Photovoltaic module comprising an encapsulation structure based on at least one polymer material and locally flexible

Abstract

Photovoltaic module (1) comprising: - a photovoltaic unit (6) comprising several photovoltaic cells (3) electrically connected in series and spaced apart, adjacent photovoltaic cells being electrically connected in pairs by a metallic interconnector (4) which extends at least partially into an interconnection space (2) separating said adjacent photovoltaic cells, - an encapsulation structure (8) made of a polymer-based encapsulation material sandwiching the opposite faces of the photovoltaic cells, defining a cell overlap zone (10), and the interconnector in the interconnection space, defining an interconnector overlap zone (11), a spacer (12) incorporated into the encapsulation structure and partially overlapping the interconnector in the interconnector overlap zone, the spacer being made of a material exhibiting, at least at a temperature of -40 °C,a modulus of elasticity lower than the modulus of elasticity of the encapsulating material.

Description

Title of the invention: Photovoltaic module comprising an encapsulation structure based on at least one polymer material and locally flexible technical field

[0001] The present invention relates to the thermal cycling resistance of photovoltaic modules comprising photovoltaic cells integrated into an encapsulation structure based on at least one polymer material. Previous technique

[0002] The integration of photovoltaic modules in buildings, infrastructure or in vehicles is a way to simply increase the surface area for capturing solar radiation for mass energy production.

[0003] However, this integration approach requires an adaptation of the shape and aesthetics of the photovoltaic modules, as well as a reduction in their mass, while guaranteeing a level of performance and durability in accordance with regulations and being part of an approach to reducing the environmental footprint in order to achieve the objective of net zero carbon by 2035.

[0004] Thermoplastic polymer materials offer low cost, good mechanical properties, low density, and good recyclability, making them good candidates for the manufacture of lightweight photovoltaic modules. They can thus be used to coat photovoltaic cells and hold them together in a rigid structure.

[0005] However, these materials are polymers. As such, they exhibit a high capacity to deform under the effect of temperature, characterized by a high coefficient of thermal expansion (CTE). Each polymer has its own specific CTE, which depends on its composition and manufacturing process. In particular, the CTE of many polymers is approximately ten times greater than the CTE of many metals and up to one hundred times greater than the CTE of silicon.

[0006] Figure 1 illustrates a first example of degradation of this type of photovoltaic module 1, known as the warping effect, following lamination manufacturing. The warping effect is a flatness defect in the photovoltaic module that develops during the cooling of the module after lamination. It is generally caused by a difference in the coefficient of thermal expansion between the front and back faces of the photovoltaic module.

[0007] Figure 2 illustrates several examples of degradation of these photo modules. photovoltaic cells, appearing after thermal cycling, which are observed at the level of Zones 2 where the electrical interconnectors cover the photovoltaic cells 3. Under the effect of high thermal stresses, delamination occurs between the photovoltaic cells and / or the interconnectors and the polymer encapsulant. The polymer materials are also torn, which testifies to the high level of stress reached in these zones.

[0008] The difference between, on the one hand, the thermal conductivity (TC) of silicon, a constituent of photovoltaic cells 4, or the TC of metals such as copper, used to form the interconnectors that electrically link the photovoltaic cells of the module, and, on the other hand, the TC of the polymer(s) of the photovoltaic module, can lead to severe localization of thermal stresses in the metallic parts of the modules. This results in degradation that greatly affects the performance of the modules.

[0009] A recurring problem observed in thermal cycling is the breakage of the interconnectors 4 that link the photovoltaic cells, which effectively leads to the shutdown, i.e., the inability to produce electricity, of the photovoltaic module. Figure 3 shows photographs acquired by optical microscopy illustrating breaks in the interconnectors 2. An example of shutdown after 60 thermal deformation cycles of a photovoltaic module comprising 8 photovoltaic cell units is shown in Figure 4, due to the interconnector breaks illustrated in Figure 3.

[0010] To prevent these degradations, reducing the thickness of the polymer encapsulation structure has already been tested, but this can lead to the photovoltaic module failing to pass regulatory certification tests, particularly impact and flexural strength tests. Reinforcing the polymer encapsulation structure with fibers or fabrics to make the module more rigid and more resistant to thermal cycling has also been considered. However, this requires significant modifications to the manufacturing processes, which complicates and slows down the industrial development of these composite modules. Furthermore, the presence of fibers alters the optical properties and degrades the energy efficiency of the photovoltaic module.

[0011] There is therefore a need to improve the thermal cycling resistance of photovoltaic modules with a polymer-based encapsulation structure. Summary of the invention

[0012] The invention proposes a photovoltaic module comprising: - a photovoltaic unit comprising several photovoltaic cells electrically connected in series and spaced apart from each other, adjacent photovoltaic cells being electrically connected in pairs by a metallic interconnector which extends at least partially into an interconnection space separating said cells adjacent photovoltaic panels, - an encapsulation structure, based on at least one polymer encapsulation material, sandwiching the opposite faces of the photovoltaic cells, defining a cell overlap zone, and the interconnector in the interconnection space, defining an interconnector overlap zone, a wedge incorporated in the encapsulation structure and partially superimposed on the interconnector in the interconnector overlap zone, the wedge being made of a material having, at least at a temperature of -40 °C, a modulus of elasticity lower than the modulus of elasticity of the encapsulation material.

[0013] During a temperature variation representative of a thermal cycle to which the PV module may be subjected in use, for example as defined in standard IEC61215, the spacer deforms more easily than the interconnector to accommodate the thermally induced deformations of the encapsulation structure. This limits the stress concentration in the interconnector and reduces the risk of breakage and shutdown of the PV module.

[0014] Preferably, the wedge material has a modulus of elasticity more than 2 times, preferably more than 5 times, or even more than 10 times lower than the modulus of elasticity of the encapsulation material at a temperature of -40 °C.

[0015] Preferably, the wedge material has a lower modulus of elasticity than the encapsulation material at a temperature of 20 °C, preferably at any temperature between -40 °C and 20 °C.

[0016] The modulus of elasticity is measured according to the standard NF EN ISO 527-1.

[0017] The wedge material may have a modulus of elasticity, measured at -40 °C, less than 1 GPa. Preferably, the wedge material has a modulus of elasticity, measured at -40 °C, between 0.1 MPa and 300 MPa, preferably between 1 MPa and 10 MPa.

[0018] Preferably, the wedge material has a coefficient of thermal expansion measured at -40°C between 107 K 1 and 10 4 K1.

[0019] Preferably, the ratio between the CTE of the wedge material and the CTE of the encapsulation material is between 0.1 and 1, the CTEs being measured at -40°C.

[0020] The coefficient of thermal expansion is measured according to the international standard ISO 11359-2.

[0021] The wedge material can be composite or polymer.

[0022] Preferably, the shim material is an elastomer, in particular selected from silicone elastomers, rubbers, fluorinated elastomers, thermoplastic elastomers and mixtures thereof. For example, the shim material is a translucent alkoxy-based silicone.

[0023] Preferably, the wedge has a thickness between 100 pm and 1500 pm.

[0024] Preferably, it has a width between 100 pm and 1500 pm.

[0025] Preferably, the ratio of the wedge width to the space width The interconnection ratio is between 0.1 and 0.5.

[0026] The width of the wedge and the width of the interconnection space are measured perpendicular to the faces opposite the adjacent PV cells. The width of the interconnection space is, for example, between 0.2 and 10 mm.

[0027] The wedge may have the shape of a ribbon, in particular with a rectangular or square cross-section.

[0028] The wedge can extend from one end to the other over the entire length of the interconnection space between the adjacent photovoltaic cells, said length being measured parallel to the lateral faces opposite said adjacent cells.

[0029] The wedge may not be superimposed on the cell cover zone.

[0030] Preferably, the wedge is entirely superimposed on the interconnection space

[0031] The wedge can be contained between the planes in which the opposite faces of the photovoltaic cells extend.

[0032] Preferably, the wedge is fully incorporated into the mass of the encapsulation structure. In particular, the outer face or faces of the wedge are in contact with the encapsulation structure.

[0033] The distance between the wedge and the interconnector is less than or equal to 1 mm, said distance being measured perpendicular to the median plane in which the PV module extends.

[0034] According to one variant, at least part of the wedge may be in contact with the interconnector.

[0035] The PV module may include several shims covering at least partially the interconnector in the interconnector overlap area.

[0036] In particular, within the thickness of the PV module, at least two of the shims are arranged on either side of the interconnector. In other words, at least one of the shims is arranged between a first face of the PV module and the interconnector, and another of the shims is arranged between the interconnector and a second face of the PV module opposite the first face. This allows the shims to better accommodate the thermal deformations of the encapsulation structure.

[0037] The encapsulation structure is preferably self-supporting. A self-supporting structure is sufficiently rigid so as not to deform substantially under the effect of its own weight.

[0038] The encapsulation structure sandwiches the photovoltaic cells and the interconnector. Preferably, it completely covers the photovoltaic cells and the interconnector. Preferably, it is in contact over the entire surface of the photovoltaic cells and over the entire surface of the interconnector.

[0039] The encapsulation material is polymer-based, i.e., it comprises, for more than 70% of its mass, preferably more than 80% of its mass, preferably more than 90% of its mass, preferably more than 95% of its mass, preferably 100% of its mass, a polymer material. The polymer material is suitable for a photovoltaic application, i.e., it has a transmittance suitable for transmitting incident solar radiation to activate the electrical production of the photovoltaic cells.

[0040] Preferably, the polymer material is transparent to solar radiation.

[0041] The encapsulation material may have a modulus of elasticity between 10 MPa and 10 GPa, at a temperature of -40 °C. It may have a Young's modulus between 0.001 GPa and 1 GPa, at a temperature of 20 °C.

[0042] Preferably, the polymer material is thermoplastic. It may have a glass transition temperature above -150 °C.

[0043] Preferably, the polymer material is chosen from ethylene-vinyl acetate, an ethylene-methyl acrylate copolymer, low-density polyethylene terephthalate, polyamide 11, polycarbonate, polyethylene terephthalate glycol, polymethyl methacrylate, polypropylene, polypropylene copolymer, polypropylene homopolymer, polytetrafluoroethylene, styrene-acrylonitrile copolymer, thermoplastic polyurethane, acrylonitrile butadiene styrene, polyethylene and mixtures thereof.

[0044] The encapsulation structure can be homogeneous, that is, it consists of the encapsulation material having an identical composition throughout the structure. As will be described later, a homogeneous encapsulation structure can result from the thermoforming of a lower and an upper layer, both made of the homogeneous polymer material.

[0045] Alternatively, the encapsulation structure is multilayered, with at least two layers of the encapsulation structure being made of different encapsulation materials. Preferably, the multilayer encapsulation structure comprises one or more inner layers that completely cover and are in contact with the photovoltaic cells and the interconnector, and lower and upper layers that sandwich the inner layers, the inner layer(s) and the lower and upper layers being made of different encapsulation materials. The lower and upper layers may be made of the same encapsulation material and may further comprise reinforcing fibers, for example, glass fibers.

[0046] Preferably, at a temperature of -40 °C, and preferably at a temperature of 20 °C, the modulus of elasticity of the encapsulating material constituting the inner layer(s) is lower than the modulus of elasticity of the encapsulating material constituting the lower and / or upper layer. The lower layers and superior thus provide the photovoltaic module with flexural rigidity and shock resistance, and the inner layer(s) allow for better distribution of thermally generated stresses in the photovoltaic module.

[0047] Preferably, the thickness of the photovoltaic module is constant in the cell overlap zone.

[0048] Preferably, the thickness of the photovoltaic module is constant, except in the interconnector overlap area.

[0049] Preferably, the thickness of the photovoltaic module is between 0.75 mm and 10 mm.

[0050] The interconnector can be made of a metal chosen from copper, silver, tin, lead and their alloys.

[0051] The interconnector links two adjacent cells of the photovoltaic unit. Preferably, it is fixed, for example welded or bonded with an electrically conductive adhesive, to each of the adjacent cells. Preferably, it is fixed to the underside of one of the adjacent photovoltaic cells and to the upper side of the other adjacent photovoltaic cell, in order to connect the positive and negative terminals of the photovoltaic cells so as to allow the photoelectric current to flow.

[0052] Preferably, the interconnector extends within the thickness of the photovoltaic module between the adjacent cells that it electrically connects.

[0053] The interconnector may have a thickness between 50 pm and 500 pm and / or a width between 200 pm and 2000 pm.

[0054] Preferably, the photovoltaic module extends along a median surface which can be flat or curved.

[0055] Photovoltaic cells preferably extend along the median surface.

[0056] The photovoltaic unit may comprise more than two photovoltaic cells, in particular at least three, or even at least five, or even at least ten photovoltaic cells.

[0057] Within the photovoltaic unit, the photovoltaic cells may be identical. Preferably, they are aligned along an alignment axis in the median surface, with the interconnection space between two adjacent photovoltaic cells extending perpendicularly to the alignment axis. Their lateral faces may be parallel, in particular aligned along the alignment axis.

[0058] In the embodiment where the photovoltaic unit comprises more than two photovoltaic cells, the interconnector can electrically connect adjacent photovoltaic cells in series, two by two. In particular, it may have a portion in contact with one face of a photovoltaic cell, extending from one edge to another opposite edge of the photovoltaic cell, and which is extended on one side by a portion extending into the interconnection space that connects the photovoltaic cell to one of the adjacent cells.

[0059] Photovoltaic cells may include, or even consist of, silicon. They may be of the perovskite / silicon tandem type.

[0060] Each photovoltaic cell preferably has the shape of a plate, by rectangular or square example. At least one of the photovoltaic cells, in particular each photovoltaic cell can have a thickness between 0.05 mm and 0.3 mm.

[0061] The photovoltaic module may comprise several photovoltaic units, which can be arranged relative to each other in the manner of a tiling along the median surface, for example along the alignment axis or along two perpendicular axes.

[0062] The invention also relates to a method for manufacturing a photovoltaic module according to the invention, the method comprising: - the supply of a multilayer stack comprising a photovoltaic unit having photovoltaic cells electrically connected in series and spaced apart, adjacent photovoltaic cells being electrically connected in pairs by an interconnector which extends at least partially into an interconnection space separating said adjacent photovoltaic cells, a spacer superimposed at least partially on the interconnector in the interconnection zone, and at least two encapsulation layers which sandwich the photovoltaic unit and - thermoforming the multilayer stack until the photovoltaic module is obtained.

[0063] Thermoforming can be carried out by thermocompression or lamination.

[0064] Preferably, thermoforming is carried out by laminating the stack. a layer between a heated lower lamination plate and a membrane onto which fluid pressure is applied.

[0065] The method may include a preliminary step of forming the multilayer stack, said step comprising placing a spacer between the interconnector and at least one encapsulation layer made of the encapsulation material. Furthermore, the invention also relates to a device selected from among a building, a motor vehicle, a train, an aircraft, and a building, the device integrating the photovoltaic module according to the invention on an external surface. The external surface may be curved. The external surface of the device is, for example, the hood or roof of a car, or a wall or roof of a building. Brief description of the drawings

[0066] [Fig.1] and [Fig.2] are photographs of art photovoltaic modules prior,

[0067] [Fig.3] is an optical microscopy photograph of a broken interconnector of a prior art photovoltaic module,

[0068] [Fig.4] are electroluminescence images of photo modules Voltaic, from left to right, according to the prior art after lamination, 30 cycles, and 60 thermal cycles,

[0069] [Fig.5] schematically represents a top, front and side view of a example of a photovoltaic module according to the invention,

[0070] [Fig.6] is a schematic, cross-sectional view of the photovoltaic module at the level of a interconnector overlap zone,

[0071] [Fig.7] schematically illustrates an example of a manufacturing process by the Installation of the photovoltaic module according to the invention,

[0072] [Fig.8] is a view of a finite element mesh of a part of a module according to the invention as illustrated in [Fig. 6], at the level of the interconnector overlap area,

[0073] [Fig.9] are images of the distribution of von Mises constraints in a reference mesh and in the mesh of [Fig.6] after a thermomechanical numerical simulation of a thermal cycle,

[0074] [Fig. 10] is a graph illustrating the evolution of the von Mises stress along the route illustrated in [Fig.6],

[0075] [Fig. 11] is a graph illustrating, for different meshes, the evolution of the maximum stress in the interconnector as a function of the elastic modulus of the shim material and the reduction, expressed as a percentage of said stress relative to the reference mesh without shim,

[0076] [Fig. 12] is a graph illustrating, for different meshes, the evolution of the maximum stress in the interconnector as a function of the shim width and reduction, expressed as a percentage of said stress relative to the reference mesh without shim, and

[0077] [Fig. 13] is a graph illustrating, for different meshes, the evolution of the maximum stress in the interconnector as a function of the thickness of the shim and the reduction, expressed as a percentage of said stress relative to the reference mesh without shim. Detailed description

[0078] Figures 1 to 4 have been described previously.

[0079] Figure 5 illustrates an example of a photovoltaic module 1 according to the invention. The photovoltaic module comprises two photovoltaic units 6, each comprising four photovoltaic cells 3, in the form of wafers, which are spaced apart from each other.

[0080] Each photovoltaic cell is separated from the photovoltaic cell adjacent to it by an interconnection space 2.

[0081] The number of photovoltaic units 6 and photovoltaic cells 3 is not limiting and other arrangements may be envisaged.

[0082] The photovoltaic module further comprises connection terminals 7, in the form of metal strips, between which the photovoltaic units are arranged in parallel and are electrically connected, in order to collect the generated current.

[0083] Within each photovoltaic unit 6, the adjacent photovoltaic cells 3 are connected in series in pairs by metallic interconnectors 4, for example made of copper, which extend in the y direction, from one side to the other between the electrical terminals 7.

[0084] Each metallic interconnector 4 comprises portions 4a in contact with a face of a photovoltaic cell, which are connected to each other by portions 4b, each extending into the interconnection space provided between the photovoltaic cells 3. The metallic interconnector 4 is successively in contact with one face of a photovoltaic cell and then with an opposite face of the adjacent photovoltaic cell. Thus, when viewed along the cross-sectional plane (x,z) illustrated in [Fig. 6], the interconnector winds its way from one connection point to the other, between the photovoltaic cells 3.

[0085] The photovoltaic module further comprises an encapsulation structure 8 based on at least one polymer material in which the photovoltaic units 6 are fully immersed.

[0086] The encapsulation structure 8 fully covers the opposite faces 9a,9b of the photovoltaic cells 3, thus defining with each photovoltaic cell 3 a cell cover zone 10.

[0087] Furthermore, the encapsulation structure 8 covers the interconnectors in the various interconnection spaces 2 between the adjacent photovoltaic cells, thus defining with the interconnector 4 an interconnector overlap zone 11. In the example illustrated in [Fig.6], shims 12 are incorporated en masse into the encapsulation structure 8. They are arranged on either side of the interconnector in each interconnection space 2 between the lower face 13i and upper face 13s of said incorporation structure 8 and the interconnector 4.

[0088] Within each interconnection space 2, the wedges 12 can extend completely along the entire length of the faces facing the adjacent photovoltaic cells, and parallel to said faces. They can also be superimposed on one another or offset from one another along the y-axis, as illustrated in [Fig. 6].

[0089] The wedges are also superimposed on the interconnector 4 in each interconnection space 2, at the level of the interconnector overlap zone, as can be seen in cross-sectional view along a plane (y,z) on [Fig.6].

[0090] The wedges are for example an elastomeric ribbon whose modulus of elasticity is between 0.1 MPa and 300 MPa.

[0091] To manufacture the photovoltaic module illustrated in [Fig. 5], a multilayer stack 20 can be prepared as follows. The photovoltaic units 6, the connecting strips 7, and the spacers 12 are arranged between lower 21i and upper 21s sheets made of a soft polymer material with a low modulus of elasticity, for example, between 10 MPa and 10 GPa at -40 °C. The sheets 21i,s thus completely cover the photovoltaic units 6, the connecting strips 7, and the spacers 12. The assembly thus formed can optionally be arranged between outer lower 22i and upper 22s sheets made of another rigid polymer material with a high modulus of elasticity, for example, between 1 GPa and 100 GPa at -40 °C to form the multilayer stack 20.After lamination between a lower lamination plate 24i and a membrane 25, a photovoltaic module 1 is obtained having a multilayer encapsulation structure having a flexible inner encapsulation layer in which the photovoltaic units are immersed, optionally sandwiched between rigid lower and upper outer encapsulation layers.

[0092] The lamination of the multilayer stack 20 is carried out conventionally by heating the multilayer stack to a temperature suitable for the flow of polymer materials and under pressure applied to the membrane 25 in order to heat-seal the different sheets 21i,s, optionally 22i,s and the photovoltaic units 6 together, then cooling until the photovoltaic module is obtained.

[0093] The effect of the wedge in the interconnection space is illustrated below.

[0094] A 2D finite element mesh of a portion of the photovoltaic module including the interconnection space 2 was created, as illustrated in [Fig. 8]. Quadrangle finite elements were chosen so that the thickness e of the interconnector is discretized with at least 4 finite elements.

[0095] The modeled encapsulation structure 8 thus comprises lower and upper layers of polyamide 11, whose modulus of elasticity at -40°C is equal to 1620 MPa and the CTE is equal to 10 4 K1. The thickness of each of the lower and upper layers is 400 pm.

[0096] The inner layer 15, with a thickness of 1200 pm, is made of thermoplastic polyolefin, whose modulus of elasticity at -40°C is 590 MPa and the CTE is equal to 5* 10 4 K1.

[0097] The photovoltaic cell 3, with a thickness of 150 pm, is made of silicon, of which the The modulus of elasticity is equal to 166 GPa and the CTE is equal to 2.6*106 K1.

[0098] The interconnector 4, with a thickness of 200 µm, is made of copper and has a modulus of elasticity of 130 GPa and a CTE of 1.4 × 10⁵ K

[0099] The wedges 12 have a thickness ecaie and a width lcaie which are parameters modified according to the simulations carried out, as well as the modulus of elasticity of the material of the wedge.

[0100] The simulations were carried out assuming a plane strain state, using thermoelastic material constitutive models and the ABAQUS simulation software. A stress-free state at 25°C was considered in each finite element, and then a cooling temperature of -40°C for the photovoltaic module was calculated, this temperature being that of the thermal cycling as established in the IEC6215 standard.

[0101] A reference mesh, such as that illustrated in [Fig.8], was produced without any wedges being present.

[0102] A comparative mesh was established, in which the elastic modulus of the wedge material is 100 GPa, more than 160 times greater than the encapsulation material of layer 15 and the encapsulation material of layers 14i and 14s. The width lcaie was 1 mm and the thickness ecaie was equal to 200 pm.

[0103] A mesh of a PV module according to the invention has been established, this being identical to the comparative mesh except that the modulus of elasticity at -40 °C of the material of the wedge is 1 MPa.

[0104] Figure 9 illustrates the effect of thermal expansion between 20 °C and -40 °C, which induces higher von Mises stresses in the interconnector in the absence of a spacer (mesh 35). The spacer, being less rigid than the encapsulating material, softens the interconnector overlap zone, resulting in locally lower von Mises stresses in the interconnector (mesh 36).

[0105] This observation is confirmed by [Fig. 10], which shows the evolution of the von Mises stresses, expressed in MPa, as a function of the abscissa S (in mm) along the path 37 illustrated in [Fig. 8] for the reference mesh 35 (without shim) (curve 40), for the comparative mesh (curve 41), and for the mesh according to the invention (curve 42). The presence of a shim with excessive rigidity, exceeding the rigidity of the encapsulating materials, increases the concentration of stresses in the interconnector in its central part. The maximum von Mises stress is 39% higher than in the reference mesh without a shim. Conversely, a shim that is more flexible than the encapsulating materials limits this stress concentration, reducing the maximum value of the von Mises stress in the interconnector by 52%.

[0106] Figure [Fig. 11] is a graph showing the maximum value of the von stress Mises along path 37 for meshes in which the wedges all have a square cross-section (same wedge width of 200 µm and same wedge thickness of 200 µm), the modulus of elasticity varying from 0.1 MPa to 330 MPa. A general increase in the von Mises stress is observed with an increase in the modulus of elasticity.

[0107] Figure 12 illustrates the evolution of the maximum value of the von Mises stress. In the interconnector, for meshes where the modulus of elasticity at -40 °C of the shim material is 1 MPa, the shim thickness is 200 pm and the shim width varies from 200 pm to 1000 pm (the case shim=0 corresponds to the reference case without a shim). It is observed that increasing the shim width induces a decrease of up to more than 50% in the maximum value of the von Mises stress in the interconnector, compared to the reference case.

[0108] Figure 13 illustrates the evolution of the maximum value of the von Mises stress. In the interconnector, for meshes where the modulus of elasticity at -40 °C of the shim material is 1 MPa, the shim width is 1000 pm and the shim thickness varies from 100 pm to 400 pm (the case shim = 0 corresponds to the reference case without a shim). It is observed that increasing the shim thickness induces a decrease of up to 80% in the maximum von Mises stress value in the interconnector, compared to the reference case.

[0109] As is apparent from reading the present description, the invention therefore reduces the risks of breakage of the interconnector in thermal cycling.

[0110] By "between A and B", we mean, in a strictly equivalent manner, "greater than or equal to A and less than or equal to B".

Claims

Demands

1. Photovoltaic module (1) comprising: - a photovoltaic unit (6) comprising several photovoltaic cells (3) electrically connected in series and spaced apart from each other, adjacent photovoltaic cells (3) being electrically connected in pairs by a metallic interconnector (4) which extends at least partially into an interconnection space (2) separating said adjacent photovoltaic cells, - an encapsulation structure (8) based on at least one polymer encapsulation material, sandwiching the opposite faces of the photovoltaic cells, defining a cell overlap zone (10), and the interconnector (4) in the interconnection space (2), defining an interconnector overlap zone (11), a wedge (12) incorporated in the encapsulation structure (8) and partially overlapping the interconnector (4) in the interconnector overlap zone (11),the wedge (12) being made of a material having, at a temperature of -40 °C, a modulus of elasticity lower than the modulus of elasticity of the encapsulating polymer material.

2. Photovoltaic module according to claim 1, the wedge material (12) having a modulus of elasticity more than 2 times, preferably more than 5 times, or even more than 10 times, lower than the modulus of elasticity of the encapsulating polymer material at a temperature of -40 °C.

3. Photovoltaic module according to any one of claims 1 and 2, the wedge material (12) having a modulus of elasticity lower than the modulus of elasticity of the encapsulation material at a temperature of 20 °C, preferably at any temperature between -40 °C and 20 °C.

4. Photovoltaic module according to any one of the preceding claims, the wedge material (12) having a modulus of elasticity, measured at -40 °C, between 0.1 MPa and 300 MPa, preferably between 1 MPa and 10 MPa.

5. Photovoltaic module according to any one of the preceding claims, the material of the wedge (12) being an elastomer, in particular selected from silicone elastomers, rubbers, fluorinated elastomers, thermoplastic elastomers and mixtures thereof.

6. Photovoltaic module according to any one of the preceding claims, the shim having a thickness between 100 µm and 1500 pm and / or a width between 100 pm and 1500 pm.

7. Photovoltaic module according to any one of the preceding claims, the wedge (12) having the shape of a ribbon, in particular of rectangular or square cross-section.

8. Photovoltaic module according to any one of the preceding claims, the wedge (12) extending through and through over the entire length of the interconnection space between the adjacent photovoltaic cells, said length being measured parallel to the lateral faces opposite said adjacent cells.

9. Photovoltaic module according to any one of the preceding claims, the photovoltaic module comprising several wedges (12) covering at least partially the interconnector (4) in the interconnector cover zone (11).

10. Photovoltaic module according to the preceding claim, in the thickness of the PV module, at least two of the shims (12) being arranged on either side of the interconnector.

11. Photovoltaic module according to any one of the preceding claims, the encapsulation material comprising, for more than 70% of its mass, preferably for more than 80% of its mass, preferably for more than 90% of its mass, preferably for more than 95% of its mass, preferably for 100% of its mass, a polymer material.

12. Photovoltaic module according to the preceding claim, the polymer material being selected from ethylene-vinyl acetate, an ethylene-methyl acrylate copolymer, low-density polyethylene terephthalate, polyamide 11, polycarbonate, polyethylene glycol terephthalate, polymethyl methacrylate, polypropylene, polypropylene copolymer, polypropylene homopolymer, polytetrafluoroethylene, styrene-acrylonitrile copolymer, thermoplastic polyurethane, acrylonitrile butadiene styrene, polyethylene and mixtures thereof.

13. PV module according to any one of the preceding claims, the encapsulation material may have a modulus of elasticity between 10 MPa and 10 GPa, at a temperature of -40 °C.

14. A method for manufacturing a photovoltaic module according to any one of the preceding claims, the method comprising: - supplying a multilayer stack (20) comprising a photovoltaic unit (6) comprising photovoltaic cells (3) electrically connected in series and spaced apart from each other, the photovoltaic cells adjacent photovoltaic cells being electrically connected in pairs by an interconnector (4) which extends at least partially into an interconnection space (2) separating said adjacent photovoltaic cells, a wedge (12) superimposed at least partially on the interconnector in the interconnection space (2), and at least two encapsulation layers (21i,21s) that sandwich the photovoltaic unit and - thermoforming the multilayer stack until the photovoltaic module is obtained.

15. A method according to the preceding claim, wherein the thermoforming is carried out by laminating the multilayer stack between a heated lower lamination plate (24i) and a membrane (25) on which fluid pressure is applied.

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