Silver-aluminum paste and preparation method thereof, electrode and solar cell

Abstract

The invention relates to silver-aluminum paste and a preparation method thereof, an electrode and a solar cell, the silver-aluminum paste at least comprises silver powder, aluminum boride powder, glass powder and an organic carrier, and the silver-aluminum paste further comprises aluminum powder or does not contain aluminum powder; according to the silver-aluminum paste, part of aluminum powder or all aluminum powder is replaced by the aluminum boride powder, so that the formation of silver-aluminum spikes is reduced, the risk that the emitter is damaged by the silver-aluminum spikes is reduced, meanwhile, the contact potential barrier between the silver-aluminum paste and p + Si is reduced, the electrical contact is improved, and the photoelectric conversion efficiency of the solar cell is improved.

Description

Technical Field

[0001] The present application relates to the technical field of solar cells, and in particular to a silver-aluminum paste and a preparation method thereof, an electrode, and a solar cell. Background Art

[0002] In the solar cell market, there are two types of crystalline silicon cells: P-type and N-type. While P-type PERC (passivated emitter and rear cell) currently holds the majority of the market share, N-type crystalline silicon cells are gradually gaining market share due to their long minority carrier lifetime and reduced light-induced degradation. As PERC cells approach their efficiency limits, TOPCon (tunneling oxide passivated contact), HJT (heterojunction), and BC (back contact) cells are becoming the mainstream in the market.

[0003] During the manufacturing process of solar cells, electrodes are screen-printed on the front and back of the cells. For the boron-diffused p+ emitter of N-type cells, the current market typically uses silver-aluminum paste screen-printed to form metallized contacts. Traditional silver-aluminum paste uses silver and aluminum powders as conductive metal powders, which can provide better electrical contact than silver and aluminum pastes. However, the metallization of traditional silver-aluminum paste with the boron-diffused p+ emitter of N-type cells faces the difficulty of balancing metal composite and electrical contact. Summary of the Invention

[0004] The present application provides a silver-aluminum paste and its preparation method, an electrode, and a solar cell to reduce the formation of silver-aluminum spikes and reduce the risk of silver-aluminum spikes damaging the emitter, while reducing the contact barrier between the silver-aluminum paste and p+Si, improving electrical contact, and thus improving the photoelectric conversion efficiency of the solar cell.

[0005] In a first aspect of the present application, a silver-aluminum paste is provided, wherein the silver-aluminum paste comprises at least silver powder, aluminum boride powder, glass powder and an organic vehicle, and the silver-aluminum paste further comprises aluminum powder or does not contain aluminum powder.

[0006] In some embodiments, based on the mass of the silver-aluminum paste, the silver-aluminum paste comprises the following components: 60 wt% to 90 wt% of the silver powder, 0.1 wt% to 20 wt% of the aluminum boride powder, 1 wt% to 20 wt% of the glass powder, 1 wt% to 40 wt% of the organic vehicle, and 0 to 20 wt% of the aluminum powder.

[0007] In some embodiments, the silver-aluminum paste contains aluminum powder, and the mass ratio of the aluminum powder to the aluminum boride powder is (0.1-10):1.

[0008] In some embodiments, the silver-aluminum paste consists of the silver powder, the aluminum boride powder, the glass powder, and the organic vehicle.

[0009] In some embodiments, the aluminum boride powder includes AlB2, AlB4 and AlB 12 One or more of .

[0010] In some embodiments, the average particle size of the aluminum boride powder is 0.1 μm to 5 μm.

[0011] In some embodiments, the silver-aluminum paste contains the aluminum powder, and the average particle size of the aluminum powder is 0.1 μm to 5 μm.

[0012] In some embodiments, the average particle size of the silver powder is 0.1 μm to 5 μm.

[0013] In some embodiments, the average particle size of the glass powder is 0.1 μm to 5 μm.

[0014] In some embodiments, the glass powder comprises the following components, based on the mass of the glass powder: Bi2O30~50wt%, PbO 0~50wt%, B2O35wt%~20wt%, SiO23wt%~20wt%, Al2O33wt%~10wt%, TeO23wt%~10wt%, SnO22wt%~4wt%, Li2O 2wt%~4wt%, ZnO 1wt%~2wt%, and BaO 0.5wt%~2wt%.

[0015] In some embodiments, the organic vehicle comprises an organic solvent, an organic binder, a surfactant, a thixotropic agent, and a diluent.

[0016] In a second aspect of the present application, a method for preparing a silver-aluminum paste is provided, comprising the following steps:

[0017] The raw materials of the silver-aluminum paste are mixed to obtain the silver-aluminum paste; the raw materials include silver powder, aluminum boride powder, glass powder and an organic carrier, and the raw materials also include aluminum powder or do not include aluminum powder.

[0018] The third aspect of the present application provides an electrode, which is made of at least one of the silver-aluminum paste described in the first aspect of the present application and the silver-aluminum paste prepared by the preparation method described in the second aspect of the present application.

[0019] In some embodiments, the electrode comprises a solar cell p+ electrode.

[0020] In a fourth aspect of the present application, a solar cell is provided, comprising the electrode described in the third aspect of the present application.

[0021] Compared with traditional technologies, the above-mentioned silver-aluminum paste and its preparation method, electrode and solar cell have at least the following advantages:

[0022] (1) The above-mentioned silver-aluminum paste uses aluminum boride powder to replace part or all of the aluminum powder. The aluminum boride powder can provide aluminum during the high-temperature sintering process. The silver-aluminum paste will still form silver-aluminum contact points with the silicon-containing solar cell, thereby reducing the contact resistance. At the same time, since aluminum boride powder has a higher melting point than aluminum powder, it limits the reaction activity of aluminum alloying with silicon during the high-temperature process, reduces the formation of silver-aluminum spikes, and reduces the risk of silver-aluminum spikes penetrating the emitter.

[0023] (2) The silver-aluminum paste can reduce the contact barrier with p+Si and improve the electrical contact, thereby increasing the open circuit voltage of the solar cell, reducing the contact resistance, increasing the fill factor, and further improving the photoelectric conversion efficiency of the solar cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a SEM image (scanning electron microscope image) of the battery cell after chemical cleaning and removal of the electrodes provided in Comparative Example 2 of this application.

[0025] Figure 2 This is an SEM image of the battery cell provided in Example 2 of the present application after chemical cleaning and removal of the electrodes.

[0026] Figure 3 This is the potential distribution diagram of the battery cell electrode and p+Si contact provided in Comparative Example 2 of this application.

[0027] Figure 4 To follow Figure 3 The red solid line in the middle is the change in the contact potential between the electrode and p+Si.

[0028] Figure 5 This is a diagram of the potential distribution of the cell electrode and p+Si contact provided in Example 2 of the present application.

[0029] Figure 6 To follow Figure 5 The contact potential change diagram between the red solid line electrode and p+Si.

[0030] Figure 7 This is a three-dimensional diagram of the potential distribution between the cell electrode and the p+Si contact provided in Comparative Example 2 of this application.

[0031] Figure 8 This is a three-dimensional diagram of the potential distribution between the cell electrode and the p+Si contact provided in Example 2 of the present application.

[0032] Figure 9 This is a statistical diagram of the potential distribution between the cell electrode and the p+Si contact provided in Comparative Example 2 of this application.

[0033] Figure 10 This is a statistical diagram of the potential distribution between the cell electrode and the p+Si contact provided in Example 2 of the present application. DETAILED DESCRIPTION

[0034] To make the above-mentioned objects, features, and advantages of the present application more clearly understood, the specific embodiments of the present application are described in detail below. The following description sets forth many specific details to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways than those described herein, and those skilled in the art can make similar modifications without violating the scope of the present application. Therefore, the present application is not limited to the specific embodiments disclosed below.

[0035] In this application, terms such as "first aspect," "second aspect," and "third aspect" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor as implicitly indicating the importance or quantity of the technical features indicated. Furthermore, terms such as "first," "second," and "third," etc., are intended only to provide a non-exhaustive enumeration and description and should not constitute a closed-ended limitation on quantity.

[0036] In this application, the terms "optionally," "optional," and "optional" mean optional or dispensable, i.e., they refer to either option being selected from two parallel options: "with" or "without." If a technical solution contains multiple "optional" clauses, each "optional" clause is independent unless otherwise specified and there are no contradictions or constraints.

[0037] In this application, when referring to numerical ranges, unless otherwise specified, the numerical ranges are considered continuous and include the minimum and maximum values of the range, as well as every value between such minimum and maximum values. Further, when a range refers to an integer, every integer between the minimum and maximum values of the range is included. In addition, when multiple ranges are provided to describe a feature or characteristic, the ranges can be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges subsumed therein.

[0038] In this application, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features.

[0039] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by those skilled in the art to which this application belongs. The terms used in this application and in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "and / or" used in this application includes any and all combinations of one or more related listed items. The term "multiple" in this application means at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0040] Traditional silver-aluminum pastes are prone to forming silver-aluminum spikes after sintering, which can damage the emitter. The silver powder and aluminum powder have significantly different activities and melting points. Based on this, one embodiment of the present application provides a silver-aluminum paste comprising at least silver powder, aluminum boride powder, glass powder, and an organic vehicle, and optionally containing aluminum powder.

[0041] Compared with traditional silver-aluminum paste, the silver-aluminum paste of the present application uses aluminum boride powder to replace part or all of the aluminum powder. Aluminum boride powder can provide aluminum during the high-temperature sintering process, and the silver-aluminum paste will still form silver-aluminum contact points with silicon-containing solar cells, thereby reducing contact resistance. At the same time, since aluminum boride powder has a higher melting point than aluminum powder, it limits the reactivity of aluminum alloying with silicon during high-temperature processes, reduces the formation of silver-aluminum spikes, and reduces the risk of silver-aluminum spikes penetrating the emitter. In addition, the above-mentioned silver-aluminum paste can reduce its contact barrier with p+Si, improve electrical contact, thereby increasing the open circuit voltage of solar cells, reducing contact resistance, and increasing fill factor, thereby increasing the photoelectric conversion efficiency of solar cells. The above-mentioned silver-aluminum paste of the present application can ensure that while boron elements are heavily doped with p+Si, the corrosion of silver-aluminum paste on p+Si is lower, and the contact barrier between the electrode formed by sintering and p+Si is lower. Therefore, compared with traditional silver-aluminum paste, the above-mentioned silver-aluminum paste has better electrical contact performance after sintering.

[0042] The silver powder, aluminum boride powder, and aluminum powder in the silver-aluminum paste are conductive components. Therefore, the silver-aluminum paste comprises at least conductive powder, glass powder, and an organic vehicle. The conductive powder comprises silver powder and aluminum boride powder, and may or may not comprise aluminum powder. Optionally, the silver powder is conductive silver powder.

[0043] In some embodiments, the silver-aluminum paste comprises the following components (raw materials), based on the mass of the silver-aluminum paste: 60-90 wt% silver powder, 0.1-20 wt% aluminum boride powder, 1-20 wt% glass powder, 1-40 wt% organic vehicle, and 0-20 wt% aluminum powder. This helps further reduce the formation of silver-aluminum spikes and further improve the photoelectric conversion efficiency of solar cells. It is understood that, based on the mass of the silver-aluminum paste, the silver-aluminum paste may comprise, for example, the following components (raw materials): 81.6 wt% silver powder, 3.4 wt% aluminum boride powder, 5 wt% glass powder, and 10 wt% organic vehicle; or 78.46 wt% silver powder, 6.54 wt% aluminum boride powder, 5 wt% glass powder, and 10 wt% organic vehicle; or 80 wt% silver powder, 3 wt% aluminum boride powder, 5 wt% glass powder, 10 wt% organic vehicle, and 2 wt% aluminum powder; or 75 wt% silver powder, 8 wt% aluminum boride powder, 5 wt% glass powder, 10 wt% organic vehicle, and 2 wt% aluminum powder, etc.

[0044] In some embodiments, based on the mass of the silver-aluminum paste, the silver-aluminum paste contains the following components (raw materials): 60 wt% to 90 wt% of silver powder, 1 wt% to 10 wt% of aluminum boride powder, 5 wt% to 20 wt% of glass powder, 4 wt% to 30 wt% of organic vehicle, and 0 to 10 wt% of aluminum powder.

[0045] In some embodiments, the silver-aluminum paste contains aluminum powder in a mass ratio of aluminum powder to aluminum boride powder of 0.1-10:1. This helps further reduce the formation of silver-aluminum spikes and further improves the photoelectric conversion efficiency of the solar cell. It is understood that the above mass ratio includes, but is not limited to, 0.1:1, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, and 10:1.

[0046] In some embodiments, the silver-aluminum paste is composed of silver powder, aluminum boride powder, glass powder, and an organic vehicle. The silver-aluminum paste does not contain aluminum powder, which can further reduce the formation of silver-aluminum spikes and further improve the photoelectric conversion efficiency of the solar cell.

[0047] In some embodiments, the conductive powder in the silver-aluminum paste consists of silver powder and aluminum boride powder.

[0048] In some embodiments, aluminum boride powder includes AlB2, AlB4 and AlB 12 Optionally, the aluminum boride powder comprises AlB2.

[0049] In some embodiments, the average particle size of the aluminum boride powder is 0.1 μm to 5 μm. Controlling the average particle size of the aluminum boride powder within the above range can improve the adhesion between the particles after sintering the silver-aluminum paste, which is beneficial for further improving the photoelectric conversion efficiency of the solar cell. It is understood that the average particle size of the aluminum boride powder includes, but is not limited to, 0.1 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, and 5 μm.

[0050] In some embodiments, the silver-aluminum paste contains aluminum powder, and the average particle size of the aluminum powder is 0.1 μm to 5 μm. Controlling the average particle size of the aluminum powder within the above range can improve the adhesion between the particles after sintering the silver-aluminum paste, which is beneficial to further improve the photoelectric conversion efficiency of the solar cell. It is understood that the average particle size of the aluminum powder includes but is not limited to: 0.1 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, and 5 μm.

[0051] In some embodiments, the average particle size of the silver powder is 0.1 μm to 5 μm. Controlling the average particle size of the silver powder within the above range can improve the adhesion between the particles after sintering the silver-aluminum paste, which is beneficial for further improving the photoelectric conversion efficiency of the solar cell. It is understood that the average particle size of the silver powder includes but is not limited to: 0.1 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, and 5 μm.

[0052] In some embodiments, the average particle size of the glass powder is 0.1 μm to 5 μm. It is understood that the average particle size of the glass powder includes but is not limited to: 0.1 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, and 5 μm.

[0053] In some embodiments, the glass powder comprises the following components (raw materials), based on the mass of the glass powder: Bi2O3 0-50wt%, PbO 0-50wt%, B2O3 5wt%-20wt%, SiO2 3wt%-20wt%, Al2O3 3wt%-10wt%, TeO2 3wt%-10wt%, SnO2 2wt%-4wt%, Li2O 2wt%-4wt%, ZnO 1wt%-2wt%, and BaO 0.5wt%-2wt%.

[0054] In some embodiments, the organic vehicle comprises an organic solvent, an organic binder, a surfactant, a thixotropic agent, and a diluent. Alternatively, the organic solvent includes, but is not limited to, one or more of terpineol, butyl carbitol, lauryl ester, and diethyl phthalate. Alternatively, the organic binder includes, but is not limited to, ethyl cellulose. Alternatively, the surfactant includes, but is not limited to, sodium dodecylbenzene sulfonate. Alternatively, the thixotropic agent includes, but is not limited to, polyamide wax. Alternatively, the diluent includes, but is not limited to, hydrogenated castor oil.

[0055] Another embodiment of the present application provides a method for preparing a silver-aluminum paste, comprising the following steps:

[0056] The raw materials of the silver-aluminum paste are mixed to obtain the silver-aluminum paste; the raw materials include silver powder, aluminum boride powder, glass powder and an organic carrier, and the raw materials also include aluminum powder or do not include aluminum powder.

[0057] Compared with traditional silver-aluminum paste, the silver-aluminum paste of the present application uses aluminum boride powder to replace part or all of the aluminum powder. Aluminum boride powder can provide aluminum during the high-temperature sintering process, and the silver-aluminum paste will still form silver-aluminum contact points with silicon-containing solar cells, thereby reducing contact resistance. At the same time, since aluminum boride powder has a higher melting point than aluminum powder, it limits the reactivity of aluminum alloying with silicon during high-temperature processes, reduces the formation of silver-aluminum spikes, and reduces the risk of silver-aluminum spikes penetrating the emitter. In addition, the above-mentioned silver-aluminum paste can reduce its contact barrier with p+Si, improve electrical contact, thereby increasing the open circuit voltage of solar cells, reducing contact resistance, and increasing fill factor, thereby increasing the photoelectric conversion efficiency of solar cells. The above-mentioned silver-aluminum paste of the present application can ensure that while boron elements are heavily doped with p+Si, the corrosion of silver-aluminum paste on p+Si is lower, and the contact barrier between the electrode formed by sintering and p+Si is lower. Therefore, compared with traditional silver-aluminum paste, the above-mentioned silver-aluminum paste has better electrical contact performance after sintering.

[0058] It should be noted that the silver-aluminum paste can be the same as the silver-aluminum paste in one embodiment of the present application. The silver-aluminum paste can be used to prepare a p+ electrode of a solar cell.

[0059] In some embodiments, after the step of mixing the raw materials of the silver-aluminum paste, the method further includes grinding the mixed raw materials. Optionally, after the step of grinding the mixed raw materials, the method further includes screening the ground paste.

[0060] The present application provides the use of the above-mentioned silver-aluminum paste in the preparation of solar cells.

[0061] Another embodiment of the present application provides an electrode, which is made using at least one of the silver-aluminum paste mentioned above and the silver-aluminum paste prepared by the above preparation method of the present application.

[0062] As a non-limiting example, the electrode is formed by sintering the silver-aluminum paste on the surface of a silicon wafer. For example, the silver-aluminum paste is printed by screen printing to form the gate lines required for the p+ emitter on the front side of an N-type TOPCon cell, and then sintered to form the electrode. Optionally, the sintering peak temperature is 750°C to 900°C. It is understood that the sintering peak temperature includes but is not limited to: 750°C, 780°C, 800°C, 830°C, 850°C, 870°C, 900°C, etc.

[0063] In some embodiments, the electrode is a solar cell p+ electrode.

[0064] Another embodiment of the present application further provides a solar cell, comprising the above-mentioned electrode of the present application.

[0065] In some embodiments, the solar cell comprises an N-type solar cell, including but not limited to an N-type TopCon cell.

[0066] To further illustrate the present application, the technical solutions of the present application are described in detail below with reference to specific examples. Where specific techniques or conditions are not specified in the examples, the techniques or conditions described in the literature in the art or in accordance with the product instructions were used. Reagents or instruments used, for which the manufacturer is not specified, are all commercially available conventional products.

[0067] Example 1

[0068] The composition of the silver-aluminum paste of this embodiment is as follows:

[0069] Based on the mass of the silver-aluminum paste, the silver-aluminum paste contains the following components (raw materials): 85 wt % of a mixture of silver powder and aluminum boride powder, 5 wt % of glass powder, and 10 wt % of an organic vehicle.

[0070] The silver powder and aluminum boride powder mixture consists of silver powder and aluminum boride powder, the mass ratio of silver powder to aluminum boride powder is 24:1, the aluminum boride powder is AlB2 powder, the average particle size of the aluminum boride powder is 1μm~3μm, and the average particle size of the silver powder is 1μm~3μm.

[0071] The glass powder comprises the following components (raw materials) by weight: PbO 30wt%, Bi2O3 30wt%, B2O3 20wt%, Al2O3 6wt%, SiO2 4wt%, SnO2 4wt%, TeO2 2wt%, BaO 2wt%, and ZnO 2wt%. The raw materials for the glass powder are uniformly mixed, melted at high temperature in a crucible, and quenched. The resulting glass frit is ground to an average particle size of 2μm to obtain the glass powder.

[0072] Based on the mass of the organic carrier, the organic carrier includes the following components (raw materials): 25 wt% of terpineol, 25 wt% of butyl carbitol, 20 wt% of lauryl ester, 15 wt% of diethyl phthalate, 8 wt% of ethyl cellulose, 2.5 wt% of polyamide wax, 2.5 wt% of hydrogenated castor oil, and 2 wt% of sodium dodecylbenzene sulfonate.

[0073] The preparation method of the silver-aluminum paste of this embodiment includes the following steps:

[0074] The raw materials of the organic carrier are mixed, heated to 80° C., stirred for 1.5 hours, and mixed uniformly to obtain an organic carrier;

[0075] According to the raw material ratio of silver-aluminum slurry, silver powder, aluminum boride powder and glass powder are weighed, added to the organic carrier, stirred and mixed evenly, and introduced into a three-roll mill for grinding and dispersion to obtain silver-aluminum slurry.

[0076] Example 2

[0077] This embodiment is basically the same as embodiment 1, except that in the silver-aluminum paste, the mass ratio of silver powder to aluminum boride powder in the mixture of silver powder and aluminum boride powder is 12:1.

[0078] Example 3

[0079] This embodiment is basically the same as the embodiment 1, except that in the silver-aluminum paste, the aluminum boride powder in the mixture of silver powder and aluminum boride powder is AlB4 powder.

[0080] Example 4

[0081] This embodiment is basically the same as embodiment 2, except that: in the silver-aluminum paste, the aluminum boride powder in the mixture of silver powder and aluminum boride powder is AlB 12 powder.

[0082] Example 5

[0083] This embodiment is basically the same as Example 1, except that: based on the mass of the silver-aluminum paste, the silver-aluminum paste contains the following components (raw materials): 85 wt % of a mixture of silver powder, aluminum boride powder and aluminum powder, 5 wt % of a glass powder, and 10 wt % of an organic vehicle; the silver powder, aluminum boride powder and aluminum powder mixture is composed of silver powder, aluminum boride powder and aluminum powder, and the mass ratio of silver powder, aluminum boride powder and aluminum powder is 48:1:1, and the average particle size of the aluminum powder is 1 μm~3 μm.

[0084] Example 6

[0085] This embodiment is basically the same as Example 1, except that: based on the mass of the silver-aluminum paste, the silver-aluminum paste contains the following components (raw materials): 85 wt % of a mixture of silver powder, aluminum boride powder and aluminum powder, 5 wt % of a glass powder, and 10 wt % of an organic vehicle; the silver powder, aluminum boride powder and aluminum powder mixture is composed of silver powder, aluminum boride powder and aluminum powder, and the mass ratio of silver powder, aluminum boride powder and aluminum powder is 48:2:0.2, and the average particle size of the aluminum powder is 1 μm~3 μm.

[0086] Example 7

[0087] This embodiment is basically the same as Example 1, except that: based on the mass of the silver-aluminum paste, the silver-aluminum paste contains the following components (raw materials): 85 wt % of silver powder, aluminum boride powder and aluminum powder mixture, 5 wt % of glass powder, and 10 wt % of organic vehicle; the silver powder, aluminum boride powder and aluminum powder mixture is composed of silver powder, aluminum boride powder and aluminum powder, and the mass ratio of silver powder, aluminum boride powder and aluminum powder is 48:0.2:2, and the average particle size of the aluminum powder is 1 μm~3 μm.

[0088] Comparative Example 1

[0089] This comparative example is basically the same as Example 1, except that: based on the mass of the silver-aluminum paste, the silver-aluminum paste contains the following components (raw materials): 85 wt % of a mixture of silver powder and aluminum powder, 5 wt % of glass powder, and 10 wt % of an organic vehicle; the silver powder and aluminum powder mixture consists of silver powder and aluminum powder, and the silver-aluminum paste does not contain aluminum boride powder; the total mass of the aluminum element in the silver powder and aluminum powder mixture is the same as the total mass of the aluminum element in the silver powder and aluminum boride powder mixture in Example 1.

[0090] Comparative Example 2

[0091] This comparative example is basically the same as Example 2, except that: based on the mass of the silver-aluminum paste, the silver-aluminum paste contains the following components (raw materials): 85 wt % of a mixture of silver powder and aluminum powder, 5 wt % of glass powder, and 10 wt % of an organic vehicle; the silver powder and aluminum powder mixture is composed of silver powder and aluminum powder, and the silver-aluminum paste does not contain aluminum boride powder; the total mass of the aluminum element in the silver powder and aluminum powder mixture is the same as the total mass of the aluminum element in the silver powder and aluminum boride powder mixture in Example 2.

[0092] Comparative Example 3

[0093] This comparative example is basically the same as Example 3, except that: based on the mass of the silver-aluminum paste, the silver-aluminum paste contains the following components (raw materials): 85 wt % of a mixture of silver powder and aluminum powder, 5 wt % of glass powder, and 10 wt % of an organic vehicle; the silver powder and aluminum powder mixture consists of silver powder and aluminum powder, and the silver-aluminum paste does not contain aluminum boride powder; the total mass of the aluminum element in the silver powder and aluminum powder mixture is the same as the total mass of the aluminum element in the silver powder and aluminum boride powder mixture in Example 3.

[0094] Comparative Example 4

[0095] This comparative example is basically the same as Example 4, except that: based on the mass of the silver-aluminum paste, the silver-aluminum paste contains the following components (raw materials): 85 wt % of a mixture of silver powder and aluminum powder, 5 wt % of glass powder, and 10 wt % of an organic vehicle; the silver powder and aluminum powder mixture consists of silver powder and aluminum powder, and the silver-aluminum paste does not contain aluminum boride powder; the total mass of the aluminum element in the silver powder and aluminum powder mixture is the same as the total mass of the aluminum element in the silver powder and aluminum boride powder mixture in Example 4.

[0096] Comparative Example 5

[0097] This comparative example is basically the same as Example 5, except that: based on the mass of the silver-aluminum paste, the silver-aluminum paste contains the following components (raw materials): 85 wt % of a mixture of silver powder and aluminum powder, 5 wt % of glass powder, and 10 wt % of an organic vehicle; the silver powder and aluminum powder mixture consists of silver powder and aluminum powder, and the silver-aluminum paste does not contain aluminum boride powder; the total mass of the aluminum element in the silver powder and aluminum powder mixture is the same as the total mass of the aluminum element in the silver powder, aluminum boride powder and aluminum powder mixture in Example 5.

[0098] Comparative Example 6

[0099] This comparative example is basically the same as Example 1, except that: based on the mass of the silver-aluminum paste, the silver-aluminum paste contains the following components (raw materials):

[0100] 85wt% mixture of silver powder and alumina powder, 5wt% glass powder, and 10wt% organic carrier; the silver powder and alumina powder mixture consists of silver powder and alumina powder, and the silver-aluminum slurry does not contain aluminum boride powder; the total mass of the aluminum element in the silver powder and alumina powder mixture is the same as the total mass of the aluminum element in the silver powder and aluminum boride powder mixture in Example 1.

[0101] Performance Testing

[0102] The process flow for preparing N-type TopCon cells is as follows: cleaning and texturing, front boron diffusion, back etching, LPCVD (low-pressure chemical vapor deposition) to prepare tunnel oxide layer and polysilicon layer, back phosphorus diffusion, cleaning and removal by plating, deposition of front and back passivation layers, and front and back metallization. During the metallization process, screen printing is used to prepare the gate electrode. The front metallization uses the silver-aluminum paste prepared in each embodiment or comparative example. The sintering peak temperature of the screen-printed gate line is 850°C, and the sintering furnace belt speed is 225 inches / min. After the metallization process is completed, a standard test sorter is used for efficiency testing and sorting, and the relevant data in Table 1 are obtained.

[0103] Figure 1-Figure 2 This is a SEM image observed using a field emission scanning electron microscope after the front electrode was removed by HNO3 cleaning. Figure 3 and Figure 5 The potential distribution diagram shown and Figure 7-Figure 8 The three-dimensional potential distribution diagram shown is the contact potential diagram between the electrode and p+Si obtained by KPFM (Kelvin probe microscopy) after polishing the contact cross section.

[0104] Figure 1 and Figure 2The SEM images of the battery cells after chemical cleaning and electrode removal provided by Comparative Example 2 and Example 2 are shown respectively. Compared with the silver-aluminum paste based on silver powder and aluminum powder in Comparative Example 2, Example 2 uses aluminum boride powder instead of aluminum powder. Figure 1 and Figure 2 It can be seen that the silver-aluminum paste in Comparative Example 2 produces a large number of silver-aluminum spikes during the sintering process, resulting in numerous corrosion pits on the silicon wafer surface after electrode removal. However, at the same aluminum content, Example 2 produces significantly fewer corrosion pits. The silver-aluminum paste in Example 2, due to the higher melting point of aluminum boride powder, limits the reactivity of aluminum alloying with silicon during high-temperature processes, reducing the generation of silver-aluminum spikes and the risk of silver-aluminum spikes damaging the p+ emitter. Consequently, damage to the p+ emitter from large silver-aluminum spikes can be reduced.

[0105] Figure 3 The contact potential distribution diagram between the cell electrode and p+Si provided in Comparative Example 2 is shown; Figure 4 Shown along Figure 3 The red solid line in the middle is the contact potential change diagram between the electrode and p+Si. Figure 5 The figure shows the contact potential distribution diagram between the cell electrode and p+Si provided in Example 2; Figure 6 Shown along Figure 5 The red solid line in the middle shows the contact potential change between the electrode and p+Si. Since the p+ electrode collects hole carriers, the higher the potential of the electrode is than that of p+Si, the more conducive it is to hole collection; therefore, the potential difference between the silver aluminum paste and p+Si is reflected as a contact barrier. The smaller the contact barrier, the more conducive it is to the transport of hole carriers. Figure 3-Figure 6 As can be seen, the contact barrier between the silver-aluminum paste in Comparative Example 2 and p+Si is 106.2 mV, while the contact barrier between the silver-aluminum paste and p+Si in Example 2 is only 53.1 mV. This is because the aluminum boride powder, while limiting aluminum activity, also enables boron-aluminum co-doping of the p+Si. Furthermore, the introduction of aluminum boride lowers the contact barrier, improving overall electrical performance. In comparison, Example 2 has a lower contact barrier than Comparative Example 2 and exhibits superior electrical performance.

[0106] Figure 7 and Figure 8 The three-dimensional diagrams of the contact potential distribution between the cell electrode and p+Si provided in Comparative Example 2 and Example 2 are shown respectively; Figure 9 and Figure 10 The distribution statistics of the contact potential between the cell electrode and p+Si provided by Comparative Example 2 and Example 2 are shown respectively. Figure 7 and Figure 8 It can be clearly seen from the comparison that the contact barrier between the silver-aluminum paste and the p+Si as a whole in Example 2 is lower than that in Comparative Example 2. Figure 9 and Figure 10The difference in contact barrier potential across the entire contact area between the cells provided by Comparative Example 2 and Example 2 can also be seen. The contact barrier potential across the entire contact area between the silver-aluminum paste and the p+Si in Comparative Example 2 is 106mV, while the contact barrier potential across the entire contact area between the silver-aluminum paste and the p+Si in Example 2 is 48mV. Comparing the entire contact area, Example 2 also exhibits significant electrical advantages over Comparative Example 2.

[0107] Table 1

[0108]

[0109] In Table 1, Eta is the battery efficiency, Uoc is the open circuit voltage, Jsc is the short circuit current density, FF is the fill factor, Rs is the series resistance, and Rsh is the parallel resistance.

[0110] As can be seen from Table 1, the battery performance obtained with the silver-aluminum pastes of Examples 1-7 is superior to that of the battery prepared with the silver-aluminum pastes of Comparative Examples 1-6. The improvement in Example 2 is the most significant, with the battery efficiency of Example 2 increasing by 0.22% compared to Comparative Example 2, primarily due to improvements in open-circuit voltage (Uoc) and fill factor (FF). The silver-aluminum pastes in Examples 1-7 use aluminum boride powder to replace all or part of the aluminum powder, limiting the reactivity of aluminum alloying with silicon during high-temperature processes and reducing the penetration of silver-aluminum spikes into the p+ emitter. This also reduces the contact barrier between the silver-aluminum electrode and p+Si, improving electrical contact and significantly increasing the open-circuit voltage, contact resistance, fill factor, and ultimately, the battery's photoelectric conversion efficiency.

[0111] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned 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.

[0112] The above-described embodiments merely represent several implementation methods of the present application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, all of which fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims, and the specification may be used to interpret the content of the claims.

Claims

1. A silver-aluminum paste, characterized in that: The silver-aluminum paste contains at least silver powder, aluminum boride powder, glass powder and an organic vehicle, and the silver-aluminum paste also contains aluminum powder or does not contain aluminum powder.

2. The silver-aluminum paste according to claim 1, characterized in that Based on the mass of the silver-aluminum paste, the silver-aluminum paste includes the following components: 60wt%~90wt% of the silver powder, 0.1wt%~20wt% of the aluminum boride powder, 1wt%~20wt% of the glass powder, 1wt%~40wt% of the organic vehicle, and 0~20wt% of the aluminum powder.

3. The silver-aluminum paste according to claim 1 or 2, characterized in that The silver-aluminum paste contains aluminum powder, and the mass ratio of the aluminum powder to the aluminum boride powder is (0.1~10):

1.

4. The silver-aluminum paste according to claim 1 or 2, characterized in that The silver-aluminum paste consists of the silver powder, the aluminum boride powder, the glass powder and the organic vehicle.

5. The silver-aluminum paste according to claim 1 or 2, characterized in that: The aluminum boride powder includes AlB2, AlB4 and AlB 12 One or more of .

6. The silver-aluminum paste according to claim 1 or 2, characterized in that: The silver-aluminum paste has one or more of the following characteristics (1) to (6): (1) The average particle size of the aluminum boride powder is 0.1 μm to 5 μm; (2) The silver-aluminum paste contains the aluminum powder, and the average particle size of the aluminum powder is 0.1 μm to 5 μm; (3) The average particle size of the silver powder is 0.1 μm to 5 μm; (4) The average particle size of the glass powder is 0.1 μm to 5 μm; (5) Based on the mass of the glass powder, the glass powder comprises the following components: Bi2O30-50wt%, PbO 0-50wt%, B2O35wt%-20wt%, SiO23wt%-20wt%, Al2O33wt%-10wt%, TeO23wt%-10wt%, SnO22wt%-4wt%, Li2O 2wt%-4wt%, ZnO 1wt%-2wt%, and BaO 0.5wt%-2wt%; (6) The organic carrier comprises an organic solvent, an organic binder, a surfactant, a thixotropic agent and a diluent.

7. A method for preparing a silver-aluminum paste, characterized in that: The steps include: The raw materials of the silver-aluminum paste are mixed to obtain the silver-aluminum paste; the raw materials include silver powder, aluminum boride powder, glass powder and an organic carrier, and the raw materials also include aluminum powder or do not include aluminum powder.

8. An electrode, characterized in that It is made from at least one of the silver-aluminum pastes described in any one of claims 1 to 6 and the silver-aluminum paste prepared by the preparation method of claim 7.

9. The electrode according to claim 8, characterized in that The electrode comprises a solar cell p+ electrode.

10. A solar cell, characterized in that: Comprising the electrode according to claim 8 or 9.

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