Solar cell, method for preparing solar cell and screen printing device

Abstract

The present invention discloses a solar cell, a method for preparing the solar cell and a screen printing device. The solar cell comprises a silicon wafer, a back electrode and an aluminum back field; the silicon wafer is provided with a back electrode surface; the back electrode comprises a first silver paste layer and a second silver paste layer, both of which are connected to the back electrode surface, the first silver paste layer is used for welding with a welding strip, the second silver paste layer at least wraps a part of the first silver paste layer, the tensile strength of the first silver paste layer is higher than that of the second silver paste layer, and the conductivity of the second silver paste layer is higher than that of the first silver paste layer; the aluminum back field is connected to the back electrode surface, and the aluminum back field is connected to the second silver paste layer. The first silver paste layer is used for welding with the welding strip, and the second silver paste layer is used for electrical contact with the aluminum back field. By setting the back electrode as an electrode composited by the first silver paste layer and the second silver paste layer, the energy conversion efficiency of the solar cell can be improved under the premise of ensuring that the back electrode has sufficient welding performance.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cells, and in particular to a solar cell sheet, a method for preparing the solar cell sheet and a screen printing device. Background Art

[0002] In the related art, the silver paste electrode on the back of the solar cell not only provides electrical contact, but also needs to provide a welding point on the back of the solar cell. Therefore, weldability and adhesion tension are also important indicators of the silver paste electrode on the back. However, in the prior art, in order to improve the welding reliability of solar cells, the back electrode is made of a silver electrode paste with high tensile strength but weak conductivity after molding, or the welding tension is increased by increasing the printing area and printing thickness of the silver electrode paste on the back, which affects the energy conversion of solar cells and increases the production cost. Therefore, it is necessary to study and solve this problem. Summary of the invention

[0003] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention provides a solar cell sheet that can improve the energy conversion efficiency of the solar cell panel while ensuring the welding performance of the back electrode.

[0004] The present invention also provides a method for preparing the solar cell sheet and a printing device used in the method for preparing the solar cell sheet.

[0005] A solar cell according to an embodiment of the present invention includes:

[0006] A silicon wafer having a back electrode surface;

[0007] A back electrode, the back electrode comprising a first silver paste layer and a second silver paste layer, the first silver paste layer and the second silver paste layer are both connected to the back electrode surface, the first silver paste layer is used for welding with a welding strip, the second silver paste layer at least wraps a portion of the first silver paste layer, the first silver paste layer has a higher tensile strength than the second silver paste layer, and the second silver paste layer has a higher electrical conductivity than the first silver paste layer;

[0008] An aluminum back field is connected to the back electrode surface, and the aluminum back field is connected to the second silver paste layer.

[0009] The solar cell according to the embodiment of the present invention has at least the following beneficial effects: Since the tensile strength of the first silver paste layer is higher than the tensile strength of the second silver paste layer, the welding performance of the first silver paste layer is higher than the welding performance of the second silver paste layer. The first silver paste layer is used as the welding part between the back electrode and the welding strip, which can ensure that the back electrode and the welding strip have a good welding effect. Since the conductivity of the second silver paste layer is higher than that of the first silver paste layer, the energy conversion efficiency of the solar cell can be improved by conducting electricity through the second silver paste layer and the aluminum back field contact. By setting the back electrode as an electrode composed of the first silver paste layer and the second silver paste layer, the energy conversion efficiency of the solar cell can be improved while ensuring that the back electrode has sufficient welding performance.

[0010] According to some embodiments of the present invention, the content of silver particles in the first silver paste layer is less than that in the second silver paste layer, and the content of silver particles in the first silver paste layer and the second silver paste layer are both less than 90%.

[0011] According to some embodiments of the present invention, materials of the first silver paste layer and the second silver paste layer both include glass powder, and the content of the glass powder in the first silver paste layer is greater than the content of the glass powder in the second silver paste layer.

[0012] According to some embodiments of the present invention, the second silver paste layer has a set length, and an end surface of the second silver paste layer along the length direction includes a curved surface.

[0013] According to some embodiments of the present invention, the second silver paste layer has a set width, and a plurality of protrusions are arranged along the width direction of the second silver paste layer, each of the protrusions is arranged along the length direction of the second silver paste layer, and the outer surface of each of the protrusions includes a curved surface.

[0014] According to some embodiments of the present invention, the second silver paste layer has a set thickness, the thickness of the aluminum back field is greater than the thickness of the second silver paste layer, and the aluminum back field at least covers a portion of the outer surface of the second silver paste layer along the thickness direction.

[0015] According to some embodiments of the present invention, a plurality of back electrodes are provided, and each of the back electrodes is evenly arranged on the back electrode surface.

[0016] According to some embodiments of the present invention, the first silver paste layer has a set width, and the width of the first silver paste layer is greater than or equal to 0.9 mm.

[0017] The method for preparing a solar cell according to an embodiment of the present invention is used for preparing a solar cell according to an embodiment of the present invention. The method for preparing a solar cell comprises the following steps:

[0018] Prepare the silicon wafer, and set the positive electrode surface and the back electrode surface;

[0019] Preparing a first silver paste, a second silver paste, a front silver electrode paste and an aluminum back field paste;

[0020] Printing the first silver paste on the back electrode surface, and drying the first silver paste to solidify to form the first silver paste layer;

[0021] Printing the second silver paste on the back electrode surface, and drying the second silver paste to solidify to form the second silver paste layer;

[0022] Printing the aluminum back field paste on the back electrode surface, and drying the aluminum back field paste to solidify to form the aluminum back field;

[0023] Printing the front silver electrode paste on the positive electrode surface, and drying the front silver electrode paste to solidify to form a positive grid line electrode;

[0024] A sintering operation is performed to complete the preparation of the solar cell.

[0025] The method for preparing a solar cell according to an embodiment of the present invention has at least the following beneficial effects: the method for preparing a solar cell of the present embodiment prepares the conductive silver paste into a first silver paste and a second silver paste respectively, and prints and solidifies the first silver paste and the second silver paste respectively on the back electrode surface, thereby forming a back electrode composed of a first silver paste layer and a second silver paste layer. The back electrode composed of the first silver paste layer and the second silver paste layer can improve the conductive contact between the back electrode and the aluminum back electrode while ensuring the welding strength between the back electrode and the welding strip, thereby improving the energy conversion efficiency of the solar cell.

[0026] The screen printing device according to the embodiment of the present invention is used in the method for preparing the solar cell according to the embodiment of the present invention, and the screen printing device includes:

[0027] A first screen plate includes a first printing area, the first silver paste layer has a set thickness, and a shape of the first printing area is adapted to a shape of the first silver paste layer along a thickness direction;

[0028] The second screen includes a second printing area, the second silver paste layer has a set thickness, the shape of the second printing area is adapted to the shape of the second silver paste layer along the thickness direction, and the second screen is also provided with a shielding portion, the shielding portion is arranged in the second printing area, and the shape of the shielding portion is adapted to the shape of the first silver paste layer along the thickness direction.

[0029] The screen printing device according to the embodiment of the present invention has at least the following beneficial effects: by applying the first screen plate and the second screen plate of the present embodiment, the back electrode of the solar cell of the embodiment of the present invention can be printed.

[0030] 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

[0031] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein:

[0032] Figure 1 is a schematic diagram of a solar cell according to an embodiment of the present invention;

[0033] Figure 2 is a cross-sectional view of a solar cell according to an embodiment of the present invention;

[0034] Figure 3 is a cross-sectional view of a solar cell according to another embodiment of the present invention;

[0035] Figure 4 is a schematic diagram of a solar cell according to another embodiment of the present invention;

[0036] Figure 5 is a flow chart of a method for preparing a solar cell according to an embodiment of the present invention;

[0037] Figure 6 is a schematic diagram of a first screen plate according to an embodiment of the present invention;

[0038] Figure 7 Schematic diagram of a second screen according to an embodiment of the present invention.

[0039] Reference numerals:

[0040] Solar cell 100, silicon wafer 110, back electrode surface 120, back electrode 130, second silver paste layer 140, protrusion 150, first silver paste layer 160;

[0041] Aluminum back field 200;

[0042] A first screen 300 and a first printing area 310;

[0043] The second screen plate 400 , the second printing area 420 , and the shielding portion 430 . DETAILED DESCRIPTION

[0044] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0045] In the description of the present invention, it should be understood that descriptions involving orientations, such as up, down, front, back, left, right, etc., and orientations or positional relationships indicated are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0046] In the description of the present invention, "several" means more than one, "many" means more than two, "greater than", "less than", "exceed", etc. are understood to exclude the number itself, and "above", "below", "within", etc. are understood to include the number itself. If there is a description of "first" or "second", it is only used for the purpose of distinguishing the technical features, and cannot be understood as indicating or implying the relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0047] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, connecting, etc. should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention based on the specific content of the technical solution.

[0048] In the description of the present invention, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" 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 representation of the above terms does 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.

[0049] The following describes the solar cell 100 , the method for preparing the solar cell 100 , and the screen printing device according to the embodiments of the present invention with reference to the accompanying drawings.

[0050] Reference Figure 1 and Figure 2 , the solar cell 100 according to the embodiment of the present invention comprises a silicon wafer 110, a back electrode 130 and an aluminum back field 200. The silicon wafer 110 is provided with a back electrode surface 120. The back electrode 130 comprises a first silver paste layer 160 and a second silver paste layer 140, both of which are connected to the back electrode surface 120, the first silver paste layer 160 is used for welding with a welding strip, the second silver paste layer 140 at least wraps a part of the first silver paste layer 160, the tensile strength of the first silver paste layer 160 is higher than that of the second silver paste layer 140, and the conductivity of the second silver paste layer 140 is higher than that of the first silver paste layer 160. The aluminum back field 200 is connected to the back electrode surface 120, and the aluminum back field 200 is connected to the second silver paste layer 140.

[0051] Since the tensile strength of the first silver paste layer 160 is higher than that of the second silver paste layer 140, the welding performance of the first silver paste layer 160 is higher than that of the second silver paste layer 140. By using the first silver paste layer 160 as the welding part between the back electrode 130 and the welding strip, it is possible to ensure that the back electrode 130 and the welding strip have a good welding effect. Since the conductivity of the second silver paste layer 140 is higher than that of the first silver paste layer 160, the energy conversion efficiency of the solar cell 100 can be improved by contacting the second silver paste layer 140 with the aluminum back surface field 200 for electrical conduction. By setting the back electrode 130 as an electrode composed of the first silver paste layer 160 and the second silver paste layer 140, the energy conversion efficiency of the solar cell 100 can be improved while ensuring that the back electrode 130 has sufficient welding performance.

[0052] Specifically, the tensile strength and conductive properties of the first silver paste layer 160 and the second silver paste layer 140 can be achieved by adjusting the properties of the silver particles, adhesives, solvents and additives of the conductive silver paste. Among them, the tensile strength can be adjusted by adjusting the content of the adhesive, for example, the content of organic polymers, glass powder, and other oxides as a bonding phase, and the selection of solvents and additives also has a certain influence on the tensile strength. The conductive properties can be adjusted by adjusting the content of silver particles in the conductive silver paste and the selection of solvents, and the selection of solvents and additives also has a certain influence on the tensile strength.

[0053] According to some embodiments of the present invention, the content of silver particles in the first silver paste layer 160 is less than that in the second silver paste layer 140 , and the content of silver particles in the first silver paste layer 160 and the second silver paste layer 140 are both less than 90%.

[0054] Silver particles are the main component of the conductive silver paste, and the conductive properties of the first silver paste layer 160 and the second silver paste layer 140 are directly related to the content of the silver particles. When the content of the silver particles is greater than 90%, the conductivity of the silver particles reaches a peak value, and the resistance value of the back electrode 130 will increase with the increase in the content of the silver particles, affecting the conductivity of the back electrode 130. When the content of the silver particles is less than 90%, the conductivity of the conductive silver paste is positively correlated with the content of the silver particles. Therefore, by setting the content of the silver particles in the first silver paste layer 160 to be less than the content of the silver particles in the second silver paste layer 140, the conductivity of the second silver paste layer 140 can be made higher than the conductivity of the first silver paste layer 160, thereby ensuring that the second silver paste layer 140 and the aluminum back surface field 200 have good conductivity.

[0055] Specifically, the content of the silver particles in the first silver paste layer 160 may be selected to be 60% to 80%, and the content of the silver particles in the second silver paste layer 140 may be selected to be 70% to 90%.

[0056] According to some embodiments of the present invention, the materials of the first silver paste layer 160 and the second silver paste layer 140 both include glass powder, and the content of the glass powder in the first silver paste layer 160 is greater than the content of the glass powder in the second silver paste layer 140 .

[0057] Glass powder can be used as a binder for the conductive silver paste to achieve the solidification and film formation of the conductive silver paste. The adhesion of the silver paste layer formed by the solidification of the conductive silver paste is positively correlated with the content of the glass powder. Therefore, by setting the content of the glass powder of the first silver paste layer 160 to be greater than the content of the glass powder of the second silver paste layer 140, the tensile strength of the first silver paste layer 160 can be higher than that of the second silver paste layer 140, thereby ensuring that the first silver paste layer 160 has sufficient tensile strength when used for welding, reducing the probability of the welding ribbon falling off or poor welding.

[0058] Furthermore, since the second silver paste layer 140 has a lower glass powder content, the second silver paste layer 140 and the aluminum back surface field 200 have less mutual diffusion after sintering, which can reduce the contact resistance, thereby improving the conductive contact between the second silver paste layer 140 and the aluminum back surface field 200. In addition, the second silver paste layer 140 with a lower glass content can effectively increase the minority carrier lifetime of the silver-silicon contact area, protect the open circuit voltage of the battery, and extend the service life of the solar cell panel.

[0059] Reference Figure 1 According to some embodiments of the present invention, the second silver paste layer 140 has a set length, and an end surface of the second silver paste layer 140 along the length direction includes a curved surface.

[0060] The second silver paste layer 140 is formed by a drying operation after the conductive silver paste is screen-printed onto the back electrode surface 120 by a screen printing device. In the screen printing operation, the right-angle shape is prone to printing missing problems during printing, affecting the printing smoothness and pattern integrity. By providing a curved surface on the end surface of the second silver paste layer 140 along the length direction, the transition surface of the right-angle shape can be changed into a curved surface, so that the conductive paste is easier to be printed from the screen printing plate onto the back electrode surface 120, reducing the probability of printing missing problems.

[0061] Reference Figure 1 According to a further embodiment of the present invention, the second silver paste layer 140 has a set width, and the second silver paste layer 140 is provided with a plurality of protrusions 150 along the width direction, each protrusion 150 is arranged along the length direction of the second silver paste layer 140, and the outer surface of each protrusion 150 includes a curved surface.

[0062] When the end face of the second silver paste layer 140 along the width direction is set as a straight face, when the screen printing device prints the second silver paste layer 140, the problem of printing missing is also easy to occur on the straight face, affecting the printing smoothness and pattern integrity. By providing a plurality of protrusions 150 on the end face of the second silver paste layer along the width direction, and the outer surface of each protrusion 150 is provided with a curved surface, the end face of the straight edge can be changed into an end face composed of a plurality of alternating undulating curved surfaces, which is more conducive to the printing of the screen printing device, so that the conductive paste is easier to be printed from the screen printing plate to the back electrode surface 120, reducing the probability of the occurrence of the printing missing problem. In addition, when the maximum width and maximum length of the back electrode 130 remain unchanged, the printing shape of the second silver paste layer 140 of this embodiment can reduce the consumption of the conductive silver paste, thereby saving the production cost of the solar cell 100, and because the second silver paste layer 140 has a high conductivity, the contact conductivity between the second silver paste layer 140 and the aluminum back field 200 can also be guaranteed.

[0063] Reference Figure 3 According to some embodiments of the present invention, the second silver paste layer 140 has a set thickness, the thickness of the aluminum back field 200 is greater than the thickness of the second silver paste layer 140, and the aluminum back field 200 covers at least a portion of the outer surface of the second silver paste layer 140 along the thickness direction.

[0064] By setting the thickness of the aluminum back field 200 to be greater than the thickness of the second silver paste layer 140, the aluminum back field 200 can wrap the second silver paste layer 140 in the thickness direction, thereby increasing the contact area between the aluminum back field 200 and the second silver paste layer 140, thereby improving the contact conductivity between the aluminum back field 200 and the second silver paste layer 140, and improving the energy conversion efficiency of the solar cell 100.

[0065] Reference Figure 4 According to some embodiments of the present invention, a plurality of back electrodes 130 are provided, and each back electrode 130 is evenly arranged on the back electrode surface 120 .

[0066] The current collection effect of a single back electrode 130 on the solar cell panel is limited. By setting multiple back electrodes 130 and evenly arranging them on the back surface 120, the radiation collection area of ​​a single electrode can be effectively utilized to evenly collect the current in each area of ​​the solar cell 100, thereby improving the power generation stability and energy conversion efficiency of the solar cell 100.

[0067] According to some embodiments of the present invention, the first silver paste layer 160 has a set width, and the width of the first silver paste layer 160 is greater than or equal to 0.9 mm.

[0068] Specifically, the width of the first silver paste layer 160 can be set to a value greater than or equal to 0.9 mm, such as 0.9 mm, 1 mm or 1.1 mm. Since the first silver paste layer 160 is used for welding with the soldering strip, the first silver paste layer 160 needs to have a certain width to ensure the welding effect with the soldering strip. When the width of the first silver paste layer 160 is greater than or equal to 0.9 mm, it can reduce the occurrence of poor welding problems such as cold welding and false welding between the first silver paste layer 160 and the soldering strip, and ensure that the first silver paste layer 160 and the soldering strip have sufficient welding area to ensure sufficient peeling strength between the first silver paste layer 160 and the soldering strip, and reduce the probability of the soldering strip peeling off the first silver paste layer 160.

[0069] Reference Figure 5 According to the method for preparing the solar cell 100 of the embodiment of the present invention, the method for preparing the solar cell 100 of the embodiment of the present invention comprises the following steps:

[0070] S100, preparing a silicon wafer 110, and setting a positive electrode surface and a back electrode surface 120;

[0071] S200, preparing a first silver paste, a second silver paste, a front silver electrode paste and an aluminum back field paste;

[0072] S300, printing a first silver paste on the back electrode surface 120, and drying the first silver paste to solidify to form a first silver paste layer 160;

[0073] S400, printing a second silver paste on the back electrode surface 120, and drying the second silver paste to solidify to form a second silver paste layer 140;

[0074] S500, printing an aluminum back field paste on the back electrode surface 120, and drying the aluminum back field paste to solidify it to form an aluminum back field 200;

[0075] S600, printing the front silver electrode slurry on the positive electrode surface, and drying the front silver electrode slurry to solidify to form a positive grid line electrode;

[0076] S700 , performing a sintering operation to complete the preparation of the solar cell 100 .

[0077] The preparation method of the solar cell 100 of the present embodiment prepares the conductive silver paste into a first silver paste and a second silver paste respectively, and prints and solidifies the first silver paste and the second silver paste respectively on the back electrode surface 120, thereby forming a back electrode 130 composed of a first silver paste layer 160 and a second silver paste layer 140. The back electrode 130 composed of the first silver paste layer 160 and the second silver paste layer 140 can improve the conductive contact between the back electrode 130 and the aluminum back surface 200 while ensuring the welding strength between the back electrode 130 and the welding strip, thereby improving the energy conversion efficiency of the solar cell.

[0078] Specifically, the temperature of the drying operation can be set between 150° C. and 180° C., which can take into account the drying efficiency while reducing the probability of the first silver paste layer 160 and / or the second silver paste layer 140 falling off the back surface 120 due to over-baking.

[0079] Reference Figure 6 and Figure 7 According to the screen printing device of the embodiment of the present invention, the method for preparing the solar cell 100 of the embodiment of the present invention is used, and the screen printing device includes a first screen plate 300 and a second screen plate 400. The first screen plate 300 includes a first printing area 310, the first silver paste layer 160 has a set thickness, and the shape of the first printing area 310 is adapted to the shape of the first silver paste layer 160 along the thickness direction. The second screen plate 400 includes a second printing area 420, the second silver paste layer 140 has a set thickness, and the shape of the second printing area 420 is adapted to the shape of the second silver paste layer 140 along the thickness direction. The second screen plate 400 is also provided with a shielding part 430, and the shielding part 430 is provided in the second printing area 420, and the shape of the shielding part 430 is adapted to the shape of the first silver paste layer 160 along the thickness direction. By applying the first screen plate 300 and the second screen plate 400 of this embodiment, the back electrode 130 of the solar cell 100 of the embodiment of the present invention can be printed.

[0080] Specifically, the printer of the screen printing device uses a conventional screen printing machine in the art. The first printing area 310 and the second printing area 420 are areas with printing channels on the screen, and the conductive silver paste can be printed onto the back electrode surface 120 through the printing channels.

[0081] The embodiments of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in the relevant technical field without departing from the purpose of the present invention. In addition, the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

Claims

1. A solar cell, characterized in that: include: A silicon wafer having a back electrode surface; A back electrode, the back electrode comprising a first silver paste layer and a second silver paste layer, the first silver paste layer and the second silver paste layer are both connected to the back electrode surface, the first silver paste layer is used for welding with a welding strip, the second silver paste layer surrounds and is connected to the first silver paste layer, the first silver paste layer has a higher tensile strength than the second silver paste layer, and the second silver paste layer has a higher conductivity than the first silver paste layer; as well as An aluminum back surface field connected to the back electrode surface, and the aluminum back surface field is connected to the second silver paste layer; Among them, the materials of the first silver paste layer and the second silver paste layer both include glass powder, and the content of glass powder in the first silver paste layer is greater than the content of glass powder in the second silver paste layer; the second silver paste layer has a set length and width, and the end face of the second silver paste layer along the length direction includes a curved surface; the second silver paste layer has a set width, and the second silver paste layer is provided with a plurality of protrusions along the width direction, each of the protrusions is arranged along the length direction of the second silver paste layer, and the outer surface of each of the protrusions includes a curved surface.

2. The solar cell according to claim 1, characterized in that: The content of silver particles in the first silver paste layer is less than that in the second silver paste layer, and the content of silver particles in the first silver paste layer and the second silver paste layer are both less than 90%.

3. The solar cell according to claim 1, characterized in that: The second silver paste layer has a set thickness, the thickness of the aluminum back surface field is greater than the thickness of the second silver paste layer, and the aluminum back surface field at least covers a portion of the outer surface of the second silver paste layer along the thickness direction.

4. The solar cell according to claim 1, characterized in that: A plurality of back electrodes are provided, and each of the back electrodes is evenly arranged on the back electrode surface.

5. The solar cell according to claim 1, characterized in that: The first silver paste layer has a set width, and the width of the first silver paste layer is greater than or equal to 0.9 mm.

6. A method for preparing a solar cell, used for preparing the solar cell according to any one of claims 1 to 5, characterized in that: The method for preparing the solar cell comprises the following steps: Prepare the silicon wafer, and set the positive electrode surface and the back electrode surface; Preparing a first silver paste, a second silver paste, a front silver electrode paste and an aluminum back field paste; Printing the first silver paste on the back electrode surface, and drying the first silver paste to solidify to form the first silver paste layer; Printing the second silver paste on the back electrode surface, and drying the second silver paste to solidify to form the second silver paste layer; Printing the aluminum back field paste on the back electrode surface, and drying the aluminum back field paste to solidify to form the aluminum back field; Printing the front silver electrode paste on the positive electrode surface, and drying the front silver electrode paste to solidify to form a positive grid line electrode; A sintering operation is performed to complete the preparation of the solar cell.

7. A screen printing device used in the method for preparing a solar cell according to claim 6, characterized in that: include: A first screen plate includes a first printing area, the first silver paste layer has a set thickness, and a shape of the first printing area is adapted to a shape of the first silver paste layer along a thickness direction; The second screen includes a second printing area, the second silver paste layer has a set thickness, the shape of the second printing area is adapted to the shape of the second silver paste layer along the thickness direction, and the second screen is also provided with a shielding portion, the shielding portion is arranged in the second printing area, and the shape of the shielding portion is adapted to the shape of the first silver paste layer along the thickness direction.

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