Tungsten oxide electrochromic thin film and preparation method thereof

Abstract

This invention provides a tungsten oxide electrochromic thin film and its preparation method. The method involves adding tungstate to deionized water and adding sulfuric acid solution to generate a precipitate; washing the precipitate to prepare a solution, adding hydrogen peroxide to obtain a transparent precursor solution; diluting to obtain solution A; adding an alcohol to obtain solution B; ultrasonically cleaning ITO conductive glass, drying it, and irradiating it under ultraviolet light; immersing the ITO conductive glass in a hydrothermal reactor containing solution B, maintaining the temperature, and cooling to room temperature to obtain an ITO substrate; removing the substrate, rinsing, and drying to obtain a deposited thin film; and annealing to obtain the tungsten oxide electrochromic thin film. The prepared thin film exhibits a coloring efficiency (CE) of 150-170 cm⁻¹. 2 ·C- 1 The electrochromic cycle stability can reach 20,000 coloring / fading cycles.

Description

Technical Field

[0001] This invention belongs to the field of electrochromic thin film preparation technology, specifically relating to a tungsten oxide electrochromic thin film and its preparation method. Background Technology

[0002] Electrochromism refers to the phenomenon where a material undergoes a stable and reversible change under the influence of an electric field. Electrochromic materials encompass two major systems: organic and inorganic materials. Inorganic materials have become a research hotspot due to their excellent cycling stability, and tungsten oxide is a highly representative material among them. Electrochromic materials prepared from tungsten oxide have attracted much attention due to their advantages such as high optical contrast, excellent coloring efficiency, fast response, stable physicochemical properties, and low driving voltage.

[0003] Hydrothermal synthesis is a commonly used method for preparing metal oxide nanostructures. Compared with traditional synthesis methods, hydrothermal synthesis has many significant advantages: it can prepare low-temperature polymorphic products, has short reaction times, fast diffusion rates leading to rapid growth, and also features simple processes, low costs, high product purity, and controllable particle size. Existing research on the hydrothermal preparation of tungsten oxide thin films for electrochromic applications shows that tungsten oxide thin films typically need to be prepared on conductive glass substrates coated with seed crystal layers. Despite many important achievements, there is still room for improvement in the electrochromic properties of tungsten oxide thin films prepared by hydrothermal synthesis. Summary of the Invention

[0004] In view of the shortcomings of the prior art described above, the purpose of this invention is to solve the problem and provide a tungsten oxide electrochromic thin film and its preparation method.

[0005] To achieve the above-mentioned objectives, the technical solution of this invention is as follows:

[0006] A method for preparing a tungsten oxide electrochromic thin film includes the following steps:

[0007] (1) Add tungstate to deionized water and stir until homogeneous. At the same time, add sulfuric acid solution dropwise to the above solution to form a precipitate.

[0008] (2) After repeatedly washing the precipitate with deionized water, prepare a solution and add hydrogen peroxide at 40-55℃ with stirring to obtain a transparent precursor solution; dilute the precursor solution with deionized water to obtain solution A;

[0009] (3) Add alcohol to solution A and stir until homogeneous to obtain solution B;

[0010] (4) The ITO conductive glass was ultrasonically cleaned with ethanol, then ultrasonically washed with deionized water, dried with nitrogen, and then irradiated with ultraviolet light.

[0011] (5) Immerse the ITO conductive glass in a hydrothermal reactor containing the above solution B, keep it warm, and then let it cool naturally to room temperature to serve as an ITO substrate;

[0012] (6) Remove the ITO substrate and rinse it with deionized water, then dry it in air to obtain the deposited film;

[0013] (7) Anneal the deposited film to obtain tungsten oxide electrochromic film.

[0014] As a preferred embodiment, the tungstate is selected from one of sodium tungstate, ammonium metatungstate, potassium tungstate, ethyl tungstate, and isopropyl tungstate;

[0015] As a preferred method, the mass ratio of tungstate to deionized water in step (1) is 1:5 to 1:20;

[0016] As a preferred method, the molar concentration of sulfuric acid in the solution in step (1) is 0.1~1 mol / L.

[0017] As a preferred embodiment, in step (2), the mass concentration of hydrogen peroxide in the transparent precursor solution is 10-50%;

[0018] As a preferred method, in step (2), the precursor solution is diluted with deionized water to obtain solution A, so that the molar concentration of solution A is 0.01~1mol / L.

[0019] As a preferred method, the alcohol in step (3) is selected from one of anhydrous ethanol, propylene glycol, glycerol, and isopropanol.

[0020] As a preferred method, in step (3), the volume ratio of solution A to alcohol is 1:0.5 to 1:10.

[0021] As a preferred method, in step (4), the ITO conductive glass is ultrasonically cleaned with ethanol for 5-10 minutes, then ultrasonically washed in deionized water for 15-30 minutes, dried with nitrogen, and then irradiated under ultraviolet light for 10-15 minutes.

[0022] As a preferred method, the heat preservation temperature in step (5) is 100~200℃ and the heat preservation time is 0.5~10h;

[0023] As a preferred method, the annealing temperature in step (7) is 300-500℃ and the annealing time is 2-7h.

[0024] The second objective of this invention is to provide a tungsten oxide electrochromic thin film obtained by the above-described preparation method.

[0025] As a preferred embodiment, the tungsten oxide electrochromic thin film has a seedless, porous tungsten oxide structure, which improves the coloring efficiency (CE) to 150-170 cm⁻¹. 2 ·C-1 The electrochromic cycle stability can reach 20,000 coloring / fading cycles.

[0026] As a preferred embodiment, the electrochemical and electrochromic performance testing of the tungsten oxide electrochromic thin film adopts a three-electrode system, with lithium perchlorate as the electrolyte, graphite as the counter electrode, and a saturated calomel electrode as the reference electrode.

[0027] This invention provides a simple hydrothermal method without a seed crystal layer for preparing tungsten oxide thin films with superior electrochromic properties. The resulting electrochromic devices exhibit improved electrochemical stability and faster response speed.

[0028] The beneficial effects of this invention are as follows:

[0029] 1. The preparation process described in this invention is simple to operate and has low raw material costs, and has the potential for industrial application in the large-scale preparation of thin films on glass surfaces.

[0030] 2. The prepared tungsten oxide nanoporous film exhibits an improved coloring efficiency (CE) of 150-170 cm⁻¹. 2 ·C -1 The electrochromic cycling stability can reach 20,000 coloring / fading cycles. CE (coloring efficiency) is a key parameter in EC (electrochemical efficiency), defined as the unit charge density (Q... i The change in ΔOD at a wavelength of 630 nm under / A) is expressed as follows:

[0031] CE = ΔOD / (Q) i / A);

[0032] ΔOD=log(T b / T c );

[0033] T b : Thin film transmittance in bleached state (%);

[0034] T c : Thin film transmittance (%) under dyed condition;

[0035] A: Area (cm²).

[0036] Table 1. Coloring efficiency (CE) values ​​of the thin films prepared according to the present invention

[0037] Attached Figure Description

[0038] Figure 1 This is a diagram showing the fading of the film during the first cycle of coloring according to the present invention;

[0039] Figure 2This is a color fading image of the thin film of the present invention after 20,000 color cycles.

[0040] from Figure 1 and Figure 2 It can be seen that the material of the membrane device was not damaged after 20,000 cycles, and its stability was good. Detailed Implementation

[0041] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0042] Examples 1-6 provide a method for preparing tungsten oxide electrochromic thin films, comprising the following steps:

[0043] (1) Add tungstate to deionized water and stir until homogeneous. At the same time, add sulfuric acid solution dropwise to the above solution to form a precipitate.

[0044] (2) After repeatedly washing the precipitate with deionized water, prepare a solution and add hydrogen peroxide at 40-55℃ with stirring to obtain a transparent precursor solution; dilute the precursor solution with deionized water to obtain solution A;

[0045] (3) Add alcohol to solution A and stir until homogeneous to obtain solution B;

[0046] (4) The ITO conductive glass was ultrasonically cleaned with ethanol, then ultrasonically washed with deionized water, dried with nitrogen, and then irradiated with ultraviolet light.

[0047] (5) Immerse the ITO conductive glass in a hydrothermal reactor containing the above solution B, keep it warm, and then let it cool naturally to room temperature to serve as an ITO substrate;

[0048] (6) Remove the ITO substrate and rinse it with deionized water, then dry it in air to obtain the deposited film;

[0049] (7) Anneal the deposited film to obtain tungsten oxide electrochromic film.

[0050] In some embodiments, the tungstate is selected from sodium tungstate, ammonium metatungstate, potassium tungstate, ethyl tungstate, and isopropyl tungstate;

[0051] In some embodiments, the mass ratio of tungstate to deionized water in step (1) is 1:5 to 1:20;

[0052] In some embodiments, the molar concentration of sulfuric acid in the solution in step (1) is 0.1~1 mol / L.

[0053] In some embodiments, the mass concentration of hydrogen peroxide in the transparent precursor solution in step (2) is 10-50%;

[0054] In some embodiments, in step (2), the precursor solution is diluted with deionized water to obtain solution A, so that the molar concentration of solution A is 0.01~1 mol / L.

[0055] In some embodiments, the alcohol in step (3) is selected from anhydrous ethanol, propylene glycol, glycerol, and isopropanol.

[0056] In some embodiments, the volume ratio of solution A to alcohol in step (3) is 1:0.5 to 1:10.

[0057] In some embodiments, in step (4), the ITO conductive glass is ultrasonically cleaned with ethanol for 5-10 minutes, then ultrasonically washed in deionized water for 15-30 minutes, dried with nitrogen, and then irradiated under ultraviolet light for 10-15 minutes.

[0058] In some embodiments, the heat preservation temperature in step (5) is 100~200℃, and the heat preservation time is 0.5~10h;

[0059] In some embodiments, the annealing temperature in step (7) is 300-500°C and the annealing time is 2-7 hours.

[0060] The above preparation method yields a tungsten oxide electrochromic thin film with a seedless, porous tungsten oxide structure, and its coloring efficiency (CE) is improved to 150-170 cm⁻¹. 2 ·C -1 The electrochromic cycling stability can reach 20,000 coloring / fading cycles. The electrochemical and electrochromic performance tests adopt a three-electrode system, with lithium perchlorate as the electrolyte, graphite as the counter electrode, and a saturated calomel electrode as the reference electrode.

[0061] Table 1

[0062] Example 1 Sodium tungstate 1:5 Anhydrous ethanol 1:0.5 100℃，0.5h 300℃,2h 1.05s, 0.98s, 70% Example 2 Ammonium metatungstate 1：10 Propylene glycol 1:1 150℃，5 h 400℃，4 h 1.25s, 1.01s, 69% Example 3 Potassium tungstate 1：5 Glycerol 1:2.5 180℃，8 h 400℃，4 h 1.09s, 0.91s, 72% Example 4 Ethyl tungstate 1:20 Isopropanol 1:5 180℃，8 h 450℃，5 h 1.21s, 1.12s, 65% Example 5 Isopropyl tungstate 1：15 Anhydrous ethanol 1:10 200℃，10h 500℃，7h 1.07s, 0.94s, 68% Example 6 Sodium tungstate 1：10 Propylene glycol 1:5 120℃，3 h 350℃，3 h 1.13s, 1.01s, 68%

[0063] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for preparing a tungsten oxide electrochromic thin film, characterized in that... Includes the following steps: (1) Add tungstate to deionized water and stir until homogeneous. At the same time, add sulfuric acid solution dropwise to the above solution to form a precipitate. (2) After repeatedly washing the precipitate with deionized water, prepare a solution and add hydrogen peroxide aqueous solution at 40-55℃ with stirring to obtain a transparent precursor solution; dilute the precursor solution with deionized water to obtain solution A; (3) Add alcohol to solution A and stir until homogeneous to obtain solution B; (4) The ITO conductive glass was ultrasonically cleaned with ethanol, then ultrasonically washed with deionized water, dried with nitrogen, and then irradiated with ultraviolet light. (5) Immerse the ITO conductive glass in a hydrothermal reactor containing the above solution B, keep it warm, and then let it cool naturally to room temperature to serve as an ITO substrate; (6) Remove the ITO substrate and rinse it with deionized water, then dry it in air to obtain the deposited film; (7) Anneal the deposited film to obtain tungsten oxide electrochromic film.

2. The method for preparing tungsten oxide electrochromic thin film according to claim 1, characterized in that: Tungstates are selected from one of sodium tungstate, ammonium metatungstate, potassium tungstate, ethyl tungstate, and isopropyl tungstate. And / or the mass ratio of tungstate to deionized water in step (1) is 1:5 to 1:20; And / or the molar concentration of sulfuric acid in the solution in step (1) is 0.1~1 mol / L.

3. The method for preparing tungsten oxide electrochromic thin film according to claim 1, characterized in that: In step (2), the mass concentration of hydrogen peroxide in the transparent precursor solution is 10-50%; And / or in step (2), the precursor solution is diluted with deionized water to obtain solution A, so that the molar concentration of solution A is 0.01~1mol / L.

4. The method for preparing tungsten oxide electrochromic thin film according to claim 1, characterized in that: In step (3), the alcohol is selected from one of anhydrous ethanol, propylene glycol, glycerol, and isopropanol; And / or the volume ratio of solution A to alcohol in step (3) is 1:0.5~1:

10.

5. The method for preparing tungsten oxide electrochromic thin film according to claim 1, characterized in that: Step (4) The ITO conductive glass is ultrasonically cleaned with ethanol for 5-10 minutes, then ultrasonically washed in deionized water for 15-30 minutes, dried with nitrogen, and then irradiated under ultraviolet light for 10-15 minutes.

6. The method for preparing tungsten oxide electrochromic thin film according to claim 1, characterized in that: Step (5) The heat preservation temperature is 100~200℃ and the heat preservation time is 0.5~10h.

7. The method for preparing tungsten oxide electrochromic thin film according to claim 1, characterized in that: Step (7) Annealing temperature 300-500℃, annealing time 2-7h.

8. A tungsten oxide electrochromic thin film, characterized in that... It is obtained by the preparation method according to any one of claims 1 to 7.

9. The tungsten oxide electrochromic thin film according to claim 8, characterized in that: The thin film is a seedless porous tungsten oxide structure, and its coloring efficiency (CE) is improved to 150~170 cm⁻¹. 2 ·C -1 The electrochromic cycle stability can reach 20,000 coloring / fading cycles.

10. The tungsten oxide electrochromic thin film according to claim 9, characterized in that: Electrochemical and electrochromic performance tests were performed using a three-electrode system, with lithium perchlorate as the electrolyte, graphite as the counter electrode, and a saturated calomel electrode as the reference electrode.

Images