A hexagonal phase tungsten oxide electrochromic thin film, a preparation method thereof and application thereof

Abstract

The present application relates to a kind of hexagonal phase tungsten oxide electrochromic film and its preparation method and its application, above-mentioned preparation method includes the following steps: ammonium tungstate, ammonium sulfate and oxalic acid are dissolved according to certain proportion, and WO3 precursor sol is formed by reaction configuration;WO3 precursor sol is coated on conductive substrate, and the conductive substrate containing WO3 seed on surface is obtained;Ammonium tungstate, ammonium sulfate and oxalic acid are dissolved in deionized water according to certain proportion, precursor mixed solution is obtained, and precursor mixed solution is transferred to hydrothermal reactor;Again, the conductive substrate containing WO3 seed is vertically placed in hydrothermal reactor, the reactor is sealed in oven and reacted for a period of time, then the conductive substrate is taken out, cleaned, dried, and the film is removed, a kind of hexagonal phase WO3 electrochromic film can be obtained.The WO3 electrochromic film synthesized by the above method has better optical modulation capacity.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrochromic devices, and particularly relates to a hexagonal phase tungsten oxide electrochromic thin film prepared by a seed-assisted hydrothermal method and a preparation method and application thereof. BACKGROUND

[0002] Electrochromism is a phenomenon that the optical properties of materials such as transmittance, reflectance and absorptance change stably and reversibly with the applied electric field. Therefore, electrochromic materials have high practical application value in intelligent windows, electrochromic display devices, anti-dazzling rearview mirrors and spacecraft thermal control devices. The tungsten oxide (WO3) electrochromic thin film has good electron and ion conductivity, high coloring efficiency, large optical modulation amplitude and good cycle stability, and is one of the earliest discovered and most widely studied cathode electrochromic materials.

[0003] The performance of electrochromic devices depends on the preparation quality of electrochromic materials. Because the parameters and conditions of different methods are not the same, the performance of the prepared WO3 thin film also has great differences, so it is very important to find the best preparation method of WO3 thin film. Common preparation methods of WO3 thin film include spin coating, magnetron sputtering, sol-gel method, electrochemical deposition and hydrothermal method. Among them, the hydrothermal method has attracted widespread attention because of its low energy consumption, simple process and no need for special preparation environment. On the other hand, the performance of electrochromic devices depends largely on their size, morphology and crystallinity. One-dimensional semiconductor nanostructure (nanorod, nanowire, nanotube, etc.) array based on conductive substrate has been proved to be an optimized electrode structure because the electronic transmission speed of one-dimensional nano-material is faster.

[0004] However, the one-dimensional nanostructure of WO3 prepared by the hydrothermal method is usually randomly oriented or assembled from the substrate, which is easy to cause the stacking of WO3, and the active surface area is not fully utilized; in addition, the contact between the WO3 thin film and the conductive substrate is poor. These shortcomings will affect the coloring and bleaching response time and coloring efficiency of the WO3 film. Therefore, it is urgent to develop a simple, low-energy and low-cost strategy for preparing high-performance WO3 electrochromic thin film. SUMMARY

[0005] In view of the above problems, a simple, low-energy and low-cost method for preparing high-performance WO3 electrochromic thin film is provided. The method has simple process, is easy to repeat and has good consistency, and the light modulation capacity of the prepared WO3 electrochromic thin film is improved.

[0006] The specific technical solutions are as follows:

[0007] The first aspect of this invention is to provide a method for preparing a hexagonal phase WO3 electrochromic thin film, comprising the following steps:

[0008] 1) (NH4) 10 W 12 O 41 (NH4)2SO4 and H2C2O4 are dissolved in deionized water in a certain proportion to obtain a mixed solution. The mixed solution is then placed in an oven and reacted for a period of time to form a WO3 precursor sol. The WO3 precursor sol is coated on a conductive substrate, and the conductive substrate is then annealed at a certain temperature to obtain a conductive substrate with WO3 seed crystals on the surface.

[0009] 2) (NH4) 10 W 12 O 41 (NH4)2SO4 and H2C2O4 are dissolved in deionized water in a certain proportion to obtain a precursor mixed solution. The precursor mixed solution is transferred to a hydrothermal reactor. The conductive substrate containing WO3 seeds obtained in step 1) is then placed vertically in the hydrothermal reactor. The reactor is sealed and placed in an oven for a period of time. After that, the conductive substrate is taken out, cleaned, dried, and the film is removed to obtain a hexagonal phase WO3 electrochromic film.

[0010] Specifically, in steps 1) and 2) (NH4) 10 W 12 O 41 The molar ratio of (NH4)2SO4 to H2C2O4 is (0.3-2.0):(50-70):(10-30).

[0011] Specifically, in step 1), the temperature inside the oven is 40-60℃, and the reaction time is 1-5 hours.

[0012] Specifically, in step 1), the annealing temperature is 200-500℃ and the annealing time is 1-6h.

[0013] Specifically, in step 2), the hydrothermal reaction temperature is 120-190℃ and the hydrothermal reaction time is 2-24h.

[0014] A second aspect of the present invention is to provide a hexagonal phase WO3 electrochromic thin film prepared by the above preparation method.

[0015] A third aspect of the present invention is to provide an application of the above-mentioned hexagonal WO3 electrochromic thin film in electrochromic devices, smart glass and other fields.

[0016] A fourth aspect of the present invention is to provide an electrochromic device comprising the above-described hexagonal WO3 thin film.

[0017] The fifth aspect of the present application provides a smart glass comprising the above-mentioned hexagonal phase WO3 film.

[0018] The above-mentioned scheme has the following advantages:

[0019] 1) The present application adopts a seed-assisted hydrothermal method to prepare a hexagonal tungsten oxide electrochromic film, and the above-mentioned preparation method has the advantages of simple process, easy repeatability, low energy consumption and low cost, and is conducive to large-scale industrial production.

[0020] 2) The hexagonal WO3 electrochromic film prepared by the present application has good optical modulation performance. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 X-ray diffraction patterns of the samples prepared in the examples and comparative examples;

[0022] Figure 2 The transmittance graph of the hexagonal phase WO3 electrochromic film prepared in Example 1 in the visible light band in the colored state and the bleached state;

[0023] Figure 3 The transmittance graph of the hexagonal phase WO3 electrochromic film prepared in Example 3 in the visible light band in the colored state and the bleached state. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of the present application.

[0025] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0026] The present application will be further described below with reference to the drawings and specific embodiments, but is not limited by the present application.

[0027] Example 1

[0028] A hexagonal phase WO3 electrochromic film, the preparation thereof comprising the following steps:

[0029] 1) 0.3 mmol of (NH4)2WO4 was dissolved in 20 mL of deionized water to prepare a solution A; 10 W 12 O 41Ammonium tungstate, 50 mmol of ammonium sulfate (NH4)2SO4, and 10 mmol of oxalic acid (H2C2O4) were dissolved in 20 mL of deionized water to obtain a mixed solution. The mixed solution was placed in an oven at 40 °C for 2 h to form a WO3 precursor sol. The WO3 precursor sol was spin-coated onto FTO conductive glass using a homogenizer (at a speed of 2000 r / s). The spin-coated FTO glass was then dried in an oven at 90 °C. Finally, the WO3 film was placed in a tube furnace and air-annealed at 300 °C for 2 h to obtain FTO conductive glass with WO3 seed crystals on the surface.

[0030] 2) Add 0.3 mmol of (NH4) 10 W 12 O 41 50 mmol of (NH4)2SO4 and 10 mmol of H2C2O4 were dissolved in 20 mL of deionized water to obtain a precursor mixture solution. The precursor mixture solution was transferred to a hydrothermal reactor. The FTO conductive glass containing WO3 seeds obtained above was then placed vertically in the hydrothermal reactor. The reactor was placed in an oven at 130 °C for hydrothermal reaction for 4 h. After removal, the obtained glass film was cleaned with ethanol and dried at 90 °C. The film was then removed to obtain a hexagonal phase WO3 electrochromic film.

[0031] Example 2

[0032] A hexagonal phase WO3 electrochromic thin film is prepared by the following steps:

[0033] 1) Add 2.0 mmol of (NH4) 10 W 12 O 41 70 mmol of (NH4)2SO4 and 30 mmol of H2C2O4 were dissolved in 20 mL of deionized water to obtain a mixed solution. The mixed solution was placed in an oven at 40 °C for 4 h to form a WO3 precursor sol. The WO3 precursor sol was spin-coated onto FTO conductive glass using a homogenizer (rotation speed of 2000 r / s). The spin-coated FTO glass was then dried in an oven at 120 °C. Finally, the WO3 film was placed in a tube furnace and air-annealed at 500 °C for 5 h to obtain FTO conductive glass with WO3 seed crystals on the surface.

[0034] 2) Add 2.0 mmol of (NH4) 10 W 12 O 4170 mmol of (NH4)2SO4 and 30 mmol of H2C2O4 were dissolved in 20 mL of deionized water to obtain a precursor mixture solution. The precursor mixture solution was transferred to a hydrothermal reactor. The FTO conductive glass containing WO3 seeds obtained above was then placed vertically in the hydrothermal reactor. The reactor was placed in an oven at 180 °C for hydrothermal reaction for 12 h. After removal, the obtained glass film was cleaned with ethanol and dried at 120 °C. The film was then removed to obtain a hexagonal phase WO3 electrochromic film.

[0035] Example 3

[0036] A hexagonal phase WO3 electrochromic thin film is prepared by the following steps:

[0037] 1) Add 1.0 mmol of (NH4) 10 W 12 O 41 60 mmol of (NH4)2SO4 and 20 mmol of H2C2O4 were dissolved in 20 mL of deionized water to obtain a mixed solution. The mixed solution was placed in an oven at 40 °C for 3 h to form a WO3 precursor sol. The WO3 precursor sol was spin-coated onto FTO conductive glass using a homogenizer (rotation speed of 2000 r / s). The spin-coated FTO glass was then dried in an oven at 110 °C. Finally, the WO3 film was placed in a tube furnace and air-annealed at 400 °C for 5 h to obtain FTO conductive glass with WO3 seed crystals on the surface.

[0038] 2) Add 1.0 mmol of (NH4) 10 W 12 O 41 60 mmol of (NH4)2SO4 and 20 mmol of H2C2O4 were dissolved in 20 mL of deionized water to obtain a precursor mixture solution. The precursor mixture solution was transferred to a hydrothermal reactor. The FTO conductive glass containing WO3 seeds obtained above was then placed vertically in the hydrothermal reactor. The reactor was placed in an oven at 150 °C for hydrothermal reaction for 8 h. After removal, the obtained glass film was cleaned with ethanol and dried at 110 °C. The film was then removed to obtain a hexagonal phase WO3 electrochromic film.

[0039] Comparative Example 1

[0040] This comparative example is basically the same as Example 1, except for (NH4). 10 W 12 O 41 The amounts of (NH4)2SO4 and H2C2O4 added were 3.0 mmol, 80 mmol, and 40 mmol, respectively, and other conditions were exactly the same as in Example 1.

[0041] Comparative Example 2

[0042] This comparative example is basically the same as Example 1, except that the ammonium salt added to the precursor mixture solution is 50 mmol of ammonium persulfate ((NH4)2S2O8), and the other conditions are exactly the same as those in Example 1.

[0043] Comparative Example 3

[0044] This comparative example is basically the same as Example 1, except that the acid added to the precursor mixture solution is 10 mmol hydrochloric acid (HCl), and the other conditions are exactly the same as in Example 1.

[0045] XRD tests were performed on the samples prepared in Implementation Cases 1-3 and Comparative Cases 1-3, and the results are as follows: Figure 1 As shown, the results indicate that hexagonal WO3 electrochromic films were synthesized in all three implementation cases, but no hexagonal WO3 electrochromic films were synthesized in the control cases.

[0046] The transmittance results of the colored and faded states of the hexagonal WO3 electrochromic films prepared in Example 1 and Example 3 in the visible light band are as follows: Figure 2 and Figure 3 As shown. By Figure 2 and Figure 3 It can be seen that the hexagonal WO3 electrochromic film prepared in Example 1 has an optical modulation range of 61.4% at 750 nm. The hexagonal WO3 electrochromic film prepared in Example 3 has an optical modulation range of 64.6% at 750 nm. This indicates that the hexagonal WO3 electrochromic film prepared by seed hydrothermal assistance has good optical modulation performance and can therefore be applied in electrochromic devices and smart glass.

[0047] The above description is merely a preferred embodiment of the present invention and does not limit the implementation and protection scope of the present invention. Those skilled in the art should realize that any equivalent substitutions and obvious changes made based on the description and illustrations of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a hexagonal phase WO3 electrochromic thin film, characterized in that, Includes the following steps: 1) (NH4) 10 W 12 O 41 (NH4)2SO4 and H2C2O4 are dissolved in deionized water in a certain proportion to obtain a mixed solution. The mixed solution is then placed in an oven and reacted for a period of time to form a WO3 precursor sol. The WO3 precursor sol is coated on a conductive substrate, and the conductive substrate is then annealed at a certain temperature to obtain a conductive substrate with WO3 seed crystals on the surface. 2) (NH4) 10 W 12 O 41 (NH4)2SO4 and H2C2O4 are dissolved in deionized water in a certain proportion to obtain a precursor mixed solution. The precursor mixed solution is transferred to a hydrothermal reactor. The conductive substrate containing WO3 seeds obtained in step 1) is then placed vertically in the hydrothermal reactor. The reactor is sealed and placed in an oven for a period of time. After that, the conductive substrate is taken out, cleaned, dried, and the film is removed to obtain a hexagonal phase WO3 electrochromic film. In steps 1) and 2), (NH4) 10 W 12 O 41 The molar ratio of (NH4)2SO4 to H2C2O4 is (0.3-2.0): (50-70): (10-30).

2. The preparation method according to claim 1, characterized in that, In step 1), the temperature inside the oven is 40-60 ℃, and the reaction time is 1-5 h.

3. The preparation method according to claim 1, characterized in that, In step 1), the annealing temperature is 200-500 ℃ and the annealing time is 1-6 h.

4. The preparation method according to claim 1, characterized in that, In step 2), the hydrothermal reaction temperature is 120-190℃ and the hydrothermal reaction time is 2-24 h.

5. A hexagonal phase WO3 electrochromic thin film, characterized in that, Obtained by the preparation method according to any one of claims 1-4.

6. The application of the hexagonal WO3 electrochromic thin film as described in claim 5 in the fields of electrochromic devices and smart glass.

7. An electrochromic device, characterized in that, Including the hexagonal phase WO3 electrochromic thin film as described in claim 5.

8. A type of smart glass, characterized in that, It includes the hexagonal phase WO3 electrochromic thin film as described in claim 5.

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