EP1200995A1 - Flexible thin-layer solar cell - Google Patents

Flexible thin-layer solar cell

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Publication number
EP1200995A1
EP1200995A1 EP00940105A EP00940105A EP1200995A1 EP 1200995 A1 EP1200995 A1 EP 1200995A1 EP 00940105 A EP00940105 A EP 00940105A EP 00940105 A EP00940105 A EP 00940105A EP 1200995 A1 EP1200995 A1 EP 1200995A1
Authority
EP
European Patent Office
Prior art keywords
layer
solar cell
substrate
intermediate layer
flexible
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP00940105A
Other languages
German (de)
French (fr)
Inventor
Ayodhya N. Tiwari
Martin Krejci
Franz Josef Haug
Hans Zogg
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Eidgenoessische Technische Hochschule Zurich ETHZ
Original Assignee
Eidgenoessische Technische Hochschule Zurich ETHZ
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Eidgenoessische Technische Hochschule Zurich ETHZ filed Critical Eidgenoessische Technische Hochschule Zurich ETHZ
Publication of EP1200995A1 publication Critical patent/EP1200995A1/en
Withdrawn legal-status Critical Current

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Classifications

    • 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
    • H01L31/1892—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof methods involving the use of temporary, removable substrates
    • H—ELECTRICITY
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    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/0248—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies
    • H01L31/0256—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by the material
    • H01L31/0264—Inorganic materials
    • H01L31/032—Inorganic materials including, apart from doping materials or other impurities, only compounds not provided for in groups H01L31/0272 - H01L31/0312
    • H01L31/0322—Inorganic materials including, apart from doping materials or other impurities, only compounds not provided for in groups H01L31/0272 - H01L31/0312 comprising only AIBIIICVI chalcopyrite compounds, e.g. Cu In Se2, Cu Ga Se2, Cu In Ga Se2
    • H—ELECTRICITY
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    • 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
    • H01L31/0392—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 thin films deposited on metallic or insulating substrates ; characterised by specific substrate materials or substrate features or by the presence of intermediate layers, e.g. barrier layers, on the substrate
    • 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
    • H01L31/0392—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 thin films deposited on metallic or insulating substrates ; characterised by specific substrate materials or substrate features or by the presence of intermediate layers, e.g. barrier layers, on the substrate
    • H01L31/03921—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 thin films deposited on metallic or insulating substrates ; characterised by specific substrate materials or substrate features or by the presence of intermediate layers, e.g. barrier layers, on the substrate including only elements of Group IV of the Periodic System
    • H—ELECTRICITY
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    • 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
    • H01L31/0392—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 thin films deposited on metallic or insulating substrates ; characterised by specific substrate materials or substrate features or by the presence of intermediate layers, e.g. barrier layers, on the substrate
    • H01L31/03925—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 thin films deposited on metallic or insulating substrates ; characterised by specific substrate materials or substrate features or by the presence of intermediate layers, e.g. barrier layers, on the substrate including AIIBVI compound materials, e.g. CdTe, CdS
    • 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
    • H01L31/0392—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 thin films deposited on metallic or insulating substrates ; characterised by specific substrate materials or substrate features or by the presence of intermediate layers, e.g. barrier layers, on the substrate
    • H01L31/03926—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 thin films deposited on metallic or insulating substrates ; characterised by specific substrate materials or substrate features or by the presence of intermediate layers, e.g. barrier layers, on the substrate comprising a flexible substrate
    • H01L31/03928—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 thin films deposited on metallic or insulating substrates ; characterised by specific substrate materials or substrate features or by the presence of intermediate layers, e.g. barrier layers, on the substrate comprising a flexible substrate including AIBIIICVI compound, e.g. CIS, CIGS deposited on metal or polymer foils
    • 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
    • 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
    • H01L31/1892—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof methods involving the use of temporary, removable substrates
    • H01L31/1896—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof methods involving the use of temporary, removable substrates for thin-film semiconductors
    • 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
    • Y02E10/541—CuInSe2 material PV cells
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • the invention relates to a method for producing solar cells and a solar cell that consists of only thin layers and is flexible, according to patent claims 1 and 8.
  • the object of the present invention is to provide a method for producing solar cells, in which a dissolvable intermediate layer allows the solar cell to be separated from a rigid support.
  • Another task is to propose a solar cell that consists only of thin layers and is flexible.
  • Fig. 2a layer stack of a second version before detaching from the substrate
  • Fig. 1 shows a layer stack before detachment from the rigid substrate on the basis of which the method is described.
  • a soluble intermediate layer 6 is applied, for example by vacuum evaporation, to a rigid substrate 7, which consists, for example, of glass, ceramic or metal.
  • This soluble intermediate layer a so-called “sacrificial layer”, consists for example of table salt (NaCl) or BaF 2 , both substances are soluble in water. Water is therefore used as a solvent in the manufacturing process at the appropriate time.
  • the carrier layer 5 is now applied to the substrate 7 covered with the soluble intermediate layer 6, for example a metal layer deposited by vacuum deposition, or a polymer layer spun on for example, such as a temperature-resistant plastic commercially available under the brand name "Kapton".
  • the further process steps are based on the example.
  • CIGS Culn x Ga y Se z with x, y, z> 0
  • the description can also be used for other cell types such as CdTe.
  • the further steps essentially correspond to the already known methods (HW Schock and A. Shah, "Status and prospects of photovoltaic thin film technologies", Proc. 14 th European Photovoltaic Solar Energy Conference, Barcelona, Spain, 1997, HS Stephens & Associates, UK, 1997, pp. 2000-2005):
  • the back contact (4) is deposited on the carrier layer (5), this consists, for example, of sputtered Mo.
  • the absorber layer ( 1) applied with a thickness of a few micrometers here the known techniques can be used to obtain the highest possible efficiency of the finished cell by, for example, grading the layer composition.
  • the temperature of the sample during the deposition is, for example, 400 ° C. At this temperature, a suitable plastic carrier layer as described above remains intact, but cells with high efficiencies can still be obtained. Also in this step, some Na can be added in a suitable form and / or compound, since it is known that adding Na has a positive effect on the properties of the finished cell.
  • the window layer (2) which consists, for example, of ZnO, CdS or ZnSe, and the front contact (3) of, for example, ITO (indium tin oxide), further differentiations such as CdS deposition depending on the method selected, or doping the upper part of the window layer, so that it also functions as a front contact part, makes sense.
  • the window layer (2) which consists, for example, of ZnO, CdS or ZnSe
  • the front contact (3) of, for example, ITO (indium tin oxide)
  • CdS deposition depending on the method selected, or doping the upper part of the window layer, so that it also functions as a front contact part, makes sense.
  • individual solar cells are structured by means of, for example, scratching or photolithography and, if necessary, antireflection and mechanical protective layers (for example an optically transparent UV-resistant additional polymer layer) are applied.
  • the intermediate layer 6 can typically now be dissolved, as a result of which the substrate 7 is separated from the carrier layer 5 and the layer package 10 applied thereon.
  • the carrier layer 5 and the layer package 10 form the now flexible solar cell.
  • the intermediate layer 6 consists, for example, of NaCl or BaF 2 , water can be used as the solvent.
  • Other solvents can be used for non-water-soluble intermediate layers or for other reasons.
  • a CIGS solar cell with 12.8% efficiency was obtained on a polyimide substrate.
  • the layer thickness of the spun NEN polyimides was approx. 20 ⁇ m, the thickness of the layers essential for the electro-optical functioning of the solar cell was less than approx. 4 ⁇ m.
  • the whole structure is flexible and can be used for the applications already described.
  • the rigid substrate 7 can be reused after the layer structure 11 has been detached.
  • the solar cell according to the invention It is therefore essential to the solar cell according to the invention that it is formed on a rigid substrate during a large part of the production steps, is subsequently detached from it and is then flexible, however. It can be used in a flexible state, but can also be reconnected to another solid substrate.
  • the entire solar cell structure remains flexible. This e.g. to bypass the relatively expensive glass substrate, to mount the solar cells on curved surfaces such as facades, bricks or curved housings of electronic consumer devices, or just to save weight, which is particularly important for space applications.
  • a large, flexible structure can also be easily rolled for transport.
  • Flexible solar cells are also interesting for small-area applications, e.g. as an energy source for pocket calculators or "smart cards", which can contain integrated electrical circuits and displays, but must meet certain flexibility requirements.
  • 2a and 2b show a variation of the manufacturing method according to the invention.
  • 2a shows a second layer stack before detachment from the substrate.
  • the intermediate layer 6 is applied to the substrate 7 for the production.
  • the carrier layer 5 is dispensed with at the current time of manufacture, but the other layers 1 - 4 of the solar cell structure are deposited directly, e.g.
  • back contact 4 for example Mo
  • CIGS 1 which may be provided with a little Na, window layer 2 and front contact 3.
  • the transparent polymer 5 is then applied as a carrier film, and the entire structure 11 is removed by dissolving the intermediate layer 6 rigid substrate 7 solved.
  • the deposition temperature can also be higher than 400 ° C., since the polymer layer is only applied subsequently; a plastic with less good temperature resistance can also be used instead of the polymer.
  • FIG. 2b shows a second layer stack in the finished state.
  • a further variant is to carefully detach the layer package from the rigid carrier before applying the upper polyimide layer, and only subsequently to apply this to one apply transparent film, possibly using a transport intermediate substrate.
  • a further protective film which can also serve for mechanical stability, can then be stuck on or in some other way applied to the underside, ie to the back contact layer.
  • the flexible composite can also be connected to a rigid substrate for certain applications.
  • glass substrates in "substrate structure" are used for conventional CIGS cells.
  • two glass panes are required, namely a second glass pane, which serves for the mechanical and chemical protection of the solar cell layers and through which the light is incident.
  • the lower pane of glass is superfluous, so a pane can be saved; such an arrangement makes sense in such a rough or corrosive environment in which light-transparent plastic covers offer insufficient protection.
  • the two methods described above correspond to the "substrate structure” described in the literature, i.e. the glass layer used as a substrate in the conventional rigid cells is not traversed by the light.
  • the light falls through the glass substrate; in the conventional manufacturing sequence, the transparent front contact is therefore deposited on the glass substrate, followed by the window layer and the other layers.
  • this configuration is mainly used for CdTe thin-film cells on glass substrates.
  • the present invention can also be used for the "Superstrat configuration”.
  • Figure 3 shows a layer stack for a "superstrate configuration" prior to detachment from the rigid substrate.
  • the substrate 7, the intermediate layer 6 and the carrier layer 5 are followed here by a transparent front contact 3, a window layer 2, an absorber layer 1 and a back contact 4.
  • the production steps are carried out analogously.
  • a large class of materials can be used as an intermediate layer.
  • Many alkali halides including NaCl, NaF, KCI, are suitable and also slightly water-soluble, the same applies to Ila fluorides such as BaF 2 .
  • Other suitable materials are all those that are sufficiently temperature-resistant and for which there is a solvent that can be used in the environment in question without endangering the functions of the layer structure.
  • the Mo layer on polyimide can be used as a contact layer
  • the NaCl intermediate layer does not prevent adhesion or further production
  • the special one spun polyimide layer withstands the temperatures during manufacture and maintains its necessary mechanical and optical properties.
  • the layers used to form the actual solar cell can also include different classes of materials. These include polycrystalline compound semiconductors such as CuInGaSeS. This notation means Culn y Ga 2 Se w S u , where the parameters y, z, w and u can have any non-negative values, but as is known, for optimal cells the values are limited to specific smaller areas.
  • This family of materials thus comprises compound semiconductor layers from the l-III-V system of the chemical periodic system, in particular they belong (the parameters y, z, w, and u are no longer described below) CulnSe, CuInGaSe, CuGaSe, CulnS, CuInGaSSe, others Materials can also be used.
  • CdTe From the ll-VI family of the chemical periodic system, CdTe as well as other compounds can be used.
  • Compounds from the III-V family of the chemical periodic system such as e.g. GaAs or Group IV semiconductors of the chemical periodic system such as Si or Ge can be used.
  • the structure of the layers can be polycrystalline, microcrystalline, nanocrystalline, micromorphic or amorphous, as the names given in the specialist literature for different structures of thin layers are called. his.
  • the layer sequence thus contains at least one absorber layer and one window layer as well as contact layers, several such layer sequences can be deposited on one another. If two such sequences are used, a "tandem cell" is created, for example, where the light first passes through a solar cell structure with a larger band gap, then a cell structure with a smaller band gap, with this arrangement the yield can be increased. Structures with more than two such layer sequences for the formation of triple cells, or multiple cells with even more such single solar cells are also possible.
  • the partially transparent electrical contact 3 is e.g. from the semiconductor ⁇ dium-tin-oxide (1TO) or ZnO or combinations of such layers, the back contact 4 can consist of a metal or semiconductor or both, as is known.

Abstract

The invention relates to a method for producing a flexible thin-layer solar cell. An intermediate layer (6), known as a sacrificial layer, for example NaCl, is applied to a rigid substrate (7) and a carrier layer (5), for example, a polyimide is deposited thereon. Additional layers are then deposited onto the support layer, for example, Mo (4), a CulnxGaySzSeu absorber (1) with x, y, z, u ≥ 0, a CdS-ZnO window layer (2) and a transparent front contact (3), the structuring of the cells is completed and they are optionally provided with a coating. The solar cell structure is separated from the rigid substrate (7) by the dissolution of the sacrificial layer, whereby the resultant solar cell becomes flexible. The invention relates to flexible solar cells produced by this method which have typical thicknesses of 25 νm with approximately 13 % effectiveness. Large-surface cells can be used for energy production both on earth and in space, whilst small-surface cells can be used for powering electronic goods, such as for example, pocket calculators and smart cards.

Description

Flexible Dünnschicht-Solarzelle Flexible thin-film solar cell
Die Erfindung betrifft ein Verfahren zur Herstellung von Solarzellen sowie eine Solarzelle, die nur aus dünnen Schichten besteht und flexibel ist, gemäss den Patentansprüchen 1 und 8.The invention relates to a method for producing solar cells and a solar cell that consists of only thin layers and is flexible, according to patent claims 1 and 8.
Die bisher bekannten flexiblen Solarzellen wurden direkt auf Metallfolien oder Kunststofffolien produziert. Bei der Verwendung von Kunststofffolien ergaben sich Probleme mit der Kompatibilität zwischen Kunststoff und eigentlicher Solarzellenstruktur wegen der beschränkten Temperaturstabilität von Polymeren. Weiter können wegen dieser beschränkten Temperaturstabilität und inhomogenen Spannungsverteilungen in den Folien unbrauchbare Oberflächen resultieren, sowie, falls die elektrisch aktiven Schichten mit Vakuumabscheidetechniken aufgebracht werden, lokale Fehler in der Oberfläche zu katastrophalen Kurzschlüssen in den fertigen Zellen führen. Bei Verwendung von Metallfolien kann die Rauhigkeit der Folienoberfläche zu Problemen führen (B.M. Basol et al., 25th IEEE Photovol. Spec. Conf. 1988, IEEE Service Center, New York, USA, 1996, S. 157-162; M.A. Contreras et al., "Fabrication methods of Cu(ln,Ga)Se2 polycrystalline materials and devices currently underdevelopment at the national renewable energy laboratory", Proc. 14,h European Photovoltaic Solar Energy Conference, Barcelona, Spain, 1997, H.S. Stephens & Associates, UK, 1997, S. 2354- 2358).The previously known flexible solar cells were produced directly on metal foils or plastic foils. When using plastic films, there were problems with the compatibility between plastic and the actual solar cell structure due to the limited temperature stability of polymers. Furthermore, because of this limited temperature stability and inhomogeneous stress distributions in the films, unusable surfaces can result, and, if the electrically active layers are applied with vacuum deposition techniques, local defects in the surface can lead to catastrophic short circuits in the finished cells. When using metal films, the roughness of the film surface Spec Conf 1996 may cause problems (BM Basol et al, 25 th IEEE Photovol 1988, IEEE Service Center, New York, USA, pp 157-162;.... MA Contreras et al., "Fabrication methods of Cu (ln, Ga) Se 2 polycrystalline materials and devices currently underdevelopment at the national renewable energy laboratory", Proc. 14 , h European Photovoltaic Solar Energy Conference, Barcelona, Spain, 1997, HS Stephens & Associates , UK, 1997, pp. 2354-2358).
Aufgabe der vorliegenden Erfindung ist es, ein Verfahren zur Herstellung von Solarzellen anzugeben, bei dem eine auflösbare Zwischenschicht die Trennung der Solarzelle von einem starren Träger erlaubt.The object of the present invention is to provide a method for producing solar cells, in which a dissolvable intermediate layer allows the solar cell to be separated from a rigid support.
Eine weitere Aufgabe besteht darin, eine Solarzelle vorzuschlagen, die nur aus dünnen Schichten besteht und flexibel ist.Another task is to propose a solar cell that consists only of thin layers and is flexible.
Erfindungsgemäss werden diese Aufgaben mit einem Verfahren gemäss dem Wortlaut des Patentanspruches 1 und einer Solarzelle gemäss dem Wortlaut des Patentan- Spruches 8 gelöst. Die Erfindung wird im Folgenden anhand der Figuren näher erläutert. Es zeigen:According to the invention, these tasks are carried out using a method according to the wording of claim 1 and a solar cell according to the wording of the patent application. Proverbs 8 solved. The invention is explained in more detail below with reference to the figures. Show it:
Fig. 1 Schichtstapel vor dem Ablösen vom starren SubstratFig. 1 layer stack before detaching from the rigid substrate
Fig. 2a Schichtstapel einer zweiten Version vor dem Ablösen vom SubstratFig. 2a layer stack of a second version before detaching from the substrate
Fig. 2b Schichtstapel der zweiten Version im fertigen ZustandFig. 2b layer stack of the second version in the finished state
Fig. 3 Schichtstapel für "Superstratkonfiguration" vor dem Ablösen vom starrenFig. 3 layer stack for "superstrate configuration" before detaching from the rigid
Substratsubstratum
Fig. 1 zeigt einen Schichtstapel vor dem Ablösen vom starren Substrat an Hand dessen das Verfahren beschrieben wird.Fig. 1 shows a layer stack before detachment from the rigid substrate on the basis of which the method is described.
Auf ein starres Substrat 7, das z.B. aus Glas, Keramik oder Metall besteht, wird eine lösliche Zwischenschicht 6 z.B. durch Vakuumverdampfen aufgebracht. Diese lösliche Zwischenschicht, eine sogenannte "Opferschicht", besteht z.B. aus Kochsalz (NaCl) oder BaF2, beide Substanzen sind in Wasser löslich. Als Lösungsmittel wird deshalb zu gegebener Zeit im Herstellungsverfahren Wasser verwendet. Auf das mit der löslichen Zwischenschicht 6 bedeckte Substrat 7 wird nun die Trägerschicht 5 aufgebracht, z.B. eine durch Vakuumabscheidung deponierte Metallschicht, oder eine z.B. aufgeschleuderte Polymerschicht wie z.B. ein kommerziell unter dem Markennamen "Kapton" erhältlicher temperaturresistenter Kunststoff.A soluble intermediate layer 6 is applied, for example by vacuum evaporation, to a rigid substrate 7, which consists, for example, of glass, ceramic or metal. This soluble intermediate layer, a so-called "sacrificial layer", consists for example of table salt (NaCl) or BaF 2 , both substances are soluble in water. Water is therefore used as a solvent in the manufacturing process at the appropriate time. The carrier layer 5 is now applied to the substrate 7 covered with the soluble intermediate layer 6, for example a metal layer deposited by vacuum deposition, or a polymer layer spun on for example, such as a temperature-resistant plastic commercially available under the brand name "Kapton".
Auf die Trägerschicht 5 wird nun eine Folge von Schichten 1 - 4, ein sog. Schichtpaket 10, aufgebracht, das Halbleiter als elektrisch aktive Schichten benutzt, welcher die elektronisch/optisch nötigen Schichten der Solarzelle enthält. Alle Schichten werden während der Herstellung auf einem starren Substrat mit Abscheidetechniken oder auch sonstwie angebracht.A sequence of layers 1 - 4, a so-called layer package 10, is applied to the carrier layer 5 and uses semiconductors as electrically active layers, which contains the electronically / optically necessary layers of the solar cell. All layers are attached to a rigid substrate using deposition techniques or otherwise during manufacture.
Die weiteren Verfahrensschritte werden am Beispiel. einer CulnxGaySez mit x,y,z > 0 (im folgenden CIGS) Solarzelle erläutert; die Beschreibung kann sinngemäss auch für andere Zellentypen wie z.B. CdTe angewendet werden. Für die CIGS Zelle entsprechen die weiteren Schritte im wesentlichen den schon bekannten Verfahren (H.W. Schock and A. Shah, "Status and prospects of photovoltaic thin film technologies", Proc. 14th European Photovoltaic Solar Energy Conference, Barcelona, Spain, 1997, H.S. Stephens & Associates, UK, 1997, S. 2000-2005): Auf die Trägerschicht (5) wird der Rückkontakt (4) abgeschieden, dieser besteht z.B. aus aufgesputtertem Mo. Mit den bekannten Techniken, z.B. durch simultanes oder sequentielles Vakuumabscheiden der in der CIGS-Verbindung enthaltenen Elemente Cu, In, Ga und Se, wird die Absorberschicht (1 ) von wenigen Mikrometern Dicke aufgebracht, hier können die bekannten Techniken angewendet werden, durch z.B. Graduierung der Schichtzusammensetzung eine möglichst hohe Effizienz der fertigen Zelle zu erhalten. Die Temperatur der Probe während der Abscheidung beträgt z.B. 400°C. Bei dieser Temperatur bleibt eine geeignete Kunststoffträgerschicht wie oben beschrieben noch intakt, aber es können trotzdem Zellen mit hohen Effizienzen erhalten werden. Ebenfalls kann bei diesem Schritt etwas Na in geeigneter Form und/oder Verbindung beigegeben werden, da bekannt ist, dass eine Na-Beigabe sich positiv auf die Eigenschaften der fertigen Zelle auswirkt. Auf die Na-Beigabe kann auch verzichtet werden, dies z.B. falls Na bereits durch die Zwischenschicht, sofern diese Na-haltig ist, in der nötigen Menge und Form geliefert wird. Darauf folgt die Deposition der Fensterschicht (2), die z.B. aus ZnO, CdS oder ZnSe besteht, und des Frontkontaktes (3) aus z.B. ITO (Indium-Zinn-Oxid), wobei je nach gewähltem Verfahren weitere Differenzierungen wie z.B. CdS-Abscheidung, oder Dotierung des oberen Teils der Fensterschicht, dass diese gleichzeitig auch als Frontkontaktteil fungiert, sinnvoll sind. Je nach lateraler Grosse der Struktur werden durch z.B. Ritzen oder Photolithographie einzelne Solarzellen strukturiert und allenfalls Antireflexions- und mechanische Schutzschichten (z.B. eine optisch transparente UV-beständige weitere Polymerschicht) aufgebracht.The further process steps are based on the example. a Culn x Ga y Se z with x, y, z> 0 (hereinafter CIGS) solar cell explained; the description can also be used for other cell types such as CdTe. For the CIGS cell, the further steps essentially correspond to the already known methods (HW Schock and A. Shah, "Status and prospects of photovoltaic thin film technologies", Proc. 14 th European Photovoltaic Solar Energy Conference, Barcelona, Spain, 1997, HS Stephens & Associates, UK, 1997, pp. 2000-2005): On the The back contact (4) is deposited on the carrier layer (5), this consists, for example, of sputtered Mo. With the known techniques, for example by simultaneous or sequential vacuum deposition of the elements Cu, In, Ga and Se contained in the CIGS connection, the absorber layer ( 1) applied with a thickness of a few micrometers, here the known techniques can be used to obtain the highest possible efficiency of the finished cell by, for example, grading the layer composition. The temperature of the sample during the deposition is, for example, 400 ° C. At this temperature, a suitable plastic carrier layer as described above remains intact, but cells with high efficiencies can still be obtained. Also in this step, some Na can be added in a suitable form and / or compound, since it is known that adding Na has a positive effect on the properties of the finished cell. It is also possible to dispense with the addition of Na, for example if Na is already supplied in the required quantity and form through the intermediate layer, provided that it contains Na. This is followed by the deposition of the window layer (2), which consists, for example, of ZnO, CdS or ZnSe, and the front contact (3) of, for example, ITO (indium tin oxide), further differentiations such as CdS deposition depending on the method selected, or doping the upper part of the window layer, so that it also functions as a front contact part, makes sense. Depending on the lateral size of the structure, individual solar cells are structured by means of, for example, scratching or photolithography and, if necessary, antireflection and mechanical protective layers (for example an optically transparent UV-resistant additional polymer layer) are applied.
Zu diesem Zeitpunkt der Fertigungssequenz kann nun typischerweise die Zwischenschicht 6 aufgelöst werden, wodurch das Substrat 7 von der Trägerschicht 5 und dem darauf aufgebrachten Schichtpaket 10 getrennt wird. Die Trägerschicht 5 und das Schichtpaket 10 bilden die nun flexible Solarzelle.At this point in the production sequence, the intermediate layer 6 can typically now be dissolved, as a result of which the substrate 7 is separated from the carrier layer 5 and the layer package 10 applied thereon. The carrier layer 5 and the layer package 10 form the now flexible solar cell.
Falls die Zwischenschicht 6 z.B. aus NaCl oder BaF2 besteht, kann Wasser als Lösungsmittel verwendet werden. Für nicht wasserlösliche Zwischenschichten oder auch aus anderen Gründen können andere Lösungsmittel verwendet werden.If the intermediate layer 6 consists, for example, of NaCl or BaF 2 , water can be used as the solvent. Other solvents can be used for non-water-soluble intermediate layers or for other reasons.
Mit diesem erfindungsgemässen Verfahren wurde z.B. eine CIGS-Solarzelle mit 12.8 % Effizienz auf einem Polyimid-Substrat erhalten. Die Schichtdicke des aufgesponne- nen Polyimides betrug ca. 20 μm, die Dicke der für das elektrisch-optische Funktionieren der Solarzelle wesentlichen Schichten weniger als ca. 4 μm. Die ganze Struktur ist flexibel und kann für die bereits beschriebenen Anwendungen eingesetzt werden.With this method according to the invention, for example, a CIGS solar cell with 12.8% efficiency was obtained on a polyimide substrate. The layer thickness of the spun NEN polyimides was approx. 20 μm, the thickness of the layers essential for the electro-optical functioning of the solar cell was less than approx. 4 μm. The whole structure is flexible and can be used for the applications already described.
Diese Prozedur bringt gegenüber bestehenden bekannten Herstellungsverfahren verschiedene Vorteile: Die Herstellung von solchen Schichtstrukturen ist meist einfacher und reproduzierbarer, wenn die Schichten auf starre Träger abgeschieden werden z.B. kann so die für hohe Effizienz der Zellen optimale Abscheidetempertatur besser kontrolliert werden. Weiter ist die dünne Trägerfolie nie alleine den allenfalls mit ihren Eigenschaften schlecht kompatiblen Bedingungen während der Schicht- abscheidungen ausgesetzt, wie z.B. hohe Temperatur und/oder mechanische Spannungen. Weiter können wegen mechanischen Spannungsinhomogenitäten in der Folie Fehler oder Inhomogenitäten in den aufgewachsenen Schichtstrukturen entstehen, die zu katastrophalen elektrischen Kurzschlüssen führen können.This procedure has several advantages over existing known production processes: The production of such layer structures is usually simpler and more reproducible if the layers are deposited on rigid supports, e.g. the deposition temperature that is optimal for high cell efficiency can be better controlled. Furthermore, the thin carrier film is never alone exposed to the conditions that are poorly compatible with its properties during the layer deposition, e.g. high temperature and / or mechanical stresses. Furthermore, due to mechanical stress inhomogeneities in the film, errors or inhomogeneities can arise in the grown layer structures, which can lead to catastrophic electrical short circuits.
Das starre Substrat 7 kann nach dem Ablösen der Schichtstruktur 1 1 wiederverwendet werden.The rigid substrate 7 can be reused after the layer structure 11 has been detached.
Wesentlich an der erfindungsgemässen Solarzelle ist somit, dass sie während eines Grossteils der Herstellungsschritte auf einem starren Substrat entsteht, von diesem anschliessend abgelöst wird und danach jedoch flexibel ist. Sie kann im flexiblen Zustand verwendet werden, aber auch mit einem weiteren festen Substrat wieder verbunden werden.It is therefore essential to the solar cell according to the invention that it is formed on a rigid substrate during a large part of the production steps, is subsequently detached from it and is then flexible, however. It can be used in a flexible state, but can also be reconnected to another solid substrate.
Gute Dünnschichtsolarzellen aus meist polykristallinen Verbindungshalbleitern wie z.B. CulnxGaySez mit x,y,z > 0 (meist mit CIGS abgekürzt) weisen z.Z. bereits sehr hohe Effizienzen auf (12% - 18%), diese können mit denen von konventionellen Solarzellen aus einkristallinem Silizium verglichen werden. Die für die Zellfertigung benötigten Schichten werden meist auf starre Glassubstrate aufgewachsen. Die Dicke der elektrisch wesentlichen Schichten beträgt nur wenige Mikrometer; pro Quadratmeter Solarzellenfläche werden dadurch nur wenige Gramm Material benötigt. Die Herstellungskosten werden bei Massenproduktion wesentlich geringer als die von kristallinen Siliziumzellen ausfallen.Good thin-film solar cells made of mostly polycrystalline compound semiconductors such as Culn x Ga y Se z with x, y, z> 0 (usually abbreviated with CIGS) currently have very high efficiencies (12% - 18%), which can be compared with those of conventional solar cells made of single crystal silicon. The layers required for cell production are mostly grown on rigid glass substrates. The thickness of the electrically essential layers is only a few micrometers; This means that only a few grams of material are required per square meter of solar cell area. The mass production costs are much lower than that of crystalline silicon cells fail.
Für einige Anwendungen ist es vorteilhaft, wenn die gesamte Solarzellenstruktur flexibel bleibt. Dies z.B. um das relativ teure Glassubstrat zu umgehen, die Solarzellen auf gekrümmte Flächen wie Fassaden, Ziegel oder auch gekrümmte Gehäuse von elektronischen Konsumgeräten anzubringen, oder auch nur um Gewicht einzusparen, was besonders für Weltraumanwendungen wichtig ist. Ebenso kann eine grossflächige flexible Struktur zum Transport einfach gerollt werden. Aber auch für kleinflächige Anwendungen sind flexible Solarzellen interessant, z.B. als Energiequelle für Taschenrechner oder "smart cards", welche integrierte elektrische Schaltkreise und auch Displays enthalten können, aber gewissen Flexibilitätsanforderungen genügen müssen.For some applications it is advantageous if the entire solar cell structure remains flexible. This e.g. to bypass the relatively expensive glass substrate, to mount the solar cells on curved surfaces such as facades, bricks or curved housings of electronic consumer devices, or just to save weight, which is particularly important for space applications. A large, flexible structure can also be easily rolled for transport. Flexible solar cells are also interesting for small-area applications, e.g. as an energy source for pocket calculators or "smart cards", which can contain integrated electrical circuits and displays, but must meet certain flexibility requirements.
Fig. 2a und 2b zeigen eine Variation des erfindungsgemässen Herstellungsverfahrens. Fig. 2a zeigt einen zweiten Schichtstapel vor dem Ablösen vom Substrat. Zur Herstellung wird hier wie bereits beschrieben die Zwischenschicht 6 auf das Substrat 7 aufgebracht. Auf die Trägerschicht 5 wird jedoch zum momentanen Herstellungszeitpunkt verzichtet, sondern direkt die weiteren Schichten 1 - 4 der Solarzellenstruktur abgeschieden, also z.B. wie bereits beschrieben Rückkontakt 4 (z.B. Mo) gefolgt von CIGS 1 , welches eventuell mit etwas Na versehen wird, Fensterschicht 2 und Frontkontakt 3. Darauf wird nun das transparente Polymer 5 als Trägerfolie aufgebracht, und die ganze Struktur 11 durch Auflösen der Zwischenschicht 6 vom starren Substrat 7 gelöst. Bei dieser Variante kann die Abscheidetemperatur auch höher als 400°C sein, da ja die Polymerschicht erst nachträglich aufgebracht wird; ebenfalls kann anstelle des Polymers ein Kunststoff mit weniger guter Temperaturbeständigkeit verwendet werden.2a and 2b show a variation of the manufacturing method according to the invention. 2a shows a second layer stack before detachment from the substrate. As already described, the intermediate layer 6 is applied to the substrate 7 for the production. However, the carrier layer 5 is dispensed with at the current time of manufacture, but the other layers 1 - 4 of the solar cell structure are deposited directly, e.g. As already described, back contact 4 (for example Mo) followed by CIGS 1, which may be provided with a little Na, window layer 2 and front contact 3. The transparent polymer 5 is then applied as a carrier film, and the entire structure 11 is removed by dissolving the intermediate layer 6 rigid substrate 7 solved. In this variant, the deposition temperature can also be higher than 400 ° C., since the polymer layer is only applied subsequently; a plastic with less good temperature resistance can also be used instead of the polymer.
Fig. 2b zeigt einen zweiten Schichtstapel im fertigen Zustand. Erkennbar ist die in Fig. 2a beschriebene Schichtsstruktur 11 und eine weitere Schicht 8, z.B. ein Kunststoff, der als Schutzschicht angebracht werden kann.2b shows a second layer stack in the finished state. The layer structure 11 described in FIG. 2a and a further layer 8, e.g. a plastic that can be applied as a protective layer.
Eine weitere Variante ist, das Schichtpaket vor dem Aufbringen der oberen Polyimid- schicht sorgfältig vom starren Träger zu lösen, und erst nachträglich dieses auf eine transparente Folie aufzubringen, möglicherweise unter Verwendung eines Transport- Zwischensubstrates. In beiden Fällen kann danach auf die Unterseite, d.h. auf die Rückkontakt-Schicht, eine weitere Schutzfolie, die auch der mechanischen Stabilität dienen kann, mit geeigneten Mitteln aufgeklebt oder sonstwie aufgebracht werden. Das flexible Komposit kann auch für gewisse Anwendungen wieder mit einem starren Substrat verbunden werden. Beispielsweise werden für konventionelle CIGS Zellen Glassubstrate in "Substrat- Struktur" verwendet. Für die vollständige Kapselung benötigt man somit zwei Glasscheiben, nämlich eine zweite Glasscheibe, die dem mechanischen und chemischen Schutz der Solarzellenschichten dient und durch die das Licht einfällt. Mit der erfindungsgemässen Solarzelle ist die untere Glasscheibe überflüssig, somit kann eine Scheibe eingspart werden, eine solche Anordnung ist in einer derart rauhen oder korrosiven Umgebung sinnvoll, in der lichttransparente Kunststoffabdeckungen ungenügenden Schutz bieten.A further variant is to carefully detach the layer package from the rigid carrier before applying the upper polyimide layer, and only subsequently to apply this to one apply transparent film, possibly using a transport intermediate substrate. In both cases, a further protective film, which can also serve for mechanical stability, can then be stuck on or in some other way applied to the underside, ie to the back contact layer. The flexible composite can also be connected to a rigid substrate for certain applications. For example, glass substrates in "substrate structure" are used for conventional CIGS cells. For complete encapsulation, two glass panes are required, namely a second glass pane, which serves for the mechanical and chemical protection of the solar cell layers and through which the light is incident. With the solar cell according to the invention, the lower pane of glass is superfluous, so a pane can be saved; such an arrangement makes sense in such a rough or corrosive environment in which light-transparent plastic covers offer insufficient protection.
Die beiden oben beschriebenen Verfahren entsprechen der in der Fachliteratur beschriebenen "Substrat-Struktur", d.h. die in den konventionellen starren Zellen verwendete Glasschicht als Substrat wird vom Licht nicht durchquert. In der ebenfalls in der Fachliteratur beschriebenen "Superstrat-Struktur" fällt das Licht durch das Glassubstrat ein; bei der konventionellen Herstellungssequenz wird deshalb auf das Glassubstrat der transparente Frontkontakt abgeschieden, gefolgt von der Fensterschicht und den weiteren Schichten. Z.B. wird bei CdTe-Dünnschichtzellen auf Glassubstraten diese Konfiguration vorwiegend angewendet.The two methods described above correspond to the "substrate structure" described in the literature, i.e. the glass layer used as a substrate in the conventional rigid cells is not traversed by the light. In the "superstrate structure" also described in the specialist literature, the light falls through the glass substrate; in the conventional manufacturing sequence, the transparent front contact is therefore deposited on the glass substrate, followed by the window layer and the other layers. For example, this configuration is mainly used for CdTe thin-film cells on glass substrates.
Die vorliegende Erfindung kann ebenfalls für die "Superstrat-Konfiguration" eingesetzt werden.The present invention can also be used for the "Superstrat configuration".
Fig. 3 zeigt einen Schichtstapel für eine "Superstratkonfiguration" vor dem Ablösen vom starren Substrat. Auf das Substrat 7, die Zwischenschicht 6 und die Trägerschicht 5 folgen hier ein transparenter Frontkontakt 3, eine Fensterschicht 2, eine Absorberschicht 1 und ein Rückkontakt 4. Die Herstellungsschritte erfolgen sinngemäss.Figure 3 shows a layer stack for a "superstrate configuration" prior to detachment from the rigid substrate. The substrate 7, the intermediate layer 6 and the carrier layer 5 are followed here by a transparent front contact 3, a window layer 2, an absorber layer 1 and a back contact 4. The production steps are carried out analogously.
Als Zwischenschicht kommt eine grosse Klasse von Materialien in Frage. Viele Alkali- Halogenide, darunter NaCl, NaF, KCI sind geeignet und zudem leicht wasserlöslich, das selbe gilt für Ila-Fluoride wie BaF2. Weitere geeignete Materialien sind alle jene denkbar, die hinreichend temperaturbeständig sind und für die ein Lösungsmittel existiert, das in der betreffenden Umgebung eingesetzt werden darf, ohne dass die Funktionen des Schichtaufbaus gefährdet werden.A large class of materials can be used as an intermediate layer. Many alkali halides, including NaCl, NaF, KCI, are suitable and also slightly water-soluble, the same applies to Ila fluorides such as BaF 2 . Other suitable materials are all those that are sufficiently temperature-resistant and for which there is a solvent that can be used in the environment in question without endangering the functions of the layer structure.
Spezielle Beachtung muss der Qualität der Schichten und insbesondere deren Haftung und allfälliger Delaminationserscheinungen geschenkt werden. Die in der Erfindung an Beispielen genannten Strukturen haben auch in der praktischen Realisierung gezeigt, dass, in nicht abschliessender Aufzählung, die Mo-Schicht auf Polyimid als Kontaktschicht brauchbar ist, die NaCI-Zwischenschicht die Haftung bzw. die weitere Herstellung nicht verunmöglicht, die spezielle aufgesponnene Polyimidschicht die Temperaturen während der Herstellung übersteht und ihre nötigen mechanischen und optischen Eigenschaften bewahrt.Special attention must be paid to the quality of the layers and in particular their adhesion and any signs of delamination. The structures mentioned in the invention using examples have also shown in practical implementation that, in a non-exhaustive list, the Mo layer on polyimide can be used as a contact layer, the NaCl intermediate layer does not prevent adhesion or further production, the special one spun polyimide layer withstands the temperatures during manufacture and maintains its necessary mechanical and optical properties.
Die für die Formierung der eigentlichen Solarzelle verwendeten Schichten können ebenfalls verschiedene Klassen von Materialien umfassen. Dazu gehören polykristalline Verbindungshalbleiter wie CuInGaSeS. Mit dieser Notation ist CulnyGa2SewSu gemeint, wobei die Parameter y, z, w und u beliebige nicht negative Werte haben können, jedoch wie bekannt, für optimale Zellen die Werte auf spezielle kleinere Bereiche beschränkt sind. Diese Materialfamilie umfasst somit Verbindungshalbleiterschichten aus dem l-lll-V System der chemischen periodischen Systems, insbesondere gehören dazu (die Parameter y, z, w, und u werden im folgenden nicht mehr niedergeschrieben) CulnSe, CuInGaSe, CuGaSe, CulnS, CuInGaSSe, weitere Materialien können ebenfalls verwendet werden.The layers used to form the actual solar cell can also include different classes of materials. These include polycrystalline compound semiconductors such as CuInGaSeS. This notation means Culn y Ga 2 Se w S u , where the parameters y, z, w and u can have any non-negative values, but as is known, for optimal cells the values are limited to specific smaller areas. This family of materials thus comprises compound semiconductor layers from the l-III-V system of the chemical periodic system, in particular they belong (the parameters y, z, w, and u are no longer described below) CulnSe, CuInGaSe, CuGaSe, CulnS, CuInGaSSe, others Materials can also be used.
Aus der ll-VI Familie des chemischen periodischen Systems können CdTe sowie ebenfalls weitere Verbindungen benutzt werden. Ebenfalls können Verbindungen aus der lll-V Familie des chemischen periodischen Systems wie z.B. GaAs oder Gruppe IV Halbleiter des chemischen periodischen Systems wie Si oder Ge verwendet werden.From the ll-VI family of the chemical periodic system, CdTe as well as other compounds can be used. Compounds from the III-V family of the chemical periodic system such as e.g. GaAs or Group IV semiconductors of the chemical periodic system such as Si or Ge can be used.
Alle diese Verbindungen liegen in den erfindungsgemässen Solarzelle meist als polykristalline Schichten vor. Die Struktur der Schichten kann jedoch polykristallin, mikrokristallin, nanokristallin, mikromorph oder amorph, wie die in der Fachliteratur genannten Bezeichnungen für verschiedene Strukturen von dünnen Schichten heissen, sein.All of these compounds are mostly present as polycrystalline layers in the solar cell according to the invention. However, the structure of the layers can be polycrystalline, microcrystalline, nanocrystalline, micromorphic or amorphous, as the names given in the specialist literature for different structures of thin layers are called. his.
Weiter können anstelle einer Schichtabfolge zur Formation einer einzigen Solarzelle, - die Schichtfolge enthält also mindestens eine Absorberschicht und eine Fensterschicht sowie Kontaktschichteπ-, mehrere solche Schichtfolgen aufeinander abgeschieden werden. Werden zwei solche Folgen verwendet, entsteht beispielsweise eine "Tandemzelle", hier passiert das Licht zuerst eine Solarzellenstruktur mit grösserer Bandlücke, danach eine Zellstruktur mit kleinerer Bandlücke, mit dieser Anordnung kann die Ausbeute erhöht werden. Strukturen mit mehr als zwei solcher Schichtfolgen zur Formation von Tripelzellen, oder Mehrfachzellen mit noch mehr solchen Einzelsolarzellen sind ebenfalls möglich.Furthermore, instead of a layer sequence for forming a single solar cell, the layer sequence thus contains at least one absorber layer and one window layer as well as contact layers, several such layer sequences can be deposited on one another. If two such sequences are used, a "tandem cell" is created, for example, where the light first passes through a solar cell structure with a larger band gap, then a cell structure with a smaller band gap, with this arrangement the yield can be increased. Structures with more than two such layer sequences for the formation of triple cells, or multiple cells with even more such single solar cells are also possible.
Der teilweise transparente elektrische Kontakt 3 besteht z.B. aus dem Halbleiter lπdium-Zinn-Oxid (1TO) oder ZnO oder Kombinationen aus solchen Schichten, der Rückkontakt 4 kann aus einem Metall oder Halbleiter oder beidem bestehen, wie bekannt ist. The partially transparent electrical contact 3 is e.g. from the semiconductor πdium-tin-oxide (1TO) or ZnO or combinations of such layers, the back contact 4 can consist of a metal or semiconductor or both, as is known.

Claims

Patentansprüche claims
1. Verfahren zur Herstellung einer Solarzelle, gekennzeichnet dadurch, dass auf einem Substrat (7) eine auflösbare Zwischenschicht (6) aufgebracht wird, dass auf diese Zwischenschicht (6) eine Schichtstruktur (11 ) aufgebracht wird, dass die Zwischenschicht (6) anschliessend aufgelöst wird, wodurch die Schichtstruktur (11 ) vom Substrat (7) getrennt wird und dass dadurch aus der Schichtstruktur (11 ) eine flexible Solarzelle gebildet wird.1. A method for producing a solar cell, characterized in that a dissolvable intermediate layer (6) is applied to a substrate (7), that a layer structure (11) is applied to this intermediate layer (6) such that the intermediate layer (6) is subsequently dissolved , whereby the layer structure (11) is separated from the substrate (7) and in that a flexible solar cell is formed from the layer structure (11).
2. Verfahren nach Anspruch 1 , dadurch gekennzeichnet, dass Schichtstruktur (11 ) aus einer Trägerschicht (5) und einem Schichtpaket (10) gebildet wird.2. The method according to claim 1, characterized in that the layer structure (11) is formed from a carrier layer (5) and a layer package (10).
3. Verfahren nach Anspruch 1 , dadurch gekennzeichnet, dass Schichtstruktur (11 ) aus einem Schichtpaket (10) gebildet wird und dass nach dem Auflösen der Zwischenschicht (6) das Schichtpaket (10) mit einer Trägerschicht (5) versehen wird.3. The method according to claim 1, characterized in that the layer structure (11) is formed from a layer package (10) and that after the dissolution of the intermediate layer (6) the layer package (10) is provided with a carrier layer (5).
4. Verfahren nach einem der Ansprüche 1 - 3, dadurch gekennzeichnet, dass nach dem Auflösen der Zwischenschicht (6) das Substrat (7) weiterverwendet wird.4. The method according to any one of claims 1-3, characterized in that after the dissolution of the intermediate layer (6), the substrate (7) is used further.
5. Verfahren nach einem der Ansprüche 1 - 4, dadurch gekennzeichnet, dass die Zwischenschicht (6) aus einem Material der Gruppe der Alkali-Halogenide wie NaCl, KCI, NaF oder der Gruppe Ila-Fluoride wie BaF2 besteht.5. The method according to any one of claims 1-4, characterized in that the intermediate layer (6) consists of a material from the group of alkali halides such as NaCl, KCI, NaF or the group Ila fluorides such as BaF 2 .
6. Verfahren nach einem der Ansprüche 1 - 5, dadurch gekennzeichnet, dass mehrere Kombinationen von Schichtpaketen (10) mit oder ohne Trennschichten zwischen den Schichtpaketen übereinander abgeschieden werden.6. The method according to any one of claims 1-5, characterized in that several combinations of layer packages (10) with or without separating layers between the layer packages are deposited one above the other.
7. Anwendung des Verfahrens nach einem der Ansprüche 1 - 6 zur Energieerzeugung auf der Erde und im Weltraum und für Konsumgüter, wie Taschenrechner und "smart cards". 7. Application of the method according to any one of claims 1-6 for energy generation on earth and in space and for consumer goods, such as calculators and "smart cards".
8. Solarzelle nach einem der Ansprüche 1 - 7, bestehend aus mindestens einer Absorberschicht (1 ) eines Halbleiters, aus mindestens einer Fensterschicht (2) eines Halbleiters zur Einkoppelung des Lichtes, aus mindestens eines mindestens teilweise transparenten Frontkontaktes (3), und mindestens eines Rückkontaktes (4), gekennzeichnet dadurch, dass die Solarzelle mindestens eine dünne Trägerschicht (5) aufweist und dass diese an den Rückkontakt (4) angrenzt oder sich auf dem Frontkontakt (3) befindet.8. Solar cell according to one of claims 1-7, consisting of at least one absorber layer (1) of a semiconductor, at least one window layer (2) of a semiconductor for coupling the light, at least one at least partially transparent front contact (3), and at least one Back contact (4), characterized in that the solar cell has at least one thin carrier layer (5) and that this adjoins the back contact (4) or is located on the front contact (3).
9. Solarzelle nach Anspruch 8, gekennzeichnet dadurch, dass die Trägerschicht (5) aus einem Kunststoff, vorzugweise aus Polyimid, oder aus Metall oder Keramik besteht, und dass sie eine Dicke von 1 - 100 μm, vorzugsweise 20 μm aufweist.9. Solar cell according to claim 8, characterized in that the carrier layer (5) consists of a plastic, preferably of polyimide, or of metal or ceramic, and that it has a thickness of 1 - 100 microns, preferably 20 microns.
10. Solarzelle nach Anspruch 8 oder 9, gekennzeichnet dadurch, dass die Absorberschicht (1 ) aus einem Material der Gruppe der l-lll-V Verbindungen des periodischen Systems besteht, wie CulnxSey, CulnxGaySez, CulnxGaySzSeu mit x,y,z,u > 0, oder der ll-VI Verbindungen des periodischen Systems CdTe, oder lll-V Verbindungen des periodischen Systems wie mit 0 < x,y,u,w < 1 oder der Gruppe IV-Elemente des periodischen Systems wie Si oder Ge.10. Solar cell according to claim 8 or 9, characterized in that the absorber layer (1) consists of a material from the group of III-III compounds of the periodic system, such as Culn x Se y , Culn x Ga y Se z , Culn x Ga y S z Se u with x, y, z, u> 0, or the ll-VI connections of the periodic system CdTe, or lll-V connections of the periodic system as with 0 <x, y, u, w <1 or the group IV elements of the periodic system such as Si or Ge.
11. Solarzelle nach einem der Ansprüche 8 - 10, gekennzeichnet dadurch, dass die Fensterschicht (2) aus einem Halbleitermaterial mit mindestens gleichgrosser Bandlücke wie die der Absorberschicht (1 ) besteht, wobei die Struktur der Schichten polykristallin oder amorph ist.11. Solar cell according to one of claims 8-10, characterized in that the window layer (2) consists of a semiconductor material with at least the same band gap as that of the absorber layer (1), the structure of the layers being polycrystalline or amorphous.
12. Solarzelle nach einem der Ansprüche 8 - 11 , gekennzeichnet dadurch, dass die Absorberschicht (1 ) aus CulnxGaySzSeu mit x,y,z,u > 0 besteht und die Fensterschicht (2) mindestens ein Material aus der Gruppe dotiertem oder undotiertem ZnO, InSnO (ITO), CdS und ZnSe enthält.12. Solar cell according to one of claims 8 - 11, characterized in that the absorber layer (1) consists of Culn x Ga y S z Se u with x, y, z, u> 0 and the window layer (2) from at least one material the group contains doped or undoped ZnO, InSnO (ITO), CdS and ZnSe.
13. Solarzelle nach einem der Ansprüche 8 - 12, gekennzeichnet dadurch, dass die flexible Solarzellenstruktur je nach Verwendungszweck ein festes Trägermaterial wie Glas, Metall oder Keramik aufweist. 13. Solar cell according to one of claims 8 - 12, characterized in that the flexible solar cell structure has a solid support material such as glass, metal or ceramic, depending on the intended use.
EP00940105A 1999-07-13 2000-07-12 Flexible thin-layer solar cell Withdrawn EP1200995A1 (en)

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