Method for improving current collection of XBC battery

Abstract

The invention discloses a method for improving current collection of an XBC battery, and relates to the technical field of battery manufacturing, and the method comprises the following steps: printing a layer of fine grid on the surface of an XBC battery substrate by adopting a one-process machine position of a screen printing machine, and then carrying out drying treatment; printing a layer of fine grids by adopting a two-process machine position, and then drying; the first process machine position, the second process machine position and the third process machine position respectively correspond to different process machine positions of the screen printing machine table, the first process machine position, the second process machine position and the third process machine position respectively correspond to different process machine positions of the screen printing machine table, the first process machine position, the second process machine position and the third process machine position are used for printing electrode Pad points, sintering treatment is carried out after printing is completed, and ohmic contact is formed between a fine grid and a poly layer of an XBC battery substrate. According to the invention, the fine grid is printed below the electrode Pad point, the tension interference of the fine grid slurry on the Pad point slurry is avoided, the fine grid can form ohmic contact with the poly layer after sintering treatment, the current is collected, the current collection efficiency is improved, and the electrode Pad point can form firm contact with the welding strip to improve the tension reliability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of battery manufacturing, and in particular to a method for improving current collection of XBC batteries. BACKGROUND

[0002] Screen printing is one of the key processes in the production process of solar cells. The current printing sequence of XBC batteries is to print the pad point electrode first, then print the N region fine grid, and then print the P region fine grid. The fine grid electrode structure is on the pad point. The pad point electrode is responsible for collecting the current of the fine grid line. The current generated at the PN junction under the electrode point cannot be collected. Moreover, the fine grid paste has no pulling advantage, which affects the pulling force of the pad point.

[0003] In the production process of solar cells, screen printing is a core process that determines the conductivity and conversion efficiency of the battery. For XBC batteries, the structural design of the electrode and the fine grid directly affects the current collection effect. The current mainstream printing process of XBC batteries is as shown in Figure 1 , which is specifically: "print the pad point electrode first, then print the N region fine grid, and then print the P region fine grid". This mainstream printing process has some defects: the pad point electrode is responsible for collecting the current of the fine grid line. A large number of carriers will be generated in the PN junction area under the electrode point. However, in the existing structure, the pad point electrode is directly covered on the substrate, which cannot form an effective current conduction path with the underlying poly layer, thereby causing current loss. Moreover, the fine grid paste needs to be covered on the surface of the pad point electrode to form a current transmission channel. However, the fine grid paste itself has weak pulling performance, which will directly weaken the bonding strength of the pad point electrode and the solder strip, resulting in insufficient pad point pulling force. During the assembly and long-term use of the battery, contact loosening is easy to occur, which affects the stability of the battery module.

[0004] Based on this, a method for improving current collection of XBC batteries is provided, which can eliminate the disadvantages of the prior art. SUMMARY

[0005] The present application aims to provide a method for improving current collection of XBC batteries to solve the problems of incomplete current collection and insufficient structural reliability in the background art.

[0006] To achieve the above-mentioned purpose, the present application provides the following technical scheme:

[0007] A method for improving current collection of XBC batteries, specifically comprising the following steps:

[0008] Step S1, using a one-step machine position of a screen printing machine to print a layer of fine grid on the surface of the substrate of the XBC battery. After completion, the printed layer printed by the one-step machine position is subjected to drying treatment;

[0009] Step S2: using the second process position of the screen printing machine to print a layer of fine grid on the substrate surface of the XBC battery, and drying the printed layer printed by the second process position after completion;

[0010] Step S3: Using the three process positions of the screen printing machine, the electrode pads are printed on the surfaces of all printed layers of the dried XBC battery. After completion, the entire structure is sintered to form an ohmic contact between the fine grids located below the pads and the poly layer of the XBC battery substrate, thereby obtaining a complete electrode-fine grid structure.

[0011] Among them, the 1st process machine position, 2nd process machine position, and 3rd process machine position respectively correspond to different process machine positions of the screen printing machine.

[0012] Preferably, the fine grid includes an N-region fine grid and a P-region fine grid. The type of the fine grid in step S1 is different from the type of the fine grid in step S2. When the N-region fine grid is preferentially printed in step S1, step S2 corresponds to printing the P-region fine grid. When the P-region fine grid is preferentially printed in step S1, step S2 corresponds to printing the N-region fine grid, and the fine grids printed twice have no overlapping area on the substrate surface of the XBC battery.

[0013] Preferably, the temperature of the drying treatment in step S1 is 120-180° C., and the drying time is 30-60 seconds.

[0014] Preferably, the line width of the fine grid printed in step S1 is 25-35 μm, and the line height is 18-22 μm.

[0015] Preferably, the temperature of the drying treatment in step S2 is 120-180° C., and the drying time is 30-60 seconds.

[0016] Preferably, the line width and line height parameters of the fine grid printed in step S2 are consistent with the line width and line height parameters of the fine grid printed in step S1.

[0017] Preferably, the temperature curve of the sintering treatment in step S3 is: the temperature rises from room temperature to 750-800°C at a heating rate of 5-8°C / s, the temperature is maintained at 800-850°C for 10-15 seconds in the holding stage, and the temperature is reduced from 850°C to room temperature at a rate of 3-5°C / s in the cooling stage.

[0018] Preferably, the electrode Pad dots printed in step S3 have a diameter of 0.8 to 1.2 mm and a height of 30 to 40 μm, and the area of ​​the electrode Pad dots accounts for 5% of the overall structural area of ​​the XBC battery.

[0019] Preferably, the paste used for the N-region fine gate and the P-region fine gate is a silver-based paste, the silver powder content in the silver-based paste is not less than 90 wt %, and 2-5 wt % of a glass phase component is added to the silver-based paste.

[0020] Preferably, the paste used for the electrode Pad point is high-tensile silver paste, and the silver powder content in the high-tensile silver paste is not less than 92 wt %.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The present invention provides a method for improving the current collection of XBC batteries. The printing method of XBC batteries continues to use the printing method of crystalline silicon batteries. The main grid position of the electrode Pad point does not collect current, but is only responsible for converging the current collected by the fine grid. The fine grid is printed below the electrode Pad point, avoiding the tension interference of the fine grid slurry on the Pad point slurry. After sintering, the fine grid can form an ohmic contact with the poly layer, thereby collecting current and improving the current collection efficiency. The electrode Pad point can form a firm contact with the welding ribbon to increase the tension reliability, enhance the power generation performance and market competitiveness of the battery, effectively reduce the risk of poor contact during the battery assembly process, and extend the service life of the battery component. The method can be achieved only by adjusting the process sequence of the screen printing machine and is compatible with the existing XBC battery production line. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of the process of the prior art.

[0024] Figure 2 Schematic diagram of the steps of the method of the present invention.

[0025] Figure 3 It is a process schematic diagram of the present invention.

[0026] Figure 4 It is a schematic diagram of the structure of the ohmic contact formed between the fine gate and the poly layer of the present invention. DETAILED DESCRIPTION

[0027] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0028] In this embodiment, if Figures 2-4 As shown in the figure, a method for improving the current collection of XBC batteries is proposed. This method adjusts the process sequence of XBC battery screen printing and optimizes the spatial structure of electrodes and fine grids to achieve efficient current collection in the pad point area and improve structural reliability. The traditional printing process of "electrode → N-region fine grid → P-region fine grid" is abandoned and a new process of "fine grid first, electrode printing later" is adopted. The specific steps include:

[0029] Step S1, using a 1-pass process station of a screen printing machine, printing a layer of fine grid on the surface of the XBC battery substrate, after completion, the printed layer printed by the 1-pass process station is subjected to drying treatment;

[0030] Specifically, this step prints the N area fine grid first, then step S2 prints the P area fine grid, and step S2 prints the N area fine grid first, and then step S2 prints the P area fine grid, thereby ensuring that the fine grid paste is preliminarily cured and closely adheres to the poly layer. The drying temperature is 120-180°C, and the drying time is 30-60 seconds. The line width of the fine grid printed in this step is 25-35μm, and the line height is 18-22μm;

[0031] Step S2, using a 2-pass process station of a screen printing machine, printing a layer of fine grid on the surface of the XBC battery substrate, after completion, the printed layer printed by the 2-pass process station is subjected to drying treatment;

[0032] Specifically, the fine grid area printed in this step is complementary to the fine grid area printed in the first pass. The drying temperature is 120-180°C, and the drying time is 30-60 seconds. The line width and line height parameters of the fine grid printed in this step are consistent with those of the fine grid printed in step S1;

[0033] Step S3, using a 3-pass process station of a screen printing machine, printing electrode Pad points on the surface of all printed layers of the XBC battery after drying, after completion, the entire structure is subjected to sintering treatment, so that the fine grid located below the Pad points forms an ohmic contact with the poly layer of the XBC battery substrate, and a complete electrode-fine grid structure is obtained;

[0034] Specifically, the temperature curve of the sintering treatment is: the temperature rises from room temperature to 750-800°C at a rate of 5-8°C / s, the temperature is kept at 800-850°C for 10-15 seconds in the holding stage, and the temperature decreases from 850°C to room temperature at a rate of 3-5°C / s. The diameter of the printed electrode Pad points is 0.8-1.2mm, the height is 30-40μm, and the area ratio of the electrode Pad points is 5% of the overall structure area of the XBC battery;

[0035] Among them, the 1-pass process station, the 2-pass process station, and the 3-pass process station correspond to different process stations of the screen printing machine;

[0036] Specifically, through the above printing sequence, the fine grid layer is located below the electrode Pad points and directly contacts the poly layer of the XBC battery. After sintering, the metal components in the fine grid paste react with the poly layer to form a stable ohmic contact, which can efficiently collect the carriers generated by the PN junction below the Pad point electrode, such as Figure 4As shown, the silver fine grid forms ohmic contact with the Poly, and leads out the carrier current at the Pad point;

[0037] As shown, the fine grid includes N-region fine grid and P-region fine grid, the type of the fine grid in step S1 is different from the type of the fine grid in step S2, when the N-region fine grid is preferentially printed in step S1, step S2 corresponds to printing the P-region fine grid, when the P-region fine grid is preferentially printed in step S1, step S2 corresponds to printing the N-region fine grid, and the fine grids printed twice do not overlap in the substrate surface of the XBC battery; Figure 3 As shown, the N-region fine grid and the P-region fine grid adopt silver-based paste, the silver powder content in the silver-based paste is not less than 90wt%, and 2-5wt% of glass phase component is added in the silver-based paste, the paste used for the electrode Pad point is high-tension silver paste, the silver powder content in the high-tension silver paste is not less than 92wt%, the paste used for the electrode Pad point is directly printed on the surface of the cured fine grid layer, the fine grid layer will not penetrate or mix into the electrode Pad point paste, the high-tension characteristics of the electrode Pad point paste are completely preserved, and stronger bonding force can be formed when the solder strip is welded.

[0038] Figure 3 As shown, the N-region fine grid and the P-region fine grid adopt silver-based paste, the silver powder content in the silver-based paste is not less than 90wt%, and 2-5wt% of glass phase component is added in the silver-based paste, the paste used for the electrode Pad point is high-tension silver paste, the silver powder content in the high-tension silver paste is not less than 92wt%, the paste used for the electrode Pad point is directly printed on the surface of the cured fine grid layer, the fine grid layer will not penetrate or mix into the electrode Pad point paste, the high-tension characteristics of the electrode Pad point paste are completely preserved, and stronger bonding force can be formed when the solder strip is welded.

[0039] Embodiment 1

[0040] Suppose that the N-region fine grid is preferentially printed by the 1-process position:

[0041] Step S1: select the 1-process position in the screen printing machine, print the N-region fine grid on the substrate surface of the XBC battery with the prepared poly layer, adopt silver-based paste with silver powder content of 90wt% and glass phase component of 5wt%, set the fine grid printing parameters to line width of 25μm and line height of 18μm, after printing, place the XBC battery piece in the 120℃ drying equipment, and continuously dry for 60 seconds to ensure that the paste is preliminarily cured and does not separate from the substrate;

[0042] Step S2: switch to the 2-process position of the screen printing machine, print the P-region fine grid on the region of the XBC battery substrate which is not covered by the N-region fine grid, use the same silver-based paste and fine grid printing parameters as the N-region fine grid to avoid fine grid overlap, after printing, also dry at 120℃ for 60 seconds to make the P-region fine grid tightly adhere to the substrate;

[0043] ​Step S3: Switch to the 3-pass machine position of the screen printing machine, print the electrode Pad point on the surface of the dried N-area fine grid and P-area fine grid, use high-tension silver paste with a silver powder content of 92wt%, control the diameter of the electrode Pad point to be 0.8mm and the height to be 30μm, ensure that the area of the electrode Pad point accounts for 5% of the total area of the battery piece, and after printing, sinter according to a specific temperature curve: start at room temperature, heat up to 750℃ at a rate of 5℃ / s, the heat preservation stage is at 800℃ for 15 seconds to promote the formation of ohmic contact between the fine grid and the poly layer, and the cooling stage is at a rate of 3℃ / s to room temperature, to obtain a complete electrode-fine grid structure.

[0044] Example 2

[0045] Assuming that the 1-pass machine position prints the P-area fine grid first:

[0046] Step S1: Select the 1-pass machine position in the screen printing machine, print the P-area fine grid on the surface of the XBC battery with the prepared poly layer, use silver-based paste with a silver powder content of 92wt% and a glass phase content of 2wt%, set the fine grid printing parameters to line width 35μm and line height 22μm, and after printing, place the XBC battery piece in a 180℃ drying device for continuous drying for 30 seconds to ensure that the paste is initially solidified and does not separate from the substrate;

[0047] Step S2: Switch to the 2-pass machine position of the screen printing machine, print the N-area fine grid on the area of the XBC battery substrate that is not covered by the P-area fine grid, use the same silver-based paste and fine grid printing parameters as the P-area fine grid to avoid fine grid overlap, and after printing, also dry at 180℃ for 30 seconds to ensure that the P-area fine grid is tightly bonded to the substrate;

[0048] Step S3: Switch to the 3-pass machine position of the screen printing machine, print the electrode Pad point on the surface of the dried P-area fine grid and N-area fine grid, use high-tension silver paste with a silver powder content of 94wt%, control the diameter of the electrode Pad point to be 1.2mm and the height to be 40μm, ensure that the area of the electrode Pad point accounts for 5% of the total area of the battery piece, and after printing, sinter according to a specific temperature curve: start at room temperature, heat up to 800℃ at a rate of 8℃ / s, the heat preservation stage is at 850℃ for 10 seconds to promote the formation of ohmic contact between the fine grid and the poly layer, and the cooling stage is at a rate of 5℃ / s to room temperature, to obtain a complete electrode-fine grid structure.

[0049] Specifically, the performance comparison between the present method and the existing process is shown in Table 1 below, where ETA is the conversion efficiency, i.e. the efficiency of the solar cell in converting light energy into electrical energy, which is the core indicator of battery performance, the higher the value, the stronger the battery power generation capacity, Uoc is the open circuit voltage, i.e. the voltage of the battery in the open circuit (no load) state, which reflects the potential difference inside the battery and affects the output voltage level of the battery to some extent, Isc is the short-circuit current, i.e. the current of the battery in the short-circuit state, which reflects the ability of the battery to generate photo-generated carriers under light, and is related to the size of the battery's generating current, FF is the fill factor, i.e. the ratio of the maximum output power of the battery to the product of the open circuit voltage and the short-circuit current, which reflects the "rectangular degree" of the battery output characteristic, the higher the fill factor, the closer the battery output power to the theoretical maximum value, RS is the series resistance, i.e. the internal series resistance of the battery, including the resistance of the electrode, semiconductor material, etc., the smaller the series resistance, the smaller the loss of current transmission in the battery, and RS is beneficial to improve the battery efficiency and output power, the pulling force is the Pad point bonding force, i.e. the bonding strength of the Pad point of the battery electrode and the battery substrate, the greater the pulling force, the less likely the Pad point to fall off during use, and the higher the reliability and service life of the battery, according to the table, it can be known that the method can significantly improve the current collection efficiency, conversion efficiency and structural reliability of the XBC battery, and meet the production needs of high-power solar cells.

[0050] Table 1 - Performance comparison table of existing process and the present method

[0051]

[0052] Specifically, the table data shows that the method significantly improves the photoelectric conversion efficiency (ETA), fill factor (FF) and reduces the series resistance (RS) of the XBC battery, while greatly enhancing the bonding force of the electrode Pad point, solving the problems of incomplete current collection and insufficient structural reliability in the background art, the method does not need to change the existing equipment hardware, only needs to adjust the program logic of the printing machine, is easy to integrate into the existing production line, and has good application prospect.

[0053] In summary, by adjusting the order of screen printing of the XBC battery, the present method places the fine grid printing before the Pad point printing, which can effectively avoid the interference between the pastes, ensure the formation of good ohmic contact between the fine grid and the poly layer, improve the current collection efficiency and the structural reliability of the electrode, and also improve the conversion efficiency (ETA), fill factor (FF) and series resistance (RS) and other electrical performance parameters, the method is simple in process, strong in compatibility with the existing production line, and has significant industrial application value and market prospect.

[0054] The above merely provides the specific implementation of the present application, but the protection scope of the present application is not limited to this. Any person skilled in the art can easily think of the changes or replacements within the technical range disclosed by the present application, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for improving the collection current of an XBC battery, characterized in that: The specific steps include: Step S1: Using the first process position of the screen printing machine, a layer of fine grid is printed on the substrate surface of the XBC battery. After completion, the printed layer printed by the first process position is dried; Step S2: using the second process position of the screen printing machine to print a layer of fine grid on the substrate surface of the XBC battery, and drying the printed layer printed by the second process position after completion; Step S3: Using the three process positions of the screen printing machine, the electrode pads are printed on the surfaces of all printed layers of the dried XBC battery. After completion, the entire structure is sintered to form an ohmic contact between the fine grids located below the pads and the poly layer of the XBC battery substrate, thereby obtaining a complete electrode-fine grid structure. Among them, the 1st process machine position, 2nd process machine position, and 3rd process machine position respectively correspond to different process machine positions of the screen printing machine.

2. The method for improving the XBC battery collection current according to claim 1, characterized in that: The fine grid includes an N-region fine grid and a P-region fine grid. The type of the fine grid in step S1 is different from the type of the fine grid in step S2. When the N-region fine grid is preferentially printed in step S1, step S2 corresponds to printing the P-region fine grid. When the P-region fine grid is preferentially printed in step S1, step S2 corresponds to printing the N-region fine grid, and the fine grids printed twice have no overlapping area on the substrate surface of the XBC battery.

3. The method for improving the XBC battery collection current according to claim 1, characterized in that: The drying temperature in step S1 is 120-180° C., and the drying time is 30-60 seconds.

4. The method for improving the collected current of an XBC battery according to claim 1, characterized in that: The line width of the fine grid printed in step S1 is 25-35 μm, and the line height is 18-22 μm.

5. The method for improving the collection current of an XBC battery according to claim 1, characterized in that: The drying temperature in step S2 is 120-180° C., and the drying time is 30-60 seconds.

6. The method for improving the collected current of an XBC battery according to claim 4, characterized in that: The line width and line height parameters of the fine grid printed in step S2 are consistent with the line width and line height parameters of the fine grid printed in step S1.

7. The method for improving the collected current of an XBC battery according to claim 1, characterized in that: The temperature curve of the sintering treatment in step S3 is as follows: the temperature is raised from room temperature to 750-800°C at a heating rate of 5-8°C / s, maintained at 800-850°C for 10-15 seconds in the holding stage, and cooled from 850°C to room temperature at a rate of 3-5°C / s in the cooling stage.

8. The method for improving the collected current of an XBC battery according to claim 1, characterized in that: The electrode Pad dots printed in step S3 have a diameter of 0.8-1.2 mm and a height of 30-40 μm, and the area of ​​the electrode Pad dots accounts for 5% of the overall structural area of ​​the XBC battery.

9. The method for improving the collected current of an XBC battery according to claim 2, characterized in that: The paste used for the N-region fine gate and the P-region fine gate is a silver-based paste, the silver powder content in the silver-based paste is not less than 90wt%, and 2-5wt% of a glass phase component is added to the silver-based paste.

10. The method for improving the collection current of an XBC battery according to claim 1, characterized in that: The slurry used for the electrode Pad point is high-tensile silver slurry, and the silver powder content in the high-tensile silver slurry is not less than 92 wt %.

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