A method for manufacturing a back contact solar cell and a back contact solar cell
By combining nanoscale non-metallic powder materials with ultrasonic cleaning, the problems of etchant residue and antireflective layer erosion were solved, achieving electrical isolation and efficiency stability of back-contact solar cells.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- JA SOLAR TECH YANGZHOU
- Filing Date
- 2026-03-30
- Publication Date
- 2026-07-14
AI Technical Summary
In existing technologies, laser grooving processes reduce the effective carrier collection area of the p-type functional layer in back-contact solar cells, incomplete etching of the resist leads to leakage and long-term reliability risks, and strong alkaline cleaning erodes the antireflection layer, reducing efficiency.
The etchant was removed by combining nanoscale non-metallic powder materials with ultrasonic cleaning. Low-corrosion cleaning solutions and alkaline solutions were used to ensure that the etchant was completely removed without eroding the antireflective layer.
It effectively removes residual etchant, avoids damage to the antireflective layer, ensures stable battery efficiency, and improves electrical isolation.
Smart Images
Figure CN122396088A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the technical field of solar cells, specifically to a method for preparing a back-contact solar cell and the back-contact solar cell itself. Background Technology
[0002] In the fabrication process of back-contact solar cells, to achieve electrical isolation between the p-type and n-type regions on the back side, it is usually necessary to locally cut the conductive film at the boundary region where they intersect or are adjacent. Currently, laser grooving technology is commonly used for this cutting process. However, the laser generates lateral thermal radiation during the grooving process, which can easily affect the adjacent p-type functional layer, resulting in a reduction in the effective carrier collection area of the p-type functional layer and a deterioration in carrier collection efficiency.
[0003] To address the aforementioned issues, some technologies use etchant instead of lasers for localized cutting. However, this method introduces new problems: the etchant needs to be cleaned after its action. If the etchant is not cleaned thoroughly during the subsequent cleaning process, its residue can easily cause large leakage current in the back contact solar cell, thus posing a long-term reliability risk.
[0004] To ensure the etchant is thoroughly cleaned, a strong alkaline solution is usually used for cleaning, or the cleaning time of a weak alkaline solution is extended. However, the manufacturing process of back contact solar cells already includes multiple alkaline cleaning steps. Additional strong alkaline treatment or prolonged alkaline washing will inevitably further erode the antireflective layer on the front of the cell, reducing the light utilization rate on the front and resulting in a loss of efficiency for back contact solar cells. Summary of the Invention
[0005] In a first aspect, this application provides a method for fabricating a back-contact solar cell, the method comprising: S10: Provide a first solar cell precursor, the first solar cell precursor includes a front side and a back side, an anti-reflection layer is provided on the front side, a first doped region and a second doped region with opposite conductivity types are provided on the back side, and a preset isolation region is also provided between the first doped region and the second doped region. S20: Forming an isolation region. A conductive thin film layer covering a first doped region, a second doped region, and a preset isolation region is formed on the back side of the first cell precursor. An etchant located in the preset isolation region is provided on the back light side of the conductive thin film layer. The etchant is used to etch the portion of the conductive thin film layer located in the preset isolation region to form a second cell precursor with an isolation region. S30: The second cell precursor is placed in a cleaning solution for ultrasonic cleaning. The cleaning solution includes water or alkaline solution and contains nano-scale non-metallic powder material. The Mohs hardness of the nano-scale non-metallic powder material is less than that of the anti-reflective layer.
[0006] In some optional embodiments of the first aspect of this application, in S30: The cleaning solution is an alkaline solution with a mass percentage of alkali of 0.01wt% to 1wt%. The ultrasonic cleaning time is 0.5min to 1.5min.
[0007] In some optional embodiments of the first aspect of this application, the mass percentage of alkali in the alkaline solution is 0.01wt% to 0.1wt%.
[0008] In some optional embodiments of the first aspect of this application, the cleaning fluid is water, and the ultrasonic cleaning time is 3 min to 5 min.
[0009] In some optional embodiments of the first aspect of this application, the difference between the Mohs hardness of the antireflective layer and the nanoscale non-metallic powder material ranges from 1 to 2.
[0010] In some optional embodiments of the first aspect of this application, the Mohs hardness of the nanoscale non-metallic powder material is less than that of the conductive thin film layer.
[0011] In some optional embodiments of the first aspect of this application, the Mohs hardness of the antireflective layer ranges from 4 to 10.
[0012] In some optional embodiments of the first aspect of this application, the particle size of the nanoscale non-metallic powder material is 10 nm to 100 nm.
[0013] In some optional embodiments of the first aspect of this application, the nanoscale non-metallic powder is silicon oxide powder.
[0014] In some optional embodiments of the first aspect of this application, the pH value of the etchant is 1 to 2.
[0015] In some optional embodiments of the first aspect of this application, the etchant includes an acid, a thickener, and a solvent, wherein the mass fraction of the acid is 5% to 10%, the mass fraction of the thickener is 50% to 70%, and the mass fraction of the solvent is 20% to 40% based on the total mass of the etchant.
[0016] In some optional embodiments of the first aspect of this application, the first cell precursor includes a silicon substrate; the first doped region includes an intrinsic silicon-containing thin film and a doped silicon-containing thin film stacked together; and the second doped region includes a tunneling oxide layer and a doped polycrystalline silicon layer stacked together.
[0017] In some optional embodiments of the first aspect of this application, the isolation region includes a tunneling oxide layer, a doped polysilicon layer, an insulating isolation layer, an intrinsic silicon-containing thin film, and a doped silicon-containing thin film stacked together.
[0018] In some optional embodiments of the first aspect of this application, the conductivity type of the first doped region is opposite to that of the silicon substrate, and the conductivity type of the second doped region is the same as that of the silicon substrate.
[0019] In some optional embodiments of the first aspect of this application, the silicon substrate is an n-type silicon substrate, the doped silicon thin film is a p-type doped silicon thin film, and the doped polycrystalline silicon layer is an n-type doped polycrystalline silicon layer.
[0020] The second aspect of this application provides a back-contact solar cell, which is prepared according to the above-described method for preparing a back-contact solar cell.
[0021] Beneficial effects: The method for fabricating a back-contact solar cell provided in the first aspect of this application involves etching a conductive thin film layer between a first doped region and a second doped region using an etchant to form an isolation region. The etchant is then removed by using a cleaning solution and nanoscale non-metallic powder material in conjunction with ultrasonic cleaning. The cleaning solution has low corrosivity, which effectively removes the etchant while reducing the corrosive effect of the cleaning solution on the antireflection layer, thereby preventing further erosion of the antireflection layer and ensuring the stability of the antireflection layer thickness.
[0022] A second aspect of this application provides a back-contact solar cell in which an isolation region is formed between a first doped region and a second doped region to achieve electrical isolation between the first doped region and the second doped region; the isolation region is locally etched with etchant and cleaned with a cleaning solution to ensure that no etchant residue remains. Attached Figure Description
[0023] Figure 1 This is a flowchart of the preparation method of the back contact solar cell in Embodiment 1 of this application; Figure 2 This is a schematic diagram of the back-contact solar cell obtained in Embodiment 1 of this application; Figure 3 This is a schematic diagram of the structure of the n-type silicon substrate after step a in Embodiment 1 of this application; Figure 4 This is a schematic diagram of the structure of the n-type silicon substrate after step b in Embodiment 1 of this application; Figure 5 This is a schematic diagram of the silicon-based device structure after step c in Embodiment 1 of this application; Figure 6 This is a schematic diagram of the silicon-based device structure after step d in Embodiment 1 of this application; Figure 7 This is a schematic diagram of the silicon-based device structure after step e in Embodiment 1 of this application; Figure 8This is a schematic diagram of the silicon-based device structure after step f in Embodiment 1 of this application; Figure 9 This is a schematic diagram of the silicon-based device structure after step g in Embodiment 1 of this application; Figure 10 This is a schematic diagram of the silicon-based device structure after step h in Embodiment 1 of this application; Figure 11 This is a schematic diagram of the silicon-based device structure after step h in Embodiment 1 of this application; Figure 12 This is a schematic diagram of the silicon-based device structure after step i in Embodiment 1 of this application; Figure 13 This is a schematic diagram of the silicon-based device structure after step j in Embodiment 1 of this application; Figure 14 This is a partial image of the back side of the silicon-based device after processing in step i in Embodiment 1 of this application; Figure 15 This is a partial image of the back side of the silicon-based device after step i in Comparative Example 1 of this application; Figure 16 This is a partial image of the back side of the silicon-based device after step i in Comparative Example 2 of this application.
[0024] Figures 1 to 16 The reference numerals in the figures are as follows: 1. Silicon substrate; 2. Passivation layer; 3. Antireflective layer; 4. Tunneling oxide layer; 5. Doped polysilicon layer; 6. Insulating isolation layer; 7. Intrinsic silicon thin film; 8. Doped silicon thin film; 9. Conductive thin film layer; 10. Etching agent; 11. First metal electrode; 12. Second metal electrode; 13. Isolation trench; A. First doped region; B. Second doped region; C. Isolation region; C'. Preset isolation region. Detailed Implementation
[0025] The present application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only for explaining the present application and are not intended to limit the present application.
[0026] The first aspect of this application provides a method for fabricating a back-contact solar cell, the method comprising: S10: Provide a first solar cell precursor, the first solar cell precursor includes a front side and a back side, an anti-reflection layer 3 is provided on the front side, a first doped region A and a second doped region B with opposite conductivity types are provided on the back side, and a preset isolation region C' is also provided between the first doped region A and the second doped region B. S20: Forming an isolation region C, a conductive thin film layer 9 covering a first doped region A, a second doped region B and a preset isolation region C' is formed on the back side of the first cell precursor, and an etchant 10 located in the preset isolation region C' is disposed on the back side of the conductive thin film layer 9. The etchant 10 is used to etch the portion of the conductive thin film layer 9 located in the preset isolation region C' to form a second cell precursor having an isolation region C. S30: The second battery cell precursor is placed in a cleaning solution for ultrasonic cleaning. The cleaning solution includes water or alkaline solution and contains nano-scale non-metallic powder material. The Mohs hardness of the nano-scale non-metallic powder material is less than that of the anti-reflection layer 3.
[0027] In a method for fabricating a back-contact solar cell provided in the first aspect of this application, a first cell precursor is prepared from a silicon substrate 1, which may be selected from an n-type silicon substrate or a p-type silicon substrate. An anti-reflection layer 3 is prepared on the front side of the silicon substrate 1, a first doped region A and a second doped region B are formed on the back side of the silicon substrate 1, and a predetermined isolation region C' is formed between the first doped region A and the second doped region B to obtain the first cell precursor. A conductive thin film layer 9 is formed on the back side of the first cell precursor, covering the first doped region A, the second doped region B, and the predetermined isolation region C'. An etchant 10 is formed on the back side of the conductive thin film layer 9, covering the predetermined isolation region C'. The etchant 10 is used to etch the portion of the conductive thin film layer 9 located in the predetermined isolation region C' to form a second cell precursor with the isolation region C. The etchant 10 on the second cell precursor is removed using a cleaning solution and ultrasonic cleaning.
[0028] During the cleaning process of the etchant 10, the second cell precursor is placed in the cleaning solution. At the same time, the nanoscale non-metallic powder material particles are driven by ultrasound to move and impact the viscous etchant 10, thereby accelerating the peeling of the etchant 10 from the surface of the second cell precursor and achieving the effect of removing the etchant 10.
[0029] In this embodiment, a low-corrosive cleaning solution is used to remove the etchant 10. Compared with a strongly alkaline cleaning solution, the cleaning solution used in this embodiment has very low corrosivity and causes little damage to the antireflection layer 3, thus avoiding erosion and thinning of the antireflection layer 3 and ensuring the thickness of the antireflection layer 3.
[0030] In this embodiment, the nanoscale non-metallic powder material contains no metal elements, thus avoiding potential contamination and interference from the introduction of metal impurities. The Mohs hardness of the nanoscale non-metallic powder material is lower than that of the antireflective layer 3, ensuring that the nanoscale non-metallic powder material will not damage the antireflective layer 3 during ultrasonic cleaning. The amount of nanoscale non-metallic powder material used depends on the actual cleaning operation.
[0031] In some optional embodiments of the first aspect of this application, the cleaning solution is an alkaline solution, wherein the mass percentage of alkali in the alkaline solution is 0.01wt% to 1wt%, and the ultrasonic cleaning time is 0.5min to 1.5min. The alkaline solution is generally an alkaline aqueous solution, such as sodium hydroxide solution or potassium hydroxide solution. The etching resist 10 is generally an acidic slurry. In this embodiment, by using a low-concentration alkaline solution and nano-scale non-metallic powder material in conjunction with ultrasonic cleaning, the alkaline solution and acidic slurry undergo a neutralization reaction, and the nano-scale non-metallic powder material moves and impacts the etching resist 10, thereby completely removing the etching resist 10 in a shorter cleaning time and avoiding damage to the antireflective layer 3.
[0032] In some optional embodiments of the first aspect of this application, the mass percentage of alkali in the alkaline solution is 0.01wt% to 0.1wt%, which further reduces the concentration of alkali in the cleaning solution and further avoids corrosion of the antireflective layer 3.
[0033] In some optional embodiments of the first aspect of this application, the cleaning solution is water, and the ultrasonic cleaning time is 3 to 5 minutes. In this embodiment, water and nano-scale non-metallic powder material are used in conjunction with ultrasonic cleaning. The movement of the nano-scale non-metallic powder material particles impacts the viscous etchant 10 to remove the etchant 10.
[0034] In some optional embodiments of the first aspect of this application, the difference between the Mohs hardness of the antireflection layer 3 and the Mohs hardness of the nanoscale non-metallic powder material is in the range of 1 to 2. Within this range, the nanoscale non-metallic powder material can be effectively prevented from damaging the antireflection layer 3 under ultrasonic conditions and the etching adhesive can be effectively removed.
[0035] In some optional embodiments of the first aspect of this application, the Mohs hardness of the nanoscale non-metallic powder material is less than the Mohs hardness of the conductive thin film layer 9, thereby avoiding damage to the conductive thin film layer 9 by the nanoscale non-metallic powder material during ultrasonic cleaning.
[0036] In some optional embodiments of the first aspect of this application, the Mohs hardness of the antireflection layer 3 is in the range of 4 to 10. The thickness of the antireflection layer 3 is 1 nm to 300 nm. The antireflection layer 3 can be a single-layer film or a multilayer film, and the single-layer film is composed of one of the following materials: silicon nitride (SiN). x ), silicon oxynitride (SiN) x O 1-x ), silicon dioxide (SiO) x ), magnesium fluoride (MgF) x (x) or lithium fluoride (LiF), where x represents a non-stoichiometric ratio that can be controlled by the deposition process. Multilayer films are made of silicon nitride (SiN). x ), silicon oxynitride (SiN) x O 1-x ), silicon dioxide (SiO)x ), magnesium fluoride (MgF) x It is composed of two or more materials with different refractive indices, such as lithium fluoride (LiF) or lithium fluoride (SiN), stacked alternately, such as periodic or aperiodic stacking of high-refractive-index and low-refractive-index materials. For example: SiN x / MgF2、SiN x / SiO x / SiN x SiN x / SiN x O 1-x / MgF2, etc.
[0037] In some optional embodiments of the first aspect of this application, the particle size of the nanoscale non-metallic powder material is 10 nm to 100 nm.
[0038] In some optional embodiments of the first aspect of this application, the pH value of the etchant 10 is 1 to 2.
[0039] In some optional embodiments of the first aspect of this application, the etchant 10 includes an acid, a thickener, and a solvent. The acid may be phosphoric acid, and the solvent may be water. Based on the total mass of the etchant 10, the mass fraction of the acid is 5% to 10%, the mass fraction of the thickener is 50% to 70%, and the mass fraction of the solvent is 20% to 40%.
[0040] In some optional embodiments of the first aspect of this application, such as Figure 2 As shown, the first doped region A includes an intrinsic silicon-containing thin film 7 and a doped silicon-containing thin film 8 stacked together.
[0041] The intrinsic silicon-containing thin film 7 can be made of at least one of elemental silicon, silicon oxide, and silicon carbide. The microstructure of the intrinsic silicon-containing thin film 7 can be amorphous, nanocrystalline, or microcrystalline, such as amorphous silicon, nanocrystalline silicon, microcrystalline silicon, amorphous silicon oxide, or nanocrystalline silicon carbide. The intrinsic silicon-containing thin film 7 can be any of the following: a single-layer film, a multilayer film, or a mixed-phase film. A single-layer film is a conductive film formed by a single dopant material. A multilayer film is formed by sequentially stacking two or more different dopant materials (or the same material but different doping concentrations), and the materials of each sublayer can be the same or different. A mixed-phase film is a homogeneous or heterogeneous conductive layer formed by mixing two or more dopant materials in the same layer through co-deposition, composite, or gradient doping. The material type, doping type and concentration, thickness, and stacking order of each layer can be designed and optimized according to the specific requirements of the device for conductivity, transmittance, work function, or environmental stability.
[0042] The material of the silicon-doped thin film 8 can be selected from at least one of elemental silicon, silicon oxide, and silicon carbide. The microstructure morphology of the material of the silicon-doped thin film 8 includes: amorphous, nanocrystalline, or microcrystalline states, such as amorphous silicon, microcrystalline silicon, nanocrystalline silicon, and amorphous / microcrystalline silicon oxide or silicon carbide. The doping concentration is adjusted according to the electrical performance requirements of the device. The structure of the silicon-doped thin film 8 can be any of the following: a single-layer film, a multilayer film, or a mixed-phase film. The conductivity type of the first doped region A can be opposite to that of the silicon substrate 1, forming a pn junction with the silicon substrate 1, serving as the emitter of the back-contact solar cell. For example, when the silicon substrate 1 is an n-type silicon substrate, the conductivity type of the first doped region A is p-type, and correspondingly, the silicon-doped thin film 8 is a p-type doped silicon-doped thin film doped with a group III element (e.g., boron, aluminum, gallium, or indium).
[0043] In some optional embodiments of the first aspect of this application, such as Figure 2 As shown, the second doped region B includes a tunneling oxide layer 4 and a doped polysilicon layer 5 stacked together.
[0044] The tunneling oxide layer 4 can be selected from the silicon oxide layer, and its thickness is 0.5 nm to 3.0 nm. The thickness of the doped polycrystalline silicon layer 5 is 30 nm to 300 nm. The conductivity type of the second doped region B can be the same as that of the silicon substrate 1, serving as the back field of the solar cell. For example, when the silicon substrate 1 is an n-type silicon substrate, the conductivity type of the second doped region B is n-type, and correspondingly, the doped polycrystalline silicon layer 5 is composed of n-type doped polycrystalline silicon material, and its doping element is selected from at least one of phosphorus, arsenic, antimony, or bismuth. The doped polycrystalline silicon layer 5 can be a single-layer structure or can form a composite stacked structure with other functional layers (such as intrinsic polycrystalline silicon, silicon oxide, silicon nitride, etc.).
[0045] In some optional embodiments of the first aspect of this application, such as Figure 2 As shown, the isolation region C includes a tunneling oxide layer 4, a doped polysilicon layer 5, an insulating isolation layer 6, an intrinsic silicon-containing thin film 7, and a doped silicon-containing thin film 8, which are stacked together.
[0046] The insulating layer 6 can be made of at least one of intrinsic silicon oxide, intrinsic silicon nitride, or intrinsic silicon oxynitride; the insulating layer 6 can be a single-layer structure or a multilayer stacked structure composed of the above materials (such as SiO2 / SiN). x SiN x / SiN x O 1-x (etc.), the insulating isolation layer 6 is used to achieve electrical isolation.
[0047] In some optional embodiments of the first aspect of this application, before the antireflection layer 3 is disposed on the front side, the method further includes: disposing a passivation layer 2 on the front side, and the antireflection layer 3 is disposed on the passivation layer 2.
[0048] In some optional embodiments of the first aspect of this application, the passivation layer 2 may be selected from an intrinsic silicon-containing thin film or an intrinsic silicon-containing thin film / doped silicon-containing thin film; wherein, the thickness of the intrinsic silicon-containing thin film is 1-15 nm, and the thickness of the doped silicon-containing thin film is 0-30 nm. The material of the intrinsic silicon-containing thin film may be selected from at least one of elemental silicon, silicon oxide, and silicon carbide; the microstructure morphology of the intrinsic silicon-containing thin film material includes amorphous, nanocrystalline, or microcrystalline states, such as amorphous silicon, nanocrystalline silicon, microcrystalline silicon, amorphous silicon oxide, or nanocrystalline silicon carbide; the structural form of the intrinsic silicon-containing thin film may be any of the following: a single-layer film, a multilayer stacked film, or a mixed-phase film. The material of the doped silicon-containing thin film may be selected from one or more of amorphous silicon, microcrystalline silicon, or nanocrystalline silicon, and the doping element is selected from phosphorus, arsenic, or antimony; the doped silicon-containing thin film may be a single-layer structure or a multilayer stacked structure composed of silicon sublayers with different crystal structures or different doping concentrations, and the thickness and doping concentration of each layer may be adjusted according to the device performance requirements. The conductivity type of the doped silicon thin film serving as passivation layer 2 can be the same as that of the silicon substrate 1. For example, when the silicon substrate 1 is an n-type silicon substrate, the doped silicon thin film serving as passivation layer 2 is an n-type doped silicon thin film doped with at least one of phosphorus, arsenic, antimony, or bismuth.
[0049] In some optional embodiments of the first aspect of this application, the material of the passivation layer 2 may be selected from silicon oxide (SiO2). x Alumina AlO x Gallium oxide (GaO) x and titanium dioxide (TiO) x At least one of the above materials. The passivation layer 2 can be a single-layer film or a multilayer film, with a thickness of 1~15nm; the single-layer film is formed by one of the above materials, and the multilayer film is formed by two or more of the above materials stacked sequentially.
[0050] A second aspect of this application provides a back-contact solar cell, fabricated according to the aforementioned method for fabricating a back-contact solar cell. In this back-contact solar cell, an isolation region C is formed between a first doped region A and a second doped region B to achieve electrical isolation between the first doped region A and the second doped region B. This isolation region C is locally etched using an etchant 10 and then cleaned with a cleaning solution to ensure that no etchant 10 residue remains.
[0051] The present application is further illustrated below with reference to embodiments and comparative examples. Unless otherwise specified, the raw materials, reagents, materials and equipment used in this application are all commercially available products conventionally used in the art.
[0052]
Example 1
[0053] Step b, as follows Figure 4 As shown, a tunneling oxide layer 4 and an n-type doped polysilicon layer 5 are sequentially formed on the back side of an n-type silicon substrate; hydrofluoric acid is used to clean and remove the PSG layers on the back and front sides of the n-type silicon substrate; an insulating isolation layer 6 is deposited on the n-type doped polysilicon layer 5. The tunneling oxide layer 4 is a silicon oxide layer with a thickness of 1.6 nm, the n-type doped polysilicon layer 5 has a thickness of 150 nm, and the insulating isolation layer 6 is silicon nitride.
[0054] Step c, as Figure 5 As shown, a silicon-based device is obtained by using a laser to remove the tunneling oxide layer 4, the n-type doped polysilicon layer 5, and the insulating isolation layer 6 on the first doped region A.
[0055] Step d, as follows Figure 6 As shown, the silicon-based device undergoes polishing and texturing steps to expose the n-type silicon substrate on the front side of the silicon-based device and the first doped region A, forming a textured surface. At this time, the tunneling oxide layer 4, the n-type doped polysilicon layer 5, and the insulating isolation layer 6 deposited around the front side of the silicon-based device have been removed.
[0056] Step e, as Figure 7 As shown, a passivation layer 2 and an antireflection layer 3 are sequentially formed on the front side of the silicon-based device. Hydrofluoric acid is used to remove the passivation layer 2 and antireflection layer 3 deposited on the back side of the silicon-based device. An intrinsic silicon-containing thin film 7 and a p-type doped silicon-containing thin film 8 are sequentially formed on the back side of the silicon-based device. The passivation layer 2 is aluminum oxide with a thickness of 5 nm, and the antireflection layer 3 is silicon nitride (with a Mohs hardness of 9) with a thickness of 80 nm. The intrinsic silicon-containing thin film 7 is intrinsic amorphous silicon, and the p-type doped silicon-containing thin film 8 is p-type doped amorphous silicon.
[0057] Step f, as follows Figure 8 As shown, the p-type doped silicon thin film 8, intrinsic silicon thin film 7, and insulating isolation layer 6 on the second doped region B are removed by laser combined with chemical cleaning.
[0058] Step g, as follows Figure 9 As shown, a conductive thin film layer 9 is formed on the back side of the silicon-based device, covering a first doped region A, a second doped region B, and a predetermined isolation region C'. The conductive thin film layer 9 is made of indium tin oxide (ITO), which is composed of 90% indium oxide and 10% tin oxide.
[0059] Step h, such as Figure 10 As shown. Etching material 10 is printed on the preset isolation area C' (the printing area of etching material 10 is allowed to extend moderately beyond both sides of the preset isolation area C'); as... Figure 11 As shown, the conductive thin film layer 9 is etched by the etchant 10 to form an isolation region C (which can be an isolation trench 13) with electrical isolation effect; wherein, the etchant 10 is an acidic paste, and the etchant 10 includes water, thickener and phosphoric acid.
[0060] Step i: Prepare the cleaning solution, which includes an alkaline solution and nano-sized non-metallic powder material. The alkaline solution contains 0.1 wt% KOH, and the nano-sized non-metallic powder material is silica powder (the Mohs hardness of silica powder is approximately 7). The Mohs hardness of the nano-sized non-metallic powder material is less than that of the antireflective layer 3. Figure 12 As shown, the silicon-based device was placed in the cleaning solution and ultrasonically cleaned for 1 minute to remove 10g of etchant.
[0061] Step j, as follows Figure 13 As shown, a first metal electrode 11 and a second metal electrode 12 are fabricated on the first doped region A and the second doped region B on the back side of the silicon-based device, respectively. The first metal electrode 11 and the second metal electrode 12 are multilayer composite electrodes, both formed by sequentially stacking pure silver electrodes / silver-copper electrodes / pure copper electrodes.
[0062] It should be noted that step S10 above is implemented by steps a to f in Example 1, step S20 is implemented by steps g to h in Example 1, and step S30 is implemented by step i in Example 1.
[0063] Comparative Example 1 The difference between Comparative Example 1 and Example 1 lies in step i; the raw materials, parameters, etc., in the remaining steps are the same as in Example 1. Step i in Comparative Example 1 is as follows: Step i: Immerse the silicon-based device in an alkaline solution to clean it for 2.5 minutes to remove residual etchant 10; wherein the mass percentage of KOH in the alkaline solution is 1 wt%.
[0064] Comparative Example 2 The difference between Comparative Example 2 and Example 1 lies in step i; the raw materials and parameters in the remaining steps are the same as in Example 1. Step i in Comparative Example 2 is as follows: Step i: Immerse the silicon-based device in an alkaline solution to clean it for 2.5 minutes to remove residual etchant 10; wherein the mass percentage of KOH in the alkaline solution is 0.5 wt%.
[0065] The back side of the silicon-based devices processed in step i in Example 1, Comparative Example 1, and Comparative Example 2 was measured using a vision measurement instrument, and the corresponding results were obtained. Figures 14 to 16 .
[0066] like Figure 14 As shown, in Example 1, after step i, the etchant on the back of the silicon-based device has been completely removed.
[0067] like Figure 15 As shown, in Comparative Example 1, after step i, the etchant on the back of the silicon-based device has been completely removed.
[0068] like Figure 16 As shown in Comparative Example 2, after step i, the etchant on the back side cannot be completely cleaned, and etchant residue remains near the isolation area C. Figure 16 The white substance is the residual etching resin. In Comparative Example 2, the alkali solution used had a higher alkali mass percentage than that in Example 1, and the cleaning time was longer, but the effect of removing the etching resin in Comparative Example 2 was not as good as that in Example 1.
[0069] It should be noted that, in this document, "comprising," "including," or any other variation thereof is intended to cover non-exclusive inclusion, such that a process, method, or article that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, or article.
[0070] The various embodiments in this specification are described in a related manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.
[0071] The above description is only a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the principles of this application should be included within the scope of protection of this application.
Claims
1. A method for fabricating a back-contact solar cell, characterized in that, The preparation method includes: S10: Provide a first solar cell precursor, the first solar cell precursor includes a front side and a back side, an anti-reflection layer is provided on the front side, a first doped region and a second doped region with opposite conductivity types are provided on the back side, and a preset isolation region is also provided between the first doped region and the second doped region. S20: Forming an isolation region, a conductive thin film layer covering the first doped region, the second doped region and the preset isolation region is formed on the back side of the first cell precursor, and an etchant located in the preset isolation region is disposed on the back light side of the conductive thin film layer, the etchant being used to etch the portion of the conductive thin film layer located in the preset isolation region to form a second cell precursor with an isolation region; S30: The second battery cell precursor is placed in a cleaning solution for ultrasonic cleaning. The cleaning solution includes water or alkaline solution and contains nanoscale non-metallic powder material. The Mohs hardness of the nanoscale non-metallic powder material is less than that of the antireflective layer.
2. The method for preparing a back-contact solar cell according to claim 1, characterized in that, In S30: The cleaning solution is an alkaline solution, and the mass percentage of alkali in the alkaline solution is 0.01wt%~1wt%. The ultrasonic cleaning time is 0.5min~1.5min. Preferably, the mass percentage of alkali in the alkaline solution is 0.01wt% to 0.1wt%.
3. The method for preparing a back-contact solar cell according to claim 1, characterized in that, The cleaning solution is water, and the ultrasonic cleaning time is 3 to 5 minutes.
4. The method for fabricating a back-contact solar cell according to claim 1, characterized in that, The difference between the Mohs hardness of the antireflective layer and the Mohs hardness of the nanoscale non-metallic powder material is in the range of 1 to 2.
5. The method for preparing a back-contact solar cell according to claim 1, characterized in that, The Mohs hardness of the nanoscale non-metallic powder material is less than that of the conductive thin film layer.
6. The method for fabricating a back-contact solar cell according to claim 1, characterized in that, The Mohs hardness range of the antireflective layer is 4 to 10.
7. The method for preparing a back-contact solar cell according to claim 1, characterized in that, The particle size of the nanoscale non-metallic powder material is 10nm~100nm; Preferably, the nanoscale non-metallic powder is silicon oxide powder.
8. The method for preparing a back-contact solar cell according to claim 1, characterized in that, The pH value of the etching resin is 1~2; Preferably, the etching adhesive includes an acid, a thickener, and a solvent. Based on the total mass of the etching adhesive, the mass fraction of the acid is 5% to 10%, the mass fraction of the thickener is 50% to 70%, and the mass fraction of the solvent is 20% to 40%.
9. The method for preparing a back-contact solar cell according to claim 1, characterized in that, The first solar cell precursor includes a silicon substrate; The first doped region includes an intrinsic silicon-containing thin film and a doped silicon-containing thin film stacked together; the second doped region includes a tunneling oxide layer and a doped polycrystalline silicon layer stacked together. Preferably, the isolation region includes a tunneling oxide layer, a doped polysilicon layer, an insulating isolation layer, an intrinsic silicon-containing thin film, and a doped silicon-containing thin film stacked together; Preferably, the conductivity type of the first doped region is opposite to that of the silicon substrate, and the conductivity type of the second doped region is the same as that of the silicon substrate; Preferably, the silicon substrate is an n-type silicon substrate, the doped silicon thin film is a p-type doped silicon thin film, and the doped polycrystalline silicon layer is an n-type doped polycrystalline silicon layer.
10. A back-contact solar cell, characterized in that, The back-contact solar cell is prepared according to any one of claims 1 to 9.