Copper paste, preparation method of copper paste and N-type crystalline silicon solar cell

Abstract

The embodiment of the invention discloses copper paste, a preparation method of the copper paste and an N-type crystalline silicon solar cell. The copper paste comprises an organic additive, micron-scale spherical copper powder, nano-scale spherical copper powder, an organic binder and glass powder, wherein the mass percent of the organic additive in the copper paste is 1.5%-2.2%; the mass percent of the micron-sized spherical copper powder in the copper paste is 70%-77%; the mass percent of the nanoscale spherical copper powder in the copper paste is 3-5%; the mass percent of the organic adhesive in the copper paste is 15.3%-21.3%; and the mass percent of the glass powder in the copper paste is 2.2-2.5%. The copper paste is low in cost and high in quality, the copper paste is applied to the preparation process of the back grid line electrode of the N-type crystalline silicon solar cell, and the problem that the production cost is increased due to the fact that existing silver paste is expensive is solved.

Description

Technical Field

[0001] The embodiments of the present invention relate to the technical field of solar cells, and in particular to a copper paste, a method for preparing the copper paste, and an N-type crystalline silicon solar cell. Background Art

[0002] The update and iteration of photovoltaic cell structure has led to the continuous accumulation of old production capacity, and cost reduction and efficiency improvement have become the key issues of the photovoltaic industry. Compared with P-type crystalline silicon cells, N-type crystalline silicon cells have a longer minority carrier life, no photoinduced degradation, good weak light effect, and a small temperature coefficient, which is the hope for crystalline silicon solar cells to break through the theoretical maximum efficiency.

[0003] The paste used for the back grid electrode of the existing N-type crystalline silicon solar cell is all silver paste. The wet weight of the back silver paste corresponding to each cell is about 45 mg, and the unit price of silver paste is about 7,000 yuan / kg, which is equivalent to the cost of the back grid electrode corresponding to each cell of 0.315 yuan. The current unit price of the finished cell is about 3.1 yuan / piece, so the cost of the back grid electrode corresponding to the cell accounts for a large proportion of the total cost of the finished cell, which also affects the profit and economic benefits of the manufacturer. Therefore, it is urgent to find a cheap and conductive metal paste to replace the silver paste, and apply this metal paste to the preparation of the back grid electrode of the N-type crystalline silicon solar cell. Summary of the invention

[0004] The embodiments of the present invention provide a copper paste, a method for preparing the copper paste, and an N-type crystalline silicon solar cell. Compared with expensive silver paste, the cheap copper paste can maintain the high photoelectric conversion efficiency of the finished battery cell or even improve the photoelectric conversion efficiency, and can also reduce the manufacturing cost of the finished battery cell.

[0005] In a first aspect, an embodiment of the present invention provides a copper paste, including an organic additive, micron-sized spherical copper powder, nano-sized spherical copper powder, an organic binder and glass powder; wherein:

[0006] The mass percentage of the organic additive in the copper slurry is between 1.5% and 2.2%;

[0007] The mass percentage of the micron-sized spherical copper powder in the copper slurry is between 70% and 77%;

[0008] The mass percentage of the nano-scale spherical copper powder in the copper slurry is between 3% and 5%;

[0009] The mass percentage of the organic binder in the copper paste is between 15.3% and 21.3%;

[0010] The mass percentage of the glass powder in the copper paste is between 2.2% and 2.5%.

[0011] Optionally, the purity of the micron-sized spherical copper powder and the nano-sized spherical copper powder is 99.9%.

[0012] Optionally, the particle size of the micron-sized spherical copper powder ranges from 3 μm to 4 μm.

[0013] Optionally, the organic additive includes at least any one of fatty alcohol ether phosphate, aluminate coupling agent, silane coupling agent, zirconium aluminate coupling agent, lauryl phosphate, silicone oil, dibasic acid ester and lauryl alcohol phosphate mixture.

[0014] Optionally, the organic binder comprises a high molecular polymer and an organic solvent; wherein,

[0015] The mass percentage of the high molecular weight polymer in the organic binder is between 10% and 15%;

[0016] The mass percentage of the organic solvent in the organic binder is between 85% and 90%.

[0017] Optionally, the organic solvent includes at least any four of terpineol, butyl carbitol, butyl carbitol acetate, tributyl citrate, Span 85 and alcohol ester twelve.

[0018] Optionally, the glass powder includes Bi2O3, AL2O3, SiO2, ZnO, Sb2O5, B2O3 and TeO3; wherein,

[0019] The mass percentage of Bi2O3 in the glass powder is between 10% and 20%;

[0020] The mass percentage of Al2O3 in the glass powder is between 10% and 15%;

[0021] The mass percentage of SiO2 in the glass powder is between 8% and 12%;

[0022] The mass percentage of ZnO in the glass powder is between 18% and 25%;

[0023] The mass percentage of Sb2O5 in the glass powder is between 15% and 20%;

[0024] The mass percentage of B2O3 in the glass powder is between 8% and 10%;

[0025] The mass percentage of TeO3 in the glass powder is between 15% and 20%.

[0026] Optionally, the glass powder has a particle size ranging from 2.2 μm to 2.5 μm.

[0027] In a second aspect, an embodiment of the present invention further provides a method for preparing a copper slurry, which is used to prepare the copper slurry as described in any one of the first aspects, and the preparation method comprises:

[0028] Mixing and dispersing the nano-scale spherical copper powder, the glass powder and the organic binder to obtain a uniformly mixed first powder;

[0029] Adding micron-sized spherical copper powder to the first powder, and dispersing and grinding the first powder and the micron-sized spherical copper powder to obtain a uniformly mixed second powder;

[0030] An organic additive is added to the second powder, and the second powder and the organic additive are dispersed to obtain the copper paste which is uniformly mixed.

[0031] In a third aspect, an embodiment of the present invention further provides an N-type crystalline silicon solar cell, comprising a back gate line electrode, wherein the back gate line electrode is prepared by using the copper paste as described in any one of the first aspects.

[0032] An embodiment of the present invention provides a copper paste, a method for preparing the copper paste, and an N-type crystalline silicon solar cell, wherein the copper paste comprises an organic additive, micron-sized spherical copper powder, nano-sized spherical copper powder, an organic binder, and glass powder; wherein the mass percentage of the organic additive in the copper paste is between 1.5% and 2.2%; the mass percentage of the micron-sized spherical copper powder in the copper paste is between 70% and 77%; the mass percentage of the nano-sized spherical copper powder in the copper paste is between 3% and 5%; the mass percentage of the organic binder in the copper paste is between 15.3% and 21.3%; and the mass percentage of the glass powder in the copper paste is between 2.2% and 2.5%. The present embodiment provides a cheap and high-quality copper paste. The copper paste in the present embodiment is applied to the preparation process of the back grid line electrode of the N-type crystalline silicon solar cell, which solves the problem that the existing silver paste is relatively expensive and leads to increased production costs. Compared with the expensive silver paste, the cheap copper paste can maintain the high photoelectric conversion efficiency of the N-type crystalline silicon solar cell or even improve the photoelectric conversion efficiency, achieve a long service life of the N-type crystalline silicon solar cell, maintain a stable short-circuit current and open-circuit voltage, thereby maintaining the stability of the fill factor and achieving the stability of the photoelectric conversion efficiency of the N-type crystalline silicon solar cell. It can also reduce the manufacturing cost of the N-type crystalline silicon solar cell and achieve cost optimization of the N-type crystalline silicon solar cell, thereby achieving the effect of reducing costs and increasing efficiency, improving the overall cost performance of the N-type crystalline silicon solar cell finally prepared, and enhancing the competitiveness of the N-type crystalline silicon solar cell in the industry. In addition, the back side of the N-type crystalline silicon solar cell has low requirements for parameters such as light utilization rate and shading area, which also provides a favorable opportunity for the application of copper paste in the preparation of the back grid line electrode of the N-type crystalline silicon solar cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0034] Figure 1 It is a schematic flow chart of a method for preparing a copper slurry provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0035] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0036] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. It should be noted that the directional words such as "upper", "lower", "left", "right" and the like described in the embodiments of the present invention are described at the angles shown in the accompanying drawings and should not be understood as limitations on the embodiments of the present invention. In addition, in the context, it is also necessary to understand that when it is mentioned that an element is formed "on" or "under" another element, it can not only be directly formed "on" or "under" another element, but also indirectly formed "on" or "under" another element through an intermediate element. The terms "first", "second", etc. are only used for descriptive purposes and do not represent any order, quantity or importance, but are only used to distinguish different components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood in specific circumstances.

[0037] The term “including” and its variations used in the present invention are open inclusions, that is, “including but not limited to.” The term “based on” means “based at least in part on.” The term “one embodiment” means “at least one embodiment.”

[0038] It should be noted that the concepts such as "first" and "second" mentioned in the present invention are only used to distinguish the corresponding contents, and are not used to limit the order or interdependence.

[0039] It should be noted that the modifications of "one" and "plurality" mentioned in the present invention are illustrative rather than restrictive, and those skilled in the art should understand that, unless otherwise clearly indicated in the context, it should be understood as "one or more".

[0040] First of all, it should be explained that the embodiment of the present invention provides a copper paste for the back gridline electrode of an N-type crystalline silicon solar cell. On the one hand, compared with expensive silver paste, the cheap copper paste can maintain the high photoelectric conversion efficiency of the N-type crystalline silicon solar cell or even improve the photoelectric conversion efficiency, solving the problem that the existing silver paste is relatively expensive and leads to increased production costs. On the other hand, this embodiment illustrates that the copper paste can be applied to the preparation process of the back gridline electrode of the N-type crystalline silicon solar cell. It can be understood that compared with the requirements of the parameters such as the front light utilization rate and the light transmission area of ​​the N-type crystalline silicon solar cell, the requirements of the parameters such as the back light utilization rate and the light transmission area of ​​the N-type crystalline silicon solar cell are lower, and the printing and preparation precision requirements of the back gridline electrode are also relatively low, which provides a favorable opportunity for the application of copper paste in the preparation of the back gridline electrode of the N-type crystalline silicon solar cell.

[0041] The copper paste provided in this embodiment includes organic additives, micron-sized spherical copper powder, nano-sized spherical copper powder, organic binder and glass powder; wherein the mass percentage of the organic additive in the copper paste is between 1.5% and 2.2%; the mass percentage of the micron-sized spherical copper powder in the copper paste is between 70% and 77%; the mass percentage of the nano-sized spherical copper powder in the copper paste is between 3% and 5%; the mass percentage of the organic binder in the copper paste is between 15.3% and 21.3%; and the mass percentage of the glass powder in the copper paste is between 2.2% and 2.5%.

[0042] Among them, the micron-sized spherical copper powder is the conductive main body of the copper paste, and the mass percentage of the micron-sized spherical copper powder in the copper paste can be adjusted according to the conductive requirements. The particle size of the micron-sized spherical copper powder directly affects the conductive properties of the copper paste. Generally, the smaller the particles of the micron-sized spherical copper powder, the larger its surface area, thus providing more contact points, reducing resistance, thereby improving the conductive efficiency, that is, the better the conductive properties. Exemplarily, the particle size range of the micron-sized spherical copper powder can be 3μm to 4μm. And, the higher the purity of the micron-sized spherical copper powder, the better the conductive properties of the prepared copper paste, and the better the conductive properties of the back grid line electrode of the prepared N-type crystalline silicon solar cell, which can effectively improve the utilization rate of the power of the N-type crystalline silicon solar cell, and extend the service life of the N-type crystalline silicon solar cell. Exemplarily, the purity of the micron-sized spherical copper powder can be 99.9% and above.

[0043] The particle size of nano-scale spherical copper powder is different from that of micron-scale spherical copper powder. The nano-scale spherical copper powder is provided because there is space between micron-scale spherical copper powders. The nano-scale spherical copper powder can be filled in the space of micron-scale spherical copper powder, which can play a role in reducing the resistivity of the grid electrode. In addition, the higher the purity of the nano-scale spherical copper powder, the better the conductivity of the copper paste prepared, and the better the conductivity of the back grid electrode of the prepared N-type crystalline silicon solar cell, which can effectively improve the utilization rate of the electricity of the N-type crystalline silicon solar cell and extend the service life of the N-type crystalline silicon solar cell. Exemplarily, the purity of the nano-scale spherical copper powder can be 99.9% or above.

[0044] Glass powder is an inorganic adhesive that can achieve the bonding of nano-scale spherical copper powder and micron-scale spherical copper powder. The mass percentage of glass powder in the copper slurry can be adjusted later according to the total amount of nano-scale spherical copper powder and micron-scale spherical copper powder. The particle size of the glass powder directly affects the fluidity of the copper slurry. Generally, glass powder with a smaller particle size is easier to disperse in the copper slurry, thereby improving the fluidity and coating properties of the copper slurry. Exemplarily, the particle size range of the glass powder can be 2.2μm to 2.5μm.

[0045] The organic binder is mainly used to disperse and print nano-scale spherical copper powder, and to bond the components before the glass powder is activated. The mass percentage of the organic binder in the copper paste can be adjusted later according to the total amount of nano-scale spherical copper powder and micron-scale spherical copper powder.

[0046] Organic additives have good weather resistance, corrosion resistance and strong activity, and can play a role in dispersion and dilution. Organic additives can improve and adjust the performance of the formed copper paste, maintain good printing and shaping, and after the copper paste is printed in the area corresponding to the back grid electrode of the N-type crystalline silicon solar cell, it is beneficial to improve the overall performance of the N-type crystalline silicon solar cell. In addition, the stability of the copper paste is an important indicator of the performance of the copper paste, including two aspects: the oxidation resistance of the copper paste and the dispersibility of the copper powder. The organic additive may also include an antioxidant to prevent the oxidation of the copper paste, a dispersant to prevent the agglomeration of the copper powder, etc. In the organic carrier, the antioxidant is mainly aimed at the problem that the copper powder is easily oxidized. To prevent the agglomeration of the copper powder, a dispersant is required to disperse the copper powder. The type of organic additive can be appropriately selected as needed. Optionally, the organic additive includes at least any one of fatty alcohol ether phosphate, aluminate coupling agent, silane coupling agent, zirconium aluminate coupling agent, laurel phosphate, silicone oil, dibasic acid ester and lauryl alcohol phosphate mixture.

[0047] Specifically, each raw material component has a certain role in the copper paste, and the above raw material components are proportioned according to their mass percentage in the copper paste, so that it is convenient to increase or decrease the solid content of each raw material component during proportioning. Exemplarily, in a specific embodiment, the mass percentage of organic additives in the copper paste is 1.5%, the mass percentage of micron-sized spherical copper powder in the copper paste is 70%, the mass percentage of nano-sized spherical copper powder in the copper paste is 5%, the mass percentage of organic binder in the copper paste is 21.3%, and the mass percentage of glass powder in the copper paste is 2.2%.

[0048] According to the technical solution in the embodiment of the present invention, the copper paste includes organic additives, micron-sized spherical copper powder, nano-sized spherical copper powder, organic binder and glass powder; wherein the mass percentage of the organic additive in the copper paste is between 1.5% and 2.2%; the mass percentage of the micron-sized spherical copper powder in the copper paste is between 70% and 77%; the mass percentage of the nano-sized spherical copper powder in the copper paste is between 3% and 5%; the mass percentage of the organic binder in the copper paste is between 15.3% and 21.3%; and the mass percentage of the glass powder in the copper paste is between 2.2% and 2.5%. The present embodiment provides a cheap and high-quality copper paste. The copper paste in the present embodiment is applied to the preparation process of the back grid line electrode of the N-type crystalline silicon solar cell, which solves the problem that the existing silver paste is relatively expensive and leads to increased production costs. Compared with the expensive silver paste, the cheap copper paste can maintain the high photoelectric conversion efficiency of the N-type crystalline silicon solar cell or even improve the photoelectric conversion efficiency, achieve a long service life of the N-type crystalline silicon solar cell, maintain a stable short-circuit current and open-circuit voltage, thereby maintaining the stability of the fill factor and achieving the stability of the photoelectric conversion efficiency of the N-type crystalline silicon solar cell. It can also reduce the manufacturing cost of the N-type crystalline silicon solar cell and achieve cost optimization of the N-type crystalline silicon solar cell, thereby achieving the effect of reducing costs and increasing efficiency, improving the overall cost performance of the N-type crystalline silicon solar cell finally prepared, and enhancing the competitiveness of the N-type crystalline silicon solar cell in the industry. In addition, the back side of the N-type crystalline silicon solar cell has low requirements for parameters such as light utilization rate and shading area, which also provides a favorable opportunity for the application of copper paste in the preparation of the back grid line electrode of the N-type crystalline silicon solar cell.

[0049] Optionally, the organic adhesive comprises a high molecular polymer and an organic solvent; wherein the mass percentage of the high molecular polymer in the organic adhesive is between 10% and 15%; and the mass percentage of the organic solvent in the organic adhesive is between 85% and 90%.

[0050] Specifically, the high molecular polymer mainly realizes a firm connection between two or more objects through the interaction between its molecular chain and the surface of the adherend, thereby improving the adhesion and bonding effect of the organic adhesive. The organic solvent can adjust the viscosity of the organic adhesive so that it can achieve the best use effect, and can also make the organic adhesive quickly solidify and improve production efficiency. Exemplarily, the organic adhesive can include a high molecular polymer with a mass percentage of 12% and an organic solvent with a mass percentage of 88%. Exemplarily, the high molecular polymer can include ethyl cellulose N50. Exemplarily, the high molecular polymer can be a polymer with a low sintering residual viscoelastic modulus. Exemplarily, the organic solvent can include at least any four of terpineol, butyl carbitol, butyl carbitol acetate, tributyl citrate, Span 85 and alcohol ester twelve. For example, in a specific embodiment, the organic solvent can be composed of five kinds of pine alcohol, butyl carbitol, butyl carbitol acetate, tributyl citrate, and Span 85, wherein the mass percentage of pine alcohol in the organic solvent is 10%, the mass percentage of butyl carbitol in the organic solvent is 20%, the mass percentage of butyl carbitol acetate in the organic solvent is 15%, the mass percentage of tributyl citrate in the organic solvent is 15%, and the mass percentage of Span 85 in the organic solvent is 40%. Each component in the organic solvent has good solubility and stability. After being proportioned into the organic solvent, the stability of the copper paste can be effectively improved, so that the copper paste prepared can be used for a long time.

[0051] Optionally, the glass powder includes Bi2O3 (bismuth trioxide), AL2O3 (aluminum trioxide), SiO2 (silicon dioxide), ZnO (zinc oxide), Sb2O5 (antimony pentoxide), B2O3 (boron trioxide) and TeO3 (tellurium trioxide); wherein the mass percentage of Bi2O3 in the glass powder is between 10% and 20%; the mass percentage of AL2O3 in the glass powder is between 10% and 15%; the mass percentage of SiO2 in the glass powder is between 8% and 12%; the mass percentage of ZnO in the glass powder is between 18% and 25%; the mass percentage of Sb2O5 in the glass powder is between 15% and 20%; the mass percentage of B2O3 in the glass powder is between 8% and 10%; and the mass percentage of TeO3 in the glass powder is between 15% and 20%.

[0052] Specifically, the glass powder can be obtained by mixing Bi2O3, AL2O3, SiO2, ZnO, Sb2O5, B2O3 and TeO3 in a certain proportion, melting at high temperature, sintering and crushing. For example, in a specific embodiment, the mass percentage of Bi2O3 in the glass powder is 15%, the mass percentage of AL2O3 in the glass powder is 12%, the mass percentage of SiO2 in the glass powder is 10%, the mass percentage of ZnO in the glass powder is 20%, the mass percentage of Sb2O5 in the glass powder is 18%, the mass percentage of B2O3 in the glass powder is 9%, and the mass percentage of TeO3 in the glass powder is 16%.

[0053] It should also be noted that the glass powder of the present embodiment does not contain lead elements, which can effectively increase the corrosion ability of the copper paste on protective film layers such as silicon nitride, and after the copper paste is prepared and applied to the printing of the back grid line electrode of the N-type crystalline silicon solar cell, it is successively subjected to high-temperature sintering treatment, light injection treatment and laser induction treatment, which reduces metal composite, improves the photoelectric conversion efficiency of the battery, reduces the manufacturing cost of the N-type crystalline silicon solar cell, improves the economic benefits of the manufacturer, and to a certain extent compensates for the problem of accelerated aging caused by the lack of lead elements in the glass powder. That is, the glass powder does not contain lead elements, and in conjunction with the subsequent laser induction step, it can maintain or even extend the service life of the prepared N-type crystalline silicon solar cell to a certain extent.

[0054] Based on the same inventive concept, an embodiment of the present invention further provides a method for preparing copper slurry. Figure 1 is a schematic flow diagram of a method for preparing a copper slurry provided in an embodiment of the present invention, wherein the method for preparing the copper slurry is used to prepare the copper slurry provided in any one of the embodiments of the present invention, such as Figure 1 As shown, the preparation method comprises:

[0055] S110, mixing and dispersing the nano-scale spherical copper powder, the glass powder and the organic binder to obtain a uniformly mixed first powder.

[0056] Specifically, after the nano-scale spherical copper powder, glass powder and organic binder are mixed, a disperser can be used to mix and stir them, which can provide a better dispersion effect, avoid aggregation or precipitation of the mixed powders, and make the powders more uniform after mixing.

[0057] S120, adding micron-sized spherical copper powder to the first powder, and dispersing and grinding the first powder and the micron-sized spherical copper powder to obtain a uniformly mixed second powder.

[0058] Specifically, micron-sized spherical copper powder is added to the first powder, and a disperser is used to mix and stir the first powder and the micron-sized spherical copper powder. The surface roughness of the mixed powder is reduced by a grinding device to obtain a finer secondary powder.

[0059] S130, adding an organic additive to the second powder, and dispersing the second powder and the organic additive to obtain a uniformly mixed copper slurry.

[0060] Specifically, the organic additive is added to the second powder, and the second powder and the organic additive are continuously dispersed and mixed at high speed using a disperser to obtain the copper paste of the present application.

[0061] The technical solution in the embodiment of the present invention first mixes and disperses nano-scale spherical copper powder, glass powder and organic binder to obtain a uniformly mixed first powder, then adds micron-scale spherical copper powder to the first powder, and disperses and grinds the first powder and the micron-scale spherical copper powder to obtain a uniformly mixed second powder, and finally adds an organic additive to the second powder, and disperses the second powder and the organic additive to obtain a uniformly mixed copper paste. Using the above method, according to the composition of the raw materials in the copper paste (organic additives, micron-scale spherical copper powder, nano-scale spherical copper powder, organic binder and glass powder) and their mass percentage, a uniform mixing treatment is performed to obtain the copper paste of the present application. The copper paste in this embodiment is applied to the preparation process of the back grid line electrode of the N-type crystalline silicon solar cell, which solves the problem that the existing silver paste is relatively expensive and leads to an increase in production costs. Compared with expensive silver paste, cheap copper paste can maintain the high photoelectric conversion efficiency of the N-type crystalline silicon solar cell or even improve the photoelectric conversion efficiency, achieve a long service life of the N-type crystalline silicon solar cell, and maintain stability. A certain short-circuit current and open-circuit voltage can be set to maintain a stable fill factor, thereby achieving a stable photoelectric conversion efficiency of N-type crystalline silicon solar cells, and reducing the manufacturing cost of N-type crystalline silicon solar cells. By achieving cost optimization of N-type crystalline silicon solar cells, the effect of reducing costs and increasing efficiency can be achieved, and the overall cost performance of the N-type crystalline silicon solar cells finally prepared can be improved, thereby enhancing the competitiveness of N-type crystalline silicon solar cells in the industry. In addition, the back side of N-type crystalline silicon solar cells has lower requirements on parameters such as light utilization rate and shading area, which also provides a favorable opportunity for the application of copper paste in the preparation of back grid line electrodes of N-type crystalline silicon solar cells.

[0062] Based on the same inventive concept, an embodiment of the present invention further provides an N-type crystalline silicon solar cell. The N-type crystalline silicon solar cell includes a back grid electrode, and the back grid electrode is prepared using the copper paste provided in any one of the embodiments of the present invention. Therefore, the N-type crystalline silicon solar cell has the corresponding beneficial effects of the copper paste, which will not be described in detail here.

[0063] Embodiment 1

[0064] In this embodiment, the copper paste includes organic additives, micron-sized spherical copper powder, nano-sized spherical copper powder, organic binder and glass powder, wherein the components and weight percentages are as follows: 1.5% organic additive, 70% micron-sized spherical copper powder, 5% nano-sized spherical copper powder, 21.3% organic binder, 2.2% glass powder. In addition, the organic binder includes a polymer and an organic solvent, wherein the components and weight percentages are as follows: 12% polymer, 88% organic solvent. In addition, the glass powder includes Bi2O3, AL2O3, SiO2, ZnO, Sb2O5, B2O3 and TeO3, wherein the components and weight percentages are as follows: Bi2O3 15%, AL2O3 12%, SiO2 10%, ZnO 20%, Sb2O5 18%, B2O3 9%, TeO3 16%. In addition, the type and composition of the organic additives and the type and composition of the organic solvent are not specifically required or limited in this embodiment, and can be selected and set according to actual conditions.

[0065] After the copper paste is prepared, it can be screen printed with 520 mesh to form a back grid electrode (i.e., copper fine grid) on an N-type crystalline silicon solar cell (e.g., a single crystal N-TOPCon silicon wafer) with a size of 182.2mm×183.75mm, and then sintered in a sintering furnace. For example, the peak sintering temperature can be 745°C (a sintering temperature reduction of 15°C). After sintering, light injection treatment is required. For example, the temperature of the light injection treatment can be 538°C, and the light intensity of the light injection treatment can be 6000W / m 2 . After the light injection treatment, laser induced synergistic treatment is also required. For example, the reverse voltage of the laser induced synergistic treatment can be 25V, and the laser power of the laser induced synergistic treatment can be 15 W. The laser induced synergistic treatment is to scan the area corresponding to the back grid line electrode of the N-type crystalline silicon solar cell. The laser induced process is performed after light injection, which can induce copper-silicon interdiffusion, thereby significantly reducing the contact resistance, improving the fill factor of the battery, and effectively improving the efficiency of the battery cell. The N-type crystalline silicon solar cell prepared by the embodiment of the present invention has been subjected to relevant electrical experiments, and it can be concluded that the open circuit voltage is 0.7405V, the short circuit current is 14.051A, the fill factor is 86.15%, and the photoelectric conversion efficiency is 26.887%. It can also be clearly seen that the photoelectric conversion efficiency of the N-type crystalline silicon solar cell in this embodiment is 0.08% higher than that of the N-type crystalline silicon solar cell in the control group, and the single-chip cost reduction of the N-type crystalline silicon solar cell in this embodiment is approximately 0.205 yuan.

[0066] Embodiment 2

[0067] In this embodiment, the copper paste includes organic additives, micron-sized spherical copper powder, nano-sized spherical copper powder, organic binder and glass powder, wherein the components and weight percentages are as follows: organic additive 1.8%, micron-sized spherical copper powder 73%, nano-sized spherical copper powder 4%, organic binder 18.9%, glass powder 2.3%. In addition, the organic binder includes a polymer and an organic solvent, wherein the components and weight percentages are as follows: polymer 13%, organic solvent 87%. In addition, the glass powder includes Bi2O3, AL2O3, SiO2, ZnO, Sb2O5, B2O3 and TeO3, wherein the components and weight percentages are as follows: Bi2O3 15%, AL2O3 12%, SiO2 10%, ZnO 20%, Sb2O5 18%, B2O3 9%, TeO3 16%. In addition, the type and composition of the organic additives and the type and composition of the organic solvents are not specifically required or limited in this embodiment, and can be selected and set according to actual conditions.

[0068] After the copper paste is prepared, it can be screen printed with 520 mesh to form a back grid electrode (i.e., copper fine grid) on an N-type crystalline silicon solar cell (e.g., a single crystal N-TOPCon silicon wafer) with a size of 182.2mm×183.75mm, and then sintered in a sintering furnace. For example, the peak sintering temperature can be 742°C (a sintering temperature reduction of 18°C). After sintering, light injection treatment is required. For example, the temperature of the light injection treatment can be 534°C, and the light intensity of the light injection treatment can be 6500W / m 2 . After the light injection treatment, laser induced synergistic treatment is also required. For example, the reverse voltage of the laser induced synergistic treatment can be 22V, and the laser power of the laser induced synergistic treatment can be 15 W. The laser induced synergistic treatment is to scan the area corresponding to the back grid line electrode of the N-type crystalline silicon solar cell. The laser induced process is performed after light injection, which can induce copper-silicon interdiffusion, thereby significantly reducing the contact resistance, improving the fill factor of the battery, and effectively improving the efficiency of the battery cell. After the relevant electrical property experiments, the N-type crystalline silicon solar cell prepared by the embodiment of the present invention can be obtained to have an open circuit voltage of 0.7401V, a short circuit current of 13.985A, a fill factor of 86.55%, and a photoelectric conversion efficiency of 26.871%. It can also be clearly seen that the photoelectric conversion efficiency of the N-type crystalline silicon solar cell in this embodiment is 0.07% higher than that of the N-type crystalline silicon solar cell in the control group, and the single-chip cost reduction of the N-type crystalline silicon solar cell in this embodiment is approximately 0.195 yuan.

[0069] Embodiment 3

[0070] In this embodiment, the copper paste includes organic additives, micron-sized spherical copper powder, nano-sized spherical copper powder, organic binder and glass powder, wherein the components and weight percentages are as follows: organic additive 2%, micron-sized spherical copper powder 75%, nano-sized spherical copper powder 3%, organic binder 17.6%, glass powder 2.4%. In addition, the organic binder includes a polymer and an organic solvent, wherein the components and weight percentages are as follows: polymer 13%, organic solvent 87%. In addition, the glass powder includes Bi2O3, AL2O3, SiO2, ZnO, Sb2O5, B2O3 and TeO3, wherein the components and weight percentages are as follows: Bi2O3 15%, AL2O3 12%, SiO2 10%, ZnO 20%, Sb2O5 18%, B2O3 10%, TeO3 15%. In addition, the type and composition of the organic additives and the type and composition of the organic solvent are not specifically required or limited in this embodiment, and can be selected and set according to actual conditions.

[0071] After the copper paste is prepared, it can be screen printed with 520 mesh to form a back grid electrode (i.e., copper fine grid) on an N-type crystalline silicon solar cell (e.g., a single crystal N-TOPCon silicon wafer) with a size of 182.2mm×183.75mm, and then sintered in a sintering furnace. For example, the peak sintering temperature can be 740°C (sintering temperature reduced by 20°C). After sintering, light injection treatment is required. For example, the temperature of the light injection treatment can be 536°C, and the light intensity of the light injection treatment can be 6800W / m 2 . After the light injection treatment, laser induced synergistic treatment is also required. For example, the reverse voltage of the laser induced synergistic treatment can be 20V, and the laser power of the laser induced synergistic treatment can be 16W. The laser induced synergistic treatment is to scan the area corresponding to the back grid line electrode of the N-type crystalline silicon solar cell. The laser induced process is performed after light injection, which can induce copper-silicon interdiffusion, thereby significantly reducing the contact resistance, improving the fill factor of the battery, and effectively improving the efficiency of the battery cell. The N-type crystalline silicon solar cell prepared by the embodiment of the present invention has been subjected to relevant electrical experiments, and it can be concluded that the open circuit voltage is 0.7395V, the short circuit current is 13.975A, the fill factor is 86.62%, and the photoelectric conversion efficiency is 26.851%. It can also be clearly seen that the photoelectric conversion efficiency of the N-type crystalline silicon solar cell in this embodiment is 0.05% higher than that of the N-type crystalline silicon solar cell in the control group, and the single-chip cost reduction of the N-type crystalline silicon solar cell in this embodiment is approximately 0.175 yuan.

[0072] Control group

[0073] In this embodiment, the existing silver paste is used to prepare the back grid line electrode of the N-type crystalline silicon solar cell. The silver paste includes organic additives, silver powder, organic adhesive and glass powder, wherein the components and weight percentages are as follows: organic additive 0.8%, silver powder 78%, organic adhesive 18.4%, glass powder 2.8%. In addition, the organic adhesive includes a polymer and an organic solvent, wherein the components and weight percentages are as follows: polymer 10%, organic solvent 90%. In addition, the glass powder includes Bi2O3, AL2O3, SiO2, ZnO, Sb2O5, B2O3 and TeO3, wherein the components and weight percentages are as follows: Bi2O3 15%, AL2O3 10%, SiO2 12%, ZnO 12%, Sb2O5 15%, B2O3 18%, TeO3 18%. In addition, the type and composition of the organic additives and the type and composition of the organic solvent are not specifically required or limited in this embodiment, and can be selected and set according to actual conditions.

[0074] After the silver paste is prepared, a back grid electrode (i.e., a silver fine grid) can be formed on an N-type crystalline silicon solar cell (e.g., a single crystal N-TOPCon silicon wafer) with a specification of 182.2mm×183.75mm by 520 mesh screen printing, and then sintered in a sintering furnace. For example, the peak temperature of sintering can be 758°C. After sintering, light injection treatment is required, and laser induced enhancement treatment is required after light injection treatment. After the relevant electrical property experiments, the N-type crystalline silicon solar cell prepared in this control group has an open circuit voltage of 0.7401V, a short circuit current of 14.012A, a fill factor of 86.178%, and a photoelectric conversion efficiency of 26.807%.

[0075] It should be noted that the copper pastes prepared in the above-mentioned embodiment 1, embodiment 2 and embodiment 3 are respectively compared with the control group. The photoelectric conversion efficiency of the N-type crystalline silicon solar cell is improved to a certain extent compared with the photoelectric conversion efficiency of the N-type crystalline silicon solar cell in the control group. There is reason to believe that with the continuous improvement of the process, the adjustment of the mass percentage of each component in the copper paste and the mutual matching, there will be opportunities for greater breakthroughs. The same is true for the electrical experimental parameters such as open circuit voltage, short circuit current, and fill factor. Compared with the control group, the performance of embodiment 1, embodiment 2 and embodiment 3 is also slightly higher. Moreover, compared with the rarer and more expensive silver paste, the copper powder used in the copper paste is cheap and has a high output, so the cost is greatly reduced. In addition, the copper paste also shows better performance than the silver paste in the aging experiment. In the process of preparing the back grid line electrode of the N-type crystalline silicon solar cell, the requirements for light utilization, light transmission area, light shielding area, grid line preparation fineness, etc. are relatively low. The copper paste in the embodiment of this aspect can replace the existing silver paste, effectively reducing the production cost of the N-type crystalline silicon solar cell.

[0076] Note that the above are only preferred embodiments of the present invention and the technical principles used. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments, combinations and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in more detail through the above embodiments, the present invention is not limited to the above embodiments, and may include more other equivalent embodiments without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A copper paste, characterized in that: It includes organic additives, micron-sized spherical copper powder, nano-sized spherical copper powder, organic adhesive and glass powder; wherein, The mass percentage of the organic additive in the copper slurry is between 1.5% and 2.2%; The mass percentage of the micron-sized spherical copper powder in the copper slurry is between 70% and 77%; The mass percentage of the nano-scale spherical copper powder in the copper slurry is between 3% and 5%; The mass percentage of the organic binder in the copper paste is between 15.3% and 21.3%; The mass percentage of the glass powder in the copper paste is between 2.2% and 2.5%.

2. The copper paste according to claim 1, characterized in that The purity of the micron-sized spherical copper powder and the nano-sized spherical copper powder is 99.9%.

3. The copper paste according to claim 1, characterized in that The particle size of the micron-sized spherical copper powder ranges from 3 μm to 4 μm.

4. The copper paste according to claim 1, characterized in that The organic additive includes at least any one of fatty alcohol ether phosphate, aluminate coupling agent, silane coupling agent, zirconium aluminate coupling agent, lauryl phosphate, silicone oil, dibasic acid ester and lauryl alcohol phosphate mixture.

5. The copper paste according to claim 1, characterized in that The organic binder comprises a high molecular polymer and an organic solvent; wherein, The mass percentage of the high molecular weight polymer in the organic binder is between 10% and 15%; The mass percentage of the organic solvent in the organic binder is between 85% and 90%.

6. The copper paste according to claim 5, characterized in that The organic solvent includes at least any four of terpineol, butyl carbitol, butyl carbitol acetate, tributyl citrate, Span 85 and alcohol ester twelve.

7. The copper paste according to claim 1, characterized in that The glass powder includes Bi2O3, AL2O3, SiO2, ZnO, Sb2O5, B2O3 and TeO3; wherein, The mass percentage of Bi2O3 in the glass powder is between 10% and 20%; The mass percentage of Al2O3 in the glass powder is between 10% and 15%; The mass percentage of SiO2 in the glass powder is between 8% and 12%; The mass percentage of ZnO in the glass powder is between 18% and 25%; The mass percentage of Sb2O5 in the glass powder is between 15% and 20%; The mass percentage of B2O3 in the glass powder is between 8% and 10%; The mass percentage of TeO3 in the glass powder is between 15% and 20%.

8. The copper paste according to claim 1, characterized in that: The particle size of the glass powder is in the range of 2.2 μm to 2.5 μm.

9. A method for preparing a copper slurry, characterized in that: For preparing the copper slurry according to any one of claims 1 to 8, the preparation method comprises: Mixing and dispersing the nano-scale spherical copper powder, the glass powder and the organic binder to obtain a uniformly mixed first powder; Adding micron-sized spherical copper powder to the first powder, and dispersing and grinding the first powder and the micron-sized spherical copper powder to obtain a uniformly mixed second powder; An organic additive is added to the second powder, and the second powder and the organic additive are dispersed to obtain the copper paste which is uniformly mixed.

10. An N-type crystalline silicon solar cell, characterized in that: It comprises a back gate line electrode, and the back gate line electrode is prepared by using the copper paste according to any one of claims 1 to 8.

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