METHOD FOR MANUFACTURING A PHOTOVOLTAIC MODULE WITH PARTIAL CROSSLINKING AND LAMINATION

Abstract

The main object of the invention is a method for manufacturing a photovoltaic module, comprising at least one photovoltaic cell (4) between a first transparent layer (1) forming a front face and a second layer (2) forming a rear face, characterised in that it includes: 1) a first step of depositing a first adhesive layer based on a crosslinkable polymer material over the first layer (1) and depositing a second adhesive layer based on a crosslinkable polymer material over the second layer (2); 2) a second step of partially crosslinking the two adhesive layers; 3) a third step of depositing said at least one photovoltaic cell (4) over one (SPR1) of the two partially crosslinked adhesive layers (SPR1, SPR2); 4) a fourth step of forming a multilayer stack; 5) a fifth step of laminating the multilayer stack.

Claims

1. A method for manufacturing a photovoltaic module, comprising at least one photovoltaic cell between a first transparent layer forming a front face of the photovoltaic module and a second layer forming a rear face of the photovoltaic module, comprising: 1) a first step of depositing a first adhesive layer based on a crosslinkable polymer material over the first layer intended to form the front face of the photovoltaic module, and in depositing a second adhesive layer based on a crosslinkable polymer material over the second layer intended to form the rear face of the photovoltaic module, 2) a second step of carrying out a partial crosslinking of the two adhesive layers based on a crosslinkable polymer material to form two partially crosslinked adhesive layers, 3) a third step of depositing said at least one photovoltaic cell over one of the two partially crosslinked adhesive layers, 4) a fourth step of forming a multilayer stack by assembling one of the two partially crosslinked adhesive layers over the other one of the two partially crosslinked adhesive layers, which comprises said at least one photovoltaic cell, 5) a fifth step of carrying out the lamination of the multilayer stack, and the completion of the crosslinking of the two partially crosslinked adhesive layers, the crosslinking rate implemented during the second step of partial crosslinking of the two adhesive layers based on a crosslinkable polymer material being comprised between 40% and 70%.

2. The method according to claim 1, characterised in wherein each adhesive layer based on a crosslinkable polymer material, deposited during the first step, has a thickness comprised between 20 and 100 μm.

3. The method according to claim 1, wherein the crosslinking rate implemented during the second step of partial crosslinking of the two adhesive layers based on a crosslinkable polymer material is comprised between 50% and 60%

4. The method according to claim 1, wherein the crosslinking time implemented during the second step of partial crosslinking of the two adhesive layers based on a crosslinkable polymer material is comprised between 1 minute and 1 hour.

5. The method according to claim 1, wherein the crosslinking temperature implemented during the second step of partial crosslinking of the two adhesive layers based on a crosslinkable polymer material is comprised between 50 and 150° C.

6. The method according to claim 4, wherein the crosslinking duration implemented during the second step of partial crosslinking of the two adhesive layers based on a crosslinkable polymer material is comprised between 5 minutes and 15 minutes, and wherein the crosslinking temperature implemented during the second step of partial crosslinking of the two adhesive layers based on a crosslinkable polymer material is comprised between 90 and 110° C.

7. The method according to claim 1, wherein the fifth lamination step is carried out at a positive pressure comprised between 100 mbar and 1 bar.

8. The method according to claim 1, wherein the fifth lamination step comprises a pump-out for a duration comprised between 5 and 10 minutes.

9. The method according to claim 1, wherein the crosslinkable polymer material is selected from the family of silicones.

10. The method according to claim 1, wherein the said at least one photovoltaic cell can be selected from among silicon-type cells, III-V semiconductors, CIGS (copper, indium, gallium, selenium), CdTe (cadmium telluride), organics, perovskites or multi junctions of these types.

11. The method according to claim 1, characterised in that wherein the first adhesive layer based on a crosslinkable polymer material and the second adhesive layer based on a crosslinkable polymer material are based on the same crosslinkable polymer material.

12. The method according to claim 1, wherein the first adhesive layer is based on a crosslinkable polymer material in the liquid state and/or wherein the second adhesive layer is based on a crosslinkable polymer material in the liquid state.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The invention could be better understood upon reading the following detailed description, of a non-limiting example of implementation thereof, as well as upon examining the, schematic and partial, figures of the appended drawing, wherein:

[0039] FIG. 1 illustrates, schematically and in section, the first step of a method of manufacturing a photovoltaic module in accordance with the invention,

[0040] FIG. 2 illustrates, schematically and in section, the second step of the manufacturing method in accordance with the invention,

[0041] FIG. 3 illustrates, schematically and in section, the third step of the manufacturing method in accordance with the invention,

[0042] FIG. 4 illustrates, schematically and in section, the fourth step of the manufacturing method in accordance with the invention, and

[0043] FIG. 5 illustrates, schematically and in section, the fifth step of the manufacturing method in accordance with the invention.

[0044] In all of these figures, identical references may refer to identical or similar elements.

[0045] In addition, the different portions represented in the figures are not necessarily according to a uniform scale, to make the figures more readable.

DETAILED DISCLOSURE OF PARTICULAR EMBODIMENTS

[0046] In the description of the example of implementation of the invention that will follow, the considered field of application is that of photovoltaic modules for space applications. Nonetheless, the invention also applies to photovoltaic modules intended for terrestrial applications.

[0047] Advantageously, the manufacturing method according to the invention enables encapsulation with a crosslinkable polymer material using two main steps of carrying out a partial crosslinking of the liquid encapsulant, and a lamination of the entirety of the formed stack.

[0048] More particularly, as illustrated in FIG. 1, the method for manufacturing a photovoltaic module 10 in accordance with the invention firstly includes a first step 1) of forming a first sub-stack I) and a second sub-stack II).

[0049] The first sub-stack I) is formed by depositing a liquid adhesive layer SL2 based on a crosslinkable polymer material over a second layer 2 intended to form the rear face of the photovoltaic module 10.

[0050] The second sub-stack II) is formed by the deposition of a liquid adhesive layer SL1 based on a crosslinkable polymer material over a first layer 1 intended to form the front face of the photovoltaic module 10.

[0051] Preferably, the crosslinkable polymer material is selected from the family of silicones. Silicone has the advantage of being transparent, electrically insulating and features an environmental and thermal stability (i.e. little or no degradation related to humidity, oxygen or acids at temperatures varying between −200° C. and 200° C.). Moreover, silicone could improve the service life of the photovoltaic module 10 in comparison with an EVA encapsulant. Silicone prevents the formation of acetic acid, unlike EVA. Silicone has a better stability to ultraviolet radiation. The silicone chemistry is flexible enough to accurately adjust the physico-chemical properties (refractive index, viscosity, hardness, tensile strength, mechanics) of the encapsulant while enabling mass production. Because of the low Young's modulus of silicone and the low glass transition temperature (for example −50° C.) of silicone, the mechanical properties of the crosslinked silicone remain constant over a wide range of temperatures. With silicone, it is possible to encapsulate one or several photovoltaic cell(s) 4 for a space application at a temperature that could vary between −65° C. and +200° C. and could be used down to −200° C.

[0052] Afterwards, as illustrated in FIG. 2, a second step 2) is carried out by the partial crosslinking, schematised by PR in FIG. 2, of the two liquid adhesive layers SL1, SL2 to form, on the first sub-stack I), a second partially crosslinked adhesive layer SPR2, visible in FIG. 3, and, on the second sub-stack II), a first partially crosslinked adhesive layer SPR1, visible in FIG. 3.

[0053] The partial crosslinking PR of the liquid silicone allows increasing its viscosity and its mechanical strength, which then allows ensuring a minimum amount of encapsulant over and beneath the photovoltaic cells 4.

[0054] Next, as illustrated in FIG. 3, a third step 3) is implemented by the deposition of the photovoltaic cells 4 over the partially crosslinked first adhesive layer SPR1. Alternatively, the deposition could also be done over the second partially crosslinked adhesive layer SPR2, in other words at the rear face. This alternative could be particularly useful in the case where the rear face 2 includes a printed circuit with conductive tracks to which the photovoltaic cells 4 should be linked/connected. In this case, it is possible to protect the interconnection elements of the cells to make them accessible after the partial crosslinking phase.

[0055] A fourth step 4) is then implemented, as visible in FIG. 4, of forming a multilayer stack, namely a stack of the constituent layers of the photovoltaic module 10, by assembling the first sub-stack I) over the second sub-stack II), schematised by the arrow A, the second partially crosslinked adhesive layer SPR2, devoid of photovoltaic cells 4, then lying above the first partially crosslinked layer SPR1 which comprises the photovoltaic cells 4.

[0056] Then, a fifth step 5), illustrated by FIG. 5, allows carrying out the lamination, schematised by the frame L, of the obtained assembly and the completion of the crosslinking of the two partially crosslinked adhesive layers SPR1, SPR2 to form a single and unique encapsulation layer E of the photovoltaic cells 4. It should be noted that, before this lamination step, it is also possible to turn the stack over so that the front face 1 is turned downwards.

[0057] Any crosslinkable polymer material referred to in the present description may include, in particular consist of, two components A and B. The component A is a base, for example of the PDMS (standing for polydimethylsiloxane) type. The component B contains a vulcanising agent, such as polysiloxane, and a catalyst to enable the polymer chains to branch to form a three-dimensional network so that the crosslinkable polymer material could, upon completion of its crosslinking, form a corresponding layer made of a solid and unmeltable material.

[0058] The crosslinkable polymer material used in the context of this manufacturing process may be selected from among: Sylgard® 184 from the company Dow Corning, Dow Corning® 93-500, Siltech® CR 12-63, Siltech® CR 13-46, Elastosil Company® RT 625 from the company Wacker, MAPSIL® 213 from the company MAP COATING, MAPSIL® 213B from the company MAP COATI NG, and MAPSIL® QS 1123 from the company MAP COATING.

[0059] A particular embodiment will now be described. In this example, it is proceeded with the preparation of the front face 1 at first.

[0060] The surface of the front face 1 is prepared using a physical surface treatment, for example of the plasma or corona type, followed by a deposition of a primer to facilitate hooking of the crosslinkable polymer material. It should be noted that the first layer 1 forming the front face is advantageously transparent, and may be glass or a polymer such as transparent polyimide, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), or else a fluorinated film such as fluoroethylene propylene (FEP), ethylene tetrafluoroethylene (ETFE), ethylene chlorotrifluoroethylene (ECTFE), polyvinylidene fluoride (PVDF), or else polyetheretherketone (PEEK), inter alia.

[0061] Afterwards, a deposition of a liquid silicone layer SL1 is carried out over this front face 1. This adhesive may be deposited by any coating means, with a brush, with a roller, with a device called “Doctor Blade”, or else by spraying. The thickness and the depositing means are adapted to the use. For example, the thickness is comprised between 20 and 100 μm. The less viscous the adhesive, the easier it will be to make thin films. An excessively small or excessively large amount of adhesive would cause the apparition of air bubbles or voids in the module 10 upon crosslinking.

[0062] Then, the adhesive layer is degassed in a vacuum bell for a period comprised between 1 and 20 minutes, preferably comprised between 5 and 10 minutes.

[0063] Afterwards, the partial crosslinking of this adhesive layer SL1 is carried out to obtain the pre-crosslinked layer SPR1. The partial crosslinking is carried out with the desired means: heating in a furnace or oven, heating by infrared or ultraviolet, inter alia.

[0064] Afterwards, the interconnected photovoltaic cells 4 are positioned, for example by means of a ribbon 6 as shown in FIG. 3, over the pre-crosslinked layer SPR1, the cells possibly being coated with a primer to maximise adhesion. These cells 4 may be based on silicon, based on III—V type materials, CIGS (copper, indium, gallium, selenium), CdTe (cadmium telluride), organics, perovskites or multi-junctions of these types.

[0065] Concomitantly, the rear face 2 is prepared through a process symmetrical to that applied for the front face 1. Nonetheless, it should be noted that the partial crosslinking parameters and the thicknesses could be identical, or not, for the front face 1 and the rear face 2.

[0066] Thus, the surface of the rear face 2 is prepared using a physical surface treatment, for example of the plasma or corona type, followed by a deposition of a primer to facilitate hooking of the crosslinkable polymer material. This rear face 2 is not necessarily transparent. It may be a composite material support, for example of the carbon/aluminum honeycomb type, or a foam, glass, a polymer film or else a fabric, inter alia.

[0067] Afterwards, a deposition of a liquid silicone layer SL2 over this rear face 2. This adhesive may be deposited by any coating means, with a brush, with a roller, with a device called “Doctor Blade” or else by spraying. The thickness and the deposition means are adapted to the use. For example, the thickness is comprised between 20 and 100 μm. It should be so that the less viscous the adhesive, the easier it will be to make thin films. An excessively small or excessively large amount of adhesive will cause the apparition of air bubbles and voids in module 10 upon crosslinking.

[0068] Then, the adhesive layer is degassed in a vacuum bell for a period comprised between 1 and 20 minutes, preferably comprised between 5 and 10 minutes.

[0069] Afterwards, the partial crosslinking of this adhesive layer SL2 is carried out to obtain the pre-crosslinked layer SPR2. The partial crosslinking is carried out with the desired means: heating in a furnace or oven, heating by infrared or ultraviolet, inter alia.

[0070] Preferably, the duration of the partial crosslinking step is comprised between 5 and 15 minutes, for example in the range of 5 to 7 minutes, and the temperature is comprised between 90° C. and 110θ C., for example 100° C.

[0071] At this stage, it is then proceeded with the assembly of the two portions and with the vacuum lamination. Thus, the two portions I) and II) are assembled so as to obtain the stack of layers 1, SPR1, 4, SPR2, 2. Afterwards, they are laminated under vacuum.

[0072] The lamination program comprises a pump-out step for 5 to 10 minutes, followed by a heating step during which a positive pressure comprised between 100 mbar and 1 bar, preferably between 500 mbar and 1 bar, or possibly 800 mbar and 1 bar, is applied. The temperature and the duration required for complete crosslinking depend on the characteristics of the adhesive. For example, to crosslink a Sylgard® 184 formulation, a lamination at 140° C. comprising 5 minutes of pumping out and 15 minutes at 1 bar is suitable.

[0073] It should be noted that, in the case where the difference in the coefficient of thermal expansion is high between the different materials, it might be judicious to lower the temperature of the lamination and therefore increase its duration. For Sylgard® 184, a lamination at 80° with 5 minutes of pumping out and 50 minutes at 1 bar is also possible. In particular, this allows limiting the thermomechanical stresses exerted on the different materials forming the photovoltaic module 10 during manufacture, and thus limiting the residual internal stresses after manufacture which could go so far as to create undesirable curvatures of the module.

[0074] Of course, the invention is not limited to the embodiment that has just been described. Various modifications could be made thereto by a person skilled in the art.