Solar cell main grid slurry and solar cell

Abstract

The present application provides a solar cell busbar paste and a solar cell. The solar cell busbar paste includes low-activity silver powder, high-activity silver powder, an organic carrier and copper-manganese-free glass powder. Among them, the copper-manganese-free glass powder is Pb-Bi-Zn-Ti-B glass powder. The initial response temperature of the low-activity silver powder is higher than 200°C and the violent reaction temperature is higher than 400°C, and the initial response temperature of the high-activity silver powder is lower than 200°C and the violent reaction temperature is lower than 380°C. While there is no copper and manganese in the glass powder, low lead is replaced by Bi, which can solve the problem of blackening of the front busbar during printing. The use of low-activity powder is because it is necessary to reduce the degree of shrinkage of the silver powder during the sintering process, thereby reducing the stress caused by the shrinkage of the silver powder on the silicon wafer, and then alleviating the blackening of the busbar (cross mark print). The present application also provides a solar cell obtained by printing any of the above-mentioned slurries on a cell and sintering it.

Description

Technical Field

[0001] The present application relates to the field of photovoltaic technology, and in particular to a solar cell busbar paste and a solar cell. Background Art

[0002] Solar cells, as a green energy source, are gaining increasing attention for their inexhaustible, pollution-free, and resource-neutral nature. Conductive paste is a key auxiliary material in the production of silicon-based solar cells. Silicon-based solar cells are typically produced by printing the conductive paste onto silicon cell wafers, followed by drying and firing to create electrodes. The conductive paste typically contains conductive metal powder, glass powder, and an organic carrier. The paste is then placed on a stainless steel mesh belt and sintered to form structures such as the front busbar.

[0003] Because the front coating of the cell is thinner than the back, the glass powder in the conductive paste is more likely to generate internal stress during the sintering process, causing internal PN damage and a change in light conversion efficiency. This is manifested externally as blackening and cross marks near the main grid (blackening and cross marks are the same thing, but the manifestations are slightly different). The back coating is thicker, and the glass is less likely to damage the coating, so it does not turn black.

[0004] In order to solve the problem of blackening of the main grid after sintering, the present application provides a solar cell main grid slurry and a solar cell. Summary of the Invention

[0005] To address the issue of blackening of the busbar after sintering, embodiments of the present application provide a solar cell busbar slurry and a solar cell. The solar cell busbar slurry comprises low-activity silver powder, high-activity silver powder, an organic vehicle, and copper-manganese-free glass powder. The slurry comprises a low-activity silver powder with a mass fraction of 25% to 35%, a high-activity silver powder with a mass fraction of 45% to 55%, an organic vehicle with a mass fraction of 13% to 20%, and a copper-manganese-free glass powder with a mass fraction of 0.6% to 1.5%. The copper-manganese-free glass powder is a Pb-Bi-Zn-Ti-B glass powder. The low-activity silver powder has an initial response temperature greater than 200°C and a violent reaction temperature greater than 400°C. The high-activity silver powder has an initial response temperature less than 200°C and a violent reaction temperature less than 380°C.

[0006] The glass frit is copper-free and manganese-free, and Bi is used as a low-lead replacement, resolving the issue of blackening during front-side busbar printing. The use of low-activity powder reduces the shrinkage of the silver powder during sintering, thereby reducing the stress exerted on the silicon wafer. This, in turn, alleviates the blackening of the busbar (fork marks), resolving the issue of blackening after sintering.

[0007] The slurry uses low-sintering active silver powder to solve the problem of low tensile strength after the glass powder is free of copper and manganese. That is, the low-sintering active silver powder is used to compensate for the tensile strength and increase the softening temperature.

[0008] Optionally, based on the total molar percentage content of the copper-free manganese glass powder as 100 mol%, the copper-free manganese glass powder includes 0.3 mol% to 0.8 mol% Pb3O4, 10 mol% to 25 mol% Bi2O3, 40 mol% to 60 mol% B2O3, 8 mol% to 15 mol% TiO2 and 10 mol% to 20 mol% alkali metal elements.

[0009] Optionally, the alkali metal element substance is an oxide or a halide, and the elements in the alkali metal element substance include one or more of Li, Na, K, and Rb.

[0010] Optionally, the alkali metal substance is a composite of alkali metal oxides that is decomposed during the preparation of the glass powder.

[0011] Optionally, the initial reaction temperature difference between the high-activity silver powder and the low-activity silver powder is 30°C-60°C.

[0012] Optionally, the copper-manganese-free glass powder further includes a copper-manganese substitute, and the elements in the copper-manganese substitute include Zn and Te.

[0013] Optionally, the copper-free manganese glass powder further includes 10 mol% to 25 mol% ZnO and 5 mol% to 10 mol% TeO2.

[0014] Optionally, the organic carrier includes an organic solvent, an organic resin, cellulose, a thickener and a surfactant. Taking the total mass percentage content of the organic carrier as 100%, the mass fraction of the organic solvent in the organic carrier is 60.0%-80.0%, the organic resin and cellulose together account for 0%-10%, the thickener accounts for 5%-20%, and the surfactant accounts for 0.1%-20%.

[0015] Optionally, the method for preparing the solar cell busbar paste specifically includes:

[0016] The raw materials of various glass components are mixed uniformly in proportion, heated and melt-reacted, cooled and dried, and then ground to obtain copper-free manganese glass powder; an organic solvent, an organic resin, cellulose, a thickener, and a surfactant are stirred uniformly in proportion, and dispersed by high-speed centrifugation to obtain the organic carrier; the copper-free manganese glass powder is mixed uniformly with low-activity silver powder, high-activity silver powder, and the organic carrier in proportion, and the slurry is obtained after slurrying, filtering, and slurrying.

[0017] The present application also provides a solar cell, which is obtained by printing any one of the solar cell busbar pastes described above on a cell sheet and then sintering the printed paste.

[0018] The present application provides a solar cell main grid paste and a solar cell. The paste includes low-activity silver powder, high-activity silver powder, an organic carrier and copper-manganese-free glass powder. The copper-manganese-free glass powder is a Pb-Bi-Zn-Ti-B glass powder. The low-activity silver powder has an initial response temperature higher than 200°C and a violent reaction temperature higher than 400°C, and the high-activity silver powder has an initial response temperature lower than 200°C and a violent reaction temperature lower than 380°C. While there is no copper and manganese in the glass powder, low lead is replaced by Bi, which can solve the problem of blackening of the front main grid during printing. The use of low-activity powder is because it is necessary to reduce the degree of shrinkage of the silver powder during the sintering process, thereby reducing the stress caused by the shrinkage of the silver powder on the silicon wafer, and then alleviating the blackening of the main grid (cross mark print). The present application also provides a solar cell obtained by printing any of the above-mentioned pastes on a cell and sintering it. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solution of the present application, the following is a brief introduction to the drawings required for use in the embodiments. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0020] Figure 1 This is a schematic diagram for analyzing the cause of the main grid turning black;

[0021] Figure 2 This is a schematic diagram of the silver powder activity test results;

[0022] Figure 3 This is a schematic diagram showing that the main grid of the battery cell has not turned black;

[0023] Figure 4 This is a schematic diagram of the blackening of the main grid of the battery cell;

[0024] Figure 5 This is a schematic diagram of the statistical results of the blackening of the battery cell main grid (the horizontal axis is the slurry name, and the vertical axis is the proportion of blackening of the battery cell main grid). DETAILED DESCRIPTION

[0025] The following embodiments are described in detail, with examples illustrated in the accompanying drawings. When the following description refers to the drawings, identical numbers in different figures represent identical or similar elements unless otherwise indicated. The embodiments described in the following embodiments are not intended to represent all possible implementations consistent with the present application. They are merely examples of systems and methods consistent with certain aspects of the present application, as detailed in the claims.

[0026] To address the issue of blackening of the busbar after sintering, the present application provides a solar cell busbar slurry and a solar cell. The slurry comprises low-activity silver powder, high-activity silver powder, an organic vehicle, and copper-manganese-free glass powder. The mass fraction of the low-activity silver powder in the slurry is 25% to 35%, the mass fraction of the high-activity silver powder is 45% to 55%, the mass fraction of the organic vehicle is 13% to 20%, and the mass fraction of the copper-manganese-free glass powder is 0.6% to 1.5%. The copper-manganese-free glass powder is a Pb-Bi-Zn-Ti-B glass powder. The low-activity silver powder has an initial response temperature greater than 200°C and a violent reaction temperature greater than 400°C. The high-activity silver powder has an initial response temperature less than 200°C and a violent reaction temperature less than 380°C.

[0027] The main reason for the cross marks on the front main grid is that it has a strong impact on etching. For example, the copper and manganese elements in the glass powder have strong shaping ability and shrinkage, resulting in obvious cross marks. Traditional main grid glass with copper and manganese has Cu, which can promote sintering (Cu melts quickly in the glass, causing nearby Ag to crystallize and form microcrystals), while Mn has good fluidity. Under the interaction of the two, a large amount of microcrystal Ag is carried to the interface. During the cooling process, the microcrystal Ag cools and shrinks. Ag expansion coefficient: 19.0x10 -6 / K, Si expansion coefficient: 2.4x10 -6 The significant difference in K / K creates significant internal stress at the interface, damaging the PN junction and causing blackening and cross-marking. Consequently, currently used conductive pastes leave traces of the mesh belt after sintering. These traces are not only aesthetically pleasing but also likely weaken the bonding strength of the silicon-aluminum layer in the marked area, leading to reduced photoelectric conversion efficiency.

[0028] like Figure 1 As shown, the main causes of busbar blackening are glass expansion and silver powder shrinkage, so the slurry is adjusted based on these two aspects. To solve the problem of busbar blackening after sintering the N-positive busbar, this application provides a solar cell busbar slurry. The glass powder of this slurry is copper-manganese-free, or copper and manganese are replaced by other elements, and the glass powder is low in lead. The conductive slurry uses low-sintering active silver.

[0029] After abandoning the use of Cu and Mn elements, low Pb and high Bi are used (Bi is used to replace Pb. The reaction activity of Bi and the surface coating of the silicon wafer is lower than that of Pb. Bi is less active than Pb, the degree of damage to the surface coating is low, the internal stress of the interface is low, and the blackening and fork marks are improved). The low sintering activity is also to allow the glass to bring less microcrystalline Ag to the interface, the internal stress of the interface is small, and there will be no fork marks or blackening problems. This application uses low Pb because Pb has a negative impact on the performance of our slurry. Pb can be partially replaced by Bi, but not completely replaced, because Pb can lower the Tg point of the glass, and Pb is also required to react with part of the coating. Bi has a relatively low reaction activity. Using Bi exclusively will result in insufficient adhesion between the slurry and the silicon wafer, and a decrease in tensile strength. Bi2O3 is used as a substitute for bismuth. Its melting point of 821°C is lower than that of 883°C for bismuth carbonate, making it easier to melt glass.

[0030] The slurry glass powder provided in this application is designed to be copper-manganese-free. The absence of Cu and Mn will weaken etching, so the Tg (glass softening temperature) of the glass can be appropriately lowered to allow the glass to react at a lower temperature. In short, this increases the reaction time. The slurry glass powder provided in this application is designed to be copper-manganese-free, and other elements can be used instead. Reducing the Pb element content makes the interface reaction milder.

[0031] Silver powder activity refers to the sintering activity of silver powder. The activity of silver powder is determined by testing the volume shrinkage ratio of silver powder during the sintering process, as follows Figure 2 As shown, the horizontal axis represents sintering temperature, and the vertical axis represents volume shrinkage ratio. The slurry uses low-sintering-activity silver powder to address the issue of low tensile strength when the glass frit is free of copper and manganese. This low-sintering-activity silver powder compensates for tensile strength, raises the softening temperature, and reduces silver powder shrinkage during sintering, thereby reducing stress on the silicon wafer caused by silver powder shrinkage and, in turn, minimizing busbar blackening (cross marks).

[0032] In some embodiments, based on the total molar percentage content of the copper-free manganese glass powder as 100 mol%, the copper-free manganese glass powder includes 0.3 mol% to 0.8 mol% Pb3O4, 10 mol% to 25 mol% Bi2O3, 40 mol% to 60 mol% B2O3, 8 mol% to 15 mol% TiO2 and 10 mol% to 20 mol% alkali metal elements.

[0033] In some embodiments, the alkali metal substance is an oxide or a halide, and the elements in the alkali metal substance include one or more of Li, Na, K, and Rb.

[0034] In some embodiments, the alkali metal substance is a composite of alkali metal oxides that is decomposed during the preparation of the glass frit.

[0035] In some embodiments, the initial reaction temperature difference between the high-activity silver powder and the low-activity silver powder is 30° C. to 60° C.

[0036] In some embodiments, the copper-manganese-free glass powder further includes a copper-manganese substitute, and the elements in the copper-manganese substitute include Zn and Te.

[0037] Violent chemical reactions at the interface can generate stress, causing cross marks on the silicon wafer. By reducing the intensity of the interfacial reaction by using low Pb, and by using high-wetting elements such as Zn and Te to improve the wettability between the busbar and the silicon wafer, more van der Waals forces and hydrogen bonds are introduced to replace the chemical bonds in the previous system, ensuring that the busbar tension is not damaged.

[0038] In some embodiments, the copper-free manganese glass powder further comprises 10 mol% to 25 mol% ZnO and

[0039] 5mol%~10mol%TeO2.

[0040] In some embodiments, the organic carrier includes an organic solvent, an organic resin, cellulose, a thickener and a surfactant. Taking the total mass percentage content of the organic carrier as 100%, the mass fraction of the organic solvent in the organic carrier is 60.0%-80.0%, the organic resin and cellulose total 0%-10%, the thickener 5%-20%, and the surfactant 0.1%-20%.

[0041] In some embodiments, the method for preparing the solar cell busbar paste specifically includes:

[0042] The raw materials of various glass components are mixed uniformly in proportion, heated and melt-reacted, cooled and dried, and then ground to obtain copper-free manganese glass powder; an organic solvent, an organic resin, cellulose, a thickener, and a surfactant are stirred uniformly in proportion, and dispersed by high-speed centrifugation to obtain the organic carrier; the copper-free manganese glass powder is mixed uniformly with low-activity silver powder, high-activity silver powder, and the organic carrier in proportion, and the slurry is obtained after slurrying, filtering, and slurrying.

[0043] The present application also provides a solar cell, which is obtained by printing any one of the solar cell busbar pastes described above on a cell sheet and then sintering the printed paste.

[0044] Example:

[0045] Taking the total molar percentage of copper-free manganese glass powder as 100 mol%, the glass powders A1 to A4 are obtained by mixing uniformly according to the proportions in Table 1, heating and melting reaction, cooling and drying, and then grinding. A1 to A4 are the copper-free manganese glass powders provided in this application.

[0046] Table 1 Example copper-free manganese glass powder component ratio

[0047] raw material A1 A2 A3 A4 <![CDATA[Pb3O4]]> 0.3 0.8 0.5 0.5 <![CDATA[Bi2O3]]> 25 22 10 25 <![CDATA[B2O3]]> 30 27 28 15 <![CDATA[TiO2]]> 9.7 15 8 15 Alkali metal substances 20 10 19.5 19.5 ZnO 10 15.2 25 16 <![CDATA[TeO2]]> 5 10 9 9 CuO 0 0 0 0 <![CDATA[MnO2]]> 0 0 0 0

[0048] Example 1:

[0049] An organic solvent, an organic resin, cellulose, a thickener, and a surfactant are uniformly stirred and dispersed by high-speed centrifugation to obtain the organic vehicle. The organic vehicle comprises, by mass, 80% organic solvent, 0% organic resin and cellulose combined, 5% thickener, and 15% surfactant.

[0050] 1.5 wt% copper-free manganese glass powder A1 was uniformly mixed with 25 wt% low-activity silver powder, 55 wt% high-activity silver powder, and 18.5 wt% organic vehicle. The alkali metal elements in the copper-free manganese glass powder A1 were oxides of Li, Na, K, and Rb. The low-activity silver powder had an initial response temperature of 240°C and a vigorous reaction temperature of 410°C, while the high-activity silver powder had an initial response temperature of 190°C and a vigorous reaction temperature of 380°C. After slurrying, filtering, and slurry adjustment, slurry K1 was obtained.

[0051] Example 2:

[0052] An organic solvent, an organic resin, cellulose, a thickener, and a surfactant are uniformly stirred and dispersed by high-speed centrifugation to obtain the organic vehicle. The organic vehicle comprises, by mass, 60% organic solvent, 5% organic resin, 5% cellulose, 10% thickener, and 20% surfactant.

[0053] 1.5 wt% copper-free manganese glass powder A2 was uniformly mixed with 35 wt% low-activity silver powder, 45 wt% high-activity silver powder, and 18.5 wt% organic vehicle. The alkali metal elements in the copper-free manganese glass powder A2 were halides of Li and Na. The low-activity silver powder had an initial response temperature of 230°C and a vigorous reaction temperature of 405°C, while the high-activity silver powder had an initial response temperature of 170°C and a vigorous reaction temperature of 370°C. After slurrying, filtering, and slurry conditioning, slurry K2 was obtained.

[0054] Example 3:

[0055] An organic solvent, an organic resin, cellulose, a thickener, and a surfactant are uniformly stirred and dispersed by high-speed centrifugation to obtain the organic vehicle. The organic vehicle comprises, by mass, 70% organic solvent, 5% organic resin, 4.5% cellulose, 20% thickener, and 0.1% surfactant.

[0056] 0.6 wt% copper-free manganese glass powder A3 was uniformly mixed with 29.4 wt% low-activity silver powder, 50 wt% high-activity silver powder, and 20 wt% organic vehicle. The alkali metal elements in the copper-free manganese glass powder A3 were oxides of K and Rb. The low-activity silver powder had an initial response temperature of 220°C and a vigorous reaction temperature of 420°C, while the high-activity silver powder had an initial response temperature of 190°C and a vigorous reaction temperature of 365°C. After slurrying, filtering, and slurry conditioning, slurry K3 was obtained.

[0057] Example 4:

[0058] An organic solvent, an organic resin, cellulose, a thickener, and a surfactant are uniformly stirred and dispersed by high-speed centrifugation to obtain the organic vehicle. The organic vehicle comprises, by mass, 70% organic solvent, 3% organic resin, 2% cellulose, 15% thickener, and 10% surfactant.

[0059] 1 wt% copper-free manganese glass powder A4 was uniformly mixed with 32 wt% low-activity silver powder, 54 wt% high-activity silver powder, and 13 wt% organic vehicle. The alkali metal elements in the copper-free manganese glass powder A4 were halides of Li, Na, K, and Rb. The low-activity silver powder had an initial response temperature of 235°C and a vigorous reaction temperature of 413°C, while the high-activity silver powder had an initial response temperature of 195°C and a vigorous reaction temperature of 372°C. After slurrying, filtering, and slurry adjustment, slurry K4 was obtained.

[0060] Comparative Example:

[0061] Based on the total molar percentage of the glass powder as 100 mol%, the glass powders B1 to B4 were uniformly mixed according to the proportions shown in Table 2, heated and melted, cooled, dried, and then ground. B1 to B4 are glass powders used in comparative examples. B1 represents the glass powder without low lead and high bismuth (Bi) content; B2 represents the glass powder without ZnO or TeO2 as copper-manganese substitutes; B3 represents the glass powder without complete ZnO or TeO2 as copper-manganese substitutes and without low lead and high bismuth content; and B4 represents the glass powder containing copper and manganese.

[0062] Table 2 Comparative Example Glass Powder Component Ratio

[0063]

[0064]

[0065] Comparative Example 1:

[0066] The organic solvent, organic resin, cellulose, thickener and surfactant are uniformly stirred and dispersed by high-speed centrifugation to obtain the organic vehicle. The organic vehicle comprises 70% by mass of the organic solvent, 3% by mass of the organic resin, 2% by mass of the cellulose, 15% by mass of the thickener and 10% by mass of the surfactant.

[0067] 1.5 wt% glass powder B1 was uniformly mixed with 25 wt% low-activity silver powder, 55 wt% high-activity silver powder, and 18.5 wt% organic vehicle. The alkali metal elements in glass powder B1 were oxides of K and Rb. The low-activity silver powder had an initial response temperature of 240°C and a vigorous reaction temperature of 410°C, while the high-activity silver powder had an initial response temperature of 190°C and a vigorous reaction temperature of 380°C. After slurrying, filtering, and slurry conditioning, slurry G1 was obtained.

[0068] Comparative Example 2:

[0069] The organic solvent, organic resin, cellulose, thickener and surfactant are uniformly stirred and dispersed by high-speed centrifugation to obtain the organic vehicle. The organic vehicle comprises 70% by mass of the organic solvent, 3% by mass of the organic resin, 2% by mass of the cellulose, 15% by mass of the thickener and 10% by mass of the surfactant.

[0070] 1.5 wt% glass frit B2 was uniformly mixed with 25 wt% low-activity silver powder, 55 wt% high-activity silver powder, and 18.5 wt% organic vehicle. The alkali metal elements in glass frit B2 were oxides of K and Rb. The low-activity silver powder had an initial response temperature of 240°C and a vigorous reaction temperature of 410°C, while the high-activity silver powder had an initial response temperature of 190°C and a vigorous reaction temperature of 380°C. After slurrying, filtering, and slurry conditioning, slurry G2 was obtained.

[0071] Comparative Example 3:

[0072] The organic solvent, organic resin, cellulose, thickener and surfactant are uniformly stirred and dispersed by high-speed centrifugation to obtain the organic vehicle. The organic vehicle comprises 70% by mass of the organic solvent, 3% by mass of the organic resin, 2% by mass of the cellulose, 15% by mass of the thickener and 10% by mass of the surfactant.

[0073] 1.5 wt% glass powder B3 was uniformly mixed with 25 wt% low-activity silver powder, 55 wt% high-activity silver powder, and 18.5 wt% organic vehicle. The alkali metal elements in glass powder B3 were oxides of K and Rb. The low-activity silver powder had an initial response temperature of 240°C and a vigorous reaction temperature of 410°C, while the high-activity silver powder had an initial response temperature of 190°C and a vigorous reaction temperature of 380°C. After slurrying, filtering, and slurry conditioning, slurry G3 was obtained.

[0074] Comparative Example 4:

[0075] The organic solvent, organic resin, cellulose, thickener and surfactant are uniformly stirred and dispersed by high-speed centrifugation to obtain the organic vehicle. The organic vehicle comprises 70% by mass of the organic solvent, 3% by mass of the organic resin, 2% by mass of the cellulose, 15% by mass of the thickener and 10% by mass of the surfactant.

[0076] 1.5 wt% glass frit B3 was uniformly mixed with 80 wt% silver powder and 18.5 wt% organic vehicle. The alkali metal elements in glass frit B3 were oxides of K and Rb, and the silver powder was spherical with a D50 of 2.0 μm. After slurrying, filtering, and slurry preparation, slurry G4 was obtained.

[0077] Comparative Example 5:

[0078] The organic solvent, organic resin, cellulose, thickener and surfactant are uniformly stirred and dispersed by high-speed centrifugation to obtain the organic vehicle. The organic vehicle comprises 70% by mass of the organic solvent, 3% by mass of the organic resin, 2% by mass of the cellulose, 15% by mass of the thickener and 10% by mass of the surfactant.

[0079] 1.5 wt% glass frit B4 was uniformly mixed with 80 wt% silver powder and 18.5 wt% organic vehicle. The alkali metal elements in glass frit B4 were oxides of K and Rb, and the silver powder was spherical with a D50 of 2.0 μm. After slurrying, filtering, and slurry preparation, slurry G5 was obtained.

[0080] Comparative Example 6:

[0081] The organic solvent, organic resin, cellulose, thickener and surfactant are uniformly stirred and dispersed by high-speed centrifugation to obtain the organic vehicle. The organic vehicle comprises 70% by mass of the organic solvent, 3% by mass of the organic resin, 2% by mass of the cellulose, 15% by mass of the thickener and 10% by mass of the surfactant.

[0082] 1.5 wt% glass frit B4 was uniformly mixed with 25 wt% low-activity silver powder, 55 wt% high-activity silver powder, and 18.5 wt% organic vehicle. The alkali metal elements in glass frit B4 were oxides of K and Rb. The low-activity silver powder had an initial response temperature of 240°C and a vigorous reaction temperature of 410°C, while the high-activity silver powder had an initial response temperature of 190°C and a vigorous reaction temperature of 380°C. After slurrying, filtering, and slurry conditioning, slurry G6 was obtained.

[0083] The slurries prepared in Examples 1-4 and Comparative Examples 1-6 were printed on N-type 182 silicon wafers using a printing machine. At least 100,000 wafers were printed for each slurry. The wafers were sintered in a sintering furnace and then processed with laser-enhanced contact optimization (LECO). The blackening of the main grid of the cell was recorded, and the proportion of blackened wafers was calculated. Three groups of parallel measurements were performed for each slurry.

[0084] Figure 3 This is a schematic diagram showing that the main grid of the battery cell has not turned black. Figure 4 The diagram of the battery main grid blackening is shown in Table 3. Figure 5 As shown, Figure 5 The blackening ratio of the main grid of the battery cell prepared with each slurry is the average value of the results of three groups of parallel tests.

[0085] Table 3 Statistics of experimental data on blackening of battery main grid

[0086] Slurry name Group 1 Group 2 Group 3 average value K1 0.06％ 0.04％ 0.05％ 0.050％ K2 0.04％ 0.07％ 0.06％ 0.057％ K3 0.11％ 0.09％ 0.04％ 0.080％ K4 0.09％ 0.07％ 0.12％ 0.093％ G1 0.32％ 0.34％ 0.42％ 0.360％ G2 0.34％ 0.22％ 0.14％ 0.233％ G3 0.36％ 0.45％ 0.51％ 0.440％ G4 0.74％ 0.67％ 0.69％ 0.700％ G5 1.56％ 1.68％ 1.65％ 1.630％ G6 1.60％ 1.40％ 1.69％ 1.563％

[0087] Pastes K1 to K4 are used in the examples of this application, while pastes G1 to G6 are used in comparative examples. The glass frit in paste G1 does not use low-Pb, high-Bi materials. The glass frit in paste G2 does not incorporate ZnO or TeO2 as copper-manganese substitutes. The glass frit in paste G3 neither fully incorporates ZnO and TeO2 as copper-manganese substitutes nor uses low-Pb, high-Bi materials. The glass frit in paste G4 is the same as that in paste G3, and ordinary silver powder is used. The glass frits in pastes G5 and G6 both contain copper-manganese, with paste G5 using ordinary silver powder.

[0088] It is clear that by improving the glass powder and silver powder, the battery produced by the slurry provided by this application has less blackening of the cell, and the improvement effect is more obvious when the glass powder is replaced with copper-manganese-free glass powder. Therefore, the slurry provided by this application can alleviate the blackening of the main grid.

[0089] The present application provides a solar cell main grid paste and a solar cell. The paste includes low-activity silver powder, high-activity silver powder, an organic carrier and copper-manganese-free glass powder. The copper-manganese-free glass powder is a Pb-Bi-Zn-Ti-B glass powder. The low-activity silver powder has an initial response temperature higher than 200°C and a violent reaction temperature higher than 400°C, and the high-activity silver powder has an initial response temperature lower than 200°C and a violent reaction temperature lower than 380°C. While there is no copper and manganese in the glass powder, low lead is replaced by Bi, which can solve the problem of blackening of the front main grid during printing. The use of low-activity powder is because it is necessary to reduce the degree of shrinkage of the silver powder during the sintering process, thereby reducing the stress caused by the shrinkage of the silver powder on the silicon wafer, and then alleviate the blackening of the main grid (cross mark print), and solve the problem of blackening of the main grid after sintering.

[0090] The present application also provides a solar cell obtained by printing any of the above-mentioned slurries on a cell sheet and sintering the printed cell sheet.

[0091] Solar cells include, but are not limited to, PERC cells (Passivated Emitter Rear Cell), IBC (Interdigitated Back Contact), TOPCon (Tunnel Oxide Passivated Contact), HIT / HJT (Heterojunction Technology) cells, thin-film solar cells, and stacked cells, or any combination thereof. Thin-film solar cells include, but are not limited to, perovskite thin-film solar cells, copper indium selenide thin-film solar cells, gallium arsenide thin-film solar cells, and cadmium sulfide thin-film solar cells. Stacked cells include, but are not limited to, perovskite cells stacked with crystalline silicon cells, perovskite cells stacked with perovskite cells, and perovskite cells stacked with thin-film cells.

[0092] Similar parts between the embodiments provided in this application can be referenced to each other. The specific implementation methods provided above are only a few examples under the overall concept of this application and do not constitute a limitation on the scope of protection of this application. For those skilled in the art, any other implementation methods expanded based on the scheme of this application without expending creative work shall fall within the scope of protection of this application.

Claims

1. A solar cell main grid paste, characterized in that: The slurry comprises low-activity silver powder, high-activity silver powder, an organic vehicle and copper-free manganese glass powder. In the slurry, the mass fraction of the low-activity silver powder is 25%-35%, the mass fraction of the high-activity silver powder is 45%-55%, the mass fraction of the organic vehicle is 13%-20%, and the mass fraction of the copper-free manganese glass powder is 0.6%-1.5%. The copper-free manganese glass powder is a Pb-Bi-Zn-Ti-B system glass powder. The initial response temperature of the low-activity silver powder is higher than 200°C and the violent reaction temperature is higher than 400°C. The initial response temperature of the high-activity silver powder is lower than 200°C and the violent reaction temperature is lower than 380°C. The total molar mass of the copper-free manganese glass powder is 0.6%. The copper-free manganese glass powder comprises 0.3 mol% to 0.8 mol% Pb3O4, 10 mol% to 25 mol% Bi2O3, 15 mol% or 27 mol% or 28 mol% or 30 mol% B2O3, 8 mol% to 15 mol% TiO2 and 10 mol% to 20 mol% alkali metal element substances, and the copper-free manganese glass powder also includes a copper-manganese substitute, and the elements in the copper-manganese substitute include Zn and Te. The copper-free manganese glass powder also includes 10 mol% to 25 mol% ZnO and 5 mol% to 10 mol% TeO2.

2. The solar cell busbar paste according to claim 1, characterized in that: The alkali metal element substance is an oxide or a halide, and the elements in the alkali metal element substance include one or more of Li, Na, K, and Rb.

3. The solar cell busbar paste according to claim 1, characterized in that: The alkali metal element substance is a composite of alkali metal element oxides decomposed during the preparation process of the glass powder.

4. The solar cell busbar paste according to claim 1, characterized in that: The initial reaction temperature difference between the high-activity silver powder and the low-activity silver powder is 30° C. to 60° C.

5. The solar cell busbar paste according to claim 1, characterized in that: The organic carrier includes an organic solvent, an organic resin, cellulose, a thickener and a surfactant. Based on the total mass percentage content of the organic carrier as 100%, the mass fraction of the organic solvent in the organic carrier is 60.0%-80.0%, the organic resin and cellulose together account for 5%-10%, the thickener accounts for 5%-20%, and the surfactant accounts for 0.1%-20%.

6. The solar cell busbar paste according to claim 1, characterized in that: The preparation method of the solar cell main grid paste specifically includes: The raw materials of the glass components are mixed uniformly according to a proportion, heated and melted, cooled and dried, and then ground to obtain copper-manganese-free glass powder; The organic solvent, organic resin, cellulose, thickener and surfactant are mixed uniformly according to a certain proportion, and dispersed by high-speed centrifugation to obtain the organic carrier; The copper-free manganese glass powder is uniformly mixed with low-activity silver powder, high-activity silver powder and an organic carrier in proportion, and the mixture is slurried, filtered and slurried to obtain the slurry.

7. A solar cell, characterized in that: The solar cell is obtained by printing the solar cell busbar paste according to any one of claims 1 to 6 on a cell sheet and then sintering the printed circuit board.

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