Preparation method of silicon-based solar cell, silicon-based solar cell and photovoltaic module

Abstract

The invention discloses a preparation method of a silicon-based solar cell, the silicon-based solar cell and a photovoltaic module. The preparation method comprises the steps that first conductive slurry and second conductive slurry are printed on a functional layer of the silicon-based solar cell, the solid content of the first conductive slurry and the solid content of the second conductive slurry are different, and the first conductive slurry and the second conductive slurry are alternately arranged in the first direction of the main surface of the functional layer; sintering the first conductive slurry and the second conductive slurry, and forming first electric connecting pieces and second electric connecting pieces which are alternately arranged in the first direction; and performing laser welding on the conductive film layer on the first electric connecting piece and the second electric connecting piece which are alternately arranged. The preparation method can effectively reduce the cost of the metal electrode of the silicon-based solar cell.

Description

Technical Field

[0001] The invention relates to a method for preparing a silicon-based solar cell, a silicon-based solar cell and a photovoltaic module. Background Art

[0002] At present, the metal electrodes of silicon-based solar cells are generally made by slurry printing, drying and high-temperature sintering, and the metal electrodes of the silicon-based solar cells are generally made of a slurry. There is currently no effective way to control the preparation cost of the metal electrodes of silicon-based solar cells, so the cost of silicon-based solar cells still has room for reduction. Summary of the invention

[0003] In view of this, the present invention provides a method for preparing a silicon-based solar cell, a silicon-based solar cell and a photovoltaic module, which can effectively reduce the cost of the metal electrode of the silicon-based solar cell, thereby achieving the purpose of reducing the cost of the silicon-based solar cell.

[0004] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0005] In a first aspect, the present invention provides a method for preparing a silicon-based solar cell, comprising:

[0006] Step 1: Printing a first conductive paste and a second conductive paste on the functional layer of the silicon-based solar cell, respectively, wherein the first conductive paste and the second conductive paste have different solid contents and are alternately arranged in a first direction on the main surface of the functional layer;

[0007] Step 2: sintering the first conductive paste and the second conductive paste to form first electrical connectors and second electrical connectors that are alternately arranged in the first direction;

[0008] Step 3: laser welding the conductive film layer to the first electrical connectors and the second electrical connectors that are alternately arranged.

[0009] In a second aspect, an embodiment of the present invention provides a silicon-based solar cell, comprising: a silicon substrate, a functional layer stacked on the silicon substrate, a first electrical connector, a second electrical connector, and a conductive film layer, wherein:

[0010] The first electrical connectors and the second electrical connectors are alternately arranged in a first direction on the main surface of the functional layer;

[0011] The conductive film layer is electrically connected to the first electrical connector and the second electrical connector;

[0012] The volume of the first electrical connector is different from the volume of the second electrical connector.

[0013] In a third aspect, an embodiment of the present invention provides a photovoltaic module, comprising a battery string of a plurality of battery cells connected in series, wherein the battery cell is a silicon-based solar cell implemented in the second aspect, or is obtained by cutting the silicon-based solar cell implemented in the second aspect;

[0014] Wherein, two adjacent battery cells are electrically connected through the connection between the conductive film layers included in the battery cells.

[0015] The technical solution of the first aspect of the above invention has the following advantages or beneficial effects:

[0016] The technical solution provided by the embodiment of the present invention is to respectively print a first conductive paste and a second conductive paste with different solid contents on the functional layer of a silicon-based solar cell. The first conductive paste and the second conductive paste with different solid contents are sintered to form alternatingly arranged first electrical connectors and second electrical connectors, and to form electrodes of the silicon-based solar cell by laser welding a conductive film layer to the alternatingly arranged first electrical connectors and second electrical connectors. The costs of the first conductive paste and the second conductive paste with different solid contents are different. By introducing the first conductive paste and the second conductive paste with different solid contents and a low-cost conductive film layer, the cost of the metal electrode of the silicon-based solar cell can be effectively reduced, thereby achieving the purpose of reducing the cost of the silicon-based solar cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the main process of the method for preparing a silicon-based solar cell provided in an embodiment of the present invention;

[0018] Figure 2 is a schematic structural diagram of a first slurry web provided according to an embodiment of the present invention;

[0019] Figure 3 is a schematic structural diagram of a second slurry screen provided according to an embodiment of the present invention;

[0020] Figure 4 is a schematic structural diagram of a first conductive paste printed on a functional layer of a silicon-based solar cell through a first paste screen according to an embodiment of the present invention;

[0021] Figure 5 is a schematic diagram of a relative position relationship between a printed first conductive paste and a second conductive paste provided according to an embodiment of the present invention;

[0022] Figure 6 is a first relative position relationship between the first electrical connector 31 and the second electrical connector 32 according to an embodiment of the present invention;

[0023] Figure 7is a second relative position relationship between the first electrical connector 31 and the second electrical connector 32 according to an embodiment of the present invention;

[0024] Figure 8 is a third relative position relationship between the first electrical connector 31 and the second electrical connector 32 according to the embodiment of the present invention;

[0025] Fig. 9 Schematic diagram of the cross-sectional structure of a silicon-based solar cell according to an embodiment of the present invention.

[0026] Reference numerals:

[0027] 001-first printed board; 002-second printed board; 10-silicon substrate; 20-functional layer; 21-tunneling oxide layer; 22-doped polysilicon layer; 23-passivation anti-reflection layer; 31-first electrical connection; 31'-first conductive paste; 32-second electrical connection; 32'-second conductive paste; 33-conductive film layer; 34-electrical connection area. DETAILED DESCRIPTION

[0028] Existing high-efficiency silicon-based solar cells such as Topcon and BC require the use of high-temperature slurry sintering to prepare conductive metal electrodes. Generally, the composition of high-temperature sintering conductive slurry is complex: it contains organic substances that make the slurry have good screen printing performance; it also contains glass materials that corrode the dielectric film layer on the surface of the battery cell to make the slurry have a relatively strong adhesion; it also contains metal particles with electrical conductivity, etc. For crystalline silicon photovoltaic cells, the slurry needs to be dried and quickly sintered after printing to complete the preparation of the electrode. After sintering, most of the organic matter disappears due to volatilization and oxidation, and most of the glass and metal particles will remain to form a conductive metal electrode.

[0029] The solid content in the conductive paste plays an important role in the performance of the metal electrode it forms. On the one hand, a higher solid content enables the electrode to have better adhesion and can ensure the tensile force requirements of the electrode; at the same time, a higher solid content can also ensure that the electrode has better conductivity. However, the conductive metal particles in the conductive paste, such as silver particles, are precious metals with high costs. Similarly, the rare metal elements in the glass are also high-cost materials; such a high solid content conductive paste is expensive and is not conducive to reducing the price of crystalline silicon solar cell production.

[0030] In order to solve the problem that existing silicon-based solar cells have a relatively high consumption of high-solid content conductive paste, embodiments of the present invention provide a method for preparing a silicon-based solar cell and a novel silicon-based solar cell.

[0031] in, Figure 1A schematic diagram showing the main process of a method for preparing a silicon-based solar cell provided by an embodiment of the present invention is shown. Figures 2 to 4 A schematic diagram showing various relative position relationships between a first electrical connector and a second electrical connector prepared by a preparation method provided by an embodiment of the present invention; Figure 5 A partial structural schematic diagram of a silicon-based solar cell provided by an embodiment of the present invention is shown.

[0032] like Figure 1 As shown, the method for preparing a silicon-based solar cell provided by an embodiment of the present invention may include the following steps:

[0033] Step S101: printing a first conductive paste 31' and a second conductive paste 32' on the functional layer 20 of the silicon-based solar cell, respectively, wherein the first conductive paste 31' and the second conductive paste 32' have different solid contents and are alternately arranged in a first direction on the main surface of the functional layer 20;

[0034] The silicon-based solar cell may be any type of solar cell, such as a TOPCon cell, a BC cell, a HJT cell, etc.

[0035] Among them, silicon-based solar cells generally include a silicon substrate 10 and a functional layer 20 provided on one main surface or two main surfaces of the silicon substrate 10. The functional layer 20 can be a single-layer structure or a stacked structure. Specifically, if the functional layer 20 is a single-layer structure, the functional layer 20 generally refers to a doping layer formed on the main surface of the silicon substrate 10 and containing N-type doping elements or P-type doping elements (the doping layer can be formed by diffusing the doping elements on the main surface of the silicon substrate 10). If the functional layer 20 is a stacked structure, the functional layer 20 can be a multi-layer doping layer stacked on the main surface of the silicon substrate 10 (each doping layer contains the same doping element such as N-type doping element or P-type doping element); in addition, the functional layer 20 of the stacked structure can also be a general term for multiple functional film layers formed by stacking. For example, Fig. 9As shown, the functional layer 20 of the stacked structure can be the general term for the tunneling oxide layer 21, the doped polysilicon layer 22 and the passivation anti-reflection layer 23 stacked sequentially from the inside to the outside on the main surface of the silicon substrate 10. For another example, the functional layer 20 of the stacked structure can also be the general term for the intrinsic silicon-containing thin film layer, the silicon-containing thin film layer containing doped elements, the passivation layer and the anti-reflection layer stacked sequentially from the inside to the outside on the main surface of the silicon substrate 10. For another example, the functional layer 20 of the stacked structure can also be the general term for the intrinsic amorphous silicon passivation layer, the doped amorphous silicon layer and the transparent conductive film layer (the transparent conductive film layer can be an ITO conductive film layer or an FTO conductive film layer) stacked sequentially from the inside to the outside on the main surface of the silicon substrate 10. Among them, ITO (Indium Tin Oxide) is mainly composed of indium oxide (In2O3) and tin oxide (SnO2), and FTO (Fluorine-doped Tin Oxide) is a material in which fluorine is doped into tin oxide (SnO2) to enhance the conductivity. The functional layer 20 can be a functional layer 20 of the light-receiving surface and / or the backlight surface of a silicon-based solar cell. Preferably, the functional layer 20 is a functional layer 20 of the backlight surface of a silicon-based solar cell.

[0036] It is worth noting that the embodiment of the present invention involves printing a conductive paste on the functional layer 20, which means that the conductive paste is printed on the side of the functional layer 20 away from the silicon substrate 10 (the silicon substrate 10 is the substrate of the silicon-based solar cell), and does not specifically mean that the electrical connector formed by the conductive paste during the use of the silicon-based solar cell is located above the functional layer 20. For example, if the functional layer 20 is the functional layer 20 on the backlight side of the silicon-based solar cell, during the printing process, if the functional layer 20 on the backlight side of the silicon-based solar cell faces upward, the first conductive paste 31' and the second conductive paste 32' are located above the functional layer 20 on the backlight side of the silicon-based solar cell; if the functional layer 20 on the backlight side of the silicon-based solar cell faces downward, the first conductive paste 31' and the second conductive paste 32' are located below the functional layer 20 on the backlight side of the silicon-based solar cell; if the functional layer 20 on the light-receiving side of the silicon-based solar cell faces upward, the first conductive paste 31' and the second conductive paste 32' are located above the functional layer 20 on the light-receiving side of the silicon-based solar cell; if the functional layer 20 on the light-receiving side of the silicon-based solar cell faces downward, the first conductive paste 31' and the second conductive paste 32' are located below the functional layer 20 on the light-receiving side of the silicon-based solar cell.

[0037] Generally speaking, the solid content of the conductive paste refers to the ratio of the mass of the entire paste to the remaining materials (such as glass, conductive metal particles and inorganic additives, etc.) after the organic substances in the paste volatilize after sintering. Among them, the glass in the conductive paste not only firmly adheres to the surface of the silicon wafer, but also firmly combines the metal particles in the electrode.

[0038] Conductive pastes with different solid contents have different performances and costs. Generally speaking, the higher the solid content, the better the conductive performance of the conductive paste, but the higher its cost. Based on this, the technical solution provided in the embodiment of the present invention can effectively reduce the cost of solar cells by selecting the first conductive paste 31' and the second conductive paste 32' with different solid contents. In order to overcome the problem of performance differences between conductive pastes with different solid contents, the technical solution provided in the embodiment of the present invention can effectively balance the difference between the performance of the first electrical connector 31 formed by the first conductive paste 31' and the performance of the second electrical connector 32 formed by the second conductive paste 32' by introducing a low-cost conductive film layer 33 in the subsequent steps, thereby ensuring that the silicon-based solar cell can stably and evenly derive current.

[0039] The different solid contents of the first conductive paste 31 ′ and the second conductive paste 32 ′ may be that the solid content of the first conductive paste 31 ′ is higher than that of the second conductive paste 32 ′ or the solid content of the first conductive paste 31 ′ is lower than that of the second conductive paste 32 ′.

[0040] The following detailed description of the subsequent steps is made by taking the solid content of the first conductive paste 31' as an example, which is higher than the solid content of the second conductive paste 32'. That is, the conductive paste with a high solid content involved in the following technical solution is used as the first conductive paste 31', and the conductive paste with a low solid content involved in the following technical solution is used as the second conductive paste 32'. It is worth noting that the high solid content and the low solid content involved in the following technical solution are relative, that is, the solid content of the first conductive paste 31' is greater than the solid content of the second conductive paste 32'.

[0041] Specifically, the percentage of the solid mass of the first conductive paste 31' used in step S101 to the mass of the entire paste (i.e., the solid content of the first conductive paste 31') is 91% to 97%. For example, the solid content of the first conductive paste 31' may be 91%, 92%, 93%, 94%, 95%, 96% or 97%. The percentage of the solid mass of the second conductive paste 32' used in step S101 to the mass of the entire paste (i.e., the solid content of the second conductive paste 32') is 60% to 90%, for example, the solid content of the second conductive paste 32' may be 60%, 65%, 68%, 70%, 75%, 80%, 85% or 90%. Preferably, the solid content of the second conductive paste 32' is 60% to 80%, for example, the solid content of the second conductive paste 32' is preferably 60%, 65%, 68%, 70%, 75% or 80%. More preferably, the solid content of the second conductive paste 32 ′ is 60% to 70%. For example, the solid content of the second conductive paste 32 ′ is more preferably 60%, 65%, 68% or 70%.

[0042] The first direction generally refers to the direction of the length or width of the silicon-based solar cell. It is worth noting that for BC cells, the first direction generally refers to the direction of the N functional region or the P functional region of the BC cell.

[0043] Specifically, the specific implementation scheme of step S101 may include: using a first paste screen 001 having multiple columns and rows of printing holes to print a first conductive paste 31' with a high solid content, wherein the multiple printing holes in each row of the first paste screen 001 are linearly spaced, each row of printing holes in the first paste screen 001 extends along a first direction, and each column of printing holes in the first paste screen 001 extends along a second direction of the main surface of the functional layer 20, and the first direction is perpendicular to the second direction; using a second paste screen 002 having multiple columns and rows of printing holes to print a second conductive paste 32' with a low solid content, wherein the multiple columns and rows of printing holes in the second paste screen 002 correspond one-to-one to the multiple columns and rows of the first paste screen 001, and the multiple printing holes belonging to the same row of the second paste screen 002 and the first paste screen 001 are staggered.

[0044] It is worth noting that there is no strict order between the use of the first paste screen 001 having multiple columns and rows of printing holes to print the first conductive paste 31' with a high solid content and the use of the second paste screen 002 having multiple columns and rows of printing holes to print the second conductive paste 32' with a low solid content. The first conductive paste 31' can be printed first and then the second conductive paste 32', or the second conductive paste 32' can be printed first and then the first conductive paste 31'. In addition, the second paste screen 002 can be used to print the first conductive paste 31', and the first printing paste screen 001 can be used to print the second conductive paste 32'.

[0045] For example, Figure 2 The structure of the first slurry web 001 shown in FIG. Figure 3 The second paste stencil 002 shown in the figure, wherein the first paste stencil 001 may include 7 columns of A1, A2, A3, A4, A5, A6 and A7 and 7 rows of printing holes of B1, B2, B3, B4, B5, B6 and B7, and the second paste stencil 002 also includes 7 columns of A1, A2, A3, A4, A5, A6 and A7 and 7 rows of printing holes of B1, B2, B3, B4, B5, B6 and B7 accordingly. The first conductive paste 31' structure printed on the functional layer 20 of the silicon-based solar cell by the first paste stencil 001 is as shown in FIG. Figure 4 As shown. Figure 4 On the basis of the above, the second conductive paste 32' is further printed through the second paste screen 002 to obtain the following Figure 5 The structure shown in the figure: in each row, the first conductive paste 31' and the second conductive paste 32' are arranged alternately, and in each column, the first conductive paste 31' and the second conductive paste 32' are also arranged alternately. With this structure, the amount of the first conductive paste 31' with a high solid content can be reduced to effectively control the cost of the conductive paste, thereby reducing the cost of silicon-based solar cells.

[0046] Furthermore, if Figure 2 As shown, for the first slurry screen 001, the plurality of printing holes in every two adjacent rows are staggered. Further, the plurality of printing holes in every two adjacent columns in the first slurry screen 001 are also staggered.

[0047] In addition, for the first slurry screen 001, a plurality of printing holes in each column may be arranged linearly.

[0048] Furthermore, if Figure 3 As shown, for the second slurry screen 002, the plurality of printing holes in each two adjacent rows are staggered. Further, the plurality of printing holes in each two adjacent columns in the second slurry screen 002 are also staggered.

[0049] In addition, for the second slurry screen 002, a plurality of printing holes in each column may be arranged linearly.

[0050] It is worth noting that for printed holes Figure 2 and Figure 3 The rectangular cross-section is given for example only. The cross-section of the printing hole may also be other shapes such as circular, elliptical, square, etc.

[0051] in addition, Figure 5 The first conductive paste 31' with a high solid content and the second conductive paste 32' with a low solid content are isolated from each other in a relative positional relationship. In addition, the first conductive paste 31' and the second conductive paste 32' may overlap or contact each other. That is, the adjacent first conductive paste 31' and the second conductive paste 32' printed in this step may overlap or be connected or spaced apart. In addition, the height, width or length of the printed first conductive paste 31' and the second conductive paste 32' may be the same or different.

[0052] In this step, the second conductive paste 32' with low solid content replaces part of the first conductive paste 31' with high solid content, thereby ensuring that the formed conductive structure is firmly combined with the functional layer 20 and making the formed conductive structure have relatively strong tensile force, and at the same time reducing the preparation cost of silicon-based solar cells.

[0053] Furthermore, in the above-mentioned two printing processes using the first paste screen 001 and the second paste screen 002 in sequence, in order to avoid the paste screen used for the second printing (which can be the first paste screen 001 or the second paste screen 002) from damaging the conductive paste printed for the first time (the conductive paste printed for the first time can be the first conductive paste 31' or the second conductive paste 32'), after the first printing is completed, the conductive paste printed for the first time is dried first, and then the second printing is performed (it can be understood that after the first printing of the first conductive paste 31', the second printing is the second conductive paste 32'; after the first printing of the second conductive paste 32', the second printing is the first conductive paste 31'). In addition, after the second printing is completed, the conductive paste printed for the second time can also be dried again to preliminarily solidify the conductive paste.

[0054] In addition, by introducing the second conductive paste 32' with a low solid content, due to the lower mass fraction of silver particles and glass components, for the functional layer 20 having a passivation layer or a passivation anti-reflection layer 23, its damage to the passivation layer or the passivation anti-reflection layer 23 can be reduced at the same sintering temperature, which is beneficial to improving the open circuit voltage of the silicon-based solar cell.

[0055] Step S102: sintering the first conductive paste 31 ′ and the second conductive paste 32 ′ to form first electrical connectors 31 and second electrical connectors 32 alternately arranged in a first direction;

[0056] The sintered first conductive paste 31 ′ forms the first electrical connection member 31 ; the sintered second conductive paste 32 ′ forms the second electrical connection member 32 .

[0057] It can be understood that, in the case where the volumes of the first conductive paste 31' and the second conductive paste 32' printed in step S101 are the same, the first electrical connector 31 and the second electrical connector 32 formed by sintering in this step have different volumes due to the different solid contents of the first conductive paste 31' and the second conductive paste 32'. Specifically, for the same volume of conductive paste, the higher the solid content, the larger the volume of the electrical connector formed after sintering. In the case where the solid content of the first conductive paste 31' is greater than the solid content of the second conductive paste 32', and the printed amount of the first conductive paste 31' is the same as the printed amount of the second conductive paste 32', the volume of the first electrical connector 31 formed by sintering the first conductive paste 31' is greater than the volume of the second electrical connector 32 formed by sintering the second conductive paste 32'.

[0058] Among them, Figures 6 to 8 As shown in FIG. 1 , the first electrical connectors 31 and the second electrical connectors 32 alternately arranged in the first direction D1 form an electrical connection area 34. Figures 6 to 8 As shown, the first electrical connectors 31 and the second electrical connectors 32 in the same row form an electrical connection area 34. In addition, for the electrical connection area 34, multiple rows of first electrical connectors 31 and second electrical connectors 32 may form an electrical connection area 34.

[0059] The relative position relationship between the first electrical connector 31 and the second electrical connector 32 obtained by combining the above steps S101 and S102 is exemplarily shown as follows: Figures 6 to 8 That is, Figures 6 to 8 As shown, the first electrical connector 31 and the second electrical connector 32 are generally arranged alternately in the first direction D1. Figure 6 and Figure 8 As shown, the first electrical connector 31 and the second electrical connector 32 are spaced apart in the first direction D1. Figure 7 As shown, the first electrical connector 31 and the second electrical connector 32 intersect in the first direction D1 (i.e., one end of the adjacent first electrical connector 31 in the same row contacts one end of the second electrical connector 32). In addition, the first electrical connector 31 and the second electrical connector 32 may also partially overlap in the first direction D1.

[0060] Step S103 : laser welding the conductive film layer 33 to the alternately arranged first electrical connectors 31 and second electrical connectors 32 .

[0061] The conductive film layer 33 is alternately arranged with the first electrical connector 31 and the second electrical connector 32 to balance the carrier transmission capacity of each region of the silicon-based solar cell and avoid imbalance in carrier transmission.

[0062] Specifically, in view of the situation that a plurality of electrical connection areas 34 are divided in the above step S102, the step S103 can connect the plurality of electrical connection areas 34 to the same conductive film layer 33; or, each electrical connection area 34 is connected to a conductive film layer 33, and any two electrical connection areas 34 are connected to different conductive film layers 33. Preferably, each row of alternately arranged first electrical connectors 31 and second electrical connectors 32 forms an electrical connection area 34, and an independent conductive film layer 33 is disposed in one electrical connection area 34.

[0063] The conductive film layer 33 may be a single-layer film layer or a laminated composite film layer composed of at least one metal, and the conductive film layer 33 has laser weldability in the corresponding position area of ​​the first electrical connector 31 and the second electrical connector 32. Specifically, the metal forming the conductive film layer 33 may be any one or more of aluminum, copper, silver, etc. Preferably, the conductive film layer 33 is an aluminum film layer, a copper film layer, or an aluminum-copper alloy film layer. The conductive film layer 33 may be consistent in shape with the first electrical connector 31 and the second electrical connector 32.

[0064] The conductive film layer 33 is welded to the sintered first electrical connector 31 and the second electrical connector 32 using laser welding technology. Specifically, the laser welding process may be to irradiate the laser to the region corresponding to the first electrical connector 31 and the region corresponding to the second electrical connector 32 in the conductive film layer 33. Since the high energy provided by the laser is instantly absorbed by the conductive film layer 33 and the first electrical connector 31 and the second electrical connector 32, the conductive film layer 33 and the surface of the first electrical connector 31 and the surface of the second electrical connector 32 are melted and metallized, and after cooling, the first electrical connector 31 and the second electrical connector 32 are welded to the conductive film layer 33. In addition, the laser welding process may also be to irradiate the laser to the region corresponding to the first electrical connector 31 or the region of the second electrical connector 32 in the conductive film layer 33. When the laser is irradiated to the region corresponding to the first electrical connector 31, the conductive film layer 33 and the surface of the first electrical connector 31 are melted and metallized, and after cooling, the first electrical connector 31 and the conductive film layer 33 are welded, so that the first electrical connector 31 and the conductive film layer 33 are fixedly connected. When the laser is irradiated to the area corresponding to the second electrical connector 32, the conductive film layer 33 and the surface of the second electrical connector 32 are melted and metallized and composited. After cooling, the second electrical connector 32 and the conductive film layer 33 are welded, so that the second electrical connector 32 and the conductive film layer 33 are fixedly connected. Preferably, the laser is simultaneously irradiated to the area corresponding to the first electrical connector 31 and the area of ​​the second electrical connector 32 in the conductive film layer 33, so that the conductive film layer 33 is metallized and composited with the surface of the first electrical connector 31 and the surface of the second electrical connector 32 at the same time.

[0065] Specifically, the laser parameters (such as wavelength, energy, action time, etc.) selected by the laser welding technology can be determined according to the energy required for melting and metallization of the first electrical connector 31, the second electrical connector 32 and the conductive film layer 33, and the selected laser parameters are not limited here.

[0066] Generally speaking, the width of the laser beam used for laser welding in step S103 does not exceed the width of the first electrical connector 31 and the width of the second electrical connector 32. More specifically, in the process of welding the conductive film layer 33 to the first electrical connector 31 and the second electrical connector 32 using the laser welding technology, the area of ​​the laser welding (the area of ​​the pattern scanned by the laser) is not larger than the area of ​​the first electrical connector 31 and the second electrical connector 32, and the pattern of the laser welding can be designed to be any shape.

[0067] Furthermore, if Fig. 9The cross-sectional schematic diagram of the structure formed after the processing of this step is shown, and the length of the conductive film layer 33 in the first direction is greater than the length of the silicon substrate 10 of the silicon-based solar cell in the first direction. Through this design, the conductive film layer 33 replaces the welding strip used for serially connecting the cells in the photovoltaic module, that is, the solar cell is divided into half cells, and the conductive film layer extending from the cell on a cell is overlapped and connected to the conductive film layer 33 of the adjacent cell, so as to realize the serial connection between the cells, reduce the production cost of the photovoltaic module, omit the welding strip alignment and welding process in the production process of the photovoltaic module, and can improve the production efficiency of the photovoltaic module.

[0068] By printing the first conductive paste 31' and the second conductive paste 32' with different solid contents (for example, the first conductive paste 31' with high solid content and the second conductive paste 32' with low solid content) on the functional layer 20 of the silicon-based solar cell, the first conductive paste 31' and the second conductive paste 32' with different solid contents are sintered to form the first electrical connectors 31 and the second electrical connectors 32 arranged alternately, and the conductive film layer 33 is laser welded to the first electrical connectors 31 and the second electrical connectors 32 arranged alternately to form the electrodes of the silicon-based solar cell. The first conductive paste 31' and the second conductive paste 32' with different solid contents have different costs. The first conductive paste 31' and the second conductive paste 32' with different solid contents and the low-cost conductive film layer 33 can effectively reduce the cost of the metal electrode of the silicon-based solar cell, thereby achieving the purpose of reducing the cost of the silicon-based solar cell.

[0069] More preferably, the technical solution provided in the embodiment of the present invention is to prepare a conductive structure on the back surface of a Topcon battery or a BC-type battery to replace the electrode on the back surface of the existing Topcon battery or BC-type battery, thereby reducing the preparation cost of the high-efficiency battery while maintaining the battery efficiency.

[0070] In addition, in the structure obtained by the above preparation method, the first electrical connector 31 formed by the first conductive paste 31' with a high solid content has good bonding properties, which can ensure the firm bonding between the conductive paste and the silicon wafer, and can also ensure the firm bonding between the conductive film layer 33 and the conductive electrode welding point, and ensure the comprehensive tensile force requirements of the electrode. The second electrical connector 32 formed by the second conductive paste 32' with a low solid content has excellent charge conduction capability, ensuring the conductivity of the solar cell. In addition, by introducing the conductive film layer 33, the conduction difference between the first electrical connector 31 and the second electrical connector 32 can also be balanced, ensuring that the silicon-based solar cell can stably transmit current.

[0071] Furthermore, an embodiment of the present invention provides a silicon-based solar cell. The silicon-based solar cell is a silicon-based solar cell prepared by the preparation method provided in the above embodiment. Fig. 9As shown, the silicon-based solar cell may include: a silicon substrate 10, a functional layer 20 stacked on the silicon substrate 10, a first electrical connection member 31, a second electrical connection member 32 and a conductive film layer 33, wherein:

[0072] The first electrical connectors 31 and the second electrical connectors 32 are alternately arranged in a first direction on the main surface of the functional layer 20; the conductive film layer 33 is electrically connected to the first electrical connectors 31 and the second electrical connectors 32;

[0073] The volume of the first electrical connection member 31 is different from the volume of the second electrical connection member 32 .

[0074] Since the volume of the first electrical connector 31 is different from that of the second electrical connector 32 , the material usage of the electrical connector can be reduced, thereby effectively reducing the cost of the silicon-based solar cell.

[0075] Among them, silicon-based solar cells generally include a silicon substrate 10 and a functional layer 20 provided on one main surface or two main surfaces of the silicon substrate 10. The functional layer 20 can be a single-layer structure or a stacked structure. Specifically, if the functional layer 20 is a single-layer structure, the functional layer 20 generally refers to a doping layer formed on the main surface of the silicon substrate 10 and containing N-type doping elements or P-type doping elements (the doping layer can be formed by diffusing the doping elements on the main surface of the silicon substrate 10). If the functional layer 20 is a stacked structure, the functional layer 20 can be a multi-layer doping layer stacked on the main surface of the silicon substrate 10 (each doping layer contains the same doping element such as N-type doping element or P-type doping element); in addition, the functional layer 20 of the stacked structure can also be a general term for multiple functional film layers formed by stacking. For example, Fig. 9As shown, the functional layer 20 of the stacked structure can be the general term for the tunneling oxide layer 21, the doped polysilicon layer 22 and the passivation anti-reflection layer 23 stacked sequentially from the inside to the outside on the main surface of the silicon substrate 10. For another example, the functional layer 20 of the stacked structure can also be the general term for the intrinsic silicon-containing thin film layer, the silicon-containing thin film layer containing doped elements, the passivation layer and the anti-reflection layer stacked sequentially from the inside to the outside on the main surface of the silicon substrate 10. For another example, the functional layer 20 of the stacked structure can also be the general term for the intrinsic amorphous silicon passivation layer, the doped amorphous silicon layer and the transparent conductive film layer (the transparent conductive film layer can be an ITO conductive film layer or an FTO conductive film layer) stacked sequentially from the inside to the outside on the main surface of the silicon substrate 10. Among them, ITO (Indium Tin Oxide) is mainly composed of indium oxide (In2O3) and tin oxide (SnO2), and FTO (Fluorine-doped Tin Oxide) is a material in which fluorine is doped into tin oxide (SnO2) to enhance the conductivity. The functional layer 20 can be a functional layer 20 of the light-receiving surface and / or the backlight surface of a silicon-based solar cell. Preferably, the functional layer 20 is a functional layer 20 of the backlight surface of a silicon-based solar cell.

[0076] Among them, the first electrical connector 31 is generally formed by a first conductive paste 31', and the second electrical connector 32 is generally formed by a second conductive paste 32', wherein the solid content of the first conductive paste 31' is different from the solid content of the second conductive paste 32'. In other words, the first electrical connector 31 and the second electrical connector 32 are formed by sintering conductive pastes with different solid contents. Exemplarily, the solid content of the first conductive paste 31' is greater than the solid content of the second conductive paste 32'. Generally speaking, the solid content of the conductive paste refers to the ratio of the mass of the entire paste to the remaining materials (such as glass, conductive metal particles, and inorganic additives, etc.) after the organic substances in the paste volatilize after the conductive paste is sintered. Among them, the glass in the conductive paste not only firmly adheres to the surface of the silicon wafer, but also firmly combines the metal particles in the electrode.

[0077] Specifically, the percentage of the solid mass of the first conductive paste 31' used to form the first electrical connection 31 to the whole paste mass (i.e., the solid content of the first conductive paste 31') is 91% to 97%. For example, the solid content of the first conductive paste 31' may be 91%, 92%, 93%, 94%, 95%, 96% or 97%. The percentage of the solid mass of the second conductive paste 32' used to form the second electrical connection 32 to the whole paste mass (i.e., the solid content of the second conductive paste 32') is 60% to 90%, for example, the solid content of the second conductive paste 32' may be 60%, 65%, 68%, 70%, 75%, 80%, 85% or 90%. Preferably, the solid content of the second conductive paste 32' is 60% to 80%, for example, the solid content of the second conductive paste 32' is preferably 60%, 65%, 68%, 70%, 75% or 80%. More preferably, the solid content of the second conductive paste 32 ′ is 60% to 70%. For example, the solid content of the second conductive paste 32 ′ is more preferably 60%, 65%, 68% or 70%.

[0078] Among them, Figures 6 to 8 As shown, there can be multiple relative positional relationships between adjacent first electrical connectors 31 and second electrical connectors 32. Specifically, the relative positional relationship can be that adjacent first electrical connectors 31 and second electrical connectors 32 overlap; that adjacent first electrical connectors 31 and second electrical connectors 32 are connected; or that adjacent first electrical connectors 31 and second electrical connectors 32 are spaced apart.

[0079] In addition, the conductive film layer 33 may be a single-layer film layer or a laminated composite film layer composed of at least one metal. Specifically, the metal forming the conductive film layer 33 may be any one or more of aluminum, copper, silver, etc. Preferably, the conductive film layer 33 is an aluminum film layer, a copper film layer, or an aluminum-copper alloy film layer. The conductive film layer 33 is generally laser welded to the first electrical connector 31 and the second electrical connector 32. The conductive film layer 33 is alternately arranged with the first electrical connector 31 and the second electrical connector 32 to balance the carrier transmission capacity of each region of the silicon-based solar cell and avoid imbalance in carrier transmission.

[0080] Furthermore, in Figures 6 to 8 The first electrical connection members 31 and the second electrical connection members 32 are alternately arranged in the first direction D1 to form an electrical connection area 34; accordingly, a plurality of electrical connection areas 34 are arranged in a second direction D2 on the main surface of the functional layer 20. Figures 6 to 8 As shown, the first direction D1 and the second direction D2 are perpendicular to each other.

[0081] Specifically, the first electrical connectors 31 and the second electrical connectors 32 of the plurality of electrical connection areas 34 are electrically connected to the same conductive film layer 33; or, each electrical connection area 34 is connected to a conductive film layer 33, and any two rows of electrical connection areas 34 are connected to different conductive film layers 33. That is, the electrical connection areas 34 correspond to the conductive film layers 33 one by one.

[0082] Furthermore, if Fig. 9 As shown, the length of the conductive film layer 33 in the first direction is greater than the length of the silicon-based solar cell in the first direction D1. With this design, the conductive film layer 33 can replace the welding strip used to connect the cells in series in the photovoltaic module, that is, the solar cell is divided into half cells, and the portion of the conductive film layer 33 of a cell extending out of the cell is overlapped and connected to the conductive film layer of the adjacent cell, so as to realize the series connection between the cells, reduce the production cost of the photovoltaic module, omit the welding strip alignment and welding process in the production process of the photovoltaic module, and improve the production efficiency of the photovoltaic module.

[0083] Furthermore, an embodiment of the present invention also provides a photovoltaic module. The photovoltaic module includes a battery string in which a plurality of battery cells are connected in series, wherein the battery cells are the silicon-based solar cells provided in the above embodiment or the battery cells are obtained by cutting the silicon-based solar cells provided in the above embodiment, and in the battery string, two adjacent battery cells are electrically connected through the connection between the conductive film layers 33 contained in the battery cells. Specifically, the formation process of the battery string is as follows: for each two adjacent battery cells in the battery string, the portion of the conductive film layer 33 of one battery cell extending out of the battery cell is overlapped on the conductive film layer 33 of another battery cell, and after the battery cells on a battery string are placed, the overlapped positions are laser welded to obtain a battery string. The entire process does not require the introduction of welding strips, and the welding strip alignment and laying processes are omitted, thereby reducing the production cost of photovoltaic modules and improving the production efficiency of photovoltaic modules.

[0084] Embodiment 1

[0085] Preparation method for Topcon battery:

[0086] A. Select a single crystal N-type silicon wafer with a resistivity of 2.5Ω•cm.

[0087] B. Use a sodium hydroxide alkaline solution with a mass fraction of 4% to anisotropically etch the silicon wafer to obtain a textured silicon wafer surface with a reflectivity of 11.8%.

[0088] C. Prepare PN junction by high-temperature boron diffusion on the back surface of silicon wafer.

[0089] D. Use wet single-sided etching equipment to etch away the boron-doped area on the back of the silicon wafer while retaining the borosilicate glass layer on the front.

[0090] E. A tunneling oxide layer with a thickness of 1.8 nm is grown on the back of the silicon wafer using a furnace tube thermal oxidation method, and SiH4 gas is introduced into the furnace tube to prepare an 80 nm Poly silicon layer.

[0091] F. Use a high-temperature furnace tube to dope the back Poly silicon layer with phosphorus, where the concentration of active phosphorus in the Poly silicon layer reaches 4E20cm -3 .

[0092] G. Use wet equipment to remove the borosilicate glass layer and phosphosilicate glass layer on the front and back of the silicon wafer, and clean the Poly silicon layer coated on the front of the silicon wafer.

[0093] H. Deposit 4nm of aluminum oxide on the front to passivate the silicon wafer surface.

[0094] I. Deposit a 78nm silicon nitride film on the surface of the aluminum oxide film layer, and deposit an 80nm silicon nitride film on the back-doped poly silicon surface.

[0095] J. Use screen printing technology to set a continuous conductive silver paste with a solid content of 93% on the positive surface of the battery and dry it.

[0096] K. Use screen printing technology to set a discontinuous conductive silver paste with a solid content of 93% on the back surface of the battery and dry it, and then use screen printing technology to set a discontinuous conductive silver paste with a solid content of 70% on the back surface of the battery, and the high and low solid content conductive silver pastes are alternately set, such as Figure 5 After rapid sintering in a high-temperature sintering furnace, the first electrical connector and the second electrical connector on the back surface of the Topcon battery are prepared.

[0097] L. Provide a conductive aluminum film, set the width of the aluminum film to be close to the width of each row of alternately arranged first electrical connectors and second electrical connectors, and cover the surfaces of the alternately arranged first electrical connectors and second electrical connectors with the aluminum film.

[0098] M. Use laser technology to weld the aluminum film to the alternately arranged first electrical connectors and the second electrical connectors to complete the preparation of the Topcon battery.

[0099] Embodiment 2

[0100] This embodiment provides a method for preparing a BC battery, the steps of which are as follows:

[0101] The BC battery structure before printing the electrode is prepared using existing processes, which will not be described in detail here. The back surface of the BC battery is composed of separated p and n regions, and the corresponding area surface is at least covered by a dielectric film layer (such as silicon nitride).

[0102] The conductive silver paste with a solid content of 92% is intermittently set on the corresponding area of ​​the back surface of the battery by screen printing technology and dried, and then the conductive silver paste with a solid content of 68% is intermittently set on the back surface of the battery by screen printing technology, and the conductive silver paste with a solid content of 92% and the conductive silver paste with a solid content of 68% are alternately set. After rapid sintering in a high-temperature sintering furnace, the first conductive connector and the second conductive connector of the back surface of the BC battery are prepared.

[0103] Provide a conductive aluminum film, set the width of the aluminum film to be close to the width of the first conductive connector and the second conductive connector, cover the first conductive connector and the second conductive connector with the aluminum film, and fix the aluminum film to the first conductive connector and the second conductive connector by laser welding.

[0104] Comparative Example:

[0105] The preparation process of this comparative example is the same as step A to step J provided in Example 1. The difference is that in step K, a conductive silver paste with a continuous shape and a solid content of 97% is directly provided on the back surface of the battery by screen printing technology, and the back surface slurry electrode of the Topcon battery is prepared after rapid sintering in a high-temperature sintering furnace. There are no steps L and M.

[0106] The electrical performance of the silicon-based solar cells prepared in the above-mentioned Example 1 and the comparative example was characterized by IV characteristic curves using a detection device. The obtained results are shown in Table 1 below.

[0107] It is worth noting that the short-circuit current (Isc), open-circuit voltage (Voc), fill factor (FF), conversion efficiency (Eta) and series resistance (Rs) in the characterization results are calculated based on the test results of the comparative example. That is, the short-circuit current (Isc), open-circuit voltage (Voc), fill factor (FF), conversion efficiency (Eta) and series resistance (Rs) of the comparative example are all based on 100%, and the Isc, Voc, FF, Eta and Rs of the Topcon battery of Example 1 are calculated. From the results shown in Table 1, it can be seen that the silicon-based solar cell prepared by the preparation method provided in the embodiment of the present invention will not have a significant impact on the Isc, Voc, FF, Eta and Rs of the solar cell while effectively reducing the cost. That is, the technical solution provided in the embodiment of the present invention can reduce the cost while making the performance of the prepared silicon-based solar cell basically unaffected.

[0108]

[0109] The introduction provided in the above steps is only used to help understand the method, structure and core idea of ​​the present invention. For ordinary technicians in this technical field, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also belong to the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a silicon-based solar cell, characterized in that: include: Step 1: Printing a first conductive paste (31') and a second conductive paste (32') on a functional layer (20) of a silicon-based solar cell, respectively, wherein the first conductive paste (31') and the second conductive paste (32') have different solid contents and are alternately arranged in a first direction on a main surface of the functional layer (20); Step 2: sintering the first conductive paste (31') and the second conductive paste to form first electrical connectors (31) and second electrical connectors (32) that are alternately arranged in the first direction; Step 3: laser welding the conductive film layer (33) to the first electrical connectors (31) and the second electrical connectors (32) that are alternately arranged.

2. The method for preparing a silicon-based solar cell according to claim 1, characterized in that: Step 1 includes: A first conductive paste (31') is printed using a first paste screen (001) having a plurality of columns and rows of printing holes, wherein the plurality of printing holes in each row of the first paste screen (001) are linearly spaced, each row of printing holes in the first paste screen (001) extends along the first direction, each column of printing holes in the first paste screen (001) extends along a second direction of the main surface of the functional layer (20), and the first direction is perpendicular to the second direction; A second conductive paste (32') is printed using a second paste screen (002) having a plurality of columns and rows of printing holes, wherein the plurality of columns and rows of printing holes of the second paste screen (32') correspond one-to-one to the plurality of columns and rows of the first paste screen (001), and the plurality of printing holes belonging to the same row of the second paste screen (002) and the first paste screen (001) are staggered; For the first slurry screen (001), the multiple printing holes in every two adjacent rows are staggered, or the multiple printing holes in every two adjacent rows are aligned; for the second slurry screen (002), the multiple printing holes in every two adjacent rows are staggered, or the multiple printing holes in every two adjacent rows are aligned.

3. The method for preparing a silicon-based solar cell according to claim 1, characterized in that: The first electrical connectors (31) and the second electrical connectors (32) alternately arranged in the first direction form an electrical connection area (34); In the case where a plurality of electrical connection areas (34) spaced apart from each other are divided in a second direction perpendicular to the first direction, Step 3 includes: Connecting a plurality of electrical connection areas (34) to the same conductive film layer (33); or, Each of the electrical connection areas (34) is connected to a conductive film layer (33), and any two of the electrical connection areas (34) are connected to different conductive film layers (33).

4. The method for preparing a silicon-based solar cell according to claim 1 or 3, characterized in that: The length of the conductive film layer (33) in the first direction is greater than the length of the silicon-based solar cell in the first direction.

5. The method for preparing a silicon-based solar cell according to claim 1, characterized in that: The adjacent first conductive paste (31') and second conductive paste (32') printed in step 1 are overlapped, connected or spaced apart; and / or, The solid content of the first conductive paste (31') used in step 1 is 91% to 97%, and the solid content of the second conductive paste (32') is 60% to 90%; and / or, The width of the laser used for laser welding in step 3 does not exceed the width of the first electrical connector (31) and the width of the second electrical connector (32).

6. The method for preparing a silicon-based solar cell according to claim 1, characterized in that: The solid content of the first conductive paste (31') used in step 1 is 91% to 97%, and the solid content of the second conductive paste (32') is 60% to 80%.

7. A silicon-based solar cell, characterized in that: include: A silicon substrate (10), a functional layer (20) stacked on the silicon substrate (10), a first electrical connector (31), a second electrical connector (32), and a conductive film layer (33), wherein the first electrical connector (31) and the second electrical connector (32) are alternately arranged in a first direction on a main surface of the functional layer (20); The conductive film layer (33) is electrically connected to the first electrical connector (31) and the second electrical connector (32); The volume of the first electrical connection member (31) is different from the volume of the second electrical connection member (32).

8. The silicon-based solar cell according to claim 7, characterized in that: The first electrical connection members (31) and the second electrical connection members (32) are alternately arranged in the first direction to form an electrical connection area (34); a plurality of electrical connection areas (34) are arranged in a second direction on the main surface of the functional layer (20) and are spaced apart from each other, and the first direction is perpendicular to the second direction; The first electrical connector (31) and the second electrical connector (32) of the plurality of electrical connection areas (34) are electrically connected to the same conductive film layer (33); or, each of the electrical connection areas (34) is connected to one conductive film layer (33), and any two of the electrical connection areas (34) are connected to different conductive film layers (33).

9. The silicon-based solar cell according to claim 7 or 8, characterized in that: The length of the conductive film layer (33) in the first direction is greater than the length of the silicon-based solar cell in the first direction; and / or, Adjacent first electrical connectors (31) and second electrical connectors (32) are overlapped, connected, or spaced apart. and / or, The first electrical connector (31) and the second electrical connector (32) are formed by sintering conductive pastes with different solid contents.

10. A photovoltaic module, comprising a battery string of a plurality of battery cells connected in series, characterized in that: The cell is the silicon-based solar cell according to any one of claims 7 to 9, or is obtained by cutting the silicon-based solar cell according to any one of claims 7 to 9; Wherein, two adjacent battery cells are electrically connected via the connection between the conductive film layers (33) contained in the battery cells.

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