WO2017220444A1 - Procédé d'interconnexion de cellules solaires - Google Patents

Procédé d'interconnexion de cellules solaires Download PDF

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Publication number
WO2017220444A1
WO2017220444A1 PCT/EP2017/064799 EP2017064799W WO2017220444A1 WO 2017220444 A1 WO2017220444 A1 WO 2017220444A1 EP 2017064799 W EP2017064799 W EP 2017064799W WO 2017220444 A1 WO2017220444 A1 WO 2017220444A1
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WIPO (PCT)
Prior art keywords
back contact
zinc
aluminum back
solar cell
metallic
Prior art date
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PCT/EP2017/064799
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German (de)
English (en)
Inventor
Henning Nagel
Jonas Bartsch
Mathias Kamp
Markus Glatthaar
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Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e. V.
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Application filed by Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e. V. filed Critical Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e. V.
Priority to EP17730486.2A priority Critical patent/EP3472869A1/fr
Priority to CN201780037485.3A priority patent/CN109463009A/zh
Publication of WO2017220444A1 publication Critical patent/WO2017220444A1/fr

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/02—Details
    • H01L31/0224—Electrodes
    • H01L31/022408—Electrodes for devices characterised by at least one potential jump barrier or surface barrier
    • H01L31/022425—Electrodes for devices characterised by at least one potential jump barrier or surface barrier for solar cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/02—Details
    • H01L31/0224—Electrodes
    • H01L31/022408—Electrodes for devices characterised by at least one potential jump barrier or surface barrier
    • H01L31/022425—Electrodes for devices characterised by at least one potential jump barrier or surface barrier for solar cells
    • H01L31/022441—Electrode arrangements specially adapted for back-contact solar cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/04—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices
    • H01L31/042—PV modules or arrays of single PV cells
    • H01L31/05—Electrical interconnection means between PV cells inside the PV module, e.g. series connection of PV cells
    • H01L31/0504—Electrical interconnection means between PV cells inside the PV module, e.g. series connection of PV cells specially adapted for series or parallel connection of solar cells in a module
    • H01L31/0512—Electrical interconnection means between PV cells inside the PV module, e.g. series connection of PV cells specially adapted for series or parallel connection of solar cells in a module made of a particular material or composition of materials
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/04—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices
    • H01L31/042—PV modules or arrays of single PV cells
    • H01L31/05—Electrical interconnection means between PV cells inside the PV module, e.g. series connection of PV cells
    • H01L31/0504—Electrical interconnection means between PV cells inside the PV module, e.g. series connection of PV cells specially adapted for series or parallel connection of solar cells in a module
    • H01L31/0516—Electrical interconnection means between PV cells inside the PV module, e.g. series connection of PV cells specially adapted for series or parallel connection of solar cells in a module specially adapted for interconnection of back-contact solar cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/04—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices
    • H01L31/06—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by potential barriers
    • H01L31/068—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by potential barriers the potential barriers being only of the PN homojunction type, e.g. bulk silicon PN homojunction solar cells or thin film polycrystalline silicon PN homojunction solar cells
    • 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
    • Y02E10/547—Monocrystalline silicon PV cells

Definitions

  • Solar cells typically include a semiconductor device comprising a first semiconductor material, a second semiconductor material, and a transition region (e.g., also referred to as a pn junction) between these two semiconductor materials.
  • a semiconductor device comprising a first semiconductor material, a second semiconductor material, and a transition region (e.g., also referred to as a pn junction) between these two semiconductor materials.
  • a transition region e.g., also referred to as a pn junction
  • Semiconductor materials may be doped. Via a first metal contact, which is electrically connected to the first semiconductor material, and a second metal contact, which is electrically connected to the second semiconductor material, the generated voltage can be tapped.
  • One of the metal contacts may be mounted on the front or front side of the solar cell (often referred to as a front contact), while the other metal contact is located on the back of the unit cell (often referred to as the back contact).
  • solar cells are also known in which the metal contacts are present exclusively on the back of the solar cell, e.g. in the form of a comb-like interdigital structure. In such exclusively
  • Aluminum is a metal which is very well suited for the backside metallization of solar cells, in particular of crystalline Si solar cells. It is characterized by a high electrical conductivity, a low price and a large one Light reflection off. For these reasons, most industrially manufactured silicon solar cells have an electrical back contact made of aluminum, which is frequently applied by screen printing. It is sintered at temperatures above 800 ° C to allow good cohesion of the aluminum particle matrix
  • BSF back-surface field
  • the electrical quality of the aluminum-doped BSF is insufficient for high-efficiency solar cells.
  • Boron-doped BSFs achieve lower saturation current densities for /? -Type solar cells. For «-type solar cells even a // - doping is necessary.
  • contact with screen-printed aluminum would lead to severe damage to the BSF or even to overcompensation due to the unavoidable alloy formation.
  • Another disadvantage of screen-printed aluminum is that the high sintering temperatures do not allow optimum surface passivation of the dielectric, which also achieves the achievement of
  • Al rear-side contacts are applied to today's high-efficiency solar cells by means of physical vapor deposition (PVD). They have the additional advantage of better light reflection compared to screen-printed AI, because they are compact layers.
  • PVD physical vapor deposition
  • Connector can not be conventionally soldered to the aluminum due to a very fast on the aluminum forming AI2O3- layer.
  • solderable metals are applied by means of thermal evaporation or sputtering.
  • the coating systems TiN / Ti / Ag, NiV / Ag and NiSi / Ag have shown high connector adhesion forces. This describe J. Kumm et al, "Development of temperature-stable, solderable PVD rear metaüization for industrial silicone solar cells," Proceedings of the 28 th European Photovoltaic Solar Energy Conference, 2013; Jung et al., "Al / Ni: V / Ag metal stacks as rear side metallization for cryogenic silicon solar cells", Progress in Photovoltaics, p. 876, 2012, and V. Jung et al., "Ni: Si as barrier material for solderable PVD
  • An object of the present invention is the interconnection of solar cells via a method with which solar cell connectors can be fastened on the metal contacts of the solar cells as simply and efficiently as possible. Another object is to provide interconnected solar cells having high adhesion between metal contact of the solar cell and solar cell connectors.
  • zinc-coated aluminum a very represents an effective substrate for attachment of the metallic connector (such as a copper ribbon). It can be realized high adhesion of the connector on the metallic contact of the solar cell.
  • the application of further metallic layers (eg by electroplating) on the galvanized aluminum before soldering the connector is eliminated. Rather, the Zn-coated aluminum is already a suitable substrate for soldering or gluing the connector.
  • a solar cell is known to contain a
  • Semiconductor device comprising a first semiconductor material, a second
  • semiconductor material and a lying between these two semiconductor materials transition region for example, also referred to as pn junction.
  • One of the semiconductor materials or even each of the semiconductor materials may be doped.
  • the solar cell is preferably a silicon solar cell, such as a monocrystalline silicon solar cell, a polycrystalline silicon solar cell or an amorphous silicon solar cell.
  • the method according to the invention is also suitable for the interconnection of other solar cells, e.g. III-V semiconductor solar cells, II-VI semiconductor solar cells, I-III-VI semiconductor solar cells or organic solar cells.
  • the interconnection of solar cells are contacted with each other via a metallic connector.
  • the metallic connector is in each case attached to one of the metal contacts of the adjacent solar cells.
  • the interconnection can be a Series connection or a parallel circuit act. A combination of series and parallel connection of the solar cells is possible.
  • the physical vapor deposition of the metallic aluminum or aluminum alloy is carried out by an evaporation method (e.g., thermal evaporation, electron beam evaporation)
  • an evaporation method e.g., thermal evaporation, electron beam evaporation
  • Ion plating or ICB (ionized cluster-beam) deposition By thermal treatment of a target made of aluminum or aluminum
  • the target material evaporates and separates on the
  • the semiconductor device is positioned to deposit the aluminum or aluminum alloy on the backside thereof.
  • the back side of the semiconductor device is the side which in use opposes the solar cell to the irradiated side (i.e., the front side), which is the side facing away from the light.
  • the present on the back of a solar cell metal contact is also referred to as back contact.
  • the person skilled in the art is fundamentally aware of how the semiconductor component is must be configured (ie type of semiconductor materials to be used, doping, etc.).
  • Front contact can be configured in a known manner.
  • the front contact may have a grid structure.
  • the front contact may be made of silver or a silver alloy, for example.
  • the front contact can already be on the
  • step (a) the aluminum back contact is attached.
  • the front contact may be applied to the semiconductor device simultaneously with the aluminum back contact or after attaching the aluminum back contact.
  • the solar cell it is alternatively also possible for the solar cell to be exclusively back contacted, ie only on the rear side of the solar cell
  • Semiconductor component metallic contacts are present. This can be realized, for example, by subjecting the aluminum or the aluminum alloy to an etching treatment after the deposition, so as to separate two
  • Aluminum back contacts e.g., in the form of a comb-like interdigital structure.
  • the purity of the deposited metallic aluminum can vary over a wide range, provided that the electrical conductivity and / or mechanical properties are not adversely affected. For example, this contains
  • Aluminum further metallic elements in a total proportion of less than 1% by weight, more preferably less than 0.1% by weight or less than 0.01% by weight. If an aluminum alloy is used as the metallic back contact for the solar cell, then this preferably has a proportion of aluminum of at least 80% by weight, more preferably at least 90% by weight. Suitable metallic elements that can be alloyed with the aluminum are known to those skilled in the art.
  • the thickness of the aluminum back contact fabricated in step (a) can be varied over a wide range.
  • the aluminum back contact has a thickness in the range of 0.3 ⁇ to 7 ⁇ , more preferably in the range of 2 ⁇ to 4.5 ⁇ .
  • the aluminum back contact before the zinc deposition step (b) may optionally be subjected to a suitable pretreatment (such as removal of possible organic oxides)
  • step (b) may be performed immediately after step (a).
  • step (b) of the process of the present invention the aluminum back contact is treated with an alkaline, aqueous medium containing Zn 2+ (ie, zinc in the +11 oxidation state) in dissolved form, so as to react on the aluminum -Back contact deposits metallic zinc to form a Zn-coated aluminum back contact.
  • Zn 2+ ie, zinc in the +11 oxidation state
  • the aqueous medium to which the aluminum back contact is treated has a relatively high concentration of Zn 2+ .
  • the Zn 2+ concentration in the alkaline aqueous medium is at least 1.5% by weight, more preferably at least 2.0% by weight, even more preferably at least 3.0% or even at least 4.0% by weight.
  • the aqueous medium contains Zn 2+ in a concentration of 1.5% by weight to 12.0% by weight, more preferably 2.0% by weight to 10.0% by weight, more preferably 3.0% by weight to 8, 0 wt% or 4.0 wt% to 8.0 wt%.
  • Zn 2+ is in dissolved form, for example, by dissolving a Zn 2+ compound in relatively alkaline conditions (ie, relatively high pH) in the aqueous medium.
  • Zn 2+ may be present under alkaline conditions, for example, as a zincate (eg, [Zn (II) (OH) 4] 2 " or similar Zn 2+ -containing species) in the aqueous medium.
  • a suitable pH of the alkaline, aqueous medium is, for example,> 10, more preferably> 13.
  • the alkaline aqueous medium may contain further transition metal cations, preferably iron cations, nickel cations or copper cations or a combination of at least two of these cations.
  • the alkaline aqueous medium still contains Fe cations in a concentration of at least 0.0003% by weight, more preferably at least 0.001% by weight, e.g. in the range of 0.0003-30% by weight or 0.0003-0.1% by weight.
  • the alkaline, aqueous medium contains nickel cations, these may be present, for example, in a concentration of 0.1-5% by weight, more preferably 0.5-3% by weight.
  • the alkaline, aqueous medium contains copper cations, these may be present, for example, in a concentration of 0.01-1% by weight, more preferably 0.05-0.5% by weight.
  • the deposition of the metallic zinc from the Zn 2+ -containing aqueous medium to the aluminum back contact takes place without current.
  • electroless metal deposition is understood to be a coating process that runs without the use of an external power source.
  • Electroless deposition of metallic zinc onto an aluminum substrate using an alkaline Zn 2+ solution is known per se to the person skilled in the art (for example as a zincate method). In this process, first on the
  • the deposited on the aluminum back contact Zn layer has a thickness in the range of 0.1 ⁇ to 5 ⁇ , more preferably 0.3 ⁇ to 2.5 ⁇ on.
  • the thickness of the aluminum back contact during the Zn deposition step (b) is reduced by a value approximately equal to the thickness of the deposited metallic Zn layer.
  • the duration of the treatment of the aluminum back contact with the alkaline, aqueous Zn 2+ -containing medium in step (b) is, for example, 15 seconds to 250 seconds.
  • the zinc deposition step (b) is preferably carried out at a temperature in the range of 5-60 ° C, more preferably 5-45 ° C.
  • the back side of the semiconductor device is held in a substantially horizontal position during the zinc deposition step (b), with the aluminum back contact facing down and being contacted with the Zn 2+ -containing aqueous medium.
  • substantially horizontal means a maximum deviation of 20%, more preferably a maximum of 10% from an ideal horizontal position.
  • the alkaline, aqueous Zn 2+ -containing medium and the downwardly facing aluminum back contact of the horizontally positioned semiconductor component can be brought into contact via conventional methods such as dipping, rinsing or spraying.
  • the Zn 2+ is - containing medium in an open-topped container and the semiconductor device is moved over these containers (for example by the semiconductor device is mounted on rollers) and the Zn 2+ -containing medium through nozzles against the
  • the semiconductor component mounted on rollers is guided over the Zn 2+ -containing medium, wherein the rollers at least partially immerse themselves in the Zn 2+ -containing medium and by their rotation bring the aqueous medium into contact with the aluminum back contact act ,
  • This horizontal positioning of the semiconductor device with downwardly facing aluminum back contact during step (b) has a positive
  • the semiconductor component Influences the microstructure of the metallic zinc layer deposited on the aluminum back contact and further improves the adhesion between the aluminum back contact and the solar cell connector mounted thereon.
  • the semiconductor component it is also possible for the semiconductor component to be positioned substantially vertically during step (b). In principle, however, every other is
  • step (b) Positioning (e.g., in oblique orientation) of the semiconductor device in step (b) possible.
  • the aluminum back contact is moved relative to the Zn 2+ -containing medium during the zinc deposition step (b).
  • the relative speed between the aluminum back contact and the aqueous Zn 2+ -containing medium is preferably at least 0.1 m / min, more preferably at least 0.2 m / min.
  • This relative movement can be realized, for example, by moving the aluminum back contact over a quiescent Zn 2+ -containing medium or by flowing a flowing Zn 2+ -containing medium via a resting aluminum back contact or by a combination of these two variants.
  • the flow velocity of the Zn 2+ -containing medium (and thus the relative velocity to the (moving or stationary)
  • Aluminum back contact can be adjusted eg via the pump output.
  • a further improvement of the adhesion force between the aluminum back contact and the solar cell connector mounted thereon can be achieved.
  • step (b) zinc crystallites with a diameter of more than 5.0 ⁇ in a number density of> 800 per mm 2 , more preferably> 1000 per mm 2 , more preferably 1000-4000 per mm 2 are present; and / or wherein at least 1.5%, more preferably at least 2.0%, more preferably 2.0-8.0% of the surface of the closed zinc layer is occupied by zinc crystallites with a diameter of more than 5.0 ⁇ .
  • the metallic zinc layer preferably contains significantly smaller zinc crystallites with a
  • the zinc crystallites with a diameter of more than 5.0 ⁇ and the zinc crystallites with a diameter of less than 1.0 ⁇ jointly occupy at least 90%>, more preferably at least 95%> of the surface of the closed zinc layer.
  • the particle size distribution of the zinc crystallites on the surface of the closed zinc layer may be, for example, bimodal. Such a closed metallic zinc layer with a relatively high
  • step (b) On the basis of the process parameters of step (b) described above, such a metallic zinc layer can be produced selectively.
  • step (b) Preferably, during the zinc deposition in step (b), only the aluminum back contact is contacted with the Zn 2+ -containing medium. This will avoided that other areas of the solar cell are chemically attacked by the aqueous medium.
  • the Zn-coated aluminum back contact obtained in step (b) is rinsed at least once with a rinsing liquid before step (c).
  • a rinsing liquid with pH> 8.5, more preferably pH> 13, is preferably used.
  • the Zn-coated aluminum back contact is subjected to drying prior to step (c), for example by suitable thermal treatment.
  • step (b) may be repeated at least once before step (c) is performed. However, considering the process efficiency, it is preferable to perform step (b) only once.
  • step (c) the attachment of the metallic connector on the Zn-coated aluminum back contact takes place, in particular by soldering. Therefore, in an optional
  • step (c) a solder material are applied to the deposited in step (b) metallic Zn layer.
  • the brazing material is preferably applied to the Zn layer at least in those areas in which the metallic connector is to be fastened. Suitable solder materials are known in the art and will be described in more detail below.
  • step (c) of the method according to the invention the Zn-coated aluminum back contact is connected by a metallic connector to a metal contact of a second solar cell, wherein the metallic connector is attached to the Zn-coated aluminum back contact of the first solar cell by soldering or gluing.
  • Metallic connectors for interconnecting solar cells are well known to those skilled in the art. Suitable metallic connectors are commercially available or can be prepared by conventional methods.
  • the metallic connector is preferably ribbon or wire, but other forms are also possible in principle.
  • the metallic connector is band-shaped.
  • the metal connector may be coated with a solder material such as tin or a tin alloy. This eliminates the separate feeding of the solder material.
  • solder material suitable tin alloys are well known. These contain as alloying elements, for example, lead, silver and / or bismuth.
  • the solder material (preferably a tin alloy) preferably has one
  • the metallic connector is a copper tape, more preferably a tin or tin alloy coated copper tape.
  • Such "tin-plated” copper strips are commercially available.
  • the soldering is preferably carried out at a temperature of less than 450 ° C. This is commonly referred to as soft soldering. More preferably, the soldering temperature is in the range of 175 ° C to 400 ° C or 175 ° C to 300 ° C.
  • the soldering process uses conventional, preferably non-corrosive fluxes The flux can be applied to the metallic material coated with the solder material (eg the tinned copper strips) and / or to the zinc layer deposited in process step (b).
  • an electrically conductive adhesive is preferably used.
  • Such adhesives are known to those skilled in the art and commercially available.
  • the second solar cell which is connected to the first solar cell, is also a solar cell on which according to the above
  • the present invention relates to a solar cell string comprising at least two solar cells interconnected by a metallic connector, wherein at least one solar cell has a metallic zinc coated aluminum back contact and the metallic connector is directly soldered or bonded to this Zn coated aluminum back contact.
  • each of the solar cells has an aluminum back contact coated with metallic zinc, and each of these Zn-coated aluminum back contacts has a respective metal connector directly soldered or bonded thereto.
  • the solar cell string is obtainable by the method described above.
  • at least one of the solar cells interconnected in the solar cell string preferably has a Zn-coated aluminum back contact, which was produced by the method described above.
  • all solar cells connected in the solar cell string have a Zn-coated aluminum back contact produced in this way.
  • the Zn-coated aluminum back contact of the solar cell has one or more areas in which a closed layer of metallic zinc is present, wherein also on the surface of the closed zinc layer zinc crystallites with a diameter of more than 5.0 ⁇ in a Number density of> 800 per mm 2 , more preferably> 1000 per mm 2 , more preferably 1000-4000 per mm 2 ; and / or wherein at least 1.5%, more preferably at least 2.0%, more preferably 2.0-8.0%) of the surface of the closed zinc layer is occupied by zinc crystallites with a diameter of more than 5.0 ⁇ m.
  • the metallic zinc layer preferably contains significantly smaller zinc crystallites with a
  • Diameter of less than 1.0 ⁇ wherein preferably the majority of the surface (eg more than 50%> or even more than 60%>) of the closed zinc layer occupied by these smaller zinc crystallites with a diameter of less than 1.0 ⁇ is.
  • the zinc crystallites with a diameter of more than 5.0 ⁇ and the zinc crystallites with a diameter of less than 1.0 ⁇ jointly occupy at least 90%>, more preferably at least 95%> of the surface of the closed zinc layer.
  • the particle size distribution of the zinc crystallites on the surface of the closed zinc layer may be, for example, bimodal.
  • Crystallite diameter, number density of Zn crystallites with a diameter of more than 5.0 ⁇ or less than 1.0 ⁇ on the surface of the Zn layer and the respective relative surface coverage by these Zn crystallites are about Scanning electron micrographs (SEM images) of the Zn layer (in plan view) and the evaluation of the images by suitable
  • the diameter of a crystallite is the diameter of a circle that corresponds in its area to the projection surface of the crystallite in the SEM image.
  • Zinc-coated aluminum back contact having such a structure, ie a closed layer of metallic zinc, wherein zinc crystallites with a diameter of more than 5 ⁇ in a number density of> 800 per mm 2 , more preferably> 1000 per mm 2 , more preferably 1000-4000 per mm 2 are present on the surface of the zinc layer; and / or wherein at least 1.5%, more preferably at least 2.0%, more preferably 2.0-8.0%) of the surface of the zinc layer is occupied by zinc crystallites having a diameter of more than 5 ⁇ m.
  • these high density, large area zinc crystallite areas may be where no metal connector has been attached.
  • the semiconductor device of a solar cell On the back of a 180 ⁇ thick, / ⁇ - doped silicon wafer (hereinafter called the semiconductor device of a solar cell) 3 ⁇ aluminum with a purity of> 95% over a large area thermally evaporated. Thus, an aluminum back contact is obtained. Between aluminum layer and solar cell is a dielectric layer stack of Al2O3 and Si x N y . This has been locally opened at several points by means of laser to produce the electrical contact of the deposited aluminum to the silicon of the semiconductor device. On the
  • Front side of the semiconductor device of the solar cell is a thermally phosphorus diffused n + -doped emitter.
  • On the emitter is a thin Si x N y antireflective layer and a screen-printed, silver-containing Metallgrid, which acts as a front contact of the semiconductor device.
  • the aluminum back contact is treated with an aqueous solution containing 4
  • Weight percent zinc ions 15 weight percent NaOH and 0.001 weight percent iron ions at room temperature for 90 s. This is the
  • FIG. 1 shows a SEM image of the surface of the Zn-coated aluminum back contact.
  • the photograph shows a closed metallic zinc layer which has a relatively high proportion of large Zn crystallites with a diameter of at least 5 ⁇ m.
  • Zinc crystallites with a diameter of more than 5 ⁇ m are present in a number density of 1736 per mm 2 .
  • 3.5% of the surface of the metallic zinc layer are coated with Zn crystallites with a diameter of at least 5 ⁇ .
  • a tinned copper tape with a copper thickness of 130 ⁇ ⁇ a double-sided Sn / Pb / Ag support of 15 ⁇ was soldered at 245 ° C for 5 s by means of a resistance-heated contact solder on the zinc-coated aluminum back contact.
  • the tinned copper strips were previously with a no-clean flux from Kester with the
  • the protruding end of the connector is soldered in a subsequent soldering in a known manner to the front of another solar cell. This gives a solar cell string in which the solar cells are connected in series.
  • Solar cell strings are laminated with glass, ethylene vinyl acetate and polymer backsheet into a module.

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Abstract

La présente invention concerne un procédé d'interconnexion de cellules solaires. Selon l'invention : (a) de l'aluminium ou un alliage d'aluminium est déposé par dépôt physique en phase vapeur sur le côté arrière d'un composant semi-conducteur d'une première cellule solaire pour former un contact arrière d'aluminium ; (b) le contact arrière d'aluminium est traité avec une substance aqueuse alcaline qui contient Zn2+ de sorte que du zinc métallique se dépose sur le contact arrière d'aluminium pour former un contact arrière d'aluminium revêtu de zinc ; (c) le contact arrière d'aluminium revêtu de zinc est relié par un élément de liaison métallique à un contact métallique d'une deuxième cellule solaire, l'élément de liaison métallique étant fixé sur le contact arrière d'aluminium revêtu de zinc par soudage ou collage.
PCT/EP2017/064799 2016-06-19 2017-06-16 Procédé d'interconnexion de cellules solaires WO2017220444A1 (fr)

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EP17730486.2A EP3472869A1 (fr) 2016-06-19 2017-06-16 Procédé d'interconnexion de cellules solaires
CN201780037485.3A CN109463009A (zh) 2016-06-19 2017-06-16 用于连接太阳能电池的方法

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DE102016210908.1A DE102016210908A1 (de) 2016-06-19 2016-06-19 Verfahren zur Verschaltung von Solarzellen
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CN109463009A (zh) 2019-03-12
DE102016210908A1 (de) 2017-12-21
EP3472869A1 (fr) 2019-04-24

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