Preparation method and application of modified EP-POSS film

Abstract

The invention provides a preparation method and application of a modified EP-POSS film, and relates to the field of molecular material synthesis. Comprising the following steps: dissolving KH560 in xylene to obtain a mixed solution 1; isopropanol and a tetramethylammonium hydroxide aqueous solution are mixed and stirred, and a mixed solution 2 is obtained; dropwise adding the mixed solution 1 into the mixed solution 2, stirring, refluxing, distilling, washing, drying and grinding one by one to obtain EP-POSS white powder; the preparation method comprises the following steps: activating a base material, dropwise adding EP-POSS onto the base material, finally preparing a fluorinated silane-toluene solution, and grafting fluorinated silane onto the surface of EP-POSS through a vapor deposition method to obtain the modified EP-POSS film. The contact angle of the prepared modified EP-POSS film is far larger than that of a common EP-POSS material, and the modified EP-POSS film has excellent hydrophobicity, light transmittance and thermal stability. In addition, the invention further provides application of the modified EP-POSS film to the photovoltaic module, the output power of the photovoltaic module can be remarkably improved, and the influence of long-time sunshine and dust covering on the output power of the photovoltaic module is reduced.

Description

Technical Field

[0001] This invention relates to the field of molecular material synthesis, and more specifically, to a method for preparing and applying a modified EP-POSS thin film. Background Technology

[0002] Solar panels have undergone years of development and iteration, evolving from the initial monocrystalline silicon photovoltaic modules to polycrystalline silicon photovoltaic modules and cadmium telluride photovoltaic modules, and then to the new chlorophyll-based photovoltaic modules. However, dust accumulation and aging can cause PID effects in photovoltaic modules, affecting their output power. Therefore, in practical applications, it is often necessary to coat photovoltaic modules with a hydrophobic coating to reduce dust accumulation and resist aging, thereby increasing the output power of the photovoltaic modules.

[0003] Traditional photovoltaic (PV) module surface coatings are mostly anti-reflective coatings, primarily designed to reduce the reflection loss of incident light and allow more light to enter the solar cells. However, existing coatings often suffer from insufficient weather resistance, poor density, weakened mechanical properties, and weak adhesion, thus reducing the output power of PV modules. Therefore, designing a new coating with good mechanical properties, excellent hydrophobicity, light transmission, and weather resistance, which can effectively protect silicon wafers, is of great significance for maintaining the long-term stable operation of PV modules. Summary of the Invention

[0004] This invention provides a method for preparing a modified EP-POSS film. By preparing an EP-POSS film and grafting fluorinated silane onto the surface of the EP-POSS film, the resulting modified EP-POSS film has a contact angle larger than that of ordinary EP-POSS and exhibits excellent hydrophobicity, light transmittance, and thermal stability.

[0005] The technical problem solved by this invention is achieved by the following technical solution.

[0006] On one hand, embodiments of this application provide a method for preparing a modified EP-POSS thin film, comprising the following steps: S1: Dissolve γ-glycidyl etheroxypropyltrimethoxysilane in xylene to obtain mixture 1; mix isopropanol and tetramethylammonium hydroxide aqueous solution and stir to obtain mixture 2; then add the above mixture 1 dropwise to the above mixture 2, and after stirring, reflux, distillation, washing, drying and grinding, EP-POSS white powder is obtained; S2: Dissolve the above-mentioned EP-POSS white powder in anhydrous toluene and stir until completely dissolved to obtain an EP-POSS toluene solution; S3: The substrate is ultrasonically cleaned in acetone and anhydrous ethanol in sequence, then dried under a protective atmosphere, and then activated with oxygen plasma after drying. S4: The above EP-POSS toluene solution is dropped onto the above substrate, and then dried and cured under vacuum to obtain a stable EP-POSS film; S5: Place the above EP-POSS film and fluorinated silane-toluene solution in a sealed desiccator and heat them; after heating, remove them and ultrasonically clean them in sequence with anhydrous toluene, acetone and anhydrous ethanol, and dry them under a protective atmosphere to obtain the modified EP-POSS film.

[0007] In some embodiments of the present invention, in step S1, the molar ratio of the above-mentioned γ-glycidyl etheroxypropyltrimethoxysilane and the above-mentioned xylene is 1:1-5, and the molar ratio of the above-mentioned isopropanol and the above-mentioned tetramethylammonium hydroxide aqueous solution is 100-300:1.

[0008] In some embodiments of the present invention, in step S2, the mass fraction of the above-mentioned EP-POSS toluene solution is 5-10 wt%.

[0009] In some embodiments of the present invention, in step S3, the substrate is a smooth and flat silicon wafer or glass sheet; the protective atmosphere is nitrogen, helium or argon.

[0010] In some embodiments of the present invention, in step S4, the solution is dropped onto the substrate by spin coating to form a uniform thin film on the substrate; then it is cured at 120-150°C for 1-2 hours to further stabilize the film.

[0011] In some embodiments of the present invention, in step S5, the fluorinated silane is perfluorooctyltrichlorosilane or perfluorodecyltrichlorosilane.

[0012] Secondly, this application provides a modified EP-POSS film, which is prepared by any of the above-mentioned preparation methods.

[0013] Thirdly, this application provides the application of the aforementioned modified EP-POSS film in photovoltaic modules. By coating the modified EP-POSS film onto the photovoltaic module, the output power of the photovoltaic module can be significantly improved, and the impact of sunlight, dust accumulation, and other factors on the output power of the photovoltaic module can be reduced.

[0014] Compared with the prior art, the embodiments of the present invention have at least the following advantages or beneficial effects: 1. The EP-POSS film prepared by this invention has a contact angle larger than that of ordinary EP-POSS, and its surface has a nanoscale barbed structure, which gives it excellent hydrophobic properties; its transmittance is about 85% in the visible light range of 300-700nm, which is excellent; the two main pyrolysis reactions occur at 410℃ and 540℃, which gives it good thermal stability. 2. The EP-POSS thin film prepared by this invention can be applied to photovoltaic modules to improve the output power of photovoltaic modules and reduce the impact of dust accumulation and ultraviolet aging on the output power of photovoltaic modules. Attached Figure Description

[0015] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a scanning electron microscope (SEM) image of the surface of the modified EP-POSS film in Example 1 of the present invention. Figure 2 These are AFM spectra of the modified EP-POSS film surface at different microscales in Example 1 of this invention; Figure 3 The absorbance of the modified EP-POSS film in Example 1 of this invention for different wavelength spectra; Figure 4 This is a DSC-TGA image of the modified EP-POSS film in Example 1 of the present invention; Figure 5 The power curves of components No. 3 and No. 6 in Embodiment 2 of the present invention under different illumination durations are shown. Figure 6 This represents the ratio of the maximum output power variation values ​​of components 3 and 6 under different illumination times in Embodiment 2 of the present invention. Figure 7 This is a comparison diagram of the output power of component 1 and component 2 in Embodiment 2 of the present invention; Figure 8 This is a comparison chart of the power curves of components No. 4 and No. 5 in Embodiment 2 of the present invention under the same illumination time; Figure 9 This is a comparison chart of the power curves of components No. 7 and No. 8 in Embodiment 2 of the present invention under the same illumination time. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0018] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to specific embodiments.

[0019] Example 1 This embodiment provides a method for preparing a modified EP-POSS thin film, comprising the following steps: S1: γ-glycidyl etheroxypropyltrimethoxysilane (KH560) was dissolved in xylene at a molar ratio of 1:2 to obtain mixture 1; isopropanol and 4.0 wt% tetramethylammonium hydroxide aqueous solution were mixed and stirred at a molar ratio of 200:1 to obtain mixture 2, which was placed in a beaker; mixture 1 was then added dropwise to mixture 2 through a dropping funnel. After the addition was complete, the mixture was stirred at room temperature for 24 hours, and then refluxed in an 80°C water bath for 2 hours; the pH was adjusted to neutral, and then stirred at room temperature for 1 hour. After stirring, isopropanol and xylene were removed by distillation, and the mixture was washed with acetone and evaporated to dryness twice; the yellow viscous liquid obtained after distillation was EP-POSS, which was dried under nitrogen and then thoroughly ground to obtain white EP-POSS powder; S2: Dissolve the above-mentioned EP-POSS white powder in anhydrous toluene and stir until completely dissolved to obtain an EP-POSS toluene solution with a mass fraction of 10 wt%. S3: Select a smooth, flat, and flawless silicon wafer or glass sheet as the substrate. Place it in acetone and anhydrous ethanol for ultrasonic cleaning for 15 minutes, then dry it with nitrogen or argon. After drying, activate the substrate with oxygen plasma under a specific plasma device to thoroughly clean the surface of the substrate and introduce a large number of hydroxyl groups on the surface, thereby enhancing the adsorption of EP-POSS film. S4: Using spin coating, the EP-POSS toluene solution is gradually added to the substrate at a rate of 3000 rpm until a uniform film is formed on the substrate; then the substrate is placed in a vacuum drying oven and cured at 120°C for 2 hours to obtain a stable EP-POSS film. S5: Select perfluorooctyltrichlorosilane (FOTS) or perfluorodecyltrichlorosilane (FDTS), dissolve them in anhydrous toluene, and stir magnetically for 10 min to ensure thorough mixing, thus obtaining a 0.2%wt fluorinated silane-toluene solution. Place the EP-POSS film and the fluorinated silane-toluene solution in a sealed desiccator (note that they should be placed separately and not in contact), and heat at 80℃ for 2-4 h. During this process, toluene vapor will carry fluorinated silane molecules to the surface of the EP-POSS film and undergo a condensation reaction with the hydroxyl groups (-OH) on its surface to form covalent bonds. After heating, remove the film and ultrasonically clean it for 5 min each with anhydrous toluene, acetone, and anhydrous ethanol to remove physically adsorbed and unreacted fluorinated silane molecules. Then, dry it with nitrogen and place it in a drying oven at 80℃ for 1 h to obtain the modified EP-POSS film.

[0020] After preparation, the contact angle was measured using the stop-drop method, with a measurement range of 0-180°, a measurement standard of 0.1°, a resolution of 0.1°, and a water droplet volume of 5 μL. The water droplet roll-off angle on the modified EP-POSS film surface was measured using the tilted-drop method, with a water droplet volume of 15 μL. Five points were selected for measurement on each individual sample coating. The measurement results show that the average contact angle of the modified EP-POSS reaches 136.2°, which is significantly higher than that of ordinary EP-POSS (typically 76°), demonstrating the stronger hydrophobic properties of the modified EP-POSS film.

[0021] Furthermore, to verify the performance of the modified EP-POSS film, this embodiment analyzes its structure, light transmittance, and thermal properties, and the specific experiments are as follows: ① The surface of the modified EP-POSS film was observed using a scanning electron microscope (SEM). The observation results are as follows: Figure 1 As shown, at a microscale of 100 μm, the modified EP-POSS film has a smooth surface with low roughness, and the small number of particles are impurities remaining after brittle fracture.

[0022] Furthermore, the modified EP-POSS film was observed at the microscales of 100 nm and 1 μm using atomic force microscopy. The observation results are as follows: Figure 2As shown, the modified EP-POSS film surface has a raised structure, which significantly improves the contact area between droplets and air. White particles are uniformly distributed on the surface of the modified EP-POSS film, exhibiting an overall spike-like appearance; that is, a smooth surface with nanoscale spike-like structures. This rough surface structure creates a barrier between the droplet and the surface, preventing the droplet from completely wetting the surface. Instead, the droplet forms an arc at the spike-like structure, creating an air interface and thus reducing the contact area between the droplet and the surface. This structure not only increases the contact angle but also significantly reduces the roll-off angle, giving the modified EP-POSS film surface a self-cleaning function.

[0023] ② To investigate the light transmittance of the prepared modified EP-POSS film, a glass slide coated with the modified EP-POSS film was vertically placed in the sample chamber of a UV-Vis spectrophotometer, and its absorbance to different wavelengths of light was measured. The experimental results are as follows: Figure 3 As shown, the results indicate that the modified EP-POSS film has a transmittance of approximately 85% in the visible light range of 300-700 nm.

[0024] ③ To investigate the thermal stability of the prepared modified EP-POSS film, this embodiment uses DSC-TGA to test the modified EP-POSS film. The results... Figure 4 As shown, the modified EP-POSS film did not undergo significant pyrolysis before 350℃. The first pyrolysis peak appeared at 406℃, indicating the pyrolysis of the epoxy segments. The second pyrolysis peak at 540℃ corresponds to the pyrolysis of the epoxy segments grafted onto the POSS groups. The 5% thermogravimetric temperature (Td5) of the modified EP-POSS film is 353℃, higher than the 300℃ of commonly used silicone resins. Its two main pyrolysis reactions occurred at 410℃ and 540℃, corresponding to the pyrolysis of the epoxy segments and the pyrolysis of the epoxy segments grafted onto the POSS cage structure, respectively. At 800℃, the char residue of the modified EP-POSS film reached 43.2%. This is attributed to the inorganic nanocage structure on the molecular framework. The high bond energy of the Si-O bonds endows the POSS cage structure with high heat resistance, while simultaneously inhibiting the thermal motion of molecular chains during heating, thus improving thermal stability. The thermal experimental results demonstrate that the modified EP-POSS film possesses excellent thermal stability.

[0025] Example 2 This embodiment provides the application of the modified EP-POSS thin film prepared in Example 1 in photovoltaic modules and verifies its impact on the output power of photovoltaic modules, specifically as follows: ① Experimental pretreatment: Eight identical photovoltaic modules (purchased from Dezhou Ranruo New Energy Co., Ltd., with specifications of 150mm×125mm×2mm, light height of 30cm, and illuminance of 35.1W / m²) were selected. 2 The modules are numbered 1-8, where 1, 3, 4, and 5 are photovoltaic modules coated with modified EP-POSS film, and 2, 6, 7, and 8 are blank modules without modified EP-POSS film coating. Module 1 is a module coated with modified EP-POSS film after being covered with ash; Module 2 is a blank module after being covered with ash; Module 3 is a modified EP-POSS module irradiated with 0 hours of UV light; Module 4 is a modified EP-POSS module irradiated with 500 hours of UV light; Module 5 is a modified EP-POSS module irradiated with 1000 hours of UV light; Module 6 is a blank module irradiated with 0 hours of UV light; Module 7 is a blank module irradiated with 500 hours of UV light; and Module 8 is a blank module irradiated with 1000 hours of UV light.

[0026] ② To investigate the impact of modified EP-POSS film on the output power of photovoltaic modules under normal conditions, illumination experiments were conducted on modules No. 3 and No. 6, and the difference in output power between the two was measured. The experimental procedure was as follows: Photovoltaic modules No. 3 and No. 6 were placed on an outdoor platform with the same light intensity. Under ideal, unobstructed illumination, they were subjected to illumination durations of 0 min, 20 min, 40 min, 60 min, and 80 min, and the output power data at different illumination durations were measured. The experimental results are as follows: Figure 5 As shown, where, Figure 5 (a) Curves for component No. 3 coated with modified EP-POSS film. Figure 5 (b) shows the power curve of blank photovoltaic module No. 6. It can be seen that the maximum output power of module No. 3 is 0.221W and the maximum output power of module No. 6 is 0.194W. That is to say, under the same light irradiation experimental conditions, the photovoltaic module coated with modified EP-POSS film has a greater output power.

[0027] Additionally, please refer to Figure 6 , Figure 6The ratio of the maximum output power changes of the two photovoltaic modules under different illumination times clearly shows that, under the same illumination conditions, the ratio of the maximum power change of the blank module is greater than that of the modified EP-POSS thin-film module over different illumination times. This indicates that the photovoltaic module coated with the modified EP-POSS thin film has a more stable output power. Specifically, the output power of the photovoltaic module suddenly changes after the initial 20 minutes of illumination. This is because the temperature coefficient of the photovoltaic module is negative; the sudden temperature increase during the initial illumination leads to an increase in open-circuit voltage and short-circuit current, causing the electronic components inside the inverter to heat up. Some of the output power is converted into heat energy and consumed, resulting in a decrease in output power. During continuous illumination, the temperature of the photovoltaic module remains stable without significant change, and the output power remains stable. At this point, the output power increases with increasing light intensity. In other words, coating the surface of the photovoltaic module with the modified EP-POSS thin film can have a positive effect on the output power.

[0028] ③ To investigate the influence of modified EP-POSS film on the output power of photovoltaic modules under ash coating, construction ash was used as the main coating material, and experimental dust was obtained by passing it through a 65-mesh sieve. This dust was then evenly dropped from a height of 30 cm onto photovoltaic modules No. 1 and No. 2, which were tilted at 40°, to obtain photovoltaic modules with ash coating. The open-circuit voltage, short-circuit current, and output power of the two photovoltaic modules were then tested. The experimental results are as follows: Figure 7 As shown in the figure, coating with modified EP-POSS film can effectively improve the output power of photovoltaic modules. Module 1 has a short-circuit current of 0.051A and a maximum output power of 0.180W; while module 2 has a short-circuit current of 0.045A and a maximum output power of 0.159W. Both the short-circuit current and maximum output power of module 1 are higher than those of module 2. In other words, photovoltaic modules coated with modified EP-POSS film have a higher output power under dust-covered conditions compared to blank photovoltaic modules, meaning that modified EP-POSS film can improve the output power of photovoltaic modules under dust-covered conditions.

[0029] ④ To investigate the effect of modified EP-POSS film on the UV resistance of photovoltaic modules, UV irradiation experiments were conducted on photovoltaic modules No. 3-8 using UV lamps for 500h and 1000h respectively. The open-circuit voltage, short-circuit current and output power of the six different photovoltaic modules were measured, and the results are shown in Table 1: Table 1:

[0030] It can be seen that photovoltaic modules coated with modified EP-POSS film exhibit better UV resistance. The impact of UV aging on the maximum output power of photovoltaic modules coated with modified EP-POSS film is significantly less than that of blank modules. After 500h and 1000h of UV aging, the open-circuit voltage and short-circuit current of both modified EP-POSS modules and blank modules remain unchanged, while the decrease in maximum output power is significantly smaller than that of blank modules. This is because the high bond energy structure of modified EP-POSS has a bond energy higher than that of UV light, making it difficult to break down. Under prolonged UV aging, its performance does not change, resulting in almost no surface aging of the photovoltaic modules. The cells can stably absorb light, and the output power of photovoltaic modules coated with modified EP-POSS film is significantly higher than that of blank modules under prolonged UV aging.

[0031] Furthermore, to investigate the output power variation of different photovoltaic modules after UV aging, continuous-duration UV irradiation experiments were conducted on modules 4, 5, 7, and 8. The experimental results are as follows: Figure 8 and Figure 9 As shown, where Figure 8 (A) is the power curve of component number 4. Figure 8 (B) shows the power curve of module 5. Figure 9 (A) is the power curve of module 7. Figure 9 (B) shows the power curve of module 8. It can be seen that the maximum output power of the photovoltaic module decreases to some extent with the extension of UV aging time. After 500 hours of UV irradiation, the maximum output power of module 4 decreased from 0.211W to 0.206W, a decrease of only 2.4% (the maximum output power of blank module 7 decreased from 0.204W to 0.191W, a year-on-year decrease of 6.4%). When the UV irradiation time was extended to 1000 hours, the maximum output power of module 5 decreased from 0.211W to 0.189W, a decrease of only 10.4% (the maximum output power of blank module 8 decreased from 0.204W to 0.171W, a year-on-year decrease of 16.2%). Analysis suggests that during UV irradiation, the silicone resin and EVA coating used in the photovoltaic module encapsulation undergo a certain degree of aging. With the extension of irradiation time, the surface temperature of the photovoltaic module increases, leading to a decrease in output power. For module #5, after 1000 hours of prolonged UV irradiation, the photovoltaic module's performance gradually stabilized, and the output power no longer decreased. The photovoltaic module coated with the modified EP-POSS film showed only a 10.4% decrease in maximum output power after 1000 hours of UV aging testing. In conclusion, coating with the modified EP-POSS film can improve the UV resistance of photovoltaic modules, which is of great significance for maintaining the photostability of photovoltaic modules under illumination conditions.

[0032] In summary, the EP-POSS film prepared by the modified EP-POSS film preparation method provided in this embodiment of the invention has a larger contact angle than ordinary EP-POSS, and its surface has a nanoscale barbed structure, exhibiting excellent hydrophobic properties; its transmittance is around 85% in the visible light range of 300-700 nm, demonstrating excellent light transmittance performance; and the two main pyrolysis reactions occur at 410℃ and 540℃, indicating good thermal stability. The EP-POSS thin film prepared by this invention can be applied to photovoltaic modules to improve the output power of photovoltaic modules and reduce the impact of dust accumulation and ultraviolet aging on the output power of photovoltaic modules.

[0033] The embodiments described above are some, but not all, embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A method for preparing a modified EP-POSS film, characterized by, Comprising the following steps: S1: dissolving γ-glycidoxypropyltrimethoxysilane in xylene to obtain mixture 1; mixing isopropanol and aqueous solution of tetramethylammonium hydroxide to obtain mixture 2; then adding the mixture 1 dropwise into the mixture 2, and after stirring, refluxing, distilling, washing, drying and grinding one by one, obtaining EP-POSS white powder; S2: dissolving the EP-POSS white powder in anhydrous toluene and stirring until completely dissolved to obtain an EP-POSS toluene solution; S3: sequentially placing the substrate into acetone and anhydrous ethanol for ultrasonic cleaning, and then drying under a protective atmosphere, and after drying, activating the substrate using oxygen plasma; S4: adding the EP-POSS toluene solution dropwise onto the substrate, and then baking and curing under vacuum conditions to obtain a stable EP-POSS film; S5: placing the EP-POSS film and fluorinated silane-toluene solution in a sealed dryer and heating; After heating, taking out, sequentially using anhydrous toluene, acetone and anhydrous ethanol for ultrasonic cleaning, and baking and drying under a protective atmosphere to obtain a modified EP-POSS film.

2. The method of claim 1, wherein the modified EP-POSS film is prepared by the steps of: In step S1, the molar ratio of the γ-glycidoxypropyltrimethoxysilane to the xylene is 1:1-5, and the molar ratio of the isopropanol to the aqueous solution of tetramethylammonium hydroxide is 100-300:

1.

3. The method for preparing a modified EP-POSS thin film according to claim 2, characterized in that, In step S2, the mass fraction of the EP-POSS toluene solution is 5-10wt%.

4. The method of claim 3, wherein the modified EP-POSS film is prepared by the steps of: In step S3, the substrate is a silicon wafer or a glass sheet with smooth and flat surface; the protective atmosphere is nitrogen, helium or argon.

5. The method of claim 1, wherein the modified EP-POSS film is prepared by the steps of: In step S4, the solution is added dropwise onto the substrate using a spin coating method to form a uniform film on the substrate; and then curing at 120-150℃ for 1-2h to further stabilize the film.

6. The method of claim 5, wherein the modified EP-POSS film is prepared by the steps of: In step S5, the fluorinated silane is perfluorooctyltrichlorosilane or perfluorodecyltrichlorosilane.

7. A modified EP-POSS film, characterized in that, Prepared by the preparation method of any one of claims 1-6.

8. Use of the modified EP-POSS film of claim 7 in a photovoltaic module.

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