Preparation method of electrochromic multicolor thin film device

Abstract

The invention discloses a preparation method of an electrochromic multicolor thin film device, and belongs to the technical field of electrochromic intelligent windows. The concentration of the electrochromic film precursor solution is regulated and controlled through the reversible chelation reaction, the progress of the chelation reaction is regulated and controlled through the conductive metal nanometer material and the modified two-dimensional material dispersion solution, and therefore efficient film forming is achieved on the surface of the conductive substrate. According to the method, the bottleneck of preparing electrochromic films of more types and colors is broken through, the preparation problem of the high-performance electrochromic film caused by spontaneous coprecipitation of all components in the precursor solution is solved, and a brand new thought is provided for preparation of more colorful electrochromic films and devices.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrochromic smart windows, and in particular relates to a method for preparing an electrochromic multicolor thin film device. Background Art

[0002] Under different applied electric fields, electrochromic materials undergo reversible redox reactions, resulting in reversible switching of optical properties, such as color change and transmittance modulation. Electrochromic materials have great application potential in architectural windows, anti-glare rearview mirrors, and display devices. Compared with organic electrochromic materials, inorganic electrochromic materials have shown fast response speed and good environmental durability since they were reported in the 1930s. However, limited by the intrinsic inherent color of inorganic materials, they can usually only reversibly switch between two states or colors, which severely limits their commercial applications.

[0003] The polychromaticity of electrochromic devices based on the inherent color of the material is often achieved by superimposing two or more electrochromic layers that can achieve different color changes. In order to realize the preparation of multicolor electrochromic devices, the patent application with publication number CN117410104B discloses a method for preparing a multicolor electrochromic device, in which the prepared electrochromic device uses a mixed system film of manganese dioxide modified with vanadium pentoxide as an electrochromic layer, and a Prussian blue film as an ion storage layer. Its advantage is that the film preparation method is simple, can achieve four color changes of orange, yellow, green and black, and has energy storage function. However, its film preparation method cannot be applied to other electrochromic materials, and the device cannot be applied to scenes requiring other colors. At present, the preparation process of most inorganic electrochromic films is relatively complicated, requiring a combination of electrochemical deposition, hydrothermal method, magnetron sputtering, spin coating and other methods, and it is difficult to adapt to a wide range of film-forming scenarios. Most of these processes are costly, complicated steps, and have high requirements on the scale and precision of film-forming equipment, making it difficult to achieve large-area uniform film formation.

[0004] Current research has revealed a variety of inorganic electrochromic films and their corresponding film-forming processes. However, many electrochromic films that theoretically have excellent performance face major challenges in actual preparation. These challenges mainly stem from the extremely low solubility and instability of the components in the precursor solution, which makes it difficult to prepare high-performance electrochromic films. These problems have seriously restricted the successful development of electrochromic films with rich and variable colors, and it is urgent to explore new film and device preparation methods to break through these technical bottlenecks. Summary of the invention

[0005] The purpose of the present invention is to propose a method for preparing an electrochromic multicolor thin film device in view of the problems existing in the background technology. The method of the present invention not only effectively improves the performance of the electrochromic film, but also significantly increases the types of optional colors of the film, providing a new technical path for the development of high-performance, multicolor electrochromic thin film devices.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0007] A method for preparing an electrochromic multicolor thin film device comprises the following steps:

[0008] Step 1. Dispersing the conductive metal nanomaterial into a dispersant;

[0009] Step 2. transferring the conductive metal to the surface of the conductive substrate;

[0010] Step 3. Dispersing the two-dimensional material in a dispersant, then adding a material containing an acidic group or a basic group for modification, stirring for 3 to 8 hours, and obtaining a modified two-dimensional material; wherein the mass ratio of the two-dimensional material to the material containing an acidic group or a basic group is 1:(1 to 10);

[0011] Step 4. Transferring the two-dimensional material modified in step 3 to the surface of the substrate treated in step 2;

[0012] Step 5. preparing an electrochromic precursor solution containing a chelating agent;

[0013] Step 6. Soaking the substrate treated in step 4 in the electrochromic precursor solution prepared in step 5 to form an electrochromic layer;

[0014] Step 7. preparing electrolyte;

[0015] Step 8. preparing an ion storage layer;

[0016] Step 9. Lay the prepared electrochromic layer and ion storage layer face to face, inject the electrolyte of step 7 into the gap formed by the electrochromic layer and the ion storage layer, and package them to obtain the electrochromic multicolor thin film device.

[0017] Furthermore, in step 1, the conductive metal nanomaterial is one or more of nanowires or nanoparticles of gold, silver, copper, or platinum; the dispersant is one or more of organic solvents such as water or ethanol, N,N-dimethylformamide (DMF), or dimethyl sulfoxide (DMSO); and the concentration of the conductive metal nanomaterial dispersion is 1 to 30 mg / ml.

[0018] Furthermore, in step 2, the conductive metal is transferred to the surface of the conductive substrate by a physical film-forming method such as spraying, spin coating, blade coating, or dip coating.

[0019] Furthermore, the conductive substrate in step 2 is one or more of FTO, ITO, IGZO, silver grid, and gold film.

[0020] Furthermore, in step 3, the two-dimensional material is one or more of MXene, graphene, transition metal sulfide, and black phosphorus; the acidic group is one or more of sulfonic acid group (-SO3H), carboxylic acid group (-COOH), phosphoric acid group (-PO3H2) or sulfuric acid group (-OSO3H); the basic group is one or more of amino group (-NH2), quaternary ammonium group (-NR3 + ) or one or more of imidazole groups; the dispersant is one or more of water or ethanol, N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO) and other organic solvents, and the concentration of the two-dimensional material in the dispersant is 1 to 30 mg / ml.

[0021] Furthermore, in step 4, the two-dimensional material modified in step 3 is transferred to the surface of the substrate treated in step 2 by a physical film-forming method such as spraying, spin coating, blade coating, or dip coating.

[0022] Furthermore, the preparation process of the electrochromic material precursor solution containing a chelating agent in step 5 is as follows:

[0023] The electrochromic material and the chelating agent are mixed in a molar ratio of 1: (0.5-2), and then added into a solvent, stirred and mixed evenly to obtain a mixed solution; the pH of the mixed solution is adjusted to 4-6 using an acid with the same anion or a base with the same cation as the precursor solution, and stirred for 0.5-2h to obtain an electrochromic precursor solution. Wherein, the chelating agent is one or more of ethylenediaminetetraacetic acid (EDTA), ethylenediaminetetraacetic acid salt (EDTA salt), diethylenetriaminepentaacetic acid (DTPA), nitrilotriacetic acid (NTA), 8-hydroxyquinoline (8-HQ), o-phenanthroline (Phen), and citric acid; the electrochromic material is one or more of inorganic materials such as Prussian blue (PB), Prussian blue analogues (PBA), transition metal oxides, etc., and the Prussian blue analogue (PBA) is one or more of cobalt-based Prussian blue analogues (CoHCF), nickel-based Prussian blue analogues (NiHCF), copper-based Prussian blue analogues (CuHCF), and manganese-based Prussian blue analogues (MnHCF); the solvent is an organic solvent or water.

[0024] Furthermore, in step 6, when the electrochromic material is Prussian blue, the electrochromic layer is formed by soaking for 0.5 to 1 hour; when the electrochromic material is a Prussian blue analogue, the electrochromic layer is formed by soaking for 2 to 4 hours; when the electrochromic material is a transition metal oxide, the electrochromic layer is formed by soaking for 1 to 4 hours.

[0025] Furthermore, the electrolyte in step 7 is formed by a lithium salt or sodium salt solvent in an organic solvent, and the concentration is 0.1 to 1.0 mol / L.

[0026] Preferably, the lithium salt includes but is not limited to lithium perchlorate, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium chloride, etc.; the sodium salt includes but is not limited to sodium perchlorate, sodium hexafluorophosphate, sodium tetrafluoroborate, sodium chloride, etc.; the organic solvent includes but is not limited to propylene carbonate (PC), ethylene carbonate (EC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), tetrahydrofuran (THF), ethylene glycol dimethyl ether (DME), acetonitrile (ACN), N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), etc.

[0027] Furthermore, in step 8, the ion storage layer is a thin film having complementary redox properties to the electrochromic layer in step 6, and is prepared by conventional electrochemical deposition, hydrothermal, magnetron sputtering or the same process as steps 1 to 6.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] The present invention provides a method for preparing an electrochromic multicolor thin film device, which utilizes conductive metal nanomaterials and modified two-dimensional materials to change the local pH of the precursor solution, and jointly regulates the progress of the reversible chelation reaction, thereby achieving the regulation of the concentration of metal cations in the electrochromic thin film precursor solution, so as to hinder the low film quality caused by its spontaneous co-precipitation. Furthermore, the high reducibility of the conductive metal nanomaterials and the modified two-dimensional materials is used to promote the reduction reaction in the film-forming process of the electrochromic thin film, thereby achieving in-situ efficient film formation on the surface of the conductive substrate. This method breaks through the bottleneck of preparing more types and colors of electrochromic thin films, solves the difficulty of preparing high-performance electrochromic thin films caused by the spontaneous co-precipitation of the components in the precursor solution, and provides a new idea for the preparation of more colorful electrochromic films and devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Flow chart of preparing Prussian blue film (PB) in Example 1;

[0031] Figure 2 This is a physical picture of the flexible Prussian blue film (PB) prepared in Example 1;

[0032] Figure 3 Schematic diagram of the structure of the Prussian blue (PB) / cobalt-based Prussian blue analog (CoHCF) electrochromic multicolor device prepared in Example 2;

[0033] Figure 4 This is a photo of the color change of the cobalt-based Prussian blue analog film (CoHCF) prepared in Example 2;

[0034] Figure 5 This is a photo of the color change of the electrochromic multicolor device prepared in Example 2;

[0035] Figure 6 Schematic diagram of 5000-cycle stability of the electrochromic multicolor device prepared in Example 2. DETAILED DESCRIPTION

[0036] The technical solution of the present invention is described in detail below in conjunction with the accompanying drawings and embodiments.

[0037] Example 1

[0038] In this example, a method for preparing a Prussian blue (PB) film on a flexible ITO / PET substrate is provided by controlling the chelation reaction of dipotassium ethylenediaminetetraacetate to iron ions by silver nanowires and a few-layer MXene modified with sulfonic acid groups. The flow chart is shown in FIG. Figure 1 As shown, the specific steps include:

[0039] Step 1. Electrode layer pretreatment

[0040] Flexible ITO / PET conductive glass was selected as the electrode layer, and ultrasonically cleaned with acetone, deionized water, and anhydrous ethanol for 10 to 30 minutes, dried, and treated under ultraviolet ozone for 10 to 30 minutes;

[0041] Step 2. Preparation of conductive metal nanomaterial dispersion

[0042] Taking silver nanowires as an example, 1.86 g of polyvinyl pyrrolidone (PVP) was dissolved in 100 ml of ethylene glycol (EG); then 1 ml of 3 mM NaCl solution was added dropwise and stirred at 160 ° C for 1 h; then 25 ml of 0.2 mM AgNO3 solution was added and reacted at 160 ° C for 2 h; the obtained precipitate was washed with acetone and ethanol several times, and then redispersed in ethanol to obtain a AgNWs dispersion with a concentration of 1 mg / mL;

[0043] Step 3. Spray the AgNWs dispersion described in step 2 onto the ITO / PET conductive glass and wait for the ethanol to evaporate naturally;

[0044] Step 4. Preparation of 2D material dispersion

[0045] Take the aqueous dispersion of MXene as an example. Prepare a mixed solution (Ti3AlC2:H2O:HF:HCl mass ratio of 1:6:2:12) and etch at 35°C for 24 hours; the obtained product is repeatedly washed with deionized water, and the precipitate is collected by centrifugation at 3500rpm for 1min; when the pH value of the supernatant exceeds 6, the precipitate is dispersed in a 0.65M LiCl solution and intercalated at 35°C for 24 hours; the product is centrifuged several times and deionized water is added (centrifugal speed 5000rpm, centrifugal time 1min), after the precipitate is fully expanded, add an appropriate amount of deionized water and centrifuge at 3500rpm for 15 minutes under continuous inert gas flow to collect the upper MXene dispersion;

[0046] Step 5. Acidic group modification of two-dimensional materials

[0047] Take sulfonic acid group modified MXene as an example. Add 0.03g Na2CO3, 0.1g p-aminobenzenesulfonic acid, 0.4g NaNO2 and 5ml 18% hydrochloric acid solution into 20ml deionized water and stir for 30min; then add MXene dispersion and stir at 0-5℃ for 5h; wash the product with deionized water several times to obtain sulfonic acid group modified MXene aqueous dispersion;

[0048] Step 6. Spray the sulfonic acid group-modified MXene aqueous dispersion described in step 5 onto the ITO / PET conductive glass and wait for the water to evaporate naturally;

[0049] Step 7. Preparation of electrochromic film precursor solution

[0050] FeCl3 and K2EDTA were dissolved in 100 ml of deionized water at a molar ratio of 1:1, and an appropriate amount of KOH was added to adjust the pH value of the system to 4-6 to obtain system 1;

[0051] Take another portion of deionized water and dissolve K3Fe(CN)6 therein to ensure that the molar ratio of FeCl3 and K3Fe(CN)6 is 1:1; then add excess KCl and stir for 30 minutes; add an appropriate amount of anhydrous KOH to adjust the pH value of the system to 4-6 to obtain system 2;

[0052] Add system 2 dropwise into system 1 to obtain a PB thin film precursor solution;

[0053] Step 8. Electrochromic layer growth

[0054] The conductive film obtained after the treatment in step 6 is immersed in the PB film precursor solution in step 7 for 0.5 h, rinsed with deionized water and ethanol, and dried to obtain Figure 2 PB film shown.

[0055] Example 2

[0056] In this example, a method for preparing a cobalt-based Prussian blue analog (CoHCF) film that can be changed to red and light yellow on a FTO glass substrate is provided by controlling the chelation reaction of dipotassium ethylenediaminetetraacetate to cobalt ions by silver nanowires and a few-layer MXene modified with sulfonic acid groups. The CoHCF film and the PB film are assembled into an electrochromic device that can achieve multi-color changes. The device structure is as follows: Figure 3 As shown. Specifically including the following steps:

[0057] Step 1. Electrode layer pretreatment

[0058] FTO glass was selected as the electrode layer, and ultrasonically cleaned with acetone, deionized water, and anhydrous ethanol for 10 to 30 minutes, dried, and treated under ultraviolet ozone for 10 to 30 minutes;

[0059] Step 2. Preparation of conductive metal nanomaterial dispersion

[0060] Taking silver nanowires as an example, 1.86 g of polyvinyl pyrrolidone (PVP) was dissolved in 100 ml of ethylene glycol (EG); then 1 ml of 3 mM NaCl solution was added dropwise and stirred at 160 ° C for 1 h; then 25 ml of 0.2 mM AgNO3 solution was added and reacted at 160 ° C for 2 h; the obtained precipitate was washed with acetone and ethanol several times, and then redispersed in ethanol to obtain a AgNWs dispersion with a concentration of 1 mg / mL;

[0061] Step 3. Spray the AgNWs dispersion described in step 2 onto the FTO glass and wait for the ethanol to evaporate naturally;

[0062] Step 4. Preparation of 2D material dispersion

[0063] Take the aqueous dispersion of MXene as an example. Prepare a mixed solution (Ti3AlC2:H2O:HF:HCl mass ratio of 1:6:2:12) and etch at 35°C for 24 hours; the obtained product is repeatedly washed with deionized water, and the precipitate is collected by centrifugation at 3500rpm for 1min; when the pH value of the supernatant exceeds 6, the precipitate is dispersed in a 0.65M LiCl solution and intercalated at 35°C for 24 hours; the product is centrifuged several times and deionized water is added (centrifugal speed 5000rpm, centrifugal time 1min), after the precipitate is fully expanded, add an appropriate amount of deionized water and centrifuge at 3500rpm for 15 minutes under continuous inert gas flow to collect the upper MXene dispersion;

[0064] Step 5. Acidic group modification of two-dimensional materials

[0065] Take sulfonic acid group modified MXene as an example. Add 0.03g Na2CO3, 0.1g p-aminobenzenesulfonic acid, 0.4g NaNO2 and 5ml 18% hydrochloric acid solution into 20ml deionized water and stir for 30min; then add MXene dispersion and stir at 0-5℃ for 5h; wash the product with deionized water several times to obtain sulfonic acid group modified MXene aqueous dispersion;

[0066] Step 6. Spray the sulfonic acid group-modified MXene aqueous dispersion described in step 5 onto the FTO glass and wait for the water to evaporate naturally;

[0067] Step 7. Preparation of electrochromic film precursor solution

[0068] CoCl2 and K2EDTA were dissolved in 100 ml of deionized water at a molar ratio of 1:1, and an appropriate amount of anhydrous KOH was added to adjust the pH value of the system to 4-6 to obtain system 1; FeCl3 and K2EDTA were dissolved in 100 ml of deionized water at a molar ratio of 1:1, and an appropriate amount of anhydrous KOH was added to adjust the pH value of the system to 4-6 to obtain system 2;

[0069] Take two portions of deionized water and dissolve K3Fe(CN)6 in them respectively, ensuring that the molar ratio of K3Fe(CN)6 and CoCl2 to FeCl3 is 1:1; add excess KCl and stir for 30 minutes; add appropriate amount of anhydrous KOH to adjust the pH value of the system to 4-6, and obtain system 3 and system 4;

[0070] System 3 is added dropwise into system 1 to obtain a CoHCF thin film precursor solution; system 4 is added dropwise into system 2 to obtain a PB thin film precursor solution;

[0071] Step 8. Growth of electrochromic layer and ion storage layer

[0072] A piece of FTO glass is immersed in the CoHCF film precursor solution described in step 7 for 4 hours, and another piece of FTO glass is immersed in the PB film precursor solution described in step 7 for 1 hour; the FTO glass is then rinsed with deionized water and ethanol, and dried to obtain a CoHCF film and a PB film, which are used as an ion storage layer and an electrochromic layer, respectively;

[0073] Step 9. Electrolyte preparation

[0074] Prepare 1 mol / L LiClO4 / PC solution as electrolyte;

[0075] Step 10. Electrochromic device assembly

[0076] The CoHCF film and the PB film described in step 8 are bonded face to face with double-sided tape, and the electrolyte described in step 9 is injected into the device using a syringe; the edge of the device is sealed with UV curing glue to prevent leakage, thereby obtaining the electrochromic multicolor thin film device.

[0077] The electrochromic performance of CoHCF film was tested, such as Figure 4 As shown, the prepared CoHCF film can present red at 0 V and pale yellow at -0.5 V.

[0078] The assembled electrochromic device was tested for electrochromic performance, such as Figure 5 As shown in the figure, the electrochromic device can realize five states: red, yellow, blue, green and purple. Figure 6 As shown, the device still retains 97.5% of its performance after 5000 cycles.

Claims

1. A method for preparing an electrochromic multicolor thin film device, characterized in that: The following steps are involved: Step 1. Dispersing the conductive metal nanomaterial into a dispersant; Step 2. transferring the conductive metal to the surface of the conductive substrate; Step 3. dispersing the two-dimensional material into a dispersant, and then adding a material containing an acidic group or a basic group to modify the two-dimensional material to obtain a modified two-dimensional material; Step 4. Transferring the two-dimensional material modified in step 3 to the surface of the substrate treated in step 2; Step 5. preparing an electrochromic precursor solution containing a chelating agent; Step 6. Soaking the substrate treated in step 4 in the electrochromic precursor solution prepared in step 5 to form an electrochromic layer; Step 7. preparing electrolyte; Step 8. preparing an ion storage layer; Step 9. Lay the prepared electrochromic layer and ion storage layer face to face, inject the electrolyte of step 7 into the gap formed by the electrochromic layer and the ion storage layer, and package them to obtain the electrochromic multicolor thin film device.

2. The method for preparing the electrochromic multicolor thin film device according to claim 1, characterized in that: In step 1, the conductive metal nanomaterial is one or more of nanowires or nanoparticles of gold, silver, copper, and platinum; the dispersant is one or more of water, ethanol, N,N-dimethylformamide, and dimethyl sulfoxide; and the concentration of the conductive metal nanomaterial dispersion is 1 to 30 mg / ml.

3. The method for preparing the electrochromic multicolor thin film device according to claim 1, characterized in that: In step 2, the conductive metal is transferred to the surface of the conductive substrate by spraying, spin coating, blade coating or dip coating.

4. The method for preparing an electrochromic multicolor thin film device according to claim 1, characterized in that: The conductive substrate in step 2 is one or more of FTO, ITO, IGZO, silver grid, and gold film.

5. The method for preparing an electrochromic multicolor thin film device according to claim 1, characterized in that: In step 3, the two-dimensional material is one or more of MXene, graphene, transition metal sulfide, and black phosphorus; the acidic group is one or more of sulfonic acid group, carboxylic acid group, phosphoric acid group or sulfuric acid group; the basic group is one or more of amino group, quaternary ammonium group or imidazole group; the dispersant is one or more of water, ethanol, N,N-dimethylformamide, and dimethyl sulfoxide, and the concentration of the two-dimensional material in the dispersant is 1 to 30 mg / ml.

6. The method for preparing an electrochromic multicolor thin film device according to claim 1, characterized in that: In step 4, the two-dimensional material modified in step 3 is transferred to the surface of the substrate treated in step 2 by spraying, spin coating, scraping or dipping.

7. The method for preparing an electrochromic multicolor thin film device according to claim 1, characterized in that: The preparation process of the electrochromic material precursor solution containing a chelating agent in step 5 is as follows: the electrochromic material and the chelating agent are mixed in a molar ratio of 1:(0.5-2), and then added to a solvent, stirred and mixed evenly to obtain a mixed solution; the mixed solution is adjusted to pH = 4-6 using an acid with the same anion or a base with the same cation as the precursor solution, and stirred for 0.5-2h to obtain an electrochromic precursor solution.

8. The method for preparing the electrochromic multicolor thin film device according to claim 7, characterized in that: The chelating agent is one or more of ethylenediaminetetraacetic acid, ethylenediaminetetraacetate, diethylenetriaminepentaacetic acid, nitrilotriacetic acid, 8-hydroxyquinoline, o-phenanthroline, and citric acid; the electrochromic material is one or more of Prussian blue, Prussian blue analogs, and transition metal oxides.

9. The method for preparing an electrochromic multicolor thin film device according to claim 8, characterized in that: In step 6, when the electrochromic material is Prussian blue, the electrochromic layer is formed by soaking for 0.5 to 1 hour; when the electrochromic material is a Prussian blue analogue, the electrochromic layer is formed by soaking for 2 to 4 hours; when the electrochromic material is a transition metal oxide, the electrochromic layer is formed by soaking for 1 to 4 hours.

10. The method for preparing an electrochromic multicolor thin film device according to claim 1, characterized in that: In step 8, the ion storage layer is a thin film having complementary redox properties to the electrochromic layer in step 6, and is prepared by conventional processes or the same process as steps 1 to 6.

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