WO2017093527A1

WO2017093527A1 - Interconnection of back-contacted solar cell, a solar panel having such interconnection

Info

Publication number: WO2017093527A1
Application number: PCT/EP2016/079658
Authority: WO
Inventors: Lambert Johan Geerligs; Bas Bernardus VAN AKEN; Evert Eugène Bende; IIkay CESAR; Nicolas Guillevin; Victor ROSCA
Original assignee: Stichting Energieonderzoek Centrum Nederland
Priority date: 2015-12-03
Filing date: 2016-12-02
Publication date: 2017-06-08
Also published as: NL2015899A; TW201731117A; NL2015899B1

Abstract

A solar cell includes a semiconductor substrate, with a front and rear surface. The solar cell is provided in the rear surface with a first type doped area of first conductivity type, and is further provided with a second type doped area of opposite second conductivity type. A dielectric layer on the rear surface covers at least the first type doped area. The rear surface includes on the dielectric layer a metallization pattern connected with the first type doped area and provided with contact pads for locally contacting the metallization pattern with an interconnection layer. The interconnection layer is provided with conductive contacts at locations of corresponding contact pads. Each contact pad is connected with a corresponding conductive contact by an intermediate conductive body, that is laterally extending outside the contact pad area over a rear surface portion covered by the dielectric layer and adjacent to the contact pad.

Description

Interconnection of back-contacted solar cell, a solar panel having such

interconnection.

Field of the invention

The present invention relates to an arrangement of a solar panel provided with an interconnection of a back contacted solar cell to a patterned conductive back-sheet. Also, the invention relates to a solar panel provided with such interconnected back contacted solar cells. Moreover, the invention relates to a method for manufacturing such an interconnected back contacted solar cell or solar panel.

Background of the invention

A back-contacted photovoltaic cell or solar cell, based on either a

monocrystalline or polycrystalline silicon substrate, comprises a metallization scheme in which contacting electrodes of positive and negative polarity are each arranged on a back side of the solar cell.

One example of such solar cell relates to configurations, in which the solar cell is provided with an emitter layer in a front radiation receiving surface.

In such a type of back contacted solar cell, metallization schemes apply either metallization wrap through (MWT) or emitter wrap through (EWT) to allow the contacting electrodes to the back side so as to have a maximal area available for photovoltaic conversion on a front side of the solar cell that in use faces a radiation source (e.g., the Sun). The top layer of the solar cell connects to a front side contacting electrode on the backside of the cell by means of one or more metal plugs in holes that extend through the wafer (MWT) or by means of many holes through which the emitter extends through the wafer (EWT).

An alternative embodiment of a back contacted solar cell relates to an

interdigitated back contacting scheme (IBC) with a doped structure in or on the rear surface of the substrate to be contacted (referred to as doped contacted areas on the rear surface ) that comprises p-type and n-type junctions that are interdigitated.

In these types of back-contacted solar cells, a cell contact metallization or contacting electrode is arranged on the rear surface as an interface with the doped semiconductor area of positive or negative polarity on the rear surface of the substrate arranged as contacting area. To avoid electrical shorts between adjacent doped back- contacted areas of different polarity, the area of the contacting electrode typically is within the area of the associated doped back-contacted area. In addition, the doped back-contacted areas are covered by a dielectric layer that provides passivation where the contacting electrode is not directly in contact with doped semiconductor, which reduces recombination.

In prior art solar panels that apply back-contacted solar cells as for example described above, the back contacting electrodes are connected to a conductive patterned layer at contact pad locations. The conductive patterned layer has a pattern layout that corresponds to the locations of the contacting electrodes of the solar cells and their respective polarity. The contact pads are defined as the areas of the back contacting electrodes that contact the conductive patterned layer, within the same polarity.

The conductive patterned layer may be a so-called back-sheet that consist of a polymer layer on which a metallized patterned layer has been created. Alternatively, the conductive patterned layer may consist of metal strips or wires.

The contacting electrodes are connected to the conductive patterned layer by an intermediate conductive body which contacts the contact pad within the area of the contact pad and contacts the area of the conductive patterned layer. Again, to avoid short-cuts between the different polarities, the area of intermediate conductive body is within the area of the contact pad.

Typically, this metallization scheme has a disadvantage that relatively large contacting pads are required with use of correspondingly large amounts of intermediate metallization material.

Also, in IBC applications this requirement has the effect that some lateral interspace must be provided in the rear surface of the substrate between the back- contact area of one polarity and the back-contact area of opposite polarity to avoid that a contact pad overlaps with the area of the adjacent back-contact area of opposite polarity. Such interspace replaces doped rear surface area and may reduce the efficiency of charge collection of the back-contact areas. Interspace also requires longer diffusion lengths of carriers in the semiconductors, which can give rise to

recombination and efficiency loss. Summary of the invention

It is an objective of the present invention to overcome one or more of the above disadvantages of the prior art.

This objective is achieved by an arrangement of a solar cell on an interconnection layer ,

the solar cell comprising a semiconductor substrate of a base conductivity type and with a base doping level, with a front surface for receiving radiation and a rear surface, the solar cell being provided in at least the rear surface with at least one first type doped layer area of a first conductivity type, and

the solar cell further being provided with at least one second type doped layer area of second conductivity type that is opposite to the first conductivity type;

a dielectric layer being arranged on the rear surface covering at least the first type doped layer area;

the rear surface comprising on the dielectric layer a metallization pattern that is conductively connected with the first type doped layer area and is provided with one or more contact pad areas for locally contacting the metallization pattern with the interconnection layer;

the interconnection layer being provided with one or more conductive patterned contacting areas each with a location corresponding with a location of said one or more contact pad areas, for contacting at said corresponding location with the contact pad area;

each of said at least one contact pad areas being connected with a corresponding conductive patterned contacting area by an intermediate conductive body;

the intermediate conductive body laterally extending outside the surface area of the contact pad over a rear surface area portion that is covered by the dielectric layer and is adjacent to the contact pad, and

the rear surface area portion over which the intermediate conductive body is extending, comprising a doped area portion of the second conductivity type comprising the second type doped layer area.

Advantageously, the arrangement provides that as a result of the relatively larger contact surface between the intermediate conductive body and the interconnection layer, the contact resistance of the electric contact between the contact pad and the patterned interconnection layer is reduced. In addition, the contact resistance reduction also allows that the contact pad on the rear surface of the solar cell can be reduced in size. The reduction of the contact pad size has the advantage that less contact material such as silver is required per contact area, thus saving on materials and on

manufacturing costs. Also, this measures causes a reduction of the recombination effect at the contact(s).

According to an aspect, the invention provides an arrangement as described above, wherein the rear surface area portion comprises a doped area portion of base conductivity type.

According to an aspect, the invention provides an arrangement as described above, wherein the rear surface area portion comprises, or additionally to the doped area of base conductivity type comprises, a doped area portion of the second conductivity type comprising the second type doped layer area.

According to an aspect, the invention provides an arrangement as described above, wherein the rear surface area portion comprises the base conductivity type doped area portion and the second conductivity type doped area portion, wherein either the base conductivity type doped area portion is arranged between the first conductivity type area portion and the contact pad area, or the second conductivity type area portion is arranged between the base conductivity type doped area portion and the contact pad area.

According to an aspect, the invention provides an arrangement as described above, wherein the solar cell is metal-wrap-through, MWT, type and the first type doped layer area is arranged in the front surface of the substrate, and the contact area comprises at least one via conductor from the first type doped layer area to the metallisation pattern on the rear surface.

According to an aspect, the invention provides an arrangement as described above, wherein the solar cell is interdigitated-back-contact, IBC, type and the first type doped layer area is arranged in the rear surface of the substrate in between either neighboring second type doped layer area portions or neighboring base conductivity type doped area portions.

According to an aspect, the invention provides an arrangement as described above, wherein the contact pad area comprises a ring structure, the ring structure comprising a ring of a conductive material, and an exposed area free from the conductive material and enclosed by the ring, in which the exposed area is covered by a dielectric layer, and in which the intermediate conductive body covers and contacts the ring, and covers the dielectric layer on the exposed area.

According to an aspect, the invention provides an arrangement as described above, wherein the solar cell comprises a second contact area, the second contact pad area being adjacent to the contact pad area but separated by an intermediate dopant region of conductivity type opposite to the type doped layer that the contact pad area is in electrical contact with, and covered by a dielectric layer, wherein the intermediate conductive body is arranged on the contact pad area and on the second contact pad area, and wherein the intermediate conductive body bridges the intermediate dopant region of opposite conductivity type while covering said dielectric layer.

According to an aspect, the invention provides an arrangement as described above, wherein the intermediate conductive body bridges multiple intermediate dopant regions of opposite conductivity type between the contact pad area and the second contact pad area while covering said dielectric layer.

According to an aspect, the invention provides an arrangement as described above, wherein the contact pad area is a region of a branched conductor network.

According to an aspect, the invention provides an arrangement as described above, wherein the branched conductor network comprises at least one busbar and fingers, the fingers extending as branches from the busbar.

According to an aspect, the invention provides an arrangement as described above, wherein the branched conductor network comprises interruptions, such that the dielectric layer is exposed and the intermediate conductive body extends over the dielectric layer in one or more of the interruptions.

According to an aspect, the invention provides an arrangement as described above, wherein the intermediate conductive body is one selected from a group comprising an electrically conductive adhesive, a composite or a mixture of non- conductive filler material and conductive material, a solder.

According to an aspect, the invention provides an arrangement as described above, wherein the interconnection layer is either a sheet provided with at least the first conductive pattern layer, or an arrangement of at least a plurality of conductive strips or wires arranged in the first conductive pattern, or a conductive material layer on a glass layer, patterned with at least the first conductive pattern. According to an aspect, the invention provides an arrangement as described above, wherein an encapsulant layer is provided between the rear surface and the interconnection layer at locations void of the intermediate conductive body.

Furthermore the invention relates to an arrangement of a solar cell on an interconnection layer, the solar cell comprising a semiconductor substrate of a base conductivity type and with a base doping level, with a front surface for receiving radiation and a rear surface, the solar cell being provided in at least the rear surface with at least one first type doped layer area of a first conductivity type, and

the solar cell further being provided with at least one second type doped layer area of second conductivity type that is opposite to the first conductivity type; a dielectric layer being arranged on the rear surface covering at least the first type doped layer area; the rear surface comprising on the dielectric layer a metallization pattern that is

conductively connected with the first type doped layer area and is provided with one or more contact pad areas for locally contacting the metallization pattern with the interconnection layer; the interconnection layer being provided with one or more conductive patterned contacting areas each with a location corresponding with a location of said one or more contact pad areas, for contacting at said corresponding location with the contact pad area; each of said at least one contact pad areas being connected with a corresponding conductive patterned contacting area by an

intermediate conductive body; the intermediate conductive body laterally extending outside the surface area of the contact pad over a rear surface area portion that is covered by the dielectric layer and is adjacent to the contact pad; the solar cell being of interdigitated-back-contact, IBC, type and the first type doped layer area being arranged in the rear surface of the substrate in between either neighboring second type doped layer area portions or neighboring base conductivity type doped area portions; the contact pad area comprising a ring structure, the ring structure comprising a ring of a conductive material, and an exposed area free from the conductive material and enclosed by the ring, in which the exposed area is covered by a dielectric layer, and in which the intermediate conductive body covers and contacts the ring, and covers the dielectric layer on the exposed area.

Advantageous embodiments are further defined by the dependent claims.

Moreover, the invention relates to a solar cell comprising a semiconductor substrate with a front surface for receiving radiation and a rear surface, the substrate having a base level conductivity type and being provided with first type doped layer areas of a first conductivity type and with second type doped layer areas of a second conductivity type opposite to the first conductivity type, with at least one first type contact area that is in connection with the first type doped layer areas, and with at least one second type contact area that is in connection with the second type doped layer areas; a first type metallization network in contact with the at least one first type contact area; a second type metallization network in contact with the at least one second type contact area; a dielectric layer being arranged on the rear surface with openings in the dielectric layer at the location of the at least one first type contact area and at the location of the at least one second type contact area, wherein at least one of the first type metallization network and the second type metallization network is provided with a ring structure, the ring structure comprising a ring of a conductive material in said at least one of the respective metallization networks, and an exposed area free from the conductive material enclosed by the ring, in which the exposed area is covered by the dielectric layer.

Furthermore, the invention relates to a solar panel comprising the arrangement as described above, and/or comprising one or more solar cells as described above.

Brief description of drawings

The invention will be explained in more detail below with reference to drawings in which illustrative embodiments thereof are shown. They are intended exclusively for illustrative purposes and not to restrict the inventive concept, which is defined by the appended claims.

Figure 1 shows a cross-section of a prior art back-contacted solar cell of MWT type;

Figure 2 shows a cross-section of a prior art back-contacted solar cell of IBC type; Figure 3 shows a cross-section of a prior art back-contacted solar cell of IBC type; Figure 4a, 4b show a cross-section of a back-contacted solar cell according to an embodiment of the invention;

Figure 5a, 5b show a cross-section of a back-contacted solar cell according to an embodiment of the invention;

Figure 6a shows a cross-section of a back-contacted solar cell according to an embodiment of the invention; Figure 7a, 7b show a plane view and a cross-section of a back-contacted solar cell according to an embodiment of the invention;

Figures 8a, 8b show a plane view and a cross-section of a back-contacted solar cell according to an embodiment of the invention, and

Figures 9a, 9b show a plane view and a cross-section of a back-contacted solar cell according to an embodiment of the invention.

Detailed description of embodiments

Several type prior art back-contacted solar cells are known, that have an arrangement of contact electrodes of negative and positive polarity on the rear surface of the substrate. By this arrangement the front surface can be optimized for capturing radiative energy, since less or virtually zero area of the front surface needs to be covered by a shadowing metallization.

To arrange the contact electrodes on the rear surface, various designs can be used: for example, emitter-wrap-through (EWT), metal-wrap-through (MWT) and

interdigitated back-contact (IBC).

Below, in the drawings elements that are identified by the same reference are either functionally or structurally identical or similar.

Figure 1 shows a cross-section of a prior art back-contacted solar cell of MWT type arranged on a backplane of a solar panel.

The back-contacted MWT solar cell 100 is arranged on a backplane patterned conductor 150 of a solar panel.

The MWT solar cell is based on a semiconductor substrate 101, e.g., a silicon substrate typically doped at basic low level in first conductivity type, for example n- type. On a front surface 102, that is intended as a surface for capturing radiation from the Sun as source, an emitter layer 103 of second conductivity type, opposite to first conductivity type, is arranged.

The emitter layer 103 is covered by an anti-reflection coating 104. Further, electrodes 105, 106, 107 are arranged on the front surface for collecting charge carriers from the emitter layer 103.

The electrodes 105, 106, 107 form an interconnected network on the front surface 102, that at a location is connected to a conductive via 108 that runs through the substrate to the rear surface 109. On the rear surface 109, a back surface field (BSF) layer 111 doped with first conductivity type at relatively high level (in comparison with the basic level), is arranged. The BSF layer 111 is patterned such that at the peripheral region 112 of the conductive via the BSF layer is absent and the semiconductor material at the rear surface has the basic dopant level of the substrate. The rear surface is covered by a passivation layer 114. On the BSF layer 111 BSF contact electrodes 113 are arranged.

The conductive via 108 extends through the passivation layer 114 and is connected to a contact electrode pattern comprising a conductive contact pad 110. The conductive contact pad 110 functions as back-contact electrode for the emitter layer 103.

The conductive contact pad 110 laterally extends over a portion of the peripheral region 112 round the via 108 with a separation between the contact pad 110 and the peripheral region provided by the passivation layer 114. To avoid recombination effects, a spacing 115 is provided between the conductive contact pad and the BSF layer 111.

The conductive contact pad 110 is connected to the backplane patterned conductor 150 by an intermediate conductive body 120 that acts as metallization and provides to contact the contact pad 110 on one side and the patterned conductor 150 on the other side.

The contact area of the intermediate conductive body with the contact pad is within the surface area of the contact pad.

In this design, the cross-section area of the contact pad 110 and the intermediate conductive body 120 is substantially the same, or the area of the intermediate conductive body 120 is less than the area of the contact pad 110, so as to have a same cross-section of the contacting area on the patterned conductor 150.

Figures 2 and 3 show a cross-section of a prior art back-contacted solar cell of IBC type, arranged on a backplane of a solar panel.

The IBC solar cell 200 is based on a semiconductor substrate 201, e.g., a silicon substrate typically doped at basic low level in first conductivity type, for example n- type. On a front surface 202, that is intended as a surface for capturing radiation from the Sun as source, an anti-reflection coating layer 203, is arranged. In or on the rear surface 207 a structure is provided of a plurality of junctions 204, 205 (i.e., doped areas) of n-type and of p-type that are interdigitated. In the embodiment shown in Figure 2, a conductive contact pad 210 is connected to the area of the associated junction 204. Likewise, the adjacent junction 205 of opposite type is connected to an associated conductive contact pad 211. In this design, each contact pad covers a significant part of the area of the associated junction (e.g. 1- 10%) to have an optimal low series resistance.

At the boundary 208 between the neighboring junctions 204, 205 the respective associated conductive contact pads 210, 211 are laterally separated by a distance, to avoid a short circuit. This distance is covered by a passivation layer 209, to avoid recombination losses.

Typically, this structure is obtained by first creating the junctions of the n-type and p-type in the rear surface, covering the junctions with a structured contact grid material layer and subsequently annealing the semi-finished product to 'fire-through' the contact grid material to create a contact (metallization) grid, including the contact pads 510; 511 at each junction.

This contact grid material is e.g. produced by a high temperature process with a Ag-based thick film paste, containing Ag particles, and a glass frit which can contribute to a fire-through property, i.e., the contact pad area is a fired metal thick film paste that extends through the dielectric layer and connects each first type doped layer area to a respective contact pad area

As described above with reference to Figure 1, the conductive contact pad 210 is connected to the backplane patterned conductor 150 by an intermediate conductive body 220, which contacts the contact pad 210 on one side and the patterned conductor 150 on the other side. The contact area of the intermediate conductive body with the contact pad is within the surface area of the contact pad.

In the embodiment of Figure 3, the IBC solar cell 250 is similar to the

embodiment of the solar cell 200 as shown in Figure 2, except with respect to the contact to the junction areas 204, 205. On top of the junctions a passivation layer 209A is arranged which covers the junctions. The passivation layer 209A is substantially fully covered by an isolation layer 305. Such isolation layer 305 is typically a dielectric layer and may be a printed isolation layer.

On the surface of the isolation layer 305 facing away from the substrate, the contact pads 310 (and the rest of the contact grid) are arranged. The connection between the junction and its associated contact pad is provided by a point contact 307 that passes through the isolation layer 305 between the contact pad 310 and the junction 204, i.e., the contact pad area is a point contact or plated contact that extends through the dielectric layer and connects each first type doped layer area to a respective contact pad.

The contact pads (and the rest of the contact grid) can be produced by e.g.

physical vapor deposition (PVD, e.g. thermal evaporation or sputtering) of metal, and/or plating of metal layers. The isolation layer 305 is provided because the contact pad is not sufficiently isolated from the junction areas 205 by the passivation layer. By providing this isolation layer 305, the contact pad 310 connected with the junction 204, can be extended above the junction of opposite polarity (205) without causing electrical shorting.

The conductive contact pad 310 is connected to the backplane patterned conductor 150 by intermediate metallization 320 that only contacts the area of the contact pad 310 on one side and the patterned conductor on the other side. The contact area of the intermediate conductive body with the contact pad is within the surface area of the contact pad.

Figures 4a and 4b show a cross-section of a respective MWT type back-contacted solar cell 400A according to an embodiment of the invention.

The solar cell is substantially similar to the MWT type solar cell as described above with reference to Figure 1.

In Figure 4a, the intermediate conductive body 420 that connects the contact pad 410 with the backplane patterned conductor 150, occupies a larger surface area S2 than the surface area SI of the contact pad 410, i.e., extends laterally outside of the area of the contact pad 410 and is in contact with a portion 116 of the passivation layer 114 adjacent to the contact pad 410, that covers the basic-level doped peripheral region 412.

In some embodiments, the contact pad area has a width of 2 mm or less, and the intermediate conductive body has a width of at least 2.5 mm. Advantageously, a short circuit is prevented since the passivation layer 114 provides isolation between the intermediate conductive body 420, and the covered portion 116 of the basic-level doped peripheral region 412. Moreover, the contact area with the interconnection layer or backplane patterned conductor 150 is enhanced since this area can be relatively larger than the area of the contact with the contact pad 410. It has been found that the contact interface between intermediate conductive body 420 and the backplane patterned conductor 150 determines the contact resistance between the solar cell electrode 410 and the backplane patterned conductor 150. As a result of the relatively larger contact surface S2 between the intermediate conductive body 420 and the patterned conductor 150, the contact resistance of the electric contact (double arrow RC) between the contact pad 410 and the backplane patterned conductor 150 is reduced. In addition, this observation also allows that the contact pad 410 on the rear surface of the solar cell can be reduced in size. The reduction of the contact pad size has the advantage that less contact material such as silver is required per contact area, thus saving on materials and on manufacturing costs. Also, the recombination effect at the contact(s) is reduced.

It is noted that the interconnecting layer may be a backsheet of a solar panel or alternatively an intermediate sheet that comprises a metallisation pattern. In a solar panel the intermediate sheet is arranged between a level in which the solar cells are positioned and a back-panel of the solar panel.

In a further embodiment 400B as is shown in Figure 4b, the intermediate conductive body 420 extends even under the BSF layer 111, i.e., the intermediate conductive body 420 overlaps with a portion 416, 418 of the basic-level doped peripheral region 412 and with a portion 415, 419 of the BSF layer 111. The passivation layer 114 provides isolation between the intermediate conductive body 420, the covered portion 416, 418 of the peripheral region 412 and the covered portion 415, 417 of the BSF layer 111.

The overlap of the intermediate conductive body 420 with portions 415, 417 of the BSF layer 111 and the basic doped regions 416, 418 also has a beneficial effect on reduction of recombination, by the fact that at location of the covered BSF portion 415, 419, and regions 416, 418, during operation of the solar cell, an electrical potential occurs which enhances the transport of first conductivity type charge carriers to the BSF layer and may direct second conductivity type charge carriers away from the BSF layer.

Figure 5a and 5b show a cross-section of a respective back-contacted solar cell of IBC type 500 A; 500B according to an embodiment of the invention.

The solar cell 500A; 500B is substantially similar to the IBC type solar cell 200 as described above with reference to Figure 2.

In Figure 5 a, the fire-through contact pad 510 is smaller than the associated junction 204 area S3, thus leaving a portion 512 of the junction covered by the passivation layer. The intermediate conductive body 520 is made to extend laterally over the contact pad 510 and onto a portion 512 of the passivation layer 209

covering/contacting the associated junction.

In a further embodiment 500B as shown in Figure 5b, the intermediate conductive body 520 is made to extend laterally over the portion 512 of the passivation layer 209 covering the associated junction 204 and over an adjacent portion 514 of the passivating layer 209 that covers a portion 530 of the adjacent junction 205.

Advantageously, a short circuit is prevented since the passivation layer 209 provides isolation between the intermediate conductive body 520, and the covered portion 514 of the adjacent junction 205. As a result, the contact area S4 between the intermediate conductive body 520 and the backplane patterned conductor 150 is relatively enlarged which has beneficial effect as the contact between intermediate conductive body 520 and the backplane patterned conductor 150 determines the contact resistance RC between the solar cell electrode 510 and the backplane patterned conductor 150.

Figure 6a shows a cross-section of a back-contacted solar cell 600 according to an embodiment of the invention.

The solar cell 600 according to this embodiment, is substantially similar to the point-contacted IBC type solar cell 300 as described above with reference to Figure 3.

As shown in Figure 6a, the IBC solar cell 600 is based on a semiconductor substrate 601, e.g., a silicon substrate typically doped at basic low level in first conductivity type, for example n-type. On a front surface 602, for capturing radiation from the Sun as source, an anti-reflection coating layer 603, is arranged. In or on the rear surface 607 a structure is provided of a plurality of junctions 204, 205 (i.e., junction layers) of n-type and of p-type that are interdigitated. On top of the junctions a passivation layer 609A is arranged which covers the junctions. On the surface of the passivation layer 609A, the contact pads 610 are arranged. The connection between the junction 204 and its associated contact pad 610 is provided by a point contact 608 that passes through the passivation layer 609A between the contact pad 610 and the junction 204.

The intermediate conductive body 620 is arranged as contacting body between the contact pad 610 and the backplane patterned conductor 150.

As shown in Figure 6a, the point-contacted contact pad 610 is smaller than the associated junction area 204, thus leaving a portion of the junction 204 covered by the passivation layer 609A. The intermediate conductive body 620 is made to extend laterally over the contact pad 610 and onto the portion 612 of the passivation layer 609A covering the associated junction.

In the embodiment of the IBC solar cell 600, the intermediate conductive body 620 is made to extend laterally also over a portion of the passivating layer 609A that covers a portion 614 of the adjacent junction 205.

The contact pad material and contact pad application process are, if they coincide with the material and application process of the contact grid or metallization grid as a whole, optimized for creating suitable electrical contact to semiconductor surfaces such as that of junctions 204 and 205. (it is noted that this coincidence of the contact grid material and process and contact pad material and process is desirable to simplify the cell production process and reduce process cost.) In contrast to this, the intermediate conductive body 620 needs to make suitable electrical contact to the metal surface of the contact pads 610 only. Therefore the contact grid needs (may need) a thick printed isolation layer (not shown here. See for reference, layer 305 in Figure 3) on top of the passivation layer 609 A, for electrical isolation from junction layer 205, while the intermediate conductive body does not (may not) need this.

An example of a material that can be used as intermediate conductive body 320; 420; 520; 620 is electrically conductive adhesive (ECA). ECAs consist of a polymer mixed with a large amount of metallic filler. The ECA is supplied as a paste and is applied onto the components that need interconnecting through dispensing or printing, i.e., the contact pad 310; 410; 510; 610 and the conductive patterned layer 150. The polymer cures upon annealing, so that the ECA becomes a solid after curing. Thanks to the metal filler particles, percolations paths are present in the cured material, delivering conductivity. Most commercially available EC As make use of a C-based polymer for the binder, typically epoxy or acrylate polymers. Also silicone materials or

organosiloxanes are possible. Such ECA is typically cured during the lamination process, at a temperature of around 150°C. An example of such an electrically conductive adhesive is DB1541, supplied by the company ECM.

As an alternative to ECA, a low temperature solder could be applied as solder bumps at the location of the contact pads. After aligning the solar cell with the conductive patterned layer and after appropriate annealing, solder connections are created at the locations between the contact pads and the conductive patterned layer.

In some embodiments, the intermediate conductive body is arranged as a lateral interconnect of neighboring metallization networks of the same polarity on back- contacted solar cells. Below some non-limiting examples of this embodiment are shown.

Figure 7a, 7b show a plane view of the rear surface and a cross-section, respectively, of a portion of an interdigitated back-contacted solar cell 700 according to an embodiment of the invention.

In Figure 7a, a plane view of the rear surface of a back-contacted solar cell 700 is shown. The rear surface is arranged with interdigitated dopant patterns of first and second conductivity types. The patterns each typically are branched with one or more main strips 701; 702 extending in a first direction Y along the rear surface and side branches 703; 704 extending from each main strip in a second direction X

perpendicular to the first direction. On each dopant pattern of main strips and side branches, a branched conductive network that has similar pattern of metallization (metal comprising lines 705;706 ) is arranged and is located on top of the doped pattern, substantially coinciding with the doped pattern.

According to an embodiment, the branched conductive network may comprise one or more busbars and fingers extending from the busbar(s). The busbar(s) is (are) located on top of the main strips of the dopant pattern, the fingers are located on top of the side branches of the dopant pattern.

According to the invention, an intermediate conductive body 720; 721 , for reason of clarity depicted here as open circles, is applied to provide an external connection between two adjacent patterns PI, P2; P3, P4 of one identical polarity across an intermediate doped busbar 722; 723 or finger of a pattern of the other opposite polarity. At the location of the external connection the metallization on top of the intermediate main conductive bar (busbar) or side branch (finger) is interrupted 722; 723. At this location the dopant patterned region of opposite polarity is covered by a passivation layer as described above. Thus, the intermediate conductive body 720; 721 covers the dopant patterned region of opposite polarity between the metal lines 705; 706 of adjacent patterns PI, P2; P3, P4 of the same polarity that are interconnected by the intermediate conductive body 720;721. The intermediate conductive body 720; 721 bridges the dopant patterned region of opposite polarity at the interruption 722; 723.

In Figure 7b a cross-section of the schematic arrangement of the solar cell 700A, the intermediate conductive body 720 and the backplane conductor 150 is shown, in which the intermediate conductive body 720 forms a connection between the contact pads 705 of the same polarity 204 and covers the isolation layer 709 on the dopant patterned region 205 of opposite polarity (i.e., the interruption 722) in between said contact pads 705.

On the rear surface of the semiconductor substrate, doped regions, i.e., junctions 204, 205 are formed in dopant patterns of first and second conductivity type, that in alternation are arranged adjacent to each other. On two junctions 204 of same one polarity contact pads 705 are located. The contact pads can be either fire-through contact pads or point contacted contact pads. The contact pads 705 are smaller than the associated junctions 204, leaving some area of the junctions free from contact pad material.

The junction 205 of opposite polarity between the junctions 204 of the one polarity is covered with a passivation layer 709. The passivation layer 709 also covers the areas 707 of the junctions 204 of the one polarity that are not covered by the contact pad 705.

The intermediate conductive body 720 contacts each of the junctions 204 of the same polarity and covers the junction 205of opposite polarity in between. The intermediate conductive body is isolated from the covered junction 205 by the passivation layer 709.

Further, the intermediate conductive body contacts the backplane conductor 150.

Figures 8a, 8b show a plane view of the rear surface and a cross-section of an interdigitated back-contacted solar cell according to an embodiment of the invention. In the arrangement shown here, the intermediate conductive body is arranged as a lateral interconnect of neighboring metallization networks of the same polarity PI, P2;P3,P4 that are separated by multiple doped regions, i.e., junctions, of opposite polarity. Similar as in the embodiment described with reference to Figure 7a and 7b, the metallization 805; 806 of the doped regions of opposite polarity that are bridged by the intermediate conductive body, are locally interrupted 822, 824, 826; 823; 825, 827, such that the bridging intermediate conductive body 820; 82 lis isolated by a passivation layer 809 located on the doped regions of the opposite polarity at the interruptions. The intermediate conductive body 820; 821 is typically elongated in the bridging direction Y.

Figures 9a, 9b show a portion of a plane view of the rear surface and a cross- section of an interdigitated back-contacted solar cell 900 according to an embodiment of the invention.

According to an embodiment, at the location of an external connection 930 between the metallization network of busbar(s) 901 and fingers 902 and the backplane conductor 150, the metallization network comprises a ring structure X* in the busbar(s) and/or finger(s). The network of opposite polarity is indicated by busbars and/or fingers 903. Also the doped regions of the junctions 204, 205 are indicated.

The ring structure X* comprises a conductive ring surrounding an exposed area 909. The conductive ring X* is connected with the network of busbar(s) and fingers. In the exposed area 909 a passivation layer or isolating layer is arranged. On the ring structure X* the intermediate conductive body 920 (not shown in Figure 9a) is located. For reason of clarity, the intermediate conductive body and backplane conductor are only schematically shown in Figure 9b.

By using a ring structure X* the consumption of materials for metallization can be reduced. Also the intermediate conductive body 920 (such as ECA) can be confined within the ring X*, which can reduce the consumption and cost of this material, moreover, the contact recombination can be reduced.

In Figure 9b, a cross-section of the back-contacted solar cell is shown at the location of the ring structure, along line VV in Figure 9a.

The ring structure X* comprises metallization lines 908 and the exposed area 909 in between the metallization lines. The exposed area in the rear surface of the semiconductor substrate is typically doped identical to the dopant 204 under the metallization lines, but in addition, the exposed area may comprise an undoped region, i.e., a region of basic level doping of the substrate. The exposed area is covered by an isolation or passivation layer.

The intermediate conductive body 920 is arranged over the ring structure X*, contacts the metallization lines 908 of the ring structure and covers the isolation or passivation layer 909, 910. In addition, the intermediate conductive body 920 contacts the backplane conductor 150.

The ring structure may be applied as a contact pad, but also may be applied in the bridging connection as shown in Figures 7a, 7b or Figures 8a, 8b for IBC type solar cells.

In addition, the ring structure can be applied in back-contacted solar cells of MWT or EWT type, in which a metallization network is provided on the rear surface that interconnects contact pads of the same polarity.

According to an embodiment of the invention, a solar cell is provided that comprises a semiconductor substrate with a front and rear surface; the front surface being arranged for capturing radiation; the rear surface being provided with plurality of back-contacts, back-contacts of a same polarity being interconnected by a network of metallization lines 901, 902 , that comprises a ring structure X* at a predetermined location of an external connection 930. The external connection is created by an intermediate conductive body 920 that contacts the ring structure X* and the backplane conductor 150 of a solar panel.

On the rear surface of the solar cell, the intermediate conductive body 920 is in contact with the ring structure X* and covers the exposed area 909. The exposed area may be covered with an isolation or passivation layer.

In the examples of embodiments shown in Figures 7a, 7b; 8a, 8b; 9a, 9b the external connection made by the intermediate conductive body may be either an emitter type contact or a BSF type contact of the solar cell.

According to an embodiment of the invention, the first conductivity type is n-type and the second conductivity type is p-type.

According to an alternative embodiment of the invention, the first conductivity type is p-type and the second conductivity type is n-type.]

According to an embodiment of the invention, the base level conductivity type is the first conductivity type. According to an alternative embodiment of the invention, the base level conductivity type is the second conductivity type.

In accordance with an embodiment, the dielectric layer (i.e.; isolation layer or passivation layer) has a thickness of about 10 - 100 nm, preferably less than 200 nm, or more preferably has a thickness less than about 1 μιη.

The invention has been described with reference to some embodiments. Obvious modifications and alterations will occur to others upon reading and understanding the preceding detailed description. It is intended that the invention be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims.

Claims

1. An arrangement of a solar cell on an interconnection layer,

the solar cell further being provided with at least one second type doped layer area of second conductivity type that is opposite to the first conductivity type; a dielectric layer being arranged on the rear surface covering at least the first type doped layer area;

2. An arrangement of a solar cell on an interconnection layer,

each of said at least one contact pad areas being connected with a corresponding conductive patterned contacting area by an intermediate conductive body; the intermediate conductive body laterally extending outside the surface area of the contact pad over a rear surface area portion that is covered by the dielectric layer and is adjacent to the contact pad;

the solar cell being of interdigitated-back-contact, IBC, type and the first type doped layer area being arranged in the rear surface of the substrate in between either neighboring second type doped layer area portions or neighboring base conductivity type doped area portions;

the contact pad area comprising a ring structure, the ring structure comprising a ring of a conductive material, and an exposed area free from the conductive material and enclosed by the ring, in which the exposed area is covered by a dielectric layer, and in which the intermediate conductive body covers and contacts the ring, and covers the dielectric layer on the exposed area.

The arrangement according to claim 1 or claim 2, wherein the rear surface area portion comprises a doped area portion of base conductivity type with a doping level near the base doping level.

The arrangement according to claim 3, wherein the rear surface area portion comprises the base conductivity type doped area portion and the second conductivity type doped area portion, wherein either the base conductivity type doped area portion is arranged between the first conductivity type area portion and the contact pad area, or the second conductivity type area portion is arranged between the base conductivity type doped area portion and the contact pad area.

The arrangement according to any one of claims 1 - 4, wherein the solar cell is metal-wrap-through, MWT, type and the first type doped layer area is arranged in the front surface of the substrate, and the contact area comprises at least one via conductor from the first type doped layer area to the metallisation pattern on the rear surface.

The arrangement according to claim 1 , wherein the solar cell is interdigitated- back-contact, IBC, type and the first type doped layer area is arranged in the rear surface of the substrate in between either neighboring second type doped layer area portions or neighboring base conductivity type doped area portions.

The arrangement according to claim 6, wherein the contact pad area comprises a ring structure, the ring structure comprising a ring of a conductive material, and an exposed area free from the conductive material and enclosed by the ring, in which the exposed area is covered by a dielectric layer, and in which the intermediate conductive body covers and contacts the ring, and covers the dielectric layer on the exposed area.

The arrangement according to claim 2 or claim 6, wherein the solar cell comprises a second contact area, the second contact pad area being adjacent to the contact pad area but separated by an intermediate dopant region of conductivity type opposite to the type doped layer that the contact pad area is in electrical contact with, and covered by a dielectric layer, wherein the intermediate conductive body is arranged on the contact pad area and on the second contact pad area, and wherein the intermediate conductive body bridges the intermediate dopant region of opposite conductivity type while covering said dielectric layer.

The arrangement according to claim 8, wherein the intermediate conductive body bridges multiple intermediate dopant regions of opposite conductivity type between the contact pad area and the second contact pad area while covering said dielectric layer.

The arrangement according to claim 9, wherein the contact pad area is a region of a branched conductor network.

The arrangement according to claim 10, wherein the branched conductor network comprises at least one busbar and fingers, the fingers extending as branches from the busbar.

The arrangement according to claim 10 or 11, wherein the branched conductor network comprises interruptions, such that the dielectric layer is exposed and the intermediate conductive body extends over the dielectric layer in one or more of the interruptions.

The arrangement according to any one of the preceding claims 1 - 12, wherein the intermediate conductive body is one selected from a group comprising an electrically conductive adhesive, a composite or a mixture of non-conductive filler material and conductive material, a solder.

The arrangement according to any one of the preceding claims 1 - 13, wherein the interconnection layer is either a sheet provided with at least the first conductive pattern layer, or an arrangement of at least a plurality of conductive strips or wires arranged in the first conductive pattern, or a conductive material layer on a glass layer, patterned with at least the first conductive pattern.

The arrangement according to any one of the preceding claims 1 - 14, wherein an encapsulant layer is provided between the rear surface and the

interconnection layer at locations void of the intermediate conductive body.

16. Solar cell comprising a semiconductor substrate of base conductivity type and with a base doping level, with a front surface for receiving radiation and a rear surface, the substrate having a base level conductivity type and being provided with first type doped layer areas of a first conductivity type and with second type doped layer areas of a second conductivity type opposite to the first conductivity type, with at least one first type contact area that is in connection with the first type doped layer areas, and with at least one second type contact area that is in connection with the second type doped layer areas;

a first type metallization network in contact with the at least one first type contact area;

a second type metallization network in contact with the at least one second type contact area;

a dielectric layer being arranged on the rear surface with openings in the dielectric layer at the location of the at least one first type contact area and at the location of the at least one second type contact area,

wherein at least one of the first type metallization network and the second type metallization network is provided with a ring structure, the ring structure comprising a ring of a conductive material in said at least one of the respective metallization networks, and an exposed area free from the conductive material enclosed by the ring, in which the exposed area is covered by the dielectric layer.

17. Solar panel comprising the arrangement according to any one of the preceding claims 1 - 15 and/or comprising one or more solar cells according to claim 16.