in a method for preparing a transparent conductive thin film according to an embodiment of the present invention. Figure 4 As shown, the substrate 40 gradually forms in the growth chamber as the temperature rises, as shown in the figure. Figure 4 The step-like facets shown are wavy, causing the carbon nanotubes to shift along the slope, thus combining the carbon nanotubes on both sides.

[0094] Step S103 involves interacting the facets with the original carbon nanotube film. By interacting the facets with the original carbon nanotube film, impurities in the original carbon nanotube film can be removed, and at least some of the carbon nanotubes in the original carbon nanotube film will shift position under the drive of the facets, with adjacent carbon nanotubes or bundles tending to move closer together, thereby reorganizing the carbon nanotube network in the original carbon nanotube film to obtain a reorganized carbon nanotube film.

[0095] In some optional embodiments, the original carbon nanotube film is generally composed of a carbon nanotube network. The steps for the facets to interact with the original carbon nanotube film generally include: continued heating to allow the facets on the substrate to gradually grow, thereby controlling the carbon nanotube network to gradually adhere to the facets, and the impurities in the original carbon nanotube film to gradually dissolve; the carbon nanotubes in the carbon nanotube network move and approach each other as the facets grow, thereby reorganizing the carbon nanotube network into a long common segment Y-type interconnect network, resulting in a reorganized carbon nanotube film. The temperature range for controlling the carbon nanotube network to gradually adhere to the facets can generally be configured to be greater than or equal to 600°C; the temperature range for the gradual dissolution of impurities can generally be configured to be greater than or equal to 500°C. During the process of the carbon nanotubes in the carbon nanotube network moving and approaching each other as the facets grow, the pore diameter (also called pore size) of the reorganized network changes because the weak carbon nanotubes and tube bundles in the original network are removed. Except for a few pore sizes that do not change significantly, most pore sizes slightly increase or decrease; the reorganized network is also constrained by the original network, and generally the pore diameter formed by reorganization does not exceed the larger pores in the original network. Therefore, under the dual effects of facet-driven and original network constraints, the network structure of the reconstituted carbon nanotube film is optimized, and the pore diameter becomes more uniform. Figure 5AThis is a schematic diagram of the substrate facet-driven carbon nanotube network prior to the recombination in a method for preparing a transparent conductive thin film according to an embodiment of the present invention. Figure 5B This is a schematic diagram of a substrate facet-driven carbon nanotube network recombination process in a method for preparing a transparent conductive thin film according to an embodiment of the present invention. Figure 5A As shown, a carbon nanotube network is deposited on the substrate surface. As the facets are gradually formed and enlarged, the carbon nanotube network gradually moves along with the facets, thus making adjacent carbon nanotubes in the network appear as... Figure 5B The process is gradually recombined as shown.

[0096] In some optional embodiments, step S101 involves depositing a multilayered, spliced ​​original carbon nanotube film on the substrate surface. At the splicing points, carbon nanotubes from different layers approach and connect with each other under the drive of faceting, resulting in a reorganization of the carbon nanotube network. This causes the pore size of the reorganized network to change compared to the pore size of the original carbon nanotube film; generally, larger pore sizes result in longer inter-nodal bundle lengths, while smaller pore sizes result in shorter inter-nodal bundle lengths. The faceting-driven process merges carbon nanotubes from different layers into a single, large-area, long-shared-segment Y-shaped interconnected network. Ultimately, the network structure of the spliced ​​carbon nanotube film is optimized, forming a continuous, large-area network, thus yielding the reorganized carbon nanotube film. Figure 6A This is a schematic diagram of the substrate faceting driven splicing of multilayer carbon nanotube network before the reorganization of a transparent conductive thin film preparation method according to an embodiment of the present invention. Figure 6B This is a schematic diagram of the substrate facet-driven splicing and reassembly process of a multilayer carbon nanotube network in a method for preparing a transparent conductive thin film according to an embodiment of the present invention. Figure 6A As shown, facet 40 is covered with three layers of virgin carbon nanotube films. The first layer contains carbon nanotubes 611 and 612, the second layer contains carbon nanotubes 621 and 622, and the third layer contains carbon nanotubes 631, 632, and 633. After facet-driven recombination, the carbon nanotubes from different layers form new connections, creating a large-area, clean, flat, and continuous long common-segment Y-shaped interconnect network, such as... Figure 6B As shown.

[0097] Figure 8A This is a typical high-resolution transmission electron microscope (HRTEM) image of pristine carbon nanotubes with a scale bar of 500 nm, prepared by a method for preparing a transparent conductive film according to an embodiment of the present invention. Figure 8B This is a typical high-resolution transmission electron microscope (HRTEM) image of pristine carbon nanotubes with a scale bar of 50 nm, produced by a method for preparing a transparent conductive thin film according to an embodiment of the present invention. Figure 8CThis is a typical high-resolution transmission electron microscope (HRTEM) image of pristine carbon nanotubes with a scale bar of 10 nm, produced by a method for preparing a transparent conductive film according to an embodiment of the present invention. Figure 8D The energy dispersive spectroscopy (EDS) results of a method for preparing a transparent conductive thin film according to an embodiment of the present invention are shown. Figure 8A As shown, multiple carbon nanotubes exist within the dashed box 80. The image is a typical high-resolution transmission electron microscope (HRTEM) image of a pristine carbon nanotube at a scale bar of 50 nm. Figure 8B As shown, images of pristine carbon nanotubes under a typical high-resolution transmission electron microscope (HRTEM) with a scale bar of 10 nm are as follows. Figure 8C As shown, multiple carbon nanotubes form a Y-shaped junction structure. And as... Figure 8B As shown, catalyst particulate impurity 81 is present, and its energy dispersive spectroscopy (EDS) results are as follows. Figure 8D As shown, 801 is C, 802 is O, 803, 806 and 807 are Fe, 804, 808 and 809 are Cu, and 805 is Si. Therefore, the spectrum shows the presence of Fe impurity.

[0098] Figure 9A This is a typical HRTEM image of recombinant carbon nanotubes with a scale bar of 500 nm, obtained by a method for preparing a transparent conductive film according to an embodiment of the present invention. Figure 9B This is a typical HRTEM image of recombinant carbon nanotubes with a scale bar of 50 nm, obtained by a method for preparing a transparent conductive film according to an embodiment of the present invention. Figure 9C The energy dispersive spectroscopy (EDS) results of a method for preparing a transparent conductive thin film according to an embodiment of the present invention are shown. Figure 9A As shown, there are dashed boxes 910, 920, 930, and 940, as... Figure 9B As shown, each dashed box exhibits numerous Y-shaped knot structural features after recombination. And as... Figure 9C As shown, 951 is C, 952 is O, 953, 955, and 956 are Cu, and 954 is Si. The Fe from catalyst particle impurity 81 has completely disappeared. Therefore, the recombinant carbon nanotubes have more Y-junction structural features compared to the original carbon nanotubes, thus optimizing the network structure of the carbon nanotube film.

[0099] Figure 12A This is a SEM image of the original spliced ​​carbon nanotube film and copper foil prepared by a method for preparing a transparent conductive film according to an embodiment of the present invention. Figure 12B This is an SEM image of a reconstituted carbon nanotube film and a copper foil prepared by a method for preparing a transparent conductive film according to an embodiment of the present invention. Figure 12AIt contains frame 1 and frame 2, where frame 1 represents the first layer of the original carbon nanotube film on the substrate surface, and frame 2 represents the second layer of the original carbon nanotube film on the substrate surface. After recombination using this method, the following is obtained: Figure 12B The state shown, Figure 12B The dashed line segment represents carbon nanotubes, which can be seen in the coil. Figure 12A The dashed segments 1 and 2 in the diagram are recombined into a Y-shaped structure. The splicing points are made of unconnected or X-shaped overlapping carbon nanotubes from different layers. After faceting-driven recombination, they undergo positional migration, and adjacent tube bundles tend to come close together to form new Y-shaped connections. Some X-shaped overlaps also form strong Y-shaped connections.

[0100] In some alternative embodiments, the step of causing the facets to interact with the original carbon nanotube film may further include: continuing heating to gradually eliminate the morphological features of the facets, wherein the temperature range at which the morphological features of the facets gradually disappear is configured to be greater than or equal to 800°C. When the heating temperature reaches the temperature range at which the morphological features of the facets gradually disappear, the carbon nanotube network reconstruction process is essentially completed. It should be noted that the specific values ​​of the above-mentioned multiple temperature ranges are specific examples of substrates of certain materials under general conditions, and those skilled in the art can determine the specific temperature range corresponding to different operations based on the actual substrate material.

[0101] The recombined carbon nanotube film obtained by this method, as a transparent conductive film, forms a more efficient conductive network inside compared to the original carbon nanotube film, improving the performance of the transparent conductive film. It can also achieve self-support, and this method can also realize the large-area preparation of transparent conductive films.

[0102] In some embodiments, the carbon nanotube transparent conductive film mainly includes carbon nanotube films (CNT–TCF) and graphene films (G–TCF), as well as composite films of carbon nanotubes and graphene (G–CNT TCF). These films are primarily grown using chemical vapor deposition (CVD). Among them, the monolayer graphene film exhibits a transmittance as high as 97.7% and a transmittance of 2.5 × 10⁻⁶. 5 cm 2The CVD-grown graphene film exhibits a room-temperature carrier mobility of 10⁵ GPa (V·s) and a theoretical Young's modulus of 10⁵ GPa. However, intrinsic defects exist in CVD-grown graphene films, and single-atom layers are difficult to self-support during subsequent film transfer. Although large-area fabrication is possible, it requires the assistance of polymers such as thermally release tape, silicone, and EVA for transfer during large-area fabrication. This significantly increases the process difficulty and inevitably leads to substantial contamination and damage to G-TCF, severely affecting its quality and physical and chemical properties. In particular, the sheet resistance of the transferred G-TCF often reaches hundreds of ohms or even exceeds 1000 Ω / sq. Another typical example of carbon nanotube transparent conductive films is CNT-TCF. Theoretically, the room-temperature carrier mobility of a single single-walled carbon nanotube can reach 10⁵ GPa. 5 cm 2 The sheet resistance of CNT-TCF is approximately 1 TPa (V·s), and it possesses a Young's modulus of about 1 TPa. However, limited by the tunneling barrier between tubes and scattering by impurities such as catalyst particles, the sheet resistance of CNT-TCF is often in the hundreds of ohms at 90% transmittance. Larger-area CNT-TCFs (side length or diameter ≥ 10 cm) with superior structures such as low junction resistance can have a sheet resistance below 200 Ω / sq, but still above 100 Ω / sq. In the mass production of transparent conductive single-walled carbon nanotube films (SWCNT-TCF), SWCNT-TCF can even be self-supported and continuously prepared using the blown aerosol CVD (BACVD) method. However, while the length of SWCNT-TCF is unlimited in continuous preparation, its width is difficult to extend due to limitations imposed by the growth principle. While the self-supporting multi-walled carbon nanotube transparent conductive film (MWCNT–TCF) prepared by super-aligned array spinning dry method can be expanded in area, its transparency and conductivity are far inferior to those of single-walled carbon nanotube films prepared by BACVD method.

[0103] In other embodiments, to avoid the detrimental effects of polymer-assisted transfer on graphene quality (contamination, cracking, etc.), a carbon nanotube-graphene composite film (G–CNT TCF) exists, in which graphene fills the pores of the carbon nanotube network. This structure combines the advantages of both graphene and carbon nanotubes. On the one hand, the mechanical strength of carbon nanotubes allows graphene to be transferred to the target substrate without polymer assistance; on the other hand, it simultaneously provides a one-dimensional conductive path for the graphene. High-quality graphene, acting as a conductive plane filling the pores of the carbon nanotube network, can connect non-contact carbon nanotubes, reducing the tunneling barrier and thus improving the carrier transport efficiency of the carbon nanotube network. In some photovoltaic heterojunctions, the filling of graphene can also significantly increase the contact area between carbon nanotubes and other semiconductors, giving the composite film a significantly enhanced carrier collection efficiency. Therefore, devices based on G–CNT TCF often exhibit better performance than those based on single films (G–TCF, CNT–TC), and are expected to play a crucial role in some high-end or special-purpose devices (such as high-stability solar cells). However, carbon nanotube-graphene composite films are still in the stage of small-area (2cm × 2cm on PET, and even smaller, 1cm × 1cm, for self-supporting areas on water) laboratory preparation. Although various preparation methods were developed in this example, the small-area carbon nanotube-graphene composite films with a transmittance of over 85% still have a sheet resistance exceeding 100Ω / sq. Since the transparency and conductivity of directly grown carbon nanotube-graphene composite films do not yet meet industrial application standards, post-treatment methods such as chemical doping (HNO3, AuCl3, TFSA, etc.) or substrate deposition (nickel, gold, etc.) are often used to improve conductivity. However, these methods not only introduce other elements into the carbon nanotube-graphene composite films but also face problems such as poor stability, high cost, and complex processes. Furthermore, most dopants and metals can lead to a decrease in transmittance and an increase in areal density. Furthermore, since the transparency and conductivity of carbon nanotube-graphene composite films are mutually restrictive, these methods can only improve the conductivity of the film individually, and may also lead to a decrease in the transparency of the film, thus failing to achieve a synergistic improvement in transparency and conductivity.

[0104] In some preferred embodiments of the present invention, to further improve the performance of the transparent conductive film, after the step of allowing the facets to interact with the original carbon nanotube film, the method may further include: introducing a carbon source and an auxiliary gas into the growth chamber to grow graphene, thereby obtaining a recombinant carbon nanotube-graphene composite film. When the facets interact with the original carbon nanotube film to obtain a recombinant carbon nanotube film, introducing a carbon source and an auxiliary gas into the growth chamber to grow graphene will result in graphene appearing within the uniform network of carbon nanotubes in the recombinant carbon nanotube film, thus forming a recombinant carbon nanotube-graphene composite film. Optionally, the carbon source may generally include, but is not limited to, any one of methane, ethane, propane, ethylene, methanol, ethanol, and acetylene; the auxiliary gas may generally include, but is not limited to, any one of hydrogen, argon, nitrogen, and helium, or a mixture of any combination of these gases. Those skilled in the art can select the introduced carbon source and corresponding auxiliary gas according to the actual situation. Figure 17 This is a schematic SEM image of a recombinant carbon nanotube-graphene composite film prepared according to an embodiment of the present invention. Figure 17 The image shown is an image obtained using a scanning electron microscope (SEM) with a scale bar of 2 μm.

[0105] This method enables the microscopic reconstruction of the network structure of composite films, thereby synergistically improving various properties of the reconstituted carbon nanotube-graphene composite films, including transparency, conductivity, mechanical strength, cleanliness, and flatness. Furthermore, this method is scalable, allowing for large-area fabrication, producing large-area reconstituted carbon nanotube-graphene composite films with unlimited length and width. Simultaneously, this method allows for large-scale, batch, and continuous fabrication of large-area carbon nanotube-graphene composite films, and the flexible, transparent, conductive carbon nanotube-graphene composite films prepared by this method can be used at any temperature. Figure 7 The mechanical strength test results of the original carbon nanotube film and the reconstituted carbon nanotube-graphene composite film prepared by a method for preparing a transparent conductive film according to an embodiment of the present invention are shown. Figure 7 As shown, the mechanical strength of the recombinant carbon nanotube-graphene composite film is greatly improved compared to the original carbon nanotube film.

[0106] In some preferred embodiments, when heating is performed as described in the above embodiments, a heating rate of 0-20°C / min can be selected, and a suitable temperature T can be selected during the process. x The temperature is maintained at a certain temperature for a specific time t to allow sufficient time for facet growth, carbon nanotube recombination, and graphene growth. The temperature T is... xAn alternative example could be one or more temperatures ≥400°C, and an alternative example of time t could be any of ≥0 min, 0-10 min, 10-60 min, or >60 min. Those skilled in the art can determine the required holding time and specific heating rate at different temperatures based on the actual situation.

[0107] Optionally, after the step of allowing the facets to interact with the original carbon nanotube film, the method further includes: cooling the reconstituted carbon nanotube film or the reconstituted carbon nanotube-graphene composite film at a preset cooling rate; eluting the substrate by floating the cooled reconstituted carbon nanotube film or the reconstituted carbon nanotube-graphene composite film in a substrate etchant, allowing it to float on the surface of the etchant, and then rinsing it. The substrate etchant can be determined according to the substrate material and structure; in some embodiments of the present invention, the substrate etchant generally includes any one of the following: ammonium persulfate solution, ferric chloride solution, hydrochloric acid solution, or a mixture of hydrochloric acid and hydrogen peroxide. Those skilled in the art can select the substrate etchant according to the actual situation. Some possible examples of preset cooling rates are: <10℃ / min, 10-100℃ / min, >100℃ / min, with a preferred embodiment being 100℃ / min.

[0108] The substrate is rinsed with a rinsing solution to remove the etchant. The rinsing solution depends on the substrate etchant. Preferably, deionized water is used. Those skilled in the art can select the rinsing solution according to the actual situation. Optionally, the rinsing step generally includes rinsing with preferred deionized water. After rinsing with deionized water, a large-area reconstituted carbon nanotube film or a self-supporting reconstituted carbon nanotube-graphene composite film can be obtained without polymer-assisted transfer. A large-area reconstituted carbon nanotube film or a self-supporting reconstituted carbon nanotube-graphene composite film can also be obtained in air. The self-supporting reconstituted carbon nanotube film or the self-supporting reconstituted carbon nanotube-graphene composite film can also be transferred non-destructively to any substrate.

[0109] Optionally, the performance of the reconstituted carbon nanotube film or the reconstituted carbon nanotube-graphene composite film obtained by this method can be characterized by the formula shown in equation (1):

[0110]

[0111] Where FOM represents the quality factor, R sq The sheet resistance is represented by T, and the transmittance is represented by T. Furthermore, the morphology, microstructure, mechanical properties, and other properties of the obtained large-area recombinant carbon nanotube-graphene composite films can all be characterized.

[0112] Figure 2This is a schematic flowchart of a method for preparing a transparent conductive film according to another embodiment of the present invention. In some optional embodiments, the process generally includes:

[0113] Step S201: Lay the original carbon nanotube film of a set area on the substrate surface and place it in the growth chamber.

[0114] Step S202: The growth chamber is purged to control the partial pressure of the gas in the growth chamber that undergoes surface reconstruction with the substrate within a set range.

[0115] Step S203: The growth chamber is heated to control the surface reconstruction of the substrate surface with the gas, thereby forming a facet.

[0116] In step S204, heating continues, causing the facets on the substrate to gradually grow, thereby controlling the carbon nanotube network to gradually adhere to the facets and the impurities in the original carbon nanotube film to gradually dissolve. Those skilled in the art can determine the heating temperature range based on the material of the actual facets.

[0117] In step S205, the carbon nanotubes in the carbon nanotube network move and move closer to each other as the facets grow, thereby reorganizing the carbon nanotube network into a Y-shaped interconnected network with a long common segment.

[0118] Step S206: Continue heating to gradually eliminate the morphological features of the facets.

[0119] Step S207: Cool the reconstituted carbon nanotube film at a preset cooling rate.

[0120] In some alternative embodiments, an oxidizing gas (e.g., oxygen) is chosen to interact with the substrate. The pristine carbon nanotube film can be laminated with copper foil at 10... -1 The SEM image of the recombinant carbon nanotube film / copper foil obtained by heating to 900℃ under Torr oxygen partial pressure and holding for 30 min followed by rapid cooling is shown in Figure 11. Figure 11A These are SEM images of the original carbon nanotube film and copper foil prepared by a method for preparing a transparent conductive film according to an embodiment of the present invention. Figure 11B This is an SEM image of a reconstituted carbon nanotube film and a copper foil prepared by a method for preparing a transparent conductive film according to an embodiment of the present invention. Figure 11A The image shown is a SEM image of the original carbon nanotube film / copper foil at a scale of 500 nm. Figure 11B The image shown is at a scale of 500nm, at 10 -1 SEM images of recombinant carbon nanotube films / copper foils obtained by heating to 900℃ under Torr oxygen partial pressure and holding for 30 min followed by rapid cooling. Figure 11A and Figure 11BDashed line 1 highlights a carbon nanotube whose position shifts after a high-temperature process. Dashed line 2 highlights two carbon nanotubes that were initially parallel and then came together after a high-temperature process. The arrows indicate the tendency of multiple carbon nanotubes to aggregate after a high-temperature process. The dashed circle highlights a string of impurities close to the copper surface that dissolves and disappears after a high-temperature process.

[0121] In some alternative embodiments, when the original carbon nanotube film on the substrate surface is two layers, Figure 13A This is a SEM image of the original two-layer carbon nanotube film and copper foil prepared by a method for preparing a transparent conductive film according to an embodiment of the present invention. Figure 13B This is an SEM image of a reconstituted carbon nanotube film and a copper foil prepared by a method for preparing a transparent conductive film according to an embodiment of the present invention. Figure 13B It shows Figure 13A The original two-layer carbon nanotube film and copper foil in 10 -1 SEM images of recombined carbon nanotube films / copper foils obtained by heating to 900℃ under Torr oxygen partial pressure and holding for 60 min followed by rapid cooling. All scale bars are 500 nm. It is clearly visible that multiple carbon nanotubes in two layers recombined together under the action of facets, forming a long, shared-segment Y-shaped interconnected network.

[0122] Step S208: The cooled reconstituted carbon nanotube film is etched away from the substrate in a substrate etchant.

[0123] Step S209: Rinse with rinsing solution.

[0124] This method enables the recombination of carbon nanotubes within a pristine carbon nanotube film through faceting, forming a long, shared-segment Y-shaped interconnect network, thus obtaining a recombined carbon nanotube film. Compared to the pristine carbon nanotube film, the recombined carbon nanotube film exhibits a more efficient conductive network, improving the performance of the transparent conductive film. It also achieves self-support and allows for the large-area fabrication of transparent conductive films.

[0125] Figure 3 This is a schematic flowchart of a method for preparing a transparent conductive film according to another embodiment of the present invention. In some optional embodiments, the process generally includes:

[0126] Step S301: Lay the original carbon nanotube film of a set area on the substrate surface and place it in the growth chamber.

[0127] Step S302: The growth chamber is purged to control the partial pressure of the gas in the growth chamber that undergoes surface reconstruction with the substrate within a set range.

[0128] Step S303: The growth chamber is heated to control the surface reconstruction of the substrate surface with the gas, thereby forming a facet.

[0129] In step S304, heating continues, causing the facets on the substrate to gradually grow, thereby controlling the carbon nanotube network to gradually adhere to the facets and the impurities in the original carbon nanotube film to gradually dissolve.

[0130] In step S305, the carbon nanotubes in the carbon nanotube network move and approach each other as the facets grow, thereby reorganizing the carbon nanotube network into a Y-shaped interconnected network with a long common segment.

[0131] Step S306: Continue heating to gradually eliminate the morphological features of the facets.

[0132] In step S307, a carbon source and an auxiliary gas are introduced into the growth chamber to grow graphene and obtain a recombinant carbon nanotube-graphene composite film.

[0133] Step S308: Cool the recombinant carbon nanotube-graphene composite film at a preset cooling rate.

[0134] Step S309: The cooled recombinant carbon nanotube-graphene composite film is floated in a substrate etchant to etch away the substrate.

[0135] Step S310: Rinse with a rinsing solution. In some preferred embodiments, deionized water can generally be used for rinsing.

[0136] This method combines carbon nanotube network recombination with graphene growth to prepare large-area recombined carbon nanotube-graphene composite films. The method has no size limitations on the prepared composite films; the size can be set according to requirements, and both length and width can be extended (optional examples include <10cm, 10cm-1m, >1m, etc.). Because the faceted-driven recombination of the carbon nanotube network enhances the mechanical strength of the recombined network, polymer-assisted transfer is unnecessary during substrate removal, avoiding the contamination and damage associated with traditional polymer-assisted transfer methods. This simplifies the transfer process and yields clean, large-area recombined carbon nanotube-graphene composite films that are self-supporting on water surfaces, and also in air. These self-supporting films can be transferred non-destructively to any substrate. Simultaneously, their quality and various properties (transmittance, conductivity, mechanical strength, cleanliness, flatness, etc.) are synergistically improved. The obtained products provide a material basis for further research and application of carbon nanotube-graphene composite films.

[0137] The following details the beneficial effects of the recombinant carbon nanotube film and the recombinant carbon nanotube-graphene composite film prepared in this invention compared to existing carbon nanotube films.

[0138] 1. This method can synergistically improve the transparency and conductivity of the original carbon nanotube film.

[0139] When a raw carbon nanotube film is deposited on a substrate, under conditions where facets can grow and the carbon nanotubes are not destroyed, the raw carbon nanotube film adheres tightly to the substrate surface on a microscopic scale as the facets grow. A small number of defective carbon nanotubes, along with catalyst particles and amorphous carbon impurities, dissolve in the substrate (where the defects are highly reactive). Driven by the facets, the carbon nanotubes shift position, with adjacent bundles tending to cluster closer together. The porosity of the film changes accordingly, and the bundle length between nodes increases, forming a large-area, long-segmented Y-shaped interconnected network. This facet-driven carbon nanotube network recombination process enables the carbon nanotubes to form a more efficient conductive network. Consequently, the sheet resistance and transmittance of the recombined carbon nanotube film and the recombined carbon nanotube-graphene composite film are significantly and synergistically improved, thus overcoming the limitation of the mutual constraint between transmittance and conductivity in TCF (transmittance-conductivity composites). Figure 16 These are transparent conductivity test patterns of various transparent conductive films prepared according to an embodiment of the present invention; such as... Figure 16 As shown, the recombinant carbon nanotube-graphene composite film prepared by this method exhibits a transmittance of 86% and a sheet resistivity of less than 70 Ω / sq without doping or post-treatment. Compared to the original carbon nanotube film, the recombinant carbon nanotube-graphene composite film shows an increase in conductivity of more than 2.3 times, an increase in transmittance of more than 11%, and a quality factor higher than 35 (an improvement of more than 4 times), basically meeting the industrial requirements for flexible TCF. Therefore, this recombinant carbon nanotube-graphene composite film, which synergistically enhances transparency and conductivity, has significant application value in the fields of flexible electronics and optoelectronic device manufacturing.

[0140] Current post-processing methods such as doping and metal deposition do not fundamentally change the network structure of carbon nanotubes. They only add some substances that are beneficial to conductivity, which can only improve the conductivity of the film in a single way. At the same time, they may also lead to a decrease in the transparency of the film, and cannot achieve a synergistic improvement in transparency and conductivity. Compared with post-processing methods such as chemical doping and metal deposition, carbon nanotube network recombination has many advantages: (1) It does not introduce any other elements, does not increase the areal density of the recombined carbon nanotube-graphene composite film, and does not limit the application scenarios of the recombined carbon nanotube-graphene composite film. (2) It does not change the conductivity type (semiconductor / metallic) of the recombined carbon nanotube-graphene composite film, and maintains the most intrinsic properties of the recombined carbon nanotube-graphene composite film. (3) It does not face problems such as dopant failure (decomposition, volatilization, hydrolysis) and metal corrosion, and ensures the long-term stability of the recombined carbon nanotube-graphene composite film. (4) It avoids some problems such as the high price of dopant and metal and the complexity of deposition process, and is a simple and economical method.

[0141] 2. It also improves the mechanical strength of recombinant carbon nanotube films and recombinant carbon nanotube-graphene composite films.

[0142] Currently, the largest self-supporting carbon nanotube films (including graphene, carbon nanotubes, and carbon nanotube-graphene composite films) on water surfaces have a maximum area of ​​only 1 cm × 1 cm. However, in the faceted-drive carbon nanotube network recombination method proposed in this invention, the carbon nanotubes shift position under the influence of the facets, causing adjacent bundles to cluster closer together, forming more robust Y-shaped connections. The carbon nanotube recombination process optimizes the network structure of the recombined carbon nanotube-graphene composite film. The recombined carbon nanotube film has a Young's modulus exceeding 40 MPa, more than eight times that of traditional carbon nanotube films. Therefore, the recombined carbon nanotube-graphene composite film based on the recombined carbon nanotube film can self-support on water surfaces and even in air. The recombined carbon nanotube film and the recombined carbon nanotube-graphene composite film have a self-supporting area of ​​at least 1 cm² in air. 2 Above, even >2cm×2cm, >4cm 2 And when the area expands to meters or even larger (<10cm) 2 10cm 2 -1 m 2 >1m 2 Reconstituted carbon nanotube films and reconstituted carbon nanotube-graphene composite films can still be self-supporting on the water surface. Self-supporting reconstituted carbon nanotube films or self-supporting reconstituted carbon nanotube-graphene composite films can also be transferred to any substrate without damage.

[0143] Currently, most existing TCFs are fabricated directly on substrates and cannot achieve self-support without a substrate. Therefore, the optical, mechanical, and even electrical properties of TCFs are limited by the substrate. This makes it difficult to achieve significant performance leaps in some advanced flexible and ultrathin devices based on these TCFs. Furthermore, non-self-supporting TCFs cannot be used in some devices based on special principles (such as radiation thermophotodetectors and thermoacoustic loudspeakers). The self-supporting large-area reconstituted carbon nanotube films and reconstituted carbon nanotube-graphene composite films prepared by the method proposed in this patent are expected to solve these problems.

[0144] 3. Significantly improves the cleanliness of recombinant carbon nanotube films and recombinant carbon nanotube-graphene composite films, expanding their application scenarios.

[0145] This invention, under the condition that faceted growth is possible and carbon nanotubes are not destroyed, allows the carbon nanotube film to adhere microscopically to the substrate surface as the faceted substrate grows. A small number of defective carbon nanotubes, as well as catalyst particles and amorphous carbon impurities, dissolve in the substrate (where the defective areas exhibit high reactivity). Therefore, the method of this invention not only synergistically improves the transparency, conductivity, and mechanical strength of the reconstituted carbon nanotube film and the reconstituted carbon nanotube-graphene composite film, but also removes impurities such as catalyst particles from the reconstituted film, significantly improving its cleanliness and broadening its application scenarios.

[0146] Carbon nanotubes prepared by chemical vapor deposition inevitably contain many catalyst particles (mostly transition metals), which not only lead to increased light absorption but also affect the conductivity of the film as scattering centers. Furthermore, the additional metal elements limit the film's application in certain special environments (such as non-magnetic environments). In the method of this invention, as the facets grow, the carbon nanotube network adheres tightly to the metal surface, allowing the catalyst particles and amorphous carbon contaminants in the network to directly contact the metal surface and dissolve first. The removal of these impurities not only reduces carrier scattering but also avoids light absorption caused by impurities, thereby resulting in a recombinant carbon nanotube-graphene network film with higher conductivity and transmittance.

[0147] Furthermore, because catalyst particles are often composed of transition metals, especially magnetic iron particles, traditional reconstituted carbon nanotube films and reconstituted carbon nanotube-graphene composite films are difficult to apply in certain special scenarios. For example, the presence of magnetic iron particles in a precision electron microscope chamber can cause equipment damage. Reconstituted carbon nanotube films and reconstituted carbon nanotube-graphene composite films, after removing impurities such as catalyst particles, have a wider range of applications.

[0148] 4. Significantly improves the flatness of recombinant carbon nanotube films and carbon nanotube-graphene composite films.

[0149] The carbon nanotube recombination process optimizes the network structure of carbon nanotube films, forming tighter connections between adjacent tube bundles, while removing impurities such as catalyst particles from the network. This significantly reduces the surface roughness of the recombined carbon nanotube films and recombined carbon nanotube-graphene composite films, and substantially improves the microscopic smoothness of these recombined films.

[0150] In the past, in some devices based on carbon nanotube films, especially ultrathin devices such as flexible organic solar cells and liquid crystal switchable windows, the rough microscopic surface of carbon nanotube films was very prone to short circuits, which greatly reduced the yield of the devices.

[0151] The reconstituted carbon nanotube films and reconstituted carbon nanotube-graphene composite networks produced by the method of this invention exhibit extremely low surface roughness (Rq as low as ~2nm, approximately 10 times lower than that of the original carbon nanotube network). This directly solves the frequent short circuits and breakdowns caused by excessively high surface roughness in carbon nanotube-based electronic and optoelectronic devices. This significantly improves device yield, enabling the reconstituted carbon nanotube films and carbon nanotube-graphene composite films to be applied in a wider range of scenarios.

[0152] 5. It can be prepared on a large scale and is environmentally friendly.

[0153] The development of any new TCF method needs to enable large-area or even large-scale fabrication to be significant in industrial production. This is because only large-area TCFs can meet the needs of practical applications in devices and equipment, and large-scale production is essential for industry to meet market demands, improve product quality, and reduce costs. However, most new TCF methods are still in the small-area (a few centimeters) laboratory research stage, and currently, very few new TCF methods can be fabricated on a large scale (tens of centimeters or even meters). Furthermore, these methods still have some problems.

[0154] Due to insufficient mechanical properties, graphene films are difficult to self-support, especially in large-area fabrication, requiring the use of polymers such as thermally release tape, silicone, and EVA for assisted transfer. This significantly increases the processing difficulty and inevitably leads to substantial contamination and damage to G-TCF, severely impacting its quality and physical and chemical properties. While the transferred G-TCF area can reach the meter scale, its sheet resistivity is often in the hundreds of ohms or even exceeds 1000 Ω / sq, greatly limiting its practical applications. For carbon nanotube films, previous work has achieved the mass production of transparent conductive single-walled carbon nanotube films (SWCNT-TCF), even enabling self-supporting and continuous fabrication via blown aerosol CVD (BACVD). However, while the length of SWCNT-TCF is unlimited (up to tens of meters) in continuous fabrication, its width is limited by the growth principle (<10 cm). While the self-supporting multi-walled carbon nanotube transparent conductive film (MWCNT–TCF) prepared by super-aligned array spinning dry method can be expanded in area (width can reach tens of centimeters and length can reach meters), its transparency and conductivity (transparency below 85% and sheet resistance in thousands of ohms) are far inferior to that of single-walled carbon nanotube films prepared by BACVD method, which limits the practical application of MWCNT–TCF.

[0155] The method for preparing recombinant carbon nanotube films provided by this invention can achieve large-area and even large-scale expansion of recombinant carbon nanotube films. The area of ​​the original carbon nanotube film is expanded by splicing. At the splicing points, unconnected or X-shaped overlap carbon nanotubes from different layers undergo positional migration after facet-driven recombination, with adjacent tube bundles tending to close together to form new Y-shaped connections. Some X-shaped overlaps can also form strong Y-shaped connections. For several layers of spliced ​​carbon nanotube films, facet-driven recombination will connect them into a large-area, long-shared Y-shaped interconnected network film of the same layer. Ultimately, under the dual effects of facet-driven recombination and the constraints of the original network, the network structure of the spliced ​​carbon nanotube film is optimized, forming a continuous, large-area film. The prepared carbon nanotube film is self-supporting, with a self-supporting area of ​​at least 1 cm². 2The above describes the process. In some embodiments, large-area self-supporting recombinant carbon nanotube films, at least the size of an A3 sheet of paper and even exceeding the meter length, have been fabricated. This demonstrates that the technology can be scaled up to larger areas and even on a large scale. Subsequently, graphene is grown in composite form to obtain large-area recombinant carbon nanotube-graphene composite films with excellent network structures. The preparation method of this invention can prepare both recombinant carbon nanotube films and recombinant carbon nanotube-graphene composite films. There are no limitations on the size of either the recombinant carbon nanotube film or the recombinant carbon nanotube-graphene composite film prepared; the size can be set according to requirements, and its characteristic dimensions (length, width, diameter, etc.) can be expanded (optionally <10cm, 10cm-1m, >1m, etc.).

[0156] The method for preparing recombinant carbon nanotube-graphene composite films provided by this invention can achieve large-area and even large-scale scaling, producing self-supporting carbon nanotube-graphene composite films with an area of ​​at least 1 cm². 2 The above describes the fabrication of large-area self-supporting recombinant carbon nanotube-graphene composite films, ranging in size from A3 paper to meters in length, in some embodiments. This demonstrates that the technology can be scaled up to larger areas and even on a large scale. This invention represents the first large-area fabrication of carbon nanotube-graphene composite films, filling a research gap in this field.

[0157] Furthermore, the method of this invention does not involve any toxic or harmful substances, which is beneficial to environmental protection in large-scale production. Our preparation process does not involve any toxic or harmful substances throughout, making it an environmentally friendly production method, which is especially important for future industrial production.

[0158] These lightweight, high-strength, highly transparent, and conductive recombinant carbon nanotube films and recombinant carbon nanotube-graphene transparent conductive films, which can be mass-produced, show broad application prospects in fields such as flexible electronics, optical engineering, artificial intelligence, modern architecture, transportation, and even aerospace.

[0159] 6. Optimize the network structure to provide new ideas for TCF design.

[0160] The faceted-drive carbon nanotube network recombination mechanism provided by this invention optimizes the network structure of recombined carbon nanotube films and carbon nanotube-graphene composite films. Due to the formation and growth of facets on the substrate surface, the tube bundles in the original carbon nanotubes undergo positional migration, changes in inter-bundle porosity, and variations in bundle length between nodes, leading to the aggregation of numerous adjacent tube bundles into a more robust connection. The pore size in the network structure tends to be more uniform, typically around 2 μm. Simultaneously, the lower-quality portions of the carbon nanotube network closely attached to the facets, along with impurities such as catalyst particles, dissolve first, resulting in a process of natural selection. Ultimately, under the dual effects of facet-driven recombination and the constraints of the original network, the carbon nanotube network recombines to form a large-area Y-shaped interconnected network. This results in a more efficient conductive network and a more robust mechanical structure. The optimized network structure synergistically enhances various properties of the carbon nanotube-graphene composite film (transmittance, conductivity, mechanical strength, cleanliness, flatness, etc.).

[0161] Previous studies have involved heating carbon nanotube films / substrates under a reducing environment, using Cu substrates as an example. However, the presence of oxidizing gases (such as oxygen) is not permitted in a reducing environment, thus preventing the formation of facets. In an optional embodiment of this invention, it was found that under these conditions, the carbon nanotube bundles do not undergo significant positional migration, and the film does not show obvious carbon consumption. The network structure of the carbon nanotube film and the carbon nanotube-graphene composite film remains essentially unchanged before and after this treatment, making it impossible to optimize the film's network structure.

[0162] The carbon nanotube network structure optimization method of this invention can not only provide a new perspective for the structural design and performance optimization of TCF, but also provide new ideas for the research of thin films for other applications (such as high-strength thin films, ultraflat thin films, etc.) and the removal of impurities from thin films.

[0163] The following detailed description of specific implementation methods illustrates the large-area preparation methods of recombinant carbon nanotube films and recombinant carbon nanotube-graphene composite films.

[0164] Example 1: Preparation method of recombinant carbon nanotube-graphene composite film

[0165] (1) Growth of carbon nanotube films

[0166] Single-walled carbon nanotube films were grown using CVD. The carbon nanotube films had a transmittance of 75%, a sheet resistivity of 162 Ω / sq, and a quality factor of 7.6.

[0167] (2) Electrochemical polishing of copper foil to make its surface smooth.

[0168] (3) Lay the carbon nanotube film flat on the surface of the copper foil. Preferably, add a few drops of ethanol to wet the carbon nanotube film / copper foil to improve the contact between the two.

[0169] (4) After the organic solvent has evaporated, place the carbon nanotube film / copper foil into the heating furnace. Purge the gas to bring the oxygen partial pressure inside the chamber to 10. -1 Torr.

[0170] (5) A heating program was set up to heat the carbon nanotube film / copper foil in a non-reducing environment. When the heating temperature exceeded 700℃, obvious facets appeared on the surface of the copper foil; as the temperature continued to rise, the facets gradually grew. When the heating temperature reached 900℃, the step width of the facets was nearly 100nm, and the interaction between the carbon nanotubes and the copper foil became significant. The carbon nanotube network adhered tightly to the copper surface, and some impurities began to dissolve. As the facets grew, the carbon nanotubes moved, and the recombination process began. As the temperature increased, the facets continued to grow, and the carbon nanotubes on them moved and approached each other more significantly. Subsequently, when the heating temperature reached 1030℃, due to the proximity to the melting point of copper, the pre-melting of the copper surface became more obvious, the morphological characteristics of the facets basically disappeared, and the recombination process was completed. A recombined carbon nanotube film / copper foil was obtained.

[0171] (6) Continue to keep warm at 1030℃, while introducing 2 sccm of methane and 40 sccm of hydrogen to grow graphene.

[0172] The heating procedure involves heating to 1030°C at a rate of 1-10°C / min, and holding at 900°C for 30-90 minutes to allow sufficient time for the facet growth process.

[0173] (7) After the heating process is over, quickly cool the recombinant carbon nanotube-graphene composite film / copper foil to room temperature and then take it out. Figure 10 This is a copper-faceted SEM image of a method for preparing a transparent conductive thin film according to an embodiment of the present invention, such as... Figure 10 The image shown is in 10 -1 SEM image of copper facets obtained by rapidly cooling copper at 10 °C / min under Torr oxygen partial pressure, with a scale bar of 2 μm.

[0174] (8) The reconstituted carbon nanotube-graphene composite film / copper foil was floated in an ammonium persulfate solution and the copper foil was etched away to obtain a reconstituted carbon nanotube-graphene composite film floating on the surface of the ammonium persulfate solution. Finally, it was rinsed with deionized water to obtain a self-supporting reconstituted carbon nanotube-graphene composite film. The self-supporting reconstituted carbon nanotube-graphene composite film was transferred to a substrate for performance testing.

[0175] SEM images of the original carbon nanotube film and the reconstituted carbon nanotube-graphene composite film are as follows: Figure 14A and Figure 14B As shown. Figure 14AThis is a raw carbon nanotube film SEM image of a method for preparing a transparent conductive film according to an embodiment of the present invention. Figure 14B This is a SEM image of a recombinant carbon nanotube-graphene composite film prepared according to a method for preparing a transparent conductive film according to an embodiment of the present invention. From... Figure 14A It can be seen that the pore size of the original carbon nanotube network is approximately 500 nm to 1 μm, and the connections between the tube bundles are X-type and Y-type connections, with some impurities on the network. Figure 14B The pore size of the reconstituted carbon nanotube-graphene network is approximately 1-2 μm, with increased pore size and longer inter-node bundle length. The carbon nanotubes are primarily connected by long, shared Y-shaped segments, and there are fewer visible impurities on the network. AFM images of the original carbon nanotube film and the reconstituted carbon nanotube-graphene composite film are shown in Figure 15. Figure 15A This is an AFM image of the original carbon nanotube film prepared by a method for preparing a transparent conductive film according to an embodiment of the present invention. Figure 15B This is an AFM image of a recombinant carbon nanotube-graphene composite film prepared by a method for preparing a transparent conductive film according to an embodiment of the present invention. Figure 15C This is an AFM image cross-sectional analysis of the original carbon nanotube thin film prepared by a method for preparing a transparent conductive thin film according to an embodiment of the present invention; Figure 15D This is an AFM image cross-sectional analysis of a recombinant carbon nanotube-graphene composite film prepared by a method for preparing a transparent conductive film according to an embodiment of the present invention. Figure 15A The surface height map of the original carbon nanotube film shows that its root mean square roughness is 21.4 nm. Figure 15C Several typical AFM cross-sectional analyses show that the height of carbon nanotubes is approximately 6-40 nm, which is the diameter of the tube bundle itself plus the distance in the height direction due to the loose stacking between the tube bundles. Figure 15B The AFM surface height map of the medium-recombined carbon nanotube-graphene composite film shows that its root mean square surface roughness is only 2.26 nm, which is about 10 times smaller than that of the original carbon nanotube. Figure 15D Several typical AFM cross-sectional analyses showed that the height of the carbon nanotube-graphene network was less than 10 nm, and the connections between the tubes were tight. This indicates that the surface of the recombinant carbon nanotube-graphene composite film is very smooth. Figure 16 These are transparent conductivity test diagrams of various transparent conductive films prepared according to an embodiment of the present invention. Figure 16 The results of transparency and conductivity tests for the original carbon nanotube film and the reconstituted carbon nanotube-graphene composite film are shown. It can be seen that, compared to the original carbon nanotube film, the reconstituted carbon nanotube-graphene composite film exhibits a significant synergistic improvement in both transmittance (86%) and conductivity (sheet resistivity 69 Ω / sq). Its quality factor (35.0) is 4.6 times higher than that of the original carbon nanotube film.

[0176] For comparison with Example 1, a carbon nanotube-graphene composite film was prepared using a conventional method, the specific process of which is shown below:

[0177] Example 2: Preparation method of carbon nanotube-graphene composite film

[0178] (1) Single-walled carbon nanotube films were grown using the CVD method.

[0179] (2) Electrochemical polishing of copper foil to make its surface smooth.

[0180] (3) A carbon nanotube film (81% transmittance, 163 Ω / sq sheet resistivity, quality factor 10) is laid flat on the surface of a copper foil. Preferably, a few drops of ethanol are added to wet the carbon nanotube film / copper foil to improve contact between the two.

[0181] (4) After the organic solvent has evaporated, place the carbon nanotube film / copper foil into the heating furnace. Evacuate the furnace and introduce hydrogen gas at 40 sccm.

[0182] (5) The same heating procedure as in Example 1 was used to heat the carbon nanotube film / copper foil in a reducing environment. When the heating temperature exceeded 700°C, no facets appeared on the copper foil surface. When the heating temperature reached 900°C, facets still did not appear; the carbon nanotube network remained on the copper surface, and impurities in the network could not adhere tightly to the copper surface. The carbon nanotubes showed almost no movement. As the temperature increased, facets still did not appear, and the carbon nanotube network on it did not show significant changes. Subsequently, the heating temperature reached 1030°C, and facets still did not appear, indicating the heating process was complete.

[0183] (6) Continue to hold at 1030℃ while introducing 2 sccm of methane and 40 sccm of hydrogen to grow graphene. The heating program is to heat to 1030℃ at a rate of 1-10℃ / min, and hold at 900℃ for 30-90min during the process to allow sufficient time for the facet growth.

[0184] (7) After the heating process is over, quickly cool the carbon nanotube-graphene composite film / copper foil to room temperature and then take it out.

[0185] (8) The carbon nanotube-graphene composite film / copper foil was floated in an ammonium persulfate solution and the copper foil was etched away to obtain a carbon nanotube-graphene composite film floating on the surface of the ammonium persulfate solution. Finally, it was rinsed with deionized water to obtain a carbon nanotube-graphene composite film floating on the water surface. The carbon nanotube-graphene composite film was transferred to a substrate for performance testing.

[0186] SEM images of carbon nanotube-graphene composite films are as follows: Figure 17 As shown, Figure 17 This is a SEM image of a recombinant carbon nanotube-graphene composite film prepared according to an embodiment of a transparent conductive film preparation method. From... Figure 17 As can be seen from the content shown, compared with the original carbon nanotube network, the network structure of the carbon nanotube-graphene composite film has not been significantly optimized. It has not formed a large-area long common segment Y-shaped connection, and the surface is still rough and contains many impurities.

[0187] Example 3: Method for preparing large-area reconstituted carbon nanotube films

[0188] (1) Single-walled carbon nanotube films were grown using the CVD method.

[0189] (2) Take a large copper foil with a surface area of ​​220mm×310mm and perform electrochemical polishing on the copper foil to make its surface flat.

[0190] (3) Take 12 carbon nanotube films and lay them flat on the surface of the copper foil as two layers. The area of ​​the carbon nanotube films is 50mm × 210mm. Viewed from above, there are no gaps between the carbon nanotube films exposing the copper foil. The upper and lower layers are stacked together with uniform thickness, and the overall surface is intact and flat. Preferably, a few drops of ethanol are added to wet the carbon nanotube films / copper foil to improve the contact between the two.

[0191] (4) After the organic solvent has evaporated, place the large-area carbon nanotube film / copper foil into the heating furnace. Purge the gas to bring the oxygen partial pressure inside the chamber to 10. -1 Torr.

[0192] (5) A heating program was set up to heat a large-area carbon nanotube film / copper foil in a non-reducing environment. When the heating temperature exceeded 700℃, obvious facets appeared on the surface of the copper foil; as the temperature continued to rise, the facets gradually grew. When the heating temperature reached 900℃, the step width of the facets was nearly 100nm, and the interaction between the carbon nanotubes and the copper foil became significant. The carbon nanotube network adhered tightly to the copper surface, and some impurities began to dissolve. As the facets grew, the carbon nanotubes moved, and the recombination process began. As the temperature increased, the facets continued to grow, and the carbon nanotubes on them moved and approached each other more significantly. Subsequently, when the heating temperature reached 1030℃, due to the proximity to the melting point of copper, the pre-melting of the copper surface became more obvious, the morphological characteristics of the facets basically disappeared, and the recombination process was completed. A large-area reconstituted carbon nanotube film / copper foil was obtained.

[0193] The heating procedure involves heating to 1030°C at a rate of 1-10°C / min, and holding at 900°C for 30-90 minutes to allow sufficient time for the facet growth process.

[0194] (6) After the heating process is over, quickly cool the large-area reconstituted carbon nanotube film / copper foil to room temperature and then take it out.

[0195] (7) The large-area reconstituted carbon nanotube film / copper foil was floated in an ammonium persulfate solution and the copper foil was etched away to obtain a large-area reconstituted carbon nanotube film floating on the surface of the ammonium persulfate solution. Finally, it was rinsed with deionized water to obtain a self-supporting large-area reconstituted carbon nanotube film.

[0196] The resulting floating, self-supporting, large-area recombinant carbon nanotube film was directly removed from the surface of the rinsing solution, yielding a large-area self-supporting recombinant carbon nanotube film in air. The area of ​​this air-supporting recombinant carbon nanotube film exceeded 15 cm × 15 cm.

[0197] Figure 18 The invention illustrates a method for preparing a transparent conductive film, specifically a self-supporting large-area recombinant carbon nanotube film floating on the surface of deionized water. Figure 18 An image of a self-supporting, large-area recombinant carbon nanotube film floating on the surface of deionized water is shown, with an area the size of an A4 sheet of paper (approximately 21 cm × 30 cm).

[0198] Example 4: Preparation method of large-area reconstituted carbon nanotube-graphene composite film

[0199] Steps (1)-(5) in this embodiment are the same as steps (1)-(5) in embodiment 3, and will not be repeated here.

[0200] (6) Continue to keep warm at 1030℃ for 20 min, while simultaneously introducing 2 sccm of methane and 40 sccm of hydrogen to grow graphene.

[0201] The heating procedure involves heating to 1030°C at a rate of 1-10°C / min, and holding at 900°C for 30-90 minutes to allow sufficient time for the facet growth process.

[0202] (7) After the heating process is over, quickly cool the large-area reconstituted carbon nanotube-graphene composite film / copper foil to room temperature and then take it out.

[0203] (8) The large-area reconstituted carbon nanotube-graphene composite film / copper foil was floated in an ammonium persulfate solution and the copper foil was etched away to obtain a large-area reconstituted carbon nanotube-graphene composite film floating on the surface of the ammonium persulfate solution. Finally, it was rinsed with deionized water to obtain a self-supporting large-area reconstituted carbon nanotube-graphene composite film.

[0204] Figure 14 shows a large-area self-supporting recombinant carbon nanotube-graphene composite film. Figure 14A This is a schematic SEM image of the original carbon nanotube film prepared by a method for preparing a transparent conductive film according to an embodiment of the present invention. Figure 14BThis is a schematic SEM image of a recombinant carbon nanotube-graphene composite film prepared by a method for preparing a transparent conductive film according to an embodiment of the present invention. Figure 14A and Figure 14B The comparison shows that the A4-sized self-supporting large-area recombinant carbon nanotube-graphene composite film floating on the surface of deionized water exhibits a transparency of over 85% and very good uniformity.

[0205] The resulting floating, self-supporting, large-area recombinant carbon nanotube-graphene composite film was directly removed from the rinsing solution surface, yielding a self-supporting, large-area recombinant carbon nanotube-graphene composite film in air. The area of ​​the self-supporting recombinant carbon nanotube-graphene composite film in air exceeded 20 cm². 2 .

[0206] Large-area recombinant carbon nanotube-graphene composite films that are self-supporting in air, such as Figure 19 As shown. Figure 19 The invention illustrates a method for preparing a transparent conductive film according to an embodiment of the present invention, which produces a large-area recombinant carbon nanotube-graphene composite film that is self-supporting in air. Figure 19 A large-area recombinant carbon nanotube-graphene composite film, self-supporting in air, with an area >5cm × 4cm and a visible light transmittance of approximately 90%, is shown. From Figure 19 As can be seen, the large-area recombinant carbon nanotube-graphene composite film that is self-supporting in air exhibits a transparency of over 85% and very good uniformity.

[0207] Example 5: Preparation method of large-area reconstituted carbon nanotube-graphene composite film

[0208] (1) Single-walled carbon nanotube films were grown using the CVD method.

[0209] (2) Take a large copper foil of 310mm×440mm and anneal it at high temperature to make its surface flat.

[0210] (3) Take 24 carbon nanotube films and lay them flat on the surface of the copper foil as two layers. The area of ​​the carbon nanotube films is 50mm × 210mm. Viewed from above, there are no gaps between the carbon nanotube films exposing the copper foil. The upper and lower layers are stacked together with uniform thickness, and the overall surface is intact and flat. Preferably, a few drops of ethanol are added to wet the carbon nanotube films / copper foil to improve the contact between the two.

[0211] (4) After the organic solvent has evaporated, place the large-area carbon nanotube film / copper foil into the heating furnace. Purge the gas to bring the oxygen partial pressure inside the chamber to 10. -1 Torr.

[0212] (5) Same as step (5) in Example 3.

[0213] (6) Same as step (6) in Example 4.

[0214] The heating procedure involves heating to 1030°C at a rate of 1-10°C / min, and holding at 900°C for 30-90 minutes to allow sufficient time for the facet growth process.

[0215] (7) and (8) are the same as steps (7) and (8) in Example 4.

[0216] Self-supporting large-area recombinant carbon nanotube-graphene composite films, such as Figure 20 As shown. Figure 20 The invention illustrates a method for preparing a transparent conductive thin film, showing a self-supporting large-area reconstituted carbon nanotube-graphene composite film floating on the surface of a substrate etchant liquid. Figure 20 This image shows a self-supporting, large-area reconstituted carbon nanotube-graphene composite film floating on the surface of a substrate etchant solution, with an area the size of an A3 sheet of paper (approximately 30cm × 42cm). From Figure 20 As can be seen, the A3-sized self-supporting large-area recombinant carbon nanotube-graphene composite film floating on the substrate etchant surface exhibits a transparency of over 85% and very good uniformity.

[0217] Example 6: Preparation method of large-area reconstituted carbon nanotube-graphene composite film

[0218] (1) Single-walled carbon nanotube films were grown using the CVD method.

[0219] (2) Take a large copper foil of 120mm×1100mm and anneal it at high temperature to make its surface flat.

[0220] (3) Take 20 carbon nanotube films and lay them flat on the surface of the copper foil as two layers. The area of ​​the carbon nanotube film is 50mm × 210mm. Viewed from above, there are no gaps between the carbon nanotube films exposing the copper foil. The upper and lower layers are stacked together with uniform thickness, and the overall surface is intact and flat. Preferably, a few drops of ethanol are added to wet the carbon nanotube film / copper foil to improve the contact between the two.

[0221] (4)-(8) are the same as steps (4)-(8) in Example 5.

[0222] Self-supporting large-area recombinant carbon nanotube-graphene composite films, such as Figure 21 As shown, Figure 21 The invention illustrates a method for preparing a transparent conductive film, specifically a self-supporting large-area recombinant carbon nanotube-graphene composite film floating on the surface of deionized water, according to another embodiment of the present invention. Figure 21A self-supported, large-area recombinant carbon nanotube-graphene composite film with an area of ​​1 m × 10 cm is shown floating on the surface of deionized water. Figure 21 As can be seen, the 1m×10cm self-supporting large-area recombinant carbon nanotube-graphene composite film floating on the surface of deionized water exhibits very good transparency and uniformity.

[0223] Example 7: Preparation method of recombinant carbon nanotube-graphene composite film

[0224] (1) Carbon nanotubes were grown using the gas phase pyrolysis method.

[0225] (2) Electrochemically polish the nickel foil to make its surface smooth.

[0226] (3) A carbon nanotube film is formed by uniformly blowing a carrier gas containing carbon nanotubes onto the surface of the nickel foil. Preferably, a few drops of acetone are added to wet the carbon nanotube film / nickel foil to improve the contact between the two.

[0227] (4) After the organic solvent has evaporated, place the carbon nanotube film / nickel foil into the heating furnace. Purge the gas to ensure the oxygen partial pressure inside the chamber is below 1 Torr. Set the heating program to heat the carbon nanotube film / nickel foil in a non-reducing environment. When the heating temperature exceeds 800℃, obvious facets appear on the nickel foil surface; as the temperature continues to rise, the facets gradually grow. When the heating temperature reaches 1000℃, the step width of the facets is nearly 100 nm, and the interaction between the carbon nanotubes and the foil becomes significant. The carbon nanotube network adheres tightly to the nickel surface, and some impurities begin to dissolve. As the facets grow, the carbon nanotubes move, initiating the recombination process. As the temperature rises, the facets continue to grow, and the carbon nanotubes on them move and approach each other more significantly. Subsequently, when the heating temperature reaches 1100℃, due to proximity to the nickel melting point, the pre-melting of the nickel surface becomes more pronounced, the morphological characteristics of the facets essentially disappear, and the recombination process is complete. Continue to hold at 1100℃ while simultaneously introducing 2 sccm of methane and 40 sccm of hydrogen to grow graphene. The heating procedure involves heating to 1100°C at a rate of 10-100°C / min, and holding at 1000°C for 3-50 minutes to allow sufficient time for the facet growth process.

[0228] (5) After the heating process is over, quickly cool the recombinant carbon nanotube-graphene composite film / nickel foil to room temperature and then remove it.

[0229] (6) The reconstituted carbon nanotube-graphene composite film / nickel foil was floated in an ammonium persulfate solution and the nickel foil was etched away to obtain a large-area reconstituted carbon nanotube-graphene composite film floating on the surface of the ammonium persulfate solution. Finally, it was rinsed with deionized water to obtain a self-supporting reconstituted carbon nanotube-graphene composite film.

[0230] Example 8: Preparation method of recombinant carbon nanotube-graphene composite film

[0231] (1) Single-walled carbon nanotubes were grown using the electric arc discharge method.

[0232] (2) Electrochemically polish the platinum foil to make its surface smooth.

[0233] (3) Carbon nanotubes are uniformly deposited on the surface of platinum foil to form a thin film. Preferably, a few drops of ethanol are added to wet the carbon nanotube film / platinum foil to improve the contact between the two.

[0234] (4) After the organic solvent has evaporated, place the carbon nanotube film / platinum foil into the heating furnace. Purge the gas to bring the oxygen partial pressure inside the chamber below 1 Torr.

[0235] (5) A heating program was set up to heat the carbon nanotube film / platinum foil in a non-reducing environment. When the heating temperature exceeded 1000℃, obvious facets appeared on the surface of the platinum foil; as the temperature continued to rise, the facets gradually grew. When the heating temperature reached 1300℃, the step width of the facets was nearly 100nm, and the interaction between the carbon nanotubes and the platinum foil became significant. The carbon nanotube network adhered tightly to the platinum surface, and some impurities began to dissolve. As the facets grew, the carbon nanotubes moved, and the recombination process began. As the temperature increased, the facets continued to grow, and the carbon nanotubes on them moved and approached each other more significantly. Subsequently, when the heating temperature reached 1600℃, due to the proximity to the melting point of platinum, the pre-melting of the platinum surface became more obvious, the morphological features of the facets basically disappeared, and the recombination process was completed.

[0236] (6) Continue to keep warm at 1600℃, while introducing 1 sccm of methane and 40 sccm of hydrogen to grow graphene.

[0237] The heating procedure involves heating to 1200°C at a rate of 10-100°C / min, and holding at 1300°C for at least 1 minute to allow sufficient time for the facet growth process.

[0238] (7) After the heating process is over, quickly cool the recombinant carbon nanotube-graphene composite film / platinum foil to room temperature and then take it out.

[0239] (8) The recombinant carbon nanotube-graphene composite film / platinum foil was floated in a hydrochloric acid-hydrogen peroxide mixed solution to etch away the platinum foil, resulting in a large-area recombinant carbon nanotube-graphene composite film floating on the surface of the hydrochloric acid-hydrogen peroxide mixed solution. Finally, it was rinsed with deionized water to obtain a self-supporting recombinant carbon nanotube-graphene composite film.

[0240] Therefore, those skilled in the art should recognize that although numerous exemplary embodiments of the present invention have been shown and described in detail herein, many other variations or modifications conforming to the principles of the present invention can be directly determined or derived from the disclosure of the present invention without departing from the spirit and scope of the invention. Thus, the scope of the present invention should be understood and construed as covering all such other variations or modifications.

Claims

1. A method for preparing a transparent conductive film, comprising: laying a raw carbon nanotube film of a given area on a substrate surface and placing it in a growth chamber; reconstructing the substrate surface and the gas in the growth chamber by heating to form facets, the facets exhibiting regular step-like patterns on the substrate surface at a mesoscopic scale, accompanied by the transport of facet atoms constituting the facets; interacting the facets and the raw carbon nanotube film by heating to remove impurities in the raw carbon nanotube film, at least part of the carbon nanotubes in the raw carbon nanotube film moving in position under the driving of the facets, adjacent carbon nanotubes or bundles of carbon nanotubes tending to be close to each other, and the carbon nanotube network in the raw carbon nanotube film recombining to obtain a recombined carbon nanotube film.

2. The method for preparing a transparent conductive film according to claim 1, wherein: the step of reconstructing the substrate surface and the gas in the growth chamber by heating further comprises: purging the growth chamber to control the partial pressure of the gas in the growth chamber that reconstructs the substrate surface to be within a given range.

3. The method for preparing a transparent conductive film according to claim 2, wherein: the gas is a gas that can reconstruct the substrate surface in the growth chamber, including a mixture of one or more gases of the same type selected from oxidizing or reducing gases; the source of the gas includes any one or a mixture of any number of the following: gas, liquid, solid.

4. The method for preparing a transparent conductive film according to claim 3, wherein: the step of interacting the facets and the raw carbon nanotube film by heating comprises: gradually growing the facets on the substrate by heating to control the carbon nanotube network gradually adhering to the facets and impurities in the raw carbon nanotube film gradually dissolving; the carbon nanotubes in the carbon nanotube network move and approach each other as the facets grow, so that the carbon nanotube network recombines into a long common segment Y-type interconnected network to obtain the recombined carbon nanotube film.

5. The method for preparing a transparent conductive film according to claim 4, wherein: the temperature range for forming the facets is configured to be greater than or equal to 400°C; the temperature range for controlling the carbon nanotube network gradually adhering to the facets is configured to be greater than or equal to 600°C; the temperature range for the impurities gradually dissolving is configured to be greater than or equal to 500°C; the step of interacting the facets and the raw carbon nanotube film further comprises: continuing to heat to gradually eliminate the topographical features of the facets, and the temperature range for gradually eliminating the topographical features of the facets is configured to be greater than or equal to 800°C.

6. The method for preparing a transparent conductive film according to claim 1, wherein: the step of interacting the facets and the raw carbon nanotube film is followed by: introducing a carbon source and an auxiliary gas into the growth chamber to grow graphene and obtain a recombined carbon nanotube-graphene composite film.

7. The method of claim 1 to 6, wherein the step of interacting the facets with the pristine carbon nanotube film further comprises: cooling the reorganized carbon nanotube film or the reorganized carbon nanotube-graphene composite film at a pre-set cooling rate; etching the reorganized carbon nanotube film or the reorganized carbon nanotube-graphene composite film in a substrate etchant to remove the substrate and float on the surface of the substrate etchant, and rinsing with a rinsing solution.

8. The method of claim 1, wherein the step of laying the pristine carbon nanotube film of a set area on the surface of the substrate further comprises: laying a plurality of the pristine carbon nanotube films on the surface of the substrate to cover the surface of the substrate with at least one layer of the pristine carbon nanotube film.

9. The method of claim 8, wherein the step of laying the pristine carbon nanotube film of a set area on the surface of the substrate further comprises: adding a volatile organic solvent to the pristine carbon nanotube film to soak the pristine carbon nanotube film to increase the contact between the pristine carbon nanotube film and the surface of the substrate; placing the pristine carbon nanotube film and the substrate in the growth chamber after the organic solvent is evaporated.

10. The method of claim 9, wherein the organic solvent comprises any one of ethanol, propanol, butanol, ethylene glycol, isopropanol, acetone, n-hexane, cyclohexane, anisole, chlorobenzene, or a mixture of any two or more of the organic solvents; the carbon nanotubes in the pristine carbon nanotube film comprise at least one of single-walled carbon nanotubes, double-walled carbon nanotubes, few-walled carbon nanotubes, multi-walled carbon nanotubes, or a mixture of any two or more of the carbon nanotubes; the pristine carbon nanotube film has a thickness greater than 0.1 nm; the substrate is made of any one of copper, platinum, gold, nickel, titanium, iron, lead, palladium, silver, tungsten, aluminum, zinc, chromium, or an alloy of any two or more of the metals. ​ ​ ​ ​

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