DEVICE FOR CONNECTING PHOTOVOLTAIC CELLS

Description

TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to the general field of photovoltaic modules, which comprise a set of photovoltaic cells electrically connected to each other, and preferably so-called "crystalline" photovoltaic cells, that is to say, which are based on monocrystalline or multicrystalline silicon, III-V materials, thin films (CIGS, CdTe, perovskites, etc.) or any combination of these different materials.

[0002] In particular, it concerns tandem photovoltaic cells combining silicon and a perovskite material, homojunction or heterojunction photovoltaic cells based on monocrystalline silicon (c-Si) and / or multicrystalline silicon (mc-Si), photovoltaic cells comprising at least one material among amorphous silicon (a-Si), microcrystalline silicon (µC-Si), cadmium telluride (CdTe), copper-indium selenide (CIS), copper-indium / gallium diselenide (CIGS), and perovskites, among others.

[0003] More specifically, the invention relates to the field of interconnecting photovoltaic cells which allows the formation of chains or series (or "strings" in English) of photovoltaic cells, and it relates in particular to the equipment and processes implemented during the welding carried out for the interconnection.

[0004] It therefore relates to the field of photovoltaic modules used for space applications, as well as for terrestrial applications, and also for applications such as electronic mobility, balloons, or drones, among others. More generally, the invention applies to photovoltaic applications for which the issue of interconnecting photovoltaic cells is relevant.

[0005] The invention thus relates to a photovoltaic cell interconnection device, as well as a method of interconnecting photovoltaic cells implemented by means of such a device. STATE OF THE ART

[0006] A terrestrial photovoltaic module typically consists of electrically connected photovoltaic cells, usually in series, encapsulated in a stack of polymer and / or glass materials. This stack protects the photovoltaic cells from the external environment, such as rain, wind, snow, humidity, ultraviolet radiation, other radiation, and thermal shock, while maintaining the photoelectric conversion function.

[0007] Thus, classically, a terrestrial photovoltaic module forms a stack comprising successively: a rear protection element called "backsheet" in English, transparent or not, such as a glass plate or a polymer film; a first encapsulating polymer film; photovoltaic cells electrically connected to each other, typically by interconnectors, most often tinned copper strips; a second encapsulating polymer film; a front protection element called "frontsheet" in English, transparent, such as a glass plate or a polymer film.

[0008] The front protective element is designed to transmit solar radiation to the photovoltaic cells to generate electricity, while protecting them from environmental stresses. This stack is then bonded together during a hot lamination process, typically between 100 and 150°C, to melt the encapsulating films and cause the polymers to cross-link, resulting in the formation of a solid encapsulating envelope for the photovoltaic cells bonded to the front and rear protective elements.

[0009] The interconnection of photovoltaic cells is necessary to extract the electrical current generated by the cells while minimizing resistance. It must be resilient to maintain performance and prevent potentially catastrophic incidents, such as fires. The article "A review of interconnection technologies for improved crystalline silicon solar cell photovoltaic module assembly," by Musa T. Zarmai et al., School of Engineering, Faculty of Science and Engineering, University of Wolverhampton, Applied Energy 154, 173-182, September 15, 2015, presents, for example, various known approaches to interconnecting photovoltaic cells in the field of terrestrial photovoltaics.

[0010] For terrestrial photovoltaic modules, interconnectors are typically copper ribbons or wires with a silver (Ag) or tin (Sn) coating. In most cases, the electrical connection between the ribbons / wires and the cells is achieved by brazing with a filler metal, without melting the base metals. This ensures good ohmic contact at temperatures below 400°C. In an interconnection device using brazing, the ribbons or wires are generally placed on the front and back faces of the photovoltaic cells. Simultaneous brazing of the front and back faces is then performed by heating to prevent bowing. A ribbon / wire retaining mask can be used on the photovoltaic cells to maintain contact between the ribbons / wires and metal pads, particularly silver pads.

[0011] In the space sector, brazing is not recommended for interconnection. At temperatures below -40°C, typical space operating temperatures, tin changes from its β to its α form, a process that results in a change in volume and weakens the material, leading to cracking (known as "embrittlement"). This phenomenon is called "tin plague."

[0012] Another approach, applicable to both terrestrial and space applications, involves using soldering with or without filler metal, which requires melting the base metals, particularly silver, copper, and aluminum. For low temperatures, around 100°C, conductive adhesives, often composed of metallic particles, especially silver, in a polymer matrix, can be used. For locally high temperatures, for example, above 600°C, typically around 1085°C for copper, 962°C for silver, and 660°C for aluminum, soldering without filler metal can be performed.Thus, it may be necessary to reach temperatures that are too high and incompatible with the use of certain categories of photovoltaic cells, such as silicon heterojunction photovoltaic cells, which require a manufacturing and processing temperature below 200°C, or tandem type cells requiring a manufacturing and processing temperature below 150°C, when the heating is global as in brazing interconnection processes.

[0013] Therefore, there is a need to obtain a localized energy input in order to reach the high temperatures required for welding.

[0014] In document CN 220445359U, a method is proposed in which a laser welding interconnection device is used to form a string of photovoltaic cells interconnected by bonding conductors.

[0015] The interconnect is critical due to its essential function of current transmission. It must withstand expansions caused by environmental stresses during manufacturing, particularly during welding, or during the operation of the photovoltaic module, for example during eclipses in Earth orbit, despite differences in the coefficient of thermal expansion (CTE). Therefore, achieving an optimal solution for localized heating should help limit the effects of CTE. DESCRIPTION OF THE INVENTION

[0016] The invention aims to remedy at least partially the needs mentioned above and the drawbacks related to prior art achievements.

[0017] In particular, the invention aims to enable the interconnection of photovoltaic cells while maintaining excellent ohmic conductivity between the cells regardless of the applied deformations, whether mechanical or thermomechanical.

[0018] Its aim is in particular to enable interconnection by welding for multiple types of photovoltaic cells, without temperature constraints, while allowing welding on both sides of the photovoltaic cells.

[0019] The invention thus relates, according to one of its aspects, to a device for interconnecting photovoltaic cells by laser welding to form at least one chain of photovoltaic cells interconnected by connecting conductors, characterized in that it comprises: a deposit area for at least one photovoltaic cell comprising a through-hole configured to expose the front and rear faces of said at least one photovoltaic cell on either side of the through-hole when said at least one photovoltaic cell is positioned on the deposit area, a first laser welding unit comprising a first laser head configured to perform at least one laser shot for the localized fusion of at least one connecting conductor positioned on the front face of said at least one photovoltaic cell, a second laser welding unit comprising a second laser head configured to perform at least one laser shot for the localized fusion of at least one connecting conductor positioned on the rear face of said at least one photovoltaic cell, the first and second laser welding units being located on either side of the through opening.

[0020] The interconnection device according to the invention may further comprise one or more of the following characteristics taken individually or in any possible technical combinations.

[0021] The laser welding interconnection device may include a conveying module, in particular a conveying belt, on either side of the through opening on which said at least one photovoltaic cell is intended to rest at the level of its opposite edges.

[0022] Furthermore, the laser welding interconnection device may include a conveying unit, in particular a belt conveyor or conveyor belt, located at a distance from the through opening, on which said at least one string of photovoltaic cells is formed and on which said at least one photovoltaic cell is intended to be conveyed by the conveying module after laser welding carried out on the front and rear faces of said at least one photovoltaic cell, the conveying module being in particular located on either side of the conveying unit.

[0023] The first laser welding unit may include a first laser beam mask through which the first laser head is capable of performing said at least one laser beam. The first laser beam mask may be configured to hold said at least one connecting conductor in position against the front face of said at least one photovoltaic cell.

[0024] The second laser welding unit may include a second laser beam mask through which the second laser head is capable of performing at least one laser beam. The second laser beam mask may be configured to hold at least one connecting conductor against the rear face of at least one photovoltaic cell.

[0025] The first laser firing mask and / or the second laser firing mask may be as described in claim 1 of French patent application FR2408965, and may include one or more of the optional features defined in the dependent claims of that application, which is incorporated herein by reference. Thus, the first laser firing mask and / or the second laser firing mask may comprise a plurality of laser firing pins through which at least one laser shot is capable of being delivered for the local fusion welding of at least one connecting conductor positioned on the front or rear face of at least one photovoltaic cell, each laser firing pin being hollow and having a conical opening. The conical opening may advantageously ensure that the laser shot correctly reaches the area to be welded, namely the connecting conductor in contact with the photovoltaic cell.

[0026] The first laser welding unit may include at least one vision system for positioning the first laser head in a predetermined position. Similarly, the second laser welding unit may include at least one second vision system for positioning the second laser head in a predetermined position.

[0027] In addition, the first laser head of the first laser welding unit can be mounted in translation relative to a first frame of the first laser welding unit, in particular mounted in translation along a first horizontal axis, in translation along a second horizontal axis and in translation along a third vertical axis, the first, second and third axes being the axes of a three-axis frame.

[0028] Similarly, the second laser head of the second laser welding unit can be mounted in translation relative to a second frame of the second laser welding unit, in particular mounted in translation along a first horizontal axis, in translation along a second horizontal axis and in translation along a third vertical axis, the first, second and third axes being the axes of a three-axis frame.

[0029] The interconnection system may also include: a photovoltaic cell stacking unit, a pickup unit, including a pickup robot, of said at least one photovoltaic cell from the stacking unit for transport to the drop zone.

[0030] The socket unit may include means for gripping said at least one photovoltaic cell, in particular in the form of suction cups for sucking said at least one photovoltaic cell.

[0031] In addition, the gripping unit may include a third vision system allowing the gripping means to be positioned according to a predetermined position.

[0032] The interconnection device may also include a unit for routing connecting conductors to the drop-off area.

[0033] Furthermore, the invention also relates, according to another aspect, to a method of interconnecting by laser welding photovoltaic cells interconnected by connecting conductors, implemented by means of a laser welding interconnection device as defined above.

[0034] The process may include the following steps: position at least one photovoltaic cell on the deposit area supported on either side of the through opening to expose the front and rear faces of said at least one photovoltaic cell, the front and rear faces being in contact with at least one connecting conductor, perform at least one laser shot for the local fusion, or localized fusion, of said at least one connecting conductor positioned on one of the front and rear faces of said at least one photovoltaic cell by means of the first laser head of the first laser welding unit, perform at least one laser shot for the local fusion, or localized fusion, of said at least one connecting conductor positioned on the other of the front and rear faces of said at least one photovoltaic cell by means of the second laser head of the second laser welding unit.

[0035] Furthermore, the process may include the following step: to move said at least one photovoltaic cell, after laser welding, by means of a conveying module, in particular a conveying belt, located on either side of the through opening and on which said at least one photovoltaic cell is supported at its opposite edges, towards a conveying unit, in particular a belt conveyor or conveyor belt, located at a distance from the through opening, and on which said at least one string of photovoltaic cells is formed.

[0036] In addition, the process may include the following step: synchronize the movement of the conveyor module and the movement of the conveyor unit so as to periodically manage the distance between two successive photovoltaic cells of the same string of photovoltaic cells to be formed and the distance between two successive strings of photovoltaic cells to be formed.

[0037] The process may also include the following steps: position a first laser firing mask in contact with the connecting conductors and one of the front and rear faces of said at least one photovoltaic cell before performing said at least one laser firing through the first laser head of the first laser welding unit, position a second laser firing mask in contact with the connecting conductors and the other of the front and rear faces of said at least one photovoltaic cell before performing said at least one laser firing through the second laser head of the second laser welding unit.

[0038] The process may also include a preliminary step using a sacrificial, or "dummy," photovoltaic cell. This step may consist of removing the first photovoltaic cell used in the process, which is then sacrificed. Such a step can be implemented, in particular, in the case of manufacturing fully interconnected chains that are separated at the end of production, for example, by a guillotine system. BRIEF DESCRIPTION OF THE FIGURES

[0039] Other advantages, purposes, and specific features of the invention will become apparent from the following non-limiting description of at least one embodiment of the present invention, with reference to the accompanying figures, in which: there figure 1 represents, according to a partial perspective view, an example of a laser welding interconnection device for photovoltaic cells according to the invention, the figure 2represents a detailed view of the interconnection device of the figure 1 allowing visualization of the first laser welding unit, the figure 3 represents a detailed view of the interconnection device of the figure 1 allowing visualization of the second laser welding unit, the figure 4 represents a detailed view of the interconnection device of the figure 1 allowing visualization of the drop-off area and the through opening, and the figure 5 illustrates the principle of forming a string of photovoltaic cells using the interconnection device of the figure 1 .

[0040] Throughout these figures, identical references may designate identical or analogous elements.

[0041] Furthermore, the different parts represented in the figures are not necessarily shown on a uniform scale, in order to make the figures more legible. DETAILED DESCRIPTION OF THE INVENTION

[0042] It should be noted that the terms "vertical" and "horizontal" are to be understood here in their usual sense, particularly with regard to the positioning of a string S of photovoltaic cells 4 extending horizontally along a conveyor unit 50 of the laser-welded interconnection device 100. Furthermore, a "vertical" axis is orthogonal to a "horizontal" axis. In addition, the expression "moving in translation along an axis" can also mean here "moving in translation parallel to an axis".

[0043] With reference to figures 1 to 5We will now describe an example of the implementation of a laser welding interconnection device 100 according to the invention, enabling the interconnection of several photovoltaic cells 4 to form a chain S, or "string," by welding involving localized melting of the pure metal(s) at high temperatures, particularly above 600°C, applicable to photovoltaic cells 4 that cannot withstand excessively high temperatures, particularly above 200°C. The success of this localized melting can depend, in particular, on the intensity, duration, and efficiency of the laser beam. It can, in particular, allow welding on a predetermined surface on either side of a connecting conductor, for example, a surface on the order of 100 µm x 100 µm.

[0044] The interconnection device 100 allows laser welding of the linking conductors 6, typically interconnecting ribbons or wires, to the front face 4a, and the rear face 4b, of the photovoltaic cells 4 to form a chain S of photovoltaic cells 4.

[0045] As seen on the figure 1 , the interconnection device 100 comprises a stacking unit 70, or stack, a socket unit 10, a first laser welding unit 20, a second laser welding unit 21, a conveying unit 50, including a belt conveyor or conveyor belt and a routing unit 40 for connecting conductors 6 to the first laser welding unit 20.

[0046] The stacking unit 70, or photovoltaic cell stack 4, comprises a plurality of photovoltaic cells 4 stacked one on top of the other which are intended to be interconnected by means of the interconnecting device 100 according to the invention.

[0047] The gripping unit 10 here corresponds to a gripping robot allowing the grasping of a photovoltaic cell 4 from the stacking unit 70 to transport it to a depositing zone ZD at the level of the first 20 and second 21 laser welding units.

[0048] For this purpose, the socket unit 10 includes means for gripping the photovoltaic cell 4, here in the form of suction cups V3 for suctioning the photovoltaic cell 4. The suction cups V3 are located at the end of a vertical post supported by a robotic arm.

[0049] In addition, the socket unit 10 includes a third vision system 10v, here a camera, which allows the photovoltaic cell 4 to be correctly grasped from the stacking unit 70 and positioned correctly at the drop zone ZD.

[0050] The ZD drop zone of the laser welding interconnection device 100 allows the drop of a photovoltaic cell 4 taken by the take-up unit 10 at the stacking unit 70 so that it can be welded to the link conductors 6 on the front face 4a and the rear face 4b.

[0051] As more clearly visible on the figures 4 And 5 , the deposit area ZD has a through opening O which allows the front face 4a and the rear face 4b of the photovoltaic cell 4 to be exposed once deposited on the deposit area ZD.

[0052] As shown by figure 2In particular, the laser-welded interconnection device 100 further comprises a conveying module 51, here two conveying belts 51 positioned on either side of the longitudinal edges of the through opening O and rotated by means of at least one first cylinder C1, visible on the figure 3 The photovoltaic cell 4 is thus placed on the conveyor belts 51 by the gripping unit 10 and is subsequently driven in horizontal translational motion by the conveyor belts 51 only at the longitudinal edges of the photovoltaic cell 4, as can be seen in the figure 5 .

[0053] Furthermore, the laser welding interconnection device 100 includes a conveying unit 50, in particular in the form of a belt conveyor or conveyor belt, which is located at a distance from the through opening O, as shown in the figure 4This conveyor unit 50 is set in motion by means of the rotation of at least one second cylinder C2, visible on the figure 3 The conveyor unit 50 is positioned after the through opening O, in the direction of movement of the photovoltaic cells 4 to form the chain S, so as to allow access to both the front face 4a and the rear face 4b for welding on both sides. The transport of the photovoltaic cells 4 onto the conveyor unit 50 is then carried out via suction ports present on the conveyor unit 50, as well as via the two conveyor belts 51 located on either side of the conveyor unit 50.

[0054] Furthermore, as depicted on the figure 2The first laser welding unit 20 comprises a first laser head 20t configured to perform one or more laser shots towards the photovoltaic cell 4 positioned in the deposition zone ZD. In this way, a local or localized fusion of the connecting conductors 6 positioned on the front face 4a of the photovoltaic cell 4 is achieved.

[0055] The laser shots are made by the first laser head 20t through a first laser shooting mask 20m which allows both the holding in position of the connecting conductors 6 against the front face 4a of the photovoltaic cell 4 and, by means of orifices through which the laser shots pass, the laser welding in a localized manner.

[0056] Similarly, as depicted on the figure 3The second laser welding unit 21 includes a second laser head 21t configured to perform one or more laser shots towards the photovoltaic cell 4 positioned in the deposition zone ZD. In this way, a localized or localized fusion of the connecting conductors 6 positioned on the rear face 4b of the photovoltaic cell 4 is achieved.

[0057] The laser shots are made by the second laser head 21t through a second laser shooting mask 21m which allows both the holding in position of the connecting conductors 6 against the rear face 4b of the photovoltaic cell 4 and, by means of orifices through which the laser shots pass, the laser welding in a localized manner.

[0058] Each 20m, 21m laser shooting mask advantageously comprises a plurality of laser shooting pins 22 through which a laser shot is suitable for local or localized fusion welding of a connecting conductor 6 positioned on the front face 4a or the rear face 4b of a photovoltaic cell 4, each laser shooting pin 22 being hollow and comprising a conical opening.

[0059] If necessary, at least one 20m or 21m laser firing mask may include a plurality of suction pins (not shown) to hold the connecting conductors 6 regardless of the position of the photovoltaic cell 4 in the string S. These suction pins can, by means of vacuum suction, hold the connecting conductors 6, particularly for the first photovoltaic cell at the start of production. The suction pins can be arranged alternately with the laser firing pins 22, for example, in one or more rows of pins.

[0060] In addition, each of the first 20 and second 21 laser welding units includes a vision system to correctly position the laser head 20t, 21t relative to the photovoltaic cell 4, here the first laser welding unit has two first vision systems 20v, on either side of the first laser head 20t, each with a camera, and the second laser welding unit has two second vision systems 21v, on either side of the second laser head 21t, each also with a camera.

[0061] Advantageously, the first laser head 20t of the first laser welding unit 20 is mounted in translation along the three axes X 0 , Y 0 , Z 0 of a three-axis frame relative to a first frame 20b of the first laser welding unit 20.

[0062] Symmetrically, the second laser head 21t of the second laser welding unit 21 is mounted in translation along the three axes X 1 , Y 1 , Z 1 of a three-axis frame relative to a second frame 21b of the second laser welding unit 21.

[0063] In particular, the first 20t laser head is translationally movable along a first horizontal axis X0 relative to a first horizontal frame 20bx, translationally movable along a second horizontal axis Y0 relative to a second horizontal frame 20by, and translationally movable along a third vertical axis Z0 relative to a third vertical frame 20bz. Motors can be provided at the ends of each of the first 20bx, second 20by, and third 20bz frames to move the first 20t laser head.

[0064] Similarly, the second laser head 20t is translationally movable along a first horizontal axis X1 relative to a first horizontal frame 21bx, translationally movable along a second horizontal axis Y1 relative to a second horizontal frame 21by, and translationally movable along a third vertical axis Z1 relative to a third vertical frame 21bz. Motors can be provided at the ends of each of the first 21bx, second 21by, and third 21bz frames to move the second laser head 21t.

[0065] The laser welding interconnection process using the laser welding interconnection device 100 described above can then be implemented as described below.

[0066] A photovoltaic cell 4 is picked up at the stacking unit 70 by the pick-up unit 10, then conveyed to the depositing zone ZD. Specifically, the photovoltaic cell 4 is placed on connecting conductors 6 already welded to the front face 4a of a previous photovoltaic cell 4 that has left the depositing zone ZD towards the conveying unit 50. The deposit is carried out with the rear face 4b in contact with these connecting conductors 6, the photovoltaic cell 4 being supported on its sides by the conveying belts 51, on either side of the through opening O.

[0067] So, the routing unit 40 allows the positioning of other connecting conductors 6 on the front face 4a of the photovoltaic cell 4.

[0068] Laser welding can be performed by the first laser welding unit 20 on the front face 4a of the photovoltaic cell 4 and also by the second laser welding unit 21 on the rear face 4b of the photovoltaic cell 4. The two laser welds may or may not be performed simultaneously. The laser welding by the second laser welding unit 21 may be performed first when the photovoltaic cell 4 is positioned on the insertion zone ZD, either before or after the positioning of the connecting conductors 6 from the feed unit 40 against the front face 4a of the photovoltaic cell 4.

[0069] Once the photovoltaic cell 4 is welded on its two front faces 4a and rear faces 4b, it can be conveyed via the conveying module 51 to the conveying unit 50. The ends of the connecting conductors 6 present on the front face 4a will then allow the rear face 4b of a new photovoltaic cell 4 taken from the stacking unit 70, or stack of photovoltaic cells 4, to be positioned.

[0070] It should be noted that laser welding can be achieved by moving the 20t, 21t laser head, in particular by moving along the X 0, X 1 and Y 0, Y 1 axes, or by changing the angle of the laser shot through the 20m, 21m laser shooting mask.

[0071] The laser welding interconnection device 100 advantageously includes means for self-aligning the photovoltaic cells 4 positioned successively on the deposition zone ZD in order to form the chain S of photovoltaic cells 4. In addition, the laser welding interconnection device 100 includes means for synchronizing the laser shots periodically according to a first distance which corresponds to the sum of the distance between two successive photovoltaic cells 4 and the size of a photovoltaic cell 4 and / or according to a second distance which corresponds to the sum of the distance between two successive chains S and the size of a photovoltaic cell 4.Advantageously, the S strings of photovoltaic cells 4 are thus manufactured automatically one after the other by means of a synchronization between the laser welding steps of the front faces 4a and rear faces 4b carried out by the laser welding units 20, 21, and the conveying steps carried out by the conveying module 51 and the conveying unit 50.

[0072] Of course, the invention is not limited to the examples of implementation that have just been described. Various modifications can be made to it by a person skilled in the art.

Claims

1. A laser-welding interconnection device (100) for photovoltaic cells (4) to form at least one string (S) of photovoltaic cells (4) interconnected by connecting conductors (6), characterised in that it comprises: - a placement area (ZD) for at least one photovoltaic cell (4) comprising a through-hole (0) configured to expose the front face (4a) and the rear face (4b) of said at least one photovoltaic cell (4) on either side of the through-opening (0) when said at least one photovoltaic cell (4) is positioned on the placement area (ZD), - a first laser welding unit (20) comprising a first laser head (20t) configured to perform at least one laser pulse for the local melting of at least one connecting conductor (6) positioned on the front face (4a) of said at least one photovoltaic cell (4), - a second laser welding unit (21) comprising a second laser head (21t) configured to perform at least one laser pulse to locally melt at least one connecting conductor (6) positioned on the rear face (4b) of said at least one photovoltaic cell (4), characterised in that the first (20) and second (21) laser welding units are situated on either side of the through-hole (0).

2. A device (100) according to claim 1, wherein the laser-welding interconnection device (100) comprises a conveying module (51), in particular a conveyor belt, on either side of the through-hole (0), on which the at least one photovoltaic cell (4) is intended to rest at its opposite edges.

3. A device (100) according to claim 2, wherein the laser-welding interconnection device (100) comprises a conveying unit (50), in particular a belt conveyor or roller conveyor, situated at a distance from the through-opening (0), on which the at least one string (S) of photovoltaic cells (4) is formed and on which the at least one photovoltaic cell (4) is intended to be conveyed by the conveying module (51) after laser welding has been carried out on the front (4a) and rear (4b) faces of the at least one photovoltaic cell (4), the conveying module (51) being situated, in particular, on either side of the conveying unit (50).

4. A device (100) according to one of the preceding claims, in which the first laser welding unit (20) comprises a first laser firing mask (20m) through which the first laser head (20t) is capable of performing said at least one laser firing, the first laser firing mask (20m) being configured to hold said at least one connecting conductor (6) in position against the front face (4a) of said at least one photovoltaic cell (4).

5. A device (100) according to any one of the preceding claims, wherein the second laser welding unit (21) comprises a second laser firing mask (21m) through which the second laser head (21t) is capable of performing said at least one laser firing, the second laser firing mask (21m) being configured to hold said at least one connecting conductor (6) in position against the rear face (4b) of said at least one photovoltaic cell (4).

6. A device (100) according to any one of the preceding claims, wherein the first laser head (20t) of the first laser welding unit (20) is mounted so as to be capable of translational movement relative to a first frame (20b) of the first laser welding unit (20), in particular mounted so as to be capable of translation along a first horizontal axis (X0 ), translation along a second horizontal axis (Y0 ) and translation along a third vertical axis (Z0 ), the first (X0 ), second (Y0 ) and third (Z0 ) axes being the axes of a three-axis coordinate system.

7. A device (100) according to any one of the preceding claims, in which the second laser head (21t) of the second laser welding unit (21) is mounted so as to be capable of translational movement relative to a second frame (21b) of the second laser welding unit (21), in particular so as to be capable of translational movement along a first horizontal axis (X1 ), along a second horizontal axis (Y1 ) and along a third vertical axis (Z1 ), the first (X1 ), second (Y1 ) and third (Z1 ) axes being the axes of a three-axis coordinate system.

8. A device (100) according to any one of the preceding claims, wherein the laser-welding interconnection device (100) further comprises: - a stacking unit (70) for photovoltaic cells (4), - a picking unit (10), in particular a robotic pick-and-place unit (10), for picking up said at least one photovoltaic cell (4) from the stacking unit (70) for transport to the placement zone (ZD).

9. A device (100) according to the preceding claim, wherein the gripping unit (10) comprises gripping means (V3) for gripping said at least one photovoltaic cell (4), in particular in the form of suction cups (V3) for suctioning said at least one photovoltaic cell (4).

10. A device (100) according to any one of the preceding claims, wherein the laser-welding interconnection device (100) comprises a unit (40) for conveying connecting conductors (6) to the placement zone (ZD).

11. A method for laser-welding photovoltaic cells (4) to form at least one string (S) of photovoltaic cells (4) interconnected by connecting conductors (6), carried out by means of a laser-welding interconnection device (100) according to any one of the preceding claims.

12. A method according to claim 11, wherein the method comprises the following steps: - positioning at least one photovoltaic cell (4) on the placement area (ZD) so that it rests on either side of the through-hole (0) to expose the front face (4a) and the rear face (4b) of said at least one photovoltaic cell (4), the front face (4a) and the rear face (4b) being in contact with at least one connecting conductor (6), - performing at least one laser pulse to locally fuse said at least one connecting conductor (6) positioned on either the front face (4a) or the rear face (4b) of said at least one photovoltaic cell (4) by means of the first laser head (20t) of the first laser welding unit (20), - performing at least one laser pulse to locally melt said at least one connecting conductor (6) positioned on the other of the front face (4a) and the rear face (4b) of said at least one photovoltaic cell (4) by means of the second laser head (21t) of the second laser welding unit (21).

13. A method according to claim 11 or 12, wherein the method comprises the following step: - moving said at least one photovoltaic cell (4), after laser welding, by means of a conveying module (51), in particular a conveyor belt, situated on either side of the through-opening (O) and on which said at least one photovoltaic cell (4) rests at its opposite edges, in the direction of a conveying unit (50), in particular a belt conveyor or conveyor belt, situated at a distance from the through-opening (0), and on which the at least one chain (S) of photovoltaic cells (4) is formed.

14. A method according to claim 13, wherein the method comprises the following step: - synchronising the movement of the conveying module (51) and the movement of the conveying unit (50) so as to periodically control the distance between two successive photovoltaic cells (4) of the same chain (S) of photovoltaic cells (4) to be formed and the distance between two successive chains (S) of photovoltaic cells (4) to be formed.

15. A method according to any one of claims 12 to 14, wherein the method comprises the following steps: - positioning a first laser firing mask (20m) in contact with the connecting conductors (6) and with either the front face (4a) or the rear face (4b) of said at least one photovoltaic cell (4) before performing said at least one laser firing by means of the first laser head (20t) of the first laser welding unit (20), - positioning a second laser firing mask (21m) in contact with the connecting conductors (6) and the other of the front face (4a) and the rear face (4b) of said at least one photovoltaic cell (4) before performing said at least one laser firing via the second laser head (21t) of the second laser welding unit (21).