CN115346862A - Silicon wafer diffusion method, solar cell, cell module and photovoltaic system - Google Patents
Silicon wafer diffusion method, solar cell, cell module and photovoltaic system Download PDFInfo
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- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 title claims abstract description 137
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- 230000008021 deposition Effects 0.000 claims abstract description 50
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims abstract description 48
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 31
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- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 claims description 11
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
- H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
- H01L21/22—Diffusion of impurity materials, e.g. doping materials, electrode materials, into or out of a semiconductor body, or between semiconductor regions; Interactions between two or more impurities; Redistribution of impurities
- H01L21/225—Diffusion of impurity materials, e.g. doping materials, electrode materials, into or out of a semiconductor body, or between semiconductor regions; Interactions between two or more impurities; Redistribution of impurities using diffusion into or out of a solid from or into a solid phase, e.g. a doped oxide layer
- H01L21/2251—Diffusion into or out of group IV semiconductors
- H01L21/2254—Diffusion into or out of group IV semiconductors from or through or into an applied layer, e.g. photoresist, nitrides
- H01L21/2255—Diffusion into or out of group IV semiconductors from or through or into an applied layer, e.g. photoresist, nitrides the applied layer comprising oxides only, e.g. P2O5, PSG, H3BO3, doped oxides
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
- H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
- H01L21/22—Diffusion of impurity materials, e.g. doping materials, electrode materials, into or out of a semiconductor body, or between semiconductor regions; Interactions between two or more impurities; Redistribution of impurities
- H01L21/225—Diffusion of impurity materials, e.g. doping materials, electrode materials, into or out of a semiconductor body, or between semiconductor regions; Interactions between two or more impurities; Redistribution of impurities using diffusion into or out of a solid from or into a solid phase, e.g. a doped oxide layer
- H01L21/2251—Diffusion into or out of group IV semiconductors
- H01L21/2254—Diffusion into or out of group IV semiconductors from or through or into an applied layer, e.g. photoresist, nitrides
- H01L21/2255—Diffusion into or out of group IV semiconductors from or through or into an applied layer, e.g. photoresist, nitrides the applied layer comprising oxides only, e.g. P2O5, PSG, H3BO3, doped oxides
- H01L21/2256—Diffusion into or out of group IV semiconductors from or through or into an applied layer, e.g. photoresist, nitrides the applied layer comprising oxides only, e.g. P2O5, PSG, H3BO3, doped oxides through the applied layer
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- 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
- H01L31/04—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 adapted as photovoltaic [PV] conversion devices
- H01L31/06—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 adapted as photovoltaic [PV] conversion devices characterised by potential barriers
- H01L31/068—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 adapted as photovoltaic [PV] conversion devices characterised by potential barriers the potential barriers being only of the PN homojunction type, e.g. bulk silicon PN homojunction solar cells or thin film polycrystalline silicon PN homojunction solar cells
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- H01L31/18—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
- H01L31/1804—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof comprising only elements of Group IV of the Periodic Table
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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Abstract
The invention is suitable for the technical field of solar cells and provides a silicon wafer diffusion method, a solar cell, a cell assembly and a photovoltaic system, wherein the silicon wafer diffusion method comprises the following steps: placing the silicon wafer in a diffusion furnace and heating and vacuumizing; introducing oxygen, nitrogen and phosphorus oxychloride to carry out primary deposition on the surface of the silicon wafer; heating and carrying out passive propulsion treatment; and cooling to 790-810 ℃, introducing 650-670 sccm of oxygen, 455-475 mg/min of nitrogen and phosphorus oxychloride to perform secondary deposition on the surface of the silicon wafer so as to obtain the diffused silicon wafer, wherein the sheet resistance of the diffused silicon wafer is 170-200 omega. Therefore, the sheet resistance of the diffused silicon wafer can be effectively improved to 170-200 omega by adjusting each process parameter in the second deposition to the range, so that the doping concentration of the surface of the silicon wafer is effectively reduced, recombination is reduced, the open-circuit voltage is improved, and the efficiency of a solar cell made of the silicon wafer is improved.
Description
Technical Field
The invention relates to the technical field of solar cells, in particular to a silicon wafer diffusion method, a solar cell, a cell module and a photovoltaic system.
Background
The PERC solar cell has simple process and low cost, and is one of the most popular high-efficiency solar cells in the market at present. The current manufacturing process of the PERC battery mainly comprises: texturing, diffusing, laser on the front side, etching and polishing, annealing, depositing a passivation film on the back side, depositing an antireflection film on the front side, laser opening, printing a back electrode, printing a positive electrode and sintering.
In the solar cell manufacturing process, diffusion is the core process and is used to form PN junctions. At present, phosphorus diffusion generally comprises three methods, namely phosphorus oxychloride (POCl 3) liquid source diffusion, chain diffusion after spraying phosphoric acid aqueous solution, and chain diffusion after screen printing of phosphorus slurry. At present, the technology of preparing an emitter region with high sheet resistance is more and more focused on the research and development of high-efficiency solar cells, when the sheet resistance is low, the doping concentration of the surface is high, the recombination is severe, and the open-circuit voltage is low, so that the technical problem of research of technicians is solved by how to improve the diffusion sheet resistance and reduce the doping concentration of the surface so as to further improve the cell efficiency.
Disclosure of Invention
The invention provides a solar cell, a preparation method thereof, a cell module and a photovoltaic system, and aims to solve the technical problem that when the sheet resistance of the solar cell in the prior art is low, the doping concentration of the surface is high, the recombination is serious, and the open-circuit voltage is low.
The invention is realized in such a way that the silicon wafer diffusion method in the embodiment of the invention comprises the following steps:
placing the silicon wafer in a diffusion furnace and heating and vacuumizing the diffusion furnace;
introducing oxygen, nitrogen and phosphorus oxychloride to carry out primary deposition on the surface of the silicon wafer;
heating and carrying out passive propulsion treatment;
and cooling to 790-810 ℃, introducing 650-670 sccm of oxygen, 455-475 mg/min of nitrogen and phosphorus oxychloride, and performing secondary deposition on the surface of the silicon wafer to obtain the diffused silicon wafer, wherein the sheet resistance of the diffused silicon wafer is 170-200 omega.
Further, the phosphorus doping concentration of the diffused surface of the silicon wafer is 2.5 to 10 20 Per cm 3 -3*10 20 Per cm 3 。
Further, the temperature in the second deposition is 800 ℃, the oxygen flow is 660sccm, and the phosphorus oxychloride flow is 465mg/min.
Further, the deposition time in the second deposition is 5min to 7min.
Furthermore, the sheet resistance of the diffused silicon wafer is 184-188 omega.
Furthermore, the step of introducing oxygen, nitrogen and phosphorus oxychloride to perform the first deposition on the surface of the silicon wafer comprises the following steps:
introducing oxygen 475sccm, nitrogen 400sccm and phosphorus oxychloride 340mg/min at the temperature of 755-775 ℃ to deposit on the surface of the silicon wafer for 3.5min;
and continuously heating and carrying out secondary deposition for 3min.
Further, after the step of placing the silicon wafer in a diffusion furnace and carrying out heating and vacuumizing treatment, before the step of introducing oxygen, nitrogen and phosphorus oxychloride to carry out first deposition on the surface of the silicon wafer, the silicon wafer diffusion method further comprises the following steps:
and introducing 1000sccm-1200sccm of oxygen and 3slm of nitrogen to perform pre-oxidation treatment on the silicon wafer.
The invention also provides a battery assembly which comprises a plurality of solar battery pieces in the embodiment of the invention.
The invention also provides a photovoltaic system which comprises the battery component.
The invention has the following beneficial effects: the temperature of the second deposition is adjusted to 790-810 ℃, the introduction amount of phosphorus oxychloride is increased to 455-475 mg/min, and the introduction amount of oxygen is increased to 650-670 sccm, so that the sheet resistance of the diffused silicon wafer 10 can be effectively improved to 170-200 omega, the doping concentration of the surface of the silicon wafer can be effectively reduced, recombination is reduced, the open-circuit voltage is improved, and the efficiency of a solar cell made of the silicon wafer is 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
FIG. 1 is a schematic diagram of a photovoltaic system provided by the present invention;
FIG. 2 is a schematic structural view of a battery pack provided by the present invention;
FIG. 3 is a schematic structural diagram of a solar cell provided by the present invention;
FIG. 4 is a schematic flow chart of a silicon wafer diffusion method provided by the present invention;
FIG. 5 is a schematic diagram of a sheet resistance test of a silicon wafer lot prepared by a diffusion method of the prior art;
FIG. 6 is a schematic diagram of a sheet resistance test of a silicon wafer set prepared by the diffusion method of the present invention;
FIG. 7 is a graph comparing the ECV test curves for a prior art diffusion process formed silicon wafer and a diffusion process of the present invention;
FIG. 8 is another schematic flow chart of a method for manufacturing a solar cell provided by the present invention;
fig. 9 is a schematic flow chart of a method for manufacturing a solar cell according to the present invention.
Description of the main element symbols:
the solar cell comprises a photovoltaic system 1000, a cell module 200, a solar cell 100, a silicon wafer 10, a front passivation film layer 20, a front electrode 30, an anti-reflection film layer 40 and a back electrode 50.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. Examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the accompanying drawings are illustrative only for the purpose of explaining the present invention and are not to be construed as limiting the present invention. Furthermore, it should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
In the description of the present invention, it is to be understood that the terms "first", "second" and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implying any number of technical features indicated. Thus, features defined as "first", "second", may explicitly or implicitly include one or more of the described features. In the description of the present invention, "a plurality" means two or more unless specifically defined otherwise.
The following disclosure provides many different embodiments, or examples, for implementing different features of the invention. To simplify the disclosure of the present invention, the components and arrangements of specific examples are described below. Of course, they are merely examples and are not intended to limit the present invention. Furthermore, the present invention may repeat reference numerals and/or letters in the various examples, such repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. In addition, the present invention provides examples of various specific processes and materials, but one of ordinary skill in the art will recognize that other processes may be used and/or other materials may be used.
In the related art, diffusion is a core process in a solar cell manufacturing process, and is used to form a PN junction. At present, phosphorus diffusion generally comprises three methods, namely phosphorus oxychloride (POCl 3) liquid source diffusion, chain diffusion after spraying phosphoric acid aqueous solution, and chain diffusion after screen printing of phosphorus slurry. At present, the technology for preparing the emitter region with high sheet resistance is more and more emphasized by the research and development of high-efficiency solar cells, and when the sheet resistance is lower, the surface doping concentration is higher, the recombination is more serious, and the open-circuit voltage is lower.
In the invention, the temperature of the second deposition is adjusted to 790-810 ℃, the introduction amount of phosphorus oxychloride is increased to 455-475 mg/min, and the introduction amount of oxygen is increased to 650-670 sccm, so that the sheet resistance of the diffused silicon wafer 10 can be effectively improved to 170-200 omega, the doping concentration of the surface of the silicon wafer 10 can be effectively reduced, recombination can be reduced, and the open-circuit voltage can be improved, and therefore, the efficiency of the solar cell made of the silicon wafer 10 can be improved, and the technical problems of recombination increase and low open-circuit voltage caused by low doping concentration of the surface of the silicon wafer 10 due to low sheet resistance in the diffusion process in the prior art can be solved.
Example one
Referring to fig. 1 and fig. 2, a photovoltaic system 1000 according to the present invention may include a cell assembly 200 according to an embodiment of the present invention, and the cell assembly 200 according to the embodiment of the present invention may include a plurality of solar cells 100 according to an embodiment of the present invention.
Referring to fig. 3, a solar cell 100 in an embodiment of the present invention includes a silicon wafer 10 prepared by a method for diffusing a silicon wafer 10 provided by the present invention, the silicon wafer 10 may be an n-type monocrystalline silicon wafer or an n-type polycrystalline silicon wafer, the silicon wafer 10 forms a p-type diffusion layer (i.e., a p-type emitter) after phosphorus diffusion, the solar cell 100 may be a PERC solar cell, and of course, other types of solar cells 100 may also be used, as long as the solar cell needs to be subjected to phosphorus diffusion on the silicon wafer 10, which is not limited herein, and in this document, the solar cell 100 is mainly used as the PERC solar cell for illustration.
Specifically, referring to fig. 3, in the PERC solar cell 100, a phosphorus diffusion layer formed after the silicon wafer 10 is diffused may be located on the front side of the silicon wafer 10, the front side of the silicon wafer 10 may further be sequentially provided with an anti-reflection film layer 20 and a front electrode 30, the front electrode 30 penetrates through the front anti-reflection film layer 30 to form ohmic contact with the diffusion layer formed on the silicon wafer 10, the anti-reflection film layer 20 may be a silicon nitride film layer, the front electrode 30 may be a silver electrode, the back side of the silicon wafer 10 may further be sequentially provided with a back passivation film layer 40 and a back electrode 50, the back electrode 50 penetrates through the back passivation film layer 40 to form ohmic contact with the back side of the silicon wafer 10, the back passivation film layer 40 may also be a silicon nitride film layer, the back electrode 50 may include a silver electrode and an aluminum electrode, the aluminum electrode is used as a main electrode on the back side to collect current, and the silver electrode on the back side is in conductive contact with the aluminum electrode for welding.
The plurality of solar cells 100 in the cell assembly 200 may be connected in series or in parallel in sequence to form a cell string, so as to output current in series or in parallel, for example, the connection of the cells may be realized by arranging solder strips.
It is understood that, in the embodiment of the present invention, the battery assembly 200 may further include a metal frame, a back sheet, a photovoltaic glass, and an adhesive film (not shown). The adhesive film may be attached to the front side and the back side of the solar cell 100, and may be a transparent adhesive with good light transmittance and aging resistance, for example, the adhesive film may be an EVA adhesive film or a POE adhesive film, which may be specifically selected according to actual situations, and is not limited herein.
The photovoltaic glass may be an ultra-white glass having high light transmittance, high transparency, and excellent physical, mechanical, and optical properties, for example, the light transmittance of the ultra-white glass may be more than 80%, which may protect the solar cell 100 without affecting the efficiency of the solar cell 100 as much as possible. Meanwhile, the adhesive film can bond the photovoltaic glass and the solar cell piece 100 together, and the existence of the adhesive film can seal, insulate, prevent water and prevent moisture for the solar cell piece 100.
The back plate can be attached to an adhesive film on the back surface of the solar cell piece 100, the back plate can protect and support the solar cell piece 100, and has reliable insulating property, water resistance and aging resistance, the back plate can be selected in multiple ways, can be generally toughened glass, organic glass, an aluminum alloy TPT composite adhesive film and the like, can be specifically arranged according to specific conditions, and is not limited herein. The whole of the back sheet, the solar cell sheet 100, the adhesive film, and the photovoltaic glass may be disposed on a metal frame, which serves as a main external support structure of the entire cell assembly 200 and may stably support and mount the cell assembly 200, for example, the cell assembly 200 may be mounted at a position where it is required to be mounted through the metal frame.
Further, in the present invention, the photovoltaic system 1000 may be applied to a photovoltaic power station, such as a ground power station, a roof power station, a water surface power station, etc., and may also be applied to a device or apparatus that generates electricity by using solar energy, such as a user solar power source, a solar street lamp, a solar car, a solar building, etc. Of course, it is understood that the application scenario of the photovoltaic system 1000 is not limited thereto, that is, the photovoltaic system 1000 may be applied in all fields requiring solar energy for power generation. Taking a photovoltaic power generation system network as an example, the photovoltaic system 1000 may include a photovoltaic array, a combiner box and an inverter, the photovoltaic array may be an array combination of a plurality of battery assemblies 200, for example, the plurality of battery assemblies 200 may form a plurality of photovoltaic arrays, the photovoltaic array is connected to the combiner box, the combiner box may combine currents generated by the photovoltaic array, and the combined currents are converted into alternating currents required by a utility grid through the inverter and then are connected to the utility grid to realize solar power supply.
Referring to fig. 4, the silicon wafer 10 in the solar cell of the present invention may be prepared by the silicon wafer 10 diffusion method in the embodiment of the present invention, and the silicon wafer 10 diffusion method in the embodiment of the present invention may include the steps of:
s10: placing the silicon wafer 10 in a diffusion furnace and heating and vacuumizing the diffusion furnace;
s20: introducing oxygen, nitrogen and phosphorus oxychloride to carry out primary deposition on the surface of the silicon wafer 10;
s30: heating and carrying out passive propulsion treatment;
s40: and cooling to 790-810 ℃, introducing 650-670 sccm of oxygen, 455-475 mg/min of nitrogen and phosphorus oxychloride, and performing secondary deposition on the surface of the silicon wafer 10 to obtain the diffused silicon wafer 10, wherein the sheet resistance of the diffused silicon wafer 10 is 170-200 omega.
In the silicon wafer 10 diffusion method, the solar cell 100, the cell module 200 and the photovoltaic system 1000 in the embodiment of the invention, the temperature of the second deposition is adjusted to 790-810 ℃, the introduction amount of phosphorus oxychloride is increased to 455-475 mg/min, and the introduction amount of oxygen is increased to 650-670 sccm, so that the sheet resistance of the diffused silicon wafer 10 can be effectively increased to 170-200 Ω, the doping concentration on the surface of the silicon wafer 10 can be effectively reduced, recombination can be reduced, and the open-circuit voltage can be increased, thereby improving the efficiency of the solar cell 100 made of the silicon wafer 10.
In the embodiment of the present invention, before the silicon wafer 10 is diffused, the silicon wafer 10 may be subjected to texturing treatment by an alkaline solution (for example, KOH solution) and cleaned, and during the diffusion, the step of placing the silicon wafer 10 in a diffusion furnace may be referred to as a boat-entering step, and during the boat-entering step, the temperature of the diffusion furnace may be 765 ℃, and at this time, nitrogen gas having a flow rate of 15slm may be introduced and the pressure may be maintained at about 1060mbar, and then constant-temperature continuous heating and vacuum-pumping treatment may be performed, and the pressure after the vacuum-pumping is about 200mbar, and the pressure may be reduced to about 50mbar when the first deposition is performed.
It should be noted that, in the embodiment of the present invention, the temperature of the first deposition is lower than that of the second deposition, and after the first deposition is completed and the passive driving is performed, the temperature of the second deposition is raised, so that the silicon wafer 10 can be further driven to achieve the purpose of diffusion while the second deposition is performed.
Further, in some embodiments, the temperature in the second deposition may preferably be 800 ℃, the oxygen flow may preferably be 660sccm, and the phosphorus oxychloride flow may preferably be 465mg/min.
Thus, after the inventors of the present invention have conducted detailed tests and research verification, it is found that the temperature, the oxygen flow rate, and the phosphorus oxychloride flow rate can enable the diffused silicon wafer 10 to stably increase the sheet resistance to 170 Ω -200 Ω. In particular, during the second deposition, 400scmm of nitrogen gas was also introduced into the diffusion furnace, the gas pressure being maintained at 50mbar.
Still further, in some embodiments, the sheet resistance of the diffused silicon wafer 10 is 184 Ω -188 Ω.
Thus, the sheet resistance of the silicon wafers 10 can be kept in a high and small difference range to ensure the uniformity of the sheet resistance of the silicon wafers 10 produced in the same batch.
Still further, in some embodiments, the surface of the diffused wafer 10 has a phosphorus doping concentration of 2.5 x 10 20 Per cm 3 -3*10 20 Per cm 3 。
Thus, the doping concentration of the diffused silicon wafer 10 is low, and surface recombination can be effectively reduced.
Specifically, in the prior art, the doping concentration at the wafer surface after diffusion is typically 3.75 x 10 20 Per cm 3 In the embodiment of the present invention, the doping concentration on the surface of the diffused silicon wafer 10 can be effectively reduced by adjusting the temperature, the oxygen flux and the flux in the second deposition step, so as to reduce surface recombination.
Referring to fig. 5 and 6, fig. 5 is a schematic diagram of a sheet set prepared by a diffusion method of the prior art for testing sheet resistance, wherein the temperature for the second deposition is 815 ℃, the oxygen flow is 600sccm, and the phosphorus oxychloride flow is 420mg/min. Fig. 6 is a schematic diagram of a sheet resistance test of a silicon wafer group prepared by the diffusion method of the present invention, the abscissa in fig. 5 and 6 represents the sheet resistance, the ordinate represents the number of silicon wafers 10, and the silicon wafer 10 samples of both are 25.
As can be seen from FIG. 5, in the prior art, in 25 silicon wafers 10, the sheet resistance of the silicon wafer 10 is between 155 Ω -185 Ω, most of them is between 165 Ω -175 Ω, the average sheet resistance in the group is 168.35 Ω, and most of the silicon wafers 10 have low sheet resistance, which results in high surface doping concentration and severe recombination. As can be seen from fig. 6, the sheet resistance of the silicon wafer 10 obtained by the silicon wafer 10 diffusion method of the present invention is between 170 Ω and 200 Ω, most of the sheet resistance of the silicon wafer 10 is concentrated between 184 Ω and 188 Ω, and the average sheet resistance in the group is 186.99 Ω, which is 18.6 Ω higher than the average sheet resistance 168.35 Ω of the silicon wafer in the prior art, and has better uniformity, most of the sheet resistance is between 184 Ω and 188 Ω, and it is obvious that the sheet resistance of the silicon wafer 10 obtained by the silicon wafer 10 diffusion method of the present invention can be effectively improved compared with the prior art. It should be noted that the silicon wafers 10 under test are all randomly extracted from the produced silicon wafers 10, and the test conditions of both are the same.
Further, referring to fig. 7, fig. 7 is a graph comparing an ECV test curve of a silicon wafer 10 formed by a prior art diffusion method with an ECV test curve of a silicon wafer 10 formed by a diffusion method of the present invention, wherein an abscissa represents a diffusion depth, and an ordinate represents a doping concentration, a curve 1 represents an ECV test curve of a silicon wafer 10 of the prior art, and a curve 2 represents an ECV test curve of a silicon wafer 10 of the present invention, and it can be seen from fig. 7 that a surface doping concentration of the silicon wafer 10 formed by a diffusion method of the present invention is lower than a surface doping concentration of the silicon wafer 10 of the prior art, and a doping concentration extending farther from the surface of the silicon wafer 10 is substantially the same as the doping concentration of the silicon wafer 10 of the prior art.
Therefore, in the invention, the oxygen throughput of oxygen is increased to 650sccm-670sccm and the source throughput of phosphorus oxychloride is increased to 455mg/min-475mg/min by reducing the temperature of the second deposition to 790-810 ℃, so that the sheet resistance of the silicon wafer 10 can be effectively improved, and the doping concentration on the surface of the silicon wafer 10 can be effectively reduced, thereby reducing the surface recombination.
Still further, referring to table 1 below, table 1 below is a comparison table of the open circuit voltage, the front fill factor and the front conversion efficiency of the comparison group of the prior art and the experimental group of the present invention for the PERC solar cell 100, wherein the difference is a difference between the experimental group data and the comparison group data.
TABLE 1
| Group of | UOC (open circuit voltage) | FF (fill factor) | Eta (conversion efficiency) |
| Comparison group | 0.6893 | 80.709 | 23.07 |
| Experimental group of the invention | 0.6904 | 80.753 | 23.137 |
| Difference value | 0.0011 | 0.044 | 0.036 |
As can be seen from table 1 above, the open circuit voltage of the front surface of the solar cell 100 of the silicon wafer 10 formed by the diffusion method of the present invention is increased by 1.1mv, the fill factor is increased by 0.044, and the conversion efficiency of the front surface is increased by 0.036%. Therefore, the solar cell 100 prepared from the silicon wafer 10 formed by the diffusion method of the present invention can effectively improve the open-circuit voltage, the fill factor and the conversion efficiency.
Still further, in some embodiments, the deposition time in the second deposition may be 5min to 7min, preferably 6min.
In this way, the diffusion depth of the silicon wafer 10 can be expected by reasonably setting the time of the second deposition, and the diffusion depth is not too shallow due to too short deposition time, and is not too deep due to the deposition time process.
Example two
Referring to fig. 8, in some embodiments, a step between step S10 and step S20 may further include:
s50: and introducing 1000sccm-1200sccm of oxygen and 3slm of nitrogen to perform pre-oxidation treatment on the silicon wafer 10.
Therefore, the surface of the silicon wafer 10 can be pre-oxidized to form a silicon oxide layer, and then a phosphosilicate glass layer is formed in the deposition process, and a phosphorus source in the phosphosilicate glass layer can be diffused into the silicon wafer 10 to form a diffusion layer during propulsion.
Specifically, in this embodiment, the pressure after the vacuum pumping process may be about 200mbar, that is, the pressure is reduced from about 1060mbar to about 200mbar, nitrogen gas with a flow rate of 3slm and oxygen gas with a flow rate of 1000sccm may be introduced to perform oxidation simultaneously while heating the vacuum pumping process, the time may be 3min, and after the vacuum pumping process is completed, the temperature may be 765 ℃, the oxygen gas flow rate may be increased to 1200scmm and continued for 3min to achieve the pre-oxidation process. After the pre-oxidation is finished, the first deposition is carried out to form the phosphorosilicate glass layer, the pressure of the first deposition can be reduced and kept at about 50mbar, and the deposition time can be 6.5min. And then carrying out passive propulsion, wherein the phosphorus oxychloride is not introduced during the passive propulsion, the temperature is increased to 780-860 ℃, the flow of the nitrogen is adjusted to 2.5slm, the introduction amount of the oxygen is adjusted to 500sccm, the pressure is increased back to about 200mbar, the heating time can be 7min, the propulsion time can be 5min, the temperature is reduced to 800 ℃ after the propulsion is finished, the pressure is reduced to 200mbar for secondary deposition, the flow of the nitrogen can be 0.6slm-1slm during the cooling, the flow of the oxygen for the secondary deposition can be 650-670 sccm, preferably 660, the flow of the nitrogen is 400 mbar, the flow of the phosphorus oxychloride is 455mg/min-475mg/min, preferably 465455mg/min, the second deposition time can preferably be 6min, the pressure is returned to about 1060 after the secondary deposition is finished, the temperature during the pressure return can be maintained at 800 ℃, the flow of the nitrogen is only 15slm, and then the silicon wafer is taken out of the diffusion furnace (namely, the diffusion furnace is taken out of the silicon wafer), and the diffusion furnace is kept at the temperature of 15 sccm and the diffusion furnace is maintained at 15 ℃ when the diffusion temperature of the silicon wafer is maintained at 10 sccm.
In the third embodiment, the first step is that,
referring to fig. 9, further, in some embodiments, the step S20 may include the steps of:
s21: introducing 475sccm of oxygen, 400sccm of nitrogen and 340mg/min of phosphorus oxychloride at the temperature of 755-775 ℃ to deposit on the surface of the silicon wafer 10 for 3.5min;
s22: and continuously heating and carrying out secondary deposition for 3min.
Thus, a low surface concentration can be obtained on the surface of the silicon wafer 10 by adopting a gradual temperature rise manner during the first deposition, and the low surface concentration can effectively reduce the recombination current density on the surface.
Specifically, in such an embodiment, the deposition temperature may preferably be 765 ℃ in step S21, 769 ℃ in step S22, and after step S22 is completed, the introduction of phosphorus oxychloride may be removed and nitrogen gas at a flow rate of 2.5slm, oxygen gas at a flow rate of 500sccm, and the temperature may be continuously raised to 780-860 ℃ followed by raising the temperature to about 875 ℃ in the advancing step S30.
Finally, the manufacturing process of the PERC solar cell 100 is described by taking the PERC solar cell 100 as an example, and may specifically include the following steps:
texturing, namely, texturing the silicon wafer 10 by adopting an alkaline solution;
when the diffusion method in the embodiment of the invention is adopted to perform diffusion treatment on the silicon wafer 10, it can be understood that, during diffusion, phosphosilicate glass layers (i.e. PSG layers) are formed on the back surface, the front surface and the side surface of the silicon wafer 10;
front laser, which is used for carrying out selective laser doping on the front of the silicon wafer 10;
etching, removing the phosphorosilicate glass layers on the back and the side faces of the silicon wafer 10 and part of n-type silicon, and removing the phosphorosilicate glass layers on the front face;
annealing, namely annealing the silicon wafer 10 by adopting a thermal oxidation annealing process;
a back side passivation film layer 40 is deposited, wherein the back side passivation film layer 40 can be deposited by using a PECVD method;
depositing an anti-reflection film layer 20 on the front surface, wherein the anti-reflection film layer can also be deposited by adopting a PECVD method;
back laser, namely grooving the back of the silicon wafer 10 by using laser;
and screen printing and sintering, wherein a front electrode 30 is formed on the front surface by using silver paste, sintering and drying are carried out to form good ohmic contact with the front surface of the silicon chip 10, and a back electrode 50 is formed on the back surface of the silicon chip 10 by using silver paste and aluminum paste.
In the description herein, references to the description of the terms "some embodiments," "exemplary embodiments," "examples," "specific examples," or "some examples," etc., mean 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 invention. In this specification, the schematic representations of the terms used above do not necessarily refer 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.
In addition, the above description is only for the preferred embodiment of the present invention and should not be taken as limiting the invention, and any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A silicon wafer diffusion method is characterized by comprising the following steps:
placing the silicon wafer in a diffusion furnace and heating and vacuumizing the diffusion furnace;
introducing oxygen, nitrogen and phosphorus oxychloride to carry out primary deposition on the surface of the silicon wafer;
heating and carrying out passive propulsion treatment;
and cooling to 790-810 ℃, introducing 650-670 sccm of oxygen, 455-475 mg/min of nitrogen and phosphorus oxychloride, and performing secondary deposition on the surface of the silicon wafer to obtain the diffused silicon wafer, wherein the sheet resistance of the diffused silicon wafer is 170-200 omega.
2. The wafer diffusion process of claim 1, wherein the diffused surface of the wafer has a phosphorus doping concentration of 2.5 x 10 20 Per cm 3 -3*10 20 Per cm 3 。
3. The silicon wafer diffusion method according to claim 1, wherein the temperature in the second deposition is 800 ℃, the oxygen flow rate is 660sccm, and the phosphorus oxychloride flow rate is 465mg/min.
4. The silicon wafer diffusion method according to claim 1, wherein the deposition time in the second deposition is 5min to 7min.
5. The silicon wafer diffusion method according to claim 1, wherein the sheet resistance of the diffused silicon wafer is 184 Ω -188 Ω.
6. The silicon wafer diffusion method according to claim 1, wherein the step of introducing oxygen, nitrogen and phosphorus oxychloride to perform the first deposition on the surface of the silicon wafer comprises:
introducing oxygen 475sccm, nitrogen 400sccm and phosphorus oxychloride 340mg/min at the temperature of 755-775 ℃ to deposit on the surface of the silicon wafer for 3.5min;
and continuously heating and carrying out secondary deposition for 3min.
7. The silicon wafer diffusion method according to claim 1, wherein after the step of placing the silicon wafer in a diffusion furnace and performing heating and vacuum treatment, and before the step of introducing oxygen, nitrogen and phosphorus oxychloride to perform first deposition on the surface of the silicon wafer, the silicon wafer diffusion method further comprises the steps of:
and introducing 1000sccm-1200sccm of oxygen and 3slm of nitrogen to perform pre-oxidation treatment on the silicon wafer.
8. A solar cell comprising a silicon wafer produced by the silicon wafer diffusion method according to any one of claims 1 to 7.
9. A battery module comprising a plurality of solar cells according to claim 8.
10. A photovoltaic system comprising the cell assembly of claim 9.
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