CN112993073B - Solar cell, manufacturing method thereof and photovoltaic module - Google Patents
Solar cell, manufacturing method thereof and photovoltaic module Download PDFInfo
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- 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 at least one potential-jump barrier or surface barrier
- 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 at least one potential-jump barrier or surface barrier 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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- 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
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- H01L31/02161—Coatings for devices characterised by at least one potential jump barrier or surface barrier
- H01L31/02167—Coatings for devices characterised by at least one potential jump barrier or surface barrier for solar cells
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- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
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- H01L31/02—Details
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- H01L31/02167—Coatings for devices characterised by at least one potential jump barrier or surface barrier for solar cells
- H01L31/02168—Coatings for devices characterised by at least one potential jump barrier or surface barrier for solar cells the coatings being antireflective or having enhancing optical properties for the solar cells
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- 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
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- 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
- H01L31/18—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 System
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- 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
- H01L31/186—Particular post-treatment for the devices, e.g. annealing, impurity gettering, short-circuit elimination, recrystallisation
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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
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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
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
Abstract
The embodiment of the invention relates to the field of photovoltaic cells, and discloses a solar cell, a manufacturing method thereof and a photovoltaic module. In the present invention, a solar cell includes: the silicon substrate comprises a base region and an emitter, and the emitter is arranged on the surface of the base region; a passivation layer on the surface of the emitter; the electrode penetrates through the passivation layer and is electrically connected with the emitter; the bottom surface of the electrode is provided with a dielectric layer, and the dielectric layer is positioned inside the emitter. The solar cell can improve the photoelectric conversion efficiency of the solar cell.
Description
Technical Field
The embodiment of the invention relates to the field of photovoltaic cells, in particular to a solar cell, a manufacturing method thereof and a photovoltaic module.
Background
A solar cell is a photoelectric semiconductor sheet which directly generates electricity by using sunlight, and is also called a solar chip or a photovoltaic cell, and can output voltage and generate current under the condition of a loop as long as the illuminance of certain illuminance conditions is met.
When a solar cell is manufactured, glass frit for sintering is doped into conductive paste of a printed electrode, a passivation layer is burnt through by high-temperature ablation, a silver electrode is formed in an ablation pit on the surface of a silicon substrate, and finally ohmic contact is formed.
The related solar cell has the following problems: the silver electrode obtained by sintering has surface defects of looseness, porosity and the like, so that the contact region of the silver electrode and the silicon substrate has a compounding problem, and the photoelectric conversion efficiency of the solar cell is reduced.
Disclosure of Invention
The embodiment of the invention aims to provide a solar cell, a manufacturing method thereof and a photovoltaic module, and improve the photoelectric conversion efficiency of the solar cell.
To solve the above technical problem, an embodiment of the present invention provides a solar cell, including: the silicon substrate comprises a base region and an emitter, and the emitter is arranged on the surface of the base region; a passivation layer on the surface of the emitter; the electrode penetrates through the passivation layer and is electrically connected with the emitter; the bottom surface of the electrode is provided with a dielectric layer, and the dielectric layer is positioned inside the emitter.
Embodiments of the present invention also provide a photovoltaic module including the solar cell as described above.
The embodiment of the invention also provides a manufacturing method of the solar cell, which comprises the following steps: providing a silicon substrate comprising a base region and an emitter electrode, wherein the emitter electrode is arranged on the surface of the base region; forming a passivation layer on the surface of the emitter; and forming an electrode and a dielectric layer, wherein the electrode penetrates through the passivation layer and is electrically connected with the emitter, the dielectric layer is arranged on the bottom surface of the electrode, and the dielectric layer is positioned inside the emitter.
Compared with the prior art, the method and the device have the advantages that the dielectric layer is arranged on the bottom surface of the electrode, holes generated in the electrode forming process are filled, the holes are prevented from capturing carriers, and the recombination of the carriers is reduced, so that the recombination loss of photogenerated carriers caused by surface defects between the electrode and the silicon substrate can be reduced, and the photoelectric conversion efficiency of the solar cell is improved.
The width of the dielectric layer is equal to or greater than the width of the bottom surface of the electrode. Therefore, the dielectric layer covers the bottom surface of the whole electrode, so that surface defects existing between the electrode and the silicon substrate are all filled by the dielectric layer, the recombination loss of current carriers between the electrode and the silicon substrate is further reduced, and the photoelectric conversion efficiency of the solar cell is improved.
The dielectric layer has a thickness of 1.2 to 2 nm. The thickness of the dielectric layer is set to be 1.2-2 nm, so that the surface defects of the electrode can be completely filled, the carrier recombination loss between the electrode and the emitter is reduced, a carrier tunneling effect is formed among the electrode, the dielectric layer and the emitter, and the conductivity between the electrode and the emitter is ensured.
In addition, a dielectric layer is selectively provided on the bottom surface of the electrode, the dielectric layer isolating the bottom surface of the electrode from the emitter. The surface defects of the bottom surface of the electrode can be ensured to be filled, holes similar to holes on the bottom surface of the electrode are reduced, and the electrode mainly forms ohmic contact with the emitter by the bottom surface, so that collection and conduction of photo-generated current of the solar cell are realized, and therefore recombination loss of photo-generated carriers caused by the surface defects between the electrode and the silicon substrate can be greatly reduced, and the photoelectric conversion efficiency of the solar cell is improved.
In addition, the dielectric layer is a silicon oxide layer, the ratio of the number of oxygen atoms to the number of silicon atoms in the silicon oxide layer is 1.5-2, the dielectric layer is obtained through the reaction of oxygen and silicon in the silicon substrate, impurities are not introduced, and other performances of the solar cell are not damaged.
In addition, the ratio of the oxygen contents of the first contact surface of the dielectric layer and the electrode and the second contact surface of the dielectric layer and the emitter is less than 2; the oxygen content of the first contact surface is greater than the oxygen content of the second contact surface. Because the passivation effect of the silicon dioxide is better than that of the silicon monoxide, the content of the silicon dioxide in the dielectric layer is controlled to be higher, so that the dielectric layer can have better passivation effect.
Drawings
One or more embodiments are illustrated by corresponding figures in the drawings, which are not to scale unless specifically noted.
Fig. 1 is a schematic structural diagram of a solar cell according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a prior art solar cell according to an embodiment of the present invention;
fig. 3 is a flowchart of a method for manufacturing a solar cell according to an embodiment of the invention;
fig. 4 is a schematic diagram of an electrode groove of a solar cell according to an embodiment of the present invention;
fig. 5 is a flowchart of another method for manufacturing a solar cell according to an embodiment of the invention;
fig. 6 is a schematic diagram of a sintering process of a solar cell according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention more apparent, embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, it will be appreciated by those of ordinary skill in the art that numerous technical details are set forth in order to provide a better understanding of the present application in various embodiments of the present invention. However, the technical solution claimed in the present application can be implemented without these technical details and various changes and modifications based on the following embodiments. The following embodiments are divided for convenience of description, and should not constitute any limitation to the specific implementation manner of the present invention, and the embodiments may be mutually incorporated and referred to without contradiction.
A solar cell, as shown in fig. 1, comprising: a silicon substrate 110, the silicon substrate 110 including a base region 112 and an emitter 111, the emitter 111 being disposed on a surface of the base region 112;
a passivation layer 120 on the surface of the emitter 111;
an electrode 130, wherein the electrode 130 penetrates the passivation layer 120 and is electrically connected with the emitter 111;
the bottom surface of the electrode 130 is provided with a dielectric layer 140, and the dielectric layer 140 is positioned inside the emitter 111.
The solar cell provided by the invention is a silicon solar cell taking silicon as a base material. As shown in fig. 1, the present embodiment is described by taking an example in which the solar cell structure is used on the front surface of the solar cell, i.e., the solar side, but the solar cell structure provided by the present invention may also be used on the back surface of the solar cell. That is, the dielectric layer in the solar cell structure provided by the present invention may be provided on the bottom surface of the front electrode electrically connected to the emitter in the solar cell, or on the bottom surface of the back electrode electrically connected to the back emitter in the solar cell, so as to fill up the surface defects of the front electrode or the back electrode and reduce the carrier recombination loss of the front electrode or the back electrode.
Specifically, the solar cell of the present invention may be a P-type solar cell or an N-type solar cell. For example, an N-type cell may be formed by forming an N-type single crystal silicon wafer with phosphorus as a doping element in a silicon substrate, performing boron diffusion on a front surface of the silicon substrate, i.e., a front surface of the silicon substrate facing a sun side, and forming a P-type emitter on the front surface of the substrate, thereby forming a PN junction inside the substrate. It can be understood that the region of the silicon substrate where boron diffusion is not performed constitutes an N-type base region, and the N-type base region and the P-type emitter form a PN junction. For another example, in a P-type cell, a P-type monocrystalline silicon wafer is formed by doping a semiconductor material with boron, phosphorus diffusion is performed on the front surface of the silicon substrate, that is, the front surface of the silicon substrate facing the sun side, and an N-type emitter is formed on the front surface of the silicon substrate, so that a PN junction is formed inside the silicon substrate. It can be understood that the region of the silicon substrate where phosphorus diffusion is not performed constitutes a P-type base region, and the P-type base region and the N-type emitter form a PN junction.
In this embodiment, a front structure of a solar cell is illustrated by taking a P-type cell as an example, and fig. 1 shows a cross section of a P-type cell, wherein the complete P-type cell structure further includes a back passivation layer 150 and a back electrode 160 in addition to the silicon substrate 110, the passivation layer 120, the electrode 130, and the like.
The silicon substrate 110 (including the emitter 111 and the base 112) includes monocrystalline silicon, polycrystalline silicon, amorphous silicon, and microcrystalline silicon, wherein the monocrystalline silicon has a regular structure and a high photoelectric conversion rate. The surface of the silicon substrate 110 may be textured, that is, subjected to texturing in advance, so that the surface of the silicon substrate 110 is uneven and rough to form a pyramid shape having an irregular size, thereby reducing the reflectivity of incident light passing through the front surface of the silicon substrate 110, reducing the loss of the incident light, and improving the photoelectric conversion efficiency. In some embodiments, a naturally occurring oxide layer may also be present on the surface of the silicon substrate 110, where the oxide layer is SiO generated by the reaction between the silicon substrate 110 exposed to air and oxygen in the air2. The passivation layer 120 is located on the outer surface of the oxide layer, and is a front surface passivation layer of the solar cell, the material of the passivation layer 120 may be silicon nitride, aluminum oxide, or silicon oxynitride, and the passivation layer 120 may be a single-layer structure or may include a multi-layer structure, where the multi-layer structure may include a first passivation layer, an anti-reflection layer, and the like. The passivation layer 120 may be a silicon nitride film containing hydrogen (i.e., SiN)xH antireflection passivation film), a silicon oxide film, a silicon oxynitride film, and an aluminum oxide film, or a multilayer structure obtained by combining any two or more kinds thereof. The provision of the passivation layer 120 may reduce solar powerThe cell reflects sunlight, but more importantly, serves a passivation function. For example, silicon nitride can saturate surface dangling bonds, and reduce minority carrier concentration on the front surface of the silicon substrate through self positive charges, so that the recombination rate of the silicon substrate is reduced, and the efficiency of the solar cell is improved.
The electrode material of the electrode 130 may be a metal material with good electrical conductivity, and commonly used electrode materials are silver, aluminum, and the like. As an example, the electrode 130 shown in fig. 1 is a front silver electrode of the solar cell, and electrons moving to the emitter 111 may move outward through the front silver electrode to form an external current, which is supplied to an external load. The electrode 130 penetrates the passivation layer 120 and the oxide layer from the outside of the passivation layer 120 to the inside, and is electrically connected to the emitter 111. In order to reduce the resistance, the electrode 130 needs to have a good ohmic contact with the emitter 111.
A dielectric layer 140 is provided on the bottom surface of the electrode 130, and the dielectric layer 140 is positioned inside the emitter 111. In a conventional solar cell, as shown in fig. 2, an electrode 230 is in direct contact with an emitter 211. Taking a silver electrode as an example, after sintering, silver is separated out from glass frit, silver crystallites in an inverted pyramid shape are arranged on the surface of the silver electrode, and the silver electrode and an emitter are conducted through the silver crystallites, so that collection and conduction of photo-generated current of the solar cell are realized, wherein the surface of the silver electrode is not completely compact and has holes similar to cavities, so that the problem of recombination between the electrode and the emitter is caused. In this embodiment, the dielectric layer 140 is disposed on the bottom surface of the electrode 130, so that the holes in the silver electrode are filled with the dielectric layer 140.
Specifically, the dielectric layer 140 may be continuously distributed in the emitter 111, and the material may be silicon nitride SiNxOr may be silicon carbide SiCxSilicon oxide SiOxAluminum oxide Al2O3Hafnium oxide HfO2Or hydrogenated amorphous silicon a-Si: H, and the like.
In the embodiment, the dielectric layer is arranged on the bottom surface of the electrode 130 to fill the holes generated in the formation process of the electrode 130, so that the holes are prevented from capturing carriers, and the recombination of the carriers is reduced, thereby reducing the recombination loss of photogenerated carriers caused by the surface defects existing between the electrode 130 and the silicon substrate 110, and improving the photoelectric conversion efficiency of the solar cell.
In some embodiments, the dielectric layer 140 may be located on the bottom surface and sidewalls of the electrode 130.
In some embodiments, the dielectric layer 140 may partially isolate the bottom surface of the electrode 130 from the emitter 111 without completely isolating the bottom surface of the electrode 130 from the emitter 111, for example, the width of the dielectric layer 140 may be set to be smaller than the bottom surface of the electrode 130, i.e., the dielectric layer 140 is only distributed on a part of the bottom surface of the electrode 130, and a part of the direct contact region may exist between the bottom surface of the electrode 130 and the emitter 111.
In some embodiments, the dielectric layer 140 may be selectively disposed on the bottom surface of the electrode 130, not on the sidewall of the electrode 130, and isolate the bottom surface of the electrode 130 from the emitter 111. The electrode 130 mainly forms ohmic contact with the emitter 111 by the bottom surface, so that collection and conduction of photo-generated current of the solar cell are realized, and the dielectric layer 140 is only distributed on the bottom surface of the electrode 130, so that the recombination loss of carriers on the substrate surface between the electrode 130 and the emitter 111 can be effectively reduced, the photoelectric conversion efficiency of the solar cell is improved, meanwhile, the material consumption of the dielectric layer 140 is reduced, and resources and manufacturing cost are saved.
In some embodiments, the width of the dielectric layer 140 is greater than or equal to the width of the bottom surface of the electrode 130, so that the dielectric layer covers the entire bottom surface of the electrode, thereby ensuring that surface defects existing between the electrode and the silicon substrate are filled with the dielectric layer 140, further reducing the recombination loss of carriers between the electrode 130 and the silicon substrate 110, and improving the photoelectric conversion efficiency of the solar cell.
In some embodiments, the bottom surface of the electrode 130 is in direct contact with only the dielectric layer 140 and not the emitter 111, i.e., the dielectric layer 140 completely isolates the electrode 130 from contact with the emitter 111. In this embodiment, the bottom surface of the electrode 130 is in direct contact with the dielectric layer 140, but not in direct contact with the emitter 111, so that the surface defects on the bottom surface of the electrode 130 can be ensured to be filled, and holes similar to holes on the bottom surface of the electrode 130 are reduced.
Specifically, the thickness of the dielectric layer 140 may be set to 1.2 to 2 nm. When the thickness of the dielectric layer 140 is less than 1.2nm, it is not possible to ensure complete filling of surface defects of the electrode 130, and when the thickness of the dielectric layer 140 is greater than 2nm, tunneling of carriers among the electrode 130, the dielectric layer 140, and the emitter 111 is hindered, and conductivity between the electrode 130 and the emitter 111 is lowered, so that the thickness of the dielectric layer 140 is set to 1.2-2 nm. In the embodiment, the thickness of the dielectric layer 140 is set to be 1.2-2 nm, so that the surface defects of the electrode 130 can be completely filled, the carrier recombination loss between the electrode 130 and the emitter 111 is reduced, and meanwhile, a carrier tunneling effect is formed among the electrode 130, the dielectric layer 140 and the emitter 111, and the electric conductivity between the electrode 130 and the emitter 111 is ensured.
In some embodiments, the dielectric layer 140 may be silicon oxide SiOxThe layer is obtained by reacting the prepared oxygen with the emitter 111 of the silicon substrate 110 for a long sintering time, the oxygen content of the dielectric layer 140 can be controlled by increasing the oxygen amount of the reaction, for example, the number of oxygen atoms in the dielectric layer 140 can be controlled to be larger than the number of silicon atoms, and the ratio of the oxygen atoms to the silicon atoms is 1.5-2, that is, the content of silicon dioxide in the dielectric layer 140 is higher than the content of silicon monoxide. Since the passivation effect of silicon dioxide is better than that of silicon monoxide, controlling the content of silicon dioxide in the dielectric layer 140 to be higher can make the dielectric layer 140 have better passivation effect.
Specifically, the oxygen content of the first contact surface of the dielectric layer 140 and the electrode 130 is greater than the oxygen content of the second contact surface of the dielectric layer 140 and the emitter 111, and the ratio of the oxygen content of the first contact surface to the oxygen content of the second contact surface is less than 2. Since the silicon oxide is obtained by reacting the prepared oxygen with the emitter 111 of the silicon substrate 110, the oxygen content of the first contact surface is greater than that of the second contact surface, and by increasing the oxygen content of the reaction, the oxygen content of the second contact surface can be higher, and the silicon dioxide content in the dielectric layer 140 can be increased, so that the dielectric layer 140 can have a better passivation effect.
In this embodiment, since the silicon oxide may be obtained by reacting oxygen with the silicon substrate 110, other impurities may not be introduced when the dielectric layer 140 of the solar cell is prepared, and it is ensured that other properties of the solar cell are not damaged.
In this embodiment, the material of the back passivation layer 150 may be one or more of aluminum oxide, silicon nitride, silicon oxynitride, silicon oxycarbonitride, and aluminum.
Correspondingly, the embodiment of the invention also provides a solar module, and the solar module comprises the solar cell. The solar cell shown in fig. 1 comprises a silicon substrate, an emitter electrode positioned on the surface of the silicon substrate, a passivation layer positioned on the surface of the emitter electrode, and an electrode, wherein the electrode penetrates through the passivation layer and is electrically connected with the emitter electrode, a dielectric layer is arranged on the bottom surface of the electrode, and the dielectric layer is positioned inside the emitter electrode. The dielectric layer arranged on the bottom surface of the electrode can fill holes generated in the electrode forming process, so that the holes are prevented from capturing carriers, and the recombination of the carriers is reduced, therefore, the recombination loss of photon-generated carriers caused by surface defects between the electrode and the silicon substrate can be reduced, and the photoelectric conversion efficiency of the solar cell is improved.
The embodiment of the invention also provides a manufacturing method of the solar cell, which is used for manufacturing the solar cell of which the electrode needs to penetrate through the external passivation layer to be electrically connected with the internal emitter. The solar cell may be a P-type solar cell or an N-type solar cell. The electrode may be a front electrode or a back electrode, that is, the method for manufacturing the solar cell of the present embodiment may be used as a method for arranging a front structure or a back structure of the solar cell. In this example, the method for manufacturing a solar cell according to the present invention is described by taking the front surface of a P-type cell as an example.
As shown in fig. 3, the method for manufacturing a solar cell includes:
In step 301, a P-type cell uses a P-type monocrystalline silicon wafer as a silicon substrate, phosphorus diffusion is performed on a front surface of the silicon substrate, and an emitter is formed on the front surface of a semiconductor material, i.e., a front surface facing a sun side, so as to form a PN junction inside the silicon substrate. The P-type monocrystalline silicon wafer can be prepared by doping boron in a semiconductor material. The emitter may be located on the front surface of the silicon substrate or on the back surface of the silicon substrate (i.e., the back surface of the silicon substrate facing away from the sun). When the emitter is located on the back surface of the silicon substrate, the electrode is a back electrode.
Specifically, the surface of the silicon substrate is also textured, i.e., texturized, before the PN junction is formed. Texturing is to make the surface of a relatively smooth original silicon substrate rough and rough by chemical corrosion and other methods, and reduce the loss of solar energy directly reaching the surface of the silicon wafer by diffuse reflection. In general, single crystal silicon is etched by a method of adding alcohol to NaOH, and a pyramid shape having an irregular size is formed on the surface by anisotropic etching of single crystal silicon.
The method for texturing the surface of the silicon substrate is not limited to the chemical etching method, but laser, mechanical method, plasma etching or other methods capable of forming a pyramid structure on the surface of the substrate may also be used in other embodiments of the present invention.
In step 302, the passivation layer may be silicon nitride, aluminum oxide, or silicon oxynitride, and in a P-type cell, the dark blue SiN is usually in a solid statexAnd the H antireflection passivation film is a front surface passivation layer. A naturally generated oxide layer is arranged between the passivation layer and the emitter, and the oxide layer is naturally generated SiO when the silicon substrate is exposed in the air2。
Specifically, the passivation layer can be formed by coating the surface of the emitter in a gas/liquid atmosphere, and can be formed by Plasma Enhanced Chemical Vapor Deposition (PECVD), passivation contact, or other techniques. For example, a silicon substrate may be placed in a tubular PECVD apparatus, and a passivation layer may be deposited on the front surface of the emitter on the front surface of the silicon substrate by using a PECVD technique, which includes the following steps: using low-temperature plasma as energy source, placing the semi-finished product of cell with emitter on the silicon substrate on the cathode of glow discharge under low pressure, using glow discharge (or other heating body) to heat the semi-finished product to preset temperature, then introducing proper ammonia gas and silane as reaction gas, after the ammonia gas and silane are undergone the processes of a series of chemical reactions and plasma reactions, forming solid deep blue SiN on the front surface of emitterxH antireflection passivation film.
Note that SiNxSiN in H antireflection passivation filmx(i.e., silicon nitride) serves as an anti-reflective function, while H (i.e., hydrogen atoms) may serve as surface and bulk passivation. On one hand, the antireflection passivation film conforms to the antireflection principle, so that the reflection of light can be reduced, and the light absorption rate of the solar cell is increased; on the other hand, in the process of preparing the antireflection passivation film, a large number of hydrogen atoms reach the surface of the emitter and enter the inside of the emitter, and can be combined with dangling bonds caused by cutting on the surface of the emitter and unsaturated covalent bonds caused by impurities and combined with unsaturated covalent bonds generated by dislocation, crystal defects or other impurities in the emitter, so that recombination centers are reduced, the collection rate of photon-generated carriers is improved, good surface passivation and body passivation effects are achieved, and the short-circuit current and open-circuit voltage of the solar cell are improved.
And 303, forming an electrode and a dielectric layer, wherein the electrode penetrates through the passivation layer and is electrically connected with the emitter, the dielectric layer is arranged on the bottom surface of the electrode, and the dielectric layer is positioned inside the emitter.
In some embodiments, the dielectric layer is silicon nitride SiNxLayer, silicon carbide SiCxLayer, silicon oxide SiOxLayer, aluminum oxide Al2O3Layer, hafnium oxide HfO2The layer is any one of hydrogenated amorphous silicon a-Si and H layers.
In some embodiments, an electrode groove may be formed at a predetermined electrode position, the electrode groove penetrates through the passivation layer, the bottom of the electrode groove is located inside the emitter, a dielectric layer is formed on the sidewall and the bottom of the electrode groove, an electrode is formed in the electrode groove, and the electrode fills the electrode groove. After the electrode is arranged, the subsequent solar cell manufacturing process is carried out, such as hydrogen passivation treatment and the like.
In some embodiments, the width of the dielectric layer is greater than or equal to the width of the bottom surface of the electrode.
In some embodiments, the dielectric layer may be formed only on the bottom surface of the electrode recess, the dielectric layer covering the bottom surface of the electrode recess, and the electrode may be formed in the electrode recess, the electrode filling the electrode recess.
Specifically, the preset electrode position can be grooved by laser to obtain a semi-finished product of the battery with electrode grooves on the front surface as shown in fig. 4. And arranging a dielectric layer and electrodes on the grooved battery semi-finished product. For example, the grooved battery semi-finished product may be placed in a gas or liquid atmosphere to perform plating of the dielectric layer, the dielectric layer may be formed on the sidewall and the bottom surface of the electrode groove, and the electrode may be disposed. In some cases, laser grooving can form a laser damage structure in the emitter, the laser damage structure can form a carrier recombination center to influence the conversion efficiency of the battery, and the laser damage structure can be improved or repaired by arranging the dielectric layer to reduce recombination.
In some embodiments, the battery semi-finished product after the groove is plated with a dielectric Layer by using an Atomic Layer Deposition (ALD) method, and then an electrode is disposed.
In some embodiments, a dielectric layer printing template can be used to selectively print a dielectric layer material on the pre-assembled electrode positions on the battery semi-finished product after slotting, so as to prepare a dielectric layer, and the electrode grooves are filled with a conductive paste to form electrodes.
In some embodiments, the dielectric layer has a thickness of 1.2-2 nm. A dielectric layer material may be printed in a pre-set thickness at the pre-electrode locations.
In some embodiments, the dielectric layer is a silicon oxide layer, and the ratio of the number of oxygen atoms to the number of silicon atoms in the silicon oxide layer is 1.5-2.
In some embodiments, the oxygen content ratio of the first contact surface of the dielectric layer and the electrode and the second contact surface of the dielectric layer and the emitter is less than 2; the oxygen content of the first contact surface is greater than the oxygen content of the second contact surface.
In the front electrode manufacturing process, it is common to manufacture the front electrode by sintering the conductive paste. In the conventional front silver electrode sintering process, an infrared chain sintering furnace is usually adopted to rapidly sinter a battery semi-finished product printed with conductive paste on a passivation layer to obtain a front electrode. The process of printing the conductive paste on the passivation layer is called a screen printing process, and the screen printing utilizes the basic principle that the mesh of the pattern part of the screen is permeable to the paste and the mesh of the non-pattern part is impermeable to the paste to perform printing. The conductive paste can be silver paste, aluminum paste or silver-aluminum paste, for example, silver paste is poured into one end of the screen during printing, a scraper is used for applying certain pressure on the silver paste part of the screen, and the conductive paste moves towards the other end of the screen. The slurry is pressed onto the passivation layer from the meshes of the pattern portion by the squeegee while moving. In the printing process, the scraper is always in line contact with the screen printing plate and the passivation layer, the contact line moves along with the movement of the scraper, and other parts of the screen printing plate are in a separation state from the passivation layer, so that the precision of the printing size is ensured, and the passivation layer is prevented from being contaminated. And when the scraper lifts up after scraping the whole printing area, the screen printing plate is separated from the passivation layer, the silver paste is lightly scraped back to the initial position by the ink returning knife, and the workbench returns to the feeding position to finish the screen printing process. The sintering process is usually the last process in the preparation process of the crystalline silicon solar cell, and aims to realize the following steps by high-temperature sintering: the silver electrode with high density and good conductivity is formed, and the silver electrode and the emitter are promoted to form good ohmic contact, so that photo-generated current collection and conduction are realized, and the silver electrode is contacted with the emitter to enable the grid line to have good adhesive force.
The silver paste is doped with an organic carrier and a glass material, the glass material is melted from a surface passivation layer and is ablated downwards to an emitter during high-temperature sintering, and silver dissolved in the glass material is gradually separated out at the contact position of the glass material emitter during cooling and is in contact with the emitter to form good ohmic contact. The sintering process can be divided into a drying stage, a combustion stage, a sintering stage and a cooling stage, and each stage is correspondingly carried out in different temperature areas of the sintering furnace. Wherein, the temperature of the temperature zone in the drying stage is generally controlled to be about 200 ℃ so as to volatilize the organic solvent in the organic carrier; the temperature of the temperature zone in the combustion stage is generally controlled to be about 300 to 400 ℃ so as to combust organic matters in the organic carrier, such as a thickening agent, a thixotropic agent, a surfactant, a dispersing agent and the like; in the sintering stage, the glass frit in the organic carrier is softened, the molten glass frit with silver dissolved therein is ablated downwards and deposited on the surface of the silicon emitter, and meanwhile, silver particles are rearranged, condensed, electrodes shrink and other processes under the action of the molten glass frit; during the cooling phase, silver dissolved in the frit gradually precipitates on the emitter surface, contacts the emitter and forms a good ohmic contact. Wherein, the sintering stage can be divided into two sub-stages, the temperature of the first sub-stage is controlled to be about 550 to 700 ℃, the fluidity of the glass material is enhanced along with the rising of the sintering temperature, and the glass material is gradually deposited on a passivation layer, such as a silicon nitride layer, while wetting the silver particles, so as to start to ablate the silicon nitride layer. The temperature of the second sub-stage is controlled to be about 700 to 850 ℃, in the stage, the silicon nitride layer is gradually completely ablated, a channel is opened for the good ohmic contact formed by the bulk silver particles and the silicon emitter, and the regenerated silver crystal grains grow, wherein the regenerated silver crystal grains are important media for forming the good ohmic contact and the current transmission with the silicon emitter.
In some embodiments, since laser grooving is performed on the position where the electrode is preset on the silicon substrate in advance, the electrode can be directly arranged in the electrode groove position through a simplified printing and sintering process. Specifically, the conductive paste may be printed in the groove of the electrode groove, and the electrode groove is filled with the conductive paste. The conductive paste is silver paste, aluminum paste or silver-aluminum paste, for example.
Specifically, the conductive paste may be a simplified conductive paste, wherein the specific gravity of the glass frit is less than that of the glass frit in a common conductive paste, the content of the glass frit in the conductive paste may be set to be less than 4wt%, that is, the weight of the glass frit in the conductive paste is less than 4% of the weight of the conductive paste, and in this embodiment, the passivation layer and the oxide layer are not ablated by the glass frit, and the silicon substrate is only fed into a sintering furnace, and undergoes solvent evaporation, organic matter decomposition and cooling processes, so that the conductive paste, for example, a silver paste is cured to obtain a silver electrode, that is, the silver electrode can be obtained without high-temperature sintering in a conventional sintering process. Because the electrode is formed without ablating the passivation layer and the oxide layer by the glass material, the proportion of the glass material in the silver paste can be less than 10 percent of that of the common silver paste, even less than 4 percent, and the manufacturing cost of the solar cell is saved.
In the embodiment, the dielectric layer is arranged on the bottom surface of the electrode and is filled with the holes generated in the electrode forming process, so that the holes are prevented from capturing carriers, and the recombination of the carriers is reduced, therefore, the recombination loss of the photon-generated carriers caused by the surface defects between the electrode and the silicon substrate can be reduced, and the photoelectric conversion efficiency of the solar cell is improved.
In some embodiments, as shown in fig. 5, step 303 may include step 3031 and step 3032. The dielectric layer is silicon oxide, and the conductive paste for manufacturing the electrode, such as silver paste, is doped with glass frit and an oxidant. As shown in fig. 6, during the sintering process, the glass frit in the silver paste ablates the passivation layer (also burns through the oxide layer on the front surface of the emitter), deposits on or inside the emitter, the oxidant decomposes to generate oxygen, the oxygen reacts with the emitter to form a dielectric layer on the surface of the glass frit, and during the cooling stage, the silver in the glass frit precipitates out to contact the dielectric layer to form a silver electrode in contact with the dielectric layer.
In step 3031, the conductive paste may be formed by doping a glass frit and an oxidizing agentAnd presetting positions of the grid line electrodes on the surface of the passivation layer through screen printing. Wherein the oxidizing agent is required to satisfy the conditions of stability at low temperature and oxygen generation by decomposition at sintering temperature, such as Pb3O4The decomposition temperature is about 500 ℃.
In some embodiments, the oxidizing agent may be KNO3. KNO at low temperature in molten salt state3Stable, and KNO when the temperature reaches 400 ℃ in the temperature rising process3The gradual decomposition starts, and the decomposition formula is as follows: 2KNO3→2KNO2+O2×) and KNO when the temperature in the sintering process is raised to above 600 and 700 DEG C3And KNO2Begin to decompose to give K2O and oxygen, the specific formula is as follows: 4KNO3→2KNO2+N2+4O2×) @. The generated oxygen can oxidize the silicon component in the emitter to generate a compound of oxygen and silicon at the sintering temperature, and the generated K2O can be added to the effect of increasing the transmittance of the battery without introducing impurities to increase the impurity removal step.
In some embodiments, the silver paste contains 0.3% -1% of an oxidant to generate enough oxygen to react with the emitter, and the passivation effect of the silicon dioxide is better than that of silicon monoxide, so that the silver paste with at least 0.3% of the oxidant ensures that the content of the silicon dioxide in the dielectric layer and the difference between the oxygen contents of the first contact surface and the second contact surface of the dielectric layer are smaller, and ensures that the ratio of the number of generated silicon oxide oxygen atoms to the number of silicon atoms is 1.5-2, so that the dielectric layer has a better passivation effect. And the upper limit of the content of the oxidant in the silver paste is set to 1 percent, so that the phenomenon that the content of the oxidant is increased inefficiently to influence the formation of a front electrode is avoided.
In step 3032, the semi-finished product of the battery with the silver paste printed on the passivation layer is sent to a sintering furnace to be heated for a first preset time to reach a first sintering temperature, so that the glass frit ablates the passivation layer and an oxide layer between the passivation layer and the emitter electrode to generate an electrode and a dielectric layer. The first preset time period is longer than the conventional sintering time period (about 40 seconds) and is at least 50 seconds. The sintering time can be prolonged by controlling the speed of a conveyor belt for conveying the semi-finished battery product in the sintering furnace and the residence time of the semi-finished battery product in each temperature area of the sintering furnace. For example, the conveyor belt may be set to move at a uniform speed lower than the normal speed. In order to control the thickness of the dielectric layer, the first preset time period can be set to be in the range of 50 to 100 seconds, so that the conductive performance between the electrode and the emitter is prevented from being influenced due to the overlarge thickness of the dielectric layer. Alternatively, the first preset time period is 50 seconds, 60 seconds, 70 seconds, 75 seconds, 80 seconds, 85 seconds, 90 seconds, 100 seconds, etc., and a suitable sintering time period may be selected according to the type of the battery or the size of the battery.
In some embodiments, the length of each stage in the sintering process may be controlled, and the thickness of the dielectric layer may be controlled. For example, the unfinished product may be heated to the second sintering temperature for a second preset time, and then heated to the first sintering temperature for a third preset time, where the first sintering temperature is 550 to 850 ℃, the third preset time is longer than 10 seconds and shorter than 35 seconds, and the first preset time is shorter than 100 seconds. Specifically, the unfinished product stays in a first sintering temperature zone of the sintering furnace, namely a third preset time period of a sintering stage (including a first sub-stage of the sintering stage and a second sub-stage of the sintering stage) is longer than 10 seconds and shorter than 35 seconds, and the second preset time period of the unfinished product staying in a second sintering temperature zone, namely a drying stage and a burning stage, is the difference between the first preset time period and the third preset time period. The detailed residence time of the unfinished battery in each temperature zone of the sintering furnace is as follows: the heating time of the drying stage is within 10 to 15 seconds, for example 10 seconds; the heating period of the combustion phase is within 30 to 40 seconds, for example 35 seconds; the heating time of the first sub-stage of the sintering stage is within 5 to 15 seconds, for example 7 seconds; the heating time of the second sub-stage of the sintering stage is within 5 to 20 seconds, for example 8 seconds; the cooling phase may be controlled to have a duration of 20 to 30 seconds, for example 25 seconds. The time taken for the battery green product to be in the sintering furnace is 70 to 120 seconds in total. It will be appreciated that the length of the above stages can be adjusted for different printing pastes.
Compared with the manufacturing method of the solar cell in the related technology, the manufacturing method of the solar cell in the embodiment has different components and sintering time in manufacturing the silver paste of the silver electrode, so that the dielectric layer can be arranged between the silver electrode and the emitter without adding other equipment and a complex manufacturing process, the existing manufacturing method of the solar cell is not required to be greatly changed, and the manpower and material resources for manufacturing the solar cell are saved.
In this embodiment, a back passivation layer and a back electrode on the back of the battery are also required to be formed, specifically, the back passivation layer may be formed on the back of the battery by using a PECVD method similar to that used for the front of the battery, the material of the back passivation layer may be aluminum oxide, and the back electrode is formed by screen printing and high-temperature sintering. The printing paste of the back electrode is different from the printing paste of the front electrode. The back of the battery is printed with aluminum paste and silver aluminum paste.
The steps of the above methods are divided for clarity, and the implementation may be combined into one step or split some steps, and the steps are divided into multiple steps, so long as the same logical relationship is included, which are all within the protection scope of the present patent; it is within the scope of the patent to add insignificant modifications to the flow or to introduce insignificant design, but not to change the core design of the flow.
Claims (12)
1. A solar cell, comprising:
the silicon substrate comprises a base region and an emitter, and the emitter is arranged on the surface of the base region;
a passivation layer on the surface of the emitter;
an electrode penetrating the passivation layer and electrically connected with the emitter;
the bottom surface of the electrode is provided with a dielectric layer, the dielectric layer is positioned in the emitter, and the dielectric layer is generated by the reaction of an oxidant in the conductive slurry and the emitter in the electrode sintering process.
2. The solar cell of claim 1, wherein the dielectric layer has a width equal to or greater than a width of a bottom surface of the electrode.
3. The solar cell according to claim 1 or 2, wherein the dielectric layer has a thickness of 1.2 to 2 nm.
4. The solar cell according to claim 3, wherein the dielectric layer is a silicon oxide layer, and a ratio of the number of oxygen atoms to the number of silicon atoms in the silicon oxide layer is 1.5 to 2.
5. The solar cell of claim 4, wherein a ratio of an oxygen content of the dielectric layer at a first contact surface with the electrode and a second contact surface with the emitter is less than 2; the oxygen content of the first contact surface is greater than the oxygen content of the second contact surface.
6. The solar cell according to claim 1 or 2, wherein the dielectric layer is selectively disposed on the bottom surface of the electrode, the dielectric layer isolating the bottom surface of the electrode and the emitter.
7. A photovoltaic module comprising the solar cell of claim 1.
8. A method for manufacturing a solar cell, comprising:
providing a silicon substrate comprising a base region and an emitter electrode, wherein the emitter electrode is arranged on the surface of the base region;
forming a passivation layer on the surface of the emitter;
and forming an electrode and a dielectric layer, wherein the electrode penetrates through the passivation layer and is electrically connected with the emitter, the dielectric layer is arranged on the bottom surface of the electrode, the dielectric layer is positioned in the emitter, and an oxidant in the conductive paste reacts with the emitter to generate the dielectric layer in the sintering process of the electrode.
9. The method of claim 8, wherein the process of forming the electrode and the dielectric layer comprises:
printing the conductive paste doped with the glass frit and the oxidant on a preset position on the surface of the passivation layer;
heating for a first preset time to a first sintering temperature, so that the passivation layer is ablated by the conductive slurry, and the electrode is generated;
during the formation of the electrode, the oxidant generates oxygen, which reacts with the emitter to generate the dielectric layer;
the first preset time period is greater than 50 seconds.
10. The method for manufacturing a solar cell according to claim 9, wherein the heating for the first predetermined time period to the first sintering temperature comprises:
and heating for a second preset time to a second sintering temperature, and then heating for a third preset time to the first sintering temperature, wherein the first sintering temperature is 550-850 ℃, the third preset time is longer than 10 seconds and shorter than 35 seconds, and the first preset time is shorter than 100 seconds.
11. The method of claim 10, wherein the oxidant is 0.3-1% by weight of the conductive paste.
12. The method of claim 8, wherein the process of forming the electrode and the dielectric layer comprises:
arranging an electrode groove at a preset electrode position, wherein the electrode groove penetrates through the passivation layer, and the bottom of the electrode groove is positioned in the emitting electrode;
forming the dielectric layer on the bottom surface of the electrode groove, wherein the dielectric layer covers the bottom surface of the electrode groove;
and forming the electrode in the electrode groove, wherein the electrode is filled in the electrode groove.
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| CN108666393A (en) * | 2018-07-16 | 2018-10-16 | 英利能源（中国）有限公司 | The preparation method and solar cell of solar cell |
| US20180320821A1 (en) * | 2016-12-20 | 2018-11-08 | Zhejiang Kaiying New Materials Co., Ltd. | Interdigitated back contact metal-insulator-semiconductor solar cell with printed oxide tunnel junctions |
| CN109524480A (en) * | 2018-11-26 | 2019-03-26 | 东方日升（常州）新能源有限公司 | A kind of p-type crystal silicon solar battery and preparation method thereof of local contact passivation |
| CN110190137A (en) * | 2019-04-28 | 2019-08-30 | 东方日升（常州）新能源有限公司 | A kind of dual layer passivation film and preparation method thereof for front face passivation |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| US20180320821A1 (en) * | 2016-12-20 | 2018-11-08 | Zhejiang Kaiying New Materials Co., Ltd. | Interdigitated back contact metal-insulator-semiconductor solar cell with printed oxide tunnel junctions |
| CN108666393A (en) * | 2018-07-16 | 2018-10-16 | 英利能源（中国）有限公司 | The preparation method and solar cell of solar cell |
| CN109524480A (en) * | 2018-11-26 | 2019-03-26 | 东方日升（常州）新能源有限公司 | A kind of p-type crystal silicon solar battery and preparation method thereof of local contact passivation |
| CN110190137A (en) * | 2019-04-28 | 2019-08-30 | 东方日升（常州）新能源有限公司 | A kind of dual layer passivation film and preparation method thereof for front face passivation |
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