WO2024115696A1

WO2024115696A1 - Assembly for a photovoltaic module, photovoltaic module and method for producing the assembly and the module

Info

Publication number: WO2024115696A1
Application number: PCT/EP2023/083817
Authority: WO
Inventors: Rémi Monna; Thibaut Desrues; Bertrand HLADYS; Frédéric JAY
Original assignee: Commissariat A L'energie Atomique Et Aux Energies Alternatives
Priority date: 2022-11-30
Filing date: 2023-11-30
Publication date: 2024-06-06
Also published as: FR3142632A1

Abstract

The invention relates to an assembly for a photovoltaic module, comprising at least two photovoltaic cells (C1, C2), each photovoltaic cell (C1, C2) comprising a substrate (2) configured to photo-generate charge carriers, and at least one transparent conductive oxide layer (3, 4) comprising at least one first zone (5) having a first electrical conductivity, and second zones (10 to 17) having a second electrical conductivity strictly greater than the first electrical conductivity, the assembly comprising at least one interconnection element (20, 21) electrically coupled with the second zones (10 to 17) electrically connecting the two cells (C1, C2) together, the at least one interconnection element (20, 21) extending in a direction perpendicular to the main direction (X).

Description

“Assembly for photovoltaic module, photovoltaic module and method of manufacturing the assembly and the module”

TECHNICAL FIELD OF THE INVENTION

The present invention relates to an assembly for a photovoltaic module forming a chain of photovoltaic cells. It also concerns a photovoltaic module as well as the manufacturing of photovoltaic assemblies.

STATE OF THE ART

Photovoltaic modules comprise several photovoltaic cells interconnected to form an assembly also called a “photovoltaic chain”. The interconnection of cells is a major issue because it defines the electrical energy production characteristics of the modules, particularly in terms of electrical power.

There are different methods for interconnecting photovoltaic cells. We can manufacture a photovoltaic module by encapsulating the photovoltaic assemblies in a stack of polymer and/or glass type materials. This stack protects the photovoltaic cells from the external environment while maintaining the photoelectric conversion function. Interconnection technologies are varied and generally adapted to the photovoltaic cell technologies used to create the modules. Furthermore, the way in which the photovoltaic cells are connected together makes it possible to improve the performance of the module independently of the individual performance of the photovoltaic cells but also to reduce electrical power losses.

Generally speaking, the interconnection of photovoltaic cells requires the use of a large quantity of silver to make the metallic contacts on the front and rear faces of the cells used for the evacuation and collection of the electrical current generated by the cells. . Thus, the photovoltaic industry currently consumes more than 10% of the silver produced worldwide for an annual production of 100 GW. Furthermore, for a higher production of 3 TW, it is estimated that the consumption will reach more than 50% of the silver produced in the world if the silver consumption is 5 mg/W. Currently, a photovoltaic cell of the HET type, that is to say heterojunction, consumes between 25 and 40 milligrams of silver per Watt, and projections indicate that 3 TW of production will be reached in 2035. In the future, it will therefore be necessary to drastically reduce d a factor of 8 to 10, the consumption of silver, with a target of around 2 mg/W in 2035. In a photovoltaic cell, the metallic parts composed of 80% silver are fine lines of a section of 540 .m ² , called fingers or “fingers” in English. These fingers serve to collect charges produced by the cell substrate. Within a photovoltaic module, these charges are then extracted through the elements which connect the cells, also called interconnectors or "wires" or "ribbon" in English (that is to say wires or ribbons ), which are conventionally composed of wires or metal ribbons, the role of which is to ensure electrical continuity between two cells, by minimizing ohmic losses. These elements must also limit the shading that they create when they cover part of the surface of one side of the cell which receives the light radiation. These ribbons or wires are generally composed of copper coated with a tin-based metal alloy, for example SnAg, SnPb, SnAgCu, SnAgBi, etc.

Currently, the most widespread interconnection uses a solder of sheathed (or tinned) copper wires on buses, also called busbars in English, located on the surface of the photovoltaic cells. Generally speaking, buses are created beforehand during a metallization step, generally by screen printing. The cells are connected to each other, in series or in parallel, using tinned copper ribbons or wires which are connected, by soldering using an addition of material from the metal alloy coating, to the buses present on one side of each cell. For a long time, three-bus technology was predominant on the market, but the growing interest in four- or six-bus architectures allows this mode of interconnection to evolve up to nine buses, or even more, what we now call Today Multi-Busbars (MBB) in English, that is to say sets with several buses. For example, Multi-Busbars technology, in addition to its power contribution to the modules, allows better resistance of the modules to accelerated aging tests, a reduction in the quantity of silver used in the module and therefore a reduction in cost. of production.

We can interconnect the copper wire connectors on the fingers of the cells, using buses, by soldering. For example, wire connectors (circular section copper wires), serving as both buses and ribbons, can be soldered directly to the surface of the cells. In addition, previously screen-printed silver paste solder pads can be used to allow the wire inter-connectors to be soldered to the busbars which interconnect the fingers of the cell between them. For example, an alloy used to make solder is based on lead, tin and silver. For example, soldering can be carried out via infrared rays using wire interconnectors with a diameter of 300 pm. But this welding using infrared rays is carried out at a temperature close to 200°C, and can locally damage the cell.

Another method involves connecting two neighboring cells without a bus by copper wires using a polymer foil. This process is commonly referred to by the trademark SmartWire Connection Technology™ (SWCT). In this process, copper wires are embedded in a polymer sheet or matrix and coated with a low-temperature solder alloy, primarily bismuth-based, with a melting point below 138°C. The use of low temperature solder alloy reduces the stress that can appear on the contact points between the copper wire and the cell fingers. Furthermore, the polymer matrix is an iron-on layer composed of two layers, a first layer with adhesive properties in the lower part and a second layer serving as mechanical support in the upper part. The copper wire is always in contact with the metallization of the cell, and the film comprising the polymer matrix and the copper wires is positioned on the cell. The fingers of the cells can be reduced in width, from 35 to 40 pm, which allows a reduction in money consumption compared to technologies using buses. The diameter of the copper wires is approximately 200 pm or 250 pm and the fingers being narrower, there is less shading on the cells. But such a process also requires using a large amount of silver to connect the fingers with the copper wires.

For example, we can cite American patent application LIS20140182675 and international application WO 2014/150235 which disclose a photovoltaic cell comprising metallization fingers located on the front face of the cell. American patent application US 20120015147 discloses a photovoltaic cell comprising a substrate, a first layer on the substrate comprising metal oxide nanoparticles and a second layer covering the first layer, the second layer comprising doping elements, such as aluminum, gallium, indium or boron.

We can also cite Korean patent application KR20130085188 which discloses a photovoltaic cell comprising a layer of a substrate for photo-generating charge carriers, a layer of transparent conductive oxide, also called TCO layer (transparent conductive oxide in English). English) or commonly TCO layer, placed on one side of the substrate. The transparent conductive oxide layer has a pattern with ribs forming grooves within which a layer of zinc oxide doped with aluminum is placed in electrical contact with metallization fingers formed on the front face of the cell.

International application WO 2014/128032 discloses a photovoltaic cell comprising metallization fingers and a transparent conductive oxide layer comprising highly conductive lines aligned under and along the metallization fingers.

But these cells do not make it possible to significantly reduce the consumption of silver used to interconnect two photovoltaic cells.

There are other techniques consisting of directly connecting copper wires in the TCO layer of a cell at the heterojunction, but we observe a loss of electrical power supplied in comparison with the same copper wires connected to fingers of the cell. Furthermore, the removal of rights leads to a sharp increase in the series resistance which therefore causes a significant drop in the power of the module. This strong increase in series resistance comes from an increase in the lateral resistance of the free carriers in the TCO layer. Indeed, in a cell at the heterojunction, the free carriers must transit laterally in the TCO layer before reaching the fingers of the cell. An object of the present invention is therefore to propose a solution for interconnecting photovoltaic cells while limiting the drawbacks mentioned above. In particular, there is a need to provide a reliable method for interconnecting photovoltaic cells, while making it possible to reduce manufacturing costs, and in particular to reduce the consumption of silver.

The other objects, characteristics and advantages of the present invention will appear on examination of the following description and the accompanying drawings. It is understood that other benefits may be incorporated.

SUMMARY OF THE INVENTION

To achieve this objective, a photovoltaic module assembly is proposed, comprising at least two photovoltaic cells.

Each photovoltaic cell includes:

- a substrate configured to photo-generate charge carriers, and

- at least one layer of transparent conductive oxide comprising at least a first zone having a first electrical conductivity, and second zones having a second electrical conductivity strictly greater than the first electrical conductivity, the second zones extending longitudinally along lines respectively parallel to a main direction.

The assembly comprises at least one interconnection element electrically coupled with the second zones of each of said at least two photovoltaic cells to electrically connect them together.

Said at least one interconnection element extends in a direction perpendicular to the main direction.

Each photovoltaic cell does not have an additional metallization line electrically connecting said at least one interconnection element with said at least one layer of transparent conductive oxide.

Thus we provide a set of photovoltaic cells interconnected with each other and devoid of additional silver metallization. Such an assembly uses a minimum quantity of conductive material.

According to another aspect, a photovoltaic module is proposed, comprising at least one assembly as defined above.

According to another aspect, a method of manufacturing a photovoltaic module assembly as defined above is proposed, comprising:

- a supply of at least two photovoltaic cells; every cell photovoltaic comprising: o a substrate configured to photo-generate charge carriers, and o at least one layer of transparent conductive oxide comprising at least a first zone having a first electrical conductivity, and

- a formation of second zones having a second electrical conductivity strictly greater than the first electrical conductivity, the second zones extending longitudinally along respectively lines parallel to a main direction.

The method comprises a deposition of at least one interconnection element electrically coupled with the second zones of each of said at least two photovoltaic cells to electrically connect them together.

BRIEF DESCRIPTION OF THE FIGURES

The aims, objects, as well as the characteristics and advantages of the invention will emerge better from the detailed description of an embodiment of the latter which is illustrated by the following accompanying drawings in which:

Figure 1 schematically represents a perspective view of an embodiment of an assembly for a photovoltaic module;

Figure 2 schematically represents a perspective view of another embodiment of a photovoltaic module assembly;

Figures 3 to 5 schematically represent sectional views of other embodiments of a photovoltaic module assembly;

Figures 6 and 7 schematically represent steps in implementing a process for manufacturing an assembly for a photovoltaic module.

The drawings are given as examples and are not limiting to the invention. They constitute schematic representations of principle intended to facilitate the understanding of the invention and are not necessarily on the scale of practical applications.

DETAILED DESCRIPTION OF THE INVENTION

Before beginning a detailed review of embodiments and implementations of the invention, optional characteristics are set out below which may possibly be used in combination or alternatively.

According to one example, at least one photovoltaic cell is of the heterojunction type in which the substrate comprises crystalline silicon and hydrogenated amorphous silicon.

According to one example, at least one photovoltaic cell comprises first and second layers of transparent conductive oxide respectively arranged in contact with first and second faces of the substrate, the second face of the substrate being located on a side opposite that of the first face.

According to one example, for at least one photovoltaic cell, the second zones are separated by a distance greater than or equal to a width of at least a second zone, the width being measured in a direction perpendicular to the main direction.

According to one example, for at least one photovoltaic cell, said at least one first zone has a face, called internal, in contact with at least one face of the substrate, and a face, called external, opposite the internal face, presenting several pairs of ribs, each pair of ribs delimiting between them a groove where a second zone is arranged.

According to one example, for at least one photovoltaic cell, the second zones are arranged in contact with at least one face of the substrate, and said at least one photovoltaic cell comprises several first zones arranged in contact with said at least one face of the substrate.

According to one example, for at least one photovoltaic cell, said at least one first zone has a face, called internal, in contact with at least one face of the substrate, and a face, called external, opposite the internal face, in contact with the second zones.

According to another example, for at least one photovoltaic cell, the second zones extend longitudinally along continuous lines respectively.

According to another example, for at least one photovoltaic cell, the second zones extend longitudinally along discontinuous lines respectively.

According to one example, said at least one interconnection element is in direct mechanical contact with the second zones of at least one photovoltaic cell.

According to one example, the assembly comprises a dielectric layer partially covering the first zone.

According to one example, for at least one photovoltaic cell, the assembly comprises metallized pads, each metallized pad being arranged in mechanical contact with a second zone of said at least one photovoltaic cell and said at least one interconnection element.

According to one example, at least one photovoltaic cell is of the single junction type comprising a single layer of transparent conductive oxide.

According to one example, at least one photovoltaic cell is of the double junction type comprising two layers of transparent conductive oxide. According to one example, said at least one interconnection element extends in a so-called secondary direction, and for each photovoltaic cell, said at least one layer of transparent conductive oxide has a thickness of between 5 and 70 nanometers, preferably between 15 and 30 nanometers, the thickness being measured in a direction perpendicular to the main direction and the secondary direction. Thus, such an assembly makes it possible to limit the quantity of material to be used to produce the transparent conductive oxide layer, compared to cells, called thin layers, which generally have a TCO layer of between 500,000 nm and 1,000 000nm.

In the present invention, types of doping will be indicated. Doping means the addition of a minimal quantity of impurities in a layer comprising a single crystal or a polycrystal, to transform it into an electrically conductive layer comprising free charge carriers. These dopings are non-limiting examples.

In Figures 1 to 5, there is shown an assembly 1 for a photovoltaic module. Set 1 comprises at least two photovoltaic cells C1, C2. A photovoltaic module comprises a set of photovoltaic cells 2, 20 interconnected to produce a current, and set 1 is also called a “photovoltaic chain”. Each photovoltaic cell C1, C2 comprises a substrate 2 and at least one layer of transparent conductive oxide 3, 4. The substrate 2 is configured to photo-generate charge carriers. For example, a cell C1, C2 can be of the HET type, that is to say the heterojunction type. A cell of the heterojunction type is a cell C1, C2 comprising a crystalline silicon substrate and at least one layer of hydrogenated amorphous silicon.

Generally speaking, a photovoltaic cell C1, C2 converts part of the light radiation into electrical energy. For this purpose, the substrate 2 is configured to generate, upon reception of the light radiation, charges free to move and intended to be collected to produce an electric current.

The conductive oxide layer 3, 4 is also called TCO layer. The cell C1, C2 may comprise a single TCO layer disposed in contact with a first face 30 of the substrate 2. Advantageously, a cell C1, C2 may comprise a first TCO layer disposed in contact with the first face 30 of the substrate 2 and a second TCO layer placed in contact with a second face 31 of the substrate 2, the second face 31 extends located on a side opposite that of the first face 30. A TCO layer 3.4 makes it possible to collect the charges produced by the substrate 2 and facilitate the movement of the loads thus produced. A photovoltaic cell C1, C2 can be a cell single junction based on crystalline silicon of heterojunction type or a cell, called tandem, that is to say double junction comprising at least one sub-cell based on crystalline silicon of heterojunction type, and in particular a tandem cell comprising a perovskite-based subcell and a heterojunction subcell. In the case of a tandem cell, there are also two TCO layers 3, 4 on both sides of the cell.

In particular, a TCO layer 3, 4 comprises at least a first zone 5 having a first electrical conductivity. Furthermore, a TCO layer 3, 4 comprises several second zones 10 to 17 having a second electrical conductivity strictly greater than the first electrical conductivity. The second zones 10 to 17 are also called highly conductive zones, and the first zone(s) 5 are weakly conductive zones. For example, the first electrical conductivity of a first zone 5 can be obtained by a first doping of the TCO layer 3, 4 at the location of the first zone 5. Furthermore, the second electrical conductivity of a second zone 10 to 17 can be obtained by a second doping of the TCO layer 3, 4 at the location of the second zone 10 to 17. According to one example, the first doping is different from the second doping so as to obtain distinct electrical conductivities. Alternatively, the first and second dopings could be identical, with the first and second zones 5 and 10 to 17 having distinct thicknesses to obtain distinct electrical conductivities, the thicknesses being measured in a direction perpendicular to the first face 30 of the substrate 2 Thus, for the same doping, by increasing the thickness of a zone of the TCO layer 3, 4, the electrical resistance of the zone is reduced. For example, for the same doping, the TCO layer 3, 4, at the location of the second zones 10 to 17 has a thickness strictly greater than that of the TCO layer 3, 4 at the location of the first zones 5.

More particularly, the second zones 10 to 17 extend longitudinally along respectively lines parallel to a main direction X.

Furthermore, set 1 comprises at least one interconnection element 20, 21 electrically coupled with the second zones 10 to 17 of each of the photovoltaic cells C1, C2 of set 1 to electrically connect them together.

More particularly, at least one interconnection element 20, 21, and preferably each interconnection element 20, 21, extends in a direction inclined relative to the main direction °, preferably at 90°. Advantageously, the interconnection elements 20,21 extend in a direction perpendicular to the main direction in interconnection elements 20, 21 with the second zones 10 to 17.

In particular, each photovoltaic cell C1, C2 is devoid of additional metallization line electrically connecting at least one interconnection element, and preferably each interconnection element 20, 21, with the transparent conductive oxide layer 3, 4 comprising the second zones 10 to 17. In other words, a cell C1, C2 does not include either a metallization line connecting the interconnection element(s) 20, 21 with a second zone 10 to 17, nor one or more lines of metallization connecting the interconnection element(s) 20, 21 with a first zone 5. These metallization lines are often referred to as “fingers”. The electrical coupling between the interconnection elements and the second zones 10 to 17 is done, for example directly, that is to say without the intermediary of metallization fingers.

The interconnection elements 20, 21 can, for example, comprise tinned copper wires or ribbons, that is to say copper wires or ribbons on which a layer of metal alloy based on has been deposited. tin, for example SnAg, SnPb, SnBiPb, SnAgCu, SnAgBi, etc., to protect them from oxidation. The interconnection elements 20, 21 can be glued or welded to the TCO layer 3, 4. Alternatively, the interconnection elements 20, 21 are placed directly on the TCO layer 3, 4, in mechanical contact with the second zones 10 to 17, and the electrical connection between the interconnection elements 20,21 and the second zones 10 to 17 can be carried out subsequently during a lamination step. By lamination is meant a step comprising a supply of heat to the photovoltaic cells C1, C2 so as to carry out soldering of at least one interconnection element 20, 21 with the second zones 10 to 17 of each photovoltaic cell C1, C2 so as to mechanically and electrically couple the interconnection elements 20, 21 with the second zones 10 to 17.

Thus, by adding second zones 10 to 17 having an electrical conductivity greater than that of the first zone(s) 5, zones 10 to 17 are created having an electrical resistance lower than that of the first zone(s) 5. The second zones zones 10 to 17 facilitate the movement of the loads produced by the substrate 2, and in particular the lateral movement in a secondary direction Y perpendicular to the main direction X. In other words, the second zones 10 to 17 avoid a significant increase in the series resistance in the module due to the increase in the lateral transport distance within the TCO layer 3, 4. In addition, the collection of charge carriers by the interconnection elements 20, 21 is improved due to the fact that the interconnection elements 20,21 extend inclined at an angle between 85° and 105°, preferably 90°, with the second zones 10 to 17. Advantageously, the collection of charge carriers is further improved when the interconnection elements 20,21 extend perpendicular to the second zones 10 to 17.

Furthermore, the interconnection elements 20, 21 are separated by a first distance 38, the first distance 38 being measured in the main direction X. For example, the first distance 38 can be between 2 and 16 millimeters , preferably between 2 and 8 mm. For example, for at least one photovoltaic cell C1, C2, the second zones 10 to 17 are separated by a second distance 40 greater than or equal to a width 39 of at least a second zone 10 to 17, the width being measured according to a direction perpendicular to the main direction in X. For example, the second distance 40 can be between 0.1 and 2 mm, preferably between 0.5 and 1 mm. Advantageously, the first distance 38 is strictly greater than the second distance 40. Thus, the distance traveled by the free charge carriers in the TCO layer 3, 4 to reach the second zones 10 to 17 is much less than the distance to be traveled to reach the interconnection elements 20, 21 passing through the first zone 5.

Generally, the doping of the second zones 10 to 17 consists of adding impurities locally in the second zones 10 to 17 so as to increase the electrical conductivity of the second zones 10 to 17. Note that the more doping of the second zones 10 to 17 17 increases, the more the electrical conductivity of the second zones 10 to 17 increases, which reduces the electrical resistance, called series resistance, of the second zones 10 to 17. Furthermore, an increase in the doping of the second zones 10 to 17 also leads to an increase of the absorption of light by the second zones 10 to 17, due in particular to the increase in the density of the charge carriers, which reduces the current generated by the photovoltaic module. In other words, the assembly 1 associates one or more regions of a TCO layer 3, 4 which are poorly conductive 5 and therefore poorly absorbent of light with highly conductive regions 10 to 17. Advantageously, for a surface Sfa of the face front 100 of a cell C1, C2, second zones 10 to 17 are created whose total surface present at the front face 100 of the cell C1, C2 is much less than the surface Sfa of the front face 100 of the cell C1, C2. Thus, we promote the collection of charge carriers, to increase the current produced, while reducing the effect of absorption of light by the second zones 10 to 17.

The second highly conductive zones 10 to 17 make it possible to reduce the resistance lateral in the TCO layer 3, 4 allowing the current to flow more easily in the TCO layer 3, 4. In addition, doping with conductive elements of the second zones 10 to 17 also makes it possible to have an electrical resistance between the second zones 10 at 17 and the interconnection elements 20.21 lower.

For example, the second zones 10 to 17 can be produced by modifying the first zone 5, by introducing hydrogen, or by introducing conductive elements locally in the first zone 5. Alternatively, the second zones 10 to 17 can be deposited by sputtering using a mask or carried out by localized laser doping or by implantation of localized hydrogen followed by annealing, that is to say heating the cell C1, C2 to a temperature between 100 and 800°C, preferably between 200°C and 300°C.

For example, hydrogen can be implanted to introduce impurities inside the first zone 5, in order to modify its electrical properties. These modifications are generated thanks to the intrinsic properties of the element introduced, in particular thanks to the interactions, that is to say the defects, which it generates in the first zone 5. This step is particularly suited to the treatment of the surface of the TCO layer 3, 4. It is also possible to use an implantation by plasma immersion, for example an ion implantation by plasma immersion (denoted PIII), an ion implantation by plasma source (denoted PSI I), or even an ion implantation based on plasma (denoted PBII).

In Figure 6, there is shown an example in which the TCO layer 3, 4 is immersed in a plasma 301 which contains ions 300 to be implanted. To produce the second zones 10 to 17, a negative voltage (between -20V and -100kV), generally pulsed, is applied to the TCO layer 3, 4 so that a sheath 302 is formed around it. 300 located in this sheath 302 are accelerated by an electric field inside the sheath 302 and are then implanted in the TCO layer 3, 4.

In Figure 7, another mode of implementation is shown for producing the second zones 10 to 17 in the TCO layer 3, 4. In this other mode of implementation, hydrogen implantation can be carried out. This implantation of hydrogen can be done selectively by implantation through a mask. To carry out hydrogen implantation, an acceleration voltage of between 0.5 and 6 kV (preferably between 1 and 4 kV) is used and the dose is between 1x10 ¹⁴ and 1x10 ¹⁶ cm ^-2 (preferably between 5x10 ¹⁴ and 5x10 ¹⁵ cm ^-2 ). In order to improve the diffusion of hydrogen in the TCO layer 3, 4, the TCO layer 3, 4 can then be annealed at different temperatures, for example a temperature between 100 and 450 ° C. By example, when using a layer of tin oxide doped with indium (ITO or Indium Tin Oxide in English), the implantation of hydrogen leads to a reduction in the electrical resistivity of the second zones 10 to 17, which whatever the subsequent annealing temperature. In particular, for an annealing temperature less than or equal to 300°C,

It is possible to divide the electrical resistivity of the TCO layer 3, 4 by two. In other words, it is possible to obtain second zones 10 to 17 having an electrical conductivity approximately equal to twice that of the first zone 5. Furthermore, by using higher annealing temperatures, that is to say greater than 300°C, the difference in electrical conductivity between the second zones 10 to 17 and the first zone 5 is less significant. Furthermore, beyond an annealing temperature of 350°C, the difference in electrical conductivity is negligible. Thus, we will use an annealing temperature less than or equal to 350°C and preferably an annealing temperature strictly less than 300°C. In general, we obtain for all annealing temperatures, second zones 10 to 17 having a resistivity less than or equal to 40 Ohms/square, that is to say a resistivity less than or equal to 1.5 x 10' ⁴ Ohm*cm, with a thickness of the second zones of 38 nm, the thickness being measured in a direction perpendicular to the first face 30 of the substrate 2.

Advantageously, the doping of the first and second zones 5, 10 to 17 makes it possible to obtain second zones 10 to 17 having an electrical conductivity of a factor of between 15 and 40 times, preferably 30 times, the electrical conductivity of the first zone 5. For example, for highly conductive zones, to obtain 5 Ohms/square, you need a thickness of 300 nm of TCO layer with a resistivity of 1.5 x 10' ⁴ Ohm*cm. For weakly conductive zones, we can obtain 400 Ohms/square by adding oxygen during deposition, for a thickness of 30 nm, we therefore obtain a resistivity of

12 x 10' ⁴ Ohm*cm; for 100 nm we obtain 40 x 10' ⁴ Ohm*cm, which makes a ratio of approximately 27.

In order to limit the absorption of light by the second zones 10 to 17, of the face 100, 101 of the cell C1, C2 intended to receive the light, doping will be used so as to obtain, for a thickness H1 of the second zones 10 to 17 equal to 70 nm, an electrical resistivity of between 300 and 400 Ohms/square. That is to say between 21x10 ^-4 Ohm*cm for 70 nm and 28x10 ^-4 Ohm*cm for 70 nm. The thickness H1, or height, of the second zones 10 to 17 is measured in a direction Z perpendicular to the main direction doping so as to obtain an electrical resistivity equal to 200 Ohms/square, that is to say an electrical resistivity equal to 3x1 O' ⁴ Ohm*cm for 15 nm or equal to 6x1 O' ⁴ Ohm*cm for 30 nm.

Furthermore, in order to produce the first weakly conductive zone 5, the density of charge carriers is limited by reducing the doping making it possible to generate these carriers. Thus, the first weakly conductive zone 5 will be more transparent to light radiation, that is to say less absorbent.

In general, we also note that the electrical conductivity o (having the unit S/m, or Siemens per meter, or even in (Ohms*meter)' ¹ ) is the inverse of the electrical resistivity p (having the unit the Ohm*meter), in other words: p = 1/ o (equation 1). In the remainder of the description, and for purposes of simplification, we will give, by way of example, electrical resistivity values p for the first and second zones 5, 10 to 17.

For example, the first zone 5 can be produced having an electrical resistivity of between 40 and 400 Ohms/square, preferably between 150 and 250 Ohms/square (with 150 Ohms/square corresponding to 10x10' ⁴ Ohm*cm for 70 nm, and 250 Ohms/square corresponding to 17x10' ⁴ for 70 nm).

Advantageously, the first zone 5 has an absorption of light, in particular light having a wavelength of between 300 and 1200 nanometers, less than 2%, and preferably less than 1%. For example, the first zone 5 can have an optical index of between 1.8 and 2.1, preferably between 1.9 and 2. Furthermore, the thickness H2 of the first zone 5 is between 5 and 70 nanometers (when the cell C1, C2 comprises a single TCO 3 layer), preferably between 15 and 30 nanometers (when the cell C1, C2 comprises two TCO 3, 4 layers). The thickness H2 is measured in the direction Z perpendicular to the main directions doped with hydrogen, or a layer of indium doped with tungsten, or a layer of indium doped with zinc, a layer of zinc oxide (ZnO) doped with aluminum, or a layer of zinc oxide (ZnO) doped with gallium, or a layer of tin oxide (SnO2) doped with arsenic.

For example, it is possible to produce second highly conductive zones 10 to 17 having a minimum achievable electrical resistivity of approximately 1.5 x 10' ⁴ Ohm*cm. In other words, the electrical conductivity of the second zones 10 to 17 is strictly greater than the conductivity of the first zone 5.

Different materials can be used to produce the second zones 10 to 17. For example, a polycrystalline ITO layer can be used with a resistivity of 1.5x10' ⁴ Ohm*cm. It is possible to use a layer of zinc oxide doped with aluminum (AZO) having for resistivity 2.2x10' ⁴ Ohm*cm. We can use a layer of zinc oxide (ZnO) doped with aluminum having a resistivity of 1.4x10 ^-4 Ohm*cm. We can use a layer of zinc oxide (ZnO) doped with Galium having a resistivity of 1.2x10' ⁴ Ohm*cm. We can use a layer of tin oxide (SnO2) doped with arsenic having a resistivity of 1.5x10' ⁴ Ohm*cm. Preferably, we choose to produce second zones 10 to 17 having a resistivity less than or equal to 1.5x10' ⁴ Ohm*cm.

For example, the second zones 10 to 17 may have a width 39 of between 5 and 30 μm. In addition, the second zones 10 to 17 can be separated by a distance 40 of between 0.1 and 1 mm. In addition, a height H1 of the second zones 10 to 17 can be between 70 and 300 nanometers. In the example illustrated in Figure 1, the second zones 10 to 17 are not in contact with the first face 30 of the substrate 2. That is to say that the height H2 of the first zone 5 is strictly greater than the height H1 of the second zones 10 to 17.

The interconnection elements 20, 21 can be brought into contact with the second zones 10 to 17 located on the front faces 100 of the cells for parallel assembly of the photovoltaic cells C1, C2. When it is desired to mount the photovoltaic cells in series, the interconnection elements 20, 21 are located on the front face 100 of a first cell C1, and on the rear face 101 of a second photovoltaic cell C2.

Advantageously, the interconnection elements 20, 21 are in direct mechanical contact with the second zones 10 to 17 of at least one photovoltaic cell C1, C2. The interconnection elements 20,21 can be copper wires, preferably tinned, that is to say comprising an external coating comprising tin, for example based on tin, bismuth and silver (SnBiAg), or based on tin, copper and silver (SnAgCu), or based on tin, bismuth and lead (SnBiPb), or based on tin and lead (SnPb) . The diameter of the section of the copper wires 20, 21 can be between 150 and 250 micrometers. Advantageously, the interconnection elements 20,21 are spaced at a distance 38 of between 2 and 8 mm.

Alternatively, as illustrated in Figure 5, for at least one photovoltaic cell C1, C2, the assembly 1 comprises metallized pads 60, each metallized pad 60 being arranged in mechanical contact with a second zone 10 to 17 of the photovoltaic cell C1, C2 and with at least one interconnection element 20, 21. More particularly a metallized pad 60 does not correspond to a metallization line, in particular due to the fact that a maximum width or length of a metallized pad 60 is strictly less than a distance separating two interconnection elements 20, 21. Thus, a metallized pad 61 is not configured to electrically connect, by itself, two distinct interconnection elements 20, 21. The metallized pads 60 can be made from a conductive glue to improve the contact between the interconnection elements 20, 21 and the second zones 10 to 17. The conductive glue can be deposited in a continuous line under the interconnection elements 20, 21 or on the second zones 10 to 17 in a localized manner at the intersection between the interconnection elements 20, 21 and the second zones 10 to 17.

In Figures 1 and 2, there is shown an embodiment of a set 1 of two photovoltaic cells C1, C2, for each cell C1, C2, the first zone 5 of at least one TCO layer 3, 4 has a face 41, called internal, in contact with at least one face 30, 31 of the substrate 2, and a face 42, called external, opposite the internal face 41. Generally, the internal faces 41 of the TCO layers 3, 4 are arranged in contact with the substrate 2. In other words, the external faces 42 of the TCO layers 3, 4 are arranged at a distance from the substrate 2. Furthermore, the external face 42 of a TCO layer 3, 4 has several pairs of ribs 43, 44, each pair of ribs 43, 44 delimiting between them a groove 45 where a second zone 10 to 17 is arranged. For example, for at least one photovoltaic cell C1, C2, the second zones 10 to 14 are arranged. extend longitudinally along continuous lines respectively. For example, the continuous lines are parallel to the main direction X. Alternatively, the second zones 15 to 17 extend longitudinally along discontinuous lines respectively. For example, the dashed lines are parallel to the main direction X.

In Figure 3, another embodiment of a photovoltaic cell C1, C2 of a set 1 is shown, for which the second zones 10 to 17 of at least one TCO layer 3, 4 are arranged in contact with at least one face 30, 31 of the substrate 2. In addition, the photovoltaic cell C1, C2 comprises several first zones 5 arranged in contact with the face 30, 31 of the substrate 2. In this embodiment, second zones can be produced 10 to 17 having a height H1 greater than or equal to a height H2 of the first zone 5. Preferably, the height H1 is strictly greater than the height H2 of the first zone 5.

In Figures 4 and 5, another embodiment of a photovoltaic cell C1, C2 is shown, for which the first zone 5 of at least one TCO layer 3, 4 is in the form of an advantageously continuous layer, having an internal face 41 arranged in contact with at least one face 30, 31 of the substrate 2, and an external face 42 opposite the internal face 41, arranged in contact with the second zones 10 to 17. In other words, the second zones 10 to 17 are deposited/formed on the surface of the first zone 5 and more particularly on the external face 42 of the first zone 5. They are then not directly in contact with the internal face 41 of the substrate 2. In this other embodiment, the first zone 5 can be partially covered a dielectric layer 61, preferably transparent. In other words, the dielectric layer 61 comprises several parts arranged between two neighboring second zones 10 to 14. The transparent dielectric layer 61 makes it possible to limit the reflection of light by the TCO layer 3, 4, in particular by the first zone 5. Indeed, when the first zone 5 has a low thickness H2, that is to say a thickness less than or equal to 30 nm, the reflection of light by the first zone 5 increases. The transparent dielectric layer 61 has a thickness H3 of between 30 and 100 nanometers. Thus, the transparent dielectric layer 61 comprises several parts respectively placed between two second zones 10 to 17. For example, the transparent dielectric layer 61 may comprise silicon nitride (Si N), silicon oxide (SiO) or silicon oxynitride (SiOxNy), alone or in combination. Advantageously, the transparent dielectric layer 61 has an optical index close to that of the TCO layer 3, 4, for example an optical index of between 1.8 and 2.1, preferably between 1.9 and 2.

It can be noted that the assembly 1 which has just been described makes it possible to avoid having to make silver fingers on a face 100, 101 of a photovoltaic cell C1, C2 electrically connected to interconnection elements 20.21. In other words, we provide a set 1 devoid of additional metallization lines electrically connecting interconnection elements 20, 21 with a TCO layer.

An example of a manufacturing process for assembly 1 as defined above will now be described. The process includes the following main steps:

- a supply of at least two photovoltaic cells C1, C2; each photovoltaic cell C1, C2 comprising a substrate 2 configured to photo-generate charge carriers, and at least one layer of transparent conductive oxide 3, 4 comprising at least a first zone 5 having a doping configured so that said at least a first zone 5 has a first electrical conductivity; And

- a formation of second zones 10 to 17 having doping configured so that the second zones 10 to 17 have a second electrical conductivity strictly greater than the first electrical conductivity, the second zones 10 to 17 extending longitudinally along parallel lines respectively to a main direction X.

The method further comprises a deposition of at least one interconnection element 20, 21 electrically coupled with the second zones 10 to 17 of each photovoltaic cell C1, C2 to electrically connect them together. In particular, at least one interconnection element is deposited extending in a direction inclined relative to the main direction X at an angle between 85° and 105°, preferably 90°.

For example, the interconnection elements 20, 21 can be deposited on the cell C1, C2 using a polymer sheet using the SmartWire Connection Technology™ (SWCT) technique.

The photovoltaic module assembly and the manufacturing process for such an assembly make it possible to very significantly reduce the consumption of silver per cell.

In addition, such an assembly eliminates the need to use silver metallization for each of the cells. Such removal would also make it possible to increase the power of the cells thanks to a reduction in shading due to silver metallization, such as fingers, on the face of the photovoltaic cell receiving the light.

Claims

CLAIMS Assembly for photovoltaic module, comprising at least two photovoltaic cells (C1, C2), characterized in that each photovoltaic cell (C1, C2) comprises:

• a substrate (2) configured to photo-generate charge carriers, and

• at least one layer of transparent conductive oxide (3, 4) comprising at least a first zone (5) having a first electrical conductivity, and second zones (10 to 17) having a second electrical conductivity strictly greater than the first conductivity electrical, the second zones (10 to 17) extending longitudinally along respectively lines parallel to a main direction (X), the assembly comprising at least one interconnection element (20, 21) electrically coupled with the second zones ( 10 to 17) of each of said at least two photovoltaic cells (C1, C2) to electrically connect them together, said at least one interconnection element (20, 21) extending in a direction perpendicular to the main direction (X ), each photovoltaic cell (C1, C2) being devoid of additional metallization line electrically connecting said at least one interconnection element (20, 21) with said at least one layer of transparent conductive oxide (3, 4). Assembly according to claim 1, in which at least one photovoltaic cell (C1, C2) comprises first and second layers of transparent conductive oxide (3, 4) arranged respectively in contact with first and second faces (30, 31) of the substrate (2), the second face (31) of the substrate (2) being located on a side opposite to that of the first face (30). Assembly according to one of claims 1 to 2, in which, for at least one photovoltaic cell (C1, C2), the second zones (10 to 17) are separated by a distance (40) greater than or equal to a width ( 39) of at least a second zone (10 to 17), the width (39) being measured in a direction (Y) perpendicular to the main direction (X). Assembly according to one of claims 1 to 3, in which at least one photovoltaic cell (C1, C2) is of the heterojunction type in which the substrate (2) comprises crystalline silicon and hydrogenated amorphous silicon. Assembly according to one of claims 1 to 4, in which, for at least one photovoltaic cell (C1, C2), said at least one first zone (5) has a face (41), called internal, in contact with at least one face (30, 31) of the substrate (2), and a face (42), called external, opposite the internal face (41), having several pairs of ribs (43, 44), each pair of ribs (43, 44) delimiting between them a groove (45) where a second zone (10 to 17) is arranged. Assembly according to one of claims 1 to 4, in which, for at least one photovoltaic cell (C1, C2), the second zones (10 to 17) are arranged in contact with at least one face (30, 31) of the substrate (2), and said at least one photovoltaic cell (C1, C2) comprises several first zones (5) arranged in contact with said at least one face (30, 31) of the substrate (2). Assembly according to one of claims 1 to 4, in which, for at least one photovoltaic cell (C1, C2), said at least one first zone (5) has a face (41), called internal, in contact with at least a face (30, 31) of the substrate (2), and a face (42), called external, opposite the internal face (41), in contact with the second zones (10 to 17). Assembly according to one of claims 1 to 7, in which, for at least one photovoltaic cell (C1, C2), the second zones (10 to 17) extend longitudinally along continuous lines respectively. Assembly according to one of claims 1 to 7, in which, for at least one photovoltaic cell (C1, C2), the second zones (10 to 17) extend longitudinally along discontinuous lines respectively. Assembly according to one of claims 1 to 9, in which said at least one interconnection element (20, 21) is in direct mechanical contact with the second zones (10 to 17) of at least one photovoltaic cell (C1, C2). Assembly according to one of claims 1 to 10, comprising a dielectric layer (61) partly covering the first zone (5). Assembly according to one of claims 1 to 9, in which, for at least one photovoltaic cell (C1, C2), the assembly comprises metallized pads (60), each metallized pad (60) being arranged in mechanical contact with a second zone (10 to 17) of said at least one photovoltaic cell (C1, C2) and said at least one interconnection element (20, 21). Assembly according to one of claims 1 to 12, in which at least one photovoltaic cell (C1, C2) is of the single junction type comprising a single layer of transparent conductive oxide (3). Assembly according to one of claims 1 to 13, in which at least one photovoltaic cell (C1, C2) is of the double junction type comprising two layers of transparent conductive oxide (3, 4). Assembly according to one of claims 1 to 14, in which said at least one interconnection element (20, 21) extends in a direction (Y), called secondary, and for each photovoltaic cell (C1, C2) , said at least one layer of transparent conductive oxide (3, 4) has a thickness (H2) of between 5 and 70 nanometers, preferably between 15 and 30 nanometers, the thickness (H2) being measured in a direction (Z ) perpendicular to the main direction (X) and the secondary direction (Y). Photovoltaic module, comprising at least one assembly according to any one of the preceding claims. Method of manufacturing an assembly for a photovoltaic module according to one of claims 1 to 15, comprising:

• a supply of at least two photovoltaic cells (C1, C2); each photovoltaic cell (C1, C2) comprising: o a substrate (2) configured to photo-generate charge carriers, and o at least one layer of transparent conductive oxide (3, 4) comprising at least a first zone (5 ) having a first electrical conductivity, and

• a formation of second zones (10 to 17) having a second electrical conductivity strictly greater than the first electrical conductivity, the second zones (10 to 17) extending longitudinally along respectively lines parallel to a main direction (X), and

• a deposition of at least one interconnection element (20, 21) electrically coupled with the second zones (10 to 17) of each of said at least two photovoltaic cells (C1, C2) to electrically connect them together, said at least one interconnection element (20, 21) extending in a direction perpendicular to the main direction (X), and each photovoltaic cell (C1, C2) being devoid of additional metallization line electrically connecting said at least one element d interconnection (20, 21) with said at least one layer of transparent conductive oxide (3, 4).