Lightweight Photovoltaic Modules Based on Polymer Multilayer Films

Abstract

The present invention provides a lightweight photovoltaic module based on a polymer multilayer film, comprising a backplane, a photovoltaic cell and a first combined film structure, wherein the first combined film structure is located on the front of the photovoltaic cell, and the first combined film structure comprises a multilayer transparent film layer, on which at least two first reflection interfaces are formed; after ultraviolet light is reflected from the two first reflection interfaces, a first reflection light and a second reflection light are formed that are away from the photovoltaic cell, and the first reflection light and the second reflection light can constructively interfere with each other, thereby selectively improving the reflection of ultraviolet light. The first combined film structure provided in the present application has good ultraviolet resistance, light weight and low cost. Therefore, the photovoltaic module using the first combined film structure has good ultraviolet resistance, light weight, low cost and good flexibility, and has a wide range of applications, and can be applied to automobiles, ships, color steel tile roofs, building curtain walls, etc.

Description

Technical Field

[0001] The present invention relates to the field of solar photovoltaic power generation, and particularly to a lightweight photovoltaic module based on a polymer multi-layer film. Background Art

[0002] Crystalline silicon photovoltaic modules have the characteristics of high power generation efficiency, strong reliability, and long service life, and their usage rate accounts for more than 90% of the entire photovoltaic power generation market. However, the unit area weight of crystalline silicon photovoltaic modules is relatively large, which restricts their application scope to a certain extent. As is well known, the weight of the glass cover plate accounts for more than 70% of the entire crystalline silicon photovoltaic module, which is the main reason for the large weight of the crystalline silicon photovoltaic module. To replace the glass to reduce the weight of the crystalline silicon module, the currently common solutions are, one is to use fluorine materials with better ultraviolet resistance, but the fluorine materials are expensive and cannot be popularized; the other is to use polyester films coated and modified with ultraviolet agents, but the ultraviolet resistance is limited, and its manufacturing process is a non-environmentally friendly chemical coating process. Summary of the Invention

[0003] The main object of the present invention is to propose a lightweight photovoltaic module based on a polymer multi-layer film, aiming to provide a photovoltaic module with light weight and good ultraviolet resistance.

[0004] To achieve the above object, the present invention proposes a lightweight photovoltaic module based on a polymer multi-layer film, including:

[0005] A backsheet;

[0006] A photovoltaic cell, having a front surface for facing sunlight and a back surface opposite to the front surface, the back surface of the photovoltaic cell being disposed on the backsheet; and,

[0007] A first composite film structure, disposed on the front surface of the photovoltaic cell, the first composite film structure including multiple transparent film layers, and at least two first reflection interfaces are formed on the multiple transparent film layers;

[0008] Object light forms a first reflected light and a second reflected light departing from the photovoltaic cell after being reflected by the two first reflection interfaces, and the first reflected light and the second reflected light can undergo constructive interference, wherein the object light is ultraviolet light and / or infrared light.

[0009] Optionally, the multi-layer transparent film layer includes a first transparent film layer, a second transparent film layer, and an adjustment film layer that are stacked on each other. The first transparent film layer is on the side of the second transparent film layer away from the photovoltaic cell. The adjustment film layer is on the side of the first transparent film layer away from the photovoltaic cell. The refractive index of the first transparent film layer is greater than that of the second transparent film layer, and the refractive index of the adjustment film layer is less than that of the first transparent film layer. Two end faces of the first transparent film layer form two first reflection interfaces.

[0010] Optionally, the refractive index of the first transparent film layer is n1, the thickness of the first transparent film layer is d1, and the wavelength of the object light is λ, where n1×d1 = m1λ / 4 and m1 is an odd number.

[0011] Optionally, the multi-layer transparent film layer includes a first transparent film layer and a second transparent film layer that are stacked on each other. The first transparent film layer is on the side of the second transparent film layer away from the photovoltaic cell. The first transparent film layer and the second transparent film layer form a reflection film group. A plurality of the reflection film groups are provided and stacked on each other;

[0012] Wherein, the refractive index of the first transparent film layer is greater than that of the second transparent film layer to form the first reflection interface at two end faces of at least part of the first transparent film layer; or,

[0013] The refractive index of the second transparent film layer is greater than that of the first transparent film layer to form the first reflection interface at two end faces of at least part of the second transparent film layer.

[0014] Optionally, the refractive index of the first transparent film layer is n1, the thickness of the first transparent film layer is d1, and the wavelength of the object light is λ, where n1×d1 = m1λ / 4 and m1 is an odd number;

[0015] The refractive index of the second transparent film layer is n2, the thickness of the second transparent film layer is d2, and the wavelength of the object light is λ, where n2×d2 = m2λ / 4 and m2 is an odd number.

[0016] Optionally, the wavelength λ of the object light satisfies: 300nm ≤ λ ≤ 400nm; and / or,

[0017] The wavelength λ of the object light satisfies: 1000nm ≤ λ ≤ 2500nm.

[0018] Optionally, among the first transparent film layer and the second transparent film layer, the material of one of them is polymethyl methacrylate, and the material of the other one is at least one of polyethylene naphthalate, polyethylene terephthalate, polycarbonate, and polystyrene.

[0019] Optionally, the total number of layers of the multiple transparent film layers is Q, and 250 ≤ Q ≤ 1100.

[0020] Optionally, the total thickness of the multiple transparent film layers is D0, and D0 ≥ 10 μm.

[0021] Optionally, an adhesive layer is provided between the back plate and the photovoltaic cell; and / or,

[0022] an adhesive layer is provided between the photovoltaic cell and the first composite film structure.

[0023] The first composite film structure provided by the present invention includes multiple transparent film layers. The refractive indices of adjacent two transparent film layers are different to form an interface at the junction of the adjacent two transparent film layers, and multiple interfaces are formed by the multiple transparent film layers. At least two first reflection interfaces exist among the multiple interfaces and the two surfaces of the first composite film structure. The first reflected light and the second reflected light formed by the ultraviolet light passing through the two first reflection interfaces undergo constructive interference, thereby selectively enhancing the reflection of ultraviolet light. By increasing the number of the first reflection interfaces, the reflection of ultraviolet light can be continuously improved, so that the first composite film structure has good ultraviolet resistance. The first composite film structure is designed based on the principle of physical optical interference, has good spectral selectivity, can selectively and highly reflect ultraviolet light, and has little influence on the transmittance of visible light. Moreover, the total thickness of the first composite film structure is small and the weight is light. In addition, the materials of the multiple transparent film layers in the first composite film structure can be non-fluorine-containing materials to reduce costs. In general, the first composite film structure provided by this application has good ultraviolet resistance, light weight and low cost. Therefore, the photovoltaic module using the first composite film structure has good ultraviolet resistance, light weight, low cost and good flexibility, and has a wide application range, and can be applied to automobiles, ships, color steel tile roofs, building facades, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on the structures shown in these drawings.

[0025] Figure 1 It is a schematic structural diagram of an embodiment of a lightweight photovoltaic module based on a polymer multi-layer film provided by the present invention;

[0026] Figure 2 is Figure 1 a schematic structural diagram of an embodiment of the composite film structure in

[0027] Figure 3 isFigure 1 Structural schematic diagram of another embodiment of the combined membrane structure;

[0028] Figure 4 Structural schematic diagram of another embodiment of the lightweight photovoltaic module based on polymer multilayer film provided by the present invention.

[0029] Explanation of the reference numerals in the drawings:

[0030]

[0031]

[0032] The realization of the object of the present invention, functional characteristics and advantages will be further described in conjunction with the embodiments with reference to the drawings. Specific embodiments

[0033] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0034] It should be noted that if there are directional indications (such as up, down, left, right, front, back, outside, inside...) involved in the embodiments of the present invention, then the directional indications are only used to explain the relative positional relationship and movement conditions between components in a certain specific posture (as shown in the drawings). If the specific posture changes, then the directional indications will also change accordingly.

[0035] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, then the descriptions of "first", "second", etc. are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one such feature. In addition, the meaning of "and / or" appearing throughout the text includes three parallel solutions. Taking "A and / or B" as an example, it includes solution A, or solution B, or a solution that satisfies both A and B simultaneously. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the fact that those of ordinary skill in the art can implement it. When the combination of technical solutions results in contradictions or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the protection scope required by the present invention.

[0036] In existing photovoltaic modules, the cover plate is commonly made of glass, fluorine materials (such as ETFE, PVD), and PET polyester film modified by coating with an anti-ultraviolet agent. However, glass is relatively heavy, which limits the application range of photovoltaic modules; fluorine materials are expensive and cannot be widely used; the anti-ultraviolet ability of the PET polyester film modified by coating is limited, and its manufacturing process is a non-environmentally friendly chemical coating process.

[0037] To solve the above problems, the present invention provides a lightweight photovoltaic module 100 based on a polymer multi-layer film. The cover plate of the photovoltaic module adopts a composite film structure, which has the characteristics of light weight, low cost, good anti-ultraviolet ability, and good flexibility, and can greatly reduce the weight of the photovoltaic module and expand its application range.

[0038] Figure 1 FIG. is a schematic structural diagram of an embodiment of the lightweight photovoltaic module 100 based on a polymer multi-layer film provided by the present invention. Refer to Figure 1 The lightweight photovoltaic module 100 based on a polymer multi-layer film provided by the present invention includes a back plate 1, a photovoltaic cell 2, and a first composite film structure 3. The photovoltaic cell 2 has a front face facing the sunlight and a back face opposite to the front face, and the back face of the photovoltaic cell is disposed on the back plate 1. The first composite film structure 3 is located on the front face of the photovoltaic cell 2, and the first composite film structure 3 includes multiple transparent film layers, and at least two first reflection interfaces are formed on the multiple transparent film layers. The object light is reflected by the two first reflection interfaces to form a first reflected light and a second reflected light that are away from the photovoltaic cell 2, and the first reflected light and the second reflected light can interfere constructively, where the object light is ultraviolet light and / or infrared light.

[0039] The first composite film structure 3 provided by the present invention includes multiple transparent film layers. The refractive indices of adjacent two transparent film layers are different to form an interface at the junction of the adjacent two transparent film layers, and multiple interfaces are formed by the multiple transparent film layers. At least two first reflection interfaces exist among the multiple interfaces and the two surfaces of the first composite film structure 3. The first reflected light and the second reflected light formed by the ultraviolet light passing through the two first reflection interfaces undergo constructive interference, thereby selectively enhancing the reflection of the ultraviolet light. By increasing the number of the first reflection interfaces, the reflection of the ultraviolet light can be continuously enhanced, such that the first composite film structure 3 has good ultraviolet resistance. The first composite film structure 3 is designed based on the physical optical interference principle, has good spectral selectivity, can selectively and highly reflect the ultraviolet light, and has less influence on the transmittance of visible light. Moreover, the total thickness of the first composite film structure 3 is small and the weight is light. In addition, the materials of the multiple transparent film layers in the first composite film structure 3 may not be fluorine-containing materials to reduce the cost. In general, the first composite film structure 3 provided by the present application has good ultraviolet resistance, is light in weight and low in cost. Therefore, the photovoltaic module using the first composite film structure 3 has good ultraviolet resistance, is light in weight, low in cost and good in flexibility, and has a wide application range, and can be applied to automobiles, ships, color steel tile roofs, building facades, etc.

[0040] Further referring to Figure 1 , an adhesive layer 4 is provided between the backsheet 1 and the photovoltaic cell 2; and / or, an adhesive layer 4 is provided between the photovoltaic cell 2 and the first composite film structure 3. The material of the adhesive layer 4 is an adhesive commonly used in the field of photovoltaic cells, including EVA, POE, PVB, etc.

[0041] To form the first reflection interface, the multiple transparent film layers include a first transparent film layer 311, a second transparent film layer 312 and an adjustment film layer which are stacked on each other. The first transparent film layer 311 is on the side of the second transparent film layer 312 away from the photovoltaic cell 2, the adjustment film layer is on the side of the first transparent film layer 311 away from the photovoltaic cell, the refractive index of the first transparent film layer 311 is greater than that of the second transparent film layer 312, the refractive index of the adjustment film layer is less than that of the first transparent film layer 311, and two end faces of the first transparent film layer 311 form two first reflection interfaces.

[0042] According to the physical optical interference principle, the condition for the first reflected light and the second reflected light formed by the object light passing through the two end faces of the first transparent film layer 311 to undergo constructive interference is:

[0043] The refractive index of the first transparent film layer 311 is n1, the thickness of the first transparent film layer 311 is d1, and the wavelength of the object light is λ, where n1×d1 = m1λ / 4, where m1 is an odd number; and

[0044] The refractive index of the adjustment film layer is less than that of the first transparent film layer 311, and the refractive index of the first transparent film layer 311 is greater than that of the second transparent film layer 312.

[0045] When the above conditions are met, after the object light ray is incident from the adjustment film layer to the first transparent film layer 311, the optical path differences of the first reflected light ray and the second reflected light ray formed by the two end faces of the first transparent film layer 311 are the same. Therefore, the first reflected light ray and the second reflected light ray formed by the two end faces of the first transparent film layer 311 undergo constructive interference.

[0046] The first combined film structure 3 includes at least one group of the above combinations, that is, the refractive indices of the three transparent film layers stacked in sequence are distributed as "low, high, low", and the object light ray can be selectively highly reflected. When the number of the above combinations increases continuously, the reflection of the first combined film structure 3 on the object light ray is continuously enhanced.

[0047] It should be noted that when the refractive index of the first transparent film layer 311 is n1, the thickness of the first transparent film layer 311 is d1, and the wavelength of the object light ray is λ, where n1×d1 = m1λ / 4, the reflection effect on the object light ray with the wavelength λ is the best.

[0048] It should also be noted that for the first combined film structure 3 with only two transparent film layers, since the refractive index of light in the air is the smallest, when the refractive index of the first transparent film layer 311 is greater than that of the second transparent film layer 312, the two end faces of the first transparent film layer 311 form two first reflection interfaces, and the first reflected light ray and the second reflected light ray of the object light ray reflected by the two end faces of the first transparent film layer 311 undergo constructive interference.

[0049] To obtain better ultraviolet resistance and improve processability. Preferably, two, three or more polymer materials with different refractive indices are used to form a reflection film group with two, three or multiple transparent film layers, and multiple reflection film groups are stacked on top of each other to form a combined film structure. The reflectivity of the object light ray is controlled by adjusting the number of the reflection film groups.

[0050] In the embodiment of the present invention, refer to Figure 2 , the multiple transparent film layers include the first transparent film layer 311 and the second transparent film layer 312 stacked on top of each other. The first transparent film layer 311 is on the side of the second transparent film layer 312 away from the photovoltaic cell 2. The refractive indices of the first transparent film layer 311 and the second transparent film layer 312 are different. The first transparent film layer 311 and the second transparent film layer 312 form a reflection film group, and multiple reflection film groups are provided and stacked on top of each other.

[0051] When the refractive index of the first transparent film layer 311 is n1, the thickness of the first transparent film layer 311 is d1, and the wavelength of the object light is λ, where n1×d1 = m1λ / 4 and m1 is an odd number; the refractive index of the second transparent film layer 312 is n2, the thickness of the second transparent film layer 312 is d2, and the wavelength of the object light is λ, where n2×d2 = m2λ / 4 and m2 is an odd number. When the refractive index of the first transparent film layer 311 is greater than that of the second transparent film layer 312, the refractive index distribution of the multi-layer transparent film layer is "photovoltaic cell 2 / high-low-high-low-high-low... high-low-high". Then there are multiple groups of "low-high-low" refractive index combinations, enabling the first combined film structure 3 to selectively and highly reflect the object light, and both end faces of the first transparent film layer 311 form a first reflection interface. That is, in the first combined film structure 3, when the refractive index of the first transparent film layer 311 is greater than that of the second transparent film layer 312, a first reflection interface is formed on both end faces of at least part of the first transparent film layer 311; when the refractive index of the second transparent film layer 312 is greater than that of the first transparent film layer 311, the refractive index distribution of the multi-layer transparent film layer is "photovoltaic cell 2 / high-low-high-low-high-low... low-high". Then there are multiple groups of "low-high-low" refractive index combinations, enabling the first combined film structure 3 to selectively and highly reflect the object light, and both end faces of the second transparent film layer 312 form a first reflection interface. That is, in the first combined film structure 3, when the refractive index of the second transparent film layer 312 is greater than that of the first transparent film layer 311, a first reflection interface is formed on both end faces of at least part of the second transparent film layer 312.

[0052] In another embodiment of the present invention, referring to Figure 3 , the multi-layer transparent film layer includes a first transparent film layer 311, a second transparent film layer 312, and a third transparent film layer 313 that are stacked on each other, and the refractive indices of the first transparent film layer 311, the second transparent film layer 312, and the third transparent film layer 313 are different from each other. The first transparent film layer 311, the second transparent film layer 312, and the third transparent film layer 313 form a reflection film group, and multiple reflection film groups are provided and stacked on each other. When the reflection film group includes three transparent film layers, regardless of the refractive index distribution of these three transparent film layers, such as "high-medium-low-high-medium-low..." or "high-low-medium-high-low-medium...", there are at least combinations of "low-high-medium" and "medium-high-low" to form a first reflection interface on both end faces of the transparent film layer with a high refractive index. Of course, among the three transparent film layers, the refractive index n a of each transparent film layer, the thickness d a of each transparent film layer, and the wavelength λ of the object light satisfy n a ×d a = m a λ / 4, where m a is an odd number, and a is 1, 2, or 3.

[0053] By analogy, when multiple transparent film layers form a reflective film group, and there are multiple reflective film groups arranged in an overlapping manner to form a first combined film structure 3, as long as the refractive indices of adjacent two transparent film layers in the multiple transparent film layers are different, and the refractive index n of each transparent film layer a , the thickness d of each transparent film layer a and the wavelength λ of the object light satisfy n a ×d a =m a λ / 4, where m a is an odd number and a is a natural number, the first combined film structure 3 selectively highly reflects the object light with wavelength λ. Preferably, the refractive indices of the multiple transparent film layers forming the reflective film group are all different. Preferably, the refractive index n of each transparent film layer a , the thickness d of each transparent film layer a and the wavelength λ of the object light satisfy n a ×d a =λ / 4, where a is a natural number.

[0054] The material of the adhesive layer 4 in the photovoltaic module (such as EVA) is a polymer material. When used outdoors, it is exposed to light, temperature, and humidity changes for a long time. Chemical reactions occur under the action of ultraviolet, temperature, humidity and other factors, which will cause optical losses of the photovoltaic cell 2 and also have a certain impact on the attenuation of the performance of the photovoltaic module; moreover, the adhesive layer 4 turns yellow, affecting the bonding effect and light transmittance. The light in the infrared wavelength region is the main factor generating heat. The increase in temperature of the photovoltaic module by absorbing infrared rays will also cause chemical reactions in the adhesive layer 4, resulting in the attenuation of the performance of the photovoltaic module and the reduction of the spectral response efficiency of the photovoltaic cell 2.

[0055] To solve the above problems, in the embodiments of the present invention, the multiple reflective film groups include a first reflective film group 31 and a second reflective film group 32. The refractive index and / or thickness of the corresponding first transparent film layer 311 and the refractive index and / or thickness of the corresponding second transparent film layer 312 in the first reflective film group 31 and the second reflective film group 32 are all different, so that the wavelength of the second object light reflected by the second reflective film group 32 is different from the wavelength of the first object light reflected by the first reflective film group 31.

[0056] Specifically, in the first reflective film group 31, the refractive index of the first transparent film layer 311 is n1, the thickness of the first transparent film layer 311 is d1, the wavelength of the first object light is λ1, and n1×d1 = m1λ1 / 4, where m1 is an odd number; the refractive index of the second transparent film layer 312 is n2, the thickness of the second transparent film layer 312 is d2, and the wavelength of the first object light is λ1, and n2×d2 = m2λ1 / 4, where m2 is an odd number. In the second reflective film group 32, the refractive index of the first transparent film layer 311 is n3, the thickness of the first transparent film layer 311 is d3, the wavelength of the second object light is λ2, and n3×d3 = m3λ2 / 4, where m3 is an odd number; the refractive index of the second transparent film layer 312 is n4, the thickness of the second transparent film layer 312 is d4, and the wavelength of the second object light is λ2, and n4×d4 = m4λ2 / 4, where m4 is an odd number.

[0057] The multiple reflective film groups are divided into the first reflective film group 31 and the second reflective film group 32, which can selectively and highly reflect the first object light and the second object light respectively. When one of the first object light and the second object light is ultraviolet light and the other is infrared light, the first combined film structure 3 of the present application can simultaneously selectively reflect ultraviolet light and infrared light, reduce the loss of ultraviolet light and infrared light to the photovoltaic module, lower the temperature of the photovoltaic module, thereby improving the power generation efficiency of the photovoltaic module and extending the service life of the photovoltaic module. When the first object light and the second object light are ultraviolet lights with different wavelengths, the first combined film structure 3 of the present application can simultaneously selectively and highly reflect ultraviolet lights of two wavelengths, improving the ultraviolet resistance of the photovoltaic module.

[0058] It should be noted that the multiple reflective film groups may but are not limited to include the first reflective film group 31 and the second reflective film group 32. In another embodiment of the present invention, the multiple reflective film groups include the first reflective film group 31, the second reflective film group 32, and the third reflective film group. The refractive index and / or thickness of the corresponding first transparent film layer 311 and the refractive index and / or thickness of the corresponding second transparent film layer 312 in the first reflective film group 31, the second reflective film group 32, and the third reflective film group are different from each other, so that the wavelengths of the third object light reflected by the third reflective film group, the second object light reflected by the second reflective film group 32, and the first object light reflected by the first reflective film group 31 are different from each other. In other embodiments of the present invention, the multiple reflective film groups include the first reflective film group 31, the second reflective film group 32, the third reflective film group,..., the Nth reflective film group, so that the first combined film structure 3 selectively reflects multiple object lights to obtain excellent ultraviolet resistance and infrared resistance.

[0059] It should also be noted that the refractive index n1 of the first transparent film layer 311 of the first reflective film group 31 and the refractive index n3 of the first transparent film layer 311 of the second reflective film group 32 may be the same or different; the refractive index n2 of the second transparent film layer 312 of the first reflective film group 31 and the refractive index n4 of the second transparent film layer 312 of the second reflective film group 32 may be the same or different, and the present invention does not make any restrictions. In the embodiments of the present invention, two polymer materials with different refractive indices are used, and by adjusting the film layer thickness, selective reflection of the first object light and the second object light is achieved. Therefore, the refractive index n1 of the first transparent film layer 311 of the first reflective film group 31 is the same as the refractive index n3 of the first transparent film layer 311 of the second reflective film group 32, and the thickness d1 of the first transparent film layer 311 of the first reflective film group 31 is different from the thickness d3 of the first transparent film layer 311 of the second reflective film group 32; the refractive index n2 of the second transparent film layer 312 of the first reflective film group 31 is the same as the refractive index n4 of the second transparent film layer 312 of the second reflective film group 32, and the thickness d2 of the second transparent film layer 312 of the first reflective film group 31 is different from the thickness d4 of the second transparent film layer 312 of the second reflective film group 32. This film system design is convenient to adjust and has high processing efficiency.

[0060] In addition, the present invention does not make any restrictions on the number of the first reflective film group 31 and the second reflective film group 32. The number of the first reflective film group 31 and the second reflective film group 32 may be the same or different. When the first combined film structure 3 is prepared by using the polymer multi-layer co-extrusion process, the number of the first reflective film group 31 and the number of the second reflective film group 32 are generally the same; or, the number of the first reflective film group 31 is an integer multiple of the number of the second reflective film group 32; or, the number of the second reflective film group 32 is an integer multiple of the number of the first reflective film group 31.

[0061] It should be noted that the present invention does not make any restrictions on the arrangement manner of the multiple first reflective film groups 31 and the multiple second reflective film groups 32. It may be that the first reflective film group 31 and the second reflective film group 32 are alternately stacked; or, it may be that some mutually stacked first reflective film groups 31 and some mutually stacked second reflective film groups 32 are alternately stacked. Preferably, in the embodiments of the present invention, the multiple mutually stacked first reflective film groups 31 are on one side of the multiple mutually stacked second reflective film groups 32 to facilitate multi-layer co-extrusion processing.

[0062] It should also be noted that in the reflectance spectrum of the first combined film structure 3 for the solar spectrum, a reflectance peak is shown at the wavelength λ1 of the target light. To broaden the width of the reflectance peak at λ1, that is, to obtain a relatively wide reflection bandwidth at the wavelength λ1, generally a reflectance peak is also obtained at λ2 near λ1, and the reflectance peak at λ1 and the reflectance peak at λ1 partially overlap to obtain a relatively wide reflection bandwidth. According to the physical optics interference theory, when the wavelength λ1 and the wavelength λ2 satisfy: 0.97λ1 ≤ λ2 ≤ 1.03λ1, the reflectance peaks of the wavelength λ1 and the wavelength λ2 can partially overlap to obtain a relatively wide reflectance peak. Therefore, when the materials of the multilayer transparent films in the first reflective film group are the same as those of the multilayer transparent films in the second reflective film group, the ratio of the total thickness D1 of the multilayer transparent film layers in the first reflective film group 31 to the total thickness D2 of the multilayer transparent film layers in the second reflective film group 32 satisfies: D1:D2 = (51-49):(49-51), so as to obtain the first combined film structure 3 with a relatively wide reflection bandwidth.

[0063] Regarding the material of the transparent film layer, the present invention does not make any restrictions as long as its refractive index meets the above requirements. However, considering processing and cost issues, preferably, the material of the transparent film layer includes at least one of polymethyl methacrylate, polyethylene naphthalate, polyethylene terephthalate, polycarbonate, and polystyrene. These several polymer materials have low costs, and any two polymer materials are partially miscible directly, which is suitable for being prepared by the process of polymer multilayer coextrusion. After extrusion molding, the multilayer transparent film layers do not delaminate, and the structure is stable. The polymer multilayer coextrusion process has high production efficiency and low production cost, can reduce the cost of photovoltaic modules, and has less environmental pollution.

[0064] In this embodiment, according to the physical optics interference principle, the greater the refractive index difference between the first transparent film layer 311 and the second transparent film layer 312, the higher the reflectance of the first combined film structure 3 for the target light. Among polymers, polymethyl methacrylate (PMMA) has a relatively small refractive index, about 1.49, the refractive index of polycarbonate (PC) is about 1.584-1.586, the refractive index of polystyrene (PS) is about 1.59-1.602, the refractive index of polyethylene naphthalate (PEN) is about 1.757-1.759, and the refractive index of polyethylene terephthalate (PET) is about 1.661-1.665. Therefore, among the first transparent film layer 311 and the second transparent film layer 312, the material of one of them is polymethyl methacrylate, and the material of the other is at least one of polyethylene naphthalate, polyethylene terephthalate, polycarbonate, and polystyrene.

[0065] Considering that the wavelength of ultraviolet rays that mainly affect photovoltaic modules is in the range of 300 nm to 400 nm, and the wavelength of infrared rays is in the range of 1000 nm to 2500 nm, that is, the wavelength λ of the target light satisfies: 300 nm ≤ λ ≤ 400 nm; and / or, the wavelength λ of the target light satisfies: 1000 nm ≤ λ ≤ 2500 nm.

[0066] Correspondingly, when the first reflective film group 31 is used to selectively highly reflect ultraviolet rays, the thickness of the first transparent film layer 311 in the first reflective film group 31 is d1, and d1 satisfies 40 nm ≤ d1 ≤ 70 nm, and the thickness of the second transparent film layer 312 in the first reflective film group 31 is d2, and d2 satisfies 40 nm ≤ d2 ≤ 70 nm; or,

[0067] When the first reflective film group 31 is used to selectively highly reflect infrared rays, the thickness of the first transparent film layer 311 in the first reflective film group 31 is d1, and d1 satisfies 140 nm ≤ d1 ≤ 420 nm, and the thickness of the second transparent film layer 312 in the first reflective film group 31 is d2, and d2 satisfies 140 nm ≤ d2 ≤ 420 nm.

[0068] When the second reflective module 32 is used to selectively highly reflect infrared light, the thickness of the first transparent film layer 311 in the second reflective film group 32 is d3, and d3 satisfies 140 nm ≤ d3 ≤ 420 nm, and the thickness of the second transparent film layer 312 in the second reflective film group 32 is d4, and d4 satisfies 140 nm ≤ d4 ≤ 420 nm; or,

[0069] When the second reflective film group 32 is used to selectively highly reflect ultraviolet rays, the thickness of the first transparent film layer 311 in the second reflective film group 32 is d3, and d3 satisfies 40 nm ≤ d3 ≤ 70 nm, and the thickness of the second transparent film layer 312 in the second reflective film group 32 is d4, and d4 satisfies 40 nm ≤ d4 ≤ 70 nm.

[0070] For the total number Q of the multi-layer transparent film layers in the first combined film structure 3, the present invention does not make any restrictions. Preferably, the total number Q of the multi-layer transparent film layers satisfies: 250 ≤ Q ≤ 1100. If the total number Q is too small, the reflectivity cannot meet the requirements; however, if the total number Q is too large, the reflectivity will decrease due to the increase in absorption and scattering losses of the target light in the combined film structure.

[0071] For the total thickness D0 of the multi-layer transparent film layers in the first combined film structure 3, the present invention does not make any restrictions. Preferably, the total thickness D0 of the multi-layer transparent film layers satisfies: D0 ≥ 10 μm. If the total thickness D0 is too small, the reflectivity of the target light is low, and the strength of the first combined film structure 3 is poor and it is easily damaged.

[0072] In this embodiment, by adjusting the materials and thicknesses of the first transparent film layer 311 and the second transparent film layer 312, and the numbers of layers of the first reflective film group 31 and the second reflective film group 32, the first object light and the second object light can be selectively reflected, and the total number of layers and the total thickness of the multiple transparent film layers in the first composite film structure 3 can be controlled.

[0073] The technical solution of the present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the following embodiments are only used to explain the present invention and are not used to limit the present invention.

[0074] Embodiment 1

[0075] Taking the design of the first composite film structure with excellent ultraviolet resistance using PMMA and PC materials as an example, in order to obtain a wider emission bandwidth at a wavelength of 365 nm, the first reflective film group 31 is designed to selectively and highly reflect ultraviolet light with a wavelength λ1 of 365 nm, and the second reflective film group 32 is designed to selectively and highly reflect ultraviolet light with a wavelength λ2 of 354 nm. According to n×d = λ / 4, in the first reflective film group 31, the thickness of the PMMA layer is 61.2 nm, and the thickness of the PC layer is 57.6 nm; in the second reflective film group 32, the thickness of the PMMA layer is 59.4 nm, and the thickness of the PC layer is 55.8 nm.

[0076] During actual operation, the set temperature ranges of the extruder are set to 280°C, 275°C, 270°C, 265°C, and 260°C, the temperatures of the multiplier and the extrusion die head are set to 260°C and 220°C respectively, and the set temperature of the casting and cooling roll is set to 120°C. First, 128 groups of reflective film groups with equal thickness are stacked using a quadruple equal division multiplier, and then 128 groups of the first reflective film group 31 and 128 groups of the second reflective film group 32 are obtained using a double non-equal division multiplier. Among them, the ratio of the total thickness of the 128 groups of the first reflective film group 31 to the total thickness of the 128 groups of the second reflective film group 32 is 50.8:49.2.

[0077] In the obtained first reflective film group 31, the thickness of the PMMA layer is 61.2 nm, and the thickness of the PC layer is 57.6 nm; in the second reflective film group 32, the thickness of the PMMA layer is 59.4 nm, and the thickness of the PC layer is 55.8 nm. It can be seen therefrom that the total thickness D1 of the transparent film layers of the multiple first reflective film groups 31 is 15.2 μm, and the total thickness D2 of the transparent film layers of the multiple second reflective film groups 32 is 14.7 μm. The total thickness of the multiple transparent film layers of the first composite film structure 3 is 29.9 μm. In the reflectivity spectrum of the solar spectrum of the first composite film structure 3 in this embodiment, a relatively wide reflectivity peak is shown at a wavelength from 354 nm to 365 nm.

[0078] Embodiment 2

[0079] Taking the design of the first composite film structure with excellent UV resistance using PMMA and PC materials as an example, a first reflective film group 31 is designed to selectively and highly reflect UV light with a wavelength λ1 of 365 nm, and a second reflective film group 31 is designed to selectively and highly reflect UV light with a wavelength λ2 of 1100 nm. According to n×d = λ / 4, in the first reflective film group 31, the thickness of the PMMA layer is 61.2 nm and the thickness of the PC layer is 57.6 nm; in the second reflective film group 32, the thickness of the PMMA layer is 184.6 nm and the thickness of the PC layer is 173.5 nm.

[0080] During actual operation, set the set temperature range of the extruder at 280°C, 275°C, 270°C, 265°C, 260°C, set the temperatures of the multiplier and the extrusion die head at 260°C and 220°C respectively, and set the temperature of the casting cooling roll at 120°C. First, use a quadruple equal division multiplier to stack 128 groups of reflective film groups with equal thickness, and then use a double non-equal division multiplier to obtain 128 groups of the first reflective film group 31 and 128 groups of the second reflective film group 32.

[0081] In the obtained first reflective film group 31, the thickness of the PMMA layer is 61.2 nm and the thickness of the PC layer is 57.6 nm; in the second reflective film group 32, the thickness of the PMMA layer is 184.6 nm and the thickness of the PC layer is 173.5 nm. Thus, the total thickness D1 of the transparent film layers of multiple first reflective film groups 31 is 15.2 μm, and the total thickness D2 of the transparent film layers of multiple second reflective film groups 32 is 45.8 μm. The total thickness of the multilayer transparent film layers of the first composite film structure 3 is 61 μm. In the reflectivity spectrum of the first composite film structure 3 of this embodiment for the solar spectrum, reflectivity peaks are shown at a wavelength of 365 nm and a wavelength of 1100 nm.

[0082] In addition, the backsheet 1 is an important component of the solar photovoltaic module, playing an insulating and protective role for the solar photovoltaic cells 2. The mainstream backsheets 1 internationally are composite backsheet materials containing fluorine materials. Most of the backsheets 1 used by domestic module manufacturers rely on imports, with a relatively high market price and the technology being monopolized by foreign enterprises. While a low-cost solar backsheet solution is to use an anti-UV agent and a PET polyester film modified by coating to replace the fluorine-containing material, but the PET material modified by anti-UV coating not only has limited anti-UV ability and poor weather resistance, but also its manufacturing process is a non-environmentally friendly chemical coating process.

[0083] In view of this, in another embodiment of the present invention, the lightweight photovoltaic module 100 based on a polymer multilayer film includes a photovoltaic cell 2 and a second composite film structure 5. The photovoltaic cell 2 has a front face facing the sunlight and a back face opposite to the front face. The second composite film structure 5 is disposed on the back face of the photovoltaic cell 2. The second composite film structure 5 includes multiple transparent film layers, and at least two second reflection interfaces are formed on the multiple transparent film layers. Object light forms a third reflected light and a fourth reflected light departing from the photovoltaic cell 2 after being reflected by the two second reflection interfaces. The third reflected light and the fourth reflected light can interfere constructively, where the object light is ultraviolet light and / or infrared light.

[0084] The second composite film structure 5 provided by the present invention includes multiple transparent film layers. The refractive indices of adjacent two transparent film layers are different to form an interface at the junction of the adjacent two transparent film layers, and the multiple transparent film layers form multiple interfaces. At least two second reflection interfaces exist among the multiple interfaces and the two surfaces of the second composite film structure 5. The third reflected light and the fourth reflected light formed by the ultraviolet light after being reflected by the two second reflection interfaces interfere constructively, thereby selectively improving the reflection of ultraviolet light. By increasing the number of second reflection interfaces, the reflection of ultraviolet light can be continuously improved, so that the second composite film structure 5 has good ultraviolet resistance. The second composite film structure 5 is designed based on the principle of physical optical interference, has good spectral selectivity, can selectively and highly reflect ultraviolet light, and has little influence on the transmittance of visible light. Moreover, the materials of the multiple transparent film layers in the second composite film structure 5 can be non-fluorine-containing materials to reduce costs. In general, the second composite film structure 5 provided in this application has good ultraviolet resistance and low cost. Therefore, the photovoltaic module using the second composite film structure 5 has good ultraviolet resistance, low cost, good flexibility, and a wide range of applications, and can be applied to automobiles, ships, color steel tile roofs, building facades, etc.

[0085] The second composite film structure 5 in the embodiment of the present invention includes all the technical solutions of the above-mentioned embodiment of the first composite film structure 3, and thus has at least all the beneficial effects brought by the technical solutions of the above-mentioned embodiment, which will not be elaborated here one by one.

[0086] Furthermore, an adhesive layer 4 is provided between the photovoltaic cell 2 and the second composite film structure 5. The material of the adhesive layer 4 is an adhesive commonly used in the field of photovoltaic cells, including EVA, POE, PVB, etc.

[0087] In yet another embodiment of the present invention, refer to Figure 4, the lightweight photovoltaic module 100 based on a polymer multi-layer film includes a photovoltaic cell 2, a first composite film structure 3, and a second composite film structure 5. The photovoltaic cell 2 has a front side facing the sunlight and a back side opposite to the front side; the first composite film structure 3 is disposed on the front side of the photovoltaic cell 2, and the second composite film structure 5 is disposed on the back side of the photovoltaic cell 2. Among them, the specific structures of the first composite film structure 3 and the second composite film structure 5 refer to the above content and will not be elaborated here one by one.

[0088] In addition, the photovoltaic cell 2 of the present invention includes, but is not limited to, crystalline silicon cells, copper indium gallium selenide cells, cadmium telluride cells, and amorphous silicon cells. When the second composite film structure 5 is used to replace the existing backplane 1 material, it can meet the usage requirements of a bifacial power generation photovoltaic module, improve the power generation efficiency of the photovoltaic module, and reduce the cost of the photovoltaic module.

[0089] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention. Any equivalent structural transformation made under the inventive concept of the present invention by using the content of the specification and drawings of the present invention, or directly / indirectly applied in other related technical fields, is included in the patent protection scope of the present invention.

Claims

1. A lightweight photovoltaic module based on a polymer multilayer film, characterized in that Comprising: Backplane; Photovoltaic cells, having a front side facing the sun and a back side opposite to the front side, the back side of the photovoltaic cells being disposed on the backplane; and, A first composite film structure, located on the front side of the photovoltaic cells, the first composite film structure comprising multiple transparent film layers, and at least two first reflection interfaces being formed on the multiple transparent film layers; Object light is reflected by the two first reflection interfaces to form a first reflected light and a second reflected light that are away from the photovoltaic cells, and the first reflected light and the second reflected light can interfere constructively, wherein the object light is ultraviolet light and / or infrared light; The multiple transparent film layers include a first transparent film layer, a second transparent film layer and an adjustment film layer that are stacked on each other. The first transparent film layer is on the side of the second transparent film layer away from the photovoltaic cells, and the adjustment film layer is on the side of the first transparent film layer away from the photovoltaic cells. The refractive index of the first transparent film layer is greater than that of the second transparent film layer, and the refractive index of the adjustment film layer is less than that of the first transparent film layer. Two end faces of the first transparent film layer form the two first reflection interfaces; The refractive index of the first transparent film layer is n1, the thickness of the first transparent film layer is d1, and the wavelength of the object light is λ, where n1×d1 = m1λ / 4 and m1 is an odd number; The total number of layers of the multiple transparent film layers is Q, and 250 ≤ Q ≤ 1100.

2. The lightweight photovoltaic module based on a polymer multilayer film according to claim 1, characterized in that, The multiple transparent film layers include a first transparent film layer and a second transparent film layer that are stacked on each other. The first transparent film layer is on the side of the second transparent film layer away from the photovoltaic cells. The first transparent film layer and the second transparent film layer form a reflection film group. A plurality of the reflection film groups are provided and are stacked on each other; Wherein, the refractive index of the first transparent film layer is greater than that of the second transparent film layer to form the first reflection interfaces at two end faces of at least part of the first transparent film layer; or, The refractive index of the second transparent film layer is greater than that of the first transparent film layer to form the first reflection interfaces at two end faces of at least part of the second transparent film layer.

3. The lightweight photovoltaic module based on a polymer multilayer film according to claim 2, wherein The refractive index of the first transparent film layer is n1, the thickness of the first transparent film layer is d1, and the wavelength of the object light is λ, where n1×d1 = m1λ / 4 and m1 is an odd number; The refractive index of the second transparent film layer is n2, the thickness of the second transparent film layer is d2, and the wavelength of the object light is λ, where n2×d2 = m2λ / 4 and m2 is an odd number.

4. The lightweight photovoltaic module based on a polymer multilayer film according to claim 1 or 3, characterized in that, The wavelength λ of the object light satisfies: 300 nm ≤ λ ≤ 400 nm; and / or, The wavelength λ of the object light satisfies: 1000 nm ≤ λ ≤ 2500 nm.

5. The lightweight photovoltaic module based on a polymer multilayer film according to claim 2, wherein, Among the first transparent film layer and the second transparent film layer, one of them is made of polymethyl methacrylate, and the other one is made of at least one of polyethylene naphthalate, polyethylene terephthalate, polycarbonate, and polystyrene.

6. The lightweight photovoltaic module based on a polymer multilayer film according to claim 1, characterized in that, The total thickness of the multiple transparent film layers is D0, and D0 ≥ 10 μm.

7. The lightweight photovoltaic module based on a polymer multilayer film according to claim 1, wherein, A bonding layer is provided between the backplane and the photovoltaic cell; and / or, A bonding layer is provided between the photovoltaic cell and the first composite film structure.

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