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US20170352769A1 - Solar cell and solar cell module - Google Patents

Solar cell and solar cell module Download PDF

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Publication number
US20170352769A1
US20170352769A1 US15/523,923 US201515523923A US2017352769A1 US 20170352769 A1 US20170352769 A1 US 20170352769A1 US 201515523923 A US201515523923 A US 201515523923A US 2017352769 A1 US2017352769 A1 US 2017352769A1
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solar cell
back surface
substrate
resistivity
cell according
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Hiroyuki Otsuka
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Shin Etsu Chemical Co Ltd
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Shin Etsu Chemical Co Ltd
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Publication of US20170352769A1 publication Critical patent/US20170352769A1/en
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    • H01L31/022441—
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
    • H10F77/00—Constructional details of devices covered by this subclass
    • H10F77/20—Electrodes
    • H10F77/206—Electrodes for devices having potential barriers
    • H10F77/211—Electrodes for devices having potential barriers for photovoltaic cells
    • H10F77/219—Arrangements for electrodes of back-contact photovoltaic cells
    • H01L31/02167—
    • H01L31/068—
    • H01L31/18—
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
    • H10F10/00—Individual photovoltaic cells, e.g. solar cells
    • H10F10/10—Individual photovoltaic cells, e.g. solar cells having potential barriers
    • H10F10/14—Photovoltaic cells having only PN homojunction potential barriers
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
    • H10F71/00—Manufacture or treatment of devices covered by this subclass
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
    • H10F77/00—Constructional details of devices covered by this subclass
    • H10F77/10—Semiconductor bodies
    • H10F77/12—Active materials
    • H10F77/122—Active materials comprising only Group IV materials
    • H10F77/1223—Active materials comprising only Group IV materials characterised by the dopants
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
    • H10F77/00—Constructional details of devices covered by this subclass
    • H10F77/10—Semiconductor bodies
    • H10F77/16—Material structures, e.g. crystalline structures, film structures or crystal plane orientations
    • H10F77/162—Non-monocrystalline materials, e.g. semiconductor particles embedded in insulating materials
    • H10F77/166—Amorphous semiconductors
    • H10F77/1662—Amorphous semiconductors including only Group IV materials
    • H10F77/1668—Amorphous semiconductors including only Group IV materials presenting light-induced characteristic variations, e.g. Staebler-Wronski effect
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
    • H10F77/00—Constructional details of devices covered by this subclass
    • H10F77/20—Electrodes
    • H10F77/206—Electrodes for devices having potential barriers
    • H10F77/211—Electrodes for devices having potential barriers for photovoltaic cells
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
    • H10F77/00—Constructional details of devices covered by this subclass
    • H10F77/30—Coatings
    • H10F77/306—Coatings for devices having potential barriers
    • H10F77/311—Coatings for devices having potential barriers for photovoltaic cells
    • 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
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy
    • 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
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy
    • Y02E10/547—Monocrystalline silicon PV cells

Definitions

  • the present invention relates to a solar cell and a solar cell module.
  • CZ method Czochralski method
  • P-type semiconductor substrates can be obtained by drawing a silicon single crystal doped with boron by a CZ method, and slicing this single crystal.
  • Single crystal silicon solar cells (solar cells made of single crystal silicon substrates) have been configured to have a structure in which the whole surface of the backside (the surface opposite to the light-receiving surface) is in contact with the electrode via a Back Surface Field (BSF) structure.
  • BSF Back Surface Field
  • the BSF structure can be easily introduced by a screen printing method, and is widely spread to be the mainstream of structures of present silicon single crystal solar cells.
  • a Passivated Emitter and Rear Contact Solar Cell (PERC) structure and a Passivated Emitter and Rear Locally Diffused Solar Cell (PERL) structure come to be introduced in order to further improve the efficiency.
  • PERC Passivated Emitter and Rear Contact Solar Cell
  • PROL Passivated Emitter and Rear Locally Diffused Solar Cell
  • the PERC structure and the PERL structure are methods to aggressively reduce the recombination rate of minority carriers on the back surface, that is, methods to reduce an effective surface recombination velocity on the back surface.
  • FIG. 9 The cross section of a previous solar cell having a PERC structure is schematically shown in FIG. 9 .
  • the solar cell 110 is provided with the N-type layer 112 on the side of the light-receiving surface of the silicon substrate 113 doped with boron (hereinafter, also described as a boron-doped substrate), and the finger electrodes 111 on this N-type layer 112 .
  • the solar cells have the passivation layer 115 on the light-receiving surface.
  • the solar cell is also provided with the passivation layer 116 on the back surface, the electrodes 114 on the back surface, and the contact areas 117 where the boron-doped substrate 113 is locally in contact with the back surface electrodes 114 .
  • the solar cell 110 ′ is the solar cell 110 that is provided with the P + layer (i.e., the layer which is doped with P-type dopant in higher concentration than the surrounding area (P-type silicon substrate)) 119 immediately under the back surface electrodes 114 .
  • P + layer i.e., the layer which is doped with P-type dopant in higher concentration than the surrounding area (P-type silicon substrate)
  • N + layer i.e., the layer which is doped with N-type dopant in higher concentration than the surrounding N-type layer 112
  • Other structures are similar to the solar cell having a PERC structure in FIG. 9 , and the explanation is omitted.
  • a solar cell has the PERC structure or the PERL structure to reduce the recombination rate of minority carriers on the back surface
  • the substrate is a boron-doped substrate
  • the interstitial boron atom combines with interstitial oxygen atoms by irradiated light to form a recombination site in the substrate bulk, which reduces the lifetime of the minority carriers to degrade the characteristics of the solar cell.
  • This phenomenon is also referred to as light-induced degradation of a solar cell using a boron-doped substrate.
  • the electrode on the back surface is localized. This generates current crowding in the vicinity of the contact (i.e., the contact area where the substrate is in contact with the back surface electrode), and tends to cause resistance loss. Accordingly, a substrate with low resistance is preferable in the solar cell having the PERC structure or the PERL structure. However, when using a substrate with low resistance, that is, in a situation in which more boron atoms are contained, the combination of a boron atom and oxygen atoms increases to make the degradation (light-induced degradation) noticeable thereby.
  • Patent Literature 1 suggests the use of gallium as P-type dopant instead of boron. It has been impossible to sufficiently prevent the resistance loss, however, only by using a silicon substrate doped with gallium (hereinafter, also referred to as a gallium-doped substrate) as the substrate of the solar cell having the PERC structure or the PERL structure.
  • a silicon substrate doped with gallium hereinafter, also referred to as a gallium-doped substrate
  • the present invention was accomplished in view of the above-described problems. It is an object of the present invention to provide a solar cell and a solar cell module having excellent conversion efficiency with the resistance loss being prevented, with the solar cell using a substrate the light-induced degradation of which is eliminated.
  • the present invention provides a solar cell comprising a P-type silicon substrate in which one main surface is a light-receiving surface and another main surface is a backside, a plurality of back surface electrodes formed on a part of the backside, an N-type layer in at least a part of the light-receiving surface of the P-type silicon substrate, and contact areas in which the P-type silicon substrate is in contact with the back surface electrodes;
  • the P-type silicon substrate is a silicon substrate doped with gallium
  • the P-type silicon substrate has a resistivity of 2.5 ⁇ cm or less
  • a back surface electrode pitch P rm [mm] of the plurality of back surface electrodes and the resistivity R sub [ ⁇ cm] of the P-type silicon substrate satisfy the relation represented by the following formula (1)
  • the substrate is a gallium-doped substrate, the light-induced degradation is eliminated.
  • the substrate is also a substrate with lower resistance, which hardly generates current crowding in the contact area to scarcely cause resistance loss.
  • the solar cell has the PERC structure with a lower resistance substrate, and can sufficiently reduce the recombination rate of the minority carriers on the back surface side.
  • the pitch of the electrodes on the back surface hereinafter, also referred to as a back surface electrode pitch
  • the resistivity of the substrate satisfy the relation represented by the foregoing formula (1), which makes it possible to minimize the resistance loss due to the current crowding and to further increase the output power.
  • the resistivity of the P-type silicon substrate be 0.2 ⁇ cm or more.
  • Such solar cells can generate current in virtually the same level even when the solar cell module is composed of solar cells with different resistivity. Accordingly, excess loss can be reduced when the solar cell module is fabricated using such solar cells.
  • the pitch of back surface electrodes be 10 mm or less.
  • Such a solar cell can be definitely a solar cell with excellent conversion efficiency.
  • each of the contact areas have a higher P-type dopant concentration than other area.
  • Such a solar cell with a PERL structure having a so-called P + layer is excellent in conversion efficiency.
  • the total area of the contact areas be 20% or less of the total backside area.
  • Such a solar cell makes it possible to further reduce the carrier recombination on the contact between the substrate and the electrode while making the contact resistance lower between the substrate and the electrode.
  • the present invention also provides a solar cell module comprising the inventive solar cell.
  • the light-induced degradation and the resistance loss are eliminated, while the conversion efficiency is excellent. Accordingly, in the solar cell module provided with the inventive solar cell, the light-induced degradation and the resistance loss are eliminated, while the conversion efficiency is excellent.
  • the substrate is a gallium-doped substrate, the light-induced degradation is eliminated.
  • the substrate is also a substrate with lower resistance, which hardly generates current crowding near the contact area to scarcely cause resistance loss.
  • the solar cell has the PERC structure or the PERL structure with a lower resistance substrate, and can sufficiently reduce the recombination rate of the minority carriers on the back surface side.
  • the electrode pitch on the back surface and the resistivity of the substrate satisfy the relation represented by the foregoing formula (1), which makes it possible to minimize the resistance loss due to the current crowding and to further increase the output power.
  • FIG. 1 is a sectional view showing an example of the inventive solar cell
  • FIG. 2 is a schematic drawing of the solar cell shown in FIG. 1 on a perspective projection of the P-type silicon substrate;
  • FIG. 3 is a sectional view showing an example of the inventive solar cell
  • FIG. 4 is a schematic drawing of the solar cell shown in FIG. 3 on a perspective projection of the P-type silicon substrate;
  • FIG. 5 is a flow diagram of an example of a method for manufacturing the inventive solar cell
  • FIG. 6 is a diagram of the average conversion efficiency of the solar cell as a function of the electrode pitch on the back surface and the substrate resistivity of the gallium-doped substrate after sufficient irradiation of the sunlight;
  • FIG. 7 is a diagram of the average conversion efficiency of the solar cell as a function of the electrode pitch on the back surface and the substrate resistivity of the boron-doped substrate after sufficient irradiation of the sunlight;
  • FIG. 8 is a diagram of the average short-circuit current density of the solar cell as a function of the electrode pitch on the back surface and the substrate resistivity of the gallium-doped substrate;
  • FIG. 9 is a sectional view schematically showing a previous solar cell having a PERC structure.
  • FIG. 10 is a sectional view schematically showing a previous solar cell having a PERL structure.
  • the inventor has diligently investigated to solve the problems. As a result, the inventor has found that the foregoing problem can be solved with the solar cell having a PERC structure or a PERL structure provided with a gallium-doped substrate having a lower resistance, with the back surface electrode pitch and the resistivity substrate satisfying a specific relation; thereby brought the inventive solar cell and the solar cell module to completion.
  • FIG. 1 is a sectional view showing an example of the inventive solar cell.
  • FIG. 2 is a schematic drawing of the solar cell shown in FIG. 1 on a perspective projection of the P-type silicon substrate 13 .
  • the inventive solar cell 10 is provided with the P-type silicon substrate (gallium-doped substrate) 13 in which one of the main surface is a light-receiving surface and another main surface is a backside. This also has a plurality of back surface electrodes 14 formed on a part of the backside of the P-type silicon substrate 13 .
  • the P-type silicon substrate 13 has an N-type layer 12 in at least a part of the light-receiving surface, and also has the contact areas 17 where the P-type silicon substrate 13 is in contact with the back surface electrodes 14 .
  • the N-type layer 12 is generally provided with the light-receiving surface electrode 11 thereon.
  • the P-type silicon substrate 13 is a gallium-doped substrate. By changing the P-type dopant from boron to gallium like this, the light-induced degradation can be eliminated.
  • the P-type silicon substrate 13 has a resistivity (specific resistance) of 2.5 ⁇ cm or less. The resistivity more than 2.5 ⁇ cm can cause current crowding in the vicinity of portions on the back surface side where the P-type silicon substrate 13 is in contact with the back surface electrodes 14 , which can cause resistance loss.
  • the inventive solar cell is provided with a gallium-doped substrate having lower resistance (i.e., a substrate with high gallium concentration).
  • the solar cell having a PERC structure or a PERL structure is particularly excellent in conversion efficiency when having a substrate with lower resistance. Accordingly, the inventive solar cell is particularly excellent in conversion efficiency.
  • the inventive solar cell, having a gallium-doped substrate with lower resistance hardly yield light-induced degradation, which occurs in a boron-doped substrate with lower resistance (i.e., a substrate with high boron concentration), and can keep the high efficiency.
  • the back surface electrode pitch P rm [mm] of the plurality of back surface electrodes 14 and the resistivity R sub [ ⁇ cm] of the P-type silicon substrate 13 satisfy the relation represented by the following formula (1)
  • the back surface electrode pitch 20 is shown in FIG. 1 .
  • the back surface electrode pitch 20 and the resistivity of the gallium-doped substrate 13 do not satisfy the relation represented by the formula (1), it is not possible to sufficiently prevent resistance loss due to current crowding, causing the decrease in the output power.
  • the relation of the formula (1) was obtained by the following computer simulation.
  • the conversion efficiency of the solar cell was simulated by using a computer, as a function of the electrode pitch on the back surface and the resistivity of the gallium-doped substrate. The results are shown in FIG. 6 .
  • the conversion efficiency of the solar cell was also simulated by using a computer, as a function of the electrode pitch on the back surface and the resistivity of the boron-doped substrate.
  • the results are shown in FIG. 7 .
  • the conversion efficiency is shown by the light and shade. It is also shown by contour lines of conversion efficiency, each of which links each point of combination of the resistivity of the substrate and the back surface electrode pitch.
  • FIG. 6 is a diagram showing the average conversion efficiency of the solar cell as a function of the electrode pitch on the back surface and the substrate resistivity of the gallium-doped substrate after sufficient irradiation of the sunlight.
  • the resistivity of the gallium-doped substrate was 2.5 ⁇ cm or less, and the back surface electrode pitch and the substrate resistivity of a gallium-doped substrate satisfied the relation represented by the foregoing formula (1), the results of conversion efficiency were excellent.
  • the conversion efficiency suddenly dropped when the resistivity was more than 2.5 ⁇ cm or when the formula (1) was not satisfied.
  • FIG. 7 is a diagram of the average conversion efficiency of the solar cell as a function of the electrode pitch on the back surface and the substrate resistivity of the boron-doped substrate after sufficient irradiation of the sunlight.
  • the conversion efficiency was inferior to the case of using a gallium-doped substrate. This shows an influence of light-induced degradation. In this instance, the conversion efficiency suddenly dropped in some cases even when the back surface electrode pitch and the substrate resistivity of a boron-doped substrate satisfied the relation represented by the formula (1).
  • FIG. 8 is a diagram showing the average short-circuit current density of the solar cell as a function of the electrode pitch on the back surface and the substrate resistivity of the gallium-doped substrate.
  • the short-circuit current density are shown by the light and shade. They are also shown as contour lines of the short-circuit current density, each of which links each point of combination of the resistivity of the substrate and the back surface electrode pitch. As shown in FIG. 8
  • the resistivity of a gallium-doped substrate was 0.2 ⁇ cm or more
  • the short-circuit current density showed much smaller variation than the substrate resistivity.
  • the thickness of the P-type silicon substrate 13 is not particularly limited, and can be a thickness of 100 to 200 ⁇ m, for example.
  • the shape and area of the main surface of the P-type silicon substrate 13 is not particularly limited.
  • the back surface electrode pitch 20 of the plurality of back surface electrodes be 10 mm or less. Such a solar cell is excellent in conversion efficiency as shown in FIG. 6 .
  • the lower limit of the back surface electrode pitch 20 is not particularly limited, and can be 1 mm, for example.
  • each P-type dopant concentration in the contact areas 17 be higher than the P-type dopant concentration in an area other than the contact areas 17 .
  • FIG. 3 is a sectional view showing an example of the inventive solar cell.
  • FIG. 4 is a schematic drawing of the solar cell shown in FIG. 3 on a perspective projection of the P-type silicon substrate 13 .
  • the same reference number is given to each of the same components as those in the solar cell shown in FIG. 1 , and the explanation is omitted.
  • the solar cell 10 ′ is the one in which the foregoing solar cell 10 is provided with N + layer 18 immediately under the light-receiving surface electrode 11 , and the P + layer 19 immediately under the back surface electrodes 14 (in the vicinity of the contact areas 17 ).
  • Such a solar cell having a PERL structure can be a solar cell that is excellent in conversion efficiency.
  • the total area of the contact areas 17 be 20% or less on the basis of the whole of the backside. In such a solar cell, it is possible to further reduce the recombination of carriers due to the contact between the substrate and the electrode while making the contact resistance much lower between the substrate and the electrode.
  • the lower limit of the total area of the contact areas 17 is not particularly limited, and can be 5%, for example.
  • The, electrode widths of the light-receiving surface electrode 11 and the back surface electrodes 14 are not particularly limited, and can be 15 to 100 ⁇ m, for example.
  • the inventive solar cell 10 is generally provided with the surface passivation layer 16 on the back surface. It is also possible to have the surface passivation layer 15 on the light-receiving surface.
  • the passivation layer 15 on the light-receiving surface can also act as an anti-reflection film, etc.
  • As these passivation layers it is possible to use a silicon nitride layer (SiNx layer) and SiO 2 layer, which can be fabricated by using a plasma CVD, and to use a thermal oxide layer too.
  • the effect on anti-reflection shows maximum value when the layer thickness of the anti-reflection film is 85 to 105 nm, which is favorable.
  • metal such as aluminum on the whole surface of the back surface passivation layer 16 to form a structure in which the plurality of back surface electrodes 14 are connected with each other (i.e., a structure in which the back surface electrodes 14 are integrated).
  • N-type dopant contained in the N-type layer 12 and the N + layer 18 include P (phosphorus), Sb (antimony), As (arsenic), and Bi (bismuth).
  • P-type dopant contained in the P + layer 19 include B (boron), Ga (gallium), Al (aluminum), and In (indium).
  • inventive solar cell module is provided with the foregoing inventive solar cell. Specifically, it can be formed by connecting a plurality of the arranged inventive solar cells in series by using an inter connector, for example. Various module structures can be applied without limiting thereto. In such a solar cell module, the light-induced degradation and resistance loss are eliminated, and the conversion efficiency is excellent.
  • FIG. 5 is a process flow diagram showing an example of a method for manufacturing the inventive solar cell.
  • the method described below is a typical example, and the method for manufacturing the inventive solar cell is not limited thereto.
  • a gallium-dopes substrate with a resistivity of 2.5 ⁇ cm or less is prepared for the P-type silicon substrate in which one main surface is a light-receiving surface and another main surface is a backside.
  • the resistivity of the gallium-doped substrate prepared in the step (a) be 0.2 ⁇ cm or more.
  • the resistivity of an ingot grown by a CZ method differs by about six times at the top and at the tail. In order to manufacture a solar cell at low cost, it is desirable to use each of these ingots entirely one piece, and it is preferable that the difference of the resistivity of a substrate be considered in the design stage.
  • a gallium-doped substrate with a resistivity of 0.2 ⁇ cm or more in the step (a) it is possible to manufacture plural solar cells having a PERC structure or a PERF structure which can show similar current even when these solar cells differ the resistivity by about six times, and to reduce excess loss when these solar cells are modularized. This makes it possible to manufacture a solar cell module at lower cost.
  • the method for measuring the resistivity of a gallium-doped substrate is not particularly limited, and includes a four-point prove method, for example.
  • the silicon single crystal from which the gallium-doped substrate is sliced can be produced by a CZ method, for example, as described above.
  • gallium and a polycrystalline material may be introduced into a crucible in a lump to form a raw material melt. It is desirable to produce dopant by producing and pulverizing a silicon single crystal doped with higher concentration of gallium, and to adjust the concentration by introducing the dopant into melted polycrystalline silicon for CZ material so as to have a desired concentration, since it is necessary to precisely adjust the concentration, particularly in mass production.
  • the gallium-doped substrate can be obtained by slicing thus obtained gallium-doped silicon single crystal.
  • slice damages on the surface of the substrate can be removed by etching with a high-concentration alkaline solution such as sodium hydroxide and potassium hydroxide in a concentration of 5 to 60%, or mixed acid of hydrofluoric acid and nitric acid, etc. as shown in FIG. 5( b ) .
  • a high-concentration alkaline solution such as sodium hydroxide and potassium hydroxide in a concentration of 5 to 60%, or mixed acid of hydrofluoric acid and nitric acid, etc.
  • the texture is an effective method to reduce the reflectance of a solar cell.
  • the texture can be produced by immersing the substrate in heated alkaline solution (concentration: 1 to 10%, temperature: 60 to 100° C.) such as sodium hydroxide, potassium hydroxide, potassium carbonate, sodium carbonate, and sodium hydrogencarbonate for about 10 minutes to 30 minutes.
  • heated alkaline solution concentration: 1 to 10%, temperature: 60 to 100° C.
  • sodium hydroxide, potassium hydroxide, potassium carbonate, sodium carbonate, and sodium hydrogencarbonate for about 10 minutes to 30 minutes.
  • IPA isopropyl alcohol
  • the cleaning can be performed by using an aqueous acid solution of hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid, or mixed solvent thereof; or pure water, for example.
  • N-type layer is formed on the light-receiving surface of the gallium-doped substrate.
  • the method for forming an N-type layer in the step (e) is not particularly restricted.
  • a method to thermally diffuse the dopant This includes a vapor phase diffusion method in which POCl 3 (phosphoryl chloride) and the like introduced into a quartz tube furnace with carrier gas are diffused or a coating diffusion method in which a phosphorus-containing material and the like applied onto a substrate is diffused by thermal treatment.
  • the coating method in the coating diffusion method includes spin-coating method, spray-coating method, ink-jet method, and screen printing method.
  • the N-type layer can be formed by coating the light-receiving surface with a material which contains N-type dopant followed by thermal treatment.
  • a material which contains N-type dopant it is possible to use a phosphorus diffusion source, which turns to glass by thermal treatment.
  • This phosphorus diffusion source includes any known ones, and can be obtained by mixing P 2 O 5 , pure water, polyvinyl alcohol (PVA), and tetraethyl orthosilicate (TEOS), for example.
  • a method for manufacturing a solar cell having a PERL structure provided with an N + layer on the light-receiving surface side and a P + layer on the back surface side it is possible to enumerate a method in which the light-receiving surface is locally coated with the N-type dopant-containing material, and the back surface is locally coated with P-type dopant-containing material, and then the substrate is subjected to a thermal treatment.
  • This boron diffusion source includes any known ones, and can be obtained by mixing B 2 O 3 , pure water, and PVA, for example.
  • the PN junction is isolated by using a plasma etcher.
  • samples are stacked so as to prevent plasma and radical from getting into the light-receiving surface or the backside, and the side faces of the substrate are dry-etched by several microns under this stacked condition.
  • This PN isolation by plasma etching may be performed before removing the boron glass and phosphorus glass or may be performed after the removal. It is also possible to form a trench with laser as an alternative method to the PN isolation.
  • step (e) After the step (e), not a little quantity of glass layer is formed on the surface of the substrate.
  • the glass on the surface is removed by hydrofluoric acid, etc., as shown in FIG. 5( g ) .
  • a surface passivation layer can be formed on the light-receiving surface of the gallium-doped substrate.
  • the light-receiving surface passivation layer it is possible to use the same ones described in the item of the solar cell.
  • a surface passivation layer can be deposited on the back surface of the gallium-doped substrate.
  • the back surface passivation layer it is possible to use the same ones described in the item of the solar cell.
  • the back surface passivation layer can be removed just on the contact area for a back surface electrode.
  • the removal of the back surface passivation layer can be performed by using a photo-lithography method or an etching paste, for example.
  • This etching paste contains at least one selected from the group consisting of phosphoric acid, hydrofluoric acid, ammonium fluoride, and ammonium hydrogen fluoride as an etching component together with water, organic solvent, and a viscosity agent, for example.
  • a paste for a back surface electrode is printed onto the backside of the gallium-doped substrate, followed by drying.
  • a paste in which Al powders are mixed with an organic binder is applied onto the backside of the substrate by screen printing.
  • Ag and so on also can be used.
  • the back surface electrode needs to be formed on the contact area at least. Alternatively, the back surface electrode may be formed and integrated to the whole back surface. In this case, the back surface electrode actually contacts the substrate locally.
  • a paste for a light-receiving surface electrode is printed onto the light-receiving surface of the gallium-doped substrate, followed by drying.
  • a paste for a light-receiving surface electrode is printed onto the light-receiving surface of the gallium-doped substrate, followed by drying.
  • an Ag paste in which Ag powders and glass frit are mixed with an organic binder is applied onto the light-receiving surface of the substrate by screen printing.
  • the step (k) and the step (l) may be performed in the opposite order.
  • the light-receiving surface electrode and the back surface electrode are formed by printing the pastes followed by firing.
  • the firing is generally performed by thermal treatment at a temperature of 700 to 800° C. for 5 to 30 minutes. This thermal treatment makes the Ag powders penetrate to the passivation layer (fire through) on the light-receiving surface side to electrically conduct the light-receiving surface electrode and the gallium-doped substrate. It is also possible to bake back surface electrode and the light-receiving surface electrode separately.
  • the solar cell shown in FIG. 1 and FIG. 3 can be manufactured.
  • the inventive solar cell module can be obtained by modularizing the solar cells thus obtained.

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US20200185552A1 (en) 2020-06-11
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TW202127679A (zh) 2021-07-16
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US11742438B2 (en) 2023-08-29
US12402434B2 (en) 2025-08-26
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EP3220424A1 (en) 2017-09-20
TWI720955B (zh) 2021-03-11
EP3220424A4 (en) 2018-04-25
WO2016075867A1 (ja) 2016-05-19
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TW201630207A (zh) 2016-08-16
US20190181280A1 (en) 2019-06-13

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