WO2016207539A1 - Method for insulating the edges of a heterojunction photovoltaic cell - Google Patents

Method for insulating the edges of a heterojunction photovoltaic cell Download PDF

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Publication number
WO2016207539A1
WO2016207539A1 PCT/FR2016/051516 FR2016051516W WO2016207539A1 WO 2016207539 A1 WO2016207539 A1 WO 2016207539A1 FR 2016051516 W FR2016051516 W FR 2016051516W WO 2016207539 A1 WO2016207539 A1 WO 2016207539A1
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Prior art keywords
photovoltaic cell
edges
stack
conductive layer
photovoltaic
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PCT/FR2016/051516
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French (fr)
Inventor
Nicolas Rey
Grégory AUDINAT
Charles Roux
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Commissariat A L'energie Atomique Et Aux Energies Alternatives
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Priority to EP16735926.4A priority Critical patent/EP3314670A1/en
Publication of WO2016207539A1 publication Critical patent/WO2016207539A1/en

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    • 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 at least one potential-jump barrier or surface barrier
    • H01L31/072—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 at least one potential-jump barrier or surface barrier the potential barriers being only of the PN heterojunction type
    • H01L31/0745—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 at least one potential-jump barrier or surface barrier the potential barriers being only of the PN heterojunction type comprising a AIVBIV heterojunction, e.g. Si/Ge, SiGe/Si or Si/SiC solar cells
    • H01L31/0747—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 at least one potential-jump barrier or surface barrier the potential barriers being only of the PN heterojunction type comprising a AIVBIV heterojunction, e.g. Si/Ge, SiGe/Si or Si/SiC solar cells comprising a heterojunction of crystalline and amorphous materials, e.g. heterojunction with intrinsic thin layer or HIT® solar cells; solar 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
    • 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 System
    • 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 technical field of the invention is that of photovoltaic cells, and more particularly that of the electrical insulation of the edges of heterojunction photovoltaic cells.
  • a photovoltaic cell is a semiconductor device that converts incident electromagnetic radiation, typically solar radiation, into electrical current by means of a PN junction.
  • the latter is formed by the stacking of a doped semiconductor layer according to a first conductivity type, typically p or n, and a doped semiconductor layer according to a second opposite conductivity type, respectively n or p.
  • the first technology is that of so-called "homojunction" photovoltaic cells for which the p and n layers forming the PN junction are composed of a single semiconductor material having the same crystallographic structure, for example monocrystalline silicon. In these photovoltaic cells, only the type and concentration of doping differ from one layer to another.
  • the second technology is that of photovoltaic cells called "heterojunction" for which the p and n layers forming the PN junction are composed of semiconductor materials having different forbidden energy bands.
  • the two semiconductor layers of the PN junction may be composed of semiconductor materials of different physical natures, or of the same semiconductor material but having different crystallographic structures, for example monocrystalline silicon and silicon. amorphous silicon.
  • electrical paths also called “shunts" are formed on the edges of the photovoltaic cell. These shunts electrically connect the two faces of the photovoltaic cell. The charge carriers generated within the PN junction can then take these shunts instead of crossing the PN junction, which has the effect of reducing the intensity of the current supplied by the photovoltaic cell.
  • HAUSER et al. "Comparison of Different Techniques for Edge Insulation,” 17 th European Photovoltaic Solar Energy Conference and Exhibition, Kunststoff, 2001, discusses various techniques of electrical insulation of the edges of a homojunction photovoltaic cell.
  • the latter comprises a PN junction formed by a p-doped silicon substrate and an n-doped emitter, and an antireflection layer composed of silicon nitride (SiN).
  • SiN silicon nitride
  • the n-type transmitter is responsible for the shunts in this homojunction photovoltaic cell, since it is formed by POCI diffusion 3 all around the p-type substrate.
  • This document notably describes techniques consisting in forming an isolation trench on the front face or on the rear face of the homojunction photovoltaic cell.
  • the depth of this isolation trench is at least equal to the thickness of the layer forming the emitter.
  • the isolation trench may be made by means of a laser or a mechanical saw used for cutting wafers.
  • This document also mentions techniques for ablation of the edges of the homojunction photovoltaic cell, that is to say that the SiN antireflection layer and the emitter located on the edges of the cell are removed.
  • the ablation of the edges is for example carried out by plasma etching, by abrasion, or by mechanical or laser cutting.
  • the document EP2682990 describes a technique in which the edges of the photovoltaic cell are masked during the deposition of a conductive coating on the rear face.
  • the masked area at the periphery of the rear face is important, which has the effect of reducing the electrical current produced by the cell.
  • the document US 5935344 (SANYO) 24.10.1996 presents a technique using a laser to proceed with the ablation of the edges of the heterojunction photovoltaic cell.
  • This technique has the particular disadvantage of reducing the active area of the photovoltaic cell, thus causing a decrease in the current produced by the photovoltaic cell.
  • the use of a laser causes a recrystallization of the semiconductor substrate in the wake of the laser. This recrystallization leads to the creation of recombinant traps on the edges of the photovoltaic cell, with the ultimate consequence of deteriorating the form factor of the photovoltaic cell.
  • the method according to the invention aims at solving the problems which have just been exposed by proposing a method of insulating the edges of a heterojunction photovoltaic cell limiting both the loss of active surface area of the photovoltaic cell and the defects created. in the semiconductor material.
  • a first aspect of the invention therefore relates to a method of electrical insulation of the edges of a heterojunction photovoltaic cell, the photovoltaic cell having a front face intended to be exposed to incident radiation and comprising:
  • a stack of semiconductor layers having a front surface, a rear surface opposite the front surface, and side surfaces;
  • a first electrically conductive layer transparent to the incident radiation placed on the front surface of the stack and on the lateral surfaces of the stack;
  • a second electrically conductive layer disposed on the rear surface of the stack and on the side surfaces of the stack, the first conductive layer and the second conductive layer being in electrical contact with the side surfaces of the stack;
  • each abraded edge of the photovoltaic cell forms an acute angle with the front face of the photovoltaic cell.
  • the abrasion technique allows precise control of the amount of conductive material removed on the photovoltaic cell edges.
  • the fact of abrading the edges of the photovoltaic cell at an acute angle with respect to the front face makes it possible to remove more conductive material on the side of the rear face than on the side of the front face.
  • the electrical contact between the front face and the rear face of the photovoltaic cell is broken while preserving the active surface of the photovoltaic cell, that is to say the collection surface of the photons on the front face of the cell.
  • the insulation method according to the first aspect of the invention may also comprise one or more of the following characteristics, taken individually or according to the technically possible combinations:
  • the acute angle between the front face of the photovoltaic cell and each abraded edge of the photovoltaic cell is between 50 ° and 88.5 °;
  • the step of mechanical abrasion of the edges of the photovoltaic cell is carried out on a thickness of between 5 ⁇ and 50 ⁇ ;
  • the stack of semiconductor layers of the photovoltaic cell comprises a semiconductor substrate textured on the surface by patterns, and the step of mechanical abrasion of the edges of the photovoltaic cell is carried out using an abrasive comprising grains having dimensions of the same order of magnitude as those of the grounds of the semiconductor substrate.
  • the grains of the abrasive are grains of silicon carbide or diamond grains.
  • a second aspect of the invention relates to a method for manufacturing a heterojunction photovoltaic cell comprising the following steps:
  • a stack of semiconductor layers having a front surface, a rear surface opposite the front surface, and side surfaces;
  • the manufacturing method being characterized in that it further comprises a method of electrical insulation of the edges of the photovoltaic cell according to any one of the preceding claims.
  • the manufacturing method according to the second aspect of the invention may also comprise one or more of the following characteristics, considered individually or according to the technically possible combinations:
  • the manufacturing method further comprises a step of cleaning the edges of the photovoltaic cell, the cleaning step being concomitant or subsequent to the method of electrical insulation of the edges of the photovoltaic cell;
  • the step of cleaning the edges of the photovoltaic cell comprises an operation of rinsing the edges of the photovoltaic cell with water and / or alcohol;
  • the step of cleaning the edges of the photovoltaic cell comprises an operation of blowing a compressed gas on the edges of the photovoltaic cell.
  • the manufacturing method further comprises a step of passivation of the edges of the photovoltaic cell, the passivation step being subsequent to the method of electrical insulation of the edges of the photovoltaic cell;
  • the first conductive layer and the second conductive layer are deposited by a plasma-assisted chemical vapor deposition technique.
  • FIGS. 1A and 1B are two cross-sectional views of an example of a heterojunction photovoltaic cell, respectively before and after the implementation of the method according to the invention
  • FIG. 2 represents, as a function of illumination, the form factor (in relative values) of a photovoltaic cell whose edges have been isolated by means of the method according to the invention and by means of a laser.
  • the figures are presented only as an indication and in no way limit the invention.
  • This method is intended to electrically isolate the PN junction of a heterojunction photovoltaic cell efficiently while having a limited impact on the performance of the photovoltaic cell.
  • the electrical isolation of the PN junction is intended to reduce electrical losses and thus increase the efficiency of the photovoltaic cell.
  • FIG. 1A is a cross-sectional view of an example of a heterojunction photovoltaic cell, before the implementation of the method according to the invention.
  • the photovoltaic cell has a front face FS intended to be exposed to incident radiation, typically solar radiation, a rear face BS opposite to the front face, and edges E surrounding the photovoltaic cell and extending between the front face FS and the rear face BS of the photovoltaic cell.
  • incident radiation typically solar radiation
  • a rear face BS opposite to the front face
  • edges E surrounding the photovoltaic cell and extending between the front face FS and the rear face BS of the photovoltaic cell.
  • the photovoltaic cell advantageously has a square or pseudo-square shape for which the angles are rounded. It then has four sides of identical lengths.
  • front will be used to designate the surfaces arranged on the side of the front face FS of the photovoltaic cell.
  • the term “rear” will be used to designate the surfaces disposed on the side of the rear face BS of the photovoltaic cell.
  • the photovoltaic cell comprises a doped semiconductor substrate 101 of a first type of conductivity, i.e. of type n or p.
  • the semiconductor substrate 101 is preferably of monocrystalline silicon.
  • the semiconductor substrate 101 is preferentially doped n.
  • a heterojunction photovoltaic cell having an n-doped monocrystalline silicon substrate has a higher efficiency than a heterojunction photovoltaic cell having a p-doped monocrystalline silicon substrate.
  • the semiconductor substrate 101 is covered with at least one semiconductor layer, doped with a conductivity type opposite to that of the substrate, forming and a stack of semiconductor layers 1 10 and a PN junction.
  • the stack 1 10 comprises, in addition to the substrate 101, a first semiconductor layer 102 and a second semiconductor layer 103.
  • the first semiconductor layer 102 covers the front face of the substrate 101, and possibly a portion of the sidewalls of the substrate 101.
  • the second semiconductor layer 103 covers the rear face of the substrate 101, and possibly a portion of the sidewalls of the substrate 101.
  • the stack 1 10 has a front surface corresponding to the first semiconductor layer 102, a rear surface corresponding to the second semiconductor layer 103, and side surfaces corresponding to the sidewalls of the substrate 101, to a portion of the first semiconductor layer 102 or a portion of the second semiconductor layer 103.
  • the first semiconductor layer 102 and the second semiconductor layer 103 are generally deposited on the semiconductor substrate 101 by means of a non-directive deposition technique, for example a plasma-assisted chemical vapor deposition, also called PECVD for "Plasma-Enhanced Chemical Vapor Deposition" in English, which explains why the semiconductor layers 102, 103 are also deposited on the sidewalls of the substrate 101.
  • PECVD plasma-assisted chemical vapor deposition
  • the first semiconductor layer 102 has a conductivity type opposite to that of the semiconductor substrate 101, thus forming the emitter of the PN junction on the front face.
  • the second semiconductor layer 103 is then of a conductivity type identical to that of the semiconductor substrate 101, thus forming a repulsive field on the backside, also called BSF for "Back Surface Field” in English.
  • BSF Back Surface Field
  • the second semiconductor layer 103 has a conductivity type opposite to that of the semiconductor substrate 101, thus forming the emitter of the PN junction on the back side.
  • the first semiconductor layer 102 is then of a type of conductivity identical to that of the semiconductor substrate 101, thus forming a repulsive field on the front face, also called FSF for "Front Surface Field” in English.
  • This configuration is commonly referred to as "reverse transmitter".
  • the face of the photovoltaic cell comprising the repulsive field that is to say the base of the PN junction, is intended to receive metal contacts, at which the recombination rate of the charge carriers is very high.
  • the role of the repulsive field is to move the minority carriers from the base of the PN junction.
  • the semiconductor layer forming the repulsive field is preferably heavily doped to maximize this effect. She has such a dopant concentration of at least 10 20 cm "3.
  • the semiconductor layers 102, 103 are in this photovoltaic cell example formed of amorphous silicon.
  • the thickness of the semiconductor layers 102, 103 is for example of the order of 8 and 14 nm respectively in the inverted transmitter configuration.
  • the stack 1 10 may comprise a larger number of semiconductor layers.
  • each of the amorphous silicon semiconductor layers 102 and 103 may be juxtaposed with an intrinsic silicon layer, the intrinsic silicon layer being disposed between the semiconductor substrate 101 and the silicon 102-103 semiconductor layer. amorphous.
  • amorphous silicon semiconductor layers 102, 103 The electrical conductivity of amorphous silicon semiconductor layers 102, 103 is too low to allow optimal transport of electrical charges. Thus, metal contacts can not be directly arranged on these layers. It is first necessary to deposit conductive layers electrically on the front and rear surfaces of the stack 1 10 to collect the electrical charges generated by the PN junction.
  • a first electrically conductive layer 104 is deposited on the front face of the stack 1 10.
  • the first electrically conductive layer 104 is generally formed of a transparent and conductive oxide, for example indium-tin, also called ITO for "Indium Tin Oxide" in English.
  • a second electrically conductive layer 105 is deposited on the rear face of the stack 1 10.
  • the second electrically conductive layer 105 may also be transparent, when it is desired to capture diffuse radiation from the rear face BS of the photovoltaic cell.
  • the second electrically conductive layer 105 is then generally formed of a transparent oxide and conductor, preferably identical to that of the first electrically conductive layer 104.
  • a photovoltaic cell of this type is called "bifacial".
  • the second electrically conductive layer 105 may be formed of a metal, for example silver.
  • a photovoltaic cell of this type is called "monofacial".
  • the first electrically conductive layer 104 and the second electrically conductive layer 105 are generally deposited by means of a non-directive deposition technique, for example by PVD .
  • the electrically conductive layers 104, 105 have for example a thickness of between 50 and 300 nm.
  • the first electrically conductive layer 104 and the second electrically conductive layer 105 are therefore also deposited on the side surfaces of the stack 1 10 forming electrical contacts. Therefore, the front face FS and the rear face BS of the photovoltaic cell are connected by electrically conductive paths, called "shunts", located at the edges E of the photovoltaic cell.
  • the photovoltaic cell is subjected to a method of electrically insulating the edges E of the heterojunction photovoltaic cell, in order to eliminate these conductive paths.
  • a quantity called "shunt resistor" symbolizing the shunts between the two faces of the photovoltaic cell is increased.
  • the isolation process comprises a step of mechanical abrasion E edges of the photovoltaic cell.
  • material is removed on the edges E of the photovoltaic cell by rubbing an abrasive on the edges E of the photovoltaic cell.
  • Figure 1B is a cross sectional view of the photovoltaic cell of Figure 1A, after the implementation of this method.
  • the mechanical abrasion is performed so as to eliminate the first electrically conductive layer 104 and the second electrically conductive layer 105 disposed on the side surfaces of the stack 1 10 of semiconductor layers and forming the edges E of the photovoltaic cell. Contacts Electrical leads arising from the encounter between the first electrically conductive layer 104 and the second electrically conductive layer 105 are then destroyed. Thus, the front face FS and the rear face BS of the photovoltaic cell are electrically insulated.
  • the abrasion is performed so that each edge E of the photovoltaic cell forms, after abrasion, an acute angle with the front face FS of the photovoltaic cell.
  • the active surface of the front face FS of the photovoltaic cell, face exposed to incident radiation remains maximum.
  • the acute angle a between the front face FS and the edges E of the photovoltaic cell makes it possible to improve the quality of the insulation between the two faces of the photovoltaic cell by increasing the distance between them.
  • the acute angle ⁇ is preferably between 50 ° and 88.5 °.
  • the abrasion step is preferably performed in an automated manner to ensure better control of the angle.
  • the abrasion of the edges E of the photovoltaic cell is preferably carried out over a thickness of between 5 ⁇ and 50 ⁇ , that is to say that 5 to 50 ⁇ of material are removed on the edges E of the photovoltaic cell. .
  • This material removed corresponds mainly to the materials of the conductive layers 104, 105.
  • the thickness of material removed is of the same order of magnitude as that of the conductive layers 104, 105.
  • the thickness of the abraded material is sufficient to completely eliminate the first electrically conductive layer 104 and the second electrically conductive layer 105 on the E edges. of the photovoltaic cell while minimizing the loss of surface on the front face FS and the rear face BS of the photovoltaic cell.
  • the prior art technique using a laser can remove up to 1 mm of material on the edges of the photovoltaic cell.
  • the amorphous silicon semiconductor layers 102, 103 on the sides of the monocrystalline silicon 101 semiconductor substrate 101 are not completely removed to protect the substrate 101. This is not detrimental to the quality of the insulation, because these layers are much less electrically conductive than the conductive layers 104, 105 of transparent oxide. Thus, unlike Prior art isolation methods, mechanical abrasion limits the creation of structural defects on the semiconductor substrate 101.
  • the abrasive used during the abrasion step is preferably in the form of a sandpaper.
  • the semiconductor substrate 101 is textured, that is to say that it has patterns on the surface in order to reduce the reflection of the incident radiation.
  • the abrasive comprises grains preferably having dimensions of the same order of magnitude as those of the surface patterns of the substrate. Thus, the elimination of matter is better controlled.
  • the surface patterns of the semiconductor substrate 101 are generally of pyramidal shape.
  • the dimensions of the surface patterns of the substrate, and therefore the grain size of the abrasive, are for example of the order of 10 ⁇ .
  • the grains of the abrasive are, for example, silicon carbide grains or diamond grains.
  • the method of manufacturing the heterojunction photovoltaic cell advantageously comprises a step of cleaning the edges E of the photovoltaic cell to remove these particles.
  • the cleaning step E edges of the photovoltaic cell can be performed during or after the abrasion step.
  • the cleaning step comprises for example an operation of rinsing the edges E of the photovoltaic cell by means of deionized water or alcohol such as isopropanol.
  • the step of cleaning the edges E of the photovoltaic cell may further comprise an operation for blowing a compressed gas, for example air or an inert gas, onto the abraded (or abrasion-abraded) edges of the photovoltaic cell. the photovoltaic cell.
  • the manufacturing method may further comprise a passivation step E edges of the photovoltaic cell to limit the surface recombination mechanism of the charge carriers.
  • the passivation step is performed after the step of isolating the edges E of the photovoltaic cell. It consists of rendering the edges E of the photovoltaic cell electrically inactive by forming an oxide therein.
  • Curves of the form factor FF of a heterojunction photovoltaic cell in an inverted transmitter configuration are illustrated in FIG. 2.
  • the curves are plotted as a function of illumination, and correspond to two methods. isolation of the edges of the photovoltaic cell different, performed on the same photovoltaic cell structure.
  • FIG. 2 shows a first curve 201 corresponding to a photovoltaic cell isolated by a technique of the prior art, by using a laser to trace a groove around the periphery of the rear face of the photovoltaic cell, and a second curve 202 corresponding to a photovoltaic cell insulated by mechanical abrasion according to the preferred embodiment of the invention.
  • the values of the form factor FF on these two curves 201, 202 are normalized with respect to the value of the shape factor obtained by the photovoltaic cell whose edges E have been isolated by laser, at an illumination of 1000 W / m 2 .
  • the form factor FF of a photovoltaic cell expresses the ratio between the actual power delivered by the photovoltaic cell and the ideal power of the photovoltaic cell, according to the following equation:
  • V max is the maximum voltage of the photovoltaic cell
  • l ma x is the maximum current of the photovoltaic cell
  • V co is the open circuit voltage of the photovoltaic cell
  • l cc is the short-circuit current of the cell photovoltaic.
  • the form factor FF is limited by parasitic resistances including shunt resistance.
  • good electrical insulation of the edges E of the photovoltaic cell results in an improvement of the form factor FF of the photovoltaic cell.
  • a significant improvement in the form factor FF can be seen when the edges E of the photovoltaic cell are isolated by mechanical abrasion rather than by laser.
  • the improvement of the FF form factor, greater than three points, is particularly important for low illumination.
  • photovoltaic cells are generally interconnected by electrical ribbons.
  • Photovoltaic cells are for example put in series by connecting the front face of a photovoltaic cell with the rear face of the next photovoltaic cell, and so on. During this setting in module, the edges of the photovoltaic cells are likely to come into contact between the ribbons interconnecting the photovoltaic cells.
  • Removing the conductive layers on the edges of the photovoltaic cell here makes it possible to reduce the risk of a short circuit between the ribbons interconnecting the photovoltaic cells of the module and the edges of the photovoltaic cells.
  • the invention is not limited to the embodiments described with reference to the figures and variants could be envisaged without departing from the scope of the invention.

Abstract

The invention relates to a method for electrically insulating the edges (E) of a heterojunction photovoltaic cell. The cell comprises a semiconductor layer stack (110) formed of a first conductive layer (104) arranged on the front surface and the side surfaces of the stack, and a second conductive layer (105) arranged on the rear surface and the side surfaces of the stack. The first and second layers are in electrical contact on the side surfaces. A step of mechanically abrading the edges is carried out so as to eliminate contact between the first and second layer on the side surfaces. Each abraded surface forms an acute angle with the front surface of the cell.

Description

PROCEDE D'ISOLATION DES BORDS D'UNE CELLULE  METHOD OF INSULATING THE EDGES OF A CELL
PHOTOVOLTAIQUE A HETEROJONCTION  PHOTOVOLTAIC HETEROJUNCTION
DOMAINE TECHNIQUE DE L'INVENTION TECHNICAL FIELD OF THE INVENTION
Le domaine technique de l'invention est celui des cellules photovoltaïques, et plus particulièrement celui de l'isolation électrique des bords des cellules photovoltaïques à hétérojonction.  The technical field of the invention is that of photovoltaic cells, and more particularly that of the electrical insulation of the edges of heterojunction photovoltaic cells.
ARRIERE-PLAN TECHNOLOGIQUE DE L'INVENTION BACKGROUND OF THE INVENTION
Une cellule photovoltaïque est un dispositif semi-conducteur qui convertit un rayonnement électromagnétique incident, typiquement le rayonnement solaire, en courant électrique au moyen d'une jonction PN. Cette dernière est formée par l'empilement d'une couche semi-conductrice dopée selon un premier type de conductivité, typiquement p ou n, et d'une couche semi-conductrice dopée selon un deuxième type de conductivité opposé, respectivement n ou p.  A photovoltaic cell is a semiconductor device that converts incident electromagnetic radiation, typically solar radiation, into electrical current by means of a PN junction. The latter is formed by the stacking of a doped semiconductor layer according to a first conductivity type, typically p or n, and a doped semiconductor layer according to a second opposite conductivity type, respectively n or p.
Deux technologies différentes sont notamment utilisées pour produire des cellules photovoltaïques. La première technologie est celle des cellules photovoltaïques dites « à homojonction » pour lesquelles les couches p et n formant la jonction PN sont composées d'un unique matériau semi-conducteur ayant la même structure cristallographique, par exemple du silicium monocristallin. Dans ces cellules photovoltaïques, seuls le type et la concentration du dopage diffèrent d'une couche à l'autre.  Two different technologies are used in particular to produce photovoltaic cells. The first technology is that of so-called "homojunction" photovoltaic cells for which the p and n layers forming the PN junction are composed of a single semiconductor material having the same crystallographic structure, for example monocrystalline silicon. In these photovoltaic cells, only the type and concentration of doping differ from one layer to another.
La deuxième technologie est celle des cellules photovoltaïques dites « à hétérojonction » pour lesquelles les couches p et n formant la jonction PN sont composées de matériaux semi-conducteurs ayant des bandes d'énergie interdites différentes. Pour ce faire, les deux couches semi-conductrices de la jonction PN peuvent être composées de matériaux semi-conducteurs de natures physiques différentes, ou d'un même matériau semi-conducteur mais ayant des structures cristallographiques différentes, par exemple du silicium monocristallin et du silicium amorphe.  The second technology is that of photovoltaic cells called "heterojunction" for which the p and n layers forming the PN junction are composed of semiconductor materials having different forbidden energy bands. To do this, the two semiconductor layers of the PN junction may be composed of semiconductor materials of different physical natures, or of the same semiconductor material but having different crystallographic structures, for example monocrystalline silicon and silicon. amorphous silicon.
Au cours de la fabrication d'une cellule photovoltaïque, des chemins électriques, également appelés « shunts », se forment sur les bords de la cellule photovoltaïque. Ces shunts relient électriquement les deux faces de la cellule photovoltaïque. Les porteurs de charge générés au sein de la jonction PN peuvent alors emprunter ces shunts au lieu de traverser la jonction PN, ce qui a pour conséquence de diminuer l'intensité du courant fourni par la cellule photovoltaïque. During the manufacture of a photovoltaic cell, electrical paths, also called "shunts", are formed on the edges of the photovoltaic cell. These shunts electrically connect the two faces of the photovoltaic cell. The charge carriers generated within the PN junction can then take these shunts instead of crossing the PN junction, which has the effect of reducing the intensity of the current supplied by the photovoltaic cell.
Il est donc important d'isoler électriquement les bords de la cellule photovoltaïque afin de supprimer les shunts et ainsi améliorer l'efficacité de la cellule photovoltaïque. Il existe actuellement différentes techniques permettant d'isoler les bords d'une cellule photovoltaïque.  It is therefore important to electrically isolate the edges of the photovoltaic cell in order to eliminate the shunts and thus improve the efficiency of the photovoltaic cell. There are currently various techniques for isolating the edges of a photovoltaic cell.
Le document HAUSER et al., « Comparison of différent techniques for edge isolation », 17th European Photovoltaic Solar Energy Conférence and exhibition, Munich, 2001 , expose différentes techniques d'isolation électrique des bords d'une cellule photovoltaïque à homojonction. Cette dernière comporte une jonction PN formée par un substrat de silicium dopé p et un émetteur dopé n, ainsi qu'une couche antireflet composée de nitrure de silicium (SiN). L'émetteur de type n est responsable des shunts dans cette cellule photovoltaïque à homojonction, car il est formé par diffusion POCI3 sur tout le pourtour du substrat de type p. HAUSER et al., "Comparison of Different Techniques for Edge Insulation," 17 th European Photovoltaic Solar Energy Conference and Exhibition, Munich, 2001, discusses various techniques of electrical insulation of the edges of a homojunction photovoltaic cell. The latter comprises a PN junction formed by a p-doped silicon substrate and an n-doped emitter, and an antireflection layer composed of silicon nitride (SiN). The n-type transmitter is responsible for the shunts in this homojunction photovoltaic cell, since it is formed by POCI diffusion 3 all around the p-type substrate.
Ce document décrit notamment des techniques consistant à former une tranchée d'isolation sur la face avant ou sur la face arrière de la cellule photovoltaïque à homojonction. La profondeur de cette tranchée d'isolation est au moins égale à l'épaisseur de la couche formant l'émetteur. La tranchée d'isolation peut être réalisée au moyen d'un laser ou d'une scie mécanique utilisée pour la découpe de plaquettes.  This document notably describes techniques consisting in forming an isolation trench on the front face or on the rear face of the homojunction photovoltaic cell. The depth of this isolation trench is at least equal to the thickness of the layer forming the emitter. The isolation trench may be made by means of a laser or a mechanical saw used for cutting wafers.
Ce document cite également des techniques d'ablation des bords de la cellule photovoltaïque à homojonction, c'est-à-dire que la couche d'antireflet en SiN et l'émetteur situés sur les bords de la cellule sont enlevés. L'ablation des bords est par exemple effectuée par gravure plasma, par abrasion, ou par découpe mécanique ou laser.  This document also mentions techniques for ablation of the edges of the homojunction photovoltaic cell, that is to say that the SiN antireflection layer and the emitter located on the edges of the cell are removed. The ablation of the edges is for example carried out by plasma etching, by abrasion, or by mechanical or laser cutting.
Concernant l'isolation électrique des bords d'une cellule photovoltaïque à hétérojonction, le document EP2682990 décrit une technique dans laquelle les bords de la cellule photovoltaïque sont masqués lors du dépôt d'un revêtement conducteur sur la face arrière. Cependant, la zone masquée en périphérie de la face arrière est importante, ce qui a pour effet de diminuer le courant électrique produit la cellule.  Concerning the electrical insulation of the edges of a heterojunction photovoltaic cell, the document EP2682990 describes a technique in which the edges of the photovoltaic cell are masked during the deposition of a conductive coating on the rear face. However, the masked area at the periphery of the rear face is important, which has the effect of reducing the electrical current produced by the cell.
Par ailleurs, le document US 5935344 (SANYO) 24.10.1996, présente une technique utilisant un laser pour procéder à l'ablation des bords de la cellule photovoltaïque à hétérojonction. Cette technique a notamment l'inconvénient de réduire la surface active de la cellule photovoltaïque, entraînant ainsi une diminution du courant produit par la cellule photovoltaïque. De plus, l'utilisation d'un laser provoque une recristallisation du substrat semi-conducteur dans le sillage du laser. Cette recristallisation conduit à la création de pièges recombinants sur les bords de la cellule photovoltaïque, avec pour conséquence in fine de détériorer le facteur de forme de la cellule photovoltaïque. Moreover, the document US 5935344 (SANYO) 24.10.1996, presents a technique using a laser to proceed with the ablation of the edges of the heterojunction photovoltaic cell. This technique has the particular disadvantage of reducing the active area of the photovoltaic cell, thus causing a decrease in the current produced by the photovoltaic cell. In addition, the use of a laser causes a recrystallization of the semiconductor substrate in the wake of the laser. This recrystallization leads to the creation of recombinant traps on the edges of the photovoltaic cell, with the ultimate consequence of deteriorating the form factor of the photovoltaic cell.
RESUME DE L'INVENTION SUMMARY OF THE INVENTION
Le procédé selon l'invention vise à résoudre les problèmes qui viennent d'être exposés en proposant un procédé d'isolation des bords d'une cellule photovoltaïque à hétérojonction limitant à la fois la perte de surface active de la cellule photovoltaïque et les défauts créés dans le matériau semi-conducteur.  The method according to the invention aims at solving the problems which have just been exposed by proposing a method of insulating the edges of a heterojunction photovoltaic cell limiting both the loss of active surface area of the photovoltaic cell and the defects created. in the semiconductor material.
Un premier aspect de l'invention concerne donc un procédé d'isolation électrique des bords d'une cellule photovoltaïque à hétérojonction, la cellule photovoltaïque ayant une face avant destinée à être exposée à un rayonnement incident et comportant :  A first aspect of the invention therefore relates to a method of electrical insulation of the edges of a heterojunction photovoltaic cell, the photovoltaic cell having a front face intended to be exposed to incident radiation and comprising:
- un empilement de couches semi-conductrices ayant une surface avant, une surface arrière opposée à la surface avant, et des surfaces latérales ;  a stack of semiconductor layers having a front surface, a rear surface opposite the front surface, and side surfaces;
- une première couche conductrice électriquement et transparente au rayonnement incident disposée sur la surface avant de l'empilement et sur les surfaces latérales de l'empilement ;  a first electrically conductive layer transparent to the incident radiation placed on the front surface of the stack and on the lateral surfaces of the stack;
- une deuxième couche conductrice électriquement disposée sur la surface arrière de l'empilement et sur les surfaces latérales de l'empilement, la première couche conductrice et la deuxième couche conductrice étant en contact électrique sur les surfaces latérales de l'empilement ;  a second electrically conductive layer disposed on the rear surface of the stack and on the side surfaces of the stack, the first conductive layer and the second conductive layer being in electrical contact with the side surfaces of the stack;
le procédé d'isolation étant caractérisé en ce qu'il comporte une étape d'abrasion mécanique des bords de la cellule photovoltaïque de sorte que : the insulation process being characterized in that it comprises a step of mechanical abrasion of the edges of the photovoltaic cell so that:
- le contact électrique entre la première couche conductrice et la deuxième couche conductrice sur les surfaces latérales de l'empilement soit éliminé ; et que  - the electrical contact between the first conductive layer and the second conductive layer on the side surfaces of the stack is eliminated; and
- chaque bord abrasé de la cellule photovoltaïque forme un angle aigu avec la face avant de la cellule photovoltaïque. Contrairement à la technique d'isolation par laser, la technique d'abrasion permet un contrôle précis de la quantité de matériau conducteur retirée sur les bords de cellule photovoltaïque. En outre, le fait d'abraser les bords de la cellule photovoltaïque selon un angle aigu par rapport à la face avant permet d'enlever davantage de matériau conducteur du côté de la face arrière que du côté de la face avant. Ainsi, on rompt le contact électrique entre la face avant et la face arrière de la cellule photovoltaïque tout en préservant la surface active de la cellule photovoltaïque, c'est-à-dire la surface de collecte des photons en face avant de la cellule. each abraded edge of the photovoltaic cell forms an acute angle with the front face of the photovoltaic cell. Unlike laser isolation technique, the abrasion technique allows precise control of the amount of conductive material removed on the photovoltaic cell edges. In addition, the fact of abrading the edges of the photovoltaic cell at an acute angle with respect to the front face makes it possible to remove more conductive material on the side of the rear face than on the side of the front face. Thus, the electrical contact between the front face and the rear face of the photovoltaic cell is broken while preserving the active surface of the photovoltaic cell, that is to say the collection surface of the photons on the front face of the cell.
Le procédé d'isolation selon le premier aspect de l'invention peut également comporter une ou plusieurs caractéristiques parmi les suivantes, considérées individuellement ou selon les combinaisons techniquement possibles :  The insulation method according to the first aspect of the invention may also comprise one or more of the following characteristics, taken individually or according to the technically possible combinations:
- l'angle aigu entre la face avant de la cellule photovoltaïque et chaque bord abrasé de la cellule photovoltaïque est compris entre 50° et 88,5° ;  the acute angle between the front face of the photovoltaic cell and each abraded edge of the photovoltaic cell is between 50 ° and 88.5 °;
- l'étape d'abrasion mécanique des bords de la cellule photovoltaïque est effectuée sur une épaisseur comprise entre 5 μιτι et 50 μιτι ;  the step of mechanical abrasion of the edges of the photovoltaic cell is carried out on a thickness of between 5 μιτι and 50 μιτι;
- l'empilement de couches semi-conductrices de la cellule photovoltaïque comporte un substrat semi-conducteur texturé en surface par des motifs, et l'étape d'abrasion mécanique des bords de la cellule photovoltaïque est effectuée au moyen d'un abrasif comportant des grains ayant des dimensions du même ordre de grandeur que celles des motifs du substrat semiconducteur.  the stack of semiconductor layers of the photovoltaic cell comprises a semiconductor substrate textured on the surface by patterns, and the step of mechanical abrasion of the edges of the photovoltaic cell is carried out using an abrasive comprising grains having dimensions of the same order of magnitude as those of the grounds of the semiconductor substrate.
- les grains de l'abrasif sont des grains en carbure de silicium ou des grains de diamant.  - The grains of the abrasive are grains of silicon carbide or diamond grains.
Un deuxième aspect de l'invention concerne un procédé de fabrication d'une cellule photovoltaïque à hétérojonction comportant les étapes suivantes :  A second aspect of the invention relates to a method for manufacturing a heterojunction photovoltaic cell comprising the following steps:
- fournir un empilement de couches semi-conductrices ayant une surface avant, une surface arrière opposée à la surface avant, et des surfaces latérales ; providing a stack of semiconductor layers having a front surface, a rear surface opposite the front surface, and side surfaces;
- déposer une première couche conductrice électriquement et transparente au rayonnement incident sur la surface avant de l'empilement ; depositing a first electrically conductive layer transparent to incident radiation on the front surface of the stack;
- déposer une deuxième couche conductrice électriquement sur la surface arrière de l'empilement ; le procédé de fabrication étant caractérisé en ce qu'il comporte en outre un procédé d'isolation électrique des bords de la cellule photovoltaïque selon l'une quelconque des revendications précédentes. depositing a second electrically conductive layer on the rear surface of the stack; the manufacturing method being characterized in that it further comprises a method of electrical insulation of the edges of the photovoltaic cell according to any one of the preceding claims.
Le procédé de fabrication selon le deuxième aspect de l'invention peut également comporter une ou plusieurs caractéristiques parmi les suivantes, considérées individuellement ou selon les combinaisons techniquement possibles :  The manufacturing method according to the second aspect of the invention may also comprise one or more of the following characteristics, considered individually or according to the technically possible combinations:
- le procédé de fabrication comporte en outre une étape de nettoyage des bords de la cellule photovoltaïque, l'étape de nettoyage étant concomitante ou postérieure au procédé d'isolation électrique des bords de la cellule photovoltaïque ;  - The manufacturing method further comprises a step of cleaning the edges of the photovoltaic cell, the cleaning step being concomitant or subsequent to the method of electrical insulation of the edges of the photovoltaic cell;
- l'étape de nettoyage des bords de la cellule photovoltaïque comporte une opération de rinçage des bords de la cellule photovoltaïque au moyen d'eau et/ou d'alcool ;  the step of cleaning the edges of the photovoltaic cell comprises an operation of rinsing the edges of the photovoltaic cell with water and / or alcohol;
- l'étape de nettoyage des bords de la cellule photovoltaïque comporte une opération de soufflage d'un gaz comprimé sur les bords de la cellule photovoltaïque.  - The step of cleaning the edges of the photovoltaic cell comprises an operation of blowing a compressed gas on the edges of the photovoltaic cell.
- le procédé de fabrication comporte en outre une étape de passivation des bords de la cellule photovoltaïque, l'étape de passivation étant postérieure au procédé d'isolation électrique des bords de la cellule photovoltaïque ;  - The manufacturing method further comprises a step of passivation of the edges of the photovoltaic cell, the passivation step being subsequent to the method of electrical insulation of the edges of the photovoltaic cell;
- la première couche conductrice et la deuxième couche conductrice sont déposées par une technique de dépôt chimique en phase vapeur assisté par plasma.  the first conductive layer and the second conductive layer are deposited by a plasma-assisted chemical vapor deposition technique.
BREVE DESCRIPTION DES FIGURES BRIEF DESCRIPTION OF THE FIGURES
L'invention et ses différentes applications seront mieux comprises à la lecture de la description qui suit et à l'examen des figures qui l'accompagnent, parmi lesquelles :  The invention and its various applications will be better understood on reading the following description and on examining the figures that accompany it, among which:
- les figures 1 A et 1 B sont deux vues en coupe transversale d'un exemple de cellule photovoltaïque à hétérojonction, respectivement avant et après la mise en œuvre du procédé selon l'invention ;  FIGS. 1A and 1B are two cross-sectional views of an example of a heterojunction photovoltaic cell, respectively before and after the implementation of the method according to the invention;
- la figure 2 représente, en fonction de l'illumination, le facteur de forme (en valeurs relatives) d'une cellule photovoltaïque dont les bords ont été isolés au moyen du procédé selon l'invention et au moyen d'un laser. Les figures ne sont présentées qu'à titre indicatif et nullement limitatif de l'invention. FIG. 2 represents, as a function of illumination, the form factor (in relative values) of a photovoltaic cell whose edges have been isolated by means of the method according to the invention and by means of a laser. The figures are presented only as an indication and in no way limit the invention.
Pour plus de clarté, les éléments identiques ou similaires sont repérés par des signes de référence identiques sur toutes les figures.  For clarity, identical or similar elements are marked with identical reference characters in all the figures.
DESCRIPTION DETAILLEE D'UN MODE DE REALISATION DE L'INVENTION DETAILED DESCRIPTION OF AN EMBODIMENT OF THE INVENTION
Un mode de mise en œuvre préférentiel du procédé d'isolation selon l'invention va maintenant être décrit. Ce procédé est destiné à isoler électriquement la jonction PN d'une cellule photovoltaïque à hétérojonction de manière efficace tout en ayant un impact limité sur les performances de la cellule photovoltaïque. L'isolation électrique de la jonction PN vise à réduire les pertes électriques et donc à augmenter le rendement de la cellule photovoltaïque.  A preferred mode of implementation of the isolation method according to the invention will now be described. This method is intended to electrically isolate the PN junction of a heterojunction photovoltaic cell efficiently while having a limited impact on the performance of the photovoltaic cell. The electrical isolation of the PN junction is intended to reduce electrical losses and thus increase the efficiency of the photovoltaic cell.
La figure 1 A est une vue en coupe transversale d'un exemple de cellule photovoltaïque à hétérojonction, avant la mise en œuvre du procédé selon l'invention. La cellule photovoltaïque possède une face avant FS destinée à être exposée à un rayonnement incident, typiquement un rayonnement solaire, une face arrière BS opposée à la face avant, et des bords E entourant la cellule photovoltaïque et s'étendant entre la face avant FS et la face arrière BS de la cellule photovoltaïque. En vue de dessus (non représentée), la cellule photovoltaïque a avantageusement une forme carré ou pseudo-carré pour laquelle les angles sont arrondis. Elle compte alors quatre côtés de longueurs identiques.  FIG. 1A is a cross-sectional view of an example of a heterojunction photovoltaic cell, before the implementation of the method according to the invention. The photovoltaic cell has a front face FS intended to be exposed to incident radiation, typically solar radiation, a rear face BS opposite to the front face, and edges E surrounding the photovoltaic cell and extending between the front face FS and the rear face BS of the photovoltaic cell. In plan view (not shown), the photovoltaic cell advantageously has a square or pseudo-square shape for which the angles are rounded. It then has four sides of identical lengths.
Dans la suite de la description, le terme « avant » sera employé pour désigner les surfaces disposées du côté de la face avant FS de la cellule photovoltaïque. De même, le terme « arrière » sera employé pour désigner les surfaces disposées du côté de la face arrière BS de la cellule photovoltaïque.  In the remainder of the description, the term "front" will be used to designate the surfaces arranged on the side of the front face FS of the photovoltaic cell. Similarly, the term "rear" will be used to designate the surfaces disposed on the side of the rear face BS of the photovoltaic cell.
La cellule photovoltaïque comporte un substrat semi-conducteur 101 dopé d'un premier type de conductivité, i.e. de type n ou p. Le substrat semi-conducteur 101 est de préférence en silicium monocristallin. Par ailleurs, le substrat semiconducteur 101 est préférentiellement dopé n. En effet, une cellule photovoltaïque à hétérojonction ayant un substrat en silicium monocristallin dopé n possède un meilleur rendement qu'une cellule photovoltaïque à hétérojonction ayant un substrat en silicium monocristallin dopé p.  The photovoltaic cell comprises a doped semiconductor substrate 101 of a first type of conductivity, i.e. of type n or p. The semiconductor substrate 101 is preferably of monocrystalline silicon. Moreover, the semiconductor substrate 101 is preferentially doped n. Indeed, a heterojunction photovoltaic cell having an n-doped monocrystalline silicon substrate has a higher efficiency than a heterojunction photovoltaic cell having a p-doped monocrystalline silicon substrate.
Le substrat semi-conducteur 101 est recouvert d'au moins une couche semi- conductrice, dopée d'un type de conductivité opposé à celui du substrat, formant ainsi un empilement de couches semi-conductrices 1 10 et une jonction PN. Dans l'exemple de la figure 1 A, l'empilement 1 10 comporte, en plus du substrat 101 , une première couche semi-conductrice 102 et une deuxième couche semi-conductrice 103. The semiconductor substrate 101 is covered with at least one semiconductor layer, doped with a conductivity type opposite to that of the substrate, forming and a stack of semiconductor layers 1 10 and a PN junction. In the example of FIG. 1A, the stack 1 10 comprises, in addition to the substrate 101, a first semiconductor layer 102 and a second semiconductor layer 103.
La première couche semi-conductrice 102 recouvre la face avant du substrat 101 , et éventuellement une partie des flancs du substrat 101 . La deuxième couche semi-conductrice 103 recouvre la face arrière du substrat 101 , et éventuellement une partie des flancs du substrat 101 .  The first semiconductor layer 102 covers the front face of the substrate 101, and possibly a portion of the sidewalls of the substrate 101. The second semiconductor layer 103 covers the rear face of the substrate 101, and possibly a portion of the sidewalls of the substrate 101.
Ainsi, l'empilement 1 10 présente une surface avant correspondant à la première couche semi-conductrice 102, une surface arrière correspondant à la deuxième couche semi-conductrice 103, et des surfaces latérales correspondant aux flancs du substrat 101 , à une portion de la première couche semi-conductrice 102 ou à une portion de la deuxième couche semi-conductrice 103.  Thus, the stack 1 10 has a front surface corresponding to the first semiconductor layer 102, a rear surface corresponding to the second semiconductor layer 103, and side surfaces corresponding to the sidewalls of the substrate 101, to a portion of the first semiconductor layer 102 or a portion of the second semiconductor layer 103.
La première couche semi-conductrice 102 et la deuxième couche semi- conductrice 103 sont généralement déposées sur le substrat semi-conducteur 101 au moyen d'une technique de dépôt non directive, par exemple un dépôt chimique en phase vapeur assisté par plasma, également appelé PECVD pour « Plasma- Enhanced Chemical Vapor Déposition » en anglais, ce qui explique pourquoi les couches semi-conductrices 102, 103 viennent également se déposer sur les flancs du substrat 101 .  The first semiconductor layer 102 and the second semiconductor layer 103 are generally deposited on the semiconductor substrate 101 by means of a non-directive deposition technique, for example a plasma-assisted chemical vapor deposition, also called PECVD for "Plasma-Enhanced Chemical Vapor Deposition" in English, which explains why the semiconductor layers 102, 103 are also deposited on the sidewalls of the substrate 101.
Dans une première configuration de la cellule photovoltaïque à hétérojonction, la première couche semi-conductrice 102 a un type de conductivité opposé à celui du substrat semi-conducteur 101 , formant ainsi l'émetteur de la jonction PN en face avant. La deuxième couche semi-conductrice 103 est alors d'un type de conductivité identique à celui du substrat semi-conducteur 101 , formant ainsi un champ répulsif en face arrière, également appelé BSF pour « Back Surface Field » en anglais. Cette configuration est communément appelée « émetteur standard ».  In a first configuration of the heterojunction photovoltaic cell, the first semiconductor layer 102 has a conductivity type opposite to that of the semiconductor substrate 101, thus forming the emitter of the PN junction on the front face. The second semiconductor layer 103 is then of a conductivity type identical to that of the semiconductor substrate 101, thus forming a repulsive field on the backside, also called BSF for "Back Surface Field" in English. This configuration is commonly referred to as "standard transmitter".
Inversement, dans une deuxième configuration, la deuxième couche semi- conductrice 103 a un type de conductivité opposé à celui du substrat semiconducteur 101 , formant ainsi l'émetteur de la jonction PN en face arrière. La première couche semi-conductrice 102 est alors d'un type de conductivité identique à celui du substrat semi-conducteur 101 , formant ainsi un champ répulsif en face avant, également appelé FSF pour « Front Surface Field » en anglais. Cette configuration est communément appelée « émetteur inversé ». La face de la cellule photovoltaïque comprenant le champ répulsif, c'est-à-dire la base de la jonction PN, est destinée à recevoir des contacts métalliques, au niveau desquels le taux de recombinaison des porteurs de charges est très élevé. Le rôle du champ répulsif est d'éloigner les porteurs de charges minoritaires de la base de la jonction PN. Ainsi, le nombre de recombinaisons des porteurs de charges au niveau des contacts métalliques est limité. La couche semi-conductrice formant le champ répulsif est de préférence fortement dopée pour maximiser cet effet. Elle a par exemple une concentration en dopants d'au moins 1020 cm"3. Conversely, in a second configuration, the second semiconductor layer 103 has a conductivity type opposite to that of the semiconductor substrate 101, thus forming the emitter of the PN junction on the back side. The first semiconductor layer 102 is then of a type of conductivity identical to that of the semiconductor substrate 101, thus forming a repulsive field on the front face, also called FSF for "Front Surface Field" in English. This configuration is commonly referred to as "reverse transmitter". The face of the photovoltaic cell comprising the repulsive field, that is to say the base of the PN junction, is intended to receive metal contacts, at which the recombination rate of the charge carriers is very high. The role of the repulsive field is to move the minority carriers from the base of the PN junction. Thus, the number of recombinations of the charge carriers at the metal contacts is limited. The semiconductor layer forming the repulsive field is preferably heavily doped to maximize this effect. She has such a dopant concentration of at least 10 20 cm "3.
Les couches semi-conductrices 102, 103 sont dans cet exemple de cellule photovoltaïque formées de silicium amorphe. L'épaisseur des couches semi- conductrices 102, 103 est par exemple de l'ordre de 8 et 14 nm respectivement dans la configuration émetteur inversé.  The semiconductor layers 102, 103 are in this photovoltaic cell example formed of amorphous silicon. The thickness of the semiconductor layers 102, 103 is for example of the order of 8 and 14 nm respectively in the inverted transmitter configuration.
Dans d'autres modes de réalisation non représentés sur les figures, l'empilement 1 10 peut comporter un plus grand nombre de couches semi- conductrices. Par exemple, chacune des couches semi-conductrices 102 et 103 en silicium amorphe peut être juxtaposée à une couche de silicium intrinsèque, la couche de silicium intrinsèque étant disposée entre le substrat semi-conducteur 101 et ladite couche semi-conductrice 102-103 en silicium amorphe.  In other embodiments not shown in the figures, the stack 1 10 may comprise a larger number of semiconductor layers. For example, each of the amorphous silicon semiconductor layers 102 and 103 may be juxtaposed with an intrinsic silicon layer, the intrinsic silicon layer being disposed between the semiconductor substrate 101 and the silicon 102-103 semiconductor layer. amorphous.
La conductivité électrique des couches semi-conductrices 102, 103 en silicium amorphe est trop faible pour permettre un transport optimal des charges électriques. Ainsi, des contacts métalliques ne peuvent être directement disposés sur ces couches. Il convient au préalable de déposer des couches conductrices électriquement sur les surfaces avant et arrière de l'empilement 1 10 pour collecter les charges électriques générées par la jonction PN.  The electrical conductivity of amorphous silicon semiconductor layers 102, 103 is too low to allow optimal transport of electrical charges. Thus, metal contacts can not be directly arranged on these layers. It is first necessary to deposit conductive layers electrically on the front and rear surfaces of the stack 1 10 to collect the electrical charges generated by the PN junction.
Une première couche conductrice électriquement 104, également transparente au rayonnement incident, est déposée sur la face avant de l'empilement 1 10. La première couche conductrice électriquement 104 est généralement formée d'un oxyde transparent et conducteur, par exemple de l'oxyde d'indium-étain, également appelé ITO pour « Indium Tin Oxide » en anglais.  A first electrically conductive layer 104, also transparent to incident radiation, is deposited on the front face of the stack 1 10. The first electrically conductive layer 104 is generally formed of a transparent and conductive oxide, for example indium-tin, also called ITO for "Indium Tin Oxide" in English.
Une deuxième couche conductrice électriquement 105 est déposée sur la face arrière de l'empilement 1 10. La deuxième couche conductrice électriquement 105 peut également être transparente, lorsque l'on veut capter un rayonnement diffus par la face arrière BS de la cellule photovoltaïque. La deuxième couche conductrice électriquement 105 est alors généralement formée d'un oxyde transparent et conducteur, de préférence identique à celui de la première couche conductrice électriquement 104. Une cellule photovoltaïque de ce type est dite « bifaciale ». A second electrically conductive layer 105 is deposited on the rear face of the stack 1 10. The second electrically conductive layer 105 may also be transparent, when it is desired to capture diffuse radiation from the rear face BS of the photovoltaic cell. The second electrically conductive layer 105 is then generally formed of a transparent oxide and conductor, preferably identical to that of the first electrically conductive layer 104. A photovoltaic cell of this type is called "bifacial".
Si la face arrière BS de la cellule photovoltaïque n'est pas destinée à être exposée à un quelconque rayonnement, la deuxième couche conductrice électriquement 105 peut être formée d'un métal, par exemple l'argent. Une cellule photovoltaïque de ce type est dite « monofaciale ».  If the rear face BS of the photovoltaic cell is not intended to be exposed to any radiation, the second electrically conductive layer 105 may be formed of a metal, for example silver. A photovoltaic cell of this type is called "monofacial".
Pareillement à la première couche semi-conductrice 102 et à la deuxième couche semi-conductrice 103, la première couche conductrice électriquement 104 et la deuxième couche conductrice électriquement 105 sont généralement déposées au moyen d'une technique de dépôt non directive, par exemple par PVD. Les couches conductrices électriquement 104, 105 ont par exemple une épaisseur comprise entre 50 et 300 nm.  Similarly to the first semiconductor layer 102 and the second semiconductor layer 103, the first electrically conductive layer 104 and the second electrically conductive layer 105 are generally deposited by means of a non-directive deposition technique, for example by PVD . The electrically conductive layers 104, 105 have for example a thickness of between 50 and 300 nm.
La première couche conductrice électriquement 104 et la deuxième couche conductrice électriquement 105 se déposent donc également sur les surfaces latérales de l'empilement 1 10 en formant des contacts électriques. Par conséquent, la face avant FS et la face arrière BS de la cellule photovoltaïque sont reliées par des chemins conducteurs électriquement, appelés « shunts », situés au niveau des bords E de la cellule photovoltaïque.  The first electrically conductive layer 104 and the second electrically conductive layer 105 are therefore also deposited on the side surfaces of the stack 1 10 forming electrical contacts. Therefore, the front face FS and the rear face BS of the photovoltaic cell are connected by electrically conductive paths, called "shunts", located at the edges E of the photovoltaic cell.
Après le dépôt des couches conductrices 104, 105 sur l'empilement 1 10, la cellule photovoltaïque est soumise à un procédé d'isolation électrique des bords E de la cellule photovoltaïque à hétérojonction, dans le but de supprimer ces chemins conducteurs. Ainsi, la valeur d'une grandeur appelée « résistance de shunt » symbolisant les shunts entre les deux faces de la cellule photovoltaïque est augmentée.  After the conductive layers 104, 105 have been deposited on the stack 1 10, the photovoltaic cell is subjected to a method of electrically insulating the edges E of the heterojunction photovoltaic cell, in order to eliminate these conductive paths. Thus, the value of a quantity called "shunt resistor" symbolizing the shunts between the two faces of the photovoltaic cell is increased.
Pour ce faire, le procédé d'isolation comporte une étape d'abrasion mécanique des bords E de la cellule photovoltaïque. Au cours de cette étape d'abrasion, on élimine de la matière sur les bords E de la cellule photovoltaïque par frottement d'un abrasif sur les bords E de la cellule photovoltaïque.  To do this, the isolation process comprises a step of mechanical abrasion E edges of the photovoltaic cell. During this abrasion step, material is removed on the edges E of the photovoltaic cell by rubbing an abrasive on the edges E of the photovoltaic cell.
La figure 1 B est une vue de coupe transversale de la cellule photovoltaïque de la figure 1 A, après la mise en œuvre de ce procédé.  Figure 1B is a cross sectional view of the photovoltaic cell of Figure 1A, after the implementation of this method.
L'abrasion mécanique est réalisée de manière à éliminer la première couche conductrice électriquement 104 et la deuxième couche conductrice électriquement 105 disposées sur les surfaces latérales de l'empilement 1 10 de couches semi- conductrices et formant les bords E de la cellule photovoltaïque. Les contacts électriques provenant de la rencontre entre la première couche conductrice électriquement 104 et la deuxième couche conductrice électriquement 105 sont alors détruits. Ainsi la face avant FS et la face arrière BS de la cellule photovoltaïque sont isolées électriquement. The mechanical abrasion is performed so as to eliminate the first electrically conductive layer 104 and the second electrically conductive layer 105 disposed on the side surfaces of the stack 1 10 of semiconductor layers and forming the edges E of the photovoltaic cell. Contacts Electrical leads arising from the encounter between the first electrically conductive layer 104 and the second electrically conductive layer 105 are then destroyed. Thus, the front face FS and the rear face BS of the photovoltaic cell are electrically insulated.
En outre, l'abrasion est effectuée de manière à ce que chaque bord E de la cellule photovoltaïque forme, après abrasion, un angle aigu a avec la face avant FS de la cellule photovoltaïque. Ainsi, la surface active de la face avant FS de la cellule photovoltaïque, face exposée au rayonnement incident, reste maximale. L'angle aigu a entre la face avant FS et les bords E de la cellule photovoltaïque permet d'améliorer la qualité de l'isolation entre les deux faces de la cellule photovoltaïque en augmentant la distance entre ces dernières. L'angle aigu a est préférentiellement compris entre 50° et 88,5° . L'étape d'abrasion estde préférence réalisée de façon automatisée pour garantir un meilleur contrôle de l'angle .  In addition, the abrasion is performed so that each edge E of the photovoltaic cell forms, after abrasion, an acute angle with the front face FS of the photovoltaic cell. Thus, the active surface of the front face FS of the photovoltaic cell, face exposed to incident radiation, remains maximum. The acute angle a between the front face FS and the edges E of the photovoltaic cell makes it possible to improve the quality of the insulation between the two faces of the photovoltaic cell by increasing the distance between them. The acute angle α is preferably between 50 ° and 88.5 °. The abrasion step is preferably performed in an automated manner to ensure better control of the angle.
L'abrasion des bords E de la cellule photovoltaïque est de préférence effectuée sur une épaisseur comprise entre 5 μιτι et 50 μιτι, c'est-à-dire qu'on élimine 5 à 50 μιτι de matière sur les bords E de la cellule photovoltaïque. Cette matière éliminée correspond principalement aux matériaux des couches conductrices 104, 105.  The abrasion of the edges E of the photovoltaic cell is preferably carried out over a thickness of between 5 μιτι and 50 μιτι, that is to say that 5 to 50 μιτι of material are removed on the edges E of the photovoltaic cell. . This material removed corresponds mainly to the materials of the conductive layers 104, 105.
L'épaisseur de matière éliminée est du même ordre de grandeur que celle des couches conductrices 104, 105. Ainsi l'épaisseur de matière abrasée est suffisante pour éliminer entièrement la première couche conductrice électriquement 104 et la deuxième couche conductrice électriquement 105 sur les bords E de la cellule photovoltaïque tout en minimisant la perte de surface sur la face avant FS et la face arrière BS de la cellule photovoltaïque. A titre de comparaison, la technique de l'art antérieur utilisant un laser peut enlever jusqu'à 1 mm de matière sur les bords de la cellule photovoltaïque.  The thickness of material removed is of the same order of magnitude as that of the conductive layers 104, 105. Thus, the thickness of the abraded material is sufficient to completely eliminate the first electrically conductive layer 104 and the second electrically conductive layer 105 on the E edges. of the photovoltaic cell while minimizing the loss of surface on the front face FS and the rear face BS of the photovoltaic cell. By way of comparison, the prior art technique using a laser can remove up to 1 mm of material on the edges of the photovoltaic cell.
Par conséquent, dans ce mode de mise en œuvre préférentiel, les couches semi-conductrices 102, 103 en silicium amorphe situées sur les flancs du substrat semi-conducteur 101 en silicium monocristallin 101 ne sont pas entièrement retirées afin de protéger le substrat 101 . Ceci n'est pas préjudiciable pour la qualité de l'isolation, car ces couches sont bien moins conductrices électriquement que les couches conductrices 104, 105 d'oxyde transparent. Ainsi, contrairement aux procédés d'isolation de l'art antérieur, l'abrasion mécanique limite la création de défauts de structure sur le substrat semi-conducteur 101 . Therefore, in this preferred embodiment, the amorphous silicon semiconductor layers 102, 103 on the sides of the monocrystalline silicon 101 semiconductor substrate 101 are not completely removed to protect the substrate 101. This is not detrimental to the quality of the insulation, because these layers are much less electrically conductive than the conductive layers 104, 105 of transparent oxide. Thus, unlike Prior art isolation methods, mechanical abrasion limits the creation of structural defects on the semiconductor substrate 101.
L'abrasif utilisé au cours de l'étape d'abrasion se présente de préférence sous la forme d'un papier de verre. Par ailleurs, le substrat semi-conducteur 101 est texturé, c'est-à-dire qu'il présente des motifs en surface afin de diminuer la réflexion du rayonnement incident. L'abrasif comporte des grains ayant de préférence des dimensions du même ordre de grandeur que celles des motifs en surface du substrat. Ainsi, l'élimination de matière est mieux contrôlée.  The abrasive used during the abrasion step is preferably in the form of a sandpaper. Moreover, the semiconductor substrate 101 is textured, that is to say that it has patterns on the surface in order to reduce the reflection of the incident radiation. The abrasive comprises grains preferably having dimensions of the same order of magnitude as those of the surface patterns of the substrate. Thus, the elimination of matter is better controlled.
Les motifs en surface du substrat semi-conducteur 101 sont généralement de forme pyramidale. Les dimensions des motifs en surface du substrat, et donc les dimensions des grains de l'abrasif, sont par exemple de l'ordre de 10 μιτι. Les grains de l'abrasif sont par exemple des grains en carbure de silicium ou des grains de diamant.  The surface patterns of the semiconductor substrate 101 are generally of pyramidal shape. The dimensions of the surface patterns of the substrate, and therefore the grain size of the abrasive, are for example of the order of 10 μιτι. The grains of the abrasive are, for example, silicon carbide grains or diamond grains.
L'abrasion mécanique générant des particules qui peuvent contaminer la cellule photovoltaïque, le procédé de fabrication de la cellule photovoltaïque à hétérojonction comporte avantageusement une étape de nettoyage des bords E de la cellule photovoltaïque pour éliminer ces particules. L'étape de nettoyage des bords E de la cellule photovoltaïque peut être réalisée pendant ou après l'étape d'abrasion.  The mechanical abrasion generating particles that can contaminate the photovoltaic cell, the method of manufacturing the heterojunction photovoltaic cell advantageously comprises a step of cleaning the edges E of the photovoltaic cell to remove these particles. The cleaning step E edges of the photovoltaic cell can be performed during or after the abrasion step.
L'étape de nettoyage comporte par exemple une opération de rinçage des bords E de la cellule photovoltaïque au moyen d'eau déionisée ou d'alcool tel que l'isopropanol. L'étape de nettoyage des bords E de la cellule photovoltaïque peut en outre comporter une opération de soufflage d'un gaz comprimé, par exemple de l'air ou un gaz inerte, sur les bords abrasés (ou en cours d'abrasion) de la cellule photovoltaïque.  The cleaning step comprises for example an operation of rinsing the edges E of the photovoltaic cell by means of deionized water or alcohol such as isopropanol. The step of cleaning the edges E of the photovoltaic cell may further comprise an operation for blowing a compressed gas, for example air or an inert gas, onto the abraded (or abrasion-abraded) edges of the photovoltaic cell. the photovoltaic cell.
L'abrasion mécanique des bords E de la cellule photovoltaïque étant susceptible de mettre à jour les surfaces latérales du substrat semi-conducteur 101 , le procédé de fabrication peut en outre comporter une étape de passivation des bords E de la cellule photovoltaïque afin de limiter le mécanisme de recombinaison surfacique des porteurs de charge. L'étape de passivation est réalisée après l'étape d'isolation des bords E de la cellule photovoltaïque. Elle consiste à rendre inactif électriquement les bords E de la cellule photovoltaïque en y formant un oxyde.  The mechanical abrasion of the edges E of the photovoltaic cell being able to update the lateral surfaces of the semiconductor substrate 101, the manufacturing method may further comprise a passivation step E edges of the photovoltaic cell to limit the surface recombination mechanism of the charge carriers. The passivation step is performed after the step of isolating the edges E of the photovoltaic cell. It consists of rendering the edges E of the photovoltaic cell electrically inactive by forming an oxide therein.
Des courbes du facteur de forme FF d'une cellule photovoltaïque à hétérojonction en configuration émetteur inversé sont illustrées sur la figure 2. Les courbes sont tracées en fonction de l'illumination, et correspondent à deux procédés d'isolation des bords de la cellule photovoltaïque différents, effectués sur une même structure de cellule photovoltaïque. Curves of the form factor FF of a heterojunction photovoltaic cell in an inverted transmitter configuration are illustrated in FIG. 2. The curves are plotted as a function of illumination, and correspond to two methods. isolation of the edges of the photovoltaic cell different, performed on the same photovoltaic cell structure.
En effet, la figure 2 montre une première courbe 201 correspondant à une cellule photovoltaïque isolée par une technique de l'art antérieur, en utilisant un laser pour tracer un sillon sur le pourtour de la face arrière de la cellule photovoltaïque, et une deuxième courbe 202 correspondant à une cellule photovoltaïque isolée par abrasion mécanique selon le mode de mise en œuvre préférentiel de l'invention.  In fact, FIG. 2 shows a first curve 201 corresponding to a photovoltaic cell isolated by a technique of the prior art, by using a laser to trace a groove around the periphery of the rear face of the photovoltaic cell, and a second curve 202 corresponding to a photovoltaic cell insulated by mechanical abrasion according to the preferred embodiment of the invention.
Les valeurs du facteur de forme FF sur ces deux courbes 201 , 202 sont normalisées par rapport à la valeur du facteur de forme obtenue par la cellule photovoltaïque dont les bords E ont été isolés par laser, à une illumination de 1000 W/m2. The values of the form factor FF on these two curves 201, 202 are normalized with respect to the value of the shape factor obtained by the photovoltaic cell whose edges E have been isolated by laser, at an illumination of 1000 W / m 2 .
Le facteur de forme FF d'une cellule photovoltaïque exprime le rapport entre la puissance réelle débitée par la cellule photovoltaïque et la puissance idéale de la cellule photovoltaïque, selon l'équation suivante :  The form factor FF of a photovoltaic cell expresses the ratio between the actual power delivered by the photovoltaic cell and the ideal power of the photovoltaic cell, according to the following equation:
où Vmax est la tension maximale de la cellule photovoltaïque, lmax est le courant maximal de la cellule photovoltaïque, Vco est la tension en circuit ouvert de la cellule photovoltaïque, et lcc est le courant en court-circuit de la cellule photovoltaïque. where V max is the maximum voltage of the photovoltaic cell, l ma x is the maximum current of the photovoltaic cell, V co is the open circuit voltage of the photovoltaic cell, and l cc is the short-circuit current of the cell photovoltaic.
Le facteur de forme FF est limité par des résistances parasites dont notamment la résistance de shunt. Plus la résistance de shunt est élevée, plus le courant de fuite est faible et plus le courant délivré par la cellule photovoltaïque est élevé. Ainsi, une bonne isolation électrique des bords E de la cellule photovoltaïque entraîne une amélioration du facteur de forme FF de la cellule photovoltaïque.  The form factor FF is limited by parasitic resistances including shunt resistance. The higher the shunt resistance, the lower the leakage current and the higher the current delivered by the photovoltaic cell. Thus, good electrical insulation of the edges E of the photovoltaic cell results in an improvement of the form factor FF of the photovoltaic cell.
Une nette amélioration du facteur de forme FF peut être constatée lorsque les bords E de la cellule photovoltaïque sont isolés par abrasion mécanique plutôt que par laser. L'amélioration du facteur de forme FF, supérieure à trois points, est particulièrement importante pour une faible illumination.  A significant improvement in the form factor FF can be seen when the edges E of the photovoltaic cell are isolated by mechanical abrasion rather than by laser. The improvement of the FF form factor, greater than three points, is particularly important for low illumination.
En effet, une baisse de l'illumination, et donc du nombre de photons, entraîne une diminution du courant. Les résistances parasites, et notamment les résistances de shunt, deviennent alors prépondérantes. Une très bonne isolation des bords de la cellule photovoltaïque est donc nécessaire à basse illumination pour obtenir un bon facteur de forme FF. L'isolation par abrasion permettant de conserver une plus grande surface active de la cellule photovoltaïque par rapport à la technique classique utilisant un laser, on constate une augmentation du courant débité par la cellule. Cette augmentation peut atteindre 100 mA dans l'exemple de cellule des figures 1 A et 1 B. Indeed, a decrease in the illumination, and therefore the number of photons, leads to a decrease in the current. The parasitic resistances, and in particular the shunt resistances, then become predominant. A very good insulation of the edges of the photovoltaic cell is therefore necessary at low illumination to obtain a good form factor FF. The abrasion insulation to maintain a larger active area of the photovoltaic cell compared to the conventional technique using a laser, there is an increase in current delivered by the cell. This increase can reach 100 mA in the cell example of FIGS. 1A and 1B.
Le rendement η, lié au facteur de forme FF par la relation suivante :  The efficiency η, linked to the form factor FF by the following relation:
"incidente où Pinddente est la puissance incidente (rayonnement incident), est quant à lui augmenté de 0,15 %. " Incident where Pinddente is the incident power (incident radiation), is increased by 0.15%.
Ainsi, grâce au procédé selon l'invention, une isolation électrique des bords de la cellule photovoltaïque est réalisée de manière performante. La perte de surface sur les faces de la cellule photovoltaïque et les dégâts structurels sont particulièrement limités.  Thus, thanks to the method according to the invention, electrical insulation of the edges of the photovoltaic cell is performed efficiently. The surface loss on the faces of the photovoltaic cell and the structural damage are particularly limited.
L'isolation électrique des bords d'une cellule photovoltaïque présente également un intérêt pour la mise en module de plusieurs cellules photovoltaïques. Dans un module photovoltaïque, les cellules photovoltaïques sont généralement interconnectées par des rubans électriques. Des cellules photovoltaïques sont par exemple mises en série en connectant la face avant d'une cellule photovoltaïque avec la face arrière de la cellule photovoltaïque suivante, et ainsi de suite. Lors de cette mise en module, les bords des cellules photovoltaïques sont susceptibles d'entrer en contact entre les rubans interconnectant les cellules photovoltaïques.  The electrical insulation of the edges of a photovoltaic cell is also of interest for the moduleization of several photovoltaic cells. In a photovoltaic module, photovoltaic cells are generally interconnected by electrical ribbons. Photovoltaic cells are for example put in series by connecting the front face of a photovoltaic cell with the rear face of the next photovoltaic cell, and so on. During this setting in module, the edges of the photovoltaic cells are likely to come into contact between the ribbons interconnecting the photovoltaic cells.
Le fait de supprimer ici les couches conductrices sur les bords de la cellule photovoltaïque permet de réduire le risque de court-circuit entre les rubans interconnectant les cellules photovoltaïques du module et les bords des cellules photovoltaïques.  Removing the conductive layers on the edges of the photovoltaic cell here makes it possible to reduce the risk of a short circuit between the ribbons interconnecting the photovoltaic cells of the module and the edges of the photovoltaic cells.
Naturellement l'invention n'est pas limitée aux modes de réalisation décrits en référence aux figures et des variantes pourraient être envisagées sans sortir du cadre de l'invention. On peut notamment effectuer l'étape d'isolation des bords de la cellule photovoltaïque après l'étape de métallisation dans laquelle des contacts métalliques sont déposés sur les couches conductrices, ou encore d'effectuer l'abrasion mécanique sur un empilement de cellules photovoltaïque afin d'augmenter le rendement du procédé.  Naturally, the invention is not limited to the embodiments described with reference to the figures and variants could be envisaged without departing from the scope of the invention. In particular, it is possible to perform the step of insulating the edges of the photovoltaic cell after the metallization step in which metal contacts are deposited on the conductive layers, or else to carry out the mechanical abrasion on a stack of photovoltaic cells in order to to increase the efficiency of the process.

Claims

Revendications claims
1 . Procédé d'isolation électrique des bords (E) d'une cellule photovoltaïque à hétérojonction, la cellule photovoltaïque ayant une face avant (FS) destinée à être exposée à un rayonnement incident et comportant : 1. A method of electrically insulating the edges (E) of a heterojunction photovoltaic cell, the photovoltaic cell having a front face (FS) for exposure to incident radiation and comprising:
- un empilement (1 10) de couches semi-conductrices ayant une surface avant, une surface arrière opposée à la surface avant, et des surfaces latérales ; - a stack (1 10) of semiconductor layers having a front surface, a rear surface opposite to the front surface, and side surfaces;
- une première couche conductrice électriquement (104) et transparente au rayonnement incident disposée sur la surface avant de l'empilement (1 10) et sur les surfaces latérales de l'empilement (1 10) ; - a first electrically conductive layer (104) and transparent to incident radiation disposed on the front surface of the stack (1 10) and on the side surfaces of the stack (1 10);
- une deuxième couche conductrice électriquement (105) disposée sur la surface arrière de l'empilement (1 10) et sur les surfaces latérales de l'empilement (1 10), la première couche conductrice (104) et la deuxième couche conductrice (105) étant en contact électrique sur les surfaces latérales de l'empilement (1 10) ;  a second electrically conductive layer (105) disposed on the rear surface of the stack (1 10) and on the side surfaces of the stack (1 10), the first conductive layer (104) and the second conductive layer (105); ) being in electrical contact with the side surfaces of the stack (1 10);
le procédé d'isolation étant caractérisé en ce qu'il comporte une étape d'abrasion mécanique des bords (E) de la cellule photovoltaïque de sorte que : the insulation method being characterized in that it comprises a step of mechanical abrasion of the edges (E) of the photovoltaic cell so that:
- le contact électrique entre la première couche conductrice (104) et la deuxième couche conductrice (105) sur les surfaces latérales de l'empilement (1 10) soit éliminé ; et que  - the electrical contact between the first conductive layer (104) and the second conductive layer (105) on the side surfaces of the stack (1 10) is eliminated; and
- chaque bord (E) abrasé de la cellule photovoltaïque forme un angle aigu (a) avec la face avant (FS) de la cellule photovoltaïque.  each abraded edge (E) of the photovoltaic cell forms an acute angle (a) with the front face (FS) of the photovoltaic cell.
2. Procédé d'isolation selon la revendication précédente dans lequel l'angle aigu (a) entre la face avant (FS) de la cellule photovoltaïque et chaque bord (E) abrasé de la cellule photovoltaïque est compris entre 50° et88,5° . 2. Insulating method according to the preceding claim wherein the acute angle (a) between the front face (FS) of the photovoltaic cell and each edge (E) abraded of the photovoltaic cell is between 50 ° and 88.5 ° .
3. Procédé d'isolation selon l'une quelconque des revendications précédentes dans lequel l'étape d'abrasion mécanique des bords (E) de la cellule photovoltaïque est effectuée sur une épaisseur comprise entre 5 μιτι et 50 μιτι. 3. Insulating method according to any one of the preceding claims wherein the step of mechanical abrasion edges (E) of the photovoltaic cell is performed on a thickness between 5 μιτι and 50 μιτι.
4. Procédé d'isolation selon l'une quelconque des revendications précédentes dans lequel l'empilement (1 10) de couches semi-conductrices de la cellule photovoltaïque comporte un substrat semi-conducteur (101 ) texturé en surface par des motifs, et dans lequel l'étape d'abrasion mécanique des bords (E) de la cellule photovoltaïque est effectuée au moyen d'un abrasif comportant des grains ayant des dimensions du même ordre de grandeur que celles des motifs du substrat semiconducteur (101 ). 4. Insulating method according to any one of the preceding claims wherein the stack (1 10) of semiconductor layers of the photovoltaic cell comprises a semiconductor substrate (101) textured on the surface by in which the step of mechanical abrasion of the edges (E) of the photovoltaic cell is carried out by means of an abrasive comprising grains having dimensions of the same order of magnitude as those of the semiconductor substrate (101 ).
5. Procédé de fabrication d'une cellule photovoltaïque à hétérojonction comportant les étapes suivantes : 5. A method of manufacturing a heterojunction photovoltaic cell comprising the following steps:
- fournir un empilement (1 10) de couches semi-conductrices ayant une surface avant et une surface arrière opposée à la surface avant ;  providing a stack (1 10) of semiconductor layers having a front surface and a rear surface opposite the front surface;
- déposer une première couche conductrice électriquement (104) et transparente au rayonnement incident sur la surface avant de l'empilement (1 10) ;  depositing a first electrically conductive layer (104) transparent to incident radiation on the front surface of the stack (1 10);
- déposer une deuxième couche conductrice électriquement (105) sur la surface arrière de l'empilement (1 10) ;  depositing a second electrically conducting layer (105) on the rear surface of the stack (1 10);
le procédé de fabrication étant caractérisé en ce qu'il comporte en outre un procédé d'isolation électrique des bords (E) de la cellule photovoltaïque selon l'une quelconque des revendications précédentes. the manufacturing method being characterized in that it further comprises a method of electrical insulation of the edges (E) of the photovoltaic cell according to any one of the preceding claims.
6. Procédé de fabrication selon la revendication 5 comportant en outre une étape de nettoyage des bords (E) de la cellule photovoltaïque, l'étape de nettoyage étant concomitante ou postérieure au procédé d'isolation électrique des bords (E) de la cellule photovoltaïque. 6. The manufacturing method according to claim 5 further comprising a step of cleaning the edges (E) of the photovoltaic cell, the cleaning step being concomitant with or subsequent to the method of electrical insulation of the edges (E) of the photovoltaic cell. .
7. Procédé de fabrication selon la revendication 6 dans lequel l'étape de nettoyage des bords (E) de la cellule photovoltaïque comporte une opération de rinçage des bords (E) de la cellule photovoltaïque au moyen d'eau et/ou d'alcool. 7. The manufacturing method according to claim 6 wherein the step of cleaning the edges (E) of the photovoltaic cell comprises an operation flushing the edges (E) of the photovoltaic cell with water and / or alcohol .
8. Procédé de fabrication selon l'une quelconque des revendications 6 et 7 dans lequel l'étape de nettoyage des bords (E) de la cellule photovoltaïque comporte une opération de soufflage d'un gaz comprimé sur les bords (E) de la cellule photovoltaïque. 8. The manufacturing method according to any one of claims 6 and 7 wherein the step of cleaning the edges (E) of the photovoltaic cell comprises an operation of blowing a compressed gas on the edges (E) of the cell. photovoltaic.
9. Procédé de fabrication selon l'une quelconque des revendications 5 à 8 comportant en outre une étape de passivation des bords (E) de la cellule photovoltaïque, l'étape de passivation étant postérieure au procédé d'isolation électrique des bords (E) de la cellule photovoltaïque. 9. The manufacturing method according to any one of claims 5 to 8 further comprising a passivation step edges (E) of the cell photovoltaic, the passivation step being subsequent to the method of electrical insulation of the edges (E) of the photovoltaic cell.
10. Procédé de fabrication selon l'une quelconque des revendications 5 à 9 dans lequel la première couche conductrice (104) et la deuxième couche conductrice (105) sont déposées par une technique de dépôt chimique en phase vapeur. 10. The manufacturing method according to any one of claims 5 to 9 wherein the first conductive layer (104) and the second conductive layer (105) are deposited by a chemical vapor deposition technique.
PCT/FR2016/051516 2015-06-26 2016-06-21 Method for insulating the edges of a heterojunction photovoltaic cell WO2016207539A1 (en)

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