Classifications

• • H—ELECTRICITY
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  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
  • H01L31/04—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
  • H01L31/0248—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies
  • H01L31/0352—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by their shape or by the shapes, relative sizes or disposition of the semiconductor regions
  • H01L31/035272—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by their shape or by the shapes, relative sizes or disposition of the semiconductor regions characterised by at least one potential jump barrier or surface barrier
  • H01L31/03529—Shape of the potential jump barrier or surface barrier
• • H—ELECTRICITY
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  • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
  • H01L31/0248—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies
  • H01L31/0352—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by their shape or by the shapes, relative sizes or disposition of the semiconductor regions
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
  • H01L31/0248—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies
  • H01L31/036—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by their crystalline structure or particular orientation of the crystalline planes
  • H01L31/0384—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by their crystalline structure or particular orientation of the crystalline planes including other non-monocrystalline materials, e.g. semiconductor particles embedded in an insulating material
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
  • H01L31/04—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices
  • H01L31/06—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by potential barriers
  • H01L31/068—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by potential barriers the potential barriers being only of the PN homojunction type, e.g. bulk silicon PN homojunction solar cells or thin film polycrystalline silicon PN homojunction solar cells
  • H01L31/0682—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by potential barriers the potential barriers being only of the PN homojunction type, e.g. bulk silicon PN homojunction solar cells or thin film polycrystalline silicon PN homojunction solar cells back-junction, i.e. rearside emitter, solar cells, e.g. interdigitated base-emitter regions back-junction cells
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
  • H01L31/18—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
  • H01L31/18—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
  • H01L31/1804—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof comprising only elements of Group IV of the Periodic Table
• • 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 invention relates to the field of photovoltaic cells, and in particular that of photovoltaic cells with back contacts, that is to say with contacts located on the face of the cell not receiving the photons.
• the invention also relates to the production of photovoltaic cells from semiconductors of inferior quality to the standard quality used in microelectronics.
• Photovoltaic cells are mainly manufactured from monocrystalline or polycrystalline silicon substrates obtained by solidifying ingots from a liquid silicon bath and then cutting slices of this ingot to obtain the substrates, or platelets. Different deposition techniques on these silicon substrates are then implemented in a clean room to produce the photovoltaic cells.
• the crystallized silicon ingots are first cut into platelets on which cells are made. These wafers are then textured by etching to improve the trapping of light by photovoltaic cells that will be made from these platelets. Pn junctions are then made by gas diffusion in these wafers. A PECVD deposit is then implemented to improve the antireflection properties of the cell and to passivate the recombinant defects. Conductive layers are then deposited by screen printing on both sides to allow the collection of photo-generated carriers and the taking of the electrical contacts of the photovoltaic cell.
• photovoltaic cells of different structures such as heterojunction photovoltaic cells (amorphous Si / crystalline Si) and / or RCC cells.
• EWT Photovoltaic cells type EWT (Emitter Wrap Through). These cells are made from a silicon wafer, for example p-type. Holes (the diameter of which is about 60 ⁇ m, and spaced about 2 mm apart) are made by laser etching through the silicon wafer. The emitter of the cell is then formed by producing a n + type layer by gas diffusion on the front face, in the walls of the holes, as well as on a portion of the rear face of the cell. Thus, the p-n + junction is distributed in the cell volume of the zones, making it possible to reduce the distance to be traveled by a minority carrier before collecting it.
• EWT cells have the major disadvantage of having a high manufacturing cost because of their realization which must necessarily be done in a clean room and the use of a laser for producing the holes in the substrate.
• An object of the present invention is to provide a novel solar cell architecture optimizing collection and transport of minority charge carriers in the photovoltaic cell, and the cost of implementation is reduced and can be made from semi ⁇ conductor lower quality than microelectronics quality.
• the present invention provides a photovoltaic cell comprising a semiconductor-based substrate of a first conductivity type having two main faces substantially parallel to each other, the substrate comprising a plurality of blind holes whose apertures are arranged at only one of the two main faces, the blind holes being filled by a semiconductor of a second conductivity type opposite to the first conductivity type forming the emitter of the photovoltaic cell, the substrate forming the base of the photovoltaic cell.
• the emitter of this photovoltaic cell is distributed in the form of several semiconductor portions distributed in blind holes, in the heart of the substrate.
• this arrangement of the pn junctions in the photovoltaic cell makes it possible to optimize the collection and transport of minority charge carriers inside the photovoltaic cell, thus allowing the use of semi-photovoltaic cells.
• -conductors of inferior quality to the microelectronic quality for its realization such as semiconductor powders mixed with polymers. This cell can therefore be produced at low cost, for example by using techniques derived from micro-plastics processing.
• the photovoltaic cell according to the invention offers greater possibilities of adjusting the dimensions, the positioning and the spacing of the semiconductor portions forming the emitter of the cell. Compared with the EWT technology, this photovoltaic cell architecture also allows the use of low levels of semiconductor doping for equivalent conductance.
• Each blind hole may comprise a central axis of symmetry substantially perpendicular to the two main faces of the substrate.
• the transmitter of the cell is thus formed by longitudinal portions of semiconductor disposed in the substrate of the photovoltaic cell.
• Each blind hole may comprise, in a plane passing through the main face of the substrate comprising the openings of the blind holes, a upper surface section to the surface of the bottom wall of said blind hole.
• the ratio between the sectional area of said blind hole at the plane passing through the main face of the substrate comprising the openings of the blind holes and the surface of the bottom wall of said blind hole can be between 1 and 3.
• Each blind hole may have a substantially conical or truncated ogival shape.
• Each blind hole may comprise, in a plane parallel to one of the main faces of the substrate, a section of polygonal shape, or for example a star shape.
• the concentration of doping atoms, or carrier atoms, per cubic centimeter in the semiconductor ⁇ of the second type of conductivity of the emitter may be between 10 16 and 10 21 , and preferably between 10 18 and 10 20 .
• the concentration of dopant atoms per cubic centimeter in the semiconductor of the first conductivity type of the substrate may be between 10 15 and 10 18 and preferably between 10 16 and 17 October.
• the thickness of the substrate may be less than 300 microns and the depth of each blind hole may advantageously be greater than half the thickness of the substrate.
• the photovoltaic cell may further comprise, on the main face of the substrate comprising the openings of the blind holes, first collecting fingers based on at least one semiconductor of the second type of conductivity in contact with the emitter of the cell. , and second collection fingers based on at least one semiconductor of the first conductivity type in contact with the substrate and interdigitated with the first collecting fingers.
• the doping atom concentrations per cubic centimeter in the semiconductors of the first conductivity type of the second collection fingers and the second conductivity type of the first collection fingers may be between 10 19 and 10 21 .
• the invention also relates to a method for producing a photovoltaic cell, comprising at least the steps of: a) producing a semiconductor-based substrate of a first conductivity type comprising two substantially parallel main faces; relative to each other, b) providing a plurality of blind holes in the substrate, openings of the blind holes being disposed at only one of the two main faces, c) filling the blind holes with a material based on a semiconductor of a second conductivity type, opposite to the first conductivity type, forming the emitter of the photovoltaic cell.
• Step a) can be implemented by injecting a semiconductor material of a first conductivity type into a mold. During this process, it is possible to keep the substrate in the initial mold by removing the bottom of the mold to facilitate any alignment problems.
• the filling step c) can furthermore, on the main face of the substrate comprising the openings of the blind holes, and through a first mask disposed against the said face of the substrate comprising the openings of the blind holes, the first fingers of collection to at least one semiconductor of the second conductivity type in contact with the emitter of the cell, and further comprising after step c), the removal of the first mask and the production of second collection fingers based on at least one semiconductor of the first conductivity type in contact with the substrate and interdigitated with the first collection fingers by injection through a second mask disposed against said face of the substrate having the openings of the blind holes.
• the substrate and / or the transmitter and / or the collection of fingers may be made from a mixture of materials based on semi powders ⁇ conductors and polymers, and the method may further comprise, after step c) filling, a debinding step of the mixture carried out at a temperature between about 300 0 C and 600 0 C, for a period of between about 12 hours and 36 hours, and a sintering step of the powders obtained after debinding carried out at a temperature between about 1000 0 C and 135O 0 C for a period of between about 1 hour and 8 hours.
• the debinding step and / or the sintering step can be carried out under a reducing atmosphere, for example under a hydrogen atmosphere.
• FIG. 1 represents a partial view, in section and in profile, of a photovoltaic cell, object of the present invention, according to a particular embodiment
• FIG. 2 represents a partial bottom view of a photovoltaic cell, object of the present invention, according to a particular embodiment
• FIG. 3 represents a partial sectional view of a photovoltaic cell, object of the present invention, according to a particular embodiment
• FIG. 4 represents examples of profiles and sections of blind holes made in photovoltaic cell substrates, objects of the present invention.
• Figure 1 shows a partial sectional view of a photovoltaic cell 100 according to a particular embodiment.
• the photovoltaic cell 100 here p-type, comprises a substrate 102 based on p-type silicon.
• This substrate 102 comprises a front face 104 intended to receive the light rays, as well as a rear face 106.
• the front face 104 is textured in order to better trap the light arriving in the photovoltaic cell 100.
• the rear face 106 could also be structured, similarly or not to the front face 104.
• the thickness of the substrate 102 is for example between about 50 microns and 300 microns, and advantageously between about 100 ⁇ m and 200 ⁇ m.
• Blind holes 108 are formed in the substrate 102, each blind hole 108 having an opening at the rear face 106 of the substrate 102. As shown in FIG. 1, the blind holes 108 have profiles such as the surface of the section. Blind holes 108 at the rear face 106 is greater than the surface of the bottom wall of the blind holes 108.
• Figure 3 which is a sectional view of the photovoltaic cell 100 along the axis AA shown in Figure 1, shows that the blind holes 108 here have a section, in a plane parallel to the rear face 106, of triangular shape.
• the blind holes 108 are filled by a semiconductor 110, here n + type silicon.
• the silicon portions 110 form the emitter of the photovoltaic cell 100 and the substrate 102 forms the base of the photovoltaic cell 100.
• pn junctions distributed throughout the volume of the photovoltaic cell 100 are obtained.
• first collection fingers 112 based on n + type silicon and in contact with the silicon portions 110, and which are interdigitated with second collection fingers 114, to p + type silicon base and in contact with the rear face 106 of the substrate 102 (see Figures 1 and 2).
• the sections of the blind holes 108 in a plane parallel to one of the main faces 104 and 106 of the substrate 102, may be of other than triangular shape, for example circular (see for example the section 110c shown in Figure 4).
• the sections of the blind holes 108 are preferably chosen from a shape other than circular, for example triangular as in FIG. 3, square, star-shaped (see for example the sections 11d0 and 11Of shown in FIG. 4), or polygonal regular or not (see for example the octagonal section 110e shown in Figure 4).
• These other forms make it possible to increase the contact area between the semiconductor 110 located in the blind holes 108 (the emitter) and the substrate 102, which makes it possible to increase the probability of collecting minority carriers in the photovoltaic cell 100.
• a triangular shaped section increases the area of the transmitter by about 30% relative to a circular section. Still with respect to a section of circular shape, a surface increase close to a factor of 2 is obtained with a section of regular hexagram shape, consisting of the superposition of two equilateral triangles. Finally, in case of need, more complex shapes can be envisaged (regular or non-n-sided polygons, or superposition of triangles and / or n-branched stars).
• the distance between two neighboring semiconductor portions 110 may be between about 40 ⁇ m and
• 300 microns and preferably between about 60 microns and 100 microns.
• the blind holes 108 have a profile such that the dimensions of the sections of the blind holes 108 decrease regularly as a function of the distance of the section relative to the rear face 106, for example a shaped profile. cone 110a ( Figure 4).
• the blind holes 108 may have profiles of different shape, such as for example a truncated ogival (reference 110b in FIG. 4) in which the reduction of the dimensions of the sections is not regular all along the profile, but takes place mainly at the bottom of the blind holes 108. It is also possible that the blind holes 108 have profiles of different shape (for example cylindrical, that is to say that the dimensions of the sections are identical throughout the profile).
• each blind hole 108 comprises, in a plane passing through the rear face 106, a section of surface greater than the surface of the bottom wall of said blind hole 108, as is the case in the example of FIG. .
• the surface sections of the blind holes 108 varies with the height in the photovoltaic cell 100 to take account of the spectral absorption of the incident photons by the semi ⁇ conductive material of the substrate 102. it may for example have a ratio between the the surface of the section of the hole 108 at the rear face 106 and the surface of the bottom wall of the hole 108 between about 1 and 3, and preferably between about 1.2 and 2.
• the value of this report is in particular chosen according to the light source via the photon absorption curve in the material used.
• the volume of the blind holes 108 can be limited as much as possible, taking into account the technological constraints related to the making of the blind holes 108 on the the form factor of the holes.
• the ratio between the height, i.e. the dimension along the y-axis, represents in FIG. 1, and the dimension of one of the sides (or the diameter in the case of a circle) of a section of one of the blind holes 108 may for example be less than or equal to 10.
• the height of the portions of semiconductor, corresponding to the depth of the blind holes 108 is at least equal to half the thickness of the substrate 102.
• the photovoltaic cell 100 described above is of the p type, that is to say has pn junctions formed by a substrate 102 based on p-type silicon and n + type silicon 110 placed in the blind holes 108.
• the photovoltaic cell 100 could be n-type, i.e., having pn junctions formed by an n-type silicon substrate 102 and p + silicon 110 disposed in the blind holes 108.
• the semiconductor used for producing the photovoltaic cell 100 may be a semiconductor other than silicon, for example germanium.
• the collection fingers 112, 114 are respectively of type n + and p +.
• the substrate (of the p or n type) has a concentration in doping atoms per cubic centimeter of between 10 15 and 10 18 , and advantageously between 10 16 and 10 17 .
• the emitter has a concentration in doping atoms per cubic centimeter of between 10 16 and 10 21 , and advantageously between 10 18 and 10 20 .
• the collecting fingers have higher concentrations of doping atoms than those of the semiconductors on which they make contact.
• the first collection fingers have a concentration of doping atoms per cubic centimeter of between 10 19 and 10 21 , and advantageously between 10 20 and 10 21 .
• the half conductor forming the emitter at a sufficiently high concentration it may be suitable to also constitute the second collecting fingers.
• These second collection fingers (base) may therefore have a concentration of doping atoms per cubic centimeter of between about 10 19 and 10 21 , and advantageously between about 5.10 19 and 5.10 20 .
• a method for producing photovoltaic cell 100 is now described. This method uses low-cost technologies derived from micro-plastics processing, from stock mixtures containing silicon powders in a polymer carrier matrix.
• the p-type photovoltaic cell 100 For the production of the p-type photovoltaic cell 100, firstly 3 masterbatches or fillers based on p, p + and n + type silicon powders and polymers which in particular protect the silicon powders of their natural oxidation.
• the polymers bearing these mixtures are of the polyolefin type, based on alkene type monomers. Copolymers of several poly-alkenes can also be used.
• the silicon powders are mixed with polyethylene, and the volume fraction of silicon powders is about 50%.
• the p-type filler has a concentration of boron atoms per cubic centimeter of about 5.10 16 .
• the p-type charge + has a boron atom concentration per centimeter cube equal to about 2.10 20.
• load type n + has a phosphorus atom concentration per centimeter cube equal to about 2.10 20.
• the first step of the method consists of injecting the p-type charge into a mold to form the substrate 102.
• the mold can reproduce the desired texture for this front face.
• the rear face 106 of the cell 100 it is also possible to structure the rear face 106 of the cell 100 to further improve the optics of the cell 100.
• the height of the mold may be slightly greater than the desired thickness of the substrate 102.
• the mold has lateral dimensions (corresponding to the dimensions along the X and Z axes shown in Figure 2) equal to about 10 cm, and a height equal to about 250 microns.
• the lower part of the mold that is to say the bottom of the mold against which is the rear face 106 of the substrate 102, is removed, and the substrate 102 is then printed by a matrix to collectively form the blind holes 108 in the substrate 102.
• this substrate 102 is printed by a nickel-based matrix that may comprise fingers ( intended to sink into the substrate 102 to form the truncated cone-shaped blind holes 108) of triangular section, the equilateral triangle side having a dimension evolving from 30 ⁇ m to 40 ⁇ m between the top and the bottom of the hole.
• the blind holes 108 are made to a depth equal to about 200 microns, and spaced from each other by a distance of about 200 microns.
• the spacing will be chosen according to the quality of the semiconductor constituting the substrate: it will advantageously be less than twice the value of the diffusion length of the minority carriers
• a first mask revealing only the locations of the collecting fingers 112 intended to be in contact with the semiconductor portions 110, is then applied against the rear face 106, and the charge n + is injected into the blind holes 108. to form the semiconductor portions 110 forming the emitter of the photovoltaic cell 100.
• This mask has a certain height, for example equal to about 20 microns, to also form the first collecting fingers 112.
• the first mask is removed, and a second mask making it possible to produce the second collection fingers 114 from the p + silicon charge is then applied against the rear face 106.
• the cell 100 is subjected to a debinding step whose duration varies between about 12 hours and 36 hours, preferably between about 18 hours and 30 hours, at a temperature between about 300 0 C and 600 ° C., preferably between about 400 ° C. to 500 ° C.
• the debinding step is carried out in a resistive oven for about 24 hours at a temperature of about 45 ° C.
• the structure obtained after debinding step is subjected to a sintering step, which vary in length between about 1 hour and 8 hours, preferably between about 3 hours and 6 hours at a temperature between about 1000 0 C and 135O 0 C, preferably between about 1200 0 C and 1300 0 C.
• the sintering step is carried out for about 4 hours at 1300 0 C.
• These debinding and / or sintering steps are preferably carried out in a reducing atmosphere, preferably in hydrogen or argon-hydrogenated to allow the hydrogenation in the silicon core of the photovoltaic cell 100.

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