A topcon solar cell with improved leakage and a method of manufacturing the same

Abstract

This application provides a TOPCon solar cell with improved leakage current and its fabrication method, relating to the photovoltaic field. After phosphorus diffusion, a patterning process is performed on the front edge and central axis of the silicon wafer using a laser, followed by acid washing and alkali washing to obtain an alkali-washed silicon wafer. An Al2O3 thin film is prepared on the front surface of the alkali-washed silicon wafer using plasma ALD, followed by annealing to form an Al2O3 layer. SiO2 is then prepared on the surface of the Al2O3 layer using plasma ALD. x N y Layer; SiH4, CM4 and CH3M gases are introduced, and ALD is used on SiO2. x N y SiN layer surface x M layer; M is a halogen element, SiN x Halogen elements in the M layer move along the path close to SiO₂ x N y One side of the layer to the side away from SiO x N y The content gradient on one side of the layer decreases; electrode printing, sintering, and light injection are performed to obtain TOPCon solar cells with improved leakage current. This can reduce recombination loss and leakage current.

Description

Technical Field

[0001] This application relates to the photovoltaic field, and more particularly to a TOPCon solar cell with improved leakage current and a method for its fabrication. Background Technology

[0002] In existing technologies, if polysilicon (poly-Si) is not completely removed by wet etching after edge or back coating, it will lead to excessive reverse current and significantly increased leakage current. Furthermore, traditional PECVD processes cannot accurately prepare high-precision and high-density film thicknesses.

[0003] Therefore, there is an urgent need to provide a method for fabricating TOPCon solar cells to solve the above problems. Summary of the Invention

[0004] The purpose of this application is to provide a TOPCon solar cell with improved leakage current and a method for its fabrication, so as to solve the above-mentioned problems.

[0005] To achieve the above objectives, the first aspect of this application provides a method for fabricating a TOPCon solar cell with improved leakage current, comprising: After phosphorus diffusion is completed, laser is used to pattern the front edge and central axis of the silicon wafer; the laser-patterned silicon wafer is then acid-washed and alkali-washed to obtain an alkali-washed silicon wafer. An Al2O3 thin film was prepared on the positive surface of the alkaline-washed silicon wafer using plasma ALD, and then annealed to form an Al2O3 layer. SiO2 was prepared on the surface of the Al2O3 layer using plasma ALD. x N y layer; SiH4, CM4 and CH3M gases are introduced, and ALD is used on the SiO2. x N y SiN layer surface z M layer; where M is a halogen element, and the SiN z The halogen elements in the M layer are located near the SiO₂ layer. x N y One side of the layer to the side away from the SiO x N y The content gradient decreases on one side of the layer; Electrode printing, sintering, and light injection are performed to obtain the TOPCon solar cell with improved leakage current.

[0006] Optionally, the method for fabricating the TOPCon solar cell with improved leakage current satisfies at least one of the following conditions: A. The line width of the graphical processing is 100µm-200µm, and the depth is 3µm-6µm; B. The power of the laser is 40W-56W, and the marking speed is 30000-50000mm / s.

[0007] Optionally, the acid used for pickling may include HF, and the alkali used for alkaline washing may include KOH.

[0008] Optionally, the thickness of the Al2O3 layer is 1nm-2nm.

[0009] Optionally, the annealing temperature is 800℃-900℃ and the time is 30s-60s.

[0010] Optionally, the method for fabricating the TOPCon solar cell with improved leakage current satisfies at least one of the following conditions: A. The SiO x N y The refractive index of the layer is 1.58-1.85; B. The SiO x N y Hydrogen content of the layer > 3 × 10 23 cm -3 ; C. The SiO x N y The thickness of the layer is 15nm-25nm.

[0011] Optionally, the SiN z The thickness of the M layer is 50nm-80nm; The SiN z The mass content of M in layer M is 0.1%-1%.

[0012] Optionally, during the SiN process... z During the preparation of the M layer, the volume of CM4 introduced into the CM4 and CH3M mixed gas gradually decreases.

[0013] Optionally, the volume ratio of CM4 to CH3M is gradually reduced from 3:1 to 1:1.

[0014] The second aspect of this application provides a TOPCon solar cell with improved leakage current, which is prepared by the method for preparing a TOPCon solar cell with improved leakage current.

[0015] Compared with the prior art, the beneficial effects of this application include: The method for fabricating TOPCon solar cells with improved leakage current provided in this application firstly involves patterning the front edge and central axis of the phosphorus-expanded silicon wafer to form leakage-isolated channels; secondly, the traditional PECVD deposition of the passivation layer is replaced by ALD process, which precisely controls the thickness of the passivation layer and achieves an ultra-thin, dense layer structure through the self-limiting reaction characteristics of ALD, thereby enhancing the chemical bonding between the passivation layer and the silicon substrate and suppressing boron-oxygen recombination centers.

[0016] This application provides a TOPCon solar cell with improved leakage current, featuring Al2O3 layer-enhanced chemical passivation; SiO x N y The layer provides a low interface state density; SiN z The M layer is gradient-doped with halogen elements. These halogens enhance the hydrophobicity and resistance to PID (potential-induced degradation) of the passivation layer, and the gradient decreases the film's refractive index, optimizing the light reflection path. This is achieved by sequentially adding Al2O3 layers followed by SiO2. x N y Layer-SiN z The stacked structure of the M layer suppresses boron diffusion. By reducing the interface state density, it reduces the adsorption of boron atoms at the silicon / passivation layer interface, further suppressing lateral boron diffusion and reducing edge leakage current. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation on the scope of this application.

[0018] Figure 1 This is a schematic diagram of the structure of the TOPCon solar cell with improved leakage current provided in Example 1; Figure 2 A 3D schematic diagram of the TOPCon solar cell with improved leakage current provided in Example 1; Figure 3 SEM image of the TOPCon solar cell with improved leakage current provided in Example 1, where the M content is 1.1 to 1.05; Figure 4 SEM image of the TOPCon solar cell with improved leakage current and an M content of 1.3-1.2 provided in Example 1; Figure 5 A schematic diagram of the TOPCon solar cell provided for Comparative Example 7; Figure 6 A 3D schematic diagram of the TOPCon solar cell provided for Comparative Example 7.

[0019] Explanation of key component symbols: 100-Al2O3 layer; 101-Al2O3-SiN x Passivation layer; 200-SiO x N y Layer; 300-SiN z M layer; 400-tunneling layer; 500-poly layer; 501-residual poly layer with deflection; 600-SiN x Layer; 700-Silicon substrate; 800-P + Emitter; 900-Ag. Detailed Implementation

[0020] As used in this article: "Prepared from" is synonymous with "comprising". The terms "comprising", "including", "having", "containing", or any other variations thereof as used herein are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.

[0021] The conjunction "composed of..." excludes any unspecified elements, steps, or components. If used in a claim, this phrase makes the claim closed, excluding materials other than those described, except for associated conventional impurities. When the phrase "composed of..." appears in a clause of the body of a claim rather than immediately following it, it limits only the elements described in that clause; other elements are not excluded from the claim as a whole.

[0022] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1–5” is disclosed, the described range should be interpreted as including ranges “1–4”, “1–3”, “1–2”, “1–2 and 4–5”, “1–3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range.

[0023] In these embodiments, unless otherwise specified, the portions and percentages are all by weight.

[0024] "Parts by mass" refers to the basic unit of measurement that expresses the mass ratio of multiple components. One part can represent any unit mass, such as 1g or 2.689g. If we say that component A has "a" parts by mass and component B has "b" parts by mass, it means the ratio of the mass of component A to the mass of component B is a:b. Alternatively, it can mean that the mass of component A is aK and the mass of component B is bK (where K is any number representing a multiplier). It is important to understand that, unlike parts by mass, the sum of the mass parts of all components is not limited to 100 parts.

[0025] "And / or" is used to indicate that one or both of the described situations may occur, for example, A and / or B includes (A and B) and (A or B).

[0026] The first aspect of this application provides a method for fabricating a TOPCon solar cell with improved leakage current, comprising: After phosphorus diffusion is completed, laser is used to pattern the front edge and central axis of the silicon wafer; the laser-patterned silicon wafer is then acid-washed and alkali-washed to obtain an alkali-washed silicon wafer. It should be noted that after acid washing removes PSG, the poly silicon is exposed. Alkali washing is then performed to remove the exposed poly silicon. An Al2O3 thin film was prepared on the positive surface of the alkaline-washed silicon wafer using plasma ALD, and then annealed to form an Al2O3 layer. SiO2 was prepared on the surface of the Al2O3 layer using plasma ALD. x N y layer; SiH4, CM4 and CH3M gases are introduced, and ALD is used on the SiO2. x N y SiN layer surface z M layer; where M is a halogen element, and the SiN z The halogen elements in the M layer are located near the SiO₂ layer. x N y One side of the layer to the side away from the SiO x N y The content gradient decreases on one side of the layer; It should be noted that the above Al2O3 layer-SiO x N y Layer-SiN z The M-layer, namely the synergistic mechanism of passivation, interface optimization, and electric field modulation, is as follows: ① Al2O3 layer: Reduces the interface state density and suppresses carrier recombination through chemical passivation (reducing dangling bonds on the silicon surface). ② SiO x N yLayer: Provides a low refractive index transition layer (n=1.58-1.85) to reduce light reflection loss, and further reduces the interface state density through the polar characteristics of Si-ON bonds. ③SiN z M-layer: Gradient doping with halogen elements creates a localized electric field, suppressing edge electric field concentration, optimizing carrier transport paths, and reducing leakage current. Al2O3 and SiO x N y The stacked passivation reduces the surface recombination rate from 10 fA / cm² in conventional TOPCon. 2 Reduced to 2fA / cm 2 The following reduces recombination loss; SiN z The gradient electric field of M homogenizes the edge electric field intensity distribution, reducing edge leakage current by more than 50%; Al2O3 layer-SiO x N y Layer-SiN z The M layer covers the exposed PN junction in the laser aperture region, reducing recombination loss and leakage current; It should also be noted that gradient doping with halogen elements creates a localized electric field, suppresses edge electric field concentration, optimizes carrier transport paths, and reduces leakage current; SiN z The gradient electric field of M makes the edge electric field intensity distribution uniform, reducing the edge leakage current by more than 50% (leakage current test).

[0027] It should also be noted that SiO x N y Layers and SiN z In layer M, the subscripts x, y, and z represent the content of their respective elements. In practical applications, the values ​​of x, y, and z can be changed by adjusting the amount of raw materials used. In some embodiments, 1≤x≤3, 1≤y≤3, and 1≤z≤3.

[0028] Electrode printing, sintering, and light injection are performed to obtain the TOPCon solar cell with improved leakage current.

[0029] In some embodiments, the method for fabricating the TOPCon solar cell with improved leakage current satisfies at least one of the following conditions: A. The line width of the graphical processing is 100µm-200µm, and the depth is 3µm-6µm; Optionally, the line width for graphical processing can be any value between 100µm, 150µm, 200µm or 100µm-200µm, and the depth can be any value between 3µm, 4µm, 5µm, 6µm or 3µm-6µm. B. The power of the laser is 40W-56W, and the marking speed is 30000-50000mm / s.

[0030] Optionally, the laser power can be any value between 40W, 45W, 50W, 55W, 56W, or 40W-56W, and the marking speed can be any value between 30000mm / s, 40000mm / s, 50000mm / s, or 30000-50000mm / s.

[0031] In some embodiments, the acid used for pickling includes HF, and the alkali used for alkaline washing includes KOH.

[0032] In some embodiments, the thickness of the Al2O3 layer is 1nm-2nm.

[0033] Optionally, the thickness of the Al2O3 layer can be any value between 1 nm, 1.5 nm, 2 nm, or 1 nm and 2 nm.

[0034] In some embodiments, the annealing temperature is 800℃-900℃ and the time is 30s-60s.

[0035] Optionally, the annealing temperature can be any value between 800℃, 850℃, 900℃ or 800℃-900℃, and the time can be any value between 30s, 40s, 50s, 60s or 30s-60s.

[0036] It is important to note that the rapid annealing (RTP) process can promote hydrogen atom diffusion, repair interface defects, increase hydrogen content, reduce surface recombination rate, and stabilize the charge density (Qf) at 1×10⁻⁶. 12 cm -2 The above enhances the passivation capability of the field effect.

[0037] In some embodiments, the method for fabricating the TOPCon solar cell with improved leakage current satisfies at least one of the following conditions: A. The SiO x N y The refractive index of the layer is 1.58-1.85; Optional, SiO x N y The refractive index of the layer can be 1.58, 1.6, 1.7, 1.8, 1.85 or any value between 1.58 and 1.85; B. The SiO x N y Hydrogen content of the layer > 3 × 10 23 cm -3 ; Optional, SiO x N y The hydrogen content of the layer can be 5 × 10 23 cm -3 10×1023 cm -3 20×10 23 cm -3 30×10 23 cm -3 50×10 23 cm -3 Or >3×10 23 cm -3 Any value; C. The SiO x N y The thickness of the layer is 15nm-25nm.

[0038] Optional, SiO x N y The thickness of the layer can be any value between 15nm, 20nm, 25nm, or 15nm-25nm.

[0039] In some embodiments, the SiN z The thickness of the M layer is 50nm-80nm; Optional, SiN z The thickness of the M layer can be 50nm, 60nm, 70nm, 80nm, or any value between 50nm and 80nm; The SiN z The mass content of M in layer M is 0.1%-1%.

[0040] Optional, SiN z The mass content of M in layer M can be any value between 0.1%, 0.5%, 1%, or 0.1%-1%.

[0041] It is important to note that the M content range of 0.1%-1% is precisely controlled through the ALD process. Low concentration (0.1%) forms the initial electric field gradient, while high concentration (1%) enhances the stability of the passivation layer, thus balancing leakage suppression and film reliability.

[0042] In some embodiments, during the SiN process z During the preparation of the M layer, the volume of CM4 introduced into the CM4 and CH3M mixed gas gradually decreases.

[0043] In some embodiments, the volume ratio of CM4 to CH3M introduced is gradually reduced from 3:1 to 1:1.

[0044] The second aspect of this application provides a TOPCon solar cell with improved leakage current, which is prepared by the method for preparing a TOPCon solar cell with improved leakage current.

[0045] The implementation schemes of this application will be described in detail below with reference to specific embodiments. However, those skilled in the art will understand that the following embodiments are only for illustrating this application and should not be regarded as limiting the scope of this application. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments used without specified manufacturers are all conventional products that can be purchased commercially.

[0046] Example 1 This embodiment provides a TOPCon solar cell with improved leakage current and its fabrication method. The specific fabrication method includes: Step S1: A tunneling oxide layer is prepared on the back side of the N-type silicon substrate 700 (temperature 600℃, oxygen flow rate 35L / min), and then poly is deposited (temperature 605℃, silane flow rate 1100sccm). Since the film is prepared by double-intercalation, there is a deflection on the front side. Step S2, then phosphorus diffusion is performed on the poly layer (using phosphorus oxychloride at a temperature of 875°C). Figure 1 The yellow part is phosphorus-doped polycrystalline silicon (phosphorus is doped in the poly layer to form an N+ layer). Because this film is prepared by double-intercalation, there is a swivel on the front side. Step S3, laser film opening: After completing the phosphorus expansion, a laser is used to make pre-openings (patterning) along the edge and central axis of the silicon wafer (210×183mm) of the solar cell. The laser power is 52W and the marking speed is 40000mm / s, forming a straight line pattern with a line width of 150µm and a depth of 4.5µm. Step S8: The solar cell that has been patterned by laser is subjected to HF acid washing to remove the PSG wrapped around the perimeter and edges, making the poly silicon bare. Then the silicon wafer is subjected to 75wt% KOH alkaline washing to block the edge leakage path. Step S9: In a mixed gas of O2 and Ar (oxygen content 10 wt%), an Al2O3 thin film is prepared on the positive surface of an alkaline-washed silicon wafer using plasma ALD with trimethylaluminum. The plasma ALD temperature is 120 °C, the pressure is 0.2 Torr, and the cycle is 80. After an 8-second TMA pulse, an Ar purge is performed for 15 seconds, followed by a 5-second O2 pulse and then an Ar purge for 15 seconds. Then, O2 plasma activation is performed (power 100 W, 5 min). Finally, rapid annealing is performed to form an Al2O3 layer 100 with a thickness of 1.5 nm. The annealing temperature is 850 °C and the time is 45 s. Step S10: SiO2 is prepared on the surface of Al2O3 layer 100 using plasma ALD in a mixed gas of silane, NH3, and Ar. x N yLayer 200, temperature 180℃, pressure 0.5 Torr, 60 cycles, SiH4 pulse 6s, NH3 pulse 4s, followed by Ar purging for 10s, controlling the initial NH3 mass concentration to 20%, increasing NH3 by 5wt% every 10 cycles; controlling SiO x N y Layer 200 (specifically SiON) has a refractive index of 1.75 and a hydrogen content of >3×10⁻⁶. 23 cm -3 The thickness is 20nm; Step S11: SiH4, CF4, and CH3F gases are introduced. The flow rates of SiH4 and CH3F remain constant at 80 sccm and 100 sccm, respectively, while the flow rate of CF4 gradually decreases from an initial 200 sccm to 60 sccm. ALD is then applied to SiO2. x N y Layer 200 has a SiN layer with a thickness of 65 nm on its surface. z M layer 300 (specifically SiNF), controlled temperature 350℃, pressure 1 Torr, 40 cycles, SiH4 pulse 4 s, CF4 pulse 8 s, CH3F pulse 4 s, Ar purge 15 s, then N2 / H2 mixed annealing (500°C, 10 min); where SiN z The F element in layer M300 moves along the path close to SiO x N y One side of layer 200 away from SiO x N y The content gradient decreases on one side of layer 200; near SiO x N y SiN on one side of layer 200 z The F content at the edge of layer M300 is 1%, far from SiO. x N y SiN on one side of layer 200 z The F content at the edge of layer M, 300 is 0.6%; Step S12: The silicon wafer is pre-textured in a 30% NaOH solution, and then boron trichloride is introduced at 890°C to prepare the P+ emitter (Step 1 S1). The back film is then cleaned in a 43% NaOH solution (Step 2 S2). Step S13: Electrode printing, sintering and light injection are performed on the front and back sides to obtain a TOPCon solar cell with improved leakage current.

[0047] The structure of the TOPCon solar cell that improves leakage current is as follows: Figure 1 As shown. A 3D schematic of this TOPCon solar cell that improves leakage current is shown below. Figure 2 As shown, there is no poly residue with no deflection at the edge.

[0048] In addition, this embodiment further tested SiN z The influence of different M values ​​(F content) in the M layer on the performance of TOPCon solar cells with improved leakage current was investigated. Additionally, layers close to SiO were also fabricated. x N y SiN on one side of layer 200 z The F content at the edge of layer M 300 is far from SiO. x N y SiN on one side of layer 200 z TOPCon solar cells with improved leakage current at the edge of M layer 300 were prepared with F contents of 0.5 to 0.1, 1.1 to 1.05, and 1.3 to 1.2, respectively. The prepared TOPCon solar cells with improved leakage current were subjected to leakage current test and anti-PID test (PID decay rate after 1000h), and the specific data are shown in Table 1.

[0049] Table 1 Leakage current test results with different M contents

[0050] The experimental results show that: Low concentration (0.5 to 0.1): forms a weak electric field, initially suppressing edge electric field concentration, but carrier transport efficiency is low; High concentration (1.1 to 1.05 and 1.3-1.2): significantly increases electric field strength, but excessive halogen may cause stress concentration in the thin film, leading to cracks.

[0051] Among them, SEM images of TOPCon solar cells with improved leakage current and M content of 1.1 to 1.05 are shown in the figure. Figure 3 As shown, the SEM images of TOPCon solar cells with improved leakage current and M content of 1.3-1.2 are as follows. Figure 4 As shown.

[0052] Example 2 The difference from Example 1 is that the thickness of the Al2O3 layer is 2nm.

[0053] Example 3 The difference from Example 1 is that SiN z The thickness of the M layer is 50 nm.

[0054] Example 4 The difference from Example 1 is that the CF4 inlet flow rate is gradually reduced from an initial 180 SCCM to 50 SCCM, causing the SiN layer near the SiOxNy layer to... z The F content at the edge of the M layer is 1.2%, and the SiN content on the side furthest from the SiOxNy layer is... z The F content at the edge of layer M is 0.5%.

[0055] Comparative Example 1 The difference from Example 1 is that patterning is performed only on the front edge of the silicon wafer.

[0056] Comparative Example 2 The difference from Example 1 is that SiO is not provided. x N y layer.

[0057] Comparative Example 3 The difference from Example 1 is that SiN is not provided. z M layer.

[0058] Comparative Example 4 The difference from Example 1 is that F in M ​​is replaced with a non-halogen element S.

[0059] Comparative Example 5 The difference from Example 1 is that the flow rate of CF4 remains constant, resulting in SiN with a uniform distribution of F element. z M layer.

[0060] Comparative Example 6 The difference from Example 1 is that the CF4 flow rate was initially increased from 50 sccm to 200 sccm, resulting in the prepared SiN z In the M layer, the F element moves along the path close to SiOxN y One side of the layer away from SiOxN y The content gradient increases on one side of the layer.

[0061] Comparative Example 7 The difference from Example 1 is that the conventional TOPCon solar cell fabrication method is used, and the specific steps are as follows: S1: Texturing process is performed on the N-type silicon substrate 700; S2: Boron diffusion treatment is performed on the front side of the silicon wafer after texturing in step S1. The boron diffusion process includes four steps: pre-oxidation, deposition, advance, and post-oxidation, to form P... + Emitter 800; S3: Remove BSG from the back and edge wrapping of the silicon wafer; S4: A tunneling oxide layer is prepared on the back side of a silicon wafer using an LPCVD device; the tunneling layer is a silicon oxide layer with a thickness of 2 nm; S5: Poly-Si layer is formed by LPCVD on the back side, using a deposition pressure of 20 Pa, a temperature of 620 °C, a silane flow rate of 1500 SCCM, and a deposition time of 24 min; S6: The silicon wafer in S7 is phosphorus-doped with phosphorus oxychloride at a flow rate of 1500 sccm / min, oxygen at a flow rate of 650 sccm / min, pressure of 160 mbar, time of 18 min, and temperature of 795℃; then the silicon wafer is heated to 885℃ and pushed forward for 25 min. S7: The silicon wafer in S8 is passed through a chain HF with the front side facing down, and the HF concentration is controlled at 9% to remove the front PSG; then the silicon wafer is washed with 75wt% KOH alkaline to remove the poly, but a winding poly layer is still formed and 501 remains. S8: The silicon wafer undergoes subsequent ALD (Al2O3-SiN) 3.5nm etching, with 76nm silicon nitride on the front side and 80nm silicon nitride on the back side, followed by printing and sintering (sintering temperature 810℃, time 50s) to form Al2O3-SiN. x Passivation layer 101.

[0062] The structure of the TOPCon solar cell prepared in this comparative example is as follows: Figure 5 As shown.

[0063] A 3D illustration of the TOPCon solar cell that improves leakage current is shown below. Figure 6 As shown.

[0064] The TOPCon solar cells obtained from the above embodiments and comparative examples were subjected to performance tests, including Uoc (open circuit voltage), Isc (short circuit current), FF (fill factor), Eta (conversion efficiency), Rsh (parallel resistance), Rs (series resistance), and Irev2 (reverse saturation current). The specific test results are shown in Table 2.

[0065] Table 2 Performance Tests

[0066] analyze: As shown in Table 2, the process parameters of Examples 1-4 are all within the range of this application, and the reverse saturation current is less than that of the conventional battery in Comparative Example 7 (the higher the reverse saturation current, the higher the leakage rate). The efficiency of Examples 1-4 is higher than that of Comparative Example 7. The electrical performance is reflected in the turn-on voltage and the high FF, indicating that the stacked passivation layer has a better effect. The absence of any step in Comparative Examples 1-6 would not achieve the desired effect. The non-gradient doping in Comparative Examples 5-6 also cannot achieve the passivation effect of the patent group.

[0067] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

[0068] Furthermore, those skilled in the art will understand that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are intended to be within the scope of this application and form different embodiments. For example, in the foregoing claims, any of the claimed embodiments can be used in any combination. The information disclosed in this background section is intended only to enhance the understanding of the general background of this application and should not be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

Claims

1. A method for fabricating a TOPCon solar cell with improved leakage current, characterized in that, include: After phosphorus diffusion is completed, laser is used to pattern the front edge and central axis of the silicon wafer; the laser-patterned silicon wafer is then acid-washed and alkali-washed to obtain an alkali-washed silicon wafer. An Al2O3 thin film was prepared on the positive surface of the alkaline-washed silicon wafer using plasma ALD, and then annealed to form an Al2O3 layer. SiO2 was prepared on the surface of the Al2O3 layer using plasma ALD. x N y layer; SiH4, CM4 and CH3M gases are introduced, and ALD is used on the SiO2. x N y SiN layer surface z M layer; where M is a halogen element, and the SiN z The halogen elements in the M layer are located near the SiO₂ layer. x N y One side of the layer to the side away from the SiO x N y The content gradient decreases on one side of the layer; Electrode printing, sintering, and light injection are performed to obtain the TOPCon solar cell with improved leakage current.

2. The method for preparing a TOPCon solar cell with improved leakage current according to claim 1, characterized in that, At least one of the following conditions must be met: A. The line width of the graphical processing is 100µm-200µm, and the depth is 3µm-6µm; B. The power of the laser is 40W-56W, and the marking speed is 30000-50000mm / s.

3. The method for preparing a TOPCon solar cell with improved leakage current according to claim 1, characterized in that, The acid used for pickling includes HF, and the alkali used for alkaline washing includes KOH.

4. The method for preparing a TOPCon solar cell with improved leakage current according to claim 1, characterized in that, The thickness of the Al2O3 layer is 1nm-2nm.

5. The method for preparing a TOPCon solar cell with improved leakage current according to claim 1, characterized in that, The annealing temperature is 800℃-900℃, and the time is 30s-60s.

6. The method for preparing a TOPCon solar cell with improved leakage current according to claim 1, characterized in that, At least one of the following conditions must be met: A. The SiO x N y The refractive index of the layer is 1.58-1.85; B. The SiO x N y The hydrogen content of the layer is > 3×10 23 cm -3 ; C. The SiO x N y The thickness of the layer is 15nm-25nm.

7. The method for preparing a TOPCon solar cell with improved leakage current according to claim 1, characterized in that, The SiN z The thickness of the M layer is 50nm-80nm; The SiN z The mass content of M in layer M is 0.1%-1%.

8. The method for preparing a TOPCon solar cell with improved leakage current according to claim 1, characterized in that, In the process of SiN z During the preparation of the M layer, the volume of CM4 introduced into the CM4 and CH3M mixed gas gradually decreases.

9. The method for preparing a TOPCon solar cell with improved leakage current according to claim 8, characterized in that, The volume ratio of CM4 to CH3M gradually decreased from 3:1 to 1:

1.

10. A TOPCon solar cell with improved leakage current, characterized in that, It is prepared by the method for preparing the TOPCon solar cell with improved leakage current according to any one of claims 1-9.

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