Solar cell module and method for producing a solar cell module

Abstract

solar cell module, with a plurality of photovoltaic solar cells, each having at least two metallic contact structures: - a metallic front-side contact structure (2) on a front side and - a metallic back contact structure (3) on a back side the solar cell (1), wherein the solar cells are arranged overlapping in a shingle arrangement, so that the rear contact structure (3) of a solar cell (1) is arranged on the front contact structure (2) of an adjacent solar cell (1) and the two contact structures are electrically conductively connected, wherein the contact structures arranged on one another and connected in an electrically conductive manner are free from an electrically conductive material connection, in particular free from an electrically conductive material connection by means of a conductive adhesive, wherein adjacent, overlapping solar cells are mechanically fixed to one another in a material-to-material and electrically non-conductive manner, and that the contact structures of adjacent solar cells arranged next to one another are fixed by means of electrically non-conductive adhesive applied between the contact structures arranged next to one another.

Description

[0001] The invention relates to a solar cell module according to claim 1 and a method for producing a solar cell module according to claim 5.

[0002] Photovoltaic solar cells typically have metallic contact structures on their front sides. Such contact structures are impermeable to incident electromagnetic radiation and thus reduce the area available for absorption on the front side. It is therefore known to design solar cell modules with a shingle arrangement. In a shingle arrangement, neighboring solar cells overlap, so that the back of one solar cell covers the front of a neighboring solar cell in an overlapping area. As a result, the metallic contact structure on the front side of a solar cell is located in the overlapping area and thus beneath the neighboring solar cell, whereby the upper solar cell in the overlapping area does not need to have a large-area metallic contact structure on its front side.In relation to the area of the solar cell module, a larger proportion of solar cell area available for light absorption can thus be achieved.

[0003] The electrical interconnection of solar cells in a shingle arrangement is typically achieved using electrically conductive adhesives (ECAs). Such conductive adhesives are typically polymer-based and contain metallic particles, typically silver.

[0004] After applying a conductive adhesive, it must be cured by heating, typically at a temperature greater than 100 °C, to form a sufficient electrical and mechanical connection. The use of such conductive adhesives to form solar cell modules in a shingle arrangement has the disadvantages that the conductive adhesives are expensive due to the metal particles they contain. Furthermore, processing, particularly the application and curing of the conductive adhesive, places high demands on mechanical performance. Furthermore, typical conductive adhesives must be stored frozen and thawed before use.

[0005] For these reasons, the mechanical, particularly automated, interconnection of solar cells in a shingle arrangement using conductive adhesives is cost-intensive and error-prone.

[0006] From US20190013428A1, an arrangement and interconnection of solar cells in the manufacture of a solar cell module is known, wherein the solar cells have elongated collectors in the overlapping areas, which are not connected by a soldering process or other metallic adhesive in the overlapping zones.

[0007] From US20160351727A1, a front-side contacting structure of a solar cell is known, which is in contact with a back-side electrode of another solar cell, whereby no electrically conductive material connection is required.

[0008] From US20120325282A1 a solar cell module is known in which the solar cells are arranged in an overlapping manner and are electrically connected to one another without requiring a materially bonded electrically conductive connection between the front-side contact structure of one cell and the back-side electrode of another cell.

[0009] The present invention is therefore based on the object of providing a solar cell module and a method for producing a solar cell module which avoids the disadvantages described above when forming a shingle arrangement.

[0010] The solar cell module according to the invention comprises a plurality of photovoltaic solar cells, each of which has at least two metallic contact structures: - a metallic back contact structure on a front side and - a metallic back contact structure on a back side of the solar cell.

[0011] The solar cells are arranged overlapping in a shingle arrangement so that the back contact structure of one solar cell is arranged on the front contact structure of an adjacent solar cell and the two contact structures are electrically connected.

[0012] It is essential that the contact structures arranged on top of one another and connected in an electrically conductive manner are free from an electrically conductive material connection, in particular free from an electrically conductive material connection by means of a conductive adhesive.

[0013] In the method according to the invention, a plurality of photovoltaic solar cells are provided, each of which has at least two metallic contact structures: - a metallic front contact structure on a front side and - a metallic back contact structure on a back side of the solar cell.

[0014] Furthermore, the solar cells are arranged in an overlapping manner in a shingle arrangement, so that the back contact structure of one solar cell is arranged on the front contact structure of an adjacent solar cell and the two contact structures are electrically connected.

[0015] It is essential that the electrically conductively connected contacting structures are arranged to one another free from an electrically conductive material connection, in particular that contacting structures are arranged to one another free from an electrically conductive material connection by means of a conductive adhesive.

[0016] The invention is based on the realization that there has previously been a scientific prejudice regarding the design of a solar cell module with a shingle arrangement: It was assumed that the use of an electrically conductive adhesive is necessary not only for mechanical stability, but in particular also for sufficiently low electrical contact between the contact structures of the solar cells lying next to one another in the overlapping area in order to avoid series resistance losses. It was therefore assumed that it was necessary for the contact structures lying next to one another, i.e. the contact structures of two adjacent solar cells that lie next to one another in the overlapping area in order to form an electrical connection of the solar cells, in particular a series connection, to be electrically conductively connected by means of a conductive adhesive.

[0017] In previous experiments, series of tests were carried out to save on conductive adhesive for cost savings, but on the other hand to ensure a sufficiently large adhesive surface between the adjacent metallic contact structures in order to minimize a reduction in module efficiency due to series resistance losses caused by contact resistances at the bonded metallic contact structures.

[0018] The present invention is based on the finding that, contrary to previous teachings, it is advantageous for the mutually arranged, electrically conductively connected contact structures to be free of an electrically conductive, integral connection, and thus, in particular, no electrically conductive adhesive, in particular no ECA, is used for the mechanical and electrical connection of the two metallic contact structures in the overlapping region. Thus, the formation of an integral, electrically conductive connection by means of a conductive adhesive can be dispensed with. Advantageously, an electrically conductive, integral connection is dispensed with in the mutually arranged, electrically connected contact structures of the solar cells of the solar cell module.

[0019] In particular, it is sufficient to ensure a mechanical connection by aligning the metallic contact structures in the overlapping area. Contrary to previous teaching, if an electrically conductive adhesive is omitted, there is no, or at least no significant, increase in the contact resistance between the two adjacent contact structures in the overlapping area, so that the module efficiency is not reduced or is only slightly reduced. In particular, the cost savings due to the savings in conductive adhesive and the simplification of the manufacturing process more than compensate for even a slight deterioration in the module efficiency.

[0020] Advantageously, the solar cell module is designed such that the contact structures arranged next to one another are mechanically fixed, in particular, positively fixed. This prevents relative movement of the solar cells, which could impair the electrical contact between the solar cells arranged next to one another. The mechanical fixation can be materially bonded and / or positively bonded. Positively bonded fixation using a flexible encapsulation element, as described below, is advantageous.

[0021] Typically, a solar cell module comprises a module carrier substrate and at least one flexible encapsulation element. The encapsulation element is fluid-tightly connected to a counter-encapsulation element, with the solar cells arranged between the encapsulation element and the counter-encapsulation element. The encapsulation element is preferably formed as an encapsulation film, in particular as an ethylene-vinyl acetate film (EVA film).

[0022] It is within the scope of the invention that the encapsulation element is arranged directly on the module carrier substrate, so that the module carrier substrate forms the encapsulation counter-element in this embodiment.

[0023] However, it is advantageous to form the encapsulation counter-element as a separate element from the module carrier substrate. In this embodiment, the encapsulation element and the encapsulation counter-element are arranged on the module carrier substrate.

[0024] Advantageously, the encapsulation counter-element is also designed as a flexible encapsulation counter-element, in particular an encapsulation counter-element film, preferably as an ethylene vinyl acetate film (EVA film).

[0025] The present invention therefore has the particular advantage that the typical, established methods for producing a solar cell module, in particular by means of lamination, achieve a positive fit and fixing of the solar cells by means of the encapsulation film.

[0026] In particular, the known layer structure of a solar cell module can be retained. Advantageously, the solar cell module therefore comprises a module carrier substrate made of glass, an encapsulation element formed as an encapsulation film, in particular EVA film, a counter-encapsulation element formed as a counter-encapsulation film, in particular EVA film, and a backsheet. These elements are advantageously arranged in the following order: glass, encapsulation film, solar cells, encapsulation film, backsheet.

[0027] In the method according to the invention, the solar cells are therefore advantageously arranged between a counter-encapsulation element and a flexible encapsulation element, in particular an encapsulation film, wherein the encapsulation element is arranged fluid-tightly on the counter-encapsulation element, and a positive connection is preferably formed at least between the encapsulation element and the solar cells in order to fix the solar cells. The connection between the flexible encapsulation element and the counter-encapsulation element is preferably achieved by lamination.

[0028] To reduce the risk of a reduction in module efficiency due to series resistance losses at the contact points between the metallic contact structures in the overlapping areas, it is advantageous for the metallic contact structures to be directly adjacent to one another, without the interposition of joining layers, in particular adhesive layers. In an advantageous embodiment, the electrically conductively connected contact structures arranged adjacent to one another are therefore free of any integral bonding, in particular free of any integral bonding by means of an adhesive.

[0029] Preferably, lamination occurs after the solar cells are arranged between the encapsulation element and the counter-encapsulation element. After lamination, arranging the solar cells between the encapsulation element and the counter-encapsulation element reduces the risk of the solar cells shifting relative to one another.

[0030] During the lamination process, at least the encapsulation element melts. It is therefore advantageous to fix the solar cells with a heat-resistant element before lamination: To prevent the solar cells arranged in a shingle arrangement from slipping during the manufacturing process, it is advantageous for adjacent, overlapping solar cells to be mechanically fixed to one another in a materially bonded and electrically non-conductive manner. Such fixation can be achieved, as described below, in an advantageous embodiment using one or more electrically non-conductive adhesive tapes as fixing elements and / or an electrically non-conductive adhesive film as fixing element. It is also within the scope of the invention to use both electrically non-conductive adhesive tapes and an electrically non-conductive adhesive film for fixing.

[0031] The adhesive tapes are therefore preferably designed as flexible, electrically non-conductive fixing elements. It is particularly advantageous for the adhesive tapes to be coated with adhesive on at least one side to form a cohesive, electrically non-conductive connection with the solar cells.

[0032] The adhesive film is thus preferably designed as a flexible, electrically non-conductive fixing element. It is particularly advantageous for the adhesive film to be coated with adhesive on at least one side to form a materially bonded, electrically non-conductive connection with the solar cells.

[0033] In an advantageous embodiment, two adjacent solar cells are each secured by a fixing element formed as an electrically non-conductive adhesive tape. The fixing elements are preferably arranged on the rear sides of the solar cells facing away from the incident radiation. It is also within the scope of the invention for the fixing elements to be arranged on the front side of the solar cells facing the incident radiation, in particular for the fixing elements to be transparent.

[0034] In an advantageous embodiment, several solar cells, in particular all solar cells of the solar cell module, are fixed by means of an electrically non-conductive fixing element, wherein the solar cells are preferably arranged integrally on the fixing element. The fixing element is preferably designed as a flexible fixing element, in particular as a film, particularly preferably as an adhesive film.

[0035] In an advantageous embodiment, a majority of the solar cells, preferably all of the solar cells, are fixed by means of an electrically non-conductive adhesive film that at least partially covers the solar cells. The adhesive film can be arranged on the rear side of the solar cells facing away from the incident radiation. It is also within the scope of the invention for the adhesive film to be arranged on the front side of the solar cells facing the incident radiation, in particular for the adhesive film to be transparent.

[0036] Preferably, the adhesive film covers the solar cells completely.

[0037] It is also within the scope of the invention for the solar cells to be fixed with an electrically non-conductive adhesive film covering several solar cells, preferably all of them, and for adjacent solar cells to be fixed with electrically non-conductive adhesive tapes. This achieves a more stable fixation. Preferably, the adhesive film and the adhesive tapes are arranged on opposite sides of the solar cells.

[0038] The fixing element, in particular all fixing elements, are preferably heat-resistant, so that the fixing elements do not melt during lamination and thus prevent relative movement of solar cells during lamination. Therefore, the fixing element, in particular all fixing elements, preferably have a melting point greater than 120°C, in particular greater than 160°C.

[0039] It is essential that the mutually arranged contact structures of adjacent solar cells are fixed by means of electrically non-conductive adhesive applied between the contact structures. Studies show that, despite these electrically non-conductive surfaces and the slight spacing of the adjacent contact structures in the bonding areas, a sufficiently low contact resistance can still be achieved. In this advantageous embodiment, the bonding surfaces are preferably formed with a thickness of less than 200 µm, in particular less than 100 µm. Advantageously, the electrically non-conductive bonding surfaces cover less than 20%, preferably less than 10%, of the contact area of the adjacent contact structures.

[0040] The electrically non-conductive adhesive preferably has a melting point greater than 120°C, in particular greater than 160°C, in order to ensure that the solar cells are fixed even during lamination.

[0041] It is within the scope of the invention for the solar cells to be fixed both with non-conductive adhesive as described above and additionally with one or more fixing elements, in particular adhesive tapes and / or an adhesive film as described above. This achieves a more stable fixation.

[0042] In the method according to the invention, it is essential that, before the solar cells are arranged between the module carrier substrate and the encapsulation element, adjacent, overlapping solar cells are advantageously mechanically fixed to one another in a materially bonded and electrically non-conductive manner, in particular by means of an electrically non-conductive adhesive. As described above, the contact structures arranged adjacent to one another and electrically conductively connected are advantageously free of any materially bonded connection, in particular free of any materially bonded connection by means of an adhesive.

[0043] In an advantageous embodiment, the mechanical fixation is achieved by means of one or more electrically non-conductive adhesive tapes and / or an adhesive film as described above. It is also within the scope of the invention for the fixation to be achieved by means of a mechanically non-conductive adhesive and additionally by means of one or more electrically non-conductive adhesive tapes and / or an adhesive film as described above. This achieves a more stable fixation.

[0044] Further advantageous features and embodiments are explained below using an exemplary embodiment and the figures. Herein: Fig. 1 Front and rear view of a photovoltaic solar cell for an embodiment of a solar cell module according to the invention; Fig. 2 shows an embodiment of a solar cell module according to the invention in side view and a modification of the embodiment; and Fig. 3 further training of the Fig. 2b shows an embodiment of a solar cell module according to the invention immediately before lamination.

[0045] All figures are schematic representations, not to scale. Identical reference symbols in the figures indicate identical or equivalent elements.

[0046] In Fig. 1 shows a front view of a schematic representation of a photovoltaic solar cell for an embodiment of a solar cell module according to the invention. The solar cell 1 has Fig. 1 a) has a metallic front-side contact structure 2, which is comb-shaped in a known manner, with several parallel contact fingers 2a that are electrically connected by a busbar 2b running perpendicular to the contact fingers 2a. The contact finger shown at the bottom is identified by reference numeral 2a.

[0047] The solar cell is designed in a manner known per se as a photovoltaic solar cell based on a silicon wafer as a semiconductor substrate and has an emitter on the front side, which is electrically contacted by means of the contact fingers 2a and the busbar 2b.

[0048] In part b) the Fig. Figure 1 shows a plan view of the back of the solar cell. The back is fully covered with an aluminum layer, which is electrically connected to a base of the solar cell. A metallic back contact structure 3, designed in the form of a busbar, is arranged at one edge and electrically connected to the aluminum layer. In this case, the back contact structure is made of silver.

[0049] It is within the scope of the invention to use further developments of this solar cell structure or other solar cell structures as solar cells for a solar cell module according to the invention.

[0050] The Fig. The solar cell shown in Figure 1 represents a partial solar cell produced by dividing a larger silicon substrate on which several partial solar cells were formed. It is also within the scope of the invention to use solar cells produced entirely on an undivided silicon wafer.

[0051] The backside contacting structure 3 and the busbar 2b of the frontside contacting structure 2 are arranged at opposite edges of the solar cell 1.

[0052] A schematic representation of an embodiment of a solar cell module according to the invention is shown in Fig. 2a) shown in side view: The solar cell module according to the exemplary embodiment has a plurality of photovoltaic solar cells 1. For greater clarity, only four photovoltaic solar cells are shown here. It is within the scope of the invention for a solar cell module according to the invention to have a large number of photovoltaic solar cells, in particular at least ten, more preferably at least twenty photovoltaic solar cells. It is also within the scope of the invention for the solar cell module to have a plurality of linear solar cell strings, wherein each solar cell string has a plurality of solar cells in a shingle arrangement. In particular, it is within the scope of the invention for a plurality of solar cell strings to be arranged next to one another in parallel.

[0053] In the solar cell module according to the embodiment in Fig. 2a), the solar cells 1 are arranged overlapping in a shingle arrangement, so that the rear contact structure 3 of a solar cell 1 is arranged on the front contact structure 2, in this case on the busbar 2b of an adjacent solar cell 1, and the two contact structures are electrically conductively connected due to their adjacent arrangement.

[0054] It is essential that the mutually arranged, electrically conductively connected contact structures 3 and 2b are free of an electrically conductive material connection. Fig. In the embodiment shown in Fig. 2a), no intermediate layers are arranged to form an electrically conductive or material-locking connection between the front-side contact structure 2 and the rear-side contact structure 3.

[0055] Due to the shingle arrangement, the solar cells overlap in an overlap area 4.

[0056] In an alternative development of the exemplary embodiment, electrically non-conductive adhesive tapes 7 are arranged between the solar cells 1 on the backs of the solar cells. This is shown in Fig. 2 b). The adhesive tapes 7 form a material bond with the solar cells and fix the solar cells together.

[0057] In an alternative embodiment, the adhesive tapes are transparent and arranged on the front side of the solar cells. In another alternative embodiment, all solar cells are fixed together by means of an adhesive film covering the backs of the solar cells.

[0058] Previously known solar cell modules typically have mounting and encapsulation elements. In further developments of the previously described embodiments of solar cell modules, the previously described solar cell modules have at least one transparent module carrier substrate made of glass, which serves to stabilize and / or protect the solar cells on the radiation-facing side.

[0059] In further modifications, the above-described embodiments of solar cell modules additionally comprise one or more, preferably all, of the following elements: - a transparent module carrier substrate, in particular made of glass, - one flexible encapsulation element formed as a film or several flexible encapsulation elements formed as a film, in particular made of EVA film, - a back cover, in particular a PET film.

[0060] In Fig. 3 is a further development of the Fig. 2b shows the embodiment of a solar cell module according to the invention immediately before lamination. The solar cells 1 are fixed by means of adhesive strips 7 applied to the back.

[0061] The solar cell module according to the embodiment comprises a module carrier substrate 5 formed as glass, a flexible encapsulation element 6, in this case an EVA film, as well as a flexible encapsulation counter element 8, in this case also an EVA film, and a back cover 9, in this case made of a PET-based film.

[0062] The encapsulation element 6 is arranged fluid-tight on the encapsulation counter-element 8, wherein the solar cells are arranged in a shingle arrangement between the encapsulation element 6 and the encapsulation counter-element 8.

[0063] Fig. 3 shows the state before a negative pressure, in this case less than 1 mbar, is generated in the lamination chamber and a membrane subsequently presses against the rear cover, in this case with a pressure of 900 mbar, so that the encapsulation element 6 rests flatly and positively, in particular, against the solar cells 1, so that the solar cells 1 and in particular the front-side contact structures 2 with the busbars 2b are fixed to the rear-side contact structures 3. This state is fixed by lamination. During lamination, the adhesive tapes 7 prevent any relative movement of the solar cells 1 to one another.

[0064] A cell connector 10 is arranged on each of the edge solar cells: on the top solar cell 1 on the back contact structure 3 and on the Fig. 3 bottom solar cell 1 to the busbar 2b. The cell connectors 10 are used to connect the solar cell string to other solar cell strings or to external circuits.

[0065] The representation according to Fig. Figure 3 is not to scale; in particular, for clarity, the solar cells are shown with a greatly enlarged thickness. The distance between the module carrier substrate 5 and the back cover 9 is considerably smaller in real modules, where solar cells typically have a thickness in the range of 50 µm to 200 µm.

[0066] In a modification of the exemplary embodiment, joining surfaces are formed at specific points between the busbar 2b of the front-side contacting structure and the rear-side contacting structure 3 for mechanical stabilization, in this case by means of a non-conductive adhesive.

[0067] In a further modification of the exemplary embodiment, the adhesive tapes 7 are omitted. Instead, all solar cells are fixed to one another by means of an adhesive film covering the backs of the solar cells. List of reference symbols 1 solar cell 2 Front contact structure 2a Contact finger 2b Busbar 3 Back contact structure 4 Overlap area 5 Module carrier substrate 6 Encapsulation element 7 Adhesive tape 8 Encapsulation counter element 9 Back cover 10 cell connectors

Claims

[1] Solar cell module, with a plurality of photovoltaic solar cells, each having at least two metallic contact structures: - a metallic front-side contact structure (2) on a front side and - a metallic back contact structure (3) on a back side the solar cell (1), wherein the solar cells are arranged overlapping in a shingle arrangement, so that the rear contact structure (3) of a solar cell (1) is arranged on the front contact structure (2) of an adjacent solar cell (1) and the two contact structures are electrically conductively connected, wherein the contact structures arranged on one another and connected in an electrically conductive manner are free from an electrically conductive material connection, in particular free from an electrically conductive material connection by means of a conductive adhesive, wherein adjacent, overlapping solar cells are mechanically fixed to one another in a material-to-material and electrically non-conductive manner, and that the contact structures of adjacent solar cells arranged next to one another are fixed by means of electrically non-conductive adhesive applied between the contact structures arranged next to one another. [2] Solar cell module according to claim 1, characterized by that the solar cell module is designed such that the contact structures arranged next to one another are mechanically fixed in a form-fitting manner. [3] Solar cell module according to claim 2, characterized by , that the solar cell module has at least one flexible encapsulation element (6), in particular an encapsulation film, wherein the encapsulation element (6) is arranged fluid-tight on a counter-encapsulation element (8) of the solar cell module and the solar cells are arranged between the counter-encapsulation element (8) and the encapsulation element (6), wherein the encapsulation element preferably rests positively on the solar cells, in particular it is advantageous that the solar cells of the solar cell module arranged on one another are fixed positively by means of the encapsulation element and the encapsulation counter-element (8). [4] Solar cell module according to one of the preceding claims, characterized by that the mechanical fixation of the overlapping solar cells is achieved by means of one or more adhesive tapes and / or an adhesive film. [5] Method for producing a solar cell module, with the procedural steps Providing a plurality of photovoltaic solar cells, each having at least two metallic contact structures: - a metallic front-side contact structure (2) on a front side and - a metallic back contact structure (3) on a back side the solar cell (1), and overlapping arrangement of the solar cells in a shingle arrangement, so that the rear contact structure (3) of a solar cell (1) is arranged on the front contact structure (2) of an adjacent solar cell (1) and the two contact structures are electrically conductively connected, wherein the electrically conductively connected contacting structures are arranged to one another free from an electrically conductive material connection, in particular contacting structures are arranged to one another free from an electrically conductive material connection by means of a conductive adhesive characterized by , that, before arranging the solar cells between the module carrier substrate (5) and the encapsulation element (6), adjacent, overlapping solar cells are mechanically fixed to one another in a material-to-material and electrically non-conductive manner, and that the contact structures of adjacent solar cells arranged on one another are fixed by means of electrically non-conductive adhesive applied between the contact structures arranged on one another. [6] Method according to claim 5, characterized by , the solar cells are arranged between a module carrier substrate (5) and a flexible encapsulation element (6), in particular an encapsulation film, wherein the encapsulation element (6) is arranged fluid-tight on the module carrier substrate (5). [7] Method according to claim 6, characterized by that the mechanical fixation of the overlapping solar cells is achieved by means of one or more adhesive tapes and / or an adhesive film.

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