Solar cell and preparation method thereof

Abstract

The invention relates to the field of photovoltaic technology, and provides a solar cell and a preparation method thereof. The preparation method of the solar cell comprises the steps of providing a substrate; sequentially forming a tunneling layer and a polycrystalline silicon layer on the substrate; performing a first doping process on the polycrystalline silicon layer on the second region to convert the polycrystalline silicon layer on the second region into a first polycrystalline silicon part containing oxygen atoms and a second polycrystalline silicon part not containing oxygen atoms; a second doping process is carried out on the polycrystalline silicon layer, the first polycrystalline silicon part and the second polycrystalline silicon part on the second surface, so that the polycrystalline silicon layer on the first region is converted into a first doped polycrystalline silicon layer containing doping elements, the second polycrystalline silicon part is converted into a second doped polycrystalline silicon layer containing doping elements, and the second doping process comprises heat treatment; performing heat treatment to convert the first polycrystalline silicon part containing the oxygen atoms into a silicon oxide layer; and removing the silicon oxide layer. The preparation efficiency and reliability of the solar cell and the performance of the solar cell can be improved at least.

Description

Technical Field

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

[0002] As fossil energy is gradually depleted, solar energy is becoming more and more widely used as a new energy alternative. Solar cells are devices that convert sunlight into electrical energy. Solar cells use the photovoltaic principle to generate carriers, and then use electrodes to lead the carriers out, which is conducive to the effective use of electrical energy.

[0003] Current solar cells mainly include IBC cells (Interdigitated Back Contact), TOPCON (Tunnel Oxide Passivated Contact), PERC cells (Passivated Emitter and Real Cell) and heterojunction cells.

[0004] However, current methods for making solar cells suffer from low reliability and efficiency. Summary of the invention

[0005] The embodiments of the present disclosure provide a solar cell and a method for manufacturing the same, which can at least improve the manufacturing efficiency and reliability of the solar cell and the performance of the solar cell.

[0006] According to some embodiments of the present disclosure, on the one hand, an embodiment of the present disclosure provides a method for preparing a solar cell, comprising: providing a substrate, the substrate comprising a first surface and a second surface relative to each other, the second surface comprising a first area and a second area arranged alternately; forming a tunneling layer and a polysilicon layer in sequence on the second surface; performing a first doping process on the polysilicon layer on the second area to transform the polysilicon layer on the second area into a first polysilicon portion containing oxygen atoms and a second polysilicon portion not containing oxygen atoms, the second polysilicon portion being located between the first polysilicon portion and the tunneling layer; performing a second doping process on the polysilicon layer, the first polysilicon portion and the second polysilicon portion on the second surface to transform the polysilicon layer on the first area into a first doped polysilicon layer containing doping elements, and transform the second polysilicon portion into a second doped polysilicon layer containing the doping elements, the second doping process comprising a heat treatment, the heat treatment transforming the first polysilicon portion containing the oxygen atoms into a silicon oxide layer; and removing the silicon oxide layer.

[0007] In some embodiments, the temperature of the heat treatment is 800° C. to 950° C., and the duration of the heat treatment is 15 min to 25 min.

[0008] In some embodiments, the first doping process is an ion implantation method, the energy of the ion implantation method is 10KeV~50KeV, the duration of the ion implantation method is 30s~90s, the ion source of the ion implantation method is an oxygen-containing gas, and the implantation dose of the ion source is 5×10 14 atoms / cm 2 ~5×10 15 atoms / cm 2 .

[0009] In some embodiments, the doping concentration of the doping element in the first doped polysilicon layer is a first doping concentration, the doping concentration of the doping element in the second doped polysilicon layer is a second doping concentration, and the ratio of the first doping concentration to the second doping concentration is 4-80.

[0010] In some embodiments, the first doping concentration is 2×10 19 atoms / cm 2 ~4×10 20 atoms / cm 2 The second doping concentration is 5×10 18 atoms / cm 2 ~5×10 19 atoms / cm 2 .

[0011] In some embodiments, performing the first doping process on the polysilicon layer on the second region includes: placing a mask plate on the second surface, the mask plate having a plurality of hollow portions passing through the mask plate, the hollow portions corresponding one-to-one to the second region on the substrate; performing the first doping process on the polysilicon layer on the second region through the hollow portions; and removing the mask plate.

[0012] In some embodiments, a ratio of a thickness of the second doped polysilicon layer to a thickness of the first doped polysilicon layer is 0.43-0.92.

[0013] In some embodiments, the thickness of the second doped polysilicon layer is 10 nm to 90 nm, and the thickness of the first doped polysilicon layer is 120 nm to 160 nm.

[0014] In some embodiments, removing the silicon oxide layer includes: using a hydrofluoric acid solution with a concentration of 0.5% to 5% for treatment, the treatment time is 30s to 120s, and the treatment temperature is 20°C to 25°C.

[0015] According to some embodiments of the present disclosure, on the other hand, the embodiments of the present disclosure further provide a solar cell, comprising: a substrate, the substrate comprising a first surface and a second surface relative to each other, the second surface comprising a first region and a second region arranged alternately; a tunneling layer, the tunneling layer being located on the second surface; a first doped polysilicon layer, the first doped polysilicon layer being located on the first region, and the first doped polysilicon layer being located on a surface of the tunneling layer away from the second surface; a second doped polysilicon layer, the second doped polysilicon layer being located on the second region, and the second doped polysilicon layer being located on a surface of the tunneling layer away from the second surface; wherein both the first doped polysilicon layer and the second doped polysilicon layer contain doping elements, the doping concentration of the doping elements in the second doped polysilicon layer is less than the doping concentration of the doping elements in the first doped polysilicon layer, and the thickness of the second doped polysilicon layer is less than the thickness of the first doped polysilicon layer.

[0016] The technical solution provided by the embodiments of the present disclosure has at least the following advantages: In the technical solution of the method for preparing a solar cell provided in the embodiment of the present disclosure, the method for preparing a solar cell includes providing a substrate, the substrate includes a first surface and a second surface opposite to each other, the second surface includes a first area and a second area arranged alternately; forming a tunneling layer and a polysilicon layer in sequence on the second surface; performing a first doping process on the polysilicon layer on the second area to convert the polysilicon layer on the second area into a first polysilicon portion containing oxygen atoms and a second polysilicon portion not containing oxygen atoms, the second polysilicon portion being located between the first polysilicon portion and the tunneling layer; performing a second doping process on the polysilicon layer, the first polysilicon portion and the second polysilicon portion on the second surface to convert the polysilicon layer on the first area into a first doped polysilicon layer containing doping elements, and convert the second polysilicon portion into a second doped polysilicon layer containing doping elements, the second doping process includes heat treatment, the heat treatment converts the first polysilicon portion containing oxygen atoms into a silicon oxide layer; and removing the silicon oxide layer.

[0017] First, the polysilicon layer is transformed into a first polysilicon portion containing oxygen atoms and a second polysilicon portion not containing oxygen atoms through a first doping process, and the first polysilicon portion containing oxygen atoms is located on the surface of the second polysilicon portion away from the tunneling layer. Then, when performing the second doping process, the first polysilicon portion containing oxygen atoms is transformed into a silicon oxide layer by heat treatment of the second doping process, and the doping elements introduced by the second doping process need to pass through the silicon oxide layer to reach the second polysilicon portion, and the silicon oxide layer will block some of the doping elements from diffusing into the second polysilicon portion, so that the doping concentration of the doping elements of the second doped polysilicon layer finally formed is low, thereby avoiding the problem of a high recombination probability of lateral flow of carriers caused by the excessive doping concentration of the doping elements in the second doped polysilicon layer, thereby improving the performance of the solar cell.

[0018] The polysilicon layer located on the second region is first transformed into the first polysilicon portion and the second polysilicon portion through the first doping process, and then transformed into the silicon oxide layer and the second doped polysilicon layer through the second doping process, and the silicon oxide layer is finally removed. In other words, only a portion of the thickness of the polysilicon layer is converted into the second doped polysilicon layer, so that the thickness of the second doped polysilicon layer can be thinner, thereby avoiding parasitic absorption caused by the excessive thickness of the second doped polysilicon layer, and further improving the performance of the solar cell.

[0019] In addition, in the above-mentioned method for preparing the solar cell, a second doped polysilicon layer with a smaller thickness is formed through the first doping process and the second doping process, and there is no need to use laser processing in the related technology. Therefore, the risk of damaging the substrate and the tunneling layer due to laser processing can be avoided, thereby improving the reliability of the method for preparing the solar cell.

[0020] In addition, compared with the preparation method of the second doped polysilicon layer with a lower doping concentration of the doped element using a mask technology including multiple process steps in the related art, the embodiment of the present disclosure completes the second doped polysilicon layer with a lower doping concentration of the doped element through the first doping process and the second doping process and removes the silicon oxide layer. The preparation method has fewer process steps, which is conducive to improving the preparation efficiency of solar cells. Among them, the first polysilicon part containing oxygen atoms is converted into a silicon oxide layer that can block the diffusion of part of the doping element by heat treatment in the second doping process, so that the first polysilicon part can be converted into a silicon oxide layer after the first doping process without adding an additional heat treatment process, which is also conducive to improving the preparation efficiency of solar cells. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] One or more embodiments are exemplarily illustrated by pictures in the corresponding drawings, and these exemplified descriptions do not constitute a limitation on the embodiments. Unless otherwise specified, the pictures in the drawings do not constitute a scale limitation. In order to more clearly illustrate the embodiments of the present disclosure or the technical solutions in the traditional technology, the drawings required for use in the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present disclosure. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1 A schematic diagram of the structure of a solar cell in the related art; Figure 2 A schematic structural diagram of a substrate provided in a method for preparing a solar cell provided in an embodiment of the present disclosure; Figure 3A schematic diagram of the structure after the first doping process is performed in the method for preparing a solar cell provided in an embodiment of the present disclosure; Figure 4 A schematic diagram of the structure after the second doping process is performed in the method for preparing a solar cell provided in an embodiment of the present disclosure; Figure 5 A schematic diagram of the structure after the silicon oxide layer is removed in the method for preparing a solar cell provided in an embodiment of the present disclosure; Figure 6 A schematic diagram of the structure after a passivation layer is formed in the method for preparing a solar cell provided in an embodiment of the present disclosure.

[0023] Description of reference numerals: 100, substrate; 110, front side; 120, back side; 130, first region; 140, second region; 101, tunneling oxide layer; 112, first doped polysilicon portion; 122, second doped polysilicon portion; 200, base; 210, first surface; 220, second surface; 230, first region; 240, second region; 201, emitter; 202, tunneling layer; 203, polysilicon layer; 213, first polysilicon portion; 223, second polysilicon portion; 204, first doped polysilicon layer; 205, second doped polysilicon layer; 206, silicon oxide layer; 207, passivation layer; 208, first anti-reflection layer; 218, second anti-reflection layer; 209, first electrode; 219, second electrode. DETAILED DESCRIPTION

[0024] Figure 1 A schematic diagram of the structure of a solar cell in the related art.

[0025] refer to Figure 1 The solar cell in the related art includes: a substrate 100, a tunneling oxide layer 101 and a doped polysilicon layer, wherein the tunneling oxide layer 101 is located between the substrate 100 and the doped polysilicon layer, and the doped polysilicon layer has doping elements.

[0026] The substrate 100 has a front side 110 and a back side 120 opposite to each other. The back side 120 includes a first region 130 and a second region 140 arranged alternately, and the doped polysilicon layer includes a first doped polysilicon portion 112 and a second doped polysilicon portion 122, wherein the first doped polysilicon portion 112 is located on the first region 130, and the second doped polysilicon portion 122 is located on the second region 140, and the first doped polysilicon portion 112 located on the first region 130 is used to electrically contact with an electrode (not shown) to conduct photogenerated carriers, and the second doped polysilicon portion 122 located on the second region 140 is not electrically contacted with the electrode.

[0027] Among them, the second doped polysilicon portion 122 is thick, and there is serious parasitic absorption, which will affect the performance of the solar cell. In addition, the concentration of the doping element in the second doped polysilicon portion 122 is high, which will increase the recombination probability of carriers when they flow laterally in the doped polysilicon layer, making the open circuit voltage of the solar cell lower, and thus making the performance of the solar cell poor.

[0028] To this end, in the preparation method of solar cells in the related art, laser processing is used to reduce the thickness of the second doped polysilicon portion to reduce the parasitic absorption caused by the second doped polysilicon portion. However, the use of laser processing has the risk of causing laser damage to the tunneling oxide layer and the substrate, resulting in low reliability of the solar cells in the related art.

[0029] In addition, in the preparation method of solar cells in the related art, mask technology is usually used to reduce the doping concentration of the second polysilicon part. Specifically, the preparation scheme includes: providing a substrate, the substrate has a relative front and back, the back includes a first area and a second area arranged alternately, and the back of the substrate has a tunneling layer and a polysilicon layer; forming a first mask layer on the surface of the polysilicon layer away from the tunneling layer; then removing the first mask layer on the first area by photolithography and other techniques to form a first window; then doping the first window with a high concentration to transform the polysilicon layer on the first area into a first doped polysilicon part; removing the first mask layer; forming a second mask layer on the surface of the polysilicon layer and the first doped polysilicon part away from the tunneling layer; removing the second mask layer on the second area by photolithography to form a second window; then doping the second window with a low concentration to transform the polysilicon layer on the second area into a second doped polysilicon part; finally removing the second mask layer.

[0030] The above method uses more process steps to reduce the doping concentration of the doping element in the second polysilicon portion, resulting in a low preparation efficiency of the solar cell.

[0031] In the method for preparing a solar cell provided by the embodiment of the present disclosure, the polysilicon layer is first converted into a first polysilicon portion containing oxygen atoms and a second polysilicon portion not containing oxygen atoms by a first doping process. When the second doping process is performed, the first polysilicon portion containing oxygen atoms is converted into a silicon oxide layer by heat treatment of the second doping process, and the doping elements introduced by the second doping process need to pass through the silicon oxide layer to reach the second polysilicon portion, and the silicon oxide layer will block part of the doping elements from diffusing into the second polysilicon portion, so that the doping concentration of the doping elements of the second doped polysilicon layer finally formed is low, thereby avoiding the problem of a high recombination probability of lateral flow of carriers caused by the excessive doping concentration of the doping elements of the second doped polysilicon layer, thereby improving the performance of the solar cell.

[0032] A partially thick polysilicon layer is converted into the final second doped polysilicon layer, so that the thickness of the second doped polysilicon layer can be thinner, thereby avoiding parasitic absorption caused by the excessive thickness of the second doped polysilicon layer, and further improving the performance of the solar cell.

[0033] In addition, in the above-mentioned method for preparing the solar cell, a second doped polysilicon layer with a smaller thickness is formed through the first doping process and the second doping process, and there is no need to use laser processing in the related technology. Therefore, the risk of damaging the substrate and the tunneling layer due to laser processing can be avoided, thereby improving the reliability of the method for preparing the solar cell.

[0034] In addition, compared with the method for preparing the second doped polysilicon layer with a lower doping concentration of the doped element using a mask technology including multiple process steps in the related art, the embodiment of the present disclosure completes the preparation of the second doped polysilicon layer with a lower doping concentration of the doped element through three process steps: the first doping process, the second doping process, and the removal of the silicon oxide layer. The preparation method has fewer process steps, which is conducive to improving the preparation efficiency of solar cells. Among them, the first polysilicon part containing oxygen atoms is converted into a silicon oxide layer that can block the diffusion of part of the doping element by heat treatment in the second doping process, so that the first polysilicon part can be converted into a silicon oxide layer after the first doping process without adding an additional heat treatment process, which is also conducive to improving the preparation efficiency of solar cells.

[0035] In the description of the embodiments of the present disclosure, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present disclosure, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0036] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present disclosure. The appearance of the phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0037] In the description of the embodiments of the present disclosure, the term "and / or" is only a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B may represent: A exists, A and B exist at the same time, and B exists. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0038] In the description of the embodiments of the present disclosure, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0039] In the description of the embodiments of the present disclosure, the orientations or positional relationships indicated by technical terms such as "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", and "circumferential" are based on the orientations or positional relationships shown in the accompanying drawings and are only for the convenience of describing the embodiments of the present disclosure and simplifying the description. They do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the embodiments of the present disclosure.

[0040] In the description of the embodiments of the present disclosure, unless otherwise clearly specified and limited, technical terms such as "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral one; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the internal connection of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present disclosure can be understood according to the specific circumstances.

[0041] In the accompanying drawings corresponding to the embodiments of the present disclosure, the thickness and area of ​​the layers are exaggerated for better understanding and ease of description. When describing a component (such as a layer, film, region, or substrate) on another component or on the surface of another component, the component may be "directly" located on the surface of the other component, or a third component may be present between the two components. On the contrary, when describing a component on the surface of another component or when another component is formed or provided on the surface of a component, it means that there is no third component between the two components. In addition, when describing a component as being "substantially" formed on another component, it means that the component is not formed on the entire surface (or front surface) of the other component, nor is it formed on a partial edge of the entire surface.

[0042] In the description of the embodiments of the present disclosure, when a component "includes" another component, unless otherwise specified, other components are not excluded, and other components may be further included. In addition, when a component such as a layer, film, region, or plate is referred to as being "on / located on" another component, it may be "directly on" the other component (i.e., located on the surface of the other component with no other components between them), or another component may exist in between. In addition, when a component such as a layer, film, region, or plate is "directly located on" another component, or when a component such as a layer, film, region, or plate is located on the surface of another component, it means that no other components are located in between.

[0043] The following will describe the various embodiments of the present disclosure in detail with reference to the accompanying drawings. However, it will be appreciated by those skilled in the art that in the various embodiments of the present disclosure, many technical details are provided in order to enable the reader to better understand the present disclosure. However, even without these technical details and various changes and modifications based on the following embodiments, the technical solutions claimed in the present disclosure can be implemented.

[0044] Figures 2 to 6 This is a schematic diagram of the structures corresponding to each step in the method for preparing a solar cell provided in an embodiment of the present disclosure.

[0045] refer to Figure 2 The method for preparing a solar cell includes: providing a substrate 200, the substrate 200 includes a first surface 210 and a second surface 220 opposite to each other, and the second surface 220 includes first areas 230 and second areas 240 arranged alternately.

[0046] The substrate 200 is used to receive incident light and generate photogenerated carriers. In some embodiments, the substrate 200 may be a semiconductor substrate 200 .

[0047] In some embodiments, the material of the substrate 200 may be an elemental semiconductor material. Specifically, the elemental semiconductor material is composed of a single element, such as silicon or germanium. The elemental semiconductor material may be in a single crystalline state, a polycrystalline state, an amorphous state, or a microcrystalline state (a state having both a single crystalline state and an amorphous state is referred to as a microcrystalline state), for example, silicon may be at least one of single crystalline silicon, polycrystalline silicon, amorphous silicon, or microcrystalline silicon.

[0048] In some embodiments, the material of the substrate 200 may also be a compound semiconductor material. Common compound semiconductor materials include but are not limited to silicon germanium, silicon carbide, gallium arsenide, indium gallium, perovskite, cadmium telluride, copper indium selenide and other materials.

[0049] The substrate 200 may also be a sapphire substrate, a silicon on insulator substrate, or a germanium on insulator substrate.

[0050] The substrate 200 may be an N-type semiconductor substrate or a P-type semiconductor substrate. The N-type semiconductor substrate is doped with an N-type doping element, which may be at least one of the V-group elements such as phosphorus (P), bismuth (Bi), antimony (Sb), or arsenic (As). The P-type semiconductor substrate is doped with a P-type element, which may be at least one of the III-group elements such as boron (B), aluminum (Al), gallium (Ga), or indium (In).

[0051] The substrate 200 has a first surface 210 and a second surface 220 that are opposite to each other. In some embodiments, the solar cell is a single-sided cell, and the first surface 210 of the substrate 200 can be used as a light-receiving surface for receiving incident light, and the second surface 220 can be used as a backlight surface. In some embodiments, the solar cell is a double-sided cell, and the first surface 210 and the second surface 220 of the substrate 200 can both be used as light-receiving surfaces, and can both be used to receive incident light. It can be understood that the backlight surface referred to in the embodiments of the present disclosure can also receive incident light, but the degree of receiving the incident light is weaker than the degree of receiving the incident light by the light-receiving surface, and therefore is defined as the backlight surface.

[0052] In some embodiments, a texturing process may be performed on at least one of the first surface 210 or the second surface 220 of the substrate 200 to form a velvet surface on at least one of the first surface 210 or the second surface 220 of the substrate 200, so that the absorption utilization rate of the first surface 210 and the second surface 220 of the substrate 200 for incident light can be enhanced. In some embodiments, the velvet surface may be a pyramid velvet surface, which, as a common velvet surface, not only reduces the reflectivity of the surface of the substrate 200, but also forms a light trap, thereby enhancing the absorption effect of the substrate 200 for incident light and improving the photoelectric conversion efficiency of the solar cell.

[0053] Specifically, if the solar cell is a single-sided cell, a velvet surface, such as a pyramid velvet surface, can be formed on the light-receiving surface of the substrate 200, and the backlight surface of the substrate 200 can be a polished surface, that is, the backlight surface of the substrate 200 is flatter than the light-receiving surface. It should be noted that for a single-sided cell, a velvet surface can also be formed on both the light-receiving surface and the backlight surface of the substrate.

[0054] If the solar cell is a bifacial cell, a textured surface may be formed on both the light-receiving side and the backlight side of the substrate.

[0055] The first area 230 on the second surface 220 is used to set a first electrode.

[0056] It should be noted that the first area 230 and the second area 240 are artificially demarcated areas. The first area 230 refers to the area where the orthographic projection of the first electrode on the substrate 200 is located, and the second area 240 refers to the area on the second surface where the first electrode is not arranged. Among them, in order to ensure that the film layer contacted by the first electrode has a large doping concentration or the areas contacted by the first electrode 209 are all high-concentration areas, thereby reducing the contact resistance, the area of ​​the first area 230 is generally set to be greater than or equal to the area of ​​the orthographic projection of the first electrode on the substrate 200. In other words, the orthographic projection area of ​​the first electrode on the substrate 200 is smaller than the area of ​​the first area 230, and the orthographic projection position of the first electrode on the substrate 200 is within the first area 230.

[0057] In some embodiments, an emitter 201 is formed on the first surface 210 of the substrate 200 , and the emitter 201 is used to electrically contact with a second electrode formed subsequently.

[0058] The conductivity type of the doping element of the emitter 201 is opposite to the conductivity type of the doping element of the substrate 200 .

[0059] In some embodiments, taking the doping element type of the substrate 200 as N-type as an example, the method for forming the emitter 201 may include: providing an initial substrate, performing a diffusion process on the initial substrate from the surface of the initial substrate, diffusing a P-type doping element from the surface of the initial substrate into a portion of the thickness of the initial substrate, so as to convert the initial substrate partially diffused with the P-type doping element into the emitter 201. The remaining portion of the initial substrate forms the substrate 200. In some embodiments, the diffusion process may be an ion implantation process or a high-temperature diffusion process.

[0060] Continue to refer Figure 2 The method for preparing a solar cell further includes: sequentially forming a tunneling layer 202 and a polysilicon layer 203 on the second surface 220 .

[0061] The tunneling layer 202 has a chemical passivation effect on the second surface 220 of the substrate 200, specifically, by saturating the dangling bonds on the second surface 220 of the substrate 200, reducing the defect state density on the second surface 220 of the substrate 200, and reducing the recombination centers on the surface of the substrate 200 to reduce the carrier recombination rate. In addition, the tunneling layer 202 can allow the majority carriers to tunnel through while blocking the minority carriers from recombination, thereby greatly reducing the metal contact recombination current and improving the open circuit voltage and short circuit current of the solar cell.

[0062] The material of the tunneling layer 202 may be silicon oxide, titanium oxide, silicon nitride, aluminum oxide, hafnium oxide, etc.

[0063] The tunnel layer 202 may be formed by a thermal oxidation process or a chemical vapor deposition method.

[0064] The polysilicon layer 203 is used to subsequently form a first doped polysilicon layer and a second doped polysilicon layer.

[0065] The polysilicon layer 203 may be formed by chemical vapor deposition.

[0066] Combined with reference Figure 2 and Figure 3 The method for preparing a solar cell also includes: performing a first doping process on the polysilicon layer 203 on the second area 240 to transform the polysilicon layer 203 on the second area 240 into a first polysilicon portion 213 containing oxygen atoms and a second polysilicon portion 223 not containing oxygen atoms, and the second polysilicon portion 223 is located between the first polysilicon portion 213 and the tunneling layer 202.

[0067] It is understandable that when the first doping process is performed, oxygen atoms diffuse from the surface of the polysilicon layer 203 away from the tunneling layer 202 into the polysilicon layer 203, and a portion of the polysilicon layer 203 with a thickness is transformed into a first polysilicon portion 213 containing oxygen atoms, and the remaining portion of the polysilicon layer 203 on the second region 240 except the first polysilicon portion 213 is the second polysilicon portion 223. The oxygen atoms are not diffused into the second polysilicon portion 223, so the second polysilicon portion 223 does not contain oxygen atoms.

[0068] In some embodiments, performing a first doping process on the first polysilicon portion 213 includes depositing a mask layer (not shown) on the surface of the polysilicon layer 203 facing away from the tunneling layer 202, and then forming a window corresponding to the second region 240 through laser processing; performing a first doping process on the first polysilicon portion 213 on the second region 240 through the window; and finally etching away the mask layer.

[0069] In some embodiments, performing a first doping process on the polysilicon layer 203 on the second region 240 includes: placing a mask (not shown) on the second surface 220, the mask having a plurality of hollow portions penetrating the mask, the hollow portions corresponding to the second region 240 on the substrate 200 one by one; performing a first doping process on the polysilicon layer 203 on the second region 240 through the hollow portions; and removing the mask. That is, the hollow portions of the mask are used to complete the doping of oxygen atoms in the polysilicon layer 203 on the second region 240, while the polysilicon layer 203 on the first region 230 will not be doped with oxygen atoms under the protection of the mask. In addition, compared with the technical solution of first depositing a mask layer by chemical method and then laser processing to form a window corresponding to the second region to complete the doping process on the second region, the use of a mask including a hollow portion to complete the doping process on the second region 240 can save process steps and avoid damage to the polysilicon layer 203 caused by laser processing, thereby improving the preparation efficiency and reliability of solar cells.

[0070] In some embodiments, the thickness of the mask is 2 mm to 8 mm, for example, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm or 8 mm, and the mask is a silicon nitride mask or a metal mask.

[0071] In some embodiments, the first doping process is an ion implantation method, the energy of the ion implantation method is 10KeV~50KeV, such as 10KeV, 20KeV, 30KeV, 40KeV or 50KeV, etc.; the duration of the ion implantation method is 30s~90s, such as 30s, 40s, 50s, 60s, 70s, 80s or 90s, etc.; the ion source of the ion implantation method is an oxygen-containing gas, such as O2 or O3, etc.; the implantation dose of the ion source can be 5×10 14 atoms / cm 2 ~5×10 15 atoms / cm 2 , for example, it can be 5×10 14 atoms / cm 2 ,7×10 14 atoms / cm 2 ,9×10 14 atoms / cm 2 , 1×10 15 atoms / cm 2 , 3×10 15 atoms / cm 2 or 5×10 15 atoms / cm 2 The relevant process parameters of the first doping process are within the above range, which can ensure that the oxygen atoms can be effectively doped into the polysilicon layer 203 on the second region 240 and transformed into the first polysilicon portion 213 containing oxygen atoms, and ensure that the oxygen content in the first polysilicon portion 213 is sufficient to allow the first polysilicon portion 213 to be transformed into a silicon oxide layer that can block the diffusion of doping elements in the subsequent second doping process.

[0072] In some embodiments, the thickness of the first polysilicon portion 213 is 70 nm to 110 nm, for example, 70 nm, 80 nm, 90 nm, 100 nm or 110 nm, etc. The thickness of the first polysilicon portion 213 is the thickness of the silicon oxide layer formed subsequently. The thickness of the first polysilicon portion 213 is within the above range, which can ensure that there is a silicon oxide layer of sufficient thickness to block the diffusion of the doping elements to the second polysilicon portion 223, so that the doping concentration of the doping elements of the second doped polysilicon layer 205 converted from the second polysilicon portion 223 is low.

[0073] refer to Figure 3 and Figure 4The method for preparing a solar cell also includes: performing a second doping process on the polysilicon layer 203, the first polysilicon portion 213 and the second polysilicon portion 223 on the second surface 220, so that the polysilicon layer 203 on the first area 230 is converted into a first doped polysilicon layer 204 containing doping elements, and the second polysilicon portion 223 is converted into a second doped polysilicon layer 205 containing doping elements, and the second doping process includes heat treatment, and the heat treatment converts the first polysilicon portion 213 containing oxygen atoms into a silicon oxide layer 206.

[0074] Normally, high-temperature annealing is required after ion implantation for doping treatment to repair the lattice damage caused by ion implantation. In the method for preparing a solar cell of the disclosed embodiment, after ion implantation, a second doping process including heat treatment is performed. During the heat treatment, not only the doping of the doping element can be completed, but also the oxygen-containing first polysilicon portion 213 can be converted into a silicon oxide layer 206, and the lattice damage caused by ion implantation can be repaired, so that the first polysilicon portion 213 does not need to add an additional heat treatment process after the first doping process, thereby improving the preparation efficiency of the solar cell. In addition, since the silicon oxide layer 206 will eventually be removed, even if the heat treatment process cannot guarantee the complete repair of the lattice damage of the silicon oxide layer 206 by ion implantation, it will not affect the performance of the solar cell finally prepared.

[0075] In some embodiments, the second doping process is a high temperature diffusion method. The second doping process provides high temperature conditions, that is, completes the introduction of doping elements by heat treatment to form the first doped polysilicon layer 204 and the second doped polysilicon layer 205. In addition, by adopting the high temperature diffusion method, the first polysilicon portion 213 containing oxygen atoms can be converted into a silicon oxide layer 206 that can block the diffusion of doping elements by heat treatment provided by the high temperature diffusion method, so that the first polysilicon portion 213 can be converted into a silicon oxide layer 206 after the first doping process without adding an additional heat treatment process, which can improve the preparation efficiency of solar cells.

[0076] The high temperature diffusion method also includes: providing a doping source containing doping elements, the gas flow rate of the doping source is 1L / min~2L / min, for example, 1L / min, 1.2L / min, 1.4L / min, 1.6L / min, 1.8L / min or 2L / min.

[0077] The doping source may be phosphorus oxychloride, boron tribromide, boron trichloride, or the like.

[0078] It should be noted that providing the doping source and the heat treatment are performed simultaneously, that is, in the high temperature environment provided by the heat treatment, a doping source containing doping elements is provided to form the first doped polysilicon layer 204 and the second doped polysilicon layer 205 .

[0079] In some embodiments, the temperature of the heat treatment is 800°C to 950°C, such as 800°C, 820°C, 850°C, 880°C, 900°C, 920°C or 950°C, etc.; the duration of the heat treatment is 15min to 25min, such as 15min, 18min, 20min, 23min or 25min, etc. The temperature and duration of the heat treatment are within the above ranges, which can ensure that the oxygen-containing first polysilicon portion 213 is converted into a silicon oxide layer 206 that can block the diffusion of dopant elements, and can also allow the dopant elements to be effectively doped into the polysilicon layer 203 on the first region 230 to form a first doped polysilicon layer 204 with a higher doping concentration of the dopant elements, and to be doped into the second polysilicon portion 223 to form a second doped polysilicon layer 205 with a lower doping concentration of the dopant elements.

[0080] The doping element may be the same type of doping element as that of the substrate 200. For example, if the doping element type of the substrate 200 is P-type, the doping element type introduced by the second doping process may also be P-type; if the doping element type of the substrate 200 is N-type, the doping element type introduced by the second doping process may also be N-type.

[0081] It should be noted that the silicon oxide layer 206 can block the diffusion of doped elements into the second polysilicon portion 223. The blocking effect of the silicon oxide layer 206 is to block the diffusion of some doped elements, or some doped elements will pass through the silicon oxide layer 206 to reach the second polysilicon portion 223, so that the second doped polysilicon layer 205 formed by the second polysilicon portion 223 contains doped elements, and the doping concentration of the doped elements is low.

[0082] In some embodiments, the doping concentration of the doping element of the first doped polysilicon layer 204 is the first doping concentration, the doping concentration of the doping element of the second doped polysilicon layer 205 is the second doping concentration, and the ratio of the first doping concentration to the second doping concentration is 4 to 80, for example, 4, 8, 10, 20, 30, 40, 50, 60, 70 or 80. The ratio of the first doping concentration to the second doping concentration is within the above range, the first doping concentration is relatively high and the second doping concentration is relatively low, so that the square resistance of the first doped polysilicon layer 204 can be smaller than the square resistance of the second doped polysilicon layer 205; and the first electrode 209 is in electrical contact with the first doped polysilicon layer 204, the contact resistance between the first electrode 209 and the first doped polysilicon layer 204 can be relatively small, and a good ohmic contact can be formed, thereby reducing the metal contact recombination between the first electrode 209 and the first doped polysilicon layer 204, which is beneficial to improving the carrier collection capability of the first electrode 209. In addition, the doping concentration of the doping element of the second doped polysilicon layer 205 is low, so that the parasitic absorption ability of the second doped polysilicon layer 205 to the incident light is weaker, which can reduce the parasitic absorption of the incident light by the second doped polysilicon layer 205 and improve the absorption utilization rate of the incident light by the substrate 200.

[0083] The ratio of the first doping concentration to the second doping concentration refers to the ratio of the average doping concentration of the doping element in the first doped polysilicon layer 204 to the average doping concentration of the doping element in the second doped polysilicon layer 205 .

[0084] In some embodiments, the first doping concentration is 2×10 19 atoms / cm 2 ~4×10 20 atoms / cm 2 , for example 2×10 19 atoms / cm 2 , 4×10 19 atoms / cm 2 , 6×10 19 atoms / cm 2 , 8×10 19 atoms / cm 2 or 1×10 20 atoms / cm 2 ; The second doping concentration is 5×10 18 atoms / cm 2 ~5×10 19 atoms / cm 2 , for example 5×10 18 atoms / cm 2 ,7×10 18 atoms / cm 2 ,9×10 18 atoms / cm 2 , 1×10 19 atoms / cm 2 , 3×10 19 atoms / cm 2 or 5×10 19 atoms / cm 2 wait.

[0085] In some embodiments, the ratio of the thickness of the second doped polysilicon layer 205 to the thickness of the first doped polysilicon layer 204 is 0.43-0.92, for example, 0.43, 0.5, 0.6, 0.7, 0.8, 0.9 or 0.92. The ratio of the thickness of the second doped polysilicon layer 205 to the thickness of the first doped polysilicon layer 204 is within the above range, so that the thickness of the second polysilicon layer 203 is small, which can reduce the parasitic absorption caused by the second polysilicon layer 203, thereby improving the performance of the solar cell.

[0086] In some embodiments, the thickness of the second doped polysilicon layer 205 is 10 nm to 90 nm, such as 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm or 90 nm, etc.; the thickness of the first doped polysilicon layer 204 is 120 nm to 160 nm, such as 120 nm, 125 nm, 130 nm, 135 nm, 140 nm, 145 nm or 150 nm, etc. When the thickness of the second doped polysilicon layer 205 is within the above range, the parasitic absorption problem caused by the excessive thickness of the second doped polysilicon layer 205 can be avoided, thereby improving the performance of the solar cell. In addition, the thickness of the first doped polysilicon layer 204 is within the above range, and the thickness of the first doped polysilicon layer 204 is relatively large, so that the square resistance of the first doped polysilicon layer 204 electrically contacting the first electrode 209 can be smaller, and the contact resistance between the first electrode 209 and the first doped polysilicon layer 204 can be smaller, so that a better ohmic contact can be formed, and the metal contact recombination between the first electrode 209 and the first doped polysilicon layer 204 is reduced, which is beneficial to improving the performance of the solar cell.

[0087] Combined with reference Figure 4 and Figure 5 The method for preparing a solar cell further includes: removing the silicon oxide layer 206 .

[0088] In some embodiments, removing the silicon oxide layer 206 includes: using a hydrofluoric acid solution with a concentration of 0.5% to 5%, such as 0.5%, 1%, 2%, 3%, 4% or 5%, etc. for treatment; the treatment time is 30s to 120s, such as 30s, 40s, 50s, 60s, 70s, 80s, 90s, 100s, 110s or 120s, etc.; the treatment temperature is 20° C. to 25° C., such as 20° C., 21° C., 22° C., 23° C., 24° C. or 25° C. The relevant parameters of the process step of removing the silicon oxide layer 206 are within the above ranges, which can ensure that the silicon oxide layer 206 is effectively removed without residue, and the first doped polysilicon layer 204 and the second doped polysilicon layer 205 are substantially not damaged.

[0089] The hydrofluoric acid may be buffered hydrofluoric acid, which is a mixture of hydrofluoric acid (HF) and ammonium fluoride (NH 4 F), and can improve etching uniformity and reduce damage to the first doped polysilicon layer 204 and the second doped polysilicon layer 205 .

[0090] In a specific example, in the buffered hydrofluoric acid, the volume ratio of hydrofluoric acid, ammonium fluoride and water may be: HF: NH4F: H20 = 1:6:10.

[0091] refer to Figure 5 and Figure 6In some embodiments, the method for preparing a solar cell may further include forming a passivation layer 207 on the first surface 210. The passivation layer 207 is located on the surface of the emitter 201 away from the first surface 210, and has a good passivation effect on the first surface 210 of the substrate 200, reduces the defect state density of the first surface 210 of the substrate 200, and better inhibits the carrier recombination of the first surface 210 of the substrate 200.

[0092] The material of the passivation layer 207 may be at least one of silicon oxide, aluminum oxide, silicon nitride or silicon oxynitride.

[0093] In some embodiments, the passivation layer 207 may be a single-layer structure. In some embodiments, the passivation layer 207 may also be a multi-layer structure, in which the materials of the layers may be different from each other, or the materials of a portion of the layers may be different from each other, and the materials of the remaining portions may be the same. For example, the passivation layer 207 may be a multi-layer structure of a silicon nitride layer and an aluminum oxide layer.

[0094] The passivation layer 207 may be formed by atomic layer deposition.

[0095] Continue to refer Figure 6 In some embodiments, the method for preparing a solar cell may further include: forming a first anti-reflection layer 208 on the surface of the passivation layer 207 facing away from the emitter 201, and forming a second anti-reflection layer 218 on the surfaces of the first doped polysilicon layer 204 and the second doped polysilicon layer 205 facing away from the tunneling layer 202.

[0096] The first anti-reflection layer 208 can play a good anti-reflection effect, reduce the reflection of the first surface 210 on the incident light, and improve the utilization rate of the incident light by the substrate 200. In addition, the first anti-reflection layer 208 can also play a good passivation effect on the first surface 210, reduce the defect state density of the first surface 210 of the substrate 200, and better inhibit the carrier recombination of the first surface 210 of the substrate 200.

[0097] The material of the first anti-reflection layer 208 may include at least one of aluminum oxide, silicon nitride, or silicon oxynitride.

[0098] The first anti-reflection layer 208 may be formed by chemical vapor deposition.

[0099] The second anti-reflection layer 218 can play a good anti-reflection effect, reduce the reflection of the second surface 220 on the incident light, and improve the utilization rate of the incident light by the substrate 200. In addition, the second anti-reflection layer 218 can also play a good passivation effect on the second surface 220, reduce the defect state density of the second surface 220 of the substrate 200, and better inhibit the carrier recombination of the second surface 220 of the substrate 200.

[0100] The material of the second anti-reflection layer 218 may include at least one of aluminum oxide, silicon nitride, or silicon oxynitride.

[0101] The second anti-reflection layer 218 may be formed by chemical vapor deposition.

[0102] Continue to refer Figure 6 In some embodiments, the method for preparing a solar cell further includes forming a first electrode 209 and a second electrode 219 , wherein the first electrode 209 is in electrical contact with the first doped polysilicon layer 204 , and the second electrode 219 is in electrical contact with the emitter 201 .

[0103] In some embodiments, the method of forming the first electrode 209 may include: printing metal paste on the surface of the second anti-reflection layer 218 on the first region 230 using a screen printing process.

[0104] In some embodiments, the metal paste may include at least one of silver, aluminum, copper, tin, gold, lead, or nickel.

[0105] The metal paste is subjected to a sintering process. In some embodiments, the metal paste contains materials with high corrosive components such as glass. Thus, during the sintering process, the corrosive components will corrode the second anti-reflection layer 218 and a portion of the first doped polysilicon layer 204, thereby allowing the metal paste to penetrate into the second anti-reflection layer 218 and a portion of the first doped polysilicon layer 204 to form a first electrode 209 electrically contacting the first doped polysilicon layer 204.

[0106] In some embodiments, the method of forming the second electrode 219 may include: using a screen printing process to print metal paste on a portion of the surface of the first anti-reflection layer 208. In some embodiments, the metal paste may include at least one of silver, aluminum, copper, tin, gold, lead or nickel.

[0107] The metal paste is subjected to a sintering process. In some embodiments, the metal paste contains materials with high corrosive components such as glass. Thus, during the sintering process, the corrosive components will corrode the first anti-reflection layer 208, the passivation layer 207 and a portion of the emitter 201, thereby allowing the metal paste to penetrate into the first anti-reflection layer 208, the passivation layer 207 and a portion of the emitter 201 to form a second electrode 219 that is in electrical contact with the emitter 201.

[0108] In the above-mentioned method for preparing a solar cell, the doping concentration of the doping element of the finally formed second doped polysilicon layer 205 is low, thereby avoiding the problem of a high recombination probability of lateral flow of carriers caused by an excessively high doping concentration of the doping element of the second doped polysilicon layer 205, thereby improving the performance of the solar cell. The thickness of the finally formed second doped polysilicon layer 205 can be small, thereby avoiding parasitic absorption caused by an excessively thick thickness of the second doped polysilicon layer 205, thereby improving the performance of the solar cell.

[0109] In addition, in the above-mentioned method for preparing a solar cell, a second doped polysilicon layer 205 with a smaller thickness is formed through a first doping process and a second doping process, and there is no need to use laser processing in the related technology. Therefore, the risk of damaging the substrate 200 and the tunneling layer 202 due to laser processing can be avoided, thereby improving the reliability of the method for preparing a solar cell.

[0110] In addition, compared with the method for preparing the second doped polysilicon layer 205 with a lower doping concentration of the doped element using a mask technology including multiple process steps in the related art, the embodiment of the present disclosure completes the preparation of the second doped polysilicon layer 205 with a lower doping concentration of the doped element through the first doping process and the second doping process and removing the silicon oxide layer 206. The preparation method has fewer process steps, which is conducive to improving the preparation efficiency of solar cells. Among them, the first polysilicon part 213 containing oxygen atoms is converted into a silicon oxide layer 206 that can block the diffusion of part of the doping element by heat treatment in the second doping process, so that the first polysilicon part 213 can be converted into a silicon oxide layer 206 after the first doping process without adding an additional heat treatment process, which is also conducive to improving the preparation efficiency of solar cells.

[0111] Accordingly, another aspect of the present disclosure also provides a solar cell prepared by the method for preparing a solar cell of any of the above embodiments. It should be noted that for the parts that are the same or corresponding to the above embodiments, reference can be made to the corresponding description of the above embodiments, and will not be repeated below.

[0112] refer to Figure 5 or Figure 6The solar cell comprises: a substrate 200, the substrate 200 comprises a first surface 210 and a second surface 220 opposite to each other, the second surface 220 comprises a first region 230 and a second region 240 arranged alternately; a tunneling layer 202, the tunneling layer 202 is located on the second surface 220; a first doped polysilicon layer 204, the first doped polysilicon layer 204 is located on the first region 230, and the first doped polysilicon layer 204 is located on the surface of the tunneling layer 202 away from the second surface 220; and the second doped polysilicon layer 20 5. The second doped polysilicon layer 205 is located on the second region 240, and the second doped polysilicon layer 205 is located on the surface of the tunneling layer 202 away from the second surface 220; wherein the first doped polysilicon layer 204 and the second doped polysilicon layer 205 both contain doping elements, the doping concentration of the doping elements of the second doped polysilicon layer 205 is less than the doping concentration of the doping elements of the first doped polysilicon layer 204, and the thickness of the second doped polysilicon layer 205 is less than the thickness of the first doped polysilicon layer 204.

[0113] In the solar cell provided by the embodiment of the present disclosure, the concentration of the doping element of the first doped polysilicon layer 204 is relatively high, so that the square resistance of the first doped polysilicon layer 204 can be smaller than that of the second doped polysilicon layer 205; and the first electrode 209 is in electrical contact with the first doped polysilicon layer 204, and the contact resistance between the first electrode 209 and the first doped polysilicon layer 204 can be relatively small, so that a good ohmic contact can be formed, and the metal contact recombination between the first electrode 209 and the first doped polysilicon layer 204 is reduced, which is conducive to improving the carrier collection ability of the first electrode 209. In addition, the doping concentration of the doping element of the second doped polysilicon layer 205 is relatively low, so that the parasitic absorption ability of the second doped polysilicon layer 205 is relatively weak, thereby improving the performance of the solar cell. The thickness of the first doped polysilicon layer 204 is relatively large, so that the square resistance of the first doped polysilicon layer 204 electrically contacting the first electrode 209 can be relatively small, and the contact resistance between the first electrode 209 and the first doped polysilicon layer 204 can be relatively small, so that a better ohmic contact can be formed, and the metal contact recombination between the first electrode 209 and the first doped polysilicon layer 204 can be reduced, and the performance of the solar cell can also be improved.

[0114] Those skilled in the art can understand that the above-mentioned embodiments are specific examples for realizing the present disclosure, and in practical applications, various changes can be made to them in form and details without departing from the spirit and scope of the present disclosure. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present disclosure, so the protection scope of the present disclosure shall be based on the scope defined in the claims.

Claims

1. A method for preparing a solar cell, characterized in that: include: Providing a substrate, the substrate comprising a first surface and a second surface opposite to each other, the second surface comprising first areas and second areas arranged alternately; forming a tunneling layer and a polysilicon layer in sequence on the second surface; performing a first doping process on the polysilicon layer on the second region, so that the polysilicon layer on the second region is transformed into a first polysilicon portion containing oxygen atoms and a second polysilicon portion not containing oxygen atoms, wherein the second polysilicon portion is located between the first polysilicon portion and the tunneling layer; performing a second doping process on the polysilicon layer, the first polysilicon portion, and the second polysilicon portion on the second surface, so that the polysilicon layer on the first region is converted into a first doped polysilicon layer containing a doping element, and the second polysilicon portion is converted into a second doped polysilicon layer containing the doping element, wherein the second doping process includes a heat treatment, and the heat treatment converts the first polysilicon portion containing the oxygen atoms into a silicon oxide layer; The silicon oxide layer is removed.

2. The method for preparing a solar cell according to claim 1, characterized in that: The temperature of the heat treatment is 800° C. to 950° C., and the duration of the heat treatment is 15 min to 25 min.

3. The method for preparing a solar cell according to claim 1, characterized in that: The first doping process is an ion implantation method, the energy of the ion implantation method is 10KeV~50KeV, the duration of the ion implantation method is 30s~90s, the ion source of the ion implantation method is an oxygen-containing gas, and the implantation dose of the ion source is 5×10 14 atoms / cm 2 ~5×10 15 atoms / cm 2 .

4. The method for preparing a solar cell according to claim 1, characterized in that: The doping concentration of the doping element in the first doped polysilicon layer is a first doping concentration, the doping concentration of the doping element in the second doped polysilicon layer is a second doping concentration, and a ratio of the first doping concentration to the second doping concentration is 4-80.

5. The method for preparing a solar cell according to claim 4, characterized in that: The first doping concentration is 2×10 19 atoms / cm 2 ~4×10 20 atoms / cm 2 ; The second doping concentration is 5×10 18 atoms / cm 2 ~5×10 19 atoms / cm 2 .

6. The method for preparing a solar cell according to claim 1, characterized in that: Performing the first doping process on the polysilicon layer on the second region includes: Placing a mask on the second surface, wherein the mask has a plurality of hollow portions penetrating the mask, and the hollow portions correspond one-to-one to the second areas on the substrate; performing the first doping process on the polysilicon layer on the second region through the hollow portion; The mask is removed.

7. The method for preparing a solar cell according to claim 1, characterized in that: The ratio of the thickness of the second doped polysilicon layer to the thickness of the first doped polysilicon layer is 0.43-0.

92.

8. The method for preparing a solar cell according to claim 7, characterized in that: The thickness of the second doped polysilicon layer is 10 nm to 90 nm, and the thickness of the first doped polysilicon layer is 120 nm to 160 nm.

9. The method for preparing a solar cell according to claim 1, characterized in that: Removing the silicon oxide layer comprises: Use a hydrofluoric acid solution with a concentration of 0.5%~5% for treatment, the treatment time is 30s~120s, and the treatment temperature is 20℃~25℃.

10. A solar cell, characterized in that: include: A substrate, the substrate comprising a first surface and a second surface opposite to each other, the second surface comprising first areas and second areas arranged alternately; a tunneling layer, wherein the tunneling layer is located on the second surface; a first doped polysilicon layer, wherein the first doped polysilicon layer is located on the first region, and the first doped polysilicon layer is located on a surface of the tunneling layer away from the second surface; a second doped polysilicon layer, wherein the second doped polysilicon layer is located on the second region, and the second doped polysilicon layer is located on a surface of the tunneling layer away from the second surface; Wherein, the first doped polysilicon layer and the second doped polysilicon layer both contain doping elements, the doping concentration of the doping elements in the second doped polysilicon layer is less than the doping concentration of the doping elements in the first doped polysilicon layer, and the thickness of the second doped polysilicon layer is less than the thickness of the first doped polysilicon layer.

Images