Improved solar cell string for use in photovoltaic modules - Patents.com

Abstract

The present invention relates to a solar cell string (1) for a photovoltaic module, comprising: (i) a string of solar cells (2a, 2b, 2c) facing each other with opposite polarities and arranged in a shingle-like arrangement in the string direction with or without overlapping portions of the solar cells, (ii) at least one elongated conductive interconnection (3a, 3b) extending in the string direction from one side of one solar cell to the opposite side of an adjacent solar cell (2a, 2b, 2c) for mechanically and electrically connecting the positive and negative electrodes of the solar cells (2a, 2b, 2c) arranged in a shingle-like arrangement in the string direction on the alternating top and bottom surfaces of the solar cells, and (iii) optionally a thermal adhesive foil (4a , 4b), wherein the at least two adhesives (4a, 4b) cover at least one elongated interconnection (3a, 3b) and at least a portion of the top or bottom surface of each solar cell including the elongated interconnection, wherein (a) there are no horizontal gaps between the solar cells arranged in a shingle-like manner, and (b) the adhesives (4a, 4b) are not in contact with each other, do not extend beyond one solar cell, and do not extend into the optional partially overlapping areas of the solar cells (2a, 2b, 2c), and at least partially cover at least one interconnection (3a, 3b) to mechanically secure the at least one interconnection (3a, 3b) to the solar cells (2a, 2b, 2c).

Description

Detailed Description of the Invention

[0001] The present invention relates to a solar cell string (1) for a photovoltaic module, comprising: (i) a string of a plurality of solar cells (2a, 2b, 2c) facing each other with opposite polarity and arranged in a shingle-like arrangement in the string direction with or without overlapping portions of the solar cells (2a, 2b, 2c), (ii) at least one elongated conductive interconnect (3a, 3b) extending in the string direction from one side of a solar cell to the opposite side of a neighboring solar cell (2a, 2b, 2c) for mechanically and electrically connecting the positive and negative electrodes of the plurality of solar cells (2a, 2b, 2c) arranged in a shingle-like arrangement in the string direction on the alternating top and bottom surfaces of the plurality of solar cells, and (iii) optionally a thermal adhesive foil (4a , 4b), covering at least one elongated interconnect portion (3a, 3b) and at least a portion of the top or bottom surface of each solar cell including the elongated interconnect portion, wherein (a) there are no horizontal gaps between the solar cells arranged in a shingle-like arrangement, and (b) the adhesives (4a, 4b) are not in contact with each other, do not extend beyond one solar cell, and do not extend into the optional partially overlapping portions of the solar cells (2a, 2b, 2c), and at least partially cover the at least one interconnect portion (3a, 3b) to mechanically secure the at least one interconnect portion (3a, 3b) to the solar cells (2a, 2b, 2c).

[0002] Typically, a photovoltaic module is assembled from many solar cell strings, i.e. solar cell panels, which are individually manufactured and shipped separately. The solar cell strings are arranged side by side to form one large flat body. The solar cells in a solar cell string are electrically interconnected by wires or ribbons that connect the electrode side of one cell with the electrode side of an adjacent cell, so that the current flows in the string direction. A solar cell string with solar cells arranged in a regular parallel arrangement is characterized by a front-front configuration. In the front-front configuration, all the front faces of the multiple cells have the same electrode charge, and a wire or ribbon will connect the front electrode of one cell with the oppositely charged rear electrode of the adjacent cell.

[0003] The most common interconnection scheme features a certain gap between adjacent cells to allow for the guidance of an interconnect from the top surface of one cell to the bottom surface of the connected cell.

[0004] In an alternative method, multiple solar cells may be connected by a slight overlap, thus allowing adjacent cells to be in direct conductive contact.

[0005] The overlapping solar cell strings in a shingled arrangement do not require traditional wire or ribbon interconnects due to the proximity of the oppositely charged cell electrodes. Mechanical and conductive contact is routinely achieved by adding low resistance conductive interconnect materials such as conductive adhesive compounds. The metallization interconnects are often quite thick to improve current flow. Because gaps for electrical insulation between solar cells in a front-front configuration are no longer required, solar cells and solar cell strings in a shingled front-back configuration can be smaller in size, providing an opportunity to achieve higher module efficiency.

[0006] However, mechanical stress on the interconnects at the overlap of multiple solar cells in a shingle arrangement can cause (micro)cracks and, in some cases, a reduction in the current flow or even an electronic short circuit due to thermomechanical stresses. A shingle arrangement of solar cells with direct contact in the overlap area has the further disadvantage that the overlap is relatively large. This is necessary to ensure good contact. The overlap is no longer available for current formation.

[0007] WO 2019 / 016118 A1 discloses a solar cell string including: (i) a string of solar cells arranged in a shingle-like arrangement in the string direction, with the positive and negative electrodes overlapping; (ii) an interconnection for electrically connecting the positive and negative electrodes of the solar cells arranged in a shingle-like arrangement; and (iii) an adhesive foil extending over at least a portion of the string, the adhesive foil being arranged on (a) the top surfaces (facing the sun) of at least two of the solar cells arranged in a shingle-like arrangement, and / or (b) the bottom surfaces (farther away) of at least two of the solar cells arranged in a shingle-like arrangement, or (c) the top surface of a solar cell and the bottom surface of a solar cell overlapping it. In this case, the adhesive foil includes the interconnection and connects the overlapping points so as to mechanically connect and arrange the solar cells arranged in a shingle-like arrangement.

[0008] US Patent No. 7,432,438 (B2) relates to an electrode for contacting a conductive surface of a photovoltaic element. The electrode comprises an electrically insulating, optically transparent film, an adhesive layer provided on the plane of the film, and a plurality of substantially parallel conductive wires embedded in the adhesive layer. The wires are present over the plane of the film, and the adhesive layer has a thickness smaller than the thickness of the wires embedded in the adhesive layer. Parts of the surfaces of the wires protrude from the adhesive layer, and at least a part of the surfaces is covered with a coating of an alloy having a low melting point to facilitate soldering of the wires to the conductive surface and to a first terminal bar.

[0009] It is an object of the present invention to provide a conductively efficient and mechanically stable solar cell string for use in the assembly of a photovoltaic module, in particular to provide a conductively efficient and mechanically stable solar cell string arranged in a shingle-like arrangement.

[0010] In a first aspect of the invention, the object of the invention is a solar cell string (1) for use in a photovoltaic module, comprising: (i) at least two strings of solar cells (2a, 2b, 2c) facing each other with opposite polarity and arranged in a shingle-like arrangement in the string direction with or without overlapping portions of said solar cells; and (ii) at least one elongated conductive interconnect (3a, 3b), optionally a wire, ribbon or busbar, extending in the string direction from one side of a solar cell to the opposite side of a neighboring solar cell (2a, 2b, 2c) for mechanically and electrically connecting the positive and negative poles of the solar cells (2a, 2b, 2c) arranged in a shingle-like arrangement in the string direction on the alternating top and bottom surfaces of the solar cells. 3b); and (iii) at least two adhesives (4a, 4b), optionally thermal adhesive foils, covering at least one elongated interconnect (3a, 3b) and at least a portion of the top or bottom surface of each solar cell including the elongated interconnect, wherein (a) there are no horizontal gaps between the solar cells arranged in a shingle-like arrangement, and (b) the adhesives (4a, 4b) are not in contact with each other, do not extend beyond one solar cell, and do not extend into the optional partially overlapping areas of the solar cells (2a, 2b, 2c), and at least partially cover the at least one interconnect (3a, 3b) to mechanically secure the at least one interconnect (3a, 3b) to the solar cells (2a, 2b, 2c).

[0011] The term "solar cell string" as defined herein includes any mechanical and conductive arrangement of two or more solar cells that photovoltaically generate and transport electrical current along a number of solar cells arranged side-by-side in a string direction, i.e., in the direction of current flow from the solar cell at one end to the solar cell at the opposite end.

[0012] The solar cell string according to the present invention is for use in a photovoltaic module, i.e. for assembly and forming part of a functional photovoltaic module. Optionally, the solar cell for use in the present invention is a conventional solar cell. For example, a semiconductor material is disposed between the top and bottom surfaces (e.g., an anode material and a cathode material, i.e., a positive electrode and a negative electrode). This may be formed, for example, by metallization or by a transparent conductive coating, e.g., a transparent film coating.

[0013] The term "shingled in string direction" as used herein is intended to indicate that adjacent solar cells are vertically offset in the string direction. In a string of solar cells arranged according to the invention, the solar cells are shingled with or without overlap (the solar cells are shingled with overlap or without overlap). This means that the successive solar cells partially cover each other, i.e., the upper cell partially shades the lower solar cell that is vertically offset, or the successive solar cells are vertically offset but do not form horizontal gaps.

[0014] The overlap edge areas of the vertically offset lower solar cells are optionally minimized to avoid loss of photovoltaic activity due to shading in the resulting solar module.

[0015] The solar cell string according to the present invention comprises at least one elongated conductive interconnect (3a, 3b) extending in the string direction from one side of a solar cell to the opposite side of a neighboring solar cell (2a, 2b, 2c) for mechanically and electrically connecting the positive and negative poles of a plurality of said solar cells (2a, 2b, 2c) arranged in a shingle-like arrangement in the string direction on the alternating top and bottom surfaces of said plurality of solar cells. The at least one elongated conductive interconnect (3a, 3b) is optionally a wire or a busbar.

[0016] In an alternative embodiment of the invention, the solar cell string (1) according to the invention is a solar cell string in which the solar cells in a shingle-like arrangement are at least partially overlapping and the interconnects (3a, 3b) are not fixed to at least one or both of the solar cells in the overlapping area. This alternative has the advantage that some additional mechanical flexibility is maintained in the overlapping area by the shingle-like arrangement of the solar cell string.

[0017] In another alternative embodiment, the solar cells in a shingle arrangement do not overlap within the solar cell string.

[0018] In the solar cell string according to the present invention, the interconnects for mechanically and electrically connecting the electrodes of the solar cells arranged in a shingle-like arrangement may be any material that performs the above functions. For example, at least one of the elongated interconnects (3a, 3b) may optionally be a wire, ribbon or busbar, and may further connect all the contact structures on each solar cell. The contact structures may optionally be contact fingers.

[0019] In an optional embodiment, the solar cell string (1) of the present invention is a solar cell string in which the height or diameter of at least one of the elongated interconnects (3a, 3b) determines a minimum vertical offset (5) of adjacent solar cells in the solar cell string (1), the minimum vertical offset (5) being optionally a gap (5). In other words, consecutive adjacent solar cells are vertically separated and mechanically connected only by the interconnects, and the mechanical flexibility of the interconnects substantially determines the flexibility of the solar cell string.

[0020] For example, at least one of the interconnects (3a, 3b) is selected from the group consisting of a busbar, a ribbon, and a metal wire, the metal wire being optionally a metal wire coated with a solderable material, the solderable material being optionally a solder containing Ag, Cu, Bi, In, Pb, Sn, and combinations thereof, the solder containing Ag, Cu, Bi, In, Pb, Sn, and combinations thereof being optionally a SnBi-containing solder or an In-containing solder. In a non-limiting embodiment, the interconnects (3a, 3b) may be in mechanical and electrical contact with a conductive layer on the solar cell.

[0021] The solar cell string according to the invention comprises at least two adhesives (4a, 4b) covering at least one of said elongated interconnects (3a, 3b) and at least a part of said top or bottom surface of each solar cell comprising said elongated interconnects, said at least two adhesives (4a, 4b) being optionally thermal adhesive foils.

[0022] It is commonly understood that an adhesive used on the top surface of a solar cell, i.e., the adhesive facing the sun, must be transparent to sunlight to initiate and continue the photovoltaic process within the solar cell. The adhesive does not have to be transparent if it does not substantially prevent sunlight from reaching the photovoltaically active top surface, or if the adhesive is placed on the bottom, i.e., light-shielded side, of the solar cell.

[0023] The adhesives (4a, 4b) are, for example, adhesive foils, optionally thermal adhesive foils. The adhesives (4a, 4b) are or include polymer foils, optionally selected from the group consisting of duroplast, optionally EVA (ethylene vinyl acetate), TPSE (thermoplastic silicone elastomer), TPU (thermoplastic polyurethane), PET (polyethylene terephthalate), TPO (thermoplastic polyolefin elastomer), ionomer, thermoplast; optionally PVB (polyvinyl butyral), silicone, polyolefin (PO), PP (polypropylene), ionomer; and thermoduroplast combinations, and the polymer foils are optionally thermally adhesive in a temperature range of 50 to 250°C, optionally in a temperature range of 60 to 200°C, optionally in a temperature range of 75 to 175°C.

[0024] The solar cell string of the present invention is unique in that (a) there are no horizontal gaps between the solar cells arranged in a shingle-like manner, i.e., the solar cells are either partially overlapping or the horizontal distance between adjacent cells, i.e., the gap (5), is zero, and (b) the adhesives (4a, 4b) are not in contact with each other and do not extend beyond a solar cell and do not extend into the optional partially overlapping areas of the solar cells (2a, 2b, 2c) and at least partially cover at least one interconnect (3a, 3b) to mechanically secure the at least one interconnect (3a, 3b) to the solar cells (2a, 2b, 2c).

[0025] The solar cell strings and embodiments thereof described herein have many advantages. For example, the adhesive, especially the adhesive foil, only bonds the interconnects / wires on each solar cell and does not extend to the neighboring solar cells. Therefore, mechanical stability, limited flexibility and connectivity are provided substantially only by the interconnects connecting the solar cells. Also, these interconnects do not span any horizontal gaps between consecutive solar cells. This avoids mechanical stress when bending the interconnects between solar cells too much, but provides some limited mechanical flexibility. This of course depends on the flexibility of the interconnect material used, as well as the dimensions and shape (e.g., wire or ribbon shape) of the interconnect material used.

[0026] Optionally, the adhesive (eg, a thermal adhesive foil) does not extend into areas where consecutive solar cells overlap.

[0027] In another embodiment of the present invention, the interconnects in the overlapping areas of consecutive solar cells in a solar cell string are not electrically or mechanically connected (e.g., not soldered) to the solar cells, thereby saving expensive connecting materials, such as solder paste (e.g., silver-containing solder paste).

[0028] Also, for the alternative where no adhesive (e.g., thermal adhesive foil) extends into the overlapping area of ​​two consecutive solar cells in a solar cell string, there is less stress during adhesive lamination, resulting in improved process yields, and the absence of adhesive foil reduces bending stress on the interconnect after lamination.

[0029] In general, the solar cell string according to the invention is more flexible but resilient against mechanical stresses, e.g., mechanical stresses during transportation, weather impact, etc. Also, the solar cell string according to the invention is easy and economical to manufacture, since, for example, the interconnects (e.g., wires) may be placed and fixed to the adhesive (e.g., foil) first, followed by the placement and fixing of the solar cells in a shingle-like arrangement. Alternatively, the interconnects (e.g., wires) may be placed and fixed to a series of solar cells first, followed by the placement and fixing of the adhesive foil.

[0030] Further aspects of the invention relate to methods of making the solar cell strings described herein, and to photovoltaic modules including the solar cell strings.

[0031] In the following, the present invention is illustrated by representative examples and figures, none of which should be construed as limiting the scope of the invention beyond the appended claims.

[0032] (List of reference numbers) (1) Solar cell string (2)(2a, 2b, 2c) Solar cells (3a, 3b) Conductive interconnects (4a, 4b) Adhesive (optionally a thermal adhesive foil) (5) Vertical offset (gap) between adjacent solar cells in a solar cell string (drawing) FIG. 1 is a schematic diagram of a solar cell string 1 arranged like a roof shingle, with three consecutive solar cells 2a, 2b, 2c partially overlapping at their edges, for use in the assembly of a photovoltaic module according to the invention. The interconnects 3a, 3b may be implemented, for example, as bus bars, ribbons and metal wires, optionally as metal wires coated with a solderable material, as described, for example, herein. The dashed lines indicate that the structure is arranged below the solar cells. For example, the interconnect 3a is arranged on the top (facing the sun) of the solar cell 2a, and continues as the (shaded) interconnect 3b when arranged below the solar cell 2b. The adhesive foil 4a is transparent. On the other hand, the adhesive foil 4b may optionally not be transparent, since in practical operation it will be shaded anyway. The adhesive foil 4a adheres the interconnect 3a to the top surface of the solar cell 2a, and extends slightly into the overlap 5 of the solar cells 2a and 2b. The adhesive foil 4a therefore contributes to the minimum vertical offset together with the height or diameter of the interconnect 3a. In an alternative embodiment, the adhesive foil 4a does not extend into the overlap 5 and the vertical offset is determined only by the height or diameter of the interconnect 3a. The adhesive foil 4b adheres, i.e. fixes, the interconnect 3b to the bottom surface of the solar cell 2b and may or may not extend into the partial overlap 5 of the solar cell 2a and the solar cell 2b. Optionally, the interconnect 3a, 3b may not be adhered, i.e. fixed, to the solar cell 2a, 2b in the overlap region 5 and the interconnect 3a, 3b may have limited mechanical flexibility, e.g. be bendable, depending on the shape, material properties and flexibility of the interconnect 3a, 3b.

[0033] Figure 2 is a side view of one embodiment of the solar cell string of Figure 1. Adhesive 4a, 4b, for example a thermal adhesive foil, bonds interconnects 3a, 3b to solar cells 2 but does not extend into the overlapping area. The vertical offset of the solar cells is substantially determined by the height or diameter of interconnects 3a, 3b.

[0034] Figure 3 is a side view of the solar cell string of Figure 2 with optional wire-shaped interconnects 3a, 3b. The vertical offset of the solar cells 2 is substantially determined by the diameter of the interconnects 3a, 3b. The adhesive foils 4a, 4b do not extend into the overlapping areas of the solar cells 2. [Brief description of the drawings]

[0035] [Figure 1] FIG. 2 shows a schematic diagram of a solar cell string 1 arranged like a roof shingle, having three consecutive solar cells 2a, 2b, 2c partially overlapping at their ends, for use in the assembly of a photovoltaic module according to the present invention. [Diagram 2] FIG. 2 is a side view of an embodiment of the solar cell string in FIG. [Diagram 3] FIG. 3 is a side view of the solar cell string of FIG. 2 with optional wire-form interconnects 3a, 3b.

Claims

1. A solar cell string (1) for use in a photovoltaic module, comprising: (i) at least two strings of solar cells (2a, 2b, 2c) facing each other with opposite polarities and having a portion where the solar cells (2a, 2b, 2c) overlap each other, the strings being arranged in a shingle-like manner in the string direction; (ii) at least one elongated conductive interconnect, wire, ribbon or busbar (3a, 3b) for mechanically and electrically connecting the positive and negative electrodes of the plurality of solar cells (2a, 2b, 2c) arranged in a shingle-like arrangement in the string direction on the alternating top and bottom surfaces of the plurality of solar cells (2a, 2b, 2c), the at least one elongated conductive interconnect, wire, ribbon or busbar (3a, 3b) extending in the string direction from one side of one of the solar cells (2a, 2b, 2c) to an opposite side of a neighboring solar cell (2a, 2b, 2c) of the one of the solar cells (2a, 2b, 2c); (iii) at least two adhesive or thermal adhesive foils (4a, 4b) covering at least one of the elongated interconnects, wires, ribbons or busbars (3a, 3b) and at least a part of the top or bottom surface of the solar cells (2a, 2b, 2c) through which the elongated interconnects, wires, ribbons or busbars (3a, 3b) extend; Including, (a) there is no gap in the string direction between the solar cells (2a, 2b, 2c) arranged in a shingle-like manner; (b) the adhesive or thermal adhesive foils (4a, 4b) are not in contact with each other, do not extend beyond one of the solar cells (2a, 2b, 2c), and do not extend into the overlapping area of ​​the solar cells (2a, 2b, 2c), and at least partially cover the at least one interconnect, wire, ribbon or busbar (3a, 3b) to mechanically fasten the at least one interconnect, wire, ribbon or busbar (3a, 3b) to the solar cells (2a, 2b, 2c).

2. The solar cells (2a, 2b, 2c) arranged in a shingle-like arrangement at least partially overlap each other, 2. The solar cell string (1) of claim 1, wherein the interconnect, wire, ribbon or busbar (3a, 3b) is not attached to at least one or both of the solar cells (2a, 2b, 2c) in the region where the ends of the solar cells (2a, 2b, 2c) overlap.

3. Further comprising a contact structure on the solar cell (2a, 2b, 2c), The solar cell string (1) according to any one of claims 1 to 2, wherein at least one of the elongated interconnects, wires, ribbons or busbars (3a, 3b) further connects all of the contact structures on the solar cells (2a, 2b, 2c).

4. A solar cell string (1) as described in any one of claims 1 to 3, wherein the height or diameter of at least one elongated interconnect, wire, ribbon or busbar (3a, 3b) determines a minimum vertical offset or gap (5) between adjacent solar cells (2a, 2b, 2c) in the solar cell string (1).

5. A solar cell string (1) as described in any one of claims 1 to 4, wherein at least one of the interconnects, wires, ribbons or busbars (3a, 3b) is selected from solders containing Ag, Cu, Bi, In, Pb, Sn and combinations thereof, or SnBi containing solders, or metal wires coated with a material solderable with In containing solders.

6. Further comprising a conductive layer on the solar cell (2a, 2b, 2c), The solar cell string (1) according to any one of claims 1 to 5, wherein the interconnects, wires, ribbons or busbars (3a, 3b) are in mechanical and electrical contact with the conductive layers on the solar cells (2a, 2b, 2c).

7. The plurality of thermal adhesive foils (4a, 4b) are or comprise polymer foils, said polymer foil is selected from the group consisting of EVA (Ethylene Vinyl Acetate), TPSE (Thermoplastic Silicone Elastomer), TPU (Thermoplastic Polyurethane), PET (Polyethylene Terephthalate), TPO (Thermoplastic Porphyrin Elastomer), ionomer, thermoplast; PVB (Polyvinyl Butyral), silicone, polyolefin (PO) and combinations of PP (Polypropylene); The solar cell string (1) according to any one of claims 1 to 6, wherein the polymer foil is a polymer foil having thermal adhesiveness within a temperature range of 50 to 250°C, a temperature range of 60 to 200°C, and a temperature range of 75 to 175°C.

8. A photovoltaic module comprising a solar cell string (1) described in any one of claims 1 to 7.

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