TBC solar cell and preparation method thereof

Abstract

The invention relates to the technical field of solar cells, and particularly discloses a TBC solar cell structure and a preparation method thereof, and the preparation method comprises the steps of double-sided polishing, deposition and diffusion, laser treatment, etching treatment, acid pickling and texturing, deposition passivation and antireflection film, screen printing of an electrode, sintering and the like on a silicon wafer. Wherein the laser processing comprises at least one of a BSG layer process of a non-metal electrode area of a laser scanning P area and a PSG layer process of a non-metal electrode area of a laser scanning N area. According to the TBC solar cell, the secondary process is carried out on the non-metal electrode area on the back face of the cell piece through the laser, effective thinning of the poly layer of the non-metal electrode area of the TBC solar cell is achieved, the problems of optical parasitic absorption and current loss caused by the fact that the poly layer is too thick in the prior art are solved, and the conversion efficiency and the overall performance of the cell are 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] As solar cell technology continues to develop, improving cell performance and conversion efficiency has always been the core research goal.

[0003] The combination of tunneling oxide layer and poly layer plays an important role in the field of photovoltaic cells. From PERC cells to TOPCON cells, it shows significant advantages in promoting the separation of electrons and holes and reducing the recombination of minority carriers, thereby promoting the improvement of cell conversion efficiency.

[0004] As a new type of photovoltaic cell technology, TBC (Tunnel Back Contact) solar cells (IBC (Interdigitated Back Contact) cells and TOPcon (Tunnel Oxide Passivated Contact) cells are stacked to form TBC solar cells) have many advantages due to their unique structural design, which places the positive and negative poles on the back of the cell and draws out the current through the tunnel structure.

[0005] The feature of no grid lines on the front not only makes it beautiful in appearance, but also avoids the grid lines blocking the light. Compared with other traditional photovoltaic cells, it has greater potential for improvement in efficiency and is extremely competitive in the future solar energy market.

[0006] However, the current mainstream TBC solar cell preparation technology generally adopts the method of constructing a tunneling oxide layer and a thicker poly layer in both the P region and the N region in pursuit of high efficiency.

[0007] Although the thicker poly layer helps to improve battery performance to a certain extent, it also brings problems such as excessive optical parasitic absorption and current loss, and there are still deficiencies in the research and solutions to these problems. Summary of the invention

[0008] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a TBC solar cell and a method for preparing the same, which solves the problems of optical parasitic absorption and current loss in the prior art and improves the cell performance by optimizing the preparation process and thinning the poly layer in the non-metallic electrode area on the back of the cell.

[0009] In order to achieve the above object, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for preparing a TBC solar cell, comprising the following steps: (1) Silicon wafer pretreatment: double-sided polishing of silicon wafers; (2) First deposition and diffusion: depositing a first tunneling oxide layer and a first polysilicon layer on the back of the silicon wafer, and performing boron diffusion to form a P-type passivation contact layer, and forming a BSG layer on the surface of the P-type passivation contact layer; (3) The first laser treatment: using laser to process part of the back side of the silicon wafer, including laser excavation of the N+GAP area; (4) Etching treatment: Etching the back of the silicon wafer using alkaline solution; (5) Second deposition and diffusion: depositing a second tunneling oxide layer and a second polysilicon layer on the back of the silicon wafer, and performing phosphorus diffusion to form an N-type passivation contact layer, and forming a PSG layer on the surface of the N-type passivation contact layer; (6) Second laser treatment: Use laser to treat the area on the back of the silicon wafer that has not been treated by the first laser treatment, including laser scanning of the P+GAP area; (7) Pickling and texturing: Pickle the silicon wafer, and after pickling, texturing the front side of the silicon wafer; (8) Post-processing: Deposition of ALO on the silicon wafer surface x Passivation layer and SiN x Anti-reflection layer, screen printing electrode, sintering, and light injection test; The laser processing further includes at least one of the following processes: a BSG layer process of laser scanning the non-metal electrode region of the P region in step (3) and a PSG layer process of laser scanning the non-metal electrode region of the N region in step (6).

[0010] N: phosphorus diffusion area, P: boron diffusion area, GAP: PN area junction isolation area.

[0011] Furthermore, in the step (2), the thickness of the first tunnel oxide layer is 1 nm-3 nm, and the thickness of the first polysilicon layer is 350 nm-550 nm.

[0012] Preferably, the first tunnel oxide layer and the first polysilicon layer are formed by sequentially depositing on the back side of the silicon wafer using a low pressure chemical vapor deposition method.

[0013] Furthermore, the step (3) comprises: first using laser ① to carve out an N+GAP area on the back side of the silicon wafer, and then using laser ② to scan the BSG layer in the non-metallic electrode area of ​​the P area; wherein the parameters of the laser ① are: wavelength 300nm-1100nm, frequency 500kHz-1000kHz, scanning speed 50m / s-200m / s, power 50W-100W; the parameters of the laser ② are: wavelength 200nm-1100nm, frequency 200kHz-600kHz, scanning speed 10m / s-80m / s, power 10W-80W.

[0014] Preferably, the laser ① and the laser ② are two groups of lasers from the same laser.

[0015] Furthermore, the step (5) includes: depositing a second tunnel oxide layer and a second polysilicon layer in sequence on the back side of the silicon wafer by low pressure chemical vapor deposition, and performing phosphorus diffusion on this basis, so that the second tunnel oxide layer, the second polysilicon layer and the PSG layer formed by the phosphorus diffusion are suspended on the BSG layer formed in the step (2) on the P region.

[0016] Furthermore, in the step (5), the thickness of the second tunnel oxide layer is 1 nm-3 nm, and the thickness of the second polysilicon layer is 250 nm-450 nm.

[0017] Furthermore, step (6) comprises: firstly using laser ③ to scan the P+GAP region on the back side of the silicon wafer, and then using laser ④ to scan the PSG layer in the non-metallic electrode region of the N region; wherein the parameters of laser ③ are: wavelength 300nm-1100nm, frequency 200kHz-1000kHz, scanning speed 10m / s-100m / s, power 30W-70W; the parameters of laser ④ are: wavelength 300nm-1100nm, frequency 100kHz-500kHz, scanning speed 5m / s-40m / s, power 10W-40W.

[0018] Preferably, the laser ③ and the laser ④ are two groups of lasers from the same laser.

[0019] Furthermore, the pickling in step (7) includes using HF with a concentration of 1%-50% to remove the PSG layer, BSG layer and oxide layer and polysilicon layer in the P region, N region and GAP region on the back side of the silicon wafer and the thinned area of ​​the non-metallic region.

[0020] Furthermore, in step (8), AlO x The thickness of the passivation layer is 1nm-10nm, SiN x The thickness of the anti-reflection layer is 20nm-200nm; the material of the electrode is one or a combination of silver, aluminum and copper; and the sintering temperature is 600℃-900℃.

[0021] In a second aspect, the present invention provides a TBC solar cell, wherein the TBC solar cell is prepared by the aforementioned TBC solar cell preparation method.

[0022] Furthermore, the thickness of the first polysilicon layer in the P-region non-metallic electrode area on the back of the battery is 100nm-180nm, and the thickness of the second polysilicon layer in the N-region non-metallic electrode area is 50nm-150nm.

[0023] In the prior art, the thickness of the poly layer in the P-zone non-metallic electrode area on the back of the TBC solar cell is 200nm-500nm, and the thickness of the poly layer in the N-zone non-metallic electrode area is 200nm-400nm. In the TBC solar cell prepared by the preparation method of the present invention, the poly layer in the non-metallic electrode area of ​​the TBC solar cell is effectively thinned.

[0024] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention achieves a significant improvement in the conversion efficiency and overall performance of the TBC solar cell by laser thinning the poly layer in the non-metallic electrode region of the TBC solar cell, thereby successfully reducing the problems of excessive optical parasitic absorption and current loss caused by the thick poly layer while retaining the many advantages brought by the combination of a thick poly layer and a tunneling oxide layer.

[0025] (2) The present invention achieves thinning of the poly layer in the non-metallic electrode area in at least one of the P and N regions on the back of the TBC solar cell, which can further improve the efficiency of the TBC solar cell; in the process of laser thinning of the poly layer, through reasonable process design and parameter control, it is ensured that the isolation performance of the metal electrode area and the GAP area is not affected, thereby maintaining the stability and functionality of the internal structure of the battery.

[0026] (3) In the process of improving battery performance, the present invention only uses the same laser to perform spectroscopic processing on different areas, without adding additional complex processes or equipment, thereby effectively avoiding the problem of increased production costs due to process improvements and improving production efficiency and economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present application or the technical solutions of 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 of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0028] Figure 1 This is a schematic diagram of the structure in step 4 involved in embodiments 1-3 of the present invention; Figure 2 This is a schematic diagram of the structure in step 7 involved in embodiments 1-3 of the present invention; Figure 3 This is a schematic diagram of the structure in step 8 involved in embodiments 1-3 of the present invention.

[0029] Description of reference numerals: 1. first polysilicon layer; 2. BSG layer; 3. GAP region; 4. second polysilicon layer; 5. AlO x Passivation layer; 6. SiN x Anti-reflection layer; 7, P-type electrode; 8, N-type electrode; 9, first tunneling oxide layer; 10, second tunneling oxide layer DETAILED DESCRIPTION

[0030] The technical solution of the present invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0031] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without making any creative work shall fall within the protection scope of the present invention.

[0032] Example 1 This embodiment provides a method for preparing a TBC solar cell, the method comprising the following steps: (1) Silicon wafer pretreatment: Double-sided polishing of silicon wafers in alkaline solution; (2) First deposition and diffusion: A first tunneling oxide layer 9 with a thickness of 1 nm and a first polysilicon layer 1 with a thickness of 350 nm are sequentially deposited on the back of the silicon wafer using low-pressure chemical vapor deposition (LPCVD), and boron diffusion is performed on this basis to form a P-type passivation contact layer on the back as a whole, and a borosilicate glass layer 2 (BSG layer) is formed on the surface; (3) The first laser treatment: First, laser ① is used to open the N+GAP area (N: phosphorus diffusion area; GAP: PN area junction isolation area) on part of the back side of the silicon wafer. Then, laser ② is used to scan the BSG layer 2 in the non-metallic electrode area of ​​the P area.

[0033] Laser ① and laser ② are two groups of lasers from the same laser, and the parameters of the two groups of lasers are: laser ①: wavelength 300nm, frequency 500kHz, scanning speed 50m / s, power 50W; laser ②: wavelength 200nm, frequency 200kHz, scanning speed 10m / s, power 10W; (4) Etching treatment: Use alkaline solution to etch the back of the silicon wafer. Due to the different etching rates between the laser area and the non-laser area, the final result is as follows: Figure 1 The structure shown; (5) Second deposition and diffusion: On the back of the silicon wafer, a second tunneling oxide layer 10 with a thickness of 1 nm and a second polysilicon layer 4 with a thickness of 250 nm are sequentially deposited by low pressure chemical vapor deposition (LPCVD), and phosphorus diffusion is performed on this basis to form an N-type passivation contact layer, and a PSG layer is formed on the surface of the N-type passivation contact layer. On the P region, the second tunneling oxide layer 10, the second polysilicon 4 and the phosphorus silicon glass layer (PSG layer) formed by phosphorus diffusion are suspended on the BSG layer 2 formed in step (2); (6) Second laser treatment: Laser ③ is used to scan the area on the back of the silicon wafer other than laser ①, which is the P+GAP area (P: boron diffusion area; GAP: PN area junction isolation area), and then laser ④ is used to scan the PSG layer in the non-metallic electrode area of ​​the N area; Laser ③ and laser ④ are two groups of lasers from the same laser, and the two groups of laser parameters are: Laser ③: wavelength 300nm, frequency 200kHz, scanning speed 10m / s, power 30W; Laser ④: wavelength 300nm, frequency 100kHz, scanning speed 5m / s, power 10W; (7) Pickling and texturing: Use HF to remove the PSG layer, BSG layer 2 and oxide layer and polysilicon layer in the thinned area of ​​the P area, N area and GAP area, where the HF concentration is 1%, and the following is obtained: Figure 2 The structure shown; using the texturing process, a velvet surface is obtained on the front side of the silicon wafer; (8) Post-treatment: Plasma enhanced chemical vapor deposition (PECVD) is used to deposit AlO with a thickness of 1 nm on the surface of the silicon wafer. x Passivation layer 5 and SiN with a thickness of 20 nm x Anti-reflection layer 6; P-type electrode 7 and N-type electrode 8 are printed by screen printing, the electrode material is silver, and sintered at 600°C, and then light injection test is performed, and finally the following is obtained: Figure 3 The structure shown.

[0034] Example 2 This embodiment provides a method for preparing a TBC solar cell, the method comprising the following steps: (1) Silicon wafer pretreatment: Double-sided polishing of silicon wafers in alkaline solution; (2) First deposition and diffusion: A first tunneling oxide layer 9 with a thickness of 3 nm and a first polysilicon layer 1 with a thickness of 450 nm are sequentially deposited on the back of the silicon wafer using low-pressure chemical vapor deposition (LPCVD), and boron diffusion is performed on this basis to form a P-type passivation contact layer on the back as a whole, and a borosilicate glass layer 2 (BSG layer) is formed on the surface; (3) The first laser treatment: First, laser ① is used to open the N+GAP area (N: phosphorus diffusion area; GAP: PN area junction isolation area) on part of the back side of the silicon wafer. Then, laser ② is used to scan the BSG layer 2 in the non-metallic electrode area of ​​the P area.

[0035] Laser ① and laser ② are two groups of lasers from the same laser, and the parameters of the two groups of lasers are: laser ①: wavelength 1100nm, frequency 1000kHz, scanning speed 200m / s, power 100W; laser ②: wavelength 1100nm, frequency 600kHz, scanning speed 80m / s, power 80W; (4) Etching treatment: Use alkaline solution to etch the back of the silicon wafer. Due to the different etching rates between the laser area and the non-laser area, the final result is as follows: Figure 1 The structure shown; (5) Second deposition and diffusion: On the back of the silicon wafer, a second tunneling oxide layer 10 with a thickness of 3 nm and a second polysilicon layer 4 with a thickness of 350 nm are sequentially deposited by low pressure chemical vapor deposition (LPCVD), and phosphorus diffusion is performed on this basis to form an N-type passivation contact layer, and a PSG layer is formed on the surface of the N-type passivation contact layer. On the P region, the second tunneling oxide layer 10, the second polysilicon 4 and the phosphorus silicon glass layer (PSG layer) formed by phosphorus diffusion are suspended on the BSG layer 2 formed in step (2); (6) Second laser treatment: Laser ③ is used to scan the area on the back of the silicon wafer other than laser ①, which is the P+GAP area (P: boron diffusion area; GAP: PN area junction isolation area), and then laser ④ is used to scan the PSG layer in the non-metallic electrode area of ​​the N area; Laser ③ and Laser ④ are two groups of lasers from the same laser, and the parameters of the two groups of lasers are: Laser ③: wavelength 1100nm, frequency 1000kHz, scanning speed 100m / s, power 70W; Laser ④: wavelength 1100nm, frequency 500kHz, scanning speed 40m / s, power 40W; (7) Pickling and texturing: Use HF to remove the PSG layer in the P region, N region, and GAP region 3, the BSG layer 2, and the oxide layer and polysilicon layer in the thinned area of ​​the non-metallic region, where the HF concentration is 50%, and the following is obtained: Figure 2 The structure shown; using the texturing process, a velvet surface is obtained on the front side of the silicon wafer; (8) Post-processing: Atomic layer deposition (ALD) is used to deposit AlO with a thickness of 10 nm on the surface of the silicon wafer.x Passivation layer 5 and SiN with a thickness of 200 nm x Anti-reflection layer 6; P-type electrode 7 and N-type electrode 8 are printed by screen printing, the electrode material is aluminum, and sintered at 900°C, and then light injection test is performed, and finally the following is obtained: Figure 3 The structure shown.

[0036] Example 3 This embodiment provides a method for preparing a TBC solar cell, the method comprising the following steps: (1) Silicon wafer pretreatment: Double-sided polishing of silicon wafers in alkaline solution; (2) First deposition and diffusion: A first tunneling oxide layer 9 with a thickness of 2 nm and a first polysilicon layer 1 with a thickness of 550 nm are sequentially deposited on the back of the silicon wafer using low-pressure chemical vapor deposition (LPCVD), and boron diffusion is performed on this basis to form a P-type passivation contact layer on the back as a whole, and a borosilicate glass layer 2 (BSG layer) is formed on the surface; (3) The first laser treatment: First, laser ① is used to open the N+GAP area (N: phosphorus diffusion area; GAP: PN area junction isolation area) on part of the back side of the silicon wafer. Then, laser ② is used to scan the BSG layer 2 in the non-metallic electrode area of ​​the P area.

[0037] Laser ① and laser ② are two groups of lasers from the same laser, and the parameters of the two groups of lasers are: Laser ①: wavelength 750nm, frequency 850kHz, scanning speed 130m / s, power 75W; Laser ②: wavelength 700nm, frequency 750kHz, scanning speed 45m / s, power 45W; (4) Etching treatment: Use alkaline solution to etch the back of the silicon wafer. Due to the different etching rates between the laser area and the non-laser area, the final result is as follows: Figure 1 The structure shown; (5) Second deposition and diffusion: On the back of the silicon wafer, a second tunneling oxide layer 10 with a thickness of 2 nm and a second polysilicon layer 4 with a thickness of 450 nm are sequentially deposited by low pressure chemical vapor deposition (LPCVD), and phosphorus diffusion is performed on this basis to form an N-type passivation contact layer, and a PSG layer is formed on the surface of the N-type passivation contact layer. On the P region, the second tunneling oxide layer 10, the second polysilicon 4 and the phosphorus silicon glass layer (PSG layer) formed by phosphorus diffusion are suspended on the BSG layer 2 formed in step (2); (6) Second laser treatment: Laser ③ is used to scan the area on the back of the silicon wafer other than laser ①, which is the P+GAP area (P: boron diffusion area; GAP: PN area junction isolation area), and then laser ④ is used to scan the PSG layer in the non-metallic electrode area of ​​the N area; Laser ③ and Laser ④ are two groups of lasers from the same laser, and the parameters of the two groups of lasers are: Laser ③: wavelength 700nm, frequency 600kHz, scanning speed 55m / s, power 50W; Laser ④: wavelength 700nm, frequency 300kHz, scanning speed 25m / s, power 25W; (7) Pickling and texturing: HF is used to remove the PSG layer in the P region, N region and GAP region 3, the BSG layer 2 and the oxide layer and polysilicon layer in the thinned area of ​​the non-metallic region, where the HF concentration is 25%, and the following is obtained: Figure 2 The structure shown; using the texturing process, a velvet surface is obtained on the front side of the silicon wafer; (8) Post-treatment: PECVD is used to deposit AlO with a thickness of 5 nm on the surface of the silicon wafer. x Passivation layer 5 and SiN with a thickness of 110 nm x Anti-reflection layer 6; P-type electrode 7 and N-type electrode 8 are printed by screen printing, the electrode material is copper, and sintered at 750°C, and then light injection test is performed, and finally the following is obtained: Figure 3 The structure shown.

[0038] Example 4 This embodiment provides a method for preparing a TBC solar cell, the method comprising the following steps: (1) Silicon wafer pretreatment: Double-sided polishing of silicon wafers in alkaline solution; (2) First deposition and diffusion: On the back of the silicon wafer, a first tunneling oxide layer of 2 nm and a first polysilicon layer of 350 nm are sequentially deposited using low-pressure chemical vapor deposition (LPCVD), and boron diffusion is performed on this basis to form a P-type passivation contact layer on the back of the wafer, and a borosilicate glass layer (BSG layer) is formed on the surface. (3) First laser treatment: First, laser ① is used to open the N+GAP area (N: phosphorus diffusion area; GAP: PN area junction and separation area) on part of the back of the silicon wafer. Then, laser ② is used to scan the BSG layer in the non-metallic electrode area of ​​the P area. Laser ① and laser ② are two groups of lasers from the same laser. The parameters of the two groups of lasers are as follows: Laser ①: wavelength 750nm, frequency 850kHz, scanning speed 130m / s, power 75W; Laser ②: wavelength 700nm, frequency 750kHz, scanning speed 45m / s, power 45W. (4) Etching treatment: Use alkaline solution to etch the back of the silicon wafer. Due to the different etching rates between the laser area and the non-laser area, the polysilicon layer in the P area is thinned. (5) Second deposition and diffusion: A second tunneling oxide layer of 2 nm and a second polysilicon layer of 250 nm are sequentially deposited on the back of the silicon wafer using low-pressure chemical vapor deposition (LPCVD), and phosphorus diffusion is performed on this basis to form an N-type passivation contact layer, and a PSG layer is formed on the surface of the N-type passivation contact layer. On the P region, the second tunneling oxide layer, polysilicon and phosphorus diffusion formed by the phosphorus silicon glass layer (PSG layer) are suspended on the BSG layer formed in step 2; (6) Second laser treatment: Use laser ③ to scan the P+GAP area (P: boron diffusion area; GAP: PN area junction isolation area) on the back of the silicon wafer; the parameters of laser ③ are: wavelength 700nm, frequency 600kHz, scanning speed 55m / s, power 50W; (7) Pickling and texturing: Use HF to remove the PSG layer, BSG layer in the P area and the GAP area, and the oxide layer and polysilicon layer in the thinned area of ​​the non-metallic area, where the HF concentration is 25%; use the texturing process to obtain a velvet surface on the front side of the silicon wafer; (8) Post-treatment: PECVD is used to deposit AlO on the surface of the silicon wafer x Passivation layer 5nm and SiN x The anti-reflection layer is 110nm; the P-type and N-type electrodes are printed separately by screen printing, the electrode material is copper, and sintered at 750°C, and then a light injection test is performed.

[0039] Example 5 This embodiment provides a method for preparing a TBC solar cell, the method comprising the following steps: (1) Silicon wafer pretreatment: Double-sided polishing of silicon wafers in alkaline solution; (2) First deposition and diffusion: On the back of the silicon wafer, a first tunneling oxide layer of 2 nm and a first polysilicon layer of 350 nm are sequentially deposited using low-pressure chemical vapor deposition (LPCVD), and boron diffusion is performed on this basis to form a P-type passivation contact layer on the back of the wafer, and a borosilicate glass layer (BSG layer) is formed on the surface. (3) First laser treatment: Laser ① is used to open the N+GAP area (N: phosphorus diffusion area; GAP: PN area junction and separation area) on part of the back of the silicon wafer. The parameters of laser ① are: wavelength 750nm, frequency 850kHz, scanning speed 130m / s, power 75W; (4) Etching treatment: Use alkaline solution to etch the back of the silicon wafer. Due to the different etching rates between the laser area and the non-laser area, the polysilicon layer in the N area is thinned. (5) Second deposition and diffusion: A second tunneling oxide layer of 2 nm and a second polysilicon layer of 250 nm are sequentially deposited on the back of the silicon wafer using low-pressure chemical vapor deposition (LPCVD), and phosphorus diffusion is performed on this basis to form an N-type passivation contact layer, and a PSG layer is formed on the surface of the N-type passivation contact layer. On the P region, the second tunneling oxide layer, polysilicon and phosphorus diffusion formed by the phosphorus silicon glass layer (PSG layer) are suspended on the BSG layer formed in step 2; (6) Second laser treatment: First, laser ③ is used to scan the area on the back of the silicon wafer other than laser ①, which is the P+GAP area (P: boron diffusion area; GAP: PN area junction isolation area). Then, laser ④ is used to scan the PSG layer in the non-metallic electrode area of ​​the N area. Laser ③ and laser ④ are two groups of lasers from the same laser. The parameters of the two groups of lasers are: laser ③: wavelength 700nm, frequency 600kHz, scanning speed 55m / s, power 50W; laser ④: wavelength 700nm, frequency 300kHz, scanning speed 25m / s, power 25W. (7) Pickling and texturing: Use HF to remove the PSG layer, BSG layer in the N area and the GAP area, and the oxide layer and polysilicon layer in the thinned area of ​​the non-metallic area, where the HF concentration is 25%; use the texturing process to obtain a textured surface on the front side of the silicon wafer; (8) Post-treatment: PECVD is used to deposit AlO on the surface of the silicon wafer x Passivation layer 5nm and SiN x The anti-reflection layer is 110nm; the P-type and N-type electrodes are printed separately by screen printing, the electrode material is copper, and sintered at 750°C, and then a light injection test is performed.

[0040] Comparative Example 1 The difference between this comparative example and Example 1 is that the laser ② in step (3) and the laser ④ in step (6) are omitted, and the remaining preparation methods and parameters are consistent with those in Example 1.

[0041] Performance Testing The electrical performance of the TBC solar cells prepared in Examples 1-5 and Comparative Example 1 was tested.

[0042] The test method is: using an IV tester to measure various parameters of the solar cell, and the results are shown in Table 1.

[0043] Table 1 Test results of battery of examples and comparative examples

[0044] Performance test data conclusion analysis: As can be seen from the above table, the present invention performs laser thinning on the poly layer in the non-metallic electrode area of ​​the TBC solar cell, thereby effectively solving the problems of optical parasitic absorption and current loss caused by the thicker poly layer in the prior art without affecting the battery isolation performance.

[0045] In addition, the cell prepared based on the method for preparing the TBC solar cell provided by the present invention has excellent conversion efficiency.

[0046] First, compared with Example 4 in which only the poly layer in the non-metallic electrode area of ​​the P region is thinned, Examples 1-3 in which the poly layer in the non-metallic electrode area of ​​the P region of the TBC solar cell is thinned at the same time, have an improvement effect of nearly 40 mA on the short-circuit current while keeping the open-circuit voltage and the fill factor basically unchanged, and the photoelectric conversion efficiency of the obtained battery is higher; compared with Example 5 in which only the poly layer in the non-metallic electrode area of ​​the N region is thinned, Example 1 has an improvement effect of nearly 60 mA on the short-circuit current while keeping the open-circuit voltage and the fill factor basically unchanged, and the photoelectric conversion efficiency of the obtained battery is more greatly improved than the thinning of the P region.

[0047] Secondly, compared with Example 1 in which the poly layer in the non-metallic electrode regions of the P and N regions is thinned, Example 1 has an increase of nearly 100 mA in short-circuit current and an increase of about 0.25% in conversion efficiency while the open circuit voltage and fill factor remain basically unchanged.

[0048] In the prior art, the thickness of the poly layer in the P-zone non-metallic electrode area on the back of the TBC solar cell is 200nm-500nm, and the thickness of the poly layer in the N-zone non-metallic electrode area is 200nm-400nm. The TBC solar cell prepared by the preparation method of the present invention can reduce the thickness of the poly layer (first polysilicon layer) in the P-zone non-metallic electrode area to 100nm-180nm, and the thickness of the poly layer (second polysilicon layer) in the N-zone non-metallic electrode area to 50nm-150nm.

[0049] Therefore, the present invention realizes the thinning of the poly layer in the non-metallic electrode area in at least one of the P and N areas on the back of the TBC solar cell, which is much better than the thinning of a single area and can further improve the efficiency of the TBC solar cell; by combining laser and wet processes to thin the poly in the non-metallic electrode area of ​​the P and N areas, it is possible to ensure the gain effect of the thicker poly in the electrode area while reducing the disadvantages caused by the thick poly in the non-metallized area.

[0050] The present invention is further described above with the aid of specific embodiments. However, it should be understood that the specific description here should not be construed as limiting the essence and scope of the present invention. Various modifications made to the above embodiments by ordinary technicians in the field after reading this specification are all within the scope of protection of the present invention.

Claims

1. A method for preparing a TBC solar cell, characterized in that: The steps include: (1) Silicon wafer pretreatment: double-sided polishing of silicon wafers; (2) First deposition and diffusion: depositing a first tunneling oxide layer and a first polysilicon layer on the back of the silicon wafer, and performing boron diffusion to form a P-type passivation contact layer, and forming a BSG layer on the surface of the P-type passivation contact layer; (3) The first laser treatment: using laser to process part of the back side of the silicon wafer, including laser excavation of the N+GAP area; (4) Etching treatment: Etching the back of the silicon wafer using alkaline solution; (5) Second deposition and diffusion: depositing a second tunneling oxide layer and a second polysilicon layer on the back of the silicon wafer, and performing phosphorus diffusion to form an N-type passivation contact layer, and forming a PSG layer on the surface of the N-type passivation contact layer; (6) Second laser treatment: Use laser to treat the area on the back of the silicon wafer that has not been treated by the first laser treatment, including laser scanning of the P+GAP area; (7) Pickling and texturing: Pickle the silicon wafer, and after pickling, texturing the front side of the silicon wafer; (8) Post-processing: Deposition of AlO on the surface of silicon wafer x Passivation layer and SiN x Anti-reflection layer, screen printing electrode, sintering, and light injection test; The laser processing further includes at least one of the following processes: a BSG layer process of laser scanning the non-metal electrode region of the P region in step (3) and a PSG layer process of laser scanning the non-metal electrode region of the N region in step (6).

2. The method for preparing a TBC solar cell according to claim 1, characterized in that: In the step (2), the thickness of the first tunnel oxide layer is 1 nm-3 nm, and the thickness of the first polysilicon layer is 350 nm-550 nm.

3. The method for preparing a TBC solar cell according to claim 1, characterized in that: The step (3) comprises: first using laser ① to carve out an N+GAP area on the back side of the silicon wafer, and then using laser ② to scan the BSG layer in the non-metallic electrode area of ​​the P area; wherein the parameters of the laser ① are: wavelength 300nm-1100nm, frequency 500kHz-1000kHz, scanning speed 50m / s-200m / s, power 50W-100W; the parameters of the laser ② are: wavelength 200nm-1100nm, frequency 200kHz-600kHz, scanning speed 10m / s-80m / s, power 10W-80W.

4. The method for preparing a TBC solar cell according to claim 1, characterized in that: The step (5) comprises: depositing a second tunnel oxide layer and a second polysilicon layer in sequence on the back side of the silicon wafer by low pressure chemical vapor deposition, and performing phosphorus diffusion on this basis, so that the second tunnel oxide layer, the second polysilicon layer and the PSG layer formed by the phosphorus diffusion are suspended on the BSG layer formed in the step (2) on the P region.

5. The method for preparing a TBC solar cell according to claim 1, characterized in that: In the step (5), the thickness of the second tunnel oxide layer is 1 nm-3 nm, and the thickness of the second polysilicon layer is 250 nm-450 nm.

6. The method for preparing a TBC solar cell according to claim 1, characterized in that: The step (6) comprises: firstly using laser ③ to scan the P+GAP area on the back side of the silicon wafer, and then using laser ④ to scan the PSG layer in the non-metallic electrode area of ​​the N area; wherein the parameters of the laser ③ are: wavelength 300nm-1100nm, frequency 200kHz-1000kHz, scanning speed 10m / s-100m / s, power 30W-70W; the parameters of the laser ④ are: wavelength 300nm-1100nm, frequency 100kHz-500kHz, scanning speed 5m / s-40m / s, power 10W-40W.

7. The method for preparing a TBC solar cell according to claim 1, characterized in that: The pickling in step (7) includes using HF with a concentration of 1%-50% to remove the PSG layer, BSG layer and oxide layer and polysilicon layer in the P region, N region and GAP region on the back side of the silicon wafer and the thinned area of ​​the non-metallic region.

8. The method for preparing a TBC solar cell according to claim 1, characterized in that: In the step (8), AlO x The thickness of the passivation layer is 1nm-10nm, SiN x The thickness of the anti-reflection layer is 20nm-200nm; the material of the electrode is one or a combination of silver, aluminum and copper; and the sintering temperature is 600℃-900℃.

9. A TBC solar cell, characterized in that: The TBC solar cell is prepared by the method for preparing a TBC solar cell according to any one of claims 1 to 8.

10. The TBC solar cell according to claim 9, characterized in that: The thickness of the first polysilicon layer in the P-region non-metallic electrode area on the back of the TBC solar cell is 100nm-180nm, and the thickness of the second polysilicon layer in the N-region non-metallic electrode area is 50nm-150nm.

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