WO2010100947A1 - Solar cell and method for manufacturing solar cell - Google Patents

Solar cell and method for manufacturing solar cell Download PDF

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Publication number
WO2010100947A1
WO2010100947A1 PCT/JP2010/001562 JP2010001562W WO2010100947A1 WO 2010100947 A1 WO2010100947 A1 WO 2010100947A1 JP 2010001562 W JP2010001562 W JP 2010001562W WO 2010100947 A1 WO2010100947 A1 WO 2010100947A1
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power generation
cell
substrate
generation layer
solar cell
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PCT/JP2010/001562
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French (fr)
Japanese (ja)
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渡井美和
斎藤一也
砂賀芳雄
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株式会社アルバック
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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
    • H01L31/075—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 PIN type
    • H01L31/076—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
    • H01L31/0248—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies
    • H01L31/0256—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by the material
    • H01L31/0264—Inorganic materials
    • H01L31/028—Inorganic materials including, apart from doping material or other impurities, only elements of Group IV of the Periodic System
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/0248—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies
    • H01L31/036—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by their crystalline structure or particular orientation of the crystalline planes
    • H01L31/0368—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by their crystalline structure or particular orientation of the crystalline planes including polycrystalline semiconductors
    • H01L31/03682—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by their crystalline structure or particular orientation of the crystalline planes including polycrystalline semiconductors including only elements of Group IV of the Periodic System
    • H01L31/03685—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by their crystalline structure or particular orientation of the crystalline planes including polycrystalline semiconductors including only elements of Group IV of the Periodic System including microcrystalline silicon, uc-Si
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/0248—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies
    • H01L31/036—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by their crystalline structure or particular orientation of the crystalline planes
    • H01L31/0376—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by their crystalline structure or particular orientation of the crystalline planes including amorphous semiconductors
    • H01L31/03762—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by their crystalline structure or particular orientation of the crystalline planes including amorphous semiconductors including only elements of Group IV of the Periodic System
    • 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
    • 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
    • Y02E10/548—Amorphous silicon PV cells

Definitions

  • the present invention relates to a solar cell in which a plurality of cells are stacked and stacked, and a method for manufacturing the solar cell.
  • a silicon-based solar cell As this solar cell, a silicon-based solar cell is known, and specifically, a silicon solar cell using single crystal silicon, a polysilicon solar cell using a polysilicon layer, and amorphous silicon were used. Amorphous silicon solar cells and the like are known.
  • a silicon-based solar cell includes a light-receiving surface electrode that functions as a transparent electrode made of TCO or the like on a glass substrate, a power generation layer that is formed on the light-receiving surface electrode and is made of silicon, and an Ag thin film that functions as a back electrode. Includes stacked cells.
  • the power generation layer has a layer structure called a pin junction. In this layer structure, a silicon film (i-type) that generates electrons and holes when receiving light is sandwiched between p-type and n-type silicon films.
  • tandem solar cell in which a plurality of power generation layers having different wavelength bands in which sunlight is absorbed is laminated on a substrate has been promoted.
  • this tandem solar cell light in a short wavelength region is absorbed in one power generation layer (for example, amorphous silicon), and light in a long wavelength region is absorbed in the other power generation layer (for example, crystalline silicon).
  • the energy of sunlight is used without waste, and the power generation efficiency is improved.
  • Patent Document 1 and Patent Document 2 a structure in which a plurality of power generation layers having different band gaps are stacked and integrated is known. .
  • an insulating layer that partially insulates between the first light absorption layer of the first power generation layer and the second light absorption layer of the second power generation layer is provided.
  • a connection electrode that is provided and connects between a first power generation layer and a second power generation layer is provided.
  • the energy output from each of the power generation layers may be lower than the energy at the time of maximum output in the single power generation layer.
  • the conventional solar cell is adjusted so that the maximum output of each power generation layer can be obtained when sunlight is incident on the incident surface on average.
  • the light intensity or spectrum of sunlight changes, there is a problem that a desired output cannot be obtained from each of the power generation layers, and the photoelectric conversion efficiency obtained in the plurality of power generation layers as a whole decreases.
  • a tandem solar cell for example, after forming a power generation layer made of amorphous silicon on the substrate as a first power generation layer, the wavelength of light longer than the wavelength of light absorbed by amorphous silicon is formed.
  • a power generation layer that absorbs light is formed sequentially.
  • a material for the power generation layer that absorbs light having a long wavelength for example, microcrystalline silicon is known.
  • the optimum film formation conditions differ according to the physical properties of the constituent materials, and in particular, the temperature conditions in the film formation process differ. Therefore, when a plurality of power generation layers are sequentially stacked, there is a problem in that the performance of the power generation layer formed earlier is deteriorated due to the film formation conditions of the power generation layer formed later.
  • the present invention has been made in view of the above circumstances, and an object of the present invention is to provide a solar cell that can improve power generation efficiency and manufacturing efficiency, and a method for manufacturing the solar cell.
  • the performance of the power generation layer formed earlier is deteriorated due to the film formation conditions of the power generation layer formed later.
  • intensive study was conducted.
  • a tandem type in which an amorphous silicon pin layer is formed as the power generation layer closest to the light receiving surface, and a pin power generation layer made of microcrystalline silicon is laminated on the amorphous silicon structure.
  • the maximum temperature is about 200 ° C. (180 to 230 ° C.).
  • the maximum temperature (substrate temperature) is about 300 ° C. (250 to 350 ° C.). Therefore, in the manufacturing process of the tandem solar cell as described above, the amorphous silicon is exposed to a high temperature atmosphere of about 300 ° C. (250 to 350 ° C.) which is the maximum temperature in the microcrystalline silicon film forming process. As a result of the exposure of the amorphous silicon to a high temperature atmosphere, the present inventors have released a hydrogen atom present in the amorphous silicon and the dangling bond in which the hydrogen atom is terminated is in the power generation layer of the amorphous silicon. Found to increase.
  • the present inventors have found a problem that the battery characteristics including the conversion efficiency of the power generation layer and the like are lowered, and the production efficiency is lowered.
  • the present inventors have found that the above-described phenomenon occurs when the maximum temperature (substrate temperature) during the film forming process is about 200 ° C. (180 to 230 ° C.) instead of the amorphous silicon pin layer. It has been found that this also occurs when a pin layer made of some amorphous silicon germanium is produced.
  • the present inventors have found that the above phenomenon is caused by a power generation layer formed in a high-temperature process (250 ° C. or higher), for example, CdS, Cu, instead of the pin layer made of microcrystalline silicon.
  • a solar cell includes a substrate having light permeability, a first power generation cell disposed near the substrate and including a first power generation layer, and the substrate.
  • a second power generation cell including a second power generation layer disposed at a position away from the first power generation layer and having a band gap smaller than a band gap of the first power generation layer, and between the first power generation cell and the second power generation cell And an arranged insulating portion.
  • the solar cell of the first aspect of the present invention has a structure in which a plurality of cells in which a light-receiving surface electrode, a power generation layer, and a back electrode are sequentially stacked are stacked on a light-transmitting substrate.
  • the band gap of the power generation layer constituting the cell disposed on the light incident side is larger than the band gap of the power generation layer disposed at a position away from the substrate.
  • An insulating part is disposed between the plurality of cells. Further, in this configuration, the distance between the second power generation cell (second power generation layer) and the substrate is larger than the distance between the first power generation cell (first power generation layer) and the substrate.
  • the first power generation cell and the second power generation cell are stacked.
  • Each of the cells functions as an independent power generation cell in the electrical connection structure. For this reason, the electric current which flows into each of the 1st power generation cell and the 2nd power generation cell can be set up independently. Thereby, the energy output when the current flowing through each power generation layer of the first power generation cell and the second power generation cell is maximum can be extracted regardless of the light intensity or spectrum of sunlight. Therefore, the maximum output in each of the first power generation cell and the second power generation cell can be taken out.
  • the power generation amount in one power generation layer and the power generation in the other power generation layer When the amount is different, the electric resistance of the power generation layer having a small power generation amount is larger than the electric resistance of the power generation layer having a large power generation amount. Therefore, the amount of current in the series circuit is determined by the electric resistance of the power generation layer with a small amount of power generation. For this reason, there is a problem that a loss occurs in the current output from the power generation layer with a large power generation amount.
  • the solar cell of the present invention since a parallel circuit structure in which a plurality of power generation layers are independent from each other is adopted, the amount of current in each power generation layer is not limited, and each of the plurality of power generation layers is The power can be generated while obtaining the maximum current. Therefore, a solar cell with a low voltage and a large current can be realized, and a solar cell with high power generation efficiency can be provided.
  • the solar cell has a plurality of power generation cells including the first power generation cell and the second power generation cell, and the position farthest from the substrate among the plurality of power generation cells It is preferable that the second power generation cell is disposed in a band gap, and the band gap of the second power generation layer is 1.3 eV or less.
  • the “plurality of power generation cells” means two or more power generation cells, and includes three power generation cells or four power generation cells. Further, in this configuration, among the plurality of power generation cells including the first power generation cell and the second power generation cell, the distance between the second power generation cell (second power generation layer) and the substrate is different from the other power generation cells and the substrate. Greater than the distance.
  • the band gap of the power generation layer (second power generation layer) of the power generation cell (second power generation cell) arranged at the position farthest from the substrate is 1.3 eV or less, the position is close to the substrate.
  • Power generation can be performed using light in a long wavelength region that cannot be extracted in the power generation layer arranged on the (incident side). That is, among the plurality of power generation cells stacked in the sunlight incident direction (substrate thickness direction), the first power generation layer of the first power generation cell arranged at a position close to the substrate emits light in a short wavelength region.
  • the second power generation layer disposed at the position farthest from the substrate generates power using light in a long wavelength region.
  • the intermediate power generation layer of the intermediate power generation cell When the intermediate power generation cell is disposed between the first power generation cell and the second power generation cell, the intermediate power generation layer of the intermediate power generation cell emits light in the intermediate wavelength range between the short wavelength range and the long wavelength range. Use it to generate electricity.
  • a plurality of intermediate power generation cells may be provided between the first power generation cell and the second power generation cell.
  • the solar cell of the present invention can use the energy of sunlight without waste and can improve the power generation efficiency.
  • the first power generation cell and the second power generation cell are electrically connected in parallel. According to this configuration, since the first power generation cell and the second power generation cell are electrically connected in parallel, it is not necessary to match the current flowing through the first power generation layer with the current flowing through the second power generation layer. For this reason, the amount of current in the first power generation layer and the second power generation layer is not limited, and power can be generated while obtaining the maximum current in each of the plurality of power generation layers.
  • by connecting the first power generation cell and the second power generation cell in parallel for example, even when a problem occurs in only one power generation cell among a plurality of power generation cells and no current flows, A current flows normally through the power generation cell. That is, since a malfunction in one power generation cell does not affect the operating state of the entire power generation cell, the power generation efficiency of the solar cell can be maintained.
  • each of the said 1st power generation cell and the said 2nd power generation cell is provided with the protection circuit.
  • an individual protection circuit is connected to each of the first power generation cell and the second power generation cell, an overvoltage is applied to either the first power generation cell or the second power generation cell.
  • the current that flows only to the power generation cell to which the overvoltage is applied is passed through the protection circuit. Thereby, failure of the power generation cell can be prevented. That is, since a malfunction in one power generation cell does not affect the operating state of the entire power generation cell, the power generation efficiency of the solar cell can be maintained.
  • a method for manufacturing a solar cell provides a substrate having light permeability, forms a first power generation cell including a first power generation layer, and performs the first power generation.
  • the second power generation cell is overlapped with the first power generation cell so that the first power generation cell is disposed at a position and the second power generation cell is disposed at a position away from the substrate.
  • the first power generation cell and the second power generation cell are individually manufactured, the first power generation cell and the second power generation cell are arranged so that an insulating portion is disposed between the first power generation cell and the second power generation cell. Overlapping. Therefore, before the second power generation cell is overlaid on the first power generation cell, the layers (for example, the power generation layer) constituting each of the first power generation cell and the second power generation cell can be formed under optimum film formation conditions. it can. In the conventional method of sequentially laminating a plurality of power generation layers, in order to maintain the film quality of the power generation layer located in the already formed lower layer, the film formation conditions of the power generation layer located in the upper layer are limited. .
  • each of the first power generation cell and the second power generation cell can be formed without limiting the film forming conditions of the power generation layer formed in the upper layer.
  • a power generation layer having a good film quality can be formed. Therefore, according to the production method of the present invention, the film quality of the power generation layer is improved, the power generation efficiency of the solar cell is increased, and the production efficiency is improved.
  • the maximum temperature in the film formation process for forming the first power generation cell is different from the maximum temperature in the film formation process for forming the second power generation cell.
  • the highest temperature condition range is 250 in the film formation process for forming the first power generation cell and the film formation process for forming the second power generation cell. It is preferable that the range of the lowest temperature condition is 180 to 230 ° C. According to this method, the first power generation cell and the second power generation cell are manufactured even when the maximum temperature in the film formation process of the first power generation cell is different from the maximum temperature in the film formation process of the second power generation cell.
  • the first power generation cell and the second power generation cell can be overlapped regardless of the order in which they are performed. That is, in the process of manufacturing each of the first power generation cell stack and the second power generation cell stack, the order of manufacturing the cells is not limited due to the difference in temperature conditions in the film formation process, A power generation layer having an appropriate film quality can be formed. In addition, the first power generation cell and the second power generation cell including the power generation layer having good film quality can be overlapped. For example, a case where amorphous silicon having a maximum temperature during the film forming process of 180 to 230 ° C. and microcrystalline silicon having a maximum temperature during the film forming process of 250 to 400 ° C. will be described.
  • the deposition temperature of microcrystalline silicon is higher than the deposition temperature of amorphous silicon. Desorption occurs due to an increase in process temperature during film formation. In this case, the conversion efficiency in amorphous silicon may be reduced.
  • the manufacturing method of the present invention since the first power generation cell and the second power generation cell are manufactured separately, the order of manufacturing the cells is not limited, and the formation of the microcrystalline silicon cell is not limited. The maximum temperature in the film process does not adversely affect the performance of the amorphous silicon cell.
  • the first power generation cell and the second power generation cell functions as an independent power generation cell in the electrical connection structure.
  • the electric current which flows into each of the 1st power generation cell and the 2nd power generation cell can be set up independently.
  • the energy output when the current flowing through each power generation layer of the first power generation cell and the second power generation cell is maximum can be extracted regardless of the light intensity or spectrum of sunlight. Therefore, the maximum output in each of the first power generation cell and the second power generation cell can be taken out.
  • the amount of current in the tandem structure is determined by the electric resistance of the power generation layer with a small amount of power generation, and the current output from the power generation layer with a large amount of power generation is lost. There is a problem that occurs.
  • the amount of current output from each of the plurality of power generation layers is not limited, and power can be generated while obtaining the maximum current in each of the plurality of power generation layers. Therefore, a solar cell with a low voltage and a large current can be realized, and a solar cell with high power generation efficiency can be provided.
  • the first power generation cell and the second power generation cell are separately manufactured, and then the insulating portion is disposed between the first power generation cell and the second power generation cell.
  • the 1 power generation cell and the second power generation cell are overlapped. Therefore, before the second power generation cell is overlaid on the first power generation cell, the layers (for example, the power generation layer) constituting each of the first power generation cell and the second power generation cell can be formed under optimum film formation conditions. it can. That is, the layers (for example, the first power generation layer and the second power generation layer) constituting each of the first power generation cell and the second power generation cell can be formed under optimum film formation conditions.
  • the 1st electric power generation layer and the 2nd electric power generation layer which have favorable film quality can be formed. Therefore, according to the manufacturing method of the present invention, the film quality of the power generation layer is improved, the conversion efficiency of the solar cell is increased, and the manufacturing efficiency is improved.
  • FIG. 1 is a cross-sectional view showing a solar cell in the first embodiment of the present invention.
  • the solar cell 100 includes two cells 12 and 22 formed on a substrate 11.
  • the substrate 11 is formed of an insulating material having excellent sunlight permeability and durability such as glass or transparent resin.
  • solar cell 100 of the first embodiment sunlight is incident on one surface of substrate 11, that is, surface 11 a (hereinafter referred to as surface 11 a) in which cells 12 and 22 are not formed on substrate 11. That is, the surface 11 a is a light receiving surface of the solar cell 100.
  • the cell 12 corresponds to the first power generation cell of the present invention.
  • a light receiving surface electrode 13 a power generation layer (first power generation layer) 14, and a back electrode 15 are sequentially stacked on the substrate 11.
  • the light-receiving surface electrode 13 has a texture structure and is formed on the other surface (hereinafter referred to as the back surface 11b) of the substrate 11.
  • the light-receiving surface electrode 13 is made of a light-transmitting metal oxide, for example, a so-called TCO (transparent conductive oxide) such as GZO or ITO (Indium Tin Oxide).
  • TCO transparent conductive oxide
  • ITO Indium Tin Oxide
  • a power generation layer 14 having a pin junction structure is formed on the light receiving surface electrode 13.
  • this pin junction structure for example, an i-type amorphous silicon film (not shown) is sandwiched between a p-type amorphous silicon ( ⁇ -Si) film (not shown) and an n-type amorphous silicon film (not shown). Yes.
  • a p-type amorphous silicon film, an i-type amorphous silicon film, and an n-type amorphous silicon film are sequentially stacked on the light-receiving surface electrode 13.
  • the band gap (optical band gap) of the power generation layer 14 is, for example, about 1.7 eV.
  • an amorphous silicon germanium ( ⁇ -SiGe) film or the like can be used in addition to the amorphous silicon film.
  • the back electrode 15 is laminated on a surface opposite to the surface of the power generation layer 14 on which the light receiving surface electrode 13 is formed.
  • the back electrode 15 is made of TCO as with the light receiving surface electrode 13 described above. In other words, in the first cell 12, the power generation layer 14 is sandwiched between the light-receiving surface electrode 13 and the back surface electrode 15 having optical transparency.
  • the cell 22 corresponds to the second power generation cell of the present invention.
  • the cell 22 (hereinafter referred to as the second cell 22) includes a silicon substrate (second power generation layer) 23, a diffusion layer 24, an antireflection film 25, a BSF (Back Surface Field) layer 26, a first back electrode 27, a second A back electrode 28 and a grid electrode 29 are provided.
  • the silicon substrate 23 p-type single crystal silicon in which p-type dopants such as boron (B), gallium (Ga), aluminum (Al), and indium (In) are diffused in single crystal silicon or polycrystalline silicon.
  • a substrate can be used.
  • an n-type single crystal silicon or polycrystalline silicon substrate in which an n-type dopant such as phosphorus (P), arsenic (As), or antimony (Sb) is diffused in single crystal silicon or polycrystalline silicon is used. It can.
  • the silicon substrate in which such a dopant is diffused is appropriately selected and used depending on the application.
  • a texture structure (not shown) having a minute uneven shape formed by etching (texture etching) is formed.
  • a substrate on which a texture is previously formed may be used.
  • a substrate on which no texture is formed may be prepared, and the texture may be formed on the substrate by dry etching.
  • the band gap (optical band gap) of the silicon substrate 23 is smaller than the band gap of the power generation layer 14 and is, for example, about 1.1 eV. That is, the band gap of the power generation layer 14 constituting the cell 12 is larger than the band gap of the silicon substrate 23 constituting the cell 22. That is, among the plurality of power generation layers stacked in the thickness direction of the substrate 11, a power generation layer (for example, the first cell 12) (for example, the first cell 12) disposed at a position close to the substrate 11 on which sunlight is incident. The band gap of the power generation layer 14) is larger than the band gap of the power generation layer (for example, the silicon substrate 23) constituting the cell (for example, the second cell 22) disposed at a position far from the substrate 11.
  • the power generation layer for example, the silicon substrate 23
  • the band gap of the constituent material is preferably 1.3 eV or less, for example.
  • n-type dopants such as phosphorus (P), arsenic (As), and antimony (Sb) are diffused near the surface of the silicon substrate 23. It is a thin layer. Further, when the silicon substrate 23 is an n-type silicon substrate, the diffusion layer 24 has a p-type dopant such as boron (B), gallium (Ga), aluminum (Al), indium (In), etc. 23 is a thin layer diffused in the vicinity of the surface 23.
  • the antireflection film 25 As the structure of the antireflection film 25, a multilayer structure composed of a multilayer in which a high refractive index film and a low refractive index film are laminated, or a single layer structure is adopted.
  • the material of the film constituting the multilayer structure include silicon nitride (SiNx), titanium oxide (TiO 2 ), and niobium oxide having a refractive index of 1.0 to 4.0. (Nb 2 O 5 ), magnesium fluoride (MgF 2 ), magnesium oxide (MgO), silicon oxide (SiO 2 ) and the like are preferably used.
  • the antireflection film 25 has a single layer structure
  • a film made of a transparent material such as silicon nitride (SiNx) formed on the diffusion layer 24 by a CVD method is used.
  • n-type dopants such as phosphorus (P), arsenic (As), and antimony (Sb) are used to form the antireflection film 25 that forms a single layer structure. Contained in the membrane.
  • p-type dopants such as boron (B), gallium (Ga), and aluminum (Al) are used to form the antireflection film 25 that forms a single layer structure. Contained in the membrane.
  • silicon nitride (SiNx) and titanium oxide (TiO 2 ) are preferably used.
  • the diffusion layer 24 is obtained by diffusing the dopant contained in the antireflection film 25 on the surface of the silicon substrate 23 by heat-treating the antireflection film 25.
  • the dopant concentration of the diffusion layer 24 is determined so that a pn junction necessary for the solar cell 100 is generated. For example, since the dopant concentration of the diffusion layer 24 is determined by the amount of diffusion from the antireflection film 25, the dopant concentration of the diffusion layer 24 is often lower than the dopant concentration of the antireflection film 25 after diffusion.
  • the dopant concentration of the antireflection film 25 to be formed is set higher than the dopant concentration required for the diffusion layer 24.
  • the method for setting the dopant concentration is not limited to the above method.
  • the dopant concentration of the antireflection film 25 is higher than the dopant concentration of the diffusion layer 24 before the diffusion step, the reflection is not caused after the diffusion step.
  • the dopant concentration of the prevention film 25 is lower than the dopant concentration of the diffusion layer 24.
  • the BSF layer 26 is a thin layer formed by diffusing constituent materials such as the first back electrode 27 and the second back electrode 28 into the silicon substrate 23 by heat treatment.
  • the first back electrode 27 and the second back electrode 28 containing aluminum are formed on the back surface of the p-type silicon substrate 23, and then the BSF layer 26 is formed by diffusing aluminum into the silicon substrate 23 by heat treatment.
  • the 1st back electrode 27, the 2nd back electrode 28, and the grid electrode 29 are metal electrodes obtained by baking the paste containing electroconductive metals, such as silver and aluminum.
  • the second back electrode 28 is provided so as to cross the central portion of the back surface of the silicon substrate 23 and is formed in a strip shape.
  • the first back electrode 27 is provided on both sides of the second back electrode 28 so as to sandwich the second back electrode 28, and is formed in a rectangular shape.
  • the grid electrode 29 is formed on the antireflection film 25 along a direction parallel to the surface of the silicon substrate 23.
  • the grid electrode 29 is connected to the silicon substrate 23 using a so-called fire-through process. Specifically, in the method of forming the grid electrode 29, first, a silver paste having a predetermined pattern is applied on the antireflection film 25. Next, the silver paste is fired. Thereafter, the silver electrode formed by baking penetrates the antireflection film 25, contacts the diffusion layer 24, and is connected to the silicon substrate 23.
  • the sunlight that has entered the surface 11 a of the substrate 11 and has passed through the first cell 12 enters the silicon substrate 23 through a gap (opening) between the grid electrodes 29.
  • a metal oxide having optical transparency such as TCO may be adopted as a constituent material of the grid electrode 29.
  • the heat treatment for forming the diffusion layer 24, the heat treatment for forming the BSF layer 26, and the heat treatment for forming the grid electrode 29 (fire-through process) can be performed individually. If two steps or all steps are performed simultaneously, the number of steps and the processing time can be reduced, and the number of processing apparatuses can be reduced.
  • An insulating part 30 is formed between the back electrode 15 of the first cell 12 and the grid electrode 29 of the second cell 22.
  • the insulating unit 30 electrically insulates between the first cell 12 and the second cell 22.
  • the insulating part 30 is provided on the entire surface between the back electrode 15 and the grid electrode 29, and is formed so as to fill the gap (opening) between the grid electrodes 29 with the constituent material of the insulating part.
  • the constituent material of the insulating part 30 is a material having insulating properties and transparency. As such a material, for example, a paste material such as SiO 2 or a UV curable resin, an adhesive sheet having an insulating property, or the like is preferably used.
  • the insulating unit 30 is sandwiched between the first cell 12 and the second cell 22, and the first cell 12 is electrically connected to the second cell 22.
  • the first cell 12 and the second cell 22 are stacked so as to be insulated.
  • the cells 12 and 22 are mutually electrically connected in parallel in each edge part of the cells 12 and 22.
  • FIG. The solar cell 100 of the first embodiment has a plurality of partition elements that are electrically partitioned and have a predetermined size.
  • the cells 12 and 22 are formed in each of a plurality of partition elements.
  • the partition elements adjacent to each other are electrically connected in series (so-called integrated structure).
  • Each of the cells 12 and 22 is provided with a separate protection circuit (not shown). When an overvoltage is applied to each of the cells 12 and 22, the overcurrent does not flow to each of the cells 12 and 22, but flows to the protection circuit. Thereby, failure of each electric circuit of cells 12 and 22 can be prevented.
  • a texture structure (not shown) in which minute irregularities are formed on the front and back surfaces of each of the plurality of layers described above is provided.
  • the prism effect that extends the optical path of sunlight incident on each layer and the effect of confining light can be achieved, the conversion efficiency of light energy in the solar cell 100 can be improved.
  • the surface 11a (incident surface) of the substrate 11 is irradiated with sunlight, the sunlight is transmitted through the substrate 11, and the sunlight is incident on the first cells 12 and 22. Then, light in a short wavelength region (for example, light having a wavelength of less than 730 nm) included in sunlight incident on the first cell 12 is absorbed in the power generation layer 14 of the first cell 12.
  • a short wavelength region for example, light having a wavelength of less than 730 nm
  • electrons and holes are generated due to the photovoltaic effect. Electrons move toward the n-type amorphous silicon film, and holes move toward the p-type amorphous silicon film. Electrons and holes are extracted by the light-receiving surface electrode 13 and the back surface electrode 15, and light energy can be converted into electrical energy (photoelectric conversion).
  • the energy extracted in each of the cells 12 and 22 is extracted via an electric circuit (not shown).
  • the band gap of the constituent material of the power generation layer for example, the silicon substrate 23
  • the band gap of the constituent material of the power generation layer for example, the silicon substrate 23
  • the power generation layer for example, the power generation layer 14 disposed near the substrate 11 (incident side) generates power using light in a short wavelength region.
  • the power generation layer for example, the silicon substrate 23 disposed at a position away from the substrate 11 generates power using light in a long wavelength region.
  • a configuration in which the insulating unit 30 is sandwiched between the first cell 12 and the second cell 22 is employed.
  • the cells 12 and 22 are stacked with the insulating portion 30 interposed therebetween, and each of the cells 12 and 22 functions as an independent cell. For this reason, the amount of current flowing through each of the cells 12 and 22 can be set independently.
  • energy output when the current flowing through the power generation layer 14 of the cell 12 and the silicon substrate 23 of the cell 22 is maximum can be extracted regardless of the light intensity or spectrum of sunlight. Therefore, the maximum output in each of the cells 12 and 22 can be obtained.
  • the amount of current in the tandem structure is determined by the electrical resistance of the power generation layer with a small amount of power generation, and output from the power generation layer with a large amount of power generation There is a problem in that a loss occurs in the generated current.
  • the amount of current output from each of the power generation layer 14 and the silicon substrate 23 is not limited, and power is generated while obtaining the maximum current in each of the plurality of power generation layers. Can do. Therefore, the solar cell 100 with a low voltage and a large current can be realized, and the solar cell 100 with high power generation efficiency can be provided.
  • each of the cells 12 and 22 is electrically connected in parallel, it is not necessary to match the current flowing through the power generation layer 14 with the current flowing through the silicon substrate 23. For this reason, the amount of current accompanying power generation in each of the cells 12 and 22 can be varied. Therefore, the amount of current flowing through the power generation layer 14 and the silicon substrate 23 (power generation layer) is not determined by the electrical resistance of the power generation layer with a small power generation amount. That is, no loss occurs in the current output from the power generation layer where the power generation amount is large, and it is possible to prevent the current amount from being limited.
  • each of the cells 12 and 22 is connected in parallel, for example, when a failure occurs in only one cell (for example, the first cell 12) of the plurality of cells 12 and 22, no current flows. Even so, the current normally flows through other cells (for example, the second cell 22).
  • a protection circuit is connected to each of the cells 12 and 22, when an overvoltage is applied to one of the cells 12 and 22 (for example, the first cell 12), a current flowing only in the cell is protected. It is possible to flow through the circuit, and cell failure can be prevented. That is, since the malfunction that has occurred in one cell does not affect the operating state of the entire cell, the power generation efficiency of the solar battery 100 can be maintained.
  • FIG. 2 is a cross-sectional view of the solar cell in the second embodiment.
  • the same members as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted or simplified.
  • a CuInSe 2 film is used as the power generation layer of the second cell. This structure is different from the structure of the first embodiment described above.
  • two cells 12 and 42 are provided between a pair of substrates 11 and 41 (hereinafter referred to as the first substrate 11 and the second substrate 41). It is pinched.
  • first cell 12 a light-receiving surface electrode 13, a power generation layer (hereinafter referred to as a first power generation layer) 14, and a back electrode 15 formed on the first substrate 11 are sequentially stacked.
  • the structure of the first cell 12 is the same as the structure of the first embodiment described above. Further, the back surface 11 b of the first substrate 11 faces the second substrate 41.
  • the cell 42 corresponds to the second power generation cell of the present invention.
  • a back electrode 45, a second power generation layer 44, and a grid electrode (light receiving surface electrode) 43 are sequentially stacked on a second substrate 41 made of glass or transparent resin.
  • the second substrate 41 has a facing surface 41 a (hereinafter referred to as the front surface 41 a) that faces the back surface 11 b of the first substrate 11.
  • the back electrode 45 is formed on the front surface 41a and is made of a metal film having a relatively high conductivity and reflectivity such as Ag, Al, and Cu.
  • the back electrode 45 is formed using, for example, a low-temperature firing nano ink metal (Ag).
  • the back electrode 45 also functions as a reflective layer that reflects sunlight transmitted through the cells 12 and 42 and supplies the sunlight again to the power generation layer 14 of the cell 12 and the power generation layer 44 of the cell 42.
  • a second power generation layer 44 is formed on the back electrode 45.
  • the second power generation layer 44 has a pn junction structure made of, for example, a p-type CuInSe 2 film (not shown) and an n-type CuInSe 2 film (not shown).
  • an n-type CuInSe 2 film and a p-type CuInSe 2 film are sequentially stacked on the back electrode 45.
  • the band gap (optical band gap) of the second power generation layer 44 is smaller than the band gap of the first power generation layer 14 and is, for example, about 1.04 eV.
  • grid electrodes 43 formed in a lattice shape along a direction parallel to the surface of the second power generation layer 44 are arranged.
  • the grid electrode 43 is formed of the same material as that of the back electrode 45, and sunlight that has entered the front surface 11 a of the substrate 11 and transmitted through the first cell 12 passes through a gap (opening) between the grid electrodes 43.
  • a metal oxide having optical transparency such as TCO.
  • the same insulating portion 30 as that in the first embodiment is formed between the back electrode 15 of the first cell 12 and the grid electrode 43 of the second cell 42.
  • the first cell 12 and the second cell 42 are bonded together via the insulating part 30.
  • the first cell 12 and the second cell 42 are stacked so as to sandwich the insulating portion 30, and the first cell 12 and the second cell 42 are electrically connected. Is electrically insulated.
  • the cells 12 and 42 are mutually electrically connected in parallel.
  • the second embodiment an effect similar to that of the first embodiment described above can be obtained. Further, since the CuInSe 2 film is used for the second power generation layer 44, the band gap is made narrower than when the silicon substrate 23 (see FIG. 1) made of crystalline silicon is used as the power generation layer. Can do. Therefore, since it becomes easier to take out light in the long wavelength region, the power generation efficiency of the solar cell 200 can be improved.
  • first cell 12 a light-receiving surface electrode 13, a power generation layer (hereinafter referred to as a first power generation layer) 14, and a back electrode 15 formed on the first substrate 11 are sequentially stacked.
  • the structure of the first cell 12 is the same as the structure of the first embodiment described above. Further, the back surface 11 b of the first substrate 11 faces the second substrate 41.
  • the cell 42 corresponds to the second power generation cell of the present invention.
  • a back electrode 45, a second power generation layer 44, and a grid electrode (light receiving surface electrode) 43 are sequentially stacked on a second substrate 41 made of glass or transparent resin.
  • the second substrate 41 has a facing surface 41 a (hereinafter referred to as the front surface 41 a) that faces the back surface 11 b of the first substrate 11.
  • the back electrode 45 is formed on the front surface 41a and is made of a metal film having a relatively high conductivity and reflectivity such as Ag, Al, and Cu.
  • the back electrode 45 is formed using, for example, a low-temperature firing nano ink metal (Ag).
  • the back electrode 45 also functions as a reflective layer that reflects sunlight transmitted through the cells 12 and 42 and supplies the sunlight again to the power generation layer 14 of the cell 12 and the power generation layer 44 of the cell 42.
  • a second power generation layer 44 is formed on the back electrode 45.
  • the second power generation layer 44 is a pin in which an i-type Cu 2 S film (not shown) is sandwiched between a p-type Cu 2 S film (not shown) and an n-type Cu 2 S film (not shown). It has a junction structure.
  • an n-type Cu 2 S film, an i-type Cu 2 S film, and a p-type Cu 2 S film are sequentially stacked on the back electrode 45.
  • the band gap (optical band gap) of the second power generation layer 44 is smaller than the band gap of the first power generation layer 14 and is, for example, about 1.2 eV.
  • grid electrodes 43 formed in a lattice shape along a direction parallel to the surface of the second power generation layer 44 are arranged.
  • the grid electrode 43 is formed of the same material as that of the back electrode 45, and sunlight that has entered the front surface 11 a of the substrate 11 and transmitted through the first cell 12 passes through a gap (opening) between the grid electrodes 43.
  • a metal oxide having optical transparency such as TCO.
  • the same insulating portion 30 as that in the first embodiment is formed between the back electrode 15 of the first cell 12 and the grid electrode 43 of the second cell 42.
  • the first cell 12 and the second cell 42 are bonded together via the insulating part 30.
  • the 1st cell 12 and the 2nd cell 42 are laminated
  • the cells 12 and 42 are mutually electrically connected in parallel.
  • the same effect as that of the first embodiment described above can be obtained. Further, since the Cu 2 S film is used for the second power generation layer 44, the band gap is made narrower than when the silicon substrate 23 (see FIG. 1) made of crystalline silicon is used as the power generation layer. be able to. Therefore, since it becomes easier to take out light in the long wavelength region, the power generation efficiency of the solar cell 200 can be improved.
  • FIG. 3 is a cross-sectional view of the solar cell in the third embodiment.
  • the same members as those in the first and second embodiments are denoted by the same reference numerals, and the description thereof is omitted or simplified.
  • a CdS film is used as the power generation layer of the second cell. This structure is different from the structures of the first and second embodiments described above.
  • two cells 12 and 52 are provided between a pair of substrates 11 and 51 (hereinafter referred to as the first substrate 11 and the second substrate 51). It is pinched.
  • the light receiving surface electrode 13 the power generation layer (hereinafter referred to as the first power generation layer) 14, and the back electrode 15 formed on the first substrate 11 are sequentially laminated.
  • the structure of the first cell 12 is the same as that of the first embodiment described above.
  • the cell 42 corresponds to the second power generation cell of the present invention.
  • a back electrode 55, a second power generation layer 54, and a grid electrode (light-receiving surface electrode) 53 are formed on the surface 51a of the second substrate 51 made of glass or transparent resin. Are sequentially stacked.
  • the configurations of the back electrode 55 and the grid electrode 53 are the same as the configurations of the back electrode 45 and the grid electrode 43 in the second embodiment described above.
  • the second power generation layer 54 of the second cell 52 includes a CdS film and the above-described CuInSe 2 film.
  • the second power generation layer 54 has a pn junction structure in which a p-type CuInSe 2 film 54a and an n-type CdS film 54b are stacked.
  • a p-type CdS film 54 a and an n-type CuInSe 2 film 54 b are sequentially stacked on the back electrode 55. That is, the n-type film 54b is formed after the p-type film 54a is formed.
  • the performance of the solar cell may be deteriorated due to the influence of impurities remaining in the film forming apparatus.
  • the band gap of the second power generation layer 54 is about 2.4 to 3.2 eV.
  • a configuration in which an i-type CdS film is formed between the p-type CdS film 54a and the n-type CuInSe 2 film 54b may be employed.
  • the band gap of the power generation layer 54 is larger than the band gap (1.7 eV) of the power generation layer 14. Therefore, in this configuration, the power generation layer 54 functions as the first power generation layer of the present invention, and the power generation layer 14 functions as the second power generation layer of the present invention. That is, the second cell 52 functions as the first power generation cell of the present invention, and the first cell 12 functions as the second power generation cell of the present invention. In this configuration, since sunlight needs to be incident on the second substrate 51 to generate power in the power generation layers 14 and 54, a translucent substrate is used as the second substrate 51.
  • the same effects as those of the first and second embodiments are obtained. be able to.
  • the light receiving surface electrode 13 the power generation layer (hereinafter referred to as the first power generation layer) 14, and the back electrode 15 formed on the first substrate 11 are sequentially laminated.
  • the structure of the first cell 12 is the same as that of the first embodiment described above.
  • the cell 42 corresponds to the second power generation cell of the present invention.
  • a back electrode 55, a second power generation layer 54, and a grid electrode (light-receiving surface electrode) 53 are formed on the front surface 51a of the second substrate 51 made of glass or transparent resin.
  • the second substrate 51 does not necessarily need to be made of a light-transmitting material.
  • the configurations of the back electrode 55 and the grid electrode 53 are the same as the configurations of the back electrode 45 and the grid electrode 43 in the second embodiment described above.
  • the second power generation layer 54 of the second cell 52 includes a CdS film and the above-described Cu 2 S film.
  • the second power generation layer 54 has a pn junction structure in which a p-type Cu 2 S film 54 a and an n-type CdS film 54 b are stacked.
  • a p-type CdS film 54 a and an n-type Cu 2 S film 54 b are sequentially stacked on the back electrode 55.
  • the band gap of the second power generation layer 54 is about 2.4 to 3.2 eV.
  • a configuration in which an i-type CdS film is formed between the p-type Cu 2 S film 54a and the n-type CdS film 54b may be employed.
  • FIG. 4 is a cross-sectional view of the solar cell in the fourth embodiment.
  • the same members as those in the first to third embodiments are denoted by the same reference numerals, and the description thereof is omitted or simplified.
  • a triple solar cell in which three cells are stacked is employed. This structure is different from the first to third embodiments described above.
  • three cells 12, 62, 72 are sandwiched between a pair of substrates 11, 71.
  • the cell 72 corresponds to the second power generation cell of the present invention.
  • the light receiving surface electrode 13, the first power generation layer 14, and the back electrode 15 are sequentially stacked on the first substrate 11.
  • the structure of the first cell 12 is the same as that of the first embodiment described above.
  • the cell 72 (hereinafter referred to as the third cell) has the same configuration as the second cell 42 (see FIG. 2) in the second embodiment described above.
  • a back electrode 75, a third power generation layer 74 (corresponding to a second power generation layer of the present invention) made of a CuInSe 2 film, and a grid electrode 73 are sequentially stacked on the second substrate 71.
  • the band gap of the third power generation layer 74 is 1.04 eV.
  • the structure of the third cell 72 a pn junction structure in which a p-type CuInSe 2 film and an n-type CuInSe 2 film are joined may be employed.
  • the band gap of the third power generation layer 74 is 1.04 eV.
  • a cell structure using the silicon substrate 23 of the first embodiment may be employed as the structure of the third cell 72. In this case, the band gap of the silicon substrate of the third cell 72 is 1.1 eV.
  • a cell 62 (hereinafter referred to as a second cell) is disposed.
  • the cell 62 corresponds to the second power generation cell of the present invention.
  • the cell 62 corresponds to the above-described intermediate power generation cell.
  • the second cell 62 is stacked on the grid electrode 73 of the third cell 72 via the insulating part 32.
  • a back electrode 65 formed on the insulating portion 32, a second power generation layer 64 (intermediate power generation layer), and a grid electrode (light receiving surface electrode) 63 are sequentially stacked.
  • the configuration of the grid electrode 63 is the same as the configuration of the grid electrode 43 in the above-described second embodiment, but may be configured of the same TCO as that of the light-receiving surface electrode 13 in the above-described first embodiment.
  • the configuration of the back electrode 65 is the same as the configuration of the light receiving surface electrode 13 in the first embodiment described above, and is made of TCO.
  • the second power generation layer 64 is, for example, a pin junction in which an i-type microcrystalline silicon film (not shown) is sandwiched between a p-type microcrystalline silicon film (not shown) and an n-type microcrystalline silicon film (not shown). Includes structure. In this pin junction structure, an n-type microcrystalline silicon film, an i-type microcrystalline silicon film, and a p-type microcrystalline silicon film are sequentially stacked in a direction from the back electrode 65 to the grid electrode 63.
  • the band gap of the second power generation layer 64 is smaller than the band gap of the first power generation layer 14 and larger than the third power generation layer 74, for example, about 1.1 eV.
  • the second cell 62 and the first cell 12 are stacked via the insulating unit 30.
  • the insulating unit 30 is disposed between the grid electrode 63 of the second cell 62 and the back electrode 15 of the first cell 12.
  • the structure of the second power generation layer 64 a pn junction structure in which a p-type CdS film and an n-type CdS film are joined may be employed.
  • the band gap of the second power generation layer 64 is 1.68 eV.
  • the power generation layer so that the band gaps of the first cell 12, the second cell 62, and the third cell 72 are sequentially reduced in the direction from the substrate 11 to the substrate 71.
  • Each of the constituent materials 14, 64, and 74 is selected. Therefore, in the triple solar cell 400 in which the three cells 12, 62, 72 are stacked, the power generation layers 14, 64, 74 having different wavelength bands are used. , 74 absorb light in a plurality of wavelength bands included in sunlight.
  • Each of the power generation layers 14, 64, and 74 has an optimum wavelength range for obtaining sunlight energy. Depending on this wavelength range, sunlight is absorbed by the triple solar cell 400. For this reason, the energy of sunlight can be utilized more wastefully. Therefore, in the fourth embodiment, the power generation efficiency can be further improved as compared with the first to third embodiments described above.
  • the light receiving surface electrode 13, the first power generation layer 14, and the back electrode 15 are sequentially stacked on the first substrate 11.
  • the structure of the first cell 12 is the same as that of the first embodiment described above.
  • the cell 72 (hereinafter referred to as the third cell) has the same configuration as the second cell 42 (see FIG. 2) in the second embodiment described above.
  • a back electrode 75, a third power generation layer 74 made of a Cu 2 S film, and a grid electrode 73 are sequentially stacked on the second substrate 71.
  • FIGS. 5A to 5C are cross-sectional views showing a method for manufacturing a solar cell, and show a method for manufacturing the cell 12.
  • the light-receiving surface electrode 13 is formed on the back surface 11b of the substrate 11 by sputtering, CVD (Chemical Vapor Deposition), arc plasma, or the like. Thereafter, as shown in FIG.
  • the power generation layer 14 is formed on the light-receiving surface electrode 13 by plasma CVD.
  • the above layers are formed by using a film forming apparatus in which an anode and a cathode for generating plasma are arranged in a chamber (not shown).
  • the substrate 11 on which the light-receiving surface electrode 13 is formed is placed on the anode in the chamber, and the pressure in the chamber is reduced. Thereafter, the substrate 11 is heated to about 200 ° C. (the highest temperature during the film forming process), and a reaction gas (eg, silane gas, diborane gas, hydrogen, etc.) is introduced into the chamber.
  • a reaction gas eg, silane gas, diborane gas, hydrogen, etc.
  • the power generation layer 14 may be formed by a thermal CVD method, glow discharge, sputtering method, ion plating method, or the like.
  • the back electrode 15 is formed on the power generation layer 14. Specifically, the back electrode 15 is formed using a sputtering method, a CVD method, an arc plasma method, or the like, similarly to the light receiving surface electrode 13 described above. Through the above steps, the first cell 12 is formed on the substrate 11. Next, the insulating portion 30 (see FIG. 1) is formed on the back electrode 15. Specifically, the paste material 30a of the insulating part 30 is applied to the entire surface of the back electrode 15 by using a spin coat method or the like. When an insulating adhesive sheet is used as the constituent material of the insulating portion 30, the insulating adhesive sheet is provided on the entire surface of the back electrode 15.
  • FIG. 6A to 6E are cross-sectional views showing a method for manufacturing a solar cell, and show a method for manufacturing the cell 22.
  • a p-type single crystal silicon substrate 23 having a textured structure formed of fine irregularities formed by etching (texture etching) is prepared.
  • the p-type single crystal silicon substrate 23 is a rectangular substrate having a thickness of 220 ⁇ m and a length of 156 mm.
  • a coating material containing phosphorus (P) is applied to the surface of the p-type single crystal silicon substrate 23.
  • FIG. 6B the silicon substrate 23 is heat-treated at 900 ° C. for 10 minutes, and an n-type diffusion layer 24 having a thickness of about 0.5 ⁇ m is formed in the vicinity of the surface of the silicon substrate 23. .
  • an antireflection film 25 made of silicon nitride (SiNx) is formed on the diffusion layer 24 by CVD.
  • the substrate temperature is about 300 ° C. (the highest temperature during the film formation process)
  • the flow rate of SiH 4 gas is 150 sccm
  • the flow rate of NH 3 gas is 350 sccm
  • the flow rate of N 2 gas as a carrier gas is 800 sccm.
  • the power is preferably set to 400W.
  • a silver paste is applied on the surface of the silicon substrate 23 in a lattice shape so as to have a thickness of 10 ⁇ m using a screen printing method. Thereafter, the silver paste is dried at 150 ° C. for 10 minutes to form the grid electrode 29.
  • a silver paste is applied to the region where the second back electrode 28 is formed on the back surface of the silicon substrate 23 using a screen printing method so as to have a thickness of 10 ⁇ m. Thereafter, the silver paste is dried at 150 ° C. for 10 minutes.
  • an aluminum paste is applied to a region where the first back electrode 27 is formed on the back surface of the silicon substrate 23 by using a screen printing method so as to have a thickness of 40 ⁇ m. Thereafter, the aluminum paste is dried at 150 ° C. for 10 minutes.
  • the silicon substrate 23 is heat-treated at 750 ° C. for 3 seconds to form the first back electrode 27, the second back electrode 28, and the grid electrode 29.
  • a BSF layer 26 having a depth of about 10 ⁇ m is formed on the back surface of the silicon substrate 23.
  • the grid electrode 29 penetrates the antireflection film 25 made of silicon nitride (SiNx) and comes into contact with the diffusion layer 24 (fire through).
  • the cell 22 (second cell) is formed by the above process.
  • FIG. 7A to 7C are cross-sectional views showing a method for manufacturing a solar cell, and show a method for manufacturing the cell 42.
  • FIG. 7A a back electrode 45 is formed on the surface 41a of the second substrate 41 by a sputtering method, a CVD method, an arc plasma method, or the like.
  • the second power generation layer 44 is formed on the back electrode 45 formed on the second substrate 41.
  • the film is formed by a sputtering method or the like.
  • the second substrate 41 is preferably heated to, for example, about 300 to 350 ° C. (maximum temperature during the film forming process).
  • the grid electrode 43 is formed on the power generation layer 44.
  • a metal film is formed on the entire surface of the power generation layer 44 by sputtering, CVD, arc plasma, or the like.
  • a photoresist is formed on the entire surface of the metal film, an opening of the photoresist is formed using a photolithography method, and an etching mask is formed on the metal film.
  • the metal film is patterned to form a grid-like grid electrode 43.
  • the cell 42 (second cell) is formed by the above process.
  • a silver paste is applied in a lattice shape so as to have a thickness of 10 ⁇ m by using a screen printing method. Then, the grid electrode 43 may be formed by drying the silver paste at 150 ° C. for 10 minutes.
  • the manufacturing method of the cell 52 of 3rd Embodiment is demonstrated based on FIG.
  • the back electrode 55 is formed on the surface 51a of the second substrate 51 by using a method similar to the method of forming the cell 42, that is, by sputtering, CVD, arc plasma, or the like.
  • the second power generation layer 54 p-type CuInSe 2 film 54a and n-type CdS film 54b
  • the film is formed by an evaporation method or the like.
  • the grid electrode 53 is formed on the power generation layer 54 using a method similar to the method for forming the cell 42.
  • the cell 52 (second cell) is formed by the above process.
  • a cell 72 (third cell) is formed on the surface 71 a of the second substrate 71 using a method similar to the method for forming the cell 42 described above.
  • the cell 62 (second cell) is stacked on the substrate 71 on which the cell 72 is formed.
  • the paste material of the insulating part 32 is applied onto the grid electrode 73 of the cell 72 by using a spin coat method or the like.
  • the insulating adhesive sheet is provided on the entire surface of the grid electrode 73.
  • the back electrode 65 is formed on the insulating portion 32 by using a sputtering method, a CVD method, an arc plasma method, or the like.
  • the second power generation layer 64 is formed on the back electrode 65 by vapor deposition or the like.
  • the grid electrode 63 is formed on the power generation layer 64 by a method similar to the method of forming the cell 42. As described above, the cell 62 is stacked on the cell 72.
  • the first cell 12 and the second cell 22 are individually manufactured. Further, after preparing the first cell 12 and the second cell 22 individually, the insulating part 30 is disposed between the first cell 12 and the second cell 22, and the first cell 12 and the second cell 22 are attached. It is matched. According to this configuration, even if the maximum temperature in the film formation process of the first cell 12 is different from the maximum temperature in the film formation process of the second cell 22, each of the first cell 12 and the second cell 22. Can be formed individually, and the first cell 12 and the second cell 22 can be overlapped with each other through the insulating portion 30.
  • the film formation conditions of the power generation layer located in the upper layer are limited in order to maintain the film quality of the power generation layer located in the lower layer already formed. That is, in the conventional film formation process of sequentially laminating a plurality of power generation layers, since the process temperatures for forming each of the power generation layers are different from each other, when producing a power generation layer that requires a high temperature process, The power generation layer formed by the low temperature process is exposed to a high temperature atmosphere.
  • amorphous silicon having a maximum temperature during the film formation process of 180 to 230 ° C. in the first embodiment, the maximum temperature during the film formation process of amorphous silicon is 200 ° C.
  • the maximum temperature during the film formation process of microcrystalline silicon is 300 ° C.
  • the deposition temperature of microcrystalline silicon is higher than the deposition temperature of amorphous silicon. Desorption occurs due to an increase in process temperature during film formation. In this case, the conversion efficiency in amorphous silicon may be reduced.
  • the film forming process of the cell 12 and the film forming process of the cell 22 are separate. For this reason, for example, even if high-temperature heat treatment is performed on the silicon substrate 23 to form the diffusion layer 24 or the BSF layer 26 in the formation process of the second cell 22, the second cell 22 is formed separately from the second cell 22.
  • the first cell 12 is not affected by heat. Therefore, the second cell 22 can be formed without deterioration of the power generation layer 14 already formed on the substrate 11. That is, when forming a layer (for example, the power generation layer 14) constituting each of the cells 12 and 22, the film can be formed by setting optimum formation conditions. Therefore, each of the power generation layer 14 and the silicon substrate 23 having good film quality can be formed. Therefore, according to the present invention, the film quality of the power generation layer is improved, the conversion efficiency of the solar cell 100 is increased, and the manufacturing efficiency is improved.
  • the first cells 12 and the second cells 22 are individually manufactured by providing individual protection circuits for the cells 12 and 22, respectively, the first cell 12 and the second cell 22 are attached. Prior to matching, defects occurring during the manufacture of each of the cells 12 and 22 can be individually detected. Thereby, when bonding the 1st cell 12 and the 2nd cell 22, since it becomes possible to use only the quality cells 12 and 22, the high performance solar cell 100 can be provided as a whole.
  • the solar cells 200, 300, and 400 of the second to fourth embodiments can also be manufactured by the same method as the method for manufacturing the solar cell 100 described above. That is, when forming the solar cell 200 of the second embodiment, the cell 12 and the cell 42 are individually manufactured as shown in FIG. 2 (see FIGS. 5A to 5C and 7). Further, the cell 12 and the cell 42 are bonded through the insulating portion 30 by the same method as the method of bonding the cells 12 and 22 described above. Moreover, when forming the solar cell 300 of 3rd Embodiment, as shown in FIG. 3, the cell 12 and the cell 52 are each produced separately. Further, the cell 12 and the cell 52 are bonded through the insulating portion 30 by the same method as the method of bonding the cells 12 and 22 described above.
  • the cell 12 and the cell 72 are each produced separately.
  • the cell 62 is disposed on the cell 72 via the insulating portion 32. Thereafter, the cell 12 and the cell 62 are bonded together via the insulating portion 30 by the same method as the method of bonding the cells 12 and 22 described above.
  • a solar cell in which a plurality of cells having different film forming process conditions, for example, a plurality of cells having different process temperatures, are stacked can be easily manufactured. Therefore, a tandem solar cell or a triple solar cell in which a plurality of cells are stacked can be easily manufactured without lowering the power generation efficiency of the power generation layer that is manufactured first in the stacked structure. Therefore, a solar cell with relatively high conversion efficiency can be produced efficiently.
  • the independent second cell 62 a translucent substrate is prepared. Thereafter, the light-receiving surface electrode, the second power generation layer 64, and the back surface electrode 65 are sequentially stacked on the translucent substrate.
  • the back electrode 65 and the light receiving surface electrode are made of TCO.
  • the second power generation layer 64 has a pin junction structure in which an i-type microcrystalline silicon film (not shown) is sandwiched between a p-type microcrystalline silicon film (not shown) and an n-type microcrystalline silicon film (not shown). Including.
  • the 2nd cell 62 is formed separately.
  • the first cell 12 and the third cell 72 are formed in the same manner as described above. As a result, three independent cells are obtained.
  • the first cell 12 and the second cell 62 are bonded together.
  • the first cell 12 and the second cell 62 are bonded so that the translucent substrate of the second cell 62 and the back electrode 15 of the first cell 12 face each other.
  • An insulating portion made of a paste material is disposed between the translucent substrate and the back electrode 15.
  • an insulating portion is also provided between the second cell 62 and the third cell 72, and the second cell 62 and the third cell 72 are bonded together.
  • three cells are bonded together.
  • the paste material 30a of the insulating portion 30 is applied to the entire surface of the back electrode 15 by using a spin coating method or the like.
  • the first cell 12 and the second cell 62 are bonded together via the paste material 30a, and the paste material 30a is cured.
  • the paste material of the insulating portion 32 is applied to the entire surface of the grid electrode 73 by using a spin coating method or the like.
  • the second cell 62 and the third cell 72 are bonded together via the paste material, and the paste material is cured.
  • the second cell 62 and the third cell 72 are joined via the insulating portion 32.
  • the insulating adhesive sheet is provided on the entire surface of the back electrode 15 or the entire surface of the grid electrode 73.
  • the configuration in which the second cell 62 includes the light receiving surface electrode has been described.
  • the second cell 62 may include the grid electrode 63 as in FIG.
  • the paste material 30 a of the insulating part 30 may be applied to the entire surface of the grid electrode 63.
  • the same effect as the above-described embodiment can be obtained.
  • the technical scope of the present invention is not limited to the above-described embodiments, and various modifications can be made to the above-described embodiments without departing from the spirit of the present invention.
  • the configuration in which the gap between the back electrode of the first cell and the grid electrode of the second cell is filled with the constituent material of the insulating portion has been described.
  • the present invention is not limited to this configuration, and an insulating portion is formed at least between the back electrode of the first cell and the grid electrode of the second cell, and the first cell and the second cell are electrically insulated.
  • the configuration is adopted.
  • the structure in which the two layers of the first cell 12 and the second cell 22 are overlapped has been described, but not limited to two layers, a plurality of layers of two or more layers You may employ
  • the present invention is widely applicable to solar cells and solar cell manufacturing methods that can improve power generation efficiency and manufacturing efficiency.

Abstract

A solar cell includes: a substrate (11) having light transparency; a first power generating cell (12), which is arranged at a position close to the substrate (11) and includes a first power generating layer (14); a second power generating cell (22, 42, 52, 62, 72), which is arranged at a position separated from the substrate (11) and includes a second power generating layer (23, 44, 54, 64, 74) having a band gap smaller than that of the first power generating layer (14); and an insulating section (30, 32), which is arranged between the first power generating cell (12) and the second power generating cell (22, 42, 52, 62, 72).

Description

太陽電池及び太陽電池の製造方法Solar cell and method for manufacturing solar cell
　本発明は、複数のセルを重ねて積層される太陽電池及び太陽電池の製造方法に関する。
　本願は、２００９年３月５日に出願された特願２００９－０５２０９４号に基づき優先権を主張し、その内容をここに援用する。 The present invention relates to a solar cell in which a plurality of cells are stacked and stacked, and a method for manufacturing the solar cell.
This application claims priority based on Japanese Patent Application No. 2009-052094 filed on Mar. 5, 2009, the contents of which are incorporated herein by reference.
　近年、エネルギーの効率的な利用の観点から、太陽電池は広く一般に利用されている。この太陽電池としては、シリコン系の太陽電池が知られており、具体的に、単結晶シリコンが用いられたシリコン太陽電池、ポリシリコン層が用いられたポリシリコン太陽電池、アモルファスシリコンが用いられたアモルファスシリコン太陽電池等が知られている。
　シリコン系の太陽電池は、例えば、ガラス基板上にＴＣＯ等からなる透明電極として機能する受光面電極と、受光面電極上に形成されシリコンからなる発電層と、裏面電極として機能するＡｇ薄膜とが積層されたセルを含む。
　発電層は、ｐｉｎ接合と呼ばれる層構造を有する。この層構造においては、光を受けると電子及びホールを発生するシリコン膜（ｉ型）がｐ型及びｎ型のシリコン膜で挟まれている。 In recent years, solar cells have been widely used from the viewpoint of efficient use of energy. As this solar cell, a silicon-based solar cell is known, and specifically, a silicon solar cell using single crystal silicon, a polysilicon solar cell using a polysilicon layer, and amorphous silicon were used. Amorphous silicon solar cells and the like are known.
For example, a silicon-based solar cell includes a light-receiving surface electrode that functions as a transparent electrode made of TCO or the like on a glass substrate, a power generation layer that is formed on the light-receiving surface electrode and is made of silicon, and an Ag thin film that functions as a back electrode. Includes stacked cells.
The power generation layer has a layer structure called a pin junction. In this layer structure, a silicon film (i-type) that generates electrons and holes when receiving light is sandwiched between p-type and n-type silicon films.
　また、近年では、太陽光が吸収される波長帯域が互いに異なる複数の発電層が基板上に積層された、例えば、タンデム型の太陽電池の開発が進められている。
　このタンデム型の太陽電池においては、短波長域の光が一方の発電層（例えば、アモルファスシリコン）において吸収され、長波長域の光が他方の発電層（例えば、結晶シリコン）において吸収される。このような２つの発電層を有する構造においては、太陽光のエネルギーが無駄なく利用され、発電効率が向上する。
　このようなタンデム型の太陽電池としては、例えば、特許文献１及び特許文献２に開示されているように、バンドギャップが異なる複数の発電層が積層され、一体化された構造が知られている。また、特許文献３に開示されているように、第１発電層の第１光吸収層と第２発電層の第２光吸収層との間に、両者間を部分的に絶縁する絶縁層が設けられ、かつ、第１発電層と第２発電層との間を結線する結線電極が設けられている構成が知られている。 In recent years, for example, development of a tandem solar cell in which a plurality of power generation layers having different wavelength bands in which sunlight is absorbed is laminated on a substrate has been promoted.
In this tandem solar cell, light in a short wavelength region is absorbed in one power generation layer (for example, amorphous silicon), and light in a long wavelength region is absorbed in the other power generation layer (for example, crystalline silicon). In such a structure having two power generation layers, the energy of sunlight is used without waste, and the power generation efficiency is improved.
As such a tandem solar cell, for example, as disclosed in Patent Document 1 and Patent Document 2, a structure in which a plurality of power generation layers having different band gaps are stacked and integrated is known. . Further, as disclosed in Patent Document 3, an insulating layer that partially insulates between the first light absorption layer of the first power generation layer and the second light absorption layer of the second power generation layer is provided. There is known a configuration in which a connection electrode that is provided and connects between a first power generation layer and a second power generation layer is provided.
特開２００２－３６８２３８号公報JP 2002-368238 A 特開２００１－０２８４５２号公報JP 2001-028452 A 特開２００５－２１７０４１号公報JP 2005-217041 A
　しかしながら、上述の従来技術では、複数の発電層が電気的に接続（直列接続）されている構造であるため、複数の発電層の各々に流れる電流を一致させる必要がある。具体的に、複数の発電層が電気的に接続された直列回路（直列接続）において、一方の発電層における発電量と他方の発電層における発電量とが異なる場合、発電量が大きい発電層の電気抵抗よりも発電量が小さい発電層の電気抵抗が大きくなる。従って、発電量が小さい発電層の電気抵抗によって直列回路における電流量が決定される。このため、発電量が大きい発電層から出力された電流に損失が生じる。そのため、直列接続された積層構造の太陽電池では、発電層の各々から出力されるエネルギーが、単層の発電層における最大出力時におけるエネルギーによりも低くなる場合がある。
　具体的に、従来の太陽電池においては、太陽光が入射面に平均的に入射する際に、発電層の各々の最大出力が得られるように調整されている。しかしながら、太陽光の光強度又はスペクトルが変化した場合には、発電層の各々から所望の出力が得られず、複数の発電層全体において得られる光電変換効率が低下するという問題がある。 However, since the above-described conventional technology has a structure in which a plurality of power generation layers are electrically connected (series connection), it is necessary to match the currents flowing through each of the plurality of power generation layers. Specifically, in a series circuit (series connection) in which a plurality of power generation layers are electrically connected, if the power generation amount in one power generation layer and the power generation amount in the other power generation layer are different, The electric resistance of the power generation layer whose power generation amount is smaller than the electric resistance is increased. Therefore, the amount of current in the series circuit is determined by the electric resistance of the power generation layer with a small amount of power generation. For this reason, a loss occurs in the current output from the power generation layer where the power generation amount is large. Therefore, in solar cells having a stacked structure connected in series, the energy output from each of the power generation layers may be lower than the energy at the time of maximum output in the single power generation layer.
Specifically, the conventional solar cell is adjusted so that the maximum output of each power generation layer can be obtained when sunlight is incident on the incident surface on average. However, when the light intensity or spectrum of sunlight changes, there is a problem that a desired output cannot be obtained from each of the power generation layers, and the photoelectric conversion efficiency obtained in the plurality of power generation layers as a whole decreases.
　また、タンデム型の太陽電池を製造する場合、基板上に１層目の発電層として、例えば、アモルファスシリコンからなる発電層を形成した後、アモルファスシリコンによって吸収される光の波長よりも長い波長の光を吸収する発電層を順次形成していく。長波長の光を吸収する発電層の材料としては、例えば、微結晶シリコンが知られている。
　この場合、複数の発電層の各々においては、構成材料の物性に応じて最適な成膜条件が異なり、特に成膜工程における温度条件が異なる。そのため、複数の発電層を順次に積層する場合、後に形成される発電層の成膜条件に起因して、先に形成された発電層の性能低下が生じるという問題がある。 When a tandem solar cell is manufactured, for example, after forming a power generation layer made of amorphous silicon on the substrate as a first power generation layer, the wavelength of light longer than the wavelength of light absorbed by amorphous silicon is formed. A power generation layer that absorbs light is formed sequentially. As a material for the power generation layer that absorbs light having a long wavelength, for example, microcrystalline silicon is known.
In this case, in each of the plurality of power generation layers, the optimum film formation conditions differ according to the physical properties of the constituent materials, and in particular, the temperature conditions in the film formation process differ. Therefore, when a plurality of power generation layers are sequentially stacked, there is a problem in that the performance of the power generation layer formed earlier is deteriorated due to the film formation conditions of the power generation layer formed later.
　本発明は、上記事情に鑑みてなされたもので、発電効率及び製造効率を向上させることができる太陽電池と、この太陽電池を製造する方法を提供することを目的とする。 The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a solar cell that can improve power generation efficiency and manufacturing efficiency, and a method for manufacturing the solar cell.
　本発明者等は、複数の発電層が順次に積層されている従来構造においては、後に形成される発電層の成膜条件に起因して、先に形成された発電層の性能低下が生じるという問題を解決するために鋭意検討を行った。
　例えば、受光面に最も近い発電層としてアモルファスシリコンのｐ－ｉ－ｎ層が形成された、このアモルファスシリコン構造上に微結晶シリコンからなるｐ－ｉ―ｎ層の発電層が積層されたタンデム型太陽電池を作製する場合について説明する。
　アモルファスシリコンの成膜プロセスにおいては、最高温度（基板温度）が２００℃程度（１８０～２３０℃）である。一方、微結晶シリコンの成膜プロセスにおいては、最高温度（基板温度）が３００℃程度（２５０～３５０℃）である。そのため、上記のようなタンデム型太陽電池の製造プロセスにおいては、アモルファスシリコンは、微結晶シリコンの成膜プロセスにおける最高温度である３００℃程度（２５０～３５０℃）という高温雰囲気にさらされる。
　本発明者等は、アモルファスシリコンが高温雰囲気にさらされることに起因して、アモルファスシリコン中に存在する水素原子が脱離し、その水素原子が終端化していたダングリングボンドがアモルファスシリコンの発電層中に増加することを見出した。この結果、本発明者等は、この発電層の変換効率等を含む電池特性が低下し、製造効率が低下するという問題を見出した。
　また、本発明者等は、上記のような現象は、アモルファスシリコンのｐ－ｉ－ｎ層の代わりに、成膜プロセス中の最高温度（基板温度）が２００℃程度（１８０～２３０℃）であるアモルファスシリコンゲルマニウムからなるｐ－ｉ－ｎ層を作製する場合においても生じることを見出した。また、本発明者等は、上記のような現象は、微結晶シリコンからなるｐ－ｉ－ｎ層の代わりに、高温プロセス（２５０℃以上）において成膜される発電層、例えば、ＣｄＳ，Ｃｕ２Ｓ，ＣｕＩｎＳｅ２等を作製する場合にも生じることを見出した。
　また、従来、太陽電池製造においては、不純物拡散工程又はファイヤスルー工程等の高温プロセス（２５０℃以上の温度雰囲気）によって、結晶シリコンの発電層とアモルファスシリコンの発電層とが積層されている。このように積層する方法においては、アモルファスシリコンにダングリングボンドが増加することを防ぐため、結晶シリコンの発電層の上にアモルファスシリコンの発電層を積層するという順序において２つの発電層を積層する必要があった。即ち、２つの発電層を積層する順番が制限された方法によって太陽電池を製造しなければならなかった。
　本発明者等は、このような事情に鑑み、本発明を完成するに至った。 According to the inventors, in the conventional structure in which a plurality of power generation layers are sequentially stacked, the performance of the power generation layer formed earlier is deteriorated due to the film formation conditions of the power generation layer formed later. In order to solve the problem, intensive study was conducted.
For example, a tandem type in which an amorphous silicon pin layer is formed as the power generation layer closest to the light receiving surface, and a pin power generation layer made of microcrystalline silicon is laminated on the amorphous silicon structure. A case where a solar cell is manufactured will be described.
In the amorphous silicon film forming process, the maximum temperature (substrate temperature) is about 200 ° C. (180 to 230 ° C.). On the other hand, in the microcrystalline silicon film forming process, the maximum temperature (substrate temperature) is about 300 ° C. (250 to 350 ° C.). Therefore, in the manufacturing process of the tandem solar cell as described above, the amorphous silicon is exposed to a high temperature atmosphere of about 300 ° C. (250 to 350 ° C.) which is the maximum temperature in the microcrystalline silicon film forming process.
As a result of the exposure of the amorphous silicon to a high temperature atmosphere, the present inventors have released a hydrogen atom present in the amorphous silicon and the dangling bond in which the hydrogen atom is terminated is in the power generation layer of the amorphous silicon. Found to increase. As a result, the present inventors have found a problem that the battery characteristics including the conversion efficiency of the power generation layer and the like are lowered, and the production efficiency is lowered.
In addition, the present inventors have found that the above-described phenomenon occurs when the maximum temperature (substrate temperature) during the film forming process is about 200 ° C. (180 to 230 ° C.) instead of the amorphous silicon pin layer. It has been found that this also occurs when a pin layer made of some amorphous silicon germanium is produced. Further, the present inventors have found that the above phenomenon is caused by a power generation layer formed in a high-temperature process (250 ° C. or higher), for example, CdS, Cu, instead of the pin layer made of microcrystalline silicon. It has been found that this also occurs when 2 S, CuInSe 2 or the like is produced.
Conventionally, in solar cell manufacturing, a crystalline silicon power generation layer and an amorphous silicon power generation layer are laminated by a high-temperature process (temperature atmosphere of 250 ° C. or higher) such as an impurity diffusion process or a fire-through process. In this method of stacking, it is necessary to stack two power generation layers in the order of stacking the amorphous silicon power generation layer on the crystalline silicon power generation layer in order to prevent dangling bonds from increasing in the amorphous silicon. was there. That is, the solar cell had to be manufactured by a method in which the order of stacking the two power generation layers was limited.
In view of such circumstances, the present inventors have completed the present invention.
　上記課題を解決するために、本発明の第１態様の太陽電池は、光透過性を有する基板と、前記基板に近い位置に配置され、第１発電層を含む第１発電セルと、前記基板から離れた位置に配置され、前記第１発電層のバンドギャップよりも小さいバンドギャップを有する第２発電層を含む第２発電セルと、前記第１発電セルと前記第２発電セルとの間に配置された絶縁部とを含む。
　即ち、本発明の第１態様の太陽電池は、受光面電極，発電層，及び裏面電極が順に積層されている複数のセルが光透過性を有する基板上に積層されている構造を有する。また、光入射側に配置される前記セルを構成する前記発電層のバンドギャップは、基板から離れた位置に配置された発電層のバンドギャップよりも大きい。また、複数のセルの間には、絶縁部が配置されている。
　また、この構成においては、第１発電セル（第１発電層）と基板との距離よりも、第２発電セル（第２発電層）と基板との距離が大きい。
　この構成によれば、第１発電セルと第２発電セルとの間に絶縁部が配置され、第１発電セル上に第２発電セルが積層されているので、第１発電セル及び第２発電セルの各々は、電気接続構造において独立した発電セルとして機能する。このため、第１発電セル及び第２発電セルの各々に流れる電流を独立して設定することができる。
　これにより、太陽光の光強度又はスペクトル等に関わらず、第１発電セル及び第２発電セルの各々の発電層に流れる電流が最大である時に出力されるエネルギーを取り出すことができる。そのため、第１発電セル及び第２発電セルの各々における最大出力を取り出すことができる。
　つまり、例えば、従来のタンデム型の太陽電池のように、複数の発電層が電気的に直列に接続された構造（直列回路）においては、一方の発電層における発電量と他方の発電層における発電量とが異なる場合、発電量が大きい発電層の電気抵抗よりも発電量が小さい発電層の電気抵抗が大きくなる。従って、発電量が小さい発電層の電気抵抗によって直列回路における電流量が決定される。このため、発電量が大きい発電層から出力された電流に損失が生じるという問題がある。これに対し、本発明の太陽電池においては、複数の発電層が互いに独立している並列回路構造が採用されているので、各々の発電層における電流量が制限されず、複数の発電層の各々において最大の電流を得ながら発電することができる。従って、低電圧・大電流の太陽電池を実現することができ、発電効率の高い太陽電池を提供することができる。 In order to solve the above-described problems, a solar cell according to a first aspect of the present invention includes a substrate having light permeability, a first power generation cell disposed near the substrate and including a first power generation layer, and the substrate. A second power generation cell including a second power generation layer disposed at a position away from the first power generation layer and having a band gap smaller than a band gap of the first power generation layer, and between the first power generation cell and the second power generation cell And an arranged insulating portion.
That is, the solar cell of the first aspect of the present invention has a structure in which a plurality of cells in which a light-receiving surface electrode, a power generation layer, and a back electrode are sequentially stacked are stacked on a light-transmitting substrate. In addition, the band gap of the power generation layer constituting the cell disposed on the light incident side is larger than the band gap of the power generation layer disposed at a position away from the substrate. An insulating part is disposed between the plurality of cells.
Further, in this configuration, the distance between the second power generation cell (second power generation layer) and the substrate is larger than the distance between the first power generation cell (first power generation layer) and the substrate.
According to this configuration, since the insulating portion is disposed between the first power generation cell and the second power generation cell and the second power generation cell is stacked on the first power generation cell, the first power generation cell and the second power generation cell are stacked. Each of the cells functions as an independent power generation cell in the electrical connection structure. For this reason, the electric current which flows into each of the 1st power generation cell and the 2nd power generation cell can be set up independently.
Thereby, the energy output when the current flowing through each power generation layer of the first power generation cell and the second power generation cell is maximum can be extracted regardless of the light intensity or spectrum of sunlight. Therefore, the maximum output in each of the first power generation cell and the second power generation cell can be taken out.
That is, for example, in a structure (series circuit) in which a plurality of power generation layers are electrically connected in series as in a conventional tandem solar cell, the power generation amount in one power generation layer and the power generation in the other power generation layer When the amount is different, the electric resistance of the power generation layer having a small power generation amount is larger than the electric resistance of the power generation layer having a large power generation amount. Therefore, the amount of current in the series circuit is determined by the electric resistance of the power generation layer with a small amount of power generation. For this reason, there is a problem that a loss occurs in the current output from the power generation layer with a large power generation amount. On the other hand, in the solar cell of the present invention, since a parallel circuit structure in which a plurality of power generation layers are independent from each other is adopted, the amount of current in each power generation layer is not limited, and each of the plurality of power generation layers is The power can be generated while obtaining the maximum current. Therefore, a solar cell with a low voltage and a large current can be realized, and a solar cell with high power generation efficiency can be provided.
　また、本発明の第１態様の太陽電池においては、前記第１発電セル及び前記第２発電セルを含む複数の発電セルを有し、前記複数の発電セルのうち、前記基板から最も離れた位置に前記第２発電セルが配置され、前記第２発電層のバンドギャップは、１．３ｅＶ以下であることが好ましい。
　ここで、「複数の発電セル」とは、２つ以上の発電セルを意味し、３つの発電セル或いは４つの発電セルを含む。また、この構成においては、第１発電セル及び第２発電セルを含む複数の発電セルの中で、第２発電セル（第２発電層）と基板との距離が、他の発電セルと基板との距離よりも大きい。
　この構成によれば、基板から最も離れた位置に配置された発電セル（第２発電セル）の発電層（第２発電層）のバンドギャップが、１．３ｅＶ以下であるので、基板に近い位置（入射側）に配置された発電層において取り出すことができない長波長域の光を利用して発電を行うことができる。
　即ち、太陽光の入射方向（基板の厚さ方向）に積層された複数の発電セルの中で、基板に近い位置に配置された第１発電セルの第１発電層は短波長域の光を利用して発電し、基板から最も離れた位置に配置される第２発電層は長波長域の光を利用して発電する。また、第１発電セルと第２発電セルの間に中間発電セルが配置されている場合、中間発電セルの中間発電層は、短波長域と長波長域との間の中間波長域の光を利用して発電する。また、第１発電セルと第２発電セルの間に、複数の中間発電セルが設けられていてもよい。
　このように、本発明の太陽電池においては、第１発電層（基板に近い位置に配置された発電層）から第２発電層（基板から離れた位置に配置された発電層）に向けた方向において、発電に利用される波長域が短波長から長波長に漸次変化している。このように、複数の発電層において発電層の各々が吸収する波長領域が互いに異なっている構造においては、広い波長域において太陽光のエネルギーを取り出すことができる。従って、本発明の太陽電池は、太陽光のエネルギーを無駄なく利用することができ、発電効率を向上することができる。 Moreover, in the solar cell of the first aspect of the present invention, the solar cell has a plurality of power generation cells including the first power generation cell and the second power generation cell, and the position farthest from the substrate among the plurality of power generation cells It is preferable that the second power generation cell is disposed in a band gap, and the band gap of the second power generation layer is 1.3 eV or less.
Here, the “plurality of power generation cells” means two or more power generation cells, and includes three power generation cells or four power generation cells. Further, in this configuration, among the plurality of power generation cells including the first power generation cell and the second power generation cell, the distance between the second power generation cell (second power generation layer) and the substrate is different from the other power generation cells and the substrate. Greater than the distance.
According to this configuration, since the band gap of the power generation layer (second power generation layer) of the power generation cell (second power generation cell) arranged at the position farthest from the substrate is 1.3 eV or less, the position is close to the substrate. Power generation can be performed using light in a long wavelength region that cannot be extracted in the power generation layer arranged on the (incident side).
That is, among the plurality of power generation cells stacked in the sunlight incident direction (substrate thickness direction), the first power generation layer of the first power generation cell arranged at a position close to the substrate emits light in a short wavelength region. The second power generation layer disposed at the position farthest from the substrate generates power using light in a long wavelength region. When the intermediate power generation cell is disposed between the first power generation cell and the second power generation cell, the intermediate power generation layer of the intermediate power generation cell emits light in the intermediate wavelength range between the short wavelength range and the long wavelength range. Use it to generate electricity. A plurality of intermediate power generation cells may be provided between the first power generation cell and the second power generation cell.
Thus, in the solar cell of the present invention, the direction from the first power generation layer (power generation layer disposed at a position close to the substrate) to the second power generation layer (power generation layer disposed at a position away from the substrate). , The wavelength range used for power generation gradually changes from a short wavelength to a long wavelength. As described above, in the structure in which the wavelength regions absorbed by the power generation layers in the plurality of power generation layers are different from each other, it is possible to extract sunlight energy in a wide wavelength range. Therefore, the solar cell of the present invention can use the energy of sunlight without waste and can improve the power generation efficiency.
　また、本発明の第１態様の太陽電池においては、前記第１発電セル及び前記第２発電セルは、電気的に並列に接続されていることが好ましい。
　この構成によれば、第１発電セル及び第２発電セルが電気的に並列に接続されているので、第１発電層に流れる電流と第２発電層に流れる電流とを一致させる必要がない。このため、第１発電層及び第２発電層における電流量が制限されず、複数の発電層の各々において最大の電流を得ながら発電することができる。また、第１発電セル及び第２発電セルを並列に接続することで、例えば、複数の発電セルのうち、１つの発電セルのみに不具合が生じて電流が流れない場合であっても、他の発電セルには正常に電流が流れる。つまり、１つの発電セルにおいて不具合が、全体の発電セルの作動状態に影響を及ぼすことがないため、太陽電池の発電効率を維持することができる。 In the solar battery of the first aspect of the present invention, it is preferable that the first power generation cell and the second power generation cell are electrically connected in parallel.
According to this configuration, since the first power generation cell and the second power generation cell are electrically connected in parallel, it is not necessary to match the current flowing through the first power generation layer with the current flowing through the second power generation layer. For this reason, the amount of current in the first power generation layer and the second power generation layer is not limited, and power can be generated while obtaining the maximum current in each of the plurality of power generation layers. In addition, by connecting the first power generation cell and the second power generation cell in parallel, for example, even when a problem occurs in only one power generation cell among a plurality of power generation cells and no current flows, A current flows normally through the power generation cell. That is, since a malfunction in one power generation cell does not affect the operating state of the entire power generation cell, the power generation efficiency of the solar cell can be maintained.
　また、本発明の第１態様の太陽電池においては、前記第１発電セル及び前記第２発電セルの各々には、保護回路が設けられていることが好ましい。
　この構成によれば、第１発電セル及び第２発電セルの各々に個別の保護回路が接続されているので、第１発電セル及び第２発電セルのうちいずれか発電セルに過電圧が印加された時には、過電圧が印加された発電セルのみに流れる電流を保護回路に流す。これによって、発電セルの故障を防ぐことができる。
　つまり、１つの発電セルにおいて不具合が、全体の発電セルの作動状態に影響を及ぼすことがないため、太陽電池の発電効率を維持することができる。 Moreover, in the solar cell of the 1st aspect of this invention, it is preferable that each of the said 1st power generation cell and the said 2nd power generation cell is provided with the protection circuit.
According to this configuration, since an individual protection circuit is connected to each of the first power generation cell and the second power generation cell, an overvoltage is applied to either the first power generation cell or the second power generation cell. Sometimes, the current that flows only to the power generation cell to which the overvoltage is applied is passed through the protection circuit. Thereby, failure of the power generation cell can be prevented.
That is, since a malfunction in one power generation cell does not affect the operating state of the entire power generation cell, the power generation efficiency of the solar cell can be maintained.
　上記課題を解決するために、本発明の第２態様の太陽電池の製造方法は、光透過性を有する基板を準備し、第１発電層を含む第１発電セルを形成し、前記第１発電層のバンドギャップよりも小さいバンドギャップを有する第２発電層を含む第２発電セルを形成し、前記第１発電セルと前記第２発電セルとの間に絶縁部を配置し、前記基板に近い位置に前記第１発電セルを配置し、かつ、前記基板から離れた位置に前記第２発電セルを配置するように、前記第１発電セルに前記第２発電セルを重ね合わせる。
　この方法においては、第１発電セル及び第２発電セルを個別に作製した後に、第１発電セル及び第２発電セルの間に絶縁部を配置するように第１発電セル及び第２発電セルを重ね合わせている。従って、第１発電セルに第２発電セルを重ね合わせる前に、第１発電セル及び第２発電セルの各々を構成する層（例えば、発電層）を最適な成膜条件において成膜することができる。
　従来のような複数の発電層を順次積層する方法においては、既に成膜された下層に位置する発電層の膜質を維持するために、上層に位置する発電層の成膜条件が制限されてしまう。
　これに対して、本発明の製造方法によれば、上層に形成される発電層の成膜条件が制限されずに、第１発電セル及び第２発電セルの各々を形成できる。
　これにより、第１発電セル及び第２発電セルの各々の発電層を最適な成膜条件で成膜することができるため、良好な膜質を有する発電層を形成することができる。
　従って、本発明の製造方法によれば、発電層の膜質が改善し、太陽電池の発電効率が増大し、製造効率が向上する。 In order to solve the above problems, a method for manufacturing a solar cell according to a second aspect of the present invention provides a substrate having light permeability, forms a first power generation cell including a first power generation layer, and performs the first power generation. Forming a second power generation cell including a second power generation layer having a band gap smaller than the band gap of the layer, disposing an insulating portion between the first power generation cell and the second power generation cell, and being close to the substrate The second power generation cell is overlapped with the first power generation cell so that the first power generation cell is disposed at a position and the second power generation cell is disposed at a position away from the substrate.
In this method, after the first power generation cell and the second power generation cell are individually manufactured, the first power generation cell and the second power generation cell are arranged so that an insulating portion is disposed between the first power generation cell and the second power generation cell. Overlapping. Therefore, before the second power generation cell is overlaid on the first power generation cell, the layers (for example, the power generation layer) constituting each of the first power generation cell and the second power generation cell can be formed under optimum film formation conditions. it can.
In the conventional method of sequentially laminating a plurality of power generation layers, in order to maintain the film quality of the power generation layer located in the already formed lower layer, the film formation conditions of the power generation layer located in the upper layer are limited. .
On the other hand, according to the manufacturing method of the present invention, each of the first power generation cell and the second power generation cell can be formed without limiting the film forming conditions of the power generation layer formed in the upper layer.
Thereby, since each power generation layer of the first power generation cell and the second power generation cell can be formed under optimum film formation conditions, a power generation layer having a good film quality can be formed.
Therefore, according to the production method of the present invention, the film quality of the power generation layer is improved, the power generation efficiency of the solar cell is increased, and the production efficiency is improved.
　また、本発明の第２態様の太陽電池の製造方法においては、前記第１発電セルを形成する成膜プロセスにおける最高温度は、前記第２発電セルを形成する成膜プロセスにおける最高温度と異なることが好ましい。
　また、本発明の第２態様の太陽電池の製造方法においては、前記第１発電セルを形成する成膜プロセス及び前記第２発電セルを形成する成膜プロセスにおいて、最も高い温度条件の範囲は２５０～４００℃であり、最も低い温度条件の範囲は１８０～２３０℃であることが好ましい。
　この方法によれば、第１発電セルの成膜プロセスにおける最高温度と、第２発電セルの成膜プロセスにおける最高温度とが異なる場合であっても、第１発電セル及び第２発電セルを作製する順序によらず、第１発電セルと第２発電セルとを重ね合わせることができる。即ち、第１発電セルの積層体及び第２発電セルの積層体の各々を製造する工程において、上記の成膜プロセスにおける温度条件の相違によって各セルの製造の順序が制限されることなく、良好な膜質を有する発電層を形成することができる。また、良好な膜質を有する発電層を含む第１発電セル及び第２発電セルを重ね合わせることができる。
　例えば、成膜プロセス中の最高温度が１８０～２３０℃であるアモルファスシリコンと、成膜プロセス中の最高温度が２５０～４００℃である微結晶シリコンとを積層する場合について説明する。この場合、先に形成されたアモルファスシリコン上に微結晶シリコンを積層すると、アモルファスシリコンの成膜温度よりも微結晶シリコンの成膜温度が高いので、アモルファスシリコン中に含まれる水素が微結晶シリコンを成膜する際のプロセス温度の上昇によって脱離する。この場合、アモルファスシリコンにおける変換効率が低下するおそれがある。
　これに対し、本発明の製造方法によれば、第１発電セル及び第２発電セルを別々に製造するため、各セルを製造する順序が制限されることがないうえ、微結晶シリコンセルの成膜プロセスにおける最高温度がアモルファスシリコンセルの性能に悪影響を及ぼさない。 In the method for manufacturing a solar cell according to the second aspect of the present invention, the maximum temperature in the film formation process for forming the first power generation cell is different from the maximum temperature in the film formation process for forming the second power generation cell. Is preferred.
In the method for manufacturing a solar cell according to the second aspect of the present invention, the highest temperature condition range is 250 in the film formation process for forming the first power generation cell and the film formation process for forming the second power generation cell. It is preferable that the range of the lowest temperature condition is 180 to 230 ° C.
According to this method, the first power generation cell and the second power generation cell are manufactured even when the maximum temperature in the film formation process of the first power generation cell is different from the maximum temperature in the film formation process of the second power generation cell. The first power generation cell and the second power generation cell can be overlapped regardless of the order in which they are performed. That is, in the process of manufacturing each of the first power generation cell stack and the second power generation cell stack, the order of manufacturing the cells is not limited due to the difference in temperature conditions in the film formation process, A power generation layer having an appropriate film quality can be formed. In addition, the first power generation cell and the second power generation cell including the power generation layer having good film quality can be overlapped.
For example, a case where amorphous silicon having a maximum temperature during the film forming process of 180 to 230 ° C. and microcrystalline silicon having a maximum temperature during the film forming process of 250 to 400 ° C. will be described. In this case, if microcrystalline silicon is stacked on the previously formed amorphous silicon, the deposition temperature of microcrystalline silicon is higher than the deposition temperature of amorphous silicon. Desorption occurs due to an increase in process temperature during film formation. In this case, the conversion efficiency in amorphous silicon may be reduced.
On the other hand, according to the manufacturing method of the present invention, since the first power generation cell and the second power generation cell are manufactured separately, the order of manufacturing the cells is not limited, and the formation of the microcrystalline silicon cell is not limited. The maximum temperature in the film process does not adversely affect the performance of the amorphous silicon cell.
　本発明の太陽電池によれば、第１発電セルと第２発電セルとの間に絶縁部が配置され、第１発電セル上に第２発電セルが積層されているので、第１発電セル及び第２発電セルの各々は、電気接続構造において独立した発電セルとして機能する。このため、第１発電セル及び第２発電セルの各々に流れる電流を独立して設定することができる。
　これにより、太陽光の光強度又はスペクトル等に関わらず、第１発電セル及び第２発電セルの各々の発電層に流れる電流が最大である時に出力されるエネルギーを取り出すことができる。そのため、第１発電セル及び第２発電セルの各々における最大出力を取り出すことができる。
　つまり、例えば、従来のタンデム型の太陽電池においては、発電量が小さい発電層の電気抵抗によってタンデム構造（直列回路）における電流量が決定され、発電量が大きい発電層から出力された電流に損失が生じるという問題がある。これに対し、本発明の太陽電池においては、複数の発電層の各々から出力される電流量が制限されず、複数の発電層の各々において最大の電流を得ながら発電することができる。従って、低電圧・大電流の太陽電池を実現することができ、発電効率の高い太陽電池を提供することができる。
　また、本発明の太陽電池の製造方法によれば、第１発電セル及び第２発電セルを個別に作製した後に、第１発電セル及び第２発電セルの間に絶縁部を配置するように第１発電セル及び第２発電セルを重ね合わせている。従って、第１発電セルに第２発電セルを重ね合わせる前に、第１発電セル及び第２発電セルの各々を構成する層（例えば、発電層）を最適な成膜条件において成膜することができる。
　つまり、第１発電セル及び第２発電セルの各々を構成する層（例えば、第１発電層及び第２発電層）を最適な成膜条件下において成膜することができる。これにより、良好な膜質を有する第１発電層及び第２発電層を形成することができる。
　従って、本発明の製造方法によれば、発電層の膜質が改善し、太陽電池の変換効率が増大し、製造効率が向上する。 According to the solar battery of the present invention, since the insulating portion is disposed between the first power generation cell and the second power generation cell, and the second power generation cell is stacked on the first power generation cell, the first power generation cell and Each of the second power generation cells functions as an independent power generation cell in the electrical connection structure. For this reason, the electric current which flows into each of the 1st power generation cell and the 2nd power generation cell can be set up independently.
Thereby, the energy output when the current flowing through each power generation layer of the first power generation cell and the second power generation cell is maximum can be extracted regardless of the light intensity or spectrum of sunlight. Therefore, the maximum output in each of the first power generation cell and the second power generation cell can be taken out.
That is, for example, in a conventional tandem solar cell, the amount of current in the tandem structure (series circuit) is determined by the electric resistance of the power generation layer with a small amount of power generation, and the current output from the power generation layer with a large amount of power generation is lost. There is a problem that occurs. On the other hand, in the solar cell of the present invention, the amount of current output from each of the plurality of power generation layers is not limited, and power can be generated while obtaining the maximum current in each of the plurality of power generation layers. Therefore, a solar cell with a low voltage and a large current can be realized, and a solar cell with high power generation efficiency can be provided.
In addition, according to the method for manufacturing a solar cell of the present invention, the first power generation cell and the second power generation cell are separately manufactured, and then the insulating portion is disposed between the first power generation cell and the second power generation cell. The 1 power generation cell and the second power generation cell are overlapped. Therefore, before the second power generation cell is overlaid on the first power generation cell, the layers (for example, the power generation layer) constituting each of the first power generation cell and the second power generation cell can be formed under optimum film formation conditions. it can.
That is, the layers (for example, the first power generation layer and the second power generation layer) constituting each of the first power generation cell and the second power generation cell can be formed under optimum film formation conditions. Thereby, the 1st electric power generation layer and the 2nd electric power generation layer which have favorable film quality can be formed.
Therefore, according to the manufacturing method of the present invention, the film quality of the power generation layer is improved, the conversion efficiency of the solar cell is increased, and the manufacturing efficiency is improved.
本発明の第１実施形態における太陽電池の断面図である。It is sectional drawing of the solar cell in 1st Embodiment of this invention. 本発明の第２実施形態における太陽電池の断面図である。It is sectional drawing of the solar cell in 2nd Embodiment of this invention. 本発明の第３実施形態における太陽電池の断面図である。It is sectional drawing of the solar cell in 3rd Embodiment of this invention. 本発明の第４実施形態における太陽電池の断面図である。It is sectional drawing of the solar cell in 4th Embodiment of this invention. 本発明の実施形態における太陽電池（セル１２）の製造方法を示す断面図である。It is sectional drawing which shows the manufacturing method of the solar cell (cell 12) in embodiment of this invention. 本発明の実施形態における太陽電池（セル１２）の製造方法を示す断面図である。It is sectional drawing which shows the manufacturing method of the solar cell (cell 12) in embodiment of this invention. 本発明の実施形態における太陽電池（セル１２）の製造方法を示す断面図である。It is sectional drawing which shows the manufacturing method of the solar cell (cell 12) in embodiment of this invention. 本発明の実施形態における太陽電池（セル２２）の製造方法を示す断面図である。It is sectional drawing which shows the manufacturing method of the solar cell (cell 22) in embodiment of this invention. 本発明の実施形態における太陽電池（セル２２）の製造方法を示す断面図である。It is sectional drawing which shows the manufacturing method of the solar cell (cell 22) in embodiment of this invention. 本発明の実施形態における太陽電池（セル２２）の製造方法を示す断面図である。It is sectional drawing which shows the manufacturing method of the solar cell (cell 22) in embodiment of this invention. 本発明の実施形態における太陽電池（セル２２）の製造方法を示す断面図である。It is sectional drawing which shows the manufacturing method of the solar cell (cell 22) in embodiment of this invention. 本発明の実施形態における太陽電池（セル２２）の製造方法を示す断面図である。It is sectional drawing which shows the manufacturing method of the solar cell (cell 22) in embodiment of this invention. 本発明の実施形態における太陽電池（セル４２）の製造方法を示す断面図である。It is sectional drawing which shows the manufacturing method of the solar cell (cell 42) in embodiment of this invention. 本発明の実施形態における太陽電池（セル４２）の製造方法を示す断面図である。It is sectional drawing which shows the manufacturing method of the solar cell (cell 42) in embodiment of this invention. 本発明の実施形態における太陽電池（セル４２）の製造方法を示す断面図である。It is sectional drawing which shows the manufacturing method of the solar cell (cell 42) in embodiment of this invention.
　以下、本発明に係る太陽電池及び太陽電池の製造方法の最良の形態について、図面に基づき説明する。
　また、以下の説明に用いる各図においては、各構成要素を図面上で認識し得る程度の大きさとするため、各構成要素の寸法及び比率を実際のものとは適宜に異ならせてある。 Hereinafter, the best mode of a solar cell and a method for manufacturing a solar cell according to the present invention will be described with reference to the drawings.
In the drawings used for the following description, the dimensions and ratios of the respective components are appropriately changed from the actual ones in order to make the respective components large enough to be recognized on the drawings.
（太陽電池）
（第１実施形態）
　図１は、本発明の第１実施形態における太陽電池を示す断面図である。
　図１に示すように、太陽電池１００は、基板１１上に形成された２つのセル１２，２２を含む。基板１１は、ガラス又は透明樹脂等、太陽光の透過性に優れ、かつ耐久性を有する絶縁材料で形成されている。第１実施形態の太陽電池１００においては、基板１１の一方の面、つまり基板１１におけるセル１２，２２が形成されていない面１１ａ（以下、表面１１ａと称する）に太陽光が入射する。即ち、表面１１ａは、太陽電池１００の受光面である。 (Solar cell)
(First embodiment)
FIG. 1 is a cross-sectional view showing a solar cell in the first embodiment of the present invention.
As shown in FIG. 1, the solar cell 100 includes two cells 12 and 22 formed on a substrate 11. The substrate 11 is formed of an insulating material having excellent sunlight permeability and durability such as glass or transparent resin. In solar cell 100 of the first embodiment, sunlight is incident on one surface of substrate 11, that is, surface 11 a (hereinafter referred to as surface 11 a) in which cells 12 and 22 are not formed on substrate 11. That is, the surface 11 a is a light receiving surface of the solar cell 100.
　セル１２は、本発明の第１発電セルに相当する。セル１２（以下、第１セル１２と称する）においては、基板１１上に受光面電極１３、発電層（第１発電層）１４、及び裏面電極１５が順次積層されている。受光面電極１３は、テクスチャ構造を有し、基板１１の他方の面（以下、裏面１１ｂと称する）上に形成されている。受光面電極１３は、光透過性を有する金属酸化物、例えば、ＧＺＯ又はＩＴＯ（Ｉｎｄｉｕｍ　Ｔｉｎ　Ｏｘｉｄｅ）等のいわゆるＴＣＯ（ｔｒａｎｓｐａｒｅｎｔ　ｃｏｎｄｕｃｔｉｖｅ　ｏｘｉｄｅ）からなる。 The cell 12 corresponds to the first power generation cell of the present invention. In the cell 12 (hereinafter referred to as the first cell 12), a light receiving surface electrode 13, a power generation layer (first power generation layer) 14, and a back electrode 15 are sequentially stacked on the substrate 11. The light-receiving surface electrode 13 has a texture structure and is formed on the other surface (hereinafter referred to as the back surface 11b) of the substrate 11. The light-receiving surface electrode 13 is made of a light-transmitting metal oxide, for example, a so-called TCO (transparent conductive oxide) such as GZO or ITO (Indium Tin Oxide).
　受光面電極１３上には、ｐｉｎ接合構造を有する発電層１４が形成されている。このｐｉｎ接合構造においては、例えば、ｐ型アモルファスシリコン（α－Ｓｉ）膜（不図示）とｎ型アモルファスシリコン膜（不図示）との間にｉ型アモルファスシリコン膜（不図示）が挟まれている。このｐｉｎ接合構造においては、受光面電極１３上にｐ型アモルファスシリコン膜、ｉ型アモルファスシリコン膜、及びｎ型アモルファスシリコン膜が順次積層されている。なお、発電層１４のバンドギャップ（光学的バンドギャップ）は、例えば、１．７ｅＶ程度である。このようなバンドギャップを有する材料としては、アモルファスシリコン膜の他に、アモルファスシリコンゲルマニウム（α－ＳｉＧｅ）膜等を用いることが可能である。裏面電極１５は、受光面電極１３が形成されている発電層１４の面とは反対の面上に積層されている。この裏面電極１５は、上述の受光面電極１３と同様にＴＣＯからなる。つまり、第１セル１２においては、光透過性を有する受光面電極１３及び裏面電極１５の間に、発電層１４が挟持されている。 A power generation layer 14 having a pin junction structure is formed on the light receiving surface electrode 13. In this pin junction structure, for example, an i-type amorphous silicon film (not shown) is sandwiched between a p-type amorphous silicon (α-Si) film (not shown) and an n-type amorphous silicon film (not shown). Yes. In this pin junction structure, a p-type amorphous silicon film, an i-type amorphous silicon film, and an n-type amorphous silicon film are sequentially stacked on the light-receiving surface electrode 13. The band gap (optical band gap) of the power generation layer 14 is, for example, about 1.7 eV. As a material having such a band gap, an amorphous silicon germanium (α-SiGe) film or the like can be used in addition to the amorphous silicon film. The back electrode 15 is laminated on a surface opposite to the surface of the power generation layer 14 on which the light receiving surface electrode 13 is formed. The back electrode 15 is made of TCO as with the light receiving surface electrode 13 described above. In other words, in the first cell 12, the power generation layer 14 is sandwiched between the light-receiving surface electrode 13 and the back surface electrode 15 having optical transparency.
　一方、セル２２は、本発明の第２発電セルに相当する。セル２２（以下、第２セル２２と称する）は、シリコン基板（第２発電層）２３，拡散層２４，反射防止膜２５，ＢＳＦ（Ｂａｃｋ　Ｓｕｒｆａｃｅ　Ｆｉｅｌｄ）層２６，第１裏面電極２７，第２裏面電極２８，及びグリッド電極２９を備えている。シリコン基板２３としては、単結晶シリコン又は多結晶シリコン中にホウ素（Ｂ），ガリウム（Ｇａ），アルミニウム（Ａｌ），インジウム（Ｉｎ）等のｐ型のドーパントが拡散されたｐ型の単結晶シリコン基板を用いることができる。また、単結晶シリコンまたは多結晶シリコン中にリン（Ｐ）、ヒ素（Ａｓ）、アンチモン（Ｓｂ）等のｎ型のドーパントが拡散されたｎ型の単結晶シリコン又は多結晶シリコン基板を用いることができる。このようなドーパントが拡散されたシリコン基板は、用途に応じて適宜選択され、使用される。シリコン基板２３の表面は、エッチング（テクスチャエッチング）によって形成された微小な凹凸形状を有するテクスチャ構造（図示略）が形成されている。シリコン基板２３としては、予めテクスチャが形成された基板を用いてもよい。また、テクスチャが形成されていない基板を用意し、ドライエッチングによりテクスチャを基板上に形成してもよい。 On the other hand, the cell 22 corresponds to the second power generation cell of the present invention. The cell 22 (hereinafter referred to as the second cell 22) includes a silicon substrate (second power generation layer) 23, a diffusion layer 24, an antireflection film 25, a BSF (Back Surface Field) layer 26, a first back electrode 27, a second A back electrode 28 and a grid electrode 29 are provided. As the silicon substrate 23, p-type single crystal silicon in which p-type dopants such as boron (B), gallium (Ga), aluminum (Al), and indium (In) are diffused in single crystal silicon or polycrystalline silicon. A substrate can be used. Alternatively, an n-type single crystal silicon or polycrystalline silicon substrate in which an n-type dopant such as phosphorus (P), arsenic (As), or antimony (Sb) is diffused in single crystal silicon or polycrystalline silicon is used. it can. The silicon substrate in which such a dopant is diffused is appropriately selected and used depending on the application. On the surface of the silicon substrate 23, a texture structure (not shown) having a minute uneven shape formed by etching (texture etching) is formed. As the silicon substrate 23, a substrate on which a texture is previously formed may be used. Alternatively, a substrate on which no texture is formed may be prepared, and the texture may be formed on the substrate by dry etching.
　ここで、シリコン基板２３のバンドギャップ（光学的バンドギャップ）は、発電層１４のバンドギャップより小さく、例えば、１．１ｅＶ程度である。つまり、セル１２を構成する発電層１４のバンドギャップは、セル２２を構成するシリコン基板２３のバンドギャップよりも大きい。即ち、基板１１の厚さ方向に積層された複数の発電層のうち、太陽光が入射される基板１１に近い位置に配置されたセル（例えば、第１セル１２）を構成する発電層（例えば、発電層１４）のバンドギャップは、基板１１から遠い位置に配置されたセル（例えば、第２セル２２）を構成する発電層（例えば、シリコン基板２３）のバンドギャップよりも大きい。さらに、複数の発電層が配置されている複数位置のうち、基板１１の厚さ方向に沿って、基板１１から最も遠い位置（最下層）に配置される発電層（例えば、シリコン基板２３）の構成材料のバンドギャップは、例えば、１．３ｅＶ以下であることが好ましい。 Here, the band gap (optical band gap) of the silicon substrate 23 is smaller than the band gap of the power generation layer 14 and is, for example, about 1.1 eV. That is, the band gap of the power generation layer 14 constituting the cell 12 is larger than the band gap of the silicon substrate 23 constituting the cell 22. That is, among the plurality of power generation layers stacked in the thickness direction of the substrate 11, a power generation layer (for example, the first cell 12) (for example, the first cell 12) disposed at a position close to the substrate 11 on which sunlight is incident. The band gap of the power generation layer 14) is larger than the band gap of the power generation layer (for example, the silicon substrate 23) constituting the cell (for example, the second cell 22) disposed at a position far from the substrate 11. Furthermore, among the multiple positions where the multiple power generation layers are arranged, the power generation layer (for example, the silicon substrate 23) arranged at the position farthest from the substrate 11 (lowermost layer) along the thickness direction of the substrate 11 The band gap of the constituent material is preferably 1.3 eV or less, for example.
　拡散層２４は、シリコン基板２３がｐ型のシリコン基板である場合においては、リン（Ｐ），ヒ素（Ａｓ），アンチモン（Ｓｂ）等のｎ型のドーパントがシリコン基板２３の表面近傍に拡散された薄厚の層である。また、拡散層２４は、シリコン基板２３がｎ型のシリコン基板である場合においては、ホウ素（Ｂ），ガリウム（Ｇａ），アルミニウム（Ａｌ），インジウム（Ｉｎ）等のｐ型のドーパントがシリコン基板２３の表面近傍に拡散された薄厚の層である。 In the diffusion layer 24, when the silicon substrate 23 is a p-type silicon substrate, n-type dopants such as phosphorus (P), arsenic (As), and antimony (Sb) are diffused near the surface of the silicon substrate 23. It is a thin layer. Further, when the silicon substrate 23 is an n-type silicon substrate, the diffusion layer 24 has a p-type dopant such as boron (B), gallium (Ga), aluminum (Al), indium (In), etc. 23 is a thin layer diffused in the vicinity of the surface 23.
　反射防止膜２５の構造としては、高屈折率の膜と低屈折率の膜が積層された多層からなる多層構造、又は単層構造が採用される。反射防止膜２５が多層構造を有する場合、多層構造を構成する膜の材料としては、例えば、屈折率が１．０～４．０の窒化珪素（ＳｉＮｘ），酸化チタン（ＴｉＯ２），酸化ニオブ（Ｎｂ２Ｏ５），フッ化マグネシウム（ＭｇＦ２），酸化マグネシウム（ＭｇＯ），酸化ケイ素（ＳｉＯ２）等が好適に用いられる。また、反射防止膜２５が単層構造を有する場合、例えば、拡散層２４上にＣＶＤ法により成膜された窒化珪素（ＳｉＮｘ）等の透明材料からなる膜が用いられる。また、シリコン基板２３がｐ型のシリコン基板である場合においては、リン（Ｐ），ヒ素（Ａｓ），アンチモン（Ｓｂ）等のｎ型のドーパントが、単層構造を形成する反射防止膜２５の膜に含まれている。また、シリコン基板２３がｎ型のシリコン基板である場合においては、ホウ素（Ｂ），ガリウム（Ｇａ），アルミニウム（Ａｌ）等のｐ型のドーパントが、単層構造を形成する反射防止膜２５の膜に含まれている。なお、ファイヤスループロセスを行う場合には、窒化珪素（ＳｉＮｘ）、酸化チタン（ＴｉＯ２）が好適に用いられる。 As the structure of the antireflection film 25, a multilayer structure composed of a multilayer in which a high refractive index film and a low refractive index film are laminated, or a single layer structure is adopted. When the antireflection film 25 has a multilayer structure, examples of the material of the film constituting the multilayer structure include silicon nitride (SiNx), titanium oxide (TiO 2 ), and niobium oxide having a refractive index of 1.0 to 4.0. (Nb 2 O 5 ), magnesium fluoride (MgF 2 ), magnesium oxide (MgO), silicon oxide (SiO 2 ) and the like are preferably used. When the antireflection film 25 has a single layer structure, for example, a film made of a transparent material such as silicon nitride (SiNx) formed on the diffusion layer 24 by a CVD method is used. When the silicon substrate 23 is a p-type silicon substrate, n-type dopants such as phosphorus (P), arsenic (As), and antimony (Sb) are used to form the antireflection film 25 that forms a single layer structure. Contained in the membrane. When the silicon substrate 23 is an n-type silicon substrate, p-type dopants such as boron (B), gallium (Ga), and aluminum (Al) are used to form the antireflection film 25 that forms a single layer structure. Contained in the membrane. In the case of performing the fire-through process, silicon nitride (SiNx) and titanium oxide (TiO 2 ) are preferably used.
　拡散層２４は、反射防止膜２５を熱処理することにより、この反射防止膜２５に含まれるドーパントをシリコン基板２３の表面に拡散させることによって得られている。この拡散層２４のドーパント濃度は、太陽電池１００に必要なｐｎ接合が生じるように決められる。例えば、拡散層２４のドーパント濃度は、反射防止膜２５から拡散量により決まるので、拡散後の反射防止膜２５のドーパント濃度よりも拡散層２４のドーパント濃度が低くなる場合が多い。通常、成膜される反射防止膜２５のドーパント濃度は、拡散層２４に要求されるドーパント濃度より高めに設定される。但し、ドーパント濃度の設定方法は上記の方法に限定されない。シリコンと反射防止膜２５の間での拡散の平衡状態に起因して、拡散工程の前では反射防止膜２５のドーパント濃度が拡散層２４のドーパント濃度よりも高くても、拡散工程の後では反射防止膜２５のドーパント濃度が拡散層２４のドーパント濃度よりも低くなる場合もある。 The diffusion layer 24 is obtained by diffusing the dopant contained in the antireflection film 25 on the surface of the silicon substrate 23 by heat-treating the antireflection film 25. The dopant concentration of the diffusion layer 24 is determined so that a pn junction necessary for the solar cell 100 is generated. For example, since the dopant concentration of the diffusion layer 24 is determined by the amount of diffusion from the antireflection film 25, the dopant concentration of the diffusion layer 24 is often lower than the dopant concentration of the antireflection film 25 after diffusion. Usually, the dopant concentration of the antireflection film 25 to be formed is set higher than the dopant concentration required for the diffusion layer 24. However, the method for setting the dopant concentration is not limited to the above method. Due to the equilibrium state of diffusion between the silicon and the antireflection film 25, even if the dopant concentration of the antireflection film 25 is higher than the dopant concentration of the diffusion layer 24 before the diffusion step, the reflection is not caused after the diffusion step. In some cases, the dopant concentration of the prevention film 25 is lower than the dopant concentration of the diffusion layer 24.
　ＢＳＦ層２６は、第１裏面電極２７及び第２裏面電極２８等の構成材料が熱処理によりシリコン基板２３に拡散して形成された薄厚の層である。例えば、ｐ型のシリコン基板２３の裏面にアルミニウムを含む第１裏面電極２７及び第２裏面電極２８を形成し、その後、熱処理によってアルミニウムをシリコン基板２３に拡散させることによってＢＳＦ層２６は形成される。第１裏面電極２７，第２裏面電極２８，及びグリッド電極２９は、銀、アルミニウム等の導電性金属を含むペーストを焼成することによって得られる金属電極である。第２裏面電極２８は、シリコン基板２３の裏面の中央部を横断するように設けられ、帯状に形成されている。第１裏面電極２７は、第２裏面電極２８を挟むように第２裏面電極２８の両側に設けられ、矩形状に形成されている。 The BSF layer 26 is a thin layer formed by diffusing constituent materials such as the first back electrode 27 and the second back electrode 28 into the silicon substrate 23 by heat treatment. For example, the first back electrode 27 and the second back electrode 28 containing aluminum are formed on the back surface of the p-type silicon substrate 23, and then the BSF layer 26 is formed by diffusing aluminum into the silicon substrate 23 by heat treatment. . The 1st back electrode 27, the 2nd back electrode 28, and the grid electrode 29 are metal electrodes obtained by baking the paste containing electroconductive metals, such as silver and aluminum. The second back electrode 28 is provided so as to cross the central portion of the back surface of the silicon substrate 23 and is formed in a strip shape. The first back electrode 27 is provided on both sides of the second back electrode 28 so as to sandwich the second back electrode 28, and is formed in a rectangular shape.
　グリッド電極２９は、反射防止膜２５上に、シリコン基板２３の面に平行な方向に沿って形成されている。このグリッド電極２９は、いわゆるファイヤスループロセスを用いてシリコン基板２３と接続されている。具体的に、グリッド電極２９の形成方法においては、まず、反射防止膜２５上に所定のパターンを有する銀ペーストが塗布される。次に、銀ペーストを焼成する。その後、焼成によって形成された銀電極は、反射防止膜２５を貫通し、拡散層２４と接触し、シリコン基板２３に接続されている。基板１１の表面１１ａに入射して第１セル１２を透過した太陽光は、グリッド電極２９間の隙間（開口部）を通ってシリコン基板２３に入射する。なお、グリッド電極２９の構成材料としては、ＴＣＯ等の光透過性を有する金属酸化物を採用してもよい。上記の拡散層２４を形成する熱処理と、ＢＳＦ層２６を形成する熱処理と、グリッド電極２９を形成する熱処理（ファイヤスループロセス）とを個別に行うことができるが、これら複数の処理工程のうちの２工程もしくは全工程を同時に行えば、工程数及び処理時間を短縮することができ、処理装置の個数を削減することができる。 The grid electrode 29 is formed on the antireflection film 25 along a direction parallel to the surface of the silicon substrate 23. The grid electrode 29 is connected to the silicon substrate 23 using a so-called fire-through process. Specifically, in the method of forming the grid electrode 29, first, a silver paste having a predetermined pattern is applied on the antireflection film 25. Next, the silver paste is fired. Thereafter, the silver electrode formed by baking penetrates the antireflection film 25, contacts the diffusion layer 24, and is connected to the silicon substrate 23. The sunlight that has entered the surface 11 a of the substrate 11 and has passed through the first cell 12 enters the silicon substrate 23 through a gap (opening) between the grid electrodes 29. In addition, as a constituent material of the grid electrode 29, a metal oxide having optical transparency such as TCO may be adopted. The heat treatment for forming the diffusion layer 24, the heat treatment for forming the BSF layer 26, and the heat treatment for forming the grid electrode 29 (fire-through process) can be performed individually. If two steps or all steps are performed simultaneously, the number of steps and the processing time can be reduced, and the number of processing apparatuses can be reduced.
　第１セル１２の裏面電極１５と第２セル２２のグリッド電極２９との間には、絶縁部３０が形成されている。この絶縁部３０は、第１セル１２と、第２セル２２との間を電気的に絶縁する。絶縁部３０は、裏面電極１５とグリッド電極２９との間の全面に設けられ、グリッド電極２９間の隙間（開口部）を絶縁部の構成材料で満たすように形成されている。絶縁部３０の構成材料は、絶縁性を有しかつ透明性を有する材料である。このような材料としては、例えば、ＳｉＯ２，ＵＶ硬化性樹脂等のペースト材料，絶縁性を有する接着シート等が好適に用いられる。 An insulating part 30 is formed between the back electrode 15 of the first cell 12 and the grid electrode 29 of the second cell 22. The insulating unit 30 electrically insulates between the first cell 12 and the second cell 22. The insulating part 30 is provided on the entire surface between the back electrode 15 and the grid electrode 29, and is formed so as to fill the gap (opening) between the grid electrodes 29 with the constituent material of the insulating part. The constituent material of the insulating part 30 is a material having insulating properties and transparency. As such a material, for example, a paste material such as SiO 2 or a UV curable resin, an adhesive sheet having an insulating property, or the like is preferably used.
　このように、第１実施形態の太陽電池１００においては、第１セル１２と第２セル２２との間に絶縁部３０が挟まれており、第１セル１２が第２セル２２から電気的に絶縁されるように第１セル１２及び第２セル２２が積層されている。また、第１実施形態の太陽電池１００においては、セル１２，２２の各々の端部において、セル１２，２２は互いに電気的に並列に接続されている。また、第１実施形態の太陽電池１００は、電気的に区画され、所定のサイズを有する複数の区画素子を有する。セル１２，２２は、複数の区画素子の各々に形成されている。互いに隣接する区画素子は、電気的に直列に接続（いわゆる集積構造）されている。また、セル１２，２２の各々には、個別の保護回路（不図示）が設けられている。セル１２，２２の各々に過電圧が印加された時に、過電流はセル１２，２２の各々へ流れず、保護回路に流れる。これにより、セル１２，２２の各々の電気回路の故障を防ぐことができる。 As described above, in the solar cell 100 of the first embodiment, the insulating unit 30 is sandwiched between the first cell 12 and the second cell 22, and the first cell 12 is electrically connected to the second cell 22. The first cell 12 and the second cell 22 are stacked so as to be insulated. Moreover, in the solar cell 100 of 1st Embodiment, the cells 12 and 22 are mutually electrically connected in parallel in each edge part of the cells 12 and 22. FIG. The solar cell 100 of the first embodiment has a plurality of partition elements that are electrically partitioned and have a predetermined size. The cells 12 and 22 are formed in each of a plurality of partition elements. The partition elements adjacent to each other are electrically connected in series (so-called integrated structure). Each of the cells 12 and 22 is provided with a separate protection circuit (not shown). When an overvoltage is applied to each of the cells 12 and 22, the overcurrent does not flow to each of the cells 12 and 22, but flows to the protection circuit. Thereby, failure of each electric circuit of cells 12 and 22 can be prevented.
　なお、上述のセル１２，２２の各々においては、上述の複数層の各々の表面及び裏面に微小凹凸が形成されたテクスチャ構造（不図示）が設けられていることが好ましい。この場合、各層に入射された太陽光の光路を伸ばすプリズム効果と、光を閉じ込める効果を達成することができるため、太陽電池１００における光エネルギーの変換効率を向上させることができる。 In addition, in each of the above-described cells 12 and 22, it is preferable that a texture structure (not shown) in which minute irregularities are formed on the front and back surfaces of each of the plurality of layers described above is provided. In this case, since the prism effect that extends the optical path of sunlight incident on each layer and the effect of confining light can be achieved, the conversion efficiency of light energy in the solar cell 100 can be improved.
　このような太陽電池１００においては、基板１１の表面１１ａ（入射面）に太陽光が照射され、太陽光は基板１１を透過し、太陽光は第１セル１２，２２に向けて入射される。そして、第１セル１２に入射される太陽光に含まれる短波長域の光（例えば、７３０ｎｍ未満の波長の光）は、第１セル１２の発電層１４内で吸収される。この時、太陽光に含まれるエネルギー粒子がｉ型アモルファスシリコン膜に当たると、光起電力効果により、電子とホールとが発生する。電子はｎ型アモルファスシリコン膜に向かって移動し、ホールはｐ型アモルファスシリコン膜に向かって移動する。電子及びホールが受光面電極１３及び裏面電極１５によって取り出され、光エネルギーを電気エネルギーに変換することができる（光電変換）。 In such a solar cell 100, the surface 11a (incident surface) of the substrate 11 is irradiated with sunlight, the sunlight is transmitted through the substrate 11, and the sunlight is incident on the first cells 12 and 22. Then, light in a short wavelength region (for example, light having a wavelength of less than 730 nm) included in sunlight incident on the first cell 12 is absorbed in the power generation layer 14 of the first cell 12. At this time, when energetic particles contained in sunlight hit the i-type amorphous silicon film, electrons and holes are generated due to the photovoltaic effect. Electrons move toward the n-type amorphous silicon film, and holes move toward the p-type amorphous silicon film. Electrons and holes are extracted by the light-receiving surface electrode 13 and the back surface electrode 15, and light energy can be converted into electrical energy (photoelectric conversion).
　一方、第１セル１２においてエネルギーに変換されなかった光、つまり高波長域の光（例えば、９５０ｎｍ以上の波長の光）は、第１セル１２及び絶縁部３０を透過して第２セル２２に入射する。第２セル２２に入射された太陽光は、グリッド電極２９間の隙間を通ってシリコン基板２３内で吸収される。この時、上述の発電層１４と同様に、シリコン基板２３に太陽光が入射し、太陽光に含まれるエネルギー粒子がｉ型単結晶シリコン膜に当たると、光起電力効果により、電子とホールとが発生する。電子はｎ型単結晶シリコン膜、ホールはｐ型単結晶シリコン膜に向かって移動する。電子及びホールがグリッド電極２９及び第１裏面電極２７及び第２裏面電極２８により取り出され、光エネルギーを電気エネルギーに変換することができる。 On the other hand, light that has not been converted into energy in the first cell 12, that is, light in a high wavelength region (for example, light having a wavelength of 950 nm or more) is transmitted through the first cell 12 and the insulating unit 30 to the second cell 22. Incident. Sunlight incident on the second cell 22 is absorbed in the silicon substrate 23 through the gap between the grid electrodes 29. At this time, similarly to the power generation layer 14 described above, when sunlight enters the silicon substrate 23 and energy particles contained in the sunlight hit the i-type single crystal silicon film, electrons and holes are generated due to the photovoltaic effect. appear. Electrons move toward the n-type single crystal silicon film and holes move toward the p-type single crystal silicon film. Electrons and holes are extracted by the grid electrode 29, the first back electrode 27, and the second back electrode 28, and light energy can be converted into electrical energy.
　そして、セル１２，２２の各々において取り出されたエネルギーは、それぞれ電気回路（不図示）を介して取り出される。この場合、基板１１の厚さ方向に沿って配置されている複数の発電層の位置のうち、基板１１から最も遠い位置に配置される発電層（例えば、シリコン基板２３）の構成材料のバンドギャップは、１．３ｅＶ以下である。この構成によれば、基板１１に近い位置（入射側）に配置された発電層（例えば、発電層１４）において取り出すことができない長波長域の光を利用し、発電することができる。即ち、太陽光の入射方向に積層された複数の発電層において、基板１１（入射側）に近い位置に配置される発電層（例えば、発電層１４）は短波長域の光を利用して発電し、基板１１から離れた位置に配置される発電層（例えば、シリコン基板２３）は長波長域の光を利用して発電する。このように、複数の発電層において発電層の各々が吸収する波長領域が互いに異なっている構造においては、広い波長域において太陽光のエネルギーを取り出すことができる。従って、本発明に係る太陽電池１００は、太陽光のエネルギーを無駄なく利用することができ、発電効率を向上することができる。 The energy extracted in each of the cells 12 and 22 is extracted via an electric circuit (not shown). In this case, the band gap of the constituent material of the power generation layer (for example, the silicon substrate 23) disposed farthest from the substrate 11 among the positions of the plurality of power generation layers disposed along the thickness direction of the substrate 11. Is 1.3 eV or less. According to this configuration, it is possible to generate power using light in a long wavelength region that cannot be extracted in a power generation layer (for example, the power generation layer 14) disposed near the substrate 11 (incident side). That is, in a plurality of power generation layers stacked in the sunlight incident direction, the power generation layer (for example, the power generation layer 14) disposed near the substrate 11 (incident side) generates power using light in a short wavelength region. The power generation layer (for example, the silicon substrate 23) disposed at a position away from the substrate 11 generates power using light in a long wavelength region. As described above, in the structure in which the wavelength regions absorbed by the power generation layers in the plurality of power generation layers are different from each other, it is possible to extract sunlight energy in a wide wavelength range. Therefore, the solar cell 100 according to the present invention can use the energy of sunlight without waste, and can improve the power generation efficiency.
　上述の第１実施形態においては、第１セル１２と第２セル２２との間に絶縁部３０が挟持された構成が採用されている。この構成によれば、絶縁部３０を挟んでセル１２，２２が積層され、セル１２，２２の各々は、独立したセルとして機能する。このため、セル１２，２２の各々に流れる電流量をそれぞれ独立して設定することができる。この構成により、太陽光の光強度又はスペクトル等に関わらず、セル１２の発電層１４及びセル２２のシリコン基板２３に流れる電流が最大である時に出力されるエネルギーを取り出すことができる。そのため、セル１２，２２の各々における最大出力を得ることができる。つまり、従来のタンデム型の太陽電池のように発電層の各々が直列に接続されている構造に比べて、第１実施形態の２つの発電層の各々において十分な電流量を得ることができる。具体的に、複数の発電層が直列に接続されている構造においては、発電量が小さい発電層の電気抵抗によってタンデム構造（直列回路）における電流量が決定され、発電量が大きい発電層から出力された電流に損失が生じるという問題がある。これに対し、第１実施形態の太陽電池においては、発電層１４及びシリコン基板２３の各々から出力される電流量が制限されず、複数の発電層の各々において最大の電流を得ながら発電することができる。従って、低電圧・大電流の太陽電池１００を実現することができ、発電効率の高い太陽電池１００を提供することができる。 In the above-described first embodiment, a configuration in which the insulating unit 30 is sandwiched between the first cell 12 and the second cell 22 is employed. According to this configuration, the cells 12 and 22 are stacked with the insulating portion 30 interposed therebetween, and each of the cells 12 and 22 functions as an independent cell. For this reason, the amount of current flowing through each of the cells 12 and 22 can be set independently. With this configuration, energy output when the current flowing through the power generation layer 14 of the cell 12 and the silicon substrate 23 of the cell 22 is maximum can be extracted regardless of the light intensity or spectrum of sunlight. Therefore, the maximum output in each of the cells 12 and 22 can be obtained. That is, a sufficient amount of current can be obtained in each of the two power generation layers of the first embodiment as compared to a structure in which each of the power generation layers is connected in series as in a conventional tandem solar cell. Specifically, in a structure in which multiple power generation layers are connected in series, the amount of current in the tandem structure (series circuit) is determined by the electrical resistance of the power generation layer with a small amount of power generation, and output from the power generation layer with a large amount of power generation There is a problem in that a loss occurs in the generated current. In contrast, in the solar cell of the first embodiment, the amount of current output from each of the power generation layer 14 and the silicon substrate 23 is not limited, and power is generated while obtaining the maximum current in each of the plurality of power generation layers. Can do. Therefore, the solar cell 100 with a low voltage and a large current can be realized, and the solar cell 100 with high power generation efficiency can be provided.
　また、セル１２，２２の各々が電気的に並列に接続されているので、発電層１４に流れる電流とシリコン基板２３に流れる電流とを一致させる必要がない。このため、セル１２，２２の各々における発電に伴う電流量を異ならせることができる。従って、発電層１４及びシリコン基板２３（発電層）のうち、発電量が小さい発電層の電気抵抗によって両者に流れる電流量は決定されない。即ち、発電量が大きい発電層から出力された電流に損失は生じず、電流量が制限されることを防止することができる。また、セル１２，２２の各々が並列に接続されているので、例えば、複数のセル１２，２２のうち、１つのセル（例えば、第１セル１２）のみに不具合が生じて電流が流れない場合であっても、他のセル（例えば、第２セル２２）には正常に電流が流れる。さらに、セル１２，２２の各々に保護回路が接続されているので、セル１２，２２のうち１つのセル（例えば、第１セル１２）に過電圧が印加された時に、セルのみに流れる電流を保護回路に流すことができ、セルの故障を防ぐことができる。つまり、１つのセルにおいて生じた不具合が、全体のセルの作動状態に影響を及ぼすことがないため、太陽電池１００の発電効率を維持することができる。 In addition, since each of the cells 12 and 22 is electrically connected in parallel, it is not necessary to match the current flowing through the power generation layer 14 with the current flowing through the silicon substrate 23. For this reason, the amount of current accompanying power generation in each of the cells 12 and 22 can be varied. Therefore, the amount of current flowing through the power generation layer 14 and the silicon substrate 23 (power generation layer) is not determined by the electrical resistance of the power generation layer with a small power generation amount. That is, no loss occurs in the current output from the power generation layer where the power generation amount is large, and it is possible to prevent the current amount from being limited. In addition, since each of the cells 12 and 22 is connected in parallel, for example, when a failure occurs in only one cell (for example, the first cell 12) of the plurality of cells 12 and 22, no current flows. Even so, the current normally flows through other cells (for example, the second cell 22). Further, since a protection circuit is connected to each of the cells 12 and 22, when an overvoltage is applied to one of the cells 12 and 22 (for example, the first cell 12), a current flowing only in the cell is protected. It is possible to flow through the circuit, and cell failure can be prevented. That is, since the malfunction that has occurred in one cell does not affect the operating state of the entire cell, the power generation efficiency of the solar battery 100 can be maintained.
（第２実施形態）
　次に、本発明の第２実施形態について説明する。
　図２は、第２実施形態における太陽電池の断面図である。
　第２実施形態においては、第１実施形態と同一部材には同一符号を付して、その説明は省略または簡略化する。
　第２実施形態においては、第２セルの発電層として、ＣｕＩｎＳｅ２膜が用いられている。この構造は、上述の第１実施形態の構造と相違している。図２に示すように、第２実施形態の太陽電池２００においては、一対の基板１１，４１（以下、第１基板１１及び第２基板４１と称する）の間に、２つのセル１２，４２が挟持されている。第１セル１２においては、第１基板１１上に形成された受光面電極１３，発電層（以下、第１発電層と称する）１４，及び裏面電極１５が順次に積層されている。第１セル１２の構造は、上述の第１実施形態の構造と同じである。また、第１基板１１の裏面１１ｂは、第２基板４１に対向している。 (Second Embodiment)
Next, a second embodiment of the present invention will be described.
FIG. 2 is a cross-sectional view of the solar cell in the second embodiment.
In the second embodiment, the same members as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted or simplified.
In the second embodiment, a CuInSe 2 film is used as the power generation layer of the second cell. This structure is different from the structure of the first embodiment described above. As shown in FIG. 2, in the solar cell 200 of the second embodiment, two cells 12 and 42 are provided between a pair of substrates 11 and 41 (hereinafter referred to as the first substrate 11 and the second substrate 41). It is pinched. In the first cell 12, a light-receiving surface electrode 13, a power generation layer (hereinafter referred to as a first power generation layer) 14, and a back electrode 15 formed on the first substrate 11 are sequentially stacked. The structure of the first cell 12 is the same as the structure of the first embodiment described above. Further, the back surface 11 b of the first substrate 11 faces the second substrate 41.
　セル４２は、本発明の第２発電セルに相当する。セル４２（以下、第２セル４２と称する）においては、ガラス又は透明樹脂等からなる第２基板４１上に裏面電極４５，第２発電層４４，及びグリッド電極（受光面電極）４３が順次積層されている。第２基板４１は、第１基板１１の裏面１１ｂに対向する対向面４１ａ（以下、表面４１ａと称する）を有する。裏面電極４５は、表面４１ａ上に形成され、Ａｇ、Ａｌ、Ｃｕ等の比較的高い導電率及び反射率を有する金属膜からなる。また、裏面電極４５は、例えば、低温焼成型ナノインクメタル（Ａｇ）を用いて形成されている。また、裏面電極４５は、セル１２，４２を透過した太陽光を反射させ、セル１２の発電層１４及びセル４２の発電層４４に太陽光を再び供給する反射層としても機能する。 The cell 42 corresponds to the second power generation cell of the present invention. In the cell 42 (hereinafter referred to as the second cell 42), a back electrode 45, a second power generation layer 44, and a grid electrode (light receiving surface electrode) 43 are sequentially stacked on a second substrate 41 made of glass or transparent resin. Has been. The second substrate 41 has a facing surface 41 a (hereinafter referred to as the front surface 41 a) that faces the back surface 11 b of the first substrate 11. The back electrode 45 is formed on the front surface 41a and is made of a metal film having a relatively high conductivity and reflectivity such as Ag, Al, and Cu. The back electrode 45 is formed using, for example, a low-temperature firing nano ink metal (Ag). The back electrode 45 also functions as a reflective layer that reflects sunlight transmitted through the cells 12 and 42 and supplies the sunlight again to the power generation layer 14 of the cell 12 and the power generation layer 44 of the cell 42.
　裏面電極４５上には、第２発電層４４が形成されている。この第２発電層４４は、例えば、ｐ型ＣｕＩｎＳｅ２膜（不図示）及びｎ型ＣｕＩｎＳｅ２膜（不図示）からなるｐｎ接合構造を有する。第２発電層４４においては、裏面電極４５上にｎ型ＣｕＩｎＳｅ２膜及びｐ型ＣｕＩｎＳｅ２膜が順次積層されている。第２発電層４４のバンドギャップ（光学的バンドギャップ）は、第１発電層１４のバンドギャップより小さく、例えば、１．０４ｅＶ程度である。 A second power generation layer 44 is formed on the back electrode 45. The second power generation layer 44 has a pn junction structure made of, for example, a p-type CuInSe 2 film (not shown) and an n-type CuInSe 2 film (not shown). In the second power generation layer 44, an n-type CuInSe 2 film and a p-type CuInSe 2 film are sequentially stacked on the back electrode 45. The band gap (optical band gap) of the second power generation layer 44 is smaller than the band gap of the first power generation layer 14 and is, for example, about 1.04 eV.
　第２発電層４４上には、第２発電層４４の面に平行な方向に沿って格子状に形成されたグリッド電極４３が配置されている。このグリッド電極４３は、裏面電極４５と同じ材料で形成されており、基板１１の表面１１ａに入射して第１セル１２を透過した太陽光は、グリッド電極４３間の隙間（開口部）を通って第２発電層４４に入射する。なお、グリッド電極４３の構成材料としては、ＴＣＯ等の光透過性を有する金属酸化物を採用することも可能である。 On the second power generation layer 44, grid electrodes 43 formed in a lattice shape along a direction parallel to the surface of the second power generation layer 44 are arranged. The grid electrode 43 is formed of the same material as that of the back electrode 45, and sunlight that has entered the front surface 11 a of the substrate 11 and transmitted through the first cell 12 passes through a gap (opening) between the grid electrodes 43. Incident on the second power generation layer 44. In addition, as a constituent material of the grid electrode 43, it is also possible to employ a metal oxide having optical transparency such as TCO.
　ここで、第１セル１２の裏面電極１５と第２セル４２のグリッド電極４３との間には、上述の第１実施形態と同じ絶縁部３０が形成されている。この絶縁部３０を介して第１セル１２と第２セル４２とが貼り合わされている。このように、第２実施形態の太陽電池２００においては、絶縁部３０を挟持するように第１セル１２及び第２セル４２が積層されており、第１セル１２と第２セル４２とは電気的に絶縁されている。そして、セル１２，４２の各々の端部において、セル１２，４２は互いに電気的に並列に接続されている。 Here, between the back electrode 15 of the first cell 12 and the grid electrode 43 of the second cell 42, the same insulating portion 30 as that in the first embodiment is formed. The first cell 12 and the second cell 42 are bonded together via the insulating part 30. Thus, in the solar cell 200 of the second embodiment, the first cell 12 and the second cell 42 are stacked so as to sandwich the insulating portion 30, and the first cell 12 and the second cell 42 are electrically connected. Is electrically insulated. And in each edge part of the cells 12 and 42, the cells 12 and 42 are mutually electrically connected in parallel.
　従って、第２実施形態によれば、上述の第１実施形態と同様の効果が得られる。また、第２発電層４４にＣｕＩｎＳｅ２膜が用いられているので、上述の結晶シリコンからなるシリコン基板２３（図１参照）が発電層として用いられている場合に比べ、バンドギャップを狭くすることができる。従って、長波長域の光がより一層取り出し易くなるため、太陽電池２００の発電効率を向上することができる。 Therefore, according to the second embodiment, an effect similar to that of the first embodiment described above can be obtained. Further, since the CuInSe 2 film is used for the second power generation layer 44, the band gap is made narrower than when the silicon substrate 23 (see FIG. 1) made of crystalline silicon is used as the power generation layer. Can do. Therefore, since it becomes easier to take out light in the long wavelength region, the power generation efficiency of the solar cell 200 can be improved.
（第２実施形態の変形例）
　次に、本発明の第２実施形態の変形例について説明する。
　第２実施形態の変形例においては、第１実施形態と同一部材には同一符号を付して、その説明は省略または簡略化する。
　第２実施形態の変形例においては、第２セルの発電層として、Ｃｕ２Ｓ膜が用いられている。この構造は、上述の第１実施形態の構造と相違している。図２に示すように、第２実施形態の変形例の太陽電池２００においては、一対の基板１１，４１（以下、第１基板１１及び第２基板４１と称する）の間に、２つのセル１２，４２が挟持されている。第１セル１２においては、第１基板１１上に形成された受光面電極１３，発電層（以下、第１発電層と称する）１４，及び裏面電極１５が順次に積層されている。第１セル１２の構造は、上述の第１実施形態の構造と同じである。また、第１基板１１の裏面１１ｂは、第２基板４１に対向している。 (Modification of the second embodiment)
Next, a modification of the second embodiment of the present invention will be described.
In the modification of the second embodiment, the same members as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted or simplified.
In the modification of the second embodiment, a Cu 2 S film is used as the power generation layer of the second cell. This structure is different from the structure of the first embodiment described above. As shown in FIG. 2, in the solar cell 200 according to the modification of the second embodiment, two cells 12 are interposed between a pair of substrates 11 and 41 (hereinafter referred to as the first substrate 11 and the second substrate 41). , 42 are sandwiched. In the first cell 12, a light-receiving surface electrode 13, a power generation layer (hereinafter referred to as a first power generation layer) 14, and a back electrode 15 formed on the first substrate 11 are sequentially stacked. The structure of the first cell 12 is the same as the structure of the first embodiment described above. Further, the back surface 11 b of the first substrate 11 faces the second substrate 41.
　セル４２は、本発明の第２発電セルに相当する。セル４２（以下、第２セル４２と称する）においては、ガラス又は透明樹脂等からなる第２基板４１上に裏面電極４５，第２発電層４４，及びグリッド電極（受光面電極）４３が順次積層されている。第２基板４１は、第１基板１１の裏面１１ｂに対向する対向面４１ａ（以下、表面４１ａと称する）を有する。裏面電極４５は、表面４１ａ上に形成され、Ａｇ、Ａｌ、Ｃｕ等の比較的高い導電率及び反射率を有する金属膜からなる。また、裏面電極４５は、例えば、低温焼成型ナノインクメタル（Ａｇ）を用いて形成されている。また、裏面電極４５は、セル１２，４２を透過した太陽光を反射させ、セル１２の発電層１４及びセル４２の発電層４４に太陽光を再び供給する反射層としても機能する。 The cell 42 corresponds to the second power generation cell of the present invention. In the cell 42 (hereinafter referred to as the second cell 42), a back electrode 45, a second power generation layer 44, and a grid electrode (light receiving surface electrode) 43 are sequentially stacked on a second substrate 41 made of glass or transparent resin. Has been. The second substrate 41 has a facing surface 41 a (hereinafter referred to as the front surface 41 a) that faces the back surface 11 b of the first substrate 11. The back electrode 45 is formed on the front surface 41a and is made of a metal film having a relatively high conductivity and reflectivity such as Ag, Al, and Cu. The back electrode 45 is formed using, for example, a low-temperature firing nano ink metal (Ag). The back electrode 45 also functions as a reflective layer that reflects sunlight transmitted through the cells 12 and 42 and supplies the sunlight again to the power generation layer 14 of the cell 12 and the power generation layer 44 of the cell 42.
　裏面電極４５上には、第２発電層４４が形成されている。この第２発電層４４は、例えば、ｐ型Ｃｕ２Ｓ膜（不図示）とｎ型Ｃｕ２Ｓ膜（不図示）との間にｉ型Ｃｕ２Ｓ膜（不図示）が挟まれたｐｉｎ接合構造を有する。第２発電層４４においては、裏面電極４５上にｎ型Ｃｕ２Ｓ膜，ｉ型Ｃｕ２Ｓ膜，及びｐ型Ｃｕ２Ｓ膜が順次積層されている。第２発電層４４のバンドギャップ（光学的バンドギャップ）は、第１発電層１４のバンドギャップより小さく、例えば、１．２ｅＶ程度である。 A second power generation layer 44 is formed on the back electrode 45. For example, the second power generation layer 44 is a pin in which an i-type Cu 2 S film (not shown) is sandwiched between a p-type Cu 2 S film (not shown) and an n-type Cu 2 S film (not shown). It has a junction structure. In the second power generation layer 44, an n-type Cu 2 S film, an i-type Cu 2 S film, and a p-type Cu 2 S film are sequentially stacked on the back electrode 45. The band gap (optical band gap) of the second power generation layer 44 is smaller than the band gap of the first power generation layer 14 and is, for example, about 1.2 eV.
　第２発電層４４上には、第２発電層４４の面に平行な方向に沿って格子状に形成されたグリッド電極４３が配置されている。このグリッド電極４３は、裏面電極４５と同じ材料で形成されており、基板１１の表面１１ａに入射して第１セル１２を透過した太陽光は、グリッド電極４３間の隙間（開口部）を通って第２発電層４４に入射する。なお、グリッド電極４３の構成材料としては、ＴＣＯ等の光透過性を有する金属酸化物を採用することも可能である。 On the second power generation layer 44, grid electrodes 43 formed in a lattice shape along a direction parallel to the surface of the second power generation layer 44 are arranged. The grid electrode 43 is formed of the same material as that of the back electrode 45, and sunlight that has entered the front surface 11 a of the substrate 11 and transmitted through the first cell 12 passes through a gap (opening) between the grid electrodes 43. Incident on the second power generation layer 44. In addition, as a constituent material of the grid electrode 43, it is also possible to employ a metal oxide having optical transparency such as TCO.
　ここで、第１セル１２の裏面電極１５と第２セル４２のグリッド電極４３との間には、上述の第１実施形態と同じ絶縁部３０が形成されている。この絶縁部３０を介して第１セル１２と第２セル４２とが貼り合わされている。このように、第２実施形態の変形例の太陽電池２００においては、絶縁部３０を挟持するように第１セル１２及び第２セル４２が積層されており、第１セル１２と第２セル４２とは電気的に絶縁されている。そして、セル１２，４２の各々の端部において、セル１２，４２は互いに電気的に並列に接続されている。 Here, between the back electrode 15 of the first cell 12 and the grid electrode 43 of the second cell 42, the same insulating portion 30 as that in the first embodiment is formed. The first cell 12 and the second cell 42 are bonded together via the insulating part 30. Thus, in the solar cell 200 of the modification of 2nd Embodiment, the 1st cell 12 and the 2nd cell 42 are laminated | stacked so that the insulation part 30 may be pinched | interposed, and the 1st cell 12 and the 2nd cell 42 are laminated | stacked. Is electrically insulated. And in each edge part of the cells 12 and 42, the cells 12 and 42 are mutually electrically connected in parallel.
　従って、第２実施形態の変形例によれば、上述の第１実施形態と同様の効果が得られる。また、第２発電層４４にＣｕ２Ｓ膜が用いられているので、上述の結晶シリコンからなるシリコン基板２３（図１参照）が発電層として用いられている場合に比べ、バンドギャップを狭くすることができる。従って、長波長域の光がより一層取り出し易くなるため、太陽電池２００の発電効率を向上することができる。 Therefore, according to the modification of the second embodiment, the same effect as that of the first embodiment described above can be obtained. Further, since the Cu 2 S film is used for the second power generation layer 44, the band gap is made narrower than when the silicon substrate 23 (see FIG. 1) made of crystalline silicon is used as the power generation layer. be able to. Therefore, since it becomes easier to take out light in the long wavelength region, the power generation efficiency of the solar cell 200 can be improved.
（第３実施形態）
　次に、本発明の第３実施形態について説明する。
　図３は、第３実施形態における太陽電池の断面図である。
　第３実施形態においては、第１，２実施形態と同一部材には同一符号を付して、その説明は省略または簡略化する。
　第３実施形態においては、第２セルの発電層として、ＣｄＳ膜が用いられている。この構造は、上述の第１，２実施形態の構造と相違している。図３に示すように、第３実施形態の太陽電池３００においては、一対の基板１１，５１（以下、第１基板１１及び第２基板５１と称する）の間に、２つのセル１２，５２が挟持されている。セル１２（以下、第１セル１２と称する）においては、第１基板１１上に形成された受光面電極１３，発電層（以下、第１発電層と称する）１４，及び裏面電極１５が順次積層されている。第１セル１２の構造は、上述の第１実施形態と同じである。 (Third embodiment)
Next, a third embodiment of the present invention will be described.
FIG. 3 is a cross-sectional view of the solar cell in the third embodiment.
In the third embodiment, the same members as those in the first and second embodiments are denoted by the same reference numerals, and the description thereof is omitted or simplified.
In the third embodiment, a CdS film is used as the power generation layer of the second cell. This structure is different from the structures of the first and second embodiments described above. As shown in FIG. 3, in the solar cell 300 of the third embodiment, two cells 12 and 52 are provided between a pair of substrates 11 and 51 (hereinafter referred to as the first substrate 11 and the second substrate 51). It is pinched. In the cell 12 (hereinafter referred to as the first cell 12), the light receiving surface electrode 13, the power generation layer (hereinafter referred to as the first power generation layer) 14, and the back electrode 15 formed on the first substrate 11 are sequentially laminated. Has been. The structure of the first cell 12 is the same as that of the first embodiment described above.
　セル４２は、本発明の第２発電セルに相当する。セル５２（以下、第２セル５２と称する）においては、ガラス又は透明樹脂等からなる第２基板５１の表面５１ａ上に裏面電極５５，第２発電層５４，及びグリッド電極（受光面電極）５３が順次積層されている。裏面電極５５及びグリッド電極５３の構成は、上述の第２実施形態における裏面電極４５及びグリッド電極４３の構成と同じである。第２セル５２の第２発電層５４は、ＣｄＳ膜と上述のＣｕＩｎＳｅ２膜とを含む。具体的に、第２発電層５４は、ｐ型ＣｕＩｎＳｅ２膜５４ａとｎ型ＣｄＳ膜５４ｂとが積層されたｐｎ接合構造を有する。このｐｎ接合構造においては、裏面電極５５上にｐ型ＣｄＳ膜５４ａとｎ型ＣｕＩｎＳｅ２膜５４ｂとが順次積層されている。即ち、ｐ型膜５４ａが形成された後に、ｎ型膜５４ｂが形成されている。ｎ型膜５４ｂを形成した後にｐ型膜５４ａを形成する場合では、成膜装置に残留する不純物の影響により、太陽電池の性能が低下する恐れがある。そのため、ｐ型膜５４ａ上にｎ型膜５４ｂが形成されているｐｎ接合構造においては、不純物の影響が低減された太陽電池を実現することができる。この構成において、第２発電層５４のバンドギャップは、２．４～３．２ｅＶ程度である。なお、ｐ型ＣｄＳ膜５４ａとｎ型ＣｕＩｎＳｅ２膜５４ｂとの間にｉ型ＣｄＳ膜が形成された構成が採用されてもよい。 The cell 42 corresponds to the second power generation cell of the present invention. In the cell 52 (hereinafter referred to as the second cell 52), a back electrode 55, a second power generation layer 54, and a grid electrode (light-receiving surface electrode) 53 are formed on the surface 51a of the second substrate 51 made of glass or transparent resin. Are sequentially stacked. The configurations of the back electrode 55 and the grid electrode 53 are the same as the configurations of the back electrode 45 and the grid electrode 43 in the second embodiment described above. The second power generation layer 54 of the second cell 52 includes a CdS film and the above-described CuInSe 2 film. Specifically, the second power generation layer 54 has a pn junction structure in which a p-type CuInSe 2 film 54a and an n-type CdS film 54b are stacked. In this pn junction structure, a p-type CdS film 54 a and an n-type CuInSe 2 film 54 b are sequentially stacked on the back electrode 55. That is, the n-type film 54b is formed after the p-type film 54a is formed. In the case where the p-type film 54a is formed after the n-type film 54b is formed, the performance of the solar cell may be deteriorated due to the influence of impurities remaining in the film forming apparatus. Therefore, in the pn junction structure in which the n-type film 54b is formed on the p-type film 54a, a solar cell in which the influence of impurities is reduced can be realized. In this configuration, the band gap of the second power generation layer 54 is about 2.4 to 3.2 eV. A configuration in which an i-type CdS film is formed between the p-type CdS film 54a and the n-type CuInSe 2 film 54b may be employed.
　また、この構成においては、発電層５４のバンドギャップは、発電層１４のバンドギャップ（１．７ｅＶ）よりも大きくなる。従って、この構成においては、発電層５４は、本発明の第１発電層として機能し、発電層１４は、本発明の第２発電層として機能する。即ち、第２セル５２は、本発明の第１発電セルとして機能し、第１セル１２は、本発明の第２発電セルとして機能する。この構成においては、太陽光を第２基板５１に入射させて発電層１４，５４において発電する必要があるため、第２基板５１としては透光性基板が用いられる。 In this configuration, the band gap of the power generation layer 54 is larger than the band gap (1.7 eV) of the power generation layer 14. Therefore, in this configuration, the power generation layer 54 functions as the first power generation layer of the present invention, and the power generation layer 14 functions as the second power generation layer of the present invention. That is, the second cell 52 functions as the first power generation cell of the present invention, and the first cell 12 functions as the second power generation cell of the present invention. In this configuration, since sunlight needs to be incident on the second substrate 51 to generate power in the power generation layers 14 and 54, a translucent substrate is used as the second substrate 51.
　従って、第３実施形態によれば、第２発電層５４の構成材料としてＣｕＩｎＳｅ２膜とＣｄＳ膜とが用いられた場合であっても、上述の第１，２実施形態と同様の効果を得ることができる。 Therefore, according to the third embodiment, even when the CuInSe 2 film and the CdS film are used as the constituent materials of the second power generation layer 54, the same effects as those of the first and second embodiments are obtained. be able to.
（第３実施形態の変形例）
　次に、本発明の第３実施形態の変形例について説明する。
　第３実施形態の変形例においては、第１，２実施形態と同一部材には同一符号を付して、その説明は省略または簡略化する。
　第３実施形態の変形例においては、第２セルの発電層として、ＣｄＳ膜が用いられている。この構造は、上述の第１，２実施形態の構造と相違している。図３に示すように、第３実施形態の変形例の太陽電池３００においては、一対の基板１１，５１（以下、第１基板１１及び第２基板５１と称する）の間に、２つのセル１２，５２が挟持されている。セル１２（以下、第１セル１２と称する）においては、第１基板１１上に形成された受光面電極１３，発電層（以下、第１発電層と称する）１４，及び裏面電極１５が順次積層されている。第１セル１２の構造は、上述の第１実施形態と同じである。 (Modification of the third embodiment)
Next, a modification of the third embodiment of the present invention will be described.
In the modification of the third embodiment, the same members as those in the first and second embodiments are denoted by the same reference numerals, and the description thereof is omitted or simplified.
In the modification of the third embodiment, a CdS film is used as the power generation layer of the second cell. This structure is different from the structures of the first and second embodiments described above. As shown in FIG. 3, in the solar cell 300 according to the modification of the third embodiment, two cells 12 are interposed between a pair of substrates 11 and 51 (hereinafter referred to as the first substrate 11 and the second substrate 51). , 52 are sandwiched. In the cell 12 (hereinafter referred to as the first cell 12), the light receiving surface electrode 13, the power generation layer (hereinafter referred to as the first power generation layer) 14, and the back electrode 15 formed on the first substrate 11 are sequentially laminated. Has been. The structure of the first cell 12 is the same as that of the first embodiment described above.
　セル４２は、本発明の第２発電セルに相当する。セル５２（以下、第２セル５２と称する）においては、ガラス又は透明樹脂等からなる第２基板５１の表面５１ａ上に裏面電極５５，第２発電層５４，及びグリッド電極（受光面電極）５３が順次積層されている。しかし、この場合においては、第１セル１２及び第２セル５２が第１基板１１及び第２基板５１の間に配置されているため、第２基板５１は必ずしも透光性材料からなる必要はない。裏面電極５５及びグリッド電極５３の構成は、上述の第２実施形態における裏面電極４５及びグリッド電極４３の構成と同じである。第２セル５２の第２発電層５４は、ＣｄＳ膜と上述のＣｕ２Ｓ膜とを含む。具体的に、第２発電層５４は、ｐ型Ｃｕ２Ｓ膜５４ａとｎ型ＣｄＳ膜５４ｂとが積層されたｐｎ接合構造を有する。このｐｎ接合構造においては、裏面電極５５上にｐ型ＣｄＳ膜５４ａとｎ型Ｃｕ２Ｓ膜５４ｂとが順次積層されている。この構成において、第２発電層５４のバンドギャップは、２．４～３．２ｅＶ程度である。なお、ｐ型Ｃｕ２Ｓ膜５４ａとｎ型ＣｄＳ膜５４ｂとの間にｉ型ＣｄＳ膜が形成された構成が採用されてもよい。 The cell 42 corresponds to the second power generation cell of the present invention. In the cell 52 (hereinafter referred to as the second cell 52), a back electrode 55, a second power generation layer 54, and a grid electrode (light-receiving surface electrode) 53 are formed on the front surface 51a of the second substrate 51 made of glass or transparent resin. Are sequentially stacked. However, in this case, since the first cell 12 and the second cell 52 are disposed between the first substrate 11 and the second substrate 51, the second substrate 51 does not necessarily need to be made of a light-transmitting material. . The configurations of the back electrode 55 and the grid electrode 53 are the same as the configurations of the back electrode 45 and the grid electrode 43 in the second embodiment described above. The second power generation layer 54 of the second cell 52 includes a CdS film and the above-described Cu 2 S film. Specifically, the second power generation layer 54 has a pn junction structure in which a p-type Cu 2 S film 54 a and an n-type CdS film 54 b are stacked. In this pn junction structure, a p-type CdS film 54 a and an n-type Cu 2 S film 54 b are sequentially stacked on the back electrode 55. In this configuration, the band gap of the second power generation layer 54 is about 2.4 to 3.2 eV. A configuration in which an i-type CdS film is formed between the p-type Cu 2 S film 54a and the n-type CdS film 54b may be employed.
　従って、第３実施形態の変形例によれば、第２発電層５４の構成材料としてＣｕ２Ｓ膜とＣｄＳ膜とが用いられた場合であっても、上述の第１，２実施形態と同様の効果を得ることができる。 Therefore, according to the modification of the third embodiment, even when a Cu 2 S film and a CdS film are used as the constituent materials of the second power generation layer 54, the same as in the first and second embodiments described above. The effect of can be obtained.
（第４実施形態）
　次に、本発明の第４実施形態について説明する。
　図４は、第４実施形態における太陽電池の断面図である。
　第４実施形態においては、第１～第３実施形態と同一部材には同一符号を付して、その説明は省略または簡略化する。
　第４実施形態においては、３つのセルが積層されたトリプル型の太陽電池が採用されている。この構造は、上述の第１～第３実施形態と相違している。図４に示すように、第４実施形態の太陽電池４００においては、一対の基板１１，７１の間に、３つのセル１２，６２，７２が挟持されている。セル７２は、本発明の第２発電セルに相当する。 (Fourth embodiment)
Next, a fourth embodiment of the present invention will be described.
FIG. 4 is a cross-sectional view of the solar cell in the fourth embodiment.
In the fourth embodiment, the same members as those in the first to third embodiments are denoted by the same reference numerals, and the description thereof is omitted or simplified.
In the fourth embodiment, a triple solar cell in which three cells are stacked is employed. This structure is different from the first to third embodiments described above. As shown in FIG. 4, in the solar cell 400 of the fourth embodiment, three cells 12, 62, 72 are sandwiched between a pair of substrates 11, 71. The cell 72 corresponds to the second power generation cell of the present invention.
　第１セル１２においては、第１基板１１上に受光面電極１３，第１発電層１４，及び裏面電極１５が順次積層されている。第１セル１２の構造は、上述の第１実施形態と同じである。また、セル７２（以下、第３セルと称する）は、上述の第２実施形態における第２セル４２（図２参照）と同じ構成を有する。第３セル７２においては、第２基板７１上に裏面電極７５，ＣｕＩｎＳｅ２膜からなる第３発電層７４（本発明の第２発電層に相当），及びグリッド電極７３が順次積層されている。この構成において、第３発電層７４のバンドギャップは、１．０４ｅＶである。 In the first cell 12, the light receiving surface electrode 13, the first power generation layer 14, and the back electrode 15 are sequentially stacked on the first substrate 11. The structure of the first cell 12 is the same as that of the first embodiment described above. The cell 72 (hereinafter referred to as the third cell) has the same configuration as the second cell 42 (see FIG. 2) in the second embodiment described above. In the third cell 72, a back electrode 75, a third power generation layer 74 (corresponding to a second power generation layer of the present invention) made of a CuInSe 2 film, and a grid electrode 73 are sequentially stacked on the second substrate 71. In this configuration, the band gap of the third power generation layer 74 is 1.04 eV.
　また、第３セル７２の構造としては、ｐ型ＣｕＩｎＳｅ２膜とｎ型ＣｕＩｎＳｅ２膜とが接合されたｐｎ接合構造が採用されてもよい。この場合、第３発電層７４のバンドギャップは、１．０４ｅＶである。
　また、第３セル７２の構造としては、第１実施形態のシリコン基板２３が用いられたセル構造が採用されてもよい。この場合、第３セル７２のシリコン基板のバンドギャップは、１．１ｅＶである。 In addition, as the structure of the third cell 72, a pn junction structure in which a p-type CuInSe 2 film and an n-type CuInSe 2 film are joined may be employed. In this case, the band gap of the third power generation layer 74 is 1.04 eV.
Further, as the structure of the third cell 72, a cell structure using the silicon substrate 23 of the first embodiment may be employed. In this case, the band gap of the silicon substrate of the third cell 72 is 1.1 eV.
　第１セル１２と第３セル７２との間には、セル６２（以下、第２セルと称する）が配置されている。セル６２は、本発明の第２発電セルに相当する。また、セル６２は、上述した中間発電セルに相当する。第２セル６２は、第３セル７２のグリッド電極７３上に絶縁部３２を介して積層されている。第２セル６２においては、絶縁部３２上に形成された裏面電極６５，第２発電層６４（中間発電層），及びグリッド電極（受光面電極）６３が順次積層されている。なお、グリッド電極６３の構成は、上述の第２実施形態におけるグリッド電極４３の構成と同じであるが、上述の第１実施形態における受光面電極１３と同じＴＣＯから構成されてもよい。また、裏面電極６５の構成は、上述の第１実施形態における受光面電極１３の構成と同じであり、ＴＣＯからなる。 Between the first cell 12 and the third cell 72, a cell 62 (hereinafter referred to as a second cell) is disposed. The cell 62 corresponds to the second power generation cell of the present invention. The cell 62 corresponds to the above-described intermediate power generation cell. The second cell 62 is stacked on the grid electrode 73 of the third cell 72 via the insulating part 32. In the second cell 62, a back electrode 65 formed on the insulating portion 32, a second power generation layer 64 (intermediate power generation layer), and a grid electrode (light receiving surface electrode) 63 are sequentially stacked. The configuration of the grid electrode 63 is the same as the configuration of the grid electrode 43 in the above-described second embodiment, but may be configured of the same TCO as that of the light-receiving surface electrode 13 in the above-described first embodiment. The configuration of the back electrode 65 is the same as the configuration of the light receiving surface electrode 13 in the first embodiment described above, and is made of TCO.
　第２発電層６４は、例えば、ｐ型微結晶シリコン膜（不図示）とｎ型微結晶シリコン膜（不図示）との間にｉ型微結晶シリコン膜（不図示）が挟まれたｐｉｎ接合構造を含む。このｐｉｎ接合構造においては、裏面電極６５からグリッド電極６３に向く方向に、ｎ型微結晶シリコン膜，ｉ型微結晶シリコン膜，及びｐ型微結晶シリコン膜が順次積層されている。第２発電層６４のバンドギャップは、第１発電層１４のバンドギャップより小さく、かつ第３発電層７４より大きく、例えば、１．１ｅＶ程度である。そして、第２セル６２と第１セル１２とは、絶縁部３０を介して積層されている。絶縁部３０は、第２セル６２のグリッド電極６３と第１セル１２の裏面電極１５との間に配置されている。 The second power generation layer 64 is, for example, a pin junction in which an i-type microcrystalline silicon film (not shown) is sandwiched between a p-type microcrystalline silicon film (not shown) and an n-type microcrystalline silicon film (not shown). Includes structure. In this pin junction structure, an n-type microcrystalline silicon film, an i-type microcrystalline silicon film, and a p-type microcrystalline silicon film are sequentially stacked in a direction from the back electrode 65 to the grid electrode 63. The band gap of the second power generation layer 64 is smaller than the band gap of the first power generation layer 14 and larger than the third power generation layer 74, for example, about 1.1 eV. The second cell 62 and the first cell 12 are stacked via the insulating unit 30. The insulating unit 30 is disposed between the grid electrode 63 of the second cell 62 and the back electrode 15 of the first cell 12.
　また、第２発電層６４の構造としては、ｐ型ＣｄＳ膜とｎ型ＣｄＳ膜とが接合されたｐｎ接合構造が採用されてもよい。この場合、第２発電層６４のバンドギャップは、１．６８ｅＶである。 Further, as the structure of the second power generation layer 64, a pn junction structure in which a p-type CdS film and an n-type CdS film are joined may be employed. In this case, the band gap of the second power generation layer 64 is 1.68 eV.
　上述した第４実施形態の太陽電池４００においても、基板１１から基板７１に向う方向において、第１セル１２，第２セル６２，及び第３セル７２のバンドギャップが順に小さくなるように、発電層１４，６４，７４の各々の構成材料が選択されている。従って、３つのセル１２，６２，７２が積層されたトリプル型の太陽電池４００においては、吸収される波長帯域が互いに異なる発電層１４，６４，７４が用いられているため、発電層１４，６４，７４は、太陽光に含まれる複数の波長帯域の光を吸収する。発電層１４，６４，７４の各々は、太陽光のエネルギーを得るために最適な波長域を有している。この波長域に応じて、太陽光はトリプル型の太陽電池４００において吸収される。このため、太陽光のエネルギーをより無駄なく利用することができる。従って、第４実施形態においては、上述の第１～３実施形態に比べて、発電効率をより一層向上することができる。 Also in the solar cell 400 of the fourth embodiment described above, the power generation layer so that the band gaps of the first cell 12, the second cell 62, and the third cell 72 are sequentially reduced in the direction from the substrate 11 to the substrate 71. Each of the constituent materials 14, 64, and 74 is selected. Therefore, in the triple solar cell 400 in which the three cells 12, 62, 72 are stacked, the power generation layers 14, 64, 74 having different wavelength bands are used. , 74 absorb light in a plurality of wavelength bands included in sunlight. Each of the power generation layers 14, 64, and 74 has an optimum wavelength range for obtaining sunlight energy. Depending on this wavelength range, sunlight is absorbed by the triple solar cell 400. For this reason, the energy of sunlight can be utilized more wastefully. Therefore, in the fourth embodiment, the power generation efficiency can be further improved as compared with the first to third embodiments described above.
（第４実施形態の変形例）
　次に、本発明の第４実施形態の変形例について説明する。
　第４実施形態の変形例においては、第１～第３実施形態と同一部材には同一符号を付して、その説明は省略または簡略化する。
　第４実施形態の変形例においては、３つのセルが積層されたトリプル型の太陽電池が採用されている。この構造は、上述の第１～第３実施形態と相違している。図４に示すように、第４実施形態の変形例の太陽電池４００においては、一対の基板１１，７１の間に、３つのセル１２，６２，７２が挟持されている。セル７２は、本発明の第２発電セルに相当する。 (Modification of the fourth embodiment)
Next, a modification of the fourth embodiment of the present invention will be described.
In the modification of the fourth embodiment, the same members as those in the first to third embodiments are denoted by the same reference numerals, and the description thereof is omitted or simplified.
In the modification of the fourth embodiment, a triple solar cell in which three cells are stacked is employed. This structure is different from the first to third embodiments described above. As shown in FIG. 4, in the solar cell 400 of the modified example of the fourth embodiment, three cells 12, 62, 72 are sandwiched between a pair of substrates 11, 71. The cell 72 corresponds to the second power generation cell of the present invention.
　第１セル１２においては、第１基板１１上に受光面電極１３，第１発電層１４，及び裏面電極１５が順次積層されている。第１セル１２の構造は、上述の第１実施形態と同じである。また、セル７２（以下、第３セルと称する）は、上述の第２実施形態における第２セル４２（図２参照）と同じ構成を有する。第３セル７２においては、第２基板７１上に裏面電極７５，Ｃｕ２Ｓ膜からなる第３発電層７４，及びグリッド電極７３が順次積層されている。 In the first cell 12, the light receiving surface electrode 13, the first power generation layer 14, and the back electrode 15 are sequentially stacked on the first substrate 11. The structure of the first cell 12 is the same as that of the first embodiment described above. The cell 72 (hereinafter referred to as the third cell) has the same configuration as the second cell 42 (see FIG. 2) in the second embodiment described above. In the third cell 72, a back electrode 75, a third power generation layer 74 made of a Cu 2 S film, and a grid electrode 73 are sequentially stacked on the second substrate 71.
（太陽電池の製造方法）
（セル１２の製造方法）
　次に、図５Ａ～図５Ｃに基づいて太陽電池の製造方法について説明する。
　まず、上述の第１実施形態のセル１２（図１参照）の製造方法について説明する。図５Ａ～図５Ｃは、太陽電池の製造方法を示す断面図であり、セル１２の製造方法を示している。
　まず、図５Ａに示すように、スパッタリング法，ＣＶＤ（Ｃｈｅｍｉｃａｌ　Ｖａｐｏｒ　Ｄｅｐｏｓｉｔｉｏｎ）法，アークプラズマ法等により、基板１１の裏面１１ｂ上に受光面電極１３を形成する。
　その後、図５Ｂに示すように、受光面電極１３上にプラズマＣＶＤ法により発電層１４を形成する。具体的に、プラズマを生成するための陽極及び陰極がチャンバ（不図示）内に配置された成膜装置を用いることによって、上記の層は形成される。この場合、まず、受光面電極１３が形成された基板１１をチャンバ内の陽極上に配置し、チャンバ内を減圧する。その後、基板１１を２００℃程度（成膜プロセス中の最高温度）に加熱し、チャンバ内に反応ガス（例えば、シランガス，ジボランガス，水素等）を導入する。その後、陽極と陰極との間に高周波電圧を印加し、陽極と陰極との間に反応ガスのプラズマを生成し、反応ガスが電離し、反応性イオンが陽極と陰極との間に生じる。この反応性イオンが基板１１上において反応し、受光面電極１３上に発電層１４が成膜される。なお、発電層１４の成膜方法としては、プラズマＣＶＤ法の他に、熱ＣＶＤ法，グロー放電，スパッタリング法，イオンプレーティング法等を用いてもよい。 (Method for manufacturing solar cell)
(Manufacturing method of cell 12)
Next, a method for manufacturing a solar cell will be described with reference to FIGS. 5A to 5C.
First, a method for manufacturing the cell 12 (see FIG. 1) of the first embodiment will be described. 5A to 5C are cross-sectional views showing a method for manufacturing a solar cell, and show a method for manufacturing the cell 12.
First, as shown in FIG. 5A, the light-receiving surface electrode 13 is formed on the back surface 11b of the substrate 11 by sputtering, CVD (Chemical Vapor Deposition), arc plasma, or the like.
Thereafter, as shown in FIG. 5B, the power generation layer 14 is formed on the light-receiving surface electrode 13 by plasma CVD. Specifically, the above layers are formed by using a film forming apparatus in which an anode and a cathode for generating plasma are arranged in a chamber (not shown). In this case, first, the substrate 11 on which the light-receiving surface electrode 13 is formed is placed on the anode in the chamber, and the pressure in the chamber is reduced. Thereafter, the substrate 11 is heated to about 200 ° C. (the highest temperature during the film forming process), and a reaction gas (eg, silane gas, diborane gas, hydrogen, etc.) is introduced into the chamber. Thereafter, a high frequency voltage is applied between the anode and the cathode to generate a reactive gas plasma between the anode and the cathode, the reactive gas is ionized, and reactive ions are generated between the anode and the cathode. The reactive ions react on the substrate 11 to form the power generation layer 14 on the light-receiving surface electrode 13. In addition to the plasma CVD method, the power generation layer 14 may be formed by a thermal CVD method, glow discharge, sputtering method, ion plating method, or the like.
　続いて、図５Ｃに示すように、発電層１４上に裏面電極１５を形成する。具体的には、上述の受光面電極１３と同様に、スパッタリング法，ＣＶＤ法，アークプラズマ法等を用いて裏面電極１５が形成される。上記の工程により、基板１１上に第１セル１２が形成される。次に、裏面電極１５上に絶縁部３０（図１参照）を形成する。具体的には、スピンコート法等を用いることにより、絶縁部３０のペースト材料３０ａを裏面電極１５の全面に塗布する。なお、絶縁部３０の構成材料として絶縁接着シートを用いる場合には、裏面電極１５の全面に絶縁接着シートを設ける。 Subsequently, as shown in FIG. 5C, the back electrode 15 is formed on the power generation layer 14. Specifically, the back electrode 15 is formed using a sputtering method, a CVD method, an arc plasma method, or the like, similarly to the light receiving surface electrode 13 described above. Through the above steps, the first cell 12 is formed on the substrate 11. Next, the insulating portion 30 (see FIG. 1) is formed on the back electrode 15. Specifically, the paste material 30a of the insulating part 30 is applied to the entire surface of the back electrode 15 by using a spin coat method or the like. When an insulating adhesive sheet is used as the constituent material of the insulating portion 30, the insulating adhesive sheet is provided on the entire surface of the back electrode 15.
（セル２２の製造方法）
　次に、第１実施形態のセル２２（図１参照）の製造方法について説明する。
　図６Ａ～図６Ｅは、太陽電池の製造方法を示す断面図であり、セル２２の製造方法を示している。
　図６Ａに示すように、エッチング（テクスチャエッチング）によって形成された微小な凹凸形状からなるテクスチャ構造を有するｐ型単結晶シリコン基板２３を準備する。このｐ型単結晶シリコン基板２３は、厚さ２２０μｍ、長さ１５６ｍｍの矩形基板である。
　次に、このｐ型単結晶シリコン基板２３の表面に、リン（Ｐ）を含む塗料を塗布する。
　次いで、図６Ｂに示すように、シリコン基板２３を９００℃、１０分間の熱処理を施し、このシリコン基板２３の表面近傍に、約０．５μｍの厚さを有するｎ型の拡散層２４を形成する。 (Manufacturing method of cell 22)
Next, the manufacturing method of the cell 22 (refer FIG. 1) of 1st Embodiment is demonstrated.
6A to 6E are cross-sectional views showing a method for manufacturing a solar cell, and show a method for manufacturing the cell 22.
As shown in FIG. 6A, a p-type single crystal silicon substrate 23 having a textured structure formed of fine irregularities formed by etching (texture etching) is prepared. The p-type single crystal silicon substrate 23 is a rectangular substrate having a thickness of 220 μm and a length of 156 mm.
Next, a coating material containing phosphorus (P) is applied to the surface of the p-type single crystal silicon substrate 23.
Next, as shown in FIG. 6B, the silicon substrate 23 is heat-treated at 900 ° C. for 10 minutes, and an n-type diffusion layer 24 having a thickness of about 0.5 μm is formed in the vicinity of the surface of the silicon substrate 23. .
　次いで、図６Ｃに示すように、ＣＶＤ法を用いて、窒化珪素（ＳｉＮｘ）からなる反射防止膜２５を拡散層２４上に成膜する。成膜条件として、基板温度が約３００℃（成膜プロセス中の最高温度）、ＳｉＨ４ガスの流量が１５０ｓｃｃｍ、ＮＨ３ガスの流量が３５０ｓｃｃｍ、キャリアガスであるＮ２ガスの流量が８００ｓｃｃｍ、供給電力が４００Ｗに設定されていることが好ましい。さらに、シリコン基板２３の表面にスクリーン印刷法を用いて銀ペーストを１０μｍの厚みを有するように格子状に塗布する。その後、１５０℃、１０分間にて銀ペーストを乾燥させ、グリッド電極２９を形成する。 Next, as shown in FIG. 6C, an antireflection film 25 made of silicon nitride (SiNx) is formed on the diffusion layer 24 by CVD. As film formation conditions, the substrate temperature is about 300 ° C. (the highest temperature during the film formation process), the flow rate of SiH 4 gas is 150 sccm, the flow rate of NH 3 gas is 350 sccm, and the flow rate of N 2 gas as a carrier gas is 800 sccm. The power is preferably set to 400W. Further, a silver paste is applied on the surface of the silicon substrate 23 in a lattice shape so as to have a thickness of 10 μm using a screen printing method. Thereafter, the silver paste is dried at 150 ° C. for 10 minutes to form the grid electrode 29.
　次いで、図６Ｄに示すように、シリコン基板２３の裏面において第２裏面電極２８が形成される領域に、スクリーン印刷法を用いて銀ペーストを１０μｍの厚みを有するように塗布する。その後、１５０℃、１０分間にて銀ペーストを乾燥させる。次いで、このシリコン基板２３の裏面において第１裏面電極２７が形成される領域に、スクリーン印刷法を用いてアルミニウムペーストを４０μｍの厚みを有するように塗布する。その後、１５０℃、１０分間にてアルミニウムペーストを乾燥させる。 Next, as shown in FIG. 6D, a silver paste is applied to the region where the second back electrode 28 is formed on the back surface of the silicon substrate 23 using a screen printing method so as to have a thickness of 10 μm. Thereafter, the silver paste is dried at 150 ° C. for 10 minutes. Next, an aluminum paste is applied to a region where the first back electrode 27 is formed on the back surface of the silicon substrate 23 by using a screen printing method so as to have a thickness of 40 μm. Thereafter, the aluminum paste is dried at 150 ° C. for 10 minutes.
　次いで、図６Ｅに示すように、シリコン基板２３を７５０℃にて３秒間熱処理し、第１裏面電極２７，第２裏面電極２８，及びグリッド電極２９を形成する。これと同時に、このシリコン基板２３の裏面には、深さ約１０μｍのＢＳＦ層２６が形成される。さらに、グリッド電極２９は、窒化珪素（ＳｉＮｘ）からなる反射防止膜２５を貫通し、拡散層２４と接触する（ファイヤスルー）。上記の工程により、セル２２（第２セル）が形成される。 Next, as shown in FIG. 6E, the silicon substrate 23 is heat-treated at 750 ° C. for 3 seconds to form the first back electrode 27, the second back electrode 28, and the grid electrode 29. At the same time, a BSF layer 26 having a depth of about 10 μm is formed on the back surface of the silicon substrate 23. Furthermore, the grid electrode 29 penetrates the antireflection film 25 made of silicon nitride (SiNx) and comes into contact with the diffusion layer 24 (fire through). The cell 22 (second cell) is formed by the above process.
（セル４２の製造方法）
　次に、第２実施形態のセル４２（図２参照）の製造方法について説明する。
　図７Ａ～図７Ｃは、太陽電池の製造方法を示す断面図であり、セル４２の製造方法を示している。
　まず、図７Ａに示すように、第２基板４１の表面４１ａ上に、スパッタリング法，ＣＶＤ法，アークプラズマ法等により裏面電極４５を形成する。
　次に、図７Ｂに示すように、第２基板４１上に形成された裏面電極４５上に第２発電層４４を形成する。具体的には、スパッタリング法等により成膜する。
　なお、発電層４４の形成時において、第２基板４１を、例えば、３００～３５０℃程度（成膜プロセス中の最高温度）に加熱することが好ましい。 (Manufacturing method of the cell 42)
Next, the manufacturing method of the cell 42 (refer FIG. 2) of 2nd Embodiment is demonstrated.
7A to 7C are cross-sectional views showing a method for manufacturing a solar cell, and show a method for manufacturing the cell 42. FIG.
First, as shown in FIG. 7A, a back electrode 45 is formed on the surface 41a of the second substrate 41 by a sputtering method, a CVD method, an arc plasma method, or the like.
Next, as shown in FIG. 7B, the second power generation layer 44 is formed on the back electrode 45 formed on the second substrate 41. Specifically, the film is formed by a sputtering method or the like.
In forming the power generation layer 44, the second substrate 41 is preferably heated to, for example, about 300 to 350 ° C. (maximum temperature during the film forming process).
　次に、図７Ｃに示すように、発電層４４上にグリッド電極４３を形成する。
　具体的には、スパッタリング法，ＣＶＤ法，アークプラズマ法等により発電層４４上の全面に金属膜を成膜する。その後、金属膜の全面にフォトレジストを形成し、フォトリソグラフィ法を用いてフォトレジストの開口部を形成し、エッチングマスクを金属膜上に形成する。その後、ドライエッチング法等を用いることにより、金属膜をパターニングし、格子状のグリッド電極４３を形成する。上記の工程により、セル４２（第２セル）が形成される。なお、グリッド電極４３の形成方法としては、第１実施形態のセル２２のグリッド電極２９を形成する方法と同様に、スクリーン印刷法を用いて銀ペーストを１０μｍの厚みを有するように格子状に塗布し、その後、１５０℃、１０分間にて銀ペーストを乾燥させてグリッド電極４３を形成してもよい。 Next, as shown in FIG. 7C, the grid electrode 43 is formed on the power generation layer 44.
Specifically, a metal film is formed on the entire surface of the power generation layer 44 by sputtering, CVD, arc plasma, or the like. Thereafter, a photoresist is formed on the entire surface of the metal film, an opening of the photoresist is formed using a photolithography method, and an etching mask is formed on the metal film. Thereafter, by using a dry etching method or the like, the metal film is patterned to form a grid-like grid electrode 43. The cell 42 (second cell) is formed by the above process. In addition, as a method of forming the grid electrode 43, similarly to the method of forming the grid electrode 29 of the cell 22 of the first embodiment, a silver paste is applied in a lattice shape so as to have a thickness of 10 μm by using a screen printing method. Then, the grid electrode 43 may be formed by drying the silver paste at 150 ° C. for 10 minutes.
（セル５２の製造方法）
　次に、図３に基づいて第３実施形態のセル５２の製造方法について説明する。
　図３に示すように、セル４２の形成方法と同様の方法を用いて、即ち、スパッタリング法，ＣＶＤ法，アークプラズマ法等により、第２基板５１の表面５１ａ上に裏面電極５５を形成する。
　次に、第２基板５１上に形成された裏面電極５５上に第２発電層５４（ｐ型ＣｕＩｎＳｅ２膜５４ａ及びｎ型ＣｄＳ膜５４ｂ）を形成する。具体的には、蒸着法等により成膜する。なお、発電層５４の形成時において、第２基板５１を、例えば、３００～４００℃程度に加熱することが好ましい。
　次に、セル４２の形成方法と同様の方法を用いて、発電層５４上にグリッド電極５３を形成する。上記の工程により、セル５２（第２セル）が形成される。 (Manufacturing method of the cell 52)
Next, the manufacturing method of the cell 52 of 3rd Embodiment is demonstrated based on FIG.
As shown in FIG. 3, the back electrode 55 is formed on the surface 51a of the second substrate 51 by using a method similar to the method of forming the cell 42, that is, by sputtering, CVD, arc plasma, or the like.
Next, the second power generation layer 54 (p-type CuInSe 2 film 54a and n-type CdS film 54b) is formed on the back electrode 55 formed on the second substrate 51. Specifically, the film is formed by an evaporation method or the like. When forming the power generation layer 54, it is preferable to heat the second substrate 51 to about 300 to 400 ° C., for example.
Next, the grid electrode 53 is formed on the power generation layer 54 using a method similar to the method for forming the cell 42. The cell 52 (second cell) is formed by the above process.
（セル６２，７２の製造方法）
　次に、図４に基づいて、第４実施形態のセル６２，７２の製造方法について説明する。
　図４に示すように、まず、第２基板７１の表面７１ａ上に、上述のセル４２の形成方法と同様の方法を用いてセル７２（第３セル）を形成する。
　次に、セル７２が形成された基板７１上にセル６２（第２セル）を積層する。具体的に、スピンコート法等を用いることにより、絶縁部３２のペースト材料をセル７２のグリッド電極７３上に塗布する。なお、絶縁部３２の構成材料として、絶縁接着シートを用いる場合には、グリッド電極７３の全面に絶縁接着シートを設ける。
　次に、絶縁部３２を乾燥させた後、絶縁部３２上にスパッタリング法，ＣＶＤ法，アークプラズマ法等を用いて裏面電極６５を形成する。
　次に、蒸着法等により裏面電極６５上に第２発電層６４を形成する。なお、発電層６４の形成時において、第２基板５１を、例えば、３００～４００℃程度（成膜プロセス中の最高温度）に加熱することが好ましい。
　次に、セル４２の形成方法と同様の方法により、発電層６４上にグリッド電極６３を形成する。以上により、セル７２上にセル６２が積層される。 (Manufacturing method of cells 62 and 72)
Next, based on FIG. 4, the manufacturing method of the cells 62 and 72 of 4th Embodiment is demonstrated.
As shown in FIG. 4, first, a cell 72 (third cell) is formed on the surface 71 a of the second substrate 71 using a method similar to the method for forming the cell 42 described above.
Next, the cell 62 (second cell) is stacked on the substrate 71 on which the cell 72 is formed. Specifically, the paste material of the insulating part 32 is applied onto the grid electrode 73 of the cell 72 by using a spin coat method or the like. In the case where an insulating adhesive sheet is used as the constituent material of the insulating portion 32, the insulating adhesive sheet is provided on the entire surface of the grid electrode 73.
Next, after the insulating portion 32 is dried, the back electrode 65 is formed on the insulating portion 32 by using a sputtering method, a CVD method, an arc plasma method, or the like.
Next, the second power generation layer 64 is formed on the back electrode 65 by vapor deposition or the like. When forming the power generation layer 64, it is preferable to heat the second substrate 51 to, for example, about 300 to 400 ° C. (the highest temperature during the film forming process).
Next, the grid electrode 63 is formed on the power generation layer 64 by a method similar to the method of forming the cell 42. As described above, the cell 62 is stacked on the cell 72.
（セルの貼り合わせ方法）
　次に、上述のように個別に作製された複数のセルを貼り合わせる方法について説明する。
　以下の説明では、主としてセル１２とセル２２とを貼り合わせて第１実施形態の太陽電池１００を製造する場合について説明する。
　図１，５，６に示すように、セル１２が形成された第１基板１１とセル２２とは、大気中で貼り合わせる。具体的に、第１基板１１上に形成された絶縁部３０のペースト材料３０ａと、シリコン基板２３上に形成されたグリッド電極２９とを向かい合わせながら、絶縁部３０とグリッド電極２９とを貼り合わせる。この時、第１基板１１に対してシリコン基板２３を押圧することで、ペースト材料３０ａがグリッド電極２９の間の隙間（開口部）に流動する。これによって、グリッド電極２９及び反射防止膜２５を覆うようにペースト材料３０ａが配置される。その後、ペースト材料３０ａを硬化することにより、第１実施形態の太陽電池１００が形成される（図１参照）。 (Cell pasting method)
Next, a method for bonding a plurality of cells individually manufactured as described above will be described.
In the following description, the case where the solar cell 100 of 1st Embodiment is manufactured mainly by bonding the cell 12 and the cell 22 is demonstrated.
As shown in FIGS. 1, 5, and 6, the first substrate 11 on which the cells 12 are formed and the cells 22 are bonded together in the air. Specifically, the insulating portion 30 and the grid electrode 29 are bonded together while the paste material 30a of the insulating portion 30 formed on the first substrate 11 and the grid electrode 29 formed on the silicon substrate 23 face each other. . At this time, by pressing the silicon substrate 23 against the first substrate 11, the paste material 30 a flows into the gaps (openings) between the grid electrodes 29. Thus, the paste material 30a is disposed so as to cover the grid electrode 29 and the antireflection film 25. Then, the solar cell 100 of 1st Embodiment is formed by hardening the paste material 30a (refer FIG. 1).
　このように、第１実施形態においては、第１セル１２と第２セル２２とをそれぞれ個別に作製している。更に、第１セル１２と第２セル２２と個別に準備した後、第１セル１２と第２セル２２との間に絶縁部３０を配置し、第１セル１２と第２セル２２とを貼り合わせている。
　この構成によれば、第１セル１２の成膜プロセスにおける最高温度と、第２セル２２の成膜プロセスにおける最高温度とが異なる場合であっても、第１セル１２及び第２セル２２の各々を個別に形成することができ、絶縁部３０を介して第１セル１２及び第２セル２２を重ねることができる。従って、上述した実施形態によれば、先に形成されている発電層の成膜条件に関わらず、成膜条件が異なる複数の発電層を有する太陽電池を製造することができる。
　一方、複数の発電層が順次積層された構成においては、既に成膜された下層に位置する発電層の膜質を維持するために、上層に位置する発電層の成膜条件が制限されてしまう。
　即ち、従来のような複数の発電層を順次積層する成膜プロセスにおいては、発電層の各々を形成するためのプロセス温度が互いに異なるために、高温プロセスが必要である発電層を作製する際、低温プロセスによって形成される発電層が高温雰囲気にさらされる。この場合、低温プロセスによって形成される発電層において、ダメージが生じる。
　例えば、成膜プロセス中の最高温度が１８０～２３０℃であるアモルファスシリコン（第１実施形態においてはアモルファスシリコンの成膜プロセス中の最高温度は２００℃である）と、成膜プロセス中の最高温度が２５０～４００℃である微結晶シリコン（第１実施形態においては微結晶シリコンの成膜プロセス中の最高温度は３００℃である）とを積層する場合について説明する。
　この場合、先に形成されたアモルファスシリコン上に微結晶シリコンを積層すると、アモルファスシリコンの成膜温度よりも微結晶シリコンの成膜温度が高いので、アモルファスシリコン中に含まれる水素が微結晶シリコンを成膜する際のプロセス温度の上昇によって脱離する。この場合、アモルファスシリコンにおける変換効率が低下するおそれがある。 As described above, in the first embodiment, the first cell 12 and the second cell 22 are individually manufactured. Further, after preparing the first cell 12 and the second cell 22 individually, the insulating part 30 is disposed between the first cell 12 and the second cell 22, and the first cell 12 and the second cell 22 are attached. It is matched.
According to this configuration, even if the maximum temperature in the film formation process of the first cell 12 is different from the maximum temperature in the film formation process of the second cell 22, each of the first cell 12 and the second cell 22. Can be formed individually, and the first cell 12 and the second cell 22 can be overlapped with each other through the insulating portion 30. Therefore, according to the above-described embodiment, it is possible to manufacture a solar cell having a plurality of power generation layers having different film formation conditions regardless of the film formation conditions of the power generation layer previously formed.
On the other hand, in the configuration in which a plurality of power generation layers are sequentially stacked, the film formation conditions of the power generation layer located in the upper layer are limited in order to maintain the film quality of the power generation layer located in the lower layer already formed.
That is, in the conventional film formation process of sequentially laminating a plurality of power generation layers, since the process temperatures for forming each of the power generation layers are different from each other, when producing a power generation layer that requires a high temperature process, The power generation layer formed by the low temperature process is exposed to a high temperature atmosphere. In this case, damage occurs in the power generation layer formed by the low temperature process.
For example, amorphous silicon having a maximum temperature during the film formation process of 180 to 230 ° C. (in the first embodiment, the maximum temperature during the film formation process of amorphous silicon is 200 ° C.) and the maximum temperature during the film formation process A case of stacking microcrystalline silicon having a temperature of 250 to 400 ° C. (in the first embodiment, the maximum temperature during the film forming process of microcrystalline silicon is 300 ° C.) will be described.
In this case, if microcrystalline silicon is stacked on the previously formed amorphous silicon, the deposition temperature of microcrystalline silicon is higher than the deposition temperature of amorphous silicon. Desorption occurs due to an increase in process temperature during film formation. In this case, the conversion efficiency in amorphous silicon may be reduced.
　これに対して、第１実施形態においては、セル１２の成膜プロセスとセル２２の成膜プロセスとが別々である。このため、例えば、第２セル２２の形成工程において、拡散層２４又はＢＳＦ層２６を形成するためにシリコン基板２３に対して高温の熱処理を行ったとしても、第２セル２２と別個に形成された第１セル１２に熱による影響は生じない。そのため、基板１１上に既に成膜された発電層１４が劣化することなく、第２セル２２を形成することができる。
　つまり、セル１２，２２の各々を構成する層（例えば、発電層１４）を成膜する際には、最適な形成条件を設定して成膜することができる。従って、良好な膜質を有する発電層１４及びシリコン基板２３の各々を形成することができる。
　従って、本発明によれば、発電層の膜質を改善し、太陽電池１００の変換効率を増大し、製造効率が向上する。 On the other hand, in the first embodiment, the film forming process of the cell 12 and the film forming process of the cell 22 are separate. For this reason, for example, even if high-temperature heat treatment is performed on the silicon substrate 23 to form the diffusion layer 24 or the BSF layer 26 in the formation process of the second cell 22, the second cell 22 is formed separately from the second cell 22. The first cell 12 is not affected by heat. Therefore, the second cell 22 can be formed without deterioration of the power generation layer 14 already formed on the substrate 11.
That is, when forming a layer (for example, the power generation layer 14) constituting each of the cells 12 and 22, the film can be formed by setting optimum formation conditions. Therefore, each of the power generation layer 14 and the silicon substrate 23 having good film quality can be formed.
Therefore, according to the present invention, the film quality of the power generation layer is improved, the conversion efficiency of the solar cell 100 is increased, and the manufacturing efficiency is improved.
　また、上述のようにセル１２，２２の各々に個別の保護回路を設けて第１セル１２及び第２セル２２の各々を個別に作製するので、第１セル１２と第２セル２２との貼り合わせる前に、セル１２，２２の各々の製造時に生じた不具合を個別に検出することができる。
　これにより、第１セル１２と第２セル２２とを貼り合わせる時には、良質なセル１２，２２のみを用いることが可能になるため、全体として高性能な太陽電池１００を提供することができる。 Further, as described above, since the first cells 12 and the second cells 22 are individually manufactured by providing individual protection circuits for the cells 12 and 22, respectively, the first cell 12 and the second cell 22 are attached. Prior to matching, defects occurring during the manufacture of each of the cells 12 and 22 can be individually detected.
Thereby, when bonding the 1st cell 12 and the 2nd cell 22, since it becomes possible to use only the quality cells 12 and 22, the high performance solar cell 100 can be provided as a whole.
　なお、第２～４実施形態の太陽電池２００，３００，４００も上述の太陽電池１００の製造方法と同様の方法により作製することができる。
　即ち、第２実施形態の太陽電池２００を形成する場合には、図２に示すように、セル１２とセル４２とがそれぞれ個別に作製される（図５Ａ～図５Ｃ，７参照）。また、上述のセル１２，２２を貼り合わせる方法と同様の方法により絶縁部３０を介してセル１２とセル４２とが貼り合わされる。
　また、第３実施形態の太陽電池３００を形成する場合には、図３に示すように、セル１２とセル５２とがそれぞれ個別に作製される。また、上述のセル１２，２２を貼り合わせる方法と同様の方法により絶縁部３０を介してセル１２とセル５２とが貼り合わされる。
　また、第４実施形態の太陽電池４００を形成する場合には、図４に示すように、セル１２とセル７２とがそれぞれ個別に作製される。また、セル７２上に絶縁部３２を介してセル６２が配置される。
　その後、上述のセル１２，２２を貼り合わせる方法と同様の方法により絶縁部３０を介してセル１２とセル６２とが貼り合わされる。 The solar cells 200, 300, and 400 of the second to fourth embodiments can also be manufactured by the same method as the method for manufacturing the solar cell 100 described above.
That is, when forming the solar cell 200 of the second embodiment, the cell 12 and the cell 42 are individually manufactured as shown in FIG. 2 (see FIGS. 5A to 5C and 7). Further, the cell 12 and the cell 42 are bonded through the insulating portion 30 by the same method as the method of bonding the cells 12 and 22 described above.
Moreover, when forming the solar cell 300 of 3rd Embodiment, as shown in FIG. 3, the cell 12 and the cell 52 are each produced separately. Further, the cell 12 and the cell 52 are bonded through the insulating portion 30 by the same method as the method of bonding the cells 12 and 22 described above.
Moreover, when forming the solar cell 400 of 4th Embodiment, as shown in FIG. 4, the cell 12 and the cell 72 are each produced separately. In addition, the cell 62 is disposed on the cell 72 via the insulating portion 32.
Thereafter, the cell 12 and the cell 62 are bonded together via the insulating portion 30 by the same method as the method of bonding the cells 12 and 22 described above.
　本発明によれば、個別に作成されたセル（例えば、セル１２，２２，４２，５２，７２）を適宜選択し、複数のセルの間に絶縁部を挟み、セルを互いに貼り合わせることによって、成膜プロセス条件が互いに異なる複数のセル、例えば、プロセス温度が互いに異なる複数のセルが積層された太陽電池を容易に製造することができる。従って、積層構造において先に製作される発電層の発電効率が低下することなく、複数のセルが積層されたタンデム型太陽電池又はトリプル型太陽電池を容易に作製することができる。従って、比較的変換効率の高い太陽電池を効率的に作製することができる。 According to the present invention, by appropriately selecting individually created cells (for example, cells 12, 22, 42, 52, 72), sandwiching an insulating portion between a plurality of cells, and bonding the cells together, A solar cell in which a plurality of cells having different film forming process conditions, for example, a plurality of cells having different process temperatures, are stacked can be easily manufactured. Therefore, a tandem solar cell or a triple solar cell in which a plurality of cells are stacked can be easily manufactured without lowering the power generation efficiency of the power generation layer that is manufactured first in the stacked structure. Therefore, a solar cell with relatively high conversion efficiency can be produced efficiently.
（セル１２，６２，７２の製造方法及び構造の変形例）
　上記のセル１２，６２，７２の製造方法においては、第３セル７２を形成した後に、第３セル７２上に絶縁部３２を形成し、絶縁部３２上に第２セル６２を構成する裏面電極６５，第２発電層６４，及びグリッド電極６３が積層されている。その後、セル６２，７２からなるセル積層体と、セル１２とが絶縁部３０を介して貼り合わされている。本発明は、このようなセル１２，６２，７２の製造方法の製造方法を限定しない。セル１２，６２，７２の各々を別個に形成した後に、これら３つのセルを絶縁部を介して貼り合わせてもよい。
　以下に、製造方法の変形例を説明する。
　まず、独立した第２セル６２を形成するために、透光性基板を準備する。その後、透光性基板上に、受光面電極，第２発電層６４，及び裏面電極６５を順次積層する。この場合、裏面電極６５及び受光面電極は、ＴＣＯからなる。第２発電層６４は、ｐ型微結晶シリコン膜（不図示）とｎ型微結晶シリコン膜（不図示）との間にｉ型微結晶シリコン膜（不図示）が挟まれたｐｉｎ接合構造を含む。このように、変形例においては、第２セル６２は、別個に形成される。
　次に、第１セル１２及び第３セル７２を上述した方法と同様に形成する。これによって、独立した３つのセルが得られる。
　次に、第１セル１２と第２セル６２とを貼り合わせる。この場合、第２セル６２の透光性基板と、第１セル１２の裏面電極１５とが対向するように第１セル１２と第２セル６２とが貼り合わされる。透光性基板と裏面電極１５との間には、ペースト材料からなる絶縁部が配置される。また、第２セル６２と第３セル７２との間にも絶縁部を設け、第２セル６２と第３セル７２とを貼り合わせる。これによって、３つのセルが貼り合わされる。
　具体的に、図５Ｃに示す方法と同様に、スピンコート法等を用いることにより、絶縁部３０のペースト材料３０ａを裏面電極１５の全面に塗布する。その後、ペースト材料３０ａを介して第１セル１２と第２セル６２とが貼り合わされ、ペースト材料３０ａが硬化される。これによって、第１セル１２と第２セル６２とが絶縁部３０を介して接合される。更に、図４に示すように、スピンコート法等を用いることにより、絶縁部３２のペースト材料をグリッド電極７３の全面に塗布する。その後、ペースト材料を介して第２セル６２と第３セル７２とが貼り合わされ、ペースト材料が硬化される。これによって、第２セル６２と第３セル７２とが絶縁部３２を介して接合される。なお、絶縁部３０，３２の構成材料として絶縁接着シートを用いる場合には、裏面電極１５の全面又はグリッド電極７３の全面に絶縁接着シートを設ける。
　なお、上記の変形例においては、第２セル６２が受光面電極を有する構成について説明したが、第２セル６２は、図４と同様に、グリッド電極６３を有してもよい。また、この場合、絶縁部３０のペースト材料３０ａをグリッド電極６３の全面に塗布してもよい。
　上記のような変形例においても、上述した実施形態と同様の効果が得られる。 (Modification of manufacturing method and structure of cells 12, 62, 72)
In the manufacturing method of the cells 12, 62, and 72 described above, after the third cell 72 is formed, the insulating portion 32 is formed on the third cell 72, and the back electrode that constitutes the second cell 62 on the insulating portion 32. 65, the second power generation layer 64, and the grid electrode 63 are laminated. Thereafter, the cell stack composed of the cells 62 and 72 and the cell 12 are bonded together via the insulating part 30. The present invention does not limit the manufacturing method of such a cell 12, 62, 72. After each of the cells 12, 62, 72 is formed separately, these three cells may be bonded together via an insulating portion.
Below, the modification of a manufacturing method is demonstrated.
First, in order to form the independent second cell 62, a translucent substrate is prepared. Thereafter, the light-receiving surface electrode, the second power generation layer 64, and the back surface electrode 65 are sequentially stacked on the translucent substrate. In this case, the back electrode 65 and the light receiving surface electrode are made of TCO. The second power generation layer 64 has a pin junction structure in which an i-type microcrystalline silicon film (not shown) is sandwiched between a p-type microcrystalline silicon film (not shown) and an n-type microcrystalline silicon film (not shown). Including. Thus, in a modification, the 2nd cell 62 is formed separately.
Next, the first cell 12 and the third cell 72 are formed in the same manner as described above. As a result, three independent cells are obtained.
Next, the first cell 12 and the second cell 62 are bonded together. In this case, the first cell 12 and the second cell 62 are bonded so that the translucent substrate of the second cell 62 and the back electrode 15 of the first cell 12 face each other. An insulating portion made of a paste material is disposed between the translucent substrate and the back electrode 15. Further, an insulating portion is also provided between the second cell 62 and the third cell 72, and the second cell 62 and the third cell 72 are bonded together. As a result, three cells are bonded together.
Specifically, similar to the method shown in FIG. 5C, the paste material 30a of the insulating portion 30 is applied to the entire surface of the back electrode 15 by using a spin coating method or the like. Thereafter, the first cell 12 and the second cell 62 are bonded together via the paste material 30a, and the paste material 30a is cured. Thus, the first cell 12 and the second cell 62 are joined via the insulating unit 30. Furthermore, as shown in FIG. 4, the paste material of the insulating portion 32 is applied to the entire surface of the grid electrode 73 by using a spin coating method or the like. Thereafter, the second cell 62 and the third cell 72 are bonded together via the paste material, and the paste material is cured. As a result, the second cell 62 and the third cell 72 are joined via the insulating portion 32. In the case where an insulating adhesive sheet is used as the constituent material of the insulating portions 30 and 32, the insulating adhesive sheet is provided on the entire surface of the back electrode 15 or the entire surface of the grid electrode 73.
In the above modification, the configuration in which the second cell 62 includes the light receiving surface electrode has been described. However, the second cell 62 may include the grid electrode 63 as in FIG. In this case, the paste material 30 a of the insulating part 30 may be applied to the entire surface of the grid electrode 63.
Also in the above modification, the same effect as the above-described embodiment can be obtained.
　なお、本発明の技術範囲は、上述の実施形態に限定されることなく、本発明の趣旨を逸脱しない範囲において、上述の実施形態に種々の変更を加えることが可能である。
　例えば、上述の実施形態においては、第１セルの裏面電極と第２セルのグリッド電極との間の隙間が絶縁部の構成材料によって満たされている構成について説明した。本発明は、この構成を限定せず、少なくとも第１セルの裏面電極と第２セルのグリッド電極との間に絶縁部が形成され、第１セルと第２セルとが電気的に絶縁されている構成が採用される。 The technical scope of the present invention is not limited to the above-described embodiments, and various modifications can be made to the above-described embodiments without departing from the spirit of the present invention.
For example, in the above-described embodiment, the configuration in which the gap between the back electrode of the first cell and the grid electrode of the second cell is filled with the constituent material of the insulating portion has been described. The present invention is not limited to this configuration, and an insulating portion is formed at least between the back electrode of the first cell and the grid electrode of the second cell, and the first cell and the second cell are electrically insulated. The configuration is adopted.
　また、上述の実施形態においては、図１に示すように、第１セル１２及び第２セル２２の２層が重ねられた構造を説明したが、２層に限らず、２層以上の複数層が重なる構成を採用してもよい。 Moreover, in the above-mentioned embodiment, as shown in FIG. 1, the structure in which the two layers of the first cell 12 and the second cell 22 are overlapped has been described, but not limited to two layers, a plurality of layers of two or more layers You may employ | adopt the structure which overlaps.
　本発明は、発電効率及び製造効率を向上させることができる太陽電池及び太陽電池の製造方法に広く適用可能である。 The present invention is widely applicable to solar cells and solar cell manufacturing methods that can improve power generation efficiency and manufacturing efficiency.
１１…第１基板（基板）　１２…セル（第１発電セル）　２２，４２，５２，６２，７２…セル（第２発電セル）　１３…受光面電極　１４…発電層(第１発電層）　４４，５４，６４，７４…発電層(第２発電層）　１５，４５，５５，６５，７５…裏面電極　２３…シリコン基板（第２発電層）　２７…第１裏面電極（裏面電極）　２８…第２裏面電極（裏面電極）　２９，４３，５３，６３，７４…グリッド電極（受光面電極）　３０，３２…絶縁部　１００，２００，３００，４００…太陽電池。 DESCRIPTION OF SYMBOLS 11 ... 1st board | substrate (board | substrate) 12 ... Cell (1st power generation cell) 22, 42, 52, 62, 72 ... Cell (2nd power generation cell) 13 ... Light-receiving surface electrode 14 ... Power generation layer (1st power generation layer) 44 , 54, 64, 74 ... power generation layer (second power generation layer) 15, 45, 55, 65, 75 ... back electrode 23 ... silicon substrate (second power generation layer) 27 ... first back electrode (back electrode) 28 ... first 2 Back electrodes (back electrodes) 29, 43, 53, 63, 74 ... Grid electrodes (light receiving surface electrodes) 30, 32 ... Insulating parts 100, 200, 300, 400 ... Solar cells.

Claims (7)

  1. 　太陽電池であって、
    　光透過性を有する基板と、
    　前記基板に近い位置に配置され、第１発電層を含む第１発電セルと、
    　前記基板から離れた位置に配置され、前記第１発電層のバンドギャップよりも小さいバンドギャップを有する第２発電層を含む第２発電セルと、
    　前記第１発電セルと前記第２発電セルとの間に配置された絶縁部と
    　を含むことを特徴とする太陽電池。     A solar cell,
    A substrate having optical transparency;
    A first power generation cell disposed near the substrate and including a first power generation layer;
    A second power generation cell including a second power generation layer disposed at a position away from the substrate and having a band gap smaller than a band gap of the first power generation layer;
    A solar cell comprising: an insulating portion disposed between the first power generation cell and the second power generation cell.
  2. 　請求項１に記載の太陽電池であって、
    　前記第１発電セル及び前記第２発電セルを含む複数の発電セルを有し、
    　前記複数の発電セルのうち、前記基板から最も離れた位置に前記第２発電セルが配置され、前記第２発電層のバンドギャップは、１．３ｅＶ以下であることを特徴とする太陽電池。     The solar cell according to claim 1,
    A plurality of power generation cells including the first power generation cell and the second power generation cell;
    The solar cell, wherein the second power generation cell is disposed at a position farthest from the substrate among the plurality of power generation cells, and a band gap of the second power generation layer is 1.3 eV or less.
  3. 　請求項１又は請求項２に記載の太陽電池であって、
    　前記第１発電セル及び前記第２発電セルは、電気的に並列に接続されていることを特徴とする太陽電池。     The solar cell according to claim 1 or 2,
    The solar cell, wherein the first power generation cell and the second power generation cell are electrically connected in parallel.
  4. 　請求項１から請求項３のいずれか一項に記載の太陽電池であって、
    　前記第１発電セル及び前記第２発電セルの各々には、保護回路が設けられていることを特徴とする太陽電池。     It is a solar cell as described in any one of Claims 1-3,
    Each of the first power generation cell and the second power generation cell is provided with a protection circuit.
  5. 　太陽電池の製造方法であって、
    　光透過性を有する基板を準備し、
    　第１発電層を含む第１発電セルを形成し、
    　前記第１発電層のバンドギャップよりも小さいバンドギャップを有する第２発電層を含む第２発電セルを形成し、
    　前記第１発電セルと前記第２発電セルとの間に絶縁部を配置し、
    　前記基板に近い位置に前記第１発電セルを配置し、かつ、前記基板から離れた位置に前記第２発電セルを配置するように、前記第１発電セルに前記第２発電セルを重ね合わせることを特徴とする太陽電池の製造方法。     A solar cell manufacturing method comprising:
    Preparing a substrate having light transparency;
    Forming a first power generation cell including a first power generation layer;
    Forming a second power generation cell including a second power generation layer having a band gap smaller than the band gap of the first power generation layer;
    An insulating part is disposed between the first power generation cell and the second power generation cell,
    The first power generation cell is overlaid on the first power generation cell so that the first power generation cell is disposed at a position close to the substrate and the second power generation cell is disposed at a position away from the substrate. A method for manufacturing a solar cell.
  6. 　請求項５に記載の太陽電池の製造方法であって、
    　前記第１発電セルを形成する成膜プロセスにおける最高温度は、前記第２発電セルを形成する成膜プロセスにおける最高温度と異なることを特徴とする太陽電池の製造方法。     It is a manufacturing method of the solar cell of Claim 5, Comprising:
    The method for manufacturing a solar cell, wherein a maximum temperature in a film formation process for forming the first power generation cell is different from a maximum temperature in a film formation process for forming the second power generation cell.
  7. 　請求項６に記載の太陽電池の製造方法であって、
    　前記第１発電セルを形成する成膜プロセス及び前記第２発電セルを形成する成膜プロセスにおいて、最も高い温度条件の範囲は２５０～４００℃であり、最も低い温度条件の範囲は１８０～２３０℃であることを特徴とする太陽電池の製造方法。     It is a manufacturing method of the solar cell according to claim 6,
    In the film forming process for forming the first power generation cell and the film forming process for forming the second power generation cell, the range of the highest temperature condition is 250 to 400 ° C., and the range of the lowest temperature condition is 180 to 230 ° C. A method for producing a solar cell, wherein
PCT/JP2010/001562 2009-03-05 2010-03-05 Solar cell and method for manufacturing solar cell WO2010100947A1 (en)

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