CN117423773A - Method for improving chemical tinning drain electrode layer of solar cell and application thereof - Google Patents
Method for improving chemical tinning drain electrode layer of solar cell and application thereof Download PDFInfo
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- CN117423773A CN117423773A CN202311148263.2A CN202311148263A CN117423773A CN 117423773 A CN117423773 A CN 117423773A CN 202311148263 A CN202311148263 A CN 202311148263A CN 117423773 A CN117423773 A CN 117423773A
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- 238000000034 method Methods 0.000 title claims abstract description 71
- 239000000126 substance Substances 0.000 title claims abstract description 22
- 239000010410 layer Substances 0.000 claims abstract description 238
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 claims abstract description 108
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims abstract description 66
- 229910052802 copper Inorganic materials 0.000 claims abstract description 66
- 239000010949 copper Substances 0.000 claims abstract description 66
- 238000005530 etching Methods 0.000 claims abstract description 30
- 238000005406 washing Methods 0.000 claims abstract description 27
- 239000011241 protective layer Substances 0.000 claims abstract description 25
- 239000007788 liquid Substances 0.000 claims abstract description 23
- 238000007747 plating Methods 0.000 claims abstract description 23
- 238000002844 melting Methods 0.000 claims abstract description 20
- 230000008018 melting Effects 0.000 claims abstract description 20
- 239000002184 metal Substances 0.000 claims description 45
- 229910052751 metal Inorganic materials 0.000 claims description 45
- 238000002161 passivation Methods 0.000 claims description 33
- 239000004065 semiconductor Substances 0.000 claims description 20
- 239000000758 substrate Substances 0.000 claims description 19
- 238000004519 manufacturing process Methods 0.000 claims description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 abstract description 20
- 238000003466 welding Methods 0.000 abstract description 12
- 238000005286 illumination Methods 0.000 abstract description 9
- 238000013508 migration Methods 0.000 abstract description 9
- 230000005012 migration Effects 0.000 abstract description 9
- JPVYNHNXODAKFH-UHFFFAOYSA-N Cu2+ Chemical compound [Cu+2] JPVYNHNXODAKFH-UHFFFAOYSA-N 0.000 abstract description 8
- 229910001431 copper ion Inorganic materials 0.000 abstract description 8
- 210000004027 cell Anatomy 0.000 description 37
- 238000009713 electroplating Methods 0.000 description 16
- 239000000243 solution Substances 0.000 description 15
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 12
- 229920002120 photoresistant polymer Polymers 0.000 description 10
- 229910021417 amorphous silicon Inorganic materials 0.000 description 8
- AFVFQIVMOAPDHO-UHFFFAOYSA-N Methanesulfonic acid Chemical compound CS(O)(=O)=O AFVFQIVMOAPDHO-UHFFFAOYSA-N 0.000 description 6
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 6
- 229910052710 silicon Inorganic materials 0.000 description 6
- 239000010703 silicon Substances 0.000 description 6
- 230000000052 comparative effect Effects 0.000 description 5
- 230000007797 corrosion Effects 0.000 description 5
- 238000005260 corrosion Methods 0.000 description 5
- 230000000694 effects Effects 0.000 description 5
- 238000005240 physical vapour deposition Methods 0.000 description 5
- 238000010586 diagram Methods 0.000 description 4
- 238000005516 engineering process Methods 0.000 description 4
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 description 3
- 230000007547 defect Effects 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 238000000623 plasma-assisted chemical vapour deposition Methods 0.000 description 3
- 229910052709 silver Inorganic materials 0.000 description 3
- 239000004332 silver Substances 0.000 description 3
- 239000000654 additive Substances 0.000 description 2
- 210000003850 cellular structure Anatomy 0.000 description 2
- 239000003153 chemical reaction reagent Substances 0.000 description 2
- 239000011248 coating agent Substances 0.000 description 2
- 238000000576 coating method Methods 0.000 description 2
- 239000003292 glue Substances 0.000 description 2
- 238000002347 injection Methods 0.000 description 2
- 239000007924 injection Substances 0.000 description 2
- 229940098779 methanesulfonic acid Drugs 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 238000004544 sputter deposition Methods 0.000 description 2
- 238000012546 transfer Methods 0.000 description 2
- 230000002159 abnormal effect Effects 0.000 description 1
- 238000010420 art technique Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 239000008139 complexing agent Substances 0.000 description 1
- 238000000151 deposition Methods 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 230000005611 electricity Effects 0.000 description 1
- 239000003792 electrolyte Substances 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- AMGQUBHHOARCQH-UHFFFAOYSA-N indium;oxotin Chemical compound [In].[Sn]=O AMGQUBHHOARCQH-UHFFFAOYSA-N 0.000 description 1
- 230000010354 integration Effects 0.000 description 1
- 238000007648 laser printing Methods 0.000 description 1
- 238000010309 melting process Methods 0.000 description 1
- 239000012528 membrane Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229910021421 monocrystalline silicon Inorganic materials 0.000 description 1
- 230000007935 neutral effect Effects 0.000 description 1
- 238000007639 printing Methods 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 230000001681 protective effect Effects 0.000 description 1
- 238000007650 screen-printing Methods 0.000 description 1
- 239000011265 semifinished product Substances 0.000 description 1
- 238000002791 soaking Methods 0.000 description 1
- 239000003381 stabilizer Substances 0.000 description 1
- 239000002344 surface layer Substances 0.000 description 1
- 239000004094 surface-active agent Substances 0.000 description 1
Classifications
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/18—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/02—Details
- H01L31/0224—Electrodes
- H01L31/022408—Electrodes for devices characterised by at least one potential jump barrier or surface barrier
- H01L31/022425—Electrodes for devices characterised by at least one potential jump barrier or surface barrier for solar cells
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- Engineering & Computer Science (AREA)
- Computer Hardware Design (AREA)
- Physics & Mathematics (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- Electromagnetism (AREA)
- General Physics & Mathematics (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Power Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Life Sciences & Earth Sciences (AREA)
- Sustainable Development (AREA)
- Sustainable Energy (AREA)
- Photovoltaic Devices (AREA)
Abstract
The invention provides a method for improving an electroless tin plating drain electrode layer of a solar cell and application thereof, wherein the method comprises the following steps: removing the film and etching back the battery piece with the electrode layer; under the condition of a first darkroom, placing the battery piece subjected to film removal and back etching in tin melting liquid for chemical tin plating so as to form a tin protection layer on the surface of the electrode layer; and (3) washing the battery piece with the tin protective layer under the condition of a second darkroom. According to the invention, the introduction of illumination is avoided from the aspects of a chemical tinning process and a water washing process, the surface of the battery piece after water washing is free of tin liquid residue, and the condition that copper is exposed due to the fact that the battery piece absorbs light to generate electric potential is avoided, so that the copper leakage probability of the battery piece is obviously reduced, the copper leakage probability of 60% in the prior art is reduced to below 1%, and the appearance yield of the battery piece is improved; and the weldability of the battery piece grid line is improved, and the welding yield of the battery assembly and the reliability of copper ion migration type LID failure are improved.
Description
Technical Field
The invention relates to the technical field of solar cells, in particular to a method for improving an electroless tin plating drain electrode layer of a solar cell and application thereof.
Background
The solar cell adopts a technical route that silver paste is printed after coating, and silver grid lines are formed on the surface of an ITO conductive film after printing and curing. There are also prior art techniques in which PVD sputtering is performed on an ITO (TCO) conductive film to deposit a seed layer of copper for conducting electricity, and then pattern transfer is performed on the conductive layer to plate a gate line. And then plating a layer of protective tin on the surface of the electroplated copper grid line by using an electroless tin plating method, and replacing a scheme of screen printing the silver grid line by using electroplated copper and electroless tin plating grid lines. The technology is an organic integration of solar cell fabrication and metal plating technology. In the copper interconnection cell technology, a copper electrode grid line is realized by performing pattern transfer, electroplating, film removal and tin melting on a photoresist. However, in the process of fusing the two technologies, the defect that copper cannot be wrapped (namely copper leakage) after tin melting occurs, so that the appearance yield and the efficiency of a copper electroplating technical route are severely limited.
Disclosure of Invention
The present invention aims to solve at least one of the technical problems in the related art to some extent. The object of the invention is to provide a method for improving an electroless tin-plated drain electrode layer of a solar cell and the use thereof. According to the invention, the introduction of illumination is avoided from the aspects of a chemical tinning process and a water washing process, the surface of the battery piece after water washing is free of tin liquid residue, and the condition that copper is exposed due to the fact that the battery piece absorbs light to generate electric potential is avoided, so that the copper leakage probability of the battery piece is obviously reduced, the copper leakage probability of 60% in the prior art is reduced to below 1%, and the appearance yield of the battery piece is improved; and the weldability of the battery piece grid line is improved, and the welding yield of the battery assembly and the reliability of copper ion migration type LID failure are improved.
In one aspect of the invention, a method of improving an electroless tin plated drain electrode layer of a solar cell is provided. According to an embodiment of the invention, the method comprises:
removing the film and etching back the battery piece with the electrode layer;
under the condition of a first darkroom, placing the battery piece subjected to film removal and back etching in tin melting liquid for chemical tin plating so as to form a tin protection layer on the surface of the electrode layer;
and (3) washing the battery piece with the tin protective layer under the condition of a second darkroom.
According to the method for improving the chemical tinning drain electrode layer of the solar cell, the introduction of illumination is avoided from the aspects of the chemical tinning process and the water washing process, the surface of the battery piece after water washing is free of tin liquid residues, the condition that the battery piece absorbs light to generate electric potential to cause copper exposure is avoided, so that the copper leakage probability of the battery piece is obviously reduced, the copper leakage probability of 60% in the prior art is reduced to below 1%, and the appearance yield of the battery piece is improved; and the weldability of the battery piece grid line is improved, and the welding yield of the battery assembly and the reliability of copper ion migration type LID failure are improved.
In addition, the method of improving an electroless tin plating drain electrode layer of a solar cell according to the above-described embodiment of the present invention may further have the following additional technical features:
in some embodiments of the invention, the darkness of the first darkroom is 50% or more.
In some embodiments of the invention, the darkness of the second darkroom is greater than or equal to 50%.
In some embodiments of the present invention, the battery sheet with the tin protective layer formed thereon is water washed to ph=7.
In some embodiments of the invention, the time for transferring the battery sheet formed with the tin protective layer from the tin bath to the rinse bath is less than or equal to 5s.
In some embodiments of the invention, the electrode layer has a thickness of 8-10 μm and the tin protective layer has a thickness of 2-3 μm.
In some embodiments of the invention, the electrode layer is a copper electrode layer.
In yet another aspect of the invention, a method of making a solar cell is provided. According to the embodiment of the invention, the tin protective layer of the solar cell is prepared by adopting the method described in the embodiment. Therefore, the method improves the appearance yield of the solar cell, and improves the weldability of the grid line of the solar cell, so that the welding yield of a cell assembly and the reliability of copper ion migration type LID failure are improved.
In addition, the method according to the above embodiment of the present invention may further have the following technical solutions:
in some embodiments of the invention, the method comprises:
providing a semiconductor substrate;
forming a first passivation layer on one side of the semiconductor substrate, and forming a second passivation layer on one side of the semiconductor substrate away from the first passivation layer;
forming an N-type doped layer on one side of the first passivation layer far away from the semiconductor substrate, and forming a P-type doped layer on one side of the second passivation layer far away from the semiconductor substrate;
forming a first conductive layer on one side of the N-type doped layer far away from the first passivation layer, and forming a second conductive layer on one side of the P-type doped layer far away from the second passivation layer;
forming a first metal seed layer on one side of the first conductive layer far away from the N-type doped layer, and forming a second metal seed layer on one side of the second conductive layer far away from the P-type doped layer;
forming a first electrode layer on one side of the first metal seed layer far away from the first conductive layer, and forming a second electrode layer on one side of the second metal seed layer far away from the second conductive layer;
forming a first tin protection layer on a side of the first electrode layer away from the first metal seed layer by the method described in the above embodiment; and/or forming a second tin protection layer on a side of the second electrode layer away from the second metal seed layer by the method described in the above embodiment.
In a third aspect of the invention, the invention proposes a solar cell. According to an embodiment of the invention, the solar cell is prepared by the method described in the above embodiment. Therefore, the appearance yield of the solar cell is improved, and the weldability of the grid line of the solar cell is improved, so that the welding yield of a cell component and the reliability of copper ion migration type LID failure are improved.
Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.
Drawings
The foregoing and/or additional aspects and advantages of the invention will become apparent and may be better understood from the following description of embodiments taken in conjunction with the accompanying drawings in which:
FIG. 1 is a schematic flow chart of a method for improving an electroless tin plating drain electrode layer of a solar cell according to an embodiment of the invention;
FIG. 2 is a schematic diagram of a process flow of a copper interconnect wafer in the related art;
FIG. 3 is a schematic diagram of copper leakage of a copper interconnect die in the related art;
FIG. 4 is a schematic view of the photovoltaic effect of a solar cell;
FIG. 5 is a schematic diagram of a grid line light-receiving copper leakage of a copper interconnect die in the related art;
fig. 6 is a schematic structural diagram of a solar cell according to an embodiment of the invention.
Reference numerals:
11-a semiconductor substrate; 12-a first passivation layer; 13-a second passivation layer; a 14-N type doped layer; a 15-P type doped layer; 16-a first conductive layer; 17-a second conductive layer; 18-a first metal seed layer; 19-a second metal seed layer; 20-a first electrode layer; 21-a second electrode layer; 22-a first tin protective layer; 23-a second tin protective layer.
Detailed Description
Embodiments of the present invention are described in detail below. The following examples are illustrative only and are not to be construed as limiting the invention. The examples are not to be construed as limiting the specific techniques or conditions described in the literature in this field or as per the specifications of the product. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.
In one aspect of the present invention, referring to fig. 1, a method of improving an electroless tin plated drain electrode layer of a solar cell is presented, comprising: s710: removing the film and etching back the battery piece with the electrode layer; s720: under the condition of a first darkroom, placing the battery piece subjected to film removal and back etching in tin melting liquid for chemical tin plating so as to form a tin protection layer on the surface of the electrode layer; s730: and (3) washing the battery piece with the tin protective layer under the condition of a second darkroom. According to the invention, the introduction of illumination is avoided from the aspects of a chemical tinning process and a water washing process, the surface of the battery piece after water washing is free of tin liquid residue, and the condition that copper is exposed due to the fact that the battery piece absorbs light to generate electric potential is avoided, so that the copper leakage probability of the battery piece is obviously reduced, the copper leakage probability of 60% in the prior art is reduced to below 1%, and the appearance yield of the battery piece is improved; and the weldability of the battery piece grid line is improved, and the welding yield of the battery assembly and the reliability of copper ion migration type LID failure are improved.
The following describes in detail the principle that the method for improving the electrotinning drain electrode layer of the solar cell can realize the beneficial effects:
the processing flow of the copper interconnection battery piece is shown in fig. 2, firstly, the N-type monocrystalline silicon wafer is subjected to texturing cleaning treatment, then, intrinsic amorphous silicon and N-type amorphous silicon films are deposited on the front surface of the silicon wafer, intrinsic amorphous silicon and P-type amorphous silicon films are deposited on the back surface of the silicon wafer, then, a transparent conductive film (TCO conductive layer) is plated on the amorphous silicon, a seed layer PVD CU is plated on the transparent conductive film (a semi-finished product for completing seed layer deposition is called a yellow membrane, the NP surface and the side surface of the battery body are covered with PVD copper in the sputtering process), then, a copper grid line grows in an electroplating solution by utilizing the advantage of good conductive effect of the copper seed layer, and finally, a metal tin layer is chemically plated on the copper grid line to protect the copper grid line and serve as welding metal for component welding. However, after the battery piece is subjected to tin plating, the phenomenon that tin plating fails to completely cover the grid line and the copper grid line is exposed (namely copper leakage) often occurs, for example, the P position in fig. 3 is the copper leakage position, so that the appearance is affected. And the tin layer is used as a welding metal layer, so that poor welding of the component is caused once the defect occurs, and the yield of the component is affected.
The inventors found that the copper leakage occurred at the position contacting with the basket or at the four corners of the battery piece, and studied the whole tin melting process, and found that the battery piece had primary cell corrosion, resulting in removal of chemically plated tin and thus copper exposure, which is a special abnormal defect that only occurs in the stacked slot type tin melting machine for HJT-cell copper interconnection cells. It should be explained that the basket is a device for holding the cell sheets.
Specifically, first, the HJT cell rationale is to utilize the photovoltaic effect of the PN junction of semiconductor materials, as shown in fig. 4, where 100 is N-type silicon (p+), 200 is P-type silicon (N-), and 300 is a bulb. Specifically, under the irradiation of sunlight, the PN junction absorbs photon energy to generate holes and electrons, the holes move towards the P-type amorphous silicon, the electrons move towards the N-type amorphous silicon, and the free charges directionally move and accumulate and generate a certain potential, so that current can be supplied to an external circuit. Since the cell has undergone a stripping and etching process before electroless tin plating, the surface ITO layer is exposed and is provided with copper grid lines, and the cell has the properties of a finished cell, and when irradiated by light, electric potential is generated, so that electron movement of photovoltaic effect is formed. When the basket lifts the battery piece from the tin melting liquid, the tin melting liquid is remained at the contact position of the battery piece and the basket, so that a small primary battery is formed locally on the battery piece, primary battery corrosion occurs, electrons of tin simple substance on the surface layer can be lost and oxidized into the tin melting liquid, and a copper grid line below the tin simple substance is exposed, as shown in fig. 5, wherein 100 is N-type silicon (P+), 200 is P-type silicon (N-), and 400 is tin melting residual liquid. Once the effect occurs, the tin protection layer is lost, the copper grid lines are exposed, the appearance yield is reduced, and the assembly is not welded.
The reason why the stripping and back etching process is provided before the electroless tin plating step in the present invention is that: through the step of film removing and back etching, photoresist between adjacent electroplating electrode layers can be removed, so that the side surfaces of the electroplating electrode layers are exposed; therefore, when the electroless tin plating is performed after the film removal and back etching step, a tin protection layer can be formed on the surface of the electroplating electrode layer far away from the metal seed layer and the side surface of the electroplating electrode layer, so that the electroplating electrode layer can be better protected.
In order to solve the problems, the invention places the process of chemically tinning the battery piece after stripping and back etching under the condition of a darkroom, avoids the introduction of illumination, and reduces the condition that the battery piece absorbs light to generate electric potential in the process of chemically tinning to cause copper exposure. Meanwhile, the battery piece with the tin protective layer is washed under the dark room condition, so that the condition that the battery piece absorbs light to generate electric potential in the washing process to cause copper exposure is reduced. The surface of the battery piece after water washing has no tin liquid residue, and completely isolates the occurrence of corrosion reaction of the primary battery, thereby avoiding the occurrence of copper exposure. Therefore, the invention avoids the introduction of illumination from the aspects of a chemical tinning process and a water washing process, and the surface of the battery piece after water washing has no tin liquid residue, thereby avoiding the condition that the battery piece absorbs light to generate electric potential to cause copper exposure, obviously reducing the copper leakage probability of the battery piece, reducing the copper leakage probability of 60 percent to below 1 percent in the prior art, and improving the appearance yield of the battery piece; and the weldability of the battery piece grid line is improved, and the welding yield of the battery assembly and the reliability of copper ion migration type LID failure are improved.
According to some embodiments of the invention, the darkness of the first darkroom is greater than or equal to 50%, thereby reducing the situation that the battery piece absorbs light to generate electric potential in the chemical tinning process to cause copper exposure. If the darkness of the first darkroom is less than 50%, the introduction of illumination cannot be effectively avoided, and the situation that the battery piece absorbs light to generate electric potential in the chemical tinning process to cause copper exposure cannot be effectively reduced.
According to other embodiments of the invention, the darkness of the second darkroom is 50% or more, thereby reducing the situation that the battery piece absorbs light to generate electric potential in the water washing process to cause copper exposure. If the darkness of the second darkroom is less than 50%, the introduction of illumination cannot be effectively avoided, and the situation that the battery piece absorbs light to generate electric potential in the water washing process to cause copper exposure cannot be effectively reduced.
According to other specific embodiments of the invention, the battery piece with the tin protection layer is washed to pH=7, namely, the battery piece is washed to be neutral, so that the surface of the battery piece after washing is further ensured to be free of tin liquor residue, the occurrence of corrosion reaction of a primary battery is completely isolated, and the condition of copper exposure is further avoided.
According to other specific embodiments of the invention, the time for transferring the battery piece with the tin protection layer from the tin melting tank to the washing tank is less than or equal to 5s, so that the liquid carrying time of the battery piece when the battery piece leaves the tin melting tank is further shortened, the occurrence of photoinduced electron migration is weakened, and the situation that the battery piece absorbs light to generate electric potential in the process of transferring the battery piece from the tin melting tank to the washing tank to cause copper exposure is effectively reduced.
As some specific examples, the electrode layer has a thickness of 8-10 μm and the tin protective layer has a thickness of 2-3 μm. As some specific examples, the electrode layer is a copper electrode layer.
In yet another aspect of the invention, a method of making a solar cell is provided. The structure and preparation method of the battery sheet are described below:
according to some embodiments of the invention, referring to fig. 6, a method of preparing a solar cell includes:
s100: providing a semiconductor substrate;
as some specific examples, the providing semiconductor substrate 11 may be subjected to a texturing process to remove impurities and mechanically damaged layers from the surface of the providing semiconductor substrate 11, forming a regular pyramid-shaped textured surface.
S200: forming a first passivation layer and a second passivation layer
In this step, the first passivation layer 12 is formed on one side of the semiconductor substrate 11, and the second passivation layer 13 is formed on the side of the semiconductor substrate 11 remote from the first passivation layer 11. The specific types of the first passivation layer 12 and the second passivation layer 13 are not particularly limited, and may be, for example, intrinsic amorphous silicon layers, respectively. The method of preparing the first passivation layer and the second passivation layer is also not particularly limited. For example, the first passivation layer 12 and the second passivation layer 13 may be prepared by PECVD (plasma enhanced chemical vapor deposition). Specifically, the thickness of the first passivation layer may be 3nm to 6nm; and/or the thickness of the second passivation layer may be 3nm to 9nm.
S300: forming an N-type doped layer and a P-type doped layer
In this step, an N-type doped layer 14 is formed on a side of the first passivation layer 12 remote from the semiconductor substrate 11, and a P-type doped layer 15 is formed on a side of the second passivation layer 13 remote from the semiconductor substrate 11. The method of preparing the N-type doped layer 14 and the P-type doped layer 15 is not particularly limited. For example, the N-type doped layer 14 and the P-type doped layer 15 may be prepared by PECVD, and specific process parameters may be referred to the preparation methods of the N-type doped layer 14 and the P-type doped layer 15 in the related art. As some specific examples, the thickness of N-type doped layer 14 may be 5nm-10nm; and/or the thickness of the P-type doped layer 15 may be 5nm-15nm.
S400: forming a first conductive layer and a second conductive layer
In this step, a first conductive layer 16 is formed on the side of the N-type doped layer 14 remote from the first passivation layer 12, and a second conductive layer 17 is formed on the side of the P-type doped layer 15 remote from the second passivation layer 13. The method of preparing the first conductive layer 16 and the second conductive layer 17 is not particularly limited. For example, the first conductive layer 16 and the second conductive layer 17 may be formed by physical vapor deposition, and the first conductive layer 16 and the second conductive layer 17 may be ITO (indium tin oxide) transparent conductive films, and for specific process parameters, reference may be made to a method of preparing the first conductive layer 16 and the second conductive layer 17 in the related art. As some specific examples, the thicknesses of the first conductive layer 16 and the second conductive layer 17 may be 90nm to 110nm, respectively and independently.
S500: forming a first metal seed layer and a second metal seed layer
In this step, a first metal seed layer 18 is formed on the side of the first conductive layer 16 remote from the N-type doped layer 14, and a second metal seed layer 19 is formed on the side of the second conductive layer 17 remote from the P-type doped layer 15. The method of preparing the first and second metal seed layers 18 and 19 is not particularly limited, and for example, the first and second metal seed layers 18 and 19 may be formed by PVD. As some specific examples, the thicknesses of the first metal seed layer 18 and the second metal seed layer 19 are independently 150nm to 250nm, respectively. Further, mask wrapping may be performed at the edge where the semiconductor substrate 11 is provided, and specifically, the degree of glue may be 30 μm to 60 μm and the thickness of glue may be 10 μm to 14 μm.
S600: forming a first electrode layer and a second electrode layer
In this step, a first electrode layer 20 is formed on the side of the first metal seed layer 18 remote from the first conductive layer 16, and a second electrode layer 21 is formed on the side of the second metal seed layer 19 remote from the second conductive layer 17.
As some specific examples, when the electrode layer is a copper gate line layer, the formation process of the copper gate line layer may refer to the following steps: respectively coating photoresist on one side of the first metal seed layer 18 far away from the first conductive layer 16 and one side of the second metal seed layer 19 far away from the second conductive layer 17, wherein the photoresist covers the exposed first metal seed layer 18 and the exposed second metal seed layer 19; exposing the photoresist according to the designed grid line pattern by laser printing, removing the unexposed photoresist by using a developing solution to form a groove, exposing the metal seed layer at the bottom layer, and forming a copper grid line layer in the groove by taking the metal seed layer as a cathode in the electroplating process.
As some specific examples, the developer may be Na 2 CO 3 Solution, na 2 CO 3 The concentration of the solution may be 8-13g/L.
As some specific examples, the electrolyte may be CuSO during copper electroplating 4 Solution, cuSO 4 The concentration of the solution may be 20-100g/L. Further, the method can also be used in CuSO 4 Additives are added to the solution. As some specific examples, the thickness of the copper gate line layer formed may be 8-10 μm.
S700: forming a tin protection layer
In this step, the first tin protection layer 22 is formed on the side of the first electrode layer 20 away from the first metal seed layer 18 by the method of the above embodiment, and the second tin protection layer 23 is formed on the side of the second electrode layer 21 away from the second metal seed layer 19 by the method of the above embodiment.
The method specifically comprises the following steps:
s710: removing film and etching back the battery piece with electrode layer
In the step, the battery piece with the electrode layer is subjected to film removal and back etching, and photoresist, the first metal seed layer and the second metal seed layer in the non-electroplating area are removed to expose the conductive layer. As some specific examples, removal by NaOH solutionThe photoresist and the side package Bian Jiao remained on the surface of the cell are immersed in the etching solution to remove the exposed first metal seed layer 18 and second metal seed layer 19. As some specific examples, the concentration of NaOH solution may be 10-20g/L; h in etching liquid 2 The concentration of SO4 can be 2.5g/L, and H in the etching solution is recovered 2 O 2 May be 10g/L.
S720: chemical tinning of the removed film and etched battery piece
In this step, the battery sheet after the film removal and back etching is placed in a tin bath under a first darkroom condition to be subjected to chemical tin plating so as to form a tin protection layer on the surface of the electrode layer, specifically, a first tin protection layer 22 is formed on the side of the first electrode layer 20 away from the first metal seed layer 18, and a second tin protection layer 23 is formed on the side of the second electrode layer 21 away from the second metal seed layer 19. According to the invention, the process of chemically plating the tin on the battery piece after film removal and back etching is placed under the darkroom condition, so that the introduction of illumination is avoided, and the condition that the battery piece absorbs light to generate electric potential in the process of chemically plating the tin to cause copper exposure is reduced.
As some specific examples, sn is included in the tin bath 2+ Methanesulfonic acid and additives (e.g., surfactant, stabilizer, complexing agent, etc.), sn in the tin bath 2+ The concentration of (2) may be 10-50g/L and the concentration of methylsulfonic acid may be 100-300g/L. As some specific examples, the tin layer formed may have a thickness of 2 μm to 3 μm.
The reason why the step of stripping back engraving is provided before the electroless tin plating step in the present invention is that: through the step of film removing and back etching, photoresist between adjacent electroplating electrode layers can be removed, so that the side surfaces of the electroplating electrode layers are exposed; therefore, when the electroless tin plating is performed after the film removal and back etching step, a tin protection layer can be formed on the surface of the electroplating electrode layer far away from the metal seed layer and the side surface of the electroplating electrode layer, so that the electroplating electrode layer can be better protected.
S730: washing the battery piece with the tin protective layer by water
In this step, the battery piece with the tin protective layer is washed under the condition of the second darkroom, so that the condition that the battery piece absorbs light to generate electric potential in the washing process to cause copper exposure is reduced. The surface of the battery piece after water washing has no tin liquid residue, and completely isolates the occurrence of corrosion reaction of the primary battery, thereby avoiding the occurrence of copper exposure.
As some specific examples, the battery sheet may be further subjected to light injection treatment, and the light injection may be performed at a temperature of 200-220 ℃ for a time of 60-120s.
In a third aspect of the invention, the invention proposes a solar cell. According to an embodiment of the present invention, a battery sheet is prepared by the method of the above embodiment. Therefore, the appearance yield of the solar cell is improved, and the weldability of the grid line of the solar cell is improved, so that the welding yield of a cell component and the reliability of copper ion migration type LID failure are improved.
The following detailed description of embodiments of the invention is provided for the purpose of illustration only and is not to be construed as limiting the invention. In addition, all reagents employed in the examples below are commercially available or may be synthesized according to methods herein or known, and are readily available to those skilled in the art for reaction conditions not listed, if not explicitly stated.
Example 1
The method comprises the following steps:
1) And removing the film and back etching the HJT battery piece with the electrode layer, removing the residual photoresist and the side bag Bian Jiao on the surface of the battery piece by using NaOH solution, and removing the exposed metal seed layer by soaking in the back etching solution. The concentration of the NaOH solution is 15g/L; h in etching liquid 2 SO4 concentration is 2.5g/L, and H in the etching solution is recovered 2 O 2 Is 10g/L.
2) And (3) under the darkness of 70%, placing the battery piece subjected to film removal and back etching in a tin melting liquid for chemical tin plating so as to form a tin protective layer on the surface of the electrode layer. The tin melting liquid comprises Sn 2+ Methanesulfonic acid, sn 2+ The concentration of (2) was 30g/L and the concentration of methylsulfonic acid was 200g/L.
3) Transferring the battery piece with the tin protective layer from the tin melting tank to the water washing tank, wherein the transferring time is controlled within 5 seconds; the battery sheet on which the tin protective layer was formed was washed with water to ph=7 under a darkness of 70%.
Example 2
Example 2 differs from example 1 only in that:
under the darkness of 50%, placing the battery piece subjected to film removal and back etching in tin melting liquid for chemical tinning; the battery sheet on which the tin protective layer was formed was washed with water under a darkness of 50% in a darkroom. The other contents are the same as in example 1.
Example 3
Example 3 differs from example 1 only in that:
under the darkness of 100%, placing the battery piece subjected to film removal and back etching in tin melting liquid for chemical tinning; the battery sheet on which the tin protective layer was formed was washed with water under a darkness of 100%. The other contents are the same as in example 1.
Comparative example 1
Comparative example 1 differs from example 1 only in that:
under the normal brightness condition, placing the battery piece subjected to film removal and back etching in tin melting liquid for chemical tinning; and (3) washing the battery piece with the tin protective layer under the normal brightness condition. The other contents are the same as in example 1.
100 battery pieces were prepared by the methods of examples 1 to 3 and comparative example, respectively, and then the copper leakage probability of the battery pieces was counted, and the results are shown in table 1.
TABLE 1
| Example 1 | Example 2 | Example 3 | Comparative example 1 | |
| Probability of copper leakage | 0.8％ | 1％ | 0.4％ | 60％ |
As can be seen from the above table, the copper leakage probability of examples 1-3 is significantly reduced compared to comparative example 1.
In the description of the present specification, a description referring to terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, the different embodiments or examples described in this specification and the features of the different embodiments or examples may be combined and combined by those skilled in the art without contradiction.
While embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and not to be construed as limiting the invention, and that variations, modifications, alternatives and variations may be made to the above embodiments by one of ordinary skill in the art within the scope of the invention.
Claims (10)
1. A method of improving an electroless tin plated drain electrode layer of a solar cell, comprising:
removing the film and etching back the battery piece with the electrode layer;
under the condition of a first darkroom, placing the battery piece subjected to film removal and back etching in tin melting liquid for chemical tin plating so as to form a tin protection layer on the surface of the electrode layer;
and (3) washing the battery piece with the tin protective layer under the condition of a second darkroom.
2. The method of claim 1, wherein the darkness of the first darkroom is greater than or equal to 50%.
3. The method of claim 1, wherein the darkness of the second darkroom is greater than or equal to 50%.
4. The method according to claim 1, wherein the battery sheet formed with the tin protective layer is water-washed to ph=7.
5. The method according to claim 1, wherein the time for transferring the battery sheet formed with the tin protective layer from the tin bath to the washing bath is 5s or less.
6. The method according to claim 1, wherein the thickness of the electrode layer is 8-10 μm and the thickness of the tin protection layer is 2-3 μm.
7. The method of claim 1, wherein the electrode layer is a copper electrode layer.
8. A method for producing a solar cell, characterized in that a tin protective layer of the solar cell is produced by the method according to any one of claims 1 to 7.
9. The method according to claim 8, characterized in that the method comprises:
providing a semiconductor substrate;
forming a first passivation layer on one side of the semiconductor substrate, and forming a second passivation layer on one side of the semiconductor substrate away from the first passivation layer;
forming an N-type doped layer on one side of the first passivation layer far away from the semiconductor substrate, and forming a P-type doped layer on one side of the second passivation layer far away from the semiconductor substrate;
forming a first conductive layer on one side of the N-type doped layer far away from the first passivation layer, and forming a second conductive layer on one side of the P-type doped layer far away from the second passivation layer;
forming a first metal seed layer on one side of the first conductive layer far away from the N-type doped layer, and forming a second metal seed layer on one side of the second conductive layer far away from the P-type doped layer;
forming a first electrode layer on one side of the first metal seed layer far away from the first conductive layer, and forming a second electrode layer on one side of the second metal seed layer far away from the second conductive layer;
forming a first tin protective layer on a side of the first electrode layer remote from the first metal seed layer using the method of any one of claims 1-7; and/or forming a second tin protective layer on a side of the second electrode layer remote from the second metal seed layer using the method of any one of claims 1-7.
10. A solar cell prepared by the method of claim 8 or 9.
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