CN104332506A - Photovoltaic cell and printing screen plate used for printing gate lines of photovoltaic cell - Google Patents

Abstract

The invention relates to the technical field of photovoltaic components, in particular to a photovoltaic cell and a printing screen for printing its grid lines. The light-receiving surface of the photovoltaic cell has grid lines, and the farther away from the closest electrical connection point, the smaller the cross-sectional area of the thin grid lines. There is a pre-break grid on the thin grid line between two adjacent electrical connection points. The printing screens used to print the above grid lines include screen screens and metal plate screens. The screen screens adjust the spacing and diameter of the longitudinal mesh to match the change in the cross-sectional area of the fine grid lines, while the metal plate screens By adjusting the permeability of the screen opening array of the metal plate screen, the cross-sectional area of the fine grid line can be changed. The beneficial effects of the invention are: while not reducing the current collection ability and product quality, the amount of precious metal used for making grid lines is greatly reduced. Secondly, by pre-breaking the grid, the defects such as broken grid only appear in the pre-designed position, so as to control the influence of the defect and greatly improve the reliability and safety of photovoltaic cells.

Description

Photovoltaic cells and printing screens for printing their grid lines

technical field

The invention relates to the technical field of photovoltaic components, in particular to a photovoltaic cell and a printing screen for printing its grid lines.

Background technique

Since 2004, China's photovoltaic cell manufacturing and application have developed rapidly. At present, China is not only the world's largest photovoltaic manufacturing country, but also has become the world's largest photovoltaic market. The manufacture and application of photovoltaic power generation products will maintain rapid growth in the future. The noble metal Ag, as the core material in photovoltaic cell products, has been receiving great attention from the industry. On different occasions such as the European Photovoltaic Technology Conference and the Shanghai Photovoltaic Technology Exhibition, Martin Green and other technical experts in the photovoltaic industry have expressed concerns about whether the future Ag production can meet the photovoltaic development. It has become the consensus of experts in the photovoltaic industry to reduce the amount of Ag used in photovoltaic cells and at the same time look for battery electrode designs that can replace or partially replace Ag. In the utility model patent CN 203250753U of China Power Electric (Nanjing) Photovoltaic Company, the existing electrode design technology is described in a relatively simple and clear manner.

At present, there are five main research directions in the industry: 1) Silver paste companies represented by DuPont and Hollis, mainly to reduce the amount of Ag in the silver paste, and at the same time print the Ag thin grid lines to be more "thin and taller" . 2) Photovoltaic module manufacturers represented by Trina Solar mainly reduce the amount of Ag used in the busbars in screen printing. For example, the utility model patent ZL200920041761.6 and the utility model patent CN202076273U improved on this basis are both ways to save the amount of Ag by reducing the amount of busbar silver paste. 3) Photovoltaic module manufacturers represented by Suntech Power adopt the "Pluto" technology, that is, the method of electroplating thin conductive grid lines with Ni/Cu/Sn three layers. Due to the high post-processing requirements of electroplating for environmental protection, the technical difficulty of weldability, and the need to invest in new equipment, it is difficult to introduce it to the market. 4) Represented by Hitachi Chemical and other companies, they try to partially replace the conductive silver paste under the busbar of photovoltaic cells through conductive film (CF) film. 5) Represented by Japan Industrial Research Institute (AIST), it is trying to replace Ag paste with conductive copper paste, and research in this direction has just begun.

Among these 5 methods, methods 1) and 2) have been widely adopted in the industry. Several others are still being tested. Either way, the main goal is to minimize cost while meeting the stringent reliability requirements of photovoltaic cells.

Contents of the invention

The technical problem to be solved by the invention is to reduce the amount of noble metal used in photovoltaic cells.

The technical scheme adopted by the present invention to solve the technical problem is: a photovoltaic cell, which has a grid line on the light-receiving surface of the battery sheet, the grid line is composed of a main grid line and a thin grid line, and the thin grid line has an electrical connection point. The grid line is electrically connected to the interconnection bar through the main grid line at the electrical connection point. The farther away from the closest electrical connection point, the smaller the cross-sectional area of the thin grid line. The distance here does not refer to the distance of the straight line in space. It refers to the distance of the current transmission path, the tendency of the cross-sectional area reduction is continuous or discontinuous transition, and the thin grid line reduces the cross-sectional area of the thin grid line by reducing the height of the thin grid line; or the grid The wire is only composed of thin grid wires, and the thin grid wires are directly electrically connected to the interconnection strips at the electrical connection points. The farther away from the nearest electrical connection point, the smaller the cross-sectional area of the thin grid wires, and the decreasing trend of the cross-sectional area is Continuous or non-continuous transition, and the thin grid lines reduce the cross-sectional area of the thin grid lines by reducing the height of the thin grid lines.

It is further defined that there is a pre-break grid on the thin grid line between two adjacent electrical connection points.

Further defined, the width of the pre-break grid is D, where 0mm<D≤3mm.

It is further defined that the pre-break grid is located in the middle of the fine grid lines.

It is further defined that when the grid lines are only composed of thin grid lines, the number of interconnection bars is 18-50.

It is further defined that the interconnection strips are electrically connected by welding or conductive adhesive bonding.

In order to realize the design of the above grid lines, the present invention provides a photovoltaic cell screen printing screen, including a screen frame and a screen fixed on the screen frame, and the screen is composed of interlaced horizontal meshes and longitudinal meshes , the through-hole area and the mask area of the printed grid line are formed on the screen by covering the mask, and the extension direction of the through-hole area of the through-hole area for printing the fine grid line is consistent with the extension direction of the transverse mesh , the diameter of the transverse mesh and the spacing between the horizontal meshes are the same, and in the fine grid through-hole area, the spacing between the vertical meshes is the same, and the diameter of the longitudinal mesh is inversely proportional to the cross-sectional area of the fine grid line to be printed ; or the diameter of the longitudinal mesh is the same, and the interval between the longitudinal mesh is proportional to the cross-sectional area of the fine grid line to be printed; or the diameter of the longitudinal mesh is inversely proportional to the cross-sectional area of the fine grid line to be printed, while the longitudinal The spacing between mesh wires is directly proportional to the cross-sectional area of the fine grid lines to be printed.

In order to realize the design of the above-mentioned grid lines, the present invention additionally provides a photovoltaic cell metal plate printing screen, including a metal plate, and a screen opening array composed of screen openings is set on the metal plate, and the screen opening array is The through-hole area and the mask area of the printed grid line are formed by covering the mask. In the through-hole area of the fine grid through-hole area for printing the fine grid line, the transmittance of the screen opening array and the to-be The cross-sectional area of the printed fine grid lines is directly proportional.

It is further defined that the screen opening is a simple geometric figure, preferably an ellipse or a rectangle.

The beneficial effects of the invention are: while not reducing the current collecting ability and the quality of photovoltaic products, the amount of precious metal used for making grid lines is greatly reduced. Secondly, through pre-broken grids, defects such as broken grids only appear in pre-designed positions, thereby controlling the impact of defects and greatly improving the reliability and safety of photovoltaic cells.

Description of drawings

Below in conjunction with accompanying drawing and embodiment the present invention is further described;

FIG. 1 is a schematic diagram of the overall structure of grid lines of current photovoltaic cells;

FIG. 2 is an exaggerated top view of the thin grid lines in FIG. 1;

Fig. 3 is a side view of the exaggerated scale of the fine grid lines in Fig. 1;

4 is a schematic diagram of the overall structure of the grid lines of the photovoltaic cell in Embodiment 1 of the present invention;

Fig. 5 is an exaggerated top view of the fine grid lines in Embodiment 1 of the present invention;

Fig. 6 is an exaggerated side view of the thin grid lines in Embodiment 1 of the present invention;

Fig. 7 is an exaggerated top view of the thin grid lines in Embodiment 2 of the present invention;

Fig. 8 is an exaggerated top view of the thin grid lines in Embodiment 3 of the present invention;

Fig. 9 is an exaggerated side view of the thin grid lines in Embodiment 3 of the present invention;

Fig. 10 is a relationship diagram between the electrical transmission distance of the fine grid lines and the saving limit of the Ag-containing paste under different numbers of interconnecting strips of the present invention;

Fig. 11a is a partial enlarged view of the first silk screen version before mask processing of the present invention;

Fig. 11b is a partial enlarged view of the first screen screen after the mask treatment of the present invention;

Figure 11c is a partial enlarged view of the second silk screen version of the present invention;

Figure 11d is a partial enlarged view of the fourth silk screen version of the present invention;

Fig. 12a is a partial enlarged view of the first metal plate screen before the mask treatment of the present invention;

Fig. 12b is a partially enlarged view of the first metal plate screen after the mask treatment of the present invention;

Fig. 12c is a partial enlarged view of the second metal plate screen before the mask treatment of the present invention;

Fig. 12d is a partially enlarged view of the second metal plate screen after the mask treatment of the present invention;

Fig. 12e is a partial enlarged view of the third metal plate screen before the mask treatment of the present invention;

Fig. 12f is a partial enlarged view of the third metal plate screen after the mask treatment of the present invention;

In the figure, 1. thin grid line, 2. main grid line, 3. interconnection bar, 4. pre-broken grid, 5. horizontal mesh, 6. vertical mesh, 7. mask, 7-1. forming pre-broken grid Mask, 8. Fine grid through-hole area, 9. Metal plate, 10. Screen opening.

Detailed ways

The core of the present invention is to adopt a non-uniform photovoltaic cell light-receiving surface grid line design, while not reducing the current collection capacity and photovoltaic product quality, while greatly reducing the amount of precious metal (generally Ag) used to make the grid line. The thin grid lines 1 close to the electrical connection points of the grid lines and the interconnection bars 3 have the most precious metals and the best electrical conductivity. The amount of precious metal used in the thin grid wire 1 at the end portion of the current collection farthest from the electrical connection point is relatively the least, and the conductivity is the weakest. The amount of noble metal in the thin grid lines 1 between the closest to the electrical connection point and the farthest from the electrical connection point transitions gradually.

In the following, on the basis of introducing the existing electrode design, the characteristics of the present invention will be described in comparison.

Common photovoltaic cells usually have two specifications of 125×125mm or 156×156mm, and the number of busbars 2 is usually designed to be 2 to 5. Figures 1, 2 and 3 show typical gridline designs of existing common photovoltaic cells. In Fig. 1, the specification of the photovoltaic cell is 156×156mm, and the light-receiving surface of the photovoltaic cell has 3 main grid lines 2, and 60-80 thin grid lines 1 with a width of 30-120um and a height of 15-30um. The grid lines are designed for uniform distribution. The main grid lines 2 and the thin grid lines 1 are formed by transferring the Ag-containing paste to the light-receiving surface of the photovoltaic cell by screen printing, and then sintering at a temperature of 500-900° C. at a high temperature. This Ag-containing slurry is generally composed of conductive phase Ag powder, inorganic binder glass frit, organic carrier and trace additives to improve battery performance, and the preparation process is complicated and the price is high. In order to reduce the cost of the Ag-containing paste, the formulation of the Ag-containing paste for the busbar 2 generally reduces the Ag content, and the cost is reduced by hollowing out. The interconnection bar 3 is electrically connected to the thin grid line 1 at the electrical connection point through the main grid line 2 by means of welding or conductive adhesive bonding, and the interconnection bar 3 includes copper-tin soldering strips and copper-indium soldering strips.

Embodiment 1, as shown in Figures 4, 5 and 6:

A photovoltaic cell, with a grid line on the light-receiving surface of the battery sheet, the grid line is only composed of a thin grid line 1, the main grid line 2 is omitted, and the thin grid line 1 has an electrical connection point, and the thin grid line 1 is at the electrical connection point It is directly electrically connected with the interconnecting bars 3, and the number of interconnecting bars 3 is 18-50. In the figure, the number of interconnecting bars 3 is 22. The cost of saving the amount of Ag for the busbar 2 accounts for 1/3 of the cost of the Ag-containing paste for the photovoltaic cell, which is a significant improvement.

For the design of 3 busbar lines 2, the transmission distance of the thin grid lines 1 is 52 mm; for the design of 22 interconnection bars 3, the transmission distance of the thin grid lines 1 is 7 mm. To achieve the same transmission capacity, the requirement for the conductive carrying capacity of the fine grid wire 1 is reduced by 8 times. For the design of 30 interconnecting bars 3, the transportation distance of the thin grid wire 1 is 3.9 mm, and the requirement for the conductive carrying capacity of the thin grid wire 1 is reduced by 10 times. This part of the current load is directly transferred to the interconnection bar 3 , which is equivalent to using the interconnection bar 3 to replace the grid lines made of noble metal. The saving effect of the design of significantly more interconnecting strips 3 on the amount of Ag-containing paste is shown in FIG. 10 .

The farther away from the closest electrical connection point, the smaller the cross-sectional area of the thin grid wire 1 , so that the amount of precious metal used in the thin grid wire 1 at the end part of the current collection is relatively minimum, and the amount of Ag can be greatly saved. In this embodiment, the width of the fine grid lines 1 of the photovoltaic cell is consistent, which is no different from the design of the existing thin grid lines 1 of the photovoltaic cell in Figs. 1, 2 and 3. The height of the wire 1 is used to reduce the cross-sectional area of the fine grid line 1, the farther away from the closest electrical connection point, the smaller the height of the fine grid line 1, and the trend of height reduction can be a discontinuous transition. The design of the thin grid line 1 can save about 10% of Ag consumption compared with the design of the existing thin grid line 1 of photovoltaic cells.

Embodiment 2, as shown in Figure 7,

Compared with Example 1, the width and height of the thin grid lines 1 of the photovoltaic cell are inconsistent, and the thin grid lines 1 reduce the cross-sectional area of the thin grid lines 1 by reducing the height and width of the thin grid lines 1 at the same time. The farther the closest electrical connection point is, the smaller the height of the thin grid line 1 is, and the smaller the width of the thin grid line 1 is.

Embodiment 3, as shown in Figures 8 and 9,

Compared with embodiment 1, the trend of decreasing the height of the fine grid lines 1 is a continuous transition, and there is a pre-broken grid 4 on the thin grid lines 1 between two adjacent electrical connection points. The width of the pre-broken grid 4 is D, where 0mm<D≤3mm. The pre-break grid 4 is located in the middle of the fine grid line 1 . In FIG. 4 , assuming that there are 78 thin grid lines 1 arranged horizontally and 22 interconnection bars 3 arranged vertically, there are (22−1)×78=1638 pre-break grids 4 .

The function of the pre-broken grid 4 is: the grid lines of the photovoltaic cell often break the grid during the printing process, and the parts where the grid breaks occur are not accurate, which greatly affects the collection of the current by the grid lines. In the embodiment, by designing the pre-broken grid 4 at the place where the thin grid wire 1 has the least impact on the battery current collection capability and reliability, the pre-broken grid 4 will reduce the stress of the weak point where the grid may be broken, so that the weak point where the grid may be broken Will not break the grid. At the same time, the pre-break grid 4 is also beneficial to reduce the amount of Ag-containing paste.

In Embodiments 1 and 2, because the cross-sectional area of the middle position of the fine grid wire 1 between two adjacent electrical connection points is the smallest, when there is a factor of broken grid, the middle position will also be broken preferentially. To a certain extent, it also has the effect of preventing other parts of the thin grid wire 1 from being broken.

According to the thinking of above-mentioned example 1, 2 and 3, the engineering technical personnel of this industry is very easy to draw inferences about other cases from one instance, and the method of embodiment 1, 2 and 3 is combined, for these changes, all belong to the scope of invention protection, not in the patent of the present invention Let me repeat them one by one.

In order to illustrate the essence of the present invention more simply and vividly, the thought of the present invention can be compared with the structure of leaves (or human blood vessels) in nature. The characteristics of these transportation pipelines are that they become smaller towards the end, because the collection and transportation load borne by the pipeline at the end is also the smallest. Ordinary leaf veins or ordinary blood vessels use the same material, and nature cannot use different materials, so the simplest biological design is used. In the present invention, the electrode materials of the photovoltaic cell are changed from the original 3 types (high Ag-containing thin grid lines, low Ag-containing bus bars and interconnecting bars) to 2 types (high Ag-containing thin grid lines and interconnecting bars), At the same time, the number of interconnection bars 3 is greatly increased, so that the transportation distance of the thin grid wires 1 is greatly reduced.

In order to realize the above grid line design, the present invention also discloses a photovoltaic cell screen printing screen:

The first design of the photovoltaic cell screen printing stencil is:

As shown in Figures 11a and 11b, the screen printing screen is used to realize Embodiment 1, including a screen skeleton and a screen fixed on the screen skeleton, and the screen is composed of interlaced horizontal mesh 5 and vertical mesh 6, there is a through-hole area for printing grid lines on the screen, and other areas of the screen outside the through-hole area cover the mask 7, because the light-receiving surface of the photovoltaic cell in embodiment 1 only has thin grid lines 1, so The through-hole area of the screen printing screen only includes the fine-grid through-hole area 8 for printing fine grid lines 1, and the extension direction of the fine-grid through-hole area 8 is consistent with the extension direction of the transverse mesh 5, that is, the transverse mesh 5 The extension direction of the mask 7 is consistent with the extension direction of the fine grid line 1 to be printed, the diameter of the transverse mesh 5 and the interval between the transverse mesh 5 are the same, and the preparation method of the mask 7 is: firstly, the photosensitive colloid is coated on the screen. layer, through exposure, development and etching to form a mask area and a through-hole area, and the Ag-containing paste will be printed on the surface of the photovoltaic cell through the through-hole area. In the fine grid through-hole area 8, the intervals between the longitudinal meshes 6 are the same, and the diameter of the longitudinal meshes 6 is inversely proportional to the cross-sectional area of the thin grid lines 1 to be printed, so that in the printing and manufacturing process of photovoltaic cells, the When the Ag paste leaks down to the surface of the battery through the through-hole region, the non-uniform grid lines of Embodiment 1 can be formed.

The second design of the photovoltaic cell screen printing stencil is:

As shown in Figure 11c, compared with the first design of the screen printing screen, the difference is that in the fine grid through-hole area 8, the diameters of the longitudinal meshes 6 are the same, and the distance between the longitudinal meshes 6 is the same as The cross-sectional area of the fine grid lines 1 to be printed is directly proportional.

The third design of the photovoltaic cell screen printing stencil is:

Compared with the first design of the screen printing screen, the difference is that in the fine grid through-hole area 8, the diameter of the longitudinal mesh 6 is inversely proportional to the cross-sectional area of the fine grid line 1 to be printed, while the longitudinal mesh The distance between the wires 6 is directly proportional to the cross-sectional area of the fine grid lines 1 to be printed.

The fourth design of the photovoltaic cell screen printing stencil:

As shown in Figure 11d, this screen printing screen is used to realize embodiment 3. Compared with the first design of the screen printing screen, the difference is that in the fine grid through-hole area 8, the longitudinal mesh 6 The diameters are the same, the spacing between the longitudinal meshes 6 is proportional to the cross-sectional area of the fine grid line 1 to be printed, and there is a mask 7-1 for forming a pre-broken grid between each fine grid through-hole area 8, that is, the distance The closer the mask 7-1 for forming the pre-break grid is, the smaller the mesh spacing of the longitudinal mesh 6 is.

In order to realize the above-mentioned grid line design, in addition to the above-mentioned screen printing screen, the present invention also discloses a photovoltaic cell metal plate printing screen:

The metal plate printing screen includes a metal plate 9, on which a screen opening array composed of screen openings 10 is set, and the pattern of printing grid lines is formed on the screen opening array by covering the mask 7. In the through-hole area and the mask area, in the through-hole area for printing the fine grid line 1 in the fine grid through-hole area 8, the permeability of the screen opening array is proportional to the cross-sectional area of the fine grid line 1 to be printed. Proportional. The advantages of the photovoltaic cell metal plate printing screen are: on the one hand, it can avoid the protrusion of the weaving node caused by the mesh weaving, realize the screen pattern completely on the same plane, and can print the grid line with a higher aspect ratio; On the other hand, the metal plate printing screen can also achieve different transmittances at different parts of the grid line more conveniently through the change of the opening array pattern of the screen. Therefore, it is particularly suitable for printing the non-uniform cross-sectional area grid lines of the present invention.

The first design of this photovoltaic cell metal plate printing screen:

As shown in Figures 12a and 12b, the metal plate printing screen is used to realize Embodiment 1, and a screen opening array similar to the screen pattern of Figures 11a and 11b is formed on the metal plate 9 by etching, the metal plate 9 is a stainless steel thin plate material, and the screen opening 10 of the screen opening array is square, and the through-hole area and the mask area of the printed grid line are formed on the screen opening array by covering the mask 7, because the embodiment 1, the light-receiving surface of the photovoltaic cell only has fine grid lines 1, so the through-hole area of the metal plate screen only includes the fine grid through-hole area 8 for printing the fine grid lines 1, and in the fine grid through-hole area 8, the mesh The permeability of the plate opening array is non-uniform and proportional to the cross-sectional area of the fine grid lines 1 to be printed. The screen opening array can only be in the through hole area and a certain range around it. The preparation method of the mask 7 is as follows: firstly, a photosensitive colloid coating is coated on the screen opening array, and the screen is exposed, developed and etched. A mask area and a through-hole area are formed on the plate opening array, and the Ag-containing paste will be printed on the surface of the photovoltaic cell through the screen openings 10 in the through-hole area, because the permeability of the screen opening array is non-uniform , so that the non-uniform grid lines of Embodiment 1 can be formed.

The second design of the photovoltaic cell metal plate printing screen:

As shown in Figure 12c and Figure 12d, the stencil opening array pattern of the metal plate screen is not the same as the screen pattern, although the screen openings 10 are all square compared to the first design of the metal plate printing screen , but there is only one row of screen openings 10 in the longitudinal direction of each fine grid through-hole area 8, and the extension direction of each fine grid through-hole area 8 is transverse, and the farther away from the closest electrical connection point, the finer grid line The smaller the cross-sectional area of 1 is, the lower the permeability of the screen hole array is, and the smaller the aperture of the screen hole 10 is.

The third design of the photovoltaic cell metal plate printing screen:

As shown in Figure 12e and Figure 12f, compared with the second design of the metal plate printing screen, the difference is that the opening 10 of the screen is elliptical, and the farther away from the nearest electrical connection point, the elliptical screen The smaller the hole diameter of the plate opening 10 is.

In fact, the screen opening 10 of the metal plate screen can also adopt other shapes of figures, such as regular hexagon, regular pentagonal shape, etc., which will not be repeated here. Those skilled in the art can easily draw inferences from one instance and make reasonable deformations without changing the principle of the invention.

Claims (10)

1. A photovoltaic cell has a grid line on the light-receiving surface of the battery sheet, and it is characterized in that: the grid line is composed of a main grid line and a thin grid line, and the thin grid line has an electrical connection point, and the thin grid line is connected to the grid line. The connection point is electrically connected to the interconnection bar through the main grid line. The farther the distance from the closest electrical connection point is, the smaller the cross-sectional area of the thin grid line is. The tendency of the cross-sectional area reduction is continuous or discontinuous transition, and The grid line reduces the cross-sectional area of the thin grid line by reducing the height of the thin grid line; Or the grid lines are only composed of thin grid lines, and the thin grid lines are directly electrically connected to the interconnection bars at the electrical connection points. The farther away from the closest electrical connection point, the smaller the cross-sectional area of the thin grid lines is. The decreasing trend is continuous or discontinuous transition, and the thin grid lines reduce the cross-sectional area of the thin grid lines by reducing the height of the thin grid lines. 2. The photovoltaic cell according to claim 1, characterized in that: there is a pre-break grid on the thin grid line between two adjacent electrical connection points. 3. The photovoltaic cell according to claim 2, characterized in that: the width of the pre-broken grid is D, 0mm<D≤3mm. 4. The photovoltaic cell according to claim 2, characterized in that: said pre-break grid is located in the middle of the thin grid lines. 5. The photovoltaic cell according to claim 1, characterized in that: when the grid lines are only composed of thin grid lines, the number of interconnecting bars is 18-50. 6 . The photovoltaic cell according to claim 1 , characterized in that: the interconnection strips are electrically connected by welding or conductive adhesive bonding. 7. A photovoltaic cell screen printing screen for printing the grid lines of the light-receiving surface of the photovoltaic cell according to claim 1 or 2 or 3 or 4 or 5 or 6, characterized in that: it includes a screen skeleton and a fixed The screen on the screen skeleton, the screen is composed of interlaced horizontal wires and vertical wires, and the through-hole area and mask area of the printed grid line are formed on the screen by covering the mask. The extension direction of the fine grid through hole area for printing fine grid lines in the through hole area is consistent with the extension direction of the transverse mesh, and the diameter of the transverse mesh and the interval between the transverse mesh are the same. In the fine grid through-hole area, the spacing between the longitudinal meshes is the same, and the diameter of the longitudinal meshes is inversely proportional to the cross-sectional area of the fine grid lines to be printed; or the diameter of the longitudinal meshes is the same, and the spacing between the longitudinal meshes It is directly proportional to the cross-sectional area of the fine grid lines to be printed; or the diameter of the longitudinal mesh is inversely proportional to the cross-sectional area of the fine grid lines to be printed, and the interval between the longitudinal meshes is proportional to the cross-sectional area of the fine grid lines to be printed Proportional. 8. A photovoltaic cell metal plate printing screen for printing the grid lines of the light-receiving surface of the photovoltaic cell described in claim 1 or 2 or 3 or 4 or 5 or 6, characterized in that: it comprises a metal plate, A screen opening array composed of screen openings is set on the board, and the through-hole area and mask area of the printed grid line are formed on the screen opening array by covering the mask. In the through-hole area of the through-hole area for printing fine grid lines, the transmittance of the screen opening array is directly proportional to the cross-sectional area of the fine grid lines to be printed. 9. The photovoltaic cell metal plate printing screen according to claim 8, characterized in that: the openings of the screen are simple geometric figures. 10. The photovoltaic cell metal plate printing screen according to claim 9, characterized in that: the opening of the screen is oval or rectangular.