CN119300515A - A method for preparing a solar cell, a solar cell and a photovoltaic module - Google Patents

Abstract

The present application relates to a method for preparing a solar cell, a solar cell and a photovoltaic module, comprising a substrate, wherein the substrate comprises a first surface and a second surface. The first surface comprises a metal region and a non-metal region, and an electrode is arranged in the metal region. A first velvet structure is arranged in the metal region, and a second velvet structure is arranged in the non-metal region. The reflectivity of the second velvet structure is less than that of the first velvet structure. Therefore, the first velvet structure in the metal region is relatively flat, and the second velvet structure in the non-metal region has a large fluctuation amplitude. A doping layer is arranged in the metal region to prepare an emitter. The relatively flat first velvet structure makes the uniformity of the doping layer higher, which can improve the photoelectric conversion efficiency and stability of the metal region. The second velvet structure with a large fluctuation amplitude improves the absorption capacity of the non-metal region to sunlight. A passivation film layer and an anti-reflection film layer are arranged on the first velvet structure and the second velvet structure to improve the efficiency and performance of the battery.

Description

A method for preparing a solar cell, a solar cell and a photovoltaic module

Technical Field

The present application relates to the technical field of solar cells, and in particular to a method for preparing a solar cell, a solar cell and a photovoltaic module.

Background Art

Solar cells are mainly prepared by doping heterogeneous elements on a silicon substrate to form a PN junction to convert light energy into electrical energy. A metal electrode is set on the emitter to form a metal area to collect the current generated by the PN junction and transport the current to the terminal circuit. The doping layer can make the metal area form an ohmic contact to reduce the metal-semiconductor contact resistance. In the prior art, the reflectivity of the solar cell surface is relatively high, resulting in a low absorption rate of solar light by the solar cell.

Summary of the invention

The present application provides a method for preparing a solar cell, a solar cell and a photovoltaic module, which are used to solve the problem of low absorption rate of solar light by solar cells.

The present application provides a method for preparing a solar cell. The solar cell includes a substrate. The substrate includes a first surface and a second surface. The first surface includes a metal region and a non-metal region. The preparation method includes:

Performing texturing and diffusion of doping elements on the first surface and the second surface of the substrate, so that the first surface and the second surface both form a first texturing structure, a doping layer and a doping oxide layer;

removing the doped oxide layer in the non-metallic region of the first surface;

Etching the doped layer in the non-metallic region to a depth of 0.5 μm to 10 μm, and etching the first velvet structure in the non-metallic region;

Secondary velveting, forming a second velvet structure in the non-metallic area;

An oxide layer is formed on the second textured structure.

In a possible embodiment, when removing the doped oxide layer in the non-metallic region of the first surface, the preparation method includes:

The non-metallic region in the first surface is scanned by laser, the power of the laser is 1 W to 50 W, and the scanning speed of the laser is 5 m/s to 40 m/s.

In a possible embodiment, when etching the doped layer in the non-metallic region, the preparation method includes:

1L to 30L of alkaline solution and 0L to 20L of alkaline polishing additive are added to the first etching tank, the temperature of the first etching tank is 50° C. to 90° C., and the concentration of the alkaline solution is 0.2% to 6%;

The substrate is placed in the first etching tank, and the etching time is 10s to 400s.

In a possible embodiment, during the secondary texturing, the preparation method includes:

0.5L to 20L of alkaline solution and 0.5L to 10L of texturing additive are added into the second etching tank, and the temperature of the second etching tank is 60°C to 90°C.

The substrate is placed in the second etching tank, and the etching time is 50s to 500s.

The present application also provides a solar cell, which is prepared by any of the above-mentioned solar preparation methods, and includes:

A substrate, wherein the substrate comprises a first surface and a second surface, the first surface comprises a metal region and a non-metal region, the metal region is provided with a first velvet structure, the non-metal region is provided with a second velvet structure, and the reflectivity of the second velvet structure is less than that of the first velvet structure; a doping layer is provided in the metal region; and a passivation film layer and an anti-reflection film layer are provided on both the first velvet structure and the second velvet structure;

Electrode: The electrode is arranged in the metal area.

In a possible embodiment, the second velvet structure includes a plurality of first pyramid structures protruding from the substrate, in a cross section along the thickness direction of the solar cell, an angle _α1 at the top of the first pyramid structure is less than 90°, a height of the first pyramid structure is 0.5 μm to 5 μm, and a reflectivity of the second velvet structure is 2% to 15%.

In a possible embodiment, the second velvet structure includes a plurality of second pyramid structures protruding from the substrate, and in a cross section along the thickness direction of the solar cell, an angle _α2 at the top of the second pyramid structure is greater than or equal to 90°, a height of the second pyramid structure is 0.5 μm to 5 μm, and a reflectivity of the second velvet structure is 10% to 30%.

In a possible embodiment, the second velvet structure includes a plurality of third pyramid structures protruding from the substrate, the height of the third pyramid structures is 0.5 μm to 5 μm, the sidewalls of the third pyramid structures include a plurality of grooves, and the reflectivity of the second velvet structure is 2% to 20%.

In a possible embodiment, the second velvet structure includes a plurality of fourth pyramid structures recessed in the substrate, the recessed depth of the fourth pyramid structures is 0.5 μm to 5 μm, and the reflectivity of the second velvet structure is 2% to 20%.

The present application also provides a photovoltaic module, the photovoltaic module comprising:

A battery string, the battery string comprises a plurality of electrically connected solar cells, the solar cells being any of the solar cells described above; a film layer and a packaging layer are sequentially arranged on both sides of the battery string.

The present application relates to a method for preparing a solar cell, a solar cell and a photovoltaic module, comprising a substrate, wherein the substrate comprises a first surface and a second surface. The first surface comprises a metal region and a non-metal region, and an electrode is arranged in the metal region. A first velvet structure is arranged in the metal region, and a second velvet structure is arranged in the non-metal region. The reflectivity of the second velvet structure is less than that of the first velvet structure. Therefore, the first velvet structure in the metal region is relatively flat, and the second velvet structure in the non-metal region has a large fluctuation amplitude. A doping layer is arranged in the metal region to prepare an emitter. The relatively flat first velvet structure makes the uniformity of the doping layer higher, which can improve the photoelectric conversion efficiency and stability of the metal region. The second velvet structure with a large fluctuation amplitude improves the absorption capacity of the non-metal region to sunlight. . A passivation film layer and an anti-reflection film layer are arranged on both the first velvet structure and the second velvet structure to improve the efficiency and performance of the battery.

It should be understood that the foregoing general description and the following detailed description are exemplary only and are not restrictive of the present application.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of the structure of a solar cell provided in an embodiment of the present application;

FIG2 is a schematic structural diagram of an embodiment of a substrate structure provided in an embodiment of the present application;

FIG3 is a partial scanning electron microscope image of an embodiment of the second velvet surface provided in the embodiment of the present application;

FIG4 is a schematic structural diagram of another embodiment of a substrate structure provided in an embodiment of the present application;

FIG5 is a partial scanning electron microscope image of another embodiment of the second velvet surface provided in the embodiment of the present application;

FIG6 is a schematic structural diagram of another embodiment of a substrate structure provided in an embodiment of the present application;

FIG7 is a partial SEM image of another embodiment of the second velvet surface provided in the embodiment of the present application;

FIG8 is a scanning electron microscope image of a cross section of a third pyramid structure provided in an embodiment of the present application;

FIG9 is a schematic structural diagram of another embodiment of a substrate structure provided in an embodiment of the present application;

FIG10 is a partial SEM image of another embodiment of the second velvet surface provided in the embodiment of the present application;

11 to 15 are schematic diagrams of states of various stages from S1 to S5 in the method for preparing a solar cell provided in an embodiment of the present application.

Reference numerals:

1- substrate;

11-Metal area;

12- non-metallic area;

2- first suede structure;

3- second suede structure;

31-First pyramid structure;

32-Second pyramid structure;

33- The third pyramid structure;

34- Fourth pyramid structure;

4-passivation film layer;

5-anti-reflection film layer;

6- doping layer;

7-Electrode;

8-doped oxide layer;

9-Oxide layer.

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

DETAILED DESCRIPTION

In order to better understand the technical solution of the present application, the embodiments of the present application are described in detail below with reference to the accompanying drawings.

It should be clear that the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a", "said" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

It should be understood that the term "and/or" used in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and/or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character "/" in this article generally indicates that the associated objects before and after are in an "or" relationship.

It should be noted that the directional words such as "upper", "lower", "left", and "right" described in the embodiments of the present application are described at the angles shown in the accompanying drawings and should not be understood as limiting the embodiments of the present application. In addition, in the context, it is also necessary to understand that when it is mentioned that an element is connected to another element "upper" or "lower", it can not only be directly connected to another element "upper" or "lower", but also indirectly connected to another element "upper" or "lower" through an intermediate element.

As shown in FIG1 , an embodiment of the present application provides a solar cell, including a substrate 1, the substrate 1 including a first surface and a second surface, the first surface and the second surface are two surfaces opposite to each other in the thickness direction of the substrate 1. The first surface includes a metal region 11 and a non-metal region 12, the electrode 7 is arranged on the metal region 11, the metal region 11 has a metal contact area, has good conductivity, is responsible for collecting and transmitting photocurrent, and is one of the main channels of current in the solar cell, the width of the non-metal region 12 is greater than the width of the electrode 7, so as to improve the performance and stability of the battery; the non-metal region 12 is a part that does not include the metal contact area, and the non-metal region 12 may have specific functions through specific structural settings, such as surface chemical passivation, reducing the probability of carrier recombination, and blocking the diffusion of phosphorus in the doped silicon film layer into the silicon substrate 1. This distinction enables the solar cell to convert solar energy into electrical energy more efficiently while protecting the battery from damage. The metal region 11 is responsible for efficient current transmission, while the non-metal region 12 enhances the performance and stability of the battery through its specific physical and chemical properties.

The metal region 11 is provided with a first velvet structure 2, and the non-metal region 12 is provided with a second velvet structure 3, and the reflectivity of the second velvet structure 3 is lower than the reflectivity of the first velvet structure 2. The metal region 11 is provided with a doping layer 6, and the first velvet structure 2 and the second velvet structure 3 are both provided with a passivation film layer 4 and an anti-reflection film layer 5.

The first velvet structure 2 is located in the metal region 11, and the metal electrode 7 is arranged on the first velvet structure 2. A doping layer 6 is arranged in the first velvet structure 2, which can form a PN junction in the metal region 11 to prepare an emitter, thereby reducing the contact resistance of the metal region 11, thereby improving the output voltage and current of the solar cell. The design of the first velvet structure 2 is relatively gentle, which improves the uniformity of the doping layer 6. The fluctuation amplitude of the design of the second velvet structure 3 is relatively large, so that the reflectivity of the second velvet structure 3 is less than the reflectivity of the first velvet structure 2, thereby improving the solar cell's ability to absorb sunlight. A passivation film layer 4 is arranged on the first velvet structure 2 and the second velvet structure 3 to reduce the recombination rate and increase the minority carrier lifetime. An anti-reflection film layer 5 is arranged on the passivation film layer 4, and the anti-reflection film layer 5 can reduce the reflectivity of the solar cell surface and increase the absorption of light, thereby improving the photoelectric conversion efficiency.

The present application does not limit the structure of the battery cell. The types of battery cells include but are not limited to Passivated Emitter Rear Cell (PERC), Tunnel Oxide Passivated Contact (TOPCon), Intrinsic Thin-film Heterojunction (HJT), Interdigitated Back Contact (IBC), etc.

For PERC cells, the substrate 1 is a P-type silicon substrate 1, and the first surface of the substrate 1 is sequentially provided with a phosphorus layer emitter, a silicon nitride passivation film layer 4, an anti-reflection film layer 5, and a metal silver electrode 7, and the second surface of the substrate 1 is sequentially provided with a local aluminum back field, a metal aluminum back electrode 7, and a back passivation layer (Al2O3/SiNx). The structure of the first surface in the present application can be applied to PERC cells, and the first surface of the P-type silicon substrate 1 includes a metal region 11 and a non-metal region 12, the metal region 11 is provided with a first velvet surface, and the non-metal region 12 is provided with a second velvet surface, and the reflectivity of the second velvet surface is less than the reflectivity of the first velvet surface, the phosphorus layer emitter is provided on the first velvet surface, the silicon nitride passivation film layer 4 and the anti-reflection film layer 5 cover the first surface, and the metal silver electrode 7 is provided on the metal region 11.

For TOPCon cells, substrate 1 is an N-type silicon substrate 1, and the first surface of substrate 1 is provided with a boron-doped emitter, a silicon nitride passivation layer, and a metal silver electrode 7 in sequence, and the second surface of substrate 1 is provided with a diffuse doping layer 6, ultra-thin silicon oxide, doped polysilicon, silicon nitride, and a metal silver electrode 7 in sequence. The second surface of the battery is composed of a layer of ultra-thin silicon oxide (1nm-2nm) and a layer of phosphorus-doped microcrystalline amorphous mixed Si film, which together form a passivation contact structure. This structure can block the recombination of minority carriers and holes, and improve the open circuit voltage and short circuit current of the battery. The ultra-thin oxide layer 9 can allow majority electrons to tunnel into the polysilicon layer while blocking the recombination of minority carriers and holes. The good passivation effect of ultra-thin silicon oxide and heavily doped silicon film causes the energy band on the surface of the silicon wafer to bend, thereby forming a field passivation effect, greatly increasing the probability of electron tunneling, reducing the contact resistance, and improving the open circuit voltage and short circuit current of the battery, thereby improving the battery conversion efficiency. The structure of the first surface in the present application can be applied to TOPCon batteries. The first surface of the N-type silicon substrate 1 includes a metal area 11 and a non-metal area 12. The metal area 11 is provided with a first velvet surface, and the non-metal area 12 is provided with a second velvet surface. The reflectivity of the second velvet surface is less than the reflectivity of the first velvet surface. The boron-doped emitter is provided on the first velvet surface. The silicon nitride passivation film layer 4 and the anti-reflection film layer 5 cover the first surface. The metal silver electrode 7 is provided on the metal area 11.

For HJT cells, the substrate 1 is an N-type silicon substrate 1, and the first surface of the substrate 1 is sequentially provided with an intrinsic amorphous silicon film, an N-type amorphous silicon film, a conductive film, and a low-temperature silver electrode 7, and the second surface of the substrate 1 is sequentially provided with an intrinsic amorphous silicon film, a P-type amorphous silicon film, a conductive film, and a low-temperature silver electrode 7. The structure of the first surface in the present application can be applied to HJT cells, the first surface of the N-type silicon substrate 1 includes a metal region 11 and a non-metal region 12, the metal region 11 is provided with a first velvet surface, the non-metal region 12 is provided with a second velvet surface, and the reflectivity of the second velvet surface is less than the reflectivity of the first velvet surface, the intrinsic amorphous silicon film, the N-type amorphous silicon film, and the conductive film are provided on the first velvet surface, and the low-temperature silver electrode 7 is provided on the metal region 11.

For IBC cells, the substrate 1 is an N-type silicon substrate 1, and the first surface of the substrate 1 is provided with an N+ front surface field and a silicon nitride anti-reflection layer in sequence, and the second surface is provided with a P+ emitter, an N+ back field, an aluminum oxide passivation layer, a silicon nitride anti-reflection layer, and a metal silver electrode 7 in sequence. The first surface of the substrate 1 is a velvet structure. In order to reduce the reflectivity of the IBC cell, the velvet structure of the first surface can adopt the above-mentioned second velvet structure 3. The IBC cell uses ion implantation technology to obtain P and N regions with good uniformity and precisely controllable junction depth. There is no grid line blocking on the front of the cell, which can eliminate the shading current loss of the metal electrode 7 and realize the maximum utilization of the incident photons. Compared with conventional solar cells, the short-circuit current can be increased by about 7%; due to the back contact structure, there is no need to consider the grid line blocking problem, and the grid line ratio can be appropriately widened, thereby reducing the series resistance and having a high fill factor; the surface passivation and surface light trapping structure can be optimized to obtain a lower front surface recombination rate and surface reflection.

As shown in Fig. 2 and Fig. 3, in a possible embodiment, the second velvet structure 3 includes a plurality of first pyramid structures 31 protruding from the substrate 1. The first pyramid structure 31 is a structure similar to a quadrangular pyramid, and its height is 0.5 μm to 5 μm. The angle of the top of the first pyramid structure 31 is α ₁ , and α ₁ is less than 90°, so that the reflectivity of the second velvet structure 3 is 2% to 15%. The top angle of the first pyramid structure 31 refers to the angle formed by the relative inclined surfaces of the first pyramid structure 31 in the cross section after the vertex of the first pyramid structure 31 and a pair of ridges sandwiching the vertex are vertically cut by a plane parallel to the thickness direction of the solar cell.

The height of the first pyramid structure 31 can be 0.5 μm, 2 μm, 3.5 μm, 5 μm, etc., which increases the number of light reflections between the multiple first pyramid structures 31 and reduces the reflectivity of the second velvet structure 3. If the height of the first pyramid structure 31 is less than 0.5 μm, the fluctuation amplitude of the second velvet structure 3 is small, which will reduce the number of light reflections between the multiple first pyramid structures 31, resulting in an increase in the reflectivity of the second velvet structure 3 and a reduction in the photoelectric conversion efficiency of the solar cell; if the height of the first pyramid structure 31 is greater than 5 μm, part of the light will not be reflected twice, which will increase the reflectivity of the second velvet structure 3 and increase the stress inside the solar cell, thereby affecting the service life and stability of the solar cell. The angle of the top of the first pyramid structure 31 is less than 90°, which increases the slope of the side wall of the first pyramid structure 31, reduces the spacing between adjacent first pyramid structures 31, and enables light to be reflected and absorbed multiple times between adjacent first pyramid structures 31, which is conducive to reducing the reflectivity of the second velvet structure 3. The reflectivity of the second velvet structure 3 is 2% to 15%, which improves the absorption efficiency of the solar cell to light, thereby improving the photoelectric conversion efficiency of the solar cell.

As shown in Fig. 4 and Fig. 5, in a possible embodiment, the second velvet structure 3 includes a plurality of second pyramid structures 32 protruding from the substrate 1. The second pyramid structure 32 is a structure similar to a quadrangular pyramid, and its height is 0.5 μm to 5 μm. In the cross section along the thickness direction of the solar cell, the angle of the top of the second pyramid structure 32 is α ₂ , and α ₂ is greater than or equal to 90°, so that the reflectivity of the second velvet structure 3 is 10% to 30%. The top angle of the second pyramid structure 32 refers to the angle formed by the relative inclined surfaces of the second pyramid structure 32 in the cross section after the vertex of the second pyramid structure 32 and a pair of ridges sandwiching the vertex are vertically cut by a plane parallel to the thickness direction of the solar cell.

The height of the second pyramid structure 32 can be 0.5 μm, 2 μm, 3.5 μm, 5 μm, etc., which increases the number of reflections of light between the multiple second pyramid structures 32 and reduces the reflectivity of the second velvet structure 3. If the height of the second pyramid structure 32 is less than 0.5 μm, the fluctuation amplitude of the second velvet structure 3 is small, which will reduce the number of reflections of light between the multiple second pyramid structures 32, resulting in an increase in the reflectivity of the second velvet structure 3 and a reduction in the photoelectric conversion efficiency of the solar cell; if the height of the second pyramid structure 32 is greater than 5 μm, it will cause part of the light to fail to be reflected twice, which will increase the reflectivity of the second velvet structure 3 and increase the stress inside the solar cell, thereby affecting the service life and stability of the solar cell. The angle of the top of the second pyramid structure 32 is greater than or equal to 90°, so that the second velvet structure 3 is relatively gentle, which is convenient for setting a passivation layer and an anti-reflection layer on the second velvet structure 3. The reflectivity of the second velvet structure 3 is 10% to 30%, so that the solar cell has a higher photoelectric conversion efficiency.

As shown in Figures 6, 7 and 8, in a possible embodiment, the second velvet structure 3 includes a plurality of third pyramid structures 33 protruding from the substrate 1, the third pyramid structure 33 is similar to a quadrangular pyramid structure, and its height is 0.5μm to 5μm, and the side wall of the third pyramid structure 33 includes a plurality of grooves, so that the reflectivity of the second velvet structure 3 is 2% to 20%.

The height of the third pyramid structure 33 can be 0.5μm, 2μm, 3.5μm, 5μm, etc., which increases the number of reflections of light between multiple third pyramid structures 33 and reduces the reflectivity of the second velvet structure 3. If the height of the third pyramid structure 33 is less than 0.5μm, the fluctuation amplitude of the second velvet structure 3 is small, which will reduce the number of reflections of light between multiple third pyramid structures 33, resulting in an increase in the reflectivity of the second velvet structure 3 and a reduction in the photoelectric conversion efficiency of the solar cell; if the height of the third pyramid structure 33 is greater than 5μm, part of the light will fail to be reflected for the second time, which will increase the reflectivity of the second velvet structure 3 and increase the stress inside the solar cell, thereby affecting the service life and stability of the solar cell. The sidewall of the third pyramid structure 33 includes a plurality of grooves, the depth of the grooves may be 0.2 μm to 2.5 μm, so that light can be reflected and absorbed in the grooves to reduce the reflectivity of the second velvet structure 3, the velvet rate on the surface of the third pyramid structure 33 may be 15 w/mm ² to 35 w/mm ² , and the specific surface area of the grooves on the surface of the third pyramid structure 33 may be 1.5-3, so that the reflectivity of the second velvet structure 3 is 2% to 20%, thereby improving the light absorption efficiency of the solar cell, thereby improving the photoelectric conversion efficiency of the solar cell.

As shown in Figures 9 and 10, in a possible embodiment, the second velvet structure 3 includes a plurality of fourth pyramid structures 34, and the fourth pyramid structure 34 is similar to an inverted quadrangular pyramid structure, which is recessed into the substrate 1, and the recess depth is 0.5μm to 5μm, so that the reflectivity of the second velvet structure 3 is 2% to 20%.

The fourth pyramid structure 34 is an inverted quadrangular pyramid structure, which can make the light reflect multiple times in the fourth pyramid structure 34, increase the light path, make the reflectivity of the second velvet structure 3 2% to 20%, reduce the reflectivity of the second velvet structure 3 to sunlight, make more light absorbed by the solar cell, and thus improve the photoelectric conversion efficiency of the solar cell.

The embodiment of the present application also provides a method for preparing a solar cell, which is used to prepare the above-mentioned solar cell.

S1, performing texturing and doping element diffusion on the first surface and the second surface of the substrate 1, so that the first surface and the second surface both form a first texturing structure 2, a doping layer 6 and a doped oxide layer 8;

S2, removing the doped oxide layer 8 in the non-metallic region 12 in the first surface;

S3, etching the doping layer 6 of the non-metallic region 12, the etching depth is 0.5 μm to 10 μm, and the first textured structure 2 of the non-metallic region 12 is etched;

S4, secondary texturing, forming a second texturing structure 3 in the non-metallic area 12;

S5 , preparing an oxide layer 9 on the second textured structure 3 .

As shown in FIG11 , through the texturing process, the first velvet structure 2 can be formed on the first surface and the second surface. Then, through the doping process, the first velvet structure 2 is doped with heterogeneous elements, and a PN junction is generated in the first velvet structure 2, so that the solar cell can generate electrical energy. While doping heterogeneous elements, a doped oxide layer 8 is formed on the surface as a protective layer for the doped layer 6. As shown in FIG12 , the doped oxide layer 8 in the non-metallic area 12 of the first surface is removed, and the protective layer doped on the surface is removed, which facilitates the etching of the doped layer 6 in the non-metallic area 12, while the doped layer 6 in the metal area 11 will not be damaged. As shown in FIG13 , the doped layer 6 in the non-metallic area 12 is etched, and the etching depth is 0.5 μm to 10 μm, so that the doped layer 6 in the non-metallic area 12 is completely etched. Since the doped layer 6 is arranged in the first velvet structure 2, the first velvet structure 2 in the non-metallic area 12 is also etched. As shown in FIG14, secondary texturing is performed on the etched non-metallic region 12 to form a second velvet structure 3 in the non-metallic region 12. By adjusting the texturing procedure, the reflectivity of the second velvet structure 3 can be made lower than the reflectivity of the first velvet structure 2, so as to improve the photoelectric conversion efficiency of the solar cell. As shown in FIG15, after the secondary texturing, the solar cell after the secondary texturing can be placed in an oxidation furnace for heating by a tubular or chain oxidation method to form an oxide layer 9 on the second velvet structure 3. The thickness of the oxide layer 9 is 5nm to 100nm, so as to reduce the possibility of the second velvet structure 3 being damaged in the subsequent alkali polishing process.

In a possible embodiment, when removing the doped oxide layer 8 in the non-metallic region 12 in the first surface, the preparation method includes:

S21. Scan the non-metallic area 12 in the first surface using a laser, wherein the power of the laser is 1 W to 50 W and the scanning speed is 5 m/s to 40 m/s.

The laser can be an infrared laser, a green laser, an ultraviolet laser, etc., which scans the non-metallic area 12 to remove the doped oxide layer 8 of the non-metallic area 12, so that the doped layer 6 of the non-metallic area 12 is exposed, and the doped oxide layer 8 of the metal area 11 will not be affected, which is convenient for subsequent etching processing. The laser power can be 1W, 25W, 50W, etc., so that the scanning speed of the laser is 5m/s to 40m/s, which can improve the efficiency of removing the doped oxide layer 8 of the non-metallic area 12. If the laser power is less than 1W, it is necessary to reduce the laser scanning speed to remove the doped oxide layer 8 of the non-metallic area 12, which reduces the production efficiency of the solar cell; if the laser power is greater than 50W, it may affect the substrate 1 and cause damage to the substrate 1.

In a possible embodiment, when etching the doping layer 6 of the non-metallic region 12, the preparation method includes:

S31, adding 1L to 30L of alkaline solution and 0L to 20L of alkaline polishing solution into the first etching tank, the temperature of the first etching tank is 50° C. to 90° C., and the concentration of the alkaline solution is 0.2% to 6%;

S32, placing the substrate 1 into the first etching tank, and the etching time is 10s to 400s.

The alkaline solution can be a 0.2% to 6% potassium hydroxide solution or a 0.2% to 6% sodium hydroxide solution. Placing the alkaline solution in the first etching tank can etch away the exposed doping layer 6 in the non-metallic region 12, while the doping layer 6 protected by the doped oxide layer 8 in the metal region 11 will not be affected, and the temperature of the first etching tank is maintained at 50° C. to 90° C. to ensure the reaction rate and etching effect of the etching process. Before placing the substrate 1 in the first etching tank, 0L to 20L of alkaline polishing solution can be added to the alkaline solution. The alkaline polishing solution can be an organic additive. The doping layer 6 in the non-metallic region 12 can be etched away without adding the alkaline polishing solution to the alkaline solution. Adding the alkaline polishing solution to the alkaline solution can improve the alkaline polishing effect on the non-metallic region 12. The depth of the doping layer 6 in the non-metallic region 12 is about 1 μm. After the substrate 1 is etched in the first etching groove for 10s to 400s, the etching depth is 0.5 μm to 10 μm, so as to etch away the doping layer 6 in the non-metallic region 12 . After etching, a tower base structure is formed on the first surface of the substrate 1. The tower base structure is a structure similar to a cube. The size of the tower base structure surface is 3μm to 30μm, and its reflectivity is 30% to 45%. During the secondary texturing, a second velvet structure 3 will be etched on the basis of the tower base to reduce the reflectivity of the non-metallic area 12. If the size of the tower base is less than 3μm, the size of the second velvet structure 3 will be smaller, which is not conducive to the absorption of light, resulting in a higher reflectivity, thereby reducing the conversion efficiency of the battery cell; if the size of the tower base is greater than 30μm, the size of the second velvet structure 3 will be larger, the height of the pyramid structure will be higher, and the angle of the top of the pyramid structure will be smaller. The selective emitter laser re-doping will easily cause the tower tip to ablate, and the protective effect on the front side will be weakened during alkali polishing, which will easily damage the p-n junction of the re-doped area, resulting in an increase in leakage current.

In a possible embodiment, during the secondary texturing, when the second textured structure 3 is formed in the non-metallic area 12, the preparation method includes:

S41, adding 0.5L to 20L of alkaline solution and 0.5L to 10L of texturing additive into the second etching tank, and the temperature of the second etching tank is 60°C to 90°C.

S42, placing the substrate 1 into a second etching tank, and the etching time is 50s to 500s.

The alkaline solution may be a potassium hydroxide solution or a sodium hydroxide solution. The texturing additive may include a surfactant, a defoaming agent, sodium acetate, potassium sorbate, deionized water, etc., which are used to assist the alkaline solution etching to form a second velvet structure 3 with a pyramid structure of uniform size in the non-metallic region 12. 0.5L to 20L of the alkaline solution and 0.5L to 10L of the texturing additive are placed in the second etching tank, and the temperature of the second etching tank is maintained between 60° C. and 90° C. to ensure the reaction rate and etching effect of the etching process. The solar cell with the doped layer 6 etched off from the non-metallic region 12 is taken out from the first etching tank and placed in the second etching tank for etching for 50s to 500s. A pyramid structure is etched on the basis of the tower base formed in the previous step to form a second velvet structure 3 to reduce the reflectivity of the non-metallic region 12. If the etching time is less than 50s, the non-metallic region 12 cannot be covered by the pyramid structure to form a velvet structure. If the etching time is greater than 500s, the top of the pyramid structure will collapse, resulting in an increase in the reflectivity of the second velvet structure 3.

By adjusting the composition and ratio of the texturing additive, a first pyramid structure 31 , a second pyramid structure 32 , a third pyramid structure 33 and a fourth pyramid structure 34 are etched in the non-metallic region 12 to meet the different reflectivity requirements of different solar cells for the non-metallic region 12 .

The process after step S5 can refer to the conventional production process of solar cells after doping, taking TOPCon cells as an example:

S6, etching process: remove the doped oxide layer 8 on the first surface and the prepared oxide layer 9 on the second textured structure 3, as well as the doped oxide layer 8, doped layer 6 and textured structure on the second surface by alkaline polishing process.

S7, preparing a tunneling oxide layer 9 and a polysilicon layer: depositing a tunneling oxide layer 9 on the second surface, and then depositing a polysilicon layer on the tunneling oxide layer 9 to form a passivation structure.

S8. Preparing an anti-reflection film layer 5 on the second surface: Preparing an anti-reflection film layer 5 on the second surface increases light absorption. Meanwhile, hydrogen atoms generated during the formation of the anti-reflection film layer 5 have a passivation effect on the silicon wafer.

S9, screen printing-laser transfer: preparing electrodes on the first surface and the second surface by screen printing 7

S10, sintering: forming a good ohmic contact through high temperature sintering.

The embodiment of the present application also provides a photovoltaic module, including a battery string, with a film layer and a packaging layer provided on both sides of the battery string, and a photovoltaic module is formed after lamination. The battery string includes a plurality of solar cells, and the solar cells are any of the solar cells described above, so the technical effects of the above solar cells are obtained.

The present application relates to a method for preparing a solar cell, a solar cell and a photovoltaic module, comprising a substrate 1, wherein the substrate 1 comprises a first surface and a second surface. The first surface comprises a metal region 11 and a non-metal region 12, and an electrode 7 is arranged in the metal region 11. The metal region 11 is provided with a first velvet structure 2, and the non-metal region 12 is provided with a second velvet structure 3. The reflectivity of the second velvet structure 3 is less than the reflectivity of the first velvet structure 2. Therefore, the first velvet structure 2 in the metal region 11 is relatively flat, and the second velvet structure 3 in the non-metal region 12 has a large fluctuation amplitude. A doping layer 6 is arranged in the metal region 11 to prepare an emitter. The relatively flat first velvet structure 2 makes the uniformity of the doping layer higher, which can improve the photoelectric conversion efficiency and stability of the metal region 11. The second velvet structure 3 with a large fluctuation amplitude improves the absorption capacity of the non-metal region 12 to sunlight. A passivation film layer 4 and an anti-reflection film layer 5 are arranged on both the first velvet structure 2 and the second velvet structure 3 to improve the efficiency and performance of the battery.

The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims (10)

1. A method for preparing a solar cell, the solar cell comprising a substrate (1), the substrate comprising a first surface and a second surface, the first surface comprising a metal region (11) and a non-metal region (12), wherein the preparation method comprises: The first surface and the second surface of the substrate (1) are subjected to texturing and doping element diffusion, so that the first surface and the second surface both form a first texturing structure (2), a doping layer (6) and a doped oxide layer (8); removing the doped oxide layer (8) in the non-metallic region (12) in the first surface; Etching the doped layer (6) of the non-metallic region (12) to a depth of 0.5 μm to 10 μm, so that the first velvet structure (2) of the non-metallic region (12) is etched; Secondary texturing to form a second textured surface structure (3) in the non-metallic region (12); An oxide layer (9) is prepared on the second textured structure (3). 2. The method for preparing a solar cell according to claim 1, characterized in that when removing the doped oxide layer (8) of the non-metallic area (12) in the first surface, the method comprises: The non-metallic area (12) in the first surface is scanned by laser, the power of the laser is 1W to 50W, and the scanning speed of the laser is 5m/s to 40m/s. 3. The method for preparing a solar cell according to claim 1, characterized in that when etching the doped layer (6) of the non-metallic region (12), the method comprises: 1L to 30L of alkaline solution and 0L to 20L of alkaline polishing additive are added into the first etching tank, the temperature of the first etching tank is 50° C. to 90° C., and the concentration of the alkaline solution is 0.2% to 6%; The substrate (1) is placed in a first etching tank, and the etching time is 10s to 400s. 4. The method for preparing a solar cell according to claim 1, characterized in that during the secondary texturing, the method comprises: 0.5L to 20L of alkaline solution and 0.5L to 10L of texturing additive are added into the second etching tank, and the temperature of the second etching tank is 60°C to 90°C. The substrate (1) is placed in a second etching tank, and the etching time is 50s to 500s. 5. A solar cell, wherein the solar cell is prepared by the method for preparing a solar cell according to any one of claims 1 to 4, wherein the solar cell comprises: A substrate (1), the substrate (1) comprising a first surface and a second surface, the first surface comprising a metal region (11) and a non-metal region (12), the metal region (11) being provided with a first velvet structure (2), the non-metal region (12) being provided with a second velvet structure (3), the reflectivity of the second velvet structure (3) being lower than the reflectivity of the first velvet structure (2); the metal region (11) being provided with a doping layer (6); and a passivation film layer (4) and an anti-reflection film layer (5) being provided on both the first velvet structure (2) and the second velvet structure (3); An electrode (7), wherein the electrode (7) is arranged in the metal area (11). 6. The solar cell according to claim 5 is characterized in that the second velvet structure (3) comprises a plurality of first pyramid structures (31) protruding from the substrate (1); in a cross section along the thickness direction of the solar cell, an angle _α1 at the top of the first pyramid structure (31) is less than 90°, a height of the first pyramid structure (31) is 0.5 μm to 5 μm, and a reflectivity of the second velvet structure (3) is 2% to 15%. 7. The solar cell according to claim 5 is characterized in that the second velvet structure (3) includes a plurality of second pyramid structures (32) protruding from the substrate (1); in a cross section along the thickness direction of the solar cell, an angle _α2 at the top of the second pyramid structure (32) is greater than or equal to 90°, a height of the second pyramid structure (32) is 0.5 μm to 5 μm, and a reflectivity of the second velvet structure (3) is 10% to 30%. 8. The solar cell according to claim 5 is characterized in that the second velvet structure (3) comprises a plurality of third pyramid structures (33) protruding from the substrate (1), the height of the third pyramid structures (33) is 0.5 μm to 5 μm, the sidewalls of the third pyramid structures (33) comprise a plurality of grooves, and the reflectivity of the second velvet structure (3) is 2% to 20%. 9. The solar cell according to claim 5, characterized in that the second velvet structure (3) comprises a plurality of fourth pyramid structures (34) recessed in the substrate (1), the recessed depth of the fourth pyramid structures (34) is 0.5 μm to 5 μm, and the reflectivity of the second velvet structure (3) is 2% to 20%. 10. A photovoltaic assembly, characterized in that the photovoltaic assembly comprises: A battery string, the battery string comprising a plurality of electrically connected solar cells, the solar cell being a solar cell prepared by the preparation method described in any one of claims 1 to 4, or a solar cell described in any one of claims 5 to 9; a film layer and an encapsulation layer are sequentially provided on both sides of the battery string.