FR2514565A1 - SOLAR CELL ASSEMBLY AND METHOD OF FIXING AN OMNIBUS BAR TO A SOLAR CELL - Google Patents

Abstract

THE INVENTION RELATES TO A PROCESS FOR FIXING OMNIBUS BARS TO A SOLAR BATTERY. THE OMNIBUS 30 BARS ARE FIRST ATTACHED PROVISIONALLY BY DOTS OF ADHESIVE 36, CONSTITUTED OF A DOUBLE-SIDED STICKER, ON THE PREMETALLIZED SURFACE FORMING A NETWORK 32 OF ELECTRODES ON THE BATTERY, THEN THE ASSEMBLY IS IMMERSE IN THE SODA WHICH PENETS BY CAPILLARITY BETWEEN THE OMNIBUS BARS 30 AND THE ADJACENT SURFACE OF THE SOLAR BATTERY SO THAT THE BARS 30 ARE WELDED AT 34 TO THE ELECTRODES NETWORK 32. FIELD OF APPLICATION: PRODUCTION OF SOLAR PANELS.

Description

2514565-

  The invention relates to solar cells, and more particularly to solar cells having a network of conductive electrodes and bus bar interconnects which are applied to the solar cell in a single immersion welding operation. Photovoltaic devices such as

  silicon solar cells look like an alterna-

  to the generation of energy from

  Fossil cells that do not regenerate The energy of the light (photons) arriving on the surface of a solar cell must enter the cell and be absorbed by it.

  to be converted into an electric current The current -

  Electrical is driven by electrodes to bus bars which are connected to inter-connectors connecting many batteries to each other to form a solar panel. In the prior art, bus bars are sometimes attached directly to the solar cell. by

  heating by induction or other welding means.

  Drivers leading to common connections are

  also sometimes soldered directly to the solar cell.

  This has the disadvantage of subjecting the solar cell to an additional heating step and to a constraint

  additional heat may result in a deterioration

  On the other hand, according to the invention, the bus bars are fixed by a dip-welding process and constitute a means for interconnecting batteries without otherwise subjecting them to a heating which risks damaging them. cracking of the solar cell is eliminated or significantly reduced According to the invention, the bus bars protrude from the periphery of the solar cell and thus serve as inter-connectors for electrically connecting the solar cells to each other, thereby eliminating direct welding on the solar cell. In addition, the present invention also relates to a means for fixing the bus bars and producing a premetallized conductive gate in a single operation.

immersion in the weld.

  US Pat. Nos. 3,553,030 and 4,312,692 disclose, respectively, the use of adhesives for attaching electrical components to substrates prior to welding. These patents generally disclose coating by solder of the component pasted From

  large substrate surfaces are coated with adhesives that

  allow the weld to infiltrate below the component by capillarity Usually, only the periphery of the component is fixed directly to the substrate This type of adhesion does not achieve a robust mechanical connection

and a good electrical connection.

  On the other hand, the present invention uses a double-sided, high-temperature, self-adhesive adhesive applied by points between the bus bar and the surface of the solar cell. This dot application leaves a clearance allowing the solder to flow by capillarity between the underside of the bus bar and the surface of the solar cell In practice, the entire underside of the busbar is mechanically and electrically connected to the surface of the solar cell, thus achieving a very robust connection. -tights

  according to the invention also has the added advantage of

  not to require a separate hardening step.

  to be fixed in position, as described in

aforementioned Patent No. 3,553,030.

  The high temperature adhesive according to the invention

  resists attack by the molten solder bath, and the application

  two-sided cation provides easy laying

does not exist in the prior art.

  The invention relates to a method for laying bus bars on a solar cell surface, which comprises the steps of setting the bus bars to the solar cell by spot and to immersion welding the solar cell to which the bus bars are attached, in such a way that the solder flows between the bus bars and the solar cell by capillarity The point fixing leaves a gap between the bus bars and the surface of the solar cell to allow the molten solder to flow between them. by the welding between the bus bars and the surface of the solar cell increases the robustness of the mechanical and electrical connection between the bus bars and the conductive surface of the bus.

solar cell.

  The upper surface of the stack may comprise-

  a conductive surface constituting a grid A network

  pre-metallized grid is made conductive by the application

  weld connection which also serves to fix the busbars at the same time to the solar cell The busbars can be fixed in points to the solar cell by means of a double-sided adhesive in the preferred form

of realization.

  The invention will be described in more detail with reference to the accompanying drawings by way of non-limiting examples and in which: FIG. 1 is a top view of a stack

  solar system to which bus bars are fixed in accordance

  according to the invention; Figures 2 and 3 are cross-sections on an enlarged scale of the solar cell during successive steps of the manufacturing technique; Figure 4 is an enlarged cross section of a variant of a solar cell to which bus bars are fixed by the implementation of the method of the invention; Fig. 5 is an enlarged sectional cut along the line 5-5 of Fig. 1, showing a solar cell to which bus bars are fixed by the method of the invention; and FIG. 6 is an enlarged cross-sectional view of two interconnected solar cells in accordance with FIG.

to the present invention.

  The invention thus relates to a solar cell

  having a particular network of electrodes and an agency

  of bus bars, as well as a method of fixing the electrode array and bus bars

  to the solar cell in a single operation allowing the inter-

  connection of solar cells, without reflow of the material

  conductor of the electric current (for example from the

  hard) which fixes the bus bars to the stack and forms the

electrodes of the battery.

  FIG. 1 is a top view of a solar cell including the array of electrodes and the bus bars

  have been made in accordance with the present invention.

  Figures 2 and 3 show how the electrode array is formed.

  Figures 4 and 5 show the arrangement of the bus bars.

  Figure 6 shows the interconnection of two solar cells.

  In Fig. 2, a silicon wafer 8 having a region of a first conductivity type, which may comprise P-type or N-type silicon, is diffused to form a conductivity type region 12. opposite to that of the conductivity of the region 10 to form a semiconductor junction otherwise referred to as a PN (or NP) junction in the region of the interface between the regions 10 and 12. The diffusion and junction formation processes are Well known to those skilled in the art Furthermore, the method of the invention can be used both on N / P type batteries.

only on P / N batteries.

  As shown in FIG. 1, electrodes 20 (six electrodes being shown chemically)

  are arranged perpendicularly to bus bars 30.

  The total area occupied by the electrodes and the bus bars is first rendered conductive and weldable by depositing a suitable metal layer, for example nickel, or any other suitable weldable materials including silver and copper. methods for depositing such metal layers, which make the primary electrical contact with the silicon, are well

known to those skilled in the art.

  For example, a thin layer 18 of nickel is deposited without electrical current. This layer may be insufficiently conductive to serve as suitable current-carrying electrodes in most solar cell applications. Therefore, second layers 20 and 21 forming conductive electrodes and

  consisting of a metal of relative electrical conductivity

  In a preferred embodiment, the area of the surface of the cell comprising at least the nickel electrode 18 is brought into contact with a solder flux, which can be formed by immersion in solder, electrodeposition or the like. then with molten solder to form a solder layer after the bus bars have been attached to the surface

nickel.

  FIG. 5 shows in section the arrangement of a bus bar. Before the application of the solder 20 to the stack as described above, the bus bars 30 are mechanically fixed to a portion 32 of the electrode array coated with nickel In this fixed position, the bus bars 30 and the network 32 coated nickel located

'4565

  below the bus bars are co-linear and form a gap between them The busbar 30 is fixed to the network 32 nickel by a means resistant to high temperatures This resistance to high temperatures is required in that the bus bar is fixed to the network of nickel electrodes by an electrical connection

  at the same time as the electrode layer 20 is formed.

  The conductive material of the electric current is usually

  applied or formed at high temperatures. For example, if the conductive material of the electric current

  is solder 34 as is the case in the pre-form

  realization, the means for fixing the omni-

  Bus 30 to the network 32 of nickel electrodes must operate at a temperature of about 2000 C. The bus bars 30 may be made of any suitable weldable material, although the preferred materials are copper or a

alloy "Invar" coated with copper.

  A preferred method for attaching the bus bars to the nickel electrode array 32 is to bond the bars to the nickel by means of a double-sided self-adhesive tape 36 capable of operating in the temperature range of 180 to 220 degrees. A tape of this type generally comprises an acrylic polymer adhesive strip. The strip 36 is applied under intermittent firm pressure along the bus bars. These are then attached to the nickel electrode array 32 using the The stack can then be dip-welded so that the solder 34 fills the space formed between the bus bars 30 and the network 32 of nickel electrodes, in addition to covering the remaining electrode array so that the solder 20 and 34 form an electrically continuous conductor The space between the bus bars and the nickel can be filled by capillarity by the solder An example of suitable acrylic tape is the 3M acrylic tape "A-10 ISOTAC Type Y-9469" The tape covers only a small area of the busbar surface and remains on the stack once it is completed. does not require maturation and provides an elastic cushion that eliminates internal stresses between related materials

  having different thermal expansion properties.

  Another consequence of the use of an acrylic adhesive

  It consists of a non-corrosive, substantially inert, low-gaseous polymer having,

  by its nature, lasting stability and resilience.

  Figures 3 and 5 show an ohmic electrode and bus bars 40 formed on the lower surface, together with the formation of layers 18 and 20 and the bus bars 30, however, since the lower surface is not exposed to incident solar rays, the layer 22 of nickel may be a continuous layer completely covering the lower surface of the region 10 The bus bars 40 are fixed to the nickel layer 22 in a manner similar to that used on the top of the stack Otherwise said bus bars 40 are attached to the nickel layer 22 by means of a double-sided adhesive tape 26 of acrylic polymer, placed intermittently along these bars The surface of the nickel layer 22 is coated with a material 21 conducting the electric current, for example welding, and the space between the bus bars 40 and the nickel layer 22 is filled with a similar material 24 so

  that the conductive material 21 and 24 forms a continuous layer

naked from the electrical point of view.

  Figure 4 shows another embodiment of the bus bars 30 (only the upper bus bars being shown) In this case, the bars may be deformed around the tape to reduce the thickness of the solder discharge 8 t 34 by capillarity between the bus bars 30 and the electrode network 32 of

  nickel This reduced thickness of the weld achieves -

  however a robust mechanical and electrical connection.

  The bus bars 30 of the upper surface and the bus bars 40 of the lower surface of the stack 8 protrude from the edge of this stack 8 over a distance

  sufficient to allow the interconnection of solar cells.

  These projections 28 of the busbar 30 and 42 of the busbar 40 serve as interconnection electrically connecting a solar cell 8 to adjacent solar cells (see Figure 6) if more than one solar cell is used to form a network. Therefore, the end 28 of the bus bar 30 can be connected to the end 42 of the bus bar 42 without causing reflow of the weld

applied to the battery 8.

  It goes without saying that many modifications can be made to the stack described and shown

  without departing from the scope of the invention.

, 51 456 5

Claims (8)

  1 solar battery assembly, characterized in that it comprises a solar cell which has a conductive surface, at least one bus bar (30) connected to said conductive surface of the solar cell, and means for connecting the bus bar to the solar cell, said means comprising at least a portion (36) of adhesive material disposed between the bus bar and the solar cell and at least a portion (34) of solder arranged below   of the bus bar, close to the adhesive material.   Solar cell assembly according to claim 1, characterized in that a plurality of adhesive points (36) are spaced along the solar cell and the solder portion comprises solder (34) disposed between the points of the solar cell. adhesive and between the bus bar and the conductive surface.   3 Solar battery assembly, characterized in that it comprises a solar cell on which is disposed a conductive mesh (32), and at least one busbar (30) attached to the solar cell by means of a combination of an adhesive and welding, this combination comprising adhesive spots (36) applied between the bus bar and the solar cell and welding (34) disposed between the bus bar and the grid, close to the points adhesive.   4 A solar cell assembly, characterized in that it comprises spaced bus bars (30) attached to and in electrical contact with a solar cell   stack by means of welding parts (34)   immersed, the weld being disposed beneath the bus bars, substantially under all of a portion of the bus bars where the latter are in contact electric with the solar cell.   Solar cell assembly according to Claim 4, characterized in that the bus bars are also   attached to the solar cell by adhesive spots (36).   A method of attaching a bus bar to a solar cell, characterized by the steps of spot-fixing the bus bar (30) to a pre-metallized solar cell, and immersion welding the pre-metallized solar cell to the bus bar as well as fixed so that the solder (34) flows by capillarity between the   bus bar and the pre-metallized solar cell.   Method according to claim 6, characterized in that an adhesive (36) is used to fix by points   the bus bar to the solar cell.   8 Method of fixing bus bars to a surface of a premetallised solar cell, characterized   in that it consists in applying an adhesive (36) on certain   parts of the bus bars (30), which bus bars are then secured by solder (34) to the premetallized solar cell.   9 A method of manufacturing a solar cell assembly, characterized in that it consists in fixing bus bars (30, 40) on surfaces of a solar cell by immersion in a solder bath of this solar cell   to which the bus bars are temporarily fixed   each bus bar extending beyond the solar cell to allow interconnection of this battery with other solar cells.   A method of fixing a grid network and at least one bus bar to a solar cell surface by means of a single immersion in the solder, characterized in that it consists of immersion welding a solar cell having a premetallized grid (32) and bus bars (30) provisionally fixed to this grid.