Photovoltaic module

Abstract

The present invention provides a photovoltaic module, including a photovoltaic cell and a first combined film structure, wherein the first combined film structure is on the back of the photovoltaic cell, and the first combined film structure includes a multi-layer transparent film layer, and at least two first reflection interfaces are formed on the multi-layer transparent film layer; after ultraviolet light is reflected from the two first reflection interfaces, a first reflection light and a second reflection light away from the photovoltaic cell are formed, 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 and low cost. Therefore, the photovoltaic module using the first combined film structure has good ultraviolet resistance, 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 photovoltaic modules. Background Art

[0002] The solar backsheet is an important part of the structure of a solar photovoltaic cell, and plays an insulating and protective role for the solar photovoltaic cell. The mainstream solar backsheets internationally are composite backsheet materials containing fluorine materials. Most of the backsheets 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 uses an ultraviolet absorber and a PET polyester film modified by coating to replace the fluorine-containing material, but the PET material modified by ultraviolet-resistant coating not only has limited ultraviolet resistance and poor weather resistance, but also 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 photovoltaic module, aiming to provide a photovoltaic module with good ultraviolet resistance and relatively low cost.

[0004] To achieve the above object, the present invention proposes a photovoltaic module, including:

[0005] A photovoltaic cell, having a front face for facing sunlight and a back face opposite to the front face; and,

[0006] A first composite film structure, disposed on the back face 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;

[0007] The 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.

[0008] Optionally, the photovoltaic module further includes a second composite film structure, the second composite film structure is disposed on the front face of the photovoltaic cell, and at least two second reflection interfaces are formed on the second composite film structure;

[0009] The object light forms a third reflected light and a fourth reflected light departing from the photovoltaic cell after being reflected by the two second reflection interfaces, and the third reflected light and the fourth reflected light can undergo constructive interference, wherein the object light is ultraviolet light and / or infrared light.

[0010] Optionally, the multi-layer transparent film layer includes a first transparent film layer and a second transparent film layer stacked on top of 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 top of each other;

[0011] 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,

[0012] 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.

[0013] Optionally, the plurality of reflection film groups include a first reflection film group and a second reflection film group. The refractive index and / or thickness of the corresponding first transparent film layer and the refractive index and / or thickness of the corresponding second transparent film layer in the first reflection film group and the second reflection film group are different from each other, so that the wavelength of the second object light reflected by the second reflection film group is different from the wavelength of the first object light reflected by the first reflection film group.

[0014] Optionally, the total thickness of the transparent film layers of the plurality of first reflection film groups is D1, and the total thickness of the transparent film layers of the plurality of second reflection film groups is D2, where D1:D2=(51-49):(49-51).

[0015] Optionally, the thickness of the first transparent film layer in the first reflection film group is d1, and d1 satisfies 40nm≤d1≤70nm;

[0016] The thickness of the second transparent film layer in the first reflection film group is d2, and d2 satisfies 40nm≤d2≤70nm.

[0017] Optionally, the thickness of the first transparent film layer in the second reflection film group is d3, and d3 satisfies 140nm≤d3≤420nm;

[0018] The thickness of the second transparent film layer in the second reflection film group is d4, and d4 satisfies 140nm≤d4≤420nm.

[0019] Optionally, among the first transparent film layer and the second transparent film layer, one of the materials is polymethyl methacrylate, and the other is at least one of polyethylene naphthalate, polyethylene terephthalate, polycarbonate, and polystyrene.

[0020] Optionally, an adhesive layer is provided between the photovoltaic cell and the first composite film structure.

[0021] Optionally, the total number of the multiple transparent film layers is Q, and Q satisfies 250 ≤ Q ≤ 1100.

[0022] The first combined 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 joint of the adjacent two transparent film layers, and the multiple transparent film layers form multiple interfaces. At least two first reflection interfaces exist among the multiple interfaces and the two surfaces of the first combined film structure. The first reflected light and the second reflected light formed by the ultraviolet light passing through the two first reflection interfaces interfere constructively, 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, so that the first combined film structure has good ultraviolet resistance. The first combined 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 materials of the multiple transparent film layers in the first combined film structure can be non-fluorine-containing materials to reduce costs. In short, the first combined film structure provided by the present application has good ultraviolet resistance and low cost. Therefore, the photovoltaic module using the first combined film structure has good ultraviolet resistance, low cost and good flexibility, and has a wide range of applications, and can be applied to automobiles, ships, color steel tile roofs, building facades, etc. Description of the Drawings

[0023] 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, other drawings can be obtained based on the structures shown in these drawings without creative efforts.

[0024] Figure 1 It is a schematic structural diagram of an embodiment of the photovoltaic module provided by the present invention;

[0025] Figure 2 is Figure 1 a schematic structural diagram of an embodiment of the combined film structure in

[0026] Figure 3 is Figure 1 a schematic structural diagram of another embodiment of the combined film structure in

[0027] Figure 4 It is a schematic structural diagram of another embodiment of the photovoltaic module provided by the present invention.

[0028] Explanation of the Reference Numerals in the Drawings:

[0029]

[0030]

[0031] The realization, functional features and advantages of the present invention will be further described with reference to the embodiments and the accompanying drawings. Detailed implementation manners

[0032] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying 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. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0033] 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, the directional indications are only used to explain the relative positional relationship and movement conditions between components in a specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indications will also change accordingly.

[0034] In addition, if there are descriptions such as "first", "second", etc. involved in the embodiments of the present invention, 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, solution B, or a solution that satisfies both A and B at the same time. In addition, the technical solutions between the 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 them. When the combination of technical solutions is contradictory 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.

[0035] In existing photovoltaic modules, the solar backplane mainly uses a composite backplane material containing fluorine materials. However, this composite backplane material mainly relies on imports, has a relatively high market price, and the technology is monopolized by foreign enterprises. While low-cost solar backplanes use PET polyester films modified by coating to replace fluorine materials, but the PET materials modified by coating with ultraviolet light absorbers have limited ultraviolet resistance and poor weather resistance, and their manufacturing process is a non-environmentally friendly chemical coating process.

[0036] To solve the above problems, the present invention provides a photovoltaic module 100. The backsheet of the photovoltaic module 100 adopts a composite film structure, which has the characteristics of low cost, good ultraviolet resistance and good flexibility, can greatly reduce the cost of the photovoltaic module 100, and expand the application range of the photovoltaic module 100.

[0037] Figure 1 FIG. 4 is a schematic structural diagram of an embodiment of the photovoltaic module 100 provided by the present invention. Refer to Figure 1 , the photovoltaic module 100 includes a photovoltaic cell 2 and a first composite film structure 3. The photovoltaic cell 2 has a front surface facing the sunlight and a back surface opposite to the front surface; the first composite film structure 3 is disposed on the back surface of the photovoltaic cell 2. 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 forms a first reflected light and a second reflected light departing from the photovoltaic cell 2 after being reflected by the two first reflection interfaces. The first reflected light and the second reflected light can interfere constructively, where the object light is ultraviolet light and / or infrared light.

[0038] 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 the multiple transparent film layers form multiple interfaces. 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 interfere constructively, thereby selectively increasing 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 3 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 materials of the multiple transparent film layers in the first composite film structure 3 can be non-fluorine-containing materials to reduce costs. In general, the first composite film structure 3 provided by the present application has good ultraviolet resistance and low cost. Therefore, the photovoltaic module 100 using the first composite film structure 3 has good ultraviolet resistance, low cost, good flexibility, and a wide application range, and can be applied to automobiles, ships, color steel tile roofs, building facades, etc.

[0039] Further, 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.

[0040] The photovoltaic module 100 further includes a cover plate 1. The cover plate is disposed on the front surface of the photovoltaic cell 2. An adhesive layer 4 is provided between the photovoltaic cell 2 and the cover plate 1. 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 a first reflection interface, the multi-layer transparent film layer includes a first transparent film layer 311, a second transparent film layer 312, and an adjustment film layer that are 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, and 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, and the refractive index of the adjustment film layer is less than that of the first transparent film layer 311. Two end faces of the first transparent film layer 311 form two first reflection interfaces.

[0042] According to the principle of physical optical interference, the condition for the constructive interference of 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 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. Among them, 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 is incident on the first transparent film layer 311 from the adjustment film layer, the optical path differences of the first reflected light and the second reflected light formed by the two end faces of the first transparent film layer 311 are the same. Therefore, the first reflected light and the second reflected light 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-layer transparent film layers stacked in sequence are distributed as "low, high, low", and the object light can be selectively highly reflected. When the number of the above combinations increases, the reflection of the first combined film structure 3 on the object light 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 is λ, where n1×d1 = m1λ / 4, the reflection effect on the object light 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 and the second reflected light of the object light 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 target light is controlled by adjusting the number of reflection film groups.

[0050] In the embodiments of the present invention, referring to Figure 2 , the multiple transparent film layers include a first transparent film layer 311 and a 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. 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 target 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 target 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 the refractive index of the second transparent film layer 312, the refractive index distribution of the multiple transparent film layers is "photovoltaic cell 2 / low high low high low high... high low high". Then there are multiple "low high low" refractive index combinations, enabling the first combined film structure 3 to selectively and highly reflect the target light. And the two 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 the refractive index of the second transparent film layer 312, a first reflection interface is formed at least at the two 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 the refractive index of the first transparent film layer 311, the refractive index distribution of the multiple transparent film layers is "photovoltaic cell 2 / high low high low high low... high low". Then there are multiple "low high low" refractive index combinations, enabling the first combined film structure 3 to selectively and highly reflect the target light. And the two 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 the refractive index of the first transparent film layer 311, a first reflection interface is formed at least at the two 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 top of 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. A plurality of reflection film groups are provided and are stacked on top of each other. When the reflection film group includes three transparent film layers, regardless of how the refractive indices of these three transparent film layers are distributed, such as "high, medium, low, high, medium, low..." or "low, high, medium, low, high, medium...", there are at least combinations of "low, high, medium" and "medium, low, high" to form a first reflection interface at 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 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, m a is an odd number, and a is 1, 2, 3.

[0053] By analogy, when a plurality of transparent film layers form a reflection film group, and a plurality of reflection film groups are provided and stacked on top of each other to form a first combined film structure 3, as long as the refractive indices of adjacent transparent film layers in the multi-layer transparent film layer are different, 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, m a is an odd number, and when a is a natural number, the first combined film structure 3 selectively highly reflects the object light with a wavelength of λ. Preferably, the refractive indices of the multi-layer transparent film layers forming the reflection film group are different from each other. 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, and 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 factors such as ultraviolet rays, temperature, and humidity, which can 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 for generating heat. The increase in temperature of the photovoltaic module due to the absorption of 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 different from each other, 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, and the wavelength of the first object light is λ1, satisfying 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, satisfying 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, and the wavelength of the second object light is λ2, satisfying 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, satisfying: n4×d4 = m4λ2 / 4, where m4 is an odd number.

[0057] Dividing the multiple reflective film groups into the first reflective film group 31 and the second reflective film group 32 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 100, lower the temperature of the photovoltaic module 100, thereby improving the power generation efficiency of the photovoltaic module 100 and extending the service life of the photovoltaic module 100. 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 100.

[0058] It should be noted that the multiple reflective film groups may but are not limited to including 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. 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, obtaining better 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 the selective reflection of the first object light and the second object light is achieved by regulating the film layer thickness. 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 regulate 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 limit 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 groups 31 and the second reflective film groups 32 are alternately stacked; or it may be that some of the mutually stacked first reflective film groups 31 and some of the 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, so as to facilitate multi-layer co-extrusion processing.

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

[0063] The present invention does not limit the material of the transparent film layer, 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 of the polymer materials are partially miscible directly, which is suitable for being prepared by the polymer multi-layer co-extrusion process. After extrusion molding, the multi-layer transparent film layers do not delaminate and the structure is stable. The polymer multi-layer co-extrusion process has high production efficiency and low production cost, can reduce the cost of the photovoltaic module 100, and has less environmental pollution.

[0064] In this embodiment, according to the principle of physical optical interference, the greater the refractive index difference between the first transparent film layer 311 and the second transparent film layer 312, the higher the reflectivity of the first combined film structure 3 to the object light. Among polymers, polymethyl methacrylate (PMMA) has a relatively small refractive index, approximately 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, one of them is made of polymethyl methacrylate, and the other is made of 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 300nm - 400nm, and the wavelength of infrared rays is in the range of 1000nm - 2500nm, that is, the wavelength λ of the object light satisfies: 300nm ≤ λ ≤ 400nm; and / or, the wavelength λ of the object light satisfies: 1000nm ≤ λ ≤ 2500nm.

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

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

[0068] When the second reflective module 32 is used for selectively highly reflecting infrared rays, the thickness of the first transparent film layer 311 in the second reflective film group 32 is d3, and d3 satisfies 140nm ≤ d3 ≤ 420nm, the thickness of the second transparent film layer 312 in the second reflective film group 32 is d4, and d4 satisfies 140nm ≤ d4 ≤ 420nm; 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 40nm ≤ d3 ≤ 70nm. The thickness of the second transparent film layer 312 in the second reflective film group 32 is d4, and d4 satisfies 40nm ≤ d4 ≤ 70nm.

[0070] Regarding the total number Q of the multiple 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 multiple 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] Regarding the total thickness D0 of the multiple 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 multiple transparent film layers satisfies: D0 ≥ 10μm. 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, the materials and thicknesses of the first transparent film layer 311 and the second transparent film layer 312, and the number of groups of the first reflective film group 31 and the second reflective film group 32 can be adjusted to selectively reflect the first target light and the second target light, and to control the total number and total thickness of the multiple transparent film layers in the first combined film structure 3.

[0073] The technical solutions 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 combined film structure with excellent ultraviolet resistance using PMMA and PC materials as an example, in order to obtain a relatively wide emission bandwidth at a wavelength of 365nm, the first reflective film group 31 is designed to selectively highly reflect ultraviolet rays with a wavelength λ1 of 365nm, and the second reflective film group 32 is designed to selectively highly reflect ultraviolet rays with a wavelength λ2 of 354nm. According to n×d = λ / 4, in the first reflective film group 31, the thickness of the PMMA layer is 61.2nm, and the thickness of the PC layer is 57.6nm; in the second reflective film group 32, the thickness of the PMMA layer is 59.4nm, and the thickness of the PC layer is 55.8nm.

[0076] In actual operation, set the set temperature range of the extruder to 280°C, 275°C, 270°C, 265°C, 260°C, set the temperatures of the multiplier and the extrusion die head to 260°C and 220°C respectively, and set the temperature of the casting cooling roll to 120°C. First, use a quadruple equal-dividing multiplier to stack to obtain 128 groups of reflective film groups with equal thickness, and then use a double non-equal-dividing multiplier to obtain 128 groups of first reflective film groups 31 and 128 groups of second reflective film groups 32. Among them, the ratio of the total thickness of the 128 groups of first reflective film groups 31 to the total thickness of the 128 groups of second reflective film groups 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. 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 14.7 μm. The total thickness of the multi-layer transparent film layer of the first combined film structure 3 is 29.9 μm. In the reflectivity spectrum of the solar spectrum of the first combined film structure 3 in this embodiment, a relatively wide reflectivity peak is shown at a wavelength from 354 nm to 365 nm.

[0078] Example Two

[0079] Taking the design of the first combined film structure with excellent ultraviolet resistance using PMMA and PC materials as an example, design the first reflective film group 31 to selectively highly reflect ultraviolet rays with a wavelength λ1 of 365 nm, and the second reflective film group 32 to selectively highly reflect ultraviolet rays 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] In actual operation, set the set temperature range of the extruder to 280°C, 275°C, 270°C, 265°C, 260°C, set the temperatures of the multiplier and the extrusion die head to 260°C and 220°C respectively, and set the temperature of the casting cooling roll to 120°C. First, use a quadruple equal-dividing multiplier to stack to obtain 128 groups of reflective film groups with equal thickness, and then use a double non-equal-dividing multiplier to obtain 128 groups of first reflective film groups 31 and 128 groups of second reflective film groups 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. From this, it can be obtained that 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 multi-layer transparent film layer of the first composite film structure 3 is 61 μm. In the reflectivity spectrum of the solar spectrum of the first composite film structure 3 in this embodiment, reflectivity peaks are shown at a wavelength of 365 nm and a wavelength of 1100 nm.

[0082] In addition, in existing photovoltaic modules, the material of the cover plate 1 is commonly glass, fluorine materials (such as ETFE, PVD), and PET polyester film modified by coating with an anti-ultraviolet agent. However, the weight of glass is relatively large, which limits the application range of photovoltaic modules; fluorine materials are expensive and cannot be popularized; 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.

[0083] In view of this, in another embodiment of the present invention, referring to Figure 4 , the photovoltaic module 100 further includes a second composite film structure 5. The second composite film structure 5 is disposed on the front surface of the photovoltaic cell 2, and at least two second reflection interfaces are formed on the second composite film structure 5; the 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, and 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 combined film structure 5 provided by the present invention includes multiple transparent film layers. The refractive indices of adjacent transparent film layers are different to form an interface at the junction of adjacent transparent film layers, and multiple interfaces are formed by the multiple transparent film layers. At least two second reflection interfaces exist among the multiple interfaces and the two surfaces of the second combined film structure 5. The third and fourth reflected light rays formed by the ultraviolet light passing through the two second reflection interfaces undergo constructive interference, thereby selectively enhancing the reflection of ultraviolet light. By increasing the number of second reflection interfaces, the reflection of ultraviolet rays can be continuously improved, enabling the second combined film structure 5 to have good ultraviolet resistance. The second combined 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 impact on the transmittance of visible light. Moreover, the total thickness of the second combined film structure 5 is small and the weight is light. In addition, the materials of the multiple transparent film layers in the second combined film structure 5 can be non-fluorine-containing materials to reduce costs. In summary, the second combined film structure 5 provided in this application has good ultraviolet resistance and low cost. Therefore, the photovoltaic module 100 using the second combined film structure 5 has good ultraviolet resistance, 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.

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

[0086] Further, an adhesive layer 4 is provided between the photovoltaic cell 2 and the second combined 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 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 combined film structure 5 is used to replace the existing cover plate 1 material, it can meet the usage requirements of the double-sided power generation photovoltaic module 100, improve the power generation efficiency of the photovoltaic module 100, reduce the weight of the photovoltaic module 100, and reduce costs.

[0088] 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 using the description and drawings of the present invention under the inventive concept of the present invention, or direct / indirect application in other related technical fields, is included in the patent protection scope of the present invention.

Claims

1. A photovoltaic module, characterized in that, Comprising: A photovoltaic cell having a front face facing sunlight and a back face opposite to the front face; and, A first composite film structure disposed on the back face 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; 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; the multiple transparent film layers include a first transparent film layer and a second transparent film layer 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, and multiple reflection film groups are provided and 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 interface 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 interface at two end faces of at least part of the second transparent film layer; The multiple reflection film groups include a first reflection film group and a second reflection film group, and the refractive index and / or thickness of the corresponding first transparent film layer and the refractive index and / or thickness of the corresponding second transparent film layer in the first reflection film group and the second reflection film group are different from each other, so that the wavelengths of the second object light reflected by the second reflection film group and the first object light reflected by the first reflection film group are different; The total thickness of the transparent film layers of the multiple first reflection film groups is D1, and the total thickness of the transparent film layers of the multiple second reflection film groups is D2, wherein, D1:D2=(51~49):(49~51); An adhesive layer is provided between the photovoltaic cell and the first composite film structure.

2. The photovoltaic module according to claim 1, characterized in that, The photovoltaic module further includes a second composite film structure, the second composite film structure is disposed on the front face of the photovoltaic cell, and at least two second reflection interfaces are formed on the second composite film structure; Object light forms a third reflected light and a fourth reflected light departing from the photovoltaic cell after being reflected by the two second reflection interfaces, and the third reflected light and the fourth reflected light can undergo constructive interference, wherein the object light is ultraviolet light and / or infrared light.

3. The photovoltaic module according to claim 1, wherein The multiple reflection film groups include a first reflection film group and a second reflection film group, and the refractive index and / or thickness of the corresponding first transparent film layer and the refractive index and / or thickness of the corresponding second transparent film layer in the first reflection film group and the second reflection film group are different from each other, so that the wavelengths of the second object light reflected by the second reflection film group and the first object light reflected by the first reflection film group are different.

4. The photovoltaic module according to claim 1, wherein The thickness of the first transparent film layer in the first reflection film group is d1, and d1 satisfies 40nm≤d1≤70nm; The thickness of the second transparent film layer in the first reflective film group is d2, and d2 satisfies 40nm ≤ d2 ≤ 70nm.

5. The photovoltaic module according to claim 1, characterized in that The thickness of the first transparent film layer in the second reflective film group is d3, and d3 satisfies 140nm ≤ d3 ≤ 420nm; The thickness of the second transparent film layer in the second reflective film group is d4, and d4 satisfies 140nm ≤ d4 ≤ 420nm.

6. The photovoltaic module according to claim 1, wherein Among the first transparent film layer and the second transparent film layer, one of them is made of polymethyl methacrylate, and the other is made of at least one of polyethylene naphthalate, polyethylene terephthalate, polycarbonate, and polystyrene.

7. The photovoltaic module according to claim 1, characterized in that The total number of layers of the multiple transparent film layers is Q, and Q satisfies 250 ≤ Q ≤ 1100.

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