Photovoltaic cell piece, preparation method of photovoltaic cell piece and photovoltaic module

Abstract

The invention relates to a photovoltaic cell piece, a preparation method of the photovoltaic cell piece and a photovoltaic module, and relates to the technical field of photovoltaics. The photovoltaic battery piece comprises a substrate and a bonding pad group which are in ohmic contact, the bonding pad group comprises a middle bonding pad and two outer bonding pads which are arranged at intervals in the same bonding pad group, the middle bonding pad is located between the two outer bonding pads, the middle bonding pad and the outer bonding pads are used for welding the same welding strip, the middle bonding pad has a first thickness H1, the outer bonding pads have a second thickness H2, and the first thickness H1 is larger than the second thickness H2. H2 > H1. After the welding pads of the photovoltaic cell are welded with the welding strip, the outer side welding pad with the relatively large thickness can generate relatively large plastic deformation, and the relatively large plastic deformation can absorb or dissipate relatively much energy, so that the acting force or energy transmitted to the substrate by the welding strip through the outer side welding pad is relatively small; the warping amount of the substrate can be relatively small or the substrate does not warp, so that the possibility of structural damage of the photovoltaic cell is reduced.

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] According to the above, after the pads of the photovoltaic cell of the application are welded with the ribbons, the relatively thick outer pads can be relatively plastically deformed, and the relatively plastic deformation can absorb or dissipate relatively more energy, so that the force or energy transmitted by the ribbons to the substrate through the outer pads is relatively small, and accordingly, the amount of warping of the substrate is relatively small, or the substrate can not be warped. In the subsequent preparation process of the photovoltaic module, especially in the process of laminating the photovoltaic cell to form a stack, if the photovoltaic cell without warping or with relatively small warping is used, the gap or bubble between the photovoltaic cell and the packaging material is not easy to produce, and the yield of the photovoltaic module is relatively large. In addition, the degree of local stress concentration in the photovoltaic cell without warping or with relatively small warping is relatively small, and the photovoltaic cell is not easy to have structural damage problems such as micro-cracking or breaking. Furthermore, the stress in the relatively thick outer pad can be dispersed in the thickness direction of the outer pad, so that the reliability of the connection structure between the outer pad and the corresponding welded ribbon is relatively high, and the problem of false welding is not easy to occur.

[0015] It should be understood that the above general description and the following detailed description are only exemplary and do not limit the application. BRIEF DESCRIPTION OF DRAWINGS

[0016] In order to more clearly illustrate the technical solutions of the embodiments of the application, the drawings needed in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor.

[0017] Figure 1 Structure schematic diagram of a back contact photovoltaic cell in an embodiment; Figure 2 Structure schematic diagram of a back contact photovoltaic cell in an embodiment; Figure 1 Structure schematic diagram of a back contact photovoltaic cell in an embodiment; Figure 3 Structure schematic diagram of a back contact photovoltaic cell in an embodiment; Figure 1 Structure schematic diagram of a back contact photovoltaic cell in an embodiment; Figure 4 Structure schematic diagram of a back contact photovoltaic cell in an embodiment; Figure 1 Structure schematic diagram of a back contact photovoltaic cell in an embodiment; Figure 5 Structure schematic diagram of a back contact photovoltaic cell in an embodiment; Figure 1 Structure schematic diagram of a back contact photovoltaic cell in an embodiment; Figure 6 Welding schematic diagram of a ribbon and a back contact photovoltaic cell in an embodiment; Figure 1 Welding schematic diagram of a ribbon and a back contact photovoltaic cell in an embodiment; Figure 7 Welding state change schematic diagram of an outer pad of a substrate and a ribbon in an embodiment; Figure 8 Figure 1 is a schematic diagram of a back contact photovoltaic cell in accordance with an embodiment of the application; Figure 5 Figure 2 is a schematic diagram of a partial structure of a back contact photovoltaic cell in accordance with an embodiment of the application; Figure 9 Figure 3 is a schematic diagram of a partial structure of a back contact photovoltaic cell in accordance with another embodiment of the application; Figure 1 Figure 4 is a schematic diagram of a partial structure of a back contact photovoltaic cell in accordance with another embodiment of the application; Figure 10 Figure 5 is a schematic diagram of a partial structure of a back contact photovoltaic cell in accordance with another embodiment of the application; Figure 1 Figure 6 is a schematic diagram of a partial structure of a back contact photovoltaic cell in accordance with another embodiment of the application; Figure 11 Figure 7 is a schematic diagram of a partial structure of a back contact photovoltaic cell in accordance with another embodiment of the application; Figure 12 Figure 8 is a schematic diagram of a partial structure of a back contact photovoltaic cell in accordance with another embodiment of the application; Figure 13 Figure 9 is a schematic diagram of a partial structure of a back contact photovoltaic cell in accordance with another embodiment of the application; Figure 14 Figure 10 is a schematic diagram of a partial structure of a back contact photovoltaic cell in accordance with another embodiment of the application; Figure 15 Figure 11 is a schematic diagram of a partial structure of a back contact photovoltaic cell in accordance with another embodiment of the application; Figure 16 Figure 12 is a schematic diagram of a partial structure of a back contact photovoltaic cell in accordance with another embodiment of the application; Figure 15 Figure 13 is a schematic diagram of a partial structure of a back contact photovoltaic cell in accordance with another embodiment of the application; Figure 17 Figure 14 is a schematic diagram of a partial structure of a back contact photovoltaic cell in accordance with another embodiment of the application; Figure 15 Figure 15 is a schematic diagram of a partial structure of a back contact photovoltaic cell in accordance with another embodiment of the application; Figure 18 Figure 15 Figure 16 is a schematic diagram of a partial structure of a back contact photovoltaic cell in accordance with another embodiment of the application; Figure 19 Figure 17 is a schematic diagram of a partial structure of a back contact photovoltaic cell in accordance with another embodiment of the application; Figure 17 Figure 18 is a schematic diagram of a partial structure of a back contact photovoltaic cell in accordance with another embodiment of the application; Figure 20 Figure 15 Figure 19 is a schematic diagram of a partial structure of a back contact photovoltaic cell in accordance with another embodiment of the application; Figure 21 Figure 20 is a schematic diagram of a partial structure of a back contact photovoltaic cell in accordance with another embodiment of the application; Figure 22 Figure 21 is a schematic diagram of a partial structure of a back contact photovoltaic cell in accordance with another embodiment of the application; Figure 23 Figure 22 is a schematic diagram of a partial structure of a back contact photovoltaic cell in accordance with another embodiment of the application; Figure 24 Figure 23 is a schematic diagram of a partial structure of a back contact photovoltaic cell in accordance with another embodiment of the application; Figure 25 ​​Structure diagram of a photovoltaic cell with a tunneling oxide passivated contact structure in one embodiment; Figure 26 Structure diagram of a photovoltaic cell with a tunneling oxide passivated contact structure in another embodiment; Figure 27 Structure diagram of a photovoltaic cell with a tunneling oxide passivated contact structure in yet another embodiment; Figure 28 Structure diagram of a substrate in one embodiment; Figure 29 Structure diagram of a first screen, a squeegee and a substrate in the process of printing the middle solder pad paste; Figure 30 Structure diagram of a second screen, a squeegee and a substrate in the process of printing the outer solder pad paste; Figure 31 Structure diagram of a second screen, a squeegee and a substrate in the process of printing another outer solder pad paste; Figure 32 Structure diagram of a cross section of a first screen; Figure 33 Structure diagram of a cross section of a second screen; Figure 34 Structure diagram of a cell string of a photovoltaic module in one embodiment; Figure 35 Structure diagram of a warpage of a photovoltaic cell in one embodiment.

[0018] Reference numerals: 10-photovoltaic cell, 1-substrate, 11-first part, 12-second part, 13-third part, 14-fourth part, 15-fifth part, 16-sixth part, 17-seventh part, 18-eighth part, 19-ninth part, 2-solder pad group, 2a-middle solder pad group, 2b-outer solder pad group, 2c-transition solder pad group, 21-middle solder pad, 21a-printing area of middle solder pad, 21b-paste of middle solder pad, 22-outer solder pad, 22a-printing area of outer solder pad, 22b-paste of outer solder pad, 23-transition solder pad, 3-first grid line, 4-second grid line, 20-solder ribbon, 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

[0019] In order to better understand 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, 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 work 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 an "or" relationship between the front and rear associated objects.

[0020] In the first aspect, the present application provides some embodiments of photovoltaic cells, which relates to the field of photovoltaic technology. In some embodiments, please refer to Figure 1 As shown in the figure, the photovoltaic cell 10 can include a substrate 1, which is the main structure or body structure of the photovoltaic cell 10, and the substrate 1 can include an N region structure and a P region structure inside. The N region structure is doped with at least one N type element (fifth main group element in the periodic table of chemical elements), such as phosphorus element, arsenic element, antimony element, etc. The P region structure is doped with at least one P type element (third main group element in the periodic table of chemical elements), such as boron element, aluminum element, gallium element, etc. A P-N junction can be formed between the N region structure and the P region structure, and the P-N junction can form a built-in electric field. Under the condition of light, electron-hole pairs can be generated in the photovoltaic cell 10, and the built-in electric field can separate the electron-hole pairs. The N region structure is used to collect electrons with negative electricity, and the P region structure is used to collect holes with positive electricity, thereby forming a photovoltaic voltage.

[0021] In some embodiments, please refer to Figure 1 As shown in the figure, the photovoltaic cell 10 can include grid lines (for example, the grid lines include first grid lines 3 and second grid lines 4), and the substrate 1 and the grid lines are ohmic contact (also known as metallization contact). A part of the number of grid lines (for example Figure 2 The first grid lines 3 and the second grid lines 4 shown in the figure) can be ohmic contact with the N region structure, and the other part of the number of grid lines (for example Figure 3The 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.

[0022] 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.

[0023] Additionally, please refer to Figures 1-3 As 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.

[0024] 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 2The shown pad group 2 (may also be referred to as a negative pad group) conducts to a partial number of ribbon wires (may also be referred to as negative ribbon wires) in the external circuit, and the electrons in turn conduct through another partial number of ribbon wires (may also be referred to as positive ribbon wires) in the external circuit, Figure 3 The shown pad group 2 (may also be referred to as a positive pad group) and Figure 3 The shown positive grid line conducts to the P region structure of the photovoltaic cell piece 10.

[0025] Among them, please refer to Figure 1 As shown, the photovoltaic cell piece 10 can include four pad groups 2, which can include two middle pad groups 2a and two outer pad groups 2b, and the two middle pad groups 2a are located between the two outer pad groups 2b. Any middle pad group 2a and any outer pad group 2b are relatively independent pad groups 2, and the setting position of the middle pad group 2a relative to the substrate 1 and the setting position of the outer pad group 2b relative to the substrate 1 are different. In Figure 1 And Figure 2 In the viewing angle shown, the relatively left outer pad group 2b and the relatively left middle pad group 2a can be negative pad groups 2, and in Figure 1 And Figure 3 In the viewing angle shown, the relatively right outer pad group 2b and the relatively right middle pad group 2a can be positive pad groups 2.

[0026] In addition, please refer to Figures 1-4 As shown, in the same pad group 2, the pad group 2 can include at least three pads of the same polarity (such as the middle pad 21 and the outer pad 22), and it can be understood that in the same pad group 2, all pads included by the pad group 2 are electrically connected with the grid line of the same polarity, and it can also be understood that in the same pad group 2, all pads (Pad) included by the pad group 2 are electrically connected with the same ribbon wire, that is, one pad group 2 corresponds to one ribbon wire.

[0027] 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 cell string, all pads of the same pad group 2 can be welded with the same ribbon wire 20 to form, for example, Figure 6The structure is shown. During the soldering process, the volume of the substrate 1 and the volume of the solder strip 20 are both increased due to the absorption of the soldering heat, and after the soldering is completed, the substrate 1 is connected with the corresponding solder strip 20 through each solder pad group 2, and after the soldering, the volume of the substrate 1 and the volume of the solder strip 20 are both decreased due to the heat dissipation to the outside. However, the thermal expansion coefficient of the substrate 1 and the thermal expansion coefficient of the solder strip 20 are different, and during the soldering process, the increasing amplitude of the volume of the substrate 1 is smaller than the increasing amplitude of the volume of the solder strip 20, and after the soldering, the decreasing amplitude of the volume of the substrate 1 is smaller than the decreasing amplitude of the volume of the solder strip 20. Therefore, after the soldering, the solder strip 20 exerts a pulling force F on the substrate 1 through each outer solder pad 22, and the direction of the pulling force F is the direction in which the outer solder pad 22 points to the middle solder pad 21. Please refer to Figure 7 The outer solder pad 22 subjected to the pulling force F can be plastically deformed, for example, the shape of the outer solder 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 during the shrinkage. Please refer to Figure 8 In the thickness direction (the direction parallel to the direction Z) of the substrate 1, the middle solder pad 21 can have a first thickness H1, and the outer solder pad 22 can have a second thickness H2, and H2>H1 is satisfied. Under this arrangement, after the photovoltaic cell piece 10 is soldered with the solder strip 20, the relatively thicker outer solder pad 22 can be relatively more plastically deformed, and the relatively more plastic deformation can absorb or dissipate relatively more energy, so that the acting force or energy transmitted to the substrate 1 through the outer solder pad 22 is relatively smaller, and accordingly, the amount of warping of the substrate 1 is relatively smaller, or the substrate 1 can not be warped. In the subsequent preparation process of the photovoltaic module, especially in the process of laminating the photovoltaic cell pieces to form a laminate, if the photovoltaic cell piece 10 without warping or with relatively smaller warping is used, the gap or bubble between the photovoltaic cell piece 10 and the encapsulating material is not easy to be generated, and the yield of the photovoltaic module is relatively larger. In addition, the degree of local stress concentration in the photovoltaic cell piece 10 without warping or with relatively smaller warping is relatively smaller, and the photovoltaic cell piece 10 is not easy to be damaged in structure, such as micro-cracking or breaking. Furthermore, the stress in the relatively thicker outer solder pad 22 can be dispersed in the thickness direction of the outer solder pad 22, so that the reliability of the connection structure between the outer solder pad 22 and the corresponding soldered solder strip 20 is relatively higher, that is, the problem of false soldering is not easy to occur.

[0028] In some embodiments, please refer to Figure 8As 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 side pad 22 after welding can absorb or dissipate relatively more energy from the solder strip 20 shrinkage, on the other hand, the metal (e.g., silver) required for the outer side pad 22 to use will not be too much, provided that the first thickness H1 can meet the welding requirements of the middle pad 21.

[0029] 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 side pad 22 after welding can absorb or dissipate relatively more energy from the solder strip 20 shrinkage, on the other hand, the metal (e.g., silver) required for the outer side pad 22 to use will not be too much, provided that the first thickness H1 can meet the welding requirements of the middle pad 21.

[0030] In some embodiments, referring to Figure 8 As shown, the first thickness H1 can be in the range of 5 micrometers (µm)-7 micrometers (µm), and specifically, the first thickness H1 can be 5 µm, 5.1 µm, 5.2 µm, 5.3 µm, 5.4 µm, 5.5 µm, 5.6 µm, 5.7 µm, 5.8 µm, 5.9 µm, 6 µm, 6.1 µm, 6.2 µm, 6.3 µm, 6.4 µm, 6.5 µm, 6.6 µm, 6.7 µm, 6.8 µm, 6.9 µm, or 7 µm.

[0031] The first thickness H1 can be in a range from 5 µm to 6 µm, and specifically can be 5 µm, 5.1 µm, 5.2 µm, 5.3 µm, 5.4 µm, 5.5 µm, 5.6 µm, 5.7 µm, 5.8 µm, 5.9 µm, or 6 µm. Alternatively, the first thickness H1 can be in a range from 6 µm to 7 µm, and specifically can be 6 µm, 6.1 µm, 6.2 µm, 6.3 µm, 6.4 µm, 6.5 µm, 6.6 µm, 6.7 µm, 6.8 µm, 6.9 µm, or 7 µm.

[0032] In some embodiments, referring to FIG. 1A, Figure 8 The second thickness H2 can be in a range from 9 µm to 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.

[0033] The second thickness H2 can be in a range from 9 µm to 10 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, or 10 µm. Alternatively, the second thickness H2 can be in a range from 10 µm to 11 µm, and specifically can be 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.

[0034] 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 strip 20 located on both sides of the middle pad 21 will shrink to the structure segments 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. It can be known that 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 the range of 7 µm~9 µm, and the average thickness 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 the photovoltaic cell piece 10 after soldering can not be warped.

[0035] In some embodiments, the elongation of the material of the outer pad 22 can be greater than the elongation of the material of the middle pad 21. The elongation refers to the elongation at break, which is a key index for measuring the plastic deformation energy in the mechanical properties of the material, and the definition of the elongation is that the length (plastic deformation amount) of the gauge length part of the material sample after being pulled to break in the tensile test is increased by the percentage of the original gauge length. After the photovoltaic cell piece 10 is soldered with the solder strip 20, the outer pad 22 with relatively large elongation can have relatively large plastic deformation, and the relatively large plastic deformation can absorb or dissipate more energy, so that the force or energy transmitted to the substrate 1 through the outer pad 22 is relatively small, and accordingly, the warping amount of the substrate 1 is relatively small, or the substrate 1 can not be warped.

[0036] In some embodiments, the ratio of silver, glass powder and modifier included in the outer pad 22 and the ratio of silver, glass powder and modifier included in the middle pad 21 can be adjusted to be different, so that the elongation of the material of the outer pad 22 is greater than the elongation of the material of the middle pad 21.

[0037] In some embodiments, please refer to Figure 9As 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.

[0038] 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. 22 The thickness H can be greater than that of the outer pad 22 of the middle pad group 2a. 21 In this configuration, after the photovoltaic cell 10 is welded to the solder ribbon 20, the plastic deformation that can occur on the outer pad 22 of the outer pad group 2b is greater than that that can occur on the outer pad 22 of the middle pad group 2a. The relatively larger plastic deformation can absorb or dissipate a relatively larger amount of energy, so that the force or energy transmitted to the corner of the substrate 1 through the outer pad 22 of the outer pad group 2b is relatively smaller. The warpage of each corner of the substrate 1 can be less than or equal to the warpage of the second part 12. Similarly, the warpage of each corner of the substrate 1 can be less than or equal to the warpage of the eighth part 18. The corner of the substrate 1 is less likely to suffer structural damage problems such as microcracks or breakage. The outer pad 22 located at the corner of the substrate 1 and the corresponding solder ribbon 20 are also less likely to suffer from poor soldering problems.

[0039] Alternatively, substrate 1 can be divided into other numbers of parts using different partitioning methods, such as sixteen parts arranged in a 4x4 pattern, twenty-five parts arranged in a 5x5 pattern, or multiple parts distributed in other ways. Regardless of how substrate 1 is internally divided, it always includes four corners. The following content will mainly focus on how... Figure 10The nine-square distribution shown is an example to describe the structure of the substrate 1.

[0040] In some embodiments, referring to Figure 12 As shown, the second distance D2 between the middle pad 21 and the outer pad 22 in the outer pad group 2b is smaller than the first distance D1 between the middle pad 21 and the outer pad 22 in the middle pad group 2a, i.e. D2 < D1, the relatively smaller second distance D2 can be understood as the force arm between the middle pad 21 and the outer pad 22 in the outer pad group 2b being shortened, under the condition that the solder ribbon 20 shrinks to generate the same pulling force F, the bending moment that the pulling force F can generate on the shorter force arm is relatively smaller, in this setting, the warping amount of each corner of the substrate 1 after the photovoltaic cell piece 10 is welded with the solder ribbon 20 can be smaller than or equal to the warping amount of the second part 12, by the same logic, the warping amount of each corner of the substrate 1 can be smaller than or equal to the warping amount of the eighth part 18, the corners of the substrate 1 are not prone to structural damage problems such as micro-cracks or breakage, and the outer pad 22 at the corner of the substrate 1 is also not prone to the problem of false welding with the corresponding solder ribbon 20. In some embodiments, referring to Figure 12 In the structure shown, the thickness of the outer pad 22 of any middle pad group 2a can also be smaller than or equal to the thickness of the outer pad 22 of any outer pad group 2b.

[0041] In some embodiments, referring to Figure 13 In some embodiments, referring to Figure 14 As shown, the photovoltaic cell piece 10 can include six pad groups 2, the six pad groups 2 can include two middle pad groups 2a, two outer pad groups 2b and two transition pad groups 2c, the two middle pad groups 2a are located between the two outer pad groups 2b, one transition pad group 2c can be arranged between one middle pad group 2a and one outer pad group 2b, and one transition pad group 2c can be arranged between the other middle pad group 2a and the other outer pad group 2b. Any middle pad group 2a, any outer pad group 2b and any transition pad group 2c can each include a middle pad 21 and two outer pads 22, and the thickness of the middle pad 21 is smaller than the thickness of the outer pad 22. Figure 13 In some embodiments, referring to Figure 14 As shown, after the photovoltaic cell piece 10 is welded with the solder ribbon 20, the warping amount of the substrate 1 is relatively small, or the substrate 1 can not warp.

[0042] In other embodiments (not shown in the figures), the photovoltaic cell piece can include other even-numbered and more than six pad groups. Among them, the number of middle pad groups can be at least three, and the number of transition pad groups can be at least four.

[0043] In some embodiments, referring to Figure 14As shown, the second distance D2 between the middle pad 21 and the outer pad 22 in the outer pad group 2b is 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 is 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, after the photovoltaic cell sheet 10 is welded with the solder strip 20, the warping amount of each corner of the substrate 1 can be less than or equal to the warping amount of the second portion 12, and by the same token, the warping amount of each corner of the substrate 1 can be less than or equal to the warping amount of the eighth portion 18, and the corners of the substrate 1 are less likely to be structurally damaged, such as micro-cracking or breaking, and the outer pads 22 at the corners of the substrate 1 are also less likely to be falsely welded with the corresponding solder strip 20.

[0044] In some embodiments, as shown in Figure 13 or Figure 14 As shown, the thickness of the outer pad 22 in any middle pad group 2a can be less than the thickness of the outer pad 22 in any transition pad group 2c, and the thickness of the outer pad 22 in any transition pad group 2c can be less than the thickness of the outer pad 22 in any outer pad group 2b. In this arrangement, the corners of the substrate 1 are less likely to be structurally damaged, such as micro-cracking or breaking, and the outer pads 22 at the corners of the substrate 1 are also less likely to be falsely welded with the corresponding solder strip 20.

[0045] In other embodiments, as shown in Figure 13 or Figure 14 As shown, the thickness of the outer pad 22 in any middle pad group 2a can be equal to the thickness of the outer pad 22 in any transition pad group 2c, and the thickness of the outer pad 22 in any transition pad group 2c can be equal to the thickness of the outer pad 22 in any outer pad group 2b.

[0046] In some embodiments, as shown in Figures 15-17 As shown, in the same pad group 2, the pad group 2 can include at least two transition pads 23, and the transition pad 23 can be arranged between the middle pad 21 and any outer pad 22, and the middle pad 21, the outer pad 22 and the transition pad 23 are arranged in intervals. In the process of forming a cell string, all pads in the same pad group 2 can be welded with the same solder strip 20 to form a structure as shown in Figure 18 As shown, in the process of forming a cell string, all pads in the same pad group 2 can be welded with the same solder strip 20 to form a structure as shown in Figure 19As shown, in the thickness direction of the substrate 1, the middle pads 21 have a first thickness H1, the outer pads 22 have a second thickness H2, and the transition pads have a third thickness H3, and H2>H3>H1. In this arrangement, the plastic deformation that can occur in the outer pads 22 is greater than the plastic deformation that can occur in the transition pads 23, and the plastic deformation that can occur in the transition pads 23 is greater than the plastic deformation that can occur in the middle pads 21. The energy that can be absorbed or dissipated by the outer pads 22 is greater than the energy that can be absorbed or dissipated by the transition pads 23, and the energy that can be absorbed or dissipated by the transition pads 23 is greater than the energy that can be absorbed or dissipated by the middle pads 21. Therefore, the force or energy transmitted to the substrate 1 through the outer pads 22 is less than the force or energy transmitted to the substrate 1 through the middle pads 21, and the force or energy transmitted to the substrate 1 through the transition pads 23 is also less than the force or energy transmitted to the substrate 1 through the middle pads 21. In addition, the energy or force borne by each of the outer pads 22, the transition pads 23, and the middle pads 21 is relatively small, and it can also be said that the number of pads welded to the same solder strip is relatively large, and the smaller the energy or force dispersed to each pad. Therefore, Figures 15-19 After the photovoltaic cell sheet 10 is welded to the solder strip 20, the amount of warping of the substrate 1 is relatively small, or the substrate 1 can not be warped.

[0047] In some embodiments, referring to Figure 19 As 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 sheet 10 is welded to the solder strip 20, although the energy that can be absorbed or dissipated by the transition pads 23 is less than the energy that can be absorbed or dissipated by the outer pads 22, the energy that can be absorbed or dissipated by the transition pads 23 is still relatively large, so that the amount of warping of the substrate 1 is relatively small, or the substrate 1 can not be warped.

[0048] In other embodiments, the absolute value of the second difference can also be equal to the absolute value of the first difference.

[0049] In some embodiments, referring to 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, or it can also be said that 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.

[0050] In some embodiments, referring to 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 H31 In this configuration, after the photovoltaic cell 10 is welded to the solder ribbon 20, the plastic deformation that can occur in the transition pad 23 of the outer pad group 2b is greater than that that can occur in the transition pad 23 of the middle pad group 2a. The relatively larger plastic deformation can absorb or dissipate a relatively larger amount of energy, so that the force or energy transmitted to the corner of the substrate 1 through the transition pad 23 of the outer pad group 2b is relatively smaller. The warpage of each corner of the substrate 1 can be less than or equal to the warpage of the second part 12. Similarly, the warpage of each corner of the substrate 1 can be less than or equal to the warpage of the eighth part 18. The corner of the substrate 1 is less likely to suffer structural damage problems such as microcracks or breakage. The transition pad 23 located at the corner of the substrate 1 and the corresponding solder ribbon 20 are also less likely to suffer from cold solder joint problems. In some other embodiments (not shown in the figures), within the same pad group, the thickness of the transition pad can be the same as the thickness of the intermediate 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 intermediate pad.

[0051] In some other embodiments (not shown in the figures), within the same pad group, the thickness of the transition pad can be the same as the thickness of the outer pad, the thickness of the intermediate pad can be less than the thickness of the transition pad, and the thickness of the intermediate pad can be less than the thickness of the outer pad.

[0052] In some embodiments, please refer to Figure 16 As shown, within any pad group 2, for the outer pad 22 and the transition pad 23 located on the same side of the middle pad 21, the spacing D between the outer pad 22 and the transition pad 23 is... 23 It can be less than the spacing D between the intermediate pad 21 and the transition pad 23. 13 D 23 <D 13 In this configuration, after the photovoltaic cell 10 is soldered to the solder ribbon 20, the adjacent outer pads 22 and transition pads 23 can work together to absorb or dissipate more energy, and the adjacent outer pads 22 and transition pads 23 can further limit the shrinkage of the structural segment in the solder ribbon 20 located between the outer pads 22 and transition pads 23. Therefore, the warpage of the substrate 1 can be relatively small, or the substrate 1 can be warped.

[0053] In some other embodiments (not shown in the figures), within any pad group, for the outer pad and the transition pad located on the same side of the intermediate pad, the spacing between the outer pad and the transition pad can be equal to the spacing between the transition pad and the intermediate pad.

[0054] In some embodiments, please refer to Figure 22As shown, the interval distance between the transition pad 23 and the middle pad 21 in the outer pad group 2b is smaller than the interval distance between the transition pad 23 and the middle pad 21 in the middle pad group 2a, and the interval distance between the outer pad 22 and the middle pad 21 in the outer pad group 2b is smaller than the interval distance between the outer pad 22 and the middle pad 21 in the middle pad group 2a. In this arrangement, after the photovoltaic cell 10 is soldered with the solder strip 20, the warping amount of each corner of the substrate 1 can be smaller than or equal to the warping amount of the second portion 12, and by the same token, the warping amount of each corner of the substrate 1 can be smaller than or equal to the warping amount of the eighth portion 18, and the corners of the substrate 1 are less likely to be structurally damaged, such as micro-cracking or breaking, and the outer pads 22 at the corners of the substrate 1 are also less likely to be falsely soldered with the corresponding soldered solder strip 20. The relevant principles have been described above and will not be repeated here.

[0055] In some embodiments, referring to Figure 23 or Figure 24 As shown, the photovoltaic cell 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, with 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. Any middle pad group 2a, any outer pad group 2b, and any transition pad group 2c can each include a middle pad 21, two outer pads 22, and two transition pads 23, with the middle pad 21 being located between the two outer pads 22, one transition pad 23 being arranged between the middle pad 21 and any one of the outer pads 22, the thickness of the middle pad 21 being smaller than the thickness of the transition pad 23, and the thickness of the transition pad 23 being smaller than the thickness of the outer pad 22. Figure 23 or Figure 24 As shown, after the photovoltaic cell 10 is soldered with the solder strip 20, the warping amount of the substrate 1 can be relatively small, or the substrate 1 can not warp.

[0056] In other embodiments (not shown in the figures), the photovoltaic cell can include other even-numbered pad groups and a number of pad groups greater than six.

[0057] In some embodiments, referring to Figure 24As 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, which 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, which is less than the distance between the middle pad 21 and the transition pad 23 in the middle pad group 2a. In this arrangement, after the photovoltaic cell 10 is soldered with the solder strip 20, the warping amount of each corner of the substrate 1 can be less than or equal to the warping amount of the second portion 12, and by the same token, the warping amount of each corner of the substrate 1 can be less than or equal to the warping amount of the eighth portion 18, the corners of the substrate 1 are less likely to be structurally damaged, such as micro-cracking or breaking, the outer pads 22 at the corners of the substrate 1 are less likely to be poorly soldered with the corresponding solder strip 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 strip 20. The relevant principles have been described above and will not be repeated here.

[0058] In some other embodiments (not shown in the figures), at least two transition pads can be arranged between the middle pad and either of the outer pads in the same pad group, and the thickness of the transition pad closer to the middle pad can be less than the thickness of the transition pad closer to the outer pad.

[0059] In some other embodiments (not shown in the figures), two or more spaced-apart middle pads can be arranged in the same pad group, and no other type of pad can be arranged between any two adjacent middle pads.

[0060] 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 either of the pad groups can include a middle pad and two outer pads, the middle pad is between the two outer pads, and the thickness of the outer pads is greater than the thickness of the middle pad.

[0061] In some other embodiments, the photovoltaic cell 10 can also be a tunnel oxide passivated contact solar cell. The light-receiving side of the photovoltaic cell 10 can be provided with busbars and pads, and the back side of the photovoltaic cell 10 can also be provided with busbars and pads, wherein the busbars and pads on one side can be in ohmic contact with the N region structure, and the busbars and pads on the other side can be in ohmic contact with the P region structure. The distribution of the first busbar 3, the second busbar 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 busbar 3, the second busbar 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 , the thickness of the outer pad 22 is greater than the thickness of the middle pad 21 in any pad group 2. In Figure 26 , 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 any pad group 2. 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.

[0062] In some other embodiments (not shown in the drawings), the light-receiving side of the tunnel oxide passivated contact solar cell can also be provided with two pad groups, and by analogy, the back side of the tunnel oxide passivated contact solar cell can also be provided with two pad groups. Any pad group can include a middle pad and two outer pads, the middle pad is located between the two outer pads, and the thickness of the outer pads is greater than the thickness of the middle pad.

[0063] In some other embodiments (not shown in the drawings), regardless of whether the photovoltaic cell is a back contact photovoltaic cell or a tunnel oxide passivated contact solar cell, the photovoltaic cell can also not be provided with a second busbar as a main busbar, and it can be understood that the first busbar 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).

[0064] 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.

[0065] In some embodiments, the pad can also be referred to as a soldering point.

[0066] In a second aspect, the present application provides some embodiments of a method for manufacturing a photovoltaic cell, which can include: providing a substrate 1 as shown in Figure 28 which is provided with an intermediate pad printing area 21a and two outer pad printing areas 22a, and the intermediate pad printing area 21a is located between the two outer pad printing areas 22a. The intermediate pad printing area 21a and the outer pad printing area 22a are both pre-set paste printing areas on the substrate 1. The relevant structure and function of the substrate 1 have been described above and will not be repeated here.

[0067] Referring to Figure 29 , the intermediate pad paste 21b is printed on the intermediate pad printing area 21a of the substrate 1 by using a first screen 30.

[0068] Referring to Figures 30-31 , the outer pad paste 22b is printed on the outer pad printing area 22a of the substrate 1 by using a second screen 40.

[0069] 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, so that the thickness of the outer pad paste 22b formed after printing is greater than the thickness of the intermediate pad paste 21b, or for example, the mesh count (the number of mesh holes per unit area) of the second screen 40 can be less than the mesh count of the first screen 30, so that the thickness of the outer pad paste 22b formed after printing can also be greater than the thickness of the intermediate pad paste 21b.

[0070] The intermediate pad paste 21b and the outer pad paste 22b are sintered to form the outer pad 22 and the intermediate pad 21 mentioned above, and the thickness of the outer pad 22 can be greater than the thickness of the intermediate pad 21. The technical effects brought by the thickness of the outer pad 22 being greater than the thickness of the intermediate pad 21 have been described above and will not be repeated here.

[0071] Referring to Figures 29-31 , a squeegee 50 is also needed to be used in the printing process. The squeegee 50 makes the paste press into the mesh holes 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.

[0072] In addition, please refer to Figure 32 As shown in FIG. 3, the first screen 30 can include a first screen frame 301, a first screen 302, and a first mask pattern 303. The first screen frame 301 fixes and supports the first screen 302, and the first screen 302 is a carrier of the first mask pattern 303. The method of forming the first mask pattern 303 can include: applying a latex film (polymer film) on the first screen 302, the latex film plugging the first screen holes 302a of the first screen 302, selectively irradiating a portion of the latex film by a UV lamp, the irradiated portion of the latex film being solidified on the first screen 302, and the un-irradiated portion of the latex film being washed away, so that the latex film solidified on the first screen 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 of the first screen holes 302a. Similarly, please refer to Figure 33 As shown in FIG. 4, the second screen 40 can include a second screen frame 401, a second screen 402, and a second mask pattern 403. The second screen frame 401 fixes and supports the second screen 402, and the second screen 402 is a carrier of the second mask pattern 403. The method of forming the second mask pattern 403 can include: applying a latex film (polymer film) on the second screen 402, the latex film plugging the second screen holes 402a of the second screen 402, selectively irradiating a portion of the latex film by a UV lamp, the irradiated portion of the latex film being solidified on the second screen 402, and the un-irradiated portion of the latex film being washed away, so that the latex film solidified on the second screen 402 forms the second mask pattern 403, and the second mask pattern 403 is provided with second leakage holes 403a for the paste to pass through, and the second leakage holes 403a are also used to expose some of the second screen holes 402a. The greater the thickness of the latex film, the greater the depth of the leakage holes of the mask pattern, the more paste that can be accommodated in the leakage 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 latex film (the second mask pattern 403) of the second screen 40 is greater than the thickness S1 of the latex film (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, if the fewer the mesh count 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 mesh count of the second screen 402 of the second screen 40 is less than the mesh count of the first screen 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.

[0073] In some embodiments, the thickness of the emulsion film of the second screen 40 can be made greater than the thickness of the emulsion film of the first screen 30, and the mesh number of the second screen 40 can also be made smaller than the mesh number of the first screen 30, so that the thickness of the outer pad paste 22b 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 with the single change of the thickness of the emulsion film of the screen or the single change of the mesh number of the screen, this embodiment can also have the advantages that the resistance of the paste to fill the mesh can be relatively small, and accordingly, the printing pressure of the squeegee 50 can be relatively low, thereby reducing the possibility of structural damage such as micro-cracking or breaking of the substrate 1, and this embodiment can also reduce the adsorption force between the paste and the mesh, improve the success rate of demolding, and improve the printing speed.

[0074] Under the condition that the distance between the screen and the substrate is relatively small, the paste printed on the substrate is not easy to overflow, so that the thickness of the paste printed on the substrate can be relatively large. Therefore, in some embodiments, the method for preparing a photovoltaic cell can further include: 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 pad paste 22b 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.

[0075] In some embodiments, the middle pad paste 21b can be printed on the middle pad printing area 21a of the substrate 1 by using the first screen 30 first, and then the outer pad paste 22b can be printed on the outer pad printing area 22a of the substrate 1 by using the second screen 40. Alternatively, the outer pad paste 22b can be printed on the outer pad printing area 22a of the substrate 1 by using the second screen 40 first, and then the middle pad paste 21b can be printed on the middle pad printing area 21a of the substrate 1 by using the first screen 30. Alternatively, the middle pad paste 21b can be printed on the middle pad printing area 21a of the substrate 1 by using the first screen 30, and the outer pad paste 22b can be printed on the outer pad printing area 22a of the substrate 1 by using the second screen 40 at the same time. If printing is needed at the same time, 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 accordingly, the number of squeegees is two, one of which is used to print the middle pad paste 21b on the first screen 30, and the other of which is used to print the outer pad paste 22b on the second screen 40.

[0076] In some embodiments, the method for preparing a photovoltaic cell can further comprise printing a paste for forming at least one of the first grid line 3 and the second grid line 4 on the substrate 1 using the first screen 30. It can also be understood that the paste for forming the first grid line 3, the second grid line 4 and the intermediate pad 21 is printed on the substrate 1 at the same time.

[0077] In some other embodiments, the method for preparing a photovoltaic cell can further comprise printing a paste for forming at least one of the first grid line 3 and the second grid line 4 on the substrate 1 using other screens. It can also be understood 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 intermediate pad 21 are not printed on the substrate 1 at the same time.

[0078] In some embodiments, the method for preparing a photovoltaic cell can be used to prepare a back contact photovoltaic cell or a tunnel oxide passivated contact structure photovoltaic cell.

[0079] In a third aspect, the present application provides some embodiments of a photovoltaic module, which comprises a solder ribbon and a photovoltaic cell. The photovoltaic cell can be a photovoltaic cell according to some embodiments described above, or the photovoltaic cell can be prepared by a method for preparing a photovoltaic cell according to some embodiments described above. The intermediate pad and the outer pad in the same pad group of the photovoltaic cell can be soldered to the same solder ribbon, which is used to electrically connect with an external circuit. Therefore, the photovoltaic module can also have some technical effects of the photovoltaic cell described above, which will not be repeated here.

[0080] 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.

[0081] In some embodiments, when the type of the photovoltaic cell used in the cell string is a back contact photovoltaic cell, the cell string can comprise a structure as shown in Figure 34 In some embodiments, when the type of the photovoltaic cell used in the cell string is a back contact photovoltaic cell, the cell string can comprise a structure as shown in Figure 34 In some embodiments, when the type of the photovoltaic cell used in the cell string is a back contact photovoltaic cell, the cell string can comprise a structure as shown in

[0082] In some embodiments, the photovoltaic cell used in the cell string can also be a tunnel oxide passivated contact structure photovoltaic cell.

[0083] In some embodiments, the photovoltaic module may include a laminate and a frame, with the frame mounted on the edge of the laminate. The laminate may include a first photovoltaic glass, a first encapsulating film, a battery string, a second encapsulating film, and a second photovoltaic glass, all stacked together. The battery string is located between the first and second encapsulating films, the first encapsulating film is located between the battery string and the first photovoltaic glass, and the second encapsulating film is located between the battery string and the second photovoltaic glass.

[0084] In some embodiments, the material of at least one of the first encapsulating film and the second encapsulating film may include at least one of ethylene-vinyl acetate copolymer (EVA), polyolefin elastomer (POE), and polyvinyl butyral (PVB).

[0085] In some embodiments, please refer to Figure 35 As shown, the warpage G of the photovoltaic cell 10 can be in the range of 0µm to 3µm. Specifically, the warpage G of the photovoltaic cell 10 can be 0µm, 0.1µm, 0.2µm, 0.3µm, 0.4µm, 0.5µm, 0.6µm, 0.7µm, 0.8µm, 0.9µm, 1µm, 1.1µm, 1.2µm, 1.3µm, 1.4µm, 1.5µm, 1.6µm, 1.7µm, 1.8µm, 1.9µm, 2µm, 2.1µm, 2.2µm, 2.3µm, 2.4µm, 2.5µm, 2.6µm, 2.7µm, 2.8µm, 2.9µm, or 3µm.

[0086] The warpage G of the photovoltaic cell 10 can also be in the range of 0µm~1µm, 1µm~2µm, or 2µm~3µm.

[0087] In addition, the warpage can be understood as the height of the arch of the middle part of the photovoltaic cell 10 relative to the plane, or the warpage can also be understood as the height of the raised end of the photovoltaic cell 10 relative to the plane.

[0088] In the accompanying drawings, every two of the directions X, Y and Z are perpendicular to each other. The extension direction of the second grid line 4 or the extension 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. The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A photovoltaic cell, characterized by, The photovoltaic cell piece 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 arranged at intervals, 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.

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 0.4-0.

8.

3. The photovoltaic cell of claim 2, wherein, 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.

4. The photovoltaic cell of claim 1, wherein, The photovoltaic cell piece comprises at least three pad groups, 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 two outer pads; The thickness of the outer pad of the outer pad group is greater than or equal to the thickness of the outer pad of the middle pad group.

5. The photovoltaic cell of claim 4, 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 6. The photovoltaic cell of any one of claims 1-5, 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, and 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.

7. The photovoltaic cell of claim 6, 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.

8. The photovoltaic cell of claim 6, wherein, In the same said pad group, there is a spacing distance D between the outer pad and the transition pad located at the same side of the middle pad 23 , there is a spacing distance D between the middle pad and the transition pad 13 , satisfying D 23 <D 13 .

9. A method for preparing a photovoltaic cell, characterized in that, The preparation method of the photovoltaic cell piece 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 making the thickness of the outer pad greater than the thickness of the intermediate pad.

10. A photovoltaic module, characterized by, The photovoltaic module comprises a solder strip and a photovoltaic cell piece, wherein the photovoltaic cell piece is prepared by the method of any one of claims 1-8, or the photovoltaic cell piece is prepared by the method of claim 9. The intermediate solder pad and the outer solder pad in the same solder pad group of the photovoltaic cell piece are soldered to the same solder strip.

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