Photovoltaic cell module and method for manufacturing the same

Abstract

To provide a colored photovoltaic module particularly suited for building-integrated applications, as well as to a method of manufacture thereof.SOLUTION: A photovoltaic module is provided, comprising: a front sheet disposed on a light-incident surface of a photovoltaic module; a back sheet disposed on a surface of the photovoltaic module opposite the front sheet; a photovoltaic conversion element disposed between the front sheet and the back sheet; and at least one front encapsulating layer disposed between the photovoltaic conversion element and the front sheet, and including pigment particles distributed therein, and the front encapsulating layer includes a first region and a second region, the first region is disposed closer to the front sheet than the second region and includes pigment particles having concentration higher than that of the second region.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to the technical field of photovoltaic modules, more particularly to a colored photovoltaic module that is particularly suitable for architectural integration applications and a method for manufacturing said colored photovoltaic module. [Background technology]

[0002] Photovoltaic (PV) devices - also called solar cells or solar panels - tend to be nearly black in color, usually in shades of purple or indigo, with a clearly defined pattern of individual cells visible. When such PV devices are installed in buildings, they are an eyesore, and for this reason their direct use as building cladding is usually intolerable.

[0003] To address this issue, colored PV devices that can be integrated into the building structure, particularly as external cladding, have been proposed.

[0004] US Patent No. 9,281,186 discloses a film that is applied to the front sheet of a PV device to modify the appearance of the module, but this film requires a specific profile that must be aligned with the geometry of the individual PV cells that make up the module, and relies on a complex design that includes facets in the front sheet and embedded elements in the inactive portion of the module.

[0005] US 2014 / 326292 A1 discloses a PV device that includes a graphic film inside the module that is printed with color or texture and requires a selectively reflective layer to limit the effect of the film on the efficiency of the module.

[0006] US Pat. No. 9,276,141, US Pat. No. 5,399,413 and US Pat. No. 5,499,426 disclose decorative film overlays that are provided on or within PV modules.

[0007] Patent Document 6 discloses a white photovoltaic module in which an interference filter is formed on an intermediate layer provided on the light-incident surface of the photovoltaic module so as to reflect a certain amount of light over the entire visible spectrum. Special equipment and methods are required to produce this interference film.

[0008] US Pat. No. 5,399,633 describes printing on top of a sealing layer.

[0009] However, all of these prior art solutions are complex or require the addition of additional layers to the module, essentially increasing the risk of delamination of the module since for each additional layer added to the module there is an interface between separable layers, and may require specialized manufacturing techniques or equipment.

[0010] US Patent No. 5,399,663 proposes a solution to this problem. In the embodiment of FIG. 7 of US Patent No. 5,399,663, the front encapsulation layer itself contains pigment particles randomly distributed therein. This therefore does not require an additional colored film on top of the front encapsulation layer, but creates an entirely different set of problems. The encapsulant used in US Patent No. 5,399,663 is conventional. This can lead to significant color non-uniformity. In more extreme cases, excessive encapsulant flow can lead to significant thickness variations within the module, especially in areas where PV cells are present and those where they are not. This again results in undesirable color variations across the module. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] U.S. Patent No. 9,281,186 [Patent Document 2] US Patent Application Publication No. 2014 / 326292 [Patent Document 3] U.S. Patent No. 9,276,141 [Patent Document 4] International Publication No. 2016 / 118885 [Patent Document 5] U.S. Patent No. 8,513,517 [Patent Document 6] European Patent Publication No. 2793271 [Patent Document 7] US Patent Application Publication No. 2012 / 247541 [Patent Document 8] International Publication No. 2009 / 089236 Summary of the Invention [Problem to be solved by the invention]

[0012] SUMMARY OF THE PRESENT EMBODIMENT It is therefore an object of the present invention to overcome at least some of the above-mentioned problems associated with the prior art. [Means for solving the problem]

[0013] More particularly, the present invention relates to a photovoltaic module comprising a front sheet, e.g. made of glass, transparent ceramics, polymer or other suitable transparent material, disposed on the light-incident side of the photovoltaic module, a back sheet, e.g. made of glass, metal, polymer, ceramic or other material, disposed on the side of the photovoltaic module opposite to the front sheet, a photovoltaic conversion element, which may be of any convenient type, disposed between the front sheet and the back sheet, and at least one front encapsulant layer, a thermoplastic or at least partially crosslinked polymer, e.g. EVA, polyolefin, etc., containing pigment particles distributed therein, disposed between the photovoltaic conversion element and the front sheet. If necessary, a back encapsulant may be provided between the PV conversion element and the back sheet.

[0014] According to the invention, the front encapsulation layer comprises a first region and a second region. The first region is located closer to the front sheet than the second region and contains a higher concentration of pigment particles than the second region. The second region may in particular be substantially free of pigment particles. This particle distribution not only provides a color scheme for the module, making it suitable for use, for example, as architectural cladding, but also avoids migration and agglomeration of pigment particles in the first region during lamination, thereby preventing unintended changes in the color distribution. Furthermore, the PV module does not require special manufacturing techniques, since it can be integrated by standard lamination equipment using standard front sheet configurations without special features such as textures, structuring, etc.

[0015] Advantageously, at least some of the pigment particles have a diameter in the range of 100 nm to 1 μm, preferably 300 nm to 700 nm, more preferably 400 nm to 600 nm. The diameter of the particles may be optimized to suit the desired optical properties of the front sealing layer. Similarly, the pigment particles may be provided in the front sealing layer in a mass concentration of 0.01 to 10 parts per 100 of the resin, which again may be adjusted to optimize the desired properties.

[0016] Advantageously, the pigment particles may comprise at least one of a zinc-based pigment (e.g. zinc oxide or zinc chromate), a titanium-based pigment (e.g. titanium oxide or titanium yellow), an iron-based pigment (e.g. iron oxide or Prussian blue), a chromium-based pigment (e.g. chromium oxide), a bismuth-based pigment (e.g. bismuth vanadate), a cobalt-based pigment (e.g. cobalt blue) or a cobalt stannate or cobalt / lithium / titanium oxide) aluminium-based pigment (sulphur-containing sodium silicate complex), a tin-based pigment (e.g. tin sulphide) or a copper-based pigment.

[0017] Advantageously, the photovoltaic cell module may further comprise an inner front sheet and an inner front encapsulation layer disposed between the front encapsulation layer and the photovoltaic conversion element, so that the module of the present invention can be made simply by laminating the front encapsulation layer and the front sheet onto an existing prefabricated PV module, so that the module of the present invention can be made to order based on an existing commercially available module.

[0018] Advantageously, a graphic film printed with an image, pattern, etc. may be provided on the light incident surface of the front sheet such that the colored front encapsulant provides a uniform background color (which may be, for example, white) that provides good contrast for the graphic film.

[0019] The invention also relates to a method for manufacturing a photovoltaic module, comprising the steps of providing a lamination device, for example a heated vacuum bag lamination device or other suitable device, providing in the lamination device a layer stack (note that if necessary a back encapsulant may be provided between the PV conversion element and the back sheet) comprising a front sheet, for example made of glass, transparent ceramics, polymer or other suitable transparent material, arranged on the light-incident side of the photovoltaic module, a back sheet, for example made of glass, metal, polymer, ceramic or other suitable transparent material, arranged on the side of the photovoltaic module opposite to the front sheet, a photovoltaic conversion element, which may be of any convenient type, arranged between the front sheet and the back sheet, and at least one front encapsulant layer, which is a thermoplastic or at least partially crosslinked polymer, for example EVA, polyolefin, etc., and contains pigment particles distributed therein, arranged between the photovoltaic conversion element and the front sheet, and applying heat and pressure to the layer stack to integrate the layer stack into the photovoltaic module by fusing and / or crosslinking the encapsulant layer.

[0020] According to the present invention, the front sealing layer comprises a first film and a second film, the first film being disposed closer to the front sheet than the second film and containing a higher concentration of pigment particles than the second film, in other words, the second film is substantially free of pigment particles or contains fewer pigment particles than the first film.

[0021] The particles provide the module with a color scheme, making it suitable for use, for example, as architectural cladding, and also scatter a certain amount of incident light, facilitating the concealment of the photovoltaic element structure. The two-layer film structure, resulting in the above-mentioned two-domain structure, limits or even completely eliminates migration and aggregation of the pigment particles in the first film during lamination, thereby providing the desired color distribution in the finished module. This color distribution is typically uniform, but may have a pattern. If the second film also contains pigment particles, migration of the lower concentration of pigments inside is masked by the higher concentration first film. Furthermore, the PV module does not require special manufacturing techniques, since it can be integrated by standard lamination processes using standard front sheet configurations without special features such as textures, structuring, etc.

[0022] In an alternative process, a method for manufacturing a photovoltaic module includes: The method includes providing a lamination apparatus, such as a heated vacuum bag lamination apparatus or other suitable apparatus; providing a layer stack in the lamination apparatus, the layer stack comprising a prefabricated photovoltaic module, at least one front encapsulating layer provided on a surface of the prefabricated photovoltaic module intended to receive incident light, the front sheet having pigment particles distributed therein, and disposed on a light-incident surface of the photovoltaic module; and applying heat and pressure to the layer stack to integrate the layer stack into the photovoltaic module by fusing and / or crosslinking the encapsulating layer.

[0023] Again, the front sealing layer comprises a first film and a second film, the first film being closer to the front sheet than the second film and containing a higher concentration of pigment particles than the second film.

[0024] The benefits of the present invention are therefore applicable to existing pre-manufactured PV modules. Thus, modules of the present invention can be manufactured to order based on existing commercially available modules. This is particularly efficient, as colored modules can be easily manufactured to order based on stock of standard commercially available modules.

[0025] Advantageously, the first film has a higher viscosity than the second film during application of heat and pressure - i.e., during lamination - so that migration and agglomeration of the pigment particles distributed therein is better prevented.

[0026] Advantageously, during the application of heat and pressure, the first film has a tan δ value of less than 0.8 and the second film has a tan δ value of at least 0.9, preferably at least 1.2. Furthermore, at least at the lamination temperature, the viscosity of the second film is at most 80% of the viscosity of the first film, preferably at most 50%, even when approaching the lamination temperature. This ensures that the first film behaves like a solid during lamination, while the second film behaves like a liquid, preventing migration of pigment particles and maintaining a substantially constant thickness of the pigment-containing layer.

[0027] Advantageously, the first film is non-crosslinkable and has a complex viscosity of more than 400000 Pa·s at 85° C., more than 50000 Pa·s at 105° C. and more than 1000 Pa·s at 165° C., and the second film has a complex viscosity of less than 100000 Pa·s at 85° C., less than 20000 Pa·s at 105° C. and less than 15000 Pa·s at 165° C. If the maximum lamination temperature is less than 165° C., the condition at 165° C. is optional. Even if these ranges overlap, this does not contradict the explanation in the previous paragraph regarding the viscosity relationship, which is the important criterion to be met at the lamination temperature.

[0028] Alternatively, the first film is at least partially crosslinkable and has a complex viscosity of greater than 20,000 Pa·s at 85° C., greater than 15,000 Pa·s at 105° C., and greater than 5,000 Pa·s at 165° C., and the second film has a complex viscosity of less than 100,000 Pa·s at 85° C., less than 20,000 Pa·s at 105° C., and less than 10,000 Pa·s at 165° C. Again, if the maximum lamination temperature is less than 165° C., the 165° C. condition is optional. Similarly, these overlapping ranges are not inconsistent with the discussion in the previous paragraph regarding the critical viscosity criteria to be met at the lamination temperatures.

[0029] Advantageously, the layer stack further comprises a graphic film provided on the light entrance surface of the front sheet, which may thus be directly incorporated into the module during lamination, or alternatively, which may be provided after lamination.

[0030] Advantageously, at least a portion of the pigment particles, preferably at least 50% or even at least 75%, have a diameter in the range of 100 nm to 1 μm, preferably 300 nm to 700 nm, more preferably 400 nm to 600 nm. The diameter of the particles may be optimized to suit the desired optical properties of the front sealing layer. Similarly, the pigment particles may be provided in the front sealing layer in a mass concentration of 0.01 to 10 parts per 100 of the resin, which again may be adjusted to optimize the desired properties.

[0031] Advantageously, the pigment particles comprise at least one of a zinc-based pigment (e.g. zinc oxide or zinc chromate), a titanium-based pigment (e.g. titanium oxide or titanium yellow), an iron-based pigment (e.g. iron oxide or Prussian blue), a chromium-based pigment (e.g. chromium oxide), a bismuth-based pigment (e.g. bismuth vanadate), a cobalt-based pigment (e.g. cobalt blue) or a cobalt stannate or cobalt / lithium / titanium oxide) aluminium-based pigment (sulphur-containing sodium silicate complex), a tin-based pigment (e.g. tin sulphide) or a copper-based pigment.

[0032] Advantageously, the front sealing layer is manufactured by mixing the pigment particles with a base resin and extruding the front sealing layer as a film. [Brief description of the drawings]

[0033] Further details of the invention will become apparent from the following description in conjunction with the following figures. [Figure 1] 1 is a schematic cross-sectional view of a photovoltaic module according to the present invention; [Diagram 2] 4 is a schematic cross-sectional view of another photovoltaic module according to the present invention. [Diagram 3] 1 is a schematic cross-sectional view of a portion of a photovoltaic module according to the invention provided with a graphic film; [Figure 4] 1 is a schematic diagram of a method for manufacturing a photovoltaic module using a lamination device. [Diagram 5] 1 is a graph of experimental results obtained on a photovoltaic module similar to the present invention. [Figure 6] 1 is a graph of experimental results obtained on a photovoltaic module similar to the present invention. [Figure 7] 1 is a graph of experimental results obtained on a photovoltaic module similar to the present invention. [Figure 8] 1 is a graph of experimental results obtained on a photovoltaic module similar to the present invention. [Figure 9] 1 is a schematic diagram of a building structure in which PV modules are provided. [Figure 10] 1 is a graph of complex viscosity versus temperature for a typical pair of front sealing layers. [Figure 11] 4 is a graph of tan δ values ​​for the same membranes. MODE FOR CARRYING OUT THE PRESENTINVENTION

[0034] It should be noted that hereinafter, one or more intermediate layers may also be present between the layers mentioned above, unless it is specified that a particular layer is directly disposed on an adjacent layer. Therefore, "on" should be taken to mean "directly or indirectly on" unless otherwise specified. Furthermore, the patterning of certain layers, connectors, etc. are not shown as they are well known to those skilled in the art.

[0035] FIG. 1 represents a first embodiment of a photovoltaic (PV) module according to the invention.

[0036] The module 1 has a front sheet 11 present on a light-entering side of the module that is intended to be illuminated in use (indicated by a sun symbol in the figures), and a back sheet 19 present on a side of the module 11 opposite the front sheet 11. The front sheet may be glass, a transparent ceramic, a polymer, or any other convenient substantially transparent material. The back sheet may be metal, glass, a ceramic, a polymer, or any other convenient material. The front sheet 11 may be structured and may be provided with a coating.

[0037] Disposed between the front and back sheets is a patterned and interconnected photovoltaic conversion element 15 comprising one or more PV cells having NIP, PIN, NP or PN junctions as are commonly known. The PV cells may be based on thin film silicon, crystalline silicon, germanium, perovskite, dye sensitized cells or any other type of PV technology suitable for generating electrical power from light incident on and impinging on the light incident surface of the PV module 1.

[0038] The PV conversion elements 15 are sealed on the front side by a front sealing layer 13, which seals the front side to the front sheet 11, and on the back side by a back sealing layer 17, which seals the PV conversion elements 15 to the back sheet 19. However, the back sealing layer 17 may itself constitute the back sheet. The sealing layer may be of standard materials, such as polyolefins, EVA (ethylene vinyl acetate), ionomers, polyvinyl butyral, modified fluoropolymers, etc. Each of the sealing layers 13, 17 is typically 200 μm to 1 mm thick, with a maximum of 2 mm. Furthermore, multiple front sealing layers 13 may be laminated on top of each other. In the case of a transparent (e.g. glass) or non-dark colored back sheet, the back sealing layer 17 may be colored or dyed with a dark color (e.g. black, dark brown, dark blue, etc.) to facilitate hiding the interconnects and structures present in the module. It should be noted that in the present invention, the sealing layer seals one layer to another. As a result, the front encapsulation layer 13 is an interior layer and not an exterior layer of the module structure, such as a front sheet or graphic film.

[0039] It should be noted that other intermediate layers may be provided between the layers shown, and that the layers need not be flat but may represent curved or more complex surfaces.

[0040] According to the present invention, the front encapsulation layer 13 has pigment particles 21 incorporated therein. In particular, the front encapsulation layer 13 has a first region 13a and a second region 13b. The first region 13a is disposed closer to the front sheet 11 (i.e., towards the light-incident surface of the module 1) than the second region 13b. The second region 13b is disposed closer to the PV conversion elements 15 than the first region 13a. The first region 13a and the second region 13b are typically directly adjacent to each other and thus in contact. However, the presence of an intermediate region between the first region 13a and the second region 13b is not excluded.

[0041] The first region 13a contains a higher concentration of pigment particles 21 than the second region 13b. The second region 13b is substantially free of pigment particles 21 or contains fewer pigment particles than the first region 13a. If the second region 13b contains pigment particles 21, it provides a concentration of pigment particles 21 that is up to 50%, preferably up to 30%, and more preferably up to 20% of the pigment particles in the first region 13a. If pigment particles are present in each of the first region 13a and the second region 13b, they may be the same or different.

[0042] Other areas (not shown) of the front encapsulant layer 13 may be provided on the front sheet 11 and / or on the PV device 15. These other areas are typically free of pigment particles, although it is not excluded that these other areas contain low concentrations of pigment.

[0043] The pigment particles 21 are represented very diagrammatically. At least a portion of the particles - preferably at least 50%, more preferably at least 75% (or even substantially all) - typically have a size in the range of 100 nm to 1 μm - most notably 300 nm to 700 nm, most particularly 400 nm to 600 nm. It should be noted that the pigment particles are discrete particles distinct from encapsulants made of colorants or already colored materials that are dispersed at a molecular level in the encapsulant. The pigment particles 21 are distributed throughout the entire thickness of the first region 13a (and therefore not only at or near the surface). If pigment particles are present in the second region 13b, they are similarly distributed throughout the entire thickness of this region. The manner in which the two regions 13a, 13b contained by the front encapsulation layer 13 are formed will be described below in connection with FIG. 4. The distribution of the pigment particles 21 when the film from which the first region is made is extruded may be random or may constitute a certain pattern. The distribution of dyes is maintained by the present invention (see below).

[0044] A wide range of pigments can be used, provided they are chemically stable and stable under long exposure to UV light, either alone or in combination with suitable UV stabilizers, such as hindered amine light stabilizers (HALS), hydroxyphenylbenzotriazoles, oxalic anilides, benzophenones, benzotrazol, hydroxyphenyltriazines, etc. As examples of suitable pigments, titanium oxide or zinc oxide may be used to produce white. Yellow, orange, and brown colors can be produced using various iron oxides, such as Fe2O3 for red-brown or FeO(OH) or ochre for yellow. Yellow may also be produced by bismuth vanadate, titanium yellow, zinc chromate, or tin sulfide. Green can be produced by chromium oxide or Co / Li / Ti oxide. Blue can be produced by, for example, sulfur-containing sodium silicate complexes or Prussian blue or cobalt stannate. Naturally, the invention is not limited to such pigments, and many other pigments are commercially available.

[0045] The pigment particles 21 may be provided in a concentration ranging from 0.01 to 10 parts per hundred parts (phr) of the resin that serves as the basis for the front encapsulating layer 13. More specifically, 0.1 to 5 phr, and even more specifically, 0.1 to 1 phr of pigment particles may be used, depending on the thickness of the front encapsulating layer 13. Thinner encapsulating layers typically benefit from a higher concentration of pigment particles 21.

[0046] The pigment particles 21 absorb a portion of the visible light incident on the PV device 1 to produce the desired color, and also diffuse the light to provide a uniform color and hide various features of the PV conversion element 15, such as the patterning of the PV conversion element 15, the electrical interconnections between the individual cells, the edges of the individual cells, and color misalignment between the individual cells and the back encapsulant 17 and / or backsheet 19.

[0047] This scattering effect is particularly advantageous over simply providing a front encapsulant that is colored with a colorant dispersed therein at the molecular level, because such a colorant would hide the various features of the PV conversion elements 15 described above, with much greater optical transparency due to the lack of optical scattering.

[0048] Additionally, the scattering effect facilitates diffusion of light passing through the front encapsulant 5 and incident on the photoelectrically active portion of the PV conversion element 7 in a manner similar to that of a conventional diffusing element included within the PV module 1 on the light incident face of the PV conversion element 7, thereby increasing the average optical path length of the light passing through the cell. Naturally, the overall efficiency is reduced in proportion to the light that is reflected or scattered back towards the light incident face of the PV device.

[0049] The size of the pigment particles 21 can be adjusted to increase the transmittance of the IR-light sensitive PV conversion element 5 in the infrared range. By optimizing the size and density of the pigment particles in the front encapsulation layer 5, interference between the pigment particles 21 can be generated to give a glitter, shimmer, or rainbow effect. More specifically, the size and concentration of the pigment particles, the front encapsulation layer, etc. can be adjusted by routine experimentation within the above ranges to achieve the desired color, optical effect, transmittance, reflectance, etc. The exact particle size and particle concentration can be conceived by routine experimentation to achieve the desired optical properties (color, reflectance, transmittance, special interference effect, etc.), and there is no particular a priori relationship between particle size and particle concentration, which relationship depends on the desired optical properties.

[0050] For the manufacture of the front encapsulation layer 13, the required amount of pigment particles 21 may simply be mixed with the base resin or resin precursor constituting the first region 13a of the encapsulation layer 13, and optionally with the resin precursor of the second region 13b, if colored. If necessary, a suitable UV stabilizer (see above) may also be mixed into the resin at the same time. This may then be extruded in the usual manner without the use of special equipment or methods. As a result of this construction, no colored frit glass or the like is required as the front sheet 11, so the invention can be carried out without special equipment, and the PV module 1 can be integrated by conventional lamination equipment (see below).

[0051] 2 shows another embodiment of a PV module 1 according to the invention. In this variant, the front encapsulation layer 13 and the front sheet 11 have been laminated onto the front surface of an existing pre-fabricated PV module 27. As a result, the final PV module 1 according to the invention also comprises the inner front sheet 25 and the inner front encapsulation layer 23, since these layers are already present in the existing pre-fabricated PV module 27. The remaining layers 15, 17, 19 are included in the pre-fabricated PV module and have been described above and do not need to be described again here.

[0052] This configuration makes it possible to provide the benefits of the present invention to any commercially available PV module by retrofitting the front encapsulant layer 13 and front sheet 11 to an existing module. This is particularly advantageous because it makes it easy to manufacture a variety of modules 1 according to end user requirements. In essence, a manufacturer can maintain an inventory of pre-manufactured standard PV modules 27 and laminate the front encapsulant layer 13 and front sheet 11 onto the pre-manufactured standard PV module 27 as required by selecting an appropriately colored front encapsulant layer 13 from the inventory or by manufacturing to order.

[0053] 3 partially illustrates a further variant of a PV module 1 according to the invention, which includes a graphic film 29 provided on the light-entering surface of the front sheet 11. This graphic film 29 may be, for example, a polymeric film such as a commercially available PET film. On this graphic film 29, images, patterns, etc. have been printed by any convenient means. The graphic film 29 may be provided either during lamination (described below) or at a later point after manufacture of the PV module 1 once processing other than the graphic film 29 has been completed.

[0054] The graphic film 29 may be provided in either the embodiment of Figure 1 or the embodiment of Figure 2. Therefore, other parts of the PV module 1 are not shown in Figure 3.

[0055] Alternatively, in an embodiment not shown, the graphic film 29 may be laminated between the front sealing layer 13 and the front sheet 11 .

[0056] As another possibility that may be suitably provided in any of the above-mentioned embodiments, a polymer layer containing the above-mentioned pigment particles may be used as the front sheet 11 - for example directly in contact with the front encapsulant layer 13 - or may serve as an additional layer on top of a glass or polymer sheet. In such a case, the front encapsulant 13 may contain particles according to the invention or may be conventional. A particular advantage of this particle-containing layer is a fluoroolefin, such as Lumiflon (from Asahi Glass), although other polymers are also possible.

[0057] FIG. 4 illustrates diagrammatically a method for manufacturing a PV module 1 according to the invention.

[0058] A layer stack 31, which includes at least layers 11, 13, 15, 17, 19 as well as other layers, is integrated in the lamination device 33. In the case of the embodiment of FIG. 2, the layer stack comprises a prefabricated PV module 27, on which the front encapsulation layer 13 and the front sheet 13 (and any other desired layers) have been applied. The integration of the layer stack 31 in the lamination device 33 can be with the light-incident surface of the finished PV module facing upwards or downwards. As the front encapsulation layer 13 has two regions 13a, 13b, it is produced from two independent films: a first film 13a, which is the first region (and therefore has the same reference number) and a second film 13b, which is the second region (and therefore has the same reference number). The first film 13a thus contains the particles 21 mentioned above. These are applied in the correct order in the lamination device 33 with additional films applied on one or the other of them.

[0059] The laminator may be a vacuum bag laminator, a roller type laminator, or any other convenient type. The laminator 33 then applies heat and pressure, for example at a temperature of 140° C. to 180° C. and a pressure of up to 1 bar (typically 0.4 bar to 1 bar), for a suitable period of time, which fuses and crosslinks the various encapsulation layers together into the final PV module 1.

[0060] As a result, the PV module 1 according to the present invention can be fabricated in conventional PV processing equipment without the need for special equipment.

[0061] The properties of the first and second films 13a, 13b can be optimized to better prevent migration of the dye during stacking. As mentioned above, in the prior art, the dye-infused encapsulant flows under heat and pressure, which can lead to migration and aggregation of the dye particles. This can result in migration of the dye particles around the individual cells that make up the PV conversion element 15, leading to variations in the thickness of the encapsulation layer and often very non-uniform coloring.

[0062] The solution to this particular problem is crucial in the choice of materials for the first and second membranes, each of which may have a thickness between 0.05 mm and 2 mm.

[0063] Essentially, the material of the first film 13a is chosen to limit migration of the dye particles 21, while the material of the second film 13b is chosen for its sealing properties and tendency to flow around features, such as the details of the underlying PV cells 15 if no intermediate layer is present. For this reason, the viscosity of the first film 13a during stacking is chosen to be higher than that of the second film 13b. This higher viscosity limits lateral (within the plane of the film 13a) flow, preventing migration of the dye and thus avoiding uneven distribution of the dye. Meanwhile, the second film, which has a lower viscosity, flows normally and thus seals the underlying layers normally. Additionally, the second film acts as a "buffer" layer, reducing the tendency of the first film 13a to have thickness variations due to underlying features, such as individual cells.

[0064] Furthermore, if the material of the first film 13a has viscoelastic properties, this will also further limit the variation in thickness of the completed first region, thus avoiding variations in light absorption.

[0065] In terms of the selection of the sealing material, several possibilities are possible depending on whether the first membrane 13a is made of a crosslinkable polymer or not.

[0066] In the first case, the base resin of the first film 13a is non-crosslinkable, e.g. polyethylene (PE), poly(ether ether ketone), poly(ethylene terephthalate), polyamide, nylon, poly(methylene oxide), POM, poly(4-methylpentene), poly(styrene), poly(vinyl alcohol), poly(vinyl chloride), poly(vinyl chloride), poly(vinyl fluoride), poly(vinylidene chloride), polyurethane, polyimide, polycarbonate, acrylonitrile, butadiene, styrene, polyphenylene sulfide, or styrene acrylonitrile. In any case, the required viscosity is obtained by selecting and / or adapting the composition of the encapsulant. This is a simple task for the skilled person based on the desired film properties during lamination (see below). In a simple sense, the second film 13b typically has a lower melting point than the first film 13a. The lamination temperature is chosen so that the viscosity of the second film 13b remains sufficiently smaller than that of the first film 13a. Ideally during lamination, the complex viscosity of the second film 13b remains at least 20% lower than the complex viscosity of the first film 13a, preferably at least 50% lower, and more preferably at least 10 times lower. Based on the desired properties, corresponding commercial products can be obtained off the shelf or can be appropriately adjusted.

[0067] More specifically, the desired properties are preferably: Complex viscosity greater than 400000 Pa·s at 85°C, greater than 50000 Pa·s at 105°C, greater than 1000 Pa·s at 165°C, with the complex viscosity being irrelevant above the lamination temperature Tangent δ less than 0.8 throughout the entire lamination process By adding pigment particles in the ranges mentioned above, the viscosity can be increased by up to 10%.

[0068] For reference, complex viscosity is a frequency-dependent viscosity function determined during forced harmonic oscillation of shear stress and is defined as the complex modulus divided by the angular frequency. Here, the complex modulus represents the overall resistance of a material to deformation, whether that deformation is recoverable (i.e., elastic) or non-recoverable (i.e., viscous). It is measured here with a dynamic moving die rheometer or similar device at a frequency of 1 Hz and a strain of 10%. Tangent delta - also known as the "loss tangent" - is the phase angle given by the ratio of the loss modulus (G'') to the storage modulus (G') and represents the presence and magnitude of elasticity in a fluid. Again, at a frequency of 1 Hz and a strain of 10%, a tangent delta less than 1.0 suggests predominantly elastic (i.e., solid-like) behavior, while a value greater than 1 suggests predominantly viscous (i.e., liquid-like) behavior.

[0069] The second film 13b paired with this non-crosslinkable first film 13a has the following properties: Complex viscosity less than 100000 Pa·s at 85°C, less than 20000 Pa·s at 105°C, less than 15000 Pa·s at 165°C, and again the complex viscosity is irrelevant above the lamination temperature. Tangent δ greater than 0.9 at the lamination temperature, preferably greater than 1.2.

[0070] It should be noted that if the base resin of the second membrane 13b does not exhibit significant creep resistance, the base resin of the second membrane 13b can be at least partially crosslinked before and / or during and / or after lamination.

[0071] If the first film 13a is crosslinked, the degree of prepolymerization of this film contributes to determining the viscosity. The ideal parameters are as follows: Complex viscosity is greater than 20,000 Pa·s at 85°C, greater than 15,000 Pa·s at 105°C, and greater than 5,000 Pa·s at 165°C. Complex viscosity is irrelevant at temperatures higher than the deposition temperature. Tangent δ less than 0.8 throughout the entire lamination process

[0072] It should be noted that at least some of these desired properties can be obtained by performing pre-crosslinking of the first film 13a via various curing mechanisms, such as radiation curing, moisture curing, and peroxide initiated curing.

[0073] The corresponding parameters for the second film 13b are: Complex viscosity: less than 100,000 Pa·s at 85°C, less than 20,000 Pa·s at 105°C, less than 10,000 Pa·s at 165°C Tangent δ greater than 0.9 at the lamination temperature, preferably greater than 1.2

[0074] The same base resin may be used for both layers when the encapsulation of the first film 13a is pre-crosslinked, with only the first film 13a being pre-polymerized.

[0075] It should be noted that if the viscosity of the first film 13a is too high to ensure good wetting and proper bonding of the adjacent layer (e.g. the front sheet 11) under lamination conditions, an auxiliary sealing film may be provided between the first film 13a and said adjacent layer, which is a conventional viscous sealant and performs a similar function as the second film 13b.

[0076] In any case the general principles are: The first film 13a has a value of tan δ less than 0.8 to give a more solid-like behavior during the entire deposition process. The second film 13b has a value of tan δ of at least 0.9, preferably at least 1.2, to give it a more liquid-like behaviour at least at the lamination temperature. The viscosity of the second film 13b does not exceed 80% of the viscosity of the first film 13a, preferably does not exceed 50% of the viscosity of the first film 13a, and more preferably does not exceed 10% of the viscosity of the first film 13a, at least at the lamination temperature.

[0077] FIG. 10 shows a graph of complex viscosity (vertical logarithmic scale) versus temperature (horizontal linear scale). FIG. 11 shows values ​​of tan δ (linear scale) for example materials of the first film 13a and the second film 13b. More specifically, these materials are XLPO encapsulants developed in-house at ASCE, CSEM and XLPO grades supplied by the Japanese company Mitsui Chemicals. Throughout the graph, up to about 165° C. to the right, the complex viscosity η* of the second film 13b does not reach even 50% of the complex viscosity of the first film 13a, and is therefore well within acceptable limits (maximum 80%). Thus, in this example, lamination temperatures up to 165° C. are possible when the tan δ of the second film 13b falls below 0.9. Ideally, however, the complex viscosity of the second film 13b would not exceed 10% of the complex viscosity of the first film 13a, and the tan δ of the second film 13b would remain above 1.2. This suggests a maximum lamination temperature of around 160°C.

[0078] If the first film 13a is not crosslinkable, the viscosity will essentially decrease with increasing temperature. Therefore, the material of the second film 13b must be carefully selected to withstand sufficient viscosity differentials throughout the entire lamination process. The maximum temperature must be carefully selected as well. If necessary, e.g. for use in hot weather, the second film 13b may also be crosslinkable to provide sufficient creep resistance.

[0079] When the first membrane 13a is crosslinkable and does not crosslink sufficiently after a prior pre-crosslinking, it has a low viscosity during the initial stages of lamination. This makes it easier to fill the bubbles before crosslinking increases the viscosity and gives it greater mechanical strength. At any given moment during lamination, the viscosity and tangent δ depend on the temperature and the degree of networking (crosslinking) of the membrane. This can be further increased as the lamination proceeds. Thus, the inherent decrease in viscosity and increase in tangent δ upon increasing temperature is compensated by increasing networking, which opens up a wider choice of material for the second membrane 13b, since it is relatively easier to choose a material with a sufficiently low viscosity during the lamination process. It is easier to choose a crosslinkable resin for the second membrane 13b, especially for good creep resistance, than for the non-crosslinkable first membrane 13a.

[0080] In either case, the interface between the two films 13a, 13b after lamination is perfect and bubble-free, and cross-diffusion of the pigment particles 21 is minimal across the interface.

[0081] Specific examples of material pairs for the first film 13a and the second film 13b are given in the table below: The given commercial reference symbols represent compositions that do not change, thus ensuring reproducibility. [Table 1]

[0082] Figure 5 shows a graph of experimental results obtained by manufacturing a PV module 1 according to the embodiment of Figure 2 but without the second region 13b to illustrate the effect of certain combinations of encapsulant and pigment. In this case, the front encapsulant layer 13 was made of Dow Engage PV POE XUS38660.00 polyolefin-based base resin and 1 phr of DuPont Ti-Pure R-960 titanium dioxide-based pigment. No other additives were present. The median pigment particle size was 500 nm.

[0083] Pigment particles were added and intermixed with the base resin and extruded at 170° C. through a twin screw extruder to obtain a white crosslinkable polyolefin with a thickness of 0.85 mm.

[0084] The resulting white front encapsulant sheet was combined with a 50 μm ETFE front sheet and laminated onto a prefabricated PV module at a temperature of 165° C. and a pressure of approximately 1 bar (±0.99 bar) for 720 seconds.

[0085] The metal connections of the PV module were coloured black. The back sheet 19 was also coloured black to reduce contrast.

[0086] The graph in the figure represents the external quantum efficiency (EQE) and reflectance (R) over the wavelength range from 350 nm to just over 1150 nm for a PV module according to the invention as described above (W1). Data is contrasted with that of a reference cell of identical construction but with a transparent front encapsulation layer 13. As can be seen, the EQE has decreased and the reflectance has increased over a wide wavelength range.

[0087] Additionally, the cell performance and color expressed in “Lab” color space coordinates were measured and the results are shown in the table below. [Table 2]

[0088] As can be seen from the table, constructed module 1 has a white color and a current loss of about 58%.

[0089] Figure 6 shows a graph of experimental results obtained by manufacturing another PV module 1 according to the embodiment of Figure 2 (again, without the presence of the underlying layer 13b). The front encapsulant layer 13 was made of ExxonMobil Escorene Ultra UL00728CC EVA copolymer base resin with 0.05 wt% Scholz Red 110M pigment particles dispersed therein.

[0090] Red pigment particles were intermixed into the base resin and then extruded at 95°C to produce a 0.9mm thick membrane front sealing layer. This was then combined with a 100μm thick ETFE front sheet and laminated at 150°C and substantially 1 bar pressure for 720 seconds. As in the previous example, the metal connections were coloured black. A blackened back sheet 19 was used.

[0091] The resulting PV module has a red-brown color that is particularly suitable for rooftop installation in areas where red-brown tiles are common. Again, the graph in Figure 6 shows the EQE and reflectance obtained for this PV module (T2) and contrasted with a similarly constructed reference module (R2) that used a conventional transparent front encapsulant layer. In this case, the EQE of the red-brown module T2 only decreases significantly below wavelengths of about 650 nm. The reflectance profile only increases slightly above wavelengths of about 600 nm.

[0092] Further performance and color results are presented in the table below. [Table 3]

[0093] Current losses are limited to 28.5% compared to 57.7% losses measured in previous white modules.

[0094] Figure 7 shows a graph of EQE. Figure 8 shows a graph of reflectance versus wavelength of light obtained with a PV module constructed according to Figure 1 (again, without the presence of the underlying region 13b).

[0095] In this series of experiments, various PV modules according to the invention were constructed according to the structure of FIG. 1 with various front encapsulation layers made of one or more of the following layers: [Table 4]

[0096] The base resin was Polidiemme FE1252 EP modified polyolefin from Padanaplast and the pigment particles were Ti-Pure R-960 from DuPont as mentioned above. The base resin and pigment were first compounded and pelletized on a twin screw extruder at 170°C. The pellets were then extruded on a single screw extruder at 170°C to produce films of defined thickness. The pigmentation of these films was adapted to give a light diffusion effect and a white color. The following modules were constructed: [Table 5]

[0097] Considering the graphs in Figures 7 and 8, the PV module WD_3 represents a good trade-off between performance and aesthetics.

[0098] The same PV modules were also subjected to performance testing. The reflectance tests from 380nm to 780nm and the results are reproduced below. [Table 6]

[0099] As a final example, three modules according to the embodiment of Figure 1 were produced (again without the underlying area 13b) provided with an image layer 29 according to Figure 3. Again the reference module had a transparent front encapsulation layer 13. Further layers according to WD_3 and WD_4 were then produced together with the front encapsulation layer 13. The image graphic was barely visible on the reference module, whereas it was clearly visible on the other two layers.

[0100] The performance results for the three modules are reproduced below. [Table 7]

[0101] Again, front encapsulant layer WD_3 represents a good compromise between aesthetics and power / current loss compared to the colorless reference.

[0102] 9 finally represents a photovoltaic module 1 according to the invention mounted on the ceiling of a building structure 35. Alternatively, the PV module 1 may be mounted on an external wall or integrated into the wall and / or ceiling structure - for example as a cladding. In a general sense, the PV module 1 may be mounted on or inside the building structure 35.

[0103] Although the present invention has been described in specific embodiments, variations of the invention are possible without departing from the spirit and scope of the invention as defined in the claims.

Claims

1. 1. A method for manufacturing a photovoltaic module, comprising: Providing a lamination device; Providing a layer stack in the lamination device, the layer stack comprising a front sheet disposed on a light-incident surface of the photovoltaic module, a back sheet disposed on a surface of the photovoltaic module opposite to the front sheet, a photovoltaic conversion element disposed between the front sheet and the back sheet, and at least one front encapsulation layer disposed between the photovoltaic conversion element and the front sheet, the front sheet including pigment particles distributed therein; and applying heat and pressure to the layer stack to integrate the layer stack into the photovoltaic module by fusing and / or crosslinking the encapsulation layer; the front sealing layer comprises a first film and a second film; The first film is disposed closer to the front sheet than the second film, containing a higher concentration of pigment particles than the second film; the first film is at least partially crosslinkable and has a complex viscosity of greater than 20,000 Pa s at 85° C., greater than 15,000 Pa s at 105° C., and greater than 5,000 Pa s at 165° C.; the second film has a complex viscosity of less than 100,000 Pa s at 85° C., less than 20,000 Pa s at 105° C., and less than 10,000 Pa s at 165° C.; When the lamination temperature is less than 165°C, the conditions at 165°C are arbitrary. method.

2. 1. A method for manufacturing a photovoltaic module, comprising: Providing a lamination device; Providing in the lamination device a layer stack comprising a prefabricated photovoltaic module, at least one front encapsulation layer provided on a face of the prefabricated photovoltaic module intended to receive incident light, the front encapsulation layer including pigment particles distributed therein, and a front sheet arranged on the light-incident face of the photovoltaic module; and applying heat and pressure to the layer stack to integrate the layer stack into the photovoltaic module by fusing and / or crosslinking the encapsulation layer; the front sealing layer comprises a first film and a second film; The first film is disposed closer to the front sheet than the second film, containing a higher concentration of pigment particles than the second film; the first film is at least partially crosslinkable and has a complex viscosity of greater than 20,000 Pa s at 85° C., greater than 15,000 Pa s at 105° C., and greater than 5,000 Pa s at 165° C.; the second film has a complex viscosity of less than 100,000 Pa s at 85° C., less than 20,000 Pa s at 105° C., and less than 10,000 Pa s at 165° C.; When the lamination temperature is less than 165°C, the conditions at 165°C are arbitrary. method.

3. 3. The method of claim 1 or 2, wherein the first film has a higher viscosity than the second film during the application of heat and pressure.

4. During the application of heat and pressure, the first film has a tangent δ value of less than 0.8 and the second film has a tangent δ value of at least 0.9; At the lamination temperature, the viscosity of the second film is at most 80% of the viscosity of the first film. The method according to claim 3.

5. The method according to any one of claims 1 to 4, wherein at least some of the pigment particles have a diameter in the range of from 100 nm to 1 µm.

6. The method of any one of claims 1 to 5, wherein the pigment particles are provided in the front sealing layer at a mass concentration of 0.01 to 10 parts per 100 resin.

7. 7. The method of claim 1, wherein the pigment particles comprise at least one of a zinc-based pigment, a titanium-based pigment, an iron-based pigment, a chromium-based pigment, a bismuth-based pigment, a cobalt-based pigment, an aluminum-based pigment, a tin-based pigment, and a copper-based pigment.

8. 8. The method of claim 1, wherein the front sealing layer is manufactured by mixing the pigment particles with a base resin and extruding the front sealing layer as a film.

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