Titanium seed layer, preparation method therefor, and solar cell preparation method

Abstract

The present disclosure relates to the technical field of solar cells, and relates to a titanium seed layer, a preparation method therefor, and a solar cell preparation method. The titanium seed layer preparation method comprises the following step: using a dual-pulse magnetron sputtering method to prepare a titanium seed layer within a preset grid-line region on a silicon substrate of a cell. Compared with conventional methods, the titanium seed layer prepared by the dual-pulse magnetron sputtering method of the present disclosure is smoother and finer, and has good dispersibility, lower porosity, and higher bonding strength with the substrate.

Description

Titanium seed layer and its preparation method and solar cell preparation method

[0001] Cross-references to related applications

[0002] This application claims priority to Chinese Patent Application No. 202411027581.8, filed on July 29, 2024, entitled "Titanium Seed Layer and Preparation Method Thereof and Solar Cell Preparation Method", the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure relates to the technical field of solar cells, and more specifically, to a titanium seed layer, a method for preparing the same, and a method for preparing solar cells. Background Technology

[0004] Currently, photovoltaic power generation is receiving much attention, with crystalline silicon solar cells representing a key direction for the photovoltaic industry's development. Solar energy is a clean, green, and renewable energy source, and an effective means of achieving carbon peaking and carbon neutrality, which has led to increasing interest in solar power generation.

[0005] Metallization is a key process in the fabrication of silicon solar cells, primarily used to create the electrodes and form ohmic contacts at the two ends of the PN junction to enable current output. Currently, screen printing is the most mature and widespread metallization process, but it suffers from the high cost of the silver paste it uses. To reduce solar cell costs and improve efficiency, copper electroplating technology offers the greatest potential for cost reduction by eliminating silver paste consumption.

[0006] Copper electroplating refers to the electrode fabrication process of depositing metallic copper on the surface of a base metal through electrolysis. This process reduces silver paste consumption by electroplating copper grid lines. Electroplating typically involves first depositing a seed layer at the grooved area of ​​the solar cell, followed by electroplating copper and tin as conductive and protective layers, resulting in a double-sided electroplated solar cell. Nickel has traditionally been used as a seed layer material, prepared through electroplating or electroless plating. While electroless plating can be performed simultaneously, its effectiveness is affected by the degree of activation, making it difficult to guarantee results. Electroplating is challenging to achieve simultaneous double-sided plating, leading to long processing times. Furthermore, traditional nickel plating processes often use Watt's nickel system or nickel sulfamate system as plating solutions. Watt's nickel system typically has a narrow current density range, and the electroplated nickel layer often exhibits high internal stress, high porosity, and poor dispersion. While nickel layers prepared using nickel sulfamate systems have lower internal stress and faster deposition rates, they suffer from poor stability and higher costs.

[0007] In view of this, this disclosure is hereby made.

[0008] Public content

[0009] This disclosure provides a titanium seed layer and a method for preparing the same, as well as a method for preparing a solar cell, to at least alleviate a technical problem existing in the prior art.

[0010] In order to achieve at least one of the above-mentioned objectives of this disclosure, the following technical solution is adopted:

[0011] In a first aspect, this disclosure provides a method for preparing a titanium seed layer, the method comprising the following steps:

[0012] A titanium seed layer was prepared in the pre-defined area of ​​the gate line on a silicon substrate of a battery using a dual-pulse magnetron sputtering method.

[0013] Secondly, this disclosure provides a titanium seed layer prepared using the titanium seed layer preparation method described in the first aspect.

[0014] Thirdly, this disclosure provides a method for preparing a solar cell, the method comprising the following steps:

[0015] A mask layer is prepared on a battery substrate, and the mask layer of the grid line preset area is removed to form a patterned groove. A titanium seed layer as described in the second aspect is prepared in the patterned groove, annealed, and the mask layer of the non-grid line preset area is removed. Then, a metal layer is prepared on the titanium seed layer to obtain a solar cell.

[0016] Compared with the prior art, the beneficial effects of this disclosure include:

[0017] The titanium seed layer preparation method disclosed herein can be used to form a titanium layer on a substrate during the fabrication of solar cells. The titanium layer prepared by this method has a strong bond with the substrate, making it difficult for the electrodes of the solar cell to separate from the substrate, thereby improving the structural stability of the solar cell.

[0018] The titanium seed layer disclosed herein, when applied to solar cells, can improve the density of the coating, reduce the internal stress of the coating, thereby enhancing the adhesion between the metal coating of the entire cell and the substrate, while optimizing the related metallization process. Attached Figure Description

[0019] Figure 1 is a schematic diagram of the suction cup device described in this disclosure.

[0020] Among them, 1 is the airflow groove, 2 is the suction cup body, and 3 is the through hole. Detailed Implementation

[0021] The embodiments of this disclosure will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of this disclosure. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer shall apply.

[0022] In a first aspect, this disclosure provides a method for preparing a titanium seed layer. The method includes the following steps: preparing a titanium seed layer within a pre-defined area of ​​a gate line on a battery silicon substrate using a dual-pulse magnetron sputtering method.

[0023] In this disclosure, the dual-pulse magnetron sputtering method refers to a dual-pulse output mode containing two or more sub-pulses within one pulse cycle. It can control the pulse on / off time and current density within a single pulse width. Compared with traditional methods, the seed layer prepared by the dual-pulse magnetron sputtering method in this disclosure can be smoother, finer, and more dispersed, with lower porosity and higher bonding strength with the substrate.

[0024] In an optional embodiment of this disclosure, when preparing the titanium seed layer using dual-pulse magnetron sputtering, the vacuum degree is 0.1-2 Pa, for example, it can be 0.1 Pa, 0.2 Pa, 0.3 Pa, 0.4 Pa, 0.5 Pa, 0.6 Pa, 0.7 Pa, 0.8 Pa, 0.9 Pa, 1 Pa, 1.1 Pa, 1.2 Pa, 1.3 Pa, 1.4 Pa, 1.5 Pa, 1.6 Pa, 1.7 Pa, 1.8 Pa, 1.9 Pa, 2 Pa, etc., and the pulse voltage is 200-700 V, for example, it can be 2 00V, 250V, 300V, 350V, 400V, 450V, 500V, 550V, 600V, 650V, 700V, etc., with pulse voltage ranging from 10% to 70% of the pulse voltage (e.g., 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 65%, 70%, 85%, 90%), and duty cycle ranging from 10% to 30% (e.g., 10%, 15%, 20%, 25%, 30%). The average current density is 0.2-2 A / cm². 2 For example, it could be 0.2A / cm 2 0.3A / cm 2 0.4A / cm 2 0.5A / cm 2 0.6A / cm 2 0.7A / cm 2 0.8A / cm 2 0.9A / cm 2 1A / cm 2 1.1A / cm 2 1.2A / cm 2 1.3A / cm 2 1.4A / cm 2 1.5A / cm 2 1.6A / cm 2 1.7A / cm 21.8A / cm 2 1.9A / cm 2 2A / cm 2 wait.

[0025] In optional embodiments of this disclosure, the thickness of the titanium seed layer is 0.1-1 μm, for example, it can be 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, etc.

[0026] Secondly, this disclosure provides a titanium seed layer prepared using the titanium seed layer preparation method described in the first aspect.

[0027] In this disclosure, the titanium seed layer is more uniformly distributed than that of a conventional nickel seed layer, resulting in a higher rate of titanium seed layer preparation. The titanium seed layer prepared in this disclosure also exhibits stronger adhesion to the substrate.

[0028] Thirdly, this disclosure provides a method for preparing a solar cell, the method comprising the following steps:

[0029] A mask layer is prepared on a battery substrate, and the mask layer of the grid line preset area is removed to form a patterned groove. A titanium seed layer as described in the second aspect is prepared in the patterned groove, annealed, and the mask layer of the non-grid line preset area is removed. Then, a metal layer is prepared on the titanium seed layer to obtain a solar cell.

[0030] In this disclosure, the titanium layer has a low coefficient of thermal expansion, high density, and high bonding strength after heat treatment. Avoiding the titanium stripping process optimizes the metallization process of solar cells to some extent. Simultaneously, the titanium layer possesses high conductivity, good thermal stability, and corrosion resistance, exhibits good adsorption to silicon, and high adhesion. Further metallization significantly enhances the bonding strength between the entire metal coating and the silicon substrate. The solar cell provided in this disclosure is a TOPCon solar cell with double-sided titanium seed layers. Depending on the equipment configuration, the titanium seed layer on the back of the solar cell can be prepared first, followed by the titanium seed layer on the front; or the titanium seed layer on the front of the solar cell can be prepared first, followed by the titanium seed layer on the back; or both sides can be prepared simultaneously, ultimately resulting in a solar cell with double-sided titanium seed layers. The preparation method of this disclosure can also be used to prepare deposited grid lines containing metals such as nickel, titanium, tungsten, tantalum, cobalt, and copper, and their alloys. In solar cells prepared using this method, the bonding strength between the titanium layer and the substrate is strong, making it difficult for the electrodes of the solar cell to separate from the substrate, thus improving the structural stability of the solar cell.

[0031] In an optional embodiment of this disclosure, the preparation of the mask layer includes forming a mask layer on the front and / or back of a solar cell substrate by deposition, coating, or printing.

[0032] In an optional embodiment of this disclosure, a laser is used to remove the mask layer of the preset area of ​​the gate line to form a patterned groove.

[0033] In this disclosure, since laser grooving generally causes damage, the mask layer can absorb some of the laser energy and reduce the damage.

[0034] In optional embodiments of this disclosure, the width of the patterned groove is 5-50 μm, for example, it can be 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, etc., and the depth is 50-100 nm, for example, it can be 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, 100 nm, etc.

[0035] In this disclosure, the patterned groove may include one or both of coarse and fine grooves, and the number of coarse and fine grooves can be adjusted; the thickness of the titanium seed layer is easy to control, and the groove width can be further optimized based on this. At the same time, combined with the presence of the mask layer, the damage of the laser to the battery is reduced, thereby improving efficiency.

[0036] In optional embodiments of this disclosure, the annealing temperature is 400-980℃, for example, it can be 400℃, 450℃, 500℃, 550℃, 600℃, 650℃, 700℃, 750℃, 800℃, 850℃, 900℃, 980℃, etc.

[0037] In an optional embodiment of this disclosure, after removing the mask layer of the grid line preset area and before preparing the titanium seed layer, the battery substrate is sequentially cleaned and dried; preferably, an acid pickling agent is used to clean the battery substrate; preferably, the acid pickling agent includes an aqueous solution of hydrofluoric acid; preferably, the amount of hydrofluoric acid added in the acid pickling agent is 10-20 mL / L, for example, it can be 10 mL / L, 11 mL / L, 12 mL / L, 13 mL / L, 14 mL / L, 15 mL / L, 16 mL / L, 17 mL / L, 18 mL / L, 19 mL / L, 20 mL / L, etc.; preferably, the temperature of the acid pickling agent is 25-38℃, for example, it can be 25℃, 26℃, 27℃, 28℃, 29℃, 30℃, 31℃, 32℃, 33℃, 34℃, 35℃, 36℃, 37℃, 38℃, etc.; preferably, the cleaning time is 5-50 s.

[0038] In this disclosure, the floating time of the silicon substrate in the pickling agent is 5-50s, for example, it can be 5s, 10s, 15s, 20s, 25s, 30s, 35s, 40s, 45s, 50s, etc.

[0039] In an optional embodiment of this disclosure, ultrasonic cleaning is used in the cleaning step.

[0040] In this disclosure, the cleaning step uses wet cleaning, and whether or not to connect with ultrasonic waves can be selected according to the degree of cleaning.

[0041] In optional embodiments of this disclosure, the drying temperature is 15-20°C, for example, it can be 15°C, 16°C, 17°C, 18°C, 19°C, 20°C, etc.

[0042] In an optional embodiment of this disclosure, after the battery substrate is sequentially cleaned and dried, it is subjected to vacuum plasma treatment before preparing the titanium seed layer. Preferably, when using vacuum plasma treatment, the vacuum degree is 0.01-0.04 MPa, for example, 0.01 MPa, 0.02 MPa, 0.03 MPa, 0.04 MPa, etc., the temperature is 15-20℃, for example, 15℃, 16℃, 17℃, 18℃, 19℃, 20℃, etc., the gas used is argon or nitrogen, and the treatment time is 10-30 s, for example, 10 s, 11 s, 12 s, 13 s, 14 s, 15 s, 16 s, 17 s, 18 s, 19 s, 20 s, 21 s, 22 s, 23 s, 24 s, 25 s, 26 s, 27 s, 28 s, 29 s, etc.

[0043] In this disclosure, vacuum low-temperature plasma treatment can prevent silicon oxidation on the one hand, and ensure the cleaning effect on the other hand; the solar cell substrate is subjected to dual pretreatment of wet cleaning and vacuum low-temperature plasma treatment, so that the solar cell substrate is thoroughly cleaned and the bonding strength between the grid lines and the substrate is effectively improved.

[0044] In an optional embodiment of this disclosure, the preparation of the metal layer includes sequentially forming a copper plating layer and a tin plating layer on a titanium seed layer; preferably, the thickness of the copper plating layer is 9-12 μm, for example, 9 μm, 10 μm, 11 μm, 12 μm, etc.; preferably, the thickness of the tin plating layer is 1-2 μm, for example, 1 μm, 2 μm, etc.

[0045] Fourthly, this disclosure provides a suction cup device used in the cleaning step of the third aspect, including a suction cup body 2; a first cavity is provided in the suction cup body 2 for communicating with a vacuum pump, and a plurality of through holes 3 are provided on the suction cup body 2 for communicating with the first cavity, and the suction cup body 2 is used to adsorb the battery substrate in the cleaning step.

[0046] The suction cup device provided in this disclosure can effectively adsorb solar cells during the cleaning process, ensuring the cleaning effect.

[0047] In this disclosure, when the vacuum pump is turned on, a vacuum negative pressure is generated inside the suction cup body 2. The surrounding atmospheric pressure will create a relative pressure difference between the suction cup body 2 and the battery cell, thereby generating an adsorption force to adsorb the battery cell onto the suction cup body 2.

[0048] In an optional embodiment of this disclosure, in order to improve the adsorption effect and make the adsorption force uniform at each point of the battery cell, the plurality of through holes are arranged in an array.

[0049] In an optional embodiment of this disclosure, a second cavity is provided inside the suction cup body 2, and an airflow groove 1 communicating with the second cavity is provided along its circumference. The second cavity is used to communicate with the air outlet of the fan. The airflow from the fan passes through the second cavity and flows out of the suction cup body 2 through the airflow groove 1.

[0050] The suction cup device disclosed herein is an anti-liquid-over suction cup device. When adsorbing solar cells, its negative pressure can ensure effective adsorption of solar cells. At the same time, the airflow released from all sides of the suction cup body can effectively prevent liquid from flowing to the adsorption surface of the solar cells and entering the suction cup due to the movement of the suction cup or the surge of liquid during cleaning or electroplating, which would result in poor process effect and damage to the suction cup.

[0051] The suction cup device disclosed herein has an airflow groove 1 with anti-liquid spillage function, which effectively prevents liquid from spilling at the edge of the battery cell during electroplating and improves the process effect.

[0052] In optional embodiments of this disclosure, the airflow velocity released outward from the second cavity is 5-30 m / s, for example, it can be 5 m / s, 6 m / s, 7 m / s, 8 m / s, 9 m / s, 10 m / s, 11 m / s, 12 m / s, 13 m / s, 14 m / s, 15 m / s, 16 m / s, 17 m / s, 18 m / s, 19 m / s, 20 m / s, 21 m / s, 22 m / s, 23 m / s, 24 m / s, 25 m / s, 26 m / s, 27 m / s, 28 m / s, 29 m / s, 30 m / s, etc.

[0053] The working process of the suction cup device is as follows:

[0054] First, a suction cup device is used to adsorb one side of the silicon substrate of the solar cell after the film is opened, while the other side is floated in the acid pickling agent. After cleaning, the solar cell is quickly dried in room temperature air. Then, it is flipped over and the other side of the silicon substrate of the solar cell is cleaned in the same way. After both sides are cleaned and dried, vacuum low-temperature plasma treatment is performed to finally obtain a double-sided acid-washed silicon substrate of the solar cell.

[0055] It should be noted that the suction cup device can first adsorb the front side of the silicon substrate of the solar cell after the film is opened, or it can first adsorb the back side of the silicon substrate of the solar cell after the film is opened. After cleaning the side that is adsorbed first, the other side can be cleaned.

[0056] In an optional embodiment of this disclosure, the solar cell fabrication method includes the following steps:

[0057] a. Provide solar cell substrates;

[0058] b. Forming mask layers on the front and back sides of a solar cell substrate by deposition, coating, or printing;

[0059] c. The mask layer of the grid line preset area is removed sequentially on the front and back of the silicon substrate of the solar cell by laser film opening, and then a patterned groove is formed.

[0060] d. Add an appropriate amount of hydrofluoric acid to pure water, circulate and stir evenly to prepare an acid pickling agent; then use a suction cup device to pick up one side of the silicon substrate of the solar cell after the film is opened, while the other side floats in the acid pickling agent. After cleaning, quickly dry the solar cell in room temperature air, turn it over and clean the other side of the silicon substrate of the solar cell in the same way as described above. After both sides are cleaned and dried, vacuum low temperature plasma treatment is performed to finally obtain a double-sided acid-washed silicon substrate of the solar cell.

[0061] e. A titanium seed layer is prepared in a patterned groove using a dual-pulse magnetron sputtering method;

[0062] f. Annealing is performed on solar cells with double-sided titanium seed layers to form a titanium-silicon alloy;

[0063] g. Cleaning to remove the front and back mask layers, resulting in solar cells with titanium seed layers only at preset positions on the grid lines;

[0064] h. Copper and tin are sequentially electroplated on both sides of the silicon substrate of the solar cell with a double-sided titanium seed layer to obtain a double-sided electroplated solar cell.

[0065] Example 1

[0066] This embodiment provides a method for preparing a titanium seed layer, which uses a dual-pulse magnetron sputtering method to prepare a titanium seed layer in a pre-defined area of ​​the grid line on a battery silicon substrate;

[0067] In the preparation of the titanium seed layer using the dual-pulse magnetron sputtering method, the vacuum level was 0.1 Pa, the pulse voltage was 700 V, the partial pulse voltage was 10% of the pulse voltage, the duty cycle was 30%, and the average current density was 0.2 A / cm². 2 The thickness of the titanium seed layer is 1 μm.

[0068] Example 2

[0069] This embodiment provides a method for preparing a titanium seed layer, which uses a dual-pulse magnetron sputtering method to prepare a titanium seed layer in a pre-defined area of ​​the grid line on a battery silicon substrate;

[0070] In the preparation of the titanium seed layer using the dual-pulse magnetron sputtering method, the vacuum level was 2 Pa, the pulse voltage was 200 V, the partial pulse voltage was 70% of the pulse voltage, the duty cycle was 10%, and the average current density was 2 A / cm². 2 The thickness of the titanium seed layer is 0.1 μm.

[0071] Example 3

[0072] This embodiment provides a method for preparing a titanium seed layer, which uses a dual-pulse magnetron sputtering method to prepare a titanium seed layer in a pre-defined area of ​​the grid line on a battery silicon substrate;

[0073] In the preparation of the titanium seed layer using the dual-pulse magnetron sputtering method, the vacuum level was 1 Pa, the pulse voltage was 450 V, the partial pulse voltage was 40% of the pulse voltage, the duty cycle was 20%, and the average current density was 1 A / cm². 2 The thickness of the titanium seed layer is 0.5 μm.

[0074] Example 4

[0075] This embodiment provides a method for preparing a titanium seed layer, which differs from Embodiment 3 in that the thickness of the titanium seed layer is 0.05 μm.

[0076] Example 5

[0077] This embodiment provides a method for preparing a titanium seed layer, which differs from Embodiment 3 in that the thickness of the titanium seed layer is 1.1 μm.

[0078] Example 6

[0079] This embodiment provides a method for preparing a solar cell, including the following steps:

[0080] a. Provide solar cell substrates;

[0081] b. Forming mask layers on the front and back sides of the solar cell substrate by deposition;

[0082] c. The mask layer of the grid line preset area is removed sequentially on the front and back sides of the silicon substrate of the solar cell by laser delamination to further form a patterned groove; wherein the width of the patterned groove is 5μm and the depth is 100nm;

[0083] d. Add an appropriate amount of hydrofluoric acid to pure water (the amount of hydrofluoric acid added in the pickling agent is 10 mL / L), circulate and stir evenly to prepare the pickling agent. The temperature of the pickling agent is 38℃, and the cleaning time is 5 s. Then, first use a suction cup device to adsorb the front side of the solar cell silicon substrate after the film is opened, while the back side floats in the pickling agent. After cleaning, quickly dry the solar cell in room temperature air, turn it over and clean the front side of the solar cell silicon substrate in the aforementioned method. After both sides are cleaned and dried, vacuum low-temperature plasma treatment is performed to finally obtain a double-sided pickled solar cell silicon substrate. The drying temperature is 20℃. When using vacuum plasma treatment, the vacuum degree is 0.01 MPa, the temperature is 20℃, the gas used is argon, and the treatment time is 10 s. The gas flow velocity released by the suction cup device is 30 m / s.

[0084] e. A titanium seed layer is prepared in a patterned groove using the titanium seed layer preparation method provided in Example 3;

[0085] f. Annealing is performed on a solar cell with a double-sided titanium seed layer to form a titanium-silicon alloy; wherein the annealing temperature is 400℃;

[0086] g. Wash in 25% KOH solution to remove the front and back mask layers, to obtain a solar cell with a titanium seed layer only at the preset positions of the grid lines;

[0087] h. Copper and tin are sequentially electroplated on the silicon substrate of a solar cell using a double-sided titanium seed layer to obtain a double-sided electroplated solar cell; wherein the thickness of the copper plating layer is 12 μm and the thickness of the tin plating layer is 1 μm.

[0088] Example 7

[0089] This embodiment provides a method for preparing a solar cell, including the following steps:

[0090] a. Provide solar cell substrates;

[0091] b. A mask layer is formed on the front and back sides of the solar cell substrate by printing.

[0092] c. The mask layer of the grid line preset area is removed sequentially on the front and back of the silicon substrate of the solar cell by laser delamination to further form a patterned groove; wherein the width of the patterned groove is 50μm and the depth is 50nm;

[0093] d. Add an appropriate amount of hydrofluoric acid to pure water (the amount of hydrofluoric acid added in the pickling agent is 20 mL / L), circulate and stir evenly to prepare the pickling agent. The temperature of the pickling agent is 25℃, and the cleaning time is 50 s. Then, first use a suction cup device to adsorb the front side of the solar cell silicon substrate after the film is opened, while the back side floats in the pickling agent. After cleaning, quickly dry the solar cell in room temperature air, turn it over and clean the front side of the solar cell silicon substrate in the aforementioned method. After both sides are cleaned and dried, vacuum low-temperature plasma treatment is performed to finally obtain a double-sided pickled solar cell silicon substrate. The drying temperature is 15℃. When using vacuum plasma treatment, the vacuum degree is 0.04 MPa, the temperature is 15℃, the gas used is nitrogen, and the treatment time is 30 s. The gas flow velocity released by the suction cup device is 5 m / s.

[0094] e. A titanium seed layer is prepared in a patterned groove using the titanium seed layer preparation method provided in Example 3;

[0095] f. Annealing is performed on a solar cell with a double-sided titanium seed layer to form a titanium-silicon alloy; wherein the annealing temperature is 980℃;

[0096] g. Wash in 25% KOH solution to remove the front and back mask layers, to obtain a solar cell with a titanium seed layer only at the preset positions of the grid lines;

[0097] h. Copper and tin are sequentially electroplated on the silicon substrate of a solar cell using a double-sided titanium seed layer to obtain a double-sided electroplated solar cell; wherein the thickness of the copper plating layer is 9 μm and the thickness of the tin plating layer is 2 μm.

[0098] Examples 8-12

[0099] This embodiment provides a method for preparing a solar cell, including the following steps:

[0100] a. Provide solar cell substrates;

[0101] b. A mask layer is formed on the front and back sides of the solar cell substrate by printing.

[0102] c. The mask layer of the grid line preset area is removed sequentially on the front and back of the silicon substrate of the solar cell by laser delamination to further form a patterned groove; wherein the width of the patterned groove is 25μm and the depth is 75nm;

[0103] d. Add an appropriate amount of hydrofluoric acid to pure water (the amount of hydrofluoric acid added in the pickling agent is 15 mL / L), circulate and stir evenly to prepare the pickling agent. The temperature of the pickling agent is 30℃, and the cleaning time is 25 s. Then, first use a suction cup device to adsorb the front side of the solar cell silicon substrate after film opening, while the back side floats in the pickling agent. After cleaning, quickly dry the solar cell in room temperature air, turn it over and clean the front side of the solar cell silicon substrate in the aforementioned method. After both sides are cleaned and dried, vacuum low-temperature plasma treatment is performed to finally obtain a double-sided pickled solar cell silicon substrate. The drying temperature is 18℃. When using vacuum plasma treatment, the vacuum degree is 0.025 MPa, the temperature is 18℃, the gas used is argon, and the treatment time is 20 s. The gas flow velocity released by the suction cup device is 20 m / s.

[0104] e. Prepare a titanium seed layer in a patterned groove using the titanium seed layer preparation method provided in Examples 1-5;

[0105] f. Annealing is performed on solar cells with double-sided titanium seed layers to form a titanium-silicon alloy; wherein the annealing temperature is 700℃;

[0106] g. Wash in 25% KOH solution to remove the front and back mask layers, to obtain a solar cell with a titanium seed layer only at the preset positions of the grid lines;

[0107] h. Copper and tin are sequentially electroplated on the silicon substrate of a solar cell using a double-sided titanium seed layer to obtain a double-sided electroplated solar cell; wherein the thickness of the copper plating layer is 11 μm and the thickness of the tin plating layer is 1.5 μm.

[0108] Example 13

[0109] This embodiment provides a method for preparing a solar cell. The difference between this embodiment and Embodiment 10 is that the titanium seed layer is prepared in the patterned groove on the front side of the silicon substrate of the solar cell using the titanium seed layer preparation method provided in Embodiment 3, and nickel electroplating is performed in the patterned groove on the back side of the silicon substrate of the solar cell.

[0110] The other steps are the same as in Example 10.

[0111] Example 14

[0112] This embodiment provides a method for fabricating a solar cell. The difference between this embodiment and Embodiment 10 is that in this comparative example, a titanium seed layer is prepared in the patterned groove on the back side of the silicon substrate of the solar cell using the titanium seed layer preparation method provided in Embodiment 3, and nickel electroplating is performed in the patterned groove on the front side of the silicon substrate of the solar cell. The other steps are the same as in Embodiment 10.

[0113] Comparative Example 1

[0114] This comparative example provides a method for preparing a solar cell, which differs from Example 10 in that steps g and h are reversed, i.e., copper and tin are electroplated first, and then the mask layer in the non-grid line preset area is removed.

[0115] Test case

[0116] Test samples: TOPCon solar cells prepared in Examples 6-12 and TOPCon solar cells prepared in Comparative Example 1.

[0117] Test methods: (1) Electrical performance test: offline solar IV tester; (2) Welding tensile test under low temperature conditions: tensile tester.

[0118] The test results are shown in Table 1.

[0119] Table 1

[0120] As can be seen from the data in Table 1, the solar cell with a double-sided titanium seed layer provided in this embodiment of the present disclosure has a stronger bonding force between the titanium layer and the substrate and a higher conversion efficiency. Furthermore, if the titanium seed layer is too thin or too thick, it will affect the bonding force between the titanium layer and the substrate and the efficiency of the solar cell. At the same time, compared with Comparative Example 1, this embodiment of the present disclosure adopts the method of removing the mask layer first and then plating other metals, which avoids the mask layer reacting with other plating solutions and affecting the performance of the solar cell.

Claims

1. A method for preparing a titanium seed layer, characterized by, The application relates to a solar cell manufacturing method. The thickness of the titanium seed layer is 0.1-1 microns.

2. The method of claim 1, wherein the titanium seed layer is prepared by sputtering. When the double-pulse magnetron sputtering method is used to prepare the titanium seed layer, the vacuum degree is 0.1-2 Pa, the pulse voltage is 200-700 V, the divided pulse voltage is 10-70% of the pulse voltage, the duty cycle is 10-30%, and the average current density is 0.2-2 A / cm 2 .

3. The method of claim 1, wherein the titanium seed layer is prepared by sputtering.

4. A titanium seed layer prepared by the method of any one of claims 1-3. The solar cell manufacturing method comprises the following steps:

5. A method for manufacturing a solar cell, characterized by, A mask layer is prepared on the cell substrate, the mask layer in the grid preset area is removed to form a patterned groove, the titanium seed layer of claim 4 is prepared in the patterned groove, annealing is performed, the mask layer in the non-grid preset area is removed, and then a metal layer is prepared on the titanium seed layer to obtain a solar cell. The mask layer is prepared on the front and / or back surface of the solar cell substrate by deposition, coating or printing; 6. The method for preparing a solar cell according to claim 5, characterized in that, And / or, the mask layer in the grid preset area is removed by laser. The width of the patterned groove is 5-50 microns, and the depth is 50-100 nanometers.

7. The method for preparing a solar cell according to claim 5, characterized in that, The annealing temperature is 400-980 DEG C.

8. The method for preparing a solar cell according to claim 5, characterized in that, After the mask layer in the grid preset area is removed, the cell substrate is sequentially cleaned and dried before the titanium seed layer is prepared; 9. The method for preparing a solar cell according to claim 5, characterized in that, And / or, the cell substrate is cleaned by using an acid cleaning agent; And / or, the acid cleaning agent comprises hydrofluoric acid aqueous solution; And / or, the addition amount of hydrofluoric acid in the acid cleaning agent is 10-20 mL / L; And / or, the temperature of the acid cleaning agent is 25-38 DEG C. And / or, the cleaning time is 5-50 s; And / or, ultrasonic cleaning is used in the cleaning step; And / or, the drying temperature is 15-20 DEG C. After the cell substrate is sequentially cleaned and dried, the cell substrate is subjected to vacuum plasma treatment before the titanium seed layer is prepared; 10. The method for preparing a solar cell according to claim 9, characterized in that, And / or, when the vacuum plasma treatment is used, the vacuum degree is 0.01-0.04 MPa, the temperature is 15-20 DEG C, the gas used is argon or nitrogen, and the treatment time is 10-30 s. The metal layer is prepared by sequentially forming a copper plating layer and a tin plating layer on the titanium seed layer; 11. The method of claim 5, wherein the method further comprises: And / or, the thickness of the copper plating layer is 9-12 microns; And / or, the thickness of the tin plating layer is 1-2 microns. In the cleaning step, the cell substrate is adsorbed by using a suction disc device.

12. The method for preparing a solar cell according to claim 9, characterized in that, The suction disc device comprises a suction disc body (2), a first cavity is formed in the suction disc body (2), the first cavity is used for being communicated with a vacuum pump, a plurality of through holes (3) are formed in the suction disc body (2) and communicated with the first cavity, and the suction disc body (2) is used for adsorbing the cell substrate in the cleaning step in claim 6.

13. The method of claim 12, wherein the method further comprises: The plurality of through holes (3) are arranged in an array.

14. The solar cell manufacturing method according to claim 13, wherein A second cavity is formed in the suction disc body (2), and an air flow groove (1) is formed in the suction disc body (2) and communicated with the second cavity, the second cavity is used for being communicated with the air outlet of a fan, air flow from the fan passes through the second cavity and flows out of the suction disc body (2) through the air flow groove (1).

15. The method for preparing a solar cell according to claim 13, characterized in that, The air flow speed released outwards by the second cavity is 5-30 m / s.

16. The method of claim 15, wherein the step of forming the back surface field is performed by a method comprising: depositing a layer of silicon on the back surface of the solar cell; and diffusing phosphorus into the layer of silicon. ​

Images