CN105514183B - A kind of preparation method of crystal silicon solar batteries front electrode - Google Patents

Abstract

The invention discloses a method for preparing a front electrode of a crystalline silicon solar cell, which includes the step of forming main grid lines and auxiliary grid lines on the solar cell. The method includes: S101, providing a screen printing net with a main grid line pattern plate, forming the busbar on the solar cell through the screen printing process; S102, providing a stencil printing screen plate with a sub-grid pattern, and forming the sub-grid on the solar cell through the stencil printing process; S103, forming Sintering is performed on the solar cells with the main grid lines and auxiliary grid lines. The method prepares the main grid line and the auxiliary grid line respectively through two printing processes, which can increase the aspect ratio of the auxiliary grid line, and not only reduce the power loss caused by the resistance of the grid line, but also reduce the optical loss.

Description

A kind of preparation method of front electrode of crystalline silicon solar cell

technical field

The invention relates to the technical field of solar cell manufacturing, in particular to a method for preparing a front electrode of a crystalline silicon solar cell.

Background technique

A crystalline silicon solar cell is an electronic component that converts sunlight energy into electrical energy. The preparation of crystalline silicon solar cells generally goes through processes such as texturing, diffusion, coating, screen printing, and sintering. Texturing is divided into single crystal and polycrystalline texturing. Monocrystalline cells use alkali texturing to form pyramid textures on the surface of silicon wafers. Polycrystalline cells use acid etching to form pitted textures on the surface of silicon wafers. The suede surface on the silicon surface can increase the absorption of sunlight on the surface of the battery to achieve light trapping; the diffusion process is to form a P-N junction inside the silicon wafer through thermal diffusion, so that when there is light, a voltage can be formed inside the silicon wafer. , is the basis of solar cell power generation; the coating process is to reduce the recombination of minority carriers on the surface of the cell, which can improve the conversion efficiency of crystalline silicon solar cells; the screen printing process is to make electrodes of solar cells, so that when light is irradiated The current can be exported. Screen printing is the most widely used process in the preparation of crystalline silicon cells. The process sequence is to print and dry the back electrode first, then print and dry the aluminum back field, and finally print and dry the front electrode. , during sintering, the silver paste used to prepare the electrodes is in contact with the battery.

In the front electrode of a crystalline silicon solar cell, the electrode structure usually includes criss-crossing main grid lines and sub-grid lines, and the main grid lines are electrically connected to the sub-grid lines. When there is light, the battery sheet will generate current, and the current will flow through the internal emitter to the sub-grid of the surface electrode, collect through the sub-grid and then flow to the main grid of the battery for export. The current will generate loss in the process of collecting by the auxiliary gate line, which we call the power loss of resistance. The main grid lines and auxiliary grid lines of the battery are on the light-receiving surface of the battery, which will inevitably block a part of the light from shining on the surface of the battery, thereby reducing the effective light-receiving area of the battery. This part of the loss is called optical loss. Increasing the number of main grid lines and auxiliary grid lines can improve the ability to collect the current formed by the solar cell and improve the conversion efficiency of the cell, but if the width of the grid lines is not reduced, increasing the number will increase the shading loss.

At present, the screen printing process is usually used for the preparation of the front electrode. The graphics of the main grid line and the sub grid line of the front electrode are formed in the same screen screen, and the main grid line and the sub grid line are directly prepared by a screen printing process. The pattern of the front electrode prepared by the grid line is shown in FIG. 1 . The front electrode includes main grid lines 1 and sub-grid lines 2 criss-crossing, and the main grid lines 1 and sub-grid lines 2 are electrically connected. Usually, the number of auxiliary grid lines 2 is 90, the width of the auxiliary grid lines 2 is 40 μm, and the distance between the auxiliary grid lines 2 is 1.724 mm; the number of main grid lines 1 is 3, and the maximum The width is 1.5mm, the width of the narrower part of the busbars 1 is 0.1mm, and the distance between the busbars 1 is 52mm.

Fig. 2 is a schematic diagram of the structure of the screen screen, as shown in Fig. 2, the screen screen 3 is made of wire mesh, and the graphic part of the screen inevitably has the intersection of metal wire 3a and metal wire 3a , they impede the passage of the slurry, and the slurry is viscous, resulting in more serious obstruction during the penetration of the slurry, limiting the aspect ratio. Especially for the part of the sub-grid line pattern 2a, since the width of the sub-grid line 2 itself is relatively small, the sub-grid line 2 is prepared by screen printing, which limits the aspect ratio of the sub-grid line 2 . Figure 3 is a 3D topography diagram of the auxiliary grid line prepared by screen printing. As shown in Figure 3, the surface of the prepared auxiliary grid line is not smooth due to the presence of metal wires and metal wire nodes in the screen pattern. , which increases the resistance, which is not conducive to current collection.

In the promotion and application of solar energy, the biggest obstacle is the high cost. Optimizing the process conditions of each process is an effective way to improve efficiency and reduce costs. If the width of the auxiliary grid line can be effectively reduced and the height of the auxiliary grid line can be increased, it can not only reduce the power loss caused by the resistance of the grid line, but also reduce the optical loss.

Contents of the invention

In view of the deficiencies in the prior art, the present invention provides a method for preparing the front electrode of a crystalline silicon solar cell. The method prepares the main grid line and the auxiliary grid line respectively through two printing processes, which can increase the height and width of the auxiliary grid line Ratio, not only can reduce the power loss caused by grid line resistance, but also can reduce optical loss.

In order to achieve the above object, the present invention adopts the following technical solutions:

A method for preparing a front electrode of a crystalline silicon solar cell, including the step of forming a main grid line and a sub-grid line on the solar cell, the method comprising: S101, providing a screen printing screen plate with a main grid line pattern, and passing a wire Form the main grid lines on the solar cell by the screen printing process; S102, provide a stencil printing screen plate with a sub grid line pattern, and form the sub grid lines on the solar cell through the stencil printing process; The solar cells of grid lines and auxiliary grid lines are sintered.

Wherein, step S101 specifically includes: first setting the screen printing screen on the solar cell, then adding electrode paste on the screen printing screen, and finally moving the scraper to make the electrode paste penetrate the solar cell. and screen printing a screen plate to form the busbars on the solar cell.

Among them, in the screen printing process, the moving speed of the squeegee is 180-220mm/s, the pressure of the squeegee is 7-9kgf, and the distance from the screen of the screen printing screen is 1.25-1.35mm.

Wherein, the number of the busbar lines is 4-6, and the width of the busbar lines is 0.68-1.0 mm.

Wherein, the number of the busbar lines is 5, and the width of the busbar lines is 0.8 mm.

Wherein, step S102 specifically includes: first setting the stencil printing screen on the solar cell, then adding electrode paste on the stencil printing screen, and finally moving the scraper to make the electrode paste penetrate the solar cell. Stencil printing a screen plate to form the auxiliary grid lines on the solar cell.

Among them, in the stencil printing process, the moving speed of the squeegee is 220-240mm/s, the pressure of the squeegee is 4.5-5.5kgf, and the distance from the screen of the screen printing screen is 1.48-1.55mm.

Wherein, the number of the sub-gate lines is 100-110, and the width of the sub-gate lines is 0.20-0.25 μm.

Wherein, the number of the auxiliary grid lines is 106, the width of the auxiliary grid lines is 0.25 μm, and the distance between two adjacent auxiliary grid lines is 1.7213 mm.

Wherein, the busbar includes a plurality of solid parts and a plurality of hollow parts sequentially connected, and the solid parts and the hollow parts are alternately arranged at intervals.

Compared with the prior art, in the preparation method of the front electrode of the crystalline silicon solar cell provided in the embodiment of the present invention, the preparation of the front electrode is divided into two printing processes. Prepare and form auxiliary grid lines. Since the stencil printing screen used in the stencil printing process does not have metal wires and metal wire nodes in its graphics, using this kind of screen to prepare sub-grid lines with small width and high density, the electrode paste can pass through smoothly. The stencil printing screen, the auxiliary grid line prepared by it has a larger aspect ratio, and the height of the auxiliary grid line is more flat and uniform. The final front electrode can not only reduce the power loss caused by the resistance of the grid line, but also Optical loss can be reduced to improve photoelectric conversion efficiency. Moreover, using the front electrode prepared by the method, the amount of electrode paste can be saved by about 10%, which reduces the production cost.

Description of drawings

Fig. 1 is the structural schematic diagram of the front electrode of existing crystalline silicon solar cell;

Fig. 2 is the structural illustration of screen printing screen plate;

Fig. 3 is a 3D topography diagram of the auxiliary grid line prepared by the screen printing process;

Fig. 4 is a process flow diagram of a method for preparing a front electrode of a solar cell provided by an embodiment of the present invention;

Fig. 5 is a schematic diagram of the structure of the stencil printing screen;

Fig. 6 is a 3D topography diagram of the auxiliary grid line prepared by the stencil printing process;

Fig. 7 is a schematic structural view of a front electrode of a solar cell prepared in an embodiment of the present invention.

detailed description

In order to make the object, technical solution and advantages of the present invention clearer, the specific implementation manners of the present invention will be described in detail below in conjunction with the accompanying drawings. Examples of these preferred embodiments are illustrated in the accompanying drawings. The embodiments of the invention shown in and described with reference to the drawings are merely exemplary, and the invention is not limited to these embodiments.

Here, it should also be noted that, in order to avoid obscuring the present invention due to unnecessary details, only the structures and/or processing steps closely related to the solution according to the present invention are shown in the drawings, and the related Other details are not relevant to the invention.

This embodiment provides a method for preparing a front electrode of a crystalline silicon solar cell, and the method includes the step of forming a main grid line and an auxiliary grid line on the solar cell. Referring to Figure 4, the method includes the following steps:

S101. Provide a screen printing screen plate with busbar patterns, and form busbars on solar cells through a screen printing process. Specifically, in this step, firstly, the screen printing screen is set on the solar cell, then the electrode paste is added on the screen printing screen, and finally the scraper is moved to allow the electrode paste to penetrate the solar cell. and screen printing a screen plate to form the busbars on the solar cells. Among them, in the screen printing process, the moving speed of the squeegee can be selected as 180-220mm/s, the pressure of the squeegee can be selected as 7-9kgf, and the distance between the screen printing screen and the screen can be selected as 1.25-1.35mm. Most preferably, the moving speed of the scraper is selected as 200mm/s, the pressure of the scraper is selected as 8kgf, and the distance from the screen of the screen printing screen is selected as 1.3mm.

S102. Provide a stencil printing screen plate with sub-grid patterns, and form sub-grids on the solar cell through a stencil printing process. Specifically, in this step, first set the stencil printing screen on the solar cell, then add electrode paste on the stencil printing screen, and finally move the scraper to make the electrode paste penetrate the solar cell. Stencil printing a screen plate to form the auxiliary grid lines on the solar cell. Among them, in the stencil printing process, the moving speed of the squeegee can be selected as 220-240mm/s, the pressure of the squeegee can be selected as 4.5-5.5kgf, and the distance between the screen printing screen and the screen can be selected as 1.48-1.55mm. Most preferably, the moving speed of the scraper is selected as 230mm/s, the pressure of the scraper is selected as 5kgf, and the distance from the screen of the screen printing screen is selected as 1.5mm.

S103, sintering the solar cell formed with the main grid line and the auxiliary grid line to obtain a front electrode of the crystalline silicon solar cell.

Wherein, the structural illustration of the stencil printing screen used in step S102 is as shown in Figure 5, there is no wire and wire nodes in the graphic 101 of the stencil printing screen 100, and the preparation width of this kind of screen is small. The electrode slurry can pass through the sub-grid lines with high density, and the sub-grid lines prepared by it have a larger aspect ratio. Moreover, as shown in the 3D topography diagram in Figure 6, the height of the prepared auxiliary grid lines is more flat and uniform, so the final front electrode can not only reduce the power loss caused by the resistance of the grid lines, but also reduce the optical loss Thereby improving the photoelectric conversion efficiency.

Fig. 7 is a schematic structural view of the front electrode of the solar cell obtained by the above preparation method. As shown in FIG. 7, the prepared front electrode includes a plurality of busbar lines 10 arranged in parallel along the first direction (X direction in FIG. 7), and parallel rows along the second direction (Y direction in FIG. 7). A plurality of sub-gate lines 20 are arranged, and the plurality of sub-gate lines 20 are electrically connected to the plurality of main gate lines 10; wherein, the second direction and the first direction are perpendicular to each other. The auxiliary grid line 20 is mainly used to collect the photo-generated current generated by the solar cell, and the main grid line 10 is used to collect and output the current collected by the auxiliary grid line 10 .

Wherein, the number of busbars 10 is set according to actual needs, the more the number of busbars 10, the better the current derivation performance, but the larger the shading area and the higher the production cost, so it is necessary to balance the current derivation performance The relationship with the shading area can usually be set to 3 to 6. The length of each busbar 10 needs to be set according to the size (area) of the crystalline silicon solar cell, and is usually set between 130-160 mm. Wherein, the distance between two adjacent busbars 10 is usually set as the battery size divided by the number of busbars 10, and the distance between the most side busbars 10 and the edge of the battery is usually set as the battery size divided by 2 times the number of busbars 10. Using the preparation method provided in this embodiment, the advantages are more obvious when the number of busbars 10 is set to 4 to 6, especially for solar cells that use 5 busbars 10 that have been developed so far. As shown in FIG. 7 , the front electrode in this embodiment includes five main grid lines 10 , and the width of the main grid lines 10 is 0.8 mm. The width of the busbars needs to be designed according to the number of the busbars 10 and controlled by the pattern of the screen printing screen, which can be set within the range of 0.68-1.0mm.

Wherein, the number and length of the auxiliary gate lines 20 need to be set according to the size (area) of the crystalline silicon solar cell. Using the preparation method provided in this embodiment, the number of sub-grid lines 20 can usually be set to 100-110, and the width of the sub-grid lines 20 can be 0.20-0.25 μm, which is controlled by stencil printing screen patterns. Specifically in this embodiment, the number of the sub-gate lines 20 is 106 (only part of the sub-gate lines 20 are shown in FIG. 7 ), the width of the sub-gate lines 20 is 0.25 μm, two adjacent The pitch of the auxiliary grid lines 20 is 1.7213 mm.

Wherein, as shown in FIG. 7 , the busbar 10 includes a plurality of solid parts 10a and a plurality of hollow parts 10b connected in sequence, and the solid parts 10a and the hollow parts 10b are alternately arranged at intervals. The solid part 10a is mainly used for the welding of the battery in the later stage. The solid structure makes the welding area larger, the pull-off force between the ribbon and the battery is greater, and the welding is stronger; the hollow part 10b can reduce the shading area and reduce the consumption of silver paste.

To sum up, the preparation method of the front electrode of the crystalline silicon solar cell provided in the embodiment of the present invention, the preparation of the front electrode is divided into two printing processes, the busbar is formed by the screen printing process, and the stencil printing process is used to form the front electrode. Sub grid. Since the stencil printing screen used in the stencil printing process does not have metal wires and metal wire nodes in its graphics, using this kind of screen to prepare sub-grid lines with small width and high density, the electrode paste can pass through smoothly. The stencil printing screen, the auxiliary grid line prepared by it has a larger aspect ratio, and the height of the auxiliary grid line is more flat and uniform. The final front electrode can not only reduce the power loss caused by the resistance of the grid line, but also Optical loss can be reduced to improve photoelectric conversion efficiency. Moreover, using the front electrode prepared by the method, the amount of electrode paste can be saved by about 10%, which reduces the production cost.

It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is a relationship between these entities or operations. There is no such actual relationship or order between them. Furthermore, the term "comprises", "comprises" or any other variation thereof is intended to cover a non-exclusive inclusion such that a process, method, article, or apparatus comprising a set of elements includes not only those elements, but also includes elements not expressly listed. other elements of or also include elements inherent in such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of additional identical elements in the process, method, article or apparatus comprising said element.

The above is only the specific implementation of the application, and it should be pointed out that for those of ordinary skill in the art, without departing from the principle of the application, some improvements and modifications can also be made, and these improvements and modifications are also It should be regarded as the protection scope of this application.

Claims (1)

1. a kind of preparation method of crystal silicon solar batteries front electrode, including main gate line and secondary grid are formed on the solar cell The step of line, it is characterised in that this method includes：

S101, provide one there are the screen printing screens of main grid line graph, pass through silk-screen printing technique shape on the solar cell Into main gate line；The screen printing screens are arranged on the solar cell first, then in the screen printing screens Upper addition electrode slurry, finally moving scraper makes electrode slurry pass through the screen printing screens, on the solar cell Form the main gate line；In silk-screen printing technique, the translational speed of scraper is 180~220mm/s, scraper pressure is 7~ 9kgf, the off-network spacing of screen printing screens is 1.25~1.35mm；The quantity of the main gate line is 5, the main gate line Width is 0.8mm, and the main gate line includes the multiple solid parts and multiple hollow-out parts that are sequentially connected, the solid part and described is engraved Empty portion's alternate intervals are set；

S102, offer one have the steel mesh printing screen plate of secondary grid line figure, are formed by steel mesh typography on solar cell Secondary grid line；The steel mesh printing screen plate is arranged on the solar cell first, then on the steel mesh printing screen plate Electrode slurry is added, finally moving scraper makes electrode slurry pass through the steel mesh printing screen plate, the shape on the solar cell Into the secondary grid line；In steel mesh typography, the translational speed of scraper is 220~240mm/s, scraper pressure is 4.5~ 5.5kgf, the off-network spacing of steel mesh printing screen plate is 1.48~1.55mm；The quantity of the secondary grid line is 106, the secondary grid The width of line is 0.25 μm, and the spacing of adjacent two secondary grid lines is 1.7213mm；

S103, the solar cell for being formed with the main gate line and secondary grid line is sintered.