A method for manufacturing an electrochromic device

Abstract

The application provides an electrochromic material, an electrochromic device, a preparation method of the electrochromic device and electronic equipment, and relates to the technical field of electrochromic technology. The electrochromic material comprises n-CP poly(benzodithiophene dione). The electrochromic device comprises a first transparent conductive layer, an electrochromic layer, an electrolyte layer, an ion storage layer and a second transparent conductive layer; wherein the material of the electrochromic layer comprises the electrochromic material. The preparation method of the electrochromic device comprises the following steps: coating the electrochromic material on the first transparent conductive layer to obtain a first substrate; forming the ion storage layer on the second transparent conductive layer to obtain a second substrate; and forming the electrolyte layer between the first substrate and the second substrate. By using the n-CP poly(benzodithiophene dione) with high electrical conductivity as the electrochromic material in the electrochromic device, the device has a faster response speed and can realize obvious optical contrast in a short time.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrochromic technology, and in particular to a preparation method of an electrochromic device. BACKGROUND

[0002] Electrochromism refers to a phenomenon that under the action of an applied electric field, the optical properties (such as transmittance, reflectance or absorbance) of a material in the ultraviolet-visible or near-infrared region produce stable and reversible changes, which are manifested as reversible changes in color and transparency. Electrochromic materials and devices have shown great application prospects in the fields of smart windows, camouflage materials, sunglasses, automobile anti-dazzling rearview mirrors, electronic paper, displays and the like.

[0003] The electrochromic layer is the core layer of the electrochromic device and also the layer where the color change reaction occurs. Electrochromic materials are divided into inorganic electrochromic materials and organic electrochromic materials. Among them, the typical representative of inorganic electrochromic materials is tungsten trioxide, and the electrochromic device based on this material has been industrialized, but its multi-layer structure mostly uses magnetron sputtering film coating, which is expensive, requires high equipment precision and needs a large amount of energy consumption. Organic electrochromic materials include two categories of small molecules and conductive polymers. The former is mainly triphenylmethane compounds, and the latter is a kind of material developed in the 1970s, which has the advantages of low cost, fast color conversion speed, easy processing and good stability, and has attracted the attention of researchers.

[0004] As an important component of organic polymer materials, conductive polymers have the characteristics of solution processing and flexibility, and have shown great application potential in electrochromic devices. Therefore, it is necessary to find a conductive polymer that can cause rapid color change under the condition of power supply, and has large color contrast and fast response speed. SUMMARY

[0005] The purpose of the present application is to provide an electrochromic material, an electrochromic device, a preparation method thereof and an electronic equipment. By using a novel conductive polymer material n-CP poly(benzodifuran dione) (abbreviated as PBFDO) with high electrical conductivity as an electrochromic material and in an electrochromic device, the operation is simple and convenient, the practicality is strong, and the processing complexity of the electrochromic device is greatly reduced.

[0006] To achieve the above purpose, the technical solutions of the present application are as follows:

[0007] The present application provides an electrochromic material, comprising n-CP poly(benzodifuran dione).

[0008] The present application also provides an electrochromic device, comprising: a first transparent conductive layer, an electrochromic layer, an electrolyte layer, an ion storage layer and a second transparent conductive layer.

[0009] The material of the electrochromic layer comprises the electrochromic material described above.

[0010] Preferably, the material of the electrolyte layer comprises a liquid electrolyte, a gel electrolyte or a solid-state electrolyte.

[0011] Preferably, the material of the ion storage layer comprises at least one of PEDOT:PSS, titanium dioxide nanowires, PEDOT;

[0012] The first transparent conductive layer and the second transparent conductive layer comprise ITO conductive glass, FTO conductive glass or ITO-PET film.

[0013] The present application also provides a preparation method of the electrochromic device described above, comprising:

[0014] coating the electrochromic material on the first transparent conductive layer to obtain a first substrate;

[0015] forming the ion storage layer on the second transparent conductive layer to obtain a second substrate;

[0016] forming the electrolyte layer between the first substrate and the second substrate.

[0017] Preferably, the preparation method satisfies at least one of the following conditions a-c:

[0018] a. Before the coating, further comprising: cleaning, annealing, ozone treatment on the first transparent conductive layer;

[0019] b. The coating comprises: dissolving the electrochromic material in a first solvent to obtain a mixed solution, and then using a film coater or a wire bar to coat the mixed solution on the first transparent conductive layer to form the electrochromic layer;

[0020] c. After the coating, further comprising: drying the film layer under vacuum conditions at 40-60°C for 1-2h.

[0021] Further preferably, at least one of the following conditions d-i is also satisfied:

[0022] d. The cleaning comprises ultrasonic cleaning treatment using water, anhydrous ethanol and acetone in sequence;

[0023] e. The annealing comprises annealing at 300-600°C for 20-40min;

[0024] f. The ozone treatment comprises ultraviolet ozone treatment for 20-40min;

[0025] g. the first solvent comprises at least one of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone and acetonitrile;

[0026] h. the coating speed is 0.1 m / s-1 m / s;

[0027] i. the mass ratio of the electrochromic material in the mixed solution is 0.2%-1%.

[0028] Preferably, when the material of the electrolyte layer is a solid-state electrolyte, the preparation method of the electrolyte layer comprises:

[0029] mixing raw materials including electrolyte, cross-linkable polymer, photoinitiator and second solvent to obtain a cross-linking system solution;

[0030] dropping the cross-linking system solution on the surface of the first substrate, covering the ion storage layer of the second substrate thereon, and then performing ultraviolet curing after fixation to obtain the electrolyte layer.

[0031] Further preferably, at least one of the following conditions j-q is also met:

[0032] j. the electrolyte comprises lithium salt, and the lithium salt comprises at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium tetrafluoroborate, lithium perchlorate and lithium hexafluorophosphate;

[0033] k. the cross-linkable polymer comprises at least one of methyl methacrylate, polyethylene glycol acrylate and methoxy polyethylene glycol monomethacrylate;

[0034] l. the photoinitiator comprises photoinitiator 1173, benzoin dimethyl ether, photoinitiator 184 or photoinitiator 1000;

[0035] m. the second solvent comprises at least one of propylene carbonate, vinyl ethylene carbonate and ethylene glycol carbonate;

[0036] n. based on 100% of the mass of the cross-linking system solution, the mass ratio of the electrolyte is 4%-20%, the mass ratio of the cross-linkable polymer is 40%-50%, the mass ratio of the photoinitiator is 0.15-10%, and the mass ratio of the second solvent is 40%-50%;

[0037] o. when the cross-linking system solution is dropped on the surface of the first substrate, a tape with a width of 5 μm-40 μm is used to control the distance around the first substrate;

[0038] p. when the ultraviolet curing is performed, an LED ultraviolet curing device is used, the power is 20 W-30 W, and the wavelength is 365 nm;

[0039] q. The UV curing time is 20s-180s.

[0040] This application provides an electronic device including the electrochromic device described above.

[0041] The beneficial effects of this application are:

[0042] The n-CP poly(benzodiazepine furanone) of this application, as a novel conductive polymer, has a conductivity of 2000 S·cm. -1 It has high electrical conductivity, but it also has electrochromic properties. When energized, it can undergo a rapid colorless to blue-black transition. It has excellent stability and solution handling performance and can be uniformly dispersed without additional side chains or surfactants.

[0043] The electrochromic device of this application uses the aforementioned electrochromic material, which enables the device to have a fast response speed, achieve obvious optical contrast in a very short time, and has good environmental stability.

[0044] The preparation method described in this application is simple and convenient to operate, highly practical, and has low processing complexity, making it promising for large-scale automated production. Attached Figure Description

[0045] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation on the scope of this application.

[0046] Figure 1 The image shows the color change of the electrochromic device prepared in Example 1 under oxidized and reduced voltages. Detailed Implementation

[0047] As used in this article:

[0048] "Prepared from" is synonymous with "comprising". The terms "comprising", "including", "having", "containing", or any other variations thereof as used herein are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such a composition, step, method, article, or apparatus. The conjunction "composed of" excludes any unnamed elements, steps, or components.

[0049] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1–5” is disclosed, the described range should be interpreted as including ranges “1–4”, “1–3”, “1–2”, “1–2 and 4–5”, “1–3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range.

[0050] In these embodiments, unless otherwise specified, the portions and percentages are all by weight.

[0051] "Parts by mass" refers to the basic unit of measurement that expresses the mass ratio of multiple components. One part can represent any unit mass, such as 1g or 2.689g. If we say that component A has "a" parts by mass and component B has "b" parts by mass, it means the ratio of the mass of component A to the mass of component B is a:b. Alternatively, it can mean that the mass of component A is aK and the mass of component B is bK (where K is any number representing a multiplier). It is important to understand that, unlike parts by mass, the sum of the mass parts of all components is not limited to 100 parts.

[0052] "And / or" is used to indicate that one or both of the described situations may occur, for example, A and / or B includes (A and B) and (A or B).

[0053] This application provides an electrochromic material, including n-CP poly(benzodiazepine furanedione).

[0054] It should be noted that the n-CP poly(benzodiazepine furanedione) material was developed through collaborative research by researchers from South China University of Technology, Southern University of Science and Technology, Peking University, and others. An article titled "A solution-processed n-type conducting polymer with ultrahigh conductivity" has been published in Nature. In this article, the researchers proposed a solution-processable, chain-free n-CP poly(benzodiazepine furanedione) (PBFDO) with a breakthrough conductivity of 2000 S / cm, exhibiting excellent stability and unexpected solution-processing performance, without requiring additional side chains or surfactants. After applying this material to electrochromic devices, the inventors of this application found that, in addition to its ultra-high conductivity, it also possesses excellent electrochromic properties, rapidly undergoing a colorless-to-blue-black transition under energized conditions.

[0055] This application also provides an electrochromic device, comprising: a first transparent conductive layer, an electrochromic layer, an electrolyte layer, an ion storage layer, and a second transparent conductive layer. The electrochromic layer is made of the aforementioned electrochromic material.

[0056] In a preferred embodiment, the material of the electrolyte layer includes a liquid electrolyte, a gel electrolyte, or a solid electrolyte.

[0057] It should be noted that with the development of electrochromic devices, devices with different structures have emerged, which can generally be divided into three categories: all-solid-state electrochromic devices, all-liquid or gel-based electrochromic devices, and a third category that falls between the two.

[0058] Among these, all-solid-state electrochromic devices are the most widely used, primarily in inorganic electrochromic applications. Researchers typically prepare an electrochromic thin film on conductive glass using methods such as magnetron sputtering and ultrasonic spraying. For conductive polymers, small molecules are electrochemically deposited onto conductive glass, forming a polymer that adheres to the glass through van der Waals forces and other interactions. In this type of device, the electrochromic layer is located on the surface of the conductive substrate, giving it a fast response speed and allowing it to exhibit a noticeable color change in a very short time. Simultaneously, the high ion migration impedance in the solid electrolyte provides a good memory effect, allowing the device to maintain its colored state for a certain period even after the external voltage is removed, and to fade it with a reverse voltage. However, the fabrication of each thin film layer is complex, often requiring high costs and intricate processes.

[0059] All-liquid or gel-based electrochromic devices dissolve both the electrochromic layer material and the counter electrode material in an electrolyte, forming a homogeneous liquid or gel. These devices have a slower response time than solid-state electrochromic devices, and because the resistance to ion migration during the color-changing process is lower, they do not exhibit a memory effect when the external voltage is removed, but instead fade automatically. However, the stability of the liquid or gel system still requires continuous improvement and optimization.

[0060] The last category falls between the first two. These devices have diverse structures, broadly categorized into two types. One type involves mixing the electrochromic material with an electrolyte in a homogeneous solution or gel, with the counter electrode material forming a solid film attached to the electrode surface. The other type involves mixing the counter electrode material with an electrolyte in a homogeneous solution or gel, with the electrochromic material forming a solid film attached to the electrode surface. The color-changing process and properties are related to the specific material composition.

[0061] In addition to liquid electrolytes, gel electrolytes, or solid electrolytes, other types of electrolyte layers are not excluded from the technical solutions of this application.

[0062] In a preferred embodiment, the material of the ion storage layer includes at least one of PEDOT:PSS, titanium dioxide nanowires, and PEDOT.

[0063] In a preferred embodiment, the first transparent conductive layer and the second transparent conductive layer comprise ITO conductive glass, FTO conductive glass, or ITO-PET film.

[0064] This application also provides a method for preparing the above-mentioned electrochromic device, including:

[0065] S1. The electrochromic material is coated onto the first transparent conductive layer to obtain the first substrate;

[0066] S2. The ion storage layer is prepared on the second transparent conductive layer to obtain the second substrate;

[0067] S3. The electrolyte layer is formed between the first substrate and the second substrate.

[0068] In a preferred embodiment, S1 further includes cleaning, annealing, and ozone treatment of the first transparent conductive layer before coating.

[0069] More preferably, the ultrasonic cleaning process is performed sequentially using water, anhydrous ethanol, and acetone; followed by annealing at 300℃-600℃ for 20-40 minutes; and then ultraviolet ozone treatment for 20-40 minutes.

[0070] In a preferred embodiment, the coating in S1 includes: dissolving the electrochromic material in a first solvent to obtain a mixed solution, and then using a coating applicator or wire rod to coat the mixed solution onto the first transparent conductive layer to form the electrochromic layer.

[0071] More preferably, the first solvent includes at least one of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, and acetonitrile.

[0072] More preferably, the electrochromic material accounts for 0.2%-1% of the mass of the mixed solution.

[0073] After dissolving PBFDO in the first solvent, an SZQ four-sided coating applicator or wire rod coating can be used at a coating speed of 0.1 m / s to 1 m / s, allowing the mixed solution to form a film on the first transparent conductive layer. Subsequently, the film is dried under vacuum at 40°C to 60°C for 1 to 2 hours to obtain an electrochromic layer attached to the first transparent conductive layer.

[0074] In a preferred embodiment, the method for preparing the ion storage layer on the second transparent conductive layer in S2 can be chosen by those skilled in the art based on the specific ion storage layer.

[0075] For example, when the ion storage layer material is PEDOT:PSS, it can be prepared as follows: PEDOT:PSS is dissolved in deionized water to prepare a solution of a certain concentration. This solution is then coated onto the second transparent conductive layer using a coating applicator or wire rod at a coating speed of 0.1 m / s-1 m / s, forming a film of PEDOT:PSS aqueous solution on the second transparent conductive layer. Subsequently, the film is dried under vacuum at 40°C-80°C for 1-2 hours to obtain the ion storage layer attached to the second transparent conductive layer. Preferably, the mass fraction of the PEDOT:PSS aqueous solution is 0.5%-1.0%.

[0076] In a preferred embodiment, when the electrolyte layer is made of a solid electrolyte, the method for preparing the electrolyte layer includes:

[0077] The raw materials, including electrolyte, crosslinkable polymer, photoinitiator and second solvent, are mixed to obtain a crosslinking system solution;

[0078] The crosslinking system solution is dropped onto the surface of the first substrate, and the ion storage layer of the second substrate is covered on it. After fixation, it is cured by ultraviolet light to obtain the electrolyte layer.

[0079] More preferably, the electrolyte comprises a lithium salt, which includes at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium tetrafluoroborate, lithium perchlorate, and lithium hexafluorophosphate.

[0080] More preferably, the crosslinkable polymer includes at least one of methyl methacrylate, polyethylene glycol acrylate, and methoxy polyethylene glycol monomethacrylate.

[0081] More preferably, the photoinitiator includes photoinitiator 1173, benzoin dimethyl ether, photoinitiator 184, or photoinitiator 1000.

[0082] More preferably, the second solvent includes at least one of propylene carbonate, ethylene ethylene carbonate, and ethylene glycol carbonate.

[0083] When preparing the crosslinking system solution, based on the mass of the crosslinking system solution being 100%, the mass percentage of the electrolyte is 4%-20%, the mass percentage of the crosslinkable polymer is 40%-50%, the mass percentage of the photoinitiator is 0.15-10%, and the mass percentage of the second solvent is 40%-50%.

[0084] Specifically, when the prepared crosslinking system solution is dropped onto the surface of the first substrate (dropped onto the electrochromic film layer), 5μm-40μm tape is used around the first substrate to control the spacing, ensuring that the thickness of the solid electrolyte layer obtained after final curing is also between 5μm and 40μm.

[0085] When performing ultraviolet curing, an LED ultraviolet curing device with a power of 20W-30W and a wavelength of 365nm can be used. After curing for 20s-180s, an electrochromic device is obtained.

[0086] This application employs direct coating with polymer solution and photo-initiated polymer electrolyte layer, which greatly reduces the processing complexity of multilayer all-solid-state electrochromic devices. The thickness and properties of each layer can be easily optimized and adjusted, and it is expected to enable large-scale automated roll-to-roll production.

[0087] This application also provides an electronic device including the aforementioned electrochromic device. This electronic device can serve as a casing for mobile phones, tablets, wearable devices, game consoles, etc., possessing a beautiful, vibrant, and versatile appearance that can meet users' aesthetic requirements and enhance their viewing experience.

[0088] The implementation schemes of this application will be described in detail below with reference to specific embodiments. However, those skilled in the art will understand that the following embodiments are only for illustrating this application and should not be regarded as limiting the scope of this application. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments used without specified manufacturers are all conventional products that can be purchased commercially.

[0089] Example 1

[0090] This embodiment provides an electrochromic device, comprising: a first transparent conductive layer, an electrochromic layer, an electrolyte layer, an ion storage layer, and a second transparent conductive layer, wherein the electrochromic layer is made of PBFDO material prepared using the preparation method described in the article "A solution-processed n-type conducting polymer with ultrahigh conductivity".

[0091] The fabrication method of this electrochromic device includes:

[0092] (1) Dissolve PBFDO in dimethyl sulfoxide to obtain a solution with a mass fraction of 0.5%. Use a coating tool to coat it onto the first transparent conductive layer at a coating speed of 0.5 m / s. Dry it under vacuum conditions at 60°C for 2 hours to form a thin film, and obtain an electrochromic layer attached to the first transparent conductive layer, which is called the first substrate.

[0093] (2) PEDOT:PSS was dissolved in deionized water to prepare a 0.5% PEDOT:PSS aqueous solution. This solution was then coated onto the second transparent conductive layer using a coating applicator at a speed of 0.5 m / s, forming a film on the second transparent conductive layer. The film was then dried under vacuum at 60°C for 2 hours to obtain an ion storage layer attached to the second transparent conductive layer, referred to as the second substrate.

[0094] (3) A crosslinkable polymer polyethylene glycol acrylate (molecular weight 700) of 45.4% by mass, a lithium salt electrolyte LiTFSI of 9% by mass, a photoinitiator BDK of 0.2% by mass, and a solvent ethylene carbonate of 45.4% by mass were stirred for 3 hours until completely dissolved to obtain a crosslinking system solution. The crosslinking system solution was dropped onto the electrochromic layer of the first substrate, and the spacing around the substrate was controlled by 10-micron tape. Then, the second substrate with the ion storage layer was covered on top and clamped and fixed to obtain an uncured device. An LED UV curing device with a power of 20W and a wavelength of 365nm was used to cure for 180 seconds to obtain an electrochromic device.

[0095] Example 2

[0096] This embodiment is the same as embodiment 1, except that the solvent in step (3) is replaced by propylene carbonate instead of ethylene carbonate.

[0097] Example 3

[0098] This embodiment is the same as embodiment 2, except that in step (3), the mass percentage of polyethylene glycol acrylate is 40%, the mass percentage of LiTFSI is 19.8%, the mass percentage of photoinitiator BDK is 0.2%, and the mass percentage of solvent propylene carbonate is 40%.

[0099] Example 4

[0100] This embodiment is the same as embodiment 2, except that in step (3), the mass percentage of polyethylene glycol acrylate is 42.1%, the mass percentage of electrolyte TBATFSI is 48%, the mass percentage of photoinitiator 1173 is 80.2%, and the mass percentage of solvent propylene carbonate is 45.7%.

[0101] The transmittance of the electrochromic devices of Examples 1-4 above was tested under different oxidation and reduction voltages, with the test wavelengths ranging from 380 to 760 nm. Table 1 lists the transmittance results of each device.

[0102] Table 1

[0103]

[0104] As shown in Table 1, the electrochromic device of this application has a certain transmittance under visible light in the absence of voltage. When the voltage is a positive voltage in the oxidized state, the color of the electrochromic device changes from colorless to blue-black, resulting in a decrease in the transmittance of the device. When the voltage is changed to a negative voltage in the reduced state, the color of the device changes from blue-black to colorless (e.g., ...). Figure 1 As shown in the figure, this makes the transmittance of the device higher than that in the no-voltage state. This means that the use of PBFDO material in electrochromic devices in this application results in electrochromic devices with high color contrast and fast response when energized.

[0105] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

[0106] Furthermore, those skilled in the art will understand that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are intended to be within the scope of this application and form different embodiments. For example, any of the embodiments claimed above can be used in any combination. The information disclosed in this background section is intended only to enhance the understanding of the general background of this application and should not be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

Claims

1. A method for preparing an electrochromic device, characterized in that, The electrochromic device includes: a first transparent conductive layer, an electrochromic layer, an electrolyte layer, an ion storage layer, and a second transparent conductive layer; The electrochromic layer is made of n-CP poly(benzodiazepine dione); The electrolyte layer is made of a solid electrolyte; the ion storage layer is made of at least one of PEDOT:PSS, titanium dioxide nanowires, and PEDOT. The first transparent conductive layer and the second transparent conductive layer include ITO conductive glass, FTO conductive glass, or ITO-PET film; The method for preparing the electrochromic device includes: coating the electrochromic material onto the first transparent conductive layer to obtain a first substrate; The ion storage layer is formed on the second transparent conductive layer to obtain a second substrate; The electrolyte layer is formed between the first substrate and the second substrate; The electrolyte layer is made of a solid electrolyte, and the method for preparing the electrolyte layer includes: The raw materials, including electrolyte, crosslinkable polymer, photoinitiator and second solvent, are mixed to obtain a crosslinking system solution; The crosslinking system solution is dropped onto the surface of the first substrate, and the ion storage layer of the second substrate is covered on it. After fixing, it is then cured with ultraviolet light to obtain the electrolyte layer. The electrolyte includes a lithium salt, which includes at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium tetrafluoroborate, lithium perchlorate, and lithium hexafluorophosphate. The crosslinkable polymer includes at least one of methyl methacrylate, polyethylene glycol acrylate, and methoxy polyethylene glycol monomethacrylate. The photoinitiator includes photoinitiator 1173, benzoin dimethyl ether, photoinitiator 184, or photoinitiator 1000; The second solvent includes at least one of propylene carbonate, ethylene ethylene carbonate, and ethylene glycol carbonate; Based on the mass of the crosslinking system solution being 100%, the mass percentage of the electrolyte is 4%-20%, the mass percentage of the crosslinkable polymer is 40%-50%, the mass percentage of the photoinitiator is 0.15-10%, and the mass percentage of the second solvent is 40%-50%.

2. The preparation method according to claim 1, characterized in that, At least one of the following AC conditions must be met: a. Prior to the coating, the process further includes: cleaning, annealing, and ozone treatment of the first transparent conductive layer; b. The coating process includes: dissolving the electrochromic material in a first solvent to obtain a mixed solution, and then using a coating applicator or wire rod to coat the mixed solution onto the first transparent conductive layer to form the electrochromic layer; c. After coating, the process further includes drying the film layer under vacuum conditions at 40℃-60℃ for 1-2 hours.

3. The preparation method according to claim 2, characterized in that, It also satisfies at least one of the following conditions: d. The cleaning process includes ultrasonic cleaning sequentially with water, anhydrous ethanol, and acetone; e. The annealing includes continuous annealing at 300℃-600℃ for 20min-40min; f. The ozone treatment includes ultraviolet ozone treatment for 20-40 minutes; g. The first solvent comprises at least one of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, and acetonitrile; h. The coating speed is 0.1 m / s - 1 m / s; i. The electrochromic material accounts for 0.2%-1% of the mass of the mixed solution.

4. The preparation method according to claim 3, characterized in that, It also satisfies at least one of the following conditions: o. When the crosslinking system solution is dropped onto the surface of the first substrate, the spacing is controlled by using 5μm-40μm tape around the first substrate; p. An LED UV curing device is used for UV curing, and the power of the LED UV curing device is 20W-30W, and the wavelength is 365nm; q. The UV curing time is 20s-180s.

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