Method for preparing topcon cell substrate and double-sided electroplated topcon cell prepared by method

Abstract

A method for preparing a TOPCon cell substrate and a double-sided electroplated TOPCon cell prepared by the method. The method comprises: providing a TOPCon cell silicon substrate with grooves on two sides; carrying out thermal repair treatment on the silicon substrate; and separately performing light injection treatment on the front surface and the back surface of the silicon substrate that have been subjected to thermal repair treatment, thereby obtaining a TOPCon cell substrate. Thermal repair can greatly increase the overall lattice thermal motion of silicon of the substrate, and light injection performed on the front surface and the back surface in two different light incident surface directions makes the front surface and the back surface absorb light, thereby repairing defects at the interface between amorphous silicon and a silicon wafer, and improving the quality of PN junctions.

Description

Method for preparing TOPCon battery substrate and double-sided electroplated TOPCon battery prepared thereby

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to Chinese patent application number 202311394254.1, filed with the Chinese Patent Office on October 25, 2023, entitled “A method for improving the opening voltage of double-sided electroplated TOPCon batteries and a battery assembly prepared thereby”, the entire contents of which are incorporated by reference into this application. Technical Field

[0003] The present disclosure relates to the technical field of TOPCon solar cells, and in particular to a method for preparing a TOPCon cell substrate and a double-sided electroplated TOPCon cell prepared thereby. Background Art

[0004] Currently, the technology level of TOPCon solar cells is high. The silver paste used in traditional screen printing processes is expensive, and it's difficult to effectively increase the aspect ratio of the front-side fine grid lines. Compared to this technology, TOPCon cells produced using horizontal double-sided electroplating offer the following advantages: a higher aspect ratio of the front-side fine grid lines; reduced grid width, increasing the cell's light-receiving area; and double-sided electrodes primarily using inexpensive copper for electrical conductivity, thus reducing cell production costs.

[0005] However, the traditional method for grooving double-sided electroplated TOPCon cells involves using a laser to directly groove the silicon nitride, exposing the underlying silicon to allow the electroplating process to proceed. The preparation process is: front-side laser grooving → back-side laser grooving → electroplating. During this grooving process, the laser grooving causes minimal damage to the silicon substrate due to the smooth, polished surface of the back side. However, the front side has a velvety surface with a pyramidal structure, and using a laser to remove the silicon nitride film on the surface will inevitably cause some damage to the silicon substrate, potentially destroying the PN junction on the silicon substrate, resulting in a loss in the cell's turn-on voltage, and thus reducing the conversion efficiency of the final electroplated cell. Generally, laser damage to double-sided electroplated TOPCon cells results in a turn-on voltage loss of approximately 10-20 mV, which translates to a solar cell efficiency loss of approximately 1-1.5%.

[0006] Therefore, it is urgent to develop a method that can reduce the voltage loss caused by laser damage to double-sided electroplated TOPCon cells.

[0007] Public content

[0008] The present disclosure provides a method for preparing a TOPCon battery substrate and a double-sided electroplated TOPCon battery prepared thereby, so as to at least alleviate one technical problem existing in the prior art.

[0009] In order to achieve at least one of the above-mentioned objectives of the present disclosure, the following technical solutions are particularly adopted:

[0010] In a first aspect, the present disclosure provides a method for preparing a TOPCon battery substrate, the method comprising the following steps:

[0011] Provide double-sided grooved TOPCon cell silicon substrate;

[0012] performing a thermal repair treatment on the silicon substrate;

[0013] The front and back surfaces of the silicon substrate after the thermal repair treatment are respectively subjected to light injection treatment, thereby obtaining a TOPCon cell substrate.

[0014] In a second aspect, the present disclosure provides a TOPCon battery substrate, wherein the TOPCon battery substrate is obtained by processing as described above.

[0015] In a third aspect, the present disclosure provides a double-sided electroplated TOPCon battery, wherein the double-sided electroplated TOPCon battery is obtained by subjecting the above-mentioned TOPCon battery substrate to double-sided electroplating treatment. DETAILED DESCRIPTION

[0016] The embodiments of the present disclosure are described in detail below with reference to the examples. However, those skilled in the art will appreciate that the following examples are merely illustrative of the present disclosure and should not be construed as limiting the scope of the present disclosure. Where specific conditions are not specified in the examples, conventional conditions or conditions recommended by the manufacturer were followed.

[0017] In a first aspect, the present disclosure provides a method for preparing a TOPCon cell substrate and a double-sided electroplated TOPCon cell prepared thereby.

[0018] In the present disclosure, a method for preparing a TOPCon battery substrate comprises:

[0019] Provide double-sided grooved TOPCon cell silicon substrate;

[0020] performing a thermal repair treatment on the silicon substrate;

[0021] The front and back surfaces of the silicon substrate after the thermal repair treatment are respectively subjected to light injection treatment, thereby obtaining a TOPCon cell substrate.

[0022] In this paper, a double-sided grooved TOPCon solar cell silicon substrate is first thermally repaired, significantly increasing the overall thermal motion of the base silicon lattice. Light injection is then performed twice, from different light-incident directions, on both the front and back sides, allowing light to be absorbed by both sides. This repairs defects at the interface between the amorphous silicon and the silicon wafer, improving the quality of the PN junction. After thermal repair and double-sided light injection, the open-circuit voltage after horizontal double-sided electroplating can be increased by 4-10mV, and the photoelectric conversion efficiency can be increased by 0.2-0.8%.

[0023] Furthermore, the double-sided grooved TOPCon cell silicon substrate is prepared by the following steps:

[0024] (a) Depositing a passivation film on the silicon substrate of a TOPCon solar cell to form a coating layer;

[0025] (b) The coating layers on the front and back sides of the silicon substrate are removed by laser grooving to form a grid line pattern on the surface of the coating layers.

[0026] Furthermore, in step (a), the passivation film is a silicon nitride film.

[0027] Furthermore, in step (a), the thickness of the passivation film is 80-100 nm, for example, 80 nm, 82 nm, 84 nm, 86 nm, 88 nm, 90 nm, 92 nm, 94 nm, 96 nm, 98 nm, 100 nm, etc.

[0028] Furthermore, in step (b), the laser used for laser grooving is an ultraviolet picosecond laser or an ultraviolet nanosecond laser.

[0029] Furthermore, in step (b), the beam of the laser used for laser grooving is a flat-top beam.

[0030] In the present disclosure, a flat-top beam laser is used for grooving, the light spot energy is very uniform, the passivation film in the middle and at the edge can be completely removed, and the damage to the front PN junction is relatively small.

[0031] Furthermore, in step (b), the laser peak power during the laser grooving process is 0.5 to 2 W, for example, 0.5 W, 0.6 W, 0.8 W, 1 W, 1.2 W, 1.4 W, 1.6 W, 1.8 W, 2 W, etc.

[0032] Furthermore, in step (b), the groove width of the fine grid in the grid line pattern formed after the laser grooving is 10 to 15 μm, for example, it can be 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm, 15 μm, etc.

[0033] Furthermore, in step (b), the groove depth in the gate line pattern formed after the laser grooving is 80 to 100 nm, for example, it can be 80 nm, 82 nm, 84 nm, 86 nm, 88 nm, 90 nm, 92 nm, 94 nm, 96 nm, 98 nm, 100 nm, etc.

[0034] Furthermore, in step (b), the auxiliary gas for the laser grooving is selected from any one of nitrogen, argon or helium, preferably nitrogen and / or argon.

[0035] Furthermore, the thermal repair process specifically includes the following steps:

[0036] The double-sided grooved TOPCon solar cell silicon substrate is placed with the front side facing upward in a protective gas atmosphere for thermal repair treatment.

[0037] Furthermore, the protective gas is nitrogen.

[0038] Furthermore, the flow rate of the nitrogen is 20-30 L / min, for example, 20 L / min, 21 L / min, 22 L / min, 23 L / min, 24 L / min, 25 L / min, 26 L / min, 27 L / min, 28 L / min, 29 L / min, 30 L / min, etc.

[0039] Furthermore, the temperature of the thermal repair treatment is 600-800°C, for example, it can be 600°C, 620°C, 640°C, 660°C, 680°C, 700°C, 720°C, 740°C, 760°C, 780°C, 800°C, etc.

[0040] Furthermore, the time of the thermal repair treatment is 120 to 180 s, for example, it can be 120 s, 125 s, 130 s, 135 s, 140 s, 145 s, 150 s, 155 s, 160 s, 165 s, 170 s, 175 s, 180 s, etc.

[0041] Furthermore, the light injection process specifically includes the following steps:

[0042] First, the silicon substrate after heat repair treatment is placed with one side facing up and placed in a protective gas atmosphere for light injection treatment; then it is turned over so that the other side faces up and placed in a protective gas atmosphere for light injection treatment to obtain a treated TOPCon solar cell substrate.

[0043] In the present disclosure, the front side light injection process can be performed first, and then the back side light injection process can be performed; or the back side light injection process can be performed first, and then the front and back side light injection processes can be performed.

[0044] Furthermore, the protective gas is any one of nitrogen, argon or helium, preferably nitrogen.

[0045] Furthermore, the flow rate of the protective gas is 10 to 15 L / min, for example, it can be 10 L / min, 10.5 L / min, 11 L / min, 11.5 L / min, 12 L / min, 12.5 L / min, 13 L / min, 13.5 L / min, 14 L / min, 14.5 L / min, 15 L / min, etc.

[0046] Furthermore, heating is required during the light injection process.

[0047] Furthermore, the heating temperature is 200-300°C, for example, it can be 200°C, 210°C, 220°C, 230°C, 240°C, 250°C, 260°C, 270°C, 280°C, 290°C, 300°C, etc.

[0048] Furthermore, the light radiation intensity of the light injection treatment is 10 to 30 suns, for example, 10 suns, 12 suns, 14 suns, 16 suns, 18 suns, 20 suns, 22 suns, 24 suns, 26 suns, 28 suns, 30 suns, etc.

[0049] Furthermore, the time of the light injection treatment is 60 to 120 s, for example, it can be 60 s, 65 s, 70 s, 75 s, 80 s, 95 s, 90 s, 95 s, 100 s, 105 s, 110 s, 115 s, 120 s, etc.

[0050] Furthermore, the light source for the light injection process is white light and / or infrared light.

[0051] As a preferred technical solution of the present disclosure, the method for increasing the opening voltage of a double-sided electroplated TOPCon battery specifically includes the following steps:

[0052] S1. Laser grooving

[0053] (a) Depositing an 80-100 nm thick silicon nitride passivation film on the surface of a silicon substrate of a TOPCon solar cell to obtain a coating layer;

[0054] (b) using a laser grooving method to sequentially remove the coating layers on the front and back sides of the silicon substrate, thereby forming a grid line pattern on the surface of the coating layers;

[0055] Wherein, the laser for laser grooving is an ultraviolet picosecond laser or an ultraviolet nanosecond laser; and the beam of the laser for laser grooving is a flat-top beam.

[0056] S2. Thermal Repair

[0057] Place the double-sided grooved TOPCon solar cell silicon substrate with the front side facing up in a nitrogen atmosphere for thermal repair treatment;

[0058] The flow rate of the nitrogen is 20 to 30 L / min; the temperature of the thermal repair treatment is 600 to 800° C.; and the time of the thermal repair treatment is 120 to 180 seconds.

[0059] S3, double-sided light injection processing

[0060] First, the silicon substrate after high-temperature thermal repair treatment is placed with one side facing up and placed in a nitrogen atmosphere for light injection treatment. Then, it is turned over so that the other side faces up and placed in a nitrogen atmosphere for light injection treatment, supplemented by heating to achieve passivation, to obtain the treated TOPCon solar cell substrate.

[0061] The flow rate of nitrogen is 10 to 15 L / min; the heating temperature is 200 to 300° C.; the light radiation intensity of the light injection treatment is 10 to 30 sun; and the time of the light injection treatment is 60 to 120 seconds.

[0062] In a second aspect, the present disclosure provides a TOPCon solar cell substrate, which is obtained by processing the method for improving the opening voltage of a double-sided electroplated TOPCon cell as described above.

[0063] In a third aspect, the present disclosure provides a double-sided electroplated TOPCon cell, wherein the double-sided electroplated TOPCon cell is obtained by subjecting the TOPCon solar cell substrate to double-sided electroplating treatment.

[0064] Furthermore, the double-sided electroplating treatment includes any one of electroplating nickel, electroplating copper or electroplating tin, or a combination of at least two of them, preferably a combination of electroplating nickel, electroplating copper and electroplating tin.

[0065] Furthermore, the horizontal double-sided electroplating is to sequentially electroplate nickel, copper and tin on the front and back sides of the cell after light injection to obtain a double-sided electroplated TOPCon cell.

[0066] The embodiments of the present disclosure are described in detail below with reference to the examples. However, those skilled in the art will appreciate that the following examples are merely illustrative of the present disclosure and should not be construed as limiting the scope of the present disclosure. Where specific conditions are not specified in the examples, conventional conditions or conditions recommended by the manufacturer were followed.

[0067] In order to help understand the content of the present disclosure more clearly, the following is a detailed description of the present disclosure in conjunction with specific embodiments. However, these embodiments are merely exemplary and do not constitute any limitation to the scope of the present disclosure.

[0068] Example 1

[0069] This embodiment provides a method for increasing the start-up voltage of a double-sided electroplated TOPCon battery, the method specifically comprising the following steps:

[0070] S1. Laser grooving

[0071] (a) Depositing a 90 nm thick silicon nitride passivation film on the silicon substrate of a TOPCon solar cell to obtain a coating layer;

[0072] (b) using a laser grooving method to sequentially remove the coating layers on the front and back sides of the silicon substrate, thereby forming a grid line pattern on the surface of the coating layers;

[0073] The laser used for the laser grooving is an ultraviolet picosecond laser; the beam of the laser used for the laser grooving is a flat-top beam; and the peak power of the laser during the laser grooving process is 1W;

[0074] The grating pattern formed by laser grooving has a grooving width of 12 μm and a grooving depth of 90 nm.

[0075] Wherein, the auxiliary gas for the laser grooving is nitrogen.

[0076] S2. High temperature thermal repair treatment

[0077] The double-sided grooved TOPCon solar cell silicon substrate is placed with the front side facing up in a nitrogen atmosphere for high-temperature thermal repair treatment;

[0078] The flow rate of the nitrogen gas is 25 L / min; the temperature of the high-temperature thermal repair treatment is 700° C.; and the time of the high-temperature thermal repair treatment is 150 s.

[0079] S3, double-sided light injection processing

[0080] First, the back side of the silicon substrate after high-temperature thermal repair is placed upward and placed in a nitrogen atmosphere for light injection treatment. Then, it is turned over so that the front side faces upward and placed in a nitrogen atmosphere for light injection treatment, supplemented by heating to achieve passivation, to obtain the treated TOPCon solar cell substrate.

[0081] The flow rate of nitrogen is 12 L / min; the heating temperature is 250° C.; the light radiation intensity of the light injection treatment is 20 sun; the time of the light injection treatment is 90 s; and the light source of the light injection treatment is white light.

[0082] Example 2

[0083] This embodiment provides a method for increasing the start-up voltage of a double-sided electroplated TOPCon battery, the method specifically comprising the following steps:

[0084] S1. Laser grooving

[0085] (a) Depositing an 80 nm thick silicon nitride passivation film on the silicon substrate of a TOPCon solar cell to obtain a coating layer;

[0086] (b) using a laser grooving method to sequentially remove the coating layers on the front and back sides of the silicon substrate, thereby forming a grid line pattern on the surface of the coating layers;

[0087] The laser used for the laser grooving is an ultraviolet picosecond laser; the beam of the laser used for the laser grooving is a flat-top beam; the peak power of the laser during the laser grooving process is 0.5W;

[0088] The width of the fine grid in the grid line pattern formed by the laser grooving is 10 μm, and the depth of the grooving is 80 nm.

[0089] Wherein, the auxiliary gas for the laser grooving is argon.

[0090] S2. High temperature thermal repair treatment

[0091] The double-sided grooved TOPCon solar cell silicon substrate is placed with the front side facing up in a nitrogen atmosphere for high-temperature thermal repair treatment;

[0092] The flow rate of the nitrogen gas is 20 L / min; the temperature of the high-temperature thermal repair treatment is 600° C.; and the time of the high-temperature thermal repair treatment is 180 s.

[0093] S3, double-sided light injection processing

[0094] First, the back side of the silicon substrate after high-temperature thermal repair is placed upward and placed in a nitrogen atmosphere for light injection treatment. Then, it is turned over so that the front side faces upward and placed in a nitrogen atmosphere for light injection treatment, supplemented by heating to achieve passivation, to obtain the treated TOPCon solar cell substrate.

[0095] The flow rate of nitrogen is 10 L / min; the heating temperature is 300° C.; the light radiation intensity of the light injection treatment is 10 sun; the time of the light injection treatment is 120 s; and the light source of the light injection treatment is infrared light.

[0096] Example 3

[0097] This embodiment provides a method for increasing the start-up voltage of a double-sided electroplated TOPCon battery, the method specifically comprising the following steps:

[0098] S1. Laser grooving

[0099] (a) A 100 nm thick silicon nitride passivation film was deposited on the silicon substrate of a TOPCon solar cell to obtain a coating layer.

[0100] (b) using a laser grooving method to sequentially remove the coating layers on the front and back sides of the silicon substrate, thereby forming a grid line pattern on the surface of the coating layers;

[0101] The laser used for the laser grooving is an ultraviolet nanosecond laser; the beam of the laser used for the laser grooving is a flat-top beam; the peak power of the laser during the laser grooving process is 2W;

[0102] The width of the fine grid in the grid line pattern formed by the laser grooving is 15 μm, and the depth of the grooving is 100 nm.

[0103] Wherein, the auxiliary gas for the laser grooving is nitrogen.

[0104] S2. High temperature thermal repair treatment

[0105] The double-sided grooved TOPCon solar cell silicon substrate is placed with the front side facing up in a nitrogen atmosphere for high-temperature thermal repair treatment;

[0106] The flow rate of the nitrogen gas is 30 L / min; the temperature of the high-temperature thermal repair treatment is 800° C.; and the time of the high-temperature thermal repair treatment is 120 s.

[0107] S3, double-sided light injection processing

[0108] First, the back side of the silicon substrate after high-temperature thermal repair is placed upward and placed in a nitrogen atmosphere for light injection treatment. Then, it is turned over so that the front side faces upward and placed in a nitrogen atmosphere for light injection treatment, supplemented by heating to achieve passivation, to obtain the treated TOPCon solar cell substrate.

[0109] The flow rate of nitrogen is 15 L / min; the heating temperature is 200° C.; the light radiation intensity of the light injection treatment is 30 sun; the time of the light injection treatment is 60 s; and the light source of the light injection treatment is white light.

[0110] Example 4

[0111] This embodiment provides a method for improving the opening voltage of a double-sided electroplated TOPCon battery. The only difference from Example 1 is that the beam of the laser used for laser grooving is a Gaussian beam, and the other steps are exactly the same as Example 1.

[0112] Example 5

[0113] This embodiment provides a method for improving the opening voltage of a double-sided electroplated TOPCon battery. The only difference from Example 1 is that the laser peak power during the laser grooving process is 0.1 W, and the other steps are exactly the same as Example 1.

[0114] Example 6

[0115] This embodiment provides a method for improving the opening voltage of a double-sided electroplated TOPCon battery. The only difference from Example 1 is that the laser peak power during the laser grooving process is 2.5 W, and the other steps are exactly the same as Example 1.

[0116] Example 7

[0117] This embodiment provides a method for increasing the opening pressure of a double-sided electroplated TOPCon cell. The only difference from Example 1 is that the front side of the double-sided grooved TOPCon solar cell silicon substrate is placed facing upward and subjected to high-temperature thermal repair treatment in a protective gas atmosphere; then the substrate is flipped so that the other side faces upward and subjected to high-temperature thermal repair treatment in a protective gas atmosphere; the other steps are exactly the same as in Example 1.

[0118] Example 8

[0119] This embodiment provides a method for improving the opening voltage of a double-sided electroplated TOPCon battery. The only difference from Example 1 is that the temperature of the high-temperature thermal repair treatment is 580°C, the time of the high-temperature thermal repair treatment is 200s, and the other steps are exactly the same as Example 1.

[0120] Example 9

[0121] This embodiment provides a method for improving the opening voltage of a double-sided electroplated TOPCon battery. The only difference from Example 1 is that the temperature of the high-temperature thermal repair treatment is 820°C, the time of the high-temperature thermal repair treatment is 100s, and the other steps are exactly the same as Example 1.

[0122] Example 10

[0123] This embodiment provides a method for improving the start-up voltage of a double-sided electroplated TOPCon cell. The only difference from Example 1 is that no heating treatment is performed during the light injection treatment, and the other steps are exactly the same as Example 1.

[0124] Example 11

[0125] This embodiment provides a method for improving the start-up voltage of a double-sided electroplated TOPCon battery. The only difference from Example 1 is that the light radiation intensity of the light injection treatment is 5 sun, the light injection treatment time is 150 s, and the other steps are exactly the same as Example 1.

[0126] Example 12

[0127] This embodiment provides a method for improving the start-up voltage of a double-sided electroplated TOPCon battery. The only difference from Example 1 is that the light radiation intensity of the light injection treatment is 35 sun, the light injection treatment time is 50 seconds, and the other steps are exactly the same as Example 1.

[0128] Comparative Example 1

[0129] This comparative example provides a TOPCon solar cell substrate, which is prepared by the following method:

[0130] (a) Depositing a 90 nm thick silicon nitride passivation film on the silicon substrate of a TOPCon solar cell to obtain a coating layer;

[0131] (b) using a laser grooving method to sequentially remove the coating layers on the front and back sides of the silicon substrate, thereby forming a grid line pattern on the surface of the coating layers;

[0132] The laser used for the laser grooving is an ultraviolet picosecond laser; the beam of the laser used for the laser grooving is a flat-top beam; and the peak power of the laser during the laser grooving process is 1W;

[0133] The grating pattern formed by laser grooving has a grooving width of 12 μm and a grooving depth of 90 nm.

[0134] Wherein, the auxiliary gas for the laser grooving is nitrogen.

[0135] Comparative Example 2

[0136] This embodiment provides a method for increasing the start-up voltage of a double-sided electroplated TOPCon battery, the method specifically comprising the following steps:

[0137] S1. Laser grooving

[0138] (a) Depositing a 90 nm thick silicon nitride passivation film on the silicon substrate of a TOPCon solar cell to obtain a coating layer;

[0139] (b) using a laser grooving method to sequentially remove the coating layers on the front and back sides of the silicon substrate, thereby forming a grid line pattern on the surface of the coating layers;

[0140] The laser used for the laser grooving is an ultraviolet picosecond laser; the beam of the laser used for the laser grooving is a flat-top beam; and the peak power of the laser during the laser grooving process is 1W;

[0141] The grating pattern formed by laser grooving has a grooving width of 12 μm and a grooving depth of 90 nm.

[0142] Wherein, the auxiliary gas for the laser grooving is nitrogen.

[0143] S2, double-sided light injection processing

[0144] First, the grooved silicon substrate is placed with its back side facing upwards in a nitrogen atmosphere for light injection treatment. Then, it is flipped over so that its front side faces upwards and placed in a nitrogen atmosphere for light injection treatment, supplemented by heating for passivation, to obtain the treated TOPCon solar cell substrate.

[0145] The flow rate of nitrogen is 12 L / min; the heating temperature is 250° C.; the light radiation intensity of the light injection treatment is 20 sun; the time of the light injection treatment is 90 s; and the light source of the light injection treatment is white light.

[0146] Comparative Example 3

[0147] This comparative example provides a method for increasing the opening voltage of a double-sided electroplated TOPCon battery, the method specifically comprising the following steps:

[0148] S1. Laser grooving

[0149] (a) Depositing a 90 nm thick silicon nitride passivation film on the silicon substrate of a TOPCon solar cell to obtain a coating layer;

[0150] (b) using a laser grooving method to sequentially remove the coating layers on the front and back sides of the silicon substrate, thereby forming a grid line pattern on the surface of the coating layers;

[0151] The laser used for the laser grooving is an ultraviolet picosecond laser; the beam of the laser used for the laser grooving is a flat-top beam; and the peak power of the laser during the laser grooving process is 1W;

[0152] The grating pattern formed by laser grooving has a grooving width of 12 μm and a grooving depth of 90 nm.

[0153] Wherein, the auxiliary gas for the laser grooving is nitrogen.

[0154] S2. High temperature thermal repair treatment

[0155] The double-sided grooved TOPCon solar cell silicon substrate is placed with the front side facing upward in a nitrogen atmosphere for high-temperature thermal repair treatment to obtain a treated TOPCon solar cell substrate;

[0156] The flow rate of the nitrogen gas is 25 L / min; the temperature of the high-temperature thermal repair treatment is 700° C.; and the time of the high-temperature thermal repair treatment is 150 s.

[0157] Comparative Example 4

[0158] This comparative example provides a method for improving the opening voltage of a double-sided electroplated TOPCon cell. The only difference from Example 1 is that only one side is subjected to light injection treatment. Specifically, only the back side of the silicon substrate after high-temperature thermal repair treatment is placed upward and subjected to light injection treatment in a nitrogen atmosphere; and heating is applied to achieve passivation to obtain a treated TOPCon solar cell substrate.

[0159] Comparative Example 5

[0160] This comparative example provides a method for improving the opening voltage of a double-sided electroplated TOPCon cell. The only difference from Example 1 is that only one side is subjected to light injection treatment. Specifically, only the front side of the silicon substrate after high-temperature thermal repair treatment is placed facing upward and subjected to light injection treatment in a nitrogen atmosphere; and heating is applied to achieve passivation to obtain a treated TOPCon solar cell substrate.

[0161] Test Case

[0162] Electrical performance test

[0163] Test samples: battery substrates processed by the methods of Examples 1 to 12, and battery substrates processed by the methods of Comparative Examples 1 to 5;

[0164] Test method:

[0165] (1) Preparation of double-sided electroplated TOPCon cells:

[0166] Nickel, copper and tin were electroplated on the front and back of the above battery samples in sequence to obtain a double-sided electroplated TOPCon battery.

[0167] The thickness of the nickel layer is 1.0 μm; the thickness of the copper layer is 9 μm; and the thickness of the tin layer is 1.2 μm.

[0168] (2) Data testing:

[0169] Electrical performance (mainly photoelectric conversion efficiency and open circuit voltage): The battery (size 210 mm) obtained in Example 1 was tested for electrical performance using the IV test method (test conditions 25° C., AM 1.5G).

[0170] The specific test results are shown in Table 1 below:

[0171] Table 1

[0172] As shown in the test data in Table 1, the double-sided electroplated TOPCon cell produced after double-sided electroplating using the cell substrate treated with the method described in the present disclosure can increase the open circuit voltage by 4 to 10 mV and the photoelectric conversion efficiency by 0.2 to 0.8%. A comparison of Example 1 with Comparative Examples 1 to 5 shows that the high-temperature thermal repair method disclosed in the present disclosure can significantly increase the overall thermal motion of the silicon substrate lattice. Light injection from two different light-incident directions, on the front and back sides, allows light to be absorbed by both the front and back sides, thereby repairing defects at the interface between the amorphous silicon and the silicon wafer and improving the quality of the PN junction.

[0173] From the comparison between Example 1 and Examples 5 to 6, it can be seen that the laser power of 0.1W is too low, resulting in the passivation film being unable to be opened, making it difficult to plate the electroplated metal and resulting in poor efficiency; while the laser power of 2.5W is too high, and the opening voltage loss will reach more than 30mV.

[0174] From the comparison between Example 1 and Examples 8 to 9, it can be seen that the temperature of the high-temperature thermal repair treatment is preferably 600 to 800°C, and the time is preferably 120 to 180s; otherwise, lowering the temperature even if the time is extended, or raising the temperature to shorten the treatment time, will lead to a decrease in the opening pressure and efficiency.

[0175] From the comparison between Example 1 and Example 10, it can be seen that heating treatment is required during the light injection process. Otherwise, if there is no heating temperature, light alone is useless for increasing the opening voltage.

[0176] From the comparison between Example 1 and Examples 11 to 12, it can be seen that the light radiation intensity of the light injection treatment is 10 to 30 suns and the time is 60 to 120 seconds, which helps to further improve the efficiency within this range; otherwise, reducing the light radiation intensity even if the time is extended, or increasing the light radiation intensity and shortening the treatment time will cause the efficiency of the battery to decrease.

[0177] From the comparison between Example 1 and Comparative Examples 1 to 4, it can be seen that the present disclosure adopts a synergistic mode of high-temperature thermal repair and double-sided light injection to better repair defects at the interface between amorphous silicon and silicon wafers, improve the quality of the PN junction, and thus significantly improve the start-up voltage and efficiency of the prepared battery.

[0178] Compared with the prior art, the advantages of the present invention include:

[0179] (1) The present invention uses a flat-top beam laser for grooving. The energy of the light spot is very uniform, the passivation film in the middle and at the edge can be completely removed, and the damage to the front PN junction is relatively small.

[0180] (2) The high-temperature thermal repair disclosed in the present invention can significantly increase the overall lattice thermal motion of the substrate silicon. Light injection at two different light incident directions on the front and back sides can allow both the front and back sides to absorb light, thereby repairing defects at the interface between amorphous silicon and silicon wafers and improving the quality of the PN junction.

[0181] (3) After the double-sided grooved semi-finished product is subjected to high-temperature thermal repair and double-sided light injection, the open circuit voltage after horizontal double-sided electroplating can be increased by 4 to 10 mV, and the photoelectric conversion efficiency can be increased by 0.2 to 0.8%.

[0182] This disclosure also provides the following notes:

[0183] 1. A method for increasing the opening voltage of a double-sided electroplated TOPCon battery, wherein the method comprises the following steps:

[0184] A double-sided grooved TOPCon solar cell silicon substrate is first subjected to a thermal repair treatment, and then light injection treatment is performed on the front and back sides of the thermally repaired silicon substrate to obtain a treated TOPCon solar cell substrate.

[0185] 2. The method according to Supplementary Note 1, wherein the double-sided grooved TOPCon solar cell silicon substrate is prepared by the following steps:

[0186] (a) Depositing a passivation film on the silicon substrate of a TOPCon solar cell to obtain a coating layer;

[0187] (b) The coating layers on the front and back sides of the silicon substrate are removed by laser grooving to form a grid line pattern on the surface of the coating layers.

[0188] 3. The method according to Supplementary Note 2, wherein in step (a), the passivation film is a silicon nitride film;

[0189] Preferably, in step (a), the thickness of the passivation film is 80-100 nm.

[0190] 4. The method according to Note 2 or 3, wherein in step (b), the laser used for laser grooving is an ultraviolet picosecond laser or an ultraviolet nanosecond laser;

[0191] Preferably, in step (b), the beam of the laser used for laser grooving is a flat-top beam;

[0192] Preferably, in step (b), the laser peak power during the laser grooving process is 0.5 to 2 W;

[0193] Preferably, in step (b), the groove width of the fine grid in the grid line pattern formed after the laser grooving is 10 to 15 μm;

[0194] Preferably, in step (b), the groove depth of the gate line pattern formed after the laser groove is 80 to 100 nm;

[0195] Preferably, in step (b), the auxiliary gas for the laser grooving is selected from any one of nitrogen, argon or helium, preferably nitrogen and / or argon.

[0196] 5. The method according to Supplementary Note 1, wherein the thermal repair process specifically comprises the following steps:

[0197] The double-sided grooved TOPCon solar cell silicon substrate is placed with the front side facing upward in a protective gas atmosphere for thermal repair treatment.

[0198] 6. The method according to Supplementary Note 5, wherein the protective gas is any one of nitrogen, argon or helium, preferably nitrogen;

[0199] Preferably, the flow rate of the protective gas is 20 to 30 L / min;

[0200] Preferably, the temperature of the thermal repair treatment is 600-800°C;

[0201] Preferably, the thermal repair treatment takes 120 to 180 seconds.

[0202] 7. The method according to Supplementary Note 1, wherein the light injection process specifically comprises the following steps:

[0203] First, the silicon substrate after heat repair treatment is placed with one side facing up and placed in a protective gas atmosphere for light injection treatment; then it is turned over so that the other side faces up and placed in a protective gas atmosphere for light injection treatment to obtain a treated TOPCon solar cell substrate.

[0204] 8. The method according to Supplementary Note 7, wherein the protective gas is nitrogen;

[0205] Preferably, the flow rate of the nitrogen is 10 to 15 L / min;

[0206] Preferably, heating is also required during the light injection process;

[0207] Preferably, the heating temperature is 200-300°C;

[0208] Preferably, the light radiation intensity of the light injection treatment is 10 to 30 sun;

[0209] Preferably, the light injection treatment time is 60 to 120 seconds;

[0210] Preferably, the light source for the light injection treatment is white light and / or infrared light.

[0211] 9. A TOPCon solar cell substrate, wherein the TOPCon solar cell substrate is obtained by processing according to any one of the methods described in Notes 1 to 8.

[0212] 10. A double-sided electroplated TOPCon cell, wherein the double-sided electroplated TOPCon cell is obtained by subjecting the TOPCon solar cell substrate described in Note 9 to double-sided electroplating treatment;

[0213] Preferably, the double-sided electroplating treatment includes any one of electroplating nickel, electroplating copper or electroplating tin, or a combination of at least two of them, preferably a combination of electroplating nickel, electroplating copper and electroplating tin.

[0214] Although the present disclosure has been illustrated and described with particular embodiments, it will be appreciated that numerous other changes and modifications may be made without departing from the spirit and scope of the present disclosure. It is therefore intended that the appended claims include all such changes and modifications that fall within the scope of the present disclosure.

Claims

1. A method for preparing a TOPCon battery substrate, comprising: Provide double-sided grooved TOPCon cell silicon substrate; Performing thermal repair treatment on the silicon substrate; The front and back sides of the silicon substrate after the thermal repair treatment are respectively subjected to light injection treatment, thereby obtaining a TOPCon cell substrate.

2. The method according to claim 1, wherein: The double-sided grooved TOPCon solar cell silicon substrate is prepared by the following steps: (a) Depositing a passivation film on the silicon substrate surface of a TOPCon solar cell to form a coating layer; (b) The coating layers on the front and back sides of the silicon substrate are removed by laser grooving to form a gate line pattern on the surface of the coating layers.

3. The method according to claim 2, wherein: In step (a), the passivation film is a silicon nitride film; wherein the thickness of the passivation film is 80 to 100 nm.

4. The method according to claim 2, wherein: In step (b), the laser used for laser grooving is an ultraviolet picosecond laser or an ultraviolet nanosecond laser.

5. The method according to claim 4, wherein: In step (b), the beam of the laser used for laser grooving is a flat-top beam; Wherein, during the laser grooving process, the laser peak power is 0.5-2W.

6. The method according to claim 4, wherein: In step (b), the groove width of the fine grid in the grid line pattern formed after the laser groove is 10-15 μm; the groove depth of the grid line pattern formed after the laser groove is 80-100 nm.

7. The method according to claim 4, wherein: In step (b), the auxiliary gas for laser grooving is selected from any one of nitrogen, argon or helium.

8. The method according to claim 1, wherein: The thermal repair process specifically includes the following steps: The double-sided grooved TOPCon solar cell silicon substrate is placed with the front side facing upward in a protective gas atmosphere for thermal repair treatment.

9. The method according to claim 8, wherein: The protective gas is any one of nitrogen, argon or helium.

10. The method according to claim 8, wherein: The flow rate of the protective gas is 20 to 30 L / min.

11. The method according to claim 8, wherein: The temperature of the thermal repair treatment is 600-800° C.; the time of the thermal repair treatment is 120-180 seconds.

12. The method according to claim 1, wherein: The light injection process specifically comprises the following steps: First, the silicon substrate after thermal repair treatment is placed with one side facing upward and placed in a protective gas atmosphere for light injection treatment; then it is turned over so that the other side faces upward and placed in a protective gas atmosphere for light injection treatment to obtain a treated TOPCon solar cell substrate.

13. The method according to claim 12, wherein: The protective gas is nitrogen.

14. The method according to claim 13, wherein: The flow rate of the nitrogen is 10-15 L / min.

15. The method according to claim 12, wherein: Heating is also required during the light injection process; the heating temperature is 200-300°C.

16. The method according to claim 12, wherein: The light radiation intensity of the light injection treatment is 10 to 30 suns; the time of the light injection treatment is 60 to 120 seconds; the light source of the light injection treatment is white light and / or infrared light.

17. A TOPCon battery substrate, wherein: The TOPCon battery substrate is obtained by processing according to any one of claims 1 to 16.

18. A double-sided electroplated TOPCon battery, wherein: The double-sided electroplated TOPCon cell is obtained by subjecting the TOPCon cell substrate as claimed in claim 17 to double-sided electroplating treatment.

19. The double-sided electroplated TOPCon cell according to claim 18, wherein: The double-sided electroplating process includes any one of nickel electroplating, copper electroplating or tin electroplating, or a combination of at least two of them.

20. The double-sided electroplated TOPCon cell according to claim 19, wherein: The double-sided electroplating process is a combination of three metals: nickel electroplating, copper electroplating and tin electroplating.

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