Electrochromic device

Abstract

The present application relates to an electrochromic device and a method for manufacturing the electrochromic device. The present application can provide an electrochromic device having increased productivity and improved electrochromic rate and durability, and a method for manufacturing the electrochromic device. The electrochromic device may be advantageously used in various devices such as smart windows, smart mirrors, displays, electronic papers and adaptive camouflage.

Claims

1. An electrochromic device sequentially comprising a first electrode layer, a composite electrochromic layer, an electrolyte layer, an ion storage layer and a second electrode layer, wherein said composite electrochromic layer comprises a laminate structure of a plurality of electrochromic layers, at least two electrochromic layers among said plurality of electrochromic layers have densities different from each other, and the electrochromic layer having a higher density among said at least two electrochromic layers having different densities is disposed closer to said first electrode layer than the electrochromic layer having a lower density, wherein each of said two electrochromic layers comprises metal oxide and said two electrochromic layers have a density difference of 0.1 g/cm.sup.3 or more, and wherein said electrochromic layer having the higher density has a density of 5.0 g/cm.sup.3 to 8.0 g/cm.sup.3.

2. The electrochromic device according to claim 1, wherein said two electrochromic layers having different densities are driven adjacent to each other.

3. The electrochromic device according to claim 1, wherein said two electrochromic layers having different densities are directly laminated to each other.

4. The electrochromic device according to claim 1, wherein said electrochromic layer having the lower density has a density of 3.0 g/cm.sup.3 to 7.0 g/cm.sup.3.

5. The electrochromic device according to claim 1, wherein each of said two electrochromic layers having different densities has a thickness of 10 nm to 800 nm.

6. The electrochromic device according to claim 1, wherein said electrochromic layer having the lower density is a porous film as compared to said electrochromic layer having the higher density.

7. The electrochromic device according to claim 1, wherein each of said two electrochromic layers having different densities comprises at least one metal oxide of metal oxides of tungsten (W), titanium (Ti), vanadium (V), molybdenum (Mo), niobium (Nb), chromium (Cr), manganese (Mn), iron (Fe), nickel (Ni), cobalt (Co), iridium (Ir) and lithium nickel (LiNi).

8. The electrochromic device according to claim 1, wherein each of said two electrochromic layers having different densities comprises the same kind of electrochromic material.

9. The electrochromic device according to claim 1, wherein said ion storage layer comprises an oxidatively conductive material when the composite electrochromic layer comprises a reductively electrochromic material, or a reductively conductive material when the composite electrochromic layer comprises an oxidatively electrochromic material.

10. The electrochromic device according to claim 1, wherein said electrolyte layer comprises an electrolyte salt, and said electrode layer comprises a transparent conductive material.

11. A method for manufacturing an electrochromic device, comprising a process of sequentially laminating on a first electrode layer a composite electrochromic layer, an electrolyte layer, an ion storage layer and a second electrode layer, wherein said composite electrochromic layer comprises a laminate structure of a plurality of electrochromic layers, and at least two electrochromic layers among said plurality of electrochromic layers have densities different from each other and are laminated such that the electrochromic layer having a higher density among said two electrochromic layers having different densities is disposed adjacent to said first electrode layer as compared to the electrochromic layer having a lower density, wherein each of said two electrochromic layers comprises metal oxide and said two electrochromic layers have a density difference of 0.1 g/cm.sup.3 or more, and wherein said electrochromic layer having the higher density has a density of 5.0 g/cm.sup.3 to 8.0 g/cm.sup.3.

12. The method for manufacturing the electrochromic device according to claim 11, wherein the adjustment of density in said plurality of electrochromic layers to be different from each other is performed by laminating any one electrochromic layer among said plurality of electrochromic layers in the form of a porous film as compared to any other electrochromic layer.

13. The method for manufacturing the electrochromic device according to claim 12, wherein the lamination of said electrochromic layer in the form of a porous film is performed by applying a sputtering process thereto, with a proviso that the process pressure condition is adjusted, or by applying an electron beam evaporation process thereto, with a proviso that the gas condition is adjusted.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 illustratively shows an electrochromic device according to one embodiment of the present application.

(2) FIGS. 2 to 5 are current graphs of Examples 1 to 3 and Comparative Example 1, respectively.

(3) FIG. 6 is coloring and bleaching images of Example 1 at 750 cycles.

(4) FIG. 7 is coloring and bleaching images of Example 2 at 750 cycles.

(5) FIG. 8 is a coloring image of Example 3 at 400 cycles.

(6) FIGS. 9 to 11 are charge amount graphs of Examples 1 to 3, respectively.

(7) FIGS. 12 to 14 are transmittance and charge amount graphs of Examples 1 to 3, respectively.

(8) FIGS. 15 to 16 are charge amount graphs of Example 2 and Comparative Example 2, respectively.

(9) FIG. 17 is a coloring image of Comparative Example 2 at 50 cycles.

(10) FIG. 18 is a transmittance and charge amount graph of Comparative Example 2.

MODE FOR INVENTION

(11) Hereinafter, the contents of the present application will be described in more detail through Examples and Comparative Examples, but the scope of the present application is not limited to the following contents.

Measurement Example 1

(12) The thin film density of the electrochromic layer was measured by one second every 0.002 degrees from 0.2 degrees to 2.4 degrees of 2 theta using XRR (X-ray reflectometry) analysis method.

Example 1

Stack: Glass/ITO/WOx (1)/WOx (2)/GPE/LiNixOy/ITO/PET Film

Manufacture of Working Electrode

(13) A first electrochromic layer (121) was formed by forming plasma on a W (tungsten) target by using a DC sputter on an ITO layer laminated on a glass substrate and injecting Ar and O.sub.2 gas into a chamber through an active reaction such that the WOx (tungsten oxide) was provided in a form of a thin film having a thickness of about 30 nm. A second electrochromic layer (122) was formed on the first electrochromic layer (121) by the electron beam evaporation setting the WOx source at a high voltage of 6.03 kV and an evaporation rate of 0.5 nm/sec such that the WOx (tungsten oxide) was provided in a form of a thin film having a thickness of about 150 nm. The first electrochromic layer (121) has a density of about 6.30.1 g/cm.sup.3, and the second electrochromic layer (122) has a density of about 5.80.1 g/cm.sup.3.

Manufacture of Counter Electrode

(14) An ion storage layer (22) was formed by forming plasma on a LiNiO.sub.2 target using a DC sputter on an ITO layer laminated on a PET film and injecting Ar and O.sub.2 gas into a chamber through an active reaction such that the LiNixOy was provided in a form of a thin film having a thickness of about 75 nm.

Manufacture of Electrochromic Device

(15) Using a gel polymer electrolyte comprising a mixture of PC (propylene carbonate) and LiClO.sub.4, an electrochromic device was manufactured by bonding the working electrode and the counter electrode together such that the second electrochromic layer (122) and the ion storage layer (22) were in contact with the gel polymer electrolyte (3).

Example 2

Stack: Glass/ITO/WOx (1)/WOx (2)/GPE/LiNixOy/ITO/PET Film

(16) An electrochromic device was manufactured in the same manner as in Example 1, except that in forming the first electrochromic layer (121) in Example 1, it was provided in a form of a thin film having a thickness of about 60 nm by increasing the DC sputter time twice. The first electrochromic layer thin film (121) has a density of about 6.30.1 g/cm.sup.3, and the second electrochromic layer thin film (122) has a density of about 5.80.1 g/cm.sup.3.

Example 3

Stack: Glass/ITO/WOx (1)/WOx (2)/GPE/LiNixOy/ITO/PET Film

(17) An electrochromic device was manufactured in the same manner as in Example 1, except that in forming the first electrochromic layer thin film (121) in Example 1, it was provided in a form of a thin film having a thickness of about 90 nm by increasing the DC sputter time three times. The first electrochromic layer thin film (121) has a density of about 6.30.1 g/cm.sup.3, and the second electrochromic layer thin film (122) has a density of about 5.80.1 g/cm.sup.3.

Comparative Example 1

Stack: Glass/ITO/WOx/GPE/LiNixOy/ITO/PET Film

(18) An electrochromic device was manufactured in the same manner as in Example 1, except that in manufacturing the working electrode and forming the first electrochromic layer thin film (121) in Example 1, the electrochromic layer was formed in a single layer structure of a thin film having a thickness of about 420 nm by increasing the DC sputter time fourteen times. The electrochromic layer thin film has a density of about 6.30.1 g/cm.sup.3.

Comparative Example 2

Stack: Glass/ITO/WOx (2)/WOx (1)/GPE/LiNixOy/ITO/PET Film

(19) An electrochromic device was manufactured in the same manner as in Example 2, except that in manufacturing the working electrode in Example 2, the second electrochromic layer (122) having a density of about 5.80.1 g/cm.sup.3 was first formed on the ITO electrode layer, and the first electrochromic layer (121) having a density of about 6.30.1 g/cm.sup.3 was formed on the second electrochromic layer (122).

Drive and Degradation Evaluation of Electrochromic Device

(20) The electrochromic device manufactured in Examples and Comparative Examples were driven under the following conditions to evaluate presence of degradation, and the results were shown in FIGS. 2 to 9. Driving Bias: AC voltage of 2 to +2 V Duration Time: 100 s (coloring)100 s (bleaching)

(21) FIGS. 2 to 5 show changes in the current amount of the electrochromic devices of Examples 1 to 3 and Comparative Example 1 upon coloring and bleaching according to the elapsed time and the cycle number, respectively. As shown in FIGS. 2 to 5, in Comparative Example 1, degradation occurs after 100 cycles, while in Examples 1 and 2, degradation does not occur even at 800 cycles or more and in Example 3, degradation does not occur up to about 150 cycles, and thus it can be confirmed that Example 3 has superior durability to that of Comparative Example 1. FIGS. 7 and 8 are coloring and bleaching images of the electrochromic devices of Examples 1 and 2 after driving 750 cycles, respectively, and FIG. 9 is a coloring image of Example 3 after driving 400 cycles. In Example 3, degradation proceeded at 400 cycles and there was no color difference between coloring and bleaching. FIGS. 9 to 11 show changes in the charge amount of the electrochromic devices of Examples 1 to 3 upon coloring and bleaching according to the elapsed time, respectively. As the charge amount increases, it may mean that Li+ ions contribute highly to coloring and bleaching or electrochromism. As shown in FIGS. 9 and 11, it can be confirmed that in the case of Examples 1 and 2, the electrochromic devices exhibit the stable electrochromic characteristics up to about 750 cycles without decreasing the charge amount. FIGS. 12 to 14 show changes in the transmittance and the charge amount of the electrochromic devices of Examples 1 to 3 upon coloring and bleaching according to the cycle number, respectively.

(22) FIGS. 15 to 16 show changes in the charge amount of the electrochromic devices of Example 2 and Comparative Example 2 upon coloring and bleaching according to the elapsed time, respectively. As shown in FIGS. 15 to 16, it can be confirmed that in Example 2, the electrochromic device shows stable electrochromic characteristics without decreasing the charge amount according to the elapsed time, whereas in Comparative Example 2, the charge amount decreases after 50 cycles. FIG. 17 is a coloring image of Comparative Example 2 after driving 50 cycles. In Comparative Example 2, degradation proceeded after driving 50 cycles and there was no color difference between coloring and bleaching. FIG. 18 shows changes in the transmittance and the charge amount of the electrochromic device of Comparative Example 2 upon coloring and bleaching according to the cycle number.

EXPLANATION OF REFERENCE NUMERALS

(23) 10: first substrate, 11: first electrode layer, 12: composite electrochromic layer, 122: second electrochromic layer, 121: first electrochromic layer, 20: second substrate, 21: second electrode layer, 22: ion storage layer, 3: electrolyte layer