Solar cell, preparation method thereof and photovoltaic module

Abstract

The invention provides a solar cell, a preparation method thereof and a photovoltaic module, and relates to the field of photovoltaic technology. The solar cell includes: a silicon substrate; the N-type doped layer is positioned on the N region of the silicon substrate; the P-type doped layer is positioned on the P region of the silicon substrate; the first electrode comprises a first seed layer, and the first seed layer is in contact with the P-type doped layer; the second electrode comprises a second seed layer, and the second seed layer is in contact with the N-type doped layer; wherein the thickness of the second seed layer is greater than that of the first seed layer. The cost of the solar cell can be reduced, recombination is reduced, and the performance of the solar cell is improved.

Description

Technical Field

[0001] The present invention relates to the field of photovoltaic technology, and particularly to a solar cell, a preparation method thereof, and a photovoltaic module. Background Art

[0002] A solar cell is a device that directly converts light energy into electrical energy through the photovoltaic effect. Due to its use of clean energy, it has broad application prospects. The electrodes of a solar cell are used to collect and conduct current. Currently, silver paste is usually used to form silver electrodes in solar cells.

[0003] However, with the continuous expansion of the photovoltaic industry market and production capacity, the demand for silver paste in the industry has also increased synchronously, and the price of silver paste has risen accordingly, resulting in a continuous increase in the cost of solar cells. Moreover, the metal elements in the electrodes are prone to diffuse towards the silicon substrate direction, introducing more recombination of holes and electrons. Summary of the Invention

[0004] The present invention provides a solar cell, a preparation method thereof, and a photovoltaic module, aiming to solve the problems that the silver electrodes in existing solar cells lead to too high costs and the metal elements in the electrodes are prone to diffuse towards the silicon substrate direction.

[0005] In the first aspect of the present invention, a solar cell is provided, including:

[0006] A silicon substrate: The silicon substrate includes an N region and a P region;

[0007] An N-type doping layer, located on the N region of the silicon substrate;

[0008] A P-type doping layer, located on the P region of the silicon substrate;

[0009] A first electrode, the first electrode includes: a first seed layer, the first seed layer is in contact with the P-type doping layer;

[0010] A second electrode, the second electrode includes: a second seed layer, the second seed layer is in contact with the N-type doping layer;

[0011] Wherein, the thickness of the second seed layer is greater than the thickness of the first seed layer.

[0012] In the present application, the N-type doped layer (such as phosphorus doping) is usually negatively charged, the P-type doped layer (such as boron doping) is usually positively charged, and the metal ions are usually positively charged. According to the principle that like charges repel each other and opposite charges attract each other, the N-type doped layer is more likely to attract and recombine positively charged metal ions relative to the P-type doped layer, so a thicker second seed layer is required to block the diffusion of metal ions, while only a thinner first seed layer is required to have a good blocking effect on metal ions. In summary, in the present application, the thicker second seed layer can better block the diffusion of metal ions, thereby reducing recombination; the thinner first seed layer has a good blocking effect on the metal ions in the first electrode, can also reduce recombination, and can further reduce costs. On the one hand, it can well block the penetration of metal ions in the electrode, reduce recombination, and balance the blocking effect of the P region and the N region. On the other hand, setting the thickness of the seed layer as needed can also reduce material waste. In addition, the material of the remaining part of the electrode has more choices, and some metals with mature technology and low price can be selected to replace silver, which can reduce the cost of the electrode, and then reduce the cost of the solar cell.

[0013] Optionally, the ratio of the thickness of the second seed layer to the thickness of the first seed layer is greater than 1 and less than or equal to 2; and / or,

[0014] A difference between a thickness of the second seed layer and a thickness of the first seed layer is greater than 0 and less than or equal to 200 nm.

[0015] Optionally, a first passivation anti-reflection layer is located on a side of the P-type doped layer away from the silicon substrate; the first passivation anti-reflection layer has a first opening; the first seed layer is located in the first opening and extends in a direction away from the silicon substrate;

[0016] The second passivation anti-reflection layer is located on a side of the N-type doped layer away from the silicon substrate; the second passivation anti-reflection layer has a second opening; the second seed layer is located in the second opening and extends in a direction away from the silicon substrate.

[0017] Optionally, along a direction away from the silicon substrate: the first seed layer exceeds the adjacent first passivation anti-reflection layer, and the second seed layer exceeds the adjacent second passivation anti-reflection layer;

[0018] Along the direction away from the silicon substrate: the height of the portion of the first seed layer exceeding the first surface of the adjacent first passivation anti-reflection layer is a first height, and the height of the portion of the second seed layer exceeding the second surface of the adjacent second passivation anti-reflection layer is a second height;

[0019] Wherein, the second height is greater than the first height.

[0020] Optionally, the ratio of the second height to the first height is greater than 1 and less than or equal to 2.

[0021] Optionally, the width of the first opening is greater than or equal to the width of the second opening; the direction in which the width lies is perpendicular to the direction in which the thickness of the silicon substrate lies; and / or,

[0022] In the direction in which the thickness of the silicon substrate lies: the horizontal projection area of the first opening is greater than or equal to the horizontal projection area of the second opening.

[0023] Optionally, the ratio of the width of the second opening to the width of the first opening is greater than or equal to 0.5 and less than 1; and / or,

[0024] The ratio of the horizontal projection area of the second opening to the horizontal projection area of the first opening is greater than or equal to 0.5 and less than 1.

[0025] Optionally, the surface roughness of the side of the first seed layer facing away from the silicon substrate is greater than the surface roughness of the side of the second seed layer facing away from the silicon substrate; and / or,

[0026] The sheet resistance of the P-type doping layer is greater than the sheet resistance of the N-type doping layer; and / or,

[0027] Both the first seed layer and the second seed layer contain a number of stacked spherical particles inside.

[0028] Optionally, the solar cell further comprises:

[0029] A first intermediate layer, located between the first seed layer and the P-type doping layer; the first intermediate layer contains an alloy formed by silicon and the metal element in the first seed layer;

[0030] A second intermediate layer, located between the second seed layer and the N-type doping layer; the second intermediate layer contains an alloy formed by silicon and the metal element in the second seed layer.

[0031] Optionally, the first electrode further comprises: a first metal layer, located on the first seed layer; the second electrode further comprises: a second metal layer, located on the second seed layer;

[0032] The solar cell further comprises:

[0033] A first alloy layer, located between the first seed layer and the first metal layer; the first alloy layer contains an alloy formed by the metal element in the first seed layer and the metal element in the first metal layer;

[0034] A second alloy layer, located between the second seed layer and the second metal layer; the second alloy layer contains an alloy formed by a metal element in the second seed layer and a metal element in the second metal layer.

[0035] Optionally, the material of the first seed layer is selected from at least one of: titanium, tungsten, chromium, nickel, cobalt, molybdenum, tin, lead, palladium, copper, niobium, ruthenium, indium, zinc, titanium boride, tantalum nitride, tungsten nitride, titanium nitride, titanium-tungsten alloy, titanium-silicon compound, titanium-silicon-nitride, tantalum-silicon-nitride, nickel vanadium, hexagonal boron nitride; and / or,

[0036] The material of the second seed layer is selected from at least one of: titanium, tungsten, chromium, nickel, cobalt, molybdenum, tin, lead, palladium, copper, niobium, ruthenium, indium, zinc, titanium boride, tantalum nitride, tungsten nitride, titanium nitride, titanium-tungsten alloy, titanium-silicon compound, titanium-silicon-nitride, tantalum-silicon-nitride, nickel vanadium, hexagonal boron nitride; and / or,

[0037] The material of the first metal layer is selected from at least one of: copper, nickel, silver, chromium, lead, tin, indium, aluminum; and / or,

[0038] The material of the second metal layer is selected from at least one of: copper, nickel, silver, chromium, lead, tin, indium, aluminum.

[0039] Optionally, along the direction of the thickness of the silicon substrate, the silicon substrate includes opposite first and second surfaces;

[0040] The N region is located on one of the first surface and the second surface, and the P region is located on the other of the two surfaces; or,

[0041] Both the N region and the P region are located on the first surface.

[0042] In a second aspect of the present invention, a method for manufacturing a solar cell is provided, including:

[0043] Providing a silicon substrate; the silicon substrate includes: an N region and a P region;

[0044] Forming an N-type doped layer on the N region of the silicon substrate and forming a P-type doped layer on the P region of the silicon substrate;

[0045] Forming a first seed layer and a second seed layer; the first seed layer is in contact with the P-type doped layer; the second seed layer is in contact with the N-type doped layer; the thickness of the second seed layer is greater than the thickness of the first seed layer.

[0046] Optionally, forming the first seed layer and the second seed layer by at least one of electroplating and electroless plating; and / or,

[0047] The method further includes: printing and forming a first metal layer on the first seed layer; and / or,

[0048] printing and forming a second metal layer on the second seed layer.

[0049] In a third aspect of the present invention, there is provided a photovoltaic module, including: several solar cells as described in any one of the preceding claims.

[0050] The above-mentioned solar cell, its preparation method and photovoltaic module have the same or similar beneficial effects. For the sake of avoiding repetition, they will not be elaborated here. Description of the Drawings

[0051] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required to be used in the description of the embodiments of the present invention. Obviously, the following-described drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0052] Figure 1 It shows a partial structural schematic diagram of a solar cell in an embodiment of the present invention;

[0053] Figure 2 and Figure 3 It shows an SEM schematic diagram of the first seed layer on the P-type doping layer of two solar cells in an embodiment of the present invention;

[0054] Figure 4 and Figure 5 It shows an SEM schematic diagram of the second seed layer on the N-type doping layer of two solar cells in an embodiment of the present invention;

[0055] Figure 6 It shows an SEM schematic diagram of a second seed layer in an embodiment of the present invention;

[0056] Figure 7 It shows an SEM schematic diagram of a first seed layer in an embodiment of the present invention;

[0057] Figure 8 It shows an SEM schematic diagram of the surface of a second seed layer close to the second metal layer in an embodiment of the present invention;

[0058] Figure 9 It shows an SEM schematic diagram of the surface of a first seed layer close to the first metal layer in an embodiment of the present invention.

[0059] Description of the drawing reference numerals:

[0060] 1 - Silicon substrate, 2 - P-type doped layer, 3 - N-type doped layer, 4 - First seed layer, 5 - Second seed layer, 6 - First passivation and antireflection layer, 7 - Second passivation and antireflection layer, 8 - First metal layer, 9 - Second metal layer, 10 - Front passivation and antireflection layer. Detailed implementation mode

[0061] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0062] The following combines Figures 1 to 9 to explain the present application. In the present application, SEM refers to a scanning electron microscope. In the present application, Figure 1 except that d1, d2, d3, and d4, as well as W1 and W2 conform to the corresponding size relationships, the sizes of the remaining parts are only schematic and do not represent the relative size relationships of the actual respective structures. The present application provides a solar cell, including: a silicon substrate 1, a P-type doped layer 2, an N-type doped layer 3, a first electrode, and a second electrode. The silicon substrate 1 can be an N-type single crystal silicon or a P-type single crystal silicon, which can provide long-lived carriers; the silicon ingot can be cut by a diamond wire to obtain the silicon substrate; in order to minimize the influence of the cutting line marks on the surface recombination, the silicon substrate can be surface cleaned and polished before preparing other structures. The silicon substrate 1 includes an N region and a P region, and both the N region and the P region are part of the surface of the silicon substrate. Along the direction Q where the thickness of the silicon substrate is located, the silicon substrate includes: opposite first and second surfaces. During the operation of the solar cell, the surface of the silicon substrate that mainly receives light is its light-facing surface, and the backlight surface is opposite to the light-facing surface. Among the first surface and the second surface here, the first surface can be the backlight surface of the silicon substrate, and the second surface can be the light-facing surface of the silicon substrate. Optionally, both the N region and the P region are located on the first surface of the silicon substrate, then the solar cell is a back-contact solar cell. Here, both the first electrode and the second electrode are located on the backlight side of the silicon substrate, and there is no electrode blockage on the light-facing side of the silicon substrate, which has better performance and may be more aesthetically pleasing. It should be noted that when both the N region and the P region are located on the first surface of the silicon substrate, the relative sizes of the areas of the N region and the P region are not limited.

[0063] For example, Figure 1 in, both the N region and the P region are located on the first surface of the silicon substrate, Figure 1In it, the area to the left of the dashed line L1 is the N region, and the area between the dashed line L1 and the dashed line L2 is the P region. The dashed lines L1 and L2 here are only for the purpose of distinguishing the N region and the P region and do not actually exist in the solar cell. It should be noted that when both the N region and the P region are located on the first surface of the silicon substrate, there may also be an isolation region between the adjacent N region and P region. Or, the N region is located on one of the first surface and the second surface, and the P region is located on the other surface, that is, the N region is located on one of the light-facing surface and the backlight surface, and the P region is located on the other surface of the light-facing surface and the backlight surface. Specifically, whether the P region is located on the light-facing surface or the backlight surface, or whether the N region is located on the light-facing surface or the backlight surface is not specifically limited. Then, this solar cell is a double-sided solar cell with electrodes on both sides.

[0064] The P-type doping layer 2 may contain one or more elements of Group IIIA (for example, it may be boron). The N-type doping layer may contain one or more elements of Group VA (for example, it may be phosphorus). The materials of the N-type doping layer and the P-type doping layer may include any semiconductor material such as silicon, silicon-germanium, germanium, or gallium arsenide. In terms of the arrangement form of substances, the crystal phase of the doping layer may be amorphous, microcrystalline, nanocrystalline, single crystal, or polycrystalline, etc. Among them, the materials of the N-type doping layer and the P-type doping layer may be the same or different. For example: The materials of the N-type doping layer and the P-type doping layer may both include doped polysilicon. Another example: The material of the P-type doping layer may include doped polysilicon, and the material of the N-type doping layer may include at least one of doped amorphous silicon, doped microcrystalline silicon, and doped nanocrystalline silicon. Another example: The material of the P-type doping layer may be doped single crystal silicon, that is, formed by diffusion on the surface of the P region of the silicon substrate, and the material of the N-type doping layer may be doped polysilicon. The P-type doping layer can be prepared by in-situ doping or non-in-situ doping. The N-type doping layer can also be prepared by in-situ doping or non-in-situ doping.

[0065] The P-type doped layer 2 is located in the P region on the surface of the silicon substrate 1, and the N-type doped layer 3 is located in the N region on the surface of the silicon substrate 1. The P-type doped layer 2 located in the P region on the surface of the silicon substrate 1 includes: disposing a P-type doped layer in the P region on the surface of the silicon substrate, and an inward diffusion doped layer formed by inward diffusion of P-type doping elements into the silicon substrate during processing by laser or other means. The N-type doped layer 3 located in the N region on the surface of the silicon substrate 1 includes: disposing an N-type doped layer in the N region on the surface of the silicon substrate, and an inward diffusion doped layer formed by inward diffusion of N-type doping elements into the silicon substrate during processing by laser or other means. The relative sizes of the two regions are not specifically limited. The first electrode includes: a first seed layer 4, and the first seed layer 4 is in contact with the P-type doped layer 2. The second electrode includes: a second seed layer 5, and the second seed layer 5 is in contact with the N-type doped layer 3 to achieve current collection and conduction. In this application, through the first seed layer 4 and the second seed layer 5, a good contact effect is achieved, and the metal elements in the first electrode and the second electrode thereon can be blocked from diffusing into the silicon substrate, which can reduce recombination. At the same time, there are more choices for the remaining parts of the first electrode and the second electrode. Some metals with mature processes and low prices can be selected to replace silver, which can reduce the cost of the electrodes, and thus can reduce the cost of the solar cell.

[0066] Referring to Figure 1 , the thickness d2 of the second seed layer 5 in contact with the N-type doped layer 3 is greater than the thickness d1 of the first seed layer 4 in contact with the P-type doped layer 2. Specifically, the N-type doped layer 3 (such as phosphorus doping) is usually negatively charged, the P-type doped layer 2 (such as boron doping) is usually positively charged, and metal ions are usually positively charged. According to the principle of like charges repelling and opposite charges attracting, compared with the P-type doped layer 2, the N-type doped layer 3 is more likely to attract and recombine positively charged metal ions. Therefore, a thicker second seed layer 5 is required to block the infiltration of metal ions in the second electrode, while only a thinner first seed layer 4 has a good blocking effect on the metal ions in the first electrode. In summary, in this application, the thicker second seed layer 5 can well block the infiltration of metal ions in the second electrode, reduce recombination, and the thinner first seed layer 4 has a good blocking effect on the metal ions in the first electrode, can also reduce recombination, and can further reduce the cost. On the one hand, it can well block the infiltration of metal ions in the electrode and reduce recombination. On the other hand, setting the thickness of the seed layer as needed can also reduce material waste.

[0067] It should be noted that Figure 1As shown by Q in the figure, it represents the thickness direction of the silicon substrate. In this application, in the thickness direction of the silicon substrate, the starting point for setting the first seed layer 4 is the surface of the P-type doping layer 2 facing away from the silicon substrate 1. The thickness of the first seed layer 4 refers to the dimension of the first seed layer 4 in the thickness direction of the silicon substrate 1 starting from the surface of the P-type doping layer 2 facing away from the silicon substrate 1. In the thickness direction of the silicon substrate 1, the starting point for setting the second seed layer 5 is the surface of the N-type doping layer 3 facing away from the silicon substrate 1. The thickness of the second seed layer 5 refers to the dimension of the second seed layer 5 in the thickness direction of the silicon substrate 1 starting from the surface of the N-type doping layer 3 facing away from the silicon substrate 1.

[0068] Regarding the measurement and evidence-taking method for the thickness of the seed layer, specifically, in the thickness direction of the silicon substrate 1, the starting point for setting the first seed layer 4 is the surface of the P-type doping layer 2 facing away from the silicon substrate 1, and this surface can be a flat surface and / or a concave-convex surface. In the thickness direction of the silicon substrate, the starting point for setting the second seed layer 5 is the surface of the N-type doping layer 3 facing away from the silicon substrate 1, and this surface can be a flat surface and / or a concave-convex surface. The surface of the first seed layer 4 away from the P-type doping layer 2 can be a flat surface and / or a concave-convex surface, and the surface of the second seed layer 5 away from the N-type doping layer 3 can be a flat surface and / or a concave-convex surface.

[0069] For example, when all these four surfaces are only flat surfaces, all these four surfaces are perpendicular to the direction Q where the thickness of the silicon substrate is located. At this time, any point on the surface of the P-type doping layer 2 facing away from the silicon substrate 1 can be selected to any point on the surface of the first seed layer 4 away from the P-type doping layer 2, and the distance between the two in the direction Q where the thickness of the silicon substrate is located can be used as the thickness of the first seed layer. Also, the average value of several thicknesses can be selected as the thickness of the first seed layer; the evidence-taking method for the thickness of the second seed layer is consistent with that of the first seed layer.

[0070] For another example, when all these four surfaces include concave-convex surfaces, the concave-convex surfaces can have a peak structure and / or a valley structure. At this time, the lowest / highest point among all the peak structures on the surface of the P-type doping layer 2 facing away from the silicon substrate 1 can be selected to the lowest / highest point among all the peak structures on the surface of the first seed layer 4 away from the P-type doping layer 2, and the distance between the two in the direction Q where the thickness of the silicon substrate is located can be used as the thickness of the first seed layer. Also, the average value of several thicknesses can be selected as the thickness of the first seed layer; the evidence-taking method for the thickness of the second seed layer is consistent with that of the first seed layer.

[0071] For another example, when all four surfaces include concave-convex surfaces, the concave-convex surfaces may have peak structures and / or valley structures. In this case, the distance between the lowest / highest point of all the valley structures on the surface of the P-type doping layer 2 facing away from the silicon substrate 1 and the lowest / highest point of all the valley structures on the surface of the first seed layer 4 away from the P-type doping layer 2 in the direction Q where the thickness of the silicon substrate is located can be used as the thickness of the first seed layer. Alternatively, the average value of several thicknesses can be selected as the thickness of the first seed layer. The method for obtaining the thickness of the second seed layer is the same as that of the first seed layer.

[0072] In the present application, other vertices of the peak structures and valley structures on the above surfaces can also be selected to determine the thicknesses of the first seed layer and the second seed layer, which will not be elaborated here. It should be noted that in the present application, during the process of thickness comparison, the determination methods of the several thicknesses to be compared are correspondingly the same. For the determination methods of other thicknesses in the present application, they can all be referred to the foregoing examples and will not be elaborated here.

[0073] It should be noted that in the present application, when the solar cell further includes a first passivation and antireflection layer and a second passivation and antireflection layer, in the present application, the thickness of the first seed layer is the thickness of the first seed layer whose projection is located within the first opening in the first passivation and antireflection layer, and the thickness of the second seed layer is the thickness of the second seed layer whose projection is located within the second opening in the second passivation and antireflection layer. The projection here refers to the projection on a plane perpendicular to the thickness direction of the silicon substrate.

[0074] Optionally, the sheet resistance of the N-type doping layer 3 is small, the plating activity is high, it is easier to deposit the second seed layer 5, and a relatively thick second seed layer 5 can be easily obtained. The sheet resistance of the P-type doping layer 2 is large, the plating activity is low, the metal deposition is slow, and a relatively thin first seed layer 4 can be easily obtained. That is to say, the sheet resistance of the P-type doping layer 2 is greater than that of the N-type doping layer 3, and it is easier to obtain the seed layer with the required thickness. Thus, in order to achieve the blocking problem to be solved in the present application, in the same plating process with the same plating duration, it is technically feasible to achieve different thicknesses of the seed layers on the P region and the N region, and it is easier to operate in terms of process and is suitable for mass production and promotion.

[0075] The sheet resistance of the N-type doping layer 3 refers to the sheet resistance exhibited by the N-type doping layer 3, which refers to the resistance between the edges of a square thin film region in the N-type doping layer 3. The sheet resistance of the P-type doping layer 2 is similar.

[0076] Optionally, the ratio of the thickness d2 of the second seed layer 5 to the thickness d1 of the first seed layer 4 is greater than 1 and less than or equal to 2. Controlling the thickness ratio within this range has a good blocking effect on the infiltration of metal ions in the first electrode and the second electrode, and the thickness difference between the two is not too large, avoiding problems such as cracks and poor mechanical properties introduced during the lamination process.

[0077] For example, the ratio of the thickness d2 of the second seed layer 5 to the thickness d1 of the first seed layer 4 can be 1.01, 1.03, 1.05, 1.1, 1.2, 1.15, 1.3, 1.35, 1.4, 1.45, 1.5, 1.55, 1.6, 1.65, 1.7, 1.75, 1.8, 1.85, 1.9, 1.95, 2.

[0078] Optionally, the difference between the thickness d2 of the second seed layer 5 and the thickness d1 of the first seed layer 4 is greater than 0 and less than or equal to 200 nm (nanometers). Controlling the thickness difference between the two within this range provides good blocking effects on the penetration of metal ions in the first electrode and the second electrode. Moreover, the thickness difference between the two is not too large, which will not cause adverse effects during the subsequent preparation processes of the first metal layer and the second metal layer, and will not introduce mechanical damage during the subsequent lamination process.

[0079] For example, the difference between the thickness d2 of the second seed layer 5 and the thickness d1 of the first seed layer 4 can be 1 nm, 10 nm, 50 nm, 70 nm, 30 nm, 5 nm, 100 nm, 120 nm, 150 nm, 180 nm, 190 nm, 200 nm.

[0080] Refer to Figure 1 , Figure 2 , Figure 3 , in this application, the thickness d1 of the first seed layer 4 can be 260 nm, 300 nm, 350 nm, 400 nm, 448.2 nm, 448 nm, 504 nm, 500 nm, 503 nm, 503.2 nm, 504 nm, 600 nm, 743 nm, 700 nm, 800 nm, 900 nm, 1000 nm, 1100 nm, 1200 nm, 1300 nm. Refer to Figure 1 , Figure 4 , Figure 5 , in this application, the thickness d2 of the second seed layer 5 can be 460 nm, 500 nm, 550 nm, 562 nm, 562.2 nm, 600 nm, 605.4 nm, 606 nm, 629 nm, 700 nm, 754.8 nm, 755 nm, 843 nm, 1300 nm, 800 nm, 900 nm, 1000 nm, 1100 nm, 1200 nm, 1400 nm, 1500 nm. It should be noted that during the process of determining the thicknesses of the first seed layer 4 and the second seed layer 5, it is necessary to ensure that the thickness d2 of the second seed layer 5 is greater than the thickness d1 of the first seed layer 4.

[0081] Optionally, the solar cell further includes: a first passivation and antireflection layer 6 located on the side of the P-type doping layer away from the silicon substrate. The first passivation and antireflection layer 6 can achieve good passivation and antireflection effects. Refer to Figure 1 , a first opening is provided in the first passivation and antireflection layer. The first electrode or the first seed layer is disposed in the first opening of the first passivation and antireflection layer 6 and extends away from the P-type doping layer 2 or away from the silicon substrate from the first opening in the first passivation and antireflection layer 6. Along the direction away from the silicon substrate 1, the first seed layer 4 can be flush with the adjacent first passivation and antireflection layer, or the first seed layer 4 can extend beyond the adjacent first passivation and antireflection layer, or the first seed layer 4 can be lower than the adjacent first passivation and antireflection layer. The specific thickness relationship between the seed layer and the passivation and antireflection layer is determined according to the specific blocking effect. In addition, along the direction away from the silicon substrate 1, when the first seed layer is flush with the adjacent first passivation and antireflection layer or the first seed layer is lower than the adjacent first passivation and antireflection layer, compared with the case where the first seed layer 4 extends beyond the adjacent first passivation and antireflection layer along the direction away from the silicon substrate 1, the first seed layer can be thinner, and the thickness of the part of the first electrode other than the first seed layer is greater. Since the part of the first electrode other than the first seed layer has more selectivity and base metals, etc. can be selected, the cost can be further reduced.

[0082] Optionally, along the direction away from the silicon substrate 1, the first seed layer 4 can extend beyond the adjacent first passivation and antireflection layer. During the preparation process of the remaining part of the first electrode, such as the first metal layer 8, the first seed layer can better block the diffusion of metal layer ions from the junction of the passivation and antireflection layer and the seed layer to the silicon substrate, without strictly controlling the preparation precision of the metal layer, allowing the metal layer to epitaxially grow to the passivation and antireflection layer, which is easier to realize mass production and promotion in terms of process.

[0083] The solar cell further includes: a second passivation and antireflection layer 7 located on the side of the N-type doping layer 3 away from the silicon substrate. The second passivation and antireflection layer 7 can achieve good passivation and antireflection effects. A second opening is provided in the second passivation and antireflection layer. The second electrode or the second seed layer is disposed in the second opening of the second passivation and antireflection layer and extends away from the N-type doping layer 3 or away from the silicon substrate from the second opening in the second passivation and antireflection layer. Along the direction away from the silicon substrate 1, the second seed layer 5 can be flush with the adjacent second passivation and antireflection layer, or the second seed layer 5 can extend beyond the adjacent second passivation and antireflection layer, or the second seed layer 5 can be lower than the adjacent second passivation and antireflection layer. The specific effects are similar to those of the first seed layer and will not be elaborated.

[0084] Optionally, along the direction away from the silicon substrate 1, the second seed layer 5 can extend beyond the adjacent second passivation and antireflection layer. During the preparation process of the remaining part of the second electrode, such as the second metal layer 9, the specific effects are similar to those of the first seed layer and will not be elaborated.

[0085] It should be noted that in this application, the materials and thicknesses of the first passivation and antireflection layer and the second passivation and antireflection layer are not specifically limited. For example, both the first passivation and antireflection layer and the second passivation and antireflection layer can be composed of an aluminum oxide layer and a silicon nitride layer arranged in a stack. Among them, the aluminum oxide layer is closer to the silicon substrate, and the thickness of the silicon nitride layer can be 60nm, 80nm, 100nm, 150nm, 200nm, 250nm, 260nm, 120nm, 300nm, etc. The thickness of the aluminum oxide layer can be 4nm, 4.5nm, 5nm, 6nm, 5.5nm, 6.5nm, 7nm, 7.5nm, 8nm, 8.5nm, 9nm, 9.5nm, 10nm, etc. The direction in which this thickness is located is parallel to the direction in which the thickness of the silicon substrate is located.

[0086] In the case where the solar cell is a back-contact solar cell, both the first passivation and antireflection layer 6 and the second passivation and antireflection layer 7 here are located on the backlight side of the silicon substrate. Refer to Figure 1 A front passivation and antireflection layer 10 can also be provided on the light-facing side of the silicon substrate. In the case where the solar cell is a bifacial solar cell with electrodes on both sides, one of the first passivation and antireflection layer and the second passivation and antireflection layer here is located on the light-facing side of the silicon substrate, and the other is located on the backlight side of the silicon substrate.

[0087] Optionally, refer to Figure 1 , along the direction away from the silicon substrate 1, the height of the part of the first seed layer 4 in contact with the P-type doping layer 2 that exceeds the adjacent first passivation and antireflection layer 6 is the first height d3, and along the direction away from the silicon substrate 1, the height of the part of the second seed layer 5 in contact with the N-type doping layer 3 that exceeds the adjacent second passivation and antireflection layer 7 is the second height d4. Here, the second height d4 is greater than the first height d1. On the one hand, it is beneficial to enhance the corresponding effect that the thickness of the aforementioned second seed layer 5 is greater than the thickness of the first seed layer 4. On the other hand, the thickness requirements of the aforementioned first seed layer 4 and the second seed layer 5 are easy to achieve. The first passivation and antireflection layer and the second passivation and antireflection layer can be a flat surface and / or a concave-convex surface. The starting point and ending point for obtaining evidence of the first height and the second height are the same as the method for obtaining evidence of the thickness of the aforementioned seed layer, which will not be elaborated here.

[0088] Optionally, the ratio of the second height d4 to the first height d3 is greater than 1 and less than or equal to 2. When the ratio of the two is within this range, it is easy to implement the process, and the height difference between the two is not too large, avoiding mechanical damage such as cracks introduced during the lamination process due to the too large height difference between the two. For example, the ratio of the second height d4 to the first height d3 can be 1.01, 1.05, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.

[0089] Optionally, the difference between the second height d4 and the first height d3 here can be greater than 0 and less than or equal to 200 nm. The depths of the first opening in the first passivation and antireflection layer and the second opening in the second passivation and antireflection layer can be approximately equal, or in other words, the thicknesses of the first passivation and antireflection layer and the second passivation and antireflection layer can be approximately equal. The process parameters for preparing the first passivation and antireflection layer and the second passivation and antireflection layer, as well as the process parameters for forming the openings therein, can be approximately compatible or universal, and the processes for forming the first passivation and antireflection layer, the second passivation and antireflection layer, and the openings therein are simple.

[0090] For example, the difference between the second height d4 and the first height d3 can be 1 nm, 10 nm, 50 nm, 100 nm, 150 nm, 180 nm, 200 nm.

[0091] The first height d3 here can be 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, 550 nm, 600 nm, 650 nm, 700 nm, 750 nm, 800 nm, 850 nm, 900 nm, 950 nm, 1000 nm. The second height d4 here can be 400 nm, 450 nm, 500 nm, 550 nm, 600 nm, 650 nm, 700 nm, 750 nm, 800 nm, 850 nm, 900 nm, 950 nm, 1000 nm, 1100 nm, 1150 nm, 1200 nm.

[0092] Optionally, referring to Figure 1, the width W2 of the first opening in the first passivation and antireflection layer 6 located on the P-type doped layer 2 is greater than the width W1 of the second opening in the second passivation and antireflection layer 7 located on the N-type doped layer 3. The direction in which the width is located is the direction shown by the dotted line M, which is perpendicular to the direction Q of the thickness of the silicon substrate. Since the sheet resistance of the N-type doped layer 3 is lower than that of the P-type doped layer 2, and the concentration of active silicon in the N-type doped layer 3 is higher than that in the P-type doped layer 2, when designing the opening width, a smaller opening width can be used for the second opening in the second passivation and antireflection layer 7 to reduce the PL (photoluminescence) loss, while a larger width can be used for the first opening in the first passivation and antireflection layer to improve the plating activity of the P-type doped layer, facilitate the deposition of the first seed layer, and also reduce the contact resistance. For example, if the first opening in the first passivation and antireflection layer and the second opening in the second passivation and antireflection layer here are both realized by a laser process, the laser will have a certain impact on the silicon substrate and the doped layer, resulting in a certain degree of PL loss. The larger the opening width, the greater the PL loss and the smaller the open voltage of the solar cell. At the same time, the opening width needs to take into account the contact resistance. The smaller the opening width, the greater the difficulty of plating on the seed layer and the greater the contact resistance. Therefore, in this application, the width W2 of the first opening in the first passivation and antireflection layer is greater than the width W1 of the second opening in the second passivation and antireflection layer, which is an optimized balance of multiple factors such as PL loss, plating activity, and contact resistance, and can improve the performance of the solar cell.

[0093] In this application, the direction M in which the width of the mentioned opening is located is perpendicular to the direction Q of the thickness of the silicon substrate, and the lengths of the first opening in the first passivation and antireflection layer and the second opening in the second passivation and antireflection layer can be equal.

[0094] Optionally, the ratio of the width W1 of the second opening in the second passivation and antireflection layer to the width W2 of the first opening in the first passivation and antireflection layer is greater than or equal to 0.5 and less than 1. When the ratio of the two is within this range, a better balance is achieved among PL loss, plating activity, contact resistance, etc., and the process control of the widths of the two is relatively simple and easy to implement.

[0095] For example, the ratio of the width W1 of the second opening in the second passivation and antireflection layer to the width W2 of the first opening in the first passivation and antireflection layer can be 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 0.99. For another example, the width W1 of the second opening in the second passivation and antireflection layer can be 3μm, 5μm, 7μm, 9μm, 10μm, 11.5μm, 12μm, 15μm, 17.5μm, 20μm. The width W2 of the first opening in the first passivation and antireflection layer can be 5μm, 7μm, 9μm, 10μm, 11.5μm, 12μm, 15μm, 17.5μm, 20μm, 20μm, 25μm, 30μm, 18μm. It should be noted that during the process of designing the widths of the first opening in the first passivation and antireflection layer and the second opening in the second passivation and antireflection layer, it is necessary to ensure that the width W2 of the first opening in the first passivation and antireflection layer is greater than the width W1 of the second opening in the second passivation and antireflection layer. For another example, on the basis that the width W2 of the first opening in the first passivation and antireflection layer is greater than the width W1 of the second opening in the second passivation and antireflection layer, the difference between the two can be 5μm, 7μm, 9μm, 10μm, 0.5μm, 1μm, 2μm, 5μm, 2.5μm, 4μm, 5.5μm.

[0096] Optionally, the width W2 of the first opening in the first passivation and antireflection layer is equal to the width W2 of the second opening in the second passivation and antireflection layer. Furthermore, the process parameters corresponding to the width designs of the two can be compatible or shared, and the process is relatively simple. For example, the widths of the second opening in the second passivation and antireflection layer and the first opening in the first passivation and antireflection layer can be 5μm, 7μm, 9μm, 10μm, 11.5μm, 12μm, 15μm, 17.5μm, 20μm.

[0097] It should be noted that during the process of forming the first opening in the first passivation and antireflection layer and the second opening in the second passivation and antireflection layer in the form of laser, continuous laser spots or discontinuous laser spots can be used. Continuous laser spots mean that the laser spots overlap or are tangent to each other, and discontinuous laser spots mean that there is a spacing between the laser spots. The actual opening width of the discontinuous spots is equivalent to a smaller opening width when the continuous spots are used. Specifically, assume that the discontinuous laser spot is a circular spot with a radius of r, and the distance between the centers of two adjacent circular spots is L. Then the equivalent opening width of the discontinuous laser spot is: πr 2 / L. The units of r and L are the same, and the unit of the equivalent opening width is the same as the units of r and L. The above-mentioned opening widths in this application can all correspond to the opening width of the continuous laser. During the process of laser opening, the selection of the continuity of the laser spots and the equivalent opening width is comprehensively considered based on factors such as the open voltage and resistance of the battery, taking into account various factors.

[0098] Optionally, in the direction of the thickness of the silicon substrate 1: the horizontal projected area of the second opening in the second passivation and antireflection layer is smaller than the horizontal projected area of the first opening in the first passivation and antireflection layer. As described above, on the basis that the lengths of the first opening in the first passivation and antireflection layer and the second opening in the second passivation and antireflection layer are approximately equal, the width of the second opening in the second passivation and antireflection layer is smaller than the width of the first opening in the first passivation and antireflection layer. Therefore, the horizontal projected area of the second opening in the second passivation and antireflection layer is smaller than the horizontal projected area of the first opening in the first passivation and antireflection layer. The benefits here correspond to the width of the second opening in the second passivation and antireflection layer being smaller than the width of the first opening in the first passivation and antireflection layer. To avoid repetition, it will not be elaborated here. In the direction of the thickness of the silicon substrate 1, the horizontal projection of the second opening in the second passivation and antireflection layer means the projection obtained by projecting the second opening onto a plane perpendicular to the direction of the thickness of the silicon substrate 1. Similarly, in the direction of the thickness of the silicon substrate 1, the horizontal projection of the first opening in the first passivation and antireflection layer is the same.

[0099] Optionally, the ratio of the horizontal projected area of the spacer second opening in the second passivation and antireflection layer to the horizontal projected area of the first opening in the first passivation and antireflection layer is greater than or equal to 0.5 and less than 1. As described above, on the basis that the lengths of the first opening in the first passivation and antireflection layer and the second opening in the second passivation and antireflection layer are approximately equal, the ratio of the width of the second opening in the second passivation and antireflection layer to the width of the first opening in the first passivation and antireflection layer is greater than or equal to 0.5 and less than 1. Therefore, the ratio of the horizontal projected area of the second opening in the second passivation and antireflection layer to the horizontal projected area of the first opening in the first passivation and antireflection layer is greater than or equal to 0.5 and less than 1. The benefits here correspond to the ratio of the width of the second opening in the second passivation and antireflection layer to the width of the first opening in the first passivation and antireflection layer being greater than or equal to 0.5 and less than 1. To avoid repetition, it will not be elaborated here.

[0100] Figure 6 and Figure 7 are partial SEM schematic diagrams inside the seed layer. Optionally, referring to Figure 6 and Figure 7 , both the first seed layer and the second seed layer contain a number of stacked spherical particles inside. The spherical particles here have a large specific surface area, which is beneficial to improving the contact performance. The spherical shape here can be spherical, ellipsoidal, etc.

[0101] Optionally, referring to Figure 8 and Figure 9, the surface roughness of the first seed layer 4 in contact with the P-type doping layer 2 on the surface facing away from the silicon substrate or close to the first metal layer side is greater than that of the second seed layer 5 in contact with the N-type doping layer 3 on the surface facing away from the silicon substrate or close to the second metal layer side. Specifically, since the N-type doping layer 3 has strong plating activity, better conductivity, and a faster deposition rate, it is beneficial to accelerate the nucleation process of the plating grains, contributing to the formation of a second seed layer 5 with fine and dense grains. At the same time, the surface of the first seed layer 4 in contact with the P-type doping layer 2 facing away from the silicon substrate or close to the first metal layer 8 is rougher, which is conducive to increasing the bonding sites between the remaining electrodes on the first seed layer, such as the first metal layer 8 and the first seed layer 4, and increasing the bonding area between the remaining electrodes on the first seed layer, such as the first metal layer 8 and the first seed layer 4, thereby improving the conductivity of the P region. It should be noted that relative roughness or relative smoothness can be observed in the SEM image.

[0102] In this application, the surface roughness of the first seed layer 4 in contact with the P-type doping layer 2 on the surface facing away from the silicon substrate or close to the first metal layer side is closely related to the undulation of the surface wave peaks and valleys: on the surface of the first seed layer 4 facing away from the silicon substrate, within an area of 0.5μm×0.5μm, the distance or the average value of several distances between the vertex of any wave peak and the valley point of any wave valley in the direction along the thickness of the silicon substrate; the determination of the surface roughness of the second seed layer 5 in contact with the N-type doping layer 3 on the surface facing away from the silicon substrate or close to the second metal layer side is similar or the same as this, and for the sake of avoiding repetition, it will not be elaborated here. That is to say, in the case where the silicon substrate has a textured structure, the roughness of the above two surfaces is not caused by the different heights of the tips and bases of the textured structure, but by the undulation degree of the surface of the seed layer brought about by the plating process. The unit of the surface roughness of the above two seed layers is usually in the nanometer level.

[0103] For example, the surface roughness of the first seed layer 4 in contact with the P-type doping layer 2 on the surface facing away from the silicon substrate or close to the first metal layer side can be 45 - 300nm, specifically: 45nm, 50nm, 55nm, 80nm, 100nm, 150nm, 200nm, 255nm, 239.8nm, 275nm, 300nm. For example, the surface roughness of the second seed layer 5 in contact with the N-type doping layer 3 on the surface facing away from the silicon substrate or close to the second metal layer side can be 25 - 200nm, specifically: 25nm, 30nm, 40nm, 43.2nm, 50nm, 70nm, 90nm, 100nm, 110nm, 125.8nm, 150nm, 200nm. The surface roughness of the first seed layer 4 on the surface facing away from the silicon substrate or close to the first metal layer side is greater than that of the second seed layer 5 on the surface facing away from the silicon substrate or close to the second metal layer side, and the technical effects will not be elaborated.

[0104] Optionally, the solar cell further includes: a first intermediate layer located between the first seed layer 4 and the P-type doping layer 2; the first intermediate layer contains an alloy formed by silicon and the metal element in the first seed layer 4, that is, the first intermediate layer contains a metal silicon alloy. The first intermediate layer is mainly a metal silicon alloy layer formed by the metal element in the first seed layer 4 and silicon in the P-type doping layer 2. The formation of this first intermediate layer improves the contact performance between the first seed layer 4 and the P-type doping layer 2, which is beneficial to reducing the resistance of the P region. For example, if the first seed layer 4 contains nickel element, the first intermediate layer contains nickel silicon alloy. Another example, if the first seed layer 4 contains zinc element, the first intermediate layer contains zinc silicon alloy.

[0105] Optionally, the solar cell further includes: a second intermediate layer located between the second seed layer 5 and the N-type doping layer 3; the second intermediate layer contains an alloy formed by silicon and the metal element in the second seed layer 5, that is, the second intermediate layer contains a metal silicon alloy. The second intermediate layer is mainly a metal silicon alloy layer formed by the metal element in the second seed layer 5 and silicon in the N-type doping layer 3. The formation of this second intermediate layer improves the contact performance between the second seed layer 5 and the N-type doping layer 3, which is beneficial to reducing the resistance of the N region. For example, if the second seed layer 5 contains nickel element, the second intermediate layer contains nickel silicon alloy. Another example, if the second seed layer 5 contains zinc element, the second intermediate layer contains zinc silicon alloy.

[0106] Optionally, the first electrode further includes: a first metal layer 8 located on the first seed layer 4, and there is a good electrical connection effect between the first seed layer 4 and the first metal layer 8. The second electrode further includes: a second metal layer 9 located on the second seed layer 5, and there is a good electrical connection effect between the second seed layer 5 and the second metal layer 9. The solar cell further includes: a first alloy layer located between the first seed layer 4 and the first metal layer 8; the first alloy layer contains an alloy formed by the metal element in the first seed layer 4 and the metal element in the first metal layer 8. The formation of this first alloy layer strengthens the conductive channel between the first seed layer 4 and the first metal layer 8 and strengthens the mechanical properties of the first electrode. For example, if the first seed layer 4 contains nickel element and the first metal layer 8 contains copper element, the first alloy layer contains nickel copper alloy.

[0107] Optionally, the solar cell further includes: a second alloy layer located between the second seed layer 5 and the second metal layer 9; the second alloy layer contains an alloy formed by the metal element in the second seed layer 5 and the metal element in the second metal layer 9. The formation of this second alloy layer strengthens the conductive channel between the second seed layer 5 and the second metal layer 9 and strengthens the mechanical properties of the second electrode. For example, if the second seed layer 5 contains nickel element and the second metal layer 9 contains copper element, the second alloy layer contains nickel copper alloy.

[0108] Optionally, the material of the first seed layer 5 is selected from: titanium (Ti), tungsten (W), chromium (Cr), nickel (Ni), cobalt (Co), molybdenum (Mo), tin (Sn), lead (Pb), palladium (Pd), copper (Cu), niobium (Nb), ruthenium (Ru), indium (In), zinc (Zn), titanium boride (TiB x ), tantalum nitride (TaN x ), tungsten nitride (WN x ), titanium nitride (TiN x ), titanium-tungsten alloy (TiW x ), titanium silicide (TiSi x ), titanium silicon nitride (TiSiN), tantalum silicon nitride (TaSiN x ), nickel vanadium (NiV), hexagonal boron nitride (WBN), etc.; and / or, the material of the second seed layer is selected from: titanium (Ti), tungsten (W), chromium (Cr), nickel (Ni), cobalt (Co), molybdenum (Mo), tin (Sn), lead (Pb), palladium (Pd), copper (Cu), niobium (Nb), ruthenium (Ru), indium (In), zinc (Zn), titanium boride (TiB x ), tantalum nitride (TaN x ), tungsten nitride (WN x ), titanium nitride (TiN x ), titanium-tungsten alloy (TiW x ), titanium silicide (TiSi x ), titanium silicon nitride (TiSiN), tantalum silicon nitride (TaSiN x ), nickel vanadium (NiV), hexagonal boron nitride (WBN), etc. Specifically, the materials of the first seed layer and the second seed layer are selected from the above materials, and the properties such as the resistance and the barrier property to metal elements of the above materials are more suitable for making seed layers. In particular, when the materials of the first seed layer and the second seed layer are selected as nickel and / or zinc, on the one hand, both nickel and zinc have good contact properties; on the other hand, nickel and zinc basically do not penetrate into the silicon substrate and have less compounding; on the third hand, nickel and zinc have good barrier effects on the metals in the metal layer above, which can prevent the metals in the metal layer from penetrating into the silicon substrate and reduce the compounding. Whether the materials of the first seed layer and the second seed layer are the same is not specifically limited and can be the same or different. It should be noted that x in the above chemical formula is a number greater than 0. The materials of the first seed layer and the second seed layer can be the same or different, and this is not specifically limited.

[0109] Optionally, the material of the first metal layer is selected from at least one of copper, nickel, silver, chromium, lead, and aluminum (Al); and / or, the material of the second metal layer is selected from at least one of copper, nickel, silver, chromium, lead, and aluminum (Al). On the one hand, the above materials have good electrical conductivity; on the other hand, except for silver, the cost of the above materials is relatively low, which can reduce the cost of the electrodes; on the third hand, the seed layer has a good blocking effect on the above materials, avoiding their infiltration into the silicon substrate and reducing recombination; on the fourth hand, the above materials can be used in low-temperature processes to form metal layers, avoiding introducing thermal effects into the solar cells. Whether the materials of the first metal layer and the second metal layer are the same is not specifically limited, and they can be the same or different. For example, copper, nickel, and silver can be used to form metal layers in low-temperature processes. The materials of the first metal layer and the second metal layer can be the same or different, and this is not specifically limited.

[0110] In a solar cell, for the part other than the electrodes, the structure can be successively: a silicon substrate, a doping layer, and a passivation and antireflection layer starting from the silicon substrate. In the solar cell, at the position corresponding to the electrodes, the structure can be successively: a silicon substrate, a doping layer, an intermediate layer, a seed layer, an alloy layer, and a metal layer starting from the silicon substrate. That is, at the position corresponding to the first electrode, the structure can be successively: a silicon substrate, a P-type doping layer, a first intermediate layer, a first seed layer, a first alloy layer, and a first metal layer starting from the silicon substrate. At the position corresponding to the second electrode, the structure can be successively: a silicon substrate, an N-type doping layer, a second intermediate layer, a second seed layer, a second alloy layer, and a second metal layer starting from the silicon substrate.

[0111] In this application, when the electrode includes a current collecting grid line and a bus bar, the seed layer here can be a part of the current collecting grid line, and the metal layer can be the bus bar and a part of the current collecting grid line. The bus bar collects carriers or current on the current collecting grid lines with the same polarity.

[0112] This application also provides a method for manufacturing a solar cell, which is used to manufacture any one of the foregoing solar cells. The manufacturing method includes the following steps.

[0113] Step 101: Provide a silicon substrate; the silicon substrate includes an N region and a P region.

[0114] The silicon substrate here can be a textured silicon substrate, and this is not specifically limited.

[0115] Step 102: Form an N-type doping layer on the N region of the silicon substrate, and form a P-type doping layer on the P region of the silicon substrate.

[0116] The N-type doping layer and the P-type doping layer can be formed by diffusion processes or the like, and this is not specifically limited.

[0117] Step 103: Form a first seed layer and a second seed layer; the first seed layer is in contact with the P-type doped layer; the second seed layer is in contact with the N-type doped layer; the thickness of the second seed layer is greater than that of the first seed layer.

[0118] The first seed layer and the second seed layer can be formed by a metal deposition process. Optionally, at least one of electroplating and electroless plating can be used to form the first seed layer; and / or, at least one of electroplating and electroless plating can be used to form the second seed layer. The above processes for forming the first seed layer and the second seed layer are relatively mature and easy to achieve mass production. Electroplating utilizes the principle of electrochemical reduction, and metal ions are reduced and deposited on the surface of the doped layer by applying an external current to form a seed layer. Electroplating can select methods such as horizontal plating, rack plating, direct current electroplating, pulse electroplating, and photoinduced electroplating. Electroless plating is an autocatalytic reaction that does not require an external current. It uses a reducing agent in a solution containing metal ions to reduce and deposit metal ions on the surface of the doped layer to form a seed layer.

[0119] In the case where a first passivation and antireflection layer is formed on the P-type doped layer and a second passivation and antireflection layer is formed on the N-type doped layer, for example, referring to Figure 1 , the preparation method further includes a process of forming openings in the first passivation and antireflection layer and the second passivation and antireflection layer. Picosecond laser can be used to open the above passivation and antireflection layers according to the grid line pattern to form openings, and no specific limitation is imposed on the specific opening process. Figure 1 In, passivation and antireflection layers are provided on both opposite sides of the silicon substrate 1. The passivation and antireflection layers can both include an alumina layer and a silicon nitride layer. The alumina layer is closer to the silicon substrate 1, and the alumina layer and the silicon nitride layer exist together as the passivation and antireflection layer. After opening or setting the openings, pretreatment and activation can also be performed to enhance the activity of the doped layer, and then the seed layer is prepared.

[0120] Optionally, the method may further include: forming a first metal layer on the first seed layer and forming a second metal layer on the second seed layer.

[0121] The first metal layer and the second metal layer can be formed by using a method of printing low-temperature electrode paste, and no specific limitation is imposed thereon. Since low-temperature electrode paste is used, on the one hand, the energy consumption is reduced and the cost is reduced, and on the other hand, excessive heat brought into the solar cell is avoided. For example, low-temperature silver paste, low-temperature silver-coated copper paste, etc. can be used to form the metal layer.

[0122] The present application also provides a photovoltaic module, including a plurality of any one of the foregoing solar cells. The photovoltaic module may further include encapsulation adhesive films on both sides of the solar cells, etc., and no specific limitation is imposed on other structures in the photovoltaic module.

[0123] It should be noted that in this application, the relevant parts among the photovoltaic module, the solar cell, and the preparation method of the solar cell can be referred to each other, and the same or similar beneficial effects can be achieved. To avoid repetition, they will not be elaborated here.

[0124] It should be noted that in this text, the term "including", "comprising", or any other variant thereof is intended to cover non-exclusive inclusion, such that a process, method, article, or device including a series of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or device. Without further limitation, an element defined by the phrase "including one..." does not exclude the presence of another identical element in the process, method, article, or device including that element.

[0125] The embodiments of the present application have been described above in conjunction with the accompanying drawings. However, the present application is not limited to the above specific embodiments. The above specific embodiments are merely illustrative and not restrictive. Under the inspiration of the present application, those of ordinary skill in the art can also make many forms without departing from the purpose of the present application and the scope protected by the claims. All of these are within the protection scope of the present application.

Claims

1. A solar cell, characterized in that, include: Silicon substrate: The silicon substrate includes an N region and a P region; An N-type doped layer, located on the N region of the silicon substrate; A P-type doped layer, located on the P region of the silicon substrate; A first electrode, the first electrode comprising: a first seed layer, the first seed layer being in contact with the P-type doping layer; A second electrode, the second electrode comprising: a second seed layer, the second seed layer being in contact with the N-type doped layer; Wherein, the thickness of the second seed layer is greater than the thickness of the first seed layer.

2. The solar cell according to claim 1, characterized in that, The ratio of the thickness of the second seed layer to the thickness of the first seed layer is greater than 1 and less than or equal to 2; and / or, A difference between a thickness of the second seed layer and a thickness of the first seed layer is greater than 0 and less than or equal to 200 nm.

3. The solar cell according to claim 1 or 2, characterized in that, Also includes: A first passivation anti-reflection layer is located on a side of the P-type doped layer away from the silicon substrate; The first passivation anti-reflection layer has a first opening; The first seed layer is located in the first opening and extends in a direction away from the silicon substrate; The second passivation anti-reflection layer is located on a side of the N-type doped layer away from the silicon substrate; the second passivation anti-reflection layer has a second opening; the second seed layer is located in the second opening and extends in a direction away from the silicon substrate.

4. The solar cell according to claim 3, characterized in that, Along the direction away from the silicon substrate: the first seed layer exceeds the adjacent first passivation anti-reflection layer, and the second seed layer exceeds the adjacent second passivation anti-reflection layer; Along the direction away from the silicon substrate: the height of the portion of the first seed layer exceeding the adjacent first passivation anti-reflection layer is a first height, and the height of the second seed layer exceeding the adjacent second passivation anti-reflection layer is a second height; Wherein, the second height is greater than the first height.

5. The solar cell according to claim 4, characterized in that, The ratio of the second height to the first height is greater than 1 and less than or equal to 2.

6. The solar cell according to claim 3, characterized in that, The width of the first opening is greater than or equal to the width of the second opening; the direction of the width is perpendicular to the direction of the thickness of the silicon substrate; and / or, In the direction where the thickness of the silicon substrate is located: a horizontal projection area of ​​the first opening is greater than or equal to a horizontal projection area of ​​the second opening.

7. The solar cell according to claim 6, wherein The ratio of the width of the second opening to the width of the first opening is greater than or equal to 0.5 and less than 1; and / or, A ratio of a horizontal projection area of ​​the second opening to a horizontal projection area of ​​the first opening is greater than or equal to 0.5 and less than 1.

8. The solar cell according to claim 1 or 2, characterized in that, The surface roughness of the first seed layer facing away from the silicon substrate is greater than the surface roughness of the second seed layer facing away from the silicon substrate; and / or, The sheet resistance of the P-type doped layer is greater than the sheet resistance of the N-type doped layer; and / or, The first seed layer and the second seed layer both contain a plurality of stacked spherical particles.

9. The solar cell according to claim 1 or 2, characterized in that, Also includes: A first intermediate layer, located between the first seed layer and the P-type doped layer; the first intermediate layer contains an alloy formed by silicon and the metal element in the first seed layer; The second intermediate layer is located between the second seed layer and the N-type doping layer; the second intermediate layer contains an alloy formed by silicon and the metal element in the second seed layer.

10. The solar cell according to claim 1 or 2, characterized in that, The first electrode further includes: a first metal layer located on the first seed layer; the second electrode further includes: a second metal layer located on the second seed layer; a first alloy layer located between the first seed layer and the first metal layer; the first alloy layer contains an alloy formed by the metal elements in the first seed layer and the metal elements in the first metal layer; a second alloy layer located between the second seed layer and the second metal layer; the second alloy layer contains an alloy formed by the metal elements in the second seed layer and the metal elements in the second metal layer.

11. The solar cell according to claim 10, characterized in that, The material of the first seed layer is selected from at least one of: titanium, tungsten, chromium, nickel, cobalt, molybdenum, tin, lead, palladium, copper, niobium, ruthenium, indium, zinc, titanium boride, tantalum nitride, tungsten nitride, titanium nitride, titanium tungsten alloy, titanium silicon compound, titanium silicon nitride, tantalum silicon nitride, nickel vanadium, hexagonal boron nitride; and / or, The material of the second seed layer is selected from at least one of: titanium, tungsten, chromium, nickel, cobalt, molybdenum, tin, lead, palladium, copper, niobium, ruthenium, indium, zinc, titanium boride, tantalum nitride, tungsten nitride, titanium nitride, titanium tungsten alloy, titanium silicon compound, titanium silicon nitride, tantalum silicon nitride, nickel vanadium, hexagonal boron nitride; and / or, The material of the first metal layer is selected from at least one of: copper, nickel, silver, chromium, lead, tin, indium, aluminum; and / or, The material of the second metal layer is selected from at least one of: copper, nickel, silver, chromium, lead, tin, indium, aluminum.

12. The solar cell according to claim 1 or 2, characterized in that, Along the direction of the thickness of the silicon substrate, the silicon substrate includes opposite first and second surfaces; The N region is located on one of the first surface and the second surface, and the P region is located on the other of the two surfaces; or, Both the N region and the P region are located on the first surface.

13. A method for preparing a solar cell, characterized in that, including: providing a silicon substrate; The silicon substrate includes: an N region and a P region; forming an N-type doping layer on the N region of the silicon substrate and forming a P-type doping layer on the P region of the silicon substrate; forming a first seed layer and a second seed layer; the first seed layer is in contact with the P-type doping layer; the second seed layer is in contact with the N-type doping layer; the thickness of the second seed layer is greater than the thickness of the first seed layer.

14. The method for preparing a solar cell according to claim 13, wherein forming the first seed layer and the second seed layer by at least one of electroplating and electroless plating; and / or, The method further includes: printing and forming a first metal layer on the first seed layer; and / or, printing and forming a second metal layer on the second seed layer.

15. A photovoltaic module, characterized in that, including: several solar cells according to any one of claims 1 to 12.

Images