DE102012201888A1 - Solar module has wiring film formed with recesses at distant from center of solar cell such that distortion of substrate during temperature changes is reduced while temperature is reduced in relation to assembly temperature - Google Patents

Abstract

The solar module (1) has planar insulating substrate that are interconnected to external connecting solar cells (3) over conductive track. The connecting contacts are provided for interconnection only one of two surfaces of solar cells. The insulating substrate is coated with isolating wiring film (5). The recesses (15) are formed in wiring film at the distant from the center of the respective solar cell such that distortion of the substrate during temperature changes is reduced while the temperature is reduced in relation to assembly temperature.

Description

The invention relates to a solar module with a plurality of arranged on a flat insulating support and designed via interconnects or connected to an external terminal solar cells, which have connection contacts for interconnection exclusively on one of its two surfaces, which represents the back in the use position, and at their Rear connection contacts are connected at connection points with the interconnects. It further relates to a cell connector means for producing such a solar module.

State of the art

Increased use of renewable energy sources, as part of international efforts to reduce the carbon footprint of fossil energy production and avert the risk of nuclear energy exploitation, has led to a significant increase in the use of solar energy in a number of countries. Regardless of the fundamentally considerable potential of large-scale solar thermal plants, the direct conversion of solar energy into electricity (photovoltaic) is still the carrier of this development, and solar cells based on (one) crystalline silicon dominate here because of their relatively high energy yield.

In photovoltaics, solar cells are connected in series for solar module production. For solar cell connectors (cell tabs, Ribbon, Soldersleeve etc.) are usually soldered to the busbars of the solar cells. The solar cell connector is guided from the light-active cell side to the back of the adjacent cell. Due to the process characteristics, the connector dimensions are limited in thickness, although for physical reasons, thicker connectors are desirable. This cell connection leads to losses in the light output of the solar cells due to shading by the solar cell connector.

In order to increase the light output of crystalline solar cells, the cell contacts in novel cell types (MWT, EWT, IBC, etc.) are moved from the photoactive side to the back of the cell. This has the consequence that contacts are distributed on the entire back and must be contacted with different potentials. The contacting process is therefore subject to much more critical requirements. In addition, processes suitable for mass production must meet the increasing price pressure in the photovoltaic industry. For the novel back contact cells, an interconnection on the back can be implemented by means of a foil. An important advantage of this connection technique lies in the better electrical conductivity due to a higher connector cross-section.

The use of films as Verschaltungssträger for solar modules is basically known, such as from US 2009/0065043 A1 , From the DE 10 2005 039 052 A1 a solar module is known, which is formed using embedded in a plate or foil-like carrier cell connectors. The cell connectors are interconnected electrically with interconnects which are applied to a suitable carrier material. The DE 10 2008 020 383 A1 teaches a method and a device for attaching solar cells to a conductive foil by wave soldering, wherein a defined wetting with flux and solder is ensured by special embodiments of each associated with a solder joint openings.

1 shows the basic structure of a solar module in back-to-back contact technology with a carrier on which the cell connectors are applied as interconnects. The illustration is purely schematic and in no way true to scale. A solar module 1 is made of solar cells 3 formed by means of a Leitbahnstruktur 7 interconnected with each other. In the example shown, the solar module comprises a solar cell array of 16 solar cells, which are mounted on a rear carrier 9a made of insulating material are placed. A front laminating film 9b becomes in this structure - usually with the inclusion of an additional (not shown) film between the solar cells 3 and the back carrier 9a - directly with the backside foil 9a laminated, and the construction is made by a front glass 11 completed.

Such structures have basically proven both technologically and in use. However, problems can occur due to the different thermal expansion coefficients of the solar cells on the one hand and the wiring film on the other hand, which can lead to ripples (Warpage) or to a delay of the solar module network. Specifically, it is important here that the solar cells have a lower coefficient of thermal expansion than conventional substrates (wiring foils) and the latter, therefore, starting from a stress-free temperature at a mounting of more than 100 ° C, when operating at room temperature or up to minus temperatures stronger contracts as the solar cell. These effects can adversely affect the operating parameters and reliability of the solar module.

Disclosure of the invention

With the invention, a solar module with the features of claim 1 is provided. Furthermore, a cell connector means for producing such a solar module with the features of Claim 9 provided. Advantageous further developments of the inventive concept are the subject of the respective dependent claims.

The invention is based on the idea of providing means for compensating for the different thermal expansion of the two components in the mechanically selectively firmly connected state in the network between the solar cells and the wiring film or cell connector structure. It further includes the idea of assigning these balancing means locally to the connection points or arranging between connection points. Furthermore, the invention includes the idea of creating these compensating means by means of a special embodiment of the wiring foil or cell connector structure. Finally, the invention results in the idea of providing recesses, cuts or perforations at least at the connecting points far from the center of the respective solar cell, which are designed in such a way that distortions of the carrier with temperature changes, u. a. in reducing the temperature compared to the mounting temperature, can be reduced.

In special embodiments, the recesses have Kreisabschnitts- or sickle shape. In other embodiments, it may be provided that the recesses have a triangular or trapezoidal shape or at least the edge of the recess remote from the respective connection point spans a triangle or trapezoid. If cuts or merely predetermined breaking points (perforations) are provided in the wiring foil or cell connector structure instead of recesses, they can be designed in a linear, curved, angled, zigzag-shaped, wavy, spiral or other form adapted to the specific application.

In another embodiment, recesses, cuts or perforations are provided at all connection points, optionally with the exception of one or less central connection points. In an embodiment which is particularly suitable for solar modules which are mounted at a relatively high temperature, recesses, cuts or perforations are provided in particular between the respective connection point and the center of the respective solar cell. In solar module structures, in which the invention is particularly used to avoid mechanical stresses during thermal cycling, the recesses, sections or perforations, however, placed differently and in particular also be arranged on the side facing away from the center of the solar cell side or on both sides of the respective connection points ,

With the invention, the wiring foil or cell connector structure, ie the substrate for back contact solar cells is optimized so that the mechanical stress entry under thermal stress, especially when operating at temperatures far from the temperature at which the mechanical and electrical connection of the solar cell with the Substrate was prepared, and / or is minimized at thermal cycling. Even thermo-mechanical stresses that occur during the assembly process are thereby mitigated. As a result, the risk of warpage of the solar modules is significantly reduced and potentially increases the reliability and extends the average life.

In further embodiments, recesses are also provided on the side facing away from the center of the respective solar cell on at least a part of the connection points. This embodiment takes into account the fact that not only one solar cell is mounted on a substrate, but several solar cells in a regular arrangement, and it contributes to the stress relief in the overall composite of the solar cell array with the substrate.

In further embodiments it is provided that a solder or metallic connecting means or a conductive adhesive is provided on the wiring film at the locations of the connection points contact pads and / or bumps and between the contact pads or bumps and the rear terminal contacts of the solar cells, the / an electrical contact between the interconnects and the connection contacts manufactures.

For the structure of the substrate, there are various variants in which the invention is basically equally advantageous. Thus, in preferred embodiments, the insulating support has a multi-layer structure comprising an insulating film or layer interspersed at the connection points of the one electrical contact between the wiring foil and the solar cell backside. In further embodiments, it is provided that the wiring film has a multilayer interconnect structure and that the recesses penetrate the multilayer interconnect structure at least partially.

The recesses, cuts or perforations do not necessarily penetrate the entire thickness of the wiring foil or cell connector structure, although from a current point of view this is the preferred embodiment. Rather, embodiments in which only part of the thickness or of a multi-layered construction of recesses or cuts is penetrated or correspondingly perforated are also advantageous.

Advantageous embodiments of the invention for the production of the solar module used wiring sheet resulting from the above-mentioned features of the module and are therefore not explained again here.

drawings

Further advantages and advantageous embodiments of the subject invention are illustrated by the drawings and explained in the following description. It should be noted that the drawings have only descriptive character and are not intended to limit the invention in any way. Show it:

1 a schematic perspective view of a solar module made of back contact solar cells,

2 and 2A a top view of a section of a solar module, namely a solar cell with associated portion of a wiring foil, and a detailed view of this,

3A to 3D Variations (layout variants) of the wiring foil for a solar module according to the invention,

4 a plan view of a according to 2A designed wiring foil with marked contact finger structure,

5A to 5G schematic cross-sectional views of usable for carrying out the invention wiring films and

6A and 6B a plan view of a formed with band-shaped cell connectors solar module.

Embodiments of the invention

2 and 2A show a schematic plan view and a detailed view of a section of a solar module 1 By mounting multiple back contact solar cells 3 on an insulating wiring foil 5 is formed with (not shown here) Leitbahnstruktur. A mechanical and electrical connection between the solar cell 3 and the wiring foil 5 is in each case at a plurality of connection points by solder points arranged there 13 or joints with conductive adhesive o. Ä. Made. The compound may also be made by another common bonding method such as bonding.

In the case of thermal stress, forces typically act at the individual connecting points, the direction of action of which is illustrated with the arrows associated with the connecting points. In order to prevent this force effect lead to a warping of the composite of solar cells and wiring foil, in the latter at the connection points in each case a crescent-shaped recess 15 provided that a contact tongue 15a encloses, on which the respective contact element (contact pad and / or bump) of the wiring foil is placed. In 2 it can be seen that the alignment of the recesses 15 is different according to the expected force effects, wherein the recesses in the illustrated configuration are each substantially centered around an imaginary connecting line between the respective connection point and the center of the solar cell.

3A and 3B show modified configurations of a wiring foil 5 ' respectively. 5 '' in which each connection point is associated with two recesses, one of which lies between the respective connection point and the center of the cell and the other on the opposite side of the connection point. It is in accordance with 3A around circular segment-shaped recesses 15 ' or according to 3B around triangular recesses 15 '' , 3C shows a selection of geometric configurations of cuts or perforations, which may be assigned to the connection points of a solar module instead of recesses. Since these configurations are self-explanatory, no further verbal description is given. 3D Finally, two of the shows in 3C illustrated configurations with approximately centrally disposed in the formed by the U-shaped section or the two crescent-shaped sections tongue or via (not separately designated).

4 shows another wiring foil similar to the one in 2 , which as in that figure with numeral 5 is designated, although the number of provided connection points and associated recesses 15 larger than when running after 2 is. In this case, a contact finger structure can be recognized as a configuration of a conductive coating (interconnect structure) which is customary in practice. This is through an interruption track 17a in an otherwise full-surface conductive coating (such as Cu) 17 educated.

The 5A to 5G show a selection of substrate variants (wiring foil constructions) that can be used in the implementation of the invention. This selection is only to be understood as an example, and combinations of these as well as numerous additions are possible in the context of special layouts.

5A shows a wiring foil 51 with top-lying Cu-lamination 51a , 5B shows a wiring foil 52 with bottom lying Cu-lamination 52a and upper structured insulating layer 52b , 5C shows a wiring foil 53 with top-lying Cu-lamination 53a and a frame-shaped patterned insulating layer disposed thereon 53c , 5D shows a wiring foil 54 with top-lying Cu-lamination 54a and surface-applied structured insulating layer 54c , 5E shows a three-layer wiring foil 55 with internal Cu-lamination 55a and a lower unstructured insulating support layer 55b and an upper structured insulating layer 55c , 5F shows a wiring foil 56 with a similar structure as in 5E , with on the structured insulating foil 56c applied contact pads 56d , 5G finally shows a multilayer wiring film 57 which alternately comprises three insulating layers and two conductive layers (each not separately designated).

In all the illustrated configurations, solder bumps may be respectively arranged on the exposed sections of the Cu coating or on the contact pads at intended connection points with which the solar cell to be mounted on the wiring film is fused during the assembly process. Alternatively, corresponding solder bumps may be provided on the back side contacts of the solar cell itself, or there may be a selective conductive adhesive application on the wiring film or solar cell, or alternative connection point structures may be provided.

6 schematically shows a section of a solar module in the manner of a plan view 1' with two solar cells 3 ' and a band-shaped cell connector structure 6 , as a Cu-coated polymer strip with separating cuts 6a . 6b and an isolation track 6c is configured in the lamination. At the connection points 13 ' Incidentally, recesses, cuts or perforations with one of each of the solar cells and the cell connector structure can be made in each case 2 to 4 shown configurations, in coordination with the assumed temperature load of the composite, be provided. Here are the additional cuts 6b as a means of stress relief also provided between connection points. Such a cell connector structure can have a width of only a few millimeters or 1 to 2 cm and does not have to extend over the entire module.

The invention is applicable to both cell connector means (wiring foils or structured narrower cell connectors) whose track plane is formed by a Cu cladding, as well as cell connector means made with an Al, Sn or alloy conduction plane.

Under procedural aspects, both the supply of previously provided with the recesses, cuts or perforations cell connectors according to the invention into the assembly process into consideration, as well as the generation of recesses, cuts or perforations only after the lamination step directly on the solar module, such as using laser structuring method , Optionally, this is followed by a contacting of the cells. In this latter method context, the invention contributes primarily to the avoidance of mechanical stresses due to thermal cycling in the operation of the solar modules.

Within the scope of expert action, further refinements and embodiments of the method described here by way of example only arise.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 2009/0065043 Al [0005]
• DE 102005039052 A1 [0005]
• DE 102008020383 A1 [0005]

Claims (11)

Solar module ( 1 ) arranged with a plurality of on a flat insulating support and via interconnects ( 7 ; 17 ) connected or connected to an external terminal solar cells ( 3 ), which have connection contacts for interconnection exclusively on one of its two surfaces, which in the position of use represents the rear side, and at their rear connection contacts at connection points ( 13 ) are connected to the interconnects, the isolating support having a cell connector means coated with the interconnects ( 5 ; 5 '; 5 ''; 6 ), in particular a wiring film, and at least at and / or between the center of the respective solar cell far away connection points recesses, cuts or perforations, which are designed such that distortions of the carrier with temperature changes, inter alia in reducing the temperature with respect to the assembly -Temperature, be reduced. Solar module according to claim 1, wherein the recesses ( 15 ; 15 '; 15 '' ) Have a circular or sickle-shaped or triangular or trapezoidal shape or at least the more distant from the respective connection point edge of the recess spans a triangle or trapezoid. Solar module according to claim 1, wherein the cuts or perforations are rectilinear, U-shaped, wave or zigzag, sickle-shaped or spiral. Solar module according to one of the preceding claims, wherein recesses ( 15 ; 15 '; 15 '' ) are provided at all connection points, optionally with the exception of one or less central connection points. Solar module according to one of the preceding claims, wherein on at least a part of the connection points recesses, cuts or perforations ( 15 '; 15 '' ) are provided between the respective connection point and the center of the solar cell and / or at the side facing away from the center of the respective solar cell side. Solar module according to one of the preceding claims, wherein on the wiring foil ( 56 ) at the locations of the connection points contact pads and / or bumps and between the contact pads ( 56d ) or bumps and the rear terminal contacts of the solar cells, a solder or metallic connecting means or a conductive adhesive is provided which / makes an electrical contact between the interconnects and the terminal contacts. Solar module according to one of the preceding claims, wherein the insulating support ( 53 ; 54 . 55 ) has a multilayer structure comprising an insulating film or layer penetrated at the connection points of the one electrical contact between the wiring film and the solar cell back side. Solar module according to one of the preceding claims, wherein the recesses, cuts or perforations penetrate at least the interconnect structure of the cell connector means, in particular the wiring foil ( 57 ) has a multilayer interconnect structure and the recesses, cuts or perforations at least partially penetrate the multilayer interconnect structure. Cell bonding agent ( 5 ; 5 '; 5 ''; 6 ; 51 ; 52 ; 53 ; 54 ; 55 ; 56 ) for producing a solar module according to one of the preceding claims, which has at least one insulating layer and a conductor track structure with predetermined connection points arranged at least on a surface thereof, wherein at least on and / or between a part of the connection points recesses, cuts or perforations ( 15 . 15 '; 15 '' ) are provided for mechanical stress discharge, which penetrate at least the interconnect layer. A cell connector according to claim 9, wherein the recesses ( 15 . 15 '; 15 '' ) Have Kreisabschnitts- or sickle or triangular or trapezoidal shape or at least the more distant from the respective connection point edge spans a triangle or trapezoidal, or are zigzag, sickle-shaped or spiral. A cell connector according to claim 9 or 10, wherein at at least a part of the connection points are recesses (2). 15 '; 15 '' ), Cuts or perforations are provided.

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