Back contact solar cell and photovoltaic module

Abstract

The back contact solar cell comprises a silicon substrate, a first passivation layer, a protection layer, a first electrode and a second electrode, the silicon substrate is provided with a first surface and a second surface which are opposite to each other, and one side of the second surface of the silicon substrate is provided with a P-type conductive region and an N-type conductive region which are arranged at intervals; the first passivation layer is arranged on the first surface of the silicon substrate, the protection layer is arranged on the side, away from the silicon substrate, of the first passivation layer, the first electrode is electrically connected with the P-type conductive region, and the second electrode is electrically connected with the N-type conductive region. The protection layer can prevent other stacked back contact solar cells or other objects from making contact with the surface of the first passivation layer, and the surface of the first passivation layer is prevented from being scratched or damaged by other objects, so that the passivation effect of the first passivation layer on the first surface is guaranteed, and the photoelectric conversion efficiency of the back contact solar cells is improved. In addition, due to the arrangement of the protective layer, the surface of the first passivation layer can still be well protected when the multiple back contact solar cells are stacked irregularly, and an isolation part does not need to be additionally arranged between every two adjacent back contact solar cells in the sorting and collecting process. The sorting and collecting efficiency of a plurality of back contact solar cells can be improved, the structure is simple, preparation is convenient, and the preparation cost is saved.

Description

Technical Field

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

[0002] A solar cell is a photoelectric semiconductor wafer that uses sunlight to generate electricity directly. It is also called a "solar chip" or "photovoltaic cell". As long as it is illuminated by light that meets certain illumination conditions, it can instantly output voltage and generate current in the presence of a circuit.

[0003] Back contact solar cells, referred to as IBC (Interdigitated back contact) cells, have no metal grid lines on the front, and the positive and negative metal electrodes are arranged in a cross-finger shape on the back. Because there is no grid line blocking the front, it has a good photoelectric conversion efficiency. However, in the process of printing metal grid lines on the cell and sending it to the assembly, it is easy to cause damage to the film layer on the front of the cell. At present, separators are usually added between two cells, but in the process of sorting and collecting, uneven collection of cells or misalignment of separators will still increase the risk of scratching the film layer on the front of the cell. Summary of the invention

[0004] In view of this, the present application provides a back-contact solar cell and photovoltaic module, so as to solve the problem in the prior art that the front film layer of the cell is easily damaged during the process of printing metal grid lines on the cell and then delivering it to the module.

[0005] In a first aspect, the present application provides a back-contact solar cell, comprising a silicon substrate, a first passivation layer, a protective layer, a first electrode, and a second electrode, wherein the silicon substrate has a first surface and a second surface opposite to each other, a P-type conductive region and an N-type conductive region arranged at intervals are arranged on one side of the second surface of the silicon substrate, the first passivation layer is arranged on the first surface of the silicon substrate, the protective layer is arranged on a side of the first passivation layer away from the silicon substrate, the first electrode is electrically connected to the P-type conductive region, and the second electrode is electrically connected to the N-type conductive region.

[0006] In a possible design, along the thickness direction of the back contact solar cell, the projected area of ​​the protection layer is 2% to 3% of the projected area of ​​the silicon substrate.

[0007] In a possible design, the thickness of the protective layer is H1, 5 μm≤H1≤60 μm.

[0008] In a possible design, the protection layer includes a plurality of support members, and the plurality of support members are arranged at intervals on a side of the first passivation layer facing away from the silicon substrate.

[0009] In a possible design, the distance between the geometric centers of two adjacent support members is d, 0<d≤20 mm.

[0010] In one possible design, in a direction perpendicular to the thickness of the back-contact solar cell, the cross-sectional shape of the support member is one or more combinations of circular, semicircular, annular, rectangular, triangular, diamond, W-shaped, and V-shaped.

[0011] In a possible design, in a direction perpendicular to the thickness of the back-contact solar cell, the cross-sectional shape of the support member is circular, and the radius of the circle is R1, where 0<R1≤4 mm.

[0012] In one possible design, in the direction perpendicular to the thickness of the back-contact solar cell, the cross-sectional shape of the support member is a strip structure formed by a combination of a semicircle and a rectangle, the radius of the semicircle is R2, 0<R2≤2mm, and the length of the rectangle is L, 1≤L / R2≤5.

[0013] In a possible design, the protective layer is a transparent protective layer.

[0014] In a possible design, the material of the protective layer is one or more combinations of acrylic resin, epoxy resin, polyurethane, and silicone.

[0015] A second aspect of the present application provides a photovoltaic module, which includes a cell string, a packaging layer and a cover plate. The cell string is formed by connecting a plurality of back-contact solar cells as in any embodiment. The packaging layer is used to cover the surface of the cell string protective layer, and the cover plate is used to cover the surface of the packaging layer away from the cell string.

[0016] In the present application, the protective layer is arranged on one side of the first surface of the back silicon substrate of the first passivation layer, and can block the contact between other back-contact solar cells or other objects stacked on each other and the surface of the first passivation layer, so that the first passivation layer can be protected during sorting and collection after the first electrode and the second electrode are printed on the back-contact solar cell or during the process of assembling into a photovoltaic module, and the surface of the first passivation layer is prevented from being scratched or damaged by other objects, thereby ensuring the passivation effect of the first passivation layer on the first surface and improving the photoelectric conversion efficiency of the back-contact solar cell.

[0017] In addition, since the protective layer is directly arranged on the side of the first passivation layer away from the silicon substrate, it will not produce relative displacement with respect to the surface of the first passivation layer. It can still have a good protective effect on the surface of the first passivation layer when multiple back-contact solar cells are not stacked evenly. There is no need to add an isolation component between two adjacent back-contact solar cells during the sorting and collection process. The sorting and collection efficiency of multiple back-contact solar cells can be improved. The structure is simple and easy to prepare, which saves the preparation cost of the back-contact solar cells.

[0018] It should be understood that the foregoing general description and the following detailed description are exemplary only and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0020] Figure 1 A cross-sectional structural diagram of a back-contact solar cell provided in the present application in a specific embodiment;

[0021] Figure 2 A cross-sectional structural diagram of another specific embodiment of a back-contact solar cell provided in the present application;

[0022] Figure 3 A schematic diagram of a portion of the structure of a back-contact solar cell provided in this application;

[0023] Figure 4 A top view of a back-contact solar cell provided in the present application in a specific embodiment;

[0024] Figure 5 for Figure 4 A partial enlarged view of the middle A;

[0025] Figure 6 A top view of a back-contact solar cell provided in the present application in another specific embodiment;

[0026] Figure 7 for Figure 6 A partial enlarged view of point B in the middle;

[0027] Figure 8 This is a schematic diagram of the structure of the photovoltaic module provided in this application.

[0028] Reference numerals:

[0029] 100-back contact solar cell;

[0030] 1-Silicon substrate;

[0031] 11- first surface;

[0032] 12- second surface;

[0033] 121-P type conductive area;

[0034] 122-N type conductive area;

[0035] 2- first electrode;

[0036] 3- second electrode;

[0037] 4- Protective layer;

[0038] 41- support member;

[0039] 5- first passivation layer;

[0040] 6-a first doped conductive layer;

[0041] 7- a second doped conductive layer;

[0042] 8- second passivation layer;

[0043] 9- anti-reflection layer;

[0044] 10a-a first tunnel dielectric layer;

[0045] 10b- a second tunnel dielectric layer;

[0046] 110-battery string;

[0047] 120-encapsulation layer;

[0048] 130-cover plate;

[0049] X-first direction;

[0050] Y-second direction;

[0051] Z-thickness direction.

[0052] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application. DETAILED DESCRIPTION

[0053] In order to better understand the technical solution of the present application, the embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0054] In the description of this application, unless otherwise clearly specified and limited, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance; unless otherwise specified or explained, the term "plurality" refers to two or more; the terms "connected" and "fixed" should be understood in a broad sense, for example, "connected" can be a fixed connection, a detachable connection, an integral connection, or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0055] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a", "said" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0056] It should be understood that the term "and / or" used in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0057] It should be noted that the directional words such as "upper", "lower", "left", and "right" described in the embodiments of the present application are described at the angles shown in the accompanying drawings and should not be understood as limiting the embodiments of the present application. In addition, in the context, it is also necessary to understand that when it is mentioned that an element is connected to another element "upper" or "lower", it can not only be directly connected to another element "upper" or "lower", but also indirectly connected to another element "upper" or "lower" through an intermediate element.

[0058] Back contact solar cells, referred to as IBC (Interdigitated back contact) cells, have no metal grid lines on the front, and the positive and negative metal electrodes are arranged in a cross-finger shape on the back. Because there is no grid line blocking the front, it has a good photoelectric conversion efficiency. However, when the cell is printed with metal grid lines and sent to the assembly, multiple cells are stacked on each other, which can easily cause damage to the film layer on the front of the cell. At present, separators are usually added between two cells, but in the process of sorting and collecting, uneven collection of cells or misalignment of separators will still increase the risk of scratching the film layer on the front of the cell.

[0059] Based on this, the present application provides a back-contact solar cell and a photovoltaic module. The back-contact solar cell includes but is not limited to, for example, an interdigitated back contact (IBC) cell, a hybrid passivated back contact (HPBC) cell, a tunneling oxide passivated contact Back Contact (TBC) cell, a heterojunction Back Contact (HBC) cell, etc., and is not limited here.

[0060] The present application is further described in detail below through specific embodiments and in conjunction with the accompanying drawings.

[0061] Among them, Figure 1 As shown, the back contact solar cell 100 has a length direction, a width direction and a thickness direction Z. For ease of understanding, the width direction of the back contact solar cell 100 is defined as a first direction X, and the length direction is defined as a second direction Y below.

[0062] like Figure 1 As shown, the back contact solar cell 100 includes a silicon substrate 1, a first passivation layer 5, a protective layer 4, a first electrode 2, and a second electrode 3. The silicon substrate 1 has a first surface 11 and a second surface 12 opposite to each other, the first passivation layer 5 is arranged on the first surface 11 of the silicon substrate 1, and the protective layer 4 is arranged on the side of the first passivation layer 5 away from the silicon substrate 1. A P-type conductive region 121 and an N-type conductive region 122 arranged at intervals are arranged on one side of the second surface 12 of the silicon substrate 1, the first electrode 2 is electrically connected to the P-type conductive region 121, and the second electrode 3 is electrically connected to the N-type conductive region 122.

[0063] Among them, the silicon substrate 1 is used to receive incident light and generate photogenerated carriers. The first surface 11 of the silicon substrate 1 can refer to the light-receiving surface, that is, the surface irradiated by the structured sunlight, and the second surface 12 of the silicon substrate 1 refers to the surface opposite to the first surface 11. In some embodiments, the silicon substrate 1 is a silicon substrate, which can include one or more of single crystal silicon, polycrystalline silicon, amorphous silicon or microcrystalline silicon. In other embodiments, the material of the silicon substrate 1 can also be silicon carbide, organic material or multi-component compound. Multi-component compounds can include but are not limited to materials such as perovskite, gallium arsenide, cadmium telluride, copper indium selenide, etc. Exemplarily, in the present application, the silicon substrate 1 is a single crystal silicon substrate. The silicon substrate 1 has doping elements, and the conductivity type of the doping elements can be N-type or P-type. The N-type element can be a V-group element such as phosphorus (P), bismuth (Bi), antimony (Sb) or arsenic (As), and the P-type element can be a III-group element such as boron (B), aluminum (Al), gallium (Ga) or indium (In). For example, when the silicon substrate 1 is a P-type silicon substrate, the conductivity type of the doped element inside it is P-type. For another example, when the silicon substrate 1 is an N-type silicon substrate, the conductivity type of the doped element inside it is N-type. Exemplarily, in the embodiment of the present application, the silicon substrate 1 is an N-type silicon substrate to improve the photoelectric conversion efficiency of the back contact solar cell 100 and reduce the manufacturing cost.

[0064] The first electrode 2 and the second electrode 3 are used to collect and aggregate the current of the back contact solar cell 100. Exemplarily, the first electrode 2 and the second electrode 3 can be prepared by screen printing and sintering. In some embodiments, the metal paste used to prepare the first electrode 2 and the second electrode 3 can be one or more of aluminum, silver, gold, nickel, molybdenum or copper, which is not limited here.

[0065] The first passivation layer 5 can achieve good passivation of the first surface 11 of the silicon substrate 1, reduce the interface state density, reduce the recombination of minority carriers, improve the transmission efficiency of carriers at the interface, and improve the photoelectric conversion efficiency of the back contact solar cell 100. Exemplarily, the first passivation layer 5 can be deposited by plasma enhanced chemical vapor deposition. Of course, other methods, such as organic chemical vapor deposition, can also be used to form the first passivation layer 5. Among them, the first passivation layer 5 can be a single-layer structure or a stacked structure, and the thickness of each layer can be designed accordingly. Specifically, the first passivation layer 5 can be a combination of any one or more of a silicon nitride layer, a silicon oxynitride layer, a silicon oxide layer, and an aluminum oxide layer. Of course, the first passivation layer 5 can also use other types of passivation layers, which are not limited here.

[0066] In this embodiment, Figure 1 As shown, the protective layer 4 is arranged on one side of the first surface 11 of the back silicon substrate 1 of the first passivation layer 5, and can block the contact between other back-contact solar cells 100 or other objects stacked on each other and the surface of the first passivation layer 5, so that the first passivation layer 5 can be protected during sorting and collection after the first electrode 2 and the second electrode 3 are printed on the back-contact solar cell 100, or during the process of assembling into a photovoltaic module, to prevent the surface of the first passivation layer 5 from being scratched or damaged by other objects, thereby ensuring the passivation effect of the first passivation layer 5 on the first surface 11 and improving the photoelectric conversion efficiency of the back-contact solar cell 100.

[0067] In addition, since the protective layer 4 is directly arranged on the side of the first passivation layer 5 away from the silicon substrate 1, it will not produce relative displacement with respect to the surface of the first passivation layer 5. It can still have a good protective effect on the surface of the first passivation layer 5 when multiple back-contact solar cells 100 are not stacked neatly, and there is no need to add an isolation component between two adjacent back-contact solar cells 100 during the sorting and collection process. The sorting and collection efficiency of multiple back-contact solar cells 100 can be improved, and the structure is simple and easy to prepare, which saves the preparation cost of the back-contact solar cells 100.

[0068] Among them, Figure 1 and Figure 2 As shown, the back-contact solar cell 100 further includes a first doped conductive layer 6 , a second doped conductive layer 7 and a second passivation layer 8 .

[0069] The first doped conductive layer 6 is disposed in the P-type conductive region 121 of the second surface 12 of the silicon substrate 1. The first doped conductive layer 2 can be used as an emitter, and the first doped conductive layer 2 and the substrate 1 have different doping element types, and the two can together form a PN junction structure. Exemplarily, when the substrate 1 is an N-type silicon substrate, the P-type first doped conductive layer 2 can be formed by boron diffusion of the silicon substrate 1 at the P-type conductive region 121.

[0070] The second doped conductive layer 7 is arranged on the N-type conductive region 122 of the second surface 12 of the silicon substrate 1. The doping elements in the second doped conductive layer 7 are the same as those in the silicon substrate 1, and a concentration difference is formed between the second doped conductive layer 7 and the silicon substrate 1, so that the second doped conductive layer 7 can form a good contact with the second electrode 3, and can form a band bending on the surface of the N-type conductive region 122, realize the selective transmission of carriers, and reduce the recombination loss. The second doped conductive layer 7 can be deposited on the N-type conductive region 122 by any one of physical vapor deposition, chemical vapor deposition, plasma enhanced chemical vapor deposition, and atomic layer deposition.

[0071] The second passivation layer 8 is arranged on the side of the first doped conductive layer 6 and the second doped conductive layer 7 away from the silicon substrate 1 and at least a portion of the second surface 12. The second passivation layer 8 can achieve a good passivation effect on the side of the first doped conductive layer 6 and the second doped conductive layer 7 away from the silicon substrate 1 and at least a portion of the second surface 12. Exemplarily, the second passivation layer 8 can be deposited by plasma enhanced chemical vapor deposition. Of course, other methods, such as organic chemical vapor deposition, can also be used to form the second passivation layer 8. Among them, the second passivation layer 8 can be a single-layer structure or a stacked structure, and the thickness of each layer can be designed accordingly. Specifically, the second passivation layer 8 can be a combination of any one or more of a silicon nitride layer, a silicon oxynitride layer, a silicon oxide layer, and an aluminum oxide layer. Of course, the second passivation layer 8 can also use other types of passivation layers, which are not limited here.

[0072] The first electrode 2 is electrically connected to the first doped conductive layer 6 through the second passivation layer 8 , and the second electrode 3 is electrically connected to the second doped conductive layer 7 through the second passivation layer 8 .

[0073] It should be noted that, for example, Figure 1 As shown, the P-type conductive region 121 and the N-type conductive region 122 can be formed on the surface of the second surface 12 of the silicon substrate 1; illustratively, the P-type conductive region 121 and the N-type conductive region 122 can also be formed under the surface of the second surface 12 of the silicon substrate 1, that is, the P-type conductive region 121 and the N-type conductive region 122 are formed inside the silicon substrate 1. Of course, the P-type conductive region 121 and the N-type conductive region 122 can also be partially formed on the second surface 12, or partially formed under the second surface 12, which can be specifically set according to actual needs and is not limited here.

[0074] In addition, if Figure 2 As shown, the back-contact solar cell 100 may further include an anti-reflection layer 9 , which is disposed between the first passivation layer 5 and the protective layer 4 .

[0075] The anti-reflection layer 9 can reduce or eliminate the reflected light on the surface of the back contact solar cell 100, increase the light transmittance, and further improve the photoelectric conversion efficiency of the back contact solar cell 100. Among them, the anti-reflection layer 9 can be a silicon nitride layer, so as to further reduce the difficulty of preparing the back contact solar cell 100 and improve the preparation efficiency. Of course, the anti-reflection layer 9 can also be a silicon oxynitride layer or a single layer or stacked layer structure composed of silicon nitride and silicon oxynitride, or it can also be other anti-reflection film layer structures, which are not limited here.

[0076] In a specific embodiment, Figure 2 As shown, the back-contact solar cell 100 may further include a first tunneling dielectric layer 10a and a second tunneling dielectric layer 10b, wherein the first tunneling dielectric layer 10a is disposed between the first doped conductive layer 6 and the silicon substrate 1, and the second tunneling dielectric layer 10b is disposed between the second doped conductive layer 7 and the silicon substrate 1.

[0077] like Figure 2 As shown, the first tunnel dielectric layer 10a and the second tunnel dielectric layer 10b reduce the interface state density between the silicon substrate 1 and the first doped conductive layer 6 and the second doped conductive layer 7 through chemical passivation, reduce the recombination of minority carriers and holes, and improve the passivation effect on the surface of the silicon substrate 1. The first tunnel dielectric layer 10a and the second tunnel dielectric layer 10b can also allow the majority carriers to tunnel into the first doped conductive layer 6 and the second doped conductive layer 7, thereby allowing the majority carriers and to be laterally transmitted in the first doped conductive layer 6 and the second doped conductive layer 7, thereby facilitating the first electrode 2 and the second electrode 3 to collect carriers, and facilitating the improvement of the open circuit voltage and short circuit current of the back contact solar cell 100. In addition, the first tunnel dielectric layer 10a and the second tunnel dielectric layer 10b can also form a passivation contact structure with the first doped conductive layer 6 and the second doped conductive layer 7, respectively, which can achieve excellent interface passivation and selective collection of carriers, and improve the photoelectric conversion efficiency of the back contact battery 100.

[0078] Among them, the materials of the first tunneling dielectric layer 10a and the second tunneling dielectric layer 10b may include but are not limited to silicon oxide, silicon nitride, silicon oxynitride, molybdenum oxide, hafnium oxide, silicon carbide, magnesium fluoride, nanocrystalline silicon, intrinsic amorphous silicon and intrinsic polycrystalline silicon, etc., which are dielectric materials with tunneling effects, and are made of a single layer or a stacked layer structure. In other embodiments, the first tunneling dielectric layer 10a and the second tunneling dielectric layer 10b may also be an oxygen-containing silicon nitride layer, an oxygen-containing silicon carbide layer, etc., which are not limited here. In some feasible implementations, a tunneling layer may be formed on the second surface 12 side of the silicon substrate 1 by methods such as ozone oxidation, high-temperature thermal oxidation, nitric acid oxidation, chemical vapor deposition, and low-pressure chemical vapor deposition.

[0079] In a specific embodiment, Figure 3 As shown, the thickness of the protective layer 4 is H1, 5μm≤H1≤60μm. For example, the thickness H1 of the protective layer 4 can be 5μm, 10μm, 15μm, 20μm, 25μm, 30μm, 35μm, 40μm, 45μm, 50μm, 55μm, 60μm, etc. Of course, the thickness H1 of the protective layer 4 can also be other values ​​within the above range, which can be designed according to actual needs and is not limited here.

[0080] In this embodiment, Figure 1 to Figure 3 As shown, if the thickness H1 of the protective layer 4 is too large, for example, H1>60μm, then the overall thickness of the back contact solar cell 100 will increase, and the preparation cost of the back contact solar cell 100 will increase. In addition, when assembled into a photovoltaic module, the excessive thickness H1 of the protective layer 4 may also easily lead to a decrease in the fit between the back contact solar cell 100 and other components, and increase the difficulty of setting a film structure such as an encapsulation layer on the surface of the back contact solar cell 100, thereby increasing the difficulty of assembling the photovoltaic module. If the thickness H1 of the protective layer 4 is too small, for example, H1<5μm, the protective isolation effect of the protective layer 4 is poor, and when multiple back contact solar cells 100 are stacked on each other, the surface of the first passivation layer 5 is still at risk of being scratched and damaged.

[0081] Therefore, when the thickness H1 of the protective layer 4 satisfies 5μm≤H1≤60μm, the thickness of the protective layer 4 is moderate, has a high protective isolation effect, can protect the surface of the first passivation layer 5 from being scratched and damaged, and has a low preparation cost and is easy to prepare and form, which is beneficial to the mass production of back-contact solar cells 100 and also facilitates the assembly of photovoltaic modules.

[0082] Furthermore, if Figure 1 and Figure 2 As shown, the maximum thickness H2 between the surface of the second passivation layer 8 facing away from the silicon substrate 1 and the surface of the first passivation layer 5 (or the anti-reflection layer 9) facing away from the silicon substrate 1 in the back-contact solar cell 100, that is, the sum of the maximum thicknesses of each film layer of the back-contact solar cell 100 except the protective layer 4, the first electrode 2 and the second electrode 3, can be between 90μm and 210μm, so as to enhance the design freedom of the back-contact solar cell 100, which can be specifically set according to actual needs and is not limited here.

[0083] In a specific embodiment, Figure 4As shown, along the thickness direction Z of the back contact solar cell 100, the projected area of ​​the protective layer 4 is 2% to 3% of the projected area of ​​the silicon substrate 1. For example, the projected area of ​​the protective layer 4 is 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3%, etc. of the projected area of ​​the silicon substrate 1. Of course, other values ​​within the above range are also possible, which can be set according to actual needs and are not limited here.

[0084] like Figure 1 and 4 As shown, if the projection area of ​​the protective layer 4 is too large, for example, greater than 3% of the projection area of ​​the silicon substrate 1, it will affect the absorption of light by the silicon substrate 1, resulting in more obvious optical loss and more current loss, which can easily reduce the photoelectric conversion efficiency of the back-contact solar cell 100. For example, when the projection area of ​​the protective layer 4 is greater than 5% of the projection area of ​​the silicon substrate 1, the current loss is greater than 50 mA, and the photoelectric conversion efficiency of the back-contact solar cell 100 is reduced.

[0085] If the projection area of ​​the protective layer 4 is too small, for example, less than 2% of the projection area of ​​the silicon substrate 1, the exposed area of ​​the first passivation layer 5 is large. When two adjacent back-contact solar cells 100 are stacked unevenly and staggered with each other, the surface of the first passivation layer 5 is still at risk of being scratched and damaged, and the protective isolation effect of the protective layer 4 is poor.

[0086] In this embodiment, Figure 4 As shown, when the projection area of ​​the protective layer 4 is 2% to 3% of the projection area of ​​the silicon substrate 1, the protective layer 4 has little effect on the light absorption of the silicon substrate 1, the optical loss is small, and the current loss is low. In this embodiment, when the projection area of ​​the protective layer 4 is 2% to 3% of the projection area of ​​the silicon substrate 1, the current loss is less than 30Ma. At the same time, the protective layer 4 has a good protective isolation effect, and can protect the first passivation layer 5 and other film layers on the first surface 11 of the silicon substrate 1 from being scratched and damaged, thereby ensuring that the back contact solar cell 100 has a high photoelectric conversion efficiency.

[0087] In a specific embodiment, the protective layer 4 is a transparent protective layer, which allows light to penetrate the protective layer 4 and enter the first surface 11 , thereby further reducing optical losses and improving the photoelectric conversion efficiency of the back contact solar cell 100 .

[0088] In a specific embodiment, the material of the protective layer 4 is one or more combinations of acrylic resin, epoxy resin, polyurethane, and silicone.

[0089] The acrylic resin, epoxy resin, polyurethane, silicone and other materials of the adhesive system have high transparency, good light and color retention, water and chemical resistance, low cost, and are not easy to damage the film layers such as the first passivation layer 5 on the first surface 11 and the back contact solar cell 100 in contact therewith, further reducing optical losses and saving costs.

[0090] In a specific embodiment, Figures 4 to 6 As shown, the protection layer 4 includes a plurality of support members 41 , and the plurality of support members 41 are arranged at intervals on a side of the first passivation layer 5 facing away from the silicon substrate 1 .

[0091] In this embodiment, Figure 4 and Figure 6 As shown, the support member 41 can maintain a certain distance between the first passivation layer 5 disposed on the first surface 11 and other back-contact solar cells 100 or other objects stacked on each other, thereby preventing the surface of the first passivation layer 5 from contacting other objects and causing scratches and damage. Moreover, a plurality of support members 41 form a protective layer, which can make the protective layer 4 uniformly disposed on the side of the first passivation layer 5 away from the silicon substrate 1, thereby improving the protective layer 4 to provide uniform support force to the objects stacked on its surface, so that relative sliding is not easy to occur, thereby ensuring the stability of the plurality of back-contact solar cells 100 in the process of stacking each other, and further reducing the risk of scratches and damage to the first passivation layer 5 and other film layers on the first surface 11. In addition, the protective layer 4 is composed of a plurality of support members 41, which can further reduce the projection area of ​​the protective layer 4 on the silicon substrate 1, thereby ensuring that the protective layer 4 has a high protective isolation effect while further reducing the optical loss of the back-contact solar cell 100.

[0092] In a specific embodiment, Figure 5 and Figure 7 As shown, the distance between the geometric centers of two adjacent support members 41 is d, 0<d≤20mm. For example, the distance d between the geometric centers of two adjacent support members 41 can be 1mm, 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, 11mm, 12mm, 15mm, 18mm, 20mm, etc. Of course, the distance d between the geometric centers of two adjacent support members 41 can also be other values ​​within the above range, which can be set according to actual needs and is not limited here.

[0093] like Figure 4 to Figure 7As shown, if the distance d between the geometric centers of two adjacent support members 41 is too large, for example d>20mm, the distance between the two adjacent support members 41 is too far, so that the back-contact solar cell 100 or other objects stacked on the protective layer 4 can easily pass through the gap between the two adjacent support members 41 and come into contact with the first passivation layer 5 and other film structures on the first surface 11, thereby scratching and damaging the first passivation layer 5 and other film structures on the first surface 11.

[0094] In this embodiment, Figure 4 to Figure 7 As shown, when the distance d between the geometric centers of two adjacent support members 41 satisfies 0<d≤20mm, the distance between the two adjacent support members 41 is moderate, and the back-contact solar cell 100 or other objects stacked on the protective layer 4 are not easy to extend between the two adjacent support members 41, thereby further improving the protective isolation effect of the protective layer 4, avoiding the back-contact solar cell 100 or other objects from contacting the film structure such as the first passivation layer 5 on the first surface 11, and reducing the risk of scratches and damage to the film structure such as the first passivation layer 5 on the first surface 11.

[0095] In a specific embodiment, in the thickness direction Z perpendicular to the back-contact solar cell 100, the cross-sectional shape of the support member 41 is one or more combinations of circular, semicircular, annular, rectangular, triangular, diamond, W-shaped, and V-shaped. The structure is simple, which facilitates the preparation of the protective layer 4 and can enhance the design freedom of the back-contact solar cell 100.

[0096] Of course, the cross-sectional shape of the support member 41 may also be a pentagon, a hexagon or other irregular pattern shapes, which can be specifically set according to actual needs and is not limited here.

[0097] In a specific embodiment, Figure 4 and Figure 5 As shown, in the thickness direction Z perpendicular to the back contact solar cell 100, that is, in the plane of the first direction X and the second direction Y, the cross-sectional shape of the support member 41 is circular. This structure is simple and easy to prepare, thereby further reducing the difficulty of preparing the protective layer 4 and saving costs.

[0098] like Figure 4 and Figure 5 As shown, the radius of the circle is R1, 0<R1≤4mm. For example, R1 can be 0.5mm, 0.75mm, 0.8mm, 1mm, 1.2mm, 1.5mm, 1.6mm, 1.8mm, 2mm, 2.5mm, 3mm, 3.5mm, 4mm, etc. Of course, the radius R1 of the circle can also be other values ​​within the above range, which can be set according to actual needs and is not limited here.

[0099] When the cross-sectional shape of the support member 41 is circular, the projected area S of the protective layer 4 can be calculated by the formula: Calculated. Where S is the projected area of ​​the protective layer 4, in mm 2 R1 is the cross-sectional radius of the support member 41, in mm; M is the projection area of ​​the silicon substrate 1 in the thickness direction Z, in mm 2 ; d is the distance between the geometric centers of the two adjacent support members 41, in mm.

[0100] According to the formula It can be seen that the projection area S of the protective layer 4 is proportional to the cross-sectional radius R1 of the support member 41. Therefore, if R1 is too large, the projection area of ​​a single support member 41 will be larger, which will easily make the projection area S of the protective layer 4 too large, and easily increase the optical loss of the back contact solar cell 100, thereby reducing the photoelectric conversion efficiency of the back contact solar cell 100.

[0101] Therefore, when the cross-sectional shape of the support member 41 is circular and its radius R1 satisfies 0<R1≤4mm, the projection area of ​​a single support member 41 will not be too large, which can ensure that the support member 41 has a certain supporting force, so that the protective layer 4 can have a good protective isolation effect. At the same time, this structural setting can prevent the projection area S of the protective layer 4 from being too large, thereby reducing the optical loss caused by the protective layer 4, thereby ensuring that the back contact solar cell 100 can have a higher photoelectric conversion efficiency.

[0102] In another specific embodiment, Figure 6 and Figure 7 As shown, in the thickness direction Z perpendicular to the back contact solar cell 100, that is, in the plane of the first direction X and the second direction Y, the cross-sectional shape of the support member 41 is a strip structure formed by combining a semicircle and a rectangle. The support member 41 of this structure has the advantages of simple structure and easy preparation, and can improve the supporting effect of the support member 41.

[0103] Specifically, the support member 41 of the strip structure is composed of a rectangle and two semicircles arranged at opposite ends of the rectangle. Figure 7 As shown, two semicircles are arranged on opposite sides of the rectangle along the second direction Y, and the width of the rectangle along the first direction X is the same as the diameter of the semicircle.

[0104] like Figure 6 and Figure 7As shown, the radius of the semicircle in the cross section of the support member 41 is R2, 0<R2≤2mm. For example, R2 can be 0.5mm, 0.75mm, 0.8mm, 1mm, 1.2mm, 1.5mm, 1.6mm, 1.8mm, 2mm, etc. Of course, the radius R2 of the semicircle can also be other values ​​within the above range, which can be set according to actual needs and is not limited here.

[0105] The length of the rectangle in the cross section of the support member 41 is L, 1≤L / R2≤5. For example, L / R2 can be 1, 2, 3, 4, 5, etc. Of course, L / R2 can also be other values ​​within the above range, which is not limited here.

[0106] When the cross-sectional shape of the support member 41 is circular, the projected area S of the protective layer 4 can be calculated by the formula: Calculated. Where S is the projected area of ​​the protective layer 4, in mm 2 ; R2 is the radius of the semicircle in the cross section of the support member 41, in mm; L is the length L of the rectangle in the cross section of the support member 41, in mm; M is the projection area of ​​the silicon substrate 1 in the thickness direction Z, in mm 2 ; d is the distance between the geometric centers of the two adjacent support members 41, in mm.

[0107] According to the formula It can be seen that the projection area S of the protective layer 4 is proportional to the radius R2 of the semicircle and the length L of the rectangle in the cross section of the support member 41. Therefore, if R2 and L are too large, the projection area of ​​a single support member 41 is relatively large, which makes the projection area S of the protective layer 4 easy to be too large, and it is easy to increase the optical loss of the back contact solar cell 100, thereby reducing the photoelectric conversion efficiency of the back contact solar cell 100.

[0108] Therefore, when the cross-sectional shape of the support member 41 is a strip structure formed by combining a semicircle and a rectangle, and the radius R2 of the semicircle in its cross-sectional shape satisfies 0<R2≤2mm, and the length L of the rectangle satisfies 1≤L / R2≤5, the projection area of ​​a single support member 41 will not be too large, which can ensure that the support member 41 has a better supporting force, so that the protective layer 4 can have a better protective isolation effect. At the same time, this structural setting can prevent the projection area S of the protective layer 4 from being too large, thereby reducing the optical loss caused by the protective layer 4, thereby ensuring that the back contact solar cell 100 can have a higher photoelectric conversion efficiency.

[0109] A second aspect of the present application provides a photovoltaic module, such as Figure 8As shown, the photovoltaic module includes a cell string 110, an encapsulation layer 120 and a cover plate 130. The cell string 110 is formed by connecting a plurality of back-contact solar cells 100 in any of the above embodiments, the encapsulation layer 120 is used to cover the surface of the protective layer 4 of the cell string 110, and the cover plate 130 is used to cover the surface of the encapsulation layer 120 away from the cell string 110. Since the back-contact solar cell 100 has the above technical effects, the photovoltaic module including the solar cell 100 should also have the above technical effects, which will not be repeated here.

[0110] Among them, Figure 8 As shown, the back contact solar cell 100 is electrically connected in the form of a whole piece or multiple pieces to form a plurality of cell strings 110, and the plurality of cell strings 110 are electrically connected in series and / or in parallel. Specifically, the plurality of cell strings 110 may be electrically connected through a conductive tape.

[0111] The encapsulation layer 120 covers the front and back sides of the back-contact solar cell. Specifically, the encapsulation layer 120 can be an organic encapsulation film such as ethylene-vinyl acetate copolymer (EVA) film, polyethylene octene co-elastomer (POE) film, polyethylene terephthalate (PET) film or polyvinyl butyral (PVB).

[0112] The cover plate 130 may be a glass cover plate, a plastic cover plate or the like with a light-transmitting function. Specifically, the surface of the cover plate 130 facing the encapsulation layer 120 may be a concave-convex surface, thereby increasing the utilization rate of the incident light.

[0113] In this specification, the same or similar parts between the various embodiments can be referred to each other. In particular, for the device embodiment and the terminal embodiment, since they are basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the description in the method embodiment.

[0114] The above is only a specific implementation of the embodiment of the present application, but the protection scope of the embodiment of the present application is not limited thereto, and any changes or replacements within the technical scope disclosed in the embodiment of the present application should be included in the protection scope of the embodiment of the present application. Therefore, the protection scope of the embodiment of the present application should be based on the protection scope of the claims.

Claims

1. A back contact solar cell, characterized in that: include: A silicon substrate (1), the silicon substrate (1) having a first surface (11) and a second surface (12) opposite to each other, and a P-type conductive region (121) and an N-type conductive region (122) arranged at intervals are provided on one side of the second surface (12) of the silicon substrate (1); A first passivation layer (5) is disposed on a first surface (11) of the silicon substrate (1); A protective layer (4) is arranged on a side of the first passivation layer (5) facing away from the silicon substrate (1); A first electrode (2) electrically connected to the P-type conductive region (121); The second electrode (3) is electrically connected to the N-type conductive region (122).

2. The back contact solar cell according to claim 1, characterized in that: Along the thickness direction (Z) of the back-contact solar cell (100), the projection area of ​​the protective layer (4) is 2% to 3% of the projection area of ​​the silicon substrate (1).

3. The back contact solar cell according to claim 1, characterized in that: The thickness of the protective layer (4) is H1, 5 μm≤H1≤60 μm.

4. The back contact solar cell according to claim 1, characterized in that: The protective layer (4) comprises a plurality of support members (41), and the plurality of support members (41) are arranged at intervals on a side of the first passivation layer (5) facing away from the silicon substrate (1).

5. The back contact solar cell according to claim 4, characterized in that: The distance between the geometric centers of two adjacent support members (41) is d, 0<d≤20mm.

6. The back contact solar cell according to claim 4, characterized in that: In a direction (Z) perpendicular to the thickness of the back-contact solar cell (100), the cross-sectional shape of the support member (41) is one or more combinations of circular, semicircular, annular, rectangular, triangular, diamond, W-shaped, and V-shaped.

7. The back contact solar cell according to claim 4, characterized in that: In a direction (Z) perpendicular to the thickness of the back-contact solar cell (100), the cross-sectional shape of the support member (41) is circular, the radius of the circle is R1, and 0<R1≤4mm.

8. The back contact solar cell according to claim 4, characterized in that: In a direction (Z) perpendicular to the thickness of the back-contact solar cell (100), the cross-sectional shape of the support member (41) is a strip structure formed by combining a semicircle and a rectangle; The radius of the semicircle is R2, 0<R2≤2mm; The length of the rectangle is L, 1≤L / R2≤5.

9. The back contact solar cell according to any one of claims 1 to 8, characterized in that: The protective layer (4) is a transparent protective layer.

10. The back contact solar cell according to any one of claims 1 to 8, characterized in that: The material of the protective layer (4) is one or more combinations of acrylic resin, epoxy resin, polyurethane and silicone.

11. A photovoltaic module, characterized in that: The photovoltaic module comprises: A battery string (110), wherein the battery string (110) is formed by connecting a plurality of back-contact solar cells (100) as claimed in any one of claims 1 to 10; An encapsulation layer (120), the encapsulation layer (120) being used to cover the surface of the protective layer (4) of the battery string (110); A cover plate (130), the cover plate (130) being used to cover a surface of the packaging layer (120) away from the battery string (110).

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