CN115411138A - Preparation method of selective emitter and solar cell - Google Patents
Preparation method of selective emitter and solar cell Download PDFInfo
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- CN115411138A CN115411138A CN202110592048.6A CN202110592048A CN115411138A CN 115411138 A CN115411138 A CN 115411138A CN 202110592048 A CN202110592048 A CN 202110592048A CN 115411138 A CN115411138 A CN 115411138A
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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
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- 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
- H01L31/04—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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- 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 application discloses a preparation method of a selective emitter and a solar cell comprising the selective emitter. The preparation method sequentially comprises the following steps: carrying out diffusion of doping elements on the surface of the silicon substrate so as to form a diffusion layer and a silicon oxide layer on the surface of the silicon substrate from inside to outside; grooving a partial region of the surface of the silicon oxide layer on one surface of the silicon substrate by adopting laser, and enabling the groove bottom to reach the diffusion layer; removing the porous silicon in the laser grooving area and reserving at least part of laser damage; and performing secondary diffusion of the doping elements on the diffusion layer in the laser grooving region to enable the diffusion layer to comprise a light doping region with first doping concentration and a heavy doping region with second doping concentration. The selective emitter can improve the contact performance between the metal grid line electrode and the silicon substrate, and further improves the conversion efficiency of the corresponding solar cell.
Description
Technical Field
The present disclosure relates to the field of solar cells, and more particularly, to a method for manufacturing a selective emitter and a solar cell including the selective emitter.
Background
A solar cell is a photoelectric conversion device that directly generates electricity using sunlight, and can instantaneously output a voltage and generate a current in the presence of a circuit as long as it receives light under a certain illumination condition. Specifically, the solar cell comprises a semiconductor p-n junction, a new hole-electron pair is formed when the semiconductor p-n junction is illuminated, under the action of an electric field built in the p-n junction, photogenerated holes flow to a p region, photogenerated electrons flow to an n region, and current can be generated after an electric circuit is connected, namely a photoelectric effect, and the working principle of the solar cell is also disclosed.
In solar cells, homogeneous emitters were originally used, which however have the following disadvantages: when the semiconductor sheet resistance of the emitter region is higher, the emitter recombination is lower, and the metal grid line electrode recombination is higher; when the sheet resistance of the emitter region is low, the metal grid line electrode recombination is low, and the emitter recombination is high, which both affect the conversion efficiency of the solar cell. In this regard, a selective emitter solar cell has been further developed, that is, heavy doping is performed at the semiconductor substrate where the metal gate line electrodes are located, and light doping is performed at the positions between the electrodes, so as to optimize the emitter region. Therefore, the hole-electron pair recombination of the diffusion layer can be reduced, the contact resistance of the electrode and the substrate is reduced, and meanwhile, the emitter recombination and the metal grid line electrode recombination are both ensured to be at a lower level, so that the conversion efficiency of the solar cell is improved.
However, for the selective emitter solar cell, how to further improve the selective emitter preparation process to further improve the conversion efficiency of the solar cell has an important significance.
Disclosure of Invention
Aiming at the defects in the prior art, the application provides a preparation method of a selective emitter and a solar cell comprising the selective emitter. According to the preparation method of the selective emitter, surface damage and defects are manufactured through laser grooving at the position, where the metal grid line electrode is to be arranged, of the silicon substrate, then the degree of laser damage is adjusted, and secondary doping is carried out at the position of the groove, so that the selective emitter according to the application is obtained, the selective emitter can improve the contact performance between the metal grid line electrode and the silicon substrate, the contact resistance is reduced, and the conversion efficiency of a solar cell comprising the selective emitter is improved.
In order to achieve the above object, in a first aspect, the present application provides a method for preparing a selective emitter, which sequentially comprises the following steps:
carrying out diffusion of doping elements on the surface of a silicon substrate to form a diffusion layer and a silicon oxide layer on the surface of the silicon substrate from inside to outside, wherein the diffusion layer comprises doping elements with a first doping concentration;
grooving a partial region of the surface of the silicon oxide layer on one surface of the silicon substrate by adopting laser, and enabling the groove bottom to reach the diffusion layer;
removing the porous silicon in the laser grooving area and reserving at least part of laser damage; and
and carrying out secondary diffusion of the doping elements on the diffusion layer in the laser grooving region to enable the diffusion layer to comprise a light doping region with a first doping concentration and a heavy doping region with a second doping concentration, wherein the heavy doping region corresponds to the laser grooving region, and the second doping concentration is greater than the first doping concentration.
With reference to the first aspect, in one possible implementation manner, the removing of the porous silicon in the laser trench area and the retaining of at least part of the laser damage includes the following steps: KOH with the mass concentration of 1 to 5 percent and H with the mass concentration of 3 to 5 percent are adopted under the temperature condition of 60 to 80 DEG C 2 O 2 The solution of (2) etches the laser grooving region for 1min to 3min.
In another possible embodiment, with reference to the first aspect, the removing of the porous silicon in the laser trench area and the retaining of at least part of the laser damage includes: oxidizing the laser grooving area for 30-60 min at the temperature of 800-900 ℃ under the condition of oxygen atmosphere, and then cleaning for 3-6 min by adopting hydrofluoric acid with the mass concentration of 2-8%.
In a further possible implementation manner, with reference to the first aspect, the removing of the porous silicon in the laser trench area and the retaining of at least part of the laser damage includes: and irradiating the laser grooving area for 5-10 min by adopting plasma at the output power of 1000-1500W.
In a possible embodiment, when the silicon substrate is an N-type silicon substrate, the diffusion layer is a P + doping layer. Further, in a possible embodiment, the doping element is at least one of boron, aluminum, gallium or indium, preferably boron.
Further, under the P-type doping condition, the sheet resistance of the diffusion layer is 150-250 omega/sqr; the diffusion thickness of the diffusion layer is 0.4-0.8 μm; and the thickness of the silicon oxide layer is 0.07-0.11 μm.
Further, under the P-type doping condition, the sheet resistance of the lightly doped region is 150-250 omega/sqr, and the sheet resistance of the heavily doped region is 10-100 omega/sqr; and the thickness of the heavily doped region is 0.7-1.2 μm.
In a possible embodiment, when the silicon substrate is a P-type silicon substrate, the diffusion layer is an N + doped layer. Further, in a possible embodiment, the doping element is at least one of phosphorus, arsenic or antimony, preferably phosphorus.
Further, under the N-type doping condition, the sheet resistance of the diffusion layer is 150-250 omega/sqr; the diffusion thickness of the diffusion layer is 0.2-0.4 μm; and the thickness of the silicon oxide layer is 0.04 to 0.08 μm.
Further, under the N-type doping condition, the sheet resistance of the lightly doped region is 150-250 omega/sqr, and the sheet resistance of the heavily doped region is 10-100 omega/sqr; and the thickness of the heavily doped region is 0.4-1.0 μm.
In a possible embodiment, in combination with the first aspect, the diffusing in step (1) and the diffusing in step (4) are performed independently by any one or more methods of a high temperature diffusion process, a slurry doping process, or an ion implantation process.
In a second aspect, the present application provides a solar cell, which is made by a method comprising the steps of, in order:
texturing the surface of the silicon substrate;
preparing a selective emitter on the front surface of the silicon substrate according to the preparation method of the first aspect;
etching the front surface and the back surface of the silicon substrate to remove the silicon oxide layer;
performing single-side etching on the back surface of the silicon substrate to remove the diffusion layer;
depositing a passivation layer and/or an antireflection layer on the surface of the silicon substrate; and
and carrying out metallization treatment on the surface of the selective emitter and the back surface of the silicon substrate to obtain a front electrode and a back electrode, wherein the front electrode and the back electrode respectively penetrate through the antireflection layer and/or the passivation layer to form ohmic contact with the silicon substrate.
In a third aspect, the present application provides a solar cell, which is obtained by the preparation method of the second aspect, and includes a front electrode (metal grid line electrode), a front anti-reflection layer and/or a passivation layer, a selective emitter, a silicon substrate, a back passivation layer and a back electrode, which are sequentially arranged from top to bottom, the selective emitter, the silicon substrate, the back passivation layer and the back electrode being prepared according to the preparation method of the first aspect.
In a fourth aspect, the present application provides a photovoltaic module, the photovoltaic module comprises glass, a packaging material, at least one solar cell, the packaging material and a back plate, which are sequentially arranged from top to bottom.
The technical scheme that this application provided compares and has following beneficial effect at least in prior art:
according to the preparation method of the selective emitter, damage and defects are manufactured through laser grooving, then the damage of porous silicon left in the groove is removed, at least part of laser damage below the porous silicon is reserved, and finally a heavy doping area is formed at the grooving position, so that the selective emitter is obtained, the contact performance between a metal grid line electrode and a silicon substrate can be improved through the selective emitter, the contact resistance is reduced, and the conversion efficiency of a solar cell comprising the selective emitter is improved.
In the preparation process of the selective emitter, a low-cost simplified process scheme capable of realizing large-scale production is adopted, the preparation procedure is simple, the operation and the control are convenient and fast, the efficiency is high, particularly, the selective emitter is formed by a method of doping twice and laser grooving, surface defects are specially formed in a heavily doped region, certain laser damage is reserved, the contact resistance of a metal semiconductor is reduced, and the performance of the selective emitter is improved.
The solar cell according to the present application, which includes the above-described selective emitter, has high conversion efficiency.
Drawings
Fig. 1 is a schematic flow diagram of a method of fabricating a selective emitter according to an embodiment of the present application;
FIG. 2 is a Scanning Electron Microscope (SEM) image of a portion of a trench bottom of a silicon substrate after laser grooving but without removing porous silicon according to example 1 of the present application;
FIG. 3 is a Scanning Electron Microscope (SEM) image of another portion of the trench bottom of a silicon substrate after laser grooving but without removing porous silicon according to example 1 of the present application;
FIG. 4 is a Scanning Electron Microscope (SEM) image of a portion of the bottom of a trench of a silicon substrate after laser grooving and porous silicon removal according to example 1 of the present application;
fig. 5 is a Scanning Electron Microscope (SEM) image of another portion of the trench bottom of a silicon substrate after laser grooving and porous silicon removal according to example 1 of the present application.
Drawings
1. A silicon substrate; 2. a diffusion layer; 3. a silicon oxide layer; 4. a laser grooving region; 41. porous silicon; 42. laser damage; 5. a lightly doped region; 6. and a heavily doped region.
Detailed Description
In order to make the present application more clearly understood by those skilled in the art, the present application is described in further detail below with reference to examples and drawings, but it should be understood that the following examples are only preferred embodiments of the present application, and the scope of the present application is defined by the scope of the claims.
It should be understood that in the present application, the directional terms "front", "upper", "front" and the like refer to the direction corresponding to the side of the solar cell or the silicon substrate from which the solar cell is to be made facing or is to be made facing the light source; accordingly, the terms "back", "under", "back" and the like refer to the direction corresponding to the side of the solar cell or the silicon substrate from which the solar cell is to be made, which faces away or is to face away from the light source.
It will be understood that when an element is referred to as being "on" or "under" or the like in this application, it can be directly on or under another element or intervening elements may also be present.
It should be understood that in the present application, the units of sheet resistance may be expressed as "ohm/sq", "Ω/sq", or "Ω/sq", which all represent the same meaning and the same unit measure, and may be used interchangeably.
In a first aspect, the present application provides a method for preparing a selective emitter, which sequentially comprises the following steps:
carrying out diffusion of doping elements on the surface of a silicon substrate to form a diffusion layer and a silicon oxide layer on the surface of the silicon substrate from inside to outside, wherein the diffusion layer comprises doping elements with a first doping concentration;
grooving a partial region of the surface of the silicon oxide layer on one surface of the silicon substrate by adopting laser, and enabling the groove bottom to reach the diffusion layer;
removing the porous silicon in the laser grooving area and reserving at least part of laser damage; and
and carrying out secondary diffusion of the doping elements on the diffusion layer in the laser grooving region to enable the diffusion layer to comprise a light doping region with a first doping concentration and a heavy doping region with a second doping concentration, wherein the heavy doping region corresponds to the laser grooving region, and the second doping concentration is greater than the first doping concentration.
In the present application, according to the preparation method of the selective emitter of the present application, element doping is performed on the surface of the silicon substrate to form a diffusion layer and a silicon oxide layer, then laser grooving penetrates through the silicon oxide layer to produce surface damage and defects on the diffusion layer, then the degree of laser damage is adjusted (i.e. a porous silicon structure formed in the groove after the laser grooving is removed, but at least part of laser burning damage of the surface below the porous silicon structure is remained), and finally secondary element doping is performed at the grooving position (to form a heavily doped region), so that the selective emitter of the present application is obtained. The selective emitter can improve the contact performance between the metal grid line electrode and the silicon substrate, reduce the contact resistance and further improve the conversion efficiency of the solar cell comprising the selective emitter.
In the present application, the silicon substrate may be any one of a polycrystalline silicon substrate, a single crystal silicon substrate, or a single crystal-like silicon substrate, which is suitable for the technical solution of the present application, and thus, a specific type of the silicon substrate is not particularly limited in the embodiments of the present application.
In the step of diffusing the doping elements on the surface of the silicon substrate, the diffusion can be performed by any one or more methods of a high-temperature diffusion process, a slurry doping process or an ion implantation process, which are all applicable to the technical scheme of the application, and preferably, the high-temperature diffusion process is adopted, so that the operation is simple and the cost is low. Furthermore, the diffusion of the doping elements of the present application is carried out at least on the side of the silicon substrate, which may be the front side intended to face the sunlight, in order to facilitate the preparation of a selective emitter. Whether the diffusion occurs on the back surface of the silicon substrate opposite to the front surface or not is not particularly limited in the present application, but the back surface is not masked in general, that is, both surfaces of the silicon substrate are diffused at the same time, so that the masking process can be reduced, the cost can be reduced, and the diffusion layer and the silicon oxide layer on the back surface and the silicon oxide layer on the front surface can be removed by etching in the subsequent preparation process of the solar cell, so that the diffusion on both surfaces does not affect the performance of the solar cell.
The silicon oxide layer is formed on the outer side of the silicon substrate surface while forming a diffusion layer on the surface. The silicon oxide layer does not need to be removed in the preparation process of the selective emitter, and has the following purposes: the silicon oxide layer can be used as a blocking layer, and corresponding doping elements are blocked from being deposited in a diffusion layer area covered by the silicon oxide layer in the secondary diffusion process in the step (4), so that the area covered by the silicon oxide layer is ensured to keep higher sheet resistance, and a lightly doped area is formed.
In the present application, the silicon substrate may be a P-type silicon substrate or an N-type silicon substrate, which are suitable for the technical solution of the present application, and thus, the specific type of the silicon substrate is not limited in the embodiments of the present application.
Alternatively, when the silicon substrate is an N-type silicon substrate, it may be P-doped to form a P + doped layer (diffusion layer), and the doping element may be at least one of P-type elements such as boron, aluminum, gallium, or indium, and preferably boron.
Under the above P-type doping condition, the sheet resistance of the obtained diffusion layer may be 150 Ω/sqr-250 Ω/sqr, for example, 150 Ω/sqr, 160 Ω/sqr, 170 Ω/sqr, 180 Ω/sqr, 190 Ω/sqr, 200 Ω/sqr, 210 Ω/sqr, 220 Ω/sqr, 230 Ω/sqr, 240 Ω/sqr, 250 Ω/sqr, or other specific values in the range; the resulting diffusion thickness may be 0.4 μm to 0.8 μm, for example, 0.4 μm, 0.45 μm, 0.5 μm, 0.55 μm, 0.6 μm, 0.65 μm, 0.7 μm, 0.75 μm, 0.8 μm, or other specific values within the stated ranges; the thickness of the resulting silicon oxide layer may be 0.07 μm to 0.11. Mu.m, for example, 0.07 μm, 0.075 μm, 0.08 μm, 0.085. Mu.m, 0.09 μm, 0.095. Mu.m, 0.10. Mu.m, 0.105. Mu.m, 0.11. Mu.m, or other specific values within the above range.
Optionally, when the silicon substrate is a P-type silicon substrate, it is doped N-type to form an N + doped layer (diffusion layer), and the doping element may be at least one of N-type elements such as phosphorus, arsenic, or antimony, and is preferably phosphorus.
Under the N-type doping condition, the sheet resistance of the obtained diffusion layer can be 150 Ω/sqr to 250 Ω/sqr, for example, 150 Ω/sqr, 160 Ω/sqr, 170 Ω/sqr, 180 Ω/sqr, 190 Ω/sqr, 200 Ω/sqr, 210 Ω/sqr, 220 Ω/sqr, 230 Ω/sqr, 240 Ω/sqr, 250 Ω/sqr, or other specific values in the range; the resulting diffusion thickness may be 0.2 μm to 0.4 μm, for example, 0.2 μm, 0.25 μm, 0.3 μm, 0.35 μm, 0.4 μm, or other specific values within the stated range; the thickness of the resulting silicon oxide layer may be 0.04 μm to 0.08. Mu.m, for example, 0.04 μm, 0.045 μm, 0.05 μm, 0.055 μm, 0.06 μm, 0.065 μm, 0.07 μm, 0.075 μm, 0.08 μm, or other specific values within the above range.
By appropriately controlling the first doping concentration of the doping element of the P-type doping or the N-type doping, the diffusion layer can have the sheet resistance described above. In addition, the formed diffusion layer and the silicon substrate form a PN junction structure through doping of the type opposite to that of the silicon substrate, so that a photoelectric effect is generated.
And then, slotting a partial region of the surface of the silicon oxide layer on one surface of the silicon substrate by adopting laser, and enabling the slot bottom to reach the silicon substrate where the diffusion layer is located. The slotted region is a position where a selective emitter is to be formed and a metal gate line electrode is to be arranged. The energy of the laser is very concentrated, and extremely high temperature can be generated on an irradiation area, so that substances in the area are directly gasified and volatilized, and a groove is generated. Firing through laser irradiation, firing through the silicon oxide layer on the uppermost layer until the diffusion layer is exposed at the bottom of the groove, wherein if the oxide layer still exists at the bottom of the groove, the oxide layer can generate adverse effect on secondary diffusion of the doping elements after the step, and the firing is not needed to be continued after the diffusion layer is exposed at the bottom of the groove, so that energy can be wasted, and the diffusion layer which is too thin or even completely removed is not beneficial to the secondary diffusion.
Next, the porous silicon in the laser grooving region is removed and at least part of the laser damage is remained. Because the laser grooving is realized by heating and volatilizing irradiated substances, silicon (namely porous silicon) with a porous structure formed by incomplete volatilization or secondary condensation after volatilization is left on the groove bottom and the groove side wall, the structure is porous and fluffy, the surface area is large, the silicon is attached and accumulated on the outermost sides of the groove bottom and the groove side wall, and the silicon substrate (laser damage) with the inner side which is burnt and has uneven pits and compact structure is covered. Although the surface damage defect in the heavily doped region is generally considered by those skilled in the art to improve the contact performance between the metal electrode and the semiconductor substrate, it is found through research that the substrate surface with the porous silicon structure is not easy to passivate due to an excessively fluffy structure, and although the contact area with the metal electrode deposited on the surface is increased, the porous structure rather makes the recombination current larger, which has an adverse effect on the improvement of the conversion efficiency of the solar cell. Therefore, by removing the porous silicon structure, a part of depression and compact structure of the silicon substrate are still remained and damaged by laser firing, the contact area between the metal electrode and the semiconductor can be increased, the contact resistance is reduced, and the combined current with the metal electrode can be reduced, so that the conversion efficiency of the solar cell is further improved.
As a possible embodiment, the porous silicon structure present on the trench bottom and on the trench sidewalls can be removed and at least part of the laser damage after removal is retained; in another embodiment of the present application, the trench sidewalls may be masked with a masking agent in advance, and then only the porous silicon structure present on the trench bottom may be removed to expose at least a portion of the laser damage under the porous silicon of the trench bottom, and then the masking agent may be removed, thereby only the porous silicon of the trench bottom may be removed while the porous silicon on the trench sidewalls remains. The site for removing porous silicon can be selected as desired by those skilled in the art.
As a possible implementation, the removing the porous silicon in the laser trench opening region and retaining at least part of the laser damage may include the following steps: at 60-80 deg.cUnder the temperature condition, KOH with the mass concentration of 1-5 percent and H with the mass concentration of 3-5 percent are adopted 2 O 2 The solution is used for etching the laser grooving area for 1-3 min. Wherein the concentration of KOH and H are selected 2 O 2 The concentration of the silicon oxide is low, so that the integral oxidation of the solution is moderate, the porous silicon structure is fluffy and has large surface area, therefore, the reaction activity is strong, and the silicon substrate is easy to be oxidized and etched, but the surface area of the silicon substrate is relatively small, the structure is compact, the reaction activity and the speed are far inferior to those of the porous silicon and the porous silicon substrate is covered by the porous silicon, so the silicon substrate is difficult to be etched, the porous silicon and the silicon substrate show larger etching difference, and the cleaning of the porous silicon on the side wall and/or the bottom of the groove and the retention of laser burning damage traces are facilitated. In addition, the laser grooving area can be etched only by selectively adopting an area etching mode, the whole silicon substrate containing the laser grooving area can also be subjected to dip etching, and the part of the silicon substrate not subjected to laser grooving is not easy to be oxidized and etched because the silicon oxide layer is covered on the silicon substrate and the structure is also compact.
In another possible embodiment, the removing the porous silicon in the laser trench area and retaining at least part of the laser damage may include the following steps: oxidizing the laser grooving area for 30-60 min at the temperature of 800-900 ℃ under the condition of oxygen atmosphere, and then cleaning for 3-6 min by adopting hydrofluoric acid with the mass concentration of 2-8%. The relative surface area difference between the porous silicon on the side wall and/or the bottom of the groove and the silicon substrate at the laser burning damage trace is large, so that the reaction activity is obvious, and the porous silicon is on the surface layer and covers the silicon substrate at the laser burning damage trace, so most of the porous silicon is oxidized by oxygen firstly and then cleaned and removed by hydrofluoric acid, the oxidation degree of the silicon substrate is small, and the generated silicon oxide is completely removed in the subsequent hydrofluoric acid cleaning.
In addition, because the part of the silicon substrate not subjected to laser grooving is covered with the silicon oxide layer and is reinforced in the oxidation process, and the concentration of hydrofluoric acid is lower and the cleaning time is shorter, a part of the silicon oxide layer in the area not subjected to laser grooving still can be remained, and the effect of the silicon oxide layer is not influenced. For example, the silicon oxide layer formed during P-type doping may remain 0.06 μm to 0.09 μm thick after being cleaned by hydrofluoric acid, and the silicon oxide layer formed during N-type doping may remain 0.03 μm to 0.06 μm thick after being cleaned by hydrofluoric acid.
In one possible embodiment, the removing the porous silicon in the laser trench area and retaining at least part of the laser damage may include the following steps: and irradiating the laser grooving area for 5-10 min by adopting plasma at the output power of 1000-1500W. The output power of the plasma is low, so that the formed plasma is low in concentration and low in energy, the laser grooving region is irradiated in an area or the whole surface of one surface of the silicon substrate containing the laser grooving region is irradiated, the porous silicon structure is loose and is on the surface layer, so that the porous silicon structure is easy to react and remove, laser burning damage is covered by the porous silicon structure, the silicon substrate is not covered by the compact silicon oxide layer in the laser grooving region, obvious bombardment damage is avoided, and the irradiated silicon substrate does not need to be cleaned. The source of the plasma gas is not particularly limited as long as it can be ionized under appropriate conditions to generate plasma, and for example, an inert gas such as helium, neon, or argon, or another suitable gas such as nitrogen or ammonia may be used.
In the present application, the secondary diffusion is performed using the same type of doping element as the diffusion, i.e., when the diffusion is P-type doping, the secondary diffusion is also P-type doping; and when the diffusion is N-type doping, the secondary diffusion is also N-type doping. Through the secondary diffusion, the concentration (second doping concentration) of doping elements can be further improved on the basis of the doping (first doping concentration) at the diffusion layer in the laser grooving region, the sheet resistance of the region is reduced, and therefore the heavily doped region is formed, and the region without the secondary diffusion (namely the diffusion layer part between the laser grooving regions) is higher in sheet resistance due to the fact that the doping concentration of the region is lower relative to the heavily doped region, and therefore the region becomes a lightly doped region, and therefore the selective emitter according to the application can be formed.
Further, under the condition that the second diffusion is P-type doping, the sheet resistance of the obtained lightly doped region is also in the range of 150 Ω/sqr to 250 Ω/sqr, for example, 150 Ω/sqr, 160 Ω/sqr, 170 Ω/sqr, 180 Ω/sqr, 190 Ω/sqr, 200 Ω/sqr, 210 Ω/sqr, 220 Ω/sqr, 230 Ω/sqr, 240 Ω/sqr, 250 Ω/sqr, or other specific values in the range; the thickness of the resulting lightly doped region is also in the range of 0.4 μm to 0.8 μm, and may be, for example, 0.4 μm, 0.45 μm, 0.5 μm, 0.55 μm, 0.6 μm, 0.65 μm, 0.7 μm, 0.75 μm, 0.8 μm, or other specific values within the range; the sheet resistance of the obtained heavily doped region can be 10 Ω/sqr to 100 Ω/sqr, for example, 10 Ω/sqr, 15 Ω/sqr, 20 Ω/sqr, 25 Ω/sqr, 30 Ω/sqr, 35 Ω/sqr, 40 Ω/sqr, 45 Ω/sqr, 50 Ω/sqr, 55 Ω/sqr, 60 Ω/sqr, 65 Ω/sqr, 70 Ω/sqr, 75 Ω/sqr, 80 Ω/sqr, 85 Ω/sqr, 90 Ω/sqr, 95 Ω/sqr, 100 Ω/sqr, or other specific values in the range; and the resulting heavily doped region may have a thickness of 0.7 μm to 1.2 μm, for example, 0.7 μm, 0.75 μm, 0.8 μm, 0.85 μm, 0.9 μm, 0.95 μm, 1.0 μm, 1.05 μm, 1.1 μm, 1.15 μm, 1.2 μm, or other specific values within the range. Due to the influence of the second diffusion, the sheet resistance and the thickness of the resulting lightly doped region may be relatively greater than or equal to those of the corresponding diffusion layer.
Further, under the condition that the second diffusion is an N-type doping, the sheet resistance of the obtained lightly doped region is also in the range of 150 Ω/sqr to 250 Ω/sqr, for example, 150 Ω/sqr, 160 Ω/sqr, 170 Ω/sqr, 180 Ω/sqr, 190 Ω/sqr, 200 Ω/sqr, 210 Ω/sqr, 220 Ω/sqr, 230 Ω/sqr, 240 Ω/sqr, 250 Ω/sqr, or other specific values in the range; the thickness of the resulting lightly doped region is also in the range of 0.2 μm to 0.4 μm, and may be, for example, 0.2 μm, 0.25 μm, 0.3 μm, 0.35 μm, 0.4 μm, or other specific values within the range; the sheet resistance of the obtained heavily doped region can be 10 Ω/sqr to 100 Ω/sqr, for example, 10 Ω/sqr, 15 Ω/sqr, 20 Ω/sqr, 25 Ω/sqr, 30 Ω/sqr, 35 Ω/sqr, 40 Ω/sqr, 45 Ω/sqr, 50 Ω/sqr, 55 Ω/sqr, 60 Ω/sqr, 65 Ω/sqr, 70 Ω/sqr, 75 Ω/sqr, 80 Ω/sqr, 85 Ω/sqr, 90 Ω/sqr, 95 Ω/sqr, 100 Ω/sqr, or other specific values in the range; and the resulting heavily doped region may have a thickness of 0.4 μm to 1.0 μm, for example, 0.4 μm, 0.45 μm, 0.5 μm, 0.55 μm, 0.6 μm, 0.65 μm, 0.7 μm, 0.75 μm, 0.8 μm, 0.85 μm, 0.9 μm, 0.95 μm, 1.0 μm, or other specific values within the range. Due to the influence of the second diffusion, the sheet resistance and the thickness of the resulting lightly doped region may be greater than or equal to those of the corresponding diffusion layer.
In addition, the secondary diffusion can be performed by any one or more methods of a high-temperature diffusion process, a slurry doping process or an ion implantation process, which are all applicable to the technical scheme of the application, and preferably, the high-temperature diffusion process is adopted, so that the operation is simple and the cost is low.
Through the square resistance and the thickness of the appropriate heavily doped region and the light doped region, the formation of good ohmic contact between the heavily doped region and the metal electrode is facilitated, the contact resistance is reduced, the light doped layer can fully absorb short-wavelength light, the short-circuit current is improved, the photoelectric conversion efficiency of the solar cell is improved, and the performance of the solar cell is improved.
Furthermore, the present application also provides a selective emitter, which is prepared by the preparation method according to the first aspect. The selective emitter can improve the contact performance between the metal grid line electrode and the silicon substrate, reduce the contact resistance and further improve the conversion efficiency of the solar cell comprising the selective emitter.
In a second aspect, the present application provides a solar cell, which is made by a method comprising the steps of, in order:
texturing the surface of the silicon substrate;
preparing a selective emitter on the front side of the silicon substrate according to the preparation method of the selective emitter in the first aspect of the application;
etching the front surface and the back surface of the silicon substrate to remove the silicon oxide layer;
performing single-side etching on the back surface of the silicon substrate to remove the diffusion layer;
depositing a passivation layer and/or an antireflection layer on the surface of the silicon substrate; and
and carrying out metallization treatment on the surface of the selective emitter and the back surface of the silicon substrate to obtain a front electrode and a back electrode, wherein the front electrode and the back electrode respectively penetrate through the antireflection layer and/or the passivation layer to form ohmic contact with the silicon substrate.
The solar cell according to the present application exhibits high conversion efficiency due to the use of the selective emitter having excellent contact properties.
In the step of texturing the surface of the silicon substrate, mechanical damage to the surface of the silicon wafer in the cutting process can be removed through texturing; forming a texture surface to increase the surface area of the cell, such as forming a regular pyramid type, an inverted pyramid type, a hole-shaped rough surface made by RIE (reactive ion texturing) or MCT (metal catalyst assisted texturing), and the like; the light trapping effect is generated, the absorption quantity of the solar cell to light is increased, and the surface reflectivity of the cell is greatly reduced. In an embodiment of the present application, the texturing may be performed by a chemical etching method, a laser etching method, a mechanical method, a plasma etching method, or the like, which is not particularly limited in the present application.
In addition, the method for preparing the solar cell may further include a step of cleaning the silicon substrate to remove metal and organic contaminants on the surface before the texturing.
In the above step of fabricating a selective emitter, the selective emitter is fabricated by the fabrication method described in the above first aspect of the present application. Wherein the surface of the silicon substrate is first subjected to diffusion of a doping element to form a diffusion layer and a silicon oxide layer, wherein the sheet resistance and the thickness of the diffusion layer under P-type doping conditions may be 150 Ω/sqr to 250 Ω/sqr and 0.4 μm to 0.8 μm, or any specific value within the range, respectively, and the thickness of the silicon oxide layer may be 0.07 μm to 0.11 μm, or any specific value within the range, and the sheet resistance and the thickness of the diffusion layer under N-type doping conditions may be 150 Ω/sqr to 250 Ω/sqr and 0.2 μm to 0.4 μm, respectively, or any specific value within the rangeAny specific value within the range, and the thickness of the silicon oxide layer may be 0.04 μm to 0.08 μm or any specific value within the range; then, laser grooving is carried out, and the groove bottom reaches the diffusion layer, the laser groove area is the position of the selective emitter which is prepared later, and the position of a front electrode (metal grid line electrode) is obtained through subsequent metallization treatment, so that a plurality of laser grooves can be formed in the front of the silicon substrate in proper patterns, shapes and intervals, and proper groove width and groove depth are set, so that the photovoltaic current is fully collected in an optimal mode; the porous silicon in the laser-grooved region is then removed and at least part of the laser damage is retained, which may be by KOH/H as described in the first aspect of the present application 2 O 2 Any one of solution etching, oxidation, hydrofluoric acid cleaning and plasma irradiation; and performing secondary diffusion of the doping element on the diffusion layer in the laser grooving region to form a lightly doped region and a heavily doped region, wherein the sheet resistance and the thickness of the lightly doped region under the P-type doping condition can be respectively 150 Ω/sqr-250 Ω/sqr and 0.4 μm-0.8 μm or any specific value in the range, the sheet resistance and the thickness of the heavily doped region can be respectively 10 Ω/sqr-100 Ω/sqr and 0.7 μm-1.2 μm or any specific value in the range, the sheet resistance and the thickness of the lightly doped region under the N-type doping condition can be respectively 150 Ω/sqr-250 Ω/sqr and 0.2 μm-0.4 μm or any specific value in the range, and the sheet resistance and the thickness of the heavily doped region can be respectively 10 Ω/sqr-100 Ω/sqr and 0.4 μm-1.0 μm or any specific value in the range, and the preferred secondary diffusion performance and the above-mentioned performance can be obtained by the heavily doped region. Thus, a selective emitter according to the present application is obtained.
In the steps of removing the silicon oxide layer by etching and removing the diffusion layer by single-sided etching, because whether the diffusion of the doping element occurs on the back surface of the silicon substrate is not limited in the process of preparing the selective emitter, the silicon oxide layer on the two surfaces of the silicon substrate needs to be removed by etching on the two surfaces of the silicon substrate, and then the diffusion layer on the back surface is removed by single-sided etching on the back surface, so that only the diffusion layer on the front surface can be remained. In addition, since the silicon oxide layer in the groove area is burnt out by laser grooving in the preparation process of the selective emitter, the etching has no influence on the selective emitter.
In the step of depositing the passivation layer and/or the anti-reflective layer, the passivation layer and/or the anti-reflective layer may be deposited on the surface (front and back surfaces) of the silicon substrate by using a Plasma Enhanced Chemical Vapor Deposition (PECVD), a Metal Organic Chemical Vapor Deposition (MOCVD), or the like, and other methods may be used.
In a solar cell, a film layer directly contacting a silicon substrate or being close to the silicon substrate is generally called a passivation layer, which mainly plays a role in passivating dangling bonds on the surface of the substrate and preventing carriers from being compounded in a surface area, while a layer above the passivation layer and far away from the front surface of the silicon substrate is called an anti-reflection layer, and the anti-reflection layer is far away from the surface of the silicon substrate, so that the anti-reflection layer is mainly used for adjusting the refractive index of the whole light-transmitting film layer and reducing the reflection of light rays, thereby increasing the quantity of light rays absorbed by the solar cell, and further improving the weather resistance of the solar cell, and preventing factors such as oxygen, water, metal ions and the like in the external environment from entering the solar cell to generate defects to cause the attenuation of conversion efficiency. That is, the passivation layer and the anti-reflection layer are functional partitions, and both may have the same material composition or similar material composition, and specifically, the passivation layer and the anti-reflection layer may be formed of a stacked film, and the stacked film may include alumina, silicon oxide, silicon oxynitride, silicon nitride, gallium oxide, silicon carbide, amorphous silicon, silicon oxycarbide, or the like, or other materials having similar functions, which is not particularly limited in this application. Furthermore, hydrogen atoms may also be incorporated into the passivation layer to optimize the passivation effect. Moreover, because the subsequent metallization treatment can enable the passivation layer and the antireflection layer to be burned through when the front electrode and the back electrode are formed by metal, the positions of the selective emitter and the back electrode do not need to be masked when the passivation layer and/or the antireflection layer are deposited, and the silicon substrate is subjected to overall deposition.
In the above-mentioned metallization step, a front electrode (metal gate line electrode) may be formed by performing metallization at the laser grooving portion (i.e., at the selective emitter), and a back electrode may be formed by performing metallization at the side of the silicon substrate that does not include the selective emitter, the front electrode and the back electrode being determined as the front electrode and the back electrode, respectively, according to the type of the silicon substrate. In addition, the shape and arrangement of the front electrode and the back electrode may be suitably designed and selected according to the requirements of the solar cell, and the present application does not particularly limit the shape and arrangement of the front electrode and the back electrode.
In the embodiment of the present application, the metallization process may be achieved by applying a conductive paste, followed by drying and sintering. The coating may be performed, for example, by a screen printing technique, but the present application is not limited thereto. The conductive paste may be any one of silver paste, aluminum-containing silver paste, or aluminum paste, but the application is not limited thereto.
In addition, although the passivation layer and/or the anti-reflection layer are deposited on the back surfaces of the selective emitter and the silicon substrate, the passivation layer and/or the anti-reflection layer can penetrate through the passivation layer and/or the anti-reflection layer to be in direct contact (ohmic contact) with the silicon substrate in the sintering process after the conductive paste is coated, so that the electrical connection can be realized, and carriers generated due to the photoelectric effect can be collected and led out. The front electrode is directly contacted with the heavily doped region of the silicon substrate, and the back electrode is directly contacted with the back of the silicon substrate.
In the application, due to the fact that the porous silicon in the laser groove is removed and at least part of laser damage is reserved in the preparation process of the selective emitter, on the basis that the contact area of the porous silicon and the metal electrode is increased, contact resistance is greatly reduced, composite current is reduced, and therefore conversion efficiency of the solar cell can be improved.
In a third aspect, the present application provides a solar cell, which may be obtained by the preparation method of the second aspect, and may include a front electrode (metal gate line electrode), a front anti-reflection layer and/or a passivation layer, a selective emitter prepared by the preparation method of the first aspect, a silicon substrate, a back passivation layer, and a back electrode, which are sequentially arranged from top to bottom. The selective emitter removes porous silicon in the laser groove and retains at least part of laser damage, so that the selective emitter has excellent ohmic contact with a front electrode (metal grid line electrode), greatly reduces composite current, and can improve the conversion efficiency of the solar cell.
Further, the solar cell according to the present application may further include a specific module and structure at any position as necessary without departing from the technical purpose and spirit of the present application, and the present application is not particularly limited thereto.
In a fourth aspect, the present application provides a photovoltaic module, which may include, for example, a glass, an encapsulant, at least one solar cell according to the second or third aspect of the present application, an encapsulant, and a back sheet arranged in sequence from top to bottom. The solar cells according to the second or third aspect of the present invention are usually plural and electrically connected in series or in parallel. The packaging material can be EVA, POE and other packaging materials commonly used in the field.
Further, referring to fig. 1, according to an exemplary embodiment of the present application, there is provided a method of manufacturing a selective emitter, which includes the following steps in order:
s1: diffusing doping elements on the surface of a silicon substrate 1 to form a diffusion layer 2 and a silicon oxide layer 3 on the surface of the silicon substrate 1 from inside to outside, wherein the diffusion layer 2 comprises doping elements with a first doping concentration;
s2: grooving a partial region of the surface of the silicon oxide layer 3 on one surface of the silicon substrate 1 by adopting laser, and enabling the depth of the groove bottom to reach the diffusion layer 2;
s3: removing the porous silicon 41 in the laser grooving region 4 and retaining at least part of the laser damage 42; and
s4: and performing secondary diffusion of the doping element on the diffusion layer 2 in the laser grooving region 4, so that the diffusion layer 2 comprises a lightly doped region 5 with a first doping concentration and a heavily doped region 6 with a second doping concentration, wherein the heavily doped region 6 corresponds to the laser grooving region 4, and the second doping concentration is greater than the first doping concentration.
The selective emitter prepared by the preparation method can improve the contact performance between the metal grid line electrode and the silicon substrate, reduce the contact resistance and further improve the conversion efficiency of the corresponding solar cell.
The technical solution of the present application is exemplarily described below by specific embodiments:
each of the compounds used in the present application is commercially available or commercially ordered, and can be commercially obtained on the market by those skilled in the art as needed.
Example 1
The following preparation method of the selective emitter according to the application is adopted to prepare the selective emitter;
carrying out doping diffusion of boron element on the surface of the N-type silicon substrate to form a diffusion layer with a diffusion thickness of 0.6 mu m and a sheet resistance of 170 omega/sqr and a silicon oxide layer with a thickness of 0.09 mu m, wherein the diffusion layer has a first doping concentration, and the silicon oxide layer is arranged on the surface from inside to outside;
grooving a partial region of the surface of the silicon oxide layer on one surface of the silicon substrate by adopting laser, and enabling the groove bottom to reach the diffusion layer;
the grooves formed by the laser are processed at 80 ℃ by adopting a solution containing 2 mass percent of KOH and 4 mass percent of H 2 O 2 Etching for 2min; and
and performing secondary diffusion of the doping elements on the diffusion layer in the laser grooving region to form a heavily doped region with a second doping concentration which is greater than the first doping concentration and is 1.0 mu m thick and 80 omega/sqr square resistance at the diffusion layer in the laser grooving region, and enabling the diffusion layer part between the laser grooving regions to be a lightly doped region (with the thickness of 0.8 mu m and the square resistance of 200 omega/sqr), thereby obtaining the selective emitter according to the application.
Reference is made to fig. 2 and 3, which are Scanning Electron Microscope (SEM) images of the trench bottoms at two locations after completion of the above-described laser grooving and without removal of the porous silicon. In the two surface topography maps of the groove bottom, a large number of fluffy porous structures can be clearly seen, namely porous silicon, the surface containing the porous silicon is not easy to passivate, and the metal composite current deposited on the surface is large, which is not beneficial to improving the conversion efficiency of the solar cell.
Reference is made to fig. 4 and 5, which are Scanning Electron Microscope (SEM) images of the trough bottom at two locations after completion of the above-described step of removing porous silicon. In the two surface topography maps of the groove bottom, a part of pit-shaped laser damage structures are still remained on the surface of the groove bottom by removing the porous silicon structures, the damage structures are relatively easy to passivate, and the contact performance between the metal electrode and the semiconductor can be improved, so that the conversion efficiency of the solar cell is improved.
The effects of the other two methods for removing porous silicon of the present application are similar to those shown in fig. 4 and 5 described above, and a description thereof will not be repeated.
Example 2
A solar cell comprising a metal grid line electrode, a front anti-reflection layer and/or a passivation layer, a selective emitter electrode, a silicon substrate, a back passivation layer and a back electrode, which are arranged in sequence, prepared according to the preparation method of embodiment 1, and prepared by a method comprising the following steps in sequence:
cleaning and texturing the surface of the silicon substrate;
preparing a selective emitter on the front side of the silicon substrate by adopting the preparation method of embodiment 1;
etching the front surface and the back surface of the silicon substrate to remove the silicon oxide layer;
performing single-side etching on the back surface of the silicon substrate to remove the diffusion layer;
depositing a silicon nitride layer on the surface of the silicon substrate by adopting a PECVD method to be used as a passivation layer and an antireflection layer; and
and coating silver paste on the laser grooving position and the back surface of the silicon substrate by adopting screen printing, drying and sintering to form a front electrode and a back electrode, thereby preparing the solar cell.
Comparison ofExample 1
A solar cell was manufactured in the same manner as in example 2, except that the step of removing porous silicon was not performed when the method of manufacturing the selective emitter of example 1 was employed. The solar cell thus produced has a considerable amount of porous silicon between the metal electrode and the selective emitter.
Comparative example 2
Except that the step of removing porous silicon in the selective emitter fabrication method of example 1 was performed by using a solution containing 20% by mass of KOH and 40% by mass of H in the laser-opened trenches at a temperature of 80 deg.C 2 O 2 A solar cell was manufactured in the same manner as in example 2, except that the solution of (1) was etched for 2 min. In the solar cell manufactured by the method, not only the porous silicon in the laser groove is removed, but also the laser damage under the porous silicon is removed.
The performance of the solar cells of example 2 and comparative examples 1 and 2 was measured, and the results are shown in table 1 below.
[ Table 1]
As can be seen from table 1, the solar cell according to embodiment 2 of the present application removes porous silicon and retains a portion of laser damage when fabricating a selective emitter, so that the fill factor and the conversion efficiency are improved. In contrast, comparative example 1 did not perform the operation of removing porous silicon at all, while comparative example 2 performed deeper removal of porous silicon and underlying laser damage, both of which had inferior fill factor and conversion efficiency to example 2 of the present application.
The above-described embodiments of the present application are only examples of the present application and should not be construed as limiting the present application, and those skilled in the art can make modifications without inventive contribution as required after reading the present specification, however, any modifications, equivalents, improvements, etc. within the spirit and principle of the present application should be included in the scope of the present application.
Claims (11)
1. The preparation method of the selective emitter is characterized by sequentially comprising the following steps of:
diffusing doping elements on the surface of a silicon substrate to form a diffusion layer and a silicon oxide layer on the surface of the silicon substrate from inside to outside, wherein the diffusion layer comprises the doping elements with a first doping concentration;
grooving a partial region of the surface of the silicon oxide layer on one surface of the silicon substrate by adopting laser, and enabling the groove bottom to reach the diffusion layer;
removing the porous silicon in the laser grooving area and reserving at least part of laser damage; and
and carrying out secondary diffusion of the doping elements on the diffusion layer in the laser grooving region to enable the diffusion layer to comprise a light doping region with a first doping concentration and a heavy doping region with a second doping concentration, wherein the heavy doping region corresponds to the laser grooving region, and the second doping concentration is greater than the first doping concentration.
2. The preparation method according to claim 1, wherein the step of removing the porous silicon in the laser grooving region and retaining at least part of the laser damage comprises the following steps:
KOH with the mass concentration of 1 to 5 percent and H with the mass concentration of 3 to 5 percent are adopted under the temperature condition of 60 to 80 DEG C 2 O 2 The solution of (2) etches the laser grooving region for 1min to 3min.
3. The preparation method according to claim 1, wherein the step of removing the porous silicon in the laser grooving region and retaining at least part of the laser damage comprises the following steps:
oxidizing the laser grooving area for 30-60 min at the temperature of 800-900 ℃ under the condition of oxygen atmosphere, and then cleaning for 3-6 min by adopting hydrofluoric acid with the mass concentration of 2-8%.
4. The preparation method according to claim 1, wherein the step of removing the porous silicon in the laser grooving region and retaining at least part of the laser damage comprises the following steps:
and irradiating the laser grooving area for 5-10 min by adopting plasma at the output power of 1000-1500W.
5. The production method according to any one of claims 1 to 4, wherein when the silicon substrate is an N-type silicon substrate, the diffusion layer is a P + doped layer, and the doping element is at least one of boron, aluminum, gallium, or indium.
6. The method according to claim 5,
the sheet resistance of the diffusion layer is 150 omega/sqr to 250 omega/sqr; the diffusion thickness of the diffusion layer is 0.4-0.8 μm; and the thickness of the silicon oxide layer is 0.07-0.11 μm;
the square resistance of the light doping region is 150-250 omega/sqr, the thickness of the light doping region is 0.4-0.8 mu m, and the square resistance of the heavy doping region is 10-100 omega/sqr; and the thickness of the heavily doped region is 0.7-1.2 μm.
7. The production method according to any one of claims 1 to 4, wherein when the silicon substrate is a P-type silicon substrate, the diffusion layer is an N + doped layer, and the doping element is at least one of phosphorus, arsenic, or antimony.
8. The production method according to claim 7,
the sheet resistance of the diffusion layer is 150 omega/sqr to 250 omega/sqr; the diffusion thickness of the diffusion layer is 0.2-0.4 μm; and the thickness of the silicon oxide layer is 0.04-0.08 μm;
the sheet resistance of the lightly doped region is 150-250 omega/sqr, and the thickness of the lightly doped region is 0.2-0.4 mu m; the sheet resistance of the heavily doped region is 10-100 omega/sqr; and the thickness of the heavily doped region is 0.4-1.0 μm.
9. A solar cell is characterized by being prepared by a method comprising the following steps in sequence:
texturing the surface of the silicon substrate;
the production method according to any one of claims 1 to 8, producing a selective emitter on the front side of the silicon substrate;
etching the front surface and the back surface of the silicon substrate to remove the silicon oxide layer;
performing single-side etching on the back surface of the silicon substrate to remove the diffusion layer;
depositing a passivation layer and/or an antireflection layer on the surface of the silicon substrate; and
and carrying out metallization treatment on the surface of the selective emitter and the back surface of the silicon substrate to obtain a front electrode and a back electrode, wherein the front electrode and the back electrode respectively penetrate through the antireflection layer and/or the passivation layer to form ohmic contact with the silicon substrate.
10. A solar cell, characterized in that it is produced by the method used in claim 9 and comprises, in order from top to bottom, a front electrode, a front antireflective layer and/or a passivation layer, a selective emitter produced by the production method according to any one of claims 1 to 8, a silicon substrate, a back passivation layer and a back electrode.
11. A photovoltaic module, comprising a glass, an encapsulant, at least one solar cell according to claim 9 or 10, an encapsulant and a back sheet arranged in this order from top to bottom.
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