Solar cell, method for manufacturing solar cell, and photovoltaic module

Abstract

The application relates to a solar cell, a preparation method of the solar cell and a photovoltaic module, and belongs to the photovoltaic technical field.The solar cell comprises a substrate and a first doped conductive layer, and the substrate has a first surface with a pyramid structure along the thickness direction; the pyramid structure comprises a top part, a middle part and a bottom part arranged in sequence along the thickness direction of the substrate; and the first doped conductive layer is formed in the interior of the first surface; the average doping concentration of the doped elements in the first doped conductive layer is n1 in the top part, the average doping concentration of the doped elements in the first doped conductive layer is n2 in the middle part, the average doping concentration of the doped elements in the first doped conductive layer is n3 in the bottom part, 1.05 < n1 / n2 <= 2, and 1.05 < n2 / n3 <= 2; the function areas of the first doped conductive layer in the pyramid structure are more distinct, the better passivation effect is ensured, and better ohmic contact with the metal electrode can be formed.

Description

Technical Field

[0001] This application relates to the field of photovoltaic cell technology, specifically to a solar cell, a method for preparing a solar cell, and a photovoltaic module. Background Technology

[0002] A solar cell is a thin film of photoelectric semiconductor that generates electricity directly using sunlight. It is also known as a "solar chip" or "photovoltaic cell". As long as the illuminance conditions are met, it can output voltage and generate current in the presence of a circuit. At present, the contact performance and passivation effect of solar cells still need to be improved. Summary of the Invention

[0003] In view of this, this application provides a solar cell, a method for preparing a solar cell, and a photovoltaic module to improve the contact performance and passivation effect of the solar cell.

[0004] This application provides a first aspect of a solar cell, the solar cell comprising a substrate and a first doped conductive layer, the substrate having a first surface along its thickness direction; the first surface having a pyramid structure, the pyramid structure comprising a apex, a middle section, and a bottom section sequentially disposed along the thickness direction of the substrate, the first doped conductive layer being formed inside the first surface; the average doping concentration of the dopant element in the first doped conductive layer at the apex is n1, the average doping concentration of the dopant element in the first doped conductive layer at the middle section is n2, the average doping concentration of the dopant element in the first doped conductive layer at the bottom section is n3, 1.05 < n1 / n2 ≤ 2, 1.05 < n2 / n3 ≤ 2.

[0005] In one possible design, along the thickness direction of the substrate and from the outside of the substrate to the inside of the substrate, the doping concentration of the dopant element in the first doped conductive layer gradually decreases in the apex of the tower.

[0006] In one possible design, the dopant elements in the first doped conductive layer are uniformly doped in the middle of the tower along the thickness direction of the substrate.

[0007] In one possible design, the doping concentration of the dopant element in the first doped conductive layer in the middle of the tower is 2 × 10⁻⁶. 18 toms / m 3 ~1×10 19 toms / m 3 .

[0008] In one possible design, along the thickness direction of the substrate and from the outside of the substrate to the inside of the substrate, the doping concentration of the dopant element in the first doped conductive layer gradually decreases at the bottom of the tower.

[0009] In one possible design, the doping element is boron or phosphorus.

[0010] A second aspect of this application provides a method for preparing a solar cell, used to prepare the solar cell described in any of the above embodiments, the method comprising the following steps:

[0011] Preparation of substrate;

[0012] A texturing process is performed on a first surface of the substrate; wherein the first surface has a pyramid structure, and along the thickness direction of the substrate, the pyramid structure includes a apex, a middle section, and a base arranged sequentially.

[0013] A doping source is deposited on the first surface, and the doping element in the doping source diffuses into the substrate to form a first doped conductive layer; wherein the average doping concentration of the doping element in the first doped conductive layer at the top of the tower is n1, the average doping concentration of the doping element in the first doped conductive layer at the middle of the tower is n2, and the average doping concentration of the doping element in the first doped conductive layer at the bottom of the tower is n3, 1.05 < n1 / n2 ≤ 2, 1.05 < n2 / n3 ≤ 2.

[0014] In one possible design, depositing a dopant source on the first surface and diffusing the dopant element from the dopant source into the substrate to form a first doped conductive layer specifically includes:

[0015] Raise the temperature to 800℃~930℃ and hold for 50s~200s;

[0016] A dopant source and oxygen are introduced for 8 to 15 minutes to allow the dopant source to be deposited on the first surface.

[0017] The temperature is raised to 870℃~970℃ and held for 10min~20min before being lowered to room temperature to allow the dopant elements in the dopant source to diffuse into the substrate.

[0018] In one possible design, depositing a dopant source on the first surface and diffusing the dopant element from the dopant source into the substrate to form a first doped conductive layer specifically includes:

[0019] Raise the temperature to 800℃~930℃ and hold for 150s~400s;

[0020] A dopant source and oxygen are introduced for 8 to 15 minutes to allow the dopant source to be deposited on the first surface.

[0021] Raise the temperature to 870℃~970℃ and keep it at that temperature for 10min~20min, then lower it to room temperature;

[0022] The first surface is laser-treated to allow the dopant elements in the dopant source to diffuse into the substrate.

[0023] In one possible design, the laser is continuous red light, the laser spot size is 100μm, the laser power is 300w~450w, and the laser scanning speed is 21000mm / s~39000mm / s.

[0024] In one possible design, after raising the temperature to 870°C~970°C and holding it at that temperature for 10 min~20 min, then lowering it to room temperature to allow the dopant element in the dopant source to diffuse into the substrate, or after laser treatment of the first surface to allow the dopant element in the dopant source to diffuse into the substrate, the method for fabricating the solar cell further includes:

[0025] The first surface is subjected to wet alkaline etching;

[0026] The first surface is oxidized so that the doping element diffuses further into the substrate to form the first doped conductive layer.

[0027] A third aspect of this application provides a photovoltaic module, the photovoltaic module including a battery string, an encapsulation layer and a cover plate, the battery string being formed by connecting multiple solar cells from any of the above embodiments, the encapsulation layer being used to cover the surface of the battery string, and the cover plate being used to cover the surface of the encapsulation layer away from the battery string.

[0028] In this application, the average doping concentration of the dopant element in the first doped conductive layer decreases sequentially at the top, middle and bottom of the tower, so that a high-low junction can be formed between the top, middle and bottom of the tower, forming a band bending, realizing selective transport of charge carriers, and reducing electron-hole recombination losses.

[0029] Furthermore, during the metallization process of solar cells, the first doped conductive layer at the top of the tower is typically the core region that forms contact with the metal electrode; for example, the first electrode usually contacts the first doped conductive layer at the top. Therefore, the higher doping concentration of the dopant element in the first doped conductive layer at the top allows for better ohmic contact performance with the metal electrode, improving the fill factor of the solar cell. In the middle section, connecting the top and bottom of the tower, the doping concentration of the first doped conductive layer is lower than at the top but higher than at the bottom, enabling better lateral current transmission and reducing Auger recombination. At the bottom of the tower, the first doped conductive layer is far from the metal electrode, having a relatively smaller impact on the ohmic contact performance. The lower doping concentration of the first doped conductive layer at the top minimizes Auger recombination, ensuring better passivation of the surface in this region, improving the open-circuit voltage and fill factor of the solar cell, and thus increasing its conversion efficiency.

[0030] Furthermore, when the average doping concentration n1 of the dopant element in the first doped conductive layer at the top of the tower, the average doping concentration n2 of the dopant element in the first doped conductive layer at the middle of the tower, and the average doping concentration n3 of the dopant element in the first doped conductive layer at the bottom of the tower satisfying 1.05 < n1 / n2 ≤ 2 and 1.05 < n2 / n3 ≤ 2, the doping concentration of the dopant element at the top, middle, and bottom of the tower can be significantly different, thus making the functional distinction of each region more significant. This ensures better passivation effect while forming a better ohmic contact with the metal electrode. It also avoids the average doping concentration n1 of the dopant element at the top of the tower being much higher than the average doping concentration n2 in the middle of the tower, and the doping concentration of the dopant element at the bottom of the tower being too low. This allows for a smooth transition in the doping concentration of the dopant element at the top, middle, and bottom of the tower, which is beneficial for carrier transport, improves the fill factor and open-circuit voltage, and thus improves the conversion efficiency of the solar cell.

[0031] It should be understood that the above general description and the following detailed description are merely exemplary and do not limit this application. Attached Figure Description

[0032] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 A cross-sectional view of the substrate provided for an embodiment of this application in one specific embodiment;

[0034] Figure 2 A schematic diagram of a structure in which a first doped conductive layer is formed on the first surface of a substrate;

[0035] Figure 3 A cross-sectional structural diagram of a solar cell provided in an embodiment of this application;

[0036] Figure 4 A schematic diagram showing the concentration of doping elements in different regions of the pyramid structure in the first doped conductive layer provided in the embodiments of this application;

[0037] Figure 5 A flowchart illustrating a method for fabricating a solar cell according to an embodiment of this application;

[0038] Figure 6 This is a schematic diagram of the structure of the photovoltaic module provided in this application.

[0039] Figure label:

[0040] 100-Solar Cell;

[0041] 1-Base;

[0042] 11-First surface;

[0043] 111 - Pyramid structure;

[0044] 111a - Spire;

[0045] 111b - Middle of the tower;

[0046] 111c tower base;

[0047] 12-Second surface;

[0048] 2- First doped conductive layer;

[0049] 3-First electrode;

[0050] 4-Second doped conductive layer;

[0051] 5-Second electrode;

[0052] 6-First passivation layer;

[0053] 7-Second passivation layer;

[0054] 110-battery string;

[0055] 120 - Encapsulation layer;

[0056] 130 - Cover plate;

[0057] Z - Thickness direction.

[0058] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application. Detailed Implementation

[0059] To better understand the technical solution of this application, the embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0060] In the description of this application, unless otherwise expressly specified and limited, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance; unless otherwise specified or explained, the term "multiple" refers to two or more; the terms "connected," "fixed," etc., should be interpreted broadly. For example, "connected" can be a fixed connection, a detachable connection, an integral connection, or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0061] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0062] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0063] It should be noted that the directional terms such as "upper," "lower," "left," and "right" described in the embodiments of this application are used to describe the angles shown in the accompanying drawings and should not be construed as limiting the embodiments of this application. Furthermore, in the context, it should be understood that when it is mentioned that an element is connected "upper" or "lower" to another element, it can be directly connected to the other element "upper" or "lower," or indirectly connected to the other element "upper" or "lower" through an intermediate element.

[0064] Solar cells typically consist of a substrate and a doped conductive layer formed within the substrate surface, which is used for connection to metal electrodes. The substrate surface of a solar cell is usually textured, containing multiple pyramidal structures to reduce light reflection and thus improve the solar cell's conversion efficiency. In existing solar cells, the doping concentration of the dopant element in the conductive layer is essentially the same across the pyramidal structures, which can negatively impact the solar cell's contact performance and passivation effect.

[0065] Based on this, this application provides a solar cell, a photovoltaic module, and a method for fabricating a solar cell to improve the contact performance and passivation effect of the solar cell. The solar cell can be applied to various cell structures, including but not limited to tunnel oxide passivated contact (TOPCon), interdigitated back contact (IBC), and passivated emitter rear cell (PERC), etc., without limitation.

[0066] like Figure 1 As shown, the solar cell 100 includes a substrate 1, which is used to receive incident light and generate photogenerated carriers. In some embodiments, the substrate 1 is a silicon substrate, which may include one or more of monocrystalline silicon, polycrystalline silicon, amorphous silicon, or microcrystalline silicon. In other embodiments, the material of the substrate 1 may also be silicon carbide, organic materials, or multi-component compounds. Multi-component compounds may include, but are not limited to, perovskite, gallium arsenide, cadmium telluride, copper indium selenide, etc. Exemplarily, the substrate 1 in this application is a monocrystalline silicon substrate. The substrate 1 contains dopant elements, and the conductivity type of the dopant elements can be N-type or P-type. The N-type elements can be group V elements such as phosphorus (P), bismuth (Bi), antimony (Sb), or arsenic (As), and the P-type elements can be group III elements such as boron (B), aluminum (Al), gallium (Ga), or indium (In). For example, when the substrate 1 is a P-type silicon substrate, the conductivity type of its internal dopant elements is P-type. As another example, when the substrate 1 is an N-type silicon substrate, the conductivity type of its internal dopant elements is N-type. For example, in this embodiment of the application, substrate 1 is an N-type silicon substrate to improve the conversion efficiency of solar cell 100 and reduce manufacturing costs.

[0067] Wherein, substrate 1 refers to a sheet structure that includes at least a silicon substrate. In addition, in some embodiments, substrate 1 may also include a tunneling layer and an intrinsic layer.

[0068] like Figure 1As shown, the substrate 1 includes a first surface 11, which has a pyramid structure 111. In one embodiment, the pyramid structure 111 can be formed by texturing the first surface 11 using laser or chemical etching. Along the thickness direction Z of the substrate 1, the pyramid structure 111 includes a apex 111a, a middle portion 111b, and a base 111c arranged sequentially. Specifically, along the thickness direction Z of the substrate 1, the apex 111a accounts for 10% to 30% of the height of the pyramid structure 111, the base 111c accounts for 10% to 30% of the height of the pyramid structure 111, and the remaining portion is the middle portion 111b.

[0069] Since the height dimensions of each pyramid structure 111 on the first surface 11 may differ, the height range of the apex 111a corresponding to different pyramid structures 111 may also be different, the height range of the bottom 111c corresponding to different pyramid structures 111 may also be different, and the height range of the middle part 111b corresponding to different pyramid structures 111 may also be different.

[0070] It should be noted that, as Figure 1 and Figure 2 As shown, the first surface 11 can be either the light-receiving surface or the back-lighting surface of the solar cell 100. When the first surface 11 is a light-receiving surface, for example, the first doped conductive layer 2 can be a P-type emitter layer formed by boron expansion on the first surface 11, where the doping element can be boron. When the first surface 11 is a back-lighting surface, for example, the first doped conductive layer 2 can be an N-type doped conductive layer formed by phosphorus expansion on the first surface 11, where the doping element can be phosphorus. The specific configuration can be adjusted according to actual needs, and this application does not impose any limitations on this. This application uses the example of the first surface 11 being a light-receiving surface and the first doped conductive layer 2 being a P-type emitter layer formed by boron expansion on the first surface 11 for illustration.

[0071] like Figure 2As shown, the first doped conductive layer 2 is formed inside the first surface 11. Taking the first surface 11 as the light-receiving surface as an example, the first doped conductive layer 2 can be a P-type emitter layer formed by boron diffusion on the first surface 11. The first doped conductive layer 2 has a different conductivity type from the dopant element in the substrate 1, so that the two can jointly form a PN junction structure. Exemplarily, the first doped conductive layer 2 can also be made of doped polycrystalline silicon, microcrystalline silicon, or amorphous silicon with a conductivity type opposite to that of the dopant element in the substrate 1. For example, when the substrate 1 is an N-type silicon substrate, a tunneling layer and a polycrystalline silicon, microcrystalline silicon, or amorphous silicon layer can be formed on the first surface 11 of the substrate 1 by low-pressure chemical vapor deposition (LPCVD) or plasma-enhanced chemical vapor deposition (PECVD), and the first doped conductive layer 2 is formed by doping the polycrystalline silicon, microcrystalline silicon, or amorphous silicon layer with a P-type dopant element. The specific configuration can be set according to actual needs and is not limited here.

[0072] like Figure 2 As shown, the average doping concentration of the doped element in the first doped conductive layer 2 at the top of the tower 111a is n1, the average doping concentration of the doped element in the first doped conductive layer 2 at the middle of the tower 111b is n2, and the average doping concentration of the doped element in the first doped conductive layer 2 at the bottom of the tower 111c is n3, where 1.05 < n1 / n2 ≤ 2 and 1.05 < n2 / n3 ≤ 2. For example, the ratio n1 / n2 of the average doping concentration n1 of the doped element in the first doped conductive layer 2 at the top 111a of the tower to the average doping concentration n2 of the doped element in the first doped conductive layer 2 at the middle 111b of the tower can be 1.06, 1.08, 1.1, 1.12, 1.14, 1.16, 1.18, 1.2, 1.4, 1.6, 1.8, 2, etc., and the ratio n2 / n3 of the average doping concentration n2 of the doped element in the first doped conductive layer 2 at the middle 111b of the tower to the average doping concentration n3 of the doped element in the first doped conductive layer 2 at the bottom 111c of the tower can be 1.06, 1.08, 1.1, 1.12, 1.14, 1.16, 1.18, 1.2, 1.4, 1.6, 1.8, 2, etc., can be set according to actual needs, and no restrictions are imposed here.

[0073] In this embodiment, the average doping concentration of the dopant element in the first doped conductive layer 2 decreases sequentially at the top 111a, middle 111b, and bottom 111c, so that a high-low junction can be formed between the top 111a, middle 111b, and bottom 111c, forming a band bending, realizing selective transport of charge carriers, and reducing electron-hole recombination losses.

[0074] Furthermore, during the metallization process of the solar cell 100, the first doped conductive layer 2 of the spire 111a typically contacts the core region that forms contact with the metal electrode, i.e., as shown in the image. Figure 3 As shown, the first electrode 3 is typically in contact with the first doped conductive layer 2 of the tower tip 111a. Therefore, the doping concentration of the doped element in the first doped conductive layer 2 is higher in the tower tip 111a, enabling better ohmic contact performance with the metal electrode and improving the fill factor of the solar cell 100. The middle section 111b connects the tower tip 111a and the tower bottom 111c. The doping concentration of the doped element in the first doped conductive layer 2 in the middle section 111b is lower than that in the tower tip 111a but higher than that in the tower bottom 111c, allowing for better lateral current transmission and reducing Auger recombination. The first doped conductive layer 2 in the tower bottom 111c is far from the metal electrode, having a relatively small impact on the ohmic contact performance with the metal electrode. The lower doping concentration of the doped element in the first doped conductive layer 2 in the tower tip 111a minimizes Auger recombination, ensuring better passivation of the surface in this region, improving the open-circuit voltage and fill factor of the solar cell 100, thereby increasing the conversion efficiency of the solar cell 100.

[0075] Furthermore, when the average doping concentration n1 of the doped element in the first doped conductive layer 2 at the top 111a, the average doping concentration n2 of the doped element in the first doped conductive layer 2 at the middle 111b, and the average doping concentration n3 of the doped element in the first doped conductive layer 2 at the bottom 111c satisfying 1.05 < n1 / n2 ≤ 2 and 1.05 < n2 / n3 ≤ 2, the doping concentration of the doped element at the top 111a, the middle 111b, and the bottom 111c can be significantly different, thereby enabling functional differentiation of each region. More significantly, while ensuring better passivation effect, it can form a better ohmic contact with the metal electrode, and can avoid the average doping concentration n1 of the dopant element at the top of the tower 111a being much higher than the average doping concentration n2 at the middle of the tower 111b and the doping concentration of the dopant element at the bottom of the tower 111c being too low. This makes the doping concentration of the dopant element gradually transition between the top of the tower 111a, the middle of the tower 111b and the bottom of the tower 111c, which is conducive to the transport of charge carriers, improves the fill factor and open circuit voltage, and thus improves the conversion efficiency of the solar cell 100.

[0076] It should be noted that the average doping concentration is the average doping concentration of the dopant element within a depth of 100 nm on the surface of each region. For example, n1 is the average doping concentration of the dopant element within a depth of 100 nm on the surface of the top 111a of the tower; n2 is the average doping concentration of the dopant element within a depth of 100 nm on the surface of the middle 111b of the tower; and n3 is the average doping concentration of the dopant element within a depth of 100 nm on the surface of the bottom 111c of the tower.

[0077] The measurement process for the average doping concentration of the doped element in the tip 111a is as follows: The relationship curve between the doping concentration and the doping depth of the tip 111a can be obtained using the electrochemical capacitance-voltage (ECV) method. Then, the doping concentration within a depth range of 100 nm is integrated to obtain the integration area. Dividing the integration area by the depth of 100 nm yields the average doping concentration of the tip 111a within the 100 nm depth range, which is the average doping concentration n1 of the tip 111a. Alternatively, the average doping concentration of the tip 111a within the 100 nm depth range can be directly read using certain equipment. Of course, an energy-dispersive X-ray spectrometer (EDS) can be used in conjunction with a sample electron microscope (SEM / TEM) to perform compositional analysis by detecting the characteristic X-rays excited when the electron beam bombards the sample, and to measure the average doping concentration of 111a at the top of the column. Alternatively, atomic probe tomography (APT) can be used to evaporate the atoms at the top of the sample one by one using lasers and high-voltage pulses, and to reconstruct the three-dimensional compositional distribution of the sample, thereby measuring the average doping concentration of 111a at the top of the column. Alternatively, secondary ion mass spectrometry (SIMS) can be used to bombard the sample with a primary ion beam, sputtering "secondary ions", and then using a mass spectrometer to analyze the composition of these ions for compositional analysis and to measure the average doping concentration of 111a at the top of the column. The specific settings can be configured according to actual needs and are not limited here.

[0078] Similarly, the average doping concentration of the doped element in the middle part 111b of the tower and the average doping concentration of the doped element in the bottom part 111c of the tower can also be measured.

[0079] In one specific embodiment, such as Figure 4 As shown, along the thickness direction Z of the substrate 1, and from the outside to the inside of the substrate 1, the doping concentration of the doped element in the first doped conductive layer 2 gradually decreases in the tip 111a. This ensures that the first doped conductive layer 2 can form a good ohmic contact with the metal electrode, reducing contact resistance and thus reducing carrier recombination losses and improving the conversion efficiency of the solar cell 100. Furthermore, this arrangement allows for a smooth transition in the doping concentration between the tip 111a and the middle section 111b, which is beneficial for carrier transport.

[0080] In one specific embodiment, such as Figure 4 As shown, the dopant elements in the first doped conductive layer 2 are uniformly doped in the middle section 111b of the tower, which ensures uniform and efficient transverse current transmission, reduces energy loss during transverse transmission, and thus helps to further improve the fill factor and reduce Auger recombination. The uniform doping of the dopant elements in the first doped conductive layer 2 in the middle section 111b of the tower also reduces process complexity, facilitates preparation, and saves costs.

[0081] It should be noted that the doping element in the first doped conductive layer 2 is uniformly doped in the middle part 111b of the tower, that is, the doping concentration of the doping element in each region of the middle part 111b of the tower is approximately the same. In other words, due to measurement accuracy and other reasons, based on the understanding of those skilled in the art, a small fluctuation range can also be regarded as the same.

[0082] Specifically, the doping concentration of the dopant element in the first doped conductive layer 2 in the middle part 111b of the tower is 2 × 10⁻⁶. 18 atoms / cm 3 ~1×10 19 atoms / cm 3 This ensures that the current is transmitted uniformly and efficiently in the lateral direction while reducing Auger recombination.

[0083] In one specific embodiment, such as Figure 4 As shown, along the thickness direction of the substrate 1 and from the outside to the inside of the substrate 1, the doping concentration of the doped element in the first doped conductive layer 2 gradually decreases at the bottom 111c of the tower. This minimizes Auger recombination at the bottom 111c, resulting in better passivation and improving open-circuit voltage and short-circuit current, thereby increasing the conversion efficiency of the solar cell 100. Furthermore, this arrangement allows for a smooth transition in doping concentration between the middle sections 111b and 111c of the tower, which is beneficial for carrier transport.

[0084] In one specific embodiment, such as Figure 3 As shown, the solar cell 100 also includes a first electrode 3, a second doped conductive layer 4, a second electrode 5, a first passivation layer 6, and a second passivation layer 7.

[0085] like Figure 3 As shown, along the thickness direction Z of the substrate 1, the first electrode 3 is disposed on the side of the first doped conductive layer 2 facing away from the substrate 1, and the first electrode 3 is electrically connected to the first doped conductive layer 2. Specifically, the first electrode 3 can contact the first doped conductive layer 2 directly or indirectly to form an electrical connection structure. The first electrode 3 is used to collect and summarize the current of the solar cell 100. Exemplarily, the first electrode 3 can be prepared by screen printing and sintering. In some embodiments, the metal paste used to prepare the first electrode 3 can be one or more of aluminum, silver, gold, nickel, molybdenum, or copper, without limitation.

[0086] Along the thickness direction Z of the substrate 1, a second doped conductive layer 4 is disposed on the second surface 12 of the substrate 1. The second surface 12 is disposed opposite to the first surface 11, and the second surface 12 can be a textured or polished surface. Specifically, the second doped conductive layer 4 can be disposed within or above the second surface 12 of the substrate 1. Taking the second surface 12 as a backlight surface as an example, the second doped conductive layer 4 can serve as a field passivation layer, improving the passivation effect on the second surface 12 of the substrate 1. The doping elements in the second doped conductive layer 4 are the same as those in the substrate 1, and a concentration difference is formed between them, thereby forming a high-low junction. This allows the second doped conductive layer 4 to form good contact with the metal electrode and to form band bending on the second surface 12 of the substrate 1, achieving selective carrier transport and reducing recombination losses. Exemplarily, any one of physical vapor deposition, chemical vapor deposition, plasma-enhanced chemical vapor deposition, or atomic layer deposition can be used to deposit a tunneling layer and a doped polycrystalline silicon, microcrystalline silicon, or amorphous silicon layer on the second surface 12 to form the second doped conductive layer 4. For example, a second doped conductive layer 4 can also be formed directly on the second surface 12 side of the substrate 1 by diffusion of doping elements into the interior of the substrate 1. The diffusion depth of the doping elements is about 200 nm, which can be set according to actual needs and is not limited here.

[0087] The second electrode 5 is disposed on the side of the second doped conductive layer 4 facing away from the substrate 1, and the second electrode 5 is electrically connected to the second doped conductive layer 4. Specifically, the second electrode 5 can contact the second doped conductive layer 4 directly or indirectly to form an electrical connection structure. The second electrode 5 is used to collect and summarize the current of the solar cell 100. Exemplarily, the second electrode 5 can be prepared by screen printing and sintering. In some embodiments, the metal paste used to prepare the second electrode 5 can be one or more of aluminum, silver, gold, nickel, molybdenum, or copper, without limitation.

[0088] A first passivation layer 6 is disposed on the surface of the first doped conductive layer 2 facing away from the substrate 1. The first passivation layer 6 effectively passivates the surface of the first doped conductive layer 2 facing away from the substrate 1, reducing the interface state density, thereby reducing minority carrier recombination, improving carrier transport efficiency at the interface, and increasing the efficiency of the solar cell 100. The first passivation layer 6 can also reduce or eliminate reflected light from the solar cell surface and increase light transmittance, further improving the photoelectric conversion efficiency of the solar cell. Exemplarily, the first passivation layer 6 can be deposited using plasma-enhanced chemical vapor deposition (PECVD). Other methods, such as organic chemical vapor deposition (OCCVD), can also be used to form the first passivation layer 6. The first passivation layer 6 can be a single-layer structure or a multilayer structure, and the refractive index and thickness of each layer can be designed accordingly. Specifically, the first passivation layer 6 can be any one or more combinations of silicon nitride, silicon oxynitride, and silicon oxide layers. Of course, other types of passivation layers can also be used for the first passivation layer 6, and this is not limited here.

[0089] The second passivation layer 7 is disposed on the surface of the second doped conductive layer 4 facing away from the substrate 1. The second passivation layer 7 effectively passivates the surface of the second doped conductive layer 4 facing away from the substrate 1, reducing the interface state density, reducing minority carrier recombination, improving carrier transport efficiency at the interface, and increasing the efficiency of the solar cell 100. Exemplarily, the second passivation layer 7 can be deposited using plasma-enhanced chemical vapor deposition (PECVD). Other methods, such as organic chemical vapor deposition (OCCVD), can also be used to form the second passivation layer 7. The second passivation layer 7 can be a single-layer structure or a multilayer structure, and the thickness of each layer can be designed accordingly. Specifically, the second passivation layer 7 can be any one or a combination of silicon nitride, silicon oxynitride, silicon oxide, and aluminum oxide. Of course, other types of passivation layers can also be used for the second passivation layer 7, and this is not limited here.

[0090] This application also provides a method for preparing a solar cell, used to prepare the solar cell 100 in any of the above embodiments, such as... Figure 5 As shown, the method for fabricating a solar cell includes the following steps:

[0091] Step S1: Prepare substrate 1.

[0092] In this step, such as Figure 1As shown, substrate 1 is used to receive incident light and generate photogenerated carriers. In some embodiments, substrate 1 is a silicon substrate, which may include one or more of monocrystalline silicon, polycrystalline silicon, amorphous silicon, or microcrystalline silicon. In other embodiments, the material of substrate 1 may also be silicon carbide, organic materials, or multi-component compounds. Multi-component compounds may include, but are not limited to, perovskite, gallium arsenide, cadmium telluride, copper indium selenide, etc. Exemplarily, substrate 1 in this application is a monocrystalline silicon substrate. Substrate 1 contains dopant elements, and the conductivity type of the dopant elements can be N-type or P-type. N-type elements can be group V elements such as phosphorus (P), bismuth (Bi), antimony (Sb), or arsenic (As), and P-type elements can be group III elements such as boron (B), aluminum (Al), gallium (Ga), or indium (In). For example, when substrate 1 is a P-type silicon substrate, the conductivity type of its internal dopant elements is P-type. As another example, when substrate 1 is an N-type silicon substrate, the conductivity type of its internal dopant elements is N-type. For example, in this embodiment of the application, substrate 1 is an N-type silicon substrate to improve the conversion efficiency of solar cell 100 and reduce manufacturing costs. Substrate 1 refers to a sheet-like structure that includes at least a silicon substrate. In some embodiments, substrate 1 may also include a tunneling layer and an intrinsic layer.

[0093] Step S2: Texturing is performed on the first surface 11 of the substrate 1. The first surface 11 has a pyramid structure 111, which includes a apex 111a, a middle part 111b, and a bottom 111c arranged sequentially along the thickness direction of the substrate 1.

[0094] In this step, such as Figure 1 As shown, a pyramid structure 111 can be formed by texturing the first surface 11 using laser or chemical etching methods. Along the thickness direction Z of the substrate 1, the pyramid structure 111 includes a apex 111a, a middle section 111b, and a base 111c arranged sequentially. Specifically, along the thickness direction Z of the substrate 1, the apex 111a accounts for 10% to 30% of the height of the pyramid structure 111, the base 111c accounts for 10% to 30% of the height of the pyramid structure 111, and the remaining part is the middle section 111b.

[0095] It should be noted that, as Figure 1 and Figure 2As shown, the first surface 11 can be either the light-receiving surface or the back-lighting surface of the solar cell 100. When the first surface 11 is a light-receiving surface, for example, the first doped conductive layer 2 can be a P-type emitter layer formed by boron expansion on the first surface 11, where the doping element can be boron. When the first surface 11 is a back-lighting surface, for example, the first doped conductive layer 2 can be an N-type doped conductive layer formed by phosphorus expansion on the first surface 11, where the doping element can be phosphorus. The specific configuration can be adjusted according to actual needs, and this application does not impose any limitations on this. This application uses the example of the first surface 11 being a light-receiving surface and the first doped conductive layer 2 being a P-type emitter layer formed by boron expansion on the first surface 11 for illustration.

[0096] Step S3: A dopant source is deposited on the first surface 11, and the dopant element in the dopant source diffuses into the substrate 1 to form a first doped conductive layer 2. The average doping concentration of the dopant element in the first doped conductive layer 2 at the top 111a is n1, the average doping concentration of the dopant element in the first doped conductive layer 2 at the middle 111b of the tower is n2, and the average doping concentration of the dopant element in the first doped conductive layer 2 at the bottom 111c of the tower is n3, where 1.05 < n1 / n2 ≤ 2 and 1.05 < n2 / n3 ≤ 2.

[0097] In this step, such as Figure 2 As shown, the first doped conductive layer 2 is formed inside the first surface 11. Taking the first surface 11 as the light-receiving surface as an example, the first doped conductive layer 2 can be a P-type emitter layer formed by boron diffusion on the first surface 11. The first doped conductive layer 2 has a different conductivity type than the dopant element in the substrate 1, so that the two can jointly form a PN junction structure. Exemplarily, the first doped conductive layer 2 can also be made of doped polycrystalline silicon, microcrystalline silicon, or amorphous silicon with a conductivity type opposite to that of the dopant element in the substrate 1. For example, when the substrate 1 is an N-type silicon substrate, a tunneling layer and a polycrystalline silicon, microcrystalline silicon, or amorphous silicon layer can be formed on the first surface 11 of the substrate 1 by low-pressure chemical vapor deposition (LPCVD) or plasma-enhanced chemical vapor deposition (PECVD), and the first doped conductive layer 2 is formed by doping the polycrystalline silicon, microcrystalline silicon, or amorphous silicon layer with a P-type dopant element. The specific configuration can be set according to actual needs and is not limited here.

[0098] In this embodiment, as Figure 2As shown, the average doping concentration of the doped elements in the first doped conductive layer 2 decreases sequentially at the top 111a, middle 111b, and bottom 111c, allowing a high-low junction to be formed between the top 111a, middle 111b, and bottom 111c, resulting in band bending, selective carrier transport, and reduced electron-hole recombination losses.

[0099] Furthermore, during the metallization process of the solar cell 100, the first doped conductive layer 2 of the spire 111a typically contacts the core region that forms contact with the metal electrode, i.e., as shown in the image. Figure 3 As shown, the first electrode 3 is typically in contact with the first doped conductive layer 2 of the tower tip 111a. Therefore, the doping concentration of the doped element in the first doped conductive layer 2 is higher in the tower tip 111a, enabling better ohmic contact performance with the metal electrode and improving the fill factor of the solar cell 100. The middle section 111b connects the tower tip 111a and the tower bottom 111c. The doping concentration of the doped element in the first doped conductive layer 2 in the middle section 111b is lower than that in the tower tip 111a but higher than that in the tower bottom 111c, allowing for better lateral current transmission and reducing Auger recombination. The first doped conductive layer 2 in the tower bottom 111c is far from the metal electrode, having a relatively small impact on the ohmic contact performance with the metal electrode. The lower doping concentration of the doped element in the first doped conductive layer 2 in the tower tip 111a minimizes Auger recombination, ensuring better passivation of the surface in this region, improving the open-circuit voltage and fill factor of the solar cell 100, thereby increasing the conversion efficiency of the solar cell 100.

[0100] Furthermore, when the average doping concentration n1 of the doped element in the first doped conductive layer 2 at the top 111a, the average doping concentration n2 of the doped element in the first doped conductive layer 2 at the middle 111b, and the average doping concentration n3 of the doped element in the first doped conductive layer 2 at the bottom 111c satisfying 1.05 < n1 / n2 ≤ 2 and 1.05 < n2 / n3 ≤ 2, the doping concentration of the doped element at the top 111a, the middle 111b, and the bottom 111c can be significantly different, thereby enabling functional differentiation of each region. More significantly, while ensuring better passivation effect, it can form a better ohmic contact with the metal electrode, and can avoid the average doping concentration n1 of the dopant element at the top of the tower 111a being much higher than the average doping concentration n2 at the middle of the tower 111b and the doping concentration of the dopant element at the bottom of the tower 111c being too low. This makes the doping concentration of the dopant element gradually transition between the top of the tower 111a, the middle of the tower 111b and the bottom of the tower 111c, which is conducive to the transport of charge carriers, improves the fill factor and open circuit voltage, and thus improves the conversion efficiency of the solar cell 100.

[0101] In one specific embodiment, a doping source is deposited on the first surface 11, and the doping element in the doping source diffuses into the substrate 1 to form a first doped conductive layer 2, specifically including:

[0102] Step S31: Raise the temperature to 800℃~930℃ and hold for 50s~200s.

[0103] In this step, the substrate 1 can be heated at a relatively gentle rate from room temperature to 800℃~930℃ within 10min~20min, and held at this temperature for 50s~200s to make the temperature of the substrate 1 uniform and consistent, so as to provide a stable process environment for subsequent deposition steps.

[0104] In some embodiments, the temperature is raised to 800°C to 930°C, specifically 800°C, 830°C, 850°C, 880°C, 900°C, 930°C, etc. Within the above range, the temperature of the substrate 1 is much higher than the starting temperature of the diffusion reaction, but lower than the final advance temperature, thereby providing a stable process environment for subsequent deposition steps.

[0105] In some embodiments, the heat preservation time is 50s to 200s, specifically 50s, 80s, 100s, 120s, 150s, 180s, 200s, etc., which can be set according to the heating temperature. Within the above range, the temperature of the substrate 1 in the furnace can be made highly consistent, avoiding batch-to-batch differences in solar cell performance.

[0106] Step S32: Introduce the dopant source and oxygen for 8 min to 15 min to allow the dopant source to be deposited on the first surface 11.

[0107] In this step, a doped glass layer can be formed on the first surface 11 of the substrate 1. Taking boron as the doping source as an example, the doped glass layer is a borosilicate glass layer. Specifically, the boron source can be BCl3 or BBr3, etc., and there are no restrictions on its application.

[0108] Step S33: Raise the temperature to 870℃~970℃ and hold it for 10min~20min, then lower it to room temperature so that the dopant elements in the dopant source diffuse into the substrate 1.

[0109] In this step, by further increasing the temperature, the dopant elements in the dopant source can be pushed into the substrate 1 using high temperature.

[0110] In some embodiments, the temperature may be further increased to 870°C to 970°C, specifically 870°C, 890°C, 900°C, 920°C, 940°C, 950°C, 970°C, etc., within the above range, to ensure that the dopant element in the dopant source can diffuse into the substrate 1.

[0111] In some embodiments, the heat preservation time is 10 min to 20 min, specifically 10 min, 12 min, 14 min, 16 min, 18 min, 20 min, etc., which can be set according to the temperature rise. Within the above range, thermal radiation and thermal convection do not reach complete equilibrium, thereby creating a temperature difference between the top 111a, middle 111b, and bottom 111c of the pyramid structure 111, so as to facilitate the formation of concentration differences of dopant elements in the top 111a, middle 111b, and bottom 111c.

[0112] In this embodiment, as Figure 2 As shown, the higher the temperature, the easier it is for the dopant source to diffuse into the substrate 1. Furthermore, due to the relatively short holding time, thermal radiation and convection are not completely balanced, resulting in a temperature difference between the pyramid structure 111's tip 111a, middle section 111b, and bottom section 111c. The tip 111a has the highest temperature, while the bottom section 111c has the lowest. Therefore, the dopant source at the tip 111a diffuses more easily into the substrate 1. This allows for differences in dopant concentration at the tip 111a, middle section 111b, and bottom section 111c during the dopant's propagation into the substrate 1, creating a differentiated doping effect where the average dopant concentration decreases sequentially from the tip 111a, middle section 111b, and bottom section 111c.

[0113] In addition, since the volume of the top part 111a, the middle part 111b, and the bottom part 111c increases sequentially, during the diffusion process, the doping concentration of the same number of dopant atoms is more likely to be higher in the top part 111a and lower in the bottom part 111c.

[0114] Furthermore, after raising the temperature to 870℃~970℃ and holding it at that temperature for 10min~20min, and then lowering it to room temperature to allow the dopant element in the dopant source to diffuse into the substrate 1, the deposition of the dopant source on the first surface 11 and the diffusion of the dopant element in the dopant source into the substrate 1 to form the first doped conductive layer 2 further includes:

[0115] Step S38: Perform wet alkaline etching on the first surface 11.

[0116] In this step, wet etching can preserve the morphology of the first surface 11 to reduce optical loss.

[0117] Step S39: Oxidize the first surface 11 to allow the doped elements to diffuse further into the substrate 1 to form the first doped conductive layer 2.

[0118] In this step, the dopant element can be further diffused into the substrate 1 to form the doping concentration and doping depth required for the solar cell 100, so as to meet the usage requirements of the solar cell 100. Specifically, the temperature can be further raised to 1000℃~1060℃, oxygen can be introduced, and the temperature can be maintained for 30min~90min, and then cooled to room temperature.

[0119] In this embodiment, during wet alkaline etching, the alkaline etching concentration is affected by the doping concentration. The alkaline etching rate is inversely correlated with the doping concentration within a certain range; that is, within a certain range, the higher the doping concentration, the slower the alkaline etching rate. During the etching of the first surface 11 using wet alkaline etching, the average doping concentration of the dopant element decreases sequentially from the top 111a, middle 111b, to the bottom 111c. Therefore, the etching rate of the alkaline etching at the top 111a, middle 111b, and bottom 111c increases sequentially. This means the bottom 111c is more easily etched than the top 111a, further reducing the doping element concentration and thus further decreasing the doping concentration in the bottom 111c. Therefore, wet alkaline etching can maintain the morphology of the first surface 11, reducing optical losses, while further increasing the difference in the sequential decrease in the average doping concentration of the dopant element at the top 111a, middle 111b, and bottom 111c. Oxidation enables the dopant elements to diffuse further into the substrate 1, forming the doping concentration and doping depth required for the solar cell 100, so as to meet the usage requirements of the solar cell 100.

[0120] In another specific embodiment, a doping source is deposited on the first surface 11, and the doping element in the doping source diffuses into the substrate 1 to form a first doped conductive layer 2, specifically including:

[0121] Step S34: Raise the temperature to 800℃~930℃ and hold for 150s~400s.

[0122] In this step, the substrate 1 can be heated at a relatively gentle rate from room temperature to 800℃~930℃ within 10min~20min, and held at this temperature for 150s~400s to make the temperature of the substrate 1 uniform and consistent, so as to provide a stable process environment for subsequent deposition steps.

[0123] In some embodiments, the temperature is raised to 800°C to 930°C, specifically 800°C, 830°C, 850°C, 880°C, 900°C, 930°C, etc. Within the above range, the temperature of the substrate 1 is much higher than the starting temperature of the diffusion reaction, but lower than the final advance temperature, thereby providing a stable process environment for subsequent deposition steps.

[0124] In some embodiments, the heat preservation time is 150s~400s, specifically 150s, 180s, 200s, 200s, 250s, 300s, 350s, 400s, etc., which can be set according to the heating temperature. Within the above range, the temperature of the substrate 1 in the furnace can be made highly consistent, avoiding batch-to-batch differences in solar cell performance.

[0125] Step S35: Introduce the dopant source and oxygen for 8 min to 15 min to allow the dopant source to be deposited on the first surface 11.

[0126] In this step, a doped glass layer can be formed on the first surface 11 of the substrate 1. Taking boron as the doping source as an example, the doped glass layer is a borosilicate glass layer. Specifically, the boron source can be BCl3 or BBr3, etc., and there are no restrictions on its application.

[0127] Step S36: Raise the temperature to 870℃~970℃, keep it at that temperature for 10min~20min, and then lower it to room temperature.

[0128] In this step, by further increasing the temperature, the dopant elements in the dopant source can be pushed into the substrate 1 using high temperature.

[0129] In some embodiments, the temperature may be further increased to 870°C to 970°C, specifically 870°C, 890°C, 900°C, 920°C, 940°C, 950°C, 970°C, etc., within the above range, to ensure that the dopant element in the dopant source can diffuse into the substrate 1.

[0130] In some embodiments, the heat preservation time is 10 min to 20 min, specifically 10 min, 12 min, 14 min, 16 min, 18 min, 20 min, etc., which can be set according to the temperature rise. Within the above range, thermal radiation and thermal convection do not reach complete equilibrium, thereby creating a temperature difference between the top 111a, middle 111b, and bottom 111c of the pyramid structure 111, so as to facilitate the formation of concentration differences of dopant elements in the top 111a, middle 111b, and bottom 111c.

[0131] Step S37: Laser treatment is performed on the first surface 11 to diffuse the dopant elements in the dopant source into the substrate 1.

[0132] In this step, red nanosecond light, continuous red light, green nanosecond light, continuous green light, etc., can be used to laser process the first surface 11 so that the dopant elements in the dopant source diffuse into the substrate 1.

[0133] In this embodiment, the higher the temperature, the easier it is for the dopant source to diffuse into the substrate 1. Furthermore, due to the relatively short heat preservation time, thermal radiation and thermal convection are not completely balanced, resulting in a temperature difference between the pyramid structure 111's apex 111a, middle 111b, and bottom 111c. The apex 111a has the highest temperature, and the bottom 111c has the lowest temperature. Additionally, when the first surface 11 is treated with a laser, the apex 111a of the pyramid structure 111 absorbs energy more easily, causing its temperature to rise further. Therefore, the dopant source at the apex 111a diffuses more easily into the substrate 1. This allows for a difference in dopant concentration between the apex 111a, middle 111b, and bottom 111c as the dopant element propagates into the substrate 1, creating a differentiated doping effect where the average dopant concentration decreases sequentially between the apex 111a, middle 111b, and bottom 111c.

[0134] In addition, since the volume of the top part 111a, the middle part 111b, and the bottom part 111c increases sequentially, during the diffusion process, the doping concentration of the same number of dopant atoms is more likely to be higher in the top part 111a and lower in the bottom part 111c.

[0135] In one specific embodiment, the laser is continuous red light, the laser spot size is 100 μm, the laser power is 300 W to 450 W, and the laser scanning speed is 21000 mm / s to 39000 mm / s. In some other embodiments, the laser may be other lasers with the same function, and this is not limited thereto.

[0136] Furthermore, after laser processing the first surface 11 to diffuse the dopant element from the dopant source into the substrate 1, depositing the dopant source on the first surface 11 and diffusing the dopant element from the dopant source into the substrate 1 to form the first doped conductive layer 2 further includes:

[0137] Step S38: Perform wet alkaline etching on the first surface 11.

[0138] In this step, wet etching can preserve the morphology of the first surface 11 to reduce optical loss.

[0139] Step S39: Oxidize the first surface 11 to allow the doped elements to diffuse further into the substrate 1 to form the first doped conductive layer 2.

[0140] In this step, the dopant element can be further diffused into the substrate 1 to form the doping concentration and doping depth required for the solar cell 100, so as to meet the usage requirements of the solar cell 100. Specifically, the temperature can be further raised to 1000℃~1060℃, oxygen can be introduced, and the temperature can be maintained for 30min~90min, and then cooled to room temperature.

[0141] In this embodiment, during wet alkaline etching, the alkaline etching concentration is affected by the doping concentration. The alkaline etching rate is inversely correlated with the doping concentration within a certain range; that is, within a certain range, the higher the doping concentration, the slower the alkaline etching rate. During the etching of the first surface 11 using wet alkaline etching, the average doping concentration of the dopant element decreases sequentially from the top 111a, middle 111b, to the bottom 111c. Therefore, the etching rate of the alkaline etching at the top 111a, middle 111b, and bottom 111c increases sequentially. This means the bottom 111c is more easily etched than the top 111a, further reducing the doping element concentration and thus further decreasing the doping concentration in the bottom 111c. Therefore, wet alkaline etching can maintain the morphology of the first surface 11, reducing optical losses, while further increasing the difference in the sequential decrease in the average doping concentration of the dopant element at the top 111a, middle 111b, and bottom 111c. Oxidation enables the dopant elements to diffuse further into the substrate 1, forming the doping concentration and doping depth required for the solar cell 100, so as to meet the usage requirements of the solar cell 100.

[0142] This application also provides a photovoltaic module, such as Figure 6 As shown, the photovoltaic module includes a cell string 110, an encapsulation layer 120, and a cover plate 130. The cell string 110 is formed by connecting multiple solar cells 100 from any of the embodiments. The encapsulation layer 120 is used to cover the surface of the cell string 110, and the cover plate 130 is used to cover the surface of the encapsulation layer 120 away from the cell string 110. Since the solar cell 100 has the above-mentioned technical effects, the photovoltaic module including the solar cell 100 should also have the above-mentioned technical effects, which will not be elaborated further here.

[0143] Among them, such as Figure 6As shown, the solar cell 100 is electrically connected in a single piece or in multiple segments to form multiple cell strings 110, which are electrically connected in series and / or parallel. Specifically, the multiple cell strings 110 can be electrically connected to each other via conductive links. An encapsulation layer 120 covers the front and back of the solar cell. Specifically, the encapsulation layer 120 can be an organic encapsulation film such as ethylene-vinyl acetate copolymer (EVA) film, polyvinyl octene copolymer elastomer (POE) film, polyethylene terephthalate (PET) film, or polyvinyl butyral (PVB). The cover plate 130 can be a light-transmitting cover plate such as a glass cover plate or a plastic cover plate. Specifically, the surface of the cover plate 130 facing the encapsulation layer 120 can be an uneven surface to increase the utilization rate of incident light.

[0144] The same or similar parts between the various embodiments in this specification can be referred to mutually. In particular, the device embodiments and terminal embodiments are basically similar to the method embodiments, so the description is relatively simple, and the relevant parts can be referred to the description in the method embodiments.

[0145] The above descriptions are merely specific implementations of the embodiments of this application, but the protection scope of the embodiments of this application is not limited thereto. Any changes or substitutions within the technical scope disclosed in the embodiments of this application should be covered within the protection scope of the embodiments of this application. Therefore, the protection scope of the embodiments of this application should be determined by the protection scope of the claims.

Claims

1. A solar cell, characterized in that, The solar cell includes: The base (1) has a first surface (11) along the thickness direction (Z) of the base (1); the first surface (11) has a pyramid structure (111) along the thickness direction (Z) of the base (1), the pyramid structure (111) including a apex (111a), a middle part (111b) and a bottom (111c) arranged sequentially. A first doped conductive layer (2) is formed inside the first surface (11); the average doping concentration of the doped element in the first doped conductive layer (2) at the top of the tower (111a) is n1, the average doping concentration of the doped element in the first doped conductive layer (2) at the middle part of the tower (111b) is n2, and the average doping concentration of the doped element in the first doped conductive layer (2) at the bottom of the tower (111c) is n3, 1.05 < n1 / n2 ≤ 2, 1.05 < n2 / n3 ≤ 2; The average doping concentration is the average doping concentration of the doping element within a depth of 100 nm on the surface of each region.

2. The solar cell according to claim 1, characterized in that, Along the thickness direction (Z) of the substrate (1) and from the outside of the substrate (1) to the inside of the substrate (1), the doping concentration of the doped element in the first doped conductive layer (2) gradually decreases in the top part (111a).

3. The solar cell according to claim 1, characterized in that, Along the thickness direction (Z) of the substrate (1), the doping elements in the first doped conductive layer (2) are uniformly doped in the middle part (111b) of the tower.

4. The solar cell according to claim 3, characterized in that, The doping concentration of the dopant element in the first doped conductive layer (2) in the middle part (111b) of the tower is 2 × 10⁻⁶. 18 atoms / cm 3 ~1×10 19 atoms / cm 3 .

5. The solar cell according to claim 1, characterized in that, Along the thickness direction (Z) of the substrate (1) and from the outside of the substrate (1) to the inside of the substrate (1), the doping concentration of the doped element in the first doped conductive layer (2) gradually decreases at the bottom of the tower (111c).

6. The solar cell according to claim 1, characterized in that, The doping element is boron or phosphorus.

7. A method for preparing a solar cell, characterized in that, The method for preparing the solar cell according to any one of claims 1 to 6 comprises the following steps: Preparation of substrate (1); A flocking is made on the first surface (11) of the substrate (1); wherein the first surface (11) has a pyramid structure (111) along the thickness direction (Z) of the substrate (1), the pyramid structure (111) includes a apex (111a), a middle part (111b) and a bottom (111c) arranged sequentially. A doping source is deposited on the first surface (11), and the doping element in the doping source diffuses into the substrate (1) to form a first doped conductive layer (2); wherein the average doping concentration of the doping element in the first doped conductive layer (2) at the top of the tower (111a) is n1, the average doping concentration of the doping element in the first doped conductive layer (2) at the middle part of the tower (111b) is n2, the average doping concentration of the doping element in the first doped conductive layer (2) at the bottom of the tower (111c) is n3, 1.05 < n1 / n2 ≤ 2, 1.05 < n2 / n3 ≤ 2.

8. The method for preparing a solar cell according to claim 7, characterized in that, The step of depositing a doped source on the first surface (11) and allowing the doped element in the doped source to diffuse into the substrate (1) to form a first doped conductive layer (2) specifically includes: Raise the temperature to 800℃~930℃ and hold for 50s~200s; A dopant source and oxygen are introduced for 8 min to 15 min to allow the dopant source to be deposited on the first surface (11). The temperature is raised to 870℃~970℃ and held for 10min~20min before being lowered to room temperature so that the dopant elements in the dopant source diffuse into the substrate (1).

9. The method for preparing a solar cell according to claim 7, characterized in that, The step of depositing a doped source on the first surface (11) and allowing the doped element in the doped source to diffuse into the substrate (1) to form a first doped conductive layer (2) specifically includes: Raise the temperature to 800℃~930℃ and hold for 150s~400s; A dopant source and oxygen are introduced for 8 min to 15 min to allow the dopant source to be deposited on the first surface (11). Raise the temperature to 870℃~970℃ and keep it at that temperature for 10min~20min, then lower it to room temperature; The first surface (11) is laser-processed to allow the dopant elements in the dopant source to diffuse into the substrate (1).

10. The method for preparing a solar cell according to claim 9, characterized in that, The laser is continuous red light, the laser spot size is 100μm, the laser power is 300w~450w, and the laser scanning speed is 21000mm / s~39000mm / s.

11. The method for preparing a solar cell according to claim 8 or 9, characterized in that, After raising the temperature to 870℃~970℃ and holding it at that temperature for 10min~20min, then lowering it to room temperature to allow the dopant element in the dopant source to diffuse into the substrate (1), or after laser processing the first surface (11) to allow the dopant element in the dopant source to diffuse into the substrate (1), the method for fabricating the solar cell further includes: The first surface (11) is subjected to wet alkaline etching; The first surface (11) is oxidized so that the doped element diffuses further into the substrate (1) to form the first doped conductive layer (2).

12. A photovoltaic module, characterized in that, The photovoltaic module includes: A battery string (110) is formed by connecting a plurality of solar cells (100) as described in any one of claims 1 to 6; An encapsulation layer (120) is used to cover the surface of the battery string (110); A cover plate (130) is used to cover the surface of the encapsulation layer (120) away from the battery string (110).

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