Back contact solar cell and preparation method thereof

Abstract

The invention relates to a back-contact solar cell and a preparation method thereof, the back-contact solar cell comprises a silicon substrate, and the back surface of the silicon substrate is provided with a first region, a second region and an isolation region. The isolation region is composed of a first isolation region connected with the first region and a second isolation region located between the first isolation region and the second region. The first region comprises a diffusion layer of first type doping atoms, the second region comprises a carrier collection layer of second type doping atoms, and the two types of doping atoms are opposite in conductive type. The gray value ratio of the first isolation region to the first region in the photoluminescence detection image is controlled to reach more than 0.94, so that the first isolation region is free of carrier residue and recombination center, effective electrical isolation is realized, the non-radiative recombination rate is reduced, and the open-circuit voltage, the fill factor and the conversion efficiency of the cell are improved.

Description

Technical Field

[0001] The present invention relates to a back-contact solar cell and a method for manufacturing the same. Background Art

[0002] Since the positive and negative electrodes of the back-contact solar cell are both disposed on its back surface, there is no metal electrode shielding on the front surface, so that the light absorption efficiency on the front surface of the cell is greatly improved, thereby improving the conversion efficiency of the back-contact solar cell.

[0003] The structure of an existing back-contact solar cell includes: an n-type silicon substrate, a p-region, an n-region are defined on the back surface of the n-type silicon substrate, and an isolation region is located between the p-region and the n-region. A p-type diffusion layer (p + emitter) is formed in the silicon substrate corresponding to the p-region, a tunneling oxide layer is formed on the surface of the silicon substrate corresponding to the n-region, and an n-type doped polysilicon layer (n + Poly Si) is formed on the tunneling oxide layer. The manufacturing method of this solar cell mainly includes: first performing boron diffusion to form a p-type diffusion layer on the back surface of the silicon substrate, and then removing the p-type diffusion layer at the corresponding positions of the isolation region and the n-region by means of alkaline solution cleaning, and forming a tunneling oxide layer and an n-type doped polysilicon layer on the surface of the silicon substrate corresponding to the n-region.

[0004] The back-contact solar cell obtained by the above manufacturing method has black lines in the photoluminescence (PL) detection image, which affects the performance of the back-contact solar cell. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a back-contact solar cell and a method for manufacturing the same, and there are no black lines in the photoluminescence detection image of this back-contact solar cell.

[0006] To solve the above technical problems, the present invention provides the following technical solutions:

[0007] In a first aspect, the present invention provides a back-contact solar cell, including: a silicon substrate, the back surface of the silicon substrate includes a first region, a second region, and an isolation region disposed between the first region and the second region;

[0008] The isolation region includes a first isolation region connected to the first region and a second isolation region disposed between the first isolation region and the second region;

[0009] Wherein,

[0010] The first region forms a diffusion layer including first-type doping atoms;

[0011] The second region forms a carrier collection layer including second-type doping atoms;

[0012] The conduction types of the first type of doping atoms and the second type of doping atoms are opposite;

[0013] The ratio of the gray value of the first isolation region in the photoluminescence detection image to the gray value of the first region in the photoluminescence detection image is 0.94 or more.

[0014] In a second aspect, the present invention provides a method for manufacturing a back-contact solar cell, characterized in that the method includes:

[0015] S1. Form a first-type doping source layer including first-type doping atoms on the back surface of a silicon substrate. Some of the first-type doping atoms in the first-type doping source layer diffuse into the silicon substrate to form a diffusion intermediate layer. The back surface of the silicon substrate includes a first region, a second region, and an isolation region provided between the first region and the second region. The isolation region includes a first isolation region connected to the first region and a second isolation region provided between the first isolation region and the second region;

[0016] S2. Remove the first-type doping source layer corresponding to the second region and the isolation region, and remove the diffusion intermediate layer corresponding to the second region and the isolation region. The first isolation region further includes an unremoved diffusion intermediate layer;

[0017] S3. By performing aerobic propulsion on the first-type doping source layer corresponding to the first region, a diffusion layer is formed. At the same time, some of the first-type doping atoms in the first-type doping source layer corresponding to the first region and / or the diffusion intermediate layer diffuse into the first isolation region, and the first-type doping atoms in the unremoved diffusion intermediate layer diffuse in the first isolation region, so that the first isolation region includes the first-type doping atoms, and the second isolation region basically does not include the first-type doping atoms;

[0018] S4. Form a carrier collection layer including second-type doping atoms in the second region and the isolation region. At the same time, some of the second-type doping atoms in the carrier collection layer diffuse into the first isolation region, so that the first isolation region further includes the second-type doping atoms, and the first carriers generated by the first-type doping atoms in the first isolation region are offset by the second carriers generated by the second-type doping atoms.

[0019] The technical solution of the present invention has the following beneficial effects:

[0020] For the back-contact solar cell provided by the present invention, the ratio of the gray value of the first isolation region to that of the first region in the photoluminescence detection image is controlled to reach above 0.94. Within such a range of gray value ratios, there are no carrier residues and recombination centers formed in the first isolation region, achieving effective electrical isolation. This optimization significantly reduces the non-radiative recombination rate, making the electrical properties of the isolation region tend to be consistent with those of the normal region, thereby effectively improving the open-circuit voltage, fill factor, and overall conversion efficiency of the back-contact solar cell.

[0021] For the preparation method of the back-contact solar cell provided by the present invention, by removing the diffusion intermediate layers of the second region and the isolation region, the first isolation region further includes the diffusion intermediate layer that is not removed. Through the diffusion of some second-type doping atoms in the carrier collection layer formed in the isolation region into the first isolation region, the first carriers generated by the first-type doping atoms in the first isolation region are offset by the second carriers generated by the second-type doping atoms, forming an electrically neutral region, achieving effective electrical isolation, reducing carrier recombination, and thus effectively avoiding the adverse effects of the residual first-type doping atoms in the first isolation region on the cell performance.

[0022] In addition, by first forming a first-type doping source layer including first-type doping atoms on the back surface of the silicon substrate without performing oxygen push, the doping concentration of the diffusion intermediate layer formed in the silicon substrate is relatively low, facilitating the removal of the diffusion intermediate layers of the second region, the second isolation region, and part of the diffusion intermediate layer of the first isolation region, such that there are fewer first-type doping atoms remaining in the first isolation region, which is beneficial for the first carriers generated by the first-type doping atoms in the first isolation region to be offset by the second carriers generated by the second-type doping atoms to ensure the performance of the back-contact solar cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic cross-sectional structure diagram of a back-contact solar cell according to an embodiment of the present invention;

[0024] Figure 2 It is a schematic flow diagram of a preparation method of a back-contact solar cell according to an embodiment of the present invention;

[0025] Figure 3 It is a schematic cross-sectional structure diagram of the silicon substrate obtained after step S21 according to an embodiment of the present invention;

[0026] Figure 4 It is a schematic cross-sectional structure diagram of the silicon substrate obtained after step S22 according to an embodiment of the present invention;

[0027] Figure 5 It is a schematic cross-sectional structure diagram of the silicon substrate obtained after step S24 according to an embodiment of the present invention;

[0028] Figure 6Schematic cross-sectional structure diagram of the silicon substrate obtained after step S25 of the embodiment of the present invention;

[0029] Figure 7 Schematic cross-sectional structure diagram of the silicon substrate obtained after step S26 of the embodiment of the present invention;

[0030] Figure 8 Schematic cross-sectional structure diagram of the silicon substrate obtained after step S27 of the embodiment of the present invention;

[0031] Figure 9 Schematic cross-sectional structure diagram of the silicon substrate obtained after step S28 of the embodiment of the present invention;

[0032] Figure 10 Schematic cross-sectional structure diagram of the silicon substrate obtained after step S30 of the embodiment of the present invention;

[0033] Figure 11 PL schematic diagram of the back-contact solar cell provided in Embodiment 1;

[0034] Figure 12 PL schematic diagram of the back-contact solar cell provided in Embodiment 2;

[0035] Figure 13 PL schematic diagram of the back-contact solar cell provided in Embodiment 3;

[0036] Figure 14 PL schematic diagram of the back-contact solar cell provided in Comparative Example 1;

[0037] Figure 15 PL schematic diagram of the back-contact solar cell provided in Comparative Example 2.

[0038] Among them, 1 - silicon substrate; 2 - first-type doping source layer; 3 - diffusion intermediate layer; 4 - diffusion layer; 5 - first-type doped silicon glass layer; 6 - first oxide layer; 7 - tunneling oxide layer; 8 - second-type doped silicon layer; 9 - second-type doped silicon glass layer; 10 - passivation and antireflection layer; 11 - first electrode; 12 - second electrode; 13 - carrier collection layer; 14 - first region; 15 - second region; 16 - isolation region; 161 - first isolation region; 162 - second isolation region. Specific embodiments

[0039] For a better understanding of the technical solutions of the present invention, the embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0040] It should be clear that the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0041] The terms used in the embodiments of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The singular forms "a", "said", and "the" used in the embodiments of the present invention and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0042] It should be understood that the term "and / or" used herein is merely a description of the associated relationship of the associated objects, indicating that three relationships may exist. For example, A and / or B may represent: A exists alone, A and B exist simultaneously, and B exists alone.

[0043] In the back-contact solar cell prepared by the prior art, black lines will appear in the isolation region 16 of the cell in the photoluminescence detection image. This is mainly because the isolation region 16 is contaminated by p-type doping atoms during the boron diffusion process, and in the subsequent alkali washing process, due to the anisotropic etching characteristics of crystalline silicon, the p-type doping atoms in a part of the isolation region (i.e., the first isolation region 161) connected to the p-region cannot be completely removed, resulting in the remaining p-type doping atoms forming a high-concentration recombination center in the first isolation region 161, capturing carriers and increasing the recombination rate, thus showing black lines in the photoluminescence detection image. Such a recombination center will significantly reduce the open-circuit voltage and fill factor of the cell, and further affect the overall conversion efficiency of the cell.

[0044] To solve the above technical problems, the embodiments of the present invention provide a back-contact solar cell, as Figure 1 shown, the back-contact solar cell may include a silicon substrate 1, wherein the back surface of the silicon substrate 1 may include a first region 14, a second region 15, and an isolation region 16 provided between the first region 14 and the second region 15. The isolation region 16 may include a first isolation region 161 connected to the first region 14 and a second isolation region 162 provided between the first isolation region 161 and the second region 15.

[0045] Wherein, a diffusion layer 4 including first-type doping atoms may be formed in the first region 14, and a carrier collection layer 13 including second-type doping atoms may be formed in the second region 15, and the conductive types of the first-type doping atoms and the second-type doping atoms are opposite. And the ratio of the gray value of the first isolation region 161 in the photoluminescence detection image to the gray value of the first region 14 in the photoluminescence detection image is 0.94 or more.

[0046] The back-contact solar cell provided by the present invention ensures that there are no residual doped atoms and no formation of recombination centers in the first isolation region 161 by controlling the ratio of the gray value of the first isolation region 161 to that of the first region 14 in the photoluminescence detection image to be above 0.94, achieving effective electrical isolation and eliminating the black line phenomenon in the photoluminescence detection image of the cell. This optimization significantly reduces the non-radiative recombination rate, making the electrical properties of the isolation region 16 tend to be consistent with those of the normal region, and effectively improving the open-circuit voltage, fill factor, and overall conversion efficiency of the back-contact solar cell.

[0047] Further, the ratio of the gray value of the first isolation region 161 to that of the first region 14 in the photoluminescence detection image is above 0.97, thereby making the performance of the back-contact solar cell better.

[0048] In some embodiments, the ratio of the gray value of the first isolation region 161 to that of the second region 15 in the photoluminescence detection image is above 0.86. Preferably, the ratio of the gray value of the first isolation region 161 to that of the second region 15 in the photoluminescence detection image is above 0.89. The black line phenomenon in the photoluminescence detection image of the back-contact solar cell is eliminated, thereby improving the open-circuit voltage, fill factor, and overall conversion efficiency of the back-contact solar cell.

[0049] In some embodiments, the open-circuit voltage of the back-contact solar cell is above 0.73 V to ensure the photoelectric conversion efficiency of the cell.

[0050] In some embodiments, the first isolation region 161 may include first-type doped atoms and second-type doped atoms, and the doping concentration ratio of the first-type doped atoms to the second-type doped atoms in the first isolation region 161 is 1:100 - 100:1. The second isolation region 162 basically does not include first-type doped atoms.

[0051] Further, the doping concentration ratio of the first-type doped atoms to the second-type doped atoms in the first isolation region 161 is 1:1 - 1:100, so that the first carriers generated by the first-type doped atoms can be completely offset by the second carriers generated by the second-type doped atoms, thereby effectively avoiding the adverse effects of the residual first-type doped atoms in the first isolation region 161 on the cell performance.

[0052] In some embodiments, the first isolation region 161 includes an inclined surface connected to the first region 14, and the second isolation region 162 includes a matte surface to improve the light absorption efficiency of the isolation region 16. Among them, the first isolation region 161 is higher than the second isolation region 162, and the maximum height H1 of the inclined surface of the first isolation region 161 relative to the matte surface of the second isolation region 162 is greater than the maximum vertical height H2 of the matte surface of the second isolation region 162. The lower matte surface height of the second isolation region 162 can reduce the surface defect density and the surface recombination rate, thereby improving the performance of the back-contact solar cell.

[0053] Further, the maximum height H1 of the inclined surface of the first isolation region 161 relative to the matte surface of the second isolation region 162 is 4 - 7 μm, the maximum vertical height H2 of the matte surface of the second isolation region 162 is 0.5 - 1.1 μm, and the inclined surface length of the first isolation region 161 is 4.5 - 8.5 μm.

[0054] In some embodiments, the second isolation region 162 may include second-type doping atoms.

[0055] In some embodiments, the first region 14 may be higher than the second isolation region 162, and the lowest point of the first region 14 is 3 - 5 μm higher than the lowest point of the second isolation region 162 to improve the carrier collection efficiency of the first region 14, thereby enhancing the fill factor and conversion efficiency of the back-contact solar cell.

[0056] In some embodiments, the doping type of the second-type doping atoms is the same as that of the silicon substrate 1. Among them, the first-type doping atoms are p-type doping atoms, the second-type doping atoms are n-type doping atoms, and the silicon substrate 1 is an n-type silicon substrate. Specifically, the p-type doping atoms may include boron atoms, and the n-type doping atoms may include phosphorus atoms.

[0057] Further, the doping concentration of phosphorus atoms in the n-type silicon substrate is 5×10 14 -2×10 16 atoms / cm 3 , so as to optimize the conductivity of the silicon substrate 1, enhance the built-in electric field of the pn junction, and improve the conversion efficiency of the back-contact solar cell.

[0058] The doping concentration of phosphorus atoms in the first isolation region 161 is 2.4×10 17 -2×10 19 atoms / cm 3 , to ensure that the electrons generated by the phosphorus atoms can completely offset the holes generated by the residual boron atoms. The doping concentration of the phosphorus atoms may specifically be 2.5×10 17 atoms / cm 3 、6×10 17 atoms / cm 3 、5×10 18atoms / cm 3 , 8×10 18 atoms / cm 3 , 1.5×10 19 atoms / cm 3 etc.

[0059] The doping concentration of boron atoms in the diffusion layer 4 is 1×10 18 -2×10 19 atoms / cm 3 , specifically it can be 2×10 18 atoms / cm 3 , 5×10 18 atoms / cm 3 , 8×10 18 atoms / cm 3 , 1.5×10 19 atoms / cm 3 etc.; the junction depth of the diffusion layer 4 is 1.0 - 3.0 μm, specifically it can be 1.2 μm, 1.5 μm, 1.8 μm, 2.0 μm, 2.5 μm, 2.8 μm, etc., where the junction depth can be understood as the diffusion depth of the diffusion layer 4 in the silicon substrate 1. If it exceeds the above doping concentration of boron atoms or the junction depth range, the passivation effect of the diffusion layer 4 will deteriorate, and it will also affect the subsequent collection of carriers by the electrode.

[0060] In some embodiments, the carrier collection layer 13 includes a tunneling oxide layer 7 located on the surface of the silicon substrate 1 and a second - type doped silicon layer 8 located on the surface of the tunneling oxide layer 7. Among them, the doping concentration of phosphorus atoms in the second - type doped silicon layer 8 is 2×10 20 -7×10 20 atoms / cm 3 , to enhance the surface passivation effect of the second region 15 and reduce the surface recombination rate. The doping concentration of phosphorus atoms can specifically be 2.5×10 20 atoms / cm 3 , 4×10 20 atoms / cm 3 , 5×10 20 atoms / cm 3 , 6×10 20 atoms / cm 3 etc.

[0061] In some embodiments, the first region 14, the isolation region 16, and the front surface of the back-contact solar cell can be textured surfaces, thereby enhancing the light absorption rate. The second region 15 can be a polished surface, such that the tunneling passivation effect of the carrier collection layer 13 in the second region 15 is better. Among them, the maximum vertical height H3 of the textured surface on the front surface is 0.7 - 1.1 μm, thereby optimizing the light absorption efficiency.

[0062] In some embodiments, the back-contact solar cell further includes a passivation and antireflection layer 10 disposed on the front and back surfaces of the silicon substrate 1, which includes a stacked Al 2 O 3 layer and a SiNx layer, thereby reducing the surface recombination of the cell, isolating external impurities, and reducing the light reflection loss.

[0063] In some embodiments, the back-contact solar cell further includes a first electrode 11 and a second electrode 12. The first electrode 11 is in ohmic contact with the diffusion layer 4, and the second electrode 12 is in ohmic contact with the second-type doped silicon layer 8.

[0064] An embodiment of the present invention also provides a method for manufacturing a back-contact solar cell, as Figure 2 shown, the method includes:

[0065] S11, as Figure 4 shown, form a first-type doped source layer 2 including first-type doped atoms on the back surface of the silicon substrate 1. A part of the first-type doped atoms in the first-type doped source layer 2 diffuses into the silicon substrate 1 and forms a diffusion intermediate layer 3. The back surface of the silicon substrate 1 may include a first region 14, a second region 15, and an isolation region 16 disposed between the first region 14 and the second region 15. The isolation region 16 includes a first isolation region 161 connected to the first region 14 and a second isolation region 162 disposed between the first isolation region 161 and the second region 15.

[0066] It should be noted that the first region 14, the second region 15, and the isolation region 16 are different regions on the back surface of the silicon substrate 1. The film layer corresponding to each region can be called the film layer of the corresponding region. For example, the first-type doped source layer 2 in the first region 14 refers to forming the first-type doped source layer 2 on the surface of the silicon substrate 1 corresponding to the first region 14. The numbers of the first region 14, the second region 15, and the isolation region 16 are all multiple, and the first region 14 and the second region 15 are alternately arranged, and the isolation region 16 is located between the first region 14 and the second region 15.

[0067] The diffusion intermediate layer 3 is formed in the silicon substrate 1 simultaneously when forming the first-type doped source layer 2, rather than formed by high-temperature diffusion. Its doping concentration is relatively low, which is beneficial to subsequent processing of the diffusion intermediate layer 3 corresponding to the second region 15 and the isolation region 16.

[0068] Among them, S11 includes: depositing on the back surface of the silicon substrate 1 for 4 - 12 minutes under the condition of 800 °C - 900 °C to form a first-type doping source layer 2, and the concentration of the first-type doping atoms in the first-type doping source layer 2 is 5×10 20 -9×10 22 atoms / cm 3 . The first-type doping source layer 2 can be a p-type doping source layer or an n-type doping source layer. Preferably, the first-type doping source layer 2 can be a p-type doping source layer, and the first-type doping atoms can include boron atoms. Exemplarily, when the first-type doping source layer 2 includes a boron source layer, boron trichloride can be deposited on the back surface of the silicon substrate 1 by chemical deposition using a tube diffusion furnace to form the boron source layer.

[0069] Set the temperature to 800 °C - 900 °C, and the deposition time to 4 - 12 minutes to ensure that the doping concentration of the diffusion intermediate layer 3 is relatively low. Among them, the temperature can be 800 °C, 820 °C, 850 °C, 880 °C or 900 °C, etc., and the deposition time can be 4 minutes, 7 minutes, 8 minutes, 10 minutes or 12 minutes, etc.

[0070] Set the concentration of the first-type doping atoms in the first-type doping source layer 2 to 5×10 20 -9×10 22 atoms / cm 3 , to ensure that the doping concentration of the diffusion layer 4 in the first region 14 is within the required range in the subsequent steps. The concentration of the first-type doping atoms in the first-type doping source layer 2 can be 6×10 20 atoms / cm 3 , 10×10 21 atoms / cm 3 , 5×10 22 atoms / cm 3 , or 9×10 22 atoms / cm 3 , etc.

[0071] The first-type doping atoms can include boron atoms, and the doping concentration of boron atoms in the diffusion intermediate layer 3 ≤ 2.4×10 17 atoms / cm 3 , for example, it can be ≤ 2.16×10 17 atoms / cm 3 , ≤ 2×10 17 atoms / cm 3 , ≤ 1.9×10 17 atoms / cm 3 , ≤ 1.7×10 17 atoms / cm 3 , ≤ 1.5×10 17atoms / cm 3 , ≤ 1.2×10 17 atoms / cm 3 , ≤ 1×10 17 atoms / cm 3 , ≤ 0.8×10 17 atoms / cm 3 , ≤ 0.5×10 17 atoms / cm 3 , ≤ 0.2×10 17 atoms / cm 3 or ≤ 0.1×10 17 atoms / cm 3 etc. In addition, the doping concentration of boron atoms in the diffusion intermediate layer 3 can also be 0.6×10 17 atoms / cm 3 , 1.1×10 17 atoms / cm 3 , 1.3×10 17 atoms / cm 3 , 1.4×10 17 atoms / cm 3 , 1.6×10 17 atoms / cm 3 , 1.8×10 17 atoms / cm 3 , 2.1×10 17 atoms / cm 3 or 2.2×10 17 atoms / cm 3 etc., which are not listed one by one here. In this way, it can be ensured that in the subsequent steps, part of the second-type doping atoms in the carrier collection layer 13 diffuse into the first isolation region 161, and the second carriers generated by them can cancel out the first carriers generated by the remaining first-type doping atoms in the first isolation region 161.

[0072] S12. As Figures 5 - 6 shown, remove the first-type doping source layer 2 corresponding to the second region 15 and the isolation region 16, and remove the diffusion intermediate layer 3 corresponding to the second region 15 and the isolation region 16. The first isolation region 161 further includes the diffusion intermediate layer 3 that is not removed.

[0073] Specifically, the first-type doping source layer 2 corresponding to the second region 15 and the isolation region 16 can be removed by laser. The diffusion intermediate layer 3 corresponding to the second region 15 and the second isolation region 162 and a part of the diffusion intermediate layer 3 corresponding to the first isolation region 161 are removed by means of alkaline solution polishing, so that the first isolation region 161 further includes the diffusion intermediate layer 3 that is not removed.

[0074] In this step, the laser can be a picosecond laser or a nanosecond laser with a wavelength less than 550 nm. Such a setting can avoid the first-type doped atoms in the first-type doped source layer 2 being pushed into the silicon substrate 1 during the laser removal process, resulting in more first-type doped atoms remaining in the first isolation region 161, which affects the effect of the second carriers generated by the second-type doped atoms to offset them subsequently.

[0075] The alkali solution can include a potassium hydroxide solution or a sodium hydroxide solution, with a mass fraction of 0.5 wt% - 10 wt%. Alkali solution polishing will form alkali corrosion pits. In the wet chemical alkali polishing process, since the corrosion rate of the <111> crystal plane in crystalline silicon is much smaller than that of the <100> crystal plane, and the inclined plane at the junction of the first isolation region 161 and the diffusion intermediate layer 3 of the first region 14 is the <111> crystal plane, the alkali solution can only remove the diffusion intermediate layer 3 corresponding to the second region 15 and the second isolation region 162, and cannot completely remove the diffusion intermediate layer 3 of the first isolation region 161. Therefore, the second isolation region 162 does not include the diffusion intermediate layer 3, the first isolation region 161 includes an inclined plane connected to the first region 14, and the second isolation region 162 includes a polished surface provided between the first isolation region 161 and the second region 15. At this time, the maximum height H4 of the inclined plane of the first isolation region 161 relative to the second isolation region 162 is 2 - 3 μm, and the length of the inclined plane of the first isolation region 161 is 2.5 - 4 μm.

[0076] S13, as Figure 7 shown, by performing aerobic diffusion on the first-type doped source layer 2 corresponding to the first region 14, a diffusion layer 4 is formed. At the same time, some of the first-type doped atoms in the first-type doped source layer 2 and / or the diffusion intermediate layer 3 corresponding to the first region 14 diffuse into the first isolation region 161, and the first-type doped atoms in the unremoved diffusion intermediate layer 3 diffuse in the first isolation region 161, such that the first isolation region 161 includes first-type doped atoms, and the second isolation region 162 basically does not include first-type doped atoms.

[0077] Specifically, the aerobic diffusion of the first-type doped source layer 2 of the first region 14 can be performed under the conditions of a temperature of 850°C - 1050°C and a time of 50 - 90 min to form the diffusion layer 4. Among them, the diffusion layer 4 is formed by combining aerobic diffusion on the basis of the diffusion intermediate layer 3. Specifically, the temperature of the aerobic diffusion can be 860°C, 900°C, 960°C, or 1020°C, etc., and the time can be 50 min, 60 min, 80 min, or 90 min, etc., so as to ensure that the junction depth of the formed diffusion layer 4 is within the optimal range and does not affect the passivation effect of the diffusion layer 4.

[0078] The temperature for forming the first-type doping source layer 2 can be lower than the temperature of the aerobic promotion. The doping concentration of the diffusion intermediate layer 3 is lower than that of the diffusion layer 4 to ensure that there are fewer first-type doping atoms remaining in the first isolation region 161.

[0079] In this step, the first-type doping atoms may include boron atoms, and the doping concentration of the obtained diffusion layer 4 can be 1×10 18 -2×10 19 atoms / cm 3 , for example, the doping concentration can be 2×10 18 atoms / cm 3 , 6×10 18 atoms / cm 3 , 1.5×10 19 atoms / cm 3 or 1.8×10 19 atoms / cm 3 etc. The junction depth is 1.0 - 3.0 μm, specifically it can be 1.1 μm, 1.6 μm, 1.9 μm or 2.6 μm etc.

[0080] S14. As Figure 9 shown, in the second region 15 and the isolation region 16, a carrier collection layer 13 including second-type doping atoms is formed. At the same time, some of the second-type doping atoms in the carrier collection layer 13 diffuse into the first isolation region 161, so that the first isolation region 161 also includes second-type doping atoms, and the first carriers generated by the first-type doping atoms in the first isolation region 161 are offset by the second carriers generated by the second-type doping atoms.

[0081] In the present invention, the doping type of the second-type doping atoms is the same as that of the silicon substrate. The carriers generated by the first-type doping atoms and the second-type doping atoms can offset each other. When the doping concentration of the second-type doping atoms in the second-type doped silicon layer is relatively high, after the second carriers generated by the second-type doping atoms in the first isolation region 161 offset the first carriers generated by the remaining first-type doping atoms, there may be remaining second-type doping atoms. However, since the doping type of the second-type doping atoms is the same as that of the silicon substrate, it will not affect the performance of the back-contact solar cell.

[0082] In some embodiments, the silicon substrate 1 can be an n-type silicon substrate or a p-type silicon substrate. The first-type doping atoms can be p-type doping atoms, and the second-type doping atoms can be n-type doping atoms, or the first-type doping atoms can be n-type doping atoms, and the second-type doping atoms can be p-type doping atoms. Preferably, the silicon substrate 1 is an n-type silicon substrate, the first-type doping atoms are p-type doping atoms, and the second-type doping atoms are n-type doping atoms. Among them, the p-type doping atoms may include boron atoms, and the n-type doping atoms may include phosphorus atoms.

[0083] As Figure 9 shown, the carrier collection layer 13 may include a tunneling oxide layer 7 and a p-type doped silicon layer 8. S4 includes: sequentially forming a tunneling oxide layer 7, an intrinsic layer, and a p-type doped source layer from the inside to the outside in the second region 15 and the isolation region 16, and performing a diffusion process to form a p-type doped silicon layer 8 and a p-type doped silicon glass layer 9 from the intrinsic layer and the p-type doped source layer.

[0084] Among them, the intrinsic layer may include an intrinsic polysilicon layer or an intrinsic amorphous silicon layer. Exemplarily, when the p-type doping atom is phosphorus and the n-type doping atom is boron, a tunneling oxide layer 7, an intrinsic layer, and a phosphorus-doped source layer are sequentially formed from the inside to the outside in the second region 15 and the isolation region 16, and a diffusion process is performed to form a phosphorus-doped silicon layer and a phosphorus-silicon glass layer. The electrons generated by the phosphorus atoms can offset the holes generated by the remaining boron atoms in the first isolation region 161, thereby ensuring that the first isolation region 161 does not form a recombination center. In addition, when the silicon substrate is an n-type silicon substrate, when the doping concentration of phosphorus atoms in the phosphorus-doped silicon layer is relatively high, there may still be remaining phosphorus atoms after the electrons generated by the phosphorus atoms in the first isolation region 161 offset the holes generated by the remaining boron atoms, but the doping type is the same as that of the n-type silicon substrate, which does not affect the performance of the back-contact solar cell.

[0085] Further, the doping concentration of phosphorus atoms in the phosphorus-doped silicon layer is 2×10 20 -7×10 20 atoms / cm 3 , which can effectively improve the conductivity and ohmic contact performance. The doping concentration of phosphorus atoms can be 2.5×10 20 atoms / cm 3 , 3×10 20 atoms / cm 3 , 4×10 20 atoms / cm 3 , 5×10 20 atoms / cm 3 , 6×10 20 atoms / cm 3 and so on.

[0086] The concentration of phosphorus atoms diffused from the phosphorus-doped silicon layer into the first isolation region 161 is 2.4×10 17 -2×10 19 atoms / cm 3 , to ensure that the free electrons generated by the phosphorus atoms can offset the holes generated by the boron atoms. Specifically, the doping concentration of phosphorus atoms can be 6×10 17 atoms / cm 3 , 5×10 18 atoms / cm3 and 8×10 18 atoms / cm 3 and 1×10 19 atoms / cm 3 etc.

[0087] The preparation method of the back - contact solar cell provided by the present invention removes the diffusion intermediate layer 3 corresponding to the second region 15 and the second isolation region 162 and part of the diffusion intermediate layer 3 of the first isolation region 161, so that the first isolation region 161 still includes the unremoved diffusion intermediate layer 3. By diffusing part of the second - type doping atoms in the carrier collection layer 13 formed in the isolation region 16 into the first isolation region 161, the first carriers generated by the first - type doping atoms in the first isolation region 161 are offset by the second carriers generated by the second - type doping atoms, forming an electrically neutral region, realizing effective electrical isolation, reducing carrier recombination, and thus effectively avoiding the adverse effects of the remaining first - type doping atoms in the first isolation region 161 on the battery performance.

[0088] In addition, by first forming a first - type doping source layer 2 including first - type doping atoms on the back surface of the silicon substrate 1 without performing oxygen - assisted diffusion, the doping concentration of the diffusion intermediate layer 3 formed in the silicon substrate 1 is relatively low, which is convenient for removing the diffusion intermediate layer 3 of the second region 15 and the second isolation region 162 and part of the diffusion intermediate layer 3 of the first isolation region 161, so that there are fewer unremoved first - type doping atoms in the first isolation region 161, which is beneficial for the first carriers generated by the first - type doping atoms in the first isolation region 161 to be offset by the second carriers generated by the second - type doping atoms, so as to ensure the performance of the back - contact solar cell.

[0089] To more clearly understand the technical solution provided by the present invention, a more detailed preparation method of the back - contact solar cell is given, and this method includes:

[0090] S21, as Figure 3 shown, perform texturing treatment on the silicon substrate 1 to form a textured surface on the front and back surfaces of the silicon substrate 1.

[0091] Specifically, the silicon substrate 1 can be textured with a potassium hydroxide solution or a sodium hydroxide solution with a mass fraction of 0.5wt% - 10wt% to form a textured surface on the front and back surfaces of the silicon substrate 1 and remove the damage layer generated during the cutting of the silicon substrate 1.

[0092] S22, as Figure 4As shown, a first-type doping source layer 2 including first-type doping atoms is formed on both the back and front surfaces of the silicon substrate 1, and part of the first-type doping atoms in the first-type doping source layer 2 diffuse into the silicon substrate 1 to form a diffusion intermediate layer 3. Among them, the back surface of the silicon substrate 1 includes a first region 14, a second region 15, and an isolation region 16 provided between the first region 14 and the second region 15. The isolation region 16 includes a first isolation region 161 connected to the first region 14 and a second isolation region 162 provided between the first isolation region 161 and the second region 15. Relevant explanations for this step can be found in S11.

[0093] S23. Remove the first-type doping source layer 2 corresponding to the isolation region 16 and the second region 15. Specifically, picosecond laser or nanosecond laser with a wavelength less than 550 nm can be used for removal.

[0094] S24. As Figure 5 shown, remove the first-type doping source layer 2 on the front surface of the silicon substrate 1 by acid cleaning. Specifically, the acid solution can be hydrofluoric acid with a mass fraction of 5 wt% - 30 wt%, such as 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt% or 30 wt%, etc.

[0095] S25. As Figure 6 shown, polish the front and back surfaces of the silicon substrate 1 with an alkaline solution to remove the diffusion intermediate layer 3 corresponding to the front surface, the second region 15, and the isolation region 16. The first isolation region 161 still includes the unremoved diffusion intermediate layer 3, and the front surface and the second region 15 are bare silicon polished structures. Specifically, the alkaline solution can include potassium hydroxide solution or sodium hydroxide solution with a mass fraction of 0.5 wt% - 10 wt%, such as 0.5 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt% or 10 wt%, etc.

[0096] S26. As Figure 7 shown, form a diffusion layer 4 by aerobic propulsion of the first-type doping source layer 2 corresponding to the first region 14. At the same time, part of the first-type doping atoms in the first-type doping source layer 2 and / or the diffusion intermediate layer 3 corresponding to the first region 14 diffuse into the first isolation region 161, and the first-type doping atoms in the unremoved diffusion intermediate layer 3 diffuse in the first isolation region 161, so that the first isolation region 161 includes first-type doping atoms, and the second isolation region 162 basically does not include first-type doping atoms. At the same time, a first-type doped silicon glass layer 5 is formed on the outside of the first region 14, and a first oxide layer 6 is formed on the second region 15, the isolation region 16, and the front surface of the silicon substrate 1. Relevant explanations can be found in S13.

[0097] S27. As Figure 8As shown, an acid solution is used to remove the first oxide layer 6. Specifically, the acid solution can be hydrofluoric acid, and its mass fraction is 5wt%-30wt%, such as 6wt%, 10wt%, 15wt%, 20wt%, 25wt% or 28wt%, etc. The treatment time is 5-300 seconds, such as 6, 10, 20, 50, 70, 100, 150, 200, 250 or 280 seconds.

[0098] In this step, since the first oxide layer 6 (SiO 2 ) can react with hydrofluoric acid rapidly, while the reaction activity of the first-type doped silicon glass layer 5 with hydrofluoric acid is relatively low. Under the same conditions such as concentration and treatment time of hydrofluoric acid, the etching rate of the first-type doped silicon glass layer 5 is much slower than that of the first oxide layer 6 (SiO 2 ). Therefore, hydrofluoric acid can be used to selectively etch the first oxide layer 6 (SiO 2 ) corresponding to the front side, the second region 15 and the isolation region 16. Further, when treating with hydrofluoric acid, it is also necessary to ensure that the thickness of the first-type doped silicon glass layer 5 in the first region 14 is ≥20 nm, so that the first-type doped silicon glass layer 5 can protect the diffusion layer 4 in the first region 14 from being damaged during the subsequent alkaline texturing process.

[0099] S28. As Figure 9 shown, a carrier collection layer 13 including second-type doped atoms is formed in the second region 15 and the isolation region 16, where the carrier collection layer 13 can include a tunneling oxide layer 7 and a second-type doped silicon layer 8. Specifically, a tunneling oxide layer 7, an intrinsic layer and a second-type doped source layer are sequentially formed from the inside to the outside in the second region 15 and the isolation region 16, and a diffusion treatment is performed to form a second-type doped silicon layer 8 and a second-type doped silicon glass layer 9. At the same time, some of the second-type doped atoms in the second-type doped silicon layer 8 diffuse into the first isolation region 161, and the first carriers generated by the first-type doped atoms in the first isolation region 161 are offset by the second carriers generated by the second-type doped atoms. At the same time, a tunneling oxide layer 7, a second-type doped silicon layer 8 and a second-type doped silicon glass layer 9 are formed on the front side of the silicon substrate 1, and a second-type doped silicon layer 8 and a second-type doped silicon glass layer 9 are formed in the first region 14. For the relevant explanations of this step, reference can be made to S14.

[0100] S29. The second-type doped silicon glass layer 9 corresponding to the first region 14 and the isolation region 16 is removed by laser etching. Specifically, a green picosecond laser can be used for removal.

[0101] S30. As Figure 10 shown, an acid solution is used to remove the second-type doped silicon glass layer 9 on the front side of the silicon substrate 1. Specifically, a single-sided etching method is used for removal, and the acid solution can be hydrofluoric acid, and the mass fraction can be 5wt%-30wt%.

[0102] S31. Use an alkaline solution to remove the second-type doped silicon layer 8 and the tunneling oxide layer 7 corresponding to the front surface of the silicon substrate 1 and the isolation region 16, and the second-type doped silicon layer 8 corresponding to the first region 14, and form a textured structure on the front surface of the silicon substrate 1 and the isolation region 16. Specifically, the alkaline solution may include a sodium hydroxide solution or a potassium hydroxide solution, with a mass fraction of 0.5 wt%-10 wt%.

[0103] In this step, since the first-type doped silicon glass layer 5 in the first region 14 is not corroded by the alkaline solution, the diffusion layer 4 in the first region 14 can be protected; the second-type doped silicon glass layer 9 in the second region 15 is not corroded by the alkaline solution, so the second-type doped silicon layer 8 in the second region 15 can be protected; a textured structure will be formed on the front surface and the isolation region 16.

[0104] S32. Use an acid solution to remove the second-type doped silicon glass layer 9 corresponding to the second region 15 and the first-type doped silicon glass layer 5 corresponding to the first region 14. Specifically, the acid solution can be hydrofluoric acid, with a mass fraction of 5 wt%-30 wt%.

[0105] S33. Form a passivation and antireflection layer 10 on the front and back surfaces of the silicon substrate 1 respectively. Specifically, an Al 2 O 3 layer can be deposited by atomic layer deposition, and a SiN x layer can be deposited by plasma-enhanced chemical vapor deposition, so as to reduce the surface recombination of the cell, isolate external impurities, and reduce the light reflection loss.

[0106] S34. As Figure 1 shown, form a first electrode 11 in ohmic contact with the diffusion layer 4 in the first region 14 of the silicon substrate 1, and form a second electrode 12 in ohmic contact with the second-type doped silicon layer 8 in the second region 15.

[0107] The preparation method provided by this embodiment may further include other steps besides S20-S34, which will not be elaborated one by one here.

[0108] To understand the present invention more clearly, the following specific examples and comparative examples are given.

[0109] Example 1

[0110] Example 1 provides a preparation method for a back-contact solar cell, including the following steps:

[0111] Step 1: Use a potassium hydroxide solution with a mass fraction of 5.5 wt% to perform texturing treatment on the n-type silicon substrate 1 in a texturing machine, so as to form a textured surface on the front and back surfaces of the silicon substrate 1;

[0112] Step 2: Place the silicon substrate 1 in a quartz boat, push it into a tube diffusion furnace, control the temperature of the tube diffusion furnace at 810 °C, introduce boron trichloride gas and nitrogen gas into the furnace, and deposit for 4 minutes on the front and back of the silicon substrate 1 to form a boron source layer. The atomic concentration of boron atoms in the boron source layer is measured to be 4×10 21 atoms / cm 3 . At the same time, some boron atoms in the boron source layer diffuse into the silicon substrate 1 to form a boron-doped diffusion intermediate layer. The doping concentration of the boron-doped diffusion intermediate layer is measured to be 1.46×10 17 atoms / cm 3 . The back of the silicon substrate 1 includes a first region 14, a second region 15, and an isolation region 16 disposed between the first 14 and the second region 15. The isolation region 16 includes a first isolation region 161 connected to the first region 14 and a second isolation region 162 disposed between the first isolation region 161 and the second region 15;

[0113] Step 3: Use a picosecond laser with a wavelength of 532 nm to remove the boron source layer corresponding to the isolation region 16 and the second region 15;

[0114] Step 4: Use a hydrofluoric acid solution with a mass fraction of 22 wt% to remove the boron source layer on the front of the silicon substrate 1;

[0115] Step 5: Polish the front and back of the silicon substrate 1 with a potassium hydroxide solution with a mass fraction of 1.6 wt% to remove the boron-doped diffusion intermediate layer corresponding to the front of the silicon substrate 1, the second region 15, and the isolation region 16. The first isolation region 161 still includes the boron-doped diffusion intermediate layer that has not been removed. The front and the second region 15 are bare silicon polished structures;

[0116] Step 6: Place the silicon substrate 1 in an oxidation furnace, control the furnace temperature at 1020 °C, and introduce oxygen. Place it in the oxidation furnace for 55 minutes. The boron source layer corresponding to the first region 14 is pushed forward by oxygen to form a boron-doped diffusion layer, and its doping concentration is 2.7×10 18 atoms / cm 3 , and the junction depth is 1.1 μm. At the same time, a borosilicate glass layer is formed on the outside of the first region 14, and a SiO 2 layer is formed on the second region 15, the isolation region 16, and the front of the silicon substrate 1;

[0117] Step 7: Use a hydrofluoric acid solution with a mass fraction of 7.5 wt% to remove the SiO 2 layer, and the treatment time is 100 seconds;

[0118] Step 8: Prepare the tunneling oxide layer 7 on the front and back of the silicon substrate 1 by low-pressure chemical vapor deposition (LPCVD). Subsequently, introduce silane gas to thermally decompose it, and deposit an intrinsic polysilicon layer on the oxide layer. Then, in a tube diffusion furnace, carry out phosphorus diffusion with nitrogen as the carrier gas to carry phosphorus oxychloride. Process parameters: the temperature in the source introduction stage is 880 °C, the time is 25 min, the carrier gas flow rate is 1300 sccm, and the temperature in the pushing stage is 880 °C, the time is 40 min. In this process, the tunneling oxide layer 7, the phosphorus-doped silicon layer, and the phosphosilicate glass layer are sequentially formed from the inside to the outside on the front of the silicon substrate 1, the second region 15, and the isolation region 16, and the phosphorus-doped silicon layer and the phosphosilicate glass layer are formed in the first region 14. At the same time, the free electrons generated by the phosphorus atoms diffused in the phosphorus-doped silicon layer in the first isolation region 161 compensate for the holes generated by the boron atoms.

[0119] Step 9: Use a green picosecond laser to remove the phosphosilicate glass layer corresponding to the first region 14 and the isolation region 16;

[0120] Step 10: Use a hydrofluoric acid solution with a mass fraction of 18 wt% to remove the phosphosilicate glass layer on the front of the silicon substrate 1;

[0121] Step 11: Use a sodium hydroxide solution with a mass fraction of 2.5 wt% to remove the phosphorus-doped silicon layer and the tunneling oxide layer 7 corresponding to the front of the silicon substrate 1 and the isolation region 16, and the phosphorus-doped silicon layer corresponding to the first region 14, and form a textured structure on the front of the silicon substrate 1 and the isolation region 16;

[0122] Step 12: Use a hydrofluoric acid solution with a mass fraction of 22 wt% to remove the phosphosilicate glass layer corresponding to the second region 15 and the borosilicate glass layer corresponding to the first region 14;

[0123] Step 13: Deposit an Al 2 O 3 layer on the front and back of the silicon substrate 1 by atomic layer deposition, and deposit a SiN x layer by plasma-enhanced chemical vapor deposition to form a passivation and antireflection layer 10;

[0124] Step 14: Screen-print silver-aluminum paste and silver paste on the first region 14 and the second region 15 of the silicon substrate 1 respectively and dry and sinter them. The first electrode 11 in contact with the boron-doped diffusion layer is formed in the first region 14, and the second electrode 12 in contact with the phosphorus-doped silicon layer is formed in the second region 15 to obtain a back-contact solar cell.

[0125] Step 15: Test the back-contact solar cell prepared by the method provided in Example 1. The open-circuit voltage of the back-contact solar cell is 0.739 V, the average gray value of the PL image is 14,816, the average gray value of the first region 14 is 26,832, the average gray value of the second region 15 is 29,500, and the average gray value of the first isolation region 161 is 26,940. Its PL image is as Figure 11 shown. Among them, the PL (Photoluminescence) image refers to the photoluminescence detection image, which is detected by a photoluminescence tester of model LIS-R3; the open-circuit voltage of the back-contact solar cell is detected by a minority carrier lifetime tester of model WCT-120.

[0126] Example 2

[0127] Example 2 provides a preparation method of a back-contact solar cell, and the differences from Example 1 include steps 2, 6, and 15, and the other steps are the same as the corresponding steps in Example 1.

[0128] Step 2: Place the silicon substrate 1 in a quartz boat, push it into a tube diffusion furnace, control the temperature of the tube diffusion furnace to be 830 °C, and introduce boron trichloride gas and nitrogen gas into the furnace, and deposit for 5 minutes on the front and back of the silicon substrate 1 to form a boron source layer. The atomic concentration of boron atoms in the boron source layer is measured by a secondary ion mass spectrometer to be 8×10 21 atoms / cm 3 . At the same time, part of the boron atoms in the boron source layer diffuse into the silicon substrate 1 to form a boron-doped diffusion intermediate layer. The doping concentration of the boron-doped diffusion intermediate layer is measured by the electrochemical capacitance-voltage method to be 1.86×10 17 atoms / cm 3 ;

[0129] Step 6: Place the silicon substrate 1 in an oxidation furnace, control the temperature in the furnace to be 1020 °C, and introduce oxygen, and place it in the oxidation furnace for 55 minutes. The boron source layer corresponding to the first region 14 is advanced with oxygen to form a boron-doped diffusion layer, and its doping concentration is 3.5×10 18 atoms / cm 3 , and the junction depth is 1.2 μm. At the same time, a borosilicate glass layer is formed on the outside of the first region 14, and a SiO 2 layer is formed on the second region 15, the isolation region 16, and the front of the silicon substrate 1;

[0130] Step 15: The back-contact solar cell prepared by the method provided in Example 2 was tested. The open-circuit voltage of this back-contact solar cell was 0.738 V, the average gray value of the PL image was 14792, the average gray value of the first region 14 was 26790, the average gray value of the second region 15 was 28988, and the average gray value of the first isolation region 161 was 26034. Its PL image is as Figure 12 shown.

[0131] Example 3

[0132] Example 3 provides a method for preparing a back-contact solar cell. The differences from Example 1 include Steps 2, 6, and 15, and the other steps are the same as the corresponding steps in Example 1.

[0133] Step 2: Place the silicon substrate 1 in a quartz boat, push it into a tube diffusion furnace, control the temperature of the tube diffusion furnace at 840 °C, and introduce boron trichloride gas and nitrogen gas into the furnace, and deposit for 5 min on the front and back of the silicon substrate 1 to form a boron source layer. The atomic concentration of boron atoms in the boron source layer was measured by secondary ion mass spectrometry to be 8×10 21 atoms / cm 3 . At the same time, part of the boron atoms in the boron source layer diffuse into the silicon substrate 1 to form a boron-doped diffusion intermediate layer. The doping concentration of the boron-doped diffusion intermediate layer was measured by electrochemical capacitance-voltage method to be 2.16×10 17 atoms / cm 3 ;

[0134] Step 6: Place the silicon substrate 1 in an oxidation furnace, control the temperature in the furnace at 1020 °C, and introduce oxygen, and place it in the oxidation furnace for 55 min. The boron source layer corresponding to the first region 14 is advanced with oxygen to form a boron-doped diffusion layer, and its doping concentration is 3.7×10 18 atoms / cm 3 , and the junction depth is 1.1 μm. At the same time, a borosilicate glass layer is formed on the outside of the first region 14, and a SiO 2 layer is formed on the second region 15, the isolation region 16, and the front of the silicon substrate;

[0135] Step 15: The back-contact solar cell prepared by the method provided in Example 3 was tested. The open-circuit voltage of this back-contact solar cell was 0.739 V, the average gray value of the PL image was 14979, the average gray value of the first region 14 was 25186, the average gray value of the second region 15 was 26554, and the average gray value of the first isolation region 161 was 24444. Its PL image is as Figure 13 shown.

[0136] Comparative Example 1

[0137] Comparative Example 1 provides a method for preparing a back-contact solar cell, and the differences from Example 1 include Steps 2, 6, and 15. The other steps are the same as the corresponding steps in Example 1.

[0138] Step 2: Place the silicon substrate 1 in a quartz boat, push it into a tube diffusion furnace, control the temperature of the tube diffusion furnace at 850 °C, and introduce boron trichloride gas and nitrogen gas into the furnace, and deposit for 15 min on the front and back of the silicon substrate 1 to form a boron source layer. The atomic concentration of boron atoms in the boron source layer is measured by secondary ion mass spectrometry to be 3.1×10 22 atoms / cm 3 . At the same time, part of the boron atoms in the boron source layer diffuse into the silicon substrate 1 to form a boron-doped diffusion intermediate layer. The doping concentration of the boron-doped diffusion intermediate layer is measured by electrochemical capacitance-voltage method to be 2.5×10 17 atoms / cm 3 ;

[0139] Step 6: Place the silicon substrate 1 in an oxidation furnace, control the temperature in the furnace at 1020 °C, and introduce oxygen, and place it in the oxidation furnace for 55 min. The boron source layer corresponding to the first region 14 is pushed forward by oxygen to form a boron-doped diffusion layer, and its doping concentration is 4.3×10 18 atoms / cm 3 , and the junction depth is 1.3 μm. At the same time, a borosilicate glass layer is formed outside the first region 14, and a SiO 2 layer is formed on the front of the second region 15, the isolation region 16, and the silicon substrate 1.

[0140] Step 15: Test the back-contact solar cell prepared by the method provided in Comparative Example 1. The open-circuit voltage of the back-contact solar cell is 0.724 V, the average gray value of the PL image is 12618, the average gray value of the first region 14 is 20362, the average gray value of the second region 15 is 22166, and the average gray value of the first isolation region 161 is 19004. Its PL image is as Figure 14 shown.

[0141] Comparative Example 2

[0142] Comparative Example 2 provides a method for preparing a back-contact solar cell, and the differences from Example 1 include Steps 2, 6, and 15. The other steps are the same as the corresponding steps in Example 1.

[0143] Step 2: Place the silicon substrate 1 in a quartz boat, push it into a tube diffusion furnace, control the temperature of the tube diffusion furnace at 870 °C, and introduce boron trichloride gas and nitrogen gas into the furnace, and deposit for 15 min on the front and back of the silicon substrate 1 to form a boron source layer. The atomic concentration of boron atoms in the boron source layer is measured by secondary ion mass spectrometry to be 3.2×10 22atoms / cm 3 . At the same time, some boron atoms in the boron source layer diffuse into the silicon substrate 1 to form a boron-doped diffusion intermediate layer. The doping concentration of the boron-doped diffusion intermediate layer is measured by the electrochemical capacitance-voltage method to be 3.3×10 17 atoms / cm 3 ;

[0144] Step 6: Place the silicon substrate 1 in an oxidation furnace, control the furnace temperature at 1020 °C, and introduce oxygen. Place it in the oxidation furnace for 55 min. The boron source layer corresponding to the first region 14 is advanced with oxygen to form a boron-doped diffusion layer, and its doping concentration is 4.1×10 18 atoms / cm 3 , and the junction depth is 1.3 μm. At the same time, a borosilicate glass layer is formed outside the first region 14, and an SiO 2 layer is formed on the front surfaces of the second region 15, the isolation region 16, and the silicon substrate 1.

[0145] Step 15: Test the back-contact solar cell prepared by the method provided in Comparative Example 2. The open-circuit voltage of this back-contact solar cell is 0.692 V, the average gray value of the PL image is 9764, the average gray value of the first region 14 is 15502, the average gray value of the second region 15 is 17214, and the average gray value of the first isolation region 161 is 14508. Its PL image is as Figure 15 shown.

[0146] Test the performance of the back-contact solar cells prepared by the methods of the above Examples 1-3 and Comparative Examples 1-2 respectively, and obtain the performance data comparison results shown in Table 1 below:

[0147] Table 1 Comparison table of battery performance data

[0148]

[0149] It can be seen from Table 1 that the back-contact solar cells prepared in Examples 1-3 of the present invention are significantly superior to the comparative examples in terms of performance, specifically manifested as an increase in the open-circuit voltage (Voc) and the average gray value of the photoluminescence (PL) image. Among them, a higher open-circuit voltage indicates an increase in the photoelectric conversion efficiency and output power of the back-contact solar cell. The increase in the average gray value of the PL image reflects the improvement in the quality of the back-contact solar cell, the reduction of non-radiative recombination, and the extension of the carrier lifetime, thereby improving the short-circuit current (Jsc) density, fill factor (FF), and overall efficiency.

[0150] Therefore, it can be concluded that by optimizing the ratio of the gray value of the first isolation region 161 to that of the first region 14 in the photoluminescence detection image to be above 0.94, and / or the ratio of the gray value of the first isolation region 161 to that of the second region 15 in the photoluminescence detection image to be above 0.86, the carrier residue in the first isolation region 161 can be effectively eliminated, the formation of recombination centers can be inhibited, and the carrier recombination loss can be reduced, ultimately achieving an overall improvement in the performance of the back-contact solar cell.

[0151] The embodiments of the present invention provide the following technical solutions:

[0152] Technical solution 1. A back-contact solar cell, characterized in that the back-contact solar cell includes: a silicon substrate 1, the back surface of the silicon substrate 1 includes a first region 14, a second region 15, and an isolation region 16 provided between the first region 14 and the second region 15;

[0153] The isolation region 16 includes a first isolation region 161 connected to the first region 14 and a second isolation region 162 provided between the first isolation region 161 and the second region 15;

[0154] Wherein,

[0155] The first region 14 forms a diffusion layer 4 including first-type doping atoms;

[0156] The second region 15 forms a carrier collection layer 13 including second-type doping atoms;

[0157] The conductive types of the first-type doping atoms and the second-type doping atoms are opposite;

[0158] The ratio of the gray value of the first isolation region 161 in the photoluminescence detection image to the gray value of the first region 14 in the photoluminescence detection image is 0.94 or more.

[0159] Technical solution 2. The back-contact solar cell according to technical solution 1, characterized in that the ratio of the gray value of the first isolation region 161 in the photoluminescence detection image to the gray value of the first region 14 in the photoluminescence detection image is 0.97 or more.

[0160] Technical solution 3. The back-contact solar cell according to technical solution 1, characterized in that the ratio of the gray value of the first isolation region 161 in the photoluminescence detection image to the gray value of the second region 15 in the photoluminescence detection image is 0.86 or more.

[0161] Technical solution 4. The back-contact solar cell according to technical solution 3, wherein the ratio of the gray value of the first isolation region 161 in the photoluminescence detection image to the gray value of the second region 15 in the photoluminescence detection image is 0.89 or more.

[0162] Technical solution 5. The back-contact solar cell according to any one of technical solutions 1-4, wherein the open-circuit voltage of the back-contact solar cell is 0.73 V or more.

[0163] Technical solution 6. The back-contact solar cell according to technical solution 1, wherein the first isolation region 161 includes the first-type doping atoms and the second-type doping atoms, and the doping concentration ratio of the first-type doping atoms to the second-type doping atoms in the first isolation region 161 is 1:100-100:1;

[0164] The second isolation region 162 basically does not include the first-type doping atoms.

[0165] Technical solution 7. The back-contact solar cell according to technical solution 6, wherein the doping concentration ratio of the first-type doping atoms to the second-type doping atoms in the first isolation region 161 is 1:1-1:100.

[0166] Technical solution 8. The back-contact solar cell according to technical solution 1, wherein the first isolation region 161 includes an inclined surface connected to the first region 14, and the second isolation region 162 includes a textured surface.

[0167] Technical solution 9. The back-contact solar cell according to technical solution 8, wherein the first isolation region 161 is higher than the second isolation region 162;

[0168] and / or, the maximum height H1 of the inclined surface of the first isolation region 161 relative to the textured surface of the second isolation region 162 is greater than the maximum vertical height H2 of the textured surface of the second isolation region 162.

[0169] Technical solution 10. The back-contact solar cell according to technical solution 9, wherein the maximum height H1 of the inclined surface of the first isolation region 161 relative to the textured surface of the second isolation region 162 is 4-7 μm.

[0170] Technical solution 11. The back-contact solar cell according to technical solution 9, wherein the length of the inclined surface of the first isolation region 161 is 4.5-8.5 μm.

[0171] Technical solution 12. The back-contact solar cell according to technical solution 9, characterized in that the maximum vertical height H2 of the matte surface of the second isolation region 162 is 0.5 - 1.1 μm.

[0172] Technical solution 13. The back-contact solar cell according to technical solution 1, characterized in that the second isolation region 162 includes the second type of doped atoms.

[0173] Technical solution 14. The back-contact solar cell according to technical solution 1, characterized in that the first region 14 is higher than the second isolation region 162, and the lowest point of the first region 14 is 3 - 5 μm higher than the lowest point of the second isolation region 162.

[0174] Technical solution 15. The back-contact solar cell according to technical solution 1, characterized in that the doping type of the second type of doped atoms is the same as that of the silicon substrate 1.

[0175] Technical solution 16. The back-contact solar cell according to technical solution 15, characterized in that the first type of doped atoms is p-type doped atoms, the second type of doped atoms is n-type doped atoms, and the silicon substrate 1 is an n-type silicon substrate.

[0176] Technical solution 17. The back-contact solar cell according to technical solution 16, characterized in that the p-type doped atoms include boron atoms, and the n-type doped atoms include phosphorus atoms.

[0177] Technical solution 18. The back-contact solar cell according to technical solution 17, characterized in that the doping concentration of phosphorus atoms in the n-type silicon substrate is 5×10 14 -2×10 16 atoms / cm 3 。

[0178] Technical solution 19. The back-contact solar cell according to technical solution 17, characterized in that the doping concentration of phosphorus atoms in the first isolation region 161 is 2.4×10 17 -2×10 19 atoms / cm 3 。

[0179] Technical solution 20. The back-contact solar cell according to technical solution 17, characterized in that the doping concentration of boron atoms in the diffusion layer 4 is 1×10 18 -2×10 19 atoms / cm 3 ,the junction depth of the diffusion layer 4 is 1.0 - 3.0 μm.

[0180] Technical solution 21. The back-contact solar cell according to technical solution 17, characterized in that the carrier collection layer 13 comprises a tunneling oxide layer 7 on the surface of the silicon substrate 1 and a second-type doped silicon layer 8 on the surface of the tunneling oxide layer 7.

[0181] Technical solution 22. The back-contact solar cell according to technical solution 21, characterized in that the doping concentration of phosphorus atoms in the second-type doped silicon layer 8 is 2×10 20 -7×10 20 atoms / cm 3 ³.

[0182] Technical solution 23. The back-contact solar cell according to technical solution 1, characterized in that the first region 14, the isolation region 16 and the front surface are matte surfaces, and the second region 15 is a polished surface.

[0183] Technical solution 24. The back-contact solar cell according to technical solution 23, characterized in that the maximum vertical height H3 of the matte surface on the front surface is 0.7 - 1.1 μm.

[0184] Technical solution 25. The back-contact solar cell according to technical solution 1, characterized in that the back-contact solar cell further comprises a passivation and antireflection layer 10 provided on the front and back surfaces of the silicon substrate 1.

[0185] Technical solution 26. The back-contact solar cell according to technical solution 25, characterized in that the passivation and antireflection layer 10 comprises a stacked Al 2 O 3 layer and a SiNx layer.

[0186] Technical solution 27. The back-contact solar cell according to technical solution 21, characterized in that the back-contact solar cell further comprises a first electrode 11 and a second electrode 12, the first electrode 11 is in ohmic contact with the diffusion layer 4, and the second electrode 12 is in ohmic contact with the second-type doped silicon layer 8.

[0187] Technical solution 28. A method for manufacturing a back-contact solar cell, characterized in that the method comprises:

[0188] S1. Form a first-type doping source layer 2 including first-type doping atoms on the back surface of the silicon substrate 1. Part of the first-type doping atoms in the first-type doping source layer 2 diffuse into the silicon substrate 1 to form a diffusion intermediate layer 3. Wherein, the back surface of the silicon substrate 1 includes a first region 14, a second region 15, and an isolation region 16 disposed between the first region 14 and the second region 15. The isolation region 16 includes a first isolation region 161 connected to the first region 14 and a second isolation region 162 disposed between the first isolation region 161 and the second region 15;

[0189] S2. Remove the first-type doping source layer 2 corresponding to the second region 15 and the isolation region 16, and remove the diffusion intermediate layer 3 corresponding to the second region 15 and the isolation region 16. The first isolation region 161 further includes an unremoved diffusion intermediate layer 3;

[0190] S3. By performing aerobic propulsion on the first-type doping source layer 2 corresponding to the first region 14, a diffusion layer 4 is formed. At the same time, part of the first-type doping atoms in the first-type doping source layer 2 corresponding to the first region 14 and / or the diffusion intermediate layer 3 diffuse into the first isolation region 161, and the first-type doping atoms in the unremoved diffusion intermediate layer 3 diffuse in the first isolation region 161, so that the first isolation region 161 includes the first-type doping atoms, and the second isolation region 162 basically does not include the first-type doping atoms;

[0191] S4. Form a carrier collection layer 13 including second-type doping atoms in the second region 15 and the isolation region 16. At the same time, part of the second-type doping atoms in the carrier collection layer 13 diffuse into the first isolation region 161, so that the first isolation region 161 further includes the second-type doping atoms, and the first carriers generated by the first-type doping atoms in the first isolation region 161 are offset by the second carriers generated by the second-type doping atoms.

[0192] Technical solution 29. The preparation method according to technical solution 28, characterized in that, in the S2, the second isolation region 162 does not include the diffusion intermediate layer 3.

[0193] Technical solution 30. The preparation method according to technical solution 28, characterized in that, in the S2, the first isolation region 161 includes an inclined surface connected to the first region 14, and the second isolation region 162 includes a polished surface disposed between the first isolation region 161 and the second region 15.

[0194] Technical solution 31. The preparation method according to technical solution 30 is characterized in that the maximum height H4 of the inclined plane of the first isolation region 161 relative to the second isolation region 162 is 2-3 μm, and / or the length of the inclined plane of the first isolation region 161 is 2.5-4 μm.

[0195] Technical solution 32. The preparation method according to technical solution 28 is characterized in that the doping type of the second type of doping atoms is the same as that of the silicon substrate 1;

[0196] and / or, the first type of doping atoms are p-type doping atoms, the second type of doping atoms are n-type doping atoms, and the silicon substrate 1 is an n-type silicon substrate;

[0197] and / or, the first type of doping atoms include boron atoms, and the second type of doping atoms include phosphorus atoms.

[0198] Technical solution 33. The preparation method according to technical solution 28 is characterized in that the first type of doping atoms include boron atoms, and the silicon substrate 1 is an n-type silicon substrate. The doping concentration of boron atoms in the diffusion intermediate layer 3 ≤ 2.4×10 17 atoms / cm 3 .

[0199] Technical solution 34. The preparation method according to technical solution 33 is characterized in that the doping concentration of boron atoms in the diffusion intermediate layer 3 ≤ 2.4×10 16 atoms / cm 3 .

[0200] Technical solution 35. The preparation method according to technical solution 33 is characterized in that the doping concentration of boron atoms in the diffusion intermediate layer 3 ≤ 2×10 15 atoms / cm 3 .

[0201] Technical solution 36. The preparation method according to technical solution 33 is characterized in that the doping concentration of boron atoms in the diffusion intermediate layer 3 ≤ 2×10 13 atoms / cm 3 .

[0202] Technical solution 37. The preparation method according to technical solution 33 is characterized in that the doping concentration of boron atoms in the diffusion intermediate layer 3 ≤ 2×10 10 atoms / cm 3 .

[0203] Technical solution 38. The preparation method according to technical solution 33 is characterized in that the doping concentration of boron atoms in the diffusion intermediate layer 3 ≤ 2×10 8atoms / cm 3 。

[0204] Technical solution 39. The preparation method according to technical solution 28, characterized in that the temperature for forming the first-type doping source layer 2 is lower than the temperature of the aerobic propulsion, and the doping concentration of the first-type doping atoms in the diffusion intermediate layer 3 is lower than the doping concentration of the first-type doping atoms in the diffusion layer 4.

[0205] Technical solution 40. The preparation method according to technical solution 28, characterized in that S1 includes: depositing on the back surface of the silicon substrate 1 for 4 - 12 minutes at 800°C - 900°C to form the first-type doping source layer 2, and the concentration of the first-type doping atoms in the first-type doping source layer 2 is 5×10 20 -9×10 22 atoms / cm 3 。

[0206] Technical solution 41. The preparation method according to technical solution 28, characterized in that S2 includes: removing the first-type doping source layer 2 corresponding to the second region 15 and the isolation region 16 by laser, and the laser is a picosecond laser or a nanosecond laser with a wavelength less than 550 nm.

[0207] Technical solution 42. The preparation method according to technical solution 28, characterized in that S2 includes: removing the diffusion intermediate layer 3 corresponding to the second region 15, the diffusion intermediate layer 3 corresponding to the second isolation region 162, and a part of the diffusion intermediate layer 3 corresponding to the first isolation region 161 by means of alkaline solution polishing, so that the first isolation region 161 further includes the diffusion intermediate layer 3 that has not been removed.

[0208] Technical solution 43. The preparation method according to technical solution 28, characterized in that in S3, the temperature of the aerobic propulsion is 850°C - 1050°C, and the time is 50 - 90 minutes.

[0209] Technical solution 44. The preparation method according to technical solution 28, characterized in that the first-type doping atoms include boron atoms, and the doping concentration of boron atoms in the diffusion layer 4 is 1×10 18 -2×10 19 atoms / cm 3 , and the junction depth of the diffusion layer 4 is 1.0 - 3.0 μm.

[0210] Technical solution 45. The preparation method according to technical solution 28, characterized in that before S1, the preparation method further includes: performing a texturing treatment on the silicon substrate 1 to form a textured surface on the front and back surfaces of the silicon substrate 1.

[0211] Technical solution 46. The preparation method according to technical solution 28 is characterized in that in the S1, the first-type doping source layer 2 is also formed on the front surface of the silicon substrate 1. After removing the first-type doping source layer 2 corresponding to the isolation region 16 and the second region 15 in the S2, the method further includes: cleaning and removing the first-type doping source layer 2 on the front surface of the silicon substrate 1 by pickling, and polishing the front surface of the silicon substrate 1 with an alkali solution.

[0212] Technical solution 47. The preparation method according to technical solution 28 is characterized in that the S3 further includes: forming a first-type doped silicon glass layer 5 outside the first region 14, and forming a first oxide layer 6 on the front surface of the second region 15, the isolation region 16 and the silicon substrate 1;

[0213] Before the S4, the first oxide layer 6 is removed by using an acid solution.

[0214] Technical solution 48. The preparation method according to technical solution 47 is characterized in that the acid solution is hydrofluoric acid, the mass fraction is 5wt%-30wt%, and the treatment time is 5-300 seconds.

[0215] Technical solution 49. The preparation method according to technical solution 28 is characterized in that the carrier collection layer 13 includes a tunneling oxide layer 7 and a second-type doped silicon layer 8. The S4 includes: sequentially forming the tunneling oxide layer 7, the intrinsic layer and the second-type doping source layer from the inside to the outside in the second region 15 and the isolation region 16, and performing a diffusion treatment to form the second-type doped silicon layer 8 and the second-type doped silicon glass layer 9 from the intrinsic layer and the second-type doping source layer.

[0216] Technical solution 50. The preparation method according to technical solution 49 is characterized in that the second-type doping atoms include phosphorus atoms, and the doping concentration of phosphorus atoms in the second-type doped silicon layer 8 is 2×10 20 -7×10 20 atoms / cm 3 , The concentration of phosphorus atoms diffused from the second-type doped silicon layer 8 into the first isolation region 161 is 2.4×10 17 -2×10 19 atoms / cm 3 。

[0217] Technical solution 51. The preparation method according to technical solution 49 is characterized in that the S4 further includes: forming the tunneling oxide layer 7, the second-type doped silicon layer 8 and the second-type doped silicon glass layer 9 on the front surface of the silicon substrate 1, and forming the second-type doped silicon layer 8 and the second-type doped silicon glass layer 9 in the first region 14;

[0218] The method further includes: removing the p-type doped silicon glass layer 9 corresponding to the first region 14 and the isolation region 16 by laser etching;

[0219] Using an acid solution to remove the p-type doped silicon glass layer 9 on the front surface of the silicon substrate 1;

[0220] Using an alkaline solution to remove the p-type doped silicon layer 8 and the tunneling oxide layer 7 corresponding to the front surface of the silicon substrate 1 and the isolation region 16, and the p-type doped silicon layer 8 corresponding to the first region 14, and forming a textured structure on the front surface of the silicon substrate 1 and the isolation region 16;

[0221] Using an acid solution to remove the p-type doped silicon glass layer 9 corresponding to the second region 15 and the n-type doped silicon glass layer 5 corresponding to the first region 14.

[0222] Technical solution 52. The preparation method according to technical solution 51, wherein the first isolation region 161 includes an inclined surface, and the second isolation region 162 includes a textured surface; and / or,

[0223] The maximum height H1 of the inclined surface of the first isolation region 161 relative to the textured surface of the second isolation region 162 is 4 - 7 μm; and / or,

[0224] The length of the inclined surface of the first isolation region 161 is 4.5 - 8.5 μm; and / or,

[0225] The maximum vertical height H2 of the textured surface of the second isolation region 162 is 0.5 - 1.1 μm; and / or,

[0226] The vertical height H3 of the textured structure on the front surface of the silicon substrate 1 is 0.7 - 1.1 μm.

[0227] Technical solution 53. The preparation method according to technical solution 51, wherein after S4, the method further includes: forming a passivation and antireflection layer 10 on the front and back surfaces of the silicon substrate 1;

[0228] Forming a first electrode 11 in ohmic contact with the diffusion layer 4 in the first region 14 of the silicon substrate 1, and forming a second electrode 12 in ohmic contact with the p-type doped silicon layer 8 in the second region 15.

[0229]

[0230] In summary, the above are only the preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.​

Claims

1. A back contact solar cell, characterized in that: The back-contact solar cell comprises: a silicon substrate (1), wherein the back side of the silicon substrate (1) comprises a first region (14), a second region (15), and an isolation region (16) disposed between the first region (14) and the second region (15); The isolation region (16) includes a first isolation region (161) connected to the first region (14) and a second isolation region (162) provided between the first isolation region (161) and the second region (15); in, The first region (14) forms a diffusion layer (4) including first-type doping atoms; The second region (15) forms a carrier collection layer (13) including second type dopant atoms; The conductivity type of the first-type doping atoms is opposite to that of the second-type doping atoms; The ratio of the grayscale value of the first isolation area (161) in the photoluminescence detection image to the grayscale value of the first area (14) in the photoluminescence detection image is greater than 0.

94.

2. The back contact solar cell according to claim 1, characterized in that: The ratio of the grayscale value of the first isolation area (161) in the photoluminescence detection image to the grayscale value of the second area (15) in the photoluminescence detection image is greater than 0.

86.

3. The back contact solar cell according to any one of claims 1 to 2, characterized in that: The open circuit voltage of the back contact solar cell is greater than 0.73V.

4. The back contact solar cell according to claim 1, characterized in that: The first isolation region (161) includes the first type doping atoms and the second type doping atoms, and the doping concentration ratio of the first type doping atoms to the second type doping atoms in the first isolation region (161) is 1:100-100:1; The second isolation region (162) substantially does not include the first type dopant atoms.

5. The back contact solar cell according to claim 4, characterized in that: The doping concentration of phosphorus atoms in the first isolation region (161) is 2.4×10 17 -2×10 19 atoms / cm 3 .

6. A method for preparing a back contact solar cell, characterized in that: The method comprises: S1. A first-type doping source layer (2) comprising first-type doping atoms is formed on the back side of a silicon substrate (1), and part of the first-type doping source layer (2) diffuses into the silicon substrate (1) to form a diffusion intermediate layer (3), wherein the back side of the silicon substrate (1) comprises a first region (14), a second region (15), and an isolation region (16) arranged between the first region (14) and the second region (15), and the isolation region (16) comprises a first isolation region (161) connected to the first region (14) and a second isolation region (162) arranged between the first isolation region (161) and the second region (15); S2, removing the first type doping source layer (2) corresponding to the second region (15) and the isolation region (16), and removing the diffusion intermediate layer (3) corresponding to the second region (15) and the isolation region (16), wherein the first isolation region (161) further includes the diffusion intermediate layer (3) that has not been removed; S3, forming a diffusion layer (4) by aerobic propulsion of the first type doping source layer (2) corresponding to the first region (14), and at the same time, a portion of the first type doping atoms in the first type doping source layer (2) corresponding to the first region (14) and / or the diffusion intermediate layer (3) diffuses into the first isolation region (161), and the first type doping atoms in the diffusion intermediate layer (3) that have not been removed diffuse in the first isolation region (161), so that the first isolation region (161) includes the first type doping atoms, and the second isolation region (162) substantially does not include the first type doping atoms; S4. A carrier collection layer (13) including second-type doping atoms is formed in the second region (15) and the isolation region (16), and at the same time, part of the second-type doping atoms in the carrier collection layer (13) diffuses into the first isolation region (161), so that the first isolation region (161) also includes the second-type doping atoms, and the first carriers generated by the first-type doping atoms in the first isolation region (161) are offset by the second carriers generated by the second-type doping atoms.

7. The preparation method according to claim 6, characterized in that: The doping type of the second-type doping atoms is the same as that of the silicon substrate (1); And / or, the first-type doping atoms are p-type doping atoms, the second-type doping atoms are n-type doping atoms, and the silicon substrate (1) is an n-type silicon substrate; And / or, the first-type doping atoms include boron atoms, and the second-type doping atoms include phosphorus atoms.

8. The preparation method according to claim 6, characterized in that: The first-type doping atoms include boron atoms, the silicon substrate (1) is an n-type silicon substrate, and the doping concentration of the boron atoms in the diffusion intermediate layer (3) is ≤2.4×10 17 atoms / cm 3 .

9. The preparation method according to claim 6, characterized in that: The step S1 comprises: depositing the first type doping source layer (2) on the back side of the silicon substrate (1) for 4-12 minutes at a temperature of 800° C. to 900° C., wherein the concentration of the first type doping atoms in the first type doping source layer (2) is 5×10 20 -9×10 22 atoms / cm 3 .

10. The preparation method according to claim 1, characterized in that: After S4, the method further includes: Forming a passivation anti-reflection layer (10) on the front side and the back side of the silicon substrate (1) respectively; A first electrode (11) in ohmic contact with the diffusion layer (4) is formed in the first region (14) of the silicon substrate (1), and a second electrode (12) in ohmic contact with the second type doped silicon layer (8) is formed in the second region (15).

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