Photovoltaic titanium paste, preparation method and application thereof, and solar cell

Abstract

The present invention provides a photovoltaic titanium paste, a preparation method and application thereof, and a solar cell, and relates to the technical field of solar cells. The photovoltaic titanium paste comprises the following components: titanium powder, glass powder, titanium-tungsten alloy powder, and an organic carrier solution. The photovoltaic titanium paste provided by the present invention can adapt to the process of laser-assisted sintering in the titanium seed layer process, so that the titanium seed layer has a higher bonding force with the battery silicon substrate.

Description

Technical Field

[0001] The invention relates to the technical field of solar cells, and in particular to a photovoltaic titanium paste, a preparation method and application thereof, and a solar cell. Background Art

[0002] Metallization is one of the key processes in the preparation of silicon solar cells. It is mainly used to make silicon solar cell electrodes, forming ohmic contacts at both ends of the PN junction to achieve current output. Currently, screen printing is the most mature and common metallization process, but due to the high cost of the silver paste it uses, it has become an important factor restricting the promotion of the industry. In order to reduce the cost of solar cells and improve battery efficiency, copper electroplating technology can achieve no silver paste consumption and has the greatest cost reduction potential.

[0003] Copper electroplating refers to the electrode preparation process of depositing metallic copper on the surface of the base metal by electrolysis, and the purpose of reducing the consumption of silver paste is achieved by electroplating copper grid lines. Electroplating technology usually first plates a seed layer at the slot position of the cell, and then electroplates copper and tin as a conductive layer and a protective layer to obtain a double-sided electroplated solar cell. At present, nickel is often used as a seed layer material, but the traditional electroplated nickel layer has disadvantages such as large internal stress, high porosity, and poor dispersion ability. In addition, the nickel plating layer can only form an effective nickel-silicon alloy after annealing, and the thermal expansion coefficient of the nickel-silicon alloy and nickel is greatly different, which leads to the need to remove the unreacted nickel after annealing to ensure the bonding force between nickel and copper, which increases the metallization step. Titanium has good conductivity, can also be alloyed with silicon, can prevent the diffusion of copper, and has good corrosion resistance, but titanium is not easy to electroplate. In addition, the traditional electroplating seed layer is slow, which may lead to problems such as low yield.

[0004] In view of this, the present invention is proposed. Summary of the invention

[0005] One of the purposes of the present invention is to provide a photovoltaic titanium paste. The photovoltaic titanium paste comprises the following components: titanium powder, glass powder, titanium-tungsten alloy powder and organic carrier solution. The photovoltaic titanium paste provided by the present invention can adapt to the process of laser-assisted sintering in the titanium seed layer process, so that the titanium seed layer has a higher bonding force with the battery silicon substrate.

[0006] The second object of the present invention is to provide a method for preparing photovoltaic titanium paste. The process flow in the preparation method is simple and efficient, and the photovoltaic titanium paste prepared by the preparation method can better adapt to the laser-assisted sintering process.

[0007] The third object of the present invention is to provide an application of photovoltaic titanium paste in the preparation of solar cells.

[0008] The fourth object of the present invention is to provide a solar cell in which the titanium seed layer and the silicon substrate have strong bonding strength, and the laser-assisted sintering technology can promote the alloying of titanium and silicon, the contact resistance of the solar cell is significantly reduced, and an effective conductive path is generated.

[0009] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:

[0010] In a first aspect, the present invention provides a photovoltaic titanium paste, which comprises the following components: titanium powder, glass powder, titanium-tungsten alloy powder and an organic carrier solution.

[0011] In the present invention, the raw materials of photovoltaic titanium paste are titanium powder, glass powder, titanium-tungsten alloy powder and organic carrier solution, wherein the titanium-tungsten alloy powder has good stability, is not easy to react with oxygen, nitrogen and the like, and can inhibit the oxidation of the paste. The titanium-tungsten alloy has strong adhesion to silicon, which can further enhance the adhesion of the paste and the adhesion on the subsequent electroplating layer, and can also improve the diffusion barrier performance of the paste under high temperature conditions. The titanium-tungsten alloy powder and other components cooperate with each other to further enhance the adhesion and diffusion barrier performance; titanium powder, as the main conductive phase, can form an effective alloy contact and reduce the contact resistance; the glass powder increases the adhesion of the titanium paste and enhances its conductivity, while improving the fluidity and promoting its uniform distribution on the surface of the battery cell, thereby improving the photoelectric conversion efficiency of the solar cell; the organic carrier solution can stabilize the titanium powder particles and prevent the particles from agglomerating, etc. With the cooperation of each component, under the action of laser-assisted sintering, the paste can be quickly heated to achieve the reaction of titanium and silicon, and then can be quickly cooled to avoid oxidation; at the same time, the burn-through area is reduced and the contact effect is enhanced.

[0012] Preferably, the photovoltaic titanium paste comprises the following components by weight:

[0013] 80-90 parts of titanium powder, 0.3-6 parts of glass powder, 0.1-3 parts of titanium-tungsten alloy powder and the balance of organic carrier solution;

[0014] Based on 100 parts by weight of the photovoltaic titanium paste, the amount of the titanium powder added is 80 parts, 81 parts, 82 parts, 83 parts, 84 parts, 85 parts, 86 parts, 87 parts, 88 parts, 89 parts, 90 parts, etc.;

[0015] Based on 100 parts by weight of the photovoltaic titanium paste, the amount of the glass powder added is 0.3 parts, 0.5 parts, 1 parts, 1.5 parts, 2 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts, 4.5 parts, 5 parts, 5.5 parts, 6 parts, etc.;

[0016] Based on 100 parts by weight of the photovoltaic titanium paste, the amount of the titanium-tungsten alloy powder added is 0.1 parts, 0.5 parts, 1 parts, 1.5 parts, 2 parts, 2.5 parts, 3 parts, etc.;

[0017] Preferably, the average particle size of the titanium powder is 0.1-2 μm, for example, 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, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2 μm, etc.;

[0018] Preferably, the titanium powder includes at least one of spherical titanium powder, flaky titanium powder, needle-shaped titanium powder, plate-shaped titanium powder and sponge-shaped titanium powder;

[0019] Preferably, the organic carrier solution comprises at least one of terpineol, butyl carbitol acetate, ethylene glycol ethyl ether acetate, tributyl citrate, dibutyl phthalate and lecithin;

[0020] Preferably, the average particle size of the titanium-tungsten alloy powder is 0.1-2 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, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2 μm, etc.;

[0021] Preferably, the particle size of the glass powder is 0.5-3 μm, for example, it can be 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, 2.5 μm, 2.6 μm, 2.7 μm, 2.8 μm, 2.9 μm, 3 μm, etc.;

[0022] Preferably, the glass powder is boron glass powder;

[0023] Preferably, the glass powder comprises the following components by mass percentage:

[0024] PbO: 10-35%, Bi2O3: 10-35%, SiO2: 5-15%, CuO: 5-15%, MnO2: 1-10%, B2O3: 1-10%, Al2O3: 1-10%, TiO2 : 5-15%, Li2O: 0-4%, ZnO: 0-5%, MgO: 0-5%, Cr2O3: 0-5%, NiO: 0-5%, TeO2: 0-5%, Na2O: 0-5%, K2O: 0-5%.

[0025] Taking the total mass percentage of the glass powder as 100%, the addition amount of PbO is 10-35%, for example, it can be 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, etc.;

[0026] Taking the total mass percentage of the glass powder as 100%, the addition amount of Bi2O3 is 10-35%, for example, it can be 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, etc.;

[0027] Taking the total mass percentage of the glass powder as 100%, the added amount of SiO2 is 5-15%, for example, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, etc.;

[0028] Taking the total mass percentage of the glass powder as 100%, the addition amount of CuO is 5-15%, for example, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, etc.;

[0029] Taking the total mass percentage of the glass powder as 100%, the addition amount of the MnO2 is 1-10%, for example, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc.;

[0030] Taking the total mass percentage of the glass powder as 100%, the addition amount of B2O3 is 1-10%, for example, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc.;

[0031] Taking the total mass percentage of the glass powder as 100%, the addition amount of Al2O3 is 1-10%, for example, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc.;

[0032] Taking the total mass percentage of the glass powder as 100%, the addition amount of the TiO2 is 5-15%, for example, it can be 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, etc.;

[0033] Taking the total mass percentage of the glass powder as 100%, the addition amount of Li2O is 0-4%, for example, 0%, 1%, 2%, 3%, 4%, etc.;

[0034] Taking the total mass percentage of the glass powder as 100%, the added amount of ZnO is 0-5%, for example, 0%, 1%, 2%, 3%, 4%, 5%, etc.;

[0035] Taking the total mass percentage of the glass powder as 100%, the addition amount of MgO is 0-5%, for example, 0%, 1%, 2%, 3%, 4%, 5%, etc.;

[0036] Taking the total mass percentage of the glass powder as 100%, the addition amount of Cr2O3 is 0-5%, for example, it can be 0%, 1%, 2%, 3%, 4%, 5%, etc.;

[0037] Taking the total mass percentage of the glass powder as 100%, the addition amount of NiO is 0-5%, for example, 0%, 1%, 2%, 3%, 4%, 5%, etc.;

[0038] Taking the total mass percentage of the glass powder as 100%, the addition amount of TeO2 is 0-5%, for example, 0%, 1%, 2%, 3%, 4%, 5%, etc.;

[0039] Taking the total mass percentage of the glass powder as 100%, the addition amount of the Na2O is 0-5%, for example, 0%, 1%, 2%, 3%, 4%, 5%, etc.;

[0040] Taking the total mass percentage of the glass powder as 100%, the added amount of K2O is 0-5%, for example, it can be 0%, 1%, 2%, 3%, 4%, 5%, etc.

[0041] Preferably, the components of the photovoltaic titanium paste also include an antioxidant;

[0042] In the present invention, the antioxidant protects the conductive powder and prevents it from being oxidized, thereby reducing the resistivity of the slurry after molding, maintaining good conductivity, and facilitating subsequent electroplating.

[0043] Preferably, the antioxidant is present in an amount of 0.2-1 part by weight;

[0044] Based on 100 parts by weight of the photovoltaic titanium paste, the amount of the antioxidant added is 0.2 parts, 0.3 parts, 0.4 parts, 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts, 1 part, etc.;

[0045] Preferably, the antioxidant includes at least one of 2,6-di-tert-butyl-p-cresol, 2,4,6-tri-tert-butylphenol, thioglycolic acid and thioacetic acid.

[0046] Preferably, the components of the photovoltaic titanium paste further include additives;

[0047] Preferably, the weight portion of the additive is 0.1-0.5 parts;

[0048] Based on 100 parts by weight of the photovoltaic titanium paste, the additive is added in an amount of 0.1 parts, 0.2 parts, 0.3 parts, 0.4 parts, 0.5 parts, etc.;

[0049] Preferably, the additive includes at least one of a thickener, a surfactant, a leveling agent and a lubricant;

[0050] In the present invention, the thickener can increase the viscosity of the entire slurry, can keep the slurry in a uniform and stable state, can keep each component or substance in this state after being evenly mixed, will not float or sink due to density or size, can also effectively improve the cohesion and adhesion of the slurry, and make the contact between the slurry and the substrate closer; the surfactant can reduce the tension of the contact interface between the organic carrier and the powder particles, so that the powder particles can be fully wetted and evenly dispersed in the organic carrier, and can prevent the appearance of gaps in the slurry drying process; the leveling agent can reduce the surface tension of the slurry during the printing process, so that the slurry can fully contact with the substrate, increase the contact area between the slurry and the substrate, which is conducive to improving the adhesion, and on the other hand, can inhibit the infiltration of gas during the printing process and speed up the printing speed. The lubricant can reduce the friction between the components of the slurry, make it easier to fully mix, easier to fill small gaps, speed up the printing speed, thereby improving the printing effect, and can also reduce the friction between the slurry and the equipment, and increase the service life.

[0051] Preferably, the thickener comprises at least one of polyamide wax, hydroxypropyl methyl and hydrogenated rosin;

[0052] Preferably, the surfactant comprises at least one of stearic acid and lecithin;

[0053] Preferably, the leveling agent comprises at least one of phthalic acid and furoic acid;

[0054] Preferably, the lubricant includes at least one of butyl oleate and diethyl fumarate.

[0055] In a second aspect, the present invention provides a method for preparing the photovoltaic titanium paste, the method for preparing the photovoltaic titanium paste comprising the following steps:

[0056] The raw materials of the photovoltaic titanium paste in the formula amount are mixed to prepare the photovoltaic titanium paste.

[0057] In the present invention, raw material components of the photovoltaic titanium paste in a prescribed amount are uniformly mixed and ground to obtain the conductive photovoltaic titanium paste.

[0058] Preferably, the glass powder is prepared by the following steps:

[0059] The glass powder raw materials of the formula amount are sequentially mixed, melted, ball-milled, dried and sieved to obtain the glass powder;

[0060] Preferably, the melting temperature is 900-1400°C, for example, 900°C, 950°C, 1000°C, 1050°C, 1100°C, 1150°C, 1200°C, 1250°C, 1300°C, 1350°C, 1400°C, etc.;

[0061] Preferably, the ball milling is performed using a ball mill, and the ball milling time is 0.5-5 h, for example, 0.5 h, 1 h, 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h, 5 h, etc.;

[0062] Preferably, the drying time is 0.5-2 h, for example, 0.5 h, 1 h, 1.5 h, 2 h, etc.

[0063] In a third aspect, the present invention provides an application of the photovoltaic titanium paste in the preparation of solar cells.

[0064] In a fourth aspect, the present invention provides a solar cell, wherein the solar cell is prepared by the following preparation steps:

[0065] A patterned groove is formed in a preset grid line area of ​​a silicon substrate of a solar cell, the photovoltaic titanium paste is applied in the groove, and then laser-assisted sintering is used to form a titanium seed layer in the groove by laser irradiation of the titanium paste, and a metal layer is prepared on the titanium seed layer to obtain the solar cell.

[0066] Compared with silver printing, the present invention mainly uses titanium in the seed layer, and its consumption is much lower than that of traditional silver, which can effectively reduce costs and improve work efficiency. At the same time, the titanium slurry is solidified by laser-assisted sintering. This method has fast heating and cooling speeds, shortens the deposition and solidification time, and can promote the mutual diffusion of slurry and silicon, which will significantly reduce the contact resistance between metal and silicon, and enhance the bonding strength between the seed layer and the silicon substrate without additional heat treatment. Moreover, the titanium seed layer prepared by this method has high density, uniform distribution, and low internal stress in the coating, thereby improving the bonding strength between the metal coating of the entire battery cell and the substrate, avoiding processes such as stripping. The preparation method can effectively shorten the seed layer preparation rate and optimize the metallization process.

[0067] Preferably, the solar cell silicon substrate comprises a silicon substrate and a coating layer deposited on the surface of the silicon substrate;

[0068] Preferably, the coating layer is a silicon nitride film;

[0069] Preferably, the thickness of the silicon nitride film is 50-100 nm, for example, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, 100 nm, etc.;

[0070] Preferably, the groove has a width of 5-50 μm, for example, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, etc., and a depth of 50-100 nm, for example, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, 100 nm, etc.;

[0071] In the present invention, the width and depth of the patterned grooves can be adjusted and set according to actual needs. The patterned grooves can include one or both of coarse grooves and fine grooves, and the number of coarse grooves and fine grooves can be adjusted according to actual needs.

[0072] Preferably, after the patterned grooves are formed in the solar cell silicon substrate, the solar cell silicon substrate is pickled before the titanium slurry is applied in the grooves;

[0073] Preferably, the pickling comprises: placing the grooved surface of the solar cell silicon substrate in a pickling solution, and after the cleaning is completed, blowing it dry;

[0074] Preferably, the temperature of the pickling solution is 25-38°C, for example, it can be 25°C, 26°C, 27°C, 28°C, 29°C, 30°C, 31°C, 32°C, 33°C, 34°C, 35°C, 36°C, 37°C, 38°C, etc.;

[0075] Preferably, the pickling liquid is a hydrofluoric acid solution, and the concentration of the hydrofluoric acid solution is 1-4%, for example, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, etc.;

[0076] Preferably, the grooved surface is placed in the pickling solution for 5-50 s, for example, 5 s, 10 s, 15 s, 20 s, 25 s, 30 s, 35 s, 40 s, 45 s, 50 s, etc.;

[0077] Preferably, the drying temperature is 15-20°C, for example, 15°C, 16°C, 17°C, 18°C, 19°C, 20°C, etc.

[0078] Preferably, applying the photovoltaic titanium paste in the groove comprises: applying the titanium paste in the groove by a printing process;

[0079] In the present invention, the seed layer slurry is coated on the silicon substrate of the solar cell by using printing technology to form a predetermined electrode pattern of the mold. Compared with the traditional printing technology, less slurry is required and the printing speed is faster.

[0080] Preferably, the printing process comprises screen printing;

[0081] Preferably, the printing screen in the printing process matches the pattern of the patterned grooves;

[0082] Preferably, after applying the photovoltaic titanium paste into the groove, the solar cell silicon substrate is dried before laser sintering;

[0083] Preferably, the drying temperature is 150-350° C., for example, 150° C., 200° C., 250° C., 300° C., 350° C., etc., and the drying time is 5-10 s, for example, 5 s, 6 s, 7 s, 8 s, 9 s, 10 s, etc.;

[0084] Preferably, the preparing the metal layer comprises: electroplating copper and tin in sequence on the titanium seed layer;

[0085] Preferably, the thickness of the copper plating layer is 9-12 um, for example, it can be 9 um, 9.5 um, 10 um, 10.5 um, 11 um, 11.5 um, 12 um, etc.;

[0086] Preferably, the thickness of the tin-plated layer is 1-2 um, for example, 1 um, 1.5 um, 2 um, etc.

[0087] Furthermore, the solar cell is prepared by the following preparation steps:

[0088] Providing a solar cell silicon substrate, the solar cell substrate comprising a silicon substrate and a silicon nitride film deposited on the surface of the silicon substrate, wherein the thickness of the silicon nitride film is 50-100 nm;

[0089] A patterned groove is formed by laser film opening in the preset grid line area on the front and back of the solar cell silicon substrate, and the width of the groove is 5-50μm and the depth is 50-100nm;

[0090] The silicon substrate of the solar cell after the film is opened is pickled: first, one side (for example, the front side) of the silicon substrate of the solar cell after the film is opened is sucked with a suction cup, and the other side (for example, the back side) is floated in the pickling liquid. After the cleaning is completed, the solar cell is quickly blown dry in room temperature air, and the unwashed side (for example, the front side) of the silicon substrate of the solar cell is turned over and cleaned according to the above method. After both sides are cleaned and dried, a double-sided pickled silicon substrate of the solar cell is obtained;

[0091] The titanium paste is applied to the grooves of the silicon substrate of the solar cell by screen printing to form a predetermined electrode pattern for film opening;

[0092] After the titanium paste is printed, the silicon wafer is dried at 150-350°C for 5-10 seconds and then laser-assisted sintering is performed. Through the laser-assisted sintering technology, the laser is irradiated on the titanium paste to locally and quickly heat the titanium paste on the silicon substrate of the solar cell for sintering.

[0093] The solar cell sheet with double-sided titanium seed layer is electroplated with copper and tin in sequence on both sides to obtain a solar cell.

[0094] Compared with the prior art, the present invention has the following beneficial effects:

[0095] The photovoltaic titanium paste provided by the present invention comprises titanium-tungsten alloy powder which can help to enhance the bonding force with the silicon substrate; titanium powder as the main conductive phase can form effective alloy contact and reduce contact resistance; glass powder increases the adhesion of the titanium paste and enhances its conductivity, while improving fluidity and promoting its uniform distribution on the surface of the battery cell, thereby improving the photoelectric conversion efficiency of the solar cell; the organic carrier solution can stabilize the titanium powder particles and prevent the particles from agglomerating; with the coordination of various components and under the action of laser-assisted sintering, the paste can be quickly heated to achieve the reaction between titanium and silicon, and can then be quickly cooled to avoid oxidation; at the same time, the burn-through area is reduced and the contact effect is enhanced.

[0096] The solar cell provided by the present invention has a strong bonding force between the titanium seed layer and the silicon substrate, so that the bonding force between the entire metallization layer and the silicon substrate is good, and the welding tensile force is large. At the same time, the laser-assisted sintering heating and cooling speed is fast, the deposition and curing time is shortened, and the work efficiency of double-sided seed layer preparation is improved. In addition, the seed layer does not need additional heat treatment or seed layer surface removal processes, thereby reducing the metallization process steps. DETAILED DESCRIPTION

[0097] Unless otherwise defined herein, scientific and technical terms used in conjunction with the present invention shall have the meanings commonly understood by those of ordinary skill in the art. The meaning and scope of the terms should be clear, however, in the case of any potential ambiguity, the definitions provided herein take precedence over any dictionary or external definitions. In this application, unless otherwise stated, the use of "or" means "and / or". In addition, the use of the term "including" and other forms is non-limiting.

[0098] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0099] The present invention is further described below by way of examples. Unless otherwise specified, the materials in the examples are prepared according to existing methods or directly purchased from the market.

[0100] Example 1

[0101] This embodiment provides a photovoltaic titanium paste, which includes the following components by weight:

[0102]

[0103]

[0104] Example 2

[0105] This embodiment provides a photovoltaic titanium paste, which includes the following components by weight:

[0106]

[0107] Example 3

[0108] This embodiment provides a photovoltaic titanium paste, which includes the following components by weight:

[0109]

[0110]

[0111] Example 4

[0112] This embodiment provides a photovoltaic titanium paste, which is different from the embodiment 3 in that the components of the photovoltaic titanium paste also include:

[0113]

[0114] Example 5

[0115] This embodiment provides a photovoltaic titanium paste, which is different from the embodiment 3 in that the components of the photovoltaic titanium paste also include:

[0116]

[0117] Example 6

[0118] This embodiment provides a photovoltaic titanium paste, which is different from the embodiment 3 in that the components of the photovoltaic titanium paste also include:

[0119]

[0120] Example 7

[0121] This embodiment provides a photovoltaic titanium paste, which is different from the embodiment 6 in that the components of the photovoltaic titanium paste also include:

[0122]

[0123] Example 8

[0124] This embodiment provides a photovoltaic titanium paste, which is different from the embodiment 6 in that the components of the photovoltaic titanium paste also include:

[0125]

[0126] Example 9

[0127] This embodiment provides a photovoltaic titanium paste, which is different from the embodiment 6 in that the components of the photovoltaic titanium paste also include:

[0128]

[0129] Example 10

[0130] This embodiment provides a photovoltaic titanium paste, which is different from Embodiment 9 in that it contains 78 parts of titanium powder and the rest is the same as Embodiment 9.

[0131] Embodiment 11

[0132] This embodiment provides a photovoltaic titanium paste, which is different from Embodiment 9 in that it contains 92 parts of titanium powder and the rest is the same as Embodiment 9.

[0133] Example 12

[0134] This embodiment provides a photovoltaic titanium paste, which is different from Embodiment 9 in that: 0.2 parts of glass powder, and the rest is the same as Embodiment 9.

[0135] Example 13

[0136] This embodiment provides a photovoltaic titanium paste, which is different from Embodiment 9 in that it contains 7 parts of glass powder and is consistent with Embodiment 9 in other aspects.

[0137] Embodiment 14

[0138] This embodiment provides a photovoltaic titanium paste, which is different from Embodiment 9 in that: 4 parts of titanium-tungsten alloy powder are used, and the rest is the same as Embodiment 9.

[0139] Embodiment 15

[0140] This embodiment provides a method for preparing photovoltaic titanium paste, comprising the following steps:

[0141] The raw materials of the photovoltaic titanium paste in the formula amount of Example 9 are uniformly mixed and ground to prepare photovoltaic titanium paste;

[0142] The glass powder is prepared by the following steps: the glass powder raw materials of the formula amount are mixed, melted, ball-milled, dried and sieved in sequence to obtain glass powder; the melting temperature is 900°C, the ball mill is used for ball milling, the ball milling time is 5 h, and the drying time is 0.5 h.

[0143] Example 16

[0144] This embodiment provides a method for preparing photovoltaic titanium paste, which is different from embodiment 15 in that:

[0145] The glass powder is prepared by the following steps: the glass powder raw materials of the formula amount are mixed, melted, ball-milled, dried and sieved in sequence to obtain glass powder; the melting temperature is 1400° C., the ball milling is performed using a ball mill, the ball milling time is 0.5 h, and the drying time is 2 h.

[0146] Examples 17-30

[0147] This embodiment provides a method for preparing a photovoltaic titanium paste, wherein the raw materials of the photovoltaic titanium pastes in the formula amounts in embodiments 1-14 are uniformly mixed and ground to obtain the photovoltaic titanium pastes of embodiments 17-30 in sequence;

[0148] The glass powder is prepared by the following steps: the glass powder raw materials of the formula amount are mixed, melted, ball-milled, dried and sieved in sequence to obtain glass powder; the melting temperature is 1200°C, the ball milling is carried out using a ball mill, the ball milling time is 2.5 hours, and the drying time is 1 hour.

[0149] Embodiment 31

[0150] This embodiment provides a solar cell, which is prepared by the following preparation steps:

[0151] S1: providing a solar cell silicon substrate, the solar cell substrate comprising a silicon substrate and a silicon nitride film deposited on the surface of the silicon substrate, the thickness of the silicon nitride film being 50 nm;

[0152] S2: A patterned groove is formed by laser film opening in the preset grid line area on the front and back of the solar cell silicon substrate. The width of the groove is 5 μm and the depth is 100 nm.

[0153] S3: acid-washing the silicon substrate of the solar cell after the film is opened: first, use a suction cup to absorb the front side of the silicon substrate of the solar cell after the film is opened, and float the back side in the acid-washing solution. After the cleaning is completed, the solar cell is quickly blown dry in room temperature air, and the front side of the silicon substrate of the solar cell is turned over and cleaned according to the above method. After both sides are cleaned and dried, a double-sided acid-washed silicon substrate of the solar cell is obtained, wherein the temperature of the hydrofluoric acid solution is 25°C, the concentration is 4%, the floating time of the silicon substrate in the acid-washing solution is 5 s, and the drying temperature is 20°C;

[0154] S4: using screen printing to apply the titanium paste prepared in Example 25 to the groove on the back side of the silicon substrate of the solar cell to form a predetermined electrode pattern for film opening;

[0155] S5: The silicon wafer after printing the titanium paste is dried at 150°C for 10 seconds and then laser-assisted sintering is performed. Through the laser-assisted sintering technology, the laser is irradiated on the titanium paste to locally and quickly heat the titanium paste on the back side of the solar cell silicon substrate for sintering;

[0156] S6: turning over the solar cell sheet, and applying the titanium paste prepared in Example 25 to the front groove of the solar cell silicon substrate by screen printing to form a predetermined electrode pattern;

[0157] S7: The silicon wafer after printing the titanium paste is dried at 150°C for 10 seconds and then laser-assisted sintering is performed. Through the laser-assisted sintering technology, the laser is irradiated on the titanium paste to locally and quickly heat the front titanium paste of the solar cell silicon substrate for sintering, thereby obtaining a solar cell with a double-sided titanium seed layer prepared by laser-assisted sintering;

[0158] S8: Electroplating copper and tin on both sides of the solar cell with double-sided titanium seed layer in sequence to obtain a solar cell, wherein the thickness of the copper plating layer is 9 um; the thickness of the tin plating layer is 2 um.

[0159] Embodiment 32

[0160] This embodiment provides a solar cell, which is different from Embodiment 31 in that:

[0161] In S1, the thickness of the silicon nitride film is 100 nm;

[0162] In S2, the groove has a width of 50 μm and a depth of 50 nm;

[0163] In S3, the temperature of the hydrofluoric acid solution is 38°C, the concentration is 1%, the floating time of the silicon substrate in the pickling solution is 50 s, and the drying temperature is 15°C;

[0164] In S5 and S7, the silicon wafer after printing the titanium paste was dried at 350 °C for 5 s and then laser-assisted sintering was performed;

[0165] In S8, the thickness of the copper plating layer is 12 um; the thickness of the tin plating layer is 1 um.

[0166] Examples 33-46

[0167] This embodiment provides a solar cell, which is different from Embodiment 31 in that:

[0168] In S1, the thickness of the silicon nitride film is 75 nm;

[0169] In S2, the groove has a width of 30 μm and a depth of 75 nm;

[0170] In S3, the temperature of the hydrofluoric acid solution is 32°C, the concentration is 2.5%, the floating time of the silicon substrate in the pickling solution is 30 seconds, and the drying temperature is 18°C;

[0171] In S4, the titanium pastes prepared in Examples 17 to 30 are sequentially coated in the grooves on the back side of the silicon substrate of the solar cell by screen printing to form a predetermined electrode pattern for film opening;

[0172] In S5, the silicon wafer after printing the titanium paste is dried at 250 °C for 8 s and then laser-assisted sintering is performed;

[0173] In S6, the titanium paste prepared in Examples 17-30 is applied to the front groove of the silicon substrate of the solar cell by screen printing to form a predetermined electrode pattern;

[0174] In S7, the silicon wafer after printing the titanium paste is dried at 250°C for 8 s and then laser-assisted sintering is performed;

[0175] In S8, the thickness of the copper plating layer is 10 um; the thickness of the tin plating layer is 1.5 um, and finally the solar cells of Examples 33-46 are prepared.

[0176] Comparative Example 1

[0177] This comparative example provides a photovoltaic titanium paste, which is different from Example 9 in that it does not contain glass powder.

[0178] Comparative Example 2

[0179] This comparative example provides a photovoltaic titanium paste, which is different from Example 9 in that it does not contain titanium-tungsten alloy powder.

[0180] Comparative Examples 3-4

[0181] This comparative example provides a solar cell, which differs from Example 25 in that the titanium paste prepared in Comparative Examples 1-2 is sequentially coated on the grooves on the front and back sides of the solar cell silicon substrate.

[0182] Test Case

[0183] Test samples: solar cells prepared in Examples 31-46, and solar cells prepared in Comparative Examples 3-4.

[0184] Test methods: (1) Electrical performance test: offline solar IV tester;

[0185] (2) Welding tension under low temperature conditions: tensile gauge.

[0186] The test results are shown in Table 1.

[0187] Table 1

[0188]

[0189] As shown in Table 1, the photovoltaic titanium paste with a component in a specific range is used to prepare solar cells, and the welding tension of the cells is large and the cell efficiency is high. In addition, the present invention adjusts the particle size of titanium powder, selects a suitable ratio of glass powder elements, and prepares titanium paste that can be adapted to laser-assisted sintering, providing a new titanium seed layer preparation method with good bonding strength and efficiency.

[0190] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A solar cell, characterized in that: The solar cell is prepared by the following preparation steps: A patterned groove is formed in a preset grid line area of ​​a silicon substrate of a solar cell, a photovoltaic titanium paste is applied in the groove, and then a laser-assisted sintering is performed to form a titanium seed layer in the groove by irradiating the titanium paste with a laser, and a metal layer is prepared on the titanium seed layer to obtain the solar cell; The photovoltaic titanium paste comprises the following components by weight: 80-90 parts of titanium powder, 0.3-6 parts of glass powder, 0.1-3 parts of titanium-tungsten alloy powder and the balance of organic carrier solution.

2. The solar cell according to claim 1, characterized in that The particle size of the titanium powder is 0.1-2 μm.

3. The solar cell according to claim 1, characterized in that The titanium powder includes at least one of spherical titanium powder, flaky titanium powder, needle-shaped titanium powder, plate-shaped titanium powder and sponge-shaped titanium powder.

4. The solar cell according to claim 1, characterized in that The organic carrier solution includes at least one of terpineol, butyl carbitol acetate, ethylene glycol ethyl ether acetate, tributyl citrate, dibutyl phthalate and lecithin.

5. The solar cell according to claim 1, characterized in that The particle size of the titanium-tungsten alloy powder is 0.1-2 μm.

6. The solar cell according to claim 1, characterized in that The particle size of the glass powder is 0.5-3 μm.

7. The solar cell according to claim 1, characterized in that The glass powder is boron glass powder.

8. The solar cell according to claim 1, characterized in that The glass powder comprises the following components by mass percentage: PbO: 10-35%, Bi2O3: 10-35%, SiO2: 5-15%, CuO: 5-15%, MnO2: 1-10%, B2O3: 1-10%, Al2O3: 1-10%, TiO2 : 5-15%, Li2O: 0-4%, ZnO: 0-5%, MgO: 0-5%, Cr2O3: 0-5%, NiO: 0-5%, TeO2: 0-5%, Na2O: 0-5%, K2O: 0-5%.

9. The solar cell according to claim 1, characterized in that: The photovoltaic titanium paste also includes antioxidants.

10. The solar cell according to claim 9, characterized in that: The weight portion of the antioxidant is 0.2-1 part.

11. The solar cell according to claim 10, characterized in that The antioxidant includes at least one of 2,6-di-tert-butyl-p-cresol, 2,4,6-tri-tert-butylphenol, thioglycolic acid and thioacetic acid.

12. The solar cell according to claim 1, characterized in that The components of the photovoltaic titanium paste also include additives.

13. The solar cell according to claim 12, characterized in that: The weight portion of the additive is 0.1-0.5 parts.

14. The solar cell according to claim 12, characterized in that: The additive includes at least one of a thickener, a surfactant, a leveling agent and a lubricant.

15. The solar cell according to claim 14, characterized in that: The thickener includes at least one of polyamide wax, hydroxypropyl methyl and hydrogenated rosin.

16. The solar cell according to claim 14, characterized in that: The surfactant includes at least one of stearic acid and lecithin.

17. The solar cell according to claim 14, characterized in that: The leveling agent includes at least one of phthalic acid and furoic acid.

18. The solar cell according to claim 14, characterized in that: The lubricant includes at least one of butyl oleate and diethyl fumarate.

19. The solar cell according to claim 1, characterized in that The method for preparing the photovoltaic titanium paste comprises the following steps: The raw materials of the photovoltaic titanium paste in the formula amount are mixed to prepare the photovoltaic titanium paste.

20. The solar cell according to claim 1, characterized in that The glass powder is prepared by the following steps: The glass powder is obtained by sequentially mixing, melting, ball milling, drying and sieving the glass powder raw materials in the formula amount.

21. The solar cell according to claim 20, characterized in that The melting temperature is 900-1400°C.

22. The solar cell according to claim 20, characterized in that The ball milling is performed using a ball mill, and the ball milling time is 0.5-5 h.

23. The solar cell according to claim 20, characterized in that The drying time is 0.5-2 h.

24. The solar cell according to claim 1, characterized in that The solar cell silicon substrate comprises a silicon substrate and a coating layer deposited on the surface of the silicon substrate.

25. The solar cell according to claim 24, characterized in that The coating layer is a silicon nitride film.

26. The solar cell according to claim 25, characterized in that The thickness of the silicon nitride film is 50-100 nm.

27. The solar cell according to claim 26, characterized in that The groove has a width of 5-50 μm and a depth of 50-100 nm.

28. The solar cell according to claim 1, characterized in that After patterned grooves are formed on the solar cell silicon substrate, the solar cell silicon substrate is acid-washed before titanium paste is applied into the grooves.

29. The solar cell according to claim 28, characterized in that The pickling comprises: placing the grooved surface of the solar cell silicon substrate in a pickling solution, and drying after the cleaning is completed.

30. The solar cell according to claim 28, characterized in that The temperature of the pickling solution is 25-38°C.

31. The solar cell according to claim 28, characterized in that The pickling liquid is a hydrofluoric acid solution, and the concentration of the hydrofluoric acid solution is 1-4%.

32. The solar cell according to claim 29, wherein: The grooved surface is placed in the pickling solution for 5-50 s.

33. The solar cell according to claim 29, characterized in that The drying temperature is 15-20°C.

34. The solar cell according to claim 1, characterized in that The photovoltaic titanium paste is applied into the groove, comprising: applying the titanium paste into the groove by a printing process.

35. The solar cell according to claim 34, characterized in that The printing process includes screen printing.

36. The solar cell according to claim 35, characterized in that The printing screen in the printing process matches the pattern of the patterned grooves.

37. The solar cell according to claim 34, characterized in that After applying the photovoltaic titanium paste into the grooves, the solar cell silicon substrate is dried before laser sintering.

38. The solar cell according to claim 37, characterized in that The drying temperature is 150-350°C and the drying time is 5-10 s.

39. The solar cell according to claim 1, characterized in that The preparing of the metal layer comprises: electroplating copper and tin in sequence on the titanium seed layer.

40. The solar cell according to claim 39, characterized in that The thickness of the copper plating layer is 9-12 um.

41. The solar cell according to claim 39, wherein The thickness of the tin plating layer is 1-2 um.

Images