A thiophene derivative, its preparation method and application, and electrochromic film and its preparation method

Abstract

The present invention relates to the technical field of electrochromic materials, and in particular to a thiophene derivative and its preparation method and application as well as an electrochromic film and its preparation method. In the present invention, 2,5-bis(4'-bromophenyl)-3,4-ethylenedioxythiophene and tributyl(3,3-dimethyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxane-6-yl)stannane are used to prepare the required 2,5-diphenyl-3,4-ethylenedioxythiophene derivative in combination with a catalyst and a solvent. The derivative is then polymerized into an electrochromic material by cyclic voltammetry, which can change color at a voltage of 0 to 0.9V, and there is no obvious attenuation of the optical contrast under a wavelength range of 469nm after 600 cycles.

Description

Technical Field

[0001] The present invention relates to the technical field of electrochromic materials, and in particular to a thiophene derivative, a preparation method and application thereof, and an electrochromic film and a preparation method thereof. Background Art

[0002] Electrochromic materials exhibit different optical absorption under different voltages, undergoing reversible and long-lasting changes between different colors.

[0003] Existing electrochromic materials can be divided into inorganic electrochromic materials, organic small molecule electrochromic materials, organic polymer electrochromic materials, and chelate electrochromic materials.

[0004] Polymer electrochromic materials can exhibit a wide range of colors through molecular structural design. Currently, considerable research has focused on developing solution-processable polymers that are yellow in their neutral state. This work focuses on improving material stability, reducing their oxidation potential, and increasing their oxidized-state transmittance. However, achieving polymer electrochromic materials that can switch between khaki and transparent colors requires further effort from those skilled in the art. Summary of the Invention

[0005] The present invention aims to provide a thiophene derivative and a preparation method and application thereof, as well as an electrochromic film and a preparation method thereof.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] A 2,5-diphenyl-3,4-ethylenedioxythiophene derivative, the structure of which is shown in formula (I):

[0008]

[0009] The present invention provides a method for preparing the 2,5-diphenyl-3,4-ethylenedioxythiophene derivative, comprising the following steps:

[0010] Under a protective atmosphere, 2,5-bis(4'-bromophenyl)-3,4-ethylenedioxythiophene, tributyl(3,3-dimethyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxane-6-yl)stannane, a catalyst, and a solvent are mixed and reacted to obtain a 2,5-diphenyl-3,4-ethylenedioxythiophene derivative represented by formula (I).

[0011] Optionally, the molar ratio of the 2,5-bis(4'-bromophenyl)-3,4-ethylenedioxythiophene to tributyl(3,3-dimethyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxane-6-yl)stannane is 1:2.5-3.5;

[0012] The ratio of the solvent to 2,5-bis(4'-bromophenyl)-3,4-ethylenedioxythiophene is 35-50 mL:1 g;

[0013] The molar ratio of the catalyst to 2,5-bis(4'-bromophenyl)-3,4-ethylenedioxythiophene is 3 to 10:100.

[0014] Optionally, the catalyst comprises tetrakis(triphenylphosphine)palladium;

[0015] The solvent comprises at least one of N,N-dimethylformamide and 1,4-dioxane;

[0016] The protective atmosphere contains nitrogen.

[0017] Optionally, the reaction temperature is 140-175° C., and the reaction time is 12-24 hours.

[0018] The present invention provides application of the 2,5-diphenyl-3,4-ethylenedioxythiophene derivative in an electrochromic film.

[0019] The present invention also provides an electrochromic film, the polymerization monomer of which is a 2,5-diphenyl-3,4-ethylenedioxythiophene derivative described in formula (I).

[0020] The present invention also provides a method for preparing the electrochromic film, comprising the following steps:

[0021] The 2,5-diphenyl-3,4-ethylenedioxythiophene derivative represented by formula (I) is dissolved in a tetrabutylammonium hexafluorophosphate solution to obtain a mixed solution; and the mixed solution is subjected to electrochemical polymerization to obtain the electrochromic film.

[0022] Optionally, the concentration of the 2,5-diphenyl-3,4-ethylenedioxythiophene derivative in the mixed solution is 0.5 to 1.5 mmol / L;

[0023] The concentration of the tetrabutylammonium hexafluorophosphate solution is 0.09 to 0.12 mol / L;

[0024] The solvent of the tetrabutylammonium hexafluorophosphate solution comprises dichloromethane and acetonitrile;

[0025] The volume ratio of dichloromethane to acetonitrile is 5 to 12:2;

[0026] The volume ratio of dichloromethane to acetonitrile in the mixed solvent is 5-12:2.

[0027] Optionally, the voltage of the electrochemical polymerization is 0-1.1 V, and the scanning speed is 50-125 mV / s.

[0028] The preparation route of the 2,5-diphenyl-3,4-ethylenedioxythiophene derivatives of the present invention is:

[0029]

[0030] 2,5-bis(4'-bromophenyl)-3,4-ethylenedioxythiophene (Formula II) and tributyl(3,3-dimethyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxane-6-yl)stannane (Formula III) are reacted with a catalyst and a solvent to prepare a 2,5-diphenyl-3,4-ethylenedioxythiophene derivative shown in Formula (I), namely 5,7-bis(4-(3,3-dimethyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxane-6-yl)phenyl)-2,3-dihydrothieno[3,4-b][1,4]dioxane.

[0031] The present invention designed and synthesized a D-π-D-π-D compound QBEBQ (a 2,5-diphenyl-3,4-ethylenedioxythiophene derivative) consisting of an alternating chain of EDOT derivatives, benzene, EDOT, benzene, and EDOT derivatives. The invention introduces a para-substituted phenyl group into QBEBQ. The para-substituted phenyl group exhibits high aromaticity and subtle steric hindrance, which increases the repulsion of ortho-CH units, thereby increasing the energy gap of the polymer. Combined with the presence of EDOT and its derivatives, the polymer exhibits a yellow color in its neutral state while still allowing for sufficient electrochemical doping to promote a shift in absorption peaks from the visible to the near-infrared (NIR) region, rendering its oxidized state transparent.

[0032] The present invention has the beneficial effect of successfully preparing an electrochromic material using a D-π-D-π-D compound QBEBQ, consisting of an alternating EDOT derivative-benzene-EDOT-benzene-EDOT derivative, as a monomer via cyclic voltammetry. During the polymerization process, if the voltage is too low, the monomer cannot undergo electropolymerization, while if the voltage is too high, overvoltage will damage the resulting polymer. The lower the scan speed during the polymerization process, the more uniform the surface of the electropolymerized material will be, while higher the scan speed, the rougher the surface will be. The prepared electrochromic material exhibits a khaki color in its neutral state and changes color to transparent at a voltage of 0 to 0.9 V. The film exhibits an optical contrast of 44.2% at a wavelength of 469 nm, with a coloring time of 2 seconds and a fading time of 0.8 seconds; and an optical contrast of 46% at a wavelength of 706 nm, with a coloring time of 0.9 seconds and a fading time of 1.38 seconds. After 600 cycles, there is no significant degradation in the optical contrast at 469 nm, indicating a new high-performance khaki-transparent electrochromic material with great potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 1 is a cyclic voltammetry polymerization curve of the 2,5-diphenyl-3,4-ethylenedioxythiophene derivative prepared in Example 1;

[0034] Figure 2 The UV-visible absorption spectra of the 2,5-diphenyl-3,4-ethylenedioxythiophene derivative polymer film prepared in Example 1 at different voltages;

[0035] Figure 3 This is a response time graph of the 2,5-diphenyl-3,4-ethylenedioxythiophene derivative polymer film prepared in Example 1 at 469 nm;

[0036] Figure 4 This is a response time diagram of the 2,5-diphenyl-3,4-ethylenedioxythiophene derivative polymer film prepared in Example 1 at 706 nm;

[0037] Figure 5 This is a dynamic test graph of the 2,5-diphenyl-3,4-ethylenedioxythiophene derivative polymer film prepared in Example 1 at 469nm;

[0038] Figure 6 This is a dynamic test diagram of the 2,5-diphenyl-3,4-ethylenedioxythiophene derivative polymer film prepared in Example 1 at 706nm. DETAILED DESCRIPTION

[0039] The present invention provides a 2,5-diphenyl-3,4-ethylenedioxythiophene derivative, the structure of which is shown in formula (I):

[0040]

[0041] The present invention provides a method for preparing the 2,5-diphenyl-3,4-ethylenedioxythiophene derivative, comprising the following steps:

[0042] Under a protective atmosphere, 2,5-bis(4'-bromophenyl)-3,4-ethylenedioxythiophene, tributyl(3,3-dimethyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxane-6-yl)stannane, a catalyst, and a solvent are mixed and reacted to obtain a 2,5-diphenyl-3,4-ethylenedioxythiophene derivative represented by formula (I).

[0043] In the present invention, the molar ratio of 2,5-bis(4'-bromophenyl)-3,4-ethylenedioxythiophene to tributyl(3,3-dimethyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxane-6-yl)stannane is 1:2.5-3.5, preferably 1:2.7-3.4, more preferably 1:2.8-3.3, and even more preferably 1:2.9-3.1;

[0044] The ratio of the solvent to 2,5-bis(4'-bromophenyl)-3,4-ethylenedioxythiophene is 35-50 mL:1 g, preferably 38-48 mL:1 g, more preferably 40-46 mL:1 g, and even more preferably 42-44 mL:1 g;

[0045] The molar ratio of the catalyst to 2,5-bis(4'-bromophenyl)-3,4-ethylenedioxythiophene is 3 to 10:100, preferably 4 to 9:100, more preferably 5 to 8:100, and even more preferably 6 to 7:100.

[0046] In the present invention, the structural formula of the 2,5-bis(4'-bromophenyl)-3,4-ethylenedioxythiophene is Formula (II):

[0047]

[0048] The structural formula of the tributyl (3,3-dimethyl-3,4-dihydro-2H-thieno [3,4-b] [1,4] dioxane-6-yl) stannane is formula (III):

[0049]

[0050] In the present invention, the catalyst comprises tetrakis(triphenylphosphine)palladium;

[0051] The solvent comprises at least one of N,N-dimethylformamide and 1,4-dioxane;

[0052] The protective atmosphere contains nitrogen.

[0053] In the present invention, under a protective atmosphere, 2,5-bis(4'-bromophenyl)-3,4-ethylenedioxythiophene, tributyl(3,3-dimethyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxane-6-yl)stannane, a catalyst, and a solvent are mixed, heated to a reaction temperature, and kept in a reflux state for reaction.

[0054] In the present invention, the reaction temperature is 140-175°C, preferably 145-170°C, more preferably 150-165°C, and even more preferably 155-160°C. The reaction time is 12-24h, preferably 14-22h, more preferably 15-20h, and even more preferably 16-18h.

[0055] In the present invention, after the reaction is completed, post-treatment is performed. The reaction mixture is extracted with dichloromethane, and the obtained organic phase is washed with saturated saline, the number of washings is preferably ≥3 times, more preferably ≥4 times, and more preferably ≥5 times; after washing, the organic layers are combined and dried with anhydrous sodium sulfate; after drying, silica gel is added for stirring, and the mesh number of the silica gel is 200-300 mesh; the mass of the silica gel is preferably 3-8 times, more preferably 4-7 times, and more preferably 5-6 times the total mass of all reactants; then chromatography is performed, and the eluent of the chromatography column comprises dichloromethane and petroleum ether, and the volume ratio of the dichloromethane and petroleum ether is preferably 1:0.5-2, more preferably 1:0.75-1.75, and more preferably 1:1-1.5; the stationary phase of the chromatography column is silica gel, and the mesh number of the silica gel is 300-400 mesh, and finally an orange solid is obtained, which is a 2,5-diphenyl-3,4-ethylenedioxythiophene derivative.

[0056] The present invention also provides the use of the 2,5-diphenyl-3,4-ethylenedioxythiophene derivative in an electrochromic film.

[0057] The present invention also provides an electrochromic film, wherein the polymerized monomer of the electrochromic film is a 2,5-diphenyl-3,4-ethylenedioxythiophene derivative described in formula (I).

[0058] The present invention also provides a method for preparing the electrochromic film, comprising the following steps:

[0059] The 2,5-diphenyl-3,4-ethylenedioxythiophene derivative represented by formula (I) is dissolved in a tetrabutylammonium hexafluorophosphate solution to obtain a mixed solution; and the mixed solution is subjected to electrochemical polymerization to obtain the electrochromic film.

[0060] In the present invention, the concentration of the 2,5-diphenyl-3,4-ethylenedioxythiophene derivative in the mixed solution is 0.5 to 1.5 mmol / L, preferably 0.6 to 1.3 mmol / L, more preferably 0.7 to 1.2 mmol / L, and even more preferably 0.9 to 1.1 mmol / L;

[0061] The concentration of the tetrabutylammonium hexafluorophosphate solution is 0.09 to 0.12 mol / L, preferably 0.095 to 0.115 mol / L, more preferably 0.10 to 0.11 mol / L, and even more preferably 0.102 to 0.106 mol / L;

[0062] The solvent of the tetrabutylammonium hexafluorophosphate solution comprises dichloromethane and acetonitrile;

[0063] The volume ratio of dichloromethane to acetonitrile is 5 to 12:2, preferably 6 to 11:2, more preferably 7 to 10:2, and even more preferably 8 to 9:2.

[0064] In the present invention, the voltage of the electrochemical polymerization is 0-1.1 V, preferably 0.1-1.0 V, more preferably 0.3-0.8 V, and even more preferably 0.5-0.6 V; the scanning speed is 50-125 mV / s, preferably 60-120 mV / s, more preferably 75-110 mV / s, and even more preferably 90-105 mV / s.

[0065] In the present invention, after the electrochemical polymerization is completed, post-treatment is carried out, and the film is cleaned in a mixed cleaning agent of dichloromethane and acetonitrile to remove unpolymerized monomers or oligomers and residual electrolyte on the surface of the film, and then naturally dried in the air for use; the mixed cleaning agent contains dichloromethane and acetonitrile, and the volume ratio of dichloromethane and acetonitrile is preferably 8:1 to 4, preferably 8:1.2 to 3.5, more preferably 8:1.5 to 3, and even more preferably 8:2 to 2.5.

[0066] The technical solutions provided by the present invention are described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0067] Example 1

[0068] Step 1): Weigh 2,5-bis(4'-bromophenyl)-3,4-ethylenedioxythiophene (0.45 g, 1 mmol), tributyl(3,3-dimethyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxane-6-yl)stannane (1.42 g, 3 mmol), and 57.78 mg of Pd(PPh3)4 into a 100 mL two-necked round-bottom flask. Under nitrogen, add 20 mL of ultra-dry DMF solution and reflux at 155°C for 18 hours. After the reaction, cool naturally to room temperature. Extract the reaction mixture with dichloromethane and wash three times with saturated brine. Dry the combined organic layers over anhydrous Na2SO4, add 200-300 mesh silica gel (5 times the mass of the reactants), and concentrate under vacuum. The product was chromatographed on a column using dichloromethane / petroleum ether (volume ratio of 1:1) as eluent and 300-400 mesh fine silica gel as stationary phase to obtain an orange solid, which is the 2,5-diphenyl-3,4-ethylenedioxythiophene derivative represented by formula (I), namely 5,7-bis(4-(3,3-dimethyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepin-6-yl)phenyl)-2,3-dihydrothieno[3,4-b][1,4]dioxane (0.53 g, yield 80%).

[0069] Its nuclear magnetic hydrogen spectrum characterization is as follows: 1 HNMR (600MHz, CDCl3) δ7.75 (dd, J = 19.6, 8.6 Hz, 8H), 6.47 (s, 2H), 4.40 (s, 4H), 3.85 (d, J = 21.4Hz, 8H), 1.10 (s, 12H).

[0070] Step 2): QBEBQ (6.58 mg, 0.01 mmol) and tetrabutylammonium hexafluorophosphate (0.387 g, 1 mmol) prepared in Step 1) were added to a 10 mL volumetric flask and diluted to 10 mL with a mixture of dichloromethane and acetonitrile (v / v = 8:2) as the electrolyte. Ultrasonication was performed for 5 minutes to allow complete dissolution, followed by electrochemical polymerization. Polymerization films were formed by cyclic voltammetry using an ITO glass (0.9 x 4 cm) working electrode, a platinum wire as the counter electrode, and an Ag / AgCl electrode as the reference electrode. The voltage range was 0-1.1 V, and the scan rate was 100 mV / s.

[0071] After the electropolymerization is completed, the film is cleaned in a mixed cleaning agent of dichloromethane and acetonitrile (V / V=8:2) to remove unpolymerized monomers or oligomers and residual electrolyte on the surface of the film, and then naturally dried in air to obtain the khaki-transparent electrochromic film.

[0072] Figure 11 is a cyclic voltammetry polymerization curve of the 2,5-diphenyl-3,4-ethylenedioxythiophene derivative prepared in this example.

[0073] 0.387 g of tetrabutylammonium hexafluorophosphate was added to a 10 mL volumetric flask, and the volume was adjusted to 8 mL of dichloromethane and 2 mL of acetonitrile as a blank solution. The 2,5-diphenyl-3,4-ethylenedioxythiophene derivative polymer film prepared in this example at different voltages was detected using a UV-visible spectrophotometer. Figure 2 ,pass Figure 2 It can be found that the prepared film can change color at a voltage of 0 to 0.9V.

[0074] The response time of the 2,5-diphenyl-3,4-ethylenedioxythiophene derivative polymer film prepared in this embodiment was measured at 469 nm. Figure 3 ,from Figure 3 It can be seen that the coloring time is 2s and the fading time is 0.8s in the 469nm wavelength range;

[0075] The response time of the 2,5-diphenyl-3,4-ethylenedioxythiophene derivative polymer film prepared in this embodiment was measured at 706 nm. Figure 4 ,pass Figure 4 It can be seen that the coloring time in the 706nm wavelength range is 0.9s and the fading time is 1.38s.

[0076] The 2,5-diphenyl-3,4-ethylenedioxythiophene derivative polymer film prepared in this embodiment was subjected to a dynamic test at 469 nm. Figure 5 ,from Figure 5 It can be seen that the optical contrast ratio at the wavelength range of 469 nm is 44.2%;

[0077] The kinetic test of the 2,5-diphenyl-3,4-ethylenedioxythiophene derivative polymer film prepared in this embodiment at 706 nm was carried out. Figure 6 ,from Figure 6 It can be seen that the optical contrast ratio in the 706nm wavelength range is 46%;

[0078] After 600 cycles, there is no obvious attenuation of the optical contrast in the 469nm wavelength range, indicating that it is a new type of high-performance electrochromic material with great potential in khaki-transparent color.

[0079] Example 2

[0080] Step 1): Weigh 2,5-bis(4'-bromophenyl)-3,4-ethylenedioxythiophene (0.45 g, 1 mmol), tributyl(3,3-dimethyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxane-6-yl)stannane (1.18 g, 2.5 mmol), and 80 mg of Pd(PPh3)4 into a 50 mL two-necked round-bottom flask. Under nitrogen, add 20 mL of ultra-dry DMF solution, heat to 150°C, and reflux for 24 hours. After the reaction, cool naturally to room temperature. Extract the reaction mixture with dichloromethane and wash three times with saturated brine. Dry the combined organic layers over anhydrous Na2SO4, add 200-300 mesh silica gel (4 times the mass of the reactants), and concentrate under vacuum. The product was chromatographed on a column using dichloromethane / petroleum ether (volume ratio 1:2) as eluent and 300-400 mesh fine silica gel as stationary phase to obtain an orange solid, which is a 2,5-diphenyl-3,4-ethylenedioxythiophene derivative, namely 5,7-bis(4-(3,3-dimethyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepin-6-yl)phenyl)-2,3-dihydrothieno[3,4-b][1,4]dioxane.

[0081] Step 2): QBEBQ (13.16 mg, 0.02 mmol) and tetrabutylammonium hexafluorophosphate (0.774 g, 2 mmol) prepared in Step 1 were added to a 20 mL volumetric flask. A mixture of dichloromethane and acetonitrile (v / v = 7:3) was used as the electrolyte solvent, and the volume was adjusted to 20 mL. Ultrasonication was performed for 30 minutes to allow complete dissolution, followed by electrochemical polymerization. Polymerization films were formed by cyclic voltammetry using an ITO glass (2.5 x 4 cm) working electrode, a platinum sheet as the counter electrode, and an Ag / AgCl electrode as the reference electrode. The voltage range was 0-1.1 V, and the scan rate was 50 mV / s.

[0082] After the electropolymerization is completed, the film is cleaned in a mixed cleaning agent of dichloromethane and acetonitrile (V / V=7:3) to remove unpolymerized monomers or oligomers and residual electrolyte on the surface of the film, and then naturally dried in air to obtain the khaki-transparent electrochromic film.

[0083] As can be seen from the above examples, the present invention provides a 2,5-diphenyl-3,4-ethylenedioxythiophene derivative. Using cyclic voltammetry, a khaki-transparent electrochromic material can be obtained by forming the 2,5-diphenyl-3,4-ethylenedioxythiophene derivative into a thin film. This material changes color at a voltage of 0 to 0.9 V. At a wavelength of 469 nm, the optical contrast is 44.2%, with a coloring time of 2 seconds and a fading time of 0.8 seconds. At a wavelength of 706 nm, the optical contrast is 46%, with a coloring time of 0.9 seconds and a fading time of 1.38 seconds. After 600 cycles, there is no significant attenuation of the optical contrast at a wavelength of 469 nm.

[0084] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A 2,5-diphenyl-3,4-ethylenedioxythiophene derivative, characterized in that: The structure of the derivative is shown in formula (I):

2. The method for preparing the 2,5-diphenyl-3,4-ethylenedioxythiophene derivative according to claim 1, characterized in that: The following steps are involved: Under a protective atmosphere, 2,5-bis(4'-bromophenyl)-3,4-ethylenedioxythiophene, tributyl(3,3-dimethyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxane-6-yl)stannane, a catalyst, and a solvent are mixed and reacted to obtain a 2,5-diphenyl-3,4-ethylenedioxythiophene derivative represented by formula (I).

3. The preparation method according to claim 2, characterized in that The molar ratio of the 2,5-bis(4'-bromophenyl)-3,4-ethylenedioxythiophene to tributyl(3,3-dimethyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxane-6-yl)stannane is 1:2.5-3.5; The ratio of the solvent to 2,5-bis(4'-bromophenyl)-3,4-ethylenedioxythiophene is 35-50 mL:1 g; The molar ratio of the catalyst to 2,5-bis(4'-bromophenyl)-3,4-ethylenedioxythiophene is 3 to 10:

100.

4. The preparation method according to claim 2 or 3, characterized in that The catalyst comprises tetrakis(triphenylphosphine)palladium; The solvent comprises at least one of N,N-dimethylformyl and 1,4-dioxane; The protective atmosphere contains nitrogen.

5. The preparation method according to claim 2 or 3, characterized in that The reaction temperature is 140-175° C., and the reaction time is 12-24 hours.

6. Use of the 2,5-diphenyl-3,4-ethylenedioxythiophene derivative according to claim 1 in an electrochromic film.

7. An electrochromic film, characterized in that: The polymerized monomer of the electrochromic film is the 2,5-diphenyl-3,4-ethylenedioxythiophene derivative according to claim 1.

8. The method for preparing the electrochromic film according to claim 7, characterized in that: The following steps are involved: The 2,5-diphenyl-3,4-ethylenedioxythiophene derivative represented by formula (I) is dissolved in a tetrabutylammonium hexafluorophosphate solution to obtain a mixed solution; and the mixed solution is subjected to electrochemical polymerization to obtain the electrochromic film.

9. The preparation method according to claim 8, characterized in that The concentration of the 2,5-diphenyl-3,4-ethylenedioxythiophene derivative in the mixed solution is 0.5 to 1.5 mmol / L; The concentration of the tetrabutylammonium hexafluorophosphate solution is 0.09 to 0.12 mol / L; The solvent of the tetrabutylammonium hexafluorophosphate solution comprises dichloromethane and acetonitrile; The volume ratio of the dichloromethane to acetonitrile is 5-12:

2.

10. The preparation method according to claim 8 or 9, characterized in that: The voltage of the electrochemical polymerization is 0-1.1V, and the scanning speed is 50-125mV / s.

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