WO2011095485A2

WO2011095485A2 - Solar cell string and method for producing same

Info

Publication number: WO2011095485A2
Application number: PCT/EP2011/051403
Authority: WO
Inventors: Michael Bisges
Original assignee: Reinhausen Plasma Gmbh
Priority date: 2010-02-05
Filing date: 2011-02-01
Publication date: 2011-08-11
Also published as: DE102010007131A1; WO2011095485A3

Abstract

The invention relates to a solar cell string comprising a plurality of solar cells disposed adjacent to each other and spaced apart in a row, having an active front face and a rear face, wherein a gap remains between adjacent solar cells, wherein each solar cell comprises at least one first contact region having a first polarity and at least one second contact region having a second polarity, and the contact regions of adjacent solar cells having different polarity and having at least one contact element are electrically connected to each other. In order to provide a solar cell string, in which damage to the contact elements by mechanical loads is extensively prevented and that is advantageous in production, an adhesive introduced into each gap between adjacent solar cells connects adjacent solar cells to each other, and each contact element is designed as an electrically conductive coating between two contact regions to be connected on the rear faces of the solar cells, bonding to both the rear faces of the two solar cells to be connected and the adhesive in the gap.

Description

Solar cell string and method for its production

The invention relates to a solar cell string comprising a plurality of solar cells spaced apart next to one another in a row and having an active, solar facing

Front side and a back side, wherein a gap between adjacent solar cells remains, each solar cell at least a first contact region with a first

Polarity and at least one second contact region having a second polarity and the contact regions of adjacent solar cells with different polarity with at least one contact element are electrically connected. Moreover, the invention relates to a method for

Production of such a solar cell string. Solar cells convert light into electrical energy. The

Solar cell-forming semiconductors have areas

different polarity. For example, one is

Emitter region formed with a first polarity of an n-type semiconductor, where against a base region with a second polarity of a p-type semiconductor is formed.

Commercially available solar cells made of semiconductor materials currently consist predominantly of silicon. By at the interface between the areas of different

Polarity formed pn junction are pairs of charge carriers, which are formed in the absorption of incident light, separated. In order to be able to supply the charge carriers thus separated to an external circuit, each solar cell has a first contact region with the first polarity and a second contact region with the second polarity.

For energy production solar cells are usually interconnected to solar modules. For this purpose, first the individual solar cells with strip-shaped contact elements, in particular solder ribbons, to individual strands, so-called solar cell strings, connected and on a transparent Cover in the form of a glass pane with one on top

positioned arranged EVA film. If the solar module comprises several solar cell strings, the individual solar cell strings are electrically connected to one another with the aid of cross connectors. Subsequently, with the active, the sun-facing front side resting on the cover solar cells with a cut EVA film and a back cover, especially a Tedlar film laminated.

Finally, the lamination of the solar module takes place at a negative pressure and about 150 degrees Celsius. During lamination, the EVA film forms a clear, three-dimensionally crosslinked and non-fusible plastic layer, in which the solar cells are embedded and firmly connected to the cover and the backsheet. After lamination, the edges of the solar module are lined and the

electrical connections made. Possibly. the solar module is provided with a frame.

The invention relates to a solar cell string with solar cells, whose first and second contact regions are arranged with different polarity on the rear side facing away from the sun. The advantage of such

Reverse contact solar cells is that shading by the contact areas and the adjacent solar cells connecting contact elements are avoided. Furthermore, the solar cells adjacent to the solar module are easier to connect in series from back to back than in conventional solar cells in which

strip-shaped contact elements from the back of a

Solar cell must be made electrically conductive to the front of the adjacent solar cell. For the production of high-quality solar modules, it is necessary that the solar cell strings in the Processing to solar modules as well as during subsequent use by mechanical stress should not be damaged, in particular must be prevented that the solar cells in the solar cell string interconnecting

Contact elements are damaged. When the contact elements in the form of contact strips at the contact areas of

Solar cells are contacted by means of a soldering there is a risk that the contact is damaged by a bending load in the solar cell string before it is potted in the solar module. Furthermore, such

Damage to the contact caused by bending loads of the finished solar module or by temperature fluctuations. In order to provide a solar cell string, in the mechanical loads, in particular relative movements of adjacent solar cells, the contact elements not

Damage, DE 41 04 160 AI suggests that the extending between the solar cells contact element has a deliberately predetermined course, so that without

Damage to the contact elements a relative movement

between the solar cells is possible. The course of the

Contact element between the solar cells is this

preferably curved. However, the curved course of the contact element has the consequence that this in the gap between two adjacent solar cells on the

Front of the solar cells protrudes. Furthermore, the production of the solar cell string is complicated. The solar cells must first be spaced apart at a distance on a flat surface on both sides of a

height-adjustable cam can be arranged, which projects with its free upper edge on the active front of the two adjacent solar cells. About the cam is soldered to the back of a solar cell soldered contact element, then to the front of the adjacent

Solar cell to be soldered. The height of the over Front of the adjacent solar cells protruding

Portion of the cam specifies the length of the curved section that allows relative movement between adjacent solar cells. Another disadvantage of the solar cell string is that the active front side is partially shaded by the contact strip.

Based on this prior art, the invention is based on the object to provide a solar cell string, in which damage to the contact elements by

Mechanical stresses largely excluded and the manufacturing technology is advantageous. In particular, the production costs and production times are to be reduced and the possible degree of automation in the production increased. Finally, shadows of the

Solar cell strings are excluded by contact elements on the active front.

This object is achieved in a solar cell string of the type mentioned in that one in each gap

adhesive introduced between adjacent solar cells interconnects adjacent solar cells and each contact element as an electrically conductive coating between two contact areas to be connected to the

Rear sides of the solar cell is configured, which adheres both to the backs of the two to be connected solar cells and the adhesive in the gap.

The adjacent solar cells are joined together only by the adhesive introduced into each gap

connected. The active sun-facing front is free of adhesive.

In procedural terms, the object is achieved by a method having the features of claim 6. The in each gap between adjacent solar cells

introduced adhesive creates a mechanical connection between the arranged in a row solar cells of the solar cell string, the relative movements between the

Solar cells largely prevented. At the same time the introduced into the gap adhesive serves as a surface for the

electrically conductive coating between the two to be connected contact areas of the adjacent solar cells on the back. The coatings are readily capable of completing minor bends in the solar cell string or solar modules made therefrom without compromising the electrical connection between the contact areas. At the same time, the efficiency of the solar cells contacted by coatings is improved by reduced contact resistances to the contact areas. With the application of the coatings, without the need for ultrasonic welding or soldering, the contact element becomes

manufactured and connected at the same time with the contact areas. Since the contact areas to be joined together

different polarity are all arranged on the backs of the solar cells, shadows are excluded by the contact elements. At the same time, the

Significantly simplify the manufacturing process, since all contacts between adjacent solar cells from one side fully automatically in the way of

Can be carried out coating process, in particular without the need to contact individual solar cells or have to perform a two-sided coating process. The adhesive used is preferably a silicone, in particular a silicone rubber, which withstands temperatures between at least -40 degrees Celsius and +90 degrees Celsius. The silicone is in the stated temperature range

moisture and frost resistant. Particularly suitable is an adhesive with non-corrosive Vernetzungsart. A sealing of the connected to a solar cell string solar cells against ingress of moisture, in particular

between a arranged on the active front, transparent cover and the front of the solar cell can be achieved when the adhesive is not only in the

Gap is introduced between adjacent solar cells, but circumferentially applied along the edges of each solar cell. The adhesive ring then extends beyond the gaps between adjacent solar cells to the lateral edges of the solar cell string, so that even there, no moisture or liquid can infiltrate the front of the solar cell. The attachment of the circumferential

Adhesive ring allows in particular a

production technology advantageous and cost-effective

Production of solar modules without a frame construction surrounding the module. Even with a circumferential

Adhesive is applied only along the edges, while the active, sun-facing front remains free of adhesive.

Furthermore, it is advantageous in terms of production technology if the solar cell string on the active front sides of the solar cells is connected to a transparent cover by means of the adhesive in the gaps or the adhesive ring. Of the

Adhesive then serves not only the connection of the solar cells with each other, but at the same time the connection of the

Solar cells with the transparent cover, in particular a glass pane to protect the brittle solar cells from mechanical damage, the ingress of moisture and from the weather. The previously required, arranged on the transparent cover EVA film

(Ethylene vinyl acetate), in which the solar cells are embedded by a lamination process, can be completely eliminated. In particular, in conjunction with the circumferential adhesive ring along the edges of each solar cell can waive a rear second glass pane, a cover layer spanning the solar cell string at the back, at least up to a

Adhesive edges of the solar cells is applied. When

Materials for backside coating of the

Solar cell strings come in particular silicone as well

thermoplastics, such as PVB and EVA, into consideration.

To produce the solar cell string according to the invention, all solar cells preferably have matching dimensions. Furthermore, the contact areas of different polarity in all solar cells

executed concurrently. The matching solar cells are aligned in the same orientation in a row, in particular a straight line, spaced apart side by side on the surface of the transparent cover. The active tops of the solar cells point towards the transparent cover. In the consistently wide

Columns between adjacent solar cells then the adhesive, in particular the silicone is introduced. After curing, the adhesive is applied by way of a

Coating process between contact areas of adjacent solar cells of different polarity an electrically conductive coating applied as a contact element. The conductive coatings are in particular strip-shaped, but can widen at the contact areas of the solar cells to reduce the contact resistance.

Before the coating process is carried out, metallizations can be applied to the contact areas of the solar cells to be connected to one another, which are subsequently coated by the particular strip-like coatings

electrically connected to each other. To ensure good adhesion of the electrically conductive material to the solar cells and a uniform order

ensure the electrically conductive coating is preferably applied by means of a plasma coating process. The plasma is in particular with a

Beam generator generates, to generate a low-pressure plasma, a working gas, usually argon, via a

Inlet is supplied. In the jet generator, the low-pressure plasma is ignited by way of arc discharge. In the plasma jet of the jet generator, a powder-gas mixture is introduced with a metallic powder in the region of the outlet of the jet generator. That fine

Distributed metal powder is selectively deposited with the plasma jet between the contact areas of the solar cells to be connected.

After production of all contact elements by way of

Plasma coating is applied over the entire surface of the cover layer on the back of the solar cell string so that the gaps between adjacent solar cells are covered by the cover layer. Insofar as the adhesive has also been applied circumferentially along the lateral edges of each solar cell, the covering layer extends at least as far as the

Adhere adhesive, leaving the back of the string

is completely sealed by the cover layer.

The invention will be explained in more detail with reference to the embodiments illustrated in FIGS. Show it:

Figure la) is a plan view of an inventive

Solar cell string, Figure lb) a side view of the solar cell string after

Figure la), FIG. 2a) shows a plan view of the solar cell string according to FIG. 1a), with the adhesive ring applied peripherally,

FIG. 2b) shows a side view of the solar cell string according to FIG

FIG. 2a),

FIG. 2c) shows a connection of the solar cell string according to FIG

Figure 2a) with a transparent cover and

FIG. 2d) shows the solar cell string according to FIG. 2c) with a cover layer applied on the back side,

Figure 3a) is a representation for illustrating a

Process for the preparation of a

Solar cell strings according to the invention, Figure 3b) is a plan view of a gem. the procedure

according to Figure 3a) produced solar cell string and

FIG. 3c) shows a side view of the solar cell string according to FIG

FIG. 3b).

The solar cell string (1) according to FIG. 1a) comprises three

electrically connected in series solar cells (2 a - c) with an active, the sun facing front (3) and a back (4). The illustrated solar cells (2) are so-called back-contact solar cells (2 a-c), each solar cell (2 a-c) having on its rear side (4) a contact region (5) with a negative polarity and a further contact region (6 ) with positive polarity. By the distance that the charge carriers have to travel laterally in the plane of each solar cell (2 a - c) to become one Contact area (5 or 6) to get to keep as small as possible, go from the contact areas (5, 6) more

Metal fingers (7, 8) like a comb. The contact fingers are substantially uniformly distributed over the entire back of the solar cells (2 a - c). In the embodiment, the contact areas (5, 6) as elongated, transverse to the

Metal fingers running stripes shown. The

However, contact areas (5, 6) can also be shaped differently. The contact areas (5, 6) serve to collect the charge carriers guided in the metal fingers (7, 8) and to supply them to a contact element (9 a, b) which electrically connects adjacent solar cells (2 a - c).

The solar cells (2 a - c) are in a row in one

Distance arranged side by side, so that between the solar cells (2 a, b) a gap (11 a) and between the

Solar cells (2 b, c) forms a gap (11 b). In both

Columns (11 a, b), an adhesive (12), in particular a silicone is introduced, the adjacent solar cell (3 a-c) connects to each other. This gives the solar cell string (1) mechanical stability, the bends around an axis parallel to the columns (11 a, b) extending axis

largely prevented. As can be seen in particular from FIG. 1b), the gaps (11 a, b) are completely filled with the adhesive (12), so that its surface is flush with the surface of the front or rear side (3, 4) of the solar cells (2 a). c) completes.

The solar cells (2 a - c) of the solar cell string shown only schematically in FIGS. 1 a), b) become

electrically connected in series by being arranged side by side in the same orientation and the

Contact region (5) with a negative polarity of a solar cell (2 a, b) with the contact region (6) of positive polarity of an adjacent solar cell (2 b, c) by means of the contact element (9 a, b) is connected. The contact element (9 a, b) is as metallic coating (13 a) between the contact areas to be connected (5, 6) executed. As can be seen from the illustrated embodiment, the coating (13 a) extends in the longitudinal direction of the solar cell string (1) and adheres both to the back sides (4) of the two to be joined

Solar cells (2 a, b and 2 b, c) and on the adhesive (12). The coating (13 a) extends at least as far as the metallized contact regions (5 or 6). Of course, it is within the scope of the invention, in the production of such a solar cell string (1) and the metallization of the contact areas (5, 6) by way of

Apply coating. The contact areas and the contact element forming coating can in one

Operation be applied.

The solar cell string of Figure 2a) differs from the solar cell string of Figure 1) in that the

Adhesive (12) is not only in the columns (11 a, b) between adjacent solar cells (2 a - c) is introduced, but as an adhesive ring circumferentially along all the edges of each solar cell (2 a - c). By means of this simple measure, as will be explained below with reference to FIGS. 2c), 2d), a solar module with at least one solar cell string (1) can be produced in a particularly simple manner, facing both the front side and the rear side

Weather conditions is effectively protected.

FIG. 2c) illustrates that the solar cells (2 a - c) are arranged on a transparent cover (14) as shown in FIG. 2 a).

can be aligned side by side at a distance (10), wherein the active front side (3) of each solar cell (2 a - c) points in the direction of the transparent cover. The circulating adhesive (12) connects the solar cells (2 a-c) with each other and with the transparent cover (14).

At the same time, the adhesive (12) forms after curing required bridge in order subsequently to apply the electrically conductive coating (13) between the contact regions (5, 6) of adjacent solar cells (2 a - c). Finally, in a last processing step, as can be seen from FIG. 2d), a cover layer (15) is applied over the entire surfaces of the backs of the solar cells (2 a - c), in particular by spraying or metering in silicon, which forms the gaps (11 a, b). spans between the solar cells (2 a - c) and extends at least as far as the adhesive (12) around each solar cell (2 a - c). This effectively prevents penetration of moisture.

Due to the design of the contact elements (9 a, b) as a coating (13) and the connection of the solar cells by the adhesive (12) contact disturbances in the handling of the solar cell strings (1) by mechanical loads and by different thermal expansion coefficients of the solar cell substrates on the one hand and On the other hand, contact elements made of metal are avoided, in particular, a

Tearing or even tearing out pieces of the solar cell due to thermal stresses excluded.

FIG. 3) illustrates the production of a differently structured solar cell string (1) with a

Plasma coating process and further processing to a solar module. Matching parts become the

For simplicity, provided with the same reference numerals. From the plan view of the solar cell string (1) according to FIG. 3 b), two solar cells (2 a, b) to be connected to one another can be seen. Deviating from the embodiments according to

Figures 1 and 2, in which both the contact region with negative and the contact region with positive polarity exclusively on the back (4) of the solar cell

In the present case, these are so-called EWT solar cells (emitter wrap-through) or MWT Solar cells (metal wrap-through), in which a transparent emitter electrode (16) on the front side (3) of the solar cell (2 a, b) is arranged and charge carriers on the

2 a, b) through which the emitter electrode 16 or a separate metallization passes, to the chamber-like one

Contact areas (5) on the back (4) of the solar cell (2 a, b) are passed. The contact regions (6) with positive polarity on the back (4) of each solar cell (2 a, b) are in the exemplary embodiment as two rectangles (6)

executed. Two each in the longitudinal direction of

Solar cell strings (1) running, strip-shaped

Coatings (13) connect the comb-like contact region (5) with the two rectangular contact regions (6) of the respectively adjacent solar cell (2b).

The application of the two strip-shaped coatings (13) takes place with the aid of FIG. 3a)

Beam generator (18). The jet generator (18) comprises an elongated tube (19) on which a pin electrode (20)

is arranged. At the upper end of the tube (19) is fed via an inlet (21), a gas, for example, argon under a working pressure. The existing of electrically conductive material tube (19) and the pin electrode (20) are connected to a power supply (22). The

Power supply (22) ignited by electrical

Arc discharge a low-pressure plasma between the tube (19) and the pin electrode (20). In the bundled

Plasma jet (23) of the beam generator (18) is a

metallic powder in the region of the mouth of the tube (19) via a powder inlet (24) blown. The finely distributed metallic powder is deposited with the plasma jet (23) on the back (4) of the solar cells (2 a, b) of the solar cell string (1). In the embodiment, the

Contact areas (5,6) before making the contact elements (9a,) on the back (4) of the solar cells (2

a, b) metallized. However, it is readily possible with the coating process in one operation, the

Metal contact areas (5,6) and the

Establish contact elements.

The introduction of the adhesive (12) and the connection of the solar cells (2 a, b) with the transparent cover (14) and the application of the cover layer (15) on the back of the solar cell string (1) corresponds to the manufacturing process of the solar cell string (1) Figure 2), so that reference is made to the statements there.

LIST OF REFERENCE NUMBERS

No. Designation

1 solar cell string

2 a - c solar cells

3 front side

4 back side

5 contact area (negative polarity)

6 contact area (positive polarity)

7 metal fingers

8 metal fingers

9 a, b contact elements

10 distance

11 a, b gap

12 glue

13 coating

14 transparent cover

15 topcoat

16 emitter electrode (transparent)

17 holes

18 beam generator

19 casing pipe

20 pcs

21 inlet

22 Power supply

23 plasma jet

24 powder inlet

Claims

claims

1. Solar cell string comprising several in a row

spaced juxtaposed solar cells with an active, facing the sun front and a back, leaving a gap between adjacent solar cells, each solar cell has at least a first contact region with a first polarity and at least a second contact region with a second polarity and the contact regions of adjacent solar cells with different polarity with at least one contact element are electrically conductively connected, characterized in that in each gap (11 a, b) between adjacent solar cells (2 ac) introduced adhesive (12) adjacent

Connecting solar cells together and each one

Contact element (9 a, b) as an electrically conductive coating (13) between two to be connected

Contact areas (5,6) on the backs (4) of

Solar cells (2 a-c) is configured, which adheres both to the backs (4) of the two to be connected solar cells (2 a-c) and the adhesive (12) in the gap.

2. Solar cell string according to claim 1, characterized

characterized in that the adhesive (12) is a silicone.

3. solar cell string according to claim 1 or 2, characterized

in that the adhesive (12) is applied peripherally along the edges of each solar cell (2 a-c). Solar cell string according to one of claims 1 to 3, characterized in that the solar cell string (1) on the active front sides (3) of the solar cells (2 ac) with a transparent cover (14) by means of

Adhesive (12) is connected.

Solar cell string according to one of claims 1 to 4, characterized in that a cover layer (15) the solar cell string (1) on the back sides (4) of

Solar cells (2 a-c) spans.

Process for producing a solar cell string according to one of Claims 1 to 5, characterized in that

(A) the solar cells (2 a-c) are aligned in a row next to each other on a surface, wherein the active front side (3) of the

Solar cells (2 a-c) towards the surface,

(b) the adhesive (12) is introduced exclusively into each gap (11 a, b) between adjacent solar cells (2 a-c) or is applied exclusively circumferentially along the edges of each solar cell (2 a-c),

(C) the adhesive (12) is cured and

(d) subsequently between the contact areas (5, 6)

neighboring solar cells (2 a-c) with

different polarity one electric

conductive coating (13) for forming the

Konatktelemente (9a, 9b) is applied.

7. The method according to claim 6, characterized in that aligned solar cells (2 a-c) are aligned in the same orientation on the surface.

8. The method according to claim 4 and 6 or 7, characterized

in that the transparent cover (14) is used as the surface.

9. The method according to claim 5 and one of claims 6 to 8, characterized in that the entire surface of the

Cover layer (15) on the back of the

Solar cell strings (1) is applied.

10. The method according to any one of claims 6 to 9, characterized

characterized in that the electrically conductive

Coating (13) with the help of a

Plasma coating process is applied.