Classifications

• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
  • H10F71/00—Manufacture or treatment of devices covered by this subclass
  • H10F71/137—Batch treatment of the devices
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
  • H10F19/00—Integrated devices, or assemblies of multiple devices, comprising at least one photovoltaic cell covered by group H10F10/00, e.g. photovoltaic modules
  • H10F19/80—Encapsulations or containers for integrated devices, or assemblies of multiple devices, having photovoltaic cells
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
  • H10F19/00—Integrated devices, or assemblies of multiple devices, comprising at least one photovoltaic cell covered by group H10F10/00, e.g. photovoltaic modules
  • H10F19/80—Encapsulations or containers for integrated devices, or assemblies of multiple devices, having photovoltaic cells
  • H10F19/85—Protective back sheets
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
  • H10F19/00—Integrated devices, or assemblies of multiple devices, comprising at least one photovoltaic cell covered by group H10F10/00, e.g. photovoltaic modules
  • H10F19/90—Structures for connecting between photovoltaic cells, e.g. interconnections or insulating spacers
  • H10F19/902—Structures for connecting between photovoltaic cells, e.g. interconnections or insulating spacers for series or parallel connection of photovoltaic cells
  • H10F19/906—Structures for connecting between photovoltaic cells, e.g. interconnections or insulating spacers for series or parallel connection of photovoltaic cells characterised by the materials of the structures
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
  • H10F19/00—Integrated devices, or assemblies of multiple devices, comprising at least one photovoltaic cell covered by group H10F10/00, e.g. photovoltaic modules
  • H10F19/90—Structures for connecting between photovoltaic cells, e.g. interconnections or insulating spacers
  • H10F19/902—Structures for connecting between photovoltaic cells, e.g. interconnections or insulating spacers for series or parallel connection of photovoltaic cells
  • H10F19/908—Structures for connecting between photovoltaic cells, e.g. interconnections or insulating spacers for series or parallel connection of photovoltaic cells for back-contact photovoltaic cells

Definitions

• a method of producing a solar panel curved in two directions A method of producing a solar panel curved in two directions.
• the invention relates to a method of producing a solar panel curved in two directions, the method comprising:
• a multitude of solar cells are interconnected, typically using‘finger electrodes’, to connect the photosensitive side of one solar cell with the backside of a neighboring cell.
• These interconnected cells are then laminated between two sheets, for example sheets of a polyolefin or one of its copolymers, such as EVA (ethylene vinyl acetate), or polyvinylbutyral (PVB), after which the sheets are bonded to glass to form a (flat) solar panel.
• EVA ethylene vinyl acetate
• PVB polyvinylbutyral
• laminated in this context is also known as bonded or encapsulated (with an encapsulant). Therefore laminated, bonded and encapsulated are used interchangeable.
• the solar cells are typically thin wafers of semiconductor material. Such solar cells can only be deformed into cylindrical shapes and some other shapes (e.g. cones) in a limited way due to the stresses that occur in the solar cells. If these stresses exceed the fracture limit, fracture of the solar cell occurs and may leave the cell useless.
• wafers of semiconductor material include mono-crystalline, poly- crystalline and amorphous wafers of silicon, GaAs, InP, or the like.
• flexible sheet describes a sheet of, for example, polyimide or polyester (or more generic: an insulating synthetic material) with a conductive layer or pattern thereon (typically copper, silver).
• a conductive layer or pattern thereon typically copper, silver.
• a disadvantage of this method is that the coverage of solar cells is lower due to the gaping of the incisions. Also, the use of finger electrodes will reduce to area of the solar cell available for solar conversion. Also, although this does not present a technical problem, the esthetic appearance is less than for a uniformly covered solar panel.
• a disadvantage of this methods is that on a curved surface, such as a solar roof for a car, the coverage of the solar cells is less than with a flat surface. Also, the use of finger electrodes diminishes the amount of semiconductor area available for solar conversion. Also, the positioning of the cells prior to lamination is difficult, as they are positioned in an irregular matrix by the finger electrodes. Also, although this does not present a technical problem, the esthetic appearance is less than for a uniformly covered solar panel.
• the present invention provides a method to overcome these problems.
• Two or more flexible foils with a conductive pattern thereon are provided,
• the solar cells are grouped in subgroups, each subgroup associated with an area on the curved surface and one flexible foil, the method comprising the subsequent steps of: • a solder step comprising, for each of the subgroups, soldering the solar cells to the flexible foil or bonding the solar cells to the flexible foil with a conductive adhesive,
• a positioning step comprising draping the two or more subgroups on the curved
• a laminate implies a maximum lamination thickness (the thickness of the initial lamination layer). However, during the laminating process, the thickness may locally change due to the viscosity of the (uncured, not yet crosslinked) lamination sheet.
• the lamination sheet (and the embedded solar cells) are molded and cured at a pressure of, for example one atmosphere (10 N/cm 2 ), a
• each subgroup associated with an area on the curved surface with a small or negligible curvature in at least one direction, it is possible to form subgroups that can be bonded (laminated) to the curved surface. .When properly divided in subgroups, it thus results in subgroups with a mechanical stress below the fracture limit of the solar cells and below the limit where the flexible foil shows wrinkling when laminated to the curved surface.
• the bonding material (lamination material) need not have a constant thickness between solar cell and curved surface, but for efficiency, thermal behavior and esthetic reasons the thickness preferably should not change too much over the solar cell and the multitude of solar cells.
• a solder step the solar cells are electrically and mechanically connected to the flexible foil.
• This step may involve soldering of, for example, solder paste at a temperature in excess of 200 °C, or it may involve bonding with an electrically conductive adhesive such as an epoxy filled with conductive material, such as copper, silver, etc. Curing of such an adhesive is typically performed at a temperature of between 100 - 150 °C, and may take place during lamination.
• each of these subgroups are then positioned (draped) on the curved surface.
• a flexible foil also known as a back-contact foil or BCF
• BCF back-contact foil
• a polyester/copper foil in most cases a polyester/copper foil is used, but polyimide is known for the carrier as well, and silver is known as a conductor
• the use of such a foil on a curved surface is not, as, without the steps according to the invention, a flexible foil tends to show wrinkles when folded/draped over or in a curved surface curved in two directions, making it unfit for use under these conditions.
• a first lamination step is inserted, the first lamination step comprising:
• the positioning step comprising draping the partial crosslinked laminate comprising solar cells and flexible foil on or in the curved surface
• the final lamination step comprises laminating the partial crosslinked laminated comprising solar cells and flexible foil to the curved surface, thereby completely crosslinking the lamination applied in the first lamination step.
• a first lamination step is inserted, the first lamination step comprising:
• the final laminating step comprises laminating the laminated subgroups to the curved surface.
• This embodiment resembles to embodiment described before, with the difference that a complete crosslinking occurred in the first lamination step.
• a tight control of temperature and time is needed, but this may be preferred as the intermediate product (a laminated web of solar cells and flexible foil) is better to handle as it is less sticky than an incompletely cured (a partially cured) lamination sheet, and offers better protection of the solar cells.
• This embodiment described the possibility to place multiple layers of lamination material (for example layers of EVA -ethylene vinyl acetate-) between the solar cells and the curved surface, which results in more lamination material (encapsulant material) that may show local thickness variations, resulting in reduced mechanical stress.
• lamination material for example layers of EVA -ethylene vinyl acetate-
• the method further comprises: before providing the solar cells estimating the mechanical stress occurring in the solar cells resulting from the curvature of the curved surface at the location of the solar cell and, based on this estimate, resize the solar cells to such a size that the mechanical stress in each solar cell is below the stress where fracture of the solar cells occurs.
• Determining the size (the maximum area) of a subgroup is best done with an iterative recipe, starting with a first size of solar cells, determine in a simulation what stresses result when the cells are forced to follow the curved surface, if the stresses are too high with what is assumed to be an allowable maximum (for example half the fracture limit of the solar cell), lower the size of the solar panels in the direction where the high stress occurred, etc.
• the method further comprises: before providing the solar cells estimating the mechanical stress occurring in the solar cells resulting from the curvature of the curved surface at the location of the solar cell and, based on this estimate, at least locally change the thickness of laminate material to such a value that the stresses occurring in the solar cell are below the stress where fracture of the solar cells occurs.
• the stresses occurring in the solar cells can be reduced due to the viscosity of uncured lamination material.
• Local variation of the thickness of the lamination material can be realized by building a 3D form of material by locally adding rings, circles or other forms before curing the lamination material. It is noted that locally adding material may be used to reach this solution, but also using a thicker layer of encapsulant (lamination material, or the use of several layers, as the encapsulant will during the lamination process slightly.
• 3D forming of for example EVA may be realized by placing one or more sheets upon each other, where at least one sheet shows perforations or the like. Also 3D printing of EVA is known.
• FIG. 1A schematically shows a solar cell used in the invention, seen from the photosensitive side
• Figure 1 B schematically shows a solar cell used in the invention, seen from the side opposite to the photosensitive side
• Figure 2 schematically shows one possible cut-through of a solar panel fabricated according to the invention.
• Figure 3A schematically shows a planar view of solar panel, showing the areas forming each subgroup,
• Figure 3B schematically shows a planar view of solar panel, showing the solar cells forming each subgroup
• Figure 1 A schematically shows a solar cell used in the invention, seen from the photosensitive side.
• FIG. 1A schematically shows a solar cell 100 used in the invention.
• the solar cell shows a photosensitive area 102 and an insulating edge portion 104. It is noted that this insulated portion (actually an insulating side wall) only occurs at so-called passivated cells.
• An advantage is that it enables the cells to be placed against each other. Cells without passivation on the sides must be separated to avoid shorts. Most commercially available cells are cut from a large wafer and do not show a passivation of the side walls, so they need to be spaced from each other to avoid electrical shorting.
• a typical thickness for a solar cell is in the order of 200 pm, but for more flexible solar cells thinner cells, for example with a thickness of 150 pm, are preferred.
• Figure 1 B schematically shows a solar cell used in the invention, seen from the side opposite to the photosensitive side.
• cutouts are provided that provide contact areas to anode 108-i and cathode 110-j.
• Figure 2 schematically shows one possible cut-through of a solar panel fabricated according to the invention.
• lamination material for example EVA (Ethylene Vinyl Acetate) or a polyolefin to solar cells 102 a .
• the photosensitive side is facing the glass.
• the flexible foil comprises a polyester or polyimide film 206 and copper tracks 208.
• the solar cell is soldered on a flexible foil, either by soldering the cells and the flexible foil with solder paste that is heated to, for example, 200 °C or more, or by using electrically conductive adhesive (typically a metal filled epoxy) that is cured at a temperature of, for example, less than 150 °C.
• electrically conductive adhesive typically a metal filled epoxy
• Solar cells 102 b and 102 c are here depicted as belonging to another subgroup (the flexible foil -although not depicted for these cells- is not the same as the flexible foil of cell 102 a .
• a further layer of material can be placed, either as a solder mask (or a mask for electrically conductive adhesive), or as an esthetic screen to obscure the copper tracks on the flexible foil, or for any other purpose. This need not be a transparent material.
• a lamination layer may be added on this layer (thereby completely encapsulating the flexible foil), but is not necessary.
• the flexible foil may comprise only one layer of insulating material as a carrier, such as polyimide or polyester, with a conductive pattern thereon, or it may comprise further layers with or without cut-outs to act as a solder mask, or for other purposes, the further layers either on the side of the solar cells or on the opposite side.
• a carrier such as polyimide or polyester
• the further layers either on the side of the solar cells or on the opposite side.
• the amount of lamination material (bonding material, encapsulant) between the solar cell may be the result of one lamination layer but may comprise several layer of lamination material.
• Figure 3A schematically shows a planar view of solar panel, showing the areas forming each subgroup.
• Figure 3A shows a curved surface 300 that is divided in areas 302L, 302R, 304L, 304R, 306L, 306R and 308.
• the distribution of the curved surface is the result of an analysis of the maximum stresses occurring when flexible foil and solar cells are adhered (laminated) to the curved surface. These stresses can occur in any direction, but in many applications (such as a car roof) there is an axis of symmetry (here the x-axis) simplifying the problem. Empirically (or using another method, for example computer based) a division of areas is then found that result in acceptable stresses for both the solar cells and the foils.
• a stress problem in a solar cell need not result in a problem in the flexible foil, and vice versa: the size of a solar cell is often much more limited than the (maximum) size of a flexible foil. Therefore, at modest curvatures a problem may first occur in the flexible foil. However, at a large local curvature may result in a problem in the solar cells before a problem in the flexible foil occurs.
• Figure 3B schematically shows a planar view of solar panel, showing the solar cells forming each subgroup.
• Figure 3B can be thought to be derived from figure 3A.
• the solar cells are depicted that form the subgroups (borders of subgroups indicated by thicker lines).
• the orientation of the cells can be changed, even within a subgroup, as shown in for example group 304L.
• subgroup used here has no relation to the definition of“group” usually used in solar technology.
• the standard definition of group comprises a group of cells, typically being part of a string, and in state of the art panels each group is associated with an optimizer (a Maximum Power Point Tracker).
• the definition of subgroup according to the invention is used to denote cells that are attached to a (doubly) curved surface without exceeding predetermined stress levels.
• one subgroup may comprise more than one group, or one group may extend over more than one subgroup, or any combination thereof. It is thus possible that two subgroups comprise three groups or vice versa, while each group may be associated with its own optimizer.
• the curved surface is a transparent or translucent curved surface, but it is also possible to use the method with a non- transparent curved surface (for example a metal curved surface) and that the
• electrical connections between one flexible foil to another flexible foil, or to other PCB’s or FBC’s can be made by soldering or bonding another flexible foil (preferably formed as a strip with several lines forming the electrical connections) on the first flexible foil. Also electrical connections via wires can be used.
• laminating may describe a total encapsulation, but may also describe bonding one part (for example the solar cells) to another (for example the curved surface) using a bonding or lamination material, such as of a polyolefin or one of its copolymers, such as EVA (ethylene vinyl acetate), or polyvinylbutyral (PVB).
• a bonding or lamination material such as of a polyolefin or one of its copolymers, such as EVA (ethylene vinyl acetate), or polyvinylbutyral (PVB).
• EVA ethylene vinyl acetate
• PVB polyvinylbutyral
• An exemplary curing cycle is, for example,
• Laminating the before described sandwich to a curved surface, such as the glass roof of a solar car, is done by, for example:

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• 2018
  • 2018-09-26 NL NL2021711A patent/NL2021711B1/en not_active IP Right Cessation
• 2019
  • 2019-09-18 WO PCT/EP2019/075088 patent/WO2020064474A1/en not_active Ceased
  • 2019-09-18 US US17/278,568 patent/US12224370B2/en active Active
  • 2019-09-18 CN CN201980063097.1A patent/CN112789735B/zh active Active
  • 2019-09-18 JP JP2021542258A patent/JP7609788B2/ja active Active
  • 2019-09-18 ES ES19769174T patent/ES2993284T3/es active Active
  • 2019-09-18 EP EP19769174.4A patent/EP3857613B1/en active Active

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