FR3043252B1 - PROCESS FOR PRODUCING A COMPOSITE SUBSTRATE - Google Patents

Abstract

The method comprises the following steps: a) providing bricks (1) to be assembled to form at least one assembly, the bricks (1) having joining surfaces, b) forming layers of electrical insulation (3) so as to cover the assembly surfaces of the bricks (1), c) forming an electrical conduction layer (4) between the electrical insulation layers (3) so as to assemble bricks (1) neighbors in a plane d assembling and forming at least one assembly (5), d) subjecting the at least one assembly (5) to a heat treatment, and e) cutting the at least one assembly (5) in a plane perpendicular to the plane of the assembly, the at least one assembly (5) cut forming a brick paving (1) cut. The invention also relates to a composite substrate obtained by said method.

Description

The present invention relates to the field of composite substrates, in particular for the manufacture of photovoltaic cells and modules for solar panels, as well as for the manufacture of LED arrays. The invention particularly relates to a method of manufacturing a composite substrate and said composite substrate obtained by this method.

The current architectures of cells and photovoltaic modules made from silicon have two major drawbacks:

The supply of a DC voltage of too low value (<60 V) to be distributed directly on the network. It is therefore essential to add a complex inverter to amplify this voltage and convert the current into alternating current.

The cells are interconnected in series by welding or gluing metal strips arranged alternately above and below successive cells. Mechanical stresses are thus generated on the edges of the latter and promote damage or even breakage of the cells. In addition, this interconnection involves respecting a minimum distance between two successive cells so that the ribbon can be correctly placed from the front of one cell to the back of the next. This results in active surface losses and thus power losses.

An alternative proposed today to these standard photovoltaic modules is the realization of photovoltaic modules with high voltage (HT). In this case, part of the aforementioned first drawback is addressed while reducing the resistive losses. The intensity of the current generated is reduced by the fact that the cells of a high-voltage module have a smaller surface area than for conventional modules, they are therefore more numerous.

However the second disadvantage mentioned above takes even more weight because it is necessary to connect a larger number of cells for the same surface so that the risk of breakage increases. In addition, the spacing between the larger cells in total covers a larger area in the final module compared to a conventional module.

The present invention thus aims to overcome at least these two disadvantages. To this end, the invention proposes a method for manufacturing a composite substrate intended for applications in the photovoltaic or optoelectronic field, the method comprising the following steps: a) Providing bricks intended to be assembled to form at least one assembly , bricks with joining surfaces, b) forming layers of electrical insulation so as to cover the joining surfaces of the bricks, c) forming an electrical conduction layer between the layers of electrical insulation covering the surfaces of the bricks, assembly so as to assemble neighboring bricks, according to an assembly plane, and to form at least one assembly, d) subjecting the at least one assembly to a heat treatment, and e) cutting the at least one assembly according to a plane perpendicular to the assembly plane, the at least one cut assembly forming a cut brick paving.

Thus, this process leads in few steps to obtaining a composite substrate suitable for the manufacture of series-connected electronic components, the composite substrate being constituted by the result of the cutting of a plurality of bricks (commonly called Slab in the English terminology), assembled by an electrical conduction layer so as to form at least one assembly, the bricks being electrically isolated from each other by two layers of electrical insulation between which the conduction layer is disposed.

After cutting according to step e), the bricks form cobblestones assembled through the electric conduction layer and the cut brick assembly becomes a pavement, formed of assembled blocks.

It is understood in this document that the assembly plan of the bricks is a plane parallel to the planes defined by the assembly surfaces of said bricks.

The composite substrate, as defined, can thus be used as a precursor in the manufacture of cells and assemblies of photovoltaic cells, capable of delivering high voltage from the serial connection of the blocks via the layer electrical conduction. Part of the interconnection is advantageously obtained by the method of manufacturing the composite substrate itself, using the conduction layer which also plays the role of an assembly layer between the blocks for forming the PV cells. In this method, the conventional welding step between the cells is avoided so that the risks of breakage and cell damage are reduced. In addition, the lost space for the connection between the cells is limited only by the thickness of the electrical conduction layer and the insulation layers and not by the space required to deposit a conductive ribbon between neighboring cells. .

Furthermore, this method allows the manufacture of photovoltaic modules (PV) of the desired size by varying the number of blocks or cells put in series and their size (standard 156x156mm2 or other). Indeed, the bricks, from which the cells are derived, are obtained by cutting, to the desired dimensions, blocks or ingots available commercially. Thus, once the bricks of the desired dimensions are assembled and then cut, a tiling, of the desired PV module size, is obtained.

Thus, all these pavers, or in other words this paving, makes it possible to supply high voltage with a higher surface coverage rate than a conventional module because of the fact that little active surface is lost and the interconnection is easily achieved via the electrical conduction layer between the blocks.

Preferably, step a) comprises providing bricks made of generally p-doped and / or doped type n-type semiconductor material, the semiconductor material being selected from GaN-based alloys and elements or alloys of elements of column IV, and preferably the semiconductor material is silicon and generally crystalline silicon. The composite substrate is thus formed of materials that are particularly suitable for applications in the photovoltaic field, microelectronics and optoelectronics.

The bricks are for example obtained by cutting ingots or from blocks of material, commonly called 'bulk'. The cutting is performed so as to obtain a sufficient thickness of bricks to obtain the optimum yields according to the intended applications. It is generally between 100 and 800 micrometers.

Advantageously, the electrical insulation layers are formed in step b) from silicon oxide, such as SiOx or SiO2, or from an oxide powder of TiO2, Al2O3, ZnO , SiO2, a mixture of these oxide powders, or a mixture of these oxide powders with at least one organic binder and / or inorganic.

The layers of electrical insulation between two bricks may be of different natures, especially if it is necessary to passivate surface conditions of one of the bricks.

The formation of the SiO2 silicon oxide electrical insulation layer is conventionally deposited by PECVD (acronym for Plasma Enhanced Chemical Vapor Deposition) over a thickness that makes it possible to insure the electrical insulation of the conduction layer, once the composite substrate formed. The thickness is thus from a few tens of nanometers to a few micrometers and preferably the thickness is in a range from 10 nm to 5 micrometers.

The SiOx electrical insulation layer is obtained by thermal oxidation of the silicon brick by annealing in an oven to a thickness of a few microns and preferably a thickness in the range of 10 nm to 500 nm.

When using a powder of TiO2 oxide, Al2O3, ZnO, SiO2 or a mixture of these powders, a sintering step is necessary in order to melt the outer shell of the beads (forming the powder) and ensure the bonding and the cohesion of the balls between them. This sintering step typically comprises an annealing of 30 to 300 minutes carried out over a temperature range from 700 to 1200 ° C, associated with the application of a pressure exerted in a direction perpendicular to the assembly plane. The use of an organic and / or inorganic binder mixed with these powders advantageously makes it possible to reduce the annealing temperature of the sintering step and a very good mechanical adhesion between the silicon bricks. The final thickness of an electrical insulation layer formed by this method varies between about 20 nm and 200 micrometers.

It is understood in this document that the thickness of the electrical insulation layers varies according to the materials used so as always to have the insulation properties necessary to isolate the two bricks together and isolate them from the conduction layer. Stage d) of the process advantageously makes it possible to anneal the oxide powders mixed or not with binders. When associated with the application of pressure, the sintering step is obtained.

According to one embodiment, step c) of the method according to the invention comprises: - the formation of a silicon layer directly on the silicon oxide electrical insulation layers formed in step b) and covering the assembly surfaces of the bricks, and - the formation of a metal layer directly on each of the silicon layers, the metal being in particular chosen to form a eutectic with silicon, such as aluminum, silver, gold , platinum, barium, copper or an alloy of these metals, and - contacting the metal layers in pairs, so as to obtain the electrical conduction layer between the layers of electrical insulation and to assemble the bricks . The advantage of using a metal and especially a low-melting point metal, such as aluminum, to form the electrical conduction layer is that the heat treatment applied in step d) allows to liquefy at least partly the metal layers in contact so as to homogenize the electric conduction layer and to ensure a good bond between the bricks. Furthermore, the heat treatment guarantees the diffusion of the adjacent silicon in the liquid aluminum phase, which, after cooling, allows the formation of an Al-Si alloy whose composition is close to that of the eutectic when the heat treatment applied reaches 650 ° C. In addition, the electrical insulation layers deposited upstream on the silicon bricks form an effective barrier to the diffusion of the metal to the bricks so that the electrical insulation between the bricks is well maintained.

Another advantage to the presence of electrical insulation layers is that they act as barrier layers for the diffusion of impurities from the metal to the bricks, which could have adverse effects on the performance of the cells.

In this embodiment, the material of the electrical insulation layers may be of any of the aforementioned types, namely a deposited silicon oxide, thermal, in the form of powder and oxide powders.

The metal layer is advantageously formed by sputtering or by evaporation or by full plate screen printing of a conductive paste whose conductive element forms a eutectic with silicon.

Of course, the nature of the metal of said metal layers is chosen so that the bonding resulting from the contacting and the annealing is resistant to the temperatures applied in the rest of the process, in particular in the case of the manufacture of homojunction or heterojunction photovoltaic cells. .

The nature of the metal present in the metal layer is also chosen so that the metal layer has an electrical resistivity of less than or equal to 10 -4 ohm.cm.

Preferably, the heat treatment of step d) is carried out at a temperature between the eutectic formation temperature between the silicon and said metal and 900 ° C.

These conditions are indeed favorable to obtaining the diffusion of silicon in the metal so as to obtain after cooling, an assembly of bricks bonded together by means of a stack formed of an electrical insulation layer, for example, a SiOx thermal oxide, a residual silicon layer, a Si-metal alloy layer, a residual metal layer, a Si-metal alloy layer, a residual layer of silicon and an SiOx electrical insulation layer.

According to an alternative embodiment, step c) comprises the disposition of at least one metal element, such as an Al, Ar, Au, Zn, Cu, Pt or Ba insert, so as to form the electrical conduction between the layers of electrical insulation. The metallic element can take a multitude of forms, such as a perforated metal plate, in which at least one through hole has been formed, a plurality of wires or metal blades, patterns formed by screen printing through a mechanical mask, insofar as regions of the electrical insulation layer on which the metal element is disposed are not covered. The contacting of these regions with the second layer of electrical insulation makes it possible to assemble the bricks in step c) of the process.

It is understood in this document that the discontinuous electrical conduction layer must still provide continuity in at least one direction so that current can be collected.

Thus, the electrical conduction layer is continuous or discontinuous depending on the embodiments considered and for the needs of future applications.

The arrangement of at least one metal element is chosen especially in the case where the electrical insulation layers are formed by at least one oxide powder which will be sintered, so as to obtain good electrical conduction. Of course, the use of the metallic elements can be combined with layers of electrical insulation formed by thermal SiO2 or SiO2 deposited. This configuration makes it possible to combine the advantages of good electrical conduction and good mechanical adhesion of the electrical insulating material.

According to yet another variant, step c) of forming the electrical conduction layer comprises a screen-printing deposit of a layer of conductive paste on at least one of the electrical insulation layers formed in step b).

The screen printed conductive paste layer has a thickness of between 20 and 500 microns and preferably about 100 microns.

This layer is deposited in the form of patterns, especially if the conducting element of the conductive paste does not form eutectic with silicon.

The conductive paste consists, for example, of a fairly viscous mixture of a matrix, such as glass frit, and metal billets, such as aluminum billets.

In this case, step d) is carried out at a temperature ranging from 300 to 900 ° C and preferably about 500 ° C so as to anneal or activate the screen-printed conductive paste, which increases the conductive character of the conductive paste and increases the bonding efficiency between the layers of electrical insulation forming the assembly between the bricks.

Thus, whatever the embodiment used, step d) of applying a heat treatment is generally involved in reinforcing the bonding energy between the bricks. This bonding is particularly adapted to withstand the temperatures applied for the manufacture of electronic components, such as homojunction or heterojunction cells.

Preferably, the method comprises, after step e), a step f) for forming protection elements of the exposed surfaces of the electrical conduction layer and of the electrical insulation layers of the composite substrate. These protective elements of insulating material are indeed intended to limit the risk of short circuit between two neighboring bricks assembled. The exposed surfaces on which the protective elements are formed may be considered as exposed wafers of said layers of the composite substrate from the cut-out of the assembly.

These protection elements also serve to protect the layers of insulation and electrical conduction during the chemical treatments performed in the following process for the manufacture of microelectronic components.

These protection elements are formed from insulating materials such as silicon oxide, alumina Al2O3, ΓΑΙΝ, SiN, resin, etc. These protection elements are mainly obtained by a PECVD deposit, ALD (acronym English for Atomic Layer Depostion), by printing a screen-printing resin, such as an epoxy-based polymer, or by spraying through the apertures of a mechanical mask.

The resin is mainly used in the case where it is intended to remove the protective elements later, or if the subsequent heat treatments are performed at low temperatures.

These protection elements have a width of about several tens of micrometers and a thickness of between 1 nm and 10 microns and on average a thickness of a few hundred nanometers according to the deposition technique used. These protection elements make it possible to insulate the insulation layers and the electrical conduction layers of the assembly interface between the blocks and to protect these layers against the attacks of acidic and basic reagents used during the manufacture of the components. such as photovoltaic cells.

Advantageously, the method comprises, after step f), a step h) of screen printing of metal contacts configured to ensure the conduction of an electric current, via the electric conduction layer, between two bricks assembled and then cut to size. step e), said cut bricks forming two bonded blocks.

According to one possibility, a step g) is carried out between step f) and step h) comprising removing a portion of the protection elements so as to discover the surface of the underlying electrical conduction layer. The metal contacts are then easily formed on the exposed surface of the electrical conduction layer.

The removal of a portion of the protection elements according to step g) is advantageously carried out by laser ablation.

In a variant, the nature of the dough deposited by screen printing and the deposition temperature used are configured for a targeted consumption of a portion of the protection elements, so that the contacts are formed without requiring a separate step of removing the portions of the protective elements.

It is understood in this document that for the production of photovoltaic cells, the method may comprise, before step h), the formation of a layer of n-doped semiconductor material and a layer of p-doped semiconductor material. respectively on both sides of the composite substrate and an antireflection layer on the face intended to receive the light radiation.

Advantageously, the process comprises, before step d) a step i) of bonding at least two assemblies. Thus the composite substrate is formed of at least two bonded assemblies adapted to the formation of modules for photovoltaic applications.

The heat treatment of step d) is then useful for reinforcing the bonding energy of the assembly of the bricks and also the bonding of the assemblies together.

More precisely, step i) comprises: a step j) of supplying at least two assemblies comprising assembly faces, a step k) of forming layers of electrical insulation, so as to cover the faces assembly, and - a step I) of forming an electrical conduction layer between two electrical insulation layers covering the assembly faces so as to bond the at least two assemblies.

According to one possibility, the electrical insulation layers covering the assembly faces intersect with the electrical conduction layers assembling two neighboring bricks.

Thus, the electrical conduction layers between two assemblies are isolated from the electrical conduction layers between the bricks by the presence of the electrical insulation layers connecting two assemblies.

According to a second aspect, the present invention provides a composite substrate, intended for applications in the photovoltaic field, comprising: - blocks each comprising assembly surfaces, the blocks being assembled via the assembly surfaces so forming at least one paving, an electric insulation layer covering an assembly surface of the pavers, and an electrical conduction layer between the electrical insulation layers of the assembled pavers, the electrical conduction layer being electrically insulated by the insulation layers.

It is understood in this document that the at least one paving is the result of the cutting of an assembly of assembled bricks, in a plane perpendicular to the brick assembly plane, each brick becoming a paving unit after having been cut out, in other words a pavement.

Preferably, the blocks are in p-type doped silicon and / or doped n-type. Thus, the paving can consist of successive blocks of p-type or n-type silicon, or alternating n-type and p-type blocks.

According to one arrangement, the electrical insulation layers are made of silicon oxide and the electrical conduction layers comprise aluminum. A very good vertical electrical conduction is thus obtained between the blocks.

Advantageously, the composite substrate comprises at least two pavements bonded laterally to one another by means of an electrical conduction layer, electrically insulated between two layers of electrical insulation covering the bonded lateral sides of the at least two tilings. Thus, the electric conduction layer serves two functions, that of ensuring the assembly / bonding between the paving stones and the tilings respectively, resistant to temperature, and that of ensuring electrical interconnection between the pavers and between the tessellations. In general, the nature of the materials and the thicknesses of the electrical insulation layers are chosen according to the material of the blocks, the nature of the conduction layer and the temperatures that will be applied thereafter, so as to form a barrier to the diffusion of the elements constituting the conduction layer to the cobblestones. Thus, the properties of these are not altered.

Preferably, the composite substrate comprises metal contacts configured to ensure the conduction of the electric current between the blocks and between the at least two tilings bonded via the electric conduction layers. Each of the blocks can thus be used as an active element in an electronic component, such as a photovoltaic cell.

When the pavers are formed of a GaN-based alloy, these pavings are judiciously used to form LED arrays.

According to a third aspect, the invention relates to a photovoltaic module comprising at least one composite substrate as previously described. Other aspects, objects and advantages of the present invention will appear better on reading the following description of three embodiments thereof, given by way of non-limiting example and with reference to the accompanying drawings. The figures do not necessarily respect the scale of all the elements represented so as to improve their readability. In the remainder of the description, for the sake of simplification, identical, similar or equivalent elements of the various embodiments bear the same numerical references. - Figures 1 to 9 schematically illustrate a first embodiment of the method according to the invention. - Figures 10 to 11 schematically illustrate a second embodiment of the method according to the invention. - Figures 12 to 15 schematically illustrate a third embodiment of the method according to the invention. - Figures 16 and 17 schematically illustrate a top view of two examples of a photovoltaic cell.

Figure 1 illustrates a front view of two bricks 1 (or slab) of silicon having a thickness of 78 mm and side dimensions of 156 mm x 156 mm, provided according to step a) of the method. These silicon bricks 1 are initially obtained by prior steps of cutting silicon ingots (conventionally generated), p-type doped with a boron doping rate of 1015 atoms.cm'3. Once the ingot has been cut to the desired dimensions to form rough bricks, the latter are etched with a basic solution to remove the silicon zones hardened at the cutting step. The assembly surfaces 2 of the bricks 1 then have the flatness and roughness necessary for their subsequent assembly, for example a roughness of less than 10 μm and preferably 2 μm. According to step b) of the process, the bricks 1 are then placed in a thermal oxidation oven for the application of a heat treatment at 850 ° C for a period of 30 min. These conditions allow the formation of a layer of silicon oxide SiOx, a few nanometers thick on the bricks 1, forming the electrical insulation layers 3 covering the assembly surfaces 2.

According to one variant, the electrical insulation layers 3 may be formed of other insulating materials, such as deposited silicon oxide SiO 2, an oxide powder based on TiO 2, Al 2 O 3, ZnO, SiO 2 powder, a mixture of these oxide powders, or a mixture of these oxide powders with at least one organic and / or inorganic binder. The presence of the binders makes it possible to lower the temperature necessary for sintering the powders.

Then a silicon layer 6 of a few micrometers thick is formed on each electrical insulation layer 3 by evaporation followed by a metal layer 7 of aluminum formed with the same technique to a similar thickness.

Alternatively, depending on the desired future applications and the associated heat treatment temperatures, the metal of the metal layer 7 is selected from aluminum, silver, gold, platinum, barium, copper or an alloy of these metals make it possible to reach a eutectic with silicon.

Then, the joining surfaces 2 of the two bricks 1 are placed facing for a contacting according to step c) of the method and obtaining an assembly 5 of the two bricks 1 (Figure 2). The assembly 5 is then subjected to a heat treatment commonly called "bonding annealing" according to step d). This treatment is carried out at 650 ° C. for 30 minutes in an oven under atmospheric pressure so as to liquefy the aluminum layer 7, to promote the diffusion of the silicon in the aluminum so as to obtain a layer of Al-Si alloy of the composition of the eutectic after cooling (eutectic: 12.6% weight of silicon at 577 ° C.).

Depending on the metal used in the metal layer 7, the conditions of the heat treatment varies between the temperature of the silicon eutectic with the corresponding metal and 700 ° C.

As illustrated in FIG. 3, at the assembly interface of the two bricks 1 comprises an electric conduction layer 4 comprising an aluminum layer resulting from the assembly of the two aluminum layers 7 initially formed by evaporation. This aluminum layer is framed on either side of a layer of an Al-Si alloy. The set of aluminum layers 7 and layers of an Al-Si alloy form the electric conduction layer 4, further framed by an SiOx electrical insulation layer 3. This electrical insulation layer 3 is moreover configured to form a barrier to the diffusion of aluminum towards the bricks 1 and to ensure good electrical insulation between the two bricks 1 assembled. This electrical insulation layer 3 is also configured to electrically isolate the conduction layer 4 and the two bricks 1 from each other. When formed by SiO 2, the required thickness of the electrical insulation layer 3 is about 15 nm. In the case of oxide powder, the thickness of the electrical insulation layer 3 after sintering is between about 20 nm and 200 micrometers.

As illustrated in FIGS. 3 and 4, the assembly 5 of the two bricks 1 is then cut in a plane perpendicular to the assembly plane of the bricks 1, that is to say in a vertical plane with respect to FIGS. according to step e) of the method. The cut, illustrated in FIG. 3 by dashed lines, is carried out by any conventional method known to those skilled in the art such as cutting by band saw, wire with diamond inserts or using SiC grains as abrasive, so form a paving 8, with a thickness chosen according to the desired cell and which may be between 100 to 800 microns, typically about 200 microns, formed by the assembly of two pavers 9 from the two cut bricks 1.

The composite substrate 100 thus formed of bricks 1 assembled and then cut is assimilated to a paving 8 consisting of two blocks 9 interconnected by means of an electrical conduction layer 4, insulated between two layers of electrical insulation 3. The FIG. 5 illustrates a perspective view of the composite substrate 100 rotated at an angle of 90 ° with respect to the view of FIG. 4. According to this view, the assembly plane of the bricks 1 is a horizontal plane.

According to one variant, more than two bricks 1 can be assembled using the method mentioned above for obtaining a paving 8 consisting of 3, 4 or more blocks 9 assembled (FIGS. 16 and 17).

Of course, the present invention also proposes the bonding between several assemblies each comprising several bricks, followed by cutting to form a PV module (FIG. 17). According to one possibility, the method comprises providing three brick assemblies 1 formed in step c of the method, each of the three assemblies having assembly faces 11 (step j). An electrical insulation layer 3 of the same type as that formed on the assembly surfaces 2 of the bricks 1 is formed on the assembly faces 11 according to step k. Then an electric conduction layer 4 (step I) of the same type as previously described for the assembly 5 of the bricks 1, is formed between two layers of electrical insulation 3 so as to stick the three assemblies 5 in pairs. Thanks to this method, the electric conduction layers 3 between the three assemblies 5 are electrically isolated from the electrical conduction layers 4 connecting the bricks 1 of the same assembly 5.

After annealing according to step d) of the method, the bonded assemblies 5 are cut according to step e) of the process so as to obtain the composite substrate 100 comprising the result of the cutting of three assemblies 5 bonded together in pairs comprising each three bricks 1 of silicon, ie a composite substrate 100 comprising three tilings 8 glued in pairs, each of the tessellations 8 comprising three assembled blocks 9 of silicon, as illustrated in FIG. 17.

FIGS. 6 to 9 illustrate steps of functionalization of the composite substrate 100, in particular for the manufacture of high voltage photovoltaic modules from a paving 8 comprising two assembled silicon blocks 9 measuring 78 mm wide and 156 mm thick. long, as shown in Figure 5.

Protection elements 12 of the exposed surfaces of the assembly interface between the two blocks 9 are formed on either side of the electrical conduction layer 4. These elements 12 are formed by CVD deposition of an electrical insulating material through the openings of a mechanical mask (step f, Figure 6). According to an alternative, the protective elements 12 are deposited by screen printing of a resin or an insulating paste. An n-doped silicon layer is formed by doping the blocks about 500 nm deep from one of the paving surfaces 8 to receive the light, followed by a p-doped silicon layer 10 'formed on the opposite face then an antireflection layer 16 (ARC for Anti Reflective Coat) on the n-doped layer 10 and / or on the p-doped layer 10 '. Then, as illustrated in FIG. 7, a portion of each of the protection elements 12 is removed, for example by laser ablation, so as to discover the underlying electrical conduction layer 4 (step g). Metal contacts 13 (Al and Ag) are then screen-printed at the location of the removed portions, so as to ensure electrical conduction, schematically illustrated by the arrow in FIG. 9, between two blocks 9 via the coating layer. electrical conduction 4 (step h). Of course, other methods of forming conventional contacts and known to those skilled in the art can be used.

It is thus obtained a photovoltaic cell (PV) with a size of approximately 156x156mm2 comprising two assembled blocks 9, or two p-type homojunction silicon cells, electrically connected in series. Thanks to the method of the present invention, the placing in series of pavers 9 or PV cells is performed by pads 13 of silver and aluminum, connected to each other via the conduction layer 4 of aluminum, also used for assembly and gluing respectively between the paving stones 9 and the pavings 8. Thus, the conventional interconnection by welding generating breakage and limiting the active surface is avoided. The assembly between the bricks 1 and the bonding between the assemblies 5 are configured to withstand the heat treatments used in the manufacture of homo-junction PV cells (850 ° C.) as heterojunction (230 ° C.) thanks to the nature of the materials used. to form the electrical insulation layers 3 and the formation of the electrical conduction layer 4 of bonding and / or assembly, their deposition mode, and the heat treatment applied in step d).

Of course, the same method applies for the serialization of more than two PV cells in the same tiling 8 and the serialization of several PV cells (by gluing of several tilings 8) to manufacture PV panels. The configuration of the tiling 8 is adaptable according to the number of cells desired for example 1x4 (illustrated in Figure 16), 2x2, 3x3 (illustrated in Figure 17), etc.

Thus, the number of cells formed in a single composite substrate 100 is not limited and may vary depending on the desired applications.

When a conventional PV panel has between 60 and 72 standard cells of 156x156mm2 put in series, the open-circuit voltage is between 30 and 50V. If each of the conventional cells is replaced by a composite substrate 100 comprising 4 cells in series according to the present invention, for a similar PV panel surface, the open-circuit voltage obtained is between 120 and 200V. It is then possible to remove a high voltage conversion stage from the inverter and reduce system costs.

For mobile applications that often require a voltage of less than 12V, more compact tilings 8 can be provided by comparison with conventional cell tilings.

FIGS. 10 and 11 illustrate a second embodiment of the invention which differs from the previous one in that step c) is performed by depositing a layer of conductive paste 14 based on aluminum and a matrix of glass frit on an electrical insulation layer 3 of silicon oxide to form the electric conduction layer 4 having finally a thickness of about 100 microns.

Alternatively, the metal contained in the conductive paste 14 may be silver or copper. According to still other variants, the thickness of the electric conduction layer 4 may vary between 5 and 500 μm and preferably between 10 and 100 micrometers.

Finally, the heat treatment according to step d), serving to stiffen the conductive paste 14 ensuring the mechanical adhesion of the assembly 5, is applied for 200 minutes at a temperature of about 700 ° C.

Depending on the nature of the alternative materials, the duration of the heat treatment may vary between 1 and 300 minutes and the temperature may be between 200 and 900 ° C.

FIGS. 12 to 15 illustrate a third embodiment which differs from the first embodiment by the formation of the electric conduction layer 4. The conduction layer formation step c) is carried out by the insertion of several blades. 15 of aluminum (FIG. 12) between the electrical insulation layers 3. As represented in FIGS. 13 and 14, all of these blades 15 thus form a discontinuous conduction layer 4 in the paving 8, and passing vertically at the joint between two blocks 9, (also visible in Figure 15 which is a cross-sectional view of the paving 8 along the plane A of Figure 14, at the electrical contacts 13). Electrical contacts 13, illustrated by a block diagram (FIGS. 14 and 15), are formed from these blades 15 for current conduction in subsequent applications. The inserted metal element 15 can take any form (wire, perforated plate, etc.) insofar as it ultimately allows the electrical conduction and the putting into series of the PV cells. The nature of the metal of the inserted element used may be chosen from Ar, Au, Zn, Cu, Pt or Ba or other insofar as this metal makes it possible to obtain good electrical conduction between the blocks 9 and the tilings 8, resistant to the thermal treatments used later in the manufacture of the desired electronic components.

Depending on the intended applications, other semiconductor materials may be used in place of the silicon bricks in the embodiments described above, including GaN-based alloys and elements or alloys of elements of the invention. column IV of the periodic table.

Thus, the method of the present invention makes it possible to manufacture composite substrates 100 adapted to the formation of PV cells of desired size, delivering high voltage, a part of the interconnection being made in the manufacturing process of the composite substrate 100 This process makes it possible to produce mono or bifacial cells. Since the step of placing the cells in modules represents approximately 40% of the total cost of a PV installation (excluding cabling), this innovation guarantees a significant improvement in the cost / performance ratio of the cells while allowing high-voltage work to be performed directly exit.

It goes without saying that the invention is not limited to the embodiments described above as examples but that it includes all the technical equivalents and variants of the means described as well as their combinations.

Claims (15)

A method of manufacturing a composite substrate (100) for applications in the photovoltaic or optoelectronic field, the method comprising the following steps: a) providing bricks (1) to be assembled to form at least one assembly, bricks (1) having joining surfaces (2), b) forming layers of electrical insulation (3) so as to cover the joining surfaces (2) of the bricks (1), c) forming a layer electrical conduction (4) between the electrical insulation layers (3) so as to assemble bricks (1) adjacent, according to an assembly plane, and to form at least one assembly (5), said electric conduction layer (4) having an electrical resistivity of less than or equal to 10 4 ohm.cm, d) subjecting the at least one assembly (5) to a heat treatment, and e) cutting the at least one assembly (5) according to a plane perpendicular to the assembly plane, the at least one assembly (5) dec oupé forming a paving (8) bricks (1) cut. 2. Method according to claim 1, wherein step a) comprises the supply of bricks (1) of p-type doped semiconductor material and / or doped n-type, the semiconductor material being selected from alloys Based on GaN and elements or alloys of elements of column IV, and preferably the semiconductor material is a crystalline material and more preferably, the semiconductor material is crystalline silicon. 3. Method according to one of claims 1 to 2, wherein, in step b), the electrical insulation layers (3) are formed from silicon oxide, such as SiOx or SiO? or from a powder of TiO 2 oxide, AkO 2, ZnO, a mixture of these oxide powders, or a mixture of these oxide powders with at least one organic binder and / or inorganic. 4. Method according to one of claims 1 to 3, wherein step c) comprises: - the formation of a silicon layer (6) on the electrical insulation layers (3) of silicon oxide covering the assembly surfaces (2) bricks (1) formed in step b), and - the formation of a metal layer (7) on at least one of the silicon layers, the metal being chosen in particular to form a eutectic with silicon, such as aluminum, silver, gold, platinum, barium, copper or an alloy of these metals, and - contacting the metal layers (7) two by two, so as to obtain the electric conduction layer (4) between the electrical insulation layers (3) and to assemble the bricks (1). 5. The method of claim 4, wherein the heat treatment of step d) is performed at a temperature between the eutectic forming temperature between silicon and said metal and 300 ° C. The process according to claim 3, wherein step c) comprises disposing at least one metal element, such as an Al, Ar, Au, Zn, Cu, Pt or Ba insert, so that forming the electrical conduction layer (4) between the electrical insulation layers (3). 7. The method of claim 3, wherein the step c) of forming an electrical conduction layer (4) comprises a screen-printing deposit of a layer of conductive paste (14) on at least one layer of insulation electric (3) formed in step b). 8. Method according to one of claims 1 to 7, comprising after step e), a step f) of forming protection elements (12) of the exposed surfaces of the electric conduction layer (4) and layers electrical insulation (3) of the composite substrate (100). 9. The method according to claim 8, comprising, after step f), a step h) of screen printing of metal contacts (13) configured to condense an electric current, via the electric conduction layer (4). ), between two bricks (1) assembled and then cut in step e). 10. A method according to one of claims 1 to 9, comprising before step d) a step I) of bonding at least two assemblies (5). 11. The method of claim 10, wherein step I) comprises: a step j) of providing at least two assemblies (5) comprising assembly faces (11), a training step k) electrical insulation layers (3), so as to cover the assembly faces (11), and - a step I) for forming an electrical conduction layer (4) between two layers of electrical insulation (3). ) covering the assembly faces (11) so as to bond the at least two assemblies (5). 12. Composite substrate (100) for applications in the photovoltaic or optoelectronic field, the composite substrate (100) comprising: - pavers (9) each having assembly surfaces (2), the blocks (9) being assembled through the joining surfaces (2) so as to form a tiling (8), -electric insulation layers (3) each covering an assembly surface (2), and -an electric conduction layer (4) between the electrical insulation layers (3) of assembled blocks (9), the electric conduction layer (4) being insulated between two electrical insulation layers (3) and said electric conduction layer (4) having an electrical resistivity less than or equal to 10 -4 ohm.cm. 13. Composite substrate (100) according to claim 12, comprising at least two tilings (8) bonded laterally to each other via an electrical conduction layer (4), electrically insulated between two layers of electrical insulation (3). ) covering the bonded sides of the at least two pavings (8). 14. Composite substrate (100) according to one of claims 12 or 13, comprising metal contacts (15) configured to conduct the conduction of electric current through layers of electrical conduction (4) between the blocks (9) and between the at least two pavings (8) glued. Photovoltaic module comprising at least one composite substrate according to one of claims 12 to 14.