Silver electrode manufacturing method, photovoltaic cell and preparation method thereof, photovoltaic module and power station

Abstract

The invention relates to the technical field of photovoltaic cells, and discloses a silver electrode manufacturing method, a photovoltaic cell, a preparation method, a photovoltaic module and a power station. The manufacturing method of the silver electrode comprises the following steps: printing electrode slurry on the front and back surfaces of a silicon wafer; at least the electrode slurry on the front surface of the silicon wafer is aluminum-silver-free slurry, and metal powder of the aluminum-silver-free slurry comprises silver powder; drying the silicon wafer to cure the electrode slurry; sintering the cured electrode slurry to form an electrode which is in primary contact with the silicon wafer; and reverse bias voltage is applied to the sintered electrode, and laser is adopted to scan and irradiate the surface of the silicon wafer so as to carry out laser electric injection treatment on the electrode, so that the treated electrode and the silicon wafer form ohmic contact. According to the manufacturing method of the silver electrode, the aluminum-free silver paste is combined with the laser electric injection technology, the silver electrode which forms excellent ohmic contact with Si can be manufactured, metal contact recombination can be reduced, the open-circuit voltage and filling factors can be improved, the battery efficiency can be improved, and the risk of electric leakage can be avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic cells, and in particular to a method for manufacturing a silver electrode based on laser electrical injection, a photovoltaic cell and a preparation method thereof, a photovoltaic module and a power station. Background Art

[0002] TOPCon cells are photovoltaic cells that use an ultra-thin tunneling oxide layer and a doped polysilicon layer as a passivation contact structure. TOPCon cells have the advantages of high cell conversion efficiency, high bifaciality, low light decay and temperature coefficient, and are gradually becoming the mainstream of the market. In practice, the selection of technical routes is closely related to the performance and cost of the cells. If TOPCon cells want to continue to increase their market share and gain wider application, it is critical to continue to improve the cell efficiency and reduce the cost of TOPCon cells. Generally, every 1% increase in efficiency is equivalent to a 7-8% reduction in battery cost, so improving efficiency is also one of the important means to reduce the application cost of photovoltaic systems.

[0003] See also Figure 1 The front side of the existing TOPCon cell is usually a boron-doped p+ front field 22, while the front side of the TOPCon cell in the current industry usually uses silver-aluminum paste (generally 1-5% Al powder by mass is added to the Ag paste) as the electrode paste of the p+ front field 22, and the front silver-aluminum electrode 32 is obtained through the existing conventional high-temperature sintering process. The high-temperature sintering process of the silver-aluminum paste on the front side of the silicon wafer is as follows: during the high-temperature sintering process (peak temperature > 700°C), the glass body in the silver-aluminum paste will corrode and burn through the front passivation anti-reflection layer 21 of the silicon wafer. After the temperature is raised to 600°C, the aluminum begins to melt, and the molten aluminum will dissolve in the glass body formed by the glass powder, and will also dissolve the silver in the silver-aluminum paste. The molten aluminum and silver will flow along the corrosion channel with the glass body to the interface in contact with Si (such as the P+ front field 22), corroding Si, and then forming a silver-aluminum alloy during the cooling process. The silver-aluminum alloy will form a contact point on the Si surface of the p+ front field 22; at the same time, the silver-aluminum alloy will further form spike-shaped silver crystals of varying sizes (such as Figure 1 As shown. In this process, aluminum will catalyze and promote the formation and growth of spike-like silver crystals, which penetrate into Si to form ohmic contact.

[0004] The reason why the front side of the TOPCon cell uses silver-aluminum paste as the electrode paste for the p+ front field 22 is that: during the high-temperature sintering process, aluminum can combine with the glass body formed by the glass powder in the silver-aluminum paste to burn through the front passivation anti-reflection layer 21 and further dope the p+ front field 22, which helps the p+ front field 22 to form a good ohmic contact with the front silver-aluminum electrode 32.

[0005] However, the high-temperature sintering process of the silver-aluminum paste on the front side of the silicon wafer has the following defects: 1) During the high-temperature sintering process, when the sintering temperature is greater than 700°C, Al and Si will form an alloy melt (Al-Si eutectic temperature Tm = 577°C), which will continue to corrode the Si surface, and at the same time Al will be doped into Si. Transitional doping of Al in Si will cause serious recombination, which is the reason for the reduction in open circuit voltage. 2) The distribution of aluminum at the silver-aluminum alloy interface will generally form an Al-Si alloy layer or an Al-doped Si surface or Al crystals. The spike-like silver crystals (such as the Al-Si crystals) formed by the front silver-aluminum electrode 32 Figure 1 As shown in the figure, if the size is too large, (the silver-aluminum paste is prone to form overgrown electrode crystals during high-temperature sintering, and the crystals are in the shape of inverted pyramid spikes) they will pierce the pn junction formed by the p+ front field 22 and the N-type silicon substrate 23, thereby causing leakage risk. 3) In addition, the ohmic contact performance of the spike-shaped silver crystals and Si also has room for further improvement.

[0006] In addition, at present, laser electric injection technology is in the early stages of development. As shown in CN116013999A, if laser electric injection technology is directly applied to the preparation process of silver aluminum paste, there will be defects such as narrow process window and low battery efficiency improvement, and even deterioration of the ohmic contact of the electrode, reducing the open circuit voltage. This is because: the electrode paste currently used in photovoltaic cells basically forms an ohmic contact with Si through the mechanism of Ag thorns (or Ag nails) (Al in the electrode paste will promote this process). The conventional electrode paste industry is accustomed to using high-temperature sintering to form a lot of such spike-shaped metal crystals to form a contact area with Si (such as P+ front field 22); in this case, if laser electric injection treatment is performed again, because the contact area of ​​such spike-shaped metal crystals is already very large, the current generated by laser irradiation will not be high enough when passing through these contact areas, and it is difficult to form a very high temperature, and thus there will be no effect of improving the ohmic contact. Instead, there is a certain risk of changing the contact state formed during high-temperature sintering, resulting in a decrease in battery performance. Therefore, the application effect of laser electric injection technology combined with conventional silver aluminum paste is not ideal, and sometimes even has a counterproductive effect, which limits its application. Summary of the invention

[0007] The purpose of the present invention is to provide a silver electrode manufacturing method based on laser electrical injection, a photovoltaic cell and a manufacturing method, a photovoltaic module and a power station in view of the deficiencies in the prior art.

[0008] Based on this, the present invention discloses a method for manufacturing a silver electrode, comprising the following steps:

[0009] S11, printing electrode paste on the front and back sides of the silicon wafer; wherein at least the electrode paste on the front side of the silicon wafer is an aluminum-free silver paste, and the aluminum-free silver paste is made by mixing and grinding metal powder, glass powder, organic additives and organic solvent, and the metal powder includes silver powder;

[0010] S12, drying the silicon wafer to remove the organic solvent in the electrode slurry and solidify the electrode slurry;

[0011] S13, sintering the solidified electrode slurry to form an electrode that makes preliminary contact with the silicon wafer;

[0012] S14. Apply a reverse bias voltage to the sintered electrode, and use a laser to scan and irradiate the surface of the silicon wafer to perform laser electrical injection treatment on the electrode, so that the treated electrode forms an ohmic contact with the silicon wafer.

[0013] In the present invention, the aluminum-free silver paste is a silver paste without aluminum added; the metal powder in the aluminum-free silver paste may be other non-aluminum metal powders in addition to silver powder. The aluminum-free silver paste of the present invention is preferably a pure silver paste (in this case, the metal powder is only silver powder, and does not contain other metal powders).

[0014] Preferably, in step S11, the sum of the mass percentages of the metal powder and the glass powder in the aluminum-free silver paste is greater than or equal to 90%, the sum of the mass percentages of the organic additive and the organic solvent in the aluminum-free silver paste is less than or equal to 10%, and the mass percentage of the metal powder in the aluminum-free silver paste is greater than or equal to 80%.

[0015] Among them, in the aluminum-free silver paste, the glass powder is one or more of PbO, B2O3, SiO2, Bi2O3, ZnO or Al2O3; the organic additive is ethyl cellulose; the organic solvent is one or more of pinene alcohol, alcohol ester dodecanedioate, dimethyl adipate or diethylene glycol butyl ether acetate.

[0016] Further preferably, the aluminum-free silver paste is a pure silver paste with a product model of STP946Y49N provided by Changzhou Juhe New Materials Co., Ltd. Of course, other existing aluminum-free silver pastes (i.e., silver pastes that do not contain aluminum) on the market may also be used.

[0017] Preferably, in step S14, an external power source is used to apply the reverse bias, the voltage range of the reverse bias is 5-30V, and the application time of the reverse bias is 0.5-5s.

[0018] Further preferably, in step S14, the laser is a continuous laser or a pulsed laser of 100-10000kHz, the laser spot size is 20-200μm, the laser power is 1-30W, the laser scanning irradiation speed is 40-200m / s; the laser scanning irradiation time is the same as the reverse bias application time.

[0019] Preferably, in step S14, the front side of the silicon wafer is scanned and irradiated with the laser;

[0020] The laser scanning irradiation method is: the laser starts from one side of the silicon wafer, and the laser scanning line is parallel to the fine grid of the electrode sintered on the front side of the silicon wafer, scanning and irradiating line by line until the scanning and irradiation of the entire front side of the silicon wafer is completed; wherein, the interval between two adjacent laser scanning lines is minus 20 to 150μm.

[0021] The existing technology usually involves laser scanning and irradiation of the entire front side of the silicon wafer. Although this method can improve ohmic contact, the entire surface laser scanning and irradiation will greatly increase the processing time of laser power injection. At the same time, it is also possible that heat accumulation due to excessive laser scanning will damage the cell, thereby causing a decrease in the efficiency of the photovoltaic cell.

[0022] Based on this, it is further preferred that in step S14, the laser is used to perform patterned scanning irradiation on both sides of the fine grid of the sintered electrode on the front side of the silicon wafer;

[0023] The laser patterned scanning irradiation method is: the laser starts from the first fine grid of the electrode sintered on the front side of the silicon wafer, and the laser scanning line is parallel to the front side of the silicon wafer, and scans and irradiates 1-10 times on the left and right sides of the fine grid respectively, and the distance between the laser scanning line and the center position of the fine grid is in the range of 10-150μm; after scanning and irradiating the first fine grid, jump to the next adjacent fine grid until all the fine grids of the electrode sintered on the front side of the silicon wafer are scanned and irradiated.

[0024] More preferably, before the laser patterned scanning irradiation, the method further includes: positioning the front side of the silicon wafer to determine the electrode pattern on the front side of the silicon wafer after sintering.

[0025] The use of laser patterned scanning and irradiation effectively avoids the defects of long processing time and heat accumulation damaging the cell caused by full-surface laser scanning. This laser patterned scanning and irradiation method only allows the laser spot to scan and irradiate within a certain range of the fine grid (such as the left and right sides of the fine grid). The current generated by the laser within this range can effectively act on the area where the pure silver electrode contacts the silicon (such as the P+ back field) under the action of reverse bias, achieving low-metal contact composite and excellent ohmic contact, while avoiding the risk of leakage, and greatly shortening the processing time of laser electric injection, further improving the preparation efficiency of the silver electrode, and avoiding damage to the cell caused by heat accumulation, further improving the battery efficiency.

[0026] In step S14 of the present invention, the electrodes on the front and back sides of the silicon wafer are loaded with a reverse bias voltage of 5-30V, and a pulsed or continuous laser beam is used to irradiate from above the front side of the silicon wafer, and scan line by line along the direction of the fine grid. The silicon wafer area irradiated by the laser generates a photocurrent, which is collected by the fine grid and flows through a local area where the fine grid contacts Si (such as the P+ front field on the front side of the silicon wafer) under the action of the reverse bias voltage. The current density in this local area can be as high as tens of kiloA / mm 2 According to Ohm's law, this local area can instantly generate a high temperature of several hundred or even thousands of degrees Celsius, resulting in a sintering effect, prompting the mutual diffusion of Ag and Si, and further promoting the formation of Ag-Si alloy, thereby obtaining a silver electrode that forms an excellent ohmic contact with Si. The aluminum-free silver paste has no aluminum doping, and can also reduce the metal contact recombination of the silver electrode.

[0027] Preferably, in step S13, the sintering temperature is 400-800°C.

[0028] In the present invention, the mechanism of combining aluminum-free silver paste with laser electric injection technology to form a front electrode in ohmic contact with the p+ front field is as follows:

[0029] During the sintering process, the glass powder will melt and form a flowing glass body to corrode and burn through the front passivation anti-reflection layer. After the temperature exceeds 700°C, the Ag powder will deform and soften. At this time, the sintering process begins and grain boundaries begin to form. At the same time, due to the existence of the glass body, some Ag will melt into the glass body and migrate to the Si surface as the glass body flows. Since the eutectic temperature of the Ag-Si alloy is 840°C, the eutectic temperature of the Ag-Si alloy is relatively high and will not cause significant corrosion to Si. Therefore, the Ag melted into the glass body will precipitate from the glass body during the cooling process to form smaller silver crystals. Some small silver crystals are located in the glass body, and some will be in direct contact with silicon (such as the P+ front field on the front of the silicon wafer). Pure silver has little corrosion on silicon, so the size of the silver crystal formed is small, much smaller than the size of the pn junction.

[0030] Furthermore, in the subsequent laser electric injection process, the strong current generated by laser irradiation flows through the contact area of ​​Ag and Si under the action of reverse bias, thus forming an instantaneous high temperature of more than a thousand degrees Celsius. Therefore, under such a short-term high temperature, Ag and Si will diffuse with each other to form a hemispherical electrode contact area (such as Figure 2 As shown in the figure, due to the short time, the size of the hemispherical silver crystals will not be very large, and there will be no phenomenon of burning through the pn junction, so the risk of leakage can be effectively avoided.

[0031] The present invention also discloses a method for preparing a photovoltaic cell, comprising the following steps:

[0032] Step S21, preparing a silicon wafer; wherein the photovoltaic cell is an N-type TOPCon cell; the silicon wafer comprises a silicon substrate, a P+ front field and a front passivation anti-reflection layer sequentially arranged on the front side of the silicon substrate, and a passivation contact structure and a back passivation layer sequentially arranged on the back side of the silicon substrate;

[0033] Step S22: Process the front and back sides of the silicon wafer using the silver electrode manufacturing method described above in the present invention to obtain electrodes that form ohmic contact with the silicon wafer, thereby obtaining a photovoltaic cell.

[0034] The present invention also discloses a photovoltaic cell, which is prepared by using the preparation method of the photovoltaic cell described above in the present invention.

[0035] The present invention also discloses a photovoltaic module, comprising a photovoltaic front panel, a photovoltaic cell and a photovoltaic back panel stacked in sequence from top to bottom, wherein the photovoltaic cell is a photovoltaic cell as described above in the present invention.

[0036] The present invention also discloses a photovoltaic power station, comprising at least one photovoltaic module, wherein the photovoltaic module is a photovoltaic module as described above in the present invention.

[0037] Compared with the prior art, the present invention has at least the following beneficial effects:

[0038] The present invention adopts aluminum-free silver paste and combines it with laser electric injection technology. The instantaneous high temperature formed on the Ag-Si interface during the laser electric injection process can produce Ag and Si mutual diffusion phenomenon to form Ag-Si alloy, thereby preparing a silver electrode that forms excellent ohmic contact with Si. The aluminum-free silver paste has no aluminum doping and can also reduce the metal contact recombination of the silver electrode and improve the open circuit voltage. At the same time, the line resistance of the pure silver grid line is better than that of the silver-aluminum paste grid line, so the fill factor can be significantly improved, thereby further improving the battery efficiency. Moreover, the present invention adopts aluminum-free silver paste in combination with laser electric injection technology, and will not form large-sized Ag nails, effectively avoiding the Ag nails from breaking through the pn junction, thereby avoiding the risk of leakage. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a schematic diagram of the partial cross-sectional structure of a photovoltaic cell obtained by conventional high-temperature sintering of silver-aluminum paste on the front side of a silicon wafer in the prior art.

[0040] Figure 2 This is a schematic diagram of the partial cross-sectional structure of a photovoltaic cell prepared by the method for preparing a photovoltaic cell in Example 2.

[0041] Figure 3 This is a working principle diagram of a silver electrode manufacturing method in Example 1.

[0042] Figure 4This is a schematic diagram of the laser scanning irradiation method of Example 1.

[0043] Figure 5 Schematic diagram of the scanning irradiation method of laser patterning in Example 1.

[0044] Description of the accompanying drawings: laser beam 1; laser scanning line 11;

[0045] Silicon wafer 2; front passivation anti-reflection layer 21; front silicon nitride film 211; aluminum oxide film 212; P+ front field 22; N-type silicon substrate 23; tunneling oxide layer 24; doped polysilicon layer 25; back silicon nitride film 26; front silver electrode 31; front silver aluminum electrode 32; fine gate 33; back silver electrode 4;

[0046] Reverse bias 5. DETAILED DESCRIPTION

[0047] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0048] Example 1

[0049] A method for making a silver electrode in this embodiment, see Figure 2-5 , including the following steps:

[0050] S11, printing electrode paste on the front and back sides of the silicon wafer 2; wherein at least the electrode paste on the front side of the silicon wafer 2 is aluminum-free silver paste, which is made by mixing and grinding metal powder, glass powder, organic additives and organic solvent, and the metal powder includes silver powder. The aluminum-free silver paste is preferably pure silver paste.

[0051] Among them, the sum of the mass percentages of the metal powder and the glass powder in the aluminum-free silver paste is greater than or equal to 90%, the sum of the mass percentages of the organic additive and the organic solvent in the aluminum-free silver paste is less than or equal to 10%, and the mass percentage of the metal powder in the aluminum-free silver paste is greater than or equal to 80%.

[0052] Among them, the aluminum-free silver paste is preferably the pure silver paste with product model STP946Y49N provided by Changzhou Juhe New Materials Co., Ltd.

[0053] Preferably, the electrode paste is printed on the front and back sides of the silicon wafer 2 by screen printing.

[0054] S12, drying the silicon wafer 2 to remove the organic solvent in the electrode slurry and solidify the electrode slurry.

[0055] S13, sintering the solidified electrode slurry to form an electrode that makes preliminary contact with the silicon wafer 2.

[0056] In step S13, the sintering temperature is 400-800°C, preferably 700-800°C, and the peak sintering temperature is preferably 740°C.

[0057] S14, applying a reverse bias voltage of 5 (such as Figure 3 As shown), a laser beam 1 is used to scan and irradiate the surface of the silicon wafer 2 to perform laser electrical injection treatment on the electrode, so that the treated electrode forms an ohmic contact with the silicon wafer 2 (as shown). Figure 3 shown).

[0058] Wherein, an external power source is used to apply the reverse bias voltage 5, the voltage range of the reverse bias voltage 5 is 5-30V (preferably 18V), and the application time is 0.5-5s (such as 1.5s).

[0059] In practice, an external power source is connected to a probe, and the positive and back electrodes of the battery are pressed down through the probe, and the external power source is turned on to apply a reverse bias voltage 5 to the positive and back electrodes.

[0060] The laser is a continuous laser or a pulsed laser of 100-10000kHz (preferably 3MHz), the laser spot size is 20-200μm (such as 80μm), the laser power is 1-30W (such as 8W), and the laser scanning irradiation speed is 40-200m / s (preferably 120m / s).

[0061] In this embodiment, Example 1 is: in step S14, the front side of the silicon wafer 2 is scanned and irradiated with laser;

[0062] The laser scanning irradiation method is: Figure 4 The laser starts from one side of the silicon wafer 2, and the laser scanning line 11 emitted by the laser beam 1 is parallel to the fine grid 33 of the electrode sintered on the front side of the silicon wafer 2, and scans and irradiates line by line until the scanning and irradiation of the entire front side of the silicon wafer 2 is completed; wherein, the interval between two adjacent laser scanning lines 11 is minus 20 to 150 μm (such as 25 μm, a negative value indicates that there is overlap between the laser scanning lines 11).

[0063] In this embodiment, Example 2 is: in step S14, a laser is used to perform patterned scanning irradiation on both sides of the fine grid 33 of the sintered electrode on the front side of the silicon wafer 2 (i.e., scanning is performed only on the left and right sides of the fine grid 33);

[0064] Before the laser patterned scanning irradiation, the method further includes: positioning the front side of the silicon wafer 2 to determine the electrode pattern after sintering on the front side of the silicon wafer 2;

[0065] The scanning irradiation method of laser patterning is: Figure 5, the laser starts from the first fine grid 33 of the electrode sintered on the front side of the silicon wafer 2, and the laser scanning line 11 emitted by the laser beam 1 is parallel to the front side of the silicon wafer 2, and the left and right sides of the fine grid 33 are scanned and irradiated 1-10 times (preferably 1-2 times, more preferably 2 times), and the distance between the laser scanning line 11 and the center position of the fine grid 33 is in the range of 10-150μm (such as 50μm); after scanning and irradiating the first fine grid 33, jump to the next adjacent fine grid 33 until all the fine grids 33 of the electrode sintered on the front side of the silicon wafer 2 are scanned and irradiated.

[0066] It should be noted that in step S14, when the laser scanning irradiation is performed on the front side of the silicon wafer 2 in the manner of Example 1, the laser scanning irradiation time is preferably 1.5 s; and when the laser patterned scanning irradiation is performed on the front side of the silicon wafer 2 in the manner of Example 2, the laser patterned scanning irradiation time can be shortened to 0.5 s.

[0067] Therefore, in this embodiment, the aluminum-free silver paste on the front side of the silicon wafer 2 is irradiated by laser patterned scanning, combined with the application of reverse bias 5, which can not only achieve low metal contact composite and good ohmic contact, but also avoid leakage risk, and can greatly shorten the processing time of laser electric injection, further improve the preparation efficiency of silver electrodes, and avoid cell damage caused by heat accumulation. Therefore, it is preferred to use laser patterned scanning irradiation.

[0068] The laser scanning irradiation time is the same as the application time of the reverse bias voltage 5.

[0069] Example 2

[0070] A method for preparing a photovoltaic cell in this embodiment, see Figure 2-5 , including the following steps:

[0071] Step S21, preparing a silicon wafer 2.

[0072] Among them, see Figure 3 , the photovoltaic cell is an N-type TOPCon cell. Figure 2-3 The silicon wafer 2 includes a silicon substrate, a P+ front field 22 and a front passivation anti-reflection layer 21 sequentially arranged on the front side of the silicon substrate, and a passivation contact structure and a back passivation layer sequentially arranged on the back side of the silicon substrate.

[0073] Specifically, see Figure 2-3 The silicon substrate is preferably an N-type silicon substrate 23. The front passivation anti-reflection layer 21 is preferably an aluminum oxide film 212 disposed on the front of the P+ front field 22 and a front silicon nitride film 211 disposed on the front of the aluminum oxide film 212. The passivation contact structure is a tunneling oxide layer 24 disposed on the back of the silicon substrate and a doped polysilicon layer 25 disposed on the back of the tunneling oxide layer 24. The back passivation layer is a back silicon nitride film 26 disposed on the back of the doped polysilicon layer 25.

[0074] The preparation process of the silicon wafer 2 can refer to the prior art, so it will not be described in detail here.

[0075] Step S22, using a silver electrode manufacturing method described in Example 1 to process the front and back sides of the silicon wafer 2 to obtain a front silver electrode 31 that forms an ohmic contact with the P+ front field 22 of the silicon wafer 2, and to obtain a back silver electrode 4 that forms an ohmic contact with the doped polysilicon layer 25 of the silicon wafer 2, thereby obtaining a photovoltaic cell.

[0076] Specifically, each of the front silver electrode 31 and the back silver electrode 4 includes a plurality of fine grids 33 .

[0077] It should be noted that whether the electrode paste on the back of the silicon wafer 2 also uses aluminum-free silver paste can be determined according to the type of semiconductor actually in contact. In practice, for an N-type TOPCon cell, since the passivation contact structure on the back of the silicon wafer 2 is n+ type, the electrode paste on the back also uses aluminum-free silver paste; at this time, the method for making the aluminum-free silver paste on the front and back of the silicon wafer 2 is carried out with reference to the method for making a silver electrode described in Example 1.

[0078] In step S22, preferably, a laser is used to perform patterned scanning irradiation on both sides of the fine grid 33 of the sintered electrode on the front side of the silicon wafer 2 (eg Figure 5 shown).

[0079] A photovoltaic module of the present embodiment includes a photovoltaic front panel, a photovoltaic cell and a photovoltaic back panel stacked in sequence from top to bottom, and the photovoltaic cell is a photovoltaic cell described above in the present embodiment.

[0080] A photovoltaic power station of the present embodiment includes at least one photovoltaic module, and the photovoltaic module is a photovoltaic module described above in the present embodiment.

[0081] Comparative Example 1

[0082] The preparation method of a photovoltaic cell in this comparative example has the same preparation steps as those in Example 2, and the difference between the comparative example and Example 2 is that:

[0083] In step S11, the electrode paste printed on the front side of the silicon wafer is the existing silver-aluminum paste (rather than the aluminum-free silver paste), and after drying the silver-aluminum paste, a conventional high-temperature sintering process is used to complete the preparation process of the silver-aluminum paste to prepare the front silver-aluminum electrode 32 (such as Figure 1 shown).

[0084] Compared with the peak sintering temperature of step S13, the peak sintering temperature of the conventional high temperature sintering process is higher, which is 760°C.

[0085] Comparative Example 2

[0086] The preparation method of a photovoltaic cell in this comparative example has the same preparation steps as those in Example 2, and the difference between the comparative example and Example 2 is that:

[0087] In step S11, the electrode paste printed on the front side of the silicon wafer is the existing silver-aluminum paste, and the remaining steps are the same as those in Example 2, thereby obtaining a silver-aluminum electrode on the front side of the silicon wafer.

[0088] Performance Testing

[0089] The photovoltaic cells prepared in Example 2 and Comparative Examples 1-2 were tested for performance, and the test results are shown in Table 1 below:

[0090] Table 1

[0091]

[0092]

[0093] As can be seen from Table 1, in the method for making the silver electrode of the present invention, the aluminum-free silver paste combined with the laser electrical injection technology can significantly increase the open circuit voltage, improve the fill factor, reduce the series resistance, and the parallel resistance and leakage are maintained at a level better than that of comparative examples 1-2, thereby further improving the battery efficiency.

[0094] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the embodiments of the present invention.

[0095] The technical solution provided by the present invention is introduced in detail above. Specific examples are used in this article to illustrate the principle and implementation mode of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation mode and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A method for manufacturing a silver electrode, characterized in that: The steps include: S11, printing electrode paste on the front and back sides of the silicon wafer; wherein at least the electrode paste on the front side of the silicon wafer is an aluminum-free silver paste, and the aluminum-free silver paste is made by mixing and grinding metal powder, glass powder, organic additives and organic solvent, and the metal powder includes silver powder; S12, drying the silicon wafer to remove the organic solvent in the electrode slurry and solidify the electrode slurry; S13, sintering the solidified electrode slurry to form an electrode that makes preliminary contact with the silicon wafer; S14. Apply a reverse bias voltage to the sintered electrode, and use a laser to scan and irradiate the surface of the silicon wafer to perform laser electrical injection treatment on the electrode, so that the treated electrode forms an ohmic contact with the silicon wafer.

2. A method for manufacturing a silver electrode according to claim 1, characterized in that: In step S11, the sum of the mass percentages of the metal powder and the glass powder in the aluminum-free silver paste is greater than or equal to 90%, the sum of the mass percentages of the organic additive and the organic solvent in the aluminum-free silver paste is less than or equal to 10%, and the mass percentage of the metal powder in the aluminum-free silver paste is greater than or equal to 80%.

3. A method for manufacturing a silver electrode according to claim 1, characterized in that: In step S14, an external power source is used to apply the reverse bias voltage, and the voltage range of the reverse bias voltage is 5-30V and the application time is 0.5-5s.

4. A method for manufacturing a silver electrode according to claim 1 or 3, characterized in that: In step S14, the laser is a continuous laser or a pulsed laser of 100-10000kHz, the laser spot size is 20-200μm, the laser power is 1-30W, the laser scanning irradiation speed is 40-200m / s; the laser scanning irradiation time is the same as the reverse bias application time.

5. The method for manufacturing a silver electrode according to claim 1, characterized in that: In step S14, the front side of the silicon wafer is scanned and irradiated with the laser; The laser scanning irradiation method is: the laser starts from one side of the silicon wafer, and the laser scanning line is parallel to the fine grid of the electrode sintered on the front side of the silicon wafer, scanning and irradiating line by line until the scanning and irradiation of the entire front side of the silicon wafer is completed; wherein, the interval between two adjacent laser scanning lines is minus 20 to 150μm.

6. A method for manufacturing a silver electrode according to claim 1, characterized in that: In step S14, the laser is used to perform patterned scanning irradiation on both sides of the fine grid of the sintered electrode on the front side of the silicon wafer; The laser patterned scanning irradiation method is: the laser starts from the first fine grid of the electrode sintered on the front side of the silicon wafer, and the laser scanning line is parallel to the front side of the silicon wafer, and scans and irradiates 1-10 times on the left and right sides of the fine grid respectively, and the distance between the laser scanning line and the center position of the fine grid is in the range of 10-150μm; after scanning and irradiating the first fine grid, jump to the next adjacent fine grid until all the fine grids of the electrode sintered on the front side of the silicon wafer are scanned and irradiated.

7. A method for manufacturing a silver electrode according to claim 6, characterized in that: Before the laser patterned scanning irradiation, the method further includes: positioning the front side of the silicon wafer to determine the electrode pattern after sintering on the front side of the silicon wafer.

8. A method for manufacturing a silver electrode according to claim 1, characterized in that: In step S13, the sintering temperature is 400-800°C.

9. A method for preparing a photovoltaic cell, characterized in that: The steps include: Step S21, preparing a silicon wafer; wherein the photovoltaic cell is an N-type TOPCon cell; the silicon wafer comprises a silicon substrate, a P+ front field and a front passivation anti-reflection layer sequentially arranged on the front side of the silicon substrate, and a passivation contact structure and a back passivation layer sequentially arranged on the back side of the silicon substrate; Step S22: Process the front and back sides of the silicon wafer using a silver electrode manufacturing method as described in any one of claims 1 to 8 to obtain an electrode that forms an ohmic contact with the silicon wafer, thereby obtaining a photovoltaic cell.

10. A photovoltaic cell, characterized in that: It is prepared by the method for preparing a photovoltaic cell as described in claim 9.

11. A photovoltaic module, comprising a photovoltaic front panel, a photovoltaic cell and a photovoltaic back panel stacked in sequence from top to bottom, characterized in that: The photovoltaic cell is a photovoltaic cell as claimed in claim 10.

12. A photovoltaic power station, comprising at least one photovoltaic module, characterized in that: The photovoltaic module is a photovoltaic module as claimed in claim 11.

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