Method for connecting plurality of solar cells into solar cell string, solar cell string, and method for manufacturing solar module

Abstract

The invention relates to a method for connecting a plurality of solar cells (1) into a solar cell string, comprising the following steps: a) providing a plurality of solar cells (1), each having a front side (5) and a rear side (6); b) providing a film (2) in which electrical conductor tracks (3) are embedded; c) electrically connecting the front side (5) of one of the plurality of solar cells (1) to the rear side (6) of the adjacent other of the plurality of solar cells (1) by means of the film (2) embedded with the electrical conductor track (3) in order to produce a solar cell string. In addition, the invention also relates to a solar cell string obtained by the method and a method for manufacturing a solar module by using the solar cell string.

Description

Technical Field

[0001] This invention relates to a method for connecting multiple solar cells into a solar cell string, a solar cell string, and a method for manufacturing a solar module. Specifically, this invention relates to a method for connecting multiple solar cells into a solar cell string using electrical conductor lines, a solar cell string obtained by this method, and a method for manufacturing a solar module using the solar cell string. Background Technology

[0002] As is well known, solar cells can be connected using a soldering process. For this purpose, solar cells have dedicated areas, also known as busbars, for soldering. Busbars are applied to the cells during solar cell manufacturing, for example, through a screen printing process, using expensive silver paste. Due to positioning tolerances in the cell connectors (such as wires) used to connect the solar cells during module manufacturing, some areas of the busbar will always be shaded, even when the cell connectors are perfectly aligned with the busbar; furthermore, poor alignment can lead to additional shading. Shading results in power loss.

[0003] To achieve circuit connections, for example in a soldering process, round wires with copper cores and solder layers are placed on the busbar as battery connectors and secured to the solar cells with pressure plates during soldering. A strong connection is formed after cooling. However, misalignment often occurs when placing the battery connectors on the busbar.

[0004] Alternatively, solder paste or conductive adhesive can be applied to the solar cells, and then the cell connectors can be placed on top and heated. The cell connectors must also be aligned with the coated structure to minimize shading. Another drawback is the need to apply more solder paste or adhesive than necessary, which increases cost and causes shading.

[0005] In subsequent module manufacturing, encapsulation materials, such as ethylene-vinyl acetate copolymer, are used to achieve optical coupling between the solar cell strings formed by the circuit connections and the front and rear glass or film elements. These encapsulation materials must be thick enough to encapsulate the cell connectors and prevent damage from pressure. At the same time, the encapsulation materials absorb incident light, and the greater the thickness, the greater the absorption, leading to power loss. Furthermore, a balance must be struck between light shading and energy loss caused by the resistance of the cell connectors.

[0006] Furthermore, solar cell modules experience temperature fluctuations during operation. The different coefficients of thermal expansion between the cell connectors and the various materials used in the solar cells, such as copper and silicon, create stress on the solder joints and the solar cells. Over time, this can lead to solder joint failure, resulting in significant performance loss.

[0007] EP 3 165 361 A1 also discloses a device similar to a solar module, which has a polymer conductive foil. The polymer conductive foil comprises a polymer film having at least two adjacent regions and an elongated conductor. A first region has sufficient ductility and / or adhesiveness to fix the elongated conductor in position on the outside of the polymer film. A second region adjacent to the first region has a different degree of polymerization and / or crosslinking than the first region. The elongated conductor is disposed on the surface of the first region, which constitutes the outside of the polymer film.

[0008] However, it is still necessary to minimize shading caused by battery connectors or conductors. Furthermore, it is desirable to provide more complex conductor structures that also minimize shading. Summary of the Invention

[0009] The objective of this invention is to provide a method for connecting multiple solar cells into a solar cell string, a solar cell string, and a method for manufacturing a solar module. This method can achieve complex conductor shapes and minimize shading when connecting solar cells.

[0010] According to the invention, this task is accomplished by the method of claim 1, the solar cell string with the corresponding features as described in claim 13, and the method of claim 14. Advantageous improvements and modifications are given in the dependent claims.

[0011] The electrical conductors embedded in the film can have more complex shapes for the circuit connections in solar cells. Furthermore, a smaller shading area can be achieved. Both of these contribute to higher performance.

[0012] This invention relates to a method for connecting multiple solar cells into a solar cell string, comprising the following steps:

[0013] a) Provide multiple solar cells, each with a front and a back side.

[0014] b) Provide a film with embedded electrical conductor lines,

[0015] c) Using the film embedded with electrical conductor lines, the front side of one of a plurality of solar cells is electrically connected to the back side of an adjacent solar cell to manufacture a solar cell string.

[0016] According to the present invention, electrical conductor lines are embedded in the film. This allows for the use of more complex-shaped electrical conductor lines to achieve the circuit connections of the solar cell. Furthermore, it reduces light shading. The film can be multi-layered. A single-layer film made of a single material is even more advantageous.

[0017] "A membrane with embedded electrical conductor lines" refers to a membrane having recesses (e.g., grooves) where the electrical conductor lines are embedded, i.e., integrated within the membrane. Preferably, the embedded electrical conductor lines do not protrude from the membrane surface. Instead, the membrane preferably protrudes relative to the embedded electrical conductor lines, or is flush with them.

[0018] "Adjacent solar cells" refers to the solar cells that are immediately adjacent to the first solar cell mentioned in the generated solar cell string.

[0019] In a preferred embodiment, the film with embedded electrical conductor lines provided in step b) is a single piece in a first variant, and the electrical conductor lines are arranged in the film in a manner extending from one surface of the film to the opposite surface, wherein step c) applies the film with embedded electrical conductor lines to the front side of a solar cell and the back side of an adjacent solar cell to achieve a circuit connection. In this connection, the back side of one solar cell must be circuitically connected to the front side of an adjacent solar cell, and vice versa. The film with embedded electrical conductor lines is guided from the back side of one solar cell to the front side of an adjacent solar cell, or vice versa. The electrical conductor lines embedded in the film are accordingly designed to form contact with the metallization layer of the solar cell, which exists in the form of a front or back electrode of the solar cell. The above embodiment achieves this in a simple manner by providing recesses on the film for embedding electrical conductor lines.

[0020] In the first variant, the electrical conductor lines embedded in the film are preferably rigid conductors, and more preferably wires. The electrical conductor lines embedded in the film are preferably arranged freely in such a way that they can make full or substantially full contact along their extension direction when applied to the front or back of adjacent solar cells.

[0021] In a preferred embodiment, prior to step b), electrical conductor lines are embedded in the film such that the electrical conductor lines extend from one surface of the film to another opposite surface, wherein the resulting first variant of the film with embedded electrical conductor lines is put into use as a single piece in step c).

[0022] In another preferred embodiment, the film with embedded electrical conductor lines provided in step b) has multiple interconnected or connected segments in step c), wherein in step c), one segment is placed on the front side of one solar cell and another segment is placed on the back side of another solar cell. These segments may be the same or different.

[0023] Preferably, the film is single-sided structured prior to step b) to provide a second variant of the film with grooves on one side. For example, the film is structured using a roll-to-roll process with embossing rollers. The embossing is designed to create the grooves, which subsequently exhibit advantageous optical properties. For example, the grooves are triangular in shape. Then, electrical conductor lines are embedded into the grooves by, for example, selective electroplating, and the film is segmented into multiple segments; these two steps can be performed in any order.

[0024] To manufacture a second variant of the film with embedded electrical conductor lines, different materials and / or layers can be used. Preferably, a highly reflective material and a highly conductive material, along with an optional conductive adhesive, are embedded within grooves in the film. It is particularly advantageous to ensure that the electrical conductor lines embedded in the film have the highest possible direct reflectance, thereby making it visually transparent. The first layer is suitable for using a highly reflective material, followed by filling the grooves with a highly conductive material, such as copper. In a next step, the conductive adhesive can be filled into the film, for example, via a roll-to-roll process.

[0025] In a preferred embodiment, multiple embedded electrical conductor lines extend along an extension direction within each segment, with one embedded electrical conductor line extending across this extension direction, preferably perpendicular to it, to form a connection region for connection with another connection region of another segment. The electrical conductor line extending across the extension direction can be designed as a segment. Thus, adhesive membrane regions can exist between the electrical conductor line segments. The connection of these membrane regions can be achieved, for example, by pressure and / or temperature.

[0026] In a preferred embodiment, the segments are preferably connected to form a single film. For this purpose, segments embedded with electrical conductors are stacked so that their connection areas overlap, and then the segments are electrically connected, for example by applying pressure and / or temperature, to form a connector. The resulting connector is then connected to an adjacent solar cell. If the connection area would cause severe shading, it can be positioned on the back side of the solar cell string when connecting adjacent solar cells.

[0027] In another variation of the method, it is preferable not to connect the segments before connecting the solar cells. Instead, it is preferable to place the solar cells and segments sequentially, and then connect them. Preferably, one of the multiple solar cells is positioned first, followed by the positioning of one segment next to it, then another segment is positioned on top of the positioned solar cell, and then another solar cell is positioned on top of the positioned segment. The resulting assembly is preferably bonded together. The electrical connection of the connector is preferably achieved by utilizing temperature and, if necessary, applying pressure. Temperature bonds the film to the solar cell and presses the embedded electrical conductor lines onto the front and back electrodes of the solar cell, forming pressure contacts. If conductive adhesive is used between the electrical conductor lines and the solar cell, the adhesive is activated by temperature, establishing an electrical connection between the electrical conductor lines and the front and back electrodes of the solar cell.

[0028] The temperature required for circuit connection is preferably below 220°C, which is typically the temperature used in soldering processes. This significantly reduces thermal stress. This method is well-suited for temperature-sensitive solar cells.

[0029] Preferably, a film with embedded electrical conductor lines is fixed to the front or back of an adjacent solar cell using conductive adhesive. This simplifies the electrical connection of the metallized portions of the solar cell, which are in the form of front and back electrodes.

[0030] Step c) is preferably performed using heat and / or pressure. This allows for efficient circuit connection.

[0031] The electrical conductor lines embedded in the film are preferably designed to allow vertically incident light to be fully coupled into the solar module during solar cell string integration. In a preferred embodiment, the cross-section of the electrical conductor lines embedded in the film is triangular. This effectively achieves this coupling. Because the electrical conductor lines embedded in the film are optically transparent, a large number of conductor lines can be used. This reduces power loss at the front electrode of the solar cell (e.g., solar cell finger electrodes) because the current path is shorter.

[0032] Preferably, the ratio of the height (Y) to the width (X) of each electrical conductor line embedded in the film is in the range Y / X > 0.19.

[0033] Multiple solar cells can each form a solar cell with a front electrode and / or busbar and a back electrode. Step c) preferably includes making electrical conductor lines embedded in the film to the front electrode and / or busbar of one of the multiple solar cells and the back electrode of the adjacent solar cell.

[0034] Within the scope of this invention, the term "solar cell" refers to a semiconductor structure having a photovoltaic active junction, particularly a pn junction, and in its final state used to convert sunlight into electrical energy. For the characteristics of a solar cell, it is not required that the semiconductor structure possess all the structural features of a fully fabricated solar cell. For example, the metallized electrode structure may not yet be formed. That is, a partially fabricated semiconductor structure having a photovoltaic active junction, particularly a pn junction, also meets the characteristics of a "solar cell" as described in this invention.

[0035] In a preferred embodiment, each of the multiple solar cells is without busbars, a front electrode, and / or a back electrode. These solar cells are more efficient due to less shading. There is no shading or recombination loss due to busbars or pads. Therefore, the performance is relatively high. In particular, a film with embedded electrical conductor lines can replace finger electrodes. Preferably, the multiple solar cells are without busbars and without front electrodes. Step c) preferably connects the embedded electrical conductor lines in the film to a doped layer circuit, which partially or entirely forms the front of one of the multiple solar cells and is circuitally connected to the back electrode of the adjacent solar cells, wherein the film with embedded electrical conductor lines serves not only as a cell connector but also as the front electrode of the solar cell.

[0036] The invention also relates to a solar cell string obtained by the method described in any of the above embodiments.

[0037] The design of the electrical conductor circuit that makes electrical contact with the front of a solar cell can differ from that of the electrical conductor circuit that makes electrical contact with the back of an adjacent solar cell; the number of electrical conductor circuits may also vary. Furthermore, stress relief rings can be incorporated into the electrical conductor circuit to reduce stress between the solar cells.

[0038] The present invention also relates to a method for manufacturing a solar cell module, comprising:

[0039] - Provide the solar cell strings described above,

[0040] - The front-side encapsulation element is placed on the light-incident surface of the solar cell string, and the back-side encapsulation element is placed on the side of the solar cell string away from the light-incident surface to obtain a sandwich structure, and

[0041] - The sandwich structure is laminated.

[0042] Since the electrical conductors are embedded in the film, encapsulation materials such as EVA can be omitted. Alternatively, a relatively thin encapsulation material, such as <500µm, can be used. This relatively thin encapsulation material is more transparent than thicker ones, thus improving the performance of the solar cell module. Furthermore, encapsulation materials with different properties can be used, offering advantages in reliability, cost, and optical coupling.

[0043] The method may also include establishing cross-connections, i.e., using a film embedded with electrical conductor lines to connect solar cell strings in series, as described in the aforementioned method for manufacturing solar cell strings. In this case, the electrical conductor lines can be arranged on the back surface of the solar cells, thereby achieving a higher encapsulation density. This improves the efficiency of the solar module. Attached Figure Description

[0044] Other features and advantages of the invention will be described in relation to preferred embodiments, which will be illustrated in detail in the following figures.

[0045] Illustration:

[0046] Figure 1 A partial cross-sectional view of the solar cell string described in the invention;

[0047] Figure 2 Figure 1 A partial top view of the solar cell string shown;

[0048] Figure 3 A partial side view of the solar cell string described in the invention;

[0049] Figure 4 Figure 3 A perspective partial view of the solar cell string shown;

[0050] Figure 5 Figure 3 Another perspective partial view of the solar cell string shown;

[0051] Figures 6a to 6g These are the individual steps involved in manufacturing a film with embedded electrical conductor circuitry.

[0052] Figure 7 Figure 6g The diagram shows a cross-sectional view of the solar cell string. Detailed Implementation

[0053] Figure 1 This is a partial cross-sectional view of the solar cell string of the present invention. The solar cell string includes multiple solar cells 1 having a front side 5 and a back side 6, wherein... Figure 1One of them can be seen in the figure. In this example, a film 2 with embedded electrical conductor lines 3 is disposed on the surface 4 of the front side 5 of the solar cell 1, and one of the electrical conductor lines is shown in the figure. The electrical conductor line 3 is triangular in shape. The front side 5 is the light-receiving surface of the solar cell 1. During operation, the light beam 10 also shines on the electrical conductor line 3 embedded in the film 2, but as shown in the figure, its shading effect is relatively small.

[0054] Figure 2 for Figure 1 The image shows a partial top view of the solar cell string. A transparent film 2 is disposed on surface 4 of the front side 5 of the solar cell 1. Electrical conductor lines 3 are disposed in a portion of surface 4.

[0055] Figure 3 This is a partial side view of the solar cell string of the present invention. The solar cell string includes a plurality of solar cells 1 having surfaces 4, each surface forming a front side 5 and a back side 6 of the solar cell 1. Furthermore, the solar cell string also includes an integral film 2 in which electrical conductor lines 3 are embedded. The electrical conductor lines 3 are arranged in the film 2 in such a way that they extend from one surface 21 of the film 2 to another surface 22 opposite to surface 21, thereby achieving circuit connection by applying the film 2 with the embedded electrical conductor lines 3 to the front side 5 of one solar cell 1 and the back side 6 of an adjacent solar cell 1.

[0056] Figure 4 for Figure 3 The diagram shows a partial perspective view of the solar cell string along line IV-IV. The electrical conductor line 3 is triangularly embedded in the surface (not shown) so that it does not protrude, while surface 22 has no electrical conductor line.

[0057] Figure 5 for Figure 3 Another perspective partial view of the solar cell string shown along line VV. The electrical conductor line 3 is triangularly embedded in surface 22 so as not to protrude, while the opposite surface (not shown) has no electrical conductor line.

[0058] Figures 6a to 6g The various steps involved in manufacturing a film with embedded electrical conductor circuitry are shown. Figure 6a In the demonstrated steps, the membrane 2 in the partial cross-sectional view is structured on one side, giving it a groove 7 on one side. Figure 6bIn the demonstrated steps, an electrical conductor line 3 is embedded in the groove 7 of the membrane 2 shown in the partial cross-sectional view, forming a triangular shape. To embed the electrical conductor line 3 into the membrane, a highly reflective material (not shown) and a highly conductive material (not shown) can be embedded respectively. Step 6c shows that conductive adhesive 8 is further embedded on the electrical conductor line 3 in the groove 7 of the membrane 2 shown in the partial cross-sectional view. Step 6d is a top view of the membrane 2, which has three segments 2a, 2b, and 2c, which can be cut and separated along the cutting area 11. In each segment 2a, 2b, and 2c, multiple embedded electrical conductor lines 3 extend along the extension direction E, one of which extends in a direction perpendicular to the extension direction E, for forming a connection with another connection area of ​​another segment 2a, 2b, and 2c. Step 6e shows a top view of two segments 2a and 2b, which are separated by cutting, wherein segment 2b is compared to Figure 6d The circuit is rotated 180°, as indicated by the arrow, so that the electrical conductor line 3 of segment 2a is opposite to the electrical conductor line 3 of segment 2b. The electrical conductor line 3 of segment 2b is not actually visible in the figure, so it is represented by a dashed line. Figure 6f In the steps shown from the top view of segments 2a and 2b, the connection area of ​​the two segments is connected by using temperature and applying pressure when necessary. The electrical conductor line 3 of segment 2b is not actually visible in the figure, so it is represented by a dashed line. Figure 6g In the demonstrated steps, each solar cell 1 is connected to one of the circuits in segments 2a and 2b, respectively. The resulting solar cell string is shown in a top view. The electrical conductor line 3 of segment 2b is not actually visible in the figure and is therefore represented by a dashed line. The back side (not shown) of one solar cell 1 is connected to the circuit in segment 2a, while the surface 4 of the front side 5 of the adjacent solar cell 1 is connected to the circuit in segment 2b.

[0059] Figure 7 for Figure 6g The diagram shows a cross-sectional view of the solar cell string. The surface 4 of the back side 6 of one solar cell 1 is electrically connected to the conductor line 3 of segment 2a, while the surface 4 of the front side 5 of the adjacent solar cell 1 is electrically connected to the conductor line 3 of segment 2b. Furthermore, the connection area 3b between the two segments 2a and 2b is also electrically connected to each other.

[0060] exist Figures 6a to 6g In a variant of the method shown, segments 2a and 2b cannot be connected before being connected to solar cell 1 to generate Figure 6g , 7The solar cell string shown is an example. Instead of placing solar cells 1 and segments 2a and 2b sequentially, they can be connected. To do this, first position one of the multiple solar cells 1, then position segment 2b next to it, then position segment 2a on top of the already positioned solar cell 1, and finally position the other solar cell 1 on top of the already positioned segment 2b. Preferably, the assembly is bonded and the circuit interconnected under conditions of temperature and, if necessary, pressure.

[0061] List of reference numerals in the attached diagram:

[0062] 1. Solar cell

[0063] 2. Membrane

[0064] Sections 2a, 2b, and 2c

[0065] 3 Electrical conductor circuits

[0066] 3a busbar

[0067] 3b Connection Area

[0068] 4 Surface

[0069] 5. Front

[0070] 6. Back

[0071] 7 slots

[0072] 8 glue

[0073] 10 beams

[0074] 11 Cutting Area

[0075] 21 Surface

[0076] 22 Other surfaces

Claims

1. A method for connecting multiple solar cells (1) into a solar cell string, comprising the following steps: a) Provide multiple solar cells (1), each having a front (5) and a back (6), b) Provide a membrane (2) with embedded electrical conductor lines (3), c) Using a film (2) with embedded electrical conductor lines (3), the front side (5) of one of the multiple solar cells (1) is connected to the back side (6) of another adjacent solar cell (1) to create a solar cell string.

2. The method according to claim 1, characterized in that, In the first variant, the membrane (2) with embedded electrical conductor lines (3) provided in step b) is an integral structure, and the electrical conductor lines (3) are arranged in the membrane (2) to extend from one surface (21) of the membrane (2) to another surface (22) opposite to the surface (21). In step c), the membrane (2) with embedded electrical conductor lines (3) is applied to the front side (5) of a solar cell (1) and the back side (6) of an adjacent solar cell (1) to achieve circuit connection.

3. The method according to claim 2, characterized in that, The electrical conductor circuit (3) embedded in the membrane (2) is a rigid conductor, preferably a wire.

4. The method according to any one of claims 1 to 3, characterized in that, Before step b), an electrical conductor line (3) is embedded in the membrane (2) such that the electrical conductor line (3) extends from one surface (21) of the membrane (2) to another surface (22) opposite to that surface (21), and the membrane (2) thus made with the embedded electrical conductor line (3) is put into use as a single piece in step c).

5. The method according to claim 1, characterized in that, The membrane (2) with embedded electrical conductor lines (3) provided in step b) has multiple segments (2a, 2b) that are electrically connected to each other or connected in step c) in the second variant, wherein in step c), one segment (2b) is placed on the front side (5) of one solar cell (1) and another segment (2a) is placed on the back side (6) of another solar cell (1).

6. The method according to claim 5, characterized in that, Before step b), the membrane (2) is integrally structured so that it has a groove (7) on one side, the electrical conductor line (3) is embedded in the groove (7), and the membrane (2) is divided into multiple segments (2a, 2b, 2c).

7. The method according to claim 6, characterized in that, In order to embed the electrical conductor line (3) into the film, a highly reflective material and a highly conductive material, as well as an optional conductive adhesive (8), are embedded in the groove (7).

8. The method according to any one of claims 5 to 7, characterized in that, Each segment (2a, 2b, 2c) contains a large number of embedded electrical conductor lines (3) that extend along an extension direction (E), and one of the embedded electrical conductor lines (3) extends along a direction intersecting the extension direction (E), preferably perpendicular to the extension direction, to form a connection area for connecting with another connection area of ​​another segment (2a, 2b, 2c).

9. The method according to any of the preceding claims, characterized in that, Step c) is carried out under conditions of heat and / or pressure.

10. The method according to any of the preceding claims, characterized in that, The cross-section of the electrical conductor circuit (3) embedded in the membrane (2) is triangular.

11. The method according to any of the preceding claims, characterized in that, The ratio of height (Y) to width (X) of each of the electrical conductor lines (3) embedded in the membrane (2) is in the range of Y:X > 0.

19.

12. The method according to any of the preceding claims, characterized in that, Multiple solar cells (1) are each without busbars, front electrodes and / or back electrodes.

13. A solar cell string obtained according to the method of any of the preceding claims.

14. A method for manufacturing a solar cell module, comprising: - Provide a solar cell string obtained according to claim 13, - A front-side encapsulation element is placed on the light-incident surface of the solar cell string, and a back-side encapsulation element is placed on the back-side surface of the solar cell string to obtain a sandwich structure, and - The sandwich structure is laminated.

15. The method according to claim 14, characterized in that, Multiple solar cell strings are provided, which are connected in series using a film with embedded electrical conductor lines.

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