Method for manufacturing solar cell and solar cell

Abstract

The embodiment of the present disclosure relates to the photovoltaic field, and provides a manufacturing method of a solar cell and the solar cell, wherein the manufacturing method of the solar cell comprises the following steps: providing a substrate; forming an amorphous silicon layer on one side of the substrate; performing a first doping treatment, the first doping treatment induces the amorphous silicon layer to be converted into an initial polycrystalline silicon layer, and the initial polycrystalline silicon layer contains a plurality of crystal nuclei; performing a second doping treatment, the second doping treatment converts the polycrystalline silicon into a doped conductive layer, and during the second doping treatment, the crystal nuclei increase to become crystal grains; and forming a passivation layer, the passivation layer is located on the surface of the doped conductive layer away from the substrate. The doping concentration of the formed doped conductive layer can be improved.

Description

Technical Field

[0001] This disclosure relates to the photovoltaic field, and in particular to a method for manufacturing a solar cell and the solar cell itself. Background Technology

[0002] Currently, with the gradual depletion of fossil fuels, solar cells are becoming increasingly widely used as a new energy alternative. A solar cell is a device that converts solar energy into electrical energy. Solar cells utilize the photovoltaic principle to generate charge carriers, and then use electrodes to extract these carriers, thus facilitating the efficient use of electrical energy.

[0003] Photovoltaic conversion efficiency is one of the important indicators for measuring the performance of solar cells. Therefore, it is necessary to improve the photovoltaic conversion efficiency of solar cells. Summary of the Invention

[0004] This disclosure provides a method for manufacturing a solar cell and a solar cell, which can at least improve the photoelectric conversion efficiency of the solar cell.

[0005] According to some embodiments of this disclosure, one aspect of this disclosure provides a method for manufacturing a solar cell, comprising: providing a substrate; forming an amorphous silicon layer on one side of the substrate; performing a first doping treatment, wherein the first doping treatment induces the amorphous silicon layer to transform into an initial polycrystalline silicon layer, the initial polycrystalline silicon layer containing a plurality of crystal nuclei; performing a second doping treatment, wherein the second doping treatment transforms the initial polycrystalline silicon layer into a doped conductive layer, and during the second doping treatment, the crystal nuclei increase in size to become grains; and forming a passivation layer, the passivation layer being located on the surface of the doped conductive layer away from the substrate.

[0006] In some embodiments, the first doping process includes: a first heating stage, wherein the first heating stage raises the process temperature of the first doping process to a first preset temperature; and a first isothermal stage, wherein the first isothermal stage maintains the process temperature of the first doping process at the first preset temperature; wherein a doping source gas is introduced during the first heating stage and the first isothermal stage.

[0007] In some embodiments, the process parameters of the first heating stage include: a gas flow rate of 50 sccm to 80 sccm for the dopant source gas, a gas flow rate of 100 sccm to 150 sccm for oxygen, and a time of 100 s to 300 s.

[0008] In some embodiments, the process parameters of the first isothermal stage include: process temperature of 850℃~900℃, gas flow rate of dopant source gas of 50sccm~80sccm, gas flow rate of oxygen of 100sccm~150sccm, and time of 500s~600s.

[0009] In some embodiments, the second doping process includes: a second heating stage, wherein the second heating stage heats the second doping process to a second preset temperature, the second preset temperature being greater than the maximum process temperature of the first doping process; and a second isothermal stage, wherein the process temperature of the second doping process is maintained at the second preset temperature; wherein a doping source gas is introduced during the second heating stage and the second isothermal stage.

[0010] In some embodiments, the flow rate of the dopant source gas introduced in the second doping process is greater than the flow rate of the dopant source gas introduced in the first doping process.

[0011] In some embodiments, the process parameters for the second heating stage include: a gas flow rate of 200 sccm to 500 sccm for the dopant source gas, a gas flow rate of 8000 sccm to 20000 sccm for oxygen, and a time of 1200 s to 2000 s.

[0012] In some embodiments, the process parameters of the second isothermal stage include: process temperature of 870℃~960℃, gas flow rate of dopant source gas of 200sccm~500sccm, gas flow rate of oxygen of 8000sccm~20000sccm, and time of 1200s~2000s.

[0013] In some embodiments, the sheet resistance of the initial polycrystalline silicon layer formed by the first doping treatment is 700 Ω / sq to 1000 Ω / sq, and the doping concentration of the doped conductive layer formed by the second doping treatment is 5E19 atoms / cm². 3 ~9E19atoms / cm 3 .

[0014] According to some embodiments of this disclosure, another aspect of this disclosure also provides a solar cell formed using the solar cell manufacturing method described above.

[0015] The technical solution provided by the embodiments of this disclosure has at least the following advantages: through the first doping treatment, crystal nuclei are formed in the amorphous silicon layer, increasing the crystallization degree of the amorphous silicon layer. Moreover, the crystal nuclei can reduce the activation energy of dopant ions, facilitating the diffusion of dopant ions in the initial polycrystalline silicon layer. At the same time, the grain boundaries between crystal nuclei can increase the channels for dopant ions. During the second doping treatment, due to the increase in dopant ion channels, the diffusion of dopant ions is further facilitated, and the crystal nuclei become grains, improving the passivation effect of the formed doped conductive layer. Attached Figure Description

[0016] One or more embodiments are illustrated by way of example with corresponding pictures in the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Unless otherwise stated, the pictures in the accompanying drawings do not constitute a limitation on scale. In order to more clearly illustrate the technical solutions in the embodiments of this disclosure or the conventional technology, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figures 1 to 4 This is a schematic diagram of the structure corresponding to each step of a method for manufacturing a solar cell according to an embodiment of this disclosure.

[0018] Explanation of reference numerals in the attached figures: 100. Substrate; 101. Amorphous silicon layer; 102. Initial polycrystalline silicon layer; 103. Doped conductive layer; 104. Passivation layer; 105. Tunneling layer. Detailed Implementation

[0019] As is known from the background technology, the current process of forming a doped conductive layer usually involves directly doping the polycrystalline silicon layer. However, direct doping can lead to an increase in defects within the polycrystalline silicon layer, and the diffusion during the doping process is uncontrollable, resulting in low doping efficiency and poor doping effect, which can have an adverse impact on the passivation of the polycrystalline silicon layer.

[0020] Currently, there are methods to improve the passivation effect of the doped conductive layer by adding pre-doping to the polycrystalline silicon layer. However, pre-doping will cause the grain size of the polycrystalline silicon layer to increase further and the grain boundaries to decrease, which will limit the diffusion and effective doping of dopants and reduce the concentration of dopants in the doped conductive layer.

[0021] In this embodiment of the present disclosure, a crystal nucleus is formed in the amorphous silicon layer through the first doping treatment, which increases the crystallization degree of the amorphous silicon layer. Moreover, the crystal nucleus can reduce the activation energy of the dopant ions, which facilitates the diffusion of the dopant ions in the initial polycrystalline silicon layer. At the same time, the grain boundaries between the crystal nuclei can increase the channels for the dopant ions. During the second doping treatment, as the channels for the dopant ions increase, it is further facilitated for the diffusion of the dopant ions. Meanwhile, the crystal nucleus becomes a grain, which improves the passivation effect of the formed doped conductive layer.

[0022] In the description of the embodiments of this disclosure, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary or secondary relationship of the indicated technical features. In the description of the embodiments of this disclosure, "a plurality of" means two or more, unless otherwise explicitly defined.

[0023] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this disclosure. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0024] In the description of the embodiments of this disclosure, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent three cases: A exists, A and B exist simultaneously, and B exists. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0025] In the description of embodiments of this disclosure, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0026] In the description of the embodiments of this disclosure, the technical terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this disclosure and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this disclosure.

[0027] In the description of the embodiments of this disclosure, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this disclosure according to the specific circumstances.

[0028] In the accompanying drawings corresponding to the embodiments of this disclosure, the thickness and area of ​​the layers are enlarged for better understanding and ease of description. When describing a component (such as a layer, film, region, or substrate) on or on the surface of another component, the component may be "directly" located on the surface of the other component, or there may be a third component between the two components. Conversely, when describing a component on the surface of another component, or when another component is formed or disposed on the surface of a component, it indicates that there is no third component between the two components. Furthermore, when describing a component as being "generally" 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 portion of the edge of the entire surface.

[0029] In the description of embodiments of this disclosure, when a component "includes" another component, other components are not excluded unless otherwise stated, and may be further included. Furthermore, when a component such as a layer, film, region, or plate is referred to as being "on / located" on another component, it can 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 be present therein. Additionally, 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 indicates that no other components are located therein.

[0030] The terminology used in the description of the various embodiments herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used in the description and claims of the various embodiments described, the term "component" is also intended to include the plural form unless the context clearly indicates otherwise. Components include layers, films, regions, or plates, etc.

[0031] The embodiments of this disclosure will now be described in detail with reference to the accompanying drawings. However, those skilled in the art will understand that many technical details have been provided in the embodiments of this disclosure to facilitate a better understanding of the disclosure. However, the technical solutions claimed in this disclosure can be implemented even without these technical details and various variations and modifications based on the following embodiments.

[0032] refer to Figures 1 to 4 ,in, Figure 1 This is a schematic diagram of a structure in which an amorphous silicon layer is formed on a substrate. Figure 2 In order to be in Figure 1 A schematic diagram of the structure of the initial polycrystalline silicon layer formed on the basis of the above. Figure 3 In order to be in Figure 2 A schematic diagram of a structure in which a doped conductive layer is formed based on the above. Figure 4 In order to be in Figure 3 A schematic diagram of the structure on which a passivation layer is formed.

[0033] In some embodiments, a method of manufacturing a solar cell may include providing a substrate 100.

[0034] The method of manufacturing a solar cell may also include forming an amorphous silicon layer 101 on one side of a substrate 100.

[0035] The method for manufacturing a solar cell may further include: performing a first doping treatment, which induces the amorphous silicon layer 101 to be converted into an initial polycrystalline silicon layer 102, the initial polycrystalline silicon layer 102 containing multiple crystal nuclei.

[0036] The method for manufacturing solar cells may further include: performing a second doping treatment, wherein the second doping treatment converts the initial polycrystalline silicon layer 102 into a doped conductive layer 103, and during the second doping treatment, the crystal nuclei increase in size and become grains.

[0037] The method of manufacturing a solar cell may further include: forming a passivation layer 104, wherein the passivation layer 104 is located on the side of the doped conductive layer 103 away from the substrate 100.

[0038] In this embodiment of the present disclosure, a crystal nucleus is formed in the amorphous silicon layer 101 through the first doping treatment, which increases the crystallization degree of the amorphous silicon layer 101. Moreover, the crystal nucleus can reduce the activation energy of the dopant ions, which facilitates the diffusion of the dopant ions in the initial polycrystalline silicon layer 102. At the same time, the grain boundaries between the crystal nuclei can increase the channels for the dopant ions. During the second doping treatment, as the channels for the dopant ions increase, it further facilitates the diffusion of the dopant ions. Meanwhile, the crystal nuclei become grains, which improves the passivation effect of the formed doped conductive layer 103.

[0039] In some embodiments, the substrate 100 may be an N-type semiconductor substrate or a P-type semiconductor substrate. The N-type semiconductor substrate is doped with an N-type dopant element, which may be at least one of group V elements such as phosphorus (P), bismuth (Bi), antimony (Sb), or arsenic (As). The P-type semiconductor substrate is doped with a P-type dopant element, which may be at least one of group III elements such as boron (B), aluminum (Al), gallium (Ga), or indium (In).

[0040] The substrate 100 may include a first surface and a second surface opposite to each other. The first surface can serve as the light-receiving surface of the solar cell, used to receive incident light, and the second surface can serve as the backlight surface. In some embodiments, the solar cell is a bifacial cell, where both the first and second surfaces can serve as light-receiving surfaces and can both be used to receive incident light. It is understood that the second surface referred to in the embodiments of this disclosure can also receive incident light, but the degree of reception of incident light is weaker than that of the light-receiving surface, and therefore it is defined as the second surface.

[0041] The amorphous silicon layer 101 can be disposed on the second side.

[0042] In some embodiments, a texturing process can be performed on at least one of the first or second surfaces of the substrate 100 to form a textured surface on at least one of the first or second surfaces of the substrate 100. This can enhance the absorption and utilization efficiency of incident light on the first and second surfaces of the substrate 100. In some embodiments, the textured surface can be a pyramid textured surface. As a common textured surface, pyramid textured surface not only reduces the reflectivity of the substrate 100 surface but also forms light traps, enhancing the absorption effect of the substrate 100 on incident light and improving the photoelectric conversion efficiency of the solar cell.

[0043] Specifically, if the solar cell is a single-sided cell, a textured surface, such as a pyramidal textured surface, can be formed on the light-receiving surface of the substrate 100, while the back-lighting surface of the substrate 100 can be a polished surface, meaning the back-lighting surface of the substrate 100 is flatter than the light-receiving surface. It should be noted that for single-sided cells, a textured surface can also be formed on both the light-receiving and back-lighting surfaces of the substrate 100.

[0044] If the solar cell is a bifacial cell, a textured surface can be formed on both the light-receiving side and the back-lighting side of the substrate 100.

[0045] In some embodiments, a tunneling layer 105 may be formed before forming the amorphous silicon layer 101. The tunneling layer 105 has a chemical passivation effect on the surface of the substrate 100. Specifically, by saturating the dangling bonds on the surface of the substrate 100, the defect state density on the surface of the substrate 100 is reduced, and the recombination centers on the surface of the substrate 100 are reduced, thereby reducing the carrier recombination rate.

[0046] In some embodiments, the material of the tunneling layer 105 may include at least one of silicon oxide, silicon nitride, silicon oxynitride, silicon carbide, or magnesium fluoride.

[0047] In some embodiments, an amorphous silicon layer 101 can be formed at a low temperature. At a low temperature, the atoms / groups adsorbed on the substrate 100 have weak migration ability and cannot move to the lattice sites. They can only bond in a random manner, thereby forming an amorphous silicon layer 101 with long-range disorder and short-range order.

[0048] It should be noted that the low temperature here can refer to 150℃~350℃.

[0049] In some embodiments, the amorphous silicon layer 101 has a large number of dangling bond defects, which causes the amorphous silicon layer 101 to become a carrier recombination center. Therefore, hydrogen (H) introduced during the deposition process combines with these dangling bonds to form Si-H bonds, thereby passivating these defect states and significantly improving the electrical properties of the amorphous silicon. Therefore, the resulting material is often referred to as hydrogenated amorphous silicon.

[0050] In some embodiments, the first doping process may include: a first heating stage, in which the process temperature of the first doping process is raised to a first preset temperature; and a first isothermal stage, in which the process temperature of the first doping process is maintained at the first preset temperature; wherein a dopant source gas is introduced during the first heating stage and the first isothermal stage. The first heating stage is used to gradually increase the ambient temperature of the amorphous silicon layer 101, thereby avoiding abnormalities in the formed solar cell due to sudden temperature changes, and thus improving the reliability of the solar cell. The first isothermal stage is used to guide the formation of crystal nuclei and facilitate the diffusion of doped ions into the initial polycrystalline silicon layer 102 through the carrier channels between crystal nuclei.

[0051] By introducing dopant source gas during the first heating stage and the first isothermal stage, the nucleation process of amorphous silicon can be induced by dopant ions during the first heating stage, thereby reducing the difficulty of crystal nucleus formation during the first isothermal stage and reducing the process time of the entire first doping process.

[0052] In some embodiments, the process parameters for the first heating stage include: the flow rate of the dopant source gas is 50 sccm to 80 sccm, for example, 50 sccm, 60 sccm, 70 sccm or 80 sccm, etc.; the flow rate of the oxygen gas is 100 sccm to 150 sccm, for example, 100 sccm, 110 sccm, 120 sccm, 130 sccm, 140 sccm or 150 sccm, etc.; and the time is 100 s to 300 s, for example, 100 s, 130 s, 160 s, 180 s, 200 s, 250 s or 300 s, etc.

[0053] For the doping source gas, if the gas flow rate of the doping source gas is too high, it will result in too many doping ions entering the amorphous silicon layer 101 during the first heating stage. This will cause the doping ions to excessively induce the nucleation of amorphous silicon, which will reduce the crystal plane between crystal nuclei and affect the doping effect of the subsequent second doping process.

[0054] As for oxygen, it is used to passivate defects generated during the first doping process when dopants diffuse into the amorphous silicon layer 101, thereby reducing the surface defect state density of the initial polycrystalline silicon layer 102. Therefore, if the oxygen gas flow rate is too high, the initial polycrystalline silicon layer 102 will be oxidized, and if the oxygen gas flow rate is too low, the ability to passivate the surface defects of the initial polycrystalline silicon layer 102 will be weak.

[0055] In terms of time, the longer the time, the smoother the heating process in the first heating stage will be, and there will be no sudden temperature changes. If the time is too long, the crystal nuclei will become too large, which will reduce the crystal plane between the crystal nuclei and affect the doping effect of the subsequent second doping process. Therefore, the time is set to 100s~300s to make the heating process smooth while forming a certain number of crystal nuclei, which will facilitate the doping process of the second doping process.

[0056] In some embodiments, the process parameters of the first isothermal stage include: a process temperature of 850°C to 900°C, such as 850°C, 860°C, 870°C, 880°C, 890°C, or 900°C, etc.; a dopant source gas flow rate of 50 sccm to 80 sccm, such as 50 sccm, 60 sccm, 70 sccm, or 80 sccm; an oxygen gas flow rate of 100 sccm to 150 sccm, such as 100 sccm, 110 sccm, 120 sccm, 130 sccm, 140 sccm, or 150 sccm, etc.; and a time of 500 s to 600 s, such as 500 s, 530 s, 550 s, 560 s, 580 s, or 600 s, etc.

[0057] The first isothermal stage is used to pre-dope the amorphous silicon layer 101. At the same time, the dopant ions diffused into the amorphous silicon layer 101 simultaneously induce amorphous silicon nucleation. Among the above process parameters, the efficiency of nucleation in the first isothermal stage can be improved while avoiding excessively large crystal nuclei, thus providing a process basis for the subsequent second doping process.

[0058] Regarding temperature, if the temperature is too high, the crystal nuclei will become too large, resulting in fewer grain boundaries between crystal nuclei and affecting the doping effect of the subsequent second doping process. If the temperature is too low, the efficiency of the first doping process will be slow, affecting the rate at which crystal nuclei are formed in the first doping process.

[0059] For the doping source gas, if the gas flow rate of the doping source gas is too high, it will result in too many doping ions entering the amorphous silicon layer 101 during the first isothermal stage. This will cause the doping ions to excessively induce the nucleation of amorphous silicon, which will reduce the crystal plane between crystal nuclei and affect the doping effect of the subsequent second doping treatment.

[0060] As for oxygen, it is used to passivate defects generated during the first doping process when dopants diffuse into the amorphous silicon layer 101, thereby reducing the surface defect state density of the initial polycrystalline silicon layer 102. Therefore, if the oxygen gas flow rate is too high, the initial polycrystalline silicon layer 102 will be oxidized, and if the oxygen gas flow rate is too low, the ability to passivate the surface defects of the initial polycrystalline silicon layer 102 will be weak.

[0061] Regarding the time, the first isothermal stage requires a certain amount of time to allow the amorphous silicon layer 101 to nucleate. Therefore, the time of the first isothermal stage is set to be greater than or equal to 500 seconds to avoid the situation where the amorphous silicon layer 101 has not yet nucleated before the first doping process is completed, thus providing a process basis for the subsequent second doping process. At the same time, if the time of the first isothermal stage is too long, it will lead to the formation of excessively large crystal nuclei, resulting in a reduction of grain boundaries. Therefore, the time of the first isothermal stage is set to be less than or equal to 600 seconds to avoid affecting the second doping process.

[0062] It should be noted that nucleation here refers to the formation of crystal nuclei.

[0063] In some embodiments, the gas flow rate of the dopant source gas in the first heating stage can be the same as the gas flow rate of the dopant source gas in the first isothermal stage, and / or the gas flow rate of oxygen in the first heating stage can be the same as the gas flow rate of oxygen in the first isothermal stage, thereby reducing the process difficulty of the first doping treatment.

[0064] In other embodiments, the flow rate of the dopant source gas in the first heating stage may be less than the flow rate of the dopant source gas in the first isothermal stage, and / or the flow rate of oxygen in the first heating stage may be less than or the same as the flow rate of oxygen in the first isothermal stage. The first heating stage plays a transitional role in the first doping process. Therefore, reducing the flow rate of the dopant source gas and / or the flow rate of oxygen introduced during the first heating stage can reduce the process cost of solar cells.

[0065] In some embodiments, the second doping process may include: a second heating stage, in which the second doping process is heated to a second preset temperature, which is greater than the maximum process temperature of the first doping process; and a second isothermal stage, in which the process temperature of the second doping process is maintained at the second preset temperature; wherein a dopant source gas is introduced during the second heating stage and the second isothermal stage. The second heating stage is used to raise the temperature to the temperature required for the second doping process, thereby avoiding abnormalities in the solar cell caused by sudden temperature changes, thereby improving the reliability of the solar cell. The second isothermal stage is used to induce crystal nuclei into grains at a suitable temperature, thereby facilitating the reduction of defects in the initial polycrystalline silicon layer 102, and also facilitating the diffusion of dopant ions to increase the doping concentration of the formed doped conductive layer 103.

[0066] In some embodiments, the flow rate of the dopant source gas introduced in the second doping process is greater than that in the first doping process. The core objective of the first doping process is to induce the amorphous silicon layer 101 to transform into the initial polycrystalline silicon layer 102. Therefore, the flow rate of the dopant source gas in the first doping process is set to be smaller to avoid excessive induction of crystal nuclei formation during the first doping process. The core objective of the second doping process is to form a doped conductive layer 103 with a certain doping concentration and to convert crystal nuclei into grains, thereby reducing defects in the doped conductive layer 103. Therefore, the flow rate of the dopant source gas in the second doping process is set to be larger to increase the doping concentration of the formed doped conductive layer 103, thereby improving the performance of the solar cell.

[0067] Understandably, for the doped conductive layer 103, grain boundaries are enriched regions of defect states. These defect states act as recombination centers for charge carriers, severely reducing minority carrier lifetime and thus impairing the passivation effect and efficiency of the battery. Therefore, a second doping process is needed to drive the crystal nuclei to grow through grain boundary migration or solid-state crystallization, merging adjacent small grains to form larger grains, thereby reducing the density of recombination centers introduced by grain boundaries.

[0068] In some embodiments, the process parameters of the second heating stage include: the flow rate of the dopant source gas is 200 sccm to 500 sccm, for example, 200 sccm, 300 sccm, 400 sccm or 500 sccm, etc.; the flow rate of the oxygen gas is 8000 sccm to 20000 sccm, for example, 8000 sccm, 10000 sccm, 12000 sccm, 14000 sccm, 16000 sccm, 18000 sccm or 20000 sccm, etc.; and the time is 1200 s to 2000 s, for example, 1200 s, 1400 s, 1600 s, 1800 s or 2000 s, etc.

[0069] If the doping source gas is not introduced in the second heating stage, but only in the second isothermal stage, the doping concentration on the surface will increase sharply, while the concentration inside will be lower, resulting in a large concentration gradient. At the same time, introducing the doping source gas in the second heating stage can also facilitate the uniform distribution of doped ions during the second isothermal stage.

[0070] For oxygen, defects in the doped conductive layer 103 can be repaired during the second heating stage, thereby reducing the interface state density of the doped conductive layer 103. At the same time, oxygen can accelerate the doping process. Therefore, the oxygen gas flow rate is set to be greater than 8000 sccm. When the oxygen concentration is greater than 20000 sccm, it may cause oxidation of the doped conductive layer 103, affecting the carrier transport performance of the doped conductive layer 103. Therefore, the oxygen gas flow rate is set to be less than 20000 sccm.

[0071] In some embodiments, the process parameters of the second isothermal stage include: a process temperature of 870°C to 960°C, such as 870°C, 890°C, 900°C, 920°C, 940°C, or 960°C, etc.; a dopant source gas flow rate of 200 sccm to 500 sccm, such as 200 sccm, 300 sccm, 400 sccm, or 500 sccm, etc.; an oxygen gas flow rate of 8000 sccm to 20000 sccm, such as 8000 sccm, 10000 sccm, 12000 sccm, 14000 sccm, 16000 sccm, 18000 sccm, or 20000 sccm, etc.; and a time of 1200 s to 2000 s, such as 1200 s, 1400 s, 1600 s, 1800 s, or 2000 s, etc.

[0072] The second isothermal stage is used to complete high-concentration doping. Therefore, the process temperature is set to 870℃~960℃ to promote the rapid and deep diffusion and activation of dopant ions, forming the final high-conductivity doped conductive layer 103.

[0073] The dopant source gas is used to provide dopant ions to facilitate the formation of a high-doped conductive layer 103. Therefore, the flow rate of the dopant source gas is set to be greater than 200 sccm to provide sufficient dopant source gas for the diffusion of dopant ions. At the same time, there is a certain upper limit to the diffusion efficiency of dopant ions. When the flow rate of the dopant source gas exceeds 500 sccm, even if the flow rate is further increased, the doping efficiency will not be improved significantly. Instead, it will further increase the cost of the solar cell manufacturing method.

[0074] For oxygen, it serves to catalyze the doping process. If only the doping source gas is introduced, the diffusion rate of doped ions will be slow. Therefore, the oxygen gas flow rate is set to be greater than 8000 sccm. When the oxygen concentration is greater than 20000 sccm, it may cause oxidation of the doped conductive layer 103, affecting the carrier transport performance of the doped conductive layer 103. Therefore, the oxygen gas flow rate is set to be less than 20000 sccm.

[0075] In some embodiments, the sheet resistance of the initial polysilicon layer 102 formed by the first doping treatment is 700 Ω / sq to 1000 Ω / sq, for example, 700 Ω / sq, 800 Ω / sq, 900 Ω / sq, or 1000 Ω / sq, etc., and the doping concentration of the doped conductive layer 103 formed by the second doping treatment is 5E19 atoms / cm. 3 ~9E19atoms / cm 3 For example, 5E19 atoms / cm 3 6E19atoms / cm 3 7E19atoms / cm 3 8E19atoms / cm 3 Or 9E19atoms / cm 3 etc.

[0076] It is understandable that the doping concentration affects the sheet resistance of the initial polycrystalline silicon layer 102. The higher the doping concentration, the lower the sheet resistance of the initial polycrystalline silicon layer 102 can be. At the same time, the number of dopant ions in the first doping treatment cannot be too many, as the doping efficiency of the first doping treatment is relatively slow. If too many dopant ions are required, it will take a long time, which will affect the production efficiency of the solar cell. Therefore, the sheet resistance of the initial polycrystalline silicon layer is set to be less than 1000 Ω / sq. Similarly, the doping concentration in the first doping treatment cannot be too low, as it will affect the effect of the first doping treatment on improving the second doping treatment. Therefore, the sheet resistance of the initial polycrystalline silicon layer is set to be greater than 700 Ω / sq.

[0077] For the second doping process, the doping concentration of the conductive layer formed after the first doping process can exceed 5E19 atoms / cm. 3 This increases the doping concentration of the conductive layer. However, the concentration of the conductive layer cannot be too high. On the one hand, an excessively high doping concentration will result in a longer time required for the second doping process, leading to a longer manufacturing process for the entire solar cell and affecting the production efficiency of the solar cell. On the other hand, excessively high concentrations of dopant ions will diffuse into the substrate, resulting in additional doping of the substrate. The path of these dopant ions is through the conductive layer and tunneling layer into the substrate, affecting the reliability of the entire solar cell.

[0078] In some embodiments, during the second doping process, dopant ions may also diffuse to the side of the substrate 100 near the doped conductive layer 103.

[0079] In some embodiments, the material of the passivation layer 104 may be one of silicon oxide, aluminum oxide, silicon nitride, or silicon oxynitride.

[0080] The passivation layer 104 can be a single-layer structure or a multi-layer structure. In the case of a multi-layer structure, the materials of different layers can be different from each other, or some layers can be made of the same material but different from the materials of other layers. For example, the passivation layer 104 can be a multi-layer structure of silicon nitride and aluminum oxide layers.

[0081] The solar cell may also include a plurality of first electrodes (not shown), all of which are located on the surface of the passivation layer 104, and the first electrodes also penetrate a portion of the passivation layer 104 and a portion of the thickness of the doped conductive layer 103, forming an ohmic contact with the doped conductive layer 103.

[0082] In this embodiment of the present disclosure, a crystal nucleus is formed in the amorphous silicon layer 101 through the first doping treatment, which increases the crystallization degree of the amorphous silicon layer 101. Moreover, the crystal nucleus can reduce the activation energy of the dopant ions, which facilitates the diffusion of the dopant ions in the initial polycrystalline silicon layer 102. At the same time, the grain boundaries between the crystal nuclei can increase the channels for the dopant ions. During the second doping treatment, as the channels for the dopant ions increase, it further facilitates the diffusion of the dopant ions. Meanwhile, the crystal nuclei become grains, which improves the passivation effect of the formed doped conductive layer 103.

[0083] Another embodiment of this disclosure also provides a solar cell, which can be formed using the manufacturing method of solar cells as described in some or all of the above embodiments. The solar cell provided in another embodiment of this disclosure will be described below. It should be noted that the same or corresponding parts as those in the above embodiments can be referred to the above embodiments, and will not be repeated below.

[0084] In some embodiments, the solar cell can be any one of a PERC cell (Passivated Emitter and Rear Cell), a PERT cell (Passivated Emitter and Rear Totally-diffused cell), a TOPCon cell (Tunnel Oxide Passivated Contact cell), a HIT / HJT cell (Heterojunction Technology cell), or a BC cell (Back Contact cell). In other embodiments, the solar cell can also be a tandem cell comprising any of the above-mentioned cells (where the top cell is a perovskite cell and the bottom cell is any one of the above-mentioned cells), or a half-cell of any of the above-mentioned cells, etc. Based on this, the initial cell described above can have a corresponding structure to the solar cell described above.

[0085] Those skilled in the art will understand that the above embodiments are specific examples of implementing this disclosure, and in practical applications, various changes in form and detail may be made without departing from the spirit and scope of the embodiments of this disclosure. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the embodiments of this disclosure; therefore, the scope of protection of the embodiments of this disclosure should be determined by the scope defined in the claims.

Claims

1. A method for manufacturing a solar cell, characterized in that, include: Provide a base; An amorphous silicon layer is formed on one side of the substrate; A first doping process is performed, which induces the amorphous silicon layer to be converted into an initial polycrystalline silicon layer, the initial polycrystalline silicon layer containing multiple crystal nuclei; A second doping process is performed, which converts the initial polycrystalline silicon layer into a doped conductive layer, and during the second doping process, the crystal nuclei grow into grains. A passivation layer is formed on the surface of the doped conductive layer away from the substrate.

2. The method for manufacturing a solar cell according to claim 1, characterized in that, The first doping process includes: In the first heating stage, the process temperature of the first doping treatment is raised to a first preset temperature. The first isothermal stage maintains the process temperature of the first doping treatment at the first preset temperature. During the first heating stage and the first isothermal stage, a doping source gas is introduced.

3. The method for manufacturing a solar cell according to claim 2, characterized in that, The process parameters for the first heating stage include: a flow rate of 50 sccm to 80 sccm for the dopant source gas, a flow rate of 100 sccm to 150 sccm for oxygen, and a time of 100 s to 300 s.

4. The method for manufacturing a solar cell according to claim 2, characterized in that, The process parameters for the first isothermal stage include: process temperature 850℃~900℃, gas flow rate of dopant source gas 50sccm~80sccm, gas flow rate of oxygen 100sccm~150sccm, and time 500s~600s.

5. The method for manufacturing a solar cell according to claim 1, characterized in that, The second doping process includes: In the second heating stage, the second doping treatment is heated to a second preset temperature, which is greater than the maximum process temperature of the first doping treatment. The second isothermal stage maintains the process temperature of the second doping treatment at the second preset temperature. During the second heating stage and the second isothermal stage, a doped source gas is introduced.

6. The method for manufacturing a solar cell according to claim 5, characterized in that, The flow rate of the dopant source gas introduced in the second doping process is greater than the flow rate of the dopant source gas introduced in the first doping process.

7. The method for manufacturing a solar cell according to claim 5, characterized in that, The process parameters for the second heating stage include: a flow rate of 200 sccm to 500 sccm for the dopant source gas, a flow rate of 8000 sccm to 20000 sccm for the oxygen gas, and a time of 1200 s to 2000 s.

8. The method for manufacturing a solar cell according to claim 5, characterized in that, The process parameters for the second isothermal stage include: process temperature 870℃~960℃, gas flow rate of dopant source gas 200sccm~500sccm, gas flow rate of oxygen 8000sccm~20000sccm, and time 1200s~2000s.

9. The method for manufacturing a solar cell according to claim 1, characterized in that, The sheet resistance of the initial polysilicon layer formed by the first doping treatment is 700 Ω / sq to 1000 Ω / sq, and the doping concentration of the doped conductive layer formed by the second doping treatment is 5E19 atoms / cm. 3 ~9E19atoms / cm 3 .

10. A solar cell, characterized in that, It is formed using the method for manufacturing a solar cell as described in any one of claims 1 to 9.

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