Preparation method of double-sided TOPCon battery and double-sided TOPCon battery

Abstract

The invention discloses a preparation method of a double-sided TOPCon battery and the double-sided TOPCon battery, and relates to the technical field of TOPCon battery preparation. The preparation method comprises the following steps: S1, texturing; s2, thermally growing a tunneling oxide layer SiOx and an intrinsic amorphous silicon layer; s3, boron diffusion; s4, polishing the back surface; s5, thermally growing a tunneling oxide layer SiOx and an intrinsic amorphous silicon layer on the polished surface; s6, phosphorus diffusion; s7, BSG is removed through a chain type wet method; s8, carrying out laser patterning treatment; s9, performing alkali texturing; s10, deposition of double-sided AlOx is carried out; s11, depositing a SiNx film or a SiNx laminated film; and S12, carrying out silk-screen printing, sintering light injection and laser injection to obtain the double-sided TOPCon cell. The invention provides a preparation method of a double-sided TOPCon battery and the double-sided TOPCon battery, which can effectively reduce front recombination and improve passivation quality.

Description

Technical Field

[0001] The present invention relates to the technical field of TOPCon battery preparation, and in particular to a preparation method of a double-sided TOPCon battery and a double-sided TOPCon battery. Background Art

[0002] Currently, the key factors restricting the further improvement of Topcon technology are front emitter passivation and front metal recombination. How to improve front emitter passivation and front metal recombination is the direction that needs to be worked on at present.

[0003] The invention provides a preparation method of a double-sided TOPCon battery and a double-sided TOPCon battery, which can reduce metal composite on the front side. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a method for preparing a double-sided TOPCon battery and a double-sided TOPCon battery.

[0005] The specific technical solutions include the following:

[0006] In a first aspect, a method for preparing a double-sided TOPCon cell is provided, comprising the following steps:

[0007] S1: Select N-type single crystal silicon wafer as the base material and perform texturing process on the N-type single crystal silicon wafer;

[0008] S2: On the velvet surface obtained in the velvet process, a tunnel oxide layer SiOx is thermally grown on the front side of the bifacial TOPCon cell, followed by a layer of intrinsic amorphous silicon.

[0009] S3: Boron is diffused into the intrinsic amorphous silicon layer to obtain a boron-doped polysilicon layer, and BSG is formed on the surface of the boron-doped polysilicon layer;

[0010] S4: polishing the back side of the N-type single crystal silicon wafer;

[0011] S5: thermally growing a back tunneling oxide layer SiOx on the polished surface after the polishing treatment, and then thermally growing a back intrinsic amorphous silicon layer;

[0012] S6: performing phosphorus diffusion on the back intrinsic amorphous silicon layer of step S5 to obtain a phosphorus-doped polysilicon layer, and forming a PSG protective film layer on the surface of the phosphorus-doped polysilicon layer;

[0013] S7: removing the BSG formed in step S3 by a chain wet process;

[0014] S8: performing laser patterning on the front side of the N-type single crystal silicon wafer after the BSG is removed, that is, performing laser processing on the gate line area thereof so that the concentration of active boron in the laser processed area reaches the limit of solid concentration;

[0015] S9: Perform alkali texturing on the front side of the N-type single crystal silicon wafer after laser patterning, remove the boron-doped polysilicon layer in the non-laser area of ​​the front side, repair the melting state of the pyramid caused by the laser, and texturing the area again, and use HF to remove the tunneling oxide layer SiOx on the front side and the protective film layer of PSG on the back side;

[0016] S10: depositing AlOx on both sides of the N-type single crystal silicon wafer to obtain a front AlOx passivation layer and a back AlOx passivation layer;

[0017] S11: depositing a SiNx film or a SiNx stacked film on an N-type single crystal silicon wafer to obtain a front anti-reflection layer and a back anti-reflection layer;

[0018] S12: Screen printing, sintering light injection, laser injection, and finally testing are performed on the N-type monocrystalline silicon wafer to obtain a double-sided TOPCon cell.

[0019] The beneficial effects of the present invention are:

[0020] The present invention provides a preparation method of a double-sided TOPCon cell and a double-sided TOPCon cell, which eliminates the steps of first diffusing boron and then wet de-plating in a conventional preparation method. In the preparation method of the present invention, a tunneling oxide layer SiOx is thermally grown on the velvet surface obtained in the velvet process, followed by thermal growth of an intrinsic amorphous silicon layer, and then the intrinsic amorphous silicon layer is subjected to boron diffusion to obtain a boron-doped polycrystalline silicon layer. In addition, the present invention uses an infrared nanosecond pulse laser for laser patterning to process the boron-doped polycrystalline silicon in the metallized area, so that the concentration of active boron in the laser-processed area reaches the limit of solid concentration. This high active boron concentration can act as an etching stop layer in an alkaline solution, that is, the boron-doped Poly-Si after laser processing does not react with the alkali, the area of ​​laser action is small, the precision requirement of the equipment is lower than that of the conventional step using a laser picosecond laser, and the overall equipment cost is low. In addition, the present invention uses the tunneling oxide layer and the boron-doped polysilicon in the metallized area as a PN junction, and directly removes the PN junction structure in the non-metallized area, thereby reducing the boron-doped area on the front side, reducing front side recombination, and improving the passivation quality of the front side. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying any creative work.

[0022] Figure 1 This is a flow chart of a method for preparing a double-sided TOPCon battery according to Example 1 of the present invention;

[0023] Figure 2 Schematic diagram of the structure of a double-sided TOPCon battery prepared by the method for preparing a double-sided TOPCon battery in Example 1 of the present invention;

[0024] Description of the symbols in the figure:

[0025] 1-N-type single crystal silicon wafer; 2-tunneling oxide layer SiOx; 3-boron-doped polysilicon layer; 4-front AlOx passivation layer; 5-front anti-reflection layer; 6-back tunneling oxide layer SiOx; 7-phosphorus-doped polysilicon layer; 8-back AlOx passivation layer; 9-back anti-reflection layer; 10-front electrode; 11-back electrode. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. 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.

[0027] It should be understood that when used in this specification and the appended claims, the terms "include" and "comprises" indicate the presence of described features, integers, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or combinations thereof.

[0028] It should also be understood that the terms used in this specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the specification of the present invention and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include plural forms.

[0029] It should be further understood that the term "and / or" used in the present description and the appended claims refers to any and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0030] In order to more fully understand the technical content of the present invention, the technical solution of the present invention is further introduced and illustrated in conjunction with specific embodiments below.

[0031] Example 1

[0032] A method for preparing a double-sided TOPCon battery comprises the following steps:

[0033] S1: Select N-type single crystal silicon wafer as the base material and perform texturing process on the N-type single crystal silicon wafer;

[0034] S2: On the velvet surface obtained in the velvet process, the front side of the bifacial TOPCon cell is subjected to thermal growth of a tunnel oxide layer SiOx using LPCVD equipment, followed by thermal growth of an intrinsic amorphous silicon layer; wherein the thickness of the tunnel oxide layer SiOx is 2nm, and the thickness of the intrinsic amorphous silicon layer is 100nm;

[0035] S3: Boron is diffused into the intrinsic amorphous silicon layer to obtain a boron-doped polysilicon layer (the intrinsic amorphous silicon layer becomes partially crystallized p+poly), and BSG is formed on the surface of the boron-doped polysilicon layer; the surface concentration of the boron-doped polysilicon layer is 1*10 19 atom / cm 3 ;

[0036] S4: polishing the back side of the N-type single crystal silicon wafer;

[0037] S5: thermally growing a back tunneling oxide layer SiOx on the polished surface after the polishing treatment by using LPCVD equipment, and then thermally growing a back intrinsic amorphous silicon layer (Poly-Si);

[0038] S6: performing phosphorus diffusion on the back intrinsic amorphous silicon layer of step S5 to obtain a phosphorus-doped polysilicon layer (to convert Poly-Si into n+poly), and at the same time forming a PSG protective film layer on the surface of the phosphorus-doped polysilicon layer;

[0039] S7: removing the BSG formed in step S3 by a chain wet process using an HF solution;

[0040] S8: Perform laser patterning on the front side of the N-type single crystal silicon wafer after the BSG is removed, that is, perform laser processing on the gate line area so that the concentration of active boron in the laser processed area reaches the limit of solid concentration (1*10 21 atom / cm 3 ); wherein the laser patterning process uses an infrared nanosecond pulse laser, the wavelength of the infrared nanosecond pulse laser is 1080nm, and the laser energy is 2.6J / cm 2The spot shape of laser patterning is a square shaped spot with a spot size of 120μm*120μm and a frequency of 500k. The surface concentration of N-type single crystal silicon wafer after laser patterning is equal to 1*10 21 atom / cm 3 ;

[0041] S9: Perform alkali texturing on the front side of the N-type single crystal silicon wafer after laser patterning, remove the boron-doped polysilicon layer (p+poly-Si) in the non-laser area of ​​the front side, repair the melting state of the pyramid caused by the laser, and texturing the area again, and use HF to remove the tunneling oxide layer SiOx on the front side and the protective film layer of PSG on the back side;

[0042] S10: depositing AlOx on both sides of the N-type single crystal silicon wafer to obtain a front AlOx passivation layer and a back AlOx passivation layer;

[0043] S11: depositing a SiNx film or a SiNx stacked film on an N-type single crystal silicon wafer to obtain a front anti-reflection layer and a back anti-reflection layer;

[0044] S12: Screen printing, sintering light injection, laser injection, and finally electrical performance testing are performed on the N-type single crystal silicon wafer to obtain the double-sided TOPCon cell of Example 1.

[0045] In step S3, the doping concentration of p+poly silicon in the boron diffusion reaches 2.2×10 19 atom / cm 3 The etch rate decreases at a concentration of , because at this doping level the energy levels of the silicon material degenerate and the Fermi level enters the valence band, causing silicon to behave like a metal. Since the space charge layer on the surface of degenerate silicon shrinks to the order of a single atomic layer, the electrons in the conduction band are no longer confined to the silicon surface, but instead travel through the bulk of the silicon, where they have a high probability of recombination with holes. As a result, these electrons cannot participate in the reduction of water in the etching reaction. Thus, the reduction of water, a component of the etching reaction, continues because holes are unavailable. The fourfold decrease in the etch rate with electron concentration is explained by the fact that four charges are required to dissolve one silicon atom.

[0046] Reaction equation: Si+2OH - →Si(OH) 2 2+ +4e (oxidation);

[0047] Si(OH) 2 2+ +2H2O+4e→Si(OH )6 2- +2H 2 (reduction).

[0048] In step S8, since the concentration of active boron in the laser-processed area reaches the limit of solid concentration, this high active boron concentration acts as an etching stop layer in the alkaline solution.

[0049] Figure 1 This is a flow chart of a method for preparing a double-sided TOPCon battery according to Example 1 of the present invention; Figure 2 Schematic diagram of the structure of a double-sided TOPCon battery prepared by the method for preparing a double-sided TOPCon battery in Example 1 of the present invention.

[0050] The structure of the double-sided TOPCon cell of Example 1 includes an N-type monocrystalline silicon wafer 1, and the front side of the N-type monocrystalline silicon wafer 1 is provided with a tunneling oxide layer SiOx2, a boron-doped polycrystalline silicon layer 3, a front AlOx passivation layer 4, a front anti-reflection layer 5 and a front electrode 10 in sequence from the inside to the outside. The back side of the N-type monocrystalline silicon wafer 1 is provided with a back tunneling oxide layer SiOx6, a phosphorus-doped polycrystalline silicon layer 7, a back AlOx passivation layer 8, a back anti-reflection layer 9 and a back electrode 11 in sequence from the inside to the outside.

[0051] Comparative Example 1

[0052] S1: First, boron diffusion is performed on the front side of the cell;

[0053] S2: Then wet-dip plating;

[0054] S3: Thermally grow tunnel oxide layer + polysilicon layer + boron diffusion on the entire surface;

[0055] S4: Then use a picosecond laser to laser ablate or laser modify the BSG in the non-metallic contact area. The laser processing area is very large, which has very high requirements on the equipment's production capacity and accuracy, and the overall laser cost is also high.

[0056] S5: Wet etching is performed on the laser processed area to completely remove the tunneling oxide layer + polysilicon layer in the non-metallic contact area, thereby obtaining the double-sided TOPCon battery of Comparative Example 1.

[0057] Comparative Example 1 is a conventional double-sided TOPCon structure: a tunneling oxide layer + polysilicon layer structure is prepared on the structure of the front metallization area, and the back side is a conventional TOPCon structure.

[0058] Compared with comparative example 1, Example 1 omits the steps of first diffusing boron and then wet de-plating in step S1 and step S2 of the preparation method of comparative example 1. In the preparation method of Example 1 of the present invention, a tunneling oxide layer SiOx is thermally grown on the velvet surface obtained in the velvet making process, followed by thermal growth of an intrinsic amorphous silicon layer, and then the intrinsic amorphous silicon layer is subjected to boron diffusion to obtain a boron-doped polysilicon layer. In addition, the present invention also adopts the BSG formed by the chain wet removal step S3. The present invention adopts an infrared nanosecond pulse laser for laser patterning to process the boron-doped polysilicon in the metallized area, so that the concentration of active boron in the laser-treated area reaches the limit of solid concentration. This high active boron concentration can act as an etching stop layer in an alkaline solution, that is, the boron-doped Poly-Si after laser treatment does not react with alkali, the area of ​​laser action is small, the precision requirement of the equipment is lower than the requirement of the laser picosecond laser in the conventional step, and the overall equipment cost is low. The embodiment of the present invention also adopts an alkali velvet method to remove the boron-doped polysilicon layer in the non-laser area of ​​the front side. In addition, the present invention reduces front-side recombination and improves passivation quality by using the tunneling oxide layer in the metallization region and the boron-doped polysilicon as a PN junction.

[0059] The electrical performance of the double-sided TOPCon cells of Example 1 and Comparative Example 1 was tested, and the test results are shown in Table 1 below:

[0060] Table 1 Electrical performance test results of double-sided TOPCon cells of Example 1 and Comparative Example 1

[0061]

[0062]

[0063] From the test results in Table 1, it can be seen that there are two reasons for the high opening voltage (Uoc). In the embodiment of the present invention, the area where the laser acts is small, so the damage caused by the laser is also small, which reduces the recombination. At the same time, the front non-gate line area does not undergo traditional boron diffusion, which also reduces the front recombination. The overall opening voltage is increased by nearly 5mv; the efficiency is increased by 0.22%

[0064] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed by the present invention, and these modifications or replacements should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A method for preparing a double-sided TOPCon battery, It is characterized in that The following steps are involved: S1: Select N-type single crystal silicon wafer as the base material and perform texturing process on the N-type single crystal silicon wafer; S2: On the velvet surface obtained in the velvet process, a tunnel oxide layer SiOx is thermally grown on the front side of the bifacial TOPCon cell, followed by a layer of intrinsic amorphous silicon. S3: Boron is diffused into the intrinsic amorphous silicon layer to obtain a boron-doped polysilicon layer, and BSG is formed on the surface of the boron-doped polysilicon layer; S4: polishing the back side of the N-type single crystal silicon wafer; S5: thermally growing a back tunneling oxide layer SiOx on the polished surface after the polishing treatment, and then thermally growing a back intrinsic amorphous silicon layer; S6: performing phosphorus diffusion on the back intrinsic amorphous silicon layer of step S5 to obtain a phosphorus-doped polysilicon layer, and forming a PSG protective film layer on the surface of the phosphorus-doped polysilicon layer; S7: removing the BSG formed in step S3 by a chain wet process; S8: performing laser patterning on the front side of the N-type single crystal silicon wafer after the BSG is removed, that is, performing laser processing on the gate line area thereof so that the concentration of active boron in the laser processed area reaches the limit of solid concentration; S9: Perform alkali texturing on the front side of the N-type single crystal silicon wafer after laser patterning, remove the boron-doped polysilicon layer in the non-laser area of ​​the front side, repair the melting state of the pyramid caused by the laser, and texturing the area again, and use HF to remove the tunneling oxide layer SiOx on the front side and the protective film layer of PSG on the back side; S10: depositing AlOx on both sides of the N-type single crystal silicon wafer to obtain a front AlOx passivation layer and a back AlOx passivation layer; S11: depositing a SiNx film or a SiNx stacked film on an N-type single crystal silicon wafer to obtain a front anti-reflection layer and a back anti-reflection layer; S12: Screen printing, sintering light injection, laser injection, and finally testing are performed on the N-type monocrystalline silicon wafer to obtain a double-sided TOPCon cell.

2. The method for preparing a double-sided TOPCon cell according to claim 1, It is characterized in that In step S2, the thickness of the tunnel oxide layer SiOx is 1.5 nm-3 nm.

3. The method for preparing a double-sided TOPCon cell according to claim 1, It is characterized in that In step S2, the thickness of the intrinsic amorphous silicon layer is 50nm-150nm.

4. The method for preparing a double-sided TOPCon cell according to claim 1, It is characterized in that In step S3, the surface concentration of the boron-doped polysilicon layer is controlled to be 8*10 18 atom / cm 3 -1*10 19 atom / cm 3 .

5. The method for preparing a double-sided TOPCon cell according to claim 1, It is characterized in that In step S8, the laser patterning process is performed by using an infrared nanosecond pulse laser, the wavelength of the infrared nanosecond pulse laser is between 800nm ​​and 1200nm, and the laser energy is 1J / cm 2 -5J / cm 2 .

6. The method for preparing a double-sided TOPCon cell according to claim 5, It is characterized in that In step S8, the spot morphology of the laser patterning process is a square shaped spot, the spot size is (50 μm-500 μm)*(50 μm-500 μm), and the frequency is 100 k-1000 k.

7. The method for preparing a double-sided TOPCon cell according to claim 6, It is characterized in that The surface concentration of the N-type single crystal silicon wafer after the laser patterning process in step S8 is greater than or equal to 1*10 21 atom / cm 3 .

8. The method for preparing a double-sided TOPCon cell according to claim 1, It is characterized in that In step S7, the chain wet method uses HF solution.

9. The method for preparing a double-sided TOPCon cell according to claim 1, It is characterized in that In step S8, the solid concentration limit is 1*10 21 atom / cm 3 .

10. A double-sided TOPCon battery, It is characterized in that The double-sided TOPCon battery is prepared by the preparation method of any one of claims 1 to 9.

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