A heterojunction solar cell

Abstract

This utility model discloses a heterojunction solar cell, including a cell body, a TCO layer disposed on a side surface of the cell body in the thickness direction, a conductive layer disposed on the side of the TCO layer away from the cell body that covers the TCO layer, and a metal grid layer disposed on the side of the conductive layer away from the TCO layer. The conductive layer of this application covers the TCO layer, eliminating the need to etch and remove the conductive layer on the surface of the cell. This solves the problem that in traditional copper seed layer fabrication, after electroplating, the copper seed layer must be etched and removed with chemicals, which not only increases production costs but also causes erosion damage to the TCO layer of the cell with the etching solution.

Description

Technical Field

[0001] This utility model relates to the field of photovoltaic cells, specifically to a heterojunction solar cell. Background Technology

[0002] Currently, the industry is continuously improving the power generation efficiency of solar modules across two main sectors. One is in cell production, where the introduction of copper electroplating combined with photolithography allows for finer grid lines, typically less than 15µm. This reduces shading and contact resistance. Furthermore, this method represents a complete solution for improving efficiency and reducing costs by eliminating the need for silver plating.

[0003] When introducing the process of electroplating copper metal grid lines, the preparation of a seed layer is crucial. In the HJT solar cell process, after depositing the surface TCO layer, a seed layer (usually copper) is prepared using vacuum deposition methods such as PVD or RPD, with a thickness ranging from 50 to 150 nm. Next, the openings for the metal grid lines to be electroplated are patterned, followed by electroplating of copper and tin metals. Afterward, the patterned mask layer is removed, and the exposed copper seed layer is etched away. Because the copper seed layer must be etched away with chemicals after electroplating, this not only increases production costs, but the etching solutions used can also corrode and damage the TCO layer of the solar cell, leading to a decrease in the cell's electrical performance. Utility Model Content

[0004] To overcome the above-mentioned shortcomings, the purpose of this utility model is to provide a heterojunction solar cell that replaces the copper seed layer with a conductive layer. After electroplating, the conductive layer on the surface of the solar cell does not need to be etched, thus solving the problem that etching solutions can cause erosion damage to the TCO layer of the solar cell.

[0005] To achieve the above objectives, the technical solution adopted by this utility model is as follows: a heterojunction solar cell, comprising a solar cell body, a TCO layer disposed on a side surface of the solar cell body in the thickness direction, a conductive layer disposed on a side of the TCO layer away from the solar cell body that can cover the TCO layer, and a metal grid layer disposed on a side of the conductive layer away from the TCO layer.

[0006] The conductive layer of this application covers the TCO layer, eliminating the need to etch and remove the conductive layer on the surface of the solar cell. This solves the problem that in the traditional preparation of copper seed layers, after electroplating, the copper seed layer must be etched and removed with chemicals, which not only increases production costs but also causes corrosion damage to the TCO layer of the solar cell due to the etching solution used.

[0007] The conductive layer has good conductivity. During the use of the solar cell, there is no charge accumulation, no carrier recombination, and the solar cell current and opening voltage will not decrease.

[0008] Furthermore, the conductive layer is a titanium nitride layer or a metal layer, wherein the titanium nitride layer is made of titanium nitride, and the metal layer is made of any one of titanium, silver, gold, platinum, and palladium.

[0009] Titanium nitride is a ceramic material with a metallic luster, excellent electrical conductivity and light transmittance, eliminating the need for etching to remove it from the surface of the solar cells after electroplating. It also possesses high hardness and wear resistance, which can extend the lifespan of the solar cells.

[0010] Metallic titanium, silver, gold, platinum, and palladium have excellent electrical conductivity. They can be prepared using PVD or vapor deposition processes and have good light transmittance. After electroplating, it is not necessary to etch and remove the metal layer on the surface of the solar cell.

[0011] Furthermore, the thickness of the conductive layer is 0.5–5 nm. In conventional solar cells, the thickness of the copper seed layer is typically between 50 nm and 150 nm to provide stronger adhesion, which is beneficial for the subsequent fabrication of copper grid lines. In this application, the thickness of the conductive layer can be set between 0.5 and 5 nm, providing sufficient adhesion. The TiN film has low resistivity, thereby improving conductivity. Furthermore, the TiN film has high light transmittance, eliminating the need for etching to remove the titanium nitride on the surface of the solar cell after electroplating.

[0012] Furthermore, the conductive layer is prepared using either ALD or PVD processes. ALD is an advanced thin-film deposition technique that uses alternating reactive gases to create a self-limiting reaction on the substrate surface, thereby achieving atomic layer deposition. ALD technology allows for precise control of the film thickness, keeping the conductive layer thickness between 0.5 and 5 nm. The cost of ALD is approximately 50% lower than that of traditional vacuum deposition processes for preparing copper seed layers. It also avoids the degradation of the solar cell's electrical properties caused by high-energy plasma bombardment and charge accumulation during vacuum sputtering of the copper seed layer in vacuum deposition processes.

[0013] Metal layers are deposited using PVD or vapor deposition processes. Physical vapor deposition (PVD) is a technique that uses physical methods to change materials from a solid state to a gaseous state under vacuum conditions and deposits them on the surface of a substrate to form a thin film. It has high precision and can form uniform and dense films on the substrate with precise thickness control.

[0014] Furthermore, the TCO layer, the conductive layer, and the metal grid layer are sequentially disposed on two sides of the battery cell body in the thickness direction.

[0015] Furthermore, the thickness of the metal grid layer is 5–25 μm, and the material of the metal grid layer is selected from any one of gold, silver, copper, and bismuth.

[0016] Furthermore, the system also includes a mask layer disposed on the side of the conductive layer away from the cell body. The mask layer has a thickness of 8–35 μm. Openings are formed on the mask layer using a patterning process, and these openings are used for electroplating deposition to prepare the metal grid line layer. In conventional processes, during the exposure process of patterning the copper seed layer, the high brightness reflection of the copper seed layer easily leads to uncontrollable scattering at the bottom of the transparent mask layer, resulting in a non-linear shape. This causes either outward expansion (increased light-blocking area, resulting in decreased Isc current) or inward shrinkage (too small bonding area, resulting in grid line detachment) at the bottom of the grid lines after electroplating. This solution uses a titanium nitride layer instead of a copper seed layer, solving the problem of decreased Isc current or metal grid line detachment caused by the high brightness reflection of the copper seed layer.

[0017] Furthermore, it also includes a microcrystalline silicon layer disposed between the solar cell body and the TCO layer, the microcrystalline silicon layer including a P-doped microcrystalline silicon layer disposed on one side of the solar cell body and an N-doped microcrystalline silicon layer disposed on the other side of the solar cell body.

[0018] The TCO layer is a transparent conductive oxide layer used to collect and transport photogenerated carriers, reducing carrier losses during transport. The material is selected from any one of indium tin oxide (ITO), fluorine-doped tin oxide (FTO), and aluminum-doped zinc oxide (AZO).

[0019] A method for preparing a heterojunction solar cell includes the following steps:

[0020] S1. Prepare TCO layers on the front and back sides of a solar cell body 1 that has already been prepared with P-doped and N-doped microcrystalline silicon layers.

[0021] S2. Prepare a conductive layer that can cover the TCO layer on the surface of the TCO layer using ALD or PVD processes.

[0022] S3. A mask layer is prepared by coating the mask onto the surface of the guide layer using a printing process; then a development process is performed to create openings in the mask layer.

[0023] S4. Electroplating deposition is performed at the opening to prepare a copper metal gate layer;

[0024] S5. Remove the mask layer to obtain a heterojunction solar cell.

[0025] Furthermore, titanium nitride layers were prepared using the ALD process. During the preparation process, the titanium-containing precursors were titanium tetrachloride (TiCl4) and titanium tetraisopropoxy (Ti(OiPr)4), with a flow rate ranging from 0.2 to 5.0 sccm. The nitrogen precursor was anhydrous hydrazine (N2H4), with a flow rate ranging from 0.2 to 5.0 sccm. The deposition temperature ranged from 100 to 300 °C. The sputtering current ranged from 0.1 to 5 A. The deposition pressure ranged from 0.1 to 10 Torr, and the deposition time ranged from 1 to 60 min.

[0026] Furthermore, a metal layer was prepared using a PVD process, achieving a power operating range of 1 kW / cm². 2 ~10kw / cm 2 Power; Time: 3 seconds to 300 seconds; The background pressure of the sputtering chamber is reduced to 10 using a vacuum pumping system. -4 -10 -5 After torr, argon gas is used as the working gas, and the working pressure of the sputtering chamber is controlled to be 5×10 through a throttle valve. -3 The metal target material is selected from any one of titanium, gold, silver, palladium, and platinum. Attached Figure Description

[0027] The accompanying drawings, which form part of this application, are used to provide a further understanding of the present invention. The illustrative embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention.

[0028] To more clearly illustrate the technical solutions in the embodiments of this utility model, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 A schematic diagram of the fabrication of a TCO layer on an HJT solar cell;

[0030] Figure 2 A schematic diagram showing the fabrication of a conductive layer on an HJT solar cell;

[0031] Figure 3 A schematic diagram showing the fabrication of a mask layer on an HJT solar cell;

[0032] Figure 4 A schematic diagram showing the fabrication of a metal grid layer on an HJT solar cell;

[0033] Figure 5 This is a schematic diagram of an HJT solar cell.

[0034] In the figure: 1. Solar cell body; 2. Microcrystalline silicon layer; 2a. P-doped microcrystalline silicon layer; 2b. N-doped microcrystalline silicon layer; 3. TCO layer; 4. Conductor layer; 5. Mask layer; 6. Opening; 7. Metal grid line layer. Detailed Implementation

[0035] To make the above-mentioned objects, features, and advantages of this utility model more apparent and understandable, the specific embodiments of this utility model will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a full understanding of this utility model. However, this utility model can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this utility model. Therefore, this utility model is not limited to the specific embodiments disclosed below.

[0036] See appendix Figure 5 As shown, a heterojunction solar cell in this embodiment includes a solar cell body 1. Microcrystalline silicon layers 2 are disposed on two sides of the solar cell body 1 in the thickness direction. The microcrystalline silicon layers 2 include a P-doped microcrystalline silicon layer 2a disposed on the front side of the solar cell body and an N-doped microcrystalline silicon layer 2b disposed on the back side of the solar cell body. A TCO layer 3 is disposed on the microcrystalline silicon layers 2.

[0037] A conductive layer 4 is disposed on the side of the TCO layer 3 away from the cell body 1. The conductive layer 4 is a titanium nitride layer or a metal layer. The titanium nitride layer is made of titanium nitride, and the metal layer is made of any one of titanium, silver, gold, platinum, and palladium. The thickness of the conductive layer ranges from 0.5 to 5 nm. The conductive layer 4 is prepared by ALD or PVD processes.

[0038] A metal grid layer 7 is provided on the side of the conductive layer 4 away from the TCO layer 3. The thickness of the metal grid layer 7 is 5-25 μm, and the material of the metal grid layer 7 is selected from any one of gold, silver, copper, and bismuth.

[0039] A method for preparing a heterojunction solar cell includes the following steps:

[0040] S1. Prepare a TCO layer 3 on the front and / or back of a solar cell body 1 that has been prepared with a P-doped microcrystalline silicon layer 2a and an N-doped microcrystalline silicon layer 2b.

[0041] S2. Prepare a conductive layer 4 on the surface of TCO layer 3 by ALD or PVD process;

[0042] S3. A mask layer 5 is prepared by coating the mask onto the surface of the guide layer 4 using a printing process; a development process is performed to create an opening 6 in the mask layer 5.

[0043] S4. Electroplating deposition is performed at opening 6 to prepare copper metal grid layer 7;

[0044] S5. Remove mask layer 5 to obtain heterojunction solar cell.

[0045] In some embodiments, in S2, the conductive layer 4 is a titanium nitride layer, prepared by an ALD process. The preparation process is as follows: the solar cell is fed into an ALD deposition apparatus, and a conductive layer 4 covering the TCO layer 3 is deposited on the surface of the TCO layer 3. The production parameters and ranges for preparing the titanium nitride layer are as follows: the titanium-containing precursor includes, but is not limited to, titanium tetrachloride (TiCl4) and titanium tetraisopropoxy (Ti(OiPr)4), with a flow rate range of 0.2–5.0 sccm; the nitrogen precursor includes, but is not limited to, anhydrous hydrazine (N2H4), with a flow rate range of 0.2–5.0 sccm; the deposition temperature range is 100–300°C; the sputtering current range is 0.1–5 A; the deposition pressure range is 0.1–10 Torr; and the deposition time range is 1–60 min. The conductive layer 4 is then prepared on the other side of the solar cell.

[0046] In some embodiments, in S2, the conductive layer 4 is a metal layer, which is prepared by PVD process, and the power operating range is 1 kW / cm². 2 ~10kw / cm 2 Power; Time: 3 seconds to 300 seconds; The background pressure of the sputtering chamber is reduced to 10 using a vacuum pumping system. -4 -10 -5 After torr, argon gas is used as the working gas, and the working pressure of the sputtering chamber is controlled to be 5×10 through a throttle valve. -3 The metal target material is selected from any one of titanium, gold, silver, palladium, and platinum.

[0047] In some embodiments, in S3, a mask layer 5 is provided on the side of the conductive layer 4 away from the battery cell body 1. The thickness of the mask layer 5 is 8 to 35 μm. An opening 6 is prepared on the mask layer by a patterning process. The opening 6 is used for electroplating deposition to prepare a metal grid line layer 7.

[0048] In some embodiments, in S4, a metal grid layer 7 is deposited at the opening 6 by an electroplating deposition process. The thickness of the metal grid layer 7 is 5 to 25 μm, and the material of the metal grid layer 7 is selected from any one of gold, silver, copper, and bismuth.

[0049] In some embodiments, in step S5, the aforementioned battery cell is then fed into a mask removal section for mask layer 5 removal. The operating temperature range is 45–65°C; the operating spray pressure is 0.5–2.5 kg / cm². 2 The operation time is 30 to 600 seconds, the removal solution is 0.5 to 5% NaOH, and the mask layer 5 is removed by the mask layer removal process to obtain an HJT cell with composite metal electrode.

[0050] Example 1

[0051] S1, see appendix Figure 1 As shown, a solar cell body 1 is prepared with a P-doped microcrystalline silicon layer 2a, an N-doped microcrystalline silicon layer 2b, and a double-sided TCO layer 3.

[0052] S2, see appendix Figure 2 As shown, the battery cells obtained from the above steps were loaded into an ALD (Alternating Current Deposition) apparatus, and a conductive layer 4 was prepared on the surface of the TCO layer 3. The cells were loaded into the ALD apparatus, and titanium tetrachloride (TiCl4) gas was used as the titanium source at a flow rate of 3.0 sccm; anhydrous hydrazine (N2H4) was used as the nitrogen precursor at a flow rate of 1.0 sccm; the deposition temperature was 200 °C; the sputtering current was 3 A; the deposition pressure was 2.5 Torr; and the deposition time was 3 min. The resulting conductive layer 4 had a thickness of 2.4 nm.

[0053] S3, see appendix Figure 3 As shown, the mask layer 5 is coated onto the surface of the conductive layer 4 using a printing process on the battery cell that has completed the above steps, and then dried and cured under atmospheric conditions. Specifically, the drying temperature is controlled at 90℃~100℃, and the drying time is 600 seconds. The thickness of the mask layer 5 is 13µm~15µm.

[0054] The battery cells that have completed the above steps are then subjected to a developing process. The suitable developer is sodium carbonate, with an operating concentration range of 1.5%; the operating temperature range is 30℃~35℃; and the operating spray pressure range is 3.0Kg / cm². 2 ~3.5Kg / cm 2 The operation time range is 200 seconds. The final result is a solar cell with a patterned linewidth of 15µm (opening 6 has a width of 15µm).

[0055] S4. For the battery cell that has completed the above steps, use an electroplating process to deposit a copper metal grid layer with a thickness of 10 μm.

[0056] S5, see appendix Figure 5 As shown, for the battery cell that has completed the above steps, a mask layer 5 removal process is performed, with an appropriate operating temperature of 65°C. The appropriate sodium carbonate concentration is 3%; the operating spray pressure is 3.5 kg / cm². 2 The adaptation operation time is 300 seconds. After removing the mask layer 5, an HJT cell with composite metal electrodes is obtained.

[0057] Example 2

[0058] Example 2 is basically the same as Example 1, the main difference being that the thickness of the conductive layer prepared in step S2 is 2.6 nm.

[0059] Example 3

[0060] Example 3 is basically the same as Example 1, the main difference being that the thickness of the conductive layer prepared in step S2 is 1.5 nm.

[0061] Example 4

[0062] Example 4 is basically the same as Example 1, the main difference being that the thickness of the conductive layer prepared in step S2 is 1.6 nm.

[0063] Example 5

[0064] Example 5 is basically the same as Example 1, the main difference being that in step S2, a conductive layer is prepared by PVD process, the conductive layer material is metallic titanium, and the thickness of the prepared conductive layer is 2.5 nm.

[0065] The specific preparation process conditions for step 2 are: power of 5 kW / cm². 2 Power; Time 150 seconds; The background pressure of the sputtering chamber is reduced to 10 using a vacuum pumping system. -5 After torr, argon gas is used as the working gas, and the working pressure of the sputtering chamber is controlled to be 5×10 through a throttle valve. -3 The metal target for torr is made of titanium.

[0066] Example 6

[0067] Example 6 is basically the same as Example 5, the main difference being that the thickness of the conductive layer prepared in step S2 is 2.0 nm.

[0068] Example 7

[0069] Example 7 is basically the same as Example 5, the main difference being that the thickness of the conductive layer prepared in step S2 is 1.6 nm.

[0070] Example 8

[0071] Example 8 is basically the same as Example 5, the main difference being that the thickness of the conductive layer prepared in step S2 is 1.2 nm.

[0072] Example 9

[0073] Example 9 is basically the same as Example 5, the main difference being that in step S2, the conductive layer material is platinum and the conductive layer thickness is 2.5 nm.

[0074] Example 10

[0075] Example 10 is basically the same as Example 9, the main difference being that the thickness of the conductive layer prepared in step S2 is 2.0 nm.

[0076] Example 11

[0077] Example 11 is basically the same as Example 9, the main difference being that the thickness of the conductive layer prepared in step S2 is 1.5 nm.

[0078] Example 12

[0079] Example 12 is basically the same as Example 9, the main difference being that the thickness of the conductive layer prepared in step S2 is 1.2 nm.

[0080] Example 13

[0081] Example 13 is basically the same as Example 5, the main difference being that in step S2, the conductive layer material is metallic silver and the conductive layer thickness is 2.3 nm.

[0082] Example 14

[0083] Example 14 is basically the same as Example 13, the main difference being that the thickness of the conductive layer prepared in step S2 is 2.0 nm.

[0084] Example 15

[0085] Example 15 is basically the same as Example 13, the main difference being that the thickness of the conductive layer prepared in step S2 is 1.5 nm.

[0086] Example 16

[0087] Example 16 is basically the same as Example 13, the main difference being that the thickness of the conductive layer prepared in step S2 is 1.2 nm.

[0088] Example 17

[0089] Example 17 is basically the same as Example 5, the main difference being that in step S2, the conductive layer material is metallic gold and the conductive layer thickness is 2.4 nm.

[0090] Example 18

[0091] Example 18 is basically the same as Example 17, the main difference being that the thickness of the conductive layer prepared in step S2 is 2.0 nm.

[0092] Example 19

[0093] Example 19 is basically the same as Example 17, the main difference being that the thickness of the conductive layer prepared in step S2 is 1.6 nm.

[0094] Example 20

[0095] Example 20 is basically the same as Example 17, the main difference being that the thickness of the conductive layer prepared in step S2 is 1.2 nm.

[0096] Example 21

[0097] Example 21 is basically the same as Example 5, the main difference being that in step S2, the conductive layer material is palladium and the conductive layer thickness is 2.7 nm.

[0098] Example 22

[0099] Example 22 is basically the same as Example 21, the main difference being that the thickness of the conductive layer prepared in step S2 is 2.1 nm.

[0100] Example 23

[0101] Example 23 is basically the same as Example 21, the main difference being that the thickness of the conductive layer prepared in step S2 is 1.6 nm.

[0102] Example 24

[0103] Example 24 is basically the same as Example 21, the main difference being that the thickness of the conductive layer prepared in step S2 is 1.4 nm.

[0104] Comparative Example 1

[0105] Comparative Example 1 and Example 1 are basically the same, the main difference being that in step S2, a copper seed layer is prepared to replace the conductive layer. The thickness of the copper seed layer is 100 nm.

[0106] Experimental Example 1

[0107] The performance of the solar cells prepared in Examples 1-4 and Comparative Example 1 was tested, and the test data are shown in Table 1.

[0108] Table 1

[0109] Eta Voc FF Rs Example 1 1.08 3.35 1.05 0.9928 Example 2 1.11 3.34 1.06 0.9921 Example 3 1.1 4.37 1.14 0.9936 Example 4 1.06 4.39 1.16 0.9946 Example 5 1.12 3.34 1.07 0.9924 Example 6 1.11 3.33 1.06 0.9927 Example 7 1.13 3.78 1.13 0.9948 Example 8 1.07 3.89 1.18 0.9949 Example 9 1.07 3.27 1.06 0.9936 Example 10 1.14 3.34 1.03 0.9941 Example 11 1.08 3.41 1.08 0.9952 Example 12 1.06 3.41 1.04 0.9958 Example 13 1.14 3.25 1.11 0.9912 Example 14 1.12 3.31 1.09 0.9911 Example 15 1.09 4.12 1.08 0.9927 Example 16 1.09 4.06 1.14 0.9929 Example 17 1.15 3.57 1.17 0.9916 Example 18 1.14 3.59 1.16 0.9915 Example 19 1.12 4.08 1.13 0.9925 Example 20 1.14 4.09 1.12 0.9927 Example 21 1.06 3.24 1.09 0.9936 Example 22 1.09 3.23 1.08 0.9941 Example 23 1.05 3.22 1.04 0.9952 Example 24 1.04 3.18 1.01 0.9958 Comparative Example 1 1 1 1 1

[0110] The experimental data in Table 1 show that by replacing the copper seed layer in the traditional process with conductive layers on the front and back of the HJT cell, the photoelectric conversion efficiency (Eta), turn-on voltage (Voc), and fill factor (FF) of the cell are all improved, especially the turn-on voltage (Voc), which is improved by 3 to 5 times. Furthermore, the series resistance (Rs) is reduced. Therefore, in this scheme, replacing the traditional copper seed layer with conductive layers with good conductivity improves the performance of the cell.

[0111] The above embodiments are only for illustrating the technical concept and features of this utility model. Their purpose is to enable those skilled in the art to understand the content of this utility model and implement it. They cannot be used to limit the protection scope of this utility model. All equivalent changes or modifications made in accordance with the spirit and essence of this utility model should be covered within the protection scope of this utility model.

Claims

1. A heterojunction cell, characterized by, The device includes a battery cell body (1), a TCO layer (3) is provided on the side of the battery cell body (1) in the thickness direction, a conductive layer (4) is provided on the side of the TCO layer (3) away from the battery cell body (1) to cover the TCO layer (3), and a metal grid layer (7) is provided on the side of the conductive layer (4) away from the TCO layer (3).

2. The heterojunction solar cell according to claim 1, characterized in that, The conductive layer (4) is a titanium nitride layer or a metal layer. The titanium nitride layer is made of titanium nitride, and the metal layer is made of any one of titanium, silver, gold, platinum, or palladium.

3. The heterojunction solar cell according to claim 1, characterized in that, The thickness of the conductive layer (4) is 0.5 to 5 nm.

4. The heterojunction solar cell according to claim 1, characterized in that, The conductive layer (4) is prepared by ALD process or PVD process.

5. The heterojunction solar cell according to claim 1, characterized in that, The TCO layer (3), the conductive layer (4), and the metal grid layer (7) are sequentially disposed on two sides of the battery cell body (1) in the thickness direction.

6. The heterojunction solar cell according to claim 1, characterized in that, The thickness of the metal grid layer (7) is 5 to 25 μm, and the material of the metal grid layer (7) is selected from any one of gold, silver, copper and bismuth.

7. The heterojunction solar cell according to claim 1, characterized in that, It also includes a mask layer (5) disposed on the side of the conductive layer (4) away from the battery cell body (1), the thickness of the mask layer (5) is 8 to 35 μm, and an opening (6) is prepared on the mask layer (5) by a patterning process, the opening (6) being used for electroplating deposition to prepare a metal grid line layer (7).

8. The heterojunction solar cell according to claim 1, characterized in that, It also includes a microcrystalline silicon layer (2) disposed between the cell body (1) and the TCO layer (3), the microcrystalline silicon layer (2) including a P-doped microcrystalline silicon layer (2a) disposed on one side of the cell body (1) and an N-doped microcrystalline silicon layer (2b) disposed on the other side of the cell body.

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