KR20170112183A - An Electrochromic Device - Google Patents

Abstract

The present application relates to an electrochromic device and a method of manufacturing an electrochromic device. The present application can provide an electrochromic device having improved coloring speed and durability and high productivity as compared with the prior art.

Description

[0001] An Electrochromic Device [

The present application relates to an electrochromic device. Specifically, the present application relates to an electrochromic device having improved color fading efficiency and switching time.

Electrochromism refers to a phenomenon in which optical properties such as color and light transmittance of an electrochromic active material change depending on electrochemical oxidation and reduction reactions. Electrochromic devices using such a phenomenon are attracting attention in various fields such as smart windows, smart mirrors, and electronic paper because they can be manufactured with a small-sized device with a small area and low power consumption.

1 is a cross-sectional view of a general electrochromic device. As shown in the figure, 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, 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 of transparent glass or polymer resin may be further included on the outer surface of each of the electrodes 110 and 150.

In general, the electrochromic layer and / or the ion storage layer may contain an inorganic substance such as tungsten oxide (WO _x ) or lithium nickel oxide (LiNiO) as an electrochromic material. Specifically, when a specific potential is applied to the electrode, electrolyte ions such as H ⁺ or Li ⁺ and Na ⁺ move between the electrochromic layer and the ion storage layer through the electrolyte layer, and at the same time, As a result of being injected into the discoloration layer or leaving the discoloration layer, the oxidation / reduction reaction of the discoloration substance is alternated and the discoloration or bleaching of the discoloration layer or the ion storage layer is performed. As described above, since the movement of the ionic material is presupposed in the change of the optical characteristic of the electrochromic device, there is a need for a technique which can take a predetermined time, that is, a switching time, and thereby reduce the discoloration time.

An object of the present invention is to provide an electrochromic device excellent in discoloration efficiency and improved in discoloration rate.

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

The above and other objects of the present application can be resolved 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 mean a structure capable of supplying electric charge to the electrochromic layer. In one example, the electrode may include at least one of a transparent conductive oxide, a conductive polymer, an Ag nanowire, or a metal mesh. More specifically, it is possible to use a metal oxide such as ITO (indium tin oxide), FTO (fluoro-doped tin oxide), AZO (aluminum doped zinc oxide), GZO (gallium doped zinc oxide), ATO (antimony doped tin oxide), IZO , Niobium-doped Titanium Oxide (NTO), ZnO, Oxide / Metal / Oxide (OMO), and Cadmium Tin Oxide (CTO). In another example, the electrode layer may be formed by stacking two or more electrode materials into a plurality of layers.

The method for forming the electrode layer is not particularly limited, and known methods can be used without any limitation. For example, an electrode layer can be provided by forming an electrode material containing 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 in the range of 1 nm to 1 占 퐉. The upper limit of the thickness of the electrode layer is not particularly limited, but the electrode layer may have a thickness of 800 nm or less, 700 nm or less, or 500 nm or less for low resistance implementation.

The electrochromic layer may include an electrochromic material whose color changes depending on an electrical signal. Examples of electrochromic materials that can be used include conductive polymers, organic coloring materials and / or inorganic coloring materials. As the conductive polymer, polypyrrole, polyaniline, polypyridine, polyindole, polycarbazole, and the like can be used. As the organic coloring material, materials such as viologen, anthraquinone, and phenothiazine can be used. But is not limited to.

In one example, the electrochromic layer may include an oxide of at least one of Ti, Nb, Mo, Ta, W, V, Cr, Mn, Fe, Co, Ni, Rh, have. Specifically, such as _{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, or IrO ₂ But are not limited to, inorganic usable coloring materials.

More specifically, the electrochromic layer may include tungsten oxide (WO _x ) as a coloring material. The tungsten oxide (WO _x ) can be colored or discolored, for example, through the reaction as follows. In the following scheme, M may be an electrolyte ion such as H ⁺ , Li ⁺ , or Na ⁺ .

[Reaction Scheme]

WO ₃ (discoloration: colorless) + xe ^- + xM ⁺ ⇔ M _x WO ₃ (coloring: blue)

In this reaction, when the electrochromic layer is discolored, the electrochromic device transmits incident light. When the electrochromic device is colored, the amount of incident light is reduced, and the optical characteristics of the electrochromic device can be changed. The coloring and decoloring reactions may occur alternately depending on the polarity of the applied voltage or the direction of the current flow.

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

In another example, the electrochromic layer may have a thickness in the range of 50 nm to 400 nm. When the thickness is less than 50 nm, the reaction for discoloration is difficult to occur sufficiently. When the thickness exceeds 400 nm, the electrochromic device of thin film can not be provided.

The ion storage layer may mean a layer that can be inserted or removed from the charge particles necessary for the oxidation-reduction reaction of the electrochromic layer, and can participate in the discoloration reaction. In the prior art, a complementary electrochromic material was used for each of the electrochromic layer and the ion storage layer in consideration of the role of the ion storage layer. For example, when the electrochromic layer contains a reducing discoloration substance such as tungsten oxide (WO _x ), the ion storage layer contains an oxidative discoloring substance such as lithium nickel oxide (LiNiO _x ). However, the electrochromic device having the above-described structure has a disadvantage that the coloring efficiency is poor and the switching time is slow.

The present application can include niobium oxide (NbO _x ) in the ion storage layer to improve the discoloration efficiency and the switching time . Since niobium oxide (NbO _x ) is excellent in thin film deposition property and can sufficiently store and store charges even at a thickness of 150 nm or less or 100 nm or less, the switching time required for discoloration and discoloration of the device is reduced .

In one example, the niobium oxide may have a mass ratio in the range 0.5 ≦ O / Nb ≦ 2.5. More specifically, the niobium oxide may have a mass ratio in the range of 1.0? O / Nb? 2.0. When the mass ratio is more than 2.0, the niobium oxide thin film may be unstable thermodynamically, so that it may be difficult to produce an ion storage layer. If the niobium oxide thin film is less than 0.5, it may be difficult to realize a transparent thin film.

In another example, the thickness of the ion storage layer may be 150 nm or less in order to impart a light-transmitting property, that is, a transparent property, to the ion storage layer containing niobium oxide. For example, the ion storage layer can 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 in the range of 10 nm or more. The ion storage layer may have a sufficient ion storage capacity required for the oxidation and reduction reaction of the electrochromic material, even when the ion storage layer has a thickness of the thin film as described above.

In addition, when the electrochromic layer is colored and discolored, the ion storage layer according to the present application does not change the transmittance with respect to visible light. Specifically, the niobium oxide (NbOx) may exhibit a certain level of light transmittance without being colored or discolored even when electrolyte ions are inserted into or removed from the ion storage layer when a specific electric potential is applied as described later. In one example, the transmittance of the ion storage layer to visible light may be up to 95%, 90%, or 80%, and the lower limit may be 60% or more, 70% or more, or 80% . Also, the refractive index of the ion storage layer with respect to visible light may range from 1.5 to 3.3.

The electrolyte layer may include ions involved in the electrochromic reaction such as lithium ion (Li ^< ^{+ &} gt ^; ). 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 comprising 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 compounds such as PC (propylene carbonate), EC (ethylene carbonate), DMC (dimethyl carbonate), DEC (diethyl carbonate) and EMC (ethylmethyl carbonate) may be used. Lithium compounds are 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.

In another example, when the electrolyte is an inorganic solid electrolyte, the electrolyte may include lithium phosphorus oxynitride (LIPON) or lithium ion-doped transition metal oxide, which is called LIPON (Lithium Phosphorous Oxynitride). Specifically, the electrolyte layer may be a solid electrolyte in which lithium metal is doped in a transition metal oxide 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 and the durability thereof is lowered as the charge / discharge cycle is increased. On the other hand, when the inorganic solid electrolyte is used, the durability and lifetime of the device can be increased because no bubbles are generated.

The electrolyte layer may have a thickness in the range of 30 [mu] m to 200 [mu] m, and the transmittance to 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 an electrode layer through an external circuit. Apparatuses and methods for applying a voltage can be appropriately selected by a person skilled in the art and are not particularly limited.

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

In another example of this application, the present application relates to a method of manufacturing an electrochromic device. More specifically, the method comprises: providing a niobium oxide layer having a mass ratio in a 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 can be used as the ion storage layer of the electrochromic device of the present application, and the tungsten oxide layer can be used as the electrochromic layer of the electrochromic device of the present application.

The interlayer deposition method may be performed by appropriately selecting a known method. In one example, the substrate may be deposited by sputtering, sol-gel method, e-beam evaporation, pulsed laser deposition, chemical vapor deposition (CVD), spin coating or dip coating dip coating, and dip coating.

In one example, the niobium oxide layer may be deposited on one side of the electrode layer by a sputtering method. More specifically, a power of 100 W to 300 W is applied in a chamber in which a Nb target of approximately 30 to 60 nm thickness is formed and a process pressure of 5 mTorr to 60 mTorr is applied and oxygen (O ₂ ) gas and argon (Ar) gas at a flow rate of 1 sccm to 10 sccm and a flow rate of 40 sccm to 60 sccm, respectively, so that the niobium oxide layer can be provided on the electrode layer. At this time, the partial pressure ratio (O / Ar) of argon and oxygen supplied into the chamber may be in a range of, for example, 1% to 15%, and preferably 4% to 10%. If 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 productivity may be deteriorated. If the partial pressure ratio exceeds 10%, the transmittance and refractive index It is difficult to sufficiently fulfill its role as an ion storage layer.

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

The present application can provide an electrochromic device having not only excellent thin film productivity, but also an improved discoloration efficiency and a reduced discoloration rate.

1 schematically shows a cross-sectional view of an electrochromic device according to an example of the present application.
2 (a) is a photograph of an electrochromic layer according to an example of the present application, followed by decolorization after voltage application.
FIG. 2B is a photograph of an electrochromic layer according to coloring after voltage application according to an example of the present application. FIG.

Hereinafter, the present invention will be described in detail with reference to Examples. However, the scope of protection of the present invention is not limited by the following embodiments.

Experimental Example  1: Measurement of optical characteristics and driving characteristics of half-cell

The driving characteristics and the optical characteristics of each cell were measured at a temperature of 25 ° C using a potentiostat apparatus (Princeton Applied Research, PMC-1000) and a UV-vis spectrometer apparatus (Solidspec 3700) . A voltage of -2 V was applied before the coloring, and a voltage of + 2 V was applied before the coloring. At this time, the size of each specimen used was matched to 2.5 cm × 10 cm = 25 cm ² . The results are shown in Table 1 below.

Example

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

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 using a DC sputter method, and a working electrode including a second electrode and an ion storage layer .

Comparative Example

An electrochromic layer and an ion storage layer were formed on different ITO electrodes using a DC sputtering method, except that a LiNiOx layer having a thickness of 100 nm was used as the ion storage layer.

Comparison of optical and driving characteristics of half-cell Half-cell: Working electrode containing electrochromic layer Half-cell: a counter electrode including an ion storage layer Measure
Item TCO surface resistance
(Ω / □) Charge quantity
(mC) ΔT (%) Time (s)
Col. / Ble. TCO surface resistance Charge quantity
(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 surface resistance: sheet resistance value of ITO electrode
ΔT: Difference in transmittance between coloring and decoloring of each electrode
Time (s) Col. : The time it takes the electrode to transition from bleaching to coloring. Can be measured as the time taken to have an 80% transmittance versus a completely colored state.
Time (s) Ble. : The time it takes for the electrode to change from a coloring to a bleaching state. Can be measured as the time taken to have an 80% transmittance versus a completely discolored state.

As shown in Table 1, unlike the ion storage layer of the comparative example, the ion storage layer included in the counter electrode of the present application shows no change in transmittance. This means that the coloring and decolorization occur depending on the applied voltage of the lithium nickel oxide included in the comparative example ion storage layer, whereas the niobium oxide contained in the ion storage layer of the embodiment does not substantially cause discoloration and discoloration.

Experimental Example  2: Measurement of optical characteristics and driving characteristics of full-cell

The working electrode and the counter electrode prepared in each of the above Examples and Comparative Examples were cemented through a gel polymer electrolyte prepared from a mixture of PC (propylene carbonate) and LiClO ₄ to prepare an electrochromic device. Optical and drive characteristics of the electrochromic device were measured using the same apparatus as in Experiment 1. The results are shown in Table 2 below.

Comparison of optical characteristics and driving characteristics of full-cell Electrochromic devices (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 between coloring and decolorization of all devices
Bleaching Time (s): The time required when the electrochromic device is bleached in the coloring state. Can be measured as the time taken to have an 80% transmittance versus a completely colored state.
Coloring Time (s): The time required when the electrochromic device is coloring in a bleaching condition. Can be measured as the time taken to have an 80% transmittance versus a completely discolored 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 in the comparative example. However, in the case of the discoloration efficiency (coloration efficiency = DELTA T / charge amount) which can be represented by the change in the transmittance with respect to the charge amount, it can be confirmed that the elements of the embodiment are much higher than those of the comparative example. Furthermore, it is confirmed that the device of the embodiment has a switching time shortened by 50% or more as compared with the device of the comparative example.

Claims (19)

An electrochromic device comprising two oppositely disposed electrode layers, an electrochromic layer, an ion storage layer, and an electrolyte layer,
Wherein the electrochromic layer comprises tungsten oxide (WO _x ), and the ion storage layer comprises niobium oxide (NbO _x ).
The electrochromic device according to claim 1, wherein the niobium oxide (NbO _x ) has a mass ratio in the range of 0.5 ≦ O / Nb ≦ 2.5.
The electrochromic device according to claim 1, wherein the ion storage layer has a thickness ranging from 10 nm to 150 nm and a refractive index with respect to visible light ranges from 1.3 to 3.3.
The electrochromic device according to claim 1, wherein the ion storage layer is not colored or discolored even when electrolyte ions are inserted or removed.
5. The electrochromic device according to claim 4, wherein a transmittance of the ion storage layer with respect to visible light ranges from 60% to 80%.
The electrochromic device according to claim 1, wherein the electrochromic layer has a thickness of 50 nm to 400 nm.
The electrochromic device according to claim 1, wherein the electrochromic layer has a transmittance of visible light of 20% to 60% and a transmittance of visible light of 65% to 85%.
The method according to claim 1, wherein the electrode layer is formed of a material selected from the group consisting of indium tin oxide (ITO), fluorine doped tin oxide (FTO), aluminum doped zinc oxide (AZO), gallium doped zinc oxide (GZO), antimony doped tin oxide (ATO) doped zinc oxide (ITO), niobium doped titanium oxide (NTO), ZnO, oxide / metal / oxide (OMO), metal meshes, Ag nanowires and cadmium tin oxide device.
The electrochromic device according to claim 1, wherein the electrode layer has a thickness in the range of 1 nm to 1 占 퐉.
The electrochromic device according to claim 1, wherein the electrolyte layer contains any one of a liquid electrolyte, a gel-type polymer electrolyte, and an inorganic solid electrolyte, and has a thickness of 30 탆 to 200 탆.
The electrochromic device according to claim 10, wherein the electrolyte layer has an inorganic solid electrolyte containing LiPON or Ta ₂ O ₅ .
The electrochromic device according to 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.
13. The method of claim 12, wherein the carbonate compound is at least one compound selected from the group consisting of propylene carbonate (EC), ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethylmethyl carbonate 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 Wherein the electrochromic device is at least one selected from the group consisting of 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 comprises a power source, and the absolute value of the coloring potential and decoloring potential of the electrochromic device is 2 V or less.
Providing a niobium oxide layer having a mass ratio of oxygen and niobium in a range of 0.5? O / Nb? 2.5 on one electrode layer; And
And forming a tungsten oxide (WO _x ) layer on the other electrode layer.
17. The method of claim 16, wherein the interlayer deposition is performed by sputtering, sol-gel method, e-beam evaporation, pulsed laser deposition, CVD (chemical vapor deposition) ) Or a dip coating method according to the present invention.
18. The electrochromic device according to claim 17, wherein the niobium oxide layer is deposited on one surface of the electrode layer by a sputtering process, and the partial pressure ratio (O / Ar) of argon and oxygen injected in the sputtering process ranges from 1 to 15% Gt;
17. The method of claim 16, further comprising providing an electrolyte layer on one side 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, or an inorganic solid electrolyte layer Gt; to &lt; / RTI &gt; the electrochromic device.

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