A boron diffusion method, a crystalline silicon solar cell and a preparation method thereof
By adjusting the duration of the boron diffusion process and optimizing the thermal budget, the passivation level of P-type doped polycrystalline silicon was improved, solving the problem of poor passivation performance in TOPCon cells and achieving a dual improvement in cell performance and efficiency.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- ZHUHAI FUSHAN AIKO SOLAR ENERGY TECH CO LTD
- Filing Date
- 2026-05-20
- Publication Date
- 2026-07-14
AI Technical Summary
In existing TOPCon technology, the passivation performance of P-type doped polycrystalline silicon is poor, which makes it difficult for the open-circuit voltage and photoelectric conversion efficiency of the battery to reach the level of N-type doped polycrystalline silicon. In addition, the existing boron diffusion process requires a long time, which affects the yield and cost.
By adjusting the duration of the heating, isothermal, and cooling stages in the boron diffusion process, especially by keeping the isothermal stage relatively short, the thermal budget is optimized, the passivation level of P-type doped polycrystalline silicon is improved, and the photoelectric performance of the battery is enhanced.
It significantly improves the open-circuit voltage and fill factor of the battery, while also taking into account the fabrication efficiency, achieving a dual improvement in time and performance.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of photovoltaic cell technology, and in particular to a boron diffusion method, a crystalline silicon solar cell, and a method for preparing the same. Background Technology
[0002] As a core energy conversion device in the renewable energy field, solar cells essentially convert the energy of photons in solar radiation directly into electrical energy through the photovoltaic effect of semiconductor materials. Currently, with the widespread application of solar cells and the increasing performance requirements, the photoelectric conversion efficiency and mass production stability of solar cells have become the core directions of technological iteration. Currently, mainstream mass-produced solar cells widely adopt tunnel oxide passivated contact (TOPCon) technology. This technology, with its excellent passivation performance and carrier transport efficiency, has become a key solution to overcome the efficiency bottleneck of traditional cells.
[0003] TOPCon technology was first formally proposed by Fraunhofer in Germany in 2013. Its core lies in abandoning the aluminum back field or local contact structure of traditional batteries. Instead, it precisely constructs a composite stacked structure of "ultra-thin silicon oxide layer and doped polycrystalline silicon layer" on the surface of a crystalline silicon wafer. The thickness of the ultra-thin silicon oxide layer (tunneling oxide layer) is 1-2 nm, and the thickness of the doped polycrystalline silicon layer is typically 50-200 nm. This structure allows minority carriers to pass through the oxide layer through quantum tunneling or pinholes. At the same time, the introduction of doping elements forms a conductive semiconductor layer that selectively blocks majority carriers, allowing only the tunneled minority carriers to be efficiently discharged. This significantly reduces the surface recombination rate, improves the open-circuit voltage, fill factor, and photoelectric conversion efficiency, and thus achieves synergistic optimization of passivation performance and conductivity performance.
[0004] However, in practical applications of TOPCon technology, tunneling passivation contact structures with different doping types exhibit significant differences in passivation levels. Specifically, the passivation performance of P-type doped polycrystalline silicon (P-poly) tunneling passivation contact structures formed with boron (B) as the dopant is significantly inferior to that of N-type doped polycrystalline silicon (N-poly) tunneling passivation contact structures formed with phosphorus (P) as the dopant. This is mainly due to the order-of-magnitude difference in J0 between the two. This significant difference in passivation performance makes it difficult for TOPCon cells using P-poly structures (such as the back contact layer of P-type TOPCon cells) to achieve the same open-circuit voltage and photoelectric conversion efficiency as N-poly structures. Furthermore, the currently used boron (B) diffusion processes require long diffusion times to achieve the required performance. In the current competitive photovoltaic industry, in addition to improving the photoelectric performance and conversion efficiency of cells, increasing production volume, reducing product costs, and enhancing product competitiveness within the same timeframe are also core challenges.
[0005] Therefore, how to provide a boron diffusion method that can simultaneously improve battery fabrication efficiency and increase production volume while significantly enhancing the photoelectric performance of the battery is a technical problem that urgently needs to be solved. Summary of the Invention
[0006] To address the aforementioned technical problems, this invention provides a boron diffusion method, a crystalline silicon solar cell, and a method for fabricating the same. This invention regulates the time proportions of the heating, isothermal, and cooling stages within a certain range, with the isothermal stage accounting for a relatively small proportion. By controlling the total thermal budget of the boron diffusion process, the passivation level of P-type doped polycrystalline silicon is improved, thereby enhancing the cell's photoelectric performance, particularly significantly increasing the open-circuit voltage and fill factor. Furthermore, the combination of processing times at each stage also considers fabrication efficiency, thus achieving a dual improvement in efficiency and performance through time optimization.
[0007] To achieve this objective, the present invention adopts the following technical solution: In a first aspect, the present invention provides a boron diffusion method, the boron diffusion method comprising subjecting the silicon-based material to be boron diffusion to a heating stage treatment, a isothermal stage treatment, and a cooling stage treatment to complete the boron diffusion; The duration of the heating phase accounts for 17% to 33% of the total duration of the heating, isothermal, and cooling phases, for example, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, or 33%, etc.; the duration of the isothermal phase accounts for 32% to 48% of the total duration of the heating, isothermal, and cooling phases, for example, 32% or 33%. 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, or 48%, etc.; the duration of the cooling stage accounts for 27% to 43% of the total duration of the heating stage, the constant temperature stage, and the cooling stage, for example, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, or 43%, etc.
[0008] This invention regulates the duration of the heating stage to be 17%–33% of the total duration of the heating, isothermal, and cooling stages; the isothermal stage to be 32%–48% of the total duration of the heating, isothermal, and cooling stages; and the cooling stage to be 27%–43% of the total duration of the heating, isothermal, and cooling stages. This regulates the overall thermal budget of the boron diffusion process, improves the passivation level of P-type doped polycrystalline silicon, and enhances the photoelectric performance of the battery, especially significantly improving the open-circuit voltage and fill factor. Furthermore, the combination of processing times for each stage can also consider preparation efficiency, thus achieving a dual improvement in efficiency and performance through time optimization.
[0009] In this invention, the duration of the isothermal treatment is controlled to account for 32% to 48% of the total duration of the heating, isothermal, and cooling treatments, thus achieving a balance between preparation efficiency, diffusion effect, and cost. If the isothermal treatment time is too short and the heating and cooling times are too long, a significant amount of time is wasted, reducing the effective utilization rate of time. Conversely, if the isothermal treatment time is too long and the heating and cooling times are too short, the diffusion effect will be reduced, leading to overdoping.
[0010] As a preferred technical solution of the present invention, the isothermal section treatment includes a deposition process and a propulsion process performed sequentially.
[0011] Preferably, the propulsion process includes an anaerobic propulsion process and / or an aerobic propulsion process.
[0012] Preferably, the deposition process includes at least one deposition.
[0013] Preferably, the propulsion process includes performing at least one propulsion.
[0014] Preferably, the duration of the deposition process accounts for 15% to 35% of the duration of the isothermal treatment, for example, 15%, 18%, 20%, 22%, 25%, 28%, 30%, 32%, or 35%.
[0015] Preferably, the duration of the propulsion process accounts for 50% to 80% of the duration of the constant temperature section processing, such as 50%, 52%, 55%, 58%, 60%, 62%, 65%, 68%, 70%, 72%, 75%, 78%, or 80%.
[0016] This invention regulates the deposition process time to be 15%~35% of the isothermal treatment time, and the advancement process time to be 50%~80% of the isothermal treatment time, which can satisfy the formation of suitable field passivation and chemical passivation effects. If the deposition process time is too long, excessive doping will form an inactive "dead layer" on the silicon wafer surface. The "dead layer" acts as a defect recombination center, capturing electron-hole pairs, reducing the cell's on-state voltage, and thus affecting the cell efficiency. If the deposition process time is too short, the doping concentration requirements for forming the necessary field passivation cannot be met. If the advancement process time is too long, on the one hand, boron will diffuse excessively in the substrate, becoming a defect recombination center in the substrate. On the other hand, the excessively long advancement time introduces an excessive thermal budget, which also fails to achieve the optimal chemical passivation level of the cell. If the advancement time is too short, on the one hand, the kinetic conditions for dopant activation cannot be met, and on the other hand, the thermal budget for forming the optimal chemical passivation level of the cell cannot be adapted.
[0017] As a preferred embodiment of the present invention, the heating stage process includes at least one heating process.
[0018] Preferably, the cooling section includes at least one cooling process.
[0019] The heating stage of this invention includes all heating processes in the entire boron diffusion process, and the cooling stage includes all cooling processes in the entire boron diffusion process.
[0020] As a preferred technical solution of the present invention, the deposition temperature during the deposition process is 800℃~1000℃, such as 800℃, 820℃, 850℃, 880℃, 900℃, 920℃, 950℃, 980℃ or 1000℃.
[0021] Preferably, the boron source introduced during the deposition process includes boron trichloride and / or boron tribromide.
[0022] Preferably, the boron source is introduced using a carrier gas.
[0023] Preferably, the carrier gas includes argon and / or nitrogen.
[0024] Preferably, the flow rate of the boron source is 100 sccm to 400 sccm, such as 100 sccm, 150 sccm, 200 sccm, 250 sccm, 300 sccm, 350 sccm or 400 sccm.
[0025] Preferably, the propulsion temperature during the propulsion process is 900℃~1100℃, such as 900℃, 920℃, 950℃, 980℃, 1000℃, 1020℃, 1050℃, 1080℃ or 1100℃.
[0026] As a preferred technical solution of the present invention, when the deposition process includes performing a deposition, the deposition temperature is obtained by heating a first temperature through a heating process.
[0027] Preferably, the first temperature is 500℃~800℃, such as 500℃, 520℃, 550℃, 580℃, 600℃, 620℃, 650℃, 680℃, 700℃, 720℃, 750℃, 780℃ or 800℃.
[0028] Preferably, the propulsion process includes performing one propulsion, and after the propulsion process is completed, a cooling process is initiated to cool down to a second temperature.
[0029] Preferably, the second temperature is 750℃~950℃, such as 750℃, 780℃, 800℃, 820℃, 850℃, 880℃, 900℃, 920℃ or 950℃.
[0030] As a preferred technical solution of the present invention, the deposition process includes at least one deposition, after which a heating process or a cooling process is performed before the next deposition begins, until the deposition process is completed.
[0031] In this invention, when the deposition process includes at least one deposition (each deposition at a different temperature), if a higher temperature deposition is required after the previous deposition is completed, a heating process is required to raise the temperature to the next deposition temperature; if a lower temperature deposition is required, a cooling process is required to lower the temperature to the next deposition temperature, until the deposition process is completed.
[0032] Preferably, the propulsion process includes at least one propulsion step, followed by a heating or cooling process after the previous propulsion step is completed before the next propulsion step begins, until the propulsion process ends.
[0033] In this invention, when the propulsion process includes at least one propulsion (each propulsion has a different temperature), if a higher temperature is required for the next propulsion after the previous propulsion is completed, a heating process is required to raise the temperature to the temperature of the next propulsion. If a lower temperature is required for the next propulsion, a cooling process is required to lower the temperature to the temperature of the next propulsion, until the propulsion process ends.
[0034] Preferably, the deposition process and the propulsion process further include a heating process or a cooling process.
[0035] In this invention, if there is a difference between the temperature of the deposition process and the temperature of the propulsion process, a heating or cooling process is required to reach the target propulsion process temperature.
[0036] As a preferred technical solution of the present invention, the total duration of the heating stage, the constant temperature stage, and the cooling stage is 90 min to 180 min, for example, 90 min, 100 min, 110 min, 120 min, 130 min, 140 min, 150 min, 160 min, 170 min, or 180 min.
[0037] As a preferred technical solution of the present invention, the boron-diffused silicon-based material is obtained by sequentially growing a tunneling oxide layer and depositing an intrinsic polycrystalline silicon layer on the surface of a silicon-based material.
[0038] It should be noted that the present invention does not impose specific requirements or special limitations on the thickness of the tunneling oxide layer and the intrinsic polysilicon layer. The thickness of conventional tunneling oxide layers and intrinsic polysilicon layers in the art is applicable to the present invention. Those skilled in the art can make adaptive selections and adjustments according to actual conditions. For example, the tunneling oxide layer can be 1nm~2nm and the intrinsic polysilicon layer can be 150nm~300nm.
[0039] It should be noted that the present invention does not impose specific requirements or special limitations on the method of sequentially growing a tunneling oxide layer and depositing an intrinsic polycrystalline silicon layer on the surface of silicon-based materials. Commonly used methods in the art are applicable to the present invention. Those skilled in the art can make adaptive selections and adjustments according to actual conditions. For example, the tunneling oxide layer can be produced by thermal oxidation, chemical oxidation, plasma oxidation, or atomic layer deposition, etc., and the intrinsic polycrystalline silicon layer can be produced by chemical vapor deposition, atomic layer deposition, or physical vapor deposition, etc.
[0040] Preferably, the silicon-based material includes a silicon wafer.
[0041] It should be noted that the present invention does not impose specific requirements or special limitations on silicon wafers. Those skilled in the art can make adaptive selections and adjustments according to actual conditions. For example, it can be a single-crystal N-type silicon wafer with a thickness of 100μm~200μm.
[0042] Secondly, the present invention also provides a method for preparing a crystalline silicon solar cell, the method comprising a boron diffusion method, wherein the boron diffusion method employs the boron diffusion method described in the first aspect.
[0043] Thirdly, the present invention also provides a crystalline silicon solar cell, which is prepared by the method for preparing a crystalline silicon solar cell described in the second aspect.
[0044] Preferably, the crystalline silicon solar cell includes a TOPCon solar cell or a back-contact solar cell.
[0045] Compared with the prior art, the present invention has at least the following beneficial effects: This invention regulates the time proportions of the heating, isothermal, and cooling stages within a certain range, with the isothermal stage accounting for a relatively small proportion. By controlling the total thermal budget of the boron diffusion process, the passivation level of P-type doped polycrystalline silicon is improved, thereby enhancing the photoelectric performance of the battery, especially significantly improving the open-circuit voltage and fill factor. At the same time, the combination of processing times for each stage can also take into account the preparation efficiency, thus achieving a dual improvement in efficiency and performance through time optimization. Detailed Implementation
[0046] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.
[0047] Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available products or can be prepared by known methods.
[0048] Example 1 This embodiment provides a boron diffusion method, which includes the following steps: S1. After cleaning commercially available monocrystalline N-type silicon wafers (resistivity 1Ω·cm~100Ω·cm, thickness 150μm), a tunneling oxide layer (SiO2) with a thickness of 1.5nm is grown on the surface of the silicon wafer using thermal oxidation. Subsequently, an intrinsic polycrystalline silicon layer with a thickness of 200nm is formed on the surface of the tunneling oxide layer by chemical vapor deposition, resulting in a tunneling oxide layer / intrinsic polycrystalline silicon composite stack (silicon wafer to be diffused with boron). S2. The silicon wafer to be diffused with boron undergoes a heating stage, a isothermal stage, and a cooling stage, specifically including: The silicon wafer to be boron diffusion is placed in a diffusion furnace and heated from 600°C to 850°C for 900 seconds. Boron trichloride (using argon gas) is introduced at a flow rate of 300 sccm and deposited at 850°C for 720 seconds. Then, the temperature is increased from 850°C to 950°C for 500 seconds. Oxygen is then introduced and the wafer is aerobically propelled at 950°C for 1800 seconds. Finally, the temperature is reduced from 950°C to 880°C and exited the tube for 1900 seconds, completing the boron diffusion process. The total duration of the heating, isothermal, and cooling processes was 5820 seconds. The heating process took 1400 seconds (24%), the isothermal process took 2520 seconds (43%), and the cooling process took 1900 seconds (33%). The isothermal treatment lasted 2520s, the deposition time was 720s (29%), and the aerobic propulsion time was 1800s (71%).
[0049] Example 2 This embodiment provides a boron diffusion method, which includes the following steps: S1. After cleaning commercially available monocrystalline N-type silicon wafers (resistivity 1Ω·cm~100Ω·cm, thickness 150μm), a tunneling oxide layer (SiO2) with a thickness of 1.5nm is grown on the surface of the silicon wafer using thermal oxidation. Subsequently, an intrinsic polycrystalline silicon layer with a thickness of 200nm is formed on the surface of the tunneling oxide layer by chemical vapor deposition, resulting in a tunneling oxide layer / intrinsic polycrystalline silicon composite stack (silicon wafer to be diffused with boron). S2. The silicon wafer to be diffused with boron undergoes a heating stage, a isothermal stage, and a cooling stage, specifically including: The silicon wafer to be boron diffused was placed in a diffusion furnace and heated from 550°C to 800°C for 800 seconds. Boron trichloride (using argon gas) was introduced at a flow rate of 100 sccm and deposited at 800°C for 1200 seconds. Then, the temperature was increased from 800°C to 900°C for 700 seconds. Nitrogen gas was then introduced and oxygen-free diffusion was carried out at 900°C for 2500 seconds. Finally, the temperature was reduced from 900°C to 750°C and exited the tube for 2500 seconds, completing the boron diffusion process. The total duration of the heating, isothermal, and cooling processes was 7700 seconds. The heating process took 1500 seconds (19%), the isothermal process took 3700 seconds (48%), and the cooling process took 2500 seconds (33%). The isothermal treatment lasted 3700s, the deposition time was 1200s (32%), and the aerobic propulsion time was 2500s (68%).
[0050] Example 3 This embodiment provides a boron diffusion method, which includes the following steps: S1. After cleaning commercially available monocrystalline N-type silicon wafers (resistivity 1Ω·cm~100Ω·cm, thickness 150μm), a tunneling oxide layer (SiO2) with a thickness of 1.5nm is grown on the surface of the silicon wafer using thermal oxidation. Subsequently, an intrinsic polycrystalline silicon layer with a thickness of 200nm is formed on the surface of the tunneling oxide layer by chemical vapor deposition, resulting in a tunneling oxide layer / intrinsic polycrystalline silicon composite stack (silicon wafer to be diffused with boron). S2. The silicon wafer to be diffused with boron undergoes a heating stage, a isothermal stage, and a cooling stage, specifically including: The silicon wafer to be boron diffused was placed in a diffusion furnace and heated from 800°C to 1000°C for 1000 seconds. Boron trichloride (using argon gas) was introduced at a flow rate of 400 sccm and deposited at 1000°C for 600 seconds. Then, the temperature was increased from 1000°C to 1100°C for 800 seconds. Oxygen was then introduced and the wafer was aerobically propelled at 1100°C for 2000 seconds. Finally, the temperature was reduced from 1100°C to 950°C and removed from the tube for 2400 seconds, thus completing the boron diffusion. The total duration of the heating, isothermal, and cooling processes was 6800 seconds. The heating process took 1800 seconds (26%), the isothermal process took 2600 seconds (38%), and the cooling process took 2400 seconds (35%). The isothermal treatment lasted 2600s, the deposition time was 600s (23%), and the aerobic propulsion time was 2000s (77%).
[0051] Example 4 This embodiment provides a boron diffusion method, which includes the following steps: S1. After cleaning commercially available monocrystalline N-type silicon wafers (resistivity 1Ω·cm~100Ω·cm, thickness 150μm), a tunneling oxide layer (SiO2) with a thickness of 1.5nm is grown on the surface of the silicon wafer using thermal oxidation. Subsequently, an intrinsic polycrystalline silicon layer with a thickness of 200nm is formed on the surface of the tunneling oxide layer by chemical vapor deposition, resulting in a tunneling oxide layer / intrinsic polycrystalline silicon composite stack (silicon wafer to be diffused with boron). S2. The silicon wafer to be diffused with boron undergoes a heating stage, a isothermal stage, and a cooling stage, specifically including: The silicon wafer to be boron diffused was placed in a diffusion furnace and heated from 600°C to 850°C for 900 seconds. Boron trichloride (using argon gas) was introduced at a flow rate of 300 sccm. The wafer was deposited once at 850°C for 600 seconds, followed by a second deposition at 950°C for 300 seconds, then heated from 950°C to 1050°C for 600 seconds. Oxygen was then introduced and the wafer was propelled aerobically at 1050°C for 1600 seconds, followed by a second aerobic propelling at 1100°C for 800 seconds, then cooled from 1100°C to 900°C for 3200 seconds, thus completing the boron diffusion process. The total duration of the heating, isothermal, and cooling processes was 8900 seconds. The heating process took 2400 seconds (27%), the isothermal process took 3300 seconds (37%), and the cooling process took 3200 seconds (36%). The isothermal treatment lasted 3300s, the deposition time was 900s (27%), and the aerobic propulsion time was 2400s (73%).
[0052] Example 5 This embodiment provides a boron diffusion method. The difference between the boron diffusion method and that in Embodiment 1 is that in step S2, the duration of the isothermal treatment is 2520s, of which the deposition time is 1000s (40%) and the aerobic propulsion time is 1520s (60%). The remaining preparation methods and parameters are consistent with those in Embodiment 1.
[0053] Example 6 This embodiment provides a boron diffusion method. The difference between the boron diffusion method and that in Embodiment 1 is that in step S2, the isothermal treatment time is 2520s, of which the deposition time is 1520s (60%) and the aerobic propulsion time is 1000s (40%). The remaining preparation methods and parameters are consistent with those in Embodiment 1.
[0054] Example 7 This embodiment provides a boron diffusion method. The difference between the boron diffusion method and that in Embodiment 1 is that in step S2, the isothermal treatment time is 2520s, of which the deposition time is 300s (12%) and the aerobic propulsion time is 2220s (88%). The remaining preparation methods and parameters are consistent with those in Embodiment 1.
[0055] Comparative Example 1 This comparative example provides a boron diffusion method. The difference between this boron diffusion method and Example 1 is that in step S2, deposition is performed at 850°C for 960 s, followed by aerobic propulsion at 950°C for 2360 s. The total duration of the heating, isothermal, and cooling processes is 6620 s. The heating process lasts for 1400 s (21%), the isothermal process for 3320 s (50%), the cooling process for 1900 s (29%), the isothermal process for 3320 s, the deposition time for 960 s (29%), and the aerobic propulsion time for 2360 s (71%). The remaining preparation methods and parameters are consistent with those of Example 1.
[0056] Comparative Example 2 This comparative example provides a boron diffusion method. The difference between this boron diffusion method and Example 1 is that in step S2, deposition is performed at 850°C for 420 s, followed by aerobic propulsion at 950°C for 1000 s. The total duration of the heating, isothermal, and cooling processes is 4720 s. The heating process lasts for 1400 s (30%), the isothermal process for 1420 s (30%), the cooling process for 1900 s (40%), the isothermal process for 1420 s, the deposition time for 420 s (29%), and the aerobic propulsion time for 1000 s (71%). The remaining preparation methods and parameters are consistent with those of Example 1.
[0057] Application Example 1 This application example provides a method for fabricating a TOPCon solar cell. The fabrication method includes a boron diffusion method, which adopts the boron diffusion method provided in Example 1. The specific fabrication method of the TOPCon solar cell includes: cleaning and texturing → boron diffusion (Example 1) → etching → laser grooving → phosphorus diffusion → front-side decoupling → etching and texturing → coating → printing electrode.
[0058] Application Examples 2-7 and Comparative Application Examples 1-2 Application Examples 2-7 and Comparative Application Examples 1-2 each provide a method for preparing a TOPCon solar cell. The difference between the preparation method and Application Example 1 is that the boron diffusion method provided in Examples 2-7 and Comparative Examples 1-2 is used respectively, while the other preparation methods and parameters are consistent with Application Example 1.
[0059] The photoelectric performance of the TOPCon solar cells provided in Application Examples 1-7 and Comparative Application Examples 1-2 was tested. A standard solar intensity calibration was performed using a solar simulator, and the solar cells with an area of 349.44 cm² were tested. 2 IV tests were performed on the TOPCon solar cells, including photoelectric conversion efficiency (PCE), fill factor (FF), and open-circuit voltage (Voc). The sheet resistance of the boron diffusion layer was tested at 25°C using the four-probe method (T / CPIA 0100-2024), and the test results are shown in Table 1.
[0060] Table 1 The test results show that: (1) As can be seen from Application Examples 1 to 4, the present invention controls the duration of the heating stage to account for 17% to 33% of the total duration of the heating stage, isothermal stage, and cooling stage; the duration of the isothermal stage to account for 32% to 48% of the total duration of the heating stage, isothermal stage, and cooling stage; and the duration of the cooling stage to account for 27% to 43% of the total duration of the heating stage, isothermal stage, and cooling stage. This controls the total thermal budget of the boron diffusion process, improves the passivation level of P-type doped polycrystalline silicon, and enhances the photoelectric performance of the battery, especially significantly improving the open-circuit voltage and fill factor. At the same time, the combination of the processing time of each stage can also take into account the preparation efficiency. Thus, the efficiency and performance are improved by time optimization. Specifically, Voc is 0.748V to 0.753V, FF is 86.22% to 86.45%, PCE is 26.82% to 27.00%, and sheet resistance is 144Ω / □ to 191Ω / □.
[0061] (2) As can be seen from Application Examples 5 to 7, the present invention further regulates the deposition process duration to be 15% to 35% of the isothermal treatment duration and the advancement process duration to be 50% to 80% of the isothermal treatment duration, which can satisfy the formation of suitable field passivation effect and chemical passivation effect, and can further improve the battery open circuit voltage and photoelectric conversion efficiency.
[0062] (3) By comparing application examples 1 to 2, it can be seen that the present invention further adjusts the duration of the isothermal treatment to 32% to 48% of the total duration of the heating, isothermal and cooling treatments, which can achieve a balance between preparation efficiency, diffusion effect and cost. Through time optimization, efficiency and performance are improved.
[0063] In summary, the present invention controls the time proportions of the heating stage, the isothermal stage, and the cooling stage within a certain range, especially the isothermal stage, which accounts for a relatively small proportion. By controlling the total thermal budget of the boron diffusion process, the passivation level of P-type doped polycrystalline silicon is improved, thereby enhancing the photoelectric performance of the battery, especially the open-circuit voltage and fill factor. At the same time, the combination of processing times in each stage can also take into account the preparation efficiency, thus achieving a dual improvement in efficiency and performance through time optimization.
[0064] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.
Claims
1. A boron diffusion method, characterized in that, The boron diffusion method includes treating the silicon-based material to be boron diffused in a heating section, a isothermal section, and a cooling section to complete the boron diffusion. The duration of the heating stage accounts for 17% to 33% of the total duration of the heating stage, the isothermal stage, and the cooling stage. The duration of the isothermal treatment section accounts for 32% to 48% of the total duration of the heating section, the isothermal treatment section, and the cooling section. The cooling stage accounts for 27% to 43% of the total time of the heating stage, the constant temperature stage, and the cooling stage.
2. The boron diffusion method according to claim 1, characterized in that, The isothermal treatment includes a deposition process and a propulsion process performed sequentially. Preferably, the propulsion process includes an anaerobic propulsion process and / or an aerobic propulsion process; Preferably, the deposition process includes at least one deposition; Preferably, the propulsion process includes performing at least one propulsion. Preferably, the duration of the deposition process accounts for 15% to 35% of the duration of the isothermal treatment. Preferably, the duration of the propulsion process accounts for 50% to 80% of the duration of the isothermal treatment.
3. The boron diffusion method according to claim 1 or 2, characterized in that, The heating section process includes at least one heating process; Preferably, the cooling section includes at least one cooling process.
4. The boron diffusion method according to claim 2, characterized in that, The deposition temperature during the deposition process is 800℃~1000℃; Preferably, the boron source introduced during the deposition process includes boron trichloride and / or boron tribromide; Preferably, the flow rate of the boron source is 100 sccm to 400 sccm; Preferably, the propulsion temperature during the propulsion process is 900℃~1100℃.
5. The boron diffusion method according to claim 2, characterized in that, When the deposition process includes performing a single deposition, the deposition temperature is obtained by heating a first temperature through a heating process; Preferably, the first temperature is 500℃~800℃; Preferably, the propulsion process includes performing one propulsion, and after the propulsion process is completed, a cooling process is initiated to cool down to a second temperature; Preferably, the second temperature is 750℃~950℃.
6. The boron diffusion method according to claim 2, characterized in that, When the deposition process includes at least one deposition, after the previous deposition step is completed, a heating or cooling process is performed before the next deposition step begins, until the deposition process is completed; Preferably, when the propulsion process includes performing at least one propulsion, after the previous propulsion step is completed, a heating process or a cooling process is performed before the next propulsion step begins, until the propulsion process ends; Preferably, the deposition process and the propulsion process further include a heating process or a cooling process.
7. The boron diffusion method according to any one of claims 1 to 6, characterized in that, The total duration of the heating stage, the isothermal stage, and the cooling stage is 90 min to 180 min.
8. The boron diffusion method according to any one of claims 1 to 7, characterized in that, The silicon-based material to be diffused by boron is obtained by sequentially growing a tunneling oxide layer and depositing an intrinsic polycrystalline silicon layer on the surface of the silicon-based material.
9. A method for preparing a crystalline silicon solar cell, characterized in that, The preparation method includes a boron diffusion method, wherein the boron diffusion method is the boron diffusion method according to any one of claims 1 to 8.
10. A crystalline silicon solar cell, characterized in that, The crystalline silicon solar cell is prepared using the method for preparing a crystalline silicon solar cell as described in claim 9.