The present invention relates to back-contact photovoltaic modules with glass back-sheets, and to processes for making such photovoltaic modules with conductive circuitry integrated into the modules.
A photovoltaic cell converts radiant energy, such as sunlight, into electrical energy. In practice, multiple photovoltaic cells are electrically connected together in series or in parallel and are protected within a photovoltaic module or solar module.
As shown in
In back-contact photovoltaic cells, all of the electrical contacts are moved to the back side of the photovoltaic cell. With both the positive and negative polarity electrical contacts on the back side of the photovoltaic cells, electrical circuitry is needed to provide electrical connections to the positive and negative polarity electrical contacts on the back of the photovoltaic cells. U.S. Patent Application No. 2011/0067751 discloses a back contact photovoltaic module with a back-sheet having patterned electrical circuitry that connects to the back contacts on the photovoltaic cells during lamination of the solar module. The circuitry is formed from a metal foil that is adhesively bonded to a carrier material such as polyester film or Kapton® film. The carrier material may be adhesively bonded to a protective layer such as a Tedlar® fluoropolymer film. The foil is patterned using etching resists that are patterned on the foil by photolithography or by screen printing according to techniques used in the flexible circuitry industry. The back contacts on the photovoltaic cells are adhered to and electrically connected to the foil circuits by adhesive conductive paste. There is a need for alternative back-contact photovoltaic modules in which conductive circuitry is integrated with a rigid glass back-sheet. There is also a need for moisture impermeable back-sheets that maintain moisture integrity for the long service life of the photovoltaic modules which may extend for decades. There is also a need for photovoltaic back contact modules in which the back contacts securely attach to the conductive circuitry and remain securely attached for multiple decades.
The detailed description will refer to the following drawings which are not drawn to scale and wherein like numerals refer to like elements:
a and 2b are schematic plan views of the back side of arrays of back-contact solar cells.
a and 3b are schematic representations of back-sheets with integrated wire circuits.
a is a plan view of a wire mounting layer with adhered conductive wires, and
a is a plan view of a an interlayer dielectric (ILD), and
a-6e are cross-sectional views illustrating one disclosed process for forming a back-contact solar cell module in which integrated conductive wires are connected to the back contacts of solar cells.
a and 8b are cross-sectional views illustrating one disclosed process for forming a back-contact solar cell module in which integrated conductive wires are connected to the back contacts of solar cells.
a is a plan view of a polymeric wire mounting layer, and
a-10f illustrate steps of a process for forming a back-contact solar cell module in which an array of back-contact solar cells are electrically connected in series by conductive wires that are integrated with a glass back-sheet of the solar cell module.
To the extent permitted by the United States law, all publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety.
The materials, methods, and examples herein are illustrative only and the scope of the present invention should be judged only by the claims.
The following definitions are used herein to further define and describe the disclosure.
As used herein, the terms “comprises,” “comprising,” “includes,” “including,” “has,” “having” or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a process, method, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Further, unless expressly stated to the contrary, “or” refers to an inclusive or and not to an exclusive or. For example, a condition A or B is satisfied by any one of the following: A is true (or present) and B is false (or not present), A is false (or not present) and B is true (or present), and both A and B are true (or present).
As used herein, the terms “a” and “an” include the concepts of “at least one” and “one or more than one”.
Unless stated otherwise, all percentages, parts, ratios, etc., are by weight.
When the term “about” is used in describing a value or an end-point of a range, the disclosure should be understood to include the specific value or end-point referred to.
As used herein, the terms “sheet”, “layer” and “film” are used in their broad sense interchangeably. A “front sheet” is a sheet, layer or film on the side of a photovoltaic module that faces a light source and may also be described as an incident layer. Because of its location, it is generally desirable that the front sheet has high transparency to the incident light. A “back-sheet” is a sheet, layer or film on the side of a photovoltaic module that faces away from a light source, and is generally opaque. In some instances, it may be desirable to receive light from both sides of a device (e.g., a bifacial device), in which case a module may have transparent layers on both sides of the device.
As used herein, “encapsulant” layers are used to encase the fragile voltage-generating photoactive layer, to protect it from environmental or physical damage, and hold it in place in the photovoltaic module. Encapsulant layers may be positioned between the solar cell layer and the front incident layer, between the solar cell layer and the back-sheet, or both. Suitable polymer materials for the encapsulant layers typically possess a combination of characteristics such as high transparency, high impact resistance, high penetration resistance, high moisture resistance, good ultraviolet (UV) light resistance, good long term thermal stability, good long term weatherability, and adequate adhesion strength to frontsheets, back-sheets, other rigid polymeric sheets and solar cell surfaces.
As used herein, “inter layer dielectric” (ILD) is a layer of a low dielectric constant k material used to electrically separate closely spaced electrically conductive layers or lines arranged in several levels of an electrical circuit or device such as a photovoltaic module.
As used herein, the terms “photoactive” and “photovoltaic” may be used interchangeably and refer to the property of converting radiant energy (e.g., light) into electric energy.
As used herein, the terms “photovoltaic cell” or “photoactive cell” or “solar cell” mean an electronic device that converts radiant energy (e.g., light) into an electrical signal. A photovoltaic cell includes a photoactive material layer that may be an organic or inorganic semiconductor material that is capable of absorbing radiant energy and converting it into electrical energy. The terms “photovoltaic cell” or “photoactive cell” or “solar cell” are used herein to include photovoltaic cells with any types of photoactive layers including, crystalline silicon, polycrystalline silicon, microcrystal silicon, and amorphous silicon-based solar cells, copper indium (gallium) diselenide solar cells, cadmium telluride solar cells, compound semiconductor solar cells, dye sensitized solar cells, and the like.
As used herein, the term “photovoltaic module” or “solar module” (also “module” for short) means an electronic device having at least one photovoltaic cell protected on one side by a light transmitting front sheet and protected on the opposite side by an electrically insulating protective back-sheet.
As used herein, the term “back-contact solar cell” means a solar cell having both positive and negative polarity contacts located on its back side, including metal wrap through (MWT), metal wrap around (MWA), emitter wrap through (EWT), emitter wrap around (EWA), and interdigitated back contact (IBC) solar cells.
Disclosed herein are back-contact solar modules with a glass back-sheet and integrated conductive wire circuitry and processes for forming such back-contact solar modules with integrated circuitry.
Arrays of back-contact solar cells are shown in
Each of the solar cells 22 has multiple positive and negative polarity contacts on back side of the solar cell. The contacts on the back side of the solar cells are typically made of a metal to which electric contacts can be readily formed, such as silver or platinum contact pads. The contacts are typically formed from a conductive paste comprising an organic medium, glass frit and silver particles, and optionally inorganic additives, which is fired at high temperature to form metal contact pads. The solar cells shown in
a shows an embodiment of the disclosed integrated back-sheet. The integrated back-sheet 30 shown in
In the embodiment of the disclosed integrated glass back-sheet 30 shown in
In the integrated back-sheet 31 shown in
The wire mounting layer 38 preferably comprises a polymeric material such as a thermoplastic or thermoset material. The wire mounting layer 38 preferably has a thickness sufficient to be self supporting and sufficient to support wires mounted on the wire mounting layer. For example, the wire mounting layer typically has a thickness in the range of 1 mils to 25 mils, and more preferably in the range of 4 mils to 18 mils. The wire mounting layer can include more than one layer of polymer material, wherein each layer may include the same material or a material different from the other layer(s). The wire mounting layer may be comprised of polymer with adhesive properties, or an adhesive coating can be applied to the surface(s) of the wire mounting layer to hold the wires in place. The side of the wire mounting layer opposite to the electrically conductive wires attaches to the glass back-sheet. The wire mounting layer may be formed of a polymeric material that adheres directly to the glass back-sheet during thermal lamination of the photovoltaic module. Alternatively, adhesives such as reactive adhesives (e.g., polyurethane, acrylic, epoxy, polyimide, or silicone adhesives) or non-reactive adhesives (e.g., polyethylenes (including ethylene copolymers) or polyesters) can be used to attach the wire mounting layer to the glass back-sheet.
Depending upon when the conductive wires are anchored to the back contacts of the solar cells, it may be desirable for the wire mounting layer to be made of a polymer that does not melt or deform when the photovoltaic module is laminated. As more fully discussed below, when the conductive wires have already been anchored to the solar cell back contacts prior to lamination of the photovoltaic module, it may be less of an issue if the wire mounting layer deforms or melts during lamination of the photovoltaic module. If, on the other hand, the conductive wires are anchored to the back contacts of the solar cells during the lamination of the photovoltaic module or if the wire mounting layer must act to electronically insulate the wires from the back side of the solar cells, it will be important that the wire mounting layer not melt or deform during the module lamination step. Where the wire mounting layer must not melt or deform, the wire mounting layer should be formed of a polymer with a melting temperature that is higher than the module lamination temperature. Cross-linked or cured encapsulant materials typically have softening and melting temperatures above the module lamination temperature, which typically range from 120° C. to 180° C. Polymeric materials useful in the wire mounting layer include ethylene methacrylic acid and ethylene acrylic acid, ionomers derived therefrom, or combinations thereof. Exemplary comonomers that may be in the precursor acid copolymers include, but are not limited to, methyl acrylates, methyl methacrylates, butyl acrylates, butyl methacrylates, glycidyl methacrylates, vinyl acetates, and mixtures of two or more thereof.
The wire mounting layer may also be films or sheets comprising poly(vinyl butyral)(PVB), ionomers, ethylene vinyl acetate (EVA), poly(vinyl acetals) (including acoustic grade poly(vinyl acetals)), polyurethanes, polyvinylchlorides, polyethylenes, polyolefin block elastomers, copolymers of a-olefins and a,β-ethylenically unsaturated carboxylic acid esters (e.g., ethylene methyl acrylate copolymers and ethylene butyl acrylate copolymers), silicone elastomers, polycarbonate resins, epoxy resins, nylon resins and combinations of two or more thereof. As used herein, the term “ionomer” means and denotes a thermoplastic resin containing both covalent and ionic bonds derived from ethylene/acrylic or methacrylic acid copolymers. In some embodiments, monomers formed by partial neutralization of ethylene-methacrylic acid copolymers or ethylene-acrylic acid copolymers with inorganic bases having cations of elements from Groups I, II, or III of the Periodic table, notably, sodium, zinc, aluminum, lithium, magnesium, and barium may be used. The term ionomer and the resins identified thereby are well known in the art, as evidenced by Richard W. Rees, “Ionic Bonding In Thermoplastic Resins”, DuPont Innovation, 1971, 2(2), pp. 1-4, and Richard W. Rees, “Physical 30 Properties And Structural Features Of Surlyn lonomer Resins”, Polyelectrolytes, 1976, C, 177-197. Other suitable ionomers are further described in European patent EP1781735, which is herein incorporated by reference.
Ethylene copolymers which may be used as an adhesive in the wire mounting layer are more fully disclosed in PCT Patent Publication No. WO2011/044417 which is hereby incorporated by reference. Such ethylene copolymers are comprised of ethylene and one or more monomers selected from the group of consisting of C1-4 alkyl acrylates, C1-4 alkyl methacrylates, methacrylic acid, acrylic acid, glycidyl methacrylate, maleic anhydride and copolymerized units of ethylene and a comonomer selected from the group consisting of C4-C8 unsaturated anhydrides, monoesters of C4-C8 unsaturated acids having at least two carboxylic acid groups, diesters of C4-C8 unsaturated acids having at least two carboxylic acid groups and mixtures of such copolymers, wherein the ethylene content in the ethylene copolymer preferably accounts for 60-90% by weight. A preferred ethylene copolymer adhesive layer includes a copolymer of ethylene and another a-olefin. The ethylene content in the copolymer accounts for 60-90% by weight, preferably accounting for 65-88% by weight, and ideally accounting for 70-85% by weight of the ethylene copolymer. The other comonomer(s) preferably constitute 10-40% by weight, preferably accounting for 12-35% by weight, and ideally accounting for 15-30% by weight of the ethylene copolymer. The ethylene copolymer adhesive layer is preferably comprised of at least 70 weight percent of the ethylene copolymer. The ethylene copolymer may be blended with up to 30% by weight, based on the weight of the adhesive layer, of other thermoplastic polymers such as polyolefins, as for example linear low density polyethylene, in order to obtain desired properties. Ethylene copolymers are commercially available, and may, for example, be obtained from DuPont under the trade-name Bynel®.
The wire mounting layer may further contain additives, fillers or reinforcing agents known within the art. Such exemplary additives include, but are not limited to, plasticizers, processing aides, flow enhancing additives, lubricants, pigments, titanium dioxide, calcium carbonate, dyes, flame retardants, impact modifiers, nucleating agents to increase crystallinity, antiblocking agents such as silica, thermal stabilizers, hindered amine light stabilizers (HALS), UV absorbers, UV stabilizers, anti-hydrolytic agents, dispersants, surfactants, chelating agents, coupling agents, adhesives, primers, reinforcement additives, such as glass fiber, and the like. There are no specific restrictions to the content of the additives and fillers in the wire mounting layer as long as the additives do not produce an adverse impact on the adhesion properties or stability of the layer.
A polymeric wire mounting layer 38 is shown in
The wires 42 and 44 are preferably conductive metal wires or metal foil strips. The metal wires are preferably comprised of metal selected from copper, nickel, tin, silver, aluminum, indium, lead, and combinations thereof. In one embodiment, the metal wires are coated with tin, nickel or a solder and/or flux material. Where the wires are coated with a solder and optionally with a flux, the wires can more easily be soldered to the back contacts of the solar cells as discussed in greater detail below. For example, aluminium wires may be coated with an aluminum/silver alloy that can be easily soldered using conventional methods. Where the wires are coated with solder, such as an alloy, the solder may be coated on the wires along their full length or only on the portions of the wires that will come into contact with the solar cell back contacts in order to reduce the amount of the coating material used. The conductive wires may be coated with an electrically insulating material such as a plastic sheath so as to help prevent short circuits in the solar cells when the wires are positioned over the back of an array of solar cells. Where the conductive wires are coated with an insulating material, the insulating material can be formed with breaks where the wires are exposed to facilitate the electrical connection of the wires to the back contacts of the solar cells. Alternatively, the insulating material may be selected such that it will melt or burn off when the wires are soldered or welded to the back contacts on the solar cells. The electrically conductive wires preferably each have a cross sectional area of at least 70 square mils along their length, and more preferably have a cross sectional area of at least 200 square mils along their length, and more preferably have a cross sectional area of 500 to 1200 square mils along their length. This wire cross section provides the strength, current carrying ability, low bulk resistivity, and wire handling properties desired for module efficiency and manufacturability. The electrically conductive wires may have any cross sectional shape, but ribbon shaped wires or tabbing wires having a width and thickness where the wire width is at least three times greater than the wire thickness, and more preferably where the wire width is 3 to 15 times the wire thickness, have been found to be especially well suited for use in the integrated back-sheet because wider wires makes it easier to align the wires with the back contacts of the solar cells when the wire mounting layer is applied to an array of back-contact solar cells.
The wire mounting layer 38 should be long enough to cover multiple solar cells, and is preferably long enough to cover all of the solar cells in a column of solar cells in the solar cell array, and may even be long enough to cover columns of solar cells in multiple solar cell arrays, as for example where the wires are applied to a long strip of the wire mounting layer in a continuous roll-to-roll process. For example, the wire mounting layer and the electrically conductive wires can be continuously fed into a heated nip where the wires are brought into contact with and adhered to the wire mounting layer by heating the wire mounting layer at the nip so as to make it tacky. Alternatively, the wire mounting layer can be die extruded with the wires fed into the wire mounting layer during the extrusion process. In another embodiment, the wires and the wire mounting layer can be heated and pressed in a batch lamination press to partially or fully embed the wires into the wire mounting layer. Pressure may be applied to the wires at the heated nip so as to partially or fully embed the conductive wires in the wire mounting layer. Preferably a surface of the wires remains exposed on the surface of the wire mounting layer after the wire is partially or fully embedded in the wire mounting material so that it will still be possible to electrically connect the wires to the back contacts of an array of back-contact solar cells.
Where the solar cells of the solar cell array will be connected in parallel, the full length wires can be used as shown in
In order to prevent electrical shorting of the solar cells, it may be necessary to apply an electrically insulating dielectric material between the conductive wires and the back of the solar cells of the back-contact solar cell array. This dielectric layer is provided to maintain a sufficient electrical separation between the conductive wires and the back of the solar cells. The dielectric layer, known as an interlayer dielectric (ILD), may be applied as a sheet over all of the wires and the wire mounting layer, or it may be applied as strips of dielectic material over only the electrically conductive wires. It is necessary to form openings in the ILD, as for example by die cutting or punching sections of the ILD, that will be aligned over the back contacts of the solar cells and through which the back contacts will be electrically connected to the conductive wires. Alternatively, the ILD may be applied by screen printing. The printing can be on the back side of the solar cells or on the wire mounting layer and wires, and can cover the entire area between the wire mounting layer and the solar cell array or just selected areas where the wires are present. A printed ILD layer can be UV cured after application so that the ILD will remain in place throughout module lamination and use. Where the ILD is printed, it may be printed only in the areas where the wires need to be prevented from contacting the back of the solar cells. The ILD can be applied to the wires and the wire mounting layer or it can be applied to the back of the solar cells before the conductive wires and the wire mounting layer are applied over the back of the solar cell array. Alternatively, the ILD may be applied as strips over the wires on the wire mounting layer or as strips over the portions of the back side of the solar cells over which the conductive wires will be positioned. The thickness of the ILD will depend in part on the insulating properties of the material comprising the ILD, but preferred polymeric ILDs have a thickness in the range of 5 to 500 microns, and more preferably 10 to 300 microns and most preferably 25 to 200 microns.
Where the conductive wires have a complete insulating coating or sheath, it may be possible to eliminate the ILD between the electrically conductive wires of the integrated back-sheet and the back side of the back-contact solar cells to which the integrated back-sheet is applied.
An ILD layer is shown in
An encapsulant layer is preferably provided between the ILD and the back side of the solar cells. Encapsulant layers are used to encase the fragile voltage-generating photoactive layer so as to protect it from environmental or physical damage and hold it in place in the photovoltaic module. Suitable polymer materials for the encapsulant layer typically possess a combination of characteristics such as high impact resistance, high penetration resistance, high moisture resistance, good ultraviolet (UV) light resistance, good long term thermal stability, adequate adhesion strength to other rigid polymeric sheets and cell surfaces, and good long term weatherability. The uncured polymers that may be used in the wire mounting layer described above can also be used in encapsulant layers, as for example, ethylene methacrylic acid and ethylene acrylic acid, ionomers derived therefrom, or combinations thereof. Exemplary comonomers that may be in the precursor acid copolymers include, but are not limited to, methyl acrylates, methyl methacrylates, butyl acrylates, butyl methacrylates, glycidyl methacrylates, vinyl acetates, and mixtures of two or more thereof. Suitable encapsulants include poly(vinyl butyral)(PVB), ionomers, ethylene vinyl acetate (EVA), poly(vinyl acetals) (including acoustic grade poly(vinyl acetals)), polyurethanes, polyvinylchlorides, polyethylenes, polyolefin block elastomers, copolymers of a-olefins and a,β-ethylenically unsaturated carboxylic acid esters (e.g., ethylene methyl acrylate copolymers and ethylene butyl acrylate copolymers), silicone elastomers, polycarbonate resins, epoxy resins, nylon resins and combinations of two or more thereof.
In one embodiment, the ILD is comprised of a PET polymer film that is coated with or laminated to an adhesive or an encapsulant layer such as an EVA film. During lamination, the adhesive or encapsulant layer adheres to the back to the solar cells and serves to seal and protect the cells while the polyester layer remains intact to serve as an insulator between the conductive wires and the back of the solar cells. Preferably the ILD and the encapsulant layer are comprised of a material that can be die cut or punched, or that can be formed with openings in it. The ILD may also be coated with an adhesive, such as a pressure sensitive adhesive, on the side of the ILD that will initially be contacted with the conductive wires and wire mounting layer. Suitable adhesive coatings on the ILD include pressure sensitive adhesives, thermoplastic or thermoset adhesives such as the ethylene copolymers discussed above, or acrylic, epoxy, vinyl butryal, polyurethane, or silicone adhesives. As shown in
a-6d illustrate in partial cross section the steps of one disclosed process for making a back-contact solar module with an integrated glass back-sheet.
a-6d show one photoactive solar cell 58 of the solar cell array, such as a crystalline silicon solar cell, provided on the encapsulant layer 56. The solar cell has all of its electrical contacts on the back side of the solar cell. The best known types of back-contact solar cells are metal wrap through (MWT), metal wrap around (MWA), emitter wrap through (EWT), emitter wrap around (EWA), and interdigitated back contact (IBC). Electrical conductors on the light receiving front side of the solar cell (facing the transparent front sheet) are connected through vias in the solar cell to back side conductive pads 60, while a back side conductive layer (not shown) is electrically connected to back side contact pads 61. The back contact pads are typically silver pads fired on the solar cells from a conductive paste of silver particles and glass frit in an organic carrier medium.
A small portion of a solder or of a polymeric electrically conductive adhesive is provided on each of the contact pads 60 and 61. The portions of solder or conductive adhesive are shown as balls 62 in
b shows the application of a back encapsulant layer 57 and an ILD 50, like the layer shown and described with regard to
As shown in
When a conductive adhesive is used to attach and electrically connect the conductive wires to the back contacts of the solar cells, the conductive adhesive may be heated above its softening temperature with the heated pins 65 as described above with regard to
This can be accomplished by making the wire mounting layer 38 more rigid by curing the wire mounting layer after the conductive wires are applied and adhered to the mounting layer and before the solar module lamination steps. Curing of the wire mounting layer is done by heating the wire mounting layer to a point above the cross linking temperature of a curable polymer that makes up the wire mounting layer in a range of 120 to 160° C. for a specified time of 5 to 60 minutes. As shown in
a and 8b illustrate an alternative process for holding the conductive wires in place over the solar cell back contacts where a conductive adhesive 62 is used to bond and electrically connect the solar cell back contacts and the conductive wires. The conductive adhesive 62 is selected to have a curing temperature that is sufficiently below the melting and curing temperature of the encapsulant such that conductive adhesive can be cured after the conductive wires are applied over the solar cell back contacts but before the solar module is laminated. For example, the conductive adhesive may be selected to have a curing temperature of from room temperature to about 100° C. so that the conductive adhesive can be melted and cured so as to firmly attach the conductive wires 42 and 44 to the back contacts 60 and 61, respectively, before the overall module is laminated. Subsequently, the module is laminated and cured at a higher temperature of about 100 to 180° C. during which the wire mounting layer 38 (as shown in
In an alternative embodiment, the ILD can serve as the both the wire mounting layer and as the ILD between the back side of the solar cells and the conductive wires. As shown in
The wire mounting layer is then cured, as for example by heating the wire mounting layer above a temperature where cross-linking occurs in the wire mounting layer. As shown in
A process for forming a back contact solar cell module with a solar cells connected in series by an integrated back-sheet is shown in
In
In
As shown in
f shows the application of bus connections 94, 96, and 98 on the ends of the solar module. The terminal buss 94 connects to the wires 44 that are over and will connect to the positive back-contacts on the solar cell at the bottom left hand side of the solar cell array. Likewise, the terminal buss 98 connects to the wires 44 that are over the negative back-contacts on the solar cell at the bottom right hand side of the solar cell array. Positive terminal buss 94 is connected to a positive lead 93 and the negative terminal buss 98 is connected to a negative lead 97. The intermediate buss connectors 96 connect the positive or negative back contacts at the top or bottom of one column of solar cells to the oppositely charged contacts at the same end of the adjoining column of solar cells. The terminal buss connections may alternately be extended through the “Z” direction out through the glass back sheet. This would eliminate the need for extra space at the ends of the module for running the buss wires to the junction box. Such “extra space” would reduce the packing density of the cells and reduce the electric power output per unit area of the module.
The solar cell array shown in
The photovoltaic module of
Air trapped within the laminate assembly may be removed using a nip roll process. For example, the laminate assembly may be heated in an oven at a temperature of about 80° C. to about 120° C., or preferably, at a temperature of between about 90° C. and about 100° C., for about 30 minutes. Thereafter, the heated laminate assembly is passed through a set of nip rolls so that the air in the void spaces between the photovoltaic module outside layers, the photovoltaic cell layer and the encapsulant layers may be squeezed out, and the edge of the assembly sealed. This process may provide a final photovoltaic module laminate or may provide what is referred to as a pre-press assembly, depending on the materials of construction and the exact conditions utilized. The pre-press assembly may then be placed in an air autoclave where the temperature is raised to about 120° C. to about 160° C., or preferably, between about 135° C. and about 160° C., and the pressure is raised to between about 50 psig and about 300 psig, or preferably, about 200 psig (14.3 bar). These conditions are maintained for about 15 minutes to about 1 hour, or preferably, about 20 to about 50 minutes, after which, the air is cooled while no more air is added to the autoclave. After about 20 minutes of cooling, the excess air pressure is vented and the photovoltaic module laminates are removed from the autoclave. The described process should not be considered limiting. Essentially, any lamination process known within the art may be used to produce the back contact photovoltaic modules with integrated back circuitry as disclosed herein.
If desired, the edges of the photovoltaic module may be sealed to reduce moisture and air intrusion by any means known within the art. Such moisture and air intrusion may degrade the efficiency and lifetime of the photovoltaic module. Edge seal materials include, but are not limited to, butyl rubber, polysulfide, silicone, polyurethane, polypropylene elastomers, polystyrene elastomers, block elastomers, styrene-ethylene-butylene-styrene (SEBS), and the like.
While the presently disclosed invention has been illustrated and described with reference to preferred embodiments thereof, it will be appreciated by those skilled in the art that various changes and modifications can be made without departing from the scope of the present invention as defined in the appended claims.
Number | Date | Country | |
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61579014 | Dec 2011 | US |