NL2034501A - Solar cell and method for manufacturing solar cell - Google Patents

Abstract

A solar cell and a method for manufacturing solar cell. The solar cell includes a substrate. A surface of the substrate has coatings arranged at intervals along a width direction of the solar cell. The coatings each have a plurality of pits, and at least part of the pits overlap each other. The method includes: adding one of an emulsifier, conductive particles, and non- conductive particles to a plating solution; and treating the substrate with the plating solution, and forming the coatings with pits on the surface of the substrate. (Fig. 1)

Description

SOLAR CELL AND METHOD FOR MANUFACTURING SOLAR CELL

TECHNICAL FIELD

[0001] The present disclosure relates to the field of photovoltaic technologies and, in particular, to a solar cell and a method for manufacturing solar cell.

BACKGROUND

[0002] In the field of solar cells, technological research and development are proceeding to improve performance and application range of screen printing silver paste in solar cell industries, other processes for electrode manufacturing and metallization are also making progress, including technologies such as electroplating, inkjet, engraving, grooved buried contact, laser boron expansion selective emitter, and local back field. Among the above processes, the coating process has developed rapidly in recent years. A silver- containing electroplating solution is generally used for the electroplating process, and three coatings of nickel, copper, and silver are used, or only nickel and copper coatings are used, which helps to reduce costs through reducing silver amount and can produce electrodes with smaller widths and low contact resistance, thereby manufacturing solar cells with a higher cell efficiency.

[0003] Generally, during the manufacturing of the electrode of a solar cell, a seed layer is manufactured by electroplating or electroless plating. For example, a nickel electroplated layer or an electroless nickel plated layer is used as the seed layer. Then, a metal layer is electroplated, which is generally a copper layer. Finally, a protective layer is electroplated on a surface thereof, which is generally a silver layer or tin layer. Certain diffusion may occur between the nickel layer and the silicon base. Therefore, adhesion between nickel and silicon is good, but adhesion between nickel and copper may be poor, and electrode fall-off may easily occur between the nickel layer and the copper layer.

SUMMARY

[0004] The present disclosure provides a solar cell and a method for manufacturing solar cell, for solving the problem of easy fall-off of coatings and metal layers.

[0005] The present disclosure provide a solar cell, the solar cell includes: a substrate including coatings arranged at intervals along a width direction of the solar cell. Each of the coatings has a plurality of pits, and at least part of the pits overlap each other.

[0006] In one or more embodiments, a projection of at least one of the pits along a direction perpendicular to a thickness direction of the solar cell is at least one of a circle, an ellipse, or a strip.

[0007] In one or more embodiments, a maximum distance between any two points of a projection of one of the pits perpendicular to a thickness direction of the solar cell is L1, and 0.1 um=L1=500 um; and/or a maximum depth of one of the pits is H1, and 0.01 umsH122

Um.

[0008] In one or more embodiments, a surface roughness of the coatings is Ra, and

O.5sRas4.

[0009] In one or more embodiments, a dimension of the coating (2) in the width direction (YY) of the solar cell is L2, and 1 umsL25100 um; and/or a dimension of the coating (2) in a thickness direction (Z) of the solar cell is H2, and 0.01 umsH2510 um.

[0010] In one or more embodiments, a metal layer is provided at a surface of the coating, and the metal layer is located on a side of the coating away from the substrate.

[0011] The present disclosure further provides a method for manufacturing solar cell described in any one of the above, the method includes: adding one of an emulsifier, conductive particles, and non-conductive particles to a plating solution; and treating the substrate with the plating solution, and forming the coatings with pits on the surface of the substrate.

[0012] In one or more embodiments, prior to the treating the substrate with the plating solution, the method further includes: stirring the plating solution to so that the emulsifier,

the conductive particles, or the non-conductive particles are evenly distributed in the plating solution.

[0013] In one or more embodiments, the adding one of an emulsifier, conductive particles, and non-conductive particles to a plating solution includes: adding the emulsifier to the plating solution, the emulsifier including 1% to 10% primary brightener, 5% to 25% nonionic surfactant, and 0.1% to 1% stabilizer.

[0014] In one or more embodiments, the adding one of an emulsifier, conductive particles, and non-conductive particles to a plating solution includes: adding one of the conductive particles and the non-conductive particles to the plating solution, a maximum length of the conductive particles and the non-conductive particles being R, and 0.01

HM=R<50 um.

[0015] In one or more embodiments, the adding one of an emulsifier, conductive particles, and non-conductive particles to a plating solution includes: adding one of the conductive particles and the non-conductive particles to the plating solution, the conductive particles and the non-conductive particles being in shapes of spheres or ellipsoids.

[0016] In one or more embodiments, the adding one of an emulsifier, conductive particles, and non-conductive particles to a plating solution includes: adding the non- conductive particles to the plating solution, the non-conductive particles being one of SiO»,

BaSQ., graphite, kaolin, and glass.

[0017] In one or more embodiments, the adding one of an emulsifier, conductive particles, and non-conductive particles to a plating solution includes: adding the conductive particles to the plating solution, the conductive particles being one of aluminum and silver.

[0018] In one or more embodiments, the treating the substrate with the plating solution, and forming the coatings with pits on the surface of the substrate includes: treating the substrate by electroless plating or electroplating.

[0019] In one or more embodiments, the plating solution is a low-phosphorus electroless nickel plating solution, and the treating the substrate by electroless plating or electroplating includes: treating the substrate by electroless plating in the plating solution at a temperature in a range of 80°C to 95°C for 10 min to 50 min.

[0020] In one or more embodiments, the plating solution is a Watts nickel plating solution, and the treating the substrate by electroless plating or electroplating includes: treating the substrate by electroplating in the plating solution at a temperature in a range of 25°C to 55°C for 1 s to 300 s, current density of the electroplating ranging from 1 ASD to 60

ASD.

[0021] In one or more embodiments, prior to the treating the substrate with the plating solution, the method further includes: treating the substrate with hydrofluoric acid.

[0022] In one or more embodiments, subsequent to the treating the substrate with the plating solution, the method further includes: treating the substrate by electroplating, and forming metal layers on sides of the coatings away from the substrate.

[0023] It should be understood that the general description above and the detailed description in the following are merely exemplary and illustrative, and cannot limit the present disclosure.

BRIEF DESCRIPTION OF DRAWINGS

[0024] FIG. 1 is a schematic structural diagram of a solar cell according to one or more embodiments of the present disclosure;

[0025] FIG. 2 is a schematic structural diagram of a solar cell according to one or more embodiments of the present disclosure;

[0026] FIG. 3 is a schematic structural diagram of a solar cell according to one or more embodiments of the present disclosure from another perspective;

[0027] FIG. 4 is a schematic structural diagram of pits according to one or more embodiments of the present disclosure;

[0028] FIG. 5 is a schematic diagram of conductive particles and non-conductive particles according to one or more embodiments of the present disclosure;

[0029] FIG. 6 is a schematic diagram of conductive particles and non-conductive particles according to one or mare embodiments of the present disclosure; and

[0030] FIG. 7 is a schematic diagram of conductive particles and non-conductive particles according to one or more embodiments of the present disclosure. 5 [0031] The accompanying drawings herein are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present disclosure and, together with the specification, serve to explain the principles of the present disclosure.

DESCRIPTION OF EMBODIMENTS

[0032] In order to better understand the technical solution of the present disclosure, embodiments of the present disclosure are described in detail below with reference to the accompanying drawings.

[0033] It is to be made clear that the described embodiments are only some rather than all of the embodiments of the present disclosure. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present disclosure without creative efforts fall within the protection scope of the present disclosure.

[0034] The terms used in the embodiments of the present disclosure are intended only to describe particular embodiments and are not intended to limit the present disclosure. As used in the embodiments of the present disclosure and the appended claims, the singular forms of "a/an", "the", and "said" are intended to include plural forms, unless otherwise clearly specified by the context.

[0035] It is to be understood that the term "and/or" used herein is merely an association relationship describing associated objects, indicating that there may have three relationships. For example, A and/or B indicates that there are three cases of A alone, A and B together, and B alone. In addition, the character "/" herein generally means that associated objects before and after it are in an "or" relationship.

[0036] It is to be noted that the location terms such as "above", "below", "left", and

"right" described in the embodiments of the present disclosure are described with reference to the angles shown in the accompanying drawings, and should not be construed as limitations on the embodiments of the present disclosure. In addition, in the context, it is to be further understood that, when one element is referred to as being connected "above" or "below" another element, the one element may be directly connected "above" or "below" another element, or connected "above" or "below" another element via an intermediate element.

[0037] Generally, an electroplating process of a solar cell is to electroplate or electroless plate a seed layer, generally a nickel electroplated layer or an electroless nickel plated layer, then electroplate a metal layer, generally a copper layer, and finally electroplate a protective layer, generally a silver layer or tin layer. Such a solar cell has poor adhesion during electroplating, mainly poor adhesion between nickel and copper, and electrode fall- off easily occurs between the nickel layer and the copper layer. Certain diffusion may occur between the nickel layer and the silicon base. Therefore, adhesion between nickel and silicon is good. The silver layer is plated on the surface of the copper layer by replacement plating, and adhesion between silver and copper is also good.

[0038] As shown in FIG. 1 to FIG. 3, some embodiments of the present disclosure provide a solar cell. The solar cell includes a substrate 1. A surface of the substrate 1 has coatings 2, and the coatings 2 are arranged at intervals along a width direction Y of the solar cell. The coatings 2 have a plurality of pits 3, and at least part of the pits 3 are capable of overlapping each other.

[0039] The solar cell according to some embodiments of the present disclosure includes the substrate 1. The surface of the substrate 1 has the coatings 2. The coatings 2 can be used as a seed layer, such as a nickel layer, which may be formed on the surface of the substrate 1, ie., on a front surface or a rear surface of the substrate 1 by electroplating or chemical means. The substrate 1 is made of silicon. Certain diffusion may occur between nickel and the substrate 1. Therefore, the nickel and the substrate 1 have strong adhesion and do not easily fall off, which can reduce the possibility of electrode fall- off. Surfaces of the coatings 2 have a plurality of pits 3, and at least part of the pits 3 overlap each other. When the pits 3 overlap each other, a projection area thereof in a thickness direction Z of the solar cell can be increased, and a depth thereof can be increased, thereby increasing the volume of the pits 3 and further increasing the specific surface area of the coatings 2. Therefore, the pits 3 can greatly increase the specific surface area of the coatings 2, thereby facilitating subsequent plating of other metal layers on the surfaces of the coatings 2. The coatings 2 are arranged at intervals along the width direction Y of the solar cell, which facilitates manufacturing of electrodes, such as copper plating on the surfaces of the coatings 2, to collect and transfer currents. When the copper layer is bonded with the coatings 2, the pits 3 can greatly increase the area of bonding between the coatings 2 and the copper layer. Therefore, adhesion between the coatings 2 and other metal layers can be improved, stability of the coatings 2 can be improved, the possibility of electrode fall-off of the solar cell can be reduced, and the service life of the solar cell can be prolonged.

[0040] As shown in FIG. 4 to FIG. 7, in some embodiments, projections of the pits 3 along a direction perpendicular to the thickness direction Z of the solar cell are in shapes of circles, ellipses, or strips.

[0041] Cross sections of the pits 3 along a direction perpendicular to the thickness direction Z of the solar cell are in shapes of circles, ellipses, or strips, and the pits 3 are recessed on the surfaces of the coating 2 along the thickness direction of the solar cell and can be superimposed on each other. During subsequent forming of the metal layer, metal can increase the area of contact with the coatings 2 through the pits 3, thereby improving adhesion between the metal and the coatings 2 and reducing the possibility of fall-off of the metal from the coatings 2.

[0042] As shown in FIG. 1 and FIG. 2, in some embodiments, a maximum distance between any two points of the projections of the pits 3 perpendicular to the thickness direction Z of the solar cell is L1, and 0.1 umsL15500 um, and/or a maximum depth of the pits 3 is H1, and 0.01 umsH122 um.

[0043] The coatings 2 are provided on the surface of the substrate 1, and have dimensions of L1 in the width direction of the solar cell and dimensions of L2 in the thickness direction of the solar cell. The surface of the coating 2 has a plurality of pits 3. The pits 3 are recessed along the thickness direction of the solar cell. The pits 3 are irregularly distributed and can overlap each other or be superimposed on each other, and can also be partially formed by several pits 3 to increase the area of contact between other metal layers and the coatings 2, thereby improving the adhesion.

[0044] In some embodiments, surface roughness of the coatings 2 is Ra, and 0.5sRa<4.

[0045] The surface roughness refers to a small distance between machining surfaces and unevenness of tiny peaks and troughs. A distance between two peaks or two troughs is very small, which belongs to an error in a microscopic geometric shape. The smaller the surface roughness, the smoother the surface. The surface roughness Ra of the coatings 2 refers to an arithmetic mean difference of contours, specifically refers to an arithmetic mean of absolute values of distances between points on a contour line along a measurement direction and a reference line within a sampling length. The measurement direction is the thickness direction of the solar cell. Contours on upper and lower sides of the reference line within the sampling length have equal areas. When the surface roughness of the coatings 2 is Ra and 0.5sRa=4, the surfaces of the coatings 2 can ensure relatively smoothness to facilitate practical use and subsequent machining, and can also have a larger specific surface area, so as to facilitate strong adhesion between other metal layers and the coatings 2.

[0046] As shown in FIG. 1, in some embodiments, dimensions of the coatings 2 in the width direction Y of the solar cell are L2, and 1 umsL25100 um, and/or dimensions of the coatings 2 in the thickness direction Z of the solar cell are H2, and 0.01 um=H2<10 um.

[0047] The coatings 2 are provided on the surface of the substrate 1, having specific dimensions of L2 along the width direction of the solar cell, and 1 um=<L2<100 um, which facilitates subsequent forming of other metal layers on the coatings 2 as electrodes to collect ar transfer currents. The dimensions of the coatings 2 in the thickness direction of the solar cell are H2, and 0.01 umsH2510 um. The coatings 2 may be made of nickel. The nickel is not easy to interdiffuse with the substrate 1, and is thus generally provided on the surface of the substrate 1 as a seed layer to facilitate subsequent forming of other metal layers such as copper.

[0048] In some embodiments, surfaces of the coatings 2 have metal layers, and the metal layers are located on sides of the coatings 2 away from the substrate 1.

[0049] The metal layers, such as copper layers, are provided on the surfaces of the coatings 2. Copper easily interdiffuses with silicon. However, the surface of the substrate 1 is provided with the coatings 2, such as nickel, which can prevent diffusion of the copper to the substrate 1 and reduce the influence on performance of the product. The copper layers arranged on the surfaces of the coatings 2 can be configured to collect or transfer currents.

In addition, silver layers or tin layers can be arranged on surfaces of the copper layers as protective layers to protect the copper.

[0050] The present disclosure provides a method for manufacturing solar cell according to any one of the above embodiments. The method for manufacturing solar cell includes the following steps.

[0051] In S1, one of an emulsifier, conductive particles, and non-conductive particles is added to a plating solution.

[0052] In S2, the substrate 1 is treated with the plating solution, and the coatings 2 with pits 3 are formed on the surface of the substrate 1.

[0053] One of the emulsifier, the conductive particles, and the non-conductive particles is added to the plating solution, so that, when electroplating or electroless plating is performed on the substrate 1 to generate the coatings 2, a plurality of pits 3 are fomred on surfaces of the coatings 2, and the plurality of pits 3 can be superimposed on each other, thereby greatly increasing the specific surface area of the surfaces of the coatings 2 and facilitating generation of strong adhesion to subsequent metal layers. For example, the coatings 2 may be nickel, which can improve adhesion of copper on the surfaces of the coatings 2, thereby reducing the possibility of mutual detachment of copper and nickel, which can reduce occurrence of electrode fall-off.

[0054] In some embodiments, prior to step S2, the method for manufacturing solar cell further includes the following step.

[0055] In S20, the plating solution is stirred to cause the emulsifier, the conductive particles, or the non-conductive particles to be evenly distributed in the plating solution.

[0056] Before the substrate 1 is treated with the plating solution, the plating solution should be fully stirred. When a substance added to the plating solution is the conductive particles or the non-conductive particles, the conductive particles or the non-conductive particles can be evenly distributed in the plating solution, so that, when the substrate 1 is treated with the plating solution, uniform coatings 2 can be formed, and a number of fine pits 3 can be formed on the surfaces of the coatings 2. The pits 3 can be superimposed on each other or overlap each other, thereby increasing the specific surface area. When the substance added to the plating solution is the emulsifier, the emulsifier enables two or more immiscible components in the plating solution to form a high-temperature emulsion. This is based on the principle that, during the emulsification, the emulsifier can reduce interfacial tension of components of a mixed system and form a relatively strong film on surfaces of droplets or form a double electrode layer on the surface of the droplets due to charges given by the emulsifier, thereby preventing mutual aggregation of the droplets and maintaining the emulsion. Stirring after the addition of the emulsifier can fully dissolve the emulsifier to achieve the emulsification effect. After the plating solution is stirred, the coatings 2 with the pits 3 can be formed on the surface thereof after the substrate 1 is treated with the plating solution, which increases the specific surface area of the coatings 2 and improves adhesion between the coatings 2 and other metals.

[0057] In some embodiments, step S1 may further include the following step.

[0058] In S11, the emulsifier is added to the plating solution, the emulsifier including 1% to 10% primary brightener, 5% to 25% nonionic surfactant, and 0.1% to 1% stabilizer.

[0059] The primary brightener may be saccharin, sodium 2,7-benzenedisulfonate, p- toluenesulfonamide, sodium naphthalenetrisulfonate, or the like. The primary brightener can reduce grain sizes of the coatings 2 and have certain luster, and can reduce tensile stress of the coatings 2 and improve ductility of the coatings 2. The primary brightener can use newly deposited nickel as a catalyst to cause the coatings 2 to have a lower potential.

The primary brightener is further adsorbed on a crystal growth site on a surface of a cathode through unsaturated bonds thereof, such as at the top end or the edge of crystal. The nonionic surfactant includes fatty alcohol polyoxyethylene ether, alkylphenol ethoxylates, polyoxyethylene fatty amine, sorbitan fatty acid ester polyoxyethylene ether, ethylene oxide- propylene oxide block copolymer, and the like. The nonionic surfactant has high surface activity, good solubilization, washing, antistativity, lime soap dispersion, and other properties. The stabilizer includes animal glue, lecithin, gum arabic, starch, polyvinyl alcohol, and the like. The stabilizer is used as an additive for emulsifier coagulation, which can achieve coagulation and stabilization effects. 1% to 10% primary brightener, 5% to 25% nonionic surfactant, and 0.1% to 1% stabilizer are included. Each percentage is a mass ratio to the plating solution.

[0060] In some embodiments, step S1 may further include the following step.

[0061] In S12, one of the conductive particles and the non-conductive particles is added to the plating solution, a maximum length of the conductive particles and the non-conductive particles is R, and 0.01 umsRs50 Hm.

[0062] The conductive particles or the non-conductive particles with a maximum length of R (0.01 um=R<50 um) are added to the plating solution. When the conductive particles or the non-conductive particles are in shapes of spheres, R denotes a diameter thereof.

When the conductive particles or the non-conductive particles are in shapes of squares or other irregular shapes, R denotes the maximum length thereof. The addition of the conductive particles or the non-conductive particles of appropriate sizes to the plating solution enables the coatings 2 with pits 3 to be formed on the surface of the substrate 1 after treated with the plating solution. Shapes and dimensions of the pits 3 can be controlled by controlling the sizes of the conductive particles or the non-conductive particles, which can increase the specific surface area while the coatings 2 remain relatively flat.

[0063] In some embodiments, step S1 may further include the following step.

[0064] In S13, one of the conductive particles and the non-conductive particles are added to the plating solution, the conductive particles and the non-conductive particles are in shapes of spheres or ellipsoids.

[0065] The addition of the conductive particles or the non-conductive particles in shapes of spheres or ellipsoids to the plating solution enables the pits 3 to be formed on the surfaces of the coatings 2 formed by the treatment of the substrate 1 with the plating solution. The pits 3 can be relatively evenly distributed on the surface of the substrate 1 and can be superimposed on each other or at least partially overlap, thereby increasing the specific surface area of the coatings 2.

[0066] In some embodiments, the step of adding one of an emulsifier, conductive particles, and non-conductive particles to a plating solution includes: adding the non- conductive particles to the plating solution, the non-conductive particles is one of SiO2,

BaSQ., graphite, kaolin, and glass.

[0067] The non-conductive particles added to the plating solution have relatively stable properties, so that the surfaces of the formed coatings 2 have pits 3 when the substrate 1 is treated with the plating solution.

[0068] In some embodiments, step S1 may further include the following step.

[0069] In S14, the conductive particles are added to the plating solution, the conductive particles is one of aluminum and silver.

[0070] The conductive particles added to the plating solution have relatively stable properties, so that the surfaces of the formed coatings 2 have pits 3 when the substrate 1 is treated with the plating solution.

[0071] In some embodiments, step S2 further includes the following step.

[0072] In S21, the substrate 1 is treated by electroless plating or electroplating.

[0073] By electroless plating or electroplating, the coatings 2 can be formed on the surface of the substrate 1, and the surfaces of the coatings 2 have the pits 3.

[0074] In some embodiments, the plating solution is a low-phosphorus electroless nickel plating solution, and step S21 further includes the following step.

[0075] In S211, the substrate 1 is treated by electroless plating in the plating solution at a temperature in a range of 80°C to 95°C for 10 min to 50 min.

[0076] In the case of electroless plating, by using the low-phosphorus electroless nickel plating solution and performing treatment at an appropriate temperature for an appropriate time period, the coatings 2 can be formed on the surface of the substrate 1, and the surfaces of the coatings 2 have the pits 3, thereby increasing the specific surface area of the coatings 2.

[0077] In some embodiments, the plating solution is a Watts nickel plating solution, and step S21 further includes the following step.

[0078] In $212, the substrate is treated by electroplating in the plating solution at a temperature in a range of 25°C to 55°C for 1 s to 300 s, a current density of the electroplating ranging from 1 ASD to 60 ASD.

[0079] In the case of electroplating, by using the Watts nickel plating solution and performing treatment at an appropriate temperature and under appropriate current density for an appropriate time period, the coatings 2 can be formed on the surface of the substrate 1, and the surfaces of the coatings 2 have the pits 3, thereby increasing the specific surface area of the coatings 2.

[0089] In some embodiments, step S20 further includes the following step.

[0081] In S201, the substrate 1 is treated with hydrofluoric acid.

[0082] The hydrofluoric acid is used to clean or etch the substrate 1 to keep the surface of the substrate 1 clean, and after the etching, facilitate the substrate 1 to be subsequently further treated by the plating solution to form a coating film.

[0083] In some embodiments, the method for manufacturing solar cell further includes the following step.

[0084] In S3, the substrate 1 is treated by electroplating, and metal layers are formed on sides of the coatings 2 away from the substrate 1.

[0085] The coatings 2 are arranged on the surface of the substrate 1 and may be made of materials that are not easy to diffuse into silicon, such as nickel. The surfaces of the coatings 2 have pits 3, and the pits 3 can increase the specific surface area of the coatings 2. The metal layers arranged on the surfaces of the coatings 2 can have strong adhesion to the coatings 2, thereby reducing the possibility of detachment of the metal layers from the surfaces of the coatings 2. For example, copper layers may be arranged on the surfaces of the coatings 2 to collect or transfer currents. The coatings 2 can isolate the metal layers, reducing the possibility of diffusion between the metal layers and the substrate 1. Other metals, such as silver or tin, may be arranged on surfaces of the copper layers to play a role of protection.

[0086] In some embodiments, after plasma enhanced chemical vapor deposition (PECVD) of the Topcon solar cell, an opening is formed on the front surface and the rear surface thereof respectively by laser, and SiNx layers on the surfaces is removed. A width of the laser film opening ranges from 1 um to 100 um. The Topcon solar cell after laser film opening undergoes HF etching to remove oxide layers formed on the surface during film opening. Concentration of HF ranges from 0.1% to 50%, and the time of etching of the solar cell may range from 1 s to 600 s. For the Topcon solar cell after HF etching, a seed layer is nickel-plated by electroless plating. That is, the coatings 2 are formed on the surface of the substrate 1. During the nickel-plating, small SiO; particles with diameters ranging from 0.01

Hm to 50 um are added to the plating solution, and the small SiO: particles are stirred to be evenly suspended in the plating solution. The electroless nickel plating solution is a low-

phosphorus electroless nickel plating solution, the electroless nickel plating solution is at a temperature ranging from 80°C to 95°C, and the time of the electroless nickel plating solution ranges from 10 min to 50 min. After simple cleaning, the solar cell coated with the coatings 2 is placed in a copper bath for electroplating copper layers. Copper is electroplated by rack plating. That is, metal layers are formed on the surfaces of the coatings 2. An electroplating temperature ranges from 25°C to 55°C, electroplating time ranges from 5 min to 50 min, and current density of the electroplating ranges from 1 ASD to 60 ASD. The solar cell coated with the copper layers undergoes silver plating pretreatment and silver plating treatment after cleaning. The two treatments are both performed at room temperature. The time of silver plating pretreatment ranges from 30 s to 300 s, and the time of silver plating treatment ranges from 1 min to 10 min. Silver plating is used to form a protective layer. The solar cell after electroplating is subjected to argon-hydrogen gas annealing (FGA). An annealing temperature ranges from 150°C to 550°C, and the time of annealing ranges from 3 min to 300 min.

[0087] In some embodiments, after PEVCD, a Passivated Emitter and Rear Contact (PERC) solar cell is coated with photoresist on a surface thereof and exposed to expose positions of corresponding electrodes, and then is placed in an HF solution for etching to completely remove SiNx layers at the electrodes. The time of etching ranges from 20 min to 60 min. Then, the photoresist on a surface of a silicon wafer is washed off. The solar cell after the HF etching is cleaned, and then is subjected to electroplating to form the coatings 2 with dotted pits 3. That is, the coatings 2 are formed on the surface of the substrate 1. A base plating solution of a nickel layer with the pits 3 is the composition of conventional

Watts nickel, 1% to 10% saccharin and 1% to 10% p-toluenesulfonamide are added, a certain amount of nonionic surfactant, such as 5% to 25% alkylphenol ethoxylates and polyoxyethylene fatty amine, is added thereto, and then a certain amount of emulsifier coagulant, such as 0.1% to 1% polyvinyl alcohol, is added. An electroplating temperature ranges from 25°C to 55°C, electroplating time ranges from 1 s to 300 s, and current density of the electroplating ranges from 1 ASD to 60 ASD. The solar cell coated with the coatings 2 undergoes copper electroplating. Copper is electroplated by horizontal electroplating.

Firstly, a P side of the solar cell is electroplated under conditions that an electroplating temperature ranges from 22°C to 55°C, electroplating time ranges from 5 min to 50 min, and current density of the electroplating ranges from 1 ASD to 60 ASD. Then, an N side of the solar cell is electroplated under conditions that an electroplating temperature ranges from 22°C to 55°C, electroplating time ranges from 5 min to 50 min, and current density of the electroplating ranges from 1 ASD to 60 ASD. During the electroplating, the solar cell is required to be illuminated with certain intensity to provide an electroplating current. The solar cell coated with the copper layers is cleaned and then is placed in a tin plating bath for electro-tinning under conditions that an electroplating temperature ranges from 22°C to 55°C, electroplating time ranges from 1 s to 300 s, and current density of the electroplating ranges from 1 ASD to 80 ASD. A tin layer formed is used as a protective layer.

[0088] The present disclosure provides a solar cell and a method for manufacturing solar cell. The solar cell includes a substrate 1. A surface of the substrate 1 has coatings 2.

The coatings 2 are arranged at intervals along a width direction Y of the solar cell. The coatings 2 have a plurality of pits 3, and at least part of the pits 3 are overlapping each other.

The pits 3 can increase the specific surface area of the coatings 2, thereby improving adhesion between other metals and the coatings.

[0089] The above are merely some embodiments of the present disclosure, and are not intended to limit the present disclosure. For those skilled in the art, the present disclosure may be subject to various modifications and changes. Any modification, equivalent replacement, improvement and the like within the spirit and principle of the present disclosure all fall within the protection scope of the present disclosure.

Claims (20)

CONCLUSIONS A solar cell, comprising: a substrate (1) comprising coatings (2) applied at intervals along a width direction (Y) of the solar cell; wherein each of the coatings (2) has a plurality of depressions (3), and at least some of the depressions (3) overlap each other Solar cell according to claim 1, wherein a projection of at least one of the depressions (3) over a length perpendicular to a thickness direction (Z) of the solar cell is at least a circle, an elliptical shape and/or a strip. 3. Solar cell according to claim 1, wherein a maximum distance between each of any two points of a projection of one of the floors (3) perpendicular to a thickness direction (Z) of the solar cell is L1, and where 0.1 um = L1 s 500 pm. 4. Solar cell according to claim 1, wherein a maximum depth of one of the recesses (3) is H1, and wherein 0.01 um s H1 < 2 um. 5. Solar cell according to claim 1, wherein the surface roughness of the coating (2) is Ra, and O where .5 <= Ra =< 4. 6. Solar cell according to claim 1, wherein a dimension of the coating (2) in the width direction (Y) of the solar cell is L2, and wherein 1 µm < L2 < 100 µm. 7. Solar cell according to claim 1, wherein a dimension of the coating (2) in a thickness direction (Z) of the solar cell is H2, and wherein 0.01 µm < H2 < 10 µm. Solar cell according to any one of claims 1 to 7, wherein a metal layer is provided on a substrate of the coating (2), and the metal layer is located on a side of the coating (2) that faces away from the substrate (1). A method for manufacturing a solar cell according to any one of claims 1 to 8, wherein the method comprises: adding an emulsifier, conductive particles, or non-conductive particles to a plating solution; and treating the substrate (1) with the plating solution, and forming the coatings (2) with depressions (3) on a surface of the substrate (1). A method for manufacturing a solar cell according to claim 9, wherein, prior to treating the substrate (1) with the plating solution, the method further comprises: stirring the plating solution such that the emulsifier, the conductive particles or the non-conductive particles are uniformly distributed in the plating solution. A method for manufacturing a solar cell according to claim 9, wherein adding an emulsifier, conductive particles, or non-conductive particles to a plating solution comprises: adding the emulsifier to the plating solution, the emulsifier comprising 1% to 10% primary brightener, 5% to 25% nonionic surfactant, and 0.1% to 1% stabilizer. A method of manufacturing a solar cell according to claim 9, which includes adding an emulsifier, conductive particles, or non-conductive particles to a plating solution; adding the conductive particles or the non-conductive particles to the plating solution, where a maximum length of the conductive particles and the non-conductive particles is R, and where 0.01 um = R = 50 um. 13. Method for manufacturing a solar cell according to claim 9, wherein adding an emulsifier, conductive particles or non-conductive particles to a plating solution comprises: adding the conductive particles and/or the non-conductive particles to the plating solution, wherein the conductive particles and non-conductive particles have shapes of spheres or ellipses. A method for manufacturing a solar cell according to claim 9, wherein adding an emulsifier, conductive particles or non-conductive particles to plating solution comprises: adding the non-conductive particles to the plating solution, wherein the non-conductive particles are SiO2, BaSO, , graphite, kaolin or glass. A method for manufacturing a solar cell according to claim 9, wherein adding an emulsifier, conductive particles or non-conductive particles to a plating solution comprises: adding the conductive particles to the plating solution, where the conductive particles are aluminum or silver. A method of manufacturing a solar cell according to claim 14, comprising treating the substrate (1) with the plating solution, and forming the coatings (2) with depressions (3) on the surface of the substrate (1) : treating the substrate (1) by means of electroless plating or electroplating. A method of manufacturing a solar cell according to claim 16, wherein the plating solution is a nickel plating solution for electroless plating with a low phosphorus content, and wherein treating the substrate (1) by means of electroless plating or electroplating comprises: treating the substrate (1) by electroless plating in the plating solution at a temperature in the range of 80°C to 95°C for 10 min to 50 min. A method of manufacturing a solar cell according to claim 16, wherein the plating solution is a Watts type nickel plating solution, and wherein treating the substrate (1) by means of electroless plating or electroplating comprises: treating the substrate ( 1) by electroplating in the plating solution at a temperature in the range of 25°C to 55°C for 1 s to 300 s, with an electroplating current density in the range of 1 ASD to 60 ASD . A method of manufacturing a solar cell according to any one of claims 14 to 18, wherein, prior to treating the substrate (1) with the plating solution, the method further comprises: treating the substrate (1) with phosphoric acid. A method of manufacturing a solar cell according to any one of claims 14 to 18, wherein, after treating the substrate (1) with the plating solution, the method further comprises: treating the substrate (1) by means of of electroplating, and forming a metal layer on a side of the coating (2) facing away from the substrate (1).