Amorphous molybdenum-doped tungsten oxide electrochromic material and preparation method thereof

Abstract

The present invention discloses an amorphous molybdenum-doped tungsten oxide electrochromic material and a preparation method thereof. The method comprises the following steps: making the pre-vacuum degree of the magnetron sputtering coating instrument reach 2*10 ‑4 Pa below, and in an argon-oxygen mixed atmosphere, an amorphous molybdenum-doped WO3 target is sputtered by radio frequency reactive deposition onto a conductive glass substrate to produce a Mo-doped WO3 thin film. The Mo-doped WO3 thin film is then annealed to produce an amorphous molybdenum-doped tungsten oxide electrochromic material. The present invention exhibits high transmittance in the faded state and low transmittance in the tinted state, achieving a contrast ratio of 56.6% to 72.8%. It can reversibly switch between transparent and gray-black at different voltages, demonstrating chromaticity changes during the tungsten oxide film's color change process. It can be applied to a variety of applications, including electrochromic smart windows, anti-glare rearview mirrors, and sunroofs for new energy vehicles.

Description

Technical Field

[0001] The present invention relates to the field of electrochromism, and in particular to an amorphous molybdenum-doped tungsten oxide electrochromic material and a preparation method thereof. Background Art

[0002] Electrochromism refers to changes in optical properties such as transmittance, reflectivity, and absorptivity of a material when driven by an applied electric potential. Macroscopically, this manifests as changes in color and transparency. Electrochromic materials typically change between a tinted and faded state, or directly between two distinct tinted states. Electrochromic materials require the deposition of electrochromic thin films on a substrate, primarily using chemical and physical methods. Chemical methods include chemical vapor deposition, hydrothermal deposition, spin coating, chemical solution deposition, and electrodeposition; physical methods include sputtering and thermal evaporation. Tungsten oxide was one of the earliest cathodic electrochromic materials studied and can be divided into crystalline and amorphous forms. Tungsten oxide electrochromic thin films offer numerous advantages, including a wide optical modulation range in the visible and infrared wavelengths, high tinting efficiency, and good reversibility. Compared to organic electrochromic materials, tungsten oxide thin films also maintain stable, reversible color changes over multiple cycles and can operate continuously in harsh environments.

[0003] In the process of industrialization of existing tungsten oxide electrochromic materials, due to its blue or dark blue coloring, in actual use, blue can make people depressed and produce some negative emotions in color psychology. Summary of the Invention

[0004] The purpose of the present invention is to provide an amorphous molybdenum-doped tungsten oxide electrochromic material and a preparation method thereof. The material is prepared by a physical vapor deposition (PVD) method such as magnetron sputtering, and the color of the amorphous tungsten oxide in a PC / LiClO4 solution is transformed from dark blue to gray-black under the doping effect of the molybdenum element. The material is suitable for various occasions such as electrochromic smart windows, anti-glare rearview mirrors, and sunroofs of new energy vehicles.

[0005] In one aspect of the present invention, a method for preparing a molybdenum-doped tungsten oxide electrochromic material is provided. According to an embodiment of the present invention, the method comprises the following steps:

[0006] Make the pre-vacuum degree of magnetron sputtering coating instrument reach 2*10 -4 Pa below, and in an argon-oxygen mixed atmosphere, an amorphous molybdenum-doped WO3 target is subjected to radio frequency reactive deposition sputtering on the surface of a conductive glass substrate to obtain a Mo-doped WO3 thin film, and the Mo-doped WO3 thin film is annealed to obtain an amorphous molybdenum-doped tungsten oxide electrochromic material.

[0007] In addition, the method for preparing an amorphous molybdenum-doped tungsten oxide electrochromic material according to the above embodiment of the present invention may also have the following additional technical features:

[0008] In some embodiments of the present invention, the conductive glass substrate is ultrasonically cleaned in acetone, anhydrous ethanol, and deionized water in sequence for 10-20 minutes and dried before magnetron sputtering. The conductive glass substrate is ITO conductive glass or FTO conductive glass.

[0009] In some embodiments of the present invention, the Mo doping amount of the amorphous Mo-doped WO3 target is 1 wt% to 10 wt%.

[0010] In some embodiments of the present invention, the volume fraction of oxygen in the RF reactive deposition sputtering is 5% to 30%, the sputtering power is 50 to 100 W, the sputtering pressure is 0.8 to 3.0 Pa, the sputtering time is 100 to 150 min, the working distance is 5 to 10 cm, and the conductive glass substrate temperature is 20-110°C.

[0011] In some embodiments of the present invention, the volume fraction of oxygen in the mixed atmosphere varies uniformly with time from 5% to 20% at a rate of 1% over time as the sputtering time progresses.

[0012] In some embodiments of the present invention, the annealing temperature of the annealing treatment is 300-400° C., and the annealing time is 0.5-2 hours.

[0013] In some embodiments of the present invention, the thickness of the amorphous molybdenum-doped tungsten oxide electrochromic material is 300-350 nm, the film is dense and uniform, and the sputtered morphology is a columnar crystal granular shape.

[0014] In another aspect of the present invention, the present invention provides an amorphous molybdenum-doped tungsten oxide electrochromic material prepared by the method for preparing the amorphous molybdenum-doped tungsten oxide electrochromic material.

[0015] In addition, the amorphous molybdenum-doped tungsten oxide electrochromic material according to the above embodiment of the present invention may also have the following additional technical features:

[0016] In some embodiments of the present invention, the amorphous molybdenum-doped tungsten oxide electrochromic material is initially colorless and transparent, and undergoes a color transition from a gray-black colored state to a colorless and transparent faded state in a lithium-ion liquid electrolyte (such as PC / LiClO4 solution).

[0017] In another aspect, the present invention provides an electrochromic device comprising a substrate layer, a conductive layer, and an electrochromic material layer. According to an embodiment of the present invention, the electrochromic material layer is the amorphous molybdenum-doped tungsten oxide electrochromic material.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1. The present invention utilizes the magnetron sputtering method to reduce the randomness brought by wet chemistry in the experimental process. At the same time, the method of doping the doping element Mo into the WO3 target material is adopted. By using single-target sputtering instead of double-target sputtering, the cost of equipment and target materials is reduced. Through reactive sputtering of the doped target, amorphous tungsten oxide with more uniform composition is obtained.

[0020] 2. The present invention adjusts the stoichiometric ratio of tungsten oxide by introducing an argon-oxygen mixed gas to participate in reactive sputtering. Argon gas, as a protective atmosphere, is ionized to form plasma (argon ions) under the action of the magnetron sputtering electric field. Under the action of the magnetic field, it bombards the target material so that the atoms on the target surface are bombarded by argon ions and sputtered out, depositing on the substrate to form a thin film. Oxygen causes the target atoms to react to form oxides or regulate oxygen defects. By adjusting the ratio of argon to oxygen, the sputtering yield, that is, the ratio of sputtering speed to molybdenum element, can be adjusted. By adjusting the ratio of argon to oxygen to regulate the molybdenum element doping content, changes in sputtering yield and doping content are achieved, thereby forming a gradient distribution of molybdenum element doping content from small to large from the inside to the outside in the tungsten oxide electrochromic material. While preventing molybdenum element enrichment, the inner layer retains the substrate bonding force, and the surface layer achieves the effect of color conversion. Overall, the stability of the amorphous tungsten oxide film structure and the improvement of electrochromic performance are achieved.

[0021] 3. The colored state of the tungsten oxide electrochromic material not doped with molybdenum is blue or dark blue. The present invention introduces molybdenum element by means of doping, and adds an impurity energy level to the wide-bandgap semiconductor tungsten oxide, so that the light absorption changes, and the absorption of amorphous tungsten oxide is improved, thereby changing the color of the colored state of the tungsten oxide electrochromic film, so that the colored state color becomes a more neutral gray-black on a macro scale, and the faded state color becomes more transparent, realizing less chromaticity change in the coloring-fading change process, which is concentratedly reflected in the reversible change from gray-black to colorless and transparent, thereby realizing the chromaticity change of the tungsten oxide film.

[0022] 4. The present invention has a high transmittance in the faded state (can reach 79.0% to 85.1%), a low transmittance in the colored state (can reach 9.1% to 26.4%), and a contrast ratio of 56.6% to 72.8%. It can achieve reversible conversion between transparent and gray-black under different voltages, and realizes the chromaticity change during the color change of tungsten oxide film (a * and b * The absolute value of the coordinate is less than 0.5). It can be applied to various occasions such as electrochromic smart windows, anti-glare rearview mirrors, and sunroofs of new energy vehicles.

[0023] 5. The preparation method of the present invention is a magnetron sputtering method, which has a simple and stable preparation process, and the size and thickness of the sample are controllable, which is conducive to large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is an X-ray diffraction pattern of an amorphous undoped tungsten oxide electrochromic film prepared in a comparative example of the present invention;

[0025] Figure 2 This is the X-ray diffraction pattern of the molybdenum-doped tungsten oxide electrochromic thin film prepared in Example 1 of the present invention;

[0026] Figure 3 This is an X-ray diffraction pattern of the molybdenum-doped tungsten oxide electrochromic thin film prepared in Example 2 of the present invention;

[0027] Figure 4 This is an X-ray diffraction pattern of the molybdenum-doped tungsten oxide electrochromic thin film prepared in Example 3 of the present invention;

[0028] Figure 5 This is a Raman spectrum of the molybdenum-doped tungsten oxide electrochromic thin film prepared in Example 2 of the present invention;

[0029] Figure 6 This is a Raman spectrum of the molybdenum-doped tungsten oxide electrochromic thin film prepared in Example 3 of the present invention;

[0030] Figure 7 This is a scanning electron microscope image of the molybdenum-doped tungsten oxide electrochromic thin film prepared in Example 2 of the present invention;

[0031] Figure 8 This is a transmission spectrum performance diagram of the molybdenum-doped tungsten oxide electrochromic film prepared in Example 1 of the present invention;

[0032] Figure 9 This is a transmission spectrum performance diagram of the molybdenum-doped tungsten oxide electrochromic film prepared in Example 2 of the present invention;

[0033] Figure 10 This is a transmission spectrum performance diagram of the molybdenum-doped tungsten oxide electrochromic film prepared in Example 3 of the present invention;

[0034] Figure 11 This is a transmission spectrum performance diagram of the molybdenum-doped tungsten oxide electrochromic film prepared in Example 4 of the present invention;

[0035] Figure 12 This is the electrochromic kinetic performance diagram of the molybdenum-doped tungsten oxide thin film prepared in Example 2 of the present invention (633nm, -1V~1V);

[0036] Figure 13This is the electrochromic kinetic performance diagram of the molybdenum-doped tungsten oxide thin film prepared in Example 3 of the present invention (633nm, -1V~1V);

[0037] Figure 14 This is the electrochromic kinetics CA cycle current density diagram (-1v~1v) of the molybdenum-doped tungsten oxide film prepared in Example 3;

[0038] Figure 15 This is the electrochromic kinetics CA cycle current density diagram (-1v~1v) of the molybdenum-doped tungsten oxide film prepared in Example 4. DETAILED DESCRIPTION

[0039] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0040] Example 1

[0041] A method for preparing an amorphous molybdenum-doped tungsten oxide electrochromic material, comprising the following steps:

[0042] (1) The ITO glass substrate was ultrasonically cleaned in acetone, anhydrous ethanol, and deionized water for 15 minutes respectively, and then dried;

[0043] (2) Installing a Mo-doped WO3 target and a dried ITO glass substrate in a magnetron sputtering coating apparatus and evacuating the apparatus;

[0044] (3) When the pre-vacuum degree reaches 2*10 -4 Pa or less, using 5% molybdenum-doped WO3 with a purity of 99.99% as a target, performing radio frequency reactive deposition sputtering at a substrate temperature of 110°C in an argon-oxygen mixed atmosphere, wherein the oxygen volume fraction in the mixed atmosphere is 15%, the sputtering power is 100 W, the sputtering pressure is 2 Pa, the sputtering time is 150 minutes, and the working distance is 10 cm to obtain a Mo-doped WO3 thin film;

[0045] (4) The Mo-doped WO3 film obtained in step (3) is placed in a tube furnace for annealing at a temperature of 300° C. for 0.5 hours to obtain an amorphous molybdenum-doped tungsten oxide electrochromic film.

[0046] Example 2

[0047] A method for preparing an amorphous molybdenum-doped tungsten oxide electrochromic material, comprising the following steps:

[0048] (1) The ITO glass substrate was ultrasonically cleaned in acetone, anhydrous ethanol, and deionized water for 15 minutes and dried;

[0049] (2) Installing a Mo-doped WO3 target and a dried ITO glass substrate in a magnetron sputtering coating apparatus and evacuating the apparatus;

[0050] (3) When the pre-vacuum degree reaches 2*10 -4 Pa below, using 8% by mass of molybdenum doped WO3 with a purity of 99.99% as a target, performing radio frequency reactive deposition sputtering at a substrate temperature of 25°C in an argon-oxygen mixed atmosphere, wherein the volume fraction of oxygen in the mixed atmosphere is 5%, the sputtering power is 50W, the sputtering pressure is 1Pa, the sputtering time is 120 minutes, and the working distance is 5cm, to obtain a Mo-doped WO3 thin film;

[0051] (4) The Mo-doped WO3 film obtained in step (3) is placed in a tube furnace for annealing at a temperature of 350° C. for 1.5 hours to obtain an amorphous molybdenum-doped tungsten oxide electrochromic film.

[0052] Example 3

[0053] A method for preparing an amorphous molybdenum-doped tungsten oxide electrochromic material, comprising the following steps:

[0054] (1) The ITO glass substrate was ultrasonically cleaned in acetone, anhydrous ethanol, and deionized water for 15 minutes respectively, and then dried;

[0055] (2) Installing a Mo-doped WO3 target and a dried ITO glass substrate in a magnetron sputtering coating apparatus and evacuating the apparatus;

[0056] (3) When the pre-vacuum degree reaches 2*10 -4 Pa or less, using 2% by mass molybdenum-doped WO3 with a purity of 99.99% as a target material, performing radio frequency reactive deposition sputtering at a substrate temperature of 25°C in an argon-oxygen mixed atmosphere, wherein the volume fraction of oxygen in the mixed atmosphere changes uniformly with time from 5% to 20% at a rate of 1% every 8 minutes as the sputtering time progresses, the sputtering power is 50 W, the sputtering pressure is 1 Pa, the sputtering time is 120 minutes, and the working distance is 5 cm, to obtain a Mo-doped WO3 thin film;

[0057] (4) The Mo-doped WO3 film obtained in step (3) is placed in a tube furnace for annealing at a temperature of 350° C. for 1.5 hours to obtain an amorphous molybdenum-doped tungsten oxide electrochromic film.

[0058] Example 4

[0059] A method for preparing an amorphous molybdenum-doped tungsten oxide electrochromic material, comprising the following steps:

[0060] (1) The ITO glass substrate was ultrasonically cleaned in acetone, anhydrous ethanol, and deionized water for 15 minutes and dried;

[0061] (2) Installing a Mo-doped WO3 target and a dried ITO glass substrate in a magnetron sputtering coating apparatus and evacuating the apparatus;

[0062] (3) When the pre-vacuum degree reaches 2*10 -4 Pa below, using 2% by mass of molybdenum doped WO3 with a purity of 99.99% as a target, radio frequency reactive deposition sputtering was performed at a substrate temperature of 25°C in an argon-oxygen mixed atmosphere, the oxygen volume fraction in the mixed atmosphere was fixed at 15%, the sputtering power was 50W, the sputtering pressure was 1Pa, the sputtering time was 120 minutes, and the working distance was 5cm to obtain a Mo-doped WO3 thin film;

[0063] (4) The Mo-doped WO3 film obtained in step (3) is placed in a tube furnace for annealing at a temperature of 350° C. for 1.5 hours to obtain an amorphous molybdenum-doped tungsten oxide electrochromic film.

[0064] Comparative Example

[0065] A method for preparing an amorphous undoped tungsten oxide electrochromic material, comprising the following steps:

[0066] (1) The ITO glass substrate was ultrasonically cleaned in acetone, anhydrous ethanol, and deionized water for 15 minutes and dried;

[0067] (2) Install the WO3 target and the dried ITO glass substrate in the magnetron sputtering coating instrument and evacuate the chamber;

[0068] (3) When the pre-vacuum degree reaches 2*10 -4 Pa or less, using WO3 with a purity of 99.99% as a target, radio frequency reactive deposition sputtering was performed at a substrate temperature of 110°C in an argon-oxygen mixed atmosphere, wherein the oxygen volume fraction in the mixed atmosphere was 15%, the sputtering power was 100W, the sputtering pressure was 2Pa, the sputtering time was 150 minutes, and the working distance was 10cm;

[0069] (4) The amorphous undoped tungsten oxide thin film obtained in step (3) is placed in a tube furnace for annealing at a temperature of 300° C. for 0.5 hours to obtain an amorphous undoped tungsten oxide electrochromic thin film.

[0070] from Figure 1-4The X-ray diffraction pattern shows that the diffraction peaks of the tungsten oxide electrochromic material prepared in the comparative example as the control group are consistent with those of the ITO substrate, with no new phase diffraction peaks, indicating that the material is amorphous. The molybdenum-doped tungsten oxide electrochromic materials prepared in Examples 1, 2, and 3 also have diffraction peaks consistent with those of the ITO substrate, confirming that the prepared electrochromic films are all amorphous.

[0071] Figure 5-6 The Raman spectrum is located at about 650-850 cm -1 The broad peak at 6+ -O, the presence of this broad peak indicates the amorphous nature of Examples 2 and 3 and is consistent with the conclusions obtained from the XRD test results. The peak in the spectrum is located at about 950cm -1 The peak at W6 can be attributed to water molecules + =O terminal stretch.

[0072] Figure 7 It can be seen that the surface of the amorphous molybdenum-doped tungsten oxide electrochromic material prepared in Example 2 is dense and flat, and the thickness is about 300-350 nm.

[0073] Figure 8-13 The transmitted light spectrum performance graph and electrochromic kinetic performance graph show that in a three-electrode system, with a platinum wire as the counter electrode, Ag / AgCl as the reference electrode, and the prepared amorphous molybdenum-doped tungsten oxide electrochromic material as the working electrode, a voltage of -1 to 1V was applied for performance testing. The molybdenum-doped tungsten oxide electrochromic film sample of Example 1 had a maximum transmittance of 79.0% in the faded state at 633nm and a minimum transmittance of 26.4% in the colored state, with an electrochromic contrast of 52.6%. The electrochromic film prepared in Example 2 had a maximum transmittance of 84.0% and a minimum transmittance of 13.9% at 633nm, an electrochromic contrast of 70.1%, a coloring time of 48.6 seconds, and a fading time of 63.0 seconds. The electrochromic film prepared in Example 3 had a maximum transmittance of 85.1% and a minimum transmittance of 12.3% at 633nm, and an electrochromic contrast of 72.8%. The response time for coloring and fading was significantly improved compared to Example 2. The electrochromic film prepared in Example 4 has a maximum transmittance of 81.2% at 633 nm, a minimum transmittance of 9.1%, and an electrochromic contrast ratio of 72.1%.

[0074] Figure 14-15It can be seen from the electrochromic kinetics CA cycle current density diagram that after 400 cycles, the peak current of the electrochromic film prepared in Example 3 is very stable compared to Example 4. This shows that the electrochromic film prepared in Example 3 achieves a change in doping content by dynamically adjusting the ratio of argon and oxygen while reducing the doping amount, forming a gradient distribution of molybdenum doping content from less to more from the inside to the outside of the tungsten oxide electrochromic material. While preventing molybdenum enrichment, the inner layer retains the substrate bonding force and the surface layer achieves the effect of color conversion. Overall, the stability of the amorphous tungsten oxide film structure and the improvement of electrochromic performance are achieved.

[0075] Table 1 is the CIE L values ​​of the chromaticity of the control group of molybdenum-doped tungsten oxide electrochromic films prepared in Examples 1, 2, and 3. * a * b * Chromaticity coordinate comparison table, L * Indicates the degree of brightness, a * Indicates the degree of red-green tendency of the color, b * Indicates the degree of yellow-blue tendency in color. The amorphous molybdenum-doped tungsten oxide electrochromic materials prepared in Examples 1-3 were compared with the comparative examples. We found that in the faded state, b * The value increases and the absolute value approaches 0, which indicates that the color of the film changes from blue to light in the faded state, that is, the faded state is closer to the colorless and transparent state. * Compared with the undoped control, the color of the film has also been improved, and the absolute value is closer to 0, which shows that the color of the film changes from dark blue to gray-black during the coloring state change. From the chromaticity coordinates of Example 2, it can be seen that this example involves less color change during the coloring-fading process, and is more reflected in the film L * The change in brightness is the change in darkness, that is, the reversible change of the film from gray-black to colorless and transparent, realizing the color change of the tungsten oxide film.

[0076] Table 1

[0077]

[0078]

[0079] Example 5

[0080] An electrochromic device comprises a substrate layer, a conductive layer, and an electrochromic material layer. The electrochromic material layer is the amorphous molybdenum-doped tungsten oxide electrochromic material prepared in Examples 1-4.

[0081] The above content is merely an example and explanation of the structure of the present invention. Those skilled in the art may make various modifications or additions to the described specific embodiments or replace them in a similar manner. As long as they do not deviate from the structure of the present invention or exceed the scope defined by the claims, they should all fall within the scope of protection of the present invention.

Claims

1. A method for preparing an amorphous molybdenum-doped tungsten oxide electrochromic material, characterized in that: The following steps are involved: Make the pre-vacuum degree of magnetron sputtering coating instrument reach 2*10 -4 Pa or less, and in an argon-oxygen mixed atmosphere, an amorphous molybdenum-doped WO3 target is subjected to radio frequency reactive deposition sputtering on the surface of a conductive glass substrate to obtain a Mo-doped WO3 thin film, and the Mo-doped WO3 thin film is annealed to obtain an amorphous molybdenum-doped tungsten oxide electrochromic material; The oxygen volume fraction in the mixed atmosphere changes uniformly with time from 5% to 20% at a rate of 1% over time as the sputtering time increases; the annealing temperature of the annealing treatment is 300 to 400° C., and the annealing time is 0.5 to 2 hours.

2. The method for preparing an amorphous molybdenum-doped tungsten oxide electrochromic material according to claim 1, characterized in that: The conductive glass substrate is ultrasonically cleaned in acetone, anhydrous ethanol and deionized water in sequence for 10-20 minutes before magnetron sputtering, and then dried. The conductive glass substrate is ITO conductive glass or FTO conductive glass.

3. The method for preparing an amorphous molybdenum-doped tungsten oxide electrochromic material according to claim 1, characterized in that: The Mo doping amount of the amorphous molybdenum-doped WO3 target is 1 wt% to 10 wt%.

4. The method for preparing an amorphous molybdenum-doped tungsten oxide electrochromic material according to claim 1, characterized in that: The volume fraction of oxygen in the radio frequency reactive deposition sputtering is 5% to 30%, the sputtering power is 50 to 100 W, the sputtering pressure is 0.8 to 3.0 Pa, the sputtering time is 100 to 150 minutes, the working distance is 5 to 10 cm, and the conductive glass substrate temperature is 20-110° C.

5. The method for preparing an amorphous molybdenum-doped tungsten oxide electrochromic material according to claim 1, characterized in that: The thickness of the amorphous molybdenum-doped tungsten oxide electrochromic material is 300-350 nm, the film is dense and uniform, and the sputtering morphology is a columnar crystal granular shape.

6. An amorphous molybdenum-doped tungsten oxide electrochromic material prepared according to the method for preparing an amorphous molybdenum-doped tungsten oxide electrochromic material according to any one of claims 1 to 5.

7. The amorphous molybdenum-doped tungsten oxide electrochromic material according to claim 6, characterized in that: The amorphous molybdenum-doped tungsten oxide electrochromic material is transparent in an initial state and realizes a color transition from a gray-black colored state to a faded transparent state in a lithium ion liquid electrolyte.

8. An electrochromic device comprising a substrate layer, a conductive layer, and an electrochromic material layer, characterized in that: The electrochromic material layer is the amorphous molybdenum-doped tungsten oxide electrochromic material according to claim 7.

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