Colorful stretchable electrochromic device based on gold nanowires and preparation method thereof

Abstract

The invention discloses a colorful stretchable electrochromic device based on gold nanowires and a preparation method thereof.The preparation method adopts a wet process to prepare vertically-arranged gold nanowire electrodes, the gold nanowire electrodes are embedded into a flexible stretchable substrate, the device keeps high conductivity and good optical transparency, and meanwhile, the device has the advantages of being high in electrochromic efficiency, good in electrical conductivity and good in optical transparency. Excellent mechanical performance and structural stability are realized; the solid electrolyte is used to avoid the problems of volatilization and leakage of the liquid electrolyte, so that the reliability and the service life of the device are remarkably improved; according to the electrochromic device, different organic electrochromic materials can be deposited through electro-polymerization to achieve colorful changes in a wide spectral range, the spectral range covers a region from visible light to near-infrared light, and the electrochromic device is widely applied to the fields of flexible display devices, optics and the like due to the patterned design and the colorful display function of the electrochromic device; in addition, by optimizing the embedding mode of the gold nanowire and the substrate, the device can maintain stable electrical and optical performance under the conditions of multiple times of stretching and complex mechanical deformation.

Description

Technical Field

[0001] The present invention relates to the technical field of flexible electronic devices and electrochromic technology, and in particular to a colorful stretchable electrochromic device based on gold nanowires and a preparation method thereof. Background Art

[0002] With the booming development of flexible electronic technology, stretchable electronic devices have attracted much attention due to their ability to maintain functionality under complex mechanical deformations such as stretching, bending or twisting. Such devices show broad application prospects in the fields of wearable devices, electronic skin, smart displays and flexible sensors. To achieve these functions, flexible conductive materials are key, among which gold nanowires have become a hot topic of research due to their excellent conductive properties, good chemical stability and significant ductility. Through reasonable design, gold nanowires can self-assemble to form a conductive film with a network structure, which not only exhibits excellent conductivity but also can withstand large mechanical deformation. This property makes gold nanowires an ideal choice for flexible transparent electrodes, flexible sensors and other multifunctional composite materials; especially in the flexible field, integrating gold nanowire materials into stretchable systems has further promoted their application in advanced electronic devices.

[0003] As a functional device that can regulate color or optical transmittance under the action of an electric field, electrochromic devices have shown great potential in the fields of smart windows, optical displays, optical storage, and wearable optical devices due to their low power consumption, fast response, and strong tunability. However, traditional electrochromic devices are usually based on rigid substrates and cannot meet the requirements of use in flexible and stretchable scenarios. With the in-depth development of flexible technology, flexible and stretchable electrochromic devices have gradually become a research hotspot. The core challenge lies in the development of electrode materials with high transmittance, excellent conductivity, and stable optical properties. Under tensile deformation, the device needs to maintain conductivity and electrochromic properties, which places strict requirements on the design of electrodes and color-changing layers. Existing flexible electrochromic technology still needs to be improved in terms of tensile stability, color contrast, and cycle life. Summary of the invention

[0004] The main purpose of the present invention is to provide a method for preparing a colorful stretchable electrochromic device based on gold nanowires, aiming to solve the problem that it is difficult to balance the stretchability and conductivity of traditional flexible electrochromic devices and how to use gold nanowires to prepare transparent or translucent stretchable electrodes.

[0005] In order to achieve the above object, the present invention proposes a method for preparing a colorful stretchable electrochromic device based on gold nanowires, and the method for preparing a colorful stretchable electrochromic device based on gold nanowires comprises the following steps: S1. Ultrasonic cleaning of the Si / SiO2 substrate using deionized water and isopropanol solution, and then storing in a constant temperature oven after cleaning; S2, spin coating, printing or spraying a polymethyl methacrylate solution on the cleaned surface of the Si / SiO2 substrate, and performing thermal annealing; S3, spin coating, printing or spraying a positive photoresist on the thermally annealed polymethyl methacrylate film, exposing and developing the photoresist with ultraviolet light and a developer, and then performing a secondary thermal annealing; S4, subjecting the Si / SiO2 substrate treated in the previous step to oxygen plasma surface treatment, placing it in a vacuum oven, dropping octadecyltrichlorosilane and heating to volatilize it; S5, spin coating, printing or spraying the precursor solution on the surface of the Si / SiO2 substrate treated in the previous step; S6, after washing with deionized water and drying with nitrogen, drop the gold nanowire growth solution on the surface of the Si / SiO2 substrate to obtain gold nanowires grown vertically on the Si / SiO2 substrate; S7, after washing with anhydrous ethanol and drying with nitrogen, the stretchable substrate material is spin-coated on the surface of the gold nanowire, and heated, cured and peeled off to obtain a translucent stretchable patterned gold nanowire electrode; S8, placing the gold nanowire electrode obtained in the previous step in a three-electrode workstation, adding electrolyte and electrochromic material, and performing electrochemical deposition; S9. An electrolyte organic solution is dropped onto the surface of the patterned stretchable gold nanowire electrode after electrochemical deposition and dried and volatilized to obtain a solid electrolyte, and finally a colorful stretchable patterned electrochromic device based on gold nanowires is obtained.

[0006] The present invention also proposes a colorful stretchable electrochromic device based on gold nanowires, which comprises a stretchable substrate, vertically arranged gold nanowire electrodes embedded in the stretchable substrate, an organic electrochromic layer and a solid electrolyte layer; the colorful stretchable electrochromic device based on gold nanowires is obtained by the above-mentioned method for preparing the colorful stretchable electrochromic device based on gold nanowires.

[0007] In one embodiment, the stretchable substrate includes any one of polydimethylsiloxane, hydrogenated styrene-butadiene block copolymer, and water-soluble polyurethane.

[0008] In one embodiment, the organic electrochromic layer may be any electrochromic material of polythiophene, polyaniline, or polyphenylene.

[0009] In one embodiment, the solid electrolyte is a polymer solid electrolyte.

[0010] The technical solution of the present invention realizes the patterned peeling of gold nanowires on a stretchable substrate by taking advantage of the different adhesion of vertically grown gold nanowires on polymethyl methacrylate and positive photoresist; a semi-transparent or even higher transparency stretchable patterned gold nanowire film can be obtained by controlling the concentration of the precursor solution and the gold nanowire growth solution; compared with the vacuum thermal evaporation method, the present invention adopts a wet method to prepare the gold nanowire film, which has a simple process flow and saves time, and can be prepared on a large scale at room temperature; the addition of solid electrolytes can avoid the defects of traditional liquid electrolytes that are easy to volatilize and leak while providing excellent ion conductivity; by changing different electrochromic materials, electrochromism in a larger spectral range can be achieved, which can be widely used in smart windows and display devices, optical camouflage, military and other fields; the gold nanowires are embedded in the stretchable substrate, so that the electrode has excellent mechanical strength, and can still maintain excellent conductivity under large strain stretching, bending and twisting conditions; the colorful stretchable patterned electrochromic device based on gold nanowires can be combined with a variety of sensor modules to achieve integrated intelligent sensing display. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is a schematic diagram of the cross-sectional structure of a colorful stretchable electrochromic device based on gold nanowires of the present invention; Figure 2 This is a schematic diagram of the overall structure of the colorful stretchable electrochromic device based on gold nanowires of the present invention; Figure 3 The absorption and transmission curves of the precursor solution and the gold nanowire growth solution with different concentrations are shown; In the figure: 1-solid electrolyte, 2-organic electrochromic material, 3-gold nanowire electrode, 4-stretchable substrate. DETAILED DESCRIPTION

[0012] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0013] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0014] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0015] In the description of the present invention, it should be understood that the terms "upper", "lower", "inside", "outside", "left", "right", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, or are directions or positional relationships in which the product of the invention is usually placed when in use, or are directions or positional relationships commonly understood by those skilled in the art. These directions or positional relationships are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the present invention.

[0016] Furthermore, the terms “first”, “second”, etc. are merely used for distinguishing descriptions and should not be understood as indicating or implying relative importance.

[0017] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms such as "setting" and "connection" should be understood in a broad sense. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0018] like Figure 1-3 As shown, the preparation method of the colorful stretchable electrochromic device based on gold nanowires includes the following steps: S1. Clean the Si / SiO2 substrate with deionized water and isopropyl alcohol, and store it in a constant temperature drying oven at 80°C after cleaning; S2, coating the cleaned Si / SiO2 substrate surface with a polymethyl methacrylate (PMMA) solution by spin coating, printing or spraying, and then performing a thermal annealing treatment at a temperature range of 180° C. to 230° C. for 2 to 10 minutes; S3, spin-coating, printing or spraying a positive photoresist on the polymethyl methacrylate film treated in the previous step, covering a metal mask with a pattern on the substrate, exposing the positive photoresist with 365nm ultraviolet light and developing it with a special developer, washing it with deionized water and drying it, and then performing a secondary thermal annealing; the positive photoresist is any one of the AZ5214E ​​and AZ1500 series, the exposure time is 30-180s, the secondary thermal annealing temperature range is 80-120°C, and the time range is 2-15min; S4, subjecting the Si / SiO2 substrate treated in the previous step to oxygen plasma surface treatment. The treatment power is 100-200W, the oxygen flow rate is 80-150ml / min, and the treatment time is 5-10min; S5. Place the Si / SiO2 substrate treated in the previous step evenly around a glass culture dish, drop octadecyltrichlorosilane (OTS) solution in the middle of the culture dish, place the culture dish in a vacuum oven and heat it to allow OTS to evaporate and fill the entire oven; the heating temperature is 80-150°C, and the heating time is 2-4 hours; S6, spin coating, printing or spraying the precursor solution on the Si / SiO2 substrate treated with OTS in the previous step; the precursor solution is obtained by reducing the chloroauric acid solution with weak reducing agent sodium citrate and strong reducing agent sodium borohydride, and the concentration of chloroauric acid in the precursor solution is 0.25-1mM, the concentration of sodium citrate is 0.25-1mM, and the concentration of sodium borohydride is 5-20mM; S7, after washing with deionized water and drying with nitrogen, dripping the gold nanowire growth solution on the surface of the substrate treated in the above steps to obtain gold nanowires vertically grown on the Si / SiO2 substrate; the concentration of chloroauric acid in the gold nanowire growth solution is 6.9-12 mM, the concentration of 4-mercaptobenzoic acid is 1.1-3.3 mM, and the concentration of L-ascorbic acid is 16.4-30 mM; the time for dripping the gold nanowire growth solution on the surface of the substrate is 10-30 min; S8, after washing with anhydrous ethanol and drying with nitrogen, drop the stretchable material on the Si / SiO2 substrate, heat and solidify it, and then peel it off to obtain the stretchable patterned gold nanowire electrode 3; S9, adding an electrochromic material to the electrolyte solution, and depositing an electrochromic layer on the surface of the gold nanowire electrode 3 using a standard three-electrode system; the electrochromic material is one of the thiophene organic polymers; in the standard three-electrode system, the working electrode is the gold nanowire electrode 3, the reference electrode is the silver / silver chloride electrode, and the counter electrode is the platinum sheet electrode; S10, the electrolyte material and the gel material are mixed in proportion and dissolved in an organic solvent, and then dropped on the surface of the stretchable patterned gold nanoelectrode treated in the previous step, and solidified after ultraviolet light irradiation to obtain solid electrolyte 1; finally, a stretchable patterned electrochromic device based on gold nanowires is obtained. The gel material is poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-co-HFP), and the electrolyte material is 1-ethyl-3-methylimidazoline bis (trifluoromethylsulfonyl) imide (EMIM-TFSI).

[0019] In this embodiment, gold nanowires become an ideal candidate material for realizing high-performance stretchable electrochromic devices due to their excellent conductivity and flexibility. By applying gold nanowires to the electrode part of the stretchable electrochromic device, its high conductivity and mechanical stability can be effectively combined to significantly improve the performance of the device under deformation conditions. At the same time, with the help of patterning technology, electrochromic devices can be given more functionality and design freedom, thereby realizing a wider range of application scenarios.

[0020] In this embodiment, the stretchable electrochromic device based on gold nanowires combines the high conductivity and flexibility of gold nanowires with the optical regulation ability of electrochromic devices. In particular, by adopting solid electrolyte 1, it can effectively replace the traditional liquid electrolyte and significantly improve the structural stability, packaging convenience and use safety of the device. Solid electrolyte 1 can not only provide excellent ion conduction performance, but also has the advantages of anti-leakage and anti-volatilization, making the device more reliable and adaptable in practical applications.

[0021] The preparation method of the colorful stretchable electrochromic device based on gold nanowires of the present invention combines the technical scheme of solid electrolyte 1 and wet preparation of gold nanowire electrode 3, which not only helps to expand the functions and application fields of flexible electronic devices, but also provides new technical support for the research and development of future intelligent flexible display and sensing systems.

[0022] In order to verify that the colorful stretchable electrochromic device based on gold nanowires obtained by the preparation method of the colorful stretchable electrochromic device based on gold nanowires described in the embodiment of the present invention has better performance, multiple embodiments and comparative examples are provided below to test the colorful stretchable electrochromic device based on gold nanowires obtained by this method.

[0023] Example 1 (control group): (1) The Si / SiO2 substrate was ultrasonically cleaned and dried with isopropyl alcohol, and the surface of the substrate was treated with a UV-ozone cleaner for 15 min; (2) Polymethyl methacrylate (950, A6) was spin-coated on the surface of the Si / SiO2 substrate at 3000 rpm / s. After annealing at 180°C for 2 minutes, positive photoresist AZ5214E ​​was spin-coated on the film surface at 3000 rpm / s. (3) Patterning was performed on the positive photoresist AZ5214E ​​using a standard photolithography process. Specifically, a photolithography mask was covered on AZ5214E ​​and then irradiated with a 300W, 365nm UV lamp for 30 seconds. After exposure, the substrate was immersed in a developer (MIF300) for development, and then immersed in deionized water for cleaning to obtain a patterned area. A secondary annealing was performed at 110°C for 2 minutes; (4) Place the Si / SiO2 substrate in a 100 mm glass culture dish, leaving the center position; drop 20 μl of octadecyltrichlorosilane solution in the center of the culture dish, and place the culture dish in a vacuum oven at 120 °C for 2 hours; (5) Take the substrate out of the vacuum oven and spin-coat it with a precursor solution of 0.3 mM chloroauric acid, 0.25 mM sodium citrate, and 8 mM sodium borohydride at 3000 rpm / s, and blow dry with nitrogen gas; (6) dripping a gold nanowire growth solution containing 12 mM chloroauric acid, 1.1 mM 4-mercaptobenzoic acid, and 30 mM L-ascorbic acid onto the dried substrate surface, washing with anhydrous ethanol after 5 minutes and drying with nitrogen gas; (7) Spin coating a PDMS colloid with a ratio of PDMS (Dow Corning SYLGARD184) to curing agent of 15:1 on the gold nanowire electrode at 450 rpm / s, and then peeling it off after heating in an oven at 80 °C for 1 hour to obtain a stretchable patterned gold nanowire electrode; (8) Using a standard three-electrode system with a working electrode of a stretchable patterned gold nanowire electrode, a counter electrode of a platinum sheet, and a reference electrode of Ag / AgCl, 10 mC 3,6-dimethoxythienothiophene was deposited on the surface of the gold nanowire electrode. The electrolyte was an ultra-dry acetonitrile solution of 1 mM tetrabutylammonium hexafluorophosphate. (9) PVDF-co-HFP was dissolved in acetone at 12.5 wt / wt%, and then [EMIM][TFSI] and PVDF-co-HFP were mixed in proportion. An ion gel with a volume ratio of [EMIM][TFSI] to PVDF-co-HFP of 9:1 was dropped on the surface of the gold nanowire electrode and cured after irradiation with 200 nm ultraviolet light for 10 min to obtain a stretchable patterned electrochromic device based on gold nanowires.

[0024] Embodiment 2: The difference from Example 1 is that in step (5), the concentration of chloroauric acid in the precursor solution is 1.5 mM, the concentration of sodium citrate is 1.25 mM, and the concentration of sodium borohydride is 40 mM.

[0025] Embodiment 3: The difference from Example 1 is that in step (5), the concentration of chloroauric acid in the precursor solution is 3 mM, the concentration of sodium citrate is 2.5 mM, and the concentration of sodium borohydride is 80 mM.

[0026] Embodiment 4: The difference from Example 1 is that in step (6), the concentration of chloroauric acid in the gold nanowire growth solution is 6 mM, the concentration of 4-mercaptobenzoic acid is 0.55 mM, and the concentration of L-ascorbic acid is 15 mM.

[0027] Embodiment 5: The difference from Example 1 is that in step (6), the concentration of chloroauric acid in the gold nanowire growth solution is 24 mM, the concentration of 4-mercaptobenzoic acid is 2.2 mM, and the concentration of L-ascorbic acid is 60 mM.

[0028] Embodiment 6: The difference from Example 1 is that in step (8), 20 mC 3,6-dimethoxythienothiophene is deposited on the surface of the gold nanowire electrode using a standard three-electrode system.

[0029] Embodiment 7: The difference from Example 1 is that in step (8), 100 mC 3,6-dimethoxythienothiophene is deposited on the surface of the gold nanowire electrode using a standard three-electrode system.

[0030] Embodiment 8: The difference from Example 1 is that in step (8), 20 mC of conductive polyacetylene is deposited on the surface of the gold nanowire electrode using a standard three-electrode system.

[0031] Embodiment 9: The difference from Example 1 is that in step (8), 20 mC sulfonated polyaniline is deposited on the surface of the gold nanowire electrode using a standard three-electrode system.

[0032] The test results of the stretchable patterned electrochromic devices based on gold nanowires in Examples 1-7 are shown in the following table:

[0033] It can be seen from the above table: By comparing Examples 1-5 respectively, the resistance and transmittance of the flexible stretchable electrode based on gold nanowires can be controlled by regulating the concentration of the precursor solution and the gold nanowire growth solution. When the concentration of the precursor solution increases, the density of the vertical arrangement of the gold nanowires increases, and the conductivity and stretchability of the gold nanowire electrode are better. Correspondingly, its transmittance to visible light will be significantly reduced. This can be improved by appropriately reducing the concentration of the gold nanowire growth solution so that the diameter and length of the gold nanowires are reduced. Comparing Examples 1 and 6-7, depositing electrochromic materials of different thicknesses on the surface of the stretchable patterned gold nanowire electrode will significantly sacrifice transmittance to improve the stretchability of the material. Comparing Examples 1 and 8-9, by depositing different organic electrochromic polymers, full-band electrochromism in the visible light range can be achieved, providing a new choice for flexible sensing imaging, display, and optical camouflage.

[0034] The present invention also proposes a colorful stretchable electrochromic device based on gold nanowires, which includes a stretchable substrate 4, a vertically arranged gold nanowire array embedded in the stretchable substrate 4, an organic electrochromic layer and a solid electrolyte layer 1; the colorful stretchable electrochromic device based on gold nanowires is obtained by the above-mentioned preparation method of the colorful stretchable electrochromic device based on gold nanowires; the specific steps of the preparation method of the colorful stretchable electrochromic device based on gold nanowires refer to the above-mentioned embodiments. Since the colorful stretchable electrochromic device based on gold nanowires adopts all the technical solutions of all the above-mentioned embodiments, it at least has all the beneficial effects brought by the technical solutions of the above-mentioned embodiments, which are not repeated here one by one.

[0035] In one embodiment, the stretchable substrate 4 includes any one of polydimethylsiloxane, hydrogenated styrene-butadiene block copolymer, and water-soluble polyurethane.

[0036] In one embodiment, the organic electrochromic layer includes any one of polythiophene, polyaniline, and polyfluorene electrochromic materials.

[0037] In one embodiment, the solid electrolyte 1 is a polymer solid electrolyte 1 .

[0038] In this embodiment, the diameter of the gold nanowire is 5-20 nm, and the length is 0.5-2 μm; the thickness of the organic electrochromic layer is 0.01-1 μm.

[0039] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a colorful stretchable electrochromic device based on gold nanowires, characterized in that: The method for preparing the colorful stretchable electrochromic device based on gold nanowires comprises the following steps: S1. Ultrasonic cleaning of the Si / SiO2 substrate using deionized water and isopropanol solution, and then storing in a constant temperature oven after cleaning; S2, spin coating, printing or spraying a polymethyl methacrylate solution on the cleaned surface of the Si / SiO2 substrate, and performing thermal annealing; S3, spin coating, printing or spraying a positive photoresist on the thermally annealed polymethyl methacrylate film, exposing and developing the photoresist with ultraviolet light and a developer, and then performing a secondary thermal annealing; S4, subjecting the Si / SiO2 substrate treated in the previous step to oxygen plasma surface treatment, placing it in a vacuum oven, dropping octadecyltrichlorosilane and heating to volatilize it; S5, spin coating, printing or spraying the precursor solution on the surface of the Si / SiO2 substrate treated in the previous step; S6, after washing with deionized water and drying with nitrogen, drop the gold nanowire growth solution on the surface of the Si / SiO2 substrate to obtain gold nanowires grown vertically on the Si / SiO2 substrate; S7, after washing with anhydrous ethanol and drying with nitrogen, the stretchable substrate material is spin-coated on the surface of the gold nanowire, and heated, cured and peeled off to obtain a translucent stretchable patterned gold nanowire electrode; S8, placing the gold nanowire electrode obtained in the previous step in a three-electrode workstation, adding electrolyte and electrochromic material, and performing electrochemical deposition; S9. An electrolyte organic solution is dropped onto the surface of the patterned stretchable gold nanowire electrode after electrochemical deposition and dried and volatilized to obtain a solid electrolyte, and finally a colorful stretchable patterned electrochromic device based on gold nanowires is obtained.

2. A colorful stretchable electrochromic device based on gold nanowires, characterized in that: The colorful stretchable electrochromic device based on gold nanowires comprises a stretchable substrate, a vertically arranged gold nanowire electrode embedded in the stretchable substrate, an organic electrochromic layer and a solid electrolyte layer; the colorful stretchable electrochromic device based on gold nanowires is obtained by the preparation method of the colorful stretchable electrochromic device based on gold nanowires according to claim 1.

3. The colorful stretchable electrochromic device based on gold nanowires according to claim 2, characterized in that: The stretchable substrate includes any one of polydimethylsiloxane, hydrogenated styrene-butadiene block copolymer, and water-soluble polyurethane.

4. The colorful stretchable electrochromic device based on gold nanowires according to claim 2, characterized in that: The organic electrochromic layer includes any one of polythiophene, polyaniline and polyfluorene electrochromic materials.

5. The colorful stretchable electrochromic device based on gold nanowires according to claim 2, characterized in that: The solid electrolyte is a polymer solid electrolyte.

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