Electrode structure of BC battery and preparation method

Abstract

The invention discloses an electrode structure of a BC battery and a preparation method, and relates to the technical field of batteries, the electrode structure comprises n positive electrode main grids and n-1 negative electrode main grids, one negative electrode main grid is located between the two positive electrode main grids, each positive electrode main grid is provided with m groups of positive electrode auxiliary grids, each negative electrode main grid is provided with m groups of negative electrode auxiliary grids, two adjacent groups of positive electrode auxiliary grids are respectively positioned on two sides of one positive electrode main grid, two adjacent groups of negative electrode auxiliary grids are respectively positioned on two sides of one negative electrode main grid, one group of negative electrode auxiliary grids is positioned between two adjacent positive electrode auxiliary grids on the same side, and n and m are positive integers not less than 2; a plurality of P / N regions corresponding to the main electrode and the auxiliary electrode are designed in parallel at intervals, the length of each P / N region is 15-24 mm, the width of each P / N region is 10-18 mm, and the interval between every two adjacent P / N regions is 2-4 mm. The number of the P / N areas on the back face is 20-60, the electrode printing area of the whole single PN area is kept, and the problem of printing deviation can be effectively solved.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to an electrode structure and a preparation method of a BC battery. Background Art

[0002] The particularity of the performance of an IBC (back contact) battery lies in that there is no grid line occlusion on the front side, and all emitters are on the back side of the battery, reducing the metal shading on the front side. It is a new type of structured battery in which both the positive and negative electrodes are designed on the back side of the battery, and electrons and holes are separated on the back side of the battery and collected through the positive and negative electrodes on the back side respectively. The electrodes of existing IBC batteries are as Figure 1 shown. Such electrodes are composed of a positive electrode main grid 1, a negative electrode main grid 3, an Ag sub-grid 2, and an Ag sub-grid 4. The Ag sub-grid 4 and the negative electrode main grid 3 are vertically intersected and conduct, and the Ag sub-grid 2 and the positive electrode main grid 1 are vertically intersected and conduct. The Ag sub-grids 2 and 4 correspond to the P / N regions of the battery. Currently, the designed P / N regions maintain a width range of 2 mm - 3 mm, as Figure 2 shown. This width requires high precision in screen printing, is prone to printing deviation, resulting in positive and negative conduction, and affecting the battery efficiency and module power. Summary of the Invention

[0003] The purpose of the present invention is to design an electrode structure and a preparation method of a BC battery to solve the above problems.

[0004] The present invention achieves the above purpose through the following technical solutions: An electrode structure of a BC battery, including n positive electrode main grids and n - 1 negative electrode main grids, with one negative electrode main grid located between two positive electrode main grids. Each positive electrode main grid is provided with m groups of positive electrode sub-grids, and each negative electrode main grid is provided with m groups of negative electrode sub-grids. Adjacent two groups of positive electrode sub-grids are respectively located on both sides of a positive electrode main grid, and adjacent two groups of negative electrode sub-grids are respectively located on both sides of a negative electrode main grid. One group of negative electrode sub-grids is located between two adjacent positive electrode sub-grids on the same side. Both n and m are positive integers not less than 2.

[0005] A preparation method of an electrode structure of a BC battery, used to prepare the above-mentioned electrode structure of a BC battery, including: 1) The original N-type silicon wafer undergoes an alkaline polishing process and is polished on both sides; 2) The polished silicon wafer undergoes a laser process to engrave laser grooves under the grid lines in the back P / N regions; 3) A tunneling layer and a polysilicon layer are formed on the back through LPCVD; 4) Boron diffusion is carried out in a high-temperature diffusion furnace to form a P-type semiconductor on the front side, constituting a PN junction with a sheet resistance range of 320 - 450 ohms, and a P+poly polysilicon doping layer is formed on the back; 5) Locally remove the outermost layer of silicon oxide on the back side to open the film and form a patterned structure; 6) Clean the polysilicon layer on the back side after opening the film with a slot cleaning machine; 7) Generate a tunneling layer and an N+ poly polysilicon layer in the area where the film has been opened on the back side through LPCVD; 8) Locally remove the outermost layer of silicon oxide on the back side of the N+ poly polysilicon layer to open the film; 9) Clean the positive film PSG layer and the silicon oxide layer on the back side with a chain cleaning machine, then clean the polysilicon layer on the back side with a slot texturing cleaning machine, and texture the front side; 10) Deposit 3 - 8 nm aluminum oxide on both sides using an ALD device; 11) Deposit the silicon nitride antireflection film layer on the front side respectively through PECVD; 12) Deposit the silicon nitride antireflection film layer on the back side respectively through PECVD; 13) Screen - print the silver paste for the P / N area on the back side, print the graphic electrodes, form the back - side metal grid lines to transmit current; 14) Form ohmic contacts through a sintering device and a light injection technique.

[0006] The beneficial effects of the present invention are as follows: The positive and negative sub - grids of the positive and negative electrodes correspond to the P / N areas and adopt a design with multiple intervals in parallel. The length of a single P / N area is 15 - 24 mm, the width is 10 - 18 mm, and the interval between adjacent P / N areas is 2 - 4 mm. The number of P / N areas on the back side is 20 - 60, maintaining the electrode printing area of the overall single PN area, which can effectively solve the problem of printing deviation. Description of the Drawings

[0007] Figure 1 is the structure diagram of the positive and negative electrodes on the back side of the existing BC technology; Figure 2 is the schematic diagram of the back - side sub - grid corresponding to the PN area of the existing BC technology in the prior art; Figure 3 is the schematic diagram of the back - side PN area of the electrode structure of a BC battery of the present invention; Figure 4 is the structure diagram of the positive and negative electrodes on the back side of the electrode structure of a BC battery of the present invention; Figure 5 is the enlarged structure diagram of the positive and negative electrodes on the back side of the electrode structure of a BC battery of the present invention; Figure 6 is the flowchart of the preparation method of the electrode structure of a BC battery of the present invention; Among them, the corresponding reference numerals are: 1 - positive - electrode sub - grid, 2 - positive - electrode main grid, 3 - negative - electrode main grid, 4 - negative - electrode sub - grid. Detailed Embodiments

[0008] To make the objectives, 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 with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. The components of the embodiments of the present invention generally described and illustrated in the accompanying drawings herein can be arranged and designed in a variety of different configurations.

[0009] Therefore, the detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0010] It should be noted that like reference numerals and letters denote like items in the following drawings. Therefore, once an item is defined in one drawing, it does not require further definition and explanation in subsequent drawings.

[0011] In the description of the present invention, it should be understood that the orientation or positional relationships indicated by the terms "upper", "lower", "inner", "outer", "left", "right", etc. are based on the orientation or positional relationships shown in the accompanying drawings, or the orientation or positional relationships in which the inventive product is customarily placed during use, or the orientation or positional relationships commonly understood by those skilled in the art. These are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the present invention.

[0012] In addition, the terms "first", "second", etc. are only used for descriptive distinction and should not be construed as indicating or implying relative importance.

[0013] In the description of the present invention, it should also be noted that unless otherwise clearly specified and defined, terms such as "set", "connected", etc. should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0014] The following will specifically describe the embodiments of the present invention in detail with reference to the accompanying drawings.

[0015] Such as Figure 3 、 Figure 4 、 Figure 5As shown, an electrode structure of a BC cell includes n positive electrode main grids and n - 1 negative electrode main grids. One negative electrode main grid is located between two positive electrode main grids. Each positive electrode main grid is provided with m groups of positive electrode sub - grids, and each negative electrode main grid is provided with m groups of negative electrode sub - grids. Adjacent two groups of positive electrode sub - grids are respectively located on both sides of one positive electrode main grid, and adjacent two groups of negative electrode sub - grids are respectively located on both sides of one negative electrode main grid. One group of negative electrode sub - grids is located between two adjacent positive electrode sub - grids on the same side. Both n and m are positive integers not less than 2, which is convenient for laser pattern engraving and reduces the difficulty of the process. One group of positive electrode sub - grids serves as a P region, and one group of negative electrode sub - grids serves as an N region. The length range of the P region or N region is 15 - 24 mm, and the width range is 10 - 18 mm to collect current.

[0016] The interval range between two adjacent P regions and N regions is 2 - 4 mm, which is convenient for laser film opening and reduces leakage.

[0017] The number of the back - side P regions and N regions is 20 - 60, and they are cross - distributed to improve efficiency and Uoc.

[0018] The shapes of the positive electrode main grid and the negative - positive electrode main grid are both straight - through types. The positive electrode main grid is perpendicularly intersected and conducted with the positive electrode sub - grid, and the negative electrode main grid is perpendicularly intersected and conducted with the negative electrode sub - grid to conduct current.

[0019] The width range of the positive electrode sub - grid and the negative electrode sub - grid is 13 - 16 mm. The number range of the positive electrode sub - grids in one group of positive electrode sub - grids is 25 - 45, and the number range of the negative electrode sub - grids in one group of negative electrode sub - grids is 25 - 45, which reduces the warpage degree and the fragmentation rate.

[0020] The interval between two adjacent positive electrode sub - grids in the same group and two adjacent negative electrode sub - grids in the same group is 0.5 - 1.5 mm.

[0021] As Figure 6 shown, a preparation method of an electrode structure of a BC cell is used to prepare an electrode structure of a BC cell as described above, including: 1) The original N - type silicon wafer undergoes an alkaline polishing process and is polished on both sides. 2) After polishing, the silicon wafer undergoes a laser process to engrave laser grooves under the P / N region grids on the back side. The laser pattern is as Figure 4 ; 3) A tunneling layer and a polysilicon layer are formed on the back side through LPCVD, and the deposition film thickness range is 70 - 150 nm. 4) Boron diffusion is carried out in a high - temperature diffusion furnace to form a P - type semiconductor on the front side to form a PN junction, and the sheet resistance range is 320 - 450 ohms, and a P + poly polysilicon doping layer is formed on the back side. 5) Locally remove the outermost silicon oxide on the back side to open the film and form a patterned structure. 6) The slot cleaning machine cleans the polysilicon layer after opening the film on the back side; 7) Through LPCVD, a tunneling layer and an N+ poly polysilicon layer are formed in the area where the film has been opened on the back side, and the deposition film thickness ranges from 60 to 150 nm; 8) Locally remove the outermost silicon oxide of the back N+ poly polysilicon layer to open the film; 9) The chain cleaning machine cleans the positive film PSG layer and the silicon oxide layer on the back side, and then the slot texturing cleaning machine cleans the polysilicon layer on the back side and textures the front side; 10) Use an ALD device to deposit 3 - 8 nm aluminum oxide on both sides; 11) Through PECVD, deposit the silicon nitride antireflection film layer on the front side respectively, and the deposition film thickness ranges from 60 to 100 nm; 12) Through PECVD, deposit the silicon nitride antireflection film layer on the back side respectively, and the deposition film thickness ranges from 60 to 100 nm; 13) Screen-print the silver paste for the P / N area on the back side, print the graphic electrodes, form the back metal grid lines, and transmit current; 14) Through the sintering equipment and the light injection technology, form an ohmic contact; 15) Test the efficiency of the solar cell.

[0022] The technical solution of the present invention is not limited to the limitations of the above specific embodiments. Any technical deformation made according to the technical solution of the present invention falls within the protection scope of the present invention.

Claims

1. An electrode structure of a BC battery, characterized in that: There are n positive electrode main grids and n-1 negative electrode main grids, one negative electrode main grid is located between two positive electrode main grids, each positive electrode main grid is provided with m groups of positive electrode sub-grids, each negative electrode main grid is provided with m groups of negative electrode sub-grids, two adjacent groups of positive electrode sub-grids are respectively located on both sides of a positive electrode main grid, two adjacent groups of negative electrode sub-grids are respectively located on both sides of a negative electrode main grid, one group of negative electrode sub-grids is located between two adjacent positive electrode sub-grids on the same side, and n and m are both positive integers not less than 2.

2. The electrode structure of a BC battery according to claim 1, characterized in that: A group of positive electrode sub-grids serves as a P region, and a group of negative electrode sub-grids serves as an N region. The length of the P region or the N region ranges from 15 to 24 mm, and the width ranges from 10 to 18 mm.

3. The electrode structure of a BC battery according to claim 2, characterized in that: The interval between two adjacent P regions and N regions is 2-4 mm.

4. The electrode structure of a BC battery according to claim 2, characterized in that: The number of P and N regions on the back side ranges from 20 to 60.

5. The electrode structure of a BC battery according to claim 1, characterized in that: The positive electrode main grid and the negative positive electrode main grid are both straight-through types, the positive electrode main grid and the positive electrode sub-grid are vertically intersecting and conducting, and the negative electrode main grid and the negative electrode sub-grid are vertically intersecting and conducting.

6. The electrode structure of a BC battery according to claim 1, characterized in that: The width of the positive sub-grid and the negative sub-grid ranges from 13 to 16 mm, the number of positive sub-grids in a group of positive sub-grids ranges from 25 to 45, and the number of negative sub-grids in a group of negative sub-grids ranges from 25 to 45.

7. The electrode structure of a BC battery according to claim 6, characterized in that: The interval between two adjacent positive electrode sub-grids in the same group and the interval between two adjacent negative electrode sub-grids in the same group is 0.5-1.5 mm.

8. A method for preparing an electrode structure of a BC battery, for preparing an electrode structure of a BC battery as claimed in any one of claims 1 to 7, characterized in that: include: 1) The original N-type silicon wafer undergoes an alkali polishing process and double-sided polishing; 2) The polished silicon wafer undergoes a laser process to engrave laser grooves under the P / N region gate lines on the back side; 3) Generate a tunneling layer and polysilicon layer on the back side through LPCVD; 4) Boron diffusion is carried out in a high-temperature diffusion furnace, a P-type semiconductor is formed on the front side, forming a PN junction with a square resistance value ranging from 320-450 ohms, and a P+poly polysilicon doped layer is formed on the back side; 5) Partially remove the outermost layer of silicon oxide on the back to form a patterned structure; 6) The tank cleaning machine cleans the polysilicon layer after the film is opened on the back; 7) Generate a tunneling layer and N+poly polysilicon layer in the film-opened area on the back through LPCVD; 8) Partially remove the outermost silicon oxide layer of the N+poly polysilicon layer on the back side; 9) Use a chain cleaning machine to clean the PSG layer on the front film and the silicon oxide layer on the back, and then use a tank texturing cleaning machine to clean the polysilicon layer on the back and the front texturing; 10) Use ALD equipment to deposit 3-8nm aluminum oxide on both sides; 11) Depositing the front silicon nitride anti-reflection film layer by PECVD; 12) Depositing the silicon nitride anti-reflection film layer on the back by PECVD; 13) Screen print silver paste on the back P / N area, print graphic electrodes, form metal grid lines on the back, and transmit current; 14) Ohmic contact is formed through sintering equipment and light injection technology.

9. The method for preparing an electrode structure of a BC battery according to claim 8, characterized in that: In 3), the deposited film thickness ranges from 70 to 150 nm; in 7), the deposited film thickness ranges from 60 to 150 nm; and in 11) and 12), the deposited film thickness ranges from 60 to 100 nm.

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