Heterojunction battery piece and production equipment thereof

Abstract

The utility model provides a heterojunction battery piece and production equipment thereof, and the heterojunction battery piece comprises an N-type silicon wafer, a first intrinsic amorphous silicon layer which is formed on the front surface of the N-type silicon wafer, an N-type doped microcrystalline silicon layer which is formed on the front surface of the first intrinsic amorphous silicon layer, and a second intrinsic amorphous silicon layer which is formed on the front surface of the N-type doped microcrystalline silicon layer. The N-type doped microcrystalline silicon layer is formed on the back surface of the N-type silicon wafer, the first transparent conductive thin film layer is formed on the front surface of the N-type doped microcrystalline silicon layer, the electrode is formed on the front surface of the first transparent conductive thin film layer, the second intrinsic amorphous silicon layer is formed on the back surface of the N-type silicon wafer, and the P-type doped microcrystalline silicon layer is formed on the back surface of the second intrinsic amorphous silicon layer. The first transparent conductive thin film layer is formed on the back surface of the P-type doped microcrystalline silicon layer, the second transparent conductive thin film layer is formed on the back surface of the P-type doped microcrystalline silicon layer, the third transparent conductive thin film layer is formed on the back surface of the second transparent conductive thin film layer, the copper film layer is formed on the whole back surface of the third transparent conductive thin film layer, and the protective layer is formed on the back surface of the copper film layer.

Description

Technical Field

[0001] This utility model belongs to the field of photovoltaic product technology, specifically relating to a heterojunction solar cell and its production equipment. Background Technology

[0002] This section is intended to provide background or context for the embodiments of the present invention set forth in the claims. The description herein does not constitute an admission that it is prior art simply because it is included in this section.

[0003] With the increasing global demand for clean energy, solar photovoltaic power generation has received widespread attention as an efficient and environmentally friendly energy solution. Among various solar cell technologies, heterojunction (HJT) cells have gradually become one of the research hotspots in the photovoltaic field due to their unique structure and excellent photoelectric conversion performance.

[0004] The structure of a heterojunction solar cell is typically as follows: First, a very thin intrinsic amorphous silicon film (ia-Si:H) and a p-type doped microcrystalline silicon film (pa-Si:H) are deposited on the front side of an N-type monocrystalline silicon wafer (c-Si). Then, a very thin intrinsic amorphous silicon film (ia-Si:H) and an n-type doped microcrystalline silicon film (na-Si:H) are deposited on the back side of the silicon wafer to form a back surface field. Next, transparent conductive oxide (TCO) films are deposited on both sides of the cell using PVD. The TCO can not only reduce the series resistance when collecting current, but also play a role in anti-reflection. Finally, metal electrodes are fabricated on the TCO.

[0005] Although heterojunction solar cells have high photoelectric conversion efficiency, currently reaching over 25.5%, there are still some shortcomings in practical applications that need to be addressed, limiting further improvements in their performance and cost-effectiveness.

[0006] 1. Lacks internal reflective design on the back.

[0007] Most existing heterojunction solar cells employ a double-sided structure design, lacking internal reflection on the back side. When light passes through the cell, unabsorbed light passes directly through without secondary reflection and absorption. This design results in low light utilization, failing to fully exploit the cell's photoelectric conversion potential and thus limiting further improvements in its conversion efficiency.

[0008] 2. High contact resistance between the back metal electrode and the blue film.

[0009] The contact resistance between the back metal electrode and the blue film in a heterojunction solar cell is relatively high. This high contact resistance hinders the transport of charge carriers, leading to increased energy loss and consequently affecting the overall performance of the cell.

[0010] Furthermore, the back electrode of heterojunction solar cells is currently typically made using silver paste. Silver paste is not only expensive, but its preparation also requires complex processes and equipment, which further increases the production cost of the solar cells.

[0011] Against the backdrop of increasingly fierce competition in the global photovoltaic market, companies face enormous cost pressures and a demand for performance improvements. Developing modules with higher conversion efficiency and lower costs has become a key core technology for companies to survive and thrive in the global photovoltaic market. Therefore, addressing the aforementioned shortcomings of existing heterojunction solar cells and developing a heterojunction solar cell structure that can effectively improve light utilization, reduce contact resistance, and lower costs has significant practical implications and broad application prospects. Summary of the Invention

[0012] The purpose of this invention is to provide a heterojunction solar cell with improved photoelectric conversion efficiency and reduced raw material costs, as well as its production equipment.

[0013] To achieve the above objectives, the technical solution adopted by this utility model is as follows:

[0014] This utility model provides a first aspect of a heterojunction solar cell, comprising an N-type silicon wafer, a first intrinsic amorphous silicon layer formed on the front side of the N-type silicon wafer, an N-type doped microcrystalline silicon layer formed on the front side of the first intrinsic amorphous silicon layer, a first transparent conductive thin film layer formed on the front side of the N-type doped microcrystalline silicon layer, an electrode formed on the front side of the first transparent conductive thin film layer, a second intrinsic amorphous silicon layer formed on the back side of the N-type silicon wafer, a P-type doped microcrystalline silicon layer formed on the back side of the second intrinsic amorphous silicon layer, a second transparent conductive thin film layer formed on the back side of the P-type doped microcrystalline silicon layer, a third transparent conductive thin film layer formed on the back side of the second transparent conductive thin film layer, a copper film layer formed on the entire back side of the third transparent conductive thin film layer, and a protective layer formed on the back side of the copper film layer.

[0015] According to some specific embodiments, the first transparent conductive film layer and the second transparent conductive film layer are made of indium tin oxide.

[0016] According to some specific embodiments, the material of the third transparent conductive film layer is aluminum-doped zinc oxide or tin oxide.

[0017] According to some specific embodiments, the heterojunction solar cell further includes a seed layer located between the third transparent conductive thin film layer and the copper film layer.

[0018] Furthermore, the seed layer is made of titanium or nickel.

[0019] Furthermore, the thickness of the seed layer is 5-30 nm.

[0020] According to some specific embodiments, the protective layer is made of tin or silver.

[0021] According to some specific embodiments, the electrode is made of silver or low-temperature silver-coated copper paste.

[0022] According to some specific embodiments, the thickness of the second transparent conductive film layer is 10-50 nm.

[0023] According to some specific embodiments, the thickness of the third transparent conductive film layer is 50-100 nm.

[0024] According to some specific embodiments, the thickness of the copper film layer is 0.5-10 μm.

[0025] According to some specific embodiments, the resistivity of the copper film layer is ≤2.0μΩ·cm.

[0026] According to some specific embodiments, the thickness of the protective layer is 0.1-1 μm.

[0027] According to some specific embodiments, the front side of the N-type silicon wafer is textured, and the roughness of the back side is ≤0.3μm.

[0028] According to some specific embodiments, the thickness of the N-type silicon wafer is 90–120 μm.

[0029] According to some specific implementations, the thicknesses of the first intrinsic amorphous silicon layer and the second intrinsic amorphous silicon layer are independently 5-10 nm.

[0030] According to some specific embodiments, the thickness of the N-type doped microcrystalline silicon layer is 10-25 nm.

[0031] According to some specific embodiments, the thickness of the P-type doped microcrystalline silicon layer is 15-30 nm.

[0032] According to some specific embodiments, the thickness of the first transparent conductive film layer is 70-110 nm.

[0033] According to some specific embodiments, the width of each electrode is 15-30 μm and the height is 5-12 μm.

[0034] The second aspect of this utility model provides a production apparatus for producing heterojunction solar cells as described above, comprising a texturing and cleaning apparatus, an enhanced plasma chemical vapor deposition apparatus, a physical vapor deposition apparatus, a magnetron sputtering apparatus or a thermal evaporation apparatus, an electroplating apparatus or a sputtering apparatus, and a screen printing apparatus connected in sequence.

[0035] According to some specific embodiments, the texturing and cleaning equipment includes a texturing module and an alkaline chemical polishing module.

[0036] Due to the application of the above technical solution, this utility model has the following advantages compared with the prior art:

[0037] The heterojunction solar cell of this invention significantly reduces the transmission resistance on the back of the battery, improves the internal reflection of light absorbed by the battery, thereby improving the battery conversion efficiency and reducing the amount of silver used, thus effectively reducing the cost of raw materials.

[0038] Meanwhile, the production equipment of this utility model only requires the addition of two sets of equipment to the original production line, resulting in minimal changes to the production line. Attached Figure Description

[0039] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0040] Figure 1 This is a cross-sectional schematic diagram of the heterojunction solar cell of this utility model. Detailed Implementation

[0041] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the present invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0042] In the description of this utility model, it should be understood that the front side refers to the side of the solar cell facing the sun, and the back side refers to the side of the solar cell facing away from the sun, that is, the side opposite to the front side; wherein, the attached... Figure 1 The top is the front, and the bottom is the back. The above description of directional terms is only for the convenience of describing the embodiments of this utility model and simplifying the description, and is not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the embodiments of this utility model.

[0043] In the description of this utility model, unless otherwise explicitly specified and limited, the terms "connected," "fixed," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this utility model according to the specific circumstances.

[0044] Unless otherwise specified, all components of this invention can be manufactured using materials conventionally used in the field. All raw materials used in this invention are existing materials and can be provided by suppliers.

[0045] The embodiments of this utility model will now be described in detail with reference to the accompanying drawings.

[0046] Prior to this application, heterojunction solar cells all featured a bifacial structure design with no internal reflection on the back side, meaning light passing through the cell was not subject to secondary reflection or absorption. The high contact resistance between the back metal electrode and the blue film (i.e., the transparent conductive film) negatively impacted carrier transport efficiency. Using silver paste to fabricate the electrodes was also costly.

[0047] To address this, this application designs a novel heterojunction solar cell structure that eliminates the back-side metal grid design, replacing it with a full-surface copper metal film to collect current. The full-surface copper metal film layer on the back enhances internal light reflection, thereby improving the utilization rate of incident light and thus increasing the efficiency of the heterojunction solar cell. Furthermore, the elimination of the silver paste-prepared metal electrodes on the back reduces the manufacturing cost of the heterojunction solar cell. The full-surface copper film layer on the back provides better overall conductivity, reducing transmission resistance and improving cell efficiency. Simultaneously, a tin-plated or silver-plated protective layer on the back protects the copper film from oxidation and reduces the contact resistance between the cell and the solder wire during module fabrication, thereby reducing current transmission loss and increasing the power output of the solar module.

[0048] Furthermore, the textured surface on the back of the battery is polished and the surface roughness is controlled to be ≤0.3μm to improve the passivation effect of the intrinsic amorphous silicon & microcrystalline silicon layer.

[0049] The heterojunction solar cell of this application has higher conversion efficiency and lower cost, which can meet the market's increasingly urgent demand for high-efficiency, high-power products.

[0050] Backside polishing refers to the polishing of the backside surface after texturing during the solar cell manufacturing process to remove the pyramid-shaped light-limiting effect and obtain a smoother backside structure.

[0051] Specifically, the structure of the heterojunction solar cell in this application is as follows: Figure 1As shown, it includes an N-type silicon wafer 1, a first intrinsic amorphous silicon layer 2 formed on the front side of the N-type silicon wafer 1, an N-type doped microcrystalline silicon layer 3 formed on the front side of the first intrinsic amorphous silicon layer 2, a first transparent conductive thin film layer 4 formed on the front side of the N-type doped microcrystalline silicon layer 3, an electrode 5 formed on the front side of the first transparent conductive thin film layer 4, a second intrinsic amorphous silicon layer 6 formed on the back side of the N-type silicon wafer 1, a P-type doped microcrystalline silicon layer 7 formed on the back side of the second intrinsic amorphous silicon layer 6, a second transparent conductive thin film layer 8 formed on the back side of the P-type doped microcrystalline silicon layer 7, a third transparent conductive thin film layer 9 formed on the back side of the second transparent conductive thin film layer 8, a copper film layer 11 formed on the entire back side of the third transparent conductive thin film layer 9, and a protective layer 12 formed on the back side of the copper film layer 11.

[0052] According to some specific embodiments, the first transparent conductive film layer 4 and the second transparent conductive film layer 8 are made of indium tin oxide.

[0053] According to some specific embodiments, the material of the third transparent conductive thin film layer 9 is aluminum-doped zinc oxide or tin oxide.

[0054] According to some specific embodiments, the heterojunction solar cell further includes a seed layer 10 located between the third transparent conductive thin film layer 9 and the copper film layer 11. According to other embodiments, the heterojunction solar cell does not require a seed layer.

[0055] Furthermore, the seed layer 10 is made of titanium or nickel.

[0056] Furthermore, the thickness of the seed layer 10 is 5-30 nm.

[0057] According to some specific embodiments, the protective layer is made of tin or silver. Furthermore, the protective layer is made of tin, which helps to reduce the production cost of the product.

[0058] According to some specific embodiments, the electrode 5 is made of silver or low-temperature silver-coated copper paste.

[0059] According to some specific embodiments, the thickness of the N-type silicon wafer 1 is 90-120 μm.

[0060] According to some specific embodiments, the thicknesses of the first intrinsic amorphous silicon layer 2 and the second intrinsic amorphous silicon layer 6 are independently 5-10 nm.

[0061] According to some specific embodiments, the thickness of the N-type doped microcrystalline silicon layer 3 is 10-25 nm.

[0062] According to some specific embodiments, the thickness of the P-type doped microcrystalline silicon layer 7 is 15-30 nm.

[0063] According to some specific embodiments, the thickness of the first transparent conductive thin film layer 4 is 70-110 nm.

[0064] According to some specific embodiments, the width of each electrode 5 is 15-30 μm and the height is 5-12 μm.

[0065] According to some specific embodiments, the thickness of the second transparent conductive thin film layer 4 is 10-50 nm.

[0066] According to some specific embodiments, the thickness of the third transparent conductive thin film layer 8 is 50-100 nm.

[0067] According to some specific embodiments, the thickness of the copper film layer 11 is 0.5-10 μm.

[0068] According to some specific embodiments, the resistivity of the copper film layer 11 is ≤2.0μΩ·cm.

[0069] According to some specific embodiments, the thickness of the protective layer 12 is 0.1-1 μm.

[0070] According to some specific embodiments, the front side of the N-type silicon wafer 1 is textured, and the roughness of the back side is ≤0.3μm.

[0071] The thickness of each layer in this application is the average thickness. The layers in the accompanying drawings are only illustrative and do not represent the actual structure of the product.

[0072] This application uses a gridless heterojunction cell with a full-surface metal film conductive design on the back side, which significantly reduces the transmission resistance on the back side of the cell, increases the number of metal film layers on the back side, improves the internal reflection of light absorbed by the cell, and improves the cell conversion efficiency.

[0073] The method for preparing the heterojunction solar cell of this application includes the following steps:

[0074] 1) Obtain a qualified N-type silicon wafer 1 for heterojunction solar cells, complete double-sided texturing of N-type silicon wafer 1 using heterojunction solar cell technology, then perform alkaline chemical polishing on the back side of the silicon wafer until the surface roughness is reduced to ≤0.3μm, and then clean the silicon wafer.

[0075] 2) Perform the PECVD process using PECVD (enhanced plasma chemical vapor deposition) to deposit a 5-10 nm first intrinsic amorphous silicon layer 2 and a 10-25 nm N-type doped microcrystalline silicon layer 3 on the front side, and a 5-10 nm second intrinsic amorphous silicon layer 6 and a 15-30 nm P-type doped microcrystalline silicon layer 7 on the back side. The doping sources for the N-type doped microcrystalline silicon layer 3 and the P-type doped microcrystalline silicon layer 7 are process gases PH3 and B2H6, respectively, and the deposition temperature is 180-250℃.

[0076] 3) A first transparent conductive thin film layer 4 (ITO, indium tin oxide) of 70-110 nm is deposited on the front side using PVD (physical vapor deposition); then a second transparent conductive thin film layer 8 (ITO, indium tin oxide) of 10-50 nm is deposited on the back side to contact the microcrystalline silicon, and then a third transparent conductive thin film layer 9 (AZO, aluminum-doped zinc oxide) of 50-100 nm is fabricated to form a composite film with ITO, thereby reducing the amount of indium used.

[0077] 4) After the composite film is fabricated, a 5-30nm metallic titanium layer is fabricated by magnetron sputtering or thermal evaporation, and annealed to form an ohmic contact, which serves as the seed layer 10 for electroplating / sputtering copper film layer 11.

[0078] 5) After completing the seed layer 10, a copper film layer 11 is fabricated on the entire back side using electroplating or sputtering, achieving a copper thickness of 0.5-10 μm and a resistivity ≤2.0 μΩ·cm to ensure conductivity across the entire back side and enable back reflection of light. Then, a layer of tin (0.1-1 μm thick) is electroplated or sputtered onto the copper film layer 11 as a protective layer 12 to prevent oxidation and improve the contact between the module's solder wires and the cells.

[0079] 6) After the above fabrication is completed, a metal electrode 5 is fabricated on the front side of the blue film (i.e., the first transparent conductive film layer 4) using silver or silver-coated copper low-temperature paste screen printing. The width of the metal electrode 5 is 15-30μm and the height is 5-12μm. Then, it is cured (190-230℃, 5-20min) and light injected, and then tested and sorted.

[0080] The specific methods and parameters, such as texturing, alkaline chemical polishing, PECVD, PVD, magnetron sputtering, thermal evaporation, electroplating, sputtering, and screen printing, shall be carried out in accordance with conventional methods in the field, as long as they can achieve the corresponding purpose of this application.

[0081] The equipment for preparing the above-mentioned heterojunction solar cell can be based on the existing heterojunction solar cell production line by adding magnetron sputtering equipment or thermal evaporation equipment to deposit a metal (titanium, nickel) thin film seed layer 10 on the back of the silicon wafer, and adding electroplating equipment or sputtering equipment to complete the preparation of copper film to the μm level, while forming a layer of tin to protect the copper film from oxidation.

[0082] Specifically, the production equipment for producing heterojunction solar cells includes texturing and cleaning equipment, enhanced plasma chemical vapor deposition equipment, physical vapor deposition equipment, magnetron sputtering equipment or thermal evaporation equipment, electroplating equipment or sputtering equipment, and screen printing equipment connected in sequence.

[0083] The texturing and cleaning equipment includes a texturing module and an alkaline chemical polishing module to adapt to silicon wafer texturing and the polishing treatment of the back side of the silicon wafer after texturing.

[0084] The heterojunction solar cell structure of this application achieves a conversion efficiency of over 25.8% and a module power of over 720W. Compared to heterojunction solar cells that use silver paste to fabricate electrodes on the back of the second transparent conductive film, the conversion efficiency is improved by 0.3%, the module power is increased by over 5W, the cost of metal electrode raw materials is reduced by 30%, and the total cost is reduced by 10%.

[0085] The above are merely preferred embodiments of this utility model and are not intended to limit the scope of this utility model. Various modifications and variations can be made to this utility model by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. A heterojunction solar cell, characterized in that: The device includes an N-type silicon wafer, a first intrinsic amorphous silicon layer formed on the front side of the N-type silicon wafer, an N-type doped microcrystalline silicon layer formed on the front side of the first intrinsic amorphous silicon layer, a first transparent conductive thin film layer formed on the front side of the N-type doped microcrystalline silicon layer, an electrode formed on the front side of the first transparent conductive thin film layer, a second intrinsic amorphous silicon layer formed on the back side of the N-type silicon wafer, a P-type doped microcrystalline silicon layer formed on the back side of the second intrinsic amorphous silicon layer, a second transparent conductive thin film layer formed on the back side of the P-type doped microcrystalline silicon layer, a third transparent conductive thin film layer formed on the back side of the second transparent conductive thin film layer, a copper film layer formed on the entire back side of the third transparent conductive thin film layer, and a protective layer formed on the back side of the copper film layer.

2. The heterojunction solar cell according to claim 1, characterized in that: The first and second transparent conductive film layers are made of indium tin oxide, and the third transparent conductive film layer is made of aluminum-doped zinc oxide or tin oxide.

3. The heterojunction solar cell according to claim 1, characterized in that: The heterojunction solar cell further includes a seed layer located between the third transparent conductive thin film layer and the copper film layer, wherein the seed layer is made of titanium or nickel and has a thickness of 5-30 nm. The protective layer is made of tin or silver.

4. The heterojunction solar cell according to claim 1, characterized in that: The electrode is made of silver or low-temperature silver-coated copper paste.

5. The heterojunction solar cell according to any one of claims 1 to 3, characterized in that: The thickness of the second transparent conductive film layer is 10-50 nm; The thickness of the third transparent conductive film layer is 50-100 nm.

6. The heterojunction solar cell according to any one of claims 1 to 3, characterized in that: The thickness of the copper film layer is 0.5-10 μm; and / or the resistivity of the copper film layer is ≤2.0 μΩ·cm; The thickness of the protective layer is 0.1-1 μm.

7. The heterojunction solar cell according to any one of claims 1 to 3, characterized in that: The front side of the N-type silicon wafer is textured, and the roughness of the back side is ≤0.3μm.

8. The heterojunction solar cell according to any one of claims 1 to 3, characterized in that: The thickness of the N-type silicon wafer is 90–120 μm; The thicknesses of the first intrinsic amorphous silicon layer and the second intrinsic amorphous silicon layer are independently 5-10 nm; and / or, The thickness of the N-type doped microcrystalline silicon layer is 10-25 nm; and / or, The thickness of the P-type doped microcrystalline silicon layer is 15-30 nm; and / or, The thickness of the first transparent conductive film layer is 70-110 nm; and / or, Each electrode has a width of 15-30 μm and a height of 5-12 μm.

9. A production apparatus for producing heterojunction solar cells as described in any one of claims 1 to 8, characterized in that: It includes a texturing and cleaning device, an enhanced plasma chemical vapor deposition device, a physical vapor deposition device, a magnetron sputtering device or a thermal evaporation device, an electroplating device or a sputtering device, and a screen printing device connected in sequence.

10. The production equipment according to claim 9, characterized in that: The texturing and cleaning equipment includes a texturing module and an alkaline chemical polishing module.

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