WO2013125251A1 - Thin film solar cell - Google Patents

Thin film solar cell Download PDF

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Publication number
WO2013125251A1
WO2013125251A1 PCT/JP2013/050174 JP2013050174W WO2013125251A1 WO 2013125251 A1 WO2013125251 A1 WO 2013125251A1 JP 2013050174 W JP2013050174 W JP 2013050174W WO 2013125251 A1 WO2013125251 A1 WO 2013125251A1
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cell
layer
film
solar cell
thin film
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PCT/JP2013/050174
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French (fr)
Japanese (ja)
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松山　秀昭
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富士電機株式会社
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/0248—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies
    • H01L31/036—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
    • H01L31/075—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
    • H01L31/18—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
    • H01L31/1804—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof comprising only elements of Group IV of the Periodic System
    • H01L31/1812—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof comprising only elements of Group IV of the Periodic System including only AIVBIV alloys, e.g. SiGe
    • H01L31/1816—Special manufacturing methods for microcrystalline layers, e.g. uc-SiGe, uc-SiC
    • 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
    • Y02E10/545—Microcrystalline silicon PV cells
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • 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 thin film solar cell in which at least two or more layers of cells are laminated on a film substrate.
  • a solar cell is a power generation device that converts light energy into electric power.
  • attempts have been made to make a multi-junction structure by stacking a plurality of cells having different absorption wavelength bands.
  • Patent Documents 1 and 2 disclose solar cells having a multi-junction structure in which amorphous silicon cells and microcrystalline silicon cells are stacked from the light incident side.
  • the amorphous silicon cell is a cell using amorphous silicon, amorphous silicon alloy such as silicon germanium or silicon carbide as a material.
  • the microcrystalline silicon cell is a cell using a thin film made of a microcrystalline silicon alloy such as microcrystalline silicon, silicon germanium, or silicon carbide.
  • the microcrystalline silicon cell has higher sensitivity to long wavelength light than the amorphous silicon cell, and can use long wavelength light that cannot be absorbed by the amorphous silicon cell for power generation. For this reason, power generation efficiency is further improved by stacking an amorphous silicon cell and a microcrystalline silicon cell in this order from the light incident side to form a multi-junction structure.
  • an object of the present invention is to provide a thin film solar cell excellent in power generation efficiency.
  • the thin film solar cell of the present invention was laminated on a film substrate, a back electrode laminated on the film substrate, a plurality of nip type cells laminated on the back electrode, and an outermost nip type cell.
  • the plurality of nip-type cells include at least one microcrystalline silicon-based cell, and at least one amorphous silicon-based cell disposed on the transparent electrode side of the microcrystalline silicon-based cell, In the microcrystalline silicon cell, the ratio (I 520 / I 480 ) of the peak height (I 520 ) of 520 cm ⁇ 1 and the peak height (I 480 ) of 480 cm ⁇ 1 in the Raman spectroscopy of the i layer is 2 or more.
  • the impurity concentration is 2 ⁇ 10 19 atoms / cm 3 or less
  • the current generated in the amorphous silicon cell is in the range of 95% to 115% with respect to the current generated in the microcrystalline silicon cell
  • the product of the film thickness and the refractive index of the transparent electrode is 100 nm or more and 200 nm or less.
  • a peak height of 520 cm -1 in Raman spectroscopy of the i layer, the ratio of the peak height of the 480cm -1 (I 520 / I 480 ) is at 2 to 9, the impurity concentration
  • the current generated in the amorphous silicon cell with stabilized power generation efficiency can be brought close to the current generated in the microcrystalline silicon cell. For this reason, the movement loss of the current generated in each nip type cell is reduced, and the power generation efficiency is excellent. And since the product of the film thickness and refractive index of a transparent electrode is 100 nm or more and 200 nm or less, the sunlight which penetrate
  • the p layer is preferably composed of a microcrystalline silicon film having a thickness of 10 nm to 30 nm. According to this aspect, a thin-film solar cell with more excellent power generation efficiency can be obtained.
  • the n layer is composed of an amorphous silicon film
  • the i layer is composed of a microcrystalline silicon film
  • the microcrystalline silicon is between the n layer and the i layer.
  • a seed layer made of a film is preferably inserted.
  • the initial growth layer of microcrystalline silicon formed on the n layer made of an amorphous silicon film becomes amorphous silicon.
  • the i layer of amorphous silicon is sandwiched between the n layer and the i layer, it is considered that electrons hardly flow into the n layer.
  • an interface layer made of an amorphous silicon film to which boron is added is preferably inserted between the i layer and the p layer. According to this aspect, the interface layer makes it difficult for electrons to move to the p-layer side, and the power generation efficiency is improved.
  • the boron concentration in the interface layer is preferably 1/1000 or more and 1/10 or less of the impurity concentration in the p layer.
  • the interface layer preferably has a thickness of 5 nm to 20 nm.
  • the thin film solar cell of the present invention it is possible to effectively use sunlight even though it is a thin layer, and the power generation efficiency is excellent.
  • the thin film solar cell of the present invention will be described by taking the thin film solar cell shown in FIG. 1 as an example.
  • a microcrystalline silicon cell ( ⁇ c-Si cell) is used as the microcrystalline silicon cell
  • an amorphous silicon cell (a-Si cell) is used as the amorphous silicon cell.
  • the microcrystalline silicon cell 30 is referred to as a ⁇ c-Si cell
  • the amorphous silicon cell 50 is referred to as an a-Si cell 50.
  • the material of the film substrate 10 is not particularly limited.
  • a polyimide film, a polyethylene terephthalate film, a polyethylene naphthalate film, a polyether sulfone film, an acrylic film, an aramid film, and the like can be given.
  • the film thickness of the film substrate 10 is not particularly limited. Considering flexibility, strength, and weight, it is preferably 15 ⁇ m or more and 200 ⁇ m or less.
  • the back electrode 20 is laminated on the film substrate 10.
  • the back electrode 20 is not particularly limited, and is made of a conductive metal such as Ag, Ag alloy, Ni, Ni alloy, Al, or Al alloy.
  • a layer formed of a transparent conductive oxide such as ITO, SnO, or ZnO may be stacked on the layer formed of these conductive metals.
  • the film thickness of the back electrode 20 is preferably 0.1 ⁇ m or more and 2 ⁇ m or less, and more preferably 0.1 ⁇ m or more and 1 ⁇ m or less. If it is less than 0.1 ⁇ m, the electrical conductivity is low, and if it exceeds 2 ⁇ m, it takes time to form a film.
  • the ⁇ c-Si cell 30 is laminated on the back electrode 20.
  • the ⁇ c-Si cell 30 is composed of a nip type cell formed by joining an n layer, an i layer, and a p layer.
  • the n layer of the ⁇ c-Si cell 30 includes a microcrystalline silicon film (hereinafter referred to as ⁇ c-Si) containing n-type impurities such as phosphorus at a concentration of 1 ⁇ 10 19 atoms / cm 3 or more and 1 ⁇ 10 21 atoms / cm 3 or less. And an amorphous silicon film (hereinafter referred to as an a-Si film).
  • the thickness of the n layer is preferably 10 nm to 100 nm, and more preferably 10 nm to 50 nm. When the film thickness of the n layer is within the above range, good power generation efficiency can be obtained.
  • the i layer of the ⁇ c-Si cell 30 is composed of a ⁇ c-Si film having an impurity concentration of 2 ⁇ 10 19 atoms / cm 3 or less.
  • the impurity concentration is more preferably 1 ⁇ 10 19 atoms / cm 3 or less.
  • the impurity concentration is 2 ⁇ 10 19 atoms / cm 3 or less, the carrier mobility of electrons and holes is good, and excellent power generation efficiency is obtained.
  • the i layer has a ratio (I 520 / I 480 ) of a peak height (I 520 ) of 520 cm ⁇ 1 and a peak height (I 480 ) of 480 cm ⁇ 1 in Raman spectroscopy of 2 or more and 9 or less, 2 or more and 7 or less are more preferable. If the ratio is less than 2 or exceeds 9, the power generation efficiency decreases as shown in the examples described later. Note that a peak height of 520 cm ⁇ 1 means a peak attributed to crystalline silicon, and a peak height I 480 of 480 cm ⁇ 1 means a peak attributed to amorphous silicon. Therefore, when the value of the ratio is large, it means that the crystallinity of the i layer is high. In order to increase the value of the ratio, the silane concentration relative to the hydrogen gas in the raw material gas used for film formation may be increased.
  • the film thickness of the i layer is preferably 0.5 ⁇ m or more and 4 ⁇ m or less, and more preferably 1 ⁇ m or more and 3 ⁇ m or less. When the film thickness of the i layer is within the above range, good power generation efficiency can be obtained.
  • the p layer of the ⁇ c-Si cell 30 is a ⁇ c-Si film or an a-Si film containing p-type impurities such as boron at a concentration of 1 ⁇ 10 19 atoms / cm 3 or more and 1 ⁇ 10 21 atoms / cm 3 or less. Composed.
  • the thickness of the p layer is more preferably 10 nm or more and 30 nm or less. If it is less than 10 nm or exceeds 30 nm, the power generation efficiency tends to decrease as shown in the examples described later.
  • the n layer is composed of an a-Si film
  • a seed layer made of the ⁇ c-Si film is inserted between the n layer and the i layer.
  • the ⁇ c-Si film is difficult to form on the a-Si film and tends to be amorphous. For this reason, the film quality at the interface between the ⁇ c-Si film and the a-Si film may deteriorate, and the power generation efficiency may be impaired.
  • the unevenness at the interface between the n layer and the i layer can be reduced to 10 nm or less, and an i layer made of a ⁇ c-Si film with good film quality is formed. it can. As a result, excellent power generation efficiency can be obtained.
  • the film thickness of the seed layer is preferably 5 nm or more and 200 nm or less.
  • the film thickness of the seed layer is less than 5 nm, the effect of improving the film quality of the i layer may not be sufficient. If it exceeds 200 nm, it takes time to form a film.
  • the ⁇ c-Si cell 30 has an interfacial layer made of an a-Si film to which boron is added inserted between the i layer and the p layer.
  • the boron concentration of the interface layer is preferably 1/1000 or more and 1/10 or less of the impurity concentration of the p layer.
  • the thickness of the interface layer is preferably 5 nm or more and 20 nm or less. If the boron concentration and film thickness of the interface layer are within the above ranges, excellent power generation efficiency can be obtained.
  • the tunnel junction layer 40 is laminated on the ⁇ c-Si cell 30, and the ⁇ c-Si cell 30 and the a-Si cell 50 are joined via the tunnel junction layer 40.
  • the thickness of the tunnel junction layer 40 is preferably 0.5 ⁇ m or less, and more preferably 0.1 ⁇ m or less.
  • the material of the tunnel junction layer 40 is preferably a ⁇ c-Si film.
  • the ⁇ c-Si cell 30 and the a-Si cell 50 may be directly joined without providing the tunnel junction layer 40. However, by joining the two via the tunnel junction layer 40, more excellent power generation efficiency can be obtained. can get.
  • the a-Si cell 50 is laminated on the tunnel junction layer 40.
  • the a-Si cell 50 is composed of a nip type cell in which an n layer, an i layer, and a p layer are joined.
  • the n layer of the a-Si cell 50 is composed of an a-Si film containing n-type impurities such as phosphorus at a concentration of 1 ⁇ 10 19 atoms / cm 3 or more and 1 ⁇ 10 21 atoms / cm 3 or less.
  • the thickness of the n layer is preferably 5 nm to 50 nm, and more preferably 10 nm to 30 nm. When the film thickness is within the above range, good power generation efficiency can be obtained.
  • the i layer of the a-Si cell 50 is composed of an a-Si film having an impurity concentration of 2 ⁇ 10 19 atoms / cm 3 or less.
  • the film thickness of the i layer is preferably 100 nm or more and 1000 nm or less, and more preferably 100 nm or more and 300 nm or less.
  • good power generation efficiency can be obtained.
  • photodegradation increases.
  • the p-layer of the a-Si cell 50 is composed of an a-Si film containing p-type impurities such as boron at a concentration of 1 ⁇ 10 19 atoms / cm 3 or more and 1 ⁇ 10 21 atoms / cm 3 or less.
  • the thickness of the p layer is preferably 5 nm or more and 50 nm or less. When the film thickness is within the above range, good power generation efficiency can be obtained.
  • the current generated in the a-Si cell 50 is preferably in the range of 95% to 115% with respect to the current generated in the ⁇ c-Si cell 30.
  • the a-Si cell 50 is easily deteriorated by light irradiation and the power generation efficiency is easily lowered, and the power generation efficiency is reduced by about 10% compared to that immediately after film formation.
  • the current generated in the a-Si cell 50 can be 95% to 115% of the current generated in the ⁇ c-Si cell 30.
  • the current generated in the a-Si cell 50 in the performance after light irradiation can be reduced to ⁇ c-Si.
  • the current generated in the cell 30 can be approached. For this reason, the power generation efficiency of a thin film solar cell can be improved.
  • the current generated in each cell increases as the thickness of the cell (particularly the i layer) increases, and decreases as it decreases.
  • the current generated in the ⁇ c-Si cell 30 and the current generated in the a-Si cell 50 are evaluated by spectral sensitivity measurement.
  • the spectral sensitivity measurement is performed in a state in which the power generation of the ⁇ c-Si cell 30 is suppressed except for the long wavelength light in the excitation light.
  • spectral sensitivity measurement is performed in a state where power generation in the a-Si cell 50 is suppressed except for the short wavelength light in the excitation light.
  • a transparent electrode 60 is laminated on the a-Si cell 50.
  • the configuration of the transparent electrode 60 is not particularly limited, and examples thereof include transparent conductive oxides such as ITO, SnO, and ZnO.
  • the film thickness of the transparent electrode 60 is preferably 0.1 ⁇ m or more and 1 ⁇ m or less. When the thickness is less than 0.1 ⁇ m, the electrical conductivity decreases, and when it exceeds 1 ⁇ m, the light transmittance decreases. Further, the product of the film thickness and the refractive index of the transparent electrode 60 is preferably 100 nm or more and 200 nm or less.
  • the refractive index of the transparent electrode means the refractive index for light having a wavelength of 700 nm.
  • the thin film solar cell shown in FIG. 1 is a tandem thin film solar cell in which two layers of nip type cells are stacked, but may be a multi-junction type in which three or more layers of nip type cells are stacked. When three or more nip type cells are stacked, they are arranged in ascending order of the band gap, and a transparent electrode is stacked thereon.
  • a conductive metal such as Ag, Ag alloy, Ni, Ni alloy, Al, Al alloy is deposited on the film substrate 10 by sputtering, vacuum deposition, spray film forming, screen printing, ink jet printing, plating.
  • a conductive metal layer is formed by forming a film by a conventionally known method such as a method. If necessary, a transparent conductive oxide layer may be formed by forming a transparent conductive oxide such as ITO, SnO, or ZnO in the same manner on the conductive metal layer. In this way, the back electrode 20 is formed on the film substrate 10.
  • the film substrate 10 thus formed with the back electrode 20 is introduced into a plasma CVD apparatus, and a source gas containing a silicon-containing gas and hydrogen gas is introduced into the apparatus, and ⁇ c ⁇
  • a source gas containing a silicon-containing gas and hydrogen gas is introduced into the apparatus, and ⁇ c ⁇
  • the respective semiconductor layers constituting the Si cell 30, the tunnel junction layer 40, and the a-Si cell 50 are formed.
  • Examples of the silicon-containing gas used as the source gas include monosilane (SiH 4 ), disilane (Si 2 H 6 ), silicon tetrafluoride (SiF 4 ), silicon tetrachloride (SiCl 4 ), and dichlorosilane (SiH 2 Cl 2). ) Is an example.
  • examples of the dopant gas used when forming the p layer include diborane (B 2 H 6 ).
  • Examples of the dopant gas used for forming the n layer include phosphine (PH 3 ).
  • FIG. 2 is a schematic view showing an example of a plasma CVD apparatus that can be used for forming a semiconductor layer of the thin film solar cell of the present invention.
  • a cathode electrode 2 and an anode electrode 3, which are two parallel plate electrodes, are placed facing each other with a distance (interelectrode distance) therebetween.
  • a high frequency power source 6 is connected to the cathode electrode 2 via a matching unit 5 so that a high frequency can be applied between the electrodes.
  • the cathode electrode 2 is provided with a number of holes (not shown), and the source gas sent through the introduction pipe (not shown) is supplied in a shower shape from the cathode electrode 2 side toward the film substrate 10. ing.
  • the anode electrode 3 is provided with a heating device (not shown) so that the anode electrode 3 and the film substrate 10 can be heated to a predetermined temperature.
  • the exhaust system of the plasma CVD apparatus 1 is provided with a pressure control device (not shown) that keeps the pressure inside the apparatus constant.
  • each semiconductor layer may be formed using the same plasma CVD apparatus, or each semiconductor layer may be formed using a different plasma CVD apparatus by changing the plasma CVD apparatus for each semiconductor layer.
  • a transparent conductive oxide such as ITO, SnO, ZnO or the like is formed on the a-Si cell 50.
  • the transparent electrode 60 is formed by depositing an object by a conventionally known method such as a sputtering method, a vacuum deposition method, a spray film forming method, a screen printing method, an ink jet printing method, or a plating method.
  • Test Example 1 As the film substrate 10, a polyimide film having a film thickness of 50 ⁇ m was used. A 300 nm Ag film was formed on this polyimide film, and then a 30 nm ZnO film was formed on the Ag layer to form the back electrode 20. Then, using the plasma CVD apparatus shown in FIG. 2, various silicon films are formed by plasma CVD under the conditions shown in Table 1, using a mixed gas of SiH 4 and H 2 as a source gas, and a back electrode On the substrate 20, a ⁇ c-Si cell 30, a tunnel junction layer 40, and an a-Si cell 50 were formed.
  • the i layer of the ⁇ c-Si cell 30 has a ratio (I 520 / I 480 ) of a peak height (I 520 ) of 520 cm ⁇ 1 to a peak height (I 480 ) of 480 cm ⁇ 1 in Raman spectroscopy of 4.2.
  • the impurity concentration was 8 ⁇ 10 18 atoms / cm 3 .
  • the impurity concentration was measured by SIMS analysis (Secondary Ion-microprobe Mass Spectrometry). Nitrogen and carbon were detected as impurities in addition to oxygen, but they were very small, so the oxygen concentration was taken as the impurity concentration.
  • a thin film solar cell shown in FIG. 1 was manufactured by laminating an ITO film of 70 nm as a transparent electrode 60 on the a-Si cell 50 by DC sputtering under the condition of 200 ° C.
  • the product of the film thickness of the transparent electrode 60 and the refractive index for light having a wavelength of 700 nm was 140 nm.
  • the thin-film solar cell was measured with a solar simulator under a light of 100 mW / cm 2 to measure a current-voltage curve, and power generation efficiency (photoelectric conversion efficiency) was obtained.
  • the power generation efficiency immediately before irradiation with light was 11.2%, and the power generation efficiency after 300 hours of light irradiation was 9.7%.
  • Test Example 2 A thin film solar cell was manufactured in the same manner as in Test Example 1 except that the film thickness of the i layer of the a-Si cell 50 was changed in the range of 400 nm to 600 nm in Test Example 1.
  • the manufactured thin film solar cell was measured for the current (short circuit current density) of each cell with a spectral sensitivity measuring device. Moreover, after performing 100 mW / cm ⁇ 2 > light irradiation with a solar simulator for 300 hours, the short circuit current density of the thin film solar cell was measured.
  • the current ratio before light irradiation (current generated in the a-Si cell 50 / current generated in the ⁇ c-Si cell 30) and the short-circuit current density (Jsc) of the thin-film solar cell after light irradiation are shown in FIG. As shown in FIG. 3, it can be seen that the short-circuit current density after light irradiation is high when the current ratio is 95% or more and 115% or less.
  • the i layer of the ⁇ c-Si cell thus produced has a ratio (I 520 / I 480 ) of the peak height (I 520 ) of 520 cm ⁇ 1 and the peak height (I 480 ) of 480 cm ⁇ 1 in Raman spectroscopy. ) was in the range of 1 to 11.
  • the current-voltage curve was measured for the ⁇ c-Si cell under irradiation of 100 mW / cm 2 of light with a solar simulator to determine the power generation efficiency.
  • the results are shown in FIG. As shown in FIG. 4, it can be seen that excellent power generation efficiency is obtained when I 520 / I 480 is in the range of 2 to 9. If I 520 / I 480 is less than 2, it is considered that the power generation efficiency is lowered because it is close to an amorphous property.
  • Test Example 4 The impurity concentration in the i layer of the ⁇ c-Si cell was examined.
  • the deposition conditions for the i-layer of the ⁇ c-Si cell are as follows: power 120 W, pressure 480 Pa (3.6 Torr), SiH 4 gas flow rate 15 sccm, dilution rate 50 times, and the conditions for degassing treatment in the plasma CVD deposition apparatus are changed.
  • the impurity concentration of the i layer was changed.
  • each thin film was formed on the back electrode under the film forming conditions of the ⁇ c-Si cell shown in Table 1 of Test Example 1 to manufacture a ⁇ c-Si cell.
  • the impurity concentration of the i layer of the ⁇ c-Si cell was measured by the SIMS method. Nitrogen and carbon were detected as impurities in addition to oxygen, but they were very small, so the oxygen concentration was taken as the impurity concentration. Then, an ITO film of 70 nm was laminated on the surface layer of the ⁇ c-Si cell in the same manner as in Test Example 1.
  • the current-voltage curve was measured by irradiating 100 ⁇ W / cm 2 of light on the ⁇ c-Si cell with a solar simulator to determine the power generation efficiency. The results are shown in FIG. As shown in FIG. 5, when the impurity concentration exceeded 2 ⁇ 10 19 atoms / cm 3 , the power generation efficiency of the ⁇ c-Si cell was lowered.
  • Test Example 5 The film thickness of ITO was examined.
  • the conditions for forming the i layer of the ⁇ c-Si cell were as follows: power 300 W, pressure 2133 Pa (16 Torr), SiH 4 gas flow rate 33 sccm, and dilution rate 50 times. Except for the i layer, each thin film was formed on the back electrode under the film forming conditions of the ⁇ c-Si cell shown in Table 1 of Test Example 1 to manufacture a ⁇ c-Si cell.
  • the film formation time is adjusted to change the film thickness of ITO in the range of 25 nm to 125 nm, and the film thickness of ITO and the refractive index with respect to light having a wavelength of 700 nm are ⁇ c-Si cells having different product (hereinafter referred to as optical film thickness) were manufactured.
  • the current-voltage curve was measured by irradiating 100 ⁇ W / cm 2 of light on the ⁇ c-Si cell with a solar simulator to determine the power generation efficiency.
  • the results are shown in FIG.
  • high power generation efficiency was obtained when the optical film thickness of the transparent electrode was in the range of 100 nm to 200 nm.
  • Particularly high power generation efficiency was obtained when the optical film thickness was 140 nm.
  • Test Example 6 The thickness of the p layer of the ⁇ c-Si cell was examined. Except that the film thickness of the p layer of the ⁇ c-Si cell was changed in the range of 5 nm to 50 nm, the film was formed on the back electrode under the film formation conditions of the ⁇ c-Si cell shown in Table 1 of Test Example 1. Each thin film was formed into a ⁇ c-Si cell. The boron concentration in the p layer of this ⁇ c-Si cell was about 5 ⁇ 10 20 atoms / cm 3 . Then, an ITO film of 70 nm was laminated on the surface layer of the ⁇ c-Si cell in the same manner as in Test Example 1.
  • the produced ⁇ c-Si cell was measured with a solar simulator under irradiation of light of 100 mW / cm 2 to measure a current-voltage curve, and power generation efficiency was obtained.
  • the results are shown in Table 2.
  • high power generation efficiency was obtained when the thickness of the p layer was in the range of 10 nm to 30 nm.
  • Test Example 7 In Test Example 6, the film thickness of the p layer was 20 nm, and the film thickness of the n layer was changed in the range of 20 nm to 100 nm. The phosphorus concentration in the p layer of this ⁇ c-Si cell was about 5 ⁇ 10 20 atoms / cm 3 . Then, an ITO film of 70 nm was laminated on the surface layer of the ⁇ c-Si cell in the same manner as in Test Example 1.
  • the manufactured ⁇ c-Si cell was irradiated with 100 mW / cm 2 of light for 300 hours with a solar simulator, and then a current-voltage curve was measured under the same condition of light irradiation to determine the power generation efficiency.
  • the power generation efficiency of the ⁇ c-Si cell was almost the same. There was no significant difference in power generation efficiency when the thickness of the n layer was in the range of 20 nm to 100 nm.
  • the current-voltage curve was measured by irradiating 100 ⁇ W / cm 2 of light on the ⁇ c-Si cell with a solar simulator to determine the power generation efficiency.
  • the power generation efficiency of the ⁇ c-Si cell with the seed layer (Table 3) was 7.2%, whereas the power generation efficiency of the ⁇ c-Si cell without the seed layer (Table 4) was 6.2%. Power generation efficiency could be improved by inserting a seed layer between the n layer and i layer of the ⁇ c-Si cell.
  • the ⁇ c-Si cell with a seed layer (Table 3) was a ⁇ c-Si film in which the i layer was grown almost uniformly, and the n layer and the i layer.
  • the unevenness of the interface with was 10 nm or less.
  • the ⁇ c-Si cell without the seed layer (Table 4) has a structure in which the amorphous part of the n layer penetrates into the i layer and the part of the microcrystalline part enters into a saw shape, The unevenness at the interface between them was several hundred nm.
  • Test Example 9 In the ⁇ c-Si cell, an interface layer made of an a-Si film having a wide band gap was inserted as an interface layer between the i layer and the p layer.
  • the ⁇ c-Si cell deposition conditions were the same as the ⁇ c-Si cell deposition conditions shown in Table 1 of Test Example 1, and an interface layer composed of an a-Si film was inserted between the i layer and the p layer. .
  • the film formation conditions for the interface layer are as follows: substrate temperature 140 ° C., RF power 5 W, pressure 67 Pa (0.5 Torr), silane flow rate 4 sccm, hydrogen dilution rate 10 times, diborane gas concentration relative to silane (B 2 H 6 / SiH 4 concentration) ) was changed in the range of 0 ppm to 1000 ppm, and an interface layer having a film thickness changed in the range of 5 nm to 40 nm was formed. Then, an ITO film of 70 nm was laminated on the surface layer of the ⁇ c-Si cell in the same manner as in Test Example 1.
  • the current-voltage curve was measured by irradiating 100 ⁇ W / cm 2 of light on the ⁇ c-Si cell with a solar simulator to determine the power generation efficiency. The results are shown in Table 5.
  • the borane concentration of the p layer of the ⁇ c-Si cell is about 1% (Table of Test Example 1). 1). As shown in Table 5, excellent power generation efficiency was obtained when the borane concentration of the interface layer was in the concentration range of 1/1000 or more and 1/10 or less of the p layer. In particular, particularly excellent power generation efficiency was obtained when the thickness of the interface layer was in the range of 5 nm to 20 nm.
  • Plasma CVD apparatus 2 Cathode electrode 3: Anode electrode 5: Matching device 6: High frequency power supply 10: Film substrate 20: Back electrode 30: Microcrystalline silicon cell, ⁇ c-Si cell 40: Tunnel junction layer 50: Amorphous silicon Cell, a-Si cell 60: transparent electrode

Abstract

Provided is a thin film solar cell which has excellent power generation efficiency. A thin film solar cell which is provided with: a film substrate (10); a backside electrode (20) that is laminated on the film substrate (10); a plurality of nip type cells laminated on the backside electrode (20); and a transparent electrode (60) that is laminated on the outermost nip type cell. The nip type cells include a μc-Si cell (30) and an a-Si cell (50). The μc-Si cell (30) has a ratio of the peak height at 520 cm-1 to the peak height at 480 cm-1 of from 2 to 9 (inclusive) in Raman spectroscopy of the i-layer, while having an impurity concentration of 2 × 1019 atoms/cm3 or less. The current generated in the a-Si cell (50) is within the range from 95% to 115% (inclusive) of the current generated in the μc-Si cell (30). The product of the film thickness and the refractive index of the transparent electrode (60) is from 100 nm to 200 nm (inclusive).

Description

薄膜太陽電池Thin film solar cell
　本発明は、フィルム基板上に、少なくとも２層以上のセルが積層された薄膜太陽電池に関する。 The present invention relates to a thin film solar cell in which at least two or more layers of cells are laminated on a film substrate.
　太陽電池は、光エネルギーを電力に変換する発電装置である。太陽電池の発電効率を向上させるために、吸収波長帯域が異なるセルを複数積層して、多接合型構造とする試みが行われている。 A solar cell is a power generation device that converts light energy into electric power. In order to improve the power generation efficiency of solar cells, attempts have been made to make a multi-junction structure by stacking a plurality of cells having different absorption wavelength bands.
　例えば、特許文献１，２には、光入射側から、アモルファスシリコン系セル、微結晶シリコン系セルを積層して多接合型構造とした太陽電池が開示されている。アモルファスシリコン系セルは、アモルファスシリコン、シリコンゲルマニウムやシリコンカーバイドなどのアモルファスシリコン合金を材料として用いたセルである。微結晶シリコン系セルは微結晶シリコン、シリコンゲルマニウムやシリコンカーバイドなどの微結晶シリコン合金を材料とする薄膜を用いたセルである。 For example, Patent Documents 1 and 2 disclose solar cells having a multi-junction structure in which amorphous silicon cells and microcrystalline silicon cells are stacked from the light incident side. The amorphous silicon cell is a cell using amorphous silicon, amorphous silicon alloy such as silicon germanium or silicon carbide as a material. The microcrystalline silicon cell is a cell using a thin film made of a microcrystalline silicon alloy such as microcrystalline silicon, silicon germanium, or silicon carbide.
　微結晶シリコン系セルは、アモルファスシリコン系セルに比べて長波長光に対する感度が高く、アモルファスシリコン系セルでは吸収できない長波長光を発電に利用できる。このため、光入射側から、アモルファスシリコン系セル、微結晶シリコン系セルの順に積層して多接合型構造とすることで、発電効率がより向上する。 The microcrystalline silicon cell has higher sensitivity to long wavelength light than the amorphous silicon cell, and can use long wavelength light that cannot be absorbed by the amorphous silicon cell for power generation. For this reason, power generation efficiency is further improved by stacking an amorphous silicon cell and a microcrystalline silicon cell in this order from the light incident side to form a multi-junction structure.
特開２００８－２０５０６３号公報JP 2008-205063 A 特開２００９－２００４４１号公報JP 2009-200441 A
　しかしながら、近年においては、更なる発電効率の向上が求められており、従来の薄膜太陽電池では十分ではなかった。 However, in recent years, further improvement in power generation efficiency has been demanded, and conventional thin film solar cells have not been sufficient.
　よって、本発明の目的は、発電効率に優れた薄膜太陽電池を提供することにある。 Therefore, an object of the present invention is to provide a thin film solar cell excellent in power generation efficiency.
　本発明の薄膜太陽電池は、フィルム基板と、該フィルム基板上に積層された裏面電極と、該裏面電極上に積層された複数のｎｉｐ型セルと、最外層のｎｉｐ型セル上に積層された透明電極とを備えた薄膜太陽電池において、
　前記複数のｎｉｐ型セルとして、少なくとも１つの微結晶シリコン系セルと、該微結晶シリコン系セルよりも前記透明電極側に配置された、少なくとも１つのアモルファスシリコン系セルとを有し、
　前記微結晶シリコン系セルは、ｉ層のラマン分光における５２０ｃｍ－１のピーク高さ（Ｉ５２０）と４８０ｃｍ－１のピーク高さ（Ｉ４８０）との比（Ｉ５２０／Ｉ４８０）が２以上９以下で、不純物濃度が２×１０１９原子／ｃｍ３以下であり、
　前記アモルファスシリコン系セルで発生する電流が、前記微結晶シリコン系セルで発生する電流に対して、９５％以上１１５％以下の範囲にあり、
　前記透明電極の膜厚と屈折率との積が１００ｎｍ以上２００ｎｍ以下であることを特徴とする。 The thin film solar cell of the present invention was laminated on a film substrate, a back electrode laminated on the film substrate, a plurality of nip type cells laminated on the back electrode, and an outermost nip type cell. In a thin film solar cell with a transparent electrode,
The plurality of nip-type cells include at least one microcrystalline silicon-based cell, and at least one amorphous silicon-based cell disposed on the transparent electrode side of the microcrystalline silicon-based cell,
In the microcrystalline silicon cell, the ratio (I 520 / I 480 ) of the peak height (I 520 ) of 520 cm −1 and the peak height (I 480 ) of 480 cm −1 in the Raman spectroscopy of the i layer is 2 or more. 9 or less, the impurity concentration is 2 × 10 19 atoms / cm 3 or less,
The current generated in the amorphous silicon cell is in the range of 95% to 115% with respect to the current generated in the microcrystalline silicon cell,
The product of the film thickness and the refractive index of the transparent electrode is 100 nm or more and 200 nm or less.
　本発明の薄膜太陽電池によれば、ｉ層のラマン分光における５２０ｃｍ－１のピーク高さと、４８０ｃｍ－１のピーク高さとの比（Ｉ５２０／Ｉ４８０）が２以上９以下で、不純物濃度が２×１０１９原子／ｃｍ３以下である微結晶シリコン系セルと、アモルファスシリコン系セルとを組み合わせて用いることにより、太陽光の有効利用が可能となり、発電効率に優れた太陽電池とすることができる。
　また、アモルファスシリコン系セルは、光照射により劣化し易いが、アモルファスシリコン系セルで発生する電流を、微結晶シリコン系セルで発生する電流の９５％以上１１５％以下としたことで、光照射後の発電効率が安定化したアモルファスシリコン系セルで発生する電流を、微結晶シリコン系セルで発生する電流に近づけることができる。このため、各ｎｉｐ型セルで発生した電流の移動ロスが小さくなり、発電効率に優れる。
　そして、透明電極の膜厚と屈折率との積が１００ｎｍ以上２００ｎｍ以下であることにより、太陽電池内部に侵入した太陽光が、太陽電池内部に閉じ込められ易くなり、太陽光を有効利用できる。 According to the thin-film solar cell of the present invention, a peak height of 520 cm -1 in Raman spectroscopy of the i layer, the ratio of the peak height of the 480cm -1 (I 520 / I 480 ) is at 2 to 9, the impurity concentration By using a combination of a microcrystalline silicon cell that is 2 × 10 19 atoms / cm 3 or less and an amorphous silicon cell, solar light can be effectively used and a solar cell with excellent power generation efficiency can be obtained. it can.
In addition, although amorphous silicon cells are easily deteriorated by light irradiation, the current generated in the amorphous silicon cells is 95% to 115% of the current generated in the microcrystalline silicon cells. The current generated in the amorphous silicon cell with stabilized power generation efficiency can be brought close to the current generated in the microcrystalline silicon cell. For this reason, the movement loss of the current generated in each nip type cell is reduced, and the power generation efficiency is excellent.
And since the product of the film thickness and refractive index of a transparent electrode is 100 nm or more and 200 nm or less, the sunlight which penetrate | invaded the inside of a solar cell becomes easy to be confine | sealed inside a solar cell, and sunlight can be used effectively.
　本発明の薄膜太陽電池の前記微結晶シリコン系セルは、ｐ層が厚さ１０ｎｍ以上３０ｎｍ以下の微結晶シリコン膜で構成されていることが好ましい。この態様によれば、より発電効率に優れた薄膜太陽電池とすることができる。 In the microcrystalline silicon cell of the thin film solar cell of the present invention, the p layer is preferably composed of a microcrystalline silicon film having a thickness of 10 nm to 30 nm. According to this aspect, a thin-film solar cell with more excellent power generation efficiency can be obtained.
　本発明の薄膜太陽電池の前記微結晶シリコン系セルは、ｎ層がアモルファスシリコン膜で構成され、ｉ層が微結晶シリコン膜で構成されており、ｎ層とｉ層との間に微結晶シリコン膜からなるシード層が挿入されていることが好ましい。シード層がない場合は、アモルファスシリコン膜からなるｎ層上に形成した微結晶シリコンの初期成長層がアモルファスシリコンとなる。このため、ｎ層とｉ層との間にアモルファスシリコンのｉ層が挟まれるため、電子がｎ層に流れ難くなると考えられる。 In the microcrystalline silicon cell of the thin film solar cell of the present invention, the n layer is composed of an amorphous silicon film, the i layer is composed of a microcrystalline silicon film, and the microcrystalline silicon is between the n layer and the i layer. A seed layer made of a film is preferably inserted. When there is no seed layer, the initial growth layer of microcrystalline silicon formed on the n layer made of an amorphous silicon film becomes amorphous silicon. For this reason, since the i layer of amorphous silicon is sandwiched between the n layer and the i layer, it is considered that electrons hardly flow into the n layer.
　本発明の薄膜太陽電池の前記微結晶シリコン系セルは、ｉ層とｐ層との間に、ボロンが添加されたアモルファスシリコン膜からなる界面層が挿入されていることが好ましい。この態様によれば、界面層によって、電子がｐ層側に移動し難くなり、発電効率が向上する。 In the microcrystalline silicon cell of the thin film solar cell of the present invention, an interface layer made of an amorphous silicon film to which boron is added is preferably inserted between the i layer and the p layer. According to this aspect, the interface layer makes it difficult for electrons to move to the p-layer side, and the power generation efficiency is improved.
　本発明の薄膜太陽電池は、前記界面層のボロン濃度が、ｐ層の不純物濃度の１／１０００以上１／１０以下であることが好ましい。 In the thin film solar cell of the present invention, the boron concentration in the interface layer is preferably 1/1000 or more and 1/10 or less of the impurity concentration in the p layer.
　本発明の薄膜太陽電池は、前記界面層の厚みが５ｎｍ以上２０ｎｍ以下であることが好ましい。 In the thin film solar cell of the present invention, the interface layer preferably has a thickness of 5 nm to 20 nm.
　本発明の薄膜太陽電池によれば、薄層でありながら太陽光の有効利用が可能となり、発電効率に優れる。 According to the thin film solar cell of the present invention, it is possible to effectively use sunlight even though it is a thin layer, and the power generation efficiency is excellent.
本発明の薄膜太陽電池の一実施形態の概略構成図である。It is a schematic block diagram of one Embodiment of the thin film solar cell of this invention. 同薄膜太陽電池の半導体層の形成に用いることができるプラズマＣＶＤ装置の概略構成図である。It is a schematic block diagram of the plasma CVD apparatus which can be used for formation of the semiconductor layer of the thin film solar cell. ａ－Ｓｉセル５０とμｃ－Ｓｉセル３０との電流比と、安定化後の薄膜太陽電池の短絡電流密度との関係を示す図である。It is a figure which shows the relationship between the electric current ratio of the a-Si cell 50 and the μc-Si cell 30, and the short circuit current density of the thin film solar cell after stabilization. 微結晶シリコンセルのｉ層のＩ５２０／Ｉ４８０と、薄膜太陽電池の発電効率の関係を示す図である。And I 520 / I 480 of the i layer of microcrystalline silicon cell is a diagram showing the relationship between the power generation efficiency of a thin-film solar cell. 微結晶シリコンセルのｉ層の不純物濃度と、薄膜太陽電池の発電効率の関係を示す図である。It is a figure which shows the relationship of the impurity concentration of i layer of a microcrystal silicon cell, and the power generation efficiency of a thin film solar cell. 透明電極の光学膜厚と、薄膜太陽電池の発電効率の関係を示す図である。It is a figure which shows the relationship between the optical film thickness of a transparent electrode, and the electric power generation efficiency of a thin film solar cell.
　本発明の薄膜太陽電池について、図１に示す薄膜太陽電池を例に挙げて説明する。 The thin film solar cell of the present invention will be described by taking the thin film solar cell shown in FIG. 1 as an example.
　図１に示す薄膜太陽電池は、フィルム基板１０に、裏面電極２０、微結晶シリコン系セル３０、トンネル接合層４０、アモルファスシリコン系セル５０、透明電極６０が積層されて形成されている。この実施形態では、微結晶シリコン系セルとして微結晶シリコンセル（μｃ－Ｓｉセル）を用い、アモルファスシリコン系セルとしてアモルファスシリコンセル（ａ－Ｓｉセル）を用いた。以下、微結晶シリコン系セル３０を、μｃ－Ｓｉセル３０と記し、アモルファスシリコン系セル５０を、ａ－Ｓｉセル５０と記す。 1 is formed by laminating a back electrode 20, a microcrystalline silicon cell 30, a tunnel junction layer 40, an amorphous silicon cell 50, and a transparent electrode 60 on a film substrate 10. In this embodiment, a microcrystalline silicon cell (μc-Si cell) is used as the microcrystalline silicon cell, and an amorphous silicon cell (a-Si cell) is used as the amorphous silicon cell. Hereinafter, the microcrystalline silicon cell 30 is referred to as a μc-Si cell 30, and the amorphous silicon cell 50 is referred to as an a-Si cell 50.
　フィルム基板１０の材質としては、特に限定されない。例えば、ポリイミドフィルム、ポリエチレンテレフタレートフィルム、ポリエチレンナフタレートフィルム、ポリエーテルスルホンフィルム、アクリルフィルム、アラミドフィルム等が挙げられる。 The material of the film substrate 10 is not particularly limited. For example, a polyimide film, a polyethylene terephthalate film, a polyethylene naphthalate film, a polyether sulfone film, an acrylic film, an aramid film, and the like can be given.
　フィルム基板１０の膜厚は、特に限定はない。柔軟性、強度、重量を考慮すると、１５μｍ以上２００μｍ以下が好ましい。 The film thickness of the film substrate 10 is not particularly limited. Considering flexibility, strength, and weight, it is preferably 15 μm or more and 200 μm or less.
　フィルム基板１０上に裏面電極２０が積層されている。裏面電極２０は、特に限定はなく、Ａｇ、Ａｇ合金、Ｎｉ、Ｎｉ合金、Ａｌ、Ａｌ合金などの導電性金属で構成される。また、これらの導電性金属で形成される層に、ＩＴＯ、ＳｎＯ、ＺｎＯなどの透明導電性酸化物で形成される層が積層されていてもよい。裏面電極２０を、導電性金属層と透明導電性酸化物層との積層体とすることで、電極金属のＳｉ膜中への拡散の防止および光学的なマッチングによる反射率の向上を図ることができる。 The back electrode 20 is laminated on the film substrate 10. The back electrode 20 is not particularly limited, and is made of a conductive metal such as Ag, Ag alloy, Ni, Ni alloy, Al, or Al alloy. In addition, a layer formed of a transparent conductive oxide such as ITO, SnO, or ZnO may be stacked on the layer formed of these conductive metals. By making the back electrode 20 a laminate of a conductive metal layer and a transparent conductive oxide layer, it is possible to prevent diffusion of the electrode metal into the Si film and improve the reflectance by optical matching. it can.
　裏面電極２０の膜厚は、０．１μｍ以上２μｍ以下が好ましく、０．１μｍ以上１μｍ以下がより好ましい。０．１μｍ未満であると電気導電性が低くなり、２μｍを超えると製膜に時間を要する。 The film thickness of the back electrode 20 is preferably 0.1 μm or more and 2 μm or less, and more preferably 0.1 μm or more and 1 μm or less. If it is less than 0.1 μm, the electrical conductivity is low, and if it exceeds 2 μm, it takes time to form a film.
　裏面電極２０上にμｃ－Ｓｉセル３０が積層されている。μｃ－Ｓｉセル３０は、ｎ層とｉ層とｐ層とが接合してなるｎｉｐ型セルで構成される。 The μc-Si cell 30 is laminated on the back electrode 20. The μc-Si cell 30 is composed of a nip type cell formed by joining an n layer, an i layer, and a p layer.
　μｃ－Ｓｉセル３０のｎ層は、リンなどのｎ型不純物を１×１０１９原子／ｃｍ３以上１×１０２１原子／ｃｍ３以下の濃度で含む、微結晶シリコン膜（以下、μｃ－Ｓｉ膜という）又はアモルファスシリコン膜（以下、ａ－Ｓｉ膜という）で構成される。ｎ層の膜厚は、１０ｎｍ以上１００ｎｍ以下が好ましく、１０ｎｍ以上５０ｎｍ以下がより好ましい。ｎ層の膜厚が上記範囲内であると、良好な発電効率が得られる。 The n layer of the μc-Si cell 30 includes a microcrystalline silicon film (hereinafter referred to as μc-Si) containing n-type impurities such as phosphorus at a concentration of 1 × 10 19 atoms / cm 3 or more and 1 × 10 21 atoms / cm 3 or less. And an amorphous silicon film (hereinafter referred to as an a-Si film). The thickness of the n layer is preferably 10 nm to 100 nm, and more preferably 10 nm to 50 nm. When the film thickness of the n layer is within the above range, good power generation efficiency can be obtained.
　μｃ－Ｓｉセル３０のｉ層は、不純物濃度が２×１０１９原子／ｃｍ３以下のμｃ－Ｓｉ膜で構成される。不純物濃度は、１×１０１９原子／ｃｍ３以下がより好ましい。不純物濃度が２×１０１９原子／ｃｍ３以下であれば、電子や正孔のキャリア移動度が良好であり、優れた発電効率が得られる。 The i layer of the μc-Si cell 30 is composed of a μc-Si film having an impurity concentration of 2 × 10 19 atoms / cm 3 or less. The impurity concentration is more preferably 1 × 10 19 atoms / cm 3 or less. When the impurity concentration is 2 × 10 19 atoms / cm 3 or less, the carrier mobility of electrons and holes is good, and excellent power generation efficiency is obtained.
　ｉ層は、ラマン分光における５２０ｃｍ－１のピーク高さ（Ｉ５２０）と、４８０ｃｍ－１のピーク高さ（Ｉ４８０）との比（Ｉ５２０／Ｉ４８０）が、２以上９以下であり、２以上７以下がより好ましい。前記比が２未満であったり、９を超えると、後述する実施例に示すように発電効率が低下する。なお、５２０ｃｍ－１のピーク高さは、結晶シリコンに起因するピークを意味し、４８０ｃｍ－１のピーク高さＩ４８０は、アモルファスシリコンに起因するピークを意味する。したがって、前記比の値が大きい場合は、ｉ層の結晶化度が高いことを意味する。上記比の値を大きくしたい場合は、製膜に用いる原料ガス中の水素ガスに対するシラン濃度を高めればよい。 The i layer has a ratio (I 520 / I 480 ) of a peak height (I 520 ) of 520 cm −1 and a peak height (I 480 ) of 480 cm −1 in Raman spectroscopy of 2 or more and 9 or less, 2 or more and 7 or less are more preferable. If the ratio is less than 2 or exceeds 9, the power generation efficiency decreases as shown in the examples described later. Note that a peak height of 520 cm −1 means a peak attributed to crystalline silicon, and a peak height I 480 of 480 cm −1 means a peak attributed to amorphous silicon. Therefore, when the value of the ratio is large, it means that the crystallinity of the i layer is high. In order to increase the value of the ratio, the silane concentration relative to the hydrogen gas in the raw material gas used for film formation may be increased.
　ｉ層の膜厚は、０．５μｍ以上４μｍ以下が好ましく、１μｍ以上３μｍ以下がより好ましい。ｉ層の膜厚が上記範囲内であると、良好な発電効率が得られる。 The film thickness of the i layer is preferably 0.5 μm or more and 4 μm or less, and more preferably 1 μm or more and 3 μm or less. When the film thickness of the i layer is within the above range, good power generation efficiency can be obtained.
　μｃ－Ｓｉセル３０のｐ層は、ホウ素などのｐ型不純物を１×１０１９原子／ｃｍ３以上１×１０２１原子／ｃｍ３以下の濃度で含む、μｃ－Ｓｉ膜又はａ－Ｓｉ膜で構成される。ｐ層の膜厚は、１０ｎｍ以上３０ｎｍ以下がより好ましい。１０ｎｍ未満であったり、３０ｎｍを超えると、後述する実施例に示すように、発電効率が低下する傾向にある。 The p layer of the μc-Si cell 30 is a μc-Si film or an a-Si film containing p-type impurities such as boron at a concentration of 1 × 10 19 atoms / cm 3 or more and 1 × 10 21 atoms / cm 3 or less. Composed. The thickness of the p layer is more preferably 10 nm or more and 30 nm or less. If it is less than 10 nm or exceeds 30 nm, the power generation efficiency tends to decrease as shown in the examples described later.
　本発明において、μｃ－Ｓｉセル３０は、ｎ層がａ－Ｓｉ膜で構成される場合、ｎ層とｉ層との間にμｃ－Ｓｉ膜からなるシード層が挿入されていることが好ましい。μｃ－Ｓｉ膜はａ－Ｓｉ膜上に製膜し難く、アモルファスの性状になり易い。このため、μｃ－Ｓｉ膜とａ－Ｓｉ膜との界面における膜品質が悪化して、発電効率が損なわれることがある。しかし、ｎ層とｉ層との間にシード層を挿入することで、ｎ層とｉ層との界面の凹凸を１０ｎｍ以下にでき、膜品質の良好なμｃ－Ｓｉ膜からなるｉ層を形成できる。その結果、優れた発電効率が得られる。 In the present invention, in the μc-Si cell 30, when the n layer is composed of an a-Si film, it is preferable that a seed layer made of the μc-Si film is inserted between the n layer and the i layer. The μc-Si film is difficult to form on the a-Si film and tends to be amorphous. For this reason, the film quality at the interface between the μc-Si film and the a-Si film may deteriorate, and the power generation efficiency may be impaired. However, by inserting a seed layer between the n layer and the i layer, the unevenness at the interface between the n layer and the i layer can be reduced to 10 nm or less, and an i layer made of a μc-Si film with good film quality is formed. it can. As a result, excellent power generation efficiency can be obtained.
　シード層の膜厚は、５ｎｍ以上２００ｎｍ以下が好ましい。シード層の膜厚が５ｎｍ未満であると、ｉ層の膜質の改善効果が十分でないことがある。２００ｎｍを超えると、製膜に時間を要する。 The film thickness of the seed layer is preferably 5 nm or more and 200 nm or less. When the film thickness of the seed layer is less than 5 nm, the effect of improving the film quality of the i layer may not be sufficient. If it exceeds 200 nm, it takes time to form a film.
　また、本発明において、μｃ－Ｓｉセル３０は、ｉ層とｐ層との間に、ボロンが添加されたａ－Ｓｉ膜からなる界面層が挿入されていることが好ましい。この界面層を挿入することで発電効率を向上できる。界面層のボロン濃度は、ｐ層の不純物濃度の１／１０００以上１／１０以下が好ましい。界面層の厚みは、５ｎｍ以上２０ｎｍ以下が好ましい。界面層のボロン濃度や膜厚が上記範囲内であれば、優れた発電効率が得られる。 In the present invention, it is preferable that the μc-Si cell 30 has an interfacial layer made of an a-Si film to which boron is added inserted between the i layer and the p layer. By inserting this interface layer, the power generation efficiency can be improved. The boron concentration of the interface layer is preferably 1/1000 or more and 1/10 or less of the impurity concentration of the p layer. The thickness of the interface layer is preferably 5 nm or more and 20 nm or less. If the boron concentration and film thickness of the interface layer are within the above ranges, excellent power generation efficiency can be obtained.
　この実施形態では、μｃ－Ｓｉセル３０上にトンネル接合層４０が積層されて、トンネル接合層４０を介してμｃ－Ｓｉセル３０とａ－Ｓｉセル５０とが接合している。トンネル接合層４０の膜厚は０．５μｍ以下が好ましく、０．１μｍ以下がより好ましい。トンネル接合層４０の材質としては、μｃ－Ｓｉ膜が好ましい。なお、トンネル接合層４０を設けず、μｃ－Ｓｉセル３０とａ－Ｓｉセル５０を直接接合してもよいが、トンネル接合層４０を介して両者を接合することで、より優れた発電効率が得られる。 In this embodiment, the tunnel junction layer 40 is laminated on the μc-Si cell 30, and the μc-Si cell 30 and the a-Si cell 50 are joined via the tunnel junction layer 40. The thickness of the tunnel junction layer 40 is preferably 0.5 μm or less, and more preferably 0.1 μm or less. The material of the tunnel junction layer 40 is preferably a μc-Si film. The μc-Si cell 30 and the a-Si cell 50 may be directly joined without providing the tunnel junction layer 40. However, by joining the two via the tunnel junction layer 40, more excellent power generation efficiency can be obtained. can get.
　トンネル接合層４０上には、ａ－Ｓｉセル５０が積層されている。ａ－Ｓｉセル５０は、ｎ層とｉ層とｐ層が接合してなるｎｉｐ型セルで構成される。 An a-Si cell 50 is laminated on the tunnel junction layer 40. The a-Si cell 50 is composed of a nip type cell in which an n layer, an i layer, and a p layer are joined.
　ａ－Ｓｉセル５０のｎ層は、リンなどのｎ型不純物を１×１０１９原子／ｃｍ３以上１×１０２１原子／ｃｍ３以下の濃度で含むａ－Ｓｉ膜で構成される。ｎ層の膜厚は、５ｎｍ以上５０ｎｍ以下が好ましく、１０ｎｍ以上３０ｎｍ以下がより好ましい。膜厚が上記範囲内であると、良好な発電効率が得られる。 The n layer of the a-Si cell 50 is composed of an a-Si film containing n-type impurities such as phosphorus at a concentration of 1 × 10 19 atoms / cm 3 or more and 1 × 10 21 atoms / cm 3 or less. The thickness of the n layer is preferably 5 nm to 50 nm, and more preferably 10 nm to 30 nm. When the film thickness is within the above range, good power generation efficiency can be obtained.
　ａ－Ｓｉセル５０のｉ層は、不純物濃度が２×１０１９原子／ｃｍ３以下のａ－Ｓｉ膜で構成される。ｉ層の不純物濃度が２×１０１９原子／ｃｍ３以下であれば、電子や正孔のキャリア移動度が良好であり、優れた発電効率が得られる。ｉ層の膜厚は、１００ｎｍ以上１０００ｎｍ以下が好ましく、１００ｎｍ以上３００ｎｍ以下がより好ましい。ｉ層の膜厚が上記範囲内であると、良好な発電効率が得られる。ただし、膜厚が厚いと光劣化が大きくなる。 The i layer of the a-Si cell 50 is composed of an a-Si film having an impurity concentration of 2 × 10 19 atoms / cm 3 or less. When the impurity concentration of the i layer is 2 × 10 19 atoms / cm 3 or less, the carrier mobility of electrons and holes is good, and excellent power generation efficiency is obtained. The film thickness of the i layer is preferably 100 nm or more and 1000 nm or less, and more preferably 100 nm or more and 300 nm or less. When the film thickness of the i layer is within the above range, good power generation efficiency can be obtained. However, when the film thickness is thick, photodegradation increases.
　ａ－Ｓｉセル５０のｐ層は、ホウ素などのｐ型不純物を１×１０１９原子／ｃｍ３以上１×１０２１原子／ｃｍ３以下の濃度で含む、ａ－Ｓｉ膜で構成される。ｐ層の膜厚は５ｎｍ以上５０ｎｍ以下が好ましい。膜厚が上記範囲内であると、良好な発電効率が得られる。 The p-layer of the a-Si cell 50 is composed of an a-Si film containing p-type impurities such as boron at a concentration of 1 × 10 19 atoms / cm 3 or more and 1 × 10 21 atoms / cm 3 or less. The thickness of the p layer is preferably 5 nm or more and 50 nm or less. When the film thickness is within the above range, good power generation efficiency can be obtained.
　本発明において、ａ－Ｓｉセル５０で発生する電流は、μｃ－Ｓｉセル３０で発生する電流に対して、９５％以上１１５％以下の範囲にあることが好ましい。ａ－Ｓｉセル５０は光照射により劣化して発電効率が低下し易く、製膜直後のものに比べて発電効率が１０％程度低下する。ａ－Ｓｉセル５０で発生する電流をμｃ－Ｓｉセル３０で発生する電流の９５％以上１１５％以下とすることで、光照射後の性能においてａ－Ｓｉセル５０で発生する電流をμｃ－Ｓｉセル３０で発生する電流に近づけることができる。このため、薄膜太陽電池の発電効率を向上できる。 In the present invention, the current generated in the a-Si cell 50 is preferably in the range of 95% to 115% with respect to the current generated in the μc-Si cell 30. The a-Si cell 50 is easily deteriorated by light irradiation and the power generation efficiency is easily lowered, and the power generation efficiency is reduced by about 10% compared to that immediately after film formation. By setting the current generated in the a-Si cell 50 to 95% to 115% of the current generated in the μc-Si cell 30, the current generated in the a-Si cell 50 in the performance after light irradiation can be reduced to μc-Si. The current generated in the cell 30 can be approached. For this reason, the power generation efficiency of a thin film solar cell can be improved.
　各セルで発生する電流は、セル（特にｉ層）の厚みが大きいほど大きくなり、小さいほど小さくなる。ａ－Ｓｉセル５０の厚みとμｃ－Ｓｉセル３０の厚みとを調整することで、電流を上記範囲にできる。なお、本発明では、μｃ－Ｓｉセル３０で発生する電流とａ－Ｓｉセル５０で発生する電流は分光感度測定で評価する。μｃ－Ｓｉセル３０で発生する電流は、励起光の内の長波長光を除き、μｃ－Ｓｉセル３０の発電を抑制した状態で分光感度測定を行う。ａ－Ｓｉセル５０で発生する電流は、励起光の内の短波長光を除き、ａ－Ｓｉセル５０の発電を抑制した状態で分光感度測定を行う。 The current generated in each cell increases as the thickness of the cell (particularly the i layer) increases, and decreases as it decreases. By adjusting the thickness of the a-Si cell 50 and the thickness of the μc-Si cell 30, the current can be in the above range. In the present invention, the current generated in the μc-Si cell 30 and the current generated in the a-Si cell 50 are evaluated by spectral sensitivity measurement. With respect to the current generated in the μc-Si cell 30, the spectral sensitivity measurement is performed in a state in which the power generation of the μc-Si cell 30 is suppressed except for the long wavelength light in the excitation light. With respect to the current generated in the a-Si cell 50, spectral sensitivity measurement is performed in a state where power generation in the a-Si cell 50 is suppressed except for the short wavelength light in the excitation light.
　ａ－Ｓｉセル５０上には、透明電極６０が積層されている。透明電極６０の構成としては、特に限定はなく、ＩＴＯ、ＳｎＯ、ＺｎＯなどの透明導電性酸化物が挙げられる。透明電極６０の膜厚は、０．１μｍ以上１μｍ以下が好ましい。０．１μｍ未満であると、電気導電性が小さくなり、１μｍを超えると光の透過率が低くなる。また、透明電極６０の膜厚と屈折率との積は、１００ｎｍ以上２００ｎｍ以下が好ましい。膜厚と屈折率との積が上記範囲内であれば、太陽電池内部に侵入した太陽光が、太陽電池内部に閉じ込められ易くなり、太陽光を有効利用できる。なお、本発明において、透明電極の屈折率は、波長７００ｎｍの光に対する屈折率のことを意味する。 A transparent electrode 60 is laminated on the a-Si cell 50. The configuration of the transparent electrode 60 is not particularly limited, and examples thereof include transparent conductive oxides such as ITO, SnO, and ZnO. The film thickness of the transparent electrode 60 is preferably 0.1 μm or more and 1 μm or less. When the thickness is less than 0.1 μm, the electrical conductivity decreases, and when it exceeds 1 μm, the light transmittance decreases. Further, the product of the film thickness and the refractive index of the transparent electrode 60 is preferably 100 nm or more and 200 nm or less. If the product of the film thickness and the refractive index is within the above range, the sunlight that has entered the solar cell is easily confined inside the solar cell, and sunlight can be used effectively. In the present invention, the refractive index of the transparent electrode means the refractive index for light having a wavelength of 700 nm.
　なお、図１に示す薄膜太陽電池は、ｎｉｐ型セルを２層積層したタンデム型の薄膜太陽電池であるが、ｎｉｐ型セルを３層以上積層した多接合型としてもよい。ｎｉｐ型セルを３層以上積層する場合、そのバンドギャップが小さい順に配置し、その上に透明電極を積層する。 The thin film solar cell shown in FIG. 1 is a tandem thin film solar cell in which two layers of nip type cells are stacked, but may be a multi-junction type in which three or more layers of nip type cells are stacked. When three or more nip type cells are stacked, they are arranged in ascending order of the band gap, and a transparent electrode is stacked thereon.
　次に、上記薄膜太陽電池の製造方法について説明する。 Next, a method for manufacturing the thin film solar cell will be described.
　まず、フィルム基板１０上に、Ａｇ、Ａｇ合金、Ｎｉ、Ｎｉ合金、Ａｌ、Ａｌ合金などの導電性金属を、スパッタリング法、真空蒸着法、スプレー製膜法、スクリーン印刷法、インクジェット印刷法、めっき法など従来公知の方法により製膜して、導電性金属層を形成する。必要に応じて、導電性金属層上に、ＩＴＯ、ＳｎＯ、ＺｎＯなどの透明導電性酸化物を、同様にして製膜し、透明導電性酸化物層を形成してもよい。このようにしてフィルム基板１０上に裏面電極２０を形成する。 First, a conductive metal such as Ag, Ag alloy, Ni, Ni alloy, Al, Al alloy is deposited on the film substrate 10 by sputtering, vacuum deposition, spray film forming, screen printing, ink jet printing, plating. A conductive metal layer is formed by forming a film by a conventionally known method such as a method. If necessary, a transparent conductive oxide layer may be formed by forming a transparent conductive oxide such as ITO, SnO, or ZnO in the same manner on the conductive metal layer. In this way, the back electrode 20 is formed on the film substrate 10.
　次に、このようにして裏面電極２０を形成したフィルム基板１０を、プラズマＣＶＤ装置に導入し、装置内にシリコン含有ガスと水素ガスとを含む原料ガスを導入して、プラズマＣＶＤ法によりμｃ－Ｓｉセル３０、トンネル接合層４０、ａ－Ｓｉセル５０を構成する各半導体層の製膜を行う。 Next, the film substrate 10 thus formed with the back electrode 20 is introduced into a plasma CVD apparatus, and a source gas containing a silicon-containing gas and hydrogen gas is introduced into the apparatus, and μc− The respective semiconductor layers constituting the Si cell 30, the tunnel junction layer 40, and the a-Si cell 50 are formed.
　原料ガスに用いるシリコン含有ガスとしては、例えば、モノシラン（ＳｉＨ４）、ジシラン（Ｓｉ２Ｈ６）、四フッ化シリコン（ＳｉＦ４）、四塩化シリコン（ＳｉＣｌ４）、ジクロロシラン（ＳｉＨ２Ｃｌ２）などが一例として挙げられる。また、ｐ層を形成する際に用いるドーパンドガスとしては、ジボラン（Ｂ２Ｈ６）等が挙げられる。ｎ層を形成する際に用いるドーパンドガスとしては、ホスフィン（ＰＨ３）等が挙げられる。 Examples of the silicon-containing gas used as the source gas include monosilane (SiH 4 ), disilane (Si 2 H 6 ), silicon tetrafluoride (SiF 4 ), silicon tetrachloride (SiCl 4 ), and dichlorosilane (SiH 2 Cl 2). ) Is an example. In addition, examples of the dopant gas used when forming the p layer include diborane (B 2 H 6 ). Examples of the dopant gas used for forming the n layer include phosphine (PH 3 ).
　図２に、本発明の薄膜太陽電池の半導体層の形成に用いることができるプラズマＣＶＤ装置の一例を表す概略図を示す。このプラズマＣＶＤ装置１は、２つの平行平板電極であるカソード電極２とアノード電極３とが互いに間隔（電極間距離）を置いて対向して設置されている。そして、カソード電極２に整合器５を介して高周波電源６が接続され、電極間に高周波が印加できるようになっている。カソード電極２には、図示しないが多数の穴が設けられており、図示しない導入管を通して送られた原料ガスが、カソード電極２側からフィルム基板１０に向けてシャワー状に供給されるようにされている。また、アノード電極３には、加熱装置（図示しない）が備えられ、アノード電極３、フィルム基板１０を所定温度に昇温できるようになっている。プラズマＣＶＤ装置１の排気系には、装置内の圧力を一定に保つ圧力制御装置（図示しない）が備えられている。 FIG. 2 is a schematic view showing an example of a plasma CVD apparatus that can be used for forming a semiconductor layer of the thin film solar cell of the present invention. In this plasma CVD apparatus 1, a cathode electrode 2 and an anode electrode 3, which are two parallel plate electrodes, are placed facing each other with a distance (interelectrode distance) therebetween. A high frequency power source 6 is connected to the cathode electrode 2 via a matching unit 5 so that a high frequency can be applied between the electrodes. The cathode electrode 2 is provided with a number of holes (not shown), and the source gas sent through the introduction pipe (not shown) is supplied in a shower shape from the cathode electrode 2 side toward the film substrate 10. ing. The anode electrode 3 is provided with a heating device (not shown) so that the anode electrode 3 and the film substrate 10 can be heated to a predetermined temperature. The exhaust system of the plasma CVD apparatus 1 is provided with a pressure control device (not shown) that keeps the pressure inside the apparatus constant.
　製膜条件は特に限定は無く、従来公知の方法で行うことができる。また、各半導体層は、同一のプラズマＣＶＤ装置にて製膜してもよく、半導体層毎にプラズマＣＶＤ装置を変えて、各半導体層を異なるプラズマＣＶＤ装置にて製膜してもよい。 The film forming conditions are not particularly limited, and can be performed by a conventionally known method. In addition, each semiconductor layer may be formed using the same plasma CVD apparatus, or each semiconductor layer may be formed using a different plasma CVD apparatus by changing the plasma CVD apparatus for each semiconductor layer.
　裏面電極２０上に各半導体層として、μｃ－Ｓｉセル３０、トンネル接合層４０、ａ－Ｓｉセル５０を形成したのち、ａ－Ｓｉセル５０上に、ＩＴＯ、ＳｎＯ、ＺｎＯなどの透明導電性酸化物を、スパッタリング法、真空蒸着法、スプレー製膜法、スクリーン印刷法、インクジェット印刷法、めっき法など従来公知の方法により製膜して透明電極６０を形成する。このようにして、本発明の薄膜太陽電池を製造できる。 After forming the μc-Si cell 30, the tunnel junction layer 40, and the a-Si cell 50 as the respective semiconductor layers on the back electrode 20, a transparent conductive oxide such as ITO, SnO, ZnO or the like is formed on the a-Si cell 50. The transparent electrode 60 is formed by depositing an object by a conventionally known method such as a sputtering method, a vacuum deposition method, a spray film forming method, a screen printing method, an ink jet printing method, or a plating method. Thus, the thin film solar cell of this invention can be manufactured.
　（試験例１）
　フィルム基板１０として、膜厚５０μｍのポリイミドフィルムを用いた。このポリイミドフィルムに、Ａｇを３００ｎｍ製膜した後、Ａｇ層上にＺｎＯを３０ｎｍ製膜して裏面電極２０を形成した。
　そして、図２に示すプラズマＣＶＤ装置を用い、原料ガスとして、ＳｉＨ４とＨ２との混合ガスを用い、表１に示す条件にてプラズマＣＶＤ法により各種シリコン膜を製膜して、裏面電極２０上に、μｃ－Ｓｉセル３０、トンネル接合層４０、ａ－Ｓｉセル５０を形成した。μｃ－Ｓｉセル３０のｉ層はラマン分光における５２０ｃｍ－１のピーク高さ（Ｉ５２０）と４８０ｃｍ－１のピーク高さ（Ｉ４８０）との比（Ｉ５２０／Ｉ４８０）が４．２であり、不純物濃度が８×１０１８原子／ｃｍ３であった。不純物濃度はＳＩＭＳ分析法（Ｓｅｃｏｎｄａｒｙ　Ｉｏｎ－ｍｉｃｒｏｐｒｏｂｅ　Ｍａｓｓ　Ｓｐｅｃｔｒｏｍｅｔｒｙ）で測定した。不純物として酸素以外に窒素や炭素が検出されたが、ごく微量であったので酸素濃度を不純物濃度とした。
　そして、各半導体層が形成されたポリイミドフィルムをスパッタ装置に入れ、Ａｒ－Ｏ２ガス（Ｏ２濃度６％）を流量２０ｓｃｃｍでスパッタ装置に供給し、圧力４００ｍＰａ（３ｍＴｏｒｒ）、パワー３００Ｗ、基板温度２００℃の条件で、直流スパッタ法によりａ－Ｓｉセル５０上に透明電極６０としてＩＴＯ膜を７０ｎｍ積層し、図１に示す薄膜太陽電池を製造した。透明電極６０の膜厚と波長７００ｎｍの光に対する屈折率との積は１４０ｎｍであった。 (Test Example 1)
As the film substrate 10, a polyimide film having a film thickness of 50 μm was used. A 300 nm Ag film was formed on this polyimide film, and then a 30 nm ZnO film was formed on the Ag layer to form the back electrode 20.
Then, using the plasma CVD apparatus shown in FIG. 2, various silicon films are formed by plasma CVD under the conditions shown in Table 1, using a mixed gas of SiH 4 and H 2 as a source gas, and a back electrode On the substrate 20, a μc-Si cell 30, a tunnel junction layer 40, and an a-Si cell 50 were formed. The i layer of the μc-Si cell 30 has a ratio (I 520 / I 480 ) of a peak height (I 520 ) of 520 cm −1 to a peak height (I 480 ) of 480 cm −1 in Raman spectroscopy of 4.2. The impurity concentration was 8 × 10 18 atoms / cm 3 . The impurity concentration was measured by SIMS analysis (Secondary Ion-microprobe Mass Spectrometry). Nitrogen and carbon were detected as impurities in addition to oxygen, but they were very small, so the oxygen concentration was taken as the impurity concentration.
Then, the polyimide film on which each semiconductor layer is formed is put into a sputtering apparatus, Ar—O 2 gas (O 2 concentration 6%) is supplied to the sputtering apparatus at a flow rate of 20 sccm, pressure 400 mPa (3 mTorr), power 300 W, substrate temperature. A thin film solar cell shown in FIG. 1 was manufactured by laminating an ITO film of 70 nm as a transparent electrode 60 on the a-Si cell 50 by DC sputtering under the condition of 200 ° C. The product of the film thickness of the transparent electrode 60 and the refractive index for light having a wavelength of 700 nm was 140 nm.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　この薄膜太陽電池を、ソーラーシミュレータで１００ｍＷ／ｃｍ２の光を照射の下、電流―電圧曲線を計測し、発電効率（光電変換効率）を求めた。光を照射直前の発電効率は１１．２％で、光照射を３００時間行った後の発電効率は９．７％であった。 The thin-film solar cell was measured with a solar simulator under a light of 100 mW / cm 2 to measure a current-voltage curve, and power generation efficiency (photoelectric conversion efficiency) was obtained. The power generation efficiency immediately before irradiation with light was 11.2%, and the power generation efficiency after 300 hours of light irradiation was 9.7%.
　（試験例２）
　試験例１において、ａ－Ｓｉセル５０のｉ層の膜厚を４００ｎｍ以上６００ｎｍ以下の範囲で変化させて製膜した以外は、試験例１と同様にして薄膜太陽電池を製造した。 (Test Example 2)
A thin film solar cell was manufactured in the same manner as in Test Example 1 except that the film thickness of the i layer of the a-Si cell 50 was changed in the range of 400 nm to 600 nm in Test Example 1.
　製造した薄膜太陽電池を分光感度測定装置により、各セルの電流（短絡電流密度）を測定した。また、ソーラーシミュレータで１００ｍＷ／ｃｍ２の光照射を３００時間行った後に、薄膜太陽電池の短絡電流密度を計測した。光照射前の電流比（ａ－Ｓｉセル５０で発生する電流／μｃ－Ｓｉセル３０で発生する電流）と光照射後の薄膜太陽電池の短絡電流密度（Ｊｓｃ）を図３に示す。図３に示されるように、電流比が９５％以上１１５％以下であると、光照射後の短絡電流密度が高いことが分かる。 The manufactured thin film solar cell was measured for the current (short circuit current density) of each cell with a spectral sensitivity measuring device. Moreover, after performing 100 mW / cm < 2 > light irradiation with a solar simulator for 300 hours, the short circuit current density of the thin film solar cell was measured. The current ratio before light irradiation (current generated in the a-Si cell 50 / current generated in the μc-Si cell 30) and the short-circuit current density (Jsc) of the thin-film solar cell after light irradiation are shown in FIG. As shown in FIG. 3, it can be seen that the short-circuit current density after light irradiation is high when the current ratio is 95% or more and 115% or less.
　（試験例３）
　μｃ－Ｓｉセルのｉ層の結晶化について検討した。μｃ－Ｓｉセルのｉ層の製膜条件における水素流量を１７００ｓｃｃｍと一定にしてＳｉＨ４ガスの流量を１２ｓｃｃｍ以上２０ｓｃｃｍ以下の範囲で変化させた以外は、試験例の表１に示すμｃ－Ｓｉセルの製膜条件で、裏面電極上に各薄膜を製膜してμｃ－Ｓｉセルを製造した。そして、μｃ－Ｓｉセルの表層に、試験例１と同様にしてＩＴＯ膜を７０ｎｍ積層した。このようにして製造したμｃ－Ｓｉセルのｉ層は、ラマン分光における５２０ｃｍ－１のピーク高さ（Ｉ５２０）と４８０ｃｍ－１のピーク高さ（Ｉ４８０）との比（Ｉ５２０／Ｉ４８０）が１以上１１以下の範囲のものであった。 (Test Example 3)
The crystallization of the i layer of the μc-Si cell was examined. The μc-Si cell shown in Table 1 of the test example, except that the flow rate of SiH 4 gas was changed in the range of 12 sccm to 20 sccm while the hydrogen flow rate was kept constant at 1700 sccm under the i-layer deposition conditions of the μc-Si cell. Under the film forming conditions, each thin film was formed on the back electrode to manufacture a μc-Si cell. Then, an ITO film of 70 nm was laminated on the surface layer of the μc-Si cell in the same manner as in Test Example 1. The i layer of the μc-Si cell thus produced has a ratio (I 520 / I 480 ) of the peak height (I 520 ) of 520 cm −1 and the peak height (I 480 ) of 480 cm −1 in Raman spectroscopy. ) Was in the range of 1 to 11.
　μｃ－Ｓｉセルを、ソーラーシミュレータで１００ｍＷ／ｃｍ２の光を照射の下で電流－電圧曲線を計測し、発電効率を求めた。結果を図４に記す。図４に示されるように、Ｉ５２０／Ｉ４８０が２以上９以下の範囲で優れた発電効率が得られることが分かる。Ｉ５２０／Ｉ４８０が２未満であると、アモルファスの性状に近くなったため発電効率が低下したものと考えられる。 The current-voltage curve was measured for the μc-Si cell under irradiation of 100 mW / cm 2 of light with a solar simulator to determine the power generation efficiency. The results are shown in FIG. As shown in FIG. 4, it can be seen that excellent power generation efficiency is obtained when I 520 / I 480 is in the range of 2 to 9. If I 520 / I 480 is less than 2, it is considered that the power generation efficiency is lowered because it is close to an amorphous property.
　（試験例４）
　μｃ－Ｓｉセルのｉ層中の不純物濃度について検討した。μｃ－Ｓｉセルのｉ層の製膜条件を、パワー１２０Ｗ、圧力４８０Ｐａ（３．６Ｔｏｒｒ）、ＳｉＨ４ガス流量１５ｓｃｃｍ、希釈率５０倍とし、プラズマＣＶＤ製膜装置内の脱ガス処理の条件を変化させて、ｉ層の不純物濃度を変化させた。ｐ層とｎ層は、試験例１の表１に示すμｃ－Ｓｉセルの製膜条件で、裏面電極上に各薄膜を製膜してμｃ－Ｓｉセルを製造した。μｃ－Ｓｉセルのｉ層の不純物濃度をＳＩＭＳ法により測定した。不純物として酸素以外に窒素や炭素が検出されたが、ごく微量であったので、酸素濃度を不純物濃度とした。そして、μｃ－Ｓｉセルの表層に、試験例１と同様にしてＩＴＯ膜を７０ｎｍ積層した。 (Test Example 4)
The impurity concentration in the i layer of the μc-Si cell was examined. The deposition conditions for the i-layer of the μc-Si cell are as follows: power 120 W, pressure 480 Pa (3.6 Torr), SiH 4 gas flow rate 15 sccm, dilution rate 50 times, and the conditions for degassing treatment in the plasma CVD deposition apparatus are changed. Thus, the impurity concentration of the i layer was changed. For the p layer and the n layer, each thin film was formed on the back electrode under the film forming conditions of the μc-Si cell shown in Table 1 of Test Example 1 to manufacture a μc-Si cell. The impurity concentration of the i layer of the μc-Si cell was measured by the SIMS method. Nitrogen and carbon were detected as impurities in addition to oxygen, but they were very small, so the oxygen concentration was taken as the impurity concentration. Then, an ITO film of 70 nm was laminated on the surface layer of the μc-Si cell in the same manner as in Test Example 1.
　μｃ－Ｓｉセルをソーラーシミュレータで１００ｍＷ／ｃｍ２の光を照射の下で電流―電圧曲線を計測し、発電効率を求めた。結果を図５に記す。図５に示されるように、不純物濃度が２×１０１９原子／ｃｍ３を超えると、μｃ－Ｓｉセルの発電効率が低下した。 The current-voltage curve was measured by irradiating 100 μW / cm 2 of light on the μc-Si cell with a solar simulator to determine the power generation efficiency. The results are shown in FIG. As shown in FIG. 5, when the impurity concentration exceeded 2 × 10 19 atoms / cm 3 , the power generation efficiency of the μc-Si cell was lowered.
　（試験例５）
　ＩＴＯの膜厚について検討した。μｃ－Ｓｉセルのｉ層の製膜条件を、パワー３００Ｗ、圧力２１３３Ｐａ（１６Ｔｏｒｒ）、ＳｉＨ４ガス流量３３ｓｃｃｍ、希釈率５０倍とした。ｉ層以外は、試験例１の表１に示すμｃ-Ｓｉセルの製膜条件で、裏面電極上に各薄膜を製膜してμｃ－Ｓｉセルを製造した。そして、μｃ－Ｓｉセルの表層に、製膜時間を調整してＩＴＯの膜厚を２５ｎｍ以上１２５ｎｍ以下の範囲で変化させて製膜し、ＩＴＯの膜厚と７００ｎｍの波長の光に対する屈折率との積（以下、光学膜厚という）が異なるμｃ－Ｓｉセルを製造した。 (Test Example 5)
The film thickness of ITO was examined. The conditions for forming the i layer of the μc-Si cell were as follows: power 300 W, pressure 2133 Pa (16 Torr), SiH 4 gas flow rate 33 sccm, and dilution rate 50 times. Except for the i layer, each thin film was formed on the back electrode under the film forming conditions of the μc-Si cell shown in Table 1 of Test Example 1 to manufacture a μc-Si cell. Then, on the surface layer of the μc-Si cell, the film formation time is adjusted to change the film thickness of ITO in the range of 25 nm to 125 nm, and the film thickness of ITO and the refractive index with respect to light having a wavelength of 700 nm are Μc-Si cells having different product (hereinafter referred to as optical film thickness) were manufactured.
　μｃ－Ｓｉセルをソーラーシミュレータで１００ｍＷ／ｃｍ２の光を照射の下で電流－電圧曲線を計測し、発電効率を求めた。結果を図６に記す。図６に示されるように、透明電極の光学膜厚が１００ｎｍ以上２００ｎｍ以下の範囲で高い発電効率が得られた。光学膜厚が１４０ｎｍで特に高い発電効率が得られた。 The current-voltage curve was measured by irradiating 100 μW / cm 2 of light on the μc-Si cell with a solar simulator to determine the power generation efficiency. The results are shown in FIG. As shown in FIG. 6, high power generation efficiency was obtained when the optical film thickness of the transparent electrode was in the range of 100 nm to 200 nm. Particularly high power generation efficiency was obtained when the optical film thickness was 140 nm.
　（試験例６)
　μｃ－Ｓｉセルのｐ層の膜厚について検討した。μｃ－Ｓｉセルのｐ層の膜厚を５ｎｍ以上５０ｎｍ以下の範囲で変化させて製膜させた以外は、試験例１の表１に示すμｃ－Ｓｉセルの製膜条件で、裏面電極上に各薄膜を製膜してμｃ－Ｓｉセルを製造した。このμｃ－Ｓｉセルのｐ層のボロン濃度は、５×１０２０原子／ｃｍ３程度であった。そして、μｃ－Ｓｉセルの表層に、試験例１と同様にしてＩＴＯ膜を７０ｎｍ積層した。 (Test Example 6)
The thickness of the p layer of the μc-Si cell was examined. Except that the film thickness of the p layer of the μc-Si cell was changed in the range of 5 nm to 50 nm, the film was formed on the back electrode under the film formation conditions of the μc-Si cell shown in Table 1 of Test Example 1. Each thin film was formed into a μc-Si cell. The boron concentration in the p layer of this μc-Si cell was about 5 × 10 20 atoms / cm 3 . Then, an ITO film of 70 nm was laminated on the surface layer of the μc-Si cell in the same manner as in Test Example 1.
　製造したμｃ－Ｓｉセルをソーラーシミュレータで１００ｍＷ／ｃｍ２の光を照射の下で電流－電圧曲線を計測し、発電効率を求めた。結果を表２に記す。表２に示すようにｐ層の膜厚が１０ｎｍ以上３０ｎｍ以上の範囲で高い発電効率が得られた。 The produced μc-Si cell was measured with a solar simulator under irradiation of light of 100 mW / cm 2 to measure a current-voltage curve, and power generation efficiency was obtained. The results are shown in Table 2. As shown in Table 2, high power generation efficiency was obtained when the thickness of the p layer was in the range of 10 nm to 30 nm.
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
　（試験例７)
　試験例６において、ｐ層の膜厚を２０ｎｍとして、ｎ層の膜厚を２０ｎｍ以上１００ｎｍ以下の範囲で変化させて製膜させた。このμｃ－Ｓｉセルのｐ層のリン濃度は、５×１０２０原子／ｃｍ３程度であった。そして、μｃ－Ｓｉセルの表層に、試験例１と同様にしてＩＴＯ膜を７０ｎｍ積層した。 (Test Example 7)
In Test Example 6, the film thickness of the p layer was 20 nm, and the film thickness of the n layer was changed in the range of 20 nm to 100 nm. The phosphorus concentration in the p layer of this μc-Si cell was about 5 × 10 20 atoms / cm 3 . Then, an ITO film of 70 nm was laminated on the surface layer of the μc-Si cell in the same manner as in Test Example 1.
　製造したμｃ－Ｓｉセルにソーラーシミュレータで１００ｍＷ／ｃｍ２の光照射を３００時間行った後に同条件の光照射の下で電流－電圧曲線を計測し、発電効率を求めた。μｃ－Ｓｉセルの発電効率はほぼ同じであった。ｎ層の膜厚が２０ｎｍ以上１００ｎｍ以下の範囲では発電効率に大きな有意差がなかった。 The manufactured μc-Si cell was irradiated with 100 mW / cm 2 of light for 300 hours with a solar simulator, and then a current-voltage curve was measured under the same condition of light irradiation to determine the power generation efficiency. The power generation efficiency of the μc-Si cell was almost the same. There was no significant difference in power generation efficiency when the thickness of the n layer was in the range of 20 nm to 100 nm.
　（試験例８）
　μｃ－Ｓｉセルについて、ｎ層がａ－Ｓｉ膜で構成されているときｉ層の製膜初期層（シード層）を挿入することで発電効率が向上することについて確認した。 (Test Example 8)
Regarding the μc-Si cell, it was confirmed that the power generation efficiency was improved by inserting an initial i-layer (seed layer) when the n-layer was composed of an a-Si film.
　表３，４に示す条件で、裏面電極上に各薄膜を製膜してμｃ－Ｓｉセルを製造した。そして、μｃ－Ｓｉセルの表層に、試験例１と同様にしてＩＴＯ膜を７０ｎｍ積層した。 Each thin film was formed on the back electrode under the conditions shown in Tables 3 and 4 to manufacture a μc-Si cell. Then, an ITO film of 70 nm was laminated on the surface layer of the μc-Si cell in the same manner as in Test Example 1.
Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000004
Figure JPOXMLDOC01-appb-T000004
　μｃ－Ｓｉセルをソーラーシミュレータで１００ｍＷ／ｃｍ２の光を照射の下で電流－電圧曲線を計測し、発電効率を求めた。シード層ありのμｃ－Ｓｉセル（表３）は発電効率が７．２％であったのに対し、シード層なしμｃ－Ｓｉセル（表４）は発電効率が６．２％であった。μｃ－Ｓｉセルのｎ層とｉ層との間にシード層を挿入することで、発電効率を向上できた。また、μｃ－Ｓｉセルの断面を透過電子顕微鏡観察したところ、シード層ありのμｃ－Ｓｉセル（表３）は、ｉ層がほぼ均一に成長したμｃ－Ｓｉ膜であり、ｎ層とｉ層との界面の凹凸が１０ｎｍ以下であった。これに対してシード層なしのμｃ－Ｓｉセル（表４）はｎ層のアモルファスの性状の部分がｉ層に侵入し、微結晶の性状の部分が鋸状に入りこんだ構造をなしており、両者の界面の凹凸は数百ｎｍであった。 The current-voltage curve was measured by irradiating 100 μW / cm 2 of light on the μc-Si cell with a solar simulator to determine the power generation efficiency. The power generation efficiency of the μc-Si cell with the seed layer (Table 3) was 7.2%, whereas the power generation efficiency of the μc-Si cell without the seed layer (Table 4) was 6.2%. Power generation efficiency could be improved by inserting a seed layer between the n layer and i layer of the μc-Si cell. Further, when a cross section of the μc-Si cell was observed with a transmission electron microscope, the μc-Si cell with a seed layer (Table 3) was a μc-Si film in which the i layer was grown almost uniformly, and the n layer and the i layer. The unevenness of the interface with was 10 nm or less. On the other hand, the μc-Si cell without the seed layer (Table 4) has a structure in which the amorphous part of the n layer penetrates into the i layer and the part of the microcrystalline part enters into a saw shape, The unevenness at the interface between them was several hundred nm.
　（試験例９）
　μｃ－Ｓｉセルにおいて、ｉ層とｐ層との間に界面層としてバンドギャップの広いａ－Ｓｉ膜からなる界面層を挿入した。μｃ－Ｓｉセル製膜条件は、試験例１の表１に示すμｃ－Ｓｉセルの製膜条件とし、さらに、ｉ層とｐ層との間に、ａ－Ｓｉ膜からなる界面層を挿入した。界面層の製膜条件は、基板温度１４０℃、ＲＦパワー５Ｗ、圧力６７Ｐａ（０．５Ｔｏｒｒ）、シラン流量４ｓｃｃｍ、水素希釈率１０倍、シランに対するジボランガスの濃度（Ｂ２Ｈ６／ＳｉＨ４の濃度）を０ｐｐｍ以上１０００ｐｐｍ以下の範囲で変え、５ｎｍ以上４０ｎｍ以下の範囲で膜厚を変化させた界面層を製膜した。そして、μｃ－Ｓｉセルの表層に、試験例１と同様にしてＩＴＯ膜を７０ｎｍ積層した。 (Test Example 9)
In the μc-Si cell, an interface layer made of an a-Si film having a wide band gap was inserted as an interface layer between the i layer and the p layer. The μc-Si cell deposition conditions were the same as the μc-Si cell deposition conditions shown in Table 1 of Test Example 1, and an interface layer composed of an a-Si film was inserted between the i layer and the p layer. . The film formation conditions for the interface layer are as follows: substrate temperature 140 ° C., RF power 5 W, pressure 67 Pa (0.5 Torr), silane flow rate 4 sccm, hydrogen dilution rate 10 times, diborane gas concentration relative to silane (B 2 H 6 / SiH 4 concentration) ) Was changed in the range of 0 ppm to 1000 ppm, and an interface layer having a film thickness changed in the range of 5 nm to 40 nm was formed. Then, an ITO film of 70 nm was laminated on the surface layer of the μc-Si cell in the same manner as in Test Example 1.
　μｃ－Ｓｉセルをソーラーシミュレータで１００ｍＷ／ｃｍ２の光を照射の下で電流－電圧曲線を計測し、発電効率を求めた。結果を表５に示す。 The current-voltage curve was measured by irradiating 100 μW / cm 2 of light on the μc-Si cell with a solar simulator to determine the power generation efficiency. The results are shown in Table 5.
Figure JPOXMLDOC01-appb-T000005
Figure JPOXMLDOC01-appb-T000005
　界面層、ｐ層のボラン濃度は、原料ガス中のＢ２Ｈ６／ＳｉＨ４濃度とほぼ一致するので、μｃ－Ｓｉセルのｐ層のボラン濃度は約１％である（試験例１の表１参照）。表５に示すように、界面層のボラン濃度が、ｐ層の１／１０００以上１／１０以下の濃度範囲で優れた発電効率が得られた。なかでも、界面層の膜厚が５ｎｍ以上２０ｎｍ以下の範囲で特に優れた発電効率が得られた。 Since the borane concentrations of the interface layer and the p layer substantially coincide with the B 2 H 6 / SiH 4 concentration in the source gas, the borane concentration of the p layer of the μc-Si cell is about 1% (Table of Test Example 1). 1). As shown in Table 5, excellent power generation efficiency was obtained when the borane concentration of the interface layer was in the concentration range of 1/1000 or more and 1/10 or less of the p layer. In particular, particularly excellent power generation efficiency was obtained when the thickness of the interface layer was in the range of 5 nm to 20 nm.
符合の説明Explanation of sign
１：プラズマＣＶＤ装置
２：カソード電極
３：アノード電極
５：整合器
６：高周波電源
１０：フィルム基板
２０：裏面電極
３０：微結晶シリコン系セル、μｃ－Ｓｉセル
４０：トンネル接合層
５０：アモルファスシリコン系セル、ａ－Ｓｉセル
６０：透明電極 1: Plasma CVD apparatus 2: Cathode electrode 3: Anode electrode 5: Matching device 6: High frequency power supply 10: Film substrate 20: Back electrode 30: Microcrystalline silicon cell, μc-Si cell 40: Tunnel junction layer 50: Amorphous silicon Cell, a-Si cell 60: transparent electrode

Claims (7)

  1. 　フィルム基板と、該フィルム基板上に積層された裏面電極と、該裏面電極上に積層された複数のｎｉｐ型セルと、最外層のｎｉｐ型セル上に積層された透明電極とを備えた薄膜太陽電池において、
    　前記複数のｎｉｐ型セルとして、少なくとも１つの微結晶シリコン系セルと、該微結晶シリコン系セルよりも前記透明電極側に配置された、少なくとも１つのアモルファスシリコン系セルとを有し、
    　前記微結晶シリコン系セルは、ｉ層のラマン分光における５２０ｃｍ－１のピーク高さ（Ｉ５２０）と４８０ｃｍ－１のピーク高さ（Ｉ４８０）との比（Ｉ５２０／Ｉ４８０）が２以上９以下で、不純物濃度が２×１０１９原子／ｃｍ３以下であり、
    　前記アモルファスシリコン系セルで発生する電流が、前記微結晶シリコン系セルで発生する電流に対して、９５％以上１１５％以下の範囲にあり、
    　前記透明電極の膜厚と屈折率との積が１００ｎｍ以上２００ｎｍ以下であることを特徴とする薄膜太陽電池。     A thin film solar comprising a film substrate, a back electrode laminated on the film substrate, a plurality of nip cells laminated on the back electrode, and a transparent electrode laminated on the outermost nip cell In batteries,
    The plurality of nip-type cells include at least one microcrystalline silicon-based cell, and at least one amorphous silicon-based cell disposed on the transparent electrode side of the microcrystalline silicon-based cell,
    In the microcrystalline silicon cell, the ratio (I 520 / I 480 ) of the peak height (I 520 ) of 520 cm −1 and the peak height (I 480 ) of 480 cm −1 in the Raman spectroscopy of the i layer is 2 or more. 9 or less, the impurity concentration is 2 × 10 19 atoms / cm 3 or less,
    The current generated in the amorphous silicon cell is in the range of 95% to 115% with respect to the current generated in the microcrystalline silicon cell,
    The thin film solar cell, wherein the product of the film thickness and the refractive index of the transparent electrode is 100 nm or more and 200 nm or less.
  2. 　前記微結晶シリコン系セルは、ｐ層が厚さ１０ｎｍ以上３０ｎｍ以下の微結晶シリコン膜で構成されている、請求項１に記載の薄膜太陽電池。 The thin-film solar cell according to claim 1, wherein the microcrystalline silicon cell is composed of a microcrystalline silicon film having a p layer thickness of 10 nm to 30 nm.
  3. 　前記微結晶シリコン系セルは、ｎ層がアモルファスシリコン膜で構成され、ｉ層が微結晶シリコン膜で構成されており、ｎ層とｉ層との間に微結晶シリコン膜からなるシード層が挿入されている、請求項１又は２に記載の薄膜太陽電池。 In the microcrystalline silicon cell, the n layer is composed of an amorphous silicon film, the i layer is composed of a microcrystalline silicon film, and a seed layer composed of the microcrystalline silicon film is inserted between the n layer and the i layer. The thin film solar cell according to claim 1 or 2, wherein
  4. 　前記微結晶シリコン系セルは、ｉ層とｐ層との間にボロンが添加されたアモルファスシリコン膜からなる界面層が挿入されている、請求項１に記載の薄膜太陽電池。 The thin-film solar cell according to claim 1, wherein the microcrystalline silicon cell has an interface layer made of an amorphous silicon film to which boron is added inserted between the i layer and the p layer.
  5. 　前記界面層のボロン濃度が、ｐ層の不純物濃度の１／１０００以上１／１０以下である、請求項４に記載の薄膜太陽電池。 The thin film solar cell according to claim 4, wherein the boron concentration in the interface layer is 1/1000 or more and 1/10 or less of the impurity concentration in the p layer.
  6. 　前記界面層の厚みが５ｎｍ以上２０ｎｍ以下である、請求項４に記載の薄膜太陽電池。 The thin film solar cell according to claim 4, wherein the interface layer has a thickness of 5 nm to 20 nm.
  7. 　前記界面層の厚みが５ｎｍ以上２０ｎｍ以下である、請求項５に記載の薄膜太陽電池。 The thin film solar cell according to claim 5, wherein the interface layer has a thickness of 5 nm to 20 nm.
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