Solar cell boron emitter and preparation method and application thereof

Abstract

The invention discloses a solar cell boron emitter and a preparation method and application thereof, and belongs to the field of solar cells, after a monocrystalline silicon wafer is selected, cleaned and textured, a first BSG layer, a silicon oxide mask layer and a second BSG layer are sequentially deposited on the front surface of the silicon wafer, and then annealing treatment is carried out; wherein the boron atom concentration of the first BSG layer is lower than that of the second BSG layer, and the oxygen atom concentration of the first BSG layer is higher than that of the second BSG layer. The BSG layer with low-concentration boron atoms and high-concentration oxygen atoms, the silicon oxide mask layer and the BSG layer with high-concentration boron atoms and low-concentration oxygen atoms are sequentially deposited on the silicon wafer, and after annealing treatment, the surface of the formed boron emitter has high boron doping concentration and can be in better contact with a metal electrode; and meanwhile, the junction depth of the boron emitter is relatively shallow, defects caused by internal boron doping can be repaired due to existence of high-concentration oxygen atoms, and compounding of a silicon substrate is reduced.

Description

Technical Field

[0001] The present invention relates to the field of solar cells, and more particularly, to a boron emitter for solar cells, a preparation method thereof, and an application thereof. Background Art

[0002] Boron diffusion is widely used in the field of solar cells. In the preparation process of high-efficiency cells such as tunnel oxide passivated contact cells, passivated emitter rear locally diffused cells, and silicon-based heterojunction cells, boron diffusion needs to be carried out on the front surface of the silicon wafer to prepare a p-n junction. Currently, the commonly used method for preparing a boron emitter in production is the tube furnace diffusion method, that is, a boron doping source is introduced into the tube furnace, and boron atoms are diffused into the silicon wafer through high temperature. During the preparation process of the boron emitter, a layer of boron-silicon glass layer (part of the components are silicon oxide) is formed on the surface of the silicon wafer. Since the solubility of boron atoms in silicon oxide is greater than that in the silicon wafer, more boron atoms on the silicon wafer surface enter the boron-silicon glass layer (BSG). As a result, after the boron-silicon glass layer (BSG) is removed later, the concentration distribution of boron atoms in the silicon wafer shows a trend of first increasing and then decreasing, that is, more boron atoms are distributed inside the silicon wafer rather than on the surface of the silicon wafer, which leads to greater recombination of the silicon wafer; at the same time, due to the low surface boron doping concentration and the shallow contact depth formed by the laser enhanced contact technology, the contact resistance between the metal and the silicon becomes poor, affecting the efficiency of the cell. Summary of the Invention

[0003] To improve the problems of large recombination of the silicon wafer caused by the boron emitter in the solar cell and poor contact with the metal electrode, the present invention provides a boron emitter for solar cells, a preparation method thereof, and an application thereof. The technical solutions are as follows:

[0004] A preparation method of a boron emitter for solar cells includes the following steps:

[0005] Step 1, select an N-type single-crystal silicon wafer, and clean and texture the silicon wafer;

[0006] Step 2, deposit a first BSG layer on the front surface of the silicon wafer;

[0007] Step 3, deposit a layer of silicon oxide mask layer on the front surface of the silicon wafer;

[0008] Step 4, perform patterning treatment by laser to remove the silicon oxide mask layer in the metallization area;

[0009] Step 5, deposit a second BSG layer on the front surface of the silicon wafer;

[0010] Step 6, perform annealing treatment on the silicon wafer;

[0011] Among them, the boron atom concentration of the first BSG layer is lower than that of the second BSG layer, and the oxygen atom concentration of the first BSG layer is higher than that of the second BSG layer.

[0012] Preferably, step two is specifically as follows: Using PECVD method, introduce 100 - 200 sccm of boron source, 500 - 2000 sccm of SiH4 and 1000 - 4000 sccm of N2O, and deposit the first BSG layer on the front side of the silicon wafer at a temperature of 400 - 500 °C, with a thickness of 10 - 50 nm and a boron atom concentration of (0.1 - 1.0)×E16 cm -2 .

[0013] Preferably, step three is specifically as follows: Using PECVD method, introduce 500 - 1500 sccm of SiH4 and 1000 - 2000 sccm of N2O, and deposit the silicon oxide mask layer on the front side of the silicon wafer at a temperature of 400 - 500 °C, with a thickness of 10 - 50 nm.

[0014] Preferably, step five is specifically as follows: Using PECVD method, introduce 1000 - 1500 sccm of boron source, 500 - 2000 sccm of SiH4 and 500 - 1500 sccm of N2O, and deposit the second BSG layer on the front side of the silicon wafer at a temperature of 400 - 500 °C, with a thickness of 10 - 50 nm and a boron atom concentration of (0.1 - 1)×E20 cm -2 .

[0015] Preferably, the boron sources for depositing the first BSG layer and the second BSG layer in step two and step five are both trimethylboron or diborane.

[0016] Preferably, step six is specifically as follows: Place the silicon wafer in a tube diffusion furnace at a temperature of 960 - 1000 °C and anneal it in a nitrogen atmosphere for 10 - 30 min.

[0017] Preferably, the sheet resistance of the boron emitter after annealing the silicon wafer is 200 - 400 Ω / cm 2 .

[0018] The present invention also provides a boron emitter for a solar cell, which is prepared by the above preparation method.

[0019] Application of the above boron emitter for a solar cell in TOPCon cells, PERC cells, and BC cells.

[0020] Preferably, for the application of the boron emitter of the above solar cell in a TOPCon cell, after step six, the method further includes: removing the boron-doped single-crystalline silicon layer and the BSG layer around the back and sides of the silicon wafer, and at the same time polishing the back of the silicon wafer; preparing a tunneling oxide layer and a phosphorus-doped polysilicon layer on the back of the silicon wafer; removing the tunneling oxide layer and the polysilicon layer around the front and sides of the silicon wafer, as well as the BSG layer on the front and the PSG layer on the back; depositing an alumina layer on the front of the silicon wafer; depositing a silicon nitride antireflection layer on the front and back of the silicon wafer; printing metal electrodes and sintering to form an ohmic contact.

[0021] The beneficial effects of adopting the technical solution of the present invention are as follows:

[0022] In the present invention, by sequentially depositing a first BSG layer / silicon oxide mask layer with low-concentration boron atoms and high-concentration oxygen atoms and a second BSG layer with high-concentration boron atoms and low-concentration oxygen atoms on a silicon wafer, after annealing treatment, the boron emitter formed has a relatively high boron doping concentration on the surface, can form a better contact with the metal electrode; at the same time, the junction depth of the boron emitter is relatively shallow, and due to the presence of high-concentration oxygen atoms, the defects caused by internal boron doping can be repaired, reducing the recombination of the silicon substrate. Specific embodiments

[0023] To make the purpose, technical solution 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. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. Therefore, the following detailed description of the embodiments of the present invention 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 those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0024] The present invention provides a boron emitter for a solar cell, its preparation method and application. By depositing a BSG layer / silicon oxide mask layer with low-concentration boron atoms and high-concentration oxygen atoms and a BSG layer with high-concentration boron atoms and low-concentration oxygen atoms on a silicon wafer, and then after annealing treatment, a boron emitter with a relatively high surface boron doping concentration and few shallow junction defects is formed, which forms a better contact with the metal electrode while reducing the recombination of the silicon substrate. The technical solution is as follows:

[0025] A preparation method of a boron emitter for a solar cell includes the following steps:

[0026] Step one, select an N-type single-crystalline silicon wafer, and clean and texture the silicon wafer;

[0027] Step two, deposit a first BSG layer on the front of the silicon wafer;

[0028] Step 3, deposit a layer of silicon oxide mask layer on the front side of the silicon wafer;

[0029] Step 4, perform patterning by laser to remove the silicon oxide mask layer in the metallization area;

[0030] Step 5, deposit a second BSG layer on the front side of the silicon wafer;

[0031] Step 6, anneal the silicon wafer;

[0032] Wherein, the boron atom concentration of the first BSG layer is lower than that of the second BSG layer, and the oxygen atom concentration of the first BSG layer is higher than that of the second BSG layer.

[0033] As a preferred embodiment, the specific operation of Step 2 is: using PECVD method, introducing 100 - 200 sccm of boron source, 500 - 2000 sccm of SiH4 and 1000 - 4000 sccm of N2O, depositing the first BSG layer on the front side of the silicon wafer at a temperature of 400 - 500 °C, with a thickness of 10 - 50 nm and a boron atom concentration of (0.1 - 1.0)×E16 cm -2 .

[0034] As a preferred embodiment, the specific operation of Step 3 is: using PECVD method, introducing 500 - 1500 sccm of SiH4 and 1000 - 2000 sccm of N2O, depositing the silicon oxide mask layer on the front side of the silicon wafer at a temperature of 400 - 500 °C, with a thickness of 10 - 50 nm.

[0035] As a preferred embodiment, the specific operation of Step 5 is: using PECVD method, introducing 1000 - 1500 sccm of boron source, 500 - 2000 sccm of SiH4 and 500 - 1500 sccm of N2O, depositing the second BSG layer on the front side of the silicon wafer at a temperature of 400 - 500 °C, with a thickness of 10 - 50 nm and a boron atom concentration of (0.1 - 1)×E20 cm -2 .

[0036] As a preferred embodiment, the boron source for depositing the first BSG layer and the second BSG layer in Step 2 and Step 5 is trimethylboron or diborane.

[0037] As a preferred embodiment, the specific operation of Step 6 is: place the silicon wafer in a tube diffusion furnace at a temperature of 960 - 1000 °C and anneal in a nitrogen atmosphere for 10 - 30 min.

[0038] As a preferred embodiment, the sheet resistance of the boron emitter after annealing of the silicon wafer is 200-400 Ω / cm 2 .

[0039] The present invention also provides a boron emitter for a solar cell, which is prepared by the above preparation method.

[0040] Application of the boron emitter of the above solar cell in TOPCon cells, PERC cells, and BC cells.

[0041] As a preferred embodiment, for the application of the boron emitter of the above solar cell in a TOPCon cell, after step six, it further includes: removing the boron-doped single-crystalline silicon layer and the BSG layer diffused around the back and sides of the silicon wafer, and at the same time polishing the back of the silicon wafer; preparing a tunneling oxide layer and a phosphorus-doped polysilicon layer on the back of the silicon wafer; removing the tunneling oxide layer and the polysilicon layer diffused around the front and sides of the silicon wafer, as well as the BSG layer on the front and the PSG layer on the back; depositing an alumina layer on the front of the silicon wafer; depositing a silicon nitride antireflection layer on the front and back of the silicon wafer; printing a metal electrode and sintering to form an ohmic contact.

[0042] Taking the TOPCON cell as an example below, through the following examples, the beneficial effects of a boron emitter for a solar cell provided by the present invention, its preparation method and application are further evaluated.

[0043] Example 1:

[0044] This Example 1 provides a preparation method for a boron emitter of a TOPCon cell, including the following steps:

[0045] Step 1, select an N-type single-crystalline silicon wafer with a thickness of 200 µm and a resistivity of 10 Ω / cm 2 , and clean and texture the silicon wafer;

[0046] Step 2, use PECVD to introduce 200 sccm of trimethylboron, 2000 sccm of SiH4, and 4000 sccm of N2O, and deposit a first BSG layer with a thickness of 50 nm and a boron atom concentration of 1.0×E16 cm on the front of the silicon wafer at a temperature of 500 °C -2 ;

[0047] Step 3, use PECVD to introduce 1500 sccm of SiH4 and 2000 sccm of N2O, and deposit a silicon oxide mask layer with a thickness of 50 nm on the front of the silicon wafer at a temperature of 500 °C;

[0048] Step 4, perform patterning treatment with a laser to remove the silicon oxide mask layer in the metallization area;

[0049] Step 5: Introduce 1500 sccm of trimethylboron, 2000 sccm of SiH4, and 1500 sccm of N2O using PECVD method. Deposit the second BSG layer on the front side of the silicon wafer at a temperature of 500 °C, with a thickness of 50 nm and a boron atom concentration of 1.0×E20 cm -2 ;

[0050] Step 6: Place the silicon wafer in a tube diffusion furnace at a temperature of 1000 °C and anneal it in a nitrogen atmosphere for 30 min;

[0051] Step 7: Deposit a tunneling oxide layer and a phosphorus-doped polysilicon layer on the back side of the silicon wafer, remove the diffusion extension, deposit an alumina layer on the front side, deposit a silicon nitride antireflection layer on both the front and back sides, print metal electrodes, and sinter to form an ohmic contact.

[0052] Example 2:

[0053] This Example 2 provides a method for preparing a boron emitter of a TOPCon cell, including the following steps:

[0054] Step 1: Select an N-type single-crystalline silicon wafer with a thickness of 150 µm and a resistivity of 5 Ω / cm 2 , clean and texture the silicon wafer;

[0055] Step 2: Introduce 150 sccm of trimethylboron, 1000 sccm of SiH4, and 2000 sccm of N2O using PECVD method. Deposit the first BSG layer on the front side of the silicon wafer at a temperature of 450 °C, with a thickness of 30 nm and a boron atom concentration of 0.5×E16 cm -2 ;

[0056] Step 3: Introduce 1000 sccm of SiH4 and 1500 sccm of N2O using PECVD method. Deposit a silicon oxide mask layer on the front side of the silicon wafer at a temperature of 450 °C, with a thickness of 30 nm;

[0057] Step 4: Perform patterning using a laser to remove the silicon oxide mask layer in the metallization area;

[0058] Step 5: Introduce 1300 sccm of trimethylboron, 1200 sccm of SiH4, and 1000 sccm of N2O using PECVD method. Deposit the second BSG layer on the front side of the silicon wafer at a temperature of 450 °C, with a thickness of 30 nm and a boron atom concentration of 0.3×E20 cm -2 ;

[0059] Step 6: Place the silicon wafer in a tube diffusion furnace at a temperature of 980 °C and anneal it in a nitrogen atmosphere for 20 min;

[0060] Step 7: Deposit a tunneling oxide layer and a phosphorus-doped polysilicon layer on the back of the silicon wafer, remove the bypass diffusion, deposit an aluminum oxide layer on the front, deposit silicon nitride antireflection layers on both the front and back, print metal electrodes, and sinter to form an ohmic contact.

[0061] Example 3:

[0062] This Example 3 provides a method for preparing a boron emitter of a TOPCon cell, including the following steps:

[0063] Step 1: Select an N-type monocrystalline silicon wafer with a thickness of 100 µm and a resistivity of 0.5 Ω / cm 2 , clean and texture the silicon wafer;

[0064] Step 2: Using PECVD, introduce 100 sccm of diborane, 500 sccm of SiH4, and 1000 sccm of N2O, and deposit a first BSG layer with a thickness of 10 nm and a boron atom concentration of 0.1×E16 cm on the front of the silicon wafer at a temperature of 400 °C. -2 ;

[0065] Step 3: Using PECVD, introduce 500 sccm of SiH4 and 1000 sccm of N2O, and deposit a silicon oxide mask layer with a thickness of 10 nm on the front of the silicon wafer at a temperature of 400 °C.

[0066] Step 4: Perform patterning using a laser to remove the silicon oxide mask layer in the metallization area.

[0067] Step 5: Using PECVD, introduce 1000 sccm of diborane, 600 sccm of SiH4, and 500 sccm of N2O, and deposit a second BSG layer with a thickness of 10 nm and a boron atom concentration of 0.1×E20 cm on the front of the silicon wafer at a temperature of 400 °C. -2 ;

[0068] Step 6: Place the silicon wafer in a tube diffusion furnace at a temperature of 960 °C and anneal in a nitrogen atmosphere for 50 s.

[0069] Step 7: Deposit a tunneling oxide layer and a phosphorus-doped polysilicon layer on the back of the silicon wafer, remove the bypass diffusion, deposit an aluminum oxide layer on the front, deposit silicon nitride antireflection layers on both the front and back, print metal electrodes, and sinter to form an ohmic contact.

[0070] Comparative Example 1:

[0071] This Comparative Example 1 provides a method for preparing a boron emitter of a TOPCon cell, including the following steps:

[0072] Step 1: Select an N-type monocrystalline silicon wafer with a thickness of 150 µm and a resistivity of 5 Ω / cm 2, clean and texture the silicon wafer;

[0073] Step 2: Use a tube diffusion furnace to prepare a boron emitter on the front side of the silicon wafer. Introduce 200 sccm of boron source BBr3 and 400 sccm of oxygen O2, and deposit a layer of BSG at 850 °C; then introduce 2000 sccm of oxygen O2 and perform the diffusion of boron atoms at 1000 °C. The surface doping concentration of the formed boron emitter is 0.6×E19 cm -2 , and the junction depth is 0.7 µm;

[0074] Step 3: Remove the boron-doped single-crystalline silicon layer and BSG layer that are diffused around the back side and sides of the silicon wafer, and polish the back side at the same time;

[0075] Step 4: Prepare a tunneling oxide layer and a phosphorus-doped polysilicon layer on the back side of the silicon wafer. The phosphorus diffusion source is POCl3. At a temperature of 920 °C, the thickness of the tunneling oxide layer is 2 nm, the thickness of the phosphorus-doped polysilicon layer is 300 nm, and the phosphorus doping concentration is 1.0×E21 cm -2 ;

[0076] Step 5: Remove the diffusion around, deposit an alumina layer on the front side of the silicon wafer, deposit antireflection layers of silicon nitride on both the front and back sides, print metal electrodes, and sinter to form an ohmic contact.

[0077] Comparative Example 2:

[0078] This Comparative Example 2 provides a method for preparing a boron emitter of a TOPCon cell, including the following steps:

[0079] Step 1: Select an N-type single-crystalline silicon wafer with a thickness of 150 µm and a resistivity of 5 Ω / cm 2 , clean and texture the silicon wafer;

[0080] Step 2: Use the PECVD method to introduce 150 sccm of trimethylboron, 1000 sccm of SiH4, and 2000 sccm of N2O. At a temperature of 450 °C, deposit the first BSG layer on the front side of the silicon wafer with a thickness of 0.3 µm and a boron atom concentration of 0.5×E16 cm -2 ;

[0081] Step 3: Place the silicon wafer in a tube diffusion furnace at a temperature of 980 °C and anneal in a nitrogen atmosphere for 200 s;

[0082] Step 4: Prepare a tunneling oxide layer and a phosphorus-doped polysilicon layer on the back side of the silicon wafer. The phosphorus diffusion source is POCl3. At a temperature of 920 °C, the thickness of the tunneling oxide layer is 2 nm, the thickness of the phosphorus-doped polysilicon layer is 300 nm, and the phosphorus doping concentration is 1.0×E21 cm -2 ;

[0083] Step 5: Despiralize, deposit an alumina layer on the front side of the silicon wafer, deposit silicon nitride antireflection layers on both the front and back sides, print metal electrodes, and sinter to form an ohmic contact.

[0084] Comparative Example 3:

[0085] This Comparative Example 3 provides a method for preparing a boron emitter of a TOPCon cell, including the following steps:

[0086] Step 1: Select an N-type monocrystalline silicon wafer with a thickness of 150 µm and a resistivity of 5 Ω / cm 2 , clean and texture the silicon wafer;

[0087] Step 2: Use PECVD to introduce 1300 sccm of trimethylboron, 1200 sccm of SiH4, and 1000 sccm of N2O, and deposit a second BSG layer with a thickness of 30 nm and a boron atom concentration of 0.5×E20 cm on the front side of the silicon wafer at a temperature of 450 °C -2 ;

[0088] Step 3: Place the silicon wafer in a tube diffusion furnace at a temperature of 980 °C and anneal in a nitrogen atmosphere for 20 min;

[0089] Step 4: Deposit a tunneling oxide layer and a phosphorus-doped polysilicon layer on the back side of the silicon wafer, despiralize, deposit an alumina layer on the front side, deposit silicon nitride antireflection layers on both the front and back sides, print metal electrodes, and sinter to form an ohmic contact.

[0090] Next, the solar cells obtained in the above examples and comparative examples were subjected to performance tests, and the results are as follows:

[0091] Table 1 Electrical performance test results of the solar cells prepared in the examples and comparative examples

[0092] Eta (%) Uoc (mV) Isc (A) FF (%) Rsh (Ω) Rser (Ω) IRev (A) Example 1 25.990 730.17 13.995 84.82 5330 1.085 0.053 Example 2 26.065 730.84 13.997 85.30 5267 1.047 0.052 Example 3 25.942 728.58 13.999 85.15 5419 1.015 0.042 Comparative Example 1 25.792 728.65 13.989 84.71 5442 1.028 0.050 Comparative Example 2 25.753 730.79 13.993 84.31 5142 1.113 0.062 Comparative Example 3 25.767 727.01 13.992 84.80 5289 1.026 0.061

[0093] Examples 1 to 3 are boron emitters formed by sequentially depositing a first BSG layer / low-concentration boron atoms and high-concentration oxygen atoms, a silicon oxide mask layer, and a second BSG layer / high-concentration boron atoms and low-concentration oxygen atoms on the front side of the silicon wafer in this application and then performing annealing treatment; Comparative Example 1 is a conventional method for preparing a boron emitter; Comparative Example 2 is a boron emitter formed by depositing only the first BSG layer, that is, a BSG layer with low-concentration boron atoms and high-concentration oxygen atoms; Comparative Example 3 is a boron emitter formed by depositing only the second BSG layer, that is, a BSG layer with high-concentration boron atoms and low-concentration oxygen atoms.

[0094] As can be seen from Table 1 above, compared with Comparative Example 1, in Comparative Example 2, a BSG layer with a relatively high oxygen atom content and a relatively low boron atom content was deposited. After annealing, oxygen atoms and boron atoms were doped into the single-crystalline silicon to form a boron emitter. Since the defects caused by the low boron atom content in silicon are relatively small, and the doping of oxygen atoms can repair some defects, the Voc of the prepared solar cell is relatively high, reaching 730.79 mV. However, the surface doping concentration of the prepared boron emitter is relatively low, and the contact with the metal electrode is poor, so the FF is poor. In Comparative Example 3, the oxygen atom content in the deposited BSG is relatively low and the boron atom content is relatively high. After annealing, although the surface doping concentration of the formed boron emitter is high and the contact with the metal electrode is very good, and the FF is very high, the defects caused by boron atom doping result in a Voc of only 727 mV for the solar cell.

[0095] Compared with Comparative Example 1, in Examples 1 to 3, two layers of BSG were sequentially deposited in the metallization region. The first BSG layer has a high oxygen atom content and a low boron atom content. After annealing, the high-content oxygen atoms can repair the defects caused by boron atom doping. Therefore, the Voc of the solar cells in Examples 1 to 3 is > 728 mV. The second BSG layer has a relatively high boron atom content. After annealing, the surface doping concentration of the prepared boron emitter is high and can form a good contact with the metal electrode. Therefore, the FF of the solar cells in the examples is relatively high.

[0096] In summary, the boron emitter prepared in this application has a high surface doping concentration, can form a better contact with the metal electrode, has a higher solar cell conversion efficiency, and is overall superior to the boron emitters prepared in Comparative Examples 1 to 3.

[0097] The above description is only the preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A preparation method of a boron emitter for a solar cell, characterized in that, It includes the following steps: Step 1: Select an N-type monocrystalline silicon wafer and clean and texture the wafer. Step 2: Deposit a first BSG layer on the front side of the wafer. Step 3: Deposit a silicon oxide mask layer on the front side of the wafer. Step 4: Perform patterning using a laser to remove the silicon oxide mask layer in the metallization area. Step 5: Deposit a second BSG layer on the front side of the wafer. Step 6: Anneal the wafer. Wherein, the boron atom concentration of the first BSG layer is lower than that of the second BSG layer, and the oxygen atom concentration of the first BSG layer is higher than that of the second BSG layer.

2. The preparation method of the boron emitter of the solar cell according to claim 1, characterized in that, The specific content of the second step is as follows: By using the PECVD method, 100-200 sccm of boron source, 500-2000 sccm of SiH4 and 1000-4000 sccm of N2O are introduced. At a temperature of 400-500 °C, the first BSG layer is deposited on the front side of the silicon wafer, with a thickness of 10-50 nm and a boron atom concentration of (0.1-1.0)×E16 cm -2 .

3. The preparation method of the boron emitter of the solar cell according to claim 1, characterized in that, The specific operation of Step 3 is as follows: Using the PECVD method, introduce 500 - 1500 sccm of SiH4 and 1000 - 2000 sccm of N2O, and deposit the silicon oxide mask layer on the front side of the wafer at a temperature of 400 - 500 °C, with a thickness of 10 - 50 nm.

4. The preparation method of the boron emitter of the solar cell according to claim 1, characterized in that, Step five is specifically as follows: By using the PECVD method, introduce 1000 - 1500 sccm of boron source, 500 - 2000 sccm of SiH4, and 500 - 1500 sccm of N2O. At a temperature of 400 - 500 °C, deposit the second BSG layer on the front side of the silicon wafer, with a thickness of 10 - 50 nm and a boron atom concentration of (0.1 - 1)×E20 cm -2 .

5. The method for preparing a boron emitter of a solar cell according to any one of claims 2 or 4, characterized in that, The boron sources for depositing the first BSG layer and the second BSG layer in Step 2 and Step 5 are both trimethylboron or diborane.

6. The preparation method of the boron emitter of the solar cell according to claim 1, characterized in that, The specific operation of Step 6 is as follows: Place the wafer in a tube diffusion furnace at a temperature of 960 - 1000 °C and anneal in a nitrogen atmosphere for 10 - 30 minutes.

7. The preparation method of the boron emitter of the solar cell according to claim 6, characterized in that, The sheet resistance of the boron emitter after annealing of the silicon wafer is 200 - 400 Ω / cm 2 .

8. A boron emitter for a solar cell, characterized in that, Obtained by the preparation method according to any one of claims 1 - 7.

9. Application of the boron emitter of the solar cell as claimed in claim 8 in TOPCon cells, PERC cells, and BC cells.