Back contact solar cell and photovoltaic module

Abstract

The embodiment of the present application relates to the photovoltaic field, and provides a back contact solar cell and a photovoltaic module, wherein the back contact solar cell comprises: a substrate; a first doped layer and a second doped layer with opposite doping types, located on the back light surface of the substrate, the second doped layer having an overlapping part which is arranged on the first doped layer in a laminated manner; a passivation layer, the passivation layer covering at least the overlapping part; and an electrode layer, the electrode layer comprising a first main pad located at the edge area of the back contact solar cell, and a first auxiliary grid line and a second auxiliary grid line with opposite polarities, the first auxiliary grid line being in contact with and electrically connected to the first doped layer, the second auxiliary grid line being in contact with and electrically connected to the second doped layer, and the first main pad being used for electrically connecting the first auxiliary grid line and a solder ribbon, the first main pad being located on the side of the overlapping part away from the first doped layer and arranged on the passivation layer. The solar cell provided by the embodiment of the present application can improve the production efficiency while ensuring the electrical performance of the back contact solar cell.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of photovoltaics, in particular to a back contact solar cell and a photovoltaic module. BACKGROUND

[0002] A back contact solar cell designs both the front and back metal contacts on the back of the cell, thereby avoiding shading and reflection losses caused by the front surface metal grid lines, effectively improving the photoelectric conversion efficiency of the cell.

[0003] In the production process of a back contact solar cell, laser technology plays a crucial role. The laser is precisely controlled and etched on the back of the cell according to the preset pattern design to form a series of grooves or openings to accommodate the subsequent metallization layer and realize the back contact structure.

[0004] The above information disclosed in the background section is only used to enhance the understanding of the background of the technology described herein, therefore, the background section may contain certain information which is not considered as prior art known in the country by those skilled in the art. SUMMARY

[0005] The embodiments of the present application provide a back contact solar cell and a photovoltaic module, which at least improve the production efficiency of the back contact solar cell.

[0006] According to some embodiments of the present application, the embodiments of the present application provide a back contact solar cell, which comprises: a substrate; a first doped layer and a second doped layer with opposite doping types, located on the back light surface of the substrate, the second doped layer comprising an overlapping portion arranged on the first doped layer in a stacked manner; a passivation layer covering at least the overlapping portion; an electrode layer comprising a first main pad located at the edge area of the back contact solar cell and a first auxiliary grid line and a second auxiliary grid line with opposite polarities, the first auxiliary grid line being in contact with and electrically connected to the first doped layer, the second auxiliary grid line being in contact with and electrically connected to the second doped layer, the first main pad being used for electrically connecting the first auxiliary grid line and a solder ribbon, the first main pad being located on the side of the overlapping portion away from the first doped layer and arranged on the passivation layer.

[0007] In some embodiments, the electrode layer further comprises: a first gate line segment, the first gate line segment is located between the first main pad and the substrate edge closest to the first main pad, the first gate line segment is arranged in one-to-one correspondence with the first main pad and is electrically connected, the extension direction of the first gate line segment intersects the first sub-gate line and is electrically connected to at least one first sub-gate line, and the orthogonal projection of the first gate line segment on the substrate falls within the range of the orthogonal projection of the overlap on the substrate.

[0008] In some embodiments, the electrode layer further comprises: a first main gate line, the extension direction of the first main gate line intersects the first sub-gate line, and the first main gate line is electrically connected to at least one first main pad, and the orthogonal projection of the first main gate line on the substrate falls within the range of the orthogonal projection of the overlap on the substrate.

[0009] In some embodiments, the electrode layer further comprises: a first sub-pad, each first sub-pad is electrically connected to a first sub-gate line, the area of the first sub-pad is smaller than the area of the first main pad, and the orthogonal projection of the first sub-pad on the substrate at least partially overlaps the orthogonal projection of the overlap on the substrate.

[0010] In some embodiments, a plurality of first sub-pads are arranged along a certain direction, and the orthogonal projection of the plurality of first sub-pads on the substrate along the certain direction falls within the range of the orthogonal projection of the same overlap on the substrate.

[0011] In some embodiments, a plurality of first main pads and a plurality of overlaps are arranged in one-to-one correspondence, and the orthogonal projection of the first main pad on the substrate falls within the range of the orthogonal projection of the corresponding overlap on the substrate.

[0012] In some embodiments, a plurality of first main pads and a plurality of overlaps are arranged in one-to-one correspondence, the overlap comprises a first sub-part and a second sub-part, the first sub-part and the second sub-part have a spacing, the orthogonal projection of the first sub-gate line electrically connected to the first main pad on the substrate falls within the range of the orthogonal projection of the spacing on the substrate, and the orthogonal projection of the first main pad on the substrate at least partially overlaps the first sub-part and the second sub-part.

[0013] In some embodiments, the first sub-gate line extends along a first direction, a plurality of first sub-gate lines are arranged in a column along a second direction, the second direction intersects the first direction, each column of first sub-gate lines corresponds to the arrangement of two first main pads, and the two first main pads are respectively located in the two edge regions of the back contact solar cell in the second direction.

[0014] In some embodiments, the electrode layer further comprises: a second main pad located at an edge region of the back contact solar cell, the second main pad being configured to electrically connect the second auxiliary grid line and a solder ribbon, the second main pad being located at a side of the second doped layer facing away from the substrate and being staggered with the overlap portion.

[0015] According to some embodiments of the present application, another aspect of the embodiments of the present application provides a photovoltaic module, comprising: a cell string connected by a plurality of back contact solar cells according to any one of the above embodiments; an encapsulating film configured to cover a surface of the cell string; and a cover plate configured to cover a surface of the encapsulating film facing away from the cell string.

[0016] The technical solutions provided by the embodiments of the present application have at least the following advantages:

[0017] The present application relates to the field of photovoltaic technology, and provides a back contact solar cell and a photovoltaic module, wherein the back contact solar cell comprises: a substrate; a first doped layer and a second doped layer having opposite doping types, which are located on a back light surface of the substrate, the second doped layer comprising an overlap portion which is arranged in a stack on the first doped layer; a passivation layer covering at least the overlap portion; and an electrode layer comprising a first main pad located at an edge region of the back contact solar cell, and first and second auxiliary grid lines having opposite polarities, the first auxiliary grid line being in contact with and electrically connected to the first doped layer, the second auxiliary grid line being in contact with and electrically connected to the second doped layer, the first main pad being configured to electrically connect the first auxiliary grid line and a solder ribbon, the first main pad being located at a side of the overlap portion facing away from the first doped layer and being arranged on the passivation layer. By arranging the second doped layer and part of the first doped layer in a stack to form the overlap portion, the region where the overlap portion is located does not need to remove the material of the first doped layer by using a laser direct writing process, thereby reducing the number and path of laser direct writing, which is conducive to improving the production efficiency and reducing the thermal damage caused by laser direct writing, and is conducive to prolonging the service life of the cell. BRIEF DESCRIPTION OF DRAWINGS

[0018] One or more embodiments are illustrated by way of example in the figures that form a part of this disclosure and which are illustrative of various embodiments of devices and methods. These examples in which the principles of the present application can be utilized, and specific embodiments thereof are shown and described herein, it being understood that the application is not intended to be limited to the particulars control of this application. As such, the application seeks to provide a photovoltaic module, and the like, having the technical solutions provided by the embodiments of the present application.

[0019] Figure 1 A schematic diagram of a planar structure of a back contact solar cell according to an embodiment of the present application is shown in FIG. 1.

[0020] Figure 2 A cross-sectional structure schematic diagram of a back contact solar cell provided according to an embodiment of the present application;

[0021] Figure 3 A structure schematic diagram of an initial back contact solar cell provided according to an embodiment of the present application;

[0022] Figure 4 A laser moving path schematic diagram in a preparation process of a conventional back contact solar cell;

[0023] Figure 5 A laser moving path schematic diagram in a preparation process of a back contact solar cell provided according to an embodiment of the present application;

[0024] Figure 6 A partial structure schematic diagram of a back contact solar cell provided according to an embodiment of the present application;

[0025] Figure 7 A partial structure schematic diagram of a back contact solar cell provided according to an embodiment of the present application;

[0026] Figure 8 A planar structure schematic diagram of a back contact solar cell provided according to an embodiment of the present application;

[0027] Figure 9 A planar structure schematic diagram of a back contact solar cell provided according to an embodiment of the present application;

[0028] Figure 10 A partial structure schematic diagram of a back contact solar cell provided according to an embodiment of the present application;

[0029] Figure 11 A laser moving path schematic diagram in a preparation process of a back contact solar cell provided according to an embodiment of the present application;

[0030] Figure 12 A planar structure schematic diagram of a back contact solar cell 1000 provided according to an embodiment of the present application.

[0031] In the above drawings, the following reference signs are used:

[0032] 1000, back contact solar cell; 2000, initial back contact solar cell; 1, substrate; 2, first doped layer; 3, second doped layer; 4, overlapping part; 41, first subpart; 42, second subpart; 5, passivation layer; 6, electrode layer; 611, first subgrid line; 612, second subgrid line; 621, first main pad; 622, second main pad; 631, first grid segment; 632, second grid segment; 641, first subpad; 642, second subpad; 651, first main grid line; 652, second main grid line; 7, spacing area; 8, dividing line; X, first direction; Y, second direction; 91, first region; 92, second region; 93, third region; 94, fourth region. DETAILED DESCRIPTION

[0033] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is more than two, unless otherwise explicitly and specifically limited.

[0034] In this paper, the reference to "embodiments" means that the specific features, structures or characteristics described in conjunction with the embodiments can be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily mean the same embodiment, nor is it an independent or alternative embodiment to other embodiments. The skilled in the art explicitly and implicitly understands that the embodiments described herein can be combined with other embodiments.

[0035] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B, which can represent the existence of A, the existence of A and B, and the existence of B. In addition, the character " / " in this paper generally represents that the front and rear associated objects are a "or" relationship.

[0036] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two), and similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0037] In the description of the embodiments of the present application, the technical terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate the orientation or positional relationship shown in the drawings, which are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the embodiments of the present application.

[0038] In the description of the embodiments of the present application, unless otherwise explicitly specified and limited, the technical terms "mounting", "connecting", "connecting", "fixing" and the like should be understood broadly, for example, can be fixedly connected, or can be detachably connected, or can be integrated; can be mechanically connected, or can be electrically connected; can be directly connected, or can be indirectly connected through an intermediate medium; can be the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0039] In the corresponding drawings of the embodiments of the present application, the thickness and area of the layer are exaggerated for better understanding and ease of description. When describing that a component (such as a layer, a film, a region or a substrate) is on or on the surface of another component, the component can be "directly" on the surface of the other component, or a third component can exist between the two components. On the contrary, when describing that a component is on the surface of another component or that a component surface is formed or provided with another component, it means that there is no third component between the two components. In addition, when describing that a component is "formed substantially" on another component, it means that the component is not formed on the entire surface (or front surface) of the other component, nor on the edge of the entire surface.

[0040] In the description of the embodiments of the present application, when a certain component "includes" another component, unless otherwise specified, other components are not excluded and other components can be further included. In addition, when a layer, film, region or plate and the like are referred to as "on / over" another component, it can be "directly on" another component (i.e. between the surface of another component and another component without other components), or another component can exist therebetween. In addition, when a layer, film, region, plate and the like are "directly on" another component, or when a layer, film, region, plate and the like are on the surface of another component, it means that no other component is located therebetween.

[0041] The terminology used in the description of the various described embodiments herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used in the description of the various embodiments of the disclosure and the appended claims, the term "the" is also intended to include a plurality of items, unless the context clearly indicates otherwise. Wherever possible, any stated numerical values or ranges are intended to include all values and ranges within those stated values and ranges.

[0042] The embodiments of the present application will be described in detail with reference to the drawings. However, those skilled in the art can understand that, in the embodiments of the present application, many technical details are presented in order to make the reader better understand the present application. However, the technical solutions claimed by the present application can be implemented even without these technical details and various changes and modifications based on the following embodiments.

[0043] Figure 1 A schematic diagram of a planar structure of a back contact solar cell according to an embodiment of the present application, Figure 2 A schematic diagram of a cross-sectional structure of a back contact solar cell according to an embodiment of the present application, Figure 2 may represent Figure 1 a cross-sectional structure in the AA' direction, as shown in Figure 1 and Figure 2 The back contact solar cell 1000 includes a substrate 1, a first doped layer 2, a second doped layer 3, a passivation layer 5 and an electrode layer 6, which will be described in detail below.

[0044] The substrate 1 can be a silicon substrate, including but not limited to a single crystal silicon substrate, a polycrystalline silicon substrate or an amorphous silicon substrate. Impurity atoms are introduced into the silicon substrate 1 by doping to form a P-type substrate or an N-type substrate. The substrate 1 can be used as a support for the cell and as a place for photoelectric conversion.

[0045] The first doped layer 2 and the second doped layer 3 have opposite doping types, wherein the first doped layer 2 can be a P-type doped layer and the second doped layer 3 can be an N-type doped layer, or the first doped layer 2 can be an N-type doped layer and the second doped layer 3 can be a P-type doped layer. The P-type doping elements include but are not limited to at least one of boron, aluminum, gallium, indium, thallium, etc., and the N-type doping elements include but are not limited to at least one of nitrogen, phosphorus, arsenic, antimony, bismuth, etc. The specific doping types of the first doped layer 2 and the second doped layer 3 are not limited in the embodiments of the present application. In the embodiments of the present application, as shown in Figure 1 and Figure 2 As shown in

[0046] The first doped layer 2 and the second doped layer 3 are located on the back surface of the substrate 1, and the second doped layer 3 includes an overlapping portion 4 stacked on the first doped layer 2. Since the first doped layer 2 and the second doped layer 3 have different doping types, leakage may occur at the overlapping portion 4 where they contact each other. Therefore, a passivation layer 5 is also provided on the side of the first doped layer 2 and the second doped layer 3 away from the substrate 1. The passivation layer 5 at least covers the overlapping portion 4, thereby providing an insulating barrier between the electrode layer 6 and the doped layers (including the first doped layer 2 and the second doped layer 3), preventing unnecessary direct electrical contact between the electrode layer 6 and the doped layers, avoiding short circuits or leakage, and ensuring the reliability and stability of the battery operation. Figure 2 As shown, the passivation layer 5 can also cover other parts of the first doped layer 2 and the second doped layer 3, thereby reducing surface defects of the doped layer, reducing surface recombination, and improving the conversion efficiency of the battery. In practical applications, the passivation layer 5 can also be set entirely on the side of the first doped layer 2 and the second doped layer 3 away from the substrate 1, that is, the passivation layer 5 is also set in the spacer region 7, thereby providing more comprehensive protection for the battery.

[0047] Electrode layer 6 includes a first sub-gate line 611 and a second sub-gate line 612 with opposite polarities. The first sub-gate line 611 is in contact with and electrically connected to the first doped layer 2, and the second sub-gate line 612 is in contact with and electrically connected to the second doped layer 3. Figure 1 In the illustrated embodiment, the back-contact solar cell 1000 is a gridless back-contact solar cell. The first sub-grid line 611 and the second sub-grid line 612 are in contact with and electrically connected to the first doped layer 2 and the second doped layer 3 with opposite doping types, respectively. That is, the first sub-grid line 611 and the second sub-grid line 612 are sub-grid lines with opposite polarities, which are used to collect positive carriers (holes) and negative carriers (electrons), respectively. For example, when the first doped layer 2 is a P-type doped layer and the second doped layer 3 is an N-type doped layer, the first sub-grid line 611 is used to collect holes and the second sub-grid line 612 is used to collect electrons.

[0048] It should be understood that the above-mentioned "electrical connection" means that the components such as the first sub-grid line 611, the second sub-grid line 612, the first doped layer 2, and the second doped layer 3 are conductive. When the back-contact solar cell 1000 is in the power generation or power supply state, the above-mentioned electrically connected components can conduct current to achieve electrical connection. In other cases, the above-mentioned electrically connected components may only be in contact with each other without current passing through them.

[0049] The electrode layer 6 also includes a first main pad 621 located at the edge region of the back contact solar cell 1000. The first main pad 621 is used to electrically connect the first sub-gate line 611 to the solder strip. It is understood that the first main pad 621 has a larger area than the sub-gate line to ensure good electrical contact and current carrying capacity. Furthermore, the solder strip and the first main pad 621 can be soldered together using flux. The larger width is beneficial to improving the reliability of the soldering. The first main pad 621 is located on the side of the overlapping portion 4 away from the first doped layer 2 and is disposed on the passivation layer 5. The passivation layer 5 can play an insulating and protective role, preventing the first main pad 621 from directly contacting the second doped layer 3 and causing a short circuit.

[0050] It is worth noting that the back-contact solar cell 1000 in this application refers to the smallest cell unit in a photovoltaic module. It can be a whole cell or a segmented cell cut from a whole cell. The segmented cell can be 1 / 2, 1 / 3, 1 / 4, etc. of a whole cell, but is not limited to these. Different sizes of segmented cells are used to adapt to photovoltaic modules of different sizes and shapes. When the back-contact solar cell 1000 in this application uses segmented cells, a whole cell is first prepared and then it is divided along the cutting line to form segmented cells. When preparing the whole cell, the first main pad 621 and the overlapping part 4 are not only set in the edge area of ​​the whole cell, but also in the area near the dividing line. Thus, after the whole cell is divided, the first main pad 621 and the overlapping part 4 are provided in the edge area of ​​each segmented cell (i.e., the back-contact solar cell 1000 in this application).

[0051] For example, Figure 3 This is a schematic diagram of an initial back-contact solar cell according to an embodiment of this application. The initial back-contact solar cell 2000 is a whole cell to be divided during the fabrication of the back-contact solar cell 1000. Dividing the whole cell to be divided along the dividing line 8 yields two half-cell cells. In some embodiments of this application, the back-contact solar cell 1000 may be the aforementioned half-cell cell. A first main pad 621 and an overlapping portion 4 corresponding to the first main pad 621 are provided in the edge region of the whole cell and near the dividing line 8. For ease of explanation, the following embodiments all use the case where the back-contact solar cell 1000 is a whole cell as an example.

[0052] In the fabrication process of solar cells, a process is usually adopted to first deposit the entire layer and then use laser direct writing to remove part of the material to form the required film pattern. In this embodiment, by designing a partial stacking of the second doped layer 3 and the first doped layer 2 to form an overlapping part 4, the area where the overlapping part 4 is located does not need to use laser direct writing to remove the material of the first doped layer 2, thereby reducing the number of laser direct writing operations and the path, which is beneficial to improving production efficiency and reducing the thermal damage caused by laser direct writing, which is beneficial to extending the service life of the cell.

[0053] For ease of understanding, the following description is based on the fabrication method of the back contact solar cell 1000. The fabrication method of the back contact solar cell 1000 provided in this application includes the following steps:

[0054] Step S1: Form a first initial doped layer on substrate 1, and pattern the first initial doped layer using a laser direct writing process to form a first doped layer 2;

[0055] Step S2: A second initial doped layer is formed on the substrate 1 and the first doped layer 2, and the second initial doped layer is patterned using a laser direct writing process to form the second doped layer 3;

[0056] Step S3: Form a passivation layer 5 on the first doped layer 2 and the second doped layer 3;

[0057] Step S4: Form an electrode layer 6 on the passivation layer 5.

[0058] For ease of understanding, the beneficial effects of this application will be explained below by referring to the laser movement path in steps S1 and S2 above, in conjunction with a conventional back-contact solar cell 1000 and embodiments of this application.

[0059] Figure 4 This is a schematic diagram of the laser movement path during the fabrication process of a conventional back-contact solar cell. Figure 5 This is a schematic diagram of a laser movement path in the fabrication process of a back-contact solar cell according to an embodiment of this application, wherein the dashed line represents the laser movement path in step S1, and the solid line represents the laser movement path in step S2. It should be understood that... Figure 4 and Figure 5 For clarity, only a partial structure of the back-contact solar cell is shown in the diagram.

[0060] It is understandable that laser light irradiating the battery surface can form a light spot. Figure 4 and Figure 5The laser movement path shown is the movement path of the center of the laser spot. In practical applications, a single laser beam can be used to move back and forth to form the desired film pattern. When the movement paths are adjacent and parallel, multiple laser beams can also be used to move in parallel to form the desired film pattern. This application does not limit this.

[0061] Reference Figure 4 and Figure 5 The laser is configured to move along a first direction X and a second direction Y, wherein the first direction X can be the direction in which the sub-gate line extends, and the second direction Y is the direction intersecting the first direction X. Optionally, the second direction Y is perpendicular to the first direction X. In specific implementation, the laser can first pass through the path in the first direction X and then through the path in the second direction Y, or it can first pass through the path in the second direction Y and then through the path in the first direction X; this is not limited here.

[0062] contrast Figure 4 and Figure 5 As can be seen, since the overlapping portion 4 is designed in the area corresponding to the first main pad 621 (i.e., the first area 91) in this embodiment, the laser moving along the second direction Y does not need to pass through the area corresponding to the first main pad 621 (i.e., the first area 91 shown in the figure) in step S1 above. As a result, the laser path in the first area 91 is more streamlined, which can avoid the damage caused by the laser passing through the area twice for heating, and reduce the laser operation time. This means that the processing cycle of each battery is shortened, which is beneficial to improving production efficiency.

[0063] It is worth noting that both the first doped layer 2 and the second doped layer 3 are made of semiconductor materials. The vertical current conduction of semiconductor materials is mainly determined by the doping concentration and carrier concentration, while lateral transport is affected by the carrier diffusion coefficient. The diffusion coefficient is related to factors such as the material's temperature, purity, and dopant type. Generally, the lateral diffusion coefficient of a doped layer is much lower than its vertical conduction capability, meaning that carriers move slowly in the planar direction. This limitation in lateral transport capability means that carriers mainly achieve rapid vertical transport before reaching the electrode layer 6. Based on this, in the embodiments of this application, carriers are mainly collected to the nearest sub-gate line through rapid vertical movement. Although the portion of the first doped layer 2 covered by the overlapping portion 4 is continuous with other portions, the lateral transport of carriers in the region between the overlapping portion 4 and the sub-gate line has little impact on the process of carrier collection by the sub-gate line.

[0064] As can be seen from the above preparation method, the larger the area of ​​the overlapping portion 4, the simpler the laser direct writing path. However, although the poor lateral transport capability of semiconductor materials makes it difficult for the overlapping portion 4 to adversely affect the process of collecting charge carriers on the sub-gate line, improper placement or excessive size of the overlapping portion 4 may lead to a decrease in the reliability of its electrical performance. In the embodiments of this application, appropriately setting the overlapping portion 4 can avoid adversely affecting the process of collecting charge carriers on the sub-gate line.

[0065] Figure 6 This is a partial structural schematic diagram of a back-contact solar cell provided according to an embodiment of this application, such as... Figure 6 As shown, in some embodiments of this application, multiple first main pads 621 can be correspondingly arranged with multiple overlapping portions 4, and the orthographic projection of the first main pad 621 on the substrate 1 falls within the range of the orthographic projection of the corresponding overlapping portion 4 on the substrate 1. Based on the above arrangement, the area of ​​the overlapping portion 4 is at least larger than the area of ​​the first main pad 621. The range of the overlapping portion 4 is corresponding to the range of the first main pad 621. Since the main pad occupies more area than the sub-grid line in the back contact solar cell 1000 without a main grid, the overlapping portion 4 is arranged for the component that occupies a relatively large area in the cell, and the area of ​​the overlapping portion 4 is at least larger than the area of ​​its corresponding first main pad 621. This can greatly reduce the laser movement path, improve production efficiency, and is suitable for mass production.

[0066] In some embodiments of this application, the orthographic projections of the first main pad 621 and the overlapping portion 4 on the substrate 1 can overlap each other, thereby controlling the area of ​​the overlapping portion 4 within a small range. This simplifies the laser direct writing path and improves production efficiency while minimizing the impact on the electrical performance of the battery.

[0067] Reference Figure 1 and Figure 3 In some embodiments of this application, the first sub-grid line 611 extends along the first direction X, and multiple first sub-grid lines 611 are arranged in a column along the second direction Y, where the second direction Y intersects the first direction X. Each column of first sub-grid lines 611 can be correspondingly provided with two first main solder pads 621, which are located in two opposite edge regions of the back contact solar cell 1000 in the second direction Y. In the above embodiments, the first main solder pads 621 are only provided in the edge regions at both ends of the back contact solar cell 1000, which can overcome the problem of weak solder strip connection in the edge region of the cell and will not significantly increase the amount of paste used, thus improving the reliability of the cell and reducing the production cost of the cell.

[0068] Figure 7 This is a schematic diagram of another partial structure of a back-contact solar cell provided according to an embodiment of this application, as shown below.Figure 7 As shown, in some embodiments of this application, a plurality of first main pads 621 are correspondingly arranged with a plurality of overlapping portions 4. Each overlapping portion 4 includes a first sub-portion 41 and a second sub-portion 42, which are spaced apart. The orthographic projection of the first sub-gate line 611, electrically connected to the first main pad 621, onto the substrate 1 falls within the range of the orthographic projections spaced apart on the substrate 1. The orthographic projection of the first main pad 621 onto the substrate 1 at least partially overlaps with the first sub-portion 41 and the second sub-portion 42. In the above embodiments, the overlapping portions 4 avoid the contact area between the first sub-gate line 611 and the first doped layer 2, which can further reduce leakage current while simplifying the laser direct writing path, ensuring that the current collection efficiency of the first sub-gate line 611 directly connected to the first main pad 621 is not affected. Furthermore, as... Figure 7 The overlapping portion 4 shown can be utilized Figure 5 The laser direct writing path shown is formed, referencing Figure 4 and Figure 5 As can be seen, forming the overlapping portion 4, including the first sub-part 41 and the second sub-part 42, does not require modification of the laser direct writing path in the first direction X within the first region 91. Only a portion of the path in the second direction Y within the first region 91 is simplified. That is, the modification to the laser pattern is minimal, reducing the costs of redesign, simulation, and testing associated with laser pattern modifications, and lowering the risk of waste due to process adjustments. This helps reduce design and production costs, ensuring production yield and efficiency. In practical applications, this can also be omitted. Figure 5 A laser direct-write path in the first direction X within the first region 91 is used to prepare... Figure 6 The overlapping portion 4 is shown.

[0069] It should be understood that the pads are usually located in the middle of the sub-gate lines. In the fabrication of the back contact solar cell 1000, the main pads and sub-gate lines may be fabricated in steps, such as fabricating the sub-gate lines first and then the main pads, or they may be fabricated simultaneously. When the main pads and sub-gate lines are fabricated simultaneously, the embodiments of this application can be understood as follows: the orthographic projection of the connection line of the two segments of the first sub-gate lines 611 located on both sides of the first main pad 621 and electrically connected to the first main pad 621 on the substrate 1 falls within the range of the above-mentioned orthographic projections on the substrate 1.

[0070] Reference Figure 1 and Figure 3The electrode layer 6 also includes a second main pad 622, located at the edge region of the back-contact solar cell 1000. The second main pad 622 is used to electrically connect the second sub-gate line 612 to the solder ribbon. The second main pad 622 is located on the side of the second doped layer 3 facing away from the substrate 1 and is offset from the overlap portion 4. The second sub-gate line 612 connected to the second main pad 622 has a different polarity than the first sub-gate line 611 connected to the first main pad 621. Since the second sub-gate line 612 needs to contact the second doped layer 3 located closer to the passivation layer 5, if the overlap portion 4 is provided in the area corresponding to the second main pad 622, the resulting leakage current will be more significant. Therefore, the second main pad 622 needs to be offset from the overlap portion 4 to reduce the impact of the overlap portion 4 on the electrical performance of the back-contact solar cell 1000. (Refer to...) Figure 4 and Figure 5 Since the second main pad 622 needs to be offset from the overlapping part 4, the laser direct writing path in the second region 92 corresponding to the second main pad 622 remains unchanged.

[0071] It is understood that the main pads in the back contact solar cell 1000 include a first main pad 621 and a second main pad 622 with different polarities. The first main pad 621 and the second main pad 622 can be arranged alternately along the first direction X. It should be understood that, for the sake of clarity, this application only shows a small number of main pads in the accompanying drawings, and does not represent the number of main pads in the actual product. That is, more main pads can be set in the first direction X. The specific number can be set according to actual needs, and this application does not limit it here.

[0072] Figure 8 This is a schematic diagram of a planar structure of another back-contact solar cell provided according to an embodiment of this application.

[0073] like Figure 8 As shown, electrode layer 6 may further include a first gate line segment 631. The first gate line segment 631 is located between the first main pad 621 and the substrate edge closest to the first main pad 621. The first gate line segment 631 is correspondingly disposed with and electrically connected to the first main pad 621. The extension direction of the first gate line segment 631 intersects with the first sub-gate line 611 and is electrically connected to at least one first sub-gate line 611. The orthographic projection of the first gate line segment 631 on the substrate 1 falls within the range of the orthographic projection of the overlapping portion 4 on the substrate 1. It should be understood that, for clarity of illustration, Figure 8 The image shows only one of the overlapping portions 4 corresponding to the first grid line segment 631 and the first main pad 621. Overlap portions 4 can also be provided in other areas of the back contact solar cell 1000 corresponding to the first grid line segment 631 and the first main pad 621.

[0074] In this embodiment, a first gate segment 631 is provided between the first main pad 621 and its nearest edge to the substrate 1. The first gate segment 631 is electrically connected to the first sub-gate line 611 located in the edge region of the battery, thereby allowing the first gate segment 631 to collect the current collected by the first sub-gate line 611 in the edge region of the battery, improving current collection efficiency. It is understood that the first gate segment 631 can connect to multiple first sub-gate lines 611; the specific number can be designed according to actual needs and is not limited here.

[0075] Furthermore, the edge area of ​​the battery is more prone to weak connection with the solder ribbon. By setting a first grid segment 631 in the edge area of ​​the battery, and the placement direction of the solder ribbon (i.e. the extension direction of the solder ribbon) is the same as the extension direction of the first grid segment 631, the first grid segment 631 can be connected with the solder ribbon at high temperature in the subsequent lamination process of forming photovoltaic modules, thereby improving the connection strength between the solder ribbon and the electrode structure in the battery at the edge area of ​​the battery. In addition, the orthographic projection of the first grid segment 631 on the substrate 1 falls within the range of the orthographic projection of the overlapping part 4 on the substrate 1, so the laser does not need to pass through the area corresponding to the first grid segment 631 to remove the second doped layer 3, thereby further simplifying the laser direct writing path and operation time, and further improving production efficiency.

[0076] Optionally, if the line width of the first grid line segment 631 is greater than the line width of the first sub-grid line 611, then the first grid line segment 631 has a smaller resistance, which can more effectively collect the current collected by the sub-grid line, reduce the loss in the current transmission process, thereby improving the current transmission efficiency in the back contact solar cell 1000, which is beneficial to improving the photoelectric conversion efficiency and output power of the cell.

[0077] Similarly, such as Figure 8 As shown, a second grid segment 632 can be provided between the second main pad 622 and its nearest edge of the substrate 1. The polarity of the second grid segment 632 is opposite to that of the first grid segment 631, and it is used to electrically connect the second sub-grid line 612 located in the edge region of the cell. Thus, the second grid segment 632 can collect the current collected by the second sub-grid line 612 located in the edge region of the cell, improving current collection efficiency. Furthermore, providing the second grid segment 632 can also improve the connection reliability of the solder ribbon. The number of second sub-grid lines 612 connected to the second grid segment 632 can be the same as or different from the number of first sub-grid lines 611 connected to the first grid segment 631; this embodiment does not impose such a limitation. The second grid segment 632 is staggered from the overlapping portion 4 to avoid the overlapping portion 4 having a significant adverse effect on the electrical performance of the back-contact solar cell 1000.

[0078] Figure 9 This is a schematic diagram of a planar structure of another back-contact solar cell according to an embodiment of this application.Figure 9 As shown, the electrode layer 6 may also include a first sub-pad 641, each first sub-pad 641 being electrically connected to a first sub-gate line 611. The area of ​​the first sub-pad 641 is smaller than the area of ​​the first main pad 621. The orthographic projection of the first sub-pad 641 on the substrate 1 at least partially overlaps with the orthographic projection of the overlapping portion 4 on the substrate 1.

[0079] In the above embodiments, the first sub-pad 641 can be used to connect the first sub-gate line 611 to the solder ribbon. For example, the first sub-pad 641 and the solder ribbon can be connected by flux. The area of ​​the first sub-pad 641 can be smaller than the area of ​​the first main pad 621, while the width of the first sub-gate line 611 in the linewidth direction (second direction Y) is greater than the linewidth of the first sub-gate line 611. Thus, without significantly affecting the distribution of the doped layer on the back of the battery, the connection reliability between the first sub-gate line 611 and the solder ribbon is improved by setting the first sub-pad 641.

[0080] The width of the first auxiliary pad 641 and the first main pad 621 in the first direction X can be the same or different, for example, Figure 9 As shown, the width of the first sub-pad 641 and the first main pad 621 in the first direction X can be the same. The orthographic projection of the first sub-pad 641 on the substrate 1 partially overlaps with the orthographic projection of the overlapping portion 4 on the substrate 1. That is, the first sub-pad 641 can extend beyond the range of the overlapping portion 4, thereby relatively increasing the contact area with the solder strip, improving the connection strength, and reducing the contact resistance.

[0081] Figure 10 This is a partial structural schematic diagram of another back-contact solar cell provided according to an embodiment of this application, as shown below. Figure 10 As shown, multiple first sub-pads 641 are arranged along a set direction (second direction Y). The orthographic projection of the multiple first sub-pads 641 arranged along the set direction onto the substrate 1 can fall within the range of the orthographic projection of the same overlapping portion 4 onto the substrate 1. It can be understood that the aforementioned "same overlapping portion 4" means that the back contact solar cell 1000 has multiple overlapping portions 4, and a continuously arranged overlapping portion 4 is the same overlapping portion 4. If there is a gap between two overlapping portions 4, they are two different overlapping portions 4.

[0082] In the above embodiment, the overlapping portion 4 corresponding to the plurality of first sub-pads 641 arranged along the second direction Y extends along the second direction Y. Therefore, when forming the pattern of the first doped layer 2 using the laser direct writing process, the laser does not need to pass through the area where the overlapping portion 4 is to be set, that is, the area that extends from one edge of the battery along the second direction Y to its other opposite edge and has a set width, thereby simplifying the laser direct writing path to a greater extent and improving production efficiency.

[0083] Similarly, such as Figure 7 As shown, electrode layer 6 may further include a second sub-pad 642 for connecting a sub-gate line of another polarity (i.e., a second sub-gate line 612). Each second sub-pad 642 can electrically connect to one second sub-gate line 612, thereby improving the connection strength between the second sub-gate line 612 and the solder ribbon. The area of ​​the second sub-pad 642 can be smaller than the area of ​​the second main pad 622, and can be the same as the area of ​​the first sub-pad 641, to reduce processing difficulty. Similar to the second main pad 622, the orthographic projection of the second sub-pad 642 on the substrate 1 is offset from the orthographic projection of the overlapping portion 4 on the substrate 1 to avoid leakage.

[0084] In practical implementation, the two types of grid segments (i.e., the first grid segment 631 and the second grid segment 632) are usually set simultaneously, and the two types of sub-pads (i.e., the first sub-pad 641 and the second sub-pad 642) are usually set simultaneously. In the back contact solar cell 1000, only the grid segments may be set (refer to...). Figure 6 Alternatively, only the sub-pad can be set, or both the gate segment and the sub-pad mentioned above can be set simultaneously (see [reference]). Figure 7 Specifically, the design focus of the back contact solar cell 1000 can be determined. For example, if the focus is on improving the connection strength of the solder strip, both of the above can be set at the same time. If the focus is on reducing back shading and saving electrode paste, only one of the two can be set, for example, only the grid line segment can be set.

[0085] Figure 11 This is a schematic diagram of another laser movement path in the fabrication process of a back-contact solar cell according to an embodiment of this application, as shown below. Figure 10 The back-contact solar cell shown can utilize, for example Figure 11 The laser pattern shown is formed, in contrast. Figure 4 and Figure 11 visible, Figure 11 The laser pattern shown further simplifies the laser direct writing path for the area (i.e., the third region 93) in the second direction Y used to set the first sub-pad 641, which is beneficial to further improve production efficiency. Furthermore, since the orthographic projection of the second sub-pad 642 on the substrate 1 is offset from the orthographic projection of the overlapping portion 4 on the substrate 1, the laser direct writing path for the area (i.e., the fourth region 94) used to set the second sub-pad 642 remains unchanged.

[0086] In this application, the design of the overlapping portion 4 can be applied not only to the aforementioned back-contact solar cell 1000 without a main grid, but also to the back-contact solar cell 1000 with a main grid. Figure 12 This is a schematic diagram of a planar structure of another back-contact solar cell according to an embodiment of this application, as shown below. Figure 12As shown, the electrode layer 6 may further include a first main grid line 651. The extension direction of the first main grid line 651 intersects with the first sub-grid line 611 (for example, the second direction Y mentioned above), and the first main grid line 651 is electrically connected to at least one first main pad 621. The orthographic projection of the first main grid line 651 on the substrate 1 falls within the range of the orthographic projection of the overlapping portion 4 on the substrate 1. In the above embodiment, the overlapping portion 4 is provided in the area corresponding to the first main grid line 651. The overlapping portion 4 can have a large area, and under the isolation of the passivation layer 5, the leakage current caused by the overlapping portion 4 does not have a significant impact on the electrical performance of the battery. The above embodiment can greatly simplify the laser direct writing path and improve the production efficiency of the back contact solar cell 1000.

[0087] Correspondingly, the electrode layer 6 may also include a second main gate line 652, the extension direction of which intersects with the second sub-gate line 612 and may be the same as the extension direction (second direction Y) of the first main gate line 651. The second main gate line 652 is electrically connected to at least one second main pad 622.

[0088] In practical implementation, the number of main pads connected to the main gate line can be determined according to actual needs and is not limited here. For example, each end of the main gate line is connected to a main pad, that is, the two ends of the first main gate line 651 are connected to a first main pad 621, and the two ends of the second main gate line 652 are connected to a second main pad 622.

[0089] The first main gate line 651 extends along the second direction Y, and the overlapping portion 4 corresponding to the first main gate line 651 also extends along the second direction Y. When forming the pattern of the first doped layer 2 using the laser direct writing process, the laser does not need to pass through the area where the first main gate line 651 is to be set, that is, the area that extends from one edge of the battery along the second direction Y to its other opposite edge and has a set width. This can greatly simplify the laser direct writing path and improve production efficiency.

[0090] Figure 12 The back-contact solar cell shown can also utilize, for example... Figure 11 The laser pattern shown is formed, in contrast. Figure 4 and Figure 11 visible, Figure 11 The laser pattern shown further simplifies the laser direct writing path for the area (i.e., the third region 93) in the second direction Y used to set the first sub-pad 641, which is beneficial to further improve production efficiency. Furthermore, since the orthographic projection of the second sub-pad 642 on the substrate 1 is offset from the orthographic projection of the overlapping portion 4 on the substrate 1, the laser direct writing path for the area (i.e., the fourth region 94) used to set the second sub-pad 642 remains unchanged.

[0091] Based on the same concept, this application also provides a photovoltaic module, which includes: a battery string, an encapsulating film, and a cover plate. The battery string is formed by connecting multiple back-contact solar cells 1000 as described in any of the above embodiments. The encapsulating film is used to cover the surface of the battery string, isolating the solar cells from the external environment and preventing water vapor and oxygen from corroding the solar cells, thereby improving the reliability of the photovoltaic module and extending its service life. The encapsulating film can be made of, but is not limited to, ethylene-vinyl acetate copolymer (EVA) film, polyolefin elastomer (POE) film, etc. The cover plate is used to cover the surface of the encapsulating film away from the battery string, and can be used to protect the internal structure of the photovoltaic module and improve the reliability of the photovoltaic module. The cover plate can be made of materials with high hardness and good light transmittance, such as glass, so as to provide protection for the photovoltaic module while allowing as much light as possible to enter the solar cells for utilization.

[0092] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0093] Those skilled in the art will understand that the above embodiments are specific examples of implementing this application, and in practical applications, various changes in form and detail can be made without departing from the spirit and scope of this application. Any person skilled in the art can make various alterations and modifications without departing from the spirit and scope of this application; therefore, the scope of protection of this application should be determined by the scope defined in the claims.

Claims

1. A back-contact solar cell, characterized in that, The back-contact solar cell includes: Base; A first doped layer and a second doped layer with opposite doping types are located on the back surface of the substrate, and the second doped layer includes an overlapping portion stacked on the first doped layer; A passivation layer, wherein the passivation layer at least covers the overlapping portion; The electrode layer includes a first main pad located at the edge region of the back contact solar cell and a first sub-gate line and a second sub-gate line with opposite polarities. The first sub-gate line is in contact with and electrically connected to the first doped layer, and the second sub-gate line is in contact with and electrically connected to the second doped layer. The first main pad is used to electrically connect the first sub-gate line and the solder strip. The first main pad is located on the side of the overlapping portion away from the first doped layer and is disposed on the passivation layer. Multiple first main pads are provided in a one-to-one correspondence with multiple overlapping portions, and the orthographic projection of the first main pad on the substrate falls within the range of the orthographic projection of the corresponding overlapping portion on the substrate; Alternatively, multiple first main pads are provided in a one-to-one correspondence with multiple overlapping portions, each overlapping portion including a first sub-portion and a second sub-portion, the first sub-portion and the second sub-portion being spaced apart, the orthographic projection of the first sub-gate line electrically connected to the first main pad on the substrate falling within the range of the orthographic projection of the spaced sub-portion on the substrate, and the orthographic projection of the first main pad on the substrate at least partially overlapping the first sub-portion and the second sub-portion.

2. The back-contact solar cell according to claim 1, characterized in that, The electrode layer further includes: The first gate line segment is located between the first main pad and the substrate edge closest to the first main pad. The first gate line segment is provided in a one-to-one correspondence with the first main pad and is electrically connected. The extension direction of the first gate line segment intersects with the first sub-gate line and is electrically connected to at least one of the first sub-gate lines. The orthographic projection of the first gate line segment on the substrate falls within the range of the orthographic projection of the overlapping portion on the substrate.

3. The back-contact solar cell according to claim 1, characterized in that, The electrode layer further includes: The first main gate line extends in a direction that intersects with the first sub-gate line, and the first main gate line is electrically connected to at least one first main pad. The orthographic projection of the first main gate line on the substrate falls within the range of the orthographic projection of the overlapping portion on the substrate.

4. The back-contact solar cell according to claim 1, characterized in that, The electrode layer further includes: The first sub-pad, each of the first sub-pads being electrically connected to a first sub-gate line, the area of ​​the first sub-pad being smaller than the area of ​​the first main pad, and the orthographic projection of the first sub-pad on the substrate at least partially overlapping the orthographic projection of the overlapping portion on the substrate.

5. The back-contact solar cell according to claim 4, characterized in that, Multiple first sub-pads are arranged along a set direction, and the orthographic projections of the multiple first sub-pads arranged along the set direction on the substrate fall within the range of the orthographic projection of the same overlapping portion on the substrate.

6. The back-contact solar cell according to any one of claims 1 to 5, characterized in that, The first sub-gate line extends along a first direction, and multiple first sub-gate lines are arranged in a column along a second direction. The second direction intersects with the first direction. Each column of first sub-gate lines is provided with two first main pads. The two first main pads are respectively located in two opposite edge regions of the back contact solar cell in the second direction.

7. The back-contact solar cell according to any one of claims 1 to 5, characterized in that, The electrode layer further includes: The second main pad is located at the edge region of the back contact solar cell. The second main pad is used to electrically connect the second sub-gate line and the solder strip. The second main pad is located on the side of the second doped layer away from the substrate and is offset from the overlapping portion.

8. A photovoltaic module, characterized in that, The photovoltaic module includes: A battery string is formed by connecting multiple back-contact solar cells as described in any one of claims 1 to 7; An encapsulating film is used to cover the surface of the battery string; A cover plate is used to cover the surface of the encapsulating film that faces away from the battery string.

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