A method for preparing a selective emitter of a solar cell and a solar cell

Abstract

The present invention relates to a method for preparing a selective emitter of a solar cell and a solar cell, the method comprising the following steps: step S1, diffusing doping elements on a substrate, forming a lightly doped layer on the surface of the substrate and forming a heavily doped diffusion source layer containing the doping elements on the lightly doped layer; step S2, irradiating a predetermined area of ​​the heavily doped diffusion source layer with an electron beam to further diffuse the doping elements into the substrate, so that a heavily doped area is formed on the surface of the substrate corresponding to the predetermined area, and a lightly doped area is formed on the surface of the substrate outside the predetermined area. The preparation method of the present invention uses the heavily doped diffusion source layer as a diffusion source, irradiates the predetermined area of ​​the heavily doped diffusion source layer, so that the doping elements in the heavily doped diffusion source layer are further diffused into the substrate, and a patterned heavily doped area can be formed, and the obtained heavily doped area has a higher surface doping concentration.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cells, and in particular to a method for preparing a selective emitter of a solar cell and a solar cell. Background Art

[0002] In the process of manufacturing crystalline silicon solar cells, in order to reduce the recombination rate on the surface of the silicon substrate and improve the photoelectric conversion efficiency, it is necessary to make a selective emitter structure on the surface of the silicon substrate. That is, the area in contact with the metal electrode (metallized area) is heavily doped with doping elements to significantly reduce the metal contact recombination and contact resistance; while the non-contact area (non-metallized area) is lightly doped with doping elements, which can diffuse to form a pn junction to collect photogenerated carriers and the lightly doped area has better short-wave response.

[0003] There are many methods for making selective emitter structures in the prior art. The commonly used method is to use a laser to scan the phosphosilicate glass (also called PSG) or borosilicate glass (also called BSG) deposited on the surface of the silicon substrate during the thermal diffusion process in the metallized area, so that the doping elements (phosphorus or boron) in the PSG or BSG are further diffused into the silicon substrate, thereby forming a heavily doped structure in the metallized area and a lightly doped structure in the non-metallized area.

[0004] This laser heavy doping method has major disadvantages. For example, when irradiated with laser, the diffusion elements that have diffused into the surface of the silicon substrate will be excited out from the surface of the silicon substrate under the action of the high energy of the laser, so that the concentration of the doping elements on the surface of the heavily doped area formed is reduced, thereby affecting the performance of the selective emitter. Summary of the invention

[0005] In view of the above analysis, an embodiment of the present invention aims to provide a method for preparing a selective emitter of a solar cell and a solar cell including the selective emitter, so as to at least solve the above technical problems existing in the prior art.

[0006] On the one hand, an embodiment of the present invention provides a method for preparing a selective emitter of a solar cell, comprising the following steps:

[0007] Step S1, diffusing a doping element into a substrate, forming a lightly doped layer on the surface of the substrate and forming a heavily doped region diffusion source layer containing the doping element on the lightly doped layer; and

[0008] Step S2, irradiating a predetermined area of ​​the heavily doped region diffusion source layer by an electron beam to further diffuse the doping element into the substrate, so that a heavily doped region is formed on the surface of the substrate corresponding to the predetermined area, and a lightly doped region is formed on the surface of the substrate outside the predetermined area.

[0009] Optionally, before step S1, the method further includes: performing a texturing treatment on the surface of the substrate.

[0010] Optionally, after step S2, the method further includes step S3: removing the heavily doped region diffusion source layer.

[0011] Optionally, the heavily doped region diffusion source layer is removed by acid washing.

[0012] Optionally, the step S2 includes: irradiating a predetermined area of ​​the heavily doped region diffusion source layer with an electron beam for multiple times.

[0013] Optionally, the acceleration voltage of the electron beam is 0.1-50 kV; and / or,

[0014] The electron beam dose is 1.0E 14 ~1.0E 18 / cm 3 .

[0015] Optionally, the substrate is an N-type silicon wafer, and the doping element is selected from Group V elements; or

[0016] The substrate is a P-type silicon wafer, and the doping element is selected from Group III elements.

[0017] Optionally, in the step S1, the substrate is doped with elements diffused by chemical vapor deposition or physical vapor deposition.

[0018] Optionally, the surface concentration of the heavily doped region is greater than the surface concentration of the lightly doped region.

[0019] Another embodiment of the present invention further provides a solar cell, comprising a solar cell selective emitter manufactured by any of the above manufacturing methods.

[0020] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0021] In a method for preparing a selective emitter of a solar cell according to an embodiment of the present invention, a predetermined area of ​​a diffusion source layer in a heavily doped region is irradiated with an electron beam so that the diffusion element further diffuses into the substrate, thereby forming a heavily doped region of the selective emitter. Since the energy controllability of the electron beam is good, the surface concentration of the heavily doped region of the selective emitter can be prevented from decreasing, thereby obtaining a selective emitter with a high surface concentration in the heavily doped region and a low surface concentration in the lightly doped region, so that the metal contact recombination and contact resistance of the heavily doped region are lower, and the short-wave response of the lightly doped region is better, and the open circuit voltage and cell conversion efficiency of the solar cell obtained are further improved, thereby improving the performance of the solar cell.

[0022] In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can become obvious from the description, or can be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained through the contents particularly pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings are only used to illustrate specific embodiments and are not to be considered as limiting the present invention.

[0024] Figure 1 This is a schematic diagram of the structure after step S1 according to one embodiment of the present invention;

[0025] Figure 2 This is a schematic diagram of the structure after step S2 according to one embodiment of the present invention;

[0026] Figure 3 This is a schematic diagram of the structure after step S3 according to one embodiment of the present invention;

[0027] Figure 4 A schematic diagram of patterning of a heavily doped region and a lightly doped region according to an embodiment of the present invention;

[0028] Figure 5 Schematic diagram of electron beam irradiation in step S2 of one embodiment of the present invention;

[0029] Figure 6 This is an ECV test diagram of the selective emitter of the solar cell according to Example 1 of the present invention;

[0030] Figure 7 This is an ECV test diagram of the selective emitter of the solar cell according to Example 2 of the present invention;

[0031] Figure 8 This is an ECV test diagram of the selective emitter of the solar cell according to Example 3 of the present invention;

[0032] Fig. 9 This is an ECV test diagram of the selective emitter of the solar cell according to Example 4 of the present invention;

[0033] Fig.10 This is an ECV test diagram of the selective emitter of the solar cell according to Example 5 of the present invention;

[0034] Fig.11 This is an ECV test diagram of the selective emitter of the solar cell of Comparative Example 1 of the present invention;

[0035] Fig.12 This is an ECV test diagram of the selective emitter of the solar cell of Comparative Example 2 of the present invention.

[0036] The following are the descriptions of the reference numerals:

[0037] 1. Substrate; 2. Lightly doped layer; 3. Diffusion source layer of heavily doped region; 4. Heavily doped region; 5. Lightly doped region; 20. Electron gun; 21. First surface. DETAILED DESCRIPTION

[0038] The preferred embodiments of the present invention are described in detail below, wherein the accompanying drawings constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention. The "first" and "second" in the names are only used to distinguish between structures with the same name, but are not used to limit them.

[0039] Reference Figures 1 to 3 As shown, one embodiment of the present invention provides a method for preparing a selective emitter of a solar cell, comprising the following steps:

[0040] Step S1, diffusing doping elements into a substrate 1, forming a lightly doped layer 2 on the surface of the substrate 1 and forming a heavily doped diffusion source layer 3 containing doping elements on the lightly doped layer 2; and

[0041] In step S2, a predetermined area of ​​the heavily doped diffusion source layer 3 is irradiated with an electron beam to further diffuse the doping elements into the substrate 1, so that a heavily doped area 4 is formed on the surface of the substrate 1 corresponding to the predetermined area, and a lightly doped area 5 is formed on the surface of the substrate 1 outside the predetermined area.

[0042] Optionally, in step S1 , the doping elements are diffused into the substrate 1 by chemical vapor deposition or physical vapor deposition.

[0043] Optionally, before step S1, the process further includes: performing a texturing treatment on the surface of the substrate 1. After the texturing treatment is completed, the doping elements are diffused to form a lightly doped layer 2 and a heavily doped diffusion source layer 3. The texturing treatment may form a pyramid-shaped velvet structure on the surface of the substrate 1.

[0044] Optionally, after step S2, step S3 is further included: removing the heavily doped region diffusion source layer 3 to obtain Figure 3 Further, the heavily doped region diffusion source layer 3 can be removed by pickling.

[0045] The preparation method of one embodiment of the present invention uses the heavily doped region diffusion source layer 3 as the diffusion source, and irradiates a predetermined area of ​​the heavily doped region diffusion source layer 3 so that the doping elements in the heavily doped region diffusion source layer 3 are further diffused into the substrate 1, thereby forming a patterned heavily doped region 4 in the lightly doped layer 2, and the formed heavily doped region 4 has a higher doping concentration.

[0046] Optionally, the substrate 1 after diffusion of the doping elements includes a first surface 21 , and the first surface 21 is composed of a heavily doped region 4 and a lightly doped region 5 .

[0047] Optionally, the substrate 1 is an N-type silicon wafer, and the doping element in the heavily doped region 4 or the lightly doped region 5 is selected from Group III elements, such as one or more of boron, aluminum, gallium, indium, and thallium; further, the doping element may be boron.

[0048] Optionally, the substrate is a P-type silicon wafer, and the doping elements in the heavily doped region 4 or the lightly doped region 5 are selected from one or more elements of Group III, such as phosphorus and / or arsenic.

[0049] The doping concentration in the present invention refers to the number of atoms of the doping element per cubic centimeter of the doping region.

[0050] Optionally, the substrate is an N-type silicon wafer, the doping element is boron, the thickness of the lightly doped layer 2 is 0.8-1.3 μm, and the thickness of the heavily doped region 4 is 0.8-1.3 μm.

[0051] Optionally, the substrate is a P-type silicon wafer, the doping element is phosphorus, the thickness of the lightly doped layer 2 is 0.3-0.4 μm, and the thickness of the heavily doped region 4 is 0.3-0.4 μm.

[0052] Optionally, the surface concentration of the heavily doped region 4 is greater than the surface concentration of the lightly doped region 5. The surface concentration of the heavily doped region 4 and the lightly doped region 5 refers to the doping concentration within a doping depth of less than or equal to 0.04 um after removing the error surface (e.g., 0.01 um) after the substrate doping diffusion is completed.

[0053] Optionally, the substrate is an N-type silicon wafer, the doping element is boron, and the surface doping concentration of the heavily doped region 4 is 1.0×10 19 ~5.0×10 19 / cm 3 , further 3.0×10 19 ~4.0×10 19 / cm 3 .

[0054] Optionally, the substrate is a P-type silicon wafer, the doping element is phosphorus, and the surface doping concentration of the heavily doped region 4 is 1.0×10 20 ~5.0×10 20 / cm 3 , further 3.0×10 20 ~2.0×10 20 / cm 3 .

[0055] Optionally, refer to Figure 4As shown, by electron beam irradiation, the width W of the heavily doped region 4 can be 20 to 400 μm, for example, 50 μm, 100 μm, 150 μm, 200 μm, 250 μm, 300 μm, 350 μm, etc.;

[0056] Optionally, refer to Figure 4 As shown, by electron beam irradiation, the spacing d between the heavily doped regions 4 is 0.5-3.0 mm, for example, 1 mm, 1.33 mm, 1.5 mm, 2 mm, 2.5 mm.

[0057] Optionally, the predetermined area on the heavily doped region diffusion source layer 3 or the pattern of the heavily doped region 4 matches the shape of the metal electrode.

[0058] Optionally, by diffusing doping elements into the substrate 1, the doping elements diffuse into at least one surface of the substrate 1 to form a planar lightly doped layer 2 on the surface, and at the same time, a heavily doped region diffusion source layer 3 containing doping elements is formed on the lightly doped layer 2.

[0059] Optionally, refer to Figure 5 As shown, an electron gun 20 may be used to emit an electron beam.

[0060] The preparation method of one embodiment of the present invention can hit the electron beam on a predetermined area of ​​the heavily doped diffusion source layer 3 by adjusting the electric fields in two mutually perpendicular directions of x and y; and can further minimize the damage of the electron beam to the substrate surface by adjusting the acceleration voltage and the dose of the electron beam.

[0061] Optionally, the electron beam dose is 1.0E 14 ~1.0E 18 / cm 3 , for example 1.0E 14 / cm 3 , 6.0E 14 / cm 3 , 1.0E 15 / cm 3 , 4.0E 15 / cm 3 , 3.0E 16 / cm 3 , 5.0E 16 / cm 3 , 1.0E 17 / cm 3 , 5.0E 17 / cm 3 wait.

[0062] Optionally, the acceleration voltage of the electron beam is 0.1-50 kV, and may further be 10-25 kV, such as 15 kV, 20 kV, etc.

[0063] Optionally, the electron beam scans a predetermined area on the heavily doped diffusion source layer 3 at a speed of 1 to 30 m / s, such as 2 m / s, 5 m / s, 10 m / s, 15 m / s, 20 m / s, 25 m / s, etc.

[0064] Optionally, the spacing between the grid lines can be controlled by adjusting the electric field in a direction perpendicular to the electron beam scanning direction, so as to well match the requirement for the spacing between the grid lines during screen printing.

[0065] Optionally, the thickness and surface concentration of the heavily doped region 4 can be determined by the process parameters of the electron beam. On the one hand, the higher the electron beam acceleration voltage and the greater the dose, the more and deeper the diffusion of the doping element into the substrate, and the higher the overall concentration and the greater the thickness of the heavily doped region. However, on the other hand, as the electron beam acceleration voltage is higher and the dose is greater, the doping elements on the surface of the heavily doped region will be excited out by the electron beam, resulting in a decrease in the surface doping concentration of the heavily doped region 4.

[0066] Optionally, the predetermined area of ​​the heavily doped region diffusion source layer 3 can be irradiated multiple times by an electron beam, for example, twice, three times or more times. As described above, the higher the acceleration voltage of the electron beam and the greater the dose, the higher the doping concentration and doping depth of the heavily doped region formed. However, as the acceleration voltage and dose increase, the doping elements on the surface of the heavily doped region 4 will be detached from the surface under the irradiation of the electron beam, thereby reducing the doping concentration on the surface. Therefore, the present invention avoids the reduction of the doping concentration on the surface by a single irradiation of a heavy dose and a high acceleration voltage electron beam through multiple irradiations of the electron beam.

[0067] The preparation method of one embodiment of the present invention can achieve a heavily doped region with a desired depth and a desired doping concentration by step-by-step electron beam irradiation with different doses and different acceleration voltages. When the electron beam is irradiated multiple times, the dose and acceleration voltage of each electron beam can be the same or different.

[0068] The method for preparing a selective emitter for a solar cell according to one embodiment of the present invention can make the heavily doped region of the prepared selective emitter have a higher doping concentration and fewer surface defects, while not affecting the subsequent metallization process (i.e., electrode formation process).

[0069] The method for preparing a selective emitter of a solar cell according to one embodiment of the present invention has a simple process and is easy to operate, and is suitable for industrial large-scale production.

[0070] An embodiment of the present invention provides a solar cell, comprising the solar cell selective emitter described above.

[0071] In the solar cell according to one embodiment of the present invention, the heavily doped region has a relatively high doping concentration near the surface.

[0072] Hereinafter, a method for preparing a selective emitter for a solar cell according to an embodiment of the present invention will be further described in conjunction with the accompanying drawings and specific examples.

[0073] Example 1

[0074] S11: performing a texturing pretreatment on the N-type silicon wafer substrate 1;

[0075] S12: Diffusing the boron doping element on the pre-treated N-type silicon wafer substrate 1 to form a planar lightly doped layer 2 on the surface of the substrate 1; meanwhile, during the diffusion process, a heavily doped region diffusion source layer 3 is formed on the lightly doped layer 2, and the heavily doped region diffusion source layer 3 is a borosilicate glass layer containing the doping element boron;

[0076] S13: irradiating a predetermined area on the surface of the heavily doped diffusion source layer 3 with an electron beam so that the doping element further diffuses into the N-type silicon wafer substrate 1; wherein the predetermined area is Figure 4 The multiple parallel long strip regions shown correspond to the electrode regions; the acceleration voltage of the electron beam used is 15 kV, and the electron beam dose is 6.0 E 14 / cm 3 After electron beam irradiation, a plurality of heavily doped regions 4 with a spacing d of 1.5 mm are formed on the first surface 21 of the substrate 1, and the remaining areas not irradiated by the electron beam are lightly doped regions 5;

[0077] S14: Acid washing is performed to remove the heavily doped diffusion source layer 3 on the surface of the substrate 1 to obtain a selective emitter of the solar cell.

[0078] The obtained solar cell selective emitter was tested for doping concentration, namely ECV test. The specific results are shown in Figure 6 After electron beam irradiation, the surface doping concentration of the heavily doped region did not decrease but increased, and within 0.04um from the substrate surface, the doping concentration of the heavily doped region was greater than the doping concentration of the lightly doped region (ie, the lightly doped layer).

[0079] Example 2

[0080] This example uses the same raw materials and steps as Example 1, except that the dose of the electron beam used is 3.0E 16 / cm 3 The accelerating voltage is 20 kV. The doping concentration of the obtained solar cell selective emitter was tested. The specific results are shown in Figure 7 After electron beam irradiation, the surface doping concentration of the heavily doped region did not decrease but increased, and within 0.04um from the substrate surface, the doping concentration of the heavily doped region was greater than the doping concentration of the lightly doped region (ie, the lightly doped layer).

[0081] Compared with Example 1, the dose and acceleration voltage of the electron beam in Example 2 are increased, and the surface concentration of the heavily doped area is slightly decreased. However, due to the increase in the dose and acceleration voltage of the electron beam, the doping depth of the heavily doped area is increased. For example, with a concentration of 1.0E 17 / cm 3 The corresponding depth is based on that the depth of the heavily doped region in Example 1 is about 0.63um, and the depth of the heavily doped region in Example 2 is about 0.65um.

[0082] Example 3

[0083] S31: performing a texturing pretreatment on the P-type silicon wafer substrate 1;

[0084] S32: diffusing phosphorus doping elements on the pre-treated P-type silicon wafer substrate 1 to form a lightly doped layer 2 on the surface of the substrate 1; meanwhile, during the diffusion process, a heavily doped region diffusion source layer 3 is formed on the lightly doped layer 2, and the heavily doped region diffusion source layer 3 is a phosphorus silicon glass layer;

[0085] S33: irradiating a predetermined area on the surface of the heavily doped diffusion source layer 3 with an electron beam; wherein the predetermined area is Figure 4 The multiple parallel long strip regions shown in the figure; the acceleration voltage of the electron beam used is 20 kV, and the electron beam dose is 4.0E 15 / cm 3 After electron beam irradiation, a plurality of heavily doped regions 4 with a spacing d of 1.33 mm are formed on the first surface 21 of the substrate 1, and the remaining regions not irradiated by the electron beam are lightly doped regions 5;

[0086] S34: removing the heavily doped diffusion source layer 3 on the surface of the substrate 1 by pickling to obtain a selective emitter of the solar cell.

[0087] The obtained solar cell selective emitter was tested for doping concentration. The specific results are shown in Figure 8 After electron beam irradiation, the concentration of the heavily doped area within 0.01um from the substrate surface is lower than that of the lightly doped area (i.e., the lightly doped layer), but this part is removed after diffusion and surface treatment. In actual use, the doping concentration of the remaining heavily doped area is higher than that of the lightly doped area.

[0088] Example 4

[0089] This embodiment uses the same raw materials and steps as in Embodiment 1, and performs a first test on the doping element concentration of the lightly doped layer and the heavily doped region of the obtained solar cell selective emitter. Afterwards, an electron beam with the same voltage and dose is used to irradiate a predetermined area on the surface of the heavily doped region diffusion source layer 3 of the selective emitter for a second time, and a second doping concentration test is performed on the heavily doped region. Finally, an electron beam with the same voltage and dose is used to irradiate the predetermined area after the second irradiation for a third time, and a third doping concentration test is performed on the heavily doped region. The results of the three tests are shown in FIG. Fig. 9 After each electron beam irradiation, the surface doping concentration of the heavily doped region increases each time, and within a range of 0.04 um from the substrate surface, the doping concentration of the heavily doped region is greater than the doping concentration of the lightly doped region (ie, the lightly doped layer).

[0090] Comparing the curves after the first irradiation a, the second irradiation c, and the third irradiation b, it can be found that after each irradiation, the surface concentration of the heavily doped area gradually increases, and the concentration is 1.0E 17 After each irradiation, the doping depth of the heavily doped region gradually increases. Therefore, multiple distributed electron beam irradiations can obtain a better heavily doped surface concentration and doping depth, and obtain a selective emitter structure with better performance.

[0091] Example 5

[0092] This embodiment uses the same raw materials and steps as in embodiment 1, but uses different electron beam doses and voltages. Specifically, the acceleration voltage is 15 kV, the electron beam dose is 3.0 E 15 / cm 3 The electron beam irradiates the predetermined area on the surface of the heavily doped diffusion source layer 3, and the obtained solar cell selective emitter is subjected to the first test of the doping element concentration of the lightly doped layer and the heavily doped area. Afterwards, the acceleration voltage is 25 kV and the electron beam dose is 6.0 E 15 / cm 3 The electron beam is used to irradiate the predetermined area of ​​the surface of the heavily doped diffusion source layer 3 of the selective emitter for the second time, and the heavily doped area is tested for the doping concentration for the second time. The results of the two tests are shown in Fig.10 After the first electron beam irradiation, the surface doping concentration of the heavily doped area increased, which was greater than the doping concentration of the lightly doped area. The dose and acceleration voltage of the second electron beam irradiation increased. After the second electron beam irradiation, the surface doping concentration of the heavily doped area increased slightly, and the doping depth of the heavily doped area increased from 0.65um to 0.68um (with a concentration of 1.0E 17 / cm 3 The depth to be addressed shall prevail).

[0093] Comparative Example 1

[0094] This embodiment uses the same raw materials and steps as the embodiment 1, the only difference is that: the patterned area on the surface of the heavily doped diffusion source layer 3 is scanned by laser (green light, power 24W, pulse type), and the doping concentration of the obtained solar cell selective emitter is tested. For specific results, see Fig.11 It can be seen that after laser irradiation, the surface concentration of the heavily doped area is greatly reduced.

[0095] Comparative Example 2

[0096] This embodiment uses the same raw materials and steps as the embodiment 3, the only difference is that: the patterned area on the surface of the heavily doped diffusion source layer 3 is scanned by laser (green light, power 24W, pulse type), and the doping concentration of the obtained solar cell selective emitter is tested. For specific results, see Fig.12 It can be seen that after laser irradiation, the surface concentration of the heavily doped area is greatly reduced.

[0097] in, Figures 6 to 12 The vertical axis in the figure represents the doping concentration of the doping element. For example, 1.00E+16 represents 1.00×10 16 The abscissa represents the distance from the first surface 21 along a direction perpendicular to the first surface 21 .

[0098] On the contrary, see Figure 6 , 7 9, within the range of ≤0.04 μm from the first surface 21, the concentration of the doping element in the heavily doped region 4 of the embodiments 1, 2, and 4 of the present invention is greater than that in the lightly doped region 5, and is within 1.00×10 19 / cm 3 The above indicates that the heavily doped region 4 has a higher doping concentration.

[0099] Fig. 9 , 10 The results of multiple electron beam irradiation of Examples 4 and 5 of the present invention can be seen from the curves in the figure that the heavily doped region 4 formed by one, two, and three irradiations has a greater concentration of doping elements than the lightly doped region 5 within a range of ≤0.04 μm from the first surface 21. And within a range of ≤0.04 μm from the formed heavily doped region 4 to the first surface 21, the doping concentration formed by three irradiations is the largest, and the doping concentration of the heavily doped region 4 formed by one irradiation is the smallest.

[0100] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for preparing a selective emitter of a solar cell, characterized in that: The steps include: Step S1, diffusing a doping element into a substrate, forming a lightly doped layer on the surface of the substrate and forming a heavily doped region diffusion source layer containing the doping element on the lightly doped layer; as well as Step S2, irradiating a predetermined area of ​​the heavily doped region diffusion source layer with an electron beam for multiple times to further diffuse the doping element into the substrate, so that a heavily doped region is formed on the surface of the substrate corresponding to the predetermined area, and a lightly doped region is formed on the surface of the substrate outside the predetermined area, and the surface concentration of the heavily doped region is greater than the surface concentration of the lightly doped region; The accelerating voltage of the electron beam is 0.1 to 50 kV; and / or, The electron beam dose is 1.0E 14 ~1.0E 18 / cm 3 ; By adjusting the electric field in the two mutually perpendicular directions of x and y, the electron beam is irradiated on a predetermined area of ​​the heavily doped diffusion source layer; and by adjusting the electric field in the direction perpendicular to the electron beam scanning direction, the spacing of the gate lines is controlled.

2. The preparation method according to claim 1, characterized in that: Before step S1, the method further includes: performing a texturing treatment on the surface of the substrate.

3. The preparation method according to claim 1, characterized in that: After step S2, the method further includes step S3: removing the heavily doped region diffusion source layer.

4. The preparation method according to claim 3, characterized in that: The heavily doped region diffusion source layer is removed by acid washing.

5. The preparation method according to claim 1, characterized in that: The substrate is an N-type silicon wafer, and the doping element is selected from Group V elements; or The substrate is a P-type silicon wafer, and the doping element is selected from Group III elements.

6. The preparation method according to claim 1, characterized in that: In the step S1, the doping elements are diffused into the substrate by chemical vapor deposition or physical vapor deposition.

7. A solar cell, comprising the solar cell selective emitter prepared by the preparation method according to any one of claims 1 to 6.

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