Electrode structure of back contact solar cell, back contact solar cell and photovoltaic module

Abstract

The invention relates to the field of solar cells, and discloses an electrode structure of a back contact solar cell, the back contact solar cell and a photovoltaic module. Comprising a collector grid line and a bonding pad, the bus grid line is electrically connected with the grid line; l1 comprises an edge collector grid line segment connected with the end part, an edge bus grid line located between the end part and the first electric connection grid line, and the first electric connection grid line; l2 comprises a second electric connection grid line and an edge collector grid line segment located between two adjacent middle bonding pads; the L3 comprises a second electric connection grid line and a current collection grid line which is located between the first middle bonding pad and the edge bus grid line and is closest to the edge current collection grid line; 0.8 < = L1 / L2 < = 1.6, and 1.2 < = L1 / L3 < = 1.6. According to the electrode structure provided by the invention, the carrier transmission capability at the middle bonding pad and the carrier transmission capability at the edge bonding pad are equivalent, and the phenomenon of EL blackening or darkening at the edge of the back contact solar cell is avoided.

Description

Technical Field

[0001] This application relates to the field of solar cell technology, and in particular to an electrode structure for a back-contact solar cell, a back-contact solar cell, and a photovoltaic module. Background Technology

[0002] In the field of back-contact solar cells, an unreasonable electrode structure design can affect its current collection capability. In particular, the current transmission loop of the edge pads on the electrode structure is relatively long. During electroluminescence testing, the long loop will increase the current loss, which will lead to blackening of the edge EL and affect the photoelectric conversion efficiency of the back-contact solar cell. Summary of the Invention

[0003] This invention discloses an electrode structure for a back-contact solar cell, a back-contact solar cell, and a photovoltaic module. The electrode structure of this application makes the carrier transport capacity at the middle pad and the edge pad equally comparable, avoiding the phenomenon of EL blackening or darkening at the edge of the back-contact solar cell.

[0004] In a first aspect, this application discloses an electrode structure for a back-contact solar cell, the electrode structure comprising: Edge busbar, wherein the length direction of the edge busbar is a first direction; Multiple collector grid lines are spaced apart along the first direction. The collector grid lines include edge collector grid lines connected to the ends of the edge busbars. Along the direction perpendicular to the first direction, the edge collector grid lines include multiple spaced edge collector grid line segments. Multiple pads are connected to the collector grid line. The multiple pads are spaced apart along a direction perpendicular to the first direction, and the polarities of adjacent groups of pads are opposite. Along the first direction, the pads include a first row of pads closest to the edge collector grid line. The first row of pads includes an edge pad closest to the end and multiple intermediate pads. The multiple intermediate pads include a first intermediate pad closest to the edge pad. An electrical connection gate line, comprising multiple first electrical connection gate lines and multiple second electrical connection gate lines, wherein any one of the first electrical connection gate lines is connected between the edge bus gate line and the edge pad, and any one of the second electrical connection gate lines is connected between the edge collector gate line segment and the intermediate pad; Wherein, the transmission loop of the edge pad is L1, and L1 includes: the edge collector gate line segment connected to the end, the edge bus gate line located between the end and the first electrical connection gate line, and the first electrical connection gate line; The transmission loop of the intermediate pad with the same polarity as the edge pad is L2, and L2 includes: the second electrical connection gate line, and the edge collector gate line segment located between two adjacent intermediate pads; The transmission loop of the first intermediate pad is L3, and L3 includes: the second electrical connection gate line connected to the first intermediate pad, and the collector gate line that is closest to the edge collector gate line and located between the first intermediate pad and the edge bus gate line; The lengths of L1 and L2 satisfy: 0.8 ≤ L1 / L2 ≤ 1.6; The lengths of L1 and L3 satisfy the following condition: 1.2 ≤ L1 / L3 ≤ 1.6.

[0005] Furthermore, the length of the edge collector gate segment located between the first intermediate pad and the edge pad is D1, and the length of the edge collector gate segment located between two adjacent intermediate pads is D2, wherein D1 and D2 satisfy: D1≤D2.

[0006] Furthermore, the length of the first electrical connection gate wire is D3, and D1, D2, and D3 satisfy: D3 + D1 = D2.

[0007] Furthermore, D2 satisfies: 3 mm ≤ D2 ≤ 13 mm.

[0008] Furthermore, the multiple collector grid lines are parallel to each other; and / or, In the intermediate pads, the spacing between any two adjacent intermediate pads is the same; and / or, The length of the edge busbar located between the end and the first electrical connection grid line is S, and S satisfies: 4 mm ≤ S ≤ 10 mm.

[0009] Further, along the first direction, the electrode structure includes an edge region and a middle region located inside the edge region, wherein the edge region is the area enclosed by the first row pads, the edge collector grid line, and the edge busbar line located between the first row pads and the edge collector grid line; The collector grid line includes multiple first collector grid lines located in the edge region and multiple second collector grid lines located in the middle region. Along the direction perpendicular to the first direction, each of the first collector grid lines includes multiple spaced collector grid line segments. Along the first direction, the collector grid line segment includes alternating first polarity collector grid line segments and second polarity collector grid line segments, and the second collector grid line includes alternating first polarity collector grid line and second polarity collector grid line. The pads include first pads and second pads arranged alternately along a direction perpendicular to the first direction; The edge busbar includes a first edge busbar and a second edge busbar. The first edge busbar is connected to the first polarity collector gate segment and the first polarity collector gate. The second edge busbar is connected to the second polarity collector gate segment and the second polarity collector gate. Wherein, the first polarity collector gate segment and the first polarity collector gate line are connected to the first pad, the second polarity collector gate segment and the second polarity collector gate line are connected to the second pad, the position of the discontinuity of the first polarity collector gate segment corresponds to the position of the second electrical connection gate line at the second pad, and the position of the discontinuity of the second polarity collector gate segment corresponds to the position of the second electrical connection gate line at the first pad; The first pad, the first polarity collector gate segment, the first polarity collector gate line, and the first edge bus gate line are disposed in the first conductivity type region, and the second pad, the second polarity collector gate segment, the second polarity collector gate line, and the second edge bus gate line are disposed in the second conductivity type region. One of the first conductivity type and the second conductivity type is an N-type conductivity type and the other is a P-type conductivity type.

[0010] Secondly, according to an embodiment of this application, a back-contact solar cell is provided, the back-contact solar cell comprising: A silicon substrate, the silicon substrate including a profile line parallel to the edge bus gate line; The electrode structure as described in any of the first aspects is located on the surface of the silicon substrate.

[0011] Furthermore, the distance between the edge pad and the outline is D4, and the length of the first electrical connection gate is D3. The D3 and D4 satisfy: 2 mm ≤ D4 + D3 ≤ 6 mm.

[0012] Furthermore, D4 ​​satisfies: 0.5 mm ≤ D4 ≤ 1 mm.

[0013] This application discloses a photovoltaic module, which includes: a back-contact solar cell as described in any of the second aspects.

[0014] Compared with the prior art, the beneficial effects of this application are as follows: The present application provides an electrode structure of a back-contact solar cell, a back-contact solar cell, and a photovoltaic module. In the electrode structure of the present application, the ratio of the transmission loop of the edge pad to the transmission loop of the middle pad is controlled and optimized within a specific range, so that the carrier transmission capabilities at the middle pad and the edge pad are comparable, reducing the difference in carrier transmission loss between different paths, thereby avoiding the phenomenon of EL blackening or dimming at the edge of the back-contact solar cell.

[0015] Specifically, the current collector grid line of the present application is used to collect the current generated inside the battery, and the edge busbar can transmit the current collected by the current collector grid line to the pad, and then transmit it to the external circuit through the pad to achieve the transmission of the current. Among them, when transmitting the current of the edge pad, its transmission loop L1 includes: an edge current collector grid line segment connected to the end, an edge busbar located between the edge current collector grid line segment connected to the end and the edge pad, and a first electrical connection grid line. These three transmission paths form a structure similar to a "匚" shape with an opening; when transmitting the current of the middle pad with the same polarity as the edge pad, its transmission loop L2 includes: a second electrical connection grid line and an edge current collector grid line segment located between two middle pads. These two transmission paths form a structure similar to a "7" shape; when transmitting the current of the first middle pad, its transmission loop L3 includes: a second electrical connection grid line and a current collector grid line located between the first middle pad and the edge busbar and closest to the end. These two transmission paths form a structure similar to a "7" shape.

[0016] Furthermore, by analyzing the transmission loop of the edge pad and the transmission loop of the middle pad, it can be seen that the transmission path of the edge pad is longer than that of the middle pad. Therefore, in the present application, the ratio of the lengths of L1 and L2 is set to satisfy 0.8 ≤ L1 / L2 ≤ 1.6, 1.2 ≤ L1 / L3 ≤ 1.6, so as to well balance the path difference between the transmission loop of the edge pad and the transmission loop of the middle pad, make the carrier transmission capabilities of the middle pad and the edge pad comparable, reduce the difference in carrier transmission loss between different paths, and further help to reduce the EL brightness contrast at the middle pad area and the edge pad area, avoid the phenomenon of EL blackening or dimming at the edge of the back-contact solar cell, and improve the performance and EL appearance yield of the back-contact solar cell to a high degree. Description of the Drawings

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0018] Figure 1 This is a schematic diagram of the electrode structure provided in the embodiments of this application (showing the first row of pads, edge collector grid lines, and bus grid lines). Figure 2 yes Figure 1 The first enlarged view of area A in the middle (showing the middle pad, edge pad, and electrical connection gate). Figure 3 yes Figure 1 The first enlarged view of area A in the middle (showing the transmission loop of the middle pad and the edge pad). Figure 4 yes Figure 1 The second type of enlarged view of region A in the middle; Figure 5 This is a schematic diagram of the electrode structure provided in the embodiment of this application (showing the middle region and the edge region). Figure 6 This is provided by the embodiments of this application. Figure 5 A schematic diagram of the structure of the edge region in the diagram; Figure 7 This is provided by the embodiments of this application. Figure 5 A structural diagram of the middle region; Figure 8 This is a schematic diagram of the structure of a back-contact solar cell provided in an embodiment of this application; Figure 9 This is the EL test diagram provided in Embodiment 1 of this application; Figure 10 This is the EL test diagram provided in Comparative Example 1 of this application.

[0019] Icons: 1. Edge bus line; 1a. First edge bus line; 1b. Second edge bus line; 2. Collector gate line; 21. Edge collector gate line; 211. Edge collector gate line segment; 2a. First collector gate line; 21a. Collector gate line segment; 211a. First polarity collector gate line segment; 212a. Second polarity collector gate line segment; 2b. Second collector gate line; 21b. First polarity collector gate line; 22b. Second polarity collector gate line; 3. Pad; 3a. First pad; 3b. Second pad; 31. First row pad; 311. Edge pad; 312. Middle pad; 3121. First middle pad; 4. Electrical connection gate line; 41. First electrical connection gate line; 42. Second electrical connection gate line; 5. Edge region; 6. Middle region; 7. Silicon substrate; 71. Outline. Detailed Implementation

[0020] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0021] In the present application, the orientation or positional relationship indicated by terms such as "upper", "lower", "left", "right", "front", "rear", "top", "bottom", "inner", "outer", "middle", "vertical", "horizontal", "lateral", "longitudinal", etc. is based on the orientation or positional relationship shown in the accompanying drawings. These terms are mainly used to better describe the present application and its embodiments, and are not used to limit that the indicated devices, elements or components must have a specific orientation, or be constructed and operated in a specific orientation.

[0022] Moreover, in addition to being used to represent the orientation or positional relationship, some of the above terms may also be used to represent other meanings. For example, the term "upper" may also be used to represent a certain attachment relationship or connection relationship in some cases. For those of ordinary skill in the art, the specific meanings of these terms in the present application can be understood according to specific situations.

[0023] In addition, terms such as "first", "second", etc. are mainly used to distinguish different devices, elements or components (the specific types and structures may be the same or different), and are not used to indicate or imply the relative importance and quantity of the indicated devices, elements or components. Unless otherwise specified, the meaning of "plural" is two or more.

[0024] Next, the technical solutions provided by the present application will be further described in conjunction with the embodiments and the accompanying drawings.

[0025] In a back-contact solar cell, carriers will generate energy losses due to the resistance of the semiconductor itself during the process of transmitting along the semiconductor. The length of the transmission loop before being conducted to the pad reflects the degree of resistance loss caused by the transmission of carriers in the semiconductor.

[0026] In a back-contact solar cell, the transmission loop of the edge pad forms a structure similar to a "匚" shape with one opening, and the transmission loop of the middle pad forms a structure similar to a "7" shape. That is, compared with the middle pad, the transmission path of the edge pad is longer, resulting in a significant increase in the resistance loss in this area, reducing the carrier collection efficiency, and exacerbating the carrier recombination loss. This difference in collection efficiency forms a bright-dark contrast in the EL test, with the area at the middle pad being bright and the area at the edge pad being dark, thus highlighting the non-uniformity of the bright and dark in the EL appearance test of the back-contact solar cell and reducing the EL appearance yield.

[0027] Furthermore, the fixed length of the collector grid line in the electrode structure causes the transmission path length of the edge pads and the transmission path length of the middle pads to be mutually restrictive. Therefore, in order to reduce the contrast between the brightness and darkness at the middle pads and the edge pads, it is necessary to balance the path length of the transmission loops of the two to make the carrier transmission capacity comparable, thereby reducing the contrast between the brightness and darkness of the EL and avoiding the phenomenon of EL blackening or darkening at the edge of the back contact solar cell.

[0028] Based on the above problems, this application provides an electrode structure for a back contact solar cell. The distance difference between the transmission paths of the middle pad and the edge pad in the electrode structure is small, so that the carrier collection efficiency at the middle pad area and the edge pad area is comparable, which helps to avoid the phenomenon of EL blackening or darkening at the edge of the back contact solar cell.

[0029] The first aspect, such as Figures 1 to 3 As shown, where, Figure 1 and Figure 2 The black dots are to indicate the ends of the edge busbars. Figure 3 The dashed lines drawn on the edge busbar, electrical connection grid, and edge collector grid represent the carrier transport paths. This application discloses an electrode structure for a back-contact solar cell, the electrode structure comprising: Edge busbar 1, the length direction of edge busbar 1 is the first direction (see...). Figure 1 Y direction in ); Collector grid lines 2, multiple collector grid lines 2 are spaced apart along a first direction, the collector grid lines 2 include edge collector grid lines 21 connected to the ends of edge busbar lines 1, along a direction perpendicular to the first direction (see...). Figure 1 (in the X direction), the edge collector grid line 21 includes multiple spaced edge collector grid line segments 211; Multiple pads 3 are connected to the collector grid line 2. The multiple pads 3 are spaced apart along a direction perpendicular to the first direction, and the polarities of adjacent groups of pads 3 are opposite. Along the first direction, the pads 3 include a first row of pads 31 that are closest to the edge collector grid line 2. The first row of pads 31 includes an edge pad 311 that is closest to the end and multiple intermediate pads 312. The multiple intermediate pads 312 include a first intermediate pad 3121 that is closest to the edge pad 311. Electrical connection gate line 4 includes multiple first electrical connection gate lines 41 and multiple second electrical connection gate lines 42. Any one of the first electrical connection gate lines 41 is connected between the edge bus gate line 1 and the edge pad 311, and any one of the second electrical connection gate lines 42 is connected between the edge collector gate line segment 211 and the middle pad 312. The transmission loop of the edge pad 311 is L1, which includes: an edge collector gate segment 211 connected to the end, an edge bus gate 1 located between the end and the first electrical connection gate 41, and the first electrical connection gate 41. The transmission loop of the intermediate pad 312 with the same polarity as the edge pad 311 is L2. L2 includes: a second electrical connection gate line 42 and an edge collector gate line segment 211 located between two adjacent intermediate pads 312. The transmission loop of the first intermediate pad 3121 is L3, which includes: a second electrical connection gate line 42, and a collector gate line 2 that is closest to the edge collector gate line 21 and located between the first intermediate pad 3121 and the edge bus gate line 1. L1 and L2 satisfy: 0.8 ≤ L1 / L2 ≤ 1.6; L1 and L3 satisfy: 1.2≤L1 / L3≤1.6.

[0030] The first row pad 31 is the pad 3 with the shortest distance to the edge collector gate line 21. That is, whether it is the N area or the P area, the pad 3 with the shortest distance to the edge collector gate line 21 is the first row pad 31. The edge pad 311 refers to the pad 3 with the shortest straight distance to the end of the edge bus gate line 1. That is, the edge pad 311 can be understood as the pad 3 located in the first row and first column.

[0031] The middle pad 312 refers to the pad 3 located on the side of the edge pad 311 away from the edge bus line 1. For example, when the number of columns of pad 3 is ten, the middle pad 312 can be understood as the pad 3 located in the third column of the first row, the fifth column of the first row, the seventh column of the first row, etc.

[0032] Furthermore, the first electrical connection gate line 41 of this application is used to form the transmission loop of the edge pad 311, and its number corresponds to the number of edge pads 311. The second electrical connection gate line 42 is used to form the transmission loop of the middle pad 312, and its number corresponds to the number of middle pads 312.

[0033] The collector grid line 2 that is closest to the edge collector grid line 21 refers to the collector grid line 2 that has the smallest vertical distance from the edge collector grid line 21. For example, when there are five collector grid lines 2 along the first direction, the edge collector grid line 21 is the first grid line, and the collector grid line 2 that is closest to the edge collector grid line 21 is the second grid line.

[0034] Additionally, the intermediate pad 312 includes a first intermediate pad 3121 that is closest to the edge pad 311, and the polarity of the first intermediate pad 3121 is opposite to that of the edge pad 311. The length of the edge collector gate line segment 211 connected to the end includes: the length D1 of the edge collector gate line segment 211 located between the first intermediate pad 3121 and the edge pad 311, and the length of the edge collector gate line 211 located between the edge pad 311 and the end.

[0035] The current collector 2 of this application is used to collect charge carriers generated inside the battery, while the edge busbar 1 can transfer the charge carriers collected by the current collector 2 to the pad 3, and then transfer them to the external circuit through the pad 3, thereby realizing the transfer of charge carriers. Specifically, when the edge pad 311 collects charge carriers, the transfer process of the charge carriers in the transmission loop L1 is as follows: the edge current collector segment 211 can transfer the collected charge carriers through its end to the edge busbar 1, and the charge carriers transferred to the edge busbar 1 can be transferred to the edge pad 311 through the first electrical connection grid 41; in addition, when the intermediate pad 312 with the same polarity as the edge pad 311 collects charge carriers, the transfer process of its charge carriers in the transmission loop L2 includes: located on adjacent... The edge collector gate segment 211 between the intermediate pads 312 transmits the collected carriers to the intermediate pads 312 via the second electrical connection gate line 42; in addition, when the first intermediate pad 3121, which is closest to the edge pad 311 and has the opposite polarity, collects carriers, the carrier transmission process in the transmission loop L3 includes: the collector gate line 2, which is closest to the edge collector gate line 21 and has the opposite polarity, transmits the collected carriers to the first intermediate pad 3121 via the second electrical connection gate line 42.

[0036] Furthermore, analysis of the transmission loops of edge pad 311 and intermediate pad 312 reveals that when carriers are transported along a direction perpendicular to the first direction, the transmission loop of edge pad 311 comprises three segments: an edge collector gate segment 211 located between the first intermediate pad 3121 and edge pad 311, an edge collector gate segment 211 located between edge pad 311 and the end, and a first electrical connection gate line 41. The transmission loop of intermediate pad 312, which has the same polarity as edge pad 311, only includes the edge collector gate segment 211 located between two adjacent intermediate pads 312. The transmission loop of the first intermediate pad 3121 includes: a collector gate line 1 located between the edge bus gate line 1 and edge pad 311. 2. The two segments of the collector grid line 2 located between the edge pad 311 and the first intermediate pad 3121; that is, the transmission path of the edge pad 311 in this application is more than that of the intermediate pad 312, and the transmission loop distance of the edge pad 311 is longer. Therefore, this application sets 0.8≤L1 / L2≤1.6 and 1.2≤L1 / L3≤1.6, so as to effectively balance the length of the transmission loop of the edge pad 311 and the transmission loop of the intermediate pad 312, and reduce the difference in the transmission path of the carriers of the intermediate pad 312 and the edge pad 311 to a greater extent. This helps to reduce the contrast between the light and dark areas in the intermediate pad 312 area and the edge pad 311 area, and avoids the phenomenon of EL blackening or darkening at the edge of the back contact solar cell.

[0037] Specifically, when L1 / L2 > 1.6 and L1 / L3 > 1.6, it indicates a large difference in the transport path between the edge pad 311 and the middle pad 312 when collecting charge carriers. This large difference results in a higher degree of charge carrier recombination at the edge pad 311 than at the middle pad 312, leading to a significant difference in the transport capacity of charge carriers in the two regions. This, in turn, causes severe blackening or darkening of the EL (electrode photocell) at the edge pad 311. When L1 / L2 < 0.8 and L1 / L3 < 1.2, it means that the edge pad 311 is very close to the edge of the solar cell, which can easily lead to edge microcracks during edge pad soldering. For example, L1 / L2 can be 0.8, 1.0, 1.2, 1.4, or 1.6.

[0038] In summary, by controlling and optimizing the ratio of the transmission loop of the edge pad 311 to the transmission loop of the middle pad 312 within a specific range, this application helps to reduce the contrast between light and dark areas in the middle pad 312 region and the edge pad 311 region, thus avoiding the phenomenon of EL blackening or darkening at the edge of the back contact solar cell.

[0039] Further, see the return Figure 1Along the direction perpendicular to the first direction, the multiple collector gate lines 2 of this application are arranged in parallel to each other. This arrangement makes the length S of the edge bus gate line 1 located between the edge collector gate line segment 211 and the edge pad 311 equal to the length of the second electrical connection gate line 42. The length of the edge collector gate line segment 211 located between the edge pad 311 and the end is the same as the length D3 of the first electrical connection gate line 41.

[0040] At this time, L1-L2=2D3+D1-D2. This setting helps to shorten the difference between the length of the transmission loop of the middle pad 312 and the length of the transmission loop of the edge pad 311, thereby ensuring that the carrier transmission capacity in the middle pad 312 area and the edge pad 311 area is comparable to a certain extent, and avoiding the phenomenon of EL blackening or darkening at the edge of the back contact solar cell.

[0041] Further, see the return Figure 3 The intermediate pad 312 includes a first intermediate pad 3121 that is closest to the edge pad 311. The length of the edge collector gate segment 211 located between the first intermediate pad 3121 and the edge pad 311 is D1, and the length of the edge collector gate segment 211 located between two adjacent intermediate pads 312 is D2. D1 and D2 satisfy: D1≤D2.

[0042] In this context, "closest to the edge pad 311" refers to the pad 3 with the shortest vertical distance to the edge pad 311, that is, the pad 3 immediately adjacent to the edge pad 311 is the first intermediate pad 3121. Furthermore, the spacing between the pads 3 in this application refers to the distance between the centers of two pads 3.

[0043] By setting D1≤D2, the transmission lengths of the edge pad 311 and the middle pad 312 perpendicular to the first direction can be effectively balanced. This effectively balances the lengths of the carrier transmission loops in the edge pad 311 and the middle pad 312, making the recombination capacity and transmission capacity of carriers in different regions comparable. This further helps reduce the contrast between the middle pad 312 region and the edge pad 311 region, thereby preventing the EL blackening or darkening phenomenon at the edge of the back contact solar cell, reducing circuit losses, and improving the photoelectric conversion efficiency of the back contact solar cell. More preferably, when D1<D2, the transmission length of the edge pad 311 perpendicular to the first direction is reduced more effectively, which further helps to balance the lengths of L1 and L2, thereby further reducing the contrast between the middle pad 312 region and the edge pad 311 region, and further reducing the EL blackening or darkening phenomenon at the edge of the back contact solar cell.

[0044] In one alternative implementation, the spacing between two adjacent intermediate pads 312 is different. For example, the spacing between the intermediate pads 312 may exhibit a decreasing trend, or the spacing between the intermediate pads 312 may exhibit an irregular trend, for example, as... Figure 4 As shown, the spacing of the intermediate pads 312 exhibits a trend of first decreasing and then remaining the same, or the spacing of the intermediate pads 312 exhibits a trend of increasing.

[0045] In another alternative implementation, see back Figure 2 In the intermediate pads 312, the spacing between any two adjacent intermediate pads 312 is the same. By setting the spacing of the intermediate pads 312 to be the same, the carrier transport capacity in the intermediate pad 312 region is made consistent, thereby avoiding differences in EL brightness in the intermediate pad 312 region, and also improving the electrical performance of the back contact solar cell. Furthermore, by further controlling the ratio of L1 to L2 within the range of this application, the difference in brightness between the intermediate pad 312 region and the edge pad 311 region is reduced to a significant extent, avoiding the phenomenon of EL blackening or darkening at the edge of the back contact solar cell; in addition, it also helps to improve the mechanical uniformity of the screen printing plate during printing, and helps to increase the life of the screen printing plate.

[0046] Furthermore, the length of the first electrical connection grid line 41 is D3, and D1, D2, and D3 satisfy: D3 + D1 = D2. When D1, D2, and D3 satisfy the above relationship, it helps to balance the ratio of L1 and L2, thereby effectively shortening the length of the carrier transmission loop at the edge pad 311, reducing the recombination loss of carriers at the edge pad 311, and making the carrier transmission capacity at the edge pad 311 and the middle pad 312 comparable, which helps to avoid the phenomenon of EL blackening or darkening at the edge of the back contact solar cell.

[0047] D2 satisfies the following condition: 3 mm ≤ D2 ≤ 13 mm. Controlling D2 within this range helps ensure that the carrier transport capabilities at the intermediate pad 312 and the edge pad 311 are comparable, thereby effectively reducing the contrast between the light and dark areas at the intermediate pad 312 and the edge pad 311, and preventing the EL (electroluminescent film) from appearing black or dark at the edge of the back-contact solar cell. For example, D2 can be 3 mm, 5 mm, 7 mm, 11 mm, or 13 mm, etc.

[0048] The length of the edge busbar 1 located between the end and the first electrical connection gate line 41 is S, where S satisfies: 4 mm ≤ S ≤ 10 mm. By controlling S within the above range, it helps to reduce recombination losses generated when charge carriers are transported at the edge busbar 1, and further helps to improve the transport efficiency of charge carriers. For example, S is 4 mm, 5.5 mm, 7 mm, 8.5 mm, or 10 mm, etc.

[0049] Furthermore, such as Figures 5 to 7 As shown, along the first direction, the electrode structure includes an edge region 5 and a middle region 6 located inside the edge region 5. The edge region 5 is the area enclosed by the first row pads 31, the edge collector grid line 21, and the edge busbar 1 located between the first row pads 31 and the edge collector grid line 21. The collector grid line 2 includes multiple first collector grid lines 2a located in the edge region 5 and multiple second collector grid lines 2b located in the middle region 6. Along the direction perpendicular to the first direction, any one of the first collector grid lines 2a includes multiple collector grid line segments 21a arranged at intervals. Along the first direction, the collector grid line segment 21a includes alternating first polarity collector grid line segment 211a and second polarity collector grid line segment 212a, and the second collector grid line 2b includes alternating first polarity collector grid line 21b and second polarity collector grid line 22b. The pad 3 includes a first pad 3a and a second pad 3b arranged alternately along a direction perpendicular to the first direction; The edge busbar 1 includes a first edge busbar 1a and a second edge busbar 1b. The first edge busbar 1a is connected to the first polarity collector gate segment 211a and the first polarity collector gate 21b, and the second edge busbar 1b is connected to the second polarity collector gate segment 212a and the second polarity collector gate 22b. Wherein, the first polarity collector gate segment 211a and the first polarity collector gate line 21b are connected to the first pad 3a, and the second polarity collector gate segment 212a and the second polarity collector gate line 22b are connected to the second pad 3b. The position of the discontinuity of the first polarity collector gate segment 211a corresponds to the position of the second electrical connection gate line 42 at the second pad 3b, and the position of the discontinuity of the second polarity collector gate segment 212a corresponds to the position of the second electrical connection gate line 42 at the first pad 3a. The first pad 3a, the first polarity collector gate segment 211a, the first polarity collector gate line 21b, and the first edge bus gate line 1a are disposed in the first conductivity type region, and the second pad 3b, the second polarity collector gate segment 212a, the second polarity collector gate line 22b, and the second edge bus gate line 1b are disposed in the second conductivity type region. One of the first conductivity type and the second conductivity type is an N-type conductivity type and the other is a P-type conductivity type.

[0050] This application discloses a back-contact solar cell, such as... Figure 8 As shown, the back contact solar cell includes: The silicon substrate 7 includes a contour line 71 parallel to the edge bus gate line 1; As described above, the electrode structure is located on the surface of the silicon substrate 7.

[0051] The types of back-contact solar cells are back-contact solar cells, specifically tunneling back-contact solar cells (TBC), heterojunction back-contact solar cells (HBC), or hybrid back-contact solar cells (HTBC) of heterojunction and tunneling oxygen passivation contacts.

[0052] Silicon substrate 7 refers to a semi-finished product where all functional film layers have been prepared but electrode paste has not yet been printed to prepare the electrode structure. The functional film layer refers to a film structure with specific electrical or optical properties deposited on the substrate, and the type of functional film layer is related to the type of back-contact solar cell. For example, when the back-contact solar cell is a tunneling back-contact solar cell (TBC), its corresponding functional film layers include passivation layers and passivation contact structures, where the passivation contact structure includes a dielectric layer and a doped silicon layer located on the dielectric layer.

[0053] Furthermore, the distance between the edge pad 311 and the outline 71 is D4, and the length of the first electrical connection gate line 41 is D3. D3 and D4 satisfy: 2 mm ≤ D4 + D3 ≤ 6 mm. By controlling D4 and D3 within the above relationship, it is shown that the distance between the edge pad 311 and the outline 71 is appropriate. Therefore, when soldering the solder strip onto the edge pad 311, it helps to avoid the risk of edge soldering microcracks caused by the close distance between the edge pad 311 and the outline 71 during soldering. This helps to improve the solder strip soldering effect to a greater extent and improve the long-term stability of the back contact solar cell. For example, D4 ​​+ D3 is 2 mm, 3 mm, 4 mm, 5 mm, or 6 mm, etc.

[0054] Furthermore, D4 ​​satisfies the condition: 0.5 mm ≤ D4 ≤ 1 mm. When D4 is within the above range, it helps to avoid the risk of microcracks caused by solder strip welding, thereby improving the reliability of solder strip welding to a greater extent. For example, D4 ​​is 0.5 mm, 0.65 mm, 0.8 mm, 0.9 mm, or 1 mm, etc.

[0055] It should be noted that outline 71 represents the edge of the silicon substrate of the back contact solar cell.

[0056] This application discloses a photovoltaic module, which includes the aforementioned back-contact solar cell.

[0057] The technical solution of this application will be further explained below with reference to more specific embodiments and experimental test results.

[0058] Example 1: This embodiment provides a back contact solar cell (TBC), including: The silicon substrate includes an N-type silicon substrate, which includes a light-receiving surface and a back-lighting surface arranged opposite to each other. The back-lighting surface is provided with alternating first conductive regions, second conductive regions, and an isolation region located between the first conductive regions and the second conductive regions. The backlight surface has a 5 nm thick aluminum oxide passivation layer and a 100 nm thick nitride / silicon oxide antireflection layer sequentially disposed on the light-receiving surface. The first conductive region of the backlight surface has a 1.5 nm thick silicon oxide layer, a 250 nm thick phosphorus-doped polycrystalline silicon layer, a 4.5 nm thick aluminum oxide passivation layer, and a 100 nm thick nitride / silicon oxide antireflection layer sequentially disposed on the backlight surface. The second conductive region of the backlight surface has a 1.5 nm thick silicon oxide layer, a 250 nm thick boron-doped polycrystalline silicon layer, a 4.5 nm thick aluminum oxide passivation layer, and a 100 nm thick nitride / silicon oxide antireflection layer sequentially disposed on the backlight surface.

[0059] Electrode structure (see) Figure 1 The electrode structure (as shown in the image) is disposed on the back surface of the silicon substrate, wherein the electrode structure includes: Edge busbars; The collector grid line includes multiple collector grid lines that are spaced apart from each other and arranged in parallel along a first direction. The collector grid line includes an edge collector grid line connected to the end of the edge bus grid line. Along the direction perpendicular to the first direction, the edge collector grid line includes multiple spaced edge collector grid line segments. Multiple pads are connected to the collector grid line. The multiple pads are spaced apart along a direction perpendicular to a first direction. Along the first direction, the pads include a first row of pads that are closest to the end of the edge bus grid line. The first row of pads includes an edge pad that is closest to the end and multiple intermediate pads. The spacing between two adjacent intermediate pads is the same. The electrical connection gate includes multiple first electrical connection gates and multiple second electrical connection gates, wherein any one of the first electrical connection gates is connected between the edge bus gate and the edge pad, and any one of the second electrical connection gates is connected between the edge collector gate segment and the middle pad; The transmission loop of the edge pad is L1, which includes: an edge collector gate line segment connected to the end (i.e., the sum of the length D1 of the edge collector gate line segment located between the first intermediate pad and the edge pad and the length D3 of the edge collector gate line segment located between the end and the edge pad), an edge bus gate line (L) located between the end and the first electrical connection gate line, and a first electrical connection gate line (D3). The transmission loop of the intermediate pad is L2, which includes: a second electrical connection gate line (L) and an edge collector gate line segment (D2) located between two adjacent intermediate pads. Additionally, L1 / L2 = 1.1, L1 / L3 = 1.4, D1 is 7.25 mm, D2 is 9.5 mm, S is 5 mm, and the distance between the edge pad and the outline is D4, which is 0.6 mm.

[0060] Comparative Example 1 The only difference between this embodiment and Embodiment 1 is that D1=9.5 mm, L1 / L2=1.8, and L1 / L2=1.1.

[0061] The parameter variations in Example 1 and Comparative Example 1 are detailed in Table 1, which shows the parameters of the electrode structure: Table 1 Electrode structure parameters of Example 1 and Comparative Example 1

[0062] Performance testing: like Figure 9 and Figure 10 It can be seen that, among them, Figure 9 This is an EL test diagram provided in Embodiment 1 of this application. Figure 10 The EL test diagram provided in Comparative Example 1 of this application is as follows. Figure 9 No blackening or darkening of the edge EL of a single back contact solar cell was observed in the transmission loops of the edge pads and middle pads. Figure 10 In the transmission loops of the edge pads and the middle pads, there is a noticeable phenomenon of blackening or darkening of the EL at the edge of a single back-contact solar cell. It is evident that by controlling the ratio of L1 to L2 within the range specified in this application, it is helpful to ensure that the carrier transmission capacity at the edge pads and the middle pads is comparable to a certain extent, thereby helping to reduce the contrast between bright and dark EL and avoid the phenomenon of blackening or darkening of the EL at the edge of a single back-contact solar cell.

[0063] The electrode structure of the back-contact solar cell, the back-contact solar cell, and the photovoltaic module disclosed in the embodiments of this application have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. The description of the above embodiments is only for the purpose of helping to understand the electrode structure of the back-contact solar cell, the back-contact solar cell, and the photovoltaic module. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. An electrode structure for a back-contact solar cell, characterized in that, The electrode structure includes: Edge busbar, wherein the length direction of the edge busbar is a first direction; Multiple collector grid lines are spaced apart along the first direction. The collector grid lines include edge collector grid lines connected to the ends of the edge busbars. Along the direction perpendicular to the first direction, the edge collector grid lines include multiple spaced edge collector grid line segments. Multiple pads are connected to the collector grid line. The multiple pads are spaced apart along a direction perpendicular to the first direction, and the polarities of adjacent groups of pads are opposite. Along the first direction, the pads include a first row of pads closest to the edge collector grid line. The first row of pads includes an edge pad closest to the end and multiple intermediate pads. The multiple intermediate pads include a first intermediate pad closest to the edge pad. An electrical connection gate line, comprising multiple first electrical connection gate lines and multiple second electrical connection gate lines, wherein any one of the first electrical connection gate lines is connected between the edge bus gate line and the edge pad, and any one of the second electrical connection gate lines is connected between the edge collector gate line segment and the intermediate pad; Wherein, the transmission loop of the edge pad is L1, and L1 includes: the edge collector gate line segment connected to the end, the edge bus gate line located between the end and the first electrical connection gate line, and the first electrical connection gate line; The transmission loop of the intermediate pad with the same polarity as the edge pad is L2, and L2 includes: the second electrical connection gate line, and the edge collector gate line segment located between two adjacent intermediate pads; The transmission loop of the first intermediate pad is L3, and L3 includes: the second electrical connection gate line, and the collector gate line that is closest to the edge collector gate line and located between the first intermediate pad and the edge bus gate line; The lengths of L1 and L2 satisfy: 0.8 ≤ L1 / L2 ≤ 1.6; The lengths of L1 and L3 satisfy the following condition: 1.2 ≤ L1 / L3 ≤ 1.

6.

2. The electrode structure according to claim 1, characterized in that, The length of the edge collector gate line segment located between the first intermediate pad and the edge pad is D1, and the length of the edge collector gate line segment located between two adjacent intermediate pads is D2. The D1 and the D2 satisfy: D1≤D2.

3. The electrode structure according to claim 2, characterized in that, The length of the first electrical connection gate wire is D3, and D1, D2, and D3 satisfy: D3 + D1 = D2.

4. The electrode structure according to claim 2, characterized in that, The condition D2 satisfies: 3 mm ≤ D2 ≤ 13 mm.

5. The electrode structure according to claim 1, characterized in that, The multiple collector grid lines are parallel to each other; and / or, In the intermediate pads, the spacing between any two adjacent intermediate pads is the same; and / or, The length of the edge busbar located between the end and the first electrical connection grid line is S, and S satisfies: 4 mm ≤ S ≤ 10 mm.

6. The electrode structure according to any one of claims 1 to 5, characterized in that, Along a first direction, the electrode structure includes an edge region and a middle region located inside the edge region, wherein the edge region is the area enclosed by the first row pads, the edge collector grid line, and the edge busbar line located between the first row pads and the edge collector grid line; The collector grid line includes multiple first collector grid lines located in the edge region and multiple second collector grid lines located in the middle region. Along the direction perpendicular to the first direction, each of the first collector grid lines includes multiple spaced collector grid line segments. Along the first direction, the collector grid line segment includes alternating first polarity collector grid line segments and second polarity collector grid line segments, and the second collector grid line includes alternating first polarity collector grid line and second polarity collector grid line. The pads include first pads and second pads arranged alternately along a direction perpendicular to the first direction; The edge busbar includes a first edge busbar and a second edge busbar. The first edge busbar is connected to the first polarity collector gate segment and the first polarity collector gate. The second edge busbar is connected to the second polarity collector gate segment and the second polarity collector gate. Wherein, the first polarity collector gate segment and the first polarity collector gate line are connected to the first pad, the second polarity collector gate segment and the second polarity collector gate line are connected to the second pad, the position of the discontinuity of the first polarity collector gate segment corresponds to the position of the second electrical connection gate line at the second pad, and the position of the discontinuity of the second polarity collector gate segment corresponds to the position of the second electrical connection gate line at the first pad; The first pad, the first polarity collector gate segment, the first polarity collector gate line, and the first edge bus gate line are disposed in the first conductivity type region, and the second pad, the second polarity collector gate segment, the second polarity collector gate line, and the second edge bus gate line are disposed in the second conductivity type region. One of the first conductivity type and the second conductivity type is an N-type conductivity type and the other is a P-type conductivity type.

7. A back-contact solar cell, characterized in that, The back contact solar cell includes: A silicon substrate, the silicon substrate including a profile line parallel to the edge bus gate line; The electrode structure according to any one of claims 1 to 6, wherein the electrode structure is located on the surface of the silicon substrate.

8. The back-contact solar cell according to claim 7, characterized in that, The distance between the edge pad and the outline is D4, and the length of the first electrical connection gate is D3. The D3 and D4 satisfy: 2 mm ≤ D4 + D3 ≤ 6 mm.

9. The back-contact solar cell according to claim 8, characterized in that, The D4 satisfies: 0.5 mm ≤ D4 ≤ 1 mm.

10. A photovoltaic module, characterized in that, The photovoltaic module includes: the back-contact solar cell according to any one of claims 7 to 9.

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