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
  • H10F19/00—Integrated devices, or assemblies of multiple devices, comprising at least one photovoltaic cell covered by group H10F10/00, e.g. photovoltaic modules
  • H10F19/40—Integrated devices, or assemblies of multiple devices, comprising at least one photovoltaic cell covered by group H10F10/00, e.g. photovoltaic modules comprising photovoltaic cells in a mechanically stacked configuration
• • 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
  • H10F10/19—Photovoltaic cells having multiple potential barriers of different types, e.g. tandem cells having both PN and PIN junctions
• • 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
  • Y02E10/549—Organic PV cells

Definitions

• the present invention relates to a tandem photovoltaic cell with two terminals allowing conversion of the energy of light rays into electrical energy as well as a method of manufacturing such a tandem photovoltaic cell.
• tandem cells comprising a superposition of two photovoltaic cells with different absorption spectra have been developed.
• tandem cells Different configurations of tandem cells have been developed to allow the recovery of the electric currents produced and in particular tandem cells with two terminals in which the two cells are assembled in series.
• One of the difficulties of tandem cells with two terminals is therefore to obtain an assembly between the two photovoltaic cells allowing electrical conduction between the two cells while maximizing the transparency of the connection between the two photovoltaic cells.
• the two photovoltaic cells are stacked one on the other by "direct bonding", that is to say without additional intermediate layers.
• direct bonding the contact surfaces of the two cells must be treated so as to allow bonding between the two cells. This treatment requires significant means and in particular perfectly flat and non-rough surfaces, free of particles, and an atmosphere controlled in case surfaces require surface activation to promote bonding.
• the subject of the invention is a tandem photovoltaic cell with two terminals comprising:
• At least one front cell having a second light absorption spectrum associated with a second type of photons whose energy level is higher than the photons of the first type
• the thickness is such that the product of the thickness by the optical index is between 150 nm and 250 nm and configured to be arranged respectively in contact with the front cell and the rear cell,
• first and second layers of a second type based on a mesoporous transparent conductive flexible material whose pore diameter is less than 100 nm and whose optical index of refraction is less than 1.7, said first and second layers of a second type being configured to be placed respectively in contact with the first and second layers of the first type,
• a layer of a third type based on a conductive transparent flexible material whose optical index of refraction is less than 1.7 and placed between the first and the second layers of the second type and configured to allow adhesion between the first and second layers of the second type.
• the use of a plurality of transparent conductive layers with layers of a first type providing an antireflection function, layers of a second type providing refractive index contrast, mechanical adaptation (absorption of stresses) and absorption of any gases emitted during the bonding and of the layers of a third type to allow the adhesion of the layers of the second type makes it possible to obtain a bonding which does not require surface preparation while obtaining reduced optical losses.
• the refractive index contrast of the layers of a second type also makes it possible to obtain light trapping leading to an increase in the short-circuit current between the front cell and the rear cell and an increase in the circuit voltage opened in the upper cell thanks to the recycling of photons.
• the present invention also relates to a two-terminal tandem photovoltaic cell comprising:
• At least one front cell having a second light absorption spectrum associated with a second type of photons whose energy level is higher than the photons of the first type
• the thickness is such that the product of the thickness by the optical index is between 150 nm and 250 nm and configured to be arranged in contact with the rear cell and the front cell respectively,
• a layer of a second type based on a flexible transparent mesoporous conductive material whose pore diameter is less than 100 nm and whose optical index of refraction is less than 1.7, said layer of the second type being configured to allow adhesion between the first and second layers of the first type.
• the present invention also relates to a two-terminal tandem photovoltaic cell comprising:
• At least one front cell having a second light absorption spectrum associated with a second type of photons whose energy level is higher than the photons of the first type
• the thickness is such that the product of the thickness by the optical index is between 150 nm and 250 nm and configured to be arranged in contact with the rear cell and the front cell respectively,
• a layer of a third type based on a transparent conductive material whose optical index of refraction is less than 1.7 and placed between the first and second layers of the first type and configured to allow adhesion between the first and second layers of the first type.
• the first and the second layer of the first type have a contact resistance of less than 1 ⁇ .cm2 with the adjacent layers.
• the first and the second layer of the first type are formed by an indium-tin oxide (ITO) underlayer and a titanium oxide underlayer.
• ITO indium-tin oxide
• the mesoporous conductive transparent flexible material is tin oxide.
• the layer of the third type is deposited in the form of a thin layer of a metal whose oxide is a transparent conductive oxide, said metal being configured to be diffused and oxidized in the layers of the second type at low temperature ( ⁇ 400°C).
• the low temperature melting of the metal allows bonding by metal-metal or metal-ceramic brazing and then its oxidation makes it possible to obtain a transparent conductive layer.
• the layer of the third type comprises indium.
• the layer of the third type comprises a transparent conductive oxide configured to be deposited by a sol-gel route.
• the layer of the third type is produced based on a solution comprising nano-particles of transparent conductive oxide.
• the layer of the third type has a thickness of less than 40 nm and comprises a conductive polymer such as PEDOTPSS.
• the at least one front cell is a cell based on III-V elements, that is to say based on elements contained in the third and the fifth column of the periodic table of elements.
• the at least one front cell is a Perovskite-based cell.
• the at least one rear cell is a silicon-based cell.
• the layers of the first type have a thickness comprised between 80nm and 120nm and a refractive index greater than 2
• the layers of the second type have a thickness comprised between 250nm and 350nm and an optical index of refraction between 1.1 and 1.3
• the layer of the third type has a thickness between 15 and 45 nm and an optical index of refraction between 1.3 and 1.5.
• the present invention also relates to a method of manufacturing a two-terminal tandem photovoltaic cell comprising:
• At least one front cell having a second light absorption spectrum associated with a second type of photons whose energy level is higher than the photons of the first type
• a layer of a third type comprising a transparent conductive material whose refractive optical index is less than 1.7 and a thin layer of a metal whose oxide is a transparent conductive oxide, the manufacturing method comprising the diffusion and oxidation of the metal of the layer of the third type in the layers of the second type.
• the various layers and cells of the tandem photovoltaic cell are assembled by deposition, in particular deposition by coating by centrifugation or coating by immersion (dip coating), and/or by spraying (spary coating) and/ or lamination.
• FIG 1 represents a schematic view of the different layers of a tandem cell according to a first embodiment of the present invention
• FIG.2 represents a schematic view of the different layers of a tandem cell according to a second embodiment of the present invention.
• FIG.3 represents a schematic view of the different layers of a tandem cell according to a third embodiment of the present invention.
• FIG.4 represents a schematic view of the different layers of a tandem cell according to a first variant embodiment of the present invention
• FIG.5 represents a schematic view of the different layers of a tandem cell according to a second variant embodiment of the present invention.
• FIG.6 represents a flowchart of the manufacturing steps of a tandem cell associated with the first embodiment of the present invention
• FIG.7 represents a flowchart of the manufacturing steps of a tandem cell associated with the second embodiment of the present invention
• FIG.8 represents a flowchart of the manufacturing steps of a tandem cell associated with the third embodiment of the present invention.
• FIG.9 represents a schematic view of the different sub-layers of a front cell according to an embodiment of the present invention.
• FIG. 1 represents a diagram of a first embodiment of a tandem photovoltaic cell 1 with two terminals, a first terminal 3a and a second terminal 3b.
• the tandem photovoltaic cell 1 comprises a rear cell 5 associated with the first terminal 3a.
• the rear cell 5 has a first light absorption spectrum associated with a first type of photons corresponding for example to the red spectrum of light.
• the rear cell 5 is for example a cell based on silicon or a cell based on III-V elements, that is to say based on elements contained in the third and fifth column of the periodic table of elements. .
• the tandem photovoltaic cell 1 also includes a front cell 7 associated with the second terminal 3b.
• the front cell 7 has a second light absorption spectrum associated with a second type of photons which are more energetic than the photons of the first type corresponding for example to the blue spectrum of light.
• the front cell 7 is for example a cell based on III-V elements or based on Perovskite.
• the tandem photovoltaic cell 1 also comprises a plurality of transparent conductive layers 10 (“transparent conductive layers (TCL)” in English) ensuring the bonding between the front cell 7 and the rear cell 5.
• TCL transparent conductive layers
• the transparency of these layers is necessary in the range 700nm-1200nm. By transparency, we mean that least 90% of the light is transmitted.
• the total resistance of the plurality of transparent conductive layers 10 is less than 10 .cm 2
• the stack of transparent conductive layers 10 comprises a first 11a and a second 11b layers of a first type configured to be arranged respectively in contact with the rear cell 5 and the front cell 7.
• the layers of the first type 11a, 11b have an optical index of refraction denoted n greater than 1.8, for example an index n equal to or greater than 2.2 so as to limit optical reflections and form an anti-reflection layer.
• the thickness of layers of the first type 11a, 11b is such that the product of the thickness e by the optical index n is between 150 nm and 250 nm.
• the thickness of the layers of the first type 11a, 11b is for example approximately 100 nm.
• the layers of the first type 11a, 11b have a contact resistance of less than IQ.cm 2 so as to obtain a good ohmic contact.
• the layers of the first type 1 ia , 11b can be structured, in particular with nanostructures, in order to behave like a selective mirror to reflect the most energetic photons towards the front cell 7 and transmit the less energetic photons towards the rear cell 5 .
• the layers of the first type 1 la, 11b are for example formed by a first sub-layer 110a, 110b of tin oxide, in particular indium-tin oxide (“Indium-tin oxide (ITO)” in English ) whose thickness is less than 20 nm which can be deposited by sputtering and a second sub-layer 111a, 111b of titanium dioxide whose thickness is less than 100 nm which can be deposited by sol-gel.
• ITO indium-tin oxide
• the stack of transparent conductive layers 10 also comprises a first 13a and a second 13b layers of a second type configured to be arranged respectively in contact with the first 11a and the second 11b layers of the first type.
• the refractive optical index n of the first and second layers of the second type is less than 1.7, for example between 1.1 and 1.3.
• the difference in refractive optical index between the layers of the first type 11a and 11b and of the second type 13a and 13b can make it possible to obtain trapping of the light leading to an increase in the short-circuit current between the front cell 7 and the rear cell 5 and an increase in the open circuit voltage in the front cell 7 thanks to the recycling of photons (part of the electron-hole pairs formed by the absorption of photons at the level of the front cell 7 are recombined and generate new photons transmitted in all directions and can then be reabsorbed by the front cell 7 ).
• the thickness of the layers of the second type 13a, 13b is between 250 nm and 350 nm, for example 300 nm.
• the first 13a and the second 13b layers of the second type are made from a mesoporous transparent conductive flexible material whose pore diameter is less than 100 nm.
• the pores can be of different sizes making the material inhomogeneous.
• the use of a mesoporous material makes it very soft and flexible (the Young's modulus E is for example less than 100 Pa) to achieve conforming contact between the surfaces of the rear cell 5 and of the front cell 7 despite the possible presence of defects on these surfaces (roughness or nanoparticles).
• the presence of pores also makes it possible to allow the evacuation of the gases which may be trapped between the front cell 7 and the rear cell 5 during the manufacturing process of the tandem photovoltaic cell 1.
• the flexibility of the layers of the second type 13a, 13b makes it possible to at least partially absorb the mechanical stresses induced by coefficients different thermal expansion between the front cell 7 and the rear cell 5.
• the mesoporous material is for example made from tin oxide.
• the stack of transparent conductive layers 10 also comprises a layer of a third type 15 placed between the first 13a and the second 13b layers of the second type and configured to allow their adhesion.
• the layer of the third type 15 is based on a transparent conductive material whose optical index of refraction is less than 1.7, for example between 1.3 and 1.5.
• the layer of the third type 15 has for example a thickness of less than 40 nm, in particular 30 nm.
• Different embodiments can be envisaged for the layer of the third type 15.
• the layer of the third type 15 is for example obtained from a first and a second layer of the third type (each having for example a thickness of 20 nm) deposited for example by coating by centrifugation and then assembled to one another, for example by annealing.
• the layer of the third type 15 comprises a thin layer, or alternatively a network of nanoparticles, of a metal whose oxide is a transparent conductive oxide, for example indium, tin or zinc, said metal being configured to be diffused and oxidized in the layers of the second type 13a, 13b to allow the adhesion of the layers of the second type 13a, 13b between them.
• the thin layer or the network of nanoparticles is for example deposited on an already formed layer of transparent conductive oxide.
• the thin layer or network of nanoparticles can be sandwiched between two layers of transparent conductive oxide. Bonding is achieved by allowing the metal to diffuse into the layers of transparent conductive oxide. This diffusion is accompanied by oxidation of the metal which renders the layer of the third type transparent.
• the layer of the third type 15 comprises a transparent conductive oxide configured to be deposited by a sol-gel route.
• the transparent conductive oxide is for example titanium oxide or tin oxide.
• the layer of the third type 15 is produced based on a solution comprising nano-particles of transparent conductive oxide.
• the layer of the third type 15 comprises a conductive polymer such as PEDOT:PSS.
• the thickness of the conductive polymer layer may have a thickness of less than 40 nm, for example between 20 and 30 nm.
• the tandem photovoltaic cell 1 differs from the first embodiment described above in that the stack of transparent conductive layers 10 comprises only a first and a second layer of the first type 1 la and 11b as previously described and a layer of the second type 13 arranged between the first 11a and the second 11b layers of the first type and configured to ensure bonding between the layers of the first type 11a and 11b.
• Layer 13 of the second type is made from a transparent mesoporous conductive material whose pore diameter is less than 100 nm.
• the pores can be of different sizes making the material inhomogeneous.
• the mesoporous material is by example made from tin oxide.
• Layer 13 has for example a thickness comprised between 400 nm and 800 nm, in particular 600 nm.
• the tandem photovoltaic cell 1 differs from the first embodiment described previously by the fact that the stack of transparent conductive layers 10 comprises only a first and a second layer of the first type IIa and 11b as previously described and a layer of the third type 15 arranged between the first 11a and the second 11b layers of the first type and configured to ensure bonding between the layers of the first type 11a and 11b.
• the layer of the third type 15 comprises for example a conductive polymer such as PEDOT:PSS or other conductive and transparent polymers or other conductive and transparent (organic-inorganic) hybrid materials which can provide bonding.
• a conductive polymer such as PEDOT:PSS or other conductive and transparent polymers or other conductive and transparent (organic-inorganic) hybrid materials which can provide bonding.
• the layer of the third type 15 has for example a thickness comprised between 400 nm and 800 nm, in particular 600 nm.
• tandem photovoltaic cell 1 can comprise several front cells and/or several rear cells, the transparent conductive layers 10 then being arranged between the front cell(s) and the rear cell(s). These variants can be applied to the different embodiments described above from Figures 1 to 3.
• FIG. 4 represents a tandem photovoltaic cell 1 comprising two front cells denoted 7 and 7′ and a rear cell 5.
• the rear cell 5 is for example made from silicon.
• the first front cell 7 is for example made from III-V elements and the second front cell 7' is for example made from perovskite or other III-V elements.
• the two front cells 7, 7' are for example obtained by epitaxial growth.
• the use of two different front cells 7, 7' and of a rear cell 5 makes it possible to optimize the conversion of the light energy by reducing the losses by thermalization and by increasing the number of photons absorbed by the tandem photovoltaic cell 1
• the front cell 7 is configured to absorb more energetic photons than the front cell 7'.
• the front cell 7 is for example a cell based on III-V elements.
• the first rear cell 5 is for example a cell based on III-V elements and the second rear cell 5' is for example a cell based on of germanium.
• the two rear cells 5 and 5' are for example obtained by epitaxy. The use of two rear cells 5 and 5' makes it possible to optimize the conversion of light energy by reducing thermalization losses and increasing the number of photons absorbed by the tandem photovoltaic cell 1.
• tandem photovoltaic cell 1 with two terminals 3a and 3b comprising a plurality of transparent conductive layers 10 each having properties making it possible to obtain bonding between the front cell 7 and the rear cell 5 while limiting the electrical and optical losses.
• the mechanical properties of these transparent conductive layers 10 make it possible to obtain bonding without requiring a surface treatment of the front cell 7 or of the rear cell 5 or of requiring a controlled atmosphere to carry out the bonding.
• the transparent conductive layers 10 can make it possible, due to their optical properties, to obtain light trapping making it possible to further increase the efficiency of the tandem photovoltaic cell 1. d) Manufacturing process associated with the first mode of achievement
• FIG. 6 represents a flowchart of the steps of a method of manufacturing a two-terminal tandem cell associated with the first embodiment described from FIG. 1. This method of manufacturing corresponds to a particular embodiment but of other manufacturing methods can also be used to obtain such a two-terminal tandem cell.
• the first step 101 concerns the manufacture of a front cell 7.
• the front cell 7 is a cell based on III-V elements.
• the front cell is for example manufactured by molecular beam epitaxy and can be formed by a plurality of sub-layers as represented in FIG. 9.
• the front cell 7 comprises for example an n-doped GaAs growth substrate 51, a GalnP stop layer (whose thickness is example of 200 nm) doped n+ 52 (layers 51 and 52 which will be deleted later in the process), a GaAs contact layer (whose thickness is for example 200 nm) doped n+ 53 and an AlInP window layer (whose thickness is for example 25 nm) doped n+ 54.
• the pn junction is made with a layer of AlGaAs containing 25.5% aluminum (whose thickness is for example 2620 nm) 55.
• the front cell 7 also comprises a barrier layer (“back surface field (BSF)” in AlGaAs with 60% p+ doped aluminum (whose thickness is for example 75 nm) 56, a contact layer in AlGaAs to 30% aluminum (whose thickness is for example 100 nm) 57 and a thin protective protective layer in GaAs doped p++ (whose thickness is for example 10 nm) 58 which will be removed in a solution of citric acid before gluing.
• the BSF layer can be partially rough and/or nanostructured in order to improve the absorption of light in the front cell 7 while keeping the transmission of photons intended for the rear cell 5.
• the second step 102 concerns the manufacture of a rear cell 5.
• the rear cell 5 comprises a monocrystalline silicon substrate and an architecture of the TopCon type (“tunnel oxide passivated contact”) in which the structure is composed of a front contact layer in n-doped polycrystalline silicon (whose thickness is for example 100 nm) and a rear contact layer in p-doped polycrystalline silicon (whose thickness is for example 100 nm) .
• the contact layers are separated from the monocrystalline silicon substrate by a thin layer of SiOx.
• the front surface of the monocrystalline silicon substrate can be nanostructured for example with inverted pyramids in order to improve the absorption of light in the rear cell 5 made of silicon.
• the third step 103 concerns the deposition of a first 11a and a second 11b layers of the first type.
• the third step 103 comprises a first sub-step 1031 in which a layer 110b of 5 nm of tin oxide (“Indium tin oxide (ITO)” is deposited by cathodic sputtering on the rear face of the front cell 7 after 2 minutes of deoxidation in a 20% hydrochloric acid (HCl) solution and a second sub-step 1032 in which a 5nm layer 110a of tin oxide ("Indium tin oxide (ITO )” in English) on the front face of the rear cell 5 after deoxidation in a 10% hydrofluoric acid (HF) solution.
• the third step 103 also comprises a third sub-step 1033 in which two layers 11a and 111b of titanium dioxide (TiO2) are formed by a sol-gel process using a solution based on titanium isopropoxide.
• the fourth sub-step 1034 relates to the deposition of the first layer 11 la of titanium dioxide (whose thickness is for example 90 nm) on the front face of the rear cell 5 using a spinner (also called deposition by spin coating or "spin coating” in English).
• the layer formed is then calcined/crystallized via annealing (for example at a temperature of around 450°C).
• the fifth sub-step 1035 concerns the deposition of the second layer 111b of titanium dioxide (whose thickness is for example 90 nm) on the rear face of the front cell 7 using a spinner.
• the layer formed is then calcined/crystallized via annealing (for example at a temperature of around 450°C).
• the fourth step 104 concerns the deposition of a first 13a and a second 13b layers of the second type.
• the fourth step 104 includes cleaning the rear face of the sample obtained at the end of step 103 associated with the front cell 7 and the front face of the sample obtained at the end of step 103 associated to the rear cell 5 with demineralized water and the activation of these surfaces using nitrogen or oxygen plasma for 2 minutes.
• the layers 13a, 13b of the second type are formed by a layer of mesoporous tin oxide (SnOx) produced by the sol-gel route and deposited with a spinner ("spin-coating" in English) on activated surfaces.
• the sol-gel solution can be prepared from tin (II) chloride dihydrate and tin (V) chloride pentahydrate and the mesoporosity obtained using a structuring agent such as the hydrophilic nonionic surfactant Pluronic® F-127.
• the thickness of the mesoporous layers is for example about 300 nm.
• the fifth step 105 concerns the deposition of a first layer and a second layer 15 of the third type (intended to form a single layer 15 after bonding).
• the fifth step 105 includes cleaning the rear face of the sample obtained at the end of step 104 and associated with the front cell 7 and the front face of the sample obtained at the end of step 104 and associated with the rear cell 5 with water demineralised and the activation of these surfaces using nitrogen or oxygen plasma for 2 minutes.
• the layers 15 of the third type are formed from a mixture of PEDOT:PSS (Poly(3,4-ethylenedioxythiophene) polystyrene sulfonate), ethanol and PEGDE (poly(ethylene glycol) diglycidyl ether). and are deposited on the activated surfaces using a toumette.
• the layers 15 of the third type have for example a thickness of between 10 nm and 30 nm.
• the fifth step 105 also includes drying the layers 15 of the third type on a hot plate at 130° C. for 2 minutes.
• the sixth step 106 relates to the bonding of the two samples obtained after step 105, on the one hand the first sample comprising the rear cell 5 in silicon and on the other the second sample comprising the front cell 7 in III-V material.
• the sixth step 106 includes placing or fixing the first sample on a polytetrafluoroethylene (PTFE) plate.
• the second sample is then brought into contact with the first sample and then placed under a hydraulic press with an applied homogeneous pressure of approximately 40 kg/cm 2 and heated at 150° C. for 10 minutes. The temperature is then gradually lowered to ambient temperature and the system is left under the press for 1 hour.
• the PTFE plate is removed at the exit of the press.
• steps 105' and 106' replace steps 105 and 106.
• Step 105' comprises a metallic deposit of indium on the two layers 13a, 13b of the second type obtained in step 104.
• the indium layers each have, for example, a thickness of between 5 nm and 30 nm.
• Step 106' concerns the bonding of the two samples obtained after step 105, on the one hand the first sample comprising the rear cell 5 in silicon and on the other the second sample comprising the front cell 7 in III-V material.
• the sixth step 106 comprises placing or fixing the first sample on a polytetrafluoroethylene (PTFE) plate.
• the second sample is then brought into contact with the first sample then put under a hydraulic press and heated in order to form a transparent layer of indium or mixed oxide (indium-tin oxide) by diffusion and oxidation which ensures the bonding and electrical conduction.
• the seventh step 107 concerns the finishing of the tandem cell.
• the GaAs substrate of the front cell 7 is removed using a solution of 28% NH3 and 30% H2O2 (with a volume ratio of 1:4).
• the chemical etching stops selectively at the GalnP stop layer.
• the latter is removed using 37% hydrochloric acid (HCl) which gives access to the n+ GaAs contact layer.
• the contact 3b on the front face is then formed by a series of steps of lithography, evaporation and lift-off of a metal stack Ni/Au/Ge/Au/Ni/Au with a total thickness of 1200 nm.
• the n+ GaAs contact between the grid patterns is selectively etched in a solution of citric acid (Ig/mL), H2O2 with a volume ratio (5:1).
• the process continues with the mesa etching of the III-V material using a solution of H3PO4:H2O2:H2O (3:1:40 v/v), the reaction stops at the ITO layer.
• the etching of the intermediate layers (ITO, TiO2, PEDOT:PSS and of the rear cell is carried out by dry etching, up to 400nm in the silicon substrate to separate the adjacent solar cells.
• Ti/Ag/Au layers are then deposited on the rear face of the rear cell by evaporation after deoxidation by HF to form the rear contact 3a
• a bi-layer of 65 nm of Ta2O5 and 110 nm of MgF2 can be deposited on the front face to form an anti-reflection layer.
• FIG. 7 represents a flowchart of the steps of a method of manufacturing a tandem cell with two terminals associated with the second embodiment described from FIG. 2. This method of manufacturing corresponds to a particular embodiment but of other manufacturing methods can also be used to obtain such a two-terminal tandem cell.
• Steps 201 to 203 are identical to steps 101 to 103 of the manufacturing method associated with the first embodiment described starting from FIG. 6.
• the fourth step 204 concerns the formation of a first 13a and a second 13b layers of the second type (intended to form a single layer 13).
• the fourth step 204 includes cleaning the rear face of the sample obtained at the end of step 203 associated with the front cell 7 and the front face of the sample obtained at the end of step 203 associated the rear cell 5 with demineralized water and the activation of these surfaces using air plasma for 2 minutes.
• the layers 13a, 13b of the second type are formed by a layer of mesoporous tin oxide (SnOx) produced by the sol-gel route and deposited with a spin-coating on activated surfaces.
• SnOx mesoporous tin oxide
• the sol-gel solution can be prepared from tin (II) chloride dihydrate and tin (V) chloride pentahydrate and mesoporosity can be obtained using a structuring agent such as hydrophilic nonionic surfactant Pluronic® F-127.
• the thickness of the layers 13a, 13b of the second type is for example around 300 nm.
• the fourth step 204 also includes the activation of the surfaces of layers 13a, 13b of the second type by plasma process.
• Steps 205 and 206 are identical to steps 106 and 107 of the manufacturing method associated with the first embodiment described starting from FIG. 6. f) Manufacturing method associated with the third embodiment
• FIG. 8 represents a flowchart of the steps of a method of manufacturing a two-terminal tandem cell associated with the third embodiment described from FIG. 3. This method of manufacturing corresponds to a particular embodiment but of other manufacturing methods can also be used to obtain such a two-terminal tandem cell.
• Steps 301 to 303 are identical to steps 101 to 103 of the manufacturing method associated with the first embodiment described starting from FIG. 6.
• the fourth step 304 concerns the formation of a layer 15 of the third type.
• the fourth step 304 includes cleaning the rear face of the sample obtained at the end of step 303 associated with the front cell 7 and the front face of the sample obtained at the end of step 303 associated the rear cell 5 with demineralized water and the activation of these surfaces using air plasma for 2 minutes.
• the layer 15 of the third type is formed of a mixture of PEDOT:PSS (Poly (3,4-ethylenedioxythiophene) polystyrene sulfonate), ethanol and PEGDE (poly (ethylene glycol) diglycidyl ether) .
• PEDOT:PSS Poly (3,4-ethylenedioxythiophene) polystyrene sulfonate
• PEGDE poly (ethylene glycol) diglycidyl ether
• the fourth step 304 also includes drying the layers of the third type on a hot plate at 130°C for 2 minutes.
• the layers 15 of the third type each have, for example, a thickness of around 300 nm.
• Steps 305 and 306 are identical to steps 106 and 107 of the manufacturing method associated with the first embodiment described starting from FIG. 6.
• a tandem photovoltaic cell 1 with two terminals comprising at least one front cell 7, at least one rear cell 5 and a plurality of transparent conductive layers 10 whose mechanical properties make it possible to obtain effective bonding without requiring preparation of the surfaces of the rear 5 and front 7 cells nor of controlled atmosphere during bonding.
• the associated manufacturing processes are therefore simple to implement and make it possible to obtain two-terminal tandem cells with high efficiency for a limited cost price.
• these transparent conductive layers due to their optical properties, can make it possible to trap light and thus improve the efficiency of the tandem photovoltaic cell.

Landscapes

• Photovoltaic Devices (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=74592275

Family Applications (1)

Country Status (3)

Families Citing this family (1)

• 2020
  • 2020-12-24 FR FR2014115A patent/FR3118531B1/fr active Active
• 2021
  • 2021-12-16 EP EP21839942.6A patent/EP4268286A1/de active Pending
  • 2021-12-16 WO PCT/EP2021/086062 patent/WO2022136080A1/fr not_active Ceased

Also Published As

Similar Documents

Legal Events