Preparation method of solar cell and solar cell

Abstract

The invention discloses a preparation method of a solar cell and the solar cell, and relates to the technical field of solar cells. The preparation method comprises the following steps: sequentially forming a functional layer and a seed layer on a textured surface of a silicon substrate; preparing a leveling layer on the seed layer; coating a photosensitive material on the leveling layer, and performing local exposure and development to form grooves arranged at intervals; preparing metal grid lines in the grooves; and removing the remaining photosensitive material after development and the leveling layer and the seed layer below the remaining photosensitive material. According to the embodiment, the smooth flat layer is prepared on the seed layer of the silicon substrate textured surface, so that the problem that residual glue is generated due to the fact that the seed layer with a pyramid structure is directly coated with a photosensitive material is avoided, and the bottom morphology of the metal grid line is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cells, and in particular to a method for preparing a solar cell and a solar cell. Background Art

[0002] In the current process of electroplating metal grid lines for solar cells, it is necessary to coat a layer of photosensitive material on a silicon substrate on which a seed layer has been prepared, form grooves for the metal grid lines using a photolithography process based on the photosensitive material, and then prepare the metal grid lines in the grooves. However, the velvet structure on the surface of the solar cell will cause the photosensitive material to remain, and the residual photosensitive material will cause the bottom of the subsequently prepared metal grid lines to have a poor morphology and be easily broken, thereby affecting the tension of the grid lines. Therefore, there is an urgent need for a method for preparing metal grid lines that is not prone to photosensitive material residue. Summary of the invention

[0003] In view of this, an embodiment of the present invention provides a method for preparing a solar cell and a solar cell. By preparing a smooth and flat layer on the seed layer of the velvet surface of a silicon substrate, the problem of residual glue caused by directly coating a photosensitive material on the seed layer with a pyramid structure is avoided, and the bottom morphology of the metal grid line can be improved.

[0004] To achieve the above object, according to one aspect of an embodiment of the present invention, a method for preparing a solar cell is provided, comprising:

[0005] Step S1, sequentially forming a functional layer and a seed layer on the suede surface of a silicon substrate;

[0006] Step S2, preparing a flattening layer on the seed layer;

[0007] Step S3, coating a photosensitive material on the planar layer, and performing local exposure and development to form grooves arranged at intervals;

[0008] Step S4, preparing metal gate lines in the grooves;

[0009] Step S5, removing the remaining photosensitive material after development and the planarization layer and the seed layer below the remaining photosensitive material.

[0010] To achieve the above object, according to another aspect of an embodiment of the present invention, there is provided a solar cell, which is prepared by the above-mentioned method for preparing a solar cell, comprising:

[0011] A silicon substrate including a suede surface;

[0012] A functional layer disposed on the suede surface of the silicon substrate;

[0013] A seed layer arranged at intervals on the functional layer;

[0014] a planarization layer stacked on the seed layer; and

[0015] The metal grid lines are arranged on the planarization layer.

[0016] An embodiment of the above invention has the following advantages or beneficial effects: by preparing a smooth and flat layer on the seed layer of the velvet surface of the silicon substrate, and then coating the photosensitive material and preparing the metal grid line, the difficulty of development is reduced, and the problem of residual glue caused by directly coating the photosensitive material on the seed layer with a pyramid structure is avoided, thereby improving the bottom morphology of the metal grid line.

[0017] By controlling the surface hardness of the flattening layer, the mechanical properties of the solar cell are enhanced, the probability of scratches and fragments of the cell in subsequent processes is reduced, and the yield rate of the solar cell is improved.

[0018] By preparing a smooth and flat layer, the photosensitive material will not have oblique substrate reflection during exposure. Therefore, the bottom width of the groove formed after development is greater than or equal to the groove width, the metal grid line tensile test effect is better, and a finer grid line structure can be achieved.

[0019] The further effects of the above-mentioned non-conventional optional manner will be described below in conjunction with the specific implementation manner. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The accompanying drawings are used to better understand the present invention and do not constitute an improper limitation of the present invention.

[0021] Figure 1 It is a schematic diagram of the structure of a semi-finished solar cell with exposed photosensitive materials in the prior art;

[0022] Figure 2 It is a schematic diagram of the structure of a semi-finished solar cell after the photosensitive material is developed in the prior art;

[0023] Figure 3 It is a schematic diagram of the structure of a semi-finished solar cell after metal grid lines are prepared in the prior art;

[0024] Figure 4 is a schematic flow chart of a method for preparing a solar cell according to an embodiment of the present invention;

[0025] Figure 5 is a schematic diagram of a semi-finished structure of a solar cell with a flattening layer prepared according to an embodiment of the present invention;

[0026] Figure 6 is a schematic diagram of a semi-finished structure of a solar cell coated with a photosensitive material according to an embodiment of the present invention;

[0027] Figure 7is a schematic diagram of the structure of a semi-finished solar cell after development according to an embodiment of the present invention;

[0028] Figure 8 Schematic diagram of the structure of a solar cell according to an embodiment of the present invention.

[0029] Reference numerals:

[0030] 10-silicon substrate; 20-functional layer; 30-seed layer; 40-photosensitive material; 41-remaining photosensitive material; 42-residual glue; 50-groove; 60-metal grid line; 70-planarization layer. DETAILED DESCRIPTION

[0031] In the prior art, during the electroplating process of preparing the metal gate line 60, the photosensitive material 40 is directly coated on the silicon substrate 10 on which the functional layer 20 and the seed layer 30 are prepared, and a groove 50 is formed based on the photosensitive material 40, so as to facilitate the subsequent preparation of the metal gate line 60 in the groove 50. However, since the surface of the silicon substrate 10 is a velvet surface, the velvet surface presents a pyramid structure. During the exposure and development process, for example, Figure 1 As shown, the photosensitive material 40 is first partially exposed. Since the bottom of the photosensitive material 40 is a pyramid structure and is not smooth, the light irradiated to the pyramid structure will be reflected obliquely from the base, such as Figure 2 As shown, the reflected light causes the lower portion of the photosensitive material 40 to undergo polymerization reaction and solidify first, so that the bottom width of the remaining photosensitive material 41 is greater than the top width, as shown in FIG. Figure 2 As shown, the bottom width of the groove 50 after development is smaller than the groove opening width, and there is a relatively narrow gap at the bottom of adjacent pyramids in the pyramid structure, which makes it difficult to remove the residual photosensitive material 40 in the bottom of the gap, so that there is still residual glue 42 (residual photosensitive material) in the pyramid structure at the bottom of the groove.

[0032] like Figure 3 As shown, the metal grid line 60 with a width of the upper bottom greater than the width of the lower bottom is finally obtained, and there is residual glue 42 at the part where the lower bottom of the metal grid line 60 is connected to the seed layer 30, resulting in the problem of poor morphology at the bottom of the metal grid line 60 and easy grid breakage, which affects the tension of the metal grid line 60, causing the surface of the solar cell to be easily scratched, reducing the yield rate and mechanical properties of the solar cell. The insufficient contact between the seed layer 30 and the metal grid line 60 further increases the contact resistance, resulting in a decrease in the fill factor of the solar cell, affecting the photoelectric conversion efficiency of the solar cell.

[0033] In order to solve the above problems existing in the prior art, an embodiment of the present invention provides a novel method for preparing a solar cell and a solar cell obtained based on the preparation method.

[0034] The following is a description of a method for preparing a solar cell provided by an exemplary embodiment of the present invention and a solar cell obtained based on the preparation method, in conjunction with the accompanying drawings, including various details of the embodiments of the present invention to facilitate understanding, which should be considered as merely exemplary. Therefore, it should be recognized by those skilled in the art that various changes and modifications may be made to the embodiments described herein without departing from the scope and spirit of the present invention. Similarly, for the sake of clarity and conciseness, descriptions of well-known functions and structures are omitted in the following description.

[0035] It should be pointed out that the embodiments of the present invention and the technical features therein may be combined with each other without conflict.

[0036] Figure 4 FIG. 1 is a schematic diagram of the main steps of the method for preparing a solar cell according to an embodiment of the present invention. Figure 4 As shown, the method for preparing a solar cell according to an embodiment of the present invention mainly includes the following steps S1 to S5:

[0037] Step S1 : sequentially forming a functional layer 20 and a seed layer 30 on the textured surface of a silicon substrate 10 .

[0038] The silicon substrate 10 may be a single-sided velvet surface or a double-sided velvet surface. When the silicon substrate 10 is a single-sided velvet surface, the flattening layer 70 may be prepared only on the seed layer 30 on one side of the velvet surface; when the silicon substrate 10 is a double-sided velvet surface, the flattening layer 70 may be prepared on the seed layer 30 on both sides.

[0039] The functional layer 20 is a film layer used for light absorption, charge transfer, passivation and / or anti-reflection, etc. It can be a single film layer or a composite film layer formed by multiple film layers. It can be specifically configured according to actual conditions and needs, and is not limited here.

[0040] The seed layer 30 is a metal film deposited on the surface of the functional layer 20. Since the metal on the surface of the functional layer 20 has poor adhesion, directly coating the photosensitive material 40 on the surface of the functional layer 20 and preparing the metal grid line 60 will lead to problems such as difficulty in preparing the metal grid line 60, easy detachment of the prepared metal grid line 60, and large contact resistance. Therefore, the seed layer 30 is deposited between the metal grid line 60 and the functional layer 20 to improve the contact and adhesion performance of the metal grid line 60. At the same time, in the process of preparing the metal grid line 60, the seed layer 30 can also prevent the metal from diffusing into the functional layer 20 or the silicon substrate 10. Among them, the material of the seed layer 30 includes but is not limited to copper, nickel, titanium, tungsten, copper-nickel alloy, etc. Preferably, the material in which the metal element is consistent with the metal element contained in the metal grid line 60 can be selected for preparing the seed layer 30. As an example, when the metal grid line 60 is a copper grid line, the material for preparing the seed layer 30 can be selected from copper or copper-nickel alloy.

[0041] The seed layer 30 may be prepared by physical vapor deposition (PVD), chemical vapor deposition (CVD), printing or spraying.

[0042] Step S2 : preparing a planarization layer 70 on the seed layer 30 .

[0043] like Figure 5 As shown, a planarization layer 70 with a thickness of 1-5 μm is formed on the surface of the seed layer 30 away from the silicon substrate 10. As an example, the thickness of the planarization layer 70 may be 1 μm, 2 μm, 4 μm or 5 μm.

[0044] The thickness of the planarization layer 70 should be sufficient to completely cover the pyramid structure, so that the planarization layer 70 is away from the surface of the silicon substrate 10 and presents a planar structure, thereby avoiding the residue of the photosensitive material 40 .

[0045] In addition, the material used to form the planarization layer 70 contains metal elements, and the metal elements therein should be consistent with the metal elements contained in the metal grid lines 60, so that the planarization layer 70 and the metal grid lines 60 have similar conductive properties to avoid increasing the contact resistance of the metal grid lines 60. The metal grid lines 60 can be composed of a single metal element or alloy, or a stack of multiple metal elements or alloys. As an example, when the metal grid lines 60 are copper grid lines, the material used to form the planarization layer 70 can be copper or an alloy containing copper elements. The preparation method of the planarization layer 70 can include one or more of sputtering, evaporation, and electrochemical deposition, but is not limited thereto.

[0046] Step S3: coating the photosensitive material 40 on the planarization layer 70 , and performing local exposure and development to form grooves 50 arranged at intervals.

[0047] like Figure 6 As shown, a photosensitive material 40 is coated on the surface of the planarization layer 70 away from the silicon substrate 10 and dried, and the photosensitive material 40 is partially exposed and developed based on the predetermined shape of the metal grid line 60 to obtain a Figure 7 The semi-finished solar cell product shown is not prone to residual adhesive 42 due to the presence of the planarization layer 70 .

[0048] The thickness of the coated photosensitive material 40 may be 10 μm-20 μm. As an example, the thickness of the photosensitive material 40 may be 10 μm, 15 μm or 20 μm.

[0049] Further, the parameters of the development may include: the developer used may be a Na2CO3 solution with a concentration of 0.8-1.3wt%, the development temperature is 30±2°C, the spray pressure is 1.5-2kg / cm2 , developing point 40%-50%. As an example, the developer can be a Na2CO3 solution with a concentration of 0.8wt%, 1.0wt% or 1.3wt%, etc., the developing temperature can be 28℃, 30℃ or 32℃, etc., and the spray pressure can be 1.5kg / cm 2 , 1.7kg / cm 2 , 1.9kg / cm 2 or 2.0kg / cm 2 The development point can be 40%, 42%, 45% or 50%, etc.

[0050] The conditions for drying the photosensitive material 40 may include: a temperature of 80 to 90°C and a time of 5 to 10 minutes. By controlling the conditions for drying the photosensitive material 40, the photosensitive material 40 can be dried more thoroughly to avoid affecting the subsequent preparation process. As an example, the drying temperature may be 80°C, 83°C, 85°C, 88°C or 90°C, and the drying time may be 5 minutes, 7 minutes, 8 minutes or 10 minutes.

[0051] Step S4 , preparing a metal gate line 60 in the groove 50 .

[0052] The metal gate line 60 may include a copper gate line, but is not limited thereto.

[0053] Furthermore, after the metal gate line 60 is prepared, a protective layer (not shown) may be prepared on the metal gate line 60 to protect the metal gate line 60 and to serve as a soldering layer for the metal gate line 60. The material of the protective layer may be metal tin.

[0054] Step S5 , removing the remaining photosensitive material 41 after development and the planarization layer 70 and the seed layer 30 located below the remaining photosensitive material 41 .

[0055] The remaining photosensitive material 41 is removed, and the planarization layer 70 and the seed layer 30 below the photosensitive material 40 are removed by chemical etching to obtain Figure 8 The solar cell shown.

[0056] Further, the conditions for removing the planarization layer 70 and the seed layer 30 below the photosensitive material 40 by chemical etching may include: the etchant includes sulfuric acid with a volume fraction of 1-20% (v / v), hydrogen peroxide with a volume fraction of 1-12% (v / v), and a stabilizer with a volume fraction of 1-12% (v / v), the etching temperature is 20-40°C, the etching time is 1-5min, and the spray pressure is 0.5-3kg / cm 3As an example, the volume fraction of sulfuric acid in the etchant can be 1% (v / v), 5% (v / v), 10% (v / v) or 20% (v / v), etc., the volume fraction of hydrogen peroxide in the etchant can be 1% (v / v), 4% (v / v), 6% (v / v) or 12% (v / v), etc., the volume fraction of the stabilizer in the etchant can be 1% (v / v), 4% (v / v), 6% (v / v) or 12% (v / v), etc., the etching temperature can be 20°C, 25°C, 30°C, 35°C or 40°C, etc., the etching time can be 1 min, 2.5 min, 4 min or 5 min, etc., and the spray pressure can be 0.5 kg / cm 3 , 1.0kg / cm 3 , 2.0kg / cm 3 or 3.0kg / cm 3 wait.

[0057] In an optional embodiment, the surface roughness of the planarization layer 70 should be less than the surface roughness of the velvet surface. Preferably, the surface roughness of the planarization layer 70 is less than 0.123 μm. The surface roughness of the planarization layer 70 refers to the roughness of the surface of the planarization layer 70 away from the silicon substrate 10. By controlling the surface roughness of the planarization layer 70, the planarization layer 70 has a smoother surface than the velvet surface to avoid the appearance of residual glue 42.

[0058] In an optional embodiment, the surface hardness of the planarization layer 70 should be greater than the surface hardness of the metal grid line 60. Preferably, the surface hardness of the planarization layer 70 is greater than 150HV. By controlling the surface hardness of the planarization layer 70, the planarization layer 70 has a stronger ability to resist deformation and damage than the metal grid line 60, further reducing the scratch and fragmentation problems of the solar cell and improving the yield rate of the solar cell.

[0059] In an optional embodiment, the surface roughness of the planarization layer 70 can be controlled within the above range by controlling the process parameters of step S2. As an example, when the planarization layer 70 is made of metallic copper and is prepared by an electrochemical deposition method, the process parameters of the electrochemical deposition may include: the electroplating solution includes copper sulfate pentahydrate (CuSO4·5H2O) with a mass concentration of 100-250 g / L, sulfuric acid with a mass concentration of 50-250 g / L, chloride ions with a mass concentration of 30-90 ppm and an appropriate amount of leveling agent, the electroplating temperature is 20-40°C, the current density is 1-20 ASD, the electroplating time is 1-5 min, the pulse frequency is 20-50 Hz, the forward time is 10-200 ms, the reverse pulse time is 1-10 ms, and the forward and reverse current ratio is (1:1)-(1:2). As an example, the mass concentration of copper sulfate pentahydrate in the electroplating solution can be 100 g / L, 150 g / L, 200 g / L or 250 g / L, etc., the mass concentration of sulfuric acid in the electroplating solution can be 50 g / L, 100 g / L, 150 g / L or 250 g / L, the mass concentration of chloride ions in the electroplating solution can be 30 ppm, 50 ppm, 60 ppm or 90 ppm, etc., the electroplating temperature can be 20°C, 25°C, 30°C or 40°C, etc., and the current density It can be 1ASD, 5ASD, 10ASD, 15ASD or 20ASD, etc., the electroplating time can be 1min, 3min or 5min, the pulse frequency can be 20Hz, 30Hz, 40Hz or 50Hz, etc., the forward time can be 10ms, 50ms, 100ms, 150ms or 200ms, etc., the reverse pulse time can be 1ms, 5ms or 10ms, etc., the forward and reverse current ratio can be 1:1, 2:3 or 1:2, etc.

[0060] In an optional embodiment, after step S2 and before step S3, the method may further include: using an etching method to smooth the planarization layer 70. That is, using an etchant to smooth the planarization layer 70 to make the surface of the planarization layer 70 smoother and with lower surface roughness.

[0061] By preparing the planarization layer 70 and controlling the surface roughness of the planarization layer 70 within the above range, the light irradiated to the planarization layer 70 will not be reflected obliquely by the substrate, thus avoiding the oblique substrate reflection that causes the bottom of the photosensitive material 40 to be preferentially solidified, so that the width of the lower bottom surface of the remaining photosensitive material 41 after development is greater than the width of the upper bottom surface, and the light irradiated into the photosensitive material 40 may gradually decrease with the increase of the incident depth, so that the polymerization reaction at the bottom of the photosensitive material 40 slows down, the width of the lower bottom surface of the remaining photosensitive material 41 is less than or equal to the width of the upper bottom surface, and the width of the bottom of the groove 50 between adjacent remaining photosensitive materials 41 is greater than or equal to the width of the notch. It should be noted that in the embodiment of the present invention, the lower bottom surface of the remaining photosensitive material 41 refers to the side that is in direct contact with the planarization layer 70; the upper bottom surface of the remaining photosensitive material 41 refers to the side that is away from the planarization layer 70.

[0062] In an optional embodiment, the metal gate line 60 can be prepared by an electrochemical deposition method, and the process parameters may include: the electroplating solution includes copper sulfate pentahydrate (CuSO4·5H2O) with a mass concentration of 100-250g / L, sulfuric acid with a mass concentration of 50-250g / L, chloride ions with a mass concentration of 30-90ppm and an appropriate amount of leveling agent, the electroplating temperature is 20-40°C, the current density is 1-20ASD, the electroplating time is 5-10min, the pulse frequency is 20-50Hz, the forward time is 10-200ms, the reverse pulse time is 1-10ms, and the forward and reverse current ratio is (1:1)-(1:2). As an example, the mass concentration of copper sulfate pentahydrate in the electroplating solution can be 100 g / L, 150 g / L, 200 g / L or 250 g / L, etc., the mass concentration of sulfuric acid in the electroplating solution can be 50 g / L, 100 g / L, 150 g / L or 250 g / L, the mass concentration of chloride ions in the electroplating solution can be 30 ppm, 50 ppm, 60 ppm or 90 ppm, etc., the electroplating temperature can be 20°C, 25°C, 30°C or 40°C, etc., and the current density can be The pulse frequency can be 20Hz, 30Hz, 40Hz or 50Hz, the forward time can be 10ms, 50ms, 100ms, 150ms or 200ms, the reverse pulse time can be 1ms, 5ms or 10ms, and the forward and reverse current ratio can be 1:1, 2:3 or 1:2.

[0063] The protective layer can be prepared by electrochemical deposition. The process parameters may include: the electroplating solution includes 50-200 g / L methanesulfonic acid, 20-100 g / L Sn 2+, 50-250mL / L of brightener, 5-20mL / L of dispersant and 5-15mL / L of stabilizer, electroplating temperature 15-50℃, current density 1-15ASD, electroplating time 1-3min. As an example, the mass concentration of methanesulfonic acid in the electroplating solution can be 50g / L, 100g / L, 150g / L or 200g / L, etc., and the mass concentration of Sn in the electroplating solution can be 100g / L, 150g / L or 200g / L, etc. 2+ The mass concentration of can be 20g / L, 40g / L, 60g / L or 100g / L, etc., the concentration of brightener in the plating solution can be 50mL / L, 100mL / L, 180mL / L or 250mL / L, etc., the concentration of dispersant in the plating solution can be 5mL / L, 10mL / L or 20mL / L, etc., the concentration of stabilizer in the plating solution can be 5mL / L, 10mL / L or 15mL / L, etc., the electroplating temperature can be 15℃, 30℃ or 50℃, etc., the current density can be 1ASD, 5ASD, 10ASD or 15ASD, etc., the electroplating time can be 1min, 2min or 3min, etc.

[0064] It should be noted that Figure 5-Figure 8 The structure of only one main surface of a semi-finished solar cell product is shown as an example; Figure 3 and Figure 8 The exemplary embodiment only shows a complete metal grid line 60 structure in a semi-finished solar cell product. It is understandable that the embodiment of the present invention does not limit the number of metal grid lines 60, and those skilled in the art can prepare an appropriate number of metal grid lines 60 according to actual conditions.

[0065] The method for preparing a solar cell in an embodiment of the present invention reduces the difficulty of development by preparing a smooth and flat layer on the seed layer of the velvet surface of a silicon substrate, and then coating a photosensitive material and preparing a metal grid line, thereby avoiding the problem of residual glue caused by directly coating a photosensitive material on a seed layer with a pyramid structure, and improving the bottom morphology of the metal grid line.

[0066] By controlling the surface hardness of the flattening layer, the mechanical properties of the solar cell are enhanced, the probability of scratches and fragments of the cell in subsequent processes is reduced, and the yield rate of the solar cell is improved.

[0067] By preparing a smooth and flat layer, the photosensitive material will not have oblique substrate reflection during exposure. Therefore, the bottom width of the groove formed after development is greater than or equal to the groove width, the metal grid line tensile test effect is better, and a finer grid line structure can be achieved.

[0068] like Figure 8 As shown, an embodiment of the present invention provides a solar cell prepared by any of the above-mentioned methods for preparing a solar cell, comprising:

[0069] A silicon substrate 10 including a velvet surface;

[0070] A functional layer 20 disposed on the suede surface of the silicon substrate 10;

[0071] A seed layer 30 arranged at intervals on the functional layer 20;

[0072] a planarization layer 70 stacked on the seed layer 30; and

[0073] The metal gate line 60 is disposed on the planarization layer 70 .

[0074] In an optional embodiment of the present invention, the lower base width of the metal gate line 60 is greater than or equal to the upper base width.

[0075] Specifically, by setting a planarization layer 70 and controlling the surface roughness of the planarization layer 70 within the above-mentioned range, the light irradiated to the planarization layer 70 will not have an oblique substrate reflection, thereby avoiding the oblique substrate reflection causing the bottom of the photosensitive material 40 to be preferentially solidified so that the lower bottom surface width of the remaining photosensitive material 41 after development is greater than the upper bottom surface width. The light irradiated into the photosensitive material 40 may gradually decrease in intensity with increasing incident depth, so that the polymerization reaction at the bottom of the photosensitive material 40 slows down, the lower bottom surface width of the remaining photosensitive material 41 is less than or equal to the upper bottom surface width, and the bottom width of the groove 50 between adjacent remaining photosensitive materials 41 is greater than or equal to the groove width.

[0076] In an optional embodiment of the present invention, the thickness of the planarization layer 70 is 1-5 μm. The thickness of the planarization layer 70 should be sufficient to completely cover the pyramid structure, so that the planarization layer 70 is far away from the surface of the silicon substrate 10 and presents a planar structure, thereby avoiding the residue of the photosensitive material 40.

[0077] In an optional embodiment of the present invention, the material used to form the planarization layer 70 contains metal elements, wherein the metal elements should be consistent with the metal elements contained in the metal gate line 60, so that the planarization layer 70 and the metal gate line 60 have similar conductive properties to avoid increasing the contact resistance of the metal gate line 60.

[0078] In an optional embodiment of the present invention, the surface roughness of the planarization layer 70 should be less than the surface roughness of the suede surface. Preferably, the surface roughness of the planarization layer 70 is less than 0.123 μm.

[0079] In an optional embodiment of the present invention, the surface hardness of the planarization layer 70 should be greater than the surface hardness of the metal grid line 60. Preferably, the surface hardness of the planarization layer 70 is greater than 150 HV.

[0080] The solar cell of the embodiment of the present invention avoids the problem of residual glue caused by directly coating photosensitive material on the seed layer with a pyramid structure by providing a smooth flat layer between the seed layer on the velvet surface of the silicon substrate and the metal grid line, reduces the difficulty of development, and improves the bottom morphology of the metal grid line.

[0081] By controlling the surface hardness of the flattening layer, the mechanical properties of the solar cell are enhanced, the probability of scratches and fragments of the cell in subsequent processes is reduced, and the yield rate of the solar cell is improved.

[0082] By controlling the surface roughness of the planarization layer, the photosensitive material will not have oblique base reflection during exposure. Therefore, the bottom width of the groove formed after development is greater than or equal to the groove width, the metal grid line tensile test effect is better, and a finer grid line structure can be achieved.

[0083] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions may occur depending on design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a solar cell, characterized in that: include: Step S1, sequentially forming a functional layer (20) and a seed layer (30) on the suede surface of a silicon substrate (10); Step S2, preparing a planarization layer (70) on the seed layer (30); Step S3, coating a photosensitive material (40) on the planarization layer (70), and performing local exposure and development to form grooves (50) arranged at intervals; Step S4, preparing a metal gate line (60) in the groove (50); Step S5, removing the remaining photosensitive material (40) after development and the planarization layer (70) and the seed layer (30) located below the remaining photosensitive material (41).

2. The method for preparing a solar cell according to claim 1, characterized in that: The step S2 comprises: The planarization layer (70) is formed to have a thickness of 1-5 μm.

3. The method for preparing a solar cell according to claim 1, characterized in that: The material used to form the planarization layer (70) contains a metal element, wherein the metal element is consistent with the metal element contained in the metal grid line (60).

4. The method for preparing a solar cell according to claim 1, characterized in that: The surface roughness of the flattening layer (70) is smaller than the surface roughness of the suede surface; Preferably, the surface roughness of the planarization layer (70) is less than 0.123 μm.

5. The method for preparing a solar cell according to claim 1, characterized in that: The surface hardness of the planarization layer (70) is greater than the surface hardness of the metal grid line (60); Preferably, the surface hardness of the planarization layer (70) is greater than 150 HV.

6. The method for preparing a solar cell according to claim 1, characterized in that: The groove bottom width of the groove (50) is greater than or equal to the groove opening width.

7. The method for preparing a solar cell according to claim 1, characterized in that: The planarization layer (70) is prepared by sputtering, evaporation or deposition.

8. The method for preparing a solar cell according to claim 1, characterized in that: After step S2 and before step S3, the method further includes: The planarization layer (70) is smoothed by etching.

9. A solar cell, characterized in that: The solar cell is prepared by the method for preparing the solar cell according to any one of claims 1 to 8, comprising: A silicon substrate (10) comprising a velvet surface; A functional layer (20) disposed on the suede surface of the silicon substrate (10); A seed layer (30) arranged at intervals on the functional layer (20); a planarization layer (70) stacked on the seed layer (30); and A metal grid line (60) is arranged on the planarization layer (70).

10. The solar cell according to claim 9, characterized in that: The lower base width of the metal grid line (60) is greater than or equal to the upper base width.

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