KR102038184B1 - An Electrochromic Device - Google Patents

Abstract

The present application relates to an electrochromic device and a method of manufacturing the electrochromic device. The present application can improve the discoloration speed and durability compared to the prior art, it is possible to provide an electrochromic device with excellent productivity.

Description

Electrochromic Device

The present application relates to an electrochromic device. In particular, the present application relates to an electrochromic device having improved color change efficiency and switching time.

Electrochromism refers to a phenomenon in which optical properties such as color or light transmittance of an electrochromic active material change depending on an electrochemical oxidation and reduction reaction. Electrochromic devices using such a phenomenon can be manufactured in a large area of the device at a low cost, and has a low power consumption, attracting attention in various fields such as smart windows, smart mirrors, electronic paper.

1 is a cross-sectional view of a general electrochromic device. As shown in the drawing, the electrochromic device 100 includes a first electrode layer 110, an electrochromic layer 120 provided on the first electrode layer 110, an electrolyte layer 130 provided on the electrochromic layer, and the It may include an ion storage layer 140 provided on the electrolyte layer, and a second electrode layer 150 provided on the ion storage layer. Although not shown, a substrate formed from transparent glass or polymer resin may be further included on the outer surfaces of the electrodes 110 and 150.

In general, the electrochromic layer and / or the ion storage layer may include an inorganic material such as tungsten oxide (WO _x ) or lithium nickel oxide (LiNiO) as the electrochromic material. Specifically, when a specific potential is applied to the electrode, electrolyte ions such as H ⁺ , or Li ⁺ , Na ⁺ move through the electrolyte layer between the electrochromic layer and the ion storage layer, and at the same time electrons are transferred through the external circuit. Injecting into or leaving the electrochromic layer, the oxidation / reduction reaction of the electrochromic material is alternated and colored or bleached of the electrochromic layer or ion storage layer. As described above, since the change in the optical properties of the electrochromic device is premised on the movement of the ionic material, the color change takes a predetermined time, that is, a switching time, and thus a technique for reducing the color change time is required.

One object of the present application is to provide an electrochromic device having excellent discoloration efficiency and improved discoloration speed.

Another object of the present application is to provide an electrochromic device having a sufficient discoloration effect even in a thin film.

The above and other objects of the present application can be solved by the present application described below.

The present application relates to an electrochromic device. The electrochromic device may include two opposing electrodes, an electrochromic layer, an electrolyte layer, and an ion storage layer.

The electrode may refer to a configuration capable of supplying charge to the electrochromic layer. In one example, the electrode may include any one or more of a transparent conductive oxide, a conductive polymer, Ag nanowire, or a metal mesh. More specifically, ITO (Indium Tin Oxide), FTO (Fluor doped Tin Oxide), AZO (Aluminium doped Zinc Oxide), GZO (Galium doped Zinc Oxide), ATO (Antimony doped Tin Oxide), IZO (Indium doped Zinc Oxide) , NTO (Niobium doped Titanium Oxide), ZnO, OMO (Oxide / Metal / Oxide) or CTO (Cadmium Tin Oxide) may be used, but is not limited thereto. In another example, the electrode layer may have a structure in which two or more electrode materials are stacked in a plurality of layers.

The method for forming the electrode layer is not particularly limited, and known methods can be used without limitation. For example, an electrode layer may be provided by forming an electrode material including transparent conductive oxide particles in a thin film form on a transparent glass substrate through a sputtering process. The electrode layer may have a thickness of 150 nm or more, 200 nm or more, or 300 nm or more within the range of 1 nm to 1 μm. The upper limit of the electrode layer thickness is not particularly limited, but for the purpose of low resistance, the electrode layer may have a thickness of 800 nm or less, 700 nm or less, or 500 nm or less.

The electrochromic layer may include an electrochromic material that changes color according to an electric signal. Examples of the electrochromic material that can be used include conductive polymers, organic color change materials, and / or inorganic color change materials. The conductive polymer may be polypyrrole, polyaniline (Polyaniline), polypyridine, polyindole, polycarbazole and the like, and may be used as an organic discoloration material such as viologen, anthraquinone, phenocyazine, It is not limited.

In one example, the electrochromic layer may include one or more oxides of oxides of Ti, Nb, Mo, Ta, W, V, Cr, Mn, Fe, Co, Ni, Rh, and Ir as an inorganic color change material. have. Specifically, TiO _{2 ,} Nb ₂ O ₅ , MoO ₃ , Ta ₂ O ₅ , WO ₃ , V ₂ O _{5 ,} CrO _{3 ,} Li _x CoO _{2 ,} NiO, LiNiO _x , Rh ₂ O _3, IrO _{2 ,} or the like It may be an inorganic discoloration material that can be used, but is not limited thereto.

More specifically, the electrochromic layer may include tungsten oxide (WO _x ) as a color change material. Tungsten oxide (WO _x ), for example, may be colored or decolorized through the reaction as follows. In the scheme below, M may be an electrolyte ion such as H ⁺ , Li ⁺ , or Na ⁺ .

[Scheme]

WO ₃ (discoloration: ^{colorless) + xe - + xM + ⇔} M x WO 3 ( colors: blue)

In the above reaction, when the electrochromic layer is decolorized, the electrochromic device transmits incident light, and when colored, the light characteristic of the electrochromic device may be changed while the amount of incident light is reduced. The coloring and decolorizing reactions may occur alternately depending on the polarity of the applied voltage, or the direction of current flow.

In one example, the electrochromic layer may have a transmittance of 20% to 60% of visible light when coloring the electrochromic material and a transmittance of visible light of 65% to 85% when decoloring. In the present application, the visible light may mean light having a wavelength in the range of about 350 nm to 780 nm, and more specifically, may mean light having a wavelength of 550 nm.

In another example, the electrochromic layer can have a thickness in the range of 50 nm to 400 nm. When the thickness is less than 50 nm, it is difficult to sufficiently cause a reaction for discoloration, and when it exceeds 400 nm, an electrochromic device of a thin film cannot be provided.

The ion storage layer may refer to a layer in which charge particles necessary for redox reaction of the electrochromic layer may be inserted or desorbed, and thus may be involved in the discoloration reaction. In the prior art, in consideration of the role of the ion storage layer, a complementary electrochromic material was used for each of the electrochromic layer and the ion storage layer. For example, when the electrochromic layer includes a reducing discoloration material such as tungsten oxide (WO _x ), the ion storage layer includes an oxidative discoloration material such as lithium nickel oxide (LiNiO _x ). However, the electrochromic device having the above configuration has a disadvantage in that the color change efficiency is not good and the switching time is slow.

The present application may include niobium oxide (NbO _x ) in the ion storage layer to improve discoloration efficiency and switching time . Niobium oxide (NbO _x ) not only has excellent thin film deposition, but also can receive and store charge even at a thickness of 150 nm or less, or 100 nm or less, thereby reducing switching time between discoloration and discoloration of the device. Can be.

In one example, the niobium oxide may have a mass ratio of 0.5 ≦ O / Nb ≦ 2.5. More specifically, niobium oxide may have a mass ratio in the range of 1.0 ≦ O / Nb ≦ 2.0. When the mass ratio exceeds 2.0, it may be difficult to manufacture the ion storage layer because the niobium oxide thin film is thermodynamically unstable, and when it is less than 0.5, it may be difficult to implement the transparent thin film due to the predominant metal properties.

In another example, the thickness of the ion storage layer may be formed to 150 nm or less in order to give light transmission characteristics, that is, transparent properties to the ion storage layer containing the niobium oxide. For example, the ion storage layer may be formed to a thickness of 120 nm or less, 100 nm or less, or 80 nm or less. The lower limit of the thickness is not particularly limited, but may be formed in a range of 10 nm or more. The ion storage layer may have sufficient ion storage capacity required for the oxidation and reduction of the electrochromic material even when the thin film has the thickness of the thin film as described above.

In addition, during the coloring and decolorization of the electrochromic layer, the ion storage layer according to the present application does not change the transmittance to visible light. In detail, when niobium oxide (NbOx) is applied to a specific potential as described below, even when electrolyte ions are inserted or desorbed into the ion storage layer, the niobium oxide (NbOx) may exhibit a predetermined level of light transmittance without coloration or decolorization. In one example, the transmittance of visible light of the ion storage layer may be an upper limit of 95% or less, 90% or less, or 80% or less, and the lower limit may be 60% or more, 70% or more, or 80% or more. . In addition, the refractive index of the ion storage layer with respect to visible light may be in the range of 1.5 to 3.3.

The electrolyte layer may include ions involved in the electrochromic reaction, such as lithium ions (Li ⁺ ). As the electrolyte, a liquid electrolyte, a gel type polymer electrolyte, or an inorganic solid electrolyte may be used.

In one example, when the electrolyte is a gel type polymer electrolyte, it may include a cured product of a composition containing a carbonate compound and a lithium compound. Since the carbonate compound has a high dielectric constant, the conductivity of the ions provided by the lithium compound can be increased. For example, carbonate-based compounds such as propylene carbonate (PC), ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethylmethyl carbonate (EMC) may be used, but are not limited thereto. LiF, LiCl, LiBr, LiI, LiClO ₄ , LiBF ₄ , LiClO ₃ , LiAsF ₆ , LiSbF ₆ , LiAl0 ₄ , LiAlCl ₄ , LiNO ₃ , LiN (CN) ₂ , LiPF ₆ , Li (CF ₃ ) ₂ PF ₄ , Li (CF ₃ ) ₃ PF ₃ , Li (CF ₃ ) ₄ PF ₂ , Li (CF ₃ ) ₅ PF, Li (CF ₃ ) ₆ P, LiSO ₃ CF ₃ , LiSO ₃ C ₄ F ₉ , LiSO ₃ (CF ₂ ) ₇ CF ₃ , or LiN (SO ₂ CF ₃ ) ₂ , and the like, for example, but is not limited thereto.

In another example, when the electrolyte is an inorganic solid electrolyte, the electrolyte may include lithium phosphorus oxynitride or lithium ion doped transition metal oxide called LIPON (Lithium Phosphorous Oxynitride). Specifically, the electrolyte layer may be a solid electrolyte doped with lithium metal in transition metal oxides such as molybdenum (Mo), tantalum (Ta), zirconium (Zr), hafnium (Hf), and tungsten (W). In the case of the gel type polymer electrolyte, bubbles are generated as the charge / discharge cycle increases and durability thereof is decreased. However, when the inorganic solid electrolyte is used, bubbles are not generated, thereby increasing durability and lifespan of the device.

The electrolyte layer may have a thickness in the range of 30 μm to 200 μm, and transmittance of visible light may range from 70% to 95%.

The electrochromic device of the present application may further include a power source. For example, the power source may be electrically connected to the electrode layer through an external circuit. The apparatus or method for applying the voltage may be appropriately selected by those skilled in the art and is not particularly limited.

In one example, the power source may apply a potential having an absolute value within 2V to the electrochromic device. More specifically, when the electrochromic layer containing tungsten oxide (WO _x ) has a negative sign and a coloring potential of 2 V or less is applied to the electrode layer, the lithium ion is inserted into the electrochromic layer and colored. In this case, the niobium oxide may sufficiently function as an ion storage layer while maintaining transparency without discoloration during a duration time during which the electrochromic layer is colored. On the contrary, in order to decolorize the electrochromic device, the electrochromic layer should have a positive sign on the electrode layer directly provided and have a discoloration potential of less than 2V in size. When the magnitude of the coloring or discoloring potential exceeds 2 V, discoloration of niobium oxide is caused and it is difficult to sufficiently perform the role of the ion storage layer. When a voltage in the above range is applied, irrespective of the coloration or decolorization reaction of the electrochromic layer, the ion storage layer can maintain transmittance in the range of 60% to 80% with respect to visible light without large change in optical properties.

In another example of the present application, the present application relates to a method of manufacturing an electrochromic device. More specifically, the manufacturing method includes the steps of providing a niobium oxide layer having a mass ratio in the range of 0.5 ≦ O / Nb ≦ 2.5 on one electrode layer; And providing a tungsten oxide layer on the other electrode layer. As described above, the niobium oxide layer may be used as the ion storage layer of the electrochromic device of the present application, and the tungsten oxide layer may be used as the electrochromic layer of the electrochromic device of the present application.

The interlayer lamination method can be made by appropriately selecting a known method. In one example, sputtering, sol-Gel, e-beam evaporation, pulsed laser deposition, chemical vapor deposition, CVD, spin coating or dip coating Each layer can be formed using any of dip coating methods.

In one example, the niobium oxide layer may be deposited on one surface of the electrode layer by a sputtering method. More specifically, approximately 30 to 60 nm thick Nb target is formed, and in a chamber having a 5 mTorr to 60 mTorr process pressure, a power of 100 W to 300 W is applied, and oxygen (O ₂ ) gas and argon The niobium oxide layer may be provided on the electrode layer through a process of supplying (Ar) gas at a flow rate of 1 sccm to 10 sccm and 40 sccm to 60 sccm, respectively. In this case, the partial pressure ratio (O / Ar) of argon and oxygen supplied into the chamber may be, for example, in a range of 1% to 15%, preferably 4% to 10%. When the partial pressure ratio of argon and oxygen is less than 4%, the rate at which the niobium oxide layer is deposited on the electrode layer may be delayed, and the productivity may be reduced. When the partial pressure ratio exceeds 10%, the transmittance and refractive index of the niobium oxide layer may be reduced. It is difficult to sufficiently perform the role of the ion storage layer because the optical characteristics such as are not sufficiently secured.

The manufacturing method of the present application may further include providing an electrolyte layer on one surface of the copper nitride layer or the lithium nickel oxide layer. The type of electrolyte that can be used in the electrolyte layer is as mentioned above.

The present application may provide an electrochromic device having excellent thin film productivity and improved color change efficiency to reduce color change speed.

1 is a schematic cross-sectional view of an electrochromic device according to an example of the present application.
2A is a photograph of an electrochromic layer due to decolorization after voltage application according to an example of the present application.
2 b is a photograph of an electrochromic layer according to coloration after voltage application according to an example of the present application.

Hereinafter, the present invention will be described in detail through examples. However, the scope of protection of the present invention is not limited by the examples described below.

Experimental Example  1: Measurement of Optical and Driving Characteristics of Half-Cell

For the half-cell manufactured as described below, the driving and optical characteristics of each cell were measured at 25 ° C. using potentiostat equipment (Princeton Applied Research, PMC-1000) and UV-vis spectrometer equipment (Solidspec 3700). . -2V was applied as the coloring potential and + 2V voltage was applied as the discoloration potential. At this time, the size of each specimen used was consistent with 2.5 cm X 10 cm = 25 cm ² . The results are shown in Table 1 below.

Example

Preparation of Working Electrode: Electrodechromic layer formed of tungsten oxide (WO ₃ ) was deposited on the ITO electrode, which is a transparent conductive oxide, to a thickness of 300 nm by using a DC sputter method, and a working electrode including the first electrode and the electrochromic layer. Was prepared.

Preparation of counter electrode: An ion storage layer formed of niobium oxide (NbOx) was deposited to a thickness of 30 nm on a transparent conductive oxide ITO electrode by using a DC sputter method, and a working electrode including a second electrode and an ion storage layer was formed. Prepared.

Comparative example

Except that a 100 nm thick LiNiOx layer was used as the ion storage layer, the electrochromic layer and the ion storage layer were prepared on a different ITO electrode by using a DC sputter method.

Comparison of Optical and Driving Characteristics of Half-Cell Half-cell: working electrode containing an electrochromic layer Half-cell: counter electrode including ion storage layer Measure
Item TCO sheet resistance
(Ω / □) Charge
(mC) ΔT (%) Time (s)
Col. / Ble. TCO sheet resistance Charge
(mC) ΔT (%) Time (s)
Col. / Ble. Example 30 600 60 30/30 30 30 <1 - Comparative example 30 600 60 60/30 30 200 40 30/30 TCO sheet resistance: sheet resistance of ITO electrode
ΔT: Difference in transmittance during coloring and decolorization of each electrode
Time (s) Col. : Time taken for the electrode to switch from the decoloring state to the coloring state. It can be measured by the time required to have 80% transmittance relative to the transmittance of the fully colored state.
Time (s) Ble. : Time taken for the electrode to transition from a colored state to a bleaching state. It can be measured by the time required to have a transmittance of 80% relative to the transmittance of a completely bleached state.

As shown in Table 1, the ion storage layer included in the counter electrode of the present application, unlike the ion storage layer of the comparative example, it can be seen that there is no change in transmittance. This means that in the case of lithium nickel oxide included in the comparative ion storage layer, coloring and decolorization occur according to the applied voltage, whereas niobium oxide included in the example ion storage layer does not substantially color and decolorize.

Experimental Example  2: Measurement of Optical and Driving Characteristics of Full-Cell

The working electrode and the counter electrode prepared in Examples and Comparative Examples, respectively, were bonded together via a gel polymer electrolyte prepared from a mixture of propylene carbonate (PC) and LiClO ₄ to prepare an electrochromic device. For the manufactured electrochromic device, optical and driving characteristics were measured using the same apparatus as Experimental Example 1. The results are shown in Table 2 below.

Comparison of Optical and Driving Characteristics of Full-Cell Electrochromic Device (Full Cell) ΔT (%) Bleaching Time (s) Coloring Time (s) Charge amount (mC) Example 25 5 10 50 Comparative example 50 13 36 250 ΔT: Difference in transmittance during coloring and decolorization of the entire device
Bleaching Time (s): The time taken when the electrochromic device is bleached in the colored state. It can be measured by the time required to have 80% transmittance relative to the transmittance of the fully colored state.
Coloring Time (s): The time taken when the electrochromic device is colored in the bleaching state. It can be measured by the time required to have a transmittance of 80% relative to the transmittance of a completely bleached state.

As shown in Table 2, it can be seen that the charge amount of the entire electrochromic device composed of the working electrode and the counter electrode is larger than that of the comparative example. However, in the case of the coloration efficiency (coloration efficiency = ΔT / amount of charge) which can be represented by the change in the transmittance with respect to the amount of charge, it can be seen that the device of the embodiment is significantly higher than that of the comparative device. Furthermore, it can be seen that the device of the example has a switching time shortened by 50% or more than the device of the comparative example.

Claims (19)

An electrochromic device including a first electrode, an electrochromic layer, an ion storage layer, and a second electrode sequentially;
The electrochromic layer includes tungsten oxide (WO _x ), the ion storage layer comprises niobium oxide (NbO _x ),
The niobium oxide (NbO _x ) has a mass ratio in the range of 0.5 ≦ O / Nb ≦ 2.0,
The ion storage layer has a thickness in the range of 10 nm to 150 nm,
An electrochromic device that satisfies a transmittance difference (ΔT) <1 even when electrolyte ions are inserted or desorbed during coloring and decolorization.
delete The electrochromic device of claim 1, wherein the ion storage layer has a refractive index of about 1.3 to about 3.3.
delete The electrochromic device of claim 1, wherein transmittance of visible light of the ion storage layer is in a range of 60% to 80%.
The electrochromic device of claim 1, wherein the electrochromic layer has a thickness of 50 nm to 400 nm.
The electrochromic device of claim 1, wherein the electrochromic layer has a transmittance of 20% to 60% for visible light when colored and 65% to 85% for visible light when decolored.
The method of claim 1, wherein the electrode layer is indium tin oxide (ITO), fluor doped tin oxide (FTO), aluminum doped zinc oxide (AZO), gallium doped zinc oxide (GZO), antimony doped tin oxide (ATO), indium IZO (IZO) Electrochromic including one or more materials selected from the group consisting of doped Zinc Oxide (NTO), Niobium doped Titanium Oxide (NTO), ZnO, Oxide / Metal / Oxide (OMO), Metal Mesh, Ag nanowire, and Cadmium Tin Oxide (CTO) device.
The electrochromic device of claim 1, wherein the electrode layer has a thickness in a range of 1 nm to 1 μm.
The electrochromic device of claim 1, wherein the electrolyte layer comprises any one of a liquid electrolyte, a gel type polymer electrolyte, and an inorganic solid electrolyte, and has a thickness of 30 μm to 200 μm.
The electrochromic device of claim 10, wherein the electrolyte layer has an inorganic solid electrolyte containing LiPON or Ta ₂ O ₅ .
The electrochromic device of claim 10, wherein the electrolyte layer is a gel type polymer electrolyte layer formed from a cured product of a carbonate compound and a lithium compound.
The method of claim 12, wherein the carbonate compound is at least one compound selected from the group consisting of propylene carbonate (PC), ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC) and ethylmethyl carbonate (EMC). Electrochromic device.
The method of claim 12, wherein the lithium compound is LiF, LiCl, LiBr, LiI, LiClO ₄ , LiBF ₄ , LiClO ₃ , LiAsF ₆ , LiSbF ₆ , LiAl0 ₄ , LiAlCl ₄ , LiNO ₃ , LiN (CN) ₂ , LiPF ₆ , Li (CF ₃ ) ₂ PF ₄ , Li (CF ₃ ) ₃ PF ₃ , Li (CF ₃ ) ₄ PF ₂ , Li (CF ₃ ) ₅ PF, Li (CF ₃ ) ₆ P, LiSO ₃ CF ₃ , LiSO ₃ At least one electrochromic device selected from C ₄ F ₉ , LiSO ₃ (CF ₂ ) ₇ CF ₃ , and LiN (SO ₂ CF ₃ ) ₂ .
The electrochromic device according to claim 1, wherein the electrochromic device further includes a power source, and the color potential and the color loss potential of the electrochromic device have an absolute value of 2 V or less.
The mass ratio of oxygen and niobium on one electrode layer has a range of 0.5 ≦ O / Nb ≦ 2.0, has a thickness in the range of 10 nm to 150 nm, and the ion storage layer has a transmittance at the time of coloring and decolorization even if electrolyte ions are inserted or desorbed. Providing a niobium oxide layer that satisfies a difference ΔT <1; And
A method of manufacturing an electrochromic device according to claim 1, comprising providing a tungsten oxide (WO _x ) layer on another electrode layer.
17. The method of claim 16, wherein the interlayer deposition is sputtering, sol-gel, e-beam evaporation, pulsed laser deposition, chemical vapor deposition, spin coating. ) Or a method of manufacturing an electrochromic device made by any one of dip coating (dip coating).
The electrochromic device of claim 17, wherein the niobium oxide layer is deposited on one surface of the electrode layer by a sputtering process, and a partial pressure ratio (O / Ar) of argon and oxygen injected during the sputtering process is in a range of 1 to 15%. Manufacturing method.
17. The method of claim 16, further comprising providing an electrolyte layer on one surface of the niobium oxide layer or tungsten oxide layer, wherein the electrolyte layer comprises any one of a liquid electrolyte, a gel type polymer electrolyte, and an inorganic solid electrolyte layer. Method for producing an electrochromic device.

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