F-P resonant cavity type multi-color electrochromic film and preparation method and application thereof

Abstract

The invention relates to an F-P resonant cavity type multi-color electrochromic film and a preparation method and application thereof, the F-P resonant cavity type multi-color electrochromic film comprises a flexible conductive substrate, an Ag reflecting layer deposited on the flexible conductive substrate and a WO3 electrochromic active layer deposited on the Ag reflecting layer, the thickness of the Ag reflecting layer is 20-60 nm, and the thickness of the WO3 electrochromic active layer is 10-30 nm. Compared with the prior art, the F-P resonant cavity type multi-color electrochromic film is compatible with the flexible conductive substrate, an F-P optical cavity is constructed through an Ag-WO3 composite structure, the structural color enhancement effect is achieved, and the color adjustable range is widened.

Description

Technical Field

[0001] The present invention relates to the technical field of functional optoelectronic materials, and in particular to an FP resonant cavity type multi-color electrochromic film and a preparation method and application thereof. Background Art

[0002] Electrochromism (EC) is a phenomenon in which a material changes color when exposed to an electric field. Due to its unique color-controlling capabilities, it has been widely researched and applied in recent years in fields such as smart windows, display technology, and wearable devices. In-depth research into electrochromic materials has revealed that EC can not only achieve single-color changes but also precisely control multiple colors, creating a rich and colorful display.

[0003] The key to the colorful regulation of electrochromic materials lies in the "adjustability" of their colors, which is inseparable from their material composition and structural design. Traditional color control methods are often limited by the physical properties of the material itself, and the range of their color changes is limited to a simple transition from transparent to dark. By combining electrochromic materials with other functional materials (such as photonic crystals, metal nanomaterials, etc.), more complex optical effects can be triggered, thereby achieving richer color regulation. For example, the use of photonic crystal structures can enhance the optical absorption or reflection characteristics of electrochromic materials, so that they exhibit different color changes in multiple wavelength ranges, which provides great freedom for product design.

[0004] The basic principle of the Fabry-Perot (FP) resonant cavity is to use an optical structure composed of two parallel mirrors, relying on the precise control of the distance between the mirrors and the adjustment of the reflectivity of the mirrors to form multiple optical modes. Light can form resonance in the cavity through the reflection and interference effect of the resonant cavity. This resonance phenomenon significantly enhances the interaction between light and matter, thereby bringing unique optical properties. In electrochromic technology, when the electrochromic material is integrated into the FP resonant cavity, the optical mode in the cavity is mutually coupled with the optical response of the electrochromic material, resulting in significant changes in the reflection, transmission and absorption characteristics of light with changes in the electric field. This optical regulation effect can make the electrochromic material show different colors under different voltages, and in some cases, it can achieve more precise and richer color adjustment than traditional methods.

[0005] At present, there is still a lack of thin film preparation methods that have both FP structural color regulation capabilities and excellent electrochromic properties, especially in the low-temperature and controllable construction methods on flexible substrates, where there are still technical bottlenecks. Summary of the Invention

[0006] The purpose of the present invention is to overcome the defects of the prior art and thus provide a FP resonant cavity type colorful electrochromic film and its preparation method and application.

[0007] The purpose of the present invention can be achieved by the following technical solutions:

[0008] One of the technical solutions of the present invention is to provide an FP resonant cavity type colorful electrochromic film, comprising a flexible conductive substrate, an Ag reflective layer deposited on the flexible conductive substrate, and a WO3 electrochromic active layer deposited on the Ag reflective layer, wherein the thickness of the Ag reflective layer is 20 to 60 nm, and the thickness of the WO3 electrochromic active layer is 10 to 30 nm.

[0009] In some specific embodiments, the flexible conductive substrate is an ITO-PET film.

[0010] A second technical solution of the present invention is to provide a method for preparing the FP resonant cavity type multi-color electrochromic film as described in one of the above technical solutions, comprising the following steps:

[0011] S1. In an inert atmosphere and vacuum environment, Ag is deposited on a flexible conductive substrate by magnetron sputtering to form an Ag reflective layer;

[0012] S2. Depositing WO3 on the Ag reflective layer obtained in step S1 by magnetron sputtering to form a WO3 electrochromic active layer, thereby obtaining an Ag-WO3 composite thin film.

[0013] Among them, Ag provides the reflective end face, and WO3 is the active medium layer that can adjust the optical path. The two construct the FP resonant cavity structure.

[0014] In some embodiments, the inert gas is selected from any one of argon and nitrogen, and the vacuum environment has a base pressure of 1×10 -5 Below Pa.

[0015] More preferably, the inert gas is argon, and the flow rate of argon is 100 sccm.

[0016] In some specific embodiments, in step S1, the magnetron sputtering process is: turn on the DC power supply, pre-sputter Ag on the flexible conductive substrate at a power of 30 W for 10 minutes, and the Ag sputtering gas pressure is 0.554 Pa, and then formal sputtering is performed at the same power for 1-5 minutes to deposit and form an Ag reflective layer.

[0017] In some specific embodiments, in step S2, the magnetron sputtering process is as follows: turn on the RF power supply, pre-sputter WO3 on the Ag reflective layer at a power of 50 W for 30 minutes, the WO3 sputtering gas pressure is 1.27 Pa, and then formal sputtering is performed at the same power for 10-60 minutes to deposit and form a WO3 electrochromic active layer.

[0018] A third technical solution of the present invention is to provide an application of the FP resonant cavity type multi-color electrochromic film as described in one of the above technical solutions in the preparation of an electrochromic device.

[0019] A fourth technical solution of the present invention is to provide an electrochromic device, comprising the FP resonant cavity type multi-color electrochromic film as described in one of the above technical solutions.

[0020] In some specific embodiments, in the electrochromic device, the FP resonant cavity type colorful electrochromic film serves as a working electrode, and the Zn(ClO4)2 / PC electrolyte serves as an ion transport liquid.

[0021] In some specific embodiments, the concentration of the Zn(ClO4)2 / PC electrolyte is 0.1 mol / L.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) The FP resonant cavity type colorful electrochromic film of the present invention is compatible with flexible conductive substrates. By adjusting the film thickness of Ag and WO3, a Fabry-Perot (FP) resonant cavity type is generated between Ag-WO3, which causes the optical signal to generate optical interference in the FP resonant cavity. Combined with different voltage control, reversible changes in multiple colors such as orange, yellow, blue, and purple occur, making it present a multi-color effect, achieving a structural color enhancement effect, and improving the color adjustable range.

[0024] (2) The preparation method provided by the present invention is simple, the equipment is universal, and it can be carried out at room temperature and has good repeatability and stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 : Schematic diagram of the Ag-WO3 composite film structure.

[0026] Figure 2 : XRD analysis of the Ag film prepared in Example 1 of the present invention.

[0027] Figure 3 : XRD analysis of the WO3 thin film prepared in Example 1 of the present invention.

[0028] Figure 4 : XPS analysis of the Ag thin film prepared in Example 1 of the present invention.

[0029] Figure 5 : XPS analysis of the WO3 thin film prepared in Example 1 of the present invention.

[0030] Figure 6 : Cross-sectional SEM image of WO3-Ag-ITO electrode.

[0031] Figure 7 : Schematic diagram of color switching under voltage change.

[0032] Figure 8 : Color switching spectral reflectance curve under voltage change.

[0033] Figure 9 : FDTD simulation results show the reflection peak migration behavior under different thickness structures. DETAILED DESCRIPTION

[0034] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0035] In the following examples, unless otherwise specified, raw materials or processing techniques are conventional commercially available raw materials or conventional processing techniques in the art.

[0036] Example 1

[0037] This embodiment provides a FP resonant cavity multi-color electrochromic film, the preparation method of which includes the following steps:

[0038] (1) Take a 25 mm × 30 mm ITO-PET flexible conductive substrate, ultrasonically clean it with acetone, ethanol, and deionized water for 15 min in sequence, and blow dry it for later use.

[0039] (2) The treated ITO-PET flexible conductive substrate was fixed on the sample stage of the magnetron sputtering system, and the chamber was evacuated to a base pressure of 1×10 -5 Pa, and introduce high-purity argon gas (100 sccm) for 10 minutes.

[0040] (3) Start the DC power supply and pre-sputter Ag (30 W, 10 min, 0.554 Pa) on the ITO-PET flexible conductive substrate, and then formally sputter for 3 min to deposit a Ag film with a thickness of about 20 nm.

[0041] (4) Start the radio frequency power supply and pre-sputter WO3 (50W, 30min, 1.27Pa) on the Ag film, and then formally sputter for 60min to deposit a WO3 film with a thickness of about 30nm to obtain an Ag-WO3 composite film sample.

[0042] like Figure 1 Schematic diagram of the structure of Ag-WO3 composite film, Ag-WO3 composite film grown on ITO-PET substrate.

[0043] The film samples prepared above were subjected to high-resolution XRD tests, such as Figure 2 is the XRD pattern of the Ag film, in which the diffraction peaks correspond to the crystal plane indices (111), (200), (220), (311) and (222), respectively.

[0044] Figure 3 Figure 2 shows the XRD pattern of the WO3 thin film. The sputtered WO3 layer exhibits diffraction peaks corresponding to the standard diffraction peaks of crystal plane indices (200), (202), and (221). The XRD spectrum of the WO3 layer has no characteristic peaks except for three broad peaks with amorphous shoulders, indicating that the tungsten oxide layer is amorphous.

[0045] In addition, XPS test analysis was performed on Ag and WO3 thin film materials, such as Figure 4 As shown, it is the Ag 3d energy spectrum of the Ag film, in which the peak difference between the binding energy of 373.38eV and 367.38eV is 6eV, proving the existence of Ag element.

[0046] like Figure 5 The following is the W 4f spectrum of WO3 film, where there are two groups of peaks at 38.1eV and 35.9eV, and 37.7eV and 35.7eV, which are caused by W 6+ and W 5+ Caused by the state. Belongs to W 6+ The relative content of the two peaks is 48.2%, which is attributed to W 5+ The relative content of the two peaks is 51.8%. The coexistence of different valence states of W indicates the presence of oxygen vacancy defects in the surface tungsten oxide layer, and the presence of oxygen vacancies is a prerequisite for tungsten oxide materials to achieve electrochromism.

[0047] like Figure 6 As shown in the figure, a cross-sectional SEM image of the WO3-Ag-ITO electrode is shown. It can be clearly observed that it is a perfect three-layer FB structure with uniform thickness and little variation. A clear and uniform interface can be seen without obvious cracks and defects.

[0048] Example 2:

[0049] Based on the method for preparing the FP resonant cavity type multi-color electrochromic film in Example 1, the following FP resonant cavity type multi-color electrochromic films with different Ag and WO3 thicknesses were prepared respectively:

[0050]

[0051] Test Example 1: Electrochromic Performance Test of Ag-WO3 Electrochromic Composite Film

[0052] Material:

[0053] ① Prepare electrolyte: 0.1 mol / L Zn(ClO4)2 dissolved in PC (propylene carbonate) and store at room temperature.

[0054] ②Construct an electrochemical three-electrode system: Ag-WO3 composite film as the working electrode, platinum sheet as the counter electrode, and Ag / AgCl as the reference electrode.

[0055] Applying different voltages (0V to -1V) can achieve multiple color tones, such as Figure 7 As shown, these are the colors at voltages of 0V, -0.3V, and -1V respectively.

[0056] Taking the electrochromic film composed of 40nm Ag and 30nm WO3 (sample 6) as an example, different voltages (0V to -1V) were applied to perform electrochromic tests and the spectral changes were recorded. Figure 8 As shown, the color changes from orange, purple to dark purple.

[0057] Test Example 2: FDTD Optical Simulation Verification

[0058] In order to verify the existence of the FP resonant cavity in the Ag-WO3 composite structure and its influence on the optical performance, the finite-difference time-domain method (FDTD) was used to simulate and calculate its electromagnetic response characteristics in this test case.

[0059] The simulation model is constructed based on the actual preparation structure: the model consists of an ITO substrate, an Ag reflective layer, a WO3 dielectric layer, and an air layer, and its thickness parameter range is defined as 60nm for the Ag layer and 10-30nm for the WO3 layer.

[0060] The boundary conditions are periodic boundary in the transverse direction and perfectly matched layer (PML) in the longitudinal direction. The incident light is a plane wave with normal incidence and the wavelength range is 400-800 nm.

[0061] The simulation results show that Figure 9 The designed Ag-WO3 composite film, at specific thicknesses, forms a stable Fabry-Pérot (FP) resonant cavity structure, exhibiting significant optical interference. As the WO3 film thickness decreases, the magnetic field strength increases at 400-500nm, indicating stronger interference, confirming the existence of a structural color modulation mechanism.

[0062] By varying the WO3 film thickness, a red- or blue-shift in the resonant wavelength was observed, further demonstrating the structure's excellent color tunability, consistent with the reversible multicolor modulation observed in experimental results. This simulation provides theoretical support for the optical response mechanism of the electrochromic structure of this invention.

[0063] The above description of the embodiments is intended to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention, without departing from the scope of the present invention, should be within the scope of protection of the present invention.

Claims

1. A FP resonant cavity type multi-color electrochromic film, characterized in that: The invention comprises a flexible conductive substrate, an Ag reflective layer deposited on the flexible conductive substrate, and a WO3 electrochromic active layer deposited on the Ag reflective layer. The thickness of the Ag reflective layer is 20 to 60 nm, and the thickness of the WO3 electrochromic active layer is 10 to 30 nm.

2. The FP resonant cavity multi-color electrochromic film according to claim 1, characterized in that: The flexible conductive substrate is an ITO-PET film.

3. A method for preparing the FP resonant cavity type multi-color electrochromic film according to any one of claims 1 or 2, characterized in that: The steps include: S1. In an inert atmosphere and vacuum environment, Ag is deposited on a flexible conductive substrate by magnetron sputtering to form an Ag reflective layer; S2. Depositing WO3 on the Ag reflective layer obtained in step S1 by magnetron sputtering to form a WO3 electrochromic active layer, thereby obtaining an Ag-WO3 composite thin film.

4. The preparation method according to claim 3, characterized in that The inert gas is selected from any one of argon and nitrogen, and the vacuum environment is at a base pressure of 1×10 -5 Below Pa.

5. The preparation method according to claim 3, characterized in that In step S1, the magnetron sputtering process is as follows: turn on the DC power supply, pre-sputter Ag on the flexible conductive substrate at a power of 30 W for 10 minutes, and the Ag sputtering gas pressure is 0.554 Pa. Then, formal sputtering is performed at the same power for 1-5 minutes to deposit and form an Ag reflective layer.

6. The preparation method according to claim 3, characterized in that In step S2, the magnetron sputtering process is as follows: turn on the RF power supply, pre-sputter WO3 on the Ag reflective layer at a power of 50W for 30 minutes, and the WO3 sputtering gas pressure is 1.27Pa. Then, formal sputtering is performed at the same power for 10-60 minutes to deposit and form a WO3 electrochromic active layer.

7. Use of the FP resonant cavity multi-color electrochromic film according to any one of claims 1 or 2 in the preparation of an electrochromic device.

8. An electrochromic device, characterized in that: It comprises the FP resonant cavity type colorful electrochromic film according to any one of claims 1 or 2.

9. The electrochromic device according to claim 8, characterized in that: In the electrochromic device, the FP resonant cavity type colorful electrochromic film serves as a working electrode, and the Zn(ClO4)2 / PC electrolyte serves as an ion transport liquid.

10. The electrochromic device according to claim 9, characterized in that: The concentration of the Zn(ClO4)2 / PC electrolyte is 0.1 mol / L.

Images