Photovoltaic module comprising a polymer-based and raised encapsulation structure

Abstract

The invention relates to a photovoltaic module (1) comprising: - a photovoltaic unit (6) comprising a plurality of photovoltaic cells (3) electrically connected in series and spaced apart from one another, wherein the adjacent photovoltaic cells are electrically connected in pairs by a metal interconnector (4) that extends at least partially into an interconnection space (2) separating the adjacent photovoltaic cells; - a polymer-based encapsulation structure (8) sandwiching the opposite faces (9, 9b) of the photovoltaic cells, wherein the encapsulation structure defines a cell overlap region (10), and wherein the interconnector in the interconnection space defines an interconnector overlap region (11), characterised in that the smallest thickness (egap) of the interconnector overlap region is less than the smallest thickness (ec) of the cell overlap region.

Description

[0001] Description

[0002] Title: Photovoltaic module comprising a polymer-based and embossed encapsulation structure

[0003] Technical field

[0004] The present invention relates to the resistance to thermal cycling of photovoltaic modules comprising photovoltaic cells integrated in an encapsulation structure based on at least one polymer material.

[0005] Prior art

[0006] Integrating photovoltaic modules into buildings, infrastructure or vehicles is a way to simply increase the surface area for capturing solar radiation for mass energy production.

[0007] 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 compliance 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.

[0008] Thermoplastic polymer materials have low cost, good mechanical properties, low density, and good recyclability, making them good candidates for the manufacture of lightweight photovoltaic modules. They can therefore be used to cover photovoltaic cells and hold them together in a rigid structure.

[0009] However, these materials are polymers. As such, they exhibit a high ability to deform under the influence of temperature, characterized by a high coefficient of thermal expansion (CTE). Each polymer has a unique CTE that depends on its composition and production 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.

[0010] Figure 1 illustrates a first example of degradation of such a type of photovoltaic module 1, called curvature effect, following the implementation of manufacturing by lamination. The curvature effect is a flatness defect of the photovoltaic module which develops during cooling of the photovoltaic module following lamination. It is generally caused by a difference in the coefficient of thermal expansion between the front face and the rear face of the photovoltaic module.

[0011] Figure 2 illustrates several examples of degradation of these photovoltaic modules, 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 appears 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.

[0012] The difference between the CTE of silicon, which makes up the photovoltaic cells 4, or the CTE of metals such as copper, used to form the interconnectors that electrically connect the photovoltaic cells of the module, and the CTE of the polymer(s) of the photovoltaic module, can lead to severe localization of thermal stresses in the metal parts of the modules. This leads to degradation that greatly affects the performance of the modules.

[0013] A recurring problem observed in thermal cycling is the breakage of the interconnectors 4 that connect the photovoltaic cells, which in fact leads to an extinction, i.e. an inability to produce electricity, of the photovoltaic module. Figure 3 shows photographs acquired by optical microscopy illustrating breakages of interconnectors 2. An example of extinction after 60 thermal deformation cycles of a photovoltaic module comprising 8 photovoltaic cell units is shown in Figure 4, due to the breakages of interconnectors illustrated in Figure 3.

[0014] To prevent these degradations from occurring, it has already been tested to reduce the thickness of the polymer encapsulation structure, but this can lead to the inability of the photovoltaic module to successfully pass regulatory certification tests, in particular impact and bending resistance tests. It has also been considered to reinforce the polymer encapsulation structure with fibers or fabrics in order to make the module more rigid and more resistant to thermal cycling. However, this involves significantly modifying the implementation processes, which complicates and slows down the industrial development of these composite modules. In addition, the presence of fibers modifies the optical properties and degrades the energy efficiency of the photovoltaic module.

[0015] There is therefore a need to improve the thermal cycling resistance of photovoltaic modules comprising a polymer-based encapsulation structure.

[0016] Summary of the invention

[0017] The invention proposes a photovoltaic module comprising:

[0018] - a photovoltaic unit comprising several photovoltaic cells electrically connected in series and spaced apart from each other, the adjacent photovoltaic cells being electrically connected two by two by a metal interconnector which extends at least partly into an interconnection space separating said adjacent photovoltaic cells,

[0019] - an encapsulation structure, based on at least one polymer material, sandwiching the opposite faces of the photovoltaic cells, defining a cell overlap zone, and F interconnector in the interconnection space, defining an interconnector overlap zone, characterized in that the smallest thickness of the interconnector overlap zone is less than the smallest thickness of the cell overlap zone.

[0020] The reduced thickness of the interconnector overlap area limits stress concentration in the interconnector and at the interface between the interconnector and the encapsulation structure during temperature variations. This results in a reduced risk of interconnector breakage during thermal cycling.

[0021] In addition, the local thickness reduction in the interconnector overlap area increases the flexibility of the photovoltaic module, which facilitates the conformation of the photovoltaic module on non-planar application surfaces.

[0022] Preferably, the ratio between the thinnest thickness of the interconnector overlap area and the thinnest thickness of the cellular overlap area is less than or equal to 0.95, preferably less than or equal to 0.3. Preferably, it is greater than or equal to 0.05, preferably greater than or equal to 0.15.

[0023] In particular, the thinnest thickness of the cell overlapping area may be between 300 pm and 4000 pm, or even between 600 pm and 1200 pm, and the thinnest thickness of the interconnector overlapping area may be between 50 pm and 500 pm, or even between 100 pm and 500 pm.

[0024] Preferably, the difference between the thinnest thickness of the cell overlapping area and the thinnest thickness of the interconnector overlapping area is greater than 200 pm, preferably greater than 300 pm, preferably greater than 500 pm, and preferably less than 800 pm, preferably less than 1000 pm.

[0025] Preferably, the thickness of the encapsulation structure in the interconnector overlap area is less than the thickness of the encapsulation structure in the cell overlap area.

[0026] The encapsulation structure preferably comprises a recessed relief that forms an extent of reduced thickness in the interconnector overlap area, the recessed relief partially or entirely covering the interconnector in the interconnector overlap area.

[0027] The hollow relief can have a depth of between 100 pm and 1500 pm.

[0028] Preferably, the ratio between the width of the recessed relief and the width of the interconnection space is greater than 0.1, preferably greater than 0.2, preferably greater than 0.3, preferably greater than 0.4, preferably greater than 0.5, preferably greater than 0.6, preferably greater than 0.7, preferably greater than 0.8, better still greater than 0.9. Such a ratio optimizes the distribution of stresses during a temperature variation in the interconnector and at the interface between the interconnector and the encapsulation structure.

[0029] The width of the relief and the width of the interconnection space are measured perpendicular to the facing faces of the adjacent photovoltaic cells.

[0030] The distance between two adjacent photovoltaic cells can be between 0.2 and 10 mm.

[0031] The width of the hollow relief may be greater than 0.2 mm, preferably greater than 0.4 mm, or even greater than 1 mm.

[0032] The recessed relief may be of various shapes. For example, it is a groove or has a hemispherical shape. Preferably, the recessed relief is a groove, preferably rectilinear and / or of hemispherical, triangular, rectangular or square cross-section, which extends in the space between the adjacent photovoltaic cells parallel to the facing side faces of said adjacent cells. Such a groove further facilitates the shaping of the photovoltaic module on a curved application surface.

[0033] Preferably, the groove extends from side to side over the entire length of the interconnection space between the adjacent photovoltaic cells, said length being measured parallel to the facing lateral faces of said adjacent cells.

[0034] The encapsulation structure may comprise an upper recessed relief and a lower recessed relief formed on the upper face and the lower face of the encapsulation structure, respectively, the lower and upper recessed reliefs being at least partially superimposed on the interconnector overlapping area. The lower and upper recessed reliefs may further be superimposed on each other.

[0035] The encapsulation structure may comprise several hollow reliefs, preferably several grooves, extending from one side to the other over the entire length of the interconnection space between the adjacent photovoltaic cells. Preferably, the grooves are parallel to each other. Preferably, the ratio between the sum of the widths of the grooves and the distance separating the adjacent photovoltaic cells is greater than 0.2, preferably greater than 0.3, preferably greater than 0.4, preferably greater than 0.5, preferably greater than 0.6, preferably greater than 0.7, preferably, preferably greater than 0.8, more preferably greater than 0.9. Each groove may have a width of between 0.2 and 1 mm.

[0036] The encapsulation structure is preferably self-supporting. A self-supporting structure is sufficiently rigid so as not to deform substantially under its own weight.

[0037] 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 area of ​​the photovoltaic cells and over the entire surface area of ​​the interconnector.

[0038] The encapsulation structure is based on at least one polymer material, i.e. it comprises 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, at least one polymer material. The polymer material is suitable for a photovoltaic application, i.e. it has a transmittance suitable for incident solar radiation to be transmitted to activate the electrical production of the photovoltaic cells. Preferably, the polymer material is transparent to solar radiation.

[0039] The polymer material may have a modulus of elasticity of between 0.001 GPa and 1 GPa at a temperature of 20°C. It may have a modulus of elasticity of between 10 MPa and 10 GPa at a temperature of -40°C.

[0040] The modulus of elasticity is measured according to standard NF EN ISO 527-1.

[0041] Preferably, the polymer material is thermoplastic. It may have a glass transition temperature above -150°C.

[0042] Preferably, the polymer material is selected from ethylene-vinyl acetate, 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.

[0043] The encapsulation structure may be homogeneous, i.e., it consists of the polymer material whose composition is identical in all areas of the encapsulation structure. As will be described later, a homogeneous encapsulation structure may result from thermoforming a bottom layer and a top layer both made of the homogeneous polymer material.

[0044] Alternatively, the encapsulation structure is multi-layered. Preferably, the multi-layered encapsulation structure comprises one or more inner layers that completely cover and are in contact with the photovoltaic cells and F 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 polymer materials. The lower and upper layers may be made of the same polymer material, and may comprise reinforcing fibers, for example glass fibers. Preferably, at a temperature of -40°C, and preferably at a temperature of 20°C, the modulus of elasticity of the polymer material constituting the inner layer(s) is lower than the modulus of elasticity of the polymer material constituting the lower layer and / or the upper layer.The lower and upper layers thus provide the photovoltaic module with bending rigidity and impact resistance, and the inner layer(s) allow stress relief in the photovoltaic module.

[0045] Preferably, the thickness of the photovoltaic module is constant in the cell overlap area.

[0046] Preferably, the thickness of the photovoltaic module is constant, except in the interconnector overlap area.

[0047] The interconnector may be made of a metal selected from copper, silver, tin, lead and their alloys.

[0048] The interconnector connects two adjacent cells of the photovoltaic unit. Preferably, it is fixed, for example soldered or glued with an electrically conductive adhesive on each of the adjacent cells. Preferably, it is fixed on a lower face of one of the adjacent photovoltaic cells and on an upper face of the other adjacent photovoltaic cell, in order to connect the positive and negative poles of the cells so as to circulate the photoelectric current.

[0049] Preferably, the interconnector extends through the thickness of the photovoltaic module between adjacent cells that it electrically connects.

[0050] The interconnector may have the form of a ribbon. The interconnector may have a thickness of between 50 pm and 500 pm and / or a width of between 200 pm and 2000 pm.

[0051] Preferably, the photovoltaic module extends along a median surface which may be flat or curved. The photovoltaic cells preferably extend along the median surface.

[0052] 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.

[0053] Within the photovoltaic unit, the photovoltaic cells may be identical. Preferably, they are aligned along an alignment axis in the medial surface, the interconnection space between two adjacent photovoltaic cells extending perpendicular to the alignment axis. Their lateral faces may be parallel, in particular aligned along the alignment axis.

[0054] In the variant where the photovoltaic unit comprises more than two photovoltaic cells, the interconnector F can electrically connect adjacent photovoltaic cells in series in pairs. In particular, it can have a portion in contact with one face of a photovoltaic cell, which extends 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 which connects the photovoltaic cell to one of the adjacent cells.

[0055] Photovoltaic cells can contain, or even consist of, silicon. They can be of the perovskite / silicon tandem type.

[0056] Each photovoltaic cell preferably has a plate shape, for example rectangular or square. At least one of the photovoltaic cells, in particular each photovoltaic cell, may have a thickness of between 0.05 and 0.3 mm.

[0057] The photovoltaic module may comprise several photovoltaic units, which may be arranged relative to each other in a tiling manner along the median surface, for example along the alignment axis or along two perpendicular axes.

[0058] The invention also relates to a method of manufacturing a photovoltaic module according to the invention, the method comprising:

[0059] - the provision of a multilayer stack comprising a photovoltaic unit comprising photovoltaic cells electrically connected in series and spaced apart from each other, the adjacent photovoltaic cells being electrically connected two by two by an interconnector which extends at least partly in an interconnection space separating said adjacent photovoltaic cells, and at least two encapsulation layers which sandwich the photovoltaic unit and

[0060] - thermoforming of the multi-layer stack until the photovoltaic module is obtained.

[0061] Thermoforming can be done by thermocompression or lamination.

[0062] Preferably, thermoforming is performed by laminating the multi-layer stack between a heated lower lamination platen and a membrane to which fluid pressure is applied.

[0063] Preferably, prior to lamination of the multi-layer stack, at least one lower indenter is disposed between the lower lamination plate and the multi-layer stack and / or an upper indenter is disposed between the membrane and the multi-layer stack, the lower indenter and / or the upper indenter at least partially covering the interconnector in the interconnection space.

[0064] The lower indenter may be integral with the lower plate. Alternatively, it may be bonded to the lower plate. The upper indenter may be positioned on the face of the stack opposite the lower plate, superimposed on the interconnector in the interconnection space, prior to covering the preform with the membrane.

[0065] The lower indenter and / or the upper indenter may be a straight bar, in order to form a lower recessed relief and / or an upper recessed relief in the form of a groove in the encapsulating structure.

[0066] According to the variant where the photovoltaic unit comprises several photovoltaic cells spaced apart from each other and connected two by two by portions of interconnector F extending into the interconnection spaces between the adjacent cells, several indenters can be arranged superimposed each on one of the interconnection spaces in order to form hollow reliefs in each interconnector overlapping zone.

[0067] The indenters, for example bars, may be connected to each other by one or more spacers, forming a grid which may be arranged between the lower plate and the multi-layer stack or between the membrane and the multi-layer stack.

[0068] Furthermore, the invention also relates to a device chosen from a building, a motor vehicle, a train, an airplane and a building, the device integrating on an external surface the photovoltaic module according to the invention. The external surface may be curved. The external surface of the device is for example a hood or a roof of a car, a wall or a roof of a building.

[0069] Brief description of the drawings

[0070] [Fig. 1] and [Fig. 2] are photographs of photovoltaic modules of prior art,

[0071] [Fig. 3] is an optical microscopy photograph of a broken interconnector of a prior art photovoltaic module, [Fig. 4] are electroluminescence images of photovoltaic modules, from left to right, according to the prior art after lamination, 30 cycles, and 60 thermal cycles,

[0072] [Fig 5] schematically represents a top, front and side view of an example of a photovoltaic module according to the invention,

[0073] [Fig 6] is a schematic, cross-sectional view of the photovoltaic module at an interconnector overlap area,

[0074] [Fig. 7] schematically illustrates an example of a manufacturing process by lamination of the photovoltaic module according to the invention,

[0075] [Fig. 8] is a top view of an indenter grid used to form a groove of lesser thickness superimposed on the various indenter overlapping areas of the module shown in Figure 5,

[0076] [Fig. 9] is a view of a finite element mesh of a part of a module according to the invention as illustrated in Figure 6, at the level of the interconnector overlap zone,

[0077] [Fig. 10] are images of the von Mises stress distribution in a reference mesh and in the mesh of Figure 6 after a thermomechanical numerical simulation of a thermal cycle,

[0078] [Fig. 11] is a graph illustrating the evolution of the von Mises stress along the path illustrated in Figure 4,

[0079] [Fig. 12] is a graph illustrating for different pairs of minimum thickness of the interconnector overlap area and width Igroove of the groove, the distribution of the maximum value of the von Mises stress calculated in F interconnector, and

[0080] [Fig. 13] is a graph illustrating the influence of the ratio between the width Igroove of the groove and the distance between adjacent photovoltaic cells on the maximum stress in F interconnector,

[0081] Detailed description

[0082] 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 plates, which are spaced apart from each other. Each photovoltaic cell is separated from the photovoltaic cell adjacent to it by an interconnection space 2.

[0083] The number of photovoltaic units 6 and photovoltaic cells 3 is not limiting and other arrangements can be envisaged.

[0084] 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.

[0085] Within each photovoltaic unit 6, the adjacent photovoltaic cells 3 are connected two by two in series by metal interconnectors 4, for example made of copper, which extend in the direction y, from one side to the other between the electrical terminals 7.

[0086] Each metal interconnector 4 comprises portions 4a in contact with one face of a photovoltaic cell which are connected to each other by portions 4b which each extend into the interconnection space provided between the photovoltaic cells 3. The metal interconnector 4 is subsequently in contact with one face of a photovoltaic cell then with an opposite face of the adjacent photovoltaic cell. Thus, when observed along the sectional plane (y,z) illustrated in Figure 6, the interconnector winds from one connection terminal to the other, between the photovoltaic cells 3.

[0087] The photovoltaic module further comprises an encapsulation structure 8 based on at least one polymer material within which the photovoltaic units 6 are fully immersed.

[0088] The encapsulation structure 8 completely covers the opposite faces 9a, 9b of the photovoltaic cells 3, thus defining with each photovoltaic cell 3 a cell covering zone 10. Preferably, the thickness e c of each cell overlap area 10 is constant, and preferably the thicknesses of the different cell overlap areas are equal.

[0089] Furthermore, the encapsulation structure 8 covers the interconnectors in the different interconnection spaces 2 between the adjacent photovoltaic cells, thus defining with the interconnector 4 an interconnector overlap zone 11. In the example illustrated in FIGS. 5 and 6, hollow reliefs being lower 12i and upper 12s grooves are provided in the encapsulation structure 8 from the lower 13i and upper 13s faces of said structure, in each of the interconnection spaces 2 between the adjacent photovoltaic cells.

[0090] Within each interconnection space 2, the lower 12i and upper 12s grooves extend from side to side over the entire length of the facing faces of the adjacent photovoltaic cells, and parallel to said faces. They may further be superimposed on one another, as illustrated, or be offset relative to one another along the y axis.

[0091] The lower and upper grooves are furthermore superimposed in each interconnection space at F interconnector, at the level of the interconnector overlap zone, as can be observed in the sectional view along a plane (x,z) in Figure 5.

[0092] In order to manufacture the photovoltaic module illustrated in FIG. 5, a multilayer stack 20 can be prepared in the following manner. The photovoltaic units 6 and the connection strips are arranged between lower 21i and upper 21s sheets made of a soft polymer material, with a low modulus of elasticity, for example between 0.001 GPa and 1 GPa at 20°C. The sheets 21i,s thus completely cover the photovoltaic units 6 and the connection strips 7. The assembly thus formed can be arranged between lower 22i and upper 22s external sheets made of another rigid polymer material, with a high modulus of elasticity, for example between 0.1 GPa and 10 GPa at 20°C to form the multilayer stack 20.After lamination, a photovoltaic module 1 is thus obtained having a multi-layer encapsulation structure having lower 14i and upper 14s rigid external encapsulation layers sandwiching a flexible internal encapsulation layer 15 in which the photovoltaic units are immersed.

[0093] In order to form the lower 12i and upper 12s grooves in the interconnection spaces 2 between the adjacent photovoltaic cells, lower indenters 23 are arranged between a lower lamination plate 24i and the multilayer stack 20 on the one hand and between the multilayer stack 20 and a membrane 25. In the example illustrated in FIG. 7, only lower indenters 23 are shown. The indenters are for example bars 29, for example metallic or ceramic, which are connected to each other by a spacer 26, in order to form a grid 27, as illustrated in FIG. 8, which can be positioned, for example manually between the multilayer stack 20 and the plate 24i, between support pins 28 which keep the stack at a distance from the plate 24i.The distance db between the bars 29 is predefined so that all the indenters 23 are arranged on a corresponding interconnection space 2, once the grid 2 is positioned on the stack. For example, one grid thus carries the lower indenters and another grid carries the upper indenters. Alternatively, the indenters 23 may be projecting reliefs formed on the surface of the lower plate, as illustrated in FIG. 7.

[0094] The lamination of the multilayer stack 20 is conventionally carried out by heating the multilayer stack to a temperature suitable for a flow of the polymer materials in contact with the cells, and under pressure applied to the membrane 25 in order to heat-seal the different sheets 21i,s and 22i,s and the photovoltaic units 6 between them, to indent the encapsulation structure 8 in formation in the interconnector overlap zones 11, then by cooling until the photovoltaic module is obtained.

[0095] The effect of the lower thickness e gap of the photovoltaic module in the interconnector overlap area is presented below.

[0096] A 2D finite element mesh 30 of a portion of the photovoltaic module including the interconnection space 2 was produced, as illustrated in Figure 9. The quadrangle finite elements were chosen so that the thickness Ci of the interconnector F is discretized with at least 4 finite elements.

[0097] The modeled encapsulation structure 8 thus comprises lower and upper layers of polyamide 11, whose modulus of elasticity at 20°C is equal to 1430 MPa and the CTE is equal to 1.6* 10' 4 K' 1 The thickness of each of the lower and upper layers is 400 pm.

[0098] The inner layer 15, 1200 pm thick, is made of thermoplastic polyolefin, whose modulus of elasticity at 20°C is 20 MPa and the CTE is equal to 5.6*10' 4 K' 1 .

[0099] The photovoltaic cell 3, with a thickness of 150 pm, is made of silicon, whose modulus of elasticity is equal to 166 GPa and the CTE is equal to 2.6*10' 6 K' 1 .

[0100] Finally, F interconnector 4, with a thickness equal to 200 pm, is made of copper and has a modulus of elasticity equal to 130 GPa and a CTE equal to 1.4*10' 5 K' 1 .

[0101] The simulations were carried out assuming a plane deformation state, with thermoelastic material behavior models, and using ABAQUS simulation software. A stress-free state at 25°C was considered in each finite element, then a cooling to a temperature of -40°C of the photovoltaic module was calculated, this temperature being that of thermal cycling as established in the IEC61215 standard.

[0102] A first reference mesh illustrated in Figure 9 was produced with a constant photovoltaic module thickness, i.e. equal in the interconnector overlap zone and in the cell overlap zone.

[0103] Other meshes identical to the reference mesh were produced by introducing superimposed lower and upper grooves as illustrated in Figure 6, and by varying the thickness of the interconnector overlap area e gap and the width Igroove of the grooves, the width of the interconnecting space l gap and the thickness e c of the cellular overlap area 11 being constant.

[0104] Figure 10 illustrates the effect of thermal expansions between 20 °C and -40 °C induces von Mises stresses which are higher in the interconnector when the thickness of the photovoltaic module is constant (reference mesh 35) than when a groove is formed in the interconnection space and results in a thinner area in the interconnector overlap area (mesh 36).

[0105] This observation is confirmed by Figure 11 which represents the evolution of the von Mises stresses G. expressed in MPa, as a function of the abscissa S (in mm) along the path 37 illustrated in Figure 9 for the reference mesh 35 with a constant thickness of 2 mm (curve 40) and for a mesh 36 having the same thickness e c constant of 2 mm in the cell overlap area and a lower thickness e gap in the 1300 pm interconnector overlap area (curve 41).

[0106] As can be observed, the presence of the grooves 12i,s induces lower von Mises stresses in the interconnector of the grooved photovoltaic modules than in the reference module.

[0107] Figure 12 is a graph showing the maximum value of the von Mises stress along path 37 for meshes with different torques (e gap , Igroove) of thickness e gap of the photovoltaic module in the grooved portion and groove width Igroove. A general decrease in the von Mises stress is observed. The meshes (1300, 2000)-1 and (1300, 2000)-2 correspond to different groove morphologies with a thickness e gap identical. It appears that the reduction of maximum stresses is little modified by the morphology of the groove. Finally, Figure 13 illustrates, for meshes in which the thickness e gap is constant and equal to 750 pm, the width of the groove l groove varying from 300 m to 3000 pm, the evolution of the maximum value of the von Mises stress along path 37 (left ordinate) and the reduction, expressed in percent, of said stress on the maximum value of the reference case, i.e. in the absence of a groove (right ordinate). It is estimated that a local reduction in the thickness e gap 63% over 93% of the width l gap of interconnection space 2 reduces the maximum value of the von Mises stress by more than 40%.

[0108] As appears from reading this description, the invention therefore reduces the risks of breakage of the interconnector during thermal cycling.

[0109] By "between A and B" we mean strictly equivalently "greater than or equal to A and less than or equal to B".

Claims

Claims 1. Photovoltaic module (1) comprising: - a photovoltaic unit (6) comprising several photovoltaic cells (3) electrically connected in series and spaced apart from each other, the adjacent photovoltaic cells being electrically connected two by two by a metal interconnector (4) which extends at least partly into an interconnection space (2) separating said adjacent photovoltaic cells, - a multi-layer encapsulation structure (8), sandwiching the opposite faces (9a, 9b) of the photovoltaic cells, defining a cell overlap area (10), and F interconnector (4) in the interconnection space (2), defining an interconnector overlap area (11), characterized in that the smallest thickness (e gap ) of the interconnector overlap area (11) is less than the smallest thickness (e c) of the cell covering area (10),, the encapsulation structure (8) comprising one or more inner layers which entirely cover and are in contact with the photovoltaic cells and F interconnector, and lower and upper layers which sandwich the inner layers, the inner layer(s) and the lower and upper layers being made of different polymer materials, the ratio between the lowest thickness (e gap ) of the interconnector overlap area (11) and the smallest thickness (e c ) of the cellular overlap area (10) being less than or equal to 0.3, and preferably greater than or equal to 0.05, preferably greater than or equal to 0.

15.

2. Photovoltaic module according to any one of claims 1 and 2, the smallest thickness (e c) of the cell covering zone (10) being between 300 pm and 4000 pm, or even between 600 pm and 1200 pm and the smallest thickness (e gap ) of the interconnector overlap zone (11) being between 50 pm and 500 pm, or even between 100 pm and 500 pm.

3. Photovoltaic module according to any one of the preceding claims, the difference between the smallest thickness (e c ) of the cellular covering zone (10) and the lowest thickness (e gap ) of the interconnector overlap area (11) being greater than 200 pm, preferably greater than 300 pm, of preferably greater than 500 pm, and preferably less than 800 pm. preferably less than 1000 pm.

4. Photovoltaic module according to any one of the preceding claims, the encapsulation structure (8) comprising a hollow relief (12i, 12s) which forms an area of ​​reduced thickness in the interconnector covering zone (11), the hollow relief (12i, 12s) partially or entirely covering the interconnector (4) in the interconnector covering zone (11).

5. Photovoltaic module according to the preceding claim, the width of the hollow relief (l gro ove) being greater than 0.2 mm, preferably greater than 0.4 mm, or even greater than 1 mm.

6. Photovoltaic module according to any one of claims 5 and 6, the hollow relief (12i, 12s) being a groove, preferably rectilinear and / or of rectangular or square cross-section, which extends in the interconnection space (2) parallel to the facing lateral faces of the adjacent photovoltaic cells (3).

7. Photovoltaic module according to any one of the preceding claims, the thickness of the photovoltaic module being constant in the cell overlap zone (10), preferably, the thickness of the photovoltaic module being constant, except in the interconnector overlap zone (11).

8. Photovoltaic module according to any one of the preceding claims, the encapsulation structure comprising for more than 70% of its mass at least one polymer material chosen 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.

9. Photovoltaic module according to any one of the preceding claims, the photovoltaic unit (6) comprising more than two photovoltaic cells (3), in particular at least three, or even at least five, or even at least ten photovoltaic cells, F interconnector (4) electrically connecting the adjacent photovoltaic cells (3) two by two in series.

10. Photovoltaic module according to any one of the preceding claims, the encapsulation structure (8) comprising an upper hollow relief (12s) and a lower hollow relief (12i) formed respectively on the upper face and on the lower face of the encapsulation structure (8).

11. Photovoltaic module according to any one of the preceding claims, having at a temperature of -40°C, and preferably at a temperature of 20°C, a modulus of elasticity of the polymer material constituting the inner layer(s) lower than the modulus of elasticity of the polymer material constituting the lower layer and / or the upper layer.

12. Method of manufacturing a photovoltaic module according to any one of the preceding claims, the method comprising: - providing a multilayer stack (20) comprising a photovoltaic unit (6) comprising photovoltaic cells (3) electrically connected in series and spaced apart from each other, the adjacent photovoltaic cells (3) being electrically connected two by two by an interconnector (4) which extends at least partly in an interconnection space (2) separating said adjacent photovoltaic cells (3), and at least two encapsulation layers (14i, 14s, 15) which sandwich the photovoltaic unit, and - the thermoforming of the multilayer stack until the photovoltaic module is obtained is carried out by laminating the multilayer stack, between a heated lower lamination plate (24i) and a membrane (25) on which a fluid pressure is applied, characterized in that prior to the lamination of the multilayer stack, at least one indenter (23) is arranged between the lower lamination plate (24i) and the multilayer stack (20) and / or at least one indenter (23) is arranged between the membrane and the multilayer stack, the indenter at least partially covering F interconnector in the interconnection space.

13. Method according to the preceding claim, the photovoltaic unit (6) comprising several photovoltaic cells (3) spaced apart from each other and connected two by two by portions of interconnector F extending into the interconnection spaces (2) between adjacent cells, several indenters (23) being arranged superimposed each on one of the interconnection spaces in order to form hollow reliefs in each interconnector overlap zone.

14. Method according to the preceding claim, the indenters (23), for example bars (29), being connected to each other by one or more spacers (26), forming a grid which is arranged between the lower plate (24i) and the multilayer stack (20) or between the membrane (25) and the multilayer stack (20).

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