Au-NPs / HfO2 / VO2 composite film, preparation method and application thereof

Abstract

The application relates to the technical field of thermochromic film, in particular to an Au-NPs / HfO2 / VO2 composite film and a preparation method and application thereof. The Au-NPs / HfO2 / VO2 composite film comprises, from bottom to top, an Au-NPs local surface plasmon control layer (3), an HfO2 covering layer (2) and a VO2 thermochromic functional film layer (1); and the Au-NPs local surface plasmon control layer (3) is combined with a substrate. In the application, an Au film is sputtered on a glass substrate, and Au-NPs are formed by annealing; the introduction of the HfO2 covering layer provides a stable medium environment for the Au-NPs, avoids the red shift or blue shift of the absorption peak position of the Au-NPs due to temperature change, and further influences the solar energy regulation efficiency of the composite film, so that the composite film achieves the balance between the optical performance and the color conforming to the architectural aesthetics.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of thermochromic thin films, in particular to an Au-NPs / HfO2 / VO2 composite thin film and a preparation method and application thereof. BACKGROUND

[0002] In order to improve the energy-saving efficiency of building glass, people have developed various energy-saving coated glasses, mainly including low-emissivity glass, electrochromic glass, photochromic glass, etc. However, the low-emissivity glass does not have the ability to regulate sunlight because the initial reflection wavelength is fixed; the electrochromic glass and the photochromic glass can adjust the visible light transmittance by the light intensity or the electric field intensity applied to the glass, and do not have the ability of environmental temperature sensing. Therefore, the intelligent window with the ability of environmental sensing and the ability to dynamically adjust solar radiation has become a research hotspot. Vanadium dioxide (VO2) can undergo reversible phase transition of metal / insulator phase at 68℃, below the critical temperature, it is an insulator phase, and shows high transmittance in the visible and near-infrared wave bands; above the critical temperature, it is a metal phase, and can play a high barrier role in the near-infrared wave band under the condition of high transmittance in the visible light. Therefore, vanadium dioxide has become one of the important materials in the field of intelligent windows. However, in practical applications, the intrinsic VO2 thin film has the undesirable brownish yellow color, the relatively high phase transition temperature (T c ), and the difficult-to-achieve visible light transmittance (T lum ) and solar energy regulation efficiency (T sol ), which seriously restricts the commercial application of the VO2 thin film intelligent window.

[0003] There are three methods to improve the performance of VO2 thin film smart windows. One is to increase the band gap of VO2 to promote the blue shift of the absorption edge. The second is to deposit an anti-reflective layer on the surface of the VO2 thin film to reduce the reflection of visible light and improve the transmittance. The third is to design and prepare sub-wavelength micro-nano structures (such as moth-eye structures) based on the effective medium theory, which can also improve the visible light transmittance and solar energy regulation efficiency of VO2 thin film by increasing the surface roughness and reducing the surface equivalent refractive index. Although the above methods can improve the thermochromic performance of VO2 thin film to some extent, they cannot control the color of VO2 thin film. Therefore, designing and preparing new structure VO2 composite thin film is the key to solve the contradiction between the performance of smart windows and the aesthetics of buildings. A large number of studies have shown that the LSPR characteristic peak of Au and other noble metal NPs is usually in the visible light range, and the LSPR effect excited under incident light will produce strong selective light absorption or scattering phenomenon and show different colors. Some studies have proposed a VO2 / Au / VO2 sandwich structure of smart window composite thin film. The addition of Au-NPs makes the composite thin film produce strong LSPR effect in the visible light range, and adjusts the VO2 thin film from yellow-brown to blue-green which meets the aesthetic requirements of building glass. However, due to the different optical properties of VO2 at high and low temperatures, the spectrum of the sandwich structure appears a clear "scissors fork" in the visible light range, which reduces the solar energy regulation efficiency of the thin film. Therefore, by designing the surface plasmon coupling structure of metal NPs to regulate its optical behavior and spectral properties, the blue shift or red shift of the LSPR characteristic peak can be achieved, and then the display color in the visible light range can be adjusted. Although this structure adjusts the color of the VO2 thin film, the thermochromic performance is often poor and the solar energy regulation ability is weak.

[0004] Therefore, it is of great significance to provide a composite thin film which can change the brown-yellow color of VO2-based thermochromic thin film to deep green without affecting the optical performance of the thin film, and improve the solar energy regulation efficiency. SUMMARY

[0005] Based on the above, the present application provides an Au-NPs / HfO2 / VO2 composite thin film and its preparation method and application. The Au-NPs / HfO2 / VO2 composite thin film can change the brown-yellow color of VO2-based thermochromic thin film to deep green without affecting the optical performance of the thin film, and improve the solar energy regulation efficiency.

[0006] To achieve the above object, the present application provides the following solutions:

[0007] One of the technical solutions of the present application is an Au-NPs / HfO2 / VO2 composite thin film, which comprises an Au-NPs local surface plasmon regulation layer, an HfO2 cover layer and a VO2 thermochromic functional thin film layer arranged in order from bottom to top.

[0008] The Au-NPs local surface plasmon control layer 3 is combined with the substrate.

[0009] In some embodiments of the present application, the average particle size of Au-NPs in the Au-NPs local surface plasmon control layer is 20-100 nm.

[0010] In the present application, the Au-NPs local surface plasmon control layer is obtained by sputtering a dense gold film on the substrate and then annealing; the thickness of the gold film is 1-10 nm. When the thickness of the gold film is too thin, the Au-NPs formed by annealing are insufficient to produce the local surface plasmon resonance effect; when the thickness of the gold film is too thick, the average particle size of the Au-NPs formed by annealing is too large, which weakens the local surface plasmon resonance effect.

[0011] In some embodiments of the present application, the thickness of the HfO2 covering layer is 25-200 nm; the thickness of the VO2 thermochromic functional thin film layer is 30-50 nm. When the thickness of the HfO2 covering layer is too thin, the Au-NPs cannot be completely covered, which weakens the local surface plasmon resonance effect of the Au-NPs; when the thickness of the HfO2 covering layer is too thick, the transmission spectrum of the composite thin film will have an interference peak, which is not conducive to obtaining high solar regulation efficiency. When the thickness of the VO2 thermochromic functional thin film layer is too thin, the solar regulation efficiency of the composite thin film is weak; when the thickness of the VO2 thermochromic functional thin film layer is too thick, the visible light transmittance of the composite thin film will be greatly reduced.

[0012] The second technical scheme of the present application is a preparation method of the above-mentioned Au-NPs / HfO2 / VO2 composite thin film, which comprises the following steps:

[0013] The Au-NPs local surface plasmon control layer is grown on the substrate by ion beam sputtering method, and then the HfO2 covering layer and the VO2 thermochromic functional thin film layer are sequentially grown on the surface of the Au-NPs local surface plasmon control layer by pulsed laser deposition method.

[0014] In some embodiments of the present application, the substrate is placed in the chamber of an ion sputtering instrument, the chamber pressure is extracted to below 5 Pa, the sputtering power is 2-15 W, the sputtering target material is an Au target, and the sputtering time is 20-120 s; the sputtered product is subjected to annealing treatment to obtain the Au-NPs local surface plasmon control layer; when the sputtering power is too low, the deposition rate of Au is too low; when the sputtering power is too high, the deposition rate of Au is too fast; when the sputtering time is too short, the Au-NPs obtained are insufficient to produce the local surface plasmon resonance effect; and when the sputtering time is too long, the average particle size of the Au-NPs is too large, which weakens the local surface plasmon resonance effect.

[0015] The vacuum degree of the annealing treatment is 10 -1 Pa, the temperature is 400-700 DEG C, and the time is 1-5h. If the annealing temperature is too high and the annealing time is too long, the grains of the Au-NPs will be merged and grown, irregular surface morphology and excessively large average particle size will be generated, the local surface plasmon resonance effect of the Au-NPs will be weakened, and thus the color regulation ability of the VO2 film will be weakened.

[0016] In some embodiments of the present application, a HfO2 cover layer is deposited on the Au-NPs local surface plasmon regulation layer, the target material used for deposition is a HfO2 target, the oxygen pressure is 0.2-4Pa, the oxygen flow rate is 5-50sccm, the substrate temperature is 150-450 DEG C, the laser frequency is 2-12Hz, and the growth rate of the HfO2 cover layer is 1-5nm / min. If the oxygen pressure, the oxygen flow rate, the substrate temperature and the laser frequency are too high or too low during the deposition of the HfO2 cover layer, the crystallinity of the HfO2 cover layer will be poor.

[0017] In some embodiments of the present application, a VO2 thermochromic functional film layer is deposited on the HfO2 cover layer, the target material used for deposition is a V target, the oxygen pressure is 0.5-3Pa, the oxygen flow rate is 15-50sccm, the substrate temperature is 450-550 DEG C, the laser frequency is 1-5Hz, and the growth rate of the VO2 thermochromic functional film layer is 0.6-2.4nm / min. If the oxygen pressure, the oxygen flow rate, the substrate temperature and the laser frequency are too high or too low during the deposition of the VO2 thermochromic functional film layer, the crystallinity of the VO2 thermochromic functional film layer will be poor, and it is not conducive to obtaining high solar regulation efficiency.

[0018] In some embodiments of the present application, the substrate is a glass substrate.

[0019] In the third aspect of the present application, the Au-NPs / HfO2 / VO2 composite film is applied to a thermochromic intelligent window.

[0020] The present application has the following technical effects:

[0021] The present application provides an Au-NPs / HfO2 / VO2 composite film, Au film is sputtered on a glass substrate, annealing is performed to form Au-NPs, a stable medium environment is provided for the Au-NPs by introducing a HfO2 cover layer, red shift or blue shift of the absorption peak position of the Au-NPs caused by temperature change is avoided, and thus the solar regulation efficiency of the composite film is affected, so that the composite film achieves a balance between optical performance and color meeting architectural aesthetics.

[0022] The Au-NPs / HfO2 / VO2 composite film has a three-layer composite structure of Au-NPs / HfO2 / VO2, changes the brownish yellow color of the VO2-based thermochromic film into deep green color which meets the building aesthetics, and improves the thermochromic performance of the VO2-based thermochromic film.

[0023] The Au film prepared by the ion sputtering instrument has good toning effect under wide annealing temperature and time, the subsequent HfO2 / VO2 film is prepared by the pulse laser deposition system, the preparation process does not depend on high-cost and high-precision process conditions and equipment such as templates and photoetching, and the preparation process is more simple, stable and low in cost. BRIEF DESCRIPTION OF DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0025] Figure 1 It is a structure schematic diagram of the Au-NPs / HfO2 / VO2 composite film of the present application, wherein 1 is a VO2 thermochromic functional film layer, 2 is a HfO2 cover layer, 3 is an Au-NPs local surface plasmon control layer, and 4 is a glass substrate.

[0026] Figure 2 It is a light transmittance spectrum of the Au-NPs / VO2 film prepared for Comparative Example 1 in a visible-near infrared wide spectrum domain, and the inserted drawing is a physical photograph of Comparative Example 1 (the example in the drawing represents Comparative Example 1).

[0027] Figure 3 It is a light transmittance spectrum of the Au-NPs / HfO2 / VO2 composite film prepared for Example 1 in a visible-near infrared wide spectrum domain, and the inserted drawing is a physical photograph of Example 1.

[0028] Figure 4 It is a light transmittance spectrum of the Au-NPs / HfO2 / VO2 composite film prepared for Example 2 in a visible-near infrared wide spectrum domain, and the inserted drawing is a physical photograph of Example 2. DETAILED DESCRIPTION

[0029] The detailed description of the various exemplary embodiments of the present application should not be considered as limiting the present application, but should be understood as a more detailed description of some aspects, characteristics and embodiments of the present application.

[0030] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application. Additionally, for a range of values of, for example, a parameter, an individual value from the range can be expressly disclosed herein to mean that each and every intermediate value of the range is also expressly disclosed. All individual values and subranges from the stated range are specifically included in the scope of the present application. When no range is specifically recited, the range of values from the lowest value to the highest value of the parameter is intended to be expressly recited.

[0031] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Although preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application. All documents mentioned herein are incorporated by reference to disclose and describe in full the methods and / or materials which are described herein. In the case of conflict between any document mentioned herein and the present specification, the present specification shall control.

[0032] Many modifications and variations of the present application described in the specification are possible without departing from the scope or spirit of the application. Other embodiments of the application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. The specification and examples are illustrative only.

[0033] As used herein, the terms "comprises", "comprising", "includes", "including", "has", "having", "contains", "containing", or variations thereof, are intended to be open-ended terms that mean inclusion, but not limited to, the listed materials and methods.

[0034] The first aspect of the present application provides an Au-NPs / HfO2 / VO2 composite film, comprising Au-NPs local surface plasmon control layer 3, HfO2 cover layer 2 and VO2 thermochromic functional film layer 1 arranged from bottom to top.

[0035] The Au-NPs local surface plasmon control layer 3 is deposited on the transparent glass substrate 4, the HfO2 cover layer 2 is formed on the Au-NPs local surface plasmon control layer 3, and the VO2 thermochromic functional film layer 1 is formed on the HfO2 cover layer 2.

[0036] The second aspect of the present application provides a preparation method of the Au-NPs / HfO2 / VO2 composite film, comprising the following steps: placing a glass substrate into an ion sputtering instrument chamber, the chamber pressure is extracted to below 5 Pa, the sputtering power is 2-15 W, the sputtering target material is Au target, and the sputtering time is 20-120 s; the sample after sputtering is subjected to vacuum annealing treatment for 1-5 h, the vacuum degree is extracted to 10 -1Pa, the annealing temperature is 400-700℃, to obtain Au-NPs local surface plasmon control layer 3; deposit HfO2 cover layer 2 on Au-NPs local surface plasmon control layer 3, the target material used for deposition is HfO2 target, the oxygen pressure is 0.2-4Pa, the oxygen flow rate is 5-50sccm, the substrate temperature is 150-450℃, the laser frequency is 2-12Hz, and the growth rate of HfO2 cover layer 2 is 1-5nm / min; deposit VO2 thermochromic functional film layer 1 on HfO2 cover layer 2, the target material used for deposition is V target, the oxygen pressure is 0.5-3Pa, the oxygen flow rate is 15-50sccm, the substrate temperature is 450-550℃, the laser frequency is 1-5Hz, the growth rate of VO2 thermochromic functional film layer 1 is 0.6-2.4nm / min, and the deposition time is 5-50min.

[0037] In the present application, Au-NPs local surface plasmon control layer 3 is used to produce an absorption peak in the visible light range, to control the color of the film, HfO2 cover layer 2 is used to provide a stable medium environment for Au-NPs local surface plasmon control layer 3, and VO2 thermochromic functional film layer 1 is used to adjust the solar transmittance.

[0038] Further preferably, other functional films can be introduced above or below the Au-NPs / HfO2 / VO2 composite film to make the composite film have better performance or function.

[0039] The third aspect of the present application provides a use of the above-mentioned Au-NPs / HfO2 / VO2 composite film in a thermochromic intelligent window.

[0040] The present application uses Au-NPs to change the brownish yellow color of VO2-based thermochromic film, so that the VO2 intelligent window film balances between excellent thermochromic performance and color that meets architectural aesthetics, and provides new ideas and theoretical guidance for the microstructure design of new high-performance VO2-based intelligent window.

[0041] The meanings of the abbreviations in this paper are as follows:

[0042] Au-NPs: gold nanoparticles

[0043] T sol : solar regulation efficiency

[0044] T c : phase transition temperature

[0045] T lum : visible light transmittance

[0046] The raw materials used in the embodiments of the present application, unless otherwise specified, can be obtained through market channels.

[0047] A schematic diagram of the Au-NPs / HfO2 / VO2 composite thin film structure of the present invention is shown below. Figure 1 As shown, 1. VO2 thermochromic functional thin film layer; 2. HfO2 capping layer; 3. Au-NPs localized surface plasmon modulation layer; 4. Glass substrate.

[0048] The present invention will be further illustrated by the following examples.

[0049] Example 1

[0050] The preparation method of Au-NPs / HfO2 / VO2 composite thin film is as follows:

[0051] The glass substrate was placed in the ion sputtering chamber, the chamber pressure was evacuated to below 5 Pa, the sputtering power was 10 W, the sputtering target was Au, and the sputtering time was 30 s. The sputtered sample (a dense gold film with a thickness of 5 nm) was then subjected to vacuum annealing for 2 hours, with the vacuum level evacuated to 10. -1 Below Pa, with an annealing temperature of 600℃, an Au-NPs localized surface plasmon resonance (LPR) layer 3 was obtained, with an average Au-NPs particle size of 52 nm. An HfO2 capping layer 2 was deposited on the LPR layer 3. The deposition target was an HfO2 target, the oxygen pressure was 0.2 Pa, the oxygen flow rate was 10 sccm, the substrate temperature was 250℃, the laser frequency was 5 Hz, the growth rate of the HfO2 capping layer 2 was 5 nm / min, and the deposition time was 5 min. A VO2 thermochromic functional thin film layer 1 was then deposited on the HfO2 capping layer 2. The deposition target was a V target, the oxygen pressure was 0.9 Pa, the oxygen flow rate was 30 sccm, the substrate temperature was 480℃, the laser frequency was 2 Hz, the growth rate of the VO2 thermochromic functional thin film layer 1 was 1.2 nm / min, and the deposition time was 30 min. The Au-NPs / HfO2 / VO2 composite thin film was obtained after deposition.

[0052] The transmittance spectrum of the Au-NPs / HfO2 / VO2 composite film was measured using a UV-3600 (Shimazu) UV-Vis-IR spectrophotometer. All tests were conducted under atmospheric conditions, and the results are as follows: Figure 1 As shown (illustration is a photograph of the actual product). By Figure 1 It can be seen that the Au-NPs / HfO2 / VO2 composite film is dark green, and its solar energy regulation efficiency is 5.6% in the wavelength range of 280-2650nm.

[0053] Example 2

[0054] The difference between the example 1 is only that the deposition time of the cover layer 2 is 20 min; the rest of the steps, parameters are the same as example 1. The Au-NPs / HfO2 / VO2 composite film is prepared.

[0055] The Au-NPs / HfO2 / VO2 composite film prepared in the example is verified with the same effect as example 1, and the results are shown in Figure 4 Figure 4 It can be seen that the Au-NPs / HfO2 / VO2 composite film is dark green, and the solar energy regulation efficiency in the wavelength range of 280-2650 nm is 8.4%.

[0056] Comparative example 1

[0057] The difference between the example 1 is only that the deposition time of the cover layer 2 is 20 min; the rest of the steps, parameters are the same as example 1. The Au-NPs / HfO2 / VO2 composite film is prepared.

[0058] The composite film prepared in the example is verified with the same effect as example 1, and the results are shown in Figure 2 Figure 2 It can be seen that the Au-NPs / HfO2 / VO2 composite film is dark green, and the solar energy regulation efficiency in the wavelength range of 280-2650 nm is 8.4%.

[0059] The above-described examples are only to describe the preferred mode of the present application, and not to limit the scope of the present application, without departing from the design spirit of the present application, the person skilled in the art to the technical scheme of the present application makes various modifications and improvements, all should fall into the protection scope determined by the claims of the present application.​​

Claims

1. An Au-NPs / HfO2 / VO2 composite thin film, characterized in that, The Au-NPs local surface plasmon control layer (3), the HfO2 cover layer (2) and the VO2 thermochromic functional film layer (1) are sequentially arranged from bottom to top. The Au-NPs local surface plasmon control layer (3) is combined with the substrate. The average particle size of Au-NPs in the Au-NPs local surface plasmon control layer (3) is 20-100 nm. The thickness of the HfO2 cover layer (2) is 25-200 nm. The thickness of the VO2 thermochromic functional film layer (1) is 30-50 nm.

2. A method for preparing the Au-NPs / HfO2 / VO2 composite film according to claim 1, characterized in that, The method comprises the following steps: The Au-NPs local surface plasmon control layer (3) is grown on the substrate by ion beam sputtering, and then the HfO2 cover layer (2) and the VO2 thermochromic functional film layer (1) are sequentially grown on the surface of the Au-NPs local surface plasmon control layer (3) by pulsed laser deposition.

3. The method for preparing the Au-NPs / HfO2 / VO2 composite thin film according to claim 2, characterized in that, The substrate is placed in the chamber of an ion sputtering instrument, the chamber pressure is extracted to below 5 Pa, the sputtering power is 2-15 W, the sputtering target material is Au target, and the sputtering time is 20-120 s; the sputtered product is annealed to obtain the Au-NPs local surface plasmon control layer (3); The vacuum degree of the annealing treatment is 10 -1 Pa, temperature is 400-700℃, and time is 1-5h.

4. The method for preparing the Au-NPs / HfO2 / VO2 composite thin film according to claim 2, characterized in that, The HfO2 cover layer (2) is deposited on the Au-NPs local surface plasmon control layer (3), the deposition target material is HfO2 target, the oxygen pressure is 0.2-4 Pa, the oxygen flow rate is 5-50 sccm, the substrate temperature is 150-450 ℃, the laser frequency is 2-12 Hz, and the growth rate of the HfO2 cover layer (2) is 1-5 nm / min.

5. The method for preparing the Au-NPs / HfO2 / VO2 composite thin film according to claim 2, characterized in that, The VO2 thermochromic functional film layer (1) is deposited on the HfO2 cover layer (2), the deposition target material is V target, the oxygen pressure is 0.5-3 Pa, the oxygen flow rate is 15-50 sccm, the substrate temperature is 450-550 ℃, the laser frequency is 1-5 Hz, and the growth rate of the VO2 thermochromic functional film layer (1) is 0.6-2.4 nm / min.

6. The method for preparing the Au-NPs / HfO2 / VO2 composite thin film according to claim 2, characterized in that, The substrate is a glass substrate.

7. Application of the Au-NPs / HfO2 / VO2 composite film in a thermochromic intelligent window according to claim 1.

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