A preparation method of P-type IBC battery

Abstract

The present invention provides a method for preparing a P-type IBC battery. Compared with the prior art, the present invention adopts a double-sided boron diffusion technology to prepare a P-type IBC battery. + The doped silicon layer can play a role in surface passivation. + The doped silicon layer can extract holes. The two functional layers are prepared in one step without edge insulation. + The doped silicon layers are connected together through the edges, which will not cause leakage. At the same time, the borosilicate glass layer generated by boron diffusion can be used as a barrier layer, so that when phosphorus is doped, phosphorus is only doped into the area where the borosilicate glass layer is removed, without the need to prepare an additional barrier layer. Furthermore, the phosphorus doping concentration is higher than the boron doping concentration, which can effectively prevent the P removal of the borosilicate glass layer. + Compensation doping is performed on the doped silicon region to convert it into N + Phosphorus-doped silicon can realize the preparation of P-type IBC cells. The preparation steps are simple and no photolithography technology is required, which can significantly reduce the cost of the battery.

Description

Technical Field

[0001] The invention belongs to the technical field of solar cells, and in particular relates to a method for preparing a P-type IBC cell. Background Art

[0002] IBC (Interdigitated back contact) cells, also known as back-contact solar cells, break the structural limitations of traditional crystalline silicon cells, providing greater space for improving cell conversion efficiency. And because there is no metal grid on the front of the IBC cell, it is highly aesthetic and very suitable for building photovoltaic integration applications.

[0003] In the prior art, the substrate of IBC solar cells is usually an N-type silicon substrate, and the conventional manufacturing process is: removing the damaged layer and texturing; double-sided diffusion to form N + layer; etch and remove PSG; deposit or print to form a mask; etch to form P + Doped region; diffused to form P + doping layer; forming a front passivation layer and an anti-reflection layer; forming a back mask N + Surface passivation layer; back mask forms P + Surface passivation layer; forming a reflection-enhancing layer on the back; etching to form electrode contact patterns; printing electrodes and sintering.

[0004] However, the above are only the main steps for making N-type IBC batteries. In the actual production process, the production of N-type IBC batteries involves a lot of technical details and corresponding operations, which makes the production process of N-type IBC batteries complicated and even requires the use of photolithography technology, which is costly and affects the promotion of IBC batteries. Summary of the invention

[0005] In view of this, the technical problem to be solved by the present invention is to provide a method for preparing a P-type IBC battery, which has simple steps and does not require photolithography technology.

[0006] The present invention provides a method for preparing a P-type IBC battery, comprising:

[0007] S1) forming texturing on the front side of the P-type crystalline silicon substrate;

[0008] S2) Perform double-sided boron diffusion on the P-type crystalline silicon after texturing to form a P + doped silicon layer and borosilicate glass layer;

[0009] S3) Remove the borosilicate glass layer in the local area on the back of the P-type crystalline silicon after double-sided boron diffusion, and expose the P + doping a silicon layer;

[0010] S4) Phosphorus is doped into the P-type crystalline silicon after the borosilicate glass layer in the local area is removed, so that phosphorus is doped into the bare P + N doped silicon layer + Phosphorus-doped silicon layer and phosphosilicate glass layer;

[0011] S5) removing the glass layer on the surface of the phosphorus-doped P-type crystalline silicon;

[0012] S6) forming a passivation layer and / or an anti-reflection layer on the surface of the P-type crystalline silicon after the glass layer is removed;

[0013] S7) on the back side of the P-type crystalline silicon formed with the passivation layer and / or the anti-reflection layer, respectively prepare + P doped silicon contact + Electrode and N + N-doped silicon layer in contact with phosphorus + electrode.

[0014] Preferably, in the step S2), the boron source for double-sided boron diffusion is BBr3 or BCl3; the temperature is 950°C to 1050°C; and the time is 40 to 60 minutes.

[0015] Preferably, in the step S3), laser is used to remove the borosilicate glass layer in a local area on the back side of the P-type crystalline silicon after double-sided boron diffusion; the local area is in a finger-shaped shape.

[0016] Preferably, the borosilicate glass layer in the local area on the back of the P-type crystalline silicon after double-sided boron diffusion is removed by laser to expose the P + After doping the silicon layer, it is treated with alkali to remove the laser damage.

[0017] Preferably, the phosphorus doping method in step S4) is phosphorus diffusion; the phosphorus source during phosphorus diffusion is POCl3; the temperature is 800°C to 900°C; and the time is 5 to 10 minutes.

[0018] Preferably, the phosphorus doping method in step S4) is ion implantation; the ion implantation temperature is 450° C. to 550° C.; and the ion energy is 50 KeV to 150 KeV.

[0019] After the ion implantation, heat treatment is performed; the temperature of the heat treatment is 800° C. to 900° C.; and the time of the heat treatment is 10 to 15 minutes.

[0020] Preferably, in step S5), hydrofluoric acid is used to remove the glass layer on the surface of the phosphorus-doped P-type crystalline silicon.

[0021] Preferably, the step S6) is specifically as follows:

[0022] A passivation layer and an anti-reflection layer are sequentially formed on the surface of the P-type crystalline silicon after the glass layer is removed;

[0023] The thickness of the passivation layer is 5-20 nm; the thickness of the anti-reflection layer is 65-85 nm.

[0024] Preferably, the passivation layer is a silicon oxide layer or a silicon oxynitride layer; and the anti-reflection layer is a silicon nitride layer.

[0025] Preferably, the step S7) is specifically:

[0026] The back side of the P-type crystalline silicon forming the passivation layer and / or the anti-reflection layer is metallized with a burn-through silver-aluminum paste and a burn-through silver paste to obtain a P + P doped silicon contact + Electrode and N + N-doped silicon layer in contact + electrode.

[0027] The present invention provides a method for preparing a P-type IBC battery, comprising: S1) texturing the front surface of a P-type crystalline silicon substrate; S2) performing double-sided boron diffusion on the texturized P-type crystalline silicon to form a P-type crystalline silicon substrate on the surface of the P-type crystalline silicon substrate; + doped silicon layer and borosilicate glass layer; S3) removing the borosilicate glass layer in the local area on the back of the P-type crystalline silicon after double-sided boron diffusion, exposing the P + S4) removing the P-type crystalline silicon of the borosilicate glass layer in the local area and doping phosphorus so that phosphorus is doped into the bare P + N doped silicon layer + S5) removing the glass layer on the surface of the P-type crystalline silicon after the phosphorus doping; S6) forming a passivation layer and / or an anti-reflection layer on the surface of the P-type crystalline silicon after the glass layer is removed; S7) preparing the P-type crystalline silicon on the back side thereof respectively. + P doped silicon contact + Electrode and N + N-doped silicon layer in contact with phosphorus + Compared with the prior art, the present invention adopts double-sided boron diffusion technology to form a positive electrode. + The doped silicon layer can play a role in surface passivation. + The doped silicon layer can extract holes. The two functional layers are prepared in one step without edge insulation. + The doped silicon layers are connected together through the edges, which will not cause leakage. At the same time, the borosilicate glass layer generated by boron diffusion can be used as a barrier layer, so that when phosphorus is doped, phosphorus is only doped into the area where the borosilicate glass layer is removed, without the need to prepare an additional barrier layer. Furthermore, the phosphorus doping concentration is higher than the boron doping concentration, which can effectively prevent the P removal of the borosilicate glass layer. + Compensation doping is performed on the doped silicon region to convert it into N +Phosphorus-doped silicon can realize the preparation of P-type IBC cells. The preparation steps are simple and no photolithography technology is required, which can significantly reduce the cost of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 A schematic diagram of the structure of a P-type IBC battery provided by the present invention;

[0029] Figure 2 A schematic diagram of the preparation process of the P-type IBC battery provided by the present invention. DETAILED DESCRIPTION

[0030] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0031] The present invention provides a method for preparing a P-type IBC battery, comprising:

[0032] S1) forming texturing on the front side of the P-type crystalline silicon substrate;

[0033] S2) Perform double-sided boron diffusion on the P-type crystalline silicon after texturing to form a P + doped silicon layer and borosilicate glass layer;

[0034] S3) Remove the borosilicate glass layer in the local area on the back of the P-type crystalline silicon after double-sided boron diffusion, and expose the P + doping a silicon layer;

[0035] S4) Phosphorus is doped into the P-type crystalline silicon after the borosilicate glass layer in the local area is removed, so that phosphorus is doped into the bare P + N doped silicon layer + Phosphorus-doped silicon layer and phosphosilicate glass layer;

[0036] S5) removing the glass layer on the surface of the phosphorus-doped P-type crystalline silicon;

[0037] S6) forming a passivation layer and / or an anti-reflection layer on the surface of the P-type crystalline silicon after the glass layer is removed;

[0038] S7) on the back side of the P-type crystalline silicon formed with the passivation layer and / or the anti-reflection layer, respectively prepare + P doped silicon contact + Electrode and N + N-doped silicon layer in contact with phosphorus + electrode.

[0039] See also Figure 1 and Figure 2 ; Figure 1 A schematic diagram of the structure of a P-type IBC battery provided by the present invention; Figure 2 Schematic diagram of the preparation process of the P-type IBC battery provided by the present invention; wherein 1 is an anti-reflection layer, 2 is a passivation layer, 3 is a P + Doped silicon, 4 is P-type crystalline silicon substrate, 5 is N + Phosphorus-doped silicon, 6 for P + Electrode, 7 is N + electrode.

[0040] Texturing is performed on the front side of a P-type crystalline silicon substrate; in the present invention, it is preferred to cut and damage the P-type crystalline silicon substrate first, and then texturing is performed on the front side; the process for texturing the front side is a process well known to those skilled in the art, and there is no special limitation. In the present invention, it is preferred to place the front side of the P-type crystalline silicon substrate in a texturing liquid for texturing; the texturing liquid preferably includes a potassium hydroxide solution with a volume ratio of 2.5% to 3.1% and a texturing additive solution with a volume ratio of 0.5% to 0.7%; the texturing temperature is preferably 80°C to 85°C; the texturing time is preferably 5 to 10 minutes.

[0041] The P-type crystalline silicon after texturing is subjected to double-sided boron diffusion to form a P + doped silicon layer and borosilicate glass layer; in the present invention, the double-sided boron diffusion preferably uses BBr3 or BCl3 as the boron source; the boron diffusion temperature is preferably 950°C to 1050°C; the boron diffusion time is preferably 40 to 60 minutes.

[0042] After the double-sided boron diffusion, the borosilicate glass layer on the back of the P-type crystalline silicon is removed to expose the P + doped silicon layer; in the present invention, laser is preferably used to remove the borosilicate glass layer in the local area on the back side of the P-type crystalline silicon after double-sided boron diffusion; the local area is preferably in a forked shape on the back side of the P-type crystalline silicon; the area of ​​the local area is 40% to 50% of the total area of ​​the back side; in the present invention, after the borosilicate glass layer in the local area is removed by laser, it is preferably treated with alkali to remove laser damage; the alkali treatment is preferably specifically treated with potassium hydroxide solution; the mass concentration of the potassium hydroxide solution is preferably 1% to 3%; the temperature is 70 to 75°C; the treatment time is preferably 15 to 30s.

[0043] The P-type crystalline silicon with the borosilicate glass layer removed from the local area is doped with phosphorus so that phosphorus is doped into the bare P + N doped silicon layer +Phosphorus-doped silicon layer and phosphorus-silicon glass layer; the phosphorus doping method is preferably phosphorus diffusion or ion implantation; when phosphorus diffusion is used for doping, the phosphorus source is POCl3; the temperature is 800°C to 900°C; the time is 5 to 10 minutes; when ion implantation of phosphorus is used for phosphorus doping, the temperature during ion implantation is preferably 450°C to 550°C, more preferably 500°C; the ion energy is preferably 50KeV to 150KeV, more preferably 80KeV to 120KeV, and more preferably 100KeV; after ion implantation of phosphorus, heat treatment is preferably performed to activate N + The phosphorus atoms in phosphorus-doped silicon; the heat treatment temperature is preferably 800°C to 900°C, more preferably 850°C; the heat treatment time is preferably 10 to 15 minutes; since the concentration of diffused boron doping is only 10 19 , while the concentration of diffuse phosphorus can reach 10 20 After phosphorus compensates for boron, it still has a high concentration, revealing P + Boron-doped silicon is partially converted to N + Phosphorus-doped silicon, in N + There is also phosphosilicate glass formed when phosphorus is diffused on the surface of phosphorus-doped silicon, while in other areas, phosphorus cannot penetrate the borosilicate glass due to the obstruction of borosilicate glass.

[0044] Removing the glass layer on the surface of the phosphorus-doped P-type crystalline silicon; in the present invention, hydrofluoric acid is preferably used to remove the glass layer on the surface of the phosphorus-doped P-type crystalline silicon, including the borosilicate glass layer and the phosphosilicate glass layer.

[0045] A passivation layer and / or an anti-reflection layer is formed on the surface of the P-type crystalline silicon from which the glass layer is removed, that is, a passivation layer and / or an anti-reflection layer is formed on both sides of the P-type crystalline silicon from which the glass layer is removed; the thickness of the passivation layer is preferably 5-20 nm, more preferably 10-20 nm; the passivation layer is preferably a silicon oxide layer or a silicon oxynitride layer; the thickness of the anti-reflection layer is preferably 65-85 nm, more preferably 70-80 nm; the anti-reflection layer is preferably a silicon nitride layer; in the present invention, this step is preferably specifically to form a passivation layer and an anti-reflection layer in sequence on the surface of the P-type crystalline silicon from which the glass layer is removed; the method for forming the passivation layer and the anti-reflection layer is a method well known to those skilled in the art, and there is no special limitation. In the present invention, it is preferred to form the passivation layer by thermal oxidation or PECVD; it is preferred to form the anti-reflection layer by PECVD.

[0046] On the back side of the P-type crystalline silicon where the passivation layer and / or the anti-reflection layer is formed, the P + P doped silicon contact + Electrode and N + N-doped silicon layer in contact with phosphorus +Electrode; In the present invention, preferably, the back of the P-type crystalline silicon forming the passivation layer and / or the anti-reflection layer is metallized with a burn-through silver-aluminum paste and a burn-through silver paste to obtain a P + P doped silicon contact + Electrode and N + N-doped silicon layer in contact + electrode.

[0047] The present invention adopts double-sided boron diffusion technology to form a positive P + The doped silicon layer can play a role in surface passivation. + The doped silicon layer can extract holes. The two functional layers are prepared in one step without edge insulation. + The doped silicon layers are connected together through the edges, which will not cause leakage. At the same time, the borosilicate glass layer generated by boron diffusion can be used as a barrier layer, so that when phosphorus is doped, phosphorus is only doped into the area where the borosilicate glass layer is removed, without the need to prepare an additional barrier layer. Furthermore, the phosphorus doping concentration is higher than the boron doping concentration, which can effectively prevent the P removal of the borosilicate glass layer. + Compensation doping is performed on the doped silicon region to convert it into N + Phosphorus-doped silicon can realize the preparation of P-type IBC cells. The preparation steps are simple and no photolithography technology is required, which can significantly reduce the cost of the battery.

[0048] In order to further illustrate the present invention, a method for preparing a P-type IBC battery provided by the present invention is described in detail below in conjunction with embodiments.

[0049] The reagents used in the following examples are all commercially available; the manufacturer and model of the texturing additive used in the examples is Shichuang TS53-V19; the manufacturer and model of the burn-through silver aluminum paste used in the examples is Dico DK71A; the manufacturer and model of the burn-through silver paste used in the examples is Dico DK93T.

[0050] Example 1

[0051] S1: P-type silicon substrate 4 is de-cut and damaged, and the front surface is textured; the texture liquid includes potassium hydroxide and a texture additive, the volume concentration of potassium hydroxide is 2.8%, the volume concentration of the texture additive is 0.6%, the texture temperature is 80°C, and the texture time is 8 minutes. (For the convenience of display, the front texture is not drawn)

[0052] S2: Boron diffusion is performed on the P-type silicon substrate 4, and the boron diffusion is performed on both sides at the same time to form a P + Boron-doped silicon 3, and borosilicate glass 8 located on the surface; boron diffusion uses BBr3 as the boron source, the temperature is 1000°C, and the time is 50 minutes.

[0053] S3: Use laser to remove the borosilicate glass 8 in a local area on the back. The area is in the shape of interdigitated fingers and accounts for 40% of the total area of ​​the back, exposing P + Boron-doped silicon 3; after laser removal, it is treated with a potassium hydroxide solution with a mass concentration of 2% at 70°C for 20s to remove the laser damage on the exposed surface.

[0054] S4: Phosphorus diffusion, phosphorus incorporation into exposed P + In boron-doped silicon 3, the phosphorus source is POCl3, the temperature is 850℃, and the time is 7.5min. Since the concentration of diffused boron is only 10 to the 19th power, while the concentration of diffused phosphorus can reach 10 to the 20th power, phosphorus still has a higher concentration after compensating for boron, P + The exposed part of boron-doped silicon 3 is converted into N + Phosphorus-doped silicon 5. In N + There is also phosphosilicate glass 9 formed when phosphorus is diffused on the surface of phosphorus-doped silicon 5. In other areas, phosphorus cannot penetrate borosilicate glass 8 due to the obstruction of borosilicate glass 8.

[0055] S5: Remove the borosilicate glass 8 and the phosphosilicate glass 9 using hydrofluoric acid.

[0056] S6: Grow silicon oxide by thermal oxidation, and grow silicon oxide layers on both sides simultaneously to form a 10 nm passivation layer 2.

[0057] S7: Silicon nitride is deposited on both sides by PECVD to form a 70nm anti-reflection layer 1.

[0058] S8: Metallization is performed using a burn-through silver aluminum paste and a burn-through silver paste to obtain a P + The silver aluminum gate line 6 in contact with the boron-doped silicon 3 and the N + Silver grid lines 7 contacting phosphorus-doped silicon 5.

[0059] The P-type IBC battery obtained in Example 1 was tested for its performance, and the battery efficiency was found to be 23.2% to 23.4%, and the test standard was IEC 60904-1:2006.

[0060] Embodiment 2:

[0061] S1: P-type silicon substrate 4 is de-cut and damaged, and the front surface is textured; the texture liquid includes potassium hydroxide and a texture additive, the volume concentration of potassium hydroxide is 2.8%, the volume concentration of the texture additive is 0.6%, the texture temperature is 80°C, and the texture time is 8 minutes. (For the convenience of display, the front texture is not drawn)

[0062] S2: Boron diffusion is performed on the P-type silicon substrate 4, and the boron diffusion is performed on both sides at the same time to form a P + Boron-doped silicon 3, and borosilicate glass 8 located on the surface; boron diffusion uses BBr3 as the boron source, the temperature is 1000°C, and the time is 50 minutes.

[0063] S3: Use laser to remove the borosilicate glass 8 in a local area on the back. The area is in the shape of interdigitated fingers and accounts for 40% of the total area of ​​the back, exposing P + Boron-doped silicon 3. After laser removal, it was treated with a 2% potassium hydroxide solution at 70°C for 20s to remove the laser damage on the exposed surface.

[0064] S4: Phosphorus diffusion, phosphorus incorporation into exposed P + In boron-doped silicon 3, the phosphorus source is POCl3, the temperature is 850℃, and the time is 7.5min. Since the concentration of diffused boron is only 10 to the 19th power, while the concentration of diffused phosphorus can reach 10 to the 20th power, phosphorus still has a higher concentration after compensating for boron, P + The exposed part of boron-doped silicon 3 is converted into N + Phosphorus-doped silicon 5. In N + There is also phosphosilicate glass 9 formed when phosphorus is diffused on the surface of phosphorus-doped silicon 5. In other areas, phosphorus cannot penetrate borosilicate glass 8 due to the obstruction of borosilicate glass 8.

[0065] S5: Remove the borosilicate glass 8 and the phosphosilicate glass 9 using hydrofluoric acid.

[0066] S6: Silicon oxynitride and silicon nitride are sequentially deposited on both sides by PECVD method, wherein the silicon oxynitride is a 15 nm passivation layer 2 and the silicon nitride is a 70 nm anti-reflection layer 1.

[0067] S7: Metallization is performed using a burn-through silver aluminum paste and a burn-through silver paste to obtain a P + The silver aluminum gate line 6 in contact with the boron-doped silicon 3 and the N + Silver grid lines 7 contacting phosphorus-doped silicon 5.

[0068] The P-type IBC battery obtained in Example 2 was tested for its performance, and the battery efficiency was found to be 23.0%-23.2%, and the test standard was IEC 60904-1:2006.

[0069] Embodiment 3:

[0070] S1: P-type silicon substrate 4 is de-cut and damaged, and the front surface is textured; the texture liquid includes potassium hydroxide and a texture additive, the volume concentration of potassium hydroxide is 2.8%, the volume concentration of the texture additive is 0.6%, the texture temperature is 80°C, and the texture time is 8 minutes. (For the convenience of display, the front texture is not drawn)

[0071] S2: Boron diffusion is performed on the P-type silicon substrate 4, and the boron diffusion is performed on both sides at the same time to form a P + Boron-doped silicon 3, and borosilicate glass 8 located on the surface; boron diffusion uses BBr3 as the boron source, the temperature is 1000°C, and the time is 50 minutes.

[0072] S3: Use laser to remove the borosilicate glass 8 in a local area on the back side. The area is in the shape of interdigitated fingers and accounts for 50% of the total area of ​​the back side, exposing P + Boron-doped silicon 3. After laser removal, it was treated with a 2% potassium hydroxide solution at 70°C for 20s to remove the laser damage on the exposed surface.

[0073] S4: Phosphorus ion implantation, phosphorus implantation exposed P + In boron-doped silicon 3, the ion implantation temperature is 500°C and the ion energy is 100 KeV; since the concentration of diffused boron is only 10 to the 19th power, while the concentration of ion-implanted phosphorus can reach 10 to the 20th power, phosphorus still has a higher concentration after compensating for boron, P + The exposed part of boron-doped silicon 3 is converted into N + Phosphorus-doped silicon 5. In other areas, phosphorus cannot penetrate borosilicate glass 8 due to the obstruction of borosilicate glass 8. Heat treatment at 850℃ for 10min activates N + Phosphorus atoms in phosphorus-doped silicon 5.

[0074] S5: removing the borosilicate glass 8 using hydrofluoric acid.

[0075] S6: Grow silicon oxide by thermal oxidation, and grow silicon oxide layers on both sides simultaneously to form a 10 nm passivation layer 2.

[0076] S7: Silicon nitride is deposited on both sides by PECVD to form a 70nm anti-reflection layer 1.

[0077] S8: Metallization is performed using a burn-through silver aluminum paste and a burn-through silver paste to obtain a P + The silver aluminum gate line 6 in contact with the boron-doped silicon 3 and the N + Silver grid lines 7 contacting phosphorus-doped silicon 5.

[0078] The P-type IBC battery obtained in Example 3 was tested for its performance, and the battery efficiency was found to be 23.1% to 23.3%, and the test standard was IEC 60904-1:2006.

Claims

1. A method for preparing a P-type IBC battery, characterized in that: include: S1) forming texturing on the front side of the P-type crystalline silicon substrate; S2) Perform double-sided boron diffusion on the P-type crystalline silicon after texturing to form a P + doped silicon layer and borosilicate glass layer; S3) Remove the borosilicate glass layer in the local area on the back of the P-type crystalline silicon after double-sided boron diffusion, and expose the P + doping a silicon layer; S4) Phosphorus is doped into the P-type crystalline silicon after the borosilicate glass layer in the local area is removed, so that phosphorus is doped into the bare P + N doped silicon layer + Phosphorus-doped silicon layer and phosphosilicate glass layer; S5) removing the glass layer on the surface of the phosphorus-doped P-type crystalline silicon; S6) forming a passivation layer and / or an anti-reflection layer on the surface of the P-type crystalline silicon after the glass layer is removed; S7) on the back side of the P-type crystalline silicon formed with the passivation layer and / or the anti-reflection layer, respectively prepare + P doped silicon contact + Electrode and N + N-doped silicon layer in contact with phosphorus + electrode; In the step S2), the boron source for double-sided boron diffusion is BBr3 or BCl3; the temperature is 950°C to 1050°C; and the time is 40 to 60 minutes; The borosilicate glass layer on the back of the P-type crystalline silicon after double-sided boron diffusion is removed by laser, exposing the P + After doping the silicon layer, it is treated with alkali to remove the laser damage.

2. The preparation method according to claim 1, characterized in that: In the step S3), laser is used to remove the borosilicate glass layer in a local area on the back side of the P-type crystalline silicon after double-sided boron diffusion; the local area is in a forked finger shape.

3. The preparation method according to claim 1, characterized in that: The phosphorus doping method in step S4) is phosphorus diffusion; the phosphorus source during phosphorus diffusion is POCl3; the temperature is 800°C to 900°C; and the time is 5 to 10 minutes.

4. The preparation method according to claim 1, characterized in that: The phosphorus doping method in step S4) is ion implantation; the ion implantation temperature is 450° C. to 550° C.; the ion energy is 50 KeV to 150 KeV; After the ion implantation, heat treatment is performed; the temperature of the heat treatment is 800° C. to 900° C.; and the time of the heat treatment is 10 to 15 minutes.

5. The preparation method according to claim 1, characterized in that: In the step S5), hydrofluoric acid is used to remove the glass layer on the surface of the phosphorus-doped P-type crystalline silicon.

6. The preparation method according to claim 1, characterized in that: The step S6) is specifically as follows: A passivation layer and an anti-reflection layer are sequentially formed on the surface of the P-type crystalline silicon after the glass layer is removed; The thickness of the passivation layer is 5-20 nm; the thickness of the anti-reflection layer is 65-85 nm.

7. The preparation method according to claim 1, characterized in that: The passivation layer is a silicon oxide layer or a silicon oxynitride layer; and the anti-reflection layer is a silicon nitride layer.

8. The preparation method according to claim 1, characterized in that: The step S7) is specifically as follows: The back side of the P-type crystalline silicon forming the passivation layer and / or the anti-reflection layer is metallized with a burn-through silver-aluminum paste and a burn-through silver paste to obtain a P + P doped silicon contact + Electrode and N + N-doped silicon layer in contact + electrode.

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