Tungsten oxide-based functional ink, preparation method thereof, electrochromic film and device
By preparing hexagonal nanocrystalline tungsten oxide particles with an average particle size of less than 100 nm, the problems of thermal stress and mechanical failure caused by high-temperature processes were solved, and the high crystallinity and stability of electrochromic films at low temperatures were achieved, supporting large-area, low-cost manufacturing.
Patent Information
- Application Number
- CN202511370625.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-24
- Publication Date
- 2025-12-05
AI Technical Summary
Existing technologies for preparing electrochromic thin films involve high-temperature processes that lead to thermal stress and mechanical failure, making them incompatible with flexible polymer substrates. Furthermore, the performance of thin films prepared using low-temperature solution methods degrades, making it difficult to achieve large-area, low-cost manufacturing.
A method for preparing tungsten oxide-based functional inks was adopted, which involves microwave-assisted heating and ultrasonic treatment to prepare hexagonal nanocrystalline tungsten oxide particles with an average particle size of less than 100 nm. These particles are then used for low-temperature coating of electrochromic films, avoiding high-temperature annealing.
High crystallinity and stability of electrochromic films at low temperatures were achieved, supporting large-area uniform preparation, reducing production costs, and improving the optical contrast and response speed of the films.
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Figure CN121064665A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to a tungsten oxide-based functional ink, a preparation method thereof, an electrochromic film and a device, and belongs to the technical field of electrochromic devices. BACKGROUND
[0002] Electrochromism refers to a phenomenon that a specific material undergoes a reversible redox reaction under the stimulation of a low applied electric field, thereby causing a significant and reversible change in optical properties (such as transmittance, reflectance and absorptance). Electrochromic devices based on electrochromic materials can be applied in many fields, including automobile anti-dazzling rearview mirrors, airplane intelligent portholes and self-adaptive light-adjusting smart goggles, etc.
[0003] At present, physical vapor deposition technologies based on low-temperature processes, such as magnetron sputtering, thermal evaporation and electron beam evaporation, are considered as promising candidate technologies for the preparation of electrochromic films. Although such technologies show good operability in the control of chemical composition and the regulation of microstructure of the films and can realize the preparation of electrochromic films at a relatively low deposition temperature, they usually face problems such as complex equipment, low deposition efficiency, high energy consumption and high production cost, which seriously limit their application potential in large-area and low-cost film manufacturing.
[0004] On the other hand, solution processing technologies (such as dip coating and spin coating) provide the possibility for low-cost and large-area preparation. However, in order to achieve good electrochromic performance (such as long cycle stability and fast optical response speed), the films obtained based on solutions usually need to be subjected to post-annealing at a high temperature (even more than 400℃) to improve their key properties such as crystallinity, stoichiometric ratio and film-substrate adhesion. The high-temperature process inevitably causes the accumulation of interfacial thermal stress due to the mismatch of the thermal expansion coefficients between the substrate and the functional layer, and even leads to interfacial failure problems such as film cracking and peeling. In addition, the high-temperature process is difficult to be compatible with flexible polymer substrates (such as polyethylene terephthalate (PET)) with low heat resistance, which greatly limits its application in the field of flexible electrochromic technology.
[0005] In order to overcome the compatibility problem between heat-sensitive substrates and high-temperature processes, researchers have developed various low-temperature solution preparation strategies in recent years, such as low-temperature spin coating, slot coating and inkjet printing, whose process temperature can be controlled below 150℃. Although these methods avoid the thermal stress and mechanical failure caused by high temperature, the obtained films usually present an amorphous-dominated structure due to the difficulty of the precursor ink to achieve sufficient diffusion and crystallization and densification processes under low-temperature conditions, thereby causing a significant decrease in key performance indicators such as optical contrast, response speed and long cycle stability of the films. SUMMARY
[0006] The technical problem solved by the present application is to overcome the defects of the prior art and provide a tungsten oxide-based functional ink preparation method.
[0007] To solve the above technical problems, the technical solution of the present application is a tungsten oxide-based functional ink preparation method, which comprises the following steps: S01: adding deionized water to tungstic acid and stirring; S02: after stirring, adding sodium hydroxide and continuing to stir to obtain a precursor solution; S03: adjusting the Ph value of the precursor solution to be between 0.5 and 2; S04: separating the precipitate from the precursor solution after adjusting the Ph value; S05: microwave-assisted heating the precipitate to obtain tungsten oxide nanoparticles with a hexagonal crystal structure; S06: crushing the tungsten oxide nanoparticles, adding deionized water and isopropyl alcohol, stirring, and then ultrasonic treatment to obtain a tungsten oxide-based functional ink.
[0008] Further, the mass ratio of tungstic acid to sodium hydroxide is 25:6.
[0009] Further, in step S01, 8-40 ml of deionized water is added to 1 g of tungstic acid.
[0010] Further, in step S03, the Ph value of the precursor solution is adjusted by adding HCl solution dropwise to the precursor solution.
[0011] Further, in step S04, the method for separating the precipitate is centrifugation, decantation or suction filtration.
[0012] Further, in step S05, the microwave-assisted heating parameters are: microwave irradiation power of 800-1000 W and / or irradiation time of 8-12 min.
[0013] Further, in step S06, 15-20 ml of deionized water is added to 1 g of tungsten oxide nanoparticles; And / or 10-15 ml of isopropyl alcohol is added to 1 g of tungsten oxide nanoparticles.
[0014] The present application also provides a tungsten oxide-based functional ink prepared by the above preparation method.
[0015] The application further provides an electrochromic film prepared from the tungsten oxide-based functional ink.
[0016] Further, the tungsten oxide-based functional ink is coated on a substrate with a temperature ranging from 60 to 80 DEG C.
[0017] The application further provides an electrochromic device comprising the electrochromic film.
[0018] By adopting the technical scheme, the application has the following beneficial effects: 1. The tungsten oxide-based functional ink is prepared by the method, and the preparation method is simple without high-temperature and high-pressure reaction.
[0019] 2. The tungsten oxide-based functional ink prepared by the method has an average particle size of less than 100 nm, a hexagonal nanocrystal structure, simple composition, good stability, and is suitable for preparing the electrochromic film by coating technology, and the prepared film can have good crystallinity without high-temperature annealing treatment.
[0020] 3. The application provides an effective solution for low-temperature, large-area and uniform preparation and low-cost of the electrochromic film. BRIEF DESCRIPTION OF DRAWINGS
[0021] Fig. 1 (a) is an average particle size distribution graph one of the tungsten oxide-based functional ink prepared by the application; Fig. 1 (b) is an average particle size distribution graph two of the tungsten oxide-based functional ink prepared by the application; Fig. 2 (a) is an X-ray diffraction (XRD) spectrum based on tungsten oxide nanoparticles and an electrochromic film; Fig. 2 (b) is a surface scanning electron microscope image of the electrochromic film of the application; Fig. 2 (c) is a W 4f high-resolution XPS spectrum of the electrochromic film of the application; Fig. 2 (d) is an O 1s high-resolution XPS spectrum of the electrochromic film of the application; Fig. 3 (a) is a SEM image of the electrochromic film of the application; Fig. 3 (b) is a SEM image of the electrochromic film of the application; Fig. 4 (a) is a HRTEM image of the tungsten oxide-based functional ink of the application; Fig. 4 (b) is a selected area electron diffraction (SAED) pattern of the tungsten oxide-based functional ink of the application; Fig. 4 (c) is an EDS mapping one of the tungsten oxide-based functional ink of the application; Fig. 4 (d) is an EDS mapping two of the tungsten oxide-based functional ink of the application; Figure 5(a) is a graph of optical transmittance spectrum of the electrochromic film of the present application; Figure 5(b) is a graph of the retention of optical contrast of the electrochromic film of the present application after 2000 continuous cycles; Figure 5(c) is a graph of in-situ optical response (at 633 nm) of the electrochromic film of the present application; Figure 5(d) is a graph of the change of optical density (ΔOD) and charge density (Q) of the electrochromic film of the present application at 633 nm wavelength; Figure 6(a) is a graph of the working principle of the WO3-Zn electrochromic device of the present application; Figure 6(b) is a graph of the optical transmittance spectrum of the WO3-Zn electrochromic device of the present application; Figure 6(c) is a graph of the switching time and transmittance curve between the colored state and bleached state of the WO3-Zn electrochromic device of the present application; Figure 6(d) is a graph of the optical density versus charge density of the WO3-Zn electrochromic device of the present application; Figure 6(e) is a graph of the in-situ transmittance spectrum of the WO3-Zn electrochromic device of the present application. DETAILED DESCRIPTION
[0022] The present application provides a tungsten oxide-based functional ink, a preparation method thereof, an electrochromic film and a device. Those skilled in the art can refer to the content herein and appropriately improve the process parameters to achieve. It is particularly pointed out that all similar substitutions and changes are obvious to those skilled in the art, and they all belong to the scope protected by the present application. The method and application of the present application have been described by preferred embodiments, and relevant personnel can obviously modify or appropriately change and combine the method and application herein without departing from the content, spirit and scope of the present application, to realize and apply the present application technology.
[0023] A preparation method of a tungsten oxide-based functional ink, the steps of the method comprise: S01: adding deionized water to tungstic acid and stirring; S02: after stirring, adding sodium hydroxide and continuing to stir to obtain a precursor solution; S03: adjusting the pH value of the precursor solution to be between 0.5 and 2; S04: separating the precipitate from the precursor solution after adjusting the pH value; S05: washing the precipitate with deionized water for more than 10 times, and then microwave-assisted heating the precipitate to obtain tungsten oxide nanoparticles with a hexagonal crystal structure; S06: grinding the tungsten oxide nanoparticles, adding deionized water and isopropyl alcohol, stirring at room temperature, and then ultrasonic treatment to obtain a tungsten oxide-based functional ink.
[0024] In step S03, the Ph value can be 0.5, 1, 1.5, 2, or a range with the above values as upper and lower limits; preferably about 1; Further, the mass ratio of tungstic acid and sodium hydroxide is 25:6.
[0025] Further, in step S01, 8-40ml of deionized water is added to 1g of tungstic acid; the amount of deionized water can be 8ml, 13ml, 18ml, 20ml, 23ml, 28ml, 33ml, 38ml, 40ml, or a range with the above values as upper and lower limits; preferably 20ml.
[0026] Further, in step S03, the Ph value of the precursor solution is adjusted by adding HCl solution to the precursor solution; specifically, the HCl solution is added to the precursor solution while stirring until the Ph value reaches the target, and then the addition of HCl solution is stopped.
[0027] Further, in step S04, the method for separating the precipitated product is centrifugal separation, decantation or suction filtration.
[0028] Further, in step S05, the parameters of microwave-assisted heating are: microwave irradiation power is 800-1000W, irradiation time is 8-12min; the microwave irradiation power can be specifically 800W, 850W, 900W, 950W, or a range with the above values as upper and lower limits 1000W, preferably 900W; the irradiation time can be specifically 8min, 9min, 10min, 11min, 12min, or a range with the above values as upper and lower limits; preferably 10min.
[0029] Further, in step S06, 15-20ml of deionized water is added to 1g of tungsten oxide nanoparticles; wherein the amount of deionized water can be specifically 15ml, 16ml, 17ml, 18ml, 19ml, 20ml, or a range with the above values as upper and lower limits; preferably 20ml.
[0030] 10-15ml of isopropyl alcohol is added to 1g of tungsten oxide nanoparticles; wherein the amount of isopropyl alcohol can be specifically 10ml, 11ml, 12ml, 13ml, 14ml, 15ml, or a range with the above values as upper and lower limits.
[0031] The present application also provides a tungsten oxide-based functional ink prepared by the above preparation method.
[0032] The present application also provides an electrochromic film prepared from the above tungsten oxide-based functional ink.
[0033] Further, the tungsten oxide-based functional ink is coated on a substrate with a temperature ranging from 60 to 80°C; the temperature can be specifically 60°C, 70°C, 80°C, or a range with the above values as upper and lower limits, and the temperature of the substrate is preferably 60°C; specifically, the temperature of the substrate is set to 60°C in combination with the coating process, the doctor blade gap is set to 25 µm to 100 µm after the substrate is heated, and the moving speed of the doctor blade is set to 2 to 4 cm / s; 10 to 20 µL of ink is taken each time, and the tungsten oxide-based functional ink is repeatedly coated on the ITO glass to obtain a WO3 film.
[0034] The present application also provides an electrochromic device comprising the above electrochromic film.
[0035] In order to make the content of the present application easier to be clearly understood, the present application is further described in detail below according to specific embodiments and in combination with the accompanying drawings.
[0036] Example One: First, 2.5 g of tungstic acid is weighed into a beaker, then 50 ml of deionized water is measured, stirred for 1 min at room temperature, and then 0.6 g of sodium hydroxide solid particles is weighed and added, and stirring is continued for 15 min, and a light white solution is obtained under continuous magnetic stirring. Then, HCl solution is added dropwise with stirring until the solution ph reaches about 1, and the addition of HCl solution is stopped at this time, at which point the solution appears dark yellow. Continue stirring for 30 min, then pour the solution into a centrifuge tube, separate the precipitate by centrifuge, and the centrifuge parameters are 8000 rpm / min for 10 min. Wash the precipitate 10 times or more with deionized water, then transfer the precipitate to a microwave oven, and irradiate with a 900 W power microwave for 10 min to obtain tungsten oxide nanoparticles. Grind the prepared tungsten oxide nanoparticles, collect 0.15 g of tungsten oxide nanoparticles, add them to a mixture of 3 ml of deionized water and 2 ml of isopropyl alcohol, stir at room temperature, and then ultrasonic treat for 4 h to obtain a tungsten oxide-based functional ink. In combination with the coating process, the temperature of the substrate is set to 60°C, the doctor blade gap is set to 50 µm after the substrate is heated for 5 min, and the moving speed of the doctor blade is 3 cm / s. Take 15 µL of ink each time, and repeatedly coat it on the ITO glass to obtain an electrochromic film.
[0037] The tungsten oxide-based functional ink prepared in Example One is subjected to dynamic light scattering particle size analysis, and the average particle size distribution graph shown in FIG. 1 is obtained, which indicates that the average particle size of the tungsten oxide-based functional ink is less than 100 nm.
[0038] Figure 2(a) shows the X-ray diffraction (XRD) pattern analysis of tungsten oxide nanoparticles and electrochromic thin film, confirming the electrochromic thin film has a hexagonal crystal structure (PDF # 33-1387). There are two obvious peaks at 20° to 30° corresponding to the (001) and (200) crystal planes of hexagonal tungsten oxide.
[0039] Figure 2(b) shows the surface scanning electron microscope image of the electrochromic thin film, the results show that the root mean square roughness of the electrochromic thin film surface is as low as 17.4 nm, indicating that it is uniform and smooth. This is due to the uniform distribution of tungsten oxide nanoparticles in the tungsten oxide-based functional ink, with an average particle size of less than 100 nm.
[0040] The surface of the electrochromic thin film was characterized by X-ray photoelectron spectroscopy to further determine the valence state of W and O elements. The peaks were fitted by Gaussian-Lorentzian function to W4f and O1s, as shown in Figure 2(c), two sets of double peaks were fitted from W4f. The first set of double peaks at 36.01 eV and 38.15 eV is attributed to W6+, and the second set of double peaks at 34.80 eV and 36.65 eV is attributed to W5+.
[0041] In addition, as shown in Figure 2(d), the high-resolution XPS spectrum of 0O1s can be fitted with three peaks, the main peak at 530.7 eV is attributed to the lattice oxygen of W-O bond in WO3; the additional shoulder peaks at 531.95 eV and 533.05 eV can be attributed to the surface adsorbed O.
[0042] Figure 3 shows the SEM image of the electrochromic thin film, the image shows that the electrochromic thin film is formed by the close packing of nanoparticles, which leads to the generation of nanoporous structure, effectively increasing the specific surface area, providing more active sites, reducing the diffusion path, and facilitating the insertion and extraction of ion conduction.
[0043] The synthesized tungsten oxide-based functional ink was characterized by transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS). The results show that the tungsten oxide nanoparticles have WO3 hexagonal structure characteristics, which is consistent with the XRD results; Figure 4(a) shows obvious lattice fringes, and the interlayer spacing is 0.375 nm and 0.381 nm, respectively, corresponding to the (001) and (200) crystal planes of WO3 (PDF #33-1387). In combination with the selected electron diffraction pattern, as shown in Figure 4(b), the corresponding crystal planes can also be found. The continuous and clear lattice fringes observed in multiple nanoparticles indicate that the structure has a high degree of crystallinity, which is confirmed by the X-ray diffraction data of the prepared powder. The WO3 with a hexagonal crystal structure has an ordered lattice structure, which can enhance the structural stability in repeated ion insertion / extraction cycles, thereby improving the cycle durability of the thin film. Such crystalline structure provides a significant advantage for electrochromic applications. The energy spectrum element mapping results in Figures 4(c) and 4(d) show that the tungsten (W) and oxygen (O) elements in the sample are uniformly distributed.
[0044] Based on a three-electrode system, the electrochromic performance of the electrochromic film was analyzed. Among them, 0.1M LiClO4-PC was used as the electrolyte, Pt sheet was used as the counter electrode, Ag / AgCl was used as the reference electrode, the coloring voltage was -1V, and the bleaching voltage was +1V. Figure 5(a) shows the transmission spectra of the electrochromic film in the colored state and the bleached state, and the optical modulation at 633 nm is 72.78%. When a voltage of -1V is applied, lithium ions migrate from the electrolyte to the electrochromic film, accompanied by electron transfer, which is consistent with the classic ion-electron double injection model in the electrochromic system. As shown in Figure 5(b), the electrochromic film shows excellent cycle stability. After 2000 electrochromic cycles, the optical modulation range decreases from the initial 60.92% to 53.79%, and the corresponding retention rate is 88.3%. As shown in Figure 5(c), the in-situ spectral response at 633 nm shows a bleaching time (tb=11s) and a coloring time (tc=20s). In order to further evaluate the electrochromic performance, the coloring efficiency of the film was calculated, and the obtained coloring efficiency was 34.48 cm² / C, as shown in Figure 5(d).
[0045] Figure 6(a) shows a schematic diagram of the structure of the WO3-Zn electrochromic energy storage device. Specifically, by combining the prepared WO3 electrode with the Zn electrode of the frame structure and adding 0.05M Zn 2+ -0.5M Li +The electrolyte with PC mixed ions was used to assemble the device. As shown in Fig. 6(b), the UV-Vis transmission spectra of the WO3-Zn electrochromic device were tested in the colored (+0.1 V) and bleached (+1.6 V) states. The device exhibited a significant optical modulation in the wavelength range of 320-1000 nm, reaching 63.86% at 633 nm. As shown in Fig. 6(c), the tband tcvalues of the WO3-Zn electrochromic device were measured to be 14 s and 24 s, respectively. This switching time is attributed to the fast insertion / extraction kinetics of Zn 2+ and Li + ions, as well as the hexagonal framework structure of WO3. The open-tunnel structure of the hexagonal phase is beneficial for fast ion insertion / extraction, which is crucial for the response speed of electrochromic devices. The calculated coloration efficiency of the device was 31.62 cm 2 C -1 -1V-1, as shown in Fig. 6(e). Impressively, even after 15,000 consecutive cycles, the device still maintained 90% of its initial optical modulation ability, demonstrating excellent long-term electrochromic performance.
[0046] The above-described specific embodiments further illustrate the technical problems solved by the present application, technical solutions, and beneficial effects. It should be understood that the above-described embodiments are merely specific embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.
Claims
1. A method for preparing a tungsten oxide-based functional ink, characterized by The steps of the method comprise: S01: adding deionized water to tungstic acid and stirring; S02: after stirring, adding sodium hydroxide and continuing to stir to obtain a precursor solution; S03: adjusting the Ph value of the precursor solution to be between 0.5 and 2; S04: separating the precipitated product from the precursor solution after adjusting the Ph value; S05: microwave-assisted heating of the precipitated product to obtain tungsten oxide nanoparticles with a hexagonal crystal structure; S06: crushing the tungsten oxide nanoparticles, adding deionized water and isopropyl alcohol, stirring, and then ultrasonic treatment to obtain a tungsten oxide-based functional ink.
2. The production method according to claim 1, characterized by, The mass ratio of tungstic acid to sodium hydroxide is 25:
6.
3. The preparation method according to claim 1, characterized in that, In step S01, 8-40 ml of deionized water is added to 1 g of tungstic acid.
4. The production method according to claim 1, characterized by, In step S03, the Ph value of the precursor solution is adjusted by adding HCl solution dropwise to the precursor solution.
5. The method of claim 1, wherein, In step S04, the method for separating the precipitated product is centrifugation, decantation, or suction filtration.
6. The method of claim 1, wherein, In step S05, the parameters for microwave-assisted heating are: microwave irradiation power of 800-1000 W and / or irradiation time of 8-12 min.
7. The preparation method according to claim 1, characterized in that, In step S06, In 1 g of tungsten oxide nanoparticles, 15-20 ml of deionized water is added; And / or in 1 g of tungsten oxide nanoparticles, 10-15 ml of isopropyl alcohol is added.
8. A tungsten oxide-based functional ink, characterized by, Prepared by the preparation method of any one of claims 1-7.
9. An electrochromic film, characterized by, Prepared from the tungsten oxide-based functional ink of claim 8.
10. The electrochromic film of claim 9, wherein, Coated on a substrate with a temperature range of 60-80°C using the tungsten oxide-based functional ink of claim 8.
11. An electrochromic device, characterized in that, An electrochromic film comprising the electrochromic film of claim 9 or 10.