KR20170112189A - An Electrochromic Device - Google Patents

Abstract

The present application relates to an electrochromic device and a manufacturing method thereof. The present application, which includes a novel ion storage layer material and an electrochromic material, provides an electrochromic device having excellent durability and thin film productivity and improved color change rate compared to the prior art.

Description

[0001] An Electrochromic Device [

The present application relates to an electrochromic device.

Electrochromism is a phenomenon in which optical properties such as color and light transmittance of an electrochromic active material are changed by electrochemical oxidation and reduction reactions. The electrochromic device using such a phenomenon is attracting attention in various fields such as a smart window, a smart mirror, and an electronic paper because the electrochromic device can be manufactured with a small area with a small area and low power consumption.

1 shows a cross section 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, an electrolyte layer 130 provided on the electrochromic layer 130, An ion storage layer 140 provided on the ion storage layer, and a second electrode layer 150 provided on the ion storage layer. Although not shown, the outer surface of each of the electrodes 110 and 150 may further include a substrate formed of transparent glass or polymer resin.

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 _x ) as an electrochromic material. When a voltage is applied to the device, the inherent color of the electrochromic material may be changed. 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, The electrochromic material is oxidized or reduced as it is injected into or separated from the electrochromic layer, resulting in coloring or bleaching of the electrochromic layer or the ion storage layer. As described above, since the movement of electrolyte ions is presumed to change the optical characteristics of the electrochromic device, a predetermined time, that is, a switching time is required for the discoloration, thereby reducing the discoloration time and improving the discoloration efficiency Technology is required.

One object of the present invention is to provide an electrochromic device having improved color shift speed and excellent color fading efficiency.

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

These and other objects of the present application can be resolved by the present application, which is described in detail below.

The present application relates to an electrochromic device. The electrochromic device may include two opposing electrode layers, 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 (TCO), a conductive polymer, a silver 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), or CTO may be used as the electrode material. 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 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.

In one example, the electrode layer may have a light transmittance in the range of 70% to 95% with respect to visible light. The visible light in the present application may mean light having a wavelength in the range of about 350 nm to 750 nm, and more specifically, light having a wavelength of 550 nm.

The electrochromic layer may include an electrochromic material whose color changes according to an electrical signal. Electrochromic materials which can be used include conductive polymers, organic coloring materials and / or inorganic coloring materials. Examples of the conductive polymer include polypyrrole, polyaniline, polypyridine, polyindole, and polycarbazole. Examples of the organic coloring material include viologen, anthraquinone, phenothiazine, and the like.

In the prior art, an inorganic oxide such as tungsten oxide (WO _x ) is mainly used as an electrochromic material. However, the inorganic oxide such as tungsten oxide (WO _x ) has a problem that the productivity is deteriorated because the thin film forming efficiency is poor. Specifically, in order to ensure a sufficient discoloring effect in the case of forming an electrochromic layer using tungsten oxide (WO _x ), a sufficient thickness of around 400 nm was required in addition to a wide reaction area. And the rate of ion movement is lowered, so that the rate of discoloration of the electrochromic device is slowed down. In view of the problems of the prior art, the present application includes copper nitride (CuN _x ) as an electrochromic material. As described below, copper nitride (CuN _x ) has excellent thin film deposition productivity and can exhibit sufficient electrochromic effect even at a thickness of 150 nm or less.

In one example, the electrochromic layer containing copper nitride may have a deep blue color due to coloration when a voltage of 2.5 V or more is applied thereto. For example, when a negative voltage exceeding 2.5 V is applied, electrolytic ions such as Li ⁺ are inserted into the electrochromic layer containing copper nitride so that the electrochromic layer has a deep blue color Wherein the electrochromic layer may have a light transmittance for visible light in the range of 40% to 55%. On the other hand, when a positive voltage of 2 V or less is applied to the electrochromic layer containing copper nitride after coloring, the electrochromic layer may be discolored, Lt; RTI ID = 0.0 > 75%. ≪ / RTI >

In one example, the copper nitride (CuN _x ) may be copper nitride in which the mass ratio of copper to nitrogen is in the range of 0.01? N / Cu? 0.3. More specifically, copper nitrides in the range of 0.05? N / Cu? 0.2 may be used. When the mass ratio of N / Cu is more than 0.2, it is difficult to prepare the electrochromic layer because the copper nitride thin film is thermodynamically unstable. When the mass ratio is less than 0.05, the metal property is dominant and it is difficult to impart transparency to the thin film.

Although not particularly limited, in one example, the electrochromic layer containing copper nitride may have a refractive index in the range of 1.0 to 3.0 for visible light.

In one example, the electrochromic layer comprising copper nitride may have a sheet resistance in the range of 1,000 ohms / square. When the range resistance value is satisfied, the response speed of the device can be increased and the switching time can be reduced.

In one example, the electrochromic layer containing copper nitride may be formed to have a thickness of 10 nm to 150 nm, 100 nm or less, 80 nm or less, or 50 nm or less. When the thickness is less than 10 nm, the discoloration reaction does not sufficiently occur. When the thickness is more than 150 nm, a thin film electrochromic device can not be provided and the productivity may be deteriorated.

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 order to balance the charge between the electrochromic layer and the ion storage layer. For example, when the electrochromic layer contains an oxidative discoloring substance such as lithium nickel oxide (LiNiO _x ), a reducing discoloring substance such as tungsten oxide (WO _x ) is included in the ion storage layer. However, the electrochromic device having the above-described structure has a disadvantage that the coloring efficiency is poor and the switching time is slow.

In consideration of the problems of the prior art, the electrochromic device according to the present application uses an ion storage layer containing a conductive graphite. Conductive graphite having a specific structure and high strength resulting therefrom can prevent cracks in the ion storage layer and improve the durability of the device. Further, the layered structure of the graphite can provide a space in which electrolyte ions involved in electrochromism can be sufficiently inserted and desorbed. Furthermore, since the conductive graphite is excellent in thin film deposition property and can sufficiently receive and store electric charge even at a thickness of 100 nm or less, the switching time required for discoloration and discoloration of the device can be reduced.

The conductive graphite may be graphite oxide. In one example, the graphite oxide may have a mass ratio of oxygen to carbon in the range 0.001? O / C? 0.5, or 0.005? O / C? 0.3. Specifically, in the XPS analysis of the constituent element distribution of the graphite thin film, the content of the C element and the O element may be slightly different depending on the measurement position, but graphite which satisfies the above range may be used as the entire thin film. When the mass ratio is less than 0.005, the conductivity is somewhat improved but the permeability is lowered. When the mass ratio is more than 0.3, the electric conductivity may be lowered.

In one example, the ion storage layer of the present application may be formed with a thickness in the range of 10 nm to 150 nm, 100 nm or less, or 80 nm or less. When the thickness is less than 10 nm, the ion storage effect is not sufficient. When the thickness exceeds 150 nm, the transparent ion storage layer of the thin film can not be provided and the productivity may be deteriorated.

In another example, the refractive index for the visible light of the ion storage layer may range from 1.0 to 3.0.

In one example, an ion storage layer formed by depositing graphite on an electrode can significantly reduce the internal resistance to ion movement. For example, in the case of an ion storage layer formed from conventional lithium nickel oxide, the internal resistance of the ion storage layer formed by depositing graphite is in the range of 1 M? /? To 10 M? /? ≪ / RTI > to 1,000 < RTI ID = 0.0 > ohm / s < / RTI >

Further, in one example, the ion storage layer may have a visible light transmittance in the range of 65% to 75%.

The electrolyte layer may include ions involved in the electrochromic reaction such as lithium ion (Li ^< ^{+ &} gt ^; ). The type of the electrolyte contained in the electrolyte layer is not particularly limited, and a liquid electrolyte, a gel-polymer electrolyte, or an inorganic solid electrolyte may be used.

In one example, when the electrolyte is a gel-polymer electrolyte, the electrolyte layer may comprise 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 salt 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. Examples of the lithium compound include LiF, LiCl, LiBr, LiI, LiClO ₄ , LiBF ₄ , LiClO ₃ , LiAsF ₆ , LiSbF ₆ , LiAlO ₄ , LiAlCl ₄ , LiNO ₃ , LiN (CN) ₂ , LiPF ₆ , Li 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 one example, the case where the electrolyte is an inorganic solid electrolyte, one, the electrolyte layer may comprise a lithium phosphorus oxynitride so-called LIPON (Lithium Phosphorous Oxynitride), or, for example, such as Ta ₂ O ₅ On the oxides of transition metals And may include an electrolyte doped with lithium ions. Examples of the transition metal that may be used for the inorganic solid electrolyte include transition metals such as molybdenum (Mo), tantalum (Ta), zirconium (Zr), hafnium (Hf), and tungsten (W). In the case of the gel polymer, bubbles are generated and durability 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 may apply an asymmetrical detachable chromatic potential. More specifically, the power source can apply a colored potential having a size of 2.5 V or more to the electrochromic device, and can apply a decoloring potential having a size of 2 V or less. In the case of this application, only the electrochromic layer is colored or discolored depending on the applied voltage, and the ion storage layer can have a certain range of light transmittance without coloring or discoloring. For example, when a negative voltage exceeding 2.5 V is applied to a layer including copper nitride, that is, an electrode layer directly stacked with the electrochromic layer, the electrochromic layer is colored, and the electrochromic layer is colored During the duration of time, the conductive graphite contained in the ion storage layer can act as an ion storage layer while maintaining transparency without discoloration. Conversely, in order for the electrochromic device to decolorize, a positive potential having a magnitude of 2 V or less must be applied to an electrode layer in which an electrochromic layer containing copper nitride is directly laminated. When the coloring potential is less than 2.5 V, copper nitride (CuN _x ) is not discolored, and discoloration and discoloration of the device can not be caused. When the voltage in the above range is applied, the ion storage layer can maintain the transmittance in the range of 65% to 75% with respect to the visible light without a large change in the optical characteristics, regardless of the attaching / detaching color reaction of the electrochromic layer.

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 copper nitride layer having a mass ratio of copper and nitrogen on one electrode layer in the range of 0.05? N / Cu? 0.2; And providing a graphite layer having a mass ratio of oxygen and carbon in the range of 0.005? O / C? 0.3 on the other electrode layer. As described above, the copper nitride layer can be used as an electrochromic layer, and the graphite layer can be used as an ion storage layer. The structure and other properties of the electrode layer, ion storage layer and electrochromic layer are the same as those mentioned above.

The method of forming each layer is not particularly limited, and a known method can be used. For example, any one of a deposition method, a spin coating method, a dip coating method, a screen printing method, a gravure coating method, a sol-Gel method, or a slot die coating method Each layer may be provided. The deposition can be performed by physical vapor deposition (PVD) or chemical vapor deposition (CVD). Examples of the physical vapor deposition method that can be used include a sputtering method, an E-beam evaporation method, a thermal evaporation method, a laser molecular beam epitaxy (L-MBE) method, or a pulsed laser deposition method Pulsed Laser Deposition (PLD)). Examples of the chemical vapor deposition method include a thermal chemical vapor deposition method, a plasma enhanced chemical vapor deposition (PECVD) method, a light chemical vapor deposition method (Light Chemical Vapor Deposition) Chemical vapor deposition (CVD), Laser Chemical Vapor Deposition, Metal-Organic Chemical Vapor Deposition (MOCVD), or Hydride Vapor Phase Epitaxy (HVPE) But is not limited thereto.

In one example, a copper nitride layer or a graphite layer may be deposited on each electrode layer by a sputtering process. More specifically, in the case of the copper nitride layer, a Cu target having a thickness of approximately 30 to 60 nm is formed, a power of 100 W to 300 W is applied in a chamber having a process pressure of 5 mTorr to 60 mTorr, (N ₂ ) gas and argon (Ar) gas at a flow rate of 5 sccm to 25 sccm and 15 sccm to 45 sccm respectively, the copper nitride layer can be provided on the electrode layer. At this time, the partial pressure ratio (N / Ar) of nitrogen and argon supplied into the chamber is not particularly limited, but may be 40% or more. In addition, the graphite layer may be formed by depositing in argon (Ar) atmosphere at a process pressure of 5 mTorr to 25 mTorr and a power of 200 W for 2,000 sec.

The manufacturing method of the present application may further comprise the step of providing a solid electrolyte layer on one side of the copper nitride layer or the graphite layer. The kind of the electrolyte that can be used for the electrolyte layer is the same as mentioned above.

The present application including a novel ion storage layer material and a electrochromic layer material can provide an electrochromic device having excellent thin film productivity as well as improved color fading efficiency and color fastness.

Fig. 1 schematically shows a cross-sectional view of a general electrochromic device.

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

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 -3 V was applied to the half-cell as a coloring potential, and a voltage of +2 V was applied before the decoloration. The size of each specimen used was 2.0 cm x 10 cm = 20 cm ² . The results are shown in Table 1 below.

Example

Preparation of Working Electrode: An electrochromic layer formed of copper nitride (CuNx) 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 first electrode and an electrochromic layer .

Preparation of counter electrode: A formed ion storage layer including a conductive graphite was deposited to a thickness of 50 nm on a transparent conductive oxide ITO electrode using a DC sputtering method, and a working electrode including a second electrode and an ion storage layer was manufactured Respectively.

Comparative Example

A 300 nm thick tungsten oxide (WOx) layer was used as the electrochromic layer, and a 100 nm thick lithium nickel oxide (LiNiOx) layer was used as the ion storage layer. An electrochromic layer and an ion storage layer were provided on the ITO electrode using a DC sputtering method.

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 50 25 10/10 30 50 - - 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 for the electrode to change 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, it can be confirmed that the electrochromic layer included in the working electrode of the present application can shorten the coloring and decolorization time in comparison with the electrochromic layer of the comparative example.

In addition, 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 the transmittance. This means that coloring and discoloration occur depending on the voltage applied to the lithium nickel oxide included in the comparative example ion storage layer, whereas graphite contained in the ion storage layer of the embodiment does not cause discoloration and discoloration.

Experiment 2: Measurement of optical 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 (%) Coloring Time (s) Bleaching Time (s) Charge amount (mC) Example 25 10 5 50 Comparative Example 50 36 13 250 ΔT: Difference in transmittance between coloring and decolorization of all devices
Bleaching Time (s): The time required when the electrochromic layer is bleached in the coloring state. Can be measured as the time taken to have an 80% transmittance versus a completely discolored state.
Coloring Time (s): The time required when the electrochromic layer is colored in bleaching. Can be measured as the time taken to have an 80% transmittance versus a completely colored 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. Further, it is confirmed that the device of the embodiment has a switching time shortened by 50% or more as compared with the comparative example.

Claims (21)

Wherein the electrochromic layer comprises copper nitride (CuN _x ), and the ion storage layer comprises conductive graphite. The electrochromic device of claim 1, wherein the electrochromic layer comprises copper nitride (CuN _x ) Lt; / RTI >
The electrochromic device according to claim 1, wherein the conductive graphite is a graphite oxide, and the mass ratio of oxygen to carbon is in a range of 0.005? O / C? 0.3.
The electrochromic device according to claim 2, wherein the ion storage layer has a resistance of 100? /? To 10,000? / ?.
The electrochromic device according to claim 2, 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 1.0 to 3.0.
The electrochromic device according to claim 2, wherein the ion storage layer has a transmittance of 65% to 75% with respect to visible light.
The electrochromic device according to claim 1, wherein the copper nitride (CuN _x ) has a mass ratio in the range of 0.05? N / Cu? 0.2.
The electrochromic device according to claim 6, wherein the electrochromic layer has a resistance of 1,000 Ω / □ or less.
The electrochromic device according to claim 6, wherein the electrochromic layer has a thickness in a range of 10 nm to 150 nm and a refractive index in a range of 2.0 to 3.5 with respect to visible light.
The electrochromic device according to claim 6, wherein the electrochromic layer has a transmittance of visible light of 40% to 55% and a transmittance of visible light of 65% to 75%.
The electrochromic device according to claim 1, wherein the electrolyte layer has a thickness of 30 to 200 占 퐉, and a light transmittance to visible light ranges from 70% to 95%.
The electrochromic device according to claim 1, wherein the electrolyte layer comprises any one of a liquid electrolyte, a gel-type polymer electrolyte, and an inorganic solid electrolyte.
The electrochromic device according to claim 11, wherein the electrolyte is an inorganic solid electrolyte containing LiPON or Ta ₂ O ₅ .
The electrochromic device according to claim 11, wherein the electrolyte is a gel type polymer electrolyte formed from a cured product of a mixture containing a carbonate compound and a lithium compound.
The method of claim 13, 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 13, 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 method according to claim 1, wherein the electrode layer is formed of a material selected from the group consisting of indium tin oxide (ITO), fluoro-doped tin oxide (FTO), aluminum oxide doped zinc oxide (AZO), antimony doped tin oxide (ATO) At least one transparent conductive compound (TCO) selected from the group consisting of Indium-doped Zinc Oxide (ITO), Niobium-doped Titanium Oxide (NTO), ZnO, Oxide / Metal / Oxide (OMO) and CTO; Conductive polymer; Silver nanowires; And a metal mesh. The electrochromic device according to claim 1,
17. The electrochromic device according to claim 16, wherein the electrode layer has a thickness in the range of 1 nm to 1 占 퐉 and a transmittance to visible light ranges from 70% to 95%.
The electrochromic device according to claim 1, wherein the electrochromic device further comprises a power source, wherein the electrochromic device has an absolute value of 2.5V or more and a decolorization potential of 2V or less.
Providing a copper nitride layer having a mass ratio of copper and nitrogen in the range of 0.05? N / Cu? 0.2 on one electrode layer; And
And providing a graphite layer having a mass ratio of oxygen and carbon in the range of 0.005? O / C? 0.3 on the other electrode layer.
The method of claim 19, wherein the copper nitride layer or the graphite layer is formed by a method selected from the group consisting of deposition, spin coating, dip coating, screen printing, gravure coating, sol-Gel method, Wherein the electrochromic device is provided by a method of a slot die.
20. The method of claim 19, further comprising the step of providing a solid electrolyte layer on one side of either the copper nitride layer or the graphite layer, wherein the solid electrolyte layer comprises a gel-polyelectrolyte or an inorganic solid electrolyte A method of manufacturing an electrochromic device.

Images