WO2020004475A1 - Multijunction photoelectric conversion element and multijunction solar battery - Google Patents

Multijunction photoelectric conversion element and multijunction solar battery Download PDF

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WO2020004475A1
WO2020004475A1 PCT/JP2019/025409 JP2019025409W WO2020004475A1 WO 2020004475 A1 WO2020004475 A1 WO 2020004475A1 JP 2019025409 W JP2019025409 W JP 2019025409W WO 2020004475 A1 WO2020004475 A1 WO 2020004475A1
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cell
electrode
photoelectric conversion
conversion element
junction
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PCT/JP2019/025409
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French (fr)
Japanese (ja)
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健 太野垣
紀久夫 牧田
武芳 菅谷
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国立研究開発法人産業技術総合研究所
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Publication of WO2020004475A1 publication Critical patent/WO2020004475A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/04—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices
    • H01L31/06—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by 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
    • H01L31/0687—Multiple junction or tandem 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
    • H01L31/04—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
    • H01L31/0693—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 the devices including, apart from doping material or other impurities, only AIIIBV compounds, e.g. GaAs or InP solar 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
    • Y02E10/544—Solar cells from Group III-V materials
    • 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 multi-junction photoelectric conversion element formed by joining cells of a plurality of photoelectric conversion elements, a multi-junction solar cell including the multi-junction photoelectric conversion element, and a method for manufacturing a multi-junction photoelectric conversion element.
  • a multi-junction solar cell has a structure in which a plurality of solar cells composed of semiconductor elements having different band gap energies are stacked.
  • solar cells that absorb sunlight of different wavelengths are connected in series, so that sunlight with a wide energy distribution can be used efficiently.
  • the output voltage of the multi-junction solar cell increases because it is the sum of the voltages of the cells.
  • Each photoelectric conversion element or each cell of a solar cell constituting a multi-junction photoelectric conversion element or a multi-junction solar cell is also referred to as a subcell.
  • a solar cell placed on the light incident side (outermost surface side) of the multi-junction solar cell is called a top cell.
  • a semiconductor having a large band gap is used, and light having a shorter wavelength is absorbed and light having a longer wavelength is transmitted.
  • the bottom cell is located farthest from the light incident side.
  • a semiconductor having a small band gap is used for the bottom cell, and absorbs light transmitted through the top cell.
  • the middle solar cell is called a middle cell.
  • FIG. 11 is a schematic cross-sectional view of a conventional two-terminal multi-junction solar cell.
  • the two-terminal type multi-junction solar cell has a stacked structure in which a top cell 2 and a bottom cell 3 are stacked, and electrodes (for extracting electric energy) are provided on the front surface and the back surface when viewed from the light incident side. It has a two-terminal structure including a top electrode 5 and a back electrode 6).
  • FIG. 12 shows an equivalent circuit diagram of the two-terminal multi-junction solar cell of FIG.
  • a two-terminal multi-junction solar cell the same current flows through each sub-cell connected in series. Equal currents I 1 and the current I 2 and the current I 3 in FIG. Due to this current matching condition, in each subcell, the amount of current flowing through the two-terminal multi-junction solar cell is determined by the photoelectric flow of the subcell in which the photoelectric flow generated by light absorption is the lowest value. In a subcell in which a high photoelectric flow rate is generated, a reverse current (dark current) is generated, and the amount of flowing current is smaller than the generated photocurrent value.
  • the photoelectric flow generated in each sub-cell varies due to fluctuations in the solar spectrum and the like. Losses due to fluctuations are likely to occur.
  • Non-Patent Document 1 As a method of reducing loss due to spectrum fluctuation, a multi-electrode terminal type multi-junction device structure such as a four-terminal type in which electrodes are arranged between subcells has been proposed (see Non-Patent Document 1).
  • FIG. 13 is an equivalent circuit diagram of a four-terminal multi-junction solar cell.
  • the four-terminal multi-junction solar cell is configured by a circuit in which the top cell 2 and the bottom cell 3 are electrically separated. Photocurrent generated by each subcell (current I 2 (current I 1), the current I 4 (current I 3)) is output as the respective output power (voltage V 1, the voltage V 2). Since no current limiting condition is imposed, loss due to fluctuations in the solar spectrum is unlikely to occur.
  • FIG. 14 is a schematic cross-sectional view of a four-terminal multi-junction solar cell.
  • the four-terminal multi-junction solar cell has a structure in which a top cell 2 and a bottom cell 3 are stacked, and has four terminals to output power of the top cell 2 and the bottom cell 3 respectively.
  • the four terminals are sequentially stacked from the light incident side on the top electrode 5 on the surface of the top cell 2, the intermediate electrode 7a electrically connected to the transparent electrode layer 8a stacked on the back surface of the top cell, and the surface of the bottom cell 3.
  • the intermediate electrode 7b provided on the transparent electrode layer 8b and the back electrode 6 on the back surface of the bottom cell.
  • an insulating adhesive layer 9 for electrically insulating the transparent electrode layers from each other is arranged.
  • a transparent material is used to reduce light absorption loss.
  • FIG. 15 is an equivalent circuit diagram of a three-terminal multi-junction solar cell.
  • the three-terminal multi-junction solar cell is constituted by a circuit in which an intermediate electrode is arranged between a top cell 2 and a bottom cell 3.
  • the current flowing to the top cell is I 2
  • the current flowing to the bottom cell is I 3
  • the current flowing to each terminal is (current I 1 , current I 4 , current I 5 )
  • the voltage of the multi-junction device is V 1 represents the voltage of the bottom cell in V 2.
  • Excess photocurrent generated in the top cell or the bottom cell is output as electric power via the intermediate electrode.
  • the top cell and the bottom cell do not need to satisfy the current matching condition, and even when the photoelectric flow generated in the top cell and the bottom cell becomes uneven due to spectrum fluctuation or the like, an excess dark current is not generated. I'm done.
  • FIG. 16 is a structural view of a conventional three-terminal multi-junction solar cell.
  • the three terminals are, in order from the light incident side, a top electrode 5 on the front surface of the top cell 2, an intermediate electrode 7, and a back electrode 6 on the back surface of the bottom cell.
  • the three-terminal type multi-junction solar cell has a method in which a top cell 2 and a bottom cell 3 are continuously grown to form a laminated structure, and an intermediate electrode 7 is attached later in the middle of the laminated structure. It has been made.
  • a method of manufacturing a multi-junction solar cell by a method of directly growing a GaAs-based top cell on a Si-based bottom cell is known (see Non-Patent Document 2).
  • FIG. 17 shows a three-terminal solar cell disclosed in Non-Patent Document 3.
  • a three-terminal solar cell in which a top electrode 5 is provided on a top cell 2 and alternate electrodes 6a and 6b are formed on the back surface of the bottom cell 3 has been proposed. However, it has a structure similar to the transistor structure (np / p- (p, n)), and has a different circuit configuration from the multi-junction solar cell (np / np).
  • Patent Document 1 Non-Patent Document 1
  • Reference 4 Non-patent Reference 5
  • a reverse current (dark current) is generated in a subcell in which a high photoelectric flow is generated, and the amount of flowing current is smaller than the generated photocurrent value.
  • the photoelectric flow generated in each subcell fluctuates due to fluctuations in the solar spectrum or the like. There's a problem.
  • Non-Patent Document 3 has a different circuit configuration from a multi-junction solar cell (np / np). That is, Non-Patent Literature 3 discloses that a back surface alternate electrode is provided to solve the following problem.
  • the normal electrode on the incident light side blocks the incident light and creates a shadow on the cell, which has been a factor of loss of current generation.
  • an alternate back type electrode has been introduced. Thereby, light loss due to the electrode on the incident surface side is reduced, and high current generation is realized.
  • Non-Patent Document 3 is a tandem (a structure in which two are arranged vertically) because a pn junction is not connected in series. The structure does not provide a high voltage.
  • the prior art proposal using bonding with conductive nanoparticles is a technology relating to a two-terminal structure, and has not been able to solve the limitation due to current limiting in a multi-junction solar cell.
  • the present invention seeks to solve these problems, and provides a multi-junction photoelectric conversion element that is robust against spectral fluctuations, has subcells of high-quality crystals, and has a reduced optical reflection loss at the junction.
  • the purpose is to do.
  • An object of the present invention is to provide a method for manufacturing the multi-junction photoelectric conversion element. Moreover, it aims at providing the multi-junction solar cell provided with the said multi-junction photoelectric conversion element.
  • the present invention has the following features to achieve the above object.
  • a multi-junction photoelectric conversion element wherein a first cell of the photoelectric conversion element located on the light incident side, a second cell of the photoelectric conversion element located on the side opposite to the light incident side, A bonding layer made of conductive nanoparticles for bonding the cell and the second cell, a first electrode located on a light incident side surface of the first cell, and a A second electrode located on the surface opposite to the light incident side, and a third electrode provided on the second cell, the electrode being located on the surface opposite to the light incident side, or a third electrode provided on the first cell side.
  • a third electrode which is an intermediate electrode located on the surface.
  • the cell of the multi-junction photoelectric conversion element is a single-junction solar cell using crystalline Si, amorphous Si, microcrystalline Si, organic, or chalcopyrite-based material, or GaAs, InP, GaSb.
  • the multi-junction photoelectric conversion element according to any one of the above (1) to (5) which is a solar cell including two or more junctions stacked on a Ge substrate or the like.
  • a multi-junction solar cell comprising the multi-junction photoelectric conversion element according to any one of (1) to (6).
  • a method for manufacturing a multi-junction photoelectric conversion element comprising: a first cell of a photoelectric conversion element located on a light incident side; and a second cell of a photoelectric conversion element located on a side opposite to the light incident side. Forming a second electrode on the second cell opposite to the light incident side, and forming a third electrode opposite the light incident side on the second cell, or a surface on the first cell side. Providing a third electrode serving as an intermediate electrode located in the first cell, bonding the first cell to the second cell with conductive nanoparticles not covered with organic molecules, Forming a first electrode on the light-incident side surface of the cell described in (1).
  • the multi-junction photoelectric conversion element of the present invention uses sub-cells made of different materials, is bonded by a bonding layer made of conductive nanoparticles, and is provided with three terminals, so that sunlight with a wide energy distribution can be used with high efficiency. It is possible to achieve the effect of suppressing the loss due to the imbalance of the photocurrent value generated in each subcell constituting the multi-junction solar cell. Therefore, the multi-junction photoelectric conversion element of the present invention is robust against spectrum fluctuation. Further, in the multi-junction photoelectric conversion element of the present invention, since each sub-cell is joined by a joining layer made of conductive nanoparticles, each sub-cell can be made of a high-quality crystal, and each sub-cell has high performance. . Moreover, the multi-junction photoelectric conversion element of the present invention can realize a multi-junction photoelectric conversion element with reduced optical reflection loss at the junction because the junction layer is a junction layer made of conductive nanoparticles.
  • the multi-junction solar cell of the present invention is constituted by the multi-junction photoelectric conversion element of the present invention, it is possible to efficiently use sunlight or the like having a wide energy distribution and is robust against spectrum fluctuation.
  • a pre-formed photoelectric conversion element with second and third electrodes is used for a bottom cell, and this and a top cell are bonded to each other to obtain a high-crystal quality cell. Since it can be used, a high-performance multi-junction photoelectric conversion element can be manufactured as compared with a conventional three-terminal device.
  • FIG. 1 is a schematic cross-sectional view of a photoelectric conversion element having a first basic structure according to the present invention. It is a perspective view of the photoelectric conversion element of the 1st basic structure of the present invention.
  • FIG. 2 is a bottom view of a bottom cell in which an alternate back electrode is formed in the first basic structure of the present invention.
  • It is a perspective view of the photoelectric conversion element of the 2nd basic structure of the present invention.
  • FIG. 9 is a top view of a bottom cell on which an intermediate electrode is formed in the second basic structure of the present invention. It is a schematic structure sectional view of a 1st embodiment of the present invention.
  • FIG. 4 is an equivalent circuit diagram of a conventional four-terminal multi-junction solar cell. It is a schematic cross section of a conventional four-terminal type multi-junction solar cell. It is an equivalent circuit diagram of the conventional three-terminal type multi-junction solar cell. It is a schematic structure sectional view of the conventional three-terminal type multi junction solar cell. It is a schematic structure sectional view of the conventional three-terminal type solar cell. It is a schematic structure sectional view of the conventional three-terminal type solar cell. It is a schematic structure sectional view of the conventional three-terminal type solar cell. It is a schematic structure sectional view of the conventional three-terminal type solar cell.
  • the present inventors have developed a junction structure and a terminal structure in a photoelectric conversion element in which a plurality of cells of a photoelectric conversion element are joined, thereby increasing the efficiency of solar energy and the like, and reducing the loss due to spectrum fluctuation of sunlight. Is realized.
  • a multi-junction photoelectric conversion element relates to a photoelectric conversion element in which cells of a plurality of photoelectric conversion elements are joined, and relates to a first cell (hereinafter, referred to as a “top cell”) of a photoelectric conversion element located on a light incident side. ), And the second cell (hereinafter, also referred to as a “bottom cell”) of the photoelectric conversion element located on the side opposite to the light incident side, and the first cell and the second cell are joined. And a bonding layer made of conductive nanoparticles that are not covered with organic molecules.
  • the multi-junction photoelectric conversion element according to the embodiment of the present invention has terminals from three electrodes, it is a three-terminal multi-junction photoelectric conversion element.
  • the three terminals include a first electrode terminal located on a light incident side surface of the first cell and a second electrode terminal located on a light incident side opposite surface of the second cell. , Terminals of a third electrode provided in the second cell.
  • the third electrode is one of an electrode located on a surface opposite to the light incident side and an intermediate electrode located on a surface on the first cell side.
  • FIG. 1 is a schematic structural sectional view of a first basic structure 10 of a three-terminal multi-junction photoelectric conversion element.
  • FIG. 2 is a perspective view of the first basic structure.
  • FIG. 3 is a diagram illustrating the alternating electrodes 16 and 17 on the back surface of the bottom cell having the first basic structure. One of the alternate electrodes on the back is n-type and the other is p-type.
  • the first basic structure has a stacked structure including a top cell 12, a bottom cell 13, and a bonding layer 14 made of conductive nanoparticles for bonding them, a top electrode 15 is provided on a light incident side surface of the top cell, and a bottom cell 13 is formed.
  • On the back surface there is an electrode structure in which a third electrode is provided in addition to the conventional second electrode.
  • the electrode structure on the back surface of the bottom cell 13 has an alternate electrode structure in which second electrodes and third electrodes are alternately arranged.
  • the electrode portion where thin linear electrodes are arranged in parallel is also called a grid.
  • the second electrode and the third electrode constituting the alternating electrode structure are connected to each other with a thicker line (bus bar electrode) or the like than the alternating electrode portion, thereby forming a second electrode and a third electrode.
  • the second electrode and the third electrode may have a comb shape, and the comb teeth of each comb may alternately enter. In addition, it is not limited to a comb shape.
  • a voltage is generated between the top electrode 15 and the electrode 17 by adding the voltages generated by the top cell 12 and the bottom cell 13. For example, when the current I 2 generated in the top cell 12 is smaller than the current I 3 generated in the bottom cell 13, the current flowing between the top electrode 15 and the electrode 17 becomes the current I 2 generated in the top cell 12. to be rate-limiting in 2, current I 2 flows. Further, a voltage generated in the bottom cell 13 is generated between the electrode 16 and the electrode 17.
  • An excess photocurrent generated in the first cell (top cell) is taken out as electric power by the first electrode (top electrode) and the second electrode (one of the backside alternating electrodes), and the second electrode (backside alternating electrode) is taken out.
  • the excess photocurrent generated in the second cell (bottom cell) is extracted as power by one of the electrodes) and the third electrode (the other of the backside alternating electrodes).
  • FIG. 4 is a schematic structural cross-sectional view of the second basic structure 20 of the three-terminal multi-junction photoelectric conversion element.
  • FIG. 5 is a perspective view of the second basic structure.
  • FIG. 6 is a top view of a bottom cell having an intermediate electrode of the second basic structure.
  • the second basic structure includes a stacked structure including a top cell 22, a bottom cell 23, and a bonding layer 24 made of conductive nanoparticles for bonding them.
  • a top electrode 25 is provided on the light incident side of the top cell.
  • FIGS. 6A and 6B show an intermediate electrode including a grid on which thin electrode lines are arranged in parallel and a thicker electrode (bus bar electrode) connecting the grid.
  • (A) is an example of a comb shape, and (b) is an example of providing a plurality of bus bar electrodes.
  • the shape of the intermediate electrode is not particularly limited. It is preferable that the grid is made of a thin electric wire so as not to block light.
  • the equivalent circuit diagram of the second basic structure is the same as the equivalent circuit diagram of the three-terminal multi-junction solar cell (FIG. 15).
  • the first cell (top cell) is formed by the first electrode (top electrode) and the second electrode (backside electrode) or the first electrode (top electrode) and the third electrode (intermediate electrode).
  • the surplus photocurrent is extracted as electric power
  • the surplus photocurrent generated in the second cell (bottom cell) is extracted as electric power by the second electrode (back surface electrode) and the third electrode (intermediate electrode).
  • each surface area of the plurality of photoelectric conversion element cells can be appropriately designed. It is preferable to design by adjusting the surface area size of each cell so that the photoelectric flow becomes uniform and the current matching condition is satisfied. For example, it is preferable to use a bottom cell having a larger surface area than the top cell so that the current of the bottom cell does not become smaller than the current of the top cell.
  • the cell of the photoelectric conversion element in the present invention is, for example, a cell of a solar cell.
  • the first or second cell of the photoelectric conversion element in the present invention is a single-junction solar cell using a crystalline Si-based, amorphous Si-based, microcrystalline Si-based, organic-based, or chalcopyrite-based material.
  • the multi-junction photoelectric conversion element of the present invention includes a first cell of the photoelectric conversion element arranged on the light incident side and a second cell of the photoelectric conversion element arranged on the side opposite to the light incident side.
  • the photoelectric conversion element of the present invention is not limited to a solar cell for sunlight.
  • the bonding layer for bonding the first cell and the second cell of the present invention is made of conductive nanoparticles that are not covered with organic molecules.
  • no transparent electrode and no transparent adhesive are inserted between the top cell and the bottom cell.
  • the size of the conductive nanoparticles is preferably not less than 5 nanometers and not more than 50 nanometers. The reason is that in order to reduce the reflection loss in the conductive nanoparticle adhesive layer, it is preferable that the thickness of the bonding layer made of the conductive nanoparticles be 5 nm or more and 50 nm or less.
  • the conductive nanoparticles include metal nanoparticles such as Pd, Au, Ag, Pt, Ni, Al, Zn, and In, and metal oxide nanoparticles such as ZnO and In 2 O 3 .
  • Examples of the shape of the conductive nanoparticles include a sphere, a hemisphere, a column, and an ellipsoid.
  • the size of the conductive nanoparticles in the bonding layer direction is preferably 10 nm or more in order to obtain good conductivity.
  • the thickness is preferably 100 nm or less in order to suppress absorption and scattering of light by the nanoparticles.
  • the arrangement interval of the conductive nanoparticles in the bonding layer is preferably 2 to 10 times the conductive nanoparticle size.
  • the conductive nanoparticles in the bonding layer are not covered with a protective film such as an organic molecule or a bonding material, and are a single layer (monolayer) in which individual independent particles are uniformly arranged.
  • the arrangement interval of the conductive nanoparticles preferably has a distance of at least twice the size of the nanoparticles in order to transmit light well. More preferably, it is three times or more.
  • the method of manufacturing the first basic structure of the three-terminal multi-junction photoelectric conversion element of the present embodiment includes the following steps.
  • (Step 3) may be performed prior to either or both of (Step 1) and (Step 2).
  • (Step 1) A step of forming a second electrode and a third electrode on the surface of the bottom cell opposite to the light incident side.
  • (Step 2) A bonding step in which the top cell is bonded to the bottom cell on which the electrodes have been formed in Step 1 by using conductive nanoparticles that are not covered with organic molecules.
  • Step 3) A step of forming a first electrode on the light incident side surface of the top cell.
  • the method for manufacturing the second basic structure of the three-terminal multi-junction photoelectric conversion element of the present embodiment includes the following steps.
  • (Step 3) may be performed prior to either or both of (Step 1) and (Step 2).
  • (Step 1) A step of forming a second electrode located on the surface opposite to the light incident side on the bottom cell and providing a third electrode serving as an intermediate electrode on the light incident side of the bottom cell.
  • (Step 2) A bonding step in which the top cell is bonded to the bottom cell on which the electrodes have been formed in Step 1 by using conductive nanoparticles that are not covered with organic molecules.
  • (Step 3) A step of forming a first electrode on the light incident side surface of the top cell.
  • FIG. 7 is a schematic cross-sectional view of a GaAs // Si multi-junction solar cell 30 having an alternate back electrode structure.
  • a GaAs solar cell having the n-type GaAs layer 31 formed on the light incident side of the p-type GaAs layer 32 is used as the top cell.
  • the top cell includes a top electrode 35 on the light incident side.
  • n-type and p-type electrodes n-type back electrode 37 and p-type back electrode 36
  • a region of the p-type Si portion 38 is formed in a partial region of the n-type Si layer 33 on the back surface side of the substrate, and a p-type back electrode 36 connected to the p-type Si 38 is formed.
  • the conventional solar spectrum in the GaAs top cell and Si bottom cell, respectively, current of about 30 mA / cm 2 and 10 mA / cm 2 is produced.
  • the size (surface area) of the subcell is adjusted so that the photoelectric flow generated in the top cell and the bottom cell becomes uniform and the current matching condition is satisfied.
  • surplus photocurrent generated in the bottom cell due to the spectrum fluctuation of sunlight is taken out as electric power from the backside alternating electrodes.
  • FIG. 8 is a schematic sectional view of a GaAs // Si multi-junction solar cell 40 having an intermediate electrode structure.
  • a GaAs solar cell in which the n-type GaAs layer 41 is formed on the light incident side of the p-type GaAs layer 42 is used.
  • the top cell includes a top electrode 45 on the light incident side.
  • an Si solar cell having an n-type Si layer 48 and an intermediate electrode 47 formed on the light incident side of the substrate of the p-type Si layer 49 is used.
  • a p-type back electrode 46 is provided on the back side of the bottom cell.
  • the bonding layer 44 made of conductive nanoparticles By bonding the top cell and the bottom cell using the bonding layer 44 made of conductive nanoparticles, a three-terminal multi-junction solar cell is formed. Pd nanoparticles are used as the conductive nanoparticles.
  • the size (surface area) of the subcell is adjusted so that the photoelectric flow generated in the top cell and the bottom cell becomes uniform and the current matching condition is satisfied.
  • the excess photocurrent generated in the GaAs top cell due to the spectrum fluctuation of sunlight is taken out as electric power using the intermediate electrode and the top electrode. Excess photocurrent generated in the bottom cell is extracted as power using the back electrode and the intermediate electrode.
  • FIG. 9 is a schematic cross-sectional view of a GaAs / GaAs // Si multi-junction solar cell 50 having an alternate back electrode structure.
  • a GaAs subcell consisting of an n-type GaAs layer 51 and a p-type GaAs layer 52
  • a tunnel junction layer 53 is used as a top cell.
  • a GaAs subcell consisting of an n-type GaAs layer 58 and a p-type GaAs layer 59
  • the top cell includes a top electrode 55 on the light incident side.
  • a Si solar cell in which n-type and p-type electrodes (n-type back electrode 57 and p-type back electrode 56) are alternately formed on the back surface side of the substrate of the n-type Si layer 61 is used.
  • a p-type Si 62 region is formed in a partial region of the n-type Si layer 61 on the back surface side of the substrate, and a p-type back electrode 56 connected to the p-type Si 62 is formed.
  • a three-terminal multi-junction (three-junction) solar cell is formed.
  • Pd nanoparticles are used as the conductive nanoparticles.
  • a current of about 10 mA / cm 2 is generated.
  • the size (surface area) of the subcell is adjusted so that the photoelectric flow generated in the top cell and the bottom cell becomes uniform and the current matching condition is satisfied.
  • surplus photocurrent generated in the bottom cell due to the spectrum fluctuation of sunlight is taken out as electric power from the backside alternating electrodes.
  • FIG. 10 is a schematic cross-sectional view of a GaInP / GaAs // GaInAsP / GaInAs multi-junction solar cell 70 having an intermediate electrode structure.
  • a GaInP subcell (consisting of an n-type GaInP layer 71 and a p-type GaInP layer 72), a tunnel junction layer 73 and a GaAs subcell (consisting of an n-type GaAs layer 78 and a p-type GaAs layer 79) are used.
  • GaInP / GaAs2 junction solar cell is used.
  • the top cell includes a top electrode 75 on the light incident side.
  • the bottom cell includes a GaInAsP subcell (consisting of an n-type GaInAsP layer 80 and a p-type GaInAsP layer 81), a tunnel junction layer 82, and a GaInAs subcell (consisting of an n-type GaInAs layer 83 and a p-type GaInAs layer 84).
  • a GaInAsP / GaInAs2 junction solar cell is used.
  • a solar cell in which an intermediate electrode 77 is formed on a part other than the junction surface on the n-type GaInAsP layer 80 located on the light incident side of the p-type GaInAsP layer 81 is used.
  • a p-type back electrode 76 is provided on the back side of the bottom cell.
  • a three-terminal multi-junction (four-junction) solar cell is formed by bonding the top cell and the bottom cell using the bonding layer 74 made of conductive nanoparticles.
  • the size (surface area) of the subcell is adjusted so that the photoelectric flow generated in the top cell and the bottom cell becomes uniform and the current matching condition is satisfied.
  • an excess photocurrent generated in the GaInP / GaAs top cell due to the fluctuation of the spectrum of sunlight is taken out as power using the intermediate electrode and the top electrode.
  • Excess photocurrent generated in the GaInAsP / GaInAs bottom cell is extracted as power using the back electrode and the intermediate electrode.
  • the multi-junction photoelectric conversion element of the present invention has been described by using examples of a plurality of types of solar cells.
  • the cells of the photoelectric conversion element used in the present invention are not limited to those illustrated.
  • the photoelectric conversion element or solar cell of the present invention is industrially useful because it is a device that improves the use efficiency of light energy such as sunlight and is robust against fluctuations in the spectrum of sunlight.
  • Second basic structure 26 Second electrode 30 GaAs // Si multi-junction solar cell with alternate back electrode structure 31, 41, 51, 58, 78 n-type GaAs layer 32, 42, 52, 59, 79 p-type GaAs layers 33, 48, 61 n-type Si layers 36, 46, 56, 76 p-type back electrode 37, 57 n-type back electrode 38, 62 p-type Si Reference Signs List 40

Abstract

Provided are: a multijunction photoelectric conversion element which has robustness against spectrum fluctuations, which is provided with high-quality crystal sub-cells, and in which optical reflection loss in a bonded portion is reduced; a multijunction solar battery; and a manufacturing method for the multijunction photoelectric conversion element. The multijunction photoelectric conversion element is provided with: a first cell (12) which is a photoelectric conversion element positioned on the light incident side; a second cell (13) which is a photoelectric conversion element positioned on a side opposite to the light incident side; a junction layer (14) with which the first cell (12) and the second cell (13) are bonded together, and which is made from conductive nanoparticles; a first electrode (15) positioned on the light incident-side surface of the first cell (12); a second electrode (16) positioned on a surface, of the second cell (13), opposite to the light incident side; and a third electrode which is provided to the second cell (13), and which is an electrode (17) positioned on the surface opposite to the light incident side or is an intermediate electrode positioned on the first cell (12)-side surface. Accordingly, a high-performance multijunction photoelectric conversion element can be implemented.

Description

多接合光電変換素子及び多接合太陽電池Multi-junction photoelectric conversion element and multi-junction solar cell
　本発明は、複数の光電変換素子のセルを接合してなる多接合光電変換素子及び該多接合光電変換素子を備える多接合太陽電池、並びに多接合光電変換素子の製造方法に関する。 The present invention relates to a multi-junction photoelectric conversion element formed by joining cells of a plurality of photoelectric conversion elements, a multi-junction solar cell including the multi-junction photoelectric conversion element, and a method for manufacturing a multi-junction photoelectric conversion element.
　近年、多接合太陽電池に代表される多接合の光電変換素子の研究開発が進められている。多接合太陽電池は、バンドギャップエネルギーの異なる半導体素子からなる太陽電池セルを複数積層した構造を有する。多接合太陽電池では、異なる波長の太陽光を吸収する太陽電池セルを直列につなぎ合わせることにより、広くエネルギー分布した太陽光を効率よく利用できる。多接合太陽電池の出力電圧は、各セルの電圧の合計になるので大きくなる。 In recent years, research and development of multi-junction photoelectric conversion elements represented by multi-junction solar cells have been promoted. A multi-junction solar cell has a structure in which a plurality of solar cells composed of semiconductor elements having different band gap energies are stacked. In a multi-junction solar cell, solar cells that absorb sunlight of different wavelengths are connected in series, so that sunlight with a wide energy distribution can be used efficiently. The output voltage of the multi-junction solar cell increases because it is the sum of the voltages of the cells.
　多接合の光電変換素子や多接合太陽電池を構成するところの、個々の光電変換素子や太陽電池の各セルを、サブセルともいう。多接合太陽電池の光入射側（最表面側）に置かれている太陽電池をトップセルという。トップセルには、バンドギャップが大きい半導体を用い、それより短波長の光を吸収して長波長の光を透過させる。一方、光入射側に対して最も反対側に置かれるのがボトムセルである。ボトムセルには、バンドギャップが小さい半導体を使用し、トップセルを透過した光を吸収する。３接合太陽電池の場合、真ん中の太陽電池をミドルセルと言う。 セ ル Each photoelectric conversion element or each cell of a solar cell constituting a multi-junction photoelectric conversion element or a multi-junction solar cell is also referred to as a subcell. A solar cell placed on the light incident side (outermost surface side) of the multi-junction solar cell is called a top cell. For the top cell, a semiconductor having a large band gap is used, and light having a shorter wavelength is absorbed and light having a longer wavelength is transmitted. On the other hand, the bottom cell is located farthest from the light incident side. A semiconductor having a small band gap is used for the bottom cell, and absorbs light transmitted through the top cell. In the case of a three-junction solar cell, the middle solar cell is called a middle cell.
　図１１は、従来の２端子型の多接合太陽電池の模式的構造断面図である。図１１のように、２端子型の多接合太陽電池は、トップセル２とボトムセル３が積層された積層構造であり、光入射側から見て表面と裏面に、電気エネルギーを取り出すための電極（トップ電極５と裏面電極６）を備える２端子構造を有する。 FIG. 11 is a schematic cross-sectional view of a conventional two-terminal multi-junction solar cell. As shown in FIG. 11, the two-terminal type multi-junction solar cell has a stacked structure in which a top cell 2 and a bottom cell 3 are stacked, and electrodes (for extracting electric energy) are provided on the front surface and the back surface when viewed from the light incident side. It has a two-terminal structure including a top electrode 5 and a back electrode 6).
　図１２に、図１１の２端子型の多接合太陽電池の等価回路図を示す。２端子型の多接合太陽電池において、直列に接続された各サブセルには同一の電流が流れる。図１２の電流Ｉ１と電流Ｉ２と電流Ｉ３が等しい。この電流整合条件のために、各サブセルにおいては、光吸収により生成された光電流量が最も低い値であるサブセルの光電流量によって、２端子型多接合太陽電池を流れる電流量が決定される。高い光電流量が生成されたサブセルにおいては、逆電流（暗電流）が生成し、流れる電流量が生成された光電流値よりも低減してしまう。また、地上で利用する際には太陽光スペクトルの変動などにより、各サブセルにおいて生成される光電流量は変動するため、電流整合条件を満たす必要のある２端子型多接合太陽電池は、太陽光スペクトル変動による損失が生じやすい。 FIG. 12 shows an equivalent circuit diagram of the two-terminal multi-junction solar cell of FIG. In a two-terminal multi-junction solar cell, the same current flows through each sub-cell connected in series. Equal currents I 1 and the current I 2 and the current I 3 in FIG. Due to this current matching condition, in each subcell, the amount of current flowing through the two-terminal multi-junction solar cell is determined by the photoelectric flow of the subcell in which the photoelectric flow generated by light absorption is the lowest value. In a subcell in which a high photoelectric flow rate is generated, a reverse current (dark current) is generated, and the amount of flowing current is smaller than the generated photocurrent value. In addition, when used on the ground, the photoelectric flow generated in each sub-cell varies due to fluctuations in the solar spectrum and the like. Losses due to fluctuations are likely to occur.
　スペクトル変動による損失を低減する方法として、電極をサブセル間に配置する４端子型等の多電極端子型の多接合デバイス構造が提案されている（非特許文献１参照）。 As a method of reducing loss due to spectrum fluctuation, a multi-electrode terminal type multi-junction device structure such as a four-terminal type in which electrodes are arranged between subcells has been proposed (see Non-Patent Document 1).
　図１３は、４端子型の多接合太陽電池の等価回路図である。４端子型の多接合太陽電池は、トップセル２とボトムセル３を電気的に分離した回路で構成される。各サブセルで生成された光電流（電流Ｉ２（電流Ｉ１）、電流Ｉ４（電流Ｉ３））が、それぞれ出力電力（電圧Ｖ１、電圧Ｖ２）として出力される。電流律速条件が課されていないため、太陽光スペクトル変動による損失が生じにくい。 FIG. 13 is an equivalent circuit diagram of a four-terminal multi-junction solar cell. The four-terminal multi-junction solar cell is configured by a circuit in which the top cell 2 and the bottom cell 3 are electrically separated. Photocurrent generated by each subcell (current I 2 (current I 1), the current I 4 (current I 3)) is output as the respective output power (voltage V 1, the voltage V 2). Since no current limiting condition is imposed, loss due to fluctuations in the solar spectrum is unlikely to occur.
　図１４は、４端子型の多接合太陽電池の模式的構造断面図である。図１４のように、４端子型の多接合太陽電池は、トップセル２とボトムセル３が積層された構造であり、トップセル２とボトムセル３の電力をそれぞれ出力するために、４端子を有する。４端子は、光入射側から順に、トップセル２の表面のトップ電極５と、トップセル裏面に積層される透明電極層８ａに電気接続される中間電極７ａと、ボトムセル３の表面に積層される透明電極層８ｂに設けられる中間電極７ｂと、ボトムセル裏面の裏面電極６とである。トップセル２の裏面の透明電極層８ａと、ボトムセル３の表面の透明電極層８ｂの間には、透明電極層を互いに電気的に絶縁するための絶縁接着層９が配置される。透明電極層及び絶縁接着層には、光吸収損失を低減するために透明な材料が用いられる。 FIG. 14 is a schematic cross-sectional view of a four-terminal multi-junction solar cell. As shown in FIG. 14, the four-terminal multi-junction solar cell has a structure in which a top cell 2 and a bottom cell 3 are stacked, and has four terminals to output power of the top cell 2 and the bottom cell 3 respectively. The four terminals are sequentially stacked from the light incident side on the top electrode 5 on the surface of the top cell 2, the intermediate electrode 7a electrically connected to the transparent electrode layer 8a stacked on the back surface of the top cell, and the surface of the bottom cell 3. The intermediate electrode 7b provided on the transparent electrode layer 8b and the back electrode 6 on the back surface of the bottom cell. Between the transparent electrode layer 8a on the back surface of the top cell 2 and the transparent electrode layer 8b on the surface of the bottom cell 3, an insulating adhesive layer 9 for electrically insulating the transparent electrode layers from each other is arranged. For the transparent electrode layer and the insulating adhesive layer, a transparent material is used to reduce light absorption loss.
　図１５は、３端子型の多接合太陽電池の等価回路図である。３端子型の多接合太陽電池は、トップセル２とボトムセル３の間に中間電極を配置した回路で構成される。図１５のように、トップセルに流れる電流をＩ２、ボトムセルに流れる電流をＩ３、各端子に流れる電流を（電流Ｉ１、電流Ｉ４、電流Ｉ５）、多接合デバイスの電圧をＶ１、ボトムセルの電圧をＶ２で表す。トップセルまたはボトムセルで生じた余剰の光電流は、中間電極を介して電力として出力される。これにより、トップセルとボトムセルは電流整合条件を満たす必要がなくなり、スペクトル変動等によりトップセルとボトムセルで生成される光電流量が不均等になった場合にも、余剰の暗電流を生成せずに済む。 FIG. 15 is an equivalent circuit diagram of a three-terminal multi-junction solar cell. The three-terminal multi-junction solar cell is constituted by a circuit in which an intermediate electrode is arranged between a top cell 2 and a bottom cell 3. As shown in FIG. 15, the current flowing to the top cell is I 2 , the current flowing to the bottom cell is I 3 , the current flowing to each terminal is (current I 1 , current I 4 , current I 5 ), and the voltage of the multi-junction device is V 1 represents the voltage of the bottom cell in V 2. Excess photocurrent generated in the top cell or the bottom cell is output as electric power via the intermediate electrode. As a result, the top cell and the bottom cell do not need to satisfy the current matching condition, and even when the photoelectric flow generated in the top cell and the bottom cell becomes uneven due to spectrum fluctuation or the like, an excess dark current is not generated. I'm done.
　図１６は、従来の３端子型の多接合太陽電池の構造図である。３端子は、光入射側から順に、トップセル２の表面のトップ電極５と、中間電極７と、ボトムセル裏面の裏面電極６とである。図１６のように、３端子型の多接合太陽電池は、トップセル２とボトムセル３を連続して成長させて積層構造を作製し、該積層構造の中間に中間電極７を後から取り付ける方法で作製されてきた。例えば、Ｓｉ系のボトムセル上にＧａＡｓ系のトップセルを直接結晶成長させる方法により、多接合型太陽電池を作製する方法が知られている（非特許文献２参照）。 FIG. 16 is a structural view of a conventional three-terminal multi-junction solar cell. The three terminals are, in order from the light incident side, a top electrode 5 on the front surface of the top cell 2, an intermediate electrode 7, and a back electrode 6 on the back surface of the bottom cell. As shown in FIG. 16, the three-terminal type multi-junction solar cell has a method in which a top cell 2 and a bottom cell 3 are continuously grown to form a laminated structure, and an intermediate electrode 7 is attached later in the middle of the laminated structure. It has been made. For example, a method of manufacturing a multi-junction solar cell by a method of directly growing a GaAs-based top cell on a Si-based bottom cell is known (see Non-Patent Document 2).
　図１７は、非特許文献３に示された３端子型太陽電池である。トップセル２にトップ電極５を設け、ボトムセル３裏面に交互電極６ａ、６ｂを形成した３端子型太陽電池が提案されている。しかし、トランジスタ構造と類似の構造（ｎｐ／ｐ－（ｐ，ｎ））となっており、多接合太陽電池（ｎｐ／ｎｐ）とは回路構成が異なっている。 FIG. 17 shows a three-terminal solar cell disclosed in Non-Patent Document 3. A three-terminal solar cell in which a top electrode 5 is provided on a top cell 2 and alternate electrodes 6a and 6b are formed on the back surface of the bottom cell 3 has been proposed. However, it has a structure similar to the transistor structure (np / p- (p, n)), and has a different circuit configuration from the multi-junction solar cell (np / np).
　本発明者らは、先に、導電性ナノ粒子を用いた接合によりトップセルとボトムセルを貼り合わせることにより、異種半導体材料のサブセルからなる多接合太陽電池を、提案した（特許文献１、非特許文献４、非特許文献５参照）。 The present inventors have previously proposed a multi-junction solar cell composed of sub-cells of heterogeneous semiconductor materials by bonding a top cell and a bottom cell by bonding using conductive nanoparticles (Patent Document 1, Non-Patent Document 1). Reference 4, Non-patent Reference 5).
特許第５８７５１２４号Patent No. 5875124
　従来技術の２端子構造の多接合光電変換素子は、高い光電流量が生成されたサブセルにおいて、逆電流（暗電流）が生成し、流れる電流量が生成された光電流値よりも低減してしまうという問題がある。また、電流整合条件を満たす必要のある２端子型多接合太陽電池は、太陽光スペクトルの変動などにより、各サブセルにおいて生成される光電流量が変動するため、太陽光スペクトル変動による損失が生じやすいという問題がある。 In a conventional multi-junction photoelectric conversion device having a two-terminal structure, a reverse current (dark current) is generated in a subcell in which a high photoelectric flow is generated, and the amount of flowing current is smaller than the generated photocurrent value. There is a problem. In addition, in a two-terminal multi-junction solar cell that needs to satisfy the current matching condition, the photoelectric flow generated in each subcell fluctuates due to fluctuations in the solar spectrum or the like. There's a problem.
　従来技術の４端子型の多接合デバイスにおいては、トップセルとボトムセルの接合部に、透明電極層及び絶縁接着層を設ける必要があった。このように、接合部には、光吸収損失を低減するために透明な材料を用いる必要があった。しかし、接合部の全材料を透明にしても、トップセルとボトムセルの間に挿入される透明電極・透明な接着剤による光学反射損失やトップセルの結晶品質が低下してしまう問題がある。また、半導体／透明電極層および透明電極層／絶縁接着層における屈折率の違いに起因した光学反射が生じてしまい、損失要因となってしまうという問題がある。 (4) In the conventional four-terminal multi-junction device, it is necessary to provide a transparent electrode layer and an insulating adhesive layer at the junction between the top cell and the bottom cell. Thus, it was necessary to use a transparent material for the joint in order to reduce light absorption loss. However, even if the entire material of the bonding portion is transparent, there is a problem that optical reflection loss due to a transparent electrode and a transparent adhesive inserted between the top cell and the bottom cell and the crystal quality of the top cell are degraded. Further, there is a problem that optical reflection occurs due to a difference in the refractive index between the semiconductor / transparent electrode layer and the transparent electrode layer / insulating adhesive layer, which causes a loss.
　従来技術の３端子型の多接合デバイスの例のように、Ｓｉボトムセル上にＧａＡｓトップセルを直接結晶成長する製造方法では、ＧａＡｓ結晶の品質が低下してしまい、良好な太陽電池特性が得られないという問題がある。 In a manufacturing method in which a GaAs top cell is directly crystal-grown on a Si bottom cell as in an example of a conventional three-terminal type multi-junction device, the quality of the GaAs crystal deteriorates, and good solar cell characteristics can be obtained. There is no problem.
　非特許文献３に示された従来技術は、多接合太陽電池（ｎｐ／ｎｐ）とは回路構成が異なっている。即ち、非特許文献３は、次の問題を解決するために裏面交互電極が設けられたものである。通常の入射光側の電極は入射光を遮りセルに影を生じてしまうため、電流生成の損失要因となっていた。この電極による光反射・散乱損失を解消する方法として、裏面交互型電極が導入された。これによって、入射面側での電極による光損失が低減され、高い電流生成が実現している。非特許文献３は、ｐｎ接合の直列接続になっていないので、タンデム（２つが縦に並んでいる構造）ではあるが、本願が目的とする多接合太陽電池のようにｐｎ接合を直列に接合することによって高い電圧が得られるような構造になっていない。 従 来 The prior art shown in Non-Patent Document 3 has a different circuit configuration from a multi-junction solar cell (np / np). That is, Non-Patent Literature 3 discloses that a back surface alternate electrode is provided to solve the following problem. The normal electrode on the incident light side blocks the incident light and creates a shadow on the cell, which has been a factor of loss of current generation. As a method of eliminating the light reflection / scattering loss due to this electrode, an alternate back type electrode has been introduced. Thereby, light loss due to the electrode on the incident surface side is reduced, and high current generation is realized. Non-Patent Document 3 is a tandem (a structure in which two are arranged vertically) because a pn junction is not connected in series. The structure does not provide a high voltage.
　また、従来技術の導電性ナノ粒子による接合を用いる提案は、２端子構造に関する技術であり、多接合太陽電池における電流律速による制限を解決できていなかった。 提案 Also, the prior art proposal using bonding with conductive nanoparticles is a technology relating to a two-terminal structure, and has not been able to solve the limitation due to current limiting in a multi-junction solar cell.
　本発明は、これらの問題を解決しようとするものであり、スペクトル変動に対して堅牢で、高品質結晶の各サブセルを備え、接合部における光学反射損失の低減した、多接合光電変換素子を提供することを目的とする。前記多接合光電変換素子の製造方法を提供することを目的とする。また、前記多接合光電変換素子を備える多接合太陽電池を提供することを目的とする。 The present invention seeks to solve these problems, and provides a multi-junction photoelectric conversion element that is robust against spectral fluctuations, has subcells of high-quality crystals, and has a reduced optical reflection loss at the junction. The purpose is to do. An object of the present invention is to provide a method for manufacturing the multi-junction photoelectric conversion element. Moreover, it aims at providing the multi-junction solar cell provided with the said multi-junction photoelectric conversion element.
　本発明は、前記目的を達成するために、以下の特徴を有するものである。 The present invention has the following features to achieve the above object.
（１）　多接合光電変換素子であって、光入射側に位置する光電変換素子の第１のセルと、光入射側の反対側に位置する光電変換素子の第２のセルと、前記第１のセルと前記第２のセルを接合する、導電性ナノ粒子からなる接合層と、前記第１のセルの、光入射側の面に位置する第１の電極と、前記第２のセルの、光入射側の反対面に位置する第２の電極と、前記第２のセルに設けた第３の電極であって、光入射側の反対面に位置する電極、または、第１のセル側の面に位置する中間電極である前記第３の電極と、を備えることを特徴とする多接合光電変換素子。
（２）　前記第３の電極を利用して、前記第１のセル又は前記第２のセルに生じた余剰の光電流を電力として取り出すことを特徴とする前記（１）記載の多接合光電変換素子。
（３）　前記第２のセルの表面積は、前記第１のセルの表面積より大であることを特徴とする前記（１）又は（２）記載の多接合光電変換素子。
（４）　前記導電性ナノ粒子の表面は有機分子で覆われていないことを特徴とする前記（１）乃至（３）のいずれか１項に記載の多接合光電変換素子。
（５）　前記接合層は、前記導電性ナノ粒子からなる接合層の厚みが、５ナノメートル以上５０ナノメートル以下であることを特徴とする前記（１）乃至（４）のいずれか１項に記載の多接合光電変換素子。
（６）　前記多接合光電変換素子の前記セルが、結晶Ｓｉ系、アモルファスＳｉ系、微結晶Ｓｉ系、有機系、もしくは、カルコパイライト系材料を用いた単接合太陽電池、またはＧａＡｓ、ＩｎＰ、ＧａＳｂ、もしくは、Ｇｅ基板上等に積層された２接合以上からなる太陽電池であることを特徴とする前記（１）乃至（５）のいずれか１項に記載の多接合光電変換素子。
（７）　前記（１）乃至（６）のいずれか１項に記載の多接合光電変換素子を備える多接合型太陽電池。
（８）　光入射側に位置する光電変換素子の第１のセルと、光入射側の反対側に位置する光電変換素子の第２のセルと、を備える多接合光電変換素子の製造方法であって、前記第２のセルに、光入射側の反対面に位置する第２の電極を形成すると共に、光入射側の反対面に位置する第３の電極、または、第１のセル側の面に位置する中間電極となる第３の電極を設ける工程と、前記第１のセルを前記第２のセルに、有機分子で覆われていない導電性ナノ粒子により接合する接合工程と、前記第１のセルの、光入射側の面に第１の電極を形成する工程と、を備えることを特徴とする多接合光電変換素子の製造方法。 (1) a multi-junction photoelectric conversion element, wherein a first cell of the photoelectric conversion element located on the light incident side, a second cell of the photoelectric conversion element located on the side opposite to the light incident side, A bonding layer made of conductive nanoparticles for bonding the cell and the second cell, a first electrode located on a light incident side surface of the first cell, and a A second electrode located on the surface opposite to the light incident side, and a third electrode provided on the second cell, the electrode being located on the surface opposite to the light incident side, or a third electrode provided on the first cell side. And a third electrode, which is an intermediate electrode located on the surface.
(2) The multi-junction photoelectric conversion according to (1), wherein an excess photocurrent generated in the first cell or the second cell is taken out as electric power using the third electrode. element.
(3) The multi-junction photoelectric conversion element according to (1) or (2), wherein the surface area of the second cell is larger than the surface area of the first cell.
(4) The multi-junction photoelectric conversion element according to any one of (1) to (3), wherein a surface of the conductive nanoparticle is not covered with an organic molecule.
(5) The bonding layer according to any one of (1) to (4), wherein a thickness of the bonding layer including the conductive nanoparticles is 5 nm or more and 50 nm or less. The multi-junction photoelectric conversion element according to the above.
(6) The cell of the multi-junction photoelectric conversion element is a single-junction solar cell using crystalline Si, amorphous Si, microcrystalline Si, organic, or chalcopyrite-based material, or GaAs, InP, GaSb. Alternatively, the multi-junction photoelectric conversion element according to any one of the above (1) to (5), which is a solar cell including two or more junctions stacked on a Ge substrate or the like.
(7) A multi-junction solar cell comprising the multi-junction photoelectric conversion element according to any one of (1) to (6).
(8) A method for manufacturing a multi-junction photoelectric conversion element, comprising: a first cell of a photoelectric conversion element located on a light incident side; and a second cell of a photoelectric conversion element located on a side opposite to the light incident side. Forming a second electrode on the second cell opposite to the light incident side, and forming a third electrode opposite the light incident side on the second cell, or a surface on the first cell side. Providing a third electrode serving as an intermediate electrode located in the first cell, bonding the first cell to the second cell with conductive nanoparticles not covered with organic molecules, Forming a first electrode on the light-incident side surface of the cell described in (1).
　本発明の多接合光電変換素子は、異種材料からなるサブセルを用い、導電性ナノ粒子からなる接合層により接合し、かつ３端子を設けることにより、広くエネルギー分布した太陽光等を高効率で利用可能とし、かつ多接合太陽電池を構成する各サブセルに生じる光電流値の不均衡による損失を抑制するという効果を奏する。よって、本発明の多接合光電変換素子は、スペクトル変動に対して堅牢である。また、本発明の多接合光電変換素子は、導電性ナノ粒子による接合層により各サブセルが接合されるので、各サブセルを高品質結晶で構成することが可能であり、各サブセルが高性能である。また、本発明の多接合光電変換素子は、接合層が導電性ナノ粒子からなる接合層であることにより、接合部における光学反射損失の低減した多接合光電変換素子を実現できる。 The multi-junction photoelectric conversion element of the present invention uses sub-cells made of different materials, is bonded by a bonding layer made of conductive nanoparticles, and is provided with three terminals, so that sunlight with a wide energy distribution can be used with high efficiency. It is possible to achieve the effect of suppressing the loss due to the imbalance of the photocurrent value generated in each subcell constituting the multi-junction solar cell. Therefore, the multi-junction photoelectric conversion element of the present invention is robust against spectrum fluctuation. Further, in the multi-junction photoelectric conversion element of the present invention, since each sub-cell is joined by a joining layer made of conductive nanoparticles, each sub-cell can be made of a high-quality crystal, and each sub-cell has high performance. . Moreover, the multi-junction photoelectric conversion element of the present invention can realize a multi-junction photoelectric conversion element with reduced optical reflection loss at the junction because the junction layer is a junction layer made of conductive nanoparticles.
　本発明の多接合太陽電池は、前記本発明の多接合光電変換素子から構成されるので、広くエネルギー分布した太陽光等を高効率で利用可能とし、かつスペクトル変動に対して堅牢である。 多 Since the multi-junction solar cell of the present invention is constituted by the multi-junction photoelectric conversion element of the present invention, it is possible to efficiently use sunlight or the like having a wide energy distribution and is robust against spectrum fluctuation.
　本発明の多接合光電変換素子の製造方法では、予め形成した第2及び第３の電極付きの光電変換素子をボトムセルに用い、これとトップセルを貼り合わせることによって、高結晶品質のセルをそれぞれ使用できるので、従来の３端子型デバイスと比較して、高性能の多接合光電変換素子を製造できる。 In the method for manufacturing a multi-junction photoelectric conversion element of the present invention, a pre-formed photoelectric conversion element with second and third electrodes is used for a bottom cell, and this and a top cell are bonded to each other to obtain a high-crystal quality cell. Since it can be used, a high-performance multi-junction photoelectric conversion element can be manufactured as compared with a conventional three-terminal device.
本発明の第１の基本構造の光電変換素子の模式的構造断面図である。1 is a schematic cross-sectional view of a photoelectric conversion element having a first basic structure according to the present invention. 本発明の第１の基本構造の光電変換素子の斜視図である。It is a perspective view of the photoelectric conversion element of the 1st basic structure of the present invention. 本発明の第１の基本構造における、交互裏面電極を形成したボトムセルの下面図である。FIG. 2 is a bottom view of a bottom cell in which an alternate back electrode is formed in the first basic structure of the present invention. 本発明の第２の基本構造の光電変換素子の模式的構造断面図である。It is a schematic structure sectional view of the photoelectric conversion element of the 2nd basic structure of the present invention. 本発明の第２の基本構造の光電変換素子の斜視図である。It is a perspective view of the photoelectric conversion element of the 2nd basic structure of the present invention. 本発明の第２の基本構造における、中間電極を形成したボトムセルの上面図である。FIG. 9 is a top view of a bottom cell on which an intermediate electrode is formed in the second basic structure of the present invention. 本発明の第１の実施形態の模式的構造断面図である。It is a schematic structure sectional view of a 1st embodiment of the present invention. 本発明の第２の実施形態の模式的構造断面図である。It is a schematic structure sectional view of a 2nd embodiment of the present invention. 本発明の第３の実施形態の模式的構造断面図である。It is a schematic structure sectional view of a 3rd embodiment of the present invention. 本発明の第４の実施形態の模式的構造断面図である。It is a schematic structure sectional view of a 4th embodiment of the present invention. 従来の２端子型の多接合太陽電池の模式的構造断面図である。It is a schematic structure sectional view of the conventional two-terminal type multi junction solar cell. 従来の２端子型の多接合太陽電池の等価回路図である。It is an equivalent circuit diagram of the conventional two-terminal type multi-junction solar cell. 従来の４端子型の多接合太陽電池の等価回路図である。FIG. 4 is an equivalent circuit diagram of a conventional four-terminal multi-junction solar cell. 従来の４端子型の多接合太陽電池の模式的構造断面図である。It is a schematic cross section of a conventional four-terminal type multi-junction solar cell. 従来の３端子型の多接合太陽電池の等価回路図である。It is an equivalent circuit diagram of the conventional three-terminal type multi-junction solar cell. 従来の３端子型の多接合太陽電池の模式的構造断面図である。It is a schematic structure sectional view of the conventional three-terminal type multi junction solar cell. 従来の３端子型の太陽電池の模式的構造断面図である。It is a schematic structure sectional view of the conventional three-terminal type solar cell.
　本発明の実施形態について以下説明する。 (4) An embodiment of the present invention will be described below.
　本発明者らは、複数の光電変換素子のセルが接合された光電変換素子において、接合構造と端子構造の開発により、太陽光エネルギー等の高効率化、及び太陽光のスペクトル変動による損失の軽減を実現したものである。 The present inventors have developed a junction structure and a terminal structure in a photoelectric conversion element in which a plurality of cells of a photoelectric conversion element are joined, thereby increasing the efficiency of solar energy and the like, and reducing the loss due to spectrum fluctuation of sunlight. Is realized.
　本発明の実施形態の多接合光電変換素子は、複数の光電変換素子のセルが接合されてなる光電変換素子に関し、光入射側に位置する光電変換素子の第１のセル（以下、「トップセル」ともいう。）と、光入射側の反対側に位置する光電変換素子の第２のセル（以下、「ボトムセル」ともいう。）と、前記第１のセルと前記第２のセルを接合する、有機分子で覆われていない導電性ナノ粒子からなる接合層と、を含む積層構造を有する。 A multi-junction photoelectric conversion element according to an embodiment of the present invention relates to a photoelectric conversion element in which cells of a plurality of photoelectric conversion elements are joined, and relates to a first cell (hereinafter, referred to as a “top cell”) of a photoelectric conversion element located on a light incident side. ), And the second cell (hereinafter, also referred to as a “bottom cell”) of the photoelectric conversion element located on the side opposite to the light incident side, and the first cell and the second cell are joined. And a bonding layer made of conductive nanoparticles that are not covered with organic molecules.
　本発明の実施形態の多接合光電変換素子は、３つの電極からの端子を有するので、３端子型の多接合光電変換素子である。３端子は、前記第１のセルの、光入射側の面に位置する第１の電極の端子と、前記第２のセルの、光入射側の反対面に位置する第２の電極の端子と、前記第２のセルに設けた第３の電極の端子である。第３の電極は、光入射側の反対面に位置する電極、または、第１のセル側の面に位置する中間電極のいずれか１つである。 多 Since the multi-junction photoelectric conversion element according to the embodiment of the present invention has terminals from three electrodes, it is a three-terminal multi-junction photoelectric conversion element. The three terminals include a first electrode terminal located on a light incident side surface of the first cell and a second electrode terminal located on a light incident side opposite surface of the second cell. , Terminals of a third electrode provided in the second cell. The third electrode is one of an electrode located on a surface opposite to the light incident side and an intermediate electrode located on a surface on the first cell side.
　第３の電極を光入射側の反対面に位置する電極で構成した、３端子型の多接合光電変換素子（以下、「第１の基本構造」という。）について、図１乃至３を参照して説明する。図１は、３端子型多接合光電変換素子の第１の基本構造１０の模式的構造断面図である。図２は、第１の基本構造の斜視図である。図３は、第１の基本構造のボトムセルの裏面の交互電極１６、１７を説明する図である。裏面の交互電極の一方がｎ型で、他方がｐ型である。第１の基本構造は、トップセル１２とボトムセル１３とこれらを接合する導電性ナノ粒子からなる接合層１４からなる積層構造を備え、トップセルの光入射側面にトップ電極１５を備え、ボトムセル１３の裏面に、従来の第２の電極の他に、さらに、第３の電極を設けた電極構造を有する。ボトムセル１３の裏面における電極構造は、第２の電極と第３の電極とが交互に配置された交互電極構造を有する。細い線状の電極が並列に配置された電極部分を、グリッドとも呼ぶ。交互電極構造を構成する第２の電極と第３の電極は、それぞれ交互電極部分より太い線（バスバー電極）等で接続されて、第２の電極、第３の電極を構成する。例えば、第２の電極と、第３の電極を、それぞれ櫛形とし、それぞれの櫛形の櫛歯が交互に入り込む構造とすることができる。なお、櫛形に限定されない。 A three-terminal multi-junction photoelectric conversion element (hereinafter, referred to as a “first basic structure”) in which a third electrode is formed of an electrode located on a surface opposite to a light incident side will be described with reference to FIGS. Will be explained. FIG. 1 is a schematic structural sectional view of a first basic structure 10 of a three-terminal multi-junction photoelectric conversion element. FIG. 2 is a perspective view of the first basic structure. FIG. 3 is a diagram illustrating the alternating electrodes 16 and 17 on the back surface of the bottom cell having the first basic structure. One of the alternate electrodes on the back is n-type and the other is p-type. The first basic structure has a stacked structure including a top cell 12, a bottom cell 13, and a bonding layer 14 made of conductive nanoparticles for bonding them, a top electrode 15 is provided on a light incident side surface of the top cell, and a bottom cell 13 is formed. On the back surface, there is an electrode structure in which a third electrode is provided in addition to the conventional second electrode. The electrode structure on the back surface of the bottom cell 13 has an alternate electrode structure in which second electrodes and third electrodes are alternately arranged. The electrode portion where thin linear electrodes are arranged in parallel is also called a grid. The second electrode and the third electrode constituting the alternating electrode structure are connected to each other with a thicker line (bus bar electrode) or the like than the alternating electrode portion, thereby forming a second electrode and a third electrode. For example, the second electrode and the third electrode may have a comb shape, and the comb teeth of each comb may alternately enter. In addition, it is not limited to a comb shape.
　第１の基本構造は、前記３端子型の多接合太陽電池のｐｎ接合の位置が裏面側に移動しているが、等価回路図としては図１５と同じである。トップ電極１５と電極１７の間にはトップセル１２とボトムセル１３で生成された電圧を足し合わせた電圧が生じる。例えば、トップセル１２で生成された電流Ｉ２がボトムセル１３で生成された電流Ｉ３よりも小さい場合には、トップ電極１５と電極１７の間を流れる電流はトップセル１２で生成された電流Ｉ２で律速されるため、電流Ｉ２が流れる。また、電極１６と電極１７の間には、ボトムセル１３で生成された電圧が生じる。ボトムセル１３で生じた電流Ｉ３のうちトップ電極１５と電極１７の間に流れる電流を差し引いた電流Ｉ５（＝Ｉ３－Ｉ２）が流れる。第１の電極（トップ電極）と第２の電極（裏面交互電極の一方）とにより、第１のセル（トップセル）に生じた余剰の光電流を電力として取り出し、第２の電極（裏面交互電極の一方）と第３の電極（裏面交互電極の他方）とにより、第２のセル（ボトムセル）に生じた余剰の光電流を電力として取り出す。 In the first basic structure, the position of the pn junction of the three-terminal type multi-junction solar cell is moved to the back side, but the equivalent circuit diagram is the same as that in FIG. A voltage is generated between the top electrode 15 and the electrode 17 by adding the voltages generated by the top cell 12 and the bottom cell 13. For example, when the current I 2 generated in the top cell 12 is smaller than the current I 3 generated in the bottom cell 13, the current flowing between the top electrode 15 and the electrode 17 becomes the current I 2 generated in the top cell 12. to be rate-limiting in 2, current I 2 flows. Further, a voltage generated in the bottom cell 13 is generated between the electrode 16 and the electrode 17. A current I 5 (= I 3 −I 2 ) obtained by subtracting a current flowing between the top electrode 15 and the electrode 17 from the current I 3 generated in the bottom cell 13 flows. An excess photocurrent generated in the first cell (top cell) is taken out as electric power by the first electrode (top electrode) and the second electrode (one of the backside alternating electrodes), and the second electrode (backside alternating electrode) is taken out. The excess photocurrent generated in the second cell (bottom cell) is extracted as power by one of the electrodes) and the third electrode (the other of the backside alternating electrodes).
　第３の電極を、第１のセル側の面に位置する中間電極で構成した、多接合光電変換素子（以下、「第２の基本構造」という。）について、図４乃至６を参照して説明する。図４は、３端子型多接合光電変換素子の第２の基本構造２０の模式的構造断面図である。図５は、第２の基本構造の斜視図である。図６は、第２の基本構造の、中間電極を形成したボトムセルの上面図である。第２の基本構造は、トップセル２２とボトムセル２３とこれらを接合する導電性ナノ粒子からなる接合層２４とからなる積層構造を備え、トップセルの光入射側にトップ電極２５を設け、ボトムセル２３の裏面に第２の電極２６を設け、さらに、ボトムセル２３の上面（トップセル側の面）に中間電極２７となる第３の電極を設けた電極構造を有する。中間電極２７は、ボトムセル２３の上面であれば、トップセル２２との接合部以外の位置であればどこでもよい。図６（ａ）（ｂ）は、細い電極線が並列に配置されたグリッドと、該グリッドを接続するより太い電極（バスバー電極）とからなる中間電極である。（ａ）は櫛形の例であり、（ｂ）はバスバー電極を複数設ける例である。なお、中間電極の形状は特に限定されない。グリッドを細い電線で構成して遮光しないことが好ましい。 Regarding a multi-junction photoelectric conversion element (hereinafter, referred to as “second basic structure”) in which a third electrode is constituted by an intermediate electrode located on the surface on the first cell side, with reference to FIGS. explain. FIG. 4 is a schematic structural cross-sectional view of the second basic structure 20 of the three-terminal multi-junction photoelectric conversion element. FIG. 5 is a perspective view of the second basic structure. FIG. 6 is a top view of a bottom cell having an intermediate electrode of the second basic structure. The second basic structure includes a stacked structure including a top cell 22, a bottom cell 23, and a bonding layer 24 made of conductive nanoparticles for bonding them. A top electrode 25 is provided on the light incident side of the top cell. Has an electrode structure in which a second electrode 26 is provided on the back surface of the substrate and a third electrode serving as an intermediate electrode 27 is provided on the upper surface (surface on the top cell side) of the bottom cell 23. The intermediate electrode 27 may be anywhere on the upper surface of the bottom cell 23 as long as it is at a position other than the junction with the top cell 22. FIGS. 6A and 6B show an intermediate electrode including a grid on which thin electrode lines are arranged in parallel and a thicker electrode (bus bar electrode) connecting the grid. (A) is an example of a comb shape, and (b) is an example of providing a plurality of bus bar electrodes. The shape of the intermediate electrode is not particularly limited. It is preferable that the grid is made of a thin electric wire so as not to block light.
　第２の基本構造の等価回路図は、前記３端子型の多接合太陽電池の等価回路図（図１５）と同じである。第１の電極（トップ電極）と第２の電極（裏面電極）、または、第１の電極（トップ電極）と第３の電極（中間電極）とにより、第１のセル（トップセル）に生じた余剰の光電流を電力として取り出し、第２の電極（裏面電極）と第３の電極（中間電極）とにより、第２のセル（ボトムセル）に生じた余剰の光電流を電力として取り出す。 等 価 The equivalent circuit diagram of the second basic structure is the same as the equivalent circuit diagram of the three-terminal multi-junction solar cell (FIG. 15). The first cell (top cell) is formed by the first electrode (top electrode) and the second electrode (backside electrode) or the first electrode (top electrode) and the third electrode (intermediate electrode). The surplus photocurrent is extracted as electric power, and the surplus photocurrent generated in the second cell (bottom cell) is extracted as electric power by the second electrode (back surface electrode) and the third electrode (intermediate electrode).
　複数の光電変換素子セルの各表面積のサイズは適宜設計することができる。光電流量が均等となり電流整合条件が満たされるように、各セルの表面積サイズを調整して設計することが好ましい。例えば、表面積がトップセルよりも大きなボトムセルを用いることにより、ボトムセルの電流がトップセルの電流より小さくならないようにすることが好ましい。 サ イ ズ The size of each surface area of the plurality of photoelectric conversion element cells can be appropriately designed. It is preferable to design by adjusting the surface area size of each cell so that the photoelectric flow becomes uniform and the current matching condition is satisfied. For example, it is preferable to use a bottom cell having a larger surface area than the top cell so that the current of the bottom cell does not become smaller than the current of the top cell.
　本発明における光電変換素子のセルは、例えば太陽電池のセルである。本発明における光電変換素子の第１又は第２のセルは、具体的には、結晶Ｓｉ系、アモルファスＳｉ系、微結晶Ｓｉ系、有機系、もしくは、カルコパイライト系材料を用いた単接合太陽電池、またはＧａＡｓ、ＩｎＰ、ＧａＳｂ、もしくは、Ｇｅ基板上等に積層された２接合以上からなる太陽電池である。 セ ル The cell of the photoelectric conversion element in the present invention is, for example, a cell of a solar cell. Specifically, the first or second cell of the photoelectric conversion element in the present invention is a single-junction solar cell using a crystalline Si-based, amorphous Si-based, microcrystalline Si-based, organic-based, or chalcopyrite-based material. Or a solar cell composed of two or more junctions stacked on a GaAs, InP, GaSb, Ge substrate or the like.
　本発明の多接合光電変換素子は、光入射側に配置される光電変換素子の第１のセルと光入射側の反対側に配置される光電変換素子の第２のセルとから構成される。 The multi-junction photoelectric conversion element of the present invention includes a first cell of the photoelectric conversion element arranged on the light incident side and a second cell of the photoelectric conversion element arranged on the side opposite to the light incident side.
　本発明の光電変換素子は、太陽光を対象とする太陽電池に限定されない。 光電 The photoelectric conversion element of the present invention is not limited to a solar cell for sunlight.
　本発明の第１のセルと前記第２のセルを接合する接合層は、有機分子で覆われていない導電性ナノ粒子からなる。本発明において、トップセルとボトムセルの間には透明電極および透明接着剤は挿入されていない。 The bonding layer for bonding the first cell and the second cell of the present invention is made of conductive nanoparticles that are not covered with organic molecules. In the present invention, no transparent electrode and no transparent adhesive are inserted between the top cell and the bottom cell.
　導電性ナノ粒子のサイズは、５ナノメートル以上５０ナノメートル以下であることが好ましい。その理由は、導電性ナノ粒子接着層における反射損失を低減させるためには導電性ナノ粒子からなる接合層の厚さが５ナノメートル以上５０ナノメートル以下であることが好ましいからである。導電性ナノ粒子としては、Ｐｄ、Ａｕ、Ａｇ、Ｐｔ、Ｎｉ、Ａｌ、Ｚｎ、Ｉｎ等の金属ナノ粒子、ＺｎＯ、Ｉｎ２Ｏ３等の金属酸化物ナノ粒子などが挙げられる。導電性ナノ粒子の形状は、球状、半球状、円柱状、楕円球状等が挙げられる。導電性ナノ粒子の接合層方向のサイズは、良好な導電性を得るために１０ナノメートル以上であることが好ましい。一方、ナノ粒子による光の吸収・散乱を抑制するために１００ナノメートル以下であることが好ましい。なお、本発明における「導電性ナノ粒子のサイズＤ」は、次のように定義される。
　　Ｄ＝（ΣＤｉ）／ｎ
　［ここで、Ｄは導電性ナノ粒子のサイズ、Ｄｉは所定の観察領域に存在する任意の粒子の粒子径〔＝（長径＋短径）／２〕、ｎは該観察領域に存在する粒子の個数（ｎは統計処理上十分に大きな数、通常２０以上）］ The size of the conductive nanoparticles is preferably not less than 5 nanometers and not more than 50 nanometers. The reason is that in order to reduce the reflection loss in the conductive nanoparticle adhesive layer, it is preferable that the thickness of the bonding layer made of the conductive nanoparticles be 5 nm or more and 50 nm or less. Examples of the conductive nanoparticles include metal nanoparticles such as Pd, Au, Ag, Pt, Ni, Al, Zn, and In, and metal oxide nanoparticles such as ZnO and In 2 O 3 . Examples of the shape of the conductive nanoparticles include a sphere, a hemisphere, a column, and an ellipsoid. The size of the conductive nanoparticles in the bonding layer direction is preferably 10 nm or more in order to obtain good conductivity. On the other hand, the thickness is preferably 100 nm or less in order to suppress absorption and scattering of light by the nanoparticles. The “size D of the conductive nanoparticles” in the present invention is defined as follows.
D = (ΣDi) / n
[Where D is the size of the conductive nanoparticle, Di is the particle diameter of any particle present in a predetermined observation area [= (long axis + minor axis) / 2], and n is the particle diameter of the particle existing in the observation area. Number (n is a number large enough for statistical processing, usually 20 or more)]
　接合層における導電性ナノ粒子の配列間隔は、導電性ナノ粒子サイズの２倍以上１０倍以下が好ましい。接合層における導電性ナノ粒子は、有機分子等の保護膜や接着用材料で覆われておらず、個々の独立した粒子が均一に配列した単一層（モノレイヤー）である。導電性ナノ粒子の配列間隔は、光を良く透過させるためにナノ粒子のサイズの少なくとも２倍以上の距離を有していることが好ましい。より好ましくは３倍以上である。 配 列 The arrangement interval of the conductive nanoparticles in the bonding layer is preferably 2 to 10 times the conductive nanoparticle size. The conductive nanoparticles in the bonding layer are not covered with a protective film such as an organic molecule or a bonding material, and are a single layer (monolayer) in which individual independent particles are uniformly arranged. The arrangement interval of the conductive nanoparticles preferably has a distance of at least twice the size of the nanoparticles in order to transmit light well. More preferably, it is three times or more.
　本実施形態の３端子型の多接合光電変換素子の第１の基本構造を製造する方法は、次の工程を備える。（工程３）は、（工程１）（工程２）のいずれか又は両方に先立って行ってもよい。
　（工程１）　ボトムセルの光入射側の反対面に、第２の電極と第３の電極を形成する工程。
　（工程２）　トップセルを、工程１で電極を形成済みのボトムセルに、有機分子で覆われていない導電性ナノ粒子により接合する接合工程。
　（工程３）　トップセルの光入射側の面に第１の電極を形成する工程。 The method of manufacturing the first basic structure of the three-terminal multi-junction photoelectric conversion element of the present embodiment includes the following steps. (Step 3) may be performed prior to either or both of (Step 1) and (Step 2).
(Step 1) A step of forming a second electrode and a third electrode on the surface of the bottom cell opposite to the light incident side.
(Step 2) A bonding step in which the top cell is bonded to the bottom cell on which the electrodes have been formed in Step 1 by using conductive nanoparticles that are not covered with organic molecules.
(Step 3) A step of forming a first electrode on the light incident side surface of the top cell.
　本実施形態の３端子型の多接合光電変換素子の第２の基本構造を製造する方法は、次の工程を備える。（工程３）は、（工程１）（工程２）のいずれか又は両方に先立って行ってもよい。
　（工程１）　ボトムセルに、光入射側の反対面に位置する第２の電極を形成すると共に、ボトムセルの光入射側の面に中間電極となる第３の電極を設ける工程。
　（工程２）　トップセルを、工程１で電極を形成済みのボトムセルに、有機分子で覆われていない導電性ナノ粒子により接合する接合工程。
　（工程３）　トップセルの光入射側の面に第１の電極を形成する工程。 The method for manufacturing the second basic structure of the three-terminal multi-junction photoelectric conversion element of the present embodiment includes the following steps. (Step 3) may be performed prior to either or both of (Step 1) and (Step 2).
(Step 1) A step of forming a second electrode located on the surface opposite to the light incident side on the bottom cell and providing a third electrode serving as an intermediate electrode on the light incident side of the bottom cell.
(Step 2) A bonding step in which the top cell is bonded to the bottom cell on which the electrodes have been formed in Step 1 by using conductive nanoparticles that are not covered with organic molecules.
(Step 3) A step of forming a first electrode on the light incident side surface of the top cell.
（第１の実施形態）
　本発明の第１の実施形態の多接合光電変換素子について、図７を参照して以下説明する。本実施形態は、第１の基本構造の例である。図７は、裏面交互電極構造のＧａＡｓ／／Ｓｉ多接合太陽電池３０の模式断面図である。トップセルとして、ｐ型ＧａＡｓ層３２の光入射側にｎ型ＧａＡｓ層３１を形成したＧａＡｓ太陽電池を用いる。トップセルは、光入射側にトップ電極３５を備える。ボトムセルとして、ｎ型Ｓｉ層３３の基板の裏面側にｎ型およびｐ型の電極（ｎ型裏面電極３７、ｐ型裏面電極３６）を交互に形成したＳｉ太陽電池を用いる。ｎ型Ｓｉ層３３の基板の裏面側の一部領域に、ｐ型Ｓｉ部３８の領域が形成され、該ｐ型Ｓｉ３８に接続するｐ型裏面電極３６が形成されている。導電性ナノ粒子からなる接合層３４を用いてトップセルとボトムセルを張り合わせることにより、３端子型多接合太陽電池を構成する。導電性ナノ粒子はＰｄ粒子を用いる。通常の太陽光スペクトルにより、ＧａＡｓトップセルおよびＳｉボトムセルにおいては、それぞれ、約３０ｍＡ／ｃｍ２および１０ｍＡ／ｃｍ２の電流が生成される。トップセルのサイズよりも大きなボトムセルを用いることで、トップセルとボトムセルで生じる光電流量が均等となり電流整合条件が満たされるように、サブセルのサイズ（表面積）を調整する。また、太陽光のスペクトル変動によりボトムセルに生じた余剰の光電流は裏面交互電極から電力として取り出す。 (1st Embodiment)
The multi-junction photoelectric conversion element according to the first embodiment of the present invention will be described below with reference to FIG. This embodiment is an example of a first basic structure. FIG. 7 is a schematic cross-sectional view of a GaAs // Si multi-junction solar cell 30 having an alternate back electrode structure. As the top cell, a GaAs solar cell having the n-type GaAs layer 31 formed on the light incident side of the p-type GaAs layer 32 is used. The top cell includes a top electrode 35 on the light incident side. As the bottom cell, a Si solar cell in which n-type and p-type electrodes (n-type back electrode 37 and p-type back electrode 36) are alternately formed on the back surface side of the substrate of the n-type Si layer 33 is used. A region of the p-type Si portion 38 is formed in a partial region of the n-type Si layer 33 on the back surface side of the substrate, and a p-type back electrode 36 connected to the p-type Si 38 is formed. By bonding the top cell and the bottom cell using the bonding layer 34 made of conductive nanoparticles, a three-terminal multi-junction solar cell is formed. Pd particles are used as the conductive nanoparticles. The conventional solar spectrum, in the GaAs top cell and Si bottom cell, respectively, current of about 30 mA / cm 2 and 10 mA / cm 2 is produced. By using a bottom cell that is larger than the size of the top cell, the size (surface area) of the subcell is adjusted so that the photoelectric flow generated in the top cell and the bottom cell becomes uniform and the current matching condition is satisfied. In addition, surplus photocurrent generated in the bottom cell due to the spectrum fluctuation of sunlight is taken out as electric power from the backside alternating electrodes.
（第２の実施形態）
　本発明の第２の実施形態の多接合光電変換素子について、図８を参照して以下説明する。本実施形態は、第２の基本構造の例である。図８は、中間電極構造のＧａＡｓ／／Ｓｉ多接合太陽電池４０の模式断面図である。トップセルとして、ｐ型ＧａＡｓ層４２の光入射側にｎ型ＧａＡｓ層４１を形成したＧａＡｓ太陽電池を用いる。トップセルは、光入射側にトップ電極４５を備える。ボトムセルとして、ｐ型Ｓｉ層４９の基板の光入射側に、ｎ型Ｓｉ層４８および中間電極４７を形成したＳｉ太陽電池を用いる。ボトムセルの裏面側にｐ型裏面電極４６を備える。導電性ナノ粒子からなる接合層４４を用いてトップセルとボトムセルを張り合わせることにより、３端子型多接合太陽電池を構成する。導電性ナノ粒子はＰｄナノ粒子を用いる。通常の太陽光スペクトルにより、ＧａＡｓトップセルおよびＳｉボトムセルにおいては、それぞれ、約３０ｍＡ／ｃｍ２および１０ｍＡ／ｃｍ２の電流が生成される。トップセルのサイズよりも大きなボトムセルを用いることで、トップセルとボトムセルで生じる光電流量が均等となり電流整合条件が満たされるように、サブセルのサイズ（表面積）を調整する。また、太陽光のスペクトル変動によりＧａＡｓトップセルにおいて余剰に生じた光電流は、中間電極とトップ電極を使って電力としてとりだす。ボトムセルに生じた余剰の光電流は裏面電極と中間電極を使って電力として取り出す。 (Second embodiment)
A multi-junction photoelectric conversion element according to a second embodiment of the present invention will be described below with reference to FIG. This embodiment is an example of the second basic structure. FIG. 8 is a schematic sectional view of a GaAs // Si multi-junction solar cell 40 having an intermediate electrode structure. As the top cell, a GaAs solar cell in which the n-type GaAs layer 41 is formed on the light incident side of the p-type GaAs layer 42 is used. The top cell includes a top electrode 45 on the light incident side. As the bottom cell, an Si solar cell having an n-type Si layer 48 and an intermediate electrode 47 formed on the light incident side of the substrate of the p-type Si layer 49 is used. A p-type back electrode 46 is provided on the back side of the bottom cell. By bonding the top cell and the bottom cell using the bonding layer 44 made of conductive nanoparticles, a three-terminal multi-junction solar cell is formed. Pd nanoparticles are used as the conductive nanoparticles. The conventional solar spectrum, in the GaAs top cell and Si bottom cell, respectively, current of about 30 mA / cm 2 and 10 mA / cm 2 is produced. By using a bottom cell that is larger than the size of the top cell, the size (surface area) of the subcell is adjusted so that the photoelectric flow generated in the top cell and the bottom cell becomes uniform and the current matching condition is satisfied. The excess photocurrent generated in the GaAs top cell due to the spectrum fluctuation of sunlight is taken out as electric power using the intermediate electrode and the top electrode. Excess photocurrent generated in the bottom cell is extracted as power using the back electrode and the intermediate electrode.
（第３の実施形態）
　本発明の第３の実施形態の多接合光電変換素子について、図９を参照して以下説明する。本実施形態は、第１の基本構造の例である。図９は、裏面交互電極構造のＧａＡｓ／ＧａＡｓ／／Ｓｉ多接合太陽電池５０の模式断面図である。トップセルとして、ＧａＡｓサブセル（ｎ型ＧａＡｓ層５１とｐ型ＧａＡｓ層５２で構成される）とトンネル接合層５３とＧａＡｓサブセル（ｎ型ＧａＡｓ層５８とｐ型ＧａＡｓ層５９で構成される）とからなるＧａＡｓ２接合太陽電池を、用いる。ＧａＡｓ層の層厚さを調整することで、通常の太陽光スペクトルにより、ＧａＡｓ１接合太陽電池の約２倍の電圧及び約１／２の電流（約１５ｍＡ／ｃｍ２）が生じるようになる。トップセルは、光入射側にトップ電極５５を備える。ボトムセルとして、ｎ型Ｓｉ層６１の基板の裏面側にｎ型およびｐ型の電極（ｎ型裏面電極５７、ｐ型裏面電極５６）を交互に形成したＳｉ太陽電池を用いる。ｎ型Ｓｉ層６１の基板の裏面側の一部領域に、ｐ型Ｓｉ６２の領域が形成され、該ｐ型Ｓｉ６２に接続するｐ型裏面電極５６が形成されている。 (Third embodiment)
A multi-junction photoelectric conversion element according to a third embodiment of the present invention will be described below with reference to FIG. This embodiment is an example of a first basic structure. FIG. 9 is a schematic cross-sectional view of a GaAs / GaAs // Si multi-junction solar cell 50 having an alternate back electrode structure. As a top cell, a GaAs subcell (consisting of an n-type GaAs layer 51 and a p-type GaAs layer 52), a tunnel junction layer 53, and a GaAs subcell (consisting of an n-type GaAs layer 58 and a p-type GaAs layer 59) are used. Is used. By adjusting the layer thickness of the GaAs layer, a normal solar spectrum can generate about twice the voltage and about half the current (about 15 mA / cm 2 ) of the GaAs1 junction solar cell. The top cell includes a top electrode 55 on the light incident side. As the bottom cell, a Si solar cell in which n-type and p-type electrodes (n-type back electrode 57 and p-type back electrode 56) are alternately formed on the back surface side of the substrate of the n-type Si layer 61 is used. A p-type Si 62 region is formed in a partial region of the n-type Si layer 61 on the back surface side of the substrate, and a p-type back electrode 56 connected to the p-type Si 62 is formed.
　導電性ナノ粒子からなる接合層５４を用いてトップセルとボトムセルを張り合わせることにより、３端子型多接合（３接合）太陽電池を構成する。導電性ナノ粒子はＰｄナノ粒子を用いる。Ｓｉボトムセルにおいては、約１０ｍＡ／ｃｍ２の電流が生成される。トップセルのサイズよりも大きなボトムセルを用いることで、トップセルとボトムセルで生じる光電流量が均等となり電流整合条件が満たされるように、サブセルのサイズ（表面積）を調整する。また、太陽光のスペクトル変動によりボトムセルに生じた余剰の光電流は裏面交互電極から電力として取り出す。 By bonding the top cell and the bottom cell using the bonding layer 54 made of conductive nanoparticles, a three-terminal multi-junction (three-junction) solar cell is formed. Pd nanoparticles are used as the conductive nanoparticles. In the Si bottom cell, a current of about 10 mA / cm 2 is generated. By using a bottom cell that is larger than the size of the top cell, the size (surface area) of the subcell is adjusted so that the photoelectric flow generated in the top cell and the bottom cell becomes uniform and the current matching condition is satisfied. In addition, surplus photocurrent generated in the bottom cell due to the spectrum fluctuation of sunlight is taken out as electric power from the backside alternating electrodes.
　また、高さ１０ナノメートル以上の導電性ナノ粒子を用いた接合界面においては、ＧａＡｓ層／金属ナノ粒子界面へ斜入射した光は、界面で全反射を起こす。スペクトル変動などによりＧａＡｓサブセル間における電流整合条件が崩れた場合にも、暗電流生成により生じる発光をＧａＡｓ層／空気界面およびＧａＡｓ層／金属ナノ粒子界面で反射することで、ＧａＡｓ層内に閉じ込め光吸収させ、ＧａＡｓ層での再光電流生成に利用することにより、ＧａＡｓサブセルとＧａＡｓサブセル間の光電流生成量の調節を行うこともできる。よって、トップセルが同一の材料からなる２つ以上のサブセルから構成される場合は、１０ナノメートル以上の導電性ナノ粒子がより好ましい。 Also, at the junction interface using conductive nanoparticles having a height of 10 nm or more, light obliquely incident on the GaAs layer / metal nanoparticle interface causes total reflection at the interface. Even when the current matching conditions between the GaAs subcells are broken due to spectrum fluctuations or the like, light emitted due to dark current generation is reflected at the GaAs layer / air interface and the GaAs layer / metal nanoparticle interface, so that light confined in the GaAs layer is obtained. By absorbing the light and utilizing it for re-photocurrent generation in the GaAs layer, it is also possible to adjust the amount of photocurrent generated between the GaAs subcells. Therefore, when the top cell is composed of two or more subcells made of the same material, conductive nanoparticles of 10 nm or more are more preferable.
（第４の実施形態）
　本発明の第４の実施形態の多接合光電変換素子について、図１０を参照して以下説明する。本実施形態は、第２の基本構造の例である。図１０は、中間電極構造のＧａＩｎＰ／ＧａＡｓ／／ＧａＩｎＡｓＰ／ＧａＩｎＡｓ多接合太陽電池７０の模式断面図である。 (Fourth embodiment)
A multi-junction photoelectric conversion element according to a fourth embodiment of the present invention will be described below with reference to FIG. This embodiment is an example of the second basic structure. FIG. 10 is a schematic cross-sectional view of a GaInP / GaAs // GaInAsP / GaInAs multi-junction solar cell 70 having an intermediate electrode structure.
　トップセルとして、ＧａＩｎＰサブセル（ｎ型ＧａＩｎＰ層７１とｐ型ＧａＩｎＰ層７２で構成される）とトンネル接合層７３とＧａＡｓサブセル（ｎ型ＧａＡｓ層７８とｐ型ＧａＡｓ層７９で構成される）とからなるＧａＩｎＰ／ＧａＡｓ２接合太陽電池を、用いる。ＧａＩｎＰ層の層厚さを調整することで、通常の太陽光スペクトルにより、約１５ｍＡ／ｃｍ２が生じるようになる。トップセルは、光入射側にトップ電極７５を備える。 As a top cell, a GaInP subcell (consisting of an n-type GaInP layer 71 and a p-type GaInP layer 72), a tunnel junction layer 73 and a GaAs subcell (consisting of an n-type GaAs layer 78 and a p-type GaAs layer 79) are used. GaInP / GaAs2 junction solar cell is used. By adjusting the thickness of the GaInP layer, about 15 mA / cm 2 is generated by a normal sunlight spectrum. The top cell includes a top electrode 75 on the light incident side.
　ボトムセルとして、ＧａＩｎＡｓＰサブセル（ｎ型ＧａＩｎＡｓＰ層８０とｐ型ＧａＩｎＡｓＰ層８１で構成される）とトンネル接合層８２およびＧａＩｎＡｓサブセル（ｎ型ＧａＩｎＡｓ層８３とｐ型ＧａＩｎＡｓ層８４で構成される）とからなるＧａＩｎＡｓＰ／ＧａＩｎＡｓ２接合太陽電池を用いる。ボトムセルは、ｐ型ＧａＩｎＡｓＰ層８１の光入射側に位置するｎ型ＧａＩｎＡｓＰ層８０上の接合面以外の一部に中間電極７７を形成した太陽電池を用いる。ボトムセルの裏面側にｐ型裏面電極７６を備える。 The bottom cell includes a GaInAsP subcell (consisting of an n-type GaInAsP layer 80 and a p-type GaInAsP layer 81), a tunnel junction layer 82, and a GaInAs subcell (consisting of an n-type GaInAs layer 83 and a p-type GaInAs layer 84). A GaInAsP / GaInAs2 junction solar cell is used. For the bottom cell, a solar cell in which an intermediate electrode 77 is formed on a part other than the junction surface on the n-type GaInAsP layer 80 located on the light incident side of the p-type GaInAsP layer 81 is used. A p-type back electrode 76 is provided on the back side of the bottom cell.
　導電性ナノ粒子からなる接合層７４を用いてトップセルとボトムセルを張り合わせることにより、３端子型多接合（４接合）太陽電池を構成する。トップセルのサイズよりも大きなボトムセルを用いることで、トップセルとボトムセルで生じる光電流量が均等となり電流整合条件が満たされるように、サブセルのサイズ（表面積）を調整する。また、太陽光のスペクトル変動によりＧａＩｎＰ／ＧａＡｓトップセルにおいて余剰に生じた光電流は、中間電極とトップ電極を使って電力としてとりだす。ＧａＩｎＡｓＰ／ＧａＩｎＡｓボトムセルに生じた余剰の光電流は、裏面電極と中間電極を使って電力として取り出す。 ト ッ プ A three-terminal multi-junction (four-junction) solar cell is formed by bonding the top cell and the bottom cell using the bonding layer 74 made of conductive nanoparticles. By using a bottom cell that is larger than the size of the top cell, the size (surface area) of the subcell is adjusted so that the photoelectric flow generated in the top cell and the bottom cell becomes uniform and the current matching condition is satisfied. In addition, an excess photocurrent generated in the GaInP / GaAs top cell due to the fluctuation of the spectrum of sunlight is taken out as power using the intermediate electrode and the top electrode. Excess photocurrent generated in the GaInAsP / GaInAs bottom cell is extracted as power using the back electrode and the intermediate electrode.
　以上、上記実施形態では、本発明の多接合光電変換素子について、複数種類の太陽電池の例で示した。本発明で用いる光電変換素子のセルは、例示したものに制限されない。 In the above embodiments, the multi-junction photoelectric conversion element of the present invention has been described by using examples of a plurality of types of solar cells. The cells of the photoelectric conversion element used in the present invention are not limited to those illustrated.
　上記実施形態等で示した例は、発明を理解しやすくするために記載したものであり、この形態に限定されるものではない。 例 The examples shown in the above embodiments and the like are described for easy understanding of the present invention, and the present invention is not limited to these embodiments.
　本発明の光電変換素子又は太陽電池は、太陽光等の光エネルギーの利用効率が向上すると共に、太陽光のスペクトル変動に堅牢なデバイスであるので、産業上有用である。 The photoelectric conversion element or solar cell of the present invention is industrially useful because it is a device that improves the use efficiency of light energy such as sunlight and is robust against fluctuations in the spectrum of sunlight.
　２、１２、２２　　トップセル
　３、１３、２３　　ボトムセル
　５、１５、２５、３５、４５、５５、７５　　トップ電極
　６　　裏面電極
　６ａ、６ｂ　　交互電極
　７、７ａ、７ｂ、２７、４７、７７　　中間電極
　８ａ、８ｂ　　透明電極層
　９　　絶縁接着層
　１０　　第１の基本構造
　１４、２４、３４、４４、５４、７４　　導電性ナノ粒子からなる接合層
　１６、１７　　（第２の電極と第３の電極の）交互電極
　２０　　第２の基本構造
　２６　　第２の電極
　３０　　裏面交互電極構造のＧａＡｓ／／Ｓｉ多接合太陽電池
　３１、４１、５１、５８、７８　　ｎ型ＧａＡｓ層
　３２、４２、５２、５９、７９　　ｐ型ＧａＡｓ層
　３３、４８、６１　　ｎ型Ｓｉ層
　３６、４６、５６、７６　　ｐ型裏面電極
　３７、５７　　ｎ型裏面電極
　３８、６２　　ｐ型Ｓｉ
　４０　　中間電極型ＧａＡｓ／／Ｓｉ多接合太陽電池
　４９　　ｐ型Ｓｉ層
　５０　　裏面交互電極構造のＧａＡｓ／ＧａＡｓ／／Ｓｉ多接合太陽電池
　５３、７３、８２　　トンネル接合層
　７０　　中間電極構造のＧａＩｎＰ／ＧａＡｓ／／ＧａＩｎＡｓＰ／ＧａＩｎＡｓ多接合太陽電池
　７１　　ｎ型ＧａＩｎＰ層
　７２　　ｐ型ＧａＩｎＰ層
　８０　　ｎ型ＧａＩｎＡｓＰ層
　８１　　ｐ型ＧａＩｎＡｓＰ層
　８３　　ｎ型ＧａＩｎＡｓ層
　８４　　ｐ型ＧａＩｎＡｓ層 2, 12, 22 Top cell 3, 13, 23 Bottom cell 5, 15, 25, 35, 45, 55, 75 Top electrode 6 Backside electrode 6a, 6b Alternate electrode 7, 7a, 7b, 27, 47, 77 Intermediate electrode 8a , 8b Transparent electrode layer 9 Insulating adhesive layer 10 First basic structure 14, 24, 34, 44, 54, 74 Alternating layers 16, 17 (of second and third electrodes) composed of conductive nanoparticles Electrode 20 Second basic structure 26 Second electrode 30 GaAs // Si multi-junction solar cell with alternate back electrode structure 31, 41, 51, 58, 78 n- type GaAs layer 32, 42, 52, 59, 79 p-type GaAs layers 33, 48, 61 n-type Si layers 36, 46, 56, 76 p-type back electrode 37, 57 n-type back electrode 38, 62 p-type Si
Reference Signs List 40 Intermediate electrode type GaAs // Si multi-junction solar cell 49 p-type Si layer 50 GaAs / GaAs // Si multi-junction solar cell 53 with alternating backside electrode structure 53, 73, 82 Tunnel junction layer 70 GaInP / GaAs / intermediate electrode structure / GaInAsP / GaInAs multi-junction solar cell 71 n-type GaInP layer 72 p-type GaInP layer 80 n-type GaInAsP layer 81 p-type GaInAsP layer 83 n-type GaInAs layer 84 p-type GaInAs layer

Claims (8)

  1. 　多接合光電変換素子であって、
    　光入射側に位置する光電変換素子の第１のセルと、
    　光入射側の反対側に位置する光電変換素子の第２のセルと、
    　前記第１のセルと前記第２のセルを接合する、導電性ナノ粒子からなる接合層と、
    　前記第１のセルの、光入射側の面に位置する第１の電極と、
    　前記第２のセルの、光入射側の反対面に位置する第２の電極と、
    　前記第２のセルに設けた第３の電極であって、光入射側の反対面に位置する電極、または、第１のセル側の面に位置する中間電極である前記第３の電極と、
    を備えることを特徴とする多接合光電変換素子。     A multi-junction photoelectric conversion element,
    A first cell of the photoelectric conversion element located on the light incident side;
    A second cell of the photoelectric conversion element located on the side opposite to the light incident side;
    A bonding layer made of conductive nanoparticles for bonding the first cell and the second cell,
    A first electrode located on a light incident side surface of the first cell;
    A second electrode located on a surface of the second cell opposite to the light incident side;
    A third electrode provided on the second cell, wherein the third electrode is an electrode located on a surface opposite to the light incident side, or an intermediate electrode located on a surface on the first cell side;
    A multi-junction photoelectric conversion element comprising:
  2. 　前記第３の電極を利用して、前記第１のセル又は前記第２のセルに生じた余剰の光電流を電力として取り出すことを特徴とする請求項１記載の多接合光電変換素子。 4. The multi-junction photoelectric conversion element according to claim 1, wherein an excess photocurrent generated in the first cell or the second cell is taken out as electric power using the third electrode.
  3. 　前記第２のセルの表面積は、前記第１のセルの表面積より大であることを特徴とする請求項１又は２記載の多接合光電変換素子。 (3) The multi-junction photoelectric conversion element according to (1) or (2), wherein the surface area of the second cell is larger than the surface area of the first cell.
  4. 　前記導電性ナノ粒子の表面は有機分子で覆われていないことを特徴とする請求項１乃至３のいずれか１項に記載の多接合光電変換素子。 4. The multi-junction photoelectric conversion device according to claim 1, wherein a surface of the conductive nanoparticle is not covered with an organic molecule. 5.
  5. 　前記接合層は、前記導電性ナノ粒子からなる接合層の厚みが、５ナノメートル以上５０ナノメートル以下であることを特徴とする請求項１乃至４のいずれか１項に記載の多接合光電変換素子。 5. The multi-junction photoelectric conversion device according to claim 1, wherein a thickness of the bonding layer made of the conductive nanoparticles is 5 nm or more and 50 nm or less. 6. element.
  6. 　前記多接合光電変換素子の前記セルが、結晶Ｓｉ系、アモルファスＳｉ系、微結晶Ｓｉ系、有機系、もしくは、カルコパイライト系材料を用いた単接合太陽電池、またはＧａＡｓ、ＩｎＰ、ＧａＳｂ、もしくは、Ｇｅ基板上等に積層された２接合以上からなる太陽電池であることを特徴とする請求項１乃至５のいずれか１項に記載の多接合光電変換素子。 The cell of the multi-junction photoelectric conversion element is a single-junction solar cell using crystalline Si-based, amorphous Si-based, microcrystalline Si-based, organic, or chalcopyrite-based material, or GaAs, InP, GaSb, or The multi-junction photoelectric conversion element according to any one of claims 1 to 5, wherein the multi-junction photoelectric conversion element is a solar cell including two or more junctions stacked on a Ge substrate or the like.
  7. 　請求項１乃至６のいずれか１項に記載の多接合光電変換素子を備える多接合型太陽電池。 A multi-junction solar cell comprising the multi-junction photoelectric conversion element according to any one of claims 1 to 6.
  8. 　光入射側に位置する光電変換素子の第１のセルと、光入射側の反対側に位置する光電変換素子の第２のセルと、を備える多接合光電変換素子の製造方法であって、
    　前記第２のセルに、光入射側の反対面に位置する第２の電極を形成すると共に、光入射側の反対面に位置する第３の電極、または、第１のセル側の面に位置する中間電極となる第３の電極を設ける工程と、
    　前記第１のセルを前記第２のセルに、有機分子で覆われていない導電性ナノ粒子により接合する接合工程と、
    　前記第１のセルの、光入射側の面に第１の電極を形成する工程と、
    を備えることを特徴とする多接合光電変換素子の製造方法。     A method for manufacturing a multi-junction photoelectric conversion element, comprising: a first cell of a photoelectric conversion element located on a light incident side; and a second cell of a photoelectric conversion element located on a side opposite to the light incident side,
    Forming a second electrode on the second cell opposite to the light incident side and forming a third electrode on the opposite side to the light incident side or a first electrode on the first cell side; Providing a third electrode to be an intermediate electrode to be formed;
    A bonding step of bonding the first cell to the second cell with conductive nanoparticles that are not covered with organic molecules;
    Forming a first electrode on the light incident side surface of the first cell;
    A method for manufacturing a multi-junction photoelectric conversion element, comprising:
PCT/JP2019/025409 2018-06-29 2019-06-26 Multijunction photoelectric conversion element and multijunction solar battery WO2020004475A1 (en)

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