Method for improving UV attenuation of battery piece

Abstract

The invention provides a method for improving the UV attenuation of a battery piece, and the method comprises the following steps: sequentially carrying out the three-stage stepped heating sintering, back light injection and dark annealing superposition processes of the battery piece after silk-screen printing, and obtaining a finished product of the battery piece. Escape of hydrogen atoms in the SiNx film layer can be accelerated by adjusting the sintering temperature of the battery piece, injection of the hydrogen atoms is further reduced in combination with the light injection process on the back face of the battery piece, and then migration of the hydrogen atoms is activated in combination with dark annealing; through the synergistic effect of the three-stage stepped heating sintering, the back light injection and the dark annealing process, the formation of weak Si-H bonds in the battery piece is reduced, and the interface defect repair of the battery piece is realized, so that the UV resistance of the battery piece is improved, and the efficiency attenuation of the solar battery piece is effectively reduced.

Description

Technical Field

[0001] The present invention relates to the field of solar cells, and particularly to a method for improving the UV attenuation of battery wafers. Background Art

[0002] With the rapid development of the solar energy industry, TOPCon cells, as advanced N-type cell technologies, have attracted much attention. However, in practical applications, the problem of UV attenuation seriously restricts the service life of TOPCon cell products. UV attenuation refers to the phenomenon that the performance of solar cell modules gradually declines after long-term exposure to ultraviolet light. Currently, the research on reducing this attenuation is still in its infancy. Conventional methods such as increasing the ALD thickness, reducing the refractive index of the bottom layer of the silicon nitride film, and using anti-ultraviolet packaging materials can improve the UV resistance of TOPCon cell wafers to a certain extent, but inevitably lead to efficiency loss and cost increase. How to effectively improve the UV attenuation effect of TOPCon cells has become an urgent problem to be solved in the development of N-type TOPCon cells.

[0003] Currently, prior art has also conducted research on improving anti-UV attenuation from the aspect of battery preparation processes. For example, document CN118588773A discloses "a cell wafer structure and its preparation method for improving the UV attenuation resistance of cell wafers", whose structure includes a single-crystalline silicon wafer. A tunneling oxide layer, a first doping layer, and a first antireflection layer are sequentially provided at the bottom of the single-crystalline silicon wafer, and a second doping layer, a silicon dioxide passivation layer, an aluminum oxide field passivation layer, and a first antireflection layer are provided on the top. This patent innovatively proposes four processes for growing silicon dioxide: introducing ozone gas into the drying tank, and generating a silicon dioxide passivation layer on the surface of the silicon wafer during drying by virtue of the strong oxidizing property of ozone; adding hydrogen peroxide to promote the formation of a silicon dioxide passivation layer on the surface of the silicon wafer; placing it in a wet oxygen environment to naturally form a silicon dioxide passivation layer on the surface of the silicon wafer; adding ozone in the furnace tube to achieve the same effect. Through these methods, attempts are made to solve the problem of UV attenuation of TOPCon cell wafers and enhance the UV resistance.

[0004] Another example is that document CN118571957A discloses "a front film layer of a TOPCon cell with an anti-UV attenuation effect and its preparation method". Using atomic layer deposition technology (ALD), with H2O as the precursor source, a two-stage reaction is carried out to obtain a stacked aluminum oxide film layer with a decreasing OH group content. Then, a silicon oxynitride thin film is added on the front stacked aluminum oxide film layer, and passivation film layers such as silicon nitride and silicon oxynitride are grown subsequently. This stacked structure can minimize the density of aluminum oxide interface states, protect the passivation film layer. At the same time, by adding a silicon oxynitride film layer and a temperature-raising process, the ability of the film layer to resist H ions after UV irradiation is improved, which helps the crystallization of the aluminum oxide film layer, increases the effective thickness, enhances the chemical passivation and field passivation effects, and reduces the UV attenuation of TOPCon cells.

[0005] However, although the solar cell wafers prepared by these prior art documents have achieved UV resistance, their manufacturing processes are complex and costly, and still need to be improved and optimized in the future. Summary of the Invention

[0006] In view of the above problems, the present invention makes up for the deficiencies of the prior art and provides a method for improving the UV attenuation of a battery, which solves the problem that the improvement of the UV attenuation performance of the solar cell wafer and low cost cannot be achieved simultaneously.

[0007] The present invention provides a method for improving the UV attenuation of a battery, comprising the following steps:

[0008] Performing three-stage stepped temperature sintering on the solar cell wafer after screen printing;

[0009] Performing light injection on the back surface of the solar cell wafer;

[0010] Performing dark annealing on the solar cell wafer after light injection to obtain a finished solar cell wafer.

[0011] Further, the three-stage sintering includes sintering in the first stage at 200-500 °C for 20-40 s in temperature zones 1-10, sintering in the second stage at 500-700 °C for 6-10 s in temperature zones 11-16, and sintering in the third stage at 700-850 °C for 3-5 s in temperature zones 17-18.

[0012] Further, in the first stage, sintering is performed at 350-500 °C for 20-40 s in temperature zones 1-10, in the second stage, sintering is performed at 600-700 °C for 5-8 s in temperature zones 11-16, and in the third stage, sintering is performed at 800-850 °C for 3-5 s in temperature zones 17-18.

[0013] Further, the light source for light injection is an infrared light source or a white light source, the light intensity is 30-50 suns, and the time is 10-20 s.

[0014] Further, the dark annealing is carried out in a closed and light-shielded environment, a protective gas is filled into the closed and light-shielded environment, and the temperature in the closed annealing furnace is raised to 200-400 °C at a heating rate of 1-5 °C / min and maintained for 30-60 min; then the temperature is lowered to room temperature at a cooling rate of 1-5 °C / min.

[0015] Further, the protective gas is nitrogen, argon or a nitrogen-hydrogen mixed gas.

[0016] Further, the three-stage sintering, the light injection and the dark annealing are all carried out in the same closed device.

[0017] Further, a sintering furnace, a light injection light source, a flipper and an annealing furnace are arranged in the closed device, and the flipper is used to flip the solar cell wafer.

[0018] Further, the cell is a TOPCon cell.

[0019] Advantages of the present invention: In the production process of the cell, by only controlling the temperature gradient of the sintering process and adding a backside light injection and dark annealing superposition process, without the need for external deposition equipment, the UV attenuation resistance of the cell can be improved at low cost. Among them, a three-stage stepped sintering is set to control the temperature gradient of the sintering process. In the first stage, the low-temperature preheating time is extended to remove the organic solvent of the slurry, reduce carbon residue, and avoid the decomposition of the film layer under accelerated UV aging caused by the accumulation of carbon impurities; in the second stage, medium-temperature sintering is carried out to promote the interfacial reaction between the tunneling oxide layer and the polysilicon layer; in the third stage, high-temperature sintering is carried out to realize the crystallization of the polysilicon layer and the densification of the passivation contact layer; optimize the passivation film performance of the cell, reduce defects and stress, and improve the interfacial bonding force, thereby enhancing its UV attenuation resistance from the cell structure aspect; moreover, increasing the peak temperature and shortening the high-temperature time accelerate the escape of hydrogen atoms in the SiNx film layer and reduce the damage to the SiNx:H film at high temperature, reduce the amount of weak Si-H bonds in the cell, and avoid the generation of excessive hydrogen atom groups caused by ultraviolet radiation, resulting in poor passivation layer performance and carrier recombination, thereby further enhancing the UV attenuation resistance of the cell. At the same time, only light injection is carried out on the backside, and hydrogen is mainly concentrated at the polysilicon / SiO2 interface to passivate defects, and will not penetrate excessively through the tunneling oxide layer into the silicon substrate, and avoid the possibility of a large amount of hydrogen in the silicon nitride and alumina film layers entering the silicon substrate during front-side light injection; combined with the dark annealing process, activate the migration of hydrogen atoms in the cell, promote the escape of hydrogen atoms from the cell, reduce the formation of Si-H, and at the same time further repair the surface defects of the cell; the combination of the three processes starts from two aspects of optimizing the cell structure and reducing the content of weak Si-H bonds in the cell, effectively reducing the UV attenuation of the cell, and the process of the present invention is simple and low-cost, meeting the requirements of both improving the UV attenuation resistance and low cost. Specific embodiments

[0020] The following will clearly and completely describe the technical solutions of the present invention in conjunction with specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the protection scope of the present invention.

[0021] The embodiment of the present invention provides a method for improving the UV attenuation of a cell, solving the problems of poor UV attenuation resistance and inability to balance cost in the prior art.

[0022] A method for improving the UV attenuation of a cell includes the following steps:

[0023] (1) Sinter the screen-printed cell wafers in the first stage with temperature zones 1 - 10 at 200 - 500 °C for 20 - 40 s, in the second stage with temperature zones 11 - 16 at 500 - 700 °C for 6 - 10 s, and in the third stage with temperature zones 17 - 18 at 700 - 850 °C for 3 - 5 s;

[0024] (2) Perform light injection on the back of the cell wafers using an infrared light source or a white light source, with a light intensity of 30 - 50 suns and a time of 10 - 20 s;

[0025] (3) Conduct the process in a closed device. Fill the closed and light-shielded device with nitrogen, argon, or a nitrogen-hydrogen mixed gas. Raise the temperature in the closed annealing furnace to 200 - 400 °C at a heating rate of 1 - 5 °C / min and hold for 30 - 60 min; then cool it down to room temperature at a cooling rate of 1 - 5 °C / min to obtain the finished cell wafers.

[0026] Example 1

[0027] A method for improving the UV attenuation of cell wafers, comprising the following steps:

[0028] (1) Place the screen-printed TOPCon cell wafers in a sintering furnace. In the first stage, adjust the temperature of temperature zones 1 - 10 of the sintering furnace to 350 - 500 °C and sinter for 20 s; in the second stage, adjust the temperature of temperature zones 11 - 16 to 600 - 700 °C and sinter for 8 s; in the third stage, adjust the temperature of temperature zones 17 - 18 to 800 - 820 °C and sinter for 4 s.

[0029] (2) Turn the sintered TOPCon cell wafers using a flipper so that the back faces the light injection source, and perform light injection using an infrared light source, with a light intensity of 40 suns and a time of 15 s.

[0030] (3) Transfer the light-injected TOPCon cell wafers into a closed and light-shielded annealing furnace, introduce nitrogen into it until the nitrogen stops escaping, raise the temperature inside to 300 °C at a heating rate of 3 °C / min, hold for 40 min, and then cool it down to room temperature at a cooling rate of 3 °C / min to obtain the finished TOPCon cell wafers.

[0031] Example 2

[0032] A method for improving the UV attenuation of cell wafers, comprising the following steps:

[0033] (1) Place the screen-printed TOPCon cell in a sintering furnace. In the first stage, adjust the temperature of the 1st - 10th zones of the sintering furnace to 200 - 500 °C and sinter for 30 s. In the second stage, adjust the temperature of the 11th - 16th zones to 500 - 700 °C and sinter for 6 s. In the third stage, adjust the temperature of the 17th - 18th zones to 800 - 850 °C and sinter for 3 s.

[0034] (2) Turn the sintered TOPCon cell using a flipper so that the back faces the light injection light source, and perform light injection using an infrared light source with a light intensity of 30 suns for 20 s.

[0035] (3) Transfer the light-injected TOPCon cell into a sealed and light-proof annealing furnace, introduce nitrogen into it until the nitrogen escapes, then increase the temperature inside at a rate of 5 °C / min until it reaches 400 °C, hold for 35 min, and then decrease the temperature at a rate of 5 °C / min to room temperature to obtain the finished TOPCon cell.

[0036] Example 3

[0037] A method for improving the UV attenuation of cells, comprising the following steps:

[0038] (1) Place the screen-printed TOPCon cell in a sintering furnace. In the first stage, adjust the temperature of the 1st - 10th zones of the sintering furnace to 350 - 400 °C and sinter for 40 s. In the second stage, adjust the temperature of the 11th - 16th zones to 500 - 650 °C and sinter for 10 s. In the third stage, adjust the temperature of the 17th - 18th zones to 800 - 835 °C and sinter for 4 s.

[0039] (2) Turn the sintered TOPCon cell using a flipper so that the back faces the light injection light source, and perform light injection using an infrared light source with a light intensity of 50 suns for 10 s.

[0040] (3) Transfer the light-injected TOPCon cell into a sealed and light-proof annealing furnace, introduce nitrogen into it until the nitrogen escapes, then increase the temperature inside at a rate of 1 °C / min until it reaches 200 °C, hold for 40 min, and then decrease the temperature at a rate of 1 °C / min to room temperature to obtain the finished TOPCon cell.

[0041] Example 4

[0042] A method for improving the UV attenuation of cells, comprising the following steps:

[0043] (1)Place the screen-printed TOPCon cell in a sintering furnace. In the first stage, adjust the temperature of the 1st - 10th zones of the sintering furnace to 350 - 500 °C and sinter for 20 s. In the second stage, adjust the temperature of the 11th - 16th zones to 600 - 700 °C and sinter for 5 s. In the third stage, adjust the temperature of the 17th - 18th zones to 700 °C - 785 °C and sinter for 5 s.

[0044] (2)Turn the sintered TOPCon cell using a flipper so that its back faces the light injection light source, and perform light injection using an infrared light source. The light intensity is 50 suns and the time is 10 s.

[0045] (3)Transfer the light-injected TOPCon cell into a sealed and light-shielded annealing furnace, introduce nitrogen into it until the nitrogen stops escaping, then raise the temperature inside at a rate of 3 °C / min until the temperature reaches 300 °C, hold for 60 min, and then lower the temperature to room temperature at a rate of 3 °C / min to obtain the finished TOPCon cell.

[0046] Comparative Example 1

[0047] The difference between Comparative Example 1 and Example 1 is that light injection is performed on the front side of the cell; the remaining operation steps and process conditions are exactly the same as those in Example 1.

[0048] Comparative Example 2

[0049] The difference between Comparative Example 2 and Example 1 is that in the third stage of sintering in Comparative Example 2, the temperature of the 17th - 18th zones is 700 - 900 °C and the sintering time is 7 s; the remaining operation steps and process conditions are exactly the same as those in Example 1.

[0050] Comparative Example 3

[0051] The difference between Comparative Example 3 and Example 1 is that Comparative Example 3 does not perform dark annealing; the remaining operation steps and process conditions are exactly the same as those in Example 1.

[0052] Label the cells prepared in Examples 1 - 4 and Comparative Examples 1 - 3 as Examples 1 - 4 and Comparative Examples 1 - 3 respectively, and perform performance tests on the cells they prepared. The test parameters are cell efficiency Eta (%) and UV attenuation rate.

[0053] Among them, the cell efficiency Eta (%) is tested using the method specified in the "IEC 60904 Series Standards" formulated by the International Electrotechnical Commission; the cell efficiency before and after UV irradiation is tested.

[0054] UV attenuation rate test method: For each example and comparative example, 6 finished battery wafers prepared were randomly selected, and the UV30 test method and UV60 specified in the "IEC 60904 series standards" formulated by the International Electrotechnical Commission were used for testing respectively; the UV30 conditions were set as the irradiation dose of 30 KWH, the temperature of 60 °C, and the irradiance of 160 KWh / m 2 ; the UV60 conditions were set as the irradiation dose of 60 KWH, the temperature of 60 °C, and the irradiance of 160 KWh / m 2 .

[0055] The test results of Examples 1-4 are shown in Table 1, and the test results of Comparative Examples 1-3 are shown in Table 2.

[0056] Table 1

[0057]

[0058] Table 2

[0059]

[0060] As shown in Table 1 and Table 2, at the same irradiation dose, the attenuation rate of the examples of the present invention is generally 0.3% - 0.6% (UV30 KWH) and 0.4% - 0.5% (UV60 KWH) lower than that of Comparative Examples 1-3; it can be seen that the battery wafers prepared by the method for improving the UV attenuation of battery wafers of the present invention can resist UV attenuation, improve the UV resistance performance of the battery wafers, and at the same time greatly reduce the loss of the battery efficiency of the battery wafers. And as the irradiation dose increases, the attenuation rates of Examples 1-3 do not increase significantly, and the attenuation rate of Example 4 is slightly higher, indicating that the battery wafers improved within the preferred range of the present invention have better performance in resisting UV attenuation.

[0061] In summary, the three-stage step sintering process of the present invention combines backside light injection and dark annealing processes, and the three processes synergistically improve the anti-UV aging ability of the battery wafers; among them, the three-stage step sintering improves the anti-UV attenuation ability from the structural aspect through impurity removal, interface optimization, and crystallization densification, and the backside light injection + dark annealing precisely regulates the distribution and escape of hydrogen atoms, and the weak Si-H bonds are greatly reduced, further effectively reducing the UV attenuation of the battery wafers; and this process only adjusts the parameters of the existing equipment and does not require additional hardware investment, realizing the low-cost and high-efficiency improvement of the anti-aging performance of the battery wafers.

[0062] The above further describes the present invention with the help of specific examples, but it should be understood that this specific description should not be construed as a limitation on the essence and scope of the present invention. Various modifications made by those of ordinary skill in the art to the above examples after reading this specification all fall within the scope protected by the present invention.

Claims

1. A method for improving UV attenuation of a cell, characterized in that: The steps include: The screen-printed cells are subjected to three-stage step-by-step sintering; Inject light into the back of the cell; The solar cell after light injection is dark annealed to obtain a finished solar cell.

2. The method for improving UV attenuation of a cell according to claim 1, characterized in that: The three-stage stepped temperature sintering includes sintering at 200-500°C for 20-40s in the first stage 1-10 temperature zone, sintering at 500-700°C for 6-10s in the second stage 17-18 temperature zone, sintering at 700-850°C for 3-5s.

3. The method for improving UV attenuation of a cell according to claim 2, characterized in that: The first section 1-10 temperature zone is sintered at 350-500°C for 20-40s, the second section 11-16 temperature zone is sintered at 600-700°C for 5-8s, and the third section 17-18 temperature zone is sintered at 800-850°C for 3-5s.

4. The method for improving UV attenuation of a cell according to claim 1, characterized in that: The light source for the light injection is an infrared light source or a white light source, the light intensity is 30-50 suns, and the time is 10-20 seconds.

5. The method for improving UV attenuation of a cell according to claim 1, characterized in that: The dark annealing is carried out in a closed and light-proof environment. A protective gas is filled into the closed and light-proof environment. The temperature in the closed annealing furnace is raised to 200-400°C at a heating rate of 1-5°C / min and maintained for 30-60min; then the temperature is lowered to room temperature at a cooling rate of 1-5°C / min.

6. The method for improving UV attenuation of a cell according to claim 4, characterized in that: The protective gas is nitrogen, argon or a nitrogen-hydrogen mixed gas.

7. The method for improving UV attenuation of a cell according to claim 1, characterized in that: The three-stage sintering, the light injection and the dark annealing are all performed in the same closed equipment.

8. The method for improving UV attenuation of a cell according to claim 7, characterized in that: The sealed device is provided with a sintering furnace, a light injection light source, a flipper and an annealing furnace, and the flipper is used for flipping the battery cell.

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