Electric control strong coupling structure based on electrochromic material and silver nano array

Abstract

The invention provides an electric control strong coupling structure based on an electrochromic material and a silver nano array. The electric control strong coupling structure comprises a silver substrate layer, a silver nano array layer, an electrochromic material layer, an ion storage layer and an ITO thin film layer which are stacked in sequence. According to the electric control strong coupling structure based on the electrochromic material and the silver nano array, active control over the strong coupling state can be achieved, the coupling strength of a coupling system can be adjusted in real time, the structure is simple and easy to integrate, and the electric control strong coupling structure is expected to be applied to optoelectronic switches and light modulators.

Description

Technical Field

[0001] The present invention relates to an electrically controlled strong coupling structure based on electrochromic materials and silver nanoarrays, belonging to the technical field of nanophotonics. Background Art

[0002] Strong coupling between light and matter means that the interaction strength between the light field and matter (such as excited states in atoms, molecules or solids) is large enough that the properties of the two cannot be described independently. At this time, light and matter form a new hybrid state, called a polariton.

[0003] In the strong coupling state, significant energy level splitting occurs in the system, manifested as two new energy levels (upper polariton and lower polariton), whose energies depend on the coupling strength of light and matter. This phenomenon is usually observed in microcavities, photonic crystals or plasmas, and is of great significance for studying photon-exciton coupling, quantum optics and other fields.

[0004] Strong coupling between light and matter leads to the formation of semi-light and semi-matter quasiparticles, which have the characteristics of both systems, such as small mass and large interaction. When the system undergoes strong coupling, significant changes in various optical properties such as reflectivity will occur. Therefore, if the coupling strength can be controlled in real time and the system can be switched from the strong coupling state to the weak coupling state, it will be of great significance and can be applied to optoelectronic switches and optical modulators.

[0005] In existing research, the strong coupling of plasmon-excitons can be actively regulated by means of light, electricity, heat, chemical control, etc. Among them, the electrical control method can combine micro-nano structures with optical or conductive materials with electrical regulation characteristics, such as semiconductor (TMDC) monolayers, liquid crystals or graphene. The regulation mechanism usually affects the coupling strength by changing the exciton density (such as exciton bleaching caused by electrical doping). However, this method has some disadvantages: the regulation voltage range is relatively high (such as 0 to 80 volts), and it mostly operates at low temperatures (below 100K); only medium Rabi splitting energy (such as 60 meV) can be achieved, as well as the switching of the weak coupling to strong coupling state. Summary of the Invention

[0006] The present invention provides an electrically controlled strong coupling structure based on electrochromic materials and silver nanoarrays, which can effectively solve the above problems.

[0007] The present invention is implemented as follows:

[0008] An electrically controlled strong coupling structure based on electrochromic materials and silver nanoarrays, comprising: a silver substrate layer, a silver nanoarray layer, an electrochromic material layer, an ion storage layer and an ITO thin film layer stacked in sequence.

[0009] In some embodiments, the thickness of the silver substrate layer is 80 - 120 nm.

[0010] In some embodiments, the period of the silver nanoarray is 280 nm - 320 nm, the width of the silver strip is 180 nm - 260 nm, and the thickness of the silver strip is 10 nm - 50 nm.

[0011] In some embodiments, the thickness of the electrochromic material layer is 10 nm - 80 nm.

[0012] In some embodiments, the thickness of the ion storage layer is 30 nm - 100 nm.

[0013] In some embodiments, the thickness of the ITO thin film layer is 25 - 35 nm.

[0014] A preparation method of the electro - controlled strong coupling structure based on electrochromic materials and silver nanoarrays as described above includes the following steps:

[0015] S1, prepare a silver substrate layer and a silver nanoarray;

[0016] S2, prepare electrochromic materials on the silver nanoarray and form an electrochromic material layer;

[0017] S3, spin - coat an ion storage layer on the electrochromic material layer;

[0018] S4, magnetron - sputter an ITO thin film layer on the ion storage layer.

[0019] In some embodiments, step S1 includes the following steps:

[0020] S11, clean the quartz substrate, and sequentially deposit a chromium layer and a silver layer on the quartz substrate by electron beam evaporation to form the silver substrate layer;

[0021] S12, spin - coat a layer of polymethyl methacrylate photoresist on the silver layer;

[0022] S13, pattern the photoresist by electron beam exposure;

[0023] S14, deposit a chromium layer and a silver layer again by electron beam evaporation in the patterned photoresist area;

[0024] S15, finally dissolve the unexposed photoresist with a solvent, strip the silver layer and chromium layer covering the photoresist, and the remaining silver layer forms a periodic photoresist pattern, which is the silver nanoarray.

[0025] In some embodiments, step S2 includes the following steps:

[0026] S21, add electrochromic materials to a solvent and fully dissolve to form a spin - coating solution;

[0027] S22. Spin-coat the spin-coating solution onto the silver nanowire array, allowing the spin-coating solution to first fill the gaps in the silver nanowire array and then continue to spin-coat on top to form a thin film.

[0028] In some embodiments, step S3 is as follows:

[0029] Fully mix and disperse electroactive molecules, a polymer matrix, an electrolyte, and a solvent, and then spin-coat them on the surface of the electrochromic material layer to form an ion storage layer.

[0030] The beneficial effects of the present invention are as follows:

[0031] By adopting a regulation structure combining electrochromic materials and silver nanowire arrays, the present invention successfully achieves a tuning effect with a low voltage of only a few volts and can achieve a coupling strength on the order of several hundred millielectron volts (meV). This regulation structure not only requires a low voltage, but also enables the system to achieve continuous and smooth tuning control by adjusting the magnitude of the voltage. Compared with simply performing on-off operations under specific voltage conditions, it has more significant advantages and flexibility. In addition, this regulation system also has the characteristic of operating at room temperature, which greatly improves its feasibility and convenience in practical applications and provides strong support for a wide range of practical application scenarios.

[0032] The present invention innovatively proposes an active electro-tuning strong coupling device using the combination of electrochromic materials and silver nanowire array structures, which can achieve active control of the strong coupling state in the visible light band. The core principle of this device is that electrochromic materials can flexibly switch between a colored state and a bleached state under the action of an applied voltage. By effectively coupling this characteristic with the surface plasmon polaritons (SPPs) generated by a silver nanowire array structure with fine-tuned dimensions, precise control of the strong coupling state and its coupling strength can be achieved when the electrochromic material switches between the colored and bleached states under precise voltage control. This innovative design not only broadens the technical path for controlling the strong coupling state but also provides new ideas and methods for research and applications in related fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] To more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the embodiments. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0034] Figure 1It is a schematic diagram of the electro - controlled strong coupling structure based on electrochromic materials and silver nano - arrays provided by this application.

[0035] Figure 2 It is the variation of the surface plasmon polariton (spp) resonance position when the incident angle changes in the TM mode for the coupling structure based on electrochromic materials and silver nano - arrays.

[0036] Figure 3 and Figure 4 They are the real - part and imaginary - part data of the corresponding dielectric constants of electrochromic materials at different voltages.

[0037] Figure 5 、 6 、7, 8, 9, 10, 11 respectively show the angle - resolved reflection spectrograms of surface plasmon coupling generated by the coupling structure based on electrochromic materials and silver nano - arrays at different voltages.

[0038] Figure 12 It is the coupling situation between surface plasmons generated by electrochromic materials and silver nano - array structures at different voltages when the incident angle of the coupling structure based on electrochromic materials and silver nano - arrays is 36 degrees.

[0039] Figure 13 It shows the preparation process of the silver grating.

[0040] Figure 14 It shows the schematic diagram of the simulation structure with the electrochromic material layer replaced by an air layer.

[0041] Figure 15 It shows the angle - resolved reflection spectrum of the silver nano - array replaced by an air layer.

[0042] Figure 16 It shows the reflection spectrum results when the electrochromic material is directly deposited on the silver substrate without including the silver nano - array. Detailed implementation manners

[0043] To make the objectives, 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 with reference to the accompanying drawings in the embodiments of the present invention. Apparently, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0044] As Figure 1 shown, an electrocontrolled strong coupling structure based on electrochromic materials and silver nanorod arrays is provided in an embodiment of the present invention. The structure is formed by sequentially laminating multiple functional layers, specifically including: a silver substrate layer, a silver nanorod array layer, an electrochromic material layer, an ion storage layer, and an ITO thin film layer. Among them, the ITO thin film layer not only has excellent light transmittance in the visible to near-infrared wavelength band, but also has good electrical conductivity, ensuring efficient conduction of the entire structure during the electrocontrol process. The ion storage layer plays a crucial role in this structure. It not only provides necessary ionic conductivity but also actively participates in redox reactions. Through this redox process, the ion storage layer can effectively assist in maintaining charge balance, enabling the electrochromic material to maintain stable working performance during multiple electrochemical cycles. The ion storage layer is composed of a specific mixture, and its main function is to assist the electrochromic process. Its optical properties, especially the refractive index, are determined by the equivalent refractive index calculated by a weighted average formula. The electrochromic material layer exhibits significant absorbance under the action of applied voltage and is highly transparent without applied voltage, allowing light to pass through this layer with almost no loss. The silver nanorod array layer and the silver substrate layer are tightly combined and work together to generate the required surface plasmon polaritons (SPPs) in the visible wavelength band, further enhancing the coupling effect and functionality of the entire structure.

[0045] In some specific embodiments, the thickness of the silver substrate layer is precisely controlled between 80 and 120 nanometers. By finely adjusting the thickness of the silver substrate to this appropriate range, the generation of higher-order surface plasmon polariton (SPP) modes can be effectively suppressed. This suppression mechanism ensures that only a low-order SPP mode exists and propagates within the target wavelength band, avoiding multimode interference and enhancing the stability and efficiency of signal transmission. In this way, the thickness optimization of the silver substrate layer becomes a key technical means for regulating SPP modes, providing an important guarantee for the design of efficient optical devices.

[0046]

[0046] In some embodiments, the period of the silver nanoarray is from 280 nm to 320 nm, the width of the silver strip is from 180 nm to 260 nm, and the thickness of the silver strip is from 10 nm to 50 nm. The adjustment of the array period directly determines the position of the plasmon resonance wavelength (i.e., the position of the resonance peak). By precisely controlling the period, the plasmon resonance peak of the array can be highly matched with the absorption peak of the electrochromic material within the wavelength range, thereby achieving higher optical absorption efficiency and energy coupling. This matching can enhance the dynamic modulation ability of the electrochromic material, making it exhibit more excellent optoelectronic properties in practical applications. Especially in optoelectronic switches and optical modulators, this matching is the key to achieving efficient functions.

[0047] The width of the silver strip mainly affects the grating duty cycle of the array structure (i.e., the ratio of the silver strip and the gap in the grating unit). The change in the duty cycle will significantly change the optical properties of the array, thereby indirectly affecting the characteristics of the plasmon resonance peak (such as resonance intensity and quality factor). By reasonably designing the width, the optical characteristics of the array can be optimized, making the plasmon resonance peak more suitable for the absorption characteristics of the target material and further improving the overall optoelectronic performance of the system.

[0048]

[0047] The adjustment of the silver strip thickness has a dual effect: one is to control the slit width of the resonance peak. The thickness change will directly affect the slit width of the plasmon resonance peak, thereby changing its quality factor. By optimizing the slit width, the selectivity and sensitivity of the optical performance can be improved; the other is to control the thickness of the electrochromic material in the gap. The silver strip thickness also affects the thickness of the electrochromic material in the gap, thereby changing the coupling strength between the plasmon and the material. This coupling optimization can improve the optical response efficiency of the system, which is particularly crucial in applications such as dynamic optical regulation and sensing.

[0049] In some embodiments, the thickness range of the electrochromic material layer is from 10 nm to 80 nm. The selection of the electrochromic material thickness is mainly based on the following three aspects:

[0050]

[0049] First, optimize the absorption peak intensity. The absorption peak intensity of the electrochromic material is directly affected by its thickness. By reasonably adjusting the thickness, its absorption characteristics can be enhanced or weakened to meet the requirements of different optical application scenarios. For example, in some scenarios, it is necessary to ensure that the absorption peak of the electrochromic material is similar to the intensity of the plasmon resonance peak to achieve the best energy transfer; while in other scenarios, a weaker absorption peak may be required to reduce the total loss of the system.

[0051] Secondly, optimize the coupling effect with the plasmon resonance peak. Changes in the thickness of the electrochromic material will significantly affect the coupling strength between it and the silver nanoarray. Although thicker materials can increase absorption, excessive thickness may cause multiple reflections and scattering of light, reducing optical efficiency. By precisely controlling the thickness, an optimal balance can be achieved between the material's absorption capacity and the plasmon coupling strength, thereby maximizing the optoelectronic performance. For example, electrochromic materials with moderate thickness can significantly improve the system's light absorption efficiency and dynamic modulation capabilities, especially in optical modulators.

[0052] Finally, dynamic optical performance is enhanced. Thickness regulation also affects the dynamic performance of electrochromic materials, such as their response time and light modulation depth under electric field regulation. Thinner materials respond faster, while thicker materials have stronger light modulation capabilities. In practical applications, choosing the right thickness according to specific needs can not only improve the dynamic performance of the system, but also enhance the overall durability and stability of the electrochromic device.

[0053] In some embodiments, the ion storage layer has a thickness of 30 nm-100 nm.

[0054] The reasons why the thickness of the ion storage layer is selected in the range of 30nm-100nm are mainly as follows:

[0055] Preparation of micro-nano structure: Since the entire structure is designed based on the micro-nano scale, the thickness of each layer needs to match this micro-nano structure. As one of the layers, if the ion storage layer is too thick, it will destroy the overall micro-nano structure design and affect the synergy between the layers.

[0056] Improve response speed: The main function of the ion storage layer is to provide ion conductivity and participate in redox reactions to maintain the charge balance of the electrochromic material. A thinner ion storage layer can reduce the distance of ion transmission, thereby improving the response speed when switching voltage.

[0057] Optimizing the electric field distribution: In an electrically controlled strong coupling structure, the distribution of the electric field is crucial to the coupling effect. A thinner ion storage layer can better control the distribution of the electric field, making the electric field more concentrated between the electrochromic material layer and the silver nanoarray layer, thereby enhancing the coupling effect. This helps to improve the coupling strength and modulation efficiency of the entire structure.

[0058] Reduce optical loss: The thickness of the ion storage layer also affects the optical performance of the entire structure. A thinner ion storage layer can reduce the scattering and absorption of light when passing through the layer, thereby reducing optical loss and improving light transmission efficiency. This is very important for achieving efficient light modulation and photoelectric switching functions.

[0059] In some specific embodiments, the thickness range of the ITO (indium tin oxide) thin film layer is precisely controlled between 25 and 35 nanometers. By introducing the ITO thin film with this specific thickness, the electromagnetic field distribution at the interface between the silver array and the electrochromic material will be significantly changed. Especially for the surface plasmon polariton (SPP) mode, the electromagnetic field will be effectively guided by the ITO thin film, resulting in a significant localization effect at this interface. This local field enhancement effect can not only significantly improve the coupling strength between the metal grating and the electrochromic material, but also further lead to a reduction in the overall reflectivity. Therefore, during the process of switching the coupling state, more obvious and significant changes in the reflection spectrum can be observed. In addition, the ITO thin film also has good conductive function, which makes its application in electrochromic devices more extensive and efficient.

[0060] An embodiment of the present invention provides a preparation method for an electro - controlled strong coupling structure based on an electrochromic material and a silver nano - array, comprising the following steps:

[0061] S1, preparing a silver substrate layer and a silver nano - array;

[0062] S2, preparing the electrochromic material on the silver nano - array to form an electrochromic material layer;

[0063] S3, spin - coating a layer of ion - storage layer on the electrochromic material layer;

[0064] S4, magnetron - sputtering a layer of ITO thin film layer on the ion - storage layer.

[0065] This coupling structure is composed of a silver micro - nano structure and an electrochromic material. The electrochromic material first fills the gaps of the silver array structure and continues to deposit to form a thin layer on the top of the array. By applying a voltage to change the absorption spectral characteristics of the electrochromic material, its reflection characteristics in the coupling structure are affected, and finally the coupling characteristics with the surface plasmon polariton (SPP) excited by the micro - nano structure are changed, realizing the adjustment of different coupling strengths under voltage control.

[0066] Its electro - controlled strong coupling principle is as follows: In the case of no applied voltage, the electrochromic material is in a transparent state, and the spectrum of the coupling structure basically presents the original spectral characteristics of the micro - nano structure, that is, the SPP excited by the silver nano - array; while in the case of applying a voltage, the electrochromic material shows absorbency, and its emission spectrum will be coupled with the SPP generated by the micro - nano structure. By controlling different voltages to change the optical characteristics of the electrochromic material, the coupling strength of the voltage - controlled coupling structure is realized, and the switching from the strong - coupling state to the weak - coupling state is achieved.

[0067] In some specific embodiments, step S1 mainly involves the fine preparation process of the silver grating. The silver grating is the most crucial bottom element in the electrochemically controlled strong coupling structure based on electrochromic materials and silver nanoarrays, and its importance is self-evident. As Figure 13 shown, this step specifically includes the following detailed operation steps:

[0068] First, step S11 is to clean the quartz substrate. This step is crucial because the cleanliness of the substrate directly affects the effect of subsequent processes. The specific operation is to thoroughly clean the quartz substrate with an appropriate solvent, deionized water, or acid-base solution to ensure that its surface has no contaminants and reaches a highly clean state. After cleaning, an electron beam evaporation process is then carried out on the quartz substrate in sequence. First, a chromium layer is evaporated, and then a silver layer is evaporated to form a silver substrate layer. Among them, the main function of the chromium layer is to act as an adhesion layer, and its thickness is usually controlled within a few nanometers. In this way, it can effectively enhance the adhesion between the silver layer and the quartz substrate without significantly affecting the overall optical properties. The thickness of the silver layer needs to be precisely controlled according to the specific requirements of the grating design, generally between dozens and hundreds of nanometers. Such a thickness selection can effectively suppress the generation of higher-order surface plasmon polaritons (SPPs) and ensure the performance of the grating.

[0069] Next, step S12 is to spin-coat a layer of polymethyl methacrylate (PMMA) photoresist on the already prepared silver layer to form a uniform and consistent-thickness coating. To ensure the stability and adhesion of the photoresist, it also needs to be baked to remove the solvent components in the coating by heating and improve the bonding force between the photoresist and the silver layer.

[0070] Subsequently, step S13 uses a high-precision electron beam exposure method to pattern the spin-coated photoresist. Through the precise scanning of the electron beam, a periodic pattern corresponding to the designed grating structure will be formed on the photoresist. After development, these patterns will clearly appear.

[0071] Immediately afterwards, step S14 is to perform the electron beam evaporation process again in the patterned photoresist area, evaporating a chromium layer and a silver layer in sequence. Here, the chromium layer still acts as an adhesion layer, and the newly evaporated silver layer will form the main structural part of the grating.

[0072] Finally, step S15 is to dissolve the unexposed photoresist part with an appropriate solvent (such as acetone) and remove the silver layer and chromium layer covering the photoresist through a lift-off process. After this series of treatments, the remaining silver layer will form a periodic structure consistent with the photoresist pattern, that is, the required silver nanoarray, thus completing the preparation of the silver grating.

[0073] In some specific embodiments, step S2 mainly involves the preparation process of the electrochromic material layer. The electrochromic material layer mainly uses a specific class of organic small molecule electrochromic materials, which include azo compounds, aromatic amine compounds, thiophene derivatives, phthalocyanine and porphyrin compounds, as well as fullerene and its various derivatives. There are many types of organic small molecule electrochromic materials, and their design is mainly based on the conjugated structure characteristics of the molecules. By introducing different substituent groups, adjusting the length of the conjugated chain or changing the metal coordination mode, the response band and absorption line width of the material can be precisely controlled to achieve a specific electrochromic effect. It should be noted that the design of specific electrochromic molecules is not the core purpose of the embodiments of the present invention; the embodiments of the present invention are mainly intended to utilize the electrically adjustable absorption characteristics of electrochromic materials to design devices with electrically controlled strong coupling structures.

[0074] The preparation process of the electrochromic material layer includes the following key steps:

[0075] S21, firstly, adding the selected electrochromic material into a suitable solvent and fully dissolving it to form a uniform spin coating solution. Commonly used solvents include toluene, dichloromethane and ethanol, etc. These solvents can effectively dissolve the electrochromic material and ensure the uniformity and stability of the spin coating solution.

[0076] S22, evenly coating the prepared spin coating liquid on the silver nanoarray by spin coating technology. First, the spin coating liquid is allowed to fully fill the gaps of the silver nanoarray to ensure that the material is evenly distributed, and then spin coating is continued on the top to form a uniform film. During the spin coating process, parameters such as the concentration of the solution, the speed and time of spin coating will directly affect the thickness of the final film: spin coating with a high concentration solution usually forms a thicker film, while a low concentration solution is conducive to the formation of a thinner film. Ultimately, the solid-state electrochromic molecules in the film formed by spin coating will form a uniform solid layer, providing a basis for subsequent electrochromic applications.

[0077] In some specific embodiments, step S3 mainly relates to a method for preparing an ion storage layer, and the detailed steps are as follows: First, the electroactive molecules, polymer matrix, electrolyte and solvent are fully mixed and evenly dispersed. The specific operation is to put these components into a suitable container and use a stirring device to stir for a long time to ensure that the components are evenly mixed. Subsequently, the mixed solution is evenly coated on the surface of the electrochromic material layer by spin coating technology, and after appropriate treatment and drying, a uniform and dense ion storage layer is finally formed.

[0078] In the selection of electroactive molecules, two molecules, benzoquinone (BQ) and hydroquinone (HBQ), can be adopted. During the electrochromic process, these electroactive molecules can provide the necessary ion supplementation through redox reactions, thereby maintaining the electrochemical balance of the entire system and ensuring the stability and durability of the electrochromic effect.

[0079] For the polymer matrix, polymethyl methacrylate (PMMA) is an ideal choice. As a commonly used polymer material, PMMA can be used as a scaffold to construct a solid-state ion-conducting matrix. This not only helps to support and fix electroactive molecules but also significantly enhances the mechanical stability and durability of the film, thereby improving the service life of the entire device.

[0080] In terms of the selection of electrolytes, tetrabutylammonium hexafluorophosphate (TBAPF6) has been proven to be an excellent option. As an electrolyte, TBAPF6 can significantly improve ion conductivity, support the smooth conversion of BQ and HBQ during the electrochemical process, and maintain the high ion conductivity of the device, ensuring a rapid response of the electrochromic reaction.

[0081] As for the solvent, propylene carbonate (PC) is a commonly used organic solvent and is widely used as a solvent for the electrolyte in electrochromic devices. PC has good polarity and chemical stability and can effectively dissolve electrolytes (such as TBAPF6), thereby further enhancing ion conductivity and maintaining the electrochemical stability of the device, ensuring its reliability during long-term use.

[0082] In the specific operation, PMMA, PC, TBAPF6, BQ, and HBQ are mixed in a preset ratio. The resulting mixture solution needs to be continuously stirred by a stirring device for several hours to ensure sufficient mixing and uniform dispersion among the components. Subsequently, the well-stirred solution is evenly coated on the surface of the electrochromic film through a spin-coating device. By precisely adjusting the rotation speed and the viscosity of the solution, the thickness of the formed film can be effectively controlled. After the coating is completed, the film is subjected to appropriate cooling treatment, and finally, a solid and uniform ion storage layer is formed, providing a solid foundation for the stable operation of the electrochromic device.

[0083] In some specific embodiments, the operation details of step S4 are as follows: First, a sputtering deposition process is carried out in a low-pressure argon environment using direct current (DC) or radio frequency (RF) magnetron sputtering technology. In this step, both the ambient air pressure and the purity of argon need to be strictly controlled to ensure the stability and uniformity of the deposition process. Then, the deposition time and sputtering power are precisely regulated. The precise control of these two parameters is crucial because they directly affect the thickness and quality of the finally formed ITO thin film. Through this delicate regulation, the goal is to obtain an ITO thin film with a thickness of 30 nanometers. This thickness is extremely delicate at the nanoscale and requires extremely high process requirements. After the deposition is completed, in order to further improve the performance of the ITO thin film, an annealing treatment is also required. The temperature of the annealing treatment is usually set between 300°C and 500°C. This temperature range can effectively optimize the conductivity and transparency of the ITO thin film, making it exhibit more excellent performance in optoelectronic applications. Given that the thickness of the ITO thin film is only a few dozen nanometers, such a thin film is extremely vulnerable to various factors during the preparation process. Therefore, to achieve an ITO thin film with excellent optoelectronic properties, choosing the magnetron sputtering method for preparation is undoubtedly an ideal and reliable technical means. The magnetron sputtering method can not only provide high-quality thin films but also maintain high controllability and repeatability during the preparation process, thereby ensuring the stable performance of the final product.

[0084] Example 1

[0085] An electrochemically controlled strong coupling structure based on electrochromic materials and silver nanowire arrays, which structure includes the following layers stacked in sequence: a silver substrate layer, a silver nanowire array layer, an electrochromic material layer, an ion storage layer, and an ITO thin film layer.

[0086] The thickness of the silver substrate layer is 100 nm. The period of the silver nanowire array is 300 nm, the width of the silver strip is 220 nm, and the thickness of the silver strip is 30 nm. The thickness of the electrochromic material layer is 50 nm. The thickness of the ion storage layer is. The thickness of the ITO thin film layer is 30 nm.

[0087] Its preparation method includes the following steps:

[0088] S1, preparing a silver substrate layer and a silver nanowire array;

[0089] S2, preparing an electrochromic material on the silver nanowire array and forming an electrochromic material layer;

[0090] S3, spin-coating an ion storage layer on the electrochromic material layer;

[0091] S4, magnetron sputtering an ITO thin film layer on the ion storage layer.

[0092] Among them, step S1 includes the following steps:

[0093] S11. Clean the quartz substrate with deionized water, and successively deposit a chromium layer and a silver layer on the quartz substrate by electron beam evaporation to form a silver substrate layer. The rotation speed of the evaporation chamber is 10 rpm; the thickness of the chromium layer is 3 nm, and the chromium plating rate is 0.5 Å / s; the thickness of the silver layer is 100 nm, and the silver plating rate is 2 Å / s.

[0094] S12. Spin-coat a layer of polymethyl methacrylate (PMMA) photoresist on the silver layer.

[0095] The specific process of spin-coating the photoresist is as follows: For the first layer of PMMA with model 200K A4, the parameters are: 7000 rpm, 2000 rpm / s, room temperature, humidity ~27%, post-baking temperature 180 °C, time 5 min;

[0096] For the second layer of PMMA with model 950K A3, the parameters are: 6000 rpm, 2000 rpm / s, room temperature, humidity ~27%, post-baking temperature 180 °C, time 5 min.

[0097] S13. Use the electron beam exposure method to pattern the photoresist, and use the electron beam exposure method to etch grooves in the PMMA photoresist layer to form a photoresist pattern area with an array structure. Figure 13 The top view of the PMMA layer in (4) is the photoresist area after patterning.

[0098] S14. Deposit a chromium layer and a silver layer again by electron beam evaporation in the patterned photoresist area; the rotation speed of the evaporation chamber is 20 rpm, the thickness of the chromium layer is 3 nm, the chromium plating rate is 0.5 Å / s, the thickness of the silver layer is 30 nm, and the silver plating rate is 1 Å / s.

[0099] S15. Finally, use acetone to dissolve the unexposed photoresist, strip the silver layer and chromium layer covering the photoresist, and the remaining silver layer forms a periodic photoresist pattern, which is a silver nanowire array.

[0100] Among them, step S2 includes the following steps:

[0101] S21. Add the electrochromic material azo compound to the solvent toluene and dissolve it thoroughly to form a spin-coating solution with a concentration of 8 mg / mL.

[0102] S22. Spin-coat the spin-coating solution on the silver nanowire array, let the spin-coating solution first fill the gaps of the silver nanowire array, and then continue to spin-coat on the top to form a film. The parameters of spin-coating are: 3000 rpm, 1500 rpm / s, suck 50 μL with a pipette, and air-dry naturally for 30 min. Environment: room temperature, humidity ~27%.

[0103] Among them, step S3 is:

[0104] Benzosemiquinone (BQ) (0.3 wt%), hydroquinone (HBQ) (0.3 wt%), polymethyl methacrylate (PMMA) (25 wt%), tetrabutylammonium hexafluorophosphate (TBAPF6) (4.5 wt%) and propylene carbonate (PC) (69.9 wt%) were fully mixed and dispersed, and then spin-coated on the surface of the electrochromic material layer to form an ion storage layer. The spin-coating parameters were: 6000 rpm, 2000 rpm / s, 50 μL was aspirated with a pipette gun, and air-dried naturally. Environment: room temperature, humidity ~27%, and the thickness of the ion storage layer was 50 nm.

[0105] Step S4 is as follows:

[0106] In a vacuum chamber, DC magnetron sputtering was used to perform sputter deposition in a low-pressure argon atmosphere to obtain an ITO thin film with a thickness of 30 nm. The sputtering parameters were: sputtering power: 150 W, argon pressure: 0.5 Pa, sputtering time: 20 minutes, target-substrate distance: 75 mm, substrate temperature: room temperature. Then, annealing was performed at 400 °C for 30 minutes to improve the conductivity and transparency of ITO.

[0107] Comparative Example 1

[0108] In the simulation, the electrochromic material layer was replaced with an air layer, and other operations were the same as in Example 1 to verify that when only the electrochromic material exists, it can have a strong coupling interaction with the silver nanorod array.

[0109] Comparative Example 2

[0110] The electrochromic material was directly deposited on the silver substrate without including the silver nanorod array, and other operations were the same as in Example 1.

[0111] The results of testing the coupling performance of Example 1 and Comparative Examples 1-2 are as follows: The test results of Example 1 are shown in detail in Figure 2 - 12 while the test results of Comparative Examples 1-2 are respectively shown in Figure 14 and Figure 16 .

[0112] As Figure 1As shown, this structure consists of a silver substrate layer, a silver nanoarray layer, an electrochromic material layer, an ion storage layer, and an ITO thin film layer. Incident light enters from the ITO thin film layer. In this embodiment, the thickness of the ITO thin film used for simulation is 30 nm, and it is parametrically described based on the Drude model. Specifically, ITO is regarded as a "metallic state" medium with typical free electron gas characteristics, and its optical properties are characterized by setting key parameters such as the plasma frequency, collision frequency, and high-frequency dielectric constant. Among them, the plasma frequency of ITO is set to about 1.3×10^15 rad / s, the collision frequency is set to about 2.6×10^14 rad / s, and the high-frequency dielectric constant is set to about 3.9.

[0113] The incident light passes through the ITO thin film layer, the ion storage layer, and the electrochromic layer in sequence, and finally reaches the silver micro-nano structure layer. Since the silver arrays are arranged along the y-axis, only the incident light in the TM mode can excite surface plasmon polaritons and couple with the electrochromic material. In the incident light of the TM mode, by adjusting the incident light angle, the wave vector of the incident light can be changed, which in turn causes the effective wavelength of the light (i.e., the wavelength on the array surface) to change. According to the Bragg condition, the SPP wavelength that can be excited at this time will also change accordingly.

[0114] In the experiment, the SPP generated by the silver nanoarrays was measured using an ARMS microscopic angle-resolved spectroscopy system, which can obtain the reflection spectrum information of the measured micro-nano structures at different incident angles. As Figure 2 shown, the corresponding SPP resonance peaks at several different incident angles are presented. From Figure 2 it can be seen that when the incident angle gradually increases, the resonance wavelength of the silver nanoarrays varies in the range of 520 nm to 570 nm, and the reflectivity varies in the range of 0.45 to 0.55.

[0115] In the experiment, an ellipsometer was used to measure the amplitude and phase information of the transmitted light of the sample, and then by fitting each parameter into the Lorentz oscillator model and adjusting the fitting parameters until the model could reproduce the experimental data, the corresponding dielectric constant was extracted. Figure 3 and Figure 4 show the dielectric constant data of the electrochromic material at different voltages, which are used to characterize the absorption characteristics of the material at different voltages in the simulation.

[0116] In the experiment, the strong coupling spectrum between the SPP generated by the silver nanoarrays and the electrochromic material was also measured using an ARMS microscopic angle-resolved spectroscopy system, which can obtain the reflection spectrum information of the measured micro-nano structures at different incident angles. In the angle-resolved reflection spectrum diagram measured using the ARMS microscopic angle-resolved spectroscopy system, the "anti-crossing" pattern formed by the strong coupling can be clearly presented. From Figures 5 to 11Analysis shows that by adjusting the applied voltage, significant changes have occurred in the surface plasmon polariton (SPP) coupling between the electrochromic material and the micro-nano structure.

[0117] It can be seen from Figure 5 that when the electrochromic material in the coupling structure is in the bleached state, as the incident angle changes, the angular-resolved reflection spectrum only shows the surface plasmon polariton (SPP) generated by the silver nanostructure. This is because at this time, the electrochromic material is almost completely transparent, has extremely high transmittance, does not couple with the SPP, and thus does not exhibit an "anti-crossing" pattern.

[0118] Under low voltage conditions (such as Figure 5 0.7V in

[0119] ), a weak coupling phenomenon is shown in the angular-resolved reflection spectrum. At this time, the electrochromic material is in a lower oxidation state or reduction state, its refractive index change is small, the absorption characteristic is weak, and the coupling effect with the micro-nano structure has not been fully activated. Figure 6 As the applied voltage is gradually increased (from Figure 7 0.8V in

[0120] Figure 11 to

[0121] 0.9V in

[0122] ), the absorption characteristic of the material is enhanced, resulting in an expanded adjustment range of the refractive index, thus significantly strengthening the excitation of the SPP mode. The coupling effect is manifested as obvious spectral changes within the angular range in the reflection spectrum, indicating that the system has entered a stronger coupling state. Figure 11As can be seen, when the electrochromic material in the coupling structure is in the colored state, as the incident angle changes, the angular-resolved reflection spectrum shows an obvious "anti-crossing" pattern, which is an important feature of strong coupling. When the incident angle is 36 degrees, the surface plasmon resonance frequency generated by the array structure is close to the transition energy of the electrochromic material. At this time, the interaction between the two is significantly enhanced, and the coupling strength reaches the maximum. After simulating the coupling structure, an obvious strong coupling state can be found.

[0123] Figure 12 It shows the spectral results of the coupling structure at different voltages under the irradiation of an incident angle of 36 degrees (in the experiment, an ARMS microscopic angular-resolved spectroscopy system was used to measure the angular-resolved reflection spectrum information of the micro-nano structure). When the voltage is 0.7V, it is in a weak coupling state. At this time, the absorption peaks of the surface plasmon and the material are simply superimposed, showing a spectral response with a modified line shape. As the voltage gradually increases, the interaction strength between the two gradually increases. When the interaction strength is sufficient to exceed their respective loss and decoherence mechanisms, the system enters the strong coupling region. At this time, the system can no longer be simply regarded as independent plasmon and absorption states, but a new type of hybrid optical mode will be formed. This hybrid state usually shows energy splitting (Rabi splitting or band splitting) in the spectrum, and two clearly resolvable, new split state peaks appear, as shown by the voltages of 1.3V, 1.5V, and 1.7V.

[0124] Figure 14 It shows the schematic diagram of the simulation structure with the electrochromic material layer replaced by an air layer (Comparative Example 1). By replacing the electrochromic material layer with an air layer, the reflection spectrum characteristics of the silver nanorod array alone are studied to verify whether the strong coupling effect completely depends on the electrochromic material. Figure 15 It shows the angular-resolved reflection spectrum of the silver nanorod array replaced by an air layer (in the experiment, an ARMS microscopic angular-resolved spectroscopy system was used to measure the angular-resolved reflection spectrum information of the micro-nano structure). The "anti-crossing" pattern no longer appears in the reflection spectrum. Instead, a continuous SPP pattern curve appears, indicating that in the absence of the electrochromic material, the silver nanorod array alone only shows the resonance behavior of surface plasmons. The absence of mode splitting is because the silver nanorod array alone cannot form a strong coupling state with the incident photons, indicating that the realization of strong coupling depends on the absorption characteristics provided by the electrochromic material and the synergistic effect with the SPP of the silver nanorod array. By comparing with the Figure 11 spectral results, the core role of the electrochromic material in the coupling structure can be clarified.

[0125] Figure 16The reflection spectrum results when the electrochromic material is directly deposited on a silver substrate (Comparative Example 2) without silver nanorods are shown. (In the experiment, an ARMS microscopic angular resolution spectroscopy system was used to measure the angular resolution reflection spectrum information of the micro-nano structure.) The reflection spectrum presents a flat absorption band without obvious splitting or coupling phenomena, and the spectrum reflects the inherent absorption characteristics of the electrochromic material. Under the action of voltage, the position and intensity of the absorption peak of the electrochromic material change, but the synergistic effect with the silver nanorods is missing, indicating that the electrochromic material alone cannot excite the SPP mode and cannot achieve strong coupling. This result further shows that the dynamic absorption regulation characteristics of the electrochromic material need to be fully exerted through the synergistic effect with the silver nanorods. The electrochromic material alone only provides optical absorption regulation and cannot achieve the regulation of the coupling strength.

[0126] The above embodiments respectively conduct a comprehensive and detailed study on the synergistic enhancement effect between the electrochromic material and the silver nanorods by constructing a fine simulation model, deeply exploring the spectral characteristics, and thoroughly analyzing the structural characteristics. Specifically, the angular resolution reflection spectrum data of the coupling structure not only clearly shows the significant strong coupling characteristics formed by the interaction of these two materials, but also reveals its internal optical mechanism. At the same time, the simulation results of the comparison structure further verify that the generation of the strong coupling effect is not accidental, but strictly depends on the complex interaction between the dynamic optical characteristics of the electrochromic material and the surface plasmon mode of the silver nanorods. This interaction not only enhances the optical response of the material, but also provides an important theoretical basis for the design of new optoelectronic devices.

[0127] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, various changes and modifications can be made to the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An electrically controlled strong coupling structure based on electrochromic material and silver nanoarray, characterized in that: include: The silver substrate layer, the silver nano-array layer, the electrochromic material layer, the ion storage layer and the ITO film layer are stacked in sequence.

2. The electrically controlled strong coupling structure based on the electrochromic material and the silver nanoarray according to claim 1, characterized in that: The thickness of the silver substrate layer is 80-120 nm.

3. The electrically controlled strong coupling structure based on the electrochromic material and the silver nanoarray according to claim 1, characterized in that: The period of the silver nanoarray is 280nm-320nm, the width of the silver strip is 180nm-260nm, and the thickness of the silver strip is 10nm-50nm.

4. The electrically controlled strong coupling structure based on the electrochromic material and the silver nanoarray according to claim 1, characterized in that: The thickness of the electrochromic material layer is 10nm-80nm.

5. The electrically controlled strong coupling structure based on electrochromic material and silver nanoarray according to claim 1, characterized in that: The thickness of the ion storage layer is 30nm-100nm.

6. The electrically controlled strong coupling structure based on the electrochromic material and the silver nanoarray according to claim 1, characterized in that: The thickness of the ITO thin film layer is 25-35 nm.

7. A method for preparing an electrically controlled strong coupling structure based on an electrochromic material and a silver nanoarray according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1, preparing a silver substrate layer and a silver nanoarray; S2, preparing an electrochromic material on the silver nanoarray to form an electrochromic material layer; S3, spin coating an ion storage layer on the electrochromic material layer; S4, magnetron sputtering an ITO thin film layer on the ion storage layer.

8. The preparation method according to claim 7, characterized in that: Step S1 includes the following steps: S11, cleaning the quartz substrate, and sequentially electron-beam evaporating a chromium layer and a silver layer on the quartz substrate to form a silver substrate layer; S12, spin coating a layer of polymethyl methacrylate photoresist on the silver layer; S13, patterning the photoresist using an electron beam exposure method; S14, electron beam evaporating a chromium layer and a silver layer again in the patterned photoresist area; S15, finally using a solvent to dissolve the unexposed photoresist, peeling off the silver layer and the chromium layer covering the photoresist, and the remaining silver layer forms a periodic photoresist pattern, which is a silver nanoarray.

9. The preparation method according to claim 7, characterized in that: Step S2 includes the following steps: S21, adding the electrochromic material into the solvent and fully dissolving it to form a spin coating solution; S22, spin coating the spin coating liquid on the silver nanoarray, allowing the spin coating liquid to first fill the gaps of the silver nanoarray, and then continue to spin coating on the top to form a thin film.

10. The preparation method according to claim 7, characterized in that: Step S3 is: The electroactive molecules, polymer matrix, electrolyte and solvent are fully mixed and dispersed, and then spin-coated on the surface of the electrochromic material layer to form an ion storage layer.

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