Back surface structure of solar cell, solar cell, and work machine

Abstract

The utility model relates to the technical field of solar cells, and discloses a back structure of a solar cell, the solar cell and an operation machine. The back surface structure of the solar cell comprises a silicon substrate layer, a tunneling oxide layer, a doping layer and a back surface electrode which are arranged in sequence, the back electrode comprises a passivation layer, a first metal electrode layer and a second metal electrode layer which are arranged in sequence, the passivation layer is arranged on the doping layer, the first metal electrode layer is arranged on a partial structure of the passivation layer, and the first metal electrode layer penetrates through the passivation layer to be in contact with the doping layer; the second metal electrode layer is arranged on the passivation layer and is in contact with the first metal electrode layer; the first metal electrode layer is a silver layer, and the second metal electrode layer is an aluminum layer or a copper layer. According to the back surface structure of the solar cell, the solar cell and the operation machine, the production cost of the cell can be reduced, and the cell efficiency can be improved.

Description

Technical Field

[0001] The utility model relates to the technical field of solar cells, in particular to a back structure of a solar cell, a solar cell and an operating machine. Background Art

[0002] At present, the electrode material of TOPCon cells (Tunnel Oxide Passivated Contact solar cell) is silver paste. As the price of silver dots in China continues to rise, the manufacturing cost of TOPCon cells is also increasing. In order to reduce the manufacturing cost, silver reduction technology or silver paste replacement technology has received widespread attention.

[0003] The back structure of the TOPCon battery includes a silicon substrate, a tunneling oxide layer, a doping layer and a back electrode arranged in sequence. In the related silver reduction or silver paste replacement technology, the back electrode usually uses copper paste, aluminum paste, etc. to partially replace or completely replace the silver paste to reduce the amount of silver paste and reduce manufacturing costs. However, the metal composite between the silver paste and the doping layer is small and the contact performance is good, while the metal composite between the copper paste or aluminum paste and the doping layer is large and the contact performance is not as good as the silver paste, resulting in a significant decrease in the open circuit voltage and fill factor of the TOPCon battery in the related silver reduction or silver paste replacement technology, thereby reducing the battery efficiency. Utility Model Content

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the technical problem of low cell efficiency in the silver-reducing or silver paste replacement technology of the back electrode structure of solar cells in the related technology, and to provide a back structure of a solar cell, a solar cell and an operating machine.

[0005] In the first aspect, the utility model provides a back structure of a solar cell, comprising a silicon substrate layer, a tunneling oxide layer, a doping layer and a back electrode arranged in sequence; the back electrode comprises a passivation layer, a first metal electrode layer and a second metal electrode layer arranged in sequence, the passivation layer is arranged on the doping layer, the first metal electrode layer is arranged on a part of the structure of the passivation layer, the first metal electrode layer penetrates the passivation layer to form contact with the doping layer; the second metal electrode layer is arranged on the passivation layer and forms contact with the first metal electrode layer; the first metal electrode layer is a silver layer, and the second metal electrode layer is an aluminum layer or a copper layer.

[0006] Optionally, the second metal electrode layer is arranged to completely cover the passivation layer and the first metal electrode layer.

[0007] Optionally, the first metal electrode layer is arranged in a dot shape or a line shape.

[0008] Optionally, the thickness of the first metal electrode layer is between 0-10 μm.

[0009] Optionally, the thickness of the second metal electrode layer is between 0-30 μm.

[0010] Optionally, the thickness of the passivation layer is between 60-100 nm.

[0011] Optionally, the silicon substrate layer is an N-type silicon substrate layer, and the doped layer is an n+poly layer.

[0012] Optionally, the silicon substrate layer is a P-type silicon substrate layer, and the doped layer is a p-poly layer.

[0013] In a second aspect, the utility model further provides a solar cell, comprising: the back surface structure as described above.

[0014] In a third aspect, the utility model further provides an operating machine, comprising: the solar cell as described above.

[0015] Compared with the solar cells in the related art, the technical solution of the present application has at least the following advantages:

[0016] 1. Reduce the amount of silver used and the production cost of solar cells, thereby improving the competitiveness of products;

[0017] 2. The first metal electrode layer contacts the doped layer to conduct carriers, the metal composite is small and the contact performance is good, the second metal electrode layer contacts the first metal electrode layer and conducts electricity, but does not contact the doped layer, which improves the efficiency of the solar cell;

[0018] 3. The passivation layer is separated between the doping layer and the second metal electrode layer, which solves the problem that the aluminum layer is easy to burn through the doping layer when in contact with the doping layer;

[0019] 4. The second metal electrode layer is set as a whole metal layer and is located at the outermost side of the back structure, which can act as a back reflector to reduce light transmission, increase short-circuit current, and thus improve battery efficiency;

[0020] 5. Simple structure, easy for mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the specific implementation methods of the utility model or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1This is a schematic structural diagram of a back surface structure of a solar cell according to an embodiment of the utility model;

[0023] Figure 2 A schematic diagram of the distribution structure of a first metal electrode layer according to an embodiment of the utility model;

[0024] Figure 3 A schematic diagram of the distribution structure of another first metal electrode layer according to an embodiment of the utility model;

[0025] Figure 4-Figure 6 It is a structural schematic diagram of the back structure of a solar cell in the process of preparing the back structure of the embodiment of the utility model.

[0026] Description of reference numerals:

[0027] 1. Silicon substrate layer; 2. Tunneling oxide layer; 3. Doping layer; 4. Passivation layer; 5. First metal electrode layer; 6. Second metal electrode layer. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solution and advantages of the embodiment of the utility model clearer, the technical solution in the embodiment of the utility model will be clearly and completely described below in conjunction with the drawings in the embodiment of the utility model. Obviously, the described embodiment is a part of the embodiment of the utility model, not all the embodiments. Based on the embodiment of the utility model, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the utility model.

[0029] Combine the following Figures 1 to 6 , describing an embodiment of the utility model.

[0030] According to an embodiment of the present invention, on the one hand, a back structure of a solar cell is provided, such as Figure 1 As shown, it includes a silicon substrate layer 1, a tunneling oxide layer 2, a doping layer 3 and a back electrode arranged in sequence. Specifically, the back electrode includes a passivation layer 4, a first metal electrode layer 5 and a second metal electrode layer 6 arranged in sequence. Among them, the passivation layer 4 is arranged on the doping layer 3, and the first metal electrode layer 5 is arranged on a part of the structure of the passivation layer 4. The first metal electrode layer 5 is arranged through the passivation layer 4 to form a contact with the doping layer 3. The second metal electrode layer 6 is arranged on the passivation layer 4 and forms a contact with the first metal electrode layer 5.

[0031] The first metal electrode layer 5 is a silver layer, which is usually made of silver paste; the second metal electrode layer 6 is an aluminum layer or a copper layer, which is usually made of aluminum paste or copper paste.

[0032] In the technical solution of the present application, the first metal electrode layer 5 is arranged in a part of the passivation layer 4 to reduce the amount of silver used; and the passivation layer 4 is blocked between the doping layer 3 and the second metal electrode layer 6, and the first metal electrode layer 5 penetrates the passivation layer 4, so that it can form contact with both the doping layer 3 and the second metal electrode layer 6, while the second metal electrode layer 6 is not in contact with the doping layer 3.

[0033] By using the technical solution of the present application, since the first metal electrode layer 5 is in direct contact with the doped layer 3, the metal composite is small and the contact performance is good, carrier conduction can be achieved using a small amount of the first metal electrode layer 5. Since the second metal electrode layer 6 is in contact with the first metal electrode layer 5, it can play a conductive role, and the second metal electrode layer 6 is not in contact with the doped layer 3, it will not increase the metal composite or affect the contact performance, and will not reduce the open circuit voltage and fill factor of the solar cell. Therefore, compared with the silver-reducing or silver paste replacement technology of the back electrode structure of the solar cell in the related art, the technical solution of the present application reduces the amount of silver used, reduces the production cost, and improves the efficiency of the solar cell.

[0034] It should be noted that if Figure 1 and Figure 6 As shown, Figure 1 It is a schematic diagram of the back structure after heat treatment. Figure 6 Schematic diagram of the back structure before heat treatment. The first metal electrode layer 5 is usually subjected to a heat treatment process so that the first metal electrode layer 5 burns through the passivation layer 4, thereby forming contact with the doping layer 3, and realizing the conduction of carriers between the first metal electrode layer 5 and the doping layer 3. The second metal electrode layer 6 and the first metal electrode layer 5 are affected by the high temperature, and the metals melt together, so that the first metal electrode layer 5 and the second metal electrode layer 6 form a reliable contact, and the conduction of carriers between the first metal electrode layer 5 and the second metal electrode layer 6 is realized.

[0035] In the related art of the technology of reducing silver or replacing silver paste in the back electrode structure of solar cells, when the aluminum layer is directly used to replace the silver layer, the aluminum layer is in contact with the doped layer 3. During the heat treatment process, the aluminum layer easily burns through the doped layer 3, resulting in a high scrap rate and increasing the cost of production. In the technical solution of the present application, the passivation layer 4 is arranged between the second metal electrode layer 6 and the doped layer 3. When the second metal electrode layer 6 is an aluminum layer, the passivation layer 4 cannot be burned through, thereby solving the problem of aluminum paste burning through in the related art and further reducing the cost of production.

[0036] It can be understood that in the back structure of the present application, the passivation layer 4 is completely covered on the outside of the doping layer 3, the first metal electrode layer 5 partially covers the outside of the passivation layer 4, and is located between the passivation layer 4 and the second metal electrode layer 6; the second metal electrode layer 6 partially covers or completely covers the outside of the passivation layer 4 and the first metal electrode layer 5. In other words, the second metal electrode layer 6 is located at the outermost side of the back electrode.

[0037] In some embodiments, the second metal electrode layer 6 completely covers the passivation layer 4 and the first metal electrode layer 5, that is, the second metal electrode layer 6 is a whole metal layer, and the cross section of the second metal electrode layer 6 is a planar structure. In this way, the whole second metal electrode layer 6 can act as a back reflector to increase the short-circuit current and further improve the battery efficiency.

[0038] In some other embodiments, the second metal electrode layer 6 may also completely cover the passivation layer 4 and be disposed around the outside of the first metal electrode layer 5 to form contact with the first metal electrode layer 5 .

[0039] In some other embodiments, the second metal electrode layer 6 may also be arranged to partially cover the passivation layer 4 and the first metal electrode layer 5 , and the cross section of the second metal electrode layer 6 is a straight line or a gate line structure.

[0040] Furthermore, the present application does not specifically limit the structure and distribution position of the first metal electrode layer 5, as long as the function of carrier conduction can be achieved. Figure 2 and 3 As shown, the first metal electrode layer 5 is disposed on a part of the passivation layer 4. For example, the first metal electrode layer 5 can be disposed in a linear shape, such as a straight line ( Figure 2 ), grid line shape, etc. Exemplarily, the first metal electrode layer 5 can also be arranged in a dot shape, such as a rectangular dot shape ( Figure 3 ), round dots, etc.

[0041] In addition, while ensuring battery efficiency, the lower the thickness of the silver layer and the smaller the setting area, the lower the production cost. In order to achieve the purpose of cost reduction, in some embodiments, the thickness of the first metal electrode layer 5 is between 0-10 μm. Preferably, the thickness of the first metal electrode layer 5 is less than 5 μm, and more preferably, the thickness of the first metal electrode layer 5 is less than 2 μm. Exemplarily, the setting area of ​​the first metal electrode layer 5 is 1-3% of the setting area of ​​the passivation layer 4.

[0042] Furthermore, in some embodiments, the thickness of the second metal electrode layer 6 is between 0-30 μm, and preferably, the thickness of the second metal electrode layer 6 is less than 20 μm. Figure 1 and 6 As shown, illustratively, the thickness of the second metal layer is greater than the thickness of the first metal electrode layer 5 and is less than 20 μm.

[0043] Further, the passivation layer 4 may be a SiNx layer or other passivation film, which is not specifically limited in the present application. Exemplarily, the thickness of the passivation layer 4 is between 60-100 nm, and preferably, the thickness of the passivation layer 4 is between 70-100 nm.

[0044] It can be understood that in this embodiment, the thickness of the first metal electrode layer 5, the second metal electrode layer 6 and the passivation layer 4 refers to the size in a direction perpendicular to the first metal electrode layer 5, the second metal electrode layer 6 and the passivation layer 4 arranged in sequence.

[0045] It should be noted that the silicon substrate layer 1 can be an N-type silicon wafer or a P-type silicon wafer, the tunneling oxide layer 2 is deposited on the back side of the silicon substrate layer 1, and the thickness is generally between 1 and 2 nm, and the doping layer 3 is doped polysilicon deposited on the outside of the tunneling oxide layer 2. The tunneling oxide layer 2 and the doping layer 3 together form a passivation contact structure to provide good interface passivation for the back side of the silicon substrate layer 1.

[0046] That is, in some embodiments, the silicon substrate layer 1 may be an N-type silicon substrate layer, and accordingly, the doped layer 3 is an n+poly layer. Alternatively, in other embodiments, the silicon substrate layer 1 may be a P-type silicon substrate layer, and accordingly, the doped layer 3 is a p-poly layer.

[0047] According to an embodiment of the present invention, on the other hand, a solar cell is provided, comprising the back surface structure described in the above embodiment.

[0048] Since the solar cell of the present invention includes the above-mentioned back structure, the solar cell of the present invention has the same technical effect as the back structure of the solar cell of the present invention, which will not be described in detail here.

[0049] According to an embodiment of the present utility model, in yet another aspect, a working machine is provided, comprising the solar cell as described in the above embodiment.

[0050] Since the working machine of the present invention includes the above-mentioned solar cell, the working machine of the present invention has the same technical effect as the solar cell of the present invention, which will not be described in detail here.

[0051] It is understandable that solar cells are widely used. The operating machinery of the present invention can be large machinery such as energy storage power generation equipment and construction machinery, or small machinery such as household appliances and automobiles for daily use. This application does not make specific limitations on this.

[0052] According to an embodiment of the present invention, in another aspect, a preparation process of a back structure of a solar cell is provided, for obtaining the back structure as described above. The preparation process of the back structure of the solar cell specifically comprises the following steps:

[0053] S1: Performing texturing treatment on the silicon substrate layer 1; in this step, the silicon substrate layer 1 is usually an N-type or P-type silicon wafer, and the texturing treatment can remove damage on the surface of the silicon wafer and form a pyramid light-trapping structure on its surface, which is beneficial to reduce reflectivity.

[0054] S2: alkaline polishing is performed on the back side of the silicon substrate layer 1; this step removes impurities such as the oxide layer on the surface and edge of the silicon wafer by acid washing, water washing, etc.

[0055] S3: A tunneling oxide layer 2 and a doping layer 3 are sequentially deposited on the back side of the silicon substrate layer 1, and heat treatment is performed; in this step, an ultra-thin tunneling oxide layer 2 is first deposited on the back side of the silicon substrate layer 1, and then a doping layer 3 is deposited, and the tunneling oxide layer 2 and the doping layer 3 together form a passivation contact structure to provide good interface passivation for the back side of the silicon substrate layer 1.

[0056] S4: The back side of the silicon substrate layer 1 is subjected to a passivation anti-reflection film treatment to obtain a passivation layer 4, such as Figure 4 As shown; in this step, the passivation layer 4 may be a SiNx film or other types of passivation films. The hydrogen atoms generated during the formation of the passivation film have a passivating effect on the back of the silicon substrate layer 1.

[0057] S5: A first metal electrode layer 5 is formed on the back of the silicon substrate layer 1 and cured. Figure 5 As shown; in this step, a first metal electrode layer 5 is prepared on the back of the silicon substrate layer 1 by using a silver paste through a printing process, or a laser pattern transfer process, or a vapor deposition process, or a sputtering process. The thickness of the obtained first metal electrode layer 5 is less than 10 μm, preferably less than 5 μm.

[0058] S6: A second metal electrode layer 6 is formed on the back of the silicon substrate layer 1 and cured. Figure 6 In this step, the second metal electrode layer 6 can be prepared by using copper paste or aluminum paste through printing process, laser pattern transfer, evaporation process, sputtering process, etc. The thickness of the obtained second metal electrode layer 6 is less than 30 μm, preferably less than 20 μm.

[0059] S7: Perform high temperature sintering treatment to make the first metal electrode layer 5 contact with the doping layer 3 and the second metal electrode layer 6 respectively. Figure 1In this step, the sintering temperature is between 650-900° C., preferably between 700-750° C. Through the high temperature sintering process, the first metal electrode layer 5 burns through the passivation layer 4 and forms contact with the doping layer 3, and the first metal electrode layer 5 forms a stable contact with the second metal electrode layer 6.

[0060] The preparation process of the present application is simple, reduces the amount of silver used, reduces production costs, and in the back structure of the solar cell, the first metal electrode layer 5 is in contact with the doping layer 3 to conduct carriers, so the efficiency of the battery is high.

[0061] In addition, the present application also provides a process for preparing a solar cell, including the steps of the process for preparing the back structure of the solar cell described above, and including processing the front side of the silicon substrate layer 1 to obtain the solar cell described above. The process for preparing the solar cell includes the steps of:

[0062] S1': performing texturing treatment on the silicon substrate layer 1.

[0063] S2': performing boron diffusion treatment on the front surface of the silicon substrate layer 1 to prepare a PN junction.

[0064] S3': performing alkali polishing on the back side of the silicon substrate layer 1.

[0065] S4': depositing a tunneling oxide layer 2 and a doping layer 3 in sequence on the back side of the silicon substrate layer 1, and performing heat treatment.

[0066] S5': removing the polysilicon layer from the silicon substrate layer 1 by wrapping around and cleaning the surface of the silicon substrate layer 1.

[0067] S6': performing passivation anti-reflection film treatment on the front and back sides of the silicon substrate layer 1.

[0068] S7': metallizing the front and back sides of the silicon substrate layer 1;

[0069] S71′: partially printing silver paste on the outer surface of the back side of the silicon substrate layer 1 to obtain the first metal electrode layer 5, and performing a curing treatment; it is understandable that in this step, the first metal electrode layer 5 can also be obtained by laser pattern transfer, or evaporation process, or sputtering process;

[0070] S72': printing aluminum paste on the entire outer surface of the back side of the silicon substrate layer 1 to obtain the second metal electrode layer 6, and performing a curing treatment; it is understandable that copper paste or other metals with lower prices and better conductivity can also be used to obtain the second metal electrode layer 6 in this step;

[0071] S73': Print silver paste on the outer surface of the front side of the silicon substrate layer 1, and perform a curing treatment to obtain a front electrode layer.

[0072] S74′: performing high temperature sintering treatment to make the first metal electrode layer 5 contact with the doping layer 3 and the second metal electrode layer 6 respectively.

[0073] S8': performing laser induced sintering treatment; in this step, the laser induced sintering treatment can improve the Ag-Si contact on the front side of the solar cell, increase the open circuit voltage and fill factor of the solar cell, and thus improve the cell efficiency.

[0074] It is understandable that the solar cell of the present application is a TOPCon cell. Compared with the TOPCon cell in the related art, the technical solution of the present application has at least the following advantages:

[0075] 1. Reduce the amount of silver used and the production cost of TOPCon batteries, thereby improving the competitiveness of the product;

[0076] 2. The first metal electrode layer 5 contacts the doped layer 3 to conduct carriers, the metal composite is small and the contact performance is good, the second metal electrode layer 6 contacts the first metal electrode layer 5 and conducts electricity, but does not contact the doped layer 3, which improves the efficiency of the TOPCon cell;

[0077] 3. The passivation layer 4 is separated between the doping layer 3 and the second metal electrode layer 6, which solves the problem that the aluminum layer is in contact with the doping layer 3 and is easy to burn through the doping layer 3;

[0078] 4. The second metal electrode layer 6 is set as a whole metal layer and is located at the outermost side of the back structure, which can act as a back reflector to reduce light transmission, increase short-circuit current, and thus improve battery efficiency;

[0079] 5. Simple structure, easy for mass production.

[0080] Although the embodiments of the present invention are described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations are all within the scope defined by the appended claims.

Claims

1. A back structure of a solar cell, comprising a silicon substrate layer (1), a tunneling oxide layer (2), a doping layer (3) and a back electrode arranged in sequence; characterized in that: The back electrode comprises a passivation layer (4), a first metal electrode layer (5) and a second metal electrode layer (6) which are arranged in sequence, the passivation layer (4) being arranged on the doped layer (3), the first metal electrode layer (5) being arranged on a part of the structure of the passivation layer (4), the first metal electrode layer (5) penetrating the passivation layer (4) to form contact with the doped layer (3); the second metal electrode layer (6) being arranged on the passivation layer (4) and forming contact with the first metal electrode layer (5); The first metal electrode layer (5) is a silver layer, and the second metal electrode layer (6) is an aluminum layer or a copper layer.

2. The back surface structure of a solar cell according to claim 1, characterized in that: The second metal electrode layer (6) is arranged to completely cover the passivation layer (4) and the first metal electrode layer (5).

3. The back surface structure of a solar cell according to claim 2, characterized in that: The first metal electrode layer (5) is arranged in a dot shape or a line shape.

4. The back surface structure of a solar cell according to claim 3, characterized in that: The thickness of the first metal electrode layer (5) is between 0 and 10 μm.

5. The back surface structure of a solar cell according to claim 3, characterized in that: The thickness of the second metal electrode layer (6) is between 0 and 30 μm.

6. The back surface structure of a solar cell according to claim 3, characterized in that: The thickness of the passivation layer (4) is between 60-100 nm.

7. The back structure of a solar cell according to any one of claims 1 to 6, characterized in that: The silicon substrate layer (1) is an N-type silicon substrate layer, and the doped layer (3) is an n+poly layer.

8. The back structure of a solar cell according to any one of claims 1 to 6, characterized in that: The silicon substrate layer (1) is a P-type silicon substrate layer, and the doped layer (3) is a p-poly layer.

9. A solar cell, characterized in that: include: The back structure according to any one of claims 1 to 8.

10. A working machine, characterized in that: include: The solar cell according to claim 9.

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