A solar cell and a manufacturing method thereof, and a photovoltaic module

Abstract

The present application discloses a solar cell and a manufacturing method thereof, and a photovoltaic module. The method comprises obtaining a silicon substrate with a passivation layer and an anti-reflection layer stacked in sequence on the front side; opening a hole in the area of ​​the passivation layer and the anti-reflection layer corresponding to the positive electrode; the depth of the opening is equal to the sum of the thickness of the passivation layer and the anti-reflection layer; depositing aluminum in the opening area by electroplating to form an aluminum electrode to obtain a battery structure; annealing the battery structure, so that the aluminum electrode and the silicon substrate undergo a eutectic reaction, and an aluminum heavily doped area is formed in the area of ​​the silicon substrate corresponding to the aluminum electrode; preparing a passivation contact structure and a back electrode on the back side of the silicon substrate to obtain a solar cell. The present application deposits aluminum in the opening area by electroplating, and the silicon substrate is locally heavily doped by the eutectic reaction between aluminum and silicon during annealing. It does not require a complex mask process, high-temperature diffusion, or high-precision alignment, and the preparation process is simple, and does not affect the body minority carrier lifetime of the silicon substrate; the aluminum electrode has a narrow width, which reduces the light shielding area on the front side of the silicon substrate.

Description

Technical Field

[0001] The present application relates to the field of photovoltaic technology, and in particular to a solar cell and a manufacturing method thereof, and a photovoltaic module. Background Art

[0002] A solar cell is a device that directly converts solar energy into electrical energy through the photoelectric effect, which can effectively alleviate the energy crisis caused by non-renewable energy sources such as natural gas, coal, and oil.

[0003] Improving the photoelectric conversion efficiency of solar cells has always been the goal pursued by the photovoltaic industry. At present, a back crystalline silicon cell based on P-type silicon wafers and passivated contact structure has a conversion efficiency of 26%. This cell heavily dopes the silicon substrate with boron in the area where it contacts the front electrode, so that there is good ohmic contact between the front electrode and the silicon substrate, improving the photoelectric conversion efficiency of the cell. When performing local heavy doping, a complex mask process is required, and the screen-printed metal grid lines need to be aligned with the local heavy doping area with high precision, which further increases the difficulty of the process and makes it difficult to mass produce the cell. At the same time, the screen-printed metal grid lines are wide, resulting in a large shading area, which makes the solar cell absorb less light. In addition, the high temperature during boron diffusion will affect the body minority carrier lifetime of the P-type silicon wafer, thereby affecting the conversion efficiency of the cell.

[0004] Therefore, how to solve the above technical problems should be the focus of technical personnel in this field. Summary of the invention

[0005] The purpose of the present application is to provide a solar cell and a method for manufacturing the same, as well as a photovoltaic module, so as to simplify the process of front electrode metallization during the manufacturing process of the solar cell and improve the conversion efficiency of the solar cell.

[0006] In order to solve the above technical problems, the present application provides a method for manufacturing a solar cell, comprising:

[0007] A silicon substrate having a passivation layer and an anti-reflection layer sequentially stacked on the front side is obtained;

[0008] Opening holes in the passivation layer and the anti-reflection layer in areas corresponding to the positive electrode; wherein the depth of the opening is equal to the sum of the thicknesses of the passivation layer and the anti-reflection layer;

[0009] Aluminum is deposited in the opening area by electroplating to form an aluminum electrode, thereby obtaining a battery structure;

[0010] Annealing the battery structure so that the aluminum electrode and the silicon substrate undergo a eutectic reaction and an aluminum heavily doped region is formed in a region of the silicon substrate corresponding to the aluminum electrode;

[0011] A passivation contact structure and a back electrode are prepared on the back side of the silicon substrate to obtain a solar cell.

[0012] Optionally, the step of opening holes in the passivation layer and the anti-reflection layer in regions corresponding to the positive electrode includes:

[0013] A laser drilling method is used to drill holes in the passivation layer and the anti-reflection layer in the region corresponding to the positive electrode.

[0014] Optionally, after the laser drilling method is used to drill holes in the passivation layer and the anti-reflection layer in the region corresponding to the positive electrode, the method further includes:

[0015] Removing laser damage in the area corresponding to the opening on the surface of the silicon substrate;

[0016] The silicon oxide in the area corresponding to the opening on the surface of the silicon substrate is removed, wherein the silicon oxide is formed when the laser damage is removed.

[0017] Optionally, before obtaining the silicon substrate having a passivation layer and an anti-reflection layer sequentially stacked on the front side, the method further comprises:

[0018] The silicon substrate is textured.

[0019] Optionally, the passivation contact structure fabrication process includes:

[0020] forming a tunneling oxide layer on the back side of the silicon substrate;

[0021] forming an intrinsic polysilicon layer on the lower surface of the tunnel oxide layer;

[0022] The intrinsic polysilicon layer is subjected to diffusion treatment to form a doped polysilicon layer.

[0023] Optionally, after depositing aluminum in the opening area by electroplating to form an aluminum electrode, the method further comprises:

[0024] A metal layer is formed on the upper surface of the aluminum electrode, wherein the electrical conductivity of the metal layer is higher than the electrical conductivity of the aluminum electrode.

[0025] Optionally, the metal layer is a stack of metal layers with different electrical conductivities.

[0026] The present application also provides a solar cell manufactured by any of the above-mentioned solar cell manufacturing methods, comprising:

[0027] Silicon substrate;

[0028] A passivation layer and an anti-reflection layer stacked in sequence on the front side of the silicon substrate;

[0029] Aluminum electrode;

[0030] A passivation contact structure and a back electrode are located on the back side of the silicon substrate.

[0031] Optionally, also include:

[0032] The metal layer is located on the upper surface of the aluminum electrode, and the electrical conductivity of the metal layer is higher than the electrical conductivity of the aluminum electrode.

[0033] The present application also provides a photovoltaic module, which includes any one of the solar cells described above.

[0034] The present application provides a method for manufacturing a solar cell, comprising: obtaining a silicon substrate with a passivation layer and an anti-reflection layer stacked in sequence on the front side; making holes in the passivation layer and the anti-reflection layer in the region corresponding to the positive electrode; wherein the hole depth is equal to the sum of the thicknesses of the passivation layer and the anti-reflection layer; using an electroplating method to deposit aluminum in the hole region to form an aluminum electrode, thereby obtaining a battery structure; performing an annealing treatment on the battery structure, causing a eutectic reaction between the aluminum electrode and the silicon substrate, thereby forming an aluminum heavily doped region in the region of the silicon substrate corresponding to the aluminum electrode; and preparing a passivation contact structure and a back electrode on the back side of the silicon substrate, thereby obtaining a solar cell.

[0035] It can be seen that after the solar cell manufacturing method in the present application opens holes in the passivation layer and the anti-reflection layer on the front side of the silicon substrate, aluminum is deposited in the opening area by electroplating, and then the silicon substrate corresponding to the opening area is locally heavily doped by eutectic reaction between aluminum and silicon during annealing. Even if the area of ​​the silicon substrate corresponding to the aluminum electrode becomes an aluminum heavily doped area, ohmic contact of the front electrode is achieved. No complicated mask process, high-temperature diffusion, or high-precision alignment is required, and the preparation process is very simple and will not affect the bulk minority carrier lifetime of the silicon substrate. In addition, the aluminum deposited by electroplating in the present application is only in the opening area, and the width of the aluminum electrode is smaller than the electrode width during screen printing, which reduces the shading area on the front side of the silicon substrate and improves the light absorption efficiency of the solar cell.

[0036] In addition, the present application also provides a solar cell and a photovoltaic module having the above advantages. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the embodiments of the present application or the technical solutions of the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0038] Figure 1 A flow chart of a method for manufacturing a solar cell provided in an embodiment of the present application;

[0039] Figures 2 to 7 A process flow chart of a method for manufacturing a solar cell provided in an embodiment of the present application. DETAILED DESCRIPTION

[0040] In order to enable those skilled in the art to better understand the present application, the present application is further described in detail below in conjunction with the accompanying drawings and specific implementation methods. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present application.

[0041] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0042] As described in the background technology section, in the current production of back crystalline silicon cells with passivated contact structures, a complex mask process is required to heavily dope the silicon substrate with boron in the area where it contacts the front electrode, and the screen-printed metal grid lines need to be aligned with the local heavily doped areas with high precision, which further increases the difficulty of the process and makes it difficult to mass produce the cells. At the same time, the screen-printed metal grid lines are wide, resulting in a large shading area, which makes the solar cell absorb less light. In addition, the high temperature during boron diffusion will affect the body minority carrier lifetime of the P-type silicon wafer, thereby affecting the conversion efficiency of the cell.

[0043] In view of this, the present application provides a method for manufacturing a solar cell, please refer to Figure 1 , Figure 1 A flow chart of a method for manufacturing a solar cell provided in an embodiment of the present application includes:

[0044] Step S101: obtaining a silicon substrate having a passivation layer and an anti-reflection layer sequentially stacked on the front side.

[0045] Step S102: drilling holes in the passivation layer and the anti-reflection layer in the region corresponding to the positive electrode; wherein the depth of the holes is equal to the sum of the thicknesses of the passivation layer and the anti-reflection layer.

[0046] Optionally, as an implementable embodiment, the opening of holes in the passivation layer and the anti-reflection layer corresponding to the positive electrode region includes: opening holes in the passivation layer and the anti-reflection layer corresponding to the positive electrode region by laser opening. The laser opening method is simple to operate. However, the opening method is not specifically limited in the present application. As another implementable embodiment, the opening of holes in the passivation layer and the anti-reflection layer corresponding to the positive electrode region may also be performed by etching.

[0047] When a laser hole-making method is used to make holes, the laser may damage the surface of the silicon substrate and affect the performance of the solar cell. Therefore, in order to avoid adverse effects on the performance of the solar cell, after the laser hole-making method is used to make holes in the areas of the passivation layer and the anti-reflection layer corresponding to the positive electrode, the method further includes:

[0048] Removing laser damage in the area corresponding to the opening on the surface of the silicon substrate;

[0049] The silicon oxide in the area corresponding to the opening on the surface of the silicon substrate is removed, wherein the silicon oxide is formed when the laser damage is removed.

[0050] Laser damage can be removed by using alkaline solutions, including but not limited to potassium hydroxide solutions and sodium hydroxide solutions.

[0051] The silicon oxide formed in the opening area corresponding to the silicon substrate surface is formed when the alkaline solution removes the laser damage in the opening area corresponding to the silicon substrate surface. The silicon oxide needs to be removed, and hydrofluoric acid can be used to remove the silicon oxide.

[0052] Step S103: Aluminum is deposited in the opening area by electroplating to form an aluminum electrode, thereby obtaining a battery structure.

[0053] The aluminum electrode is the front electrode of the solar cell.

[0054] It should be noted that the electroplating solution for aluminum deposition is an ionic liquid, and aqueous solution cannot be used. After electroplating, the ionic liquid on the surface of the battery structure needs to be cleaned with methanol or ethanol.

[0055] It should be emphasized that in this step, aluminum is deposited by electroplating to form an aluminum electrode. The aluminum electrode is only deposited in the opening area, and the aluminum electrode will not be deposited in other areas of the battery surface. The width of the aluminum electrode formed by the electroplating method is smaller than the width of the electrode formed by screen printing, which reduces the shading area of ​​the battery and improves the conversion efficiency of the battery.

[0056] Step S104: performing annealing treatment on the battery structure, causing a eutectic reaction between the aluminum electrode and the silicon substrate, and forming an aluminum heavily doped region in a region of the silicon substrate corresponding to the aluminum electrode.

[0057] The aluminum doping concentration is 10 18 cm -3 The above region is called the heavily doped region.

[0058] Step S105: preparing a passivation contact structure and a back electrode on the back side of the silicon substrate to obtain a solar cell.

[0059] The manufacturing process of the passivation contact structure includes:

[0060] forming a tunneling oxide layer on the back side of the silicon substrate;

[0061] forming an intrinsic polysilicon layer on the lower surface of the tunnel oxide layer;

[0062] The intrinsic polysilicon layer is subjected to diffusion treatment to form a doped polysilicon layer.

[0063] It should be pointed out that the method for forming the doped polysilicon layer is not specifically limited in the present application, and the intrinsic polysilicon can also be doped by ion implantation to form the doped polysilicon layer.

[0064] The solar cell manufacturing method in the present application opens holes in the passivation layer and the anti-reflection layer on the front side of the silicon substrate, and then deposits aluminum in the opening area by electroplating. Then, the aluminum and silicon undergo a eutectic reaction during annealing to locally heavily dope the silicon substrate corresponding to the opening area. Even if the area of ​​the silicon substrate corresponding to the aluminum electrode becomes an aluminum heavily doped area, ohmic contact of the front electrode is achieved. No complicated mask process, high-temperature diffusion, or high-precision alignment is required, and the preparation process is very simple and will not affect the bulk minority carrier lifetime of the silicon substrate. In addition, the aluminum deposited by electroplating in the present application is only in the opening area, and the width of the aluminum electrode is smaller than the electrode width during screen printing, which reduces the shading area on the front side of the silicon substrate and improves the light absorption efficiency of the solar cell.

[0065] On the basis of the above embodiments, in one embodiment of the present application, the solar cell manufacturing method further comprises, before obtaining a silicon substrate having a passivation layer and an anti-reflection layer sequentially stacked on the front side:

[0066] The silicon substrate is textured.

[0067] Texturing forms a velvet light-trapping structure on the surface of the silicon substrate, which increases the solar cell's absorption of light and improves the efficiency of the solar cell.

[0068] Based on any of the above embodiments, in one embodiment of the present application, after the aluminum electrode is formed by depositing aluminum in the opening area by electroplating, the method further includes:

[0069] A metal layer is formed on the upper surface of the aluminum electrode, wherein the electrical conductivity of the metal layer is higher than the electrical conductivity of the aluminum electrode.

[0070] The metal layer is also deposited by electroplating, and the electrolyte is an aqueous solution.

[0071] It should be pointed out that an oxidation reaction may occur on the upper surface of the aluminum electrode to form aluminum oxide. Before preparing the metal layer, the aluminum oxide needs to be removed. A hydrochloric acid solution can be used to remove the aluminum oxide.

[0072] The material of the metal layer is not specifically limited in the present application, as long as the electrical conductivity is higher than that of aluminum. For example, the metal layer can be copper or silver.

[0073] Forming a metal layer with higher conductivity on the upper surface of the aluminum electrode can reduce the line resistance of the front electrode grid line, making the line resistance lower than the line resistance of the screen-printed front electrode, thereby reducing the battery series resistance.

[0074] Preferably, the metal layer is a stack of metal layers with different electrical conductivities. The electrical conductivity of any of the stacked metal layers with different electrical conductivities is greater than the electrical conductivity of aluminum. For example, the metal layer can be a stack of copper layers and silver layers, or a stack of other metal layers.

[0075] The metal layer is a stacked metal layer with different conductivity, which can further reduce the battery series resistance.

[0076] The following uses a P-type silicon wafer as an example to illustrate the method for manufacturing a solar cell in the present application.

[0077] Step 1: deposit a passivation layer 2 and an anti-reflection layer 3 on the front side of a P-type silicon wafer 1 in sequence. Figure 2 As shown;

[0078] Step 2: Use laser to open holes in the passivation layer 2 and the anti-reflection layer 3 to expose the P-type silicon wafer 1, and use hydrofluoric acid solution to clean the surface of the exposed P-type silicon wafer 1, use alkaline solution to remove laser damage on the exposed silicon surface, and use hydrofluoric acid solution to remove silicon oxide on the exposed silicon surface. Figure 3 As shown;

[0079] Step 3: Deposit aluminum electrode 4 on the exposed silicon surface by electroplating, the electroplating solution is ionic liquid; after electroplating, clean the ionic liquid on the sample surface with methanol or ethanol, and obtain a battery structure such as Figure 4 As shown;

[0080] Step 4: Use a sintering furnace to quickly anneal the battery structure, so that aluminum and silicon react eutectically to form a partially aluminum-heavy doped silicon 11 below the aluminum electrode 4. Figure 5 As shown;

[0081] Step 5: After cleaning the aluminum oxide on the surface of the aluminum electrode 4 with a hydrochloric acid solution, a copper metal layer 5 with higher conductivity is deposited on the aluminum electrode 4 by electroplating. The electrolyte is an aqueous solution, such as Figure 6 As shown;

[0082] Step 6: Prepare a tunneling oxide layer 6, a doped polysilicon layer 7 and a back electrode 8 on the back of the P-type silicon wafer 1 to obtain a solar cell. Figure 7 shown.

[0083] The present application also provides a solar cell manufactured by the solar cell manufacturing method described in any of the above embodiments, comprising:

[0084] Silicon substrate;

[0085] A passivation layer and an anti-reflection layer stacked in sequence on the front side of the silicon substrate;

[0086] Aluminum electrode;

[0087] A passivation contact structure and a back electrode are located on the back side of the silicon substrate.

[0088] The silicon substrate in this application is a P-type silicon wafer.

[0089] The passivation layer may be an aluminum oxide layer, and the anti-reflection layer may be a silicon nitride layer or a silicon oxynitride layer; the passivation contact structure includes a tunneling oxide layer and a doped polysilicon layer, the tunneling oxide layer is a silicon oxide layer, and the doped polysilicon layer is an N-type doped polysilicon layer.

[0090] On the basis of the above embodiments, in one embodiment of the present application, the solar cell further comprises:

[0091] The metal layer is located on the upper surface of the aluminum electrode, and the electrical conductivity of the metal layer is higher than the electrical conductivity of the aluminum electrode.

[0092] Forming a metal layer with higher conductivity on the upper surface of the aluminum electrode can reduce the line resistance of the front electrode grid line, making the line resistance lower than the line resistance of the screen-printed front electrode, thereby reducing the battery series resistance.

[0093] The metal layer may be a single metal layer, or the metal layer may be stacked metal layers with different electrical conductivities, which is not specifically limited in the present application.

[0094] The present application also provides a photovoltaic module, which includes the solar cell described in any one of the above embodiments.

[0095] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0096] The solar cell and its manufacturing method and photovoltaic module provided by the present application are introduced in detail above. Specific examples are used in this article to illustrate the principle and implementation method of the present application. The description of the above embodiment is only used to help understand the method and its core idea of ​​the present application. It should be pointed out that for ordinary technicians in this technical field, without departing from the principle of the present application, several improvements and modifications can be made to the present application, and these improvements and modifications also fall within the scope of protection of the claims of the present application.

Claims

1. A method for manufacturing a solar cell, characterized in that: include: A silicon substrate having a passivation layer and an anti-reflection layer sequentially stacked on the front side is obtained; Opening holes in the passivation layer and the anti-reflection layer in areas corresponding to the positive electrode; wherein the depth of the opening is equal to the sum of the thicknesses of the passivation layer and the anti-reflection layer; Aluminum is deposited in the opening area by electroplating to form an aluminum electrode, thereby obtaining a battery structure; the aluminum electrode is only deposited in the opening area, and the aluminum electrode is not deposited in other areas of the battery surface. The width of the aluminum electrode formed by the electroplating method is smaller than the width of the electrode formed by the screen printing method; The battery structure is annealed, the aluminum electrode and the silicon substrate undergo a eutectic reaction, and an aluminum heavily doped region is formed in the silicon substrate corresponding to the aluminum electrode; the aluminum doping concentration is 10 18 cm -3 When it is on, it is called the heavily doped region; Prepare a passivation contact structure and a back electrode on the back side of the silicon substrate to obtain a solar cell; After the aluminum is deposited in the opening area by electroplating to form an aluminum electrode, the method further includes: A metal layer is formed on the upper surface of the aluminum electrode, wherein the electrical conductivity of the metal layer is higher than the electrical conductivity of the aluminum electrode; the metal layer is a stacked metal layer with different electrical conductivities; the electrical conductivity of any layer of the stacked metal layers with different electrical conductivities is greater than the electrical conductivity of aluminum, and the metal layer is a stacked copper layer and a silver layer.

2. The method for manufacturing a solar cell according to claim 1, wherein: The step of opening holes in the passivation layer and the anti-reflection layer in the region corresponding to the positive electrode comprises: A laser drilling method is used to drill holes in the passivation layer and the anti-reflection layer in the region corresponding to the positive electrode.

3. The method for manufacturing a solar cell according to claim 2, wherein: After the laser drilling method is used to drill holes in the passivation layer and the anti-reflection layer in the region corresponding to the positive electrode, the method further includes: Removing laser damage in the area corresponding to the opening on the surface of the silicon substrate; The silicon oxide in the area corresponding to the opening on the surface of the silicon substrate is removed, wherein the silicon oxide is formed when the laser damage is removed.

4. The method for manufacturing a solar cell according to claim 1, wherein: Before obtaining the silicon substrate having a passivation layer and an anti-reflection layer sequentially stacked on the front side, the method further comprises: The silicon substrate is textured.

5. The method for manufacturing a solar cell according to claim 1, wherein: The fabrication process of the passivation contact structure includes: forming a tunneling oxide layer on the back side of the silicon substrate; forming an intrinsic polysilicon layer on the lower surface of the tunnel oxide layer; The intrinsic polysilicon layer is subjected to diffusion treatment to form a doped polysilicon layer.

6. A solar cell manufactured by the solar cell manufacturing method according to any one of claims 1 to 5, characterized in that: include: Silicon substrate; A passivation layer and an anti-reflection layer stacked in sequence on the front side of the silicon substrate; Aluminum electrode; A passivation contact structure and a back electrode are located on the back side of the silicon substrate.

7. The solar cell according to claim 6, characterized in that Also includes: The metal layer is located on the upper surface of the aluminum electrode, and the electrical conductivity of the metal layer is higher than the electrical conductivity of the aluminum electrode.

8. A photovoltaic module, characterized in that: The photovoltaic module comprises the solar cell according to claim 6 or 7.

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