Battery electrode printing method, back contact battery and photovoltaic module

Abstract

The invention relates to the technical field of solar cells, and provides a cell electrode printing method, a back contact cell and a photovoltaic module. The method comprises the steps that a screen printing plate is not changed, an N-type auxiliary grid and a P-type auxiliary grid are firstly printed, a main grid is finally printed, main grid printing is a sequence of overlapping and printing the main grid in three working procedures, and a composite electrode structure is formed on the back face of the battery. According to the invention, the step effect of the auxiliary grid printing can be eliminated and the forming uniformity of the main grid can be optimized through the matching of the printing sequence of the first auxiliary grid and the multi-channel main grid, so that the line width of the auxiliary grid is effectively reduced, the height-width ratio is improved by about 3-5%, the unit consumption of silver paste is saved by about 5-10% under the condition that the design line width of the screen printing plate is not changed, and meanwhile, a foundation is laid for 1-3 mu m lower detection of the design line width of the screen printing plate; and the series resistance and electrode shading loss can be effectively reduced.

Description

Battery electrode printing method, back contact battery and photovoltaic module Technical Field

[0001] This invention relates to the field of solar cell technology, and more particularly to a method for printing battery electrodes, a back contact battery, and a photovoltaic module. Background Technology

[0002] In existing technologies, back-contact solar cells, due to their structure with no grid lines on the front and a full back electrode, possess high conversion efficiency and aesthetic appeal, making them an important direction for photovoltaic technology development. The metallization process of BC-type solar cells is the core and most challenging aspect of their manufacturing; the printing quality of the main and sub-busbars directly determines the cell's series resistance and current collection efficiency.

[0003] Currently, because the main and sub-grid lines of BC-type batteries are located on the back side, and the N and P grids are alternating fine grid lines, with the main grid being a wider bus electrode, the industry's battery electrode printing method typically adopts a "main grid first, sub-grid later" sequence. That is, the main grid is printed on the back of the battery first, and then the N-type and P-type sub-grids are printed on the corresponding doped areas respectively. Since the main grid is printed first, the unsintered paste is a three-dimensional, highly wet film. When the sub-grid is printed immediately next to it, the pressure of the squeegee and the fluidity of the paste cause the sub-grid paste to come into contact with the wet film of the main grid. The sub-grid paste partially "climbs" onto the slope of the main grid, increasing its own height. After the two pastes come into contact, the surface tension pulls on each other, causing the side of the sub-grid closer to the main grid to widen. Therefore, printing the electrodes of BC-type batteries in the current way results in the main grid increasing the printing height of the N and P grids, and the sub-grid being wider, leading to poor printing uniformity of the sub-grid, as shown in Figure 1, and even high silver paste consumption.

[0004] Therefore, there is a need in the field for a new electrode printing method for batteries that can break through the existing sub-gate linewidth limit, significantly reduce silver paste consumption, and optimize the overall performance of the main gate, thereby improving the uniformity of battery sub-gate printing. Summary of the Invention

[0005] This invention aims to propose a battery electrode printing method, a back contact battery, and a photovoltaic module, in order to at least partially solve the technical problems of how to narrow the width of the sub-busbar lines and reduce the height of the sub-busbar lines to improve the aspect ratio and significantly save silver paste consumption by changing the printing sequence, and further solve the problem of how to improve the uniformity of sub-busbar printing to improve the performance and reliability of the main busbar.

[0006] To achieve the above objectives, the first aspect of the present invention provides a battery electrode printing method, comprising: printing an N-type sub-gate on the back side of a silicon substrate on which P-type doped regions and N-type doped regions have been formed, with the screen printing plate remaining unchanged; printing a P-type sub-gate during the curing of the N-type sub-gate; printing the main gate using three-pass printing during the curing of the P-type sub-gate, and completing the curing process.

[0007] Optionally, it also includes using the same paste when printing N-type sub-grids and P-type sub-grids and when printing the main grid in three passes.

[0008] Optionally, the N-type sub-grids are printed first, including: using an existing screen and a paste with a high silver content to print the N-type sub-grids, and then curing the printed N-type sub-grids.

[0009] Optionally, high silver content pastes include those with a silver content ranging from 85wt% to 96wt%.

[0010] Optionally, printing the P-type sub-gate during the curing of the N-type sub-gate includes: using an existing screen, printing the P-type sub-gate with a low silver content paste during the curing of the already printed N-type sub-gate but before it is fully cured, and then curing the printed P-type sub-gate.

[0011] Alternatively, low silver content pastes include those with a silver content of less than 80 wt%.

[0012] Optionally, during the curing of the P-type sub-grid, the main grid is printed using three printing passes and then cured, including: using an existing screen, during the curing of the already printed P-type sub-grid but before it is fully cured, the main grid is printed using the same paste for the three printing passes, or the main grid is printed using different pastes for the three printing passes; and the printed main grid is cured and the curing of the N-type and P-type sub-grids is continued.

[0013] Optionally, it also includes: when the slurry is the same, the silver content is 80wt% or less; when the slurry is different, the silver content of the first slurry used in the first main grid layer is 75-85wt%; the silver content of the second slurry used in the second main grid layer is 88-92wt%; and the silver content of the third slurry used in the third main grid layer is 80wt% to 87wt%.

[0014] To achieve the above objectives, a second aspect of the present invention provides a back contact battery having a main grid and a sub-grid printed on a silicon substrate by the battery electrode printing method described in any of the preceding claims.

[0015] To achieve the above objectives, a third aspect of the present invention provides a photovoltaic module comprising: at least one back-contact cell as described above.

[0016] Beneficial Effects: This invention, by changing the printing order of the main and secondary grids and the number of printing passes for the main grids, can effectively narrow the linewidth of the secondary grids, increase the aspect ratio, and save on silver paste consumption while keeping the screen printing plate unchanged. This allows for a certain depth reduction in the screen printing plate's linewidth design. In particular, by first printing N-type secondary grids, then P-type secondary grids, and finally printing the three main grids with the same paste, the linewidth of the secondary grids can be effectively narrowed, the aspect ratio increased by approximately 3-5%, and silver paste consumption saved by approximately 5-10% while keeping the screen printing plate unchanged. The screen printing plate's linewidth can be reduced by approximately 1-3 μm. Furthermore, the use of three different pastes for the final three main grids synergistically achieves a significant reduction in the linewidth of the secondary grids, an increase in the aspect ratio, a decrease in silver paste consumption, and enhanced soldering reliability, while also improving adhesion and contact, high conductivity, solderability, and oxidation resistance. Furthermore, the electrode printing method of printing the sub-gate first and then the main gate, especially the N-type sub-gate first and then the P-type sub-gate, and finally the three main gates, avoids the situation of printing the main gate first and raising the sub-gate, and no longer causes the sub-gate to thicken / increase or widen. This effectively narrows the sub-gate linewidth. In addition, printing the sub-gate first and then printing the three main gates increases the aspect ratio by about 3-5%, making the printed electrodes more uniform and improving the uniformity of the printed electrodes.

[0017] Furthermore, by separating the fine grid and the main grid and using different pastes, while ensuring good ohmic contact of the fine grid electrode and good solderability of the main grid, the silver content of the paste in the second step of P-type sub-grid printing is reduced, as is the silver content of the main grid paste, saving costs and reducing silver paste consumption by about 5% to 10%; the screen design linewidth can be reduced by about 1 to 3 μm.

[0018] Furthermore, the original screen can be reused without changing the screen printing plate. The main grid is printed in the last three printing passes, which improves the aspect ratio of the fine grid. Thus, under the premise of using printing paste, the conductivity is guaranteed to be close to or reach the conductivity achieved by using electroplated silver solution. This ensures the performance of the battery electrodes while saving costs in multiple ways. Attached Figure Description

[0019] To make the technical problems solved by the present invention, the technical means adopted, and the technical effects achieved clearer, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, it should be noted that the drawings described below are merely drawings of exemplary embodiments of the present invention. Those skilled in the art can obtain drawings of other embodiments based on these drawings without any creative effort.

[0020] Figure 1 is a cross-sectional micrograph of the electrodes of an IBC solar cell formed by printing the main grid first and then printing the N-type and P-type sub-grids in the prior art; Figure 2 is an example of a cross-sectional micrograph of the electrodes of an IBC solar cell obtained by the battery electrode printing method according to the present invention. Detailed Implementation

[0021] The features and exemplary embodiments of various aspects of the present invention will now be described in detail. To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only configured to explain the present invention and are not configured to limit the present invention. For those skilled in the art, the present invention can be practiced without some of these specific details. The following description of the embodiments is merely intended to provide a better understanding of the present invention by illustrating examples of the invention.

[0022] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus; the terms "and / or" or "and / or" include any and all combinations of any one or more of the associated listed items. Without further limitations, an element defined by the phrase "comprising..." does not exclude the presence of additional identical elements in the process, method, article, or apparatus that includes said element.

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0024] This invention, without changing the screen printing plate, first prints N-type and P-type sub-grids, and finally prints the main grid. The main grid printing is a three-step process that is superimposed on the main grid, forming a composite electrode structure on the back of the battery. This invention, through the combination of printing the sub-grid first and the main grid in multiple steps, eliminates the step effect of sub-grid printing and optimizes the uniformity of main grid forming. Under the condition that the screen design linewidth remains unchanged, it effectively narrows the sub-grid linewidth, increases the aspect ratio by about 3%~5%, and saves about 5%~10% of silver paste consumption. At the same time, it lays the foundation for reducing the screen design linewidth by 1~3μm, and can effectively reduce series resistance and electrode light-shielding loss.

[0025] In one main embodiment of the present invention, on the back side of a silicon substrate in which P-type doped regions and N-type doped regions have been formed, an N-type sub-gate is first printed, a P-type sub-gate is printed during the N-type sub-gate curing period (before it is fully cured), and a main gate is printed using three-pass printing during the P-type sub-gate curing period (before it is fully cured), and then curing is completed.

[0026] Example 1 The battery electrode printing method of this example mainly includes: S1: On the back side of the silicon substrate where the back P-type doped region and N-type doped region have been formed, the N-type sub-gate is first printed and cured; wherein, the N-type sub-gate (fine gate line, negative electrode) is printed using the original screen, that is, under the premise that the screen remains unchanged, the N-type sub-gate is first printed and cured.

[0027] Alternatively, curing can be achieved by drying, sintering, rapid annealing, or infrared / ultraviolet curing.

[0028] Optionally, the silver content of the paste used for printing N-type subgrids is approximately 85wt%-96wt%, preferably 88wt%-95wt%.

[0029] S2: Then, the P-type sub-gate is printed and cured. The P-type sub-gate (fine gate lines, positive electrode) is printed using the existing screen printing plate. That is, with the screen printing plate unchanged, after the N-type sub-gate has been printed and cured, the P-type sub-gate is printed on the back side of the silicon substrate where the back-side P-type and N-type doped regions have already been formed, and then cured. Alternatively, curing can be performed by drying, sintering, rapid annealing, or infrared / ultraviolet curing.

[0030] Optionally, the silver content of the printing P-type subgrid paste is about 80wt%-95wt%, or it is a paste with a silver content of less than 80wt% and mixed with copper, nickel and aluminum, or a silver-free paste.

[0031] S3: On top of the printed and cured N-type and P-type sub-grids, the main grid is printed in three passes. For example: First pass: With the main grid area and screen unchanged, the first layer of paste is printed and cured. The printed main grid establishes a preliminary and stable connection with the cured sub-grids below, forming the bottom outline of the main grid. Here, the paste needs to have good wettability to ensure a sufficiently low ohmic contact resistance with the sub-grids.

[0032] The second printing: Continue printing while the first printing paste is not fully cured (usually within a very short time interval). Maintaining the original screen, print the second layer of paste, increasing the height and volume of the main grid (i.e., thickening the main grid) to provide sufficient cross-section to ensure current transmission capacity. After printing, cure. This is completed while the first paste is still in a "wet" or "semi-dry" state to ensure good fusion of the two layers and avoid delamination.

[0033] The third printing: Based on the main outline of the grid formed by the first and second printings, the screen remains unchanged, and the final layer of paste is printed to form a smooth, elegant, and aesthetically pleasing top shape. The smooth, curved top significantly optimizes subsequent welding processes, reduces stress concentration, and improves welding tensile strength and reliability. After printing, the surface is cured.

[0034] Optionally, a brief infrared or hot air pre-drying process can be performed between the second and third printing processes to prevent the pattern from collapsing and to avoid complete curing that could affect interlayer bonding.

[0035] Optionally, after the three printing processes are completed, the battery will be placed in a sintering furnace for a final co-sintering process, which will completely alloy the three layers of paste and the main grid and the sub-grid, forming a strong mechanical and electrical connection.

[0036] The three-stage printing creates a gentle slope, allowing the adhesive film to flow smoothly and fill the gaps. This avoids the risk of microcracks or fragmentation of the cells during lamination or transportation due to stress concentration caused by the adhesive film not filling the steep gaps formed by the single-stage printed main grid. The smooth grid top allows for tighter and more uniform bonding of the solder ribbons, reducing incomplete soldering and improving welding tensile strength. Precise control of the amount and shape of the paste in each stage allows for an optimized structure with locally high and gently sloping sides on the main grid while meeting conductivity requirements. Compared to simply stacking height, this reduces overall silver paste consumption. For BC-class cells with ultra-fine, low sub-grid designs, excessively high main grid "walls" can pose a risk of pulling or obscuring the sub-grids. Therefore, the battery electrode printing scheme using the three-stage printed main grid of this invention can construct a more refined main grid structure that is more favorable to the sub-grids. Optionally, the same paste is used for the three printing stages of the main grid.

[0037] Optionally, the silver content in the paste used for printing the three main grids is 80wt% or less, and the silver powder is a mixture of spherical and flake shapes with a particle size D50 of about 1.5-3.0μm.

[0038] The printed main grid is cured, which includes curing the sub-grids and main grid together, such as drying, sintering, rapid annealing, ultraviolet / infrared curing, etc.

[0039] Example 2 The battery electrode printing method of this embodiment includes: S1: On the back side of the silicon substrate where the back P-type doped region and N-type doped region have been formed, the N-type sub-gate is first printed and cured; wherein, the N-type sub-gate (fine gate line, negative electrode) is printed using the original screen, that is, under the premise that the screen remains unchanged, the N-type sub-gate is first printed and cured.

[0040] Alternatively, curing can be achieved by drying, sintering, rapid annealing, or infrared / ultraviolet curing.

[0041] Optionally, the silver content of the paste used for printing N-type subgrids is approximately 88wt%-96wt%, preferably 92wt%-96wt%.

[0042] S2: Then, the P-type sub-gate is printed and cured. The P-type sub-gate (fine gate lines, positive electrode) is printed using the existing screen printing plate. That is, with the screen printing plate unchanged, after the N-type sub-gate has been printed and cured, the P-type sub-gate is printed on the back side of the silicon substrate where the back-side P-type and N-type doped regions have already been formed, and then cured. Alternatively, curing can be performed by drying, sintering, rapid annealing, or infrared / ultraviolet curing.

[0043] Optionally, the silver content of the paste used for printing P-type subgrids is approximately 75wt%-80%, or it is a paste with a silver content of less than 75wt% and mixed with copper, nickel, and aluminum, or a silver-free paste.

[0044] S3: On top of the printed and cured N-type and P-type sub-grids, the main grid is printed in three passes. For example, the first pass involves printing a first layer of paste in the main grid area with the screen unchanged, followed by curing. This establishes a preliminary and stable connection between the printed main grid and the cured sub-grids below, forming the bottom outline of the main grid. Here, the paste needs to have good wettability to ensure a sufficiently low ohmic contact resistance with the sub-grids.

[0045] The second printing: Continue printing while the first printing paste is not fully cured (usually within a very short time interval). Maintaining the original screen, print the second layer of paste, increasing the height and volume of the main grid (i.e., thickening the main grid) to provide sufficient cross-section to ensure current transmission capacity. After printing, cure. This is completed while the first paste is still in a "wet" or "semi-dry" state to ensure good fusion of the two layers and avoid delamination.

[0046] The third printing: Based on the main outline of the grid formed by the first and second printings, the screen remains unchanged, and the final layer of paste is printed to form a smooth, elegant, and aesthetically pleasing top shape. The smooth, curved top significantly optimizes subsequent welding processes, reduces stress concentration, and improves welding tensile strength and reliability. After printing, the surface is cured.

[0047] Optionally, a brief infrared or hot air pre-drying process can be performed between the second and third printing processes to prevent the pattern from collapsing and to avoid complete curing that could affect interlayer bonding.

[0048] Optionally, after the three printing processes are completed, the battery will be placed in a sintering furnace for a final co-sintering process, which will completely alloy the three layers of paste and the main grid and the sub-grid, forming a strong mechanical and electrical connection.

[0049] The three-stage printing creates a gentle slope, allowing the adhesive film to flow smoothly and fill the gaps. This avoids the risk of microcracks or fragmentation of the cells during lamination or transportation due to stress concentration caused by the adhesive film not filling the steep gaps formed by the single-stage printed main grid. The smooth top of the grid lines allows for tighter and more uniform bonding of the solder ribbons, reducing incomplete soldering and improving welding tensile strength. Precise control of the amount and shape of the paste in each stage allows for an optimized structure with locally high and gently sloping sides on the main grid while meeting conductivity requirements. Compared to simply stacking height, this reduces overall silver paste consumption. For BC-class cells with ultra-fine, low sub-grid designs, excessively high main grid "walls" can pose a risk of pulling or obscuring the sub-grids. Therefore, the battery electrode printing scheme using the three-stage printed main grid of this invention can construct a more refined main grid structure that is more favorable to the sub-grids. Optionally, different pastes are used for the three printing stages of the main grid.

[0050] In one embodiment, the first paste used for printing the first main grid is prepared from spherical silver powder and bismuth-based glass powder, with a silver content of 75-85 wt%; the second paste used for printing the second main grid is prepared from a mixture of flake and spherical silver powder, with a silver content of 88-92 wt%; and the third paste used for printing the third main grid contains silver powder and antioxidant additives, with a silver content of 80 wt% to 87 wt%. Optionally, the antioxidant additive is bismuth oxide, and its addition amount is 0.1% to 2% of the total mass of the third paste. The printed main grid is then cured, and the curing includes further curing of the sub-grids and main grids together, such as drying, sintering, rapid annealing, ultraviolet / infrared curing, etc.

[0051] The scheme in Example 1, which uses N-type sub-grids first, then P-type sub-grids, and finally three main grid printings using the same paste (the same paste is used for three main grid printings), can effectively narrow the sub-grid linewidth and increase the aspect ratio by about 3-5% while keeping the screen unchanged. It also saves about 5%-10% of silver paste consumption. The screen design linewidth can be reduced by about 1-3 μm.

[0052] In Example 2, an N-type sub-gate is first applied, followed by a P-type sub-gate, and finally, the main gate is printed in three layers using three different pastes with different functional characteristics. These pastes emphasize adhesion and contact, high conductivity, and solderability and oxidation resistance, respectively. This synergistically achieves a significant reduction in sub-gate linewidth, an increase in aspect ratio, a reduction in silver paste consumption, and an enhancement in soldering reliability, while simultaneously improving adhesion and contact, high conductivity, solderability, and oxidation resistance.

[0053] The steps in Examples 1 and 2 can be combined as needed.

[0054] In the conventional printing sequence of the prior art, after printing, the aspect ratio of the N-type sub-gate is about 30.1% and that of the P-type sub-gate is about 27.2%; while with the solution of this embodiment, after printing, the aspect ratio of the N-type sub-gate is about 34.2% and that of the P-type sub-gate is about 31.1%.

[0055] Example 3 can be modified from the first two examples. In the three-stage printing of the main grid, the first main grid printing can be performed simultaneously when printing the N-type sub-grid, provided that the screen plate remains unchanged. Then, when the N-type sub-grid is not yet cured, the P-type sub-grid is printed. The second main grid printing is performed simultaneously when printing the P-type sub-grid. Then, when the P-type sub-grid is not yet cured, the third main grid printing is performed.

[0056] The first two main grid printings can use the same paste as when printing the secondary grids. The third main grid printing can use the same paste as the first two or a different paste.

[0057] Compared with the prior art, the present invention has at least the following beneficial effects: 1. The electrode printing method of printing the sub-gate first and then the main gate, especially the method of printing the N-type sub-gate first and then the P-type sub-gate, and finally the three main gates, avoids the situation of printing the main gate first and raising the sub-gate, and no longer causes the sub-gate to thicken / increase or widen. It effectively narrows the sub-gate linewidth. Moreover, the sub-gate is printed first and the three main gates are printed, which increases the aspect ratio by about 3~5%, making the printed electrodes more uniform and improving the uniformity of the printed electrodes.

[0058] 2. By separating the fine grid and the main grid of the electrodes and using different pastes, the silver content of the paste used for the second step of P-type sub-grid printing is reduced, and the silver content of the main grid paste is also reduced, while ensuring good ohmic contact of the fine grid electrode and good solderability of the main grid. This saves costs by approximately 5% to 10% in silver paste consumption per unit. The screen design linewidth can be reduced by approximately 1 to 3 μm.

[0059] 3. The original screen can be reused without changing the screen plate. The main grid is printed in the last three printing passes, which improves the aspect ratio of the fine grid. Thus, under the premise of using printing paste, the conductivity is close to or reaches the conductivity achieved by using electroplated silver solution. This ensures the performance of the battery electrodes while saving costs in many ways.

[0060] Comparison of practical results: In the traditional printing sequence of existing technologies, after printing, the aspect ratio of the N-type sub-grid is generally 6.5 / 21.8, which is approximately 30.1%, and the aspect ratio of the P-type sub-grid is generally 6.3 / 23.2, which is approximately 27.2%. However, with the technical solution of this invention, after printing, the aspect ratio of the N-type sub-grid is generally 6.0 / 17.5, which is approximately 34.2%, and the aspect ratio of the P-type sub-grid is generally 6.0 / 19.3, which is approximately 31.1%. These data are verified through practical application.

[0061] The present invention also provides a back contact battery having a main gate and a sub-gate formed on a silicon substrate based on the aforementioned battery electrode printing method.

[0062] The present invention also provides a photovoltaic module, comprising: at least one of the aforementioned back contact cells.

[0063] This invention utilizes a sequence of printing N-type and P-type sub-grids first, followed by superimposing the main grid through at least two printing processes to form a composite electrode structure on the back of the battery. This invention, through the coordinated printing sequence of sub-grids first and main grids in multiple passes, eliminates the step effect in sub-grid printing and optimizes the uniformity of main grid forming. This effectively narrows the sub-grid linewidth, increases the aspect ratio by approximately 3%–5%, and saves approximately 5%–10% of silver paste consumption while maintaining the same screen design linewidth. Simultaneously, it lays the foundation for reducing the screen design linewidth by 1–3 μm, effectively reducing series resistance and electrode light-shielding loss. Furthermore, the printing method of this invention synergistically achieves significant narrowing of the sub-grid linewidth, increase in aspect ratio, reduction in silver paste consumption, and enhanced soldering reliability, while also improving adhesion and contact, high conductivity, solderability, and oxidation resistance.

[0064] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or basic characteristics. Therefore, the embodiments should be considered exemplary and non-limiting in all respects. The scope of the invention is defined by the appended claims rather than the foregoing description, and thus all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims. Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This method of description is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in the various embodiments can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for printing battery electrodes, characterized in that, include: On the back side of a silicon substrate where P-type and N-type doped regions have already been formed, the N-type sub-gate is printed first, without changing the screen printing plate. The P-type sub-gate is printed during the curing of the N-type sub-gate; During the curing of the P-type sub-gate, the main gate is printed using three printing passes, and then cured.

2. The method as described in claim 1, characterized in that, Also includes: The same paste is used when printing N-type and P-type sub-grids and when printing the main grid in three passes.

3. The method as described in claim 1, characterized in that, First, the N-type sub-grid is printed, including: using an existing screen and a high silver content paste to print the N-type sub-grid, and then curing the printed N-type sub-grid.

4. The method as described in claim 3, characterized in that, High silver content pastes include those with a silver content range of 85wt%-96wt%.

5. The method as described in claim 1, characterized in that, Printing P-type sub-gates during the curing of N-type sub-gates includes: using an existing screen, printing P-type sub-gates with a low silver content paste during the curing of the already printed N-type sub-gates but before they are fully cured, and then curing the printed P-type sub-gates.

6. The method as described in claim 5, characterized in that, Low silver content pastes include those with a silver content of less than 80 wt%.

7. The method as described in claim 1, characterized in that, During the curing of the P-type sub-grid, the main grid is printed using three printing passes and then cured, including: using an existing screen, during the curing of the already printed P-type sub-grid but before it is fully cured, the main grid is printed using the same paste for the three printing passes, or the main grid is printed using different pastes for the three printing passes; and the printed main grid is cured and the curing of the N-type and P-type sub-grids is continued.

8. The method as described in claim 1, characterized in that, Also includes: When the slurry is the same, the silver content is 80wt% or less; When the slurries are different, the silver content of the first slurry used in the first main grid layer is 75-85 wt%; the silver content of the second slurry used in the second main grid layer is 88-92 wt%. The third paste used in the third main busbar layer has a silver content of 80wt% to 87wt%.

9. A back-contact battery, characterized in that, include: It has a main gate and a sub-gate printed on a silicon substrate by the battery electrode printing method according to any one of claims 1 to 8.

10. A photovoltaic module, characterized in that, include: At least one back-contact battery as described in claim 9.

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