Solar cell and photovoltaic module

Abstract

The present application discloses a solar cell and a photovoltaic module. The solar cell includes a substrate and a passivation layer. The passivation layer covers the surface of at least one side of the substrate. The passivation layer is provided with a conductive through hole that penetrates its thickness. The conductive through hole includes an elliptical hole. The eccentricity of the elliptical hole is e, and 0.3<e<0.98. When the major axis of the elliptical hole is equal to the diameter of the circular hole or the major axis of the elliptical hole is equal to the length of the square hole, it can ensure that the electrode and the doping layer have good ohmic contact, and can reduce the laser opening area of ​​the passivation layer, reduce laser damage, increase the open circuit voltage Voc of the battery, and enhance the photoelectric conversion effect. In addition, under the premise that the major axis of the elliptical hole remains unchanged, the greater the eccentricity of the elliptical hole, the higher the flattening degree of the elliptical hole, the smaller the laser film opening area, and the less damage to the battery, so 0.3<e<0.98, to ensure that the electrode and the doping layer have good ohmic contact while minimizing damage to the battery.

Description

Technical Field

[0001] The utility model relates to the technical field of photovoltaics, in particular to a solar cell and a photovoltaic component. Background Art

[0002] Solar cells are now being used more and more widely as a new energy alternative. Among them, photovoltaic solar cells are devices that convert sunlight into electrical energy. Specifically, solar cells use the photovoltaic principle to generate carriers, and then use electrodes to lead the carriers out, thereby facilitating the effective use of electrical energy.

[0003] In the prior art, when the electrode slurry of the solar cell is a non-burn-through slurry, it is necessary to open a window on the passivation layer so that the electrode passes through the window area to form an ohmic contact with the polysilicon layer. However, in the prior art, a Gaussian spot is generally used for laser grooving. The energy at the center of the spot is higher, so there will be a large concentrated laser damage to the cell at the center of the window area. In view of this situation, some prior arts also use square spots or circular spots for laser grooving. The grooving area is square or circular, so there is no concentrated damage but uniform damage. However, the grooving area is large, and the overall laser damage to the cell is large, resulting in a low open circuit voltage Voc of the cell, affecting the photoelectric conversion efficiency. Utility Model Content

[0004] The purpose of the present application is to provide a solar cell and a photovoltaic module. By controlling the shape of the elliptical light spot to form an elliptical hole with a high degree of flattening, the laser damage area in the center of the window opening area can be effectively reduced. The local window opening can reduce the cell film opening loss while increasing the cell open circuit voltage Voc and photoelectric conversion efficiency.

[0005] In order to achieve the above objectives, this application provides the following technical solutions:

[0006] A solar cell comprises a substrate and a passivation layer, wherein the passivation layer covers a surface of at least one side of the substrate, wherein:

[0007] The passivation layer is provided with a conductive through hole penetrating the thickness thereof, wherein the conductive through hole comprises an elliptical hole, the eccentricity of the elliptical hole is e, and 0.3<e<0.98.

[0008] In the embodiment provided by the utility model, the conductive through hole includes an elliptical hole. When the major axis of the elliptical hole is equal to the diameter of the circular hole, or the major axis of the elliptical hole is equal to the length of the square hole, it can ensure that the electrode has good ohmic contact with the doping layer or the substrate, and can also reduce the laser opening area of ​​the passivation layer, reduce laser damage, increase the open circuit voltage Voc of the battery, and enhance the photoelectric conversion effect. In addition, under the premise that the major axis of the elliptical hole remains unchanged, the greater the eccentricity of the elliptical hole, the higher the degree of flattening of the elliptical hole, the smaller the laser film opening area, and the less damage to the battery, so the eccentricity of the above-mentioned elliptical hole is e, and 0.3<e<0.98, so as to ensure that the electrode has good ohmic contact with the doping layer or the substrate while minimizing damage to the battery.

[0009] In one implementation, 0.6<e<0.98; and / or, the length of the major semi-axis of the elliptical hole is greater than 5μm and less than or equal to 40μm; and / or, the length of the minor semi-axis of the elliptical hole is greater than or equal to 5μm and less than or equal to 20μm; and / or, the ratio of the major semi-axis to the minor semi-axis of the elliptical hole is greater than 1 and less than or equal to 2, so that the major axis and the minor axis of the elliptical hole can be maintained within a reasonable ratio range, preventing the elliptical hole from being too flat, resulting in reduced stability of the ohmic contact between the electrode and the doping layer or the substrate.

[0010] In one implementation, the solar cell further includes an electrode, wherein the electrode partially passes through an elliptical hole opened in the passivation layer, and the long axis of the elliptical hole is parallel to the extension direction of the electrode, so as to ensure that the electrode forms a good ohmic contact with the doping layer or the substrate.

[0011] In one implementation, each electrode is provided with at least one row of elliptical holes in the orthographic projection area of ​​the passivation layer, and the multiple elliptical holes in each row are arranged in sequence along the extension direction of the electrode. In this way, the first sub-grid and the second sub-grid are both in ohmic contact with the doping layer or the substrate through the multiple elliptical holes, ensuring that the first doping region and the second doping region have a high carrier collection capacity.

[0012] In one implementation, two adjacent elliptical holes in the same row are tangent, have a spacing or partially overlap; when there is a spacing between two adjacent elliptical holes in the same row, the distance between the two adjacent elliptical holes in the same row is X, 0μm≤X≤110μm; wherein the spacing between adjacent elliptical holes is compared to the tangent adjacent elliptical holes, and the equivalent film opening width is reduced, further reducing the film opening loss, so that the Voc of the metallized battery is relatively increased by 2mv-5mv, and the photoelectric conversion efficiency is better.

[0013] When two adjacent elliptical holes in the same row partially overlap, the overlapping length of the two adjacent elliptical holes in the same row is less than the semi-major axis of the elliptical hole. This arrangement can prevent the overlapping area of ​​two adjacent elliptical holes in the same row from being too large, thereby preventing multiple elliptical holes in the same row from connecting to form a through hole with a larger opening, thereby reducing battery damage.

[0014] In one implementation, each electrode is provided with two rows of elliptical holes in the orthographic projection area of ​​the passivation layer, and the two rows of elliptical holes are staggered to prevent concentrated film opening of the elliptical holes. The two rows of elliptical holes are more dispersed to prevent the local film opening area from being too large and causing serious damage.

[0015] In one implementation, the solar cell further includes a doping layer, and the doping layer is at least partially located on a surface of at least one side of the substrate.

[0016] In one implementation, the doping layer includes a first doping region and a second doping region of opposite conductivity types, the passivation layer at least partially covers a surface of the doping layer on a side away from the substrate, and an elliptical hole is provided in a region of the passivation layer corresponding to the first doping region and a region corresponding to the second doping region;

[0017] The solar cell further comprises an electrode, the electrode comprising a first auxiliary grid and a second auxiliary grid, a part of the first auxiliary grid passes through the elliptical hole to be in conductive contact with the first doping region, and a part of the second auxiliary grid passes through the elliptical hole to be in conductive contact with the second doping region;

[0018] The maximum size of the elliptical hole along the direction parallel to the extension direction of the first auxiliary grid or the second auxiliary grid is L, and the maximum size of the elliptical hole along the direction perpendicular to the extension direction of the first auxiliary grid or the second auxiliary grid is L', and L>L'. In this way, the film opening distance of the elliptical hole along the direction parallel to the extension direction of the first auxiliary grid or the second auxiliary grid is large, and the film opening distance of the elliptical hole along the direction perpendicular to the extension direction of the first auxiliary grid or the second auxiliary grid is small, which can form a better ohmic contact while reducing the damage of film opening.

[0019] In one implementation, the major axis of the elliptical hole is parallel to the extension direction of the first sub-gate or the second sub-gate; and / or, 5μm<L≤40μm, and 5μm≤L'≤20μm, so that the size of the elliptical hole can be adjusted according to the width of the first doping region and the second doping region, so that the proportion of the film opening area of ​​the elliptical hole to the area of ​​the first doping region or the second doping region is lower, thereby minimizing the film opening damage. Or, the width of the first doped region is greater than the width of the second doped region, the maximum dimension of the first through hole along the direction parallel to the extension of the first auxiliary gate is La, and the maximum dimension of the second through hole along the direction parallel to the extension of the second auxiliary gate is Lb; La>Lb and the eccentricity of the first through hole is greater than the eccentricity of the second through hole, or La=Lb and the eccentricity of the first through hole is less than the eccentricity of the second through hole; the first doped region needs to collect more current, so the area required to achieve ohmic contact is larger, so the window area of ​​the first through hole should be larger than the window area of ​​the second through hole, and the eccentricity can be increased by setting the first through hole to be narrower, longer and flatter, thereby reducing the degree of damage to its center and maintaining a sufficient contact area. Or,

[0020] The width of the first doped region is equal to the width of the second doped region, the maximum size of the first through hole along the direction parallel to the first auxiliary gate is La, and the maximum size of the second through hole along the direction parallel to the second auxiliary gate is Lb; La=Lb and the eccentricity of the first through hole is equal to the eccentricity of the second through hole.

[0021] In one implementation, each first sub-grid is provided with at least one row of elliptical holes in the orthographic projection area of ​​the passivation layer, and the multiple elliptical holes in each row are arranged in sequence along the extension direction of the first sub-grid; and / or, each second sub-grid is provided with at least one row of elliptical holes in the orthographic projection area of ​​the passivation layer, and the multiple elliptical holes in each row are arranged in sequence along the extension direction of the second sub-grid. In this way, the first sub-grid and the second sub-grid are both in ohmic contact with the doping layer or the substrate through the multiple elliptical holes, ensuring that the first doping region and the second doping region have a high carrier collection capacity.

[0022] In one implementation, two adjacent elliptical holes in the same row are tangent to each other, have a spacing, or partially overlap;

[0023] When there is a spacing between two adjacent elliptical holes in the same row, the distance between the two adjacent elliptical holes in the same row is X, 0μm≤X≤110μm; wherein the spacing between adjacent elliptical holes is compared with the tangency of adjacent elliptical holes, and the equivalent film opening width is reduced, further reducing the film opening loss, so that the Voc of the metallized battery is relatively increased by 2mv-5mv, and the photoelectric conversion efficiency is better.

[0024] When two adjacent elliptical holes in the same row partially overlap, the overlapping length of the two adjacent elliptical holes in the same row is less than the semi-major axis of the elliptical hole. This arrangement can prevent the overlapping area of ​​two adjacent elliptical holes in the same row from being too large, thereby preventing multiple elliptical holes in the same row from connecting to form a through hole with a larger opening, thereby reducing battery damage.

[0025] In one implementation, the height of the first sub-grid and the second sub-grid protruding from the passivation layer is h; the difference between the width of the first sub-grid close to the elliptical hole and the width of the side away from the elliptical hole is greater than 0 and less than 2h, and / or the difference between the width of the second sub-grid close to the elliptical hole and the width of the side away from the elliptical hole is greater than 0 and less than 2h. Since the rate of side etching of the metal layer is lower than the rate of downward etching of the metal layer during the etching of the metal layer, the difference between the width of the bottom and the width of the top of the first sub-grid is greater than 0 and less than 2h, which can prevent severe etching and ensure that the height of the first sub-grid does not decrease due to etching.

[0026] In one implementation, the width of the first sub-grid close to the elliptical hole is 340 μm-436 μm; and / or, the width of the second sub-grid close to the elliptical hole is 240 μm-336 μm; and / or, the width of the first sub-grid close to the elliptical hole is greater than the width of the second sub-grid close to the elliptical hole.

[0027] In one implementation, the difference between the width of the first sub-grid close to the elliptical hole and the width of the first sub-grid away from the elliptical hole is greater than or equal to the difference between the width of the second sub-grid close to the elliptical hole and the width of the second sub-grid away from the elliptical hole; when the doping layer is wider, the width difference between the bottom and the top of the electrode needs to be smaller, so that the cross-sectional area of ​​the electrode is larger and the resistance is smaller, thereby achieving better current transmission; when the doping layer is narrower, the demand for current transmission is weaker, but the width difference between the bottom and the top of the electrode is larger, the width of the top is reduced, and shading is avoided.

[0028] And / or, the distance between the side of the first sub-gate close to the elliptical hole and the edge of the first doping region is L3, the distance between the side of the second sub-gate close to the elliptical hole and the edge of the second doping region is L4, and L3>L4; and / or, the minimum distance between the edge of the first through hole and the edge of the first doping region is greater than the minimum distance between the edge of the second through hole and the edge of the second doping region. Since the first doping region is wider and has a stronger demand for current transmission, the film opening area of ​​the first through hole needs to be larger to achieve a larger ohmic contact area, while the second doping region is narrower and has a weaker demand for current transmission, so the film opening area of ​​the second through hole can be appropriately reduced, so the window opening area of ​​the first through hole should be greater than the window opening area of ​​the second through hole. In this embodiment, by making the minimum distance between the edge of the first through hole and the edge of the first doping region greater than the minimum distance between the edge of the second through hole and the edge of the second doping region, the first through hole is made wider in the width direction of the first doping region, and at the same time, the first through hole is made narrower, longer and flatter, which is more conducive to increasing the window opening area of ​​the first through hole, which can reduce the degree of damage at its center and maintain sufficient contact area.

[0029] In one implementation, the solar cell is a back contact cell, the doping layer includes a first doping region and a second doping region that are interdigitated, the first doping region includes a first penetration region and a first vertical region, the first vertical region is perpendicular to and connected to the first penetration region, the second doping region includes a second penetration region and a second vertical region, the second vertical region is perpendicular to and connected to the second penetration region, and the first vertical region and the second vertical region are staggered;

[0030] The elliptical hole opened in the area of ​​the passivation layer corresponding to the first vertical area is a first through hole, and the elliptical hole opened in the area of ​​the passivation layer corresponding to the second vertical area is a second through hole;

[0031] Along the direction in which the first vertical region and the second vertical region are staggered, the maximum size of the first through hole is 5%-15% of the width of the first vertical region, and the maximum size of the second through hole is 2%-15% of the width of the second vertical region. In this way, the openings of the first through hole and the second through hole are kept within a reasonable range, preventing the first through hole and the second through hole from exceeding the edges of the first doping region and the second doping region to cause leakage risk, while ensuring good stability of ohmic contact between the electrode and the doping layer.

[0032] In one implementation, along the direction in which the first doping region and the second doping region are staggered, the distance from the edge of the first sub-gate to the edge of the elliptical hole is Z1, and the distance from the edge of the second sub-gate to the edge of the elliptical hole is Z2;

[0033] 155μm≤Z1≤213μm; and / or, 105μm≤Z2≤163μm; and / or, Z1>Z2. According to the width of the first doping region and the second doping region, the safety distance around the edge of the first sub-gate is made larger, and the safety distance around the edge of the second sub-gate is made smaller, so that the elliptical hole in the area corresponding to the passivation layer and the first doping region is closer to a circle, and the elliptical hole in the area corresponding to the passivation layer and the second doping region is narrower, longer and flatter, so that the film opening area of ​​the elliptical hole accounts for a lower proportion of the area of ​​the first doping region or the second doping region, and the film opening damage is minimized, while ensuring good ohmic contact.

[0034] A photovoltaic module comprises any one of the above-mentioned solar cells. Compared with the prior art, the beneficial effects of the photovoltaic module provided by the embodiment of the present application are the same as the beneficial effects of the above-mentioned solar cells, which will not be described in detail here. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0036] Figure 1 A partial cross-sectional view of the solar cell provided in the present application before etching the metal layer;

[0037] Figure 2 A partial cross-sectional view of the solar cell provided in the present application after etching the metal layer;

[0038] Figure 3 A top view of the position of the first auxiliary grid of the solar cell provided in the embodiment of the present application;

[0039] Figure 4 A top view of the position of the second auxiliary grid of the solar cell provided in the embodiment of the present application;

[0040] Figure 5 A schematic diagram of the arrangement of multiple rows of elliptical holes provided in an embodiment of the present application.

[0041] Reference numerals:

[0042] 1-substrate, 2-doping layer, 2a-first doping region, 2b-second doping region, 2c-isolation region, 3-passivation layer, 3a-elliptical hole, 4-metal layer, 4a-first sub-gate, 4b-second sub-gate, 4c-local protrusion, 5-mask layer. DETAILED DESCRIPTION

[0043] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0044] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0045] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, "multiple" means two or more, unless otherwise clearly and specifically defined. "Several" means one or more, unless otherwise clearly and specifically defined.

[0046] In the description of the present application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", etc., indicating directions or positional relationships are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the present application.

[0047] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0048] Solar cells are now being used more and more widely as a new energy alternative. Among them, photovoltaic solar cells are devices that convert sunlight into electrical energy. In the actual working process, solar cells use the photovoltaic principle to generate carriers, and then use electrodes to lead the carriers out, thereby facilitating the effective use of electrical energy.

[0049] The solar cell provided by the utility model comprises a substrate 1 and a passivation layer 3. The passivation layer 3 covers the surface of at least one side of the substrate 1. For a double-sided solar cell, the passivation layer 3 covers the two opposite surfaces of the substrate 1; for a back contact cell, the passivation layer 3 covers the surface of one side of the substrate 1.

[0050] Wherein, the substrate 1 is a semiconductor substrate. The material of the substrate 1 can be selected from materials such as silicon (Si) or germanium (Ge) or materials such as gallium arsenide (GaAs). Obviously, in terms of conductivity type, the substrate 1 can be an intrinsic conductive substrate, an n-type conductive substrate or a p-type conductive substrate. Preferably, the substrate 1 is a p-type conductive substrate or an n-type conductive substrate. Compared with the intrinsic conductive substrate, the p-type conductive substrate or the n-type conductive substrate has better conductivity, so that the final solar cell has a lower body resistivity, thereby improving the efficiency of the solar cell.

[0051] Exemplarily, the substrate 1 is an n-type silicon substrate. Compared with a p-type conductive substrate, an n-type conductive substrate has the advantages of a long minority carrier lifetime, no light decay, and good weak light performance.

[0052] The passivation layer 3 can play an insulating and passivating role, which is beneficial to reduce the carrier recombination rate and improve the photoelectric conversion efficiency of the solar cell. The specific material can be selected according to the actual situation. For example, the material of the passivation layer 3 can be one or more of silicon nitride, silicon oxide, silicon oxynitride, aluminum oxide, silicon carbide, and amorphous silicon. In the embodiment of the present application, the material of the passivation layer 3 can be silicon nitride.

[0053] The passivation layer 3 is provided with conductive through holes that penetrate the thickness of the passivation layer 3. The electrodes of the solar cell need to partially pass through the conductive through holes to make conductive contact with the substrate 1 or the doping layer 2. In the process of forming the electrodes, Figure 1 As shown, a metal layer 4 is first formed on the surface of the passivation layer 3 facing away from the substrate 1, and the metal layer 4 covers the entire upper surface of the passivation layer 3. The metal layer 4 can be formed by chemical deposition. Then, a mask layer 5 is set on the surface of the metal layer 4 facing away from the passivation layer 3, and the mask layer 5 has hollow holes. Then, the metal layer 4 is etched to remove the areas of the metal layer 4 corresponding to the hollow holes of the mask layer 5, and the areas of the metal layer 4 covered by the mask layer 5 are retained to form electrodes. Figure 2 As shown, after etching the metal layer 4, the unetched portion of the metal layer 4 includes the electrode. It should be noted that in the process of etching and removing the metal layer 4, it is inevitable to corrode the side of the electrode, resulting in side corrosion.

[0054] Before forming the metal layer 4 on the surface of the passivation layer 3 facing away from the substrate 1, it is necessary to first open a conductive through-hole in the passivation layer 3 so that when the metal layer 4 is deposited, metal is simultaneously deposited in the conductive through-hole, enabling the metal layer 4 to form an ohmic contact with the substrate 1 or the doped layer 2 through the metal in the conductive through-hole. As in the background art, in order to prevent concentrated damage, circular or square conductive through-holes can be opened. However, the grooving area of circular or square conductive through-holes is relatively large, resulting in a large overall laser damage to the battery, a low open-circuit voltage Voc of the battery, and an impact on the photoelectric conversion efficiency.

[0055] Based on the above situation, as Figure 3-Figure 5 shown, in the embodiment provided by the present utility model, the conductive through-hole includes an elliptical hole 3a. When the major axis of the elliptical hole 3a is equal to the diameter of the circular hole, or the major axis of the elliptical hole 3a is equal to the length of the square hole, it can not only ensure good ohmic contact between the electrode and the substrate 1 or the doped layer 2, but also reduce the laser opening area of the passivation layer 3, reduce laser damage, increase the open-circuit voltage Voc of the battery, and enhance the photoelectric conversion effect. In addition, on the premise that the major axis of the elliptical hole 3a remains unchanged, the greater the eccentricity of the elliptical hole 3a, the higher the degree of flattening of the elliptical hole 3a, the smaller the laser film opening area, and the smaller the damage to the battery. Therefore, the eccentricity of the above-mentioned elliptical hole 3a is e, and 0.3 < e < 0.98, so as to ensure good ohmic contact between the electrode and the substrate 1 or the doped layer 2 while minimizing the damage to the battery as much as possible.

[0056] Exemplarily, the eccentricity e of the elliptical hole 3a is 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 0.98. Preferably, 0.6 < e < 0.98.

[0057] It should be noted that the main process parameters for controlling the laser are laser type, pulse energy, lens, laser rate, laser frequency, etc. The laser spot forming technology is an important factor affecting laser processing. The original laser beam shape is usually cylindrical when it exits the laser. The shape of the laser spot is changed through different processing means, such as the mask method, cylindrical lens method, etc. The reason for damage during the laser process is thermal damage caused by the absorption of the substrate. Taking purple skin laser as an example, the corresponding laser parameters are as follows: laser type purple skin 40, pulse energy 60 - 100%, laser rate 25 - 60 m / s, laser frequency 500 - 2000. During the laser film opening process, tooth-shaped edges will inevitably form on the edge and side wall of the formed conductive through-hole. Therefore, in this utility model, the elliptical hole 3a refers to the fitting edge of the conductive through-hole being elliptical, and the eccentricity of the fitting edge of the conductive through-hole is 0.3 < e < 0.98, preferably 0.6 < e < 0.98. The parameter limitations for the elliptical hole 3a in this utility model are all for the fitting edge of the elliptical conductive through-hole.

[0058] In a specific embodiment, the length of the major semi-axis of the elliptical hole 3a is A, and the length of the minor semi-axis is B. Then the equation of the edge of the elliptical hole 3a can be expressed by x 2 / A 2 +y 2 / B 2 = 1. The length A of the long semi-axis of the elliptical hole 3a is greater than 5 μm and less than or equal to 40 μm. For example, the length A of the long semi-axis can be 6 μm, 8 μm, 10 μm, 12 μm, 15 μm, 18 μm, 20 μm, 22 μm, 25 μm, 28 μm, 30 μm, 32 μm, 35 μm, 38 μm or 40 μm.

[0059] In addition, the length B of the short semi-axis of the elliptical hole 3a is greater than or equal to 5μm and less than or equal to 20μm. Exemplarily, the length B of the short semi-axis is 5μm, 8μm, 10μm, 12μm, 15μm, 18μm or 20μm.

[0060] The ratio of the major semi-axis to the minor semi-axis of the elliptical hole 3a is greater than 1 and less than or equal to 2. In this way, the major axis and the minor axis of the elliptical hole 3a can be kept within a reasonable ratio range, preventing the elliptical hole 3a from being too flat, which may reduce the stability of the ohmic contact between the electrode and the doping layer 2 or the substrate 1. For example, the ratio of the major semi-axis to the minor semi-axis of the elliptical hole 3a is 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9 or 2.

[0061] Preferably, the long axis of the elliptical hole 3a is parallel to the electrode extension direction, and the short axis of the elliptical hole 3a is perpendicular to the electrode extension direction. At this time, the size of the elliptical hole 3a parallel to the electrode extension direction reaches the maximum, and the size of the elliptical hole 3a perpendicular to the electrode extension direction reaches the minimum, which further reduces the film opening damage and improves the good stability of the ohmic contact between the electrode and the substrate 1 or the doping layer 2. In addition, the long axis direction distance of the elliptical hole 3a is large, which is conducive to carrier collection, and the short axis direction distance is small, which reduces the J0 damage of the battery cell.

[0062] Furthermore, each electrode is provided with at least one row of elliptical holes 3a in the orthographic projection area of ​​the passivation layer 3, and the multiple elliptical holes 3a in each row are arranged in sequence along the extension direction of the electrode. In this way, each electrode is in ohmic contact with the substrate 1 or the doping layer 2 through the multiple elliptical holes 3a, ensuring a high carrier collection capacity of the solar cell.

[0063] Exemplarily, each electrode is provided with one, two or more rows of elliptical holes 3a in the orthographic projection area of ​​the passivation layer 3. There is a spacing between two adjacent elliptical holes 3a in the same row, that is, the multiple elliptical holes 3a in the same row are distributed at intervals. Alternatively, two adjacent elliptical holes 3a in the same row may also be tangent to each other. Alternatively, two adjacent elliptical holes 3a in the same row may also partially overlap.

[0064] In the above embodiment, the distance between two adjacent elliptical holes 3a in the same row is X, 25μm≤X≤110μm, to prevent the distance between two adjacent elliptical holes 3a in the same row from being too large, reducing the carrier collection capacity, and at the same time avoid the distance between two adjacent elliptical holes 3a in the same row from being too small, resulting in a large film opening area and serious damage. Therefore, the distance between two adjacent elliptical holes 3a in the same row is within a reasonable range of greater than or equal to 25μm and less than or equal to 110μm. For example, X can be 25μm, 30μm, 40μm, 50μm, 60μm, 70μm, 80μm, 90μm, 100μm or 110μm.

[0065] In the above embodiment, when two adjacent elliptical holes 3a in the same row partially overlap, along the extension direction of the electrode, the overlapping length of the two adjacent elliptical holes 3a in the same row is less than the semi-major axis of the elliptical hole 3a. This arrangement can prevent the overlapping area of ​​the two adjacent elliptical holes 3a in the same row from being too large, thereby preventing multiple elliptical holes 3a in the same row from connecting to form a through hole with a larger opening, thereby reducing battery damage.

[0066] In addition, each electrode is preferably provided with two rows of elliptical holes 3a in the orthographic projection area of ​​the passivation layer 3, and the two rows of elliptical holes 3a are arranged in a staggered manner. That is, in the two rows of elliptical holes 3a, the gap between adjacent elliptical holes 3a in one row is opposite to the elliptical holes 3a in the other row. Compared with the two rows of elliptical holes 3a arranged side by side, the concentrated film opening of the elliptical holes 3a can be prevented, and the two rows of elliptical holes 3a are more dispersed, which prevents the local film opening area from being too large and causing serious damage.

[0067] In another optional embodiment, the solar cell further includes a doping layer 2. The doping layer 2 is at least partially located on the surface of at least one side of the substrate 1. That is, one side surface of the substrate 1 is partially covered with the doping layer 2, or both side surfaces of the substrate 1 are partially covered with the doping layer 2. For a bifacial solar cell, both opposite side surfaces of the substrate 1 are partially covered with the doping layer 2, and the passivation layer 3 covers the doping layer 2 and the substrate 1. A portion of the electrode passes through the elliptical hole 3a of the passivation layer 3 to make conductive contact with the substrate 1, and another portion of the electrode passes through the elliptical hole 3a of the passivation layer 3 to make conductive contact with the doping layer 2. For a back contact cell, one side surface of the substrate is covered with a doping layer, and the doping layer 2 includes a first doping region 2a and a second doping region 2b, and the first doping region 2a and the second doping region 2b have opposite conductivity types. An isolation region 2c is provided between the first doping region 2a and the second doping region 2b to avoid leakage of the solar cell; and the reliability performance of the cell in later products can be improved.

[0068] The first doping region 2a and the second doping region 2b are also semiconductor doping layers. In terms of the internal arrangement of the material, the first doping region 2a and the second doping region 2b can be amorphous, microcrystalline, single crystal, nanocrystalline or polycrystalline. In terms of specific materials, the materials of the first doping region 2a and the second doping region 2b can be silicon (Si), germanium (Ge), silicon carbide (SiCx) or gallium arsenide (GaAs). In terms of conductivity type, the first doping region 2a and the second doping region 2b can be n-type doping layers or p-type doping layers.

[0069] In some examples, when the substrate 1 is an n-type substrate, the first doping region 2a can be a p-type doping layer, and the second doping region 2b can be an n-type doping layer; or, when the substrate 1 is a p-type substrate, the first doping region 2a can be an n-type doping layer, and the second doping region 2b can be a p-type doping layer.

[0070] Exemplarily, the substrate 1 is an n-type silicon substrate, the first doped region 2a is a boron-doped p-type doped layer, and the second doped region 2b is a phosphorus-doped n-type doped layer. At this time, since the heavily phosphorus-doped region has a greater solubility for metal impurities, the phosphorus in the second doped region 2b can provide phosphorus gettering passivation for the first doped region 2a, thereby improving the battery efficiency.

[0071] In this embodiment, the electrode includes a first sub-gate 4a and a second sub-gate 4b. Conductive through holes are provided in the region corresponding to the passivation layer 3 and the first doping region 2a and the region corresponding to the passivation layer 3 and the second doping region 2b. A portion of the first sub-gate 4a passes through the elliptical hole 3a to be in conductive contact with the first doping region 2a, and a portion of the second sub-gate 4b passes through the elliptical hole 3a to be in conductive contact with the second doping region 2b. Specifically, the elliptical hole 3a provided in the region corresponding to the passivation layer 3 and the first doping region 2a is a first through hole, and a portion of the first sub-gate 4a passes through the first through hole to be in conductive contact with the first doping region 2a. The elliptical hole 3a provided in the region corresponding to the passivation layer 3 and the second doping region 2b is a second through hole, and a portion of the second sub-gate 4b passes through the second through hole to be in conductive contact with the second doping region 2b.

[0072] In a specific embodiment, the maximum dimension of the elliptical hole 3a along the direction parallel to the extension direction of the first auxiliary grid 4a or the second auxiliary grid 4b is L, and the maximum dimension of the elliptical hole 3a along the direction perpendicular to the extension direction of the first auxiliary grid 4a or the second auxiliary grid 4b is L', and L>L'. In this embodiment, the long axis of the elliptical hole 3a can be parallel to the extension direction of the first auxiliary grid 4a or the second auxiliary grid 4b, or the angle between the long axis of the elliptical hole 3a and the extension direction of the first auxiliary grid 4a or the second auxiliary grid 4b is less than or equal to 90°. The long axis of the elliptical hole 3a can be perpendicular to the extension direction of the first auxiliary grid 4a or the second auxiliary grid 4b, or the angle between the short axis of the elliptical hole 3a and the extension direction of the first auxiliary grid 4a or the second auxiliary grid 4b is an acute angle. Along the extension direction parallel to the first auxiliary grid 4a or the second auxiliary grid 4b, the maximum film opening distance of the elliptical hole 3a is L; along the extension direction perpendicular to the first auxiliary grid 4a or the second auxiliary grid 4b, the maximum film opening distance of the elliptical hole 3a is L'; L>L', so the film opening distance of the elliptical hole 3a along the extension direction parallel to the first auxiliary grid 4a or the second auxiliary grid 4b is larger, and the film opening distance of the elliptical hole 3a along the extension direction perpendicular to the first auxiliary grid 4a or the second auxiliary grid 4b is smaller, which can form a better ohmic contact while reducing the damage of film opening.

[0073] In practical applications, the size of the elliptical hole 3a can be adjusted according to the width of the first doping region 2a and the second doping region 2b, so that the ratio of the film opening area of ​​the elliptical hole 3a to the area of ​​the first doping region 2a or the second doping region 2b is maintained within a certain range, and the film opening damage is minimized. Usually, the widths of the first doping region 2a and the second doping region 2b are set differently. In this embodiment, taking the example that the width of the first doping region 2a is greater than the width of the second doping region 2b, the maximum size of the first through hole along the extension direction parallel to the first auxiliary gate 4a is La, and the maximum size of the second through hole along the extension direction parallel to the second auxiliary gate 4b is Lb; when La>Lb, the eccentricity of the elliptical hole in the region corresponding to the passivation layer 3 and the first doping region 2a is greater than the eccentricity of the elliptical hole in the region corresponding to the passivation layer 3 and the second doping region 2b, that is, the eccentricity of the first through hole is greater than the eccentricity of the second through hole. The area corresponding to the passivation layer 3 and the first doped region 2a is wider, and the first doped region 2a needs to collect more current, so the area required to achieve ohmic contact is larger. Therefore, the window area of ​​the first through hole should be larger than the window area of ​​the second through hole. The eccentricity can be increased to make the first through hole narrower, longer and flatter, thereby reducing the degree of damage at the center and maintaining a sufficient contact area. When La=Lb, the eccentricity of the first through hole is smaller than that of the second through hole, that is, the eccentricity of the elliptical hole in the area corresponding to the passivation layer 3 and the first doping region 2a is smaller, and the elliptical hole in the area corresponding to the passivation layer 3 and the first doping region 2a is closer to a circle; and the area corresponding to the passivation layer 3 and the second doping region 2b is narrower, so the eccentricity of the elliptical hole in the area corresponding to the passivation layer 3 and the second doping region 2b is larger, and the elliptical hole in the area corresponding to the passivation layer 3 and the second doping region 2b is narrower, longer and flatter. Such a setting ensures that the wider doping region has a larger ohmic contact area, which can ensure that the electrode forms a better ohmic contact with the doping layer after passing through the first through hole and the second through hole. However, this scheme may cause more damage in the first doping region 2a due to film opening than the previous scheme, which will affect the battery efficiency to a certain extent.

[0074] When the widths of the first doping region 2a and the second doping region 2b are set to be the same, L1=L2, the eccentricity of the elliptical hole in the area corresponding to the passivation layer 3 and the first doping region 2a can be equal to the eccentricity of the elliptical hole in the area corresponding to the passivation layer 3 and the second doping region 2b, that is, the eccentricity of the first through hole can be equal to the eccentricity of the second through hole.

[0075] Among them, 5μm≤L≤40μm to ensure that the electrode forms a good ohmic contact with the doping layer 2. Exemplarily, L is 5μm, 8μm, 10μm, 12μm, 15μm, 18μm, 20μm, 22μm, 25μm, 28μm, 30μm, 32μm, 35μm, 38μm or 40μm. In addition, 5μm≤L'≤20μm to minimize the damage caused by film opening. Exemplarily, L' is 5μm, 8μm, 10μm, 12μm, 15μm, 18μm or 20μm. Of course, the value of L needs to be reasonably set according to the width of the first doping region 2a and the first sub-gate 4a, and the value of L' needs to be reasonably set according to the width of the second doping region 2b and the second sub-gate 4b.

[0076] Preferably, the long axis of the elliptical hole 3a is parallel to the extension direction of the first auxiliary grid 4a or the second auxiliary grid 4b, and the short axis of the elliptical hole 3a is perpendicular to the extension direction of the first auxiliary grid 4a or the second auxiliary grid 4b. That is, L=2A, L'=2B. At this time, the size of the elliptical hole 3a along the direction parallel to the extension direction of the first auxiliary grid 4a or the second auxiliary grid 4b reaches the maximum, and the size of the elliptical hole 3a along the direction perpendicular to the extension direction of the first auxiliary grid 4a or the second auxiliary grid 4b reaches the minimum, which further reduces the film opening damage and improves the good stability of the ohmic contact between the electrode and the doping layer 2. In addition, the long axis direction distance of the elliptical hole 3a is large, which is conducive to carrier collection, and the short axis direction distance is small, which reduces the J0 damage of the battery cell.

[0077] If the long semi-axis of the elliptical hole 3a is parallel to the extension direction of the first auxiliary grid 4a or the second auxiliary grid 4b, the short semi-axis of the elliptical hole 3a is perpendicular to the extension direction of the first auxiliary grid 4a or the second auxiliary grid 4b. In the first embodiment, the long semi-axis length of the elliptical hole 3a is 25 μm, the short semi-axis length is 5 μm, and the eccentricity is 0.98. In the second embodiment, the long semi-axis length of the elliptical hole 3a is 12.5 μm, the short semi-axis length is 10 μm, and the eccentricity is 0.6. In the above two embodiments, the area of ​​the elliptical hole 3a in the first embodiment is equal to the area of ​​the elliptical hole 3a in the second embodiment, but the opening distance in the direction parallel to the auxiliary grid in the first embodiment is greater than the opening distance in the direction parallel to the auxiliary grid in the second embodiment, so the first embodiment can form a better ohmic contact than the second embodiment.

[0078] In the above embodiment, the laser scanning direction may be consistent with the long axis direction of the elliptical hole 3a.

[0079] In a possible embodiment, each first sub-gate 4a is provided with at least one row of elliptical holes 3a in the orthographic projection area of ​​the passivation layer 3, and the multiple elliptical holes 3a in each row are arranged in sequence along the extension direction of the first sub-gate 4a. Each second sub-gate 4b is provided with at least one row of elliptical holes 3a in the orthographic projection area of ​​the passivation layer 3, and the multiple elliptical holes 3a in each row are arranged in sequence along the extension direction of the second sub-gate 4b. In this way, the first sub-gate 4a and the second sub-gate 4b are both in ohmic contact with the doping layer 2 through the multiple elliptical holes 3a, ensuring that the first doping region 2a and the second doping region 2b have a high carrier collection ability.

[0080] Exemplarily, each first sub-grid 4a is provided with one, two or more rows of elliptical holes 3a in the orthographic projection area of ​​the passivation layer 3. Each second sub-grid 4b is provided with one, two or more rows of elliptical holes 3a in the orthographic projection area of ​​the passivation layer 3.

[0081] like Figures 3 to 5 As shown, there is a spacing between two adjacent elliptical holes 3a in the same row, that is, a plurality of elliptical holes 3a in the same row are distributed at intervals. Alternatively, two adjacent elliptical holes 3a in the same row may be tangent to each other. Alternatively, two adjacent elliptical holes 3a in the same row may partially overlap.

[0082] For elliptical holes 3a of the same shape and size, the laser loss under the film opening of different overlapping states of elliptical holes 3a is compared. When there is a spacing between adjacent elliptical holes 3a, the equivalent film opening width is reduced compared to the tangent adjacent elliptical holes 3a, and the film opening loss is further reduced, so that the Voc of the metallized battery is relatively increased by 2mv-5mv, and the photoelectric conversion efficiency is better. Therefore, it is preferred that there is a spacing between two adjacent elliptical holes 3a in the same row.

[0083] In the above embodiment, the distance between two adjacent elliptical holes 3a in the same row is X, 25μm≤X≤110μm. The distance between two adjacent elliptical holes 3a in the same row can be reasonably set according to the width of the first doping region 2a and the second doping region 2b to prevent the distance between the two adjacent elliptical holes 3a in the same row from being too large, reducing the carrier collection capacity of the first doping region 2a and the second doping region 2b, and at the same time avoiding the distance between the two adjacent elliptical holes 3a in the same row from being too small, resulting in serious damage to the film opening area. Therefore, the distance between the two adjacent elliptical holes 3a in the same row is within a reasonable range of greater than or equal to 25μm and less than or equal to 110μm, ensuring that the first doping region 2a and the second doping region 2b have a higher carrier collection capacity and lower film opening damage. For example, X can be 25μm, 30μm, 40μm, 50μm, 60μm, 70μm, 80μm, 90μm, 100μm or 110μm.

[0084] In addition, each first sub-grid 4a or second sub-grid 4b is preferably provided with two rows of elliptical holes 3a in the orthographic projection area of ​​the passivation layer 3, and the two rows of elliptical holes 3a are arranged in a staggered manner. That is, in the two rows of elliptical holes 3a, the gap between adjacent elliptical holes 3a in one row is opposite to the elliptical holes 3a in the other row. Compared with the two rows of elliptical holes 3a arranged side by side, the concentrated film opening of the elliptical holes 3a can be prevented, and the two rows of elliptical holes 3a are more dispersed, which prevents the local film opening area from being too large and causing serious damage.

[0085] Preferably, the bottom of the electrode has a local protrusion 4c, the local protrusion 4c passes through the elliptical hole 3a and is in conductive contact with the first doping region 2a or the second doping region 2b, and the local protrusion 4c fills the elliptical hole 3a. In this embodiment, the metal deposited in the elliptical hole 3a fills the elliptical hole 3a, and the elliptical hole 3a is filled with metal in both the height and width directions, further ensuring good ohmic contact between the metal and the doping layer 2, reducing resistivity, and improving carrier collection capacity.

[0086] like Figure 2 As shown, the height of the first auxiliary grid 4a and the second auxiliary grid 4b protruding from the passivation layer 3 is h, the bottom of the first auxiliary grid 4a and the second auxiliary grid 4b is close to the substrate 1, and the top of the first auxiliary grid 4a and the second auxiliary grid 4b is away from the substrate 1. The distance from the bottom to the top of the first auxiliary grid 4a and the second auxiliary grid 4b is the height h of the first auxiliary grid 4a and the second auxiliary grid 4b. The difference between the width of the side of the first auxiliary grid 4a close to the elliptical hole 3a and the width of the side away from the elliptical hole 3a is greater than 0 and less than 2h, that is, the difference between the width of the bottom of the first auxiliary grid 4a and the width of the top is greater than 0 and less than 2h. Since the rate of side etching of the metal layer 4 is lower than the rate of downward etching of the metal layer 4 during the etching process of the metal layer 4, the difference between the width of the bottom of the first auxiliary grid 4a and the width of the top is greater than 0 and less than 2h, so as to prevent severe etching and ensure that the height of the first auxiliary grid 4a does not decrease due to etching.

[0087] Similarly, the difference between the width of the side of the second auxiliary grid 4b close to the elliptical hole 3a and the width of the side away from the elliptical hole 3a is greater than 0 and less than 2h, that is, the difference between the width of the bottom and the width of the top of the second auxiliary grid 4b is greater than 0 and less than 2h. Since the side etching rate of the metal layer 4 is lower than the downward etching rate of the metal layer 4 during the etching process of the metal layer 4, the difference between the width of the bottom and the width of the top of the second auxiliary grid 4b is greater than 0 and less than 2h, which can prevent severe etching and ensure that the height of the second auxiliary grid 4b does not decrease due to etching.

[0088] In addition, since the metal layer 4 is etched from top to bottom, the side etching on the upper side of the metal layer 4 is more serious than that on the lower side, and the width of the top of the first sub-gate 4a and the second sub-gate 4b formed after etching is smaller than the width of the bottom. It should be noted that the smaller the width difference between the top and bottom of the first sub-gate 4a and the width difference between the top and bottom of the second sub-gate 4b, the lighter the side etching of the first sub-gate 4a and the second sub-gate 4b, the larger the cross-sectional area of ​​the first sub-gate 4a and the second sub-gate 4b, the smaller the resistance, and the higher the current.

[0089] Preferably, the width of the first auxiliary grid 4a on one side close to the elliptical hole 3a is 340 μm-436 μm, that is, the width of the bottom of the first auxiliary grid 4a is 340 μm-436 μm. Exemplarily, the width of the first auxiliary grid 4a on one side close to the elliptical hole 3a is 340 μm, 350 μm, 360 μm, 370 μm, 380 μm, 390 μm, 410 μm, 420 μm, 430 μm or 436 μm.

[0090] The width of the second auxiliary grid 4b on the side close to the elliptical hole 3a is 240μm-336μm, that is, the width of the bottom of the second auxiliary grid 4b is 340μm-436μm. Exemplarily, the width of the second auxiliary grid 4b on the side close to the elliptical hole 3a is 340μm, 350μm, 360μm, 370μm, 380μm, 390μm, 410μm, 420μm, 430μm or 436μm.

[0091] Since the etching rate of the first doped region 2a is greater than that of the second doped region 2b, the width of the first sub-gate 4a close to the elliptical hole is greater than that of the second sub-gate 4a close to the elliptical hole, that is, the width of the bottom of the first sub-gate 4a is greater than that of the bottom of the second sub-gate 4a.

[0092] like Figure 2 As shown, as an implementable manner, the height h of the first sub-gate 4a and the second sub-gate 4b is 7μm-10μm, for example, h can be 7μm, 7.3μm, 7.5μm, 7.7um, 8μm, 8.4μm, 8.9μm, 9.1um, 9.6um, 10um, etc.

[0093] The height difference between the first doping region 2a and the second doping region 2b is greater than or equal to 2μm, for example but not limited to 2μm, 2.2μm, 2.7μm, 3um, 3.5μm, 3.8μm, 4um, 4.5μm, 4.7um, 5μm, 6um, 6.5μm, etc.

[0094] like Figure 2As shown, the lateral etching amount of the first auxiliary grid 4a on the side away from the conductive through hole is L1, that is, the distance that the two sides of the top of the first auxiliary grid 4a are etched inward along the width direction is L1. The lateral etching amount of the second auxiliary grid 4b on the side away from the conductive through hole is L2, that is, the distance that the two sides of the top of the second auxiliary grid 4b are etched inward along the width direction is L2. The lateral etching amount of the first auxiliary grid 4a on the side close to the conductive through hole is L3, that is, the distance that the two sides of the bottom of the first auxiliary grid 4a are etched inward along the width direction is L3. The lateral etching amount of the second auxiliary grid 4b on the side close to the conductive through hole is L4, that is, the distance that the two sides of the bottom of the second auxiliary grid 4b are etched inward along the width direction is L4.

[0095] Preferably, L1, L2, L3 and L4 are all smaller than h. Since during the etching process of the metal layer 4, the side etching rate of the metal layer 4 is smaller than the downward etching rate of the metal layer 4, the lateral etching amount at the top and bottom of the first sub-gate 4a and the second sub-gate 4b needs to be smaller than h to prevent severe etching, thereby preventing the height of the first sub-gate 4a and the second sub-gate 4b from being too small after etching, thereby affecting the transmission of current.

[0096] During the etching process of the metal layer 4, the etching rate gradually decreases, so the side of the first sub-grid 4a and the second sub-grid 4b is a concave surface, and the concave amount in the middle is the largest. The above etching can adopt a wet etching process, and the etching solution used in the wet etching process includes 50-70g of sodium m-nitrobenzene sulfonate, such as but not limited to 50g / L, 52g / L, 55g / L, 58g / L, 60g / L, 62g / L, 65g / L, 70g / L, etc.; 90-110g of sulfuric acid, such as but not limited to 90g / L, 95g / L, 100g / L, 105g / L, 110g / L, etc.

[0097] In addition, the etching rate of the first doping region 2a is greater than the etching rate of the second doping region 2b, so the lateral etching amount of the first doping region 2a is greater than the lateral etching amount of the second doping region 2b, that is, L1>L2 and L3>L4. Figure 2 As shown, the distance between the side of the first auxiliary gate 4a close to the elliptical hole 3a and the edge of the first doping region 2a is L3, and the distance between the side of the second auxiliary gate 4b close to the elliptical hole 3a and the edge of the second doping region 2b is L4. Since the etching rate of the first doping region 2a is greater than the etching rate of the second doping region 2b, L3>L4. That is, the distance between the bottom of the first auxiliary gate 4a and the edge of the first doping region 2a is L3, and the distance between the bottom of the second auxiliary gate 4b and the edge of the second doping region 2b is L4, and L3>L4.

[0098] In the above embodiment, half of the difference between the bottom width and the top width of the first auxiliary gate 4a is less than or equal to L1, and half of the difference between the bottom width and the top width of the second auxiliary gate 4b is less than or equal to L2. The difference between the bottom width and the top width of the first auxiliary gate 4a is related to the lateral etching amount of the top and bottom of the first auxiliary gate 4a, and the difference between the bottom width of the second auxiliary gate 4b and the top width of the second auxiliary gate 4b is related to the lateral etching amount of the top and bottom of the second auxiliary gate 4b. In this way, the lateral etching amount of the top and bottom of the first auxiliary gate 4a and the lateral etching amount of the top and bottom of the second auxiliary gate 4b can be adjusted by adjusting the etching time, so as to obtain a suitable electrode morphology.

[0099] The width difference between the bottom and the top of the electrode can be adjusted according to different doping region designs. When the doping layer is wide, the width difference between the bottom and the top of the electrode needs to be small, so that the cross-sectional area of ​​the electrode is large and the resistance is small, so as to achieve better transmission of current. When the doping layer is narrow, the demand for current transmission is weak, but by adjusting the width difference between the bottom and the top of the electrode to be large, the width of the top is reduced to avoid shading. For example, when the width of the first doping region 2a is greater than the width of the second doping region 2b, the difference between the width of the side of the first sub-grid 4a close to the elliptical hole 3a and the width of the side away from the elliptical hole 3a is smaller than the difference between the width of the side of the second sub-grid 4b close to the elliptical hole 3a and the width of the side away from the elliptical hole 3a, that is, the difference between the width of the bottom and the width of the top of the first sub-grid 4a is smaller than the difference between the width of the bottom and the width of the top of the second sub-grid 4b. When the width of the first doping region 2a is smaller than the width of the second doping region 2b, the difference between the width of the first auxiliary gate 4a on the side close to the elliptical hole 3a and the width of the side away from the elliptical hole 3a is greater than the difference between the width of the second auxiliary gate 4b on the side close to the elliptical hole 3a and the width of the side away from the elliptical hole 3a, that is, the difference between the width of the bottom and the top of the first auxiliary gate 4a is greater than the difference between the width of the bottom and the top of the second auxiliary gate 4b. When the width of the first doping region 2a is equal to the width of the second doping region 2b, the difference between the width of the first auxiliary gate 4a on the side close to the elliptical hole 3a and the width of the side away from the elliptical hole 3a is equal to the difference between the width of the second auxiliary gate 4b on the side close to the elliptical hole 3a and the width of the side away from the elliptical hole 3a, that is, the difference between the width of the bottom and the top of the first auxiliary gate 4a is equal to the difference between the width of the bottom and the top of the second auxiliary gate 4b.

[0100] Preferably, half of the difference between the bottom width and the top width of the first sub-gate 4a is less than 10μm. Exemplarily, the difference between the bottom width and the top width of the first sub-gate 4a is 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm or 9.9μm.

[0101] Half of the difference between the bottom width and the top width of the second sub-gate 4b is less than 10μm. Exemplarily, the difference between the bottom width and the top width of the second sub-gate 4b is 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm or 9.9μm.

[0102] In addition, the distance between the edge of the first sub-gate 4a and the edge of the first doping region 2a is equal to the lateral etching amount L3 of the side of the first sub-gate 4a close to the conductive via, that is, the distance between the edge of the first sub-gate 4a and the edge of the first doping region 2a is L3. The distance between the edge of the second sub-gate 4b and the edge of the second doping region 2b is equal to the lateral etching amount L4 of the side of the second sub-gate 4b close to the conductive via, that is, the distance between the edge of the second sub-gate 4b and the edge of the second doping region 2b is L4.

[0103] In a possible embodiment, the solar cell is a back contact cell, and the first doping region 2a and the second doping region 2b are arranged in an interdigitated manner, that is, the first doping region 2a includes a first penetration region and a first vertical region, the first vertical region is perpendicular to the first penetration region, and one end of the first vertical region is connected to the first penetration region. The second doping region 2b includes a second penetration region and a second vertical region, the second vertical region is perpendicular to the second penetration region, and one end of the second vertical region is connected to the second penetration region. The first penetration region and the second penetration region are arranged in parallel, and the first vertical region and the second vertical region are arranged in an interdigitated manner, so that the first doping region 2a and the second doping region 2b are arranged in an interdigitated manner.

[0104] Along the direction in which the first doping region 2a and the second doping region 2b are staggered, that is, along the direction in which the first vertical region and the second vertical region are staggered, the width of the first doping region 2a is greater than the width of the second doping region 2b; the width of the first doping region 2a is 360μm-450μm, and the width of the second doping region 2b is 260μm-350μm. Based on this, the width of the first doping region 2a is greater than the width of the second doping region 2b, and the width range of the formed pn junction is also larger, that is, the area of ​​carrier separation is relatively large, which is conducive to the separation of carriers, thereby improving the photoelectric conversion efficiency of the battery. For example, the width of the first doping region 2a is 360μm, 380μm, 400μm, 420μm or 450μm. The width of the second doping region 2b is 260μm, 280μm, 300μm, 320μm or 350μm.

[0105] Exemplarily, the width of the first doping region 2a is 370 μm, and the width of the second doping region 2b is 270 μm; or the width of the first doping region 2a is 390 μm, and the width of the second doping region 2b is 290 μm; or the width of the first doping region 2a is 410 μm, and the width of the second doping region 2b is 310 μm.

[0106] Among them, the conductive through hole opened in the area corresponding to the passivation layer 3 and the first doping region 2a is a first through hole, and a part of the first auxiliary gate 4a passes through the first through hole to be in conductive contact with the first doping region 2a. The conductive through hole opened in the area corresponding to the passivation layer 3 and the second doping region 2b is a second through hole, and a part of the second auxiliary gate 4b passes through the second through hole to be in conductive contact with the second doping region 2b. Along the direction in which the first doping region 2a and the second doping region 2b are staggered, that is, along the direction in which the first vertical region and the second vertical region are staggered, the maximum size of the first through hole is 5%-15% of the width of the first doping region 2a, and the maximum size of the second through hole is 2%-15% of the width of the second doping region 2b. In other words, along the direction in which the first vertical region and the second vertical region are staggered, the maximum size of the first through hole is 5%-15% of the width of the first vertical region, and the maximum size of the second through hole is 2%-15% of the width of the second vertical region. Such arrangement keeps the openings of the first through hole and the second through hole within a reasonable range, preventing the first through hole and the second through hole from exceeding the edges of the first doping region 2a and the second doping region 2b to cause leakage risk, while ensuring good stability of the ohmic contact between the electrode and the doping layer 2.

[0107] An isolation region 2c is provided between the first doping region 2a and the second doping region 2b to avoid leakage of the solar cell and improve the reliability of the cell in later products.

[0108] like Figure 3 and Figure 4 As shown, along the direction in which the first doping region 2a and the second doping region 2b are staggered, the distance from the edge of the first sub-gate 4a to the edge of the elliptical hole 3a is Z1, 155μm≤Z1≤213μm. Z1 is set within a reasonable range to prevent the substrate 1 from being damaged by excessive film opening area while ensuring the carrier collection capability. Exemplarily, Z1 can be 155μm, 160μm, 170μm, 180μm, 190μm, 200μm, 210μm, 213μm, etc.

[0109] Along the direction in which the first doping region 2a and the second doping region 2b are staggered, the distance from the edge of the second sub-gate 4b to the edge of the elliptical hole 3a is Z2, 105μm≤Z2≤163μm. Z2 is set within a reasonable range to prevent the substrate 1 from being damaged by excessive film opening area while ensuring the carrier collection capability. Exemplarily, Z2 can be 105μm, 120μm, 130μm, 140μm, 150μm, 160μm, 163μm, etc.

[0110] like Figure 2As shown, along the direction in which the first doping region 2a and the second doping region 2b are staggered, the distance from the edge of the first vertical region to the edge of the elliptical hole 3a is L5, L5 = (the width of the first vertical region - 2B) / 2, 155 μm ≤ L5 ≤ 220 μm. The distance from the edge of the second vertical region to the edge of the elliptical hole 3a is L6, L6 = (the width of the second vertical region - 2B) / 2, 110 μm ≤ L6 ≤ 170 μm.

[0111] Preferably, considering that the width of the first doping region 2a is greater than the width of the second doping region 2b, the distance Z1 from the edge of the first sub-gate 4a to the edge of the elliptical hole 3a is greater than the distance Z2 from the edge of the second sub-gate 4b to the edge of the elliptical hole 3a, that is, Z1>Z2. In this way, according to the widths of the first doping region 2a and the second doping region 2b, the safety distance around the edge of the first sub-gate 4a is larger, and the safety distance around the edge of the second sub-gate 4b is smaller, so that the elliptical hole in the area corresponding to the passivation layer 3 and the first doping region 2a is closer to a circle, and the elliptical hole in the area corresponding to the passivation layer 3 and the second doping region 2b is narrower, longer and flatter, so that the film opening area of ​​the elliptical hole 3a accounts for a lower proportion of the area of ​​the first doping region 2a or the second doping region 2b, and the film opening damage is minimized, while ensuring good ohmic contact.

[0112] Furthermore, the minimum distance between the edge of the first through hole and the edge of the first doping region 2a is greater than the minimum distance between the edge of the second through hole and the edge of the second doping region 2b, wherein when Z1 and Z2 take minimum values, the minimum distance between the edge of the first through hole and the edge of the first doping region 2a is equal to the sum of L3 and Z1, and the minimum distance between the edge of the second through hole and the edge of the second doping region 2b is equal to the sum of L4 and Z2. Since the first doped region 2a is wider and has a stronger demand for current transmission, the opening area of ​​the first through hole needs to be larger to achieve a larger ohmic contact area, while the second doped region 2b is narrower and has a weaker demand for current transmission, so the opening area of ​​the second through hole can be appropriately reduced. Therefore, the window area of ​​the first through hole should be larger than the window area of ​​the second through hole. In this embodiment, by making the minimum distance between the edge of the first through hole and the edge of the first doped region 2a greater than the minimum distance between the edge of the second through hole and the edge of the second doped region 2b, the first through hole is made wider in the width direction of the first doped region 2a, and at the same time, the first through hole is made narrower, longer and flatter, which is more conducive to increasing the window area of ​​the first through hole, which can reduce the degree of damage at its center and maintain a sufficient contact area.

[0113] The embodiment of the present application also provides a photovoltaic module, which includes the solar cell provided by any of the above embodiments. Compared with the prior art, the beneficial effects of the photovoltaic module provided by the embodiment of the present application are the same as the beneficial effects of the above solar cell, which will not be described in detail here.

[0114] In the description of the above embodiments, specific features, structures, materials or characteristics may be combined in a suitable manner in any one or more embodiments or examples.

[0115] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art who is familiar with the present technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A solar cell, characterized in that: It comprises a substrate and a passivation layer, wherein the passivation layer covers a surface of at least one side of the substrate, wherein: The passivation layer is provided with a conductive through hole penetrating the thickness thereof, wherein the conductive through hole comprises an elliptical hole, the eccentricity of the elliptical hole is e, and 0.3<e<0.

98.

2. The solar cell according to claim 1, characterized in that 0.6<e<0.98; and / or, the length of the major semi-axis of the elliptical hole is greater than 5μm and less than or equal to 40μm; and / or, the length of the minor semi-axis of the elliptical hole is greater than or equal to 5μm and less than or equal to 20μm; and / or, the ratio of the major semi-axis to the minor semi-axis of the elliptical hole is greater than 1 and less than or equal to 2.

3. The solar cell according to claim 1, characterized in that The solar cell further comprises an electrode, wherein the electrode partially passes through the elliptical hole opened in the passivation layer, and the major axis of the elliptical hole is parallel to the extension direction of the electrode.

4. The solar cell according to claim 3, characterized in that: Each of the electrodes is provided with at least one row of elliptical holes in the orthographic projection area of ​​the passivation layer, and the multiple elliptical holes in each row are arranged in sequence along the extension direction of the electrode.

5. The solar cell according to claim 4, characterized in that: Two adjacent elliptical holes in the same row are tangent to each other, have a spacing or partially overlap each other; When there is a spacing between two adjacent elliptical holes in the same row, the distance between the two adjacent elliptical holes in the same row is X, 0 μm≤X≤110 μm; When two adjacent elliptical holes in the same row partially overlap, the overlapping length of the two adjacent elliptical holes in the same row is less than the semi-major axis of the elliptical hole.

6. The solar cell according to claim 3, characterized in that: Each of the electrodes is provided with two rows of elliptical holes in the orthographic projection area of ​​the passivation layer, and the two rows of elliptical holes are staggered.

7. The solar cell according to claim 1, characterized in that The solar cell further includes a doping layer, wherein the doping layer is at least partially located on a surface of at least one side of the substrate.

8. The solar cell according to claim 7, characterized in that: The doping layer comprises a first doping region and a second doping region of opposite conductivity types, the passivation layer at least partially covers a surface of the doping layer on a side away from the substrate, the elliptical hole opened in the region of the passivation layer corresponding to the first doping region is a first through hole, and the elliptical hole opened in the region of the passivation layer corresponding to the second doping region is a second through hole; The solar cell further comprises an electrode, wherein the electrode comprises a first auxiliary grid and a second auxiliary grid, wherein a portion of the first auxiliary grid passes through the first through hole to be in conductive contact with the first doping region, and a portion of the second auxiliary grid passes through the second through hole to be in conductive contact with the second doping region; The maximum dimension of the elliptical hole along the direction parallel to the extension of the first auxiliary grid or the second auxiliary grid is L, the maximum dimension of the elliptical hole along the direction perpendicular to the extension of the first auxiliary grid or the second auxiliary grid is L', and L>L'.

9. The solar cell according to claim 8, characterized in that The long axis of the elliptical hole is parallel to the extension direction of the first sub-grid or the second sub-grid; or, 5μm<L≤40μm, and 5μm≤L'≤20μm; or, The width of the first doped region is greater than the width of the second doped region, the maximum dimension of the first through hole along the direction parallel to the extension direction of the first auxiliary gate is La, and the maximum dimension of the second through hole along the direction parallel to the extension direction of the second auxiliary gate is Lb; La>Lb and the eccentricity of the first through hole is greater than the eccentricity of the second through hole, or La=Lb and the eccentricity of the first through hole is less than the eccentricity of the second through hole; or, The width of the first doped region is equal to the width of the second doped region, the maximum size of the first through hole along the direction parallel to the first auxiliary gate is La, and the maximum size of the second through hole along the direction parallel to the second auxiliary gate is Lb; La=Lb and the eccentricity of the first through hole is equal to the eccentricity of the second through hole.

10. The solar cell according to claim 8, characterized in that Each of the first sub-grids is provided with at least one row of elliptical holes in the orthographic projection area of ​​the passivation layer, and the multiple elliptical holes in each row are arranged in sequence along the extension direction of the first sub-grid; and / or each of the second sub-grids is provided with at least one row of elliptical holes in the orthographic projection area of ​​the passivation layer, and the multiple elliptical holes in each row are arranged in sequence along the extension direction of the second sub-grid.

11. The solar cell according to claim 10, characterized in that Two adjacent elliptical holes in the same row are tangent to each other, have a spacing or partially overlap; When there is a spacing between two adjacent elliptical holes in the same row, the distance between the two adjacent elliptical holes in the same row is X, 0 μm≤X≤110 μm; When two adjacent elliptical holes in the same row partially overlap, the overlapping length of the two adjacent elliptical holes in the same row is less than the semi-major axis of the elliptical hole.

12. The solar cell according to claim 8, characterized in that: The height of the first sub-gate and the second sub-gate protruding from the passivation layer is h; the difference between the width of the first sub-gate on the side close to the elliptical hole and the width on the side away from the elliptical hole is greater than 0 and less than 2h, and / or the difference between the width of the second sub-gate on the side close to the elliptical hole and the width on the side away from the elliptical hole is greater than 0 and less than 2h.

13. The solar cell according to claim 8, characterized in that The width of the first sub-grid on the side close to the elliptical hole is 340μm-436μm; and / or, the width of the second sub-grid on the side close to the elliptical hole is 240μm-336μm; and / or, the width of the first sub-grid on the side close to the elliptical hole is greater than the width of the second sub-grid on the side close to the elliptical hole.

14. The solar cell according to claim 8, characterized in that The difference between the width of the first auxiliary gate on the side close to the elliptical hole and the width on the side away from the elliptical hole is greater than or equal to the difference between the width of the second auxiliary gate on the side close to the elliptical hole and the width on the side away from the elliptical hole; and / or, the distance between the side of the first auxiliary gate close to the elliptical hole and the edge of the first doped region is L3, the distance between the side of the second auxiliary gate close to the elliptical hole and the edge of the second doped region is L4, and L3>L4; and / or, the minimum distance between the edge of the first through hole and the edge of the first doped region is greater than the minimum distance between the edge of the second through hole and the edge of the second doped region.

15. The solar cell according to any one of claims 8 to 14, characterized in that: The solar cell is a back contact cell, the doping layer comprises a first doping region and a second doping region in a finger-shaped cross pattern, the first doping region comprises a first penetration region and a first vertical region, the first vertical region is perpendicular to and connected to the first penetration region, the second doping region comprises a second penetration region and a second vertical region, the second vertical region is perpendicular to and connected to the second penetration region, and the first vertical region and the second vertical region are arranged in a staggered manner; The elliptical hole opened in the area of ​​the passivation layer corresponding to the first vertical area is a first through hole, and the elliptical hole opened in the area of ​​the passivation layer corresponding to the second vertical area is a second through hole; Along the direction in which the first vertical regions and the second vertical regions are staggered, the maximum size of the first through hole is 5%-15% of the width of the first vertical region, and the maximum size of the second through hole is 2%-15% of the width of the second vertical region.

16. The solar cell according to claim 15, characterized in that: Along the direction in which the first doping regions and the second doping regions are staggered, the distance from the edge of the first auxiliary grid to the edge of the elliptical hole is Z1, and the distance from the edge of the second auxiliary grid to the edge of the elliptical hole is Z2; 155μm≤Z1≤213μm; and / or, 105μm≤Z2≤163μm; and / or, Z1>Z2.

17. A photovoltaic module, characterized in that: Comprising the solar cell according to any one of claims 1 to 16.

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