DE102009035703A1 - Method for generation of ally flexible thin layered solar cells by interconnected individual cells or cell complexes, involves piercing thin layered solar cells from front side through carrier in narrow region on flexible carrier - Google Patents

Abstract

The method involves piercing the thin layered solar cells from the front side through the carrier in a narrow region on a flexible carrier. An insulated electro-conductive wire is guided through the formed opening. The insulation of the electric conductive wire is electrically etched locally.

Description

The The invention relates to a method of making a system more flexible Thin-film solar cells by interconnection of individual flexible Thin film solar cells. An interconnection is the electrical one Connection of individual solar cells to solar cell networks.

The Invention further relates to the composite of the thin-film solar cells, which has been manufactured according to the new technology.

starting point are thin-film solar cells on flexible substrate, preferred Polymer substrate z. Example, polyimide, wherein the method to others Cell technologies can be extended.

It is already known to produce thin-film solar cells and to unite them into networks. Thin-film solar cells z. B. the Solarion AG have the structure in is shown. above shows a top view, Below shows a cross section of such a thin-film solar cell. The production of such thin film solar cells follows a well-known technology.

On a substrate ( 1 ) is a metallic layer ( 2 ) deposited in a vacuum process. This metallic layer serves as a back contact, also referred to as backside electrode, the thin film solar cell. The photoactive layer ( 3 ), which usually happens in a vacuum process. A transparent, electrically conductive layer ( 5 ) is applied as a front contact or front side electrode. Between front contact and photoactive layer, various buffer layers ( 4 ) built-in. To support the conductivity of the front contact can also metallic contact fingers and collective contacts ( 6 ) are applied.

Frequently, a polyimide film is used as the substrate. Thus, contacting the metallic back contact layer from the backside is not readily possible. However, a contacting of the back contact can be achieved from the front side of the solar cells by removing all layers lying above this layer. An additional application of metallic collecting contacts ( 7 ) on the exposed back contact layer improves the dissipation of the charge carriers generated in the photoactive layer. Both contacts - both the back contact and the front contact are in this variant on the front of the solar cell and must be further structured by the material ( 8th ) are electrically separated from each other.

to Production of solar modules must be the described thin-film solar cells interconnected with each other. For a series connection must while the front contact of a solar cell with the back contact to be connected to a following cell. In case of a parallel connection must each have the front contacts and the back contacts two or more solar cells are interconnected.

The Thin-film solar cells, which are on flexible substrates (eg polyimide film) are characterized by a high degree of flexibility in the mechanical sense out. Of course, this flexibility is also intended for the solar modules are preserved. So the task is set, to find an interconnection technology that gives the flexibility does not restrict the solar cell.

DE 3 317 309 C2 describes an interconnection wherein individual solar cells are placed on a carrier foil provided with integrated metal wires. By means of laser radiation, the metal wires are exposed locally and connected to the contacts of the solar cells.

In the case of a conductive substrate, the in US 3,769,091 apply proposed shingling of individual solar cells, wherein the electrically conductive back overlapping placed on the front of an adjacent cell and electrically connected. With a flexible substrate, a flexible interconnection can then be achieved. However, this concept can not be transferred to solar cells with an electrically insulating substrate.

In US 3,903,427 and in US 7,276,724 It is proposed to create holes through the entire layer package and to effect the actual via in the deposition of the transparent conductive oxide on the sun-facing side or to apply an electrically conductive paste. For both methods, however, there is a risk of short-circuiting the front contact and the back contact of the solar cells during through-hole plating and thus disturbing the function of the solar cell. To overcome this problem, insulation of the inner walls of the hole is proposed in both patents. This can be z. Example by depositing an electrically non-conductive layer in a vacuum process (usually sputtering (for improved coverage of the inner walls of the hole) or by applying a dielectric in the form of an electrically non-conductive paste.

Sewing is an interesting option for interconnecting flexible thin-film solar cells. The idea itself is not new and is, for. For example, see [1] on page 57. The sewing takes place here on specially exposed areas of the metallic back contact of the solar cells. On the frontkon Cells of the wire, the wire is only glued. In the method shown in [1], therefore, only the substrate and the metallic back contact are pierced. All other layers are not pierced by the thread. This procedure is understandable insofar as a puncture of the front and back contact at one and the same point with a conductive wire to an electrical short circuit of both contacts (see ) and thus lead to failure of the solar cell. Moreover, the method shown in [1] has the disadvantage that the seam area does not contribute to the generation of a photocurrent, since all layers are removed up to the metallic back contact layer.

The in the two U.S. Patents 3,903,427 and 7,276,724 The presented methods have the disadvantage that an additional process step for insulating the inner wall of the holes is necessary. In addition, a complete covering of the hole inner walls is technologically demanding and expensive. If parts of the interior walls remain free after insulation, there is still the danger of a short circuit.

The Invention has the task of thin-film solar cells with a to sewn conductive wire without short circuiting it. In addition, for sewing no further be provided inactive areas. This should be in technological simple manner, with high productivity and energy yield.

A central idea of the present invention is to the isolation to abandon the holes. The problem of short circuit when piercing all layers of the thin-film solar cell with an electrically conductive wire is solved with that the insulation, d. H. the electrically insulating sheath same with the actual connecting material, the "metallic core material" is brought along. So the problem is solved from a completely different angle as is known in the art. After the generation of a Loches will leave this as it is without any extra elaborate Coat the inner walls of the hole.

The Covering of commercially available coated wires is complete (a complete isolation of the Inner walls of a hole are as already mentioned technologically challenging). The risk of a short circuit through the wire is complete according to the invention prevented.

The The object is thus achieved according to the invention, that a thin-film solar cell is pierced, wherein a hole is formed through which an insulated conductor passes becomes. The previously occurring danger of short-circuiting on front and back contact when piercing the opening is achieved by using a wire sheathed with an insulation Fixed. After thin film solar cells with this modified Wire sewn, there is a selective removal the sheathing of the wire (eg by means of laser radiation) and thus a Exposure of the metallic core material in very specific areas. Subsequently, the exposed wire with the contacts the solar cell are electrically connected, z. B. by means of electrically conductive Adhesive.

Detailed description of the process flow

The detailed description of the process flow is based on ,

The thin-film solar cells to be connected ( 10 and 11 ) are positioned next to each other so that the collecting contact ( 13 ) of the front contact of the thin-film solar cell ( 11 ) parallel to the collecting contact of the back contact ( 14 ) of the thin-film solar cell ( 10 ) lies. The individual thin-film solar cells can both be positioned exposed and positioned and fixed on a common carrier.

Subsequently the sewing of the thin-film solar cells takes place using a sheathed and thus electrically insulated wire. Such coated wires are z. B. in the form of polyurethane-coated Copper wires commercially available. The fat The insulating sheath of the wire can in principle arbitrary to get voted. Sewing can be done in the usual way Senses using a needle.

To the machine manufacturing the seam can sewing and Embroidery machines or modifications thereof are used. It can in principle used industrial sewing machines become.

However, it is also possible first to create holes in the thin-film solar cells and to thread the wire through these holes. The holes can be generated, for example, with a laser beam or a mechanical punching tool. The shape of the seam can in principle be chosen arbitrarily. shows a possible shape.

In order to the collective contacts of the solar cells with the electrically conductive Wires can be connected, the electric insulating sheath of the wires are selectively removed. In the case of polyurethane-coated copper wires is the sheath be removed chemically or by means of a laser. The latter is a well-known method and leaves a defined and clean removal to [2].

To remove an insulating polyurethane coating around a wire, for. As pulsed excimer laser or pulsed CO ₂ laser can be used, with the former system slightly better (cleaner) results are achieved in the removal of the insulation. The wavelength of these laser systems are typically in the infrared (CO ₂ ) or in the ultraviolet (excimer). The laser fluences per pulse used for the removal of the insulation can be in the range from 100 mJ / cm ² to 100 J / cm ² . The repetition rates of the laser range from a few Hz to several kHz. The number of laser pulses that are necessary for a clean removal depend on the type and thickness of the insulating sheath.

Becomes one of the above-described laser on the surface of focused on insulating coating of the wire, a removal can achieved this layer via a laser ablation of the material become. The removal of well-defined areas can over the Using masks between laser and coated Wire to be positioned.

The lateral extent of the exposures of the metallic wire can while in a range of a few microns to several cm be adjusted arbitrarily.

Subsequently become the exposed metal wires with the contacts connected to the thin film solar cells. This can be z. B. using an electrically conductive adhesive, which at the same time the mechanical connection of the wires to the thin-film solar cells is guaranteed. The order of a conductive adhesive can doing so using a dispenser. Commercially available Dispensers work z. B. with pressurized cartridges, spindle valves or jet valves, the latter higher throughputs expected in a mass production.

To Applying a conductive adhesive must be done according to the instruction be cured by the Leitkleherstellers in a drying oven.

Modifications to the above process

The Thin-film solar cells can also after the Methodology of the process described above will be interconnected if no additional collecting contacts are present on the cells. Connecting the exposed wires can also be done directly on the transparent front contact or on the exposed back contact layer respectively.

• • Kupfer-Indium-Gallium-Diselenid, Kupfer-Indium-Diselenid, Kupfer-Gallium-Dieselenid (bzw. Selen substituiert durch Schwefel)
• • Amorphes Silizium
• • Cadmium-Tellurid
• • Mikrokristallines Silizium
• • Gallium-Arsenid

In principle, the method according to the invention can be applied to any type of thin-film solar cell on a flexible substrate. The following types are examples

• Copper Indium Gallium Diselenide, Copper Indium Diselenide, Copper Gallium Diesel Enid (or Selenium Substituted by Sulfur)
• • Amorphous silicon
• • cadmium telluride
• • Microcrystalline silicon
• • gallium arsenide

When flexible substrate can plastic sheeting, z. B. polyimide film, Metal foils, z. As copper, steel or titanium foils or composites such as B. glass fiber reinforced fabric can be used.

deviant From the above description of the process, the thin-film solar cells can first provided with holes and then accordingly be positioned next to each other.

To the Sewing the cells can be in principle any use metallic wire (copper, silver, aluminum wire, etc.). As an insulating coating of the wires can z. As polyurethane, PVC, PET, PTFE, etc. are used.

The electrical connection of the exposed wire with the contacts The solar cell can be used in addition to applying an electrically conductive adhesive also achieved via a soldering or welding process become.

Of the Soldering process can z. B. in the so-called reflow process over led the application and melting of a solder paste become. A welding of the exposed wire on the Contacts can z. B. laser beam welding respectively. Used for connecting the wire to the contacts the solar cell uses laser welding, removal can be the insulating sheathing of the wire and the connection of the wire Wire with the contacting of the surface in one process step be carried out and thus the throughput in a mass production increase.

When Device for sewing the thin-film solar cells Industrial sewing machines can be used.

With the method presented here, it is possible to generate both pure series circuits and parallel circuits as well as a combination as a series-parallel circuit of thin-film solar cells ( ). A preferred number of series-connected thin-film solar cells is 50 to 200, without being limited in any way to this number. In principle, the sewing of hundreds of thin-film solar cells after the solution according to the invention is technically possible.

LIST OF REFERENCE NUMBERS

1

substrate carrier

2

metallic Layer which serves as the back contact of the solar cell

3

photoactive layer

4

buffer layers

5

transparent, electrically conductive oxide, which as a front contact of Solar cell is used

6

metallization to support the conductivity of the front contact, Contacting the front

7

contact of the exposed back contact

8th

isolation trench for electrical separation of the front contact and on the front laid back contact

9

wire which pierces all layers of the solar cell

10

Thin film solar cell

11

Thin film solar cell

12

contact of the front contact

13

contact of the front contact

14

contact of the back contact

15

contact of the back contact

16

wire with which the solar cells are sewn

17

exposed metallic wire by selectively removing the electrically insulating jacket

18

electrical Connection of the exposed wire with the contacts of the solar cell

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 3317309 C2 [0009]
• US 3769091 [0010]
• US 3903427 [0011, 0013]
• US 7276724 [0011, 0013]

Claims (9)

Process for producing networks of flexible thin-film solar cells by interconnecting individual cells or cell complexes, characterized in that thin-film solar cells are pierced on a flexible support from the front to the carrier in a narrow range, through the resulting opening an insulated electrically conductive wire is passed whose isolation is then removed locally and a contacting of the exposed wire with the front contact or the back contact access of the thin-film solar cell takes place. Method according to claim 1, characterized in that that the interconnection is parallel or in series. A method according to claim 1 and claim 2, characterized characterized in that the piercing is done mechanically. A method according to claim 1 and claim 2, characterized characterized in that the introduction of an opening with a Laser beam takes place. Process according to claim 1 to claim 4, characterized characterized in that the stripping is done with a laser beam. A method according to claim 1 to claim 5, characterized characterized in that the interconnection with an electrically conductive Paste takes place. A method according to claim 1 to claim 6, characterized characterized in that the stitching is continuous. Method according to Claims 1 and 2, characterized that 50 to 200 cells are connected in series. Composite of thin-film solar cells, consisting from individual interconnected thin-film solar cells on flexible support, characterized in that the Pierce thin-film solar cells and sew after sewing combined with insulated wire to form a composite.

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