Solar cell electrode and preparation method therefor, and topcon cell and preparation method therefor

Abstract

A solar cell electrode and a preparation method therefor. The preparation method for a solar cell electrode comprises: providing a cell sheet precursor of an electrode to be prepared, and forming an electrode slurry at an electrode preset position of the cell sheet precursor; performing sintering processing on the cell sheet precursor having the electrode slurry to obtain an initial electrode, steps of the sintering processing comprising heating, first constant-temperature sintering, first cooling, second constant-temperature sintering, and second cooling, the temperature of the first constant-temperature sintering being 760°C to 800°C and the duration of the first constant-temperature sintering being 3 to 10 seconds, and the temperature of the second constant-temperature sintering being 700°C to 740°C and the duration of the second constant-temperature sintering being 10 to 20 seconds; and performing laser processing on the cell sheet precursor having the initial electrode to obtain an electrode.

Description

Solar cell electrodes and their fabrication methods, TOPCon cells and their fabrication methods

[0001] Related applications

[0002] This application claims priority to Chinese Patent Application No. 202411467837.7, filed on October 18, 2024, entitled "Solar Cell Electrode and Preparation Method Thereof, TOPCon Cell and Preparation Method Thereof", the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to the field of solar cell technology, and in particular to solar cell electrodes and their preparation methods, and TOPCon cells and their preparation methods. Background Technology

[0004] Cell sintering is a crucial step in the production of solar cells. During sintering, the electrode paste reacts with silicon to form a silver-silicon alloy, creating an ohmic contact between the silicon wafer and the metal electrode. Lower contact resistance results in a better ohmic contact and a higher fill factor (FF) for the cell. Currently, increasing the sintering temperature is commonly used to improve the ohmic contact. However, higher sintering temperatures cause greater damage to the passivation film, leading to a decrease in the cell's open-circuit voltage. Therefore, current sintering processes cannot simultaneously improve the ohmic contact while minimizing damage to the passivation film, making it difficult to achieve both a high fill factor and a high open-circuit voltage. Summary of the Invention

[0005] According to various embodiments of this application, a solar cell electrode and a method for preparing the same, as well as a TOPCon cell and a method for preparing the same, are provided.

[0006] A method for preparing a solar cell electrode includes the following steps:

[0007] A cell precursor for preparing electrodes is provided, and an electrode slurry is formed at a predetermined electrode position on the cell precursor;

[0008] The battery cell precursor with the electrode slurry is sintered to obtain the initial electrode. The sintering process includes heating, first isothermal sintering, first cooling, second isothermal sintering and second cooling. The first isothermal sintering is performed at a temperature of 760℃-800℃ for 3s-10s, and the second isothermal sintering is performed at a temperature of 700℃-740℃ for 10s-20s.

[0009] The battery cell precursor with the initial electrode is laser-processed to obtain the electrode.

[0010] In one embodiment, the temperature difference between the first isothermal sintering and the second isothermal sintering is more than 40°C.

[0011] In one embodiment, the time for the first isothermal sintering is shorter than the time for the second isothermal sintering.

[0012] In one embodiment, the first isothermal sintering time is 3s-8s.

[0013] In one embodiment, the heating rate of the heating step is 30°C / s-40°C / s.

[0014] In one embodiment, the cooling rate of the second cooling step is 20°C / s-30°C / s.

[0015] In one embodiment, the laser power in the laser processing step is 50W-200W, the bias voltage is 5V-15V, and the laser processing time is 0.4s-1s.

[0016] This application also provides a solar cell electrode prepared by the method described above.

[0017] This application also provides a method for preparing a TOPCon cell, including the method for preparing the solar cell electrode.

[0018] This application also provides a TOPCon battery prepared by the method described above.

[0019] Details of one or more embodiments of this application are set forth in the following drawings and description. Other features, objects, and advantages of this application will become apparent from the specification, drawings, and claims. Attached Figure Description

[0020] To better describe and illustrate embodiments and / or examples of the inventions disclosed herein, reference may be made to one or more accompanying drawings. Additional details or examples used to describe the drawings should not be considered as limiting the scope of any of the disclosed inventions, the currently described embodiments and / or examples, or the best mode of these inventions as currently understood.

[0021] Figure 1 is a schematic diagram of an electrode obtained by the preparation method of this application.

[0022] Figure 2 is another schematic diagram of the electrode obtained by the preparation method of this application.

[0023] Figure 3 is a partial SEM image of the TOPCon battery electrode obtained in Example 1.

[0024] Figure 4 is a partial SEM image of the TOPCon battery electrode obtained in Example 4.

[0025] Figure 5 shows the energy spectrum corresponding to Figure 4.

[0026] Figure 6 shows the distribution of Si in Figure 5.

[0027] Figure 7 shows the distribution of Ag in Figure 5.

[0028] In the figure: 10, silicon substrate; 11, bulk region; 12, through region; 13, contact region; 14, passivation film. Detailed Implementation

[0029] To facilitate understanding of this application, it will be described in more detail below. However, it should be understood that this application can be implemented in many different forms and is not limited to the embodiments or examples described herein. Rather, these embodiments or examples are provided to provide a more thorough and complete understanding of the disclosure of this application.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the specification of this application is for the purpose of describing particular implementations or embodiments only and is not intended to be limiting of this application. The optional range of the term "and / or" as used herein includes any one of two or more of the related listed items, as well as any and all combinations of the related listed items, including any two related listed items, any more related listed items, or a combination of all related listed items.

[0031] In this application, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0032] The method for preparing solar cell electrodes provided in this application includes the following steps:

[0033] S1, providing a cell precursor for the electrode to be prepared, and forming an electrode slurry at a preset electrode position on the cell precursor;

[0034] S2, the battery cell precursor with electrode slurry is sintered to obtain the initial electrode. The sintering process includes heating, first isothermal sintering, first cooling, second isothermal sintering and second cooling. The temperature of the first isothermal sintering is 760℃ to 800℃ and the time is 3s to 10s. The temperature of the second isothermal sintering is 700℃ to 740℃ and the time is 10s to 20s.

[0035] S3, the battery cell precursor with initial electrodes is laser-processed to obtain electrodes.

[0036] The electrode preparation method of this application is applicable to solar cells such as PERC cells, TOPCon cells and BC cells. In step S1, the cell precursor of the electrode to be prepared can be a cell precursor of PERC cells, a cell precursor of TOPCon cells, or a cell precursor of BC cells. It can be understood that the cell precursor has completed processes such as texturing and front and back coating.

[0037] In solar cells, electrode pastes typically include silver-aluminum paste, silver paste, etc. In step S1, in some embodiments, silver-aluminum paste is printed on the front side of the cell precursor and silver paste is printed on the back side of the cell precursor.

[0038] In step S2, during the sintering process of the battery cell precursor with electrode paste, a preliminary silver-silicon alloy is formed during the first isothermal sintering. Simultaneously, due to the control of temperature and time, a large amount of silver microcrystals are melted at the opening of the passivation film. Then, during the second isothermal sintering at a lower temperature, the passivation film is essentially no longer damaged by the temperature and time control. Instead, it only corrodes the silicon substrate below the passivation film laterally and vertically, forming a dense and large-area silver-silicon alloy. Therefore, it can reduce the damage to the passivation film and reduce the opening area of ​​the passivation film, while increasing the silver-silicon alloy content inside the silicon substrate, thus forming a good ohmic contact.

[0039] To further reduce damage to the passivation film and increase the content of silver-silicon alloy inside the silicon substrate, thereby improving the sintering effect, optionally, the temperature difference between the first and second isothermal sintering is more than 40°C, and / or, the time of the first isothermal sintering is shorter than the time of the second isothermal sintering. In some embodiments, the time of the first isothermal sintering is 3s-8s, including but not limited to 3s, 4s, 5s, 6s, 7s, 8s, etc.

[0040] It is understood that before sintering the battery cell precursor with electrode slurry, this application will dry the battery cell precursor with electrode slurry to remove diluents and other substances from the electrode slurry. Therefore, in the heating step of the sintering process, the temperature is generally raised directly from the drying temperature to the temperature of the first isothermal sintering. For example, if the drying temperature is 250°C, the temperature can be raised directly from 250°C to the temperature of the first isothermal sintering. The heating rate of the heating step is 30°C / s-40°C / s, including but not limited to 30°C / s, 31°C / s, 32°C / s, 33°C / s, 34°C / s, 35°C / s, 36°C / s, 37°C / s, 38°C / s, 39°C / s, 40°C / s, etc. This ensures that the heat energy has sufficient transfer time in the electrode slurry, ensuring the uniformity of sintering, while keeping energy consumption within a reasonable range and ensuring production capacity.

[0041] Similarly, after the second isothermal sintering, the temperature can be reduced to a certain range, such as 250℃, 200℃, etc. The cooling rate of the second cooling step is 20℃ / s-30℃ / s, including but not limited to 20℃ / s, 21℃ / s, 22℃ / s, 23℃ / s, 24℃ / s, 25℃ / s, 26℃ / s, 27℃ / s, 28℃ / s, 29℃ / s, 30℃ / s, etc.

[0042] After the sintering process in step S2, the cell precursor with the initial electrode is subjected to laser irradiation. During laser treatment, the silver-silicon alloy can further propagate and grow inside the silicon substrate, improving the ohmic contact effect and also enhancing the stability of the formed silver-silicon alloy.

[0043] Optionally, the laser power in the laser processing step is 50W-200W, including but not limited to 50W, 60W, 70W, 80W, 90W, 100W, 110W, 120W, 130W, 140W, 150W, 160W, 170W, 180W, 190W, 200W, etc., the bias voltage is 5V-15V, including but not limited to 5V, 6V, 7V, 8V, 9V, 10V, 11V, 12V, 13V, 14V, 15V, etc., and the laser processing time is 0.4s-1s, including but not limited to 0.4s, 0.5s, 0.6s, 0.7s, 0.8s, 0.9s, 1s, etc.

[0044] Therefore, this application employs a dual-peak sintering process of high-temperature rapid sintering followed by low-temperature slow sintering, combined with laser processing assistance. This process can reduce damage to the passivation film and decrease the opening area of ​​the passivation film, while also increasing the content of silver-silicon alloy inside the silicon substrate to form a good ohmic contact. As a result, the battery can simultaneously have a high fill factor and open-circuit voltage.

[0045] This application also provides a solar cell electrode prepared according to the above-described method for preparing a solar cell electrode. As shown in Figures 1 and 2, the solar cell electrode includes a body region 11, a through region 12, and a contact region 13. The contact region 13 is located within the silicon substrate 10, and the through region 12 penetrates the passivation film 14 and connects the body region 11 and the contact region 13, respectively.

[0046] The electrode prepared by the method of this application has a small opening in the through region 12. In the width direction of the electrode, the opening width of the through region 12 is generally 200nm-1000nm, and the opening area is small, which reduces the damage to the passivation film 14 and results in a high open-circuit voltage of the battery.

[0047] Furthermore, in the electrode prepared by the method of this application, both the through region 12 and the contact region 13 are composed of silver-silicon alloy, but the proportions of silver and silicon are different. The through region 12 is a silver-rich phase with a silver content of 60%-80%, while the contact region 13 is generally a silicon-rich phase with a silver content of 20%-40%. Meanwhile, the morphology of the silver-silicon alloy constituting the contact region 13 can be a cluster as shown in Figure 1, or a filament as shown in Figure 2, etc.

[0048] Based on this, this application also provides a method for preparing a TOPCon cell, including a method for preparing solar cell electrodes.

[0049] It is understandable that the fabrication method of solar cells first involves texturing and cleaning to form a pyramidal textured surface on the front side of the silicon substrate, which has an anti-reflection effect. Then, boron diffusion is performed to form a PN junction. Next, etching and cleaning are performed to remove the PN junction plating around the sides and back, and the back side is polished. Then, a tunneling silicon oxide layer and an intrinsic amorphous silicon layer are deposited on the back side using LPCVD. Then, a doped amorphous silicon layer is formed by phosphorus diffusion on the back side. Then, the plating area around the front side is etched and cleaned. Finally, passivation films are deposited on the front and back sides to complete the fabrication of the TOPCon cell precursor. Then, the solar electrode is fabricated using the fabrication method of the solar electrode in this application.

[0050] This application also provides a method for preparing a TOPCon battery.

[0051] The following specific embodiments will further illustrate the above-mentioned solar cell electrode and its preparation method, as well as the TOPCon cell and its preparation method.

[0052] Example 1

[0053] A pyramidal textured surface is formed on the front side of the silicon substrate, followed by boron diffusion to form a PN junction. Then, etching and cleaning are performed to remove the PN junction plating around the sides and back, and the back side is polished. Then, a tunneling silicon oxide layer and an intrinsic amorphous silicon layer are deposited on the back side using LPCVD. Then, a doped amorphous silicon layer is formed by phosphorus diffusion on the back side. Then, the plating area around the front side is etched and cleaned. Finally, silicon oxide and silicon nitride are deposited on the front and back sides as passivation films to obtain the TOPCon cell precursor.

[0054] Silver-aluminum paste is printed on the front side of the TOPCon cell precursor, and silver paste is printed on the back side to form a cell precursor with electrode paste.

[0055] The battery cell precursor with electrode slurry was dried at 250°C and then sintered. During the sintering process, the temperature was first raised from 250°C to 780°C at a heating rate of 35°C / s, sintered at 780°C for 5s, then cooled to 720°C and sintered for 15s, and finally cooled to 250°C at a cooling rate of 25°C / s to obtain the initial electrode.

[0056] The cell precursor with initial electrodes was irradiated with a laser at a power of 150W and a bias voltage of 13V for 0.8s to obtain a TOPCon cell.

[0057] Example 2

[0058] The difference between Example 2 and Example 1 lies only in that the cell precursor with electrode slurry is dried at 250°C and then sintered. During sintering, the temperature is first increased from 250°C to 800°C at a heating rate of 40°C / s, sintered at 800°C for 10s, then cooled to 740°C and sintered for 20s, and finally cooled back to 250°C at a cooling rate of 30°C / s to obtain the initial electrode. The cell precursor with the initial electrode is then subjected to laser irradiation with a laser power of 200W, a bias voltage of 15V, and a laser treatment time of 1s to obtain the TOPCon cell.

[0059] Example 3

[0060] The difference between Example 3 and Example 1 lies only in that the cell precursor with electrode slurry is dried at 250°C and then sintered. During sintering, the temperature is first increased from 250°C to 770°C at a heating rate of 30°C / s, sintered at 770°C for 8 seconds, then cooled to 710°C and sintered for 13 seconds, and finally cooled back to 250°C at a cooling rate of 20°C / s to obtain the initial electrode. The cell precursor with the initial electrode is then subjected to laser irradiation with a laser power of 50W, a bias voltage of 5V, and a laser treatment time of 0.4 seconds to obtain the TOPCon cell.

[0061] Example 4

[0062] The difference between Example 4 and Example 1 lies only in that the battery cell precursor with electrode slurry is dried at 250°C and then sintered. During the sintering process, the temperature is first increased from 250°C to 760°C at a heating rate of 35°C / s, sintered at 760°C for 3 seconds, then cooled to 700°C and sintered for 10 seconds, and finally cooled back to 250°C at a cooling rate of 25°C / s to obtain the initial electrode. The battery cell precursor with the initial electrode is then subjected to laser irradiation with a laser power of 150W, a bias voltage of 13V, and a laser treatment time of 0.4 seconds to obtain the TOPCon battery.

[0063] Example 5

[0064] The difference between Example 5 and Example 4 lies only in that the battery cell precursor with electrode slurry is dried at 250°C and then sintered. During the sintering process, the temperature is first increased from 250°C to 760°C at a heating rate of 35°C / s, sintered at 760°C for 3 seconds, then cooled to 740°C and sintered for 10 seconds, and finally cooled back to 250°C at a cooling rate of 25°C / s to obtain the initial electrode. The battery cell precursor with the initial electrode is then subjected to laser irradiation with a laser power of 150W, a bias voltage of 13V, and a laser treatment time of 0.4 seconds to obtain the TOPCon battery.

[0065] Example 6

[0066] The difference between Example 6 and Example 4 lies only in that the battery cell precursor with electrode slurry is dried at 250°C and then sintered. During the sintering process, the temperature is first increased from 250°C to 760°C at a heating rate of 35°C / s, sintered at 760°C for 3 seconds, then cooled to 730°C and sintered for 10 seconds, and finally cooled back to 250°C at a cooling rate of 25°C / s to obtain the initial electrode. The battery cell precursor with the initial electrode is then subjected to laser irradiation with a laser power of 150W, a bias voltage of 13V, and a laser treatment time of 0.4 seconds to obtain the TOPCon battery.

[0067] Comparative Example 1

[0068] The only difference between Comparative Example 1 and Example 1 is that when sintering the battery cell precursor with electrode slurry, the temperature is increased from 250°C to 760°C, sintered at 760°C for 10 seconds, and then cooled from 760°C to 250°C, and no laser treatment is performed.

[0069] Comparative Example 2

[0070] The only difference between Comparative Example 2 and Example 1 is that laser treatment is not performed.

[0071] Comparative Example 3

[0072] The only difference between Comparative Example 3 and Example 1 is that when sintering the battery cell precursor with electrode slurry, the temperature is increased from 250°C to 720°C, sintered at 720°C for 15 seconds, and then increased from 720°C to 780°C, and sintered at 780°C for 5 seconds.

[0073] Comparative Example 4

[0074] The only difference between Comparative Example 4 and Example 1 is that when sintering the battery cell precursor with electrode slurry, the temperature is increased from 250°C to 750°C, sintered at 750°C for 5 seconds, and then increased from 750°C to 720°C, and sintered at 720°C for 15 seconds.

[0075] Comparative Example 5

[0076] The only difference between Comparative Example 5 and Example 1 is that when sintering the battery cell precursor with electrode slurry, the temperature is increased from 250°C to 810°C, sintered at 810°C for 5 seconds, and then increased from 810°C to 720°C, and sintered at 720°C for 15 seconds.

[0077] Comparative Example 6

[0078] The only difference between Comparative Example 6 and Example 1 is that when sintering the battery cell precursor with electrode slurry, the temperature is increased from 250°C to 780°C, sintered at 780°C for 15 seconds, and then increased from 780°C to 720°C, and sintered at 720°C for 15 seconds.

[0079] Comparative Example 7

[0080] The only difference between Comparative Example 7 and Example 1 is that when sintering the battery cell precursor with electrode slurry, the temperature is increased from 250°C to 780°C, sintered at 780°C for 5 seconds, and then increased from 780°C to 750°C, and sintered at 750°C for 15 seconds.

[0081] Comparative Example 8

[0082] The only difference between Comparative Example 8 and Example 1 is that when sintering the battery cell precursor with electrode slurry, the temperature is increased from 250°C to 780°C, sintered at 780°C for 5 seconds, and then increased from 780°C to 720°C, and sintered at 720°C for 8 seconds.

[0083] The open-circuit voltage (Uoc), short-circuit current (Isc), fill factor (FF), and battery conversion efficiency (Eta) of the TOPCon batteries prepared in the above embodiments and comparative examples were tested, and the results are shown in Table 1.

[0084] Table 1

[0085] Furthermore, as shown in Figures 3 and 4, the passivation film openings in Embodiments 1 and 4 of this application are relatively small, preserving more passivation structures. The silver-silicon alloy is distributed in flocculent and clustered forms in the two figures, respectively, both of which increase the contact area. Meanwhile, as shown in Figures 5-7, the silver-silicon alloy is divided into silver-rich and silicon-rich regions. The silver content in the silver-rich region is 70%, with silver mainly concentrated at the passivation layer openings, providing good contact. The silver content in the silicon-rich region is 30%, and the opening in the silver-rich region is 500 nm.

[0086] As can be seen from Table 1 and Figures 3 to 7, this application uses a bimodal sintering process of high-temperature fast sintering followed by low-temperature slow sintering, combined with laser processing assistance. This process can reduce damage to the passivation film, decrease the opening area of ​​the passivation film, and increase the content of silver-silicon alloy inside the silicon substrate, thus forming a good ohmic contact. Therefore, the battery can simultaneously have a high fill factor, high open-circuit voltage, low contact resistance, and high battery conversion efficiency.

[0087] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0088] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for producing a solar cell electrode, characterized by, Includes the following steps: A cell precursor for preparing electrodes is provided, and an electrode slurry is formed at a predetermined electrode position on the cell precursor; The battery cell precursor with the electrode slurry is sintered to obtain the initial electrode. The sintering process includes heating, first isothermal sintering, first cooling, second isothermal sintering and second cooling. The first isothermal sintering is performed at a temperature of 760℃-800℃ for 3s-10s, and the second isothermal sintering is performed at a temperature of 700℃-740℃ for 10s-20s. The battery cell precursor with the initial electrode is laser-processed to obtain the electrode.

2. The method for producing a solar cell electrode according to claim 1, wherein, The temperature difference between the first and second isothermal sintering is more than 40°C.

3. The method for preparing a solar cell electrode according to claim 1, wherein, The time for the first isothermal sintering is shorter than the time for the second isothermal sintering.

4. The method for producing a solar cell electrode according to claim 3, wherein The first isothermal sintering time is 3s-8s.

5. The method for preparing a solar cell electrode according to claim 1, wherein, The heating rate of the heating step is 30℃ / s-40℃ / s.

6. The method for preparing a solar cell electrode according to claim 1, wherein, The cooling rate of the second cooling step is 20℃ / s-30℃ / s.

7. The method for preparing a solar cell electrode according to claim 1, wherein, The laser power in the laser processing step is 50W-200W, the bias voltage is 5V-15V, and the laser processing time is 0.4s-1s.

8. A solar cell electrode prepared by a method for preparing a solar cell electrode according to any one of claims 1 to 7.

9. A method for manufacturing a TOPCon cell, characterized by, The method includes the preparation method of a solar cell electrode as described in any one of claims 1 to 7.

10. A TOPCon battery prepared by the method for preparing a TOPCon battery as described in claim 9.

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