Back-contact solar cell, battery assembly and photovoltaic system

Abstract

The present application is suitable for the technical field of solar cells, and provides a back-contact solar cell (100), a battery assembly (200) and a photovoltaic system (1000). In the back-contact solar cell (100), several first polarity-doped layers (20) and several second polarity-doped layers (30) are stacked on a back surface (11) of a silicon substrate (10), are sequentially and alternately arranged at intervals in a first direction, and all extend in a second direction. Back passivation film layers (40) are stacked on the first polarity-doped layers (20) and the second polarity-doped layers (30), first fine grids (50) are correspondingly arranged on the first polarity-doped layers (20), and second fine grids (60) are correspondingly arranged on the second polarity-doped layer (30). In the second direction, several third polarity-doped layers (70) arranged at intervals are arranged below the first fine grids (50), the first fine grids (50) are made of burn-through slurry, and the polarity of the third polarity-doped layer (70) is opposite to that of the first polarity-doped layers (20). In the second direction, at positions corresponding to the third polarity-doped layers (70), the first fine grids (50) burn through the back passivation film layers (40) to be in contact with the third polarity-doped layers (70), and between two adjacent third polarity-doped layers (70), the first fine grid (50) burns through the corresponding back passivation film layer (40) to be in contact with the corresponding first polarity-doped layer (20). The third polarity-doped layers (70) are obtained by partially removing the formed winding-plating layers on the first polarity-doped layers (20) in the process of forming the second polarity-doped layers (30).

Description

Back-contact solar cells, modules and photovoltaic systems

[0001] Priority information

[0002] This application claims priority and benefits of patent applications with patent application numbers 202311786045.1 and 202323525988.7 filed with the State Intellectual Property Office of China on December 22, 2023, and the entire text of which is incorporated herein by reference. Technical Field

[0003] The present application relates to the technical field of solar cell wafers, and in particular to a back-contact solar cell, a cell assembly and a photovoltaic system. Background Art

[0004] Solar cell power generation is a sustainable source of clean energy. It uses the photovoltaic effect of semiconductor pn junction to convert sunlight into electrical energy.

[0005] In solar cells, a back-contact solar cell is one in which both the emitter and base contact electrodes are placed on the back side (non-light-receiving side) of the cell. This leaves the light-receiving side unobstructed by any metal electrodes, effectively increasing the cell's short-circuit current. Back-contact solar cells typically begin with a P-type doped layer formed on the back side, followed by trenching and forming an N-type doped layer. Further trenching is then performed to separate the P-type and N-type doped layers, followed by the preparation of fine grids and busbars.

[0006] In related technologies, the fine grid of a back-contact battery usually penetrates the passivation film layer and contacts the doping layer. In this case, the contact area between the fine grid and the doping layer is large, which easily leads to a large recombination current in the metal area and low conversion efficiency. Summary of the Invention

[0007] The present application provides a back-contact solar cell, a cell module and a photovoltaic system.

[0008] The present application is implemented as follows: a back-contact solar cell according to an embodiment of the present application comprises:

[0009] Silicon substrate;

[0010] A plurality of first polarity doped layers and a plurality of second polarity doped layers are stacked on the back side of the silicon substrate, wherein the plurality of first polarity doped layers and the plurality of second polarity doped layers are alternately arranged in sequence along a first direction and extend along a second direction, wherein the second direction intersects the first direction;

[0011] a back passivation film layer, the back passivation film layer being stacked on the first polarity doped layer and the second polarity doped layer;

[0012] a plurality of first fine gates and a plurality of second fine gates, wherein the first fine gates are correspondingly arranged on the first polarity doped layer and used to collect current of the first polarity doped layer, and the second fine gates are correspondingly arranged on the second polarity doped layer and used to collect current of the second polarity doped layer;

[0013] In the second direction, a plurality of third polarity doped layers are provided below the first fine gate and arranged at intervals. The third polarity doped layers are located between the back passivation film layer and the first polarity doped layers. The first fine gate is made of a burn-through paste. The polarity of the third polarity doped layers is opposite to that of the first polarity doped layers.

[0014] In the second direction, at a position corresponding to the third polarity doped layer, the first fine gate burns through the back passivation film layer and contacts the third polarity doped layer; between two adjacent third polarity doped layers, the first fine gate burns through the back passivation film layer and contacts the first polarity doped layer, and the second fine gate at least partially penetrates the back passivation film layer and contacts the second polarity doped layer;

[0015] The third polarity doping layer is obtained by partially removing a wrap-around layer formed on the first polarity doping layer during the process of forming the second polarity doping layer.

[0016] Furthermore, in the second direction, a ratio of a length of the first fine gate in contact with the first polarity doped layer to a total length of the first fine gate is 30%-80%.

[0017] Furthermore, in the second direction, a ratio of a length of the first fine gate in contact with the first polarity doped layer to a total length of the first fine gate is 40%-60%.

[0018] Furthermore, an insulating isolation layer is provided between the third polarity doping layer and the first polarity doping layer, and the insulating isolation layer is also obtained by partially removing the wrap-around coating formed on the first polarity doping layer during the process of forming the second polarity doping layer.

[0019] Furthermore, in the first direction, the width of the third polarity doped layer is greater than or equal to the width of the first fine gate.

[0020] Furthermore, the first polarity doped layer is a P-type doped layer, and the second polarity doped layer and the third polarity doped layer are both N-type doped layers.

[0021] Furthermore, the bonding tension between the third polarity doped layer and the back passivation film layer is greater than the bonding tension between the first polarity doped layer and the back passivation film layer.

[0022] Furthermore, the back-contact solar cell further includes a solder joint electrically connected to the first fine grid, wherein the solder joint is disposed on the back passivation film layer and is at least partially located above the third polarity doping layer.

[0023] Furthermore, a projected area of ​​the third polarity doped layer on the silicon substrate is greater than or equal to a projected area of ​​the solder joint on the silicon substrate, and the solder joint is completely located within the projected area of ​​the third polarity doped layer.

[0024] Furthermore, in the second direction, at positions corresponding to the second fine grids, a plurality of barrier layers arranged at intervals are provided between the second polarity doped layer and the back passivation film layer, and the second fine grids are also made of a burn-through paste;

[0025] At the position corresponding to the barrier layer, the second fine gate burns through the back passivation film layer and contacts the barrier layer. Between two adjacent barrier layers, the second fine gate burns through the back passivation film layer and contacts the second polarity doped layer. The barrier layer includes a phosphosilicate glass layer or a borosilicate glass layer.

[0026] The present application also provides a battery assembly, which includes several of the above-mentioned back-contact solar cells.

[0027] The present application also provides a photovoltaic system, which includes the above-mentioned battery assembly.

[0028] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become obvious from the description below, or will be learned through practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] FIG1 is a module schematic diagram of a photovoltaic system provided in an embodiment of the present application.

[0030] FIG2 is a module schematic diagram of a battery assembly provided in an embodiment of the present application.

[0031] FIG3 is a schematic diagram of the planar structure of a back-contact solar cell provided in an embodiment of the present application;

[0032] FIG4 is a schematic cross-sectional view of the back-contact solar cell along line IV-IV in FIG2 ;

[0033] FIG5 is a schematic cross-sectional view of the back contact solar cell along line VV in FIG2 ;

[0034] FIG6 is another schematic cross-sectional view of the back-contact solar cell along line IV-IV in FIG2 ;

[0035] FIG7 is another schematic plan view of the back contact solar cell structure according to an embodiment of the present application;

[0036] FIG8 is a schematic cross-sectional view of the back-contact solar cell along line VIII-VIII in FIG7 ;

[0037] FIG9 is a schematic cross-sectional view of the back-contact solar cell along line IX-IX in FIG7 .

[0038] Description of main component symbols:

[0039] Photovoltaic system 1000, battery assembly 200, back contact solar cell 100, silicon substrate 10, back side 11, first polarity doping layer 20, second polarity doping layer 30, back side passivation film layer 40, first fine gate 50, second fine gate 60, third polarity doping layer 70, insulating isolation layer 80, and blocking layer 90. Modes for Carrying Out the Invention

[0040] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application is further described in detail below with reference to the accompanying drawings and embodiments. Examples of the embodiments are shown in the accompanying drawings, in which the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. It should be noted that the embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and are not to be construed as limiting the present application. In addition, it should be understood that the specific embodiments described herein are merely used to explain the present application and are not intended to limit the present application.

[0041] In the description of this application, it should be understood that the terms "up", "down", "left", "right", "horizontal", "longitudinal", etc., indicating directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they should not be understood as limitations on this application.

[0042] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Thus, features defined as "first" or "second" may explicitly or implicitly include one or more of the described features. In the description of this application, "several" means two or more, unless otherwise specifically defined.

[0043] In this application, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Moreover, a first feature being "above," "above," and "above" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may include the first feature being directly below or obliquely below the second feature, or may simply mean that the first feature is lower in level than the second feature.

[0044] The disclosure below provides many different embodiments or examples for realizing different structures of the present application. In order to simplify the disclosure of the present application, the components and settings of specific examples are described below. Of course, they are merely examples and are not intended to limit the present application. In addition, the present application may repeat reference numbers and / or reference letters in different examples. Such repetition is for the purpose of simplicity and clarity and does not in itself indicate the relationship between the various embodiments and / or settings discussed. In addition, the present application provides examples of various specific processes and materials, but those skilled in the art will appreciate the application of other processes and / or the use scenarios of other materials.

[0045] Example 1

[0046] Referring to Figures 1 and 2 , a photovoltaic system 1000 in an embodiment of the present application may include a battery assembly 200 in an embodiment of the present application. The battery assembly 200 in an embodiment of the present application may include several back-contact solar cells 100 in an embodiment of the present application. The multiple back-contact solar cells 100 in the battery assembly 200 may be serially connected together via welding ribbons to form a battery string. The individual battery strings in the battery assembly 200 may be connected in series, in parallel, or in a combination of series and parallel to achieve current bus output. For example, bus bars may be used to connect the individual battery strings.

[0047] 3-5 , the back-contact solar cell 100 in the embodiment of the present application may include a silicon substrate 10 , a plurality of first polarity doped layers 20 , a plurality of second polarity doped layers 30 , a back passivation film layer 40 , a plurality of first fine gates 50 , a plurality of second fine gates 60 and a third polarity doped layer 70 .

[0048] A plurality of first polarity doped layers 20 and a plurality of second polarity doped layers 30 are stacked on the back side 11 of the silicon substrate 10 and are alternately arranged in sequence along a first direction. The first polarity doped layers 20 and the second polarity doped layers 30 both extend along a second direction, which intersects the first direction. Specifically, the first direction and the second direction may preferably be the lateral direction and the longitudinal direction of the back-contact solar cell 100, respectively, and the two directions are perpendicular to each other. Of course, in other embodiments, the first direction and the second direction may also be directions other than the lateral direction and the longitudinal direction, as long as they intersect. For example, the first direction and the second direction may be diagonal directions of the back-contact solar cell 100, and this is not limited to this.

[0049] The backside passivation film layer 40 is stacked on the first polarity doped layer 20 and the second polarity doped layer 30. The first fine gate 50 is correspondingly disposed on the first polarity doped layer 20 and is used to collect current from the first polarity doped layer 20. The second fine gate 60 is correspondingly disposed on the second polarity doped layer 30 and is used to collect current from the second polarity doped layer 30. In other words, the first fine gate 50 and the second fine gate 60 also extend along the second direction.

[0050] As shown in FIG3 and FIG4 , in the second direction, a plurality of third polarity doped layers 70 are arranged at intervals below the first fine gate 50. The third polarity doped layers 70 are located between the back passivation film 40 and the first polarity doped layer 20. The first fine gate 50 is made of a burn-through paste. The polarity of the third polarity doped layer 70 is opposite to that of the first polarity doped layer 20.

[0051] In the second direction, at a position corresponding to the third polarity doped layer 70, the first fine gate 50 burns through the back passivation film layer 40 and contacts the third polarity doped layer 70. Between two adjacent third polarity doped layers 70, the first fine gate 50 burns through the back passivation film layer 40 and contacts the first polarity doped layer 20. The second fine gate 60 at least partially penetrates the back passivation film layer 40 and contacts the second polarity doped layer 30.

[0052] The third polarity doped layer 70 is formed by partially removing the wrap-around layer formed on the first polarity doped layer 20 during the formation of the second polarity doped layer 30. This removal can be performed using conventional etching methods such as acid etching, alkaline etching, and laser etching. (It should be noted that FIG4 is a cross-sectional view of the first fine gate 50 along the second direction. At this location, the back passivation film 40 is substantially completely ablated. Therefore, the back passivation film 40 is not shown in FIG3 ).

[0053] In the back-contact solar cell 100, battery assembly 200 and photovoltaic system 1000 in the embodiments of the present application, the back side 11 of the silicon substrate 10 is stacked with a plurality of first polarity doping layers 20 and second polarity doping layers 30 that are alternately spaced in sequence along the first direction. The first polarity doping layers 20 and the second polarity doping layers 30 both extend along the second direction. The first fine gate 50 is arranged corresponding to the first polarity doping layer 20, and the second fine gate 60 is arranged corresponding to the second polarity doping layer 30. The first fine gate 50 is made of a burn-through slurry. In the second direction, a number of spaced third polarity doping layers 70 are provided below the first fine gate 50. The third polarity doping layer 70 is located between the back passivation film layer 40 and the first polarity doping layer 20. At the position corresponding to the third polarity doping layer 70, the first fine gate 50 burns through the back passivation film layer 40 and contacts the third polarity doping layer 70. Between two adjacent third polarity doping layers 70, the first fine gate 50 burns through the back passivation film layer 40 and contacts the first polarity doping layer 20. The second fine gate 60 at least partially penetrates the back passivation film layer 40 and contacts the second polarity doping layer 30. In this way, in the process of using the burn-through paste to make the first fine grid 50, the first fine grid 50 will only burn through the back passivation film layer 40 and contact the first polarity doping layer 20 at the gap between the third polarity doping layer 70, and at the position corresponding to the third polarity doping layer 70, it will only burn through the back passivation film layer 40 and contact the third polarity doping layer 70 without direct contact with the first polarity doping layer 20. In this way, selective burn-through of the burn-through paste can be achieved, which can reduce the metallization contact area between the first fine grid 50 and the first polarity doping layer 20, reduce the recombination current, and improve the efficiency of the back contact solar cell 100.

[0054] At the same time, the third polarity doping layer 70 is obtained by partially removing the winding-plated layer formed on the first polarity doping layer 20 in the process of forming the second polarity doping layer 30. In this way, there is no need to adopt other deposition means to form the third polarity doping layer 70. It can be obtained by only partially removing the winding-plated layer formed on the first polarity doping layer 20, which can save process.

[0055] It is not difficult to understand that in the traditional technical solution, a first polarity doping layer 20 is first deposited on the entire back side 11 of the silicon substrate 10. After the first polarity doping layer 20 is formed, part of the first polarity doping layer 20 is removed by etching or laser grooving to form a groove on the first polarity doping layer 20 for making the second polarity doping layer 30. Subsequently, the second polarity doping layer 30 is formed on the groove, and then a groove treatment is performed at the contact point between the first polarity doping layer 20 and the second polarity doping layer 30 to achieve isolation between the first polarity doping layer 20 and the second polarity doping layer 30, thereby forming the first polarity doping layer 20 and the second polarity doping layer 30 arranged alternately in sequence.

[0056] It can be understood that in the process of making the second polarity doping layer 30, a wrap-around layer of the third polarity doping layer 70 having the same polarity as the second polarity doping layer 30 will be formed on the first polarity doping layer 20. In the traditional technical solution, the wrap-around layer formed on the first polarity doping layer 20 needs to be completely removed, or it is not removed and the first fine grid 50 is set in a place where there is no wrap-around layer, or the first fine grid 50 is directly burned through the wrap-around layer to contact the first polarity doping layer 20. In the present application, only the wrap-around layer is partially removed, and part of the wrap-around layer is retained to form the third polarity doping layer 70. The first fine grid 50 is set above the third polarity doping layer 70 to achieve selective burning of the slurry and realize local contact between the first fine grid 50 and the first polarity doping layer 20. In this way, there is no need to adopt an additional process to form the third polarity doping layer 70, which can save process steps.

[0057] In the present application, the silicon substrate 10 can be a P-type silicon substrate or an N-type silicon substrate, the first polarity doped layer 20 can be a P-type doped layer or an N-type doped layer, and one of the first fine gate 50 and the second fine gate 60 is a P-type fine gate, and the other is an N-type fine gate.

[0058] It should be noted that, in this application, the term "burn-through paste" refers to a metal paste with strong burn-through capability, which may be a silver paste or a silver-aluminum paste, etc., and is capable of completely burning through the back passivation film layer 40 so that the first fine grid 50 can contact the first polarity doped layer 20 and the third polarity doped layer 70 below the back passivation film layer 40. For example, in one possible embodiment, the glass frit content of the burn-through paste may be higher than that of a traditional paste, thereby providing it with stronger burn-through capability.

[0059] Example 2

[0060] Please refer to Figure 6. In some embodiments, there is an insulating isolation layer 80 between the third polarity doping layer 70 and the first polarity doping layer 20. The insulating isolation layer 80 is also obtained by partially removing the plating layer formed on the first polarity doping layer 20 during the process of forming the second polarity doping layer 30. The local removal can be performed by etching methods in the existing technology such as acid etching, alkaline etching and laser etching.

[0061] Thus, the presence of the insulating isolation layer 80 can prevent the third polarity doped layer 70 from directly contacting the first polarity doped layer 20 and causing leakage.

[0062] In such an embodiment, the insulating isolation layer 80 may include at least one of a borosilicate glass layer, a phosphosilicate glass layer, and a borophosphosilicate glass layer, or a combination of multiple thereof.

[0063] Specifically, in the present application, during the deposition of the second polarity doped layer 30, a wrap-around layer having a third polarity doped layer 70 is formed on the first polarity doped layer 20. When the first polarity doped layer 20 is a P-type doped layer and the second polarity doped layer 30 is an N-type doped layer, the wrap-around layer includes a phosphosilicate glass layer and an N-type doped layer (i.e., the third polarity doped layer 70) stacked on the phosphosilicate glass layer. In this way, the insulating isolation layer 80 and the third polarity doped layer 70 can be obtained by only partially removing the wrap-around layer, and the phosphosilicate glass layer serves as the insulating isolation layer 80, while the N-type doped layer serves as the third polarity doped layer 70.

[0064] When the first polarity doping layer 20 is an N-type doping layer and the second polarity doping layer 30 is a P-type doping layer, the winding coating layer includes a borosilicate glass layer and a P-type doping layer stacked on the borosilicate glass layer. In this way, only partial removal of the winding coating layer is required to obtain the insulating isolation layer 80 and the third polarity doping layer 70, and the borosilicate glass layer is the insulating isolation layer 80, and the P-type doping layer is the third polarity doping layer 70.

[0065] Of course, it is understandable that in the process of forming the first polarity doped layer 20, a phosphosilicate glass layer or a borosilicate glass layer will be formed on the first polarity doped layer 20. If the phosphosilicate glass layer or the borosilicate glass layer is not removed before forming the second polarity doped layer, then a borosilicate glass layer will be formed in the process of forming the second polarity doped layer 30. In this case, the insulating isolation layer 80 is a borosilicate glass layer.

[0066] Example 3

[0067] In some embodiments, in the second direction, a ratio of a length of the first fine gate 50 in contact with the first polarity doped layer 20 to a total length of the first fine gate 50 is 30%-80%.

[0068] In this way, setting the contact length between the first fine gate 50 and the first polarity doped layer 20 within the above-mentioned ratio range can effectively reduce the metallization contact area to reduce recombination while avoiding excessive resistance caused by too small a contact area. That is, the relationship between recombination and resistance can be balanced to improve the efficiency of the back-contact solar cell 100.

[0069] Specifically, in such an embodiment, the ratio between the length of the first fine gate 50 in contact with the first polarity doped layer 20 and the total length of the first fine gate 50 can be, for example, 30%, 40%, 50%, 60%, 70%, 80% or any value between 30% and 80%.

[0070] Furthermore, in such an embodiment, after careful research and derivation by the inventors of the present application, it was discovered that in order to maximize the balance between metallization recombination and resistance while improving the conversion efficiency of the back-contact solar cell 100 as much as possible, the ratio between the length of the first fine grid 50 in contact with the first polarity doped layer 20 and the total length of the first fine grid 50 may preferably be in the range of 40%-60%, for example, 40%, 45%, 50%, 55%, 60% and any value between 40%-60%.

[0071] Example 4

[0072] In some embodiments, in the first direction, the width of the third polarity doping layer 70 is greater than or equal to the width of the first fine gate 50 .

[0073] Thus, by setting the width of the first polarity doped layer 20 to be greater than or equal to the width of the first fine gate 50 , the first fine gate 50 will not have any contact with the first polarity doped layer 20 in the corresponding region of the third polarity doped layer 70 , thereby reducing recombination.

[0074] Example 5

[0075] In some embodiments, the first polarity doping layer 20 may be a P-type doping layer, and the second polarity doping layer 30 and the third polarity doping layer 70 may both be N-type doping layers.

[0076] In this way, when the third polarity doping layer 70 on the P-type doping layer is an N-type doping layer, by setting the N-type doping layer on the P-type doping layer, the bonding tension between the back passivation film layer 40 and the N-type doping layer is greater than the bonding tension between the passivation film layer and the P-type doping layer. When the solder joints are subsequently set, the welding tension of the solder joints can be effectively increased, thereby effectively avoiding the detachment of the solder joints during welding and improving the reliability of welding.

[0077] Example 6

[0078] In some embodiments, the coupling tension between the first fine gate 50 and the third polarity doped layer 70 is greater than the coupling tension between the first fine gate 50 and the first polarity doped layer 20 .

[0079] In this way, the provision of the third polarity doping layer 70 can improve the stability of the first fine gate 50 and effectively prevent the first fine gate 50 from being deflected or falling off.

[0080] Example 7

[0081] In some embodiments, the bonding tension between the third polarity doped layer 70 and the back passivation film layer 40 is greater than the bonding tension between the first polarity doped layer 20 and the back passivation film layer 40 .

[0082] In this way, the bonding tension between the third polarity doped layer 70 and the back passivation film layer 40 is relatively large, which can effectively increase the tension of the solder joints provided on the back passivation film layer 40 and prevent the solder joints from falling off during welding.

[0083] Specifically, in such an embodiment, the first polarity doped layer 20 is a P-type doped layer, the third polarity doped layer 70 is an N-type third polarity doped layer 70, and the bonding tension between the N-type doped layer and the back passivation film layer 40 is greater than the tension between the P-type doped layer and the back passivation film layer 40.

[0084] Furthermore, in such an embodiment, in some embodiments, the back-contact solar cell 100 further includes a solder joint (not shown) connected to the first fine grid 50 , and the solder joint is disposed on the back passivation film layer 40 and at least partially located above the third polarity doping layer 70 .

[0085] In this way, disposing the solder joint at least partially above the third polarity doping layer 70 can increase the soldering tension of the solder joint during soldering.

[0086] Furthermore, in some embodiments, the solder joint at least partially burns through the back passivation film layer 40 and contacts the third polarity doped layer 70 , and the bonding tension between the solder joint and the third polarity doped layer 70 is greater than the bonding tension between the solder joint and the first polarity doped layer 20 .

[0087] In this way, the bonding tension between the solder joint and the third polarity doped layer 70 is relatively large, and the welding tension of the solder joint during welding can also be effectively improved.

[0088] Specifically, in such an embodiment, the solder joint may be a P-type solder joint, and the paste used to form the solder joint may be the same as or different from the paste used to form the first fine grid 50 , which is not specifically limited herein.

[0089] Furthermore, in some embodiments, the projected area of ​​the third polarity doped layer 70 on the silicon substrate 10 is greater than or equal to the projected area of ​​the solder joint on the silicon substrate 10 , and the solder joint is completely located within the projected area of ​​the third polarity doped layer 70 .

[0090] In this way, the solder joint is completely located in the area where the third polarity doped layer 70 is located, and the entire area below the solder joint has the third polarity doped layer 70 , which can maximize the welding tension at the solder joint, thereby ensuring the reliability of welding.

[0091] Specifically, in such an embodiment, the area of ​​the third polarity doping layer 70 may preferably be just equal to the projected area of ​​the solder joint or slightly larger than the projected area of ​​the solder joint, which is not specifically limited here.

[0092] Example 8

[0093] Please refer to Figures 7 to 9. In some embodiments, in the second direction, at the position corresponding to the second fine gate 60, a plurality of barrier layers 90 are arranged between the second polarity doped layer 30 and the back passivation film layer 40. The second fine gate 60 is also made of a burn-through slurry. At the position corresponding to the barrier layer 90, the second fine gate 60 burns through the back passivation film layer 40 and contacts the barrier layer 90. Between two adjacent barrier layers 90, the second fine gate 60 burns through the back passivation film layer 40 and contacts the second polarity doped layer 30. The barrier layer 90 includes a phosphosilicate glass layer or a borosilicate glass layer.

[0094] In this way, by setting the barrier layer 90, during the process of manufacturing the second fine grid 60, the second fine grid 60 partially burns through the back passivation film layer 40 and contacts the second polarity doping layer 30, while at the barrier layer 90, only the back passivation film layer 40 will be burned through and contact the barrier layer 90, and there will be no direct contact with the second polarity doping layer 30. In this way, selective burn-through of the burn-through paste can be achieved, and the metallized contact area between the second fine grid 60 and the second polarity doping layer 30 can be reduced, reducing the recombination of the metallized area, thereby further improving the conversion efficiency of the back-contact solar cell 100.

[0095] Specifically, in such an embodiment, the second polarity doping layer 30 can be formed by deposition or diffusion. When the second polarity doping layer 30 is an N-type doping layer, a phosphosilicate glass layer will be formed on the second polarity doping layer 30 during the process of forming the second polarity doping layer 30. In the subsequent removal process, the phosphosilicate glass layer at the second blocking area of ​​the second polarity doping layer 30 is retained to form the blocking layer 90, that is, the blocking layer 90 is a phosphosilicate glass layer.

[0096] When the second polarity doped layer 30 is a P-type doped layer, a borosilicate glass layer will be formed on the second polarity doped layer 30 during the process of forming the second polarity doped layer 30. In the subsequent removal process, the borosilicate glass layer at the second blocking area of ​​the second polarity doped layer 30 is retained to form the blocking layer 90, that is, the blocking layer 90 is a borosilicate glass layer.

[0097] Throughout this specification, reference to terms such as "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples" means that a specific feature, structure, material, or characteristic described in conjunction with the embodiment or example is included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0098] In addition, the above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present application should be included in the scope of protection of the present application.

Claims

1. A back contact solar cell, characterized in that: include: Silicon substrate; A plurality of first polarity doped layers and a plurality of second polarity doped layers are stacked on the back side of the silicon substrate, wherein the plurality of first polarity doped layers and the plurality of second polarity doped layers are alternately arranged in sequence along a first direction and extend along a second direction, and the second direction intersects the first direction; A back side passivation film layer, wherein the back side passivation film layer is stacked on the first polarity doping layer and the second polarity doping layer; A plurality of first fine gates and a plurality of second fine gates, wherein the first fine gates are correspondingly arranged on the first polarity doping layer and used to collect the current of the first polarity doping layer, and the second fine gates are correspondingly arranged on the second polarity doping layer and used to collect the current of the second polarity doping layer; In the second direction, a plurality of third polarity doping layers are arranged at intervals below the first fine grid, the third polarity doping layers are located between the back passivation film layer and the first polarity doping layers, the first fine grid is made of a burn-through paste, and the polarity of the third polarity doping layers is opposite to that of the first polarity doping layers; In the second direction, at a position corresponding to the third polarity doped layer, the first fine gate burns through the back passivation film layer and contacts the third polarity doped layer, and between two adjacent third polarity doped layers, the first fine gate burns through the back passivation film layer and contacts the first polarity doped layer, and the second fine gate at least partially penetrates the back passivation film layer and contacts the second polarity doped layer; The third polarity doping layer is obtained by partially removing a wrap-around layer formed on the first polarity doping layer during the process of forming the second polarity doping layer.

2. The back contact solar cell according to claim 1, characterized in that: In the second direction, a ratio of a length of the first fine gate in contact with the first polarity doping layer to a total length of the first fine gate is 30%-80%.

3. The back contact solar cell according to claim 2, characterized in that: In the second direction, a ratio of a length of the first fine gate in contact with the first polarity doping layer to a total length of the first fine gate is 40%-60%.

4. The back contact solar cell according to claim 1, characterized in that: An insulating isolation layer is also provided between the third polarity doping layer and the first polarity doping layer. The insulating isolation layer is also obtained by partially removing the plating layer formed on the first polarity doping layer during the process of forming the second polarity doping layer.

5. The back contact solar cell according to claim 1, characterized in that: In the first direction, the width of the third polarity doping layer is greater than or equal to the width of the first fine gate.

6. The back contact solar cell according to claim 1, characterized in that: The first polarity doping layer is a P-type doping layer, and the second polarity doping layer and the third polarity doping layer are both N-type doping layers.

7. The back contact solar cell according to claim 6, characterized in that: The bonding tension between the third polarity doping layer and the back passivation film layer is greater than the bonding tension between the first polarity doping layer and the back passivation film layer.

8. The back contact solar cell according to claim 7, characterized in that: The back-contact solar cell further includes a solder joint electrically connected to the first fine grid, wherein the solder joint is disposed on the back passivation film layer and is at least partially located above the third polarity doping layer.

9. The back contact solar cell according to claim 8, characterized in that: The projection area of ​​the third polarity doping layer on the silicon substrate is greater than or equal to the projection area of ​​the solder joint on the silicon substrate, and the solder joint is completely located within the projection area of ​​the third polarity doping layer.

10. The back contact solar cell according to claim 1, characterized in that: In the second direction, at the position corresponding to the second fine grid, a plurality of barrier layers arranged in intervals are arranged between the second polarity doping layer and the back passivation film layer, and the second fine grid is also made of a burn-through paste; At the position corresponding to the barrier layer, the second fine gate burns through the back passivation film layer and contacts the barrier layer. Between two adjacent barrier layers, the second fine gate burns through the back passivation film layer and contacts the second polarity doping layer. The barrier layer includes a phosphosilicate glass layer or a borosilicate glass layer.

11. A battery assembly, characterized in that: A back-contact solar cell comprising any one of claims 1-10.

12. A photovoltaic system, characterized in that: A battery assembly comprising the battery assembly of claim 11.

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