Preparation method of main-grid-free solar cell

Abstract

The invention discloses a preparation method of a main-grid-free solar cell, which belongs to the technical field of solar cells, and comprises the following steps: replacing a second machine and a fourth machine of a silk screen with a main-grid-free screen printing plate, and not turning on a first machine and a third machine; a TOPCon process flow is carried out; the positive and negative electrode grid lines of the solar cell piece comprise a plurality of parallel fine grid lines, and no main grid line is arranged, that is, when the grid line screen printing plate pattern is designed, no main grid line is arranged; after the grid line screen printing plate pattern is designed, the solar cell positive electrode grid line is printed on the surface of the cell positive electrode. According to the preparation method of the main-grid-free solar cell, cost reduction is achieved mainly through silver reduction, efficiency improvement, reduction of the thickness of a silicon wafer and the use amount of an adhesive film, a main grid is replaced with a welding strip, so that part of silver paste of the main grid is saved, efficiency improvement is achieved through reduction of a shading area and shortening of a current transmission path, and the module power can be improved by more than 5W; the problems of hidden cracks and grid breakage caused by welding after thinning can be solved, and breakthrough of a battery piece with the thickness within 100 micrometers can be achieved.

Description

Technical Field

[0001] The invention relates to the technical field of solar cell sheets, and in particular to a method for preparing a busbar-free solar cell sheet. Background Art

[0002] The metal electrodes on the front and back of the battery cell are used to conduct internal current and can be divided into a main grid (Busbar) and a sub-grid (also known as a finger). The main grid mainly collects the current of the sub-grid and connects them in series, while the sub-grid is used to collect photogenerated carriers.

[0003] The grid pattern has developed from 4BB and 5BB to MBB (Multiple-Busbar, 9-15 grids) and SMBB (Super-Multiple Busbar, 16 grids and above). The main grid has become thinner (reducing shading loss and silver consumption) and more (ensuring conductivity). The battery efficiency depends on the shading area, which in turn depends on the number of main grids * the contact area between each main grid and the cell. The silver paste cost depends on the number of main grids * the silver consumption of each main grid. The thinning of the main grid can reduce the surface's blocking of sunlight and reduce the amount of silver paste used, but the thinning will increase resistance. In order to ensure conductivity, a certain number of main grids need to be added to ensure the cross-sectional area for current to pass through. Therefore, the core of the main grid design lies in achieving a balance between width and number.

[0004] 0BB (no main grid) is a further upgrade of SMBB technology. On the one hand, the main grid of the cell is directly eliminated to further reduce silver consumption; on the other hand, copper welding strips are used to replace the original main grid to derive current in the component link. In the past, the diameter of the MBB component welding strip was between 0.2-0.4mm, while the 0BB welding strip is thinner, with a diameter of 0.2mm, and a smaller shading area, which can theoretically increase the power of the component.

[0005] At present, in the grid line layout of the positive electrode of a conventional solar cell, multiple fine grid lines are arranged in parallel, and multiple main grid lines are designed inside the entire grid line layout, so that the multiple main grid lines are perpendicular to the fine grid lines and divide the fine grid lines into equal parts. Due to such a design, after the grid lines are printed on the surface of the positive electrode of the cell, the main grid lines occupy a certain surface of the positive electrode of the cell in the middle position, which will increase the shading area of ​​the solar cell, resulting in a decrease in short-circuit current and more consumption of positive silver paste. At the same time, when multiple solar cells are connected, since it is necessary to use welding strips to connect the main grid lines of adjacent cells, the grid line layout of the prior art makes welding between cells inconvenient and consumes a lot of manpower and material resources. Summary of the invention

[0006] In order to solve the problem that welding between solar cells is inconvenient and consumes a lot of manpower and material resources, the present invention provides a method for preparing a busbar-free solar cell, and the technical solution is as follows:

[0007] A method for preparing a busbar-free solar cell comprises the following steps:

[0008] S1: Replace the screen machines 2 and 4 with screens without main grids, and do not start the machines 1 and 3;

[0009] S2: TOPCon process;

[0010] S3: The positive and negative electrode grid lines of the solar cell include multiple parallel thin grid lines, and no main grid lines, that is, when designing the grid line screen pattern, no main grid lines are set;

[0011] S4: After the grid line screen pattern is designed, the positive electrode grid line of the solar cell is printed on the positive electrode surface of the cell.

[0012] Using solder strips instead of main grids can save some silver paste on the main grid, improve efficiency by reducing the shading area and shortening the current transmission path, and can increase the component power by more than 5W.

[0013] Preferably, the TOPCon process flow includes the following processes in order: texturing, boron diffusion, BSG removal + alkaline polishing, deposition of tunneling oxide layer and intrinsic polysilicon layer, phosphorus diffusion, PSG removal + RCA, deposition of ALOx, deposition of front anti-reflection layer, deposition of back anti-reflection layer, printing + sintering of front and back Ag pastes and light-assisted micro-conductor processing of front silver paste.

[0014] Preferably, the screen pattern uses a straight-through pattern on the main grid instead of a traditional harpoon.

[0015] Preferably, the busbar-free technology can be divided into the following types according to the different contact modes between the soldering ribbon and the battery cell: the busbar-free technology can be divided into the SmartWire solution, the ordinary glue dispensing solution and the welding glue dispensing solution.

[0016] Preferably, the SmartWire solution comprises the following steps: firstly, an organic film with an embedded circular copper welding strip is manufactured, the battery cells are connected in series, and then the welding strip and the battery cells are alloyed by lamination.

[0017] Preferably, the common glue dispensing scheme includes the following steps: firstly applying glue dot body (UV glue, hot melt glue and other adhesives), using UV lamp to glue and solidify the whole solder strip on the battery cell, and then realizing alloying of the solder strip and the battery cell by lamination.

[0018] Preferably, the welding and gluing scheme includes the following steps: first welding the solder strip to the battery cell, then gluing to further stick the solder strip to the battery cell, and then laminating and alloying. This scheme is different from the gluing and laminating scheme in that welding is required, welding is used to achieve preliminary fixation, and gluing is used for further fixation.

[0019] Preferably, the organic film of the SmartWire solution is a copper wire composite film, and the glue dot body of the common glue dot solution is an adhesive such as UV glue and hot melt glue.

[0020] Preferably, the glue dispensing of the common glue dispensing scheme and the welding glue dispensing scheme can also be achieved by printing glue dots, and the glue dispensing method is performed by a needle.

[0021] It can solve the problems of hidden cracks and broken grids caused by welding after thinning, help achieve a breakthrough in battery cells with a thickness of less than 100 microns, and eliminate the main grid line.

[0022] Beneficial effects:

[0023] The beneficial effects produced by the technical solution of the present invention are as follows:

[0024] 1. The preparation method of the busbar-free solar cell mainly reduces costs by reducing silver, improving efficiency, reducing silicon wafer thickness and film usage, and using welding strips instead of busbars to save silver paste on the busbar. Efficiency is improved by reducing the shading area and shortening the current transmission path, which can increase the component power by more than 5W.

[0025] 2. The preparation method of the main grid-free solar cell can solve the problems of hidden cracks and broken grids caused by welding after thinning, which is helpful to achieve a breakthrough in the thickness of solar cells within 100 microns, eliminate the main grid line, and use thinner welding strips. At the same time, due to the use of thinner welding strips, the corresponding film weight can be further reduced by about 100g. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0027] Figure 1 It is a TOPCon process flow chart of a method for preparing a busbar-free solar cell of the present invention;

[0028] Figure 2 It is a graphic diagram of 18 main grid screens of a method for preparing a main grid-free solar cell of the present invention;

[0029] Figure 3 It is a graphic diagram of 8 main grid screens of a method for preparing a main grid-free solar cell of the present invention;

[0030] Figure 4 It is a four-busbar screen pattern diagram of a method for preparing a busbar-free solar cell of the present invention;

[0031] Figure 5 It is a two-busbar screen pattern diagram of a method for preparing a busbar-free solar cell of the present invention;

[0032] Figure 6 The invention discloses a method for preparing a solar cell without a main grid and a 0-main grid screen graphic diagram. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents the selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] like Figure 1 As shown, a method for preparing a busbar-free solar cell comprises the following steps:

[0035] S1: Replace the screen machines 2 and 4 with screens without main grids, and do not start the machines 1 and 3;

[0036] S2: TOPCon process flow, including the following processes: texturing, boron diffusion, BSG removal + alkali polishing, deposition of tunneling oxide layer and intrinsic polysilicon layer, phosphorus diffusion, PSG removal + RCA, deposition of ALOx, deposition of front anti-reflection layer, deposition of back anti-reflection layer, printing + sintering of front and back Ag pastes and light-assisted micro-conductor processing of front silver paste;

[0037] S3: The positive and negative electrode grid lines of the solar cell include multiple parallel thin grid lines, and no main grid lines, that is, when designing the grid line screen pattern, no main grid lines are set;

[0038] S4: After the grid line screen pattern is designed, the positive electrode grid line of the solar cell is printed on the positive electrode surface of the cell.

[0039] like Figure 2-6 As shown, the present invention designs a version with different numbers of main grids, which is different from the conventional TOPCon battery in the main grid, and adopts a straight-through to replace the traditional harpoon.

[0040] According to the different contact methods between the welding ribbon and the solar cell, the busbar-free technology can be divided into three solutions: SmartWire solution, glue dispensing and welding glue dispensing:

[0041] (1) SmartWire solution: First, an organic film (copper wire composite film) with a circular copper welding strip embedded in it is made, and then the battery cells are connected in series and then the welding strip and the battery cells are alloyed by lamination. The biggest difference between this solution and other solutions is that a copper wire composite film is required;

[0042] (2) Ordinary glue dispensing solution: first apply glue (UV glue, hot melt glue and other adhesives), use UV lamp to glue and solidify the entire solder strip on the battery cell, and then achieve alloying of the solder strip and the battery cell through lamination. This solution is different from the welding glue dispensing solution in that it does not require welding and can be fixed by glue dispensing;

[0043] (3) Welding and gluing scheme: First, weld the solder ribbon to the battery cell, then glue it to the battery cell, and then laminate and alloy it. This scheme is different from the glue lamination scheme in that welding is required. Welding is used to achieve preliminary fixation, and glue is used to further fix it.

[0044] Among them, the dispensing of the ordinary dispensing solution and the welding dispensing solution can also be achieved by printing glue dots, and the dispensing method is carried out through a needle.

[0045] Group ρc(mΩcm2) 18BB 2.16 8BB 2.96 4BB 4.04 2BB 5.57 0BB 6.98

[0046] Table 1 Comparison of contact resistance of 18BB-0BB

[0047] It can be found from Table 1 that as the main grid decreases, the contact resistance will become larger and larger, and the contact will become worse and worse. This is because as the main grid decreases, the conduction of current will gradually become difficult during laser sintering, which will cause the contact to deteriorate. This is a defect of OBB cells after laser sintering and needs to be solved. In addition, for OBB cells, the probe row needs to be modified before laser and subsequent tests can be performed.

[0048] Group Eta Uoc Isc FF Irev2 0BB 26.291 0.7284 14.036 86.10 0.019 2BB 26.212 0.7295 14.031 85.78 0.021 4BB 26.117 0.7279 14.012 85.69 0.024 8BB 26.055 0.7277 14.021 85.43 0.048 18BB 26.200 0.7275 14.017 85.98 0.044

[0049] Table 2 Comparison of electrical properties of 18BB-0BB

[0050] From Table 2, it can be found that the current and filling of 0BB cells are higher, and the efficiency is improved by about 0.1%.

[0051] The present invention has the following advantages:

[0052] 0BB mainly reduces costs by reducing silver, improving efficiency, and reducing silicon wafer thickness and film usage;

[0053] Economical: 0BB uses solder strips to replace the main grid, thus saving some silver paste on the main grid;

[0054] Improve efficiency: Improve efficiency by reducing the shading area and shortening the current transmission path, which can increase the component power by more than 5W;

[0055] 0BB is conducive to thinning silicon wafers: it can solve the problems of hidden cracks and broken grids caused by welding after thinning, and help achieve a breakthrough in cell thickness within 100 microns;

[0056] 0BB can achieve thinner solder ribbons and thinner adhesive films: 0BB eliminates the main grid line and uses thinner solder ribbons. At the same time, due to the use of thinner solder ribbons, the corresponding adhesive film weight can be further reduced by about 100g.

[0057] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a busbar-free solar cell, characterized in that: The following steps are involved: S1: Replace the screen machines 2 and 4 with screens without main grids, and do not start the machines 1 and 3; S2: TOPCon process; S3: The positive and negative electrode grid lines of the solar cell include multiple parallel thin grid lines, and no main grid lines, that is, when designing the grid line screen pattern, no main grid lines are set; S4: After the grid line screen pattern is designed, the grid line of the positive electrode of the solar cell is printed on the positive electrode surface of the cell.

2. The method for preparing a busbar-free solar cell according to claim 1, characterized in that: The TOPCon process flow includes the following processes in order: texturing, boron diffusion, BSG removal + alkaline polishing, deposition of tunneling oxide layer and intrinsic polysilicon layer, phosphorus diffusion, PSG removal + RCA, deposition of ALOx, deposition of front anti-reflection layer, deposition of back anti-reflection layer, printing + sintering of front and back Ag pastes and light-assisted micro-conductor processing of front silver paste.

3. The method for preparing a busbar-free solar cell according to claim 1, characterized in that: The screen pattern uses a straight-through on the main grid to replace the traditional harpoon.

4. The method for preparing a busbar-free solar cell according to claim 1, characterized in that: The busbar-free technology can be divided into the following types according to the different contact methods between the soldering ribbon and the battery cell: the busbar-free technology can be divided into the SmartWire solution, the ordinary glue dispensing solution and the welding glue dispensing solution.

5. The method for preparing a busbar-free solar cell according to claim 4, characterized in that: The SmartWire solution includes the following steps: firstly, an organic film with an embedded circular copper welding strip is manufactured, and then, after the battery cells are connected in series, alloying of the welding strip and the battery cells is achieved by lamination.

6. The method for preparing a busbar-free solar cell according to claim 5, characterized in that: The common glue dispensing scheme includes the following steps: firstly applying glue (UV glue, hot melt glue and other adhesives), using UV lamp to glue and solidify the entire solder strip on the battery cell, and then laminating to achieve alloying of the solder strip and the battery cell.

7. The method for preparing a busbar-free solar cell according to claim 6, characterized in that: The welding and gluing scheme includes the following steps: first welding the solder strip to the battery cell, then gluing to further stick the solder strip to the battery cell, and then laminating and alloying. This scheme is different from the gluing and laminating scheme in that welding is required, welding is used to achieve preliminary fixation, and gluing is used for further fixation.

8. The method for preparing a busbar-free solar cell according to claim 6, characterized in that: The organic film of the SmartWire solution is a copper wire composite film, and the glue dot body of the common glue dispensing solution is an adhesive such as UV glue and hot melt glue.

9. The method for preparing a busbar-free solar cell according to claim 7, characterized in that: The glue dispensing of the common glue dispensing scheme and the welding glue dispensing scheme can also be achieved by printing glue dots, and the glue dispensing method is performed by a needle.

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