Back contact solar cell, preparation method thereof, cell module and photovoltaic system

Abstract

The invention relates to the technical field of solar cells, in particular to a back contact solar cell, a preparation method thereof, a cell module and a photovoltaic system. The back contact solar cell comprises a semiconductor substrate, the semiconductor substrate is provided with a light receiving surface and a backlight surface which are opposite to each other, the backlight surface of the semiconductor substrate comprises a first region, a second region and a spacer region, and the spacer region separates the first region from the second region; the tunneling oxide layer and the first doping layer are sequentially stacked on the first region; the tunneling oxide layer, the second doping layer and the metal layer are sequentially stacked on the second region; the polarity of the first doped layer is opposite to that of the second doped layer. The laminated solar cell can reduce the contact resistance and improve the photoelectric conversion efficiency, and is simple to prepare and easy for mass production.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cells, and in particular to a back-contact solar cell and a preparation method thereof, a cell assembly, and a photovoltaic system. Background Art

[0002] As the efficiency of TOPCon cells gradually approaches the theoretical efficiency limit, people have begun to explore better process routes, among which TBC solar cells with back contact structures have gradually attracted attention. Since the electrode is set on the backlight side of the cell, it can effectively reduce short-circuit current losses and has broad application prospects. However, in existing back-contact solar cells, the contact resistance is usually large, which reduces the cell efficiency of the back-contact cell.

[0003] In the prior art, there are methods of contacting different electrodes through multiple layers of different types of conductive layers to achieve corresponding low contact resistance, but the battery preparation process is cumbersome, costly, and cannot be mass-produced. In addition, there are methods of shortening the carrier collection path and optimizing the contact resistance by designing a new back-contact solar cell structure, but its structure processing is complex and not conducive to mass production. And the contact resistance is reduced by designing a porous tunneling oxide layer, but it is difficult to accurately control the arrangement of holes on the ultra-thin tunneling oxide layer. Therefore, it is necessary to provide a back-contact solar cell that can reduce the contact resistance, and the preparation method is simple and easy to industrially produce. Summary of the invention

[0004] The present invention aims to solve one of the technical problems in the related art to at least some extent. To this end, the present invention provides a back-contact solar cell and a method for preparing the same, wherein the stacked solar cell can reduce contact resistance, improve photoelectric conversion efficiency, and is simple to prepare and easy to mass produce.

[0005] To this end, the first aspect of the present invention provides a back-contact solar cell, comprising:

[0006] A semiconductor substrate, wherein the semiconductor substrate has a light-receiving surface and a backlight surface opposite to each other, wherein the backlight surface of the semiconductor substrate comprises a first region, a second region and a spacer region, wherein the spacer region separates the first region from the second region;

[0007] A tunneling oxide layer and a first doping layer are sequentially stacked on the first region;

[0008] A tunneling oxide layer, a second doping layer and a metal layer are sequentially stacked on the second region;

[0009] The first doping layer and the second doping layer have opposite polarities.

[0010] In order to solve the deficiencies in the prior art, the present invention improves the contact interface, reduces the contact resistance and improves the photoelectric conversion efficiency by arranging a metal layer on the second doping layer as an electrode slurry contact stop layer.

[0011] According to an embodiment of the present invention, the metal layer includes a plurality of structural units arranged at intervals;

[0012] And / or, the distance between adjacent structural units is 500-1000 μm, thereby further reducing the absorption or reflection of light by the metal layer.

[0013] According to an embodiment of the present invention, the thickness of the tunnel oxide layer is 1.1-1.5 nm;

[0014] And / or, the thickness of the first doping layer is 200-500 nm;

[0015] And / or, the thickness of the second doping layer is 200-500 nm;

[0016] And / or, the thickness of the metal layer is 30-100 nm.

[0017] According to an embodiment of the present invention, the polarity of the first doping layer is opposite to that of the second doping layer.

[0018] According to an embodiment of the present invention, the first doped layer is a P-type doped polysilicon layer, and the second doped layer is an N-type doped polysilicon layer.

[0019] According to an embodiment of the present invention, the material of the metal layer is selected from at least one of aluminum, silver-silicon alloy, and aluminum-silicon alloy.

[0020] According to an embodiment of the present invention, the back-contact solar cell further comprises an anti-reflection layer, and the anti-reflection layer is arranged on a side of the first doping layer away from the backlight surface, a surface of the spacer region, and a side of the metal layer.

[0021] The second aspect of the present invention provides a method for preparing the back-contact solar cell according to the first aspect, comprising:

[0022] Providing a semiconductor substrate, wherein the semiconductor substrate has a light-receiving surface and a backlight surface opposite to each other, a tunneling oxide layer, a first doping layer and an oxide layer are sequentially formed on the backlight surface, and the backlight surface of the semiconductor substrate includes a first region, a second region and a spacer region;

[0023] removing the first doping layer and the oxide layer corresponding to the second region and the spacer, so that the second region and the spacer expose the tunnel oxide layer;

[0024] forming a second doping layer and a metal layer in sequence on the backlight surface of the semiconductor substrate;

[0025] The portions of the metal layer and the second doping layer corresponding to the first region and the spacer region are removed, and the portion of the tunneling oxide layer corresponding to the spacer region is removed so that the spacer region exposes the semiconductor substrate, the first region and the second region are physically isolated, and the remaining oxide layer is removed.

[0026] The preparation method of the back-contact solar cell provided by the present invention is relatively simple. It only requires an additional metal layer to be prepared in the original preparation process. The metal layer serves as a contact stop layer for the electrode slurry, thereby improving the contact interface between the doping layer and the electrode. The contact resistance of the obtained back-contact solar cell is low, and the photoelectric conversion efficiency is improved.

[0027] According to an embodiment of the present invention, the oxide layer is PSG or BSG.

[0028] According to an embodiment of the present invention, the preparation method further includes: removing the remaining oxide layer, and patterning the metal layer located on the second region so that the metal layer forms a plurality of spaced-apart structural units.

[0029] According to an embodiment of the present invention, the preparation method further comprises: forming an anti-reflection layer on the backlight surface of the semiconductor substrate after removing the remaining oxide layer.

[0030] A third aspect of the present invention provides a battery assembly, comprising the back-contact solar cell described in the first aspect.

[0031] A fourth aspect of the present invention provides a photovoltaic system, comprising the battery assembly described in the third aspect or a back-contact solar cell obtained according to the preparation method described in the second aspect.

[0032] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0034] Figure 1 One of the structural schematic diagrams of the back contact solar cell provided by the present invention is shown;

[0035] Figure 2 The second structural schematic diagram of the back contact solar cell provided by the present invention is shown;

[0036] Figure 3 The third structural schematic diagram of the back contact solar cell provided by the present invention is shown;

[0037] Figure 4 One of the structural schematic diagrams of the back contact solar cell preparation process provided by the present invention is shown;

[0038] Figure 5 The second structural schematic diagram of the back contact solar cell preparation process provided by the present invention is shown;

[0039] Figure 6 The third structural schematic diagram of the back contact solar cell preparation process provided by the present invention is shown;

[0040] Figure 7 The fourth structural schematic diagram of the back contact solar cell preparation process provided by the present invention is shown;

[0041] Figure 8 The fifth structural schematic diagram of the back contact solar cell preparation process provided by the present invention is shown.

[0042] Reference numerals:

[0043] Semiconductor substrate 1, tunneling oxide layer 2, first doping layer 3, second doping layer 4, metal layer 5, structural unit 5-1, anti-reflection layer 6, oxide layer 7, anti-reflection layer 8.

[0044] The first region has a width w1, the second region has a width w2, and the isolation region has a width w3. DETAILED DESCRIPTION

[0045] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be understood as limiting the present invention.

[0046] It should be understood that when an element or layer is referred to as "on ...", "adjacent to ...", "connected to" or "coupled to" other elements or layers, it can be directly on, adjacent to, connected to or coupled to other elements or layers, or there can be intervening elements or layers. On the contrary, when an element is referred to as "directly on ...", "directly adjacent to ...", "directly connected to" or "directly coupled to" other elements or layers, there is no intervening element or layer. It should be understood that although the terms first, second, third, etc. can be used to describe various elements, components, regions, layers and / or parts, these elements, components, regions, layers and / or parts should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or part from another element, component, region, layer or part. Therefore, without departing from the teachings of the present disclosure, the first element, component, region, layer or part discussed below can be represented as the second element, component, region, layer or part. And when the second element, component, region, layer or part is discussed, it does not mean that the present disclosure necessarily has the first element, component, region, layer or part.

[0047] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. Further, in the description of the present invention, unless otherwise specified, the meaning of "plurality" is two or more.

[0048] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0049] In order to make the present invention more easily understood, certain technical and scientific terms are specifically defined below. Unless otherwise clearly defined elsewhere in this document, all other technical and scientific terms used herein have the meanings commonly understood by those skilled in the art to which the present invention belongs.

[0050] In this document, the terms “include” or “comprising” are open expressions, that is, including the contents specified in the present invention but not excluding other contents.

[0051] In related technologies, in order to improve the high contact resistance in back-contact solar cells, multiple layers of different types of conductive layers are designed to contact different electrodes to achieve low contact resistance, but the battery preparation process is cumbersome, costly, and cannot be mass-produced. The contact resistance can also be optimized by designing a new battery structure to shorten the carrier collection path, but its structure processing is complex and is also not conducive to mass production. In addition, the contact resistance can be reduced by designing a porous tunneling oxide layer, but it is difficult to accurately control the arrangement of holes on the ultra-thin tunneling oxide layer.

[0052] The present invention proposes a back-contact solar cell and a method for preparing the same. The back-contact solar cell comprises: a semiconductor substrate, the semiconductor substrate having a relative light-receiving surface and a back-light surface, the back-light surface of the semiconductor substrate comprising a first region, a second region and a spacer region, the spacer region separating the first region from the second region; a tunneling oxide layer and a first doping layer stacked in sequence on the first region; a tunneling oxide layer, a second doping layer and a metal layer stacked in sequence on the second region. By arranging a metal layer on the second doping layer as an electrode slurry contact stop layer, the disadvantages of the electrode penetrating uncontrollably into the doping layer and causing an increase in contact resistance are avoided, the contact interface is improved, the contact resistance is reduced, and the photoelectric conversion efficiency is thereby improved. At the same time, the preparation process of the back-contact solar cell is simple, and only an additional metal layer needs to be prepared in the original preparation process, which is suitable for mass production.

[0053] According to an embodiment of the present invention, a first aspect of the present invention provides a back contact solar cell, the structure of which is shown in FIG. Figure 1 .

[0054] According to a specific embodiment of the present invention, the back-contact solar cell includes: a semiconductor substrate 1, the semiconductor substrate 1 has a relative light-receiving surface and a backlight surface, the backlight surface of the semiconductor substrate includes a first region, a second region and a spacer region, the spacer region separates the first region from the second region; a tunneling oxide layer 2 and a first doping layer 3 stacked in sequence on the first region; a tunneling oxide layer 2, a second doping layer 4 and a metal layer 5 stacked in sequence on the second region.

[0055] According to a specific embodiment of the present invention, the semiconductor substrate 1 can be a single crystal silicon substrate, and its doping type is not particularly limited. Those skilled in the art can select it according to actual needs. For example, the single crystal silicon substrate is an N-type doped silicon substrate, or a P-type doped silicon substrate. The semiconductor substrate 1 includes a light-receiving surface and a backlight surface, which are relatively distributed. The backlight surface of the semiconductor substrate 1 includes a first area, a second area and a spacing area, wherein the spacing area separates the first area from the second area. Among them, the relative position and relative size of each area are not particularly limited. Those skilled in the art can select it according to actual needs, for example Figure 1 The first region is located on the left side of the second region, the width w1 of the first region is 500-600 μm, the width w2 of the second region is 400-500 μm, and the width w3 of the isolation region is 50-100 μm. The number of regions is not particularly limited, for example, the backlight of the semiconductor substrate 1 has two isolation regions.

[0056] According to a specific embodiment of the present invention, the material of the tunnel oxide layer 2 is not particularly limited, and those skilled in the art can select it according to actual needs. For example, the material of the tunnel oxide layer 2 is silicon oxide. Its thickness is also not specifically limited. For example, the thickness of the tunnel oxide layer 2 is 1.1-1.5 nm. As some specific examples, the thickness of the tunnel oxide layer 2 is 1.1 nm, 1.2 nm, 1.3 nm, 1.4 nm, 1.5 nm, etc.

[0057] According to a specific embodiment of the present invention, the polarity of the first doping layer 3 is opposite to that of the second doping layer 4. Preferably, the first doping layer 3 is a P-type doped polysilicon layer, and the second doping layer 4 is an N-type doped polysilicon layer. Specifically, the first doping layer 3 is a boron-doped polysilicon layer, and the second doping layer 4 is a phosphorus-doped polysilicon layer. The thickness thereof is not specifically limited. For example, the thickness of the first doping layer 3 is 200-500nm. As some specific examples, the thickness of the first doping layer 3 is 200nm, 300nm, 400nm, 500nm, etc.; the thickness of the second doping layer 4 is 200-500nm. As some specific examples, the thickness of the second doping layer 4 is 200nm, 300nm, 400nm, 500nm, etc.

[0058] According to a specific embodiment of the present invention, the material of the metal layer 5 is not particularly limited, and is preferably aluminum, silver silicon alloy, aluminum silicon alloy, etc. The above materials have narrow band gaps, low melting points, low energy required for film opening, and are resistant to laser damage. The thickness of the metal layer 5 is not specifically limited, and can be selected from 30-100nm, such as 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, etc.

[0059] According to a specific embodiment of the present invention, the metal layer 5 includes a plurality of spaced-apart structural units 5-1, see Figure 2 This further reduces the absorption or reflection of light by the metal layer, thereby avoiding a reduction in battery efficiency. Specifically, the number of the structural units 5-1 is not particularly limited, and those skilled in the art can select according to actual needs.

[0060] According to a specific embodiment of the present invention, the distance between adjacent structural units 5-1 is 500-1000 μm, thereby minimizing the absorption or reflection of light by the metal layer. Specifically, the distance between adjacent structural units should be understood as the distance between the centers of two adjacent structural units. The distance between adjacent structural units 5-1 can be 500 μm, 600 μm, 700 μm, 800 μm, 900 μm, 1000 μm, etc.

[0061] According to a specific embodiment of the present invention, the isolation area may be a velvet surface, which has a certain light trapping effect.

[0062] According to a specific embodiment of the present invention, the back contact solar cell further comprises an anti-reflection layer 6, see Figure 3 The anti-reflection layer 6 is disposed on the surface of the first doping layer 3 away from the backlight surface, the surface of the spacer area, and the surface of the metal layer 5. The material of the anti-reflection layer 6 is not particularly limited, and silicon nitride or the like may be selected. The thickness thereof is also not specifically limited, for example, 60-90 nm. As some specific examples, the thickness of the anti-reflection layer 6 may be 60 nm, 70 nm, 80 nm, 90 nm, etc.

[0063] According to an embodiment of the present invention, a second aspect of the present invention provides a method for preparing a back-contact solar cell according to the first aspect. The preparation method comprises:

[0064] (1) A semiconductor substrate 1 is provided, wherein the semiconductor substrate 1 has a light-receiving surface and a backlight surface opposite to each other, and a tunneling oxide layer 2, a first doping layer 3 and an oxide layer 7 are sequentially formed on the backlight surface, and the backlight surface of the semiconductor substrate 1 includes a first region, a second region and a spacer region. Figure 4 .

[0065] According to a specific embodiment of the present invention, the oxide layer 7 can be used as a protective layer to achieve subsequent selective etching. The oxide layer can be PSG or BSG. For example, when the first doped layer is a boron-doped polysilicon layer, the oxide layer corresponds to BSG; when the first doped layer is a phosphorus-doped polysilicon layer, the oxide layer corresponds to PSG.

[0066] The formation method of the tunneling oxide layer 2, the first doping layer 3 and the oxide layer 7 is not particularly limited, and those skilled in the art can choose according to actual needs, for example, by PECVD (plasma enhanced chemical vapor deposition) to sequentially deposit the tunneling oxide layer 2, the first doping layer 3 and the oxide layer 7 on the backlight surface.

[0067] (2) removing the first doping layer 3 and the oxide layer 7 corresponding to the second region and the spacer, so that the second region and the spacer expose the tunnel oxide layer 2. Figure 5 .

[0068] According to a specific embodiment of the present invention, the method for removing part of the first doping layer 3 and the oxide layer 7 is not particularly limited, and those skilled in the art can make a choice according to actual needs. For example, a picosecond green laser is used to perform grooving in the second region and the spacing region to form a laser opening region. The opening width is not particularly limited and can be 400-500 μm, for example, 400 μm, 410 μm, 420 μm, 430 μm, 440 μm, 450 μm, 460 μm, 470 μm, 480 μm, 490 μm, 500 μm, etc.

[0069] (3) A second doping layer 4 and a metal layer 5 are sequentially formed on the backlight surface of the semiconductor substrate 1. Figure 6 .

[0070] According to a specific embodiment of the present invention, a second doping layer 4 and a metal layer 5 are sequentially formed on the tunneling oxide layer of the second region and the spacer region, the remaining first doping layer, and the remaining oxide layer. The formation method of the second doping layer 4 and the metal layer 5 is not particularly limited, and those skilled in the art can select according to actual needs, for example, the second doping layer 4 is deposited by PECVD, and the metal layer 5 is deposited by electroplating or PVD (physical vapor deposition).

[0071] (4) removing the portions of the metal layer 5 and the second doping layer 4 corresponding to the first region and the spacer, removing the portion of the tunneling oxide layer 2 corresponding to the spacer, so that the spacer exposes the semiconductor substrate 1, the first region and the second region are physically isolated, and removing the remaining oxide layer 7. Figure 7 .

[0072] According to a specific embodiment of the present invention, the portion of the metal layer 5 corresponding to the first region and the spacer region is removed, and the removal method is not specifically limited, for example, the metal layer is grooved by laser, and the opening width can be selected to be 540-600μm, such as 540μm, 550μm, 560μm, 570μm, 580μm, 590μm, 600μm, etc. At the same time, because the material of the metal layer is a material with a narrow band gap and a low melting point, the energy required for laser film opening is relatively low, and the damage to the film is also small.

[0073] According to a specific embodiment of the present invention, the removal of the portion of the second doping layer 4 corresponding to the first region and the spacer, the portion of the tunneling oxide layer 2 corresponding to the spacer, and the remaining oxide layer 7 are not specifically limited, for example, they are removed by chain cleaning.

[0074] According to a specific embodiment of the present invention, the preparation method may further include: removing the remaining oxide layer 7, and patterning the metal layer 5 located on the second region so that the metal layer 5 forms a plurality of spaced structural units. Specifically, the patterning includes but is not limited to laser ablation, photolithography, etc.

[0075] According to a specific embodiment of the present invention, the exposed isolation area can be subjected to a texturing treatment to form a suede surface having a certain light trapping effect.

[0076] According to a specific embodiment of the present invention, the preparation method may further include: forming an anti-reflection layer 8 on the backlight surface of the semiconductor substrate 1. The material of the anti-reflection layer 8 is not particularly limited, and silicon nitride or the like may be selected and metallized.

[0077] According to an embodiment of the present invention, a third aspect of the present invention provides a battery assembly, comprising the back-contact solar cell described in the first aspect or the back-contact solar cell obtained according to the preparation method described in the second aspect. The battery assembly has the same or similar beneficial effects as the back-contact solar cell, which will not be described in detail here.

[0078] According to an embodiment of the present invention, a fourth aspect of the present invention provides a photovoltaic system, comprising the battery assembly described in the third aspect. The photovoltaic system and the battery assembly have the same or similar beneficial effects, which will not be described in detail here.

[0079] The scheme of the present invention will be explained below in conjunction with the embodiments. It will be appreciated by those skilled in the art that the following embodiments are only used to illustrate the present invention and should not be considered as limiting the scope of the present invention. Where specific techniques or conditions are not indicated in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. The reagents or instruments used are not indicated by the manufacturer and are all conventional products that can be obtained commercially.

[0080] Example 1

[0081] A method for preparing a back contact solar cell comprises the following steps:

[0082] (1) depositing a tunnel oxide layer, a boron-doped polysilicon layer and an oxide layer on a crystalline silicon substrate by PECVD, wherein the oxide layer is made of borosilicate glass (BSG), and the thicknesses of the tunnel oxide layer, the boron-doped polysilicon layer and the oxide layer are 1.1 nm, 350 nm and 50 nm, respectively;

[0083] (2) using a picosecond green laser to open grooves in the oxide layer and the boron-doped polysilicon layer corresponding to the second region and the spacer region to form a laser opening region with an opening width of 480 μm;

[0084] (3) depositing a phosphorus-doped polysilicon layer by PECVD with a thickness of 350 nm; and then depositing a metal layer by electroplating with a thickness of 30 nm, the material of the metal layer being aluminum;

[0085] (4) Laser grooves are made in the metal layer corresponding to the first region and the spacer region, with an opening width of 650 μm; chain cleaning is used to remove the portion of the phosphorus-doped polysilicon layer corresponding to the first region and the spacer region and the portion of the tunnel oxide layer corresponding to the spacer region, exposing the isolation region for texturing;

[0086] (5) Deposit an anti-reflection layer of silicon nitride on the backlight surface and metallize it.

[0087] Example 2

[0088] A method for preparing a back contact solar cell comprises the following steps:

[0089] (1) depositing a tunnel oxide layer, a boron-doped polysilicon layer and an oxide layer on a crystalline silicon substrate by PECVD, wherein the oxide layer is made of borosilicate glass, and the thicknesses of the tunnel oxide layer, the boron-doped polysilicon layer and the oxide layer are 1.1 nm, 350 nm and 50 nm, respectively;

[0090] (2) using a picosecond green laser to open grooves in the oxide layer and the boron-doped polysilicon layer corresponding to the second region and the spacer region to form a laser opening region with an opening width of 480 μm;

[0091] (3) depositing a phosphorus-doped polysilicon layer by PECVD with a thickness of 350 nm; and then depositing a metal layer by PVD with a thickness of 40 nm, the material of the metal layer being a silver-silicon alloy;

[0092] (4) Laser grooves are made in the metal layer corresponding to the first region and the spacer region, with an opening width of 600 μm; chain cleaning is used to remove the portion of the phosphorus-doped polysilicon layer corresponding to the first region and the spacer region and the portion of the tunnel oxide layer corresponding to the spacer region, exposing the isolation region for texturing;

[0093] (5) Deposit an anti-reflection layer of silicon nitride on the backlight surface and metallize it.

[0094] Example 3

[0095] A method for preparing a back contact solar cell comprises the following steps:

[0096] (1) depositing a tunnel oxide layer, a boron-doped polysilicon layer and an oxide layer on a crystalline silicon substrate by PECVD, wherein the oxide layer is made of borosilicate glass, and the thicknesses of the tunnel oxide layer, the boron-doped polysilicon layer and the oxide layer are 1.1 nm, 350 nm and 50 nm, respectively;

[0097] (2) using a picosecond green laser to open grooves in the oxide layer and the boron-doped polysilicon layer corresponding to the second region and the spacer region to form a laser opening region with an opening width of 480 μm;

[0098] (3) depositing a phosphorus-doped polysilicon layer by PECVD with a thickness of 350 nm; and then depositing a metal layer by electroplating with a thickness of 50 nm, the material of the metal layer being an aluminum-silicon alloy;

[0099] (4) Laser grooves are made in the metal layer corresponding to the first region and the spacer region, with an opening width of 550 μm; chain cleaning is used to remove the portion of the phosphorus-doped polysilicon layer corresponding to the first region and the spacer region and the portion of the tunnel oxide layer corresponding to the spacer region, exposing the isolation region for texturing;

[0100] (5) Deposit an anti-reflection layer of silicon nitride on the backlight surface and metallize it.

[0101] Example 4

[0102] A method for preparing a back contact solar cell comprises the following steps:

[0103] (1) depositing a tunnel oxide layer, a boron-doped polysilicon layer and an oxide layer on a crystalline silicon substrate by PECVD, wherein the oxide layer is made of borosilicate glass, and the thicknesses of the tunnel oxide layer, the boron-doped polysilicon layer and the oxide layer are 1.1 nm, 350 nm and 50 nm, respectively;

[0104] (2) using a picosecond green laser to open grooves in the oxide layer and the boron-doped polysilicon layer corresponding to the second region and the spacer region to form a laser opening region with an opening width of 480 μm;

[0105] (3) depositing a phosphorus-doped polysilicon layer by PECVD with a thickness of 350 nm; and then depositing a metal layer by PVD with a thickness of 50 nm, the material of the metal layer being an aluminum-silicon alloy;

[0106] (4) Laser grooves are formed in the metal layer corresponding to the first region and the spacer region, with an opening width of 500 μm; chain cleaning is used to remove the portion of the phosphorus-doped polysilicon layer corresponding to the first region and the spacer region and the portion of the tunnel oxide layer corresponding to the spacer region, exposing the isolation region for texturing; laser ablation is performed on the metal layer located in the second region to form a plurality of spaced structural units, with a distance of 500 μm between adjacent structural units;

[0107] (5) Deposit an anti-reflection layer of silicon nitride on the backlight surface and metallize it.

[0108] Comparative Example 1

[0109] The difference between Comparative Example 1 and Example 1 is only that:

[0110] The formation of the metal layer is not included.

[0111] The back-contact solar cells prepared in Examples 1-4 and Comparative Example 1 were tested for contact resistance and photoelectric conversion efficiency, and the results are shown in Table 1. The results show that the back-contact solar cells prepared by the method provided by the present invention have lower contact resistance and improved photoelectric conversion efficiency.

[0112] Table 1

[0113] <![CDATA[Contact resistance / mΩ*cm 2 > Photoelectric conversion efficiency / % Example 1 1.16 24.90 Example 2 0.97 24.99 Example 3 0.82 25.14 Example 4 0.91 25.26 Comparative Example 1 1.56 24.89

[0114] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0115] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A back contact solar cell, characterized in that: include: A semiconductor substrate, wherein the semiconductor substrate has a light-receiving surface and a backlight surface opposite to each other, wherein the backlight surface of the semiconductor substrate comprises a first region, a second region and a spacer region, wherein the spacer region separates the first region from the second region; A tunneling oxide layer and a first doping layer are sequentially stacked on the first region; A tunneling oxide layer, a second doping layer and a metal layer are sequentially stacked on the second region; The first doping layer and the second doping layer have opposite polarities.

2. The back contact solar cell according to claim 1, characterized in that: The metal layer includes a plurality of structural units arranged at intervals; And / or, the distance between adjacent structural units is 500-1000 μm.

3. The back contact solar cell according to claim 1, characterized in that: The thickness of the tunnel oxide layer is 1.1-1.5 nm; And / or, the thickness of the first doping layer is 200-500 nm; And / or, the thickness of the second doping layer is 200-500 nm; And / or, the thickness of the metal layer is 30-100 nm.

4. The back contact solar cell according to claim 1, characterized in that: The first doped layer includes a P-type doped polysilicon layer, and the second doped layer includes an N-type doped polysilicon layer.

5. The back contact solar cell according to claim 1, characterized in that: The material of the metal layer includes at least one of aluminum, silver silicon alloy, and aluminum silicon alloy.

6. The back contact solar cell according to claim 1, characterized in that: The back-contact solar cell further includes an anti-reflection layer, and the anti-reflection layer is arranged on a side of the first doping layer away from the backlight surface, a surface of the spacer region, and a side of the metal layer.

7. A method for preparing a back contact solar cell according to any one of claims 1 to 6, characterized in that: include: Providing a semiconductor substrate, wherein the semiconductor substrate has a light-receiving surface and a backlight surface opposite to each other, a tunneling oxide layer, a first doping layer and an oxide layer are sequentially formed on the backlight surface, and the backlight surface of the semiconductor substrate includes a first region, a second region and a spacer region; removing the first doping layer and the oxide layer corresponding to the second region and the spacer, so that the second region and the spacer expose the tunnel oxide layer; forming a second doping layer and a metal layer in sequence on the backlight surface of the semiconductor substrate; The portions of the metal layer and the second doping layer corresponding to the first region and the spacer region are removed, and the portion of the tunneling oxide layer corresponding to the spacer region is removed so that the spacer region exposes the semiconductor substrate, the first region and the second region are physically isolated, and the remaining oxide layer is removed.

8. The preparation method according to claim 7, characterized in that: The oxide layer is PSG or BSG.

9. The preparation method according to claim 7, characterized in that: The preparation method further includes: removing the remaining oxide layer, and patterning the metal layer located on the second region so that the metal layer forms a plurality of spaced structural units.

10. The preparation method according to claim 7, characterized in that: The preparation method further comprises: after removing the remaining oxide layer, forming an anti-reflection layer on the backlight surface of the semiconductor substrate.

11. A battery assembly, characterized in that: A back-contact solar cell comprising the back-contact solar cell according to any one of claims 1 to 6 or a back-contact solar cell obtained according to the preparation method according to any one of claims 7 to 10.

12. A photovoltaic system, characterized in that: A battery assembly comprising the battery assembly of claim 11.

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