FR3043493A1 - ELECTRONIC STRUCTURE ON CERAMIC SUPPORT - Google Patents

Abstract

The invention relates to an electronic structure comprising a ceramic support and at least one active layer disposed on the support. The support has a lower surface than the surface presented by the structure. The invention also relates to a photovoltaic cell composed of four sub-cells resting on bars.

Description

ELECTRONIC STRUCTURE ON CERAMIC SUPPORT

Field

The present application relates to the field of semiconductors, and in particular semiconductor structures that can be used in various fields, such as electronics, microelectronics, nanoelectronics, optics, optoelectronics, thermoelectrics and photovoltaics.

Presentation of the prior art

In the French patent application No. 03/04676 (B5957), of the same inventor, is particularly described a method of manufacturing silicon wafers by sintering silicon powders.

European Patent No. 2,368,265 (B9167), of the same inventor, discloses a structure comprising a sintered silicon layer sumontée a monocrystalline silicon layer.

French Patent Application No. 15/55520 (B13913), filed June 17, 2015 discloses a photovoltaic cell having a plurality of photovoltaic sub-cells integrated on a sintered silicon support. summary

The present invention aims to overcome all or part of the disadvantages of the prior art, and / or to propose an alternative to what exists in the prior art. Thus, the present invention provides an electronic structure, as well as a method for making the structure, which are novel, inventive and industrially applicable.

Thus, the present invention provides an electronic structure comprising a ceramic support and at least one active layer disposed on the support, wherein the support has a surface smaller than the surface presented by the structure.

According to one embodiment, the support comprises disjoint parts.

According to one embodiment, the support comprises rectangular bars arranged parallel to an edge of the structure.

According to one embodiment, the active layer comprises several disjoint parts.

According to one embodiment, the active layer comprises at least two superimposed layers.

According to one embodiment, the active layer comprises at least two photovoltaic sub-cells.

According to one embodiment, at least two photovoltaic sub-cells are connected in series.

According to one embodiment, each of the bars comprises at least two conductive boxes isolated from each other.

According to one embodiment, each of the boxes comprises a conductive strip to facilitate the attachment of the active layer.

According to one embodiment, the support is made of sintered silicon, and / or monocrystalline silicon, and / or polycrystalline silicon, and / or multicrystalline silicon, and / or silicon of non-electronic quality, and / or metallurgical silicon .

According to one embodiment, the active layer is made of monocrystalline silicon and / or multicrystalline silicon and / or polycrystalline silicon.

The present invention also provides a method for producing an electronic structure comprising a support and at least one active layer, in which the method comprises the following steps: a) producing a ceramic support, b) fixing on the support an active layer, the medium having a surface smaller than the surface presented by the structure.

According to one embodiment, the support comprises disjoint parts.

According to one embodiment, the active layer comprises several disjoint parts.

According to one embodiment, the active part comprises at least two photovoltaic sub-cells connected in series. Brief description of the drawings

These and other features and advantages will be set forth in detail in the following description of particular embodiments in a nonlimiting manner in connection with the accompanying figures, in which: Figure 1 shows a structure according to the present invention; Figures 2 and 3 show structural supports according to the present invention; Figure 4 shows an electronic structure according to the present invention; and Figures 5 to 12 show embodiments of photovoltaic cells according to the present invention. detailed description

The same elements may have been designated by the same references in the various figures and, in addition, the various figures are not drawn to scale. For the sake of clarity, only the elements that are useful for understanding the described embodiments have been shown and are detailed.

In the following description, when reference is made to absolute position qualifiers, such as the terms "forward", "backward", etc., reference is made to the orientation of the figures or to a state in a normal position of use. Unless otherwise specified, the terms "substantially" and "of the order of" mean within 10%, preferably within 5%.

In FIG. 1, reference numeral 1 denotes a ceramic substrate serving as a support. The substrate or support 1 may be of sintered silicon, but also of any other suitable ceramic, such as, for example, a suitable silicon aluminate. The support 1 can also be monocrystalline silicon, polycrystalline or multi-crystalline. The thickness of the support 1 can vary in large proportions. For example, the thickness of the support 1 can vary from a few tens of micrometers to several millimeters.

The support 1 is surmounted by an active layer 3. The active layer 3 may be a monocrystalline semiconductor layer, polycrystalline or multi-crystalline. It is recalled that the term "polycrystalline" rather refers to a material in which the grains are of microscopic size, not visible to the naked eye, whereas the term "multi-crystalline" refers to a material whose macroscopic grains are visible to the eye. naked eye. However, since these terms are often interchanged in the scientific literature, in the following, the terms multi-crystalline or multi-crystalline can be used for each other and signify one or other of the definitions. The thickness of the layer 3 can be very variable and depend on the desired application. For example, in an application in the field of microelectronics, the thickness of the active layer may be a few pm, or even less than 1 pm. For an application in the photovoltaic field, the thickness of the active layer may be of the order of a few tens of pm to a few hundred pm. For other applications, such as Wafer on Silicon Support (WSS) techniques where a silicon wafer is attached to a wafer, the silicon wafer may be thicker.

The active layer 3 can be fixed on the support 1 by molecular bonding, as described in European Patent No. 2,368,265 (B9157), cited above. The active layer 3 can also be fixed by eutectic bonding, as described in French Patent Application No. 15/55520 (B 13913), mentioned above and incorporated herein by reference for all that relates to the fixing of the active layer or semiconductor elements on the support. The active layer 3 can also be fixed to the support 1 by any other means, such as by bonding, soldering, brazing, etc.

The support 1 is remarkable in that it comprises openings 4, the trace of which is shown in dashed lines in FIG. 1. The openings 4 may correspond to places where the support 1 has been hollowed out, or to places where the support 1 was not trained. Indeed, the support 1 generally results from the sintering of powders, and it is easy to give the support 1 any desired shape, by sintering the powders in a suitable mold.

Figures 2 and 3 illustrate embodiments of the openings of the support 1.

In Figure 2, a support 1 ', corresponding to the support 1 of Figure 1, comprises four openings 4' of circular shape. Of course, the number of openings 4 'can be different from four. For example, there may be only one circular opening 4 '. The openings 4 'may also have a larger or smaller diameter and be arranged irregularly on the support 1'.

In FIG. 3, a support 1 ", corresponding to the support 1 of FIG. 1, comprises two openings 4" of rectangular shape. Of course, the number of the openings 4 "may be different from 2. For example, there may be only a rectangular opening 4". The openings 4 "may have a length and / or a greater or lesser width and, in the case of a plurality of openings 4", the openings 4 "are not necessarily all of the same size.

We will now explain how the openings of the support are advantageous.

Indeed, the openings of the support 1, 1 'or 1 "create voids and make the support surface is smaller than the surface of the active layer.This surface reduction has special technical effects that solve various technical problems The surface reduction can be as low as 5%, or large, as about 80% voids.

One of the technical effects is that the support has less material, resulting in a reduction in the cost and weight of the structure.

Cost reduction can be important. For example, if the support surface is half the area, the material gain is 50%. The choice to reduce the surface of the media to reduce manufacturing costs may seem simple, but it is nonetheless new and inventive. For example, it is not certain that the solution adopted in the present invention is economically viable in the case where the support is a mono- or multi-crystalline silicon wafer. Indeed, a mono- or multi-crystalline wafer results from sawing a billet of molten silicon. To obtain a support according to FIGS. 2 or 3, it would be necessary to hollow out the plates mechanically, which introduces an additional step; then, the residues obtained would be difficult to recover, as well as the broken or defective platelets. It will be noted here that another problem likely to discourage the skilled person to consider the solution adopted in the present invention is the problem of the mechanical strength of the active layer at the openings. Indeed, it is not at all obvious that active layers having a thickness as low as a few pm or tens of pm can have a sufficient mechanical behavior during manipulations of the structure. By tests, the applicant has proved that the solution adopted in the present invention was conceivable even in case of significant openings, as will be seen later.

Weight reduction can also be important. Indeed, the active layers are often thin and the weight of the structure is mainly determined by the weight of the support. If the support has 70% voids, the structure will weigh only 30% of the weight it would have had if the support had been full. It goes without saying that in most common applications, the weight of the structure is of little importance and is not a factor that one seeks to diminish. However, in some applications, such as for space vehicles or for solar aircraft as they are today, the question of weight can be fundamental. Thus, the use of electronic circuits or photovoltaic panels made with structures according to the present invention will be advantageous or even very advantageous in particular fields.

Another technical advantage of the present invention is that the active layer can be used both on the front side and on the back side, at the openings. For example, back contacts can be created without the need to drill the media. Also, various components or all kinds of more complex circuits like integrated circuits can be made on the back side of the active layer at the openings, realizing kinds of integration in three dimensions.

An important advantage of the structures according to the present invention will also be noted. When the support is formed of disjointed parts, for example formed of bars, these disjoint parts can be used to transmit the electric current, as will be seen later. Other advantages and technical problems solved by the present invention will become apparent in the description which follows. For example, if the structure according to the present invention is a photovoltaic cell, the photovoltaic cell can receive light not only from the front face, but also from the rear face through the openings of the support, which increases the efficiency of the cell . This aspect will be discussed later, when describing a photovoltaic cell according to the present invention.

FIG. 4 illustrates the principle of an embodiment of a structure according to the present invention, in which the support is formed of disjoint parts.

In Figure 4, three rectangular bars 10-1, 10-2 and 10-3, denoted where appropriate 10-i, form the support of the structure. The bars 10-i are for example made of sintered silicon. The bars 10-i are separated from each other by large intervals.

The length of the bars 10-i corresponds substantially to the length L1 of the structure and is not critical. For example, the length of the bars 10-i is 156 mm, which corresponds to a size usually used for a photovoltaic cell. The length of the bars 10-i may also be smaller or larger, the size of a sintered silicon bar being limited only by the size of the apparatus used by the sintering. For example, the bars 10-i may be 250 mm long.

In the example shown in FIG. 4, the bars 10-i have a small width with respect to their length. For example, the bars 10-i may have a width of between 5 mm and 2 cm. The bars 10-1, 10-2 and 10-3 are therefore widely spaced from each other, the space between them being typically of the order of 6 cm in the example shown. Thus, in FIG. 4, the surface of the support can be as small as 20 or 30% of the surface of the structure. The thickness of the bars 10-i is typically of the order of 150 to 300 μm, but it can of course be less or thicker as desired.

In FIG. 4, the active layer is composed of four disjoint bands 12-1, 12-2, 12-3 and 12-4, noted as appropriate 12-i. In FIG. 4, the active layer is represented in several disjoint parts to show the great variability of shape that the structure according to the present invention can take. The strips 12-i are preferably of mono- or multi-crystalline silicon.

The strips 12-i have a length substantially corresponding to the width L2 of the structure, the width L2 may be equal to the length L1 in the case of a square-shaped structure. The width of the strips 12-i is for example between 1 and 4 cm and the gap between them can be large or rather low, such as of the order of 0.5 mm. This interval may also be zero in some embodiments, the edges of the bands 12-i then being joined. The thickness of the strips 12-i depends on the field of application of the structure.

For example, if the structure is used in the photovoltaic field, the bands 12-i may correspond to photovoltaic cells or sub-cells. The strips 12-i then comprise a doped absorber of the P or N type with a thickness of, for example, between 40 to 200 μm and a doped emitter of the opposite type of thickness, for example between 0.1 and 0.2 μm.

An advantage of the structure of Figure 4 is that if the strips 12-i are not too thick, for example less than 100 ym thick, the structure has a flexibility that can be significant. The structure can thus be curved with respect to the bars 10-i, which remain rigid.

Thus, the structure according to the present invention, in which the surface of the support is smaller than the surface of the structure, particularly solves the technical problem of making a semiconductor structure flexible. Various applications can be made. For example, a structure according to the present invention may be plated on or integrated with a curved shape, such as a roof or a vehicle passenger compartment, a tile, or any other product having a non-planar shape. This can be particularly advantageous, for example in the case of the solar plane mentioned above, curved photovoltaic cells that can cover the wings or the fuselage without having projecting angles, which reduces the resistance to the passage of air .

An embodiment of the present invention will now be described, in relation to FIGS. 5 to 8, in which a square structure of side L, comparable to the structure of FIG. 4, is used to form a photovoltaic cell formed of four photovoltaic cells C1, C2, C3 and C4 connected in series.

In FIG. 5, a bar 20 corresponds to one of the bars 10-i of FIG. 4. The bar 20 is for example of the same nature and of the same size as one of the bars 10-i.

The bar 20 is preferably of sintered silicon. The bar 20 is undoped, and as a result, the bar 20 is insulating or virtually insulating. Length L of bar 20 corresponds to the length of one side of the structure.

On the bar 20 are four conductive boxes 22-1, 22-2, 22-3 and 22-4. The boxes 22-i can be formed in various ways. For example, the boxes 22-i can be formed by aluminum deposition by screen printing followed by a rapid annealing (for example from 1 to 10 seconds) at high temperature, for example between 800 and 900 ° C. The boxes 22-i can also be formed using tin deposited by screen printing, by printing a strip or a liquid containing tin, or by liquid tin spray. The boxes 22-i have for example a depth of between 10 and 50 pm.

On each box 22-i, rests a conductive strip 24-i, i ranging from 1 to 4. Each strip 24-i has a smaller surface area than the corresponding box surface and is thinner. The strips 24-i are, for example, metal strips, such as strips of tin or pure silver.

The role of the bands 24-i is, as will be seen later, to fix the sub-cells of the structure. The caissons thus have the function of effectively fixing the strips 24-i while ensuring electrical contact between the box and the rear face of the sub-cells.

FIG. 6A represents the front face, intended to be presented in the sun, of the photovoltaic sub-cell C1 of the structure. Sub-cell C1 has a length L substantially equal to the length of one side of the structure. The width 1 of the sub-cell C1 is substantially equal to L / 4. The internal structure of the sub-cell Cl is not detailed. Of course, the sub-cell C1 comprises an absorber, an emitter and one or more other layers, such as passivation or antireflection layers.

In FIG. 6A, only a collection comb formed of elements 26 connected by a conducting strip 28 is represented.

The comb members 26 are made of a conductive material; for example they are in silver. To achieve them, one can for example drop the elements 26 on the passivation layer or the antireflection layer of the sub-cell Cl and heat. Silver burns the passivation or antireflection layer and comes into contact with the transmitter where it provides electrical conduction. The elements 26 may also be aluminum. For example, the passivation or antireflection layer may be etched with a laser and aluminum, or any other metal, may be deposited in contact with the emitter.

The elements 26 are parallel to the short side of the sub-cell C1. Their length is substantially equal to L / 4. The elements 26 are very thin and quite numerous. For example, the width of the elements 26 can be between 10 and 50 μm and there is an element 26 every millimeter or every 2 millimeters.

The band 28 connects the elements 26 to each other. The band 28 has a length substantially equal to the length L on the side of the structure. The strip 28 is placed on the right in FIG. 6A, and runs along the edge of the sub-cell C1. The strip 28 serves firstly to collect the current received by the elements 26 and secondly to ensure the connection with the next sub-cell, as will be seen later. The width of the strip 28 is greater than the width of an element 26, because the strip 28 is intended to collect more electric current. For example, the band 28 is 1 or 2 mm wide. The band 28 is of the same material as the elements 26 and is manufactured at the same time. Note that the elements 26 and the band 28 may be made differently. For example, the elements 26 may consist of oblique patterns, branched in the manner of a sheet and converging towards one or more points of contact. This reduces the electrical resistance of the elements 26 and thus optimize the current collection. In this case, the band 28 may be limited to a much smaller area.

FIG. 6B represents the rear face of the photovoltaic sub-cell C1. In FIG. 6B, only the rear collector comb of the sub-cell C1 is represented.

The rear collector comb of the sub-cell C1 is formed of collecting elements 30 connected by three conductive strips 32-1, 32-2 and 32-3.

In FIG. 6B, the comb elements 30 are arranged parallel to the long side of the sub-cell C1. Their length is substantially equal to the L side of the structure. Like the elements 26, the elements 30 can be very thin and quite numerous. For example, the width of the elements 30 is from 10 to 50 μm and there is one every millimeter or every two millimeters. The elements 30 can also be much wider, or even cover the entire rear face of the sub-cells to form a conductive plane. In this case, if the conductive plane is not transparent, the photocell will not be able to capture the light falling on the back side. It will be appreciated that metal oxides, such as tin and indium oxides, may form transparent conductive planes which in some applications may advantageously replace the front or rear collector combs of the sub-cell.

The conductive strips 32-i connect the elements 30 to each other. The bands 32-i are for example identical to each other. Each band 32-i has a length substantially equal to the width 1 of the sub-cell Cl. The width of each band 32-i is of the order of 1 to 2 mm. The band 32-2 is arranged substantially in the middle of the sub-cell C1. The bands 32-1 and 32-3 are arranged towards the edges of the sub-cell C1. The bands 32-i serve firstly to collect the current received by the elements 30 and secondly to fix the sub-cell Cl on the support.

The elements 30 of the rear collecting comb may be silver or aluminum, such as the elements 26 of the front collecting comb. The strips 32-i may be made of the same material as the elements 30 and manufactured at the same time.

In FIG. 7, three bars 20-1, 20-2 and 20-3 are identical to the bar 20 of FIG. 5. The three bars 20-i thus each comprise four conductive boxes 22-i each carrying a conductive strip 24. i, the index i varying from 1 to 4.

In FIG. 7, the photovoltaic sub-cell C1 is fixed to the bars 20-i by welding each of the three conductive strips 32-i of the rear collection comb to the conductive strip 24-1 of the first box of each of the bars 20-i. For the sake of clarity, the first boxes 22-1 bars 20-i are not shown in Figure 7, as well as some hidden parts.

The photovoltaic sub-cell C2, identical to the sub-cell C1, is arranged parallel to the sub-cell C1 so as to slightly cover the lateral edge of the sub-cell C1. The sub-cell C2 is fixed to the support of the same manner as the sub-cell C1. Thus, the three conductive strips 32-i of the rear collector comb of the sub-cell C2 are welded to the conductive strips 24-2 of the second box 22-2 of the bars 20-i. The recovery of the sub-cells C1 and C2 takes place over a short distance, typically of the order of 1 to 2 mm.

The C3 and C4 photovoltaic sub-cells, identical to the C1 or C2 sub-cells, are fixed to the support in the same manner as the C1 or C2 sub-cells. For the sake of clarity, so as not to mask the underlying structures of the bars 20-1, 20-2 and 20-3, the sub-cells C2, C3 and C4 are incompletely represented to reveal some of the boxes underlying. The sub-cell C3, as well as the sub-cell C4, covers the sub-cell that precedes it in the same way that the sub-cell C2 covers the sub-cell C1.

In FIG. 7, the sub-cell C1 is represented with the elements 26 of the front collecting comb. The conductive strip 28 which connects the elements 26 is not completely represented because it is covered by the edge of the sub-cell C2 when the latter is represented. To better explain how the sub-cells are connected to each other, the sub-cell C2 is shown without its front collecting comb but its rear collecting comb has been shown in dashed lines. Thus, the collecting elements 30 and the collector strips 32-i of the sub-cell C2 appear in dashed lines in FIG.

The sub-cells C1 and C2 are connected in series. From the rear collector comb of the C1 sub-cell, the electrical charges migrate to the front collector comb of the C1 sub-cell, which is connected to the rear collector comb of the C2 sub-cell. Indeed, during the welding of the collector strips 32-i on the strips 24-i of the boxes, the strip 28 of the sub-cell C1 is pressed onto the strips 32-i of the rear collector comb of the sub-cell C2, which ensures the electrical connection.

Figure 8 shows the entire structure of Figure 7 sectional view along the line AA.

In FIG. 8, the bar 22-1 is thus represented in the form of a rectangle of dimensions L x e, L being the length of the bar and its thickness. The boxes 22-i of the bar 20-1 are shown. On the bar 20-1 rest the four photocell C1, C2, C3 and C4.

The sub-cell C2 covers the sub-cell C1 in a zone 40-1 which, as explained above, allows the passage of the electric current of the conductive strip 28 of the sub-cell C1 to the three conductive strips 32 -i of the sub-cell C2. Likewise, the sub-cell C3 covers the sub-cell C2 over a zone 40-2 and the sub-cell C4 covers the sub-cell C3 over a zone 40-3. The sub-cells C1, C2, C3 and C4 are thus connected in series.

Since sub-cell C2 overlaps sub-cell C1, there is an area 42-1 where sub-cell C2 does not contact bar 20-1. It is the same for the sub-cells C3 and C4, which respectively have 42-2 and 42-3 areas where the sub-cells are not in contact with the bar 20-1. Zones 42-i in no way impede the mechanical strength or electrical conduction of the photovoltaic cell, because the areas 42-i are very small. The areas 42-i are further reduced as the sub-cells Ci are thin. Below 100 μm in thickness, the Ci sub-cells are deformable and the 42-i areas are practically non-existent.

In Figure 8, an element 42 is connected to the box 22-1 of the bar 20-1. The element 42 can serve as a terminal of the photovoltaic cell and allow the evacuation of electrical charges to the outside. Element 42, for example a ribbon, may be copper. The other terminal of the cell may be formed by another conductive element, not shown, connected to the conductive strip 28 of the sub-cell C4.

Some advantages of a photovoltaic cell as described in FIGS. 5 to 8 will now be noted.

Firstly, the fact of connecting four photovoltaic sub-cells in series instead of producing a single cell makes it possible, at equal power, to increase the voltage produced and to reduce the intensity of the produced current, divided by approximately four. This decrease in intensity makes it possible to make contacts between sub-cells and / or finer collector elements and to use less metal, hence a decrease in cost. The decrease in cost is especially noticeable when the metal is a noble metal like silver. For example, with the structure of Figures 5 to 8, it is a saving of 50% silver compared to what would have been used if it had been realized a single cell of the same power.

In addition, when several photovoltaic cells according to the present invention are grouped together to form a photovoltaic panel, the links between cells can also be finer, hence a saving of material. In addition, the Joule resistive losses within the module, at the contacts and the connectors from one cell to another, are reduced by a factor of 16 when each cell comprises 4 sub-cells, which increases the output power of the module. This power gain can be important, for example 5%.

It will also be noted that the particular arrangement of the collecting combs, without bus bars (busbars in English), avoids a masking of the light reaching the cell. Here again, a power gain of approximately 5% is obtained with respect to the prior art, from which it follows that a module consisting of cells according to the present invention may have a power greater than 10% compared to a module of the same dimensions of the prior art.

Another advantage, suggested above, is that the back of the sub-cells is largely transparent. Indeed, the light arriving on the rear face, not exposed to the sun, is blocked only at the bars 20-i and rear collector combs 30, 32-i. As a result, between 70 and 80% of the light reaching the back of the photovoltaic cell can be used to create additional carriers, which increases the efficiency. The present invention is therefore remarkable in that the problem of seeking to increase the efficiency of a photovoltaic cell is solved by decreasing the surface of the support of the cell.

It may be thought that this advantage is insignificant, but it is not the case: as soon as a photovoltaic panel is placed a few tens of centimeters from a wall, generally of a light color, or a reflective surface, the reflected light on the back of the panel can be important. In addition, when a photovoltaic panel is used to make an awning or canopy, or any type of solar shading, the back of the panel receives almost as much light as the front panel.

Another advantage of the photovoltaic cell described in connection with FIGS. 5 to 8 can be noted, this advantage consisting of a reduction in the losses caused by the leakage currents flowing through the substrate. Indeed, even if an undoped silicon substrate is considered relatively insulating, it nevertheless has a certain residual conductivity that can produce a slight loss of power. As the substrate has a smaller surface area than in the prior art, the losses due to the substrate are reduced accordingly.

An embodiment of a photovoltaic cell formed of four sub-cells in series, in which the sub-cells do not overlap, will now be described in connection with FIGS. 9 and 10. The non-recovery of the sub-cells constitutes the main difference between the photovoltaic cell of FIGS. 9 and 10 and the cell of FIGS. 5 to 8, and of the same references may be used for corresponding elements.

In FIG. 9, a sintered silicon bar 50 corresponds to the bar 20-1 of FIG. 8. Like the bar 20-1, the bar 50 comprises four conductive boxes, referenced herein 52-1 to 52-4. On each of the boxes 52-i is arranged a photoelectric sub-cell Ci, identical to the cells Ci of FIGS. 6 to 8. Only the elements of the sub-cells necessary for understanding the following will be described.

In FIG. 9, each of the cells Ci comprises an absorber surmounted by a transmitter, not referenced. The cells Ci are arranged next to each other, and made integral boxes 52-i as described above. The cells Ci are connected in series with the aid of three identical conducting strips 55, referenced 55-1, 55-2 and 55-3. The ribbons 55i are made for example of copper, but other metals or conductive materials can be used. Each ribbon 55i is made in one piece and comprises three parts, referenced 55a, 55b and 55c.

The portion 55a of a ribbon 55-i is connected to the front collecting comb of the sub-cell which precedes it. The portion 55a of the ribbon 55-1 is thus electrically connected to the emitter of the sub-cell Cl.

The portion 55c of a ribbon 55-i is connected to the rear collecting comb of the sub-cell that follows it. Thus, the portion 55c of the ribbon 55-1 is electrically connected to the absorber of the sub-cell C2.

The portion 55b of a ribbon 55-i has a rectangular shape. The portion 55b runs along the edges of two consecutive sub-cells so that the portions 55a and 55b of the ribbon 55-i are level to allow their connection. It goes without saying that the adjacent edges of two consecutive sub-cells are covered with an insulating layer to avoid short circuits. For example, this insulating layer, not shown, is formed during the formation of the passivation layer of the sub-cell, a passivation layer that can surround the sub-cell in its entirety.

Figure 10 shows a top view of the photovoltaic cell of Figure 9, to better understand the appearance of the cell and the shape of ribbons 55-i.

In FIG. 10, the three bars 50-1, 50-2, 50-3 and the sub-cell C1 are represented. The sub-cells C2, C3 and C4 are not represented. The ribbon 55-1 is also shown in FIG.

The ribbon 55-1 thus comprises its three parts 55a, 55b and 55c. Part 55b is a rectangular strip of length substantially equal to the length L of the cell and of width substantially equal to the thickness of a sub-cell. In order to minimize the hiding of light on the front part of the sub-cell and to save the ribbon material 55, the portion 55a is not a continuous band. The portion 55a is formed of a series of discontinuous elements 55a1, which connect the portion 55b to the collector band 28 of the sub-cell C1, on which they are soldered. Also, part 55c is not a continuous part. Part 55c is formed of three legs 55c1, 55c2 and 55c3. The legs 55ci are opposite the boxes 52-2 and are fixed there. The fixing of the legs 55ci can be performed at the same time and in the same way as the fixation of the sub-cells on the bars 50-i. The fact that the portion 55c is made in the form of three legs and not a continuous band has two advantages. Of course a significant saving of the material in which the ribbon 55 is made is ensured. In addition, the absence of part 55c between the bars 50-i avoids masking of the rear part of the photovoltaic cell, which, as mentioned, promotes an increase in the yield. With the ribbon 55-1, the photovoltaic sub-cells C1 and C2 are connected in series and it is the same for the other sub-cells, using the ribbons 55-2 and 55-3. Elements 58 and 59, whose connection is within the reach of those skilled in the art, can serve as terminals for the photocell.

The photovoltaic cell described in relation with FIGS. 9 and 10 has the same advantages as the photovoltaic cell described in relation to FIGS. 5 to 8. In addition, the photovoltaic cell described in relation to FIGS. 9 and 10 has the advantage of to be flat, which minimizes stress and may also be advantageous when a slightly rough surface is not desired.

Two other embodiments of a photovoltaic cell according to the present invention will now be briefly described in relation with FIGS. 11 and 12.

The photovoltaic cells according to FIGS. 11 and 12 show little difference with the cells of FIGS. 5 to 10. Like the latter, they comprise a support formed of three sintered silicon bars and four photovoltaic sub-cells C1, C2, C3 and C4. connected in series. Only the elements necessary for understanding are represented in figures 11 and 12.

In FIG. 11, a sintered silicon bar 60 is shown in longitudinal section. The bar 60 corresponds, in kind and in function, bars 20-1 and 50-1 of Figures 8 and 9, but it comprises only two conductive boxes 62 and 64. The boxes 62 and 64 are of the same nature as the caissons 22-i and 52-i of Figures 8 and 9 but they are longer. In Figure 11, the boxes 62 and 64 are shown substantially twice as long as the boxes of Figures 8 and 9. However, their length can be reduced to a distance slightly greater than the spacing between two sub-cells. The photovoltaic sub-cells C1, C2, C3 and C4, also shown in section, are identical to the sub-cells C1, C2, C3 and C4 of the preceding embodiments.

In FIG. 11, each of the Ci sub-cells comprises a P-type doped absorber 66-i and an N + doped 68-i transmitter. The sub-cells Ci do not overlap and are arranged next to each other.

The sub-cell C1 is fixed on the casing 62 so that its absorber 66-1 rests and is in electrical contact with the casing 62. The sub-cell C2, identical to the sub-cell C1, is arranged head-to-tail. relative to the sub-cell C1. Thus, the sub-cell C2 is fixed on the casing 62 so that its emitter 68-2 rests and is in electrical contact with the casing 62. The provision head to tail makes the sub-cells C1 and C2 cells are connected in series via the box 62 without the need for additional connection.

The C3 and C4 sub-cells are also arranged head-to-tail on the support. Thus, the sub-cell C3 is fixed on the box 64 so that its absorber 66-3 rests and is in electrical contact with the box 64. The sub-cell C4 is fixed on the box 64 so that its transmitter 68 4 rests and is in electrical contact with the box 64.

A conductive member 70, for example a copper ribbon, connects absorber 66-2 of sub-cell C2 to emitter 68-3 of sub-cell C3. Thus, the four sub-cells of the photovoltaic cell of FIG. 11 are connected in series. Other conductive elements 72-1 and 72-2 connected respectively to the transmitter 68-1 of the sub-cell C1 and to the absorber 66-4 of the sub-cell C4 can, if necessary, form terminals of the photovoltaic cell.

An advantage of the photovoltaic cell of FIG. 11 with respect to the photovoltaic cell of FIGS. 9 and 10 is that the connecting elements between cells require less material, hence a saving in weight and material.

FIG. 12 illustrates a variant of the embodiment of the photovoltaic cell according to FIG. 11, in which the sub-cells are of two types.

In FIG. 12, a bar 80, preferably of sintered silicon, is similar to the bar 60 of FIG. 11 and comprises two boxes 82 and 84.

In FIG. 12, each of the sub-cells C1 to C4 comprises a P-type or N-type doped 86-i absorber and a N + -type or P + type 88 + emitter. The sub-cells Ci do not overlap and are arranged next to each other.

The C1 sub-cell has a P-type absorber 86-1 and an N + type 88-1 emitter. The sub-cell C1 is fixed on the casing 82 so that its emitter 88-1 rests and is in electrical contact with the casing 82.

Sub-cell C2 has an N-type 86-2 absorber and a P + type 88-2 emitter. The sub-cell C2 is fixed on the box 82 so that its transmitter 88-2 rests and is in electrical contact with the box 82. In addition, the sub-cell C2 comprises, on the absorber 86-2, a layer 89-2 doped N + type to promote electrical contact with the front collector comb of the sub-cell, not shown.

Sub-cell C3 has an 86-3 P-type absorber and an 88-3 N + type transmitter. The sub-cell C3 is fixed on the casing 84 so that its emitter 88-3 rests and is in electrical contact with the casing 84.

The C4 sub-cell has an N-type 86-4 absorber and a P + type 88-4 emitter. The sub-cell C4 is fixed on the casing 84 so that its transmitter 88-4 rests and is in electrical contact with the casing 84. In addition, the sub-cell C4 comprises, on the absorber 86-4, a layer 89-4 doped N + type to promote electrical contact with the front collector comb of the sub-cell, not shown.

It may be noted that there is no P + layer on the absorbers 86-1 and 86-3 of the C1 and C3 sub-cells. Indeed, such a layer is useless because, during the formation of the front collector comb, usually aluminum, aluminum melts and naturally creates a P + zone around the comb which promotes electrical contact.

In FIG. 12, a conductive element 90, for example in the form of a copper ribbon, for example tinned, provides a connection between the N-type 86-2 absorber of the C2 sub-cell and the 86-3 absorber. type P of the C3 sub-cell. Thus, the four sub-cells of the photovoltaic cell of FIG. 12 are connected in series. Other conducting elements 92-1 and 92-2 respectively connected to the absorber 86-1 of the sub-cell C1 and to the absorber 86-4 of the sub-cell C4 can, if necessary, form terminals of the photovoltaic cell.

It will be noted that in FIG. 12, the sub-cells Ci are all fixed on the support by means of their emitter.

As for the photovoltaic cell of FIG. 11, the connection elements between the sub-cells of the photovoltaic cell of FIG. 12 require less material than in the photovoltaic cell of FIGS. 9 and 10.

It will be appreciated that various embodiments and variations of the present invention have been described above. It will be appreciated that those skilled in the art may combine various elements of these various embodiments and variants or make other modifications without demonstrating inventive step.

For example, the shapes of the support may be different from those described above as an example.

In the realization of photovoltaic cells according to the present invention, the support is not necessarily in the form of rectangular bars. For example, trapezoidal bars or bars having one or more non-rectilinear sides may be used. Also, the bars may not be flat. Also a support may comprise several bars or several parts of different shape.

Also, the number of bars may be different from three, for example equal to two or four. The bars may also be more numerous, for example equal to six.

The support, or parts of the support such as bars, have mainly been described as being made of sintered silicon. The support or its parts may of course be monocrystalline silicon, or multicrystalline silicon, or polycrystalline silicon. The support or its parts may also be silicon of non-electronic quality (which extends from metallurgical silicon to solar grade silicon - solar grade in English), for example metallurgical silicon (in this case, it will be possible, for example, to surround the supporting a layer of silicon oxide to avoid contamination and the caissons or the conductive portions of the support, if any, may be less deep and formed on the oxide layer).

The support may also be composed of separate parts formed of different materials.

The number of sub-cells forming the photocell may be different from four, for example equal to two, three or more than four. Depending on the application envisaged, a number of sub-cells much larger than four, such as 10 to 20, may be used if it is desired that the cell provides a high voltage.

Also, a photovoltaic cell according to the present invention may have a fome other than square, for example be rectangular, trapezoidal, hexagonal or any shape. Likewise, the photovoltaic sub-cells of a cell according to the present invention may have a constitution different from those which have been described above. Also, on the support or fixed to the support of a photovoltaic cell according to the present invention, a zone of the active layer may be used to fix at least one semiconductor device.

Claims (15)

An electronic structure comprising a ceramic support (1, 1 ', 1 ", 10-i, 20-i, 50-i, 60, 80) and at least one active layer (3, 12-i, Ci) arranged on the support, wherein the support has a lower surface than the surface presented by the structure. 2. Structure according to claim 1, wherein the support comprises disjoint parts. 3. Structure according to claim 1 or claim 2, wherein the support comprises rectangular bars arranged parallel to an edge of the structure (10-i, 20-i, 50-i, 60, 80). 4. Structure according to one of the preceding claims, wherein the active layer comprises several disjoint parts. 5. Structure according to any one of the preceding claims, wherein the active layer comprises at least two superposed layers. 6. Structure according to any one of the preceding claims, wherein the active layer comprises at least two photovoltaic sub-cells (C1, C2, C3, C4). 7. Structure according to claim 6, wherein at least two photovoltaic sub-cells are connected in series. 8. Structure according to any one of claims 3 to 7, wherein each of the bars comprises at least two conductive boxes isolated from each other (22-i, 52-i, 62, 64, 82, 84). 9. Structure according to claim 8, wherein each of the boxes comprises a conductive strip (24-i, 54-i) to facilitate the attachment of the active layer. 10. Structure according to any one of the preceding claims, wherein the support is sintered silicon, and / or monocrystalline silicon, and / or polycrystalline silicon, and / or multicrystalline silicon, and / or silicon of non-quality. electronics, and / or metallurgical silicon. 11. Structure according to any one of the preceding claims, wherein the active layer is monocrystalline silicon and / or multicrystalline silicon and / or polycrystalline silicon. 12. Process for producing an electronic structure comprising a support (1, 1 ', 1 ", 10-i, 20-i, 50-i, 60, 80) and at least one active layer (3, 12-i, Ci ), wherein the method comprises the following steps: a) making a ceramic support, b) fixing on the support an active layer, the support having a surface smaller than the surface presented by the structure. The method of claim 12, wherein the support comprises disjoint portions. The method of any of claims 12 and 13, wherein the active layer comprises a plurality of disjoint portions. The method of any one of claims 12 to 14, wherein the active portion comprises at least two photovoltaic sub-cells connected in series.