WO2015141620A1 - Method for producing thin-film solar cell, and thin-film solar cell - Google Patents

Method for producing thin-film solar cell, and thin-film solar cell Download PDF

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WO2015141620A1
WO2015141620A1 PCT/JP2015/057688 JP2015057688W WO2015141620A1 WO 2015141620 A1 WO2015141620 A1 WO 2015141620A1 JP 2015057688 W JP2015057688 W JP 2015057688W WO 2015141620 A1 WO2015141620 A1 WO 2015141620A1
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graphene
solar cell
layer
substrate
thin film
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French (fr)
Japanese (ja)
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亮佑 石川
晋介 宮島
誠 小長井
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独立行政法人科学技術振興機構
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    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01BCABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B1/00Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
    • H01B1/04Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors mainly consisting of carbon-silicon compounds, carbon or silicon
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01LSEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00Semiconductor 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
    • H01L31/02Details
    • H01L31/0224Electrodes
    • H01L31/022466Electrodes made of transparent conductive layers, e.g. TCO, ITO layers
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01LSEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00Semiconductor 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
    • H01L31/04Semiconductor 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
    • H01L31/042PV modules or arrays of single PV cells
    • H01L31/0445PV modules or arrays of single PV cells including thin film solar cells, e.g. single thin film a-Si, CIS or CdTe solar cells
    • H01L31/046PV modules composed of a plurality of thin film solar cells deposited on the same substrate
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01LSEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00Semiconductor 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
    • H01L31/18Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
    • H01L31/1884Manufacture of transparent electrodes, e.g. TCO, ITO
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01LSEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00Semiconductor 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
    • H01L31/18Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
    • H01L31/1892Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof methods involving the use of temporary, removable substrates
    • YGENERAL 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
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00Energy generation through renewable energy sources
    • Y02E10/50Photovoltaic [PV] energy

Definitions

  • the present invention relates to a method for manufacturing a thin film solar cell and a thin film solar cell.
  • Silicon-based thin-film solar cells can be easily formed into multi-junctions by continuously forming each cell (Patent Document 1), but a technique for peeling off is required for bonding with other thin-film solar cells. Although it is possible to peel off a thin-film silicon solar cell using an oxide film as a peeling layer (Patent Document 2), the structure itself such as a through hole necessary for the peeling process is complicated, and the peeling layer is removed after peeling. It is necessary to form a new electrode layer.
  • Non-patent Document 1 a compound-based thin film solar cell can be peeled off from the interface between the base metal electrode layer and the absorption layer (Non-patent Document 1), it is necessary to deposit a new electrode layer for multi-junction.
  • Non-patent Document 2 When peeling off using graphene oxide, it is necessary to remove the insulating graphene oxide layer after peeling and form a new electrode layer (Non-patent Document 2).
  • a plurality of graphene layers formed on a substrate are peeled off directly or indirectly from the surface of the substrate without substantially impairing the characteristics thereof.
  • the present invention provides the following inventions. (1) In the manufacture of a thin film solar cell comprising a first electrode comprising a graphene layer; a semiconductor thin film; and a second electrode, Forming a plurality of graphene layers on a substrate; forming a semiconductor thin film and a second electrode on the graphene layer; and then peeling the graphene layer directly or indirectly from the substrate to form a peeled graphene layer A manufacturing method of a thin film solar cell, wherein a self-supporting thin film solar cell including a semiconductor thin film is manufactured by using the first electrode.
  • the graphene layer is peeled off from a) the substrate, b) between the graphene layers, or c) from the sacrifice sacrificial layer provided adjacent to or between the graphene layers.
  • the peeling sacrificial layer is a chalcogenite-based layered material, graphene oxide, or hexagonal boron nitride.
  • a thin film solar cell comprising a first electrode including a graphene layer peeled off directly or indirectly from a substrate; a semiconductor thin film; and a second electrode.
  • multilayer graphene that is a layered compound that is flat at an atomic level and has sufficient conductivity as an electrode can be easily peeled off between graphene layers or between a graphene layer and a substrate, and further, graphene can be used as an electrode as it is.
  • a method for manufacturing a self-supporting thin film solar cell can be provided.
  • the ability to peel the thin film solar cell from the substrate and become self-supporting provides a great degree of freedom in designing a multi-junction solar cell.
  • a multilayer graphene film as the transparent electrode layer, it can operate as a self-supporting thin film solar cell as it is after peeling. Since the graphene layer after peeling becomes an electrode, it can be easily connected to, for example, a solar cell manufactured by other means, and the degree of freedom in designing a highly efficient multi-junction thin film solar cell can be improved. It becomes.
  • the conceptual diagram of peeling of the thin film solar cell using a multilayer graphene film The conceptual diagram which shows the aspect which peels off a graphene layer.
  • An example of a scanning electron microscope (SEM) photograph (500 times) of the peeled graphene surface is shown.
  • the structure of the peeled thin film silicon solar cell in Example 1 is shown.
  • the solar cell characteristic before and behind peeling in Example 1 is shown.
  • the SEM photograph 150 times) of the applied graphene oxide in Example 2.
  • FIG. The SEM photograph (20,000 times) of the silicon nanowire array in Example 3.
  • the method of manufacturing a thin film solar cell according to the present invention includes forming a plurality of graphene layers on a substrate in manufacturing a thin film solar cell including a first electrode including a graphene layer; a semiconductor thin film; and a second electrode; The semiconductor thin film and the second electrode are formed on the graphene layer, and then the graphene layer is peeled off directly or indirectly from the substrate, and the peeled graphene layer is used as the first electrode, so that the self-supporting structure including the semiconductor thin film is obtained.
  • a type thin film solar cell is manufactured.
  • the “plurality of graphene layers” refers to stacked graphene layers.
  • the graphene includes a graphene derivative to which various functional groups are added while maintaining a graphene skeleton composed of a 6-membered ring carbon sheet, and examples thereof include graphene oxide modified with an oxygen-containing functional group (conducted by reduction). A film can be easily formed). Further, graphene may contain a dopant in order to increase the carrier concentration and improve the conductivity.
  • the graphene layer When peeling off the graphene layer directly or indirectly from the substrate, the graphene layer is a) from the substrate, b) between the graphene layers, or c) from the sacrificial layer for peeling provided adjacent to or between the graphene layers. Is preferably peeled off.
  • the peeling sacrificial layer is provided to facilitate the peeling of the graphene layer.
  • the peeling sacrificial layer is not on the semiconductor element side including the graphene layer. Will remain on the side. a) is when the graphene layer is peeled off directly from the substrate, while b) or c) is when it is peeled off indirectly from the substrate.
  • FIG. 1 is a conceptual diagram of peeling of a thin film solar cell using a multilayer graphene film, in which a graphene layer is indirectly peeled off from a substrate b) and a graphene layer.
  • FIG. 1 (a) stacks a graphene film on a substrate 1 to form a plurality of graphene layers 2, and (b) further forms a semiconductor element including a semiconductor film (production of a thin film solar cell). Peeling is performed between the graphene layers, and as a result, (c) shows that a self-supporting thin-film solar cell having a graphene layer as an electrode is manufactured as the semiconductor element 12.
  • FIG. 2 (a) to (c) are conceptual diagrams showing an embodiment in which the graphene layer is peeled off directly or indirectly from the substrate according to the above embodiments a), b) and c) (on the graphene layer) Layers to be stacked are not shown).
  • 1 is a substrate
  • 2 is a graphene layer
  • 3 is a peeling sacrificial layer.
  • first to third three graphene layers 2 are stacked on a substrate 1, and after forming a semiconductor element (solar cell) including a semiconductor film (not shown), the substrate Peeling is performed between the first graphene layer 2 and the first graphene layer 2, and the three graphene layers 2 are held on the semiconductor element side (FIG. 2D).
  • the graphene layer 2 is peeled off directly from the substrate.
  • first to fourth four-layer graphene layers 2 are stacked on a substrate 1, and after forming a semiconductor element including a semiconductor film (not shown), the first graphene layer 2 and the second graphene layer 2 are peeled off, and the third to fourth graphene layers 2 are held on the semiconductor element side (FIG. 2D), and the first graphene layer 2 is It will come off with the substrate.
  • a peeling sacrificial layer 3 is formed on a substrate 1, and then first to third graphene layers 2 are stacked, and a semiconductor element including a semiconductor film is further formed.
  • Preparation method chalcogenide-based layered materials such as GaSe, known bulk cleavage method, deposition method and the like.
  • soda lime, glass such as alkali-free glass, other ceramics, plastics, etc.
  • the plastics include polycarbonate, polystyrene, polyethylene, polypropylene, polyethylene terephthalate, polyimide, polyacrylate, etc. Can be mentioned.
  • the thickness is usually selected from about 50 ⁇ m to 5 mm.
  • a metal catalyst foil or a metal catalyst foil by a thermal CVD (thermal chemical vapor deposition) method using oxygen-containing hydrocarbons such as methane as a raw material.
  • a method of transferring a graphene single layer formed on a plate (copper foil, nickel plate, etc.) onto a substrate and repeating the transfer to form a plurality of graphene layers is suitably employed. That is, the thermal CVD method is performed at 900 to 1000 ° C., can be formed in a large area, and the number of layers can be easily controlled, but a graphene film formed on a metal catalyst foil or a plate is applied to a desired substrate.
  • the transfer method itself can be a conventional method.
  • a transfer method using PMMA polymethyl methacrylate
  • a method of transferring a plurality of graphene layers at once can also be adopted.
  • a solution coating method in which a graphene oxide solution is applied to a substrate to form a film and then reduced may be used.
  • the plurality of graphene layers are usually about 2 to 10 layers depending on the purpose, but it is preferable that 3 to 4 layers are included in the semiconductor element as a conductive film after peeling.
  • the peeled graphene layer becomes a transparent conductive film (first electrode), on which a semiconductor thin film is laminated according to the purpose, and then a second electrode can be formed.
  • Peeling is preferably performed after the second electrode is formed, but immediately before the second electrode is formed when the semiconductor thin film and the conductive substrate or film corresponding to the back electrode can be in good contact. Can be done.
  • the peeling is performed by applying a tensile stress and a shear stress so that the peeling occurs uniformly at a predetermined position.
  • an adhesive sheet, a protective sheet, or the like can be used as appropriate.
  • apply a resin such as epoxy resin or PDMS (polydimethylsiloxane)
  • place a cover glass or attach an adhesive sheet, and apply tensile or shear stress as appropriate using a hand or tweezers. It is possible to carry out peeling off uniformly.
  • the semiconductor element obtained by peeling the graphene layer directly or indirectly from the substrate is a self-supporting type. Since there is no substrate, it can be affixed freely to any support and multi-junction is easy.
  • a solar cell As the semiconductor element, a solar cell can be cited. Particularly preferred is a thin film solar cell comprising a first electrode comprising a graphene layer peeled directly or indirectly from a substrate; a semiconductor thin film; and a second electrode.
  • the semiconductor thin film is not particularly limited, and includes silicon such as microcrystalline silicon and amorphous silicon; and compound semiconductors such as III-V group, CdTe system, CIGS system, and the like, and a hybrid system can also be adopted.
  • amorphous silicon a pin junction that is usually hydrogenated (a-Si: H) and in which an i layer is inserted between the p layer and the n layer is preferably used.
  • a-Si: H layer (p layer, i layer, n layer) and a back electrode (second electrode) are laminated on a glass substrate provided with a transparent conductive film (first electrode).
  • the semiconductor thin film may include nanostructures such as superlattices, quantum dots, and nanowires. These films can be formed by a conventional method.
  • the thin film solar cell includes a nanowire array type solar cell.
  • a nanowire is a linear structure having a diameter of about 1 ⁇ m or less and a length of about several ⁇ m or more, The optical confinement effect is large, and the band gap can be controlled by the quantum size effect. For this reason, the nanowire array type solar cell is expected as a highly efficient solar cell.
  • Examples of the material of the nanowire include silicon, GaAs, and ZnO.
  • the graphene layer peeled off directly or indirectly from the substrate is a transparent conductive film and can be suitably used as the first electrode.
  • ITO indium tin oxide
  • Graphene has the same sheet resistance as ITO, better light transmission, and smaller absorption in the entire wavelength region.
  • the graphene layer according to the present invention includes a defect region accompanying peeling.
  • FIG. 3 shows an example of an SEM photograph (500 times) of the peeled graphene surface.
  • a bulge of about several ⁇ m to several tens of ⁇ m that was not seen before peeling was observed as a defect region accompanying peeling.
  • the density (frequency) of the defect region depends on the peeling conditions, etc., but the conductivity of the graphene layer is slightly reduced due to the presence of the defect region, but the sheet resistance is 100 ⁇ / ⁇ or less, so it can be used in applications. However, it can be sufficiently put into practical use.
  • Example 1 Single layer graphene was grown on copper foil by thermal CVD (Chemical Vapor Deposition) using methane and hydrogen (Science 324 (2009) 1312). “EAGLE-XG” glass (non-alkali glass) substrate with a thickness of 0.7 mm was ultrasonically cleaned with acetone and ethanol solutions for 10 minutes each, then blown with nitrogen, and then treated with UV-ozone for 5 minutes to make the surface hydrophilic. did. The grown single-layer CVD graphene film was transferred onto a hydrophilic glass substrate using PMMA (Poly (methyl methacrylate)) (Nano Lett. 9 (2009) 4359). By repeating the transfer, a 5-layer CVD graphene film was deposited.
  • PMMA Poly (methyl methacrylate)
  • an amorphous silicon solar cell was deposited.
  • the above graphene-coated glass substrate was put into a sample tube reaction tube of a plasma CVD apparatus, and after evacuation, the substrate was transferred to a p-layer formation reaction tube and placed on a substrate holder electrode set at 200 ° C. .
  • SiH 4 , monomethylsilane (MMS), H 2 and B 2 H 6 gas for forming the p layer were flowed, and the gas pressure was maintained at 70 Pa.
  • a high frequency of 13.56 MHz was applied to the electrode to deposit a p-layer. Thereafter, the high frequency and each gas were stopped and evacuated, and transferred to the i-layer forming reaction tube to deposit the i-layer.
  • SiH 4 and H 2 gases for forming the i layer were flowed, and the gas pressure was maintained at 50 Pa. Further, a high frequency of 60 MHz was applied to the electrode to deposit an i layer. Thereafter, the high frequency and each gas were stopped and evacuated, and transported to an n-layer forming reaction tube to deposit a seed layer and an intermediate layer. After forming the cell, the sample was taken out into a reaction tube for sample intake and purged with nitrogen gas, and then the sample was taken out. Subsequently, a backside silver electrode was deposited to a thickness of 500 nm using a vacuum evaporator.
  • an epoxy resin is applied, a cover glass is placed, tensile and shear stress is applied, the multilayer graphene layer is peeled off between the second layer and the third layer, and the solar cell is peeled off together with the graphene conductive film ((( b)).
  • an epoxy resin was applied after fixing the silver wire in advance, and after being covered with another glass substrate and cured overnight, peeling and peeling were confirmed.
  • FIG. 4 shows the structure of the thin film silicon solar cell that has been peeled off
  • FIG. 5 shows the solar cell characteristics before and after the peeling.
  • a thin film silicon solar cell as shown in FIG. 4 The layer structure is as follows.
  • Substrate 1 (glass) / graphene layer 2 (5 layers) / pa-SiC (10 nm) 4 / p-buffer layer 5 / ia-Si (500 nm) 6 / n-mc (microcrystal) -SiO (40 nm) 7 / Ag8 / A l9 In (b), after forming the Ag / Al electrode (here, p-a-SiC (10 nm) 4 / p-buffer layer 5 / ia-Si (500 nm) 6 / n-mc-SiO (40 nm) 7 The epoxy resin 10 was applied to the “a-Si battery”, and a cover glass 11 was placed thereon for further uniform peeling.
  • Example 2 The EAGLE-XG glass substrate was ultrasonically cleaned with an acetone and ethanol solution for 10 minutes each, and then blown with nitrogen, followed by UV-ozone treatment for 5 minutes to make the surface hydrophilic. A 1 wt% APTES ((3-aminopropyl) triethoxysilane) solution was impregnated for 15 minutes, rinsed with ultrapure water, blown with nitrogen, and then fired at 150 ° C. for 30 minutes.
  • APTES ((3-aminopropyl) triethoxysilane
  • FIG. 6 shows an SEM photograph (150 times) of the applied graphene oxide in Example 2.
  • FIG. Example 3 An amorphous silicon thin film was formed on the graphene laminated film, and a nanowire array was fabricated by metal-assisted chemical etching (Adv. Mater. 23 (2011) 285).
  • the base agent of PDMS (poly (dimethylsiloxane)) used as the resin and the curing agent were mixed and stirred for 5 minutes. This was spin-cast on a sample substrate and baked at 120 ° C. for 15 minutes after natural drying for about 12 hours. After the resin was cured, it was peeled off using a protective sheet. The peeling was performed between graphene oxide and graphene, which are sacrificial layers for peeling (aspect (c) in FIG. 2).
  • FIG. 7 shows an SEM photograph (20,000 times) of the obtained silicon nanowire array.
  • a multilayer graphene having a flat layered compound at an atomic level and sufficient conductivity as an electrode can be easily peeled off between graphene layers or between a graphene layer and a substrate, and the graphene layer can be used as an electrode as it is.
  • a method for producing a self-supporting thin film solar cell can be provided.

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Abstract

The degree of freedom of design of electronic elements such as highly-efficient multi-junction thin-film solar cells is improved as a consequence of creating electronic elements such as self-standing thin-film solar cells which do not need a support substrate by directly or indirectly peeling off multiple graphene layers, which are formed on a substrate, from the surface of said substrate without essentially losing the properties of the graphene layers. The present invention pertains to a method for producing a thin-film solar cell which contains: a first electrode containing a graphene layer; a semiconductor thin film; and a second electrode. Said method for producing a thin-film solar cell is characterized by producing a self-standing thin-film solar cell containing a semiconductor thin film by: forming multiple graphene layers on a substrate; forming the semiconductor thin film and the second electrode on the graphene layers; and directly or indirectly peeling off the graphene layers from the substrate to use the peeled graphene layers as the first electrode.

Description

薄膜太陽電池の製造方法および薄膜太陽電池Thin film solar cell manufacturing method and thin film solar cell
 本発明は、薄膜太陽電池の製造方法および薄膜太陽電池に関する。 The present invention relates to a method for manufacturing a thin film solar cell and a thin film solar cell.
 シリコン系の薄膜太陽電池は各セルを連続製膜することで容易に多接合化できるが(特許文献1)、他の薄膜太陽電池との接合には引き剥がす技術が必要となる。剥離層として酸化膜を用いて薄膜シリコン太陽電池を引き剥がすことが可能であるが(特許文献2)、剥離プロセスに必要なスルーホールなど構造自体が煩雑であり、剥離後に剥離層を除去して新たな電極層を形成する必要がある。 Silicon-based thin-film solar cells can be easily formed into multi-junctions by continuously forming each cell (Patent Document 1), but a technique for peeling off is required for bonding with other thin-film solar cells. Although it is possible to peel off a thin-film silicon solar cell using an oxide film as a peeling layer (Patent Document 2), the structure itself such as a through hole necessary for the peeling process is complicated, and the peeling layer is removed after peeling. It is necessary to form a new electrode layer.
 化合物系の薄膜太陽電池は下地金属電極層と吸収層との界面から引き剥がすことが可能であるが(非特許文献1)、多接合化には新たに電極層を堆積する必要がある。 Although a compound-based thin film solar cell can be peeled off from the interface between the base metal electrode layer and the absorption layer (Non-patent Document 1), it is necessary to deposit a new electrode layer for multi-junction.
 酸化グラフェンを用いて引き剥がすと、引き剥がし後に絶縁性である酸化グラフェン層を除去して新たな電極層を形成する必要がある(非特許文献2)。 When peeling off using graphene oxide, it is necessary to remove the insulating graphene oxide layer after peeling and form a new electrode layer (Non-patent Document 2).
特公昭63-48197号公報Japanese Patent Publication No.63-48197 特開平7-226528号公報Japanese Unexamined Patent Publication No. 7-226528
 本発明は、基板上に形成した、複数のグラフェン層をその特性を実質的に損なわないで、基板表面から直接または間接的に引き剥がすことにより、支持基板の不要な自立型薄膜太陽電池等の半導体素子を作製することで、高効率な多接合薄膜太陽電池等の設計の自由度を向上させるものである。 In the present invention, a plurality of graphene layers formed on a substrate are peeled off directly or indirectly from the surface of the substrate without substantially impairing the characteristics thereof. By producing a semiconductor element, the degree of freedom in designing a highly efficient multi-junction thin film solar cell or the like is improved.
  本発明は上記の課題を解決するために、以下の発明を提供するものである。
(1)グラフェン層を含む第1電極;半導体薄膜;および第2電極を含んでなる薄膜太陽電池の製造において、
 基板上に複数のグラフェン層を形成すること、該グラフェン層上に半導体薄膜および第2電極を形成すること、ついでグラフェン層を基板から直接または間接的に引き剥がして、引き剥がされたグラフェン層を第1電極とすることにより、半導体薄膜を含む自立型薄膜太陽電池を製造することを特徴とする薄膜太陽電池の製造方法。
(2)a)該基板から、b)該グラフェン層間で、またはc)該基板に隣接して、もしくは該グラフェン層間に設けられた剥離用犠牲層から、グラフェン層を引き剥がす上記(1)に記載の薄膜太陽電池の製造方法。
(3)複数のグラフェン層が、化学蒸着法により触媒金属箔もしくは板上に形成されたグ
ラフェン層を基板上に転写して形成される上記(1)または(2)に記載の薄膜太陽電池の製造方法。
(4)剥離用犠牲層が、カルコゲナイト系層状物質、酸化グラフェンまたは六方晶窒化ホウ素である上記(2)に記載の薄膜太陽電池の製造方法。
(5)基板から直接または間接的に引き剥がされたグラフェン層を含む第1電極;半導体薄膜;および第2電極を含んでなる薄膜太陽電池。
(6)上記(1)または(2)に記載の製造方法により得られた薄膜太陽電池。
In order to solve the above problems, the present invention provides the following inventions.
(1) In the manufacture of a thin film solar cell comprising a first electrode comprising a graphene layer; a semiconductor thin film; and a second electrode,
Forming a plurality of graphene layers on a substrate; forming a semiconductor thin film and a second electrode on the graphene layer; and then peeling the graphene layer directly or indirectly from the substrate to form a peeled graphene layer A manufacturing method of a thin film solar cell, wherein a self-supporting thin film solar cell including a semiconductor thin film is manufactured by using the first electrode.
(2) The graphene layer is peeled off from a) the substrate, b) between the graphene layers, or c) from the sacrifice sacrificial layer provided adjacent to or between the graphene layers. The manufacturing method of the thin film solar cell of description.
(3) The thin film solar cell according to (1) or (2), wherein the plurality of graphene layers are formed by transferring a graphene layer formed on a catalytic metal foil or a plate by chemical vapor deposition onto a substrate. Production method.
(4) The method for producing a thin-film solar cell according to (2), wherein the peeling sacrificial layer is a chalcogenite-based layered material, graphene oxide, or hexagonal boron nitride.
(5) A thin film solar cell comprising a first electrode including a graphene layer peeled off directly or indirectly from a substrate; a semiconductor thin film; and a second electrode.
(6) A thin film solar cell obtained by the production method according to (1) or (2) above.
 本発明によれば、原子レベルで平坦な層状化合物で電極としても十分な導電性を有する多層グラフェンを、グラフェン層間もしくはグラフェン層-基板間等で容易に剥離でき、さらにはグラフェンをそのまま電極として活かすことで自立型薄膜太陽電池を作製する方法を提供し得る。 According to the present invention, multilayer graphene that is a layered compound that is flat at an atomic level and has sufficient conductivity as an electrode can be easily peeled off between graphene layers or between a graphene layer and a substrate, and further, graphene can be used as an electrode as it is. Thus, a method for manufacturing a self-supporting thin film solar cell can be provided.
 たとえば、高効率な多接合太陽電池を自由に設計するためには太陽電池を引き剥がして別のセル構造や基板に接合するのが好適である。多接合による高効率化は、各セルの分光感度特性と出力特性のバランスを考えて設計する必要があるが、プロセス上の制約から制限されている面が多い。そのため、薄膜太陽電池を基板から剥離し自立できることは多接合太陽電池の設計に大きな自由度をもたらすことになる。本発明では、たとえば透明電極層として多層グラフェン膜を用いることにより、剥離後にそのまま自立型薄膜太陽電池として動作し得る。引き剥がされた後のグラフェン層が電極となるので、例えば他の手段で作製された太陽電池とも容易に接続でき、高効率な多接合薄膜太陽電池等の設計の自由度を向上させることが可能となる。 For example, in order to freely design a high-efficiency multi-junction solar cell, it is preferable to peel off the solar cell and bond it to another cell structure or substrate. High efficiency by multi-junction needs to be designed in consideration of the balance between spectral sensitivity characteristics and output characteristics of each cell, but is often limited due to process restrictions. For this reason, the ability to peel the thin film solar cell from the substrate and become self-supporting provides a great degree of freedom in designing a multi-junction solar cell. In the present invention, for example, by using a multilayer graphene film as the transparent electrode layer, it can operate as a self-supporting thin film solar cell as it is after peeling. Since the graphene layer after peeling becomes an electrode, it can be easily connected to, for example, a solar cell manufactured by other means, and the degree of freedom in designing a highly efficient multi-junction thin film solar cell can be improved. It becomes.
多層グラフェン膜を用いた薄膜太陽電池の引き剥がしの概念図。The conceptual diagram of peeling of the thin film solar cell using a multilayer graphene film. グラフェン層を引き剥がす態様を示す概念図。The conceptual diagram which shows the aspect which peels off a graphene layer. 引き剥がされたグラフェン表面の走査型電子顕微鏡(SEM)写真(500倍)の一例を示す。An example of a scanning electron microscope (SEM) photograph (500 times) of the peeled graphene surface is shown. 実施例1における、引き剥がされた薄膜シリコン太陽電池の構造を示す。The structure of the peeled thin film silicon solar cell in Example 1 is shown. 実施例1における、引き剥がし前後の太陽電池特性を示す。The solar cell characteristic before and behind peeling in Example 1 is shown. 実施例2における、塗布した酸化グラフェンのSEM写真(150倍)。The SEM photograph (150 times) of the applied graphene oxide in Example 2. FIG. 実施例3におけるシリコンナノワイヤーアレイのSEM写真(2万倍)。The SEM photograph (20,000 times) of the silicon nanowire array in Example 3. FIG.
 本発明の薄膜太陽電池の製造方法は、グラフェン層を含む第1電極;半導体薄膜;および第2電極を含んでなる薄膜太陽電池の製造において、基板上に複数のグラフェン層を形成すること、該グラフェン層上に半導体薄膜および第2電極を形成すること、ついでグラフェン層を基板から直接または間接的に引き剥がして、引き剥がされたグラフェン層を第1電極とすることにより、半導体薄膜を含む自立型薄膜太陽電池を製造することを特徴とする。「複数のグラフェン層」は、積層しているグラフェン層をいう。 The method of manufacturing a thin film solar cell according to the present invention includes forming a plurality of graphene layers on a substrate in manufacturing a thin film solar cell including a first electrode including a graphene layer; a semiconductor thin film; and a second electrode; The semiconductor thin film and the second electrode are formed on the graphene layer, and then the graphene layer is peeled off directly or indirectly from the substrate, and the peeled graphene layer is used as the first electrode, so that the self-supporting structure including the semiconductor thin film is obtained. A type thin film solar cell is manufactured. The “plurality of graphene layers” refers to stacked graphene layers.
 グラフェンとしては、6員環炭素シートからなるグラフェン骨格を維持して、種々の官能基が付加されたグラフェン誘導体も含まれ、たとえば酸素含有官能基で修飾された酸化グラフェンが挙げられる(還元により導電膜を容易に形成し得る)。さらに、グラフェンは、キャリア濃度を大きくし、導電性を向上させるために、ドーパントを含んでいてもよい。 The graphene includes a graphene derivative to which various functional groups are added while maintaining a graphene skeleton composed of a 6-membered ring carbon sheet, and examples thereof include graphene oxide modified with an oxygen-containing functional group (conducted by reduction). A film can be easily formed). Further, graphene may contain a dopant in order to increase the carrier concentration and improve the conductivity.
 グラフェン層を基板から直接または間接的に引き剥がすに際しては、a)基板から、b)グラフェン層間で、またはc)基板に隣接して、もしくはグラフェン層間に設けられた剥離用犠牲層から、グラフェン層を引き剥がすのが好適である。剥離用犠牲層は、グラフェン層の引き剥がしを円滑にするために設けられ、剥離用犠牲層とグラフェン層の間で引き剥がされると、剥離用犠牲層はグラフェン層を含む半導体素子側ではなく基板側に残ることになる。a)はグラフェン層を基板から直接に引き剥がす場合にあたり、一方、b)またはc)は基板から間接的に引き剥がす場合にあたる。 When peeling off the graphene layer directly or indirectly from the substrate, the graphene layer is a) from the substrate, b) between the graphene layers, or c) from the sacrificial layer for peeling provided adjacent to or between the graphene layers. Is preferably peeled off. The peeling sacrificial layer is provided to facilitate the peeling of the graphene layer. When the peeling sacrificial layer is peeled between the peeling sacrificial layer and the graphene layer, the peeling sacrificial layer is not on the semiconductor element side including the graphene layer. Will remain on the side. a) is when the graphene layer is peeled off directly from the substrate, while b) or c) is when it is peeled off indirectly from the substrate.
 図1は、グラフェン層を基板からb) グラフェン層間で間接的に引き剥がす、多層グラフェン膜を用いた薄膜太陽電池の引き剥がしの概念図である。図1において、(a)は基板1上にグラフェン膜を積層して複数のグラフェン層2を形成し、(b)はさらに半導体膜を含む半導体素子を形成(薄膜太陽電池の作製)した後に、グラフェン層間で引き剥がし、その結果、(c)は半導体素子12としてグラフェン層を電極とする自立型薄膜太陽電池が作製される、ことを示す。 FIG. 1 is a conceptual diagram of peeling of a thin film solar cell using a multilayer graphene film, in which a graphene layer is indirectly peeled off from a substrate b) and a graphene layer. In FIG. 1, (a) stacks a graphene film on a substrate 1 to form a plurality of graphene layers 2, and (b) further forms a semiconductor element including a semiconductor film (production of a thin film solar cell). Peeling is performed between the graphene layers, and as a result, (c) shows that a self-supporting thin-film solar cell having a graphene layer as an electrode is manufactured as the semiconductor element 12.
 図2において、(a)~(c)は、上記a)、b)および c) の態様により、グラフェン層を基板から直接または間接的に引き剥がす態様を示す概念図である(グラフェン層上に積層される層は図示しない)。図2において、1は基板、2はグラフェン層、3は剥離用犠牲層を示す。(a)においては、基板1上に、第1~3の3層のグラフェン層2が積層されており、さらに半導体膜を含む半導体素子(太陽電池)を形成後に(図示されていない)、基板1と第1のグラフェン層2の間で引き剥がしが行われ、3層のグラフェン層2は半導体素子側に保持されることになる(図2(d))。ここでは、グラフェン層2は、基板から直接に引き剥がされる。
(b)においては、基板1上に、第1~4の4層のグラフェン層2が積層されており、さらに半導体膜を含む半導体素子を形成後に(図示されていない)、第1のグラフェン層2と第2のグラフェン層2の間で引き剥がしが行われ、第2~4の3層のグラフェン層2は半導体素子側に保持され(図2(d))、第1のグラフェン層2は基板とともに離脱することになる。
(c)の左図においては、基板1上に、剥離用犠牲層3が成膜され、ついで第1~3の3層のグラフェン層2が積層されており、さらに半導体膜を含む半導体素子を形成後に(図示されていない)、剥離用犠牲層3と第1のグラフェン層2の間で引き剥がしが行われ、第1~3の3層のグラフェン層2は半導体素子側に保持され(図2(d))、剥離用犠牲層3は基板とともに離脱することになる。
(c)の右図においては、基板1上に、第1のグラフェン層2が成膜され、ついで剥離用犠牲層3が成膜され、さらに第2~4の3層のグラフェン層2が積層されており、半導体膜を含む半導体素子を形成後に(図示されていない)、剥離用犠牲層3と第2のグラフェン層2の間で引き剥がしが行われ、第2~4の3層のグラフェン層2は半導体素子側に保持され(図2(d))、第1のグラフェン層2および剥離用犠牲層3は基板とともに離脱することになる。以上のように、上記の(b)および(c)においては、グラフェン層2は、基板から間接的に引き剥がされる。
In FIG. 2, (a) to (c) are conceptual diagrams showing an embodiment in which the graphene layer is peeled off directly or indirectly from the substrate according to the above embodiments a), b) and c) (on the graphene layer) Layers to be stacked are not shown). In FIG. 2, 1 is a substrate, 2 is a graphene layer, and 3 is a peeling sacrificial layer. In (a), first to third three graphene layers 2 are stacked on a substrate 1, and after forming a semiconductor element (solar cell) including a semiconductor film (not shown), the substrate Peeling is performed between the first graphene layer 2 and the first graphene layer 2, and the three graphene layers 2 are held on the semiconductor element side (FIG. 2D). Here, the graphene layer 2 is peeled off directly from the substrate.
In (b), first to fourth four-layer graphene layers 2 are stacked on a substrate 1, and after forming a semiconductor element including a semiconductor film (not shown), the first graphene layer 2 and the second graphene layer 2 are peeled off, and the third to fourth graphene layers 2 are held on the semiconductor element side (FIG. 2D), and the first graphene layer 2 is It will come off with the substrate.
In the left figure of (c), a peeling sacrificial layer 3 is formed on a substrate 1, and then first to third graphene layers 2 are stacked, and a semiconductor element including a semiconductor film is further formed. After the formation (not shown), peeling is performed between the peeling sacrificial layer 3 and the first graphene layer 2, and the first to third graphene layers 2 are held on the semiconductor element side (FIG. 2 (d)), the peeling sacrificial layer 3 is detached together with the substrate.
In the right figure of (c), the first graphene layer 2 is formed on the substrate 1, the peeling sacrificial layer 3 is then formed, and the second to fourth three graphene layers 2 are stacked. After the formation of the semiconductor element including the semiconductor film (not shown), peeling is performed between the peeling sacrificial layer 3 and the second graphene layer 2, and the second to fourth layers of graphene The layer 2 is held on the semiconductor element side (FIG. 2D), and the first graphene layer 2 and the sacrificial layer 3 for separation are separated together with the substrate. As described above, in the above (b) and (c), the graphene layer 2 is indirectly peeled off from the substrate.
 上記の剥離用犠牲層としては、次のようなものが好適に用いられ得る。 As the above-mentioned sacrificial layer for peeling, the following can be suitably used.
 (1)化学剥離グラフェン(グラファイトを酸化してから単層および数層のグラフェンシートに剥離することで得られる酸化グラフェンや、グラファイトにインターカレーションして単層および数層のグラフェンシートに剥離して得られる化学修飾グラフェンなど、化学的に作製されたグラフェン)、(2)SiC上のエピタキシャルグラフェン(単結晶SiC基板を1100℃以上に加熱してSiCを還元して最表面にエピタキシャル成長させたグラフェン。条件によっては、数層のグラフェンを成長させることも可能であり、グラフェン上に素子構造を作り、引き剥がした後に再度グラフェンを成長させることで、SiC基板を再利用することも可能である)、ならびに(3)グラフェン以外の層状物質(絶縁性を示すh-BN(六方窒化ホウ素)や、MoS2やGaSeなどのカルコゲナイト系層状物質など。作製法としては、公知のバルク劈開法、成長法等が挙げられる。)
 基板としては、ソーダライム、無アルカリガラス等のガラス、その他のセラミックス、プラスチックス等が好適に使用され得、プラスチックスとしては、ポリカーボネート、ポリスチレン、ポリエチレン、ポリプロピレン、ポリエチレンテレフタレート、ポリイミド、ポリアクリレート等が挙げられる。厚さは50μm~5mm程度から選択されるのが通常である。
(1) Chemical exfoliated graphene (graphene oxide obtained by oxidizing graphite and then exfoliating it into single-layer and several-layer graphene sheets, and exfoliating into single-layer and several-layer graphene sheets by intercalation with graphite (2) Epitaxial graphene on SiC (single-crystal SiC substrate heated to 1100 ° C or higher to reduce SiC and grow epitaxially on the outermost surface) (Depending on the conditions, it is possible to grow several layers of graphene, and it is also possible to reuse the SiC substrate by creating a device structure on the graphene and growing it again after peeling off) , and (3) graphene than layered material (indicating insulating h-BN (hexagonal boron nitride) or, MoS 2 The like. Preparation method chalcogenide-based layered materials such as GaSe, known bulk cleavage method, deposition method and the like.)
As the substrate, soda lime, glass such as alkali-free glass, other ceramics, plastics, etc. can be suitably used. Examples of the plastics include polycarbonate, polystyrene, polyethylene, polypropylene, polyethylene terephthalate, polyimide, polyacrylate, etc. Can be mentioned. The thickness is usually selected from about 50 μm to 5 mm.
 基板上に複数のグラフェン層を形成するには、種々の方法が採用され得るが、たとえば、メタン等の炭化水素類等の含酸素を原料として熱CVD(熱化学蒸着)法により金属触媒箔もしくは板(銅箔、ニッケル板等)上に形成されたグラフェン単層を基板上に転写し、転写を繰り返して複数のグラフェン層を形成する方法が好適に採用される。すなわち、熱CVD法は、900~1000℃で実施され、大きな面積で成膜され得、層数制御も容易であるが、金属触媒箔もしくは板上に形成されたグラフェン膜を、所望の基板に転写する必要がある。転写法自体は、常法によることができ、たとえばPMMA(ポリメチルメタクリレート)を用いる転写法が好適に採用され得る。転写法は、複数のグラフェン層を一度で転写する方法も採用し得る。 Various methods can be adopted to form a plurality of graphene layers on a substrate. For example, a metal catalyst foil or a metal catalyst foil by a thermal CVD (thermal chemical vapor deposition) method using oxygen-containing hydrocarbons such as methane as a raw material. A method of transferring a graphene single layer formed on a plate (copper foil, nickel plate, etc.) onto a substrate and repeating the transfer to form a plurality of graphene layers is suitably employed. That is, the thermal CVD method is performed at 900 to 1000 ° C., can be formed in a large area, and the number of layers can be easily controlled, but a graphene film formed on a metal catalyst foil or a plate is applied to a desired substrate. It is necessary to transcribe. The transfer method itself can be a conventional method. For example, a transfer method using PMMA (polymethyl methacrylate) can be suitably employed. As the transfer method, a method of transferring a plurality of graphene layers at once can also be adopted.
 たとえば、酸化グラフェン溶液を基板に塗布して成膜し、還元する溶液塗布法等も使用され得る。 For example, a solution coating method in which a graphene oxide solution is applied to a substrate to form a film and then reduced may be used.
 複数のグラフェン層は、目的により異なるが、通常2~10層程度であり、引き剥がし後に3~4層が、導電膜として半導体素子に含まれるのが好適である。 The plurality of graphene layers are usually about 2 to 10 layers depending on the purpose, but it is preferable that 3 to 4 layers are included in the semiconductor element as a conductive film after peeling.
 引き剥がされたグラフェン層は、透明導電膜(第1電極)となり、その上に半導体薄膜が目的に応じて積層形成され、ついで第2電極が形成され得る。 The peeled graphene layer becomes a transparent conductive film (first electrode), on which a semiconductor thin film is laminated according to the purpose, and then a second electrode can be formed.
 引き剥がしは、第2電極が形成された後に行われるのが好適であるが、半導体薄膜と裏面電極にあたる導電性基板もしくは膜とが良好な接触が取れる場合には、第2電極を形成する直前に行われ得る。引き剥がしは、所定の位置で剥離が均一に生じるように、引張り応力、ずり応力を加えて実施される。この実施に際しては、粘着シート、保護シート等を適宜用いることができる。たとえば、エポキシ樹脂、PDMS(ポリジメチルシロキサン)等の樹脂を塗布し、カバーガラスを載せて、または粘着シートを貼付して、手またはピンセット等の器具を用いて引張り応力およびずり応力を適宜加えて、均一に引き剥がしを実施し得る。 Peeling is preferably performed after the second electrode is formed, but immediately before the second electrode is formed when the semiconductor thin film and the conductive substrate or film corresponding to the back electrode can be in good contact. Can be done. The peeling is performed by applying a tensile stress and a shear stress so that the peeling occurs uniformly at a predetermined position. In this implementation, an adhesive sheet, a protective sheet, or the like can be used as appropriate. For example, apply a resin such as epoxy resin or PDMS (polydimethylsiloxane), place a cover glass, or attach an adhesive sheet, and apply tensile or shear stress as appropriate using a hand or tweezers. It is possible to carry out peeling off uniformly.
 このようにして、グラフェン層を基板から直接または間接的に引き剥がして得られる半導体素子は自立型である。基板がないため、どのような支持体にも自由に貼付でき、多接合化も容易である。 Thus, the semiconductor element obtained by peeling the graphene layer directly or indirectly from the substrate is a self-supporting type. Since there is no substrate, it can be affixed freely to any support and multi-junction is easy.
 半導体素子としては、太陽電池が挙げられる。特に好適には、基板から直接または間接的に引き剥がされたグラフェン層を含む第1電極;半導体薄膜;および第2電極を含んでなる薄膜太陽電池である。 As the semiconductor element, a solar cell can be cited. Particularly preferred is a thin film solar cell comprising a first electrode comprising a graphene layer peeled directly or indirectly from a substrate; a semiconductor thin film; and a second electrode.
 半導体薄膜としては、特に制限されず、微結晶シリコン、アモルファスシリコン等のシリコン;ならびにIII‐V族、CdTe系、CIGS系等の化合物半導体、等が挙げられ、ハイブリッド系も採用され得る。アモルファスシリコンの場合には、通常、水素化されて用いられ(a-Si:H)、かつp層とn層に間にi層を挿入したpin接合が好適に用いられる。たとえば、透明導電膜(第1電極)を付したガラス基板にa-Si:H層(p層、i層、n層)、裏面電極(第2電極)を積層した構造を有する。半導体薄膜は、超格子、量子ドット、ナノワイヤー等のナノ構造を含んでいてもよい。これらの成膜は、常法によることができる。 The semiconductor thin film is not particularly limited, and includes silicon such as microcrystalline silicon and amorphous silicon; and compound semiconductors such as III-V group, CdTe system, CIGS system, and the like, and a hybrid system can also be adopted. In the case of amorphous silicon, a pin junction that is usually hydrogenated (a-Si: H) and in which an i layer is inserted between the p layer and the n layer is preferably used. For example, it has a structure in which an a-Si: H layer (p layer, i layer, n layer) and a back electrode (second electrode) are laminated on a glass substrate provided with a transparent conductive film (first electrode). The semiconductor thin film may include nanostructures such as superlattices, quantum dots, and nanowires. These films can be formed by a conventional method.
 本発明において、薄膜太陽電池は、ナノワイヤーアレイ型太陽電池を含む。ナノワイヤーは、直径1μm程度以下、長さが数μm程度以上の線状構造体であり、
光閉じ込め効果が大きく、量子サイズ効果によりバンドギャップ制御が可能である。このために、ナノワイヤーアレイ型太陽電池は高効率の太陽電池として期待される。ナノワイヤーの材質は、たとえば、シリコン、GaAs、ZnO等が挙げられる。
In the present invention, the thin film solar cell includes a nanowire array type solar cell. A nanowire is a linear structure having a diameter of about 1 μm or less and a length of about several μm or more,
The optical confinement effect is large, and the band gap can be controlled by the quantum size effect. For this reason, the nanowire array type solar cell is expected as a highly efficient solar cell. Examples of the material of the nanowire include silicon, GaAs, and ZnO.
 本発明において、基板から直接または間接的に引き剥がされたグラフェン層は、透明導電膜であり、第1電極として好適に使用され得る。たとえば、長波長赤外線を利用する太陽電池等のITO(インジウム・スズ酸化物)が不得手な分野においても好適に使用され得る。グラフェンは、ITOに比し、シート抵抗が同等であり、光透過性が一層良好であり、さらに全波長領域で吸収が小さい利点がある。 In the present invention, the graphene layer peeled off directly or indirectly from the substrate is a transparent conductive film and can be suitably used as the first electrode. For example, ITO (indium tin oxide) such as solar cells using long-wavelength infrared rays can be suitably used in fields where it is not good. Graphene has the same sheet resistance as ITO, better light transmission, and smaller absorption in the entire wavelength region.
 本発明に係るグラフェン層は、剥離に伴う欠損領域を含む。図3は、引き剥がされたグラフェン表面のSEM写真(500倍)の一例を示す。引き剥がされたグラフェン表面には、引き剥がし前にはみられない数μm~数十μm程度の膨らみが、剥離に伴う欠損領域として観察された。欠損領域の密度(頻度)は、引き剥がし条件等に依存するが、欠損領域の存在により、グラフェン層の導電性は若干低下するが、シート抵抗は100Ω/□以下が得られるので、用途にもよるが、十分に実用に供し得るものである。 The graphene layer according to the present invention includes a defect region accompanying peeling. FIG. 3 shows an example of an SEM photograph (500 times) of the peeled graphene surface. On the peeled graphene surface, a bulge of about several μm to several tens of μm that was not seen before peeling was observed as a defect region accompanying peeling. The density (frequency) of the defect region depends on the peeling conditions, etc., but the conductivity of the graphene layer is slightly reduced due to the presence of the defect region, but the sheet resistance is 100Ω / □ or less, so it can be used in applications. However, it can be sufficiently put into practical use.
 以下に、実施例により本発明をさらに詳細に説明する。
実施例1
 銅箔上にメタンと水素を用いて熱CVD(Chemical Vapor Deposition)により単層グラフェンを成長させた(Science 324 (2009) 1312)。厚さが0.7mm の「EAGLE-XG」ガラス(無アルカリガラス)基板をアセトン及びエタノール溶液でそれぞれ10分間超音波洗浄し、窒素ブローをした後にUV-オゾン処理を5分間行い表面を親水性化した。成長させた単層CVDグラフェン膜をPMMA(Poly(methyl methacrylate))を用いて、親水性化したガラス基板上に転写した(Nano Lett. 9 (2009) 4359)。転写を繰り返すことで5層のCVDグラフェン膜を堆積した。
Hereinafter, the present invention will be described in more detail with reference to examples.
Example 1
Single layer graphene was grown on copper foil by thermal CVD (Chemical Vapor Deposition) using methane and hydrogen (Science 324 (2009) 1312). “EAGLE-XG” glass (non-alkali glass) substrate with a thickness of 0.7 mm was ultrasonically cleaned with acetone and ethanol solutions for 10 minutes each, then blown with nitrogen, and then treated with UV-ozone for 5 minutes to make the surface hydrophilic. did. The grown single-layer CVD graphene film was transferred onto a hydrophilic glass substrate using PMMA (Poly (methyl methacrylate)) (Nano Lett. 9 (2009) 4359). By repeating the transfer, a 5-layer CVD graphene film was deposited.
 次にアモルファスシリコン太陽電池を堆積させた。上記のグラフェン付ガラス基板をプラズマCVD装置のサンプル取り入れ用反応管に投入し、真空引きした後に、基板をp層形成用反応管へ搬送し、200oCにセットされた基板ホルダー電極に設置した。p層形成用のSiH,モノメチルシラン(MMS)、H及び B2H6 ガスを流し、ガス圧力を70Paに保持した。ついで、 13.56MHz の高周波を電極に投入し、p層を堆積させた。その後、高周波及び各ガスを止めて真空引きにし、i層形成用反応管へ搬送し、i層を堆積させた。i層形成用のSiH及びH2ガスを流し、ガス圧力を50Pa に保持した。さらに、60MHzの高周波を電極に投入し、i層を堆積させた。その後、高周波及び各ガスを止めて真空引きにし、n層形成用反応管へ搬送し、シード層及び中間層を堆積させた。セルを形成した後、サンプル取り入れ用反応管に搬送し、窒素ガスでパージした後に、サンプルを取り出した。続いて真空蒸着器を用いて裏面銀電極を500nmの厚さに蒸着した。 Next, an amorphous silicon solar cell was deposited. The above graphene-coated glass substrate was put into a sample tube reaction tube of a plasma CVD apparatus, and after evacuation, the substrate was transferred to a p-layer formation reaction tube and placed on a substrate holder electrode set at 200 ° C. . SiH 4 , monomethylsilane (MMS), H 2 and B 2 H 6 gas for forming the p layer were flowed, and the gas pressure was maintained at 70 Pa. Next, a high frequency of 13.56 MHz was applied to the electrode to deposit a p-layer. Thereafter, the high frequency and each gas were stopped and evacuated, and transferred to the i-layer forming reaction tube to deposit the i-layer. SiH 4 and H 2 gases for forming the i layer were flowed, and the gas pressure was maintained at 50 Pa. Further, a high frequency of 60 MHz was applied to the electrode to deposit an i layer. Thereafter, the high frequency and each gas were stopped and evacuated, and transported to an n-layer forming reaction tube to deposit a seed layer and an intermediate layer. After forming the cell, the sample was taken out into a reaction tube for sample intake and purged with nitrogen gas, and then the sample was taken out. Subsequently, a backside silver electrode was deposited to a thickness of 500 nm using a vacuum evaporator.
 ついで、エポキシ樹脂を塗布し、カバーグラスを載せて引っ張りおよびずり応力を加えて、多層グラフェン層の第2層と第3層間で引き剥がし、太陽電池をグラフェン導電膜ごと剥離した(図2の(b)の態様)。引き剥がし後に太陽電池特性を評価するために、予め銀線を固定させた後にエポキシ樹脂を塗布し、別のガラス基板を被せて一晩硬化させた後に、引き剥がして太陽電池動作を確認した。 Next, an epoxy resin is applied, a cover glass is placed, tensile and shear stress is applied, the multilayer graphene layer is peeled off between the second layer and the third layer, and the solar cell is peeled off together with the graphene conductive film ((( b)). In order to evaluate the solar cell characteristics after peeling, an epoxy resin was applied after fixing the silver wire in advance, and after being covered with another glass substrate and cured overnight, peeling and peeling were confirmed.
 図4に、引き剥がした薄膜シリコン太陽電池の構造を示し、図5に、引き剥がし前後の太陽電池特性を示す。図4において、まず(a)に示すような薄膜シリコン太陽電池を作製した。層構成は次のとおりである。 FIG. 4 shows the structure of the thin film silicon solar cell that has been peeled off, and FIG. 5 shows the solar cell characteristics before and after the peeling. In FIG. 4, a thin film silicon solar cell as shown in FIG. The layer structure is as follows.
  基板1(ガラス)/グラフェン層2(5層)/p-a-SiC(10nm)4/p-バッファ
ー層5/i-a-Si(500nm)6/n-mc(微結晶)-SiO(40nm)7/Ag8/A l9
 (b)において、Ag/Al電極形成後(ここでは、p-a-SiC(10nm)4/p-バッファー層5/i-a-Si(500nm)6/n-mc-SiO(40nm)7を「a-Si電池」とした)に、エポキシ樹脂10を塗布し、さらに均一な引き剥がしを図るためにカバーガラス11を載せた。ついで、カバーガラスの上から引張りおよびずり応力をピンセットで加えて、グラフェン層2内(第2層と第3層間)で引き剥がした(c)。図5に示すように、引き剥がし後の太陽電池特性は、若干低下した。
実施例2
 EAGLE-XGガラス基板をアセトン及びエタノール溶液でそれぞれ10分間超音波洗浄し、窒素ブローをした後にUV-オゾン処理を5分間行い表面を親水性化した。1wt%のAPTES((3-アミノプロピル)トリエトキシシラン)溶液に15分間含浸し、超純水でリンスして窒素ブローした後に、150℃で30分間焼成した。このように表面をアミノ基終端させたガラス基板に約10wt%の酸化グラフェン分散液をスピンキャストした後に150℃で5分間焼成した。次に、銅箔上にメタンと水素を用いて熱CVD成長した単層CVDグラフェン膜をPMMAを用いて、酸化グラフェン層の上に転写した。アモルファスシリコン太陽電池の作製工程、引き剥がし工程については実施例1と同様であったが、引き剥がしは、剥離用犠牲層である酸化グラフェンとグラフェンの間で実施された(図2の(c)の態様)。
Substrate 1 (glass) / graphene layer 2 (5 layers) / pa-SiC (10 nm) 4 / p-buffer layer 5 / ia-Si (500 nm) 6 / n-mc (microcrystal) -SiO (40 nm) 7 / Ag8 / A l9
In (b), after forming the Ag / Al electrode (here, p-a-SiC (10 nm) 4 / p-buffer layer 5 / ia-Si (500 nm) 6 / n-mc-SiO (40 nm) 7 The epoxy resin 10 was applied to the “a-Si battery”, and a cover glass 11 was placed thereon for further uniform peeling. Next, tensile and shear stresses were applied from above the cover glass with tweezers, and peeled off in the graphene layer 2 (second layer and third layer) (c). As shown in FIG. 5, the solar cell characteristics after peeling were slightly lowered.
Example 2
The EAGLE-XG glass substrate was ultrasonically cleaned with an acetone and ethanol solution for 10 minutes each, and then blown with nitrogen, followed by UV-ozone treatment for 5 minutes to make the surface hydrophilic. A 1 wt% APTES ((3-aminopropyl) triethoxysilane) solution was impregnated for 15 minutes, rinsed with ultrapure water, blown with nitrogen, and then fired at 150 ° C. for 30 minutes. After spin-casting about 10 wt% graphene oxide dispersion on the glass substrate having the surface terminated with an amino group in this manner, it was baked at 150 ° C. for 5 minutes. Next, a single-layer CVD graphene film grown by thermal CVD using methane and hydrogen on a copper foil was transferred onto the graphene oxide layer using PMMA. The manufacturing process and the peeling process of the amorphous silicon solar cell were the same as in Example 1, but the peeling was performed between graphene oxide and graphene, which were the sacrificial layers for peeling ((c) in FIG. 2). Embodiment).
 図6は、実施例2における、塗布した酸化グラフェンのSEM写真(150倍)を示す。
実施例3
 グラフェン積層膜上にアモルファスシリコン薄膜を成膜し、金属触媒化学エッチング(Metal-Assisted Chemical Etching)法によりナノワイヤーアレイを作製した(Adv. Mater. 23 (2011) 285など)。樹脂として用いるPDMS(ポリ(ジメチルシロキサン))のベース剤と硬化剤を混ぜ合わせ、5分間撹拌した。これをサンプル基板上にスピンキャストし、12時間程度自然乾燥後に120℃で15分間焼成した。樹脂が硬化した後に保護シートを用いて剥離した。引き剥がしは、剥離用犠牲層である酸化グラフェンとグラフェンの間で実施された(図2の(c)の態様)。
6 shows an SEM photograph (150 times) of the applied graphene oxide in Example 2. FIG.
Example 3
An amorphous silicon thin film was formed on the graphene laminated film, and a nanowire array was fabricated by metal-assisted chemical etching (Adv. Mater. 23 (2011) 285). The base agent of PDMS (poly (dimethylsiloxane)) used as the resin and the curing agent were mixed and stirred for 5 minutes. This was spin-cast on a sample substrate and baked at 120 ° C. for 15 minutes after natural drying for about 12 hours. After the resin was cured, it was peeled off using a protective sheet. The peeling was performed between graphene oxide and graphene, which are sacrificial layers for peeling (aspect (c) in FIG. 2).
 図7は、得られたシリコンナノワイヤーアレイのSEM写真(2万倍)を示す。 FIG. 7 shows an SEM photograph (20,000 times) of the obtained silicon nanowire array.
 本発明によれば、原子レベルで平坦な層状化合物で電極としても十分な導電性を有する多層グラフェンを、グラフェン層間もしくはグラフェン層-基板間等で容易に剥離でき、さらにはグラフェン層をそのまま電極として活かすことにより、自立型薄膜太陽電池を作製する方法を提供し得る。 According to the present invention, a multilayer graphene having a flat layered compound at an atomic level and sufficient conductivity as an electrode can be easily peeled off between graphene layers or between a graphene layer and a substrate, and the graphene layer can be used as an electrode as it is. By utilizing this, a method for producing a self-supporting thin film solar cell can be provided.
 1  基板
 2  グラフェン層
 3  剥離用犠牲層
 4  p-a-SiC層
 5  p-バッファー層
 6  i-a-Si層
 7  n-mc-SiO層
 8  Ag層
 9  Al層
 10  樹脂
 11  カバーガラス
 12  半導体素子
DESCRIPTION OF SYMBOLS 1 Substrate 2 Graphene layer 3 Peeling sacrificial layer 4 p-a-SiC layer 5 p-buffer layer 6 ia-Si layer 7 n-mc-SiO layer 8 Ag layer 9 Al layer 10 Resin 11 Cover glass 12 Semiconductor element

Claims (6)

  1.  グラフェン層を含む第1電極;半導体薄膜;および第2電極を含んでなる薄膜太陽電池の製造において、
     基板上に複数のグラフェン層を形成すること、該グラフェン層上に半導体薄膜および第2電極を形成すること、ついでグラフェン層を基板から直接または間接的に引き剥がして、引き剥がされたグラフェン層を第1電極とすることにより、半導体薄膜を含む自立型薄膜太陽電池を製造することを特徴とする薄膜太陽電池の製造方法。
    In the manufacture of a thin film solar cell comprising a first electrode comprising a graphene layer; a semiconductor thin film; and a second electrode,
    Forming a plurality of graphene layers on a substrate; forming a semiconductor thin film and a second electrode on the graphene layer; and then peeling the graphene layer directly or indirectly from the substrate to form a peeled graphene layer A manufacturing method of a thin film solar cell, wherein a self-supporting thin film solar cell including a semiconductor thin film is manufactured by using the first electrode.
  2.  a)該基板から、b)該グラフェン層間で、またはc)該基板に隣接して、もしくは該グラフェン層間に設けられた剥離用犠牲層から、グラフェン層を引き剥がす請求項1に記載の薄膜太陽電池の製造方法。 The thin film solar cell according to claim 1, wherein the graphene layer is peeled off from a) the substrate, b) between the graphene layers, or c) from a peeling sacrificial layer provided adjacent to or between the graphene layers. Battery manufacturing method.
  3.  複数のグラフェン層が、化学蒸着法により触媒金属箔もしくは板上に形成されたグラフェン層を基板上に転写して形成される請求項1または2に記載の薄膜太陽電池の製造方法。 The method for producing a thin-film solar cell according to claim 1 or 2, wherein the plurality of graphene layers are formed by transferring a graphene layer formed on a catalytic metal foil or a plate by chemical vapor deposition onto a substrate.
  4.  剥離用犠牲層が、カルコゲナイト系層状物質、酸化グラフェンまたは六方晶窒化ホウ素である請求項2に記載の薄膜太陽電池の製造方法。 3. The method for producing a thin film solar cell according to claim 2, wherein the peeling sacrificial layer is a chalcogenite-based layered material, graphene oxide, or hexagonal boron nitride.
  5.  基板から直接または間接的に引き剥がされたグラフェン層を含む第1電極;半導体薄膜;および第2電極を含んでなる薄膜太陽電池。 A thin film solar cell comprising a first electrode comprising a graphene layer peeled off directly or indirectly from a substrate; a semiconductor thin film; and a second electrode.
  6.  請求項1または2に記載の製造方法により得られた薄膜太陽電池。 A thin-film solar cell obtained by the production method according to claim 1 or 2.
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