Low-haze transparent conductive film for electrochromic device, preparation method thereof and electrochromic device

Abstract

This invention provides a low-haze transparent conductive film for electrochromic devices, its preparation method, and the electrochromic device itself. The preparation method includes the following steps: providing a substrate; depositing a transparent conductive layer on the substrate; wherein the transparent conductive layer is an FTO film or an AZO film; and performing chemical mechanical polishing on the transparent conductive layer to obtain the low-haze transparent conductive film. This invention applies chemically mechanically polished FTO or AZO films to electrochromic devices to replace traditional ITO films. This not only significantly reduces the raw material cost of electrochromic devices, but more importantly, the resulting transparent conductive film maintains excellent conductivity and electrochromic performance while possessing low haze and high optical clarity comparable to ITO. This effectively solves the technical challenge of balancing performance and cost in high-end optical devices using low-cost transparent conductive materials, thus broadening its application range in high-end optical devices.

Description

Technical Field

[0001] This invention belongs to the field of functional materials and optoelectronic technology, specifically relating to a low-haze transparent conductive thin film for electrochromic devices, its preparation method, and the electrochromic device itself. Background Technology

[0002] Electrochromic technology has been widely used in fields such as smart windows, automotive anti-glare rearview mirrors, and display devices. A typical all-solid-state electrochromic thin-film module usually adopts a multi-layer structure, consisting of: a transparent conductive substrate, an ion storage layer, an ion conductor layer, an electrochromic layer, and a top transparent conductive layer.

[0003] Currently, the industry generally uses indium tin oxide (ITO) thin films prepared by magnetron sputtering as transparent conductive layers on both sides. This method has become the technical standard for high-performance electrochromic devices. Its typical preparation process is as follows: depositing ITO thin films on a glass substrate to form a transparent conductive substrate, then depositing an ion storage layer, an ion conductor layer and an electrochromic layer in sequence, and finally depositing the top ITO transparent conductive layer. After electrode encapsulation, the device is prepared. However, ITO thin films have the following defects in practical applications: (1) Indium is a rare metal, expensive and with large market fluctuations. Its scarcity and high concentration of production areas pose potential risks to the long-term stable supply of raw materials, directly increasing the manufacturing cost of electrochromic devices and becoming the main bottleneck restricting its large-scale promotion and application; (2) ITO thin films have poor toughness and are prone to cracking when applied to flexible substrates or in situations where they need to withstand a certain degree of bending, resulting in failure of conductivity.

[0004] It is evident that existing electrochromic devices face a difficult technical contradiction between performance and cost. Specifically, the following two core issues need to be addressed: (1) High-performance, high-optical-quality electrochromic devices have stringent requirements for the transparent conductive layer. To achieve low haze (high definition) and high conductivity, ITO material is generally used as the transparent conductive layer, but its high cost limits its large-scale promotion. (2) Fluorine-doped tin oxide (FTO) and aluminum-doped zinc oxide (AZO), as alternatives to ITO, have lower costs, but due to their large surface roughness and high haze, they are prone to light scattering in practical applications, resulting in electrochromic devices with severe light scattering, blurred visual effects, and low resolution, making it difficult to meet the needs of high-definition application scenarios.

[0005] Therefore, how to provide a transparent conductive film that combines low cost, high transmittance, low haze and high conductivity, and apply it to electrochromic devices, is a technical problem that urgently needs to be solved. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a low-haze transparent conductive film for electrochromic devices, its preparation method, and the electrochromic device itself. This invention applies chemically mechanically polished FTO or AZO films to electrochromic devices to replace traditional ITO films. This not only significantly reduces the raw material cost of electrochromic devices, but more importantly, the resulting transparent conductive film maintains excellent conductivity and electrochromic performance while possessing low haze and high optical clarity comparable to ITO. This effectively solves the technical challenge of balancing performance and cost in high-end optical devices using low-cost transparent conductive materials, thereby broadening its application range in high-end optical devices.

[0007] To achieve this objective, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for preparing a low-haze transparent conductive thin film for electrochromic devices, the method comprising the following steps: Provide a base.

[0008] A transparent conductive layer is deposited on the substrate. The transparent conductive layer is an FTO thin film or an AZO thin film.

[0009] The transparent conductive layer is subjected to chemical mechanical polishing to obtain the low-haze transparent conductive film.

[0010] This invention applies chemically mechanically polished FTO or AZO films to electrochromic devices to replace traditional ITO films. This not only significantly reduces the raw material cost of electrochromic devices, but more importantly, the resulting transparent conductive film maintains excellent conductivity and electrochromic performance while possessing low haze and high optical clarity comparable to ITO. This effectively solves the technical problem of balancing performance and cost in high-end optical devices using low-cost transparent conductive materials, thereby broadening its application range in high-end optical devices.

[0011] In this invention, Chemical Mechanical Polishing (CMP) is a surface planarization technology that combines chemical corrosion with mechanical abrasion. The principle is as follows: During polishing, a polishing slurry is delivered between the workpiece and the polishing pad. Under pressure, the workpiece and the polishing pad rotate relative to each other. The chemical components in the polishing slurry react with the surface of the workpiece, generating a soft and easily removable reaction layer. Simultaneously, abrasive particles remove the reaction layer through mechanical abrasion. Through the alternation of chemical and mechanical actions, the workpiece surface is ultimately planarized and smoothed.

[0012] Specifically, chemical mechanical polishing of FTO and AZO films can make their surfaces denser and smoother, which can slow down their performance degradation in humid environments and improve the long-term stability of the devices to a certain extent.

[0013] For example, the substrate can be a glass substrate or a stacked structure composed of a transparent conductive substrate, an electrochromic layer, an ion conductor layer and an ion storage layer.

[0014] It should be noted that electrochromic refers to the phenomenon that the optical properties of a material (such as reflectivity, transmittance, and absorptivity) undergo stable and reversible changes under the action of an external electric field, which manifests as reversible changes in color and transparency in appearance.

[0015] Preferably, the deposition method of the transparent conductive layer includes any one or a combination of at least two of magnetron sputtering, spray pyrolysis, or chemical vapor deposition. For example, chemical vapor deposition can be used when depositing FTO thin films; magnetron sputtering can be used when depositing AZO thin films.

[0016] Preferably, the thickness of the transparent conductive layer is 200-800nm, for example, it can be 200nm, 300nm, 400nm, 500nm, 600nm, 700nm or 800nm.

[0017] Preferably, in the chemical mechanical polishing process, the polishing solution includes silica sol.

[0018] Preferably, the particle size D50 of the silica sol is 50-100nm, for example, it can be 50nm, 60nm, 70nm, 80nm, 90nm or 100nm.

[0019] In this invention, the particle size D50 of the silica sol is 50-100nm. The appropriate particle size can ensure a sufficient mechanical removal rate while avoiding surface scratches caused by excessively large abrasive particles, thereby obtaining a polished surface with low defects and low roughness.

[0020] Preferably, in the chemical mechanical polishing treatment, the pH of the polishing solution is 4-6 (e.g., it can be 4, 4.5, 5, 5.5 or 6, etc.) or the pH is 6.5-7.5 (e.g., it can be 6.5, 7 or 7.5, etc.).

[0021] It should be noted that for FTO films, the pH of the polishing solution is 4-6; for AZO films, the pH of the polishing solution is 6.5-7.5.

[0022] In this invention, the specific pH of the polishing solution can improve polishing efficiency and avoid excessive corrosion or particle redeposition, which is beneficial to maintaining the uniformity and low haze of the film surface.

[0023] Preferably, in the chemical mechanical polishing process, the flow rate of the polishing solution is 100-200 mL / min, for example, it can be 100 mL / min, 120 mL / min, 140 mL / min, 160 mL / min, 180 mL / min or 200 mL / min, etc.

[0024] In the chemical mechanical polishing process, the present invention employs an appropriate polishing fluid flow rate, which helps maintain the stability and uniformity of the polishing process and prevents surface damage or defects caused by excessively high local temperatures or product accumulation.

[0025] Preferably, in the chemical mechanical polishing process, the polishing pressure is 2-6 psi, for example, it can be 2 psi, 3 psi, 4 psi, 5 psi or 6 psi, etc.

[0026] The present invention employs appropriate polishing pressure, which can reduce haze while ensuring polishing rate, and avoid film damage or deterioration of conductivity caused by excessive pressure.

[0027] It should be noted that "psi" is a unit of pressure, which refers to "pounds per square inch".

[0028] Preferably, in the chemical mechanical polishing process, the polishing disc rotation speed is 50-100 rpm, for example, it can be 50 rpm, 60 rpm, 70 rpm, 80 rpm, 90 rpm or 100 rpm, etc.

[0029] The present invention employs an appropriate polishing disc rotation speed, which helps to optimize the relative motion trajectory between the abrasive and the surface of the transparent conductive film, improve polishing uniformity, and control frictional heat generation to prevent changes in film structure or a decrease in conductivity caused by overheating.

[0030] Preferably, the endpoint of the chemical mechanical polishing treatment meets the following requirements: The haze of the transparent conductive layer is reduced to below 2%, for example, it can be 1.8%, 1.6%, 1.4%, 1.2% or 1%, and the sheet resistance increases by less than 50%, for example, it can be 45%, 40%, 35%, 30%, 28%, 25%, 22%, 20% or 15%.

[0031] It should be noted that the mechanical wear during the polishing process may cause the transparent conductive layer to thin or generate micro-defects on the surface, thereby increasing the sheet resistance. However, by optimizing the composition of the polishing slurry and the polishing process parameters, this invention effectively reduces the haze while controlling the increase in resistance to within 50%, thus achieving a synergistic improvement in optical quality and electrical performance.

[0032] It should be noted that sheet resistance can be measured using a four-probe tester.

[0033] Preferably, the preparation method includes the following steps: (1) Provide a glass substrate as a base.

[0034] The substrate is then cleaned and dried.

[0035] (2) A transparent conductive layer with a thickness of 200-800 nm is deposited on the glass substrate; wherein, when the transparent conductive layer is an FTO thin film, the deposition method is chemical vapor deposition; when the transparent conductive layer is an AZO thin film, the deposition method is magnetron sputtering, and the sputtering atmosphere is a mixture of inert gas (e.g., argon) and oxygen.

[0036] (3) Perform chemical mechanical polishing on the transparent conductive layer to obtain a low-haze transparent conductive film.

[0037] In the chemical mechanical polishing (CMP) process, the polishing slurry comprises silica sol with a particle size D50 of 50-100 nm, the pH of the polishing slurry is 4-6 or 6.5-7.5, and the flow rate of the polishing slurry is 100-200 mL / min; the polishing pressure is 2-6 psi, and the polishing disc rotation speed is 50-100 rpm; the endpoint of the CMP process meets the following requirements: the haze of the transparent conductive layer is reduced to below 2%, and the sheet resistance increase is less than 30%.

[0038] In a second aspect, the present invention provides a low-haze transparent conductive film for electrochromic devices, wherein the low-haze transparent conductive film is obtained by the preparation method described in the first aspect.

[0039] The haze of the low-haze transparent conductive film is <2%, for example, it can be 1.8%, 1.6%, 1.4%, 1.2% or 1%, etc.

[0040] It should be noted that haze can be tested using a haze meter.

[0041] Preferably, the haze of the low-haze transparent conductive film is <1.5%, for example, it can be 1.4%, 1.3%, 1.2%, 1.1%, 1%, 0.9% or 0.8%, etc.

[0042] Preferably, the surface roughness Ra of the low-haze transparent conductive film is less than 5 nm, for example, it can be 4 nm, 3 nm, 2 nm or 1 nm.

[0043] It should be noted that surface roughness Ra can be measured using an atomic force microscope.

[0044] Thirdly, the present invention provides an electrochromic device, the electrochromic device comprising a glass substrate, a bottom transparent conductive layer, an ion storage layer, an ion conductor layer, an electrochromic layer, and a top transparent conductive layer stacked together.

[0045] Wherein, at least one of the bottom transparent conductive layer and the top transparent conductive layer is a low-haze transparent conductive film as described in the second aspect.

[0046] It should be noted that "at least one of the bottom transparent conductive layer and the top transparent conductive layer adopts the low haze transparent conductive film as described in the second aspect" means that when the bottom transparent conductive layer adopts the low haze transparent conductive film as described in the second aspect, the top transparent conductive layer can also adopt the low haze transparent conductive film as described in the second aspect, or it can continue to use the conventional ITO film.

[0047] Preferably, the ion storage layer comprises a nickel oxide thin film. Exemplarily, the nickel oxide thin film can be deposited by magnetron sputtering or the like.

[0048] Preferably, the ion conductor layer comprises a silicon oxide thin film or a tungsten oxide thin film. Exemplarily, the deposition method for the silicon oxide thin film or tungsten oxide thin film may be magnetron sputtering, etc.

[0049] Preferably, the electrochromic layer comprises a tungsten trioxide thin film. Exemplarily, the tungsten trioxide thin film can be deposited by magnetron sputtering or the like.

[0050] Preferably, the electrochromic device further includes an encapsulation structure and electrodes.

[0051] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0052] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention applies FTO or AZO thin films treated with chemical mechanical polishing to electrochromic devices to replace traditional ITO thin films. This not only significantly reduces the raw material cost of electrochromic devices, but more importantly, the transparent conductive film obtained maintains excellent conductivity and electrochromic performance while possessing low haze and high optical clarity comparable to ITO. This effectively solves the technical problem that low-cost transparent conductive materials are difficult to balance performance and cost in high-end optical devices, thereby broadening their application range in high-end optical devices.

[0053] (2) The chemical mechanical polishing technique provided by the present invention is universal and can be applied to FTO films or AZO films obtained by various preparation methods, providing a universal technical path for performance optimization of low-cost transparent conductive materials. Detailed Implementation

[0054] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0055] The scope of this invention can be defined by lower and upper limits. The selected lower and upper limits define the boundaries of a specific range. The range defined in this way can be defined by the inclusion or exclusion of endpoints. Any endpoint can be independently selected for inclusion or exclusion, and all lower and upper limits can be arbitrarily combined to form new ranges. That is, any lower limit can be combined with any upper limit to form an effective range. For example, if the ranges of 60~120 and 80~110 are listed for specific parameters, it should be understood that the ranges of 60~110 and 80~120 also fall within the scope of this invention. In addition, if the minimum range values ​​1 and 2 are listed, and the maximum range values ​​3, 4 and 5 are also listed, then all ranges of 1~3, 1~4, 1~5, 2~3, 2~4 and 2~5 fall within the scope of this invention. In this invention, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0~5" means that all real numbers between 0 and 5 have been fully listed in this document, and "0~5" is only a shortened representation of this set of numerical combinations. When a parameter is expressed as an integer ≥2, it is equivalent to listing positive integers that meet the requirements, such as 2, 3, 4, 5, 6, 7, 8, 9, 10, etc. When a parameter is expressed as an integer selected from "2~10", it is equivalent to listing any integer among 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0056] In this invention, "a combination of at least two" refers to a quantity greater than or equal to 2 unless otherwise specified. For example, "any one or a combination of at least two" means that any one of the listed items can be selected, or a combination of at least two of the listed items formed in a manner that does not conflict and enables the implementation of this invention. In this invention, unless otherwise specified, the features or solutions corresponding to "and / or" cover any one of two or more related listed items, as well as any and all combinations of the related listed items. The arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. For example, "A and / or B" means a set consisting of A, B, and combinations of A and B, where "containing A and / or B" can be understood, depending on the context of the statement, as containing A, containing B, or simultaneously containing both A and B. In this invention, "optional" means that the corresponding feature, component, step or solution is not necessary, that is, it is selected from either "with" or "without". If there are multiple "optional" limitations in a technical solution, unless otherwise specified and there is no technical conflict or mutual constraint, each "optional" limitation is independent and does not affect the others.

[0057] In this invention, technical features or solutions described using open-ended terms such as "comprising" or "including" do not exclude additional non-conflicting elements beyond the listed elements unless otherwise specified. They are considered to disclose both closed-ended features or solutions consisting solely of the listed elements and open-ended features or solutions that may include additional non-conflicting elements beyond the listed elements. For example, if A includes a1, a2, and a3, unless otherwise specified, this means that A can consist only of a1, a2, and a3, or it can include other non-conflicting elements based on a1, a2, and a3. This corresponds to the disclosure of technical solutions such as "A consists of a1, a2, and a3," "A is selected from a1, a2, and a3," and "A not only includes a1, a2, and a3, but may also include other non-conflicting elements." All embodiments and optional embodiments of this invention, unless otherwise specified and without technical conflict, can be combined to form new technical solutions, and such combinations fall within the scope of this invention. The term "embodiment" as used in this invention means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment or implementation of the invention. The appearance of this phrase in various locations throughout the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will understand, explicitly and implicitly, that the embodiments described in this invention can be combined with other embodiments that do not conflict with the technology. The ordinal numbers "first," "second," "third," and "fourth," etc., used in the expressions "first aspect," "second aspect," "third aspect," and "fourth aspect" in this invention are for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly specifying the importance or quantity of the indicated technical features. They serve only as a non-exhaustive enumeration and do not constitute a closed limitation on quantity.

[0058] In this invention, the order in which the steps are written in the methods described in each embodiment does not imply a strict execution order. The actual execution order of each step should be determined based on its function and possible internal logic. Unless otherwise specified, all steps of this invention can be executed in the order they are written, or in any order without technical conflict. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) executed sequentially, or it may include steps (b) and (a) executed sequentially. If the method also includes step (c), then step (c) can be added to the method in any order without conflict, including but not limited to the execution order of steps (a), (b), and (c), steps (a), (c), and (b), steps (c), (a), and (b), etc.

[0059] Example 1 This embodiment provides a method for preparing a low-haze transparent conductive film for electrochromic devices, the method comprising the following steps: (1) Provide a float glass substrate as a base.

[0060] The substrate was ultrasonically cleaned sequentially with acetone, ethanol, and deionized water, and then dried.

[0061] (2) A 500 nm thick AZO thin film is deposited on the glass substrate by magnetron sputtering. In the magnetron sputtering method, the sputtering atmosphere is a mixture of argon and oxygen (the volume ratio of argon to oxygen is 98:2), and the sputtering target is ZnO:Al2O3 (the weight ratio is 98:2).

[0062] (3) The AZO film is subjected to chemical mechanical polishing to obtain a low-haze transparent conductive film.

[0063] In the chemical mechanical polishing (CMP) process, the polishing slurry comprises silica sol with a particle size D50 of 75 nm, the pH of the polishing slurry is 7, and the flow rate of the polishing slurry is 150 mL / min. In the CMP process, the polishing pressure is 4 psi and the polishing disc rotation speed is 75 rpm. The endpoint of the CMP process meets the following requirements: the haze of the transparent conductive layer is reduced to below 2%, and the sheet resistance increase is less than 30%.

[0064] This embodiment also provides an electrochromic device, which includes a glass substrate, a bottom transparent conductive layer, an ion storage layer, an ion conductor layer, an electrochromic layer, and a top transparent conductive layer stacked together; wherein, the bottom transparent conductive layer and the top transparent conductive layer are both made of low-haze transparent conductive thin films as described above; the ion storage layer is a nickel oxide thin film; the ion conductor layer is a silicon oxide thin film; the electrochromic layer is a tungsten trioxide thin film; the electrochromic device also includes an encapsulation structure and positive and negative silver electrodes.

[0065] Example 2 This embodiment provides a method for preparing a low-haze transparent conductive film for electrochromic devices, the method comprising the following steps: (1) Provide a float glass substrate as a base.

[0066] The substrate was ultrasonically cleaned sequentially with acetone, ethanol, and deionized water, and then dried.

[0067] (2) A 500 nm thick FTO film is deposited on the glass substrate by chemical vapor deposition. In the chemical vapor deposition, the atmosphere is a mixture of O2, N2 and CF4 (O2:N2:CF4=100:5:0.5), and the tin source is tin tetrachloride.

[0068] (3) The AZO film is subjected to chemical mechanical polishing to obtain a low-haze transparent conductive film.

[0069] In the chemical mechanical polishing (CMP) process, the polishing slurry comprises silica sol with a particle size D50 of 50 nm, the pH of the polishing slurry is 5, and the flow rate of the polishing slurry is 100 mL / min. In the CMP process, the polishing pressure is 2 psi and the polishing disc rotation speed is 50 rpm. The endpoint of the CMP process meets the following requirements: the haze of the transparent conductive layer is reduced to below 2%, and the sheet resistance increase is less than 30%.

[0070] This embodiment also provides an electrochromic device, which includes a glass substrate, a bottom transparent conductive layer, an ion storage layer, an ion conductor layer, an electrochromic layer, and a top transparent conductive layer stacked together; wherein, the bottom transparent conductive layer and the top transparent conductive layer are both made of low-haze transparent conductive thin films as described above; the ion storage layer is a nickel oxide thin film; the ion conductor layer is a silicon oxide thin film; the electrochromic layer is a tungsten trioxide thin film; the electrochromic device also includes an encapsulation structure and positive and negative silver electrodes.

[0071] Example 3 This embodiment provides a method for preparing a low-haze transparent conductive film for electrochromic devices, the method comprising the following steps: (1) Provide a float glass substrate as a base.

[0072] The substrate was ultrasonically cleaned sequentially with acetone, ethanol, and deionized water, and then dried.

[0073] (2) A 500 nm thick AZO thin film is deposited on the glass substrate by magnetron sputtering. In the magnetron sputtering method, the sputtering atmosphere is a mixture of argon and oxygen (the volume ratio of argon to oxygen is 98:2), and the sputtering target is ZnO:Al2O3 (the weight ratio is 98:2).

[0074] (3) The AZO film is subjected to chemical mechanical polishing to obtain a low-haze transparent conductive film.

[0075] In the chemical mechanical polishing (CMP) process, the polishing slurry comprises silica sol with a particle size D50 of 100 nm, has a pH of 6.8, and a flow rate of 200 mL / min. The polishing pressure is 6 psi, and the polishing disc rotation speed is 100 rpm. The endpoint of the CMP process meets the following requirements: the haze of the transparent conductive layer is reduced to below 2%, and the sheet resistance increase is less than 30%.

[0076] This embodiment also provides an electrochromic device, which includes a glass substrate, a bottom transparent conductive layer, an ion storage layer, an ion conductor layer, an electrochromic layer, and a top transparent conductive layer stacked together; wherein, the bottom transparent conductive layer and the top transparent conductive layer are both made of low-haze transparent conductive thin films as described above; the ion storage layer is a nickel oxide thin film; the ion conductor layer is a silicon oxide thin film; the electrochromic layer is a tungsten trioxide thin film; the electrochromic device also includes an encapsulation structure and positive and negative silver electrodes.

[0077] Example 4 The difference between this embodiment and Embodiment 1 is that the particle size D50 of the silica sol is 40 nm.

[0078] The remaining preparation methods and parameters are consistent with those in Example 1.

[0079] Example 5 The difference between this embodiment and Embodiment 1 is that the particle size D50 of the silica sol is 110 nm.

[0080] The remaining preparation methods and parameters are consistent with those in Example 1.

[0081] Example 6 The difference between this embodiment and Embodiment 1 is that the pH of the polishing solution is 6.

[0082] The remaining preparation methods and parameters are consistent with those in Example 1.

[0083] Example 7 The difference between this embodiment and Embodiment 1 is that the pH of the polishing solution is 8.

[0084] The remaining preparation methods and parameters are consistent with those in Example 1.

[0085] Example 8 The difference between this embodiment and Embodiment 1 is that the flow rate of the polishing fluid is 80 mL / min.

[0086] The remaining preparation methods and parameters are consistent with those in Example 1.

[0087] Example 9 The difference between this embodiment and Embodiment 1 is that the flow rate of the polishing fluid is 220 mL / min.

[0088] The remaining preparation methods and parameters are consistent with those in Example 1.

[0089] Example 10 The difference between this embodiment and Embodiment 1 is that the polishing pressure is 1 psi.

[0090] The remaining preparation methods and parameters are consistent with those in Example 1.

[0091] Example 11 The difference between this embodiment and Embodiment 1 is that the polishing pressure is 7 psi.

[0092] The remaining preparation methods and parameters are consistent with those in Example 1.

[0093] Example 12 The difference between this embodiment and Embodiment 1 is that the polishing disc rotates at a speed of 30 rpm.

[0094] The remaining preparation methods and parameters are consistent with those in Example 1.

[0095] Example 13 The difference between this embodiment and Embodiment 1 is that the polishing disc rotates at 120 rpm.

[0096] The remaining preparation methods and parameters are consistent with those in Example 1.

[0097] Comparative Example 1 The difference between this comparative example and Example 1 is that the chemical mechanical polishing treatment is not performed.

[0098] The remaining preparation methods and parameters are consistent with those in Example 1.

[0099] Comparative Example 2 The difference between this comparative example and Example 1 is that the chemical mechanical polishing treatment is replaced by pure mechanical polishing treatment, that is, deionized water is used to wet polish the film surface by relying solely on mechanical friction.

[0100] The remaining preparation methods and parameters are consistent with those in Example 1.

[0101] Comparative Example 3 The difference between this comparative example and Example 1 is that the chemical mechanical polishing treatment is replaced by chemical etching treatment, that is, the surface of the thin film is sprayed with an acidic etching solution (hydrochloric acid solution) to remove surface material through chemical corrosion to reduce roughness.

[0102] The remaining preparation methods and parameters are consistent with those in Example 1.

[0103] Performance testing The transparent conductive films prepared in the above embodiments and comparative examples were tested for haze, surface roughness Ra, conductivity, and sheet resistance. Haze was measured using a haze meter, surface roughness Ra was measured using an atomic force microscope, conductivity was measured using a four-probe tester coupled with an ellipsometry, and sheet resistance was measured using a four-probe tester.

[0104] The test results are shown in Table 1.

[0105] Table 1 analyze: As shown in Table 1, the present invention applies chemically mechanically polished FTO or AZO films to electrochromic devices to replace traditional ITO films. This not only significantly reduces the raw material cost of electrochromic devices, but more importantly, the resulting transparent conductive film maintains excellent conductivity and electrochromic performance while possessing low haze and high optical clarity comparable to ITO. This effectively solves the technical problem of balancing performance and cost in high-end optical devices using low-cost transparent conductive materials, thereby broadening its application range in high-end optical devices.

[0106] A comparison of Examples 1 and 4-5 shows that if the particle size D50 of the silica sol is too small, the mechanical removal ability is insufficient, the polishing efficiency is low, and the reduction in haze is not significant (the haze of Example 4 is 1.8%, which is too high); if the particle size D50 of the silica sol is too large, scratches are easily generated on the film surface, resulting in an increase in surface roughness (the surface roughness of Example 5 is 4nm, which is higher than the 3.5nm of Example 1), and may also cause an increase in local resistance.

[0107] As can be seen from the comparison between Example 1 and Examples 6-7, if the pH of the polishing solution is too low, the acidic environment will excessively corrode the ZnO material for the AZO film, resulting in corrosion pits on the surface, increased haze, and decreased conductivity; if the pH of the polishing solution is too high, the chemical reaction will be insufficient, the polishing efficiency will be reduced, and the improvement of surface roughness will be limited.

[0108] As can be seen from the comparison between Example 1 and Examples 8-9, if the flow rate of the polishing slurry is too small, the polishing products cannot be carried away in time and are prone to redeposition on the surface, resulting in an increase in surface defects (the surface roughness of Example 8 is 5 nm); if the flow rate of the polishing slurry is too large, the abrasive distribution is uneven, the polishing consistency is poor, and some areas are over-polished, resulting in an increase in resistance (the change in sheet resistance of Example 9 is 23%).

[0109] A comparison of Examples 1 and 10-11 shows that if the polishing pressure is too low, the mechanical action is insufficient and the haze reduction effect is limited (the haze in Example 10 is 2%); if the polishing pressure is too high, the film thins too quickly and the sheet resistance increases significantly (the sheet resistance in Example 11 increases by 42%), which may affect the conductivity.

[0110] A comparison of Examples 1 and 12-13 shows that if the polishing disc speed is too low, the polishing efficiency is low, the processing time is long, and it is not conducive to industrial production (the haze of Example 12 is 1.9%, which is too high); if the polishing disc speed is too high, frictional heat generation is significant, which may cause thermal damage to the thin film and worsen the surface uniformity (the sheet resistance of Example 13 increases by 32%).

[0111] As can be seen from the comparison between Example 1 and Comparative Example 1, if chemical mechanical polishing is not performed, the surface roughness and haze of the AZO film, which is an alternative to ITO, are high. In practical applications, this can easily cause light scattering, resulting in problems such as severe light scattering, blurred visual effects, and low resolution in electrochromic devices, making it difficult to meet the needs of high-definition application scenarios.

[0112] As can be seen from the comparison between Example 1 and Comparative Example 2, if a purely mechanical polishing method is used, the removal rate is slow and subsurface damage cannot be effectively eliminated by mechanical grinding alone. The reduction in haze is limited (the haze of Comparative Example 2 is 5.2%), and scratches are easily generated on the surface.

[0113] A comparison of Example 1 and Comparative Example 3 shows that if chemical etching is used, isotropic etching leads to uncontrollable surface morphology, poor film thickness uniformity, and excessive etching at grain boundaries, resulting in a significant decrease in conductivity (the conductivity of Comparative Example 3 is only 5.0 × 10⁻⁶). 3 S / m, decreased by approximately 60%.

[0114] It should be noted that the present invention is illustrated through the above embodiments, but the present invention is not limited to the above process steps, that is, it does not mean that the present invention must rely on the above process steps to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials used in the present invention, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing a low-haze transparent conductive thin film for electrochromic devices, characterized in that, The preparation method includes the following steps: Provide a base; A transparent conductive layer is deposited on the substrate; wherein the transparent conductive layer is an FTO thin film or an AZO thin film; The transparent conductive layer is subjected to chemical mechanical polishing to obtain the low-haze transparent conductive film.

2. The preparation method according to claim 1, characterized in that, The deposition method of the transparent conductive layer includes any one or a combination of at least two of magnetron sputtering, spray pyrolysis, or chemical vapor deposition. And / or, the thickness of the transparent conductive layer is 200-800 nm.

3. The preparation method according to claim 1 or 2, characterized in that, In the chemical mechanical polishing process, the polishing solution includes silica sol; The particle size D50 of the silica sol is 50-100 nm; And / or, in the chemical mechanical polishing treatment, the pH of the polishing solution is 4-6 or 6.5-7.

5.

4. The preparation method according to any one of claims 1-3, characterized in that, In the chemical mechanical polishing process, the flow rate of the polishing fluid is 100-200 mL / min.

5. The preparation method according to any one of claims 1-4, characterized in that, In the aforementioned chemical mechanical polishing treatment, the polishing pressure is 2-6 psi; And / or, in the chemical mechanical polishing process, the polishing disc rotates at a speed of 50-100 rpm.

6. The preparation method according to any one of claims 1-5, characterized in that, The endpoint of the chemical mechanical polishing treatment must meet the following requirements: The haze of the transparent conductive layer is reduced to below 2%, and the sheet resistance increases by less than 50%.

7. The preparation method according to any one of claims 1-6, characterized in that, The preparation method includes the following steps: (1) Provide a glass substrate as the base; The substrate is cleaned and dried; (2) A transparent conductive layer with a thickness of 200-800 nm is deposited on the glass substrate; wherein, when the transparent conductive layer is an FTO thin film, the deposition method is chemical vapor deposition; when the transparent conductive layer is an AZO thin film, the deposition method is magnetron sputtering, and the sputtering atmosphere is a mixture of inert gas and oxygen. (3) Perform chemical mechanical polishing on the transparent conductive layer to obtain a low-haze transparent conductive film; In the chemical mechanical polishing (CMP) process, the polishing slurry comprises silica sol with a particle size D50 of 50-100 nm, the pH of the polishing slurry is 4-6 or 6.5-7.5, and the flow rate of the polishing slurry is 100-200 mL / min; the polishing pressure is 2-6 psi, and the polishing disc rotation speed is 50-100 rpm; the endpoint of the CMP process meets the following requirements: the haze of the transparent conductive layer is reduced to below 2%, and the sheet resistance increase is less than 30%.

8. A low-haze transparent conductive film for electrochromic devices, characterized in that, The low-haze transparent conductive film is obtained by the preparation method described in any one of claims 1-7; The haze of the low-haze transparent conductive film is <2%.

9. The low-haze transparent conductive film according to claim 8, characterized in that, The haze of the low-haze transparent conductive film is <1.5%; And / or, the surface roughness Ra of the low-haze transparent conductive film is <5nm.

10. An electrochromic device, characterized in that, The electrochromic device includes a glass substrate, a bottom transparent conductive layer, an ion storage layer, an ion conductor layer, an electrochromic layer, and a top transparent conductive layer stacked together. Wherein, at least one of the bottom transparent conductive layer and the top transparent conductive layer is a low-haze transparent conductive film as described in claim 8.

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