Preparation method of heterojunction solar cell and heterojunction solar cell

Abstract

The invention provides a preparation method of a heterojunction solar cell and the heterojunction solar cell, and relates to the technical field of solar cells. According to the preparation method of the heterojunction solar cell, a first transparent conducting layer on the front face of a substrate and / or a second transparent conducting layer on the back face of the substrate are / is coated with a photosensitive material, and exposure is carried out; carrying out glue etching and edge covering treatment, and then carrying out etching and developing; preprocessing the developed first transparent conductive layer and / or second transparent conductive layer; electroplating a copper electrode on the first transparent conductive layer and / or the second transparent conductive layer after pretreatment; and removing the film. Compared with the scheme of edge covering after development and edge etching in the prior art, the edge etching glue with etching performance is adopted in the technical scheme and is coated to the to-be-etched area of the edge after exposure and before etching development, so that the transparent conductive layer in the to-be-etched area is removed in the development process, the technological process can be simplified, and the production efficiency is improved. And the process complexity is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cells, and particularly to a method for preparing a heterojunction solar cell and a heterojunction solar cell. Background Art

[0002] As a new type of solar cell, the heterojunction solar cell has become a new hotspot in the photovoltaic field in recent years. It has many advantages such as simple structure, wide range of raw material sources, high open-circuit voltage, high conversion efficiency, and low temperature coefficient. In the preparation process of traditional heterojunction solar cells, most of them use screen printing to prepare metal electrodes, which has the problem of large consumption of silver paste, resulting in relatively high cost of battery chips. Using electroplating to prepare metal (such as copper, tin, etc.) electrodes to replace the traditional screen printing method for preparing electrodes is one of the important means to reduce the cost of battery chips.

[0003] The manufacturing process of heterojunction solar cells is simple, mainly including the steps of cleaning and texturing, depositing passivation layers and doping layers on the front and back, depositing transparent conductive oxide thin films (TCO), and preparing electrodes. When preparing the doped layer and the TCO layer, if no mask is used for shielding, the deposited doped layer and TCO layer materials will completely cover one side of the battery product. In this process of full coverage preparation, it is inevitable that some materials will reach the side of the substrate or even wrap around to the opposite side. When the materials on both sides overlap at the side of the battery or the edge area of the silicon wafer, it will cause conduction between the front and back of the battery chip, and then the solar cell will short-circuit.

[0004] Currently, in the copper manufacturing process route, in order to prevent electrode short-circuit caused by edge wrap-around plating, it is necessary to coat edge protection glue after development. However, this solution requires exposing the transparent conductive layer to be etched at the edge through a mask after exposure and development, and then etching, and the process is complex. Summary of the Invention

[0005] The purpose of the first aspect of the present invention is to provide a method for preparing a heterojunction solar cell, so as to solve the technical problem of complex edge etching process in the prior art.

[0006] A further purpose of the first aspect of the present invention is to improve the structural stability of the heterojunction solar cell.

[0007] The purpose of the second aspect of the present invention is to provide a heterojunction solar cell prepared by the above method for preparing a heterojunction solar cell.

[0008] According to the purpose of the first aspect of the present invention, the present invention provides a method for preparing a heterojunction solar cell, and the method includes the following steps:

[0009] The first passivation layer and the second passivation layer are respectively formed on the front and back surfaces of the substrate. The first doping layer is formed on the first passivation layer, and the second doping layer is formed on the second passivation layer;

[0010] The first transparent conductive layer and the second transparent conductive layer are respectively formed on the first doping layer and the second doping layer;

[0011] A photosensitive material is respectively coated on the first transparent conductive layer and / or the second transparent conductive layer, and exposure is performed;

[0012] Edge photoresist encapsulation treatment is performed, and then etching and development are carried out;

[0013] The developed first transparent conductive layer and / or the second transparent conductive layer are pre-treated;

[0014] Copper electrodes are electroplated on the pre-treated first transparent conductive layer and / or the second transparent conductive layer;

[0015] The film is removed.

[0016] Optionally, before the step of respectively coating the photosensitive material on the first transparent conductive layer and / or the second transparent conductive layer and performing exposure, it further includes:

[0017] An electrode is formed by screen printing on the first transparent conductive layer or the second transparent conductive layer;

[0018] Preferably, an electrode is formed by screen printing on the first transparent conductive layer on the back surface of the substrate.

[0019] Optionally, the step of performing edge photoresist encapsulation treatment and then etching and development includes:

[0020] Edge photoresist is coated on the edge of the exposed product;

[0021] While developing the exposed photosensitive material, etching is performed to remove the first transparent conductive layer and the second transparent conductive layer at the edge part.

[0022] Optionally, the edge photoresist is selected from the edge photoresist of the phosphoric acid system or the hydrochloric acid system, and the coating width of the edge photoresist is 20 - 150 μm.

[0023] Optionally, the step of pre-treating the developed first transparent conductive layer and / or the second transparent conductive layer includes:

[0024] Adjust the pH value of the pre-treatment solution to 4 - 10;

[0025] Photoinduced electroplating is performed in the pre-treatment solution at 0.05 - 2 ASD for 5 - 120 S.

[0026] Optionally, the pretreatment solution is selected from one or more of sodium citrate 5 - 30 g / L, sodium hypophosphite 1 - 10 g / L, sodium methyl sulfonate 1 - 10 g / L, sodium aminosulfonate 2 - 15 g / L, indium sulfate 1 - 5 g / L, indium methyl sulfonate 1 - 10 g / L, indium pyrophosphate 1 - 5 g / L, stannous sulfate 1 - 5 g / L, stannous methyl sulfonate 1 - 20 g / L, stannous aminosulfonate 1 - 20 g / L, and organic additive 1 - 5 g / L.

[0027] Optionally, before the step of electroplating a copper electrode on the pretreated first transparent conductive layer and / or the second transparent conductive layer, the following steps are further included:

[0028] Optically induced electroplating at least one transition layer on the pretreated first transparent conductive layer and / or the second transparent conductive layer.

[0029] Optionally, the material of the transition layer includes nickel, tin, tin - nickel, or tin - copper.

[0030] Optionally, the step of electroplating a copper electrode on the pretreated first transparent conductive layer and / or the second transparent conductive layer includes:

[0031] By adjusting the composition of the electroplating solution, the size of the bottom of the electroplated copper electrode is made larger than that of the top; wherein, the composition of the electroplating solution includes: 300 - 900 ml CuSO4, 70 - 300 ml H 2 SO 4 (50%), 1 ml HCl (50%), 1 ml brightener, 1 ml leveling agent, 0.5 - 2.5 ml inhibitor.

[0032] Optionally, the step of electroplating a copper electrode on the pretreated first transparent conductive layer and / or the second transparent conductive layer includes:

[0033] Adopting horizontal optically induced electroplating of the copper electrode.

[0034] Optionally, after the step of stripping the film, the following steps are further included:

[0035] Electroless plating of tin / silver.

[0036] Optionally, after the step of screen - printing an electrode on the first transparent conductive layer or the second transparent conductive layer, the following steps are further included:

[0037] Forming a protective layer on the first transparent conductive layer and / or the second transparent conductive layer; wherein, the protective layer located on the electrode is discontinuous.

[0038] According to the objective of the second aspect of the present invention, the present invention also provides a heterojunction solar cell, which is prepared by using the preparation method of the above-mentioned heterojunction solar cell.

[0039] In the preparation method of the heterojunction solar cell of the present invention, a photosensitive material is respectively coated on the first transparent conductive layer on the front side of the substrate and / or the second transparent conductive layer on the back side of the substrate, and exposure is carried out; edge photoresist wrapping treatment is performed, and then etching and development are carried out; the developed first transparent conductive layer and / or the second transparent conductive layer are pretreated; a copper electrode is electroplated on the pretreated first transparent conductive layer and / or the second transparent conductive layer; and the film is removed. Compared with the solution of wrapping the edge after development and then removing the edge photoresist, the above technical solution uses edge photoresist with etching performance, which is coated on the edge area to be etched after exposure and before etching and development. In this way, during the development process, the transparent conductive layer in the area to be etched is removed simultaneously, which can simplify the process flow, reduce the process complexity, and thus reduce the cost. In addition, the edge photoresist is removed during development, and no additional de-etching process needs to be set, which can further simplify the complexity of the battery preparation process.

[0040] Further, before the step of electroplating a copper electrode on the pretreated first transparent conductive layer and / or the second transparent conductive layer in the present invention, at least one transition layer is electroplated on the pretreated first transparent conductive layer and / or the second transparent conductive layer by photoinduced electroplating. The transition layer can be used as an intermediate medium, and its composition and structure can respectively form good chemical bonding or physical adsorption with the transparent conductive layer and the electrode, which can increase the bonding force between the transparent conductive layer and the electrode, reduce the risk of electrode detachment, and thus improve the structural stability of the heterojunction solar cell.

[0041] Based on the following detailed description of the specific embodiments of the present invention in conjunction with the drawings, those skilled in the art will become more clear about the above and other objectives, advantages and features of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Some specific embodiments of the present invention will be described in detail hereinafter with reference to the drawings in an exemplary but non-limiting manner. The same reference numerals in the drawings denote the same or similar components or parts. Those skilled in the art should understand that these drawings are not necessarily drawn to scale. In the drawings:

[0043] Figure 1 is a schematic flow chart of the preparation method of the heterojunction solar cell according to a specific embodiment of the present invention Figure 1 ;

[0044] Figure 2 is a schematic flow chart of the preparation method of the heterojunction solar cell according to a specific embodiment of the present invention Figure 2 ;

[0045] Figure 3 Schematic process flow of the preparation method of a heterojunction solar cell according to a specific embodiment of the present invention Figure 3 ;

[0046] Figure 4 Schematic process flow of the preparation method of a heterojunction solar cell according to a specific embodiment of the present invention Figure 4 ;

[0047] Figure 5 Schematic structure of a heterojunction solar cell according to a specific embodiment of the present invention Figure 1 ;

[0048] Figure 6 Schematic structure of a heterojunction solar cell according to a specific embodiment of the present invention Figure 2 ;

[0049] Figure 7 Schematic structure of a heterojunction solar cell according to a specific embodiment of the present invention Figure 3 ;

[0050] Figure 8 Schematic structure of a heterojunction solar cell according to a specific embodiment of the present invention Figure 4 ;

[0051] Figure 9 Schematic structure of a heterojunction solar cell according to a specific embodiment of the present invention Figure 5 ;

[0052] Figure 10 Schematic SEM image of the transparent conductive layer of a heterojunction solar cell in the prior art;

[0053] Figure 11 Schematic SEM image of the transparent conductive layer of a heterojunction solar cell according to a specific embodiment of the present invention;

[0054] Figure 12 Schematic SEM image of the electrode of a heterojunction solar cell according to a specific embodiment of the present invention;

[0055] Figure 13 Schematic structural diagram of the electrode of a heterojunction solar cell in the prior art;

[0056] Figure 14 Schematic structural diagram of the electrode of a heterojunction solar cell according to a specific embodiment of the present invention.

[0057] Description of reference numerals:

[0058] 100 - Heterojunction solar cell, 10 - Substrate, 21 - First passivation layer, 22 - Second passivation layer, 31 - First doping layer, 32 - Second doping layer, 41 - First transparent conductive layer, 42 - Second transparent conductive layer, 51 - Copper electrode, 52 - Silver electrode, 60 - Transition layer, 70 - Tin layer, 80 - Si 3 N 4 Layer. Detailed implementation manners

[0059] In the description of this embodiment, it should be understood that the orientation or positional relationships indicated by terms such as "front", "back", "horizontal", "bottom", "inner", "outer", etc. are based on the orientation or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the present invention.

[0060] As Figures 1 - 7 shown, as a specific embodiment of the present invention, the preparation method of the heterojunction solar cell 100 includes the following steps:

[0061] Step S100, forming a first passivation layer 21 and a second passivation layer 22 on the front and back surfaces of the substrate 10 respectively;

[0062] Specifically, first form the second passivation layer 22 on the back surface of the substrate 10, and then form the first passivation layer 21 on the front surface of the substrate 10.

[0063] Step S200, forming a first doping layer 31 on the first passivation layer 21 and a second doping layer 32 on the second passivation layer 22;

[0064] Specifically, first form the first doping layer 31 on the first passivation layer 21, and then form the second doping layer 32 on the second passivation layer 22.

[0065] Step S300, forming a first transparent conductive layer 41 and a second transparent conductive layer 42 on the first doping layer 31 and the second doping layer 32 respectively.

[0066] After step S300, it further includes:

[0067] Step S520, coating a photosensitive material on the first transparent conductive layer 41 and performing exposure;

[0068] Step S600, performing edge gluing and edge wrapping treatment, and then performing etching and development;

[0069] Step S720, preprocessing the developed first transparent conductive layer 41;

[0070] Step S820: Electroplate a copper electrode 51 on the pre-treated first transparent conductive layer 41;

[0071] Step S900: Remove the film.

[0072] Alternatively, after step S300, the following steps are further included:

[0073] Step S540: Coat a photosensitive material on the second transparent conductive layer 42 and perform exposure;

[0074] Step S600: Perform edge photoresist wrapping treatment, and then perform etching and development;

[0075] Step S740: Pretreat the developed second transparent conductive layer 42;

[0076] Step S840: Electroplate a copper electrode 51 on the pre-treated second transparent conductive layer 42;

[0077] Step S900: Remove the film.

[0078] Alternatively, after step S300, the following steps are further included:

[0079] Step S560: Coat a photosensitive material on the first transparent conductive layer 41 and the second transparent conductive layer 42 respectively and perform exposure;

[0080] Step S600: Perform edge photoresist wrapping treatment, and then perform etching and development;

[0081] Step S760: Pretreat the developed first transparent conductive layer 41 and the second transparent conductive layer 42;

[0082] Step S860: Electroplate a copper electrode 51 on the pre-treated first transparent conductive layer 41 and the second transparent conductive layer 42;

[0083] Step S900: Remove the film.

[0084] Here, it can be understood that coating a photosensitive material on the transparent conductive layer (TCO) and performing exposure can form a mask on the transparent conductive layer. After exposure and development, the photosensitive material can form the required patterns, which will determine the layout and structure of the battery electrodes. The film removal process refers to removing the photosensitive material film layer. Etching and developing the edge of the transparent conductive layer after edge photoresist wrapping can reduce edge leakage and short-circuit phenomena.

[0085] In some embodiments, the substrate 10 includes two opposite side surfaces, namely the front surface and the back surface. The front surface of the substrate 10 is the surface facing the sun, that is, the surface facing the sunlight irradiation, and the back surface of the substrate 10 is the surface facing away from the sun.

[0086] In the existing mass production copper metallization process, the double-sided seeded copper barrel plating process has significant limitations, with low production capacity and poor electroplating uniformity. The double-sided horizontal electroplating process also has prominent problems, such as poor electroplating quality, weak coating adhesion, and low production efficiency. In the embodiment of the present invention, a copper electrode 51 is directly electroplated on the pretreated transparent conductive layer without the need to deposit a seed layer, which can simplify the process flow, improve electroplating uniformity, and enhance the adhesion between the electrode and the transparent conductive layer.

[0087] In this embodiment, surface pretreatment is performed on the transparent conductive layer at the opening after exposure and development. After surface pretreatment, copper can be directly electroplated, and it has good adhesion and electrical properties. This simplifies the preparation difficulty of solar cells, reduces production costs, effectively improves the photoelectric conversion efficiency, greatly increases the production capacity of the current production line copper manufacturing process, and provides an effective mass production approach for cost reduction and efficiency improvement of solar cell wafers.

[0088] The method for preparing the heterojunction solar cell 100 provided by the embodiment of the present invention performs edge photoresist encapsulation treatment after exposure, and then etching and development. In the prior art, after exposure and development, it is necessary to expose the transparent conductive layer to be etched at the edge through a mask, and then etching is carried out, with a complex process. Compared with the scheme of encapsulating the edge after development and then performing edge breaking, the present invention uses an edge photoresist with etching performance, which is coated on the edge area to be etched after exposure and before etching and development. In this way, during the development process, the transparent conductive layer in the area to be etched is removed simultaneously, which can simplify the process flow, reduce process complexity, and thus reduce costs. In addition, the edge photoresist is removed during development, and no additional degluing process is required, which can further simplify the battery preparation process.

[0089] In the embodiment of the present invention, the substrate 10 can be a silicon substrate, such as a single crystal silicon substrate, a polycrystalline silicon substrate, or a quasi-single crystal silicon substrate, etc. The embodiment of the present invention does not limit the specific type of the substrate 10. And the substrate 10 can be P-type doped or N-type doped, that is, the substrate 10 can be a P-type substrate or an N-type substrate. The heterojunction solar cell 100 of the embodiment of the present invention can be an N-type heterojunction solar cell 100, or can be a P-type heterojunction solar cell 100. Exemplarily, in some embodiments, the substrate 10 is an N-type single crystal silicon substrate (also called an N-type single crystal silicon wafer).

[0090] In some embodiments, the first transparent conductive layer 41 and the second transparent conductive layer 42 after development are respectively pretreated, and a copper electrode 51 is electroplated on the pretreated first transparent conductive layer 41 and second transparent conductive layer 42. This can achieve silver-free and reduce the production cost of the battery.

[0091] See Figure 1 and Figure 5, in some embodiments, before step S520, it further includes:

[0092] Step S420, screen-printing an electrode on the second transparent conductive layer 42.

[0093] Alternatively, referring to Figure 2 and Figure 6 , before step S540, it further includes:

[0094] Step S440, screen-printing an electrode on the first transparent conductive layer 41.

[0095] Preferably, an electrode is formed by screen-printing on the first transparent conductive layer 41 on the back surface of the substrate 10.

[0096] In some embodiments, a low-temperature silver-copper paste, or other alloy pastes or conductive film materials such as silver paste, copper paste, silver-aluminum paste, silver-nickel paste, and conductive adhesive are screen-printed or stenciled on the back (P) surface of the battery, so as to form an electrode on the back surface of the substrate 10. Preferably, a silver electrode 52 is formed by screen-printing on the back surface of the battery.

[0097] Specifically, in step S420 or step S440, the prepared transparent conductive layer is placed on the printing platform, fixed in position, and then the screen template is aligned with the transparent conductive layer. The silver paste is extruded through the mesh holes of the screen by a squeegee and deposited on the transparent conductive layer to form an electrode. The efficiency of screen-printing the silver electrode 52 is relatively high, and electrodes can be printed in batches in a short time, which is suitable for large-scale production and can further improve the production practicability of the preparation of the heterojunction solar cell 100 of the present invention, but the cost is relatively high. In this embodiment, a silver electrode 52 is screen-printed on one side of the battery, and a copper electrode 51 is electroplated on the other side, which can reduce the silver consumption and lower the cost while ensuring the electrical performance of the battery. That is, in this solution, a copper electrode 51 with a relatively large aspect ratio can be electroplated and formed on the front surface of the heterojunction solar cell 100, reducing the light shielding by the electrode and further improving the light utilization rate.

[0098] In some embodiments, step S600 includes:

[0099] Coating and edge-etching the exposed product with photoresist;

[0100] While developing the exposed photosensitive material, etching is performed to remove the first transparent conductive layer 41 and the second transparent conductive layer 42 at the edge portion.

[0101] Specifically, while developing, the first transparent conductive layer 41 and the second transparent conductive layer 42 at the edge portion are etched to completely electrically isolate the first transparent conductive layer 41 and the second transparent conductive layer 42, avoiding the short circuit caused by the overlap of the first transparent conductive layer 41 and the second transparent conductive layer 42 and improving the electrical performance of the battery.

[0102] In some embodiments, the edge photoresist is selected from edge photoresists of a phosphoric acid system or a hydrochloric acid system, and the width of the edge photoresist coating is 20 - 150 μm. For example, it can be 20 μm, 50 μm, 80 μm, 100 μm, 150 μm, etc.

[0103] By controlling the width of the edge photoresist coating within the range of 20 - 150 μm in this embodiment, on the one hand, it can avoid the situation where the width of the edge photoresist is too small to play the role of coating the battery edge, or the role played is extremely insignificant. On the other hand, it can avoid the situation where the coating width of the edge photoresist is too large, which will cause the effective area of the transparent conductive layer to become smaller, thereby affecting the efficiency of the battery.

[0104] In some embodiments, step S720, or step S740, step S760 includes:

[0105] Adjust the pH value of the pretreatment solution to 4 - 10;

[0106] Optically induced electroplate in the pretreatment solution at 0.05 - 2 ASD for 5 - 120 S.

[0107] Here, the pH value of the pretreatment solution is set within a reasonable range to avoid adverse effects on the first transparent conductive layer 41 and / or the second transparent conductive layer 42 caused by too high or too low pH.

[0108] The SEM morphology of the blue film surface before and after pretreatment is as Figure 10 and Figure 11 shown. It can be seen from the figure that the surface roughness of the transparent conductive layer increases after pretreatment, and there are metal particles. After treatment, directly electroplating copper has a good bonding force, avoiding electrode detachment.

[0109] This embodiment performs surface pretreatment on the transparent conductive layer at the opening after exposure and development. After surface pretreatment, copper can be directly electroplated, and it has good bonding force and electrical properties, simplifies the preparation difficulty of the solar cell, reduces the manufacturing cost, effectively improves the photoelectric efficiency at the same time, greatly improves the production capacity of the current production line copper manufacturing process, and provides an effective mass production way for cost reduction and efficiency improvement of solar cell wafers.

[0110] The preparation method of the heterojunction solar cell 100 provided by the embodiment of the present invention can directly electroplate the copper electrode 51 on the pretreated transparent conductive layer by pretreating the developed transparent conductive layer, without depositing a seed layer and then electroplating the electrode, with low equipment requirements, no need to etch the seed layer additionally, simple production, which can simplify the preparation difficulty of the heterojunction solar cell 100, improve production capacity and reduce production costs. Compared with the prior art, the process of the embodiment of the present invention has good adhesion, low contact resistivity and line resistance, high FF (fill factor), and excellent electrical performance. Copper can be directly electroplated after pretreatment, and there is good adhesion. This also helps to realize horizontal photoinduced electroplating, with high electroplating uniformity and high production capacity.

[0111] In some embodiments, the pretreatment solution is selected from one or more of 5-30 g / L of sodium citrate, 1-10 g / L of sodium hypophosphite, 1-10 g / L of sodium methyl sulfonate, 2-15 g / L of sodium aminosulfonate, 1-5 g / L of indium sulfate, 1-10 g / L of indium methyl sulfonate, 1-5 g / L of indium pyrophosphate, 1-5 g / L of stannous sulfate, 1-20 g / L of methylene sulfonic acid, 1-20 g / L of stannous aminosulfonate, and 1-5 g / L of organic additive.

[0112] Specifically, the pH value of the pretreatment solution is adjusted to 4-10 with H 2 SO 4 or NH 4 OH, and then photoinduced electroplating is carried out in the pretreatment solution at 0.05-2 ASD for 5-120 s to occur a chemical reduction reaction.

[0113] In the prior art, the process flow of electroplating the copper electrode 51 is long, involving multiple links such as seed layer preparation, patterning, electroplating, and post-treatment, with complex processes and high equipment costs. Moreover, the copper grid lines are finer and the adhesion is relatively poor, and the situation of grid detachment may occur, with high requirements for processes and materials. By pretreating the transparent conductive layer in this embodiment, the surface roughness of the transparent conductive layer can be improved, and its adhesion with the copper electrode 51 can be enhanced, which can ensure that the electrode is not easy to detach during the direct electroplating of the copper electrode 51 on the transparent conductive layer, simplify the preparation difficulty of the battery, and reduce the production cost.

[0114] See Figure 4 , in some embodiments, before step S820, or step S840, or step S860, it further includes ( Figure 4 taking step S820 as an example in

[0115] Step S780, photoinduced electroplating at least one transition layer 60 on the pretreated first transparent conductive layer 41 and / or the second transparent conductive layer 42.

[0116] Due to the different physical and chemical properties of the transparent conductive layer and the electrode material, there are problems such as chemical bonding mismatch and lattice constant difference at the interface between the two. The transition layer 60 can act as an intermediate medium, and its composition and structure can form good chemical bonding or physical adsorption with the transparent conductive layer and the electrode respectively, which can increase the bonding force between the transparent conductive layer and the electrode, reduce the risk of electrode detachment, and thus improve the structural stability of the heterojunction solar cell 100.

[0117] In some embodiments, the material of the transition layer 60 includes nickel, tin, tin-nickel or tin-copper. Nickel, tin, tin-nickel or tin-copper has stable chemical properties, and when used as the transition layer 60, it can increase the adhesion between the transparent conductive layer and the electrode and maintain the stability of the battery. The transition layer 60 also provides a large number of nucleation sites for the copper ions of the electroplated electrode, enabling the copper ions to start depositing and growing at these sites to form an electroplated copper electrode, which is conducive to the orderly aggregation and crystallization of the copper ions and lays a foundation for the subsequent formation of a uniform copper grid line, and is conducive to improving the electroplating rate of copper.

[0118] Currently, as Figure 12 shown, the electroplating line shape is electroplated in a rectangular / trapezoidal mask opening, and the top of the electroplated copper electrode 51 line shape is flat. The rectangular copper electrode 51 will have a large current loss after the component is laminated, reducing the power of the copper electrode 51 battery component.

[0119] As Figure 13 shown, in some embodiments, the step of electroplating the copper electrode 51 on the pretreated first transparent conductive layer 41 and / or second transparent conductive layer 42 includes: by adjusting the composition of the electroplating solution, making the size of the bottom of the electroplated copper electrode 51 larger than the size of the top; wherein, the composition of the electroplating solution includes: 300 - 900 ml of CuSO4, 70 - 300 ml of H2SO4 (50%), 1 ml of HCl (50%), 1 ml of brightener, 1 ml of leveling agent, 0.5 - 2.5 ml of inhibitor.

[0120] Specifically, the main components of the brightener include coumarin, butynediol, etc., the main components of the leveling agent include sodium polydithiopropane sulfonate (SPS), and the main components of the inhibitor include chromate, molybdate, etc.

[0121] Specifically, after exposure and development, a patterned opening in the shape of a groove is formed on the mask, and the size of the side of the opening close to the substrate 10 is larger than the size of the side away from the substrate 10, so that the formed grid line after electroplating is triangular. Compared with the conventional rectangular or trapezoidal grid lines, the triangular grid lines can greatly reduce the current loss after component lamination, improve the component power, and thus improve the performance of the battery.

[0122] In some other embodiments, a new type of photoresist is adopted. This photoresist can change the light absorption sensitivity, and different grooving angles can be obtained by adjusting different exposure conditions, so that the grid lines formed after electroplating can be triangular.

[0123] In other embodiments, by adjusting the components and ratios of the leveling agent and inhibitor in the electroplating solution and adding special electroplating additives, the copper electrode 51 formed after electroplating can be triangular, which can greatly reduce the current loss after component lamination and improve the power of the component. In this embodiment, by adjusting the components of the electroplating solution and adding electroplating additives, the upper morphology of the plated copper grid line is arched, reducing light reflection, increasing light absorption, and greatly improving the current loss after component lamination.

[0124] In some embodiments, step S820, or step S840, or step S860 includes:

[0125] Adopt horizontal light-induced electroplating for the copper electrode 51.

[0126] During the horizontal light-induced electroplating process, since the electrode and the object to be plated are in a relatively stable horizontal position, the electric field distribution is more uniform. The light-induced effect can make the copper ions in the electroplating solution deposit more uniformly on the electrode surface under the action of the electric field. Compared with other electroplating methods, this uniform deposition can effectively avoid the situation of local copper layer being too thick or too thin.

[0127] As a preferred embodiment, screen-print the electrode on one of the first transparent conductive layer 41 and the second transparent conductive layer 42, and electroplate copper with horizontal light-induced electroplated copper grid lines on the other. This can not only ensure the electrical performance of the battery but also reduce the silver consumption and cost.

[0128] See Figure 3 , in some embodiments, after step S900, it further includes:

[0129] Step S950, electroless plating of tin / silver.

[0130] In some embodiments, the tin layer can fill the tiny voids and defects at the connection interface, making the contact closer, thereby improving the fill factor and conversion efficiency of the heterojunction solar cell 100. In addition, the heterojunction solar cell 100 will face various corrosion factors in the actual use environment, such as humid air, acid rain, etc. The tin layer 70 can provide a protective film for the heterojunction solar cell 100 to prevent the electrode and other components from being corroded.

[0131] In some embodiments, the tin layer can be replaced with a silver layer, and electroless plating of silver for 1 - 3 minutes, or electroplating silver before film removal, or other alloy electroplating materials can be used to increase the lamination current of the battery module.

[0132] In some embodiments, after the step of screen printing to form electrodes on the first transparent conductive layer 41 or the second transparent conductive layer 42, the following steps are further included:

[0133] A protective layer is formed on the first transparent conductive layer 41 or the second transparent conductive layer 42; wherein, the protective layer located on the electrodes is discontinuous.

[0134] In some embodiments, the material of the protective layer is silicon nitride or silicon oxide. Silicon nitride and silicon oxide have appropriate refractive indices. By depositing the protective layer on the surface of the battery, a good optical interface can be formed, reducing light reflection and allowing more light to enter the battery interior to be absorbed, thereby improving the photoelectric conversion efficiency of the battery. Additionally, the protective layer can serve as a barrier layer for the battery, preventing external impurities from diffusing into the silicon wafer interior, protecting the internal structure of the battery from contamination, and improving the long-term stability and reliability of the battery.

[0135] An embodiment of the present invention also provides a heterojunction solar cell 100, which is prepared by using the preparation method of the above-mentioned heterojunction solar cell 100. As Figures 5 - 9 shown, the heterojunction solar cell 100 may include a substrate 10, and a first passivation layer 21, a first doping layer 31, a first transparent conductive layer 41, and an electrode are sequentially arranged on one side surface of the substrate 10; a second passivation layer 22, a second doping layer 32, a second transparent conductive layer 42, and an electrode are sequentially arranged on the other side surface of the substrate 10.

[0136] Those skilled in the art can understand that this heterojunction solar cell 100 and the preparation method of the foregoing heterojunction solar cell 100 are based on the same inventive concept. The features and advantages described above for the preparation method of the heterojunction solar cell 100 also apply to this heterojunction solar cell 100. Therefore, this heterojunction solar cell 100 has at least the same features and advantages as the preparation method of the foregoing heterojunction solar cell 100, and will not be elaborated herein.

[0137] The present invention will be further described below in conjunction with specific embodiments and comparative examples.

[0138] Comparative Example 1

[0139] 1) A first passivation layer and a second passivation layer are respectively formed on the front and back surfaces of the substrate. Among them, the substrate 10 is a 182 battery substrate.

[0140] 2) A first doping layer is formed on the first passivation layer, and a second doping layer is formed on the second passivation layer.

[0141] 3) A first transparent conductive layer and a second transparent conductive layer are respectively formed on the first doping layer and the second doping layer.

[0142] 4) Deposit seed layers on the first transparent conductive layer and the second transparent conductive layer respectively. Physically deposit seed layers with a thickness of 100 - 200 nm on both sides.

[0143] 5) Coating photosensitive material, exposing and developing. Coat photosensitive material (photoresist) on both sides, with a mask thickness of 10 - 15 μm. The width of the pattern opening is 8 - 15 μm.

[0144] 6) Coat edge - sealing glue with an edge - sealing machine.

[0145] 7) Electroplate copper electrodes. Plating on both sides by hanging, with the height of the copper grid being 8 - 15 μm.

[0146] 8) Remove the film; etch the seed layer.

[0147] Example 1

[0148] 1) Form a first passivation layer 21 and a second passivation layer 22 on the front and back of the substrate 10 respectively. Among them, the substrate 10 is a 182 - cell substrate.

[0149] 2) Form a first doping layer 31 on the first passivation layer 21 and a second doping layer 32 on the second passivation layer 22.

[0150] 3) Form a first transparent conductive layer 41 and a second transparent conductive layer 42 on the first doping layer 31 and the second doping layer 32 respectively. Among them, the transparent conductive layer can be an ITO (indium tin oxide) film, an IMO (indium molybdenum oxide) film, an IWO (indium tungsten oxide) film, a TTO (tin oxide) film, etc.

[0151] 4) Screen - print silver paste on the back (P) side, silver - coated copper (silver content 10% - 50%). Among them, the materials used for screen / stencil printing can be low - temperature silver - copper paste, or other alloy pastes or conductive film materials such as silver paste, copper paste, silver - aluminum paste, silver - nickel paste, conductive glue, etc.

[0152] 5) Coat photosensitive material on the front (N) side and expose it. The mask thickness is 10 - 15 μm. Among them, the photosensitive material can be photoresist, photosensitive ink, dry film, etc.

[0153] 6) Perform edge - coating and edge - etching treatment, and then etch and develop. Among them, the edge - coating and edge - etching glue (phosphoric acid or hydrochloric acid - based edge - etching glue) is coated by a dispenser with a thickness of 20 - 200 μm, etched at 50 - 80 °C for 10 - 60 s. After exposure and development, the width of the pattern opening is 8 - 15 μm.

[0154] 7) Pretreat the developed first transparent conductive layer 41. Use H 2 SO 4 or NH 4Adjust the pH value of the OH conditioning pretreatment solution to 4 - 10; perform photo-induced electroplating in the pretreatment solution at 0.05 - 2 ASD for 5 - 120 s with a current of 5 - 50 mA, and then wash with water N 2 Blow dry. Among them, the photo-induced pretreatment solution contains one or more of the following: sodium citrate 5 - 30 g / L, sodium hypophosphite 1 - 10 g / L, sodium methyl sulfonate 1 - 10 g / L, sodium aminosulfonate 2 - 15 g / L, indium sulfate 1 - 5 g / L, indium methyl sulfonate 1 - 10 g / L, indium pyrophosphate 1 - 5 g / L, stannous sulfate 1 - 5 g / L, stannous methyl sulfonate 1 - 20 g / L, stannous aminosulfonate 1 - 20 g / L, organic additive 1 - 5 g / L.

[0155] See Figure 10 and Figure 11 By observing the SEM morphology of the surface of the first transparent conductive layer 41 before and after pretreatment, it can be found that the surface roughness increases and there are metal particles. After treatment, direct copper plating has good adhesion, such as Figure 12 . After the transparent conductive layer of the battery is treated with the pretreatment solution, copper can be directly electroplated.

[0156] 8) Electroplate a copper electrode 51 on the pretreated first transparent conductive layer 41. Photo-induced copper plating for 5 - 15 min at 2 - 10 ASD to form a copper layer of 5 - 15 μm.

[0157] 9) Remove the film (photosensitive material).

[0158] See Figure 5 In this example, a screen-printed silver electrode 52 is used for the back electrode of the battery, and an electroplated copper electrode 51 is used for the front electrode. There is no need to deposit and etch the seed layer, which can simplify the process flow, reduce the preparation difficulty of the heterojunction solar cell 100, improve production capacity, and reduce manufacturing costs.

[0159] The performance comparison of the heterojunction solar cells 100 obtained in the above Example 1 and Comparative Example 1 is shown in the following Table 1.

[0160] Table 1

[0161]

[0162] As can be seen from Table 1, for the heterojunction solar cell 100 prepared by the method of Example 1, after direct exposure, a 20 - 150 μm phosphoric acid system / hydrochloric acid system edge photoresist is coated, and after development, the edge blue film is etched, reducing edge leakage and short-circuit phenomena and improving electrical performance.

[0163] Currently, the process of fabricating the copper grid heterojunction solar cell 100 is as shown in Comparative Example 1. First, a full-metal seed layer needs to be physically vapor deposited on the transparent conductive layer, then the copper grid lines are electroplated, and finally the excess seed layer is etched away. In this method, physical vapor deposition has high requirements for equipment and also requires an additional etching process, resulting in complex fabrication and relatively high costs.

[0164] In the embodiment of the present invention, copper can be directly electroplated after pretreatment, with good adhesion, low contact resistivity, high FF, and good electrical performance; horizontal photoinduced electroplating can be performed, with high electroplating uniformity and high productivity. In the embodiment of the present invention, edge photoresist is directly wrapped after exposure, which can reduce edge leakage and short circuits and improve electrical performance. In addition, there is no need to use an edge wrapping machine to coat the edge wrapping glue, and the edge photoresist is removed during development, which can simplify the process flow.

[0165] Example 2

[0166] 1) The same as step 1) of Example 1.

[0167] 2) The same as step 2) of Example 1.

[0168] 3) The same as step 3) of Example 1.

[0169] 4) Screen-print the front (N) side silver paste, silver-coated copper (silver content 10% - 50%). Among them, the materials used for screen / stencil printing can be low-temperature silver-copper paste, or other alloy pastes or conductive film materials such as silver paste, copper paste, silver-aluminum paste, silver-nickel paste, and conductive adhesive.

[0170] 5) Coat the photosensitive material on the back (P) side and perform exposure. The mask thickness is 10 - 15μm. Among them, the photosensitive material can be photoresist, photosensitive ink, dry film, etc.

[0171] 6) The same as step 6) of Example 1. After exposure and development, the pattern opening width is 8 - 15μm.

[0172] 7) Pretreat the developed second transparent conductive layer 42. The specific process is the same as step 7) of Example 1.

[0173] After pretreatment, the surface roughness of the second transparent conductive layer 42 increases, and there are metal particles. After direct copper electroplating, good adhesion can be obtained.

[0174] 8) Electroplate the copper electrode 51 on the pretreated second transparent conductive layer 42. Photoinduced copper electroplating for 5 - 15 minutes, 2 - 10 ASD, to form a copper layer of 5 - 15μm.

[0175] 9) Remove the film.

[0176] See Figure 6, in this embodiment, a screen-printed silver electrode 52 is used for the front electrode of the battery, and an electroplated copper electrode 51 is used for the back electrode. There is no need to deposit and etch the seed layer, which can simplify the process flow, reduce the preparation difficulty of the heterojunction solar cell 100, improve the production capacity, and reduce the manufacturing cost.

[0177] Example 3

[0178] 1) The same as step 1) of Example 1.

[0179] 2) The same as step 2) of Example 1.

[0180] 3) The same as step 3) of Example 1.

[0181] 4) Photosensitive materials are respectively coated on the front and back of the battery and exposed. The mask thickness is 10 - 15 μm. Among them, the photosensitive material can be photoresist, photosensitive ink, dry film, etc.

[0182] 5) The same as step 6) of Example 1. After exposure and development, the width of the pattern opening is 8 - 15 μm.

[0183] 6) Pretreat the developed first transparent conductive layer 41 and second transparent conductive layer 42 respectively. For the specific process, refer to step 7) of Example 1.

[0184] After pretreatment, the surface roughness of the first transparent conductive layer 41 and the second transparent conductive layer 42 increases and there are metal particles. After treatment, direct copper plating has a good bonding force.

[0185] 7) Electroplate copper electrodes 51 on the pretreated first transparent conductive layer 41 and second transparent conductive layer 42 respectively. Photo-induced copper plating for 5 - 15 min, 2 - 10 ASD, to form a copper layer of 5 - 15 μm.

[0186] 8) Remove the film.

[0187] 9) Electroless tin plating to form a tin layer 70 of 0.5 - 3 μm. Electroless tin plating is carried out after removing the film, which can provide a protective film for the battery to prevent the electrode and other components from being corroded.

[0188] The performance comparison of the heterojunction solar cells 100 obtained in the above Example 3 and Comparative Example 1 is shown in the following Table 2.

[0189] Table 2

[0190] The experimental results of Comparative Example 1 and Example 3 are shown in the following table.

[0191]

[0192] As can be seen from Table 2, and referring to Figure 7, the preparation process of Example 3 has lower contact resistivity and wire resistance compared with the seed copper process in Comparative Example 1, with high FF, good adhesion, and excellent electrical performance.

[0193] In the seed copper process, physical vapor deposition has high requirements for equipment and also requires an additional etching process. The manufacturing is complex and the cost is relatively expensive. The embodiments of the present invention can simplify the preparation difficulty of solar cells, improve production capacity, and reduce manufacturing costs. In this embodiment, the electrodes on the front and back of the battery are both copper electrodes 51, which can achieve silver-free and greatly reduce the cost of the battery.

[0194] Example 4

[0195] Steps 1) - 7) of this embodiment are respectively the same as steps 1) - 7) of Example 1. The difference is that after step 7), it further includes:

[0196] 8) Photolithographically electroplate a layer of nickel on the pretreated first transparent conductive layer 41, with the nickel layer being 1 - 2 μm. Among them, nickel can be replaced by tin, tin-nickel, or tin-copper.

[0197] 9) Electroplate the copper electrode 51 on the nickel layer. Photolithographically electroplate copper for 5 - 15 minutes at 2 - 10 ASD to form a copper layer of 5 - 15 μm.

[0198] 10) Remove the film.

[0199] See Figure 8 , in this embodiment, on the pretreated first transparent conductive layer 41, an additional nickel transition layer 60 is added to improve the electroplating rate of copper and the adhesion between the transparent conductive layer and the electrode.

[0200] Example 5

[0201] Steps 1) - 3) of this embodiment are respectively the same as steps 1) - 3) of Example 1. The difference is that after step 3), it further includes:

[0202] 4) Screen-print silver-coated copper (silver content 5% - 30%) on the P side to form an electrode 52 with a width of 15 - 30 μm and a height of 5 - 15 μm, and then grow 30 - 80 nm of Si 3 N 4 by CVD / PVD or grow 10 - 80 nm of SnO x .

[0203] Silicon nitride has a suitable refractive index. By depositing a Si 3 N 4 layer 80 on the surface of the battery, a good optical interface can be formed, reducing light reflection and allowing more light to enter the battery interior to be absorbed, thereby improving the photoelectric conversion efficiency of the battery. In addition, Si 3 N4 Layer 80 can serve as a barrier layer of the battery, preventing external impurities from diffusing into the silicon wafer, protecting the internal structure of the battery from contamination, and improving the long-term stability and reliability of the battery.

[0204] It should be further noted that during the formation of the protective layer, although a corresponding film layer is also formed on the printed electrode 52, due to the presence of the textured surface and the certain roughness of the printed electrode 52, the thickness of the protective layer can be further controlled so that the protective layer located on the electrode 52 is discontinuous, that is, the protective layer located on the electrode 52 has openings, enabling the protective layer to have a connection channel communicating with the electrode 52 externally. Therefore, during the subsequent electroplating process, the electrode 51 can be electroplated on the electrode 52.

[0205] 5) Coat the N side with a photosensitive material and perform exposure. The mask thickness is 10 - 15 μm.

[0206] 6) The same as step 6) of Example 1. After exposure and development, the patterned opening is 8 - 15 μm.

[0207] 7) Pretreat the developed first transparent conductive layer 41. Use H 2 SO 4 or NH 4 OH to adjust the pH value of the pretreatment solution to 4 - 10; in the pretreatment solution, photoinduced electroplating is 5 - 15 ASD, the time is 10 - 30 S, the current is 5 - 50 mA, and wash with water and N 2 dry.

[0208] 8) Electroplate the copper electrode 51 on the pretreated first transparent conductive layer 41. Photoinduced copper plating (the copper plating solution is different from that of Example 1) for 5 - 15 min, 5 - 15 ASD.

[0209] 9) Remove the film.

[0210] 10) Electroplate copper on the P side for 5 - 15 min, 5 - 20 ASD.

[0211] 11) Electroless tin plating for 1 - 3 min.

[0212] There are more and thicker grid lines on the P side electrode. Refer to Figure 9 , using this process can further reduce the silver consumption, and at the same time avoid the problem of low electrical performance caused by too high wet weight of the P side silver paste, and further improve the electrical performance.

[0213] Example 6

[0214] Steps 1) - 4) of this example are respectively the same as steps 1) - 4) of Example 1. The difference is that after step 4), it further includes:

[0215] 5) Coating the photosensitive material on the N surface, followed by exposure and development. The mask thickness is 10 - 15 μm, the bottom width of the patterned opening is 15 - 20 μm, and the upper opening is 8 - 12 μm.

[0216] 6) The same as step 6) of Example 1.

[0217] 7) Pretreat the developed first transparent conductive layer 41. Adjust the pH value of the pretreatment solution to 4 - 10 with H 2 SO 4 or NH 4 OH; Conduct photo-induced electroplating in the pretreatment solution at 0.05 - 2 ASD for 10 - 30 s with a current of 5 - 50 mA, then wash with water and dry. 2 Dry.

[0218] 8) LIP copper plating (the copper plating solution is different from that of Example 1) for 5 - 15 min at 5 - 15 ASD.

[0219] 9) Remove the film.

[0220] Table 3

[0221] Item Current CTM (%) Before and After Lamination Comparative Example 1 96.90 Example 6 98.09

[0222] Table 4

[0223]

[0224]

[0225] See Figure 12 , in the prior art, the electroplating line shape is electroplated in a rectangular / trapezoidal mask opening, and the top of the electroplated copper grid line shape is flat. The rectangular copper grid will have a large current loss after component lamination, reducing the power of the copper grid battery component.

[0226] In view of this, see Figure 13 , in the embodiment of the present invention, by adjusting the components and proportions of the leveling agent and inhibitor in the electroplating solution and adding a special electroplating additive, the upper morphology of the plated copper grid line is arched. Specifically, the electroplated grid line is triangular, reducing light reflection, increasing light absorption, greatly reducing the current loss after component lamination, and improving the component power.

[0227] For the conventional process, see Comparative Example 1. The differences between the electroplating solutions used in Example 6 and Comparative Example 1 are shown in Table 4 (unit: ml). For different ratios of the electroplating solution, the current conditions are adjusted accordingly. This example can change the grid line shape by adjusting the electroplating solution and the exposure and development to adjust the slot shape.

[0228] Example 7

[0229] Steps 1) to 8) of this embodiment are respectively the same as steps 1) to 8) of Embodiment 1. The difference is that after step 8), the following steps are further included:

[0230] 9) Etch with micro-etching solution for 1 - 5 minutes.

[0231] 10) Remove the film.

[0232] After copper plating in this embodiment, chemical etching is carried out, which can improve the roughness of the battery surface material, and then improve the lamination current of the battery module.

[0233] The embodiment of the present invention provides a low-cost and high-efficiency copper-grid heterojunction solar cell 100 and its preparation method. It is proposed to perform surface pretreatment on the TCO at the opening after exposure and development. After surface pretreatment, copper can be directly plated, and it has good adhesion and electrical properties. It simplifies the preparation difficulty of the heterojunction solar cell 100, reduces the manufacturing cost, effectively improves the photoelectric conversion efficiency, greatly improves the production capacity of the current production line copper manufacturing process, and provides an effective mass production way to reduce costs and improve efficiency for solar cell wafers.

[0234] At this point, those skilled in the art should recognize that although multiple exemplary embodiments of the present invention have been shown and described in detail herein, many other variations or modifications that conform to the principles of the present invention can still be directly determined or derived from the content disclosed in the present invention without departing from the spirit and scope of the present invention. Therefore, the scope of the present invention should be understood and determined to cover all these other variations or modifications.

Claims

1. A method for preparing a heterojunction solar cell, the method comprising the following steps: forming a first passivation layer and a second passivation layer on the front side and the back side of the substrate, respectively; forming a first doping layer on the first passivation layer, and forming a second doping layer on the second passivation layer; forming a first transparent conductive layer and a second transparent conductive layer on the first doped layer and the second doped layer respectively; It is characterized in that Coating a photosensitive material on the first transparent conductive layer and / or the second transparent conductive layer respectively, and performing exposure; The edge is processed by etching and then developing; Pre-treating the first transparent conductive layer and / or the second transparent conductive layer after development; Electroplating a copper electrode on the pretreated first transparent conductive layer and / or the second transparent conductive layer; Remove the membrane.

2. The method for preparing a heterojunction solar cell according to claim 1, characterized in that: Before the step of coating the photosensitive material on the first transparent conductive layer and / or the second transparent conductive layer and performing exposure, the method further comprises: Forming an electrode on the first transparent conductive layer or the second transparent conductive layer by screen printing; Preferably, the electrode is formed on the first transparent conductive layer on the back side of the substrate by screen printing.

3. The method for preparing a heterojunction solar cell according to claim 1, characterized in that: The steps of edge encapsulation processing, and then etching and developing include: Coating edge resist on the edge of the exposed product; While developing the exposed photosensitive material, etching is performed to remove the first transparent conductive layer and the second transparent conductive layer at the edge portions.

4. The method for preparing a heterojunction solar cell according to claim 3, characterized in that: The edge resist is selected from edge resists of a phosphoric acid system or a hydrochloric acid system, and the edge resist coating width is 20 to 150 μm.

5. The method for preparing a heterojunction solar cell according to any one of claims 1 to 4, characterized in that: The step of pre-treating the first transparent conductive layer and / or the second transparent conductive layer after development comprises: Adjust the pH value of the pretreatment solution to 4-10; The light-induced electroplating is carried out in the pretreatment solution at 0.05-2ASD for 5-120S.

6. The method for preparing a heterojunction solar cell according to claim 5, characterized in that: The pretreatment liquid is selected from one or more of 5-30 g / L sodium citrate, 1-10 g / L sodium hypophosphite, 1-10 g / L sodium methane sulfonate, 2-15 g / L sodium sulfamate, 1-5 g / L indium sulfate, 1-10 g / L indium methane sulfonate, 1-5 g / L indium pyrophosphate, 1-5 g / L stannous sulfate, 1-20 g / L stannous methane sulfonate, 1-20 g / L stannous aminosulfonate, and 1-5 g / L organic additives.

7. The method for preparing a heterojunction solar cell according to claim 1, characterized in that: Before the step of electroplating a copper electrode on the pre-treated first transparent conductive layer and / or the second transparent conductive layer, the step further includes: At least one transition layer is electroplated by light-induced electroplating on the first transparent conductive layer and / or the second transparent conductive layer after the pretreatment.

8. The method for preparing a heterojunction solar cell according to claim 7, characterized in that: The material of the transition layer includes nickel, tin, tin-nickel or tin-copper.

9. The method for preparing a heterojunction solar cell according to any one of claims 1 to 4 and 7, characterized in that: The step of electroplating a copper electrode on the pre-treated first transparent conductive layer and / or the second transparent conductive layer comprises: By adjusting the composition of the electroplating solution, the size of the bottom of the copper electrode formed by electroplating is larger than the size of the top; wherein the composition of the electroplating solution includes: 300-900ml CuSO4, 70-300ml H2SO4 (50%), 1ml HCl (50%), 1ml brightener, 1ml leveler, and 0.5-2.5ml inhibitor.

10. The method for preparing a heterojunction solar cell according to any one of claims 1 to 4 and 7, characterized in that: The step of electroplating a copper electrode on the pre-treated first transparent conductive layer and / or the second transparent conductive layer comprises: Horizontal light-induced electroplating of copper electrodes was used.

11. The method for preparing a heterojunction solar cell according to claim 1, characterized in that: After the membrane removal step, the following steps are also included: Chemical tin / silver plating.

12. The method for preparing a heterojunction solar cell according to claim 2, characterized in that: After the step of screen printing to form electrodes on the first transparent conductive layer or the second transparent conductive layer, the step further includes: A protective layer is formed on the first transparent conductive layer or the second transparent conductive layer; wherein the protective layer located on the electrode is discontinuous.

13. A heterojunction solar cell, characterized in that: The heterojunction solar cell is prepared by the method for preparing the heterojunction solar cell according to any one of claims 1 to 12.

Images