Method for manufacturing solar cell main grid through laser 3D printing
Through laser 3D printing technology, the problems of high cost and low efficiency in traditional screen printing technology are solved, and the precise preparation of high-profile main gate electrodes is achieved, which improves the efficiency and environmental protection of solar cells.
Patent Information
- Application Number
- CN202411659628.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-20
- Publication Date
- 2025-01-10
AI Technical Summary
Traditional screen printing technology has problems such as high cost, low efficiency, limited electrode aspect ratio, and increased battery occlusion area when making solar cell main gates, which affects the battery power generation power.
Using laser 3D printing method, metal powder is transported to the cell with powder airflow and sintered by laser instantaneous hot melt to form a metal electrode, nozzle and laser movement synchronously to form a main gate electrode, reducing the impact on battery efficiency.
The main gate electrode with a high aspect ratio of more than 100% is achieved, which reduces production costs, improves battery efficiency, reduces the occlusion area on the battery surface, and is simplified and environmentally friendly.
Smart Images
Figure CN119300528A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to a method for manufacturing a solar cell main grid. Background Art
[0002] The electrodes of crystalline silicon solar cells are divided into main grid and auxiliary grid. The auxiliary grid is used to collect the generated current, while the main grid collects the current collected by the auxiliary grid for conduction. Both need to be made very thin as much as possible without occupying too much battery area, and the resistance needs to be small enough without affecting the battery conversion efficiency, so a certain aspect ratio is required. At present, the main grid and auxiliary grid are both made using mature screen printing technology, using the basic principle that the mesh holes of the screen pattern part can pass through the slurry, and the mesh holes of the non-graphic part cannot pass through the slurry to print on the battery to form the electrode pattern. During printing, slurry is poured into one end of the screen, and a certain pressure is applied to the slurry part of the screen with a scraper 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 to form the set solar cell grid line electrode; the slurry is generally composed of a conductive functional phase, an inorganic phase, an organic solvent and other additives, wherein the conductive functional phase is mainly silver powder, which plays a conductive role, and the inorganic phase is mainly glass powder, which not only has a high-temperature bonding effect during the solidification and molding process of the metal electrode during sintering, but also serves as a flux for the sintering of silver powder and a medium material that helps to form silver-silicon ohmic contact. The organic solvent mainly includes a volatile phase solvent and a non-volatile phase resin (mainly phenolic resin and epoxy resin), which mainly plays a dispersing and encapsulating role, and evenly encapsulates the silver powder particles, so that the conductive silver paste is not easy to precipitate and oxidize.
[0003] The problems with the current traditional screen printing technology are as follows: screen printing requires many auxiliary materials such as special screens, slurries and scrapers, and after printing, it also requires drying equipment and high-temperature sintering equipment, which is costly; screen printing also has problems such as broken grids, slurry blocking the screen, virtual printing, poor sintering and over-burning, in which case the efficiency and yield of solar cells will be low; due to the use of silver paste, the aspect ratio of the battery electrode is limited, generally less than 40%, considering the need to maintain an appropriate electrode width to minimize the resistance of the electrode, which will lead to an increase in the blocked area of the battery, especially for the main grid electrode, which requires a wider cross-sectional area to reduce the resistance. The increase in the blocked area will affect the power generation of the battery. Summary of the invention
[0004] Purpose of the invention: The purpose of the present invention is to provide a method for producing a solar cell main grid by laser 3D printing, so as to accurately produce the main grid and improve the cell conversion efficiency.
[0005] Technical solution: A method for laser 3D printing to make solar cell main grids, firstly, metal powder is transported to the top of the cell by a nozzle in a powder airflow, and then the metal powder is instantly melted and sintered on the cell by a laser, and a metal electrode is formed after cooling. As the nozzle and laser move continuously on the cell in synchronization with the main grid pattern, a main grid is formed.
[0006] Furthermore, the laser is a blue laser, the laser power is 10-100W, the laser frequency is 400-1500KHz, and the spot size is 10-60μm.
[0007] Furthermore, the temperature of the laser irradiating the cell is 50-1000°C.
[0008] Furthermore, the metal powder is silver powder or copper powder, and the particle size is 0.5 to 1.2 μm.
[0009] Furthermore, the powder delivery rate of the powder airflow is 5 to 50 g / min, and the carrier gas flow rate is 5 to 30 L / min.
[0010] Furthermore, the synchronous movement speed of the nozzle and the laser is 2000-6000 mm / s.
[0011] Furthermore, the main grid has a width of 30 to 100 μm, a height of 4 to 60 μm, and an aspect ratio of 10 to 150%.
[0012] Furthermore, the manufacturing process is carried out in a vacuum environment or an inert gas environment.
[0013] Beneficial effects: The advantages of the present invention are: the main grid electrode can be accurately prepared on the battery cell at one time using metal powder through the laser 3D printing method, which can reduce the impact on the battery efficiency. The aspect ratio of the main grid can exceed 100%, reducing the obstruction of the battery cell surface, which is beneficial to improving the battery efficiency. Compared with screen printing, it has fewer processes and is environmentally friendly, and the production cost is reduced. BRIEF DESCRIPTION OF THE DRAWINGS
[0014] Figure 1 A schematic diagram of the process of manufacturing a solar cell main grid using the laser 3D printing method of the present invention;
[0015] Figure 2 Schematic diagram of the main grid produced by the traditional screen printing method;
[0016] Figure 3 Schematic diagram of a main grid produced by the laser 3D printing method of the present invention. DETAILED DESCRIPTION
[0017] The present invention will be further illustrated below in conjunction with specific embodiments.
[0018] After the solar cell has gone through the previous processes, such as: cleaning and texturing → boron diffusion (forming PN junction) → alkali polishing → tunneling oxide layer + doped polysilicon layer → front etching → aluminum oxide preparation → front and back silicon nitride, it enters the gate line manufacturing process, and the main grid of the solar cell is manufactured through the laser 3D printing method of the present application, such as: cleaning and texturing → deposition of intrinsic hydrogenated amorphous silicon on the front and back → deposition of phosphorus-doped amorphous silicon on the front → boron-doped amorphous silicon on the back → deposition of transparent conductive oxide on the front and back, and enters the gate line manufacturing process. Because the film surface is a TCO layer, no etching is required, and the main grid of the solar cell is manufactured through the laser 3D printing method of the present application.
[0019] Combined with Figure 1 As shown, after the secondary grid 4 on the battery cell 3 is manufactured, the battery cell 3 is fixed on a constant temperature controlled stage and remains stationary. According to the main grid pattern position, the metal powder 11 is delivered to the top of the battery cell, specifically to the end point of a main grid, through a fine nozzle 1. The powder amount and airflow of the nozzle are adjusted to form a powder airflow in the area close to the surface of the battery cell, and the metal powder is accurately delivered to the battery cell. Then, the laser 2 is used to instantly heat-melt and sinter the metal powder falling on the battery cell to form a metal electrode on the surface of the battery cell after cooling and solidification.
[0020] The nozzle moves according to the main grid pattern, and the angle and distance between the nozzle, laser and the battery cell can be adjusted. However, during the production process, the nozzle and laser are fixed at a certain angle and distance, and the order of nozzle powder feeding and laser powder melting is always maintained. As the nozzle and laser move continuously in a straight line on the battery cell according to the main grid pattern, the continuously formed metal electrode forms the main grid 5, which is connected to the previously produced sub-grid 4.
[0021] The metal powder is silver powder or copper powder, etc., with a particle size of 0.5 to 1.2 μm. The powder delivery rate of the powder airflow is 5 to 50 g / min, and the carrier gas flow rate is 5 to 30 L / min. The laser can use infrared light, green light, and blue light, preferably blue laser, with a laser power of 10 to 100 W, a laser frequency of 400 to 1500 KHz, and a spot size of 10 to 60 μm; compared with red light, the laser uses blue laser, which is more easily absorbed by the metal powder when melting the powder, and is easy to form instantaneous metal melting. The blue laser is absorbed by the battery cell in the surface layer, which will not cause serious thermal effects on the surface of the battery cell, and has little effect on the layer below the surface. The process is well controllable, especially the temperature control during the laser irradiation process, so that the temperature irradiated on the battery cell is controlled within 50 to 1000 ° C, which can effectively control the penetration depth of the metal electrode into the silicon nitride film, and prevent the main gate electrode from burning through the silicon nitride layer and damaging the passivation layer due to excessive temperature. The synchronous movement speed of the nozzle and the laser is 2000-6000 mm / s.
[0022] The main grid manufacturing process is carried out in a vacuum environment or an inert gas environment such as nitrogen or argon.
[0023] The main grid obtained by the laser 3D printing method of the present invention, the movement speed of the nozzle and the laser relative to the battery cell, the amount of powder and the size of the airflow, and the laser spot size all determine the size of the main grid electrode obtained. The main grid width is 30 to 100 μm, the height is 4 to 60 μm, and the aspect ratio is 10 to 150%.
[0024] Attached Figure 2 The figure shows a schematic diagram of the main grid produced by the traditional screen printing method. Over-burning or poor sintering may occur during the sintering process. The main grid indicated by red is over-burned, which destroys the passivation layer and is in direct contact with the silicon substrate of the battery, which will cause an increase in the composite current. The main grid indicated by green is poorly sintered, which may cause insufficient welding tension at the component end and cause the solder ribbon to fall off.
[0025] Attached Figure 3 The figure shows a schematic diagram of a main gate produced by the laser 3D printing method of the present invention, which can achieve precise sintering, thereby reducing damage to the passivation layer of the silicon wafer, and can also achieve better ohmic contact with the sub-gate.
[0026] Traditional screen printing forms gate line electrodes through lead-containing glass powder metal paste, and forms main gate electrodes through drying and sintering. The metal electrode forms ohmic contact with the silicon substrate and the secondary gate electrode. The metal electrode prepared by metal paste printing has a relatively small aspect ratio, and has a relatively large surface obstruction, which will block more effective area of the battery. In addition, it is difficult to accurately control the sintering temperature and glass powder melting, resulting in a relatively large composite current.
[0027] The laser 3D printing method of the present invention uses laser to accurately prepare the main grid electrode, accurately controls the size of the main grid electrode, and makes the main grid thinner, which can reduce the impact on battery efficiency. The aspect ratio of the main grid can exceed 100%, reducing the obstruction of the battery cell surface, which is beneficial to improving battery efficiency.
[0028] The present invention adopts a laser 3D printing method to prepare a main grid electrode on a battery cell at one time using metal powder. It does not need to prepare a metal slurry with other additives such as organic solvents and glass powder. It can save screen printing equipment, drying equipment, annealing equipment, and auxiliary materials such as metal slurry, screen, and scraper, which can greatly reduce the investment in production equipment and is conducive to reducing production costs. In addition, it reduces the use of lead-containing glass powder and organic solvents, which is more environmentally friendly.
Claims
1. A method for manufacturing a solar cell busbar by laser 3D printing, characterized in that: First, the metal powder is transported to the top of the battery cell through a nozzle in a powder airflow, and then the metal powder is instantly melted and sintered on the battery cell by a laser. After cooling, a metal electrode is formed. As the nozzle and laser move continuously on the battery cell in synchronization with the main grid pattern, a main grid is formed.
2. The method for manufacturing solar cell busbars by laser 3D printing according to claim 1, characterized in that: The laser is a blue laser, the laser power is 10-100W, the laser frequency is 400-1500KHz, and the spot size is 10-60μm.
3. The method for manufacturing solar cell busbars by laser 3D printing according to claim 1, characterized in that: The temperature of the laser irradiating the battery cell is 50 to 1000°C.
4. The method for manufacturing solar cell busbars by laser 3D printing according to claim 1, characterized in that: The metal powder is silver powder or copper powder, and the particle size is 0.5 to 1.2 μm.
5. The method for manufacturing solar cell busbars by laser 3D printing according to claim 1, characterized in that: The powder delivery rate of the powder airflow is 5 to 50 g / min, and the carrier gas flow rate is 5 to 30 L / min.
6. The method for manufacturing solar cell busbars by laser 3D printing according to claim 1, characterized in that: The synchronous movement speed of the nozzle and the laser is 2000-6000 mm / s.
7. The method for manufacturing solar cell busbars by laser 3D printing according to claim 1, characterized in that: The main grid has a width of 30 to 100 μm, a height of 4 to 60 μm, and an aspect ratio of 10 to 150%.
8. The method for manufacturing solar cell busbars by laser 3D printing according to claim 1, characterized in that: The manufacturing process is carried out in a vacuum environment or an inert gas environment.