Electrochromic bilayer device for dynamic light flux control and method of making the same

Abstract

Broadband electrochromic devices (ECDs) with independent band selectivity for visible and near-infrared (NIR) radiation have attracted considerable attention due to their functional benefits compared to conventional ECDs. Independent dual-band activity in ECDs typically requires special construction through blending / layering different materials with activity in two distinct regions. This invention provides a broadband electrochromic device comprising a polycrystalline nanosheet layer and an amorphous porous layer. It is demonstrated that very high visible light modulation and unprecedented NIR blocking performance are achieved by using a bilayer electrode made of the same material (i.e., a porous a-WO3 layer above polycrystalline WO3·H2O nanosheets). This simple and inexpensive electrode fabrication can provide a novel platform for realizing high-performance dynamic smart glasses with exceptional spectral selectivity and energy efficiency.

Description

Technical Field

[0001] This invention relates to electrochromic devices manufactured using dynamic luminous flux control for electrochromic coatings and devices. In particular, this invention relates to electrochromic bilayer coatings that achieve very high broadband optical modulation extending from the visible wavelength region to the infrared wavelength region, wherein the modulation wavelength of the bilayer is voltage-selective. More particularly, this invention also relates to a method for manufacturing an electrochromic device using the aforementioned bilayer electrodes.

[0002] Background of the Invention and Prior Art

[0003] Electrochromism is defined as a reversible change in optical properties caused by the application of a voltage. Electrochromic materials are used in electrochemical devices to adjust their transmittance, reflectance, absorbance, or emissivity. A typical electrochromic device (ECD) is constructed by sandwiching an ion-conducting electrolyte between two transparent conductive oxide-coated glasses (TCO / glass), at least one of which should be laminated with an active layer. The use of a complementary electrochromic coating in the other electrode is optional and can provide greater stability, neutral color reproduction, etc. Figure 1 The diagram schematically illustrates a cross-section of an ECD with cathode and anodic electrochromic coatings in a complementary substrate. The electrolyte membrane should be ion-exchange (ME) film. + Conductivity and electron (e) - The electrode layer acts as a barrier to prevent electrical short circuits between the two electrodes. When a suitable voltage pulse is applied, the electrochromic layer becomes colored or bleached, while the electrode layer acts as an ion storage / color neutralization layer. Coloring efficiency, tunable wavelength range, response time, and write-erase efficiency are some of the performance evaluation criteria for ECDs.

[0004] See patents FR2969323A1 / FR2969323B1, which describe a solid-state infrared active electrochromic device with a double-layer electrode.

[0005] See patent PCT / US2012 / 047935 for reference, which describes how to construct a WO 3-x Nanocrystals and a-NbO x A dynamic (visible light and NIR modulation) ECD was reported from a glass blend.

[0006] See the articles DJ Milliron et al., Nature 2013, 500, 323; DJ Milliron et al., Chem. Commun. 2014, 50, 10555; DJ Milliron et al., Adv. Opt. Mater. 2013, 1, 215, which developed plasmonic electrochromic (EC) nanocrystals of transparent conductive oxides (TCOs) (such as indium-doped tin oxide or aluminum-doped zinc oxide) that exhibit high-contrast NIR modulation and blended them with visible light modulation components.

[0007] See the article H. Gu et al., ACS Nano, 2018, 12, 559, which demonstrates the method of sequentially depositing crown-shaped polyoxometalates (K... 28 Li5H7P8W 48 O 184 ·92H2O) and W 18 O 49 Voltage-selective EC regulation region of electrodes made of nanowires.

[0008] See Z. Wang et al., Adv. Opt. Mater. 2017, 5, 1700194, which discusses how to facilitate tunneling in the second layer (W) by utilizing the inherent structural tunneling of the upper layer (Prussian blue). 18 O 49 This provides a simplified method for triggering the containment and transport of ions regulated by NIR in NIR.

[0009] See patent KR20170101702A, which relates to an electrochromic element with improved electrochromic speed and durability, and a method for manufacturing the same. The electrochromic element sequentially comprises a first substrate, a first electrode layer, an electrochromic layer, an electrolyte layer, an ion storage layer, and a second electrode layer.

[0010] In this invention, an electrochromic device has been developed by combining nanocrystalline and amorphous WO3 electrochromic layers. The invention disclosed herein offers benefits and novelty by circumventing many of the processing and operational drawbacks described in the prior art. Furthermore, the invention describes a process for selecting electrochromic materials such that those materials can be effectively laminated into layers for enhancing the function of the device.

[0011] The novelty of this invention lies in its description of a process for screening / selecting electrochromic materials so that those materials can be effectively stacked into layers for enhancing device functionality. Furthermore, the use of these materials in the manufacture of electrochromic devices is not found in the prior art. Additionally, this stacking sequence for preparing spectrally selective electrodes is not found in the prior art.

[0012] abbreviations used

[0013] a-WO3-amorphous tungsten oxide

[0014] WO3-tungsten oxide

[0015] ECD - Electrochromic Device

[0016] TCO - Transparent Conductive Oxide

[0017] FTO (Fluorine-doped tin oxide)

[0018] LiClO4-Lithium perchlorate

[0019] NIR (Near Infrared)

[0020] PC-propylene carbonate

[0021] PMMA (Polymethyl Methacrylate)

[0022] THF-Tetrahydrofuran

[0023] SPE - Solid Polymer Electrolyte

[0024] XRD-X-ray diffraction

[0025] SEM - Scanning Electron Microscopy

[0026] TEM - Transmission Electron Microscopy

[0027] Purpose of the invention

[0028] The main objective of this invention is to provide an electrochromic bilayer electrode by stacking two different electrochromic layers with different spectral selectivity driven by different voltages.

[0029] Another object of the present invention is to provide an electrochromic overcoating layer that can effectively allow electrolyte ions to penetrate into the underlying layer.

[0030] Another object of the present invention is to provide an electrochromic undercoating layer that, compared with the top layer, simultaneously has an operating voltage and a spectral wavelength shift.

[0031] Another object of the present invention is to provide a dynamic spectral selectivity ECD with highly efficient visible light and infrared modulation. Summary of the Invention

[0032] Therefore, the present invention provides a double-layer electrochromic electrode, the double-layer electrochromic electrode comprising:

[0033] i. A conductive substrate consisting of a substrate

[15] coated with a transparent conductive oxide[TCO]

[13] ;

[0034] ii. An electrochromic layer coated on the conductive substrate

[11] ; and

[0035] iii. An electrochromic layer

[12] deposited on the electrochromic layer

[11] ,

[0036] The thickness of the electrochromic layers [11 and 12] is in the range of 10.0 nm to 3.0 μm.

[0037] In one embodiment of the invention, the substrate is selected from the group consisting of glass, quartz, cellulose, silk, or plastic, and the plastic is selected from the group consisting of polyethylene, polyimide, polyacrylate, and polycarbonate.

[0038] In another embodiment of the invention, the sheet resistance of the conductive substrate is in the range of 1.0 μΩ / sq to 50.0 Ω / sq.

[0039] In another embodiment of the invention, the transparent conductive oxide [TCO] is selected from the group consisting of: indium zinc oxide (IZO), indium tin oxide (ITO), fluorine-doped tin oxide (FTO), fluorine-doped zinc oxide (FZO), aluminum-doped zinc oxide (AZO), and aluminum-doped tin oxide (ATO).

[0040] In another embodiment of the invention, the electrochromic layers [11 and 12] are selected from the group consisting of: organic compounds such as viologens, thiophenes, and flurenes; metal complexes such as bipyridene complexes and terpyridine complexes; conjugated polymers such as polythiophenes, polypyrroles, polyanilines, and polycarbazoles; and metal oxides having pure and substoichiometric phases such as WO3, TiO2, MoO3, NiO, V2O5, ZnO, Ta2O5, Cr2O3, MnO2, Fe2O3, CoO2, RhO2, IrO2, Nb2O5, etc., or combinations / hybrids thereof.

[0041] In another embodiment of the invention, the electrochromic layer

[12] may even have the same chemical composition as the electrochromic layer

[11] , but with different crystallinity, porosity or dopant / additive concentration.

[0042] In another embodiment of the invention, the electrochromic layer

[12] has the same voltage polarity response (cathode, anode or dual) as the electrochromic layer

[11] .

[0043] In yet another embodiment, the present invention provides a double-layer electrochromic device, the double-layer electrochromic device comprising:

[0044] a. Double-layer electrochromic electrode [active electrode];

[0045] b. An electrolyte, i.e. an ion-conducting layer

[10] , placed above the electrochromic layer

[12] of the active electrode;

[0046] c. A counter electrode placed above the exposed side of the electrolyte, the counter electrode comprising a conductive substrate consisting of a transmissive or reflective substrate

[16] coated with a transparent conductive oxide [TCO]

[14] .

[0047] In yet another embodiment of the invention, the counter electrode is optionally coated with a complementary coating comprising different electrochromic layers having opposite voltage polarity responses to the active electrode.

[0048] In another embodiment of the invention, the conductive substrates of the active electrode and the counter electrode are electrically connected to terminals having opposite polarities.

[0049] In yet another embodiment of the invention, the device exhibits a color change when a voltage is applied relative to the counter electrode in the range of ±0.5 to ±10.0V.

[0050] In another embodiment of the invention, if the lower coating and the complementary coating (if used in the counter electrode) have no spectral response within the applied voltage value, the device exhibits the spectral response of the upper coating, and vice versa.

[0051] In yet another embodiment of the invention, the solution / dispersion / polymer membrane comprises H2SO4 or is based on Li. + Na + K + And Al 3+ Salts or mixtures thereof.

[0052] In yet another embodiment of the invention, a superimposed spectral response is shown, resulting from the lower coating, upper coating, and complementary coating (if used in the counter electrode) subjected to a voltage in the range of ±0.5 to ±10.0 V relative to the counter electrode.

[0053] In yet another embodiment, the present invention provides a method for preparing a bilayer electrochromic electrode, the method comprising the following steps:

[0054] a. Dissolve tungsten powder in 50% H2O2 under stirring conditions for 24-36 hours, then filter to obtain a colorless and transparent liquid;

[0055] b. Decompose the excess hydrogen peroxide in the liquid obtained in step (a) by stirring at a temperature within the range of 80-90°C for 4-6 hours to obtain a dark yellow solution;

[0056] c. Dry the solution obtained in step (b) to obtain hydrated tungsten oxide powder;

[0057] d. Disperse the hydrated tungsten oxide powder obtained in step (c) in water, and then sonicate it for 7-10 hours to obtain a solution of hydrated tungsten oxide [WO3.H2O];

[0058] e. Disperse the hydrated tungsten oxide powder obtained in step (c) in a 10% H2O2 aqueous solution, and then sonicate it for 7-10 hours to obtain an a-WO3 solution;

[0059] f. Drop 20-30 μL of the solution obtained in step (d) onto a clean FTO substrate, and then evaporate it at a temperature in the range of 50-80 °C for a time in the range of 15-30 minutes to obtain a polycrystalline layer 1 of WO3.H2O with a thickness in the range of 800 to 1000 nm;

[0060] g. Drop 20-30 μL of the solution obtained in step (e) onto the uniform film obtained in step (i), and then evaporate it at a temperature in the range of 50-80°C for a time in the range of 15-30 minutes to obtain a porous amorphous layer 2 of a-WO3 with a thickness in the range of 600 to 1000 nm.

[0061] In yet another embodiment, the present invention provides a method for manufacturing the electrochromic device, the method comprising the following steps:

[0062] a. Anhydrous LiClO4, plasticizer, and PMMA are dissolved in a solvent selected from the group consisting of: tetrahydrofuran [THF], chloroform, DCM, DMSO, DMF, toluene, ethyl acetate, diethyl ether, acetonitrile, carbon tetrachloride, 2-propanol, hexane, benzene, or acetone, and then stirred at a temperature in the range of 60-80°C for a time in the range of 12-24 hours to obtain a homogeneous mixture;

[0063] b. Evaporate the solvent under a dry nitrogen stream at a temperature in the range of 80-90°C to obtain a solid polymer electrolyte;

[0064] c. Stack polycrystalline WO3·H2O nanosheets and porous α-WO3 layers to obtain an active electrode;

[0065] d. The solid polymer electrolyte with a thickness in the range of 130-250 μm obtained in step (b) is embedded between the active electrode and the reflective electrode to obtain the electrochromic device.

[0066] In another embodiment of the invention, the plasticizer is independently selected from the group consisting of: propylene carbonate; 4-(hydroxymethyl)-1,3-dioxane-2-one; dibutyl carbonate; 1-(3-hydroxypropyl)-2-pyrrolidone; 1-octyl-2-pyrrolidone; 5-dodecyl lactone; 1-hexyl-3-methylimidazolium chloride; 1-methyl-3-octylimidazolium chloride; 2,2-dimethyl-1,3-hexanediol; 2-methyl-1,3-pentanediol; 1-cyclohexyl-2-methyl-1,3-pentanediol; 2,4-diethyl-1,5-pentanediol; 1,3-nonanediol; 2-butyl-1,3-octanediol ; 3-Methylpentane-1,3,5-triol; 2-Ethyl-1,3-hexanediol; benzyl alcohol; 3-Methyl-1,5-pentanediol; 1-phenoxy-2-propanol; 2-(2-butoxyethoxy)ethanol; bis(2-ethylhexyl) phosphate; tributyl phosphate; and tri(2-ethylhexyl) phosphate; straight-chain carbonates; cyclic carbonates; straight-chain primary alcohols; straight-chain and branched aliphatic diols, straight-chain and branched aliphatic triols; benzyl alcohol; straight-chain and cyclic ureas; straight-chain or cyclic carbamates; thiourea; thiocarbamates; straight-chain thio-oxocarbonates; pyrrolidone-2-one; dihydrofuran-2-one; piperidine-2-one or pyran-2-one.

[0067] In another embodiment of the invention, the device can be used in smart windows, smart mirrors, electronic paper, smart displays, helmet visors, smart glasses, optical data storage devices, anti-glare devices, heat and light transmission modulators, and integrated charge storage devices. Attached Figure Description

[0068] Figure 1 The schematic diagram shows a cross-section of an ECD having cathode and anodic electrochromic coatings in a complementary substrate.

[0069] Figure 2 A schematic diagram of the electrochromic device assembly (referred to as device 1) based on polycrystalline WO3·H2O nanosheets of the present invention is shown.

[0070] Figure 3 A schematic diagram of the electrochromic device assembly (referred to as device 2) based on porous a-WO3 of the present invention is shown.

[0071] Figure 4 A schematic diagram of the double-layer electrochromic device assembly (referred to as device 3) of the present invention is shown.

[0072] Figure 5The XRD images of polycrystalline WO3·H2O nanosheets and porous a-WO3 materials on a quartz substrate are shown.

[0073] Figure 6 An AFM image of the polycrystalline WO3·H2O nanosheets of the present invention is shown.

[0074] Figure 7 An AFM image of the porous a-WO3 of the present invention is shown.

[0075] Figure 8 A TEM image of the polycrystalline WO3·H2O nanosheets of the present invention is shown.

[0076] Figure 9 A TEM image of the porous a-WO3 of the present invention is shown.

[0077] Figure 10 A two-layer SEM image of the present invention is shown.

[0078] Figure 11 Cyclic voltammetry diagrams of an electrochromic device made using polycrystalline WO3·H2O nanosheets are shown.

[0079] Figure 12 The transmittance diagram of an electrochromic device made using polycrystalline WO3·H2O nanosheets is shown.

[0080] Figure 13 Cyclic voltammetry of an electrochromic device made using a porous a-WO3 layer is shown.

[0081] Figure 14 The transmittance diagram of an electrochromic device made using a porous a-WO3 layer is shown.

[0082] Figure 15 Cyclic voltammetry diagrams of an electrochromic bilayer device made using polycrystalline WO3·H2O nanosheets and a porous α-WO3 layer are shown.

[0083] Figure 16 Transmittance diagrams of an electrochromic bilayer device made using polycrystalline WO3·H2O nanosheets and a porous a-WO3 layer are shown. Detailed Implementation

[0084] This invention presents a novel scheme for fabricating broadband ECDs with independent dual-band selectivity for visible light and NIR radiation.

[0085] This disclosure relates to the processing of high-quality, high-spectral-range, and spectrally selective electrochromic electrodes and devices. This objective is achieved by stacking two similar / different electrochromic materials with specific morphologies.

[0086] The substrate for the electrochromic electrode material is selected from the group consisting of: glass, cellulose, silk, or plastic (e.g., polyethylene, polyimide, polyacrylate, polycarbonate, etc.). To prepare the reflective electrode, the substrate is additionally coated with a material selected from the group consisting of: a metallic coating composed of chromium, silver, gold, tantalum, titanium, etc., applied to one or both sides.

[0087] The transmission (or reflection) electrode is coated with a conductive coating selected from the group consisting of: indium zinc oxide (IZO), indium tin oxide (ITO), fluorine-doped tin oxide (FTO), fluorine-doped zinc oxide (FZO), aluminum-doped zinc oxide (AZO) and aluminum-doped tin oxide (ATO), conductive metal coatings or mixtures / hybrids thereof.

[0088] The sheet resistance of the conductive coating is in the range of 1.0 μΩ / sq to 50.0 Ω / sq.

[0089] Liquid electrolytes are used to prepare electrolyte baths for testing electrodes. The electrolyte is made from a solution / dispersion containing salts selected from the group consisting of: H2SO4, LiCIO4, ZnCl2, LiBf4, LiAsF6, LiI, LiBr, LiCF3SO3, LiTFSI, KYF4, KNO3, KBrO3, KI, KBF4, KOH, KSCN, K2Cr2O7, KCl, KCH3CO2, NH4SCN, NH4CH3CO2, NH4Br, NH4Cl, NaSCN, NaPF6, NaYF4, or mixtures / hybrids / combinations thereof.

[0090] The conductive coating of the electrode is further coated with an electrochromic material to fabricate the active electrode, wherein the material is selected from the group consisting of:

[0091] (i) Select transition metal oxides from the group consisting of the following: WO3, TiO2, MoO3, NiO, V2O5, Fe2O3, Ta2O5, Cr2O3, MnO2, FeO2, CoO2, RhO2, IrO2, Nb2O5, etc.

[0092] (ii) Other metal oxides selected from the group consisting of the following: SnO2, Bi2O3 and Pb3O4;

[0093] (iii) Select organic molecules from the following groups: violet alkaloids, thiophenes, fluorenes, etc.;

[0094] (iv) Select metal complexes from the group consisting of the following: bipyridine complexes, terpyridine complexes, etc.;

[0095] (v) Select conjugated polymers from the group consisting of the following: polythiophenes, polypyrroles, polyanilines, polycarbazoles, etc.;

[0096] (vi) Their combinations and hybrids.

[0097] The thickness of the electrochromic coating ranges from 10.0 nm to 3.0 μm.

[0098] When immersed in an electrolyte solution and a suitable voltage is applied (e.g., 0.1–3.0 V relative to an Ag / AgCl reference electrode), the electrochromic coating exhibits a color change.

[0099] The electrochromic coating on the electrode is further coated with a second electrochromic layer. The material of the second electrochromic layer has a different electrochromic response than the first layer, but responds to the same voltage polarity. The material of the second electrochromic layer is selected from the group described in the previous embodiments, but has sufficient discontinuity to allow the first electrochromic layer to approach electrolyte ions. The chemical composition of the second electrochromic layer can be selected to be similar to that of the first electrochromic layer, but different in terms of electrochromic response. This can be achieved by changing the phase state, crystallinity, morphology, and dopant concentration, etc.

[0100] The thickness of the second electrochromic coating is in the range of 10.0 nm to 3.0 μm.

[0101] When immersed in an electrolyte solution and a suitable voltage (e.g., 0.1–3.0 V relative to an Ag / AgCl reference electrode) is applied, the second electrochromic coating exhibits a color change.

[0102] The conductive electrodes are optionally coated with a material selected from the group described in the previous embodiments, but in response to a voltage polarity opposite to that of the active electrode. These electrodes, with or without the aforementioned complementary coating, serve as counter electrodes in the device configuration.

[0103] Electrochromic devices are manufactured using liquid / gel / solid electrolytes. The electrolyte is made from a solution / dispersion / polymer membrane containing salts selected from the group consisting of: LiCIO4, ZnCl2, LiBf4, LiAsF6, LiI, LiBr, LiCF3SO3, LiTFSI, KYF4, KNO3, KBrO3, KI, KBF4, KOH, KSCN, K2Cr2O7, KCl, KCH3CO2, NH4SCN, NH4CH3CO2, NH4Br, NH4Cl, NaSCN, NaPF6, NaYF4, or mixtures / hybrids / combinations thereof.

[0104] The electrochromic device is manufactured by sandwiching an electrolyte layer (as described in a previous embodiment) between an active electrode and a counter electrode. The electrolyte forms a continuous, uniform interface on one side that is electrically connected to a second electrochromic layer, and forms a conductive plane (with an optional complementary coating) for the counter electrode on the other side. This device arrangement can be accomplished using spacers that prevent electrical short circuits between the active and counter electrodes. The device can be completely sealed with a sealant to protect it from weathering.

[0105] The active electrode and the counter electrode are electrically connected to opposite terminals of the voltage source.

[0106] The device exhibits a color change when a suitable voltage is applied (e.g., 0.5-10.0V relative to the counter electrode).

[0107] The device displays a superimposed spectral response caused by the first and second (and, when in use, a complementary coating in the counter electrode) electrochromic coatings. If the second electrochromic (and complementary) coating has no spectral response within the applied voltage value, the device displays a spectral response similar to that of the first electrochromic coating. If the first electrochromic (and complementary) coating has no spectral response within the applied voltage value, the device displays a spectral response similar to that of the second electrochromic coating.

[0108] When suitable materials with electrochromic responses in different spectral ranges with different bias requirements are selected, the electrochromic device exhibits spectral band selectivity.

[0109] Electrochromic electrodes are manufactured by directly coating an upper or lower coating onto a conductive substrate. For example, electrodes with only an upper coating or only a lower coating exhibit a color change when immersed in an electrolyte solution and a suitable voltage (e.g., ±0.1 to ±3.0 V relative to an Ag / AgCl reference electrode). The color change of the electrode with only an upper coating differs from that of the electrode with only a lower coating at the same applied voltage value. The polarity of the applied voltage depends on the voltage polarity response of the material used for the lower or upper coating, for example, (–)ve for the cathode, (+)ve for the anode, and either for dual electrochromic materials.

[0110] The electrolyte in which the electrodes are immersed for color switching contains H2SO4 or is Li-based + Na + K + And Al 3+ Salts or mixtures thereof.

[0111] When immersed in an electrolyte solution and subjected to ±0.1 to ±3.0 V, the electrode exhibits a superimposed spectral response caused by both the lower and upper coatings.

[0112] If the upper coating does not have a spectral response within the applied voltage value, the electrode exhibits the spectral response of the lower coating, and vice versa.

[0113] The electrolyte contains H2SO4 or is based on Li + Na + K + And Al 3+ Solutions / dispersions / polymer films of salts or mixtures thereof.

[0114] If the lower coating and complementary coating (if used in the counter electrode) have no spectral response within the applied voltage value, the electrochromic device displays the spectral response of the upper coating, and vice versa.

[0115] The electrochromic device displays a superimposed spectral response caused by the lower coating, upper coating, and complementary coating (if used in the counter electrode) subjected to a voltage in the range of ±0.5 to ±10.0 V relative to the counter electrode.

[0116] (e.g., etc.) are used for transmission electrodes, and a metal (chromium, silver, gold, tantalum, titanium, etc.) coating is applied to one or both sides for reflection electrodes.

[0117] Figure 2 and 3 Cross-sectional structural diagrams of electrochromic devices 1 and 2 are shown respectively, while Figure 4 A cross-sectional structural view of the electrochromic device 3 of the present invention is shown. The electrochromic device 3 includes an ion conductor layer 10. An electrode layer 12 is in contact with the ion conductor layer 10, and an electrode layer 11 is in contact with the electrode layer 12. Layers 11 and 12 contain an electrochromic material. Layers 10, 11, and 12 are located between conductive layers 13 and 14 disposed adjacent to outer substrates 15 and 16. Layers 10, 11, 12, 13, and 14 are collectively referred to as an electrochromic laminate 17.

[0118] Conductive layer 13 is electrically contacted with one terminal of the power supply, and conductive layer 14 is electrically contacted with the other terminal of the power supply, thereby allowing the transmittance of the electrochromic device 3 to be changed by applying voltage pulses to conductive layers 13 and 14. The pulses cause electrons and ions to move between electrode layers 11 and 12 and ion-conducting layer 10. As a result, the electrochromic materials in the first and second electrode layers change their optical states, thereby causing the electrochromic device 3 to switch from a bleached state to a colored state or vice versa.

[0119] It should be understood that the term "bleaching" refers to an optically neutral state, such as uncolored, transparent, or translucent. Furthermore, unless otherwise specified herein, the "color" of electrochromic conversion is not limited to any particular wavelength or wavelength range. Those skilled in the art will understand that appropriate electrochromism and the selection of electrode materials control the associated optical conversion. Typically, the transmittance change preferably comprises a change in the transmittance of electromagnetic radiation with wavelengths in the infrared to ultraviolet radiation range. For example, in one embodiment of the invention, the transmittance change is primarily a change in the transmittance of electromagnetic radiation within the infrared spectrum. In another embodiment of the invention, the transmittance change is directed towards electromagnetic radiation with wavelengths in the visible spectrum. In yet another embodiment, the transmittance change is directed towards electromagnetic radiation with wavelengths in both the infrared and visible light regions.

[0120] The electrochromic device reversibly cycles between a bleached state and a colored state. In the bleached state, a potential is applied to the electrochromic laminate 17 such that the available ions in the laminate that can put the electrochromic materials 11 and 12 into a colored state are mainly present in the counter electrode. When the potential on the electrochromic laminate reverses, ion transport crosses the ion-conducting layer 10 and passes through the electrochromic layer 12 to reach the electrochromic material 11, thus putting the material into a colored state.

[0121] All materials constituting the electrochromic laminate 17 are inorganic, solid (i.e., solid-state), or both inorganic and solid. Because organic materials tend to degrade over time, inorganic materials offer the advantage of a reliable electrochromic laminate that can function for a long period. Solid-state materials also offer the advantage of not having the containment and leakage problems typically present with liquid materials. Each layer in the electrochromic device is discussed in detail below. It should be understood that any one or more layers in the laminate may contain a certain amount of organic material, but in many embodiments, one or more layers contain little or no organic matter. The same applies to liquids that may be present in small amounts in one or more layers. It should also be understood that solid materials can be deposited or otherwise formed using processes employing liquid components, such as sol-gel or chemical vapor deposition.

[0122] Any material with suitable optical, electrical, thermal, and mechanical properties can be used as substrates 15 and 16. Such substrates include, for example, glass, plastic, and mirror materials. Suitable plastic substrates include, for example, acrylic resins, polystyrene, polycarbonate, allyl diethylene glycol carbonate, SAN (styrene-acetonitrile copolymer), poly(4-methyl-1-pentene), polyester, polyamide, etc. If a plastic substrate is used, it is preferred to treat it with a hard coating for barrier and abrasion protection, such as a diamond-like protective coating, a silica / silicone abrasion-resistant coating, etc., which is well known in the field of plastic glazing. Suitable glass includes clear or colored soda-lime glass, including soda-lime float glass. The glass may be tempered or untempered.

[0123] Above substrates 15 and 16 are conductive layers 13 and 14. In this invention, conductive layers 13 and 14 are both inorganic and solid. Conductive layers 13 and 14 can be made of a variety of different materials, including conductive oxides, thin metal coatings, conductive metal nitrides, etc. Typically, conductive layers 13 and 14 are transparent at least in the wavelength range in which the electrochromic layer exhibits electrochromism. Transparent conductive oxides include metal oxides and metal oxides doped with one or more metals. Examples of such metal oxides and doped metal oxides include indium oxide, indium tin oxide, doped indium oxide, tin oxide, doped tin oxide, zinc oxide, zinc aluminum oxide, doped zinc oxide, ruthenium oxide, doped ruthenium oxide, etc. Because oxides are commonly used for these layers, they are sometimes referred to as "transparent conductive oxide" (TCO) layers. A substantially transparent thin metal coating can also be used. Examples of metals used for such thin metal coatings include transition metals, including gold, platinum, silver, aluminum, nickel alloys, etc. Silver-based thin metal coatings, well-known in the glazing industry, are also used. Examples of conductive nitrides include titanium nitride, tantalum nitride, titanium oxynitride, and tantalum oxynitride. Conductive layers 13 and 14 can also be composite conductors. Such composite conductors can be fabricated by placing a pattern of highly conductive ceramic and metal wires or conductive layers on one side of a substrate, followed by over-coating with a transparent conductive material such as doped tin oxide or indium tin oxide. Ideally, such wires should be fine enough to be invisible to the naked eye (e.g., less than about 100 μm).

[0124] An electrochromic layer is deposited over the conductive layer 13. In this invention, two electrochromic layers 11 and 12 are deposited sequentially. Typically, the electrochromic layer can be inorganic, organic, hybrid, or solid, or in a general embodiment, it is inorganic / organic / hybrid and solid. The electrochromic layer can contain any one or more of a variety of different electrochromic materials, including metal oxides. Such metal oxides include tungsten oxide (WO3), molybdenum oxide (MoO3), niobium oxide (Nb2O5), titanium oxide (TiO2), copper oxide (CuO), iridium oxide (Ir2O3), chromium oxide (Cr2O3), manganese oxide (Mn2O3), vanadium oxide (V2O5), nickel oxide (Ni2O3), cobalt oxide (Co2O3), etc. Among these metal oxides, tungsten oxide (WO3) has been the most widely studied material. The metal oxide can also be doped with one or more dopants, such as lithium, sodium, potassium, molybdenum, vanadium, titanium, and / or other suitable metals or metal-containing compounds. Mixed oxides (e.g., W-Mo oxides, W-V oxides) can also be used as electrochromic layers. For organic materials, violet alkaloids have been commercialized on a small scale. Violet alkaloids are those with the general formula (C5H4NR)2 n+ Organic compounds. A wide variety of conductive polymers have also attracted attention, including polypyrrole, PEDOT, polyaniline, etc. In this invention, different morphologies of WO3 with different crystallinities are used for electrochromic layers 11 and 12.

[0125] The following describes a method for manufacturing the EC device.

[0126] First, the glass substrate 15 coated with transparent conductive oxide 13 is thoroughly cleaned to prepare it for subsequent processing. The cleaning method employed is ultrasonic conditioning of the substrate to remove unwanted particles. Then, electrochromic layers 11 and 12 are deposited on the conductive layer 13. Typically, these layers can be deposited using various techniques, including, for example, physical vapor deposition, chemical vapor deposition, plasma-enhanced chemical vapor deposition, and atomic layer deposition. As used herein, the term physical vapor deposition encompasses the full range of PVD techniques, including sputtering, evaporation, ablation, etc. Subsequently, a self-standing ion-conducting layer 10 is placed on top of the electrochromic layer, followed by another glass substrate 16 coated with transparent conductive oxide 14.

[0127] An electrochromic device 1 was fabricated by depositing an electrochromic layer 11 composed of polycrystalline WO3·H2O nanosheets on a conductive layer 13. In another embodiment of the invention, an electrochromic device 2 was fabricated by depositing an electrochromic layer 12 composed of porous α-WO3 on a conductive layer 13. Optical tuning of both device structures in the range of 300-1600 nm was recorded.

[0128] A double-layer electrochromic device 3 has been fabricated, wherein electrochromic layers 11 and 12 are sequentially deposited on a conductive layer 13. The inventors have observed excellent optical tuning and band selectivity of the double-layer electrochromic device, which establishes dynamic band selectivity as the voltage changes.

[0129] Example

[0130] The following embodiments are given by way of example and should not be construed as limiting the scope of the invention.

[0131] Example 1

[0132] Preparation of active electrodes including polycrystalline WO3·H2O nanosheets

[0133] An electrochromic layer comprising polycrystalline WO3·H2O nanosheets was prepared as follows. WO3·H2O powder was synthesized by an overnight reaction of W powder with H2O2. Initially, 5 g of W powder was dissolved in 60 ml of 50% H2O2 with continuous stirring in an ice bath for 24 hours. The solution was then filtered to obtain a colorless, transparent liquid. Excess hydrogen peroxide was decomposed by stirring the solution at 80°C for 4 hours, which turned the solution a deep yellow color; the solution was then capped and allowed to stand for one week. The solution was subsequently dried to produce yellow hydrogen hydrated tungsten oxide (WO3·H2O) powder. In a second step, 0.5 g of WO3·H2O powder was dispersed in 10 ml of distilled water by sonication for 7 hours.

[0134] The active electrode was prepared by drop-coating 20 μL of electrochromic solution onto a clean FTO substrate (1 cm × 1 cm), followed by evaporation at 50 °C for 15 min to form a uniform film. The thickness of the electrochromic layer was 800 nm.

[0135] Example 2

[0136] Preparation of active electrodes including porous a-WO3 layers

[0137] An electrochromic layer comprising a porous α-WO3 layer was prepared as follows. WO3·H2O powder was synthesized by an overnight reaction of W powder with H2O2. Initially, 5 g of W powder was dissolved in 60 mL of 50% H2O2 with continuous stirring in an ice bath for 24 hours. The solution was then filtered to obtain a colorless, transparent liquid. Excess hydrogen peroxide was decomposed by stirring the solution at 80°C for 4 hours, which turned the solution a deep yellow color; the solution was then covered and allowed to stand for one week. Subsequently, the solution was dried to produce yellow hydrogen hydrated tungsten oxide (WO3·H2O) powder. In a second step, 0.5 g of WO3·H2O powder was dissolved in 10 mL of 10% H2O2 by sonication for 7 hours.

[0138] The active electrode was prepared by drop-coating 20 μL of electrochromic solution onto a clean FTO substrate (1 cm × 1 cm), followed by evaporation at 50 °C for 15 min to form a uniform film. The thickness of the electrochromic layer was 600 nm.

[0139] Example 3

[0140] Preparation of an electrochromic bilayer including polycrystalline WO3·H2O nanosheets and porous α-WO3 layers

[0141] The active electrode was prepared by drop-coating 20 μL of the first solution mentioned in Example 1 onto a clean FTO substrate (1 cm × 1 cm), followed by evaporation at 50 °C for 15 minutes to form a uniform film. Then, 20 μL of the second solution mentioned in Example 2 was drop-coated on top of the first layer, and again evaporated at 50 °C for 15 minutes to form a uniform film. For this configuration, the measured thickness of the first layer was 880 nm, and the measured thickness of the second layer was 750 nm.

[0142] Example 4

[0143] Preparation of solid polymer electrolytes

[0144] LiClO4 was dried overnight in a vacuum oven at 110 °C. Measured amounts of salt, PC (plasticizer), and PMMA (main component, dried at 90 °C for 12 hours) were dissolved in THF and stirred at room temperature for 24 hours. The mixture was then poured into clean petri dishes and covered with perforated aluminum foil. The solvent was allowed to evaporate slowly at room temperature under a stream of dry nitrogen. After 24 hours, a self-standing electrolyte membrane (130-250 μm thick) could be peeled off from the petri dish.

[0145] Example 5

[0146] Preparation of electrochromic devices

[0147] An electrochromic device using polycrystalline WO3·H2O nanosheets is manufactured as follows: A solid polymer electrolyte is sandwiched between an active electrode prepared as described in Example 1 and a second FTO glass. Figure 9 and 10 The electrochromic properties of a device made using polycrystalline WO3·H2O nanosheets are shown.

[0148] An electrochromic device using a porous a-WO3 layer is manufactured as follows: A solid polymer electrolyte is sandwiched between an active electrode prepared as described in Example 2 and a second FTO glass. Figure 11 and 12 The electrochromic properties of a device made using a porous a-WO3 layer are shown.

[0149] An electrochromic bilayer device using polycrystalline WO3·H2O nanosheets and a porous α-WO3 layer is fabricated as follows: A solid polymer electrolyte is sandwiched between an active electrode prepared as described in Example 3 and a second FTO glass. Figure 13 and 14 The electrochromic properties of a bilayer device made using polycrystalline WO3·H2O nanosheets and a porous a-WO3 layer are shown.

[0150] Example 6

[0151] Electrochromic activity of the testing device

[0152] ECDs using polycrystalline WO3·H2O nanosheets were fabricated as detailed in Example 5, and their tuning in the 300-1600 nm range was recorded. The fabricated devices turned deep blue when -2.8 V was applied and returned to their bleached state under the same order of magnitude of reverse voltage. These devices exhibited good visible light contrast (49% at 650 nm) and excellent NIR (800-1600 nm) blocking (66% at 1500 nm). The average coloring efficiency of the devices was 39.4 cm⁻¹ at 650 nm. 2 C -1 And at 1500nm, it is 103.2cm. 2 C -1 .

[0153] ECDs using porous a-WO3 layers were fabricated as detailed in Example 5, and their tuning in the 300-1600 nm range was recorded. The fabricated devices turned deep blue when -2.5 V was applied and returned to their bleached state under the same order of magnitude of reverse voltage. These devices exhibited excellent visible light contrast (68% at 650 nm) and moderate NIR blocking (40% at 1500 nm). The average colorimetric efficiency of the devices was 119.3 cm⁻¹ at 650 nm. 2 C -1 And at 1500nm, it is 60.8cm. 2 C -1 .

[0154] An electrochromic bilayer device using polycrystalline WO3·H2O nanosheets and a porous α-WO3 layer was fabricated as described in Example 5 below. The electrochromic material used in this invention is a cathode coloring material, and the active electrode is connected to the negative terminal of a sourcemeter. The inventors achieved a contrast ratio of 79-91% in the NIR (780-1600 nm) range. With a maximum applied potential of -2.2V, the device remained dormant in the visible light range, exhibiting up to ~71% NIR modulation, and beyond this point, the device began to show activity in the visible light range. The highest NIR blocking (91%) was achieved at -2.3V, although this resulted in a ~9% transmission compromise at 600 nm. The device operation from 0V to 2.3V was defined as cold mode. The visible light transmittance of the device (300-780 nm) continued to decrease at more negative voltages above -2.3V. At -2.6V, the device exhibits 52-79% visible light modulation between bleached and colored states in the (530-780nm) range, a phenomenon known as dark mode. The entire device operates completely reversibly with the same order of magnitude of reverse voltage.

[0155] Advantages of the invention

[0156] • The ECD, manufactured using a specified double-layer structure (in which a porous a-WO3 layer is stacked on a polycrystalline WO3·H2O nanosheet layer), achieves excellent visible light modulation in the visible light range and outstanding contrast in the NIR range, setting a new global benchmark for electrochromic energy saving.

[0157] • The ECD’s modulation band can be dynamically selected by selectively adjusting the coloring voltage and can operate in four main modes, such as fully transparent (0V), transparent +71% NIR modulation (-2.2V), 9% visible light +91% NIR modulation (-2.3V), and fully opaque (-2.8V).

[0158] This inexpensive and exceptionally high-performance dynamic ECD manufacturing solution represents a significant step forward for the next generation of multifunctional dynamic glass.

[0159] The invented method will create dynamic windows that will provide highly efficient energy savings in the construction and automotive industries.

[0160] The developed method is economical and commercially viable. Therefore, by employing the method of this invention, electrochromic devices for intelligent energy utilization and conservation can be prepared.

Claims

1. A double layer electrochromic electrode comprising: i. a conductive substrate consisting of a substrate (15) coated with a transparent conductive oxide (13); ii. a first electrochromic layer (11) coated on the conductive substrate; and iii. a second electrochromic layer (12) deposited on the first electrochromic layer (11), wherein the thickness of the second electrochromic layer (12) is in the range of 10.0 nm to 3.0 pm, wherein the transparent conductive oxide is selected from the group consisting of indium zinc oxide, fluorine-doped tin oxide, fluorine-doped zinc oxide, aluminum-doped zinc oxide, and aluminum-doped tin oxide, and the second electrochromic layer (12) is a porous amorphous tungsten oxide layer, and the first electrochromic layer (11) is a polycrystalline nanosheet layer of hydrous tungsten oxide with a thickness in the range of 800 to 1000 nm.

2. The double layer electrochromic electrode according to claim 1, wherein the substrate is selected from the group consisting of glass, quartz, cellulose, silk, and plastic selected from the group consisting of polyethylene, polyimide, polyacrylate, and polycarbonate.

3. The double layer electrochromic electrode according to claim 1, wherein the sheet resistance of the conductive substrate is in the range of 1.0 pW / sq to 50.0 pW / sq.

4. The double layer electrochromic electrode according to claim 2, wherein the sheet resistance of the conductive substrate is in the range of 1.0 pW / sq to 50.0 pW / sq.

5. An electrochromic device comprising: a. an active electrode which is a double layer electrochromic electrode according to claim 1; b. an electrolyte, i.e. an ion conducting layer (10), placed over the second electrochromic layer (12) of the active electrode; c. a counter electrode placed over the exposed side of the electrolyte, the counter electrode comprising a conductive substrate consisting of a transmissive or reflective substrate (16) coated with a transparent conductive oxide (14).

6. The electrochromic device according to claim 5, wherein the counter electrode is coated with a complementary coating comprising a different electrochromic layer having a voltage polarity response opposite to that of the active electrode.

7. The electrochromic device according to claim 5, wherein the device displays a color change upon application of a voltage in the range of ±0.5 to ±10.0 V with respect to the counter electrode.

8. The electrochromic device of claim 5, wherein the electrolyte comprises a solution / dispersion / polymer film comprising H2SO4 or salts based on Li + , Na + , K + , and Al 3+ or mixtures thereof.

9. The electrochromic device according to claim 5, wherein the device displays a superimposed spectral response arising from the first electrochromic layer (11), the second electrochromic layer (12), and the complementary coating if used in the counter electrode, subjected to a voltage in the range of ±0.5 to ±10.0 V with respect to the counter electrode.

10. The electrochromic device according to claim 5, wherein the device is used for smart windows, smart mirrors, e-paper, smart displays, helmet visors, smart glasses, optical data storage devices, anti-glare devices, heat and light transmission regulators, and integrated charge storage devices.

11. A process for the preparation of the bi-layer electrochromic electrode according to claim 1, said process comprising the following steps: (a) dissolving tungsten powder in 50% H2O2 while stirring for a period of 24 - 36 hours, followed by filtration to obtain a colorless transparent liquid; (b) decomposing excess hydrogen peroxide in the liquid obtained in step (a) by stirring for a period of 4 - 6 hours at a temperature in the range of 80 - 90 o C to obtain a dark yellow solution; (c) drying the solution obtained in step (b) to obtain tungsten oxide hydrate powder; (d) dispersing the tungsten oxide hydrate powder obtained in step (c) in water followed by sonication for a period of 7-10 hours to obtain a solution of tungsten oxide hydrate; (e) dispersing the tungsten oxide hydrate powder obtained in step (c) in 10% aqueous H2O2 solution followed by sonication for a period of 7 - 10 hours to obtain a solution of amorphous tungsten oxide; (f) 20 - 30 μL of the solution obtained in step (d) is drop cast on a clean fluorine-doped tin oxide substrate and then evaporated at a temperature in the range of 50 - 80 o C for a period of 15 - 30 minutes to obtain a polycrystalline layer 1 of hydrated tungsten oxide having a thickness in the range of 800 to 1000 nm; (g) drop coating 20 - 30 μL of the solution obtained in step (e) on the layer obtained in step (f) and then evaporating at a temperature in the range of 50 - 80 °C for a period of 15 - 30 minutes to obtain a porous amorphous layer 2 of amorphous tungsten oxide having a thickness in the range of 600 to 1000 nm; and o C for a period of 15 - 30 minutes to obtain a porous amorphous layer 2 of amorphous tungsten oxide having a thickness in the range of 600 to 1000 nm; and (h) layering the polycrystalline layer 1 of tungsten oxide hydrate obtained in step (f) and the porous amorphous tungsten oxide layer obtained in step (g) to obtain the electrode.

12. A process for the manufacture of the electrochromic device according to claim 5, said process comprising the following steps: (a) dissolving anhydrous LiC104, plasticizer and PMMA in a solvent selected from the group consisting of tetrahydrofuran, chloroform, DCM, DMSO, DMF, toluene, ethyl acetate, diethyl ether, acetonitrile, carbon tetrachloride, 2-propanol, hexane, benzene and acetone, followed by stirring for a period of 12 - 24 hours at a temperature in the range of 60 - 80 o C to obtain a homogeneous mixture; (b) evaporating the solvent at a temperature in the range of 80 - 90 o C under a stream of dry nitrogen to obtain a solid polymer electrolyte; (c) layering the polycrystalline tungsten oxide hydrate nanoplatelets and the porous amorphous tungsten oxide layer to obtain an active electrode; (d) embedding the solid polymer electrolyte obtained in step (b) having a thickness in the range of 130 - 250 μιη between the active electrode and the counter electrode to obtain the electrochromic device.

13. The process according to claim 12, wherein the plasticizer is independently selected from the group consisting of propylene carbonate, 4-(hydroxymethyl)-1,3-dioxolan-2-one, dibutyl carbonate, 1-(3-hydroxypropyl) 2-pyrrolidinone, 1-octyl-2-pyrrolidinone; 5-dodecalactone, 1-hexyl-3-methylimidazolium chloride, 1-methyl-3-octylimidazolium chloride, 2,2-dimethyl-1,3-hexanediol; 2-methyl-1,3-pentanediol; 1-cyclohexyl-2-methyl-1,3-pentanediol; 2,4-diethyl-1,5-pentanediol; 1,3-nonanediol; 2-butyl-1,3-octanediol; 3-methylpentane-1,3,5-triol; 2-ethyl-1,3-hexanediol; benzyl alcohol; 3-methyl-1,5-pentanediol; 1-phenoxy-2-propanol; 2-(2-butoxyethoxy)ethanol; bis(2-ethylhexyl) phosphate; tributyl phosphate; tris(2-ethylhexyl) phosphate; linear carbonates; cyclic carbonates; linear primary alcohols; linear and branched aliphatic diols, linear and branched aliphatic triols; benzyl alcohol; linear and cyclic ureas; linear or cyclic carbamates; thiourea; thiocarbamates; linear thio-oxo carbonates; pyrrolidinone-2-one; dihydrofuran-2-one; piperidin-2-one and pyran-2-one.

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