Method for preparing topcon battery, and topcon battery prepared therefrom

Abstract

A method for preparing a TOPCon battery, and a TOPCon battery prepared therefrom. The method for preparing the TOPCon battery comprises the following steps: sequentially performing chemical nickel plating, sintering, oxide layer removal, copper electroplating and silver electroplating on a TOPCon solar cell substrate to obtain a TOPCon solar cell. According to the preparation method, the conventional screen printing technology is replaced with the chemical nickel plating and copper / silver electroplating technology, the conductivity of the nickel-plated TOPCon substrate is enhanced, and double-sided copper / silver electroplating can be implemented, greatly reducing the production cost of battery cells. A nickel layer obtained by chemical nickel plating has a uniform thickness and a small internal stress, a strong nickel-silicon alloy is formed after sintering, and then copper and silver are electroplated, so that the entire nickel-copper-silver plating has good bonding strength with a silicon substrate, and the welding tension also meets the requirements.

Description

A method for preparing a TOPCon battery and a TOPCon battery prepared thereby

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to Chinese patent application number 202310935553.5 filed with the Patent Office of China on July 26, 2023, entitled “A method for preparing a TOPCon battery and a TOPCon battery prepared thereby”, the entire contents of which are incorporated herein by reference. Technical Field

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

[0004] TOPCon solar cells, a new type of solar cell, have become a hot topic in the solar energy field in recent years. Conventional TOPCon solar cell electrodes are typically screen-printed onto silicon wafers using high-temperature silver paste. However, the sintering temperature of high-temperature silver paste is as high as 500°C, and the silver paste consumption per wafer is 150mg, resulting in high costs.

[0005] In order to reduce costs, some researchers have further proposed using electroplating technology to prepare front and back electrodes. Usually, the first layer of nickel grid lines is formed by electroplating nickel technology, which has a fast plating speed, fine crystals, smooth and bright coating, but is greatly affected by the cleanliness of the silicon wafer surface and the purity of the plating solution. At the same time, due to the uneven current distribution, the thickness of the nickel plating layer is uneven, the internal stress of the nickel layer is large, and there is a problem of poor bonding between the coating and the silicon substrate. The coating can be peeled off from the substrate by tape, and the welding tension under low temperature conditions cannot meet the requirements.

[0006] CN115117186A discloses a method for preparing a TOPCon solar cell, comprising the following steps: (1) independently laser etching a groove on the N-side and P-side of a cell substrate, and cleaning the grooves with hydrofluoric acid; (2) sequentially depositing a nickel-phosphorus alloy layer and a first copper-tin alloy layer in the grooves on the N-side; (3) sequentially depositing a nickel-boron alloy layer and a second copper-tin alloy layer in the grooves on the P-side; and (4) heat-treating the cell substrate to obtain a TOPCon cell. Using a nickel electroplating process, as mentioned above, suffers from the problem of poor bonding between the plating layer and the silicon substrate.

[0007] Public content

[0008] The present disclosure provides a method for preparing a TOPCon battery, comprising the following steps:

[0009] The TOPCon solar cell substrate is subjected to chemical nickel plating, sintering, oxidation layer removal, copper electroplating and silver electroplating in sequence to obtain the TOPCon solar cell.

[0010] Furthermore, the TOPCon solar cell substrate includes a silicon substrate and a coating layer deposited on the surface of the silicon substrate, and the surface of the coating layer has patterned grooves;

[0011] The coating layer is a silicon nitride film;

[0012] The thickness of the silicon nitride film is 80nm-100nm;

[0013] The depth of the groove is 80 nm to 100 nm, and the width of the groove is 10 μm to 60 μm.

[0014] Optionally, the method for preparing the TOPCon solar cell substrate comprises the following steps:

[0015] (a) coating both sides of a silicon substrate to form coating layers, and then removing the coating layers on the surface of the silicon substrate by laser grooving to form patterned grooves on the surface of the coating layers;

[0016] (b) Degreasing, oxidation layer removal, and activation treatment are performed in sequence on the patterned grooves of the silicon substrate to obtain a pretreated TOPCon solar cell substrate.

[0017] Furthermore, in step (a), the coating method is PECVD;

[0018] The process parameters of the PECVD method are as follows:

[0019] Pressure 1400mTorr-1800mTorr, temperature 400℃-500℃, power 8000W-12000W, time 90s-120s, pulse on-off ratio 1:(8-10), volume ratio of SiH4 and NH3 1:(4-8).

[0020] Furthermore, in step (b), the oil removal and cleaning method comprises the following steps:

[0021] The TOPCon battery substrate with patterned grooves is placed in a degreasing agent solution and subjected to ultrasonic treatment;

[0022] The volume percentage of the degreasing agent in the degreasing agent solution is 5%-20%;

[0023] The degreasing agent includes at least one of toluene, acetone and ethanol;

[0024] The process parameters of the ultrasonic treatment are as follows:

[0025] Ultrasonic temperature is 30℃-40℃, ultrasonic time is 30s-120s, and ultrasonic power is 60W-120W.

[0026] Furthermore, in step (b), the method for removing the oxidation layer comprises the following steps:

[0027] Soak the degreased and cleaned TOPCon battery substrate in a solution for removing the oxidation layer;

[0028] The deoxidation layer solution comprises the following components in parts by weight:

[0029] 0.1-5 parts of ammonium fluoride, 1-10 parts of hydrofluoric acid, 100-200 parts of water;

[0030] The immersion temperature in the oxidation layer removal solution is 25° C.-35° C., and the immersion time is 30s-90s.

[0031] Furthermore, in step (b), the activation treatment method comprises the following steps:

[0032] The TOPCon battery substrate after the oxide layer is removed is immersed in the activation solution;

[0033] The activation solution comprises the following components in parts by weight:

[0034] 0.001-0.005 parts of activator, 100-200 parts of water;

[0035] The activator is a chloride of a noble metal;

[0036] The noble metal chloride is selected from at least one of gold chloride, palladium chloride and platinum chloride;

[0037] The soaking temperature in the activation solution is 25° C.-35° C., and the soaking time is 60 s-120 s.

[0038] Furthermore, the method for chemical nickel plating comprises the following steps:

[0039] The TOPCon solar cell substrate is placed in a chemical nickel plating solution and subjected to a heat treatment;

[0040] The heating temperature is 90-100°C and the heating time is 2-5 minutes.

[0041] The chemical nickel plating solution comprises the following components in parts by weight:

[0042] 1-5 parts of nickel salt, 1-5 parts of reducing agent, 5-20 parts of complexing agent, 100-200 parts of water;

[0043] The nickel salt is selected from at least one of nickel sulfate, nickel chloride and nickel sulfamate;

[0044] The reducing agent is selected from at least one of sodium hypophosphite, sodium borohydride and borane;

[0045] The complexing agent includes sodium citrate and ammonia water, and the mass ratio of the sodium citrate to ammonia water is (1-2): (5-15);

[0046] The pH value of the chemical nickel plating solution is 8.5-9.5.

[0047] Furthermore, the sintering process parameters are as follows:

[0048] The heating rate is 5℃ / s~10℃ / s, the sintering temperature is 280℃-360℃, and the sintering time is 60s-120s.

[0049] Furthermore, the method for removing the oxidation layer comprises the following steps:

[0050] The sintered TOPCon solar cell substrate is immersed in a deoxidation layer solution;

[0051] The oxidation layer removal solution is an acid aqueous solution, and the volume percentage of the acid in the acid aqueous solution is 2%-6%;

[0052] The acid is selected from at least one of hydrofluoric acid, sulfuric acid, hydrochloric acid and nitric acid;

[0053] The soaking temperature is 25° C.-35° C., and the soaking time is 30s-60s.

[0054] Furthermore, the copper electroplating method comprises the following steps:

[0055] The TOPCon battery substrate after the oxide layer is removed is placed in a copper electroplating solution and current is applied to electroplate copper;

[0056] The copper electroplating solution comprises the following components in parts by weight:

[0057] 1-10 parts of copper salt, 0.5-3 parts of acid, 20-40 parts of water;

[0058] The copper salt includes copper sulfate and copper chloride, and the mass ratio of copper sulfate to copper chloride is (400-600):(0.1-0.5);

[0059] The acid is sulfuric acid.

[0060] Furthermore, the process parameters of the copper electroplating are as follows:

[0061] Current density 5A / dm 2 -10A / dm2 , electroplating time 5min-10min.

[0062] Furthermore, the silver electroplating method comprises the following steps:

[0063] The copper-plated TOPCon battery substrate is placed in a silver electroplating solution and current is applied for silver electroplating.

[0064] Furthermore, the silver electroplating solution comprises the following components in parts by weight:

[0065] 0.1-1 parts of silver salt, 0.5-3 parts of acid, 0.5-5 parts of ammonium salt, 20-40 parts of water;

[0066] The silver salt is silver nitrate;

[0067] The acid is sulfosalicylic acid.

[0068] Furthermore, the process parameters of the silver electroplating are as follows:

[0069] Current density 1A / dm 2 -2A / dm 2 , electroplating time 15s-30s.

[0070] The present disclosure further provides a TOPCon battery prepared by the above preparation method. BRIEF DESCRIPTION OF THE DRAWINGS

[0071] In order to more clearly illustrate the specific embodiments of the present disclosure or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present disclosure. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0072] FIG1 is a process flow chart of the preparation method of TOPCon battery. DETAILED DESCRIPTION

[0073] 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.

[0074] In order to solve one of the technical problems existing in the prior art, the present disclosure provides a method for preparing a TOPCon battery, comprising the following steps:

[0075] The TOPCon solar cell substrate is subjected to chemical nickel plating, sintering, oxidation layer removal, copper electroplating and silver electroplating in sequence to obtain the TOPCon solar cell.

[0076] The traditional screen printing technology is replaced by chemical nickel plating + copper-silver electroplating technology. After nickel plating, the conductivity of the TOPCon substrate is enhanced, and double-sided copper and silver electroplating can be achieved, which greatly reduces the production cost of the battery cell. The nickel layer obtained by chemical nickel plating has uniform thickness and low internal stress. After sintering, a strong nickel-silicon alloy is formed. Then, copper and silver are electroplated. The entire nickel-copper-silver coating has good bonding strength with the silicon substrate, and the welding tensile strength also meets the requirements.

[0077] The TOPCon battery prepared by the above preparation method provided in the present disclosure has good working performance.

[0078] In an optional embodiment of the present disclosure, a TOPCon solar cell substrate includes a silicon substrate and a coating layer deposited on the surface of the silicon substrate, and the surface of the coating layer has patterned grooves.

[0079] It should be noted that the patterned grooves are crisscrossed grooves, and the grooves include main grooves and fine grooves. The width of the main grooves may be 50 μm-60 μm; the width of the fine grooves may be 10 μm-15 μm.

[0080] In an optional embodiment of the present disclosure, the TOPCon solar cell substrate is prepared by the following method:

[0081] (a) coating both sides of a silicon substrate to form coating layers, and then removing the coating layers on the surface of the silicon substrate by laser grooving to form patterned grooves on the surface of the coating layers;

[0082] (b) Degreasing, oxidation layer removal, and activation treatment are performed in sequence on the patterned grooves of the silicon substrate to obtain a pretreated TOPCon solar cell substrate.

[0083] In an optional embodiment of the present disclosure, in step (a), the coating method is PECVD;

[0084] The process parameters of the PECVD method are as follows:

[0085] Pressure 1400mTorr-1800mTorr; temperature 400℃-500℃; power 8000W-12000W; time 90s-120s; pulse on / off ratio 1:(8-10); volume ratio of SiH4 and NH3 1:(4-8).

[0086] In an optional embodiment of the present disclosure, in step (b), the specific steps of degreasing and cleaning are: placing the TOPCon battery substrate with the patterned grooves formed therein in a degreasing agent solution and performing ultrasonic treatment.

[0087] The volume percentage of the deoiling agent in the deoiling agent solution is 5%-20%; wherein, the solvent of the deoiling agent solution can be water, and the deoiling agent is selected from any one of toluene, acetone or ethanol or a combination of at least two thereof.

[0088] In an optional embodiment of the present disclosure, the process parameters of the ultrasonic treatment are as follows: ultrasonic temperature 30°C-40°C, ultrasonic time 30s-120s, and ultrasonic power 60W-120W.

[0089] In an optional embodiment of the present disclosure, in step (b), the specific steps of removing the oxidation layer are: immersing the TOPCon battery substrate after degreasing and cleaning in a solution for removing the oxidation layer;

[0090] The immersion temperature in the oxidation layer removal solution can be 25° C.-35° C., and the immersion time can be 30s-90s. The oxidation layer removal solution comprises, by weight, 0.1-5 parts of ammonium fluoride, 1-10 parts of hydrofluoric acid, and 100-200 parts of water.

[0091] In an optional embodiment of the present disclosure, in step (b), the specific steps of the activation treatment are: immersing the TOPCon battery substrate after the oxide layer is removed in an activation solution;

[0092] The immersion temperature in the activation solution can be 25° C.-35° C., and the immersion time can be 60s-120s. The activation solution comprises, by weight, 0.001-0.005 parts of an activator and 100-200 parts of water. The activator can be a chloride of a noble metal, and the chloride of the noble metal is selected from any one or a combination of at least two of gold chloride, palladium chloride or platinum chloride.

[0093] In an optional embodiment of the present disclosure, the TOPCon solar cell substrate is prepared by the following method:

[0094] (a) PECVD is used to coat both sides of a silicon substrate to form 80nm-100nm thick silicon nitride films. The coating layer on the surface of the silicon substrate is then removed by laser grooving to form patterned grooves with a depth of 80nm-100nm and a width of 10μm-60μm on the surface of the coating layer.

[0095] (b) The TOPCon battery substrate with patterned grooves was placed in a degreasing agent solution and ultrasonically treated at 30°C-40°C and a power of 60W-120W for 30s-120s, followed by washing.

[0096] Place the degreased and cleaned TOPCon battery substrate in a deoxidation solution, soak for 30s-90s at 25℃-35℃, and then wash.

[0097] The TOPCon solar cell substrate after the oxide layer is removed is placed in an activation solution, immersed in an activation solution at 25° C. to 35° C. for 60s to 120s, and then washed to obtain a pretreated TOPCon solar cell substrate.

[0098] Through chemical immersion degreasing and the use of ultrasonic vibration, the oil and particulate contaminants on the surface of the TOPCon battery substrate are removed, the surface tension of the substrate is reduced, and the wettability is improved. By placing it in a deoxidation solution, the oxide film generated on the substrate surface can be effectively removed. And precious metal salts are used for activation. After the silicon wafer surface is treated with the activation solution, the nickel plating efficiency is high, the nickel plating solution utilization rate is high, and the subsequent chemical nickel plating layer is uniform in thickness without abnormalities such as blooming and shining.

[0099] In an optional embodiment of the present disclosure, the specific steps of chemical nickel plating are: placing the TOPCon solar cell substrate in a chemical nickel plating solution and performing a heat treatment; wherein the heating treatment temperature can be 90°C-100°C, and the heating treatment time can be 2min-5min.

[0100] By using chemical nickel plating, a nickel layer with uniform thickness and low internal stress can be formed on both sides of the pre-treated TOPCon solar cell substrate, achieving double-sided nickel plating. At the same time, by controlling the temperature and the main salt concentration during the chemical nickel plating process, the normal progress of the reaction is maintained, and the thickness is continuously and stably increased, so as to further improve the uniformity and smoothness of the surface of the chemical nickel plating layer.

[0101] In an optional embodiment of the present disclosure, the chemical nickel plating solution comprises, by weight: 1-5 parts of nickel salt, 1-5 parts of reducing agent, 5-20 parts of complexing agent, and 100-200 parts of water;

[0102] The nickel salt is selected from any one of nickel sulfate, nickel chloride or nickel sulfamate, or a combination of at least two of them; the reducing agent is selected from any one of sodium hypophosphite, sodium borohydride or borane, or a combination of at least two of them; the complexing agent includes sodium citrate and ammonia water, and the mass ratio of sodium citrate to ammonia water can be (1-2): (5-15).

[0103] The electroless nickel plating solution containing the aforementioned specific reducing agent and complexing agent is selected for nickel plating. Hypophosphite is low-priced, the plating solution is easy to control, and the alloy coating has good performance. Sodium borohydride or borane has better reducing properties, requiring only a small amount to achieve the reduction effect. The complexing agent acts synergistically to prevent precipitation in the plating solution, increase plating solution stability and extend service life, while also increasing the deposition rate. Through the configuration of the electroless nickel plating solution, the normal reaction is maintained, and the thickness is continuously and stably increased, further improving the uniformity and smoothness of the electroless nickel plating surface.

[0104] In an optional embodiment of the present disclosure, sintering is performed in an annealing furnace;

[0105] The sintering process parameters are: heating rate 5°C / s to 10°C / s; sintering temperature 280°C to 360°C; and sintering time 60s to 120s.

[0106] By adopting the above-mentioned specific sintering process parameters, nickel atoms diffuse into the interior of the silicon, and the nickel layer and the silicon layer are combined with each other. After sintering, the nickel layer and the silicon substrate form a stronger nickel-silicon alloy, and the bonding force is further improved.

[0107] In an optional embodiment of the present disclosure, the specific steps of removing the oxidation layer are: immersing the sintered TOPCon solar cell substrate in a solution for removing the oxidation layer;

[0108] The immersion temperature in the oxidation layer removal solution can be 25° C.-35° C., and the immersion time can be 30s-60s. The oxidation layer removal solution is an acid aqueous solution, and the volume percentage of the acid in the acid aqueous solution can be 2%-6%. The acid is selected from any one of hydrofluoric acid, sulfuric acid, hydrochloric acid or nitric acid, or a combination of at least two of them.

[0109] In the present disclosure, the activation treatment using dilute acid solution not only removes the oxide layer on the surface of the product, but also prevents the formation of a large amount of new pickling products attached to the surface of the sintered nickel-silicon alloy, thereby ensuring the cleanliness of the nickel-silicon alloy and further improving the bonding strength with the copper layer.

[0110] In an optional embodiment of the present disclosure, the specific steps of electroplating copper are: placing the TOPCon battery substrate after the oxide layer is removed in a copper electroplating solution, applying current to perform electroplating;

[0111] The electroplating copper solution comprises, by weight, 1-10 parts of a copper salt, 0.5-3 parts of an acid, and 20-40 parts of water; the copper salt comprises copper sulfate and copper chloride, and the mass ratio of copper sulfate to copper chloride can be (400-600):(0.1-0.5); and the acid can be sulfuric acid.

[0112] In this disclosure, the process parameters of copper electroplating are: current density 5A / dm2 -10 A / dm 2 ;Electroplating time 5min-10min.

[0113] In an optional embodiment of the present disclosure, the specific steps of electroplating silver are: placing the copper-plated TOPCon battery substrate in a silver electroplating solution, and applying current to perform electroplating;

[0114] The electroplating silver solution comprises, by weight, 0.1-1 parts of silver salt, 0.5-3 parts of acid, 0.5-5 parts of ammonium salt, and 20-40 parts of water; the silver salt may be silver nitrate, and the acid may be sulfosalicylic acid.

[0115] In this disclosure, the process parameters of silver electroplating are: current density 1A / dm 2 -2A / dm 2 .

[0116] In an optional embodiment of the present disclosure, a method for preparing a TOPCon battery includes the following steps:

[0117] S1 coating: coating both sides of the silicon substrate to form a silicon nitride coating layer, then removing the coating layer on the surface of the silicon substrate using a laser grooving method to form patterned grooves on the surface of the coating layer;

[0118] S2 pretreatment: Degreasing, cleaning, and activating the patterned grooves of the silicon substrate are performed in sequence to obtain a pretreated TOPCon solar cell substrate;

[0119] S3 chemical nickel plating: placing the pre-treated TOPCon solar cell substrate in a chemical nickel plating solution and performing a heating treatment to form a nickel plating layer;

[0120] S4 sintering: The nickel-plated TOPCon solar cell substrate is sintered at high temperature to form a nickel-silicon alloy layer;

[0121] S5: Remove the oxide layer: soak the sintered TOPCon solar cell substrate in the oxide layer removal solution to remove the oxide layer;

[0122] S6 copper electroplating: Place the TOPCon battery substrate after the oxide layer is removed in the copper electroplating solution and apply current for electroplating;

[0123] S7 Silver Electroplating: Place the copper-plated TOPCon battery substrate in a silver electroplating solution and apply current for electroplating to obtain a TOPCon battery.

[0124] 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.

[0125] Figure 1 is a process flow chart of the preparation method of the TOPCon battery. As shown in Figure 1, the process includes the following steps: S1 coating, S2 pretreatment: degreasing, cleaning, removing the oxide layer, and activation treatment are sequentially performed on the patterned grooves of the silicon substrate to obtain a pretreated TOPCon solar cell substrate, S3 chemical nickel plating, S4 sintering, S5 removing the oxide layer, S6 electroplating copper, and S7 electroplating silver to obtain a TOPCon battery.

[0126] Example 1

[0127] This embodiment provides a method for preparing a TOPCon battery, the method comprising the following steps:

[0128] S1 coating: The two sides of the silicon substrate are coated separately, forming an 80nm silicon nitride coating layer on the front and back sides respectively; then the coating layer on the surface of the silicon substrate is removed by laser grooving method, and patterned grooves are formed on the surface of the coating layer;

[0129] The coating is carried out by PECVD method, and the process parameters of the coating are: pressure 1400mTorr, temperature 400°C, power 8000W, time 90s, pulse on / off ratio 1:8, SiH4 / NH3=1:4;

[0130] The patterned grooves are crisscrossed grooves, the depth of the grooves is 80 nm, the grooves include main grooves and fine grooves, the width of the main grooves is 55 μm, and the width of the fine grooves is 12 μm.

[0131] S2 pretreatment: Place the TOPCon cell substrate with patterned grooves in a degreasing agent solution, ultrasonically treat it at 35°C and 60W power for 60s, and then rinse it with deionized water; place the TOPCon cell substrate after degreasing and cleaning in a deoxidation layer solution, soak it at 25°C for 60s, and then rinse it with deionized water; place the TOPCon cell substrate after deoxidation layer in an activation solution, soak it at 25°C for 90s, and then rinse it with deionized water to obtain a pretreated TOPCon solar cell substrate;

[0132] The degreasing agent solution is a 10 vol% toluene aqueous solution; the deoxidation layer solution is a mixture of 15 g ammonium fluoride, 60 mL hydrofluoric acid and 1500 mL deionized water; and the activation solution is a mixture of 0.025 g gold chloride and 1500 mL deionized water.

[0133] S3 chemical nickel plating: Place the pretreated TOPCon solar cell substrate in a chemical nickel plating solution and react at 95°C for 3 minutes to form a nickel plating layer;

[0134] The chemical nickel plating solution is a mixture of 35 g nickel sulfate, 30 g sodium borohydride, 15 g sodium citrate, 100 mL ammonia water and 1500 mL deionized water, and the pH is maintained at 9.

[0135] S4 sintering: Place the nickel-plated TOPCon battery substrate in an annealing furnace, set the heating rate to 7°C / s, the sintering temperature to 320°C, and the sintering time to 90s.

[0136] S5: Place the sintered TOPCon solar cell substrate in a deoxidation solution and soak it at 25°C for 45 seconds to remove the oxide layer, then rinse with deionized water.

[0137] The oxidation layer removal solution is a 4 vol% hydrofluoric acid aqueous solution.

[0138] S6 copper electroplating: Place the TOPCon battery substrate after the oxide layer is removed in the copper electroplating solution and apply a current of 7.5A / dm 2 , the electroplating time is 7.5min, and then rinsed with deionized water;

[0139] The copper electroplating solution is a mixture of 500 g of copper sulfate pentahydrate, 150 g of sulfuric acid, 0.25 g of copper chloride, and 3000 mL of deionized water.

[0140] S7 Silver Electroplating: Place the copper-plated TOPCon battery substrate in the silver electroplating solution and apply a current of 1.5A / dm 2 , the electroplating time is 20s, and then rinsed with deionized water to obtain the TOPCon battery;

[0141] The silver electroplating solution is a mixture of 45 g silver nitrate, 160 g sulfosalicylic acid, 160 g ammonium acetate, and 3000 mL deionized water.

[0142] Example 2

[0143] This embodiment provides a method for preparing a TOPCon battery, the method comprising the following steps:

[0144] S1 coating: The two sides of the silicon substrate are coated separately, forming a 90nm silicon nitride coating layer on the front and back sides respectively; then the coating layer on the surface of the silicon substrate is removed by laser grooving method, and patterned grooves are formed on the surface of the coating layer;

[0145] The coating is carried out by PECVD method, and the process parameters of the coating are: pressure 1500mTorr, temperature 430°C, power 9000W, time 100s, pulse on / off ratio 1:9, SiH4 / NH3=1:6;

[0146] The patterned grooves are crisscrossed grooves, the depth of the grooves is 90 nm, the grooves include main grooves and fine grooves, the width of the main grooves is 50 μm, and the width of the fine grooves is 10 μm.

[0147] S2 pretreatment: Place the TOPCon cell substrate with patterned grooves in a degreasing agent solution, ultrasonically treat it at 30°C and 80W power for 120s, and then rinse it with deionized water; place the TOPCon cell substrate after degreasing and cleaning in an oxidation layer removal solution, soak it at 28°C for 30s, and then rinse it with deionized water; place the TOPCon cell substrate after oxidation layer removal in an activation solution, soak it at 28°C for 60s, and then rinse it with deionized water to obtain a pretreated TOPCon solar cell substrate;

[0148] The degreasing agent solution is a 5 vol% acetone aqueous solution; the oxidation layer removal solution is a mixture of 10 g ammonium fluoride, 40 mL hydrofluoric acid and 1000 mL deionized water; and the activation solution is a mixture of 0.01 g palladium chloride and 1000 mL deionized water.

[0149] S3 chemical nickel plating: Place the pretreated TOPCon solar cell substrate in a chemical nickel plating solution and react at 90°C for 5 minutes to form a nickel plating layer;

[0150] The chemical nickel plating solution is a mixture of 50 g nickel chloride, 50 g sodium hypophosphite, 20 g sodium citrate, 150 mL ammonia water and 2000 mL deionized water, and the pH is maintained at 9.5.

[0151] S4 sintering: Place the nickel-plated TOPCon battery substrate in an annealing furnace, set the heating rate to 5°C / s, the sintering temperature to 280°C, and the sintering time to 120s.

[0152] S5: Place the sintered TOPCon solar cell substrate in a deoxidation solution and soak it at 28°C for 30 seconds to remove the oxide layer, then rinse with deionized water.

[0153] The oxidation layer removal solution is a 2 vol% sulfuric acid aqueous solution.

[0154] S6 copper electroplating: Place the TOPCon battery substrate after the oxide layer is removed in the copper electroplating solution and apply a current of 5A / dm 2 , the electroplating time is 10 min, and then rinsed with deionized water;

[0155] The copper electroplating solution is a mixture of 400 g of copper sulfate pentahydrate, 100 g of sulfuric acid, 0.1 g of copper chloride, and 2000 mL of deionized water.

[0156] S7 Silver Electroplating: Place the copper-plated TOPCon battery substrate in the silver electroplating solution and apply a current of 1A / dm 2 , the electroplating time is 30s, and then rinsed with deionized water to obtain the TOPCon battery;

[0157] The silver electroplating solution is a mixture of 30 g silver nitrate, 120 g sulfosalicylic acid, 120 g ammonium acetate, and 2000 mL deionized water.

[0158] Example 3

[0159] This embodiment provides a method for preparing a TOPCon battery, the method comprising the following steps:

[0160] S1 coating: The two sides of the silicon substrate are coated separately, forming a 100nm silicon nitride coating layer on the front and back sides respectively; then the coating layer on the surface of the silicon substrate is removed by laser grooving method, and patterned grooves are formed on the surface of the coating layer;

[0161] The coating is carried out by PECVD method, and the process parameters of the coating are: pressure 1800mTorr, temperature 480°C, power 12000W, time 120s, pulse on / off ratio 1:10, SiH4 / NH3=1:6;

[0162] The patterned grooves are crisscrossed grooves, the depth of the grooves is 100 nm, the grooves include main grooves and fine grooves, the width of the main grooves is 60 μm, and the width of the fine grooves is 15 μm.

[0163] S2 pretreatment: Place the TOPCon cell substrate with patterned grooves in a degreasing agent solution, ultrasonically treat it at 40°C and 100W power for 30 seconds, and then rinse it with deionized water; Place the TOPCon cell substrate after degreasing and cleaning in an oxidation layer removal solution, soak it at 35°C for 90 seconds, and then rinse it with deionized water; Place the TOPCon cell substrate after oxidation layer removal in an activation solution, soak it at 35°C for 120 seconds, and then rinse it with deionized water to obtain a pretreated TOPCon solar cell substrate;

[0164] The degreasing agent solution is a 20 vol% ethanol aqueous solution; the oxidation layer removal solution is a mixture of 20 g ammonium fluoride, 80 mL hydrofluoric acid and 2000 mL deionized water; and the activation solution is a mixture of 0.05 g platinum chloride and 2000 mL deionized water.

[0165] S3 chemical nickel plating: Place the pretreated TOPCon solar cell substrate in a chemical nickel plating solution and react at 100°C for 2 minutes to form a nickel plating layer;

[0166] The chemical nickel plating solution is a mixture of 25 g nickel sulfamate, 25 g borane, 10 g sodium citrate, 50 mL ammonia water and 1000 mL deionized water, and the pH is maintained at 8.5.

[0167] S4 sintering: Place the nickel-plated TOPCon battery substrate in an annealing furnace, set the heating rate to 10°C / s, the sintering temperature to 360°C, and the sintering time to 60s.

[0168] S5: Place the sintered TOPCon solar cell substrate in a deoxidation solution and soak it at 35°C for 60 seconds to remove the oxide layer, then rinse with deionized water.

[0169] The oxidation layer removal solution is a 6 vol% hydrochloric acid aqueous solution.

[0170] S6 copper electroplating: Place the TOPCon battery substrate after the oxide layer is removed in the copper electroplating solution and apply a current of 10A / dm 2 , the electroplating time is 5 min, and then rinsed with deionized water;

[0171] The copper electroplating solution is a mixture of 600 g of copper sulfate pentahydrate, 200 g of sulfuric acid, 0.5 g of copper chloride, and 4000 mL of deionized water.

[0172] S7 Silver Electroplating: Place the copper-plated TOPCon battery substrate in the silver electroplating solution and apply a current of 2A / dm 2 , the electroplating time is 15s, and then rinsed with deionized water to obtain the TOPCon battery;

[0173] The silver electroplating solution is a mixture of 60 g silver nitrate, 200 g sulfosalicylic acid, 200 g ammonium acetate, and 4000 mL deionized water.

[0174] Example 4

[0175] This embodiment provides a method for preparing a TOPCon battery. The only difference from Example 1 is that the chemical nickel plating in S3 is carried out at 85° C. for 15 minutes. The other steps are completely consistent with Example 1.

[0176] Example 5

[0177] This embodiment provides a method for preparing a TOPCon battery. The only difference from Example 1 is that the chemical nickel plating of S3 is carried out at 105° C. for 1 minute. The other steps are completely consistent with Example 1.

[0178] Example 6

[0179] This embodiment provides a method for preparing a TOPCon battery. The only difference from Example 1 is that the reducing agent is replaced by an equal mass of formaldehyde, the sodium citrate is replaced by an equal mass of citric acid, and the ammonia water is replaced by an equal volume of a 25 vol% triethylamine aqueous solution. The other steps are exactly the same as in Example 1.

[0180] Example 7

[0181] This embodiment provides a method for preparing a TOPCon battery. The only difference from Example 1 is that S4 sets the heating rate to 4°C / s, the sintering temperature to 380°C, and the sintering time to 40s. The other steps are exactly the same as Example 1.

[0182] Example 8

[0183] This embodiment provides a method for preparing a TOPCon battery. The only difference from Example 1 is that S4 sets the heating rate to 12°C / s, the sintering temperature to 260°C, and the sintering time to 180s. The other steps are exactly the same as Example 1.

[0184] Comparative Example 1

[0185] This comparative example provides a method for preparing a TOPCon battery, which differs from Example 1 only in that the S2 pretreatment step is not performed, and the other steps are exactly the same as those in Example 1.

[0186] Comparative Example 2

[0187] This comparative example provides a method for preparing a TOPCon cell. The only difference from Example 1 is that S3 uses nickel electroplating: the pretreated TOPCon solar cell substrate is placed in a nickel electroplating solution and a current of 1A / dm is applied. 2 , the electroplating time is 5 minutes, and then it is rinsed with deionized water to obtain the TOPCon battery; wherein, the nickel electroplating solution is a mixture of 150g nickel sulfate, 20g sodium chloride, 30mL boric acid and 1000mL deionized water, and the other steps are exactly the same as in Example 1.

[0188] Comparative Example 3

[0189] This comparative example provides a method for preparing a TOPCon battery, which differs from Example 1 only in that the S4 sintering step is not performed, and the other steps are exactly the same as those in Example 1.

[0190] Comparative Example 4

[0191] This comparative example provides a method for preparing a TOPCon battery, which differs from Example 1 only in that the step of removing the oxidation layer in S5 is not performed, and the other steps are completely consistent with Example 1.

[0192] Experimental Example 1

[0193] Adhesion test

[0194] Test samples: TOPCon batteries prepared in Examples 1-8 and Comparative Examples 1-4;

[0195] Test methods: (1) Adhesion between coating and silicon substrate: 3M tape test; (2) Welding tensile strength under low temperature conditions: tensile test;

[0196] The specific test results are shown in Table 1:

[0197] Table 1

[0198] It can be seen from the test data in Table 1 that the bonding strength between the TOPCon solar cell coating and the silicon substrate prepared by the preparation method disclosed in the present invention can pass the 3M tape test, and the welding tensile force under low temperature conditions is above 0.8N. Examples 1-3 are preferred technical solutions, and the welding tensile force under low temperature conditions is above 1.5N, indicating that the nickel layer obtained by chemical nickel plating according to the preparation method disclosed in the present invention has uniform thickness and low internal stress. After sintering, a strong nickel-silicon alloy is formed, and then copper and silver are electroplated. The bonding strength of the entire nickel-copper-silver coating and the silicon substrate is good, and the welding tensile force also meets the requirements.

[0199] Experimental Example 2

[0200] Electrical performance test

[0201] Test sample: TOPCon battery prepared in Examples 1-8;

[0202] Test method: The battery obtained in Example 1 was tested for electrical performance using the IV test method (test conditions: 25°C, AM1.5G);

[0203] The specific test results are shown in Table 2:

[0204] Table 2

[0205] As can be seen from the test data in Table 2, the conductivity of the TOPCon substrate is enhanced after nickel plating using the disclosed method, and double-sided electroplating of copper and silver can be achieved; it also effectively reduces the parasitic absorption and short-circuit current density loss of the silicon film on the back of the TOPCon battery, greatly reducing the production cost of the battery cell and improving the conversion efficiency of the battery.

[0206] While particular embodiments of the present disclosure have been illustrated and described, it will be understood that various other changes and modifications can be made without departing from the spirit and scope of the disclosure.

Claims

1. A method for preparing a TOPCon battery, characterized in that: The preparation method of the TOPCon battery comprises the following steps: The TOPCon solar cell substrate is subjected to chemical nickel plating, sintering, oxide layer removal, copper electroplating and silver electroplating in sequence to obtain a TOPCon solar cell.

2. The preparation method according to claim 1, characterized in that: The TOPCon solar cell substrate comprises a silicon substrate and a coating layer deposited on the surface of the silicon substrate, and the surface of the coating layer has a patterned groove; The coating layer is a silicon nitride film; The thickness of the silicon nitride film is 80nm-100nm; The depth of the groove is 80nm-100nm, and the width of the groove is 10μm-60μm.

3. The preparation method according to claim 1, characterized in that: The preparation method of the TOPCon solar cell substrate comprises the following steps: (a) coating the two sides of the silicon substrate respectively to form a coating layer, and then removing the coating layer on the surface of the silicon substrate by a laser grooving method to form a patterned groove on the surface of the coating layer; (b) Degreasing cleaning, oxide layer removal, and activation treatment are performed in sequence on the patterned grooves of the silicon substrate to obtain a pre-treated TOPCon solar cell substrate.

4. The preparation method according to claim 3, characterized in that: In step (a), the coating method is PECVD; The process parameters of the PECVD method are as follows: Pressure 1400mTorr-1800mTorr, temperature 400℃-500℃, power 8000W-12000W, time 90s-120s, pulse switching ratio 1:(8-10), volume ratio of SiH4 and NH3 1:(4-8).

5. The preparation method according to claim 3, characterized in that: In step (b), the degreasing and cleaning method comprises the following steps: The TOPCon battery substrate with the patterned grooves is placed in a degreasing agent solution and subjected to ultrasonic treatment; The volume percentage of the degreasing agent in the degreasing agent solution is 5%-20%; The degreasing agent includes at least one of toluene, acetone and ethanol; The process parameters of the ultrasonic treatment are as follows: Ultrasonic temperature is 30℃-40℃, ultrasonic time is 30s-120s, and ultrasonic power is 60W-120W.

6. The preparation method according to claim 3, characterized in that: In step (b), the method for removing the oxide layer comprises the following steps: Soak the degreased and cleaned TOPCon battery substrate in a deoxidation layer solution; The deoxidation layer solution comprises the following components by weight: 0.1-5 parts of ammonium fluoride, 1-10 parts of hydrofluoric acid, 100-200 parts of water; The immersion temperature in the oxidation layer removal solution is 25° C.-35° C., and the immersion time is 30s-90s.

7. The preparation method according to claim 3, characterized in that: In step (b), the activation treatment method comprises the following steps: The TOPCon battery substrate after the oxide layer is removed is immersed in an activation solution; The activation solution comprises the following components by weight: Activator 0.001-0.005 parts, water 100-200 parts; The activator is a chloride of a noble metal; The chloride of the noble metal is selected from at least one of gold chloride, palladium chloride and platinum chloride; The immersion temperature in the activation solution is 25° C.-35° C., and the immersion time is 60 s-120 s.

8. The preparation method according to claim 1, characterized in that: The method for chemical nickel plating comprises the following steps: The TOPCon solar cell substrate is placed in a chemical nickel plating solution and subjected to a heating treatment; The heating treatment temperature is 90°C-100°C, and the heating treatment time is 2min-5min; The chemical nickel plating solution comprises the following components by weight: 1-5 parts of nickel salt, 1-5 parts of reducing agent, 5-20 parts of complexing agent, 100-200 parts of water; The nickel salt is selected from at least one of nickel sulfate, nickel chloride and nickel sulfamate; The reducing agent is selected from at least one of sodium hypophosphite, sodium borohydride and borane; The complexing agent includes sodium citrate and ammonia water, and the mass ratio of the sodium citrate to ammonia water is (1-2):(5-15); The pH value of the chemical nickel plating solution is 8.5-9.

5.

9. The preparation method according to claim 1, characterized in that: The process parameters of the sintering are as follows: The heating rate is 5℃ / s~10℃ / s, the sintering temperature is 280℃-360℃, and the sintering time is 60s-120s.

10. The preparation method according to claim 1, characterized in that: The method for removing the oxide layer comprises the following steps: The sintered TOPCon solar cell substrate is immersed in a deoxidation layer solution; The deoxidized layer solution is an acid aqueous solution, and the volume percentage of the acid in the acid aqueous solution is 2%-6%; The acid is selected from at least one of hydrofluoric acid, sulfuric acid, hydrochloric acid and nitric acid; The soaking temperature is 25° C.-35° C., and the soaking time is 30s-60s.

11. The preparation method according to claim 1, characterized in that: The copper electroplating method comprises the following steps: The TOPCon battery substrate after the oxide layer is removed is placed in a copper electroplating solution, and current is applied to electroplate copper; The copper electroplating solution comprises the following components by weight: 1-10 parts of copper salt, 0.5-3 parts of acid, 20-40 parts of water; The copper salt includes copper sulfate and copper chloride, and the mass ratio of copper sulfate to copper chloride is (400-600):(0.1-0.5); The acid is sulfuric acid.

12. The preparation method according to claim 11, characterized in that: The process parameters of the copper electroplating are as follows: Current density 5A / dm 2 -10A / dm 2 , electroplating time 5min-10min.

13. The preparation method according to claim 1, characterized in that: The method for electroplating silver comprises the following steps: The copper-plated TOPCon battery substrate is placed in a silver electroplating solution and current is applied to perform silver electroplating.

14. The preparation method according to claim 13, characterized in that: The electroplating silver solution comprises the following components in parts by weight: 0.1-1 parts of silver salt, 0.5-3 parts of acid, 0.5-5 parts of ammonium salt, 20-40 parts of water; The silver salt is silver nitrate; The acid is sulfosalicylic acid.

15. The preparation method according to claim 14, characterized in that: The process parameters of the silver electroplating are as follows: Current density 1A / dm 2 -2A / dm 2 , electroplating time 15s-30s.

16. A TOPCon battery, characterized in that: The TOPCon battery is prepared by the preparation method according to any one of claims 1 to 15.

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