CN117558821A - Solar cell manufacturing method and solar cell - Google Patents
Solar cell manufacturing method and solar cell Download PDFInfo
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- CN117558821A CN117558821A CN202311369481.9A CN202311369481A CN117558821A CN 117558821 A CN117558821 A CN 117558821A CN 202311369481 A CN202311369481 A CN 202311369481A CN 117558821 A CN117558821 A CN 117558821A
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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
- 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
-
- 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
- H01L21/26—Bombardment with radiation
- H01L21/263—Bombardment with radiation with high-energy radiation
- H01L21/268—Bombardment with radiation with high-energy radiation using electromagnetic radiation, e.g. laser radiation
-
- 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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- 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
- H01L31/0248—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 characterised by their semiconductor bodies
- H01L31/0256—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 characterised by their semiconductor bodies characterised by the material
- H01L31/0264—Inorganic materials
- H01L31/028—Inorganic materials including, apart from doping material or other impurities, only elements of Group IV of the Periodic Table
- H01L31/0288—Inorganic materials including, apart from doping material or other impurities, only elements of Group IV of the Periodic Table characterised by the doping material
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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
- H01L31/0248—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 characterised by their semiconductor bodies
- H01L31/0352—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 characterised by their semiconductor bodies characterised by their shape or by the shapes, relative sizes or disposition of the semiconductor regions
- H01L31/035272—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 characterised by their semiconductor bodies characterised by their shape or by the shapes, relative sizes or disposition of the semiconductor regions characterised by at least one potential jump barrier or surface barrier
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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
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
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Abstract
The invention discloses a manufacturing method of a solar cell and the solar cell, relates to the technical field of solar cells, and aims to solve the problem that a lightly doped region is affected in the process of forming a heavily doped region so as to reduce the performance of the solar cell. The manufacturing method of the solar cell comprises the following steps: a first side of the semiconductor substrate is processed to form a dopant source layer. And carrying out regional treatment on the doped source layer by adopting a laser irradiation process to diffuse doping elements in the doped source layer into the semiconductor substrate so as to form a heavy doped region on one side of the first surface of the semiconductor substrate, wherein the rest doped source layer is a light doped region. The ratio of the maximum doping concentration of the doping element in the heavily doped region to the maximum doping concentration of the doping element in the lightly doped region is greater than or equal to 1 and less than or equal to 3. The ratio of the doping concentration of the doping element in any heavily doped region to the maximum doping concentration of the doping element in the heavily doped region is greater than or equal to 30% and less than or equal to 100% within the depth range of 1 micron.
Description
Technical Field
The present invention relates to the field of solar cells, and in particular, to a method for manufacturing a solar cell and a solar cell.
Background
A solar cell is a device that uses solar energy to directly convert light energy into electric energy through a photoelectric effect or a photochemical effect. In order to improve the efficiency of the solar cell, a selective emitter solar cell is generally adopted, and the solar cell is characterized in that P (phosphorus) atoms are uniformly distributed on the surface of a conventional solar cell to form P-N junctions with different depths, wherein the region where the deeper P-N junction is located is a deep diffusion region, and the region where the shallower P-N junction is located is a shallow diffusion region.
In the prior art, a mask method is generally used for preparing the selective emitter, and two times of diffusion are generally needed in the actual preparation process to form electrode regions and non-electrode regions with different doping concentrations. However, the two diffusions will interact with each other. Specifically, in the process of forming the heavily doped region of the electrode region by the second diffusion, the lightly doped region of the non-electrode region is affected, thereby reducing the performance of the solar cell.
Disclosure of Invention
The invention aims to provide a manufacturing method of a solar cell and the solar cell, which are used for reducing or avoiding the influence on a lightly doped region in the process of forming the heavily doped region so as to improve the performance of the solar cell.
In order to achieve the above object, in a first aspect, the present invention provides a method for manufacturing a solar cell. The manufacturing method of the solar cell comprises the following steps: first, a semiconductor substrate is provided, the semiconductor substrate having opposite first and second sides. Next, a first side of the semiconductor substrate is processed to form a dopant source layer. And then, carrying out regional treatment on the doped source layer by adopting a laser irradiation process to diffuse doping elements in the doped source layer into the semiconductor substrate so as to form a heavy doped region on one side of the first surface of the semiconductor substrate, wherein the rest doped source layer is a light doped region. Next, oxidation treatment is performed on the semiconductor substrate, the heavily doped region and the lightly doped region to form a selective emitter on the first face of the semiconductor substrate. Wherein the ratio of the maximum doping concentration of the doping element in the heavily doped region to the maximum doping concentration of the doping element in the lightly doped region is greater than or equal to 1 and less than or equal to 3. The ratio of the doping concentration of the doping element in any heavily doped region to the maximum doping concentration of the doping element in the heavily doped region is greater than or equal to 30% and less than or equal to 100% within the depth range of 1 micron.
Compared with the prior art, in the manufacturing method of the solar cell, the formed doping source layer is of a whole layer structure, but the doping source layer is subjected to regional treatment by adopting a laser irradiation process. At this time, only the doping element in the local region of the doping source layer diffuses into the semiconductor substrate. The doping element in the region of the doping source layer which is not treated by the laser irradiation process is not diffused into the semiconductor substrate, and remains in the doping source layer. Based on this, the effect on the remaining dopant source layer (i.e., the lightly doped region) during the formation of the heavily doped region is less or no, improving the performance of the solar cell compared to the prior art. Further, there is no second diffusion compared to the prior art, and thus the impact on the lightly doped region is also reduced. Still further, since the ratio of the maximum doping concentration of the doping element in the heavily doped region to the maximum doping concentration of the doping element in the lightly doped region is greater than or equal to 1 and less than or equal to 3. The ratio of the doping concentration of the doping element in any heavily doped region to the maximum doping concentration of the doping element in the heavily doped region is greater than or equal to 30% and less than or equal to 100% within the depth range of 1 micron. At the moment, the series resistance is reduced, the filling factor is improved, meanwhile, the recombination of carriers is also reduced, the light quantum response of the solar cell is improved, the short-circuit current density is improved, and the conversion efficiency of the solar cell is further effectively improved.
In one embodiment, the doping concentration of the doping element in the heavily doped region is greater than or equal to 5×10 18 cm -3 And less than or equal to 3X 10 19 cm -3 . In this case, the series resistance can be further reduced, and the fill factor can be improved.
In one embodiment, the doping concentration of the doping element in the lightly doped region is greater than or equal to 1.0X10 18 cm -3 And less than or equal to 1.0X10 19 cm -3 . At this time, the recombination of carriers can be further reduced, the optical quantum response of the solar cell can be improved, and the short-circuit current density can be improved.
In one implementation, at a depth of 0.6 microns in the heavily doped region, the ratio of the doping concentration of the doping element in the heavily doped region to the doping concentration of the doping element in the lightly doped region is greater than the ratio of the maximum doping concentration of the doping element in the heavily doped region to the maximum doping concentration of the doping element in the lightly doped region.
In one implementation, processing a first side of a semiconductor substrate to form a dopant source layer includes: a first side of the semiconductor substrate is subjected to diffusion treatment to form a doping source layer. The doping source layer includes a first doping layer and a second doping layer formed on the first doping layer. The temperature of the diffusion treatment is 750 ℃ or higher and 1000 ℃ or lower. The diffusion treatment time is more than 0min and less than or equal to 120min, and the doping source adopted in the diffusion treatment comprises a III group source.
In one implementation, the group iii source is a boron source and the second doped layer is a borosilicate glass layer. The borosilicate glass layer has a thickness greater than 0nm and less than or equal to 50nm. The concentration of the doping element in the first doped layer is greater than or equal to 1.0X10 19 cm -3 And less than or equal to 5.0X10 20 cm -3 。
Under the condition of adopting the technical scheme, under the comprehensive action of diffusion treatment and laser irradiation process, the doping concentration of the doping element in the semiconductor substrate is improved. Meanwhile, compared with the mode of directly doping boron by utilizing laser in the prior art, the method can reduce or avoid boron atoms from being enriched in the borosilicate glass layer or reduce or avoid the boron atoms from being enriched in the surface of the semiconductor substrate to form a dead layer so as to reduce metal recombination. Further, since the thickness of the borosilicate glass layer is greater than 0nm and less than or equal to 50nm. The borosilicate glass layer can play a role in protecting the solar cell in the subsequent treatment process, so that the risk of etching the selective emitter is reduced, and the quality of the solar cell is ensured.
In one implementation, the laser wavelength of the laser irradiation process is greater than or equal to 300nm and less than or equal to 1500nm.
In one implementation, the laser power of the laser irradiation process is greater than or equal to 20 watts and less than or equal to 500 watts.
In one implementation, the laser processing speed of the laser irradiation process is greater than or equal to 20m/s and less than or equal to 60m/s.
In one implementation, the spot of the laser irradiation process is a rectangular spot, the width of the rectangular spot being greater than or equal to 30 microns and less than or equal to 120 microns. The ratio of the length of the rectangular light spot to the width of the rectangular light spot is greater than or equal to 1 and less than or equal to 1.5.
Under the condition of adopting the technical scheme, compared with square light spots with the same width, the area for processing the square light spots is larger in the same time, and the processing efficiency is improved. Meanwhile, when the laser engraving speed is improved by utilizing the rectangular light spots, gaps between two adjacent rectangular light spots can be reduced or avoided, so that faults of laser energy are reduced, the processing efficiency is improved, the sheet resistance is reduced, and the productivity is improved.
In one implementation, the overlapping ratio of two adjacent light spots in the light spot of the laser irradiation process is greater than 0% and less than 100%.
Under the condition of adopting the technical scheme, for the area needing laser irradiation process treatment, laser energy is accumulated in the area, so that the temperature reaches the requirement in a shorter time, the damage of laser to the suede is reduced, and the processing efficiency is further improved.
In a second aspect, the invention also provides a solar cell. The solar cell includes: a semiconductor substrate having opposite first and second sides. The semiconductor device comprises a heavily doped region and a lightly doped region, wherein the heavily doped region and the lightly doped region are formed on the first surface of the semiconductor substrate, and the lightly doped region is positioned on one side of the heavily doped region. Wherein the ratio of the maximum doping concentration of the doping element in the heavily doped region to the maximum doping concentration of the doping element in the lightly doped region is greater than or equal to 1 and less than or equal to 3. The ratio of the doping concentration of the doping element in any heavily doped region to the maximum doping concentration of the doping element in the heavily doped region is greater than or equal to 30% and less than or equal to 100% within the depth range of 1 micron.
Compared with the prior art, in the solar cell provided by the invention, although the formed doping source layer is of a whole layer structure, the doping source layer is subjected to regional treatment by adopting a laser irradiation process. At this time, only the doping element in the local region of the doping source layer diffuses into the semiconductor substrate. The doping element in the region of the doping source layer which is not treated by the laser irradiation process is not diffused into the semiconductor substrate, and remains in the doping source layer. Based on this, the effect on the remaining dopant source layer (i.e., the lightly doped region) during the formation of the heavily doped region is less or no, improving the performance of the solar cell compared to the prior art. Further, there is no second diffusion compared to the prior art, and thus the impact on the lightly doped region is also reduced. Still further, since the ratio of the maximum doping concentration of the doping element in the heavily doped region to the maximum doping concentration of the doping element in the lightly doped region is greater than or equal to 1 and less than or equal to 3. The ratio of the doping concentration of the doping element in any heavily doped region to the maximum doping concentration of the doping element in the heavily doped region is greater than or equal to 30% and less than or equal to 100% within the depth range of 1 micron. At the moment, the series resistance is reduced, the filling factor is improved, meanwhile, the recombination of carriers is also reduced, the light quantum response of the solar cell is improved, the short-circuit current density is improved, and the conversion efficiency of the solar cell is further effectively improved.
In one embodiment, the doping concentration of the doping element in the heavily doped region is greater than or equal to 5×10 18 cm -3 And less than or equal to 3X 10 19 cm -3 . In this case, the series resistance can be further reduced, and the fill factor can be improved.
In one embodiment, the doping concentration of the doping element in the lightly doped region is greater than or equal to 1.0X10 18 cm -3 And less than or equal to 1.0X10 19 cm -3 . At this time, the recombination of carriers can be further reduced, the optical quantum response of the solar cell can be improved, and the short-circuit current density can be improved.
In one implementation, at a depth of 0.6 microns in the heavily doped region, the ratio of the doping concentration of the doping element in the heavily doped region to the doping concentration of the doping element in the lightly doped region is greater than the ratio of the maximum doping concentration of the doping element in the heavily doped region to the maximum doping concentration of the doping element in the lightly doped region.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention and do not constitute a limitation on the invention. In the drawings:
FIG. 1 is a schematic diagram of a rectangular spot in an embodiment of the present invention;
FIG. 2 is a schematic diagram of a square spot in the prior art;
FIG. 3 is a schematic diagram of a laser line formed by a plurality of rectangular spots according to an embodiment of the present invention;
fig. 4 is a graph showing the relationship between the doping concentration and the doping depth of the doping elements in the heavily doped region and the lightly doped region according to the embodiment of the present invention.
Reference numerals:
1-square light spot, 2-rectangular light spot and 3-laser line.
Detailed Description
In order to make the technical problems, technical schemes and beneficial effects to be solved more clear, the invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
It will be understood that when an element is referred to as being "mounted" or "disposed" on another element, it can be directly on the other element or be indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or be indirectly connected to the other element.
Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature. In the description of the present invention, the meaning of "a plurality" is two or more, unless explicitly defined otherwise. The meaning of "a number" is one or more than one unless specifically defined otherwise.
In the description of the present invention, it should be understood that the directions or positional relationships indicated by the terms "upper", "lower", "front", "rear", "left", "right", etc., are based on the directions or positional relationships shown in the drawings, are merely for convenience of describing the present invention and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the present invention.
In the description of the present invention, it should be noted that, unless explicitly specified and limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be either fixedly connected, detachably connected, or integrally connected, for example; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communicated with the inside of two elements or the interaction relationship of the two elements. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art according to the specific circumstances.
With the rapid development of global economy, serious ecological environment damage and extreme climate occurrence are caused by the massive consumption of resources such as traditional petroleum, coal, natural gas and the like, so that energy and environment problems are attracting more and more attention. How to make up for the gap of energy sources and improve the environment becomes an issue of sustainable development of human beings, solar energy is an inexhaustible clean energy source, and photovoltaic power generation by using solar cells becomes the fastest research field in recent years. In order to improve the proportion of photovoltaic power generation, cost reduction and effect improvement are two main lines of photovoltaic manufacture, factors influencing the photoelectric conversion efficiency of the solar cell include diffusion and metallization, and too high diffusion concentration is beneficial to screen printing electrodes and well contacts with silicon-based electrodes, but reduces the photon absorption efficiency, and higher defect density reduces the short-circuit current and open-circuit voltage of the cell. While a lower diffusion concentration increases the light quantum response of the battery and increases the short-circuit current density, it increases the contact resistance and decreases the fill factor. TOPCon (Tunnel Oxide Passivated Contact solar cell, tunnel oxide passivation contact solar cell) technology is one of the most potential novel high-efficiency cell technologies due to its extremely high compatibility of process routes with conventional PERC cell production lines and its obvious efficiency gains. TOPCon cells are front-side prepared with boron diffusion, and superposition of selective emitter (Selective Emitter, abbreviated as SE) technology is one of the main means of front-side recombination drop and cell efficiency improvement at present.
In the prior art, a laser doping method, a mask method and a boron paste printing co-diffusion method are generally adopted for preparing the selective emitter.
Specifically, as for the laser doping method, the laser doping method is to use energy of laser to secondarily push a doping source in phosphosilicate glass (abbreviated as PSG) or borosilicate glass (Borosilicate glass, abbreviated as BSG) to form a heavily doped region. The regions not subjected to laser treatment form shallow doped regions. For example, the P-type battery laser SE is manufactured by melting the surface of a silicon wafer by laser pulse, enabling phosphorus atoms in the PSG covered on the top of an emitter to enter the surface layer of the silicon wafer, doping the phosphorus atoms to replace the silicon atoms after solidification, and forming a doped layer with high concentration and high impurity activation rate on the laser melting layer.
However, when the SE structure is prepared by laser doping, the power, frequency, etc. of the laser need to be precisely controlled, and damage caused by the laser is unavoidable. Further, for N-type cells laser boron direct doping, on the one hand the solid solubility of boron atoms in BSG is greater than in silicon, resulting in easier enrichment of boron atoms in BSG. On the other hand, boron atoms doped into the silicon wafer are concentrated on the surface of the silicon wafer due to lattice mismatch with silicon, so that a dead layer is formed, and serious recombination is caused. Therefore, the concentration of the boron atoms directly doped by the laser is low, so that the contact resistance and metal recombination of a heavily doped region are difficult to reduce, and the open circuit voltage is not easy to improve. Meanwhile, the doping is carried out by improving the laser energy, ion sputtering can be generated, the heavily doped region is caused to be epitaxial, and damage and a composite center can be formed on the surface of the suede by the excessively high energy, so that the open voltage and the contact resistance of the battery are affected.
For the mask method, firstly, a mask is prepared, an electrode window is formed through laser ablation or photoetching, and selective doping is realized by utilizing the difference of doping effects of a doping source in a masked area and a non-masked area. For example, in the secondary diffusion: the first boron expansion (light expansion) and the laser grooving removes the gate line position BSG (heavy expansion area). And (3) carrying out secondary heavy expansion, wherein the light expansion area is blocked by BSG, so that a local heavy doping is realized to finish an SE structure.
However, for the two diffusions in the mask method, electrode regions and non-electrode regions with different doping concentrations are respectively formed, and the process has the disadvantages of excessively long process time, excessively high cost and great influence on productivity. And, multiple high temperature diffusions can affect the quality of the substrate, resulting in a loss of cell efficiency of the finally formed solar cell. Further, the uniformity of the sheet resistance of the low doped region is not easily controlled. And interference influence exists between the two boron expansion processes, and particularly, the light expansion curve is influenced by the second boron expansion because of the high-temperature process. In addition, the scheme has high requirements on laser (nondestructive film opening is needed) and increases equipment cost.
For boron paste printing co-diffusion method, boron paste printing is adoptedBrushing the position of the grid line, and then carrying liquid BBr with nitrogen 3 Tubular co-diffusion was performed. However, for boron paste printing co-diffusion, the line width cannot be precisely controlled due to boron paste epitaxy at high temperature, and residual substances at the gate line after high temperature are difficult to clean.
In order to solve the technical problems in the foregoing part, in a first aspect, an embodiment of the present invention provides a method for manufacturing a solar cell.
The manufacturing method of the solar cell comprises the following steps:
first, a semiconductor substrate is provided, the semiconductor substrate having opposite first and second sides.
In practical applications, the semiconductor substrate may be just a semiconductor substrate. The semiconductor substrate may be a silicon substrate, for example. The semiconductor substrate may be an intrinsic conductive substrate, an N-type conductive substrate, or a P-type conductive substrate in terms of conductivity type. Preferably, the semiconductor substrate is an N-type conductive substrate or a P-type conductive substrate. In terms of structure, the first surface of the semiconductor substrate can be a suede surface so as to improve the light trapping effect of the light-facing surface of the solar cell and further improve the utilization rate of the solar cell on light. Of course, the first side of the semiconductor substrate may also be planar. As for the second surface of the semiconductor substrate, it may be a polished surface or a textured surface, which is not particularly limited herein. In the embodiment of the invention, the semiconductor substrate is N-type monocrystalline silicon.
As one possible implementation, the semiconductor substrate is subjected to a cleaning process and to a texturing process of opposing first and second sides of the semiconductor substrate to form a textured structure.
Next, a first side of the semiconductor substrate is processed to form a dopant source layer.
Illustratively, the semiconductor substrate has a first side that is subjected to a diffusion process to form a dopant source layer. The doping source layer includes a first doping layer and a second doping layer formed on the first doping layer. The temperature of the diffusion treatment is 750 ℃ or higher and 1000 ℃ or lower. For example, the temperature may be 750 ℃, 800 ℃, 850 ℃, 900 ℃, 950 ℃, 1000 ℃, or the like. The diffusion treatment time is greater than 0min and less than or equal to 120min, for example, the diffusion treatment time may be 1min, 12min, 20min, 35min, 40min, 52min, 60min, 75min, 80min, 85min, 90min, 100min, 115min, 120min, or the like. Doping sources used in the diffusion process include group iii sources, which may be, for example, boron sources, gallium sources, indium sources, and the like.
In an alternative mode, the group iii source is a boron source, and the second doped layer is a borosilicate glass layer. The borosilicate glass layer has a thickness greater than 0nm and less than or equal to 50nm. For example, the borosilicate glass layer may have a thickness of 1nm, 5nm, 10nm, 15nm, 21nm, 25nm, 30nm, 35nm, 42nm, 48nm, 50nm, or the like. The concentration of the doping element in the first doped layer is greater than or equal to 1.0X10 19 cm -3 And less than or equal to 5.0X10 20 cm -3 . For example, the concentration of the doping element in the first doped layer may be 1.0X10 19 cm -3 、2.0×10 19 cm -3 、4.0×10 19 cm -3 、8.0×10 19 cm -3 、1.0×10 20 cm -3 、1.5×10 20 cm -3 、2.0×10 20 cm -3 、3.0×10 20 cm -3 Or 5.0X10 20 cm -3 Etc.
Under the condition of adopting the technical scheme, under the comprehensive action of diffusion treatment and laser irradiation process, the doping concentration of the doping element in the semiconductor substrate is improved. Meanwhile, compared with the mode of directly doping boron by utilizing laser in the prior art, the method can reduce or avoid boron atoms from being enriched in the borosilicate glass layer or reduce or avoid the boron atoms from being enriched in the surface of the semiconductor substrate to form a dead layer so as to reduce metal recombination. Further, since the thickness of the borosilicate glass layer is greater than 0nm and less than or equal to 50nm. The borosilicate glass layer can play a role in protecting the solar cell in the subsequent treatment process, so that the risk of etching the selective emitter is reduced, and the quality of the solar cell is ensured.
Specifically, in connection with the foregoing description, the boron-oxygen bonded chemical bonds in the borosilicate glass layer absorb the energy transferred by the laser and break, becoming boron atoms in a free state. Boron atoms migrate from the interior of the borosilicate glass layer toward the semiconductor substrate and into the semiconductor substrate. Boron atoms enriched on the surface of the semiconductor substrate (namely, boron atoms in the first doped layer) receive laser energy, and under the effect of high temperature, the boron atoms gradually diffuse into the semiconductor substrate due to the influence of concentration gradient.
In an alternative manner, the foregoing diffusion treatment on the first surface of the semiconductor substrate to form the doping source layer may be: placing a semiconductor substrate in a tube diffusion furnace, and diffusing boron source BCl under nitrogen and oxygen atmosphere 3 Or BBr 3 The temperature of the diffusion treatment is 750 ℃ or higher and 1000 ℃ or lower. The diffusion treatment time is more than 0min and less than or equal to 120min. At this time, a dopant source layer including a first dopant layer (i.e., doped p+ layer) and a second dopant layer (i.e., borosilicate glass layer) is formed. Illustratively, the temperature of the diffusion treatment may be 750 ℃, 800 ℃, 850 ℃, 900 ℃, 950 ℃, 1000 ℃, or the like. The diffusion treatment time may be 1min, 10min, 65min, 96min, 120min, or the like.
And then, carrying out regional treatment on the doped source layer by adopting a laser irradiation process to diffuse doping elements in the doped source layer into the semiconductor substrate so as to form a heavy doped region on one side of the first surface of the semiconductor substrate, wherein the rest doped source layer is a light doped region.
As one possible implementation, the laser wavelength of the laser irradiation process is greater than or equal to 300nm and less than or equal to 1500nm. For example, the laser wavelength may be 300nm, 400nm, 560nm, 700nm, 860nm, 900nm, 1000nm, 1200nm, 1500nm, or the like. For example, a continuous laser or a pulsed laser may be selected for processing.
As one possible implementation, the laser power of the laser irradiation process is greater than or equal to 20 watts and less than or equal to 500 watts. For example, the laser power may be 20 watts, 50 watts, 70 watts, 90 watts, 100 watts, 120 watts, 130 watts, 145 watts, 500 watts, or the like.
As one possible implementation, the laser processing speed of the laser irradiation process is greater than or equal to 20m/s and less than or equal to 60m/s. For example, the laser processing speed may be 20m/s, 25m/s, 30m/s, 35m/s, 40m/s, 45m/s, 50m/s, 55m/s, 60m/s, or the like.
Referring to fig. 1 and 2, in the actual use process, a focused light spot of the laser on the surface of the semiconductor substrate is a gaussian light spot or a flat-top light spot, and a rectangular light spot 2 is formed on the surface of the semiconductor substrate through a shaping mirror. The width W1 of the rectangular spot 2 is greater than or equal to 30 microns and less than or equal to 120 microns. The ratio of the length L1 of the rectangular light spot to the width W1 of the rectangular light spot is greater than or equal to 1 and less than or equal to 1.5. For example, the width W1 of the rectangular spot may be 30 microns, 40 microns, 45 microns, 50 microns, 60 microns, 70 microns, 80 microns, 90 microns, 100 microns, 110 microns, 120 microns, or the like. The ratio may be 1, 1.05, 1.1, 1.2, 1.3, 1.4, 1.5, etc.
Under the condition of adopting the technical scheme, compared with the square light spots 1 with the same width, the area for processing the square light spots 2 is larger in the same time, and the processing efficiency is improved. Meanwhile, when the laser engraving speed is improved by utilizing the rectangular light spots 2, gaps between two adjacent rectangular light spots 2 can be reduced or avoided, so that faults of laser energy are reduced, the processing efficiency is improved, the sheet resistance is reduced, and the productivity is improved. Further, in the embodiment of the invention, rectangular light spots are adopted, and the energy of a single rectangular light spot is controlled to ensure that the energy of the single rectangular light spot does not damage a suede.
Referring to fig. 3, as one possible implementation, the overlapping ratio of two adjacent light spots in the light spots of the laser irradiation process is greater than 0% and less than 100%; the number of times the spot is irradiated at the same position is greater than or equal to 1. For example, the overlap ratio may be 1%,5%,10%,20%,30%,40%,50%, 52%, 65%, 80%, 90%, or the like. The number of irradiation times may be 1, 2, 4, etc. At this time, for the region to be treated by the laser irradiation process, laser energy is accumulated in the region so that the temperature reaches the requirement in a short time, and boron atoms migrate into the semiconductor substrate, thereby improving the processing efficiency. The laser line formed by the above-mentioned light spots is continuous, and the width W2 of the laser line 3 is 30 micrometers or more and 120 micrometers or less. For example, the width W2 of the laser line 3 may be 30 microns, 40 microns, 45 microns, 50 microns, 60 microns, 70 microns, 80 microns, 90 microns, 100 microns, 110 microns, 120 microns, or the like.
Next, oxidation treatment is performed on the semiconductor substrate, the heavily doped region and the lightly doped region to form a selective emitter on the first face of the semiconductor substrate.
Illustratively, the semiconductor substrate, the heavily doped region, and the lightly doped region are advanced and oxidized at an elevated temperature using a tube furnace to form a selective emitter at a first side of the semiconductor substrate. Wherein the temperature of oxidation is greater than or equal to 600 ℃ and less than or equal to 1200 ℃. For example, the temperature of oxidation may be 600 ℃, 700 ℃, 800 ℃, 900 ℃, 1000 ℃, 1100 ℃, 1200 ℃, or the like. The time of the oxidation process is more than 0min and less than or equal to 240min. For example, the time of the oxidation process may be 1min, 40min, 80min, 100min, 120min, 140min, 180min, 200min, 220min, 240min, or the like.
Wherein, referring to fig. 4, the ratio of the maximum doping concentration of the doping element in the heavily doped region to the maximum doping concentration of the doping element in the lightly doped region is greater than or equal to 1 and less than or equal to 3. For example, the ratio may be 1, 1.2, 1.5, 1.8, 2, 2.3, 2.5, 2.8, or 3, etc. The ratio of the doping concentration of the doping element in any heavily doped region to the maximum doping concentration of the doping element in the heavily doped region is greater than or equal to 30% and less than or equal to 100% within the depth range of 1 micron. For example, the ratio may be 30%, 42%, 55%, 67%, 80%, 95%, 100%, or the like.
In the method for manufacturing the solar cell provided by the embodiment of the invention, the formed doped source layer has a whole layer structure, but the doped source layer is subjected to regional treatment by adopting a laser irradiation process. At this time, only the doping element in the local region of the doping source layer diffuses into the semiconductor substrate. The doping element in the region of the doping source layer which is not treated by the laser irradiation process is not diffused into the semiconductor substrate, and remains in the doping source layer. Based on this, the effect on the remaining dopant source layer (i.e., the lightly doped region) during the formation of the heavily doped region is less or no, improving the performance of the solar cell compared to the prior art. Further, there is no second diffusion compared to the prior art, and thus the impact on the lightly doped region is also reduced. Still further, since the ratio of the maximum doping concentration of the doping element in the heavily doped region to the maximum doping concentration of the doping element in the lightly doped region is greater than or equal to 1 and less than or equal to 3. The ratio of the doping concentration of the doping element in any heavily doped region to the maximum doping concentration of the doping element in the heavily doped region is greater than or equal to 30% and less than or equal to 100% within the depth range of 1 micron. At the moment, the series resistance is reduced, the filling factor is improved, meanwhile, the recombination of carriers is also reduced, the light quantum response of the solar cell is improved, the short-circuit current density is improved, and the conversion efficiency of the solar cell is further effectively improved.
Referring to fig. 4, in the embodiment of the present invention, the doping concentration of the doping element in the heavily doped region increases from the surface of the semiconductor substrate to the inside of the semiconductor substrate, and then gradually decreases. As a possible implementation manner, the doping concentration of the doping element in the heavily doped region is greater than or equal to 5×10 18 cm -3 And less than or equal to 3X 10 19 cm -3 . For example, the doping concentration may be 5×10 18 cm -3 、6×10 18 cm -3 、8×10 18 cm -3 、9×10 18 cm -3 、1×10 19 cm -3 、1.2×10 19 cm -3 、2×10 19 cm -3 、2.3×10 19 cm -3 Or 3X 10 19 cm -3 Etc. In this case, the series resistance can be further reduced, and the fill factor can be improved.
Referring to fig. 4, in the embodiment of the present invention, the doping concentration of the doping element in the lightly doped region tends to increase from the surface of the semiconductor substrate to the inside of the semiconductor substrate, and then decrease slowly. As one possible implementation, the doping concentration of the doping element in the lightly doped region is greater than or equal to 1.0x10 18 cm -3 And is smaller than orEqual to 1.0X10 19 cm -3 . For example, the doping concentration may be 1.0X10 18 cm -3 、1.6×10 18 cm -3 、2.8×10 18 cm -3 、3.9×10 18 cm -3 、4.5×10 18 cm -3 、7.6×10 18 cm -3 、8.2×10 18 cm -3 、9.3×10 18 cm -3 Or 1.0X10 19 cm -3 Etc. At this time, the recombination of carriers can be further reduced, the optical quantum response of the solar cell can be improved, and the short-circuit current density can be improved.
From the above, the doping concentration of the doping element in the heavily doped region and the doping concentration of the doping element in the lightly doped region can be controlled independently, and at this time, the ratio of the maximum doping concentration of the doping element in the heavily doped region to the maximum doping concentration of the doping element in the lightly doped region is easily greater than or equal to 1 and less than or equal to 3. Further, compared with the prior art, the doping concentration and the doping amount of the doping element in the heavily doped region are improved, and the doping concentration of the doping element in the lightly doped region is reduced.
As a possible implementation, referring to fig. 4, at a depth of 0.6 μm of the heavily doped region, a ratio of a doping concentration of the doping element in the heavily doped region to a doping concentration of the doping element in the lightly doped region is greater than a ratio of a maximum doping concentration of the doping element in the heavily doped region to a maximum doping concentration of the doping element in the lightly doped region.
As a possible implementation manner, the method for manufacturing the solar cell further includes the following steps:
the second side (backlight side) of the semiconductor substrate formed with the selective emitter is subjected to a polishing process using a chain machine and a slot machine to remove the PN junction of the second side and the edge of the semiconductor substrate. As for the specific processing procedure, the agent and the like used may refer to the prior art, and are not particularly limited herein.
A tunneling layer is formed on a second surface of the semiconductor substrate.
As for the material, thickness, etc. of the tunneling layer may be set according to practical situations, and are not particularly limited herein. Illustratively, the tunneling layer material may include one or more of silicon oxide, aluminum oxide, titanium oxide, hafnium oxide, gallium oxide, tantalum pentoxide, niobium pentoxide, silicon nitride, silicon carbonitride, aluminum nitride, titanium carbide nitride.
Next, a doped polysilicon layer is formed over the tunneling layer.
The doped polysilicon layer may be a phosphorus doped polysilicon layer, and may be doped with other substances, which is not particularly limited herein.
The chemical passivation of the tunneling layer and the field passivation of the doped polysilicon layer can significantly reduce the recombination degree of the semiconductor substrate surface. Meanwhile, the tunneling layer can also ensure the effective tunneling of multiple electrons, the doped polysilicon layer can obviously improve the conductivity of photo-generated carriers, and further the open-circuit voltage and the filling factor of the tunneling oxide layer passivation contact battery can be improved.
Next, the polysilicon and borosilicate glass layers around the first side (light receiving side) of the semiconductor substrate and the phosphor-expanded glass layers on the second side of the semiconductor substrate are removed using a chain machine and a slot machine. As for the specific processing procedure, the agent and the like used may refer to the prior art, and are not particularly limited herein.
Next, a passivation layer is formed on the first side of the semiconductor substrate.
As for the material, thickness, etc. of the passivation layer may be set according to practical situations, and are not particularly limited herein. By way of example, the material of the passivation layer may include one or more of silicon nitride, hydrogen-containing silicon nitride, silicon oxide, silicon oxynitride, aluminum oxide, zinc oxide, hafnium oxide.
Next, an anti-reflection layer is formed on the passivation layer.
As for the material, thickness, etc. of the antireflection layer may be set according to actual conditions, and are not particularly limited herein. Illustratively, the material of the anti-reflection layer may include one or more of silicon nitride, silicon nitride containing hydrogen, silicon oxide, silicon oxynitride, and aluminum oxide.
Next, electrodes are prepared on the first and second sides of the semiconductor substrate by a printing device.
The electrode is connected with the heavily doped region on the first surface of the semiconductor substrate, and the region between the electrodes is a lightly doped region.
In summary, the manufacturing method of the solar cell provided by the embodiment of the invention is used for obtaining the heavily doped region and the lightly doped region, has simple process and low equipment investment, reduces the cost compared with the prior art, saves the process time and improves the productivity. Furthermore, the invention only relates to a one-time diffusion process, compared with the prior art, the method reduces the influence on the quality of the semiconductor substrate and improves the cell efficiency of the finally formed solar cell. Still further, since the present invention does not require laser dicing, there is no need to have an excessively high requirement for laser. In addition, the invention does not need to print boron paste, so the problem that the line width cannot be accurately controlled due to boron paste epitaxy and the residual substances at the gate line after high temperature are difficult to clean is solved.
In a second aspect, the embodiment of the invention further provides a solar cell. Referring to fig. 4, the solar cell includes: a semiconductor substrate having opposite first and second sides. The semiconductor device comprises a heavily doped region and a lightly doped region, wherein the heavily doped region and the lightly doped region are formed on the first surface of the semiconductor substrate, and the lightly doped region is positioned on one side of the heavily doped region. Wherein the ratio of the maximum doping concentration of the doping element in the heavily doped region to the maximum doping concentration of the doping element in the lightly doped region is greater than or equal to 1 and less than or equal to 3. For example, the ratio may be 1, 1.2, 1.5, 1.8, 2, 2.3, 2.5, 2.8, or 3, etc. The ratio of the doping concentration of the doping element in any heavily doped region to the maximum doping concentration of the doping element in the heavily doped region is greater than or equal to 30% and less than or equal to 100% within the depth range of 1 micron. For example, the ratio may be 30%, 42%, 55%, 67%, 80%, 95%, 100%, or the like.
In the solar cell provided by the embodiment of the invention, although the formed doped source layer is of a whole layer structure, the doped source layer is subjected to regional treatment by adopting a laser irradiation process. At this time, only the doping element in the local region of the doping source layer diffuses into the semiconductor substrate. The doping element in the region of the doping source layer which is not treated by the laser irradiation process is not diffused into the semiconductor substrate, and remains in the doping source layer. Based on this, the effect on the remaining dopant source layer (i.e., the lightly doped region) during the formation of the heavily doped region is less or no, improving the performance of the solar cell compared to the prior art. Further, there is no second diffusion compared to the prior art, and thus the impact on the lightly doped region is also reduced. Still further, since the ratio of the maximum doping concentration of the doping element in the heavily doped region to the maximum doping concentration of the doping element in the lightly doped region is greater than or equal to 1 and less than or equal to 3. The ratio of the doping concentration of the doping element in any heavily doped region to the maximum doping concentration of the doping element in the heavily doped region is greater than or equal to 30% and less than or equal to 100% within the depth range of 1 micron. At the moment, the series resistance is reduced, the filling factor is improved, meanwhile, the recombination of carriers is also reduced, the light quantum response of the solar cell is improved, the short-circuit current density is improved, and the conversion efficiency of the solar cell is further effectively improved.
As a possible implementation manner, the doping concentration of the doping element in the heavily doped region is greater than or equal to 5×10 18 cm -3 And less than or equal to 3X 10 19 cm -3 . For example, the doping concentration may be 5×10 18 cm -3 、6×10 18 cm -3 、8×10 18 cm -3 、9×10 18 cm -3 、10×10 18 cm -3 、1.2×10 19 cm -3 、2×10 19 cm -3 、2.3×10 19 cm -3 Or 3X 10 19 cm -3 Etc. In this case, the series resistance can be further reduced, and the fill factor can be improved.
As one possible implementation, the doping concentration of the doping element in the lightly doped region is greater than or equal to 1.0x10 18 cm -3 And less than or equal to 1.0X10 19 cm -3 . For example, the doping concentration may be 1.0X10 18 cm -3 、1.6×10 18 cm -3 、2.8×10 18 cm -3 、3.9×10 18 cm -3 、4.5×10 18 cm -3 、7.6×10 18 cm -3 、8.2×10 18 cm -3 、9.3×10 18 cm -3 Or 1.0X10 19 cm -3 Etc. At this time, the recombination of carriers can be further reduced, the optical quantum response of the solar cell can be improved, and the short-circuit current density can be improved.
As one possible implementation, at a depth of 0.6 μm of the heavily doped region, the ratio of the doping concentration of the doping element in the heavily doped region to the doping concentration of the doping element in the lightly doped region is greater than the ratio of the maximum doping concentration of the doping element in the heavily doped region to the maximum doping concentration of the doping element in the lightly doped region.
In the description of the above embodiments, particular features, structures, materials, or characteristics may be combined in any suitable manner in any one or more embodiments or examples.
The foregoing is merely illustrative of the present invention, and the present invention is not limited thereto, and any person skilled in the art will readily recognize that variations or substitutions are within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (11)
1. A method of manufacturing a solar cell, comprising:
providing a semiconductor substrate; the semiconductor substrate has opposite first and second sides;
processing a first surface of the semiconductor substrate to form a doping source layer;
carrying out regional treatment on the doped source layer by adopting a laser irradiation process, so that doping elements in the doped source layer are diffused into the semiconductor substrate to form a heavily doped region on the side of the first surface of the semiconductor substrate; the rest of the doping source layer is a lightly doped region;
oxidizing the semiconductor substrate, the heavily doped region and the lightly doped region to form a selective emitter on a first surface of the semiconductor substrate;
the ratio of the maximum doping concentration of the doping element in the heavily doped region to the maximum doping concentration of the doping element in the lightly doped region is greater than or equal to 1 and less than or equal to 3;
the heavily doped region is within a depth range of 1 micrometer, and the ratio of the doping concentration of the doping element in any heavily doped region to the maximum doping concentration of the doping element in the heavily doped region is greater than or equal to 30% and less than or equal to 100%.
2. The method according to claim 1, wherein a doping concentration of the doping element in the heavily doped region is 5×10 or more 18 cm -3 And less than or equal to 3X 10 19 cm -3 。
3. The method according to claim 1 or 2, wherein a doping concentration of the doping element in the lightly doped region is 1.0x10 or more 18 cm -3 And less than or equal to 1.0X10 19 cm -3 。
4. The method of claim 1 or 2, wherein a ratio of a doping concentration of a doping element in the heavily doped region to a doping concentration of a doping element in the lightly doped region is greater than a ratio of a maximum doping concentration of a doping element in the heavily doped region to a maximum doping concentration of a doping element in the lightly doped region at a depth of 0.6 μm of the heavily doped region.
5. The method of claim 1, wherein processing the first side of the semiconductor substrate to form a dopant source layer comprises:
performing diffusion treatment on a first surface of the semiconductor substrate to form a doped source layer;
the doping source layer comprises a first doping layer and a second doping layer; the second doped layer is formed on the first doped layer;
the temperature of the diffusion treatment is more than or equal to 750 ℃ and less than or equal to 1000 ℃; the diffusion treatment time is more than 0min and less than or equal to 120min; the doping source used for the diffusion process includes a group iii source.
6. The method of claim 5, wherein the group iii source is a boron source; the second doped layer is a borosilicate glass layer;
the thickness of the borosilicate glass layer is more than 0nm and less than or equal to 50nm; the concentration of the doping element in the first doping layer is greater than or equal to 1.0X10 19 cm -3 And less than or equal to 5.0X10 20 cm -3 。
7. The method for manufacturing a solar cell according to claim 1, wherein a laser wavelength of the laser irradiation process is 300nm or more and 1500nm or less;
the laser power of the laser irradiation process is more than or equal to 20 watts and less than or equal to 500 watts;
the laser processing speed of the laser irradiation process is more than or equal to 20m/s and less than or equal to 60m/s;
the light spots of the laser irradiation process are rectangular light spots; the width of the rectangular light spot is larger than or equal to 30 microns and smaller than or equal to 120 microns; the ratio of the length of the rectangular light spot to the width of the rectangular light spot is greater than or equal to 1 and less than or equal to 1.5;
the overlapping rate of two adjacent light spots in the light spots of the laser irradiation process is more than 0% and less than 100%.
8. A solar cell, comprising:
a semiconductor substrate having opposite first and second sides;
the light doped region is positioned at one side of the heavy doped region;
the ratio of the maximum doping concentration of the doping element in the heavily doped region to the maximum doping concentration of the doping element in the lightly doped region is greater than or equal to 1 and less than or equal to 3;
the heavily doped region is within a depth range of 1 micrometer, and the ratio of the doping concentration of the doping element in any heavily doped region to the maximum doping concentration of the doping element in the heavily doped region is greater than or equal to 30% and less than or equal to 100%.
9. The solar cell according to claim 8, wherein a doping concentration of the doping element in the heavily doped region is 5 x 10 or more 18 cm -3 And less than or equal to 3X 10 19 cm -3 。
10. The solar cell according to claim 8 or 9, wherein a doping concentration of a doping element in the lightly doped region is 1.0 x 10 or more 18 cm -3 And less than or equal to 1.0X10 19 cm -3 。
11. The solar cell according to claim 8 or 9, wherein a ratio of a doping concentration of a doping element in the heavily doped region to a doping concentration of a doping element in the lightly doped region is greater than a ratio of a maximum doping concentration of a doping element in the heavily doped region to a maximum doping concentration of a doping element in the lightly doped region at a depth of 0.6 μm of the heavily doped region.
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