Back contact cell, back contact laminated cell and photovoltaic module

Abstract

The invention relates to a back contact battery, a back contact laminated battery and a photovoltaic module, the back contact battery comprises a battery piece, the back surface of the battery piece is provided with an insulating part and a bonding pad, the insulating part is at least located at two sides of the bonding pad along a first direction, the bonding pad is used for being connected with a welding strip, and the bonding pad is provided with a conductor; an accommodating space is formed between the bonding pad and the insulating parts on the two sides, and the ratio of the volume V1 of the electric conductor to the volume V2 of the accommodating space meets the condition that V1 / V2 is larger than or equal to 0.5 and smaller than or equal to 1. According to the invention, the relation between the volume V1 of the electric conductor and the volume V2 of the accommodating space is limited, so that the electric conductor on the bonding pad is not too many or too few, the electric conductor is not easy to overflow out of the bonding pad to cause the breakage of the fine grid, reliable connection can be provided for the welding strip and the bonding pad, and the volume of the electric conductor is convenient to determine.

Description

Technical Field

[0001] This application relates to the field of photovoltaic technology, and in particular, to a back-contact battery, a back-contact tandem battery, and a photovoltaic module. Background Art

[0002] A photovoltaic module can directly convert solar radiant energy into electrical energy, mainly based on the photovoltaic effect of crystalline silicon. That is, when the photons of sunlight are absorbed by the semiconductor crystalline silicon, electron-hole pairs are generated. When these electron-hole pairs reach the p-n junction composed of p-type crystalline silicon and n-type crystalline silicon, they are separated to both sides of the p-n junction by the junction electric field. When an external load is connected, a photocurrent is formed and electrical energy is output.

[0003] A photovoltaic module can be formed by connecting back-contact batteries. Adjacent back-contact batteries are electrically connected by welding tapes. The back-contact battery has pads for connecting with the welding tapes, and solder paste is provided on the pads. Excessive solder paste is likely to cause the grid lines on the back-contact battery to break, and too little solder paste is likely to result in poor connection strength between the welding tape and the pad, and the welding tape falls off the pad. Currently, there is a problem that it is difficult to determine the amount of solder paste. Summary of the Invention

[0004] This application provides a back-contact battery, a back-contact tandem battery, and a photovoltaic module to solve the problem that it is difficult to determine the amount of solder paste.

[0005] A back-contact battery provided by an embodiment of this application includes a cell. An insulating portion and a pad are provided on the back surface of the cell. Along a first direction, the insulating portion is at least located on both sides of the pad. The pad is used for connecting with a welding tape, and a conductor is provided on the pad. There is an accommodation space between the pad and the insulating portions on both sides. The ratio of the volume V1 of the conductor to the volume V2 of the accommodation space satisfies: 0.5 ≤ V1 / V2 ≤ 1.

[0006] In a possible design, the ratio of the volume V1 of the conductor to the volume V2 of the accommodation space is 0.8.

[0007] In a possible design, along a third direction, the area of the projection of the pad on the cell is S; along the third direction, the distance between the insulating portion and the pad is H; the volume V2 of the accommodation space = S × H.

[0008] In a possible design, along the first direction, the distance between the two insulating portions on both sides of the pad is L1; along a second direction, the size of the pad is L2; along the third direction, the distance between the insulating portion and the pad is H; the volume V2 of the accommodation space = L1 × L2 × H.

[0009] In a possible design, along the first direction, the distance L1 between the two insulating parts on both sides of the pad satisfies: 0.7 mm ≤ L1 ≤ 3 mm.

[0010] In a possible design, along the second direction, the size L2 of the pad satisfies: 0.5 mm ≤ L2 ≤ 2 mm.

[0011] In a possible design, the distance H between the insulating part and the pad satisfies: 0.015 mm ≤ H ≤ 0.08 mm.

[0012] In a possible design, the pad has a bearing surface, the conductor is arranged on the bearing surface, and along the first direction, from the edge of the bearing surface to the center of the bearing surface, the height of at least part of the bearing surface gradually decreases along the third direction.

[0013] In a possible design, along the second direction, from the edge of the bearing surface to the center of the bearing surface, the height of at least part of the bearing surface gradually decreases along the third direction.

[0014] A back-contact stacked cell provided by an embodiment of the present application includes a back-contact bottom cell and a perovskite top cell. The perovskite top cell is electrically connected to the front surface of the back-contact bottom cell, and the back-contact bottom cell is the back-contact cell described above.

[0015] A photovoltaic module provided by an embodiment of the present application includes the above-mentioned back-contact cell or the above-mentioned back-contact stacked cell.

[0016] In the present application, a conductor is arranged on the pad, and the conductor is generally solder paste. When the solder ribbon is welded to the pad, the solder paste is heated and melted to form a metal alloy solder joint. On the one hand, the metal alloy solder joint establishes an electrical connection between the solder ribbon and the pad, and on the other hand, the metal alloy solder joint provides a reliable connection between the pad and the solder ribbon, so that the solder ribbon is not easily detached from the pad.

[0017] The conductors on the pad should not be too many or too few. If there are too many conductors on the pad, when the welding ribbon is welded to the pad, the welding ribbon contacts the conductor and presses the conductor, so that the size of the conductor along the thickness direction of the battery cell (the third direction Z) is reduced and the size along the perpendicular third direction Z is increased, that is, the conductor is easy to overflow from the pad and contact the first fine grid or the second fine grid, or when the welding ribbon deviates from the preset placement position, the welding ribbon is easy to bring the conductor to the first fine grid or the second fine grid. Due to the large temperature change of the battery cell during welding, the conductor expands and contracts, which is easy to cause the first fine grid or the second fine grid in contact with it to be broken. It affects the collection of photogenerated current by the first fine grid or the second fine grid, thereby affecting the photoelectric conversion efficiency of the back-contact battery. If there are too few conductors on the pad, when the soldering ribbon is soldered to the pad, the size of the metal alloy solder joint formed between the soldering ribbon and the pad after the conductor is heated is small, which makes the resistance at the connection between the soldering ribbon and the pad large, and the photogenerated current is lost greatly in the process of being exported to the battery cell. In addition, the metal alloy solder joint cannot provide a reliable connection between the soldering ribbon and the pad, so that the soldering ribbon is easy to fall off from the pad, resulting in the current collected by the first fine grid or the second fine grid at the place where the soldering ribbon falls off cannot be exported, affecting the photoelectric conversion efficiency of the back-contact battery.

[0018] Therefore, the amount of the conductor on the pad should be set within a reasonable range, that is, the ratio of the volume V1 of the conductor to the volume V2 of the accommodating space satisfies: 0.5≤V1 / V2≤1, so that the conductor is not easy to overflow out of the pad and cause the first fine grid or the second fine grid to break, while providing a reliable connection between the solder strip and the pad, and facilitating the determination of the volume of the conductor.

[0019] It should be understood that the foregoing general description and the following detailed description are exemplary only and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A schematic diagram of a portion of the structure of a back contact cell provided in the present application in a specific embodiment;

[0021] Figure 2 for Figure 1 A partial cross-sectional view of a back contact cell in one embodiment;

[0022] Figure 3 for Figure 1 A partial cross-sectional view of a back contact cell in another embodiment;

[0023] Figure 4 for Figure 3 A schematic diagram of the structure of the pad in FIG.

[0024] Figure 5 for Figure 1 A cross-sectional view of a back contact cell in yet another embodiment;

[0025] Figure 6 This is a partial structural schematic diagram of the back-contact stacked cell provided by this application in a specific embodiment;

[0026] Figure 7 This is a structural schematic diagram of the photovoltaic module provided by this application, where the battery string is composed of back-contact cells;

[0027] Figure 8 This is a structural schematic diagram of the photovoltaic module provided by this application, where the battery string is composed of Figure 6 the back-contact stacked cells in

[0028] Reference numerals:

[0029] 1 - Battery string;

[0030] 10 - Battery cell;

[0031] 10a - Top cell;

[0032] 10b - Bottom cell;

[0033] 11 - First fine grid;

[0034] 12 - Second fine grid;

[0035] 13 - Insulating part;

[0036] 14 - Pad;

[0037] 141 - Bearing surface;

[0038] 142 - Groove;

[0039] 15 - Conductor;

[0040] 2 - Welding ribbon;

[0041] 3 - Front encapsulation structure;

[0042] 4 - Front film layer;

[0043] 5 - Back film layer;

[0044] 6 - Back encapsulation structure.

[0045] The accompanying drawings here are incorporated into the specification and constitute a part of this specification, showing embodiments in line with this application, and are used together with the specification to explain the principles of this application. Detailed implementation manners

[0046] To better understand the technical solutions of this application, the embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0047] It should be clear that the described embodiments are only some embodiments of the present application, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts belong to the scope of protection of the present application.

[0048] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application. The singular forms "a", "the", and "said" used in the embodiments of the present application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0049] It should be understood that the term "and / or" used herein is only an association relationship describing associated objects, indicating that three relationships may exist. For example, A and / or B may represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " herein generally represents an "or" relationship between the associated objects before and after.

[0050] It should be noted that the orientation terms such as "upper", "lower", "left", and "right" described in the embodiments of the present application are described from the angles shown in the drawings and should not be construed as limitations on the embodiments of the present application. In addition, in the context, it should also be understood that when it is mentioned that an element is connected "above" or "below" another element, it can not only be directly connected "above" or "below" another element, but also be indirectly connected "above" or "below" another element through an intermediate element.

[0051] The embodiments of the present application provide a back-contact battery, which can be one of an interdigitated back contact (IBC) battery, a heterojunction back contact (HBC) battery, and a tunnel oxide back contact (TBC) battery.

[0052] For an IBC cell, along its thickness direction, the IBC cell sequentially includes a silicon nitride back layer, an N+ front surface field, an N-type substrate silicon layer, a P+ emitter, an N+ back field, an aluminum oxide passivation layer, a silicon nitride antireflection layer, and a metal silver electrode. The IBC cell uses ion implantation technology to obtain P and N regions with good uniformity and precisely controllable junction depth. There are no grid lines blocking on the front side of the cell, which can eliminate the shading current loss of the metal electrode and maximize the utilization of incident photons. The short-circuit current of the IBC cell can be increased by about 7% compared with conventional solar cells. Due to the back contact structure, there is no need to consider the problem of grid line shading, and the grid line ratio can be appropriately widened, thereby reducing the series resistance and having a high fill factor. The surface passivation and surface light trapping structure can be optimized, and a lower front surface recombination rate and surface reflection can be obtained.

[0053] For an HBC cell, the HBC cell combines the advantages of IBC cells and heterojunction cells well. Its front surface passivation layer uses hydrogenated amorphous silicon, and N-type and P-type amorphous silicon thin films are respectively deposited on the back to form a heterojunction. The HBC cell makes full use of the excellent surface passivation performance of amorphous silicon. The heterojunction structure formed on the back has a good passivation effect, and can simultaneously achieve a higher short-circuit current and open-circuit voltage, thereby improving the photoelectric conversion efficiency.

[0054] For a TBC cell, the TBC cell combines the advantages of the tunneling oxide layer technology of Topcon and the back-arranged electrodes of IBC. The passivation effect and open-circuit voltage are significantly improved, and it can be economical while achieving a higher cell conversion efficiency. The complete production process of the TBC cell mainly includes depositing a tunneling oxide layer and P+ polysilicon, depositing a passivation film, printing electrodes on the back of the silicon wafer, etc. The TBC cell needs to add related processes for the back electrodes such as masking, laser grooving, PN region preparation, and etching on the basis of the TOPCon production process. The masking is mainly completed by APCVD or PECVD, the preparation of the PN region is mainly completed by PECVD, the etching mainly uses traditional wet equipment, and the grooving process needs to be completed by a laser device.

[0055] Specifically, the back contact cell includes a cell wafer 10. The cell wafer 10 has a front side and a back side. The front side of the cell wafer 10 refers to the light-receiving surface of the cell wafer 10, and the back side of the cell wafer 10 refers to the backlight surface of the cell wafer 10. As Figure 1 shown, a first fine grid 11 and a second fine grid 12 with different polarities are arranged on the back side of the cell wafer 10. Among the first fine grid 11 and the second fine grid 12, one is a positive electrode fine grid and the other is a negative electrode fine grid. Both the first fine grid 11 and the second fine grid 12 extend along a first direction X, and the first fine grid 11 and the second fine grid 12 are cross-arranged and spaced along a second direction Y. The first direction X intersects with the second direction Y to collect the photo-generated current generated by the cell wafer. The attached Figure 1The red line therein shows the first fine grid 11, and the blue line shows the second fine grid 12.

[0056] In one embodiment, the back surface of the cell 10 is provided with a first main grid and a second main grid with different polarities. The polarity of the first main grid is the same as that of the first fine grid 11, and the polarity of the second main grid is the same as that of the second fine grid 12. Both the first main grid and the second main grid extend along the second direction Y, and the first main grid and the second main grid are spaced and staggered along the first direction X, so that the first main grid is connected to the first fine grid 11 to collect the photo-generated current collected by the first fine grid 11, and the second main grid is connected to the second fine grid to collect the photo-generated current collected by the second fine grid 12. At the same time, the second fine grid 12 is disconnected at the first main grid to avoid short-circuiting due to contact between the second fine grid 12 and the first main grid, and the first fine grid 11 is disconnected at the second main grid to avoid short-circuiting due to contact between the first fine grid 11 and the second main grid. A first pad is provided on the first main grid, and the first solder tape is connected to the first main grid through the first pad. A second pad is provided on the second main grid, and the second solder tape is connected to the second main grid through the second pad. That is, the first solder tape and the second solder tape also extend along the second direction Y to export the current collected by the first main grid and the second main grid. It can be understood that the first pad and the second pad can be provided at the position where they contact the fine grids (i.e., the first fine grid 11 and the second fine grid 12), or can be provided between two adjacent fine grids.

[0057] In another embodiment, the back surface of the cell 10 is not provided with the first main grid and the second main grid. The first solder tape extending along the second direction Y is directly connected to the first fine grid 11 to collect the photo-generated current collected by the first fine grid 11 and export it, and the second solder tape extending along the second direction Y is directly connected to the second fine grid 12 to collect the photo-generated current collected by the second fine grid 12 and export it. Similarly, the second fine grid 12 is disconnected at the first solder tape to avoid short-circuiting due to contact between the second fine grid 12 and the first solder tape, and the first fine grid 11 is disconnected at the second solder tape to avoid short-circuiting due to contact between the first fine grid 11 and the second solder tape. A first pad is provided at the connection between the first fine grid 11 and the first solder tape to make the connection between the first fine grid 11 and the first solder tape reliable, and a second pad is provided at the connection between the second fine grid 12 and the second solder tape to make the connection between the second fine grid 12 and the second solder tape reliable.

[0058] Specifically, a first insulating portion is provided at the end of the first fine grid 11 disconnected at the second solder tape, and the first insulating portion is at least on both sides of the second pad, thereby further preventing the first fine grid 11 from contacting the second solder tape and causing a short circuit; a second insulating portion is provided on at least a part of the outer periphery of the second fine grid 12 disconnected at the first solder tape, and the second insulating portion is at least on both sides of the first pad, thereby further preventing the second fine grid 12 from contacting the first solder tape and causing a short circuit.

[0059] In the above two embodiments, since the first pad and the second pad have the same structure, the first solder strip and the second solder strip have the same structure, and the first insulating portion and the second insulating portion have the same structure, for the convenience of description, the first pad and the second pad are collectively referred to as pad 14, the first solder strip and the second solder strip are collectively referred to as solder strip 2, and the first insulating portion and the second insulating portion are collectively referred to as insulating portion 13. Among them, the insulating portion 13 can cover the end of the second fine grid 12 or can be arranged around the end of the second fine grid 12, as long as it can prevent short circuits between fine grids of different polarities and the main grid or short circuits between fine grids of different polarities.

[0060] A conductor 15 is provided on the pad 14. The conductor 15 is generally solder paste. When the solder strip 2 is welded to the pad 14, the solder paste is heated and melted to form a metal alloy solder joint. On the one hand, the metal alloy solder joint establishes an electrical connection between the solder strip 2 and the pad 14. On the other hand, the metal alloy solder joint provides a reliable connection between the pad 14 and the solder strip 2, making it difficult for the solder strip 2 to break away from the pad 14.

[0061] There is an accommodation space between the pad 14 and the insulating portions 13 on both sides. The ratio of the volume V1 of the conductor 15 to the volume V2 of the accommodation space satisfies: 0.5 ≤ V1 / V2 ≤ 1. For example, the ratio of the volume V1 of the conductor 15 to the volume V2 of the accommodation space can specifically be: 0.5, 0.51, 0.52, 0.53, 0.54, 0.55, 0.58, 0.59, 0.6, 0.62, 0.64, 0.65, 0.68, 0.69, 0.7, 0.72, 0.74, 0.75, 0.78, 0.79, 0.8, 0.82, 0.84, 0.85, 0.88, 0.89, 0.9, 0.92, 0.94, 0.95, 0.97, 0.99, 1, etc.

[0062] The conductor 15 on the pad 14 should not be excessive or too little. If the conductor 15 on the pad 14 is excessive (for example, V1 / V2 is greater than 1), when the welding tape 2 is welded to the pad 14, the welding tape 2 contacts the conductor 15 and presses the conductor 15, causing the size of the conductor 15 in the thickness direction (the third direction Z) of the solar cell 10 to decrease and the size in the direction perpendicular to the third direction Z to increase, that is, the conductor 15 is likely to overflow outside the pad 14 and contact the first fine grid 11 or the second fine grid 12. Or when the welding tape 2 deviates from the preset placement position, the welding tape 2 is likely to bring the conductor 15 onto the first fine grid 11 or the second fine grid 12. Due to the large temperature change of the solar cell 10 during welding, the conductor 15 expands and contracts thermally, which is likely to cause the first fine grid 11 or the second fine grid 12 in contact with it to break, affecting the collection of photocurrent by the first fine grid 11 or the second fine grid 12, and further affecting the photoelectric conversion efficiency of the back contact solar cell. If the conductor 15 on the pad 14 is too little (for example, V1 / V2 is less than 0.5), when the welding tape 2 is welded to the pad 14, the size of the metal alloy solder joint formed between the welding tape 2 and the pad 14 after the conductor 15 is heated is small, resulting in a large resistance at the connection between the welding tape 2 and the pad 14. The photocurrent has a large loss during the process of being led out to the solar cell 10, and the metal alloy solder joint cannot provide a reliable connection for the welding tape 2 and the pad 14, making the welding tape 2 easy to fall off from the pad 14, resulting in the inability to lead out the current collected by the first fine grid 11 or the second fine grid 12 at the falling-off place of the welding tape 2, affecting the photoelectric conversion efficiency of the back contact solar cell.

[0063] Therefore, the amount of the conductor 15 on the pad 14 should be set within a reasonable range so that the conductor 15 is not likely to overflow outside the pad 14 to cause the first fine grid 11 or the second fine grid 12 to break while being able to provide a reliable connection for the welding tape 2 and the pad 14. In addition, by comparing the volume V1 of the conductor 15 with the volume V2 of the accommodation space, it is convenient to judge and determine the amount of the volume of the conductor 15.

[0064] Furthermore, as Figure 1 shown, along the first direction X, there is a gap between the pad 14 and the insulating portion 13. When the pad 14 is located between adjacent fine grids and the conductor 15 overflows outside the pad 14 under the pressure of the welding tape 2, the gap between the pad 14 and the insulating portion 13 can, to a certain extent, prevent the conductor 15 from contacting the first fine grid 11 or the second fine grid 12 surrounded by the insulating portion 13, thereby preventing the conductor 15 that overflows outside the pad 14 from causing the first fine grid 11 or the second fine grid 12 to break to a certain extent.

[0065] In addition, the insulating portions 13 located on both sides of the pad 14 along the first direction X can also prevent the conductor 15 from contacting the first fine grid 11 or the second fine grid 12 surrounded by the insulating portion 13 to a certain extent, thereby preventing the conductor 15 that overflows outside the pad 14 from causing the disconnection of the first fine grid 11 or the second fine grid 12 to a certain extent.

[0066] It can be understood that the amount of the conductor 15 on the pad 14 is relative to the size of the accommodation space between the pad 14 and the insulating portions 13 on both sides.

[0067] In one embodiment, as Figure 2 shown, along the third direction Z, the area of the projection of the pad 14 on the cell 10 is S; along the third direction Z, the distance between the insulating portion 13 and the pad 14 is H, and the volume V2 of the accommodation space = S×H.

[0068] The accommodation space is defined by the area S of the projection of the pad 14 on the cell 10 and the distance H between the insulating portion 13 and the pad 14, that is, the accommodation space is the space above the pad 14 with a height lower than that of the insulating portion 13, so that the ratio of the volume V1 of the conductor 15 to the volume V2 of the accommodation space can more intuitively reflect the amount of the conductor 15.

[0069] Specifically, when the volume V1 of the conductor 15 on the pad 14 is equal to the volume V2 of the accommodation space (i.e., V1 / V2 = 1), the conductor 15 can exactly fill the space above the pad 14 with a height lower than that of the insulating portion 13. When the welding tape 2 is welded to the pad 14, the welding tape 2 presses the conductor 15, causing the dimension of the conductor 15 along the third direction Z to decrease and the dimension along the direction perpendicular to the third direction Z to increase. At this time, the conductor 15 will overflow outside the pad 14, but due to the gap between the pad 14 and the insulating portion 13 and the insulating portion 13 itself, it can further prevent the conductor 15 from contacting the first fine grid 11 or the second fine grid 12 surrounded by the insulating portion 13, so that the conductor 15 that overflows outside the pad 14 will not cause the disconnection of the first fine grid 11 or the second fine grid 12.

[0070] When the ratio of the volume V1 of the conductor 15 on the pad 14 to the volume V2 of the accommodation space is 0.5, when the welding tape 2 is welded to the pad 14, the welding tape 2 presses the conductor 15, causing the dimension of the conductor 15 along the third direction Z to decrease and the dimension along the direction perpendicular to the third direction Z to increase. At this time, along the third direction Z, the conductor 15 covers most of the upper surface of the pad 14, thereby being able to provide reliable support for the welding tape 2 and the pad 14.

[0071] In another embodiment, as Figure 1 and Figure 2As shown, along the first direction X, the distance between two insulating portions 13 on both sides of the pad 14 is L1; along the second direction Y, the size of the pad 14 is L2; along the third direction Z, the distance between the insulating portion 13 and the pad 14 is H, and the volume V2 of the accommodation space is V2 = L1×L2×H.

[0072] That is, the accommodation space is defined by the distance L1 between two insulating portions 13 on both sides of the pad 14 and the size of the pad 14 along the second direction Y, such that the maximum volume V1 of the conductor 15 that can be set in this embodiment is greater than the maximum volume V1 of the conductor 15 that can be set in the previous embodiment, so that the volume range of the conductor 15 that can be set in this embodiment is larger, reducing the requirement for the volume accuracy of the conductor 15.

[0073] Specifically, when the volume V1 of the conductor 15 on the pad 14 is equal to the volume V2 of the accommodation space (i.e., V1 / V2 = 1), and the solder strip 2 is not placed on the cell 10, the conductor 15 is entirely located on the pad 14. Along the third direction Z, the height of the conductor 15 generally exceeds the height of the insulating portion 13. When the solder strip 2 is welded to the pad 14, the solder strip 2 presses the conductor 15, causing the size of the conductor 15 along the third direction Z to decrease and the size along the direction perpendicular to the third direction Z to increase. The conductor 15 will overflow outside the pad 14. At this time, the insulating portion 13 itself can prevent the conductor 15 from contacting the first fine grid 11 or the second fine grid 12 surrounded by the insulating portion 13, so that the conductor 15 overflowing outside the pad 14 will not cause the first fine grid 11 or the second fine grid 12 to break.

[0074] Optionally, along the first direction X, the distance L1 between two insulating portions 13 on both sides of the pad 14 satisfies: 0.7 mm ≤ L1 ≤ 3 mm. For example, the distance L1 between two insulating portions 13 on both sides of the pad 14 can specifically be: 0.7 mm, 0.71 mm, 0.72 mm, 0.75 mm, 0.77 mm, 0.79 mm, 0.8 mm, 0.82 mm, 0.85 mm, 0.88 mm, 0.9 mm, 0.92 mm, 0.95 mm, 0.98 mm, 1 mm, 1.05 mm, 1.1 mm, 1.15 mm, 1.2 mm, 1.25 mm, 1.3 mm, 1.35 mm, 1.4 mm, 1.45 mm, 1.5 mm, 1.55 mm, 1.6 mm, 1.65 mm, 1.7 mm, 1.75 mm, 1.8 mm, 1.85 mm, 1.9 mm, 1.95 mm, 2 mm, 2.05 mm, 2.1 mm, 2.15 mm, 2.2 mm, 2.3 mm, 2.4 mm, 2.5 mm, 2.6 mm, 2.7 mm, 2.8 mm, 2.9 mm, 2.92 mm, 2.95 mm, 2.98 mm, 2.99 mm, 3 mm, etc.

[0075] Along the first direction X, the distance L1 between the two insulating portions 13 on both sides of the pad 14 should neither be too large nor too small. If the distance L1 between the two insulating portions 13 on both sides of the pad 14 is too large (for example, L1 is greater than 3.0 mm), the distance between the insulating portion 13 and the first fine grid 11 or the second fine grid 12 it surrounds will be relatively small. When the insulating portion 13 is printed at a position deviated from its preset position, the first fine grid 11 or the second fine grid 12 it surrounds may extend outside the insulating portion 13, resulting in the insulating portion 13 being unable to effectively isolate the fine grid from the main grid of the opposite polarity (and the solder strip 2 connected to the main grid of the opposite polarity), or being unable to effectively isolate the fine grid from the solder strip 2 connected to the fine grid of the opposite polarity, causing a short circuit. If the distance L1 between the two insulating portions 13 on both sides of the pad 14 is too small (for example, L1 is less than 0.7 mm), the distance between the insulating portion 13 and the pad 14 will be too small. When the insulating portion 13 is printed at a position deviated from its preset position, the insulating portion 13 may extend onto the pad 14, affecting the connection reliability between the solder strip 2 and the pad 14. At the same time, both a relatively small distance between the insulating portion 13 and the first fine grid 11 or the second fine grid 12 it surrounds and a relatively small distance between the insulating portion 13 and the pad 14 will increase the precision required for printing the insulating portion 13, resulting in an increase in the cost of printing the insulating portion 13.

[0076] Therefore, along the first direction X, the distance L1 between the two insulating portions 13 on both sides of the pad 14 should be set within a reasonable range to ensure that the distance between the insulating portion 13 and the first fine grid 11 or the second fine grid 12 it surrounds is not too small, and the distance between the insulating portion 13 and the pad 14 is not too small.

[0077] Optionally, the pad 14 can be square, rectangular, circular, oval, etc. For example, the specification appendix Figure 1 shows a pad 14 in a positive direction with chamfered edges. As Figure 1 shown, along the second direction Y, the size L2 of the pad 14 satisfies: 0.5 mm ≤ L2 ≤ 2 mm. For example, the size L2 of the pad 14 can specifically be: 0.5 mm, 0.55 mm, 0.6 mm, 0.65 mm, 0.7 mm, 0.75 mm, 0.8 mm, 0.85 mm, 0.9 mm, 0.95 mm, 1 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, 1.95 mm, 1.98 mm, 2 mm, etc.

[0078] Along the second direction Y, the size L2 of the pad 14 should neither be too large nor too small. If the size L2 of the pad 14 is too large (for example, L2 is greater than 2 mm), the cost of forming the pad 14 will increase, and the production cost of the back-contact battery will increase. If the size L2 of the pad 14 is too small (for example, L2 is less than 0.5 mm), the area of the pad 14 for carrying the conductor 15 is too small. On the one hand, it is easy for the conductor 15 to overflow outside the pad 14. On the other hand, the maximum connection area between the pad 14 and the welding tape 2 is relatively small, resulting in a low connection strength between the pad 14 and the welding tape 2, and the welding tape 2 is easily separated from the pad 14.

[0079] Therefore, along the second direction Y, the size L2 of the pad 14 should be set within a reasonable range to keep the cost of forming the pad 14 low while preventing the conductor 15 from overflowing outside the pad 14 and ensuring a high connection strength between the welding tape 2 and the pad 14.

[0080] Optionally, the distance H between the insulating portion 13 and the pad 14 satisfies: 0.015 mm ≤ H ≤ 0.08 mm. For example, the distance H between the insulating portion 13 and the pad 14 can specifically be: 0.015 mm, 0.016 mm, 0.018 mm, 0.019 mm, 0.02 mm, 0.022 mm, 0.025 mm, 0.028 mm, 0.03 mm, 0.032 mm, 0.035 mm, 0.038 mm, 0.04 mm, 0.042 mm, 0.045 mm, 0.048 mm, 0.05 mm, 0.052 mm, 0.055 mm, 0.058 mm, 0.06 mm, 0.062 mm, 0.065 mm, 0.068 mm, 0.07 mm, 0.072 mm, 0.075 mm, 0.078 mm, 0.079 mm, 0.08 mm, etc.

[0081] The distance H between the insulating portion 13 and the pad 14 should neither be too large nor too small. If the distance H between the insulating portion 13 and the pad 14 is too large (for example, H is greater than 0.08 mm), the height of the insulating portion 13 is too high, resulting in an increase in the cost of forming the insulating portion 13 and the production cost of the back-contact battery. If the distance H between the insulating portion 13 and the pad 14 is too small (for example, H is less than 0.015 mm), the ability of the insulating portion 13 to prevent the conductor 15 that overflows outside the pad 14 from contacting the first fine grid 11 or the second fine grid 12 surrounded by the insulating portion 13 is weak, and it is easy to occur that the first fine grid 11 or the second fine grid 12 is broken.

[0082] Therefore, the distance H between the insulating portion 13 and the pad 14 should be set within a reasonable range to keep the cost of forming the insulating portion 13 low while the insulating portion 13 has a good ability to block the conductor 15 that overflows outside the pad 14.

[0083] Preferably, the ratio of the volume V1 of the conductor 15 to the volume V2 of the accommodation space is 0.8. On the one hand, this ensures that the amount of the conductor 15 on the pad 14 is not excessive, so that when the conductor 15 is pressed by the welding tape 2, it is not likely to overflow outside the pad 14, and the cost of setting the conductor 15 is relatively low. On the other hand, it ensures that the amount of the conductor 15 on the pad 14 is not too small, so that the conductor 15 can provide a reliable connection between the pad 14 and the welding tape 2, and the welding tape 2 is not easily detached from the pad 14.

[0084] In the above embodiments, as Figure 2 、 Figure 3 and Figure 5 shown, the pad 14 has a bearing surface 141, and the conductor 15 is arranged on the bearing surface 141.

[0085] In one embodiment, as Figure 2 shown, the bearing surface 141 is a plane parallel to the first direction X and the second direction Y. At this time, the bearing surface 141 has the advantage of being easy to process and form.

[0086] In another embodiment, as Figure 3 and Figure 4 shown, along the first direction X, from the edge of the bearing surface 141 towards the center of the bearing surface 141, at least part of the height of the bearing surface 141 gradually decreases along the third direction Z, so that when the conductor 15 is heated and melted, it can stay at the center position of the bearing surface 141 under the action of gravity and is not likely to overflow outside the pad 14 along the first direction X. At the same time, when the welding tape 2 is welded to the pad 14, the welding tape 2 is also likely to be located at the center position of the bearing surface 141 under the action of gravity, so that the wrapping of the conductor 15 around the welding tape 2 is better, and the connection reliability between the conductor 15, the welding tape 2 and the pad 14 is higher. At this time, the projection of the bearing surface 141 along the second direction Y may be arc-shaped.

[0087] Optionally, along the second direction Y, from the edge of the bearing surface 141 towards the center of the bearing surface 141, the height of the bearing surface 141 remains unchanged, so that the contact area between the welding tape 2 and the conductor 15 is larger.

[0088] Optionally, along the second direction Y, from the edge of the bearing surface 141 towards the center of the bearing surface 141, at least part of the height of the bearing surface 141 also gradually decreases, so that when the conductor 15 is heated and melted, it is not likely to overflow outside the pad 14 along the second direction Y. The curvature of the bearing surface 141 in the first direction X is smaller than the curvature of the bearing surface 141 in the second direction Y to ensure a larger contact area between the conductor 15 and the welding tape 2. It can be understood that the curvature of the bearing surface 141 in the first direction X may also be equal to or greater than the curvature of the bearing surface 141 in the second direction Y.

[0089] Optionally, along the first direction X, from the edge of the bearing surface 141 towards the center of the bearing surface 141, the height of the bearing surface 141 gradually decreases; along the second direction Y, from the edge of the bearing surface 141 towards the center of the bearing surface 141, the height of the bearing surface 141 also gradually decreases; and the curvature of the bearing surface 141 in the first direction X is greater than or less than the curvature of the bearing surface 141 in the second direction Y. Preferably,

[0090] In yet another embodiment, as Figure 5 shown, a groove 142 is provided on the pad 14, and the conductor 15 is disposed in the groove 142. The groove 142 extends towards the solar cell 10 along the third direction Z and penetrates the pad 14 along the second direction Y, so that when the conductor 15 is heated and melted, it is not easy to overflow outside the pad 14 along the first direction X.

[0091] The embodiment of the present application also provides a back-contact stacked solar cell, as Figure 6 shown, the back-contact stacked solar cell includes a back-contact bottom solar cell 10b and a perovskite top solar cell 10a. The perovskite top solar cell 10a is electrically connected to the front side of the back-contact bottom solar cell 10b, and the back-contact bottom solar cell 10b is the above-mentioned back-contact solar cell. The back-contact stacked solar cell further includes an intermediate connection layer, and the intermediate connection layer is connected between the back-contact bottom solar cell 10b and the perovskite top solar cell 10a. The intermediate connection layer can be selected from transparent materials with a high refractive index, such as a transparent conductive metal oxide thin film (ITO). An effective intermediate connection layer needs to have high light transmittance to reduce the reflection and absorption of light at the interface of the intermediate connection layer, and good conductivity to reduce the influence of series resistance on the device performance.

[0092] The embodiment of the present application also provides a photovoltaic module. The photovoltaic module includes the above-mentioned back-contact solar cell or the above-mentioned back-contact stacked solar cell. The back-contact solar cell or the back-contact stacked solar cell is connected in series by solder tapes 2 to form a battery string 1, and multiple battery strings 1 are connected in parallel by bus bars to form a battery string group, and multiple battery string groups are connected in series by bus bars and jumpers.

[0093] As Figure 6 and Figure 7 shown, the photovoltaic module includes: a front encapsulation structure 3, a front film layer 4, multiple battery string groups, a back film layer 5, and a back encapsulation structure 6. Figure 6 shows a photovoltaic module in which the battery string is composed of back-contact solar cells, Figure 7 shows a photovoltaic module in which the battery string is composed of back-contact stacked solar cells.

[0094] Among them, the front encapsulation structure 3, the front film layer 4, the back film layer 5, and the back encapsulation structure 6 encapsulate the battery string group to ensure that the photovoltaic module has high mechanical strength, reduce the impacts of hail, wind, mechanical vibration, etc. on the back-contact photovoltaic module, improve the sealing performance of the back-contact photovoltaic module, and enhance its erosion resistance and safety.

[0095] Specifically, the front encapsulation structure 3 and the back encapsulation structure 6 can be one of rigid materials such as tempered glass, Polyethylene Terephthalate (PET), Polycarbonate (PC), or one of flexible materials such as Polyvinyl Fluoride (PVF), Ethylene-Tetra-Fluoro-Ethylene (ETFE), Polyvinylidene Fluoride (PVDF). These materials have high light transmittance, can improve the photoelectric conversion efficiency of the back-contact photovoltaic module, and ensure the power of the back-contact photovoltaic module. The front film layer 4 and the back film layer 5 can be one of materials such as Ethylene-Vinyl Acetate Copolymer (EVA), Polyolefin Elastomer (POE), Polyvinyl Butyral (PVB), EVA-POE-EVA co-extruded film (EPE), EVA-POE co-extruded film (EP).

[0096] The above are only the preferred embodiments of the present application and are not used to limit the present application. For those skilled in the art, various changes and modifications can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included within the protection scope of the present application.

Claims

1. A back-contact battery, characterized in that, The back-contact battery includes a battery cell (10), an insulating portion (13) and a pad (14) are provided on the back surface of the battery cell (10), the insulating portion (13) is at least located on both sides of the pad (14) along a first direction (X), the pad (14) is used for connecting with a solder strip (2), and a conductor (15) is provided on the pad (14); There is an accommodation space between the pad (14) and the insulating portions (13) on both sides, and the ratio of the volume V1 of the conductor (15) to the volume V2 of the accommodation space satisfies: 0.5 ≤ V1 / V2 ≤ 1.

2. The back-contact battery according to claim 1, characterized in that, The ratio of the volume V1 of the conductor (15) to the volume V2 of the accommodation space is 0.

8.

3. The back-contact battery according to claim 1, characterized in that, Along a third direction (Z), the area of the projection of the pad (14) on the battery cell (10) is S; along the third direction (Z), the distance between the insulating portion (13) and the pad (14) is H; The volume V2 of the accommodation space = S × H.

4. The back-contact battery according to claim 1, characterized in that, Along the first direction (X), the distance between the two insulating portions (13) on both sides of the pad (14) is L1; along a second direction (Y), the size of the pad (14) is L2; along the third direction (Z), the distance between the insulating portion (13) and the pad (14) is H; The volume V2 of the accommodation space = L1 × L2 × H.

5. The back-contact battery according to claim 4, wherein Along the first direction (X), the distance L1 between the two insulating portions (13) on both sides of the pad (14) satisfies: 0.7 mm ≤ L1 ≤ 3 mm.

6. The back-contact battery according to claim 4, characterized in that, Along the second direction (Y), the size L2 of the pad (14) satisfies: 0.5 mm ≤ L2 ≤ 2 mm.

7. The back contact battery according to claim 3 or 4, characterized in that, The distance H between the insulating portion (13) and the pad (14) satisfies: 0.015 mm ≤ H ≤ 0.08 mm.

8. The back contact battery according to any one of claims 1-6, characterized in that, The pad (14) has a bearing surface (141), the conductor (15) is provided on the bearing surface (141), and along the first direction (X), from the edge of the bearing surface (141) towards the center of the bearing surface (141), at least part of the bearing surface (141) gradually decreases in height along the third direction (Z).

9. The back-contact battery according to claim 8, characterized in that, Along the second direction (Y), from the edge of the bearing surface (141) towards the center of the bearing surface (141), at least part of the bearing surface (141) gradually decreases in height along the third direction (Z).

10. A back-contact stacked cell, characterized in that, The back-contact stacked battery includes a back-contact bottom battery (10b) and a perovskite top battery (10a), the perovskite top battery (10a) is electrically connected to the front surface of the back-contact bottom battery (10b), and the back-contact bottom battery (10b) is the back-contact battery according to any one of claims 1-9.

11. A photovoltaic module, characterized in that, The photovoltaic module includes the back-contact battery according to any one of claims 1-9 or the back-contact stacked battery according to claim 10.

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