TBC solar cell and preparation method thereof

Abstract

The invention relates to a TBC solar cell and a preparation method thereof. The preparation method comprises the following steps: carrying out primary double-sided polishing; forming a first tunneling oxide layer and a boron-doped polycrystalline silicon layer on two sides; performing first laser patterning on the back surface, and removing the borosilicate glass layers in the N region and the isolation region; performing double-sided polishing for the second time to remove the first tunneling oxide layer and the boron-doped polycrystalline silicon layer of the N region and the isolation region; forming a second tunneling oxide layer and a phosphorus-doped polycrystalline silicon layer on two sides; performing secondary laser patterning on the back surface, and removing the phosphorosilicate glass layers in the P region and the isolation region; performing wet etching on the front surface to remove all layers on the front surface, and removing a side surface winding plating layer; performing double-sided texturing, corroding a P region to a boron-doped polycrystalline silicon layer, corroding an N region to a phosphorus-doped polycrystalline silicon layer, corroding an isolation region to a silicon wafer, and forming a textured surface on the isolation region on the back surface of the silicon wafer and the front surface of the silicon wafer; depositing a passivation layer and an antireflection layer on two sides; and preparing a positive electrode in the back P region and preparing a negative electrode in the N region. The preparation method is simple in process and convenient to operate, and the conversion efficiency of the battery can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cells, and in particular to a TBC solar cell and a preparation method thereof. Background Art

[0002] TBC solar cells are cross-finger back contact solar cells combined with the excellent tunneling silicon oxide and doped polysilicon interface passivation technology of TOPCon solar cells, and are expected to achieve higher efficiency and performance, which is crucial for the next generation of solar energy solutions. However, the traditional TBC solar cell preparation method usually has the problem of bypass plating, the wet process is difficult, and the mask layer needs to be prepared. The process flow is relatively complicated and difficult to promote industrialization.

[0003] Therefore, there is an urgent need for a preparation method that is simple in process, easy to operate, and can improve the conversion efficiency of TBC solar cells. Summary of the invention

[0004] Based on this, it is necessary to provide a TBC solar cell and a preparation method thereof for the above problems. The preparation method of the present invention does not require the preparation of a mask layer, while reducing the risk of polysilicon layer plating, effectively simplifying the process, and is suitable for large-scale production. The prepared TBC solar cell has a high conversion efficiency.

[0005] A method for preparing a TBC solar cell comprises the following steps:

[0006] S1, performing the first double-sided polishing on the silicon wafer;

[0007] S2, forming a first tunneling oxide layer and a boron-doped polysilicon layer on both sides of the silicon wafer in sequence;

[0008] S3, performing the first laser patterning on the back side of the silicon wafer to remove the borosilicate glass layer in the N region and the isolation region;

[0009] S4, performing a second double-sided polishing on the silicon wafer to remove the first tunneling oxide layer and the boron-doped polysilicon layer in the N region and the isolation region;

[0010] S5, forming a second tunneling oxide layer and a phosphorus-doped polysilicon layer on both sides of the silicon wafer in sequence;

[0011] S6, performing a second laser patterning on the back side of the silicon wafer to remove the phosphorus silicon glass layer in the P region and the isolation region;

[0012] S7, wet-etching the front side of the silicon wafer to remove all layers on the front side;

[0013] S8, performing double-sided texturing on the silicon wafer, etching the P region on the back side to the boron-doped polysilicon layer, etching the N region to the phosphorus-doped polysilicon layer, etching the isolation region to the silicon wafer, and forming a texturing surface on the isolation region on the back side of the silicon wafer and the front side of the silicon wafer;

[0014] S9, depositing a passivation layer and an anti-reflection layer on both sides of the silicon wafer;

[0015] S10, preparing a positive electrode in the P region on the back of the silicon wafer and a negative electrode in the N region to obtain a TBC solar cell.

[0016] In one embodiment, the first tunneling oxide layer and the first intrinsic amorphous silicon layer are prepared by a low pressure chemical vapor deposition process, and the first intrinsic amorphous silicon layer is formed into the boron-doped polysilicon layer by boron diffusion and post-oxidation, and the process satisfies at least one of the following conditions:

[0017] (1) When depositing the first tunnel oxide layer, the flow rate of O2 is 20000 sccm to 50000 sccm, the deposition time is 5 min to 30 min, and the deposition temperature is 500° C. to 650° C.;

[0018] (2) When depositing the first intrinsic amorphous silicon layer, the SiH4 flow rate is 300 sccm to 2000 sccm, the deposition time is 50 min to 230 min, and the deposition temperature is 500° C. to 650° C.;

[0019] (3) During boron diffusion, the flow rate of BCl3 is 100 sccm to 300 sccm, the flow rate of O2 is 400 sccm to 1200 sccm, the diffusion time is 5 min to 15 min, and the diffusion temperature is 800 ° C to 900 ° C;

[0020] (4) During post-oxidation, the flow rate of O2 is 3000sccm~12000sccm, the oxidation time is 35min~60min, and the oxidation temperature is 900℃~1100℃.

[0021] In one embodiment, the second tunneling oxide layer and the second intrinsic amorphous silicon layer are prepared by a low pressure chemical vapor deposition process, and the second intrinsic amorphous silicon layer is formed into the phosphorus-doped polysilicon layer by phosphorus diffusion and post-oxidation, and the process satisfies at least one of the following conditions:

[0022] (1) When depositing the second tunnel oxide layer, the flow rate of O2 is 20000 sccm to 50000 sccm, the deposition time is 5 min to 30 min, and the deposition temperature is 500° C. to 650° C.;

[0023] (2) When depositing the second intrinsic amorphous silicon layer, the SiH4 flow rate is 300 sccm to 2000 sccm, the deposition time is 50 min to 230 min, and the deposition temperature is 500° C. to 650° C.;

[0024] (3) During phosphorus diffusion, the flow rate of POCl3 is 1000 sccm to 2000 sccm, the flow rate of O2 is 300 sccm to 800 sccm, the diffusion time is 10 min to 40 min, and the diffusion temperature is 750 ° C to 900 ° C;

[0025] (4) During post-oxidation, the flow rate of O2 is 1000sccm~5000sccm, the oxidation time is 35min~60min, and the oxidation temperature is 700℃~950℃.

[0026] In one embodiment, the thickness of the first tunnel oxide layer and the second tunnel oxide layer are independently selected from 1 nm to 4 nm.

[0027] In one embodiment, the thickness of the first tunnel oxide layer is greater than the thickness of the second tunnel oxide layer.

[0028] In one embodiment, the thickness of the boron-doped polysilicon layer and the phosphorus-doped polysilicon layer are independently selected from 150 nm to 450 nm.

[0029] In one embodiment, the thickness of the boron-doped polysilicon layer is greater than the thickness of the phosphorus-doped polysilicon layer.

[0030] In one embodiment, the doping concentration of the boron-doped polysilicon layer is 1E19 cm -3 ~8E19cm -3 ;

[0031] And / or, the doping concentration of the phosphorus-doped polysilicon layer is 1E20cm -3 ~8E20cm -3 .

[0032] In one embodiment, the thickness of the front passivation layer and the back passivation layer are independently selected from 2 nm to 5 nm;

[0033] and / or, the thickness of the front anti-reflection layer is selected from 65 nm to 85 nm;

[0034] And / or, the thickness of the back anti-reflection layer is selected from 70 nm to 95 nm.

[0035] A TBC solar cell manufactured by the manufacturing method as described above.

[0036] The above preparation method improves the symmetry of the structure by depositing the tunneling oxide layer and the doped polysilicon layer on both sides, reduces the risk of doped polysilicon layer bypass plating, and reduces the difficulty of the wet process. At the same time, through laser patterning and wet etching, the preparation of TBC solar cells can be achieved without preparing a mask layer, which effectively simplifies the process flow. In addition, the prepared TBC solar cell has high conversion performance and is suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0038] Figure 1 This is a schematic diagram of the structure of a TBC solar cell manufactured according to one embodiment of the present invention;

[0039] Figure 2 This is a schematic diagram of the structure of a TBC solar cell obtained in step S4 in one embodiment of the present invention;

[0040] Figure 3 This is a schematic diagram of the structure of a TBC solar cell obtained in step S6 in one embodiment of the present invention;

[0041] Figure 4 Schematic diagram of the TBC solar cell structure obtained in step S8 in one embodiment of the present invention.

[0042] Figure numerals: 1-silicon wafer; 21-first tunneling oxide layer; 22-second tunneling oxide layer; 3-boron-doped polysilicon layer; 4-boron-silicate glass layer; 5-phosphorus-doped polysilicon layer; 6-phosphorus-silicate glass layer; 7-passivation layer; 8-anti-reflection layer; 9-positive electrode; 10-negative electrode. DETAILED DESCRIPTION

[0043] For ease of understanding of the present invention, the present invention will be described in more detail below. However, it should be understood that the present invention can be implemented in many different forms and is not limited to the embodiments or examples described herein. On the contrary, the purpose of providing these embodiments or examples is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0044] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific implementation methods or embodiments, and are not intended to limit the present invention. The optional scope of the term "and / or" used herein includes any one of two or more related listed items, and also includes any and all combinations of related listed items, and the combinations include any two related listed items, any more related listed items, or all related listed items.

[0045] like Figure 1 As shown, a TBC solar cell is prepared in one embodiment of the present invention, and its preparation method comprises the following steps:

[0046] S1, performing double-sided polishing on silicon wafer 1 for the first time;

[0047] S2, forming a first tunnel oxide layer 21 and a boron-doped polysilicon layer 3 on both sides of the silicon wafer 1 in sequence;

[0048] S3, performing the first laser patterning on the back side of the silicon wafer 1 to remove the borosilicate glass layer 4 in the N region and the isolation region;

[0049] S4, performing a second double-sided polishing on the silicon wafer 1 to remove the first tunneling oxide layer 21 and the boron-doped polysilicon layer 3 in the N region and the isolation region;

[0050] S5, forming a second tunneling oxide layer 22 and a phosphorus-doped polysilicon layer 5 on both sides of the silicon wafer 1 in sequence;

[0051] S6, performing a second laser patterning on the back side of the silicon wafer 1 to remove the phosphorus silicon glass layer 6 in the P region and the isolation region;

[0052] S7, wet-etching the front side of the silicon wafer 1 to remove all layers on the front side;

[0053] S8, performing double-sided texturing on the silicon wafer 1, etching the P region on the back side to the boron-doped polysilicon layer 3, etching the N region to the phosphorus-doped polysilicon layer 5, etching the isolation region to the silicon wafer 1, and forming a texturing surface on the isolation region on the back side of the silicon wafer and the front side of the silicon wafer;

[0054] S9, depositing a passivation layer 7 and an anti-reflection layer 8 on both sides of the silicon wafer;

[0055] S10, preparing a positive electrode 9 in the P region and a negative electrode 10 in the N region on the back of the silicon wafer to obtain a TBC solar cell.

[0056] The above preparation method improves the symmetry of the structure by depositing the tunneling oxide layer and the doped polysilicon layer on both sides, reduces the risk of doped polysilicon layer bypass plating, and reduces the difficulty of the wet process. At the same time, through laser patterning and wet etching, the preparation of TBC solar cells can be achieved without preparing a mask layer, which effectively simplifies the process flow and is suitable for large-scale production.

[0057] It can be understood that the back side of the silicon wafer 1 includes an N region, a P region and an isolation region, wherein the gap between the N region and the P region is the isolation region; the silicon wafer 1 is preferably an N-type silicon wafer.

[0058] In step S2, a first tunneling oxide layer 21 and a boron-doped polysilicon layer 3 are formed on both sides of the silicon wafer 1, the structure has strong symmetry, the preparation process is simple, and the risk of plating around the boron-doped polysilicon layer 3 is effectively reduced. In order to improve the stability of the first tunneling oxide layer 21 and the boron-doped polysilicon layer 3, avoid the film explosion phenomenon, and improve the quality of the film, the present invention preferably adopts a low-pressure chemical vapor deposition (LPCVD deposition) process to prepare the first tunneling oxide layer 21 and the first intrinsic amorphous silicon layer.

[0059] Specifically, the first tunneling oxide layer 21 and the first intrinsic amorphous silicon layer are deposited by LPCVD, and the first intrinsic amorphous silicon layer is formed into the boron-doped polysilicon layer 3 by boron diffusion and post-oxidation. When depositing the first tunneling oxide layer, the flow rate of O2 is 20000sccm~50000sccm, the deposition time is 5min~30min, and the deposition temperature is 500℃~650℃; when depositing the first intrinsic amorphous silicon layer, the flow rate of SiH4 is 300sccm~2000sccm, and the deposition time is 5min~30min. The time is 50min~230min, and the deposition temperature is 500℃~650℃; during boron diffusion, the flow rate of BCl3 is 100sccm~300sccm, the flow rate of O2 is 400sccm~1200sccm, the diffusion time is 5min~15min, and the diffusion temperature is 800℃~900℃; during post-oxidation, the flow rate of O2 is 3000sccm~12000sccm, the oxidation time is 35min~60min, and the oxidation temperature is 900℃~1100℃.

[0060] In one embodiment, the thickness of the first tunnel oxide layer 21 is 1 nm to 4 nm, including but not limited to any value among 1 nm, 1.2 nm, 1.5 nm, 2 nm, 2.5 nm, 3 nm, and 4 nm, or a range between any two values.

[0061] In one embodiment, the boron-doped polysilicon layer 3 has a thickness of 150 nm to 450 nm, including but not limited to any value among 150 nm, 180 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, and 450 nm, or a range between any two values.

[0062] In one embodiment, the doping concentration of the boron-doped polysilicon layer 3 is 1E19 cm -3 ~8E19cm -3 .

[0063] like Figure 2 As shown, it is a schematic diagram of the solar cell structure prepared in step S4 in one embodiment of the present invention. In steps S3 and S4, the borosilicate glass layer 4 in the N region and the isolation region on the back is first removed by the first laser patterning, so that during double-sided polishing, the borosilicate glass layer 4 in the N region and the isolation region on the back is removed, while the P region on the back and the front are not corroded under the protection of the borosilicate glass layer 4.

[0064] In one embodiment, in the first laser patterning step, the laser is selected from nanosecond laser, picosecond laser or femtosecond laser, and the laser power is selected from 30W to 100W.

[0065] In step S5 , a second tunneling oxide layer 22 and a phosphorus-doped polysilicon layer 5 are formed on both sides of the silicon wafer 1 . The structure has strong symmetry, the preparation process is simple, and the risk of bypass plating of the phosphorus-doped polysilicon layer 5 is effectively reduced.

[0066] Preferably, the second tunnel oxide layer 22 and the second intrinsic amorphous silicon layer are deposited by LPCVD, which is beneficial to control the chemical composition and microstructure of the second tunnel oxide layer 22 and the second intrinsic amorphous silicon layer film, improve the uniformity and quality of the film, and avoid film explosion.

[0067] Specifically, the second tunneling oxide layer 22 and the second intrinsic amorphous silicon layer are deposited by LPCVD, and the second intrinsic amorphous silicon layer is formed into the phosphorus-doped polysilicon layer 5 by phosphorus diffusion and post-oxidation. When depositing the second tunneling oxide layer 22, the flow rate of O2 is 20000sccm~50000sccm, the deposition time is 5min~30min, and the deposition temperature is 500℃~650℃; when depositing the second intrinsic amorphous silicon layer, the flow rate of SiH4 is 300sccm~2000sccm, and the deposition time is 5min~30min. The time is 50min~230min, and the deposition temperature is 500℃~650℃; during phosphorus diffusion, the flow rate of POCl3 is 1000sccm~2000sccm, the flow rate of O2 is 300sccm~800sccm, the diffusion time is 10min~40min, and the diffusion temperature is 750℃~900℃; during post-oxidation, the flow rate of O2 is 1000sccm~5000sccm, the oxidation time is 35min~60min, and the oxidation temperature is 700℃~950℃.

[0068] In one embodiment, the thickness of the second tunnel oxide layer 22 is 1 nm to 4 nm, including but not limited to any value among 1 nm, 1.2 nm, 1.5 nm, 2 nm, 2.5 nm, 3 nm, and 4 nm, or a range between any two values.

[0069] Preferably, the thickness of the first tunnel oxide layer 21 is greater than the thickness of the second tunnel oxide layer 22, which is beneficial to improving the passivation performance of the manufactured TBC solar cell and improving the cell conversion efficiency.

[0070] In one embodiment, the thickness of the phosphorus-doped polysilicon layer 5 is 150 nm to 450 nm, including but not limited to any point value among 150 nm, 180 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm or any range value between two thereof.

[0071] Preferably, the thickness of the boron-doped polysilicon layer 3 is greater than the thickness of the phosphorus-doped polysilicon layer 5, which is beneficial to improving the contact performance of the manufactured TBC solar cell and improving the cell conversion efficiency.

[0072] Specifically, the doping concentration of the phosphorus-doped polysilicon layer 5 is 1E20cm -3 ~8E20cm -3 .

[0073] like Figure 3 As shown, it is a schematic diagram of the structure of the solar cell prepared in step S6 in one embodiment of the present invention. The phosphosilicate glass layer 6 in the P region and the isolation region on the back is removed by a second laser patterning, so that in the subsequent alkali texturing step, the second tunneling oxide layer 22 and the phosphorus-doped polysilicon layer 5 in the P region and the isolation region can be effectively removed, while the second tunneling oxide layer 22 and the phosphorus-doped polysilicon layer 5 in the N region will not be corroded under the protection of the phosphosilicate glass layer 6.

[0074] In one embodiment, in the second laser patterning step, the laser is selected from nanosecond laser, picosecond laser or femtosecond laser, and the laser power is selected from 30W to 100W.

[0075] In step S7, all layers grown on the front side of the silicon wafer 1 are removed by wet etching, including the first tunneling oxide layer 21, the boron-doped polysilicon layer 3, the borosilicate glass layer 4, the second tunneling oxide layer 22, the phosphorus-doped polysilicon layer 5, and the phosphorus-silicate glass layer 6. It should be noted that the plating layer grown on the side of the silicon wafer 1 can also be removed during the front side wet etching, and the wet etching adopts the conventional method of the industry, which will not be described in detail in the present invention.

[0076] like Figure 4As shown, it is a schematic diagram of the structure of the solar cell obtained in step S8 in one embodiment of the present invention, and step 8 includes: performing alkali texturing on both sides of the silicon wafer 1, etching the P region on the back to the borosilicate glass layer 4, etching the isolation region to the silicon wafer 1, and forming a velvet surface on the isolation region on the back of the silicon wafer 1 and the front of the silicon wafer 1; performing acid etching on the back of the silicon wafer 1, removing the borosilicate glass layer 4 in the P region and the phosphorus silicon glass layer 6 in the N region. Thus, tunneling oxide layer passivation contact of the P region and the N region is achieved without constructing a mask layer.

[0077] It should be noted that step S9 and step S10 can be prepared according to the existing method, which will not be elaborated in the present invention. The present invention has no special restrictions on the thickness and material of the passivation layer 7 and the anti-reflection layer 8.

[0078] Specifically, the thickness of the front passivation layer 7 and the back passivation layer 7 are independently selected from 2 nm to 5 nm. The thickness of the front passivation layer 7 and the back passivation layer 7 may be the same or different.

[0079] Specifically, the thickness of the front anti-reflection layer 8 is selected from 65 nm to 85 nm.

[0080] Specifically, the thickness of the back anti-reflection layer 8 is selected from 70 nm to 95 nm.

[0081] The present invention also provides a TBC solar cell prepared by the preparation method as described above, wherein the tunneling oxide layer and the doped polysilicon layer thin film in the TBC solar cell have good uniformity and excellent passivation performance, and the TBC solar cell has high conversion efficiency, high opening voltage and high current density.

[0082] The TBC solar cell and its preparation method will be further described below through the following specific examples. However, those skilled in the art will understand that the following examples are only used to illustrate the present invention and should not be considered to limit the scope of the present invention. If no specific conditions are specified in the examples, the conventional conditions or the conditions recommended by the manufacturer are followed. The reagents or instruments used without indicating the manufacturer are all conventional products that can be purchased commercially.

[0083] Example 1

[0084] S1. Perform the first double-sided polishing process on the silicon wafer.

[0085] S2, depositing the double sides of the silicon wafer after step S1 by LPCVD, depositing tunneling oxide layers on both sides of the silicon wafer, wherein the flow rate of O2 is 50000sccm, the deposition time is 5min, and the deposition temperature is 600°C; then depositing intrinsic amorphous silicon layers on both sides of the silicon wafer, wherein the flow rate of SiH4 is 700sccm, the deposition time is 230min, and the deposition temperature is 600°C; sending the silicon wafer into a boron diffusion furnace for double-sided boron doping, wherein the flow rate of BCl3 is 300sccm, the flow rate of O2 is 1200sccm, the diffusion time is 5min, and the diffusion temperature is 850°C; then sending the silicon wafer into a high-temperature oxidation furnace for high-temperature oxidation to form a double-sided boron-doped polysilicon layer, wherein the flow rate of O2 is 12000sccm, the oxidation time is 35min, and the oxidation temperature is 1000°C; the thickness of the first tunneling oxide layer formed is 2nm, the thickness of the boron-doped polysilicon layer is 250nm, and the doping concentration of the boron diffusion is 2E19cm -3 .

[0086] S3, performing the first laser patterning on the back side of the silicon wafer after step S2 to remove the borosilicate glass layer in the N region and the isolation region, with a laser power of 50W.

[0087] S4, performing a second double-sided polishing on the silicon wafer after step S3 to remove the first tunneling oxide layer and the boron-doped polysilicon layer in the N region and the isolation region.

[0088] S5. Deposit the double sides of the silicon wafer after step S4 by LPCVD, deposit tunneling oxide layers on both sides of the silicon wafer, wherein the flow rate of O2 is 40000sccm, the deposition time is 5min, and the deposition temperature is 610°C; then deposit intrinsic amorphous silicon layers on both sides of the silicon wafer, wherein the flow rate of SiH4 is 1000sccm, the deposition time is 50min, and the deposition temperature is 615°C; send the silicon wafer into a phosphorus diffusion furnace for double-sided phosphorus doping, wherein the flow rate of POCl3 is 1600sccm, the flow rate of O2 is 600sccm, the diffusion time is 20min, and the diffusion temperature is 830°C; then send the silicon wafer into a high-temperature oxidation furnace for high-temperature oxidation to form a double-sided phosphorus-doped polysilicon layer, wherein the flow rate of O2 is 3000sccm, the oxidation time is 45min, and the oxidation temperature is 900°C; the thickness of the second tunneling oxide layer formed is 1.2nm, the thickness of the phosphorus-doped polysilicon layer is 200nm, and the doping concentration of phosphorus diffusion is 2E20cm -3 .

[0089] S6. Perform a second laser patterning on the back side of the silicon wafer after step S5 to remove the phosphorus silicon glass layer in the P region and the isolation region. The laser power is 50W.

[0090] S7, wet-etching the front side of the silicon wafer after step S6 to clean the front side to the silicon substrate.

[0091] S8. Perform alkali texturing on both sides of the silicon wafer after step S7, etch the back P area to the borosilicate glass layer, etch the isolation area to the silicon substrate, and form a pyramid texture surface on the back isolation area and the front side, then perform acid etching on the back side of the silicon wafer to remove the borosilicate glass layer in the P area and the phosphosilicate glass layer in the N area.

[0092] S9. After step S8, Al2O3 layers and silicon nitride layers are sequentially deposited on both sides of the silicon wafer. The thickness of the Al2O3 layers on both sides is 4nm, the thickness of the front silicon nitride layer is 75nm, and the thickness of the back silicon nitride layer is 85nm.

[0093] S10, printing a positive electrode and a negative electrode on the back of the silicon wafer treated in step S9, and sintering to form an ohmic contact, thereby manufacturing a TBC solar cell.

[0094] Example 2

[0095] The difference between Example 2 and Example 1 is that in step S2, the silicon wafer is sent into a boron diffusion furnace for double-sided boron doping, wherein the flow rate of BCl3 is 300sccm, the flow rate of O2 is 1200sccm, the diffusion time is 15min, and the diffusion temperature is 880°C; the thickness of the first tunneling oxide layer formed is 2nm, the thickness of the boron-doped polysilicon layer is 250nm, and the doping concentration of the boron diffusion is 4.5E19cm -3 .

[0096] In step S5, the silicon wafer is sent into a phosphorus diffusion furnace for double-sided phosphorus doping, wherein the flow rate of POCl3 is 1800sccm, the flow rate of O2 is 600sccm, the diffusion time is 20min, and the diffusion temperature is 830°C; the thickness of the second tunneling oxide layer formed is 1.2nm, the thickness of the phosphorus-doped polysilicon layer is 200nm, and the doping concentration of phosphorus diffusion is 3.1E20cm -3 .

[0097] Example 3

[0098] The difference between Example 3 and Example 1 is that in step S2, when the intrinsic amorphous silicon layer is deposited on both sides of the silicon wafer, the flow rate of SiH4 is 300sccm, the deposition time is 230min, and the deposition temperature is 580°C; the thickness of the first tunneling oxide layer formed is 2nm, the thickness of the boron-doped polysilicon layer is 200nm, and the doping concentration of the boron diffusion is 2E19cm -3 .

[0099] In step S5, the silicon wafer is sent into a phosphorus diffusion furnace for double-sided phosphorus doping, wherein the flow rate of POCl3 is 1600sccm, the flow rate of O2 is 600sccm, the diffusion time is 35min, and the diffusion temperature is 840°C; the thickness of the second tunneling oxide layer formed is 1.2nm, the thickness of the phosphorus-doped polysilicon layer is 200nm, and the doping concentration of phosphorus diffusion is 3.5E20cm -3 .

[0100] The performance of the TBC solar cells prepared in Examples 1 to 3 was tested using a Halm tester to measure the open circuit voltage (Voc), short circuit current density (Jsc), fill factor (FF) and conversion efficiency (Eta). All test results are shown in Table 1.

[0101] Table 1

[0102] Voc(mV) <![CDATA[Jsc(mA / cm 2 )]]> FF(%) Eta(%) Example 1 745.00 43.00 83.41 26.72 Example 2 744.00 42.70 83.25 26.45 Example 3 743.00 42.20 83.15 26.07

[0103] According to the results in Table 1, the TBC solar cell prepared by the present invention has a high cell conversion efficiency, and has a high open circuit voltage and short circuit current density, and a low fill factor. In summary, the TBC solar cell preparation method of the present invention does not require the preparation of a mask layer, while reducing the risk of polysilicon layer winding plating, effectively simplifying the process, and is suitable for large-scale production. The prepared TBC solar cell has a high conversion efficiency and has a wide range of application prospects.

[0104] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0105] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for preparing a TBC solar cell, characterized in that: The preparation method comprises the following steps: S1, performing the first double-sided polishing on the silicon wafer; S2, forming a first tunneling oxide layer and a boron-doped polysilicon layer on both sides of the silicon wafer in sequence; S3, performing the first laser patterning on the back side of the silicon wafer to remove the borosilicate glass layer in the N region and the isolation region; S4, performing a second double-sided polishing on the silicon wafer to remove the first tunneling oxide layer and the boron-doped polysilicon layer in the N region and the isolation region; S5, forming a second tunneling oxide layer and a phosphorus-doped polysilicon layer on both sides of the silicon wafer in sequence; S6, performing a second laser patterning on the back side of the silicon wafer to remove the phosphorus silicon glass layer in the P region and the isolation region; S7, wet-etching the front side of the silicon wafer to remove all layers on the front side; S8, performing double-sided texturing on the silicon wafer, etching the P region on the back side to the boron-doped polysilicon layer, etching the N region to the phosphorus-doped polysilicon layer, etching the isolation region to the silicon wafer, and forming a texturing surface on the isolation region on the back side of the silicon wafer and the front side of the silicon wafer; S9, depositing a passivation layer and an anti-reflection layer on both sides of the silicon wafer; S10, preparing a positive electrode in the P region on the back of the silicon wafer and a negative electrode in the N region to obtain a TBC solar cell.

2. The method for preparing a TBC solar cell according to claim 1, characterized in that: The first tunneling oxide layer and the first intrinsic amorphous silicon layer are prepared by a low-pressure chemical vapor deposition process, and the first intrinsic amorphous silicon layer is formed into the boron-doped polysilicon layer by boron diffusion and post-oxidation, and the process satisfies at least one of the following conditions: (1) When depositing the first tunnel oxide layer, the flow rate of O2 is 20000 sccm to 50000 sccm, the deposition time is 5 min to 30 min, and the deposition temperature is 500° C. to 650° C.; (2) When depositing the first intrinsic amorphous silicon layer, the SiH4 flow rate is 300 sccm to 2000 sccm, the deposition time is 50 min to 230 min, and the deposition temperature is 500° C. to 650° C.; (3) During boron diffusion, the flow rate of BCl3 is 100 sccm to 300 sccm, the flow rate of O2 is 400 sccm to 1200 sccm, the diffusion time is 5 min to 15 min, and the diffusion temperature is 800 ° C to 900 ° C; (4) During post-oxidation, the flow rate of O2 is 3000sccm~12000sccm, the oxidation time is 35min~60min, and the oxidation temperature is 900℃~1100℃.

3. The method for preparing a TBC solar cell according to claim 1, characterized in that: The second tunneling oxide layer and the second intrinsic amorphous silicon layer are prepared by a low-pressure chemical vapor deposition process, and the second intrinsic amorphous silicon layer is formed into the phosphorus-doped polysilicon layer by phosphorus diffusion and post-oxidation, and the process satisfies at least one of the following conditions: (1) When depositing the second tunnel oxide layer, the flow rate of O2 is 20000 sccm to 50000 sccm, the deposition time is 5 min to 30 min, and the deposition temperature is 500° C. to 650° C.; (2) When depositing the second intrinsic amorphous silicon layer, the SiH4 flow rate is 300 sccm to 2000 sccm, the deposition time is 50 min to 230 min, and the deposition temperature is 500° C. to 650° C.; (3) During phosphorus diffusion, the flow rate of POCl3 is 1000 sccm to 2000 sccm, the flow rate of O2 is 300 sccm to 800 sccm, the diffusion time is 10 min to 40 min, and the diffusion temperature is 750 ° C to 900 ° C; (4) During post-oxidation, the flow rate of O2 is 1000sccm~5000sccm, the oxidation time is 35min~60min, and the oxidation temperature is 700℃~950℃.

4. The method for preparing a TBC solar cell according to claim 1, characterized in that: The thickness of the first tunnel oxide layer and the second tunnel oxide layer are each independently selected from 1 nm to 4 nm.

5. The method for preparing a TBC solar cell according to claim 4, characterized in that: The thickness of the first tunnel oxide layer is greater than the thickness of the second tunnel oxide layer.

6. The method for preparing a TBC solar cell according to claim 1, characterized in that: The thickness of the boron-doped polysilicon layer and the phosphorus-doped polysilicon layer are independently selected from 150 nm to 450 nm.

7. The method for preparing a TBC solar cell according to claim 6, characterized in that: The thickness of the boron-doped polysilicon layer is greater than the thickness of the phosphorus-doped polysilicon layer.

8. The method for preparing a TBC solar cell according to claim 1, characterized in that: The doping concentration of the boron-doped polysilicon layer is 1E19 cm -3 ~8E19cm -3 ; And / or, the doping concentration of the phosphorus-doped polysilicon layer is 1E20cm -3 ~8E20cm -3 .

9. The method for preparing a TBC solar cell according to claim 1, characterized in that: The thickness of the passivation layer on the front and back sides is independently selected from 2nm to 5nm; And / or, the thickness of the anti-reflection layer on the front side is selected from 65nm to 85nm; And / or, the thickness of the anti-reflection layer on the back side is selected from 70 nm to 95 nm.

10. A TBC solar cell manufactured by the method according to any one of claims 1 to 9.

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