Solar module with back-contact photovoltaic cells interconnected in metal foil.

Abstract

We provide a solar module in which back-contact photovoltaic cells are interconnected using metal foil. [Solution] The photovoltaic module includes a metal foil defining an electrical contact, each of which is electrically isolated from other electrical contacts, and a plurality of back-contact photovoltaic cells superimposed on the metal foil and electrically connected via the plurality of electrical contacts. Each photovoltaic cell includes a first side configured to absorb light and a second side including a first conductive projection and a second conductive projection. One first conductive projection of the first photovoltaic cell is in direct electrical communication with one of the first electrical contacts, and one second conductive projection of the first photovoltaic cell is in direct electrical communication with one of the second electrical contacts.

Description

Technical Field

[0001] Cross - Reference to Related Applications This application claims the benefit of U.S. Patent Application No. 62 / 861,973, filed on June 14, 2019, which is hereby incorporated by reference in its entirety.

[0002] Statement of Government Interests This invention was made with government support under award number DE - EE0007538 from the U.S. Department of Energy. The government has certain rights in this invention.

[0003] The present invention relates to a photovoltaic module incorporating a back - contact photovoltaic cell, a metal foil electrical contact, and a method for connecting the electrical contact to the cell, particularly to the architecture (materials and layer sequence) and manufacturing method (fabrication method and procedure) of the photovoltaic module.

Background Art

[0004] Photovoltaic cells within a photovoltaic module typically use metals, such as in the form of fingers and busbars, to collect and transport photo - generated charge carriers with minimal resistance losses. However, the metal on the front, or sun - facing, side of the photovoltaic cell reduces the cell's efficiency by reflecting incident light. Back - contact photovoltaic cells are those in which most or all of their metal is on their back (ground - facing) side, but also include cells with negative and positive - polarity semiconductor regions on the back side, as well as those with one or the other polarity region on the front side and the metal contacting this region wrapping through vias in the cell to reach the back side.

[0005] There are several architectures and methods for interconnecting back-contact photovoltaic cells to form series and parallel electrical connections between adjacent cells in a module. In one example, a metal tubbing ribbon may be soldered to a busbar on the photovoltaic cell, which may extend along the length of the photovoltaic cell. In another example, the metal on the back of each photovoltaic cell may be thick enough to conduct current across the width of the solar cell with minimal resistance loss, and the soldering of the metal tubbing ribbon may be done at the edge of the cell. In yet another example, metal foil is attached to the photovoltaic cell with conductive adhesive. However, these architectures have disadvantages that increase costs and reduce efficiency, reliability, and energy yield. [Overview of the Initiative] [Means for solving the problem]

[0006] This disclosure relates to the design and manufacture of a photovoltaic module having a back-contact photovoltaic cell, including methods for arranging and fabricating materials, resulting in an inexpensive, highly efficient, and reliable photovoltaic module.

[0007] The photovoltaic modules described herein include a metal foil that transports current with minimal resistance. This metal foil avoids the need for soldering, tubbing ribbons, or thick metal coatings on photovoltaic cells, both of which have been used in back-contact photovoltaic modules to perform the same current transport function. The metal foil interconnects adjacent photovoltaic cells to form series and parallel electrical connections. The foil may be separated into segments so that only selected photovoltaic cells are interconnected, with others electrically isolated by openings between the foil segments. The metal foil makes low-resistance contact with the metal areas on the photovoltaic cells, facilitated by laser welding, thin adhesive (without metal particles or flakes), or any combination thereof. Attachment by laser welding or thin adhesive contributes to highly efficient and reliable metal-foil modules.

[0008] The photovoltaic module architectures described herein facilitate attachment by laser welding or thin adhesive, both of which require that areas of the metal foil be in close proximity to, or in direct contact with, the metal areas on the photovoltaic cell. In particular, embossing may raise the areas of the metal foil that contact the photovoltaic cell relative to the rest of the foil. Embossing is particularly useful when there is a sealing layer between the metal foil and the photovoltaic cell, which may have a thickness between 10 μm and 800 μm, because the sealing material may have openings that allow the embossed areas of the foil to pass through the sealing layer into mechanical contact with the photovoltaic cell. Embossing thus avoids the need for additional conductive materials, such as conductive adhesives, in perforating the sealing layer.

[0009] The methods described herein for manufacturing back-contact photovoltaic modules include stacking or piling up module materials and laminating the resulting stacks. Some implementation examples include embossing metal foil, applying a thin adhesive during stacking before placing photovoltaic cells into the module stack, and laser welding the foil to the cells after module lamination.

[0010] In a first general embodiment, the photovoltaic module includes a metal foil defining an electrical contact, each of which is electrically isolated from other electrical contacts, and a plurality of back-contact photovoltaic cells superimposed on the metal foil and electrically connected via the plurality of electrical contacts. Each photovoltaic cell includes a first side configured to absorb light and a second side including a first conductive projection and a second conductive projection. One first conductive projection of the first photovoltaic cell is in direct electrical communication with one of the first electrical contacts of the plurality, and one second conductive projection of the first photovoltaic cell is in direct electrical communication with one of the second electrical contacts.

[0011] An example implementation of the first general embodiment includes one or more of the following features:

[0012] The plurality of electrical contacts include pairs of adjacent electrical contacts, each separated by an opening that penetrates a metal foil. In some cases, a first conductive projection of the photovoltaic cell is laser-welded to one of the plurality of electrical contacts. In some cases, a first conductive projection of the photovoltaic cell is bonded to one of the plurality of electrical contacts with a non-conductive adhesive.

[0013] In some cases, the metal foil is a layer of metal foil. Each of the numerous electrical contacts is embossed such that each embossed portion of the numerous electrical contacts extends from the plane of the metal foil toward the multiple photovoltaic cells. Each embossed portion typically extends from the plane of the metal foil by a distance between 10 μm and 800 μm. A first conductive projection of a photovoltaic cell is in direct electrical communication with a first embossed portion of the numerous electrical contacts, and a first second conductive projection of a photovoltaic cell is in direct electrical communication with a second embossed portion of the electrical contacts.

[0014] In some cases, a sealing layer is provided between the metal foil and the multiple photovoltaic cells. Each of the multiple electrical contacts is embossed such that the embossed portion of each electrical contact extends from the plane of the metal foil and through the opening in the sealing layer toward the multiple photovoltaic cells. The thickness of the sealing layer and the distance each embossed portion extends from the plane of the metal foil are substantially the same.

[0015] The photovoltaic module may include a first outer layer and a second outer layer, where metal foil and multiple photovoltaic cells are disposed between the first and second outer layers. The photovoltaic module may also include a first sealing layer between the first outer layer and the multiple photovoltaic cells and a second sealing layer between the metal foil and the second outer layer.

[0016] In a second general embodiment, manufacturing a photovoltaic module includes the steps of: separating a metal foil into a plurality of electrically isolated electrical contacts; superimposing a plurality of photovoltaic cells, each having a first conductive projection and a second conductive projection, on the plurality of electrical contacts; and forming direct electrical couplings between one first conductive projection of a photovoltaic cell and one first electrical contact, and between one second conductive projection of a photovoltaic cell and one second electrical contact.

[0017] An example implementation of the second general embodiment may include one or more of the following features:

[0018] The step of separating the metal foil may include removing a portion of the metal foil (for example, forming an opening in the metal foil, such as an extension opening). Removing a portion of the metal foil may include laser ablation or mechanical grinding of a portion of the metal foil. The metal foil may be embossed before separating the metal foil into multiple electrical contacts. The step of embossing the metal foil generates an embossed portion for each of the multiple electrical contacts extending from the plane of the metal foil.

[0019] A second general embodiment may further include the steps of forming openings in an intermediate layer (e.g., a sealing layer) before embossing the metal foil, superimposing the metal foil and the intermediate layer, and embossing the metal foil through the openings in the intermediate layer. In some cases, one first conductive projection of the photovoltaic cell is laser-welded to one of the electrical contacts. The step of directly forming an electrical coupling between one first conductive projection of the photovoltaic cell and one of the electrical contacts may include bonding the one first conductive projection of the photovoltaic cell and one of the electrical contacts with a non-conductive adhesive. [Effects of the Invention]

[0020] The photovoltaic module described herein, together with a plurality of back-contact photovoltaic cells, can be interconnected with an inexpensive metal foil such as aluminum. As the spacing between the electrical connection points between the photovoltaic cell and the metal foil decreases, the amount of metal on the photovoltaic cell required to provide maximum resistance to charge carrier transport decreases, and the current is carried in the foil instead of the metal on the photovoltaic cell. The metal applied directly to the photovoltaic cell is typically more expensive than the metal used as the metal foil, and cost reduction of the disclosed photovoltaic module can be expected. A further advantage is to provide a low-resistance electrical interconnection between the plurality of back-contact photovoltaic cells and the metal foil with laser welding or a thin adhesive where electrical conduction occurs.

[0021] Details of one or more embodiments of the subject matter of this disclosure are set forth in the accompanying drawings and the description. Other features, aspects, and advantages of the subject matter will become apparent from the description, the drawings, and the claims.

Brief Description of the Drawings

[0022] [Figure 1] It is a cross-sectional view of a part of a photovoltaic module. [Figure 2] It is a cross-sectional view of a part of a photovoltaic module. [Figure 3] It is a cross-sectional view of a part of a photovoltaic module. [Figure 4] It is an exploded perspective view of a part of a photovoltaic module. [Figure 5] It is an exploded broken view of a part of a photovoltaic module. [Figure 6] It is an exploded broken view of a part of a photovoltaic module. [Figure 7] It is a top view of a metal foil having a first arrangement of openings and embossed portions. [Figure 8] It is a top view of the metal foil of FIG. 7 aligned and connected with a photovoltaic cell. [Figure 9] It is a top view of the photovoltaic cell of FIG. 8. [Figure 10]This is a top view of a metal foil having a second arrangement of openings and embossed portions. [Figure 11] This is a top view of the metal foil in Figure 10, which is aligned and connected to the photovoltaic cell. [Figure 12] Figure 11 is a top view of the photovoltaic cell. [Figure 13] This diagram illustrates the operation of the manufacturing sequence for photovoltaic modules. [Figure 14] The current density-voltage characteristics of the photovoltaic module are illustrated. [Figure 15] The relative performance of the photovoltaic modules is illustrated as a function of the time of exposure to moist heat. [Figure 16] The relative performance of the photovoltaic modules is illustrated as a function of the number of thermal cycles. [Figure 17] The relative performance of the photovoltaic modules is illustrated as a function of humidity-freeze cycle count. [Modes for carrying out the invention]

[0023] This disclosure relates to a photovoltaic module comprising, from its first (front or sun-facing) side to its second (back or ground-facing) side, a first outer layer, a first encapsulant, a plurality of back-contact photovoltaic cells, an intermediate layer, a plurality of metal foils separated into electrically isolated electrical contacts, a second encapsulant, and a second outer layer. Each of these layers or elements may be independent before lamination and may be combined together, either as a whole or in an intermediate stage, to form an aggregate module or laminate.

[0024] The first outer layer is formed from an optically transparent material such as glass or plastic, which can withstand the hail and wind-loading test specified in the solar module product certification test (e.g., IEC61215) when used in conjunction with other layers in the module. An example of suitable glass is heat-strengthened, low-Fe, soda-lime glass. The thickness of the first outer layer is typically in the range of 1 mm to 5 mm or 2 mm to 4 mm (e.g., 3 mm). The first outer layer may have an anti-reflective coating. In one example, the anti-reflective coating contains silica particles deposited by a sol-gel or vacuum deposition process.

[0025] The first (or table) encapsulant typically comprises one or more layers, such as an ethylene vinyl acetate (EVA) layer, a polyolefin (POE) layer, or both. Other suitable materials for the first encapsulant include materials capable of forming an optically transparent layer with a refractive index of approximately 1.5 during the lamination cycle (heating and pressurizing). The first encapsulant may be between 10 μm and 800 μm in thickness and may exhibit sufficient adhesion to the first outer layer and photovoltaic cells to prevent delamination after ultraviolet (UV), thermal, and moisture content tests as specified in solar module product certification tests (e.g., IEC61215).

[0026] A back-contact photovoltaic cell has positive and negative regions in a semiconductor that terminate in a metal region (cell metal coating or conductive protrusions) on a second surface (back or rear-facing side) of the cell. The cell metal coating may include a metal such as silver, aluminum, or copper, and may be screen-printed, vacuum-deposited, or plated. The positive and negative metal coating regions may be dispersed on the second surface of the cell according to a pattern. Examples of suitable patterns include dots, intersecting finger lines, and radial spoke arrangements. A dielectric layer may be coated across the positive and negative metal coating regions according to a pattern (e.g., by screen printing) to allow these regions to be connected together by a second layer of screen-printed or vacuum-deposited metal, by metal foil, or a combination thereof.

[0027] The intermediate layer typically comprises one or more polymer materials located between the second side (or back) of the photovoltaic cell and the metal foil. The intermediate layer may be continuous or discontinuous. A first example of a suitable intermediate layer includes one or more layers of encapsulant or adhesive such as ethylene vinyl acetate (EVA) or polyolefin (POE) (e.g., between 10 μm and 800 μm in thickness). A second example of a suitable intermediate layer includes a three-layer encapsulant stack (e.g., 10 μm to 100 μm) of solid polymer sheets such as polyethylene terephthalate (PET), polyvinylidene fluoride (PVDF), or polytetrafluoroethylene (PTFE) that do not melt at the lamination temperature, sandwiched between two encapsulant layers (e.g., each with a thickness of 10 μm to 100 μm). A third example of a suitable intermediate layer includes a layer of polymer material (e.g., 1 μm to 50 μm thick) that is liquid at room temperature and cures at the lamination temperature (e.g., 130°C to 160°C), which is applied to cells or foil electrical contacts by screen printing, jet dispensing, blade coating, etc.

[0028] The intermediate layer may be patterned. In one example, a suitable pattern includes perforations or openings in areas where electrical communication or direct contact is to be made between conductive protrusions from the photovoltaic cell (e.g., metal coating, fingers, busbars) and the metal foil. Patterning of the intermediate layer forming the perforations or openings may be achieved using a laser, die-cutting, or other subtractive process. In some cases, the intermediate layer includes openings in which the metal foil is electrically coupled to the conductive protrusions of the photovoltaic cell during the lamination process.

[0029] The metal foil is separated into numerous electrical contacts. Each electrical contact is configured to be in direct electrical communication or coupling with a conductive projection of the back-contact photovoltaic cell in the photovoltaic module. As used herein, “direct electrical communication” or “direct electrical coupling” means that charge flows directly between the conductive projection of the photovoltaic cell and the metal foil in the absence of any intervening conductive material (e.g., in the absence of a conductive adhesive containing metal particles). The appropriate thickness of the metal foil is typically in the range of 20 μm to 100 μm (e.g., 40 μm to 70 μm). Examples of suitable metals for the metal foil include copper, aluminum, or any combination thereof (e.g., copper-coated aluminum, copper or aluminum coated with an antioxidant or adhesion-promoting layer).

[0030] In some cases, the metal foil is embossed or otherwise deformed into a three-dimensional shape such that portions of the metal foil intended to contact the conductive protrusions of the photovoltaic cell extend from portions of the metal foil intended to be isolated from the metal regions on the photovoltaic cell (and are not in the same plane as them). In particular, the embossed portions may protrude through perforations in the interlayer, resulting in the embossed portions of the metal foil being in direct electrical communication (e.g., direct contact) with the conductive protrusions of the photovoltaic cell. The flat (unembossed) portions of the metal foil may be isolated from the photovoltaic cell by the interlayer. The embossed portions of the metal foil may have the same or similar spatial pattern as some or all of the conductive protrusions on the photovoltaic cell, or they may have different patterns. In other cases, the metal foil is flat (e.g., planar) and in direct electrical communication everywhere with the photovoltaic cell, especially when used in conjunction with an interlayer that is liquid at room temperature and hardens during the lamination cycle, and there is no dielectric isolation layer on the cell.

[0031] Three-dimensional forming of metal foil can be achieved by several methods. A first method involves embossing an independent foil using a mandrel or a single-sided or double-sided embossing die before attaching the foil (by lamination or other means) to an intermediate layer or a second sealant. A second method involves attaching an independent foil to an intermediate layer (by lamination or other means) before forming, patterning the intermediate layer, and embossing the metal foil through the perforated areas of the intermediate layer using a mandrel or a single-sided or double-sided embossing die. A third method involves patterning the intermediate layer, embossing an independent metal foil through the perforated areas of the intermediate layer using a mandrel or a single-sided embossing die, and attaching the formed metal foil (by lamination or other means) to the patterned intermediate layer.

[0032] An embossed or flat (e.g., planar) metal foil may be separated into multiple electrical contacts in one of several stages in the module manufacturing process. The separation is such that sufficient spacing is achieved between them so that the electrical contacts are electrically isolated from one another. In one example, after the metal foil has been attached to the intermediate layer, a ribbon having a width of about 1 mm to about 5 mm is removed from the metal foil by laser ablation, mechanical crushing or other means, so that the electrically isolated electrical contacts of the coplanar foil form electrical contacts with an opening of 1 mm to 5 mm between their edges.

[0033] The isolation may be performed so that the metal foil is separated into multiple electrical contacts having any desired shape, but a preferred shape facilitates the interconnection of photovoltaic cells within the module. In particular, after the metal foil is connected to the photovoltaic cell, the isolation of the metal foil provides a first electrical contact that electrically connects the negative polarity region of the cell and is electrically isolated from the positive polarity region of the cell, and a second electrical contact that electrically connects the positive polarity region of the cell and is electrically isolated from the negative polarity region of the cell. Additionally, to form a series interconnection, the foil isolation may be configured so that the positive polarity region of the photovoltaic cell is electrically connected to the negative polarity region of the next cell in the string. The isolation of the metal foil electrical contacts provides electrical isolation from other adjacent cells. The isolation of the metal foil electrical contacts provides electrical isolation from adjacent strings, and the string ends are oriented to allow connections that bypass diodes in the junction box.

[0034] The second (or back) sealant typically comprises one or more layers, such as an EVA layer, a POE layer, or both. The thickness of the second sealant is typically in the range of 10 μm to 800 μm. The second sealant adheres to the metal foil and the second outer layer. The adhesion is sufficient to prevent delamination after UV, thermal, and moisture content tests as specified in the solar module product certification tests (e.g., IEC61215). The second outer layer may be optically transparent or optically opaque (e.g., white, black, or transparent), at least partially depending on the foil-photovoltaic cell interconnection method used. The second outer layer may define one or more openings. A junction box may be positioned adjacent to each of the one or more openings. Each junction box provides electrical connection points between the electrical contacts of the metal foil, bypass diodes, and external leads according to the photovoltaic module interconnection code. The transition between the external cable and the electrical contacts can be achieved in several ways, such as by soldering one end of a copper bushing wire to a component inside the junction box and connecting the other end to the end electrical contact of a metal foil (for example, by the same method used to connect the foil to the cell, or by another method such as resistance welding).

[0035] The photovoltaic module may be assembled in a manner similar to that used to assemble other types of photovoltaic modules, particularly those with conductive backsheets or metal foil electrical contacts. The second outer layer, second sealant, metal foil, and intermediate may be stacked or applied as appropriate, with their edges aligned. The metal foil may be embossed and separated in the manner described above, and may already be attached to the second sealant and second outer layer, or to a patterned intermediate layer, or a combination thereof. The photovoltaic cells may be placed on the intermediate layer in appropriate positions for their interconnection, for example, by a pick-and-place robot or other suitable means.

[0036] Figure 1 is a cross-sectional view of the photovoltaic module 100. The photovoltaic module 100 has a first outer layer 102, a first encapsulant 104, a back contact photovoltaic cell 106, an intermediate layer 108, a metal foil 110, a second encapsulant 112, and a second outer layer 114. The intermediate layer 108 is patterned and perforated. The metal foil 110 is embossed through the perforations in the intermediate layer. The second outer layer 114 is optically transparent.

[0037] The photovoltaic cell 106 can be placed on an intermediate layer 108, and the first sealant 104 and the first outer layer 102 are stacked on top of the photovoltaic cell. The stack of materials is heated and pressurized to form a laminate. Alternatively, any other suitable process may be used to remove bubbles from the photovoltaic module 100, melt and crosslink or cure the sealant or adhesive layer, and bring the embossed area of ​​the metal foil 110 into closer contact with the conductive protrusions 116 of the photovoltaic cell 106. Direct electrical communication between the metal foil 110 and the conductive protrusions 116 on the photovoltaic cell 106 is achieved (e.g., after lamination) using a laser to weld the two metals through the second outer layer 114 of the photovoltaic module 100 to form a laser weld 118. The laser may have any wavelength that is not significantly absorbed by the second outer layer 114 and the second sealant 112. Examples of suitable lasers include millisecond Nd:YAG lasers capable of supplying 30 mJ to 150 mJ per pulse, fiber optic lasers operating at frequencies between 10 kHz and 4 MHz, or any other laser that allows the metal of the foil electrical contact to become an alloy with the metal on the cell.

[0038] The photovoltaic module 100 may include an edge seal around at least one edge of the module, a frame mounted around at least one edge of the module, a mounting rail mounted adjacent to a second outer layer of the module, a junction box mounted on the second outer layer, or any combination thereof.

[0039] Figure 2 is a cross-sectional view of the photovoltaic module 200. The photovoltaic module 200 has a first outer layer 202, a first sealant 204, a photovoltaic cell 206, an intermediate layer 208, a metal foil 210, a second sealant 212, and a second outer layer 214. The intermediate layer 208 is a patterned sealant layer defining perforations. The metal foil 210 is embossed through perforations in the intermediate layer 208. The intermediate layer 208 also includes a layer of adhesive between the embossed areas of the metal foil 210 and the conductive protrusions 216 on the photovoltaic cell 206 to which the embossed metal foil 210 connects. The adhesive may be a room temperature liquid that cures at the lamination temperature (130°C to 160°C), and may be applied to the embossed areas of the metal foil 210 or to the conductive protrusions 216 on the photovoltaic cell 206. The adhesive may be applied to the metal foil 210 or the photovoltaic cell 206 by any suitable means such as screen printing and jet dispensing. The adhesive may be any material capable of bonding to the metal foil 210 and the conductive protrusions 216 of the photovoltaic cell 206.

[0040] A suitable adhesive is typically an electrical insulator and is typically thin enough in at least some areas to allow direct electrical communication (e.g., low-resistance electrical conduction) between the conductive protrusions 216 of the photovoltaic cell 206 and the metal foil 210. In some cases, there is direct contact between the conductive protrusions 216 and the metal foil 210. The adhesive may be, for example, epoxy, acrylate, or silicone, or any other suitable material. The surface morphology of the metal foil 210 may be modified by chemical or physical abrasion or by the application of particles (e.g., by sintering) according to a pattern or across the entire surface to create porous surface areas that facilitate bonding of the adhesive layer.

[0041] After the adhesive is applied to the desired area and the photovoltaic cell 206 is placed on the intermediate layer 208, the first sealant 204 and the first outer layer 202 may be stacked on the photovoltaic cell 206. The stack of materials may then be heated and pressurized to form a laminate. Alternatively, any other suitable process may be used to remove air bubbles from the photovoltaic module 200, melt and crosslink or cure the sealant or adhesive layer, and bring the embossed area of ​​the metal foil 210 into closer contact with the conductive protrusions 216 of the photovoltaic cell 206.

[0042] The photovoltaic module 200 may include an edge seal around at least one edge of the module, a frame mounted around at least one edge of the module, a mounting rail mounted adjacent to a second outer layer of the module, a junction box mounted on the second outer layer, or any combination thereof.

[0043] Figure 3 is a cross-sectional view of the photovoltaic module 300. The photovoltaic module 300 has a first outer layer 302, a first sealant 304, a photovoltaic cell 306, an intermediate layer 308, a metal foil 310, a second sealant 312, and a second outer layer 314. The intermediate layer 308 includes a layer of adhesive. The metal foil 310 is planar (i.e., not embossed). The photovoltaic cell 306 includes a dielectric layer covering a region of a given polarity that is not intended to be directly or electrically connected to the metal foil 310. The adhesive may be a room-temperature liquid that cures at the lamination temperature (130°C to 160°C), and it may be applied to the second side of the metal foil 310 or the photovoltaic cell 306 to cover part or all of the surface to which it is applied. The adhesive may be applied by, for example, screen printing, blade application, jet dispensing, or any other suitable method. The adhesive may be any material capable of bonding to the metal foil 310 and the conductive protrusions 316 of the photovoltaic cell 306.

[0044] A suitable adhesive is typically an insulator, but the adhesive layer can be thin enough in at least some areas so that low-resistance electrical conduction (direct electrical communication) can occur between the conductive protrusions 316 of the photovoltaic cell 306 and the metal foil 310. The adhesive may be, for example, epoxy, acrylate, or silicone, or any other suitable material. The surface morphology of the metal foil 310 may be modified by following a pattern, across the surface, by chemical or physical abrasion, or by the application of particles (e.g., by sintering) to create porous surface areas that facilitate bonding of the adhesive layer.

[0045] After the adhesive is applied and the photovoltaic cell 306 is placed on the intermediate layer 308, the first sealant 304 and the first outer layer 302 may be stacked on top of the photovoltaic cell 306. The stack of materials may then be heated and pressurized to form a laminate. Alternatively, any other suitable process may be used to remove air bubbles from the photovoltaic module 300, melt and crosslink or cure the sealant or adhesive layer, and bring the metal foil 310 into closer contact with the conductive protrusions 316 of the photovoltaic cell 306.

[0046] If the second outer layer 314 of the photovoltaic module 300 is optically transparent after lamination, a robust electrical connection between the electrical contacts of the metal foil and the conductive protrusions of the photovoltaic cell may optionally be formed using a laser that welds the two metals through the transparent second outer layer of the module. The laser may have any wavelength that is not significantly absorbed by the second outer layer 314 and the second sealant 312. Examples of suitable lasers include a millisecond Nd:YAG laser capable of supplying 30 mJ to 150 mJ per pulse, an optical fiber laser operating at frequencies between 10 kHz and 4 MHz, or any other laser that allows the metal of the electrical contacts to be alloyed with the metal on the cell.

[0047] Figure 4 is an exploded view of a portion of the photovoltaic module 400. The photovoltaic module 400 includes a first outer layer 402, a first encapsulant 404, a back contact photovoltaic cell 406, an intermediate layer 408, a metal foil 410, a second encapsulant 412, and a second outer layer 414. The metal foil 410 is separated along openings 416 to electrically isolated electrical contacts 418. Figure 4 shows a portion of the photovoltaic module 400 during stacking before lamination. After lamination, the encapsulant is compressed and bonded together with the adjacent layers.

[0048] Figure 5 is an exploded section of a portion of a photovoltaic module 500, including a back-contact photovoltaic cell 506, an intermediate layer 508, and a metal foil 510. The metal foil 510 is separated along an opening 516 to electrically isolated planar electrical contacts 518. An embossed portion 520 extends from the electrical contacts 518. The intermediate layer 508 includes a perforation or opening 522 configured to allow the embossed portion 520 to form direct electrical communication (e.g., direct contact) with conductive projections extending from the photovoltaic cell 506.

[0049] Figure 6 is an exploded section of a portion of a photovoltaic module 600, including a back-contact photovoltaic cell 606, an intermediate layer 608, and a metal foil 610. The metal foil 610 is separated along an opening 616 to electrically isolated planar electrical contacts 618. An embossed portion 620 extends from the electrical contacts 618. The intermediate layer 608 includes a perforation or opening 622 configured to allow the embossed portion 620 to form direct electrical communication with conductive protrusions extending from the photovoltaic cell 606 through a non-conductive adhesive 624.

[0050] Figure 7 is a top view of a metal foil 710 having a first arrangement of an opening 716, an electrical contact 718, and an embossed portion 720. Figure 8 is a top view of the metal foil 710 of Figure 7 aligned and connected with four photovoltaic cells 806. Figure 9 is a top view of the photovoltaic cells 806 of Figure 8. Enlarged sections illustrate the busbars 900, fingers 902, and dielectric regions 904.

[0051] Figure 10 is a top view of the metal foil 1010 having a second arrangement of the opening 1016 and the embossed portion 1020. Figure 11 is a top view of the metal foil 1010 of Figure 10 aligned and connected with four photovoltaic cells 1106. Figure 12 is a top view of the photovoltaic cell 1106 of Figure 11 illustrating the conductive projection 1200.

[0052] Figure 13 illustrates the operation of the manufacturing sequence for a photovoltaic module. At 1302, perforations are formed in the intermediate (sealing) layer. At 1304, the metal foil is embossed through the sealing layer, and the metal foil and sealing layer are bonded (e.g., glued). At 1306, the metal foil is separated to form electrical contacts, each electrical contact being electrically isolated from the other electrical contacts. At 1308, a second sealant and a second outer layer are superimposed on the metal foil and intermediate layer. At 1310, a photovoltaic cell is placed on the intermediate layer. A bushing ribbon is screwed through the openings in the foil, the second sealant, and the second outer layer. At 1312, the first sealing layer and the first outer layer are superimposed on the photovoltaic cell. At 1314, the assemblies (or stacks) formed at 1312 are stacked. At 1314, direct electrical communication is achieved between the conductive protrusions of the photovoltaic cell and the metal foil by laser welding. Additional steps include trimming the edges of the laminate, placing the trimmed laminate into the frame, and applying sealant. The photovoltaic module is then coupled to a junction box, and the photovoltaic module may be tested.

[0053] Figure 14 illustrates the current density-voltage characteristics of the photovoltaic module. Figure 15 illustrates the relative performance of the photovoltaic module as a function of the time of moist heat exposure. Figure 16 illustrates the relative performance of the photovoltaic module as a function of the number of thermal cycles. Figure 17 illustrates the relative performance of the photovoltaic module as a function of humidity-freeze cycle number.

[0054] While this disclosure includes details of many specific embodiments, these should be interpreted not as limitations on the scope of the subject matter or the scope of the claims, but rather as descriptions of features that may be specific to particular embodiments. Features described in this disclosure in the context of separate embodiments can be combined and implemented in a single embodiment. Conversely, various features described in the context of a single embodiment can be implemented separately in multiple embodiments or in any suitable subcombination. Furthermore, while the aforementioned features are described as acting in a combination and may be initially claimed as such, one or more features from the claimed combination may, in some cases, be removed from that combination, and the claimed combination may be a subcombination or a variation of a subcombination.

[0055] A specific embodiment of the subject is described. Other embodiments, modifications, and substitutions of the described embodiment are within the scope of the following claims, as will be apparent to those skilled in the art. Although actions are depicted in a specific order in the drawings or claims, this should not be understood as requiring that such actions be performed in a specific order or sequence as illustrated, or that all illustrated actions be performed (some of which may be considered optional), in order to achieve the desired result.

[0056] Therefore, the embodiments described above do not limit or restrict this disclosure. Other variations, substitutions, and modifications are also possible without departing from the spirit and scope of this disclosure.

[0057] [1] A number of electrical contacts, each electrically isolated from other electrical contacts, comprising a metal foil defining the electrical contacts, A plurality of back-contact photovoltaic cells superimposed on the metal foil and electrically connected via the plurality of electrical contacts, each of which is A first side configured to absorb light, A photovoltaic cell comprising a second side having a first conductive projection and a second conductive projection, The first conductive projection of the photovoltaic cell is in direct electrical communication with one of the first electrical contacts, and the second conductive projection of the photovoltaic cell is in direct electrical communication with one of the second electrical contacts. Photovoltaic module. [2] The photovoltaic module according to [1], wherein the number of electrical contacts includes pairs of adjacent electrical contacts, each separated by an opening that penetrates the metal foil. [3] The photovoltaic module according to [1], wherein one of the first conductive protrusions of the photovoltaic cell is laser-welded to one of the first electrical contacts of the plurality of electrical contacts. [4] The photovoltaic module according to [1], wherein one of the first conductive protrusions of the photovoltaic cell is bonded to one of the first of the plurality of electrical contacts with a non-conductive adhesive. [5] The photovoltaic module according to [1], wherein each of the plurality of electrical contacts is embossed such that the embossed portion of each of the plurality of electrical contacts extends from the plane of the metal foil toward the plurality of photovoltaic cells. [6] The photovoltaic module according to [1], wherein each embossed portion extends from the plane of the metal foil by a distance between 10 μm and 800 μm. [7] The photovoltaic module according to [1], wherein one first conductive projection of the photovoltaic cell is in direct electrical communication with one first embossed portion of the plurality of electrical contacts, and one first second conductive projection of the photovoltaic cell is in direct electrical communication with one second embossed portion of the electrical contacts. [8] The photovoltaic module according to [1], further comprising a sealing layer between the metal foil and the plurality of photovoltaic cells. [9] The photovoltaic module according to [8], wherein each of the plurality of electrical contacts is embossed such that the embossed portion of each of the plurality of electrical contacts extends toward the plurality of photovoltaic cells from the plane of the metal foil and through the opening in the sealing layer.

[10] The photovoltaic module according to [9], wherein the thickness of the sealing layer and the distance each embossed portion extends from the plane of the metal foil are substantially the same.

[11] The photovoltaic module according to [1], further comprising a first outer layer and a second outer layer, wherein the metal foil and the plurality of photovoltaic cells are disposed between the first outer layer and the second outer layer.

[12] The photovoltaic module according to [1], further comprising a first sealing layer between the first outer layer and the plurality of photovoltaic cells and a second sealing layer between the metal foil and the second outer layer.

[13] A method for manufacturing a photovoltaic module, The metal foil is separated into multiple electrical contacts, and each electrical contact is electrically isolated from each of the other electrical contacts, in the step of... A step of superimposing a plurality of photovoltaic cells above the plurality of electrical contacts, wherein each photovoltaic cell is provided with a first conductive projection and a second conductive projection, A method comprising the steps of forming a direct electrical coupling between one first conductive projection of the photovoltaic cell and one first electrical contact, and between one second conductive projection of the photovoltaic cell and one second electrical contact.

[14] The method according to

[13] , wherein the step of separating the metal foil includes removing a portion of the metal foil.

[15] The method according to

[14] , wherein removing the portion of the metal foil is to laser ablate or mechanically grind the portion of the metal foil.

[16] The method according to

[13] , further comprising the step of embossing the metal foil before separating the metal foil into the plurality of electrical contacts.

[17] The method according to

[16] , wherein the step of embossing the metal foil generates the embossed portion of the plurality of electrical contacts extending from the plane of the metal foil.

[18] The step of forming an opening in the intermediate layer before embossing the metal foil, The steps include superimposing the metal foil and the intermediate layer, The steps include: embossing the metal foil through the opening in the intermediate layer; The method described in

[17] , further including the method described in

[17] .

[19] The method according to

[16] , further comprising the step of laser welding one of the first conductive protrusions of the photovoltaic cell to one of the first electrical contacts.

[20] The method according to

[13] , wherein the step of forming the direct electrical coupling between the first one first conductive projection of the photovoltaic cell and the first one of the electrical contacts is to bond the first one first conductive projection of the photovoltaic cell and the first one of the electrical contacts with a non-conductive adhesive. [Explanation of Symbols]

[0058] 100 Photovoltaic Modules 102 First outer layer 104 First sealing agent 106 Back-contact photovoltaic cell 108 Middle Class 110 Metal foil 112 Second sealing agent 114 Second outer layer 116 Conductive protrusion 118 Laser welding 200 Photovoltaic Modules 202 First outer layer 204 First sealant 206 Photovoltaic Cells 208 Middle Class 210 Metal foil 212 Second sealing agent 214 Second outer layer 216 Conductive protrusion 300 Photovoltaic Modules 302 First outer layer 304 First sealant 306 Photovoltaic Cells 308 Middle Class 310 Metal foil 312 Second sealing agent 314 Second outer layer 316 Conductive protrusion 400 Photovoltaic Modules 402 First outer layer 404 First sealant 406 Back-contact photovoltaic cell 408 Middle Class 410 Metal foil 412 Second sealing agent 414 Second outer layer 416 Aperture 418 Electrical contacts 500 Photovoltaic Modules 506 Back-contact photovoltaic cell 508 Middle Class 510 Metal foil 516 Aperture 518 Planar electrical contact 520 Embossed part 522 Perforation, opening 600 Photovoltaic Modules 606 Back-contact photovoltaic cell 608 Middle layer 610 Metal foil 616 Aperture 618 Planar electrical contact 620 Embossed part 622 Perforation, opening 624 Non-conductive adhesive 710 Metal foil 716 Aperture 718 Electrical contacts 720 Embossed part 806 Photovoltaic Cell 900 Bus Bar 902 Finger 904 Dielectric Region 1010 Metal foil 1016 Aperture 1020 Embossed part 1106 Photovoltaic cell 1200 Conductive protrusion

Claims

1. Multiple electrical contacts, each electrically isolated from other electrical contacts, comprising a metal foil defining the electrical contacts, A plurality of back-contact photovoltaic cells superimposed on the metal foil and electrically connected via the plurality of electrical contacts, each of which is A first side configured to absorb light, It comprises a second side having a first conductive projection and a second conductive projection, A plurality of back-contact photovoltaic cells wherein the first conductive projection of the first photovoltaic cell of the plurality of back-contact photovoltaic cells is in direct electrical communication with the embossed portion of the first electrical contact of the plurality of electrical contacts, and the second conductive projection of the first photovoltaic cell of the plurality of back-contact photovoltaic cells is in direct electrical communication with the embossed portion of the second electrical contact of the electrical contact, The intermediate layer between the metal foil and the plurality of back-contact photovoltaic cells Equipped with, Each of the plurality of electrical contacts is embossed such that the embossed portion of each of the plurality of electrical contacts is raised relative to the rest of the metal foil and extends through the opening in the intermediate layer toward the plurality of back contact photovoltaic cells. The width of the first conductive protrusion is smaller than the width of the embossed portion of the first electrical contact, and the width of the second conductive protrusion is smaller than the width of the embossed portion of the second electrical contact. Photovoltaic module.

2. The photovoltaic module according to claim 1, wherein the plurality of electrical contacts include pairs of adjacent electrical contacts, each separated by an opening that penetrates the metal foil.

3. The photovoltaic module according to claim 1, wherein the first conductive projection of the first photovoltaic cell is joined to the first electrical contact without using an adhesive.

4. The photovoltaic module according to claim 1, wherein the first conductive projection of the first photovoltaic cell is bonded to the first electrical contact with a non-conductive adhesive.

5. The photovoltaic module according to claim 1, wherein each embossed portion extends from the plane of the metal foil by a distance between 10 μm and 800 μm.

6. The photovoltaic module according to claim 1, wherein the thickness of the intermediate layer and the distance of the embossed portion extending from the plane of the metal foil are the same.

7. The photovoltaic module according to claim 1, further comprising a first outer layer and a second outer layer, wherein the metal foil and the plurality of back-contact photovoltaic cells are disposed between the first outer layer and the second outer layer.

8. The photovoltaic module according to claim 7, further comprising a first sealing layer between the first outer layer and the plurality of back-contact photovoltaic cells, and a second sealing layer between the metal foil and the second outer layer.

9. The photovoltaic module according to claim 1, wherein the metal foil contains aluminum.

10. The photovoltaic module according to claim 1, wherein the thickness of the metal foil is in the range of 20 μm to 100 μm.

11. The photovoltaic module according to claim 1, wherein the thickness of the metal foil is in the range of 40 μm to 70 μm.

12. The photovoltaic module according to claim 1, wherein the metal foil connects the positive polarity region of the first photovoltaic cell of the plurality of back-contact photovoltaic cells to the negative polarity region of the second photovoltaic cell of the plurality of back-contact photovoltaic cells.

Images