Crystalline molybdenum-doped tungsten oxide nanocrystalline film as well as preparation method and application thereof

Abstract

The invention discloses a crystalline molybdenum-doped tungsten oxide nanocrystalline film and a preparation method and application thereof, and the method comprises the following steps: uniformly mixing tungsten hexachloride, an organic matter and molybdenum acetylacetonate with a solvent to prepare a molybdenum-doped precursor solution; the precursor solution is heated to 180-240 DEG C, heat preservation is conducted for 3-5 hours, and a molybdenum-doped tungsten oxide nanocrystalline solution is obtained; the preparation method comprises the following steps of: filtering and washing for multiple times, drying to obtain molybdenum-doped tungsten oxide nanocrystalline powder, dissolving the powder in methylbenzene to obtain printing ink, and spin-coating ITO (Indium Tin Oxide) conductive glass to obtain the molybdenum-doped tungsten oxide nanocrystalline film. The molybdenum-doped tungsten oxide nanocrystalline film with a high crystalline state is obtained by adopting a two-step annealing method and has the characteristics of large optical modulation range, long cycle life, good energy storage effect and the like, and neutral color conversion of the tungsten oxide film in a color changing process is realized. The material can be applied to various occasions such as new energy automobile sunroofs and electrochromic intelligent windows.

Description

Technical Field

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

[0002] Electrochromic devices, due to their reversible adjustment of optical properties under an applied electric field, are considered a core functional layer for next-generation low-energy smart windows, anti-glare rearview mirrors, and flexible displays. Tungsten oxide (WO3) has become the most widely studied inorganic electrochromic material due to its moderate band gap, high coloring efficiency, and good cycle stability. However, its intrinsic ion diffusion coefficient is low, its response speed is slow, and its coloring efficiency is limited, making it difficult to meet the requirements of dynamic dimming for second-level or even sub-second-level responses.

[0003] In recent years, introducing oxygen vacancies and controlling lattice distortion to construct fast ion channels through heterovalent / equivalent metal ion doping has become a mainstream strategy for improving the electrochromic properties of WO3. Among these strategies, molybdenum (Mo) 6 ⁺) Due to the relationship between ionic radius and W 6 ⁺ Proximity can induce lattice micro-strain while maintaining the six-coordinate structure, inhibiting grain growth and forming a high-concentration amorphous-grain boundary network, thereby simultaneously improving electron / ion transport rate and cycle stability. However, existing sol-gel, hydrothermal, or magnetron sputtering processes mostly yield amorphous or mixed-phase thin films, and the molybdenum doping amount, grain size, and crystal orientation are difficult to control independently, resulting in a trade-off between optical modulation amplitude, response speed, and neutral color.

[0004] Doping amorphous WO3 with molybdenum is beneficial because the irregular network structure of amorphous WO3 allows molybdenum ions to relatively uniformly replace tungsten ions in the lattice or exist as interstitial structures. However, doping crystalline WO3 with molybdenum leads to significant lattice distortion and stress due to the difference in ionic radii between molybdenum and tungsten ions. Furthermore, during subsequent high-temperature annealing, molybdenum ions may segregate, forming a second-phase structure. Therefore, developing a method to spin-coat crystalline molybdenum-doped WO3 nanocrystalline films on ITO conductive glass, achieving characteristics such as a wide optical modulation range, long cycle life, and good energy storage performance, is of great significance for promoting the large-scale application of high-contrast, fast-response, and long-life electrochromic devices. Summary of the Invention

[0005] The purpose of this invention is to provide a crystalline molybdenum-doped tungsten oxide nanocrystalline thin film, its preparation method and application, which can yield tungsten oxide nanocrystalline thin films with high optical modulation and long cycle stability.

[0006] In one aspect of the present invention, a method for preparing crystalline molybdenum-doped tungsten oxide nanocrystals is provided. According to an embodiment of the present invention, the method includes the following steps:

[0007] (1) Tungsten hexachloride, organic matter, molybdenum acetylacetonate and solvent are mixed evenly to prepare a molybdenum-doped precursor solution, wherein the organic matter is a mixture of oleylamine and oleic acid;

[0008] (2) Heat the precursor solution to 180-240℃ and keep it warm for 3-5h to obtain a molybdenum-doped tungsten oxide nanocrystal solution. After centrifugation and washing several times, dry it to obtain crystalline molybdenum-doped tungsten oxide nanocrystal powder.

[0009] In addition, the method for preparing crystalline molybdenum-doped tungsten oxide nanocrystals according to the above embodiments of the present invention may also have the following additional technical features:

[0010] In some embodiments of the present invention, in step (1), the mass ratio of tungsten hexachloride, oleylamine, oleic acid, and molybdenum acetylacetonate is 1.1:4:36:(1-3), and the solvent is one of isopropanol, ethanol, n-butanol, and ethylene glycol.

[0011] Tungsten hexachloride is used as the tungsten source because of its high reactivity; it releases Cl- upon reaction with alcohol. - This process generates an oxygen-containing intermediate for tungsten, while simultaneously making the reaction system acidic. Oleic acid, acting as a solvent and a strong coordinating surfactant, reacts with W... 6+ With strong coordination ability, oleylamine, as a solvent, possesses strong nonpolarity and can provide a high-temperature, high-pressure solvothermal environment for the reaction, promoting crystal nucleation and growth. Oleylamine and oleic acid are often used synergistically to precisely control the size and shape of nanocrystals. Molybdenum acetylacetonate is used as the molybdenum source because its surface acetylacetonate ligands are highly soluble in nonpolar and weakly polar organic solvents. These solvents act as reaction promoters and co-solvents, participating in and initiating the precursor conversion process.

[0012] Step (2) is a non-aqueous solvothermal reaction process. High-temperature pyrolysis of the precursor promotes grain nucleation and growth, resulting in molybdenum-doped tungsten oxide nanocrystals. The temperature during the solvothermal reaction is much higher than the usual crystallization temperature of tungsten oxide, and sufficient time is allowed for the grains to complete growth and crystallization, thereby obtaining crystalline molybdenum-doped tungsten oxide nanocrystal powder.

[0013] In another aspect of the present invention, the present invention provides a method for preparing crystalline molybdenum-doped tungsten oxide nanocrystals to obtain crystalline molybdenum-doped tungsten oxide nanocrystals.

[0014] In another aspect of the present invention, a method for preparing crystalline molybdenum-doped tungsten oxide nanocrystalline ink is provided. According to an embodiment of the present invention, the crystalline molybdenum-doped tungsten oxide nanocrystals are dissolved in a toluene solution to obtain crystalline molybdenum-doped tungsten oxide nanocrystalline ink.

[0015] In another aspect of the present invention, a method for preparing crystalline molybdenum-doped tungsten oxide nanocrystalline thin films is provided. According to an embodiment of the present invention, the method includes the following steps:

[0016] The crystalline molybdenum-doped tungsten oxide nanocrystalline ink prepared by the above method was spin-coated onto conductive glass in several layers. After each spin-coating, an annealing treatment was performed on a heating stage. After spin-coating, a second annealing treatment was performed under vacuum. Finally, after irradiation with ultraviolet light, the crystalline molybdenum-doped tungsten oxide nanocrystalline film was obtained.

[0017] In addition, the method for preparing a crystalline molybdenum-doped tungsten oxide nanocrystalline thin film according to the above embodiments of the present invention may also have the following additional technical features:

[0018] In some embodiments of the present invention, the spin coating number is 8-14 layers, the temperature of the first annealing treatment is 200-350°C, and the annealing time is 10-30 minutes. Short-term high-temperature annealing strengthens the adhesion between the film and the substrate, while simultaneously promoting the entry of molybdenum ions into the WO3 lattice.

[0019] In some embodiments of the present invention, the secondary annealing process uses argon as a protective gas, the annealing temperature is 300-400°C, and the annealing time is 90-150 minutes. This secondary, long-duration vacuum annealing allows sufficient time for the grains to complete the growth and crystallization process, while simultaneously isolating them from external air to prevent the formation of a second phase during annealing.

[0020] In some embodiments of the present invention, the ultraviolet light irradiation time is 30-120 min, and the ultraviolet light irradiation intensity is 90-150 uW / cm. 2 When ultraviolet light irradiates the surface of a tungsten oxide electrochromic film, it creates instantaneously excited electron-hole pairs, which can drive the ionization of oxygen vacancies and reduce the Li⁺ / H⁺ insertion barrier, achieving a "photo-assisted electrochemistry" effect. This can increase the charge injection amount and improve optical contrast. At the same time, ultraviolet photons can remove surface contaminants, repair surface trapped states, suppress side reactions, and extend cycle life. Moreover, the operation is simple.

[0021] In another aspect of the present invention, the present invention provides a method for preparing crystalline molybdenum-doped tungsten oxide nanocrystalline thin films, thereby obtaining crystalline molybdenum-doped tungsten oxide nanocrystalline thin films.

[0022] In another aspect of the invention, the invention proposes the use of the aforementioned crystalline molybdenum-doped tungsten oxide nanocrystalline film for the fabrication of smart windows and automotive sunroofs.

[0023] Compared with the prior art, the beneficial effects of the present invention are:

[0024] 1. This invention employs a solvothermal method, using a sealed autoclave as a reactor. The self-generated pressure of the organic solvent under high temperature and pressure significantly reduces the energy barrier for precursor decomposition, enabling rapid nucleation and oriented growth of crystalline tungsten oxide at temperatures far exceeding the crystallization temperature of WO3 (typically >120℃). The sealed system effectively suppresses solvent evaporation and leakage of toxic components, ensuring process safety and environmental friendliness. The low polarity and surface tension of the organic solvent reduce the precursor hydrolysis rate, allowing dopant ions to be uniformly embedded in the crystal lattice, achieving controllable concentration gradients. During the solvothermal process, the high-pressure environment created by the self-generated pressure in the sealed autoclave promotes atomic diffusion, resulting in nanocrystalline thin films with high crystallinity, small grain size, and large specific surface area.

[0025] 2. This invention utilizes molybdenum doping to replace W 6 ⁺ Introducing local distortions and high-density oxygen vacancies into the WO3 lattice achieves the effects of "lattice expansion, grain refinement, and bandgap modulation": On the one hand, the addition of molybdenum doping into the WO3 lattice increases grain boundaries and forms more porous structures, which is conducive to the insertion and extraction of ions and electrons. On the other hand, Mo has a lower electronegativity than W, and doping can change the band structure of tungsten oxide, thereby improving electronic conductivity. At the same time, the introduced impurity energy levels can narrow the band gap of the film, allowing the film to absorb lower-energy light sources, thus causing the film to change from deep blue to neutral color. Furthermore, the crystalline nanocrystal structure can also buffer the lattice expansion caused by ion insertion / extraction, extending the cycle life.

[0026] 3. This invention uses nanocrystalline thin films to control grain size and shorten the ion diffusion path. It utilizes surface effects to better incorporate molybdenum into the WO3 lattice. Furthermore, this invention employs a two-step vacuum annealing method. The first step involves short-time annealing after spin-coating each film layer to stabilize the adhesion between the film and the substrate, while simultaneously promoting the entry of molybdenum ions into the WO3 lattice. The second step involves long-time annealing after spin-coating to enhance the crystallinity of the film, while also isolating it from external air to prevent the formation of a second phase during the annealing process.

[0027] 4. In this invention, after obtaining molybdenum-doped tungsten oxide nanocrystalline ink, a spin coating method is used to form a film. After each layer of spin coating is formed, a short-term annealing is performed on a heating table. After spin coating is completed, a tube furnace is used for vacuum annealing. The annealing is completed at a temperature much higher than that of WO3 (usually >120°C) and with sufficient time, which is sufficient to overcome the nucleation energy barrier and promote the rearrangement of atoms to form a long-range ordered lattice, thereby improving the crystallization state of the film.

[0028] 5. The molybdenum-doped tungsten oxide nanocrystalline thin film of the present invention achieves an optical modulation amplitude of 80%-94% after two-step annealing and ultraviolet lamp irradiation, and maintains good electrochromic properties after 2000 cycles, and at 0.1 mA / cm2 The surface capacitance at that location reaches 27.6 mF / cm. 2 .

[0029] 6. The film-forming method of the present invention is spin coating. At the same time, the ink can also be used for inkjet printing, scraping and other methods. The preparation process is simple, the consumables are cheap, and it is conducive to large-scale industrial production. Attached Figure Description

[0030] Figure 1 X-ray diffraction and PDF standard card comparison diagrams of tungsten oxide nanocrystals prepared in Comparative Example 1 and Examples 1-3 of this invention;

[0031] Figure 2 The spectrum of the 1% crystalline molybdenum-doped tungsten oxide nanocrystalline thin film prepared in Example 1 of this invention;

[0032] Figure 3 The spectrum of the 2% crystalline molybdenum-doped tungsten oxide nanocrystalline thin film prepared in Example 2 of this invention;

[0033] Figure 4 The spectrum of the 4% crystalline molybdenum-doped tungsten oxide nanocrystalline thin film prepared in Example 3 of this invention;

[0034] Figure 5 The charge-discharge curve of the 2% crystalline molybdenum-doped tungsten oxide nanocrystalline thin film prepared in Example 2 of this invention;

[0035] Figure 6 Figure (a) shows Example 1; Figure (b) shows Example 2; Figure (c) shows Example 3; Figure (d) shows Comparative Example 1; Figure (e) shows a cross-sectional view and thickness of Comparative Example 2.

[0036] Figure 7 This is a cycle stability test diagram of the tungsten oxide nanocrystalline thin film prepared in Comparative Example 1 of this invention;

[0037] Figure 8 The image shows the cycle stability test results of the 2% crystalline molybdenum-doped tungsten oxide nanocrystalline thin film prepared in Comparative Example 2 of this invention.

[0038] Figure 9 This is a cycle stability test diagram of the 2% crystalline molybdenum-doped tungsten oxide nanocrystalline thin film prepared in Example 2 of the present invention;

[0039] Figure 10 The image shows the spectrum of the 2% crystalline molybdenum-doped tungsten oxide nanocrystalline film prepared in Example 2 of this invention after 2000 cycles.

[0040] Figure 11This is a photograph of the 2% crystalline molybdenum-doped tungsten oxide nanocrystalline film prepared in Example 2 of the present invention in its colored state.

[0041] Figure 12 This is a photograph of the 2% crystalline molybdenum-doped tungsten oxide nanocrystalline film prepared in Example 2 of the present invention in its faded state. 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. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill 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 crystalline molybdenum-doped tungsten oxide nanocrystalline thin film includes the following steps:

[0045] (1) 0.68 mg tungsten hexachloride, 2.5 ml oleylamine, 20 ml oleic acid, 6.1 mg molybdenum acetylacetonate and 10 ml ethanol were stirred and mixed evenly in a beaker to prepare a molybdenum-doped precursor solution;

[0046] (2) The molybdenum-doped precursor solution was placed in a 50ml reactor liner and heated in an oven at 180℃ for 3h to obtain a molybdenum-doped tungsten oxide nanocrystal solution.

[0047] (3) The molybdenum-doped tungsten oxide nanocrystal solution was centrifuged and washed twice, and then dried in an oven at 60°C for 12 hours to obtain molybdenum-doped tungsten oxide nanocrystal powder.

[0048] (4) Molybdenum-doped tungsten oxide nanocrystal powder was dissolved in 20 ml of toluene solution to prepare molybdenum-doped tungsten oxide nanocrystal ink;

[0049] (5) Molybdenum-doped tungsten oxide nanocrystals were spin-coated onto ITO conductive glass. After each layer was spin-coated, the film was heated at 350°C for 30 min. After spin-coating 12 layers, the film was placed in a tube furnace and high-purity argon gas was introduced as a protective gas. Then, it was annealed at 350°C for 2 hours. After the two-step annealing was completed, the film was placed in an 80 uW / cm 2 Irradiation under a UV lamp for 60 min yielded a crystalline molybdenum-doped tungsten oxide nanocrystalline film with an overall thickness of approximately 613 nm, which was denoted as WO3-Mo1%.

[0050] Example 2

[0051] A method for preparing a crystalline molybdenum-doped tungsten oxide nanocrystalline thin film includes the following steps:

[0052] (1) 0.68 mg tungsten hexachloride, 2.5 ml oleylamine, 20 ml oleic acid, 11.2 mg molybdenum acetylacetonate and 10 ml ethanol were stirred and mixed evenly in a beaker to prepare a molybdenum-doped precursor solution;

[0053] (2) The molybdenum-doped precursor solution was placed in a 50ml reactor liner and heated in an oven at 180℃ for 3h to obtain a molybdenum-doped tungsten oxide nanocrystal solution.

[0054] (3) The molybdenum-doped tungsten oxide nanocrystal solution was centrifuged and washed twice, and then dried in an oven at 60°C for 12 hours to obtain molybdenum-doped tungsten oxide nanocrystal powder.

[0055] (4) Molybdenum-doped tungsten oxide nanocrystal powder was dissolved in 20 ml of toluene solution to prepare molybdenum-doped tungsten oxide nanocrystal ink;

[0056] (5) Molybdenum-doped tungsten oxide nanocrystals were spin-coated onto ITO conductive glass. After each layer was spin-coated, the film was heated at 350°C for 30 min. After spin-coating 12 layers, the film was placed in a tube furnace and high-purity argon gas was introduced as a protective gas. Then, it was annealed at 350°C for 2 hours. After the two-step annealing was completed, the film was placed in an 80 uW / cm 2 Irradiation under a UV lamp for 60 min yielded a crystalline molybdenum-doped tungsten oxide nanocrystalline film with an overall thickness of approximately 625 nm, denoted as WO3-Mo2%.

[0057] Example 3

[0058] A method for preparing a crystalline molybdenum-doped tungsten oxide nanocrystalline thin film includes the following steps:

[0059] (1) 0.68 mg tungsten hexachloride, 2.5 ml oleylamine, 20 ml oleic acid, 22.4 mg molybdenum acetylacetonate and 10 ml ethanol were stirred and mixed evenly in a beaker to prepare a molybdenum-doped precursor solution;

[0060] (2) The molybdenum-doped precursor solution was placed in a 50ml reactor liner and heated in an oven at 180℃ for 3h to obtain a molybdenum-doped tungsten oxide nanocrystal solution.

[0061] (3) The molybdenum-doped tungsten oxide nanocrystal solution was centrifuged and washed twice, and then dried in an oven at 60°C for 12 hours to obtain molybdenum-doped tungsten oxide nanocrystal powder.

[0062] (4) Molybdenum-doped tungsten oxide nanocrystal powder was dissolved in 20 ml of toluene solution to prepare molybdenum-doped tungsten oxide nanocrystal ink;

[0063] (5) Molybdenum-doped tungsten oxide nanocrystals were spin-coated onto ITO conductive glass. After each layer was spin-coated, the film was heated at 350°C for 30 min. After spin-coating 12 layers, the film was placed in a tube furnace and high-purity argon gas was introduced as a protective gas. Then, it was annealed at 350°C for 2 hours. After the two-step annealing was completed, the film was placed in an 80 uW / cm 2 Irradiation under a UV lamp for 60 min yielded a crystalline molybdenum-doped tungsten oxide nanocrystalline film with an overall thickness of approximately 723 nm, which was denoted as WO3-Mo4.

[0064] Comparative Example 1

[0065] A method for preparing undoped crystalline tungsten oxide nanocrystalline ink includes the following steps:

[0066] (1) 0.68 mg tungsten hexachloride, 2.5 ml oleylamine, 20 ml oleic acid and 10 ml ethanol were stirred and mixed evenly in a beaker to obtain a precursor solution;

[0067] (2) The precursor solution was placed in a 50ml reactor liner and heated in an oven at 180℃ for 3 hours to obtain tungsten oxide nanocrystal solution.

[0068] (3) After centrifuging and washing twice, the tungsten oxide nanocrystal solution was dried in an oven at 60°C for 12 hours to obtain tungsten oxide nanocrystal powder;

[0069] (4) Tungsten oxide nanocrystal ink was prepared by dissolving tungsten oxide nanocrystal powder in 20 ml of toluene solution;

[0070] (5) Tungsten oxide nanocrystals were spin-coated onto ITO conductive glass. After each layer was spin-coated, the glass was heated at 350°C for 30 minutes. After spin-coating 12 layers, the crystalline tungsten oxide nanocrystal film was placed in a tube furnace and high-purity argon gas was introduced as a protective gas. Then, it was annealed at 350°C for 2 hours. After the two-step annealing was completed, the crystalline tungsten oxide nanocrystal film was placed in an 80 uW / cm 2 Irradiation under a UV lamp for 60 min yielded a crystalline molybdenum-doped tungsten oxide nanocrystalline film with an overall thickness of approximately 648 nm, which was denoted as WO3.

[0071] Comparative Example 2

[0072] A method for preparing crystalline molybdenum-doped tungsten oxide nanocrystals includes the following steps:

[0073] (1) 0.68 mg tungsten hexachloride, 2.5 ml oleylamine, 20 ml oleic acid, 11.2 mg molybdenum acetylacetonate and 10 ml ethanol were stirred and mixed evenly in a beaker to prepare a molybdenum-doped precursor solution;

[0074] (2) The molybdenum-doped precursor solution was placed in a 50ml reactor liner and heated in an oven at 180℃ for 3h to obtain a molybdenum-doped tungsten oxide nanocrystal solution.

[0075] (3) The molybdenum-doped tungsten oxide nanocrystal solution was centrifuged and washed twice, and then dried in an oven at 60°C for 12 hours to obtain molybdenum-doped tungsten oxide nanocrystal powder.

[0076] (4) Molybdenum-doped tungsten oxide nanocrystal powder was dissolved in 20 ml of toluene solution to prepare molybdenum-doped tungsten oxide nanocrystal ink;

[0077] (5) Molybdenum-doped tungsten oxide nanocrystals were spin-coated onto ITO conductive glass. After each layer was spin-coated, the glass was heated at 350°C for 30 min. After spin-coating 12 layers, the film was placed in an 80 uW / cm² heat exchanger. 2 Molybdenum-doped tungsten oxide nanocrystalline film was obtained by irradiation under ultraviolet light for 60 minutes. The overall thickness of the film was about 589 nm.

[0078] like Figure 1 As shown, after the two-step annealing method, the molybdenum-doped tungsten oxide nanocrystalline films prepared in Examples 1, 2, and 3 all have a crystalline structure.

[0079] like Figure 2-4 As shown, crystalline molybdenum-doped tungsten oxide nanocrystalline films prepared in Examples 1, 2, and 3 were tested using a UV-3600 UV-Vis spectrophotometer. The optical transmittance of the films in their colored and faded states was measured, and ΔT was calculated to obtain the optical modulation amplitude of the films. It can be found that all films maintain a large range of optical modulation amplitude (ΔT), and the optical modulation amplitude is the largest when the molybdenum doping content is 2%, reaching 91.98%.

[0080] like Figure 5 As shown in Example 2, the crystalline molybdenum-doped tungsten oxide nanocrystalline film was prepared. The charge-discharge process of the film was measured using a CHI760E electrochemical workstation at -0.5V and 1V. It was found that the film maintained good energy storage performance at a current density of 0.1 mA / cm². 2 The surface capacitance at this location can reach 27.6 mF / cm. 2 .

[0081] like Figure 7-9As shown, the crystalline tungsten oxide nanocrystalline film prepared in Comparative Example 1 showed poor cycle stability after 2000 cycles at operating voltages of -1V and 1V with a cycle period of 30s using a CHI760E electrochemical workstation. After doping with molybdenum, the molybdenum-doped tungsten oxide nanocrystalline film prepared in Comparative Example 2 showed improved cycle stability after 2000 cycles at operating voltages of -1V and 1V with a cycle period of 30s, but still showed a decreasing trend. After secondary annealing, the crystalline molybdenum-doped tungsten oxide nanocrystalline film prepared in Example 2 showed significantly improved cycle stability after 2000 cycles at operating voltages of -1V and 1V with a cycle period of 30s, remaining stable even after 2000 cycles.

[0082] like Figure 10 As shown, the 2% molybdenum-doped tungsten oxide nanocrystalline film prepared in Example 2 was subjected to a 2000-cycle stability test using a CHI760E electrochemical workstation at operating voltages of -1V and 1V, with a cycle period of 30s. The film prepared in Example 2 still maintained a high optical modulation amplitude, with a modulation amplitude of 86.42% in the 633nm wavelength range. It also maintained more than 93% of the electrochromic properties compared to before cycling.

[0083] like Figure 11-12 As shown, the film prepared in Example 2 maintains extremely high transmittance in the faded state. Under a D65 measuring light source and within a measuring aperture of 4 mm, the color of the film in the colored state is measured to be a neutral black.

[0084] The above description is merely an example and illustration 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, all of which should fall within the protection scope of the present invention.

Claims

1. A method for preparing crystalline molybdenum-doped tungsten oxide nanocrystals, characterized in that, Includes the following steps: (1) Tungsten hexachloride, organic matter, molybdenum acetylacetonate and solvent are mixed evenly to prepare a molybdenum-doped precursor solution, wherein the organic matter is a mixture of oleylamine and oleic acid; (2) Heat the precursor solution to 180-240℃ and keep it warm for 3-5h to obtain a molybdenum-doped tungsten oxide nanocrystal solution. After centrifugation and washing several times, dry it to obtain crystalline molybdenum-doped tungsten oxide nanocrystal powder.

2. The method for preparing crystalline molybdenum-doped tungsten oxide nanocrystals according to claim 1, characterized in that: In step (1), the mass ratio of tungsten hexachloride, oleylamine, oleic acid, and molybdenum acetylacetonate is 1.1:4:36:(1-3), and the solvent is one of isopropanol, ethanol, n-butanol, and ethylene glycol.

3. A method for preparing crystalline molybdenum-doped tungsten oxide nanocrystals according to any one of claims 1-2.

4. A method for preparing a crystalline molybdenum-doped tungsten oxide nanocrystalline ink, characterized in that: The crystalline molybdenum-doped tungsten oxide nanocrystals described in claim 3 are dissolved in toluene solution to obtain crystalline molybdenum-doped tungsten oxide nanocrystal ink.

5. A method for preparing a crystalline molybdenum-doped tungsten oxide nanocrystalline thin film, characterized in that, Includes the following steps: The crystalline molybdenum-doped tungsten oxide nanocrystalline ink prepared by the preparation method described in claim 4 was spin-coated onto conductive glass in several layers. After each spin-coating, an annealing treatment was performed on a heating stage. After spin-coating, a second annealing treatment was performed under vacuum. Finally, after irradiation with ultraviolet light, the crystalline molybdenum-doped tungsten oxide nanocrystalline film was obtained.

6. The method for preparing a crystalline molybdenum-doped tungsten oxide nanocrystalline thin film according to claim 1, characterized in that: The number of spin coating layers is 8-14, the temperature of the first annealing treatment is 200-350℃, and the annealing time is 10-30min.

7. The method for preparing a crystalline molybdenum-doped tungsten oxide nanocrystalline thin film according to claim 1, characterized in that: The secondary annealing process uses argon as a protective gas, with an annealing temperature of 300-400℃ and an annealing time of 90-150 minutes.

8. The method for preparing a crystalline molybdenum-doped tungsten oxide nanocrystalline thin film according to claim 1, characterized in that: The ultraviolet light irradiation time is 30-120 minutes, and the ultraviolet light irradiation intensity is 80 μW / cm². 2 .

9. A crystalline molybdenum-doped tungsten oxide nanocrystalline film prepared by the method of claim 5.

10. The use of the crystalline molybdenum-doped tungsten oxide nanocrystalline thin film according to claim 9, characterized in that: The crystalline molybdenum-doped tungsten oxide nanocrystalline film is used to prepare smart windows and automotive sunroofs.

Images