Photovoltaic cell, preparation method thereof and photovoltaic module

Abstract

The present application relates to the technical field of photovoltaics, and provides a photovoltaic cell, a preparation method thereof and a photovoltaic module. The photovoltaic cell provided in embodiments of the present application comprises a silicon substrate, a transparent conductive layer arranged on the front surface and / or the back surface of the silicon substrate and a metal grid line arranged on the transparent conductive layer, a pyramid texture is formed on the transparent conductive layer, and the metal grid line fills the bottom of the pyramid texture. The metal gate line fills the bottom of the pyramid texture, so that there are more contact points between the metal gate line and the transparent conductive layer, improving the contact between the metal gate line and the transparent conductive layer, reducing the contact resistance, and improving the efficiency of the photovoltaic cell. The preparation method provided in the embodiments of the present application is used for preparing the photovoltaic cell. The photovoltaic module provided in the embodiments of the present application comprises the photovoltaic cell or the photovoltaic cell prepared by the preparation method.

Description

Photovoltaic cell, method for manufacturing the same and photovoltaic module

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to the Chinese patent application No. 202410423564.X, filed on April 9, 2024, entitled “Photovoltaic cell, method for manufacturing the same and photovoltaic module”, the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0003] The present application relates to the technical field of photovoltaic, in particular to a photovoltaic cell, a method for manufacturing the same and a photovoltaic module. BACKGROUND

[0004] In a photovoltaic cell, the metal grid lines arranged on the transparent conductive layer are important structures of the photovoltaic cell, which play a role in collecting and transmitting current. The contact between the metal grid lines and the transparent conductive layer in the related art is poor, resulting in high contact resistance, which hinders the smooth collection and utilization of electrons and reduces the efficiency of the photovoltaic cell.

[0005] In view of this, the present application is proposed.

[0006] SUMMARY

[0007] The purpose of the present application includes providing a photovoltaic cell, a method for manufacturing the same and a photovoltaic module, which can improve the contact between the metal grid lines and the transparent conductive layer and improve the efficiency of the photovoltaic cell and the photovoltaic module.

[0008] Embodiments of the present application can be implemented as follows:

[0009] In a first aspect, the embodiments of the present application provide a photovoltaic cell, comprising:

[0010] a silicon substrate, a front surface and / or a back surface of the silicon substrate being provided with a transparent conductive layer, the transparent conductive layer being formed with a pyramid texture;

[0011] a metal grid line arranged on the transparent conductive layer, the metal grid line filling a bottom of the pyramid texture.

[0012] In an optional implementation, the metal grid line comprises:

[0013] a first grid line layer, the first grid line layer filling the bottom of the pyramid texture;

[0014] a second grid line layer, the second grid line layer being arranged on the first grid line layer in a stacked manner;

[0015] The first grid line layer and the second grid line layer each comprise a plurality of metal particles, and the particle size of the metal particles in the first grid line layer is smaller than the particle size of the metal particles in the second grid line layer.

[0016] In an optional embodiment, the particle size of the metal particles in the first gate line layer is less than 100 nm, and the particle size of the metal particles in the second gate line layer is greater than 300 nm.

[0017] In an optional embodiment, the metal particles in the first gate line layer and the second gate line layer both comprise silver particles, and the weight percentage of the silver particles in the metal particles of the second gate line layer is less than the weight percentage of the silver particles in the metal particles of the first gate line layer.

[0018] In an optional embodiment, the metal particles in the first gate line layer are all silver particles, the metal particles in the second gate line layer are composed of silver particles and non-silver particles, and the weight percentage of the silver particles in the metal particles of the second gate line layer is less than 50%.

[0019] In an optional embodiment, the particle size of the silver particles in the metal particles of the second gate line layer is 300-1000 nm, and the particle size of the non-silver particles is 1-5 μm.

[0020] In an optional embodiment, the non-silver particles comprise at least one of copper particles and aluminum particles.

[0021] In an optional embodiment, the silver particles in the first gate line layer and the silver particles in the second gate line layer both comprise flaky silver particles, the flaky silver particles in the silver particles of the first gate line layer account for less than 5 wt.%, and the flaky silver particles in the silver particles of the second metal paste account for more than 5 wt.%.

[0022] In an optional embodiment, the ratio of the particle size of the metal particles in the first gate line layer to the height difference between the top and the bottom of the pyramid texture is 0.005-0.35.

[0023] In an optional embodiment, the upper surface of the first gate line layer is flush with or lower than the top of the pyramid texture.

[0024] In an optional embodiment, the thickness of the first gate line layer is less than the thickness of the second gate line layer.

[0025] In an optional embodiment, the thickness of the first gate line layer is not greater than 2 μm, and the thickness of the second gate line layer is 5-30 μm.

[0026] In a second aspect, the embodiments of the present application provide a method for preparing a photovoltaic cell, comprising:

[0027] forming a pyramid texture on the front side and / or the back side of the silicon substrate;

[0028] depositing a transparent conductive layer on the pyramid texture;

[0029] The metal particles in the metal paste fill the bottoms of the pyramid surfaces.

[0030] In an optional embodiment, the step of using a metal paste to make the metal gate lines on the transparent conductive layer and filling the metal particles in the metal paste into the bottoms of the pyramid surfaces comprises:

[0031] using a first metal paste to make a first gate line layer on the transparent conductive layer, and filling the metal particles in the first metal paste into the bottoms of the pyramid surfaces;

[0032] using a second metal paste to make a second gate line layer on the first gate line layer;

[0033] wherein the particle size of the metal particles in the second metal paste is larger than the particle size of the metal particles in the first metal paste.

[0034] In an optional embodiment, the first gate line layer is made by a printing or inkjet method.

[0035] In an optional embodiment, the second gate line layer is made by a printing method.

[0036] In an optional embodiment, the upper surface of the first gate line layer is flush with or lower than the top of the pyramid surfaces.

[0037] In an optional embodiment, the step of using a first metal paste to make a first gate line layer on the transparent conductive layer and filling the metal particles in the first metal paste into the bottoms of the pyramid surfaces comprises:

[0038] calculating the volume of the space between the top and the bottom of the pyramid surfaces of the area to be printed;

[0039] filling the bottoms of the pyramid surfaces with the first metal paste in an amount equal to or less than the volume of the space between the top and the bottom of the pyramid surfaces of the area to be printed, to obtain the first gate line layer which is flush with or lower than the top of the pyramid surfaces.

[0040] In an optional embodiment, the step of using a first metal paste to make a first gate line layer on the transparent conductive layer and filling the metal particles in the first metal paste into the bottoms of the pyramid surfaces comprises:

[0041] coating the pyramid surfaces with the first metal paste in an amount exceeding the volume of the space between the top and the bottom of the pyramid surfaces;

[0042] removing the first metal paste above the top of the pyramid surfaces, so that the remaining first metal paste fills the bottoms of the pyramid surfaces and is flush with the top of the pyramid surfaces.

[0043] In a third aspect, the embodiments of the present application provide a photovoltaic module, which comprises the photovoltaic cell of any of the embodiments of the first aspect, or the photovoltaic cell prepared by the method of any of the embodiments of the second aspect.

[0044] The beneficial effects of the embodiments of the present application include, for example:

[0045] The photovoltaic cell of the embodiments of the present application comprises a silicon substrate, a transparent conductive layer arranged on the front surface and / or the back surface of the silicon substrate, and a metal grid line arranged on the transparent conductive layer, wherein a pyramid texture is formed on the transparent conductive layer, and the metal grid line fills the bottom of the pyramid texture. By making the metal grid line fill the bottom of the pyramid texture, the contact points between the metal grid line and the transparent conductive layer are more, thus the contact between the metal grid line and the transparent conductive layer can be improved, the contact resistance is reduced, and the efficiency of the photovoltaic cell is improved.

[0046] The method for preparing the photovoltaic cell of the embodiments of the present application comprises texturing on the front surface and / or the back surface of the silicon substrate to form a pyramid texture, depositing a transparent conductive layer on the pyramid texture, and using a metal paste to make a metal grid line on the transparent conductive layer, and making the metal particles in the metal paste fill the bottom of the pyramid texture. The method for preparing the photovoltaic cell provided by the embodiments of the present application can make the metal grid line and the transparent conductive layer better contact, reduce the contact resistance, and be conducive to improving the efficiency of the photovoltaic cell.

[0047] The photovoltaic module provided by the embodiments of the present application comprises the photovoltaic cell described above or the photovoltaic cell prepared by the method described above, thus the photovoltaic cell and the photovoltaic module can have higher efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0048] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed in the embodiments. It should be understood that the following drawings only show some of the embodiments of the present application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor.

[0049] FIG. 1 is a schematic diagram of larger metal particles in the paste contacting the transparent conductive layer;

[0050] FIG. 2 is a partial sectional view of a photovoltaic cell in an embodiment of the present application;

[0051] FIG. 3 is a schematic diagram of a first grid line layer laid on a transparent conductive layer in an embodiment of the present application;

[0052] FIG. 4 is a flowchart of a method for preparing a photovoltaic cell in an embodiment of the present application.

[0053] Icon: 100 - silicon substrate; 200 - transparent conductive layer; 301 - metal particles; 310 - first gate line layer; 320 - second gate line layer. DETAILED DESCRIPTION

[0054] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some but not all of the embodiments of the present application. The components of the embodiments of the present application described and shown in the drawings herein can be arranged and designed in various different configurations.

[0055] Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work under the premise that the scope of the present application is protected.

[0056] It should be noted that: similar reference numerals and letters represent similar items in the following drawings, therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0057] In the description of the present application, it should be noted that if the terms "upper", "lower", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship of the product of the present application when it is usually placed, which is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the indicated device or element must have a particular orientation, be constructed and operated in a particular orientation, therefore, it cannot be understood as a limitation on the present application.

[0058] In addition, if the terms "first", "second" and the like appear, they are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0059] It should be noted that the features in the embodiments of the present application can be combined with each other without conflict.

[0060] Heterojunction solar cells have high efficiency, high open circuit voltage and other advantages, and thus have better application prospects. As a component part of the electrode in the heterojunction solar cell, the contact between the metal grid line and the transparent conductive layer is an important factor affecting the efficiency of the solar cell. Generally, the lower the contact resistance between the transparent conductive layer and the metal grid line, the better, so that electrons and holes can be better collected by the metal grid line. The surface of the transparent conductive layer is not completely smooth. Since the silicon substrate is often textured to form a pyramid structure, the transparent conductive layer close to the surface of the silicon substrate also presents a pyramid structure with the surface of the silicon substrate. This pyramid structure can increase the contact area of the transparent conductive layer and the metal grid line, and at the same time improve the bonding strength. The metal grid line is formed by solidifying a paste containing metal particles. The inventors have found that the contact between the metal grid line and the transparent conductive layer in the related art is poor, resulting in a large contact resistance and a low cell efficiency. The reason is that the metal particles in the metal grid line often cannot fill the bottom of the pyramid texture. Figure 1 is a schematic diagram of a larger metal particle 301 in the paste contacting the transparent conductive layer 200. As shown in Figure 1, when the larger metal particle 301 is laid on the transparent conductive layer, it cannot well fill the bottom of the pyramid texture of the transparent conductive layer 200, resulting in a possible large gap between the metal grid line and the transparent conductive layer 200 (especially the gap in the two grooves on the right in Figure 1), and fewer contact points between the transparent conductive layer 200 and the metal particle 301, which results in a high contact resistance between the finally formed metal grid line and the transparent conductive layer 200.

[0061] Therefore, the embodiments of the present application provide a photovoltaic cell and a preparation method thereof, so that a part of the metal particles of the metal grid line can sufficiently fill the bottom of the pyramid texture, thereby achieving better contact between the metal grid line and the transparent conductive layer 200.

[0062] Figure 2 is a partial cross-sectional view of a photovoltaic cell in an embodiment of the present application; and Figure 3 is a schematic diagram of a first grid line layer 310 laid on a transparent conductive layer 200 in an embodiment of the present application. As shown in Figures 2 and 3, the photovoltaic cell provided by the embodiments of the present application includes a silicon substrate 100 and a metal grid line arranged on the silicon substrate 100. The front and / or back of the silicon substrate 100 is provided with a transparent conductive layer 200, and the transparent conductive layer 200 forms a pyramid texture. The metal grid line is arranged on the transparent conductive layer 200, and the metal particles in the metal grid line fill the bottom of the pyramid texture. By allowing the metal particles of the metal grid line to fill the bottom of the pyramid texture, the metal grid line has more contact points with the transparent conductive layer and has a lower contact resistance. In the embodiments of the present application, the front of the silicon substrate corresponds to the light-receiving side of the photovoltaic cell, which is the side on which light is incident when in use; and the back of the silicon substrate corresponds to the back light side of the photovoltaic cell.

[0063] In this embodiment, the silicon substrate 100 includes crystalline silicon as a main body and an amorphous silicon layer disposed on the surface of the crystalline silicon. The amorphous silicon layer follows the surface of the crystalline silicon due to the pyramid structures formed on the surface of the crystalline silicon by texturing, so that the silicon substrate 100 has a pyramid texture. After the transparent conductive layer 200 is disposed on the surface of the silicon substrate, the pyramid texture is naturally formed on the surface of the silicon substrate 100.

[0064] The pyramid texture can increase the contact area between the transparent conductive layer 200 and the metal grid lines, reduce the contact resistance, and improve the bonding strength. The distance between the top and the bottom of the pyramid texture can be set as needed; optionally, the distance between the top and the bottom of the pyramid texture is less than 2 μm, such as 0.5 μm, 1 μm, 1.5 μm, or 2 μm, or an intermediate value between any two of the above values. It can be understood that the pyramid texture includes a plurality of convex pyramid structures, and the spacing between the pyramid structures is the groove of the pyramid texture; in this embodiment, the distance between the top and the bottom of the pyramid texture is the depth of the groove, that is, the height difference between the bottom of the groove and the edge of the opening of the groove; in this embodiment, since the groove is formed by adjacent pyramid structures, the vertex of the pyramid structure is the highest point of the groove, so the depth of the groove can be regarded as the height difference (distance in the direction perpendicular to the silicon substrate 100) between the lowest point of the groove and the vertex of the pyramid structure.

[0065] In this embodiment, the metal grid line includes a first grid line layer 310 and a second grid line layer 320 stacked on each other, the first grid line layer 310 fills the bottom of the pyramid texture, and the second grid line layer 320 is stacked on the first grid line layer 310. The particle size of the metal particles in the first grid line layer 310 is smaller than the particle size of the metal particles in the second grid line layer 320. It should be understood that the first grid line layer 310 and the second grid line layer 320 are both prepared by a slurry containing metal particles, so the first grid line layer 310 and the second grid line layer 320 both include a plurality of metal particles. Optionally, the metal particles in the first grid line layer 310 and the second grid line layer 320 both include silver particles, and the weight percentage of silver particles in the metal particles of the second grid line layer 320 is less than the weight percentage of silver particles in the metal particles of the first grid line layer 310. Silver has the highest conductivity among metals, which can reduce the contact resistance between the first grid line layer 310 and the transparent conductive layer 200.

[0066] Optionally, the metal particles of the first gate line layer 310 are all silver particles, so as to improve the conductivity of the first gate line layer 310 as much as possible, and to reduce the contact resistance between the first gate line layer 310 and the transparent conductive layer 200 as much as possible. The metal particles of the second gate line layer 320 are composed of silver particles and non-silver particles, and the weight percentage of the silver particles in the metal particles of the second gate line layer 320 is less than 50%, such as 40%, 30%, 20%, 10%, or an intermediate value of any two of the above percentages. It can be understood that, since the first gate line layer 310 and the second gate line layer 320 are both metal, they do not easily have a large contact resistance between them, so the use of non-silver particles with relatively low conductivity (relative to silver) in part of the second gate line layer 320 will not cause the overall conductivity of the metal gate line to be significantly degraded; while the cost of silver is relatively high, reducing the proportion of silver particles in the second gate line layer 320 can save costs to some extent. Optionally, the non-silver particles in the second gate line layer 320 include at least one of copper particles and aluminum particles. Copper and aluminum have the characteristic of lower cost relative to silver.

[0067] In FIG. 2, the larger circles in the second gate line layer 320 represent non-silver particles or silver-coated copper particles, and the smaller circles represent silver particles; it should be noted that in FIG. 2, the size ratio of the silver particles in the second gate line layer 320 to the silver particles in the first gate line layer 310 does not represent the actual ratio, and the silver particles in the second gate line layer 320 are actually larger than the silver particles in the first gate line layer 310. Optionally, the specific materials of the metal particles of the first gate line layer 310 and the second gate line layer 320 can also be selected as needed, such as at least one of silver-coated copper particles, silver particles, gold particles, copper particles, and aluminum particles.

[0068] Optionally, the thickness of the first gate line layer 310 is less than the thickness of the second gate line layer 320. In this embodiment, since the particle size and material selection of the metal particles in the first gate line layer 310 have higher requirements (such as smaller particle size and higher conductivity), the cost is relatively high. From the perspective of saving costs, the thickness of the first gate line layer 310 is less than the thickness of the second gate line layer 320, by reducing the proportion of the first gate line layer 310 in the metal gate line, the amount of material used for the first gate line layer 310 can be saved within a certain range, thereby reducing the cost. Optionally, the thickness of the first gate line layer 310 is not greater than 2 μm.

[0069] The thickness of the first gate line layer 310 can be selected according to the distance from the bottom to the top of the pyramid surface (i.e. the depth of the trench), and can be slightly less than or greater than the distance from the bottom to the top of the pyramid surface. In an alternative embodiment, the upper surface of the first gate line layer 310 can be made to be flush with the top of the pyramid surface, i.e. the upper surface of the first gate line layer 310 can be made to be in the same height as the top of the pyramid surface, as shown in FIG. 3. It should be understood that due to process reasons, the first gate line layer 310 can have a certain amount of deformation after being cured and formed, and thus the upper surface of the first gate line layer 310 can be made to be substantially flush with the top of the pyramid surface, and can have a certain amount of deviation (e.g. a height deviation of less than 1 / 10 of the depth of the trench), without requiring absolute flushness. By making the upper surface of the first gate line layer 310 to be flush with the top of the pyramid surface, the cost increase caused by making the first gate line layer 310 too thick can be avoided. In other embodiments, in order to further save the amount of material used for the first gate line layer 310, the upper surface of the first gate line layer 310 can also be made to be slightly lower than the top of the pyramid surface.

[0070] Optionally, the particle size of the metal particles in the first gate line layer 310 is less than or equal to 100 nm, such as 1 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 80 nm, 100 nm, or any intermediate value between any two of the above values. It should be understood that the particle size of the metal particles in the first gate line layer 310 can be appropriately adjusted according to the depth of the trench, so as to ensure that the metal particles in the first gate line layer 310 can better fill the trench. For example, the ratio of the particle size of the metal particles in the first gate line layer 310 to the depth of the trench is 0.005-0.35, and preferably, the ratio of the particle size of the metal particles in the first gate line layer 310 to the depth of the trench is 0.02-0.1. It should be understood that the depth of the trench is the height difference between the top and the bottom of the pyramid surface, i.e. the height of the pyramid structure in the pyramid surface.

[0071] Optionally, the particle size of the metal particles in the second gate line layer 320 is greater than or equal to 300 nm. In the embodiment, the particle size of the silver particles in the second gate line layer 320 is 300-1000 nm, such as 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1000 nm, or a value between any two of the above point values; the particle size of the non-pure silver particles is 1-5 μm, such as 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, or a value between any two of the above point values. Smaller silver particles can be filled in the gaps of the non-silver particles, which can reduce the use of silver particles to some extent, reduce the cost, and at the same time ensure the packing density of the metal particles and maintain good conductivity. Optionally, the particle size of the silver particles in the second gate line layer 320 can be selected according to the particle size of the silver particles in the first gate line layer 310. For example, in an optional embodiment, when the particle size of the silver particles in the first gate line layer 310 is 1-30 nm, the particle size of the silver particles in the second gate line layer 320 is 300-500 nm; when the particle size of the silver particles in the first gate line layer 310 is 30-60 nm, the particle size of the silver particles in the second gate line layer 320 is 500-700 nm; and when the particle size of the silver particles in the first gate line layer 310 is 60-100 nm, the particle size of the silver particles in the second gate line layer 320 is 700-1000 nm.

[0072] The shape of the metal particles in the first gate line layer 310 and the second gate line layer 320 can be various, such as spherical, olive-shaped, flaky, etc. Using a certain proportion of flaky particles in the metal particles can improve the line resistance. In an optional embodiment, the silver particles in the first gate line layer 310 and the second gate line layer 320 both include flaky silver particles, and the flaky silver particles account for less than 5 wt.% of the silver particles in the first gate line layer 310 and account for more than 5 wt.% of the silver particles in the second gate line layer 320.

[0073] Optionally, the thickness of the first gate line layer 310 is less than or equal to 2 μm, and the thickness of the second gate line layer 320 is 5-30 μm. Since the second gate line layer 320 has a lower manufacturing cost, increasing the proportion of the second gate line layer 320 in the metal gate line is beneficial to reducing the cost.

[0074] FIG. 4 is a flowchart of a method for preparing a photovoltaic cell according to an embodiment of the present application. As shown in FIG. 4, the method for preparing a photovoltaic cell according to the embodiment of the present application includes the following steps:

[0075] In step S100, a silicon substrate is textured on the front surface and / or the back surface to form a pyramid texture.

[0076] In the present embodiment, the silicon substrate can include crystalline silicon as a main body portion and an amorphous silicon layer provided on the surface of the crystalline silicon, and the application in the production of a heterojunction solar cell is taken as an example. Before the transparent conductive layer 200 is deposited, the surface of the crystalline silicon can be textured, and the pyramidal structure can be formed on the surface of the crystalline silicon by texturing. Then, the amorphous silicon layer is produced on the textured surface of the crystalline silicon. Due to the several pyramidal structures obtained by texturing the surface of the crystalline silicon, the amorphous silicon layer follows the surface of the crystalline silicon, so that the silicon substrate finally obtained has a pyramidal textured surface.

[0077] In step S200, the transparent conductive layer is deposited on the pyramidal textured surface.

[0078] In the present embodiment, the transparent conductive layer 200 can be obtained by physical vapor deposition, such as by using a magnetron sputtering process for deposition. The transparent conductive layer 200 is deposited on the surface of the amorphous silicon layer. After the transparent conductive layer 200 is deposited, the transparent conductive layer 200 follows the surface of the silicon substrate 100, so that the side away from the silicon substrate 100 is also a pyramidal textured surface. As shown in FIGS. 1 and 3, the pyramidal textured surface has several pyramidal structures, and the region between two adjacent pyramidal structures can form a groove. The processes of texturing and deposition are mature in the field of solar cells, and can refer to the prior art, which will not be described here.

[0079] In other optional embodiments, the several grooves formed on the side of the transparent conductive layer 200 away from the silicon substrate 100 can also be formed by mechanical scribing, etching or other methods. In other embodiments, the cross-sectional shape of the groove can not be triangular as shown in FIGS. 1 to 3, but can be rectangular, semicircular, trapezoidal or other irregular shapes.

[0080] In step S300, a metal paste is used to produce metal grid lines on the transparent conductive layer, and the metal particles in the metal paste fill the bottom of the pyramidal textured surface.

[0081] In the present embodiment, step S300 can include:

[0082] In step S310, a first metal paste is used to produce a first grid line layer on the transparent conductive layer, and the metal particles in the first metal paste fill the bottom of the pyramidal textured surface.

[0083] In step S320, a second metal paste is used to produce a second grid line layer on the first grid line layer.

[0084] In the second metal paste, the particle size of the metal particles is greater than that of the metal particles in the first metal paste.

[0085] In the embodiment, the first metal paste contains metal particles and a dispersant (such as epoxy resin) for dispersing the metal particles, and the first metal paste has conductivity after curing. Since the first gate line layer 310 is a part of the metal gate line for contacting the transparent conductive layer 200, the selection of the first metal paste has an important influence on the contact between the metal gate line and the transparent conductive layer 200. Therefore, in the embodiment, the material of the metal particles in the first metal paste is all selected as silver (i.e. the first metal paste is a pure silver paste). The metal particles in the first metal paste fill the bottoms of the pyramid surfaces, which means that the metal particles in the first metal paste fill the grooves between the pyramid structures. In order to enable the metal particles in the first metal paste to enter the bottoms of the pyramid surfaces and better fill the bottoms of the pyramid surfaces, increase the contact points between the first gate line layer 310 and the transparent conductive layer 200, the metal particles in the first metal paste are selected to have a small particle size. Comparing FIG. 3 with FIG. 1, it can be seen that the smaller the particle size of the metal particles, the more metal particles enter the grooves, and the more contact points, which is beneficial to reducing the contact resistance. Optionally, the particle size of the metal particles in the first metal paste is 100 nm or less, such as 1 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 80 nm, 100 nm, or any intermediate value between any two of the above values. It should be understood that the particle size of the metal particles in the first metal paste can be appropriately adjusted according to the depth of the groove, so as to ensure that the metal particles in the first metal paste can better fill the groove. For example, the ratio of the particle size of the metal particles in the first metal paste to the depth of the groove is 0.02-0.35, and preferably, the ratio of the particle size of the metal particles in the first metal paste to the depth of the groove is 0.02-0.1.

[0086] It should be understood that the metal particles in the first metal paste can also use other metals with better conductivity, such as copper, aluminum, gold, etc. In order to save costs, non-precious metals such as copper and aluminum can be used, or precious metal particles and non-precious metal particles can be used together.

[0087] In the embodiments of the present application, the first gate line layer can be made by printing, and specifically, a screen printing process can be used to form the first gate line layer 310 with a specific pattern. It should be understood that the pattern of the first gate line layer 310 corresponds to the pattern of the metal gate line to be finally made. The screen printing process is relatively mature in the art, and its specific implementation can refer to the prior art, which will not be described here. In other optional embodiments, the first gate line layer 310 can also be formed by inkjet method.

[0088] Optionally, the thickness of the first gate line layer 310 is not greater than 2 μm. The thickness of the first gate line layer 310 can be selected according to the distance from the bottom to the top of the pyramid surface (i.e. the depth of the trench), and can be slightly less than or greater than the distance from the bottom to the top of the pyramid surface.

[0089] In the present embodiment, the first metal paste has relatively high cost due to the high requirements on the particle size and material selection of the metal particles (e.g. small particle size and high electrical conductivity). In order to save cost, the amount of the first metal paste used can be saved within a certain range. Therefore, in an optional embodiment, the upper surface of the first gate line layer 310 can be flush with the top of the pyramid surface, in other words, the upper surface of the first gate line layer 310 is consistent with the height of the top of the pyramid surface, as shown in FIG. 3. It should be understood that since the first metal paste can have a certain deformation after printing and curing, the upper surface of the first gate line layer 310 can be approximately flush with the top of the pyramid surface, and there can be a certain deviation (e.g. the height deviation is within 1 / 10 of the depth of the trench), without requiring absolute flush. By making the upper surface of the first gate line layer 310 flush with the top of the pyramid surface, the first metal paste can just fill the trench, avoiding the cost increase caused by making the first gate line layer 310 too thick. In other embodiments, in order to further save the amount of material used for the first gate line layer 310, the upper surface of the first gate line layer 310 can also be slightly lower than the top of the pyramid surface.

[0090] In order to make the first gate line layer 310 flush with the top of the pyramid surface or slightly lower than the top of the pyramid surface, step S310 can specifically include:

[0091] calculating the space volume between the top and the bottom of the pyramid surface of the to-be-printed region; and filling the bottom of the pyramid surface with the first metal paste in an amount equal to or less than the space volume between the top and the bottom of the pyramid surface of the to-be-printed region, to obtain the first gate line layer 310 flush with the top of the pyramid surface or lower than the top of the pyramid surface. The to-be-printed region is the region on the transparent conductive layer 200 where the first gate line layer 310 is to be made, i.e. the region corresponding to the metal gate line pattern.

[0092] It should be understood that in alternative embodiments, the first grid line layer 310 can be made to be flush with the top of the pyramid surface by other means. For example, the first metal paste is applied on the pyramid surface using an amount of the first metal paste that exceeds the volume of the space between the top and the bottom of the pyramid surface; the first metal paste above the top of the pyramid surface is removed so that the remaining first metal paste fills the bottom of the pyramid surface and is flush with the top of the pyramid surface. The first metal paste is applied (e.g., printed) using an excess amount of the first metal paste; the excess paste above the top of the pyramid surface is removed by physical scraping or other chemical means after the printing so that the remaining first metal paste just fills the bottom groove of the pyramid surface and forms the first grid line layer 310.

[0093] In the embodiments of the present application, the metal particles in the second metal paste have a larger particle size than the metal particles in the first metal paste. The second metal paste contains metal particles and a dispersant (e.g., epoxy resin) for dispersing the metal particles, and the second metal paste forms the second grid line layer 320 having conductivity after curing. Optionally, the second grid line layer 320 is made using a printing process, such as a screen printing process. As shown in FIG. 2, in the embodiments, the battery is a non- main grid battery, and the second grid line layer 320 and the first grid line layer 310 together form the fine grid lines in the battery. Since the second grid line layer 320 does not directly contact (or has little contact with) the transparent conductive layer 200, it is not the most important factor affecting the contact resistance between the metal grid and the transparent conductive layer 200 compared to the first grid line layer 310. Therefore, the particle size and the material of the metal particles in the second metal paste can be relatively low for cost considerations. In the embodiments, the metal particles in the second metal paste have a larger particle size than the metal particles in the first metal paste. Optionally, the particle size of the metal particles in the second metal paste is greater than 300 nm.

[0094] Optionally, the weight percentage of silver particles in the metal particles of the second metal paste is less than the weight percentage of silver particles in the metal particles of the first metal paste. Unlike the first metal paste in which the metal particles are all composed of silver particles, in the embodiments, the metal particles of the second metal paste are composed of silver particles and other non-precious metal particles, which can ensure better conductivity and lower cost. For example, the metal particles of the second metal paste can be a combination of at least one of copper, iron, nickel, and aluminum and silver particles. Optionally, the weight percentage of silver particles in the metal particles of the second metal paste is less than 50%, such as 40%, 30%, 20%, 10%, or an intermediate value of any two of the above percentages. In alternative embodiments, the metal particles of the second metal paste can also be composed of one or more particles of other materials, such as gold particles.

[0095] In this embodiment, the particle size of the silver particles in the metal particles of the second metal paste is 300 to 1000 nm, such as 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm, 1000 nm, or a value between any two of the above points; the particle size of the non-silver particles is 1 to 5 μm, such as 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, or a value between any two of the above points. Smaller silver particles can fill the gaps between the non-silver particles, which can reduce the use of silver particles to a certain extent and reduce costs, while also ensuring the packing density of the metal particles and maintaining better conductivity. Optionally, the particle size of the silver particles in the second metal paste can be selected according to the particle size of the silver particles in the first metal paste. For example, in an optional embodiment, when the particle size of the silver particles in the first metal paste is 1 to 30 nm, the particle size of the silver particles in the second metal paste is 300 to 500 nm; when the particle size of the silver particles in the first metal paste is 30 to 60 nm, the particle size of the silver particles in the second metal paste is 500 to 700 nm; when the particle size of the silver particles in the first metal paste is 60 to 100 nm, the particle size of the silver particles in the second metal paste is 700 to 1000 nm.

[0096] The metal particles in the first and second metal pastes can have a variety of shapes, such as spherical, olive, or flake. Using a certain proportion of flake particles can improve line resistance. In an optional embodiment, the silver particles in the first metal paste contain less than 5 wt.% of the silver particles, while the silver particles in the second metal paste contain more than 5 wt.%.

[0097] Optionally, the thickness of the second gateline layer 320 is greater than that of the first gateline layer 310, and can be selected to be 5 to 30 μm. Since the second metal slurry used to make the second gateline layer 320 is relatively low in cost, using more second metal slurry to make a thicker second gateline layer 320 increases the proportion of the second gateline layer 320 in the metal gateline, which helps reduce costs.

[0098] The manufacturing method of this embodiment uses a first metal paste (pure silver paste with a particle size of less than 300nm) to make the first gate line layer 310, and then uses a second metal paste (metal particles with a particle size greater than 300nm and a silver content of less than 50wt.%) to make the second gate line layer 320. Compared with using the second metal paste to make the metal gate lines, the contact resistance can be reduced by at least 20mΩ·cm. 2 The contact resistance can be obtained by using a four-probe tester using the Transmission Line Method (TLM).

[0099] The embodiment of the present application further provides a photovoltaic module (not shown in the figure) comprising the photovoltaic cell provided by the above-mentioned embodiment of the present application or the photovoltaic cell prepared by the above-mentioned preparation method. In addition to the above-mentioned photovoltaic cell, the photovoltaic module should further comprise necessary components for realizing the power generation function, and the structure and working principle of these components can be referred to the prior art, which will not be described here.

[0100] In summary, the photovoltaic cell of the embodiment of the present application comprises a silicon substrate, a transparent conductive layer arranged on the front surface and / or the back surface of the silicon substrate, and a metal grid line arranged on the transparent conductive layer, wherein a pyramid texture is formed on the transparent conductive layer, and the metal grid line fills the bottom of the pyramid texture. By allowing the metal particles in the metal grid line to fill the bottom of the pyramid texture, the contact points between the metal grid line and the transparent conductive layer are more, so that the contact between the metal grid line and the transparent conductive layer can be improved, the contact resistance is reduced, and the efficiency of the photovoltaic cell is improved.

[0101] The preparation method of the photovoltaic cell of the embodiment of the present application comprises texturing on the front surface and / or the back surface of the silicon substrate to form a pyramid texture, depositing a transparent conductive layer on the pyramid texture, and using a metal paste to make a metal grid line on the transparent conductive layer, and allowing the metal particles in the metal paste to fill the bottom of the pyramid texture. The preparation method of the photovoltaic cell provided by the embodiment of the present application can make the metal grid line and the transparent conductive layer better contact, reduce the contact resistance, and be conducive to improving the efficiency of the photovoltaic cell.

[0102] The photovoltaic module provided by the embodiment of the present application comprises the above-mentioned photovoltaic cell or the photovoltaic cell prepared by the above-mentioned preparation method, so that the photovoltaic cell and the photovoltaic module can have higher efficiency.

[0103] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, any changes or replacements within the technical range disclosed by the present application can be easily thought by those skilled in the art, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims. Industrial applicability

[0104] The photovoltaic cell and the preparation method thereof provided by the present application can reduce the contact resistance between the metal grid line and the transparent conductive layer, which is conducive to improving the photoelectric conversion efficiency of the photovoltaic cell. The photovoltaic module provided by the present application has higher photoelectric conversion efficiency.

Claims

1. A photovoltaic cell, characterized in that: include: A silicon substrate, wherein a transparent conductive layer is provided on the front and / or back side of the silicon substrate, and a pyramid velvet surface is formed on the transparent conductive layer; A metal grid line is provided on the transparent conductive layer, and the metal grid line fills the bottom of the pyramid velvet surface.

2. The photovoltaic cell according to claim 1, characterized in that The metal grid line includes: a first gate line layer, wherein the first gate line layer fills the bottom of the pyramid velvet surface; a second gate line layer, the second gate line layer being stacked on the first gate line layer; The first gate line layer and the second gate line layer both include a plurality of metal particles, and the particle size of the metal particles in the first gate line layer is smaller than the particle size of the metal particles in the second gate line layer.

3. The photovoltaic cell according to claim 2, characterized in that The particle size of the metal particles in the first gate line layer is less than 100 nm, and the particle size of the metal particles in the second gate line layer is greater than 300 nm.

4. The photovoltaic cell according to claim 2, characterized in that The metal particles in the first gate line layer and the second gate line layer both contain silver particles, and the weight percentage of the silver particles in the metal particles in the second gate line layer is smaller than the weight percentage of the silver particles in the metal particles in the first gate line layer.

5. The photovoltaic cell according to claim 4, characterized in that The metal particles of the first gate line layer are all silver particles, the metal particles of the second gate line layer are composed of silver particles and non-silver particles, and the weight percentage of silver particles in the metal particles of the second gate line layer is less than 50%.

6. The photovoltaic cell according to claim 5, characterized in that The particle size of the silver particles in the metal particles of the second gate line layer is 300-1000 nm, and the particle size of the non-silver particles is 1-5 μm.

7. The photovoltaic cell according to claim 5, characterized in that The non-silver particles include at least one of copper particles and aluminum particles.

8. The photovoltaic cell according to claim 4, characterized in that The silver particles of the first grid line layer and the silver particles of the second grid line layer both include flaky silver particles. The flaky silver particles account for less than 5 wt.% of the silver particles of the first grid line layer, and for more than 5 wt.% of the silver particles of the second grid line layer.

9. The photovoltaic cell according to claim 2, characterized in that The ratio of the particle size of the metal particles in the first gate line layer to the height difference between the top and the bottom of the pyramid velvet surface is 0.005 to 0.

35.

10. The photovoltaic cell according to any one of claims 2 to 9, characterized in that: The upper surface of the first gate line layer is flush with or lower than the top of the pyramid suede surface.

11. The photovoltaic cell according to any one of claims 2 to 9, characterized in that: The thickness of the first gate line layer is smaller than the thickness of the second gate line layer.

12. The photovoltaic cell according to claim 11, characterized in that The thickness of the first gate line layer is no more than 2 μm; the thickness of the second gate line layer is 5 to 30 μm.

13. A method for preparing a photovoltaic cell, characterized in that: include: Texturing the front and / or back surface of the silicon substrate to form a pyramid texture surface; Depositing a transparent conductive layer on the pyramid fleece surface; Metal grid lines are made on the transparent conductive layer using metal paste, and the metal particles in the metal paste are filled into the bottom of the pyramid velvet surface.

14. The method for preparing a photovoltaic cell according to claim 13, wherein: The step of using metal slurry to form metal grid lines on the transparent conductive layer and allowing metal particles in the metal slurry to fill the bottom of the pyramid velvet surface includes: Using a first metal paste to form a first gate line layer on the transparent conductive layer, so that the metal particles in the first metal paste fill the bottom of the pyramid velvet surface; Using a second metal slurry to form a second gate line layer on the first gate line layer; Wherein, the particle size of the metal particles in the second metal slurry is larger than the particle size of the metal particles in the first metal slurry.

15. The method for preparing a photovoltaic cell according to claim 14, wherein: The first gate line layer is manufactured by printing or inkjet method.

16. The method for preparing a photovoltaic cell according to claim 14, wherein: The second gate line layer is manufactured by a printing process.

17. The method for preparing a photovoltaic cell according to any one of claims 14 to 16, characterized in that: The upper surface of the first gate line layer is flush with or lower than the top of the pyramid suede surface.

18. The method for preparing a battery according to claim 17, wherein: The step of using a first metal paste to form a first gate line layer on the transparent conductive layer, so that the metal particles in the first metal paste fill the bottom of the pyramid velvet surface, comprises: Calculating the volume of the space between the top and the bottom of the pyramid pile surface in the area to be printed; The bottom of the pyramid velvet is filled with the first metal paste in an amount equal to or less than the volume of the space between the top and bottom of the pyramid velvet in the area to be printed, so as to obtain the first grid line layer that is flush with or lower than the top of the pyramid velvet.

19. The method for preparing a battery according to claim 17, wherein: The step of using a first metal paste to form a first gate line layer on the transparent conductive layer, so that the metal particles in the first metal paste fill the bottom of the pyramid velvet surface, comprises: Coating the pyramid velvet surface with the first metal slurry in an amount exceeding the volume of the space between the top and the bottom of the pyramid velvet surface; The first metal paste above the top of the pyramid velvet surface is removed, so that the remaining first metal paste fills the bottom of the pyramid velvet surface and is flush with the top of the pyramid velvet surface.

20. A photovoltaic module, characterized in that: A photovoltaic cell comprising the photovoltaic cell according to any one of claims 1 to 12, or a photovoltaic cell prepared by the method for preparing the photovoltaic cell according to any one of claims 13 to 19.

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