Organic transparent conductive electrode for replacement of the ITO electrode in indoor-compatible organic photovoltaic modules

Abstract

The present invention relates to a photovoltaic module comprising, inter alia, a lower electrode consisting of two layers: a first layer (210A) comprising a polymer blend of poly(3,4-ethylenedioxythiophene) and sodium poly(styrene sulfonate) covering the support and having an average thickness of between 50 nm and 150 nm and an organic fibrous structure, and a second layer (210B) based on an organic polymer or molecule covering said first layer, the lower electrode having a lower surface in contact with the support and an upper surface, and an upper electrode (212) comprising a polymer blend of poly(3,4-ethylenedioxythiophene) and sodium poly(styrene sulfonate) covering said photovoltaic active layer (211), said electrode being continuous and having an average thickness of between 100 nm and 400 nm and an organic fibrous structure.

Description

DESCRIPTION Title: Transparent organic conductive electrode for replacing ITO electrode in organic photovoltaic modules compatible with indoor environment Technical field of the invention

[0001] The invention relates generally to photovoltaic modules, and in particular to photovoltaic modules comprising several organic photovoltaic cells (usually designated by the English acronym OPC for “Organic Photovoltaic Cells”).

[0002] For the purposes of the present invention, the term organic photovoltaic cell means a photovoltaic cell of which at least the active layer is made of an organic material. Prior art

[0003] Photovoltaic modules comprising organic photovoltaic cells represent a real interest in the field of photovoltaics. Indeed, the possibility of substituting inorganic semiconductors generally used in photovoltaic cells, such as silicon, copper, indium, gallium, selenium, or cadmium telluride, makes it possible to increase the number of feasible systems and therefore the possibilities of use. The development of marketable photovoltaic modules comprising several organic photovoltaic cells currently represents a major challenge.

[0004] In recent years, the development of organic photovoltaic cells has evolved through the use of inkjet printing technology for their implementation. Moreover, in 2014 the Applicant developed a process for manufacturing photovoltaic cells using this technique for printing part of the layers of these cells. [3] .

[0005] Initially, many studies focused on the production of an interfacial layer by inkjet printing of an ink comprising a polymer blend of poly(3,4-ethylenedioxythiophene) and sodium poly(styrene-sulfonate), usually referred to by the acronym PEDOT:PSS. Subsequently, research in this field focused on inkjet printing of the photovoltaic active layer, which is usually composed of two organic materials, one an electron donor and the other an electron acceptor. For an active layer of organic nature, P3HT:PCBM is classically used (P3HT being the acronym for poly(3-hexylthiophene) and PCBM being the acronym for [6,6]-phenyl-C?i-methyl butanoate).

[0006] As illustrated in Figure 1, in a currently used normal or conventional structure photovoltaic cell 1, a first interfacial layer 9, for example made of PEDOT:PSS, is arranged on a layer of indium-tin oxide 3 (generally designated by the English acronym ITO for "Indium Tin Oxide") used as a lower electrode, serving here as an anode and is itself applied to a support. This layer of indium-tin oxide consists of a metal oxide which, in addition to conducting current, offers the property of being relatively transparent from 350 nm. It is the most commonly used material for collecting holes in the case of organic photovoltaic cells with normal structure.Above the first interfacial layer 9 is applied a photovoltaic active layer 5 which may for example be based on PsHTPCBM, and above this photovoltaic active layer 5 is applied a second interfacial layer 6 above which is applied an opaque upper electrode 7 usually made of aluminum, or silver when this layer is applied by inkjet printing, and which serves here as a cathode. The two electrodes, i.e. the lower electrode and the upper electrode, used in the photovoltaic cell must have specific properties to allow their integration into organic photovoltaic cells. On the one hand, the two electrodes must have conductivities high enough to allow the collection of a maximum of charges.On the other hand, the transparency of the lower electrode, i.e. generally the indium-tin oxide layer, is also a fundamental characteristic to increase the number of photo-generated charges in the active layer.

[0007] There are also currently photovoltaic cells with an inverse structure. The major difference compared to the classic structure is that the PEDOT:PSS interfacial layer is located between the active layer and the upper electrode, which is here the anode. In this configuration, the indium oxide layer, which is then assimilated to the lower electrode, serves as the cathode and therefore it will collect the electrons. It should be noted that photovoltaic cells with an inverse structure have the advantage of having better stability in air than cells photovoltaic systems with a conventional structure, and also generally present higher conversion efficiencies.

[0008] For the purposes of the present invention, the conversion efficiency of a photovoltaic cell means the ratio of the maximum electrical power delivered by the cell to the incident light power, for a given spectral distribution and intensity.

[0009] It should be noted, moreover, that the higher conversion efficiencies mentioned above are ensured when the photovoltaic modules of the current state of the art are exposed to external radiation, i.e. exposed to ultraviolet (UV), visible, and infrared radiation and can reach light intensities greater than 5000 lux and in particular to radiation under standard AM1.5 conditions which corresponds to an exposure light intensity having a power of 100 mW / cm2 which is equivalent to a light intensity approximately equal to 100000 lux (corresponding to a power approximately equal to 1000 W / m 2). In particular, the high number of photo-generated charges requires the use of an anode with very high electrical conductivity to ensure good collection of photo-generated charges in the active layer so as to minimize, among other things, the phenomenon of charge accumulation. In particular, the high number of photo-generated charges requires the use of an anode with very high electrical conductivity to ensure good collection, in the active layer, of photo-generated charges so as to minimize the phenomenon of accumulation at the interfacial layers. This is why generally, in the case of an inverse structure, the upper electrode (or anode) is opaque and made of silver. In this case, the conversion efficiency can reach, on a laboratory scale, values ​​above 15% for organic photovoltaic cells.

[0010] However, when we are on an industrial scale, due to manufacturing constraints in particular, photovoltaic modules comprising this type of photovoltaic cell have low conversion efficiencies, the latter being in particular divided by two or more compared to those obtained on a laboratory scale with cells manufactured in a controlled atmosphere (inert gas such as nitrogen). As a result, these photovoltaic modules cannot be used efficiently and sustainably under indoor radiation, i.e. under a power lower than 16.2 W / m 2 when the light intensity is less than 5000 lux, preferably less than 6.4 W / m 2 when the light intensity is less than 2000 lux, or less than 3.3 W / m 2 when the light intensity is less than 1000 lux.

[0011] In particular, this low conversion efficiency, when the photovoltaic modules are exposed to indoor radiation, is notably due to the fact that photovoltaic modules comprising organic photovoltaic cells with inverse structure of the current state of the art have a high series resistance linked to the number of layers forming the organic photovoltaic cell and therefore the photovoltaic module. As a result, these photovoltaic modules have insufficient (i.e. not high enough) shunt resistances (or parallel resistances), the shunt resistances continuing to decrease with the decrease in light intensity. These resistances therefore do not allow the performance and the fill factor of this type of organic photovoltaic modules to be optimized. In particular, it is known that the shunt resistance must be sufficiently large for better output power and a good fill factor of the photovoltaic module.Indeed, for a low shunt resistance, the current collapses sharply, which means that the power loss is high and the fill factor is low.

[0012] Furthermore, the low conversion efficiency of this type of photovoltaic module is also due to the fact that they have high dead surfaces which are linked to the fact that the deposition of the different constituent layers of each of the organic photovoltaic cells, in particular with inverse structure, are applied to the support in an offset manner, so that each layer of the organic photovoltaic cell is partly in contact with the support in order to avoid the creation of short circuits which can be caused by the reverse return effect of the material deposited in the liquid state for example. Consequently, photovoltaic modules comprising organic photovoltaic cells with inverse structure of the current state of the art have low active surfaces which does not allow sufficient photocurrent to be generated when the incident light intensity is low.

[0013] Furthermore, although the indium-tin oxide layer used as a cathode has many advantages and interesting electronic properties, it also has some disadvantages. Indeed, the availability of the materials constituting the indium-tin oxide layer, the cost of raw materials, the process associated with its implementation and its application to create the layer are all disadvantages to note. Furthermore, the techniques for depositing the material to create the indium-tin oxide layer use techniques that are difficult to reconcile with conventional deposition technologies. Indeed, the indium-tin oxide layer is generally structured to form a continuous film on a rigid or flexible substrate. The implementation of this film is usually done by chemical etching method (for example using acids) or by laser ablation. However, these techniques leave effects that can affect the performance of photovoltaic cells, and therefore of the photovoltaic modules that include them, but also impact the quality and aesthetics of these photovoltaic modules, for example because of visible edge effects.In particular, knowing the cost of indium tin oxide, when film preparation steps are implemented that require the removal of a certain amount of indium tin oxide, the overall process then inevitably becomes expensive and creates a certain amount of waste with all the disadvantages that entails.

[0014] There are therefore no organic photovoltaic modules in the current state of the art comprising organic photovoltaic cells suitable for indoor radiation as defined above and which are free from an indium-tin oxide layer as an anode.

[0015] Currently, there are also no photovoltaic modules that can be manufactured entirely by inkjet printing.

[0016] Thus, one of the aims of the invention is to remedy at least in part the inadequacies of photovoltaic modules, and their manufacturing process, of the state of the art. Statement of the invention

[0017] According to a first aspect, the invention relates to a photovoltaic module comprising: - a transparent support, - at least two photovoltaic cells, a first photovoltaic cell and a second photovoltaic cell, on said support, each of said two photovoltaic cells comprising: i. a lower electrode consisting of two layers: a first layer comprising a polymer mixture of poly(3,4-ethylenedioxythiophene) and sodium poly(styrenesulfonate) covering the support and having an average thickness of between 50 nm and 150 nm and an organic fibrous structure, and a second layer based on an organic polymer or molecule covering said first layer, the lower electrode having a lower surface in contact with the support and an upper surface, 11. a photovoltaic active layer covering said upper surface of said lower electrode; 11. an upper electrode comprising a polymer mixture of poly(3,4-ethylenedioxythiophene) and sodium poly(styrenesulfonate) covering said photovoltaic active layer, said electrode being continuous, having an average thickness of between 100 nm and 400 nm and an organic fibrous structure, the upper electrode of the first photovoltaic cell being in contact with said second layer of said lower electrode of the second photovoltaic cell.

[0018] According to this first aspect, the invention makes it possible to overcome the drawbacks inherent in the use of a tin oxide electrode such as the drawbacks mentioned above, in particular those linked to the complexity of deposition, etching, or even cleaning, while providing a photovoltaic module which can be used under indoor radiation.

[0019] Furthermore, the indium-tin oxide layer generally used as a cathode in photovoltaic modules comprising photovoltaic cells with an inverse structure of the prior art cannot be used without the presence of a first interfacial layer between it and the active layer. Indeed, the presence of the first interfacial layer is then currently necessary in the cells to facilitate the transfer of charges between each of the layers, this in particular due to the work function of the indium-tin oxide layer which is high, in particular approximately equal to 4.7 eV.

[0020] The invention then has the advantage of overcoming this problem by providing a lower electrode consisting of two layers. The second layer based on a polymer or organic molecule makes it possible to reduce the energy barrier between the active layer and the first layer of the lower electrode by reducing the output work of the latter. Rather than being in the presence of a Schottky contact, we ultimately have an ohmic contact which is favorable to the collection of charges, in particular to the collection of electrons. In particular, according to the invention, the adsorption of the polymer or the organic molecule, due to the transfer of charges, in particular protons, from the hydroxyl groups to the amino groups, generates a dipole opposite to A0 (A0 being a surface dipole) resulting in a reduction of A0, which allows the reduction of the output work of the lower electrode.

[0021] Furthermore, the second layer of the lower electrode also acts as a barrier to block positive charges passing through, which leads to further increasing the performance of photovoltaic modules as a result of reducing leakage currents.

[0022] The invention according to this first aspect also makes it possible to have a photovoltaic module which is free of an indium-tin oxide layer used as a lower electrode, this layer being generally used in photovoltaic modules of the prior art. In particular, the lower electrode here consists of two layers, this lower electrode can then be designated as a bilayer lower electrode. Each of the layers constituting the lower electrode is organic.

[0023] Furthermore, as transparent supports, we can for example cite supports made of polyethylene teraphthalate (commonly designated by the acronym PET), polyethylene naphthalate (commonly designated by the acronym PEN) or even glass.

[0024] Having a bilayer allows the photovoltaic module to operate to the extent that it is necessary for the work function of the lower electrode to be different from that of the upper electrode. In particular, using the second layer based on a polymer or organic molecule makes it possible to structurally differentiate the lower electrode from the upper electrode. Also, the presence of this second layer based on a polymer or organic molecule allows the lower bilayer electrode to ensure both, on the one hand, the role of first interfacial layer (or electron transfer layer), and on the other hand, to also ensure the role of modifier of the work function of the polymer mixture of poly(3,4-ethylenedioxythiophene) and sodium poly(styrene-sulfonate).

[0025] Preferably, the material constituting the first layer of the lower electrode may be the same as that constituting the upper electrode. In this way, it is possible to avoid the need to develop an inkjet-printable formulation dedicated solely to the formation of this first layer of the lower electrode. This also avoids the disadvantages, particularly ecological and economic, of implementing an additional formulation. Furthermore, the materials used for the manufacture of the upper electrode, and therefore possibly the first layer of the lower electrode, are present in abundance and consist of organic materials.

[0026] Preferably, the lower electrode may be sufficiently transparent to allow the passage of photons from the support to the active layer so as to collect the maximum possible amount of photo-generated charges.

[0027] In a particular embodiment, the thickness of the second layer of the lower electrode may be between 2 and 5 nm and may comprise amine groups on its lower surface in contact with the upper surface of the first layer of the lower electrode.

[0028] In a particular embodiment, the second layer of the lower electrode may be continuous, transparent, and free of metal oxide. Thus, a non-toxic second layer of the lower electrode may be obtained.

[0029] In a particular embodiment, the upper electrode may have a surface resistance of between 50 Q / n and 300 Q / n. This surface resistance is obtained by manufacturing a layer by inkjet printing.

[0030] In a particular embodiment, the upper electrode may have a root mean square (RMS) roughness equal to or less than 5 nm.

[0031] In a particular embodiment, the second layer of the lower electrode may have an RMS roughness equal to or less than 5 nm.

[0032] In a particular embodiment, the second layer of the lower electrode may comprise nitrogen.

[0033] In a particular embodiment, the layers constituting the module (apart from the support) are all organic so as to obtain a module which is ecological. Consequently, the photovoltaic module can be organic, in the sense that the module only comprises organic printed layers.

[0034] In a particular embodiment, the polymer or organic molecule may be chosen from Poly(9,9-bis(3'-(N,N-dimethyl)-N-ethylammoinium-propyl-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene))dibromide (PFN-Br), polyethyleneimine (PEI), ethoxylated polyethyleneimine (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-dimethylpropan-1-amine oxide)perylene-3,4,9,10-tetracarboxylic diimide (PDI-NO) or N,N'-Bis{3-[3-(Dimethylamino)propylamino]propyl}perylene- 3,4,9,10-tetracarboxylic diimide (PDINN).

[0035] According to a second aspect, the invention relates to a method for manufacturing a photovoltaic module as defined above, comprising the following steps: a) providing a transparent support; b) producing on said support two layers of a first lower electrode layer comprising a polymer mixture of poly(3,4-ethylenedioxythiophene) and sodium poly(styrene-sulfonate), c) producing on each of the two layers of a first lower electrode layer a second lower electrode layer based on an organic polymer or molecule, d) producing on each of the two layers of a second lower electrode layer a photovoltaic active layer; e) producing on said photovoltaic active layer an upper electrode; said method being characterized in that steps b), c), d) and e) are each carried out by depositing ink compositions by digital inkjet printing, followed by a heat treatment.

[0036] According to this second aspect, the invention makes it possible to manufacture a photovoltaic module comprising a two-layer lower electrode made from two different ink compositions by digital inkjet printing. These two compositions are both preferably made from non-toxic solvents known to those skilled in the art and from organic materials so as to allow their deposition in ambient air by digital inkjet printing. As a result, steps b) and c) of producing the first and second layers of lower electrodes respectively are simple to implement insofar as these steps make it possible to dispense with a step of structuring the indium-tin oxide layer currently used in the state of the art.

[0037] In addition, the fact that all steps of the process are carried out by depositing ink compositions by digital inkjet printing makes it possible to reduce the manufacturing costs of the photovoltaic module.

[0038] Indeed, the chemical etching step generally implemented for the structuring of the lower electrode, which comprises for example indium tin oxide, in the photovoltaic modules of the prior art requires several costly sub-steps, in particular due to the durations of implementation of the etching, the costs inherent in the use of a crosslinkable resin and the use of deposition equipment. In particular, this chemical etching step is generally at least made up of several sub-steps: a step of applying a mask, an actual etching step (using for example one or more acid baths) and a cleaning step to remove the remaining part of the mask.

[0039] In a particular embodiment, it is advantageous not to alter the support during the annealing treatment of step b). Consequently, the heat treatment of step b) may be an annealing treatment carried out at a temperature between 100°C and 160°C, for a duration between 1 and 5 minutes.

[0040] In a particular embodiment, it is advantageous not to alter the support and the layers previously produced in step c). Consequently, the heat treatment of step c) may be an annealing treatment carried out at a temperature between 100°C and 160°C, for a duration between 1 and 5 minutes.

[0041] In a particular embodiment, the wettability of the composition from which the first lower electrode layer is derived may preferably be compatible with flexible substrates made of polyethylene terephthalate for example, to facilitate the formation of a continuous film with well-defined edges by digital inkjet printing.

[0042] Preferably, during step b) of producing the two layers of a second lower electrode layer, the composition below can be applied by digital inkjet printing to the support, said composition having a viscosity of between 2 and 50 mPa.s at 20°C and comprising: - between 0.1% and 0.5% by mass of at least one polymer or organic molecule relative to the total mass of said ink composition, the polymer or the organic molecule comprising amine groups and being soluble in polar solvents, - between 2% and 10% by mass of additives relative to the total mass of said ink composition, - between 80% and 90% by mass of one or more polar solvents relative to the total mass of said ink composition, and - between 1% and 5% by mass of water relative to the total mass of said ink composition.

[0043] The polymer or organic molecule has the advantage of not being sensitive to UV radiation, this being linked to its intrinsic characteristics which are different from those of metal oxide nanoparticles usually used in the lower electrode layers of photovoltaic modules of the prior art. In particular, the metal oxides conventionally used in the prior art in the interfacial layers such as TiO2 or ZnO are not very effective under solar irradiation due to their large gap energy which only allows their activation using UV radiation. This activation will allow the charges (electrons) to circulate through the interfacial layer to reach the electrode without being trapped.The UV exposure requirement, however, can pose significant problems if the photovoltaic modules are intended for indoor applications where artificial light sources are used, generally LEDs that do not emit UV.

[0044] The additives make it possible to solubilize the polymer or the organic molecule so as to obtain a composition which is, on the one hand, defined by a high evaporation temperature in order to prevent the nozzles of a digital inkjet printing application device from becoming blocked, and on the other hand, to improve the viscosity of the ink composition.

[0045] Polar solvents are preferably non-toxic to ensure deposition of the ink composition in ambient air with nozzles of an industrial digital inkjet printing application device.

[0046] Preferably, the polymer or organic molecule may be chosen from Poly(9,9-bis(3'-(N,N-dimethyl)-N-ethylammoinium-propyl-2,7-fluorene)-alt- 2.7-(9,9-dioctylfluorene))dibromide (PFN-Br), polyethyleneimine (PEI), ethoxylated polyethyleneimine (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-dimethylpropan-1 - amine oxide)perylene-3,4,9,10-tetracarboxylic diimide (PDI-NO) or N,N'-Bis{3-[3- (Dimethylamino)propylamino]propyl}perylene-3,4,9,10-tetracarboxylic diimide (PDINN).

[0047] Preferably, said one or more solvents may be chosen from ethanol, isopropanol, hexanole, terpiniole, ethylene glycol, deionized water, saline phosphate buffer solution, butanol, diethylene glycol, glycerol.

[0048] In a particular embodiment, the polymer or organic molecule may comprise nitrogen.

[0049] Other advantages and particularities of the present invention will result from the description which follows, made with reference to the appended figures and the following examples: Brief description of the figures

[0050] [Fig 1] represents a schematic sectional view of a photovoltaic cell of conventional structure;

[0051] [Fig 2] represents a schematic sectional view of a photovoltaic module comprising photovoltaic cells according to a particular embodiment according to the invention;

[0052] [Fig 3] represents the characteristic spectrum of the Philips 60x60 cm2 LED panel used in the examples,

[0053] [Fig 4] represents the transmission spectra of the ITO electrode used for the production of the M2A and M2B modules according to the prior art and of the bilayers used for the production of the M1 A and M1 B modules according to the invention with the wavelength (λ) on the abscissa and the transmission (T) on the ordinate.

[0054] Figure 1 is described in the preceding presentation of the prior art, while Figure 2 is described in more detail in the following examples, which illustrate the invention without limiting its scope. EXAMPLES

[0055] Products

[0056] support 20 in PET or glass;

[0057] cleaning solvents:

[0058] o in the case of rigid glass supports: deionized water, Acetone, Ethanol, Isopropanol, and

[0059] o in the case of flexible substrates, the latter being protected by plastic films, they do not require cleaning as in the case of rigid substrates;

[0060] a first ink composition E11 for producing a first layer 210A comprising a polymer mixture of poly(3,4-ethylenedioxythiophene) and discontinuous sodium poly(styrene-sulfonate) so that the support is partly covered with a first layer 210A of a lower bilayer electrode 210 of the photovoltaic cells 21 and 22 of the photovoltaic module of FIG. 2 o ink E11 comprising: - PEDOT:PSS marketed by Agfa® under the trade name IJ1005, and - Triton X-100 (4-(1,1,3,3-tetramethylbutyl)phenyl-polyethylene glycol of formula Oct-C6H4-(OCH2CH2) X OH, x= 9-10) marketed by Merck® as a detergent / surfactant.

[0061] a second ink composition (E12A and E12B) for producing a second layer 210B based on an organic polymer or molecule so that the first layer 210A of the lower bilayer electrode 210 is partly covered with a second layer 210B of a lower bilayer electrode 210 to form the cathodes of the different organic photovoltaic cells 21 and 22 of the photovoltaic module of Figure 2 described below: o ink E12A comprising: - a first Solvent 1: Butanol at a mass concentration approximately equal to 91.094% relative to the total weight of the E12A ink - - a second Solvent 2: deionized water at a mass concentration approximately equal to 3.124% relative to the total weight of the E12A ink, - an additive: Ethylene glycol at a mass concentration approximately equal to 5.563% relative to the total weight of the E12A ink, - a PEI at a mass concentration approximately equal to 0.219% relative to the total weight of the E12A ink. Solvents, additives and PEI are marketed by Merck® o E12B ink including: - 9 mL of Butanol, - 500 pL of Ethylene glycol, - 1 OOpL of commercial aqueous PEIE solution (at a mass concentration approximately equal to 37% in water). Solvents, additives and PEIE are marketed by Merck®

[0062] a third ink composition E20 for producing the photovoltaic active layers 211 of the photovoltaic cells 21 and 22 of the photovoltaic module of figure 2: o polymer mixture of an acceptor fullerene derivative comprising: - PC60BM:

[0060] PCBM, 3'H-cyclopropa[1,9][5,6]fullerene-C60-lh-3'-butanoic acid 3'-phenyl methyl ester marketed by Special Carbon Products, and - a donor semiconducting polymer marketed by Raynergy Tek® under the trade name PV2000); - O-xylene as solvent (ortho-xylene of formula CeH^CHs^); and - Tetralin (1,2,3,4-tetrahydronaphthaline) as an additive. The PV2000 polymer is present in these third ink compositions at a rate of 15 mg / ml. The mass ratio between PV2000 polymer and PC60BM is 1:1.5. The volume ratio between the O-xylene solvent and the Tetraline additive is 50:50 in these second compositions. The third E20 ink composition is kept stirring for 24 hours on a hot plate at 80°C at a speed of 700 RPM.

[0063] a fourth ink composition E30 for producing the upper electrodes 212 (or anode) of the photovoltaic cells 21 and 22 of the photovoltaic module of figure 2: o PEDOT:PSS marketed by Agfa® under the trade name IJ1005, o Triton X-100 (4-(1,1,3,3-tetramethylbutyl)phenyl-polyethylene glycol of formula Oct-C6H4-(OCH2CH2) X OH, x= 9-10) marketed by Merck® as a detergent / surfactant;

[0064] Tests

[0065] RMS roughness measurement

[0066] These measurements are carried out using an atomic force microscope (Nanoscope III Multimode SPM from Brucker®, used in intermittent contact mode (or "tapping mode"), with hq:nsc15 tips marketed by MiKromasch® and having a radius of curvature of 8 nm), the measurements were carried out on different samples of photovoltaic cells according to the invention and according to the prior art.

[0067] Measurement of layer thicknesses

[0068] The thickness of the printed layers is measured using a DektakXT brand tip profilometer marketed by BRUKER from a scratch made with a cutter blade (this creates a channel with the thickness of the deposit). This is a contact profilometer that measures variations in relief by vertically moving a tip stylus that scans the surface by applying a constant contact force and reveals all the unevenness. The sample is placed on a plate that allows it to move at a given speed and over a chosen distance. The thickness values ​​presented in this patent application correspond to the average of five measurements taken at six different points on the same sample step. Before carrying out the measurements, the length of the scanned area, its duration, the stylus pressure and the measurement range must be defined.

[0069] Measurement of electrical resistivity

[0070] This measurement is carried out using the 4-point technique, as follows: - we place the 4 aligned points far from the edges of the layer to be characterized; - these 4 points are equidistant from each other; and - current is generated by a current generator between the outer tips, while voltage is measured between the inner tips. The ratio of the measured voltage to the current flowing through the sample gives the resistance of the section between the inner tips.

[0071] Viscosity measurement:

[0072] The viscosity of a fluid is manifested by its resistance to deformation or to the relative sliding of its layers. During the flow of a viscous fluid in a capillary tube, for example, the speed of the molecules (v) is maximum in the axis of the tube and decreases until it is zero at the wall, while between the layers a relative sliding develops; hence the appearance of tangential friction forces. Tangential forces in fluids depend on the nature of the fluid considered and its flow regime.

[0073] The viscometer used is of the Ubbelhode type, it is placed in a thermostat maintained at a constant temperature (25 °C in our case study). We measures the flow time of a constant volume V defined by two reference lines (M1 and M2) located on either side of a small reservoir above the capillary.

[0074] Measurement of photovoltaic performance indoors:

[0075] The study of the aging of the modules produced under permanent lighting is carried out through an indoor characterization bench. This characterization bench includes an opaque closed enclosure (to avoid any light coming from outside) equipped with an LED type lighting source (in particular a Keithley 2450 Source-meter) and a computer with a LabVIEW program allowing to automatically measure the performance of the modules (determination of the photovoltaic parameters) with a well-defined frequency (for example 10 times per day). The photovoltaic modules are permanently illuminated by a lighting source under a light intensity approximately equal to 1000 lux measured by a luxmeter (in particular by the Chauvin Arnoux Ca 1110 luxmeter) compatible with a wide variety of light sources, including LED and fluorescent light up to 200,000 lux in compliance with class C of the NF C 42-710 standard.

[0076] The lighting source used to perform the interior measurements as well as the performance measurements is a Philips 60x60 cm LED panel. 2 - 4385K with an emission spectrum in the visible (see the spectrum shown in Figure 3).

[0077] Characterization of morphology:

[0078] AFM (Atomic Force Microscope) measurements to reproduce surface topography and TEM (Transmission Electron Microscopy) to validate the crystalline nature of the materials as well as the sizes of nanoparticles present in the layers.

[0079] Measurement of bilayer transmission:

[0080] In order to determine the transmission spectra of the printed bilayers according to the invention (see the spectrum shown in Figure 3). A UV-Visible spectrometer of the Cary 5000 UV-Vis-NIR type was used. This method is based on the use of equipment that determines the transmission of a thin layer for a given wavelength or for a judiciously chosen range of wavelengths. The sample is placed on a sample holder and crossed by monochromatic radiation. A computer compares the intensity (I) from the sample to be tested (PET substrate and layer deposited on it) to that from the reference sample (PET substrate alone) (Ig) - By scanning several wavelengths located in the 300 - 800 nm range (in our case), it displays the transmission spectrum of the bilayer. This spectrum represents on the ordinate the transmission T (%) as a function of the wavelength (nm).

[0081] EXAMPLE 1: obtaining examples of first ink composition E10 for producing the first layer 210A of the lower bilayer electrode.

[0082] This first E10 ink composition for the production of the first lower electrode layer is obtained as follows: - the PEDOT:PSS solution (IJ1005) initially stored in a fridge is filtered with a 0.45 pm filter; - 30 μl of Triton X-100 is mixed with 10 ml of the filtered PEDOT:PSS solution, - the mixture thus obtained is placed under magnetic stirring at room temperature on a magnetic stirrer for 16 hours. - the final solution thus obtained E10 is degassed for 3 to 5 minutes in an ultrasonic bath before printing.

[0083] EXAMPLE 2: obtaining an example of a second ink composition E12A and E12B for producing the second layer 210B of the lower electrode 210.

[0084] Depending on whether PEI or PEIE is used, the ink compositions E12A and E12B are obtained respectively, the compositions of which are detailed below:

[0085] The preparation of the E12A ink formulation is carried out in two stages:

[0086] Step 1: Preparation of the stock solution: - Weigh 0.35 g of PEI (intermediate layer polymer) - Add 5 ml of ionized water to these 0.35 g of PEI - Stir at a temperature of 60°C for at least 4 hours to obtain the mother solution.

[0087] Step 2: Preparation of E12A ink formulation: - Take a volume of 250 pL of the mother solution, - Add 9 ml of Butanol, - Add 400 pL of ethylene glycol, - Stir the mixture at room temperature for 24 hours to obtain the E12A formulation. - The E12A formulation is filtered before any printing using an AC filter with a cut-off threshold of approximately 0.2 pm.

[0088] The preparation of the E12B ink formulation is carried out in a single step:

[0089] Preparation of E12B ink formulation: -Take a volume of 100 pL of the commercial aqueous PEIE solution -Add 9 ml of Butanol (solvent) -Add 500 pL of ethylene glycol (additive) - Stir the mixture at room temperature for 24 hours to obtain the E12B ink formulation. -The E12B formulation is filtered before any printing using an AC filter with a cut-off threshold of approximately 0.2 pm.

[0090] EXAMPLE 3: obtaining an example of a third ink composition E20 for producing the photovoltaic active layer 211.

[0091] PC60BM is used as an acceptor combined with PV2000 as a donor to obtain the E20 ink composition, the composition of which is detailed in Table 1 below: [Table 1]

[0092] The E20 ink composition is obtained as follows: - 15 mg PV2000 mixed with 22.5 mg PC60BM (corresponding to a mass ratio of 1:1.5) in 0.5 milliliter o-xylene and 0.5 milliliter tetralin. - The mixture is stirred magnetically on a hot plate at 80°C for 24 hours. - Before printing, the ink is pre-filtered with an AC filter with a cut-off threshold of approximately 0.45 micrometers.

[0093] EXAMPLE 4: Obtaining an example of a fourth ink composition E30 for producing the upper electrode layer 212.

[0094] Obtaining an example of a fourth ink composition E30 for producing the upper electrode layer 212.

[0095] This fourth ink composition E30 for producing the upper electrode layer 212 is obtained as follows: - the PEDOT:PSS solution (IJ1005) initially stored in a refrigerator is filtered with a filter having a cut-off threshold approximately equal to 0.45 pm; - 30 μl of Triton X-100 is mixed with 10 ml of the filtered PEDOT:PSS solution, - the mixture thus obtained is placed under magnetic stirring at room temperature on a magnetic stirrer for 16 hours, and - the final solution thus obtained E30 is degassed for 3 to 5 minutes in an ultrasonic bath before printing.

[0096] EXAMPLE 5: obtaining examples of photovoltaic modules according to the invention:

[0097] Two photovoltaic modules M1 A and M1 B in accordance with the invention are produced using the following method: - Supply of a transparent PET or glass support. - Production on said support of two layers of a first layer 210A of lower electrode 210 from the composition E10 of example 1. In particular, production of these layers by digital inkjet printing of the ink composition E10, then subsequent thermal annealing in a convection oven at 145°C for 3 minutes. The thickness of the first printed layers 210A of lower electrode 210 is approximately 100 nm with RMS roughnesses of less than 5 nm. - Production on each of the two layers of a first layer 210A of lower electrode 210 of a second layer 210B of lower electrode 210 originating either from the ink composition E12A of example 2 (photovoltaic module M1A), or from the ink composition E12B of example 2 (photovoltaic module M1B). In particular, production of these layers by digital inkjet printing of either the ink composition E12A or E12B, then subsequently carrying out a thermal annealing in a convection oven at 145°C for 3 minutes. The thickness of the printed second layers 210B of lower electrode 210 is between 2 and 5 nm with RMS roughnesses of less than 2 nm. - Creation of a second 210B layer on each of the two layers of lower electrode 210 of a photovoltaic active layer 211 following the application by digital inkjet printing of the ink composition E20 of Example 3 before carrying out a thermal annealing in a convection oven at 145 °C for 3 minutes. The thickness of the printed photovoltaic active layers 211 is approximately equal to 350 nm with RMS roughnesses of less than 5 nm. - Production on each of the photovoltaic active layers 211 of an upper electrode 212 following the application by digital inkjet printing of the ink composition E30 of example 4 before carrying out a thermal annealing in a convection oven at 145°C for 3 minutes. The thickness of the printed upper electrode layers 212 is approximately equal to 500 nm with RMS roughnesses of less than 10 nm. - Production of an electrical contact layer 213 composed of a copper tape with adhesive having a width of 3 mm and a length of 58 mm. This tape is marketed by "3M" and cut into strips (3*58 mm2) with a mechanical cutting machine (Kongsberg XE). Then, deposition of this electrical contact layer 213 so that it ensures contact between the upper electrode layer 212 of a first photovoltaic cell of the photovoltaic module (M1A or M1 B) and the second lower electrode layer 210B 210 of a second photovoltaic cell of the photovoltaic module (M1A or M1 B).

[0098] At the end of the manufacturing process, a photovoltaic module (either M1 A or M1 B) is obtained comprising the organic photovoltaic cells 21 and 22 which then comprise, among other things, a lower bilayer electrode according to exemplary embodiments of the invention and an upper electrode which has a micrometric organic fibrous structure.

[0099] RESULTS AND COMPARISONS: characterization of the photovoltaic modules obtained in the previous examples M1 A and M1 B and comparisons with examples of photovoltaic modules according to the prior art. [000100] The different photovoltaic modules, according to the invention and prior art, were characterized according to the tests indicated previously and the results of these characterizations in table 2 below. [000101] Two photovoltaic modules (M2A and M2B) according to the prior art were produced under the same conditions as those used for the production of the photovoltaic modules M1 A and M1 B according to exemplary embodiments according to the invention. [000102] The first photovoltaic module M2A according to the prior art differs from the photovoltaic modules M1 A and M1 B according to the invention by the presence of a lower electrode comprising a layer of indium-tin oxide and an interfacial layer based on metal oxides, in particular AZO (Aluminum Doped ZnO) and the second photovoltaic module M2B according to the prior art differs from the photovoltaic modules M1 A and M1 B according to the invention by the presence of a lower electrode comprising a layer of indium-tin oxide and an interfacial layer based on metal oxides, in particular SnO2 (Tin dioxide). AZO is marketed by the company Genesink and SnO2 is marketed by the company Avantama. [000103] The photovoltaic modules M2A and M2B according to the prior art were produced in inverse structure with the active layer PV2000: PC60BM and the PEDOT: PSS as upper electrode, that is to say with the same active layers and upper electrodes as the examples according to the invention. [000104] The photovoltaic modules M1A, M1 B according to the invention and M2A, M2B according to the prior art were characterized under the same conditions with the same characterization bench described previously under the same light intensity. [000105] The repeated production of photovoltaic modules corresponding to the module M1A made it possible to obtain the results expressed, in table 2 below, under the reference M1A'. [Table 2] 00106] Using the table above which represents the photovoltaic parameters (voltage, current, maximum power and fill factor) measured under LED-type indoor lighting (1000 LUX), it is clear that the photovoltaic modules according to the invention M2A and M2B make it possible to achieve photovoltaic performances very close to and sometimes better than those of modules produced according to the state of the art under the same conditions (same active layer and same upper electrode). The current generated by the modules according to the invention is of the same order of magnitude as that generated by the modules produced according to the prior art. [000107] The photovoltaic performances measured with the photovoltaic modules M1 A and M1 B according to the invention are very encouraging and confirm the good functionality of the lower bilayer electrode according to the invention in the case of an interior application (low brightness LED type lighting). Bibliographic references [000108] [1] Sharaf Sumaiya, Kamran Kardel, and Adel El-Shahat. “Organic Solar Cell by Inkjet Printing — An Overview.” 53, Georgia, USA: Technologies, 2017, Vol. 5. [000109] [2] Peng, X., Yuan, J., Shen, S., Gao, M., Chesman, A. S. R., & Yin, H. (2017). “Perovskite and Organic Solar Cells Fabricated by Inkjet Printing: Progress and Prospects”, Adv. Function. Mater. 2017, 1703704 [000110] [3] European patent application EP2960957 de DRACULA TECHNOLOGIES, filed on 25 June 2015 and published on 30 December 2015.

Claims

CLAIMS

1. Photovoltaic module comprising: - a transparent support, - at least two photovoltaic cells, a first photovoltaic cell and a second photovoltaic cell, on said support, each of said two photovoltaic cells comprising:

1. a lower electrode consisting of two layers: a first layer comprising a polymer mixture of poly(3,4-ethylenedioxythiophene) and sodium poly(styrene-sulfonate) covering the support and having an average thickness of between 50 nm and 150 nm and an organic fibrous structure, and a second layer based on an organic polymer or molecule covering said first layer, the lower electrode having a lower surface in contact with the support and an upper surface, 11. a photovoltaic active layer covering said upper surface of said lower electrode, 11.an upper electrode comprising a polymer mixture of poly(3,4-ethylenedioxythiophene) and sodium poly(styrene-sulfonate) covering said photovoltaic active layer, said electrode being continuous, having an average thickness of between 100 nm and 400 nm and an organic fibrous structure, the upper electrode of the first photovoltaic cell being in contact with said second layer of said lower electrode of the second photovoltaic cell.

2. Photovoltaic module (10) according to claim 1, according to which the thickness of said second layer of said lower electrode is between 2 and 5 nm and comprises amine groups on its lower surface in contact with the upper surface of the first layer of said lower electrode.

3. Photovoltaic module (10) according to one of claims 1 or 2, wherein said second layer of said lower electrode is continuous, transparent, and free of metal oxide.

4. Photovoltaic module (10) according to one of claims 1 to 3, according to which said upper electrode has a square resistance of between 50 Q / n and 300 Q / n.

5. Photovoltaic module according to one of claims 1 to 4, according to which said upper electrode has an RMS roughness equal to or less than 5 nm.

6. Photovoltaic module according to one of claims 1 to 5, according to which said second layer of said lower electrode has an RMS roughness equal to or less than 5 nm.

7. Photovoltaic module according to one of claims 1 to 6, according to which said second layer of said lower electrode comprises nitrogen.

8. Photovoltaic module according to one of claims 1 to 7, characterized in that it is organic.

9. Photovoltaic module according to one of claims 1 to 8, in which the polymer or organic molecule is chosen from Poly(9,9-bis(3'-(N,N-dimethyl)-N-ethylammoinium-propyl-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene))dibromide (PFN-Br), polyethyleneimine (PEI), ethoxylated polyethyleneimine (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-dimethylpropan-1-amine oxide)perylene-3,4,9,10-tetracarboxylic diimide (PDI-NO) or N,N'-Bis{3-[3- (Dimethylamino)propylamino]propyl}perylene-3,4,9,10-tetracarboxylic diimide (PDINN).

10. A method of manufacturing a photovoltaic module as defined in any one of claims 1 to 9, comprising the following steps: a) providing a transparent support; b) producing on said support two layers of a first lower electrode layer comprising a polymer mixture of poly(3,4-ethylenedioxythiophene) and sodium poly(styrenesulfonate), c) producing on each of the two layers of a first lower electrode layer a second lower electrode layer based on an organic polymer or molecule, d) producing on each of the two layers of a second lower electrode layer a photovoltaic active layer; e) producing on said photovoltaic active layer an upper electrode; said method being characterized in that steps b), c), d), and e) are each produced by depositing ink compositions by digital inkjet printing, followed by heat treatment.

11. Manufacturing method according to claim 10, according to which the heat treatment of step b) is an annealing treatment carried out at a temperature between 100°C and 160°C, for a duration between 1 and 5 minutes.

12. Manufacturing method according to one of claims 10 or 11, according to which the heat treatment of step c) is an annealing treatment carried out at a temperature between 100°C and 160°C, for a duration between 1 and 5 minutes.

13. Manufacturing method according to one of claims 10 to 12, according to which during step b) of producing the two layers of a second lower electrode layer, the composition below is applied by digital inkjet printing to the support, said composition having a viscosity of between 2 and 50 mPa.s at 20°C and comprising: - between 0.1% and 0.5% by mass of at least one polymer or organic molecule relative to the total mass of said ink composition, the polymer or organic molecule comprising amine groups and being soluble in polar solvents, - between 2% and 10% by mass of additives relative to the total mass of said ink composition, - between 80% and 90% by mass of one or more polar solvents relative to the total mass of said ink composition, and - between 1% and 5% by mass of water relative to the total mass of said ink composition.

14. The method of claim 13, wherein the polymer or organic molecule is selected from Poly(9,9-bis(3'-(N,N-dimethyl)-N-ethylammoinium-propyl-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene))dibromide (PFN-Br), polyethyleneimine (PEI), ethoxylated polyethyleneimine (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-dimethylpropan-1-amine oxide)perylene-3,4,9,10-tetracarboxylic diimide (PDI-NO) or N,N'-Bis{3-[3-(Dimethylamino)propylamino]propyl}perylene- 3,4,9, 10-tetracarboxylic diimide (PDINN).

15. Method according to one of claims 13 or 14, according to which said one or more solvents are chosen from ethanol, isopropanol, hexanole, terpiniole, ethylene glycol, deionized water, saline phosphate buffer solution, butanol, di-ethylene glycol, glycerol.

16. Method according to one of claims 13 to 15, according to which the polymer or the organic molecule comprises nitrogen.

Images