WO3 / Zn composite film and preparation method thereof

Abstract

The invention relates to the technical field of electrochromic materials, and discloses a WO3 / Zn composite film and a preparation method thereof.The method comprises the steps that a layer of Zn film is deposited on the conductive face of FTO glass through electro-deposition treatment, and Zn / FTO glass is obtained; and drying the Zn / FTO glass, placing the dried Zn / FTO glass in a precursor solution, and preparing the WO3 / Zn composite film through a TAIG method. The composite film with Zn < 2 + > doped in the internal structure of the WO3 film is prepared through a TAIG method, the irreversible stacking effect of Li < + > is greatly reduced, and meanwhile the conductivity of the WO3 / Zn composite film can be greatly improved through the doped Zn < 2 + > capable of being subjected to in-situ oxidation-reduction reaction; and the problems of internal structure damage caused when Zn < 2 + > is embedded into / separated from the WO3 film and long path in the ion movement process are solved.

Description

Technical Field

[0001] This invention relates to the field of electrochromic materials technology, and more specifically, to a WO3 / Zn composite thin film and its preparation method. Background Technology

[0002] Currently, the building sector accounts for over 40% of global energy consumption, with approximately half used for lighting, heating, and cooling systems. Electrochromic materials have found widespread application in this context. For example, electrochromic smart windows (ESWs) can dynamically adjust their optical transmittance through external voltage stimulation, achieving significant energy savings. Electrochromic materials are functional materials that undergo reversible redox reactions under an applied electric field, autonomously and reversibly altering their optical properties. They have been widely used in smart windows, supercapacitors, sensors, displays, and automotive anti-glare rearview mirrors. Compared to organic materials, inorganic electrochromic materials have attracted more attention due to their excellent stability, simple processing technology, and mature preparation techniques. Among them, tungsten trioxide (WO3), a transition metal oxide, has been widely used in devices such as photoelectrodes and gas sensors due to its advantages of low cost, environmental friendliness, and good chemical stability.

[0003] WO3, a wide bandgap semiconductor with a bandgap of approximately 2.5–2.8 eV, typically exhibits good stability and significant optical modulation capabilities in its thin film materials. However, its intrinsic conductivity is low, often requiring a high voltage to achieve high transmittance, which may adversely affect the electrochemical stability of the film. Common WO3 electrochromic films typically take the form of various nanosheet morphologies. Their multi-layered nanosheet structure, due to its high specific surface area, is more conducive to ion migration and interfacial reactions. Furthermore, practically prepared WO3 films often contain defects such as oxygen vacancies, bound water, or tungsten interstitial atoms. Figure 1 As shown in Figure a, during the electrochemical cycling process, the Li in the electrolyte of the WO3 thin film... + It repeatedly inserts and extracts from its crystal structure, and some Li + The gradual accumulation and irreversible doping of WO3 at the bottom layer not only limits the optical modulation capability and color-changing behavior of the thin film, but also induces the breakage of WO bonds in the microstructure of the thin film, thereby impairing the cycle stability and service life of the thin film / device.

[0004] Zinc (Zn) can be effectively doped and used to construct electrochromic heterostructures, significantly improving the structural stability and electron transfer capability of thin films. Multiple studies have shown that using Zn in electrochromic materials... 2+Doping can effectively refine grains to increase specific surface area, expand interlayer spacing to promote cation transport, thereby broadening the optical modulation range and significantly shortening the coloring / fading response time, further improving the overall performance of electrochromic devices. Although Zn 2+ The introduction of [a specific substance] is considered to improve the conductivity of WO3 thin films and alleviate the [problem] caused by Li. + Stacking is an effective strategy, but conventional Zn 2+ Both embedding / extraction methods suffer from two major drawbacks: long ion migration paths and random ion movement directions (e.g.) Figure 1 As shown in b), this ultimately leads to a decrease in the response speed of the WO3 color-changing film and exacerbates the destruction of its internal WO bond integrity structure (as shown in b). Figure 1 (As shown in c). Therefore, while making full use of the Zn optimization effect, how to avoid negative impacts on the integrity of the original thin film structure remains a challenge in current research.

[0005] Based on this, the proposed WO3 / Zn composite film has significant practical implications. Summary of the Invention

[0006] In view of this, the present invention proposes a WO3 / Zn composite thin film and its preparation method, aiming to solve at least one of the problems mentioned in the background art.

[0007] This invention proposes a method for preparing a WO3 / Zn composite thin film, comprising: The preparation steps include the following: A Zn film is deposited on the conductive surface of FTO glass by electrodeposition to obtain Zn / FTO glass; The Zn / FTO glass was dried and then placed in a precursor solution to prepare a WO3 / Zn composite film by the TAIG method.

[0008] Preferably, the electrodeposition time is 30-90s, the constant potential method is used, the deposition potential is 0.003V, and the electrolyte is a 0.2M ZnSO4 acidic solution.

[0009] Preferably, the drying temperature of the drying process is 50°C and the drying time is 5 minutes.

[0010] Preferably, the method for preparing the precursor solution is as follows: Dissolve Na2WO4·2H2O in water, add citric acid, and after dissolving, add hydrochloric acid solution and stir for 20 minutes to obtain tungsten trioxide precursor solution.

[0011] Preferably, the steps of the TAIG method are as follows: The tungsten trioxide precursor solution was poured into a beaker, and the dried Zn / FTO substrate was inverted and immersed in the solution. After heating in an oven at 60°C for 1.5 hours, the FTO was removed from the beaker, rinsed, and dried to obtain the WO3 / Zn composite film.

[0012] The present invention also provides a WO3 / Zn composite film prepared by the aforementioned method for preparing WO3 / Zn composite films.

[0013] This invention also provides an application of WO3 / Zn composite thin film in electrochromic devices.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention prepares Zn-containing products via the TAIG method. 2+ Composite films doped with WO3 in their internal structure significantly reduce Li + Doped Zn exhibits irreversible stacking effects while also undergoing in-situ redox reactions. 2+ It can significantly improve the conductivity of WO3 / Zn composite films and solve the problem of Zn 2+ Internal structural damage caused by embedding / extraction of WO3 films and long path problems during ion movement (e.g.) Figure 1 e Figure 1 (as shown in f). With the help of electrodeposition, the Zn content was quantitatively controlled, and the internal structure morphology, oxygen vacancies, and bound water of the prepared WO3 / Zn composite film were balanced and regulated, further improving the electrochemical and optical properties of the film. Attached Figure Description

[0015] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings: Figure 1 This is a schematic diagram of the defect principle of the WO3 thin film provided in an embodiment of the present invention; Figure 2 This is a schematic diagram illustrating the preparation principle of the WO3 / Zn composite film provided in this embodiment of the invention. Figure 3 This is a physical image of the WO3 / Zn composite film provided in the embodiments of the present invention; Figure 4 The images shown are of Zn / FTO glass obtained at different electrodeposition times in the embodiments of the present invention. Figure 5 SEM and EDS images of Zn / FTO glass with a 60s electrodeposition time provided in this embodiment of the invention; Figure 6 The image shows the contact angle test results of Zn / FTO glass at different deposition times provided in this embodiment of the invention. Figure 7 The images are scanning electron microscope (SEM) images of WO3 / Zn composite films with different deposition times provided in the embodiments of the present invention. Figure 8 The above are energy dispersive spectroscopy (EDS) images of WO3 / Zn composite films with different deposition times provided in the embodiments of the present invention. Figure 9 These are SEM cross-sectional images of thin films with different Zn deposition times provided in the embodiments of the present invention; Figure 10 Fourier transform infrared (FTIR) spectra of thin films with different Zn deposition times provided in this embodiment of the invention; Figure 11 This is a test diagram of the bonding strength of WO3 / Zn@60s provided in an embodiment of the present invention; Figure 12 This is a high-resolution transmission electron microscope (HRTEM) image of WO3 / Zn@60s provided in an embodiment of the present invention; Figure 13 The SAED pattern of WO3 / Zn@60s provided in the embodiments of the present invention; Figure 14 The above are structural diagrams of different crystal planes in the SAED pattern of WO3 / Zn@60s provided in the embodiments of the present invention; Figure 15 These are test images of X-ray diffraction (XRD) and Raman spectra of thin films with different Zn deposition times provided in the embodiments of the present invention; Figure 16 This is an elemental distribution detection map of WO3 / Zn@60s provided in an embodiment of the present invention; Figure 17 Optical bandgap diagrams of different WO3 / Zn ratios provided in the embodiments of the present invention; Figure 18 The above is a calculation and analysis diagram of the optical bandgap of different WO3 / Zn ratios provided in the embodiments of the present invention; Figure 19 XPS analysis plots of O 1s and W 4f orbitals for different WO3 / Zn provided in this embodiment of the invention; Figure 20 These are cyclic voltammetry (CV) test graphs for different WO3 / Zn ratios provided in this embodiment of the invention; Figure 21 This is a linear relationship graph between the peak current and the square root of the scan rate for different WO3 / Zn ratios provided in the embodiments of the present invention. Figure 22 Tangent analysis diagrams of different WO3 / Zn Tafel tests provided in the embodiments of the present invention; Figure 23 This is a graph showing the variation trend of linear polarization resistance and corrosion current for different WO3 / Zn ratios provided in the embodiments of the present invention; Figure 24 Nyquist plots of different WO3 / Zn ratios provided in embodiments of the present invention; Figure 25 This is a quantitative analysis diagram of different WO3 / Zn charge transfer resistances provided in the embodiments of the present invention; Figure 26 These are test graphs of the optical performance of different WO3 / Zn ratios provided in the embodiments of the present invention; Figure 27 The above are test graphs of response times for different WO3 / Zn ratios provided in the embodiments of the present invention. Figure 28 The image shows a performance test result of an electrochromic device prepared by WO3 / Zn@60s, as provided in an embodiment of the present invention. Figure 29 The above are performance test diagrams of a reference device prepared from pure WO3 thin films provided in this embodiment of the invention. Detailed Implementation

[0016] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention. It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the present invention.

[0017] Furthermore, regarding the numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included within this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0018] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0019] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0020] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0021] like Figure 2 As shown, this invention proposes a method for preparing a WO3 / Zn composite thin film, characterized by the following preparation steps: A Zn film is deposited on the conductive surface of FTO glass by electrodeposition to obtain Zn / FTO glass; The Zn / FTO glass was dried and then placed in a precursor solution to prepare a WO3 / Zn composite film by the TAIG method.

[0022] Specifically, when the Zn / FTO glass is dried and then placed in a precursor solution, the reactivity of Zn causes it to transform into ZnO in the acidic solution. 2+ It dissolves and detaches from the glass surface, releasing electrons in the process. Subsequently, the H2WO4 molecules in the precursor solution combine with electrons... The reaction produces WO 3-x n·H2O( ).

[0023] Specifically, before depositing a Zn film on the conductive surface of the FTO glass through electrodeposition, one end of the FTO substrate is carefully covered with copper tape to ensure uniform conductivity and facilitate subsequent processes and performance testing.

[0024] It is understandable that this invention prepares Zn-containing products via the TAIG method. 2+ Composite films doped with WO3 in their internal structure significantly reduce Li + Doped Zn exhibits irreversible stacking effects while also undergoing in-situ redox reactions. 2+ It can significantly improve the conductivity of WO3 / Zn composite films and solve the problem of Zn 2+ The internal structural damage and long path problems caused by ion movement during the insertion / extraction of WO3 films were addressed. By quantitatively controlling the Zn content with the aid of electrodeposition, the internal structural morphology, oxygen vacancies, and bound water of the fabricated WO3 / Zn composite films were balanced, further improving the electrochemical and optical properties of the films.

[0025] In this invention, the electrodeposition time is 30-90s, a constant potential method is used, the deposition potential is 0.003V, and the electrolyte is a 0.2M acidic ZnSO4 solution.

[0026] Specifically, the 0.2M ZnSO4 acidic solution is prepared by adding 0.2mM Na2SO4·12H2O and 0.1M citric acid to a 0.2M ZnSO4·7H2O aqueous solution.

[0027] In this invention, the drying temperature of the drying process is preferably 50°C, and the drying time is preferably 5 minutes.

[0028] In this invention, the precursor solution is prepared by dissolving Na2WO4·2H2O in water, adding citric acid, and after dissolving, adding hydrochloric acid solution and stirring for 20 minutes to obtain tungsten trioxide precursor solution.

[0029] Specifically, 0.3 g of Na₂WO₄·2H₂O was weighed and dissolved in 30 mL of deionized water. Then, 0.6 g of citric acid was added, ensuring complete dissolution. Next, 7 mL of 3M hydrochloric acid solution was added, and the mixture was stirred vigorously for 20 minutes to obtain a tungsten trioxide precursor solution.

[0030] In this invention, the steps of the TAIG method are as follows: pour the tungsten trioxide precursor solution into a beaker, immerse the dried Zn / FTO substrate upside down in the solution, heat it in an oven at 60°C for 1.5 hours, remove the FTO from the beaker, rinse and dry it to obtain the WO3 / Zn composite film.

[0031] Specifically, a tungsten trioxide precursor solution was poured into a beaker, and a dried Zn / FTO substrate was inverted and immersed in the solution (conductive side down). After heating in an oven at 60°C for 1.5 hours, the FTO was removed from the beaker and rinsed to ensure no deposits were present on the back side. After drying, a WO3 / Zn composite film was successfully obtained.

[0032] The present invention also provides a WO3 / Zn composite film prepared by the method for preparing the WO3 / Zn composite film.

[0033] The present invention also provides an application of the WO3 / Zn composite thin film in electrochromic devices.

[0034] Specifically, the applications include those on smart automotive glass and those on building exterior windows.

[0035] Example 1 S1. First, weigh 0.3 g of Na₂WO₄·2H₂O and dissolve it in 30 mL of deionized water. Then, add 0.6 g of citric acid, ensuring complete dissolution. Next, add 7 mL of 3M hydrochloric acid solution. Stir the mixture vigorously for 20 minutes to obtain a tungsten trioxide precursor solution for later use. S2. Cut the FTO glass into 2cm×4cm sizes. Then, ultrasonically clean the FTO glass in sequence with detergent, isopropanol, distilled water and ethanol for 30 minutes each time. After drying in an oven, treat the FTO glass with ozone for 40 minutes. Then, carefully cover one end of the FTO glass with copper tape. S3. Pour the tungsten trioxide precursor solution into a beaker. Immerse the FTO glass, covered with copper tape, upside down in the solution (conductive side down). Heat in an oven at 60°C for 1.5 hours. Remove the FTO from the beaker and rinse to ensure there is no deposit on the back side. After drying, a WO3 film is successfully obtained. Example 2 S1. First, weigh 0.3 g of Na₂WO₄·2H₂O and dissolve it in 30 mL of deionized water. Then, add 0.6 g of citric acid, ensuring complete dissolution. Next, add 7 mL of 3M hydrochloric acid solution. Stir the mixture vigorously for 20 minutes to obtain a tungsten trioxide precursor solution for later use. S2. Cut the FTO glass into 2cm×4cm sizes. Then, ultrasonically clean the FTO glass in sequence with detergent, isopropanol, distilled water and ethanol for 30 minutes each time. After drying in an oven, treat the FTO glass with ozone for 40 minutes. Then, carefully cover one end of the FTO glass with copper tape. S3. Add 0.2mM Na2SO4·12H2O and 0.1M citric acid to a 0.2M ZnSO4·7H2O aqueous solution to obtain a 0.2M ZnSO4 acidic solution. Using an electrochemical workstation, the 0.2M ZnSO4 acidic solution is used as the electrolyte. The potentiostatic method is selected, the deposition potential is 0.003V, and the electrodeposition time is 30s to obtain Zn / FTO glass. The Zn / FTO glass is then washed with deionized water and dried in an oven at 50℃ for later use. S4. Pour the tungsten trioxide precursor solution into a beaker, and immerse the dried Zn / FTO glass upside down in the solution (conductive side down). Heat in an oven at 60°C for 1.5 hours, then remove the FTO from the beaker and rinse to ensure there is no precipitate on the back side. After drying, WO3 is successfully obtained. 3 / Zn composite film.

[0036] Example 3 The only difference from Example 2 is that the electrodeposition time in step S3 is 60s.

[0037] Example 4 The only difference from Example 2 is that the electrodeposition time in step S3 is 90s.

[0038] Test Example 1 During the electrodeposition process, ensuring the uniform distribution of elemental Zn film on the FTO glass surface is a prerequisite for preparing a uniform WO3 / Zn composite film. Therefore, the Zn / FTO glasses prepared in four examples with different electrodeposition times (0s, WO3 film), Example 1 (30s), Example 2 (60s), and Example 4 (90s) were tested. The Zn / FTO glasses obtained at different electrodeposition times (0s, 30s, 60s, 90s) are shown in the figure. Figure 4 As shown: SEM and EDS tests were performed on Zn / FTO glass with a 60s electrodeposition time. The results are as follows: Figure 5 As shown, the results indicate that the elemental Zn film is granular and uniformly distributed on the FTO surface, with a thickness of 504.4 nm, and is tightly bonded to the FTO glass surface.

[0039] Contact angle tests were performed on Zn / FTO glasses obtained at different electrodeposition times (0s, 30s, 60s, 90s), and the results are as follows. Figure 6 As shown, the results indicate that with the increase of Zn electrodeposition time, the contact angle between deionized water and Zn film first decreases and then increases. A smaller contact angle helps to improve the uniformity of the coating and plating, thereby promoting the adhesion and growth of WO3 film.

[0040] Test Example 2 During the growth of WO3 thin films, Zn transforms into Zn2. 2+ The released electrons play a crucial role, therefore different Zn 2+ The content will have different effects on the properties and morphology of WO3 / Zn composite films.

[0041] Therefore, this invention systematically explores the performance of WO3 / Zn composite films prepared in Examples 1-4 with different adjusted electrodeposition times by testing their properties. 2+ Effect of WO3 content on the properties of WO3 / Zn composite films: The WO3 / Zn composite films prepared in the four examples with different electrodeposition times, namely Example 1 (0s), Example 2 (30s), Example 3 (60s), and Example 4 (90s), were named according to their electrodeposition times as WO3 / Zn@0s, WO3 / Zn@30s, WO3 / Zn@60s, and WO3 / Zn@90s, for use in subsequent testing. The crystal structure and elemental composition of the prepared thin films were analyzed in detail using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The EDS results are shown below. Figure 7 As shown, the Zn content inside different films increases with the extension of Zn electrodeposition time; scanning electron microscopy (SEM) test results are as follows. Figure 8 As shown ( Figure 8 In the image, a is the SEM image of WO3 / Zn@0s, b is the SEM image of WO3 / Zn@60s, c is the SEM image of WO3 / Zn@30s, and d is the SEM image of WO3 / Zn@90s.

[0042] As can be seen, the WO3 / Zn@0s film exhibits a large, interlocking sheet-like structure with significant size and porosity. This morphology results in poor mechanical properties, making the lattice more prone to expansion and contraction during ion incorporation and extraction, leading to the collapse and destruction of ion transport channels and thus reducing the cycling stability of the WO3 film during long-term operation. In contrast, the WO3 / Zn@60s composite film, while also exhibiting an interlocking nanosheet structure, has smaller pores and a more compact structure, resulting in better internal structural stability. While the WO3 / Zn@30s film possesses a similar surface morphology to the WO3 / Zn@60s composite film, SEM cross-sectional analysis reveals a greater thickness. The longer ion transport channels contribute to the increased stability of the Li-Zn composite film. + The prolonged ion implantation and extraction times, along with increased uncertainty in ion movement direction, reduce long-term cycling stability. The SEM morphology of the WO3 / Zn@90s film exhibits an uneven, spherical structure. This spherical structure may be due to incomplete reaction of excess Zn, resulting in WO3 molecules coating excessive and unevenly distributed Zn, leading to more crystal defects and making carrier transport more difficult. Furthermore, the presence of different spherical WO3 molecules within the same ion channel makes the underlying channel prone to collapse, further reducing the overall structural stability of the film.

[0043] SEM cross-sectional analysis was performed on WO3 / Zn@0s, WO3 / Zn@30s, WO3 / Zn@60s, and WO3 / Zn@90s, and the results are as follows: Figure 9 As shown, the film thicknesses of WO3 / Zn@0s, WO3 / Zn@30s, WO3 / Zn@60s, and WO3 / Zn@90s are 774.1 nm, 750.8 nm, 668.7 nm, and 595.3 nm, respectively. It can be seen that the film thickness gradually decreases with increasing electrodeposition time. The macroscopic reason for this may be the transformation of Zn into Zn2. 2+When the WO3 molecules detach, the attached WO3 molecules also fall into the solution; microscopically, this can be attributed to Zn consuming the bound water between WO3 molecules. This phenomenon is consistent with Fourier transform infrared spectroscopy (FTIR) testing. Figure 10 ) 923.5 cm -1 606.8nm cm -1 and 1616.6 cm -1 The corresponding decrease in OW and HOH peaks is consistent with this. Furthermore, the bonding strength of the WO3 / Zn@60s composite film was also tested, and the results are as follows: Figure 11 As shown in the figure, the results indicate that the thin film has a strong bond with the FTO glass substrate.

[0044] The atomic structure of WO3 / Zn@60s was studied using high-resolution transmission electron microscopy (HRTEM), and the results are as follows: Figure 13 As shown, by using selected area electron diffraction (SAED) mode, we further distinguished the crystal planes corresponding to spots of different intensities, where the SAED patterns correspond to the (111), (200), and (202) crystal planes, respectively. Figure 14 As shown, the lattice spacings corresponding to each crystal plane were calculated, and the results were 0.41 nm, 0.36 nm, and 0.33 nm, respectively. The WO3 / Zn@60s composite film exhibits a sheet-like interlaced structure, as shown in the figure. Figure 14 As shown, this is consistent with the aforementioned SEM results.

[0045] X-ray diffraction (XRD) and Raman spectroscopy were performed on WO3 / Zn@0s, WO3 / Zn@30s, WO3 / Zn@60s, and WO3 / Zn@90s. The results are as follows: Figure 15 As shown ( Figure 15 In the image: a represents the X-ray diffraction test result; b represents the Raman spectroscopy test result. Figure 15 As can be seen from point a, in addition to the three characteristic peaks corresponding to the FTO glass substrate, three more WO3·H2O characteristic peaks (JCPDS No. 00-043-0679, a = 5.24 Å, b = 10.70 Å, c = 5.12 Å) corresponding to the above transmission electron microscopy (TEM) test are also observed. No other impurities or phases, such as WO3·2H2O, WO3·3H2O, or WO3·0.33H2O, were detected, indicating that the Zn doping... 2+ After that, WO 3-x The ·nH2O molecules tend to transform into WO3·H2O, significantly improving the sample purity. Furthermore, the intensities of these three peaks gradually weaken with increasing Zn electrodeposition time, indicating that the water content in WO3·H2O molecules gradually decreases with increasing Zn content. Figure 15b shows that as the Zn content increases, 570 cm -1 The peak value of A1(TO) at this location is enhanced. This peak value originates from the longitudinal optical vibration mode between the Zn-O layers. No peak value was observed in pure WO3 films at this location, but the peak value of the WO3 / Zn composite films prepared with Zn modification assistance increased with the extension of electrodeposition time, indicating that some Zn... 2+ Zn is encapsulated within the internal structure of WO3 and is covered by it. 2+ The amount gradually increases with increasing electrodeposition time. Furthermore, at 790 cm⁻¹... -1 and 948cm -1 Two peaks appear at each point, corresponding to the asymmetric stretching mode and the symmetric stretching mode of WO3, respectively. The intensity of the former increases with increasing Zn deposition time, while the latter shows the opposite trend. This phenomenon is consistent with the Zn... 2+ This aligns with the increased irregularity in the internal crystal structure caused by doping within WO3. Furthermore, elemental distribution analysis of the WO3 / Zn@60s composite film sample was performed using TEM. Figure 16 As shown, by Figure 16 It can be seen that the three elements O, W and Zn are evenly distributed, which directly confirms that the Zn element is uniformly wrapped in the WO3 film.

[0046] Test Example 3: Electrochemical Performance Test To analyze the performance of different WO3 / Zn composite films, this test comprehensively tested and analyzed their electrochemical properties. Firstly, in the Raman spectrum, at 790 cm⁻¹... -1 The broadened band at a certain point indicates the presence of oxygen vacancy defects in the film. To investigate the changes in these oxygen vacancies, this invention further subjected the film to ultraviolet-visible absorption spectroscopy and X-ray photoelectron spectroscopy (XPS) analysis. The optical band gaps of different WO3 / Zn composite films were determined by ultraviolet-visible absorption spectroscopy as follows: Figure 17 As shown, Figure 17 The thin film exhibits strong light absorption near 1100 nm wavelength, and the absorption intensity gradually increases with the extension of Zn electrodeposition time in the 600–1100 nm band. The optical bandgap is calculated using the Tauc plotting method. Figure 18 As shown, their relationship is given by the formula: ( We can obtain: Where α is the absorption coefficient, A is a constant, and n depends on the transition type (n=2 represents an indirect bandgap semiconductor, and n=1 / 2 represents a direct bandgap semiconductor). It can be seen that the bandgap values ​​of the four composite films WO3 / Zn@0s, WO3 / Zn@30s, WO3 / Zn@60s, and WO3 / Zn@90s are 3.31 eV, 3.26 eV, 3.24 eV, and 3.19 eV, respectively. Their bandgap size decreases with increasing Zn electrodeposition time. This can be attributed to the increase in defect energy levels after the introduction of oxygen vacancies, which promotes electronic transitions. This indicates that the oxygen vacancy concentration is related to the Zn... 2+ The amount added is directly proportional to the amount added.

[0047] XPS analysis was performed on the O 1s and W 4f orbitals, and the results are as follows: Figure 19 As shown ( Figure 19 (a) XPS analysis results of the O 1s orbital; b) XPS analysis results of the W 4f orbital. It can be seen that the O 1s spectrum exhibits three characteristic peaks at binding energies of 530.2 eV, 531.4 eV, and 532.4 eV, corresponding to WO bonds, surface -OH groups, and adsorbed water -H2O, respectively. The intensity of each peak decreases with increasing electrodeposition time, indicating that the content of structural water and WO3 molecular weight within the film decreases. The thickness of the WO3 / Zn composite film increases with increasing Zn content. 2+ The conclusion that the content decreases with increasing concentration is consistent; in the W 4f spectrum, the peaks with binding energies of 35.4 eV and 37.5 eV are attributed to W, respectively. 6+ 4f 7 / 2 and W 6+ 4f 5 / 2 The peaks at 34.7 eV and 36.4 eV correspond to W. 5+ 4f 7 / 2 and W 5+ 4f 5 / 2 As the electrodeposition time of Zn increases, W 5+ The significantly enhanced intensity of the relevant peaks indicates that the oxygen vacancy concentration in the film increases accordingly, which is consistent with the band gap analysis results.

[0048] Cyclic voltammetry (CV) tests were performed on four different thin films using the Chi660e electrochemical workstation software. The results are as follows: Figure 20 As shown, based on the Randles-Sevcik equation: Furthermore, the diffusion coefficient (D) of Li⁺ in different thin films was calculated: In the formula, Ip is the peak current, n is the number of electrons transferred, A is the effective area of ​​the electrode, and C0 is the Li + Concentration. The peak current of different thin films showed a good linear relationship with the square root of the scan rate, such as... Figure 21 As shown ( Figure 21In the graph, a represents the linear relationship between peak current and the square root of scan rate for different thin films, and b represents the Li-C ratio of different thin films. + Diffusion coefficient), Li3 / Zn@0s, WO3 / Zn@30s, WO3 / Zn@60s and WO3 / Zn@90s composite films + The diffusion coefficients are 1.653 x 10⁻⁶. -4 1.924x10 -4 4.937x10 -4 and 3.488x10 -4 Li + The diffusion coefficient varies with Zn 2+ The diffusion coefficient of the WO3 / Zn@60s composite film showed an initial increase followed by a decrease, with the latter being approximately three times that of the pure WO3 film. This difference is mainly due to the presence of Zn. 2+ The addition of Zn improves the conductivity of the WO3 / Zn composite film, thereby increasing the electron transport rate, partly due to the presence of Zn. 2+ Doping increases the interlayer spacing of the thin film's internal structure and accelerates the Li... + The transmission speed; however, Zn in the WO3 / Zn@90s composite film 2+ Excessive accumulation of residual oxygen can also block ion passage, and increased internal structural inhomogeneity further inhibits ion transport, leading to a decrease in its diffusion coefficient. Furthermore, while oxygen vacancies enhance electron conduction, the resulting lattice distortion also creates a high diffusion barrier. Simultaneously, the significantly reduced structural water content weakens ion conduction capacity, resulting in decreased ion mobility. This explains the degradation of WO3 / Zn@90s thin films in Li... + One of the reasons is that the diffusion performance of oxygen vacancies is lower than that of WO3 / Zn@60s. Therefore, regulating and balancing the relative contents of oxygen vacancies and structural water is also of great significance for jointly promoting the ion diffusion process.

[0049] In addition, this invention also used an electrochemical workstation Chi660e to perform Tafel tests on four different thin films in a voltage range of -0.6V to 0.6V (rate 5mV / s), and analyzed the curves by plotting tangents. Figure 22 As shown, the corrosion reaction of the four different WO3 / Zn composite films during the polarization process is mainly controlled by the cathodic reaction. By fitting the original Tafel curves, the changing trends of the linear polarization resistance and corrosion current of the different WO3 / Zn composite films were further analyzed, such as... Figure 23As shown, the linear polarization resistance (corrosion current) of the WO3 / Zn@0s, WO3 / Zn@30s, WO3 / Zn@60s, and WO3 / Zn@90s composite films are 163.3Ω (248.9mA), 264.8Ω (155.3mA), 350.0Ω (129.7 mA), and 323.8Ω (135.9 mA), respectively. A higher linear polarization resistance indicates better corrosion resistance, while a lower corrosion current indicates better corrosion resistance. Among the four films, the WO3 / Zn@60s composite film has the highest linear polarization resistance and the lowest corrosion current, indicating better electrochromic performance, which is attributed to the Zn content. 2+ The in-situ redox reaction improves the crystal structure stability and conductivity of the WO3 / Zn composite film, promotes carrier transport efficiency, and makes it easier to polarize. Additionally, excess Zn... 2+ Accumulation will hinder Li + The diffusion rate is high, therefore, compared to the WO3 / Zn@60s composite film, the WO3 / Zn@90s composite film has a smaller linear polarization resistance and a larger corrosion current.

[0050] Finally, this invention used electrochemical impedance spectroscopy (EIS) to test the ion transport kinetics of the thin films. The Nyquist plots of different WO3 / Zn composite films are shown below. Figure 24 As shown in the figure, the radius of the arc in the high-frequency region reflects the charge transfer resistance (Rct) at the electrode / electrolyte interface. Quantitative analysis was performed using ZSimpWin software, as follows: Figure 25 As shown, the charge transfer resistances (Rct) of pure WO3, WO3 / Zn@30s, WO3 / Zn@60s, and WO3 / Zn@90s films are 62.53Ω, 68.64Ω, 47.91Ω, and 56.76Ω, respectively. With increasing Zn electrodeposition time, the charge transfer resistance exhibits a non-monotonic trend of first increasing, then decreasing, and then increasing again. The WO3 / Zn@60s composite film shows the lowest Rct value (47.91Ω), mainly due to the large amount of Zn encapsulated within the film. 2+ In-situ redox reactions increase electron transport efficiency, partly because the increased interlayer spacing within the thin film reduces ion diffusion resistance, decreasing the hindrance to charge transfer during ion diffusion and thus reducing resistance. It is noteworthy that a large amount of Zn... 2+ Accumulation can also clog material pores or increase ion diffusion barriers, hindering ion transport. Therefore, the charge transfer resistance of WO3 / Zn@90s composite films actually increases.

[0051] In summary, this test case introduced Zn through a combination of electrodeposition and the TAIG method. 2+It can significantly improve the conductivity of WO3 films, while altering the oxygen vacancies and structural water content of WO3 / Zn composite films, with appropriate amounts of Zn. 2+ Doping can increase the interlayer spacing of the thin film, accelerate ion transport, reduce charge transfer resistance, and improve the electrochromic properties of the thin film. However, excessive Zn... 2+ Stacking also introduces more crystal defects that hinder electron transport, thus hindering the realization of Zn. 2+ The high conductivity imparted by the redox reaction with Zn 2+ Finding the optimal balance between stacking and hindering ion transport is key to obtaining WO3 / Zn composite films with high electrochromic properties.

[0052] As can be seen, this invention successfully prepared Zn on the surface of FTO conductive glass using a simple two-step method. 2+ The WO3 / Zn composite film, uniformly distributed within its internal structure, was systematically analyzed using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD) to characterize different Zn groups. 2+ The effect of doping content on the microstructure and crystal structure of WO3 / Zn composite films shows that appropriate amounts of Zn... 2+ Doping can not only improve the sample purity of WO3 thin films, but also obtain excellent electrochromic properties such as high ion transport, low electron transfer impedance, and easy polarization.

[0053] Test Example 4: Optical Performance Test This invention relates to Zn that is uniformly distributed and capable of undergoing in-situ redox reactions. 2+ The effect of WO3 content on electrochemical performance is not a simple linear relationship. Therefore, this invention further characterizes the optical properties of the WO3 / Zn composite film, and the test results are as follows: Figure 26-27 As shown ( Figure 26 (a) Spectrophotometer results of different WO3 / Zn composite films; b) Coloring efficiency test results of different films; c) Response time test results; dg) Cyclic stability test results of four different composite films; e) Cyclic stability test results of WO3 / Zn@60s composite film. The electrochromic properties of different WO3 / Zn composite films were systematically analyzed using a UV-Vis spectrophotometer, such as... Figure 26 As shown in a, Figure 26This paper presents the optical transmittance curves of four thin films, WO3 / Zn@0s, WO3 / Zn@30s, WO3 / Zn@60s, and WO3 / Zn@90s, under applied voltages of -0.6 V (colored state) and 0.8 V (faded state). The optical modulation range (ΔT) of the different films at a wavelength of 1100 nm is 83.2%, 78.5%, 92.5%, and 81.6%, respectively. The results show that with the increase of Zn electrodeposition time, the ΔT of the composite film at 1100 nm exhibits a non-monotonic trend of first decreasing, then increasing, and then decreasing again. The WO3 / Zn@60s composite film achieves the largest optical modulation range, which is due to the Zn... 2+ The effective encapsulation of Zn within the WO3 lattice improves the conductivity of the thin film, enabling higher transmittance modulation at lower voltages. However, when the electrodeposition time is extended to 90 s, excessive Zn... 2+ Agglomeration significantly reduces the fading effect of the film, and the small film thickness also weakens its color rendering ability. The combined effect of these two factors leads to a decline in the optical properties of the WO3 / Zn@90s composite film, highlighting the importance of moderate Zn content. 2+ Doping content is key to obtaining WO3 / Zn electrochromic composite films with a high optical modulation range.

[0054] To quantitatively evaluate the electrochromic properties of WO3 / Zn composite films, this invention uses coloration efficiency (CE) as a key evaluation index. CE is defined as the ratio of optical density change (ΔOD) to the injected / extracted charge per unit area (ΔQ), and the specific calculation formula is as follows: , This parameter reflects the strength of the optical modulation capability of the thin film under unit charge driving, and is closely related to the energy consumption of the electrochromic device in actual operation. A higher CE value means that reversible switching between the colored and faded states can be achieved with lower energy consumption. The coloring efficiency of different thin films is calculated, such as... Figure 26 As shown in b, the results indicate that the WO3 / Zn composite films prepared by electrodeposition times of 0 s, 30 s, 60 s, and 90 s have CE values ​​of 78.1 cm² / C, 184.7 cm² / C, 123.4 cm² / C, and 87.8 cm² / C, respectively. This shows that Zn... 2+ The coloring efficiency of doped WO3 / Zn composite films is significantly higher than that of pure WO3 films, mainly because of the coated Zn. 2+The in-situ redox reaction of divalent cations promotes more complete ion implantation / extraction, enhancing optical modulation capability (AOD) and directly leading to higher coloring efficiency for the same charge (Q). However, the coloring efficiency of the WO3 / Zn composite film decreases as the electrodeposition time of Zn increases from 30 s to 90 s. The SEM image of WO3 / Zn@90 s shows that this is mainly due to the large amount of Zn deposited. 2+ Accumulation hindered Li + The diffusion rate is affected, and the inhomogeneity of the internal structure of the thin film also promotes a large number of crystal defects, which reduces the carrier transport efficiency.

[0055] Response time (defined as the time required for a 90% change in transmittance) test results are as follows: Figure 26 c. Figure 27 As shown, the coloring time (Tc) and fading time (Tb) of pure WO3 film at 1100 nm are 6.5 s and 11.2 s, respectively, while the coloring times (Tc) and fading times (Tb) of WO3 / Zn@30s, WO3 / Zn@60s, and WO3 / Zn@90s composite films are 8 s / 3.7 s, 3.7 s / 8.9 s, and 5.8 s / 9.5 s, respectively, for Zn-doped films. 2 + The response times (Tc+Tb) of the modified films were all shorter than those of the pure WO3 film. Among them, the WO3 / Zn@60s composite film exhibited the best overall response time, which is attributed to the Zn 2+ The in-situ redox reaction that occurs promotes carrier transport, and the doping of Zn... 2+ The interlayer spacing of the thin film's internal structure was increased, Li + Increased diffusion rate also reduces the response time of electrochromic films. Furthermore, the increased response time of the WO3 / Zn@90s composite film is due to excess Zn. 2+ The uneven distribution of internal potential and excessive crystal defects in the WO3 lattice hinder ion migration.

[0056] Cyclic stability of electrochromic materials refers to the performance indicators of maintaining their optical modulation ability and structural integrity during repeated redox cycles. During continuous charge insertion / extraction processes, the material's microstructure is prone to irreversible changes, including the collapse of the internal structure of the thin film and the accumulation of large amounts of Li. + Accumulation leads to a decrease in the optical modulation capability of WO3 / Zn composite films. Excellent cycling stability can effectively suppress performance degradation, enabling the material to maintain high optical contrast and response rate during long-term cycling. Figure 26The d–g values ​​in the figure show the cycle stability test results of four different composite films. Films with Zn electrodeposition times of 0 s, 30 s, and 90 s all exhibited significant performance degradation after 600 cycles. The ΔT of the pure WO3 film decreased from an initial 85.3% to 34.8%, a drop of 59.2%. This rapid degradation can be attributed to two factors: firstly, the large sheet-like structure within the film lacks structural stability; secondly, SEM cross-sectional images show poor adhesion to the FTO substrate, accelerating structural failure. The ΔT of the WO3 / Zn@30s and WO3 / Zn@90s films decreased from 90.9% to 63.5% and from 83.1% to 40.4%, respectively. The former's degradation is related to its larger film thickness, where long-distance ion migration makes structural damage more likely; the latter's degradation is due to residual Zn. 2+ Excessive Zn content increases the structural inhomogeneity and crystal defects within the film, both of which weaken its structural stability during cycling. In contrast, the WO3 / Zn@60s composite film exhibits excellent cycling stability, maintaining 77.4% ΔT after 6000 cycles at -0.6 V / 0.8 V, a decrease of only 16% from the initial value of 92.5%. This superior cycling stability can be attributed to the following mechanisms: firstly, the in-situ oxidation of the coated Zn2+ facilitates ion migration during cycling, reduces carrier travel distance, and enhances the electrochemical reversibility of the material; secondly, the WO3 / Zn@60s composite film exhibits better adhesion to the FTO glass substrate, a phenomenon confirmed by SEM cross-sectional images.

[0057] In conclusion, an appropriate amount of Zn 2+ Doping not only improves the conductivity of WO3 / Zn composite films and enhances the carrier transport rate, but also the in-situ redox reaction can significantly shorten the migration path of ions and reduce damage to the original internal structure of the film. The synergistic effect of the two can significantly enhance the cycle stability of electrochromic films during long-term fading / coloring processes.

[0058] Test Example 5: Application Testing To evaluate the practical application potential of electrochromic devices, this study assembled a device using a high-performance WO3 / Zn@60s composite film and a Prussian blue PB film (prepared using the previous TAIG method). The optical performance and cycling stability were systematically tested, and the test results are as follows: Figure 28-3 As shown in Figure 9 ( Figure 28 In the middle: a) is the optical modulation amplitude test result of the electrochromic device of WO3 / Zn@60s composite film and Prussian blue PB film; b) is the transmittance test result of the device after 10,000 consecutive cycles at -1 V / 1 V voltage; cd) is a physical image of the fabricated large-area electrochromic device.

[0059] like Figure 28 As shown in Figure a, the device achieves an optical modulation amplitude of 70.73% at a wavelength of 1100 nm, and after 10,000 consecutive cycles of testing at –1 V / 1 V, the device transmittance is 71.3%, close to the initial value of 71.6%. Figure 28 As shown in b, it exhibits excellent cycling stability. In contrast, the reference device (WO3-PB) based on pure WO3 thin film showed a transmittance degradation to below 60% after 1,000 cycles, as... Figure 29 As shown, this further highlights the Zn 2+ The modification significantly improves the cycling stability of the device.

[0060] In summary, this invention successfully developed a high-performance WO3 / Zn composite film using an innovative thermally assisted in-situ (TAIG) generation method combined with controlled electrodeposition. The optimized WO3 / Zn@60s film exhibits excellent electrochromic properties, achieving 92.5% optical modulation at 1100 nm and a thickness of 123.4 cm⁻¹. 2 The material exhibits high coloring efficiency (CE), rapid switching kinetics (3.7 s / coloring, 8.9 s / bleaching), and excellent cycling stability, with only a 16% degradation after 6000 cycles. These performance indicators represent a significant improvement over conventional WO3 films and set a new standard for inorganic electrochromic materials. The enhanced performance stems from multiple synergistic mechanisms: Zn 2+ The incorporation of [a substance] increases the interlayer spacing to promote Li [the process]. + The transport of oxygen vacancies was increased to improve electronic conductivity, and the nanosheet morphology was refined to enhance structural integrity. System characterization confirmed that optimal zinc doping effectively balances defect engineering and structural stability, overcoming the limitations of traditional doping methods. Practical application in fully electrochromic devices demonstrated excellent durability, maintaining 71.3% transmittance after 10,000 cycles, while a large-area prototype (10 cm² × 10 cm²) exhibited uniform switching and effective thermal regulation (10°C temperature difference). Successful integration of smart mirrors and scalable manufacturing confirmed the feasibility of building energy management and automotive applications.

[0061] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the present invention. The scope of protection of the present invention is determined by the appended claims.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a WO3 / Zn composite thin film, characterized by, The preparation steps include the following: A Zn film is deposited on the conductive surface of FTO glass by electrodeposition to obtain Zn / FTO glass; The Zn / FTO glass was dried and then placed in a precursor solution to prepare a WO3 / Zn composite film by the TAIG method.

2. The method for preparing the WO3 / Zn composite film according to claim 1, characterized in that, The electrodeposition time is 30-90 seconds, using a constant potential method with a deposition potential of 0.003V and an electrolyte of 0.2M acidic ZnSO4 solution.

3. The method for preparing the WO3 / Zn composite film according to claim 1, characterized in that, The drying temperature for the drying process is 50°C, and the drying time is 5 minutes.

4. The WO3 / Zn composite film according to claim 1, characterized in that, The method for preparing the precursor solution is as follows: Dissolve Na2WO4·2H2O in water, add citric acid, and after dissolving, add hydrochloric acid solution and stir for 20 minutes to obtain tungsten trioxide precursor solution.

5. The method for preparing the WO3 / Zn composite film according to claim 1, characterized in that, The steps of the TAIG method are as follows: The tungsten trioxide precursor solution was poured into a beaker, and the dried Zn / FTO substrate was inverted and immersed in the solution. After heating in an oven at 60°C for 1.5 hours, the FTO was removed from the beaker, rinsed, and dried to obtain the WO3 / Zn composite film.

6. A WO3 / Zn composite film prepared by the method for preparing WO3 / Zn composite films according to claims 1-5.

7. An application of a WO3 / Zn composite thin film as described in claim 6 in electrochromic devices.

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