Back-contact solar cells and photovoltaic modules

Abstract

This invention provides a back-contact solar cell and a photovoltaic module to solve the problem that the process of printing a metal grid onto a cell and then sending it to a module is prone to damaging the film layer on the front side of the cell. [Solution] The back-contact solar cell and photovoltaic module comprises a silicon substrate, a first passivation layer, a protective layer, a first electrode, and a second electrode. The silicon substrate has opposing first and second surfaces, and the second surface of the silicon substrate has spaced-apart P-type conductive regions and N-type conductive regions. The first passivation layer is provided on the first surface of the silicon substrate, and the protective layer is positioned on the 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. The protective layer prevents contact between other objects and the surface of the first passivation layer.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cells, and particularly to back contact solar cells and solar cell modules.

Background Art

[0002] A solar cell is a photovoltaic semiconductor sheet that directly generates electricity using sunlight, and is also called a "solar chip" or "photovoltaic cell". If light that satisfies a certain illumination condition is irradiated, it can instantaneously output a voltage and generate an electric current in a circuit.

[0003] A back contact solar cell called an IBC (Interdigitated back contact) cell has no metal grid on the front side, and the metal electrodes of the positive and negative poles are arranged in a fork shape on the back side. Since the front side is not blocked by grid lines, the photoelectric conversion efficiency is high. However, in the process of sending the printed metal grid lines to the module, it is easy to damage the film layer on the front side of the cell. Currently, it is common to add a paper separator between two cells, but in the process of sorting and collecting, the recovery between cells becomes uneven or the position of the paper separator shifts, which still increases the risk of damaging the front film layer of the cell. [[ID=1�]]

Summary of the Invention

Problems to be Solved by the Invention

[0004] From the above, the present invention provides a back contact solar cell and a photovoltaic module in order to easily solve the problem of the prior art that the process of printing a metal grid on the cell and then sending it to the module is likely to damage the film layer on the front side of the cell.

Means for Solving the Problems

[0005] A first aspect of the present invention 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 opposing first and second surfaces, the second surface of the silicon substrate has spaced-apart P-type conductive regions and N-type conductive regions, the first passivation layer is provided on the first surface of the silicon substrate, the protective layer is positioned on the 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 one possible design, the projected area of ​​the protective layer along the thickness direction of a back-contact solar cell is 2% to 3% of the projected area of ​​the silicon substrate.

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

[0008] In one possible design, the protective layer includes multiple support members, which are spaced apart on the side of the first passivation layer away from the silicon substrate.

[0009] In one possible design, the distance d between the geometric centers of two adjacent support members is 0 <d≦20mmである。

[0010] In a direction perpendicular to the thickness direction of a back-contact solar cell, the support member has a cross-sectional shape that is one or more combinations of the following shapes: circular, semicircular, annular, rectangular, triangular, rhombus, W-shaped, or V-shaped.

[0011] In one possible design, the cross-sectional shape of the support member is circular in the direction perpendicular to the thickness direction of the back-contact solar cell, and the radius of the circle R1 is 0 <R1≦4mmである。

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

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

[0014] In one possible design, the protective layer is made of one or a combination of acrylic resin, epoxy resin, polyurethane, and silicon.

[0015] The second aspect of the present invention provides a photovoltaic module, which includes a battery string, a sealing layer, and a cover. The battery string is composed of a plurality of connected back-contact solar cells similar to any of the embodiments. The sealing layer is used to cover the surface of the protective layer of the battery string, and the cover is used to cover the surface of the sealing layer away from the battery string.

Advantages of the Invention

[0016] In the present invention, the protective layer is provided on the side away from the first surface of the silicon substrate of the first passivation layer, and can block the contact between the surface of the first passivation layer and other back-contact solar cells or other objects stacked with each other. Thereby, in the process of sorting and collecting the back-contact solar cells after the first electrode and the second electrode are printed, or in the process of assembling them into a photovoltaic module, the first passivation layer can be protected, and it can be avoided that the surface of the first passivation layer is damaged or impaired by other objects. By doing so, the passivation effect of the first passivation layer on the first surface can be ensured, and the photoelectric conversion efficiency of the back-contact solar cell can be improved.

[0017] Furthermore, since the protective layer is provided directly on the side of the first passivation layer away from the silicon substrate, it does not shift relative to the surface of the first passivation layer. This allows for good protection of the surface of the first passivation layer even when multiple back-contact solar cells are stacked unevenly. In the sorting and collection process, there is no need to provide additional isolation members between two adjacent back-contact solar cells, thus improving the sorting and collection efficiency of multiple back-contact solar cells. Moreover, the structure is simple and easy to prepare, saving on the manufacturing costs of back-contact solar cells.

[0018] Please understand that the general explanation above and the subsequent detailed explanation are merely illustrative and not intended to limit the scope of this application.

[0019] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments are briefly introduced below. However, the accompanying drawings in the following description represent only a portion of the embodiments of the present invention, and it is clear to those skilled in the art that other accompanying drawings can be obtained based on these drawings without expending any creative effort.

[0020] The drawings accompanying this specification are incorporated herein and constitute part of this specification, illustrating embodiments consistent with this application and are used in conjunction with this specification to illustrate the principles of this application. [Brief explanation of the drawing]

[0021] [Figure 1] Figure 1 is a cross-sectional view of a back-contact solar cell provided by the present application in one specific embodiment. [Figure 2] Figure 2 is a cross-sectional view of a back-contact solar cell provided by the present application in another specific embodiment. [Figure 3] Figure 3 is a schematic diagram showing a part of the structure of a back-contact solar cell supplied in this application. [Figure 4]FIG. 4 is a top view of the back-contact type solar cell provided by the present application in a specific embodiment. [Figure 5] FIG. 5 is a partial enlarged view at A in FIG. 4. [Figure 6] FIG. 6 is a top view of the back-contact type solar cell provided by the present application in another specific embodiment. [Figure 7] FIG. 7 is a partial enlarged view at B in FIG. 6. [Figure 8] FIG. 8 is a schematic structural diagram of the photovoltaic module provided by the present application.

Embodiments for Carrying Out the Invention

[0022] In order to better understand the technical solutions of the present invention, the embodiments of the present invention will be described in detail below together with the accompanying drawings.

[0023] In the present specification, unless otherwise explicitly specified and limited, the terms "first" and "second" are used only for the purpose of explanation and are not construed as indicating or suggesting relative importance. Unless otherwise specified or indicated, the term "plural" means two or more. Terms such as "connection" and "fixation" should be understood in a broad sense. For example, "connection" may be a fixed connection. For example, "connection" may be a fixed connection, a detachable connection, a monolithic connection, or an electrical connection, and may be a direct connection or an indirect connection through an intermediate medium. For those skilled in the art, the specific meanings of the above terms in the present application can be understood on a case-by-case basis.

[0024] The terms used in the embodiments of the present invention are used only for the purpose of explaining specific embodiments and are not intended to limit the present invention. The singular forms of "one", "the above", and "the foregoing" used in this embodiment and the appended claims also include the plural forms unless the context clearly indicates otherwise or there are separate provisions in the context.

[0025] As used herein, the terms "and / or" simply describe the relationship between related objects, indicating, for example, that there may be three types of relationships: A and / or B, which may be expressed as A alone, both A and B, and B alone. Furthermore, the letter " / " in this specification generally indicates an "or" relationship between related objects before and after it.

[0026] Furthermore, the directional terms such as "up," "down," "left," and "right" described in the embodiments of the present invention are described from the viewpoint shown in the accompanying drawings and should not be interpreted as limiting the embodiments of the present invention. In addition, when the context refers to an element being connected "up" or "down" of another element, it should be understood that the element can be connected not only directly to the "up" or "down" of another element, but also indirectly to the "up" or "down" of another element via an intermediate element.

[0027] Back-contact solar cells, also known as IBC (Interdigitated back contact) cells, lack a metal grid on the front side, with positive and negative metal electrodes arranged in a fork shape on the back. While the absence of a grid on the front results in high photoelectric conversion efficiency, the metal grid lines printed on the cells are easily damaged during the process of being sent to the module, as multiple cells are stacked on top of each other. Currently, it's common to add paper separators between two cells, but during the sorting and collection process, uneven cell collection and misalignment of the paper separators still increase the risk of damage to the cell's front film layer.

[0028] Based on this, the present invention provides back-contact solar cells and photovoltaic modules, the back-contact solar cells include, but are not limited to, interdigitated back contact (IBC) cells, hybrid passivated back contact (HPBC) cells, tunneling oxide passivated contact (TBC) cells, heterojunction back contact (HBC) cells, and the like.

[0029] The present invention will be described in more detail below with reference to specific embodiments and accompanying drawings.

[0030] Here, as shown in Figure 1, 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 will be defined as the first direction X, and the length direction will be defined as the second direction Y.

[0031] As shown in Figure 1, 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 opposing first surfaces 11 and second surfaces 12. The first passivation layer 5 is provided on the first surface 11 of the silicon substrate 1, and the protective layer 4 is provided on the side of the first passivation layer 5 away from the silicon substrate 1. On the second surface 12 side of the silicon substrate 1, a P-type conductive region 121 and an N-type conductive region 122 are provided with a gap between them. 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.

[0032] Here, the silicon substrate 1 is used to receive incident light and generate photogenerated carriers. The first surface 11 of the silicon substrate 1 may refer to the light-receiving surface, i.e., the surface illuminated by sunlight, and the second surface 12 of the silicon substrate 1 is the surface opposite to the first surface 11. In some embodiments, the silicon substrate 1 is a silicon substrate and may 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 may be silicon carbide, an organic material, or a polycompound. Examples of polycompounds include, but are not limited to, chalcogenides, gallium arsenide, cadmium telluride, and copper indium selenide. Exemplarily, the silicon substrate 1 of the present invention 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. N-type elements can be Group V elements such as phosphorus (P), bismuth (Bi), antimony (Sb), or arsenic (As), while P-type elements can be Group III elements such as boron (B), aluminum (Al), gallium (Ga), or indium (In). For example, if the silicon substrate 1 is a P-type silicon substrate, the conductivity type of its internal doping elements is P-type. As another example, if the silicon substrate 1 is an N-type silicon substrate, the conductivity type of its internal doping elements is N-type. Exemplarily, in embodiments of the present invention, the silicon substrate 1 is an N-type silicon substrate to increase the photoelectric conversion efficiency of the back-contact type solar cell 100 and reduce manufacturing costs.

[0033] The first electrode 2 and the second electrode 3 are used to collect and aggregate current from the back-contact solar cell 100. Exemplarily, the first electrode 2 and the second electrode 3 may 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 may be, but are not limited herein, one or more of aluminum, silver, gold, nickel, molybdenum, or copper.

[0034] The first passivation layer 5 can achieve good passivation of the first surface 11 of the silicon substrate 1, reduce the density of the interface state, reduce the compounding of minority carriers, improve the carrier transport efficiency at the interface, and improve the photoelectric conversion efficiency of the back-contact solar cell 100. Exemplarily, the first passivation layer 5 may be formed using plasma-enhanced chemical vapor deposition, and of course, the first passivation layer 5 may also be formed using other methods such as organic chemical vapor deposition. Here, the first passivation layer 5 may be a single-layer structure or a multi-layer structure, and the thickness of each layer can be designed as appropriate. Specifically, the first passivation layer 5 may be a combination of one or more of the silicon nitride layer, silicon oxide nitride layer, silicon oxide layer, and aluminum oxide layer. Of course, the first passivation layer 5 may be other types of passivation layers and is not limited herein.

[0035] In this embodiment, as shown in Figure 1, the protective layer 4 is provided on the side of the first passivation layer 5 away from the first surface 11 of the silicon substrate 1, and is capable of blocking contact between the surface of the first passivation layer 5 and other back-contact solar cells 100 etc. that are laminated with it. This protects the back-contact solar cells 100 during the sorting and collection of the back-contact solar cells 100 after the first electrode 2 and the second electrode 3 have been printed, and during the assembly process into a photovoltaic module. During this process, the first passivation layer 5 is protected 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 increasing the photoelectric conversion efficiency of the back-contact solar cells 100.

[0036] Furthermore, since the protective layer 4 is provided directly on the side of the first passivation layer 5 away from the silicon substrate 1, it does not shift relative to the surface of the first passivation layer 5. Therefore, even when multiple back-contact solar cells 100 are stacked unevenly, a good protective effect can be exerted on the surface of the first passivation layer 5, and there is no need to provide an additional isolation member between two adjacent back-contact solar cells 100 during the sorting and collection process. As a result, the back-contact solar cell 100 can improve the sorting and collection efficiency of multiple back-contact solar cells 100, and its simple structure and ease of preparation can save on the manufacturing cost of the back-contact solar cell 100.

[0037] Here, as shown in Figures 1 and 2, the back-contact solar cell 100 further comprises a first doped conductive layer 6, a second doped conductive layer 7, and a second passivation layer 8.

[0038] The first doped conductive layer 6 is provided in the P-type conductive region 121 on the second surface 12 of the silicon substrate 1. The first doped conductive layer 2 may act as an emitter, and the first doped conductive layer 2 may be of a different type than the dopant element in the silicon substrate 1, and the two together may form a PN junction structure. Exemplarily, if the silicon substrate 1 is an N-type silicon substrate, the P-type first doped conductive layer 6 may be formed by boron diffusion in a portion of the silicon substrate 1 in the P-type conductive region 121.

[0039] The second doped conductive layer 7 is provided on the N-type conductive region 122 of the second surface 12 of the silicon substrate 1. The dopant elements in the second doped conductive layer 7 are the same as the dopant elements in the silicon substrate 1, and by creating a concentration difference with the silicon substrate 1, the second doped conductive layer 7 can form good contact with the second electrode 3, and can form energy band bending on the surface of the N-type conductive region 122, thereby achieving selective carrier transmission and reduction of compound loss. The second doped conductive layer 7 can be formed by depositing it on the N-type conductive region 122 using one of the following methods: physical vapor deposition, chemical vapor deposition, plasma-enhanced chemical vapor deposition, or atomic layer deposition.

[0040] The second passivation layer 8 is provided on the side of the first doped conductive layer 6 and the second doped conductive layer 7 away from the silicon substrate 1, and on 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 on at least a portion of the second surface 12. Exemplarily, the second passivation layer 8 can be deposited using plasma-enhanced chemical vapor deposition, and of course, other methods such as organic chemical vapor deposition can also be used to form the second passivation layer 8. Here, the second passivation layer 8 can be a single-layer structure or a multi-layer structure, and the thickness of each layer can be designed as appropriate. Specifically, the second passivation layer 8 can be one or a combination of silicon nitride layers, silicon oxide nitride layers, silicon oxide layers, and aluminum oxide layers. Of course, the second passivation layer 8 may be any other type of passivation layer, and is not limited herein.

[0041] The aforementioned first electrode 2 is electrically connected to the first doped conductive layer 6 via the second passivation layer 8, and the second electrode 3 is electrically connected to the second doped conductive layer 7 via the second passivation layer 8.

[0042] Exemplary, as shown in Figure 1, the P-type conductive region 121 and the N-type conductive region 122 may be formed on the second surface 12 of the silicon substrate 1, or exemplary, the P-type conductive region 121 and the N-type conductive region 122 may be formed below the second surface 12 of the silicon substrate 1, that is, it should be noted that 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 may also be partially formed on the second surface 12 or partially formed below the second surface 12, and can be set according to actual needs, and are not limited herein.

[0043] Furthermore, as shown in Figure 2, the back-contact solar cell 100 may further include an anti-reflective layer 9, which is provided between the first passivation layer 5 and the protective layer 4.

[0044] The anti-reflective layer 9 reduces or eliminates reflected light on the surface of the back-contact solar cell 100, increasing the amount of light transmitted and further improving the photoelectric conversion efficiency of the back-contact solar cell 100. In particular, by using a silicon nitride layer for the anti-reflective layer 9, the difficulty of manufacturing the back-contact solar cell 100 can be further reduced and manufacturing efficiency can be improved. Of course, the anti-reflective layer 9 may also be a silicon nitride oxide layer, a single-layer or multi-layer structure consisting of silicon nitride and silicon nitride oxide, or other reflection reduction film layer structures, and is not limited to these in this specification.

[0045] In one specific embodiment, as shown in Figure 2, the back-contact solar cell 100 may further include a first tunnel dielectric layer 10a and a second tunnel dielectric layer 10b, wherein the first tunnel dielectric layer 10a is disposed between the first doped conductive layer 6 and the silicon substrate 1, and the second tunnel dielectric layer 10b is disposed between the second doped conductive layer 7 and the silicon substrate 1.

[0046] As shown in Figure 2, the first tunneling dielectric layer 10a and the second tunneling dielectric layer 10b reduce the interfacial density of states between the silicon substrate 1 and the first doped conductive layer 6 and the second doped conductive layer 7 through chemical passivation, reducing the recombination of minority carriers with holes and improving the passivation effect on the surface of the silicon substrate 1. Furthermore, the first tunneling dielectric layer 10a and the second tunneling dielectric layer 10b allow majority carriers to tunnel into the first doped conductive layer 6 and the second doped conductive layer 7, thereby enabling the majority carriers to be transported laterally within the first doped conductive layer 6 and the second doped conductive layer 7, thereby facilitating the collection of carriers by the first electrode 2 and the second electrode 3, and facilitating the improvement of the open-circuit voltage and short-circuit current of the back-contact solar cell 100. Furthermore, the first tunnel dielectric layer 10a and the second tunnel dielectric layer 10b can also form passivation contact structures with the first doped conductive layer 6 and the second doped conductive layer 7, respectively, thereby achieving excellent interfacial passivation and selective carrier collection, and improving the photoelectric conversion efficiency of the back-contact solar cell 100.

[0047] Here, the materials for the first tunnel dielectric layer 10a and the second tunnel dielectric layer 10b may include, but are not limited to, a single-layer or multi-layer structure consisting of one or more dielectric materials having a tunneling effect, such as silicon oxide, silicon nitride, silicon oxide nitride, molybdenum oxide, hafnium oxide, silicon carbide, magnesium fluoride, nanocrystalline silicon, intrinsic amorphous silicon, and intrinsic polysilicon. In other embodiments, the first tunnel dielectric layer 10a and the second tunnel dielectric layer 10b may also be, but are not limited herein, oxygen-containing silicon nitride layers, oxygen-containing silicon carbide layers, and the like. In some feasible embodiments, the tunnel layers may be formed on the side of the second surface 12 of the silicon substrate 1 using methods such as ozone oxidation, high-temperature thermal oxidation, nitric acid oxidation, chemical vapor deposition, and low-pressure chemical vapor deposition.

[0048] In one specific embodiment, as shown in Figure 3, the thickness H1 of the protective layer 4 is 5 μm ≤ H1 ≤ 60 μm. For example, the thickness H1 of the protective layer 4 may be 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, etc., and of course, the thickness H1 of the protective layer 4 may be any other value within the above range, and can be designed according to actual needs, and is not limited in the present invention.

[0049] In this embodiment, as shown in Figures 1 to 3, if the thickness H1 of the protective layer 4 is too large, for example, if H1 > 60 μm, it leads to an increase in the overall thickness of the back-contact solar cell 100, which increases the manufacturing cost of the back-contact solar cell 100. Also, when assembling the photovoltaic module, if the thickness H1 of the protective layer 4 is too large, the degree of adhesion between the back-contact solar cell 100 and other components decreases, and the difficulty of providing a film layer structure such as a sealing layer on the surface of the back-contact solar cell 100 increases, which tends to increase the difficulty of assembling the photovoltaic module. Furthermore, if the thickness H1 of the protective layer 4 is too small, such as H1 < 5 μm, the protective isolation effect of the protective layer 4 becomes poor, and there remains a risk that the surface of the first passivation layer 5 may be scratched and damaged when multiple back-contact solar cells 100 are stacked.

[0050] Therefore, when the thickness H1 of the protective layer 4 satisfies 5μm ≤ H1 ≤ 60μm, the thickness of the protective layer 4 is appropriate, it has a high protective isolation effect, protects the surface of the first passivation layer 5 from scratches and damage, has low manufacturing costs, is easy to manufacture and form, contributes to the mass production of back-contact type solar cells 100, and is convenient for forming photovoltaic module assemblies.

[0051] Furthermore, as shown in Figures 1 and 2, the maximum thickness H2 between the surface of the second passivation layer 8 away from the silicon substrate 1 and the surface of the first passivation layer 5 (or anti-reflective layer 9) away from the silicon substrate 1 in the back-contact solar cell 100, i.e., the maximum thickness of the back-contact solar cell 100 excluding the protective layer 4, the first electrode 2, and the second electrode 3, can be set to 90 μm to 210 μm in order to improve the design flexibility of the back-contact solar cell 100, and the thickness can be set according to actual needs and is not limited herein.

[0052] In one specific embodiment, as shown in Figure 4, the projected area of ​​the protective layer 4 along the thickness direction Z of the back-contact solar cell 100 is 2% to 3% of the projected area of ​​the silicon substrate 1. For example, the projected area of ​​the protective layer 4 may be 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, and the specific details can be set according to the actual requirements, and are not limited in any way in this specification.

[0053] As shown in Figures 1 and 4, if the projected area of ​​the protective layer 4 is too large, for example, if it is larger than 3% of the projected area of ​​the silicon substrate 1, it will affect the absorption of light by the silicon substrate 1, resulting in increased light loss and current loss, which tends to reduce the photoelectric conversion efficiency of the back-contact solar cell 100. For example, if the projected area of ​​the protective layer 4 is larger than 5% of the projected area of ​​the silicon substrate 1, the current loss will exceed 50 mA, and the photoelectric conversion efficiency of the back-contact solar cell 100 will decrease.

[0054] If the projected area of ​​the protective layer 4 is too small, for example, less than 2% of the projected area of ​​the silicon substrate 1, and the exposed area of ​​the first passivation layer 5 is large, then when two adjacent back-contact solar cells 100 are stacked unevenly and shift, there remains a risk that the surface of the first passivation layer 5 will be scratched and damaged, resulting in a low protective isolation effect of the protective layer 4.

[0055] In this embodiment, as shown in Figure 4, when the projected area of ​​the protective layer 4 is 2% to 3% of the projected area of ​​the silicon substrate 1, the protective layer 4 has little effect on the light absorption of the silicon substrate 1, resulting in low light loss and low current loss. In this embodiment, when the projected area of ​​the protective layer 4 is 2% to 3% of the projected area of ​​the silicon substrate 1, the current loss is 30 Ma or less, and at the same time, the protective layer 4 has a better protective isolation effect and can protect film layers such as the first passivation layer 5 on the first surface 11 of the silicon substrate 1 from scratches and damage, thereby enabling the back-contact solar cell 100 to ensure a high photoelectric conversion efficiency.

[0056] In one specific embodiment, the protective layer 4 is a transparent protective layer that can guide light to the first surface 11, thereby enabling further reduction of light loss and improvement of the photoelectric conversion efficiency of the back-contact solar cell 100.

[0057] In one specific embodiment, the protective layer 4 is made of one or a combination of acrylic resin, epoxy resin, polyurethane, and silicone.

[0058] Adhesive-type acrylic resins, epoxy resins, polyurethanes, silicones, etc., have high transparency, good light and color retention, excellent water and chemical resistance, are inexpensive, and are less likely to damage film layers such as the first passivation layer 5 on the first surface 11 or the back-contact type solar cell 100 in contact with it, further reducing optical loss and saving costs.

[0059] In one specific embodiment, as shown in Figures 4 to 7, the protective layer 4 is composed of a plurality of support members 41, and the plurality of support members 41 are arranged at intervals on the side of the first passivation layer 5 away from the silicon substrate 1.

[0060] In this embodiment, as shown in FIGS. 4 and 6, by using the support member 41, a certain distance can be maintained between the first passivation layer 5 disposed on the first surface 11 and another stacked back-contact type solar cell 100 or another object, and it is possible to avoid the surface of the first passivation layer 5 from contacting other objects and causing scratches or damage. Then, with the plurality of support members 41 forming the protective layer, the protective layer 4 can be uniformly provided on the side away from the silicon substrate 1 of the first passivation layer 5. Therefore, the protective layer 4 can apply a uniform supporting force to the object on which it is stacked on its surface, making relative slippage less likely to occur, ensuring the stability when stacking the plurality of back-contact type solar cells 100, and further reducing the risk of damage to the first passivation layer 5 and other film layers on the first surface 11. Further, since the protective layer 4 is composed of a plurality of support members 41, the projected area of the protective layer 4 on the silicon substrate 1 can be further reduced, and while ensuring the high protective isolation effect of the protective layer 4, the optical loss of the back-contact type solar cell 100 can be further reduced.

[0061] In a specific embodiment, as shown in FIGS. 5 to 7, the distance d between the geometric centers of two adjacent support members 41 satisfies 0 < d ≤ 20 mm. For example, the distance d between the geometric centers of two adjacent support members 41 may be 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11 mm, 12 mm, 15 mm, 18 mm, 20 mm, etc. Of course, the distance d between the geometric centers of two adjacent support members 41 may also be other values within the above range, which is set according to actual needs and is not limited in this specification.

[0062] As shown in FIGS. 4 to 7, when the distance d between the geometric centers of two adjacent support members 41 is too large, for example, when d > 20 mm, the distance between two adjacent support members 41 is too far. Therefore, the back-contact type solar cell 100 or other objects laminated on the protective layer 4 can easily pass through the interval between two adjacent support members 41 and contact the film layer structure such as the first passivation layer 5 on the first surface 11. As a result, the film layer structure such as the first passivation layer 5 on the first surface 11 is scratched and damaged.

[0063] In this embodiment, as shown in FIGS. 4 to 7, when the distance d between the geometric centers of two adjacent support members 41 satisfies 0 < d ≤ 20 mm, the distance between two adjacent support members 41 is appropriate, and it is difficult for the back-contact type solar cell 100 or other objects laminated on the protective layer 4 to enter between two adjacent support members 41. Therefore, the protective isolation effect of the protective layer 4 is further enhanced, and the contact between the back-contact type solar cell 100 or other objects and the film layer structure such as the first passivation layer 5 on the first surface 11 is avoided, reducing the risk of damage to the film layer structure such as the first passivation layer 5 on the first surface 11.

[0064] In a specific embodiment, in a direction perpendicular to the thickness direction Z of the back-contact type solar cell 100, the cross-sectional shape of the support member 41 is any one or a combination of a circle, a semi-circle, an annulus, a rectangle, a triangle, a rhombus, a W shape, and a V shape. The structure is simple, the manufacturing of the protective layer 4 is easy, and the design freedom of the back-contact type solar cell 100 can be increased.

[0065] Of course, the cross-sectional shape of the support member 41 may also be a pentagon, a hexagon, or other irregular pattern shapes, and may be set according to actual needs, and is not limited in this specification.

[0066] In a specific embodiment, as shown in FIGS. 4 and 5, in a direction perpendicular to the thickness direction Z of the back-contact type 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. Because of its simple structure and easy manufacturing, the manufacturing difficulty of the protective layer 4 can be further reduced, and the cost can be saved.

[0067] As shown in FIGS. 4 and 5, for the radius R1 of the circle, 0 < R1 ≤ 4 mm. For example, R1 may be 0.5 mm, 0.75 mm, 0.8 mm, 1 mm, 1.2 mm, 1.5 mm, 1.6 mm, 1.8 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, etc. Of course, the radius R1 of the circle may be other values within the above range and can be set according to actual needs, and is not limited here.

[0068] Here, 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 following formula.

Equation

[0069] Here, S is the projected area of the protective layer 4, and the unit is mm 2 where R1 is the cross-sectional radius of the support member 41, the unit is mm, M is the projected area in the thickness direction Z of the silicon substrate 1, and the unit is mm 2 where d is the distance between the geometric centers of two adjacent support members 41, and the unit is mm.

[0070] According to the following formula, it is known that the projected area S of the protective layer 4 is proportional to the cross-sectional radius R1 of the support member 41. So, if R1 is too large, the projected area of each support member 41 will be large, and the projected area S of the protective layer 4 will become too large, resulting in a high optical loss of the back-contact type solar cell 100 and a tendency for the photoelectric conversion efficiency of the obtained back-contact type solar cell 100 to decrease.

Equation

[0071] Therefore, when the cross-sectional shape of the support member 41 is circular and its radius R1 satisfies 0 < R1 ≤ 4 mm, the projected area of a single support member 41 will not become too large, and a certain supporting force can be ensured for the support member 41. Thus, it becomes possible to further enhance the protective isolation effect of the protective layer 4. At the same time, by adopting a structure in which the projected area S of the protective layer 4 does not become too large, the light loss caused by the protective layer 4 can be reduced, and the high photoelectric conversion efficiency of the back-contact type solar cell 100 can be ensured.

[0072] In another specific embodiment, as shown in FIGS. 6 and 7, in a direction perpendicular to the thickness direction Z of the back-contact type 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-shaped structure formed by combining a semi-circle and a rectangle. The support member 41 with such a structure has the advantages that the structure is simple, the manufacturing is easy, and the supporting effect of the support member 41 can be enhanced.

[0073] Specifically, the strip-shaped support member 41 consists of a rectangle and two semi-circles provided at opposite ends of the rectangle. Exemplarily, as shown in FIG. 7, the two semi-circles are provided on the opposite side of the rectangle along the second direction Y, and the dimension of the width of the rectangle along the first direction X is the same as the diameter of the semi-circle.

[0074] As shown in FIGS. 6 and 7, the radius R2 of the semi-circle in the cross-section of the support member 41 satisfies 0 < R2 ≤ 2 mm. For example, R2 can be 0.5 mm, 0.75 mm, 0.8 mm, 1 mm, 1.2 mm, 1.5 mm, 1.6 mm, 1.8 mm, 2 mm, etc. Of course, the radius R2 of the semi-circle can also be other values within the above range and can be set according to actual needs and is not limited here.

[0075] The length L of the rectangle in the cross-section of the support member 41 satisfies 1 ≤ L / R2 ≤ 5. For example, L / R2 can be 1, 2, 3, 4, 5, etc. Of course, L / R2 is not limited in this specification and can be other values within the above-mentioned range.

[0076] Here, when the cross-sectional shape of the support member 41 is strip-shaped, the projected area S of the protective layer 4 can be calculated by the following formula.

Equation

[0077] According to the following formula, it is known that the projected area S of the protective layer 4 is proportional to the radius R2 of the semi-circle 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 projected area of a single support member 41 becomes large, so the projected area S of the protective layer 4 becomes too large, resulting in high optical loss of the back-contact type solar cell 100 and a tendency for the photoelectric conversion efficiency of the back-contact type solar cell 100 to decrease.

Equation

[0078] Therefore, when the cross-sectional shape of the support member 41 is a strip structure formed by combining a semi-circle and a rectangle, and the radius R2 of the semi-circle in the cross-sectional shape satisfies 0 < R2 ≤ 2 mm, and the length L of the rectangle satisfies 1 ≤ L / R2 ≤ 5, the projected area of a single support member 41 will not become too large. Thus, the supporting force of the support member 41 is ensured, and the protective layer 4 can exhibit a better protective isolation effect. At the same time, by making the structure such that the projected area S of the protective layer 4 does not become too large, the optical loss caused by the protective layer 4 can be reduced, and a high photoelectric conversion efficiency of the back-contact type solar cell 100 can be ensured.

[0079] A second aspect of the present invention provides a photovoltaic module, as shown in Figure 8, which includes a battery string 110, a sealing layer 120, and a cover 130. The battery string 110 is composed of multiple back-contact solar cells 100 connected together, one of the above embodiments; the sealing layer 120 is used to cover the surface of the protective layer 4 of the battery string 110; and the cover 130 is used to cover the surface of the sealing layer 120 away from the battery string 110. Since the back-contact solar cells 100 have the above-described technical effects, a photovoltaic module including the solar cells 100 should also have the above-described technical effects, which will not be repeated herein.

[0080] In particular, as shown in Figure 8, the back-contact solar cell 100 is electrically connected in whole or in a divided form to form multiple cell strings 110, and the multiple cell strings 110 are electrically connected in series and / or parallel. Specifically, the multiple cell strings 110 may be electrically connected to each other by conductive tape.

[0081] The sealing layer 120 covers not only the front side but also the back side of the back-contact solar cell. Specifically, the sealing layer 120 can be an organic sealing adhesive film such as an ethylene vinyl acetate copolymer (EVA) adhesive film, a polyethylene octencoelastomer (POE) adhesive film, a polyethylene terephthalate (PET) adhesive film, or a polyvinyl butyral (PVB) adhesive film.

[0082] The cover 130 may be a glass cover, a plastic cover, or the like, which has a light-transmitting function. Specifically, by making the surface of the cover 130 facing the sealing layer 120 an uneven surface, the utilization rate of incident light can be increased.

[0083] For parts that are identical or similar to each embodiment in this specification, it is sufficient to refer to the respective embodiments. In particular, the apparatus embodiments and terminal embodiments are basically the same as the method embodiments, so their description is relatively simple, and it is sufficient to refer to the description of the method embodiments for relevant points.

[0084] The above merely describes specific embodiments of the present invention; however, the scope of protection of the embodiments of the present invention is not limited thereto, and any modifications or substitutions within the scope of the technology disclosed by the embodiments of the present invention shall be included within the scope of protection of the embodiments of the present invention. Accordingly, the scope of protection of the embodiments of this application shall be subject to the scope of protection of the claims described herein. [Explanation of Symbols]

[0085] 100-Back-contact solar cells 1 - Silicon substrate 11 - First surface 12 - Second surface 121-P type conductive region 122-N type conductive region 2 - First electrode 3 - Second electrode 4 - protective layer 41 - Support Member 5 - First Passivation Layer 6. First doped conductive layer 7. Second doped conductive layer 8 - Second Passivation Layer 9 - Anti-reflection layer 10a - First tunnel dielectric layer 10b - Second tunnel dielectric layer 110 - Battery string 120 - Sealing layer 130 - Cover X - First direction Y - Second direction Z-thickness direction

Claims

1. Back-contact solar cells, A silicon substrate (1) having opposing first surfaces (11) and second surfaces (12), wherein the second surface (12) of the silicon substrate (1) is provided with spaced-apart P-type conductive regions (121) and N-type conductive regions (122), A first passivation layer (5) is provided on the first surface (11) of the silicon substrate (1), A protective layer (4) is disposed on the side of the first passivation layer (5) away from the silicon substrate (1), A first electrode (2) electrically connected to the P-type conductive region (121), The system comprises a second electrode (3) electrically connected to the N-type conductive region (122), Back-contact solar cells.

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

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

4. The back-contact solar cell according to claim 1, characterized in that the protective layer (4) includes a plurality of support members (41), and the plurality of support members (41) are spaced apart on the side of the first passivation layer (5) away from the silicon substrate (1).

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

6. The back-contact solar cell according to claim 4, characterized in that, in a direction perpendicular to the thickness direction (Z) 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, rhombus, W-shaped, and V-shaped shapes.

7. In a direction perpendicular to the thickness direction (Z) of the back-contact type solar cell (100), the cross-sectional shape of the support member (41) is circular, and the radius R of the circle １ 0 < R １ The back-contact solar cell according to claim 4, characterized in that it has ≤ 4 mm.

8. In a direction perpendicular to the thickness direction (Z) of the back-contact type solar cell (100), the cross-sectional shape of the support member (41) is a stripe formed by a combination of semicircles and rectangles. The radius R of the aforementioned semicircle ２ 0 < R ２ ≤ 2 mm, The length L of the rectangle is 1 ≤ L / R ２ The back-contact solar cell according to claim 4, characterized in that ≤ 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 protective layer (4) is made of one or a combination of acrylic resin, epoxy resin, polyurethane, and silicon.

11. A photovoltaic module, wherein the photovoltaic module is A battery string (110) consisting of multiple connected back-contact solar cells (100) according to any one of claims 1 to 10, A sealing layer (120) for covering the surface of the protective layer (4) of the battery string (110), A cover (130) for covering the surface of the sealing layer (120) away from the battery string (110), A photovoltaic module characterized by comprising the following features.

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