Preparation method of metal grid line of solar cell and solar cell

Abstract

The invention discloses a preparation method of a metal grid line of a solar cell and the solar cell. The preparation method of the metal grid line comprises the following steps: forming a first mask layer with a grid line groove on the main surface of a battery substrate, and forming a second mask layer on the side surface of the first mask layer; forming a basic metal grid line in a space defined by the second mask layer and the bottom surface of the grid line groove; the height of the basic metal grid line is smaller than the depth of the grid line groove, and removing the second mask layer; forming a conductive metal layer in a space between the top surface of the basic metal grid line and the side surface of the basic metal grid line and the side surface of the grid line groove; and removing the first mask layer. The preparation of the metal grid line ensures that the metal grid line has a relatively large depth-to-width ratio, the basic metal grid line can be protected, and meanwhile, the weldability of the metal grid line can be ensured through the conductive metal layer, so that the performance of the solar cell is improved.

Description

Technical Field

[0001] The invention relates to a method for preparing a metal grid line of a solar cell and a solar cell. Background Art

[0002] In the field of solar cells, two or more metals are stacked to form grid lines to overcome the defects of one metal and improve the performance of solar cells. For example, tin is plated on copper grid lines to protect them from oxidation, and nickel-copper stacked grid lines, nickel-silver stacked grid lines, aluminum-silver stacked grid lines, etc.

[0003] At present, the preparation method for stacked grid lines is mainly to first make a basic metal grid line, and then electroplate or print another metal on the periphery of the basic metal grid line by electroplating or printing to form a stacked metal grid line, so that the thickness of other metals stacked in various regions of the basic metal grid line is basically the same. For example, first form a copper grid line, and then electroplate metal tin on the periphery of the copper grid line by electroplating, which will form metal tin with basically the same thickness on the side and top of the copper grid line, which is inconsistent with the need for thicker metal tin on the top of the copper grid line and thinner metal tin on the side of the copper grid line. If the other metals stacked on the side of the basic metal grid line are too thick, the width of the metal grid line of the solar cell will increase, increasing shading, which is not conducive to reducing the power loss of the solar cell; if the other metals stacked on the top of the basic metal grid line are too thin, the weldability of the metal grid line cannot be guaranteed, which will also affect the performance of the solar cell. Summary of the invention

[0004] In view of this, the present invention provides a method for preparing a metal grid line of a solar cell and a solar cell, which can ensure that the metal grid line has a large aspect ratio and can protect the basic metal grid line, while ensuring the weldability of the metal grid line through a conductive metal layer, thereby improving the performance of the solar cell.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0006] In a first aspect, the present invention provides a method for preparing a metal grid line of a solar cell, comprising:

[0007] Step a, forming a first mask layer on the main surface of the battery substrate, wherein the first mask layer has a grid line groove;

[0008] Step b, forming a second mask layer on the side of the first mask layer;

[0009] Step c, forming a basic metal gate line in a space enclosed by the second mask layer and the bottom surface of the gate line groove; the height of the basic metal gate line is less than the depth of the gate line groove;

[0010] Step d, removing the second mask layer;

[0011] Step e, forming a conductive metal layer on the top surface of the basic metal gate line and the space between the side surface of the basic metal gate line and the side surface of the gate line groove;

[0012] Step f: removing the first mask layer.

[0013] In a second aspect, an embodiment of the present invention provides a solar cell, comprising: a cell substrate and metal grid lines arranged at intervals on the cell substrate, wherein:

[0014] The metal grid line includes a basic metal grid line and a conductive metal layer wrapping the basic metal grid line.

[0015] The thickness of the top surface of the conductive metal layer is greater than the thickness of the side surface of the conductive metal layer.

[0016] The technical solution of the first aspect of the above invention has the following advantages or beneficial effects:

[0017] The technical solution provided by the embodiment of the present invention forms a second mask layer on the side of the gate line groove on the basis of the gate line groove possessed by the first mask layer. Due to the existence of the second mask layer, the width of the basic metal gate line formed in the space enclosed by the second mask layer and the bottom surface of the gate line groove is limited by the second mask layer. Then, by removing the second mask layer, a gap is formed between the basic metal gate line and the side of the gate line groove, and a conductive metal layer is formed on the basis of the gap. The width of the gap can limit the thickness of the subsequent electroplated conductive metal layer on the side of the basic metal gate line. That is to say, the technical solution provided by the embodiment of the present invention matches the gate line groove possessed by the first mask layer with the second mask layer, and by controlling the thickness of the second mask layer on the side of the gate line groove, the thickness of the electroplated conductive metal layer on the side of the basic metal gate line can be controlled, thereby avoiding the formation of an excessively thick conductive metal layer on the side of the basic metal gate line, which leads to an increase in the overall width of the metal gate line, and the basic metal gate line and the conductive metal layer also have a relatively large aspect ratio when matched. Therefore, the technical solution provided by the embodiment of the present invention can ensure that the metal grid line has a large aspect ratio and can protect the basic metal grid line, while ensuring the weldability of the metal grid line through the conductive metal layer, thereby improving the performance of the solar cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the main process of a method for preparing a metal grid line of a solar cell based on a photosensitive material provided by an embodiment of the present invention;

[0019] Figure 2 is a schematic diagram of a first structural change corresponding to step S101 provided in an embodiment of the present invention;

[0020] Figure 3 is a schematic diagram of a second structural change corresponding to step S101 provided in an embodiment of the present invention;

[0021] Figure 4 The embodiment of the present invention provides Figure 2 The first structure shown is a schematic diagram of the first structure change corresponding to step S102 and step S103;

[0022] Figure 5 The embodiment of the present invention provides Figure 3 The first structure shown is a schematic diagram of a second structure change corresponding to step S102 and step S103;

[0023] Figure 6 The embodiment of the present invention provides Figure 2 The first structure shown is a schematic diagram of a third structure change corresponding to step S102 and step S103;

[0024] Figure 7 The embodiment of the present invention provides Figure 4 The schematic diagram of the structural change corresponding to the first structure after step S104 and step S105 is shown;

[0025] Figure 8 The embodiment of the present invention provides Figure 7 The structure shown is a schematic diagram of structural changes corresponding to step S106 and step S107;

[0026] Fig. 9 The embodiment of the present invention provides Figure 8 The structure shown is a schematic diagram of structural changes corresponding to step S108 and step S109;

[0027] Fig.10 is a partial structural schematic diagram of a first structure of a solar cell provided by an embodiment of the present invention;

[0028] Fig.11 is a partial structural schematic diagram of a second structure of a solar cell provided by an embodiment of the present invention;

[0029] Fig.12 It is a schematic diagram of the main process of a method for preparing a metal grid line of a solar cell provided by another embodiment of the present invention.

[0030] The reference numerals are as follows:

[0031] 10-battery substrate; 20-metal grid line; 21-basic metal grid line; 22-conductive metal layer; 30-negative photosensitive material; 30'-negative photosensitive material after exposure; 40-positive photosensitive material; 40'-negative photosensitive material after exposure; 50-grid line groove. DETAILED DESCRIPTION

[0032] In the prior art, although it has been disclosed that a negative photosensitive material or a positive photosensitive material is used to prepare a grid line groove, and then a metal grid line is grown based on the grid line groove. However, the prior art either uses a grid line groove to prepare a grid line with only one metal, or prepares a stacked grid line of two metals on the basis of the grid line groove (i.e., a metal grid line is formed in the grid line groove, and then another metal is stacked on the metal grid line), wherein, in the stacked grid lines of the two metals, due to the growth in the grid line groove, the stacked another metal cannot cover the side of the grid line, if the metal grid line is easily oxidized, the exposed side will increase the risk of oxidation of the metal grid line, affecting the performance of the solar cell. As described in the background technology, in order to reduce the oxidation of the metal grid line, a metal grid line is formed in the above-mentioned grid line groove and the negative photosensitive material or the positive photosensitive material is removed, and a stacked metal layer is formed on the metal grid line. Although this metal layer can cover the side of the metal grid line, it cannot control the thickness of the metal layer formed on the side of the metal grid line, so that the metal layer easily increases the shading area of ​​the solar cell, affecting the performance of the solar cell. In order to solve these problems existing in the prior art and effectively control the thickness of the metal layer formed on the side of the metal grid line, an embodiment of the present invention provides a method for preparing a metal grid line of a solar cell and a solar cell.

[0033] like Fig.12 As shown, it shows a method for preparing a metal grid line of a solar cell provided by an embodiment of the present invention, which may include the following steps:

[0034] Step S1201: forming a first mask layer on the main surface of the battery substrate 10, wherein the first mask layer has a grid line groove 50;

[0035] Step S1202: forming a second mask layer on the side of the gate line groove 50;

[0036] Step S1203: forming a basic metal gate line 21 in a space enclosed by the second mask layer and the bottom surface of the gate line groove 50; the height of the basic metal gate line 21 is less than the depth of the gate line groove 50;

[0037] Step S1204: removing the second mask layer;

[0038] Step S1205: forming a conductive metal layer 22 on the top surface of the basic metal gate line 21 and the space between the side surface of the basic metal gate line 21 and the side surface of the gate line groove 50;

[0039] Step S1206: removing the first mask layer.

[0040] The method for preparing a metal gate line provided in an embodiment of the present invention forms a basic metal gate line 21 by setting a first mask layer and a second mask layer, and utilizing the space enclosed by the second mask layer and the bottom surface of the gate line groove 50. After removing the second mask layer, a certain gap is formed between the side of the gate line groove 50 and the basic metal gate line 21, and this gap is used to form a conductive metal layer. Since the width of this gap can be controlled by controlling the thickness of the second mask layer, the thickness of the conductive metal layer 22 formed on the side of the basic metal gate line 21 can be controlled, so that the basic metal gate line can be completely covered and protected from oxidation, and the thickness of the side metal conductive layer can be controlled to reduce the gate line shading area.

[0041] In the embodiment of the present invention, in step S1201, the first mask layer having the gate line grooves may be formed in the following manner:

[0042] Step a1, coating a negative photosensitive material 30 on the main surface of the battery substrate 10, and performing interval exposure on the negative photosensitive material;

[0043] Step a2, developing the negative photosensitive material 30' after the interval exposure, and forming the gate line groove 50 in the unexposed area.

[0044] In the embodiment of the present invention, in step S1202 , the second mask layer may be formed specifically in the following manner.

[0045] Step b1, spraying a positive photosensitive material 40 on the bottom and side of the grid line groove 50;

[0046] Step b2, using parallel light perpendicular to the main surface of the battery substrate 10 to expose the positive photosensitive material 40;

[0047] Step b3, developing the exposed positive photosensitive material 40 ′, removing the exposed positive photosensitive material 40 ′ at the bottom of the gate line groove 50 , and retaining the positive photosensitive material 40 at the side of the gate line groove 50 .

[0048] On the basis that the negative photosensitive material 30 forms the first mask layer and the positive photosensitive material 40 forms the second mask layer, the second mask layer can be removed in the above step S1204 in the following manner: the remaining positive photosensitive material 40 is further exposed and developed sequentially to remove the positive photosensitive material 40 between the base metal gate line 21 and the side of the gate line groove 50.

[0049] In the embodiment of forming the first mask layer with the negative photosensitive material 30 , the step S1206 is specifically to remove the remaining negative photosensitive material 30 after exposure.

[0050] It can be understood that, in addition to the negative photosensitive material 30 and the positive photosensitive material 40, the first mask layer and the second mask layer of the above embodiment can also be made of other materials such as metal materials or inert materials such as quartz glass. The first mask layer and the second mask layer can be formed by curing the materials given in the above embodiment on the battery substrate 10. In addition, the first mask layer and the second mask layer can also be prepared by other methods. For example, the first mask layer and the second mask layer are formed by forming inert materials such as metal materials or quartz glass. In the process of preparing the metal grid line, it is only necessary to cover the pre-formed first mask layer and the second mask layer on the battery substrate 10. The pre-formed first mask layer and the second mask layer can be reused. That is, the above step S1201 to form the first mask layer is essentially to place and press the pre-formed first mask layer on the main surface of the battery substrate 10, and the above step S1202 to form the second mask layer is to fit the pre-formed second mask layer to the side of the grid line groove 50. In addition, the preformed first mask layer can also cooperate with the second mask layer formed by the positive photosensitive material 40 provided in the above embodiment (that is, the preformed first mask layer is placed and pressed on the main surface of the battery substrate 10, and the positive photosensitive material 40 is sprayed on the side of the grid line groove 50 of the first mask layer to form the second mask layer); the preformed second mask layer can also cooperate with the first mask layer formed by the negative photosensitive material 30 provided in the above embodiment (that is, the negative photosensitive material 30 is coated on the main surface of the battery substrate 10 to form the first mask layer, and the preformed second mask layer is attached to the side of the grid line groove 50 of the first mask layer), as long as it can be ensured that the base metal grid line and the first mask layer will not be damaged when the second mask layer is removed. It is worth noting that any technical solution based on the cooperation of two masks to independently control the width and height of the base metal grid line 21, the thickness of the conductive metal layer 22 on the side of the base metal grid line 21, and the thickness of the conductive metal layer 22 on the top surface of the base metal grid line 21, is within the protection scope of this application.

[0051] The technical solution of the present invention is further described in detail below by taking the example of forming the first mask layer and the second mask layer by using a photosensitive material.

[0052] in, Figure 1 A schematic diagram showing the main process of a method for preparing a metal grid line of a solar cell based on a photosensitive material provided by an embodiment of the present invention; Figures 2 to 7 A schematic diagram showing structural changes corresponding to a method for preparing a metal grid line of a solar cell is shown.

[0053] The embodiment of the present invention provides a method for preparing a metal grid line of a solar cell. Figure 1 As shown, the method for preparing the metal grid line of the solar cell may include the following steps:

[0054] Step S101: coating a negative photosensitive material 30 on the main surface of the battery substrate 10, and performing interval exposure on the negative photosensitive material 30;

[0055] The battery substrate 10 in this step refers to a substrate provided with various functional layers required for the battery. For example, the battery substrate 10 can be a perovskite battery substrate obtained by using glass or other materials as a substrate to prepare various functional layers of the perovskite battery, such as an electron transport layer, a hole transport layer, a perovskite absorption layer, a modification layer, etc.; the battery substrate 10 can also be a silicon-based solar cell substrate obtained by using a silicon wafer as a substrate to prepare various functional layers, such as a tunneling oxide layer, a doping layer, a passivation layer, an anti-reflection layer, a silicon film, a conductive film layer, etc.

[0056] The specific implementation of this step may include: coating a negative photosensitive material with a thickness of 10μm~15μm on the main surface of the battery substrate, and drying the negative photosensitive material, wherein the drying temperature is 80℃~90℃, and the drying time is 5min~10min; exposing the dried negative photosensitive material every 5μm~15μm.

[0057] The negative photosensitive material 30 used in this step can be selected from existing negative photosensitive materials. The exposed portion of the negative photosensitive material 30 will not be removed by the developer, while the unexposed photosensitive material can be easily removed by the developer.

[0058] Specifically, the thickness of the negative photosensitive material 30 coated in this step can be 10 μm, 10.5 μm, 11 μm, 12 μm, 12.5 μm, 13 μm, 14 μm, 14.5 μm or 15 μm, etc. The thickness of the negative photosensitive material 30 coated can effectively control the height of the subsequently formed basic metal grid line 21 and the thickness of the conductive metal layer 22 located on the top surface of the basic metal grid line 21.

[0059] The temperature for drying the negative photosensitive material 30 may be 80° C., 82° C., 83° C., 84° C., or 85° C., etc. In addition, the drying time may be 5 min., 6 min., 6.5 min., 7 min., 7.5 min., 8 min., 8.5 min., 9 min., or 10 min. Through the drying process, the negative photosensitive material 30 may be initially solidified to prevent the negative photosensitive material 30 from being lost.

[0060] Among them, the negative photosensitive material 30 that is exposed and dried every 5μm~15μm is to control the spacing between two adjacent exposure areas to be 5μm~15μm, that is, the width of the unexposed area between two adjacent exposure areas is 5μm~15μm. In other words, the negative photosensitive material 30 that is exposed and dried every 5μm~15μm is essentially to control the width of the unexposed area between two adjacent exposure areas. For example, the spacing between two adjacent exposure areas can be 5μm, 6μm, 8μm, 10μm, 12μm, 13μm, 14μm or 15μm, etc. The width of the formed metal grid line (that is, the total width of the basic metal grid line 21 and the conductive metal layer 22) can be controlled by the width of the unexposed area between the two adjacent exposure areas, thereby effectively controlling the width of the metal grid line 20 formed on the battery substrate 10 and the aspect ratio of the metal grid line 20.

[0061] The changes to the structure in step S101 are as follows: Figure 2 and Figure 3 As shown, from Figure 2 and Figure 3 It can be seen that in this step, the negative photosensitive material 30 is first coated on the battery substrate 10, and the negative photosensitive material 30 is irradiated with light to expose the photosensitive material 30 to obtain the exposed photosensitive material 30'. Among them, the exposed area and the unexposed area are arranged alternately. It is worth noting that after this step, the cross-section of the unexposed area can be a trapezoidal structure or a rectangular structure.

[0062] It is worth noting that the energy used for exposure in this step can be determined according to the negative photosensitive material 30 and the thickness of the negative photosensitive material 30. The user can determine it according to actual process requirements. No limitation is imposed on the energy used for exposure in this step.

[0063] Step S102: developing the negative photosensitive material 30' after the interval exposure to form a gate line groove 50 in the unexposed area;

[0064] The unexposed area is the area between every two adjacent exposed areas that is not irradiated by light, that is, the exposed areas and the unexposed areas are arranged alternately.

[0065] Specifically, a developer containing 0.8 wt % to 1.3 wt % of Na2CO3 is used to develop the negative photosensitive material 30' after interval exposure at 28°C to 32°C, wherein the amount of the developer is 1.5 Kg / cm² to 2 Kg / cm², and the development time is 40% to 50% of the time required to reach the development point (BP). 0.8 wt % refers to the mass percentage of Na2CO3 contained in the solution. For example, the developer may contain 0.8%, 0.9%, 1.0%, 1.1%, 1.2% or 1.3% of Na2CO3 by mass. The amount of the developer may be 1.5 Kg / cm², 1.7 Kg / cm², 1.8 Kg / cm², 1.9 Kg / cm² or 2 Kg / cm². The development time is determined by the time required for the developer to reach the development point (BP), that is, the development time controlled by this step can be 40%, 42%, 44%, 45%, 47%, 48%, 49% or 50% of the time required for the developer to reach the development point (BP).

[0066] Through the development process, the negative photosensitive material 30 in the unexposed area is removed. Figure 2 The obtained structure, after this step, can be obtained as follows Figure 4 The cross section of the grid line groove 50 is shown as a rectangle; Figure 3 The obtained structure, after this step, can be obtained as follows Figure 5 The cross section of the gate line groove 50 shown is a regular trapezoid. The width of the gate line groove 50 obtained by this step is generally 5 μm to 15 μm. Specifically, for the gate line groove 50 with a rectangular cross section, as shown in FIG. Figure 4 As shown, the width of the gate line groove 50 is D1. For the gate line groove 50 with a trapezoidal cross section, as shown in FIG. Figure 4 As shown, the width of the gate line groove 50 can be the upper bottom D2 of the trapezoidal structure. In addition, the width of the gate line groove 50 can also be the lower bottom of the trapezoidal structure. Exemplarily, the width of the gate line groove 50 can be 5μm, 7μm, 8μm, 9μm, 10μm, 12μm, 13μm, 14μm or 15μm, etc. It is worth noting that, for the case where the cross-section of the gate line groove 50 formed in this step is a trapezoidal structure, the bottom angle of the gate line groove 50 (the bottom angle is the angle formed by the side and the bottom surface of the gate line groove 50) is generally less than 90°. Preferably, the bottom angle of the gate line groove 50 is generally not less than 50° to facilitate the completion of subsequent steps. In addition, for the case where the cross-section of the gate line groove 50 formed in this step is a trapezoidal structure, the bottom angle of the gate line groove 50 is 90°.

[0067] Step S103: spraying a positive photosensitive material 40 on the area including the gate line groove 50;

[0068] The positive photosensitive material 40 may be an existing positive photosensitive material. The exposed portion of the positive photosensitive material 40 will be removed by the developer, while the unexposed photosensitive material will not be removed by the developer.

[0069] Specifically, after the battery substrate 10 is heated to 40°C to 50°C, a positive photosensitive material with a thickness of 0.5 μm to 1 μm is sprayed. The positive photosensitive material 40 is solidified during the spraying process by the heated battery substrate 10 to prevent the positive photosensitive material 40 from being lost. The temperature of heating the battery substrate 10 in this step can be 40°C, 42°C, 44°C, 45°C, 47°C, 49°C or 50°C, etc.

[0070] The thickness of the sprayed positive photosensitive material 40 can be 0.5 μm, 0.7 μm, 0.8 μm, 0.9 μm or 1.0 μm, etc. The purpose of controlling the thickness of the positive photosensitive material 40 in this step is to control the thickness of the subsequent electroplated conductive metal layer 22 on the side of the basic metal grid line 21 based on the thickness of the positive photosensitive material 40. It is worth noting that the thickness of the battery substrate 10 generally refers to the average thickness of the sprayed positive photosensitive material 40. In addition, the thickness of the conductive metal layer 22 is guaranteed by the thickness of the positive photosensitive material 40 to ensure that the conductive metal layer 22 can fully wrap the basic metal grid line 21 to avoid the basic metal grid line 21 being exposed.

[0071] For this step, you can Figure 4 and Figure 5 As shown, the positive photosensitive material 40 is sprayed on the gate line groove 50 and the epitaxial area of ​​the gate line groove 50. In addition, taking the gate line groove 50 with a rectangular cross section as an example, as shown in FIG. Figure 6 As shown, in this step, the positive photosensitive material 40 can also be sprayed on the entire main surface of the battery substrate 10 including the grid line groove 50. Preferably, the positive photosensitive material 40 is sprayed on the grid line groove 50 and the epitaxial area of ​​the grid line groove 50 to reduce the amount of the positive photosensitive material 40, thereby effectively controlling the production cost of the metal grid line 40.

[0072] Later on Figure 4 Taking the obtained structure as an example, the structural changes brought about by the subsequent processing process from step S104 to step S109 are explained.

[0073] Step S104: using parallel light perpendicular to the main surface of the battery substrate 10 to expose the positive photosensitive material 40;

[0074] Among them, the energy used for exposure in this step can be determined according to the thickness of the positive photosensitive material 40 and the positive photosensitive material 40 formed on the bottom surface of the gate line groove 50 and the area outside the gate line groove 50. The user can determine it according to actual process requirements. Here, no limitation is imposed on the energy used for exposure in the step.

[0075] like Figure 7 As shown, the thickness of the positive photosensitive material 40 formed on the side of the grid line groove 50 by the positive photosensitive material 40 sprayed in the above step S103 is h, and the thickness h of the positive photosensitive material 40 formed on the side of the grid line groove 50 is much greater than the thickness of the positive photosensitive material 40 formed on the bottom surface of the grid line groove 50 and the thickness of the positive photosensitive material 40 formed on the area extending out of the grid line groove 50. In the process of exposing the positive photosensitive material 40 by parallel light perpendicular to the main surface of the battery matrix 10 in this step, since the thickness h of the positive photosensitive material 40 formed on the side of the grid line groove 50 is much greater than the thickness of the positive photosensitive material 40 formed in other areas (the bottom surface of the grid line groove 50 and the area extending out of the grid line groove 50), the exposure in this step will only expose the positive photosensitive material 40 formed on the bottom surface of the grid line groove 50 and the positive photosensitive material 40 formed in the area extending out of the grid line groove 50, while the positive photosensitive material 40 formed on the side of the grid line groove 50 will not be completely exposed, that is, Figure 7 As shown, after this step, the exposed positive photosensitive material 40 ′ is formed on the bottom surface of the grid line groove 50 and the exposed positive photosensitive material 40 ′ is formed in the area extending out of the grid line groove 50 .

[0076] Step S105: developing the exposed positive photosensitive material 40', removing the exposed positive photosensitive material 40' at the bottom of the grid line groove 50, and retaining the positive photosensitive material 40 at the side of the grid line groove 50;

[0077] like Figure 7 As shown, since the above step S104 only exposes the positive photosensitive material 40 formed on the bottom surface of the gate line groove 50 and the positive photosensitive material 40 formed in the area extending out of the gate line groove 50, this step develops the exposed positive photosensitive material 40', removes the exposed positive photosensitive material at the bottom of the gate line groove 50 and the exposed positive photosensitive material extending out of the gate line groove 50, and retains the positive photosensitive material on the side of the gate line groove 50.

[0078] Specifically, this step uses a developer containing 0.8 wt %~1.3wt % of Na2CO3 to develop the exposed positive photosensitive material 40' at 28°C~32°C, wherein the amount of the developer is 1.5 Kg / cm²~2Kg / cm², and the development time is 40%~50% of the time required to reach the development point (BP). For example, the developer may contain 0.8%, 0.85%, 0.9%, 1.0%, 1.1%, 1.15%, 1.2% or 1.3% of Na2CO3 by mass. The amount of the developer may be 1.5 Kg / cm², 1.7 Kg / cm², 1.8 Kg / cm², 1.9 Kg / cm² or 2Kg / cm². The development time is determined by the time required for the developer to reach the development point (BP), that is, the development time controlled by this step can be 40%, 42%, 44%, 45%, 47%, 48%, 49% or 50% of the time required for the developer to reach the development point (BP).

[0079] The temperature of the developer may be 28° C., 29° C., 30° C., 31° C. or 32° C., etc.

[0080] Step S106: forming a basic metal gate line 21 in the gate line groove 50 , wherein the height of the basic metal gate line 21 is less than the depth of the gate line groove 50 ;

[0081] After processing this step, the structure changes as follows Figure 8 The difference between the depth of the gate line groove 50 and the height of the base metal gate line 21 is shown in FIG. Figure 8 Indicated d.

[0082] The step of forming the basic metal grid line 21 can be completed by using existing processes, and the process of forming the basic metal grid line 21 is not repeated here. The basic metal grid line 21 can be a copper grid line, a silver grid line, a copper-silver grid line, a nickel grid line or other metal grid lines.

[0083] Furthermore, the height of the basic metal gate line 21 formed in this step is 2 μm to 3 μm lower than the depth of the gate line groove 50. Figure 8 As shown, the difference d between the depth of the gate line groove 50 and the height of the basic metal gate line 21 may be 2 μm, 2.2 μm, 2.3 μm, 2.4 μm, 2.5 μm, 2.6 μm, 2.7 μm, 2.8 μm, 2.9 μm or 3 μm, etc.

[0084] By limiting the height of the basic metal gate line 21 to be smaller than the depth of the gate line groove 50, on the one hand, the subsequent step S107 can be completed; on the other hand, in the subsequent formation of the conductive metal layer 22, the width and thickness of the conductive metal layer 22 located on the top surface of the basic metal gate line 21 can be limited, thereby avoiding the conductive metal layer 22 significantly increasing the shading area of ​​the solar cell, so as to ensure the photoelectric conversion performance of the solar cell.

[0085] Step S107: further sequentially exposing and developing the remaining positive photosensitive material 40 to remove the positive photosensitive material 40 between the base metal grid line 21 and the side surface of the grid line groove 50;

[0086] In order to completely remove the positive photosensitive material between the base metal grid line 21 and the side of the grid line groove 50, the exposure energy used in this step is generally 10 to 20 times the exposure energy of step S104. That is, the exposure energy of this step is determined by the exposure energy of S104, and the exposure energy of this step is much higher than the exposure energy of S104. For example, the exposure energy of this step can be 10 times, 13 times, 15 times, 18 times or 20 times the exposure energy of step S104.

[0087] Furthermore, in order to completely remove the positive photosensitive material 40 between the base metal gate line 21 and the side surface of the gate line groove 50 , step S107 may be repeated multiple times after step S106 and before step S108 .

[0088] After this step, the corresponding structural changes are as follows Figure 8 shown.

[0089] Step S108: electroplating a conductive metal layer 22 on the top surface of the basic metal gate line 21 and between the basic metal gate line 21 and the side surface of the gate line groove 50;

[0090] The parameters used for electroplating in this step can be determined according to actual needs. The electroplated metal in this step can be any conductive metal, such as tin, silver, nickel, tin-silver mixed metal, tin-nickel mixed metal, etc.

[0091] In this step, the overlapping height of the electroplated conductive metal layer 22 and the basic metal grid line 21 is generally less than or equal to the depth of the grid line groove 50, so as to avoid the conductive metal layer 22 covering the exposed negative photosensitive material 30' near the grid line groove 50. On the one hand, it can ensure the width of the conductive metal layer 22 finally formed; on the other hand, it ensures that the exposed negative photosensitive material 30' can be removed cleanly in the subsequent steps.

[0092] Through the above steps, after the positive photosensitive material 40 between the base metal grid line 21 and the side of the grid line groove 50 is removed, a gap is formed between the base metal grid line 21 and the side of the grid line groove 50, and the width of the gap determines the thickness of the conductive metal layer 22 formed on the side of the base metal grid line 21. Therefore, the gap formed between the base metal grid line 21 and the side of the grid line groove 50 can be regulated by the thickness of the positive photosensitive material 40 formed in the previous step, so as to achieve the purpose of regulating the thickness of the conductive metal layer 22 on the side of the base metal grid line 21.

[0093] In addition, by coordinating the above steps, the thickness of the conductive metal layer 22 located on the side of the basic metal grid line 21 can be adjusted to be smaller than the thickness of the conductive metal layer 22 located on the top surface of the basic metal grid line 21, so that the conductive metal layer 22 located on the side of the basic metal grid line 21 does not affect the grid line width, and can ensure the welding performance of the conductive metal layer 22 located on the top surface of the basic metal grid line 21, which can effectively reduce the impact on the solar cell.

[0094] Step S109: removing the remaining exposed negative photosensitive material 30'.

[0095] In this step, the remaining exposed negative photosensitive material 30' can be removed by laser etching. It is worth noting that in the process of forming the basic metal grid line 21, a metal layer may also be formed in the area outside the grid line groove 50 at the same time. In the process of removing the remaining exposed negative photosensitive material 30' in this step, the excess metal layer formed in the area outside the grid line groove 50 will also be removed simultaneously.

[0096] The structural changes corresponding to this step are as follows Fig. 9 The basic metal grid lines 21 formed in the above steps and the conductive metal layer 22 electroplated on the side and top surfaces of the basic metal grid lines 21 constitute the metal grid lines 20 of the solar cell.

[0097] For the case where the cross section of the gate line groove 50 is a rectangular structure, the following can be obtained through the above process: Fig.10 The metal gate line 20 shown has a rectangular cross section, and includes a base metal gate line 21 with a rectangular cross section and a conductive metal layer 22 with a rectangular cross section.

[0098] For the case where the cross section of the gate line groove 50 is a trapezoidal structure, the following can be obtained through the above process: Fig.11 The metal gate line 20 shown has a trapezoidal cross-section. The metal gate line 20 includes a base metal gate line 21 with a trapezoidal cross-section and a conductive metal layer 22 with a trapezoidal cross-section.

[0099] The technical solution provided by the above embodiment is to form a grid line groove 50 by exposing and developing a negative photosensitive material 30, spray a positive photosensitive material 40 in the area containing the grid line groove 50, and remove the positive photosensitive material 40 at the bottom of the grid line groove 50 by exposing and developing the positive photosensitive material 40, and retain the positive photosensitive material 40 on the side of the grid line groove 50. Due to the presence of the positive photosensitive material 40 on the side of the grid line groove 50, the basic metal grid line 21 formed in the grid line groove 50 is actually between the positive photosensitive material 40 on the side of the grid line groove 50, and then the remaining positive photosensitive material 40 is further sequentially exposed and developed to remove the positive photosensitive material between the basic metal grid line 21 and the side of the grid line groove 50. 40, so that a gap is formed between the base metal grid line 21 and the side of the grid line groove 50, and the gap can limit the thickness of the subsequent electroplated conductive metal layer 22 on the side of the base metal grid line 21. That is to say, the technical solution provided by the embodiment of the present invention can achieve the control of the thickness of the electroplated conductive metal layer 22 on the side of the base metal grid line 21 by matching the grid line groove 50 formed in the negative photosensitive material 30 with the positive photosensitive material 40, and by controlling the thickness of the positive photosensitive material 40 on the side of the grid line groove 50, so as to avoid the formation of an excessively thick conductive metal layer 22 on the side of the base metal grid line 21, which leads to an increase in the overall width of the metal grid line 20, and the base metal grid line 21 and the conductive metal layer 22 also have a relatively large depth-to-width ratio. Therefore, the technical solution provided by the embodiment of the present invention can ensure that the metal grid line 20 has a large depth-to-width ratio, and can protect the base metal grid line 21, and at the same time can ensure the weldability of the metal grid line 20 through the conductive metal layer 22, thereby improving the performance of the solar cell.

[0100] Furthermore, due to the above technical solution, the outer side of the base metal grid line 21 can be fully wrapped by the conductive metal layer 22, thereby preventing the base metal grid line 21 from being oxidized. In addition, by matching the thickness of the above negative photosensitive material 30, the thickness of the positive photosensitive material 40, the height of the formed base metal grid line 21, and the depth of the grid line groove 50, the thickness of the conductive metal layer 22 on the side of the base metal grid line 21 and the thickness of the conductive metal layer 22 on the top surface of the base metal grid line 21 can be independently regulated to obtain a thinner conductive metal layer 22 on the side of the base metal grid line 21 and a thicker conductive metal layer 22 on the top surface of the base metal grid line 21, thereby ensuring the easy welding of the solar cell, and at the same time not increasing the grid line width at all, which is beneficial to improving the conversion efficiency of the solar cell. Furthermore, the technical solution provided by the embodiment of the present invention can be self-aligned, does not require alignment, and does not have alignment problems.

[0101] Furthermore, an embodiment of the present invention provides a solar cell. Fig.10 and Fig.11As shown, the solar cell may include: a cell substrate 10 and metal grid lines 20 arranged at intervals on the cell substrate 10, wherein:

[0102] The metal gate line 20 may include a base metal gate line 21 and a conductive metal layer 22 wrapping the base metal gate line 21.

[0103] The thickness of the top surface of the conductive metal layer 22 is greater than the thickness of the side surface of the conductive metal layer 22 .

[0104] The cross section of the basic metal gate line 21 may be a rectangular or trapezoidal structure. Preferably, the trapezoidal structure is an isosceles trapezoid.

[0105] Furthermore, the angle between the side surface of the basic metal grid line 21 and the main surface of the battery substrate 10 is less than or equal to 90°.

[0106] The width of the basic metal grid line 21 is 3 μm to 14 μm. For example, the width of the basic metal grid line 21 can be 3 μm, 5 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm or 14 μm. By controlling the width of the basic metal grid line 21, the tension of the grid line of the solar cell can be met.

[0107] The height of the basic metal grid line 21 is 7 μm to 13 μm. For example, the height of the basic metal grid line 21 can be 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm or 14 μm. The height of the basic metal grid line 21 and the width of the basic metal grid line 21 can make the basic metal grid line 21 have a relatively high aspect ratio, which helps to improve the conversion efficiency of the solar cell and reduce the square resistance of the solar cell.

[0108] The thickness of the top surface of the conductive metal layer 22 is 1 μm to 2 μm. The thickness of the top surface of the conductive metal layer 22 is the portion of the conductive metal layer 22 located on the top surface of the base metal grid line 21. For example, the thickness of the top surface of the conductive metal layer 22 may be 1 μm, 1.2 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.8 μm, 1.9 μm or 2 μm. By controlling the thickness of the top surface of the conductive metal layer 22, the weldability of the conductive metal layer 22 can be ensured, and it helps to further improve the aspect ratio of the metal grid line 20 of the solar cell.

[0109] The thickness of the side of the conductive metal layer 22 is 0.5 μm to 1 μm. The thickness of the side of the conductive metal layer 22 is the portion of the conductive metal layer 22 located on the side of the basic metal grid line 21. For example, the thickness of the side of the conductive metal layer 22 can be 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm or 1 μm. By controlling the thickness of the top surface of the conductive metal layer 22, it can be ensured that the conductive metal layer 22 fully wraps the basic metal grid line 21, and it helps to further improve the aspect ratio of the metal grid line 20 of the solar cell without increasing the grid line width, ensuring that the shielding area of ​​the solar cell does not change significantly.

[0110] The following is a detailed description of the method for preparing the metal grid line of the solar cell provided by the embodiment of the present invention with reference to a specific embodiment.

[0111] Embodiment 1:

[0112] Step A: coating a negative photosensitive material a with a thickness of 12 μm on the main surface of the battery substrate and drying the negative photosensitive material a at 80 ˚C for 10 minutes.

[0113] Step B: performing interval exposure on the negative photosensitive material a, wherein the interval between each two adjacent exposure areas is 10 μm.

[0114] Step C: using 1.3wt% Na2CO3 developing solution at 30˚C±2˚C and using 1.5Kg / cm² to develop the negative photosensitive material a, wherein the developing time is 40% of the time required to reach the developing point (BP), to form a grid line groove.

[0115] Step D: spraying a positive photosensitive material b with a thickness of 0.5 μm on the gate line groove and the area near the gate line groove and drying it. During spraying, the temperature of the battery substrate can be 50°C to accelerate the evaporation of the solvent and fix it.

[0116] Step E, parallel light exposure of the positive photosensitive material b, the light is perpendicular to the surface of the battery substrate, so that the positive photosensitive material b on the surface of the negative photosensitive material a and the bottom of the grid line groove is soluble in the developer after exposure; the positive photosensitive material b on the side wall of the grid line groove (the side wall of the grid line groove mentioned below is the side surface of the grid line groove mentioned above) has a large vertical depth, and the parallel light exposure is insufficient, so the positive photosensitive material b on the side wall of the grid line groove is not exposed and is insoluble in the developer.

[0117] Step F: Develop the positive photosensitive material b using 1.3 wt % Na 2 CO 3 developing solution at 30°C±2°C using 1.5 Kg / cm 2 , wherein the developing time is 40% of the time required to reach the developing point (BP).

[0118] Step G: electroplating metal copper to form copper grid lines, wherein the thickness of the copper grid lines is less than the depth of the groove by 3 μm.

[0119] Step H: Expose the remaining positive photosensitive material b with high energy, so that the positive photosensitive material b on the side wall of the gate line groove is fully exposed and completely soluble in the developer, wherein the exposure energy is 15 times that of step E.

[0120] Step I: Develop the remaining positive photosensitive material b using 1.3 wt % Na 2 CO 3 developing solution at 30°C ± 2°C using 1.5 kg / cm 2 , wherein the developing time is 40% of the time required to reach the developing point (BP).

[0121] Step J: electroplating a tin protective layer on the top and side surfaces of the copper grid line, wherein the thickness of the tin layer on the top surface of the copper grid line is 2 μm, and the thickness of the tin layer on the side surfaces of the copper grid line is 0.5 μm.

[0122] Step K: remove the negative photosensitive material a on the surface and etch away the excess copper seed layer.

[0123] The introduction provided in the above steps is only used to help understand the method, structure and core idea of ​​the present invention. For ordinary technicians in this technical field, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also belong to the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a metal grid line of a solar cell, characterized in that: include: Step a, forming a first mask layer on the main surface of the battery substrate (10), wherein the first mask layer has a grid line groove (50); Step b, forming a second mask layer on the side of the gate line groove (50); Step c, forming a basic metal gate line (21) in a space enclosed by the second mask layer and the bottom surface of the gate line groove (50); the height of the basic metal gate line (21) is less than the depth of the gate line groove (50); Step d, removing the second mask layer; Step e, forming a conductive metal layer (22) on the top surface of the basic metal gate line (21) and in the space between the side surface of the basic metal gate line (21) and the side surface of the gate line groove (50); Step f: removing the first mask layer.

2. The method for preparing a metal grid line according to claim 1, characterized in that: Step a includes: Step a1, coating a negative photosensitive material (30) on the main surface of the battery substrate (10), and performing interval exposure on the negative photosensitive material; Step a2, developing the negative photosensitive material (30') after the interval exposure, and forming the grid line groove (50) in the unexposed area.

3. The method for preparing a metal grid line according to claim 1, characterized in that: Step b includes: Step b1, spraying a positive photosensitive material (40) on the bottom and side of the grid line groove (50); Step b2, exposing the positive photosensitive material (40) using parallel light perpendicular to the main surface of the battery matrix (10); Step b3, developing the exposed positive photosensitive material (40'), removing the exposed positive photosensitive material (40') at the bottom of the grid line groove (50), and retaining the positive photosensitive material (40) at the side of the grid line groove (50).

4. The method for preparing a metal grid line according to claim 3, characterized in that: Step d comprises: further sequentially exposing and developing the remaining positive photosensitive material (40) to remove the positive photosensitive material (40) between the base metal grid lines (21) and the side surfaces of the grid line grooves (50).

5. The method for preparing a metal grid line according to claim 2, characterized in that: Step a1 includes: Step a11, coating a negative photosensitive material (30) with a thickness of 10 μm to 15 μm on the main surface of the battery substrate (10), and drying the negative photosensitive material (30), wherein the drying temperature is 80 to 90° C. and the drying time is 5 min to 10 min; Step a12, exposing and drying the negative photosensitive material (30) every 5 μm to 15 μm; and / or, Step a2 includes: The negative photosensitive material (30') after the interval exposure is developed at 28°C to 32°C using a developer containing 0.8 wt% to 1.3 wt% of Na2CO3, wherein the amount of the developer used is 1.5 to 2 kg / cm², and the development time is 40% to 50% of the time required to reach the development point (BP).

6. The method for preparing a metal grid line according to claim 3, characterized in that: Step b1 comprises: heating the battery substrate (10) to 40° C. to 50° C., and then spraying a positive photosensitive material (40) with a thickness of 0.5 μm to 1 μm; and / or, Step b1 includes: Spraying a positive photosensitive material (40) on the entire main surface of the battery substrate (10) including the grid line groove (50); or spraying a positive photosensitive material (40) on the grid line groove (50) and the epitaxial region of the grid line groove (50); and / or, Step b3 comprises: using a developer containing 0.8 wt % to 1.3 wt % of Na2CO3 to develop the exposed positive photosensitive material (40') at 28°C to 32°C, wherein the amount of the developer is 1.5 to 2 kg / cm², and the development time is 40% to 50% of the time required to reach the development point (BP).

7. The method for preparing a metal grid line according to claim 4, characterized in that: The exposure energy of step d is 10 to 20 times the exposure energy of step b3; and / or, After step c and before step e, step d is repeated multiple times.

8. The method for preparing a metal grid line according to any one of claims 1 to 7, characterized in that: The width of the gate line groove (50) is 5 μm to 15 μm; and / or, The bottom angle of the gate line groove (50) is less than or equal to 90°; and / or, The height of the basic metal gate line (21) formed in step c is 2 μm to 3 μm lower than the depth of the gate line groove (50).

9. A solar cell, characterized in that: include: A battery substrate (10) and metal grid lines (20) arranged at intervals on the battery substrate (10), wherein: The metal grid line (20) comprises a base metal grid line (21) and a conductive metal layer (22) wrapping the base metal grid line (21). The thickness of the top surface of the conductive metal layer (22) is greater than the thickness of the side surface of the conductive metal layer (22).

10. The solar cell according to claim 9, characterized in that: The cross section of the basic metal grid line (21) is a rectangle or an isosceles trapezoid; and / or, The angle between the side surface of the basic metal grid line (21) and the main surface of the battery matrix (10) is less than or equal to 90°; and / or, The width of the basic metal gate line (21) is 3 μm to 14 μm; and / or, The height of the basic metal grid line (21) is 7 μm to 13 μm; and / or, The thickness of the top surface of the conductive metal layer (22) is 1 μm to 2 μm; and / or, The thickness of the side surface of the conductive metal layer (22) is 0.5 μm to 1 μm.

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