Preparation method of electrode structure of solar cell and electrode structure

Abstract

The invention provides a preparation method of an electrode structure of a solar cell and the electrode structure, and relates to the technical field of solar cell preparation, and the preparation method comprises the following steps: obtaining a substrate and solder paste, the solder paste comprises a tin-based alloy, and the melting temperature is 80-160 DEG C; the electrode structure is formed by screen printing and curing of the paste formed by the solder paste on the substrate, and the problems that the cost is high and the requirement of the preparation process is high due to the fact that silver paste is adopted for preparing the electrode structure in the prior art are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cell preparation, and in particular to a method for preparing an electrode structure of a solar cell and an electrode structure. Background Art

[0002] Screen printing technology plays an important role in the manufacture of solar cells, especially in the preparation of contact electrodes for cells. This technology forms the main grid and the auxiliary grid by printing conductive materials (such as silver paste or aluminum paste) on the surface of the cell, thereby constructing the electrode structure of the solar cell.

[0003] In the manufacturing process of solar cells, the main grid and the auxiliary grid are important parts of the battery components. They not only play a conductive role, but also help collect and transmit current. Screen printing technology forms a grid structure by printing conductive materials (such as silver paste or aluminum paste) on the surface of the battery. The main grid is usually wider and serves as the main transmission path for current, while the auxiliary grid is thinner and is used to further collect current and reduce the series resistance of the battery cell.

[0004] The preparation process of screen-printed electrodes includes the steps of selecting a suitable substrate material, preparing conductive ink, printing the conductive ink, drying and curing, etc. The existing electrode structure screen printing uses silver paste to prepare the main grid and the auxiliary grid, which is costly and has high requirements for the preparation process. Summary of the invention

[0005] In order to overcome the above technical defects, the purpose of the present invention is to provide a method for preparing an electrode structure of a solar cell and an electrode structure, so as to solve the problem that silver paste is used in the existing preparation of electrode structures, which has high cost and high requirements for the preparation process.

[0006] The present invention discloses a method for preparing an electrode structure of a solar cell, comprising:

[0007] Obtain a substrate and solder paste, wherein the solder paste contains a tin-based alloy having a melting temperature of 80 to 160° C.;

[0008] The solder paste is used to form a slurry which is screen-printed and cured on the substrate to form an electrode structure.

[0009] Preferably, the solder paste contains a tin-based alloy formed by at least one of lead, silver, copper and bismuth;

[0010] Wherein, the content of tin-based alloy in the solder paste exceeds 88%.

[0011] Preferably, the solder paste includes Bi a Sn b Ag c , where a∈55~60, b∈39~45, c∈1~3;

[0012] or Sn x Bi y , where x∈20~80, y∈20~80.

[0013] Preferably, the width of the solder paste line formed on the electrode structure by screen printing is 10-100 μm.

[0014] Preferably, the solder paste is dissolved in a solvent to form a slurry;

[0015] The solvent includes alcohols, lipids, ketones, halogenated hydrocarbons, water, amine cyclic compounds, organic acids or chlorides.

[0016] Preferably, the particle size of the metal particles in the slurry;

[0017] The metal phase in the slurry is 92-96%, and the inorganic phase is 4-8%.

[0018] Preferably, before screen printing, the substrate is subjected to surface treatment, wherein the surface treatment includes roughening, cleaning and chemical treatment.

[0019] Preferably, a steel screen, a steel plate with full openings or a printing plate with preset openings is used when screen printing is performed on the substrate.

[0020] The present invention also provides an electrode structure of a solar cell, which is prepared by any of the above-mentioned methods for preparing the electrode structure.

[0021] Compared with the prior art, the above technical solution has the following beneficial effects:

[0022] The present application adopts solder paste with a melting temperature of 80 to 160°C as a slurry to prepare an electrode structure through screen printing, and controls the metal particles and solvent therein to form an electrode structure with resistivity and good conductivity as well as strong adhesion and high chemical stability, thereby solving the problem that the existing electrode structure is prepared using silver paste, which has high cost and high requirements for the preparation process. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A flow chart of a method for preparing an electrode structure of a solar cell and an embodiment of an electrode structure according to the present invention;

[0024] Figure 2 It is a microscopic magnified image of the morphology of a solder paste line in a method for preparing an electrode structure of a solar cell and an electrode structure embodiment described in the present invention. DETAILED DESCRIPTION

[0025] The advantages of the present invention are further described below in conjunction with the accompanying drawings and specific embodiments.

[0026] Exemplary embodiments will be described in detail herein, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, the same numbers in different drawings represent the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present disclosure. Instead, they are merely examples of devices and methods consistent with some aspects of the present disclosure as detailed in the appended claims.

[0027] The terms used in this disclosure are for the purpose of describing specific embodiments only and are not intended to limit the disclosure. The singular forms of "a", "said" and "the" used in this disclosure and the appended claims are also intended to include plural forms unless the context clearly indicates otherwise. It should also be understood that the term "and / or" used herein refers to and includes any or all possible combinations of one or more associated listed items.

[0028] It should be understood that although the terms first, second, third, etc. may be used in the present disclosure to describe various information, such information should not be limited to these terms. These terms are only used to distinguish the same type of information from each other. For example, without departing from the scope of the present disclosure, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information. Depending on the context, the word "if" as used herein may be interpreted as "at the time of" or "when" or "in response to determining".

[0029] In the description of the present invention, it is necessary to understand that the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0030] In the description of the present invention, unless otherwise specified and limited, it should be noted that the terms "installed", "connected" and "connected" should be understood in a broad sense. For example, it can be a mechanical connection or an electrical connection, or it can be the internal connection between two components. It can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to the specific circumstances.

[0031] In the following description, the suffixes such as "module", "component" or "unit" used to represent elements are only used to facilitate the description of the present invention, and have no specific meanings. Therefore, "module" and "component" can be used interchangeably.

[0032] Example: This embodiment provides a method for preparing an electrode structure of a solar cell, which uses solder paste as a slurry to prepare the electrode structure. This is different from the existing screen printing method that uses silver paste to prepare the electrode structure, reduces costs, and maintains better conductivity and stability. Specifically, it includes: S10: obtaining a substrate and solder paste, wherein the solder paste contains a tin-based alloy with a melting point of 80 to 160°C; S20: using the solder paste to form a slurry, screen printing and curing on the substrate to form an electrode structure. Specifically, printing can be performed at room temperature, a humidity of 40-55%, a pressure of 20-70N, and a sintering temperature of approximately 100-200°C.

[0033] In this embodiment, the above-mentioned substrate can be used to prepare solar cells, including but not limited to silicon wafers (single crystal silicon or polycrystalline silicon), non-silicon substrates with absorption layers, conductive glass or flexible plastic substrates, etc., and the specific substrate application can be selected according to the actual application scenario. It is also for illustration that the specific steps of the above-mentioned screen printing are consistent with the existing screen printing steps using silver paste. As an example, it includes preparing a silicon wafer and a printing screen, pouring a slurry (solder paste) at one end of the screen, using a scraper to apply a certain pressure on the slurry part of the screen while moving toward the other end of the screen. The slurry is squeezed from the mesh of the graphic part to the silicon wafer by the scraper during movement. During the printing process, the scraper is always in line contact with the screen printing plate and the substrate (silicon wafer). The contact line moves with the movement of the scraper, and the other parts of the screen are detached from the substrate. When the scraper scrapes across the entire printing area, it is lifted up, and the screen is also detached from the silicon wafer. The slurry is gently scraped back to the initial position by the ink return knife, and the workbench returns to the loading position to complete a printing stroke. Multiple printings can be performed, and each printed silicon wafer needs to undergo a drying and curing process to allow the organic carrier in the slurry to volatilize and solidify the metal particles to form a conductive electrode.

[0034] In this embodiment, a slurry formed by solder paste is used to replace the existing commonly used silver paste. The melting temperature of the solder paste depends on its alloy composition. Different solder pastes have different melting points, which is mainly determined by their alloy composition. By using solder paste with a melting temperature of 80 to 160°C, welding can be performed at a lower temperature, reducing the risk of damage caused by thermal stress, protecting heat-sensitive components and substrates, and having lower requirements for the preparation process.

[0035] In a preferred embodiment, the solder paste contains a tin-based alloy formed by at least one of lead, silver, copper, and bismuth; wherein the tin-based alloy content in the solder paste exceeds 88%. When the tin-based alloy content is high, the wettability of the solder paste is usually better, the mechanical strength and fatigue resistance of the solder joint can be improved, the crystal particles formed when the solder joint solidifies are denser, the solder joint strength is higher, and it is beneficial to cost control. Selecting a suitable proportion of tin powder, such as tin-lead, tin-bismuth, tin-silver-copper alloy, etc., can affect the quality of the solder joint and the reliability of welding.

[0036] Further, as an option, the solder paste includes Bi a Sn b Ag c , where a∈55~60, b∈39~45, c∈1~3; or, Sn d Pb e Bi f , where d∈30~50, e∈40~45, f∈1~15; or, Sn x Bi y , where x∈20~80, y∈20~80. For example, using Bi 57 Sn 42 Ag1, whose corresponding melting point is 148°C; or Sn 43 Pb 43 Bi 14 , the corresponding melting temperature is 144~163℃; or Sn 43 Pb 43 Bi 26 , the corresponding melting temperature is between 100℃ and 104℃; or Sn 42 Bi 58 , and its corresponding melting temperature is 138°C. Other tin-based alloys can also be used according to actual scenarios.

[0037] In a preferred embodiment, based on the above, the width of the solder paste line formed by screen printing on the electrode structure is 10-100μm, which can meet the high-precision printing requirements, provide a more uniform solder paste distribution, and help to form better quality solder joints during the welding process. Further, by precisely controlling the heating rate and temperature curve to adapt to solder pastes with different alloy compositions, the stability of the welding process and the quality of the solder joints are ensured to meet the realization of the electrode structure of this embodiment.

[0038] In a preferred embodiment, the solder paste is dissolved in a solvent to form a slurry; the solvent includes but is not limited to alcohols, lipids, ketones, halogenated hydrocarbons, water, amine cyclocompounds, organic acids or chlorides; specifically, it can be at least one of octyl ether, tetrahydrofurfuryl alcohol, ethylene glycol methyl ether, ethylene glycol ethyl ether, polyethylene glycol 400, diethylene glycol butyl ether, etc.; the particle size of the metal particles in the slurry; the metal phase in the slurry is 92-96%, and the inorganic phase is 4-8%. It can be understood that the choice of solvent, the particle size of the metal particles in the slurry, and the ratio of the metal particles to the solvent will affect the adhesion and conductivity of the solder paste line formed by screen printing, so the above restrictions are set to form a good contact between the solder paste line and the silicon wafer surface.

[0039] In a preferred embodiment, the solder paste further comprises a flux, which plays a role in removing an oxide layer, reducing surface tension, adjusting viscosity and rheology in the solder paste. The flux includes but is not limited to one or more of an organic carrier, an activator, and a thixotropic agent. Their proportion and selection have a significant effect on the performance of the solder paste. As examples, rosin, benzoic acid, salicylic acid, fluoroalkyl carboxylic acid ammonium salts, etc. can be used.

[0040] In a preferred embodiment, the solder paste further comprises additives for further improving the printing performance, welding performance and final welding quality of the solder paste. The additives include but are not limited to one or more of nanoparticles, surfactants, and conductive adhesives. The nanoparticles are used to improve the mechanical properties and melting point of the solder joints. Antioxidants, corrosion inhibitors, halogen inhibitors, etc. may also be added.

[0041] In this embodiment, preferably, the substrate is subjected to surface treatment before screen printing, and the surface treatment includes roughening, cleaning and chemical treatment, that is, appropriate pretreatment is performed on the substrate surface, such as using a specific cleaning agent or plasma treatment, to enhance the adhesion of the solder paste to the silicon wafer during screen printing. Furthermore, the sintering process can be optimized to ensure good contact and bonding between the solder paste line and the silicon wafer surface. The temperature, time and atmosphere during the sintering process need to be strictly controlled to enhance adhesion.

[0042] In the present embodiment, it can also be supplemented that, different from the existing operation of screen printing using silver paste, a steel mesh, a fully-opened steel plate or a printing plate with preset openings is used when screen printing is performed on the substrate. The printing plate is a fully-opened printing plate made by pre-fabricating an image structure corresponding to the conductive electrode on the surface of the solar cell on a metal foil. A finer screen and more precise printing equipment are used to control the line width of the formed solder paste line, so that the formed electrode structure has resistivity and good conductivity, as well as strong adhesion and high chemical stability, and low cost.

[0043] As a supplement, in the present embodiment, in response to the selection of solder paste in different implementation scenarios, the resistance and morphology of the electrode structure formed can be experimentally determined in advance. As an example, solder paste of any component can be printed on the battery cell separately, and the morphology of the printed solder paste can be observed using a microscope. The solder paste on the surface of the battery cell is dried using a heating table (50°C-30min), and the morphology of the dried solder paste is observed using a microscope. The solder paste on the surface of the battery cell is melted using a heating table (140°C-10min; 130°C-10min), and the morphology of the melted solder paste is observed using a microscope, and the resistance of the solder paste line is tested. The type of solder paste (composition of tin-based alloy, flux, additives, solvent, metal particle size, etc.) in different scenarios can be matched according to the test results.

[0044] Furthermore, this embodiment also provides an electrode structure of a solar cell, which is prepared by any of the electrode structure preparation methods described above. The electrode structure can be applied to, including but not limited to, the preparation of batches of solar cells. Through screen printing, the size and shape of the electrode pattern can be precisely controlled to increase the wide range of applications.

[0045] It should be noted that the embodiments of the present invention have better practicability and do not impose any form of limitation on the present invention. Any technician familiar with the field may use the technical content disclosed above to change or modify it into an equivalent effective embodiment. However, any modification or equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for preparing an electrode structure of a solar cell, characterized in that: include: Obtain a substrate and solder paste, wherein the solder paste contains a tin-based alloy with a melting temperature of 80 to 160° C.; The solder paste is used to form a slurry which is screen-printed and cured on the substrate to form an electrode structure.

2. The method for preparing an electrode structure according to claim 1, characterized in that: The solder paste contains a tin-based alloy formed by at least one of lead, silver, copper and bismuth; Wherein, the content of tin-based alloy in the solder paste exceeds 88%.

3. The method for preparing an electrode structure according to claim 1 or 2, characterized in that: The solder paste includes Bi a Sn b Ag c , where a∈55~60, b∈39~45, c∈1~3; or Sn d Pb e Bi f , where d∈30~50, e∈30~50, f∈1~30; or Sn x Bi y , where x∈20~80, y∈20~80.

4. The method for preparing an electrode structure according to claim 1, characterized in that: The width of the solder paste line formed on the electrode structure by screen printing is 10-100 μm.

5. The method for preparing an electrode structure according to claim 1, characterized in that: The solder paste is dissolved in a solvent to form a slurry; The solvent includes alcohols, lipids, ketones, halogenated hydrocarbons, water, amine cyclic compounds, organic acids or chlorides.

6. The method for preparing an electrode structure according to claim 5, characterized in that: The metal phase in the slurry is 92-96%, and the inorganic phase is 4-8%.

7. The method for preparing an electrode structure according to claim 1, characterized in that: Before screen printing, the substrate is subjected to surface treatment, wherein the surface treatment includes roughening, cleaning and chemical treatment.

8. The method for preparing an electrode structure according to claim 1, characterized in that: When screen printing is performed on the substrate, a steel screen, a steel plate with full openings or a printing plate with preset openings is used.

9. An electrode structure of a solar cell, characterized in that: The electrode structure is prepared by the electrode structure preparation method described in any one of claims 1 to 8.

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