Photovoltaic cell and method of manufacturing the same, photovoltaic module

Abstract

This disclosure relates to the photovoltaic field, providing a photovoltaic cell and its manufacturing method, and a photovoltaic module. The photovoltaic cell includes: a substrate with at least one surface comprising multiple tower base structures, wherein the one-dimensional dimensions of the multiple tower base structures have a first uniformity and the height has a second uniformity, the first uniformity and the second uniformity being less than or equal to 10%; among the multiple tower base structures on the same surface, the average one-dimensional dimension is a first average value, the difference between the maximum and minimum one-dimensional dimensions is a first difference and the sum of the differences is a first total, and the first uniformity is the ratio of the first difference to twice the first average value or the ratio of the first difference to the first total; among the multiple tower base structures on the same surface, the average height is a second average value, the difference between the maximum and minimum height is a second difference and the sum of the differences is a second total, and the second uniformity is the ratio of the second difference to twice the second average value or the ratio of the second difference to the second total, which at least helps to reduce the interface state density of the substrate surface.

Description

Technical Field

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

[0002] With the rapid development of solar photovoltaic technology, photovoltaic cells are becoming increasingly widely used as a sustainable and clean energy source. A photovoltaic cell is a device that uses the photovoltaic principle to generate charge carriers to convert solar energy into electrical energy. Electrodes are typically used in photovoltaic cells to extract these charge carriers, thus efficiently utilizing the electrical energy. Currently, the mainstream types of photovoltaic cells include BC cells (Back Contact), TOPCON (Tunnel Oxide Passivated Contact) cells, PERC cells (Passivated emitter and rear cell), and heterojunction cells (Heterojunction with Intrinsic Thin-film, abbreviated as HIT or HJT).

[0003] However, when designing various films on the substrate of a photovoltaic cell, the surface condition of the substrate, such as surface roughness or surface flatness, affects the contact performance between the substrate and the films, and thus the photoelectric conversion efficiency of the photovoltaic cell. Therefore, further research is needed on the surface morphology of the substrate in photovoltaic cells. Summary of the Invention

[0004] This disclosure provides a photovoltaic cell and its manufacturing method, as well as a photovoltaic module, which at least helps to reduce the interface state density on the substrate surface.

[0005] This disclosure provides a photovoltaic cell, comprising: a substrate, at least one surface of the substrate including a plurality of tower base structures, wherein the one-dimensional dimensions of the plurality of tower base structures have a first uniformity, and the height of the plurality of tower base structures has a second uniformity, wherein the first uniformity is less than or equal to 10% and the second uniformity is less than or equal to 10%; wherein, among the plurality of tower base structures on the same surface, the average of the one-dimensional dimensions is a first average value, the difference between the maximum and minimum values ​​of the one-dimensional dimensions is a first difference value, and the sum of the maximum and minimum values ​​of the one-dimensional dimensions is a first sum, and the first uniformity is the ratio of the first difference value to twice the first average value or the ratio of the first difference value to the first sum; among the plurality of tower base structures on the same surface, the average height is a second average value, the difference between the maximum and minimum values ​​of the height is a second difference value, and the sum of the maximum and minimum values ​​of the height is a second sum, and the second uniformity is the ratio of the second difference value to twice the second average value or the ratio of the second difference value to the second sum.

[0006] Optionally, the arithmetic mean deviation of the surface profile of the plurality of said tower base structures is 0.2 nm to 0.8 nm.

[0007] Optionally, the one-dimensional dimension of the tower base structure is 10µm to 80µm; and / or, the height of the tower base structure is less than or equal to 800nm.

[0008] Optionally, the substrate has a first surface and a second surface opposite each other along a first direction, the first direction being the thickness direction of the substrate; at least a portion of at least one of the first surface and the second surface includes a plurality of the tower base structures.

[0009] Optionally, at least one of the first surface and the second surface includes a first region and a second region alternately distributed along a second direction, the second direction intersecting the first direction; the first region includes a plurality of the tower base structures, and the second region includes a plurality of first pyramid structures; the photovoltaic cell further includes: a first passivation contact structure, at least located in the first region; a second passivation contact structure, at least located in the second region; the first passivation contact structure is doped with an N-type dopant element, and the second passivation contact structure is doped with a P-type dopant element.

[0010] Optionally, one of the first face and the second face includes a plurality of the base structures, and the other includes a plurality of second pyramid structures.

[0011] Optionally, the photovoltaic cell further includes a passivation layer located on the surface comprising the plurality of the tower base structures.

[0012] This disclosure also provides a method for manufacturing a photovoltaic cell, comprising: providing an initial substrate; performing alkaline polishing on at least a portion of the initial substrate to form a substrate with at least one surface including a plurality of tower base structures, wherein the one-dimensional dimensions of the plurality of tower base structures have a first uniformity, and the height of the plurality of tower base structures has a second uniformity, the first uniformity being less than or equal to 10% and the second uniformity being less than or equal to 10%; wherein, among the plurality of tower base structures on the same surface, the average of the one-dimensional dimensions is a first average value, the difference between the maximum and minimum values ​​of the one-dimensional dimensions is a first difference, and the sum of the maximum and minimum values ​​of the one-dimensional dimensions is a first sum, and the first uniformity is the ratio of the first difference to twice the first average value or the ratio of the first difference to the first sum; among the plurality of tower base structures on the same surface, the average height is a second average value, the difference between the maximum and minimum values ​​of the height is a second difference, and the sum of the maximum and minimum values ​​of the height is a second sum, and the second uniformity is the ratio of the second difference to twice the second average value or the ratio of the second difference to the second sum.

[0013] Optionally, the step of performing the alkaline polishing treatment on at least a portion of the initial substrate includes: adjusting preset process parameters in the alkaline polishing treatment to increase the one-dimensional dimension of the formed tower base structure while reducing the height of the formed tower base structure; wherein the preset process parameters include at least one of the following: the concentration of the alkaline polishing solution used in the alkaline polishing treatment, the process temperature of the alkaline polishing treatment, the process duration of the alkaline polishing treatment, the flow rate of the gas bubbled into the alkaline polishing solution in the alkaline polishing treatment, or the power percentage of the circulating pump used in the alkaline polishing treatment.

[0014] Optionally, the alkaline polishing solution includes potassium hydroxide or sodium hydroxide, wherein the mass fraction of potassium hydroxide in the alkaline polishing solution is 1 wt% to 15 wt%, or the mass fraction of sodium hydroxide in the alkaline polishing solution is 1 wt% to 15 wt%.

[0015] Optionally, the process temperature for the alkaline polishing treatment is 60℃~85℃.

[0016] Optionally, the alkaline polishing process takes 1 to 15 minutes.

[0017] Optionally, the power percentage of the circulating pump used in the alkaline polishing process is 60% to 98%.

[0018] Optionally, the flow rate of the gas bubbled into the alkaline polishing solution during the alkaline polishing treatment is 0.6 m³ / s. 3 / h to 3.0m 3 / h.

[0019] In another aspect, this disclosure provides a photovoltaic module, comprising: a battery string, formed by connecting a plurality of photovoltaic cells as described in any one of the preceding claims, or formed by connecting a plurality of photovoltaic cells formed by a manufacturing method of photovoltaic cells as described in any one of the preceding claims; an encapsulating film for covering the surface of the battery string; and a cover plate for covering the surface of the encapsulating film opposite to the battery string.

[0020] The technical solution provided in this disclosure has at least the following advantages: On the one hand, the first uniformity of the one-dimensional dimensions of multiple base structures on the same surface of the substrate is less than or equal to 10%, which helps to control the difference in the one-dimensional dimensions of two random base structures on the same surface, thereby improving the uniformity of the distribution of base structures per unit area on the surface. In other words, it makes the number of base structures distributed in different unit areas on the surface similar. On the other hand, the second uniformity of the height of multiple base structures on the same surface of the substrate is less than or equal to 10%, which helps to control the difference in the height of two random base structures on the same surface, thereby reducing the degree of unevenness caused by base structures along the first direction on the surface. Thus, it is beneficial to both promote the uniform distribution of multiple base structures on the surface and reduce the degree of unevenness along the first direction on the surface, thereby improving the microscopic smoothness of the surface from two aspects. This, in turn, reduces the interface state density of the substrate surface, increases the minority carrier lifetime at the surface, and improves the uniformity and compactness of the film thickness of the passivation layer formed on the surface, thereby further reducing the risk of carrier recombination at the interface between the surface and the passivation layer. Attached Figure Description

[0021] 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.

[0022] Figure 1 This is a partial cross-sectional schematic diagram of a photovoltaic cell provided in an embodiment of the present disclosure; Figure 2 A partial top view of the surface of a photovoltaic cell including multiple tower base structures according to an embodiment of the present disclosure; Figure 3 This is another partial top view of the surface of a photovoltaic cell including multiple tower base structures, provided in an embodiment of the present disclosure; Figure 4 This is a partial cross-sectional schematic diagram of the tower base structure in a photovoltaic cell provided in an embodiment of the present disclosure; Figure 5 This is another partial cross-sectional schematic diagram of a photovoltaic cell provided in an embodiment of the present disclosure; Figure 6 This is another partial cross-sectional schematic diagram of a photovoltaic cell provided in an embodiment of the present disclosure; Figure 7This is another partial cross-sectional schematic diagram of a photovoltaic cell provided in an embodiment of the present disclosure; Figure 8 A process flow diagram of a method for manufacturing a photovoltaic cell according to another embodiment of this disclosure; Figure 9 A partial three-dimensional structural diagram of a cell string in a photovoltaic module provided in yet another embodiment of this disclosure; Figure 10 This is a partial cross-sectional structural diagram of a photovoltaic module provided in yet another embodiment of the present disclosure.

[0023] Explanation of reference numerals in the attached figures: 100. Substrate; 10. Surface; 110. First surface; 120. Second surface; 130. First region; 140. Second region; 101. Tower base structure; 102. First pyramid structure; 103. First passivation contact structure; 113. First dielectric layer; 123. First doped layer; 104. Second passivation contact structure; 114. Second dielectric layer; 124. Second doped layer; 105. Second pyramid structure; 106. Passivation layer; 117. First electrode; 127. Second electrode; 40. Photovoltaic cell; 41. Encapsulating film; 42. Cover plate; 43. Solder ribbon. Detailed Implementation

[0024] As can be seen from the background technology, the surface morphology of the substrate in photovoltaic cells needs further research.

[0025] This disclosure provides a photovoltaic cell and its manufacturing method, as well as a photovoltaic module. In the photovoltaic cell, on one hand, the first uniformity of the one-dimensional dimensions of multiple base structures on the same surface of the substrate is less than or equal to 10%. This is beneficial for controlling the difference in the one-dimensional dimensions of two randomly selected base structures on the same surface to be small, thereby improving the uniformity of the distribution of base structures per unit area on the surface. In other words, it makes the number of base structures distributed in different unit areas on the surface similar. On the other hand, the second uniformity of the height of multiple base structures on the same surface of the substrate is less than or equal to 10%. This is beneficial for controlling the difference in the height of two randomly selected base structures on the same surface to be small, thereby reducing the degree of unevenness caused by the base structures along the first direction on the surface. Thus, it is beneficial for both promoting the uniform distribution of multiple base structures on the surface and reducing the degree of unevenness along the first direction on the surface, thereby improving the microscopic smoothness of the surface from two aspects. This, in turn, reduces the interface state density of the substrate surface, increases the minority carrier lifetime at the surface, and improves the uniformity and density of the film thickness of the passivation layer subsequently formed on the surface, thereby further reducing the risk of carrier recombination at the interface between the surface and the passivation layer.

[0026] 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, "multiple" means two or more (including two), unless otherwise explicitly defined. Similarly, "multiple sets" refers to two or more sets (including two sets), and "multiple pieces" refers to two or more pieces (including two pieces).

[0027] 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.

[0028] 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.

[0029] 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," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the embodiments of this disclosure and simplifying the description. They do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the embodiments of this disclosure. For example, if the device or element in the illustration is inverted, then the element described as "below," "under," "below," or "bottom" of other elements or features will be oriented "above" or "top" of said other elements or features. Therefore, the term "below" may, depending on the context in which the term is used, encompass both above and below orientations, which will be obvious to those skilled in the art. Materials may be oriented in other ways (e.g., rotated 90 degrees, inverted, flipped), and the spatial relative descriptive terms used herein may be interpreted accordingly.

[0030] 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.

[0031] In the description of the embodiments disclosed herein, electrical connection between one component and another means that both components are made of conductive materials, and the two components are in direct contact and connected or connected via other conductive materials, so that current flows between the two components when the device is generating electricity. Electrical contact between one component and another means that the two components are not only in contact, but also that current flows between them when the device is generating electricity because both components are made of conductive materials.

[0032] In the description of embodiments of this disclosure, the terms "about," "approximately," "roughly," or "about" for a numerical value referring to a specific parameter include the numerical value, and those skilled in the art will understand that the deviation from the numerical value is within acceptable tolerances of the specific parameter. For example, "about" or "about" for a numerical value may include additional numerical values ​​that are in the range of 90.0% to 110.0% of the numerical value, such as in the range of 95.0% to 105.0%, 97.5% to 102.5%, 99.0% to 101.0%, 99.5% to 100.5%, or 99.9% to 100.1%.

[0033] In the accompanying drawings corresponding to the embodiments of this disclosure, the thickness and / or area of ​​layers, films, panels, regions, etc., are enlarged for better understanding and ease of description. Throughout the specification, the same reference numerals denote the same elements. 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 on a portion of the edge of the entire surface.

[0034] 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. When a component (such as a layer, film, region, or substrate) is described as being 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 an intermediate component between the two components. Conversely, when a component is described as being on the surface of another component, or a component is "directly" on another component, or another component is formed or disposed on the surface of a component, it indicates that there is no intermediate component between the two components. For simplicity and clarity, various components may be drawn at any scale. In the drawings, some components may be omitted for simplicity.

[0035] 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 of the various embodiments and the appended claims, the term "the component" is also intended to include the plural form unless the context clearly indicates otherwise.

[0036] The “components” mentioned above can refer to layers, films, regions, parts, structures, etc.

[0037] 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 embodiments. However, the technical solutions claimed in the embodiments of this disclosure can be implemented even without these technical details and various variations and modifications based on the following embodiments.

[0038] This disclosure provides a photovoltaic cell according to one embodiment. The photovoltaic cell provided by this disclosure will be described in detail below with reference to the accompanying drawings.

[0039] Figure 1 This is a partial cross-sectional schematic diagram of a photovoltaic cell provided in an embodiment of the present disclosure; Figure 2 A partial top view of the surface of a photovoltaic cell including multiple tower base structures according to an embodiment of the present disclosure; Figure 3 This is another partial top view of the surface of a photovoltaic cell including multiple tower base structures, provided in an embodiment of the present disclosure; Figure 4 This is a partial cross-sectional schematic diagram of a tower base structure in a photovoltaic cell according to an embodiment of this disclosure. It should be noted that, to illustrate the flatness of surface 10 and the differences in the order of magnitude of the relevant dimensions of the tower base structure across the entire surface 10, Figure 1 The tower base structure included on surface 10 is not shown in the diagram.

[0040] Reference Figures 1 to 4The photovoltaic cell includes: a substrate 100, at least one surface 10 of the substrate 100 including a plurality of tower base structures 101, the one-dimensional dimension L of the plurality of tower base structures 101 having a first uniformity, the height H of the plurality of tower base structures 101 having a second uniformity, the first uniformity being less than or equal to 10% and the second uniformity being less than or equal to 10%.

[0041] Among the multiple tower base structures 101 on the same surface 10, the average value of one-dimensional dimension L is the first average value, the difference between the maximum and minimum values ​​of one-dimensional dimension L is the first difference value, the sum of the maximum and minimum values ​​of one-dimensional dimension L is the first sum, and the first uniformity is the ratio of the first difference value to twice the first average value or the ratio of the first difference value to the first sum.

[0042] Among the multiple tower base structures 101 on the same surface 10, the average value of height H is the second average value, the difference between the maximum and minimum values ​​of height H is the second difference value, the sum of the maximum and minimum values ​​of height H is the second sum, and the second uniformity is the ratio of the second difference value to twice the second average value or the ratio of the second difference value to the second sum.

[0043] It is worth noting that among the multiple base structures 101 on the same surface 10, the sum of the maximum and minimum values ​​of the one-dimensional dimension L is not much different from twice the average value of the one-dimensional dimension L. Therefore, both can be used as the denominator of the first uniformity to characterize the average value of the one-dimensional dimension L of the multiple base structures 101 on the same surface 10. Based on this, the numerator of the first uniformity is designed as the difference between the maximum and minimum values ​​of the one-dimensional dimension L of the multiple base structures 101 on the same surface 10, i.e., the first difference. The larger the first difference, the larger the first uniformity, thus enabling the first uniformity to characterize the difference of the one-dimensional dimension L of the multiple base structures 101 on the same surface 10. The smaller the first uniformity, the smaller the difference in one-dimensional size L between two random tower base structures 101 on the same surface 10. The more similar the one-dimensional size L of the tower base structures 101 distributed on the surface 10 in the microstructure, that is, the area occupied by different tower base structures 101 in the surface 10 is similar. This is more conducive to improving the uniformity of the distribution of tower base structures 101 in a unit area in the surface 10. In other words, it makes the number of tower base structures 101 distributed in different unit areas in the surface 10 similar, thereby improving the micro-flatness of the surface 10.

[0044] Similarly, among the multiple base structures 101 on the same surface 10, the sum of the maximum and minimum heights H is not significantly different from twice the average height H. Therefore, both can be used as the denominator of the second uniformity to characterize the average height H of the multiple base structures 101 on the same surface 10. Based on this, the numerator of the second uniformity is designed as the difference between the maximum and minimum heights H of the multiple base structures 101 on the same surface 10, i.e., the second difference. The larger the second difference, the greater the second uniformity, thus enabling the second uniformity to characterize the differences in height H among the multiple base structures 101 on the same surface 10. The smaller the second uniformity, the smaller the difference in height H between two random base structures 101 on the same surface 10, and the more similar the heights H of the base structures 101 distributed on the surface 10 in the microstructure. This results in a lower degree of unevenness caused by the base structures 101 along the first direction X on the surface 10, which also helps to improve the microscopic smoothness of the surface 10.

[0045] Therefore, in the photovoltaic cell provided in one embodiment of this disclosure, in order to improve the microscopic flatness of the surface 10 of the substrate 100, not only is the surface 10 made to include multiple tower base structures 101, but also the one-dimensional dimension L of the multiple tower base structures 101 is uniformly designed from a microscopic perspective, and the height H of the multiple tower base structures 101 is uniformly designed. That is, the first uniformity of the one-dimensional dimension L of the multiple tower base structures 101 is designed to be less than or equal to 10%, and the second uniformity of the height H of the multiple tower base structures 101 is less than or equal to 10%. This improves the uniformity of the distribution of the base structure 101 per unit area on the surface 10, and also reduces the degree of unevenness caused by the base structure 101 along the first direction X on the surface 10. This improves the microscopic smoothness of the surface 10 in two ways, thereby reducing the interface state density of the surface 10 of the substrate 100, increasing the minority carrier lifetime at the surface 10, and improving the uniformity and compactness of the film thickness of the passivation layer formed on the surface 10. This further reduces the risk of carrier recombination at the interface between the surface 10 and the passivation layer.

[0046] Wherein, the first direction X can be regarded as the thickness direction of the substrate 100.

[0047] It should be noted that, ideally, the first uniformity of the one-dimensional dimension L of the multiple tower base structures 101 can be 0%, in other words, the one-dimensional dimension L of the multiple tower base structures 101 on the same surface 10 is not different; similarly, the second uniformity of the height H of the multiple tower base structures 101 can be 0%, in other words, the height H of the multiple tower base structures 101 on the same surface 10 is not different.

[0048] In some cases, the first uniformity of the one-dimensional dimension L of multiple tower base structures 101 can be 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, or 1%, etc.

[0049] In some cases, the second uniformity of the height H of multiple tower base structures 101 can be 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2% or 1%, etc.

[0050] In some cases, the method for measuring the first uniformity of the one-dimensional dimension L of multiple tower base structures 101 can be to take a specific area in the surface 10 and measure the one-dimensional dimension L of the tower base structure 101 at five points: the upper left, upper right, lower left, lower right, and the middle of the specific area. The first uniformity is the ratio of the difference between the maximum and minimum values ​​of the one-dimensional dimension L of the tower base structure 101 at the five points to twice the average value of the one-dimensional dimension L of the tower base structure 101 at the five points.

[0051] In some cases, the method for measuring the second uniformity of the height H of multiple tower base structures 101 can be to take a specific area in the surface 10 and measure the height H of the tower base structure 101 at five points: the upper left, upper right, lower left, lower right, and middle of the specific area. The second uniformity is the ratio of the difference between the maximum and minimum height H of the tower base structure 101 at the five points to twice the average height H of the tower base structure 101 at the five points.

[0052] The photovoltaic cell provided in one embodiment of this disclosure will be described in more detail below with reference to the accompanying drawings.

[0053] In some embodiments, in conjunction with reference Figures 2 to 4 The base structure 101 can be considered as the remaining structure of a pyramid structure after removing the top and middle parts; that is, the base structure 101 is the bottom part of the pyramid structure. In other words, the base structure 101 can be considered as a frustum structure that protrudes inwards away from the base 100.

[0054] It should be noted that the one-dimensional dimension L of the tower base structure 101 includes either the side length or the diagonal length of the orthographic projection pattern of the bottom of the tower base structure 101 onto the base 100. For example, taking the orthographic projection pattern of the bottom of the tower base structure 101 onto the base 100 as a regular quadrilateral, the one-dimensional dimension L of the tower base structure 101 is either the side length or the diagonal length of the regular quadrilateral.

[0055] In practical applications, the orthographic projection pattern of the bottom of the tower base structure onto the base can also be an irregular polygon. In this case, the length of the long side or the length of the diagonal of the orthographic projection pattern of the bottom of the tower base structure onto the base is not absolute, but is artificially defined to characterize the one-dimensional dimensions of the tower base structure. For example, if the orthographic projection pattern of the bottom of the tower base structure onto the base is an irregular quadrilateral, the length of the bottom of the tower base structure can be defined as the length of the longest side of the irregular quadrilateral, the width of the bottom of the tower base structure can be defined as the length of the shortest side of the irregular quadrilateral, and the length of the diagonal of the bottom of the tower base structure can be defined as the length of the longest diagonal of the irregular quadrilateral. It should be understood that the above is only an illustrative example, and in practice, it can be flexibly defined according to actual needs. In addition, the orthographic projection pattern of the bottom of the tower base structure onto the base can be an irregular quadrilateral, or other irregular polygons, circles, or irregular shapes that are approximately circular. In this case, the one-dimensional dimension of the tower base structure is to select multiple regions with different specific areas at the bottom of the tower base structure. These specific areas can be flexibly defined according to actual needs, and then the average value of the side length, diagonal, or diameter of multiple regions with different specific areas is calculated.

[0056] In addition, refer to Figure 4 The height H of the tower base structure 101 can be considered as the height difference between the bottom surface of the tower base structure 101 and the top surface of the tower base structure 101 away from the base 100 along the first direction X.

[0057] In some embodiments, the substrate 100 may be an N-type semiconductor substrate doped with N-type dopants or a P-type semiconductor substrate doped with P-type dopants.

[0058] In some embodiments, the material of the substrate 100 may be an elemental semiconductor material. Specifically, the elemental semiconductor material is composed of a single element, such as silicon or germanium. The elemental semiconductor material may be monocrystalline, polycrystalline, amorphous, or microcrystalline; for example, silicon may be at least one of monocrystalline silicon, polycrystalline silicon, amorphous silicon, or microcrystalline silicon. In other embodiments, the material of the substrate 100 may also be a compound semiconductor material. Common compound semiconductor materials include, but are not limited to, silicon germanide, silicon carbide, gallium arsenide, indium gallium dihydrogen phosphate, perovskite, cadmium telluride, and copper indium selenide.

[0059] In some embodiments, in conjunction with reference Figure 1 and Figure 2The arithmetic mean deviation of the surface 10 of multiple tower base structures 101, i.e., Ra, can be 0.2nm to 0.8nm, for example, it can be 0.2nm, 0.25nm, 0.3nm, 0.35nm, 0.4nm, 0.45nm, 0.5nm, 0.55nm, 0.6nm, 0.65nm, 0.7nm, 0.75nm or 0.8nm, etc.

[0060] It is worth emphasizing that the one-dimensional dimensions L and height H of the multiple tower base structures 101 on the same surface 10 are designed separately to make the first uniformity less than or equal to 10% and the second uniformity less than or equal to 10%, which significantly improves the uniformity of the tower base structures 101 in both the horizontal and vertical directions. This improves the microscopic flatness of the surface 10 to a microscopic level, such as the nanometer level, and makes the arithmetic mean deviation of the profile of the surface 10 including the multiple tower base structures 101 be 0.2nm~0.8nm.

[0061] Furthermore, the arithmetic mean deviation of the profile of the surface 10, including multiple tower base structures 101, is 0.2 nm to 0.8 nm. This means the arithmetic mean deviation of the surface 10 is below 1 nm, which helps to significantly reduce the reflectivity of the surface 10 for long-wavelength light, such as light with wavelengths greater than 800 nm. In other words, reducing the arithmetic mean deviation of the profile of the surface 10, including multiple tower base structures 101, helps to reduce diffuse reflection loss of light and allows more long-wavelength light to penetrate to the surface 10 and be absorbed by the substrate 100. Moreover, the synergistic effect of the tower base structure 101 and the passivation layer formed based on the tower base structure 101 can reduce interface scattering of the passivation layer. In particular, when the passivation layer is a tandem cell, it can reduce interface scattering at the junctions of the internal layers, thereby reducing the reflectivity of the passivation layer, for example, to less than or equal to 10%, and increasing the short-circuit current density of the photovoltaic cell, for example, by approximately 1 mA / cm². 2 ~2mA / cm 2 .

[0062] In some embodiments, reference Figure 2 or Figure 3 The one-dimensional dimension L of the tower base structure 101 can be 10µm to 80µm, for example, it can be 10µm to 30µm, 30µm to 50µm, 50µm to 70µm, or 70µm to 80µm, etc. It should be noted that, for emphasis, Figure 2 and Figure 3 The specific values ​​of the one-dimensional dimension L of part of the tower base structure 101 are marked with red lines and red font.

[0063] Optionally, the one-dimensional dimension L of the tower base structure 101 can be 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm, 20μm, 21μm, 22μm, 23μm, 24μm, 25μm, 26μm, 27μm, 28μm, 29μm or 30μm, etc.

[0064] Optionally, the one-dimensional dimension L of the tower base structure 101 can be 35μm, 40μm, 45μm, 50μm, 55μm, 60μm, 65μm, 70μm, 75μm or 80μm, etc.

[0065] In some embodiments, reference Figure 4 The height H of the tower base structure 101 can be less than or equal to 800nm, for example, it can be 800nm, 750nm, 700nm, 650nm, 600nm, 550nm, 500nm, 450nm, 400nm, 350nm, 300nm, 250nm, 200nm, 150nm, 100nm or 50nm, etc.

[0066] It should be noted that on the same surface 10, the one-dimensional dimension L of multiple tower base structures 101 can all be in the range of 10µm to 80µm, and the height H of multiple tower base structures 101 can all be less than or equal to 800nm. Furthermore, for emphasis, Figure 4 The specific value of the height H of a single tower base structure 101 is marked in yellow with yellow lines and yellow font.

[0067] In some embodiments, reference Figure 5 or Figure 6 The substrate 100 has a first surface 110 and a second surface 120 opposite each other along a first direction X, where the first direction X is the thickness direction of the substrate 100; at least a portion of at least one of the first surface 110 and the second surface 120 may include a plurality of tower base structures 101. It is worth noting that for photovoltaic cells that require at least a partial surface of the substrate to have an approximate polished surface, the surface requiring an approximate polished surface can be designed as the surface 10 including a plurality of tower base structures 101 provided in an embodiment of this disclosure.

[0068] in, Figure 5 This is another partial cross-sectional schematic diagram of a photovoltaic cell provided in an embodiment of the present disclosure; Figure 6 This is another partial cross-sectional schematic diagram of a photovoltaic cell provided in an embodiment of the present disclosure.

[0069] The following provides a detailed explanation of the different types of photovoltaic cells.

[0070] In some cases, photovoltaic cells can be BC cells; refer to the reference.Figure 2 and Figure 5 At least one of the first surface 110 and the second surface 120 may include a first region 130 and a second region 140 that are alternately distributed along a second direction Y, the second direction Y intersecting the first direction X; the first region 130 includes a plurality of tower base structures 101, and the second region 140 includes a plurality of first pyramid structures 102; the photovoltaic cell may also include: a first passivation contact structure 103, at least located in the first region 130; a second passivation contact structure 104, at least located in the second region 140; the first passivation contact structure 103 is doped with an N-type dopant element, and the second passivation contact structure 104 is doped with a P-type dopant element.

[0071] It should be noted that, Figure 5 The example only uses the second surface 120, which includes a first region 130 and a second region 140 that are alternately distributed along the second direction Y.

[0072] It is worth noting that for the first passivation contact structure 103 doped with N-type dopant, the majority carriers are electrons; for the second passivation contact structure 104 doped with P-type dopant, the majority carriers are holes. Based on this, the first region 130 is designed to include multiple pyramidal structures 101, meaning the first region 130 is designed to be as close as possible to a polished surface. This facilitates the subsequent formation of a smoother and more uniform first passivation contact structure 103, improving the uniformity and density of the film thickness of the first passivation contact structure 103. This, in turn, enhances the conductivity of the first passivation contact structure 103 itself and its passivation effect on the first region 130, thereby improving the electron collection efficiency. The second region 140 is designed to include multiple first pyramidal structures 102, meaning the second region 140 is designed to have a textured surface. This helps increase the length of the effective transmission path of light inside the photovoltaic cell and reduces light reflection on the photovoltaic cell surface. This, in turn, improves the efficiency of photogenerated carriers generated in the portion of the substrate 100 located in the second region 140 from the perspective of improving light absorption utilization, thereby improving the hole collection efficiency. Thus, based on the separate design of the surface morphology of the first region 130 and the second region 140, it is beneficial to improve the carrier collection efficiency of the first passivation contact structure 103 and the second passivation contact structure 104 from different angles, thereby improving the photoelectric conversion efficiency of the photovoltaic cell.

[0073] In practical applications, the surface morphology of the second zone can be designed to approximate a polished surface, depending on the requirements. Furthermore, when the first zone of the second surface includes a pyramidal structure, the surface morphology of the first surface can approximate a polished surface or a textured surface including a pyramidal structure.

[0074] In some examples, continue to refer to Figure 5The first passivation contact structure 103 may include a first dielectric layer 113 and a first doped layer 123 stacked along the first direction X; the second passivation contact structure 104 may include a second dielectric layer 114 and a second doped layer 124 stacked along the first direction X; wherein, the first doped layer 123 is doped with an N-type dopant element, and the second doped layer 124 is doped with a P-type dopant element.

[0075] The following provides a detailed explanation of the different types of back-contact photovoltaic cells.

[0076] In some examples, the materials of the first dielectric layer 113 and the second dielectric layer 114 may both include at least one of amorphous silicon, microcrystalline silicon, or nanocrystalline silicon. Thus, the photovoltaic cell can be an HBC cell (Heterojunction Back Contact Cell).

[0077] In other examples, the materials of the first dielectric layer 113 and the second dielectric layer 114 may both include at least one of silicon oxide, aluminum oxide, silicon nitride, silicon oxynitride, titanium oxide, hafnium oxide, zirconium oxide, or silicon carbide. Thus, the photovoltaic cell can be a TBC cell (TOPCon Back Contact Cell).

[0078] In other examples, the material of one of the first dielectric layer 113 and the second dielectric layer 114 may include at least one of amorphous silicon, microcrystalline silicon, or nanocrystalline silicon, and the material of the other of the first dielectric layer 113 and the second dielectric layer 114 may include at least one of silicon oxide, aluminum oxide, silicon nitride, silicon oxynitride, titanium oxide, hafnium oxide, zirconium oxide, or silicon carbide. Thus, the photovoltaic cell can be an HTBC cell (Heterojunction Tunnel Oxide Passivated BackContact Cell).

[0079] In the various examples described above, the crystalline state of the first doped layer 123 and the crystalline state of the second doped layer 124 may include at least one of the following: amorphous, nanocrystalline, microcrystalline (a state that simultaneously possesses a monocrystalline and amorphous state is called microcrystalline), or a mixed state of nanocrystalline and microcrystalline. For example, the materials of the first doped layer 123 and the second doped layer 124 may include monocrystalline, polycrystalline, amorphous, or microcrystalline silicon material layers.

[0080] It is worth noting that when the photovoltaic cell is an HTBC cell, the first doped layer 123 can be polycrystalline, and the second doped layer 124 can be at least one of amorphous or microcrystalline. Based on this, compared to a polycrystalline first doped layer 123, designing the second region 140 to include multiple first pyramid structures 102 is beneficial for improving the passivation effect of the second doped layer 124 on the substrate 100 and reducing the subsequent contact resistance between the second doped layer 124 and the second electrode, thereby helping to reduce the series resistance of the photovoltaic cell and improve the fill factor of the photovoltaic cell.

[0081] In some examples, the N-type dopant can be at least one of group V elements such as phosphorus (P), bismuth (Bi), antimony (Sb), or arsenic (As); the P-type dopant can be at least one of group III elements such as boron (B), aluminum (Al), gallium (Ga), or indium (In).

[0082] In some examples, continue to refer to Figure 5 The photovoltaic cell may further include: a first electrode 117 located on the side of the first passivation contact structure 103 away from the substrate 100; and a second electrode 127 located on the side of the second passivation contact structure 104 away from the substrate 100.

[0083] In other cases, photovoltaic cells can be cells with electrodes on both sides; see reference. Figure 2 and Figure 6 One of the first face 110 and the second face 120 may include multiple base structures 101, and the other may include multiple second pyramid structures 105.

[0084] It should be noted that one of the first surface 110 and the second surface 120 can be the front side of the photovoltaic cell, and the other can be the back side of the photovoltaic cell. In some examples, the photovoltaic cell can be a single-sided cell, in which case the front side of the substrate 100 can serve as the light-receiving surface to receive incident light, and the back side serves as the backlight surface. In other examples, the photovoltaic cell can be a bi-sided cell, in which case both the front and back sides of the substrate 100 can serve as light-receiving surfaces and can both be used to receive incident light, wherein the front side is the primary light-receiving surface and the back side is the secondary light-receiving surface. It is worth noting that the backlight surface referred to in one embodiment 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 a backlight surface.

[0085] also, Figure 6 The first side 110 is the front side of the photovoltaic cell and includes multiple second pyramid structures 105. The second side 120 is the back side of the photovoltaic cell and includes a base structure 101 (see reference). Figure 2 ( ) is used as an example.

[0086] Thus, for the first surface 110, which is mainly used to receive light, designing it to include multiple second pyramid structures 105 helps improve the light-trapping effect of the first surface 110, thereby improving the light absorption and utilization rate of the first surface 110. For the second surface 120, which is generally designed with a passivation film layer, designing it to include multiple pyramid base structures 101 helps improve the quality of the passivation film layer formed on the second surface 120, thereby improving the passivation effect of the passivation film layer on the second surface 120. For example, it improves the passivation capability of the doped conductive parts in the TOPCON cell, and reduces the interface state density of the second surface 120, increases the minority carrier lifetime at the second surface 120, and reduces the risk of carrier recombination at the interface between the second surface 120 and the passivation film layer. This helps to improve the bifaciality of the photovoltaic cell.

[0087] In some cases, photovoltaic cells can be cells with electrodes on both sides; see reference. Figure 2 and Figure 7 , Figure 7 This is a partial cross-sectional view of a photovoltaic cell provided in an embodiment of the present disclosure. Both the first surface 110 and the second surface 120 may include multiple tower base structures 101.

[0088] In some examples, the photovoltaic cell can be a heterojunction cell. The microscopic flatness of the first surface 110 and the second surface 120 is improved by using the tower base structure 101, which is beneficial to simultaneously improve the film quality of the intrinsic layer and the amorphous silicon layer located on the first surface 110 and the second surface 120, thereby improving the passivation effect on the first surface 110 and the second surface 120.

[0089] In some embodiments, reference Figure 7 The photovoltaic cell may also include a passivation layer 106 located on the surface 10 comprising a plurality of tower base structures 101. This helps to further reduce light reflection on the photovoltaic cell surface using the passivation layer 106, thereby further improving the photovoltaic cell's light absorption and utilization efficiency.

[0090] It is worth noting that, based on the improvement of the micro-smoothness of the surface 10 by the tower base structure 101, the film quality of the passivation layer 106 disposed on the surface 10 can be improved, and the surface of the passivation layer 106 can also have good micro-smoothness. Furthermore, it can reduce the interface state density between the substrate 100 and the passivation layer 106, for example, reducing the interface state density to less than 10. 11 cm -2 ·eV -1 This reduces the recombination rate of charge carriers at surface 10, for example, by reducing the recombination rate to less than 100 cm / s.

[0091] Furthermore, when an electrode is subsequently formed on the passivation layer 106 and electrically connected to the substrate 100, the improved film quality of the passivation layer 106 due to the tower base structure 101 helps to reduce the contact resistivity between the electrode and the substrate 100, for example, reducing the contact resistivity to less than 5 mΩ·cm. 2 This also increases the fill factor of photovoltaic electronics by approximately 1% to 2%.

[0092] In some cases, the material of the passivation layer 106 may include at least one of aluminum oxide, silicon nitride, intrinsic amorphous silicon, silicon oxide, or silicon oxynitride.

[0093] In some cases, refer to Figure 5 The passivation layer (not shown in the figure) may be located on the surface of the first passivation contact structure 103 and the second passivation contact structure 104 away from the substrate 100.

[0094] In some cases, refer to Figure 5 The first passivation contact structure 103 and the second passivation contact structure 104 are located on one of the first surface 110 and the second surface 120, and the passivation layer (not shown in the figure) may also be located on the other of the first surface 110 and the second surface 120.

[0095] It should be noted that in practical applications, in the same photovoltaic cell, only the first region of the second side may include multiple tower base structures, and the passivation layer is located on the surface of the first passivation contact structure and the second passivation contact structure away from the substrate and on the first side.

[0096] In summary, designing the one-dimensional dimension L of multiple base structures 101 on the same surface 10 to have a first uniformity of less than or equal to 10% helps to control the difference in the one-dimensional dimension L of two random base structures 101 on the same surface 10 to be small, thereby improving the uniformity of the distribution of base structures 101 per unit area in the surface 10. In other words, it makes the number of base structures 101 distributed in different unit areas of the surface 10 similar. Similarly, designing the height H of multiple base structures 101 on the same surface 10 to have a second uniformity of less than or equal to 10% helps to control the difference in the height H of two random base structures 101 on the same surface 10 to be small, thereby reducing the degree of unevenness caused by the base structures 101 along the first direction X in the surface 10. This approach not only promotes the uniform distribution of multiple tower base structures 101 in the surface 10, but also reduces the unevenness of the surface 10 along the first direction X. This improves the microscopic smoothness of the surface 10 in two ways, thereby reducing the interface state density of the surface 10 of the substrate 100, increasing the minority carrier lifetime at the surface 10, and improving the uniformity and compactness of the film thickness of the passivation layer subsequently formed on the surface 10. This further reduces the risk of carrier recombination at the interface between the surface 10 and the passivation layer.

[0097] Another embodiment of this disclosure provides a method for manufacturing a photovoltaic cell, used to form the photovoltaic cell provided in the foregoing embodiment. The manufacturing method of the photovoltaic cell provided in another embodiment of this disclosure will be described in detail below with reference to the accompanying drawings. It should be noted that parts that are the same as or corresponding to those in the foregoing embodiments can be referred to the corresponding descriptions in the foregoing embodiments, and will not be repeated hereafter.

[0098] Reference Figure 8 as well as Figures 1 to 4 , Figure 8 A process flow diagram of a method for manufacturing a photovoltaic cell according to another embodiment of this disclosure; the method for manufacturing a photovoltaic cell includes at least the following steps: S1: Provides the initial base.

[0099] S2: At least a portion of the initial substrate is subjected to alkaline polishing to form at least one surface 10 of a substrate 100 comprising a plurality of tower base structures 101, wherein the one-dimensional dimension L of the plurality of tower base structures 101 has a first uniformity and the height H of the plurality of tower base structures 101 has a second uniformity, wherein the first uniformity is less than or equal to 10% and the second uniformity is less than or equal to 10%.

[0100] Among the multiple tower base structures 101 on the same surface 10, the average value of one-dimensional dimension L is the first average value, the difference between the maximum and minimum values ​​of one-dimensional dimension L is the first difference value, the sum of the maximum and minimum values ​​of one-dimensional dimension L is the first sum, and the first uniformity is the ratio of the first difference value to twice the first average value or the ratio of the first difference value to the first sum; among the multiple tower base structures 101 on the same surface 10, the average value of height H is the second average value, the difference between the maximum and minimum values ​​of height H is the second difference value, the sum of the maximum and minimum values ​​of height H is the second sum, and the second uniformity is the ratio of the second difference value to twice the second average value or the ratio of the second difference value to the second sum.

[0101] It is worth noting that using alkaline polishing to form a substrate 100 comprising at least one surface 10 including multiple tower base structures 101 not only helps to control the one-dimensional dimension L of the multiple tower base structures 101 to have a first uniformity and the height H of the multiple tower base structures 101 to have a second uniformity, and both the first uniformity and the second uniformity are less than or equal to 10%, thereby improving the microscopic smoothness of the surface 10 from two aspects, but also the process of forming the tower base structure 101 by alkaline polishing is simple and easy to implement, so as to facilitate industrialization.

[0102] In some cases, the initial substrate is a structure that has undergone etching or laser treatment in at least part of its area. With the help of alkaline treatment, it is beneficial to remove the damage caused by the etching or laser treatment of the initial substrate, to form a surface 10 with high microscopic flatness, and to reduce the interface state density of the surface 10 based on the unified control of the one-dimensional dimension L and height H of multiple tower base structures 101. This can improve the electrical performance of photovoltaic cells in three aspects, such as reducing minority carrier lifetime, improving the absorption and utilization rate of light, and improving the collection efficiency of charge carriers.

[0103] The recombination rate of minority carriers is proportional to both the interface state density and the defect density within the substrate 100. Therefore, alkaline treatment can not only remove damage in the initial substrate and reduce the defect density within the final substrate 100, but also reduce the interface state density on the surface 10, both of which help to reduce the recombination rate of minority carriers and thus improve the minority carrier lifetime. For example, the minority carrier lifetime can be improved by about 3 to 5 times.

[0104] In some cases, compared to a substrate that has not undergone the alkaline polishing treatment in the photovoltaic cell manufacturing method provided in another embodiment of this disclosure, the effective defect state density of a substrate 100 that has undergone the alkaline polishing treatment in the photovoltaic cell manufacturing method provided in another embodiment of this disclosure can be increased from 10. 15 cm -3 Reduced to 10 12 cm -3 and below.

[0105] In some cases, compared to a surface that has not undergone alkaline polishing in the manufacturing method of a photovoltaic cell provided in another embodiment of the present disclosure, which has a reflectivity greater than or equal to 35%, the reflectivity of a surface 10 that has undergone alkaline polishing in the manufacturing method of a photovoltaic cell provided in another embodiment of the present disclosure can be reduced to 25% or less, for example, 10%.

[0106] In some embodiments, in conjunction with reference Figure 8 as well as Figures 1 to 4 The step of performing alkaline polishing on at least a portion of the initial substrate may include: adjusting preset process parameters in the alkaline polishing process to increase the one-dimensional dimension L of the formed tower base structure 101 while reducing the height H of the formed tower base structure 101; wherein the preset process parameters include at least one of the following: the concentration of the alkaline polishing solution used in the alkaline polishing process, the process temperature of the alkaline polishing process, the process duration of the alkaline polishing process, the flow rate of the gas blown into the alkaline polishing solution in the alkaline polishing process, or the power percentage of the circulating pump used in the alkaline polishing process.

[0107] It is worth noting that, on the one hand, increasing the one-dimensional dimension L of the formed base structure 101 helps to reduce the number of base structures 101 per unit area on the surface 10, thereby improving the microscopic smoothness of the surface 10; on the other hand, reducing the height H of the formed base structure 101 helps to reduce the degree of unevenness or undulation of the surface 10 in the first direction X, thereby improving the microscopic smoothness of the surface 10. Thus, the microscopic smoothness of the surface 10 can be improved from different dimensions.

[0108] In addition, at least one of a plurality of preset process parameters can be selected to control the degree of etching of the initial substrate by alkaline polishing, thereby achieving the purpose of precisely controlling the microscopic smoothness of at least one surface 10 of the final substrate 100.

[0109] In some cases, compared with a surface that has not undergone alkaline polishing in the manufacturing method of a photovoltaic cell provided in another embodiment of the present disclosure, the arithmetic mean deviation of the profile of a surface 10 that has undergone alkaline polishing in the manufacturing method of a photovoltaic cell provided in another embodiment of the present disclosure can be reduced from 5 nm to 0.5 nm.

[0110] The following is a detailed description of the alkaline polishing solution used in the alkaline polishing treatment.

[0111] In some cases, the alkaline polishing solution may include potassium hydroxide. The concentration of the alkaline polishing solution is the mass fraction of potassium hydroxide in it. The mass fraction of potassium hydroxide in the alkaline polishing solution can be from 1 wt% to 15 wt%, for example, it can be 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, or 15 wt%. Preferably, the mass fraction of potassium hydroxide in the alkaline polishing solution can be from 8 wt% to 12 wt%.

[0112] In other cases, the alkaline polishing solution may include sodium hydroxide. The concentration of the alkaline polishing solution is the mass fraction of sodium hydroxide in it. The mass fraction of sodium hydroxide in the alkaline polishing solution can be from 1 wt% to 15 wt%, for example, it can be 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, or 15 wt%. Preferably, the mass fraction of sodium hydroxide in the alkaline polishing solution can be from 8 wt% to 12 wt%.

[0113] It is worth noting that if the mass fraction of potassium hydroxide or sodium hydroxide in the alkaline polishing solution is less than 1 wt%, the concentration of hydroxide ions in the alkaline polishing solution is low, resulting in a low etching rate for the initial substrate, for example, an etching rate of less than 0.5 µm / min. This makes it difficult to completely remove the damage to the initial substrate caused by previous processes, and the residual damage defects are not conducive to improving minority carrier lifetime. If the mass fraction of potassium hydroxide or sodium hydroxide in the alkaline polishing solution is higher than 15 wt%, the concentration of hydroxide ions in the alkaline polishing solution is high, the viscosity of the alkaline polishing solution increases, and it is easy for reactants to accumulate locally. For example, the diffusion of silicate ions is easily hindered, resulting in local aggregation at the reaction interface. This leads to pitting on the final substrate surface, which may cause the arithmetic mean deviation of the substrate surface profile to be greater than 10 nm. Moreover, the high concentration of hydroxide ions in the alkaline polishing solution increases the probability of hydrogen adhesion, further reducing the surface smoothness of the substrate. Based on this, the mass fraction of potassium hydroxide or sodium hydroxide in the alkaline polishing solution is designed to be 1wt% to 15wt%, which is beneficial to ensure that the concentration of hydroxide ions in the alkaline polishing solution is moderate, thereby ensuring that the etching rate of the alkaline polishing solution on the initial substrate is moderate, for example, the etching rate is 1µm / min to 2µm / min. Then the generation rate of the reactants and the diffusion rate of the reactants are matched, so as to effectively avoid the local accumulation of reactants, thereby ensuring that the surface 10 of the final substrate 100 has high microscopic smoothness.

[0114] The following provides a detailed explanation of some other process parameters in the alkaline polishing process.

[0115] In some cases, the process temperature for alkaline polishing can be between 60℃ and 85℃, for example, 60℃, 61℃, 62℃, 63℃, 64℃, 65℃, 66℃, 67℃, 68℃, 69℃, 70℃, 71℃, 72℃, 73℃, 74℃, 75℃, 76℃, 77℃, 78℃, 79℃, 80℃, 81℃, 82℃, 83℃, 84℃, or 85℃, etc. Preferably, it is between 70℃ and 75℃. More preferably, the process temperature for alkaline polishing can be between 70℃ and 80℃.

[0116] It is worth noting that if the alkaline polishing process temperature is below 60℃, the etching rate of the alkaline polishing solution on the initial substrate will also be low, for example, less than 0.8µm / min. This not only limits the removal of damage to the initial substrate from previous processes, but also makes it difficult to planarize local crystalline phases, resulting in increased surface roughness due to localized crystalline phase protrusions. If the alkaline polishing process temperature is above 85℃, the generation rate of hydrogen bubbles will increase or even surge, for example, reaching as high as 10. 4 pcs / cm 2The presence of hydrogen bubbles increases the risk of localized over-etching, leading to reduced surface smoothness of the substrate. Therefore, the alkaline polishing process temperature is designed to be between 60℃ and 85℃. This also helps ensure a moderate etching rate of the alkaline polishing solution on the initial substrate, for example, 1.2µm / min to 1.8µm / min, avoiding the generation of excessive hydrogen bubbles and thus ensuring that the final substrate 100 has a high microscopic smoothness on its surface.

[0117] In some cases, the process time for alkaline polishing can be from 1 min to 15 min, for example, it can be 1 min, 1.5 min, 2 min, 2.5 min, 3 min, 3.5 min, 4 min, 4.5 min, 5 min, 5.5 min, 6 min, 6.5 min, 7 min, 7.5 min, 8 min, 8.5 min, 9 min, 9.5 min, 10 min, 10.5 min, 11 min, 11.5 min, 12 min, 12.5 min, 13 min, 13.5 min, 14 min, 14.5 min, or 15 min, etc.

[0118] It is worth noting that the thickness of the damaged portion of the initial substrate in the previous process has a significant impact on the process time of alkaline polishing. The process time of alkaline polishing is designed to be 1 min to 15 min, which helps to ensure that the damage of the entire thickness of the initial substrate is removed.

[0119] In some cases, the power percentage of the circulating pump used in alkaline polishing can be 60% to 98%, for example, it can be 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, or 98%, etc.

[0120] It is worth noting that using a circulating pump keeps the alkaline polishing solution in a flowing state, promoting the reaction between the alkaline polishing solution and the initial substrate, and removing reactants and heat generated by the reaction. Based on this, the power percentage of the circulating pump is designed to be 60%~98%, that is, controlling the ratio of the working power to the rated power of the circulating pump to 60%~98%. This helps ensure a moderate flow rate of the alkaline polishing solution, avoiding both excessive bubbles due to an excessive power percentage and bubble retention due to an insufficient power percentage. This ensures a suitable flow rate to remove bubbles, thus preventing a decrease in the microscopic smoothness of the final substrate 100 surface 10 caused by excessive or retained bubbles. Furthermore, it avoids mechanical damage to the final substrate 100 caused by an excessive power percentage, and a moderate power percentage allows sufficient reaction time between the alkaline polishing solution and the initial substrate, avoiding waste of the alkaline polishing solution due to an excessive power percentage. In addition, it prevents the accumulation of reactants on the substrate 100.

[0121] In some cases, the flow rate of gas bubbled into the alkaline polishing solution during alkaline polishing can be 0.6 m³ / s. 3 / h to 3.0m 3 / h, for example, can be 0.6m 3 / h to 1.2m 3 / h, 1.2m 3 / h to 1.8m 3 / h, 1.8m 3 / h to 2.4m 3 / h or 2.4m 3 / h to 3.0m 3 / h etc.

[0122] Optionally, the flow rate of the gas bubbled into the alkaline polishing solution during the alkaline polishing process can be 0.6 m³ / s. 3 / h, 0.65m 3 / h, 0.7m 3 / h, 0.75m 3 / h, 0.8m 3 / h, 0.85m 3 / h, 0.9m 3 / h, 0.95m 3 / h、1m 3 / h, 1.05m 3 / h, 1.1m 3 / h, 1.15m 3 / h or 1.2m 3 / h.

[0123] Optionally, the flow rate of the gas bubbled into the alkaline polishing solution during the alkaline polishing process can be 1.3 m³ / s. 3 / h, 1.4m 3 / h, 1.5m 3 / h, 1.6m 3 / h, 1.7m 3 / h, 1.8m 3 / h, 1.9m 3 / h, 2.0m 3 / h, 2.1m 3 / h, 2.2m 3 / h, 2.3m 3 / h, 2.4m 3 / h, 2.5m 3 / h, 2.6m 3 / h, 2.7m 3 / h, 2.8m 3 / h, 2.9m 3 / h or 3.0m 3 / h.

[0124] It is worth noting that the gas bubbled into the alkaline polishing solution helps to agitate the solution, promoting a more uniform alkali concentration in different areas and resulting in more uniform etching of the initial substrate. Furthermore, it facilitates the removal of hydrogen produced during the reaction, reducing surface defects caused by hydrogen. Based on this, the gas flow rate bubbled into the alkaline polishing solution during the alkaline polishing process was designed to be 0.6 m³ / s. 3 / h to 3.0m 3 / h, which is beneficial to reduce the difference in alkali concentration in different areas of the alkali polishing solution, and can also avoid excessive stirring of the alkali polishing solution, thereby promoting the stable reaction between the alkali polishing solution and the initial substrate, and effectively removing the generated hydrogen gas, thereby improving the microscopic smoothness of the surface 10 of the final substrate 100.

[0125] It should be noted that, in the same alkaline polishing process, the concentration of the alkaline polishing solution, the process temperature of the alkaline polishing process, the process duration of the alkaline polishing process, the flow rate of the gas blown into the alkaline polishing solution during the alkaline polishing process, or the power percentage of the circulating pump used in the alkaline polishing process can all be within the range of values ​​provided above. By optimizing at least one preset process parameter in the alkaline polishing process, the microscopic smoothness of at least one surface 10 of the finally formed substrate 100 can be precisely controlled.

[0126] In some embodiments, after alkaline polishing, the method for manufacturing photovoltaic cells may further include cleaning and drying the substrate 100.

[0127] In some embodiments, in conjunction with reference Figure 2 and Figure 7 After forming the substrate 100, the method for manufacturing photovoltaic cells may further include forming a passivation layer 106 on the surface 10 including a plurality of tower base structures 101.

[0128] In some cases, ALD (Atomic Layer Deposition) processes can be used to deposit alumina and / or silicon oxide to form a passivation layer 106.

[0129] In some cases, PECVD (Plasma Enhanced Chemical Vapor Deposition) can be used to deposit silicon nitride and / or silicon oxynitride to form a passivation layer 106.

[0130] In some cases, intrinsic amorphous silicon can be deposited using PECVD (Plasma Enhanced Chemical Vapor Deposition) to form a passivation layer 106.

[0131] Another embodiment of this disclosure provides a photovoltaic module, including multiple photovoltaic cells provided in the foregoing embodiments, or photovoltaic cells formed by the manufacturing methods of multiple photovoltaic cells provided in the foregoing embodiments. The photovoltaic module is used to convert received light energy into electrical energy. It should be noted that the parts that are the same as or corresponding to the foregoing embodiments can be referred to the corresponding descriptions of the foregoing embodiments, and will not be repeated below.

[0132] Reference Figure 9 , Figure 10 as well as Figures 1 to 4 A photovoltaic module includes: a battery string, which is formed by connecting multiple photovoltaic cells 40 provided in the foregoing embodiments, or by connecting multiple photovoltaic cells 40 formed by the manufacturing method of photovoltaic cells provided in the foregoing embodiments; an encapsulating film 41 for covering the surface of the battery string; and a cover plate 42 for covering the surface of the encapsulating film 41 facing away from the battery string.

[0133] in, Figure 9 A partial three-dimensional structural diagram of a cell string in a photovoltaic module provided in yet another embodiment of this disclosure; Figure 10 This is a partial cross-sectional structural diagram of a photovoltaic module provided in yet another embodiment of the present disclosure.

[0134] In some embodiments, reference Figure 5 Photovoltaic cells can be cells with electrodes on one side only, such as back-contact cells. Back-contact cells include, but are not limited to, IBC cells (Interdigitated Back Contact), HBC cells, TBC cells, or HTBC cells.

[0135] In other embodiments, reference is made to... Figure 6 or Figure 7Photovoltaic cells can be cells with electrodes on both sides, such as TOPCON cells, PERC cells, or heterojunction cells.

[0136] In some cases, multiple photovoltaic cells 40 can be electrically connected via solder ribbons 43. It is worth noting that electrical connection actually means that both are made of conductive materials and are directly connected or connected via other conductive materials. Therefore, when the photovoltaic cells 40 are generating electricity, there is an electrical connection between them.

[0137] It should be noted that, Figure 9 and Figure 10 This illustration only shows one positional relationship between the photovoltaic cells 40, where the photovoltaic cells 40 are back-contact cells, and the side of each photovoltaic cell 40 with electrodes faces the same side. The solder ribbon 43 connects the same side of two adjacent photovoltaic cells 40 respectively. In other embodiments, the photovoltaic cells may also be located on different sides with the side of each adjacent photovoltaic cell having electrodes, in which case the solder ribbon connects the different sides of the two adjacent photovoltaic cells.

[0138] In some embodiments, the photovoltaic cells 40 are electrically connected in the form of a single cell or multiple segments to form multiple cell strings, and the multiple cell strings are electrically connected in series and / or parallel. The photovoltaic cells 40 can be a single cell or a sliced ​​cell, where a sliced ​​cell refers to a cell formed by cutting a complete single cell.

[0139] In some embodiments, the encapsulating film 41 includes a first encapsulating layer and a second encapsulating layer. The first encapsulating layer covers one of the front or back sides of the photovoltaic cell 40, and the second encapsulating layer covers the other of the front or back sides of the photovoltaic cell 40. Specifically, at least one of the first encapsulating layer or the second encapsulating layer may be an organic encapsulating film such as polyvinyl butyral (PVB), ethylene-vinyl acetate copolymer (EVA), polyolefin thermoplastic elastomer (POE), or polyethylene glycol terephthalate (PET). Alternatively, at least one of the first encapsulating layer or the second encapsulating layer may also be an EP film, an EPE film, or a PVP film. Among them, EP film refers to a co-extruded film composed of stacked EVA film and POE film; EPE film refers to a co-extruded film formed by sequentially stacking EVA film, POE film, and EVA film; and PVP film refers to a co-extruded film formed by stacking POE film, EVA film, and POE film. Co-extruded films can be prepared by sequentially extruding one or more raw materials onto another pre-made film during the film processing, or by bonding different types of pre-made films together.

[0140] In some cases, the first encapsulation layer and the second encapsulation layer still have a boundary line before lamination. After lamination, the photovoltaic module will no longer have the concept of a first encapsulation layer and a second encapsulation layer. That is, the first encapsulation layer and the second encapsulation layer have formed an integral encapsulation film 41.

[0141] In some embodiments, the cover plate 42 can be a glass cover plate, a plastic cover plate, or other cover plate with light-transmitting function. Specifically, the surface of the cover plate 42 facing the encapsulating film 41 can be an uneven surface or a textured surface containing multiple raised structures, thereby increasing the utilization rate of incident light. The cover plate 42 includes a first cover plate and a second cover plate, the first cover plate being opposite to the first encapsulation layer, and the second cover plate being opposite to the second encapsulation layer.

[0142] 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 photovoltaic cell, characterized in that, include: The substrate, at least one surface of which includes a plurality of tower base structures, wherein the one-dimensional dimensions of the plurality of tower base structures have a first uniformity and the height of the plurality of tower base structures has a second uniformity, wherein the first uniformity is less than or equal to 10% and the second uniformity is less than or equal to 10%; Among the multiple tower base structures on the same surface, the average value of the one-dimensional dimension is the first average value, the difference between the maximum and minimum values ​​of the one-dimensional dimension is the first difference value, the sum of the maximum and minimum values ​​of the one-dimensional dimension is the first sum, and the first uniformity is the ratio of the first difference value to twice the first average value or the ratio of the first difference value to the first sum. In the plurality of tower base structures on the same surface, the average height is the second average value, the difference between the maximum and minimum height is the second difference value, the sum of the maximum and minimum height is the second sum, and the second uniformity is the ratio of the second difference value to twice the second average value or the ratio of the second difference value to the second sum.

2. The photovoltaic cell according to claim 1, characterized in that, The arithmetic mean deviation of the surface profile of the multiple tower base structures is 0.2 nm to 0.8 nm.

3. The photovoltaic cell according to claim 1, characterized in that, The one-dimensional dimension of the tower base structure is 10µm to 80µm; and / or, the height of the tower base structure is less than or equal to 800nm.

4. The photovoltaic cell according to any one of claims 1 to 3, characterized in that, The substrate has a first surface and a second surface opposite each other along a first direction, the first direction being the thickness direction of the substrate; at least a portion of at least one of the first surface and the second surface includes a plurality of the tower base structures.

5. The photovoltaic cell according to claim 4, characterized in that, At least one of the first surface and the second surface includes a first region and a second region that are alternately distributed along a second direction, the second direction intersecting the first direction; The first area includes multiple base structures, and the second area includes multiple first pyramid structures; The photovoltaic cell further includes: a first passivated contact structure, at least located in the first region; a second passivated contact structure, at least located in the second region; the first passivated contact structure is doped with an N-type dopant element, and the second passivated contact structure is doped with a P-type dopant element.

6. The photovoltaic cell according to claim 4, characterized in that, One of the first face and the second face includes a plurality of the said base structures, and the other includes a plurality of second pyramid structures.

7. The photovoltaic cell according to any one of claims 1 to 3, characterized in that, Also includes: A passivation layer is located on the surface comprising the plurality of the tower base structures.

8. A method for manufacturing a photovoltaic cell, characterized in that, include: Provide the initial base; At least a portion of the initial substrate is subjected to alkaline polishing to form at least one surface comprising a plurality of tower base structures, wherein the one-dimensional dimensions of the plurality of tower base structures have a first uniformity and the height of the plurality of tower base structures has a second uniformity, wherein the first uniformity is less than or equal to 10% and the second uniformity is less than or equal to 10%. Among the multiple tower base structures on the same surface, the average value of the one-dimensional dimension is the first average value, the difference between the maximum and minimum values ​​of the one-dimensional dimension is the first difference value, the sum of the maximum and minimum values ​​of the one-dimensional dimension is the first sum, and the first uniformity is the ratio of the first difference value to twice the first average value or the ratio of the first difference value to the first sum. In the plurality of tower base structures on the same surface, the average height is the second average value, the difference between the maximum and minimum height is the second difference value, the sum of the maximum and minimum height is the second sum, and the second uniformity is the ratio of the second difference value to twice the second average value or the ratio of the second difference value to the second sum.

9. The method for manufacturing a photovoltaic cell according to claim 8, characterized in that, The step of performing the alkaline polishing treatment on at least a portion of the initial substrate includes: adjusting the preset process parameters in the alkaline polishing treatment to increase the one-dimensional dimension of the formed tower base structure while reducing the height of the formed tower base structure; The preset process parameters include at least one of the following: the concentration of the alkaline polishing solution used in the alkaline polishing treatment, the process temperature of the alkaline polishing treatment, the process duration of the alkaline polishing treatment, the flow rate of the gas blown into the alkaline polishing solution during the alkaline polishing treatment, or the power percentage of the circulating pump used in the alkaline polishing treatment.

10. The method for manufacturing a photovoltaic cell according to claim 9, characterized in that, The alkaline polishing solution includes potassium hydroxide or sodium hydroxide, wherein the mass fraction of potassium hydroxide in the alkaline polishing solution is 1 wt% to 15 wt%, or the mass fraction of sodium hydroxide in the alkaline polishing solution is 1 wt% to 15 wt%.

11. The method for manufacturing a photovoltaic cell according to claim 9, characterized in that, The process temperature for the alkaline polishing treatment is 60℃~85℃.

12. The method for manufacturing a photovoltaic cell according to claim 9, characterized in that, The alkaline polishing process takes 1 to 15 minutes.

13. The method for manufacturing a photovoltaic cell according to claim 9, characterized in that, The power percentage of the circulating pump used in the alkaline polishing process is 60%~98%.

14. The method for manufacturing a photovoltaic cell according to claim 9, characterized in that, The flow rate of the gas bubbled into the alkaline polishing solution during the alkaline polishing process is 0.6 m³ / s. 3 / h to 3.0m 3 / h.

15. A photovoltaic module, characterized in that, include: A battery string is formed by connecting multiple photovoltaic cells as described in any one of claims 1 to 7, or by connecting multiple photovoltaic cells formed by the manufacturing method of photovoltaic cells as described in any one of claims 8 to 14; An encapsulating film is used to cover the surface of the battery string; A cover plate is used to cover the surface of the encapsulating film that faces away from the battery string.

Images