Tungsten-doped nickel oxide nanocrystalline electrochromic film and preparation method thereof

Abstract

The invention discloses a tungsten-doped nickel oxide nanocrystalline electrochromic film which is formed by stacking nanocrystalline particles, and the particle size is about 4 nm. The invention further discloses a preparation method of the tungsten-doped nickel oxide nanocrystalline electrochromic film, and the tungsten-doped nickel oxide nanocrystalline film is obtained by combining a solvothermal method with a magnetron sputtering method. According to the doped thin film, the problems that an existing NiO electrochromic material is yellow in a fading state, small in charge capacity, short in cycle life and the like are well solved, and a new thought is provided for constructing a high-performance electrochromic device which is high in color changing effect, high in energy utilization rate and long in service life.

Description

Technical Field

[0001] The invention relates to the field of electrochromic film preparation, and in particular to a tungsten-doped nickel oxide nanocrystalline electrochromic film and a preparation method thereof. Background Art

[0002] Electrochromism refers to the phenomenon that certain materials stably and reversibly change their color or optical properties through redox reactions under a small external voltage. Electrochromic materials have attracted widespread attention as energy-saving and environmentally friendly materials. They can transmit and absorb sunlight of different wavelengths to regulate light energy and reduce energy consumption. NiO is a very important anode electrochromic material and is usually used in combination with WO 3 The electrochromic devices assembled with cathode electrochromic films can be applied to commercial fields such as anti-glare rearview mirrors, electronic paper, new energy vehicle sunroofs, AR glasses, smart phones and tablet back covers, and have broad prospects.

[0003] The paper titled Fast-switching electrochromic smart windows based on WO3 dopedNiO thin films proves WO 3 The doped NiO film shows a fast photoresponse speed (bleaching / coloring is 0.6s / 1.0s), which is because the defect-induced amorphous structure of the NiO film provides a large number of diffusion channels, which is conducive to the Li + Rapid embedding, and the doped film can accommodate a large number of ions, thereby enhancing the electrochromic performance. However, the transmittance of the film is about 80% in the faded state, and the actual picture has obvious yellowing. If it is actually applied to smart windows, it will affect the user's perception; in addition, the overall cycle stability of the film is poor, and the charge storage capacity can only maintain 50% of the original after 1000 cycles. At present, yellowing in the faded state, low charge capacity, and poor cycle stability are the three major problems of NiO electrochromic films, which hinder their engineering application process. Therefore, targeted solutions to the above three problems are crucial to increase the wider application of NiO films. Summary of the invention

[0004] The purpose of the present invention is to provide a tungsten-doped nickel oxide nanocrystalline electrochromic film and a preparation method thereof, which is prepared by combining a solvothermal method with a magnetron sputtering method, and is dedicated to solving the above-mentioned existing problems.

[0005] In one aspect of the present invention, the present invention provides a method for preparing a tungsten-doped nickel oxide nanocrystalline electrochromic film. According to an embodiment of the present invention, the method comprises the following steps:

[0006] S1. Heat and stir nickel acetylacetonate, toluene and oleylamine until clear to obtain a precursor solution;

[0007] S2, subjecting the precursor solution to a solvothermal reaction, then adding anhydrous ethanol to allow the solution to settle and centrifuge;

[0008] S3, dissolving the precipitate obtained in step S2 in n-hexane, adding anhydrous ethanol again, allowing to stand for precipitation and centrifuging;

[0009] S4, dissolving the precipitate obtained in step S3 in 1,3,5-trimethylbenzene to obtain nickel oxide nanocrystalline ink;

[0010] S5, spin coating the nickel oxide nanocrystal ink on the dried FTO glass to obtain the nickel oxide nanocrystal electrochromic film;

[0011] S6, placing the nickel oxide nanocrystalline electrochromic film in a magnetron sputtering vacuum chamber, and using a tungsten target to sputter and deposit on the surface;

[0012] S7, annealing the film obtained in step S6 to obtain a tungsten-doped nickel oxide nanocrystalline electrochromic film.

[0013] In addition, the method for preparing a tungsten-doped nickel oxide nanocrystalline electrochromic thin film according to the above embodiment of the present invention may also have the following additional technical features:

[0014] In some embodiments of the present invention, in step S1, the temperature of the heating and stirring is 50-70°C.

[0015] In some embodiments of the present invention, in step S2, the reaction temperature of the solvothermal reaction is 160-200° C., and the reaction time is 20-24 h.

[0016] In some embodiments of the present invention, in steps S2 and S3, the centrifugal speed is 5000-8000 r / min, and the centrifugal time is 3-8 min.

[0017] In some embodiments of the present invention, in step S4, the concentration of the nickel oxide nanocrystalline ink is 80-120 mg / mL.

[0018] In some embodiments of the present invention, in step S5, the FTO glass is firstly ultrasonically cleaned with acetone, anhydrous ethanol and deionized water, and then dried.

[0019] In some embodiments of the present invention, in step S6, the sputtering gas pressure is 1.0-2.0 Pa, and the sputtering power is 20-60 W.

[0020] In some embodiments of the present invention, in step S7, the annealing temperature is 200-400° C., the annealing time is 120-200 min, and the heating rate is 4-8° C. / min.

[0021] In another aspect of the present invention, the present invention proposes a tungsten-doped nickel oxide nanocrystalline electrochromic film prepared according to the preparation method of the tungsten-doped nickel oxide nanocrystalline electrochromic film. The tungsten-doped nickel oxide nanocrystalline electrochromic film has a nanocrystalline structure, the nanocrystalline particle size is about 4nm, and tungsten can be uniformly doped. And it has the following characteristics: the transmittance in the faded state is extremely high, which is 88.30%-94.40%, and the faded state will not turn yellow; the charge capacity becomes larger, which is 109%-135% of the undoped nickel oxide nanocrystalline film; the cycle stability is very good, and almost no attenuation occurs when the number of cycles exceeds 5000.

[0022] In addition, the tungsten-doped nickel oxide nanocrystalline electrochromic film according to the above embodiment of the present invention may also have the following additional technical features:

[0023] In some embodiments of the present invention, the electrochromic film can achieve a rapid reversible change between transparent and dark brown, with a coloring time of 2.64-3.85 s and a fading time of 1.20-2.20 s.

[0024] The beneficial effects of the present invention are:

[0025] 1. The tungsten-doped nickel oxide nanocrystalline electrochromic film of the present invention is innovatively prepared by magnetron sputtering on the basis of wet chemical method, successfully combining the advantages of the two mainstream methods. Compared with the chemical method alone, the doped film prepared by magnetron sputtering is more uniform and has higher purity; compared with the film formed by magnetron sputtering alone, the surface of the nanocrystalline film synthesized by the pre-chemical method step is not very dense, and the large number of pores on the surface of the film are conducive to the infiltration of electrolyte and reaction.

[0026] 2. The tungsten-doped nickel oxide nanocrystalline electrochromic film of the present invention produces more defects such as nickel vacancies, which increases the number of lithium ion absorption sites in the lithium ion-containing electrolyte and significantly improves the charge capacity, resulting in a higher optical contrast, making the color change of the electrochromic device more obvious and the visual effect better. It can also effectively reduce power consumption and improve the energy efficiency of the device.

[0027] 3. The tungsten-doped nickel oxide nanocrystalline electrochromic film of the present invention can increase the lattice spacing of the nanocrystalline particles, broaden the lithium ion transport channel, increase its diffusion rate, increase the conductivity of the nickel oxide nanocrystalline film, effectively improve the electrochemical kinetics, and the corresponding light response speed will be faster and the color change time will be shorter.

[0028] 4. The tungsten-doped nickel oxide nanocrystalline electrochromic film of the present invention, the tungsten doping can effectively reduce the probability of lithium ions being captured by deep potential well sites during the electrochemical cycle, thereby reducing damage to the material structure, enhancing its cycle stability, and extending the service life of the electrochromic device. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a scanning electron microscope morphology image of the tungsten-doped nickel oxide nanocrystalline electrochromic film prepared in Example 1 of the present invention;

[0030] Figure 2 This is a scanning electron microscope cross-sectional morphology image of the tungsten-doped nickel oxide nanocrystalline electrochromic film prepared in Example 1 of the present invention;

[0031] Figure 3 The X-ray diffraction pattern of the tungsten-doped nickel oxide nanocrystalline electrochromic film prepared in Example 1 of the present invention;

[0032] Figure 4 The cyclic voltammogram of the tungsten-doped nickel oxide nanocrystalline electrochromic film prepared in Example 1 of the present invention;

[0033] Figure 5 The tungsten-doped nickel oxide nanocrystalline electrochromic film prepared in Example 1 of the present invention is exposed to 1 mol / L LiClO 4 / Electrochromic performance spectrum in PC electrolyte solution;

[0034] Figure 6 The tungsten-doped nickel oxide nanocrystalline electrochromic film prepared in Example 1 of the present invention is heated to 1 mol / L LiClO 4 / Schematic diagram of the kinetic electrochromic performance in PC electrolyte solution (550nm-0.5V-+1.2V);

[0035] Figure 7 The color parameters (L*a*b*) of the tungsten-doped nickel oxide nanocrystalline electrochromic film prepared in Example 1 of the present invention under different applied voltages obtained using a D-65 light source at an observer angle of 2° in the CIE 1931 color space;

[0036] Figure 8 The chronoamperometric curve of the tungsten-doped nickel oxide nanocrystalline electrochromic film prepared in Example 1 of the present invention after 5000 cycles;

[0037] Fig. 9 This is a comparison diagram of the optical modulation amplitude of the tungsten-doped nickel oxide nanocrystalline electrochromic film prepared in Example 1 of the present invention before and after 5000 cycles;

[0038] Fig.10A comparison diagram of cyclic voltammetry curves of the tungsten-doped nickel oxide nanocrystalline electrochromic film prepared in Example 1 of the present invention before and after 5000 cycles;

[0039] Fig.11 The Ni 2p spectrum of the X-ray photoelectron spectrum of the nickel element of the tungsten-doped nickel oxide nanocrystalline electrochromic thin film prepared in Example 2 of the present invention;

[0040] Fig.12 The O1s spectrum of the X-ray photoelectron spectrum of the nickel element of the tungsten-doped nickel oxide nanocrystalline electrochromic thin film prepared in Example 2 of the present invention;

[0041] Fig.13 This is the W 4f spectrum of the X-ray photoelectron spectrum of the tungsten element in the tungsten-doped nickel oxide nanocrystalline electrochromic thin film prepared in Example 2 of the present invention. DETAILED DESCRIPTION

[0042] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. The described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] Example 1

[0044] A method for preparing a tungsten-doped nickel oxide nanocrystalline electrochromic film comprises the following steps:

[0045] S1. Add 0.514 g nickel acetylacetonate, 20 mL toluene, and 12 mL oleylamine into a beaker, heat and stir at 50° C. until clear, to obtain a precursor solution;

[0046] S2, the precursor solution of step S1 is loaded into a reaction kettle, and placed in an oven at 180°C for 24 hours for solvothermal reaction;

[0047] S3, adding 80 mL of anhydrous ethanol to the solution obtained in step S2, allowing it to settle and centrifuging at a centrifugal speed of 8000 r / min for 5 min;

[0048] S4, dissolving the precipitate obtained in step S3 in 8 mL of n-hexane, adding 80 mL of anhydrous ethanol again, allowing the precipitation to stand and centrifuging at a centrifugal speed of 8000 r / min for 5 min;

[0049] S5, dissolving the precipitate obtained in step S4 in 4 mL of 1,3,5-trimethylbenzene to obtain nickel oxide nanocrystalline ink;

[0050] S6. Ultrasonic cleaning of the FTO glass was performed with acetone, anhydrous ethanol and deionized water for 30 min respectively;

[0051] S7, placing the FTO glass of step S6 into an oven and drying at 60° C. for 5 min;

[0052] S8, spin coating the nickel oxide nanocrystalline ink obtained in step S5 on the FTO glass obtained in step S7 to obtain a nickel oxide nanocrystalline electrochromic film;

[0053] S9, placing the nickel oxide nanocrystalline film obtained in step S8 into a magnetron sputtering vacuum chamber, sputtering and depositing tungsten on the surface, using a tungsten target material with a purity of 99.999%, a sputtering pressure of 1.2 Pa, a sputtering power of 20 W, and a sputtering time of 1 min;

[0054] S10, annealing the film obtained in step S9 at a temperature of 300° C. for 120 min at a heating rate of 6° C. / min to obtain a tungsten-doped nickel oxide nanocrystalline electrochromic film.

[0055] The tungsten-doped nickel oxide nanocrystalline electrochromic film prepared in this embodiment has a nanocrystalline structure. Figure 1 As shown in the figure, the film surface is uniform and is composed of nanocrystalline particles, and the size of the nanocrystalline particles is about 4nm. Figure 2 As shown, the cross-sectional thickness is about 884 nm, the stratification between the film and FTO is not particularly obvious, and the bonding is good. Figure 3 The X-ray electron diffraction pattern shows an obvious (200) crystal plane orientation at 43°, and no new phase is generated, indicating that W can be well integrated into the NiO lattice.

[0056] Figure 4 In the cyclic voltammogram, the curve area after W doping becomes larger, indicating that W doping makes the Li + The absorption sites increase and the charge capacity increases significantly. The electrochromic performance spectrum and kinetic spectrum of the electrochromic device prepared in this embodiment under lithium ion electrolyte are shown in Figure 1. Figure 5 , Figure 6 This electrochromic material can achieve an optical modulation contrast ratio of 63.87% at 550nm, with obvious color changes; the coloring time at 550nm is 2.68s, and the fading time is 1.43s, and the light response speed is very fast.

[0057] Figure 7 The chromaticity diagram obtained under different bias voltages. Among them, the color is represented by three parameters: brightness (L*), red-green color (a*) and yellow-blue color (b*). It can be seen that after W doping, when a negative voltage is applied, the film is in a faded state, and the b* value of the film is significantly reduced, proving that W doping can effectively improve the yellowing phenomenon of the NiO electrochromic film in the faded state.

[0058] Figure 8 This is a multi-potential chronoamperometry diagram of a tungsten-doped nickel oxide nanocrystalline electrochromic film with 5000 cycles of alternating -0.5V / +1.2V for 15s. Fig. 9 and Fig.10 The cyclic voltammetry curves and optical modulation amplitude comparison diagrams before and after 5000 cycles are shown. It can be seen that after 5000 cycles, the charge storage capacity of the tungsten-doped nickel oxide nanocrystalline electrochromic film still maintains 90.35% of the original, and the optical modulation amplitude decreases from 60.43% to 57.83%, but still maintains the original 95.70%. Therefore, the tungsten-doped nickel oxide nanocrystalline electrochromic film has good cycle stability, and the performance of the electrochromic film has almost no decline after 5000 cycles.

[0059] Example 2

[0060] A method for preparing a tungsten-doped nickel oxide nanocrystalline electrochromic film comprises the following steps:

[0061] S1. Add 0.514 g nickel acetylacetonate, 20 mL toluene, and 12 mL oleylamine into beaker 1, heat and stir at 50°C until clear, to obtain a precursor solution;

[0062] S2, the precursor solution of step S1 is loaded into a reaction kettle, and placed in an oven at 180°C for 24 hours for solvothermal reaction;

[0063] S3, adding 80 mL of anhydrous ethanol to the solution obtained in step S2, allowing it to settle and centrifuging at a centrifugal speed of 8000 r / min for 5 min;

[0064] S4, dissolving the precipitate obtained in step S3 in 8 mL of n-hexane, adding 80 mL of anhydrous ethanol again, allowing the precipitation to stand and centrifuging at a centrifugal speed of 8000 r / min for 5 min;

[0065] S5, dissolving the precipitate obtained in step S4 in 4 mL of 1,3,5-trimethylbenzene to obtain nickel oxide nanocrystalline ink;

[0066] S6. Ultrasonic cleaning of the FTO glass was performed with acetone, anhydrous ethanol and deionized water for 30 min respectively;

[0067] S7, putting the FTO glass of step S6 into an oven and drying for 5 minutes;

[0068] S8, spin coating the nickel oxide nanocrystalline ink obtained in step S5 on the FTO glass obtained in step S7 to obtain a nickel oxide nanocrystalline electrochromic film;

[0069] S9, placing the nickel oxide nanocrystalline film obtained in step S8 into a magnetron sputtering vacuum chamber and pumping to 2*10 -4 Tungsten was deposited on the surface by sputtering with a tungsten target of 99.999% purity, a sputtering pressure of 1.2 Pa, a sputtering power of 20 W, and a sputtering time of 1 min.

[0070] S10, annealing the film obtained in step S9 at a temperature of 300° C., a time of 180 min, and a heating rate of 6° C. / min to obtain a tungsten-doped nickel oxide nanocrystalline electrochromic film.

[0071] Fig.11 , Fig.12 , Fig.13 Corresponding to the photoelectron spectrum of W-doped NiO nanocrystalline film. W doping makes W 6+ Replace Ni 3+ The position of Ni 3+ / Ni 2+ As the value decreases, the hole concentration in the NiO lattice increases, which in turn increases the transmittance of the electrochromic film in the visible light range and makes the light response speed faster.

[0072] The above contents are merely examples and explanations of the method of the present invention. The technicians in this technical field may make various modifications or additions to the specific embodiments described 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 protection scope of the present invention.

Claims

1. A method for preparing a tungsten-doped nickel oxide nanocrystalline electrochromic film, characterized in that: The following steps are involved: S1. Heat and stir nickel acetylacetonate, toluene and oleylamine until clear to obtain a precursor solution; S2, subjecting the precursor solution to a solvothermal reaction, then adding anhydrous ethanol to allow the solution to settle and centrifuge; S3, dissolving the precipitate obtained in step S2 in n-hexane, adding anhydrous ethanol again, allowing to stand for precipitation and centrifuging; S4, dissolving the precipitate obtained in step S3 in 1,3,5-trimethylbenzene to obtain nickel oxide nanocrystalline ink; S5, spin coating the nickel oxide nanocrystal ink on the dried FTO glass to obtain the nickel oxide nanocrystal electrochromic film; S6, placing the nickel oxide nanocrystalline electrochromic film in a magnetron sputtering vacuum chamber, and using a tungsten target to sputter and deposit on the surface; S7, annealing the film obtained in step S6 to obtain a tungsten-doped nickel oxide nanocrystalline electrochromic film.

2. The method for preparing a tungsten-doped nickel oxide nanocrystalline electrochromic thin film according to claim 1, characterized in that: In step S1, the temperature of the heating and stirring is 50-70°C.

3. The method for preparing a tungsten-doped nickel oxide nanocrystalline electrochromic film according to claim 1, characterized in that: In step S2, the reaction temperature of the solvent thermal reaction is 160-200° C., and the reaction time is 20-24 h.

4. The method for preparing a tungsten-doped nickel oxide nanocrystalline electrochromic thin film according to claim 1, characterized in that: In steps S2 and S3, the centrifugal speed is 5000-8000 r / min, and the centrifugal time is 3-8 min.

5. The method for preparing a tungsten-doped nickel oxide nanocrystalline electrochromic film according to claim 1, characterized in that: In step S4, the concentration of the nickel oxide nanocrystalline ink is 80-120 mg / mL.

6. The method for preparing a tungsten-doped nickel oxide nanocrystalline electrochromic film according to claim 1, characterized in that: In step S5, the FTO glass is firstly ultrasonically cleaned with acetone, anhydrous ethanol and deionized water, and then dried.

7. The method for preparing a tungsten-doped nickel oxide nanocrystalline electrochromic thin film according to claim 1, characterized in that: In step S6, the sputtering gas pressure is 1.0-2.0 Pa, and the sputtering power is 20-60 W.

8. The method for preparing a tungsten-doped nickel oxide nanocrystalline electrochromic thin film according to claim 1, characterized in that: In step S7, the annealing temperature is 200-400°C, the annealing time is 120-200min, and the heating rate is 4-8°C / min.

9. A tungsten-doped nickel oxide nanocrystalline electrochromic film prepared by the method for preparing a tungsten-doped nickel oxide nanocrystalline electrochromic film according to any one of claims 1 to 8.

10. The tungsten-doped nickel oxide nanocrystalline electrochromic film according to claim 9, characterized in that: The electrochromic film can achieve rapid reversible change between transparent and dark brown, with a coloring time of 2.64-3.85 s and a fading time of 1.20-2.20 s.

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