WO2013190646A1 - Cellule solaire et procédé de fabrication de celle-ci - Google Patents

Cellule solaire et procédé de fabrication de celle-ci Download PDF

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WO2013190646A1
WO2013190646A1 PCT/JP2012/065679 JP2012065679W WO2013190646A1 WO 2013190646 A1 WO2013190646 A1 WO 2013190646A1 JP 2012065679 W JP2012065679 W JP 2012065679W WO 2013190646 A1 WO2013190646 A1 WO 2013190646A1
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emitter layer
nanopillar
substrate
solar cell
conductivity type
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PCT/JP2012/065679
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English (en)
Japanese (ja)
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渡邉敬司
松村三江子
服部孝司
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株式会社日立製作所
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Priority to PCT/JP2012/065679 priority Critical patent/WO2013190646A1/fr
Priority to JP2014521135A priority patent/JP5802833B2/ja
Priority to TW102121551A priority patent/TWI503999B/zh
Publication of WO2013190646A1 publication Critical patent/WO2013190646A1/fr

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/0248—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies
    • H01L31/0352—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by their shape or by the shapes, relative sizes or disposition of the semiconductor regions
    • H01L31/035272—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by their shape or by the shapes, relative sizes or disposition of the semiconductor regions characterised by at least one potential jump barrier or surface barrier
    • H01L31/03529—Shape of the potential jump barrier or surface barrier
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/04—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices
    • H01L31/06—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by potential barriers
    • H01L31/068—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by potential barriers the potential barriers being only of the PN homojunction type, e.g. bulk silicon PN homojunction solar cells or thin film polycrystalline silicon PN homojunction solar cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/18—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
    • H01L31/1804—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof comprising only elements of Group IV of the Periodic Table
    • 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
    • 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

Definitions

  • the present invention relates to a solar battery cell and a manufacturing method thereof.
  • a texture structure formed by wet etching with an alkaline solution or an acid solution is most commonly used as a surface antireflection structure for solar cells.
  • a lower reflectance is realized by using a structure (so-called sub-wavelength structure) in which irregularities having a size equivalent to or smaller than the wavelength of sunlight are periodically formed in the surface antireflection structure. It is known. Therefore, it is expected that the reflectance can be reduced and the output current can be increased by using the sub-wavelength structure as the surface antireflection structure of the solar battery cell.
  • Non-Patent Document 1 among the sub-wavelength structures, by using a nanopillar array structure, which will be described later, as a surface antireflection structure, an output current can be increased by an antireflection effect as compared with a solar cell having a conventional structure. This is shown by simulation.
  • Nanowire here is synonymous with the nanopillar in this specification.
  • Nanowire Solar Cell subsurface-junction
  • Nanowire Solar Cell planar-junction
  • Nanowire Solar Cell planar-junction
  • NanowireSell planar shallow-junction nanopillar solar cell
  • NanowireSell NanowireSell.
  • ⁇ junction is referred to as a radial junction type nanopillar solar cell, respectively.
  • a pn junction is formed by forming an n + layer doped with impurities at a high concentration on the surface of the p-type substrate (p and n are reversed). But it ’s okay.)
  • a layer doped with an impurity at a high concentration is referred to as an “emitter layer”.
  • the role of the emitter layer is mainly to form a potential difference of the pn junction to separate electrons and holes, to serve as a conduction path until carriers collected in the emitter layer reach the electrode, and to the electrode It is the three points of the role which reduces the contact resistance.
  • the pn junction surface is formed in a planar shape parallel to the substrate surface.
  • the pn junction surface is formed in parallel with the nanopillar surface.
  • the difference between the above three types of solar cells is in the position of the emitter layer in the nanopillar.
  • the emitter layer In the planar deep junction nanopillar solar cell, the emitter layer is present in the entire area of the nanopillar.
  • the emitter layer exists on the top of the nanopillar.
  • the emitter layer In the radial junction nanopillar solar cell, the emitter layer is present on the side wall of the nanopillar.
  • the position of the emitter layer in the nanopillar is different, in any conventional nanopillar solar cell structure, the emitter layer is present in at least a part of the nanopillar region.
  • Non-Patent Document 2 describes the result of examining the carrier generation rate distribution in the nanopillar solar cell by simulation, and the carrier generation rate inside the nanopillar is compared with the carrier generation rate in the substrate immediately below it. It is shown that it is 2 to 3 digits higher.
  • Patent Document 1 discloses a solar cell in which a plurality of openings having a light confinement effect are provided on a substrate surface. At first glance, this seems to be a structure related to the third embodiment of the present invention, but the opening width of the opening is about 1 to 15 ⁇ m, which is different from the sub-wavelength structure described above. The size of the order. Therefore, the technique described in Patent Document 1 expects an optical effect different from that of the third embodiment of the present invention. Details will be described later in the third embodiment.
  • FIG. 9 shows the result of the study made by the inventors prior to the present invention.
  • FDTD method Finite Differential Time Domain method
  • a highly doped semiconductor has a high probability of Auger recombination among various recombination processes. Also, the Auger recombination lifetime decreases with increasing impurity concentration. For this reason, even if light absorption occurs in a highly doped semiconductor and electron-hole pairs are generated, there is a high probability that these carriers will disappear due to Auger recombination within a short time. Therefore, the loss due to Auger recombination becomes a problem in solar cells in which the emitter layer is present in the nanopillar.
  • the planar deep junction type nanopillar solar cell has the largest recombination loss because the volume occupied by the emitter layer is larger than the other two types of structures.
  • the recombination loss is relatively small because the emitter layer is thinned.
  • at least a part of the nanopillar is still present. Recombination loss due to the presence of a heavily doped emitter layer in the region is inevitable.
  • the carrier generation rate at the side wall of the nanopillar 2 is particularly high. Therefore, in the radial junction type nanopillar solar cell, although the emitter layer is thinned, there is a concern that the recombination loss is increased by doping all the side wall portions with high concentration. Is done.
  • the emitter layer is composed of a continuous layer. Therefore, even if the surface electrode is provided in any region of the emitter layer, carriers from the entire emitter layer can reach the surface electrode. . Therefore, the surface electrode can be provided in a region different from the nano pillar. Therefore, the surface electrode may be a finger / bus bar pattern electrode made of a non-transparent metal such as Ag or Al, which is generally used in crystalline Si solar cells, or ITO used in thin film solar cells. An electrode in which a transparent conductive oxide such as (In—Sn—O) is formed on the entire surface may also be used.
  • the electrode of the finger / bus bar pattern cannot be used as the surface electrode, and it is necessary to use the electrode formed on the entire surface, As a result, the material of the electrode is limited to a transparent conductive oxide such as ITO.
  • ITO transparent conductive oxide
  • the emitter layer is thinned as described above, so that the sheet resistance of the emitter layer is high. As a result, when a pattern electrode is used, the series resistance loss is reduced. Since it becomes large, it is necessary to use an electrode formed on the entire surface as the surface electrode.
  • the upper part of the nanopillar is also covered with the electrode, so that a metal such as Ag or Al that reflects sunlight. Cannot be used as a surface electrode. Therefore, the material of the surface electrode is limited to the transparent conductive oxide.
  • a contact resistance between the emitter layer and the transparent conductive oxide and a loss due to light absorption of the transparent conductive oxide are generated.
  • contact resistance will be described.
  • transparent conductive oxides such as ITO have a higher contact resistance with semiconductor materials such as Si.
  • the contact resistance can be reduced by increasing the surface impurity concentration of the semiconductor.
  • increasing the surface impurity concentration in the solar cell increases the recombination loss. Therefore, the surface impurity concentration cannot be arbitrarily increased to reduce the contact resistance. Therefore, when a transparent conductive oxide is used as a surface electrode, it is difficult to avoid both loss due to high contact resistance and recombination loss at the same time.
  • transparent conductive oxides are generally known to absorb ultraviolet light and infrared light, and when used as surface electrodes, the amount of light reaching the light absorption layer of the solar battery cell is reduced. Loss occurs. From the above, when a transparent conductive oxide such as ITO is used as the surface electrode, it becomes a factor that causes a decrease in the characteristics of the solar battery cell.
  • the problems of the conventional solar cell using the sub-wavelength structure, particularly the nanopillar array structure as the surface antireflection structure are as follows. First, in a solar cell in which a highly doped emitter layer exists inside the nanopillar, there is a problem that recombination loss is large. Secondly, in a solar cell in which the emitter layers are isolated from each other or a solar cell in which the emitter layer is thinned, a pattern electrode cannot be used as a surface electrode, and a transparent conductive oxide such as ITO is used on the entire surface. It is necessary to use the electrode formed in this, and as a result, a contact resistance between the emitter layer and the transparent conductive oxide and a loss due to light absorption of the transparent conductive oxide are generated. In the solar cell having the sub-wavelength structure, there has been no method for solving the above two problems.
  • This invention is made
  • a solar battery cell having a plurality of pillars extending in a predetermined direction and having a first conductivity type and a second conductivity type different from the first conductivity type provided in contact with the substrate. And a plurality of pillars made of a semiconductor of a first conductivity type, and each of the plurality of pillars is in contact with the emitter layer on a side surface thereof.
  • the solar cell has a plurality of columnar recesses on the surface thereof, a first conductivity type substrate, a surface of the substrate and a portion where the columnar recesses are not provided, and the first conductivity type.
  • a method for manufacturing a solar cell the first step of forming a second conductivity type emitter layer different from the first conductivity type on the surface of the first conductivity type substrate using the metal pattern as a mask, And a second step of forming a plurality of first conductivity type pillars on the surface of the substrate using a metal pattern.
  • a solar cell having a subwavelength structure it is possible to achieve both reduction of recombination loss inside the subwavelength structure and use of a pattern electrode as a surface electrode.
  • nanopillar photovoltaic cell concerning Example 1 of the present invention. It is sectional drawing of the nanopillar photovoltaic cell which concerns on Example 1 of this invention. It is a top view of the structure which remove
  • nano groove solar cell concerning Example 2 of the present invention. It is sectional drawing of the nano groove photovoltaic cell which concerns on Example 2 of this invention. It is a top view of the structure which remove
  • the nanopillar array structure is a structure in which columnar structures (hereinafter referred to as “nano pillars” or simply “pillars”) having a width equal to or finer than the wavelength of sunlight are periodically arranged on the substrate surface. .
  • the column axis direction of the columnar structure is perpendicular to the substrate surface.
  • a cylinder is cited as an example of a nanopillar, but a different cross-sectional shape such as a prism may be used.
  • the nanohole array structure is a structure in which voids forming a columnar structure having a width equal to or finer than the wavelength of sunlight are periodically formed on the substrate surface.
  • the column axis direction of the columnar structure is perpendicular to the substrate surface.
  • the shape of the columnar structure may be a different cross-sectional shape such as a prism instead of a cylinder.
  • convex portions having a width equal to or finer than the wavelength of sunlight are periodically arranged on the substrate surface. As a result, periodic grooves (grooves) are formed between the convex portions. It has a structure.
  • the cross-sectional shape of the convex portion As the cross-sectional shape of the convex portion, a quadrangle, a triangle, or a fan shape is generally used. When observed from the upper surface of the substrate, the nanopillar array structure and the nanohole array structure have a two-dimensional periodicity, whereas the nanogroove array structure has a one-dimensional periodicity. . Note that the “width” of the columnar structure and the convex portion is a length in a direction parallel to the substrate surface.
  • the antireflection effect of these three types of sub-wavelength structures will be described.
  • the reflectivity of the nanopillar array structure and the nanohole array structure is generally almost the same, and the nanogroove array structure is compared with the above two types of structures.
  • the reflectance is high.
  • the nanopillar array structure and the nanohole array structure show a relatively low reflectance even when incident light enters the substrate surface from an oblique direction rather than from a vertical direction. It is known that the reflectance is relatively high with respect to light entering in a vertical direction.
  • the three types of sub-wavelength structures are different from each other in terms of the antireflection effect, but as described below, any of them is an object of the present invention.
  • solar cells having a nanopillar array structure, a nanohole array structure, and a nanogroove array structure as a surface antireflection structure are referred to as a nanopillar solar cell, a nanohole solar cell, and a nanogroove solar cell, respectively.
  • the substrate and the like are described as p-type and the emitter layer is n-type.
  • the same discussion can be made for those in which these conductivity types are reversed. It belongs to the range.
  • ⁇ Cell structure> 1A and 1B are a top view and a cross-sectional view of a nanopillar solar cell according to Example 1 of the present invention.
  • the nanopillar solar battery cell of Example 1 is a nanopillar solar battery cell in which nanopillars 2 are formed on a substrate 1.
  • FIG. 1 shows a structure when the nanopillar 2 is a cylinder, as described above, the nanopillar 2 may be a columnar structure having a different cross-sectional shape such as a prism.
  • a passivation film 12 is formed on the outermost surfaces of the nanopillar 2 and the emitter layer 11, but the passivation film 12 does not exist immediately below the surface electrode 13, and the emitter layer 11 and the surface electrode 13 are in contact with each other.
  • the emitter layer 11 covers the region between the nanopillars 2 and is thus continuous over the entire surface of the substrate 1 without being isolated from each other.
  • a solar battery cell is constituted by a semiconductor pn junction or pin junction, or a Schottky junction between a semiconductor and a metal.
  • the substrate 1 and the nanopillar 2 are made of a semiconductor material of the same conductivity type (first conductivity type).
  • first conductivity type first conductivity type
  • the emitter layer 11 is a layer having a high conductivity and a conductivity type (second conductivity type) different from the first conductivity type, and the substrate 1 and the nanopillar 2 are p-type. In this case, it is an n + layer. Therefore, the substrate 1 and the nanopillar 2 and the emitter layer 11 form a pn junction. In particular, the nanopillar 2 forms a pn junction with the emitter layer 11 on its side surface, and does not form a pn junction with the emitter layer 11 at its tip.
  • a BSF (Back Surface Field) layer having the same conductivity type as that of a substrate and highly doped is generally formed between the substrate and the back electrode.
  • a BSF layer 21 made of a p + layer is formed between the substrate 1 and the back electrode 22.
  • 1 shows a structure in which the BSF layer 21 and the back electrode 22 are in contact with each other over the entire surface.
  • a passivation film is formed between the BSF layer 21 and the back electrode 22 to locally A so-called point contact structure in which the passivation film is removed and the BSF layer 21 and the back electrode 22 are in contact with each other only in such a region may be used.
  • the material which comprises the nanopillar photovoltaic cell of Example 1 is described.
  • the material of the substrate 1, the nanopillar 2, the emitter layer 11, and the BSF layer 21, which are light absorbing layers, is a semiconductor such as Si, CdTe, CuInGaSe, InP, GaAs, Ge, and these are monocrystalline, polycrystalline, Various structures such as microcrystal and amorphous can be taken.
  • the material of the passivation film 12 is an insulator such as SiO 2 , SiN (silicon nitride), amorphous Si, SiC (silicon carbide), CdS, or a laminated structure of these insulators.
  • the material of the front electrode 13 and the back electrode 22 is a metal such as Ag, Al, Ti, Pd, Ni, or Cu, or a laminated structure thereof.
  • the solar battery cell according to Example 1 includes the plurality of pillars 2 extending in a predetermined direction and the first conductivity type (p-type) substrate 1 and the first substrate provided in contact with the substrate 1.
  • a second conductivity type (n-type) emitter layer 11 different from the conductivity type, and the plurality of pillars 2 are made of a first conductivity type semiconductor, and each of the plurality of pillars 2 has an emitter layer on its side surface. 11 is in contact with.
  • the impurity concentration of the emitter layer 11 is higher than the impurity concentration of the plurality of pillars 2.
  • the solar cell according to Example 1 has the following effects.
  • the emitter layer 11 may be structured not to be provided inside the nanopillar 2. This makes it possible to reduce the probability of recombination loss inside the nanopillar while enjoying the advantages of the emitter layer 11.
  • the emitter layer 11 can be a continuous layer between the nanopillars 2.
  • the surface electrode 13 is electrically connected to a part of the emitter layer 11, carriers from the entire region of the emitter layer 11 are absorbed. Can be collected. Therefore, the solar cell according to Example 1 has a pattern electrode made of Ag, Al, Ti, Pd, Ni, Cu, or a stacked structure thereof as the surface electrode 13 electrically connected to the emitter layer 11. It can be used.
  • the nanopillar 2 is made of a p-type semiconductor and does not include an n-type emitter layer. Therefore, the passivation film 12 can be provided in contact with the nanopillar 2 and the emitter layer 11.
  • the thickness of the emitter layer 11 can be set to, for example, 500 nm or more.
  • FIG. 3 is a diagram illustrating a first manufacturing method of the nanopillar solar battery cell of Example 1.
  • the first manufacturing method nanopillars are formed by a growth method
  • the second manufacturing method nanopillars are formed by a processing method.
  • the 1st manufacturing method of the nano pillar solar cell of Example 1 is demonstrated.
  • the structure on the back side that is, the step of forming the BSF layer 21 and the back electrode 22 is omitted.
  • a resist 31 is formed on the surface of the substrate 1.
  • a top view of the structure after formation is shown in FIG. 3A, and a cross-sectional view is shown in FIG. 3B.
  • the resist 31 is first applied over the entire surface of the substrate 1 and then patterned by photolithography. After patterning, the region where the resist 31 does not exist becomes the region of the nanopillar 2 in the final solar cell structure. As shown in FIGS. 3A and 3B, it is desirable that the region where the surface electrode 13 is finally formed is not patterned and the nano pillar 2 is not formed.
  • a catalyst metal 32 is formed on the resist 31.
  • a top view of the structure after the formation is shown in FIG. 3C, and a cross-sectional view is shown in FIG.
  • the catalyst metal 32 is necessary for the growth of the nanopillar 2, and Cu, Au, Pt or the like is generally used.
  • the catalyst metal 32 is formed by vapor deposition, sputtering, CVD, or the like.
  • FIG. 3 (e) A top view of the structure after removal is shown in FIG. 3 (e), and a cross-sectional view is shown in FIG. 3 (f).
  • FIG. 3 (f) A top view of the structure after removal is shown in FIG. 3 (e), and a cross-sectional view is shown in FIG. 3 (f).
  • FIG. 3 (f) A top view of the structure after removal is shown in FIG. 3 (e), and a cross-sectional view is shown in FIG. 3 (f).
  • a structure in which the patterned catalyst metal 32 exists on the substrate 1 is formed.
  • the method using lift-off of the resist 31 has been described in the first embodiment, but there is another method as described below. That is, instead of forming the resist 31 on the surface of the substrate 1, a patterned catalyst metal 32 is formed from the beginning.
  • a vapor deposition method using a metal mask or a method of dispersing catalyst metal nanoparticles is used. These methods have the advantage that the number of steps and the cost can be reduced as compared with the method using lift-off described in the first embodiment, but on the other hand, the pattern size of the catalyst metal 32 is likely to vary. There is a problem. The variation in the pattern size of the catalyst metal 32 ultimately becomes the variation in the pattern size of the nanopillar 2. The selection of whether to use lift-off or to form the patterned catalyst metal 32 from the beginning should be made in consideration of how much variation in the pattern size of the nanopillar 2 can be tolerated.
  • the patterning is not performed only in the region where the surface electrode 13 is finally formed as described above, and the nanopillar 2 is not formed.
  • the following measures are necessary. That is, the nanoparticles in the region where patterning is not performed after the nanoparticles are dispersed on the entire surface of the substrate 1 are removed, or the chemical properties of the surface of the substrate 1 in the region where patterning is not performed before the nanoparticles are dispersed.
  • an additional step is required in which the dispersed nanoparticles are repelled so that the nanoparticles do not exist in a region where patterning is not performed. Therefore, the method using the dispersion of nanoparticles also has a problem that the number of steps and cost increase as a result of the above-described devices.
  • the emitter layer 11 is formed. Accordingly, a portion (pn junction) in contact with the emitter layer 11 is also formed in the region to be the nanopillar 2 in the process of FIG.
  • a top view of the structure after formation is shown in FIG. 3G, and a cross-sectional view is shown in FIG.
  • the emitter layer 11 is formed by an impurity implantation method such as a vapor phase diffusion method, a solid phase diffusion method, or an ion implantation method.
  • the catalyst metal 32 serves as a catalyst used for the growth of the nanopillar 2 and also serves as a mask for impurity diffusion. For this reason, the relative positions of the nanopillar 2 and the emitter layer 11 can be adjusted in a self-aligning manner.
  • the emitter layer 11 is formed by the impurity implantation method, as described above, although the catalytic metal 32 serves as a mask, the diffusion of the impurities once implanted into the substrate 1 is generally isotropic. Become. Therefore, in practice, the emitter layer 11 is partially formed also below the catalytic metal 32, that is, below the nanopillar 2. If the length of the lateral diffusion of the emitter layer 11 is larger than the diameter of the nanopillar 2, the nanopillar 2 and the substrate 1 are separated from each other by the emitter layer 11. As described above, when the substrate 1 and the nanopillar 2 are p layers and the emitter layer 11 is an n + layer, the structure in the order of the nanopillar 2, the emitter layer 11, and the substrate 1 is a pn + p structure. A loss occurs in which holes generated inside 2 recombine in the emitter layer 11 before reaching the substrate 1. Thus, it is necessary to suppress the lateral diffusion of the emitter layer 11 so that the substrate 1 and the nanopillar 2 are not separated by the emitter layer 11.
  • the nanopillar 2 is formed by growing a portion (protruding portion) of the nanopillar 2 protruding above the emitter layer 11.
  • a top view of the grown structure is shown in FIG. 3 (i), and a cross-sectional view is shown in FIG. 3 (j).
  • the nanopillar 2 is grown by a VLS (Vapor Liquid Solid) growth method or the like. It is known that the nanopillar 2 with a low defect density is realized by using Cu as the catalyst metal 32 and performing VLS growth at a high temperature of about 1000 ° C.
  • ions can be activated by the heat applied to the sample during the VLS growth. Care must be taken so that the lateral diffusion of the emitter layer 11 does not proceed as much as possible.
  • the catalyst metal 32 is removed.
  • a top view of the structure after removal is shown in FIG. 3 (k), and a cross-sectional view is shown in FIG. 3 (l).
  • the catalyst metal 32 is removed by wet etching using a solution. At that time, it is desirable to use a solution having a low etching rate with respect to the substrate 1, the nanopillar 2, and the emitter layer 11, that is, a high etching selectivity.
  • a passivation film 12 is formed.
  • a top view of the structure after formation is shown in FIG. 3 (m), and a cross-sectional view is shown in FIG. 3 (n).
  • the passivation film 12 may be formed by a film formation method such as a CVD method, a sputtering method, an epitaxy method, or an evaporation method, or the material of the passivation film 12 is an oxide of the material of the nanopillar 2 and the emitter layer 11.
  • the passivation film 12 can also be formed by surface oxidation or surface nitridation.
  • the surface electrode 13 is formed.
  • a top view of the structure after formation is shown in FIG. 3 (o), and a cross-sectional view is shown in FIG. 3 (p).
  • the surface electrode 13 is formed by a film forming method such as a printing method, a vapor deposition method, a plating method, a sputtering method, or a CVD method. Since the surface electrode 13 and the emitter layer 11 are in contact with each other, it is necessary to remove the passivation film 12 existing therebetween.
  • the method for removing the passivation film 12 can be selected from a method using photolithography and etching, a method using an etching paste, a method using a so-called fire-through method in which the surface electrode 13 is baked and electrically connected after printing.
  • the passivation film 12 immediately below the surface electrode 13 is removed over the same width as the surface electrode 13.
  • the width of the passivation film 12 to be removed is larger than the width of the surface electrode 13.
  • the contact area between the emitter layer 11 and the surface electrode 13 may be reduced by reducing the width.
  • a second conductivity type (n-type) emitter layer different from the first conductivity type is formed on the surface of the first conductivity type (p-type) substrate 1 using the metal pattern (catalyst metal 32) as a mask.
  • a step of forming a plurality of nanopillars 2 on the surface of the substrate 1 using the same metal pattern (catalyst metal 32) (FIGS. 3 (g) and (h)) (FIGS. 3 (i) and (j)) It is characterized by having.
  • the first manufacturing method can use the same catalytic metal 32 as a mask for forming the emitter layer and also as a seed for growing the nanopillar, thereby reducing the process cost.
  • the relative positions of the nanopillar 2 and the emitter layer 11 can be adjusted in a self-aligning manner.
  • the first manufacturing method has an advantage that either the isotropic injection method or the anisotropic injection method can be used when forming the emitter layer 11. .
  • heat treatment or plasma treatment for improving the crystallinity and film quality of each film or for improving the quality of the interface with the adjacent film may be added as appropriate.
  • FIG. 4 is a diagram illustrating a second manufacturing method of the nanopillar solar battery cell of Example 1.
  • the nanopillar 2 is formed by a growth method.
  • the nanopillar 2 is formed by a processing method.
  • the 2nd manufacturing method of the nano pillar solar cell of Example 1 is demonstrated. Note that, as in the first manufacturing method, the step of forming the structure on the back surface side is omitted.
  • an etching mask 33 is formed on the surface of the substrate 1.
  • FIG. 4A shows a top view of the structure after formation
  • FIG. 4B shows a cross-sectional view thereof.
  • the etching mask 33 serves as a mask for etching processing for forming the nanopillar 2 in the next step, and as the material thereof, metal nanoparticles, SiO 2 , resist, or the like is generally used.
  • the etching mask 33 can be formed by self-organization by dispersing the nanoparticles.
  • the etching mask 33 may be formed by processing a metal by a method such as lift-off or etching.
  • SiO 2 or a resist is used, the etching mask 33 can be formed by patterning using lithography.
  • a portion (protruding portion) of the nanopillar 2 that protrudes later to the upper portion of the emitter layer 11 is formed.
  • a top view of the structure after formation is shown in FIG. 4C, and a cross-sectional view is shown in FIG. 4D.
  • the protrusion is formed by a method such as dry etching, wet etching, or laser ablation. From the viewpoint of the antireflection effect, it is desirable that the aspect ratio of the nanopillar 2, that is, the “height / diameter” value is large. It is good to do. In order to increase the aspect ratio, it is also an effective method to form the etching mask 33 with a laminated structure of two or more layers.
  • FIG. 4E shows a top view of the structure after formation
  • FIG. 4F shows a cross-sectional view.
  • the emitter layer 11 is formed by an impurity implantation method as in the first manufacturing method.
  • an isotropic implantation method such as a vapor phase diffusion method is used. This means that it is necessary to use an anisotropic implantation method such as an ion implantation method. The reason is that if impurities are implanted by the isotropic implantation method in this step, the emitter layer 11 is also formed on the sidewall of the nanopillar 2.
  • the structure shown in FIGS. 3 (k) and (l) in the first manufacturing method can be obtained.
  • the nanopillar solar cell structure of Example 1 can be realized.
  • This manufacturing method uses a process of forming a plurality of nanopillars 2 on the surface of the substrate 1 by etching using the etching mask 33 as a mask (FIGS. 4A and 4B) and an anisotropic implantation method. And a step of injecting impurities into the surface of the substrate 1 and a region between the plurality of nanopillars 2 (FIGS. 4C and 4D).
  • the solar battery cell according to Example 1 can be manufactured also by this process.
  • the second manufacturing method forms the nanopillar 2 using a processing method, when a single crystal is used as the substrate 1, the nanopillar 2 formed by the processing method is more Compared with the nanopillar 2 formed by the growth method as in the production method 1, it is excellent in terms of crystallinity and purity, and therefore it is possible to reduce recombination loss.
  • FIGS. 5A and 5B are a top view and a cross-sectional view of a solar battery cell according to Example 2 of the present invention.
  • the difference from Example 1 is that the structure of Example 1 is a nanopillar solar cell, whereas the structure of Example 2 is a nanogroove solar cell, and is in a predetermined direction parallel to the surface of the substrate 1. This is a cell having a plurality of convex portions 3 to be stretched.
  • FIGS. 6A and 6B respectively show a top view and a cross-sectional view of the structure obtained by removing only the passivation layer 12 from the nanopillar solar cell structure of Example 2.
  • FIG. FIGS. 5 and 6 show the structure in the case where the extending direction of the convex portion 3 and the cross-sectional shape in the plane perpendicular to the substrate surface are squares. Different cross-sectional shapes such as molds may be used.
  • the solar cell according to Example 2 is provided with the first conductivity type (p-type) substrate 1 and a plurality of first conductivity type, which is provided on the surface of the substrate 1 and extends in a predetermined direction.
  • the projection 3 has a second conductivity type (n-type) emitter layer 11 provided on the surface of the substrate 1 and different from the first conductivity type.
  • the emitter layer 11 is interposed between the plurality of projections 3. It is provided.
  • the emitter layer 11 is continuous on the outer periphery of the plurality of convex portions 3. This is because the emitter layer 11 is made continuous over the entire surface of the substrate 1 without being isolated from each other. As a result, a pattern electrode can be used as the surface electrode 13 as in the first embodiment. .
  • Example 2 As described above, according to Example 2, as in the case of the nanopillar solar cell of Example 1, also in the nanogroove solar cell, the recombination loss inside the convex portion 3 is reduced, and the surface A patterned electrode can be used as the electrode 13.
  • the manufacturing method of the structure of Example 2 is the same as that of Example 1, but a processing method is generally used as a method of forming the protrusion 3. Therefore, the nanogroove solar cell structure of Example 2 is generally manufactured by the same method as the second manufacturing method of the nanopillar solar cell of Example 1.
  • the point of providing the region where the protrusion 3 is not formed on a part of the surface of the substrate 1 described above can be realized by designing the pattern of the etching mask 33 in the second manufacturing method of the first embodiment. .
  • Example 7 (a) and 7 (b) are a top view and a cross-sectional view of a solar battery cell according to Example 2 of the present invention.
  • the difference from Example 1 is that the structure of Example 3 is a nanohole solar battery cell, and in the nanohole solar battery cell of Example 3, the inside of the subwavelength structure, that is, the top of the side wall region of nanohole 4
  • the emitter layer 11 is formed.
  • a top view and a cross-sectional view of a structure obtained by removing only the passivation layer 12 from the nanopillar solar cell structure of Example 3 are shown in FIGS. .
  • nanohole solar cell structure of Example 3 can be regarded as a structure in which nanoholes are used instead of nanopillars in the above-described planar shallow junction nanopillar solar cell.
  • the nanohole solar battery cell of Example 3 there are the following differences between the nanohole solar battery cell of Example 3 and the planar shallow junction nanopillar solar battery cell. That is, in the planar shallow-junction nanopillar solar cell, as described above, the emitter layer 11 formed on the top of the nanopillar 2 is isolated from each other. It is necessary to use an electrode formed on the substrate.
  • the shallow emitter layer 11 formed on the surface of the substrate 1 where the nanohole 4 is not provided is shown in the top view of FIG. As shown, it is continuous over the entire surface of the substrate 1. Therefore, a pattern electrode can be used as the surface electrode 13.
  • the solar cell according to Example 3 has a plurality of columnar recesses (nanoholes 4) on the surface thereof, the first conductivity type (p-type) substrate 1, the surface of the substrate 1, and the columnar recesses. It has a second conductivity type (n-type) emitter layer 11 different from the first conductivity type and is provided in a portion that is not provided, and the width of the columnar recess is 1 ⁇ m or less.
  • the emitter layer 11 thinner than the height of the nanohole 4, the recombination loss in the nanohole solar cell can be reduced to the same extent as that of the planar shallow junction nanopillar solar cell, and Unlike the planar shallow junction type nanopillar solar cell, a pattern electrode can be used as the surface electrode 13. Specifically, the thickness of the emitter layer 11 can be set to 500 nm or less, for example.
  • the emitter layer 11 is formed over the entire surface of the substrate 1, and then the nanohole 4, and then the passivation film 12 and the surface electrode 13 may be formed.
  • the emitter layer 11 may be formed by either an impurity implantation method or a film formation method.
  • the nanoholes 4 are generally formed by etching or a processing method using a laser.
  • the passivation film 12 may be formed by surface oxidation, surface nitridation, or a film formation method, as in the case of the first embodiment.
  • the passivation film 12 is formed by a film forming method, when the nanohole 4 is viewed from above, the side wall region of the nanohole 4 is not hidden, that is, the opening area at the top of the nanohole 4 is the opening at the bottom. It is desirable to have a shape similar to or larger than the area.
  • Patent Document 1 discloses a solar cell structure having a hole array structure as a surface antireflection structure and having a shallow emitter layer formed on the side wall of the hole. This structure is similar to the structure of Example 3, but there are the following differences between the two.
  • the diameter of the hole in the structure of Patent Document 1 is 1 ⁇ m or more, whereas the width of the nanohole targeted in the present invention is 1 ⁇ m or less.
  • the reason for the width of the nanohole being 1 ⁇ m or less is that the nanohole has a diameter that is the same as or smaller than the wavelength of sunlight, and that light having a wavelength of 1 ⁇ m or less is included in the sunlight.
  • the intensity is high, and it is two points that the wavelength range is normally used in solar cells.
  • the structure of Patent Document 1 has a feature that the area of the bottom is larger than the opening of the hole.
  • the areas of the opening and the bottom are equivalent as described in the third embodiment.
  • the region between adjacent nanohole bottoms becomes narrower, increasing the series resistance, increasing the surface area of the nanoholes, increasing the surface recombination loss, and Since there is a region that is shaded when viewed from above, it is difficult to use a film formation method such as a CVD method as the surface passivation of the nanoholes. Therefore, in the structure of Patent Document 1, it is difficult to make the diameter of the opening 1 ⁇ m or less.
  • the structure of Patent Document 1 is not a sub-wavelength structure due to the size of the hole array used. Further, in the structure of Patent Document 1, if the size of the hole opening is reduced to about 1 ⁇ m or less, which is equivalent to the sub-wavelength structure, the series resistance is increased, the recombination loss is increased, and the film formation method is used. Since the three points that the passivation film is difficult are problems, the structure of Patent Document 1 is difficult to make the diameter of the opening 1 ⁇ m or less.
  • Patent Document 1 As described above, the invention described in Patent Document 1 is different from the invention according to Example 3 in configuration and effect.

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Abstract

Selon l'invention, il n'existe pas dans l'état antérieur de la technique, par rapport à une cellule solaire ayant une structure de sous-longueur d'onde, un procédé à la fois de réduction de la perte de recombinaison à l'intérieur de la structure de sous-longueur d'onde et d'utilisation d'une électrode à motifs en tant qu'électrode de surface. En réponse, cette invention est une cellule solaire comprenant : un substrat (1) d'un premier type de conductivité (type p) équipé d'une pluralité de piliers (2) s'étendant dans une direction prédéterminée ; et une couche d'émetteur (11) d'un second type de conductivité (type n), qui est différent du premier type de conductivité, disposée en contact avec le substrat. La cellule solaire est structurée de telle sorte que les piliers comprennent un semi-conducteur à premier type de conductivité, et une surface latérale de chacun des piliers est en contact avec la couche d'émetteur. Cette structure rend possible à la fois de réduire les pertes de recombinaison à l'intérieur de la structure de sous-longueur d'onde et d'utiliser une électrode à motifs en tant qu'électrode de surface, en contraste avec des cellules solaires classiques.
PCT/JP2012/065679 2012-06-20 2012-06-20 Cellule solaire et procédé de fabrication de celle-ci WO2013190646A1 (fr)

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PCT/JP2012/065679 WO2013190646A1 (fr) 2012-06-20 2012-06-20 Cellule solaire et procédé de fabrication de celle-ci
JP2014521135A JP5802833B2 (ja) 2012-06-20 2012-06-20 太陽電池セルおよびその製造方法
TW102121551A TWI503999B (zh) 2012-06-20 2013-06-18 Solar cell and manufacturing method thereof

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JP2017539093A (ja) * 2014-12-22 2017-12-28 トタル ソシエテ アノニムＴｏｔａｌ Ｓａ テクスチャが形成された表面を有する光電子デバイスおよびその製造方法
JPWO2016147970A1 (ja) * 2015-03-16 2017-12-28 シャープ株式会社 光電変換素子および光電変換素子の製造方法

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JP2011138804A (ja) * 2009-12-25 2011-07-14 Honda Motor Co Ltd ナノワイヤ太陽電池及びその製造方法
JP2012501536A (ja) * 2008-08-28 2012-01-19 コリア リサーチ インスティチュート オブ スタンダーズ アンド サイエンス 量子ドット太陽光素子及びその製造方法

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US20100112748A1 (en) * 2005-08-22 2010-05-06 Ruxandra Vidu Methods for forming nanostructures and photovoltaic cells implementing same
JP2008177539A (ja) * 2006-11-15 2008-07-31 General Electric Co <Ge> 傾斜ハイブリッド非晶質シリコンナノワイヤー太陽電池
JP2012501536A (ja) * 2008-08-28 2012-01-19 コリア リサーチ インスティチュート オブ スタンダーズ アンド サイエンス 量子ドット太陽光素子及びその製造方法
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JP2017539093A (ja) * 2014-12-22 2017-12-28 トタル ソシエテ アノニムＴｏｔａｌ Ｓａ テクスチャが形成された表面を有する光電子デバイスおよびその製造方法
JPWO2016147970A1 (ja) * 2015-03-16 2017-12-28 シャープ株式会社 光電変換素子および光電変換素子の製造方法

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