Classifications

• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
  • H10F77/00—Constructional details of devices covered by this subclass
  • H10F77/10—Semiconductor bodies
  • H10F77/16—Material structures, e.g. crystalline structures, film structures or crystal plane orientations
  • H10F77/169—Thin semiconductor films on metallic or insulating substrates
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
  • C23C16/22—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the deposition of inorganic material, other than metallic material
  • C23C16/30—Deposition of compounds, mixtures or solid solutions, e.g. borides, carbides, nitrides
  • C23C16/40—Oxides
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
  • C23C16/22—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the deposition of inorganic material, other than metallic material
  • C23C16/30—Deposition of compounds, mixtures or solid solutions, e.g. borides, carbides, nitrides
  • C23C16/40—Oxides
  • C23C16/407—Oxides of zinc, germanium, cadmium, indium, tin, thallium or bismuth
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
  • H10F10/00—Individual photovoltaic cells, e.g. solar cells
  • H10F10/10—Individual photovoltaic cells, e.g. solar cells having potential barriers
  • H10F10/17—Photovoltaic cells having only PIN junction potential barriers
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
  • H10F10/00—Individual photovoltaic cells, e.g. solar cells
  • H10F10/10—Individual photovoltaic cells, e.g. solar cells having potential barriers
  • H10F10/17—Photovoltaic cells having only PIN junction potential barriers
  • H10F10/172—Photovoltaic cells having only PIN junction potential barriers comprising multiple PIN junctions, e.g. tandem cells
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
  • H10F71/00—Manufacture or treatment of devices covered by this subclass
  • H10F71/138—Manufacture of transparent electrodes, e.g. transparent conductive oxides [TCO] or indium tin oxide [ITO] electrodes
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
  • H10F77/00—Constructional details of devices covered by this subclass
  • H10F77/20—Electrodes
  • H10F77/244—Electrodes made of transparent conductive layers, e.g. transparent conductive oxide [TCO] layers
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
  • H10F77/00—Constructional details of devices covered by this subclass
  • H10F77/20—Electrodes
  • H10F77/244—Electrodes made of transparent conductive layers, e.g. transparent conductive oxide [TCO] layers
  • H10F77/251—Electrodes made of transparent conductive layers, e.g. transparent conductive oxide [TCO] layers comprising zinc oxide [ZnO]
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
  • H10F77/00—Constructional details of devices covered by this subclass
  • H10F77/70—Surface textures, e.g. pyramid structures
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K50/00—Organic light-emitting devices
  • H10K50/80—Constructional details
  • H10K50/805—Electrodes
  • H10K50/81—Anodes
  • H10K50/816—Multilayers, e.g. transparent multilayers
• • 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
  • Y02E10/548—Amorphous silicon PV cells

Definitions

• the present invention is in the technical field of transparent conductive substrates for optoelectronic devices.
• the present invention relates to a transparent substrate, in particular glass, provided with a conductive coating for optoelectronic devices, to the method of manufacturing this transparent conductive substrate and to optoelectronic devices in which this transparent conductive substrate is incorporated.
• the transparent conductive substrate referred to in the present invention can be used as an electrode for extracting or injecting charges into optoelectronic devices such as organic electroluminescent devices known by the acronym OLED (Organic Light Emitting Device). or the light collecting devices such as photovoltaic cells, also called solar cells.
• OLED Organic Light Emitting Device
• the invention is more particularly concerned with thin-film Si-based photovoltaic cells.
• photovoltaic cells there are different types of photovoltaic cells among which there are cells based on Si films.
• optoelectronic devices in thin layers typically having a thickness of less than 10 ⁇ m, consist of of a transparent, flexible or rigid conductive substrate and deposited on the latter, an optoelectronically active layer formed of an inorganic semiconductor material or, more rarely, organic, and contacted on both sides by two electrodes of which at least one transpait nte.
• the semi-conductor is generally composed of the stack of a p-type layer, an active layer and an n-type layer, together forming a pin or nip junction.
• the material used is mainly amorphous or microcrystalline silicon.
• the useful range of absorption of photons in the absorbent is between 400 nm and 550 nm. For tandem cells, this useful absorption domain is expanded and covers 400 nm to 1100 nm.
• the transparent conductive substrate comprises a support provided with a conductive coating, this conductive coating being more often called by the specialists TCO (of the English Transparent ⁇ onductive Oxide), said support being preferably a glass support.
• TCO Transparent ⁇ onductive Oxide
• the first technique is a gas phase pyrolysis method (often referred to by the abbreviation CVD, Chemical Vapor Deposition).
• Organometallic precursors react in the gas phase at high temperature (> 600 ° C) and a deposit is formed on the surface of the glass.
• the material most often deposited is based on tin oxide doped with fluorine or antimony.
• This technique makes it possible to obtain layers having adequate electrical and optical properties.
• this technique is applied directly after the formation of the glass (in the production unit called float). This method is then called "on-line”.
• Another method consists in depositing a material on the surface of the support by vacuum process, said support being preferably n ce in glass.
• Sputtering is a process well known in the manufacture of layers for glazing used in the residential sector (individual houses) or in the architectural field (buildings and large construction).
• the deposits on the glass make it possible to obtain thermal insulation properties (low emissivity) as well as certain desired hues. In general, this type of deposit is made cold.
• TCO thermal insulation properties
• ITO indium tin oxide
• Zinc oxide, ZnO is a promising compound. Indeed, of a conductor behavior in the pure state, the resistivity decreases rapidly with the addition of a dopant such as Ai, Ga, B.
• the active layer in order to limit the manufacturing costs of the optoelectronic device, the active layer must be relatively thin (between 100 nm and a few microns).
• the active layer leads to a low amount of absorbed light and therefore reduced efficiency.
• it is therefore necessary to increase as much as possible the optical path of the light within the active layer. This is generally achieved by the use of a textured TCO substrate or layer for diffusing or diffracting light into the active layer.
• the document DE 197 13 215 describes a solar cell and the support is covered with a TCO layer, advantageously zinc oxide (ZnO), formed by cathodic sputtering in an argon atmosphere from an aluminum doped ZnO target.
• ZnO zinc oxide
• it is attacked either by a chemical process with the aid of an acid solution, or by an electrochemical process (anodic etching or reactive ion etching). The attack can be done during or after the deposition of the layer.
• the object of the invention is to provide a transparent conductive substrate for optoelectronic devices which is an alternative to existing substrates. More particularly, it is a question of providing a transparent conductive substrate for photovoltaic cells as well as its manufacturing method.
• a second object that the present invention sets is to provide a photovoltaic cell incorporating the transparent conductive substrate.
• the invention relates to a transparent conductive substrate for an optoelectronic device comprising a support and a conductive coating based on doped zinc oxide, said coating consisting of a stack of at least two layers of different electrical conductivity, a so-called layer of high electrical conductivity and a so-called low electrical conductivity layer, such as the so-called layer of high electrical conductivity is a layer based on zinc oxide doped with m% by weight of oxide of a doping element with m less than or equal to 6.0, preferably with m less than or equal to 4.0, more preferably with m equal to 2.0 and in that the so-called low conductivity layer is a zinc oxide layer doped with (m / p)% by weight of oxide of a doping element with p greater than or equal to 2, preferably with p greater than or equal to 3, more preferably with p greater than or equal to 4.
• p is preferably less than or equal to 15, more preferably p is less than or equal to 12.
• the inventors have determined that, surprisingly, such a transparent conductive substrate structure makes it possible to obtain improved electrical properties resulting in an increase in the mobility values of the order of at least a factor of 1.29 compared to transparent conductive substrates based on doped zinc oxide usually used.
• transparent conductive substrate is meant a substrate whose light absorption is at most 30%, preferably at most 20% in the wavelength range of visible light.
• a range of wavelengths ranging from wavelengths of near-infrared radiation to those of far-ultraviolet radiation may also define the range of transparency of the electrodes according to the invention.
• the range of transparency is defined by a range of wavelengths ranging from the near infrared to that of the visible light.
• the support on which is deposited the conductive coating of the transparent conductive substrate according to the invention is preferably rigid.
• the function of the support is to support and / or protect the electrode.
• the support preferably has a geometric thickness of at least 3.85 mm.
• geometric thickness By the terms “geometrical thickness", one understands the average physical thickness.
• the support comprises at least one total or partial surface structuring on at least one of the faces of the substrate.
• the method of structuring the support comprises at least one of the processes selected from etching, rolling and / or laser etching.
• the chemical etching of the support comprises at least the matting and / or etching (for example by etching with hydrofluoric acid of a silicosodocalcic glass).
• the rolling method comprises at least the step of structuring the support by the impression impression of a pattern using at least one printing roll.
• the support may be made of glass, rigid plastics material (for example: organic glass, polycarbonate) or flexible polymeric films (for example: butyral polyvinyl (PVB), polyethylene terephthalate (PET), copolymer of vinyl acetate and ethylene (EVA)).
• the support is preferably a glass sheet.
• the glasses are mineral or organic. The mineral glasses are preferred. Among these, the clear or colored silicosodocalcic glasses are preferred in the mass or on the surface. More preferably, they are extra clear silicosodocalcic glasses.
• extra clear designates a glass containing at most 0.020% by weight of the total Fe glass expressed in Fe 2 O 3 and preferably at most 0.015% by weight, the latter because of its low content of Fe oxide has a low light absorption.
• the use of the latter therefore makes it possible to obtain a higher transmission in the optoelectronic device incorporating it, more preferentially in the photovoltaic cell.
• the conductive coating based on doped zinc oxide deposited on the support consists of a stack of at least two layers of different electrical conductivity.
• the high conductivity layer is a layer based on zinc oxide doped with m% by weight of oxide of the doping element with m less than or equal to 6.0, preferably less than or equal to 4.0, more preferably equal to 2.0.
• the high conductivity layer is a layer based on zinc oxide doped with m% by weight of oxide of the doping element with m equal to 6.0, preferably with m equal to 4.0, plus preferentially with m equal to 2.0.
• the so-called low conductivity layer is a layer based on zinc oxide doped with (m / p)% by weight of oxide of the doping element with p greater than or equal to 2, preferably with p greater than or equal to 3 , more preferably with p greater than or equal to 4.
• the so-called low conductivity layer is a layer based on zinc oxide doped with (m / p)% by weight of oxide of the doping element with p equal to 2, preferably with p equal to 3, more preferably with p equal to 4.
• the doping elements used for the so-called high conductivity layer and the so-called low conductivity layer may be chemical in nature different, preferably, they are of the same nature.
• the geometric thickness of the conductive coating based on doped zinc oxide is between 400 nm and 1200 nm.
• the conductive coating has a surface texturing such that it corresponds to a RMS roughness value in the range of values from 55 nm to 200 nm, preferably at least equal to 55 nm. Such texturing is obtained after acid etching of the coating.
• the transparent conductive substrate according to the invention is such that the doping element is selected from Al and / or Ga and / or B.
• the doping element is Al and / or Ga. More preferably, the dopant is Al.
• the transparent conductive substrate according to the invention is such that the so-called high conductivity layer is a layer based on zinc oxide doped with m% by weight of aluminum oxide with m between 1.7 and 3.0 and in that the so-called low conductivity layer is a layer based on zinc oxide doped with (m / p)% by weight of aluminum oxide with m / p of between 0 , 2 and 1,2.
• the transparent conductive substrate is such that the doping element can be of different nature from one layer to another.
• the doping element can be of different nature from one layer to another.
• stacks such as AZO / GZO / AZO /.
• the transparent conductive substrate according to the invention is such that the geometric thickness of each layer constituting the conductive coating is between 35 and 200 nm, preferably between 50 and 150 nm.
• the transparent conductive substrate is such that the conductive coating comprises a so-called high conductivity layer-so-called low conductivity layer stack, said stack being reproduced n times, with n between 2 and 10, preferably with n between 3 and 10, more preferably with n between 5 and 7, most preferably with n equal to 6.
• n between x and y is understood to mean the fact that n can be equal to any natural integer between the natural integers x and y, these integers x and y being included.
• the transparent conductive substrate is such that the conductive coating comprises a so-called high conductivity layer-so-called low conductivity layer stack, said stack being reproduced n times, with n being between 2 and 10, preferably with n between 3 and 10, more preferably with n between 5 and 7, most preferably with n equal to 6, the so-called high conductivity layer being, with respect to the support, the layer closest to the so-called layer stack of high conductivity-so-called low conductivity layer.
• the transparent conductive substrate according to the invention is such that the conductive coating comprises a so-called low-conductivity so-called high conductivity layer stack, said stack being reproduced n times, with n being between 2 and 10, preferably with n between 3 and 10, more preferably with n between 5 and 7, most preferably with n equal to 6, the so-called low conductivity layer being with respect to the support, the layer closest to the stacking conductivity layer low-layer so-called high conductivity.
• the transparent conductive substrate according to the invention is such that the conductive coating comprises a buffer layer based on zinc oxide doped with Al at q% by weight of aluminum oxide with q between 0.5 and 4.0, preferably with q equal to 2.0, said buffer layer being the layer constituting the conductive coating furthest away from the support, the geometrical thickness of the buffer layer being between 100 nm to 500 nm, preferably between 100 nm to 400 nm.
• the buffer layer advantageously makes it possible to circumscribe the acid attack making it possible to texturize the surface of the conductive coating to this single buffer layer, said buffer layer having a RMS roughness value in the range of values ranging from 55 nm to 200 nm. after texturing, preferably of the order of 55 nm.
• the transparent conductive substrate according to the invention is such that the first layer or the last constituting the conductive coating may be of different doping rate.
• the transparent conductive substrate according to the invention is such that the conductive coating has a roughness value R.M.S. in the range of values from 55 nm to 200 nm.
• This roughness R.M.S. quantifies on average the height of the peaks and troughs of roughness, compared to the average height.
• the apparatus usually used to obtain these measurements is the Atomic Force Microscope (AFM).
• the roughness R.M.S. Root Mean Square
• the transparent conductive substrate according to the invention is such that the conductive coating comprises a barrier layer, said barrier layer being the layer of conductive coating closest to the support.
• the barrier layer makes it possible in particular to protect the optoelectronic device against any migration pollution of alkalis coming from the support, for example of silicosodocalcic glass, and therefore an extension of the service life of the device.
• the barrier layer comprises at least one compound selected from:
• titanium oxide zirconium oxide, aluminum oxide, yttrium oxide and the mixture of at least two of them;
• the barrier layer has a thickness between 50 nm and 300 nm.
• the transparent conductive substrate according to the invention is such that it comprises successively from the support: a so-called layer of high conductivity, said layer being based on zinc oxide doped with m% oxide weight of the doping element with m less than or equal to 6, preferably m less than or equal to 4, more preferably with m equal to 2, a so-called low conductivity layer, said layer being based on zinc oxide doped at (m / p)% by weight of the oxide of the doping element with p greater than or equal to 2, preferably p greater than or equal to 3, more preferably with p greater than or equal to 4.
• n between 2 and 10
• n is between 3 and 10
• n is between 5 and 7, most preferably with n being equal to 6
• said stack having a roughness R.m.s. in the range of values from 55 nm to 200 nm, preferably equal to 55 nm.
• the transparent conductive substrate according to the invention is such that it comprises successively from the support:
• a so-called low conductivity layer said layer being based on zinc oxide doped with (m / p)% by weight of the oxide of the doping element with p greater than or equal to 2, preferably p greater than or equal to 3, more preferably with p greater than or equal to 4.
• a so-called high conductivity layer said layer being based on zinc oxide doped with m% by weight of oxide of the doping element with m less than or equal to 6, preferably m less than or equal to 4, more preferably with m equal to 2,
• n is between 2 and 10, preferably between 3 and 10, more preferably with n between 5 and 7, most preferably with n equal to 6, said stack having RMS roughness in the range of values from 55 nm to 200 nm, preferably equal to 55 nm.
• the transparent conductive substrate according to the invention is such that it comprises successively from the support:
• a so-called high conductivity layer on the support said layer being based on zinc oxide doped with m% by weight of oxide of the doping element with m less than or equal to 6, preferably m less than or equal to 4 , more preferably with m equal to 2,
• a so-called low conductivity layer said layer being based on zinc oxide doped with (m / p)% by weight of the oxide of the doping element with p greater than or equal to 2, preferably p greater than or equal to at 3, more preferably with p greater than or equal to 4.
• n is between 2 and 10, preferentially with n ranging from 3 to 10, more preferably with n between 5 and 7, more preferably with n equal to 6.
• the transparent conductive substrate according to the invention is such that it comprises successively from the support:
• a so-called low conductivity layer said layer being based on zinc oxide doped with (m / p)% by weight of the oxide of the doping element with p greater than or equal to 2, preferably p greater than or equal to at 3, more preferably with p greater than or equal to 4.
• a so-called high conductivity layer on the support said layer being based on zinc oxide doped with m% by weight of oxide of the doping element with m less than or equal to 6, preferably m less than or equal to 4 , more preferably with m equal to 2,
• n is between 2 and 10, preferably with n being between 3 and 10, more preferably with n between 5 and 7, more preferably with n being equal to 6.
• the embodiments of the transparent conductive substrate are not limited to the modes described above but may also result from a combination of two or more of them.
• the second subject of the invention concerns the process for manufacturing the transparent conductive substrate according to the invention.
• This substrate comprises a support and a conductive coating.
• the process for producing the transparent conductive substrate according to the invention is a method in which all the layers based on doped zinc oxide constituting the conductive coating are deposited on the support by a cathodic sputtering technique assisted by a field magnetic.
• the barrier layer can be deposited by any type of vacuum process, such methods are sputtering techniques, possibly assisted by a magnetic field, plasma deposition techniques, deposition techniques.
• CVD Chemical Vapor Deposition
• PVD Physical Vapor Deposition
• the conductive coating is deposited, it is etched by a chemical process using an acid solution at room temperature (of the order of 25 ° C) in order to give the conductive coating a value of RMS roughness in the range of values from 55 nm to 200 nm, preferably of the order of 55 nm.
• acidic solutions are dilute hydrochloric acid solutions (eg 0.5% by volume HCl).
• the method of manufacturing the transparent conductive substrate according to the invention is such that it comprises the following successive steps: Sputter deposition of a so-called high conductivity layer on the support, said layer being based on zinc oxide doped with m% by weight of oxide of the doping element with m less than or equal to 6, preferably m less than or equal to 4, more preferably with m equal to 2,
• the method of manufacturing the transparent conductive substrate according to the invention is such that it comprises the following successive steps:
• the method of manufacturing the transparent conductive substrate according to the invention is such that it comprises the following successive steps:
• Sputter deposition of a so-called high conductivity layer on the support said layer being based on zinc oxide doped with m% by weight of oxide of the doping element with m less than or equal to 6, preferably m less than or equal to 4, more preferably with m equal to 2,
• the method of manufacturing the transparent conductive substrate according to the invention is such that it comprises the following successive steps:
• Sputtering deposition of a so-called low conductivity layer on the support said layer being based on zinc oxide doped with (m / p)% by weight of the oxide of the doping element with p greater than or equal to at 2, preferably p greater than or equal to 3, more preferably with p greater than or equal to 4.
• Sputtering deposition of a so-called high conductivity layer said layer being based on zinc oxide doped with m% by weight of the oxide of the doping element with m less than or equal to 6, preferably m lower or equal to 4, more preferably with m equal to 2,
• n is between 2 and 10, preferably with n ranging from 3 to 10, more preferably with n between 5 and 7, most preferably with n equal to 6.
• the process for manufacturing the transparent conductive substrate according to the invention is such that it comprises between the deposition steps of the high-conductivity layer-layer stack. of low conductivity and the acid etching step, an additional step of sputter deposition of a layer of zinc oxide doped with q% by weight of aluminum oxide with q between 0.5 and 4 , 0, preferably with q equal to 2.0%, the thickness of the layer being between 100 nm and 500 nm, preferably between 100 nm and 400 nm, said layer being the buffer layer.
• the third object of the invention relates to an optoelectronic device comprising a transparent conductive substrate according to the invention. More particularly, the invention relates to an optoelectronic device as it is a photovoltaic cell.
• the transparent conductive substrate according to the invention will now be illustrated with the aid of the following figures.
• the figures show in a nonlimiting manner a number of structures of transparent conductive substrates, more particularly layer stack structures constituting the conductive coating included in the substrate according to the invention. These figures are purely illustrative and do not constitute a presentation at the scale of the structures.
• Fig. 1 Cross section of a transparent conductive substrate according to the invention, the substrate comprising a conductive coating consisting of a stack comprising 13 layers, 12 layers representing the alternating so-called high conductivity layer - low conductivity layer, the stack being surmounted by a buffer layer of the same thickness as alternate layers.
• Fig. 2 Cross-section of a transparent conductive substrate according to the invention, the substrate comprising a conductive coating consisting of a stack comprising 9 layers, 8 layers representing the alternating so-called layer of high conductivity - low conductivity layer, the stacking being surmounted by a buffer layer thicker than the alternating layers.
• Fig. 3 Cross-section of a transparent conductive substrate according to the invention, the substrate comprising a conductive coating consisting of a stack comprising 10 layers, 1 barrier layer, 8 layers representing the so-called high conductivity layer alternation - low conductivity layer the stack being surmounted by a thicker buffer layer than the alternating layers.
• Fig. 4 Schematic representation of the pilot line with which the transparent conductive substrate according to the invention has been manufactured.
• FIG. 1 represents an example of a stack constituting a transparent conductive substrate according to the invention.
• the transparent conductive substrate (1) has the following structure from the support (10):
• a stack comprising 12 layers representing the so-called high conductivity layer alternation (12) - low conductivity layer (13),
• the stack being surmounted by a buffer layer of the same thickness as the alternating layers (14)
• FIG. 2 represents an example of a stack constituting a transparent conductive substrate according to the invention.
• the conductive substrate transparent (1) has the following structure from the support (10):
• a stack comprising 8 layers representing the so-called high conductivity layer alternation (12) - low conductivity layer (13),
• the stack being surmounted by a buffer layer of the same thickness as the alternating layers (14)
• FIG. 3 represents an example of a stack constituting a transparent conductive substrate according to the invention.
• the transparent conductive substrate (1) has the following structure from the support (10):
• a stack comprising 8 layers representing the so-called high conductivity layer alternation (12) - low conductivity layer (13),
• Figure 4 schematically shows the pilot line with which the transparent conductive substrate according to the invention has been manufactured.
• This consists of an airlock (5), a heating zone (20) comprising a heating system (2) and a deposition zone (30) comprising two targets (3, 3 ') in ZnO doped.
• the distance 5 represents the distance separating the heating system and the target, this is of the order of 600 mm.
• the heating system has two infrared lamps.
• Table 1 shows two columns, the first column shows the various steps of the method of manufacturing a transparent conductive substrate according to the invention, the second column shows the speeds of moving the glass for each step of the method of manufacturing a transparent conductive substrate according to the invention.
• the deposit is from zinc oxide (ZnO) ceramic target doped with aluminum oxide (Al 2 O 3 ) according to different doping levels (% by weight).
• the sputtering power applied to the cathode is 2 kW.
• the sputtering gases are Ar and O 2 .
• O 2 is introduced in a very small percentage. By very low percentage is meant to denote a percentage between 0% and 0.07%.
• the deposition is carried out under a total pressure of the order of 0.53 Pascal.
• the conductive coating is manufactured using several successive deposits.
• the heating system (2) of the heating zone (20) is used to heat the glass at a temperature between 250 ° C and 400 ° C, preferably at a temperature of 350 ° C.
• the transparent conductive substrate according to the invention will be illustrated by a number of examples.
• Zinc oxide (ZnO) doped with aluminum is commonly abbreviated as AZO.
• the percentage by weight (%) of aluminum oxide (Al 2 O 3 ) is also presented.
• Table 2 shows the optical and electrical properties of a substrate according to the invention, Example 1, and two comparative examples not according to the invention, Examples 1R and 2R.
• Example 1 is a transparent conductive substrate constituted of a clear 3.85 mm thick silica-lime glass coated with alternating layers of AZO 0.5% by weight Al 2 O 3 and AZO 2.0 % by weight of Al 2 O 3 .
• the layer is composed of alternating AZO of different dopings. Except for the very first layer which measures about 35 nm in AZO 2.0% by weight of Al 2 O 3 , the other layers have a thickness of about 70 nm. This corresponds to a round trip under the cathode.
• the total thickness of the conductive coating is about 875 nm.
• Example 1R is a transparent conductive substrate not according to the invention consisting of a silicosodocalcic glass covered by a layer made solely of AZO 0.5% by weight of Al 2 O 3 having a thickness of the order of 700 nm.
• Example 2R is a transparent conductive substrate not according to the invention consisting of a silicosodocalcic glass covered by a layer made solely of AZO 2% by weight of Al 2 O 3 having a thickness of the order of 700 nm .
• the comparison of optical and electrical properties shows that:
• Example 2R ⁇ 2% Al 2 O 3 (example 2R) has a lower value (76.1%) than ⁇ 0.5% Al 2 O 3 (example 1R) (80, 1%).
• Example 1 has a slightly higher (80.8%) transmission at ⁇ -0.5% Al 2 O 3 . This can be explained by a slightly lower total thickness for Example 1. o The veil is very weak (0.4 to 0.9%) for the three examples
• Example 1 shows an intermediate resistance between the respective resistors of Example 1R and 2R.
• the mobility remains surprisingly high (34.3 cm 2 / Vs) (Example 1) compared to the mobilities measured on Comparative Examples 1R and 2R (20.5 and 24.9 cm 2 / Vs).
• Example 2R has a lower transmission value (80.6%) than Example 1 R (84.3%).
• Example 1 has an intermediate transmission (82.0%).
• the optical values as well as the haze were measured by an Ultra-Scan Pro spectrophotometer apparatus from the firm Hunterlab.
• the transmission values (TIM) take into account the wavelengths useful for the power generation of the photovoltaic cell (between 400 nm and 1050 nm for tandem cells).
• the measurement is carried out in a submerged cell: a liquid of refractive index intermediate between the TCO and the glass is placed during the measurement. This method of measurement is used when the veil is too important for a correct measurement (diffusion incident light). This measurement method makes it possible to avoid any loss of light as a result of the veil.
• the haze is defined according to ASTMD 10003, which defines the haze as the percentage of light passing through the substrate which is deflected from the incident light beam at an angle greater than 2.5 degrees on average.
• the haze can be measured by methods known in the art.
• the electrical properties were measured by the Hall probe method (4 points).
• Table 3 shows the optical and electrical properties of a substrate according to the invention, Example 1, and two comparative examples not in accordance with the invention, Examples 3R and 4R.
• the following table compares the stack targeted by the invention with commercial samples (VU (Example 3R) and AN14 (Example 4R) from AGC Solar). Unlike other deposits, the VU is deposited on an extra-clear glass. These commercial samples are made by the pyrolytic technique (CVD) and do not undergo acid attack.
• CVD pyrolytic technique
• Example 1 has a resistance per square lower than Examples 3R and 4R.
• an alternative contemplated by the invention is shown in FIG. 2. In this case, an alternation of low and high doping layers is overcome by a buffer layer of AZO generating an adequate microstructure of the TCO after acid attack.
• microstructures is obtained after acid attack of a layer of AZO 2% by weight of Al 2 O 3 , it would therefore have a more adequate light distribution
• suitable microstructure is meant the microstructures recommended in the articles of Kluth et al., Thin Solid Films, 442, (2003), 80, 5836; Berginski et al., J. Appl. Phys., 101, 074903 (2007) and Rech B. et al., Thin Solid Films, 511-512 (2006), 548.
• sufficient thickness is meant a thickness such that the buffer layer remains after attack.
• Such thicknesses correspond to buffer layer thickness values before acid attack ranging from 100 to 500 nm, preferably ranging from 100 to 400 nm. Furthermore, depending on the desired microstructure, the doping rate of the last layer can be adapted. AZO 2% by weight of aluminum oxide thus have a more adequate light distribution for a photovoltaic application.

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