Electrochromic device based on viologen derivative electrolyte and hydrated tungsten oxide film and preparation method

Abstract

The invention relates to an electrochromic device based on viologen derivative electrolyte and a hydrated tungsten oxide film and a preparation method. The electrochromic device comprises an electrochromic device body with a cavity and a color-changeable electrolyte arranged in the cavity; the electrochromic device body is composed of blank transparent conductive glass and conductive glass with a hydrated tungsten oxide film. The color-changeable electrolyte includes a viologen derivative, a water-soluble metal salt, and ascorbic acid. The preparation method comprises the following steps: depositing a hydrated tungsten oxide film on transparent conductive glass; assembling the conductive glass deposited with the hydrated tungsten oxide film with blank transparent conductive glass to obtain an electrochromic device body; and injecting color-changeable electrolyte into the cavity to obtain the electrochromic device. Compared with the prior art, the electrochromic device provided by the invention can independently regulate and control the transmittance of a visible light region and a near-infrared light region, and has relatively large light modulation amplitude and an excellent color changing effect.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of electrochromic devices, and particularly relates to an electrochromic device based on a viologen derivative electrolyte and a hydrous tungsten oxide film and a preparation method. BACKGROUND

[0002] Electrochromism refers to the phenomenon that a material undergoes a reversible change in optical properties under the action of an applied electric field. Devices based on electrochromic materials have wide application prospects in the fields of smart windows, anti-dazzling rearview mirrors, energy-saving displays, and adaptive optical systems. An ideal electrochromic device should have high light modulation amplitude, fast response speed, long cycle life, low driving voltage, and good environmental stability.

[0003] Among numerous electrochromic materials, tungsten oxide has become a research hotspot due to its excellent cathodic coloring performance. Traditional methods for preparing tungsten oxide films include magnetron sputtering, chemical vapor deposition, and sol-gel method, etc. However, these methods usually require expensive equipment, complex process conditions, or high-temperature treatment, which limits their large-scale application. In contrast, electrochemical deposition has the advantages of low cost, simple process, easy control of film microstructure, and suitability for large-area preparation.

[0004] Hydrous tungsten oxide is also a type of cathodically coloring electrochromic material, and can be prepared by electrochemical deposition. For example, CN118625565A discloses an electrochromic device prepared using a polyvinyl alcohol / polyacrylic acid gel electrolyte, electrochemically deposited polyaniline, and electrochemically deposited hydrous tungsten oxide. CN119165704A discloses an electrochromic device based on electrochemically deposited copper bismuth and a hydrous tungsten oxide film. The electrochromic device is formed by depositing a hydrous tungsten oxide film on a transparent conductive glass and filling a copper bismuth electrolyte, thereby forming a hydrous tungsten oxide device with a cavity. However, the above-mentioned electrochromic device can only be changed to purple black under the control of a negative voltage coloring voltage, and is mainly used for regulating visible light. It cannot achieve obvious electrochromic control under positive voltage, which greatly limits the application range of the electrochromic device.

[0005] Therefore, there is still a need to develop a new type of electrochromic device with excellent electrochromic effect. SUMMARY

[0006] The present application is to overcome the defects of the prior art that the coloring voltage is limited and the electrochromic effect needs to be improved, and to provide an electrochromic device based on a viologen derivative electrolyte and a hydrous tungsten oxide film and a preparation method.

[0007] The object of the present application can be achieved by the following technical solutions:

[0008] The present application provides an electrochromic device based on viologen derivative electrolyte and tungsten oxide hydrate film, which comprises an electrochromic device body with a cavity and a color-variable electrolyte arranged in the cavity; the electrochromic device body is composed of blank transparent conductive glass and conductive glass with tungsten oxide hydrate film.

[0009] The color-variable electrolyte comprises the following components by weight: 2-5 parts of viologen derivative, 20-50 parts of water-soluble metal salt, and 1-5 parts of ascorbic acid.

[0010] Further, the electrochromic device is colorless in the initial state or in the bleached state; when the coloring voltage is a positive single voltage, only the color-variable electrolyte is colored, and the color changes to purple; when the coloring voltage is a negative single voltage, both the color-variable electrolyte and the tungsten oxide hydrate film are colored, and the color changes to purple black.

[0011] Further, the conductive glass comprises fluorine-doped tin oxide (FTO) glass or indium tin oxide (ITO) glass, preferably FTO glass.

[0012] Further, the blank transparent conductive glass and the conductive glass with tungsten oxide hydrate film are connected through an adhesive medium.

[0013] Further, the adhesive medium comprises one or more of double-sided tape, glass cement, adhesive tape, or glue, preferably transparent double-sided tape, with a thickness of 0.5-1 mm.

[0014] Further, the viologen derivative has the following general structure:

[0015]

[0016] In the formula, R is a C 2-6 alkyl group.

[0017] Further, the viologen derivative is prepared by mixing halogenated alkane and 4,4'-bipyridine in an organic solvent and stirring under heating conditions to react; the product is separated by solid-liquid separation, the filtrate is precipitated in an ether solvent, and the precipitate is dried to obtain the viologen derivative.

[0018] In the formula, X is any one of fluorine, chlorine, bromine, or iodine, and R is a C 2-6 alkyl group.

[0019] Further, the organic solvent comprises any one or more of acetonitrile, ethanol, tetrahydrofuran, dimethyl sulfoxide, N,N-dimethylformamide, and dichloromethane, preferably acetonitrile.

[0020] Further, the heating temperature is 50-70℃, preferably 60℃.

[0021] Further, the reaction time is 24-72h, preferably 48h.

[0022] Further, the metal element in the water-soluble metal salt is any one or more of potassium, sodium, zinc, magnesium and calcium.

[0023] Further, the water-soluble metal salt is any one or more of a chloride salt, a nitrate salt and a sulfate salt.

[0024] In the viologen derivative variable color electrolyte of the present application, the water-soluble metal salt mainly serves as a supporting electrolyte or a functional additive, and by adjusting the physical and chemical properties and electrochemical behavior of the system, the conductivity of the electrolyte, the stability of the solubility state of the viologen derivative and the electrochemical performance of the viologen derivative are improved. Ascorbic acid plays a role in antioxidant protection and redox state regulation in the viologen derivative electrolyte, and can also assist in optimizing the electrochemical kinetics and system stability. The synergistic effect of the water-soluble metal salt and ascorbic acid can significantly improve the response speed, contrast ratio and cycle stability of the viologen-based electrochromic device by improving the conductivity, stabilizing the active state of the viologen and optimizing the electrochemical kinetics, and is a key strategy for optimizing the performance of the viologen electrolyte.

[0025] The present application also provides a preparation method of an electrochromic device based on a viologen derivative electrolyte and a tungsten oxide hydrate film, which comprises the following steps:

[0026] S1: depositing a tungsten oxide hydrate film on a transparent conductive glass;

[0027] S2: assembling the conductive glass on which the tungsten oxide hydrate film is deposited with a blank transparent conductive glass to obtain an electrochromic device body with a cavity;

[0028] S3: injecting a variable color electrolyte into the cavity of the electrochromic device body to obtain the electrochromic device.

[0029] Further, in step S1, the deposition is performed by constant voltage electrodeposition, and the specific steps are as follows: in a three-electrode system, the transparent conductive glass is used as the working electrode, the platinum sheet is used as the counter electrode, and the Ag / AgCl electrode is used as the reference electrode, and electrodeposition is performed in an acidic electrolyte containing tungsten salt and hydrogen peroxide.

[0030] Further, the voltage of the constant voltage electrodeposition is-0.5 to-0.8V.

[0031] Further, the time of the constant voltage electrodeposition is 400-600s.

[0032] Further, the tungsten element in the tungsten salt has a molar ratio of (1.5-2.5):1 to hydrogen peroxide, preferably 2:1.

[0033] Further, the tungsten salt comprises any one or more of tungsten hexachloride, tungsten nitrate, sodium tungstate dihydrate, sodium tungstate, ammonium metatungstate, peroxotungstic acid and organic tungsten salt, preferably tungsten hexachloride.

[0034] Further, the electrolyte is adjusted to pH 1-2 by any one or more of hydrochloric acid, sulfuric acid and nitric acid.

[0035] Preferably, the electrolyte is adjusted to pH by a 0.1-0.8 mol / L hydrochloric acid solution.

[0036] The viologen derivative used in the application plays a key role in the electrochromic device. The viologen derivative presents a deep blue color in the reduced state and has high redox reversibility. The viologen derivative contributes additional electrochromic effects, achieving bipolar color change, thereby enhancing the overall light modulation amplitude of the device.

[0037] The application is based on a dual-band electrochromic device composed of a tungsten oxide hydrate film and a viologen derivative electrolyte. By virtue of the high efficiency of the tungsten oxide hydrate in regulating near-infrared light and the good modulation of the viologen derivative to visible light, independent or cooperative control of two bands of light is achieved, with advantages such as high efficiency, energy saving, rapid response, cycle stability, excellent optical performance and good material compatibility. The innovation points of the application are reflected in aspects such as constructing a new material system, utilizing a synergistic mechanism, realizing multifunctional integration and optimizing a preparation process, thereby providing a high-performance solution for the field of intelligent windows and the like.

[0038] The electrochromic device of the application can be applied to intelligent energy-saving windows by selectively controlling the transmittance of visible light and near-infrared light, thereby reducing building energy consumption and improving indoor comfort, and is suitable for various buildings such as residential buildings and office buildings.

[0039] Specifically, the electrochromic device prepared by the application can realize three state changes by applying different voltages. When in the "bright state", both the visible and near-infrared bands have high transmittance, which can be used in winter or on cloudy days to ensure sufficient indoor lighting and obtain solar heat, at which time the window is light yellow; in the "cold state", the near-infrared band is blocked while the visible band is transmitted, which is suitable for use in summer to block heat and provide lighting at the same time, and the window color may change to green; in the "dark state", all bands are not transmitted, which can be used when no light is needed or privacy needs to be protected, and the window is dark blue.

[0040] Compared with the prior art, the application has the following beneficial effects:

[0041] (1) The tungsten hydrate oxide film prepared by electrodeposition has a large light modulation amplitude in the visible light region and the near-infrared light region, the color-changing electrolyte containing the viologen derivative has a large light modulation amplitude in the visible light region under a small voltage, and the electrochromic device prepared by the combination of the two has a large light modulation amplitude and can independently control the transmittance in the visible light region and the near-infrared light region, thereby having excellent color-changing effect.

[0042] (2) The color-changing electrolyte prepared by the method has the components of viologen derivative, water-soluble metal salt and ascorbic acid, and the prepared electrolyte can be injected into the cavity of the electrochromic device, thereby avoiding the defects of traditional solid and gel electrolytes, such as electrochemical side reaction, insufficient free radical stability, limited ion migration rate, and influence on long-term stability and response speed of the electrochromic device.

[0043] (3) The electrochromic device uses the viologen derivative electrolyte (containing viologen derivative, water-soluble metal salt and ascorbic acid), realizes double color-changing (independent color-changing of the electrolyte to purple under positive voltage and collaborative color-changing to purple black under negative voltage) through the redox of viologen and the tungsten hydrate oxide, can independently control double wave bands, has more functions, is more suitable for more scenes, and is highly creative.

[0044] (4) The electrochromic device can realize effective adjustment of color-changing effect and transmittance under different color-changing voltages through field control, can realize color-changing effect of multiple different colors under small positive voltage and negative voltage, has excellent adjustment flexibility, and can be applied to the fields of intelligent energy-saving windows and display devices. BRIEF DESCRIPTION OF DRAWINGS

[0045] Figure 1 (a) low-magnification scanning electron microscope image, (b) high-magnification scanning electron microscope image and (c) cross-section scanning electron microscope image of the tungsten hydrate oxide film of Example 1 of the present application.

[0046] Figure 2 (a) transmittance curve and (b) solar radiation spectrum of the tungsten hydrate oxide film of Example 1 of the present application.

[0047] Figure 3 Transmittance curve of the electrochromic device of Example 3 of the present application under different voltages.

[0048] Figure 4 Coloring photos of the electrochromic device of Example 4 of the present application under different color-changing voltages.

[0049] Figure 5 Transmittance curve of the electrochromic device of Comparative Example 1 of the present application under different voltages.

[0050] Figure 61 is the transmittance curve of the electrochromic device of Comparative Example 2 of the present invention at different voltages. DETAILED DESCRIPTION

[0051] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0052] Unless otherwise specified, the reagents, methods, instruments and equipment used in the present invention are conventional reagents, methods, instruments and equipment in the art. Unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0053] The types of solvents and salt solutions in the present invention, as well as any changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principles of the present invention, are deemed to be equivalent replacement methods and are included in the scope of protection of the present invention.

[0054] Example 1:

[0055] This embodiment provides an electrochromic device based on a viologen derivative electrolyte and a hydrated tungsten oxide thin film, and the specific preparation method thereof is as follows:

[0056] (1) Preparation of hydrated tungsten oxide thin film by electrodeposition: In a three-electrode system, tungsten hexachloride, anhydrous ethanol, hydrochloric acid and hydrogen peroxide solution with set concentrations are used as electrolytes, transparent conductive substrate FTO glass is used as the working electrode, platinum sheet is used as the counter electrode, and Ag / AgCl electrode is used as the reference electrode. The hydrated tungsten oxide thin film is prepared by constant voltage electrodeposition, that is, FTO glass with hydrated tungsten oxide thin film is obtained.

[0057] The voltage of the constant voltage electrodeposition method was -0.6 V, and the electrodeposition time was 400 s.

[0058] The electrolyte was prepared by dissolving 0.7 g of tungsten hexachloride in 25 mL of anhydrous ethanol, stirring for 30 minutes, and ultrasonicating for 10 minutes; then adding 25 mL of 0.7 mol / L hydrochloric acid solution and 2 mL of hydrogen peroxide solution (concentration of 0.5 mol / L), stirring for 48 hours to prepare an electrodeposition solution.

[0059] (2) Preparation of 1-butyl-4,4′-bipyridine: 3.5 g of 1-iodobutane and 3 g of 4,4′-bipyridine were first stirred in 10 mL of acetonitrile at 60°C for 24 h. The resulting product was separated by filtration, and the filtrate was precipitated in diethyl ether. The resulting 1-butyl-4,4′-bipyridine precipitate was dried to obtain the desired orange viologen derivative for later use.

[0060] (3) Preparation of the color-changing electrolyte based on 1-butyl-4,4'-bipyridine: The electrolyte is composed of 1-butyl-4,4'-bipyridine, zinc chloride and ascorbic acid, and the specific preparation process is as follows: 0.04 g of 1-butyl-4,4'-bipyridine, 0.3 g of zinc chloride and 0.01 g of ascorbic acid are dissolved in 5 mL of deionized water, the mixture is stirred for 10 min, and ultrasonic treatment is performed for 10 min to obtain the color-changing electrolyte.

[0061] (4) First, the FTO conductive glass with a size of 2.5 x 5 cm 2 is subjected to alcohol washing, water washing and ultrasonic treatment, and dried to obtain an FTO conductive glass electrode. The prepared FTO conductive glass, 3M transparent double-sided tape with a width of 5 mm and a thickness of 1 mm, and FTO conductive glass on which tungsten hydroxide is deposited are assembled to obtain an electrochromic device with a cavity area of 3 x 1.5 cm 2 , wherein the side on which the tungsten hydroxide film is deposited faces the cavity.

[0062] (5) The electrolyte solution obtained in step (3) is injected into the cavity of the electrochromic device of step (4) to obtain an electrochromic device based on a tungsten hydroxide film and a viologen derivative electrolyte.

[0063] Example 2:

[0064] This example provides an electrochromic device based on a viologen derivative electrolyte and a tungsten hydroxide film, and the specific preparation method is as follows:

[0065] (1) Electrodeposition method for preparing tungsten hydroxide film: The process parameters of the constant voltage electrodeposition method are referred to in Example 1. The difference between this example and Example 1 is that the preparation method of the electrolyte in this example is as follows: 0.85 g of tungsten hexachloride is dissolved in 25 mL of anhydrous ethanol, stirred for 30 min, and ultrasonic treated for 10 min; then 25 mL of 0.8 mol / L hydrochloric acid solution and 1.5 mL of hydrogen peroxide solution are added, and stirred for 48 h to prepare the electrodeposition solution.

[0066] (2) Preparation of 1-butyl-4,4'-bipyridine: The preparation method is referred to in Example 1.

[0067] (3) Preparation of the color-changing electrolyte based on 1-butyl-4,4'-bipyridine: The amount is referred to in Example 1.

[0068] (4) The packaging of the electrochromic device and the injection of the electrolyte solution are referred to in Example 1.

[0069] Example 3:

[0070] This example provides an electrochromic device based on a viologen derivative electrolyte and a tungsten hydroxide film, and the specific preparation method is as follows:

[0071] (1) Preparation of the tungsten oxide hydrate thin film by electrodeposition method: the process parameters of constant voltage electrodeposition method and the preparation of electrolyte solution are both referred to Example 1.

[0072] (2) Preparation of 1-butyl-4,4'-bipyridine: the preparation method is referred to Example 1.

[0073] (3) Preparation of the color-changing electrolyte based on 1-butyl-4,4'-bipyridine: the difference from Example 1 is that the preparation process of the electrolyte in this example is as follows: 0.02 g of 1-butyl-4,4'-bipyridine, 0.2 g of potassium chloride and 0.01 g of ascorbic acid are dissolved in 5 mL of deionized water, and the mixture is stirred for 10 min and ultrasonically treated for 10 min to obtain the color-changing electrolyte.

[0074] (4) The packaging of the electrochromic device and the injection of the electrolyte solution are referred to Example 1.

[0075] Example 4:

[0076] This example provides an electrochromic device based on viologen derivative electrolyte and tungsten oxide hydrate thin film, and the specific preparation method is as follows:

[0077] (1) Preparation of the tungsten oxide hydrate thin film by electrodeposition method: the process parameters of constant voltage electrodeposition method and the preparation of electrolyte solution are both referred to Example 1.

[0078] (2) Preparation of 1-butyl-4,4'-bipyridine: the preparation method is referred to Example 1.

[0079] (3) Preparation of the color-changing electrolyte based on 1-butyl-4,4'-bipyridine: the difference from Example 1 is that the preparation process of the electrolyte in this example is as follows: 0.05 g of 1-butyl-4,4'-bipyridine, 0.2 g of zinc sulfate and 0.01 g of ascorbic acid are dissolved in 5 mL of deionized water, and the mixture is stirred for 10 min and ultrasonically treated for 10 min to obtain the color-changing electrolyte.

[0080] (4) The packaging of the electrochromic device and the injection of the electrolyte solution are referred to Example 1.

[0081] Comparative Example 1:

[0082] This comparative example provides an electrochromic device based on 1-butyl-4,4'-bipyridine color-changing electrolyte, and the specific preparation method is as follows:

[0083] (1) Preparation of 1-butyl-4,4'-bipyridine: 3.5 g of 1-iodobutane and 3 g of 4,4'-bipyridine were first dissolved in 10 mL of acetonitrile, and stirred at 60°C for 24 h. The obtained product was separated by a filtration step, and the filtrate was precipitated in diethyl ether. The obtained 1-butyl-4,4'-bipyridine precipitate was dried to obtain the desired orange viologen derivative for later use.

[0084] (2) Preparation of a color-changing electrolyte based on 1-butyl-4,4'-bipyridine: The electrolyte was composed of 1-butyl-4,4'-bipyridine, zinc chloride and ascorbic acid, and was prepared as follows: 0.04 g of 1-butyl-4,4'-bipyridine, 0.3 g of zinc chloride and 0.01 g of ascorbic acid were dissolved in 5 mL of deionized water, and the mixture was stirred for 10 min and ultrasonically treated for 10 min to obtain the color-changing electrolyte.

[0085] (3) First, a 2.5 x 5 cm 2 FTO conductive glass was subjected to alcohol washing, water washing and ultrasonic treatment, and dried to obtain an FTO conductive glass electrode. Two pieces of FTO conductive glass and 3M transparent double-sided tape with a width of 5 mm and a thickness of 1 mm were assembled to obtain an electrochromic device with a cavity area of 1.5 x 3 cm 2 .

[0086] (4) The electrolyte solution obtained in step (3) was injected into the cavity of the electrochromic device of step (4) to obtain an electrochromic device based on a 1-butyl-4,4'-bipyridine color-changing electrolyte.

[0087] Comparative Example 2:

[0088] This comparative example provides an electrochromic device based on a tungsten oxide hydrate film, and the specific preparation method is as follows:

[0089] (1) Preparation of a tungsten oxide hydrate film by electrodeposition: In a three-electrode system, a tungsten hexachloride solution with a set concentration, anhydrous ethanol, a hydrochloric acid solution and a hydrogen peroxide solution were used as the electrolyte, a transparent conductive substrate FTO glass was used as the working electrode, a platinum sheet was used as the counter electrode, and an Ag / AgCl electrode was used as the reference electrode. A tungsten oxide hydrate film was prepared by constant voltage electrodeposition, and an FTO glass with a tungsten oxide hydrate film was obtained.

[0090] The voltage of the constant voltage electrodeposition method was -0.6 V, and the electrodeposition time was 400 s.

[0091] The preparation method of the electrolyte was as follows: 0.7 g of tungsten hexachloride was dissolved in 25 mL of anhydrous ethanol, stirred for 30 min, and ultrasonically treated for 10 min; then 25 mL of a 0.7 mol / L hydrochloric acid solution and 2 mL of a hydrogen peroxide solution (concentration of 0.5 mol / L) were added, and stirred for 48 h to prepare the electrodeposition solution.

[0092] (2) First, 2.5x5cm 2 FTO conductive glass is subjected to alcohol washing, water washing and ultrasonic, and dried to obtain FTO conductive glass electrode. Two pieces of FTO conductive glass and 3M transparent double-sided adhesive with a width of 5mm and a thickness of 1mm are assembled to obtain an electrochromic device with a cavity area of 1.5x3cm 2 .

[0093] (3) A 1mol / L KCl electrolyte solution is injected into the cavity of the electrochromic device of step (2) to obtain an electrochromic device based on a tungsten oxide hydrate film.

[0094] The above electrochromic device is subjected to the following performance tests:

[0095] (1) Morphology characterization of tungsten oxide hydrate film: the surface morphology of the tungsten oxide hydrate film prepared in the present application is observed by scanning electron microscope.

[0096] (2) Transmittance curve and solar radiation spectrum of tungsten oxide hydrate film:

[0097] Test method: spectrophotometry, using a spectrophotometer, vertically irradiating the tungsten oxide hydrate film sample with light of continuous wavelength, measuring the intensity of light of different wavelengths after passing through the film, and calculating the transmittance at each wavelength by comparing with the incident light intensity.

[0098] Test instrument: electrochemical workstation, used in combination with spectrophotometer, to measure transmittance while applying a specific potential or current to the film to simulate its working state in the electrochromic device. The electrochemical workstation used is CHI series from Shanghai Chenhua.

[0099] Test conditions:

[0100] ① Environmental conditions: performed in an environment with room temperature (about 25℃) and relative humidity of 40-60% to avoid the influence of environmental factors on the performance of the film.

[0101] ② Light source conditions: the light source of the spectrophotometer needs to be preheated for 10-15min before testing to ensure the stability of the light source and the accuracy of the output intensity.

[0102] ③ Sample conditions: the film should be uniform and free of obvious defects, and needs to be fixed on a suitable sample holder to ensure that the light is vertically incident on the film surface. For electrochromic testing, the electrode should be in good contact with the film.

[0103] (3) Transmittance curve of electrochromic device:

[0104] Test method: static test method, when the electrochromic device is at a specific stable potential or color state, use a spectrophotometer to vertically irradiate the device with light of continuous wavelength, measure the intensity of light of different wavelengths after passing through the device, and calculate the transmittance at each wavelength by comparing with the incident light intensity, to obtain the transmittance curve at this state.

[0105] Test instrument: electrochemical workstation combined with spectrophotometer, used to apply specific potential or current to the electrochromic device to control its electrochromic state. Common brands include Shanghai Chenhua CHI series.

[0106] Test conditions:

[0107] ① Environmental conditions: the room temperature is 25℃, and the relative humidity is preferably maintained at 40-60%.

[0108] Electromagnetic interference: the test environment should be as far away as possible from large electrical equipment, transformers, etc. to avoid electromagnetic interference affecting the measurement results of the electrochemical workstation and the spectrophotometer.

[0109] ② Sample conditions:

[0110] Device installation: the electrochromic device needs to be firmly and flatly installed on the sample holder to ensure that the light can be vertically and uniformly irradiated to the surface of the device, avoiding the influence of light reflection, scattering, etc. caused by improper installation on the measurement results.

[0111] Electrode connection: the electrode connected with the electrochemical workstation needs to ensure good conductivity and stability, and the contact part of the electrode and the device should be clean to avoid oxidation, pollution, etc. affecting the transmission of electrical signals.

[0112] ③ Instrument conditions:

[0113] Light source preheating: before testing, the light source of the spectrophotometer needs to be preheated for 10-15min to ensure the stability of the light source and the accuracy of the output intensity.

[0114] Wavelength scanning speed: according to the test requirements, select the appropriate wavelength scanning speed, too fast scanning speed may affect the measurement accuracy, too slow scanning speed will prolong the test time. The scanning speed can be set at 100-500nm / min.

[0115] Result analysis:

[0116] Firstly, the surface morphology and optical properties of the tungsten oxide hydrate film prepared in Example 1 are explored. Figure 1 In the SEM photos of FIGS. 1 and 2, Figure 1 As can be seen from a and b, the tungsten oxide hydrate film shows a uniform surface and a dense structure, which helps to increase the specific surface area of the film, increase the ion exchange sites, and improve the electrochromic performance (response speed, light modulation amplitude).Figure 1 It can be seen that the thickness of the thin film is 310.4 nm, the cross-sectional structure is uniform, the thin film is relatively stable during growth, and the optical performance of each region of the thin film is ensured to be consistent.

[0117] The content of tungsten hexachloride directly affects the morphology (porous / dense) and performance (response speed, light modulation amplitude) of the hydrated tungsten oxide by regulating the film growth rate and particle agglomeration state. The microstructure is the result of the combined action of many factors such as preparation process, hydration degree, doping, and heat treatment. These factors ultimately determine the core properties such as electrochromic and optical properties by changing the grain size, porosity, and crystallinity.

[0118] Figure 2 The light modulation amplitude and solar radiation diagram of the hydrated tungsten oxide thin film prepared for the example have a large light modulation amplitude in the visible and near-infrared regions. Figure 2 In a, the transmittance of the hydrated tungsten oxide thin film in the initial state and the bleached state is close (good light transmittance), the transmittance in the colored state is significantly reduced, and the light modulation amplitude (ΔT) at 705 nm, 970 nm, and 1200 nm is 82.4%, 87.4%, and 98.4%, respectively. Figure 2 b shows that the bleached thin film can transmit a large amount of solar radiation (including visible light and near-infrared), and the colored thin film can significantly block visible light and near-infrared radiation. ΔT>70% in the visible region and ΔT>80% in the near-infrared region are excellent. In summary, the thin film of the present application has excellent spectral selectivity modulation capability and high light modulation amplitude, and has significant application potential in the field of intelligent energy-saving windows.

[0119] Figure 3 The transmittance curve of the electrochromic device prepared for Example 3 under different voltages. With the increase of voltage, the transmittance of the electrochromic device decreases in the visible and near-infrared regions. The initial state of the hydrated tungsten oxide thin film has a wide spectrum and high transmittance, and the maximum transmittance in the visible region (500-700 nm) and near-infrared region (1200 nm) is about 75% and 35%, respectively. When a +1.8V oxidation voltage is applied, the thin film is oxidized and bleached (W 5+ →W 6+ ), the transmittance in the near-infrared region (800-1200 nm) is significantly restored (1200 nm is consistent with the initial state ≈35%), which reflects the high transmittance of the bleached state to infrared radiation; when a -1.0V to -1.8V reduction voltage is applied, the thin film undergoes reduction and coloring (W 6+ →W 5+ / W 4+), the transmittance continuously attenuates with negative voltage shift; the coloration degree is the deepest at -1.8 V, and the transmittance in the visible region (400 nm) is about 25%, and the transmittance in the near-infrared region (800-1200 nm) is as low as 5-10%, realizing strong absorption in a wide spectrum. In summary, the thin film realizes transmittance modulation between the colored state and the bleached state through the voltage-driven redox reaction, and exhibits excellent electrochromic spectral response characteristics, providing voltage-controllable light transmission / heat insulation function switching capability for intelligent light control devices (such as energy-saving windows).

[0120] Figure 4 The color change photo of the electrochromic device prepared in Example 4 can be seen, and the bleached state (initial state) is colorless. When the coloration voltage is 1.8 V, the electrochromic device is purple; when the coloration voltage is -1.2 V, the electrochromic device is blue; and when the coloration voltage is -1.8 V, the electrochromic device is purple black. The above dynamic color change process shows that the electrochromic device prepared by the present application can dynamically change its color following the dynamic change of the coloration voltage, and has excellent color change effect.

[0121] Figure 5 The transmittance curve of the electrochromic device based on the 1-butyl-4,4'-bipyridine color-changing electrolyte (without tungsten oxide hydrate film) prepared in Comparative Example 1. The transmittance difference of the device in the long-wave region of 800-1000 nm is only 35%, the long-wave modulation ability is weak, the energy saving effect is limited when adapting to intelligent window heat insulation and other scenes; the spectral response is uneven, the light modulation amplitude of the short-wave band (400-600 nm) is about 25%, the medium-wave band (600-800 nm) is about 55%, and the long-wave band is reduced to 35%, the full-spectrum modulation is poor, which is not conducive to color display and other scenes with high uniformity requirements; the maximum light modulation amplitude in the medium-wave band is about 55%, which is difficult to meet the needs of high-end scenes such as high-contrast display.

[0122] Figure 6 The transmittance curve of the electrochromic device based on the tungsten oxide hydrate film (without 1-butyl-4,4'-bipyridine color-changing electrolyte) prepared in Comparative Example 2. As can be seen from the figure, the device has obvious short board in two-state regulation, and can only switch between the bleached state (high transmittance) and the colored state (low transmittance), and cannot realize gradient dimming; the transmittance of the bleached state and the colored state in the short-wave 400-500 nm region is about 75% and 50% respectively, and the maximum light modulation amplitude is only 25%, which is insufficient for blue light and other short-wave regulation.

[0123] The foregoing description of the embodiments has been presented for the purpose of illustration and description. It is not intended to be exhaustive or to limit the application to the precise form disclosed. Modifications and variations are possible in light of the above teachings or can be acquired from practice of the application. As well, the description is presented in the context of the preferred embodiments as a number of alternatives. It is not intended to limit the application to the precise form described.

Claims

1. An electrochromic device based on a viologen derivative electrolyte and a hydrated tungsten oxide thin film, characterized in that: The electrochromic device comprises an electrochromic device body having a cavity and a color-changing electrolyte disposed in the cavity; the electrochromic device body is composed of a blank transparent conductive glass and a conductive glass with a hydrated tungsten oxide film; The color-changing electrolyte comprises the following components in parts by weight: 2-5 parts of a viologen derivative, 20-50 parts of a water-soluble metal salt, and 1-5 parts of ascorbic acid.

2. The electrochromic device based on a viologen derivative electrolyte and a hydrated tungsten oxide thin film according to claim 1, characterized in that: The electrochromic device is colorless in an initial state or when faded; When the coloring voltage is positive, only the color-changing electrolyte is colored and the color changes to purple; When the coloring voltage is negative, both the color-changing electrolyte and the hydrated tungsten oxide film are colored, and the color changes to purple-black.

3. The electrochromic device based on a viologen derivative electrolyte and a hydrated tungsten oxide thin film according to claim 1, characterized in that: The conductive glass includes fluorine-doped tin oxide glass or indium tin oxide glass; The blank transparent conductive glass and the conductive glass with the hydrated tungsten oxide film are connected via an adhesive medium, and the adhesive medium includes one or more of double-sided adhesive, glass adhesive, adhesive tape or glue.

4. The electrochromic device based on a viologen derivative electrolyte and a hydrated tungsten oxide thin film according to claim 1, characterized in that: The viologen derivative has the following general structural formula: Where R is C 2-6 of alkyl.

5. The electrochromic device based on a viologen derivative electrolyte and a hydrated tungsten oxide thin film according to claim 1, characterized in that: The viologen derivative is prepared by the following method: The halogenated alkane and 4,4'-bipyridine are mixed in an organic solvent and stirred under heating conditions to react; the reaction system is separated into solid and liquid, the separated filtrate is precipitated in an ether solvent, and the precipitate is dried to obtain the viologen derivative; The general structural formula of the halogenated alkane is XR; wherein X is any one of chlorine, bromine, and iodine, and R is C 2-6 of alkyl.

6. The electrochromic device based on a viologen derivative electrolyte and a hydrated tungsten oxide thin film according to claim 5, characterized in that: The organic solvent includes any one or more of acetonitrile, ethanol, tetrahydrofuran, dimethyl sulfoxide, N,N-dimethylformamide and dichloromethane; The heating temperature is 50-70°C; The reaction time is 24-72h.

7. The electrochromic device based on a viologen derivative electrolyte and a hydrated tungsten oxide thin film according to claim 1, characterized in that: The metal element in the water-soluble metal salt is any one or more of potassium, sodium, zinc, magnesium and calcium; The water-soluble metal salt is any one or more of chloride, nitrate and sulfate.

8. A method for preparing an electrochromic device based on a viologen derivative electrolyte and a hydrated tungsten oxide thin film according to any one of claims 1 to 7, characterized in that: The preparation method comprises the following steps: S1: Deposition of hydrated tungsten oxide thin film on transparent conductive glass; S2: Assembling the conductive glass deposited with the hydrated tungsten oxide thin film and a blank transparent conductive glass to obtain an electrochromic device body with a cavity; S3: injecting a color-changing electrolyte into the cavity of the electrochromic device body to obtain the electrochromic device.

9. The method for preparing an electrochromic device based on a viologen derivative electrolyte and a hydrated tungsten oxide thin film according to claim 8, characterized in that: In step S1, the deposition is carried out by constant voltage electrodeposition method, and the specific steps are as follows: In a three-electrode system, transparent conductive glass is used as the working electrode, platinum sheet is used as the counter electrode, and Ag / AgCl electrode is used as the reference electrode. Electrodeposition is carried out in an electrolyte containing tungsten salt, hydrogen peroxide and acidic electrolyte.

10. The method for preparing an electrochromic device based on a viologen derivative electrolyte and a hydrated tungsten oxide thin film according to claim 9, characterized in that: The voltage of the constant voltage electrodeposition is -0.5 to -0.8 V, and the deposition time is 400 to 600 s; The molar ratio of tungsten element to hydrogen peroxide in the tungsten salt is (1.5-2.5):1; The tungsten salt includes any one or more of tungsten hexachloride, tungsten nitrate, sodium tungstate dihydrate, sodium tungstate, ammonium metatungstate, tungstic acid peroxide and organic tungsten salt; The pH of the electrolyte is adjusted to 1-2 by using any one or more of hydrochloric acid, sulfuric acid and nitric acid.

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