阅读说明：本技术 一种太阳能电池及其制作方法 (Solar cell and manufacturing method thereof ) 是由 童洪波 李华 靳玉鹏 于 2020-12-23 设计创作，主要内容包括：本发明公开一种太阳能电池及其制作方法,涉及光伏技术领域,以减少掺杂表面的损伤。该太阳能电池的制作方法包括：提供一硅基底；在硅基底上形成保护膜；在保护膜上形成掺杂源层；掺杂源层为由掺杂剂溶液或掺杂剂浆料形成的掺杂源膜；采用热处理的方式将掺杂源层中的掺杂元素穿过保护膜推进到硅基底中,以对硅基底进行掺杂。本发明提供的太阳能电池及其制作方法用于太阳能电池制造。(The invention discloses a solar cell and a manufacturing method thereof, relates to the technical field of photovoltaics, and aims to reduce damage to a doped surface. The manufacturing method of the solar cell comprises the following steps: 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 dopant solution or a dopant slurry; and pushing the doping elements in the doping source layer into the silicon substrate through the protective film by adopting a heat treatment mode so as to dope the silicon substrate. The solar cell and the manufacturing method thereof provided by the invention are used for manufacturing the solar cell.)

1. A method for manufacturing a solar cell, comprising:

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 dopant solution or a dopant slurry;

and pushing the doping elements in the doping source layer into the silicon substrate through the protective film by adopting a heat treatment mode so as to dope the silicon substrate.

2. The method of claim 1, wherein the protective film is an intrinsic semiconductor film.

3. The method for manufacturing a solar cell according to claim 1, wherein the material of the protective film comprises at least one of silicon, silicon carbide, and germanium; and/or the presence of a gas in the gas,

the material of the protective film comprises at least one of amorphous semiconductor material, polycrystalline semiconductor material, nanocrystalline semiconductor material and microcrystalline semiconductor material.

4. The method according to any one of claims 1 to 3, wherein the process for forming the protective film comprises any one of a low pressure chemical vapor deposition process, an atmospheric pressure chemical vapor deposition process, an enhanced plasma chemical vapor deposition process, a hot wire chemical vapor deposition process, and magnetron sputtering.

5. The method for manufacturing the solar cell according to any one of claims 1 to 3, wherein the dopant solution contains 2 to 30 mass percent of ethanol; the forming mode of the doping source layer is a coating mode.

6. The method for manufacturing a solar cell according to any one of claims 1 to 3,

the mass fraction of the dopant contained in the dopant slurry is 0.01-10%; the forming mode of the doping source layer is at least one of a coating mode, a printing mode and a transfer printing mode.

7. The method for manufacturing the solar cell according to claim 6, wherein the dopant paste further contains nano silicon powder, the mass fraction of the nano silicon powder is 10-80%, the particle size of the nano silicon powder is 5-500 nm, and/or,

the dopant paste also contains silicon oxide, wherein the mass fraction of the silicon oxide is 10-80%, and the particle size of the silicon oxide is 5-500 nm.

8. The method according to any one of claims 1 to 3, wherein the dopant contained in the dopant source layer is phosphoric acid, phosphate, metaphosphoric acid, metaphosphate, phosphorus pentoxide, or a phosphorus simple substance, or the dopant contained in the dopant source layer is boron nitride, boron oxide, boric acid, boron carbide, borosilicate, aluminum boride, or a borate.

9. The method according to any one of claims 1 to 3, wherein after the heat treatment, the doping concentration of the doped surface of the silicon substrate is 1 x 10¹⁸cm^-3～4×10²⁰cm^-3。

10. The method according to any one of claims 1 to 3, wherein the dopant concentration of the dopant source layer is greater than or equal to 1 x 10²¹cm^-3；

After the heat treatment, when phosphorus atoms are doped, the doping concentration of the protective film is 2 × 10²⁰cm^-3～4×10²¹cm^-3When mixingWhen the boron atom is hetero atom, the doping concentration of the protective film is 1 × 10¹⁹cm^-3～3×10²⁰cm^-3。

11. The method according to any one of claims 1 to 3, wherein the thickness of the dopant source layer is 10nm to 3000 nm; the thickness of the protective film is 30 nm-180 nm.

12. The method according to any one of claims 1 to 3, wherein forming a dopant source layer on the protective film comprises: forming a doping source layer in a local area of the protective film;

and after the heat treatment, doping the silicon substrate by doping elements locally.

13. The method for manufacturing a solar cell according to any one of claims 1 to 3, wherein the method for manufacturing a solar cell after the heat treatment comprises:

and removing the protective film and the doping source layer.

14. The method for manufacturing a solar cell according to any one of claims 1 to 3,

the silicon substrate is a silicon substrate with a tunneling passivation layer, and the protective film is formed on the tunneling passivation layer.

15. A solar cell produced by the method for producing a solar cell according to any one of claims 1 to 14.

Technical Field

The invention relates to the technical field of photovoltaics, in particular to a solar cell and a manufacturing method thereof.

Background

The process for manufacturing the solar cell mainly comprises the following steps: texturing, doping, cleaning, depositing an antireflection film, testing, sorting and the like. The doping process may be to form a doping source on the surface of the silicon substrate, and then perform an annealing process.

When the doping process is performed by using a doping source coating advancing manner, the doped surface is easily damaged, thereby affecting the performance of the solar cell.

Disclosure of Invention

The invention aims to provide a solar cell and a manufacturing method thereof, which are used for reducing the damage of a doped surface.

In a first aspect, the present invention provides a method for fabricating a solar cell. The manufacturing method of the solar cell comprises the following steps:

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 dopant solution or a dopant slurry;

and pushing the doping elements in the doping source layer into the silicon substrate through the protective film by adopting a heat treatment mode so as to dope the silicon substrate.

When the technical scheme is adopted, a protective film is formed on a silicon substrate to be doped, and then a doping source layer is formed on the protective film. On one hand, the protective film can prevent the doping source layer from directly contacting the silicon substrate, so that the silicon substrate can be prevented from being corroded and damaged by the doping source layer, and the performance of the manufactured solar cell is ensured. On the other hand, in the process of doping treatment, the doping elements in the doping source layer are pushed to the silicon substrate in the heat treatment process, the doping elements are pushed to the protective film firstly, and the doping elements are pushed to the silicon substrate along with the continuous heat treatment. At the moment, the protective film can contain more doping elements, so that the situation that the excessive doping elements are pushed to the surface of the silicon substrate is avoided, the risk that the doping concentration of the silicon substrate is too high can be further reduced, and the performance of the manufactured solar cell is further ensured. Therefore, in the doping process, the manufacturing method of the solar cell can avoid the corrosion of the doping source layer to the doped surface, can avoid the problem of overhigh doping concentration, can easily form the set doping concentration, and ensures the performance of the manufactured solar cell.

In some possible implementations, the protective film is an intrinsic semiconductor film. The intrinsic semiconductor film does not contain doping elements, and in the process of doping the silicon substrate, the intrinsic semiconductor film can contain more doping elements, so that the silicon substrate is well protected.

In some possible implementations, the material of the protective film includes at least one of silicon, silicon carbide, and germanium. At the moment, the material of the protective film and the material of the silicon substrate are both semiconductor materials, the properties of the materials are similar, the doping process is similar, and the doping process does not need to be changed, so that the cost increased by process improvement can be reduced.

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 may be selected according to the protection effect to be achieved and the doping properties of different materials.

In some possible implementations, the forming process of the protective film includes any one of a low pressure chemical vapor deposition process, an atmospheric pressure chemical vapor deposition process, an enhanced plasma chemical vapor deposition process, a hot filament chemical vapor deposition process, and magnetron sputtering.

In some possible implementations, the dopant solution contains ethanol. The mass fraction of the ethanol is 2-30 percent; the doping source layer is formed in a coating mode. The ethanol not only can play a role in diluting the dopant and adjusting the concentration, but also has the property of easy volatilization when the dopant solution is coated on the silicon substrate, so that the curing and forming of the dopant solution can be conveniently realized, and the dopant solution can quickly form a dopant source layer.

In some possible implementations, the dopant paste contains a dopant mass fraction of 0.01% to 10%. The forming mode of the doping source layer is at least one of a coating mode, a printing mode and a transfer printing mode. The dopant paste in the paste form not only has better fluidity, but also has better formability, so that a uniform doping source layer can be better formed.

In some possible implementations, the dopant paste further contains nano-silicon powder. The mass fraction of the nano silicon powder is 10-80%, and the particle size of the nano silicon powder is 5-500 nm. At this time, the nano silicon powder with smaller particle size can form uniformly dispersed slurry, so that the dopant can be uniformly dispersed in the whole slurry system, and the formation of a doping source layer with uniformly distributed dopant is facilitated.

In some possible implementations, the dopant paste further contains silicon oxide. The mass fraction of the silicon oxide is 10-80%, and the particle size of the silicon oxide is 5-500 nm. The silicon oxide material has stable property, can play a good protection role on the protective layer and the silicon substrate at the lower layer, and reduces the probability of damage of the protective layer and the silicon substrate.

In some possible implementations, the dopant contained in the doping source layer is phosphoric acid, phosphate, metaphosphoric acid, metaphosphate, phosphorus pentoxide, or elemental phosphorus, or the dopant contained in the doping source layer is boron nitride, boron oxide, boric acid, boron carbide, borosilicate, aluminum boride, or borate.

In some possible implementations, the doping concentration of the doped surface of the silicon substrate after the heat treatment is 1 × 10¹⁸cm^-3～4×10²⁰cm^-3. Therefore, due to the protection effect of the protective film, even if the doping concentration of the doping source layer is higher, the doping concentration of the doping surface of the silicon substrate is not too high, shallow doping can be formed, and carrier recombination is reduced.

In some possible implementations, the doping concentration of the doping source layer is greater than or equal to 1 × 10²¹cm^-3(ii) a After the heat treatment, the doping concentration of the doped surface of the silicon substrate is 1 × 10¹⁸cm^-3～4×10²⁰cm^-3(ii) a When phosphorus atoms are doped, the doping concentration of the protective film is 2 × 10²⁰cm^-3～4×10²¹cm^-3When boron atoms are doped, the doping concentration of the protective film is 1X 10¹⁹cm^-3～3×10²⁰cm^-3。

In some possible implementations, the thickness of the doping source layer is 10nm to 3000 nm; at this time, the doping source layer may have sufficient dopant to ensure the quality of the doping process. The thickness of the protective film is 30 nm-180 nm. At this moment, the protective film not only can play a better role in protecting the silicon substrate, but also can ensure that enough doping elements enter the silicon substrate through the protective film.

In some possible implementations, forming the dopant source layer on the protective film includes: forming a doping source layer in a local area of the protective film; after the heat treatment, the doping element is used for locally doping the silicon substrate. At this time, local doping treatment may be conveniently performed on the silicon substrate using the protective film and the doping source layer.

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

In some possible implementations, the silicon substrate is a silicon substrate having a tunneling passivation layer, and the protection film is formed on the tunneling passivation layer. In one aspect, the protective film may function to protect the tunneling passivation layer. On the other hand, under the condition of keeping the protective film, the tunneling passivation structure can be formed by utilizing the tunneling passivation layer and the doped protective film, so that the process flow can be simplified, the process difficulty can be reduced, and the manufacturing cost can be reduced.

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

The beneficial effects of the solar cell provided by the second aspect may refer to the beneficial effects of the manufacturing method of the solar cell described in the first aspect or any one of the possible implementation manners of the first aspect, and are not described herein again.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention and not to limit the invention. In the drawings:

fig. 1 is a schematic structural diagram of a solar cell according to an embodiment of the present invention;

fig. 2 to fig. 11 are schematic diagrams illustrating states of various stages of a method for manufacturing a solar cell according to an embodiment of the present invention;

fig. 12 is a schematic structural diagram of a selective emitter solar cell according to an embodiment of the present invention;

fig. 13 is a schematic structural diagram of an IBC solar cell according to an embodiment of the present invention;

fig. 14 is a schematic structural diagram of an IBC solar cell having a passivated contact structure according to an embodiment of the invention;

fig. 15 is a schematic structural diagram of an IBC solar cell having a passivated contact structure according to an embodiment of the invention.

In fig. 1 to 15, 10-substrate, 101-textured 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, and 29-isolation region.

Detailed Description

In order to facilitate clear description of technical solutions of the embodiments of the present invention, in the embodiments of the present invention, terms such as "first" and "second" are used to distinguish the same items or similar items having substantially the same functions and actions. Those skilled in the art will appreciate that the terms "first," "second," etc. do not denote any order or quantity, nor do the terms "first," "second," etc. denote any order or importance.

It is to be understood that the terms "exemplary" or "such as" are used herein to mean serving as an example, instance, or illustration. Any embodiment or design described herein as "exemplary" or "e.g.," is not necessarily to be construed as preferred or advantageous over other embodiments or designs. Rather, use of the word "exemplary" or "such as" is intended to present concepts related in a concrete fashion.

In the present invention, "at least one" means one or more, "a plurality" means two or more. "and/or" describes the association relationship of the associated objects, meaning that there may be three relationships, e.g., a and/or B, which may mean: a exists alone, A and B exist simultaneously, and B exists alone, wherein A and B can be singular or plural. The character "/" generally indicates that the former and latter associated objects are in an "or" relationship. "at least one of the following" or similar expressions refer to any combination of these items, including any combination of the singular or plural items. For example, at least one (one) of a, b, or c, may represent: a, b, c, a and b combination, a and c combination, b and c combination, or a, b and c combination, wherein a, b and c can be single or multiple.

In the manufacturing process of the solar cell, when doping treatment is carried out, doping materials such as phosphoric acid and boric acid can be directly coated on the surface to be doped. When a doping material such as phosphoric acid, boric acid, etc. is coated on the surface of the silicon substrate, since the concentration of phosphorus or boron in the coated doping material is very high, it is far more than 10²²cm^-3Therefore, the doping concentration of the doped surface is very high during the subsequent drive-in doping process. Too high a surface doping concentration can cause severe surface recombination, resulting in a significant degradation of the performance of the cell device.

In addition, when the doped polysilicon layer is directly manufactured on the tunneling passivation layer by using the nano silicon powder, the structure of the passivation layer is easily damaged by directly coating the nano silicon containing the dopant on the tunneling passivation layer due to the fact that the tunneling passivation layer is thin, and passivation performance of the passivation layer is affected. Particularly, the solution of phosphoric acid and boric acid has a great damaging effect on the passivation layer. If the thickness of the passivation layer is increased, the photogenerated carriers on the substrate cannot be led out, so that the internal resistance of the battery is greatly improved.

In order to solve the above technical problems, embodiments of the present invention provide a solar cell. As shown in fig. 1, the solar cell includes a substrate 10, an emitter, a first electrode 15, and a second electrode 24. The substrate 10 has opposing first and second sides. The first surface of the substrate 10 is formed with an emitter. A first electrode 15 is located on a first side of the substrate 10, the first electrode 15 being in electrical contact with the emitter. A second electrode 24 is located on the second side of the substrate 10. It is to be understood that the solar cell may also include other structures, as described in detail below.

The embodiment of the invention also provides a manufacturing method of the solar cell. As shown in fig. 2 to 11, the method for manufacturing a solar cell specifically includes the following steps.

As shown in fig. 2, a substrate 10 is provided. The substrate 10 may be an n-type semiconductor substrate or a p-type semiconductor substrate. The material of the substrate 10 may be silicon. The substrate 10 has opposing first and second sides. The method of fabricating the solar cell will be described below with reference to an n-type silicon semiconductor substrate, and the first side of the substrate 10 as the front side.

As shown in fig. 3, the substrate 10 is textured. Specifically, one side of the substrate 10 may be textured, or both sides of the substrate 10 may be textured. The surface of the substrate 10 after texturing has a reflectivity of less than 12%.

As an example, the texturing process may be a double-sided texturing process using an alkaline solution. The substrate 10 is processed by using an alkaline solution with an additive, so that the textured structure 101 with the pyramid morphology can be formed on the surface of the substrate 10. The texture structure 101 can play a role in trapping light, so that the reflection of the solar cell to sunlight is reduced, and the performance of the solar cell is improved. Of course, in some solar cell fabrication methods, the texturing process may be omitted.

At this time, the obtained structure may be defined as a silicon substrate. The first and second surfaces of the silicon substrate correspond to the first and second surfaces of the substrate 10 one to one. It should be understood that, when manufacturing a solar cell, the substrate 10 may be used as a starting point for the process, or the silicon substrate defined in the embodiment of the present invention may be used as a starting point for the process.

As shown in fig. 4, a protective film 11 is formed on the first face of the silicon substrate. A protective film 11 is formed on a silicon substrate to be doped, and a doping source layer 12 is subsequently formed on the protective film 11. On one hand, the protective film 11 can prevent the doping source layer 12 from directly contacting with the silicon substrate, so that corrosion and damage of the doping source layer 12 to the silicon substrate can be avoided, and the performance of the manufactured solar cell is ensured. On the other hand, in the subsequent heat treatment process, the doping element contained in the doping source layer 12 is pushed to the silicon substrate, and in the doping treatment process, the doping element is pushed to the protective film 11, and as the heat treatment continues, the doping element is pushed to the silicon substrate. At this time, the protective film 11 may contain more doping elements, so as to prevent the excessive doping elements from being pushed to the surface of the silicon substrate, thereby reducing the risk of too high doping concentration of the silicon substrate, and further ensuring the performance of the manufactured solar cell. Therefore, in the doping process, the method for manufacturing the solar cell in the embodiment of the invention can not only avoid the corrosion of the doping source layer 12 to the doped surface, but also avoid the problem of over-high doping concentration, so that the set doping concentration can be easily formed, and the performance of the manufactured solar cell can be ensured.

The protective film 11 may be an intrinsic semiconductor film from the viewpoint of doping. Because the intrinsic semiconductor film does not contain doping elements, the intrinsic semiconductor film can contain more doping elements in the subsequent doping process of the silicon substrate, and therefore the effect of better protecting the silicon substrate is achieved.

In terms 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 protection film 11 and the material of the silicon substrate are both semiconductor materials, the properties of the two materials are similar, the doping process is similar, and the doping process does not need to be changed, so that the cost increased by process improvement can be reduced.

In terms of material micro morphology, the material of the protective film 11 may include 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 may be selected according to the protection effect to be achieved and the doping properties of different materials.

Illustratively, the material of the protective film 11 may be intrinsic amorphous silicon, intrinsic microcrystalline silicon, or the like. Of course, the material of the protective film 11 may protect a plurality of materials. For example, the material of the protective film 11 may be intrinsic amorphous silicon and intrinsic microcrystalline silicon.

The thickness of the protective film 11 may be 30nm to 180 nm. For example, the thickness of the protective film 11 may be 30nm, 50nm, 76nm, 80nm, 100nm, 125nm, 150nm, 170nm, 175nm, 180nm, or the like. At this time, the protective film 11 having the thickness within the range not only can play a role of better protecting the silicon substrate, but also can ensure that enough doping elements enter the silicon substrate through the protective film 11. Preferably, the thickness of the protective film 11 may be 30nm to 100 nm. At this time, the protection film 11 not only can protect the silicon substrate, but also can save raw materials and reduce the cost.

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

In practical applications, the intrinsic amorphous silicon material may be deposited on the surface of the silicon substrate by an atmospheric pressure chemical vapor deposition apparatus to form the protective film 11.

As shown in fig. 5, a doping source layer 12 is formed on the protective film 11. The doping concentration of the doping source layer 12 is 1 × 10 or more²¹cm^-3. The dopant source layer 12 is a dopant source film formed of a dopant solution or a dopant paste.

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

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 a phosphorus simple substance. 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, borosilicate, aluminum boride, or borate.

When the dopant source layer 12 is formed using a dopant solution, 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 dopant can 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 residual amounts of solvent, such as water. The ethanol not only can play a role in diluting the dopant and adjusting the concentration, but also has the property of easy volatilization when the dopant solution is coated on the silicon substrate, so that the curing and forming of the dopant solution can be conveniently realized, and the dopant solution can quickly form the dopant source layer 12. Ethanol may be added 0.5h before the dopant solution is used.

When the doping source layer 12 is formed using a doping solution, the doping source layer 12 may be formed in a coating manner. Specifically, the coating method may be a drop coating method, a spin coating method, a blade coating method, a spray coating method, a roll coating method, or the like.

It will be appreciated that after the coating process, a drying process is required. Specifically, the drying equipment can be a crawler-type drying furnace, a chain-type drying furnace, a tubular drying furnace and the like. The temperature of the drying treatment can be 50-500 ℃, and the time of the drying treatment can be 20-30 min.

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

The main body slurry can be nano silicon powder. The mass fraction of the nano silicon powder can be 10-80%. For example, the mass fraction of the nano silicon powder may be 10%, 20%, 30%, 40%, 50%, 55%, 60%, 70%, 80%, or the like. The grain size of the nano silicon powder can be 5 nm-500 nm. At this time, the nano silicon powder with a smaller particle size can form uniformly dispersed slurry, so that the dopant can be uniformly dispersed in the whole slurry system, which is beneficial to forming the doping source layer 12 with uniformly distributed dopant.

The host slurry may also be silica. The mass fraction of the silicon oxide may be 10% to 80%. For example, the mass fraction of silicon oxide may be 10%, 20%, 30%, 40%, 50%, 55%, 60%, 70%, 80%, etc. The particle size of the silicon oxide may be 5nm to 500 nm. The silicon oxide material has stable property, can play a good protection role on the protective layer and the silicon substrate at the lower layer, and reduces the probability of damage of the protective layer and the silicon substrate.

When the doping source layer 12 is formed using a doping solution, the doping source layer 12 may be formed in at least one of a coating method, a printing method, and a transfer method. The coating method may be a drop coating method, a spin coating method, a blade coating method, a spray coating method, a roll coating method, or the like. The printing may be screen printing. The transfer means may be laser transfer. The dopant paste in the paste form has not only good fluidity but also good moldability, so that the uniform dopant source layer 12 can be well formed.

As shown in fig. 6, the doping elements in the doping source layer 12 are driven into the silicon substrate through the protective film 11 by means of heat treatment to dope the silicon substrate. At this time, a doped layer 13 is formed on the first surface of the silicon substrate. When n-type doping is performed, a front field structure may be formed on the first plane surface of the silicon substrate. When p-type doping is performed, an emitter may be formed on the first plane surface of the silicon substrate.

After the heat treatment, the doping concentration of the doped surface (doped layer 13) of the silicon substrate was 1 × 10¹⁸cm^-3～4×10²⁰cm^-3。

The sheet resistance of the doped surface of the silicon substrate (doped layer 13) may be 40-250 ohm/sq. For example, siliconThe sheet resistance of the doped surface of the substrate may be 40ohm/sq, 65ohm/sq, 88ohm/sq, 100ohm/sq, 150ohm/sq, 180ohm/sq, 200ohm/sq, 220ohm/sq, 250ohm/sq, and the like. Preferably, the square resistance of the doped surface of the silicon substrate may be 100ohm/sq to 200ohm/sq, and the doping concentration of the doped surface of the corresponding silicon substrate is 4.5 × 10¹⁹cm^-3～1×10²⁰cm^-3。

When phosphorus atoms are doped, the doping concentration of the protective film 11 is 2 × 10²⁰cm^-3～4×10²¹cm^-3. When boron atoms are doped, the doping concentration of the protective film 11 is 1 × 10¹⁹cm^-3～3×10²⁰cm^-3. It can be seen that, due to the protection effect of the protection film 11, even if the doping concentration of the doping source layer 12 is high, the doping concentration of the doping surface (doping layer 13) of the silicon substrate is not too high, and shallow doping can be formed to reduce carrier recombination.

The heat treatment equipment can be a tubular heat treatment furnace, a chain heat treatment furnace and the like. When a tubular heat treatment furnace is used for heat treatment, the doping source layer 12 can be subjected to heat treatment for 5min to 60min at the temperature of 300 ℃ to 900 ℃ under the protective atmosphere, so that the doped elements are promoted. When the chain type heat treatment furnace is used for heat treatment, the treatment temperature can be 850-1000 ℃, and the treatment time can be 5-50 min.

It should be understood that in some solar cells, heavily doped layer 16 may also be formed by heavily doping a portion of doped layer 13, as shown in fig. 12. Heavily doped layer 16 is formed in a local region of doped layer 13, and the doping concentration of heavily doped layer 16 is higher than the doping concentration of doped layer 13. At this time, a selective emitter structure may be formed.

The method for forming the heavily doped layer 16 in the local region includes: a protective film 11 is formed on a silicon substrate having a doped layer 13 (the protective film and the doping source layer required for fabricating the doped layer 13 are removed), then a doping source layer 12 is formed on a local region of the protective film 11, and then a doping element in the doping source layer 12 is driven into the doped layer 13 by means of heat treatment to form a heavily doped layer 16. The local region here corresponds to the region to be heavily doped on doped layer 13. The material, thickness, and formation method of the protection film 11 are substantially the same as those of the protection film 11 used in the above-described process for manufacturing the doped layer 13, and are not described herein again. The material, thickness, and formation method of the doping source layer 12 are substantially the same as those of the doping source layer 12 used in the above-described process for producing the doping layer 13, and the difference is that the doping source layer 12 has a high concentration of the doping element, and the doping source layer 12 partially covers the protective film 11. Specifically, the doping source layer may be coated or printed on a local region of the protective film 11.

When the heavily doped layer 16 is manufactured by the method, processes such as laser film opening and the like are not needed, so that the doped layer 13 can be prevented from being damaged by laser, and the process cost can be reduced.

In order to facilitate the removal of the protective film 11, an etch stop layer may be formed on the doping layer 13 before the protective film 11 is formed, and then the protective film 11 and the doping source layer 12 may be formed on the etch stop layer. The etch stop layer may be a thin layer of silicon oxide or the like. When it is necessary to remove the protective film 11, an alkali solution such as KOH may be used as an etchant to remove the protective film 11. At this time, the reaction rate of the alkali solution and the etching stop layer made of silicon oxide material is extremely slow, so that the doped layer 13 can be prevented from being damaged by the alkali solution etchant.

Note that the heavily doped layer 16 may be formed in a local region of the silicon substrate. In this case, the protective film 11 may be formed on the silicon substrate, the doping source layer 12 may be formed in a local region of the protective film 11, and after the heat treatment, the doping element contained in the doping source layer 12 may be partially doped into the silicon substrate through the protective film 11, thereby forming the heavily doped layer 16.

It is 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 contact resistance reduction in the solar cell, the doping concentration of the doped surface of the silicon substrate may be 5 × 10¹⁸cm^-3～4×10²⁰cm^-3. For example, when only doped layer 13 is included in the solar cell and heavily doped layer 16 is not present, doped layer 13 may have this doping concentration.

When siliconThe doping concentration of the doped surface of the silicon substrate can be properly reduced when the doped surface of the substrate only plays a role in carrier lateral transport, even only plays a role in separating electron hole carriers. Preferably, the doping concentration of the doped surface of the silicon substrate may be 1 × 10¹⁸cm^-3～1×10²⁰cm^-3. For example, when heavily doped layer 16 is included in the solar cell, doped layer 13 may have this doping concentration. Alternatively, for example, as shown in fig. 11 or fig. 14, in the case where the protective film 11 (which is converted into the doped semiconductor layer 22 after doping) remains, the doping surface (the back field structure 26 or the n-type doped layer 28) of the second surface of the silicon substrate may have the doping concentration.

When the doped surface of the silicon substrate is mainly used for contacting with the metal electrode in the solar cell, the doping concentration of the contact region can be 4.5 × 10¹⁹cm^-3～4×10²⁰cm^-3. For example, when a heavily doped layer 16 is included in a solar cell, the heavily doped layer 16 may have the doping concentration. In this case, the doping concentration is high, the lateral conductivity is high, and the contact performance between the semiconductor and the metal electrode can be better.

Obviously, as described above, the regions having different functions in the solar cell may be provided with different doping concentrations, and both structures (e.g., the doped layer 13 and the heavily doped layer 16) may exist in the same cell structure at the same time. Specifically, by locally forming a doping source layer on the protective film 11, doping of locally different concentrations can be achieved.

As shown in fig. 7, 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 tunneling passivation layer 21 may 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 tunneling passivation layer 21 may be 0.5nm to 5 nm.

The process of forming the tunnel passivation layer 21 may be a physical vapor deposition process or a chemical vapor deposition process. To simplify the process, the silicon substrate may be directly oxidized to form silicon oxide as the tunnel passivation layer 21.

In the process of manufacturing the solar cell, the substrate 10 with the tunneling passivation layer 21 formed on the second surface may also be defined as a silicon substrate. In practical applications, the cell fabrication may be performed using the silicon substrate with the tunnel passivation layer 21 as a starting point of the process.

It should be noted that, before forming the tunneling passivation layer 21, it is necessary to clean the plating layer, which is formed on the second surface of the silicon substrate by the material of the protective film 11, and partially etch the second surface of the silicon substrate, so as to improve the flatness of the second surface of the silicon substrate. In addition, the doping source layer 12 is formed and the silicon substrate is doped in a pushing mode, so that the doping on the second surface of the silicon substrate in the doping process is avoided, the process of removing the doping is omitted, and the process can be simplified.

In practical application, a chain type device and a groove type device can be adopted to remove the coiled coating. The etchant used for the removal process may be determined based on the material of the surrounding plating being removed. For example, when removing the silicon-based plating layer, an alkaline solution etchant containing KOH, NaOH, or the like may be used. It is understood that the second side of the silicon substrate may be polished to improve planarity while the cladding layer on the second side of the silicon substrate is removed.

As shown in fig. 8, a doped semiconductor layer 22 is formed on the tunneling passivation layer 21, and a passivation contact structure formed by the tunneling passivation layer 21 and the doped semiconductor layer 22 and located on the second surface of the silicon substrate is fabricated. The doped semiconductor layer 22 may be formed by a conventional manufacturing method, or the above-described protective film 11 may be formed on the tunnel passivation layer 21, and the doped semiconductor layer 22 may be formed using the protective film 11.

When the doped semiconductor layer 22 is formed using the protective film 11, on the one hand, the protective film 11 may protect the tunnel passivation layer 21 from being corroded by the doping source layer 12. On the other hand, under the condition of keeping the protective film 11, a tunneling passivation structure can be formed by using the tunneling passivation layer 21 and the doped protective film 11, so that the process flow can be simplified, the process difficulty can be reduced, and the manufacturing cost can be reduced.

When the doped semiconductor layer 22 is formed using the protective film 11, the protective film 11 may be formed on the tunneling passivation layer 21, then the doping source layer 12 may be formed on the protective film 11, and then the doping source layer 12 may be subjected to a heat treatment such that the doping element contained in the doping source layer 12 is pushed into the protective film 11 to transform the protective film 11 into the doped semiconductor layer 22. In this case, the protective film 11 does not need to be removed. Meanwhile, during the heat treatment, the doping elements of the doping source layer 12 are also pushed to the second surface of the silicon substrate, so that a field structure or an emitter is formed on the second surface of the silicon substrate. For example, when a p-type doped layer 13 is formed on a first side of an n-type substrate 10, the second side may be n-doped, thereby forming a back field structure 26 on the second side of the substrate 10.

Since the doped semiconductor layer 22 formed by using the protection film 11 can perform certain passivation contact and lateral conduction, the surface doping concentration of the second surface (back surface field structure 26) of the substrate 10 can be properly reduced in the process of forming the doped semiconductor layer 22 by using the protection film 11 and doping the second surface of the substrate 10. Preferably, the surface doping concentration of the second side (back field structure 26) of the substrate 10 may be 1 × 10¹⁸cm^-3～3×10²⁰cm^-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.

In the process of fabricating the doped semiconductor layer 22, the material and the forming manner of the protection film 11 are the same as those of the protection film 11 formed in the doping process on the first surface of the silicon substrate, and are not described herein again. In the process of fabricating the doped semiconductor layer 22, the material and the forming method of the doped source layer 12 are the same as those of the doped source layer 12 formed by doping the first surface of the silicon substrate, and are not described herein again.

The doped semiconductor layer 22 is made of polysilicon and has a thickness of 30nm to 180 nm. The doped semiconductor layer 22 has a doping type opposite to that of the first side of the silicon substrate. When phosphorus atoms are doped, the doping concentration of the doped semiconductor layer 22 is 2 × 10²⁰cm^-3～4×10²¹cm^-3When boron atoms are doped, the doping concentration of the doped semiconductor layer 22 is 1 × 10¹⁹cm^-3～3×10²⁰cm^-3。

As shown in fig. 9, the protective film 11 and the doping source layer 12 located on the first side of the substrate 10 are removed. At the same time, the dopant source layer 12 on the second side of the silicon substrate may be removed together. In addition, the doping source layer 12 is formed and the silicon substrate is doped in a pushing mode, so that the winding doping in the doping process is avoided, the winding doping removing process is saved, and the process is simplified.

In practical applications, the protective film 11 and the doping source layer 12 may be removed by using a chain apparatus or a trench apparatus. When cleaning of the first and second sides of the substrate 10 is required, a tank-type apparatus may be employed. When the substrate 10 is subjected to single-side processing, a chain apparatus may be employed. The etchant used for the removal process may be determined according to the material of the film layer being removed. For example, when the doping source layer 12 of silicon oxide material is removed, an etchant containing hydrofluoric acid may be used. When the silicon protective film 11 and the spin-coating layer are removed, an alkaline solution etchant containing KOH, NaOH, or the like may be used.

As shown in fig. 12, in practical applications, the passivation contact structure formed on the second side of the silicon substrate may be omitted. At this time, the second-side doping layer 25 may be formed on the second side. 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 doped layer 13 is p-type doped, second face doped layer 25 is n-type doped. The second surface doping layer 25 may be formed in the same manner as the doping layer 13 of the first surface of the silicon substrate. The second surface doping layer 25 not only functions to transport carriers in the lateral direction, but also reduces the contact resistance when the second surface of the substrate 10 is in contact with an electrode.

As shown in fig. 10, a first side of the substrate 10 is passivated to form a first passivation layer 14; the second side of the substrate 10 is passivated to form a second passivation layer 23.

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.

The process of 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.

As shown in fig. 11, a first electrode 15 is formed on the first side of the substrate 10, the first electrode 15 being in electrical contact with the doped layer 13. A second electrode 24 is formed on the second side of the substrate 10, the second electrode 24 being in electrical contact with the doped semiconductor layer 22. The material of each of the first electrode 15 and the second electrode 24 may include one or more of silver, copper, aluminum, nickel, titanium, tungsten, and tin.

In practice, the first electrode 15 and the second electrode 24 are formed using 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.

In forming the first electrode 15 and the second electrode 24, a process of combining a plurality of processes may be employed. For example, a paste containing silver or copper may be printed using a screen printing process, and then electrode preparation may be completed by a sintering process or an annealing process at 500 to 900 ℃. For another example, a seed layer may be prepared by a PVD process, patterned, and then an electrode may be prepared by an electroplating method, and then an electrode may be formed by annealing. For another example, an electroless plating process may be used to form a seed layer, followed by thickening using an electroplating method, and finally annealing to complete the electrode preparation.

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 exemplary structure. In an embodiment of the present invention, the second side of the substrate 10 may form a passivation contact structure, as shown in fig. 11. The second side of the substrate 10 may also form a point contact structure as shown in fig. 12. The second side of the substrate 10 may also form a second side local diffusion structure. When the first surface of the silicon substrate is doped in an n-type mode, the second surface of the silicon substrate can also form a second surface aluminum alloy contact structure.

Embodiments of the present invention also provide an Interdigitated Back Contact (IBC) solar cell. Fig. 13-15 illustrate schematic structural diagrams of three Interdigitated Back Contact (IBC) solar cells.

The method of fabricating the IBC solar cell shown in fig. 13 is similar to the conventional method of fabricating an IBC solar cell except for the manner of forming the backside partially doped layer. The locally doped layer at the back side of the back contact solar cell may be fabricated with reference to the method of fabricating the heavily doped layer 16 described 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 may be formed on the second surface of the substrate 10, the protective film 11 having a first region and a second region, and the first region and the second region not overlapping each other. A doping source layer 12 containing p-type dopants is formed on the protective film 11 at a first region, and after the heat treatment, the p-type doping element contained in the doping source layer 12 is driven to the first region on the second surface of the substrate 10 through the protective film 11, thereby forming a p-type doping layer 27 located in a partial region on the second surface of the substrate 10. A doping source layer 12 containing n-type dopants is formed on a second region on the protective film 11, and after the heat treatment, the n-type doping element contained in the doping source layer 12 is driven to the second region on the second surface of the substrate 10 through the protective film 11, thereby forming an n-type doping layer 28 located in a partial region on the second surface of the substrate 10. It should be understood that in some solar cells, the n-doped layer 28 may also be omitted. At this time, a back emitter and a field structure of the back contact solar cell may be formed. After the protective film 11 and the doping source layer 12 are removed, a passivation layer and electrodes are formed on the first and second surfaces of the substrate 10, and an IBC solar cell is formed. Preferably, an isolation region 29 may also be provided between the p-doped layer 27 and the n-doped layer 28.

In practical applications, in the process of fabricating the IBC solar cell by the method described above, the tunnel passivation layer 21 may be formed on the second surface of the substrate 10 before the protective film 11 is formed. And other manufacturing steps are unchanged, and only the doping source layer 12 is removed and the protective film 11 is reserved after the manufacturing of the back local emitter level and the field structure is completed. At this time, in the process of fabricating the back emitter and the field structure, the doping element is advanced into the protective film 11, so that the protective film 11 is converted into the doped semiconductor layer 22. The doped semiconductor layer 22 and the tunneling passivation layer 21 form a passivation contact structure on the back surface of the solar cell. By forming a passivation layer and electrodes on the first and second sides of the substrate 10, an IBC solar cell having a passivation contact structure as shown in fig. 14 may be formed. Therefore, by adopting the method of the embodiment of the invention, the IBC solar cell with the passivation contact structure can be conveniently manufactured without additionally increasing the process for manufacturing the doped semiconductor layer 22, so that the process flow can be simplified, and the cost can be saved.

In addition, in the process of manufacturing the IBC solar cell having the passivation contact structure by using the above method, not only the doping source layer 12 but also the protective film 11 of the first region or the second region is removed, and the protective film 11 of the other region is remained. That is, the doped semiconductor layer 22 is partially etched. Subsequently, a passivation layer and an electrode are formed on the first and second sides of the substrate 10, and an IBC solar cell as shown in fig. 15 may be formed.

While the invention has been described in connection with various embodiments, other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a review of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the word "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

While the invention has been described in conjunction with specific features and embodiments thereof, it will be evident that various modifications and combinations can be made thereto without departing from the spirit and scope of the invention. Accordingly, the specification and figures are merely exemplary of the invention as defined in the appended claims and are intended to cover any and all modifications, variations, combinations, or equivalents within the scope of the invention. It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.