Electrical connector, photovoltaic module and method for manufacturing a photovoltaic module

Abstract

The application provides an electrical connector, a photovoltaic module and a preparation method of the photovoltaic module. The electrical connector comprises a substrate, at least two parallel solder strips connected to one side surface of the substrate, one end of the solder strip extending beyond the substrate to form a free end or being connected to another surface of the substrate, and a nano-silver wire film arranged on the side of the substrate facing the solder strip. The photovoltaic module comprises a cell string, the cell string comprising a plurality of heterojunction cells connected in series along a first direction and an electrical connector connected to the surface of the heterojunction cells. The electrical connector for electrical connection of the heterojunction cells can improve the current collection and transmission performance of the cell surface, reduce the consumption of silver paste and the material cost, and reduce the light-shielding loss of the metal electrode after the nano-silver wire film contacts the surface of the heterojunction cell. The substrate of the electrical connector can also reduce the risk of abnormal damage of the heterojunction cell in the module process.

Description

Technical Field

[0001] This application relates to the field of photovoltaic production technology, and in particular to an electrical connector, a photovoltaic module, and a method for preparing a photovoltaic module. Background Technology

[0002] With the rapid development of the photovoltaic industry, the domestic and international markets have increasingly higher requirements for the efficiency and performance of solar cells, which has driven many manufacturers to actively conduct research on new cell structures and production processes. Among them, heterojunction (HJT) cells have advantages such as low light decay and low temperature coefficient, which can reduce energy consumption while reducing thermal damage to the silicon substrate, and have become a research hotspot in the industry in recent years.

[0003] In the manufacturing process of photovoltaic modules, different heterojunction cells are first connected in series with solder ribbons of predetermined specifications to form a cell string, and then laminated and encapsulated. The industry has also disclosed heterojunction cell structures without a main grid, using solder ribbon interconnect films to make contact interconnections with the front and back sides of the cells. Although the above solutions save on the use of silver paste and eliminate the need for screen printing and curing, in practical applications, they have higher contact resistance, poorer surface current collection, and the conversion efficiency of the cells and modules is difficult to guarantee.

[0004] Therefore, it is necessary to provide a new electrical connector, a photovoltaic module, and a method for manufacturing a photovoltaic module. Summary of the Invention

[0005] The purpose of this invention is to provide an electrical connector, a photovoltaic module, and a method for preparing a photovoltaic module, which can improve the current collection and transmission performance of the cell surface in the module product, reduce silver paste consumption and material costs, and reduce the risk of shading loss and abnormal damage.

[0006] To achieve the above-mentioned objectives, this application provides an electrical connector for electrical connection of a solar cell. The electrical connector includes a substrate and at least two parallel solder strips connected to one side surface of the substrate. One end of each solder strip extends beyond the substrate to form a free end or is connected to the surface of another substrate. A silver nanowire thin film is also disposed on the side of the substrate facing the solder strips.

[0007] As a further improvement of the embodiments of this application, the thickness of the silver nanowire film is set to 50-500 nm; the sheet resistance of the silver nanowire film is set to 40-100 Ω / sq.

[0008] As a further improvement of the embodiments of this application, the length of the silver nanowires in the silver nanowire film is set to 10-20 μm, and the diameter of the silver nanowires is set to 20-60 nm.

[0009] As a further improvement to the embodiments of this application, the thickness of the substrate is set to 20-200 μm.

[0010] This application also provides a photovoltaic module, including a battery string and a front encapsulation film and a back encapsulation film disposed on both sides of the battery string. The battery string includes a plurality of heterojunction cells connected in series along a first direction and an electrical connector connected to the surface of the heterojunction cells as described above.

[0011] As a further improvement of the embodiments of this application, the photovoltaic module further includes a busbar disposed at the end of the battery string; the electrical connector includes a first electrical connector and a second electrical connector, the first electrical connector includes a substrate, one end of the solder strip extends beyond the substrate and forms a free end, the first electrical connector is used to connect the heterojunction cell at the end of the battery string to the busbar; the second electrical connector includes two substrates, the solder strip includes a first portion disposed on the front side of one of the substrates, a second portion disposed on the back side of the other substrate, and a third portion connecting the first portion and the second portion, the second electrical connector is used to connect two adjacent heterojunction cells.

[0012] As a further improvement of the embodiments of this application, the front side of the heterojunction cell is sequentially stacked with a first intrinsic amorphous silicon layer, a first doped amorphous silicon layer, a first transparent conductive layer, and a front electrode, and the back side of the heterojunction cell is sequentially stacked with a second intrinsic amorphous silicon layer, a second doped amorphous silicon layer, a second transparent conductive layer, and a back electrode; the front electrode includes at least two front main gates extending along a first direction, and the back electrode includes at least two back main gates extending along the first direction, the positions of the front main gates and the back main gates are corresponding, and the number of front main gates and the number of back main gates are consistent with the number of solder strips.

[0013] As a further improvement of the embodiments of this application, the thickness of the first transparent conductive layer and the second transparent conductive layer is set to 50-100 nm, and the sheet resistance of the first transparent conductive layer and the second transparent conductive layer is set to 30-120 Ω / sq.

[0014] As a further improvement of the embodiments of this application, the thickness of the first intrinsic amorphous silicon layer and the second intrinsic amorphous silicon layer is set to 1-10 nm; the thickness of the first doped amorphous silicon layer and the second doped amorphous silicon layer is set to 3-10 nm.

[0015] This application also provides a method for preparing a photovoltaic module, mainly including:

[0016] An electrical connector is fabricated, comprising a first electrical connector and a second electrical connector. The first electrical connector comprises a substrate, a silver nanowire film disposed on one side surface of the substrate, and at least two parallel solder strips, one end of which extends beyond the substrate and forms a free end. The second electrical connector comprises two substrates and at least two parallel solder strips, each solder strip comprising a first portion disposed on the front side of one of the substrates, a second portion disposed on the back side of the other substrate, and a third portion connecting the first portion and the second portion. Both substrates have corresponding silver nanowire films disposed on the side surface facing the solder strips.

[0017] To fabricate a battery string, a first electrical connector is placed on a support platform with the side of the substrate containing the silver nanowire film facing upwards. A heterojunction battery is then placed onto the substrate of the first electrical connector. A substrate of the second electrical connector is placed on the aforementioned heterojunction battery, and another heterojunction battery is placed on another substrate of the second electrical connector. This process is repeated. After placing the last heterojunction battery, another first electrical connector is selected and placed on the last heterojunction battery. Heating is then performed to combine the first electrical connector, the second electrical connector, and the corresponding heterojunction battery.

[0018] The battery string is placed between the front encapsulation film and the back encapsulation film and then laminated.

[0019] As a further improvement of the embodiments of this application, the manufacturing process of the electrical connector includes coating the surface of the substrate with a silver nanowire dispersion, placing at least two solder ribbons at predetermined positions on the surface of the substrate, and then drying; controlling the thickness of the silver nanowire film to be 50-500 nm and the sheet resistance to be 40-100 Ω / sq.

[0020] As a further improvement of the embodiments of this application, the length of the silver nanowires in the silver nanowire film is set to 10-20 μm, and the diameter of the silver nanowires is set to 20-60 nm.

[0021] As a further improvement to the embodiments of this application, the thickness of the substrate is set to 20-200 μm.

[0022] As a further improvement to the embodiments of this application, the fabrication process of the heterojunction solar cell includes texturing the surface of the silicon substrate;

[0023] A first intrinsic amorphous silicon layer, a first doped amorphous silicon layer and a first transparent conductive layer are sequentially fabricated on the front side of a silicon substrate, and a second intrinsic amorphous silicon layer, a second doped amorphous silicon layer and a second transparent conductive layer are sequentially fabricated on the back side of the silicon substrate.

[0024] A predetermined low-temperature silver paste is printed onto the surfaces of the first transparent conductive layer and the second transparent conductive layer using a screen printing method, and then cured to obtain a front electrode and a back electrode. The front electrode includes at least two front main grids extending along a first direction, and the back electrode includes at least two back main grids extending along the first direction. The front main grids and back main grids are used to connect the solder strips on the electrical connector.

[0025] As a further improvement of the embodiments of this application, the first intrinsic amorphous silicon layer, the second intrinsic amorphous silicon layer, the first doped amorphous silicon layer and the second doped amorphous silicon layer are all deposited by PECVD method.

[0026] The thicknesses of the first intrinsic amorphous silicon layer and the second intrinsic amorphous silicon layer are set to 1–10 nm, and the thicknesses of the first doped amorphous silicon layer and the second doped amorphous silicon layer are set to 3–10 nm.

[0027] As a further improvement of the embodiments of this application, both the first transparent conductive layer and the second transparent conductive layer are deposited using the PVD method;

[0028] The thickness of the first transparent conductive layer and the second transparent conductive layer is set to 50-100 nm, and the sheet resistance of the first transparent conductive layer and the second transparent conductive layer is set to 30-120 Ω / sq.

[0029] The beneficial effects of this application are: by using the electrical connector, photovoltaic module and photovoltaic module preparation method of this application, after the nano-silver wire film of the electrical connector comes into contact with the surface of the heterojunction cell, it can improve the current collection and transmission performance of the cell surface, reduce the consumption of silver paste and material cost, and reduce the light loss of the metal electrode; the substrate of the electrical connector can also serve as a protective layer, reducing the risk of abnormal damage to the heterojunction cell during the module manufacturing process. Attached Figure Description

[0030] Figure 1 This is a cross-sectional structural diagram of the electrical connector of this application;

[0031] Figure 2 This is a schematic diagram of the structure of the first electrical connection component in the photovoltaic module of this application;

[0032] Figure 3 This is a schematic diagram of the structure of the second electrical connection in the photovoltaic module of this application;

[0033] Figure 4 This is a schematic diagram of the structure of the photovoltaic module of this application;

[0034] Figure 5 This is a schematic diagram of the heterojunction cell structure in the photovoltaic module of this application;

[0035] Figure 6It is a schematic diagram of the main process steps of the preparation method of the photovoltaic module of the present application.

[0036] 100 - Electrical connection component; 101 - First electrical connection component; 102 - Second electrical connection component; 11 - Substrate; 12 - Nanowire silver film; 13 - Welding tape; 131 - First part; 132 - Second part; 133 - Third part; 200 - Photovoltaic module; 201 - Battery string, 202 - Front encapsulation film; 203 - Back encapsulation film; 21 - Heterojunction cell; 210 - Silicon substrate; 211 - First intrinsic amorphous silicon layer; 212 - Second intrinsic amorphous silicon layer; 213 - First doped amorphous silicon layer; 214 - Second doped amorphous silicon layer; 215 - First transparent conductive layer; 216 - Second transparent conductive layer; 217 - Front electrode; 218 - Back electrode. Detailed implementation manners

[0037] The present invention will be described in detail below in conjunction with the embodiments shown in the drawings. However, this embodiment does not limit the present invention, and any structural, method, or functional transformation made by those of ordinary skill in the art based on this embodiment is included within the protection scope of the present invention.

[0038] Refer Figure 1 As shown, the present application provides an electrical connection component 100 for the electrical connection of solar cells. The electrical connection component includes a substrate 11, a nanowire silver film 12 provided on one side surface of the substrate 11, and at least two parallel welding tapes 13. One end of the welding tape 13 extends beyond the substrate 11 along a first direction to form a free end or is connected to the surface of another substrate 11.

[0039] The substrate 11 can be made of a flexible resin film, usually set in a rectangular or quasi-rectangular shape, and its overall size is preferably not larger than the size of a given solar cell; the substrate 11 can also be set as a two-layer or multi-layer composite film structure, with a thickness set to 20 - 200 μm. The thickness of the nanowire silver film 12 is set to 50 - 500 nm, and the sheet resistance of the nanowire silver film 12 is set to 40 - 100 Ω / sq. Among them, the length of the nanowires in the nanowire silver film 12 is set to 10 - 20 μm, and the diameter of the nanowires is set to 20 - 60 nm. The welding tape 13 can be a flat welding tape, a circular welding tape, or a metal welding tape with other cross-sectional shapes. The welding tape 13 can be regarded as being embedded on the surface of the substrate 11 for welding to the metal electrode on the surface of the solar cell.

[0040] The electrical connection component 100 includes a first electrical connection component 101 ( Figure 2 as shown) and a second electrical connection component 102 ( Figure 3(As shown). The first electrical connector 101 includes a substrate 11, a silver nanowire thin film 12 disposed on one side surface of the substrate 11, and at least two parallel solder ribbons 13 extending beyond the substrate 11. The free ends of the solder ribbons 13 can be connected to a busbar to realize the electrical output of the corresponding solar cell. The second electrical connector 102 includes two substrates 11 and at least two parallel solder ribbons 13. Each solder ribbon 13 includes a first portion 131 disposed on the front side of one of the substrates 11, a second portion 132 disposed on the back side of the other substrate 11, and a third portion 133 connecting the first portion 131 and the second portion 132. Both substrates 11 have a corresponding silver nanowire thin film 12 disposed on the side surface facing the solder ribbons 13. The second electrical connector 102 is used to realize the series connection of two adjacent solar cells. For the second electrical connector 102, the two ends of the solder strip 13 are respectively connected to the two substrates 11; the solder strip 13 extending beyond the substrate 11 means that the solder strip 13 extends beyond either of the substrates 11.

[0041] Combination Figure 4 and Figure 5 As shown, this application also provides a photovoltaic module 200 employing the aforementioned electrical connector 100, including a cell string 201 and a front encapsulating film 202 and a back encapsulating film 203 respectively disposed on both sides of the cell string 201. The cell string 201 includes a plurality of heterojunction cells 21 connected in series along a first direction. The electrical connector 100 is connected to the surface of the corresponding heterojunction cell 21; a busbar (not shown) is also provided at the end of the cell string 201.

[0042] Here, the first electrical connector 101 is used to connect the heterojunction cell 21 at the end of the battery string 201 to the bus bar; the second electrical connector 102 is used to connect two adjacent heterojunction cells 21.

[0043] The heterojunction solar cell 21 includes a silicon substrate 210. The front side of the silicon substrate 210 is sequentially stacked with a first intrinsic amorphous silicon layer 211, a first doped amorphous silicon layer 213, a first transparent conductive layer 215, and a front electrode 217. The back side of the silicon substrate 210 is sequentially stacked with a second intrinsic amorphous silicon layer 212, a second doped amorphous silicon layer 214, a second transparent conductive layer 216, and a back electrode 218.

[0044] The silicon substrate 210 is configured as an N-type or P-type crystalline silicon wafer, with a thickness of 50–300 μm and a resistivity of 0.5–3.5 Ω·cm, preferably 2–3 Ω·cm. The first doped amorphous silicon layer 213 and the second doped amorphous silicon layer 214 have opposite doping types. Here, the first doped amorphous silicon layer 213 is disposed on the front side (light-receiving surface) of the silicon substrate 210, and the second doped amorphous silicon layer 214 is disposed on the back side (backlight-receiving surface) of the silicon substrate 210. For example, the silicon substrate 210 is an N-type single-crystal silicon wafer, the first doped amorphous silicon layer 213 is a P-type doped layer, typically a boron doped layer; and the second doped amorphous silicon layer 214 is an N-type doped layer, typically a phosphorus doped layer. It should also be noted that the “front” and “back” of the aforementioned substrate 11 are descriptions relative to the connection arrangement of the heterojunction cell 21. The front of the substrate 11 is connected to the back of the heterojunction cell 21, and the back of the substrate 11 is connected to the front of the heterojunction cell.

[0045] The front electrode 217 includes at least two front main gates extending along a first direction, and the back electrode 218 includes at least two back main gates extending along the first direction. The positions of the front main gates and the back main gates correspond to each other, and the number of front main gates and back main gates is consistent with the number of solder ribbons 13. The front electrode 217 and the back electrode 218 can be obtained by screen printing and curing with appropriate low-temperature silver paste. Furthermore, the front main gates and the back main gates can be continuously extended along the first direction or intermittently arranged along the first direction, and connected to the solder ribbons 13 on the corresponding electrical connectors 100 through a number of spaced-apart pads.

[0046] Regarding a specific heterojunction cell 21 in the battery string 201, the silver nanowire film 12 of the electrical connector 100, as a conductive material layer, can work together with the first transparent conductive layer 215 and the second transparent conductive layer 216 to collect and transmit the surface current of the cell. The silver nanowire film 12 can effectively reduce the transmission resistance and enhance the surface current collection capability. Furthermore, the silver nanowire film 12 has excellent light transmittance and does not affect the absorption and utilization of light. It is easily understood that the current collection and lateral transmission performance of the heterojunction cell 21 surface is improved. Without affecting the current transmission performance, the sub-grid lines on the cell surface can be reduced or even eliminated, thus reducing light shading loss.

[0047] In this embodiment, the thicknesses of the first intrinsic amorphous silicon layer 211 and the second intrinsic amorphous silicon layer 212 are set to 1–10 nm; the thicknesses of the first doped amorphous silicon layer 213 and the second doped amorphous silicon layer 214 are set to 3–10 nm. The first intrinsic amorphous silicon layer 211 and the second intrinsic amorphous silicon layer 212 can be formed into corresponding multilayer composite structures through process adjustments. Furthermore, the overall thickness of the first intrinsic amorphous silicon layer 211 and the first doped amorphous silicon layer 213 is preferably less than the overall thickness of the second intrinsic amorphous silicon layer 212 and the second doped amorphous silicon layer 214 to reduce light absorption loss on the light-receiving surface and improve short-circuit current and conversion efficiency.

[0048] The thicknesses of the first transparent conductive layer 215 and the second transparent conductive layer 216 are set to 50–100 nm, and the sheet resistances of the first transparent conductive layer 215 and the second transparent conductive layer 216 are set to 30–120 Ω / sq. Specifically, the first transparent conductive layer 215 and the second transparent conductive layer 216 are transparent oxide conductive films, which form good electrical contacts with the first doped amorphous silicon layer 213 and the second doped amorphous silicon layer 214. The thickness and specific structure of the first transparent conductive layer 215 and the second transparent conductive layer 216 can be adjusted according to product design requirements.

[0049] Combined Figure 6 As shown, the method for manufacturing the photovoltaic module 200 includes:

[0050] A predetermined nano-silver wire dispersion is coated on the surface of substrate 11, and at least two solder ribbons 13 are placed at predetermined positions on the surface of substrate 11. After drying, an electrical connector 100 is obtained, which includes a first electrical connector 101 and a second electrical connector 102.

[0051] Prepare battery string 201;

[0052] The battery string 201 is placed between the front encapsulation film 202 and the back encapsulation film 203 for lamination.

[0053] In the preparation process of the electrical connector 100, the nano-silver wire dispersion is mainly obtained by dispersing nano-silver wires of a predetermined specification in a carrier composed of solvents such as isopropanol. By adjusting and improving the above carrier formulation, the bonding strength of the solder ribbon 13 on the surface of the substrate 11 can also be improved.

[0054] The specific process for preparing the battery string 201 is as follows:

[0055] The first electrical connector 101 is placed on the support platform, with the side surface of the substrate 11 with the silver nanowire thin film 12 facing upwards, and a heterojunction battery 21 is aligned and placed on the substrate 11 of the first electrical connector 101.

[0056] Place one substrate 11 of the second electrical connector 102 on the aforementioned heterojunction cell 21, and then place another heterojunction cell 21 on the other substrate 11 of the second electrical connector 102, and repeat the steps.

[0057] After the last heterojunction cell 21 is placed, another first electrical connector 101 is selected and placed on the last heterojunction cell 21.

[0058] The fabrication process of the aforementioned battery string 201 also includes heating to combine the first electrical connector 101 and the second electrical connector 102 with the corresponding heterojunction battery 21, thereby achieving electrical connection between the solder strip 13 and the front main grid and the back main grid.

[0059] The fabrication process of the heterojunction solar cell 21 includes:

[0060] Texturing involves etching a pyramid-shaped textured surface onto a silicon substrate 210.

[0061] A first intrinsic amorphous silicon layer 211, a first doped amorphous silicon layer 213, and a first transparent conductive layer 215 are sequentially formed on the front side of the silicon substrate 210, and a second intrinsic amorphous silicon layer 212, a second doped amorphous silicon layer 214, and a second transparent conductive layer 216 are sequentially formed on the back side of the silicon substrate 210.

[0062] A front electrode 217 is formed on the surface of the first transparent conductive layer 215, and a back electrode 218 is formed on the surface of the second transparent conductive layer 216.

[0063] The "texturing" step specifically includes performing double-sided alkaline texturing on the silicon substrate 210 using an aqueous solution of KOH, NaOH, or TMAH, controlling the texturing height on the surface of the silicon substrate 210 to be 0.5–5 μm, preferably 1–3 μm. The texturing process can adjust the surface morphology of the silicon substrate 210 by regulating the solution concentration, temperature, and reaction time. Furthermore, predetermined texturing additives can be added according to product requirements to improve the texturing quality.

[0064] The first intrinsic amorphous silicon layer 211, the first doped amorphous silicon layer 213, the second intrinsic amorphous silicon layer 212, and the second doped amorphous silicon layer 214 are all deposited using the PECVD method. In actual production, the first intrinsic amorphous silicon layer 211, the first doped amorphous silicon layer 213, the second intrinsic amorphous silicon layer 212, and the second doped amorphous silicon layer 214 are deposited in different reaction chambers. The reaction gas for the first intrinsic amorphous silicon layer 211 and the second intrinsic amorphous silicon layer 212 is usually SiH4 diluted with H2. Film growth is completed under a predetermined radio frequency power supply. By adjusting the ratio of H2 / SiH4 of the reaction gas, first intrinsic amorphous silicon layers 211 and second intrinsic amorphous silicon layers 212 with different properties can be obtained.

[0065] The reaction gases for the first doped amorphous silicon layer 213 include B2H6, SiH4, and H2; the reaction gases for the second doped amorphous silicon layer 214 include PH3, SiH4, and H2. Typically, the temperature of the reaction chamber can be set at around 180°C, and the pressure controlled between 30 and 200 Pa. By adjusting the composition of the reaction gases, temperature, and pressure, film structures with different properties can be obtained.

[0066] The first transparent conductive layer 215 and the second transparent conductive layer 216 are deposited using the PVD method. They mainly include indium oxide or zinc oxide, and may also include one or more of tin oxide, aluminum oxide, calcium oxide, tungsten oxide, titanium oxide and zirconium oxide.

[0067] The pastes used for the front electrode 217 and the back electrode 218 can be the same or different. The preparation method includes screen printing the front silver paste onto the first transparent conductive layer 215 and drying it; then flipping the silicon substrate 210 and screen printing the back silver paste onto the second transparent conductive layer 216, and drying it; then sending the silicon substrate 210 into a curing oven for low-temperature curing to obtain the front electrode 217 and the back electrode 218. The curing temperature is typically set at 150–200°C, and the curing time is typically set at 15–30 minutes. It is easily understood that the printing and drying processes on both sides of the silicon substrate 210 can be interchanged.

[0068] The method for preparing the photovoltaic module 200 also includes steps such as testing, framing, installing junction boxes, and power testing after lamination, which will not be described in detail here.

[0069] In summary, after the nanosilver wire thin film 12 of the electrical connector 100 of this application comes into contact with the first transparent conductive layer 217 and the second transparent conductive layer 218 on the surface of the heterojunction battery 21, it can improve the current collection and transmission performance of the battery surface, reduce the consumption of silver paste and material cost, reduce the light-shielding loss of the metal electrode, and improve the current density and conversion efficiency. The substrate 11 of the electrical connector 100 can also serve as a protective layer, reducing the risk of abnormal damage to the heterojunction battery 21 during the fabrication of the battery string 201 and other component processes.

[0070] It should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This way of describing the specification is only for clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0071] The detailed descriptions listed above are merely specific descriptions of feasible embodiments of the present invention, and are not intended to limit the scope of protection of the present invention. All equivalent embodiments or modifications made without departing from the spirit of the present invention should be included within the scope of protection of the present invention.

Claims

1. An electrical connector for electrical connection of a solar cell, characterized in that: The electrical connector includes a substrate and at least two parallel solder strips connected to one side surface of the substrate, one end of each solder strip extending beyond the substrate to form a free end or connected to the surface of another substrate; a silver nanowire thin film is also disposed on the side of the substrate facing the solder strips, the thickness of the silver nanowire thin film being set to 50-500 nm; the sheet resistance of the silver nanowire thin film being set to 40-100 Ω / sq, and the silver nanowire thin film being configured to contact the surface of the solar cell.

2. The electrical connector according to claim 1, characterized in that: The length of the silver nanowires in the silver nanowire film is set to 10-20 μm, and the diameter of the silver nanowires is set to 20-60 nm.

3. The electrical connector according to claim 1, characterized in that: The thickness of the substrate is set to 20–200 μm.

4. A photovoltaic module, comprising a battery string and a front encapsulating film and a back encapsulating film disposed on both sides of the battery string, wherein the battery string comprises a plurality of heterojunction cells connected in series along a first direction, characterized in that: The battery string further includes an electrical connector connected to the surface of the heterojunction battery as described in any one of claims 1-3.

5. The photovoltaic module according to claim 4, characterized in that: The photovoltaic module further includes a busbar disposed at the end of the cell string; the electrical connector includes a first electrical connector and a second electrical connector, the first electrical connector including a substrate, one end of the solder strip extending beyond the substrate and forming a free end, the first electrical connector being used to connect the heterojunction cell at the end of the cell string to the busbar; the second electrical connector including two substrates, the solder strip including a first portion disposed on the front side of one of the substrates, a second portion disposed on the back side of the other substrate, and a third portion connecting the first portion and the second portion, the second electrical connector being used to connect two adjacent heterojunction cells.

6. The photovoltaic module according to claim 4, characterized in that: The front side of the heterojunction solar cell is sequentially stacked with a first intrinsic amorphous silicon layer, a first doped amorphous silicon layer, a first transparent conductive layer, and a front electrode. The back side of the heterojunction solar cell is sequentially stacked with a second intrinsic amorphous silicon layer, a second doped amorphous silicon layer, a second transparent conductive layer, and a back electrode. The front electrode includes at least two front main gates extending along a first direction, and the back electrode includes at least two back main gates extending along the first direction. The positions of the front main gates and the back main gates correspond to each other, and the number of front main gates and back main gates is consistent with the number of solder ribbons. The silver nanowire film of the electrical connector is in contact with the first transparent conductive layer, and the silver nanowire film of the electrical connector is in contact with the second transparent conductive layer.

7. The photovoltaic module according to claim 6, characterized in that: The thickness of the first transparent conductive layer and the second transparent conductive layer is set to 50-100 nm, and the sheet resistance of the first transparent conductive layer and the second transparent conductive layer is set to 30-120 Ω / sq.

8. The photovoltaic module according to claim 6, characterized in that: The thicknesses of the first intrinsic amorphous silicon layer and the second intrinsic amorphous silicon layer are set to 1–10 nm; the thicknesses of the first doped amorphous silicon layer and the second doped amorphous silicon layer are set to 3–10 nm.

9. A method for preparing a photovoltaic module, characterized in that: An electrical connector is fabricated, comprising a first electrical connector and a second electrical connector. The first electrical connector comprises a substrate, a silver nanowire film disposed on one side surface of the substrate, and at least two parallel solder strips, one end of which extends beyond the substrate and forms a free end. The second electrical connector comprises two substrates and at least two parallel solder strips, each solder strip comprising a first portion disposed on the front side of one of the substrates, a second portion disposed on the back side of the other substrate, and a third portion connecting the first and second portions. Both substrates have corresponding silver nanowire films on their surfaces facing the solder strips, the silver nanowire films having a thickness of 50–500 nm and a sheet resistance of 40–100 Ω / sq. To fabricate a battery string, a first electrical connector is placed on a support platform with the side of the substrate containing the silver nanowire film facing upwards. A heterojunction battery is then placed onto the substrate of the first electrical connector. A substrate of the second electrical connector is placed on the aforementioned heterojunction battery, and another heterojunction battery is placed on another substrate of the second electrical connector. This process is repeated. After placing the last heterojunction battery, another first electrical connector is selected and placed on the last heterojunction battery. Heating is then performed to combine the first electrical connector, the second electrical connector, and the corresponding heterojunction battery, bringing the silver nanowire film of the first electrical connector and the second electrical connector into contact with the surface of the solar cell. The battery string is placed between the front encapsulation film and the back encapsulation film and then laminated.

10. The method for preparing a photovoltaic module according to claim 9, characterized in that: The process of manufacturing the electrical connector includes coating the surface of the substrate with a silver nanowire dispersion, placing at least two solder ribbons at predetermined positions on the surface of the substrate, and then drying.

11. The method for preparing a photovoltaic module according to claim 9, characterized in that: The length of the silver nanowires in the silver nanowire film is set to 10-20 μm, and the diameter of the silver nanowires is set to 20-60 nm.

12. The method for preparing a photovoltaic module according to claim 9, characterized in that: The thickness of the substrate is set to 20–200 μm.

13. The method for preparing a photovoltaic module according to claim 9, characterized in that: The fabrication process of the heterojunction solar cell includes texturing the surface of the silicon substrate; A first intrinsic amorphous silicon layer, a first doped amorphous silicon layer and a first transparent conductive layer are sequentially fabricated on the front side of a silicon substrate, and a second intrinsic amorphous silicon layer, a second doped amorphous silicon layer and a second transparent conductive layer are sequentially fabricated on the back side of the silicon substrate. A predetermined low-temperature silver paste is printed onto the surfaces of the first transparent conductive layer and the second transparent conductive layer using a screen printing method, and then cured to obtain a front electrode and a back electrode. The front electrode includes at least two front main grids extending along a first direction, and the back electrode includes at least two back main grids extending along the first direction. The front main grids and back main grids are used to connect the solder strips on the electrical connector. The silver nanowire film of the electrical connector is in contact with the first transparent conductive layer, and the silver nanowire film of the electrical connector is in contact with the second transparent conductive layer.

14. The method for preparing a photovoltaic module according to claim 13, characterized in that: The first intrinsic amorphous silicon layer, the second intrinsic amorphous silicon layer, the first doped amorphous silicon layer, and the second doped amorphous silicon layer were all deposited using the PECVD method. The thicknesses of the first intrinsic amorphous silicon layer and the second intrinsic amorphous silicon layer are set to 1–10 nm, and the thicknesses of the first doped amorphous silicon layer and the second doped amorphous silicon layer are set to 3–10 nm.

15. The method for preparing a photovoltaic module according to claim 13, characterized in that: Both the first transparent conductive layer and the second transparent conductive layer were deposited using the PVD method. The thickness of the first transparent conductive layer and the second transparent conductive layer is set to 50-100 nm, and the sheet resistance of the first transparent conductive layer and the second transparent conductive layer is set to 30-120 Ω / sq.

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