CN114924450A - Multicolor electrochromic device and construction method thereof - Google Patents

Abstract

The invention provides a method for constructing a multicolor electrochromic device, comprising the following steps: A) mixing silver nanowires, an amphiphilic solvent and a non-polar solvent to obtain a dispersion; B) adopting the Langmuir-Blodgett method to disperse the Add dropwise to the gas-liquid interface, and after standing, a silver nanowire film is obtained, and the silver nanowire film is assembled on a substrate to obtain a silver reflective layer; C) Dissolving the tungsten source in an organic solvent to obtain a tungsten oxide precursor solution, in A tungsten oxide precursor solution is assembled on the silver reflective layer, and a tungsten oxide electrochromic layer is obtained after annealing. The invention proposes a preparation method of an electrochromic device based on a Fabry-Perot nanocavity. The preparation method is simple and fast; and because of the strong resonance in the cavity, a series of bright, highly saturated Structural colors can obtain richer colors in the electrochromic process, expand the color control range of electrochromic materials, and meet the needs of multi-color display.

Description

A kind of multicolor electrochromic device and its construction method

technical field

The invention relates to the technical field of electrochromism, in particular to a multicolor electrochromic device and a construction method thereof.

Background technique

Electrochromism is a phenomenon in which certain materials cause reversible changes in electronic structure and optical properties (transmittance, reflectance, and absorption) under the stimulation of an external potential, which appear as reversible changes in transparency and color in appearance. There is great interest in new electrochromic display technologies that can switch between several colors. Compared with the traditional backlight and emissive display technology, the reflective electrochromic display technology has the advantages of clear display, bright color, no viewing angle blind area and low energy consumption. Therefore, electrochromic display technology has unique advantages in many fields such as electronic newspapers, signs, outdoor advertising boards and digital instruments.

Since Deb first discovered the electrochromic phenomenon of WO ₃ amorphous thin films in 1969, more and more electrochromic materials have been discovered, which are mainly divided into inorganic electrochromic materials and organic electrochromic materials. Compared with organic electrochromic materials, inorganic electrochromic materials are more expected to be used in reflective displays due to their excellent cycle performance, thermal stability, light stability and chemical stability. However, the general disadvantage of inorganic electrochromic materials is that the chromaticity modulation range is small and the color switching is single. For example, tungsten trioxide can only switch between transparent and blue, which cannot meet the requirements of multi-color display.

In view of the demand for multi-color reflective displays, some laboratories at home and abroad try to change the periodic structure of the photonic band gap of electrochromic materials to obtain multiple colors other than the intrinsic properties of the material, such as combining opal/inverse opal structures. Structures such as photonic crystals, Bragg mirrors, and plasmonic nanopolarizers are introduced into electrochromic devices, and several electrochromic materials are superimposed to obtain multiple colors. However, due to the limitation of periodicity, most of them cannot finely control colors. .

SUMMARY OF THE INVENTION

The technical problem solved by the present invention is to provide a method for preparing a multi-color electrochromic device, which is simple and fast, and can generate bright and highly saturated structural colors during the electrochromic process. More abundant colors can be obtained in the electrochromic material, which expands the color control range of electrochromic materials and can meet the needs of multi-color display.

In view of this, the present application provides a method for constructing a multicolor electrochromic device, comprising the following steps:

A) mixing silver nanowires, amphiphilic solvent and non-polar solvent to obtain dispersion;

B) using the Langmuir-Blodgett method to drop the dispersion onto the gas-liquid interface, and after standing to obtain a silver nanowire film, assemble the silver nanowire film on a substrate to obtain a silver reflective layer;

C) Dissolving a tungsten source in an organic solvent to obtain a tungsten oxide precursor solution, assembling the tungsten oxide precursor solution on the silver reflective layer, the number of assembly times ≥ 1, and obtaining a tungsten oxide electrochromic layer after annealing.

Preferably, the silver nanowires have a diameter of 20 nm to 100 nm and a length of 5 to 40 μm.

Preferably, the amphiphilic solvent is DMF, the non-polar solvent is chloroform, and the ratio of the silver nanowires, the amphiphilic solvent and the non-polar solvent is (2-4): (1- 1.5): 1.

Preferably, the tungsten source is selected from tungsten hexachloride, the organic solvent is selected from one or more of phenol, ethanol and isopropanol, the concentration of the tungsten oxide precursor solution is 5-50%, so The preparation temperature of the tungsten oxide precursor solution is 0-30°C.

Preferably, the assembling method is spin coating, and the number of times of the spin coating is 1 to 15 times.

Preferably, the speed of the spin coating is 300-5000 rpm, and the time of a single spin coating is 30-60 s.

Preferably, the humidity of the assembled tungsten oxide precursor solution is 25-80%; the tungsten source is dissolved in the organic solvent and stirred at 3-5°C.

Preferably, the temperature of the annealing is 50˜200° C., and the time is 1˜5 h.

The present application also provides a multi-color electrochromic device constructed by the construction method, which is composed of a substrate, a silver nanowire reflective layer and a tungsten oxide electrochromic layer that are stacked in sequence, and the tungsten oxide electrochromic layer has The number of layers ≥ 1.

Preferably, the substrate is a flexible transparent substrate, the thickness of the silver nanowire reflective layer is 40-80 nm, and the thickness of the tungsten oxide electrochromic layer is 110-350 nm.

The present application provides a method for preparing a multicolor electrochromic device, which includes the following steps: A) mixing silver nanowires, an amphiphilic solvent and a non-polar solvent to obtain a dispersion; B) using the Langmuir-Blodgett method to The dispersion is added dropwise to the gas-liquid interface, and after standing, a silver nanowire film is obtained, and the silver nanowire film is assembled on a substrate to obtain a silver reflection layer; C) Dissolving the tungsten source in an organic solvent to obtain an oxidized A tungsten precursor solution, the tungsten oxide precursor solution is assembled on the silver reflective layer, and the number of assembly times is ≥ 1, and a tungsten oxide electrochromic layer is obtained after annealing. This application adopts the Langmuir-Blodgett method to assemble silver nanowires on the substrate to obtain a bright, high-reflectivity silver nanowire conductive film, which is used as the bottom reflective layer of the Fabry-Perot nanocavity, and is also the conductive film of the electrochromic device. Further, tungsten oxide with different thicknesses is grown on the silver reflective layer by spin coating, which is used as the dielectric layer of the Fabry-Perot-like nanocavity and the electrochromic layer of the electrochromic device. The present invention proposes a method for preparing the electrochromic device based on a Fabry-Perot nanocavity. The preparation method is simple, fast, and does not require equipment such as magnetron sputtering. Due to the strong resonance in the cavity, the device can be A series of bright, highly saturated structural colors can be produced, and richer colors can be obtained during the electrochromic process, which expands the color control range of electrochromic materials and can meet the needs of multi-color display.

Description of drawings

1 is a scanning electron micrograph of silver nanowires prepared in Example 1 of the present invention;

FIG. 2 is a photo of the Langmuir-Blodgett groove covered with silver nanowires in Example 2;

Fig. 3 is the bright silver mirror photograph assembled on PC substrate in embodiment 2 and the electron micrograph of the silver nanowire of the assembly;

4 is a cross-sectional view of the device prepared in Example 2;

Fig. 5 is the optical photograph and ultraviolet-visible reflection spectrum of the thin film of spin-coating twice, three times and four times of tungsten oxide in Example 2;

Fig. 6 is the optical picture and chromaticity diagram of the different color films obtained by regulating and controlling different concentrations and layers in embodiment 2;

Fig. 7 is the discoloration situation of the film prepared in Example 3 under different voltages;

Fig. 8 is the ultraviolet-visible reflection spectrum of the discoloration of the film prepared in Example 3 under different voltages;

FIG. 9 is the discoloration and fading response time of the device prepared in Example 3. FIG.

Detailed ways

In order to further understand the present invention, the preferred embodiments of the present invention are described below in conjunction with the examples, but it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention.

The invention provides a preparation method of an electrochromic device based on a Fabry-Perot nanocavity, which is simple and fast, and does not need magnetron sputtering and other equipment. Due to the strong resonance in the cavity, a series of bright and highly saturated structural colors can be generated before the voltage is applied, and more abundant colors can be obtained during the electrochromic process, which expands the color control range of electrochromic materials and can meet the The need for multi-color display. Specifically, the present application first provides a method for preparing a multicolor electrochromic device, comprising the following steps:

A) mixing silver nanowires, amphiphilic solvent and non-polar solvent to obtain dispersion;

B) using the Langmuir-Blodgett method to drop the dispersion onto the gas-liquid interface, and after standing to obtain a silver nanowire film, assemble the silver nanowire film on a substrate to obtain a silver reflective layer;

C) Dissolving a tungsten source in an organic solvent to obtain a tungsten oxide precursor solution, assembling the tungsten oxide precursor solution on the silver reflective layer, the number of assembly times ≥ 1, and obtaining a tungsten oxide electrochromic layer after annealing.

The present invention uses the Langmuir-Blodgett method to assemble silver nanowires on the substrate to obtain a bright and high-reflectivity silver nanowire conductive film, which is used as the bottom reflection layer of the Fabry-Perot nanocavity and is also the conductive film of the electrochromic device. Further, tungsten oxide with different thicknesses is grown on the silver reflective layer by spin coating, which is used as the dielectric layer of the Fabry-Perot-like nanocavity and the electrochromic layer of the electrochromic device.

The preparation process of the silver nanowires described in the present application is as follows: first, the thick silver nanowires are synthesized by the polyol method, washed once with ethanol and water, respectively, and then dispersed in ethanol to obtain a silver nanowire solution, and the synthesized silver nanowire solution is taken and centrifuged. After dispersing in an amphiphilic solvent and a non-polar solvent, after obtaining the silver nanowires, the silver nanowires are assembled on the substrate by the Langmuir–Blodgett method. Specifically, the silver nanowire dispersion liquid is added dropwise with a micro syringe On the water-air interface of the Langmuir–Blodgett cell, after standing, start to press the film at a slow and uniform speed until the surface of the nanowire film is wrinkled, and a bright silver nanowire film with high reflectivity is formed on the water-air interface, which is transferred to the substrate. As the bottom reflective layer of the Fabry-Perot cavity.

In the above process, in order to facilitate the subsequent Langmuir-Blodgett assembly and ensure a certain reflectivity of the silver reflective layer, the diameter of the silver nanowire is 20-100 nm and the length is 5-40 μm; specifically, the diameter is preferably 40 to 100 nm, more preferably 50 to 80 nm, most preferably 60 to 70 nm, the length is preferably 10 to 25 μm, more preferably 14 to 20 μm, and most preferably 16 to 18 μm. The amphiphilic solvent is DMF, and the non-polar solvent is chloroform; the volume ratio of the amphiphilic solvent and the non-polar solvent is (1-1.5): 1, preferably 1.5: 1, and this The silver nanowire film at the water-air interface is the smoothest. The present invention has no special requirements on the substrate, and a flexible transparent substrate well-known to those skilled in the art can be used, including but not limited to one or more of a PVC substrate, a PDMS substrate, a PET substrate and a PC substrate, preferably a PC substrate; The thickness of the substrate is 0.1 mm to 0.8 mm, preferably 0.1 mm to 0.5 mm. The present invention does not require the number of layers of the Langmuir-Blodgett method to assemble the silver nanowires. Those skilled in the art can adjust and control the reflectivity and transmittance of the device according to the requirements of the device, preferably 1 to 2 layers (there is no requirement for the angle when there are two layers) .

The application then prepares a tungsten oxide precursor solution, dissolves a tungsten source in an organic solvent to obtain a tungsten oxide precursor solution, controls the environmental humidity to be 25%-80%, and spin-coats the tungsten oxide precursor solution on the silver nanowire substrate at 300-5000 rpm , to obtain a Fabry-Perot cavity with obvious structural color, spin coating with different layers, and obtain different colors such as green, red, and blue after annealing. In the above process, the tungsten source is tungsten hexachloride, the organic solvent is selected from one or more of phenol, ethanol and isopropanol, and the concentration of the tungsten oxide precursor solution is 5-50%, The preparation temperature of the tungsten oxide precursor solution is 0-30°C. In the present invention, in order to avoid the side reaction of tungsten hexachloride dissolved in isopropanol as much as possible, it should be stirred at a lower temperature, most preferably vigorously stirred at 3°C to 5°C, until the solution is a stable blue transparent solution. The present invention needs to ensure proper humidity during spin coating, preferably 20% to 55%, more preferably 30% to 40%; the speed of the spin coating is 300 to 5000rpm, and the time of a single spin coating is 30 to 60s . The thicknesses of the tungsten oxide layers with different thicknesses in the present application are obtained by controlling the spin coating times to be 1-15 times. The annealing temperature is 50-200°C, and the time is 1-5h; more specifically, the annealing temperature is 70-180°C, and the time is 2-4h.

The present application also provides a multi-color electrochromic device prepared by the above method, which is composed of a substrate, a silver nanowire reflective layer and a tungsten oxide electrochromic layer that are stacked in sequence, and the number of layers of the tungsten oxide electrochromic layer is ≥1.

In this application, the substrate is a flexible and transparent substrate, the thickness of the silver nanowire reflective layer is 40 nm to 80 nm, and the thickness of the tungsten oxide electrochromic layer is 110 nm to 350 nm; more specifically, the silver nanowire The thickness of the reflective layer is 50 to 60 nm, and the thickness of the tungsten oxide electrochromic layer is 150 to 300 nm.

Performance characterization of multicolor electrochromic devices provided in this application:

1) The Fabry-Perot cavity film is the working electrode, the Ag/AgCl electrode is the reference electrode, the platinum wire electrode is the counter electrode, and the electrolyte solution is 0.5mol/L LiClO ₄ /PC solution to form a three-electrode system;

2) Use an electrochemical workstation to conduct electrochromic tests on the device to observe color changes;

3) The electrochemical workstation was combined with an ultraviolet spectrophotometer to observe the change of the reflectivity of the film under the condition of discoloration, and test the discoloration and fading response time at a wavelength of 610nm under negative pressure of -0.5V and positive pressure of 0.2V.

In order to further understand the present invention, the multicolor electrochromic device provided by the present invention and the preparation method thereof will be described in detail below with reference to the examples, and the protection scope of the present invention is not limited by the following examples.

Example 1 Method for preparing silver nanowires and tungsten oxide precursor solution of the present invention

Weigh 5.86 grams of polyvinylpyrrolidone (PVP) (molecular weight ≈ 40.000) and 190 milliliters of glycerol solution into a 250 milliliter three-necked flask, and heat from room temperature to 100 degrees Celsius under stirring until PVP is completely dissolved; 1.58 grams of silver nitrate was added to the reaction system, the set temperature was heated from room temperature to 210 degrees Celsius, 59 mg of sodium chloride was weighed and dissolved in 0.5 milliliters of deionized water and 10 milliliters of glycerol was added to generate silver seeds, and added to the system at 60 degrees Celsius. Stir slowly, stop the reaction after the temperature rises to 210 degrees Celsius, add 200 ml of water, stand and centrifuge to obtain silver nanowires;

Weigh 1.870g of tungsten hexachloride in 20ml of isopropanol, and stir vigorously at 4°C until the solution turns transparent blue to obtain a tungsten oxide precursor solution; see Figure 1, which is prepared in Example 1 of the present invention SEM image of silver nanowires.

Example 2: The preparation method of electrochromic device, which aims to illustrate the necessity of Fabry-Perot cavity for structural color

Take 2ml of silver nanowire solution with a concentration of 5mg/ml, disperse it in 1.5ml DMF and 1ml chloroform after centrifugation, pipette the prepared silver nanowire solution with a 100ml syringe, and inject it on the water surface of the LB membrane analyzer until it is covered. The entire liquid surface is then used to pick up the assembled silver nanowires with a PC film to obtain a silver nanowire layer with high reflectivity, which is used as the bottom reflection layer of the Fabry-Perot cavity;

Two, three and four layers of tungsten oxide precursor solution were spin-coated on the silver nanowire substrate, and the obtained films after annealing showed red, green and blue, respectively.

The concentration of different tungsten oxide precursor solutions and the number of spin coats can be adjusted, and the color of the film can be adjusted in a wide range, see Figure 2, which is a photo of the Langmuir-Blodgett groove covered with silver nanowires in Example 2 of the present invention; Referring to Fig. 3, Fig. 3 is a photo of the bright silver mirror assembled on a PC substrate (left image) and an SEM image of the assembled silver nanowires (right image); Fig. 4, Fig. 4 is a cross-sectional view of the device; See Fig. 5, Fig. 5 is the optical photograph and ultraviolet reflection spectrum of the thin film of spin-coating two-layer, three-layer and four-layer tungsten oxide; Referring to Fig. 6, Fig. 6 is the optical picture and chromaticity diagram of the different color thin film obtained by regulating different concentrations and layers ; It can be seen from Figure 6 that the film has a broad chromaticity control range.

Experimental Example 3 Electrochromic Properties of Thin Films

The Fabry-Perot cavity film was used as the working electrode, the Ag/AgCl electrode was used as the reference electrode, the platinum wire electrode was used as the counter electrode, and the electrolyte solution was 0.5mol/L LiClO ₄ /PC solution to form a three-electrode system; Four layers of tungsten oxide films were spin-coated on the nanowire layer to form a blue Fabry-Perot cavity film. Electrochromic tests were performed on the device using an electrochemical workstation to observe the color changes. Electrochromic tests showed that at 0V, -0.5V, -1.0V, -1.5V and -2.0V, the reflected state color changed from blue to green to orange-red.

The electrochemical workstation was combined with an ultraviolet spectrophotometer to observe the change of the reflectivity of the film under the condition of discoloration, and the discoloration and fading response time was tested at a wavelength of 610nm under negative pressure of -0.8V and positive pressure of 0.2V; see Figure 7 , Figure 7 is the discoloration of the film prepared in Example 3 under different voltages, and participate in Figure 8, Figure 8 is the UV reflection spectrum of the film prepared in Example 3 under different voltages; see Figure 9, Figure 9 is an embodiment 3. The response time of discoloration and fading of the prepared device; it can be seen from Figure 8 that with the increase of voltage, the color of the film changes significantly, from yellow to green gradually, and the reflection peak shifts blue; it can be seen from Figure 9 that the color change response time of the film Only 2 seconds, and the fade response time is only 6.5 seconds.

The descriptions of the above embodiments are only used to help understand the method and the core idea of the present invention. It should be pointed out that for those skilled in the art, without departing from the principle of the present invention, several improvements and modifications can also be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

The above description of the disclosed embodiments enables any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (10)

1. A construction method of a multicolor electrochromic device comprises the following steps:

A) mixing the silver nanowires, the amphiphilic solvent and the nonpolar solvent to obtain a dispersion liquid;

B) dropwise adding the dispersion liquid to a gas-liquid interface by adopting a Langmuir-Blodgett method, standing to obtain a silver nanowire film, and assembling the silver nanowire film on a substrate to obtain a silver reflecting layer;

C) dissolving a tungsten source in an organic solvent to obtain a tungsten oxide precursor solution, assembling the tungsten oxide precursor solution on the silver reflecting layer for more than or equal to 1 time, and annealing to obtain the tungsten oxide electrochromic layer.

2. The construction method according to claim 1, wherein the silver nanowires have a diameter of 20nm to 100nm and a length of 5 μm to 40 μm.

3. The construction method according to claim 1, wherein the amphiphilic solvent is DMF, the nonpolar solvent is chloroform, and the ratio of the silver nanowires to the amphiphilic solvent to the nonpolar solvent is (2-4): (1-1.5): 1.

4. the construction method according to claim 1, wherein the tungsten source is selected from tungsten hexachloride, the organic solvent is selected from one or more of phenol, ethanol and isopropanol, the concentration of the tungsten oxide precursor solution is 5-50%, and the preparation temperature of the tungsten oxide precursor solution is 0-30 ℃.

5. The method for constructing a laminated structure according to claim 1, wherein the assembling method is spin coating, and the number of spin coating is 1 to 15.

6. The method as claimed in claim 5, wherein the spin coating speed is 300-5000 rpm, and the time for one spin coating is 30-60 s.

7. The construction method according to claim 1, wherein the humidity of the assembled tungsten oxide precursor solution is 25-80%; and dissolving the tungsten source in the organic solvent, and stirring at 3-5 ℃.

8. The construction method according to claim 1, wherein the annealing temperature is 50-200 ℃ and the annealing time is 1-5 h.

9. The multicolor electrochromic device constructed by the construction method of any one of claims 1 to 8, which consists of a substrate, a silver nanowire reflecting layer and a tungsten oxide electrochromic layer which are sequentially overlapped, wherein the number of the tungsten oxide electrochromic layers is more than or equal to 1.

10. The multicolor electrochromic device according to claim 9, wherein said substrate is a flexible transparent substrate, said silver nanowire reflective layer has a thickness of 40 to 80nm, and said tungsten oxide electrochromic layer has a thickness of 110 to 350 nm.

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