Photovoltaic Module

Abstract

The present invention relates to a photovoltaic module, in particular to a photovoltaic module comprising several Organic Photovoltaic Cells (OPC).

Description

[Technical Field]

[0001] The present invention relates generally to photovoltaic cells and photovoltaic modules, and more particularly to photovoltaic modules comprising several organic photovoltaic cells (OPCs).

[0002] In the present invention, an organic photovoltaic cell is a photovoltaic cell in which at least the photovoltaic active layer is made of an organic material. [Background technology]

[0003] Photovoltaic modules that comprise organic photovoltaic cells represent a real interest in the photovoltaic field.In fact, the possibility of replacing inorganic semiconductors that are commonly used in photovoltaic cells, such as silicon, copper, indium, gallium, selenium, or cadmium telluride, increases the number of systems that can be produced and therefore the possibilities of use.The development of marketable photovoltaic modules that comprise several organic photovoltaic cells is currently a major challenge.

[0004] In recent years, the development of organic photovoltaic cells has progressed through the use of inkjet printing technology for their implementation (Reference 1, Reference 2). In 2014, the applicant developed a process for manufacturing photovoltaic cells using this technology to print some of the layers of these cells (Reference 3).

[0005] Typically, organic photovoltaic cells use two electrodes, a top electrode and a bottom electrode, at least one of which is semi-transparent to light and the other of which is metallic and reflective. These electrodes are adapted to collect the photogenerated charges of the photovoltaic active layer. A frequently used approach to prevent leakage current and improve the extraction of these photogenerated charges consists, inter alia, of inserting an interfacial layer between the photovoltaic active layer and each of the electrodes to facilitate the transfer of charges within the photovoltaic cell, the photogenerated charges being either electrons or holes (positive charges).

[0006] For example, a photovoltaic active layer can be composed of two organic materials, one of which is an electron donor and the other of which is an electron acceptor. For organic photovoltaic active layers, P3HT:PCBM is conventionally used (P3HT is the acronym for poly(3-hexylthiophene) and PCBM is [6,6]-phenyl-C 71 -methylbutanoate).

[0007] As shown in FIG. 1, in a conventional or conventionally structured photovoltaic cell 1 currently in use, the first interfacial layer 9 comprises, for example, a polymer blend of poly(3,4-ethylenedioxythiophene) and sodium poly(styrenesulfonate) (usually represented by the acronym PEDOT:PSS), and indium tin oxide 3 (Indium tin oxide) is used as the bottom electrode. The photovoltaic active layer 5 is formed on a layer of indium tin oxide (ITO), which serves as the anode here and is itself formed on a support. This indium tin oxide layer is made of a metal oxide that, in addition to conducting current, is relatively transparent from 350 nm down. This is the material most commonly used to collect holes in organic photovoltaic cells. A photovoltaic active layer 5, which may be based on P3HT:PCBM, for example, is formed on the first interfacial layer 9. A second interfacial layer 6 is formed on the photovoltaic active layer 5, which serves as the cathode here and is typically made of aluminum or silver if this layer is formed by inkjet printing. The two electrodes used in photovoltaic cells, the bottom electrode and the top electrode, must have certain properties to allow them to be incorporated into organic photovoltaic cells. On the one hand, both electrodes must have a sufficiently high conductivity to allow maximum charge collection. On the other hand, the transparency of the bottom electrode, i.e. generally the indium tin oxide layer, is also a fundamental property for increasing the number of photo-generated charges in the photovoltaic active layer.

[0008] Photovoltaic cells with an inverted structure are also available today. The main difference with respect to the conventional structure is that an interfacial layer of PEDOTT:PSS is located between the photovoltaic active layer and the top electrode, which in this case is the anode. In this configuration, the bottom electrode, an indium oxide layer, functions as the cathode. It should be noted that photovoltaic cells with an inverted structure have the advantage of better air stability than photovoltaic cells with a conventional structure, and also generally have higher conversion efficiencies.

[0009] For the purposes of this invention, the conversion efficiency of a photovoltaic cell is defined as the ratio between the maximum electrical power delivered by the cell and the incident light output for a given spectral distribution and spectral intensity.

[0010] Furthermore, the above-mentioned high conversion efficiency is not achieved when current state-of-the-art photovoltaic modules are exposed to external radiation, i.e., a light intensity of more than 2000 lux, in particular 100 mW / cm, which is equivalent to a light brightness approximately equal to 100,000 lux. 2 It should be noted that this is ensured for radiation under standard AM1.5 conditions, which corresponds to the light brightness of an exposure with a power of 1000 kJ / s. In particular, due to the large number of photogenerated charges, it is necessary to use a negative electrode with a very high electrical conductivity to ensure good collection of the photogenerated charges in the photovoltaic active layer, especially to minimize accumulation phenomena in the interface layers. This is why, in the case of an inverted structure, the top electrode (or anode) is usually opaque and made of silver. In this case, the conversion efficiency of laboratory-scale organic photovoltaics can reach values ​​of 15-17%.

[0011] In currently used inverted structure photovoltaic cells, the first interfacial layer between the bottom electrode and the photovoltaic active layer is made of zinc oxide (ZnO), titanium oxide (TiO x ), zinc oxide (AZO) or tin dioxide (SnO2) The layer contains nanoparticles based on cerium nitride.

[0012] However, although this first interfacial layer offers many advantages and interesting electronic properties, it also has a number of drawbacks: in fact, the availability of the oxides that make up this layer, the cost of the raw materials, the processes involved in its implementation and application to produce the layer, the amount of waste, especially toxic waste, generated during its implementation, and the expensive recycling means used to treat this waste are all notable drawbacks.

[0013] This is why some manufacturers are considering replacing the first inorganic interface layer with an organic interface layer (organic polymer or molecule).

[0014] However, the mobility of photogenerated charges in organic layers is generally very low (charge mobility in semiconducting polymers is much lower than that observed in silicon (1000 cm). 2 V -1 s -1 ), which is much lower than the charge mobility (approximately 1–15 cm) measured in molecular semiconductors. 2 V -1 s -1 It should be noted that the thickness of these organic interfacial layers is generally lower than that of the organic interfacial layers of the organic semiconductor layer, which has the effect of limiting their thickness to only a few tens of nanometers if the migration of photogenerated charges is not possible. However, the deposition techniques used do not allow continuous and uniform organic interfacial layers of such thickness to be deposited in a controlled manner.

[0015] Currently, the production of photovoltaic cells including a first organic interface layer is not only costly but also does not guarantee the production of photovoltaic cells with optimal performance, or at least sufficient performance to ensure long-term use. Summary of the Invention

[0016] The object of the present invention is to remedy the above-mentioned drawbacks.

[0017] More precisely, the object of the present invention is to propose a solution that allows the sustainable use of photovoltaic cells, which include a first organic interface layer that can be deposited by inkjet printing on the first bottom electrode, in a manufacturing process that is less expensive than that of the prior art. This first interface layer is uniform and has a small thickness (typically <5 nm). The small thickness of this first organic interface layer allows for high optical transparency and therefore efficient passage of photons to reach the photovoltaic active layer, as well as a significant reduction in raw material costs.

[0018] To this end, the present invention provides a transparent support; a bottom electrode overlying the support, the bottom electrode including a top surface and a bottom surface; a first interface layer, the first interface layer including an upper surface and a lower surface; and - a photovoltaic active layer; a second interface layer covering the photovoltaic active layer, the photovoltaic cell, wherein the first interfacial layer is an organic layer having a thickness of 2 to 5 nm and including amine groups on its lower surface in contact with the upper surface of the lower electrode; A photovoltaic cell is proposed, characterized in that the first interfacial layer is continuous, transparent and free of metal oxides.

[0019] In the present invention, an amine group having a lower surface in contact with the upper surface of the lower electrode is understood to be a polar organic compound derived from ammonia resulting from the replacement of one or more hydrogen atoms in the ammonia molecule with other substituents or radicals (alkyl or aryl). When one, two, or three hydrogen atoms are replaced, the amine is primary, secondary, or tertiary, respectively. Quaternary ammonium compounds are ammonia derivatives consisting of a nitrogen atom substituted with four alkyl groups.

[0020] The photovoltaic cell according to the present invention overcomes the problem associated with the effect of long-term exposure to light radiation in an indoor environment, manifested by variations in the photovoltaic cell output power that can be measured after illumination (commonly referred to as the "light soaking effect"), in particular because the first interface layer does not contain metal oxides that are the main cause of this effect. In the absence of this effect, the photovoltaic cell can be exposed to an indoor environment and operate under both sunlight and artificial radiation.

[0021] In fact, this effect is commonly observed in prior art inverted photovoltaic cells incorporating a first interfacial layer containing an oxide, particularly zinc oxide. Particularly in outdoor environments, this effect is reflected in the improvement of photovoltaic cell performance under solar radiation over time. In particular, photovoltaic cells currently in use and exposed to outdoor environments have been observed to gradually increase in performance over a period of time before approaching a limiting value. As a result, long-term lack of exposure to UV light leads to a decrease in performance, necessitating re-exposure to light to improve performance. However, in indoor environments where UV radiation is absent (LED-type lighting with visible light radiation), the "light soaking effect" only results in a continuous deterioration of photovoltaic cell performance over time.

[0022] In the present invention, solar radiation refers to all electromagnetic waves emitted by the sun, encompassing a wide range of wavelengths from ultraviolet (about 200 to about 380 nm) to infrared (about 780 to about 10,000 nm) and the visible range (about 380 to about 780 nm).

[0023] In the present invention, artificial radiation refers to exposure to illumination defined by a light spectrum that includes little or no ultraviolet radiation. Artificial radiation generally includes visible radiation (approximately 380 nm The wavelength of the light is approximately 780 nm.

[0024] In the present invention, a transparent support or layer is a support or layer defined by a transmission coefficient of 80% or more, preferably 85% or more, when exposed to radiation encompassing the light spectrum extending between 380 nm and 780 nm.

[0025] For example, the transparent substrate may be made of glass or a polymeric material, preferably selected from polyethylene terephthalate (commonly known by the acronym PET), polyethylene naphthalate (commonly known by the acronym PEN) or glass.

[0026] For example, the bottom electrode can be a layer of indium tin oxide, a layer based on silver nanowires, a composite layer consisting of a silver grid and highly conductive PEDOT:PSS, a layer of reduced graphene oxide or a layer of carbon nanotubes.

[0027] Note that the first interfacial layer is an electron transport layer and is located between the bottom electrode and the photovoltaic active layer.

[0028] The photovoltaic active layer is composed of a "donor" material consisting of a p-type semiconducting polymer and a fullerene. and an "acceptor" material, which may be an n-type fullerene derivative or an n-type non-fullerene derivative. For example, the photovoltaic active layer may be based on poly(thienol[3,4-b]-thiophene or PBDB-T-2F (donor):IO4Cl (acceptor), PffBT4T-2OD (donor):EH-IDTBR (acceptor), D18 (donor):Y6 (acceptor), PBDB-T-2F:poly[(2,6-(4,8-bis(5-(2-ethylhexyl-3-fluoro)thiophen-2-yl)-benzo[1,2-b:4,5-b']dithiophene))-alt-(5,5-(1',3'-di-2-thienyl-5',7'-bis(2-ethylhexyl)benzo[1',2'-c:4',5'-c']dithiophene)). thiophene)]-4,8-dione)], IO4Cl: 3,9-bis[5,6-dichloro-1H-indene-1,3(2H)dione]-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2',3'-d']-s-indaceno[1,2-b:5,6-b']dithiophene], PffBT4T-2OD: poly[(5,6-difluoro-2,1,3-benzothiadiazole-4,7-diyl)-alt-(3,3'''-di(2-octyldodecyl)-2,2',5',2'',5'',2'''-quaterthiophene-5,5'''-diyl)], EH-IDTBR: C 72 H 88 Methyl[6,6]-phenyl-C in combination with N6O2S8 71 The polymer may include a polymer blend containing hydroxybutanoate.

[0029] It should be noted that in the first case, the second interfacial layer is a hole transport layer and may be disposed between the photovoltaic active layer and the top electrode, while in the second case, the second interfacial layer may be the top electrode, in which case the second interfacial layer serves as an interface between the photovoltaic active layer and the environment outside the photovoltaic cell.

[0030] For example, the second interfacial layer may be a PEDOT:PSS layer.

[0031] It should be noted that the first interfacial layer is an organic layer with a thickness of 2-5 nm so as not to interfere with the absorption of photons from external light radiation into the photovoltaic active layer and to avoid high resistance (polymers and small organic molecules have low charge mobility, and therefore thicker layers have higher resistivity). Indeed, photogenerated charges in the photovoltaic active layer must longitudinally pass through the first interfacial layer before reaching the electrode; therefore, the thicker the first interfacial layer, the longer the distance the charges must travel and the greater the possibility of losing these charges through recombination phenomena.

[0032] In the present invention, the lower surface of the first interface layer refers to the surface that is in contact with the upper surface of the lower electrode.

[0033] In the present invention, the first interface layer not containing a metal oxide is made of zinc oxide (ZnO), titanium oxide (TiO x ), zinc oxide (AZO) or tin dioxide (SnO2).

[0034] Further, by way of example only, the inventors have used poly(9,9-bis(3'-(N,N-dimethyl)-N-ethylammonium-propyl-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)) dibromide (PFN-Br), polyethyleneamine (PEI), PEIE, poly[(9,9-bis(3'-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] dibromide (PFN-Br), Layers comprising a material selected from N,N'-bis(N,N-dimethylpropane-1-amine oxide)perylene-3,4,9,10-tetracarboxylic acid diimide (PDI-NO), or N,N'-bis{3-[3-(dimethylamino)propylamino]propyl}perylene-3,4,9,10-tetracarboxylic acid diimide (PDINN) can be mentioned as alternatives to currently used metal oxides.

[0035] Advantageously, it is preferable to optimize the interface between the first interfacial layer and the adjacent layer to ensure efficient transfer of photogenerated charges, so that the first interfacial layer may have an Rms roughness (Root Mean Square Roughness) of less than 5 nm, preferably between 2 nm and 5 nm.

[0036] Advantageously, the first interfacial layer may contain nitrogen.

[0037] Advantageously, the second interfacial layer may comprise a polymer blend of poly(3,4-ethylenedioxythiophene) and sodium poly(styrenesulfonate).

[0038] In a first variant of the particular embodiment, the photovoltaic cell may further comprise a top electrode covering the second interface layer.

[0039] As an example, this top electrode can be a reflective metal electrode made of, for example, silver.

[0040] In a second variation of the particular embodiment, the second interfacial layer comprising a polymer blend of poly(3,4-ethylenedioxythiophene) and sodium poly(styrenesulfonate) can be the top electrode.

[0041] According to this second variant of the particular embodiment, the second interface layer may preferably be continuous and have a fibrous structure and an average thickness of 100 nm to 400 nm. Under these conditions, the second interface layer may have an electrical resistivity of 50 to 150 ohms / square.

[0042] In the present invention, a continuous layer is a layer that does not contain holes (the entire surface of the layer is covered by the interfacial layer material).

[0043] In the present invention, fibrous structure refers to the specific structuring of the layer on a nanometer scale by forming PEDOT:PSS fibers. The conductive PEDOT:PSS fibers are well interpenetrated between themselves, ensuring the continuity of the material and thus facilitating charge transport within the layer. That is, there is less resistance to charge transport within the layer, thus improving the conductivity of the layer.

[0044] This second variant ensures a considerable service life of the photovoltaic cell under artificial radiation. The second variant also has the advantage of ensuring the operation of the organic photovoltaic cell under artificial radiation, by eliminating the need for exposure to solar radiation, and in particular to ultraviolet radiation.

[0045] According to one or the other of the two variants of the embodiment described above, the photovoltaic cell may be entirely organic.

[0046] In the present invention, a fully organic photovoltaic cell is a photovoltaic cell in which each of its constituent layers, except for the substrate, is essentially organic and may contain, in addition to carbon, an essential component of organic materials, the elements hydrogen (H), oxygen (O), nitrogen (N), phosphorus (P), sulfur (S), and iron (Fe).

[0047] Advantageously, the photovoltaic cell comprises a first interface layer obtained by digital inkjet printing onto the lower electrode of an organic ink composition having a viscosity of 2 to 50 mPa.s at 20°C, said first interface layer comprising: - 0.1 wt % to 0.5 wt %, based on the total weight of the ink composition, of at least one organic polymer or organic molecule, the organic polymer or organic molecule containing an amine group and soluble in a polar solvent; 2 wt % to 10 wt % of an additive based on the total weight of the ink composition; and 80% to 90% by weight of one or more polar solvents, based on the total weight of the ink composition; and 1 wt % to 5 wt % of water based on the total weight of the ink composition.

[0048] The present invention also provides a photovoltaic module comprising at least two photovoltaic cells according to any one of the two variants of the aforementioned embodiments, namely a first photovoltaic cell and a second photovoltaic cell, wherein the upper electrode of the first photovoltaic cell is in contact with the lower electrode of the second photovoltaic cell.

[0049] The photovoltaic module according to the invention has the advantage that it performs well when exposed to light levels between 5000 lux and 10,000 lux, which allows it to operate under combined lighting conditions, i.e. sunlight or artificial radiation.

[0050] The photovoltaic modules according to the invention have high stability under accelerated aging in artificial light.

[0051] Photovoltaic modules according to the present invention exhibit high stability under accelerated aging in artificial light emitted by LEDs due to the fact that the first interfacial layer used according to the present invention is organic and therefore insensitive to UV radiation (no "light soaking" effect). Unlike metal oxide-based interfacial layers (commonly used in OPVs), the absence of UV does not prevent the operation of such first interfacial layers, which require UV activation to make the layer functional. In fact, the absence of UV generally leads to a significant degradation of performance over time for metal oxide-based interfacial layers.

[0052] The present invention also provides an organic ink composition that can be applied by digital inkjet printing to the bottom electrode of the above-described photovoltaic cell to form a first interface layer, the organic ink having a viscosity of 2 to 50 mPa.s at 20°C, and the first interface layer comprising: - 0.1 wt % to 0.5 wt % of at least one organic polymer or molecule, based on the total weight of the ink composition, the organic polymer or the organic molecule containing an amine group and being soluble in a polar solvent; 2% by weight to 10% by weight of an additive, based on the total weight of the ink composition; - 80% to 90% by weight of one or more polar solvents based on the total weight of the ink composition With a medium, and 1 wt % to 5 wt % of water based on the total weight of the ink composition.

[0053] Advantageously, the organic ink has a viscosity at 20°C of 2 to 50 mPa.s, preferably 2 to 20 mPa.s, even more preferably 7 to 12 mPa.s.

[0054] It is noted that such compositions are significantly more stable than metal oxide nanoparticle-based inks commonly used in the prior art to form interfacial layers in photovoltaic cells.

[0055] In particular, the inks according to the present invention also have the advantage that they do not undergo aggregation or phase separation for several hours or even days (at least 2 hours), which ensures a stable printing process without nozzle loss. Furthermore, the ink compositions allow nozzle open times of more than 5 minutes, or even more than 10 minutes, thus avoiding rapid nozzle clogging during the inkjet printing stage.

[0056] Furthermore, the present compositions have the advantage of low cost, since organic polymers and organic molecules are cheaper than metal oxides and their use concentrations are lower than the latter.

[0057] Furthermore, this composition allows for the printing of complete, uniform layers with well-defined edges, 2-5 nm thick, with a roughness of <2 nm, by digital inkjet printing, avoiding the problems associated with the use of metal oxides, particularly those that can arise from the effects of long-term exposure to optical radiation. This stable composition is formulated for digital inkjet printing using conventional, non-toxic solvents, allowing the composition to be deposited in ambient air.

[0058] In particular, organic polymers and molecules have the advantage of being insensitive to UV light, which is related to their inherent properties that differ from those of metal oxide nanoparticles.

[0059] Indeed, conventional organic photovoltaic cells containing a metal oxide electron transport layer (e.g., zinc oxide or titanium oxide) generally require exposure to UV light to form ohmic contacts between the metal oxide and other layers (the photovoltaic active layer and the electrodes). The nature of the bond between the organic intermediate layer and the bottom electrode (ITO) facilitates the formation of ohmic contacts without exposure to UV light, thus reducing damage to the organic photovoltaic cell resulting from such exposure.

[0060] Additives can be used here to solubilize organic polymers or molecules, and have a high evaporation temperature to prevent nozzle clogging and improve ink viscosity. Materials commonly used for inorganic interface layers (such as metal oxides) are soluble in certain solvents, typically highly volatile alcohols, which are undesirable for inkjet printing. Organic materials such as polymers or molecules can be soluble in a wide variety of solvents, providing more options for avoiding nozzle clogging and improving ink viscosity. Examples of additives include ethylene glycol, diethylene glycol, and glycerol.

[0061] Advantageously, the organic polymer or molecule may comprise a nitrogen-containing compound, preferably an amine compound, more preferably a primary amine group, a secondary amine group, or a tertiary amine group. The amine compound may further comprise an acyclic group (where the nitrogen atom is bonded to one or more alkyl groups), an alicyclic group (where the nitrogen atom is bonded to a non-aromatic ring), an aromatic group (where the nitrogen atom is bonded to an aromatic ring), and / or a heterocyclic group (where the nitrogen atom is bonded to a ring that may or may not be aromatic).

[0062] Advantageously, non-toxic solvents such as alcohol or water are good for polymers or organic molecules. Thus, the one or more solvents may be selected from ethanol, isopropyl alcohol, hexanol, terpineol, ethylene glycol, deionized water, phosphate buffered saline, butanol, diethylene glycol, glycerol.

[0063] Advantageously, the intermediate layer comprises an electron donating compound, preferably a nitrogen-, phosphorus-, and / or sulfur-containing compound.

[0064] Advantageously, the organic polymer or the organic molecule may be chosen from poly(9,9-bis(3'-(N,N-dimethyl)-N-ethylammonium-propyl-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)) dibromide (PFN-Br), polyethyleneimine (PEI), PEIE (polyethyleneimine ethoxylate), poly[(9,9-bis(3'-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] (PFN), N,N'-bis(N,N-dimethylpropane-1-amine oxide)perylene-3,4,9,10-tetracarboxylic acid diimide (PDI-NO), or N,N'-bis{3-[3-(dimethylamino)propylamino]propyl}perylene-3,4,9,10-tetracarboxylic acid diimide (PDINN).

[0065] The present invention has the advantage of overcoming the problems associated with the use of a lower electrode (preferably based on ITO, a material with a load power equal to 4.7 eV) that constitutes a barrier to the flow of charges from the photovoltaic active layer to the layer of the lower electrode. The metal oxide-free first organic layer reduces the energy barrier between the photovoltaic active layer and the layer of the lower electrode by lowering the load power of the lower electrode. The end result is an ohmic contact, rather than a Schottky contact, which is favorable for charge collection, especially electron collection. In particular, according to the present invention, the adsorption of the metal oxide-free first organic layer is due to the transfer of charges, especially protons, from the hydroxyl groups to the amine groups.

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[0066] Advantageously, the second layer of the bottom electrode may have a thickness of 2 to 5 nm and may comprise amine groups on its lower surface in contact with the upper surface of the first layer of the bottom electrode.

[0067] Advantageously, the organic polymer or molecule may contain nitrogen.

[0068] The present invention further provides a method for manufacturing a photovoltaic cell, the method comprising the steps of: a) providing a support; b) forming a lower electrode on the support; c) forming on the bottom electrode a first organic interface layer comprising a bottom surface comprising amine groups in contact with the bottom electrode, the first interface layer having a thickness of 2-5 nm, being continuous, transparent, free of metal oxides and obtainable after digital inkjet printing of the ink composition described above; d) forming a photovoltaic active layer on the first interfacial layer; e) forming a second interfacial layer on the photovoltaic active layer; The process proposes a method for producing a photovoltaic cell, characterized in that steps b), c), d), and e) are each carried out by depositing an ink composition by digital inkjet printing followed by a heat treatment, and the ink composition used in step c) comprises a mixture based on organic molecules soluble in a polar solvent.

[0069] Advantageously, the present invention allows for the production of photovoltaic cells comprising a first interfacial layer from an ink composition by digital inkjet printing. The composition is preferably based on non-toxic solvents and metal oxide-free organic materials known to those skilled in the art so that it can be deposited in ambient air by digital inkjet printing. As a result, step c) of forming the first organic interfacial layer is easy to implement, since it eliminates the need to use metal oxide-based interfacial layers, which require special precautions when used in a standard environment (ambient air).

[0070] Advantageously, the preformed support and layers are not modified in step c), and the heat treatment in step c) can therefore be an annealing treatment carried out at a temperature between 70°C and 130°C for a duration between 1 minute and 5 minutes.

[0071] Advantageously, the wettability of the composition from which the first organic interface layer is derived may be compatible with flexible substrates, preferably polyethylene terephthalate, to facilitate the formation of continuous films with well-defined edges, for example, by digital inkjet printing.

[0072] Further advantages and features of the present invention will become apparent from the following description, taken in conjunction with the accompanying drawings and the following examples. [Brief explanation of the drawings]

[0073] [Figure 1] 1 shows a schematic cross-sectional view of a photovoltaic cell with a conventional structure. [Figure 2] 1 shows a schematic cross-sectional view of a photovoltaic module 10 comprising photovoltaic cells 21 and 22 according to a particular embodiment of the present invention. [Example]

[0074] FIG. 1 is described in the summary of the prior art above, while FIG. 2 is described in more detail in the following examples which illustrate the invention without limiting its scope.

[0075] product

[0076] Support 20 in PET or glass,

[0077] Washing solvent:

[0078] For rigid glass supports, deionized water, acetone, ethanol, isopropanol, and

[0079] For flexible substrates, cleaning is not required as with rigid substrates, as the flexible substrate is protected by a plastic film.

[0080] A first ITO-based bottom electrode 210 already deposited on the support 20 of the photovoltaic cell 21 and a first ITO-based bottom electrode 220 already deposited on the support 20 of the photovoltaic cell 22, both of which are commercially available from Addev Materials Micel (France).

[0081] A first ink composition E11 for producing a first organic interface layer 221 including a lower surface including amine groups in contact with a discontinuous bottom electrode (ITO) such that the bottom electrode is partially covered by the first interface layer 211 of the photovoltaic cells 21 and 22 of the photovoltaic module of Figure 2. ○Ink E11 is first solvent 1: butanol in a mass concentration approximately equal to 91.094% relative to the total weight of ink E11; second solvent 2: deionized water at a concentration of about 3.124% by weight relative to the total weight of ink E11; Additive: ethylene glycol at a concentration of about 5.563% by weight based on the total weight of the E11 ink; - E11 PEI at a concentration of about 0.219 wt. % based on the total weight of the ink. Solvents, additives and PEI are commercially available from Merck®.

[0082] A second ink composition E20 for making the photovoltaic active layers 212 and 222 of the photovoltaic cells 21 and 22 of the photovoltaic module of FIG. The ink E20 for producing the photovoltaic active layer 212 of the photovoltaic cell 21 is -[6,6]-phenyl-C 71 E21 polymer blend of methyl butanoate (commercially available under the trade name PC70BM from Nano-C®) and poly(thienol[3,4-b]-thiophene (commercially available under the trade name PV2000 from Raynergy Tek®)), O-xylene (ortho-xylene of formula C6H4(CH3)2) as solvent, - Tetralin (1,2,3,4-tetrahydronaphthalene) as an additive. The ink E20 for producing the photovoltaic active layer 222 of the photovoltaic cell 22 is -[6,6]-phenyl-C 71 -E22 polymer blend of methyl butanoate (commercially available under the trade name PC70BM from Nano-C®) and poly(thienol[3,4-b]-thiophene (commercially available under the trade name PTB7-Th from 1-Materials), O-xylene (ortho-xylene of formula C6H4(CH3)2) as solvent, - Tetralin (1,2,3,4-tetrahydronaphthalene) as an additive. The PV2000 polymer of Blend E21 or the PTB7-Th polymer of Blend E22 is present in these second ink compositions in an amount of 10 mg / mL. The weight ratio of PV2000 polymer in blend E21 or PTB7-Th polymer in blend E22 to PC70BM is 1:1.5. The volume ratio of o-xylene solvent to tetralin additive is 97:3 in these second compositions. The second E20 ink composition is made by adding solvent and additives to the E21 or E22 polymer blend and maintaining the mixture on a hot plate at 80° C. with stirring at 700 RPM for 24 hours.

[0083] A second alternative E20 ink composition (E20-alt) for manufacturing the photovoltaic active layers 212 and 222 of the photovoltaic cells 21 and 22 of the photovoltaic module of FIG. ○E20-alt ink is -PC60BM:

[60] PCBM, 3'H-cyclopropa[1,9][5,6]fullerene-C60-Ih-3'-butanoic acid 3'-phenylmethyl ester, commercially available from Special Carbon Products, Inc. poly(thienol[3,4-b]-thiophene), commercially available under the trade name PV2000 from Raynergy Tek®; O-xylene (ortho-xylene of formula C6H4(CH3)2) as solvent, - Tetralin (1,2,3,4-tetrahydronaphthalene) as an additive. The PV2000 polymer is present in this second ink composition at 15 mg / mL. The weight ratio of PV2000 polymer to PC60BM polymer is 1:1.5. The volume ratio of o-xylene solvent to tetralin additive is 50:50 in these two second compositions. The second E20-alt ink composition is kept on a hot plate at 80° C. with stirring at 700 RPM for 24 hours.

[0084] A third ink composition E30 for making the top electrodes 213 and 223 (or anodes) of the photovoltaic cells 21 and 22 of the photovoltaic module of FIG. ○Ink E30 is PEDOT: PEDOT:PSS sold by Agfa® under the trade name IJ1005 or PEDOT:PSS sold by Agfa® under the trade name ORGACON S315, Triton X-100 (4-(1,1,3,3-tetramethylbutyl)phenyl-polyethylene glycol, formula Oct-CH-(OCHCH), marketed by Merck® as a detergent / surfactant xOH, x=9~10) and ethanediol (or ethylene glycol, formula HOCH2CH2OH), marketed by Merck®, glycerol (1,2,3-propanetriol or glycerin, formula HOCHCH(OH)CHOH) sold by Merck®, - Deionized water produced in a laboratory or marketed by PURELAB® classic under the water brand name ELGA®.

[0085] A third alternative E30 ink composition (E30-alt) for making the top electrodes 213 and 223 (or anodes) of the photovoltaic cells 21 and 22 of the photovoltaic module of FIG. ○E30-alt ink is PEDOT:PSS sold under the trade name IJ1005 by Agfa®, - Triton X-100 (formula Oct-C6H4-(OCH2CH2)) marketed by Merck® as a detergent / surface tension activator x OH, x=9-10 (4-(1,1,3,3-tetramethylbutyl)phenyl-polyethylene glycol).

[0086] test

[0087] Rms roughness measurement

[0088] These measurements were carried out using an atomic force microscope (Nanoscope III Multimode SPM from Brucker®, in intermittent contact mode (or "tapping mode"), using a hq:nsc15 tip marketed by MiKromasch® with a radius of curvature of 8 nm), and were carried out on various samples of photovoltaic cells according to the invention and according to the prior art.

[0089] Layer Thickness Measurement

[0090] The thickness of the printed layer was measured using a DektakXT tip profilometer commercially available from BRUKER, based on the scratches made by the cutter blade (thus leaving a groove equal to the thickness of the deposit). The measurement is based on a contact profilometer, which moves a sharp-tipped stylus vertically along the surface, applying a constant contact force and measuring the variation in location range by revealing any variations. The sample is placed on a plate that allows the sample to move over a selected distance at a given speed. The thickness values ​​given in this patent application correspond to the average of five measurements taken at six different times on the same stage of the sample. Before taking a measurement, it is necessary to define the length of the area to be scanned, the duration, the force of the stylus pressure, and the measurement range.

[0091] Electrical Resistivity Measurement

[0092] The measurements are performed using four tip techniques as follows: - the four tips are aligned away from the edge of the layer to be characterized, -These four tips are equidistant from each other, A current is generated between the outer tips by a current generator, while a voltage is measured between the inner tips. The ratio between the measured voltage and the current flowing through the sample provides the resistance of the section between the inner tips.

[0093] Viscosity measurement:

[0094] The viscosity of a fluid is reflected in the resistance of the fluid to deformation or relative sliding of its layers. For example, in the flow of a viscous fluid through a capillary tube, the velocity (v) of the molecules is greatest at the axis of the tube and decreases to zero at the wall, while relative sliding occurs between the layers, resulting in tangential friction forces. In a fluid, the tangential forces depend on the properties of the fluid and its flow regime.

[0095] The Ubbelohde viscometer is placed in an incubator maintained at a constant temperature (here, 25°C). The flow rate of a constant volume V is measured, defined by two reference marks (M1 and M2) on either side of a small reservoir surrounding the capillary tube.

[0096] Indoor photovoltaic performance measurements:

[0097] The study of module aging under permanent illumination is carried out using an indoor characterization bench. The characterization bench includes an opaque enclosure (to avoid external light) equipped with an LED light source (specifically, a Keithley 2450 source-meter) and a computer with a LabVIEW program for automated measurement of module performance (determination of photovoltaic parameters) at a defined frequency (e.g., 10 times per day). The photovoltaic modules are permanently illuminated by a light source with a light intensity of approximately 1000 lux, measured with a lux meter (specifically, a Chauvin Arnoux Ca 1110 lux meter), which is compatible with a wide variety of light sources, including LEDs and fluorescent lamps, up to 200,000 lux, in accordance with Class C of the standard NF C 42-710.

[0098] The light source used for indoor and performance measurements was a Philips LED panel 60 x 60 cm with an emission spectrum in the visible range. 2 It is -4385K.

[0099] Morphological characterization:

[0100] The surface shape was reproduced by AFM (Atomic Force Microscope) measurement, and TE The crystallinity of the material and the size of the nanoparticles present in the layer were verified by Transmission Electron Microscopy (M).

[0101] fill factor

[0102] Fill factor is the ratio between the maximum power and the product of the short circuit current and the open circuit voltage. It is generally expressed as a percentage.

[0103] Example 1: An example of an E11 ink composition for forming a first organic interface layer 211 on a layer of a bottom electrode 210 is obtained.

[0104] PEI is used to provide the E11 ink composition, the composition of which is detailed below.

[0105] The E11 ink formulation is prepared in two steps.

[0106] Step 1: Preparation of stock solution: -Weigh out 0.35 g of PEI (Intercalated Polymer) -Add 5 mL of ionized water to these 0.35 g of PEI Stir at -60°C for at least 4 hours to obtain a stock solution.

[0107] Step 2: Preparation of E11 ink formulation: -Take 250 μL of stock solution, -Add 9 mL of butanol, -Add 400 μL of ethylene glycol, The mixture is stirred at room temperature for 24 hours to give Formulation E11. - Filter the E11 formulation before printing using an AC filter with a cutoff of approximately 0.2 μm.

[0108] Example 2: An example of a second E20 ink composition for forming the photovoltaic active layer 212 is obtained.

[0109] Using PC70BM in combination with PV2000 or PC70BM in combination with PTB7-Th resulted in E201 and E202 ink compositions, respectively, the compositions of which are detailed in Table 1 below:

[0110] [Table 1]

[0111] Ink composition E201 is obtained as follows: 10 mg of PTB7-th are mixed with 15 mg of PC70BM in 1 milliliter of o-xylene and 60 microliters of tetralin (corresponding to a weight ratio of 1:1.5). The mixture is placed on a hot plate at 80° C. under magnetic stirring for 24 hours. -Before printing, the ink is filtered through a 0.45 micrometer AC filter. The printed layer is then thermally annealed on a hotplate at 85°C for 2 minutes.

[0112] The E202 ink composition is obtained as follows: - 10 mg of PV2000 are mixed with 15 mg of PC70BM in 1 milliliter of o-xylene and 60 microliters of tetralin (corresponding to a 1:1.5 mass ratio). The mixture is placed on a hot plate at 80° C. under magnetic stirring for 24 hours. - Prior to inkjet printing, the E142 ink is filtered through a 0.45 micrometer AC filter. After inkjet printing of E201 or E202, a photovoltaic active layer is obtained. Once printed, it is thermally annealed on a hotplate at 85°C for 2 minutes.

[0113] Example 3: An example of a second E20 ink composition for forming the photovoltaic active layer 212 is obtained.

[0114] PC60BM is used as the acceptor in combination with PV2000 as the donor to obtain the E203 ink composition detailed in Table 1 below. [Table 2]

[0115] The E203 ink composition is obtained as follows: - 15 mg of PV2000 are mixed with 22.5 mg of PC60BM in 0.5 mL of o-xylene and 0.5 mL of tetralin (corresponding to a weight ratio of 1:1.5). The mixture is placed on a hot plate at 80° C. under magnetic stirring for 24 hours. -Before printing, the ink is filtered using an AC filter with a cutoff of approximately 0.45 micrometers. After -E203 inkjet printing, a photovoltaic active layer is obtained, which, once printed, is thermally annealed on a hotplate at 85°C for 2 minutes.

[0116] Example 4: An example of a third ink composition E30 for making a layer of the top electrode 213 that is also the second interface layer is provided.

[0117] The third ink composition E30 for forming the layer of the upper electrode 213 is obtained as follows: - PEDOT:PSS was filtered through a 0.45 μm filter, - 500 μL of Triton X-100 (a) was mixed with 200 μL of ethylene glycol (b), 200 μL of glycerol (c), and 100 μL of ethanolamine (d) in 9 mL of deionized water (e); - the resulting mixture was stirred magnetically on a hotplate at 50°C for 30 minutes, then at room temperature for 20 minutes, - firstly, the filtered PEDOT:PSS is mixed with 30 μL of a mixture of the three additives in deionized water, after stirring, in the following proportions: 1 mL of PEDOT:PSS, and the mixture obtained (with PEDOT:PSS) is placed on a hotplate at room temperature under magnetic stirring for at least 1 hour; - The final E30 is degassed in an ultrasonic bath for 3-5 minutes before printing.

[0118] Depending on whether PEDOT:PSS IJ1005 or PEDOT:PEDOT:PSS ORGACON S315 is used, ink compositions E301 and E302 are obtained, respectively, the compositions of which are detailed in the following two Tables 2 and 3. [Table 3] [Table 4]

[0119] Example 5: An example of a third E30 ink composition for forming a layer of the top electrode 213 is obtained.

[0120] The third E303 ink composition for forming this top electrode 213 layer is obtained as follows: The PEDOT:PSS solution (IJ1005) was initially stored in a refrigerator and then filtered through a filter with a cutoff of approximately 0.45 μm. - 30 μL of Triton X-100 was mixed with 10 mL of the filtered PEDOT:PSS solution, The resulting mixture is stirred with a magnetic stirrer at room temperature for 16 hours. - The final E30 is degassed in an ultrasonic bath for 3-5 minutes before printing.

[0121] Example 6: Obtaining an example of a photovoltaic module according to the present invention

[0122] The C1 photovoltaic cell according to the present invention is manufactured by the following process: - Providing a transparent PET or glass support containing a first bottom electrode. A first organic interface layer derived from composition E11 of Example 1 is formed on the first bottom electrode. In particular, this layer is formed by digital inkjet printing of ink composition E11, followed by thermal annealing at 145°C for 3 minutes in a convection oven. The thickness of the first organic interface layer 211 printed on the layer of bottom electrode 210 is approximately 2-5 nm, and the RMS roughness is less than 2 nm. A photovoltaic active layer 212 is formed on the first organic interface layer 211 by digital inkjet printing using ink composition E203 from Example 3, followed by thermal annealing in a convection oven at 145° C. for 3 minutes. The thickness of the printed photovoltaic active layer 212 is about 350 nm and the RMS roughness is less than 5 nm. A top electrode 213 is formed on the photovoltaic active layer 212 by digital inkjet printing using ink composition E303 from Example 5, followed by thermal annealing in a convection oven at 145° C. for 3 minutes. The printed layer of the top electrode 213 has a thickness of about 500 nm and an RMS roughness of less than 10 nm.

[0123] The result of the fabrication process is, among other things, a C1A photovoltaic cell that includes a first continuous transparent interface layer that does not include a metal oxide interface layer according to an embodiment of the present invention.

[0124] Results and Comparison: Characterization of the C1 photovoltaic cell obtained in Example 5 and comparison with prior art photovoltaic cell examples.

[0125] Various photovoltaic cells according to the present invention and the prior art were characterized according to the above tests, and the results of those characterizations are shown in Table 4 below.

[0126] Two photovoltaic cells according to the prior art (C2A and C2B) were produced under the same conditions used to produce the C1 photovoltaic cell according to the invention.

[0127] The first C2A photovoltaic cell differs from the C1 photovoltaic cell by the presence of a lower electrode comprising an indium tin oxide layer and an interfacial layer based on a metal oxide, in particular AZO (aluminum doped ZnO), and the second photovoltaic cell C2B according to the prior art differs from the photovoltaic cell C1 according to the invention by the presence of a lower electrode comprising an indium tin oxide layer and an interfacial layer based on a metal oxide, in particular SnO2 (tin dioxide). AZO is marketed by Genesink and SnO2 is marketed by Avantama.

[0128] Prior art photovoltaic cells C2A and C2B were fabricated with an inverted structure having a photovoltaic active layer PV2000 and PC60BM and PEDOT:PSS as the top electrode, i.e., they have the same active layer and top electrode as in Example 5 according to the invention.

[0129] The C1 photovoltaic cell according to the present invention and the C2A and C2B photovoltaic cells according to the prior art were characterized under the same conditions and with the same light intensity using the same characterization bench described above. [Table 5]

[0130] The above table shows the photovoltaic parameters (voltage, current, maximum power and fill factor) measured under indoor LED lighting (1000 LUX (lux)) and clearly shows that the C1 photovoltaic cell achieves photovoltaic performance very close to, and in some cases better than, that of a cell made according to the prior art under the same conditions (same photovoltaic active layer and same electrodes (top and bottom)). The current generated by the cell according to the invention is of the same order of magnitude as the current generated by a cell made according to the prior art.

[0131] The fill factors obtained for cells produced according to the present invention are higher than those obtained for cells produced according to the prior art under the same conditions, indicating a better interface quality between this interfacial layer and the other layers (bottom electrode and active layer).

[0132] The photovoltaic performance measured with the C1 photovoltaic cell according to the invention is very encouraging and confirms the good functionality of the first interface layer according to the invention in the case of indoor applications (low light LED type lighting). References

[0133] Reference 1: Sharaf Sumaiya, Kamran Kardel, and Adel El-Shahat, "Organic Solar Cell by Inkjet Printing - An Overview." 53, Georgia, USA: Technologies, 2017, Vol. 5.

[0134] Reference 2: Peng, X., Yuan, J., Shen, S., Gao, M., Chesman, ASR, & Yin, H. (2017), "Perovskite and Organic Solar Cells Fabricated by Inkjet Printing: Progress and Prospects", Adv.Funct.Mater.2017, 1703704

[0135] Reference 3: European Patent Application No. 2960957 to DRACULA TECHNOLOGIES, filed June 25, 2015, published December 30, 2015.

Claims

1. A photocell, wherein the photocell is - A transparent support, - A lower electrode covering the support, wherein the lower electrode includes an upper surface and a lower surface, - A first interface layer, wherein the first interface layer includes an upper surface and a lower surface, - a photovoltaic active layer; - comprising at least a second interface layer covering the photovoltaic active layer, The photocell is such that the first interface layer has a thickness of 2 to 5 nm and is an organic layer containing an amine group on its lower surface that contacts the upper surface of the lower electrode, and A photocell characterized in that the first interface layer is continuous, transparent, and does not contain metal oxides.

2. The photocell according to claim 1, wherein the first interface layer has an Rms roughness of less than 5 nm.

3. The photocell according to claim 1, wherein the first interface layer contains nitrogen.

4. The photocell according to claim 1, wherein the second interface layer comprises a polymer blend of poly(3,4-ethylenedioxythiophene) and poly(styrenesulfonic acid) sodium.

5. The photocell according to claim 1, further comprising an upper electrode covering the second interface layer.

6. The photocell according to claim 1, wherein the second interface layer, which contains the polymer blend of poly(3,4-ethylenedioxythiophene) and poly(styrenesulfonic acid) sodium, is the upper electrode.

7. The photocell according to claim 6, wherein the second interface layer is continuous and has a fibrous structure and an average thickness of 100 nm to 400 nm.

8. The photocell according to claim 6, characterized in that it is completely organic.

9. The first interface layer comprises an organic ink composition having a viscosity of 2 to 50 mPa·s at 20°C. , obtained by digital inkjet printing on the lower electrode, the first interface layer is - At least one organic polymer or organic molecule in an amount of 0.1% to 0.5% by weight relative to the total weight of the ink composition, wherein the organic polymer or organic molecule contains an amine group and is soluble in a polar solvent, - Additives in an amount of 2% to 10% by weight relative to the total weight of the ink composition, - One or more polar solvents in an amount of 80% to 90% by weight relative to the total weight of the ink composition, - A photocell according to claim 1, comprising 1% to 5% by weight of water, based on the total weight of the ink composition.

10. The photocell according to claim 9, wherein the organic polymer or organic molecule is selected from poly(9,9-bis(3'-(N,N-dimethyl)-N-ethylammonium-propyl-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)) dibromide (PFN-Br), polyethyleneimine (PEI), PEIE, poly[(9,9-bis(3'-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)](PFN), N,N'-bis(N,N-dimethylpropane-1-amine oxide)perylene-3,4,9,10-tetracarboxylic acid diimide (PDI-NO), or N,N'-bis{3-[3-(dimethylamino)propylamino]propyl}perylene-3,4,9,10-tetracarboxylic acid diimide (PDINN).

11. The photocell according to claim 9, wherein the one or more solvents are selected from ethanol, isopropanol, hexanol, terpineol, ethylene glycol, deionized water, phosphate-buffered saline, butanol, diethylene glycol, and glycerol.

12. The photocell according to claim 9, wherein the organic polymer or the organic molecule contains nitrogen.

13. A photovoltaic module comprising at least two photocells according to claim 5, namely a first photocell and a second photocell, A photovoltaic module in which the upper electrode of the first photocell is in contact with the lower electrode of the second photocell.

14. A method for manufacturing a photocell, wherein the method is a) A step of providing a support, b) A step of forming a lower electrode on the support, c) A step of forming a first organic interface layer on the lower electrode, the first interface layer having a thickness of 2 to 5 nm, being continuous and transparent, and not containing metal oxides, the first organic interface layer having a lower surface containing amine groups in contact with the lower electrode, d) A step of forming a photovoltaic active layer on the first interface layer, e) A method for manufacturing a photocell, comprising the step of forming a second interface layer on the photovoltaic active layer.

15. The manufacturing method according to claim 14, wherein steps b), c), d), and e) are each carried out by depositing an ink composition by digital inkjet printing followed by heat treatment, and the ink composition used in step c) comprises a mixture based on organic molecules soluble in a polar solvent.

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