EP3472870A1 - Procédé d'interconnexion de cellules solaires qui présentent une feuille d'aluminium en tant que contact arrière - Google Patents

Procédé d'interconnexion de cellules solaires qui présentent une feuille d'aluminium en tant que contact arrière

Info

Publication number
EP3472870A1
EP3472870A1 EP17735407.3A EP17735407A EP3472870A1 EP 3472870 A1 EP3472870 A1 EP 3472870A1 EP 17735407 A EP17735407 A EP 17735407A EP 3472870 A1 EP3472870 A1 EP 3472870A1
Authority
EP
European Patent Office
Prior art keywords
zinc
aluminum foil
metallic
coated aluminum
solar cell
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Withdrawn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
EP17735407.3A
Other languages
German (de)
English (en)
Inventor
Henning Nagel
Jonas Bartsch
Mathias Kamp
Markus Glatthaar
Martin Graf
Jan Nekarda
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.)
Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV
Original Assignee
Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV
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 Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV filed Critical Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV
Publication of EP3472870A1 publication Critical patent/EP3472870A1/fr
Withdrawn legal-status Critical Current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
    • H01L31/02—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
    • 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

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 voltage generated in a solar cell 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
  • back contact The electrical contact on the back of solar cells such as silicon solar cells (back contact) is often a large area by screen printing of Applied aluminum paste.
  • solder pads made of silver paste are additionally printed on the back, are soldered to the connector.
  • the overhanging other end of the connector is soldered to the front of adjacent solar cells, resulting in a series connection of solar cells to so-called solar cell strings.
  • a less expensive back contact can be made by positioning a metal foil over the back of the solar cell and then by means of
  • Silicon solar cell in these areas connects.
  • a cavity filled with a filling medium forms in the adjacent areas between metal foil and solar cell, in which the
  • Metal foil was not melted, which brings advantageous optical properties for the solar cell. As a metal foil is advantageous manner
  • 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.
  • Improvement of the adhesive power should preferably not be at the expense of other properties such as the efficiency of the solar cell.
  • an aluminum foil is unilaterally treated with an alkaline, aqueous medium containing Zn 2+ , so that on the treated side of the
  • Aluminum foil deposits metallic zinc to form a one-sided Zn-coated aluminum foil
  • the unilaterally Zn-coated aluminum foil is applied over its untreated side on the back side of a semiconductor component of a first solar cell and locally heated with laser radiation, so that the aluminum foil connects to the back side of the semiconductor component and a Zn-coated aluminum - back contact is obtained
  • Connector is connected to a metal contact of a second solar cell, wherein the metallic connector is attached to the Zn-coated aluminum back contact by soldering or gluing.
  • the zinc-coated aluminum obtained via a wet-chemical process is a very effective substrate for the 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 on the galvanized aluminum (eg by electroplating) before soldering the connector is eliminated. Rather, the Zn-coated aluminum already represents a suitable substrate for soldering or Au & life of the connector.
  • the application of the metallic connector by means of conventional
  • Deterioration of the semiconductor material properties does not occur with the process of the present invention.
  • a possible reason for this could be that the deposited zinc evaporates in the areas exposed to laser radiation before the heated areas of the semiconductor material properties.
  • a solar cell includes a semiconductor device comprising a first semiconductor material, a second semiconductor material, and a transition region (eg, also referred to as pn junction) between these two semiconductor materials.
  • a transition region eg, also referred to as pn junction
  • One of the semiconductor materials or even each of the semiconductor materials may be doped.
  • the voltage generated in a solar cell can be tapped.
  • the Zn-coated aluminum back contact constitutes one of these
  • the semiconductor device i.e., type of semiconductor materials to be used, doping, etc.
  • the solar cell is preferably a silicon solar cell, for example 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.
  • step (a) of the process according to the invention an aluminum foil is treated on one side with an alkaline, aqueous medium containing Zn 2+ , so that metallic zinc forms on the treated side of the aluminum foil, forming a one-sided Zn-coated aluminum foil deposits.
  • the thickness of the aluminum foil is for example in the range of 0.5 ⁇ to 50 ⁇ , more preferably in the range of 2 ⁇ to 20 ⁇ .
  • Such aluminum foils are commercially available.
  • the aluminum foil preferably contains aluminum in an amount of at least 80% by weight, more preferably at least 90% by weight. It may be pure metallic aluminum or an aluminum alloy. The purity of the metallic aluminum may vary over a wide range, provided that the electrical conductivity and / or mechanical properties are not adversely affected. For example, the aluminum contains 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. Is the aluminum foil made of one
  • Made aluminum alloy it 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 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.
  • 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 as a zincate (eg, [Zn (II) (OH) 4] 2 ⁇ or similar Zn 2+ -containing species) in the aqueous medium. This is known in principle to the person skilled in the art.
  • 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, included.
  • 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.
  • 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 can
  • Electroless metal deposition is a coating process that operates without the use of an external power source.
  • Electroless deposition of metallic zinc onto an aluminum substrate using an alkaline Zn 2+ solution is well known to those skilled in the art.
  • an Al 2 O 3 layer present on the aluminum is first dissolved.
  • Exposed aluminum is oxidized and enters as aluminate Solution.
  • Zn 2+ eg in the form of zincate
  • metallic Zn is deposited on the remaining aluminum.
  • the deposited on the aluminum foil 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 foil during the Zn deposition step (a) is reduced by a value approximately equal to the thickness of the deposited Zn layer.
  • the duration of the treatment of the aluminum foil with the alkaline, aqueous Zn 2+ -containing medium in step (a) is, for example, 15 s to 250 s.
  • the zinc deposition step (a) is preferably carried out at a temperature in the range of 5-60 ° C, more preferably 5-45 ° C.
  • step (a) the aluminum foil is treated on one side with the Zn 2+ -containing aqueous medium. This means that only one side of the aluminum foil is brought into contact with the Zn 2+ -containing medium and provided with a metallic Zn layer, whereas on the untreated side of the foil after step (a) no metallic Zn layer is present , As explained in more detail below, the film in step (b) via this untreated, ie no Zn layer having side attached to the back of the semiconductor device of the solar cell.
  • Aluminum foils can have a rough and a smooth side due to their production. An improved light output of the solar cells has resulted when the rough side of the aluminum foil is coated with zinc and the smooth side rests on the back of the semiconductor device. In a preferred embodiment, therefore, the side of the aluminum foil is treated with the aqueous Zn 2+ -containing medium whose average surface roughness is greater compared to the opposite side.
  • the aluminum foil is held in a substantially horizontal position during the zinc deposition step (a) with the side to be coated with metallic zinc facing down and being contacted with the Zn 2+ -containing aqueous medium.
  • substantially horizontal means that the film deviates at most 20%, more preferably at most 10% from an ideal horizontal position.
  • the alkaline, aqueous Zn 2+ -containing medium is located below the side of the aluminum foil to be coated and can be brought into contact with this side of the aluminum foil by conventional methods, for example by spraying or rinsing.
  • the Zn 2+ -containing medium is in an open-topped container and the aluminum foil is moved over this container, wherein the Zn 2+ -containing medium comes into contact with the aluminum foil only on one side from below.
  • This horizontal positioning of the aluminum foil in step (a) and the resulting coating of the downwardly facing side of the aluminum foil has a positive influence on the microstructure of the deposited metallic zinc layer and leads to a further improvement of the adhesion between the aluminum back contact and the solar cell connector mounted thereon.
  • step (a) in
  • step (a) Essentially positioned vertically. In principle, however, every other is Positioning (eg in oblique orientation) of the semiconductor device in step (a) possible.
  • the aluminum foil is moved relative to the Zn 2+ -containing medium during the zinc deposition step (a).
  • the relative speed between the aluminum foil 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 by moving the underside of the aluminum foil over a quiescent Zn 2+ -containing medium or by flowing a flowing Zn 2+ medium over a resting underside of the aluminum foil or through a Combination of these two variants.
  • the relative movement of the aluminum foil to the aqueous Zn 2+ -containing medium can be realized by a roll-to-roll process.
  • step (a) The relative movement between the aluminum foil and the aqueous Zn 2+ -containing medium during the Zn deposition in step (a) has a positive influence on the microstructure of the deposited metallic zinc layer and leads to a further improvement of the adhesion between the aluminum back contact and the solar cell connector mounted thereon.
  • the metallic zinc layer deposited in step (a) is present as a closed layer also on the surface of the closed zinc layer zinc crystallites with a diameter of more than 2.0 ⁇ in a number density of> 5000 per mm 2 , more preferably> 10000 per mm 2 , more preferably 5000-60000 per mm 2 or 10000-50000 per mm 2 are present; and / or wherein at least 1.5%, more preferably at least 3.0%, even more preferably 1.5-18.0%) or 3.0-15.0%) of the surface of the closed zinc layer by zinc crystallites having a diameter occupied by more than 2.0 ⁇ .
  • the metallic zinc layer preferably contains significantly smaller zinc crystallites with a
  • the particle size distribution of the zinc crystallites on the surface of the closed zinc layer may be, for example, bimodal.
  • step (a) On the basis of the method parameters of step (a) described above, such a metallic zinc layer can be produced selectively.
  • the Zn coating obtained in step (a) is rinsed at least once with a rinsing liquid before step (b).
  • a rinsing liquid At least for a first flush and optionally also for further flushes of the Zn-coated aluminum back contact before step (b), an aqueous rinse liquid of pH> 8.5, more preferably pH> 13, is preferably used.
  • the unilaterally Zn-coated aluminum foil is preferably subjected to drying before step (b), for example by suitable thermal treatment.
  • step (a) may be repeated at least once before step (b) is performed. However, considering the process efficiency, it is preferable to perform step (a) only once.
  • step (b) of the method according to the invention the one-sided Zn-coated aluminum foil is applied over its untreated side on the back of a semiconductor component of a first solar cell and locally heated with laser radiation, so that the aluminum foil with the Rear side of the semiconductor device connects and a Zn-coated aluminum back contact is obtained.
  • 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 commonly referred to as back contact.
  • the local heating preferably takes place in such a way that as much as possible of the deposited metallic zinc evaporates in this area and the aluminum foil at least briefly melts. As a result of the melting, an effective connection between the aluminum foil and the rear side of the semiconductor component occurs in this local area. Since zinc evaporates, disturbing contamination of the semiconductor device is minimized or even completely avoided in this local connection region.
  • the metallic zinc coating is still present and can be used in step (c) for the attachment of the metallic connector by soldering or gluing.
  • the local heating preferably takes place by means of laser radiation with several
  • step (b) Laser pulses per laser point. This promotes vaporization of the metallic zinc layer in the locally heated area and minimizes the risk of unwanted contamination of the semiconductor device.
  • An advantageous embodiment of the method is that the aluminum foil is locally heated in step (b) by means of laser radiation circumferentially on the edge of the semiconductor device such that the aluminum foil is severed. This improves the adhesion of the film to the semiconductor device. Furthermore, it is advantageous if the adhesion of the aluminum foil is high, especially under the applied connectors. This is achieved, for example, by the fact that in process step (b) the area fraction of the area irradiated with laser radiation is
  • Aluminum foil in the area below and in the vicinity of the applied in step (c) connector is greater than in the remaining portion of the aluminum foil.
  • the solar cell After attaching the one-sided Zn-coated aluminum foil on the back side of the semiconductor device, it can function as a Zn-coated aluminum back contact of the solar cell.
  • the solar cell in addition to the aluminum back contact nor a metallic front contact on the
  • Front side of the solar cell has.
  • This front contact can be configured in a known manner.
  • the front contact may have a grid structure.
  • the front contact can be made of silver or a
  • the front contact can already be on the
  • step (b) Semiconductor device are present when in step (b) 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 In order to minimize shading effects, it is alternatively also possible for the solar cell to be exclusively back contacted, ie only on the rear side of the solar cell
  • 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 metallic Zn layer of the aluminum back contact. This is preferred
  • step (c) of the method of 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 on the Zn-coated aluminum back contact of the first solar cell by soldering or sticking is attached.
  • 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, with others
  • 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 has a melting temperature in the range of 180 ° C to 245 ° C.
  • 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 ("no cleari 1" ) fluxes.
  • the flux may be applied to the solder-coated metallic connectors (eg, the tinned copper tapes) and / or to the deposited zinc layer. If the attachment of the metallic connector on the Zn-coated aluminum back contact by gluing, so 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.
  • at least two, more preferably 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 in the Solar cell string connected solar cells to a Zn-coated aluminum back contact prepared 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 2.0 ⁇ in a Number density of> 5000 per mm 2 , more preferably> 10000 per mm 2 , more preferably 5000-60000 per mm 2 or 8000-55000 per mm 2 or 10000-50000 per mm 2 ; and / or wherein at least 1.5%, more preferably at least 3.0%>, even more preferably 1.5-30.0%) or 1.5-18.0%) or 3.0-15.0% of the surface the closed zinc layer is occupied by zinc crystallites with a diameter of more than 2.0 ⁇ m.
  • the metallic zinc layer preferably contains significantly smaller zinc crystallites with a
  • Diameter of less than 1.0 ⁇ is occupied.
  • the zinc crystallites with a diameter of more than 2.0 ⁇ 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 2.0 ⁇ or less than 1.0 ⁇ on the surface of the Zn layer and the respective relative surface occupancy by these Zn crystallites are via scanning electron micrographs (SEM images ) of the Zn layer (in plan view) as well as the evaluation of the images by suitable Image evaluation software determines.
  • 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 layer is occupied by zinc crystallites with a diameter of more than 2.0 ⁇ .
  • these high density, large area zinc crystallite areas may be where no metal connector has been attached.
  • the zinc-coated aluminum obtained by a wet-chemical process is a very effective substrate for the attachment of another metal by soldering or gluing.
  • the substrate was the aluminum back contact of the solar cell to which, when connected to other solar cells, metallic connector is to be attached by soldering or gluing.
  • the present invention also relates to a method for interconnecting solar cells, wherein
  • the aluminum substrate may be made of metallic aluminum or an aluminum alloy. Regarding the properties of aluminum
  • the aluminum alloy in particular aluminum content
  • the purity of the aluminum can vary over a wide range, provided that the electrical conductivity and / or mechanical properties are not adversely affected.
  • the aluminum contains 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.
  • Made aluminum alloy it 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 preferred conditions for the zinc deposition step (i) reference may be made to the above statements (see
  • the aqueous medium with which the aluminum substrate 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%.
  • 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, included.
  • 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, for example in the range of 0.0003-30% by weight or 0.0003-0, 1% by weight.
  • 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. If 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 onto the aluminum substrate preferably takes place without current.
  • the deposited on the aluminum substrate Zn layer has a thickness in the range of 0.1 ⁇ to 5 ⁇ , more preferably 0.3 ⁇ to 2.5 ⁇ on.
  • the duration of the treatment of the aluminum substrate with the alkaline, aqueous Zn 2+ -containing medium in step (i) is, for example, 15 seconds to 250 seconds.
  • the zinc deposition step (i) is preferably carried out at a temperature in the range of 5-60 ° C, more preferably 5-45 ° C.
  • the treatment of the aluminum substrate for example, by immersion in the Zn 2+ -containing medium or by rinsing or spraying with the Zn 2+ -containing medium.
  • the aluminum substrate in particular an aluminum strip
  • any other positioning eg in an oblique orientation in step (i) is possible.
  • the aluminum substrate is moved relative to the Zn 2+ -containing medium during the zinc deposition step (i).
  • 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 substrate over a quiescent Zn 2+ -containing medium or by flowing a flowing Zn 2+ medium over a resting aluminum substrate or by a combination of these two variants.
  • the flow rate of the Zn 2+ -containing medium (and thus the relative speed with respect to the (moving or stationary) aluminum substrate) can be adjusted for example via the pump power.
  • Aluminum ribbon can be achieved.
  • the Zn-coated aluminum substrate is rinsed at least once with a rinsing liquid.
  • a rinsing liquid With regard to suitable rinsing liquids and
  • the Zn-coated aluminum substrate is dried before step (ii).
  • a solder material is applied to the Zn-coated aluminum substrate prior to step (ii). Suitable solder materials will be described below.
  • soldering common solder materials known to those skilled in the art can be used, e.g. Tin alloys. These contain as alloying elements
  • the solder material preferably has a melting temperature in the range of 180 ° C to 245 ° C.
  • 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 300 ° C.
  • the soldering process uses conventional, preferably non-corrosive, fluxes.
  • an electrically conductive adhesive is preferred.
  • Such adhesives are known to those skilled in the art and commercially available.
  • the metal contacts to which the metal connector is attached may be those commonly used for solar cells.
  • the metal contact is a silver contact (e.g., a screen-printed silver contact), a Ni / Cu / Ag contact (e.g., via galvanic
  • Ni / Cu contact (eg via galvanic deposition made) or an AI contact (eg produced by screen printing).
  • AI contact eg produced by screen printing.
  • the metal contact may be a back contact or a front contact.
  • the present invention relates to a Zn-coated wire or strip-shaped aluminum substrate, which preferably has one or more areas in which a closed layer of metallic zinc on the
  • Aluminum substrate is present, wherein also on the surface of the closed zinc layer zinc crystallites with a diameter of more than 2.0 ⁇ in a number density of> 5000 per mm 2 , more preferably> 10000 per mm 2 , more preferably 5000-60000 per mm 2 or 8000-55000 per mm 2 or 10000-50000 per mm 2 ; and / or wherein at least 1.5%, more preferably at least 3.0%, even more preferably 1.5-30.0% or 1.5-18.0% or 3.0-15.0% of the surface of the closed zinc layer is occupied by zinc crystallites with a diameter of more than 2.0 ⁇ .
  • the metallic zinc layer preferably contains significantly smaller zinc crystallites with a
  • Diameter of less than 1.0 ⁇ is occupied.
  • the zinc crystallites with a diameter of more than 2.0 ⁇ 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 2.0 ⁇ or less than 1.0 ⁇ on the surface of the Zn layer and the respective relative Oberfiumbleen occupancy 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.
  • the present invention relates to the use of the above
  • a 9 ⁇ thick aluminum foil with a purity of 99% is passed from roll to roll at a speed of 1 m / min over 3 pools.
  • the first basin is filled with an aqueous solution containing Zn 2+ containing 4% by weight of zinc ions, 15% by weight of NaOH and 0.001% by weight of iron ions.
  • the second basin contains 1% caustic soda and the third basin demineralised water.
  • the first tank serves to deposit the metallic zinc on one side of the aluminum foil, while with the tanks 2 and 3 the Zn-coated aluminum foil is rinsed. All 3 pools are filled to the upper edge of the pool. Due to the surface tension, the aluminum foil is pulled down by the liquids so that they wet the aluminum foil well, only on the lower side, ie on one side. In this way, the aluminum foil is only coated on one side with zinc. Because the aluminum foil is wider than the basins perpendicular to the transport direction, the basins are completely covered by the aluminum foil and due to the
  • Transport speed and individual width of the basin results in the treatment times 90 s for tank 1, which is filled with the aqueous medium containing Zn 2+ , 20 s for tank 2, which is filled with 1% sodium hydroxide solution, and 20 s for tank 3 filled with demineralized water.
  • tank 1 which is filled with the aqueous medium containing Zn 2+
  • tank 2 which is filled with 1% sodium hydroxide solution
  • tank 3 filled with demineralized water.
  • 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 2 ⁇ m.
  • Zinc crystallites with a diameter of more than 2 ⁇ m are present in a number density of about 30,000 per mm 2 .
  • 9% of the surface of the metallic zinc layer are coated with Zn crystallites with a diameter of at least 2 ⁇ .
  • the roller with the zinc-coated aluminum foil is positioned in a film unwinder of the laser system.
  • the film is unwound, placed with the non-zinc-coated side on the back of a semiconductor device (silicon substrate) of a solar cell (silicon solar cell) and sucked there with Unterduck.
  • the zinc-coated side is locally illuminated with laser radiation.
  • at least the Zn-coated aluminum foil is locally heated, so that melting of the aluminum foil occurs for a short time in these regions, whereby it bonds to the rear side of the semiconductor component.
  • Aluminum foil is severed and the protruding over the edge of the semiconductor device film can be removed well.
  • aluminum foil Due to its production, aluminum foil has a rough and a smooth side. An improved light output of the solar cells has resulted when the rough side of the aluminum foil is coated with zinc and the smooth side rests on the back of the semiconductor device.
  • the Zn-coated aluminum foil fastened by lasers to the semiconductor device functions as a Zn-coated aluminum back contact.
  • a soldered copper ribbon (tinned copper ribbon) is soldered by means of infrared heating at 275 ° C.
  • a flux Kester 952 s
  • Figure 2 shows in cross section a SEM photograph of the area in which the metallic connector (the copper ribbon) was soldered onto the Zn coated aluminum back contact. Three layers can be seen. The uppermost layer is the aluminum layer of the back contact and the lowest layer is the copper of the metallic connector. In between lies the adhesion-promoting solder layer. In this is the solder material and the zinc of the zinc coating.
  • the copper ribbon shows good adhesion on the back contact of the solar cell.
  • the protruding end of the connector is soldered in a subsequent soldering in a known manner to the front of another solar cell.
  • the solar cell strings are laminated with glass, ethylene vinyl acetate and polymer backsheet into a module.

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  • Engineering & Computer Science (AREA)
  • Electromagnetism (AREA)
  • Sustainable Development (AREA)
  • Sustainable Energy (AREA)
  • Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Computer Hardware Design (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Power Engineering (AREA)
  • Photovoltaic Devices (AREA)
  • Electroplating Methods And Accessories (AREA)

Abstract

L'invention concerne un procédé permettant d'obtenir des cellules solaires, selon lequel (a) une feuille d'aluminium est traitée sur une face avec un milieu alcalin aqueux qui contient du Zn2+, de sorte que du zinc métallique se dépose sur la face traitée de la feuille d'aluminium, ce qui donne une feuille d'aluminium revêtue de zinc sur une face, (b) la feuille d'aluminium revêtue de zinc sur une face est appliquée par sa face non traitée sur la face arrière d'un composant semi-conducteur d'une première cellule solaire et chauffée localement par rayonnement laser, de sorte que la feuille d'aluminium se lie à la face arrière du composant semi-conducteur et qu'on obtient un contact arrière en aluminium revêtu de zinc, (c) le contact arrière en aluminium revêtu de zinc est lié par un liant métallique à un contact métallique d'une seconde cellule solaire, le liant métallique étant fixé par brasage ou collage sur le contact arrière en aluminium revêtu de zinc.
EP17735407.3A 2016-06-19 2017-06-16 Procédé d'interconnexion de cellules solaires qui présentent une feuille d'aluminium en tant que contact arrière Withdrawn EP3472870A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE102016210910.3A DE102016210910A1 (de) 2016-06-19 2016-06-19 Verfahren zur Verschaltung von Solarzellen, die Aluminiumfolie als Rückkontakt aufweisen
PCT/EP2017/064800 WO2017220445A1 (fr) 2016-06-19 2017-06-16 Procédé d'interconnexion de cellules solaires qui présentent une feuille d'aluminium en tant que contact arrière

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EP3472870A1 true EP3472870A1 (fr) 2019-04-24

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EP17735407.3A Withdrawn EP3472870A1 (fr) 2016-06-19 2017-06-16 Procédé d'interconnexion de cellules solaires qui présentent une feuille d'aluminium en tant que contact arrière

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EP (1) EP3472870A1 (fr)
CN (1) CN109417102A (fr)
DE (1) DE102016210910A1 (fr)
WO (1) WO2017220445A1 (fr)

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Publication number Priority date Publication date Assignee Title
DE102019120872A1 (de) 2019-08-01 2021-02-04 Infineon Technologies Ag Löten eines Leiters an eine Aluminiumschicht

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102009010816B4 (de) * 2009-02-27 2011-03-10 Solarworld Innovations Gmbh Verfahren zur Herstellung eines Halbleiter-Bauelements
JP2014510408A (ja) * 2011-03-11 2014-04-24 アベリー・デニソン・コーポレイション アルミニウム系電極を有するシートアセンブリー
CN103493608A (zh) * 2011-03-18 2014-01-01 应用材料公司 具有多层的导电箔及形成该导电箔的方法
DE102011075352A1 (de) * 2011-05-05 2012-11-08 Solarworld Innovations Gmbh Verfahren zum Rückseitenkontaktieren einer Silizium-Solarzelle und Silizium-Solarzelle mit einer solchen Rückseitenkontaktierung
WO2013096951A1 (fr) * 2011-12-23 2013-06-27 Solexel, Inc. Traitement de pulvérisation à haute productivité pour la métallisation de semi-conducteur et interconnexions
DE102012214253A1 (de) * 2012-08-10 2014-06-12 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Laserbasiertes Verfahren und Bearbeitungstisch zur Metallisierung der Rückseite eines Halbleiterbauelements
JP6141223B2 (ja) * 2013-06-14 2017-06-07 三菱電機株式会社 受光素子モジュールおよびその製造方法

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WO2017220445A1 (fr) 2017-12-28
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