KR20220004575A - An electrochromic material, an electrochromic device comprising the same, and a method of manufacturing the electrochromic device - Google Patents

Abstract

The present invention relates to electrochromic material comprising a conductive polymer doped with polyanion and acidic material, which is suitable for use as a large-scale electrochromic device using a solution-processable coating process, and has an effect of having high coloring efficiency, fast response time, and excellent stability when applied to the electrochromic device with an optimal doping effect.

Description

An electrochromic material, an electrochromic device comprising the same, and a method of manufacturing the electrochromic device

The present invention relates to an electrochromic material, an electrochromic device comprising the same, and a method of manufacturing the electrochromic device.

Electrochromic devices have been widely studied for use in a variety of applications, including energy-efficient buildings, optical information displays, and electronic paper. Currently, commercial electrochromic devices are mainly applied to smart windows that can effectively reduce energy consumption by controlling the amount of sunlight that enters the building. Smart windows installed in buildings can also replace curtains or blinds, improving their aesthetics.

The electrochromic material used in the electrochromic device as described above is a material in which optical properties such as transmittance, reflectance, and absorption are reversibly changed when a voltage is applied. A number of transition metal compounds (WO ₃ , MoO ₃ , NiO and iron(III) hexacyanoferrate(II)), viologens and conjugates as electrochromic materials Polymers and the like have been studied.

For example, an A4-sized electrochromic device coated with PEDOT:PSS as an electrochromic material on a nanofiber (AgNF) electrode has been reported (Non-Patent Document 1). However, since the electrochromic element disclosed in Non-Patent Document 1 is manufactured only with a transparent AgNF electrode by a roll-to-roll process, it was difficult to manufacture the electrochromic element in multiple layers. In addition, it was reported that an inorganic electrochromic material (WO ₃ ) was deposited on an indium tin oxide (ITO) electrode through sputter deposition to manufacture an electrochromic device with an area of ^{200 x 180 mm 2 (Non-Patent Document 2).} It uses transparent electrodes such as ITO, fluorine-doped tin oxide (FTO) and silver nanowires (AgNW). High-temperature heat treatment is required for deposition of inorganic materials, and electrical properties of inorganic materials are reduced by repeated bending. have.

Therefore, in order to manufacture an electrochromic device having utility that can be commercially produced, it is necessary to develop an electrochromic material that can be manufactured over a large area, has excellent processability, sufficient optical contrast, fast switching speed, and flexibility.

S. Lin, X. Bai, H. Wang, H. Wang, J. Song, K. Huang, C. Wang, N. Wang, B. Li, M. Lei, Advanced Materials 2017, 29, 1703238. G. Cai, P. Darmawan, X. Cheng, P. S. Lee, Advanced Energy Materials 2017, 7, 1602598.

An object of the present invention is to provide an electrochromic device that can be commercially produced and has sufficient optical contrast, fast switching speed and flexibility, and a method for manufacturing the same.

The present invention provides an electrochromic material comprising a conductive polymer doped with a polyanion and an acidic material.

In addition, the present invention provides a method for producing an electrochromic material comprising the steps of preparing an aqueous dispersion containing a polyanion and an acidic material, and mixing a conductive polymer monomer in the aqueous dispersion.

In addition, the present invention provides a working electrode coated with an electrode material on a substrate, a counter electrode coated with an electrode material on a substrate, and the electrochromic material of any one of claims 1 to 4, and positioned between the working electrode and the counter electrode. An electrochromic device comprising an electrolyte is provided.

In addition, the present invention provides a method for manufacturing an electrochromic device using a roll-to-roll process, comprising the steps of coating an electrode material on a substrate to prepare a working electrode, coating the working electrode with an electrolyte, and coating the electrolyte It provides a method of manufacturing an electrochromic device comprising the step of stacking a counter electrode on the working electrode.

The electrochromic material according to the present invention has an optimized doping effect, and the electrochromic device using the same exhibits high coloring efficiency, fast response time, and excellent flexibility.

In addition, the smart window using the electrochromic device is excellent in energy saving effect by controlling the transmittance of solar radiation by controlling the absorption of light.

In addition, the method for manufacturing an electrochromic device according to the present invention uses a coating process that can be treated by a solution by a roll-to-roll method, so that the electrochromic device can be manufactured on a large scale.

1 is a schematic diagram showing a method of manufacturing an electrochromic material according to the present invention.
2 is a graph showing the FT-IR spectrum of PANI.
3 is an SEM image of the electrochromic material prepared according to Comparative Example 1 (a), Preparation Example 1 (b), Preparation Example 2 (c), and Preparation Example 3 (d) of the present invention.
4 is an AFM image of the electrochromic material prepared according to Comparative Example 1 (a) and Preparation Example 2 (b) of the present invention.
5 is an image of a film using the electrochromic material of Comparative Example 1 and Preparation Example 2.
6 is a graph showing transmittance and haze measured using a UV-Vis-NIR spectrophotometer.
7 is a graph showing absorbance (a) measured using a UV-Vis-NIR spectrophotometer and absorbance measured using a UV-Vis-NIR spectrophotometer in a range of 600 to 900 nm (b).
8 is a graph showing the electrical conductivity of Preparation Examples 1 to 3 and Comparative Examples according to the present invention.
9 is a graph showing cyclic voltage and current curves of electrochromic materials according to Comparative Example 1 (a) and Preparation Example 2 (b), respectively.
10 is a schematic diagram of an electrochromic device according to the present invention.
11 is an absorption spectrum using a UV-vis-NIR spectrophotometer of the electrochromic device according to Comparative Example 2 (a) and Example (b) for different voltages.
12 is an image showing discoloration (a) and coloring (b) states of the electrochromic device of Example 2 according to the present invention.
13 is a graph showing the optical response time of the electrochromic device according to Comparative Example 2 (a) and Example 2 (b), respectively.
14 is a graph showing the coloring efficiency at 600 nm wavelength of the electrochromic device according to Comparative Example 2 (a) and Example 2 (b), respectively.
15 is a graph showing a cyclic voltage current curve (a) and an absorbance spectrum of the electrochromic device with respect to repeated bending cycles (b) of the electrochromic device according to Example 2;
16 is a two-electrode cyclic voltammetry curve (a) of the electrochromic device according to Example 6 and a two-electrode cyclic voltammetry curve (b) of the electrochromic device according to Example 7;
17 is a two-electrode cyclic voltammetry curve of the electrochromic device according to Example 4.
18 is a two-electrode cyclic voltammetry curve of the electrochromic device according to Example 5;
19 is a graph (a) showing the surface charge capacity ratio according to the sulfuric acid content of the electrochromic devices of Examples 1, 2 and Comparative Example 2, and PANI: PSS of the electrochromic devices of Examples 2 to 5; It is a graph (b) showing the surface charge capacity ratio according to the thickness.
20 is a schematic diagram of a roll-to-roll coating process for an electrochromic device according to the present invention.
21 is an image (a and b) of a large-scale electrochromic device manufactured by a roll-to-roll process according to the present invention, and a voltage-off state (c) and voltage of the electrochromic device (500 mm × 600 mm) according to the present invention, respectively; It is an image showing the on state (d).
22 is an image showing the equipment for evaluating the energy saving effect of the smart window (a), without using the smart window (b) and using the smart window (c) in a box with a size of 300 mm × 210 mm × 150 mm It is a graph.
23 is a graph showing the heat shielding efficiency of a smart window.

Since the present application can make various changes and can have various embodiments, specific embodiments are illustrated in the drawings and described in detail in the detailed description.

However, this is not intended to limit the present application to a specific embodiment, it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present application. In describing the present application, if it is determined that a detailed description of a related known technology may obscure the gist of the present application, the detailed description thereof will be omitted.

Terms such as first, second, etc. may be used to describe various elements, but the elements should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another.

The terms used in the present application are used only to describe specific embodiments, and are not intended to limit the present application. The singular expression includes the plural expression unless the context clearly dictates otherwise.

In the present application, terms such as “comprises” or “have” are intended to designate that a feature, number, step, operation, component, part, or combination thereof described in the specification exists, but one or more other features It should be understood that this does not preclude the existence or addition of numbers, steps, operations, components, parts, or combinations thereof.

Accordingly, the configuration shown in the embodiment described in the present specification is only one of the most preferred embodiments of the present application and does not represent all the technical ideas of the present application, so various equivalents that can be substituted for them at the time of the present application and variations.

In addition, it should be understood that the accompanying drawings in the present application are enlarged or reduced for convenience of description.

The present invention provides an electrochromic material comprising a conductive polymer doped with a polyanion and an acidic material.

Electrochromism refers to a phenomenon in which the color changes reversibly depending on the direction of the electric field when a voltage is applied.

The polyanion is a polymer having two or more monomer units having an anion group in a molecule, and the anion group of the polyanion may act as a dopant for the conductive polymer to improve the conductivity of the conductive polymer.

The anion group of the polyanion may be a sulfone group or a carboxyl group.

The polyanion may be, for example, polystyrene sulfonate, polyvinyl sulfonate, polyvinyl carboxylate, or polystyrene carboxylate.

The polyanion may be polystyrene sulfonate in terms of improving the conductivity of the conductive polymer.

The acidic material is dissolved in water and ionized to release hydrogen ions, and may be, for example, nitric acid, hydrochloric acid, phosphoric acid, sulfuric acid, hydrofluoric acid, hydrobromic acid, or iodic acid.

In the present invention, by adding an acidic material as a dopant to the conductive polymer, the electrical conductivity of the electrochromic material is improved, and the electrochromic device including the same can exhibit high coloring efficiency, fast response time, and excellent flexibility.

In addition, in the present invention, the polyanion and the acidic material act as a dopant for the conductive polymer, and as a synergistic effect according to the combination thereof, the electrical conductivity of the electrochromic material is improved, and the electrochromic device including the same has high coloring efficiency, It can exhibit fast response time and excellent flexibility.

The conductive polymer is a polythiophene-based polymer represented by PEDOT (poly(3,4-ethylene dioxythiophene)), polypyrrole, polyaniline, polyacetylene, polyparaphenylene, polyparaphenylene vinylene, or polyfluorenyl may be, for example, the conductive polymer may be polyaniline. When polyaniline is used as a conductive polymer, there is an advantage that it can be treated with a solution, and through this, it is possible to manufacture a large-scale electrochromic device.

The electrochromic material may have a maximum absorption peak in the range of 730 nm to 773 nm when measuring UV-vis 　 absorption spectrum, for example, 750 nm to 773 nm, 755 nm to 773 nm, 760 nm to 773 nm, 760 nm to 770 nm, or 750 nm to 760 nm have.

In this case, the electrochromic material not doped with the dopant of the acidic material may have a wavelength higher than the above range. That is, in the electrochromic material according to the present invention, the maximum absorption peak may be shifted to a shorter wavelength when measuring the UV-vis 　 absorption spectrum due to the doping effect of the acidic material.

When measuring the UV-vis　 absorption spectrum, the deviation of the maximum absorption peak (B) of the electrochromic material doped with an acid from the maximum absorption peak (A) of the electrochromic material not doped with the acidic material may be 1 to 80 nm, e.g. For example, it may be 1 to 50 nm, 1 to 30 nm, 1 to 20 nm, or 1 to 10 nm.

In addition, the electrochromic material may have a surface roughness (RMS(Rq): root mean square) value of 1.8 nm or more calculated through an atomic force microscope (AFM) image, for example, the surface roughness ( Rq) may be 2.0 nm or more, 2.5 nm or more, or 3.0 nm or more. The upper limit is not particularly limited, but may be 5 nm or less.

The electrochromic material may have an increased particle size due to the doping effect of the acidic material, and thus may have a high surface roughness, and thus the electrical conductivity of the electrochromic material may be increased.

In addition, the electrochromic material may have a haze measured by ASTM D1003 of 10.0% or less, for example, 8% or less, 7% or less, or 6% or less, and the lower limit is not particularly limited, but may be 1% or more have.

The haze may increase when the content of the acidic material increases, and when the haze is high, it is not preferable to apply the haze to the smart window.

In addition, the electrochromic material may have an electrical conductivity of 0.01Scm ^{-1 or} more, for example, 0.04Scm ^-1 or more, 0.05Scm ^-1 or more, 0.1Scm ^-1 or more, 1.0Scm ^-1 or more, or 2.0Scm ^-1 or more, and the upper limit may be 2.5Scm ^-1 or less, 3.0Scm ^-1 or less, or 3.5Scm ^-1 or less.

The transmittance of the electrochromic material using a UV-Vis-NIR spectrophotometer may be 85% or more or 87% or more.

The electrochromic material according to the present invention satisfies the haze, electrical conductivity and transmittance ranges as described above, so that it is transparent while having high coloring efficiency, fast response time, and excellent flexibility when manufacturing an electrochromic device including the same, so that it is suitable for a smart window. can

In addition, the present invention provides a method for producing an electrochromic material comprising the steps of preparing an aqueous dispersion containing a polyanion and an acidic material, and mixing a conductive polymer monomer in the aqueous dispersion.

The acidic substance may be sulfuric acid, and the concentration of the acidic substance may be 0.01 to 1M, for example, the concentration of the acidic substance is 0.01 to 0.7M, 0.01 to 0.3M, 0.1 to 0.7M, or 0.3 to 0.7 may be M.

The concentration of the acidic material may be based on the volume of deionized water used.

When the concentration of the acidic material satisfies the above range, the prepared electrochromic material may have low haze and high transmittance while having high electrical conductivity.

The polyanion may be polystyrene sulfonate.

The conductive polymer monomer may be aniline.

Since the polyanion and the acidic material act as first and second dopants for the conductive polymer, respectively, the electrochromic material prepared by the doping effect may have high electrical conductivity and low haze and high transmittance, including When manufacturing an electrochromic device, it can be suitable for a smart window because it is transparent while having high coloring efficiency, fast response time, and excellent flexibility.

In addition, the present invention is a working electrode coated with an electrode material on a substrate; a counter electrode coated with an electrode material and the electrochromic material on a substrate; and an electrolyte positioned between the working electrode and the counter electrode may be provided.

In this case, the counter electrode may be coated with an electrochromic material thereon after the electrode material is coated on the substrate.

The electrode material may be PEDOT　:　PSS (Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)).

The coating thickness of the electrochromic material may be 100 nm to 700 nm, for example, the coating thickness of the electrochromic material may be 300 nm to 700 nm, 450 nm to 700 nm, 450 nm to 600 nm, 450 nm to 580 nm.

The electrochromic device according to the present invention includes an electrochromic material as a counter electrode, so it can have high coloring efficiency, fast response time, and excellent flexibility, and can be solution processed, so that a large-scale electrochromic device can be manufactured.

In addition, the present invention provides a method for manufacturing an electrochromic device using a roll-to-roll process, comprising the steps of: preparing a working electrode by coating an electrode material on a substrate; coating the working electrode with an electrolyte; and laminating a counter electrode on the working electrode coated with the electrolyte.

The counter electrode may include a substrate; an electrode material coated on the substrate; and the aforementioned electrochromic material coated on the electrode material.

The coated electrochromic material may have a thickness of 450 nm to 600 nm. In addition, the thickness of the electrode material may be 450 nm to 600 nm. In the case of having the thickness range as described above, the amount of electric charge transferred during oxidation-reduction may be properly balanced to have an excellent electrochemical effect.

The electrolyte may include hydroquinone. By including hydroquinone in the electrolyte, the lifetime stability of the electrochromic device may be increased.

Hereinafter, specific embodiments of the present invention are presented. However, the examples described below are only for specifically illustrating or explaining the present invention, and thus the present invention is not limited thereto.

The reagent used in the present invention is 3,4-ethylenedioxythiophene (3,4-Ethylenedioxythiophene, EDOT, 97%), aniline (Ani, ≥ 99.5%), sodium persulfate (Na2S2O8, ≥ 99.0%), ferric sulfate ( Iron(III) sulfate, Fe ₂ (SO ₄ ) ₃ , 97 %], poly(styrene sulfonate) (PSS), dimethyl sulfoxide (DMSO), poly(ethylene glycol) diacrylate , PEGDA, C ₁₀ H ₁₄ O ₄ , average Mn 700), 1-hydroxycyclohexyl phenyl ketone (C ₁₃ H ₁₆ O ₂ , 99 %), hydroquinone (C ₆ H ₆ O ₂ ), Ferrocenecarboxylic acid acid, FcCOOH), cation exchange resin and anion exchange resin were purchased from Sigma Aldrich Co., and acrylamide (C ₃ H ₅ NO, 98 ⁺ %) was obtained from Thermo Fisher Scientific Inc. ( Thermo Fisher scientific Inc.,).In addition, BYK-3440 was purchased from BYK, and sulfuric acid solution (H ₂ SO ₄ ) was purchased from Duksan reagents.All reagents were used without further purification. and distilled deionized water (DDI) was used throughout the experiment.

Preparation of electrochromic material - Preparation Examples 1 to 4 and Comparative Examples

Sulfuric acid-doped PANI: PSS was synthesized as an electrochromic material in which an acidic material (sulfuric acid) and polyanion (PSS) were doped into a conductive polymer (polyaniline, PANI) through chemical oxidation polymerization.

Specifically, an aqueous dispersion of 62.54 ml of PSS solution and 0.05M sulfuric acid was gently stirred and then degassed with inert nitrogen gas (N2, 99.999%) for 30 minutes. To the stirred solution, oxidizing agent, ferric sulfate (0.057 g in distilled water) and sodium persulfate (3.43 g in distilled water) were added at room temperature and stirring was continued for 30 minutes. The solution was mixed with an aniline monomer (1.2 ml) to initiate a polymerization reaction, and the reaction was allowed to proceed for 23 hours so that the contents were dark green. To remove residual ions, the product was mixed with cation and anion exchange resins at room temperature for 1 hour. Finally, the mixture was filtered, and a dark green liquid solution was obtained as a filtrate, which was referred to as Preparation Example 1.

An electrochromic material was prepared in the same manner as in Preparation Example 1, except that the concentration of sulfuric acid was changed to 0.2M (Preparation Example 2), 0.5M (Preparation Example 3) and 1.0M (Preparation Example 4).

Comparative Example 1

In order to compare the electrochemical properties and the electrochromic properties, PANI: PSS not doped with sulfuric acid was used as a comparative example. Except for the addition of sulfuric acid, it was synthesized in the same manner as in Preparation Example.

Preparation of electrochromic device - Examples 1 to 7 and Comparative Example 2

Example 1

Manufacture of working electrode

Polyethylene terephthalate (PET) was used as a substrate, and PEDOT: PSS was used as an electrode material.

Specifically, PEDOT: PSS was coated on a PET substrate to a thickness of 550 nm by a bar-coating method, and then dried at 150° C. for 4 minutes using a convection oven.

Preparation of counter electrode

PEDOT: PSS was coated on a PET substrate to a thickness of 550 nm by a bar-coating method, and then dried at 150° C. for 4 minutes using a convection oven. Thereafter, the 0.05M sulfuric acid-doped PANI:PSS film of Preparation Example 1 was coated on the PEDOT:PSS electrode coated on the PET substrate as an anode electrochromic layer to a thickness of 550 nm.

Thereafter, a drying process was performed at 150° C. for 4 minutes using a convection oven in the same manner as in the above method.

Preparation of electrolytes

A polymer electrolyte solution was prepared by mixing the resin solution and 1M H ₂ SO ₄ in a weight ratio of 1:1. The resin solution was prepared by dissolving 0.115 g of 1-hydroxycyclohexyl phenyl ketone as a photoinitiator and 0.788 g of PEGDA as a crosslinking agent in DMSO solvent in 8 g of acrylamide. As the electron donor, hydroquinone (HQ) was added to the solution at 0.7% by weight of the total solution.

Manufacturing of electrochromic devices

Polyelectrolyte was coated on the working electrode with a doctor blade and photocured with UV light at a wavelength of 365 nm for 10 seconds. The electrochromic device was manufactured by assembling the electrolyte-coated working electrode and the counter electrode in a roll-to-roll process.

Specifically, a PEDOT: PSS coated PEDOT: PSS working electrode was coated with a polymer electrolyte on a 500 mm wide PET substrate through a roll-to-roll process consisting of a pump, slot-die head, thermal drying zone and UV curing lamp. After being deposited (deposited), a UV curing process was performed at ^{24,000J/cm 2 light quantity.}

Also, PEDOT:PSS was coated on a PET substrate in the same roll-to-roll process, and then PANI:PSS was coated and cured to prepare a counter electrode.

The electrochromic device was manufactured by laminating the previously prepared counter electrode on an electrolyte-coated PEDOT:PSS working electrode in a roll-to-roll process.

Example 2

An electrochromic device was manufactured in the same manner as in Example 1, except that the 0.2M sulfuric acid-doped PANI:PSS film of Preparation Example 2 was used as the anode electrochromic layer in the counter electrode.

Example 3

An electrochromic device was manufactured in the same manner as in Example 2, except that PANI:PSS was coated to a thickness of 250 nm on the counter electrode.

Example 4

An electrochromic device was manufactured in the same manner as in Example 2, except that PANI:PSS was coated to a thickness of 400 nm on the counter electrode.

Example 5

An electrochromic device was manufactured in the same manner as in Example 2, except that PANI:PSS was coated to a thickness of 600 nm on the counter electrode.

Example 6

An electrochromic device was prepared in the same manner as in Example 2, except that hydroquinone (HQ) was added to the solution in an amount of 0.5% by weight of the total solution as an electron donor in the electrolyte.

Example 7

An electrochromic device was prepared in the same manner as in Example 2, except that hydroquinone (HQ) as an electron donor in the electrolyte was added to the solution at 0.5% by weight of the total solution and FcCOOH at 0.1% by weight of the total solution.

Example 8

An electrochromic device was prepared in the same manner as in Example 2, except that FcCOOH was added to the solution in an amount of 0.1% by weight of the total solution as an electron donor in the electrolyte.

Example 9

An electrochromic device was prepared in the same manner as in Example 2, except that FcCOOH was added to the solution in an amount of 0.2% by weight of the total solution as an electron donor in the electrolyte.

Comparative Example 2

Sulfuric acid-doped PANI: An electrochromic device was prepared in the same manner as in Example 2, except that the PSS film was not used as the anode electrochromic layer.

The characteristics of Examples 1 to 7 and Comparative Example 2 are summarized in Table 1 below.

division counter electrode electrolyte sulfuric acid (M) Thickness (nm) electron donor content (wt%) Example 1 0.05 550 HQ 0.7 Example 2 0.2 550 HQ 0.7 Example 3 0.2 250 HQ 0.7 Example 4 0.2 400 HQ 0.7 Example 5 0.2 600 HQ 0.7 Example 6 0.2 550 HQ 0.5 Example 7 0.2 550 HQ/FcCOOH 0.5/0.1 Example 8 0.2 550 FcCOOH 0.1 Example 9 0.2 550 FcCOOH 0.2 Comparative Example 2 - - HQ 0.7

Characterization

Morphological analysis of the electrode material (PEDOT: PSS) and the electrochromic material (PANI: PSS) was performed using a field emission scanning electron microscope (FE-SEM; JEOL-7800F). The surface morphology was analyzed using an atomic force microscope (AFM; Park systems/NX-10) in tapping mode, and FT-IR spectra were analyzed using an FT-IR spectrometer (Bruker, model Vertex 70) in ATR mode. was performed. The sheet resistance of the electrode material and the electrochromic material was measured by a 4-point probe method (NAPSON, RT-70V/RG5), and the thickness of the film was measured by a surface profiler (Bruker, Dektak XT Stylus Profiler). At this time, the thickness of each film was measured using a surface profiler to measure 5 times the thickness value, and an average value was calculated. Optical properties (transmittance and absorbance) were measured using a UV-Vis-NIR spectrophotometer (Avantes, Avalight-DH-s). Cyclic voltammetry was performed using a potentiometer (Parstat MC) in a three-electrode cell with working and counter electrodes and Ag wire as reference electrode. The temperature change and heat shielding properties to confirm the energy saving effect were measured using an infrared light bulb (250W, PHILIPS) and a thermal imaging camera (Testo 868). A black box (300 mm x 210 mm x 150 mm) made of acrylate was used to obtain the thermal profile, and a thermometer and an infrared lamp were used to measure the temperature change in the presence and absence of the electrochromic smart window film. The distance between the black box and the lamp was 300 mm and the IR lamp was operated for 300 seconds. In addition, the surface charge capacity ratio (Surface charge capacity ratio) was measured by chronoamperometry using a potentiometer (Parstat MC).

1 shows the synthesis process of an electrochromic material. For the synthesis of polyaniline (PANI) in PSS solution, chemical oxidation polymerization was used, and sulfuric acid was introduced as a second dopant. PSS allows PANI to be dispersed in water, which acts as a first dopant.

Figure 2 shows the FT-IR spectral characteristic peak of PANI. The C=C stretching vibration of the quinoid ring connected to the CH bending mode appears ^{at 1510 cm −1 .} The peak at 1503 cm ⁻¹ represents benzenoid and quinoid rings highlighting the conductive conformation of PANI:PSS. C-NH ^+· -C asymmetric stretching oscillations are ^{observed at 1124 to 1184 cm -1} _{, and NC 6} H ₄ -NH ^+· para-coupling of the disubstituted benzenoid ring is confirmed at 829 to 836 cm ^{-1 .}

PANI: Sulfuric acid was used as a second dopant to improve the electrochemical properties of PSS. For micro-scale analysis, the shape of the PANI:PSS film and the deformation of the PANI:PSS particles due to sulfuric acid doping were confirmed using a scanning electron microscope (SEM) and an atomic force microscope (AFM).

Referring to FIG. 3 , the SEM image shows that the flaky particles of PANI:PSS were transformed into a round shape as the doping concentration of _{H 2} SO _{4 increased.} 0.5MH ₂ SO ₄ doped PANI:PSS particles exhibited a columnar shape. This is because numerous PANI:PSS nanoparticles aggregate to form clusters after doping with sulfuric acid.

The AFM image showed a completely different surface morphology, and Preparation Examples 1 to 4 were rougher than Comparative Examples. In particular, referring to FIG. 4 , in Comparative Example (a), the surface roughness Rq(RMS) was 1.708 nm, whereas in Preparation Example 2(b), the surface was rough at 3.024 nm. This increase in roughness is due to the increase in the particle size of PANI:PSS caused by the additional doping effect.

FIG. 5 shows that a PANI: PSS film was manufactured by bar-coating the electrochromic material of Preparation Example on a PET substrate. As shown in Fig. 6, the PANI:PSS film transmittance was approximately 88% at a wavelength of 550 nm regardless _{of the H 2} SO _{4 doping level.}

7 a shows the absorption spectrum of the PANI:PSS film for _{different H 2} SO ₄ over the wavelength range of 200 to 1300 nm. The characteristic peaks of PANI appeared at wavelengths of 350 and 620 nm, respectively, corresponding to the π-π* excitation of the para-substituted benzenoid segment and the excitation of the quinoid segment. However, referring to FIG. 7b , the absorption peak (λmax at 774 nm) of the synthesized PANI:PSS shifts to a wavelength range of 754 to 772 nm. That is, as _{the molar concentration of H 2} SO ₄ increases, the maximum absorption peak of doped PANI:PSS shifts to a shorter wavelength. This blue shift is due to the doping effect by protonation of nitrogen sites in the PANI backbone, which is due to the addition of _{H 2} SO _{4 .}

Referring to FIG. 8 , as the doping level increased, the electrical conductivity of the PANI:PSS film was improved. However, the haze value of the PANI: PSS film was _{5.4% in the case of 0.5MH 2} SO ₄ (Preparation Example 3), but increased to 15.2% in the case of _{1.0MH 2} SO _{4 (Preparation Example 4).} The high haze value is due to the irregular distribution of PANI:PSS particle size due to excessive sulfuric acid dopant. This suggests that PANI:PSS doped with a concentration higher than _{0.5MH 2} SO _{4 is not suitable for application to electrochromic devices.}

As shown in Table 2 below _{, the electrical conductivity of Preparation Example 2 (0.2MH 2} SO ₄ doped PANI: PSS) was 0.116 Scm ^{-1 , which} was 23 times greater than the electrical conductivity of the PANI: PSS of Comparative Example 0.005 Scm ^{-1 .}

division Electrical conductivity [S cm ^-1 ] Transmittance [%] Electrode material (PEDOT:PSS) 892.1 72.2 Comparative Example 1 0.005 85.5 Preparation Example 1 0.041 88.4 Preparation 2 0.116 88.5 Preparation 3 2.010 88.5

Enhanced mobility of charge carriers in doped PANI:PSS is associated with increased charge transport. In order to explain the electrochemical properties of PANI: PSS, a cyclic voltammetry (CV) experiment was performed by linearly sweeping the potential in the range of -3.0 to 1.0 V at a scan rate of ^{100 mV s -1 .} Referring to FIG. 9 a, the PANI: CV curve of the PSS film shows two pairs of redox reactions, which are typical characteristics of PANI. The first redox couple in the range of 0.1V to 0.4V is PANI: between a leucoemeraldine salt (LES) and an emeraldine salt (ES) corresponding to the pale yellow to green color change of PSS. PANI: It is the result of metastasis of PSS. The second redox couple in the range of 0.6V to 0.8V corresponds to the redox transition of PANI:PSS between emeraldine salt (ES) and pernigraniline base (PNB, blue/purple). The color change associated with PANI:PSS in different oxidation states makes it suitable for use as an electrochromic material. In particular, referring to FIG. 9B , two oxidation potentials of the PANI:PSS film were lowered after doping, and the second oxidation peak had a lower oxidation potential after doping. This result suggests that the doped PANI:PSS film has excellent electrochromic properties.

10 shows the configuration of an electrochromic device based on a conductive polymer. PEDOT: PSS (25 Ω/sq, 72% at 550 nm) coated on a polyethylene terephthalate (PET) substrate serves as a cathode electrochromic material and an electrode. A counter electrode (count electrode) was used as a charge balancing layer, and a PANI: PSS film coated on the PEDOT: PSS counter electrode was used as a charge balancing layer and a secondary electrochromic layer.

PANI: PSS is an anode electrochromic material with three redox states. Polyaniline has two oxidation states that depend on the number of hydrogen atoms and electrons on the polyaniline backbone. The electrically conductive semi-oxidized state of emeraldine alternates between reduced (benzooid ring) and *?*oxidized form (quinoid ring). When complete oxidation occurs, the benzenoid ring structure changes to the quinoid ring structure, resulting in the formation of pernigranilin with a pure blue color with a low transmittance value. When complete reduction occurs, the quinoid ring changes from an emeraldine state to a benzenoid ring structure, which turns pale yellow with a high transmittance value.

An electrochromic device (200mm × 100mm) supplemented based on the above characteristics was designed. PEDOT: PSS and PANI: PSS films were colored or bleached in an applied voltage range of -3V to 1V. Absorbance spectra of the electrochromic devices of Example 2 and Comparative Example 2 at different applied voltages are shown in FIGS. 11A and 11B , respectively. A UV-Vis spectrometer was used to investigate the optical properties of the electrochromic device. The transmittance variable range value (optical modulation) of Example 2 at 600 nm wavelength was 54.3% at an alternating voltage between -3V and 1V, which was higher than Comparative Example 2 which was 35.3% at 600 nm.

The electrochromic device was manufactured using only PEDOT:PSS film as an electrode material, and an anode electrochromic material (PANI:PSS) was introduced as a counter electrode to improve the transmittance variable range value of the electrochromic device.

12 , when PANI:PSS on the counter electrode undergoes oxidation reaction, PEDOT:PSS on the working electrode is reduced. Conversely, when the PEDOT:PSS of the working electrode is oxidized and decolorized by applying a reverse bias to change from dark blue to pale blue, the PANI:PSS of the counter electrode decreases and turns to pale yellow. The above result means that the electrochromic properties are consistent with the CV test results. In addition, by introducing PANI:PSS into the counter electrode, it was confirmed that the response speed was improved. The presence of the PANI:PSS layer added on the counter electrode can achieve charge balance of the redox reaction in the electrochromic device.

Referring to FIG. 13 , the response time of the electrochromic device of Example 2(b) having a size of 200 mm × 100 mm, defined as the time required for a 90% change in full transmittance modulation, is 6.3 seconds for coloring, and 6.3 seconds for discoloration. In the case of , it was 16.4 seconds. The response time of the electrochromic device was 23.0 seconds for coloring and 82.5 seconds for discoloration in Comparative Example 2(a) using only PEDOT:PSS.

One of the important parameters for examining the performance of an electrochromic device is the coloration efficiency (CE), denoted by the symbol η, obtained as a function of the charge used to cause the light modulation. This parameter is defined as the relationship of injected and emitted charges as a function of electrode area and optical density change (ΔOD). Therefore, it plays an important role in determining the efficiency of the electrochromic device. This efficiency parameter (η) is calculated by the following equations (1) and (2).

[Equation 1]

[Equation 2]

where ΔQ is the difference in magnitude of the injected and emitted charge densities used to actuate the electrochromic device. Tc and Tb are light transmittances in colored and bleached states, respectively.

Referring to FIG. 14 , the calculated CE of the electrochromic device (b) of Example 2 is 1889 cm ² C ^{−1 As} an anode electrochromic material, PANI: PSS is not included, and PEDOT: PSS is used only in Comparative Example The CE value of 2(a), 382 cm ² C ^{-1 ,} was significantly higher. This is due to the fact that the introduction of PANI:PSS provided high optical density even with a small amount of filling. On the other hand, the PANI:PSS film color was changed with further decrease in charge density. Therefore, these results indicate that the PANI:PSS-based electrochromic device exhibits low power consumption and is suitable for the application of electrochromic smart windows.

Conductive polymers can provide much greater flexibility than conventional inorganic rigid electrochromic materials and ITO electrodes. Electrochromic materials fabricated using PEDOT: PSS and PANI: PSS offer the obvious advantage of flexible stability.

15 shows the results of measuring CV curves and absorption spectra through repeated bending tests to confirm the electrochemical and electrochromic stability of the electrochromic device of Example 2. FIG. Measurements for the bending test were performed under a radius of curvature of 5 mm, and CV analysis was performed at a scan rate of ^{100 mV s −1 at an applied bias between -3.0 V and 1.0 V in a two-electrode system.} Despite the slight negative shift of the oxidation current peak, the CV curve of the electrochromic device did not actually reduce the area of the closure curve even after repeated bending cycles, and showed a similar shape. The magnitude of the negative shift of the oxidation current peak during 1000 repeated bending cycles was approximately 0.8 mA, which is a very small difference considering the number of repetition cycles. Through this, it can be seen that the electrochromic properties of the electrochromic device of Example 2 are quite stable even after 1000 bending cycles, indicating that deterioration of the PANI:PSS and PEDOT:PSS films hardly occurs in the electrochromic device. .

16 to 18 are two-electrode cyclic voltammogram (CV) graphs of the electrochromic smart window film according to the type and content of the electron donor of the electrolyte layer of the electrochromic device according to an embodiment of the present application.

16a) is a two-electrode cyclic voltammogram (CV) of Example 8, an electrochromic smart window film prepared by adding 0.1 wt% of FcCOOH to the total electrolyte solution as an electron donor of the electrolyte layer. Measurement of A graph, b) is a two-electrode cyclic voltammogram (CV) of Example 9, which is an electrochromic smart window film prepared by adding 0.2 wt% of FcCOOH as an electron donor of the electrolyte layer to the total electrolyte solution. This is the measured graph.

Referring to FIG. 16 , in the durability measurement, in the case of Examples 8 and 9, the activity decreased after driving 6 times and 20 times, respectively.

17 is a graph of measuring the 2-electrode 2-electrode voltammogram (CV) of Example 6, which is an electrochromic film prepared by adding 0.5 wt% of HQ as an electron donor of the electrolyte layer compared to the total electrolyte solution. .

18 is a two-electrode cyclic voltammogram of Example 7, which is an electrochromic film prepared by adding 0.1 wt% of FcCOOH to the total electrolyte solution and 0.5 wt% of HQ compared to the total electrolyte solution as the electron donor of the electrolyte layer. , CV) is a measured graph.

17 and 18 , it was confirmed that Examples 6 and 7 hardly lost activity in the durability measurement.

In particular, Example 4 maintained its activity even after 1,000 runs. When 0.5 wt% or more of hydroquinone (HQ) was added as an electric donor compared to a 50% poly(styrenesulfonic acid) solution (PSSA), the durability of the electrochromic device was excellent.

Meanwhile, the results of measuring the surface charge capacity ratio (R) of the electrochromic devices of Examples 1 to 3 according to the present invention represented by Equation 4 below are shown in FIG. 19 .

[Equation 3]

Here, the Q value means the amount of electric charge moving at the interface between the electrolyte and the electrode layer when the color change of the electrochromic element occurs. Q _in means the amount of charge transferred between the PEDOT:PSS layer and the electrolyte by reduction, and Q _out means the amount of charge transferred between PANI:PSS and the electrolyte by oxidation. If the amount of charge at the interface where each redox occurs is a balanced value, the value of the surface charge capacity ratio (R) converges to close to 100%. It can be seen that this is done smoothly.

Referring to a of FIG. 19 , when the sulfuric acid content was 0M, the R (red) value was 58.2%, but in the case of Example 1 with 0.05M and Example 2 with 0.2M, 63.8% and 86.4%, respectively. . Accordingly, it was confirmed that in the case of Example 2, the amount of electric charge transferred during oxidation-reduction was balanced.

In addition, referring to FIG. 19 b, PANI: In the case of Example 2 in which the thickness of PSS is 550 nm, the R value is 80% or more, and the thickness is 250 nm (Example 3, R = 63%), 400 nm (Example 4) , R = 69%) and 600 nm (Example 5, R = 78.2%), the R value (green) was higher than that.

Through this, it was confirmed that both the doping concentration of sulfuric acid and the thickness of PANI:PSS affected the R value.

Based on these advantages of PEDOT: PSS and PANI: PSS as an electrochromic material for the solution coating process, a large-scale electrochromic device with a roll width of 500 mm was manufactured using a roll-to-roll (R2R) coating process, and its schematic It is shown in Figure 20.

In the studies so far, electrochromic devices can be used in smart windows, the color composition can be adjusted from light to dark colors or vice versa, and the light and heat of buildings using smart windows can be controlled by controlling the voltage and energy It has been known that by saving *?* can provide great environmental benefits.

However, in order to apply the electrochromic element to a smart window and use it commercially, it must be possible to manufacture the electrochromic element in a large area. The roll-to-roll process is a manufacturing method used in the manufacturing industry to coat, print or laminate various films on a flexible rolled base material, in which the material is transferred from one roller to another. continuously supplied.

The roll-to-roll coating system in the present invention consists of a pump and slot-die head, a thermal drying zone and a UV curing lamp. First, all PEDOT:PSS and PANI:PSS films were prepared by coating and drying PEDOT:PSS and PANI:PSS solutions on PET substrates of 500 mm width, respectively. After the polymer electrolyte was deposited on the coated PEDOT: PSS roll film, a UV curing process was performed under constant light intensity for a specific time. Then, a large-scale electrochromic smart window film was prepared by laminating a PANI: PSS counter electrode and a PEDOT: PSS working electrode. Because the electrochromic material can be solution-processed and can be processed at low temperature, a large-scale electrochromic device can be manufactured by a roll-to-roll process.

21 a and b show a large-scale electrochromic device in roll-up and sheet form, respectively. In addition, as shown in c and d of FIG. 21 , a prototype was manufactured to evaluate the applicability to a smart window. It was confirmed that the heat of the building was controlled by controlling the transmittance of the sun through the color change of the smart window when voltage was applied and the absorbance of near-infrared (NIR) solar radiation, which accounts for almost half of the solar radiation propagated through the smart window. . Through this, it is possible to achieve an energy saving effect by preventing an increase in the indoor temperature caused by light entering from the outside.

In addition, the temperature change was observed using an infrared lamp to confirm the energy saving effect of the smart window film. Specifically, as shown in a of FIG. 22, the target port was placed in a black box, the distance to the lamp was fixed at 300 mm, and the infrared lamp was exposed for 5 minutes to measure the temperature change due to the presence or absence of the smart window film. Referring to b and c of FIG. 22 , after 5 minutes of exposure, the internal temperature of the box without a window increased by 12.2°C, and the internal temperature of the box with a smart window increased by 3.5°C. Also, after 30 min exposure, the internal temperature of the box without the window increased by about 30°C, whereas the internal temperature of the box with the smart window showed a temperature increase of only 9°C.

In order to quantify the energy saving effect, the heat shielding efficiency was calculated in the NIR wavelength range of 780 to 2700 nm using Equations 4 to 6 below.

[Equation 4]

[Equation 5]

[Equation 6]

Here, SE _heat is the heat shielding efficiency, TE is the transmitted efficiency, and I _T is the total transmitted intensity corresponding to the sum of spectral irradiance for each wavelength. As shown in Fig. 20, the heat shielding efficiency of the electrochromic smart window was 99.8%, and this result shows that the presence of the smart window film can dissipate the heat inside the window and prevent the indoor temperature rise in summer. Therefore, electrochromic device systems based on conductive polymers have a very high potential for energy saving.

The present invention synthesized an electrochromic material suitable for use as a large-scale electrochromic device using a solution processable coating process. All materials for the manufacture of the electrochromic device were organic materials, and polyanions (PSS) and sulfuric acid were doped into the conductive polymer (PANI) to show an optimized doping effect.

The electrochromic smart window made of doped PANI: PSS showed high tinting efficiency ( ^{maximum tinting efficiency of 1889 cm 2} C ⁻¹ ), fast response time, and excellent stability. Doped PANI: With the introduction of PSS, the electrochromic properties are improved due to the improved charge transport, and the smart window controls the light absorption to control the transmittance of solar radiation, and thus the energy saving effect is excellent. In addition, by manufacturing an electrochromic smart window based on a conductive polymer through a roll-to-roll process, it is possible to manufacture a commercially available large-area device.

Claims (15)

An electrochromic material comprising a conductive polymer doped with a polyanion and an acidic material.
According to claim 1,
An electrochromic material having a maximum absorption peak in the range of 730 nm to 773 nm when measuring UV-vis absorption spectrum.
According to claim 1,
An electrochromic material having a root mean square (RMS) value of 1.8 nm or more calculated through an atomic force microscope (AFM) image.
According to claim 1,
The haze measured by ASTM D1003 is 10.0% or less,
An electrochromic material with an electrical conductivity of 0.01Scm ^{-1 or higher.}
preparing an aqueous dispersion comprising a polyanion and an acidic material; and
A method for producing an electrochromic material comprising the step of mixing a conductive polymer monomer with the aqueous dispersion.
6. The method of claim 5,
The method for producing an electrochromic material, wherein the acidic material is sulfuric acid.
6. The method of claim 5,
A method for producing an electrochromic material wherein the concentration of the acidic material is 0.01 to 1M.
6. The method of claim 5,
The polyanion is a method of producing an electrochromic material of polystyrene sulfonate (polystyrene sulfonate).
6. The method of claim 5,
The method for producing an electrochromic material wherein the conductive polymer monomer is aniline.
a working electrode coated with an electrode material on a substrate;
A counter electrode in which the electrode material and the electrochromic material of any one of claims 1 to 4 are coated on a substrate; and
An electrochromic device comprising an electrolyte positioned between the working electrode and the counter electrode.
11. The method of claim 10,
The electrode material is PEDOT: PSS (Poly (3,4-ethylenedioxythiophene): poly (styrenesulfonate)) electrochromic device.
A method for manufacturing an electrochromic device using a roll-to-roll process, comprising:
preparing a working electrode by coating an electrode material on a substrate;
coating the working electrode with an electrolyte; and
and laminating a counter electrode on the working electrode coated with the electrolyte.
13. The method of claim 12,
The counter electrode is
write; an electrode material coated on the substrate; and a method of manufacturing an electrochromic device comprising the electrochromic material of any one of claims 1 to 4 coated on the electrode material.
14. The method of claim 13,
A method of manufacturing an electrochromic device wherein the coated electrochromic material has a thickness of 450 nm to 600 nm.
13. The method of claim 12,
The electrolyte is a method of manufacturing an electrochromic device comprising hydroquinone.

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