Classifications

• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K30/00—Organic devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation
  • H10K30/30—Organic devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation comprising bulk heterojunctions, e.g. interpenetrating networks of donor and acceptor material domains
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B82—NANOTECHNOLOGY
  • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
  • B82Y10/00—Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K71/00—Manufacture or treatment specially adapted for the organic devices covered by this subclass
  • H10K71/10—Deposition of organic active material
  • H10K71/191—Deposition of organic active material characterised by provisions for the orientation or alignment of the layer to be deposited
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K30/00—Organic devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation
  • H10K30/50—Photovoltaic [PV] devices
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K71/00—Manufacture or treatment specially adapted for the organic devices covered by this subclass
  • H10K71/10—Deposition of organic active material
  • H10K71/12—Deposition of organic active material using liquid deposition, e.g. spin coating
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K85/00—Organic materials used in the body or electrodes of devices covered by this subclass
  • H10K85/10—Organic polymers or oligomers
  • H10K85/111—Organic polymers or oligomers comprising aromatic, heteroaromatic, or aryl chains, e.g. polyaniline, polyphenylene or polyphenylene vinylene
  • H10K85/113—Heteroaromatic compounds comprising sulfur or selene, e.g. polythiophene
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K85/00—Organic materials used in the body or electrodes of devices covered by this subclass
  • H10K85/10—Organic polymers or oligomers
  • H10K85/111—Organic polymers or oligomers comprising aromatic, heteroaromatic, or aryl chains, e.g. polyaniline, polyphenylene or polyphenylene vinylene
  • H10K85/113—Heteroaromatic compounds comprising sulfur or selene, e.g. polythiophene
  • H10K85/1135—Polyethylene dioxythiophene [PEDOT]; Derivatives thereof
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K85/00—Organic materials used in the body or electrodes of devices covered by this subclass
  • H10K85/20—Carbon compounds, e.g. carbon nanotubes or fullerenes
  • H10K85/211—Fullerenes, e.g. C60
  • H10K85/215—Fullerenes, e.g. C60 comprising substituents, e.g. PCBM
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E10/00—Energy generation through renewable energy sources
  • Y02E10/50—Photovoltaic [PV] energy
  • Y02E10/549—Organic PV cells
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
  • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

• the present invention relates to a new polymeric composition with photovoltaic properties, its method of preparation and its use in photovoltaic cells.
• polymeric composition with photovoltaic properties any composition comprising at least one polymeric material capable of directly converting the light energy, in particular that of the solar rays, into positive and negative electric charges or electron-hole-linked pairs, to ensure their dissociation and transport to generate a photocurrent.
• photovoltaic cells are essentially composed of semiconductor inorganic materials such as crystalline silicon or gallium parsenide.
• the conversion efficiencies of the best inorganic photovoltaic cells currently marketed are typically of the order of 10-15%. Even if the maximum theoretical yield of a monojunction silicon cell that is close to 30% gives hope for performance improvements, the high cost associated with the manufacture of this type of cell remains a barrier to their wide distribution on the market.
• organic molecules and semiconductor polymers offer an interesting alternative because of their low production cost and implementation techniques that are inaccessible to inorganic materials. Indeed, the organic and polymeric molecules are easy to handle and their choice as a basic material would make it possible to have recourse for the whole of the engineering of the cell (that is to say of the substrate until the protective capsule) only to one and the same technology. In addition, polymers are degradable, guaranteeing clean technology in a context of sustainable development. Since the publication in 1986 by Tang (CW Tang, two-layer organic photovoltaic solar cell, Appl Phys. Lett., 48, 183, 1986, US Patent No. 4 164 431) of a hetero-junction cell ( bilayer heterojunction) with an external conversion efficiency (power conversion efficiency) close to 1%, the work in the field of organic materials has grown remarkably.
• the dissociation of excitons is improved when the photogeneration sites are distributed in volume or heterojunction.
• Such a configuration is achieved by arranging the donor / acceptor materials in interpenetrating networks that increase the area of the junction.
• the organization of the interpenetrating network materials facilitates the conduction of the charges towards the electrodes.
• the charge transport is improved when the molecular order increases.
• the challenge is therefore to organize these donor and acceptor materials into interpenetrating networks in order to optimize the exciton dissociation surface and to promote the conduction of the charges without the occurrence of recombination phenomena.
• the recombination phenomena limit the conduction and collection of charges to the electrodes of the photovoltaic devices.
• photovoltaic cells whose active layer is formed of the combination of an electron-donor soluble conjugated polymer, poly- (3-hexylthiophene) (P3HT) and a soluble derivative of Buckminsterfullerene (PCBM) acceptor Electrons have conversion efficiencies of up to 5%. Their effectiveness is not only due to the intrinsic properties of the materials but also to the molecular order and spatial organization of the active layer. P3HT is organized into a matrix of nanocrystalline structures that provide good conduction properties of holes. The second material, PCBM, which is a derivative of C60, is integrated in the matrix and ensures good conduction of electrons.
• PCBM which is a derivative of C60
• the molecular order of active layers comprising a mixture of P3HT / PCBM is dependent on the conditions of manufacture (X. Yang, et al., Nanoletters, 5, 579, 2005).
• the P3HT / PCBM active layers have a different architecture depending on whether the P3HT / PCBM mixture has been annealed or not after being deposited on a substrate. After annealing, the mixture becomes heterogeneous with areas rich in PCBM and polymer-rich areas in which the polymer chains form fibrillar structures. On the other hand, short fibrillar structures, which are not connected to each other, appear in the absence of annealing.
• annealing makes it possible to control the shape and organization of the nano-fibril polymer chains, thereby creating an interpenetrating network with the acceptor material.
• annealing is meant a heat treatment comprising heating and maintaining at an appropriate temperature followed by a slow cooling leading to a structural constitution close to equilibrium.
• the inventors have shown that it is possible to obtain organized structures in interpenetrating networks directly from the deposition of a mixture of acceptor / electron donor materials on a substrate without resorting to annealing.
• the inventors have developed a method making it possible to have a large quantity of nanofibers in solution which makes it possible to deposit them directly on a substrate in order to form a film of electron-donor semiconductive polymeric material organized in a three-dimensional network of nanofibers. sufficient thickness and length.
• This particular organization of the electron donor polymeric material is beneficial to the electron transport properties of the nanofibrils.
• Other soluble or dispersible materials in the nanofibril solution may be added to develop films comprising a mixture of two or more materials.
• Such materials that are soluble or dispersible in the nanofibril solution may be in particular electron acceptor materials when the conjugated polymeric material is electron donor in its excited state, or electron donor materials when the conjugated polymer is acceptor of electrons in its excited state.
• Films made from such nanofibril solutions have a structure comprising the entanglement of nanofibrils. Such films are advantageously used in optoelectronic and electronic applications, and are particularly suitable for photovoltaic conversion. It is particularly important that this three-dimensional network nanofibril structure is obtained directly from the deposition process, without resorting to annealing.
• the subject of the present invention is therefore a process for preparing a polymeric composition with photovoltaic properties comprising a step of solvent mixture of at least one electron donor semiconductor polymer material substantially in the form of nanofibrils and at least one electron acceptor material in the solvent, said nanofibrils representing at least 10% by weight of the polymeric material semiconductor electron donor.
• electron donor semiconductor polymer material means any material comprising at least one polymer capable of generating excitons after absorption of photons and of giving up electrons to an electron acceptor material. It may possibly be doped with p-type impurities.
• nanostructures in solution or in the solid state, of cylindrical form, formed by chains of polymers connected to each other by strong interactions.
• the diameter of these structures is between 1 and 20 nm and their length is greater than 100 nm, generally greater than 500 nm and typically between 500 nm and 5 mm.
• the electron donor semiconductor polymeric material of the polymeric composition is selected from polythiophenes, polythienylenesvinylenes, polyphenylenes, polyphenylenevinylenes, polyanilines, polyfluorenes and a mixture thereof.
• the electron-donor semiconductor polymer material is chosen from poly (3-hexylthio ⁇ hene), poly (3-hexyloxythiophene), (poly (2-methoxy) - (2'-ethylhexyloxy) p-phenylenevinylene) and poly (2-methoxy-5- (3 ', 7'-dimethyloctyloxy) -1,4-phenylenevinylene), their derivatives and a mixture thereof.
• material comprising at least one organic and / or inorganic acceptor capable of transporting electrons It may optionally contain n-type impurities.
• the electron-donor material of the polymeric composition comprises inorganic acceptor semiconductor nanocrystals which are uncoated or coated with an organic layer, semiconductor nanowires, organic acceptors or a mixture of these.
• the semiconductor nanocrystals Inorganic acceptors are coated with an organic layer comprising polythiophenes, oligothiophenes or a mixture thereof.
• the nanowires and nanocrystals of semiconductors are selected from Si, AsGa, Ge, InP, CdSe and CdTe and a mixture thereof.
• the organic acceptors are chosen from C60 flillerene derivatives, C61 fullerene derivatives, C70 fullerene derivatives, carbon nanotubes and their derivatives, perylene and its derivatives, quinoxalines and tetracyanoquinodimethane, and a mixture thereof. .
• the electron acceptor material is organic. More preferably, the organic electron donor material is 1- (3-methoxycarbonyl) -propyl-1-phenyl- [6,6] -C61.
• alkyl radical any group of 1 to 20 carbon atoms, optionally mono- or polysubstituted, linear, branched or cyclic, saturated or unsaturated, said radical may contain one or more heteroatoms such as N, O, Si, S , P or a halogen such as fluorine.
• Alkyl radical may include, in a non-limiting manner, methyl, ethyl, propyl, isopropyl, butyl, sec-butyl, tert-butyl, pentyl, hexyl, octyl, decyl, dodecyl, methoxyethyl, methoxypropyl, methoxybutyl, methoxypentyl, methoxyhexyl, methoxyoctyl, ethoxyethyl, ethoxypropyl, ethoxybutyl, ethoxypentyl, ethoxyhexyl, ethoxyoctyl, propoxymethyl, propoxyethyl, propoxypropyl.
• aryl radical is meant any aromatic or heteroaromatic carbon structure, substituted or unsubstituted, consisting of one or more aromatic or heteroaromatic rings each having from 3 to 6 atoms.
• alkoxyl radical is meant any structure of 1 to 20 carbon atoms, having an oxygen atom in the 1-position substituted by an alkyl chain as defined above.
• alkoxyl radical By “alkoxyl radical”, mention may be made, in a nonlimiting manner, of the methoxyl, ethoxyl, propoxyl, butoxyl, pentyloxyl, hexyloxyl, octyloxyl, decyloxyl, dodecyloxy, methoxyethoxyl, methoxypropoxyl, methoxybutoxyl, methoxypentyloxyl, and the like radicals. methoxyhexyloxyl, methoxyoctyloxyl, ethoxyethoxyl, ethoxypropoxyl, ethoxybutyloxyl.
• alkyl and aryl radicals mention may be made, in a nonlimiting manner, of halogens, alkyl groups, alkoxyl, haloalkyl, substituted or unsubstituted aryl groups, substituted or unsubstituted heteroaryls, amino, cyano, azido, hydroxy, mercapto, keto, carboxy, ethoxy and methoxy.
• the substituents are advantageously chosen according to the specific chemical and electronic properties that the person skilled in the art wishes to obtain for the polymeric composition.
• the presence of aliphatic chains significantly increases the solubility of the chemical compounds in aprotic apolar organic solvents.
• the delocalization of electrons from chemical compounds can be optimized by choosing the appropriate substituent through theoretical calculations that determine specific chemical potentials or electron-level energy values.
• the modeling of acceptor and donor materials makes it possible to predict the energies of the highest occupied and lowest vacant orbitals to optimize the formation of the excitons necessary for the operation of the photovoltaic cell, and to develop the desired organic polymer composition, for example by using a DFT calculation program such as Gaussian 98 ®.
• the mixture as obtained at the end of the mixing step is deposited on a substrate directly without resorting to annealing. '• *
• the mixing step is carried out with stirring. * '
• the nanofibrils of the mixture represent 25% to 93% by weight of the semiconductor electron donor material.
• the nanofibrils are prepared before the step of mixing the process according to the invention during a step of dissolving at least one electron donor semiconductor polymer material in a solvent promoting the obtaining of nanofibrils.
• the dissolution step is carried out by dissolving in a solvent at a temperature above room temperature, followed by slow cooling to room temperature.
• the The solvent is organic and is selected from p-xylene, cyclohexanone, chlorobenzene, dichlorobenzene and a mixture thereof.
• the solvent is ⁇ -xylene.
• the cooling of the solution comprising at least one electron donor semiconductor polymeric material in an organic solvent it is possible to control the cooling of the solution comprising at least one electron donor semiconductor polymeric material in an organic solvent to allow the polymer chains to associate into fibrillar structures.
• the phenomenon of association can be relatively slow and the formation of nanofibrils can require several days.
• the formation of the nanofibrils may be partial and a fraction of non-associated polymeric material may remain at the end of the nanofibril formation step.
• nanofibrils can be followed and / or controlled by any optical method adapted to the polymeric material.
• any optical method adapted to the polymeric material Preferably, those skilled in the art will consider a method for estimating the appearance of lower energy absorption bands which are characteristic of a solution of nanofibrils, which do not appear for a solution of non-polymeric material. associated. UV-visible spectrophotometry allows such an estimate.
• non-associated polymeric material any material comprising at least one polymer whose polymer-polymer interaction in solution may be neglected with respect to the polymer-solvent interaction.
• amorphous polymeric material is meant any material comprising at least one polymer that does not have polymer chains in the form of nanofibrils as defined in the present application, that is to say not associated with each other in the state solid. Typically, this phase is obtained from non-associated polymeric material by evaporation of the solvent.
• P3HT nanofibrils are prepared by dissolving P3HT in cyclohexanone.
• the solution thus obtained is heated to a temperature of about 150 ° C and then cooled slowly to room temperature.
• the P3HT is dissolved in p-xylene, the solution is brought to a temperature of about 70 ° C and then cooled to room temperature.
• the cooling speed will be chosen between 1O 0 C and 10O 0 Ch 5 preferably between 20 ° C and 25 0 Ch "1. It is also possible to perform the cooling by successive stages.
• a partial precipitation of the polymeric material can occur during cooling.
• homogeneous solution is meant a solution without apparent precipitate and stable over time (Example 1).
• the solvent is cyclohexanone
• the filtration is performed on a filter whose porosity is adapted accordingly.
• the preparation of the nano-fibrils is carried out in the absence of light and under an inert atmosphere (nitrogen or argon, for example).
• the nanofibrils are separated from the fraction of non-associated electron donor polymer material by centrifugation and / or filtration.
• the nanofibrils thus obtained can optionally be dried and isolated in the form of a powder. Solubilization of these nanofibrils at room temperature in a compatible solvent such as ⁇ -xylene generally leads to a homogeneous solution. The phenomenon of disassociation of polymer chains seems limited in p-xylene.
• the proportion of nanofibrils can range from 75% to 93% by weight of the total electron donor semiconductor polymer material.
• the solution obtained can optionally be diluted in the same organic solvent.
• the subject of the present invention is also a polymeric composition with photovoltaic properties obtained by the process according to the invention.
• the electron-donor polymer semiconductor material of the photo-voltaic polymer composition is poly (3-hexylthiophene) and the electron acceptor material is 1- (3-methoxycarbonyl) -propyl-1-phenyl - [6,6] -C61.
• the polymeric composition according to the invention contains from 0.5 to 2% by weight of the electron donor semiconductor polymer material.
• the subject of the present invention is also a process for depositing a material comprising the polymeric composition according to the invention in the form of a thin layer, the material being deposited in monolayer or multilayer on a solid substrate by immersion, by the inkjet techniques, spinning, dripping, spreading or printing.
• the solid substrate is chosen from glasses, conductive polymers and polymers coated with conductive oxide and glasses coated with a conductive layer.
• Preferred conductive polymers are polyethylenedioxythiophene (PEDOT), polyaniline or a mixture thereof.
• a layer of conjugated organic polymers may be deposited between the thin layer and the substrate. This deposit makes it possible to smooth the surface of the substrate and / or to increase the output work of the electrode.
• the conjugated organic polymers are chosen from poly (aniline) in the conducting state, PEDOT doped with polystyrene sulfonate (PSS) and a mixture of these.
• the thickness of the layer of conjugated organic polymers is generally between 10 and 150 nm, preferably 80 nm.
• the subject of the present invention is a photovoltaic cell of the heterojunction volume type comprising at least two electrodes electrically interconnected by the polymeric composition according to the invention or by the thin layer according to the invention.
• the composition is chosen such that the external conversion efficiency of the photovoltaic cell is greater than or equal to 3%.
• the electrodes can be independently conductive or semiconducting.
• a conductive electrode comprises a metal surface of metals such as gold, calcium, aluminum, silver, magnesium, chromium, lithium, or alloys. metals. It may also comprise a stack of metal layers and / or conductive oxide such as InSn 2 O 3 .
• a semiconductor electrode comprises silicon.
• the semiconductor electrode may optionally be deposited on an insulating material such as silica, alumina or glass
• at least one of the electrodes is transparent
• the semiconductor electrode may be deposited on an insulating material such as silica, alumina or glass.
• a photo voltaic cell according to the invention can be prepared on a transparent substrate (71) of a material that can be flexible or rigid, for example glass, and on which is deposited a conductive layer (72) consisting of metal oxide such as Indium Tin Oxide (ITO), the ITO film (72) can be engraved on a third of the surface, for example. advantageously sonicated in different solutions: preferably acetone, then isopropanol. It is then rinsed with deionized water and dried in an oven for example. Contacts (73), preferably chromium-gold, can then be deposited under vacuum to allow measurement of the I (V) characteristic of the cell. UV-Ozone treatment is then generally applied to the ITO substrate.
• ITO Indium Tin Oxide
• a pre-layer (74) which may be conductive poly (aniline) or PEDOT (poly (ethylenedioxy-thiophene)) doped with PSS (polystyrene sulfonate) is deposited on this substrate.
• the thin film comprises a composition comprising electron-donor semiconductor polymer material and electron-accepting material, preferably PCBM, it is liquid deposited directly on the pre-layer described above.
• the electrode consists of a film (76), generally LiF, of a thickness of 0.5 to 5 nm, preferably 1 nm, deposited for example under vacuum on the thin layer (75) and a metal layer, for example aluminum, advantageously deposited under vacuum and having a thickness of 5 to 200 nm, but preferably 100 nm which is covered with LiF film.
• a metal layer for example aluminum, advantageously deposited under vacuum and having a thickness of 5 to 200 nm, but preferably 100 nm which is covered with LiF film.
• the photovoltaic cell has generally the shape of a rectangle with for example a width of 17 mm and a length of 25 mm.
• the polymeric composition according to the invention forms a heterojunction between the two materials of the composition. Two ideally continuous networks are thus created on either side of this heterojunction.
• the process for preparing the polymeric composition makes it possible to create a three-dimensional semiconductor network without resorting to annealing.
• This process represents a decisive advance in the fields of electronics and optoelectronics, particularly in the field of organic solar cells, because of its simplicity of implementation and the control of the morphology of the layers obtained.
• This technique makes it possible to obtain in solution a mixture of two different nanostractures, for example and advantageously for the production of photovoltaic cells a mixture of nano fibrils of P3HT and PCBM in all proportions. This allows by the usual techniques of solution deposits to obtain in a single step a layer whose morphology and thickness are controlled.
• Figure 1 shows the evolution of the absorption of a 1% P3HT solution at 25 ° C in p-xylene at 2, 6, 21, 28 and 48h after cooling. !
• FIG. 2 shows the absorption spectra of a thin layer prepared from 0.5%, 0.2% and 0.1% by weight P3HT solutions in p-xylene and deposited directly on a carrier.
• glass (a) of a solution prepared from P3HT solutions at 0.5% by weight in p-xylene
• (b) of a solution prepared from P3HT solutions at 0.5% by weight in p-xylene
• Figure 3 shows the absorption spectrum of a solution prepared from 0.5% P3HT lep-xylene (a) solutions and its fluorescence spectrum at 610 nm excitation (f).
• Figure 4 shows the absorption spectrum of solutions having ratios of nanofibers and non-associated polymeric material of 100/0, 75/25, 50/50, 39/61 and 0/100.
• Figure 5 shows the fluorescence emission spectra of compositions of P3HT alone (a), P3HT + PCBM (b), and PCBM alone (c) in ⁇ -xylene.
• FIG. 6 corresponds to a two-dimensional diagrammatic representation of a composition according to the invention
• the continuous lines represent electron donor polymer nanofibrils (61), in gray the space occupied by the electron-accepting materials ( 62), and blank the vacant spaces (63).
• Figure 7 is a schematic sectional view (a) and taken from above (b) of a photovoltaic cell having a thin layer (5) incorporating the compositions according to the invention.
• Figure 8 shows the absorption spectrum of a thin layer
• P3HT PCBM of 1: 1 deposited on a glass support obtained from a 1% solution of P3HT not associated in chlorobenzene (a), of this same thin layer annealed at 100 ° C. for 30 minutes (b) and a thin layer obtained from a solution containing P3HT nanofibrils in p-xylene (c).
• FIG. 9 represents the current density Jsc in mA / cm 2 as a function of the voltage applied across a photovoltaic cell whose thin layer is obtained from a solution having a proportion of nanofibrils of 75%, relative to to the total mass of polymeric material with a P3HT: PCBM ratio of 1: 1.
• Curve (a) corresponds to a measurement made on the cell as such:
• curve (b) corresponds to a measurement made on the same cell after a annealing, carried out at 100 ° C for 30 minutes.
• Jsc in mA / cm 2 corresponds to the short-circuit current density
• Voc in V corresponds to the open circuit voltage
• FF corresponds to the FiIl factor or filling factor which characterizes the rectifying nature of the diode.
• FF I.
• the solution is filtered on a porous membrane (for example a Teflon® membrane filter with a porosity of 0.45 ⁇ m) in order to eliminate the precipitate which began to form at 70 ° C.
• a porous membrane for example a Teflon® membrane filter with a porosity of 0.45 ⁇ m
• the process of formation of nanofibrils is continued by cooling the filtrate with the same speed to room temperature.
• nanowires are then recovered and resuspended in p-xylene
• the spectrum of the solution thus obtained shows that most of the non-associated polymeric material has been removed ( Figure 4)
• These purified nanofibrils can then be used as such or in admixture with a determined amount of non-associated polymeric material.
• nanofibril deposits are made.
• a native oxide-coated silicon wafer is immersed in the solution of 0.05% by weight P3HT nanofibrils in ⁇ -xylene or cyclohexanone for a time of between 10 seconds and 10 minutes, and then the excess of solution is removed under an argon flow.
• EXAMPLE 4 Spin Deposition on Different Substrates P3HT nanofibrils at 0.5% by weight in p-xylene are spin-coated onto a silicon wafer with deposition conditions of: 1000 rpm .min "1 for 40s then 2000 rpm " 1 for 60s with an acceleration of 200 rpm "1 .
• P3HT nanofibrils at 0.5% by weight in p-xylene are deposited by spin coating on glass with deposition conditions of Example 3. The thicknesses of these films are of the order of 30-40 nm.
• P3HT nanofibrils at 1% by weight in p-xylene are deposited by spin coating on glass with the same deposition conditions, in this case the thicknesses obtained are of the order of 80 to 110 nm.
• EXAMPLE 5 Multiple Spin Deposition on Different Substrates Successive deposition of nanofibrils is carried out as follows: a first layer is deposited from a solution of nanofibrils at 0.5% by weight in / xylene in the conditions of Example 4, then the next layer is deposited from the same solution immediately after the end of the rotation of the spin and without additional drying of the underlying layer. This procedure is repeated as many times as necessary so as to increase the thickness of the deposit to the desired value.
• the deposits, of the polymer alone, carried out on glass have a thickness varying in an increasing manner by 30 nm for a layer deposited at 70 nm for two layers.
• the value of the absorbance (A) evolves according to the number of deposited layers: the maximum A max ( 555n m) - 0.45 ua for 1 layer, 0.85 for 2 layers and 1.95 for 4 layers.
• nanofibrils in solution is signaled by the emergence of several absorption bands shifted towards the lowest energies compared to the initial peak (band attributed to non-associated polymer chains and indicated by an arrow) ( Figure 1).
• Deposits made on transparent substrate (glass) are characterized by a set of three absorption bands and an absorption threshold located at about 650 nm (1.9 eV) ( Figure 1).
• nanofibril solutions For P3HT these absorption bands are around 525, 560 and 610 nm.
• the nanofibril solutions have an electron absorption spectrum characterized by the appearance of lower energy bands than for polymer chains in p-xylene solution which have an absorption maximum around 450 nm.
• Nanofibrils solutions of P3HT in cyclohexanone and p-xylene as well as solid deposits were characterized by UV-visible absorption spectroscopy (Figure 2) and fluorescence (Figure 3).
• the absorption spectra in solution or in solid have a fine structure characteristic of a good organization of the polymer chains between them.
• the use of this type of compound, thanks to its characteristics, in a photovoltaic device allows an efficient transport of the excitons towards the sites of dissociation of the charges then a good routing of the holes towards the anode.
• Solutions of nanofibrils and non-associated polymer chains are obtained by simply mixing a solution of 1% P3HT nanofibrils in p-xylene and a solution of non-associated polymer chains of P3HT (part soluble in dichloromethane) at 1% in xylene.
• the evolution of the absorption spectra in solution shows that the two forms of polymers are miscible in all proportions ( Figure 4).
• the layers deposited from this type of solution may contain variable and fully adjustable proportions of nanofibrils and amorphous polymer.
• the electron donor compound PCBM is added in solid form to a solution of P3HT nanofibrils at 1% by weight in p-xylene.
• the ratio P3HT: PCBM is 1: 1.
• the mixture is stirred to have a homogeneous solution.
• FIG. 5 the different fluorescence spectra in the p-xylene of compositions (PCBM / P3HT) according to the invention or of PCBM and P3HT are observed. There is a gradual decline (quenching) as a result of increasing PCBM input, which translates a transfer of P3HT loads to PCBM.
• composition obtained is homogeneous and stable at room temperature, its structure is schematically represented in FIG.
• Example 8 preparation of a composition nanofibrils of P3HT / PCBM • "-. ..
• the electron donor compound PCBM is added in solid form to a solution of non-associated polymer chains of 1% by weight P3HT in p-xylene.
• the ratio P3HT: PCBM is 1: 1.
• the solution is heated with stirring at 70 ° C. During the dissolution process, the solution is protected from light and ambient air, to avoid chemical oxidation and / or photooxidation processes of the polymer.
• the clear solution obtained is cooled to room temperature with a speed of 20 ° C. -1 , the passage from the orange color to the blue color observed is characteristic of the appearance of the nanofibrils. stable over time, the mixture can be stirred in order to have a homogeneous solution at 75% by weight of nanofibrils relative to the total polymer.
• EXAMPLE 9 Preparation of a P3HT / PCBM Composition A solution of 2% by weight PCBM in ⁇ -xylene is added to a solution of P3HT nanofibrils at 2% by weight in p-xylene.
• the P3HT: PCBM ratio is 1: 1 and the final concentration of 1% by weight of P3HT in p-xylene. The mixture is stirred to have a homogeneous solution.
• a photovoltaic cell used for the tests has a configuration as shown in FIG. 7. It comprises a glass substrate, covered with a layer of ITO which is itself coated with a layer of PEDOT: PSS (conductive polymer marketed by Bayer). The upper layer of PEDOT: PSS is covered with a film (nanofibrils and PCBM) according to the invention. The film or active layer is finally coated successively with a layer of LiF and an aluminum layer.
• the configuration of the cell is as follows:
• Step 1 A layer of PEDOT: PSS (product marketed by Bayer) is deposited by spinning. The thickness of the layer obtained is approximately 80 nm, the deposition is carried out in air, then dried in an oven and under vacuum.
• Step 2 The deposition of the active layer is carried out under nitrogen in a glove box.
• the active surface is 3 cm 2 .
• It is prepared by spin coating a P3HT / PCBM composition, with a percentage of nanofibrils of 75% by weight relative to the total polymeric material, with a P3HT: PCBM ratio of 1: 1, in the xylene, at a concentration of P3HT solution of 1% by mass on a glass wafer at about 1000 tr.min "1 for 40 sec then 2000 tr.min” 1 for 60 seconds with an acceleration of 200 tr.min " 1 .
• Step 3 A layer of LiF (about 1 nm) is deposited under vacuum and then an aluminum layer (100 nm) is also deposited under vacuum. The surface is about 0.3 cm 2 .
• the cell according to the invention prepared is then characterized in glove box under controlled atmosphere, Le. a nitrogen atmosphere with oxygen and water vapor levels below 1 ppm and at room temperature.
• the current-voltage characteristics (1 (V)) are recorded under illumination AM 1.5 at a power of 1000 W / m 2 .
• the table of FIG. 9 comprises the characteristics of the cells with an active layer according to the invention. The yield presented corresponds to the conversion rate of photons into electrons.

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• 2005
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• 2006
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