A solar cell and a method for manufacturing the same

Abstract

The present invention discloses a solar cell and a manufacturing method thereof, and relates to the field of photovoltaic technology, in order to reduce the damage of the doping surface. The manufacturing method of the solar cell comprises: providing a silicon substrate; forming a protective film on the silicon substrate; forming a doping source layer on the protective film; the doping source layer is a doping source film formed by a doping agent solution or a doping agent slurry; and using a heat treatment method to push the doping elements in the doping source layer through the protective film into the silicon substrate to dope the silicon substrate. The solar cell and the manufacturing method thereof provided by the present invention are used for manufacturing solar cells.

Description

Technical Field

[0001] The present invention relates to the field of photovoltaic technology, and in particular to a solar cell and a manufacturing method thereof. Background Art

[0002] The process of making solar cells mainly includes: texturing, doping, cleaning, deposition of anti-reflection film, testing, sorting, etc. Among them, the doping process can be to form a doping source on the surface of the silicon substrate and then perform annealing.

[0003] When the doping process is performed by applying and advancing the doping source, the doped surface is easily damaged, thereby affecting the performance of the solar cell. Summary of the invention

[0004] The object of the present invention is to provide a solar cell and a method for manufacturing the same, so as to reduce the damage of the doped surface.

[0005] In a first aspect, the present invention provides a method for manufacturing a solar cell. The method for manufacturing a solar cell comprises:

[0006] Providing a silicon substrate;

[0007] forming a protective film on a silicon substrate;

[0008] forming a doping source layer on the protective film; the doping source layer is a doping source film formed by a doping agent solution or a doping agent slurry;

[0009] The doping elements in the doping source layer are pushed into the silicon substrate through the protective film by heat treatment to dope the silicon substrate.

[0010] When the above technical solution is adopted, a protective film is formed on the silicon substrate to be doped, and then a doping source layer is formed on the protective film. On the one hand, the protective film can block the direct contact between the doping source layer and the silicon substrate, thereby avoiding the corrosion and damage of the silicon substrate by the doping source layer, and ensuring the performance of the solar cell manufactured. On the other hand, in the process of pushing the doping elements in the doping source layer to the silicon substrate in the heat treatment process, the doping elements are first pushed to the protective film, and as the heat treatment continues, the doping elements are pushed into the silicon substrate. At this time, the protective film can accommodate more doping elements, avoiding too many doping elements from being pushed to the surface of the silicon substrate, thereby reducing the risk of excessive doping concentration of the silicon substrate, and further ensuring the performance of the solar cell manufactured. It can be seen from this that the method for manufacturing a solar cell of the present invention can not only avoid the corrosion of the doping source layer on the doped surface during the doping process, but also avoid the problem of excessive doping concentration, and can easily form a set doping concentration to ensure the performance of the solar cell manufactured.

[0011] In some possible implementations, the protective film is an intrinsic semiconductor film. The intrinsic semiconductor film does not contain doping elements. During the process of doping the silicon substrate, the intrinsic semiconductor film can contain more doping elements, thereby playing a better role in protecting the silicon substrate.

[0012] In some possible implementations, the material of the protective film includes at least one of silicon, silicon carbide, and germanium. In this case, the material of the protective film and the material of the silicon substrate are both semiconductor materials, and the material properties of the two are similar, and the doping process is relatively similar, so there is no need to change the doping process, thereby reducing the cost of process improvement.

[0013] In some possible implementations, the material of the protective film includes at least one of an amorphous semiconductor material, a polycrystalline semiconductor material, a nanocrystalline semiconductor material, and a microcrystalline semiconductor material. At this time, one or more semiconductor materials can be selected according to the protective effect to be achieved and the doping properties of different materials.

[0014] In some possible implementations, the formation process of the above-mentioned protective film includes any one of a low-pressure chemical vapor deposition process, a normal-pressure chemical vapor deposition process, an enhanced plasma chemical vapor deposition process, a hot-wire chemical vapor deposition process, and magnetron sputtering.

[0015] In some possible implementations, the dopant solution contains ethanol. The mass fraction of ethanol is 2% to 30%; the doping source layer is formed by coating. Ethanol can not only dilute the dopant and adjust the concentration, but also when the dopant solution is coated on the silicon substrate, the ethanol is easily volatile, which can easily realize the solidification of the dopant solution, so that the dopant solution can quickly form the doping source layer.

[0016] In some possible implementations, the dopant mass fraction of the dopant contained in the dopant slurry is 0.01% to 10%. The doping source layer is formed by at least one of coating, printing, and transfer. The doping slurry in the form of slurry has not only good fluidity, but also good formability, so that a uniform doping source layer can be formed.

[0017] In some possible implementations, the dopant slurry further contains nano silicon powder. The mass fraction of the nano silicon powder is 10% to 80%, and the particle size of the nano silicon powder is 5nm to 500nm. At this time, the nano silicon powder with a smaller particle size can form a uniformly dispersed slurry, so that the dopant can be uniformly dispersed in the entire slurry system, which is conducive to forming a doping source layer with uniform distribution of the dopant.

[0018] In some possible implementations, the dopant slurry further contains silicon oxide. The mass fraction of silicon oxide is 10% to 80%, and the particle size of silicon oxide is 5nm to 500nm. The silicon oxide material is relatively stable in nature, and can provide good protection for the underlying protective layer and silicon substrate, thereby reducing the probability of the protective layer and silicon substrate being damaged.

[0019] In some possible implementations, the dopant contained in the above-mentioned doping source layer is phosphoric acid, phosphate, metaphosphoric acid, metaphosphate, phosphorus pentoxide or phosphorus element, or the dopant contained in the doping source layer is boron nitride, boron oxide, boric acid, boron carbide, borosilicide, aluminum boride or borate.

[0020] In some possible implementations, after the heat treatment, the doping concentration of the doped surface of the silicon substrate is 1×10 18 cm -3 ~4×10 20 cm -3 It can be seen that due to the protective effect of the protective film, even if the doping concentration of the doping source layer is high, the doping concentration of the doped surface of the silicon substrate will not be too high, and shallow doping can be formed to reduce carrier recombination.

[0021] In some possible implementations, the doping concentration of the doping source layer is greater than or equal to 1×10 21 cm -3 After heat treatment, the doping concentration of the doped surface of the silicon substrate is 1×10 18 cm -3 ~4×10 20 cm -3 When phosphorus atoms are doped, the doping concentration of the protective film is 2×10 20 cm -3 ~4×10 21 cm -3 When doped with boron atoms, the doping concentration of the protective film is 1×10 19 cm -3 ~3×10 20 cm -3 .

[0022] In some possible implementations, the thickness of the doping source layer is 10nm to 3000nm; in this case, the doping source layer can have enough dopants to ensure the quality of the doping process. The thickness of the protective film is 30nm to 180nm. In this case, the protective film can not only play a good role in protecting the silicon substrate, but also ensure that enough doping elements enter the silicon substrate through the protective film.

[0023] In some possible implementations, forming a doping source layer on the protective film includes: forming a doping source layer in a local area of ​​the protective film; and after heat treatment, locally doping the silicon substrate with doping elements. In this case, the protective film and the doping source layer can be used to conveniently perform local doping on the silicon substrate.

[0024] In some possible implementations, after the heat treatment, the method for manufacturing a solar cell includes: removing the protective film and the doping source layer. At this time, after removing the protective film, an emitter or a surface field structure can be formed on the silicon substrate.

[0025] In some possible implementations, the silicon substrate is a silicon substrate having a tunneling passivation layer, and the protective film is formed on the tunneling passivation layer. On the one hand, the protective film can protect the tunneling passivation layer. On the other hand, in the case of retaining the protective film, the tunneling passivation layer and the doped protective film can be used to form a tunneling passivation structure, thereby simplifying the process flow, reducing the process difficulty, and reducing the manufacturing cost.

[0026] In a second aspect, the present invention provides a solar cell. The solar cell is manufactured by using the method for manufacturing a solar cell described in the first aspect or any possible implementation of the first aspect.

[0027] The beneficial effects of the solar cell provided in the second aspect can refer to the beneficial effects of the method for manufacturing the solar cell described in the first aspect or any possible implementation of the first aspect, and will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0029] Figure 1 A schematic diagram of the structure of a solar cell provided by an embodiment of the present invention;

[0030] Figure 2 to Figure 11 A schematic diagram of each stage of the method for manufacturing a solar cell provided by an embodiment of the present invention;

[0031] Fig.12 A schematic diagram of the structure of a selective emitter solar cell provided by an embodiment of the present invention;

[0032] Fig.13 A schematic diagram of the structure of an IBC solar cell provided in an embodiment of the present invention;

[0033] Fig.14 A schematic structural diagram of an IBC solar cell with a passivated contact structure provided by an embodiment of the present invention;

[0034] Fig.15 Another schematic diagram of the structure of an IBC solar cell with a passivation contact structure provided by an embodiment of the present invention.

[0035] Figure 1 to Figure 15 In it, 10-substrate, 101-texture structure, 11-protective film, 12-doped source layer, 13-doped layer, 14-first passivation layer, 15-first electrode, 16-heavily doped layer, 21-tunneling passivation layer, 22-doped semiconductor layer, 23-second passivation layer, 24-second electrode, 25-second surface doped layer, 26-back field structure, 27-p-type doped layer, 28-n-type doped layer, 29-isolation region. DETAILED DESCRIPTION

[0036] In order to clearly describe the technical solutions of the embodiments of the present invention, in the embodiments of the present invention, words such as "first" and "second" are used to distinguish the same or similar items with substantially the same functions and effects. Those skilled in the art can understand that words such as "first" and "second" do not limit the quantity and execution order, and words such as "first" and "second" do not necessarily limit the difference.

[0037] It should be noted that, in the present invention, words such as "exemplary" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary" or "for example" in the present invention should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary" or "for example" is intended to present related concepts in a specific way.

[0038] In the present invention, "at least one" means one or more, and "plurality" means two or more. "And / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone, where A and B can be singular or plural. The character " / " generally indicates that the associated objects before and after are in an "or" relationship. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single or plural items. For example, at least one of a, b or c can mean: a, b, c, the combination of a and b, the combination of a and c, the combination of b and c, or the combination of a, b and c, where a, b, c can be single or multiple.

[0039] In the process of manufacturing solar cells, when doping is performed, phosphoric acid, boric acid and other doping materials can be directly coated on the surface to be doped. When phosphoric acid, boric acid and other doping materials are coated on the surface of the silicon substrate, the concentration of phosphorus or boron in the coated doping materials is very high, far exceeding 1022 cm -3 Therefore, in the subsequent doping process, the doping concentration of the doped surface is very high. Too high surface doping concentration will cause serious surface recombination, resulting in a significant decrease in the performance of the battery device.

[0040] In addition, when nano-silicon powder is used directly on the tunnel passivation layer to make a doped polysilicon layer, since the tunnel passivation layer is relatively thin, directly coating the nano-silicon containing dopants on the tunnel passivation layer is likely to destroy the structure of the passivation layer and affect the passivation performance of the passivation layer. In particular, phosphoric acid and boric acid solutions have a great destructive effect on the passivation layer. If the thickness of the passivation layer is increased, the photogenerated carriers of the substrate cannot be extracted, resulting in a significant increase in the internal resistance of the battery.

[0041] In order to solve the above technical problems, an embodiment of the present invention provides a solar cell. Figure 1 As shown, the solar cell includes a substrate 10, an emitter, a first electrode 15, and a second electrode 24. The substrate 10 has a first surface and a second surface opposite to each other. The first surface of the substrate 10 is formed with an emitter. The first electrode 15 is located on the first surface of the substrate 10, and the first electrode 15 is in electrical contact with the emitter. The second electrode 24 is located on the second surface of the substrate 10. It should be understood that the solar cell may also include other structures, which are described in detail below.

[0042] The present invention also provides a method for manufacturing the solar cell. Figures 2 to 11 As shown, the method for manufacturing the solar cell specifically includes the following steps.

[0043] like Figure 2 As shown, a substrate 10 is provided. The substrate 10 can be an n-type semiconductor substrate or a p-type semiconductor substrate. The material of the substrate 10 can be silicon. The substrate 10 has a first surface and a second surface opposite to each other. The following describes the method for making a solar cell using an n-type silicon semiconductor substrate and the first surface of the substrate 10 as the front surface.

[0044] like Figure 3 As shown, the substrate 10 is textured. Specifically, the texture may be applied to one side of the substrate 10 or to both sides of the substrate 10. The reflectivity of the surface of the substrate 10 after the texture treatment is less than 12%.

[0045] Exemplarily, the texturing treatment may be a double-sided texturing treatment using an alkaline solution. By treating the substrate 10 with an alkaline solution having an additive, a pyramid-shaped velvet structure 101 may be formed on the surface of the substrate 10. The velvet structure 101 may trap light, reduce the reflection of sunlight by the solar cell, and thus improve the performance of the solar cell. Of course, in some solar cell manufacturing methods, the texturing treatment process may also be omitted.

[0046] At this time, the obtained structure can be defined as a silicon substrate. The first surface and the second surface of the silicon substrate correspond one-to-one to the first surface and the second surface of the substrate 10. It should be understood that when manufacturing a solar cell, the cell can be manufactured using the substrate 10 as the process starting point, or the cell can be manufactured using the silicon substrate defined in the embodiment of the present invention as the process starting point.

[0047] like Figure 4 As shown, a protective film 11 is formed on the first surface of the silicon substrate. A protective film 11 is formed on the silicon substrate to be doped, and a doping source layer 12 is subsequently formed on the protective film 11. On the one hand, the protective film 11 can prevent the doping source layer 12 from directly contacting the silicon substrate, thereby avoiding the corrosion and damage of the silicon substrate by the doping source layer 12, and ensuring the performance of the manufactured solar cell. On the other hand, in the subsequent heat treatment process, the doping elements contained in the doping source layer 12 are pushed into the silicon substrate. During the doping treatment, the doping elements are first pushed into the protective film 11, and as the heat treatment continues, the doping elements are pushed into the silicon substrate. At this time, the protective film 11 can accommodate more doping elements, avoiding too many doping elements from being pushed into the surface of the silicon substrate, thereby reducing the risk of excessive doping concentration of the silicon substrate, and further ensuring the performance of the manufactured solar cell. It can be seen that the method for manufacturing a solar cell according to the embodiment of the present invention can not only avoid the corrosion of the doping source layer 12 on the doped surface during the doping process, but also avoid the problem of excessive doping concentration, thereby easily forming a set doping concentration, and ensuring the performance of the manufactured solar cell.

[0048] From the perspective of doping, the protective film 11 may be an intrinsic semiconductor film. Since the intrinsic semiconductor film does not contain doping elements, in the subsequent process of doping the silicon substrate, the intrinsic semiconductor film can contain more doping elements, thereby playing a better role in protecting the silicon substrate.

[0049] From the perspective of material, the material of the protective film 11 may include at least one of silicon, silicon carbide, and germanium. At this time, the material of the protective film 11 and the material of the silicon substrate are both semiconductor materials, and the material properties of the two are similar, and the doping process is relatively similar, so there is no need to change the doping process, thereby reducing the cost of process improvement.

[0050] From the perspective of material microstructure, the material of the protective film 11 may include at least one of amorphous semiconductor material, polycrystalline semiconductor material, nanocrystalline semiconductor material, and microcrystalline semiconductor material. At this time, one or more semiconductor materials may be selected according to the desired protection effect and the doping properties of different materials.

[0051] For example, the material of the protection film 11 may be intrinsic amorphous silicon, intrinsic microcrystalline silicon, etc. Of course, the material of the protection film 11 may also protect multiple materials. For example, the material of the protection film 11 may be intrinsic amorphous silicon and intrinsic microcrystalline silicon.

[0052] The thickness of the protective film 11 can be 30nm to 180nm. For example, the thickness of the protective film 11 can be 30nm, 50nm, 76nm, 80nm, 100nm, 125nm, 150nm, 170nm, 175nm, 180nm, etc. At this time, the protective film 11 in this thickness range can not only play a good role in protecting the silicon substrate, but also ensure that enough doping elements enter the silicon substrate through the protective film 11. Preferably, the thickness of the protective film 11 can be 30nm-100nm. At this time, the protective film 11 can not only play a role in protecting the silicon substrate, but also save raw materials and reduce costs.

[0053] The formation process of the protective film 11 of the above-mentioned various materials may include any one of a low-pressure chemical vapor deposition process, a normal-pressure chemical vapor deposition process, an enhanced plasma chemical vapor deposition process, a hot-wire chemical vapor deposition process, and magnetron sputtering.

[0054] In practical applications, the intrinsic amorphous silicon material can be deposited on the surface of the silicon substrate by using atmospheric pressure chemical vapor deposition equipment to form the protective film 11 .

[0055] like Figure 5 As shown, a doping source layer 12 is formed on the protective film 11. The doping concentration of the doping source layer 12 is greater than or equal to 1×10 21 cm -3 The doping source layer 12 is a doping source film formed by a doping agent solution or a doping agent paste.

[0056] The thickness of the doping source layer 12 may be 10 nm to 3000 nm. For example, the thickness of the doping source layer 12 may be 10 nm, 100 nm, 500 nm, 800 nm, 1200 nm, 1600 nm, 1800 nm, 2000 nm, 2500 nm, 2700 nm, 3000 nm, etc. At this time, the doping source layer 12 may have sufficient dopants to ensure the quality of the doping process.

[0057] When n-type doping is to be performed, the dopant contained in the doping source layer 12 may be phosphoric acid, phosphate, metaphosphoric acid, metaphosphate, phosphorus pentoxide or phosphorus. When p-type doping is to be performed, the dopant contained in the doping source layer 12 may be boron nitride, boron oxide, boric acid, boron carbide, borosilicide, aluminum boride or borate.

[0058] When the dopant solution is used to form the doping source layer 12, the dopant solution may contain a dopant and ethanol, as well as other solvents. The dopant contained in the dopant solution may be any of the above-mentioned dopants. The mass fraction of the dopant in the dopant solution may be 40% to 60%. For example, the mass fraction of the dopant may be 40%, 42%, 45%, 48%, 50%, 53%, 56%, 59%, 60%, etc. The mass fraction of ethanol in the dopant solution may be 2% to 30%. For example, the mass fraction of ethanol may be 2%, 8%, 10%, 13%, 17%, 20%, 25%, 30%, etc. Of course, the dopant solution also contains a residual amount of solvent, such as water. Ethanol can not only dilute the dopant and adjust the concentration, but also when the dopant solution is coated on the silicon substrate, the ethanol is easily volatile, which can easily realize the curing and molding of the dopant solution, so that the dopant solution can quickly form the doping source layer 12. Ethanol can be added 0.5h before the dopant solution is used.

[0059] When the doping solution is used to form the doping source layer 12, the doping source layer 12 may be formed by coating, for example, by drop coating, spin coating, scraping, spraying, roller coating, or the like.

[0060] It should be understood that after the coating process, a drying process is required. Specifically, the drying process equipment can be a crawler drying furnace, a chain drying furnace, a tubular drying furnace, etc. The drying process temperature can be 50°C-500°C, and the drying process time can be 20min-30min.

[0061] When the doping source layer 12 is formed using a dopant paste, the dopant paste may contain a dopant and a main paste. The dopant contained in the dopant paste may be any of the above-mentioned dopants, and the mass fraction of the dopant may be 0.01% to 10%. For example, the mass fraction of the dopant in the dopant paste may be 0.01%, 0.07%, 0.1%, 0.5%, 0.9%, 2%, 4%, 5%, 7%, 9%, 10%, etc.

[0062] The main slurry can be nano silicon powder. The mass fraction of nano silicon powder can be 10% to 80%. For example, the mass fraction of nano silicon powder can be 10%, 20%, 30%, 40%, 50%, 55%, 60%, 70%, 80%, etc. The particle size of nano silicon powder can be 5nm to 500nm. At this time, nano silicon powder with a smaller particle size can form a uniformly dispersed slurry, so that the dopant can be uniformly dispersed in the entire slurry system, which is conducive to forming a doping source layer 12 with uniform distribution of dopants.

[0063] The main slurry can also be silicon oxide. The mass fraction of silicon oxide can be 10% to 80%. For example, the mass fraction of silicon oxide can be 10%, 20%, 30%, 40%, 50%, 55%, 60%, 70%, 80%, etc. The particle size of silicon oxide can be 5nm to 500nm. The silicon oxide material is relatively stable in nature and can provide good protection for the underlying protective layer and silicon substrate, reducing the probability of the protective layer and silicon substrate being damaged.

[0064] When the doping solution is used to form the doping source layer 12, the doping source layer 12 may be formed by at least one of coating, printing, and transfer. The coating method may be drop coating, spin coating, scraper coating, spray coating, roller coating, etc. The printing method may be screen printing. The transfer method may be laser transfer. The dopant slurry in the form of slurry not only has good fluidity, but also has good formability, so that a uniform doping source layer 12 can be formed well.

[0065] like Figure 6 As shown, the doping elements in the doping source layer 12 are pushed into the silicon substrate through the protective film 11 by heat treatment to dope the silicon substrate. At this time, a doping layer 13 is formed on the first surface of the silicon substrate. When n-type doping is performed, a front field structure can be formed on the first surface of the silicon substrate. When p-type doping is performed, an emitter can be formed on the first surface of the silicon substrate.

[0066] After the heat treatment, the doping concentration of the doped surface (doping layer 13) of the silicon substrate is 1×10 18 cm -3 ~4×10 20 cm -3 .

[0067] The square resistance of the doped surface of the silicon substrate (doped layer 13) can be 40 ohm / sq-250 ohm / sq. For example, the square resistance of the doped surface of the silicon substrate can be 40 ohm / sq, 65 ohm / sq, 88 ohm / sq, 100 ohm / sq, 150 ohm / sq, 180 ohm / sq, 200 ohm / sq, 220 ohm / sq, 250 ohm / sq, etc. Preferably, the square resistance of the doped surface of the silicon substrate can be 100 ohm / sq-200 ohm / sq, and the corresponding doping concentration of the doped surface of the silicon substrate is 4.5×10 19 cm -3 ~1×10 20 cm -3 .

[0068] When phosphorus atoms are doped, the doping concentration of the protective film 11 is 2×10 20 cm -3 ~4×1021 cm -3 When doped with boron atoms, the doping concentration of the protective film 11 is 1×10 19 cm -3 ~3×10 20 cm -3 It can be seen that due to the protective effect of the protective film 11, even if the doping concentration of the doping source layer 12 is high, the doping concentration of the doped surface of the silicon substrate (doping layer 13) will not be too high, and shallow doping can be formed to reduce carrier recombination.

[0069] The equipment for the above heat treatment can be a tubular heat treatment furnace, a chain heat treatment furnace, etc. When a tubular heat treatment furnace is used for heat treatment, the doping source layer 12 can be heat treated for 5 to 60 minutes at 300°C to 900°C in a protective atmosphere to achieve the advancement of the doping elements. When a chain heat treatment furnace is used for heat treatment, the treatment temperature can be 850°C-1000°C, and the treatment time can be 5 to 50 minutes.

[0070] It should be understood that Fig.12 As shown, in some solar cells, a partial area of ​​the doping layer 13 may be heavily doped to form a heavily doped layer 16. The heavily doped layer 16 is formed in a local area of ​​the doping layer 13, and the doping concentration of the heavily doped layer 16 is greater than the doping concentration of the above-mentioned doping layer 13. At this time, a selective emitter structure can be formed.

[0071] The method for forming a heavily doped layer 16 in a local area is: forming a protective film 11 on a silicon substrate having a doped layer 13 (the protective film and doping source layer required for making the doping layer 13 have been removed), and then forming a doping source layer 12 in a local area of ​​the protective film 11, and then using a heat treatment method to push the doping elements in the doping source layer 12 into the doping layer 13 to form a heavily doped layer 16. The local area here corresponds to the area on the doping layer 13 to be heavily doped. The material, thickness, formation method, etc. of the protective film 11 here are basically the same as the protective film 11 used in the above-mentioned process for making the doping layer 13, and will not be repeated here. The material, thickness, formation method, etc. of the doping source layer 12 here are basically the same as the doping source layer 12 used in the above-mentioned process for making the doping layer 13, the difference being that the concentration of the doping elements contained in the doping source layer 12 here is higher, and the doping source layer 12 partially covers the protective film 11. Specifically, the doping source layer can be coated or printed on a local area of ​​the protective film 11.

[0072] When the heavily doped layer 16 is manufactured by the above method, no laser film opening process is required, which can not only avoid the damage of the laser to the doped layer 13, but also reduce the process cost.

[0073] In order to conveniently remove the protective film 11, an etching stop layer may be formed on the doping layer 13 before forming the protective film 11, and then the protective film 11 and the doping source layer 12 may be formed on the etching stop layer. The etching stop layer may be a thin layer of silicon oxide or the like. When it is necessary to remove the protective film 11, an alkaline solution such as KOH may be used as an etchant to remove the protective film 11. At this time, the reaction rate of the alkaline solution and the etching stop layer made of silicon oxide is extremely slow, thereby preventing the alkaline solution etchant from damaging the doping layer 13.

[0074] It should be noted that the heavily doped layer 16 can also be formed in a local area of ​​the silicon substrate. In this case, a protective film 11 can be formed on the silicon substrate, and a doping source layer 12 can be formed in a local area of ​​the protective film 11. After heat treatment, the doping elements contained in the doping source layer 12 locally dope the silicon substrate through the protective film 11, thereby forming the heavily doped layer 16.

[0075] It should be understood that different regions on the silicon substrate may have different doping concentrations. When the doped surface of the silicon substrate plays a role in lateral carrier transport and reducing contact resistance in the solar cell, the doping concentration of the doped surface of the silicon substrate may be 5×10 18 cm -3 ~4×10 20 cm -3 For example, when the solar cell only includes the doping layer 13 and does not include the heavily doped layer 16 , the doping layer 13 may have the doping concentration.

[0076] When the doped surface of the silicon substrate only plays a role in lateral carrier transport, or even only plays a role in separating electron-hole carriers, the doping concentration of the doped surface of the silicon substrate can be appropriately reduced. Preferably, the doping concentration of the doped surface of the silicon substrate can be 1×10 18 cm -3 ~1×10 20 cm -3 For example, when the solar cell contains a heavily doped layer 16, the doped layer 13 may have this doping concentration. Or, for example, Fig.11 or Fig.14 In the case where the protective film 11 (converted into the doped semiconductor layer 22 after doping) is retained, the doped surface of the second surface of the silicon substrate (the back field structure 26 or the n-type doped layer 28) can have the doping concentration.

[0077] When the doped surface of the silicon substrate is mainly used to contact the metal electrode in the solar cell, the doping concentration in the contact area can be 4.5×10 19 cm -3 ~4×10 20 cm -3For example, when the solar cell includes a heavily doped layer 16, the heavily doped layer 16 may have the doping concentration. At this time, the doping concentration is higher, the lateral conductivity is higher, and the contact performance between the semiconductor and the metal electrode is better.

[0078] Obviously, as described above, different regions with different functions in the solar cell can be set with different doping concentrations, and two structures (for example, the doping layer 13 and the heavily doped layer 16) can exist in the same cell structure at the same time. Specifically, by locally forming a doping source layer on the protective film 11, local doping with different concentrations can be achieved.

[0079] like Figure 7 As shown, a tunnel passivation layer 21 is formed on the second surface of the substrate 10. The material of the tunnel passivation layer 21 is a dielectric material. Specifically, the material of the tunnel passivation layer 21 can be one or more of self-hydrogenated amorphous silicon, silicon oxynitride, silicon carbide, silicon nitride, silicon oxide, metal nitride, metal carbide, and metal oxide. The thickness of the tunnel passivation layer 21 can be 0.5nm-5nm.

[0080] The process for forming the tunnel passivation layer 21 may be a physical vapor deposition process or a chemical vapor deposition process. In order to simplify the process, the silicon substrate may be directly oxidized to generate silicon oxide as the tunnel passivation layer 21 .

[0081] In the process of manufacturing solar cells, the substrate 10 with the tunnel passivation layer 21 on the second surface can also be defined as a silicon substrate. In practical applications, the silicon substrate with the tunnel passivation layer 21 can be used as the process starting point for solar cell manufacturing.

[0082] It should be noted that before forming the tunnel passivation layer 21, it is necessary to clean the coating layer formed by the protective film 11 material on the second surface of the silicon substrate and partially etch the second surface of the silicon substrate to improve the flatness of the second surface of the silicon substrate. In addition, the silicon substrate is doped by forming the doping source layer 12 and advancing it, thereby avoiding the doping of the second surface of the silicon substrate during the doping process, thereby saving the process of removing the doping, and simplifying the process.

[0083] In practical applications, chain equipment and slot equipment can be used to remove the winding coating. The etchant used in the removal process can be determined according to the material of the winding coating to be removed. For example, when removing the winding coating made of silicon, an alkaline solution etchant containing KOH, NaOH, etc. can be used. It should be understood that while removing the winding coating located on the second side of the silicon substrate, the second side of the silicon substrate can be polished to improve its flatness.

[0084] like Figure 8As shown, a doped semiconductor layer 22 is formed on the tunnel passivation layer 21, and a passivation contact structure located on the second surface of the silicon substrate and composed of the tunnel passivation layer 21 and the doped semiconductor layer 22 is manufactured. The doped semiconductor layer 22 can be manufactured by a conventional manufacturing method, or the above-mentioned protective film 11 can be manufactured on the tunnel passivation layer 21, and the doped semiconductor layer 22 is formed by using the protective film 11.

[0085] When the doped semiconductor layer 22 is formed by using the protective film 11, on the one hand, the protective film 11 can protect the tunnel passivation layer 21 from being corroded by the doping source layer 12. On the other hand, in the case of retaining the protective film 11, the tunnel passivation layer 21 and the doped protective film 11 can be used to form a tunnel passivation structure, thereby simplifying the process flow, reducing the process difficulty, and reducing the manufacturing cost.

[0086] When the protective film 11 is used to form the doped semiconductor layer 22, the protective film 11 can be formed on the tunnel passivation layer 21, and then the doping source layer 12 can be formed on the protective film 11, and then the doping source layer 12 is heat-treated to push the doping elements contained in the doping source layer 12 into the protective film 11, and the protective film 11 is transformed into the doped semiconductor layer 22. In this case, the protective film 11 does not need to be removed. At the same time, during the heat treatment process, the doping elements of the doping source layer 12 will also be pushed to the second surface of the silicon substrate, thereby forming a field structure or an emitter on the second surface of the silicon substrate. For example, when a p-type doping layer 13 is formed on the first surface of the n-type substrate 10, the second surface can be n-type doped, thereby forming a back field structure 26 on the second surface of the substrate 10.

[0087] Since the doped semiconductor layer 22 made by using the protective film 11 can play a certain role in passivation contact and lateral conduction, in the process of making the doped semiconductor layer 22 by using the protective film 11 and doping the second surface of the substrate 10, the surface doping concentration of the second surface of the substrate 10 (the back field structure 26) can be appropriately reduced. Preferably, the surface doping concentration of the second surface of the substrate 10 (the back field structure 26) can be 1×10 18 cm -3 ~3×10 20 cm -3 At this time, the surface doping concentration of the second surface of the substrate 10 is low, and the recombination rate of carriers is low, which is beneficial to improving the efficiency of the solar cell.

[0088] In the process of manufacturing the doped semiconductor layer 22, the material and formation method of the protective film 11 are the same as those of the protective film 11 formed by the doping process on the first surface of the silicon substrate, and will not be described in detail here. In the process of manufacturing the doped semiconductor layer 22, the material and formation method of the doping source layer 12 are the same as those of the doping source layer 12 formed by the doping process on the first surface of the silicon substrate, and will not be described in detail here.

[0089] The material of the doped semiconductor layer 22 formed above is polycrystalline silicon, with a thickness of 30nm to 180nm. The doping type of the doped semiconductor layer 22 is opposite to the doping type of the first surface of the silicon substrate. When phosphorus atoms are doped, the doping concentration of the doped semiconductor layer 22 is 2×10 20 cm -3 ~4×10 21 cm -3 When doped with boron atoms, the doping concentration of the doped semiconductor layer 22 is 1×10 19 cm -3 ~3×10 20 cm -3 .

[0090] like Fig. 9 As shown, the protective film 11 and the doping source layer 12 located on the first surface of the substrate 10 are removed. At the same time, the doping source layer 12 located on the second surface of the silicon substrate can be removed. In addition, the silicon substrate is doped by forming the doping source layer 12 and advancing it, thereby avoiding the doping around the doping process, thereby saving the process of removing the doping around and simplifying the process.

[0091] In practical applications, chain equipment and trough equipment can be used to remove the protective film 11 and the doping source layer 12. When the first and second surfaces of the substrate 10 need to be cleaned, a trough device can be used. When the substrate 10 is processed on one side, a chain device can be used. The etchant used in the removal process can be determined according to the material of the film layer to be removed. For example, when removing the doping source layer 12 made of silicon oxide, an etchant containing hydrofluoric acid can be used. When removing the protective film 11 and the coating layer made of silicon, an alkaline solution etchant containing KOH, NaOH, etc. can be used.

[0092] like Fig.12 As shown, in practical applications, the passivation contact structure formed on the second surface of the silicon substrate can be omitted. At this time, a second surface doping layer 25 can be formed on the second surface. The doping type of the second surface doping layer is different from the doping type of the doping layer 13 on the first surface of the silicon substrate. When the doping layer 13 is p-type doped, the second surface doping layer 25 is n-type doped. The formation method of the second surface doping layer 25 can be the same as the formation method of the doping layer 13 on the first surface of the silicon substrate. The second surface doping layer 25 can not only play a role in lateral transport of carriers, but also reduce the contact resistance when the second surface of the substrate 10 contacts the electrode.

[0093] like Fig.10 As shown, the first surface of the substrate 10 is passivated to form a first passivation layer 14 ; and the second surface of the substrate 10 is passivated to form a second passivation layer 23 .

[0094] The material of the first passivation layer 14 may include one or more of silicon nitride, silicon oxide, silicon oxynitride, aluminum oxide, silicon carbide, and amorphous silicon. The material of the second passivation layer 23 may include one or more of silicon nitride, silicon oxide, silicon oxynitride, aluminum oxide, silicon carbide, and amorphous silicon. The first passivation layer 14 and the second passivation layer 23 may be made of the same material or different materials.

[0095] The process for forming the first passivation layer 14 and the second passivation layer 23 may be one of an enhanced plasma chemical vapor deposition process and an atomic layer deposition process.

[0096] like Fig.11 As shown, a first electrode 15 is formed on the first surface of the substrate 10, and the first electrode 15 is in electrical contact with the doped layer 13. A second electrode 24 is formed on the second surface of the substrate 10, and the second electrode 24 is in electrical contact with the doped semiconductor layer 22. The materials of the first electrode 15 and the second electrode 24 may include one or more of silver, copper, aluminum, nickel, titanium, tungsten, and tin.

[0097] In practical applications, the first electrode 15 and the second electrode 24 are formed by a metallization process. Specifically, the metallization process may be one or more of a PVD process, a screen printing process, an electroplating process, an electroless plating process, a laser transfer process, and a spraying process.

[0098] When forming the first electrode 15 and the second electrode 24, a combination of multiple processes can be used. For example, a silver or copper paste can be printed using a screen printing process, and then the electrode is prepared by a sintering process or an annealing process at 500°C to 900°C. For another example, a seed layer can be prepared using a PVD process, the seed layer can be patterned, and then an electrode can be prepared using an electroplating method, and then annealing can be used to form the electrode. For another example, a seed layer can be formed using an electroless plating process, and then thickened using an electroplating method, and finally annealing can be used to complete the electrode preparation.

[0099] It should be noted that, in the embodiment of the present invention, the specific structure of the second surface of the substrate 10 is not limited to the above-mentioned structures. In the embodiment of the present invention, the second surface of the substrate 10 may form a passivation contact structure, such as Fig.11 The second surface of the substrate 10 may also form a point contact structure, such as Fig.12 The second surface of the substrate 10 may also form a second surface local diffusion structure. When the first surface of the silicon substrate is n-type doped, the second surface of the silicon substrate may also form a second surface aluminum alloy contact structure.

[0100] An embodiment of the present invention further provides an interdigitated back contact (IBC) solar cell. Figure 13-Figure 15 Schematic diagrams of the structures of three interdigitated back contact (IBC) solar cells are shown.

[0101] Make as Fig.13 The method of the IBC solar cell shown is similar to the conventional method of making an IBC solar cell, except that the method of forming the local doping layer on the back side is different. The local doping layer on the back side of the back contact solar cell can be made by referring to the method of making the heavily doped layer 16 mentioned above. Specifically, taking an n-type silicon substrate 10 having a first surface and a second surface opposite to each other as an example, a protective film 11 can be first formed on the second surface of the substrate 10, and the protective film 11 has a first region and a second region, and the first region and the second region do not overlap. A doping source layer 12 containing a p-type dopant is formed in the first region on the protective film 11. After heat treatment, the p-type doping element contained in the doping source layer 12 is pushed into the first region of the second surface of the substrate 10 through the protective film 11, forming a p-type doping layer 27 located in the local region of the second surface of the substrate 10. A doping source layer 12 containing an n-type dopant is formed in the second region on the protective film 11. After heat treatment, the n-type doping element contained in the doping source layer 12 is pushed into the second region of the second surface of the substrate 10 through the protective film 11, forming an n-type doping layer 28 located in the local region of the second surface of the substrate 10. It should be understood that in some solar cells, the n-type doping layer 28 may also be omitted. In this case, a back-side emitter and field structure of a back-contact solar cell may be formed. After removing the protective film 11 and the doping source layer 12, a passivation layer and electrodes are formed on the first and second surfaces of the substrate 10 to form an IBC solar cell. Preferably, an isolation region 29 may also be provided between the p-type doping layer 27 and the n-type doping layer 28.

[0102] In practical applications, in the process of manufacturing an IBC solar cell using the method described above, a tunneling passivation layer 21 can be first formed on the second surface of the substrate 10 before forming the protective film 11. The other manufacturing steps remain unchanged. After the manufacturing of the local emission level and field structure on the back side is completed, only the doping source layer 12 is removed and the protective film 11 is retained. At this time, in the process of manufacturing the back emission level and field structure, the doping elements are pushed into the protective film 11, so that the protective film 11 is transformed into a doped semiconductor layer 22. The doped semiconductor layer 22 and the tunneling passivation layer 21 constitute a passivation contact structure on the back side of the solar cell. By forming a passivation layer and electrodes on the first and second surfaces of the substrate 10, a structure such as Fig.14 The IBC solar cell with a passivation contact structure shown in the figure. It can be seen that by adopting the method of the embodiment of the present invention, an IBC solar cell with a passivation contact structure can be conveniently manufactured without adding an additional process for manufacturing the doped semiconductor layer 22, thereby simplifying the process flow and saving costs.

[0103] In addition, in the process of manufacturing an IBC solar cell with a passivation contact structure using the above method, not only the doping source layer 12 is removed, but also the protective film 11 in the first region or the second region is removed, and the protective film 11 in the other region is retained. In other words, the doped semiconductor layer 22 is partially etched. Subsequently, a passivation layer and an electrode are formed on the first surface and the second surface of the substrate 10, so that the structure can be formed as follows: Fig.15 The IBC solar cell shown.

[0104] Although the present invention is described herein in conjunction with various embodiments, in the process of implementing the claimed invention, those skilled in the art may understand and implement other variations of the disclosed embodiments by viewing the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other components or steps, and "a" or "an" does not exclude a plurality of components. Certain measures are recorded in different dependent claims, but this does not mean that these measures cannot be combined to produce good results.

[0105] Although the present invention has been described in conjunction with specific features and embodiments thereof, it is apparent that various modifications and combinations may be made thereto without departing from the spirit and scope of the present invention. Accordingly, this specification and the accompanying drawings are merely exemplary illustrations of the present invention as defined by the appended claims and are deemed to cover any and all modifications, variations, combinations or equivalents within the scope of the present invention. Obviously, those skilled in the art may make various modifications and variations to the present invention without departing from the spirit and scope of the present invention. Thus, the present invention is intended to include such modifications and variations if they fall within the scope of the claims of the present invention and their equivalents.

Claims

1. A method for manufacturing a solar cell, characterized in that: include: Providing a silicon substrate having a tunnel passivation layer; forming a protective film on the tunnel passivation layer on the silicon substrate, wherein the protective film is an intrinsic semiconductor film; A doping source layer is formed on a local area of ​​the protective film; the doping source layer is a doping source film formed by a doping solution or a doping slurry, and the doping element concentration of the doping source layer is greater than or equal to 1×10 21 cm -3 The protective film is used to prevent the doping source layer from directly contacting the silicon substrate, thereby preventing the doping source layer from corroding and damaging the silicon substrate; The doping elements in the doping source layer are pushed into the silicon substrate through the protective film by heat treatment to locally dope the silicon substrate. After the heat treatment, the doping concentration of the doped surface of the silicon substrate is 1×10 18 cm -3 ~4×10 20 cm -3 .

2. The method for manufacturing a solar cell according to claim 1, characterized in that: The material of the protective film includes at least one of silicon, silicon carbide and germanium; and / or, The material of the protective film includes at least one of an amorphous semiconductor material, a polycrystalline semiconductor material, a nanocrystalline semiconductor material, and a microcrystalline semiconductor material.

3. The method for manufacturing a solar cell according to any one of claims 1 to 2, characterized in that: The protective film formation process includes any one of a low-pressure chemical vapor deposition process, a normal-pressure chemical vapor deposition process, an enhanced plasma chemical vapor deposition process, a hot-wire chemical vapor deposition process, and magnetron sputtering.

4. The method for manufacturing a solar cell according to any one of claims 1 to 2, characterized in that: The dopant solution contains ethanol, and the mass fraction of the ethanol is 2% to 30%; the doping source layer is formed by coating.

5. The method for manufacturing a solar cell according to any one of claims 1 to 2, characterized in that: The dopant mass fraction contained in the dopant slurry is 0.01% to 10%; the doping source layer is formed by at least one of coating, printing and transfer.

6. The method for manufacturing a solar cell according to claim 5, characterized in that: The dopant slurry further contains nano silicon powder, the mass fraction of the nano silicon powder is 10% to 80%, the particle size of the nano silicon powder is 5nm to 500nm, and / or, The dopant slurry further contains silicon oxide, the mass fraction of the silicon oxide is 10% to 80%, and the particle size of the silicon oxide is 5nm to 500nm.

7. The method for manufacturing a solar cell according to any one of claims 1 to 2, characterized in that: The dopant contained in the doping source layer is phosphoric acid, phosphate, metaphosphoric acid, metaphosphate, phosphorus pentoxide or phosphorus element, or the dopant contained in the doping source layer is boron nitride, boron oxide, boric acid, boron carbide, borosilicide, aluminum boride or borate.

8. The method for manufacturing a solar cell according to any one of claims 1 to 2, characterized in that: After heat treatment, when phosphorus atoms are doped, the doping concentration of the protective film is 2×10 20 cm -3 ~4×10 21 cm -3 When doped with boron atoms, the doping concentration of the protective film is 1×10 19 cm -3 ~3×10 20 cm -3 .

9. The method for manufacturing a solar cell according to any one of claims 1 to 2, characterized in that: The thickness of the doping source layer is 10nm to 3000nm; the thickness of the protective film is 30nm to 180nm.

10. The method for manufacturing a solar cell according to any one of claims 1 to 2, characterized in that: After the heat treatment, the method for manufacturing the solar cell includes: The protective film and the doping source layer are removed.

11. The method for manufacturing a solar cell according to any one of claims 1 to 2, characterized in that: The solar cell is an interdigitated back contact solar cell, and the silicon substrate has a first surface and a second surface opposite to each other; The forming of the protective film on the silicon substrate comprises: forming a protective film on the second surface of the silicon substrate, wherein the protective film has a first region and a second region, and the first region does not overlap with the second region; The forming of the doping source layer on the local area of ​​the protective film is: forming a doping source layer containing a p-type dopant on the first area of ​​the protective film, and forming a doping source layer containing an n-type dopant on the second area of ​​the protective film; The method of using heat treatment to push the doping elements in the doping source layer through the protective film into the silicon substrate to locally dope the silicon substrate comprises: the p-type doping elements contained in the doping source layer are pushed through the protective film into the first area of ​​the second surface of the silicon substrate to form a p-type doping layer located in a local area of ​​the second surface of the silicon substrate; The n-type doping elements contained in the doping source layer are pushed into the second area of ​​the second surface of the silicon substrate through the protective film to form an n-type doping layer located in a local area of ​​the second surface of the silicon substrate to form the back emission level and field structure of the finger-shaped cross-back contact solar cell.

12. The method for manufacturing a solar cell according to claim 11, characterized in that: An isolation region is provided between the p-type doping layer and the n-type doping layer.

13. The method for manufacturing a solar cell according to claim 11, characterized in that: Before the step of forming a protective film on the second surface of the silicon substrate, the step further includes: Firstly, a tunnel passivation layer is formed on the second surface of the silicon substrate; In the step of forming the back emitter and field structure of the interdigitated back contact solar cell, doping elements are pushed into the protective film to transform the protective film into a doped semiconductor layer; After the step of forming the back emitter and field structure of the interdigitated back contact solar cell, the step of: The doping source layer is removed and the protective film is retained.

14. The method for manufacturing a solar cell according to claim 11, characterized in that: Before the step of forming a protective film on the second surface of the silicon substrate, the step further includes: Firstly, a tunnel passivation layer is formed on the second surface of the silicon substrate; In the step of forming the back emitter and field structure of the interdigitated back contact solar cell, doping elements are pushed into the protective film to transform the protective film into a doped semiconductor layer; After the step of forming the back-side emitter and field structure of the interdigitated back-contact solar cell, the method further comprises the steps of: The doping source layer is removed, and the protective film in the first region or the second region is removed, and the protective film in the other region is retained.

15. A solar cell, characterized in that: The solar cell is manufactured by the method for manufacturing a solar cell according to any one of claims 1 to 14.

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