Classifications

• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
  • H10F10/00—Individual photovoltaic cells, e.g. solar cells
  • H10F10/10—Individual photovoltaic cells, e.g. solar cells having potential barriers
  • H10F10/16—Photovoltaic cells having only PN heterojunction potential barriers
  • H10F10/164—Photovoltaic cells having only PN heterojunction potential barriers comprising heterojunctions with Group IV materials, e.g. ITO/Si or GaAs/SiGe photovoltaic cells
  • H10F10/165—Photovoltaic cells having only PN heterojunction potential barriers comprising heterojunctions with Group IV materials, e.g. ITO/Si or GaAs/SiGe photovoltaic cells the heterojunctions being Group IV-IV heterojunctions, e.g. Si/Ge, SiGe/Si or Si/SiC photovoltaic cells
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
  • H10F71/00—Manufacture or treatment of devices covered by this subclass
  • H10F71/121—The active layers comprising only Group IV materials
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
  • H10F71/00—Manufacture or treatment of devices covered by this subclass
  • H10F71/131—Recrystallisation; Crystallization of amorphous or microcrystalline semiconductors
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E10/00—Energy generation through renewable energy sources
  • Y02E10/50—Photovoltaic [PV] energy
  • Y02E10/547—Monocrystalline silicon PV cells
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
  • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

• the present invention relates to the field of semiconductor materials and structures including elec ⁇ tronic used in the photovoltaic field, as well as in various other fields, such as microelectronics, optics, optoelectronics etc. Presentation of the prior art
• An object of the present invention is to provide electronic structures that can be used in various electronic fields and that allow the production of high quality photovoltaic cells.
• other objects of the present invention will be deduced from the description of the present invention. It will be noted that one of the objects of the present invention is to produce electronic structures and / or photovoltaic cells which are more advantageous or more advantageously than in the prior art. summary
• an embodiment of the present invention provides an electronic structure comprising: a first zone comprising silicon grains smaller than 100 micrometers;
• a second zone superimposed on the first zone and comprising silicon grains with a size greater than or equal to 100 micrometers, the first and second support zones; and one or more layers of semi conductor material ⁇ grown epitaxially on the second zone.
• the support has a doping concentration of greater than 10 atoms / cm 2 using dopants of a first and / or a second type, and the or at least one of the epitaxial layers has a doping concentration of less than 10 - * - ° atoms / cm- ⁇ using dopants of the first and / or second type.
• the thickness of the epitaxial layer or layers is smaller than the size of the silicon grains of the second zone.
• the structure comprises a first epitaxial layer adjacent to the support and doped with a dopant of the same nature as the support and a second epitaxial layer thinner than the first layer, doped with a different kind of dopant. of the support.
• the structure comprises an epitaxial layer adjacent to the support and doped with a dopant of a different nature from that of the support.
• the support comprises third doping zones of the first alternating type with fourth doping zones of the second type, and the epitaxial layer, doped with a dopant of the second type, comprises fifth doped zones of the first or second type, the doping of the fifth zones originating from the diffusion of the dopants of the third and fourth areas.
• an epitaxial layer comprises several sub-layers of materials of different nature.
• the materials of the sublayers are either pure silicon, pure germanium or a silicon and germanium alloy of formula Si x Ge ] __ x , where x is a variable parameter. from 0 to 1 and depending on the underlayer considered.
• the doping of the first type is an N or N + type doping and the doping of the second type is a P or P + type doping.
• the thickness of the support is greater than 100 micrometers, the thickness of the first zone being between a minimum thickness equal to zero and a maximum thickness equal to the thickness of the support minus 100. micrometers.
• the support is not plane and / or has any shape.
• the present invention also relates to a photovoltaic cell comprising an electronic structure as described above.
• the photovoltaic cell comprises an antireflection layer and / or ohmic contact sockets arranged on both sides of the cell or on only one side of the cell.
• the present invention also relates to a method for producing an electronic structure comprising the following steps: a) producing a wafer by sintering silicon powders; b) doping of the wafer with dopants of a first and / or a second type, with a concentration of greater than 10 -3 atoms / cm 2, step b) being possible during step a); c) recrystallizing a face of the wafer to increase the size of the silicon grains, the majority of the silicon grains adjacent to the recrystallized face having a size greater than or equal to a determined quantity; and d) epitaxially depositing one or more layers of a semiconductor material doped with dopants of the first and / or second type, the recrystallization step c) being carried out so that the determined quantity is greater than or equal to the thickness of the epitaxial layer (s).
• the wafer is melted over its entire thickness during the recrystallization step.
• FIGS. 1-6 illustrate a method for realizing electronic structures according to the present invention
• Fig. 7 shows an electronic structure according to the present invention
• Figures 8 to 11 show photovoltaic cells according to the present invention.
• an enclosure 1 encloses a lower piston 3 and an upper piston 4. Between the lower and upper pistons has been placed silicon powder 6.
• the enclosure 1 comprises a gas inlet opening 7 and a gas outlet opening 9.
• a gas flow G is established between the openings 7 and
• the chamber 1 is brought to a temperature T.
• a pressure P is applied between the pistons 3 and 4.
• the sintering conditions can be quite varied.
• the size of powders 6 is not critical.
• the particle size of the powders may be between 10 nanometers and 100 micrometers.
• the quality of the powders is not critical either. As will be seen later, it is possible to use silicon powders of solar quality (“solar grade” in English) or electronic quality (“electronic grade” in English). It is also possible to use metallurgical type powders known as MG powders ("Metallurgical grade”) or improved metallurgical silicon powders known as U-MG powders ("Up-graded-Metallurgical silicon”).
• the temperature T can be between 1000 and
• the pressure P can be between 5 and 100 megapascals.
• the temperature T and the pressure P can be applied jointly, during one or more hot pressing steps, or successively, during one or more compression steps followed by a heat treatment.
• the temperature T and / or the pressure P are not necessarily fixed during sintering.
• the pressure of the gas G can for example vary between a few hectopascals and more or less 1000 hectopascals.
• the gas G can be argon. Hydrogen can be added to reduce the oxygen present in the powders, as well as another gas, for example a halogen gas, to purify the powders.
• French Patent Application No. 08/55149, of the same inventor, filed July 28, 2008 and entitled "Manufacture and purification of a solid semiconductor" describes various gases and procedures for purifying a sintered wafer after or in progress.
• the teaching of this patent application in the present invention may be used.
• the pistons 3 and 4 may be porous so as to allow the gas to pass through the porosity channels of the material being sintered.
• FIG. 2 represents a sintered silicon wafer 10 obtained after sintering as described in relation to FIG.
• the wafer 10 has a length L, a width 1 and a thickness h. For example, one can realize square wafers of 150 millimeters of side having a thickness h between 100 and 500 micrometers. It is also possible to produce platelets of circular, rhombic, hexagonal shape, the shape being arbitrary, but preferably pavable.
• the wafer 10 is not necessarily flat, but can be adapted to a desired shape, for example the shape of a roof tile.
• the wafer 10 is formed of small grains 12, symbolized by crosses in FIG. 2. Generally, the sintering increases little the size of the grains. For example, if powders of the order of one micrometer were used, the grains 12 will have a size ranging from 1 to 3 microns depending on the sintering conditions.
• the wafer 10 can be made in a non-porous or porous form, the porosity being controllable by the wafer forming conditions.
• the wafer 10 is doped, of the N type and / or of the P type, with a preference for the N + and / or P + types.
• the P + or N + types are understood as corresponding to dopant concentrations of greater than 10 -3 atoms / cm 2, for example between 10 -3 and 10 -3 atoms / cm 2
• the P or N are understood as corresponding to dopant concentrations below 10 - * - ° atoms / cm ⁇ , for example included between IO ⁇ e t 10- atoms / cm- ⁇ . Doping can be performed during sintering.
• the doping can also be carried out after sintering, that is to say after the formation of the wafer 10.
• the dopants can be introduced by injecting a gas, a liquid or viscous product which penetrates the wafer 10 through the porosity channels. It is also possible to brush one or both sides of the wafer with a paste containing dopants and to penetrate the dopants by diffusion. Dopants can be added in one or more times.
• the doping may be homogeneous, have a gradient or be located, that is to say present in one or more distinct parts of the wafer.
• Figure 3 shows an example of a wafer 10 with localized doping.
• the wafer 10 has N + doped zones 15 alternating with P + doped zones 17.
• the zones 15 and the zones 17 are in the form of strips occupying the entire width 1 and the entire thickness h of the wafer 10.
• the width of the zones 15 is for example of the order of 2 millimeters and the width of the zones 17 of the order of 1 millimeter.
• the doping of the zones 15 and 17 is carried out after formation of the wafer 10, which has been produced here in porous form. Doping can, for example, be carried out by injecting liquid or a viscous product into the pores of the wafer. Zones 15 and 17 can also be produced by screen printing followed by an annealing step for dopant diffusion.
• Zones 18 may contain an insulator, such as silica SiO 2.
• the insulation may have been introduced by a process similar to that used for doping, for example by brushing the parts corresponding sides of the wafer with a paste containing silica and by penetrating through the pores.
• An insulator is not necessarily injected into the zones 18. This is particularly the case if the wafer 10 has been made from undoped or lightly doped powders of solar or electronic quality, since these powders, once sintered, exhibit a resistivity much higher than that of the N + or P + doped zones. On the other hand, it is recommended to inject an insulator in zones 18 if the powders used are powders of MG or u-MG quality. Indeed, in this case, the metallurgical silicon may be conductive and create disruptive leakage currents.
• FIG. 3 is only an example of localized doping, and one can imagine non-strip patterns for zones 15 and 17.
• an enclosure 20 encloses a lower counter-piston 23 and an upper counter-piston. 24.
• the plate 10 is placed between the lower and upper counter-pistons.
• the counter-pistons 23 and 24 exert no particular pressure on the wafer 10.
• the counter-piston 23 is brought to a temperature T1 lower than the melting point of the silicon, that is to say less than 1414 ° C.
• the counter-piston 24 is brought to a temperature T2 greater than the melting point of the silicon.
• the recrystallization step is short, typically from a few seconds to a few minutes after melting of the upper face of the wafer.
• the recrystallization step can take place in the same chamber as that used for sintering FIG. 1.
• the pistons 3 and 4 then play the role of the counter-pistons 23 and 24.
• the recrystallization step can be carried out by other techniques. For example, an area melted by a beam of energy, such as a light beam, may be created on the upper surface of the wafer, and the molten zone is moved so as to scan the entire surface of the wafer. There are also other methods also using a scanning system, in which a zone is melted over the entire thickness. Depending on the technique used, to keep its shape to the wafer, we can abstain from melting the edges, which will be cut.
• Figure 5 shows a wafer 25 corresponding to wafer 10 after recrystallization. If it has not been completely melted, which is the case in FIG. 5, the wafer 25 has an upper part 26 with coarse grains 27 and a lower part 28 with small grains 29.
• the grains 29 correspond to the grains 12 of the Figure 2 and are represented in the same way.
• the grains 27 have an average size d.
• the size of the grains 27 is typically greater than or equal to 100 micrometers.
• the wafer 25 is placed on a support that is not shown in an enclosure 30 that makes it possible to deposit silicon by epitaxy.
• An epitaxial layer 32 of silicon is deposited on the upper face of the wafer.
• the thickness of the epitaxial layer is e.
• the epitaxy reproduces the structure of the surface of the wafer, and crystals 34 are formed in the layer 32 in continuity with the crystals 27.
• the crystals 34 reproduce the crystals 27 of the recrystallized zone.
• the thickness e of the epitaxial zone is chosen to be smaller than the size of crystals 27. Typically, the thickness e is of the order of 20 to 50 microns.
• the layer 32 is doped with N-type or P-type dopants, preferably during the epitaxial step.
• the concentration of the dopants is preferably less than 10 -3 atoms / cm -1.
• the epitaxy deposit can be made by CVD ("Chemical Vapor Deposition") from silane or trichlorosilane gas, by deposition or evaporation under vacuum, for example with a temperature of between 900 and 1200 ° C. It will be avoided to exceed 1200 ° C. C to avoid having impurities and dopants of the wafer 25 in the epitaxial layer. At around 1200 0 C, an epitaxial deposit of twenty micrometers generally takes about twenty minutes. It will be noted that the epitaxial deposition 32 is made on a clean surface.
• Fig. 7 shows an electronic structure 35 according to the present invention.
• the structure 35 comprises a zone 28 with small grains, a zone 26 with coarse grains and an epitaxial zone 32.
• the zone 28 may be of very small thickness, such as a micrometer. Zones 26 and 28 are heavily doped.
• the zones 26 and 28 serve as support for the structure and, because of their doping, can serve as rear electrode of the structure.
• the epitaxial zone is weakly doped.
• the role of the epitaxial zone is to serve as an active layer.
• the epitaxial zone may have homogeneous doping, or several doping layers different in nature or in concentration.
• the epitaxial zone may be made of pure silicon, or of an alloy of silicon and of another semiconductor material, such as germanium.
• the epitaxial layer may also have several layers of different types of materials.
• the structure 35 can be used to make photovoltaic cells as well as various other elements, such as electronic or optoelectronic components of the integrated circuit type.
• Zone 28 when it exists, is a zone that can be porous and have channels of open porosity. These channels can be used, if necessary, for example to inject aluminum, forming and improving the ohmic contact.
• the epitaxial zone may comprise a fairly thick P-type doped layer, for example of the order of 20 microns, surmounted by an N-type doped layer of small thickness, for example less than 1 micrometer. It will be noted here that it is possible to deposit by epitaxy a P + doped layer called BSF layer ("Back Surface Field") between the zone 26 and the zone 32. Such a BSF layer may be of interest in certain embodiments of photovoltaic cells, to prevent the recombination of carriers created by light. d) The method according to the present invention allows a saving of technological steps, insofar as there is no subsequent diffusion step to create the N or P layers.
• FIGS. 8-11 Various photo voltaic cells and their embodiments will now be described from an electronic structure according to the present invention, in connection with FIGS. 8-11.
• a photovoltaic cell 38 according to the present invention is made from an electronic structure 40 according to the present invention.
• the structure 40 comprises a zone 41 with small p + type doped silicon grains, a P + type doped zone 42 with large grains of silicon, a P type doped layer 43 and a N + or N + type doped layer 44.
• the zones 41 and 42 come from the sintering of silicon powders, the zone 42 resulting from a recrystallization at the surface, carried out as has been described previously.
• Layers 43 and 44 are two layers of silicon deposited by epitaxy.
• the zones 41 and 42 have an overall thickness of the order of 100 to 500 microns, the layer 43 has a typical thickness of the order of 20 microns, and the layer 44 has a typical thickness of about one micrometer.
• the antireflection layer 45 On the layer 44 of the structure 40, there is an antireflection layer 45, the surface of which may have been textured to capture the maximum of light.
• the antireflection layer is a very thin layer, typically of the order of 0.1 micrometer, generally made of silicon nitride.
• Metal studs 46 forming a comb are connected to an output terminal 47.
• a metallization layer 48 for example made of aluminum, connected to at a terminal 49 forming the other output terminal of the cell 38.
• the embodiment of the layer 45 and the handshakes is conventional and their embodiment will not be described specifically.
• cell 38 The operation of cell 38 is as follows. Charge carriers are created by a photon flux at the PN junction of the layers 43 and 44. The charge carriers created by the light in the zones 43 and 44 are discharged to the terminals 47 and 49 via the respective conductive zones. , P + doped and / or metallic.
• the structure 40 constitutes practically alone the entire photovoltaic cell 38.
• the cell 38 is thus advantageous because the structure 40 is inexpensive and feasible with few technological steps.
• the various dopings can be made during the formation of the different zones or layers, which avoids later steps of doping.
• Zone 41 consisting of grains generally micron, that is to say from one to a few microns, has indeed a density grain boundaries much higher than other areas, which traps any impurities introduced into the epitaxial layer or layers, such as metal impurities.
• This effect of entrapment (“gettering effect” in English) occurs especially during the manufacturing steps of the structure, especially when these steps take place at high temperature as is the case for example for the deposition steps.
• a photovoltaic cell 50 according to the present invention comprises an electronic structure 60 according to the present invention.
• the electronic structure 60 comprises a zone N + type doped with small grains of silicon, a zone 62 doped N + type with large grains of silicon, and a layer 63 doped type P.
• the zones 61 and 62 come from the sintering of powders of silicon, the zone 62 resulting from a recrystallization at the surface, carried out as has been described previously.
• the layer 63 is a layer of silicon deposited by epitaxy.
• the zones 61 and 62 have an overall thickness of the order of 100 to 500 microns, and the layer 63 has a typical thickness of the order of 20 microns.
• an antireflection layer 65 On the layer 63 of the structure 60, there is an antireflection layer 65.
• the contact points 66 are connected to an output terminal 67 of the photovoltaic cell 50.
• On the lower face of the cell 50 in contact with the zone 61 there is a metallization layer 68 connected to a terminal 69 forming the other output terminal of the cell 50.
• the antireflection layer and the various contact points of FIG. 9 are similar to the antireflection layer and to the corresponding contacts of FIG. Figure 8 and will not be further specified.
• the operation of the cell 50 of Figure 9 is as follows. During the formation of the epitaxial layer 63, the dopants of the layer 62 diffuse slightly, forming, in the epitaxial zone, an N-type doped zone 70, shown in dotted lines in FIG. 9.
• the PN junction necessary for the operation of the cell is here at the level of the zone 70 and the layer 63. Once created by the light, the Load carriers migrate to terminals 67 and 69 of the photovoltaic cell.
• the photovoltaic cell 50 has, like the cell 38 of FIG. 8, all the advantages related to the use of an electronic structure according to the present invention. In addition, it has the following advantages.
• the sintered support 61, 62 participates in the junction, it is useless to provide, as in FIG. 8, an epitaxial layer doped with N or N + type on the epitaxial layer of type P.
• the cell 50 is therefore simpler to achieve than the cell 38 and results in a saving of time and manufacturing price.
• the PN junction is at the base of the layer 63, adjacent to the layer 62, energy absorption is avoided by the layer 44 of FIG. 8, which occurs because the N or N + layer is on the surface.
• a photovoltaic cell 75 according to the present invention comprises an electronic structure 80 according to the present invention.
• the electronic structure 80 comprises a zone 81 with small grains of P + type doped silicon, a zone 82 of doped type P + with large grains of silicon, a layer 83 formed of several sub-layers 83-1 to 83-n doped type P and a layer 84 doped N or N + type.
• the zones 81 and 82 come from the sintering of silicon powders, the zone 82 coming from a surface recrystallization carried out as described previously.
• the zones 81 and 82 have an overall thickness of the order of 100 to 500 micrometers.
• the layer 84 has a typical thickness of the order of one micrometer.
• the layer 83 is formed of sub-layers 83-i, i ranging from 1 to n, which have been epitaxially deposited and p-type doped.
• Each sub-layer 83-i is formed of a material of chemical formula Si x Ge] _- x , the value of x being able to vary from 0 to 1.
• the underlayer 83-1, in contact with the zone 82 can be pure germanium, while the following sub-layers are alloys of silicon and germanium with a growing proportion of silicon, to get pure silicon in the 83-n underlayer.
• the layer 83 has a typical total thickness of the order of 20 to 50 microns.
• the number of sub-layers 83-i is limited, for example equal to three or four.
• the photovoltaic cell 75 comprises an antireflection layer 85, metallization pads 86 connected to a first terminal 87 of the cell, and a rear metallization layer 88 connected to a second terminal 89 of the cell.
• the photovoltaic cell of FIG. 10 is advantageous because it has a higher efficiency than the cell 38 of the figure 8.
• the forbidden bands of silicon, germanium and silicon-germanium alloys being different, more electron-hole pairs are created because the energy of the photons is better used than in the case of pure silicon.
• the infrared part of the solar spectrum is converted with a higher efficiency if one realizes a structure where the layers are richer in silicon on the face exposed to light and richer in germanium in the underlying layers.
• germanium makes it possible to have a higher carrier mobility and a better conductivity, as well as better ohmic contact with the conductive areas.
• Fig. 11 shows another embodiment of a photovoltaic cell according to the present invention.
• a photovoltaic cell 90 comprises an electronic structure 95 according to the present invention.
• the structure 95 comprises a lower support 100 and an upper layer 102.
• the lower support 100 comes from a wafer of sintered silicon doped as described in FIG. 3.
• the support 100 comprises zones 105 doped N + type, alternating with zones 107 doped type P +.
• the zones 105 typically have a width of the order of two millimeters and the zones 107 typically have a width of the order of one millimeter.
• Between zones 105 and 107 are zones 108 that may have been made insulating by adding an insulator in the porosity channels.
• the support 100 has large grains, typically greater than or equal to 100 micrometers in size, on its upper face, in contact with the layer 102. These coarse grains come from a surface recrystallization and have not been represented in FIG. not to overload the figure.
• the support 100 has, in general, small grains in its lower part, which remained porous.
• the thickness of the support 100 is of the order of 100 to 500 microns, as in the case of the cells described above.
• the layer 102 comes from the deposition of silicon by epitaxy on the recrystallized surface of the support 100.
• the layer 102 is p-type doped.
• the zones 110 are adjacent to the zones 105 and the zones 112 are adjacent to the zones 107.
• the zones 110 and the zones 112 have been obtained during a diffusion step which has made the dopants of the zones 105 and 107 in the layer 102.
• the diffusion can be obtained by heating at a temperature of the order of 900 0 C after the epitaxial deposition of the layer 102. Diffusion also occurs during the epitaxial deposition of the layer 102 and a subsequent diffusion step may be unnecessary.
• On the upper face of the layer 102 there is an antireflection layer 114, similar to the antireflection layer of the previously described cells.
• pads 115 facing the zones 105 and pads 117 opposite the zones 107.
• the pads 115 and 117 are metallic, for example aluminum.
• the pads 115 are connected to a terminal 120 and the pads 117 are connected to a terminal 130.
• the terminals 120 and 130 form the two output terminals of the cell 90.
• the operation of the photovoltaic cell 90 is as follows.
• the PN junction is at the zones 110 and the epitaxial layer 102.
• the zones 107 are narrower than the zones 105 because their function is different. Indeed, the zones 107 serve, through the zones 112, to facilitate the ohmic contact with the epitaxial zone 102.
• the N + doped zones 105 also serve to facilitate the ohmic contact with the metal zones 115.
• the photovoltaic cell 90 has all the advantages associated with the presence of an electronic structure according to the present invention.
• all the electrical contacts are made on the underside of the cell. There is no collecting comb on the surface of the cell exposed to radiation. As a result, a larger area is available to receive radiation, resulting in improved cell performance.
• the cell 90 does not have specific surface dopings, such as the layer 44 of FIG. 8, which are generally quite high and absorb some of the light. It will be noted that the photovoltaic cell 90 can not be made with a conventional silicon substrate monocrystalline or polycrystalline, because a monocrystalline or polycrystalline substrate does not allow to perform the doping illustrated in FIG.
• the epitaxial layer may comprise several sub-layers of varying composition Si x Ge ] __ x variable doping as in the case of the cell 75.
• the various thicknesses and sizes were given only as an indication.
• the supports of the structures or cells according to the present invention may be thicker, for example from one to several millimeters if desired.
• the thickness of the epitaxial layer has been described on the order of 20 to 50 microns. It goes without saying that the epitaxial layer may be less thick, for example 10 microns thick, or thicker, for example up to 100 or
• the nature of the dopants can be reversed.
• the P or P + doped zones of a structure or cell may be replaced by N or N + doped zones, the N or N + type doped zones of the structure or of the cell being replaced by zones of type P or P +.
• the structures according to the present invention which make it possible to produce photovoltaic cells, can be used in other devices, the epitaxial zone serving as an active zone.
• the epitaxial zone serving as an active zone. Examples of such applications are, for example, integrated circuits of the electronic or optoelectronic type.

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• 2009
  • 2009-04-02 FR FR0952110A patent/FR2944142B1/fr not_active Expired - Fee Related
• 2010
  • 2010-04-01 CN CN2010800157559A patent/CN102439736A/zh active Pending
  • 2010-04-01 WO PCT/FR2010/050628 patent/WO2010112782A2/fr not_active Ceased
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