Low-voltage electrochromic device and preparation method and application thereof

Abstract

The invention provides a low-voltage electrochromic device and a preparation method and application thereof, and belongs to the technical field of electrochromic devices. The low-voltage electrochromic device comprises a first substrate, a first transparent conductive metal oxide layer, a conductive polymer film, an electrolyte layer, a second transparent conductive metal oxide layer and a second substrate which are sequentially stacked, and the electrolyte layer contains oxidized ions. And the conductive polymer film is made of a polythiophene conductive polymer. A layer of film formed by the polythiophene conductive polymer with high redox reversibility is additionally arranged on the surface of a traditional electrode, the working voltage of a device is remarkably reduced, meanwhile, the cycle life is prolonged, the safety is improved, the polythiophene conductive polymer serves as a redox medium, and the performance of the device is improved. On the surface of the electrode, through interaction with oxidized ions in the electrolyte layer, the charge storage and release capability of the counter electrode is enhanced, the ion migration potential barrier is reduced, and the working voltage is greatly reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of electrochromic devices, and in particular to a low-voltage electrochromic device and a preparation method and application thereof. Background Art

[0002] Electrochromic devices induce redox reactions in materials through an applied electric field, achieving dynamic control of optical properties such as transmittance, reflectivity, and absorptivity. They have advantages such as low energy consumption, high optical contrast, and cyclic stability. They have great application potential in fields such as smart windows for building photothermal control, electronic displays, new energy vehicle skylights, and anti-glare rearview mirrors. In related technologies, electrochromic devices are usually composed of an electrochromic layer (such as inorganic metal oxides WO3 and NiO, organic small molecule viologen compounds, or organic conductive polymers such as polythiophene), an electrolyte layer, and an ion storage layer (counter electrode). However, existing electrochromic devices usually require a high match between the electrochromic layer material and the ion storage layer material to enable the device to switch effectively at low voltage. If the electrochromic material lacks a suitable matching ion storage layer material, the device will require a higher operating voltage to achieve effective driving, which will lead to the following problems: high voltage accelerates the degradation of the electrochromic material and the decomposition of the electrolyte, shortening the device life; electrolyte side reactions and local overheating lead to safety hazards; and increased energy consumption limits its application in low-power scenarios.

[0003] Existing electrochromic device improvement plans mostly focus on broadening the potential window of functional materials or using solid-state electrolytes. Although these can alleviate the negative effects of high voltage, they cannot directly reduce the operating voltage. Moreover, due to the different properties of various electrochromic materials, it is difficult to develop a universal method for low-voltage driving of electrochromic devices. Summary of the Invention

[0004] In light of this, the present invention aims to provide a low-voltage electrochromic device, its preparation method, and its application. The low-voltage electrochromic device of the present invention significantly reduces the operating voltage by enhancing the charge storage and release capabilities of the counter electrode through the interaction between the conductive polymer film and the oxidized ions, thereby lowering the ion migration barrier.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a low-voltage electrochromic device, comprising a first substrate, a first transparent conductive metal oxide layer, a conductive polymer film, an electrolyte layer, a second transparent conductive metal oxide layer, and a second substrate stacked in sequence, wherein the electrolyte layer contains oxidizing ions, and the conductive polymer film is made of a polythiophene conductive polymer.

[0007] Preferably, the polythiophene conductive polymer includes a polythiophene conductive polymer [poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate)]] (PEDOT:PSS), [poly(2,7-bis(2-octyldodecyl)benzo[lmn][3,8]phenanthroline-1,3,6,8(2H,7H)-tetraketone-4,9-diyl)([2,2']dithienyl-5,5'-diyl)] (N2200), [poly([2,6'-4,8-bis-(( 2-ethylhexyl)-thiophen-5-yl)benzo[1,2-b;3,3-b]dithiophene]-alt-[1,3-bis-(thiophen-5-yl)-5,7-bis-(2-ethylhexyl)benzo[1,2-c:4,5-c']dithiophene-4,8-dione])] (PBDB-T), [poly[4,8-bis(5-(2-ethylhexyl)thiophene)benzo[1,2-b;4,5-b']dithiophene-alt-(4-(2-ethylhexyl)-3-fluorothiophene]] [3,4-b]thiophene-)-2-carboxylate)]] (PTB7-Th), [poly[(2,6-(4,8-bis(5-(2-ethylhexyl-3-fluoro)thiophen-2-yl)-benzo[1,2-b:4,5-b']dithiophene])-alt-(5,5-(1',3'-di-2-thiophene-5',7'-bis(2-ethylhexyl)benzo[1',2'-c:4',5'-c']dithiophene-4,8-dione)]], [poly[(5,6-di One or more of: poly(3-hexylthiophene-2,5-diyl)-1,2-difluoro-2,1,3-benzothiadiazole)-alt-(3,3"'-di(2-octyldodecyl)-2,2';5',2";5",2"'-quaterthiophene)]], [poly[[3,3-bis[[(2-ethylhexyl)oxy]methyl]-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepin-6,8-diyl]]] (EC1003), poly(3-hexylthiophene-2,5-diyl) and 3-hexyl-substituted polythiophene.

[0008] Preferably, the thickness of the conductive polymer film is 0.5-10 μm.

[0009] Preferably, the oxidizing ions include Br - , I - 、Cl - 、S 2- 、SO3 2- 、NO2 - 、Fe 2+ 、Cu + and CN - One or more of .

[0010] Preferably, the concentration of oxidative ions in the electrolyte layer is 10 -4 ~10-1 mol / L.

[0011] Preferably, the electrolyte layer further contains an electrochromic material.

[0012] Preferably, the electrochromic material includes one or more of viologen materials, polyaniline and polypyrrole.

[0013] Preferably, an electrochromic layer is further provided between the electrolyte layer and the second transparent conductive metal oxide layer, and the material of the electrochromic layer includes one or more of WO3, NiO and TiO2.

[0014] The present invention also provides a method for preparing the low-voltage electrochromic device described in the above technical solution, comprising the following steps:

[0015] Depositing on the surface of the first substrate to obtain a first transparent conductive metal oxide layer;

[0016] coating a conductive polymer dispersion on the surface of the first transparent conductive metal oxide layer to form a film to obtain a conductive polymer film, wherein the conductive polymer dispersion includes a polythiophene conductive polymer;

[0017] Depositing on the surface of the second substrate to obtain a second transparent conductive metal oxide layer;

[0018] A spacing groove is placed on the surface of the conductive polymer film, and then the spacing groove is filled with an electrolyte material, and then covered with the second transparent conductive metal oxide layer to obtain the low-voltage electrochromic device, wherein the electrolyte material contains oxidizing ions.

[0019] The present invention also provides the use of the low-voltage electrochromic device described in the above technical solution or the low-voltage electrochromic device prepared by the preparation method described in the above technical solution in the fields of anti-glare rearview mirrors, building curtain walls, automobile glass, electronic tags, electronic billboards, smart windows or reflective displays.

[0020] The present invention provides a low-voltage electrochromic device, comprising a first substrate, a first transparent conductive metal oxide layer, a conductive polymer film, an electrolyte layer, a second transparent conductive metal oxide layer, and a second substrate stacked in sequence, wherein the electrolyte layer contains oxidizing ions, and the conductive polymer film is made of a polythiophene conductive polymer.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The present invention provides a novel low-voltage electrochromic device structure. By adding a thin film of a polythiophene-based conductive polymer with high redox reversibility to the surface of a conventional electrode, the device's operating voltage is significantly reduced, while its cycle life and safety are also improved. The polythiophene-based conductive polymer acts as a redox mediator, interacting with oxidized ions in the electrolyte layer on the electrode surface. This enhances the electrode's charge storage and release capabilities, lowers the ion migration barrier, and significantly reduces the operating voltage. This reduces the risk of electrochromic material degradation and electrolyte decomposition, extends the device's life, and avoids the potential for combustion caused by local overheating. Furthermore, low-voltage electrochromic devices are advantageous for use in low-power scenarios, broadening the application range of electrochromic technology.

[0023] The present invention also provides a method for preparing the low-voltage electrochromic device described in the above technical solution. The preparation method provided by the present invention is simple to operate, easy to implement industrial application, and low in cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematic diagram of the structure of the low-voltage electrochromic device of the present invention;

[0025] Figure 2 1 is a transmittance spectrum of the low-voltage electrochromic device in Example 1 as it changes with voltage;

[0026] Figure 3 Graph showing the transmittance spectrum of the low-voltage electrochromic device in Example 2 as it changes with voltage;

[0027] Figure 4 Graph showing the transmittance spectrum of the low-voltage electrochromic device in Example 3 as it changes with voltage;

[0028] Figure 5 Graph showing the transmittance spectrum of the low-voltage electrochromic device according to Example 4 as it changes with voltage;

[0029] Figure 6 Graph showing the transmittance spectrum of the low-voltage electrochromic device according to Example 5 as it changes with voltage;

[0030] Figure 7 Graph showing the transmittance spectrum of the low-voltage electrochromic device in Example 6 as it changes with voltage;

[0031] Figure 8 Graph showing the transmittance spectrum of the low-voltage electrochromic device according to Example 7 as it changes with voltage;

[0032] Figure 9 Graph showing the transmittance spectrum of the low-voltage electrochromic device in Example 8 as it changes with voltage;

[0033] Figure 101 is a transmittance spectrum of the electrochromic device in Comparative Example 1 as the voltage changes;

[0034] Figure 11 This is a transmittance spectrum diagram of the electrochromic device in Comparative Example 2 as the voltage changes. DETAILED DESCRIPTION

[0035] The present invention provides a low-voltage electrochromic device, comprising a first substrate, a first transparent conductive metal oxide layer, a conductive polymer film, an electrolyte layer, a second transparent conductive metal oxide layer, and a second substrate stacked in sequence, wherein the electrolyte layer contains oxidizing ions, and the conductive polymer film is made of a polythiophene conductive polymer.

[0036] Figure 1 The schematic diagram of the structure of the low voltage electrochromic device of the present invention is shown below. Figure 1 The structure of the low-voltage electrochromic device of the present invention will be described.

[0037] The low-voltage electrochromic device of the present invention includes a first substrate and a second substrate.

[0038] In the present invention, the first substrate and the second substrate are independently preferably glass or a polymer film, and the polymer film is preferably polyethylene terephthalate (PET), polyurethane (PU) or polyimide (PI). The present invention has no particular limitation on the thickness of the first substrate and the second substrate, and parameters well known to those skilled in the art can be used.

[0039] The low-voltage electrochromic device of the present invention includes a first transparent conductive metal oxide layer and a second transparent conductive metal oxide layer.

[0040] In the present invention, the first and second transparent conductive metal oxide layers are independently indium tin oxide (ITO), aluminum-doped zinc oxide (AZO), or fluorine-doped tin dioxide (FTO). The present invention does not specifically limit the thickness of the first and second transparent conductive metal oxide layers, and parameters well known to those skilled in the art can be used.

[0041] The low-voltage electrochromic device of the present invention includes a conductive polymer film, the material of which includes a polythiophene conductive polymer. The conductive polymer film has high redox reversibility and synergistically acts with oxidizing ions to significantly reduce the operating voltage of the device while improving the cycle life and safety.

[0042] In the present invention, the polythiophene conductive polymer preferably includes a polythiophene conductive polymer [poly (3,4-ethylenedioxythiophene): poly (styrene sulfonate)]] (PEDOT:PSS), [poly (2,7-bis (2-octyldodecyl) benzo [lmn] [3,8] o-diazophenanthroline-1,3,6,8 (2H,7H) -tetraketone-4,9-diyl) ([2,2'] dithienyl -5,5'-diyl)] (N2200), [poly ([2,6'-4,8-bis (2-octyldodecyl) benzo [lmn] [3,8] o-diazophenanthroline-1,3,6,8 (2H,7H) -tetraketone-4,9 ... -((2-ethylhexyl)-thiophen-5-yl)benzo[1,2-b;3,3-b]dithiophene]-alt-[1,3-bis-(thiophen-5-yl)-5,7-bis-(2-ethylhexyl)benzo[1,2-c:4,5-c']dithiophene-4,8-dione])] (PBDB-T), [poly[4,8-bis(5-(2-ethylhexyl)thiophene)benzo[1,2-b;4,5-b']dithiophene-alt-(4-(2-ethylhexyl)-3-fluorothiophene)] [(1,2-b:4,5-b']dithiophene])-alt-(5,5-(1',3'-di-2-thiophene-5',7'-bis(2-ethylhexyl)benzo[1',2'-c:4',5'-c']dithiophene-4,8-dione)]], [(5,6- One or more of difluoro-2,1,3-benzothiadiazole)-alt-(3,3"'-di(2-octyldodecyl)-2,2';5',2";5",2"'-quaterthiophene)]], [poly[[3,3-bis[[(2-ethylhexyl)oxy]methyl]-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepin-6,8-diyl]]] (EC1003), poly(3-hexylthiophene-2,5-diyl) and 3-hexyl-substituted polythiophene.

[0043] In the present invention, the thickness of the conductive polymer film is preferably 0.5 to 10 μm, specifically 0.5, 0.8, 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 μm. The thickness of the conductive polymer film is not less than 0.5 μm to ensure that the polymer film has a sufficient amount to carry out redox reaction. The thickness of the conductive polymer film is not more than 10 μm to avoid the film being too thick, resulting in low initial transmittance, which limits the improvement of the electrochromic optical modulation performance.

[0044] In the present invention, the thickness of the electrolyte layer is preferably 0.01 to 1 mm, specifically 0.01, 0.05, 0.1, 0.2, 0.4, 0.5 or 1 mm.

[0045] In the present invention, the oxidizing ions preferably include Br - , I - 、Cl - 、S 2- 、SO3 2- 、NO2 - 、Fe 2+ 、Cu + and CN - One or more of .

[0046] In the present invention, the concentration of oxidative ions in the electrolyte layer is preferably 10 -4 ~10 -1 mol / L, specifically 0.0001, 0.01, 0.02, 0.04, 0.06, 0.08 or 0.1M.

[0047] In the present invention, the oxidizing ions in the electrolyte layer are preferably added in the form of metal salts or organic salts containing oxidizing ions.

[0048] In the present invention, the electrolyte layer preferably also includes an electrolyte, and the electrolyte preferably includes one or more of lithium salts, sodium salts, potassium salts and ammonium salts. The lithium salt more preferably includes one or more of lithium perchlorate, lithium bromide and lithium chloride. The sodium salt is more preferably sodium chloride, the potassium salt is more preferably potassium chloride, and the ammonium salt is more preferably tetrabutylammonium hexafluorophosphate. The role of the electrolyte is to improve the ionic conductivity of the electrolyte layer and promote the improvement of the optical switching performance of the system.

[0049] In the present invention, the concentration of the electrolyte in the electrolyte layer is preferably 0.001 to 0.5M, specifically 0.001, 0.01, 0.05, 0.1, 0.2, 0.3, 0.4 or 0.5M.

[0050] In the present invention, the electrolyte layer preferably further contains an electrochromic material.

[0051] In the present invention, the electrochromic material preferably includes one or more of viologen materials, polyaniline and polypyrrole.

[0052] In the present invention, the concentration of the electrochromic material in the electrolyte layer is preferably 10 -4 ~10 -1 mol / L, specifically 0.0001, 0.01, 0.02, 0.04, 0.06, 0.08 or 0.1M.

[0053] In the present invention, the solvent of the electrolyte layer is preferably water or propylene carbonate.

[0054] In the present invention, an electrochromic layer is further provided between the electrolyte layer and the second transparent conductive metal oxide layer, and the material of the electrochromic layer includes one or more of WO3, NiO and TiO2.

[0055] In the present invention, the thickness of the electrochromic layer is preferably 0.1 to 10 μm, specifically 0.1, 0.5, 1, 2, 4, 5 or 10 μm.

[0056] The present invention also provides a method for preparing the electrochromic device described in the above technical solution, comprising the following steps:

[0057] Depositing on the surface of the first substrate to obtain a first transparent conductive metal oxide layer;

[0058] coating a conductive polymer dispersion on the surface of the first transparent conductive metal oxide layer to form a film to obtain a conductive polymer film, wherein the conductive polymer dispersion includes a polythiophene conductive polymer;

[0059] Depositing on the surface of the second substrate to obtain a second transparent conductive metal oxide layer;

[0060] A spacing groove is placed on the surface of the conductive polymer film, and then the spacing groove is filled with an electrolyte material, and then covered with the second transparent conductive metal oxide layer to obtain the electrochromic device, wherein the electrolyte material contains oxidizing ions.

[0061] In the present invention, unless otherwise specified, the raw materials and equipment used are commercially available products in the field.

[0062] The present invention performs deposition on the surface of a first substrate to obtain a first transparent conductive metal oxide layer.

[0063] The present invention has no particular limitation on the specific method of deposition, and any method well known to those skilled in the art may be used.

[0064] After obtaining the first transparent conductive metal oxide layer, the present invention coats a conductive polymer dispersion on the surface of the first transparent conductive metal oxide layer to obtain a conductive polymer film, wherein the conductive polymer dispersion includes a polythiophene conductive polymer.

[0065] In the present invention, the coating is preferably performed by blade coating, spin coating, drop coating or spray coating.

[0066] In the present invention, the spin coating rotation speed is preferably 4000 rpm, and the spin coating time is preferably 30 to 60 s, specifically 30, 40, 50 or 60 s.

[0067] The present invention has no particular limitation on the type of dispersant in the redox polymer dispersion and the concentration of the dispersion, as long as the film thickness can be 0.5 to 10 μm.

[0068] The present invention performs deposition on the surface of the second substrate to obtain a second transparent conductive metal oxide layer.

[0069] The present invention has no particular limitation on the specific method of deposition, and any method well known to those skilled in the art may be used.

[0070] After obtaining the conductive polymer film and the second transparent conductive metal oxide layer, the present invention places a spacing groove on the surface of the conductive polymer film, then fills the spacing groove with an electrolyte material, and then covers the second transparent conductive metal oxide layer to obtain the electrochromic device, wherein the electrolyte material contains oxidative ions.

[0071] In the present invention, the material of the spacing groove is preferably tape, polydimethylsiloxane (PDMS), light-curable resin or thermosetting resin. The present invention has no special limitation on the preparation method of the spacing groove, and a method familiar to those skilled in the art can be used.

[0072] In the present invention, the electrolyte material is preferably dripped into the spacing groove.

[0073] In a specific embodiment of the present invention, a metal salt or organic salt containing an oxidizing ion and an electrolyte are preferably mixed and dissolved in water or propylene carbonate to obtain an electrolyte solution, and then the electrolyte solution and the electrochromic material are mixed to obtain the electrolyte material.

[0074] When an electrochromic layer is further provided between the electrolyte layer and the second transparent conductive metal oxide layer, the present invention preferably coats the electrochromic material onto the surface of the second transparent conductive metal oxide layer to obtain the electrochromic layer.

[0075] Taking the electrochromic layer as WO3 as an example, the preparation method of the electrochromic layer preferably includes the following steps: dissolving a tungsten source (ammonium metatungstate) in a high-boiling point solvent (oleylamine), then degassing under vacuum at 120°C for 10 minutes, heating to 250°C under nitrogen protection, keeping at 250°C for 2 hours and then cooling naturally. After cooling to room temperature, adding a polar solvent (ethanol), centrifuging, and dispersing into a non-polar solvent (toluene) to obtain a dispersion of tungsten oxide-based electrochromic material. Then, the dispersion of the tungsten oxide-based electrochromic material is coated (scraped) on the surface of the second transparent conductive metal oxide layer, and then calcined (500°C) to obtain a working electrode containing an electrochromic layer.

[0076] In the present invention, the coating is preferably performed by scraping, spin coating, drip coating or spray coating. The present invention has no particular limitation on the specific parameters of the coating, and methods well known to those skilled in the art may be used.

[0077] The present invention also provides the application of the electrochromic device described in the above technical solution or the electrochromic device prepared by the preparation method described in the above technical solution in the fields of anti-glare rearview mirrors, building curtain walls, automobile glass, electronic tags, electronic billboards, smart windows or reflective displays.

[0078] The present invention has no particular limitation on the application, and any method familiar to those skilled in the art may be used.

[0079] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0080] Example 1

[0081] The preparation of a tungsten oxide-based low-voltage electrochromic device having a conductive polymer film and containing bromide ions comprises the following steps:

[0082] 1. Preparation of bromide ion-containing electrolyte solution: After weighing 430 mg of lithium bromide, add propylene carbonate and stir thoroughly to make a 5 mL solution.

[0083] 2. Preparation of conductive polymer film using poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS): A dispersion of PEDOT:PSS was spin-coated (rotation speed 4000 rpm, spin coating time 60 s) onto a metal oxide conductive electrode (FTO glass) to form a film with a thickness of 800 nm.

[0084] 3. Preparation of a working electrode containing an electrochromic material: A tungsten source (ammonium metatungstate) was dissolved in 50 mL of a high-boiling-point solvent (oleylamine), then vacuum degassed at 120°C for 10 minutes. The temperature was then raised to 250°C under nitrogen protection, kept at 250°C for 2 hours, and then naturally cooled. After cooling to room temperature, 50 mL of a polar solvent (ethanol) was added. The mixture was centrifuged three times (10,000 rpm for 10 minutes) and dispersed in 20 mL of a non-polar solvent (toluene) to obtain a dispersion of a tungsten oxide-based electrochromic material. This dispersion was then coated (bladed) onto the surface of a conductive glass (fluorine-doped tin dioxide, FTO) and calcined at 500°C to obtain a working electrode containing a tungsten oxide thin film (1 μm thick).

[0085] 4. Preparation of low-voltage electrochromic device: A spacer groove is placed on the surface of an FTO conductive electrode with a tungsten oxide film on one side without PEDOT:PSS coating. The spacer groove is made of a polydimethylsiloxane film with a thickness of 400μm. Then, an electrolyte solution containing bromide ions is dripped into the spacer groove, covering the FTO conductive electrode coated with PEDOT:PSS on the other side. Thus, a tungsten oxide-based low-voltage electrochromic device is obtained. Under voltage control, the device can achieve effective control of transmittance, with a turn-on voltage of -0.7V ( Figure 2 ).

[0086] Example 2

[0087] The same as Example 1, except that PEDOT:PSS is replaced by 3-hexyl-substituted polythiophene.

[0088] The low-voltage electrochromic device prepared in this embodiment can effectively control the transmittance under voltage control, and the turn-on voltage is -0.7V ( Figure 3 ).

[0089] Example 3

[0090] The same as Example 1, except that PEDOT:PSS is replaced by poly(3-hexylthiophene-2,5-diyl).

[0091] The low-voltage electrochromic device prepared in this embodiment can effectively control the transmittance under voltage control, and the turn-on voltage is -0.7V ( Figure 4 ).

[0092] Example 4

[0093] The same as Example 1, except that PEDOT:PSS was replaced with [poly[[3,3-bis[[(2-ethylhexyl)oxy]methyl]-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepin-6,8-diyl]]] (EC1003).

[0094] The low-voltage electrochromic device prepared in this embodiment can effectively control the transmittance under voltage control, and the turn-on voltage is -0.7V ( Figure 5 ).

[0095] Example 5

[0096] The preparation of a low-voltage electrochromic device having a conductive polymer film and a viologen solution containing bromide ions comprises the following steps:

[0097] 1. Preparation of an electrolyte solution containing bromide ions and a viologen compound: Weigh 31 mg of a phenyl-substituted viologen compound (electrochromic material), 19 mg of tetrabutylammonium hexafluorophosphate (electrolyte), and 16 mg of tetrabutylammonium bromide (providing oxidizing ions), add propylene carbonate, and stir thoroughly to make a 5 mL solution.

[0098] 2. Preparation of conductive polymer film using poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS): A dispersion of PEDOT:PSS was spin-coated (rotation speed 4000 rpm, spin coating time 60 s) on a metal oxide conductive electrode (ITO glass) to form a film with a thickness of 800 nm.

[0099] 3. Preparation of low-voltage electrochromic device: A spacer groove is placed on the surface of an ITO conductive electrode not coated with PEDOT:PSS on one side. The spacer groove is made of a polydimethylsiloxane film with a thickness of 400μm. Then, an electrolyte solution containing bromide ions and a viologen compound is dripped into the spacer groove, covering the ITO conductive electrode coated with PEDOT:PSS on the other side. The low-voltage electrochromic device is obtained. Under voltage control, the device can achieve effective control of transmittance, with a turn-on voltage of -1.1V ( Figure 6 ).

[0100] Example 6

[0101] The same as Example 5, except that PEDOT:PSS is replaced by 3-hexyl-substituted polythiophene.

[0102] The low-voltage electrochromic device prepared in this embodiment can effectively control the transmittance under voltage control, and the turn-on voltage is -1.1V ( Figure 7 ).

[0103] Example 7

[0104] The same as Example 5, except that PEDOT:PSS is replaced by poly(3-hexylthiophene-2,5-diyl).

[0105] The low-voltage electrochromic device prepared in this embodiment can effectively control the transmittance under voltage control, and the turn-on voltage is -1.0V ( Figure 8 ).

[0106] Example 8

[0107] The same as Example 5, except that PEDOT:PSS was replaced with [poly[[3,3-bis[[(2-ethylhexyl)oxy]methyl]-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepin-6,8-diyl]]] (EC1003).

[0108] The low-voltage electrochromic device prepared in this embodiment can effectively control the transmittance under voltage control, and the turn-on voltage is -1.0V ( Figure 9 ).

[0109] Comparative Example 1

[0110] The preparation of a tungsten oxide-based electrochromic device containing bromide ions (without a conductive polymer film) comprises the following steps:

[0111] 1. Preparation of bromide ion-containing electrolyte solution: After weighing 430 mg of lithium bromide, add propylene carbonate and stir thoroughly to make a 5 mL solution.

[0112] 2. Preparation of a working electrode containing an electrochromic material: A tungsten source (ammonium metatungstate) was dissolved in 50 mL of a high-boiling-point solvent (oleylamine), then vacuum degassed at 120°C for 10 minutes. The temperature was then raised to 250°C under nitrogen protection, kept at 250°C for 2 hours, and then naturally cooled. After cooling to room temperature, 50 mL of a polar solvent (ethanol) was added. The mixture was centrifuged three times (10,000 rpm for 10 minutes) and dispersed in 20 mL of a non-polar solvent (toluene) to obtain a dispersion of the tungsten oxide-based electrochromic material. This dispersion was then coated (bladed) onto the surface of a conductive glass (fluorine-doped tin dioxide, FTO) and calcined at 500°C to obtain a working electrode containing a tungsten oxide thin film (1 μm thick).

[0113] 3. Preparation of electrochromic device: A spacer groove is placed on the surface of an FTO conductive electrode with a tungsten oxide film on one side without PEDOT:PSS coating. The spacer groove is made of a polydimethylsiloxane film with a thickness of 400μm. Then, an electrolyte solution containing bromide ions is dripped into the spacer groove to cover the FTO conductive electrode on the other side without PEDOT:PSS coating. Thus, a tungsten oxide-based electrochromic device is obtained. Under voltage control, the device can effectively control the transmittance, and the turn-on voltage is -1.3V ( Figure 10 ).

[0114] Comparative Example 2

[0115] The preparation of an electrochromic device (without a conductive polymer film) containing a bromide ion viologen solution comprises the following steps:

[0116] 1. Preparation of an electrolyte solution containing bromide ions and a viologen compound: Weigh 31 mg of a phenyl-substituted viologen compound (electrochromic material), 19 mg of tetrabutylammonium hexafluorophosphate (electrolyte), and 16 mg of tetrabutylammonium bromide (providing oxidizing ions), add propylene carbonate, and stir thoroughly to make a 5 mL solution.

[0117] 2. Preparation of electrochromic device: A spacer groove is placed on the surface of an ITO conductive electrode not coated with PEDOT:PSS on one side. The spacer groove is made of a polydimethylsiloxane film with a thickness of 400μm. Then, an electrolyte solution containing bromide ions and a viologen compound is dripped into the spacer groove, covering the ITO conductive electrode not coated with PEDOT:PSS on the other side. Thus, a voltage electrochromic device is obtained. Under voltage control, the device can effectively control the transmittance, and the turn-on voltage is -1.4V ( Figure 11 ).

[0118] Table 1 shows the comparative results of the electrochromic devices of the embodiments of the present invention and the comparative examples. In the tungsten oxide-based electrochromic devices, Examples 1 to 4 use polythiophene-based conductive polymer films of different configurations and select bromide ions as the oxidizing electrolyte. Comparative Example 1 maintains the same electrolyte system but does not use the conductive polymer film. By comparing the operating voltages of Comparative Example 1 with those of Examples 1 to 4, it can be seen that in the electrolyte system containing oxidizing ions, the use of the polythiophene-based conductive polymer film significantly reduces the operating voltage of the electrochromic device. In the viologen-based electrochromic devices, Examples 5 to 8 use polythiophene-based conductive polymer films of different configurations and select bromide ions as the oxidizing electrolyte. Comparative Example 2 maintains the same electrolyte system but does not use the conductive polymer film. By comparing the operating voltages of Comparative Example 2 with those of Examples 5 to 8, it can be seen that in the electrolyte system containing oxidizing ions, the use of the polythiophene-based conductive polymer film significantly reduces the operating voltage of the electrochromic device.

[0119] Table 1 Comparison results of electrochromic devices of the embodiment of the present invention and the comparative example

[0120]

[0121] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation thereto. It should be noted that those skilled in the art may make various improvements and modifications without departing from the principles of the present invention, and such improvements and modifications shall also be considered within the scope of protection of the present invention.

Claims

1. A low voltage electrochromic device, characterized in that: The invention comprises a first substrate, a first transparent conductive metal oxide layer, a conductive polymer film, an electrolyte layer, a second transparent conductive metal oxide layer and a second substrate stacked in sequence. The electrolyte layer contains oxidative ions, and the conductive polymer film is made of a polythiophene conductive polymer.

2. The low-voltage electrochromic device according to claim 1, characterized in that: The polythiophene conductive polymers include polythiophene conductive polymers [poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate)], [poly(2,7-bis(2-octyldodecyl)benzo[lmn][3,8]phenanthroline-1,3,6,8(2H,7H)-tetraone-4,9-diyl)([2,2']dithienyl-5,5'-diyl)], [poly([2,6'-4,8-bis-((2-ethylhexyl)-thiophen-5-yl)benzo[1,2-b;3,3-b]dithiophene]-alt-[1,3-bis-(thiophen-5-yl)-5,7-bis-(2-ethylhexyl)benzo[1,2-c:4,5-c']dithiophene-4,8-dione])], [poly[4,8-bis(5-( 2-ethylhexyl)thienyl)benzo[1,2-b;4,5-b']dithienyl-alt-(4-(2-ethylhexyl-3-fluorothieno[3,4-b]thiophene-)-2-carboxylate)]], [poly[(2,6-(4,8-bis(5-(2-ethylhexyl-3-fluoro)thien-2-yl)benzo[1,2-b;4,5-b']dithienyl] ... Thiophene])-alt-(5,5-(1',3'-di-2-thiophene-5',7'-bis(2-ethylhexyl)benzo[1',2'-c:4',5'-c']dithiophene-4,8-dione)]], [poly[(5,6-difluoro-2,1,3-benzothiadiazole)-alt-(3,3"'-di(2-octyldodecyl)-2,2'; One or more of: [(5',2"; 5",2"'-quaterthiophene)]], [poly[[3,3-bis[[(2-ethylhexyl)oxy]methyl]-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepin-6,8-diyl]]], poly(3-hexylthiophene-2,5-diyl) and 3-hexyl-substituted polythiophene].

3. The low-voltage electrochromic device according to claim 1 or 2, characterized in that: The thickness of the conductive polymer film is 0.5-10 μm.

4. The low-voltage electrochromic device according to claim 1, characterized in that: The oxidizing ions include Br - , I - 、Cl - 、S 2- 、SO3 2- 、NO2 - 、Fe 2+ 、Cu + and CN - One or more of .

5. The low-voltage electrochromic device according to claim 1 or 4, characterized in that: The concentration of oxidative ions in the electrolyte layer is 10 -4 ~10 -1 mol / L.

6. The low-voltage electrochromic device according to claim 1, characterized in that: The electrolyte layer also contains electrochromic material.

7. The low-voltage electrochromic device according to claim 6, characterized in that: The electrochromic material includes one or more of viologen materials, polyaniline and polypyrrole.

8. The low-voltage electrochromic device according to claim 1, characterized in that: An electrochromic layer is further provided between the electrolyte layer and the second transparent conductive metal oxide layer. The material of the electrochromic layer includes one or more of WO3, NiO and TiO2.

9. The method for preparing a low-voltage electrochromic device according to any one of claims 1 to 8, characterized in that: The following steps are involved: Depositing on the surface of the first substrate to obtain a first transparent conductive metal oxide layer; coating a conductive polymer dispersion on the surface of the first transparent conductive metal oxide layer to form a film to obtain a conductive polymer film, wherein the conductive polymer dispersion includes a polythiophene conductive polymer; Depositing on the surface of the second substrate to obtain a second transparent conductive metal oxide layer; A spacing groove is placed on the surface of the conductive polymer film, and then the spacing groove is filled with an electrolyte material, and then covered with the second transparent conductive metal oxide layer to obtain the low-voltage electrochromic device, wherein the electrolyte material contains oxidizing ions.

10. Use of the low-voltage electrochromic device according to any one of claims 1 to 8 or the low-voltage electrochromic device prepared by the preparation method according to claim 9 in the fields of anti-glare rearview mirrors, building curtain walls, automotive glass, electronic tags, electronic billboards, smart windows or reflective displays.

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