Long-Life Wide-Band Tungsten Oxide Electrochromic Film and Its Preparation Method and Application

Abstract

The present invention discloses a long-life wide-band tungsten oxide electrochromic thin film having a structure of an amorphous composite hexagonal crystal, a preparation method thereof, and an application in the field of intelligent display or intelligent window. The preparation method includes: preparing a tungsten oxide thin film containing interlayer water on a conductive substrate to obtain an amorphous hydrated tungsten oxide electrode having interlayer water-supported voids; immersing the amorphous hydrated tungsten oxide electrode in an electrolyte containing metal ions, and using an electrochemical method to cause a cathodic reduction reaction on the surface of the amorphous hydrated tungsten oxide electrode, injecting metal ions into the interlayer voids of the tungsten oxide thin film with the electrochemical reaction as the driving force to obtain a metal-ionized tungsten oxide electrode; the ionic radius of the metal ions is 70-140 pm; heat-treating the metal-ionized tungsten oxide electrode to obtain a long-life wide-band tungsten oxide electrochromic thin film.

Description

Technical Field

[0001] The present invention relates to the technical field of electrochromic materials, and particularly relates to a long-life wide-band tungsten oxide electrochromic thin film, a preparation method thereof, and an application thereof. Background Art

[0002] Intelligent color change is a phenomenon in which the optical properties (reflectivity, transmittance, absorptivity, etc.) of a material are reversibly changed by external physical or chemical stimuli. According to different induced response stimuli, intelligent color change technologies can be divided into electrochromic technology, photochromic technology, gasochromic technology, thermochromic technology, etc.

[0003] Electrochromic technology refers to the occurrence of dynamically adjustable color changes under the condition of artificially applied voltage or current. Electrochromic technology has advantages such as good electrochemical oxidation-reduction reversibility, fast response speed, high color change sensitivity, long open-circuit memory time, and strong chemical stability. It has great application prospects in energy-saving windows, color-changing glasses, display devices, military camouflage, etc. Research and development of electrochromic materials and optimization of large-area low-cost preparation technologies have great economic value and social significance.

[0004] Electrochromic materials can be divided into organic electrochromic materials and inorganic electrochromic materials. Although organic materials have rich color changes, their environmental tolerance is not good; inorganic electrochromic materials have already had commercial products due to their good chemical stability and excellent modulation amplitude, but the preparation cost using magnetron sputtering technology is still relatively high.

[0005] Tungsten oxide, as the most classic inorganic electrochromic material, has been extensively studied by scientific researchers due to its high optical modulation rate, good chemical stability, and wide spectral modulation range (such as the patented technologies with publication numbers CN107555810A and CN110642526A, etc.). However, despite the long-term development, tungsten oxide electrochromic materials still have some problems that need to be urgently solved, such as in terms of cycle stability, response time, color contrast, and large-area low-cost preparation. In view of this situation, starting from the material structure and preparation cost, and aiming at the final electrochromic performance of the material, it is crucial to develop an electrochromic material with good cycle stability, excellent modulation effect, and large-area low cost, as well as its preparation technology. Summary of the Invention

[0006] In view of the above technical problems and the deficiencies in the art, the present invention provides a method for preparing a long-life wide-band tungsten oxide electrochromic film. The prepared tungsten oxide electrochromic film has an amorphous composite hexagonal crystal structure, has a large spectral modulation effect in both the visible light and near-infrared bands, has three photo-thermal regulation modes, and has excellent cycle stability (no attenuation of the spectral modulation amplitude during 600 cycles). The preparation method of the present invention first synthesizes a tungsten oxide film containing interlayer water, which is suitable for large-area preparation and can significantly reduce the cost compared with the existing magnetron sputtering technology. Then, a long-life wide-band tungsten oxide electrochromic film is obtained by combining two steps of metal ion implantation and heat treatment. The preparation process is simple, environmentally friendly, and does not require high-cost equipment investment.

[0007] The specific technical solutions are as follows:

[0008] A method for preparing a long-life wide-band tungsten oxide electrochromic film, comprising the steps of:

[0009] (1) Prepare a tungsten oxide film containing interlayer water on a conductive substrate to obtain an amorphous hydrated tungsten oxide electrode with interlayer water-supported voids;

[0010] (2) Immerse the amorphous hydrated tungsten oxide electrode in an electrolyte containing metal ions, and use an electrochemical method to cause a cathodic reduction reaction on the surface of the amorphous hydrated tungsten oxide electrode, and inject the metal ions into the interlayer voids of the tungsten oxide film driven by the electrochemical reaction to obtain a metal-ionized tungsten oxide electrode; the ionic radius of the metal ions is 70-140 pm;

[0011] (3) Heat-treat the metal-ionized tungsten oxide electrode to obtain the long-life wide-band tungsten oxide electrochromic film.

[0012] The preparation method of the present invention electrochemically injects metal ions with a specific ionic radius into the interlayer voids of amorphous tungsten oxide to ensure that the subsequent heat treatment process can achieve the crystal phase transformation of tungsten oxide from amorphous to hexagonal phase. During the process of tungsten oxide transforming from amorphous to crystalline state, without the presence of the above-mentioned metal ions with a specific ionic radius, tungsten oxide will transform into a monoclinic phase with a dense structure. The above-mentioned metal ions with a specific ionic radius play a key supporting role in the interlayer voids of tungsten oxide, thereby inducing tungsten oxide to transform into a hexagonal phase with a macroporous structure. On the other hand, due to the retention of metal ions in the pores of the hexagonal phase, metal ions with too large an ionic radius will reduce the effective diameter of the pores, hindering the transport of other ions during the electrochromic process. When the ionic radius of the metal ion is greater than that of potassium ion, the effective diameter of the formed hexagonal pores has been less than or close to the remaining triangular small pores, and no longer has the function of rapidly transporting ions through the macropores. In summary, the ionic radius of the metal ion should be between (including lithium ion and potassium ion) or close to the ionic radii of lithium ion and potassium ion.

[0013] In step (1), a tungsten oxide film containing interlayer water can be prepared on a conductive substrate by a wet chemical method. Specifically, the wet chemical method can be an electrochemical deposition method (for example, reference can be made to the prior art Laurinavichute, V.K., et al., Electrodeposited oxotungstate films: Towards the molecular nature of recharging processes. Electrochimica Acta, 2011. 56(10): p. 3530-3536), a chemical bath deposition method (for example, reference can be made to the prior art Zeng, Q., et al., Preparation of vertically aligned WO3 nanoplate array films based on peroxotungstate reduction reaction and their excellent photoelectrocatalytic performance. Applied Catalysis B: Environmental, 2017. 202: p. 388-396) or a sol-gel method (for example, reference can be made to the prior art Yang, T., Y. Zhang, and C. Li, Large scale production of spherical WO3 powder with ultrasonic spray pyrolysis assisted by sol–gel method for hydrogen detection. Ceramics International, 2014. 40(1): p. 1765-1769), etc.

[0014] In step (1), the conductive substrate can be a transparent conductive oxide (such as ITO conductive glass, FTO conductive glass, etc.), a metal material, an organic conductive material, etc.

[0015] In step (2), the metal ions are preferably at least one of lithium ions, sodium ions, magnesium ions, aluminum ions, potassium ions, and calcium ions.

[0016] In step (2), the electrolyte containing metal ions can be obtained by dissolving a salt of the metal ions in a solvent. The solvent only needs to be able to dissolve the salt of the metal ions. Specifically, the solvent can include at least one of propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, and acetonitrile.

[0017] In a preferred example, in step (2), the electrochemical method is to apply a constant potential or a constant current to the amorphous hydrated tungsten oxide electrode using a three - electrode system or a two - electrode system.

[0018] The three - electrode system may use an Ag / AgCl electrode as the reference electrode, a platinum sheet electrode as the counter electrode, and the amorphous hydrated tungsten oxide electrode as the working electrode. At this time, in a preferred example, the potential range of the constant potential is - 0.6 to - 1.2 V (with the reference electrode being the Ag / AgCl electrode), and the duration is 1 to 5 min; in a preferred example, the current range of the constant current is - 1 to - 10 mA / cm 2 , and the duration is 10 to 180 s.

[0019] The reference electrode in the above three - electrode system can also be a calomel electrode, a standard hydrogen electrode, or a lithium metal electrode in addition to the Ag / AgCl electrode. When the reference electrode is a calomel electrode, in a preferred example, the potential range of the constant potential is - 0.6 to - 1.3 V, and the duration is 1 to 5 min; in a preferred example, the current range of the constant current is - 1 to - 10 mA / cm 2 , and the duration is 10 to 180 s. When the reference electrode is a standard hydrogen electrode, in a preferred example, the potential range of the constant potential is - 0.4 to - 1.0 V, and the duration is 1 to 5 min; in a preferred example, the current range of the constant current is - 1 to - 10 mA / cm 2 , and the duration is 10 to 180 s. When the reference electrode is a lithium metal electrode, in a preferred example, the potential range of the constant potential is + 2.6 to + 2.0 V, and the duration is 1 to 5 min; in a preferred example, the current range of the constant current is - 1 to - 10 mA / cm 2 , and the duration is 10 to 180 s.

[0020] In a preferred example, in step (3), the heat treatment is carried out in an oxygen - containing atmosphere (such as air, etc.).

[0021] In a preferred example, in step (3), the temperature of the heat treatment is 300 to 500 °C, and the time is 10 to 60 min.

[0022] The present invention also provides a long - life wide - band tungsten oxide electrochromic film prepared by the described preparation method. The long - life wide - band tungsten oxide electrochromic film has a structure of amorphous composite hexagonal phase crystals.

[0023] The long - life wide - band tungsten oxide electrochromic film described in the present invention exhibits weak crystallinity and belongs to an amorphous and crystalline composite material. It has both good ion diffusion and a stable framework structure. Its crystalline part presents a hexagonal crystal form, which has a pore structure conducive to the insertion and extraction of ions, can improve the ion diffusion coefficient in the crystal and reduce the damage to the crystal structure caused by ion insertion and extraction, thereby enhancing the modulation amplitude, response rate, and cycling performance of the electrochromic film.

[0024] The present invention also provides an application of the long - life wide - band tungsten oxide electrochromic film in the fields of intelligent display or intelligent window.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] 1. The present invention first prepares a tungsten oxide film containing interlayer water, and can adopt relatively mature wet - chemical methods in the prior art, including electrochemical deposition, chemical bath deposition, or sol - gel method, etc. Its raw materials are common industrial products such as tungsten salts, acids, and hydrogen peroxide solutions. The precursor solution uses water as a solvent, and the raw materials are easily available and inexpensive. On the other hand, the wet - chemical method can be used for large - area preparation, with low input cost for production equipment, no need for a high - vacuum environment, and low energy consumption.

[0027] 2. The present invention first uses a two - step method of metal ionization - heat treatment to prepare a long - life wide - band tungsten oxide electrochromic film. The preparation process flow is simple and has good controllability. Compared with the tungsten oxide film synthesized by a simple wet - chemical method, the prepared tungsten oxide film has a composite structure of amorphous and crystalline states, and the crystal form structure, composite ratio, etc. can be regulated by the degree of metal ionization and heat - treatment temperature, significantly improving the electrochromic performance and cycling stability of the film.

[0028] 3. The long - life wide - band tungsten oxide electrochromic film provided by the present invention has a large modulation amplitude in both the visible light and near - infrared double - band, and has broad application prospects in the fields of intelligent display, intelligent window, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is an X - ray diffraction (XRD) pattern of the long - life wide - band tungsten oxide electrochromic film in Example 1 and the control group tungsten oxide electrochromic film in Comparative Example 1.

[0030] Figure 2 It is a scanning electron microscope (SEM) photograph of the long - life wide - band tungsten oxide electrochromic film in Example 1. The left figure is the surface of the tungsten oxide film, and the right figure is the cross - section of the electrode. From top to bottom, they are the tungsten oxide film, FTO layer, and glass in sequence.

[0031] Figure 3Transmission spectra of the long - life broadband tungsten oxide electrochromic film in Example 1 and the control group tungsten oxide electrochromic film in Comparative Example 1.

[0032] Figure 4 Variation of the modulation amplitude (ΔT) of the transmittance at 633 nm with the number of cycles for the long - life broadband tungsten oxide electrochromic film in Example 1 and the control group tungsten oxide electrochromic film in Comparative Example 1.

[0033] Figure 5 X - ray diffraction (XRD) patterns of the long - life broadband tungsten oxide electrochromic film in Example 2 and the control group tungsten oxide electrochromic film in Comparative Example 2.

[0034] Figure 6 Scanning electron microscope (SEM) photos of the long - life broadband tungsten oxide electrochromic film in Example 2. The left photo is the surface of the tungsten oxide film, and the right photo is the cross - section of the electrode. From top to bottom, they are the tungsten oxide film, the FTO layer, and the glass.

[0035] Figure 7 Transmission spectra of the long - life broadband tungsten oxide electrochromic film in Example 2 and the control group tungsten oxide electrochromic film in Comparative Example 2.

[0036] Figure 8 Variation of the modulation amplitude (ΔT) of the transmittance at 633 nm with the number of cycles for the long - life broadband tungsten oxide electrochromic film in Example 2 and the control group tungsten oxide electrochromic film in Comparative Example 2. Detailed implementation manners

[0037] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. For the operation methods without specific conditions noted in the following embodiments, they are generally carried out under conventional conditions or according to the conditions recommended by the manufacturer. The experimental materials and reagents used in the following embodiments, unless otherwise specified, can be obtained from commercial channels.

[0038] Example 1

[0039] Electrochemical deposition preparation of tungsten oxide film containing interlayer water:

[0040] The FTO conductive glass was ultrasonically cleaned in acetone, absolute ethanol, and deionized water respectively, and dried for later use.

[0041] 0.41 g of sodium tungstate dihydrate powder was added to 100 mL of deionized water, and it was magnetically stirred at a constant temperature of 40 °C until it was fully dissolved. Then 1.6 mL of concentrated hydrochloric acid was added, and the mixture was continuously stirred for 20 min while keeping warm. Then 265 μL of hydrogen peroxide (30 wt%) solution was added, and the mixture was continuously stirred for 40 min while keeping warm to obtain an electrodeposition precursor solution.

[0042] Transfer the precursor solution to an electrodeposition cell. The temperature of the solution in the electrodeposition cell can be controlled at 35 °C by an external circulating water bath. Using an Ag / AgCl electrode as the reference electrode, a platinum plate electrode as the counter electrode, and a clean FTO conductive glass as the working electrode, immerse the three electrodes in the precursor solution. Use a Shanghai Chenhua CHI660E electrochemical workstation to apply a constant current to the working electrode. The current magnitude is -0.01 A, and the duration is 600 s. After the reaction is completed, wash the FTO conductive glass successively with deionized water and absolute ethanol, and dry it to obtain a tungsten oxide film containing interlayer water.

[0043] Metal ionation and heat treatment of the tungsten oxide film:

[0044] Add 10.64 g of lithium perchlorate (LiClO4) to 100 mL of propylene carbonate (PC), and stir well to dissolve to prepare a 1 M PC-LiClO4 electrolyte. Using an Ag / AgCl electrode as the reference electrode, a platinum plate electrode as the counter electrode, and an FTO conductive glass coated with a tungsten oxide film as the working electrode, immerse the three electrodes in the PC-LiClO4 electrolyte. Apply a constant voltage to the working electrode by means of a Shanghai Chenhua CHI660E electrochemical workstation to carry out a cathodic reduction reaction, so that lithium ions are injected into the tungsten oxide film. The voltage is -0.8 V, and the duration is 1 min. After the electrochemical lithiation is completed, wash and dry the tungsten oxide electrode with absolute ethanol.

[0045] Put the electrochemically ionized tungsten oxide electrode into a muffle furnace for heat treatment. The atmosphere is air, the heat treatment temperature is 350 °C, the heating rate is 3 - 5 °C / min, and the holding time is 30 min. After the holding time is over, cool it to room temperature with the furnace to obtain a long-life wide-band tungsten oxide electrochromic film.

[0046] In this example, the XRD pattern of the prepared long-life wide-band tungsten oxide electrochromic film is as Figure 1 shown. The spectral peaks show an FTO substrate and hexagonal WO3. The crystallinity of the hexagonal phase is weak, and the bulging peaks indicate the existence of amorphous tungsten oxide. Therefore, it is an amorphous and crystalline composite tungsten oxide film. Figure 2 These are the SEM photos of the surface (left figure) and cross-section (right figure) of the tungsten oxide film. The surface of the film is granular, with a particle size of about 30 - 50 nm. The film is overall flat, dense, and defect-free, with a thickness of about 230 nm.

[0047] Perform a transmittance spectrum test on the tungsten oxide electrochromic film in this example in the wavelength range of 400 - 2000 nm. The transmittance spectra of the colored state and the bleached state of the tungsten oxide electrochromic film are as Figure 3As shown. The tungsten oxide electrochromic film can undergo reversible changes by applying an external voltage between the colored state and the bleached state. The large difference in transmittance (T) between the two states indicates that the film has good modulation effects on both visible light and near-infrared light. Its optical modulation amplitude (ΔT) at 633 nm can reach 74.7%, and the optical modulation amplitude (ΔT) at 1200 nm can reach 75.2%.

[0048] Perform cyclic testing on the tungsten oxide electrochromic film in this example. Apply a bias voltage of -0.8 V for 20 s / +1.5 V for 40 s in sequence during one cycle, so that the film can be converted between the colored state and the bleached state, as Figure 4 shown. The modulation amplitude (ΔT) of the tungsten oxide electrochromic film at 633 nm is calculated by the formula ΔT = T 褪色态 -T 着色态 and is obtained. The modulation amplitude does not decay after 600 cycles, showing excellent cycle stability.

[0049] Example 2

[0050] Electrochemical deposition preparation of tungsten oxide film containing interlayer water:

[0051] Put the FTO conductive glass into acetone, absolute ethanol, and deionized water respectively for ultrasonic cleaning, and dry it for later use.

[0052] Add 0.41 g of sodium tungstate dihydrate powder to 100 mL of deionized water, stir magnetically at a constant temperature of 40 °C to dissolve it fully. Then add 1.6 mL of concentrated hydrochloric acid, keep stirring for 20 min while maintaining the temperature, and then add 265 μL of hydrogen peroxide (30 wt%) solution, keep stirring for 40 min to obtain the electrodeposition precursor solution.

[0053] Transfer the precursor solution to the electrodeposition cell. The temperature of the solution in the electrodeposition cell can be controlled at 35 °C by an external circulating water bath. Use an Ag / AgCl electrode as the reference electrode, a platinum plate electrode as the counter electrode, and a clean FTO conductive glass as the working electrode. Immerse the three electrodes into the precursor solution, and use a Shanghai Chenhua CHI660E electrochemical workstation to apply a constant current to the working electrode. The current magnitude is -0.01 A, and the duration is 600 s. After the reaction ends, wash the FTO conductive glass with deionized water and absolute ethanol in sequence, and dry it to obtain a tungsten oxide film containing interlayer water.

[0054] Metal ionation and heat treatment of tungsten oxide film:

[0055] 12.24 g of sodium perchlorate (NaClO4) was added to 100 mL of propylene carbonate (PC), and after being fully stirred and dissolved, a 1 M PC-NaClO4 electrolyte was prepared. Using an Ag / AgCl electrode as the reference electrode, a platinum plate electrode as the counter electrode, and an FTO conductive glass coated with a tungsten oxide thin film as the working electrode, the three electrodes were all immersed in the PC-NaClO4 electrolyte. A constant voltage was applied to the working electrode by means of a Shanghai Chenhua CHI660E electrochemical workstation to carry out a cathodic reduction reaction, enabling lithium ions to be injected into the tungsten oxide thin film. The voltage was -0.8 V and the duration was 1 min. After the electrochemical lithiation was completed, the tungsten oxide electrode was cleaned with absolute ethanol and dried.

[0056] The electrochemically ionized tungsten oxide electrode was placed in a muffle furnace for heat treatment. The atmosphere was air, the heat treatment temperature was 450 °C, the heating rate was 3 - 5 °C / min, the holding time was 30 min, and after the holding time ended, it was cooled to room temperature with the furnace, obtaining the long-life wide-band tungsten oxide electrochromic thin film described above.

[0057] In this embodiment, the XRD pattern of the prepared long-life wide-band tungsten oxide electrochromic thin film is as Figure 5 shown. The spectral peaks show an FTO substrate and hexagonal WO3. The crystallinity of the hexagonal phase is weak, and the bulging peak indicates the existence of amorphous tungsten oxide. Therefore, it is an amorphous and crystalline composite tungsten oxide thin film. Figure 6 They are SEM photos of the surface (left figure) and cross-section (right figure) of the tungsten oxide thin film respectively. The surface of the thin film presents a long strip shape and granular shape. The whole thin film is flat, dense and defect-free, and the thickness is about 230 nm.

[0058] The tungsten oxide electrochromic thin film in this embodiment was tested for its transmittance spectrum in the wavelength range of 400 - 2000 nm. The transmittance spectra of the colored state and the bleached state of the tungsten oxide electrochromic thin film are as Figure 7 shown. The tungsten oxide electrochromic thin film can undergo reversible changes between the colored state and the bleached state by applying an external voltage. The huge difference in the transmittance (T) between the two states indicates that the thin film has a good modulation effect on both visible light and near-infrared light. Its optical modulation amplitude (ΔT) at 633 nm can reach 60.1%, and the optical modulation amplitude (ΔT) at 1200 nm can reach 72.8%.

[0059] The tungsten oxide electrochromic thin film in this embodiment was subjected to a cyclic test. A bias voltage of -0.8 V - 20 s / +1.5 V - 40 s was applied in sequence during one cycle, enabling the thin film to be converted between the colored state and the bleached state, as Figure 8 shown. The modulation amplitude (ΔT) of the tungsten oxide electrochromic thin film at 633 nm is calculated by the formula ΔT = T 褪色态 -T 着色态It is calculated that after 600 cycles, the decay rate of the modulation amplitude is only 3.75%, showing excellent cycle stability.

[0060] Comparative Example 1

[0061] Electrodeposition preparation of tungsten oxide thin film containing interlayer water:

[0062] The FTO conductive glass was ultrasonically cleaned in acetone, absolute ethanol, and deionized water respectively, and dried for later use.

[0063] 0.41 g of sodium tungstate dihydrate powder was added to 100 mL of deionized water, and it was magnetically stirred at a constant temperature of 40 °C until it was completely dissolved. Subsequently, 1.6 mL of concentrated hydrochloric acid was added, and the mixture was continuously stirred while maintaining the temperature for 20 min. Then, 265 μL of hydrogen peroxide (30 wt%) solution was added, and the mixture was continuously stirred while maintaining the temperature for 40 min to obtain an electrodeposition precursor solution.

[0064] The precursor solution was transferred to an electrodeposition cell, and the temperature of the solution in the electrodeposition cell could be controlled at 35 °C by an external circulating water bath. Using an Ag / AgCl electrode as the reference electrode, a platinum plate electrode as the counter electrode, and a clean FTO conductive glass as the working electrode, the three electrodes were immersed in the precursor solution. A constant current of -0.01 A was applied to the working electrode using a Shanghai Chenhua CHI660E electrochemical workstation for 600 s. After the reaction was completed, the FTO conductive glass was washed successively with deionized water and absolute ethanol, and dried to obtain a tungsten oxide thin film containing interlayer water.

[0065] Heat treatment of tungsten oxide thin film:

[0066] The prepared tungsten oxide thin film electrode containing interlayer water was put into a muffle furnace for heat treatment. The atmosphere was air, the heat treatment temperature was 350 °C, the heating rate was 3 - 5 °C / min, and the holding time was 30 min. After the holding time ended, it was cooled to room temperature with the furnace to obtain a control group of tungsten oxide electrochromic thin film.

[0067] In this comparative example, the XRD pattern of the prepared control group of tungsten oxide electrochromic thin film is as Figure 1 shown. The spectral peaks show the FTO substrate and monoclinic WO3, and the monoclinic phase has strong crystallinity.

[0068] The transmission spectrum test of the control group of tungsten oxide electrochromic thin film in Comparative Example 1 was carried out in the wavelength range of 400 - 2000 nm. The transmission spectra of the colored state and the bleached state of this tungsten oxide electrochromic thin film are as Figure 3As shown. The tungsten oxide electrochromic thin film can undergo reversible changes between the colored state and the bleached state by applying an external voltage. The difference in transmittance (T) between the two states is small, indicating that the modulation effect of the thin film on visible light and near-infrared light is not good. Its optical modulation amplitude (ΔT) at 633 nm is 22.8%, and the optical modulation amplitude (ΔT) at 1200 nm is 14.1%.

[0069] Perform a cyclic test on the tungsten oxide electrochromic thin film in this comparative example. Apply a bias voltage of -0.8 V for 20 s / +1.5 V for 40 s in sequence during one cycle, so that the thin film is converted between the colored state and the bleached state, as Figure 4 shown. The modulation amplitude (ΔT) of the tungsten oxide electrochromic thin film at 633 nm is calculated by the formula ΔT = T 褪色态 -T 着色态 After 600 cycles, the attenuation rate of the modulation amplitude is 55.0%, indicating that the modulation amplitude of the tungsten oxide thin film in the control group will decrease significantly during the long-term electrochromic process.

[0070] Comparative Example 2

[0071] Electrochemical deposition preparation of tungsten oxide thin film containing interlayer water:

[0072] Place the FTO conductive glass in acetone, absolute ethanol, and deionized water respectively for ultrasonic cleaning, and dry it for later use.

[0073] Add 0.41 g of sodium tungstate dihydrate powder to 100 mL of deionized water, stir magnetically at a constant temperature of 40 °C to dissolve it fully, then add 1.6 mL of concentrated hydrochloric acid, keep stirring for 20 min while maintaining the temperature, and then add 265 μL of hydrogen peroxide (30 wt%) solution, keep stirring for 40 min to obtain an electrodeposition precursor solution.

[0074] Transfer the precursor solution to an electrodeposition cell. The temperature of the solution in the electrodeposition cell can be controlled at 35 °C by an external circulating water bath. Use an Ag / AgCl electrode as the reference electrode, a platinum sheet electrode as the counter electrode, and a clean FTO conductive glass as the working electrode. Immerse the three electrodes in the precursor solution, and use a Shanghai Chenhua CHI660E electrochemical workstation to apply a constant current to the working electrode. The current magnitude is -0.01 A, and the duration is 600 s. After the reaction is completed, wash the FTO conductive glass with deionized water and absolute ethanol in sequence, and dry it to obtain a tungsten oxide thin film containing interlayer water.

[0075] Heat treatment of tungsten oxide thin film:

[0076] The prepared tungsten oxide thin film electrode containing interlayer water was placed in a muffle furnace for heat treatment. The atmosphere was air, the heat treatment temperature was 450 °C, the heating rate was 3 - 5 °C / min, the holding time was 30 min, and after the holding time ended, it was cooled to room temperature with the furnace to obtain the control group of tungsten oxide electrochromic thin films.

[0077] In this comparative example, the XRD pattern of the prepared control group of tungsten oxide electrochromic thin films is as Figure 5 shown. The spectral peaks show the FTO substrate and monoclinic WO3, and the monoclinic phase has strong crystallinity.

[0078] The control group of tungsten oxide electrochromic thin films in Comparative Example 2 was subjected to a transmittance spectrum test in the wavelength range of 400 - 2000 nm. The transmittance spectra of the colored state and the bleached state of this tungsten oxide electrochromic thin film are as Figure 7 shown. This tungsten oxide electrochromic thin film can undergo reversible changes between the colored state and the bleached state by applying an external voltage. The difference in transmittance (T) between the two states is small, indicating that the modulation effect of this thin film on visible light and near-infrared light is not good. Its optical modulation amplitude (ΔT) at 633 nm is 22.3%, and the optical modulation amplitude (ΔT) at 1200 nm is 20.4%.

[0079] The tungsten oxide electrochromic thin film in this comparative example was subjected to a cyclic test. In one cycle, a bias voltage of -0.8 V for 20 s / +1.5 V for 40 s was applied in sequence to make the thin film convert between the colored state and the bleached state, as Figure 4 shown. The modulation amplitude (ΔT) of this tungsten oxide electrochromic thin film at 633 nm was calculated by the formula ΔT = T 褪色态 -T 着色态 After 600 cycles, the attenuation rate of the modulation amplitude was 36.3%, indicating that the modulation amplitude of the control group of tungsten oxide thin films would decrease significantly during the long-term electrochromic process.

[0080] It can be seen that the preparation method of the present invention has a simple process, good controllability, can be large-area fabricated, and has low cost. The prepared tungsten oxide electrochromic thin film is flat, dense, and defect-free, has a composite structure of amorphous and hexagonal tungsten oxide, has a high electrochemistry reaction rate, short response time, has a large modulation amplitude in both the visible light and near-infrared bands, and has excellent cyclic stability, and has good application prospects in the fields of intelligent display or intelligent windows.

[0081] In addition, it should be understood that after reading the above description of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

Claims

1. A preparation method of a long-life wide-band tungsten oxide electrochromic thin film, characterized in that, Including the steps: (1) Prepare a tungsten oxide film containing interlayer water on a conductive substrate to obtain an amorphous hydrated tungsten oxide electrode with interlayer water-supported voids; (2) Immerse the amorphous hydrated tungsten oxide electrode in an electrolyte containing metal ions, and use an electrochemical method to cause a cathodic reduction reaction on the surface of the amorphous hydrated tungsten oxide electrode, and inject the metal ions into the interlayer voids of the tungsten oxide film driven by the electrochemical reaction to obtain a metal-ionized tungsten oxide electrode; the ionic radius of the metal ions is 70-140 pm; (3) Heat-treat the metal-ionized tungsten oxide electrode to obtain the long-life wide-band tungsten oxide electrochromic film; the long-life wide-band tungsten oxide electrochromic film has a structure of amorphous composite hexagonal phase crystals.

2. The preparation method according to claim 1, wherein In step (1), a tungsten oxide film containing interlayer water is prepared on a conductive substrate by a wet chemical method, and the wet chemical method is an electrochemical deposition method, a chemical bath deposition method or a sol-gel method.

3. The preparation method according to claim 1, wherein In step (1), the conductive substrate is a transparent conductive oxide, a metal material or an organic conductive material.

4. The preparation method according to claim 1, characterized in that, In step (2), the metal ions are at least one of lithium ions, sodium ions, magnesium ions, aluminum ions, potassium ions, calcium ions.

5. The preparation method according to claim 1, wherein In step (2), the electrolyte containing metal ions is obtained by dissolving a salt of the metal ions in a solvent, and the solvent includes at least one of propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, acetonitrile.

6. The preparation method according to claim 1, wherein In step (2), the electrochemical method is to apply a constant potential or a constant current to the amorphous hydrated tungsten oxide electrode using a three-electrode system or a two-electrode system.

7. The preparation method according to claim 6, wherein The three-electrode system uses an Ag / AgCl electrode as the reference electrode. The potential range of the constant potential is -0.6 to -1.2 V, and the duration is 1 to 5 min. The current range of the constant current is -1 to -10 mA / cm 2 , and the duration is 10 to 180 s; or, The three - electrode system uses a calomel electrode as the reference electrode. The potential range of the constant potential is - 0.6 to - 1.3 V, and the duration is 1 to 5 min. The current range of the constant current is - 1 to - 10 mA / cm 2 , and the duration is 10 to 180 s; or, The three-electrode system uses a standard hydrogen electrode as the reference electrode. The potential range of the constant potential is -0.4 to -1.0 V, and the duration is 1 to 5 min. The current range of the constant current is -1 to -10 mA / cm 2 , and the duration is 10 to 180 s; or, The three-electrode system uses a lithium metal electrode as the reference electrode. The potential range of the constant potential is +2.6 to +2.0 V, and the duration is 1 to 5 min. The current range of the constant current is -1 to -10 mA / cm 2 , and the duration is 10 to 180 s.

8. The preparation method according to claim 1, characterized in that, In step (3): The heat treatment is carried out in an oxygen-containing atmosphere; The temperature of the heat treatment is 300-500 °C, and the time is 10-60 min.

9. A long-life wide-band tungsten oxide electrochromic film prepared by the preparation method according to any one of claims 1-8.

10. Application of the long-life wide-band tungsten oxide electrochromic film according to claim 9 in the fields of intelligent display or intelligent window.

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