A tungsten-doped nickel oxide nanocrystal electrochromic film and a preparation method thereof

Abstract

This invention discloses a tungsten-doped nickel oxide nanocrystalline electrochromic thin film, which is composed of stacked nanocrystalline particles with a particle size of approximately 4 nm. The invention also discloses a method for preparing the tungsten-doped nickel oxide nanocrystalline electrochromic thin film, combining a solvothermal method with magnetron sputtering to obtain the tungsten-doped nickel oxide nanocrystalline thin film. The doped thin film of this invention effectively improves upon the problems of yellowing in the fading state, small charge capacity, and poor cycle life existing in current NiO electrochromic materials, providing a new approach for constructing high-performance electrochromic devices with strong color-changing effects, high energy efficiency, and long service life.

Description

Technical Field

[0001] This invention relates to the field of electrochromic thin film preparation, specifically to a tungsten-doped nickel oxide nanocrystalline electrochromic thin film and its preparation method. Background Technology

[0002] Electrochromism refers to the phenomenon where certain materials can stably and reversibly change their color or optical properties through redox reactions under a relatively small external voltage. Electrochromic materials have attracted widespread attention as energy-saving and environmentally friendly materials, capable of transmitting and absorbing sunlight of different wavelengths, thereby regulating light energy and reducing energy consumption. NiO, as a very important anodic electrochromic material, is commonly used in conjunction with cathodic electrochromic films such as WO3 to assemble electrochromic devices. These devices have broad commercial applications, including anti-glare rearview mirrors, electronic paper, sunroofs for new energy vehicles, AR glasses, and back covers for smartphones and tablets.

[0003] A paper titled "Fast-switching electrochromic smart windows based on WO3-doped NiO thin films" demonstrates that WO3-doped NiO films exhibit rapid photoresponse speeds (0.6 s for bleaching / 1.0 s for coloring). This is because the defect-induced amorphous structure of the nickel-tungsten oxide film provides numerous diffusion channels, which is beneficial for Li... + Rapid embedding and the ability of the doped film to accommodate a large number of ions enhance its electrochromic properties. However, the transmittance of this film in the faded state is approximately 80%, resulting in a noticeable yellowing in images, which would negatively impact the user experience if applied to smart windows. Furthermore, the film exhibits poor overall cycling stability, retaining only 50% of its original charge storage capacity after 1000 cycles. Currently, yellowing in the faded state, low charge capacity, and poor cycling stability are the three major problems of NiO electrochromic films, hindering their engineering applications. Therefore, addressing these three issues is crucial for expanding the applications of NiO films. Summary of the Invention

[0004] The purpose of this invention is to provide a tungsten-doped nickel oxide nanocrystalline electrochromic thin film and its preparation method, which is prepared by a combination of solvothermal method and magnetron sputtering method, aiming to solve the above-mentioned problems.

[0005] In one aspect of the present invention, a method for preparing a tungsten-doped nickel oxide nanocrystalline electrochromic thin film is provided. According to an embodiment of the present invention, the method includes the following steps:

[0006] S1. Heat and stir nickel acetylacetone, toluene, and oleylamine until clear to obtain a precursor solution;

[0007] S2. The precursor solution is subjected to a solvothermal reaction, then anhydrous ethanol is added, the mixture is allowed to stand to precipitate, and then centrifuged.

[0008] S3. Dissolve the precipitate obtained in step S2 in n-hexane, add anhydrous ethanol again, let the precipitate stand and centrifuge.

[0009] S4. Dissolve the precipitate obtained in step S3 in 1,3,5-trimethylbenzene to obtain nickel oxide nanocrystalline ink;

[0010] S5. Spin-coat nickel oxide nanocrystalline ink onto dry FTO glass to obtain a nickel oxide nanocrystalline electrochromic film.

[0011] S6. Place the nickel oxide nanocrystalline electrochromic film into the magnetron sputtering vacuum chamber and use a tungsten target to sputter and deposit it on the surface.

[0012] S7. Anneal the film obtained in step S6 to obtain a tungsten-doped nickel oxide nanocrystalline electrochromic film.

[0013] In addition, the method for preparing a tungsten-doped nickel oxide nanocrystalline electrochromic thin film according to the above embodiments of the present invention may also have the following additional technical features:

[0014] In some embodiments of the present invention, in step S1, the temperature of the heating and stirring is 50-70°C.

[0015] In some embodiments of the present invention, in step S2, the reaction temperature of the solvothermal reaction is 160-200°C and the reaction time is 20-24h.

[0016] In some embodiments of the present invention, in steps S2 and S3, the centrifugation speed is 5000-8000 r / min and the centrifugation time is 3-8 min.

[0017] In some embodiments of the present invention, in step S4, the concentration of the nickel oxide nanocrystalline ink is 80-120 mg / mL.

[0018] In some embodiments of the present invention, in step S5, the FTO glass is first ultrasonically cleaned with acetone, anhydrous ethanol, and deionized water, and then dried.

[0019] In some embodiments of the present invention, in step S6, the sputtering pressure is 1.0-2.0 Pa and the sputtering power is 20-60 W.

[0020] In some embodiments of the present invention, in step S7, the annealing temperature is 200-400°C, the annealing time is 120-200 min, and the heating rate is 4-8°C / min.

[0021] In another aspect of the invention, a tungsten-doped nickel oxide nanocrystalline electrochromic film prepared according to the aforementioned method is provided. The tungsten-doped nickel oxide nanocrystalline electrochromic film possesses a nanocrystalline structure with nanocrystalline particles approximately 4 nm in size, allowing for uniform tungsten doping. It also exhibits the following characteristics: extremely high transmittance in the faded state (88.30%-94.40%), without yellowing; increased charge capacity (109%-135% of that of the undoped nickel oxide nanocrystalline film); and excellent cycling stability, showing almost no degradation after more than 5000 cycles.

[0022] In addition, a tungsten-doped nickel oxide nanocrystalline electrochromic thin film according to the above embodiments of the present invention may also have the following additional technical features:

[0023] In some embodiments of the present invention, the electrochromic film can achieve rapid and reversible change between transparent and dark brown, with a coloring time of 2.64-3.85s and a fading time of 1.20-2.20s.

[0024] The beneficial effects of this invention are as follows:

[0025] 1. This invention discloses a tungsten-doped nickel oxide nanocrystalline electrochromic thin film, which is prepared by innovatively combining magnetron sputtering with the wet chemical method, successfully combining the advantages of the two mainstream methods. Compared with the chemical method alone, the doped film prepared by magnetron sputtering is more uniform and has higher purity. Compared with the film formed by magnetron sputtering alone, the surface of the nanocrystalline thin film synthesized by the preceding chemical step is not very dense, and the large number of pores on the film surface facilitates the penetration of electrolyte and the reaction.

[0026] 2. The tungsten-doped nickel oxide nanocrystalline electrochromic thin film of the present invention generates more nickel vacancies and other defects, which increases the number of lithium ion absorption sites in the lithium-ion electrolyte and significantly improves the charge capacity, resulting in higher optical contrast. This makes the color change of the electrochromic device more obvious and the visual effect better. It can also effectively reduce power consumption and improve the energy efficiency of the device.

[0027] 3. The tungsten-doped nickel oxide nanocrystalline electrochromic thin film of the present invention can increase the lattice spacing of the nanocrystalline particles, widen the lithium-ion transport channels, and improve their diffusion rate, thereby increasing the conductivity of the nickel oxide nanocrystalline thin film, effectively improving electrochemical kinetics, and resulting in a faster photoresponse speed and a shorter color-changing time.

[0028] 4. The present invention provides a tungsten-doped nickel oxide nanocrystalline electrochromic thin film. The doping of tungsten can effectively reduce the probability of lithium ions being trapped by deep potential well sites during electrochemical cycling, thereby reducing damage to the material structure, enhancing its cycling stability, and extending the service life of the electrochromic device. Attached Figure Description

[0029] Figure 1 This is a scanning electron microscope image of the tungsten-doped nickel oxide nanocrystalline electrochromic thin film prepared in Example 1 of this invention;

[0030] Figure 2 This is a scanning electron microscope cross-sectional image of the tungsten-doped nickel oxide nanocrystalline electrochromic thin film prepared in Example 1 of this invention;

[0031] Figure 3 This is an X-ray diffraction pattern of the tungsten-doped nickel oxide nanocrystalline electrochromic thin film prepared in Example 1 of this invention;

[0032] Figure 4 The cyclic voltammogram is shown for the tungsten-doped nickel oxide nanocrystalline electrochromic thin film prepared in Example 1 of this invention.

[0033] Figure 5 The image shows the electrochromic performance spectrum of the tungsten-doped nickel oxide nanocrystalline electrochromic film prepared in Example 1 of this invention in a 1 mol / L LiClO4 / PC electrolyte solution.

[0034] Figure 6 This is a schematic diagram of the kinetic electrochromic performance of the tungsten-doped nickel oxide nanocrystalline electrochromic film prepared in Example 1 of this invention in a 1 mol / L LiClO4 / PC electrolyte solution (550 nm - 0.5 V - + 1.2 V).

[0035] Figure 7 The color parameters (L*a*b*) of the tungsten-doped nickel oxide nanocrystalline electrochromic thin film prepared in Example 1 of this invention under different applied voltages were obtained using a D-65 light source at a 2° observer angle in the CIE 1931 color space.

[0036] Figure 8 The chronocurrent curve of the tungsten-doped nickel oxide nanocrystalline electrochromic thin film prepared in Example 1 of this invention after 5000 cycles;

[0037] Figure 9 This is a comparison of the optical modulation amplitude of the tungsten-doped nickel oxide nanocrystalline electrochromic thin film prepared in Example 1 of this invention before and after 5000 cycles.

[0038] Figure 10This is a comparison of the cyclic voltammetry curves of the tungsten-doped nickel oxide nanocrystalline electrochromic thin film prepared in Example 1 of this invention before and after 5000 cycles.

[0039] Figure 11 The Ni 2p X-ray photoelectron spectroscopy spectrum of nickel in the tungsten-doped nickel oxide nanocrystalline electrochromic thin film prepared in Example 2 of this invention;

[0040] Figure 12 The O1s spectrum of the X-ray photoelectron spectroscopy of nickel in the tungsten-doped nickel oxide nanocrystalline electrochromic thin film prepared in Example 2 of this invention;

[0041] Figure 13 The W 4f energy spectrum of the tungsten element in the tungsten-doped nickel oxide nanocrystalline electrochromic thin film prepared in Example 2 of this invention. Detailed Implementation

[0042] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. The described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0043] Example 1

[0044] A method for preparing a tungsten-doped nickel oxide nanocrystalline electrochromic thin film includes the following steps:

[0045] S1. Add 0.514g nickel acetylacetonate, 20mL toluene, and 12mL oleylamine to a beaker, heat and stir at 50°C until clear to obtain a precursor solution;

[0046] S2. The precursor solution from step S1 is loaded into a reaction vessel and placed in an oven at 180°C for 24 hours for a solvothermal reaction.

[0047] S3. Add 80 mL of anhydrous ethanol to the solution obtained in step S2, let it stand to precipitate and then centrifuge at a speed of 8000 r / min for 5 min.

[0048] S4. Dissolve the precipitate obtained in step S3 in 8 mL of n-hexane, add 80 mL of anhydrous ethanol again, let the precipitate stand and centrifuge at 8000 r / min for 5 min.

[0049] S5. Dissolve the precipitate obtained in step S4 in 4 mL of 1,3,5-trimethylbenzene to obtain nickel oxide nanocrystalline ink;

[0050] S6. The FTO glass was ultrasonically cleaned for 30 minutes each with acetone, anhydrous ethanol and deionized water respectively.

[0051] S7. Place the FTO glass from step S6 into an oven and dry it at 60°C for 5 minutes.

[0052] S8. Spin coat the nickel oxide nanocrystalline ink obtained in step S5 onto the FTO glass obtained in step S7 to obtain a nickel oxide nanocrystalline electrochromic film.

[0053] S9. Place the nickel oxide nanocrystalline thin film obtained in step S8 into a magnetron sputtering vacuum chamber and sputter-deposit tungsten on the surface using a tungsten target with a purity of 99.999%, a sputtering pressure of 1.2 Pa, a sputtering power of 20 W, and a sputtering time of 1 min.

[0054] S10. Anneal the film obtained in step S9 at a temperature of 300℃ for 120 min at a heating rate of 6℃ / min to obtain a tungsten-doped nickel oxide nanocrystalline electrochromic film.

[0055] The tungsten-doped nickel oxide nanocrystalline electrochromic film prepared in this embodiment has a nanocrystalline structure. For example... Figure 1 As shown, the film surface is uniform and composed of stacked nanocrystalline particles, with a particle size of approximately 4 nm. Figure 2 As shown, the cross-sectional thickness is approximately 884 nm, and the delamination between the thin film and FTO is not particularly obvious, indicating good adhesion. Figure 3 The X-ray electron diffraction pattern showed a clear (200) crystal plane orientation at 43°, with no new phase formation, indicating that W can be well incorporated into the NiO lattice.

[0056] Figure 4 In the cyclic voltammogram, the area of ​​the curve after W doping is significantly larger, indicating that W doping enhances the Li content of the NiO nanocrystalline film. + With an increased number of absorption sites, the charge capacity is significantly increased. The electrochromic performance spectrum and kinetic diagram of the preparation in this embodiment under lithium-ion electrolyte are shown below. Figure 5 , Figure 6 As shown, this electrochromic material achieves an optical modulation contrast of 63.87% at 550nm, with obvious color changes; the coloring time at 550nm is 2.68s, and the fading time is 1.43s, indicating a very fast photoresponse speed.

[0057] Figure 7 The images show the chromaticity diagrams obtained under different bias voltages. Color is represented by three parameters: luminance (L*), red-green hue (a*), and yellow-blue hue (b*). It can be seen that after W doping, the film is in a fading state when a negative voltage is applied, and the b* value of the film decreases significantly, proving that W doping can effectively improve the yellowing phenomenon in the fading state of NiO electrochromic films.

[0058] Figure 8 This is a multi-potential chronograph of a tungsten-doped nickel oxide nanocrystalline electrochromic thin film subjected to alternating applications of -0.5V / +1.2V for 15 seconds for 5000 cycles. Figure 9 and Figure 10 The figures show a comparison of the cyclic voltammetry curves and optical modulation amplitude before and after 5000 cycles. It can be seen that after 5000 cycles, the charge storage capacity of the tungsten-doped nickel oxide nanocrystalline electrochromic film remains at 90.35% of its original value, and while the optical modulation amplitude decreases from 60.43% to 57.83%, it still retains 95.70% of its original value. Therefore, the tungsten-doped nickel oxide nanocrystalline electrochromic film exhibits excellent cycling stability, with almost no performance degradation after 5000 cycles.

[0059] Example 2

[0060] A method for preparing a tungsten-doped nickel oxide nanocrystalline electrochromic thin film includes the following steps:

[0061] S1. Add 0.514g of nickel acetylacetonate, 20mL of toluene, and 12mL of oleylamine to beaker 1, heat and stir at 50°C until clear to obtain the precursor solution;

[0062] S2. The precursor solution from step S1 is loaded into a reaction vessel and placed in an oven at 180°C for 24 hours for a solvothermal reaction.

[0063] S3. Add 80 mL of anhydrous ethanol to the solution obtained in step S2, let it stand to precipitate and then centrifuge at a speed of 8000 r / min for 5 min.

[0064] S4. Dissolve the precipitate obtained in step S3 in 8 mL of n-hexane, add 80 mL of anhydrous ethanol again, let the precipitate stand and centrifuge at 8000 r / min for 5 min.

[0065] S5. Dissolve the precipitate obtained in step S4 in 4 mL of 1,3,5-trimethylbenzene to obtain nickel oxide nanocrystalline ink;

[0066] S6. The FTO glass was ultrasonically cleaned for 30 minutes each with acetone, anhydrous ethanol and deionized water respectively.

[0067] S7. Place the FTO glass from step S6 into an oven and dry for 5 minutes.

[0068] S8. Spin coat the nickel oxide nanocrystalline ink obtained in step S5 onto the FTO glass obtained in step S7 to obtain a nickel oxide nanocrystalline electrochromic film.

[0069] S9. Place the nickel oxide nanocrystalline thin film obtained in step S8 into a magnetron sputtering vacuum chamber and evacuate to 2*10⁻⁶. -4 Tungsten was deposited on the surface by sputtering using a tungsten target with a purity of 99.999%, a sputtering pressure of 1.2 Pa, a sputtering power of 20 W, and a sputtering time of 1 min.

[0070] S10. Anneal the film obtained in step S9 at a temperature of 300℃ for 180 min at a heating rate of 6℃ / min to obtain a tungsten-doped nickel oxide nanocrystalline electrochromic film.

[0071] Figure 11 , Figure 12 , Figure 13 The photoelectron spectrum corresponds to the W-doped NiO nanocrystalline thin film. The W doping makes W... 6+ Replace Ni 3+ The position of Ni 3+ / Ni 2+ As the value decreases, the hole concentration in the NiO lattice increases, which in turn increases the transmittance of the electrochromic film in the visible light range and makes the photoresponse speed faster.

[0072] The above description is merely an example and illustration of the method of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the structure of the present invention or exceed the scope defined in the claims, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing a tungsten-doped nickel oxide nanocrystalline electrochromic thin film, characterized in that, Includes the following steps: S1. Heat and stir nickel acetylacetone, toluene, and oleylamine until clear to obtain a precursor solution; S2. The precursor solution is subjected to a solvothermal reaction, then anhydrous ethanol is added, the mixture is allowed to stand to precipitate, and then centrifuged. S3. Dissolve the precipitate obtained in step S2 in n-hexane, add anhydrous ethanol again, let the precipitate stand and centrifuge. S4. Dissolve the precipitate obtained in step S3 in 1,3,5-trimethylbenzene to obtain nickel oxide nanocrystalline ink; S5. Spin-coat nickel oxide nanocrystalline ink onto dry FTO glass to obtain a nickel oxide nanocrystalline electrochromic film. S6. Place the nickel oxide nanocrystalline electrochromic film into the magnetron sputtering vacuum chamber and use a tungsten target to sputter and deposit it on the surface. S7. Anneal the film obtained in step S6 to obtain a tungsten-doped nickel oxide nanocrystalline electrochromic film.

2. The method for preparing a tungsten-doped nickel oxide nanocrystalline electrochromic thin film according to claim 1, characterized in that: In step S1, the heating and stirring temperature is 50-70℃.

3. The method for preparing a tungsten-doped nickel oxide nanocrystalline electrochromic thin film according to claim 1, characterized in that: In step S2, the reaction temperature of the solvothermal reaction is 160-200℃, and the reaction time is 20-24h.

4. The method for preparing a tungsten-doped nickel oxide nanocrystalline electrochromic thin film according to claim 1, characterized in that: In steps S2 and S3, the centrifugation speed is 5000-8000 r / min and the centrifugation time is 3-8 min.

5. The method for preparing a tungsten-doped nickel oxide nanocrystalline electrochromic thin film according to claim 1, characterized in that: In step S4, the concentration of the nickel oxide nanocrystalline ink is 80-120 mg / mL.

6. The method for preparing a tungsten-doped nickel oxide nanocrystalline electrochromic thin film according to claim 1, characterized in that: In step S5, the FTO glass is first ultrasonically cleaned with acetone, anhydrous ethanol, and deionized water, and then dried.

7. The method for preparing a tungsten-doped nickel oxide nanocrystalline electrochromic thin film according to claim 1, characterized in that: In step S6, the sputtering pressure is 1.0-2.0 Pa and the sputtering power is 20-60 W.

8. The method for preparing a tungsten-doped nickel oxide nanocrystalline electrochromic thin film according to claim 1, characterized in that: In step S7, the annealing temperature is 200-400℃, the annealing time is 120-200min, and the heating rate is 4-8℃ / min.

9. A tungsten-doped nickel oxide nanocrystalline electrochromic thin film prepared by the method of any one of claims 1-8.

10. The tungsten-doped nickel oxide nanocrystalline electrochromic thin film according to claim 9, characterized in that: The electrochromic film can achieve rapid and reversible changes between transparent and dark brown, with a coloring time of 2.64-3.85s and a fading time of 1.20-2.20s.

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