An adjustable light-absorbing sheet based on vertical micro-nano graphene sheets and a preparation method thereof

Abstract

The application belongs to the field of optical functional nanomaterials, and particularly relates to an adjustable light-absorbing sheet based on an upright micro-nano graphene sheet and a preparation method thereof. The method is to change the micro-morphology and size of the upright micro-nano graphene sheet by adjusting the growth parameters of a radio frequency plasma enhanced chemical vapor deposition (RF-PECVD) device, such as temperature, time, gas flow and radio frequency power, so as to realize the regulation and control of the light-absorbing performance of the light-absorbing sheet. The adjustable light-absorbing sheet has the characteristics of simple preparation process, low cost and low-temperature preparation, and does not need a catalyst. The light-absorbing rate of the adjustable light-absorbing sheet is as high as more than 99%, and the structure of the double-layer transparent substrate sandwiching the upright graphene film also protects the graphene, so that the graphene has the characteristics of scratch resistance and repeated use.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of optical functional nanomaterials, and particularly relates to an adjustable light-absorbing sheet based on an upright micro-nano graphene sheet and a preparation method thereof. BACKGROUND

[0002] With the rapid development of science and technology, the demand for high-performance light-absorbing materials is increasing in the fields of optoelectronic devices, solar light-heat conversion technology, and photoelectric catalysis technology. The performance of light-absorbing materials directly affects the photoelectric conversion efficiency and light-heat conversion efficiency. Therefore, the development of light-absorbing materials with high light-absorbing rate, tunability, and low cost has become a current research hotspot.

[0003] Graphene, as a new type of two-dimensional material, has attracted widespread attention due to its unique electronic, thermal, and optical properties. In particular, upright graphene (VG) exhibits excellent optical properties, including high light-absorbing rate and wide-band light absorption ability, due to its growth perpendicular to the substrate. However, traditional methods for preparing upright graphene, such as chemical vapor deposition (CVD) and plasma-enhanced chemical vapor deposition (PECVD), usually require high-temperature conditions and rely on catalysts, which limits their application in large-scale production and cost-effectiveness. At the same time, the light-absorbing performance of upright graphene prepared by these methods is often fixed and difficult to adjust flexibly according to specific application requirements. In addition, as a thin film material, upright graphene is prone to damage and scratching. SUMMARY

[0004] The purpose of the present application is to provide a preparation method of an adjustable light-absorbing sheet based on an upright micro-nano graphene sheet, which realizes the regulation of the light-absorbing performance of the light-absorbing sheet by changing the micro-morphology and structure of the upright graphene.

[0005] To achieve the above-mentioned purpose, the technical solutions adopted by the present application are as follows:

[0006] An adjustable light-absorbing sheet based on an upright micro-nano graphene sheet, comprising a first transparent substrate, a second transparent substrate, and an upright graphene formed between the first transparent substrate and the second transparent substrate; the micro-morphology of the upright graphene is arranged upright, and the light-absorbing performance is adjustable by adjusting the parameters of the upright graphene nanosheet, including micro-morphology, height, thickness, and spacing.

[0007] The preparation method of the above-mentioned adjustable light-absorbing sheet based on an upright graphene comprises the following steps:

[0008] Step 1: clean and dry the transparent substrate, which includes a first transparent substrate and a second transparent substrate;

[0009] Step 2: Place the first transparent substrate into the vacuum chamber of the radio frequency plasma enhanced chemical vapor deposition (RF-PECVD) equipment and evacuate it to the required vacuum level; then heat and maintain the first transparent substrate at a temperature range of 25℃ to 550℃.

[0010] Step 3: Introduce a certain amount of buffer gas into the vacuum chamber and maintain the gas pressure between 0.01 Pa and 1000 Pa; the flow rate of the buffer gas is between 1 sccm and 1000 sccm.

[0011] Step 4: Turn on the radio frequency source of the RF-PECVD equipment and use plasma-enhanced chemical vapor deposition technology to grow upright graphene with nanosheets arranged in an upright structure on the surface of the first transparent substrate, and then remove it; the radio frequency power during the growth process is 10W to 5000W, and the growth time of upright graphene is 5min to 180min.

[0012] Step 5: Cover the first transparent substrate on which upright graphene has been grown with the second transparent substrate, and fix the edges of the substrate with conductive adhesive to obtain an adjustable light-absorbing sheet based on upright graphene.

[0013] Furthermore, the transparent substrate is electronic glass, quartz glass, or conductive glass.

[0014] Furthermore, the buffer gas in step 3 is argon, methane, hydrogen, or a mixture thereof.

[0015] Furthermore, the adhesive in step 5 includes graphite conductive adhesive, conductive silver paste, epoxy resin conductive adhesive, or glass adhesive.

[0016] Furthermore, in step 5, when using conductive adhesive to fix the edges of the substrate, room temperature curing or heating curing is employed.

[0017] This invention proposes an tunable light-absorbing sheet and its preparation method. The light-absorbing material of this sheet is an upright micro / nano graphene sheet structure. The principle is as follows: the microstructure of upright graphene consists of randomly distributed, upright graphene nanosheets. The top of the nanosheets is a single layer or few layers of graphene, while the middle and bottom layers are multilayered graphene. Due to the high transmittance of single-layer or few-layer graphene, light can pass through the top of the nanosheets and enter the micro / nano structure. The multilayered graphene absorbs light. Because the graphene nanosheets are randomly distributed and upright, light undergoes multiple diffuse reflections within the upright graphene, and is subsequently absorbed by the multilayered graphene in the middle and bottom layers. Since the upright graphene consists of upright graphene nanosheets, its specific surface area is much larger than that of planar multilayered graphene, thus greatly increasing the absorption area and absorption rate.

[0018] Based on the above principles, this invention modulates the light absorption performance of the tunable light-absorbing sheet by adjusting the growth parameters of the radio frequency plasma-enhanced chemical vapor deposition (RF-PECVD) equipment, such as temperature, time, gas flow rate, and radio frequency power, thereby changing the size of the microstructure of the upright graphene. Compared with existing technologies, the tunable light-absorbing sheet of this invention has a simple and low-cost preparation process, requires no catalyst, and features low-temperature preparation. Its absorbance is as high as 99% or more. The structure of a double-layer transparent substrate sandwiching the upright graphene film also protects the graphene, giving it scratch resistance and reusability. Attached Figure Description

[0019] Figure 1 This is a schematic diagram illustrating the principle of the present invention based on an upright graphene tunable light-absorbing sheet;

[0020] Figure 2 The images show a top view and a cross-sectional view of the upright graphene prepared in Example 1 using a scanning electron microscope; where a is the top view and b is the cross-sectional view.

[0021] Figure 3 The images show a top view and a cross-sectional view of the upright graphene prepared in Example 2 using a scanning electron microscope; where a is the top view and b is the cross-sectional view.

[0022] Figure 4 The images show a top view and a cross-sectional view of the upright graphene prepared in Example 3 using a scanning electron microscope; where a is the top view and b is the cross-sectional view.

[0023] Figure 5 This is a three-dimensional structural schematic diagram of the light-absorbing sheet of the present invention;

[0024] Figure 6 The diagram shows the absorbance of the light-absorbing sheets obtained in Examples 1, 2, and 3.

[0025] Figure label:

[0026] 1 is a transparent substrate, and 2 is an upright graphene film.

[0027] Specific implementation methods

[0028] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0029] Example 1

[0030] like Figure 1 As shown in this embodiment, a method for preparing a tunable light-absorbing sheet based on an upright micro / nano graphene sheet structure is provided, comprising:

[0031] Step 1: Select two pieces of electronic glass with dimensions of 20mm*20mm*1mm as substrates, clean and dry them for later use. The two transparent substrates are the first transparent substrate and the second transparent substrate.

[0032] Step 2: Place the first transparent substrate after the treatment in Step 1 into the vacuum chamber of the RF-PECVD equipment, and then heat the first transparent substrate to room temperature of 25°C and keep it at a constant temperature.

[0033] Step 3: Introduce a mixture of argon and methane gas at 20 sccm into the vacuum chamber containing the first transparent substrate, so that the gas pressure inside the chamber is maintained at 50 Pa.

[0034] Step 4: Turn on the RF source of the RF-PECVD equipment to perform plasma-enhanced chemical vapor deposition. The RF source power is set to 2000W, and the growth time of the upright graphene is 30 minutes. The height of the formed upright graphene is approximately 2 μm, and the size of the graphene nanosheets is between 300-400 nm. The top view of the upright graphene under a scanning electron microscope is shown below. Figure 2 As shown in Figure a, the scanning electron microscope cross-sectional image is as follows: Figure 2 As shown in b.

[0035] Step 5: A second transparent substrate is applied to the electronic glass substrate with vertically grown graphene, with the vertically grown graphene sandwiched between the two electronic glass substrates, thus forming a... Figure 5 The structure shown is as follows. The two opposite edges of the substrate are fixed with graphite conductive adhesive and placed at a temperature of 25-30°C for 12-24 hours. Then, it is heated to 80°C and held at that temperature for 2 hours. Next, it is heated to 120°C and held at that temperature for 2 hours. Finally, it is slowly cooled to obtain an tunable light-absorbing sheet based on vertical graphene.

[0036] Step 6: The prepared upright graphene was subjected to visible light reflection and transmission measurements using a spectrometer. The absorbance of the sample in the wavelength range of 400nm-800nm ​​was obtained, and the absorbance was greater than 87.86%.

[0037] Example 2

[0038] The preparation steps in this embodiment are the same as in Embodiment 1, with the only difference being:

[0039] Step 1: When growing vertical graphene, the temperature of the first transparent substrate is first heated to 300℃ and held for 15 minutes, then heated to 400℃ and held for 5 minutes. Then, vertical graphene is grown at a substrate temperature of 400℃. Segmented heating and holding makes the substrate heat more uniformly, which is conducive to the uniform growth of vertical graphene and improves the quality of the vertical graphene layer.

[0040] The top view of the upright graphene sheet obtained in this embodiment under a scanning electron microscope is shown below. Figure 3 As shown in Figure a, the cross-sectional view is as follows: Figure 3 As shown in b; from Figure 3 a and Figure 3As can be seen from b, the upright graphene sheets obtained after adjusting the temperature of the first transparent substrate, the holding time, and the staged heating are larger and taller than those in Example 1. The height of the upright graphene is approximately 1.2 μm, and the size of the graphene nanosheets is between 400 and 600 nm. The absorber has an absorbance of greater than 92.29% at wavelengths between 400 nm and 800 nm.

[0041] Example 3

[0042] The preparation steps in this embodiment are the same as in Embodiment 1, with the only difference being:

[0043] Step 1: When growing vertical graphene, the substrate temperature is first heated to 300℃ and held for 15 minutes, then raised to 540℃ and held for 5 minutes. Vertical graphene is then grown at the substrate temperature of 540℃. Segmented heating and holding ensures more uniform heating of the substrate, which is beneficial for the uniform growth of vertical graphene and improves the quality of the vertical graphene layer.

[0044] Top view of scanning electron microscope as shown Figure 4 As shown in Figure a, the cross-sectional view is as follows: Figure 4 As shown in b; from Figure 4 a and Figure 4 As can be seen from b, after adjusting the temperature and holding time of the first transparent substrate, the resulting upright graphene sheet is larger and taller than the upright graphene sheet in Example 1. The height of the upright graphene is approximately 2.3 μm, and the size of the graphene nanosheets is between 600-800 nm. The absorber has an absorbance greater than 99.03% at wavelengths between 400 nm and 800 nm, with a maximum absorbance of 99.83%.

[0045] Figure 6 This is an absorbance graph of the light-absorbing sheets obtained in Examples 1, 2, and 3. Figure 6 As can be seen, the absorbance of the upright graphene absorber gradually increases from Example 1 to Example 3, through combination Figures 1-5 As can be seen, changing the preparation parameters can alter the microstructure of upright graphene, thereby affecting its absorbance.

[0046] In summary, this invention achieves the modification of the microstructure and size of upright graphene by altering the preparation parameters, thereby controlling the light absorption performance of the absorber. Furthermore, upright graphene, as a thin film material, is easily damaged and scratched. The structure of this invention protects the upright graphene film through the placement of a first and second transparent substrate, giving it good environmental stability. The graphene film prepared under low-temperature conditions exhibits a highly uniform and ordered structure, maintaining consistent light absorption performance in multiple experiments, demonstrating repeatability. The absorbance of the absorber can also be adjusted according to different application requirements, providing a high-performance light-absorbing material solution for optoelectronic devices, solar photothermal conversion, and photoelectrocatalysis technologies.

Claims

1. A tunable light-absorbing sheet based on upright micro / nano graphene sheets, comprising a first transparent substrate, a second transparent substrate, and an upright graphene layer formed between the first and second transparent substrates; characterized in that: The upright graphene layer is composed of several upright graphene nanosheets. The graphene nanosheets have a gradually changing layer structure along their growth direction, wherein the top of the nanosheet is a single layer of graphene, and the middle and bottom of the nanosheet are multilayer graphene, forming a three-dimensional light-absorbing structure that is thin at the top and thick at the bottom. By adjusting the growth parameters and subsequent processing conditions of the upright graphene nanosheets, the microstructure, height, thickness, spacing, and top thinning degree of the graphene nanosheets can be changed, thereby achieving continuous and adjustable light absorption performance of the light-absorbing sheet.

2. A method for preparing a tunable light-absorbing sheet based on upright micro / nano graphene sheets, characterized in that, Includes the following steps: Step 1: Clean and dry the transparent substrate, which includes a first transparent substrate and a second transparent substrate; Step 2: Place the first transparent substrate into the vacuum chamber of the radio frequency plasma enhanced chemical vapor deposition (RF-PECVD) equipment and evacuate it to the required vacuum level; then heat and maintain the first transparent substrate at a temperature range of 25℃ to 550℃. Step 3: Introduce a certain amount of buffer gas into the vacuum chamber and maintain the gas pressure between 0.01 Pa and 1000 Pa; the flow rate of the buffer gas is between 1 sccm and 1000 sccm. Step 4: Turn on the radio frequency source of the RF-PECVD equipment and use plasma-enhanced chemical vapor deposition technology to grow upright graphene with nanosheets arranged in an upright structure on the surface of the first transparent substrate, and then remove it; the radio frequency power during the growth process is 10W~5000W, and the growth time of upright graphene is 5min~180min. Step 5: Cover the first transparent substrate on which the vertical graphene has grown with the second transparent substrate, so that the vertical graphene layer is sandwiched between the two transparent substrates, and fix the edges of the substrate with conductive adhesive. The process then involves a curing process, which includes heating in an oxygen-containing environment to cause controlled oxidation and thinning of the top of the upright graphene nanosheets, forming a three-dimensional light-absorbing structure with a thin top and thick bottom as described in claim 1, thereby obtaining the tunable light-absorbing sheet.

3. The method for preparing a tunable light-absorbing sheet based on an upright micro / nano graphene sheet structure according to claim 2, characterized in that, The transparent substrate is electronic glass.

4. The method for preparing a tunable light-absorbing sheet based on an upright micro / nano graphene sheet structure according to claim 2, characterized in that, The buffer gas in step 3 is argon, methane, hydrogen, or a mixture thereof.

5. The method for preparing a tunable light-absorbing sheet based on an upright micro / nano graphene sheet structure according to claim 2, characterized in that, The conductive adhesive used in step 5 includes graphite conductive adhesive, conductive silver paste, epoxy resin conductive adhesive, or glass adhesive.

6. The method for preparing a tunable light-absorbing sheet based on an upright micro / nano graphene sheet structure according to claim 2, characterized in that, When using conductive adhesive to fix the edges of the substrate in step 5, room temperature curing or heating curing is employed.

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