Photovoltaic cell, method for preparing photovoltaic cell and photovoltaic module

Abstract

The application relates to a photovoltaic cell, a preparation method of the photovoltaic cell and a photovoltaic module, and relates to the technical field of photovoltaics. The photovoltaic cell comprises a substrate with ohmic contact and a pad group. In the same pad group, the pad group comprises an intermediate pad and two outer pads arranged at intervals, the intermediate pad is located between the two outer pads, the intermediate pad and the outer pads are both used for welding the same solder strip, the intermediate pad has a first thickness H1, the outer pads have a second thickness H2, and H2>H1 is satisfied. After the pads of the photovoltaic cell are welded with the solder strip, the outer pads with relatively large thickness can have relatively large plastic deformation, the relatively large plastic deformation can absorb or dissipate relatively more energy, so that the force or energy transmitted to the substrate by the outer pads from the solder strip is relatively small, the warping amount of the substrate can be relatively small or the substrate is not warped, thereby reducing the possibility of structural damage of the photovoltaic cell.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of photovoltaic cell, and particularly relates to a photovoltaic cell, a preparation method of the photovoltaic cell and a photovoltaic module. BACKGROUND

[0002] The photovoltaic module comprises the photovoltaic cell and the solder strip, and the photovoltaic cell and the solder strip are welded. Due to the difference between the thermal expansion coefficients of the photovoltaic cell and the solder strip, after the photovoltaic cell and the solder strip are welded, the shrinkage amount of the solder strip is greater than that of the photovoltaic cell, which is easy to cause the photovoltaic cell to be warped, and the warped photovoltaic cell is easy to be damaged in structure, such as micro-cracking or breaking. SUMMARY

[0003] Therefore, the present application provides a photovoltaic cell, a preparation method of the photovoltaic cell and a photovoltaic module, which can reduce the warping amount of the photovoltaic cell after welding, thereby reducing the possibility of structural damage of the photovoltaic cell.

[0004] In a first aspect, the present application provides a photovoltaic cell, which comprises a substrate and at least two solder pad groups, the substrate and the solder pad groups are in ohmic contact, in the same solder pad group, the solder pad group comprises an intermediate solder pad and two outer solder pads which are arranged at intervals, the intermediate solder pad is located between the two outer solder pads, the intermediate solder pad and the outer solder pads are used for welding the same solder strip, in the thickness direction of the substrate, the intermediate solder pad has a first thickness H1, the outer solder pad has a second thickness H2, and H2>H1 is satisfied, that is, the first thickness H1 is greater than the second thickness H2.

[0005] Optionally, the ratio of the first thickness H1 to the second thickness H2 is in the range of 0.4-0.8.

[0006] Optionally, the first thickness H1 is in the range of 5-7 µm, and / or the second thickness H2 is in the range of 9-11 µm.

[0007] Optionally, the photovoltaic cell comprises at least three solder pad groups, the at least three solder pad groups comprise a middle solder pad group and two outer solder pad groups, the middle solder pad group is located between the two outer solder pad groups, the middle solder pad group and the outer solder pad groups each comprise an intermediate solder pad and two outer solder pads, and the thickness of the outer solder pad of the outer solder pad group is greater than or equal to the thickness of the outer solder pad of the middle solder pad group.

[0008] Optionally, in the same middle solder pad group, the distance between the outer solder pad and the intermediate solder pad is a first distance D1, and in the same outer solder pad group, the distance between the outer solder pad and the intermediate solder pad is a second distance D2, and D2

[0009] Optionally, in the same pad group, the pad group further comprises at least two transition pads, the transition pads are arranged between any of the intermediate pads and the outer pads, the intermediate pads, the outer pads and the transition pads are arranged at intervals, in the thickness direction of the substrate, the transition pads have a third thickness H3, and H2>H3>H1 is satisfied.

[0010] Optionally, in the same pad group, the difference between the third thickness H3 and the first thickness H1 is a first difference, the difference between the second thickness H2 and the third thickness H3 is a second difference, and the absolute value of the second difference is less than the absolute value of the first difference.

[0011] Optionally, in the same pad group, there is a spacing distance D 23 between the outer pads and the transition pads on the same side of the intermediate pads. 13 There is a spacing distance D 23 between the intermediate pads and the transition pads. 13 .

[0012] In a second aspect, the application provides a preparation method of a photovoltaic cell, the preparation method of the photovoltaic cell comprising: providing a substrate, the substrate being arranged at intervals with an intermediate pad printing area and two outer pad printing areas, the intermediate pad printing area being located between the two outer pad printing areas, printing an intermediate pad paste in the intermediate pad printing area of the substrate by using a first screen, and printing an outer pad paste in the outer pad printing area of the substrate by using a second screen, wherein the thickness of the latex film of the second screen is greater than the thickness of the latex film of the first screen, and / or the mesh number of the second screen is less than the mesh number of the first screen, so that the thickness of the outer pad paste is greater than the thickness of the intermediate pad paste, and the thickness of the outer pad is greater than the thickness of the intermediate pad by sintering the intermediate pad paste and the outer pad paste to form the outer pad and the intermediate pad.

[0013] In a third aspect, the application provides a photovoltaic module, the photovoltaic module comprising a solder strip and a photovoltaic cell, the photovoltaic cell can adopt the photovoltaic cell provided in the first aspect of the application, or the photovoltaic cell can be prepared by the preparation method of the photovoltaic cell provided in the second aspect of the application, and the intermediate pad and the outer pad in the same pad group of the photovoltaic cell are welded to the same solder strip.

[0014] As described above, after the solder pads and solder ribbons of the photovoltaic cell of this application are welded, the relatively thick outer solder pads can undergo relatively large plastic deformation. This relatively large plastic deformation can absorb or dissipate relatively more energy, resulting in a relatively small force or energy transferred from the solder ribbon to the substrate through the outer solder pads. Consequently, the warpage of the substrate is relatively small, or the substrate may not warp at all. In the subsequent manufacturing process of photovoltaic modules, especially during the lamination of photovoltaic cells to form a stack, if photovoltaic cells with no warpage or relatively small warpage are used, gaps or bubbles are less likely to form between the photovoltaic cells and the encapsulation material, leading to a relatively high yield rate for the photovoltaic modules. Furthermore, the degree of localized stress concentration within photovoltaic cells with no warpage or relatively small warpage is relatively small, making the photovoltaic cells less prone to structural damage such as microcracks or breakage. Moreover, the stress within the relatively thick outer solder pads can be dispersed along the thickness direction of the outer solder pads, resulting in a relatively high reliability of the connection structure between the outer solder pads and the corresponding solder ribbons, reducing the likelihood of incomplete soldering.

[0015] It should be understood that the above general description and the following detailed description are merely exemplary and do not limit this application. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the structure of a back-contact photovoltaic cell in one embodiment.

[0018] Figure 2 for Figure 1 A partial structural diagram of a photovoltaic cell with a center-back contact.

[0019] Figure 3 for Figure 1 A partial structural diagram of a photovoltaic cell with a center-back contact.

[0020] Figure 4 for Figure 1 A partial structural diagram of a photovoltaic cell with a center-back contact.

[0021] Figure 5 for Figure 1 A schematic diagram of the structure of a back-contact photovoltaic cell viewed from the side.

[0022] Figure 6 For solder strip and Figure 1Schematic of soldering of middle back contact photovoltaic cell;

[0023] Figure 7 Schematic of soldering of middle back contact photovoltaic cell;

[0024] Figure 8 Schematic of soldering of middle back contact photovoltaic cell; Figure 5 Schematic of soldering of middle back contact photovoltaic cell;

[0025] Figure 9 Schematic of soldering of middle back contact photovoltaic cell; Figure 1 Schematic of soldering of middle back contact photovoltaic cell;

[0026] Figure 10 Schematic of soldering of middle back contact photovoltaic cell; Figure 1 Schematic of soldering of middle back contact photovoltaic cell;

[0027] Figure 11 Schematic of soldering of middle back contact photovoltaic cell;

[0028] Figure 12 Schematic of soldering of middle back contact photovoltaic cell;

[0029] Figure 13 Schematic of soldering of middle back contact photovoltaic cell;

[0030] Figure 14 Schematic of soldering of middle back contact photovoltaic cell;

[0031] Figure 15 Schematic of soldering of middle back contact photovoltaic cell;

[0032] Figure 16 Schematic of soldering of middle back contact photovoltaic cell; Figure 15 Schematic of soldering of middle back contact photovoltaic cell;

[0033] Figure 17 Schematic of soldering of middle back contact photovoltaic cell; Figure 15 Schematic of soldering of middle back contact photovoltaic cell;

[0034] Figure 18 Schematic of soldering of middle back contact photovoltaic cell; Figure 15 Schematic of soldering of middle back contact photovoltaic cell;

[0035] Figure 19 Schematic of soldering of middle back contact photovoltaic cell; Figure 17 Schematic of soldering of middle back contact photovoltaic cell;

[0036] Figure 20 Schematic of soldering of middle back contact photovoltaic cell; Figure 15 Schematic of soldering of middle back contact photovoltaic cell;

[0037] Figure 21 Partial structure diagram of a back contact photovoltaic cell in yet another embodiment;

[0038] Figure 22 Partial structure diagram of a back contact photovoltaic cell in still another embodiment;

[0039] Figure 23 Partial structure diagram of a back contact photovoltaic cell in another embodiment;

[0040] Figure 24 Partial structure diagram of a back contact photovoltaic cell in still another embodiment;

[0041] Figure 25 Structure diagram of a tunnel oxide passivated contact structure photovoltaic cell in one embodiment;

[0042] Figure 26 Structure diagram of a tunnel oxide passivated contact structure photovoltaic cell in another embodiment;

[0043] Figure 27 Structure diagram of a tunnel oxide passivated contact structure photovoltaic cell in still another embodiment;

[0044] Figure 28 Structure diagram of a substrate in one embodiment;

[0045] Figure 29 Diagram of a first screen, squeegee, and substrate during printing of interpad paste;

[0046] Figure 30 Diagram of a second screen, squeegee, and substrate during printing of outside pad paste;

[0047] Figure 31 Diagram of a second screen, squeegee, and substrate during printing of another outside pad paste;

[0048] Figure 32 Diagram of a cross-sectional structure of a first screen;

[0049] Figure 33 Diagram of a cross-sectional structure of a second screen;

[0050] Figure 34 Structure diagram of a string of photovoltaic cells in one embodiment;

[0051] Figure 35 Diagram of a warp amount of a photovoltaic cell in one embodiment.

[0052] 10 - photovoltaic cell, 1 - substrate, 11 - first portion, 12 - second portion, 13 - third portion, 14 - fourth portion, 15 - fifth portion, 16 - sixth portion, 17 - seventh portion, 18 - eighth portion, 19 - ninth portion, 2 - pad group, 2a - middle pad group, 2b - outer pad group, 2c - transition pad group, 21 - middle pad, 21a - middle pad printing area, 21b - middle pad paste, 22 - outer pad, 22a - outer pad printing area, 22b - outer pad paste, 23 - transition pad, 3 - first grid line, 4 - second grid line, 20 - solder strip, 30 - first screen, 301 - first screen frame, 302 - first screen mesh, 302a - first screen hole, 303 - first mask pattern, 303a - first leakage hole, 40 - second screen, 401 - second screen frame, 402 - second screen mesh, 402a - second screen hole, 403 - second mask pattern, 403a - second leakage hole, 50 - squeegee. DETAILED DESCRIPTION

[0053] For better understanding of the technical solutions of the present application, the embodiments of the present application are described in detail below with reference to the drawings. It should be clear that the described embodiments are only some of the embodiments of the present application, not 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 labor fall within the scope of protection of the present application. The terms used in the embodiments of the present application are only for the purpose of describing the specific embodiments, and are not intended to limit the present application. The singular forms "a", "an" and "the" used in the embodiments of the present application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise. It should be understood that the term "and / or" used herein is only to describe the association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B, which can represent the three cases of A alone, A and B together, and B alone. In addition, the character " / " in this paper generally represents that the front and rear associated objects are a "or" relationship.

[0054] In the first aspect, the present application provides some embodiments of photovoltaic cells, which are related to the field of photovoltaic technology. In some embodiments, please refer to Figure 1As shown, the photovoltaic cell 10 may include a substrate 1, which is the main structure or body structure of the photovoltaic cell 10. The substrate 1 may include an N-region structure and a P-region structure. The N-region structure is doped with at least one N-type element (a group 5 element in the periodic table), such as phosphorus, arsenic, antimony, etc. The P-region structure is doped with at least one P-type element (a group 3 element in the periodic table), such as boron, aluminum, gallium, etc. A PN junction can be formed between the N-region structure and the P-region structure, and the PN junction can generate a built-in electric field. Under illumination, electron-hole pairs can be generated in the photovoltaic cell 10. The built-in electric field can separate the electron-hole pairs. The N-region structure is used to collect negatively charged electrons, and the P-region structure is used to collect positively charged holes, thereby forming a photogenerated voltage.

[0055] In some embodiments, please refer to Figure 1 As shown, the photovoltaic cell 10 may include grid lines (e.g., the grid lines include a first grid line 3 and a second grid line 4), a substrate 1, and ohmic contacts (also known as metallized contacts) between the grid lines. A portion of the grid lines (e.g.) Figure 2 The first gate line 3 and the second gate line 4 shown can make ohmic contact with the N-region structure, and another number of gate lines (e.g.) Figure 3 The first gate line 3 and the second gate line 4 shown can make ohmic contact with the P-region structure. The gate line making ohmic contact with the N-region structure is the negative gate line, and the gate line making ohmic contact with the P-region structure is the positive gate line. When the negative gate line is electrically connected to the positive gate line through an external circuit to form a closed loop, electrons located in the N-region structure can be conducted to the P-region structure in sequence through the negative gate line, the external circuit, and the positive gate line, thereby forming a photocurrent.

[0056] Please refer to Figures 1-3 As shown, the first gate line 3 can be also called a fine gate line or a sub-gate line, and the second gate line 4 can be also called a thick gate line or a main gate line. Both the first gate line 3 and the second gate line 4 are ohmic contacts with the substrate 1, and the first gate line 3 and the second gate line 4 are electrically connected. Please refer to... Figure 2 As shown, a portion of the first gate lines 3 and a portion of the second gate lines 4 are electrically connected and serve as negative gate lines. The negative second gate lines 4 are used to collect the electrons collected by the multiple negative first gate lines 3. Please refer to... Figure 3 As shown, another portion of the first gate line 3 and another portion of the second gate line 4 are electrically connected and serve as positive gate lines. The positive second gate line 4 is used to disperse and transfer electrons to the multiple positive first gate lines 3.

[0057] Additionally, please refer to Figures 1-3As shown, the photovoltaic cell 10 can be a back-contact solar cell (BC Solar Cell). All grid lines of the photovoltaic cell 10 can be located on the back side (the side facing away from sunlight) of the substrate 1, and the light-receiving side (the side facing sunlight) of the photovoltaic cell 10 can be without grid lines.

[0058] In some embodiments, please refer to Figures 1-3 As shown, the photovoltaic cell 10 may include a pad group 2. The substrate 1 and the pad group 2 can be in ohmic contact. The pad group 2 can be electrically connected to the grid lines (e.g., the second grid line 4 included in the grid lines). The pad group 2 is used for soldering to solder ribbon (not shown in the figure). The solder ribbon can also be referred to as an interconnect strip, conductive strip, or connecting strip. For the photovoltaic cell 10, the solder ribbon is equivalent to a part of the external circuit structure. Please refer to... Figure 2 As shown, a portion of pad group 2 is electrically connected to the negative gate line. Please refer to [reference needed]. Figure 3 As shown, another portion of the pad group 2 is electrically connected to the positive grid line. It can be understood that, under the condition that the pad group 2 is soldered to the solder ribbon, electrons within the N-region structure of the photovoltaic cell 10 can sequentially pass through... Figure 2 The negative grid line shown and Figure 2 The solder pad group 2 shown (also known as the negative electrode solder pad group) conducts electrons to a portion of the solder strips (also known as the negative electrode solder strips) in the external circuit, and then the electrons pass through another portion of the solder strips (also known as the positive electrode solder strips) in the external circuit. Figure 3 The pad group 2 shown (also known as the positive electrode pad group) and Figure 3 The positive grid lines shown are conducted to the P-region structure of the photovoltaic cell 10.

[0059] Please refer to Figure 1 As shown, the photovoltaic cell 10 may include four pad groups 2, which may include two central pad groups 2a and two outer pad groups 2b. The two central pad groups 2a are located between the two outer pad groups 2b. Each central pad group 2a and each outer pad group 2b is a relatively independent pad group 2. The positioning of the central pad group 2a relative to the substrate 1 is different from that of the outer pad group 2b relative to the substrate 1. Figure 1 and Figure 2 From the perspective shown, the outer pad group 2b, which is relatively to the left, and the middle pad group 2a, which is relatively to the left, can be the negative pad group 2. Figure 1 and Figure 3 From the perspective shown, the outer pad group 2b, which is relatively to the right, and the middle pad group 2a, which is relatively to the right, can be the positive pad group 2.

[0060] Additionally, please refer to Figures 1-4As shown, in the same pad group 2, the pad group 2 can include at least three pads of the same polarity (for example, the middle pad 21 and the two outer pads 22), and it can be understood that all the pads included in the same pad group 2 are electrically connected to the grid line of the same polarity, and it can also be understood that all the pads (Pad) included in the same pad group 2 are electrically connected to the same solder strip, that is, one pad group 2 corresponds to one solder strip.

[0061] In some embodiments, please refer to Figures 1-5 As shown, in the same pad group 2, the pad group 2 can include the middle pad 21 and the two outer pads 22, and the middle pad 21 and the two outer pads 22 are arranged at intervals, and the middle pad 21 is located between the two outer pads 22. In the process of forming the battery string, all the pads of the same pad group 2 can be welded to the same solder strip 20 to form a structure as shown. Figure 6 As shown, in the welding process, the volume of the substrate 1 and the volume of the solder strip 20 increase due to the absorption of welding heat, and after the welding is completed, the substrate 1 is connected to the corresponding solder strip 20 through each pad group 2, and after the welding, the volume of the substrate 1 and the volume of the solder strip 20 decrease due to the heat dissipation to the outside. But the thermal expansion coefficient of the substrate 1 and the thermal expansion coefficient of the solder strip 20 are different, and in the welding process, the increase in the volume of the substrate 1 is less than the increase in the volume of the solder strip 20, and after the welding, the decrease in the volume of the substrate 1 is less than the decrease in the volume of the solder strip 20. Therefore, after the welding, the solder strip 20 exerts a pulling force F on the substrate 1 through each outer pad 22, and the direction of the pulling force F is the direction in which the outer pad 22 points to the middle pad 21. Please refer to Figure 7 As shown, the outer pad 22 subjected to the pulling force F can be plastically deformed, for example, the shape of the outer pad 22 is changed from the state (a) in Figure 7 to the state (b) in Figure 7 , and this plastic deformation can absorb or dissipate part of the elastic strain energy generated by the solder strip 20 in the contraction process. Please refer to Figure 8As shown, in the thickness direction (the direction parallel to the direction Z) of the substrate 1, the middle pad 21 can have a first thickness H1, and the outer pad 22 can have a second thickness H2, which satisfies H2>H1. In this arrangement, after the photovoltaic cell 10 is soldered with the solder ribbon 20, the outer pad 22 with the relatively larger thickness can have a relatively larger plastic deformation, which can absorb or dissipate a relatively larger amount of energy, so that the force or energy transmitted to the substrate 1 through the outer pad 22 is relatively smaller, and accordingly, the amount of warping of the substrate 1 is relatively smaller, or the substrate 1 can have no warping. In the subsequent process of preparing the photovoltaic module, especially in the process of laminating the photovoltaic cells to form a stack, if the photovoltaic cell 10 without warping or with a relatively smaller amount of warping is used, the photovoltaic cell 10 and the encapsulating material are less likely to have a gap or a bubble therebetween, and the yield of the photovoltaic module is relatively larger. In addition, the photovoltaic cell 10 without warping or with a relatively smaller amount of warping has a relatively smaller degree of local stress concentration, and the photovoltaic cell 10 is less likely to have a structural damage problem such as micro-cracking or breaking. Furthermore, the stress in the outer pad 22 with the relatively larger thickness can be dispersed in the thickness direction of the outer pad 22, so that the reliability of the connection structure between the outer pad 22 and the corresponding soldered solder ribbon 20 is relatively higher, i.e., the problem of false soldering is less likely to occur.

[0062] In some embodiments, referring to Figure 8 As shown, the ratio of the first thickness H1 to the second thickness H2 can be in the range of 0.4-0.8, and specifically, the ratio of the first thickness H1 to the second thickness H2 can be 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, or 0.8. When the ratio of the first thickness H1 to the second thickness H2 is in the range of 0.4-0.8, on the one hand, the outer pad 22 after soldering can absorb or dissipate a relatively larger amount of energy from the solder ribbon 20, and on the other hand, the metal (e.g., silver) used in the outer pad 22 is not excessive.

[0063] The ratio of the first thickness H1 to the second thickness H2 can be in the range of 0.4 to 0.5, and specifically, the ratio of the first thickness H1 to the second thickness H2 can be 0.4, 0.41, 0.42, 0.43, 0.44, 0.45, 0.46, 0.47, 0.48, 0.49, or 0.5. Alternatively, the ratio of the first thickness H1 to the second thickness H2 can be in the range of 0.5 to 0.6, and specifically, the ratio of the first thickness H1 to the second thickness H2 can be 0.5, 0.51, 0.52, 0.53, 0.54, 0.55, 0.56, 0.57, 0.58, 0.59, or 0.6. Alternatively, the ratio of the first thickness H1 to the second thickness H2 can be in the range of 0.6 to 0.7, and the specific ratio of the first thickness H1 to the second thickness H2 can be 0.6, 0.61, 0.62, 0.63, 0.64, 0.65, 0.66, 0.67, 0.68, 0.69, or 0.7. Alternatively, the ratio of the first thickness H1 to the second thickness H2 can be in the range of 0.7 to 0.8, and the specific ratio of the first thickness H1 to the second thickness H2 can be 0.7, 0.71, 0.72, 0.73, 0.74, 0.75, 0.76, 0.77, 0.78, 0.79, or 0.8.

[0064] In some embodiments, please refer to Figure 8 As shown, the first thickness H1 can be in the range of 5 micrometers (µm) to 7 micrometers (µm). Specifically, the first thickness H1 can be 5µm, 5.1µm, 5.2µm, 5.3µm, 5.4µm, 5.5µm, 5.6µm, 5.7µm, 5.8µm, 5.9µm, 6µm, 6.1µm, 6.2µm, 6.3µm, 6.4µm, 6.5µm, 6.6µm, 6.7µm, 6.8µm, 6.9µm, or 7µm.

[0065] The first thickness H1 can be in the range of 5µm to 6µm, specifically 5µm, 5.1µm, 5.2µm, 5.3µm, 5.4µm, 5.5µm, 5.6µm, 5.7µm, 5.8µm, 5.9µm, or 6µm. Alternatively, the first thickness H1 can be in the range of 6µm to 7µm, specifically 6µm, 6.1µm, 6.2µm, 6.3µm, 6.4µm, 6.5µm, 6.6µm, 6.7µm, 6.8µm, 6.9µm, or 7µm.

[0066] In some embodiments, please refer to Figure 8As shown, the second thickness H2 can be in a range of 9 µm ~ 11 µm, and specifically can be 9 µm, 9.1 µm, 9.2 µm, 9.3 µm, 9.4 µm, 9.5 µm, 9.6 µm, 9.7 µm, 9.8 µm, 9.9 µm, 10 µm, 10.1 µm, 10.2 µm, 10.3 µm, 10.4 µm, 10.5 µm, 10.6 µm, 10.7 µm, 10.8 µm, 10.9 µm, or 11 µm.

[0067] As shown, the second thickness H2 can be in a range of 9 µm ~ 11 µm, and specifically can be 9 µm, 9.1 µm, 9.2 µm, 9.3 µm, 9.4 µm, 9.5 µm, 9.6 µm, 9.7 µm, 9.8 µm, 9.9 µm, 10 µm, 10.1 µm, 10.2 µm, 10.3 µm, 10.4 µm, 10.5 µm, 10.6 µm, 10.7 µm, 10.8 µm, 10.9 µm, or 11 µm.

[0068] In some embodiments, according to the above, although the second thickness H2 of the outer pad 22 is greater than the first thickness H1 of the middle pad 21, the structure segments of the solder ribbon 20 located on both sides of the middle pad 21 will shrink towards the structure segment soldered to the middle pad 21, and the resultant force acting on the middle pad 21 is relatively small, which can also be understood as the requirement for the soldering strength of the middle pad 21 is relatively small, and thus the first thickness H1 of the middle pad 21 can be relatively small, for example, the first thickness H1 can be in the range of 5 µm ~ 6 µm, 6 µm ~ 7 µm, or 5 µm ~ 7 µm mentioned above. As can be seen, the average thickness of all pads (including the middle pad 21 and the outer pad 22) in the same pad group 2 of the photovoltaic cell piece 10 can be in a range of 7 µm ~ 9 µm, and specifically can be 7 µm, 7.1 µm, 7.2 µm, 7.3 µm, 7.4 µm, 7.5 µm, 7.6 µm, 7.7 µm, 7.8 µm, 7.9 µm, 8 µm, 8.1 µm, 8.2 µm, 8.3 µm, 8.4 µm, 8.5 µm, 8.6 µm, 8.7 µm, 8.8 µm, 8.9 µm, or 9 µm. Therefore, compared with some related technologies, some embodiments of the photovoltaic cell piece 10 of the present application do not excessively increase or do not increase the consumption of the material (paste) for forming the pad, but can reduce the warping amount of the photovoltaic cell piece 10 after soldering, or can make the photovoltaic cell piece 10 after soldering have no warping.

[0069] In some embodiments, the elongation of the material of the outer pad 22 can be greater than that of the material of the middle pad 21. Elongation refers to elongation at break, a key indicator in the mechanical properties of materials that measures plastic deformation energy. Elongation is defined as the percentage increase in length (plastic deformation) of the gauge length of a material specimen after it breaks in a tensile test, relative to the original gauge length. After the photovoltaic cell 10 is welded to the solder ribbon 20, the outer pad 22 with a relatively larger elongation can undergo relatively larger plastic deformation. This larger plastic deformation can absorb or dissipate more energy, resulting in a relatively smaller force or energy transferred to the substrate 1 through the outer pad 22. Consequently, the warpage of the substrate 1 is relatively small, or the substrate 1 may not warp at all.

[0070] The ratio of silver, glass powder and modifier included in the outer pad 22 can be adjusted to be different from that included in the middle pad 21, so that the elongation of the material of the outer pad 22 is greater than that of the material of the middle pad 21.

[0071] In some embodiments, please refer to Figure 9 As shown, each pad group 2 can include an outer pad 22. The second thickness H2 of the outer pads 22 of each pad group 2 can be the same. In other words, the second thickness H2 of the outer pads 22 of the middle pad group 2a can be the same as the second thickness H2 of the outer pads 22 of the outer pad group 2b.

[0072] Please refer to Figure 10 As shown, for a substrate 1 with a sheet-like structure, the substrate 1 can be divided into nine parts: part 11, part 12, part 13, part 14, part 15, part 16, part 17, part 18, and part 19. Parts 11, 12, 13, 14, 15, 16, 17, 18, and 19 can be arranged in a 3x3 grid or a 3x3 grid. Parts 11, 13, 17, and 19 are all considered corners of the substrate 1. After the substrate 1 is soldered to the corresponding solder strips 20 through each pad group 2, the number of constraints at the corners of the substrate 1 is less than the number of constraints at other parts of the substrate 1 (e.g., part 12 and part 18). If soldered under the same conditions, the warpage at the corners of the substrate 1 is greater than the warpage at other parts of the substrate 1 (e.g., part 12 and part 18). To address this issue, in some embodiments, please refer to Figure 11 As shown, the outer pad 22 of the outer pad group 2b has a thickness H. 22may be greater than the thickness H of the outer side pads 22 of the middle pad group 2a 21 In this arrangement, after the photovoltaic cell 10 is soldered with the solder strip 20, the plastic deformation that can occur in the outer side pads 22 of the outer pad group 2b is greater than the plastic deformation that can occur in the outer side pads 22 of the middle pad group 2a, and the relatively greater plastic deformation can absorb or dissipate relatively more energy, so that the force or energy transmitted by the outer side pads 22 of the outer pad group 2b to the corners of the substrate 1 is relatively small, and the amount of warping of each corner of the substrate 1 can be less than or equal to the amount of warping of the second portion 12, and for the same reason, the amount of warping of each corner of the substrate 1 can be less than or equal to the amount of warping of the eighth portion 18, and the corners of the substrate 1 are not prone to structural damage problems such as micro-cracking or breaking, and the outer side pads 22 located at the corners of the substrate 1 are also not prone to false soldering problems with the corresponding soldered solder strip 20.

[0073] In addition, the substrate 1 can also be divided into other numbers of portions according to other division methods, such as sixteen portions in a four-by-four distribution, twenty-five portions in a five-by-five distribution, or other multiple portions in other distributions. Regardless of how the substrate 1 is divided internally, the substrate 1 includes four corners, and the subsequent content herein mainly describes the structure of the substrate 1 taking the nine-square distribution as shown in Figure 10 for example.

[0074] In some embodiments, referring to Figure 12 the second distance D2 between the middle pad 21 and the outer side pad 22 in the outer pad group 2b is less than the first distance D1 between the middle pad 21 and the outer side pad 22 in the middle pad group 2a, i.e. D2 < D1, and the relatively smaller second distance D2 can be understood as a shorter force arm between the middle pad 21 and the outer side pad 22 in the outer pad group 2b, and under the condition that the solder strip 20 shrinks to generate the same tensile force F, the bending moment that the tensile force F can generate on the shorter force arm is relatively small, and in this arrangement, after the photovoltaic cell 10 is soldered with the solder strip 20, the amount of warping of each corner of the substrate 1 can be less than or equal to the amount of warping of the second portion 12, and for the same reason, the amount of warping of each corner of the substrate 1 can be less than or equal to the amount of warping of the eighth portion 18, and the corners of the substrate 1 are not prone to structural damage problems such as micro-cracking or breaking, and the outer side pads 22 located at the corners of the substrate 1 are also not prone to false soldering problems with the corresponding soldered solder strip 20.

[0075] In the structure shown in Figure 12 the thickness of the outer side pads 22 of any middle pad group 2a can also be less than or equal to the thickness of the outer side pads 22 of any outer pad group 2b.

[0076] In some embodiments, referring to Figure 13 or Figure 14As shown, the photovoltaic cell sheet 10 can include six pad groups 2, which can include two middle pad groups 2a, two outer pad groups 2b, and two transition pad groups 2c, the two middle pad groups 2a being located between the two outer pad groups 2b, one transition pad group 2c being arranged between one middle pad group 2a and one outer pad group 2b, and another transition pad group 2c being arranged between the other middle pad group 2a and the other outer pad group 2b. Each of the middle pad group 2a, the outer pad group 2b, and the transition pad group 2c can include a middle pad 21 and two outer pads 22, and the thickness of the middle pad 21 can be less than the thickness of the outer pads 22. Figure 13 or Figure 14 After the photovoltaic cell sheet 10 is soldered with the solder strip 20, the amount of warping of the substrate 1 can be relatively small, or the substrate 1 can not be warped.

[0077] In some other embodiments (not shown), the photovoltaic cell sheet can include other even-numbered and more than six pad groups. In these embodiments, the number of the middle pad groups can be at least three, and the number of the transition pad groups can be at least four.

[0078] In some embodiments, please refer to Figure 14 As shown, the second distance D2 between the middle pad 21 and the outer pad 22 in the outer pad group 2b can be less than the third distance D3 between the middle pad 21 and the outer pad 22 in the transition pad group 2c, and the third distance D3 between the middle pad 21 and the outer pad 22 in the transition pad group 2c can be less than the first distance D1 between the middle pad 21 and the outer pad 22 in the middle pad group 2a. In this arrangement, the amount of warping of each corner of the substrate 1 after the photovoltaic cell sheet 10 is soldered with the solder strip 20 can be less than or equal to the amount of warping of the second portion 12, and the amount of warping of each corner of the substrate 1 can be less than or equal to the amount of warping of the eighth portion 18, and the corners of the substrate 1 are not prone to structural damage problems such as micro-cracking or breaking, and the outer pads 22 at the corners of the substrate 1 are not prone to false soldering problems with the corresponding soldered solder strip 20.

[0079] In some embodiments, please refer to Figure 13 or Figure 14 As shown, the thickness of the outer pad 22 of each middle pad group 2a can be less than the thickness of the outer pad 22 of each transition pad group 2c, and the thickness of the outer pad 22 of each transition pad group 2c can be less than the thickness of the outer pad 22 of each outer pad group 2b. In this arrangement, the corners of the substrate 1 are not prone to structural damage problems such as micro-cracking or breaking, and the outer pads 22 at the corners of the substrate 1 are not prone to false soldering problems with the corresponding soldered solder strip 20.

[0080] In some other embodiments, please refer to Figure 13 or Figure 14 As shown, the thickness of the outer pad 22 of any middle pad group 2a can be equal to the thickness of the outer pad 22 of any transition pad group 2c, and the thickness of the outer pad 22 of any transition pad group 2c can be equal to the thickness of the outer pad 22 of any outer pad group 2b.

[0081] In some embodiments, please refer to Figures 15-17 As shown, within the same pad group 2, the pad group 2 may include at least two transition pads 23. A transition pad 23 may be provided between the intermediate pad 21 and any outer pad 22, with the intermediate pad 21, outer pad 22, and transition pad 23 spaced apart. During the formation of the battery string, all pads within the same pad group 2 can be soldered to the same solder strip 20 to form a... Figure 18 The structure shown. Please refer to... Figure 19 As shown, in the thickness direction of substrate 1, the intermediate pad 21 has a first thickness H1, the outer pad 22 has a second thickness H2, and the transition pad has a third thickness H3, satisfying H2 > H3 > H1. Under this configuration, the plastic deformation that can occur on the outer pad 22 is greater than that on the transition pad 23, and the plastic deformation that can occur on the transition pad 23 is greater than that on the intermediate pad 21. Therefore, the energy absorbed or dissipated by the outer pad 22 is greater than that absorbed or dissipated by the transition pad 23, and the energy absorbed or dissipated by the transition pad 23 is greater than that absorbed or dissipated by the intermediate pad 21. Consequently, the force or energy transmitted to substrate 1 through the outer pad 22 is less than that transmitted to substrate 1 through the intermediate pad 21, and the force or energy transmitted to substrate 1 through the transition pad 23 is also less than that transmitted to substrate 1 through the intermediate pad 21. Furthermore, the outer pad 22, transition pad 23, and middle pad 21 each experience relatively small amounts of energy or force. In other words, the number of pads soldered to the same solder strip is relatively large, resulting in less energy or force distributed to each pad. Therefore, Figures 15-19 After the photovoltaic cell 10 shown is welded to the solder ribbon 20, the warpage of the substrate 1 is relatively small, or the substrate 1 may not warp at all.

[0082] In some embodiments, please refer to Figure 19As shown, the difference between the third thickness H3 and the first thickness H1 is a first difference, and the difference between the second thickness H2 and the third thickness H3 is a second difference, and the absolute value of the second difference can be less than the absolute value of the first difference. In this arrangement, after the photovoltaic cell 10 is soldered with the solder strip 20, although the energy that can be absorbed or dissipated by the transition pad 23 is less than the energy that can be absorbed or dissipated by the outer pad 22, the energy that can be absorbed or dissipated by the transition pad 23 is relatively large, so that the amount of warping of the substrate 1 is relatively small, or so that the substrate 1 can not warp.

[0083] In some other embodiments, the absolute value of the second difference can also be equal to the absolute value of the first difference.

[0084] In some embodiments, as shown in Figure 20 As shown, each pad group 2 can include a transition pad 23, and the third thickness H3 of the transition pad 23 of each pad group 2 can be the same, that is, the third thickness H3 of the transition pad 23 of the middle pad group 2a can be the same as the third thickness H3 of the transition pad 23 of the outer pad group 2b.

[0085] In some embodiments, as shown in Figure 21 As shown, the thickness H 32 of the transition pad 23 of the outer pad group 2b can be greater than the thickness H 31 of the transition pad 23 of the middle pad group 2a. In this arrangement, after the photovoltaic cell 10 is soldered with the solder strip 20, the plastic deformation that can occur in the transition pad 23 of the outer pad group 2b is greater than the plastic deformation that can occur in the transition pad 23 of the middle pad group 2a, and the relatively large plastic deformation can absorb or dissipate relatively more energy, so that the force or energy that is transmitted to the corner of the substrate 1 through the transition pad 23 of the outer pad group 2b is relatively small, and the amount of warping of each corner of the substrate 1 can be less than or equal to the amount of warping of the second portion 12, and for the same reason, the amount of warping of each corner of the substrate 1 can be less than or equal to the amount of warping of the eighth portion 18, and the corner of the substrate 1 is not prone to structural damage problems such as micro-cracking or breaking, and the transition pad 23 located at the corner of the substrate 1 is also not prone to false soldering problems with the corresponding soldered solder strip 20.

[0086] In some other embodiments (not shown in the drawings), within the same pad group, the thickness of the transition pad can be the same as the thickness of the middle pad, the thickness of the outer pad can be greater than the thickness of the transition pad, and the thickness of the outer pad can be greater than the thickness of the middle pad.

[0087] In some embodiments, as shown in FIG. 1, the thickness of the outer pads 22 and the thickness of the transition pads 23 can be the same in any pad group 2, and the thickness of the middle pads 21 can be less than the thickness of the outer pads 22 and the thickness of the transition pads 23.

[0088] In some embodiments, as shown in FIG. 1, the thickness of the outer pads 22 and the thickness of the transition pads 23 can be the same in any pad group 2, and the thickness of the middle pads 21 can be less than the thickness of the outer pads 22 and the thickness of the transition pads 23. Figure 16 In some embodiments, as shown in FIG. 1, the thickness of the outer pads 22 and the thickness of the transition pads 23 can be the same in any pad group 2, and the thickness of the middle pads 21 can be less than the thickness of the outer pads 22 and the thickness of the transition pads 23. 23 In some embodiments, as shown in FIG. 1, the thickness of the outer pads 22 and the thickness of the transition pads 23 can be the same in any pad group 2, and the thickness of the middle pads 21 can be less than the thickness of the outer pads 22 and the thickness of the transition pads 23. 13 In some embodiments, as shown in FIG. 1, the thickness of the outer pads 22 and the thickness of the transition pads 23 can be the same in any pad group 2, and the thickness of the middle pads 21 can be less than the thickness of the outer pads 22 and the thickness of the transition pads 23. 23 In some embodiments, as shown in FIG. 1, the thickness of the outer pads 22 and the thickness of the transition pads 23 can be the same in any pad group 2, and the thickness of the middle pads 21 can be less than the thickness of the outer pads 22 and the thickness of the transition pads 23. 13 In this arrangement, after the photovoltaic cell 10 is soldered with the solder strip 20, the adjacent outer pads 22 and transition pads 23 can jointly absorb or dissipate more energy, and the adjacent outer pads 22 and transition pads 23 can more limit the shrinkage of the structural section of the solder strip 20 between the outer pads 22 and the transition pads 23, so that the amount of warping of the substrate 1 can be relatively small, or the substrate 1 can not warp.

[0089] In some embodiments, as shown in FIG. 1, the thickness of the outer pads 22 and the thickness of the transition pads 23 can be the same in any pad group 2, and the thickness of the middle pads 21 can be less than the thickness of the outer pads 22 and the thickness of the transition pads 23.

[0090] In some embodiments, as shown in FIG. 1, the thickness of the outer pads 22 and the thickness of the transition pads 23 can be the same in any pad group 2, and the thickness of the middle pads 21 can be less than the thickness of the outer pads 22 and the thickness of the transition pads 23. Figure 22 In some embodiments, as shown in FIG. 1, the thickness of the outer pads 22 and the thickness of the transition pads 23 can be the same in any pad group 2, and the thickness of the middle pads 21 can be less than the thickness of the outer pads 22 and the thickness of the transition pads 23. In this arrangement, after the photovoltaic cell 10 is soldered with the solder strip 20, the amount of warping of each corner of the substrate 1 can be less than or equal to the amount of warping of the second portion 12, and the amount of warping of each corner of the substrate 1 can be less than or equal to the amount of warping of the eighth portion 18, so that the corners of the substrate 1 are not prone to structural damage problems such as micro-cracking or breaking, and the outer pads 22 at the corners of the substrate 1 are not prone to false soldering problems with the corresponding soldered solder strip 20. The relevant principles have been described above and will not be repeated here.

[0091] In some embodiments, as shown in FIG. 1, the thickness of the outer pads 22 and the thickness of the transition pads 23 can be the same in any pad group 2, and the thickness of the middle pads 21 can be less than the thickness of the outer pads 22 and the thickness of the transition pads 23. Figure 23 In some embodiments, as shown in FIG. 1, the thickness of the outer pads 22 and the thickness of the transition pads 23 can be the same in any pad group 2, and the thickness of the middle pads 21 can be less than the thickness of the outer pads 22 and the thickness of the transition pads 23. Figure 24As shown, the photovoltaic cell sheet 10 can include six pad groups 2, which can include two middle pad groups 2a, two outer pad groups 2b, and two transition pad groups 2c, the two middle pad groups 2a being located between the two outer pad groups 2b, one transition pad group 2c being arranged between one of the middle pad groups 2a and one of the outer pad groups 2b, and another transition pad group 2c being arranged between the other of the middle pad groups 2a and the other of the outer pad groups 2b. Each of the middle pad groups 2a, the outer pad groups 2b, and the transition pad groups 2c can include a middle pad 21, two outer pads 22, and two transition pads 23, the middle pad 21 being located between the two outer pads 22, one transition pad 23 being arranged between the middle pad 21 and one of the outer pads 22, and the other transition pad 23 being arranged between the middle pad 21 and the other of the outer pads 22, the thickness of the middle pad 21 being less than the thickness of the transition pads 23, and the thickness of the transition pads 23 being less than the thickness of the outer pads 22. Figure 23 or Figure 24 After the photovoltaic cell sheet 10 is soldered with the solder strips 20, the amount of warpage of the substrate 1 can be relatively small, or the substrate 1 can not be warped.

[0092] In some other embodiments (not shown in the figures), the photovoltaic cell sheet can include other even numbers of pad groups and numbers greater than six.

[0093] In some embodiments, please refer to Figure 24 As shown, the distance between the middle pad 21 and the outer pad 22 in the outer pad group 2b is less than the distance between the middle pad 21 and the outer pad 22 in the transition pad group 2c, the distance between the middle pad 21 and the outer pad 22 in the transition pad group 2c is less than the distance between the middle pad 21 and the outer pad 22 in the middle pad group 2a, the distance between the middle pad 21 and the transition pad 23 in the outer pad group 2b is less than the distance between the middle pad 21 and the transition pad 23 in the transition pad group 2c, and the distance between the middle pad 21 and the transition pad 23 in the transition pad group 2c is less than the distance between the middle pad 21 and the transition pad 23 in the middle pad group 2a. In this arrangement, the amount of warpage of each corner of the substrate 1 after the photovoltaic cell sheet 10 is soldered with the solder strips 20 can be less than or equal to the amount of warpage of the second portion 12, and the amount of warpage of each corner of the substrate 1 can be less than or equal to the amount of warpage of the eighth portion 18. As a result, the corners of the substrate 1 are less likely to be structurally damaged, such as being cracked or broken, and the outer pads 22 at the corners of the substrate 1 are less likely to be poorly soldered with the corresponding solder strips 20, and the transition pads 23 at the corners of the substrate 1 are also less likely to be poorly soldered with the corresponding solder strips 20. The relevant principles have been described above and will not be repeated here.

[0094] In some other embodiments (not shown in the figures), at least two transition pads can also be provided between the middle pad and any of the outer pads in the same pad group, and the thickness of the transition pad closer to the middle pad can be smaller than the thickness of the transition pad closer to the outer pad.

[0095] In some other embodiments (not shown in the figures), two or more numbers of spaced-apart middle pads can be provided in the same pad group, and no other type of pad can be provided between any two adjacent middle pads.

[0096] In some other embodiments (not shown in the figures), the back side of the photovoltaic cell can be provided with two pad groups, one of which is in ohmic contact with the N region structure, and the other of which is in ohmic contact with the P region structure, and any of the pad groups can include a middle pad and two outer pads, the middle pad being located between the two outer pads, and the thickness of the outer pads being greater than the thickness of the middle pad.

[0097] In some other embodiments, the photovoltaic cell 10 can also be a tunnel oxide passivated contact solar cell (TOPCon Solar Cell). The light-receiving side of the photovoltaic cell 10 can be provided with grid lines and pads, and the back side of the photovoltaic cell 10 can also be provided with grid lines and pads, and the grid lines and pads on one side can be in ohmic contact with the N region structure, and the grid lines and pads on the other side can be in ohmic contact with the P region structure. The distribution of the first grid line 3, the second grid line 4, and the pad group 2 on the light-receiving side of the photovoltaic cell 10 relative to the substrate 1 can be as shown in Figure 25 、 Figure 26 or Figure 27 The distribution of the first grid line 3, the second grid line 4, and the pad group 2 on the back side of the photovoltaic cell 10 relative to the substrate 1 can also be as shown in Figure 25 、 Figure 26 or Figure 27 In Figures 25-27 , in any of the pad groups 2, the thickness of the outer pad 22 is greater than the thickness of the middle pad 21. In Figure 26 , in any of the pad groups 2, the thickness of the outer pad 22 is greater than the thickness of the transition pad 23, and the thickness of the transition pad 23 is greater than the thickness of the middle pad 21. In Figures 25-27 , the thickness of the outer pad 22 in the outer pad group 2b can be greater than or equal to the thickness of the outer pad 22 in the middle pad group 2a. In Figure 26 , the thickness of the outer pad 22 in the outer pad group 2b can be greater than or equal to the thickness of the outer pad 22 in the transition pad group 2c, and the thickness of the outer pad 22 in the transition pad group 2c can be greater than or equal to the thickness of the outer pad 22 in the middle pad group 2a.

[0098] In some other embodiments (not shown in the figures), the light-receiving side of the tunnel-oxide-passivated-contact-structured photovoltaic cell can also be provided with two pad groups, and the back side of the tunnel-oxide-passivated-contact-structured photovoltaic cell can also be provided with two pad groups. Any pad group can include a middle pad and two outer pads, the middle pad being located between the two outer pads, and the outer pads having a thickness greater than that of the middle pad.

[0099] In some other embodiments (not shown in the figures), regardless of whether the photovoltaic cell is a back-contact photovoltaic cell or a tunnel-oxide-passivated-contact-structured photovoltaic cell, the photovoltaic cell can also not be provided with a second grid line as a main grid, and it can be understood that the first grid line and each pad in the pad group are directly electrically connected, i.e., the photovoltaic cell can be a zero-busbar solar cell (0BB solar cell).

[0100] In some embodiments, the shape of each pad in the pad group 2, as viewed along the thickness direction of the photovoltaic cell 10, can include a rectangle, a circle, an ellipse, or a dumbbell shape.

[0101] In some embodiments, the pad can also be referred to as a soldering point.

[0102] In a second aspect, the present application provides some embodiments of a method for manufacturing a photovoltaic cell, which can include:

[0103] providing a substrate 1 as shown in Figure 28 The substrate 1 is provided with a middle pad printing area 21a and two outer pad printing areas 22a, the middle pad printing area 21a being located between the two outer pad printing areas 22a. The middle pad printing area 21a and the outer pad printing area 22a are both pre-set paste printing areas on the substrate 1. In addition, the related structures and functions of the substrate 1 have been described above and will not be described here again.

[0104] As shown in Figure 29 The middle pad paste 21b is printed on the middle pad printing area 21a of the substrate 1 by using the first screen 30.

[0105] As shown in Figures 30-31 The outer pad paste 22b is printed on the outer pad printing area 22a of the substrate 1 by using the second screen 40.

[0106] The first screen 30 and the second screen 40 used can be different, for example, the thickness of the emulsion film (also referred to as a mask pattern) of the second screen 40 can be greater than the thickness of the emulsion film (also referred to as a mask pattern) of the first screen 30, the thickness of the outer pad paste 22b formed after printing can be greater than the thickness of the middle pad paste 21b, or for example, the mesh number (the number of screen holes per unit area) of the second screen 40 can be less than the mesh number of the first screen 30, and the thickness of the outer pad paste 22b formed after printing can also be greater than the thickness of the middle pad paste 21b.

[0107] The middle pad paste 21b and the outer pad paste 22b are sintered to form the outer pad 22 and the middle pad 21 mentioned above, wherein the thickness of the outer pad 22 can be greater than the thickness of the middle pad 21. The technical effects brought by "the thickness of the outer pad 22 is greater than the thickness of the middle pad 21" have been described above and will not be repeated here.

[0108] Please refer to Figures 29-31 During the printing process, a squeegee 50 is also needed to be used in cooperation, the squeegee 50 makes the paste press into the leakage hole of the first screen 30 or the second screen 40 at a set speed and angle, so that the paste is printed on the substrate 1.

[0109] In addition, please refer to Figure 32 The first screen 30 can include a first screen frame 301, a first screen mesh 302, and a first mask pattern 303. The first screen frame 301 fixes and supports the first screen mesh 302, and the first screen mesh 302 is a carrier of the first mask pattern 303. The method for forming the first mask pattern 303 can include: coating the first screen mesh 302 with an emulsion film (polymer film), the emulsion film plugging the first screen holes 302a of the first screen mesh 302, selectively irradiating a part of the emulsion film with a UV lamp, the irradiated part of the emulsion film being solidified on the first screen mesh 302, the part of the emulsion film not irradiated can be washed away, so that the emulsion film solidified on the first screen mesh 302 forms the first mask pattern 303, and the first mask pattern 303 is provided with first leakage holes 303a for the paste to pass through, and the first leakage holes 303a are also used to expose some first screen holes 302a. Similarly, please refer to Figure 33As shown, the second screen 40 can include a second screen frame 401, a second screen mesh 402, and a second mask pattern 403. The second screen frame 401 fixes and supports the second screen mesh 402, and the second screen mesh 402 is a carrier of the second mask pattern 403. The method of forming the second mask pattern 403 can include: applying a film of emulsion (polymer film) on the second screen mesh 402, the film of emulsion plugging the second screen holes 402a of the second screen mesh 402, selectively irradiating a portion of the film of emulsion with a UV lamp, the irradiated portion of the film of emulsion solidifying on the second screen mesh 402, and the non-irradiated portion of the film of emulsion being washed away, so that the film of emulsion solidified on the second screen mesh 402 forms the second mask pattern 403, and the second mask pattern 403 is provided with second screen holes 403a for the paste to pass through, and the second screen holes 403a are also used to expose some of the second screen holes 402a. The greater the thickness of the film of emulsion, the greater the depth of the screen holes of the mask pattern, the more paste that can be accommodated in the screen holes of the mask pattern, and the greater the thickness of the pad paste that can be printed on the substrate. Therefore, under the condition that the thickness S2 of the film of emulsion (the second mask pattern 403) of the second screen 40 is greater than the thickness S1 of the film of emulsion (the first mask pattern 303) of the first screen 30, the thickness of the outer pad paste 22b that can be printed on the substrate 1 can be greater than the thickness of the middle pad paste 21b, and after sintering, the thickness of the outer pad 22 can be greater than the thickness of the middle pad 21. In addition, the fewer the number of meshes of the screen, the greater the opening area of the screen holes of the screen, the greater the amount of paste passing through, and the greater the thickness of the pad paste that can be printed on the substrate. Therefore, under the condition that the number of meshes of the second screen mesh 402 of the second screen 40 is less than the number of meshes of the first screen mesh 302 of the first screen 30, the thickness of the outer pad paste 22b that can be printed on the substrate 1 can be greater than the thickness of the middle pad paste 21b, and after sintering, the thickness of the outer pad 22 can be greater than the thickness of the middle pad 21.

[0110] In some embodiments, the thickness of the film of emulsion of the second screen 40 can be greater than the thickness of the film of emulsion of the first screen 30, and at the same time, the number of meshes of the second screen 40 can be less than the number of meshes of the first screen 30, the thickness of the outer pad paste 22b that can be printed on the substrate 1 can be greater than the thickness of the middle pad paste 21b, and after sintering, the thickness of the outer pad 22 can be greater than the thickness of the middle pad 21. Compared to only changing the thickness of the film of emulsion of the screen or only changing the number of meshes of the screen, this embodiment can also have the advantages that the resistance of the paste to filling the screen holes can be relatively small, accordingly, the printing pressure of the squeegee 50 can be relatively low, thereby reducing the degree of possibility of structural damage problems such as micro-cracking or breaking of the substrate 1, and this embodiment can also reduce the adsorption force between the paste and the screen holes, improve the success rate of demolding, and improve the printing speed.

[0111] In some embodiments, the method for manufacturing a photovoltaic cell can further comprise: controlling the distance G2 between the second screen 40 and the substrate 1 to be smaller than the distance G1 between the first screen 30 and the substrate 1, so that the thickness of the outer busbar paste 22b printed on the substrate 1 can be greater than the thickness of the middle busbar paste 21b, and after sintering, the thickness of the outer busbar 22 can be greater than the thickness of the middle busbar 21.

[0112] In some embodiments, the middle busbar paste 21b can be printed on the middle busbar printing area 21a of the substrate 1 by using the first screen 30 first, and then the outer busbar paste 22b can be printed on the outer busbar printing area 22a of the substrate 1 by using the second screen 40. Alternatively, the outer busbar paste 22b can be printed on the outer busbar printing area 22a of the substrate 1 by using the second screen 40 first, and then the middle busbar paste 21b can be printed on the middle busbar printing area 21a of the substrate 1 by using the first screen 30. Alternatively, the middle busbar paste 21b can be printed on the middle busbar printing area 21a of the substrate 1 by using the first screen 30, and at the same time, the outer busbar paste 22b can be printed on the outer busbar printing area 22a of the substrate 1 by using the second screen 40. If printing is needed to be performed simultaneously, the first screen 30 and the second screen 40 can be spliced together first, and then the spliced first screen 30 and the second screen 40 can be placed on the substrate 1, and correspondingly, the number of squeegees can be two, one of which is used for printing the middle busbar paste 21b on the first screen 30, and the other of which is used for printing the outer busbar paste 22b on the second screen 40.

[0113] In some embodiments, the method for manufacturing a photovoltaic cell can further comprise: printing the paste for forming at least one of the first grid line 3 and the second grid line 4 on the substrate 1 by using the first screen 30, which can also be understood as that the paste for forming the first grid line 3, the second grid line 4 and the middle busbar 21 is printed on the substrate 1 simultaneously.

[0114] In some other embodiments, the method for manufacturing a photovoltaic cell can further comprise: the paste for forming at least one of the first grid line 3 and the second grid line 4 can be printed on the substrate 1 by using other screens, which can also be understood as that the paste for forming at least one of the first grid line 3 and the second grid line 4 and the paste for forming the middle busbar 21 are not printed on the substrate 1 simultaneously.

[0115] In some embodiments, the method for manufacturing a photovoltaic cell can be used to manufacture a back contact photovoltaic cell or a tunneling oxide passivation contact structure photovoltaic cell.

[0116] In a third aspect, the present application provides some embodiments of a photovoltaic module, which comprises the solder ribbons and the photovoltaic cells. The photovoltaic cells can be the photovoltaic cells according to some embodiments described above, or the photovoltaic cells prepared by the preparation method of the photovoltaic cells according to some embodiments described above. The middle pads and the outer pads in the same pad group of the photovoltaic cells can be soldered to the same solder ribbon, which is used to electrically connect with the external circuit. Therefore, the photovoltaic module can also have some technical effects of the photovoltaic cells described above, which will not be repeated here.

[0117] In some embodiments, the photovoltaic module can comprise a cell string, which can comprise at least two photovoltaic cells and at least three solder ribbons. In this arrangement, the at least two photovoltaic cells can be soldered and connected in series by the solder ribbons.

[0118] In some embodiments, when the type of the photovoltaic cells used in the cell string is the back contact photovoltaic cell, the cell string can comprise a structure as shown in Figure 34 In some embodiments, the cell string comprises two back contact photovoltaic cells. Similarly, the cell string can also comprise three or more connected back contact photovoltaic cells. Figure 34 In some embodiments, the photovoltaic cells used in the cell string can also be the tunnel oxide passivation contact structure photovoltaic cells.

[0119] In some embodiments, the photovoltaic module can comprise a laminate and a frame, which is mounted on the edge of the laminate. The laminate can comprise a first photovoltaic glass, a first encapsulation adhesive film, a cell string, a second encapsulation adhesive film and a second photovoltaic glass, which are arranged in a stack. The cell string is located between the first encapsulation adhesive film and the second encapsulation adhesive film, the first encapsulation adhesive film is located between the cell string and the first photovoltaic glass, and the second encapsulation adhesive film is located between the cell string and the second photovoltaic glass.

[0120] In some embodiments, the material of at least one of the first encapsulation adhesive film and the second encapsulation adhesive film can comprise at least one of ethylene-vinyl acetate copolymer (EVA), polyolefin elastomer (POE) and polyvinyl butyral (PVB).

[0121] In some embodiments, please refer to

[0122] Figure 35 ​As shown, the warping amount G of the photovoltaic cell sheet 10 can be in the range of 0 µm~3 µm, and specifically can be 0 µm, 0.1 µm, 0.2 µm, 0.3 µm, 0.4 µm, 0.5 µm, 0.6 µm, 0.7 µm, 0.8 µm, 0.9 µm, 1 µm, 1.1 µm, 1.2 µm, 1.3 µm, 1.4 µm, 1.5 µm, 1.6 µm, 1.7 µm, 1.8 µm, 1.9 µm, 2 µm, 2.1 µm, 2.2 µm, 2.3 µm, 2.4 µm, 2.5 µm, 2.6 µm, 2.7 µm, 2.8 µm, 2.9 µm or 3 µm.

[0123] In some embodiments, the warping amount G of the photovoltaic cell sheet 10 can be in the range of 0 µm~1 µm, 1 µm~2 µm or 2 µm~3 µm.

[0124] In addition, the warping amount can be understood as the arching height of the middle part of the photovoltaic cell sheet 10 relative to the plane, or the warping amount can also be understood as the lifting height of the raised end part of the photovoltaic cell sheet 10 relative to the plane.

[0125] In the drawings herein, each two of the directions X, Y and Z are perpendicular to each other, and the extending direction of the second grid line 4 or the extending direction of the solder strip 20 can be parallel to the direction X, and the thickness direction of the substrate 1 can be parallel to the direction Z.

[0126] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Various modifications and changes can be made by those skilled in the art based on the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A photovoltaic cell, characterized by, The photovoltaic cell comprises a substrate and at least two pad groups, and the substrate and the pad groups are in ohmic contact; In the same pad group, the pad group comprises an intermediate pad and two outer pads, the intermediate pad is located between the two outer pads, and the intermediate pad and the outer pads are used for welding the same welding strip; In the thickness direction of the substrate, the intermediate pad has a first thickness H1, and the outer pad has a second thickness H2, and H2>H1 is satisfied; The photovoltaic cell comprises at least three pad groups, and the at least three pad groups comprise a middle pad group and two outer pad groups, the middle pad group is located between the two outer pad groups, and the middle pad group and the outer pad group each comprise the intermediate pad and the two outer pads; The thickness of the outer pad of the outer pad group is greater than the thickness of the outer pad of the middle pad group.

2. The photovoltaic cell of claim 1, wherein, The ratio of the first thickness H1 to the second thickness H2 is in the range of 0.4 to 0.

8.

3. The photovoltaic cell of claim 2, wherein, The first thickness H1 is in the range of 5 µm to 7 µm, and / or the second thickness H2 is in the range of 9 µm to 11 µm.

4. The photovoltaic cell of claim 1, wherein, In the same middle pad group, the distance between the outer pad and the intermediate pad is a first distance D1, and in the same outer pad group, the distance between the outer pad and the intermediate pad is a second distance D2, and D2 5. The photovoltaic cell of any one of claims 1 to 4, wherein, In the same pad group, the pad group further comprises at least two transition pads, the transition pads are arranged between the intermediate pad and any of the outer pads, the intermediate pad, the outer pad and the transition pad are arranged at intervals, in the thickness direction of the substrate, the transition pad has a third thickness H3, and H2>H3>H1 is satisfied.

6. The photovoltaic cell of claim 5, wherein, In the same pad group, the difference between the third thickness H3 and the first thickness H1 is a first difference, the difference between the second thickness H2 and the third thickness H3 is a second difference, and the absolute value of the second difference is less than the absolute value of the first difference.

7. The photovoltaic cell of claim 5, wherein, Within the same said group of pads, there is a separation distance D between the outer pad and the transition pad, both located on the same side of the intermediate pad 23 , there is a separation distance D between the intermediate pad and the transition pad 13 , satisfying D 23 <D 13 .

8. A method for preparing a photovoltaic cell, characterized in that, The preparation method of the photovoltaic cell is used to prepare the photovoltaic cell of any one of claims 1-7, and the preparation method of the photovoltaic cell comprises: Providing a substrate, the substrate is arranged at intervals with an intermediate pad printing area and two outer pad printing areas, and the intermediate pad printing area is located between the two outer pad printing areas; Printing an intermediate pad paste on the intermediate pad printing area of the substrate by using a first screen, and printing an outer pad paste on the outer pad printing area of the substrate by using a second screen, wherein the thickness of the latex film of the second screen is greater than the thickness of the latex film of the first screen, and / or the mesh number of the second screen is less than the mesh number of the first screen, so that the thickness of the outer pad paste is greater than the thickness of the intermediate pad paste; Sintering the intermediate pad paste and the outer pad paste to form an outer pad and an intermediate pad, and the thickness of the outer pad is greater than the thickness of the intermediate pad.

9. A photovoltaic module, characterized by The photovoltaic module comprises solder strips and photovoltaic cell pieces, the photovoltaic cell pieces are the photovoltaic cell pieces according to any one of claims 1-7, and the middle solder pad and the outer solder pad in the same solder pad group of the photovoltaic cell pieces are soldered to the same solder strip.

10. A photovoltaic module, characterized by, The photovoltaic module comprises solder strips and photovoltaic cell pieces, the photovoltaic cell pieces are the photovoltaic cell pieces prepared by the preparation method of the photovoltaic cell pieces according to claim 8, and the middle solder pad and the outer solder pad in the same solder pad group of the photovoltaic cell pieces are soldered to the same solder strip.

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