SE538786C2 - Method of Interconnecting Single Solar Cells into Solar CellModules - Google Patents

Description

Method of Interconnecting Single Solar Cells into Solar Cell Modules Field of the Invention The present invention relates to a method of interconnecting individual solar cells into solar cell modules Background to the Invention The invention originates from difficulties in interconnecting individual solar cells into solar cells modules. The solar cells are in literature also called Photovoltaic cells (PV cells) and the solar cell modules are called PV modules. In the following we will use the denominations "PV cells" and "PV modules" or just "cells" and "modules".

In a PV cell electric power is generated by the inflow of solar radiation into an active layer in the PV cell. The PV cell comprises a number of thin layers on a supporting plate. The size of the most used silicon cell is generally 156 by 156 mm. The individual PV cells are interconnected into larger units called PV modules. The PV cells in a module are, in order to increase the output voltage from the module, interconnected in series. The wires used in interconnecting PV cells are called tabbing wires. The traditional method of interconnecting PV cell is, as will be explained later, complicated and costly and the method of interconnections contributes substantially to the total production cost of the PV module.

The objective of the invention is to enable an effective method to interconnect PV cells into modules. The method will in the ensuing text be called the "new method" or the "invention". The invention gives several positive effects such as: Interconnection of PV cells at a low cost, and at an increased reliability of the cell. Also, the amount silver in the PV module can be reduced. The new method will be described in detail later in the text The present invention relates to a method of interconnect the PV cells into modules by a new method in which continuous strips of tabbing wires are laid out on the PV cells and that the tabbing wires are carried by a carrier in form of a tape or sheet. The continuous wires carried by tape or sheet are after being placed on the PV cells cut to a length to fit the position of the PV cells. The cut will be made in such a manner that an interconnection in series between cells is obtained in the lamination or after lamination. To clarify the advantages of the invention a more detailed description is needed of PV cells, PV modules and the method used today when interconnecting PV cells.

PV cell The PV cell comprises a number of thin layers on a supporting plate. The layers have different functions which together results in a functional PV cell. There are a number of different types of PV cells, but the two main types are: thin film PV cells and silicon PV cells. In the following we will describe a silicon cell. The incoming radiation from the sun creates a voltage across the active layer in the PV cell and an electric current can be taken from the PV cell via electrical connections on the top- and backside of the PV cell. The topside and backside have different polarities. The topside is the side which receives the incoming solar radiation. The electrical connection on the topside is called topcontact and the contact on the backside backcontact. The connection on the topside is made on a thin transparent layer which is electrical conductive. The transparent conduction layer is called TCO (Transparent Conduction Oxide). The TCO layer is thin and can thus only handle small current densities. Therefore, a matrix (a grid) of highly conducting material is imposed on top of the TCO layer to collect the current. The grid consists of a pattern with fingers and busbars. The fingers are narrow (small width) metallic strips with a width of 0,1 to 0,3 mm. The distance between individual fingers are 2 to 10 mm. Busbars are running across and mostly perpendicular to the fingers. The busbars contact the fingers and it is the busbars that conduct the current from the PV cell. The number of busbars is usually two to three but other numbers can be used. The busbars have a width between 1,5 - 2,5 mm but other widths may be used. As noted above the width of the fingers are in the order 0,1 to 0,3 mm. The grid with fingers and busbars will however reduce the efficiency of the PV cell because the nontransparent material in the grid shadows the surface of the PV cell from the solar radiation. In the making of the PV cell, it is thus important to have a small as possible shadowing area from the grid. It is essential to choose a material in the grid that has a high conductivity for the electrical current. The material in the grid on the PV cells today is silver. Other materials are possible but they have disadvantages. The grid pattern is applied by screen printing a silver paste on top of the PV cell.

The production methods for PV cells and modules are continuously developed and the cost of production is going down. But the cost of the silver is not going down and the cost of silver is emerging as a dominant cost. It can also be noted that the cost of silver is not expected to go down in the future. The backside of the PV cell do not need to be transparent to light and the contact on the backside can be made on a metalized surface that partially or completely covers the backside of the PV cell. Other material than silver are used on the backside of the PV cell. A commonly used material is aluminum.

Module A number of individual PV cells are electrical connected to each other to form a PV module. The PV cells are interconnected in series in which the positive electrode (usually the backside of the PV cell) is connected to the negative electrode of the PV cell (usually the topside of the cell) of a neighbor cell. The cells are placed in a row and the cells in the row are interconnected in series. In this it is the busbars on the topside of the PV cell which is connected to the metalized backside. The number of cells in the row can vary but a typical number is 10. The cell voltage of an individual cell is of about 0,5 volts. Ten cells interconnected in series thus have a voltage of 5 volt. Six of the rows described above are placed close and parallel to each other to form the module. The distance between two rows is usually between 2 to 10 mm but other distances may be used. The rows are then interconnected in series and 6 rows with 10 cells in each row give a module having a voltage of 30 volt and a surface area of 1,6 m<2>. The description above describes a typical PV module but other modes of interconnections and other numbers of PV cells in the module than that described above can be used. PV cells and the row of PV cells are strengthened and mechanically supported by different sheets in the process of production which will be described in the next section.

The Production Method Used Today The electrical interconnection of PV cells to form a module is today achieved in a rather complicated process. This process and the different steps used in the production are, in detail, described below.

Again we note that the individual PV cells are interconnected in series and the positive electrode on one PV cell is connected to the negative electrode on a neighbor PV cell or the other way around. And that the positive electrode is on one side of the cell (usually on the backside) and that the negative electrode is on the other side (usually the topside) of the PV cell. This gives that an interconnecting electrical conduction strip goes from the topside of one PV cell to the backside of a neighbor PV cell. This electrical conduction strip is called "tabbing wire". In the following text we will use "tabbing wire" when referring to the "interconnecting electrical conduction strip". Further, it can be noted that certain types of PV cells can be manufactured in such a manner that the topcontact of the PV cells is draw through the PV cell to the backside of the cell. Still, the plus and minus electrodes have to be interconnected in series. In the ensuing description we will describe interconnection of PV cells which have a topcontact on the topside and a backcontact on the backside. But, it can here be noted the invention also can be used to connect PV cells having electrodes on one side only.

The first step in the production of a module is to place one PV cell on a carrier plate. The backside of the cell is facing the carrier plate. Tabbing wires (electrical interconnecting lines) are placed on the PV cell, perpendicular to the fingers and on the busbars. The fingers and busbars are described in the foregoing section. The number of tabbing wires is usually two or three (the same as the number of busbars). The tabbing wires extend across the length of the topside of the PV cells and further a free length which is the same as the length of a PV cell. The "free length" of the tabbing wire will not, at this stage, be in contact with a PV cell. The next step in the production is to place a second PV cell on the carrier plate close to the first PV cell and on the above said tabbing wire. The backside of the second PV cell will now be on and in contact with the earlier mentioned free length of the tabbing wire. Thus, an electrical connection is established between the topside of one cell and the backside of a neighbor PV cell via the tabbing wire. The procedure is repeated and tabbing wires are placed on the topside of the second PV cell and the tabbing wire extends across the topside of the second cell plus the above described free length. Cell number three is now placed on the free length of the tabbing wire. The process is now repeated until a row with the desired number (usually 10) of PV cells is obtained. The tabbing wires are soldered to the topside and backside of the PV cells. This soldering is usually made after each placing of a PV cell on the carrier plate. The soldering can also take place after a complete row has been laid out.

The row of PV cells is now moved to and placed with the topside down on a sealing sheet which in turn rests on a topglas. The topside of the PV cells is the side which receives the incoming sun light. Note here that the topglas is facing down in the further building of the module. On the topglas there is as mentioned above a sealing sheet which is of a polymer material. The most common material in the sealing sheet is a material called EVA (Ethylene Vinyl Acetate) but other materials can be used. In the ensuing building of the module a second row of PV cells will be placed along and parallel to the first row. The second row of PV cells comprises a row of PV cells interconnected with tabbing wires in the same manner as the first row. This process continuous until the desired number (usually 6) of rows in the module is reached. The rows are connected in series in a soldering process and outgoing contacts for the completed module are soldered in place. The module with the PV cells is covered with a second sealing sheet (EVA). The second sealing sheet is of the same type as the above mentioned first sealing sheet which is resting on the topglas. The second sealing sheet is thereafter covered with a backsheet of a suitable material. This backsheet faces the outer environment and is the backside is of the module. The complete module with topglas, sealing sheet 1, PV cells with interconnecting tabbing wires, sealing sheet 2 and backsheet is heated (baked) in vacuum at a temperature of 150 °C . In the baking the sealing sheets softens, melts and fix the module into a robust and sealed unit that can withstand the outer environment. The baking process is also called "lamination".

A more detailed description of the lamination is given in the following.

The complete module with topglas, sealing sheet 1, PV cells with interconnecting tabbing wires, sealing sheet 2 and backsheet is placed on a heated (150 °C) plate in a laminator chamber. The chamber is closed and evacuated to vacuum. The vacuum chamber has a rubber membrane in the lid at the inside of the vacuum chamber. At start of the lamination process the membrane is sucked up against the lid by the vacuum. When the chamber is evacuated the space between the lid and the membrane is opened to the ambient air and the membrane will, due to the vacuum in the chamber, push the module against the heated lower part of the chamber. This "push" will be exerted on the module for about 10 minutes. The push and the heat will soften and melt the sealing sheets and fix the module to a robust unit. The vacuum in the chamber is vented, the chamber is opened and the finished module is removed from the chamber.

Finally, it is noted that placing and soldering of tabbing wires to the topside of the PV cells has to be made on to busbars on the PV cells. Soldering to the finger only will not work because the mechanical strength will be to low and the fingers will be torn lose from the topside of the PV cell when handling. I.e., when the row comprising 10 cells is moved to the topglas with the sealing sheet. That is, busbars are needed and the tabbing wires are soldered to the busbars. With the new method the busbars on the PV cells will not be needed as explained below.

New Method ( NM) The New Method (NM) is a method to interconnect PV cells into modules. The NM reduces the cost of production and cost of material. These advantages are obtained by using continuous strips of tabbing wires to electrically interconnect individual PV cell into a module. The tabbing wires are made of a material which has a high conductivity for electricity, preferably a metallic material. The continuous strips of tabbing wires are laid out on the topside and backside of the PV cells. The continuous strips of tabbing wires are according to the invention attached to and carried by a tape or a sheet. The tabbing wires can also be integrated on the earlier described sealing sheets which are used in the manufacturing process. The sealing sheets have thus already in the manufacturing of the sealing sheets been furnished with continuous strips of tabbing wires. Thereafter the tabbing wires are, according to the invention, interrupted at certain intervals in a pattern that enables an interconnection of the PV cells in series. With "interrupted" is here meant that the tabbing wire is cut and the path for current is hindered. The final interconnection of all of the PV cells in the module and closing of the electrical circuit is obtained in the laminating step. It may also be possible to cut the tabbing wires after the laminating step. The NM is preferably suited to use there the individual PV cells have their plus and minus electrodes on the top- and backsides, respectively. In this case continuous strips of tabbing wires carried by tape or sheet will be applied both on the topside and the backside of the PV cells. However, the NM can be used to interconnect PV cells having plus and minus electrodes on one side of the PV cell. In the following we will describe a manufacturing method used in the NM. It is noted beforehand that the improvement and the invention is to use continuous strips of tabbing wires carried by tape or sheet and that the tabbing wires are, after being placed on the PV cells, cut in such a manner that an interconnection in series is obtained in the lamination. The tabbing wires are preferable cut before lamination. But, it is possible to cut the tabbing wires after lamination. We will also draw the attention to the fact that continuous strips of with tabbing wires also can be used to interconnect rows of PV cells in a final interconnection of the PV module. That is, the tabbing wires do not only interconnect PV cells in a row but also interconnect rows.

The process in the NM starts with a topglas being put on a carrier in the process line. A first sealing sheet (EVA) is placed on the topglas. Continuous strips of tabbing wires carried by tape or sheet are placed on the sealing sheet. With continuous is here meant that the tabbing wires are in a form of a continuous and uninterrupted strips. The number of tabbing wires may vary depending on the number of tabbing wires to be used. The tabbing wires consist of a material that can conduct current. The material in the tabbing wire is preferably solderable to the fingers on the PV cells and also to each other. The solderability to the fingers is not needed if a good electrical contact between finger and tabbing wire can be obtained. A number (usually 10) of PV cells is now placed in a row with the topside of the PV cell down and facing the tabbing wires. The cells in the row are separated with a small distance, a gap, between adjacent PV cells and that sections of the tabbing wires crossing the gap are not covered by the PV cells. The building of the module continues and a second set of continuous tabbing wires carried by tape or sheet is placed on the PV cells that just have been placed in a row. The tabbing wires in the second set are now resting on and contact the backcontacts on the backsides of the PV cells. The tabbing wires on topside and backside are laid out above each other so that the tabbing wires crossing the gap (the space) between two cells can contact each other later in the process. The material in the tabbing wire can preferably be soldarable to the material in the backcontact. We now have continuous tabbing wires on the topside and on the backside of the PV cells. Actually, the PV cells are at this stage connected in parallel. The process above is now repeated until the wanted number of rows in the module is obtained. An alternative is to place all the PV cells to be used in the module on a topglas and sealing sheet on which a set of continuous of tabbing wires have been laid out. Thereafter, the backside of the cells is contacted with continuous strips of tabbing wires which are carried by tape or sheet. The now laid out tabbing wires on topsides and backsides of the PV cells have to be configured to facilitate a connection in series. The tabbing wires on the topside are, further, according to the invention cut (interrupted) in the space between two cells in a row. This cut is made in close proximity to one of the edges of the PV cell. The tabbing wires on the backside are according to the invention cut in a similar manner but close to the edge opposite to the above said edge. In the space between two PV cells we now have tabbing wires that extend over the space between PV cells. The tabbing wires also overlap in said space. By foregoing a later description it is noted that it is these overlapping tabbing wires that contact each other in the interconnection of PV cells thus forming the contact in series between the plus and minus electrodes of adjacent PV cells.

The process continues with a sealing sheet that covers the PV cells in the module. This is not needed if a sealing sheet having tabbing wires already has been placed on the PV cells. Finally, a backsheet is placed on top.

It is noted that continuous tabbing wires also can be used to interconnect the rows in series and that the final interconnection of the rows takes place in the step of lamination.

In the above we have noted that the continuous strip of tabbing wire can be carried by tapes or sheets. This is further clarified below. Preferably the continuous strips of tabbing wires can be carried by a tape. The tape can also be a sheet carrying several strips of tabbing wires. The tape is made out of a suitable materiel i.e. a polymer but other materials may be possible. The tape can also have an adhesive applied on one or both sides of the tape. This ensure a good fixing of the tape to the sealing sheet or/and the PV cell. The tabbing wires can also be integrated in the sealing sheets. The tabbing wires carried by a tape or a sheet are as described above cut after being placed on the PV cells in such a manner that a contact in series between cells is obtained in the lamination. The cutting can also be made after lamination.

In the above the general word "cut" and "interrupted" is used. The cutting and interruption of the tabbing wires can be made mechanically with a knife or a plunge. Preferably laser cutting is used. In the above description the cutting is made when both topside and backside tabbing wires have been laid out. Other orders of cutting are also possible. I.e. the topside tabbing wire is cut before the backside tabbing wire has been laid out. It is also possible to cut the tabbing wires after lamination. The cutting will in this case be made with a laser through the topglas to cut the top tabbing wire and the backside tabbing wire is cut by a laser beam through the backsheet. This requires that the topglas and the backsheet sheet are transparent to wavelength of the laser beam.

A combination of precut tabbing wires and cutting after laying out the tabbing wires can be used. As an example: The topside tabbing wires carried by the tape can be already cut when laid out. Preferably a tape or sheet is here used to fix and hold the tabbing wires in place. And the PV cells are placed in the correct position relative to the cuts. The backside tabbing wires are, thereafter, laid out as a continuous tabbing wires and the continuous tabbing wires are cut after been laid out. Preferable laser cutting is used here. In the above it is said that the tabbing wires are cut in the space between two adjacent PV cells. In the cutting of one tabbing wire in the space between two cells there is a risk of damaging an underlying tabbing wire. This can be avoided if the position of the cut is so that a shielding of the topside tabbing wire is obtained when the laser cutting the backside tabbing wire or vice versa. The PV cell functions here as a shield. This requires that the surface of the PV cell is non-conducting close to the edges of the PV cell. One way to have a non-conduction backside is to let a part of the backside close to the cell edge being non- metalized when using the new method.

Here it shall be noted that the PV module is from start build on a topglas and no lifting of rows of PV cells is needed which much reduces the stress on the PV cells. Also, a strong fixing of the tabbing wires to busbars is not needed. Thus the PV cells can be made and used without busbars.

The module is now ready for the baking process, the lamination. The lamination, done at a temperature of about 150 °C, is as described earlier. At the temperature of 150 °C the sealing sheets soften and melt. The earlier described push from the outside and the vacuum on the inside will bring the free tabbing wires in the space between the PV cells in contact with each outer. We shall also note the distance between two cells is usually between 2 to 10 mm but can be larger and the thickness of PV cell is of about 0,2 mm. That is, the free tabbing wires just have to be pushed 0,2 mm to be in contact. During the pushing and heating the tabbing wires also securely contact the fingers on the topside and the metalized backside of the PV cells.

Preferably can the tabbing wires be furnished with a solder that melts and solders at the lamination temperature and thus the tabbing wires are soldered to each other, to the fingers and to the backcontact. Once again we note that the outside push and the vacuum have brought the free parts of the tabbing wire in the space between PV cells in contact with each other.

Advantages with the invention Simpler: Interconnection of individual PV cells is much simplified by using continuous strips of tabbing wires carried by tape or sheet. Soldering is simplified as the soldering can be made in final lamination.

Robust: The process will be more robust when busbars not are needed. In the traditional building method, the interconnecting tabbing wires have to be applied on the busbar with a high precision which put high demands on the precision of the handling equipment. Reduction of Material: Not needing the busbars reduces the amount of silver used with about 40 to 50 %. The silver constitutes of about 25 % of the total cost of material in the PV cell. A reduction of this cost is therefore essential.Reduce of the Number of Rejects: The number of handling steps in the process is reduced which reduces the risk of PV cell breakage during handling.

Increased efficiency: The rather wide busbars used in the conventional method shadows the PV cell. The tabbing wires used on a busbarless PV cell can have a smaller shadowing area.

Summary of the Invention The objective of the invention is to achieve an improved method for interconnecting individual PV cells into a PV module at a substantial reduction of cost of the process of interconnection and also a reduction of cost for the material used in the topcontact on the PV cell. Further, can according to the invention, the efficiency of the module be increased. According to the presented invention the method set forth by description ischaracterizedof features of claim 1. Thus according to the principle of the invention are interconnection between individual PV cells obtained by continuous strips of electrical conduction tabbing wires laid out on the surface of the two sides of the PV cells. The continuous strips of tabbing wires are carried by tape or sheet. The tabbing wires on the topside are, further, according to the invention cut (interrupted) in the space between two cells in a row. The cut is made in close proximity to one of the edges of the PV cell. The tabbing wire on the backside is cut in a similar manner but close to the edge opposite to the above said edge. This cutting is made after the continuous tabbing wires have been laid out on the PV cells. The cutting can be made before or after lamination. In the space between two cells we now have tabbing wires that extend over the space between PV cells. The tabbing wires also overlap in said space.

The invention also relates to a method of interconnecting individual PV cells into a module according to claim 2 in which the continuous tabbing wires carried by tape or sheet are cut before lamination.

The invention also relates to a method of interconnecting individual PV cells into a module according to claim 3 in which the continuous tabbing wires carried by tape or sheet are cut after lamination.

The invention also relates to a method of interconnecting individual PV cells into a module according to claim 4 in which the continuous tabbing wires carried by tape or sheet are cut with a laser.

The invention also relates to a method of interconnecting individual PV cells into a module according to claim 5 in which the continuous tabbing wires are carried by a tape or sheet. The tabbing wires are cut with a laser after being laid out on the PV cells. When cutting the tabbing wires underlying tabbing wires are shielded by the PV cells.

The invention also relates to a method of interconnecting individual PV cells into a module according to claim 6 in which the topside tabbing wires carried by tape or sheet are pre-cut. The backside tabbing wires carried by tape or sheet are in the form of continuous strips which are cut after being placed on the backside of the cells.

The invention also relates to a method of interconnecting individual PV cells into a module according to claim 7 in which the topside tabbing wires carried by tape or sheet are pre-cut. The backside tabbing wires carried by tape or sheet are in the form of continuous strips which are cut after being placed on the backside of the cells. He cutting of the backside tabbing wire is made with a laser.

The invention also relates to a method of interconnecting individual PV cells into a module according to claim 8 in which the topside tabbing wires carried by tape or sheet are pre-cut. The backside tabbing wires carried by tape or sheet are in the form of continuous strips which are cut after being placed on the backside of the cells. He cutting of the backside tabbing wire is made with a laser and the PV cell shields the topside tabbing wires during the cutting of the backside tabbing wires.

Brief Description of the Drawings Figure 1 shows a Photovoltaic Cell (PV cell) with an active layer, a topcontact and a backcontact. Figure 2 shows the contact pattern (the grid) used to transport current from the topside of a PV cell. Figure 3 shows the interconnection in series between the topcontact and backcontact of PV cells.

Figure 4 shows a module with tabbing wires drawn between the PV cells.

Figure 5 shows a tape or sheet with continuous tabbing wires used to interconnect PV cells according to the invention. Figure 6 shows a module according to the invention with continuous tabbing wires applied on both topside and backside of the PV cells. The figure shows the module before cutting of tabbing wires and before lamination. Figure 7 shows a module with the continuous tabbing wires cut according to the invention. The figure shows the module before lamination.

Figure 8 shows a module according to the invention after lamination.

Figure 9 shows schematically how the PV cells can shield underlying tabbing wires from being damaged when cutting overlaying tabbing wires.

Detailed Description of Preferred Embodiments Figure 1 shows a PV cell 1 having an active layer 2, a topcontact 3 and a backcontact 4. A topside 6 receives incoming solar radiation 5. The solar radiation is schematically shown with arrows. Figure 1 also defines a backside 7 of the PV cell. The incoming solar radiation 5 generates a voltage in the active layer. The voltage sets up a current which is led from the PV cell via the topcontact 3 and the backcontact 4. Figure 1 shows a PV cells having the topcontact and the backcontact on the two sides of the PV cell. There are also PV cells in which the topcontact 3 has been led down to the backside 7 of the PV cell, this is not shown in a figure. Figure 2 shows a PV cell 20 on which a grid has been applied on the topside 6 of the PV cell. The grid comprises fingers 21 and busbars 22. Figure 2 show a common pattern of a grid on a PV cell but other types of patterns may occur. Figure 3 shows how PV cells 34 are interconnected in series via tabbing wires 31 which extends from an electrode 33 having positive polarity (plus electrode) to an electrode 32 having negative polarity (minus electrode). Figure 3 shows a PV cell having electrodes on each side of the PV cell. Figure 4 shows a module build with the traditional method in which tabbing wires are drawn from a topcontact of one PV cell to the backcontact of a neighboring PV cell. PV cells 1 are assembled into a module 40. Figure 4 shows only a side view of a section of a row with a number of the PV cells 1. The module has a topglas 41 which is facing down in the figure, a first transparent sealing sheet 42. The sealing sheet 42 is usually made of a polymer material called EVA (Ethylene Vinyl Acetate). Solar radiation passes through the topglas and the sealing sheet 42. The individual PV cells 1 in the module are interconnected via tabbing wires 43. The tabbing wires 43 extend from a topcontact 44 to a backcontact 45 on an adjacent PV cells. On the PV cells there is a second sealing sheet 46. The assembly of the module is finished with a backsheet 47. After this, the module is baked in a laminator, not shown with a figure. Figure 4 only shows a part of a row in a complete module. A complete module usually has 6 rows with ten PV cells in each row. For clarity it shall be pointed out that figure 4 shows the module with distorted scales. The actual PV cell 1 has in reality a thickness of about 0,2 mm and the length of the normally used silicon PV cell is 156 mm. The distance between two adjacent cells is of about 2 to 10 mm. Figure 5 shows a side view 50a and a top view 50b of a tape or sheet 51 carrying continuous strips of tabbing wires 52. The tabbing wires 52 are electrical conduction strips that interconnect PV cells and conduct current between cells. The tabbing wires can have a solder which enables the tabbing wires to be soldered to each other and also soldered to the topcontact 3 and the backcontact 4. The solder can be Bi/Sn but other solders are possible. Figure 6 shows a side view of a module being built according to the invention with tabbing wires 64a and 64b. Figure 6 shows the tabbing wires 64a, 64b being carried by tape or sheet 62a, 62b. The module is shown before cutting of the tabbing wires and also before lamination. The figure also shows a topglas 61. A sealing sheet 63 is placed on the topglas 61. On top of the sealing sheet 63 we here show the tape or sheet 62a with the continuous strip of tabbing wires 64a. The tabbing wire 64a contacts the topcontact 3. The topcontact can be the busbars 22 shown in figure 2. Preferably the PV cell is a cell without busbars and the topcontact is in this case the fingers 21. The PV cells are separated by a space 65. The second sheet 62b with continuous tabbing wires 64b is placed on the PV cells. The tabbing wires 64b contacts the backcontact 4 on the PV cells. The tabbing wires can also be integrated into the sealing sheets 41, 46. Figure 6 shows a not complete module before cutting of the tabbing wires and before lamination. The module after cutting the tabbing wires is shown in figure 7. The completed module after lamination is shown in figure 8. We can already here note that it is the parts of the tabbing wires extending over the space 65 that contact each other during lamination. Figure 7 shows the module being built after the tabbing wires 64a, 64b have been cut into discontinuous tabbing wires 71a, 71b. The position of the cut is shown with interruptions 72, 73. Figure 8 shows a module 80 after lamination with PV cells 81 interconnected by tabbing wires 82, 83 carried by the tape or sheet 62a, 62b or directly by the sealing sheets 41, 46. The tabbing wire 82 contacts the topcontact 3 and the tabbing wire 83 contacts the backcontact 4. Figure 8 shows the module after lamination and the tabbing wires 82, 83 are now brought in contact with each other in the space 65 and a contact in series between individual PV cells has been obtained. The sealing sheets 41, 46 have softened, melted and filled the space 65 between the PV cells. The melted sealing sheet is indicated with pointers 84, 85. For clarification consult figure 6 in which one of the sealing sheets 63 on the topglas 61 is shown before lamination. In the cases where the tabbing wires are carried by the tape or sheet have the tapes or sheets merged with the sealing sheets. The figure 8 also shows a topglas 86 and a backsheet 87. Figure 9 shows how tabbing wires 91a, 91b carried by a tape, sheet or sealing sheet 92a, 92b can be shielded by PV cell 93. Interruptions 94a, 94b are cut by lasers 95a, 95b. Laser beams are schematically shown with arrows 96a, 96b. Sections of a surface of the PV cell 93 being under a part of tabbing wire 97a, 97b are non-conducting. A section 98 under the part of the tabbing wire 97b is shown in figure 90b.The figure 9 shows the module before lamination. After lamination the tabbing wires on both sides of the PV cells will contact each other. This is not shown with a figure.

In the description of the invention it is noted the method of interconnection of cells also can be used to interconnect row of cells. Such an interconnection is not shown with a figure.

Other modes of shielding, than those above, when cutting with laser are possible. I.e. the topside tabbing wires 64a can be cut with a laser in the space 65 before the backside tabbing wires 64b have been placed. The cutting of the backside tabbing 64b wires can thereafter be made on the PC cells as shown in figure 9. Thus, the topside tabbing wire is shielded from being damaged by the laser beam.

Claims (8)

1. Method of electrical interconnecting individual Photovoltaic solar cells, PV cells, used in the making of a PV module. The said PV module comprises a topglas (41,61, 86), sealing sheets (42, 46), a number of PV cells (1) and a backsheet (47, 87). The PV cells have an active (2) layer in which an electrical current is generated, a topcontact (3) on the topside (6) and a backcontact (4) on the backside (7) and electrical current is drawn from the PV cell via the backcontact and topcontact. The PV cells are placed in rows with a space (65) between individual PV cells in the row and the rows are placed with a distance between the rows. Said PV cells are interconnected by tabbing wires (31, 43) of an electrical conductive material and the tabbing wires contacts the topside (6) and the backside (7) of the PV cells, characterized in that the tabbing wires on the topside and backside are , in the building of the module laid out as continuous strips of tabbing wires (52, 64a, 64b) and that said tabbing wires are carried by tape or sheet (51, 62a, 62b) and that an interconnection in series between the individual PV cells is obtained by cutting the topside tabbing wires (64a) and the backside tabbing wire (64b) in the space (65) between two cells and that the cutting is made after the continuous strips of tabbing wire have been laid out on the topside and backside of the cells.

2. Method according to claim 1, characterized in that the cutting of the tabbing wires (64a, 64b) is made before lamination and that an interconnection in series is obtained in the lamination process.

3. Method according to claim 1, characterized in that the cutting of the tabbing wires (64a, 64b) is made after lamination and the cutting is made in such a manner that an interconnection in series between adjacent cells is obtained.

4. Method according to any of the claims 1, 2, 3 characterized in that the cutting of the tabbing wires (64a, 64b) is made with a laser (95a, 95b).

5. Method according to claim 4, characterized in that the tabbing wires (64a, 64b) are cut with the laser (95a, 95b) and the tabbing wire being under the tabbing wire being cut is shielded by a PV cell (93).

6. Method of electrical interconnecting individual Photovoltaic solar cells, PV cells, used in the making of a PV module. The said PV module comprises a topglas (41,61, 86), sealing sheets (42, 46), a number of PV cells (1) and a backsheet (47, 87). The PV cells have an active layer in which an electrical current is generated, a topcontact (3) on the topside (6) and a backcontact (4) on the backside (7) and electrical current is drawn from the PV cell via the backcontact and topcontact. The PV cells are placed in rows with a space (65) between individual PV cells in the row and the rows are placed with a distance between the rows. Said PV cells are interconnected by tabbing wires (31, 43) of an electrical conductive material and the tabbing wires contacts the topside (6) and the backside (7) of the PV cells, characterized in that continuous strips of tabbing wires (64a, 64b) are laid out in the topside and the backside of the PV cells and that the tabbing wires (64a, 64b) are carried by tape or sheet (51, 62a, 62b) and that an interconnection in series between the individual PV cells is obtained by pre-cutting tabbing wire (64a) before placing the tape or sheet (51, 62a) with the tabbing wire (52, 64a) on the topside and that the backside tabbing wire carried by tape or sheet is cut after being laid out on the PV cells and the cuts of the top- and backside tabbing wires are made in such a manner that an interconnection in series is obtained in the process of lamination.

7. Method according to claim 6 characterized in that the cutting of the tabbing wires on the backside (52, 64b) is made with a laser (95b).

8. Method according to claim 7, characterized in that the backside tabbing wires (64b) are cut with the laser (95b) and the topside tabbing (64a) wire being under the tabbing wire being cut is shielded by the PV cell (93).