A tungsten trioxide electrochromic thin film with a high modulation ratio and a preparation method thereof

Abstract

The present invention provides a high modulation ratio tungsten trioxide electrochromic thin film and a preparation method thereof. The preparation method includes weighing Na2WO4·2H2O and dissolving it into a sodium tungstate solution; adding strong acid dropwise to the sodium tungstate solution for a metathesis reaction to obtain a tungstic acid solution, and then decomposing the tungstic acid solution by oil bath heating to obtain flaky WO3; drying the flaky WO3 to obtain WO3 nano powder; adding the WO3 nano powder and ITO nano powder to a film-forming agent according to a preset ratio, and after ultrasonic cleaning machine oscillation dispersion and ball milling, forming an ITO / WO3 dispersion; spin-coating the ITO / WO3 dispersion on ITO conductive glass on a spin coater and calcining to obtain an electrochromic thin film. The electrochromic thin film prepared by the present invention has a light modulation amplitude of up to 91% in the visible light band and a significantly improved coloring efficiency, and this method has a high yield and is suitable for large-scale preparation.

Description

Technical Field

[0001] The present invention relates to the technical field of inorganic nano electrochromic materials, and particularly relates to a high modulation ratio tungsten trioxide electrochromic thin film and a preparation method thereof. Background Art

[0002] An electrochromic material refers to a material whose color can reversibly change under the action of an external electric field. Nano tungsten trioxide is considered to be the most promising inorganic electrochromic material because of its low preparation cost, stable chemical properties, fast response time, and good cycle stability. In past studies, people have effectively regulated and optimized the performance of tungsten trioxide, such as the light modulation amplitude, response time, and coloring efficiency, through different methods, such as chemical doping, crystal morphology control, and the combination of crystalline and amorphous states.

[0003] For example, Patent CN 107216045 A proposes a method for growing a tungsten trioxide nano thin film by growing a seed layer on a conductive glass and then immersing the conductive glass with the grown seed layer in a precursor solution for hydrothermal reaction. Although this method obtains an electrochromic glass with a high coloring / fading modulation ratio (about 72.7%) near the wavelength of 633 nm and fast coloring / fading response, this method is restricted by the space volume of the hydrothermal reaction kettle due to the sample size, so this electrochromic glass is not suitable for large-scale and large-area mass production.

[0004] Patent CN 108863101B adds PEO to the precursor and generates CO2 and H2O gases through high-temperature annealing to form a porous and high specific surface area WO3 thin film, greatly increasing the contact area between the electrolyte and WO3, and obtaining an electrochromic thin film with a coloring / fading modulation ratio of up to about 63%. The modulation ratio of the electrochromic thin film prepared by this preparation method is still relatively low.

[0005] Patent CN 114180850 A uses an electrochemical deposition method to introduce crystal vanadium doping into the crystalline tungsten trioxide thin film to prepare an electrochromic thin film. Although the preparation method is simple and easy to obtain, its optical modulation ability is very limited (about 16.5% at 633 nm).

[0006] Therefore, the present invention proposes a high modulation ratio tungsten trioxide electrochromic thin film and a preparation method thereof that can improve the electrochemical performance of WO3, enhance the modulation ability and coloring efficiency of electrochromism. Summary of the Invention

[0007] Based on this, the object of the present invention is to provide a tungsten trioxide electrochromic film with a high modulation ratio and a preparation method thereof. By introducing the conductive material ITO nanoparticles and doping them into WO3 nanosheets through mechanical doping, the conductivity of the electrochromic material nano-WO3 and the transparent electrode ITO substrate is improved by utilizing the conductivity of ITO nanoparticles, so as to achieve the purpose of improving key indicators such as the electrochemical performance of WO3, enhancing the modulation ability and coloring efficiency of electrochromism, and a tungsten trioxide electrochromic film with a high modulation ratio with a light modulation amplitude of up to 91% and a coloring efficiency of up to 133.5 cm 2 / C is prepared by spin-coating a mixed solution, and the mixed solution can be coated on a transparent conductive substrate by a wire bar method to achieve large-area preparation, so as to solve the deficiencies in the above related technologies.

[0008] On the one hand, the present invention proposes a preparation method of a tungsten trioxide electrochromic film with a high modulation ratio, and the preparation method includes the following steps:

[0009] (1) Weigh a preset mass of Na2WO4·2H2O, put it into a round-bottom flask filled with deionized water, and stir magnetically at room temperature until completely dissolved to obtain a sodium tungstate solution;

[0010] (2) Dropwise add nitric acid or sulfuric acid to the sodium tungstate solution for a double decomposition reaction to obtain a tungstic acid solution, and then decompose the tungstic acid solution by oil bath heating to obtain flaky WO3;

[0011] (3) Dry the flaky WO3 to obtain WO3 nano powder;

[0012] (4) Add the WO3 nano powder and ITO nano powder to a film-forming agent in a preset ratio, stir evenly, disperse by oscillating in an ultrasonic cleaner, and then put it into a ball mill for ball milling to uniformly disperse the ITO nano powder into the WO3 nano powder to form ITO-doped WO3 nanosheets, and obtain an ITO / WO3 dispersion;

[0013] (5) Spin-coat the ITO / WO3 dispersion on ITO conductive glass on a spin coater and calcine it in a muffle furnace to obtain an electrochromic film.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: By means of mechanical doping, conductive nanoparticles ITO are doped into WO3 nanosheets to form ITO-doped WO3 nanosheets. The prepared ITO-doped WO3 nanosheets are added with a dispersant and ball-milled to form a nano-ITO / WO3 dispersion liquid. Then, it is stirred and mixed evenly with an appropriate amount of film-forming agent, spin-coated on ITO conductive glass and calcined. Tests show that the electrochromic film prepared by this method has a light modulation amplitude of up to 91% in the visible light band and a significantly improved coloring efficiency. The WO3 prepared by the liquid-phase method has a high yield, requires simple equipment and is prepared under low-pressure conditions, and a relatively uniform electrochromic film can be obtained. Therefore, the high-modulation ratio tungsten trioxide electrochromic film prepared by the present invention has a high yield and is suitable for large-scale preparation.

[0015] Preferably, in the step (2), sulfuric acid with a mass fraction of 96% - 98% or nitric acid with a mass fraction of 68% is added dropwise to the sodium tungstate solution for a metathesis reaction to obtain a tungstic acid solution. The dropping rate of nitric acid or sulfuric acid is controlled to keep the temperature of the tungstic acid solution below 80°C, and it is refluxed and condensed at a temperature below 160°C in an oil bath for 4.5 h. After it is cooled to room temperature, flaky WO3 is obtained.

[0016] Preferably, the step (3) includes: centrifugally washing the flaky WO3 with deionized water and absolute ethanol repeatedly for 3 times respectively to obtain WO3 nanosheets, and drying the WO3 nanosheets in a drying oven at 60°C for 12 h to obtain WO3 nano-powder.

[0017] Preferably, in the step (4), the preset ratio is 76%:24% - 92%:8%.

[0018] Preferably, in the step (4), the film-forming agent is obtained by adding polyethylene glycol 600 and dispersant BYK2013 in a ratio of 3:2 to absolute ethanol and stirring evenly.

[0019] Preferably, in the step (4), the length and width range of the ITO-doped WO3 nanosheets is 400 nm - 600 nm, and the thickness range is 150 nm - 240 nm.

[0020] Preferably, in the step (4), the oscillation and dispersion time of the ultrasonic cleaner is 20 min, the rotation speed of the ball mill is 400 r / min, and the ball milling time is 6 h.

[0021] Preferably, before the step (5), the method further includes: ultrasonically cleaning the ITO conductive glass in acetone, absolute ethanol, and deionized water for 20 min respectively, and drying it in a drying oven for later use.

[0022] Preferably, in the step (5), the rotational speed of the spin coater is 4000 r / min, the temperature of the muffle furnace is 300 °C, and the calcination time is 1 h.

[0023] On the other hand, the present invention provides a tungsten trioxide electrochromic film with a high modulation ratio, which is prepared by using the above-mentioned preparation method of the tungsten trioxide electrochromic film with a high modulation ratio. Description of the Drawings

[0024] Figure 1 It is the XRD test result diagram of the ITO-doped WO3 nanosheets provided in the first embodiment of the present invention;

[0025] Figure 2 It is the SEM test diagram of the ITO-doped WO3 nanosheets provided in the first embodiment of the present invention;

[0026] Figure 3 It is the cyclic voltammetry curve (C-V curve) diagram of the electrochromic films provided in the embodiments and the control example of the present invention;

[0027] Figure 4 It is the transmission spectrum diagram of the electrochromic films provided in the embodiments and the control example of the present invention in the colored state and the bleached state;

[0028] Figure 5 It is the test result diagram of the coloring efficiency of the electrochromic films provided in the embodiments and the control example of the present invention.

[0029] The following specific embodiments will further illustrate the present invention in conjunction with the above-mentioned drawings. Specific Embodiments

[0030] Example 1

[0031] A preparation method of a tungsten trioxide electrochromic film with a high modulation ratio, the preparation method comprising the following steps:

[0032] (1) Weigh 2.64 g of Na2WO4·2H2O, put it into a round-bottom flask containing 80 mL of deionized water, and magnetically stir it at room temperature for 10 min until it is completely dissolved to obtain a sodium tungstate solution;

[0033] (2) Dropwise add 80 mL of sulfuric acid with a mass concentration of 96% - 98% or 68% nitric acid to the sodium tungstate solution for a metathesis reaction to obtain a tungstic acid solution. Control the dropping rate of the strong acid to keep the temperature of the tungstic acid solution below 80 °C, and carry out condensation reflux at 160 °C or below in an oil bath for 4.5 h. After it cools to room temperature, obtain flaky WO3;

[0034] (3) Wash the flaky WO3 with deionized water and absolute ethanol by centrifugation three times respectively to obtain WO3 nanosheets. Put the WO3 nanosheets into a drying oven and dry at 60 °C for 12 h to obtain light yellow WO3 nano-powder;

[0035] (4) Add 1 g of the WO3 nano-powder and ITO nano-powder in a ratio of 92%:8% to a film-forming agent, stir evenly, disperse by oscillation in an ultrasonic cleaner for 20 min, and then ball-mill in a ball mill at 400 r / min for 6 h to uniformly disperse the ITO nano-powder into the WO3 nano-powder, forming ITO-doped WO3 nanosheets and obtaining an ITO / WO3 dispersion. The film-forming agent is obtained by adding 0.27 g of polyethylene glycol 600 and 0.18 g of dispersant BYK2013 to 8.55 g of absolute ethanol and stirring evenly;

[0036] (5) Ultrasonically clean the ITO conductive glass in acetone, absolute ethanol, and deionized water for 20 min each, and place it in a drying oven to dry for later use;

[0037] (6) Spin-coat the ITO / WO3 dispersion on the ITO conductive glass at a speed of 4000 r / min on a spin coater, and calcine in a muffle furnace at 300 °C for 1 h to obtain an electrochromic film;

[0038] In step (4), the ITO nano-powder is uniformly dispersed into the WO3 nano-powder to form ITO-doped WO3 nanosheets. Perform XRD testing on the ITO-doped WO3 nanosheets and generate corresponding test results. The test results are as Figure 1 shown, Figure 1 in which the spectral lines a and b represent the data of the standard card WO3 (JCPDS No. 87-2385) and the data of the standard card In2O3 (JCPDS No. 65-3170) respectively. In2O3 is the main component of ITO. The curves c and d represent the test data of undoped ITO and doped ITO WO3 respectively. From Figure 1 the XRD test data shown, Figure 1 it can be seen that the spectrum shown by curve d in

[0039] matches the JCPDS card number, indicating that ITO has been successfully doped into the WO3 nanosheets, so as to be mixed with the film-forming agent to form an ITO / WO3 dispersion and spin-coated on the ITO conductive glass, and an electrochromic film is obtained after calcination. Figure 2 At the same time, it can be known from

[0040] Example 2

[0041] A preparation method of a tungsten trioxide electrochromic film with a high modulation ratio, the preparation method comprising the following steps:

[0042] (1) Weigh 2.64 g of Na2WO4·2H2O, put it into a round-bottom flask containing 80 mL of deionized water, and magnetically stir at room temperature for 10 min until completely dissolved to obtain a sodium tungstate solution;

[0043] (2) Dropwise add 80 mL of sulfuric acid with a mass concentration of 96% - 98% or 68% nitric acid to the sodium tungstate solution for a metathesis reaction to obtain a tungstic acid solution. Control the dropping rate of the strong acid to keep the temperature of the tungstic acid solution below 80 °C, and carry out condensation reflux in an oil bath at a temperature below 160 °C for 4.5 h. After it cools to room temperature, obtain flaky WO3;

[0044] (3) Centrifuge and wash the flaky WO3 with deionized water and absolute ethanol repeatedly 3 times each to obtain WO3 nanosheets. Put the WO3 nanosheets into a drying oven and dry at 60 °C for 12 h to obtain pale yellow WO3 nano-powder;

[0045] (4) Add a total of 1 g of the WO3 nano-powder and ITO nano-powder in a ratio of 84%:16% to a film-forming agent, stir evenly, disperse by ultrasonic cleaning machine for 20 min, and then put it into a ball mill at 400 r / min for ball milling for 6 h to uniformly disperse the ITO nano-powder into the WO3 nano-powder to form ITO-doped WO3 nanosheets and obtain an ITO / WO3 dispersion. The film-forming agent is obtained by adding 0.27 g of polyethylene glycol 600 and 0.18 g of dispersant BYK2013 to 8.55 g of absolute ethanol and stirring evenly;

[0046] (5) Ultrasonically clean the ITO conductive glass in acetone, absolute ethanol, and deionized water for 20 min each, and put it in a drying oven to dry for later use;

[0047] (6) Spin-coat the ITO / WO3 dispersion on the ITO conductive glass at a rotation speed of 4000 r / min on a spin coater, and calcine in a muffle furnace at 300 °C for 1 h to obtain an electrochromic film.

[0048] Example Three

[0049] A preparation method of a tungsten trioxide electrochromic film with a high modulation ratio, the preparation method comprising the following steps:

[0050] (1) Weigh 2.64 g of Na2WO4·2H2O, put it into a round-bottom flask containing 80 mL of deionized water, and magnetically stir at room temperature for 10 min until completely dissolved to obtain a sodium tungstate solution;

[0051] (2) Add 80 mL of sulfuric acid with a mass concentration of 96% - 98% or 68% nitric acid dropwise to the sodium tungstate solution for metathesis reaction to obtain tungstic acid solution. Control the dropping rate of the strong acid to keep the temperature of the tungstic acid solution below 80 °C, and carry out condensation reflux at 160 °C or below in an oil bath for 4.5 h. After it cools to room temperature, flaky WO3 is obtained.

[0052] (3) Wash the flaky WO3 with deionized water and absolute ethanol by centrifugation three times respectively to obtain WO3 nanosheets. Put the WO3 nanosheets into a drying oven and dry at 60 °C for 12 h to obtain light yellow WO3 nanopowder.

[0053] (4) Add 1 g of the WO3 nanopowder and ITO nanopowder in a ratio of 76%:24% to the film-forming agent, stir evenly, disperse by oscillation in an ultrasonic cleaner for 20 min, and then ball mill in a ball mill at 400 r / min for 6 h to uniformly disperse the ITO nanopowder into the WO3 nanopowder, forming ITO-doped WO3 nanosheets and obtaining an ITO / WO3 dispersion. The film-forming agent is obtained by adding 0.27 g of polyethylene glycol 600 and 0.18 g of dispersant BYK2013 to 8.55 g of absolute ethanol and stirring evenly.

[0054] (5) Ultrasonically clean the ITO conductive glass in acetone, absolute ethanol, and deionized water for 20 min respectively, and put it in a drying oven to dry for standby.

[0055] (6) Spin-coat the ITO / WO3 dispersion on the ITO conductive glass at a rotation speed of 4000 r / min on a spin coater, and calcine in a muffle furnace at 300 °C for 1 h to obtain an electrochromic film.

[0056] To further illustrate the preparation method of the high modulation ratio tungsten trioxide electrochromic film provided in each embodiment of the present invention, a control example is introduced in each embodiment of the present invention. The difference between the preparation method of the high modulation ratio tungsten trioxide electrochromic film provided in the control example and the preparation method of the high modulation ratio tungsten trioxide electrochromic film provided in the above embodiment is that: the doping ratio of the ITO nanopowder is 0%.

[0057] Perform cyclic voltammetry tests on the electrochromic films prepared in the above Example 1, Example 2, Example 3, and the control example, and the test results are as Figure 3 shown;

[0058] From Figure 3It can be seen that there are two cyclic voltammograms for Example 1, Example 2, Example 3, and the control example respectively. The area enclosed between the two cyclic voltammograms represents the electrochemistry activity of the corresponding sample. Therefore, the areas enclosed by the two cyclic voltammograms of the electrochromic films prepared from ITO-doped WO3 nanosheets doped with 16% ITO, the areas enclosed by the two cyclic voltammograms of the electrochromic films prepared from ITO-doped WO3 nanosheets doped with 8% ITO, the areas enclosed by the two cyclic voltammograms of the electrochromic films prepared from ITO-doped WO3 nanosheets doped with 24% ITO, and the areas enclosed by the two cyclic voltammograms of the electrochromic films prepared from ITO-doped WO3 nanosheets doped with 0% ITO are arranged in descending order, which represents the gradual decrease of the electrochemistry activity of the corresponding samples;

[0059] Therefore, it can be known that the electrochemistry activities of the electrochromic films prepared in Example 1, Example 2, and Example 3 are all better than those of the electrochromic film prepared in the control example. By comparing Example 1 and Example 3, it can be seen that the electrochemistry activity of the electrochromic film prepared in Example 2 of the present invention is the best.

[0060] After the electrochromic films are prepared, the electrochromic films prepared by the preparation method of the high modulation ratio tungsten trioxide electrochromic film provided in Example 1, Example 2, Example 3, and the control example are tested for the optical modulation amplitude and the coloring efficiency. The test results are as Figure 4 、 5 shown;

[0061] In Figure 4 , the solid line with symbols represents the transmittance of the electrochromic film in the colored state, and the dotted line with symbols represents the transmittance of the electrochromic film in the bleached state. The optical modulation amplitude is the difference between the transmittance of the electrochromic film in the colored state and the transmittance of the electrochromic film in the bleached state. In Figure 5 , the dotted line represents the optical density of the electrochromic film, and the solid line represents the coloring efficiency. The slope of the optical density curve corresponds to the coloring efficiency;

[0062] According to Figure 4 、 Figure 5 it can be known that for the electrochromic film prepared in the control example, the optical modulation amplitude at a wavelength of 633 nm is 52%, and the coloring efficiency is 51.34 cm 2 / C;

[0063] For the electrochromic film prepared in Example 1, the optical modulation amplitude at a wavelength of 633 nm is 81%, and the coloring efficiency is 64.8 cm 2 / C;

[0064] The electrochromic film prepared in Example 2 has a light modulation amplitude of 88% at a wavelength of 633 nm and a coloring efficiency of 133.5 cm 2 / C. Its light modulation amplitude reaches the maximum at a wavelength of 750 mm, and its light modulation amplitude is 91%.

[0065] The electrochromic film prepared in Example 3 has a light modulation amplitude of 71% at a wavelength of 633 nm and a coloring efficiency of 196.5 cm 2 / C;

[0066] Therefore, the light modulation amplitude and coloring efficiency of the electrochromic film prepared in this Example 1 are both superior to those of the electrochromic film prepared in the control example. Compared with the electrochromic film prepared in the control example, its light modulation amplitude at a wavelength of 633 nm is increased by 29%, and its coloring efficiency is increased by 13.46 cm 2 / C;

[0067] The light modulation amplitude and coloring efficiency of the electrochromic film prepared in this Example 2 are both superior to those of the electrochromic film prepared in the control example. Compared with the electrochromic film prepared in the control example, its light modulation amplitude at a wavelength of 633 nm is increased by 36%, and its coloring efficiency is increased by 82.16 cm 2 / C;

[0068] The light modulation amplitude and coloring efficiency of the electrochromic film prepared in this Example 3 are both superior to those of the electrochromic film prepared in the control example. Compared with the electrochromic film prepared in the control example, its light modulation amplitude at a wavelength of 633 nm is increased by 19%, and its coloring efficiency is increased by 145.16 cm 2 / C.

[0069] It should be noted that the embodiments of the present invention also provide a high modulation ratio tungsten trioxide electrochromic film, which is prepared by using the preparation method of the high modulation ratio tungsten trioxide electrochromic film provided in the above embodiments.

[0070] In summary, the electrochromic film prepared from ITO-doped WO3 nanosheets with 16% ITO doping has the best electrochemical performance, the highest light modulation amplitude of 91% at a wavelength of 750 nm, and a relatively high coloring efficiency of 133.53 cm 2 / C. In the present invention, by introducing the conductive material of ITO nanoparticles and doping them into WO3 nanosheets through mechanical doping, the conductivity of the electrochromic material nano-WO3 and the transparent electrode ITO substrate is improved by utilizing the conductivity of ITO nanoparticles, thereby achieving the purpose of improving key indicators such as the electrochemical performance of WO3, enhancing the electrochromic modulation ability and coloring efficiency, etc. And by means of spin-coating a mixed solution, a tungsten trioxide electrochromic thin film with good electrochemical performance, a light modulation amplitude of up to 91% in the visible light band, and a coloring efficiency of up to 133.5 cm 2 / C with a high modulation ratio is prepared. The mixed solution can be coated on the transparent conductive substrate by means of a wire bar, thereby realizing large-area preparation.

Claims

1. A preparation method of a tungsten trioxide electrochromic film with a high modulation ratio, characterized in that, The preparation method includes the following steps: (1) Weigh a preset mass of Na2WO4·2H2O, put it into a round-bottom flask filled with deionized water, and stir magnetically at room temperature until completely dissolved to obtain a sodium tungstate solution; (2) Dropwise add nitric acid or sulfuric acid to the sodium tungstate solution for a metathesis reaction to obtain a tungstic acid solution, and then decompose the tungstic acid solution by oil bath heating to obtain flaky WO3; (3) Dry the flaky WO3 to obtain WO3 nano powder; (4) Add the WO3 nano powder and ITO nano powder to a film-forming agent in a preset ratio, stir evenly, disperse by ultrasonic cleaning machine oscillation, and then put it into a ball mill for ball milling to uniformly disperse the ITO nano powder into the WO3 nano powder to form ITO-doped WO3 nano sheets and obtain an ITO / WO3 dispersion; (5) Spin-coat the ITO / WO3 dispersion on ITO conductive glass on a spin coater and calcine it in a muffle furnace to obtain an electrochromic film; In the step (2), dropwise add sulfuric acid with a mass fraction of 96% - 98% or nitric acid with a mass fraction of 68% to the sodium tungstate solution for a metathesis reaction to obtain a tungstic acid solution. Control the dropping rate of nitric acid or sulfuric acid to keep the temperature of the tungstic acid solution below 80°C, and carry out condensation reflux at 160°C or below in an oil bath for 4.5 h. After it cools to room temperature, obtain flaky WO3; The step (3) includes: repeatedly centrifugally wash the flaky WO3 with deionized water and absolute ethanol 3 times each to obtain WO3 nano sheets, and put the WO3 nano sheets into a drying oven at 60°C for drying for 12 h to obtain WO3 nano powder.

2. The preparation method of the high modulation ratio tungsten trioxide electrochromic film according to claim 1, characterized in that, In the step (4), the preset ratio is 76%:24% - 92%:8%.

3. The preparation method of the high modulation ratio tungsten trioxide electrochromic film according to claim 1, characterized in that, In the step (4), the film-forming agent is obtained by adding polyethylene glycol 600 and dispersant BYK2013 in a ratio of 3:2 to absolute ethanol and stirring evenly.

4. The preparation method of the high modulation ratio tungsten trioxide electrochromic film according to claim 1, characterized in that, In the step (4), the length and width range of the ITO-doped WO3 nano sheets is 400 nm - 600 nm, and the thickness range is 150 nm - 240 nm.

5. The preparation method of the high modulation ratio tungsten trioxide electrochromic film according to claim 1, characterized in that, In the step (4), the oscillation dispersion time of the ultrasonic cleaning machine is 20 min, the rotation speed of the ball mill is 400 r / min, and the ball milling time is 6 h.

6. The preparation method of the high modulation ratio tungsten trioxide electrochromic film according to claim 1, characterized in that, Before the step (5), the method further includes: ultrasonically clean the ITO conductive glass in acetone, absolute ethanol, and deionized water for 20 min each, and put it in a drying oven for drying for later use.

7. The preparation method of the high modulation ratio tungsten trioxide electrochromic film according to claim 1, characterized in that, In the step (5), the rotation speed of the spin coater is 4000 r / min, the temperature of the muffle furnace is 300°C, and the calcination time is 1 h.

8. A tungsten trioxide electrochromic film with a high modulation ratio, characterized in that, It is prepared by using the preparation method of the high modulation ratio tungsten trioxide electrochromic film according to any one of claims 1 to 7.

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