A prussian blue / polyaniline composite electrochromic film and a preparation method and application thereof

Abstract

This invention relates to the field of electrochromic functional thin film preparation technology, and particularly to a Prussian blue / polyaniline composite electrochromic thin film, its preparation method, and its applications. The invention employs a constant current method to deposit a Prussian blue underlayer on the surface of a transparent conductive substrate; the obtained Prussian blue underlayer is pre-activated in a potassium-containing electrolyte; subsequently, a polyaniline surface layer is deposited in a polymerization solution containing aniline monomers and an acidic electrolyte using a segmented constant potential method; and finally, a post-conditioning treatment is performed to obtain the Prussian blue / polyaniline composite electrochromic thin film. By introducing a pre-activation step, a segmented deposition step, and a post-conditioning step, this invention improves the interfacial bonding, ion transport, and surface uniformity of the composite film, reducing agglomeration and scattering losses caused by continuous overgrowth of polyaniline. This results in a composite film with fast response, high transmittance adjustment capability, and good cycling stability, making it suitable for electrochromic display devices, smart windows, and transmittance-adjustable optical devices.

Description

Technical Field

[0001] This invention relates to the field of electrochromic functional film preparation technology, and in particular to a Prussian blue / polyaniline composite electrochromic film, its preparation method and application. Background Technology

[0002] Electrochromic materials can achieve reversible color changes and transmittance adjustment under the action of an external electric field, and are widely used in electrochromic displays, smart windows, visual information signs and transmittance adjustable optical devices.

[0003] Prussian blue exhibits significant electrochromic properties, and Prussian blue films on transparent conductive substrates can achieve reversible color changes during ion insertion and extraction. Polyaniline, as a conductive polymer material, possesses electron transport capabilities, ion permeability, and film-forming properties, making it suitable as a functional interface layer on the surface of Prussian blue.

[0004] Existing methods for preparing Prussian blue / polyaniline composite electrochromic films typically involve first forming a Prussian blue underlayer and then continuously depositing a polyaniline surface layer. While this method can produce composite electrochromic films, it still has the following drawbacks: First, continuous deposition of polyaniline in a single step can easily lead to localized overgrowth, resulting in surface agglomeration, increased surface roughness, and increased light scattering. Second, the interfacial state of the Prussian blue underlayer is unstable in the subsequent polymerization environment, which can easily affect the uniformity of the composite layer bonding. Third, the existing Prussian blue / polyaniline composite electrochromic films exhibit poor cycling stability.

[0005] Therefore, it is necessary to provide a new method for preparing Prussian blue / polyaniline composite electrochromic films to improve the uniformity of the composite interface, reduce the adverse effects of surface overgrowth, and improve the transmittance adjustment capability, response speed, and cycle stability of the obtained films. Summary of the Invention

[0006] In view of this, the purpose of this invention is to provide a Prussian blue / polyaniline composite electrochromic film and its preparation method. This invention can improve the interfacial bonding, ion transport and surface uniformity of the composite film, reduce the aggregation and scattering loss caused by continuous over-growth of polyaniline, and make the obtained composite film have fast response, high transmittance adjustment capability and good cycle stability. It is suitable for electrochromic display devices, smart windows and transmittance adjustable optical devices.

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing Prussian blue / polyaniline composite electrochromic films by segmented electrodeposition, comprising the following steps: (1) A transparent conductive substrate is placed in a deposition solution and used as a working electrode for constant current deposition to form a Prussian blue underlayer on the surface of the transparent conductive substrate, thereby obtaining Prussian blue / substrate; the deposition solution includes ferricyanide, iron salt and potassium-containing supporting electrolyte; (2) The Prussian blue / substrate is pre-activated to obtain activated Prussian blue / substrate; the pre-activation treatment includes: immersing the Prussian blue / substrate in a first potassium-containing electrolyte solution in an open circuit, or immersing it in an open circuit and then subjecting it to a first low / high constant potential square wave pulse cycle, with the low potential being -0.10~0.20 V and the high potential being 0.40~0.80 V relative to the Ag / AgCl reference electrode, and the duration of a single pulse being 0.5~5 s; (3) The activated Prussian blue / substrate is placed in a polymerization solution containing aniline monomer and acidic electrolyte and used as a working electrode for segmented constant potential deposition. There is an open-circuit standing interval of 5~60 s between adjacent segments to form a polyaniline surface layer and obtain Prussian blue / polyaniline / substrate. (4) The Prussian blue / polyaniline / substrate is post-conditioned to obtain the Prussian blue / polyaniline composite electrochromic film on the surface of the transparent conductive substrate; The post-tuning includes: placing the Prussian blue / polyaniline / substrate in a second potassium-containing electrolyte solution for a second low / high constant potential square wave pulse cycle. Relative to the Ag / AgCl reference electrode, the low potential is -0.6~0.2 V, the high potential is 0.6~1.0 V, the low and high potentials are maintained for 1~5 s each, and a 0~2 s open circuit interval is set between the two pulses.

[0008] Preferably, in step (3), the potential of the segmented constant potential deposition is 0.7~1.1 V, the total deposition time is 40~100 s, divided into 2~5 segments, each segment lasting 10~30 s.

[0009] Preferably, in step (1), the sedimentation solution comprises 0.005~0.05 mol / L of ferricyanide, 0.005~0.05 mol / L of iron salt, and 0.05~0.5 mol / L of potassium-containing supporting electrolyte; the potassium-containing supporting electrolyte comprises one or more of KCl, KNO3, K2SO4, KClO4, and potassium acetate; the ferricyanide comprises potassium ferricyanide, and the iron salt comprises ferric chloride.

[0010] Preferably, in step (1), the current density of the constant current deposition is 20~100 μA / cm. 2 The deposition time is 200~600 s.

[0011] Preferably, in step (2), the concentration of the first potassium-containing electrolyte solution is 0.5~2.0 mol / L, the open-circuit soaking time is 30~300 s, the number of cycles of the first low / high constant potential square wave pulse is 1~20 times, and an open-circuit interval of 0~2s is set between two adjacent pulses.

[0012] Preferably, in step (3), the concentration of aniline monomer in the polymerization solution is 0.05~0.30 mol / L, and the concentration of acidic electrolyte is 0.10~1.00 mol / L; the acidic electrolyte is one or more of sulfuric acid, hydrochloric acid and p-toluenesulfonic acid.

[0013] Preferably, in step (4), the concentration of the second potassium-containing electrolyte solution is 0.5~2.0 mol / L; and the number of cycles of the second low / high constant potential square wave pulse is 10~500.

[0014] Preferably, before performing the post-tuning of step (4), the Prussian blue / polyaniline / substrate is washed and dried.

[0015] The present invention provides a Prussian blue / polyaniline composite electrochromic film prepared by the method described above.

[0016] The present invention provides the application of the Prussian blue / polyaniline composite electrochromic film described above in electrochromic display devices, smart windows, or transmittance-adjustable optical devices.

[0017] This invention introduces a potassium-containing electrolyte pre-activation step between the Prussian blue (PB) underlayer and the polyaniline (PANI) surface layer, enabling the newly deposited PB film to establish a stable potassium electrolyte before entering the acidic aniline polymerization solution. + The invention addresses the exchange state and surface hydration state of PANI. Furthermore, it replaces the existing one-time continuous constant-potential deposition of PANI with a "segmented constant-potential deposition + inter-segment open-circuit resting" method. This allows for the redistribution of aniline monomers, protons, and ions between deposition segments, reducing agglomeration and roughening caused by localized preferential growth. An electrochemical post-tuning step is added after film formation, using gentle potassium-containing electrolyte pulse cycling to stabilize the ion transport channels and electron transport network of the PB / PANI composite interface, reducing irreversible losses in the first cycle. In summary, by introducing a pre-activation step, a segmented deposition step, and a post-tuning step, this invention improves the interfacial bonding, ion transport, and surface uniformity of the composite film, mitigating agglomeration and scattering losses caused by continuous overgrowth of polyaniline. The resulting composite film exhibits fast response, high transmittance adjustment capability, and good cycling stability, making it suitable for electrochromic display devices, smart windows, and transmittance-tunable optical devices. Detailed Implementation

[0018] This invention provides a method for preparing Prussian blue / polyaniline composite electrochromic films by segmented electrodeposition, comprising the following steps: (1) A transparent conductive substrate is placed in a deposition solution and used as a working electrode for constant current deposition to form a Prussian blue underlayer on the surface of the transparent conductive substrate, thereby obtaining Prussian blue / substrate; the deposition solution includes ferricyanide, iron salt and potassium-containing supporting electrolyte; (2) The Prussian blue / substrate is pre-activated to obtain activated Prussian blue / substrate; the pre-activation treatment includes: immersing the Prussian blue / substrate in a first potassium-containing electrolyte solution in an open circuit, or immersing it in an open circuit and then subjecting it to a first low / high constant potential square wave pulse cycle, with the low potential being -0.10~0.20 V and the high potential being 0.40~0.80 V relative to the Ag / AgCl reference electrode, and the duration of a single pulse being 0.5~5 s; (3) The activated Prussian blue / substrate is placed in a polymerization solution containing aniline monomer and acidic electrolyte and used as a working electrode for segmented constant potential deposition. There is an open-circuit standing interval of 5~60 s between adjacent segments to form a polyaniline surface layer and obtain Prussian blue / polyaniline / substrate. (4) The Prussian blue / polyaniline / substrate is post-conditioned to obtain the Prussian blue / polyaniline composite electrochromic film on the surface of the transparent conductive substrate; The post-tuning includes: placing the Prussian blue / polyaniline / substrate in a second potassium-containing electrolyte solution for a second low / high constant potential square wave pulse cycle. Relative to the Ag / AgCl reference electrode, the low potential is -0.6~0.2 V, the high potential is 0.6~1.0 V, the low and high potentials are maintained for 1~5 s each, and a 0~2 s open circuit interval is set between the two pulses.

[0019] Unless otherwise specified, all raw materials used in this invention are commercially available products well known in the art.

[0020] The present invention places a transparent conductive substrate in a deposition solution and uses it as a working electrode to perform constant current deposition, forming a Prussian blue underlayer on the surface of the transparent conductive substrate, thus obtaining a Prussian blue / substrate.

[0021] In this invention, the transparent conductive substrate is preferably ITO conductive glass, FTO conductive glass, or transparent conductive oxide coated glass.

[0022] Before placing the transparent conductive substrate in the deposition solution, the present invention preferably washes the transparent conductive substrate first. In the present invention, the washing preferably includes sequential acid washing, alcohol washing, and deionized water washing; the acid washing preferably uses dilute hydrochloric acid or dilute sulfuric acid; the alcohol washing preferably uses ethanol or isopropanol; the acid washing, alcohol washing, and deionized water washing are all performed using ultrasonic treatment, and the duration of each ultrasonic treatment is preferably 3-10 min. The present invention improves the uniformity of PB nucleation by removing the weakly attached contaminant layer and organic residues on the surface of the transparent conductive substrate through washing.

[0023] In this invention, the deposition solution comprises ferricyanide, an iron salt, and a potassium-containing supporting electrolyte, more preferably comprising 0.005~0.05 mol / L of ferricyanide, 0.005~0.05 mol / L of an iron salt, and 0.05~0.5 mol / L of a potassium-containing supporting electrolyte. In specific embodiments, the concentration of ferricyanide in the deposition solution can be 0.005, 0.01, 0.02, 0.03, 0.04, or 0.05 mol / L; the concentration of the iron salt can be 0.005, 0.01, 0.02, 0.03, 0.04, or 0.05 mol / L; and the concentration of the potassium-containing supporting electrolyte can be 0.05, 0.1, 0.2, 0.3, 0.4, or 0.5 mol / L. In this invention, the solvent of the deposition solution is water.

[0024] In this invention, the potassium-containing supporting electrolyte preferably includes one or more of KCl, KNO3, K2SO4, KClO4 and potassium acetate; the ferricyanide preferably includes potassium ferricyanide; and the iron salt preferably includes ferric chloride.

[0025] In this invention, the current density of the constant current deposition is preferably 20~100 μA / cm. 2 In specific embodiments, the value can be 20, 25, 30, 35, 40, 45, 50, 55, or 60 μA / cm. 2 The deposition time for the constant current deposition is preferably 200-600 s, and in specific embodiments it can be 200, 300, 400, 500, or 600 s. In this invention, the constant current deposition preferably uses a platinum wire as the counter electrode and Ag / AgCl as the reference electrode. This invention forms a PB underlayer through constant current deposition.

[0026] After obtaining the Prussian blue / substrate, the present invention pre-activates the Prussian blue / substrate to obtain activated Prussian blue / substrate.

[0027] In this invention, the pre-activation treatment includes: immersing the Prussian blue / substrate in a first potassium-containing electrolyte solution for open-circuit immersion, or immersing it in an open-circuit solution followed by a first low / high constant potential square wave pulse cycle, with the low potential being -0.10~0.20 V and the high potential being 0.40~0.80 V relative to the Ag / AgCl reference electrode, and each pulse lasting 0.5~5 s.

[0028] In this invention, the concentration of the first potassium-containing electrolyte solution is preferably 0.5~2.0 mol / L, and in specific embodiments it can be 0.5, 1.0, 1.5 or 2.0 mol / L. In this invention, the first potassium-containing electrolyte preferably includes one or more of KCl, KNO3, K2SO4, KClO4 and potassium acetate. In this invention, the open-circuit soaking time is 30~300 s, and in specific embodiments it can be 30, 50, 100, 150, 200, 250 or 300 s.

[0029] In this invention, the low potential of the first low / high constant potential square wave pulse cycle can specifically be -0.10, 0.0, 0.10, or 0.20 V; the high potential can specifically be 0.40, 0.50, 0.60, 0.70, or 0.80 V; and the duration of a single pulse can be 0.5, 1, 2, 3, 4, or 5 s. In this invention, a 0-2 s open-circuit interval is preferably set between two adjacent pulses, more preferably 0-1 s. In this invention, the number of cycles of the first low / high constant potential square wave pulse cycle is preferably 1-20 times, more preferably 3-10 times, and specifically 5 times in the embodiments of this invention. This invention stabilizes the ion exchange state of the PB substrate through pre-activation treatment, reducing interfacial disturbance when it directly enters the acidic polymerization solution, thereby improving the PB / PANI interfacial coupling and subsequent nucleation uniformity.

[0030] After obtaining the activated Prussian blue / substrate, the present invention places the activated Prussian blue / substrate in a polymerization solution containing aniline monomer and acidic electrolyte, and uses it as a working electrode for segmented constant potential deposition. There is an open-circuit resting interval of 5 to 60 s between adjacent segments to form a polyaniline surface layer, thus obtaining Prussian blue / polyaniline / substrate.

[0031] In this invention, the concentration of aniline monomer in the polymerization solution is preferably 0.05~0.30 mol / L, and in specific embodiments it can be 0.05, 0.10, 0.15, 0.20, 0.25 or 0.30 mol / L; the concentration of acidic electrolyte is preferably 0.10~1.00 mol / L, and in specific embodiments it can be 0.1, 0.3, 0.5, 0.7 or 1.0 mol / L; the acidic electrolyte is preferably one or more of sulfuric acid, hydrochloric acid and p-toluenesulfonic acid. In this invention, acidic conditions are beneficial to the electrochemical polymerization of aniline and the formation of the PANI conductive state.

[0032] In this invention, the potential of the segmented constant potential deposition is preferably 0.7~1.1 V, and in specific embodiments it can be 0.7, 0.8, 0.9, 1.0 or 1.1 V; the total deposition time of the segmented constant potential deposition is preferably 40~100 s, and in specific embodiments it can be 40, 50, 60, 70, 80, 90 or 100 s, preferably 50~80 s; by adjusting the total time of the segmented constant potential deposition, this invention can adjust the coloring efficiency and response speed of the composite electrochromic film. In this invention, the segmented constant potential deposition is preferably divided into 2~5 segments, each segment lasting 10~30 s, and in specific embodiments it can be divided into 2, 3, 4 or 5 segments, each segment lasting 10, 15, 20, 25 or 30 s. In this invention, an open-circuit rest interval of 5 to 60 seconds is provided between two adjacent segments. In specific embodiments, the open-circuit rest interval can be set to 5, 10, 20, 30, 40, 50 or 60 seconds.

[0033] In this invention, the segmented constant potential deposition can achieve concentration mitigation, polymer chain rearrangement, and local stress release during the inter-segment open-circuit resting stage, thereby suppressing dendritic or blocky agglomeration. Through segmented constant potential deposition and inter-segment open-circuit resting, this invention can effectively suppress surface agglomeration, enhanced scattering, and lengthened ion diffusion paths caused by continuous excessive growth of PANI, resulting in a more uniform conductive capping layer.

[0034] After obtaining the Prussian blue / polyaniline / substrate, the present invention performs post-conditioning on the Prussian blue / polyaniline / substrate to obtain the Prussian blue / polyaniline composite electrochromic film on the surface of the transparent conductive substrate.

[0035] Prior to the post-setting process, the present invention preferably further includes washing and drying the Prussian blue / polyaniline / substrate. In this invention, the washing is preferably done with water, and if necessary, further rinsing with ethanol or isopropanol can be used. The present invention removes unreacted monomers, electrolyte residues, and weakly adhering polymers through washing. In this invention, the drying is preferably staged drying; the staged drying preferably includes: first drying at 25~40℃ for 5~30 min, then drying at 40~70℃ for 5~60 min. The staged drying method used in this invention can reduce shrinkage stress caused by rapid solvent escape from the wet film.

[0036] In this invention, the post-tuning includes: placing the Prussian blue / polyaniline / substrate in a second potassium-containing electrolyte solution for a second low / high constant potential square wave pulse cycle. Relative to the Ag / AgCl reference electrode, the low potential is -0.6~0.2 V, the high potential is 0.6~1.0 V, the low and high potentials are maintained for 1~5 s each, and a 0~2 s open circuit interval is set between the two pulses.

[0037] In this invention, the concentration of the second potassium-containing electrolyte solution is preferably 0.5~2.0 mol / L, and in specific embodiments it can be 0.5, 1.0, 1.5 or 2.0 mol / L; the type of the second potassium-containing electrolyte is the same as that of the first potassium-containing electrolyte, and will not be described again here.

[0038] In this invention, the low potential of the second low / high constant potential square wave pulse cycle can specifically be -0.6, -0.4, -0.2, 0.0, or 0.2 V; the high potential can specifically be 0.6, 0.7, 0.8, 0.9, or 1.0 V; the low and high potential holding time (i.e., the duration of a single pulse) can be 1, 2, 3, 4, or 5 s; and an open-circuit interval of 0, 0.5, 1, or 2 s can be set between two pulses. In this invention, the number of cycles of the second low / high constant potential square wave pulse cycle is preferably 10 to 500 times, and in specific embodiments, it can be 10, 50, 100, 150, 200, 250, 300, 350, 400, 450, or 500 times. This invention can further establish a stable K through post-tuning processing. + The migration channel and PB / PANI interface contact structure improve the cyclic reversibility and long-term stability of the film, enabling the PB / PANI composite film to achieve a better balance between transmittance modulation, switching speed and cycle retention.

[0039] The present invention provides a Prussian blue / polyaniline composite electrochromic film prepared by the above method.

[0040] The present invention also provides the application of the Prussian blue / polyaniline composite electrochromic film described above in electrochromic display devices, smart windows, or transmittance-adjustable optical devices.

[0041] The following detailed description, in conjunction with embodiments, illustrates the Prussian blue / polyaniline composite electrochromic film, its preparation method, and its applications provided by the present invention. However, these descriptions should not be construed as limiting the scope of protection of the present invention.

[0042] Example 1 (Preferred window, 60 s segmented deposition type) ITO conductive glass was used as a substrate and ultrasonically cleaned in dilute hydrochloric acid, ethanol and deionized water for 5 min each, and then dried for later use.

[0043] PB deposition solution was prepared using 0.01 mol / L K3Fe(CN)6, 0.01 mol / L FeCl3, and 0.10 mol / L KCl. ITO was used as the working electrode, platinum wire as the counter electrode, and Ag / AgCl as the reference electrode, at 50 μA / cm². 2 A PB underlayer was obtained by deposition for 400 s under constant current conditions.

[0044] The PB substrate was pre-activated in 1.0 mol / L KCl. It was first soaked in an open circuit for 120 s, and then subjected to 5 alternating low / high potential pulse cycles, with a low potential of 0.0 V and a high potential of 0.6 V, each pulse lasting 2 s.

[0045] Prepare the PANI polymerization solution: 0.10 mol / L aniline + 0.50 mol / L H2SO4. Use segmented constant potential deposition at 0.90 V for a total time of 60 s, divided into 3 segments of 20 s each, with an open-circuit setting period of 15 s between adjacent segments.

[0046] After deposition, the sample was washed with deionized water, then dried at 30°C for 10 min and then at 55°C for 20 min.

[0047] The composite membrane was placed in 1.0 mol / L KCl for post-tuning and cyclically subjected to a constant potential square wave pulse of -0.4 V / 0.8 V for 50 times, with the low and high potentials held for 2 s each, to obtain the PB / PANI composite electrochromic film.

[0048] Example 2 (High coloring efficiency type, 75 s segmented deposition) The remaining steps are the same as in Example 1, except that: the total time for PANI segmented constant potential deposition is 75 s, divided into 3 segments, each segment is 25 s, and adjacent segments are left open for 20 s; the number of subsequent cycles is 80.

[0049] This embodiment is used to obtain higher PANI coverage and higher coloring efficiency.

[0050] Example 3 (Fast response type, 50 s segmented deposition) The remaining steps are the same as in Example 1, except that: the total time for PANI segmented constant potential deposition is 50 s, divided into 2 segments of 25 s each, with an open circuit and a resting period of 20 s in between; and the number of cycles is set to 30.

[0051] This embodiment is used to obtain a thinner PANI surface layer and a faster switching response.

[0052] Comparative Example 1 (pre-activation omitted) Compared with Example 1, the PB underlying pre-activation treatment is omitted, and the remaining steps are exactly the same.

[0053] Comparative Example 2 (Continuously Deposited PANI) Compared with Example 1, the difference is that segmented constant potential deposition is not used when depositing PANI. Instead, continuous constant potential deposition is performed at 0.90 V for 60 s without inter-segment open circuit resting. The other steps are exactly the same.

[0054] Comparative Example 3 (adjusted after omission) Compared to Example 1, after deposition and graded drying, no post-setting treatment was performed, and the remaining steps were exactly the same.

[0055] Performance testing Using a composite electrochromic thin film as the working electrode, a platinum wire as the counter electrode, and Ag / AgCl as the reference electrode, a three-electrode system and a 1.0 mol / L KCl electrolyte were employed to test the electrochromic performance of each embodiment and comparative example. The transmittance modulation amplitude ΔT at 700 nm, coloring / fading time Tc / Tb, coloring efficiency CE, and areal capacitance Sc were recorded.

[0056] Coloring / fading time was determined using a constant potential square wave switching method, with test potentials of -0.4 V / 0.8 V and a single potential holding time of 10 s. Coloring time Tc and fading time Tb were defined as the time required for transmittance to reach 90% of the total change. Coloring efficiency CE was calculated based on the ratio of optical density change to unit charge, and areal capacitance Sc was calculated based on unit area charge. Long-term stability was assessed by continuously cycling under the same potential switching conditions for 1000 cycles, and the ΔT retention rate was measured at a wavelength of 700 nm. The ΔT retention rate was the ratio of ΔT after 1000 cycles to the initial ΔT.

[0057] Table 1. Reference performance data for each embodiment and comparative example.

[0058] As shown in Table 1, compared with Comparative Example 2, under the same total deposition time (60 s), Example 1, after adopting "segmented constant potential deposition + inter-segment open-circuit resting", saw ΔT increase from 19.4% to 20.6%, and the coloring / fading time shorten from 2.3 / 3.1 s to 1.5 / 2.0 s. This indicates that segmented deposition helps to suppress the aggregation and scattering caused by continuous excessive growth of PANI, and reduces ion diffusion resistance.

[0059] Compared with Comparative Example 1, in Example 1, after the introduction of pre-activation, ΔT increased from 18.1% to 20.6%, the coloring / fading time decreased from 1.9 / 2.6 s to 1.5 / 2.0 s, and the ΔT retention rate increased from 79% to 88% after 1000 cycles. This indicates that the pre-activation step helps to stabilize the ion sites on the PB surface and homogenize the charge transfer at the PB / PANI interface.

[0060] Compared to Comparative Example 3, in Example 1, after adding post-tuning, the ΔT retention rate after 1000 cycles increased from 75% to 88%, indicating that the post-tuning step can effectively establish a more stable K. + Transmission channel and PB / PANI interface structure.

[0061] The comparison of different embodiments shows that Embodiment 2 exhibits the highest coloring efficiency and areal capacitance due to its longer total PANI deposition time, making it suitable for scenarios that emphasize high efficiency and high charge storage; Embodiment 3 has a shorter deposition time, balancing fast response and acceptable modulation amplitude; Embodiment 1 shows the most balanced performance in terms of overall optical modulation, switching speed and cycle stability.

[0062] The above results show that the present invention does not simply extend or shorten the PANI deposition time, but rather optimizes the interface stability, surface morphology and ion transport simultaneously through a synergistic design of "pre-activation - segmented deposition - post-tuning", thereby obtaining a more balanced electrochromic performance than existing continuous deposition methods.

[0063] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing Prussian blue / polyaniline composite electrochromic thin films by segmented electrodeposition, characterized in that, Includes the following steps: (1) A transparent conductive substrate is placed in a deposition solution and used as a working electrode for constant current deposition to form a Prussian blue underlayer on the surface of the transparent conductive substrate, thereby obtaining Prussian blue / substrate; the deposition solution includes ferricyanide, iron salt and potassium-containing supporting electrolyte; (2) The Prussian blue / substrate is pre-activated to obtain activated Prussian blue / substrate; the pre-activation treatment includes: immersing the Prussian blue / substrate in a first potassium-containing electrolyte solution in an open circuit, or immersing it in an open circuit and then subjecting it to a first low / high constant potential square wave pulse cycle, with the low potential being -0.10~0.20V and the high potential being 0.40~0.80V relative to the Ag / AgCl reference electrode, and the duration of a single pulse being 0.5~5 s; (3) The activated Prussian blue / substrate is placed in a polymerization solution containing aniline monomer and acidic electrolyte and used as a working electrode for segmented constant potential deposition. There is an open-circuit standing interval of 5~60 s between adjacent segments to form a polyaniline surface layer and obtain Prussian blue / polyaniline / substrate. (4) The Prussian blue / polyaniline / substrate is post-conditioned to obtain the Prussian blue / polyaniline composite electrochromic film on the surface of the transparent conductive substrate; The post-tuning includes: placing the Prussian blue / polyaniline / substrate in a second potassium-containing electrolyte solution for a second low / high constant potential square wave pulse cycle. Relative to the Ag / AgCl reference electrode, the low potential is -0.6~0.2 V, the high potential is 0.6~1.0 V, the low and high potentials are maintained for 1~5 s each, and a 0~2 s open circuit interval is set between the two pulses.

2. The method according to claim 1, characterized in that, In step (3), the potential of the segmented constant potential deposition is 0.7~1.1 V, the total deposition time is 40~100 s, divided into 2~5 segments, each segment lasting 10~30 s.

3. The method according to claim 1, characterized in that, In step (1), the sedimentation solution includes 0.005~0.05 mol / L of ferricyanide, 0.005~0.05 mol / L of iron salt and 0.05~0.5 mol / L of potassium-containing supporting electrolyte; the potassium-containing supporting electrolyte includes one or more of KCl, KNO3, K2SO4, KClO4 and potassium acetate; the ferricyanide includes potassium ferricyanide and the iron salt includes ferric chloride.

4. The method according to claim 1 or 3, characterized in that, In step (1), the current density of the constant current deposition is 20~100 μA / cm. 2 The deposition time is 200~600 s.

5. The method according to claim 1, characterized in that, In step (2), the concentration of the first potassium-containing electrolyte solution is 0.5~2.0 mol / L, the open-circuit soaking time is 30~300 s, the number of cycles of the first low / high constant potential square wave pulse is 1~20 times, and an open-circuit interval of 0~2s is set between two adjacent pulses.

6. The method according to claim 1, characterized in that, In step (3), the concentration of aniline monomer in the polymerization solution is 0.05~0.30 mol / L, and the concentration of acidic electrolyte is 0.10~1.00 mol / L; the acidic electrolyte is one or more of sulfuric acid, hydrochloric acid and p-toluenesulfonic acid.

7. The method according to claim 1, characterized in that, In step (4), the concentration of the second potassium-containing electrolyte solution is 0.5~2.0 mol / L; the number of cycles of the second low / high constant potential square wave pulse is 10~500.

8. The method according to claim 1, characterized in that, Before performing the post-tuning in step (4), the Prussian blue / polyaniline / substrate is washed and dried.

9. The Prussian blue / polyaniline composite electrochromic film prepared by the method according to any one of claims 1 to 8.

10. The application of the Prussian blue / polyaniline composite electrochromic film of claim 9 in electrochromic display devices, smart windows, or transmittance-tunable optical devices.

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