ASSEMBLY FOR PHOTOVOLTAIC MODULE with optimized quantity of electrically conductive adhesive

Abstract

The invention relates to an assembly comprising: at least one photovoltaic cell having a face on which a collection grid is formed, at least one interconnecting ribbon fixed to said face and intended for electrically and mechanically connecting the photovoltaic cell to another photovoltaic cell, and at least one adhesive line (30), made of an electrically conductive material, disposed between the collection grid and the interconnecting ribbon, the adhesive line (30) being adapted to mechanically and electrically connect the interconnecting ribbon to the photovoltaic cell, the adhesive line (30) extending substantially along a principal longitudinal axis (X) and having a substantially constant width (l). The adhesive line (30) is arranged in a zigzag pattern formed by a plurality of segments (31), each forming an angle (α) less than or equal to 30° with the principal longitudinal axis (X). Figure for the abstract: Fig. 2

Description

Title of the invention: ASSEMBLY FOR PHOTOVOLT AIQUE MODULE with optimized quantity of electrically conductive glue Technical field

[0001] The invention relates to the field of photovoltaic modules, which comprise a set of photovoltaic cells electrically connected to each other, and more precisely, on the interconnection of the photovoltaic cells.

[0002] The invention can be implemented for numerous applications, in particular civil and / or military, for example autonomous and / or embedded applications. It can thus in particular be applied to buildings such as homes or industrial premises (tertiary, commercial, etc.), for example for the construction of their roofs, for the design of street furniture, for example for public lighting, road signs or even the recharging of electric cars, or even be used for nomadic applications (solar mobility), in particular for integration on vehicles, such as cars, buses or boats, drones, airships, among others. STATE OF THE PRIOR ART

[0003] A photovoltaic module is formed of chains or even strings, more commonly called "strings", which are an assembly of several photovoltaic cells connected in series and / or in parallel by interconnection strips, for example tinned copper strips.

[0004] The interconnection ribbon can be electrically and mechanically connected to a photovoltaic cell by welding or by gluing with an electrically conductive glue (or ECA for “Electrically Conductive Adhesive” in English).

[0005] The use of an electrically conductive adhesive is preferred due to the high sensitivity of photovoltaic cells, in particular heterojunction cells, to temperature. Indeed, the polymerization temperature of the electrically conductive adhesive is particularly low, for example of the order of 160°C to 180°C. It is thus lower than the temperature used during welding, which can be of the order of 260°C to 280°C.

[0006] The electrically conductive glue comprises conductive particles, typically silver particles. As a result, its use consumes silver, the resources of which are limited, and is relatively expensive.

[0007] Several known solutions thus propose to reduce the consumption of electrically conductive glue for the electrical and mechanical connection of a ribbon interconnection to a photovoltaic cell.

[0008] These solutions propose to deposit the glue in the form of a continuous straight line or dotted lines, as shown in particular in the article by Kaiser et al. entitled Reduction of ECA amount for the ribbon interconnection of heterojunction solar cells, 37th European PV Solar Energy Conference and Exhibition, 7-11 September 2020, whose dimensions (width, length) are close to those of the interconnection ribbon.

[0009] These solutions require that the glue line and the interconnection tape are perfectly aligned to obtain a maximum contact surface and ensure satisfactory adhesion of the interconnection tape to the photovoltaic cell.

[0010] However, the deposition of the electrically conductive glue and / or the interconnection tape may be associated with a positioning uncertainty, which is notably linked to the precision of the equipment used for the deposition. In the solutions described, such uncertainty may then lead to a misalignment of the glue and the interconnection tape, and may thus reduce the adhesion of the interconnection tape to the photovoltaic cell. Statement of the invention

[0011] The invention aims to remedy at least in part the drawbacks of the prior art, and more particularly to propose a solution for improving the adhesion of an interconnection ribbon to a photovoltaic cell, in particular when the interconnection ribbon and the line of glue are misaligned, while limiting the consumption of electrically conductive glue.

[0012] For this, the object of the invention is an assembly comprising: • at least one photovoltaic cell comprising a face on which a collection grid is provided, • at least one interconnection strip fixed on said face, said interconnection strip being intended to electrically and mechanically connect the photovoltaic cell to another photovoltaic cell, and • at least one line of glue, made of an electrically conductive material, arranged between the collection grid and the interconnection strip, the line of glue being adapted to mechanically and electrically connect the interconnection strip to the photovoltaic cell, the line of glue extending substantially along a main longitudinal axis and having a substantially constant width.

[0013] According to the invention, the glue line is arranged in a zigzag pattern formed of a plurality of segments each forming an angle less than or equal to 30° with the main longitudinal axis, and with an amplitude of variation, along a transverse axis per pendicular to the main longitudinal axis, which is greater than the width of the glue line.

[0014] Some preferred but non-limiting aspects of this assembly are as follows.

[0015] The angle formed by the segments with the main longitudinal axis can be between 15° and 30°.

[0016] A ratio between the amplitude of variation of the glue line and a width of the interconnecting ribbon can be between 0.5 and 1.5.

[0017] The width of the interconnection ribbon may be between 0.2 mm and 1.2 mm.

[0018] The electrically conductive glue line may be made of a material chosen from glues comprising conductive particles, for example silver and / or copper particles, carbon nanotubes or silver nanowires, or a polymer matrix, for example of the acrylate, epoxy or silicone type. Brief description of the drawings

[0019] Other aspects, aims, advantages and characteristics of the invention will appear better on reading the following detailed description of preferred embodiments thereof, given by way of non-limiting example, and made with reference to the appended drawings in which:

[0020] [Fig.l] schematically and partially represents, in a top view, an assembly according to an embodiment of the invention, comprising a photovoltaic cell, interconnection strips and lines of electrically conductive glue arranged between the photovoltaic cell and a respective interconnection element;

[0021] [Fig.2] shows one of the electrically conductive glue lines of [Fig.l] taken in isolation;

[0022] Figures 3A and 3B show an interconnecting ribbon arranged on a glue line without misalignment, with a straight and thin glue line ([Fig.3A]) and with a glue line similar to that of [Fig.2] ([Fig.3B]);

[0023] Figures 4A and 4B show an interconnecting ribbon arranged on a glue line with misalignment, with the glue line straight and thin ([Fig.4A]) and with a glue line similar to that of [Fig.2] ([Fig.4B]);

[0024] Figures 5A and 5B show an interconnecting ribbon arranged on a glue line without misalignment, with a straight and wide glue line ([Fig.5A]) and with a glue line similar to that of [Fig.2] ([Fig.5B]); and

[0025] Figures 6A and 6B show an interconnecting ribbon arranged on a glue line with misalignment, with the glue line straight and wide ([Fig.6A]) and with a glue line similar to that of [Fig.2] ([Fig.6B]).

[0026] DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS

[0027] In the figures and in the remainder of the description, the same references represent identical or similar elements. Furthermore, the different elements are not shown to scale so as to enhance the clarity of the figures. Furthermore, the different embodiments and variants are not mutually exclusive and may be combined with each other. Unless otherwise indicated, the terms "substantially", "approximately", "of the order of" mean to within 10%, and preferably to within 5%. Furthermore, the terms "between ... and ..." and equivalents mean that the limits are included, unless otherwise indicated.

[0028] [Fig.l] schematically and partially represents, in top view, an assembly 1 according to an embodiment of the invention.

[0029] Generally speaking, such a set 1 comprises: • a 10 photovoltaic cell, • one or more interconnection strips 20 intended to electrically and mechanically connect the photovoltaic cell 10 to another photovoltaic cell in order to form a chain of photovoltaic cells, and • one or more lines of electrically conductive glue 30 each electrically and mechanically connecting an interconnection strip 20 to the photovoltaic cell 10.

[0030] The assembly 1 according to the invention is thus intended to be electrically and mechanically connected to a photovoltaic cell, by means of one or more interconnection strips 20, in order to form a chain of photovoltaic cells.

[0031] The photovoltaic cell 10 comprises a general plate shape with a front face 11 and a rear face (not shown) opposite the front face. The photovoltaic cell 10 here comprises on its front face 11 a contact grid 13 adapted to ensure the collection of photogenerated charges. Of course, the photovoltaic cell can also comprise a collection grid on its rear face.

[0032] The collection grid 13 is generally obtained by screen printing a paste of silver, copper and / or aluminum or any other type of base on the front face 11 of the photovoltaic cell 10. The collection grid 13 is here formed of a succession of parallel collection lines spaced from one another. Optionally, the collection grid may further comprise a conductive track called a Busbar, arranged so as to electrically connect the contact lines together. In this case, the conductive Busbar track preferably extends perpendicular to the collection lines.

[0033] Generally speaking, the interconnection strip 20 has a generally planar and elongated shape. It is made of an electrically conductive material, preferably copper with a silver coating. It can be made from other materials.

[0034] The interconnection strip 20 is arranged on the front face 11 of the photovoltaic cell 10 so as to be connected to several collection lines, or, in the case where the collection grid comprises a Busbar conductive line, so as to be aligned with the latter. The strip has a length, along a longitudinal axis, which can vary depending on the dimensions of the photovoltaic cell, and a width, along a transverse axis perpendicular to the longitudinal axis, which can be between 0.2 mm and 1.2 mm.

[0035] The interconnection strip 20 may comprise a free portion 21 which is not superimposed on the photovoltaic cell 10. The advantage of having a free portion 21 of the interconnection strip 20 is to facilitate the interconnection of the photovoltaic cells 20.

[0036] For example, the free portion 21 is included in the same plane as the rest of the interconnection strip 20, which is thus adapted to connect the front face 11 of the photovoltaic cell 10 to a face, generally rear, of another photovoltaic cell located in the same plane as the front face 11. In this case, we speak of monolithic interconnection architecture. Alternatively, the free portion 21 may be included in a separate plane than the rest of the interconnection strip, which is then adapted to connect the front face 11 of the photovoltaic cell with a face, generally rear, of another photovoltaic cell located in a plane separate from the front face 11. In this case, we speak of standard interconnection architecture.

[0037] Generally speaking, the glue line 30, made of an electrically conductive material, is arranged between the front face 11 of the photovoltaic cell 10 and the interconnection strip 20. It extends here so as to be connected to several collection lines 13 of the photovoltaic cell, and preferably extends perpendicularly to the latter.

[0038] The electrically conductive adhesive may, for example, be chosen from adhesives comprising conductive particles, for example silver and / or copper particles, carbon nanotubes or silver nanowires, or a polymer matrix, for example of the acrylate, epoxy or silicone type. The electrically conductive adhesive 30 advantageously has a crosslinking temperature of between 160 and 180°C.

[0039] [Fig. 2] represents the glue line 30 considered in isolation. The glue line 30 has a main longitudinal axis X and a transverse axis Y perpendicular to the main longitudinal axis X.

[0040] The glue line 30 is arranged in a zigzag pattern formed of a plurality of segments 31 each forming an angle α with the main longitudinal axis X. By zigzag pattern or line is meant a broken line forming alternately projecting and re-entrant angles.

[0041] The glue line 30 has a relative length L, defined along the main longitudinal axis X, and an amplitude A of variation (or relative width) defined along the transverse axis Y. The relative length L, or total projected length, corresponds to the sum of the length Ls of the segments 31 defined along the main longitudinal axis X. The length Ls, or projected elementary length, corresponds to the length of the segments 31 projected along the axis X. The amplitude of variation A corresponds to the difference, along the transverse axis 31, between the opposite vertices of the segments 31. Preferably, the amplitude A is constant along the main longitudinal axis X.

[0042] The glue line 30 has a width 1, corresponding to the width of the segments 31, which is substantially constant. The amplitude A of variation of the glue line 30 is greater than the width 1.

[0043] The glue line 30 thus has a surface Szz, which is literally expressed:

[0044] S^nxL.yxZQ)

[0045] noting n the number of segments 31, Ls the projected length of a segment 31, 1 being the width of the glue line 30.

[0046] This surface Szz can also be expressed:

[0047] s;: = <2)

[0048] This surface Szz tends towards a minimum value Lxl when the angle a tends towards zero (corresponding to a straight and thin line), but it tends towards a maximum value LxA when the angle tends towards 90° (corresponding to a straight and wide line).

[0049] Figures 3A and 4A show an interconnecting ribbon 20 arranged on a straight and thin glue line 40 without misalignment ([Fig.3A]) and with misalignment ([Fig.4A]).

[0050] The straight and thin glue line 40 has a length L along a longitudinal axis XI, and a width 11 along a transverse axis Y1 perpendicular to the longitudinal axis XL. The width 11 of the glue line 40 is here chosen to be substantially equal to the width Ir of the interconnection strip 20 (here slightly greater). It should be noted that the straight and thin glue line 40 corresponds to a solution of the prior art previously described.

[0051] With reference to [Fig.3A], it appears that, when the interconnection strip 20 and the straight and thin glue line 40 are aligned, the contact surface Sci between the glue line 40 and the strip 20 is maximum: Sci>max = L x Ir.

[0052] With reference to [Fig.4A], it also appears that, when the interconnection strip 20 and the straight and thin glue line 40 are offset, the contact surface Sci between the glue line 40 and the interconnection strip 20 is reduced, or may even become zero (as illustrated here). The adhesion of the strip 20 to the photovoltaic cell is thus degraded. The lateral offset here corresponds to a misalignment of the tape 20 opposite the glue line 40 along the transverse axis.

[0053] Also, the contact surface Sci becomes zero when the lateral offset d between the interconnection strip 20 and the glue line 40 reaches a critical offset threshold d th, corresponding to the sum of half the width Ir of the interconnection strip 20 and half the width 11 of the glue line 40: dth = lr / 2 + 11 / 2.

[0054] Figures 3B and 4B show the interconnecting ribbon arranged on the glue line 30 in a zigzag pattern without misalignment ([Fig.3B]) and with misalignment ([Fig.4B]). It should be noted that the misalignment is the same in Figures 4A and 4B.

[0055] To facilitate comparison with the straight and thin glue line 40, the width 1 of the zigzag glue line 30 is considered to be equal to the width 11 of the straight and thin glue line 40. It is also considered that the zigzag glue line 30 and the straight and thin glue line 40 have an identical thickness.

[0056] With reference to [Fig. 3A] and 3B, it appears that, when the interconnecting strip 20 and the zigzag glue line 30 are aligned, the contact surface Sczz between the zigzag glue line 30 and the interconnecting strip 20 is less than the contact surface Sci between the straight and thin glue line 40 and the interconnecting strip 20.

[0057] With reference to [Fig.4A] and 4B, it appears on the other hand that, when the interconnection strip 20 and the zigzag glue line 30 are offset beyond the critical offset threshold dth, the contact surface Sczz between the zigzag glue line 30 and the interconnection strip 20 may be non-zero even though the contact surface Sci between the straight and thin glue line 40 and the interconnection strip 20 is zero.

[0058] Furthermore, it appears that, as the misalignment d increases and exceeds a threshold value, the contact surface Sczz between the zigzag glue line 30 and the interconnecting strip 20 becomes greater than the contact surface Sci between the straight and thin glue line 40 and the interconnecting strip 20. Indeed, the zigzag glue line 30 extends over a dimension along the transverse axis Y, namely the amplitude A of variation, which is greater than the dimension along the transverse axis Yl, namely the width 11, over which the straight and thin glue line 40 extends. In fact, the zigzag line of glue 30 makes it possible to improve the adhesion of the interconnection strip 20 to the photovoltaic cell in the presence of a misalignment d between the interconnection strip and the line of glue 30, even though, for an equivalent misalignment, the adhesion of the interconnection strip 20 via a straight line of glue of the same width may be degraded.

[0059] The surface S of the zigzag glue line 30 is however greater than a surface SI of the straight and thin glue line 40. Indeed, the surface of the straight and thin glue line 30 is literally expressed:

[0060] 51 = L x / 1 (3)

[0061] By taking up equation (2), the ratio AS between the surface SI of the glue line 40 straight and thin and the surface S of the glue line 30 in zigzag is written:

[0062] A ~ Lxll

[0063] When the width 1 of the zigzag glue line 30 and the width 11 of the straight and thin glue line 40 are equal, we therefore have:

[0064] = (5)

[0065] Thus in this case, the surface area ratio AS (and therefore excess glue consumption) between the zigzag glue line 30 and the straight and thin glue line 40 is solely determined by the angle α formed by the segments 31 with the main longitudinal axis X. The angle α is therefore determined so as to improve the adhesion of the ribbon to the photovoltaic cell in the presence of a lateral offset while limiting the excess glue consumption.

[0066] Figures 5A and 6A show an interconnecting ribbon 20 arranged on a straight and wide glue line 40 without misalignment ([Fig.5A]) and with misalignment ([Fig.6A]).

[0067] The straight and wide glue line 50 has a length L along a main longitudinal axis X2, and a width 12 along a transverse axis Y2 perpendicular to the longitudinal axis X2. The width 12 of the straight and wide glue line 50 is greater than the width 11 of the straight and thin glue line 40.

[0068] The width 12 of the straight and wide glue line 50 is such that, in the presence of a misalignment d2 equal to the misalignment dl of FIGS. 3B and 4B, the contact surface Sc2 between the glue line 50 and the interconnection strip 20 is maximum: Sc2max = L xlr. The width 12 is here equal to three times the width 11 of the straight and thin glue line 40.

[0069] The straight and wide glue line 50 thus has a surface S2 which is three times larger than the surface SI of the straight and thin glue line 40. This represents an additional glue consumption of 200% for the same thickness.

[0070] Figures 5B and 6B are similar to Figures 3B and 4B. They illustrate the comparison between the zigzag glue line 30 and the straight and wide glue line 50. To facilitate this comparison, the amplitude A of variation of the zigzag glue line 30 is considered to be equal to the width 12 of the straight and wide glue line 50. It is also considered that the zigzag glue line 30 and the straight and wide glue line 50 have an identical thickness.

[0071] With reference to [Fig.5A] to 6B, it appears that the contact surface Sczz between the zigzag glue line 30 and the interconnecting strip 20 is less than the contact surface Sc2 between the straight and wide glue line 50 and the interconnecting strip 20, with and without misalignment.

[0072] It should be noted, as previously indicated, that when the angle formed by the segments 31 with the main longitudinal axis X tends towards 90°, the surface Szz of the zigzag glue line 30 tends to approach the surface S2 of the straight and wide glue line 50.

[0073] Also, by increasing the value of the angle α, the adhesion of the interconnection ribbon to the cell is improved but the glue consumption is increased. However, it has been found that when the angle α is greater than 30°, the improvement in adhesion is not significant compared to the increase in excess glue consumption. In other words, it has been found that a value of the angle α less than or equal to 30° represents an interesting compromise between adhesion and excess glue consumption.

[0074] By taking equation (5), we observe that the additional consumption of glue, compared to the straight and thin line, when the angle a is equal to 30° is 15.5%.

[0075] Furthermore, it has been found that when the angle α is greater than 15°, the adhesion is significantly improved. Thus, preferably, the angle α is between 15° and 30°.

[0076] The zigzag glue line makes it possible, thanks to its amplitude which is greater than its width, to improve the adhesion of the ribbon to the photovoltaic cell in the event of misalignment of the ribbon and the glue line compared to a straight glue line of the same width. By limiting the value of the angle formed by the segments and the main longitudinal axis to 30°, it is possible to limit the additional consumption of glue to 15.5% compared to a straight glue line of the same width. In addition, this also makes it possible to reduce the consumption of glue compared to a straight and continuous line having a width equal to the amplitude of variation of the zigzag glue line.

[0077] Thus, the zigzag glue line makes it possible to improve the adhesion of the ribbon to the photovoltaic cell in the event of misalignment between the ribbon and the glue line, while limiting glue consumption.

[0078] For example, in the case of a straight glue line having a relative length equal to 100 mm and a width equal to 0.3 mm and an interconnection strip having a width equal to 0.6 mm, it appears that for a zigzag glue line having the same relative length and the same width, an amplitude of 0.5 mm and an angle ranging from 5° to 10° allow an improvement in the contact surface for significant offsets, for example 0.4 mm, between the interconnection strip and the glue line. The improvement is 40% for an angle of 10° and 74% for an angle of 5°. Furthermore, the angle of 10° makes it possible to limit the excess consumption of glue to 1.5% compared to the straight glue line, while the angle of 5% makes it possible to limit the excess consumption to 0.4%.

[0079] For an angle ranging from 15° to 30°, it appears that the zigzag glue line allows an improvement in the contact surface for smaller offsets, for example of 0.3 mm, between the interconnecting tape and the glue line. The improvement is 33% for a 30° angle when the offset is 0.3 mm. The improvement is 20% for a 15° angle and 200% for a 30° angle when the offset is 0.4 mm. Furthermore, the 30° angle limits the excess glue consumption to 15.5% compared to the straight glue line, while the 15% angle limits the excess consumption to 3.5%.

[0080] By way of example, the photovoltaic cell may be of the half M2 type, i.e. having a rectangular shape having a length approximately equal to 78 mm and a width approximately equal to 156 mm.

[0081] In this case, the assembly may comprise a plurality of glue lines. The number of lines may be between 4 and 20 and preferably between 6 and 9. In the case where the collection grid comprises one or more conductive tracks, the assembly may comprise as many glue lines as there are conductive tracks.

[0082] Each glue line may for example have an amplitude of between 0.1 mm and 1.5 mm, a width of between 0.1 mm and 1.2 mm, preferably between 0.3 mm and 0.8 mm, and a length which is less than or equal to the length of the photovoltaic cell, which is here equal to 78 mm. The number of segments is for example between 3 and 21, and more particularly between 13 and 16.

[0083] The assembly may also comprise a plurality of interconnecting ribbons. Each ribbon may have a width of between 0.2 mm and 1.2 mm, preferably between 0.4 mm and 0.8 mm, and a thickness of between 0.1 and 0.4 mm.

[0084] The method of manufacturing such an assembly 1 thus comprises a step of producing a photovoltaic cell similar to that described with reference to [Fig.l], and a step of producing an interconnection strip similar to that described with reference to [Fig.l],

[0085] The method then comprises a step of depositing an electrically conductive glue line on a face, for example front and / or rear, of the cell. The glue line is arranged so as to intercept, preferably perpendicularly, collection lines of the cell. The glue line is deposited so as to define a zigzag pattern formed of a plurality of segments each forming an angle of less than 30° with the main longitudinal axis of the glue line, and having an amplitude of variation, along the transverse axis, which is less than the width of the glue line and which, preferably, is between 0.5 and 1.5 times the width of the interconnection strip.

[0086] The method then comprises a step of depositing the interconnection ribbon on the face of the cell, in contact with the glue line.

[0087] We thus obtain an assembly 1 in which the adhesion of the interconnection ribbon is improved in the event of misalignment of the ribbon and the line and electrically bonds conductive, and in which glue consumption is limited.

Claims

Claims

1. Assembly comprising: • at least one photovoltaic cell (10) comprising a face (11) on which a collection grid (13) is arranged, • at least one interconnection strip (20) fixed on said face (11), said interconnection strip (20) being intended to electrically and mechanically connect the photovoltaic cell (10) to another photovoltaic cell, and • at least one line of glue (30), made of an electrically conductive material, arranged between the collection grid (13) and the interconnection strip (20), the line of glue (30) being adapted to mechanically and electrically connect the interconnection strip (20) to the photovoltaic cell (10), the line of glue (30) extending substantially along a main longitudinal axis (X) and having a substantially constant width (1),• characterized in that the glue line (30) is arranged in a zigzag pattern formed of a plurality of segments (31) each forming an angle (a) less than or equal to 30° with the main longitudinal axis (X), and with an amplitude (A) of variation, along a transverse axis (Y) perpendicular to the main longitudinal axis (X), which is greater than the width (1) of the glue line (30).,

2. Assembly according to claim 1, in which the angle (a) formed by the segments (31) with the main longitudinal axis (X) is between 15° and 30°.

3. An assembly according to claim 1 or 2, wherein a ratio between the amplitude (A) of variation of the glue line (30) and a width of the interconnecting ribbon (20) is between 0.5 and 1.

5.

4. An assembly according to claim 3, wherein the width of the interconnecting ribbon (20) is between 0.2 mm and 1.2 mm.

5. An assembly according to any one of claims 1 to 4, in which the electrically conductive glue line (30) is made of a material chosen from glues comprising conductive particles, for example silver and / or copper particles, nanotubes of carbon or silver nanowires, or a polymer matrix, for example acrylate, epoxy or silicone.

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