Back-contacted solar cell and photovoltaic module

Abstract

Back-contacted solar cell (40), comprising: a cell substrate (100) which is divided into soldering areas (101) arranged along a first direction (X); Fingers (104) arranged on the cell substrate (100) along a second direction (Y); Solder pads (105) arranged in the soldering areas (101) and in edge sections (102) of the substrate, wherein each solder pad (105) of the solder pads (105) is in contact with at least two adjacent fingers (104) of the same polarity; Solder joints (106) arranged in the soldering areas (101) and in a central section (103) of the substrate surrounded by the edge section (102), each solder joint (106) being in contact with a respective finger (104); and Connecting leads (107) extending along the second direction (Y) to connect the solder joints (106) to the solder pads (105).

Description

TECHNICAL AREA

[0001] The present disclosure relates to the field of photovoltaics and in particular to a back-contacted solar cell and a photovoltaic module. BACKGROUND

[0002] As fossil fuel resources dwindle, solar cells are increasingly being used as an alternative source of renewable energy. A solar cell is a device that converts solar energy into electrical energy. The solar cell generates charge carriers based on the photoelectric effect, and these charge carriers are carried away by grid lines to enable efficient use of the generated electrical energy. The grid lines of the solar cell play a crucial role in collecting and transferring electrons. When multiple solar cells are assembled into a photovoltaic module, solder pads and / or solder joints are typically provided at the grid lines. Solar strips then make electrical contact with these solder pads and / or solder joints, thus electrically connecting the grid lines of adjacent solar cells.

[0003] To further reduce the shading of the grid lines on the front sides of solar cells, research on interdigitating back-contacted (IBC) solar cells has been increasingly advanced.

[0004] However, in IBC cells, during the electrical connection process of solar strips to solder pads and / or solder joints, the start and end sections of the solar strip on a single back-contacted solar cell are subject to significant influences from the solder paste distribution and mechanical stresses exerted by the solar strip. This often leads to unstable electrical connections between the start and end sections of the solar strip and the grid lines, thereby reducing the photoelectric conversion efficiency of the back-contacted solar cell. Accordingly, there remains a need for a more suitable configuration to improve the photoelectric conversion efficiency of back-contacted solar cells. SUMMARY

[0005] The embodiments of the present disclosure provide a back-contacted solar cell and a photovoltaic module which at least contribute to improving the photoelectric conversion efficiency of the back-contacted solar cell.

[0006] A back-contacted solar cell is provided according to one aspect of the embodiments of the present application. The back-contacted solar cell includes: a cell substrate divided into solder areas arranged along a first direction; fingers arranged on the cell substrate along a second direction; solder pads arranged in the solder areas and in edge sections of the substrate, each solder pad being in contact with at least two adjacent fingers of the same polarity; solder joints arranged in the solder areas and in a central section of the substrate surrounded by the edge sections, each solder joint being in contact with a respective finger; and connecting leads extending along the second direction to connect the solder joints to the solder pads.

[0007] In some embodiments, a subset of connecting leads is in contact with a respective solder pad of the solder pads, each being in contact with at least one solder joint adjacent to the respective solder pad.

[0008] In some embodiments, at least one connecting lead comprises a first end adjacent to the solder pad and a second end adjacent to the solder joint, and a width of the first end is greater than a width of the second end along the first direction.

[0009] In some embodiments, at least one connecting lead comprises a first end adjacent to the solder pad and a second end adjacent to the solder joint, and a width of the first end is greater than a width of the second end along the first direction.

[0010] In some embodiments, the back-contacted solar cell further includes a current-collecting section located on the side of the solder pad facing away from the solder joint and within the solder area. A single current-collecting section is in contact with a plurality of fingers of the same polarity.

[0011] In some embodiments, the number of fingers of the same polarity that are in contact with the individual current collection section is greater than the number of fingers of the same polarity that are in contact with the individual solder pad.

[0012] In some embodiments, the connecting line along the second direction is shorter than the current collection section; and / or a cross-section of the connecting line is smaller than a cross-section of the current collection section along a section perpendicular to the second direction.

[0013] In some embodiments, at least one connecting line has a first cross-sectional area along a section perpendicular to the second direction, at least one finger has a second cross-sectional area along a section perpendicular to the first direction, and the first cross-sectional area is larger than the second cross-sectional area.

[0014] In some embodiments, an orthographic projection of the solder pad onto the cell substrate is larger than an orthographic projection of the solder joint onto the cell substrate; and / or a thickness of the solder pad is smaller than a thickness of the solder joint along a third direction.

[0015] In some embodiments, the number of solder joints in contact with the connecting wire differs between different soldering areas.

[0016] A photovoltaic module is provided according to another aspect of the embodiments of the present application. The photovoltaic module includes: a solar cell string formed by connecting a plurality of back-contacted solar cells as described above, or formed by connecting a plurality of back-contacted solar cells produced by the method described above; an encapsulation configured to cover a surface of the solar cell string; and a cover plate configured to cover a surface of the encapsulation facing away from the solar cell string.

[0017] The technical solution in the embodiments of the present disclosure has at least the following advantages.

[0018] The solder pads and solder joints located in the same soldering area are positioned in the edge and central sections of the substrate, respectively. The solder pad can be considered the starting or ending soldering point, depending on whether a solar strip subsequently makes electrical contact with the back-contacted solar cell. Accordingly, each solder pad is designed to be electrically connected to at least two adjacent fingers of the same polarity, while each solder joint is electrically connected to a single finger. This arrangement improves the current collection efficiency of the solder pad, allowing current from more fingers of the same polarity to be transferred to the pad more quickly, thus creating a denser current collection network. This reduces the transmission distance of photogenerated charge carriers and decreases the series resistance of the back-contacted solar cell.On the other hand, as the starting or ending soldering point of a subsequent solar strip, the solder pad connecting more fingers of the same polarity can be designed with larger dimensions. This not only reduces the transfer resistance of the solder pad to accommodate more fingers of the same polarity, but also improves the alignment accuracy and connection strength between the solder pad and the solar strip, preventing problems such as cold solder joints or delamination caused by excessive pressure of the solar strip on the solder pad. This contributes to improving the current collection efficiency of the solder pad and increases the connection stability between the solar strip and the solder pad. In summary, these measures help to increase the current collection efficiency and the photoelectric conversion efficiency of the back-contacted solar cell.

[0019] Furthermore, the solder pad and at least one solder joint adjacent to the solder pad along the second direction can be electrically connected by the connecting lead. In other words, the connecting lead can electrically connect solder joints near the solder pad that are prone to cold solder joints, defects, or delamination. Even if these adjacent solder joints do not make good contact with the solar strip and cannot transfer current to it, the connecting lead allows current to be transferred directly to the solder pad and then to the solar strip. Thus, the connecting lead further ensures that the subsequent solar strip can collect current from all fingers of the same polarity, thereby further improving the photoelectric conversion efficiency of the back-contacted solar cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] One or more embodiments are illustrated with reference to figures in the drawings. Unless expressly stated otherwise, these illustrations do not constitute a limitation of the embodiments, and the drawings are not to scale. For the purpose of a clearer description of the technical solution of the embodiments of the present disclosure or of conventional techniques, a brief introduction to the drawings used in the embodiments is provided below. It is obvious that the drawings described below represent only some embodiments of the present disclosure and that those skilled in the art can derive further drawings from these drawings without inventive step. Fig. 1 is a first partial view from above of a rear-contacted solar cell according to an embodiment of the present disclosure; Fig. 2 is a second partial view from above of the rear-contacted solar cell according to an embodiment of the present disclosure; Fig. 3 is a first partially enlarged top view of the rear-contacted solar cell according to an embodiment of the present disclosure; Fig. 4 is a second partially enlarged top view of the rear-contacted solar cell according to an embodiment of the present disclosure; Fig. 5 is a third partially enlarged top view of the rear-contacted solar cell according to an embodiment of the present disclosure; Fig. Figure 6 is a fourth partially enlarged top view of the rear-contacted solar cell according to an embodiment of the present disclosure. Fig. 7 is a partial cross-sectional diagram of the in Fig. 6 shown back-contacted solar cells, recorded along a first section line AA1; Fig. Figure 8 is a partially perspective diagram of a photovoltaic module according to another embodiment of the present disclosure. Fig. 9 is a partial schematic cross-sectional diagram of the in Fig. 8 photovoltaic modules shown, recorded along a second section line BB1. REFERENCE MARK

[0021] 100, cell substrate; 101, soldering area; 111, first soldering area; 121, second soldering area; 102, marginal section; 103, central section; 104, finger of the same polarity; 114, first finger; 124, second finger; 105, solder pad; 106, soldered connection; 107, connecting wire; 117, first end; 127, second end; 108, power collection section; 118, third end; 128, fourth end; 109, marginal section; 40, back-contacted solar cell; 41, encapsulation; 42, Cover plate; 43, Solar strip. DETAILED DESCRIPTION OF THE EXECUTION FORMS

[0022] Based on the current state of the art, it is evident that the power collection efficiency of back-contacted solar cells needs improvement.

[0023] The embodiments of the present disclosure provide a back-contacted solar cell and a photovoltaic module. In the back-contacted solar cell, the solder pads and solder joints located in the same soldering area are positioned at the periphery and central regions, respectively. The solder pad can be considered the starting or ending soldering point if a solar strip subsequently makes electrical contact with the back-contacted solar cell. Based on this, each solder pad is designed to make electrical contact with at least two adjacent fingers, while each solder joint makes electrical contact with a single finger. On the one hand, this arrangement contributes to improving the current collection efficiency of the solder pad, allowing current from more fingers of the same polarity to be transferred to the solder pad more quickly, thus creating a denser current collection network.This reduces the transmission path of photogenerated charge carriers and decreases the series resistance of the back-contacted solar cell. Furthermore, as the starting or ending soldering point of a subsequent solar strip, the solder pad connecting more fingers of the same polarity can be designed with larger dimensions. This not only reduces the transmission resistance of the solder pad to accommodate more fingers of the same polarity but also improves the alignment accuracy and connection strength between the solder pad and the solar strip, preventing problems such as cold solder joints or loosening solder joints caused by excessive pressure of the solar strip on the solder pad. This contributes to improved current collection efficiency of the solder pad and increases the connection stability between the solar strip and the solder pad.In summary, these measures contribute to increasing the power harvesting efficiency and the photoelectric conversion efficiency of the back-contacted solar cell. Furthermore, the solder pad and at least one solder joint adjacent to the solder pad along the second direction can be electrically connected by the connecting lead. In other words, the connecting lead can electrically connect solder joints near the solder pad, which are prone to cold solder joints, defects, or delamination, to the solder pad. Even if these adjacent solder joints do not make good contact with the solar strip and cannot transfer current to the solar strip, the connecting lead allows the current to be transferred directly to the solder pad and then to the solar strip.Thus, the connecting line also ensures that the subsequent solar strip can collect current from all fingers of the same polarity, thereby further improving the photoelectric conversion efficiency of the rear-contacted solar cell.

[0024] In the description of embodiments of this disclosure, the technical terms "first," "second," and the like are used solely to distinguish between different elements or features and should not be interpreted as indicating or suggesting the relative importance, specific order, number, or hierarchical relationship of the features designated. In the description of embodiments of this disclosure, the term "multiple" means two or more, unless expressly defined otherwise.

[0025] The term "embodiment" as used here means that a particular feature, structure, or property described in connection with the embodiment may be included in at least one embodiment of the present disclosure. The expression "in one embodiment," which appears at various points in this patent specification, does not necessarily refer to the same embodiment, nor does it mean that the embodiments are mutually exclusive or alternative. Persons skilled in the art should understand that the embodiments described herein may be combined with other embodiments.

[0026] In the description of the embodiments of the present disclosure, the term "and / or" is intended to describe only an associative relationship between associated objects, meaning that three possible relationships exist. For example, "A and / or B" can indicate the presence of A alone, the simultaneous presence of A and B, or the presence of B alone. Additionally, the symbol " / " generally indicates an "or" relationship between the associated objects.

[0027] In the description of the embodiments of this disclosure, the term "multiple" refers to two or more (including two). Similarly, "several groups" refers to two or more (including two) groups, and "several pieces" refers to two or more (including two) pieces.

[0028] In the description of the embodiments of this disclosure, technical terms such as "center," "longitudinal," "transverse," "length," "width," "thickness," "top," "bottom," "front," "back," "left," "right," "vertical," "horizontal," "above," "below," "inside," "outside," "clockwise," "counterclockwise," "axial," "radial," and "circumferential," as well as similar terms, are used to describe positional or directional relationships based on the orientations or positions shown in the drawings. These expressions are used solely to facilitate the description and simplification of the embodiments of this disclosure and are not intended to indicate or imply that the referenced devices or elements must have a specific orientation, structure, or mode of operation. Therefore, this terminology should not be interpreted as limiting the embodiments of this disclosure.

[0029] In the description of the embodiments of this disclosure, technical terms such as "assembled," "connected," "coupled," and "fastened" are to be understood in a broad sense, unless expressly stated otherwise. For example, the connection may be a fixed connection or a detachable connection, or be formed in one piece; it may be a mechanical connection or an electrical connection; it may be a direct connection or an indirect connection via an intermediate medium; and it may also represent communication or interaction between two components. Persons skilled in the art may understand the specific meanings of the foregoing terms in the embodiments of this disclosure based on the particular context.

[0030] In the drawings corresponding to the embodiments of this disclosure, the thicknesses and areas of the layers are exaggerated for clarity and ease of description. When a component (for example, a layer, film, region, or substrate) is described as being "on" or "over" another component, the component may be positioned directly on the surface of the other component, or one or more additional components may be arranged between them. Conversely, when a component is described as being on the surface of another component, or when another component is described as being formed on the surface of a component or arranged on the surface of a component, it means that no additional component is present between the two.Furthermore, when a component is described as being formed “essentially” on another component, it means that the component is formed neither on the entire surface (or front face) of the other component, nor on any part of the edge of the entire surface.

[0031] When, in the description of the embodiments of this disclosure, a component is described as "including" another component, this does not preclude the presence of other components unless otherwise specified, and further components may also be included. Furthermore, when a component such as a layer, film, region, or plate is described as "on" or "arranged on" another component, it may be directly on top of the other component (i.e., located on the surface of the other component without an intervening component), or one or more other components may be arranged between them. Additionally, when a layer, film, region, or plate is described as being directly on top of another component or as being on the surface of another component, this indicates that no other component is arranged between them.

[0032] The terminology used in the description of the various embodiments set forth herein is intended solely to describe specific embodiments and is not intended to limit the scope of protection of this disclosure. As used in the descriptions of the various embodiments and the claims, the term "the component" is intended to include the plural form unless the context clearly indicates otherwise. The term "component" may refer to elements such as layers, films, regions, or plates.

[0033] The various embodiments of the present disclosure are described in detail with reference to the drawings. However, it should be understood by those skilled in the art that numerous technical details are presented herein solely for the purpose of clarifying the disclosed embodiments. Even in the absence of such technical details, or with various changes and modifications based on the following embodiments, the technical solutions that are to be protected by the present disclosure can still be implemented.

[0034] A back-contacted solar cell is provided according to an embodiment of the present disclosure. The back-contacted solar cell according to the embodiment of the present disclosure is described in detail below with reference to the drawings.

[0035] Referring to Fig. 1 or Fig. 2 includes a back-contacted solar cell: a cell substrate 100 divided into first solder areas 111 and second solder areas 121 arranged alternately along a first direction X, two opposing edge sections 102 along a second direction Y, and a central section 103 located between the two edge sections 102; a plurality of first fingers 114 and second fingers 124 arranged alternately on the cell substrate 100 along the second direction Y, the first fingers 114 being interrupted in the second solder areas 121 and the second fingers 124 being interrupted in the first solder areas 111; solder pads 105 located in sections of the solder areas 101 corresponding to the edge sections 102, each solder pad 105 being in contact with at least two adjacent fingers 104 of the same polarity;A plurality of solder joints 106 located in sections of the solder pads 101 corresponding to the central section 103, each solder joint 106 being in contact with a finger 104, and M fingers 104 of the same polarity being located between adjacent solder pads 105 and solder joints 106 along the second direction Y, where M is an integer greater than or equal to zero; and a plurality of connecting leads 107, each electrically connected to a solder pad 105 and at least one solder joint 106 located along the second direction Y adjacent to the solder pad 105. Each finger 104 positioned between two opposing connecting leads 107 along the second direction Y encloses a solder joint 106. In particular: The solder pad 101 is the first solder pad 111, and the fingers 104 of the same polarity are the first fingers 114.and / or solder area 101 is the second solder area 121, and the fingers 104 of the same polarity are the second fingers 124. It should be noted that the "cell substrate" used herein refers to a silicon base and several thin-film layers on it, such as the passivation layer, the doping layer, and the antireflection layer. It should also be noted that the terms "solder area," "edge section," and "central section" herein do not refer to actual physical structures on the cell substrate, but rather to areas artificially defined to simplify the description of finger / solder pad positions.

[0036] Fig. Figure 1 is a first partial view from above of a rear-contacted solar cell according to an embodiment of the present disclosure. Fig. Figure 2 is a second partial view from above of the back-contacted solar cell according to an embodiment of the present disclosure. It should be noted that in Fig. 1 and Fig. 2 the first fingers 114 are illustrated by thicker solid lines, while the second fingers 124 are illustrated by thinner solid lines.

[0037] It should be noted that solder pad 105 is located in solder area 101 at the edge section 102; that is, solder pad 105 lies where solder area 101 and edge section 102 coincide. Solder joint 106 is located in solder area 101 at the central section 103; that is, solder joint 106 lies where solder area 101 and central section 103 coincide. Thus, within the same solder area 101, solder pad 105 and solder joint 106 are positioned at edge section 102 and central section 103, respectively. Solder pad 105 can be considered the starting solder position, i.e., the initial soldering position, or the final solder position, i.e., the final contact position of the solar strip during the subsequent electrical connection with the back-contacted solar cell.In practical applications, when the solar tape comes into contact with the solder pad 105 and the solder joint 106, the mechanical stress exerted by the solar tape on the solder pad 105, which serves as the starting or ending soldering point, is greater than the mechanical stress acting on the solder joint 106. Furthermore, the outer section 102 is more susceptible to external forces compared to the central section 103, making the solder pad 105 more likely to experience greater mechanical stress than the solder joint 106.

[0038] Based on this, a single solder pad 105 is in contact with at least two adjacent fingers 104 of the same polarity, while a single solder joint 106 is in contact with a single finger 104. In other words, the number of fingers 104 of the same polarity connected to a single solder pad 105 is greater than the number of fingers 104 of the same polarity connected to a single solder joint 106. On the one hand, this configuration improves the current collection efficiency of the solder pad 105, allowing current from more fingers 104 of the same polarity to be transferred to the solder pad 105 more quickly, thus forming a denser current collection network. This effectively shortens the transmission distance of photogenerated charge carriers and reduces the series resistance of the back-contacted solar cell.On the other hand, since the solder pad 105 serves as the start or end soldering position for a subsequent solar strip, the solder pad 105, which is connected to more fingers 104 of the same polarity, can be made larger. A larger solder pad not only reduces its own transmission resistance to better accommodate the increased number of connected fingers, but also improves the alignment accuracy and bond strength between the solar strip and the solder pad 105. This helps prevent cold solder joints or delamination caused by excessive stress exerted by the solar strip on the start or end soldering position. In summary, these features contribute to improving the current collection efficiency of the back-contacted solar cell and further increase its photoelectric conversion efficiency.

[0039] The size of the solder pad 105 can be at least one of a diameter, length or width of the solder pad 105.

[0040] In some cases, an orthographic projection of a single solder pad 105 onto the cell substrate 100 may be larger than an orthographic projection of a single solder joint 106 onto the cell substrate 100.

[0041] Furthermore, the solder pad 105 can be electrically connected via the connecting line 107 to at least one solder joint 106 located along the second direction Y adjacent to the solder pad 105. It should be noted that, generally, the subsequent solar strip is in contact with the solder pad 105, which serves as the starting or ending soldering position. For example, since a larger amount of solder paste is typically required at these positions, the section of the solar strip directly opposite the solder pad 105 may be raised due to a buildup of solder paste. Consequently, the solder joint 106 adjacent to the solder pad 105 is most affected by the solder paste from the solar strip.Since it is difficult to sharply bend the solar strip over a short distance to contact the solder joint 106 near the pad 105, poor solder joints or unsoldered areas can occur between the solar strip and the nearby solder joint 106. Furthermore, because the height drop of the solar strip is relatively large over a short distance, subsequent delamination between the solar strip and the solder joint 106 adjacent to the solder pad 105 can easily occur. Therefore, the connecting wire 107 directly connects the solder joint 106, which is prone to poor, missing, or detached solder joints with the subsequent solar strip, to the solder pad 105.Even if the solder joint 106 adjacent to pad 105 has poor contact with the solar strip and cannot transfer current to the solar strip, the solder joint 106 can still transfer current directly to the solder pad 105 and then to the solar strip via the connecting line 107. In other words, the connecting line 107 helps to further ensure that the subsequent solar strip can collect current from all fingers 104 of the same polarity, e.g., from all first fingers 114 or from all second fingers 124, thereby further improving the photoelectric conversion efficiency of the back-contacted solar cell.

[0042] Additionally, each finger 104 located between two connecting leads 107 opposite each other along the second direction Y is provided with a solder connection 106. It should be noted that the connecting lead 107 has a limited length along the second direction Y and does not extend over the entire length of the central section 103 in the second direction Y. By providing a solder connection 106 on each finger 104 between the two connecting leads 107, the current in each finger 104 located between the two connecting leads 107 can be effectively collected through its corresponding solder connection 106. Furthermore, the solder connections 106 that are not in contact with the connecting lead 107 are located further away from the solder pad 105 along the second direction Y.Even if the section of the solar tape directly opposite solder pad 105 is raised due to solder paste buildup, the solar tape can still bend over a considerable distance to make contact with the solder joints 106 located further away from solder pad 105 without exerting excessive tensile force on these solder joints 106 during soldering. As a result, a poor solder joint or delamination between the solder joints 106 located further away from solder pad 105 and the solar tape can be effectively prevented, thus ensuring the connection stability between such solder joints 106 and the solar tape.

[0043] It should be noted that the section of the solar strip directly adjacent to solder pad 105 may be raised due to solder paste accumulation. Over time, the solar strip may bend downwards under its own weight to make contact with the solder joints 106 located further away from solder pad 105.

[0044] It should be noted that between solder pad 105 and solder joint 106, which are adjacent along the second direction Y, M fingers 104 of the same polarity are provided. For example, as in Fig. Figure 1 shows no fingers 104 of the same polarity between the solder pad 105 and the solder joint 106 when M equals 0. As shown in Fig. As shown in Figure 2, when M is greater than 0, fingers 104 of the same polarity are spaced apart between the solder pad 105 and the solder joint 106 along the second direction Y. Furthermore, the connecting wire 107 is in contact with at least both the solder pad 105 and the solder joint 106 that are adjacent along the second direction Y.

[0045] If fingers 104 of the same polarity are spaced apart between solder pad 105 and solder joint 106, which are adjacent along the second direction Y, the connecting lead 107 can, on the one hand, also contact the fingers 104 of the same polarity located between solder pad 105 and solder joint 106, thereby collecting current from a larger number of fingers 104 of the same polarity. On the other hand, providing fingers 104 of the same polarity between solder pad 105 and solder joint 106, which are adjacent along the second direction Y, increases the distance between the solder pad 105 and the solder joint 106, which are adjacent along the second direction Y. This increases the length over which the solar ribbon can bend from the elevated height at solder pad 105 down to the height of the solder joint 106, which is adjacent to solder pad 105.In other words, this reduces the required bending height per unit length along the second direction Y, thereby decreasing the degree of bending to which the solar tape must be subjected per unit length. This facilitates bending the solar tape to reach the solder joint 106 adjacent to the solder pad 105, further reduces the stress exerted on the solder joint by the solar tape, and effectively prevents conditions such as cold solder joints or delamination between the solder joint 106 adjacent to the solder pad 105 and the solar tape, thus ensuring a stable electrical connection.

[0046] Since the solder area 101 includes two types, namely a first solder area 111 and a second solder area 121, and the fingers 104 of the same polarity include two types, namely a first finger 114 and a second finger 124, the solder pad 105 can, in some cases, also include two types, namely a first solder pad and a second solder pad. Specifically, the first solder pad is located in the first solder area 111 and is in contact with a section of the first finger 114, while the second pad is located in the second solder area 121 and is in contact with a section of the second finger 124. Additionally, the solder connection 106 can also include two types, namely a first solder connection and a second solder connection.The first solder joint is located in the first soldering area 111 and is in contact with a first finger 114, and the second solder joint is located in the second soldering area 121 and is in contact with a second finger 124. It should be noted that in the following description, the solder pad 105 mentioned can refer to at least one of the first or second solder pads, and the solder joint 106 can refer to at least one of the first or second solder joints.

[0047] A more detailed description of the embodiments of the present disclosure is provided below with reference to the accompanying drawings.

[0048] In some embodiments, with reference to Fig. 1 or Fig. 2. The number of connecting leads 107 that are electrically connected to the same solder pad 105 is only one. This arrangement helps to reduce the amount of raw material required for the manufacture of the connecting lead 107, thereby lowering the manufacturing costs of the back-contacted solar cell.

[0049] In other embodiments, with reference to Fig. 3 or Fig. 4. The number of connecting leads 107 electrically connected to the same solder pad 105 can be multiple, with each of these connecting leads 107 being electrically connected to at least one solder joint 106 adjacent to the solder pad 105. In other words, multiple connecting leads 107 connected to the same solder pad 105 can be considered a connecting lead set. Even if some of the connecting leads 107 in a connecting lead set fail, for example, if a break occurs that prevents current from being transferred from the solder joint 106 to the solder pad 105, the remaining connecting leads 107 in the connecting lead set can still transfer current from the solder joint 106 to the solder pad 105. This further contributes to ensuring high current collection efficiency of the back-contacted solar cell.

[0050] Fig. 3 is a first partially enlarged top view of the rear-contacted solar cell according to an embodiment of the present disclosure; Fig. 4 is a second partially enlarged top view of the back-contacted solar cell according to an embodiment of the present disclosure; it should be noted that in Fig. 3 and Fig. 4 the first finger 114 is illustrated by thick solid lines, while the second finger 124 is illustrated by thin solid lines.

[0051] It should be noted that the example in Fig. 3 and Fig. Figure 4 shows that several connecting leads 107, electrically connected to the same solder pad 105, are all connected to the solder joint 106 closest to the solder pad 105. In actual applications, the number of solder joints 106 contacted by different connecting leads in the same connecting lead set can be the same or different. For example, in a connecting lead set, one connecting lead may be in contact with only one solder joint, while another connecting lead may be in contact with 2, 3, or 4 solder joints.

[0052] In some embodiments, with reference to Fig. 4 or Fig. 5, where Fig. 5. A third, partially enlarged top view of the back-contacted solar cell according to an embodiment of the present disclosure shows that at least one connecting line 107 can have a first end 117 adjacent to the solder pad 105 and a second end 127 adjacent to the solder joint 106. Along the first direction X, the width of the first end 117 is greater than the width of the second end 127.

[0053] It should be noted that if a subsequent solar strip contacts the solder pad 105 as a starting or ending soldering point, for example, at locations where a relatively large amount of solder paste is applied, the area near the solder pad 105 is more likely to come into contact with molten solder paste compared to the solder joint 106. Therefore, in the connecting line 107, the first end 117, which is adjacent to the solder pad 105, is more susceptible to breakage due to contact with molten solder paste than the second end 127, which is adjacent to the solder joint 106. For example, after cooling, the thermal expansion or contraction of the solder paste can cause the first end 117 to break. Based on this, the width of the first end 117 along the first direction X is greater than that of the second end 127.On the one hand, the wider first end 117 reduces the risk of breakage caused by molten solder paste, thereby improving the structural stability of the connecting lead 107. On the other hand, if a finger 104 is provided between the solder pad 105 and the solder joint 106 adjacent along the second direction Y, the connecting lead 107 can also collect the current from the fingers 104 of the same polarity located between the solder pad 105 and the adjacent solder joint 106 in the direction from the central area 103 (see . Fig. 2) to the marginal section 102 (see Fig. 2) The number of fingers 104 of the same polarity electrically connected to the connecting lead 107 gradually increases, and the current collected by the connecting lead 107 increases accordingly. A wider first end 117 helps to reduce its own transmission resistance and increases the contact resistance between the first end 117 and the solder pad 105, thereby reducing the overall transmission resistance along the path from the connecting lead 107 to the solder pad 105. This improves the current collection capacity of the connecting lead 107 to accommodate multiple fingers 104 of the same polarity, thereby reducing the risk of overheating at the first end 117 due to current concentration and improving the electrical performance and yield of the back-contacted solar cell.Additionally, when the subsequent solar strip contacts the solder pad 105 and the solder joint 106, the stress exerted on the solder pad 105 as the initial or final position is greater. A wider first end 117 increases the contact area with the solder pad 105, strengthens the connection between the first end 117 and the solder pad 105, and reduces the risk of detachment between the first end 117 and the solder pad 105 due to high stress on the solder joint.

[0054] In addition, the connecting line 107 is designed with varying widths along the first direction X at different positions along the second direction Y, which helps to appropriately reduce the amount of raw material for the manufacture of the connecting line 107, thereby reducing the manufacturing costs of the back-contacted solar cell.

[0055] In some cases, with reference to Fig. 4 or Fig. 5, points under the solder pads 105 and the solder joints 106, which are located in the same soldering area 101, along the direction from the solder joint 106 to the solder pad 105, that is, from the central area 103 to the edge section 102 (see Fig. 2) at least one connecting line 107 has a width that gradually increases along the first direction X. As a result, the transmission resistance of the connecting line 107 gradually decreases, which facilitates the collection of current from more fingers 104 of the same polarity along its path, thereby improving the current collection capability of the connecting line 107. This helps to reduce the risk of overheating at the connecting line 107 adjacent to the solder pad 105 due to current concentration, further improving the electrical performance and yield of the back-contacted solar cell.

[0056] It should be noted that several connecting leads 107 are located within a single back-contacted solar cell. The width of each connecting lead 107 along the first direction X at various sections along the second direction Y can be adjusted according to the actual requirements. Along the first direction X, if the width of the first end 117 of any connecting lead 107 is greater than that of its second end 127, the structural stability of the connecting lead 107 can be improved, the current collection capability of the connecting lead 107 can be enhanced, and the bond strength between the first end 117 and the solder pad 105 can be increased, thereby reducing the risk of delamination between the first end 117 and the solder pad 105.

[0057] In some embodiments, with reference to Fig. 1 to 6, is Fig. 6 A fourth partially enlarged top view of a back-contacted solar cell according to an embodiment of the present disclosure. The back-contacted solar cell can further include a current collection section 108, which is arranged on a side of the solder pad 105 facing away from the solder joint 106 and which is located in the solder area 101. A single current collection section 108 is in contact with several fingers 104 of the same polarity. In this way, several fingers 104 of the same polarity, which are located in the edge region 102 and are not in contact with the solder pad 105, can be connected to the current collection section 108, so that the current collection section 108 can collect currents from the several fingers 104 of the same polarity that are located in the edge region 102 and are not in contact with the pad 105, and can finally transfer the collected currents to the solder pad 105.

[0058] In some cases, with reference to Fig. 6, at least one current collection section 108, a third end 118 located adjacent to the solder pad 105, and a fourth end 128 located away from the solder pad 105. Along the first direction X, the width of the third end 118 is greater than that of the fourth end 128.

[0059] On the one hand, when a solar strip is subsequently connected to the solder pad 105, which serves as the starting or ending soldering position, a relatively large amount of solder paste may be required during the soldering process. This means that the section adjacent to the solder pad 105 is more likely to come into contact with molten solder paste. Accordingly, in the current collection section 108, compared to the fourth end 128, which is furthest from the solder pad 105, the third end 118, which is adjacent to the solder pad 105, is more susceptible to cracking due to contact with molten solder paste. Therefore, the design, in which the third end 118 has a greater width than the fourth end 128 along the first direction X, helps to reduce the risk of cracking of the third end 118 caused by molten solder paste, thereby improving the structural stability of the current collection section 108.

[0060] On the other hand, the boundary sections 102 (see Fig. 2) compared to the central section 103 (see Fig. 2) more susceptible to greater external forces. Based on this, the design in which the width of the third end 118 is greater than that of the fourth end 128 along the first direction X helps to increase the contact area between the third end 118 and the solder pad 105, thereby increasing their connection strength and reducing the risk of the third end 118 detaching from the solder pad 105 due to large external forces.

[0061] In another aspect, since the current collection section 108 can collect current from several fingers 104 of the same polarity located in the edge section 102 and not connected to the solder pad 105, the number of fingers 104 of the same polarity electrically connected to the current collection section 108 gradually increases from the edge section 102 to the central section 103. Accordingly, the current collected in the current collection section 108 gradually increases along this direction. The design, in which the third end 118 has a greater width, helps to reduce the transmission resistance of the third end 118 itself, as well as the contact resistance between the third end 118 and the solder pad 105.This reduces the overall transmission resistance along the path from the current collection section 108 to the solder pad 105, thereby improving the current collection capability of the current collection section 108 to accommodate multiple fingers 104 of the same polarity. As a result, this can reduce the risk of overheating at the third end 118 due to current concentration, thus improving the electrical performance and yield of the back-contacted solar cell.

[0062] In addition, the current collection section 108, which has varying widths at different positions along the first direction X and along the second direction Y, facilitates an optimized reduction of the amount of raw material required for the manufacture of the current collection section 108, thereby reducing the manufacturing costs of the back-contacted solar cell.

[0063] In some cases, referring to Fig. 6 the width of at least one collector section 108 along the first direction X in the direction from the edge section 102 (see Fig. 2) to the central section 103 (see Fig. 2) gradually. In this way, the transmission resistance of the current collection section 108 itself gradually decreases, which facilitates the collection of current from an increasing number of fingers 104 of the same polarity along its path. This improves the current collection capability of the current collection section 108 and also helps to reduce the risk of overheating at the current collection section 108 adjacent to the solder pad 105 due to current accumulation, thereby improving the electrical performance and yield of the back-contacted solar cell.

[0064] It should be noted that several current collection sections 108 are provided in a single back-contacted solar cell. The width of a current collection section 108 along the first direction X at different positions along the second direction Y can be adjusted according to practical requirements. By designing the width of the third end 118 of any current collection section 108 to be greater than the width of its fourth end 128 along the first direction X, the structural stability of the current collection section 108 can be improved, its current collection capacity can be increased, and the bond strength between the third end 118 and the solder pad 105 can be enhanced to reduce the risk of delamination between the third end 118 and the solder pad 105.

[0065] In some cases, with reference to Fig. 1 to 6, the number of fingers 104 of the same polarity in contact with a single current collection section 108 is greater than the number of fingers 104 of the same polarity in contact with a single solder pad 105. In this way, a substantially equal distance between any two adjacent fingers 104 of the same polarity along the second direction Y is advantageous for positioning the solder pad 105 in a section of the edge section 102 adjacent to the central section 103. This avoids placing the solder pad 105 too close to the outer edge of the cell substrate 100, thus preventing damage to the outer edge of the cell substrate 100 when the solar strip is subsequently soldered to the solder pad 105.

[0066] In some cases, with reference to Fig. 1 to 6, the length of the connecting wire 107 along the second direction Y is shorter than the length of the current collection section 108. It should be noted that along the second direction Y, the length of the connecting wire 107 is designed such that the required bending angle for the solar strip per unit length is relatively small, thus ensuring that at least one solder joint 106 in contact with the connecting wire 107 can be stably connected to the solar strip. Accordingly, the solder joints 106 that are not in contact with the connecting wire 107 can also be stably connected to the solar strip. This configuration enables stable current collection from each finger 104 located between two solder pads 105 aligned along the second direction Y, while minimizing the length of the connecting wire 107 as much as possible.

[0067] As a result, the amount of raw materials required for the manufacture of the connecting line 107 can be reduced, thereby lowering the manufacturing costs of the back-contacted solar cell.

[0068] In some cases, with reference to Fig. 1 to 6 the cross-sectional area of ​​the connecting line 107 in a cross-section perpendicular to the second direction Y is smaller than that of the current collecting section 108.

[0069] It should be noted that the number of fingers 104 of the same polarity located between solder pad 105 and solder joint 106, adjacent along the second direction Y, is relatively small, for example, zero. Consequently, the number of fingers 104 of the same polarity from which the connecting lead 107 collects current is smaller than the number of fingers 104 of the same polarity located in the edge section 102, from which the current-collecting section 108 collects current. Therefore, compared to the current density transferred from connecting lead 107 to solder pad 105, the current density transferred from current-collecting section 108 to solder pad 105 is higher.The cross-sectional area of ​​the connecting conductor 107 is smaller than that of the current collection section 108, and therefore the transmission resistance of the current collection section 108 can be further reduced, allowing the current collection section 108 to collect current from a larger number of fingers 104 of the same polarity along its path. This configuration improves the current collection capability of the current collection section 108 and reduces the risk of overheating at the current collection section 108 adjacent to the solder pad 105 due to high current concentration, thereby improving the electrical performance and yield of the back-contacted solar cell.

[0070] In some embodiments, with reference to Fig. In a cross-section perpendicular to the second direction Y, connecting lead 107 has a cross-sectional area defined as the first area. In a cross-section perpendicular to the first direction X, finger 104 has a cross-sectional area defined as the second area. The first area may be larger than the second area. It should be noted that connecting lead 107 conducts the current collected from finger 104 at the solder joint 106 to the solder pad 105 and can additionally transfer a portion of the current from other fingers 104 of the same polarity to the solder pad 105. Therefore, connecting lead 107 must have a higher current collection capacity than finger 104. Furthermore, connecting lead 107 must maintain good electrical contact with both the solder joint 106 and the solder pad 105.Based on this, the connecting wire 107, with a cross-sectional area larger than that of the finger 104, helps to reduce the transmission resistance of the connecting wire 107, thereby improving its current collection efficiency. This also helps to reduce the risk of overheating caused by excessive current concentration within the connecting wire 107 and reduces the risk of detachment between the connecting wire 107 and the solder joint 106 or the solder pad 105.

[0071] In some embodiments, with reference to Fig. 1 to 6 The solder pad 105 has an orthographically projected area on the cell substrate 100 that is larger than the orthographically projected area of ​​the solder joint 106 on the cell substrate 100. Such a configuration not only helps to reduce the transmission resistance of the solder pad 105 to improve its current collection capability, but also increases the alignment accuracy and bond strength between the solder pad 105 and a subsequently attached solar strip. This prevents conditions such as weak solder joints or delamination that can occur when excessive pressure is exerted by the solar strip on the solder pad 105, which serves as the start or end soldering point, thereby improving the bond stability between the solar strip and the solder pad 105.

[0072] In some embodiments, with reference to Fig. 7, which is a partial schematic cross-sectional diagram of the in Fig. In the 6 shown back-contacted solar cell along a first section line AA1, the thickness of the solder pad 105 is smaller than the thickness of the solder joint 106 along the third direction Z. The third direction Z represents the thickness direction of the cell substrate 100.

[0073] It should be noted that, generally, when a subsequent solar tape contacts a solder pad 105 serving as the start or end soldering point, as in cases where a relatively large amount of solder paste is required, the section of the solar tape directly opposite the solder pad 105 may be raised due to the accumulation of solder paste. Consequently, the solder pad 105 will have a thinner profile than the solder joint 106. If the section of the solar tape facing the solder pad 105 and the section facing the solder joint 106 are at the same level, a certain gap can be maintained between the solar tape and the solder pad 105, as the solar tape contacts the solder joint 106 to receive the solder paste applied to the solder pad 105.This effectively prevents poor contact between the solar strip and the solder pad 105 caused by the increased thickness due to applied solder paste, and further reduces bending of the solar strip. This allows, for example, the strip to be electrically connected to both the solder pad 105 and the solder joint 106 without bending downwards. In addition, the reduced thickness of the solder pad 105 prevents the section of the solar strip facing the solder pad 105 from being excessively raised relative to the cell substrate 100 due to the increased amount of solder paste.

[0074] In some embodiments, with reference to Fig. 1 or Fig. 2. The number of solder joints 106 that are in contact with the connecting lead 107 on different solder pads 101 varies. It should be noted that, since different solder pads 101 are subjected to different orders of magnitude of external pressure, the number of solder joints 106 that are in contact with the connecting leads 107 varies in different solder pads 101. This can effectively reduce the risk that a solder joint 106 adjacent to the solder pad 105 might have poor contact with the solar strip, which could otherwise prevent current transfer to the solar strip, while adequately controlling the length of the connecting lead 107 in the second direction Y. Accordingly, the amount of raw material for manufacturing the connecting lead 107 can be limited, thereby controlling the manufacturing costs of the back-contacted solar cell.

[0075] In some cases, with reference to Fig. 1 or Fig. 2 In contrast to a soldering area 101 exposed to relatively low external pressure, more solder joints 106 are designed to be electrically connected by the connecting line 107 in a soldering area 101 that is susceptible to higher external pressure. This helps to reduce the risk of poor contact between the solder joints 106 and the solar tape caused by greater external pressure, allowing the connecting line 107 to compensate for the solder joints 106 that are more susceptible to pressure-induced failures and ensuring proper current collection.

[0076] In some examples, the cell substrate can be 100 with reference to Fig. 1 or Fig. 2 further include two edge sections 109, which are arranged opposite each other along the first direction X. In this case, the number of solder connections 106 that are electrically connected to the connecting line 107 in the solder area 101 closest to the edge section 109 is three, while the number of solder connections 106 that are electrically connected to the connecting line 107 in other solder areas 101 is one.

[0077] In some embodiments, the cell substrate 100 can be described with reference to Fig. 2 further include two edge sections 109 arranged opposite each other along the first direction X. In the same soldering area 101, the solder joint 106 closest to the solder pad 105 is defined as the target solder joint. The number of fingers 104 of the same polarity between the target solder joints and the solder pad 105 in the two soldering areas 101 closest to the edge sections 109 is a first number, while the number of fingers 104 of the same polarity between the target solder joints and the solder pad 105 in the other soldering areas 101 is a second number, the first number being less than the second number.

[0078] It should be noted that no solder joints 106 of the same polarity are provided on the fingers 104 between the target solder joints and the solder pad 105. Since the first number is smaller than the second number, more solder joints 106 are provided in the two solder areas 101 that are closest to the edge sections 109 than in the other solder areas 101. This configuration is advantageous in situations where the two solder areas 101 that are closest to the edge sections 109 are more susceptible to greater external forces, as the greater number of solder joints 106 in these areas helps to improve the connection stability between the solar strip and the solder pads 105, as well as the solder joints 106 in the two solder areas 101 that are closest to the edge sections 109.Furthermore, the reduction of the number of solder joints 106 in the other soldering areas 101 contributes to lowering the manufacturing costs of the back-contacted solar cell.

[0079] In some examples, with further reference to Fig. 2. In the two soldering areas 101 that are closest to the edge sections 109, no finger 104 is located between the target solder joints and the solder pad 105. However, three fingers 104 of the same polarity are located between the target solder joints and the solder pad 105 in the other soldering areas 101.

[0080] In summary, within the same soldering area 101, the solder pad 105 and the solder joint 106 are located in the edge section 102 and the central section 103, respectively. The solder pad 105 can be considered the starting or ending soldering position if a solar strip subsequently makes electrical contact with the back-contacted solar cell. Based on this, a single solder pad 105 contacts at least two adjacent fingers 104 of the same polarity, while a single solder joint 106 contacts a single finger 104. On the one hand, this improves the current collection efficiency of the solder pad 105, allowing current from more fingers 104 of the same polarity to be transferred more quickly to the solder pad 105. This results in a denser current collection network, reduces the transmission distance of photogenerated charge carriers, and decreases the series resistance of the back-contacted solar cell.On the other hand, the solder pad 105, which connects more fingers 104 of the same polarity, can be larger as the starting or ending soldering position for the subsequent solar strip. This not only reduces the transmission resistance of the solder pad 105 to accommodate more fingers 104 of the same polarity, but also improves the alignment accuracy and connection strength between the subsequent solar strip and the solder pad 105, thereby preventing potentially poor solder joints or delamination that could be caused by excessive pressure from the solar strip. Overall, these design considerations help to improve the current collection efficiency of the solder pad 105 and increase the connection stability between the subsequent solar strip and the solder pad 105, which in turn contributes to an overall increase in the current collection efficiency and the photoelectric conversion efficiency of the back-contacted solar cell.

[0081] Furthermore, the solder pad 105 can be electrically connected via the connecting line 107 to at least one solder joint 106 located along the second direction Y adjacent to the solder pad 105. In other words, the connecting line 107 can directly connect the solder joints 106 adjacent to the solder pad 105, which are susceptible to poor contact, defects, or delamination with the downstream solar strip, to the solder pad 105. Even if a solder joint 106 adjacent to the solder pad 105 cannot conduct current to the solar strip due to poor contact, this solder joint 106 can still conduct current to the solder pad 105 and then to the solar strip via the connecting line 107. Therefore, the connecting line 107 further ensures that the downstream solar strip can collect current from all fingers of the same polarity, thereby improving the photoelectric conversion efficiency of the back-contacted solar cell.

[0082] A photovoltaic module is provided according to another embodiment of the present disclosure. The photovoltaic module is formed by connecting a plurality of the aforementioned back-contacted solar cells or by connecting a plurality of back-contacted solar cells produced by the aforementioned method. The following description refers to the drawings to illustrate the photovoltaic module. It should be noted that sections identical or analogous to those in the preceding embodiments are not repeated herein.

[0083] With reference to Fig. 8 and Fig. 9 together with Fig. 1 to 7 includes the photovoltaic module: a solar cell string formed by connecting a plurality of the aforementioned back-contacted solar cells 40; an encapsulation 41 configured to cover one surface of the solar cell string; and a cover plate 42 configured to cover one surface of the encapsulation 41 facing away from the solar cell string.

[0084] Here is Fig. 8 a partial perspective view of the photovoltaic module according to an embodiment of the present disclosure. Fig. Figure 9 is a partial cross-sectional view of the photovoltaic module along a second cross-sectional direction BB 1, as shown in Fig. 8 shown.

[0085] In some embodiments, the back-contacted solar cell 40 is a BC cell (back-contacted cell), which includes, but is not limited to, IBC solar cells (interdigitating back-contacted solar cells), HBC solar cells (hetero-transitioning back-contacted solar cells), TBC solar cells (TOPCon back-contacted solar cells), or HPBC solar cells (hybrid-passivated back-contacted solar cells). Furthermore, the back-contacted solar cells 40 can be electrically connected either as whole cells or as cut cells to form multiple solar cell strings, and these strings can be electrically connected in series and / or parallel. The back-contacted solar cells 40 can be either whole cells or cut cells, wherein a cut cell refers to a cell obtained by cutting a whole cell using a cutting process.

[0086] In some embodiments, with reference to Fig. 8 or Fig. 9 several rear-contacted solar cells 40 are electrically connected by solar strips 43. Fig. 8 and Fig. Figure 9 merely illustrates one possible positional relationship between the back-contacted solar cells 40. In practical applications, the grid lines of adjacent back-contacted solar cells may be located on different sides, in which case the solar band connects the different sides of two adjacent back-contacted solar cells.

[0087] In some embodiments, the encapsulation 41 comprises a first encapsulation layer and a second encapsulation layer, wherein the first encapsulation layer covers either the front or back side of the back-contacted solar cell 40, and the second encapsulation layer covers the other side. In particular, at least one of the first or second encapsulation layers is an organic encapsulation film, such as a polyvinyl butyral film (PVB film), an ethylene vinyl acetate film (EVA film), a polyolefin elastomer film (POE film), or a polyethylene terephthalate film (PET film). Alternatively, at least one of the first or second encapsulation layers can be an EP film, an EPE film, or a PVP film.Here, EP film refers to a co-extruded film formed by laminating EVA and POE films; EPE film refers to a co-extruded film formed by successive lamination of EVA, POE, and EVA films; and PVP film refers to a co-extruded film formed by lamination of POE, EVA, and POE films. Co-extrusion can include the successive extrusion of one or more materials onto a pre-formed film during film processing, or the lamination of pre-formed films of different types together.

[0088] In some cases, the first and second encapsulation layers may still have an interface before lamination. However, after the lamination process to form the photovoltaic module, the distinction between the first and second encapsulation layers no longer exists, and the two layers form an integrated encapsulation.41

[0089] In some embodiments, the cover plate 42 can be a glass plate, a plastic plate, or another translucent cover plate. In particular, the surface of the cover plate 42 facing the encapsulation 41 can be textured or include several projecting structures to increase the utilization of the incident light. The cover plate 42 includes a first cover plate and a second cover plate, the first cover plate facing the first encapsulation layer and the second cover plate facing the second encapsulation layer.

[0090] In some scenarios, the surface of the back-contacted solar cell 40 encloses several fingers arranged at intervals along the second direction. During the construction of a solar cell string using the back-contacted solar cells 40, the solar strips 43 electrically connect the multiple fingers on each of two adjacent back-contacted solar cells 40.

[0091] Those skilled in the art should understand that the embodiments described above are specific examples for implementing the present disclosure. In practical applications, various changes in the shapes and details can be made without deviating from the scope of protection of the present disclosure. Any person skilled in the art can make modifications and variations within the scope of protection of the present disclosure. The scope of protection of the embodiments of the present disclosure should therefore be defined by the claims.

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