Solar cell structure based on wide-spectrum composite anti-reflection film and preparation

Abstract

The invention relates to a solar cell structure based on a wide-spectrum composite anti-reflection film and preparation, the developed wide-spectrum composite anti-reflection film is a film system structure formed by 20 layers of film materials with different refractive indexes in an up-and-down alternating mode, reflected light on the surface of a cell is reduced through destructive interference, the minimum reflectivity of vertical incident light within the wavelength range of 400 nm to 1100 nm is as low as 0.34%, and the maximum reflectivity of the vertical incident light within the wavelength range of 400 nm to 1100 nm is 0.34%. When the incident angle is changed between 0 degree and 46 degrees, the reflectivity is only changed by 0.59%, and good anti-reflection effect and angle sensitivity of visible-near infrared broadband are shown. The anti-reflection film is high in hydrophobicity, low in adhesion, obvious in self-cleaning effect, good in weather resistance and durability, high in chemical stability and high in mechanical strength; the method can be prepared by adopting an ultrasonic spraying technology, has the advantages of high coating uniformity, high raw material utilization rate, high control precision, good economical efficiency and the like, and can be widely applied to the solar cell industry.

Description

Technical Field

[0001] The present invention is applied to the field of solar cell production and manufacturing, and relates to the structure and preparation of a solar cell based on a wide-spectrum composite anti-reflection film. Background Art

[0002] Over the past 30 years, solar photovoltaic power generation technology has rapidly developed and been applied. By 2040, solar energy is expected to become the world's largest source of electricity, with installed photovoltaic capacity projected to account for 15%-20% of global power generation. Improving solar photovoltaic conversion efficiency is a key approach to reducing photovoltaic power generation costs and further promoting the development of the photovoltaic industry. A key factor limiting photovoltaic conversion efficiency is the reflection loss of incident light on the cell surface. For perpendicularly incident light, the theoretical reflectivity of ordinary glass is approximately 4.0%. In actual projects, the reflectivity of cleaned glass surfaces can reach as high as 8.0%. Research has shown that increasing the transmittance of photovoltaic glass by just 1% can significantly reduce the cost-benefit ratio of various photovoltaic modules, thereby significantly shortening the payback period for photovoltaic power generation.

[0003] Anti-reflection coatings utilize the principle of destructive interference of light to reduce or eliminate reflection loss and stray light on the surface of solar cells, thereby increasing the intensity of light incident on the cells and improving their conversion efficiency. Anti-reflection coatings have a long history. As early as 1817, J. Frauhofer created the first anti-reflection coatings using an acid etching method. Frauhofer etches a finely polished flat glass half in concentrated sulfuric acid or nitric acid. After rinsing the glass with the acid solution, he discovered that the light intensity reflected by the acid-etched half is much lower than that of the other half. This is because the acid-etched surface loses certain components, forming a tarnished layer. In 1886, Lord Rayleigh stated in a report to the Royal Society of London that tarnished crown glass has excellent light transmittance. The reason its surface reflectivity is lower than that of polished glass is that a film with a lower refractive index than the glass substrate forms on the tarnished surface. In 1891, Dennis Taylor discovered that a tarnished film applied to a telescope objective lens can enhance its transmittance. SiO2 thin films, prepared by high-temperature thermal oxidation, were among the first to be used in crystalline silicon solar cells for anti-reflection coatings, achieving excellent anti-reflection performance. However, due to the spectral response range of crystalline silicon solar cells, which is approximately 400nm-1100nm, and the time-varying nature of the incident angle of sunlight, higher requirements were placed on the anti-reflection spectral bandwidth and incident angle sensitivity of the anti-reflection coating. Subsequent research has continuously developed new thin film materials and optimized film structures and preparation processes to achieve even better anti-reflection performance.

[0004] As the outermost layer of solar cells, anti-reflection coatings must not only exhibit excellent transmittance reduction properties but also possess strong self-cleaning properties. my country's photovoltaic power stations are primarily located in the deserts and Gobi regions of Northwest China. These vast areas boast open terrain, but are also prone to severe sandstorms. Dust particles are often carried in air currents, and these particles, due to gravity and other factors, accumulate on the surface of solar panels, affecting power generation efficiency. An experimental study of a 2MW photovoltaic power station in a certain region found that dusty panels experienced an average daily power reduction of 1.2% compared to dust-free panels. Furthermore, anti-reflection coatings must be able to withstand external mechanical wear and tear, such as bumps during transportation and the removal of surface dust, to prevent scratching, cracking, or even peeling over time due to insufficient mechanical strength and weak bonding between the film and the substrate.

[0005] FEP, also known as fluorinated ethylene propylene copolymer, has the characteristics of high light transmittance, non-stickiness and super hydrophobicity, weather resistance and chemical resistance, high tensile strength, thermoplasticity, etc., and can be used on the surface of solar cells. Chinese invention patent CN214176030U discloses a high-transmittance FEP film for photovoltaic panels. By providing a conductive coating and a conductive medium on the outermost anti-reflection film layer, the static electricity on the surface of the film is removed, and the light transmittance is increased, thereby improving the photoelectric conversion efficiency. The bandwidth of the anti-reflection effect of a single-layer anti-reflection film is very narrow, and it is difficult to meet the requirements of solar cells to maintain a low reflectivity within the spectral response wavelength range, and it is highly dependent on the incident angle. A multi-layer anti-reflection film is formed by stacking multiple layers of thin films. The thickness and refractive index of each layer of the film are different, and the reflectivity of light of different wavelengths will be different. The reflected light of each layer of the film will produce destructive interference with the reflected light of the adjacent film, thereby achieving the purpose of low reflectivity within a wider wavelength range. In order to give full play to the comprehensive advantages of FEP film, we should further explore and develop composite FEP anti-reflection film, so that the anti-reflection film not only has good anti-reflection and anti-transmittance properties and self-cleaning effects, but also needs to maintain long-term stability in complex environments and meet the preparation requirements of large area, low cost, and uniform film formation in the photovoltaic industry. Summary of the Invention

[0006] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a solar cell structure and preparation method based on a wide spectrum composite anti-reflection film.

[0007] The present invention solves the technical problem by adopting the following technical solutions:

[0008] Solar cell structure based on wide-spectrum composite anti-reflection film, including: back sheet, EVA film, cell, EVA film, glass substrate, wide-spectrum composite anti-reflection film, frame, etc.

[0009] Furthermore, the backsheet plays a role in protecting the back of the battery, accelerating heat dissipation, reducing battery temperature, and improving photoelectric conversion efficiency. It also needs to have good weather resistance and insulation properties. Types include TPT and TPE.

[0010] Furthermore, the EVA film is a hot-melt adhesive film located between the backsheet and the battery cell and between the battery cell and the glass substrate. It contains a cross-linking agent, is non-sticky at room temperature and has anti-adhesion properties. It can undergo melt bonding and cross-linking curing under certain hot pressing conditions to bond the backsheet, battery cell, and glass substrate together.

[0011] Furthermore, the cell converts light energy into electrical energy and is made of monocrystalline silicon, polycrystalline silicon, etc.

[0012] Furthermore, the glass substrate is located above the cell, plays the role of protecting, supporting and transmitting light to the cell, and is coated with a wide-spectrum composite anti-reflection film on the surface;

[0013] Furthermore, the wide spectrum composite anti-reflection film is composed of a low refractive index film material and a high refractive index film material alternately stacked up and down;

[0014] Furthermore, the low refractive index film material is FEP, which has the advantages of low refractive index, good light transmittance, strong weather resistance and stability, and high mechanical strength, and can be used as an external coating;

[0015] Furthermore, the high refractive index film material is Al2O3, which has a higher refractive index than the glass substrate and has excellent durability and chemical stability. It is a good high refractive index film material, but is usually not used as an independent anti-reflection film, but is combined with a low refractive index film material to form a multi-layer anti-reflection film;

[0016] Furthermore, the wide-spectrum composite anti-reflection film obtains a lower reflectivity R by adjusting the number of film layers, the thickness of each layer, and the matching degree of the refractive index. The reflectivity R is related to the optical admittance of the incident medium, the optical admittance of the glass substrate, the refractive index of the film material, the thickness of the film material, the incident angle, the wavelength of the incident light, etc., and can be obtained using the equivalent layer theory and optimization algorithm:

[0017] Where η0 is the optical admittance of the incident medium; Y is the optical admittance of the film system:

[0018] Among them, δ j is the phase thickness of the jth layer of the k-layer film system, which is related to the refractive index and thickness of the film material, as well as the incident angle and wavelength of the incident light; η j is the optical admittance of the jth film; η k+1is the optical admittance of the glass substrate.

[0019] Furthermore, the film system structure formed by the wide spectrum composite anti-reflection film is: air / 1.22L0.81H0.06L1.51H0.49L0.29H1.59L0.28H0.54L0.85H0.10L1.59H0.09L0.10H0.13L0.52H0.09L0.15H0.20L0.13H / substrate, wherein 1L is a low-refractive-index film material FEP with an optical thickness of 1 / 4 the center wavelength, and 1H is a high-refractive-index film material Al2O3 with an optical thickness of 1 / 4 the center wavelength;

[0020] Furthermore, the wide-spectrum composite anti-reflection film is prepared using nanotechnology and ultrasonic spraying technology. The ultrasonic atomizing nozzle atomizes the solution or suspension into fine droplets, which are sprayed onto the substrate surface. By optimizing parameters such as nozzle height, power, spraying time and number of spraying, a film that meets the requirements is prepared.

[0021] Furthermore, the thickness of the wide spectrum composite anti-reflection film is less than 2 μm, which is much thinner than the thickness of glass, and can avoid the problem of poor environmental stability of the film layer caused by excessive stress;

[0022] Furthermore, the frame is made of aluminum alloy, which has good corrosion resistance, high strength, and strong resistance to mechanical impact, and can play the role of fixing, supporting and protecting the entire solar panel.

[0023] Furthermore, the beneficial effects of the present invention are:

[0024] 1. The wide-spectrum composite anti-reflection coating developed by this invention is composed of alternating layers of low-refractive-index FEP film and high-refractive-index Al2O3 film. The optical matching of the outer low-refractive-index film and the inner high-refractive-index film causes multiple destructive interferences in the reflection of sunlight, thereby reducing the reflectivity of the entire film system. This invention achieves an anti-reflection effect across a wide wavelength range from the visible to the infrared region. The minimum theoretical reflectivity of glass coated with the composite anti-reflection coating for vertically incident light is reduced from 4.0% to 0.34%. The average reflectivity within the spectral range of 400-1100nm is reduced to 0.61%. The reflectivity varies little within this wavelength range, significantly enhancing the photoelectric conversion efficiency of solar cells.

[0025] 2. The wide-spectrum composite anti-reflection film developed by the present invention has a reflectivity ranging from 0.57% to 1.16% at a reference wavelength of 550nm and an incident angle range of 0-46°, both lower than 1.2%. This indicates that the wide-spectrum composite anti-reflection film can maintain a low reflectivity over a wide range of incident angles, has low dependence on the incident angle of sunlight, and exhibits good angular sensitivity.

[0026] 3. The wide-spectrum composite anti-reflection film developed by the present invention has low surface free energy, self-cleaning, anti-adhesion and other properties, can reduce the adhesion of dust on the surface, has obvious self-cleaning effect, can effectively alleviate the adverse effects of dust accumulation, and reduce the maintenance requirements caused by glass surface pollution.

[0027] 4. The wide-spectrum composite anti-reflection film developed by the present invention has an outermost layer made of FEP, which has high surface flatness, good weather resistance, high mechanical strength, and can be protected from the influence of the external environment; the innermost layer is made of Al2O3, which has excellent durability and chemical stability. The wide-spectrum composite anti-reflection film prepared by compounding with FEP has the common high-quality characteristics of the two. Each layer of the film is very dense and uniform, can be used for a long time without damage, and can be used in various harsh environments.

[0028] 5. The wide-spectrum composite anti-reflection film developed by the present invention is prepared by ultrasonic spraying technology. Compared with traditional two-fluid spraying, ultrasonic spraying has the advantages of high coating uniformity (greater than 95%), high raw material utilization rate (greater than 90%), high coating thickness control accuracy, no nozzle clogging, and low maintenance cost; compared with vacuum coating technology, ultrasonic spraying is more economical. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a schematic diagram of the appearance of a solar cell according to this embodiment;

[0030] Figure 2 Schematic diagram of the solar cell structure of this embodiment;

[0031] Figure 3 Schematic diagram of the structure of the wide spectrum composite anti-reflection film of this embodiment;

[0032] Figure 4 spectral curve of the glass coated with wide spectrum composite anti-reflection film in this embodiment for vertically incident light;

[0033] Figure 5 : is a curve showing the change of reflectivity of the glass coated with a wide spectrum composite anti-reflection film as a function of the incident angle;

[0034] Figure 6 This is a curve showing the change of dust deposition over time on the surface of the glass coated with the wide-spectrum composite anti-reflection film in this embodiment.

[0035] In the figure: 1. Backplane; 2. EVA film; 3. Cell; 4. Glass substrate; 5. Broad spectrum composite anti-reflection film; 6. Frame; 7. Low refractive index film; 8. High refractive index film. DETAILED DESCRIPTION

[0036] The present invention will be further described below in conjunction with the accompanying drawings and specific implementation methods. It should be noted that, under the premise of no conflict, the various technical features described below can be arbitrarily combined to form new embodiments.

[0037] like Figure 1-2 As shown, the solar cell structure based on the wide-spectrum composite anti-reflection film includes: a backplane 1, an EVA film 2, a cell 3, an EVA film 2, a glass substrate 4, a wide-spectrum composite anti-reflection film 5, a frame 6, etc. The backplane 1 should protect the back of the battery, accelerate heat dissipation, reduce battery temperature, and improve photoelectric conversion efficiency. At the same time, it should also have good weather resistance and insulation properties. There are types such as TPT type and TPE type; EVA film 2 is a hot-melt adhesive film, which is located between the backplane and the battery cell and between the battery cell and the glass substrate. Under certain hot pressing conditions, it can undergo melt bonding and cross-linking curing to bond the backplane, battery cell and glass substrate together; the battery cell 3 converts light energy into electrical energy, and includes single crystal silicon, polycrystalline silicon, etc.; the glass substrate 4 is located above the battery cell, and plays a role in protecting, supporting and transmitting light to the battery cell, and the surface is coated with a wide-spectrum composite anti-reflection film 5; the wide-spectrum composite anti-reflection film 5 is composed of a low-refractive index film material 7 and a high-refractive index film material 8 alternating up and down, and is coated on the surface of the glass substrate 4; the frame 6 is made of aluminum alloy, has strong impact resistance, and plays a role in fixing, supporting and protecting the battery panel.

[0038] like Figure 1-2 The solar cell based on the wide-spectrum composite anti-reflection film is prepared as shown: the glass 4+5 coated with the wide-spectrum composite anti-reflection film, the battery cell 3, the EVA film 2, and the back panel 1 are squeezed and bonded using a laminator. During this process, a vacuum treatment is first performed to make it into a vacuum state, and then the EVA is melted by heating. After a certain period of pressurization, the various components can be bonded into a whole; the laminated components are installed in an aluminum alloy frame 6 and sealed with an automatic glue machine. The frame is provided with a glue overflow groove to prevent glue overflow from affecting the power generation of the component; during the preparation process and after completion, appearance inspection, function inspection, safety inspection and other links of each component should be set up.

[0039] like Figure 3As shown in FIG. 5 , the specific structure of the wide-spectrum composite anti-reflection film 5 is formed by alternating stacking of a low-refractive-index film material FEP 7 and a high-refractive-index film material Al2O38. The film is optimized and designed using optical simulation software and prepared using an ultrasonic spraying process. The total number of film layers is 20, and the film system structure formed is: air / 1.22L0.81H0.06L1.51H0.49L0.29H1.59L0.28H0.54L0.85H0.10L1.59H0.09L0.10H0.13L0.52H0.09L0.15H0.20L0.13H / substrate, where 1L is an FEP film with an optical thickness of 1 / 4 the center wavelength, and 1H is an Al2O3 film with an optical thickness of 1 / 4 the center wavelength.

[0040] like Figure 3 The specific steps for making the wide spectrum composite anti-reflection film 5 are as follows:

[0041] 1. Use deionized water and anhydrous ethanol to ultrasonically clean the glass substrate to remove all dirt and impurities, dry and cool it, and then place it on the base in the ultrasonic spraying system;

[0042] 2. Prepare Al2O3 suspension, stir nano-Al2O3 powder, deionized water and dispersant with a magnetic stirrer and disperse with ultrasonic to form spray liquid 1 for standby use;

[0043] 3. Prepare FEP solution, stir nano FEP powder, chlorinated hydrocarbon solvent, and surfactant using a magnetic stirrer, and ultrasonically treat to form spray solution 2 for standby use;

[0044] 4. Use an ultrasonic spraying system to atomize the spraying liquid 1 into fine droplets and then spray them. The droplets collide and coat the surface of the glass substrate to form an Al2O3 film. The spraying liquid feed rate is about 0.3 mL / min. The photovoltaic glass and the coating are dried and cured at a temperature of about 120-150°C.

[0045] 5. Atomize and spray the spray liquid 2 in the same manner to deposit an FEP film on the surface of the film formed in step 4 to form a double-layer FEP / Al2O3 film. The spray liquid feed rate is about 0.3 mL / min. Dry and cure at a temperature of about 120-150°C.

[0046] 6. Repeat steps 4 and 5 to deposit 10 layers of Al2O3 film and FEP film respectively to form a 20-layer FEP / Al2O3 film structure, and then perform high-temperature heat treatment and cooling to obtain a wide-spectrum composite anti-reflection film.

[0047] like Figure 4Figure 2 shows the reflectivity spectrum of glass coated with a wide-spectrum composite anti-reflection coating at normal incidence. Within the 400nm-1100nm wavelength range, the minimum reflectivity is as low as 0.34%, and the average reflectivity is as low as 0.61%. The reflectivity does not vary much across the entire wavelength range.

[0048] like Figure 5 The figure shows the effect of incident angle on the reflectivity of glass coated with a wide-spectrum composite anti-reflection coating at a reference wavelength of 550nm. When the incident angle ranges from 0-46°, the reflectivity varies between 0.57% and 1.16%, and the reflectivity has little dependence on the incident angle.

[0049] like Figure 6 The figure below shows the time-dependent dust accumulation curve on the glass surface coated with a wide-spectrum composite anti-reflection coating. Except for the influence of strong winds and rain, the dust density of both the glass coated with a wide-spectrum composite anti-reflection coating and the glass without the coating generally increases over time. However, the dust density of the former is significantly reduced compared to the latter. On the 75th day, the difference between the two was 1.61 g / m 2 , reflecting the super strong self-cleaning effect of the anti-reflection film.

[0050] The above is only a preferred embodiment of this patent. The above embodiment only illustrates the structure, preparation and efficacy of this patent, and does not limit this patent in any form or substance. It should be pointed out that ordinary technicians in this technical field can make several improvements and supplements without departing from the method of this patent. These improvements and supplements should also be regarded as the scope of protection of this patent.

Claims

1. A solar cell structure based on a wide spectrum composite anti-reflection film, characterized in that: include: Backboard (1), EVA film (2), battery cell (3), EVA film (2), glass substrate (4), wide spectrum composite anti-reflection film (5), frame (6), etc.

2. The solar cell structure based on a wide spectrum composite anti-reflection film according to claim 1, characterized in that: The back plate (1) should play the role of protecting the back of the battery, accelerating heat dissipation, reducing battery temperature, and improving photoelectric conversion efficiency, and should also have good weather resistance and insulation properties; the EVA film (2) is located between the back plate (1) and the battery cell (3) and between the battery cell (3) and the glass substrate (4), and can undergo melt bonding and cross-linking curing under certain hot pressing conditions to bond the back plate, battery cell, and glass substrate together; the battery cell (3) is located between two layers of EVA film (2) and converts light energy into electrical energy; the glass substrate (4) is located above the battery cell (3) and is coated with a wide-spectrum composite anti-reflection film (5) on its surface; the frame (6) plays the role of fixing, supporting, and protecting the entire battery panel and is made of high-strength aluminum alloy.

3. The wide spectrum composite anti-reflection film according to claim 2, characterized in that: The wide spectrum composite anti-reflection film (5) is formed by alternately stacking a low refractive index film material (7) and a high refractive index film material (8) up and down, wherein the low refractive index film material (7) is FEP, and the high refractive index film material (8) is Al2O3.

4. The wide spectrum composite anti-reflection film according to claim 2, characterized in that: The wide spectrum composite anti-reflection film (5) is designed by optimizing the film system structure using the equivalent layer theory. After optimization, the number of film layers is 20 in total, and the formed film system structure is: air / 1.22L0.81H0.06L1.51H0.49L0.29H1.59L0.28H0.54L0.85H0.10L1.59H0.09L0.10H0.13L0.52H0.09L0.15H0.20L0.13H / substrate, wherein 1L is FEP with an optical thickness of 1 / 4 of the central wavelength, and 1H is Al2O3 with an optical thickness of 1 / 4 of the central wavelength.

5. The wide spectrum composite anti-reflection film according to claim 2, characterized in that: The wide spectrum composite anti-reflection film (5) adopts a multilayer film combination of nanotechnology, with a total thickness of less than 2 μm, and can avoid the problem of poor environmental stability of the film layer caused by excessive stress.

6. Preparation of solar cells based on wide-spectrum composite anti-reflection film, characterized by: The preparation method comprises the following steps: using a laminator to bond glass (4+5) coated with a wide-spectrum composite anti-reflection film, a battery cell (3), an EVA film (2), and a back plate (1); in the process, vacuum treatment is first performed to make them into a vacuum state; then, the EVA film (2) is melted by heating; and after a certain period of pressurization treatment, the various components can be bonded into a whole; the laminated components are installed in an aluminum alloy frame (6) and sealed with an automatic glue machine, wherein a glue overflow groove is provided on the frame to prevent glue overflow from affecting the power generation of the component.

7. The preparation of a wide spectrum composite anti-reflection film according to claim 6, characterized in that: The wide spectrum composite anti-reflection film (5) is prepared by an ultrasonic spraying process, wherein an ultrasonic atomizing nozzle atomizes a uniformly dispersed Al2O3 suspension and an FEP solution into fine particles, which are sprayed layer by layer onto the surface of a glass substrate. The thickness and uniformity of each layer of the film are controlled by optimizing parameters such as nozzle height, power, spraying time, and number of spraying times. The process is completed after the coating is dried, solidified, subjected to high-temperature heat treatment, and cooled.

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