Back contact solar cell, preparation method and photovoltaic module

Abstract

The invention relates to the technical field of solar cells, particularly provides a back contact solar cell, a preparation method and a photovoltaic module, and aims to solve the problem that the output power of the photovoltaic module is reduced when a hot spot effect in the photovoltaic module is solved by using a bypass diode in the prior art. In order to achieve the purpose, the back contact solar cell comprises a plurality of cell units, each cell unit comprises a first electrode and a second electrode, and at least part of the cell units are further provided with first connecting pieces used for conductively connecting the first electrodes and the second electrodes of the corresponding cell units. The first electrodes and the second electrodes of the battery units are conductively connected through the first connecting pieces, so that leakage current gain can be generated, the back contact solar cells with faults and the back contact solar cells connected in series with the back contact solar cells can be prevented from being reversely cut off by the bypass diodes, and the output power of the photovoltaic module can be improved while the hot spot effect is solved.

Description

Technical Field

[0001] The present application relates to the technical field of solar cells, and specifically provides a back-contact solar cell, a preparation method and a photovoltaic module. Background Art

[0002] Photovoltaic modules, also known as solar panels, are mainly used to convert solar energy into electrical energy and are the core part of solar power generation systems. They are composed of multiple solar cells, which are the basic units of photovoltaic modules. Multiple solar cells are connected in series and parallel and tightly sealed to form an integrated photovoltaic module. Among them, solar cells can use back-contact solar cells. When one or several back-contact solar cells in a photovoltaic module are blocked, a "hot spot effect" will occur, causing overheating and reducing the power output capacity of the photovoltaic module.

[0003] To address the above problem, a bypass diode can usually be set in parallel with the back contact solar cell. When the back contact solar cell is blocked, the bypass diode can bypass the conduction to prevent the blocked back contact solar cell from affecting the entire photovoltaic module. However, this solution will reduce the output power of the photovoltaic module. Summary of the invention

[0004] The present application aims to solve the above technical problem, that is, to solve the problem that the output power of photovoltaic modules will be reduced when bypass diodes are used to solve the hot spot effect in photovoltaic modules.

[0005] In a first aspect, the present application provides a back-contact solar cell, characterized in that it comprises a plurality of battery cells, each of which comprises a first electrode and a second electrode, and at least some of the plurality of battery cells are further provided with a first connecting member for conductively connecting the first electrode and the second electrode of the corresponding battery cell.

[0006] In some embodiments, the resistance between the first electrode and the second electrode on the battery cell provided with the first connector is a preset percentage of the initial resistance between the first electrode and the second electrode of the corresponding battery cell when the first connector is not provided, wherein the preset percentage is greater than 30% and less than 100%.

[0007] In some embodiments, the first connecting member is disposed between the first electrode and the second electrode of the corresponding battery cell in at least one of a straight line, an oblique line, and a bend.

[0008] In some embodiments, the first connector includes a plurality of connection sub-components, and the plurality of connection sub-components are spaced apart between the first electrode and the second electrode of the corresponding battery cell.

[0009] In some embodiments, a second connector is further included, and the second connector is used to conductively connect the first electrode of any one of the plurality of battery cells to the second electrode of another adjacent battery cell.

[0010] In some embodiments, the plurality of battery cells are arranged in an array.

[0011] In some embodiments, the second connecting member is used to conductively connect a second electrode of one battery cell to a first electrode of another battery cell of two battery cells in the same column.

[0012] In some embodiments, the second connecting member is used to conductively connect the second electrode of one battery cell to the first electrode of the other battery cell in two battery cells in adjacent columns and adjacent rows.

[0013] In some embodiments, the battery cell comprises an HBC battery cell or a TBC battery cell.

[0014] In some embodiments, the battery cell comprises a TBC battery cell, wherein the TBC battery cell comprises:

[0015] A substrate, the substrate comprising a first surface and a second surface arranged opposite to each other; the first surface comprising a first area, a second area and an isolation area between the first area and the second area;

[0016] A first tunneling oxide layer and a first polysilicon layer are sequentially disposed in the first region of the first surface and in a direction away from the substrate;

[0017] A second tunnel oxide layer and a second polysilicon layer are sequentially disposed in the second region of the first surface and in a direction away from the substrate;

[0018] A stacked structure, the stacked structure comprising a first passivation layer, a first anti-reflection layer, the first connecting member, a first via hole and a second via hole; the first passivation layer is at least arranged on the surface of the first polysilicon layer and the second polysilicon layer away from the substrate; the first anti-reflection layer is arranged on the first passivation layer; the first via hole is arranged in the first region, and the second via hole is arranged in the second region;

[0019] the first electrode and the second electrode;

[0020] A second passivation layer and a second anti-reflection layer are sequentially disposed on a side of the second surface away from the substrate;

[0021] Wherein, the first electrode is disposed in the first via hole and is electrically connected to the first polysilicon layer through the first via hole;

[0022] The second electrode is disposed in the second via hole and is electrically connected to the second polysilicon layer through the second via hole;

[0023] The first connecting member is disposed on the surface of the first polysilicon layer, the second polysilicon layer, and the isolation region away from the substrate.

[0024] In some embodiments, the first connecting member is disposed on a surface of the first anti-reflection layer away from the substrate.

[0025] In a second aspect, the present application provides a photovoltaic module, which includes any of the back-contact solar cells described above.

[0026] In a third aspect, the present application provides a method for preparing a back-contact solar cell, comprising:

[0027] A plurality of battery cells are formed on a substrate; each of the plurality of battery cells comprises a first electrode and a second electrode, and at least some of the plurality of battery cells are further provided with a first connector for conductively connecting the first electrode and the second electrode of the corresponding battery cell.

[0028] In the case of adopting the above technical solution, the present application can provide a back-contact solar cell, which includes a plurality of battery cells, each of which includes a first electrode and a second electrode, and at least some of the plurality of battery cells are also provided with a first connector for conductively connecting the first electrode and the second electrode of the corresponding battery cell. Conductively connecting the first electrode and the second electrode of the battery cell through the first connector can generate leakage current gain, which can prevent the faulty back-contact solar cell and the back-contact solar cell connected in series with it from being reversely cut off by the bypass diode, and while solving the hot spot effect, it is beneficial to improve the output power of the photovoltaic module. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The preferred embodiments of the present application are described below in conjunction with the accompanying drawings, in which:

[0030] Figure 1A is a schematic diagram of a top view structure of a back contact solar cell provided in the present application; Figure 1B yes Figure 1A The corresponding equivalent circuit diagram;

[0031] Figure 2 is a schematic diagram of the cross-sectional structure of a battery unit provided in an embodiment of the present application along the CC' line in FIG1;

[0032] Figure 3 is a schematic diagram of the structure of a battery unit provided with a first connecting member provided in an embodiment of the present application;

[0033] Figure 4is a schematic structural diagram of a battery unit provided with a first connecting member provided in another embodiment of the present application;

[0034] Figure 5 is a schematic structural diagram of a battery unit provided with a first connecting member provided in another embodiment of the present application;

[0035] Fig. 6A is a schematic diagram of a top view of a back-contact solar cell provided by another embodiment of the present application; Figure 6B yes Fig. 6A The corresponding equivalent circuit diagram;

[0036] Figure 7 is a schematic diagram of a top view of a back-contact solar cell provided with a second connector according to an embodiment of the present application;

[0037] Figure 8 is a schematic diagram of a top view of a back-contact solar cell provided with a second connector provided in another embodiment of the present application;

[0038] Fig. 9 is a schematic cross-sectional structure diagram of a TBC battery unit provided in an embodiment of the present application;

[0039] Fig.10 is a schematic diagram of a top view of a back-contact solar cell provided by another embodiment of the present application;

[0040] Figures 11 to 18 is a schematic cross-sectional structure diagram corresponding to each step of forming a battery cell provided in an embodiment of the present application;

[0041] Fig.19 It is a schematic diagram of the volt-ampere characteristic curve of the back-contact solar cell provided in the specific example of this application. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical solution and advantages of the embodiments of the present disclosure clearer, the technical solution of the embodiments of the present disclosure will be clearly and completely described below in conjunction with the drawings of the embodiments of the present disclosure. Obviously, the described embodiments are part of the embodiments of the present disclosure, not all of the embodiments. Based on the described embodiments of the present disclosure, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present disclosure.

[0043] Unless otherwise defined, the technical terms or scientific terms used in the present disclosure should be understood by people with ordinary skills in the field to which the present disclosure belongs. The words "first", "second" and similar words used in the present disclosure do not indicate any order, quantity or importance, but are only used to distinguish different components. "Include" or "comprise" and similar words mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Up", "down" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0044] A back contact (BC) solar cell is a cell in which both the p+ doped region and the n+ doped region are placed on the back side of the cell (non-light-receiving side, i.e., the back-lighting side). The light-receiving side of the cell is not blocked by any metal electrode, thereby effectively increasing the short-circuit current of the cell and improving the energy conversion efficiency of the cell. In some embodiments, BC solar cells may include multiple types. For example, the structure of a BC solar cell may be combined with the structure of a TOPCon (Tunnel oxide passivated contact) cell to obtain a TBC cell, or the structure of a BC solar cell may be combined with the structure of a HJT (Heterojunction with Intrinsic Thinfilm) cell to obtain a HBC cell.

[0045] Based on the description in the background section, it can be known that solar cells can be back-contact solar cells. When one or several back-contact solar cells in a photovoltaic module are blocked, a "hot spot effect" will occur. The reason is that when one or a group of cells in a photovoltaic module are blocked or damaged, the blocked cell or battery group is placed in a reverse bias state, and the short-circuit current of the blocked cell or battery group is reduced, while the actual working current exceeds the reduced short-circuit current of the cell or battery group, consuming power, and hot spot heating will occur in the photovoltaic module, that is, the hot spot effect. When a bypass diode is used to solve the hot spot effect in a photovoltaic module, the blocked cell or battery group is under reverse bias, and the reverse voltage increases to reverse bias the entire battery string where the blocked cell or battery group is located, the battery string will be cut off by the bypass diode and cannot work, thereby greatly reducing the output power of the photovoltaic module.

[0046] Based on this, the present application provides a back-contact solar cell, which may include a plurality of battery cells, each of which includes a first electrode and a second electrode, and at least some of the plurality of battery cells are also provided with a first connector for conductively connecting the first electrode and the second electrode of the corresponding battery cell. The leakage current of the back-contact solar cell can be increased by providing the first connector. When the back-contact solar cell is blocked and can only work in a reverse biased state, the voltage of the blocked battery cell when it reaches the working current of the entire battery string in which it is located can be reduced, so that the entire battery string is in a forward voltage working state, avoiding reverse cutoff by the bypass diode, thereby effectively avoiding a reduction in output power. At the same time, the flow of leakage current can make the back-contact solar cell evenly heated under the hot spot, reducing the risk of partial heating.

[0047] In some embodiments, the first electrode may be an N-type electrode, and the second electrode may be a P-type electrode; in other embodiments, the first electrode may be a P-type electrode, and the second electrode may be an N-type electrode.

[0048] In some embodiments, the first connector can be made of conductive paste and / or gallium nitride with relatively low conductivity. The resistivity of gallium nitride is 109Ω·cm, and the resistivity range of the conductive paste line is 106-109Ω·cm, which can increase the leakage current while reducing the impact of the leakage current on the normal operation of the battery unit.

[0049] In some embodiments, the resistance between the first electrode and the second electrode on the battery cell provided with the first connector is a preset proportion of the initial resistance between the first electrode and the second electrode of the corresponding battery cell when the first connector is not provided, wherein the preset proportion is greater than 30% and less than 100%. That is, the first connector is conductive and can conductively connect the first electrode and the second electrode of the corresponding battery cell, increase the leakage current of the back contact solar cell, thereby preventing the blocked battery string from being reversely cut off and preventing the output power from being reduced, and at the same time, enable the back contact solar cell to be evenly heated under the hot spot, reducing the risk of partial heating.

[0050] The preset ratio can be set according to actual needs. In some embodiments, while realizing the conductive connection between the first electrode and the second electrode, in order to avoid the influence of leakage current on the normal operation of the battery unit, a larger value can be selected within the range of greater than 30% and less than 100% to be set as the preset ratio, and at the same time, by setting the material, size and layout of the first connector, the resistance between the first electrode and the second electrode provided with the first connector is equal to the preset ratio of the initial resistance between the first electrode and the second electrode of the corresponding battery unit when the first connector is not provided. That is, the first connector provided accordingly has poor conductivity, and while realizing the increase of leakage current, the influence of leakage current on the normal operation of the battery unit can be reduced.

[0051] For example, when the first connecting member is not set, the initial resistance between the first electrode and the second electrode of the battery cell is R. After the first connecting member is set, the resistance between the first electrode and the second electrode of the battery cell is R', and the preset ratio is 70%. The first connecting member has a lower conductivity. While realizing the conductive connection between the first electrode and the second electrode and increasing the leakage current, it can reduce the influence of the leakage current on the normal operation of the battery cell.

[0052] In some embodiments, see Figure 1A As shown, Figure 1A is a schematic diagram of a top view of a back contact solar cell provided in an embodiment of the present application, wherein the back contact solar cell may include a plurality of battery cells (each battery cell having Figure 1A ), each of the plurality of battery cells includes a first electrode 11 and a second electrode 12. Figure 1A exemplarily shows that some of the battery cells in the plurality of battery cells are provided with the first connector 13, which is used to conductively connect the first electrode 11 and the second electrode 12 of the corresponding battery cell. In other embodiments, the first connector 13 may also be provided for all of the plurality of battery cells.

[0053] The plurality of first electrodes 11 in the same row may be connected via a first metal gate line, and the plurality of second electrodes 12 in the same row may be connected via a second metal gate line.

[0054] See also Figure 1B As shown, Figure 1B yes Figure 1A In the corresponding equivalent circuit diagram, a back-contact solar cell, i.e., a solar cell, can be equivalent to a diode. By setting a first connector 13 between the first electrode and the second electrode, it is equivalent to adding a leakage branch in parallel with the diode. The resistance of the leakage branch can be expressed as R13, which can achieve the desired target resistance based on the conductive material, layout, size, thickness, quantity, etc. of the first connector 13.

[0055] In some embodiments, see Figure 2 As shown, Figure 2 The battery unit provided in the embodiment of the present application is Figure 1A Schematic diagram of the cross-sectional structure of the C-C' line. Figure 2 As shown, the battery cell may include a battery main structure 10, a first electrode 11, a second electrode 12 and a first connector 13. The backlight surface of the battery main structure 10 is provided with two doping regions with different doping types, and the two doping regions are isolated from each other. The first electrode 11 is provided on the backlight surface of one of the two doping regions, and the second electrode 12 is provided on the backlight surface of the other of the two doping regions. Figure 2 In order to more clearly illustrate the two electrodes, it is exemplarily shown that the first electrode 11 and the second electrode 12 have certain lateral dimensions.

[0056] The first connector 13 partially covers the backlight surface of the battery main structure 10 and is disposed between the first electrode 11 and the second electrode 12. In some embodiments, the first connector 13 can be obtained by applying a conductive paste between the first electrode 11 and the second electrode 12 by screen printing or steel screen printing. The thickness of the first connector 13 can be the same as that of the first electrode 11 and / or the second electrode 12. In other embodiments, the first connector 13 can also be disposed in other ways, and details can be found in the description of other embodiments below.

[0057] The battery main structure 10 may also be configured in other ways according to the type of battery unit, which is not particularly limited here.

[0058] In some embodiments, in order to achieve that the resistance between the first electrode and the second electrode on the battery cell provided with the first connector is a preset proportion of the initial resistance between the first electrode and the second electrode of the corresponding battery cell when the first connector is not provided, that is, even if the resistance between the first electrode and the second electrode provided with the first connector meets the target resistance, the first electrode and the second electrode can be interconnected in different forms and achieve the target resistance by flexibly setting the layout of the first connector. For details, please refer to the following description.

[0059] See also Figure 3-5 As shown, Figure 3-5 It is a schematic diagram of a battery cell structure provided with a first connector provided in an embodiment of the present application. The first connector is arranged in different layouts to form different connection paths between the first electrode and the second electrode to achieve respective target resistances.

[0060] like Figure 3 As shown, the first connector 13 is arranged in a straight line between the first electrode 11 and the second electrode 12 of the corresponding battery cell. The straight line arrangement may be arranged in a direction perpendicular to the extension direction of the first electrode 11 or the second electrode 12. Figure 4 As shown, the first connector 13 is disposed obliquely between the first electrode 11 and the second electrode 12 of the corresponding battery cell. The oblique arrangement may be disposed in a direction that forms a preset angle with the extension direction of the first electrode 11 or the second electrode 12, and the preset angle is not equal to 90°. Figure 5 As shown, the first connector 13 is disposed in a bent manner between the first electrode 11 and the second electrode 12 of the corresponding battery cell. In other embodiments, the first connector 13 may be disposed in other ways that can realize conductive connection between the first electrode 11 and the second electrode 12.

[0061] In some embodiments, when the first connector is prepared by screen printing, the size of the single connector formed by different screen types will also be different. In order to achieve the target resistance, see Fig. 6A As shown, Fig. 6A FIG. 1 is a schematic diagram of a top view of a back contact solar cell provided by another embodiment of the present application. In this embodiment, based on FIG. 1 , the first connector 13 is replaced by a layout method in which multiple connecting subcomponents are arranged to interconnect the first electrode and the second electrode and achieve the target resistance. Fig. 6A As shown, the back contact solar cell includes a plurality of battery cells, and a first connector 13' is arranged between the first electrode 11 and the second electrode 12 of some of the battery cells in the plurality of battery cells, wherein the first connector 13' may include a plurality of connecting sub-components, and the plurality of connecting sub-components are arranged at intervals between the first electrode 11 and the second electrode 12 of the corresponding battery cells. The number of connecting sub-components can be determined based on the specifications of the screen, the conductivity of the conductive paste, and the target resistance, Fig. 6A FIG. 1 shows an exemplary case where the first connector 13' includes three connector sub-components. In other embodiments, the back contact solar cell may be used simultaneously. Figure 1A and Fig. 6A The first connecting member is arranged in a manner as described above.

[0062] See also Figure 6B As shown, Figure 6B yes Fig. 6A The corresponding equivalent circuit diagram shows that by setting a first connecting member 13' between the first electrode and the second electrode, each connecting sub-component can be equivalent to a resistor after being connected to the first electrode and the second electrode, and multiple connecting sub-components can be equivalent to multiple resistors arranged in parallel. The multiple resistors arranged in parallel can be used as diodes, that is, multiple leakage branches of the back-contact solar cell, and the resistance of the multiple leakage branches can be expressed as R13'.

[0063] In other embodiments, in order to further reduce the impact of the hot spot effect and achieve uniform heating, the back-contact solar cell may also be provided with at least one second connector on the basis of being provided with a first connector (13 and / or 13') to realize a leakage current transmission path based on the first connector (13 and / or 13') and the second connector, wherein the second connector is used to conductively connect the first electrode 11 of any one of the multiple battery cells to the second electrode 12 of another adjacent battery cell.

[0064] Here, the second connecting member is provided on the basis of the first connecting member 13 as an example for explanation. Figure 7 and Figure 8 As shown, Figure 7is a schematic diagram of a top view of a back contact solar cell provided with a second connector according to an embodiment of the present application, Figure 8 It is a schematic diagram of a top view of the structure of a back-contact solar cell provided with a second connecting member provided in another embodiment of the present application.

[0065] like Figure 7 and Figure 8 As shown, a back-contact solar cell may include a plurality of battery cells, and the plurality of battery cells are arranged in an array, and the first electrodes 11 and the second electrodes 12 of the plurality of battery cells are arranged in a forked finger shape, that is, in the same row, the plurality of first electrodes 11 and the plurality of second electrodes 12 are arranged at intervals, and the second electrode 12 is arranged between two adjacent first electrodes 11, and the plurality of second electrodes 12 are arranged alternately with the plurality of first electrodes 11.

[0066] In some embodiments, Figure 7 As shown, a plurality of second connectors 14 may be provided, and the plurality of second connectors 14 may be provided between different battery cells. The second connector 14 is used to conductively connect the second electrode 12 of one battery cell to the first electrode 11 of another battery cell in the same column. Figure 8 As shown, the second connecting member 14 ′ is used to electrically conductively connect the second electrode 12 of one battery cell and the first electrode 11 of the other battery cell in two battery cells in adjacent columns and adjacent rows.

[0067] In some embodiments, the second connecting member (14, 14') can be made of the same material as the first connecting member (13, 13') and achieve the same beneficial effects.

[0068] In some embodiments, the second connector (14, 14') may be disposed between the two battery cells in at least one of a straight line, an oblique line, and a bend, so as to form different connection paths between the two battery cells and achieve respective target resistances.

[0069] In some embodiments, the second connector (14, 14') may include a plurality of connecting subcomponents, which are spaced apart between the two battery cells, so that the target resistance between the two battery cells can be achieved by setting the number of connecting subcomponents based on the specifications of the screen and the conductivity of the conductive paste for different screen types.

[0070] In some embodiments, the resistance between the first electrode and the second electrode of the two battery cells provided with the second connector (14, 14') is a preset proportion of the initial resistance between the first electrode and the second electrode when the second connector (14, 14') is not provided, wherein the preset proportion is greater than 30% and less than 100%. That is, the second connector is conductive and can conductively connect the two battery cells, further increasing the leakage current of the back-contact solar cell, effectively preventing the blocked battery string from being reversely cut off and reducing the output power, and at the same time enabling the back-contact solar cell to be evenly heated under the hot spot, reducing the risk of partial heating.

[0071] It should be noted that the preset proportion corresponding to the second connecting member (14, 14') can be the same as or different from the preset proportion corresponding to the first connecting member 13, and no special limitation is made here, and it can be flexibly set according to actual needs.

[0072] In some embodiments, in order to avoid the influence of leakage current on the normal operation of the battery unit, a larger value within the range of greater than 30% and less than 100% may be selected to be set as the preset proportion corresponding to the second connecting member (14, 14').

[0073] In some embodiments, a TBC battery cell is used as an example for description, see Fig. 9 As stated, Fig. 9 : is a schematic diagram of a cross-sectional structure of a TBC battery unit provided in an embodiment of the present application. It may include:

[0074] A substrate 80, the substrate 80 includes a first surface S1 and a second surface S2 disposed opposite to each other; the first surface S1 includes a first area A1, a second area A2, and an isolation area A3 located between the first area A1 and the second area A2;

[0075] A first tunnel oxide layer 81 and a first polysilicon layer 82 are sequentially disposed in a first area A1 of the first surface S1 and in a direction away from the substrate 80;

[0076] A second tunnel oxide layer 83 and a second polysilicon layer 84 are sequentially disposed in a second area A2 of the first surface S1 and in a direction away from the substrate 80;

[0077] The stacked structure 85 includes a first passivation layer 851, a first anti-reflection layer 852, a first connector 13″, a first via hole 853 and a second via hole 854; the first passivation layer 851 is at least arranged on the surface of the first polysilicon layer 82 and the second polysilicon layer 84 away from the substrate 80; the first anti-reflection layer 852 is arranged on the first passivation layer 851; the first via hole 853 is arranged in the first area A1, and the second via hole 854 is arranged in the second area A2;

[0078] A first electrode 11 and a second electrode 12;

[0079] A second passivation layer 86 and a second anti-reflection layer 87 are sequentially disposed on a side of the second surface S2 away from the substrate 80;

[0080] The first electrode 11 is disposed in the first via hole 853 and is electrically connected to the first polysilicon layer 82 through the first via hole 853;

[0081] The second electrode 12 is disposed in the second via hole 854 and is electrically connected to the second polysilicon layer 84 through the second via hole 854;

[0082] The first connection member 13 ″ is disposed on the first polysilicon layer 82 , the second polysilicon layer 84 , and the surface of the isolation region A3 away from the substrate 80 .

[0083] In this embodiment, at least one of the material, layout, size and quantity of the first connecting member 13" can be arranged in the same manner as in any of the above embodiments.

[0084] In some embodiments, the first connector 13'' can be formed by coating. Compared with printing methods such as screen printing, the coating method is conducive to obtaining a first connector 13'' with a more uniform thickness and easier to control layer thickness, which is conducive to ensuring that the target resistance between the first electrode 11 and the second electrode 12 is accurately reached after the first connector 13'' is set. In addition, the first connector 13'' can be integrated with other structural layers in the battery in the same preparation equipment. For example, the coating method may include chemical vapor deposition or physical vapor deposition. The first connector 13'' can be prepared by chemical vapor deposition or physical vapor deposition together with other structural layers in the battery, which can avoid equipment replacement and simplify the process flow. In other embodiments, the first connector 13'' can also be obtained by printing methods such as screen printing.

[0085] It should be noted that when the first connecting member 13" is formed by coating, Fig. 9 As shown, in a direction parallel to the substrate 80, the first connector 13" not only covers the area between the first electrode 11 and the second electrode 12 in the battery cell, but also can at least cover the area on the side of the first electrode 11 away from the second electrode 12 and the area on the side of the second electrode 12 away from the first electrode 11.

[0086] In some embodiments, the resistance between the first electrode 11 and the second electrode 12 on the TBC battery cell provided with the first connector 13" is a preset proportion of the initial resistance between the first electrode 11 and the second electrode 12 of the corresponding TBC battery cell when the first connector 13" is not provided. The preset proportion is greater than 30% and less than 100%. That is, the first connector 13" is conductive and can conductively connect the first electrode 11 and the second electrode 12 of the corresponding battery cell to increase the leakage current, thereby preventing the blocked battery string from being reversely cut off and preventing the output power from being reduced. At the same time, the TBC battery can be evenly heated under the hot spot, reducing the risk of partial heating.

[0087] The preset ratio can be set according to actual needs. In some embodiments, while realizing the conductive connection between the first electrode 11 and the second electrode 12, in order to avoid the influence of leakage current on the normal operation of the battery cell, a larger value can be selected in the range of greater than 30% and less than 100% as the preset ratio, and at the same time, by setting the material, size and layout of the first connector 13", the resistance between the first electrode 11 and the second electrode 12 provided with the first connector 13" is equal to the preset ratio of the initial resistance between the first electrode 11 and the second electrode 12 of the corresponding battery cell when the first connector 13" is not provided. That is, the corresponding first connector 13" has poor conductivity, which can reduce the influence of leakage current on the normal operation of the battery cell while increasing the leakage current.

[0088] In some embodiments, Fig. 9 As shown, a first doping region 801 and a second doping region 802 are further provided on one side of the substrate 80 close to the first surface S1. The orthographic projection of the first polysilicon layer 82 on the substrate 80 coincides with the first doping region 801, and the orthographic projection of the second polysilicon layer 84 on the substrate 80 coincides with the second doping region 802. In some embodiments, the substrate 80 may be made of silicon material, the first doping region 801 may be an N-type doping region, and the second doping region 802 may be a P-type doping region. Accordingly, the first polysilicon layer 82 may be an N-type polysilicon layer, and the second polysilicon layer 84 may be a P-type polysilicon layer.

[0089] In the embodiment of the present application, the first connector 13 ″ can be disposed at different layers of the first polysilicon layer 82 and the second polysilicon layer 84 away from the substrate 80 based on different subsequent application scenarios and requirements, as described below for details.

[0090] like Fig. 9As shown, in some embodiments, a groove is provided at a position of the substrate 80 corresponding to the isolation region A3; the first passivation layer 851 can be provided on the surface of the first polysilicon layer 82 and the second polysilicon layer 84 away from the substrate 80 and on the sidewall and bottom surface of the groove of the isolation region A3; wherein the first anti-reflection layer 852 can be conformally covered on the surface of the first passivation layer 851 away from the substrate 80, and the first connecting member 13" can be conformally covered on the surface of the first anti-reflection layer 852 away from the substrate 80.

[0091] In other embodiments, the first connecting member 13" may also be disposed on the surface of the first polysilicon layer 82, the second polysilicon layer 84 away from the substrate 80 and the side wall and bottom surface of the groove in the isolation area A3, and the first passivation layer 851 and the first anti-reflection layer 852 are sequentially disposed on the first connecting member 13".

[0092] In some other embodiments, the first passivation layer 851 may be disposed on the surface of the first polysilicon layer 82, the second polysilicon layer 84 away from the substrate 80, and the sidewall and bottom surface of the trench in the isolation area A3, and the first connecting member 13″ and the first anti-reflection layer 852 are sequentially disposed on the first passivation layer 851.

[0093] In other embodiments, the position of the substrate 80 corresponding to the isolation region A3 may not be provided with a groove, and the Figure 2 The isolation region is set in a similar manner, that is, on the backlight side of the substrate 80, a certain horizontal distance is spaced between the first doping region 801 and the second doping region 802, and the substrate surfaces corresponding to the isolation region A3, the first doping region 801 and the second doping region 802 are on the same plane.

[0094] In the embodiment of the present application, the second connector can also be prepared by coating to obtain a second connector with more uniform thickness and easier to control layer thickness, so as to ensure that the target resistance is achieved between different battery cells. The second connector can be arranged in the same layer or in a different layer as the first connector 13".

[0095] In some embodiments, the first passivation layer 851 and the second passivation layer 86 may be made of aluminum oxide, and the first anti-reflection layer 852 and the second anti-reflection layer 87 may be made of stacked silicon nitride.

[0096] In some embodiments, the first connecting member and the second connecting member may be disposed in the same layer and obtained synchronously. Disposing in the same layer means that they may be formed using the same material and the same preparation process (eg, patterning process, etc.).

[0097] In some other embodiments, the functions of the first connector and the second connector can also be realized based on the conductive connection layer 15 formed by coating and covering the entire battery cell except the first electrode and the second electrode regions. For details, see Fig.10 As shown, Fig.10 It is a schematic diagram of a top view structure of a back-contact solar cell provided in another embodiment of the present application, which can maximize the leakage current, avoid the reduction of output power, make the back-contact solar cell evenly heated under the hot spot, and reduce the risk of partial heating.

[0098] In some embodiments, the thickness of the conductive connection layer may be set based on the target resistance to be achieved between the first electrode 11 and the second electrode 12 after the conductive connection layer 15 is provided, the coverage area of ​​the conductive connection layer 15 , and the like.

[0099] The conductive connection layer 15 can be made of the same material as the first connection member and / or the second connection member in any of the above embodiments. In some embodiments, the conductive connection layer 15 can also be arranged in the same layer position as the first connection member and / or the second connection member in any of the above embodiments.

[0100] In another aspect of the present application, a photovoltaic module is provided, which may include the back-contact solar cell described in any of the above embodiments, and achieve the same beneficial effects as any of the above embodiments.

[0101] Another aspect of the present application further provides a method for preparing a back-contact solar cell, which may include:

[0102] A plurality of battery cells are formed on a substrate; each of the plurality of battery cells comprises a first electrode and a second electrode, and at least some of the plurality of battery cells are further provided with a first connector for conductively connecting the first electrode and the second electrode of the corresponding battery cell.

[0103] To prepare Fig. 9 The battery cell shown is taken as an example, see Figures 11 to 18 As shown, forming a battery cell on a substrate may include:

[0104] Provide a substrate 80, such as Fig.11 As shown, the substrate 80 includes a first surface S1 and a second surface S2 that are opposite to each other; the first surface S1 includes a first area A1, a second area A2, and an isolation area A3 located between the first area A1 and the second area A2.

[0105] like Fig.12 As shown, a first tunneling oxide layer 81 and a first polysilicon layer 82 are sequentially arranged in a first area A1 of a first surface S1 and in a direction away from a substrate 80, and a first heat treatment is performed on the substrate 80; wherein the first tunneling oxide layer 81 may be silicon oxide; and the first polysilicon layer 82 may be an N-type polysilicon layer, and through the first heat treatment, doped ions in the N-type polysilicon layer may pass through the first tunneling oxide layer 81 to form a first doped region 801 in the substrate 80.

[0106] like Fig.13 As shown, a second tunneling oxide layer 83 and a second polysilicon layer 84 are sequentially arranged in a second area A2 of the first surface S1 and in a direction away from the substrate 80, and the substrate 80 is subjected to a second heat treatment; it should be noted that the second tunneling oxide layer 83 can be arranged in the same layer as the first tunneling oxide layer 81; the second polysilicon layer 84 can be a P-type polysilicon layer, and through the second heat treatment, the doped ions in the P-type polysilicon layer can pass through the second tunneling oxide layer 83 to form a second doped region 802 in the substrate 80.

[0107] like Fig.14 As shown, a trench is formed in the isolation region A3 of the first surface S1 , and the depth of the trench may be greater than the distance from the first doping region 801 or the second doping region 801 to the first surface S1 .

[0108] like Fig.15 As shown, a pyramid velvet structure is formed on the second surface S2 and the bottom surface of the groove. In some embodiments, an alkaline etching solution containing a velvet-making additive can be used to form the pyramid velvet structure on the second surface S2 and the bottom surface of the groove.

[0109] like Fig.16 As shown, in Fig.15 A first passivation layer 851 is conformally covered on the structure close to the first surface S1 of the substrate 80, and a first anti-reflection layer 852 and a first connecting member 13" are sequentially formed on the first passivation layer 851. The first passivation layer 851 can cover the surface of the first polysilicon layer 82 and the second polysilicon layer 84 away from the substrate 80, as well as the sidewall and bottom surface of the trench in the isolation area A3.

[0110] In some embodiments, the first connector 13 ″ may be formed on the first anti-reflection layer 852 by depositing a gallium nitride layer on the first anti-reflection layer 852 using a chemical vapor deposition process, and obtaining the first connector 13 ″ by a patterning process.

[0111] like Fig.17 As shown, in Fig.16 A second passivation layer 86 and a second anti-reflection layer 87 are sequentially disposed on the structure close to the second surface S2 of the substrate 80 .

[0112] like Fig.18 As shown, a first via hole 853 penetrating the first connector 13 ″, the first anti-reflection layer 852 and the first passivation layer 851 may be provided in the first region A1, and the first electrode 11 may be provided in the first via hole 853; and a second via hole 854 penetrating the first connector 13 ″, the first anti-reflection layer 852 and the first passivation layer 851 may be provided in the second region A2, and the second electrode 12 may be provided in the second via hole 854, so as to obtain the following: Fig. 9 The structure shown.

[0113] See also Fig.19 As shown, Fig.19 1 is a schematic diagram of the volt-ampere characteristic curve of a back-contact solar cell provided by a specific example of the present application. The back-contact solar cell may include N cells connected in series. When working normally, as shown in curve 1, the working current of the N cells is lower than the short-circuit current I SC , for I MP When a single cell among N cells is blocked, the volt-ampere characteristic curve of the blocked cell in forward operation is shown in curve 2. At this time, the operating current I of the remaining N-1 cells in the battery string is MP Greater than the short-circuit current I of the shaded cell SC ', since N cells are connected in series, the current of N-1 cells will become I SC ', so the battery will be in a reverse bias state. In the reverse bias state, the current of the blocked battery cell will increase further until it increases to I MP . As the current increases, once the voltage of (N-1) cells, i.e., Voc+0.7V, is reached, the overall voltage of the N cells is zero; as the current continues to increase, the entire battery string will be reverse biased, and the bypass diode in the battery string will work, reversely blocking the battery string. When a first connector and / or a second connector is provided between the first electrode and the second electrode of the shielded cell, a leakage current gain will be generated, as shown in curve 3, so that the current of the shielded cell reaches the working current I of the battery string. MP When the voltage of the shaded cell does not exceed the breakdown voltage of the entire battery string when it is reverse biased, that is, Voc+0.7V. At this time, the entire battery string will not be reversely cut off by the bypass diode, thus protecting the entire battery string. While solving the hot spot effect, it is also beneficial to increase the output power of the photovoltaic module.

[0114] So far, the technical solutions of the present application have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present application is obviously not limited to these specific embodiments. Without departing from the principles of the present application, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the protection scope of the present application.

Claims

1. A back contact solar cell, characterized in that: It comprises a plurality of battery cells, each of which comprises a first electrode and a second electrode, and at least some of the battery cells are further provided with a first connector for conductively connecting the first electrode and the second electrode of the corresponding battery cell.

2. The back contact solar cell according to claim 1, characterized in that: The resistance between the first electrode and the second electrode on the battery cell provided with the first connector is a preset percentage of the initial resistance between the first electrode and the second electrode of the corresponding battery cell when the first connector is not provided, wherein the preset percentage is greater than 30% and less than 100%.

3. The back contact solar cell according to claim 1, characterized in that: The first connecting member is disposed between the first electrode and the second electrode of the corresponding battery cell in at least one of a straight line, an oblique line, and a bend.

4. The back contact solar cell according to claim 1, characterized in that: The first connection member includes a plurality of connection sub-components, and the plurality of connection sub-components are disposed at intervals between the first electrode and the second electrode of the corresponding battery cell.

5. The back-contact solar cell according to any one of claims 1 to 4, characterized in that: It also includes a second connector, which is used to conductively connect the first electrode of any one of the multiple battery cells to the second electrode of another adjacent battery cell.

6. The back contact solar cell according to claim 5, characterized in that: The plurality of battery cells are arranged in an array.

7. The back contact solar cell according to claim 6, characterized in that: The second connecting member is used to electrically conductively connect a second electrode of one battery cell to a first electrode of the other battery cell of two battery cells in the same column.

8. The back contact solar cell according to claim 6, characterized in that: The second connecting member is used to electrically conductively connect the second electrode of one battery cell to the first electrode of the other battery cell of two battery cells in adjacent columns and adjacent rows.

9. The back contact solar cell according to claim 1, characterized in that: The battery cell includes an HBC battery cell or a TBC battery cell.

10. The back contact solar cell according to claim 9, characterized in that: The battery cell comprises a TBC battery cell, and the TBC battery cell comprises: A substrate, the substrate comprising a first surface and a second surface arranged opposite to each other; the first surface comprising a first area, a second area and an isolation area between the first area and the second area; A first tunneling oxide layer and a first polysilicon layer are sequentially disposed in the first region of the first surface and in a direction away from the substrate; A second tunnel oxide layer and a second polysilicon layer are sequentially disposed in the second region of the first surface and in a direction away from the substrate; A stacked structure, the stacked structure comprising a first passivation layer, a first anti-reflection layer, the first connecting member, a first via hole and a second via hole; the first passivation layer is at least arranged on the surface of the first polysilicon layer and the second polysilicon layer away from the substrate; the first anti-reflection layer is arranged on the first passivation layer; the first via hole is arranged in the first region, and the second via hole is arranged in the second region; the first electrode and the second electrode; A second passivation layer and a second anti-reflection layer are sequentially disposed on a side of the second surface away from the substrate; Wherein, the first electrode is disposed in the first via hole and is electrically connected to the first polysilicon layer through the first via hole; The second electrode is disposed in the second via hole and is electrically connected to the second polysilicon layer through the second via hole; The first connecting member is disposed on the surface of the first polysilicon layer, the second polysilicon layer, and the isolation region away from the substrate.

11. The back contact solar cell according to claim 10, characterized in that: The first connecting member is disposed on a surface of the first anti-reflection layer away from the substrate.

12. A photovoltaic module, characterized in that: A back-contact solar cell comprising the method according to any one of claims 1 to 11.

13. A method for preparing a back contact solar cell, characterized in that: include: A plurality of battery cells are formed on a substrate; each of the plurality of battery cells comprises a first electrode and a second electrode, and at least some of the plurality of battery cells are further provided with a first connector for conductively connecting the first electrode and the second electrode of the corresponding battery cell.

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