Solar cell and method for preparing solar cell

Abstract

The present application provides a solar cell and a method for preparing the solar cell, wherein the solar cell comprises a semiconductor region, a dielectric layer located above the semiconductor region, and a secondary grid, wherein the secondary grid comprises contact segments and connecting segments arranged alternately, wherein the bottom surface of the contact segment passes through the dielectric layer and contacts the semiconductor region, the connecting segment is located above the dielectric layer, and the side surface of the connecting segment contacts the adjacent contact segment, wherein the ratio between the length of the contact segment and the length of the connecting segment is equal to or greater than 1:1.5. The solar cell and the method for preparing the present application can reduce recombination.

Description

Technical Field

[0001] The present application mainly relates to the field of photovoltaic technology, and in particular to a solar cell and a method for preparing the solar cell. Background Art

[0002] Metal grid lines have the function of collecting carriers. When metal grid lines contact semiconductor regions, they will cause recombination, which will lead to a decrease in solar cell efficiency. Reducing recombination can improve solar cell efficiency. How to reduce recombination is one of the important research directions in this field. Summary of the invention

[0003] The technical problem to be solved by the present application is to provide a solar cell and a method for preparing the solar cell, wherein the solar cell and the method for preparing the solar cell can reduce recombination.

[0004] To solve the above technical problems, the present application provides a solar cell, which includes a semiconductor region, a dielectric layer located above the semiconductor region, and a secondary grid, wherein the secondary grid includes contact segments and connecting segments arranged alternately, wherein the bottom surface of the contact segment passes through the dielectric layer and contacts the semiconductor region, the connecting segment is located above the dielectric layer, and the side surface of the connecting segment contacts the adjacent contact segment, wherein the ratio between the length of the contact segment and the length of the connecting segment is equal to or greater than 1:1.5.

[0005] In one embodiment of the present application, the contact segment includes a stacked top layer and a bottom layer, the material of the bottom layer includes silver, and the material of the top layer is the same as that of the connecting segment, wherein the top surface of the contact segment is flush with the top surface of the connecting segment, and the porosity of the top layer is less than the porosity of the bottom layer.

[0006] In one embodiment of the present application, the interface between the top layer and the bottom layer is higher than the dielectric layer.

[0007] In an embodiment of the present application, the porosity of the connecting segment is smaller than the porosity of the contact segment, and the top surface of the contact segment is higher than the top surface of the connecting segment.

[0008] In one embodiment of the present application, the connecting section includes a first portion, a main portion, and a second portion connected in sequence, the first portion and the second portion cover part of the side surface and at least part of the top surface of the contact section, and the top surface of the main portion is lower than the top surface of the contact section.

[0009] In an embodiment of the present application, the width of the contact segment is greater than the width of the connecting segment.

[0010] In an embodiment of the present application, the width of the side surface of the contact segment is greater than the width of the connecting segment in contact with the side surface.

[0011] In an embodiment of the present application, the bottom surface of the contact segment has a plurality of grooves, and the dielectric layer fills the plurality of grooves.

[0012] In one embodiment of the present application, the cross-section of the connecting section is rectangular.

[0013] In an embodiment of the present application, the material of the contact segment includes silver, and the material of the connecting segment includes base metal.

[0014] On the other hand, the present application also proposes a method for preparing a solar cell, wherein the solar cell includes a semiconductor region, a dielectric layer located above the semiconductor region, and a secondary grid, wherein the secondary grid includes contact segments and connecting segments arranged alternately, and the preparation method includes: printing a first paste on the dielectric layer; printing a second paste on the dielectric layer; heat treating the first paste and the second paste, wherein the first paste burns through the dielectric layer, and the second paste does not burn through the dielectric layer, to form the contact segments and the connecting segments, wherein the ratio between the length of the contact segment and the length of the connecting segment is equal to or greater than 1:1.5, and the side surfaces of the connecting segments are in contact with adjacent contact segments.

[0015] In one embodiment of the present application, the weight proportion of the first glass in the second slurry is greater than the weight proportion of the first glass in the first slurry, wherein the glass transition temperature of the first glass is lower than 600°C.

[0016] In one embodiment of the present application, the first slurry and the second slurry include silver particles, the proportion of silver particles with a particle size equal to or less than 1 μm in the second slurry is greater than the proportion of silver particles with a particle size equal to or less than 1 μm in the first slurry, and / or the roughness of the silver particles in the second slurry is greater than the roughness of the silver particles in the first slurry.

[0017] In one embodiment of the present application, the contact section includes a stacked top layer and a bottom layer, the second slurry covers the first slurry, the first slurry is heat-treated to form the bottom layer, and the second slurry located on the first slurry is heat-treated to form the top layer.

[0018] In one embodiment of the present application, the contact section includes a stacked top layer and a bottom layer, the first slurry is heat-treated to form the bottom layer, the second slurry covers the bottom layer, and the second slurry on the bottom layer is heat-treated to form the top layer.

[0019] In one embodiment of the present application, the first slurry and the second slurry do not overlap.

[0020] In one embodiment of the present application, the second slurry covers the side surface and a portion of the top surface of the first slurry, the first slurry forms the contact section after heat treatment, and the second slurry forms the connection section after heat treatment.

[0021] In one embodiment of the present application, the first slurry forms the contact section after heat treatment, the second slurry covers part of the side surface and part of the top surface of the contact section, and the second slurry forms the connecting section after heat treatment.

[0022] Compared with the prior art, this application has the following advantages:

[0023] (1) The auxiliary gate includes contact segments and connecting segments that are alternately arranged. The contact segments are in contact with the semiconductor region, while the connecting segments are not in contact with the semiconductor region. This can reduce the contact area between the auxiliary gate and the semiconductor region, thereby reducing recombination.

[0024] (2) The top layer with lower porosity can prevent water vapor from corroding the interface between the contact segment and the semiconductor region, thereby improving the moisture and heat resistance reliability of the solar cell.

[0025] (3) The porosity of the connecting segment is smaller than that of the contact segment, and the top surface of the contact segment is higher than the top surface of the connecting segment. In this way, the line resistance of the contact segment can be reduced, so that the line resistance of the contact segment is consistent with the line resistance of the connecting segment.

[0026] (4) Using base metals to prepare the connecting segment can reduce the amount of silver used, thereby reducing the cost of the secondary grid. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings are included to provide a further understanding of the present application. They are included and constitute a part of the present application. The accompanying drawings illustrate embodiments of the present application and together with the present specification serve to explain the principles of the present application. In the accompanying drawings:

[0028] Figure 1 is a schematic top view of a solar cell in one embodiment of the present application;

[0029] Figure 2 yes Figure 1 A schematic cross-sectional view of a solar cell along line AA;

[0030] Figure 3 is a schematic top view of a secondary grid in an embodiment of the present application;

[0031] Figure 4 is a cross-sectional schematic diagram of a solar cell in one embodiment of the present application;

[0032] Figure 5 is a cross-sectional schematic diagram of a solar cell in another embodiment of the present application;

[0033] Figure 6 is a schematic flow chart of a method for preparing a solar cell in one embodiment of the present application;

[0034] Figure 7 is a scanning electron microscope image of a cross section of a contact segment in an embodiment of the present application;

[0035] Figure 8 is a scanning electron microscope image of a cross section of a connecting section in one embodiment of the present application;

[0036] Fig. 9 It is the influence of the length ratio between different contact segments and connecting segments on the electrical parameters of solar cells.

[0037] Reference numerals: semiconductor region 110, dielectric layer 120, auxiliary gate 130, contact segment 131, top layer 131a, bottom layer 131b, bottom surface 131c, first side surface 131d, second side surface 131e, connecting segment 132, first portion 132a, main body portion 132b, second portion 132c. DETAILED DESCRIPTION

[0038] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for the description of the embodiments. Obviously, the drawings described below are only some examples or embodiments of the present application. For ordinary technicians in this field, the present application can also be applied to other similar scenarios based on these drawings without creative work. Unless it is obvious from the language environment or otherwise explained, the same reference numerals in the figures represent the same structure or operation.

[0039] As shown in this application and claims, unless the context clearly indicates an exception, the words "a", "an", "an" and / or "the" do not refer to the singular and may also include the plural. Generally speaking, the terms "include" and "comprise" only indicate the inclusion of the steps and elements that have been clearly identified, and these steps and elements do not constitute an exclusive list. The method or device may also include other steps or elements.

[0040] Unless otherwise specifically stated, the relative arrangement, numerical expressions and numerical values ​​of the parts and steps set forth in these embodiments do not limit the scope of the present application. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to the actual proportional relationship. The technology, method and equipment known to those of ordinary skill in the relevant field may not be discussed in detail, but in appropriate cases, the technology, method and equipment should be considered as a part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so that once a certain item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0041] In the description of the present application, it should be understood that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "lateral, vertical, perpendicular, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the device or element referred to must have a specific direction or be constructed and operated in a specific direction, and therefore cannot be understood as limiting the scope of protection of the present application; the directional words "inside and outside" refer to the inside and outside relative to the contours of each component itself.

[0042] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0043] In addition, it should be noted that the use of words such as "first" and "second" to define components is only for the convenience of distinguishing the corresponding components. If not otherwise stated, the above words have no special meaning and cannot be understood as limiting the scope of protection of this application. In addition, although the terms used in this application are selected from well-known and commonly used terms, some terms mentioned in the specification of this application may be selected by the applicant at his or her discretion, and their detailed meanings are explained in the relevant parts of the description of this article. In addition, it is required to understand this application not only by the actual terms used, but also by the meaning implied by each term.

[0044] Flowcharts are used in the present application to illustrate the operations performed by the system according to the embodiments of the present application. It should be understood that the preceding or following operations are not necessarily performed accurately in order. On the contrary, various steps may be processed in reverse order or simultaneously. At the same time, other operations may be added to these processes, or one or more operations may be removed from these processes.

[0045] Next, the solar cell and the preparation method of the present application are described by way of examples.

[0046] Figure 1 is a schematic top view of a solar cell in one embodiment, Figure 2 yes Figure 1 Schematic diagram of the cross-section of the solar cell along line AA. Figure 1 and Figure 2 As shown, the solar cell includes a semiconductor region 110, a dielectric layer 120 located above the semiconductor region 110, and a secondary gate 130. Carriers are transmitted to the external through the semiconductor region 110. In order to more clearly understand the semiconductor region 110 of the present application, an example is given here. For a solar cell including a tunneling passivated contact structure (Tunnel Oxide Passivated Contact), the semiconductor region 110 can be a tunneling passivated contact structure. The dielectric layer 120 is insulated, and the dielectric layer 120 can be an aluminum oxide (Al2O3) film, a silicon nitride (SiN x ) thin film, silicon oxynitride (SiO x N y ) One or more of the films.

[0047] The auxiliary gate 130 includes contact segments 131 and connecting segments 132 arranged alternately in the extension direction thereof. The contact segments 131 are in contact with the semiconductor region 110, and the connecting segments 132 are not in contact with the semiconductor region 110, so that the contact area between the auxiliary gate and the semiconductor region 110 can be reduced, thereby reducing recombination. Figure 2In the embodiment, the bottom surface 131 c of the contact segment 131 penetrates the dielectric layer 120 and contacts the surface of the semiconductor region 110 . In some other embodiments, the bottom surface 131 c may penetrate into the semiconductor region 110 to a certain depth.

[0048] exist Figure 2 In the embodiment, the contact section 131 includes a stacked top layer 131a and a bottom layer 131b. The top layer 131a and the bottom layer 131b will be described in detail later and will not be expanded here.

[0049] The connecting section 132 is located above the dielectric layer 120, and the left and right sides of the connecting section 132 are in contact with the adjacent contact sections 131 (eg Figure 2 As shown in FIG. 1 ), the connecting segment 132 is electrically connected to the contact segment 131. The connecting segment 132 is directly in contact with the surface of the dielectric layer 120 facing away from the semiconductor region 110, and other film layers may also be disposed between the connecting segment 132 and the dielectric layer 120.

[0050] In one embodiment, the material of the contact segment 131 includes silver, and the material of the connection segment 132 includes base metals. The meaning of "base metals" is opposite to that of precious metals. Base metals include metals such as copper and aluminum that are relatively cheaper than precious metals. For example, the material of the connection segment 132 is aluminum. The connection segment 132 may contain silver or may not contain silver. The fact that the connection segment 132 does not contain silver can reduce the amount of silver used to manufacture the secondary grid. Preferably, when the connection segment 132 contains silver, the content of silver in the connection segment 132 is less than the content of silver in the contact segment 131, so that the amount of silver can be reduced, thereby reducing the cost of the secondary grid.

[0051] refer to Figure 1 As shown, the ratio between the length of the contact segment 131 and the length of the connecting segment 132 is equal to or greater than 1:1.5, and "length" refers to the dimension in the extension direction of the auxiliary gate. The ratio between the length of the contact segment 131 and the length of the connecting segment 132 can be 1:1.5, 1.1:1.5, 1.2:1.5, 1.3:1.5, 1.4:1.5, 1.5:1.5 (i.e., 1:1) or 1.6:1.5. When the length ratio between the contact segment 131 and the connecting segment 132 is equal to or greater than 1:1.5, excellent conversion efficiency (Eta) can be obtained. Reference Fig. 9 As shown, Fig. 9 The effects of different length ratios between the contact segment and the connection segment on the electrical parameters of the solar cell are given. Specifically, the length ratios of No. 1 to 3 are equal to or greater than 1:1.5, and the length ratios of No. 4 and 5 are less than 1:1.5. By comparison, it can be found that the conversion efficiency of No. 1 to 3 is greater than that of No. 4 and 5, among which the conversion efficiency of No. 2 is the highest.

[0052] refer to Figure 2 As shown, in Figure 2In the embodiment of the present invention, the contact segment 131 includes a stacked top layer 131a and a bottom layer 131b, the bottom layer 131b is in contact with the semiconductor region 110, and the top surface of the contact segment 131 (i.e., the top surface of the top layer 131a) is flush with the top surface of the connecting segment 132. The material of the bottom layer 131b includes silver, and the material of the top layer 131a is the same as that of the connecting segment 132.

[0053] Continue to refer Figure 2 As shown, the porosity of the top layer 131a is less than that of the bottom layer 131b, so that the moisture and heat resistance reliability of the solar cell can be improved. Specifically, water vapor can enter the sub-grid along the pores in the sub-grid, and then corrode the interface between the contact segment 131 and the semiconductor region 110. The top layer 131a located above the contact segment 131 covers the bottom layer 131b located below, and the porosity of the top layer 131a is less than that of the bottom layer 131b, so that the top layer 131a with lower porosity can prevent water vapor from corroding the interface between the contact segment 131 and the semiconductor region 110, thereby improving the moisture and heat resistance reliability of the solar cell.

[0054] It can be formed by the following method Figure 2 The contact section 131 and the connection section 132 in the bottom layer 131b are formed by printing a slurry for forming the bottom layer 131b, and heat-treating the slurry to form the bottom layer 131b; then, printing a slurry covering the bottom layer 131b and the dielectric layer located in the predetermined area, and heat-treating the slurry to form the connection section 132 and the top layer 131a, wherein the "predetermined area" refers to the area where the connection section 132 is located, and the portion of the slurry covering the bottom layer 131b is transformed into the top layer 131a after heat treatment. In the process of printing the slurry for forming the connection section 132 and the top layer 131a, the slurry will fill the pores on the surface of the bottom layer 131b, thereby making the surface layer of the bottom layer 131b denser, thereby preventing water vapor from invading the bottom layer 131b.

[0055] refer to Figure 1 As shown, in one embodiment, when viewed from a top view, the contact segment 131 and the connecting segment 132 are both rectangular, and the width of the contact segment 131 is greater than the width of the connecting segment 132. The larger width of the contact segment 131 can increase the process window for printing the slurry used to form the connecting segment 132, that is, it can ensure that the slurry contacts the contact segment 131 during the printing process of the slurry used to form the connecting segment 132. Figure 2 As shown, the interface between the top layer 131a and the bottom layer 131b is higher than the dielectric layer 120. Thus, after printing the slurry for forming the connecting segment 132, in addition to covering the top surface of the bottom layer 131b, the slurry also covers the exposed side surfaces of the bottom layer 131b. This allows the connecting segment 132 to simultaneously wrap the three surfaces of the contact segment 131 after heat treatment, which can improve the connection stability between the contact segment 131 and the connecting segment 132.

[0056] refer to Figure 3 As shown, in one embodiment, the width of the first side surface 131d of the contact segment 131 is greater than the width of the connecting segment 132 in contact therewith, and the width of the second side surface 131e of the contact segment 131 is greater than the width of the connecting segment 132 in contact therewith. The first side surface 131d and the second side surface 131e are opposite to each other in the extension direction of the auxiliary gate. Figure 3 As shown, the width of the first side surface 131d and the width of the second side surface 131e can be increased by thickening the two ends of the contact segment 131. The larger width of the side surface of the contact segment 131 is beneficial to increasing the collection effect of the auxiliary gate on carriers and ensuring that the connection segment 132 is in contact with the contact segment 131.

[0057] In one embodiment, the cross section of the connecting segment is a rectangle. When the height and width are the same, the rectangular cross section can reduce the transmission resistance of the auxiliary gate compared with the cross section of the arc surface or the like.

[0058] refer to Figure 4 As shown, in Figure 4 In the embodiment of the present invention, the porosity of the connecting segment 132 is less than the porosity of the contact segment 131, and the top surface of the contact segment 131 is higher than the top surface of the connecting segment 132. The present application has found that in order to enable the slurry used to form the contact segment 131 to burn through the dielectric layer 120, the composition of the slurry used to form the contact segment 131 is adjusted. The adjustment of the composition causes the porosity of the contact segment 131 to be greater than the porosity of the connecting segment 132, thereby causing the line resistance of the contact segment 131 to be greater than the line resistance of the connecting segment 132. In order to solve the problem of inconsistent line resistance, Figure 4 In the embodiment, the top surface of the contact segment 131 is higher than the top surface of the connecting segment 132 , so that the line resistance of the contact segment 131 can be reduced, so that the line resistance of the contact segment 131 is consistent with the line resistance of the connecting segment 132 .

[0059] Continue to refer Figure 4 As shown, in one embodiment, the bottom surface 131c of the contact segment 131 has a plurality of grooves (not shown), and the dielectric layer 120 fills the plurality of grooves. Specifically, during the heat treatment of the slurry used to form the contact segment 131, part of the slurry does not burn through the dielectric layer 120, and grooves are formed at the unburned portion, and there is a dielectric layer 120 that is not burned through between the groove and the semiconductor region 110 (that is, the dielectric layer 120 fills the groove). The grooves located at the bottom surface 131c are conducive to reducing recombination, and the number of grooves can be increased by reducing the content of lead oxide, tellurium oxide, etc. in the slurry.

[0060] refer to Figure 5As shown, in one embodiment, the connecting section 132 includes a first portion 132a, a main body portion 132b and a second portion 132c which are connected in sequence. The first portion 132a and the second portion 132c are arranged at two ends of the main body portion 132b in the extension direction of the auxiliary gate, and are both located above the main body portion 132b. The first portion 132a and the second portion 132c cover part of the side surface and part of the top surface of the contact section 131, and the top surface of the main body portion 132b is lower than the top surface of the contact section 131. Figure 5 In the embodiment, the first portion 132a and the second portion 132c cover a portion of the top surface of the contact segment 131. In other embodiments, the first portion 132a and the second portion 132c may jointly cover the entire top surface of the contact segment 131. The first portion 132a and the second portion 132c may increase the contact area between the connection segment 132 and the contact segment 131, thereby improving the connection stability between the two.

[0061] On the other hand, the present application also provides a method for preparing a solar cell. Figure 1 and Figure 2 As shown, the solar cell includes a semiconductor region 110 and a dielectric layer 120 located above the semiconductor region 110, and a plurality of auxiliary grids 130 are arranged at intervals above the semiconductor region 110, and the auxiliary grids 130 are electrically connected to the semiconductor region 110. The auxiliary grids 130 include contact segments 131 and connecting segments 132 alternately arranged in the extending direction thereof, and the ratio between the length of the contact segment 131 and the length of the connecting segment 132 is equal to or greater than 1:1.5, and the left and right sides of the connecting segment 132 are in contact with the adjacent contact segments 131 (such as Figure 2 as shown).

[0062] refer to Figure 6 As shown, the method for preparing the auxiliary grid includes the following steps:

[0063] Step S210: printing a first slurry on the dielectric layer;

[0064] Step S220: printing a second slurry on the dielectric layer;

[0065] Step S230: heat-treating the first slurry and the second slurry, wherein the first slurry burns through the dielectric layer, while the second slurry does not burn through the dielectric layer, so as to form a contact segment and a connection segment.

[0066] Next, steps S210 to S230 are described in detail.

[0067] In step S210, a first paste is printed on the dielectric layer. The first paste may be in direct contact with the surface of the dielectric layer away from the semiconductor region 110. The first paste may be screen printed. The first paste may include silver particles. The first paste may also include other materials, for example, the first paste may also include any of tellurium oxide, zinc oxide, bismuth oxide, and boron oxide.

[0068] In step S220, a second slurry is printed on the dielectric layer. The second slurry may be in direct contact with the surface of the dielectric layer away from the semiconductor region 110, and the second slurry may be screen printed. The second slurry may include particles made of base metals, for example, the second slurry includes copper particles and / or aluminum particles, and the second slurry may also include other materials, for example, the second slurry may also include any of tellurium oxide, zinc oxide, bismuth oxide, and boron oxide. Step S210 may be performed first, and then step S220, or step S220 may be performed first, and then step S210.

[0069] In one embodiment, the first slurry and the second slurry both contain a first glass, and the weight proportion of the first glass in the second slurry is greater than the weight proportion of the first glass in the first slurry, and the first glass refers to a glass with a glass transition temperature lower than 600° C., such as tellurium oxide, zinc oxide, bismuth oxide, and boron oxide. The weight proportion of the first glass in the second slurry is greater than that of the first slurry, so that the porosity of the heat-treated product of the second slurry is lower than that of the heat-treated product of the first slurry.

[0070] The second slurry may include any of copper particles, aluminum particles, silver particles, and particles having a core-shell structure (eg, silver-coated copper).

[0071] In step S230, the first slurry and the second slurry are heat-treated, the first slurry burns through the dielectric layer, and the second slurry does not burn through the dielectric layer, so as to form a contact section and a connection section. The first slurry and the second slurry can be heat-treated at the same time, or the first slurry and the second slurry can be heat-treated separately. Specifically, printing and heat treatment can be performed in the following order:

[0072] Step 1: Printing the first slurry;

[0073] Step 2: heat treating the first slurry;

[0074] Step 3: Printing the second slurry;

[0075] Step 4: heat treating the second slurry.

[0076] Printing and heat treatment can also be performed in the following order:

[0077] Step 1: Printing the first slurry and the second slurry; the first slurry may be printed first and then the second slurry, or the second slurry may be printed first and then the first slurry, or the first slurry and the second slurry may be printed simultaneously.

[0078] Step 2: heat-treating the first slurry and the second slurry at the same time.

[0079] The present application does not limit the method of heat treatment. For example, heat treatment can be performed by heating equipment such as a heating furnace, laser, or hot air blower.

[0080] refer to Figure 2 As shown, it can be prepared by the method in the following examples 1 and 2 Figure 2 The contact section 131 and the connecting section 132 in the embodiment.

[0081] Example 1

[0082] exist Figure 2 In the embodiment, the contact section 131 includes a stacked top layer 131a and a bottom layer 131b. The first slurry for forming the bottom layer 131b is printed first, and then the second slurry for forming the top layer 131a and the connection section 132 is printed. The second slurry covers the side and top surface of the first slurry. The first slurry and the second slurry are heat-treated. The first slurry forms the bottom layer 131b after the heat treatment. The second slurry located on the first slurry forms the top layer 131a after the heat treatment. The second slurry at other positions forms the connection section 132 after the heat treatment.

[0083] Example 2

[0084] The main difference between Example 2 and Example 1 is that in Example 2, the second slurry is printed after the bottom layer 131b is formed. Specifically, the first slurry used to form the bottom layer 131b is printed, and the first slurry is sintered to form the bottom layer 131b. Then, the second slurry is printed, and the second slurry covers the top surface and the exposed side surface of the bottom layer 131b. The second slurry is sintered, and the second slurry located on the bottom layer 131b is heat-treated to form the top layer 131a, and the second slurry at other positions is heat-treated to form the connecting section 132.

[0085] refer to Figure 4 As shown, it can be prepared by the method in Example 3 below Figure 4 The contact section 131 and the connecting section 132 in the embodiment.

[0086] Example 3

[0087] The first slurry and the second slurry are printed, and the first slurry and the second slurry do not overlap (that is, the first slurry is only in contact with the second slurry, the first slurry does not cover the second slurry, and the second slurry does not cover the first slurry). After the first slurry and the second slurry are heat-treated, the first slurry forms a contact section 131, and the second slurry forms a connection section 132. Example 3 does not limit the order of printing the first slurry and the second slurry, and the first slurry and the second slurry can be heat-treated at the same time, or the first slurry and the second slurry can be heat-treated separately.

[0088] refer to Figure 5 As shown, it can be prepared by the method in the following examples 4 and 5 Figure 5 The contact section 131 and the connecting section 132 in the embodiment.

[0089] Example 4

[0090] The first slurry and the second slurry are printed successively, the second slurry covers the side surface and part of the top surface of the first slurry, the first slurry is heat-treated to form a contact section 131, and the second slurry is heat-treated to form a connecting section 132, the connecting section 132 has a first part 132a and a second part 132c covering part of the top surface and part of the side surface of the contact section 131.

[0091] Example 5

[0092] The first slurry is printed, and the first slurry is heat-treated to form the contact segment 131 after the heat treatment. After the contact segment 131 is formed, the second slurry is printed, and the second slurry covers the exposed side surface and part of the top surface of the contact segment 131, and the second slurry is heat-treated to form the connecting segment 132 after the heat treatment. The connecting segment 132 has a first portion 132a and a second portion 132c covering part of the top surface and part of the side surface of the contact segment 131.

[0093] In one embodiment, the heat treatment temperature of the first slurry is greater than the heat treatment temperature of the second slurry, for example, the heat treatment temperature of the first slurry is greater than 600° C., and the heat treatment temperature of the second slurry is less than 600° C. The lower heat treatment temperature of the second slurry can prevent the second slurry from burning through the dielectric layer. The heat treatment method of the first slurry can include sintering, and the heat treatment method of the second slurry can include sintering, drying or laser heating.

[0094] In one embodiment, the first slurry and the second slurry include silver particles, and the proportion of silver particles with a particle size equal to or less than 1 μm in the second slurry is greater than the proportion of silver particles with a particle size equal to or less than 1 μm in the first slurry. The large proportion of silver particles with a particle size equal to or less than 1 μm in the second slurry can reduce the porosity of the product after the second slurry is heat-treated. In another embodiment, the roughness of the silver particles in the second slurry is greater than the roughness of the silver particles in the first slurry, so that the porosity of the product after the second slurry is heat-treated can be reduced.

[0095] Figure 7 is a scanning electron microscope image of a cross section of the contact segment 131 in one embodiment, Figure 8 is a scanning electron microscope image of a cross section of the connecting section 132 in one embodiment, Figure 7 The contact section 131 is formed by heat treating the first slurry. Figure 8 The connecting section 132 in the embodiment is formed by heat treating the second slurry. Figure 7 and Figure 8It can be seen that the product after the first slurry is heat-treated has more pores (higher porosity), and the product after the second slurry is heat-treated has fewer pores (lower porosity). Figure 2 , Figure 7 and Figure 8 As shown, the bottom layer 131b is formed by heat-treating the first slurry, and the connecting section 132 and the top layer 131a are formed by heat-treating the second slurry. The top layer 131a and the connecting section 132 wrap the top surface and side surfaces of the bottom layer 131b. In this way, the top layer 131a and the connecting section 132 with lower porosity can protect the bottom layer 131b from water vapor corrosion.

[0096] The basic concepts have been described above. Obviously, for those skilled in the art, the above application disclosure is only an example and does not constitute a limitation of the present application. Although not explicitly stated herein, those skilled in the art may make various modifications, improvements and amendments to the present application. Such modifications, improvements and amendments are suggested in the present application, so such modifications, improvements and amendments still belong to the spirit and scope of the exemplary embodiments of the present application.

[0097] At the same time, the present application uses specific words to describe the embodiments of the present application. For example, "one embodiment", "an embodiment", and / or "some embodiments" refer to a certain feature, structure or characteristic related to at least one embodiment of the present application. Therefore, it should be emphasized and noted that "one embodiment" or "an embodiment" or "an alternative embodiment" mentioned twice or more in different positions in this specification does not necessarily refer to the same embodiment. In addition, some features, structures or characteristics in one or more embodiments of the present application can be appropriately combined.

[0098] Similarly, it should be noted that in order to simplify the description of the disclosure of this application and thus help understand one or more application embodiments, in the above description of the embodiments of this application, multiple features are sometimes merged into one embodiment, figure or description thereof. However, this disclosure method does not mean that the features required by the object of this application are more than the features mentioned in the claims. In fact, the features of the embodiments are less than all the features of the single embodiment disclosed above.

[0099] In some embodiments, numbers describing the number of components and attributes are used. It should be understood that such numbers used for the description of the embodiments are modified by the modifiers "about", "approximately" or "substantially" in some examples. Unless otherwise specified, "about", "approximately" or "substantially" indicate that the numbers are allowed to vary by ±20%. Accordingly, in some embodiments, the numerical parameters used in the specification and claims are approximate values, which can be changed according to the required features of individual embodiments. In some embodiments, the numerical parameters should take into account the specified significant digits and adopt the method of general digit retention. Although the numerical domains and parameters used to confirm the breadth of the range in some embodiments of the present application are approximate values, in specific embodiments, the setting of such numerical values ​​is as accurate as possible within the feasible range.

[0100] Although the present application has been described with reference to the current specific embodiments, ordinary technicians in this technical field should recognize that the above embodiments are only used to illustrate the present application, and various equivalent changes or substitutions may be made without departing from the spirit of the present application. Therefore, as long as the changes and modifications to the above embodiments are within the essential spirit of the present application, they will fall within the scope of the claims of the present application.

Claims

1. A solar cell, comprising a semiconductor region, a dielectric layer located above the semiconductor region, and a secondary grid, characterized in that: The auxiliary gate includes contact segments and connecting segments arranged alternately, the bottom surface of the contact segment passes through the dielectric layer and contacts the semiconductor region, the connecting segment is located above the dielectric layer, and the side surface of the connecting segment contacts the adjacent contact segment, wherein the ratio between the length of the contact segment and the length of the connecting segment is equal to or greater than 1:1.5, the bottom surface of the contact segment has a plurality of grooves, the dielectric layer fills the plurality of grooves, the connecting segment includes a first portion, a main portion, and a second portion connected in sequence, the first portion and the second portion cover a portion of the side surface and a portion of the top surface of the contact segment, the top surface of the main portion is lower than the top surface of the contact segment, the contact segment passes through the dielectric layer and penetrates into the semiconductor region, and the porosity of the connecting segment is less than the porosity of the contact segment.

2. The solar cell according to claim 1, wherein: The contact section includes a stacked top layer and a bottom layer, the material of the bottom layer includes silver, and the material of the top layer is the same as that of the connecting section, wherein the porosity of the top layer is smaller than that of the bottom layer.

3. The solar cell according to claim 2, characterized in that An interface between the top layer and the bottom layer is higher than the dielectric layer.

4. The solar cell according to claim 1, wherein: A top surface of the contact segment is higher than a top surface of the connecting segment.

5. The solar cell according to claim 1, wherein: The width of the contact section is greater than the width of the connecting section.

6. The solar cell according to claim 5, characterized in that The width of the side surface of the contact segment is greater than the width of the connecting segment in contact with the side surface.

7. The solar cell according to claim 1, wherein: The cross section of the connecting section is rectangular.

8. The solar cell according to claim 1, wherein: The material of the contact section includes silver, and the material of the connecting section includes a base metal.

9. A method for preparing a solar cell, wherein the solar cell comprises a semiconductor region, a dielectric layer located above the semiconductor region, and a secondary grid, wherein: The auxiliary grid includes contact segments and connection segments arranged alternately, and the preparation method includes: Printing a first slurry on the dielectric layer; printing a second slurry on the dielectric layer; The first slurry and the second slurry are heat-treated, the first slurry burns through the dielectric layer, and the second slurry does not burn through the dielectric layer, so as to form the contact segment and the connecting segment, wherein the ratio between the length of the contact segment and the length of the connecting segment is equal to or greater than 1:1.5, the side surface of the connecting segment contacts the adjacent contact segment, the connecting segment includes a first portion, a main portion, and a second portion connected in sequence, the first portion and the second portion cover part of the side surface and part of the top surface of the contact segment, the top surface of the main portion is lower than the top surface of the contact segment, the contact segment penetrates the dielectric layer and penetrates into the semiconductor region, and the porosity of the connecting segment is less than the porosity of the contact segment.

10. The method for preparing a solar cell according to claim 9, characterized in that: The weight proportion of the first glass in the second slurry is greater than the weight proportion of the first glass in the first slurry, wherein the glass transition temperature of the first glass is lower than 600°C.

11. The method for preparing a solar cell according to claim 9, characterized in that: The first slurry and the second slurry include silver particles, the proportion of silver particles with a particle size equal to or less than 1 μm in the second slurry is greater than the proportion of silver particles with a particle size equal to or less than 1 μm in the first slurry, and / or the roughness of the silver particles in the second slurry is greater than the roughness of the silver particles in the first slurry.

12. The method for preparing a solar cell according to claim 9, characterized in that: The contact section includes a stacked top layer and a bottom layer, the second slurry covers the first slurry, the first slurry is heat-treated to form the bottom layer, and the second slurry located on the first slurry is heat-treated to form the top layer.

13. The method for preparing a solar cell according to claim 9, characterized in that: The contact section includes a stacked top layer and a bottom layer, the first slurry is heat-treated to form the bottom layer, the second slurry covers the bottom layer, and the second slurry on the bottom layer is heat-treated to form the top layer.

14. The method for preparing a solar cell according to claim 9, wherein: The second slurry covers the side surface and a part of the top surface of the first slurry. The first slurry forms the contact section after heat treatment, and the second slurry forms the connection section after heat treatment.

15. The method for preparing a solar cell according to claim 9, wherein: The first slurry forms the contact section after heat treatment, the second slurry covers part of the side surface and part of the top surface of the contact section, and the second slurry forms the connection section after heat treatment.

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