GB2424512A - Method of forming photovoltaic device - Google Patents

Method of forming photovoltaic device Download PDF

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GB2424512A
GB2424512A GB0505885A GB0505885A GB2424512A GB 2424512 A GB2424512 A GB 2424512A GB 0505885 A GB0505885 A GB 0505885A GB 0505885 A GB0505885 A GB 0505885A GB 2424512 A GB2424512 A GB 2424512A
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conducting polymer
layer
electrode
hole conducting
groups
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Frederik Christian Krebs
Holger Spanggaard
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Riso National Laboratory
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    • 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
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    • H01L51/0034—
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    • H—ELECTRICITY
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    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B33/00—Electroluminescent light sources
    • H05B33/10—Apparatus or processes specially adapted to the manufacture of electroluminescent light sources
    • 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
    • H10K30/20—Organic devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation comprising organic-organic junctions, e.g. donor-acceptor junctions
    • H—ELECTRICITY
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    • 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
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    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K71/00—Manufacture or treatment specially adapted for the organic devices covered by this subclass
    • H10K71/40—Thermal treatment, e.g. annealing in the presence of a solvent vapour
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    • 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
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    • 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
    • H10K85/114—Poly-phenylenevinylene; Derivatives thereof
    • H—ELECTRICITY
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    • 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
    • H10K85/151—Copolymers
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G2261/00—Macromolecular compounds obtained by reactions forming a carbon-to-carbon link in the main chain of the macromolecule
    • C08G2261/30—Monomer units or repeat units incorporating structural elements in the main chain
    • C08G2261/32—Monomer units or repeat units incorporating structural elements in the main chain incorporating heteroaromatic structural elements in the main chain
    • C08G2261/322—Monomer units or repeat units incorporating structural elements in the main chain incorporating heteroaromatic structural elements in the main chain non-condensed
    • C08G2261/3223—Monomer units or repeat units incorporating structural elements in the main chain incorporating heteroaromatic structural elements in the main chain non-condensed containing one or more sulfur atoms as the only heteroatom, e.g. thiophene
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G2261/00—Macromolecular compounds obtained by reactions forming a carbon-to-carbon link in the main chain of the macromolecule
    • C08G2261/30—Monomer units or repeat units incorporating structural elements in the main chain
    • C08G2261/34—Monomer units or repeat units incorporating structural elements in the main chain incorporating partially-aromatic structural elements in the main chain
    • C08G2261/342—Monomer units or repeat units incorporating structural elements in the main chain incorporating partially-aromatic structural elements in the main chain containing only carbon atoms
    • C08G2261/3422—Monomer units or repeat units incorporating structural elements in the main chain incorporating partially-aromatic structural elements in the main chain containing only carbon atoms conjugated, e.g. PPV-type
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G2261/00—Macromolecular compounds obtained by reactions forming a carbon-to-carbon link in the main chain of the macromolecule
    • C08G2261/70—Post-treatment
    • C08G2261/80—Functional group cleavage, e.g. removal of side-chains or protective groups
    • H—ELECTRICITY
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    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K2102/00—Constructional details relating to the organic devices covered by this subclass
    • H10K2102/10—Transparent electrodes, e.g. using graphene
    • H10K2102/101—Transparent electrodes, e.g. using graphene comprising transparent conductive oxides [TCO]
    • H10K2102/103—Transparent electrodes, e.g. using graphene comprising transparent conductive oxides [TCO] comprising indium oxides, e.g. ITO
    • 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
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    • 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
    • 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

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  • Manufacturing & Machinery (AREA)
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  • Physics & Mathematics (AREA)
  • Nanotechnology (AREA)
  • Electromagnetism (AREA)
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  • Theoretical Computer Science (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Photovoltaic Devices (AREA)

Abstract

A method of forming a conducting polymer based photovoltaic device includes providing a first electrode with a layer of hole conducting polymer, providing the hole conducting layer with a layer of electron conducting material and providing the layer of electron conducting material with a second electrode. The hole conducting polymer layer may contain thermally cleavable groups, in which case heating the layer causes thermal cleavage. The hole conducting polymer may comprise a polythiophene or PPV substituted with ester groups. Subsequent to cleaving, the hole conducting polymer layer contains groups capable of strong, non-covalent interactions such as free carboxylic acid groups or thioacids, and polymer chains lock together forming a hard matrix. The device may also be an electroluminescent device.

Description

METHOD OF FORMING PHOTOVOLITAIC DEVICE
The present invention relates to a method of forming a photovoltaic device, to a photovoltaic device so formed, and to an assembly including such a device. Photovoltaic devices inter-convert light and electricity.
Solar power is an important renewable energy source, and can be harvested using photovoltaic cells (solar cells) Renewable energy sources are desirable for a number of reasons. First, such energy sources enable a reduction in consumption of non-renewable energy sources. Second, such energy sources enable the use of electrical devices without the need for a mains power source or for batteries which must periodically be replaced. This is of particular interest in remote locations, for example at sea or in developing countries.
In solar cells, photons are absorbed and the energy of the photon forms an exciton consisting of ap electron and a hole which initially are bound together. These can be separated into free charge carriers and caused to migrate towards respective electrodes by an electric field, suitably produced by electrodes of differing work functions. Cells containing two components (heterojunction cells) can give much higher efficiency than cells containing a single component because of increased charge separation at the interface between the two components.
In electroluminescent devices, which can also be photovoltaic devices, electrons and holes injected at opposed electrodes reach one another by conduction and recombine to produce light.
Solar cells may rely on photovoltaic polymers. It has been recognised that potentially such devices have advantages over the conventional, similar devices based on inorganic semiconductors. These potential advantages include cheapness of the materials and versatility of processing methods, flexibility (lack of rigidity) and toughness.
Photovoltaic polymers can be derived from chemically doped conjugated polymers, for example partially oxidised (p-doped) polypyrrole. The article Conjugated polymers: New materials for photovoltaics', Wallace et al, Chemical Innovation, April 2000, Vol. 30, No. 1, 14-22 reviews the
field.
Previously known solar cells have suffered from the disadvantage of short lifetime. The half-lives of such solar cells have been measured in minutes, hours or days rather than weeks or months.
The present inventors have appreciated that solar cells based on photovoltaic polymers which have a long lifetime require high polymer density. Chemical reaction of oxygen and electrode material (such as aluminium) with the polymer is the primary degradation mechanism. High density slows the diffusion of oxygen and electrode atoms into the polymer film.
The conjugated polymers normally used in solar cells (poly(p-phenylenevinylene) polythiophene, etc.) are of high density, but are not soluble in normal organic solvents.
Solubility is of great importance if a polymer film is to be prepared from solution, e.g. by spincoating or silkscreen printing.
The present inventors have recognised the need for solar cells which have a long lifetime, and have appreciated that it would be particularly advantageous if such cells could be produced by preparing polymer films from solution.
In a first aspect, the present invention relates to a method of forming a conducting polymer based photovoltaic device comprising the steps of: providing a first electrode with a layer of hole conducting polymer containing thermally cleavable groups; providing the hole conducting polymer layer with a layer of electron conducting material; and providing the layer of electron conducting material with a second electrode, wherein the hole conducting polymer layer is heated to cause thermal cleavage of the thermally cleavable groups.
Preferably, the step of heating the hole conducting polymer layer is carried out between the steps of providing the first electrode with the layer of hole conducting polymer and providing the hole conducting polymer layer with the layer of electron conducting material. This allows the groups which have been thermally cleaved to escape from the hole conducting polymer layer.
Preferably, the photovoltaic device is a solar cell.
However, the device may also be an electroluminescent device.
Preferably, the first electrode is provided on a substrate. Suitable substrates include glass, plastics and cloth. It is preferred for the first electrode and the substrate to be substantially transparent, to allow light to reach the layers of hole conducting polymer and electron conducting material. This gives high cell efficiency.
Suitable hole conducting polymers include poly(terphenylene-vinylene), polyaniline, polythiophene, poly(2-vinyl-pyridine), poly(N-vinylcarbazole), poly- acetylene, poly(p-phenylenevinylene) (PPV), poly-o- phenylene, poly-m-phenylene, poly-p-phenylene, poly-2,6- pyridine, poly(3-alkyl-thjophene) or polypyrrole substituted with thermally cleavable groups. Of these, PPV and polythiophene substituted with thermally cleavable groups are particularly preferred.
Preferably, the thermally cleavable groups improve solubility of the hole conducting polymer in one or more solvents.
Preferably, after thermal cleavage the hole conducting polymer contains groups capable of strong, non-covalent interactions (most preferably free carboxylic acid groups) so that the polymer forms a hard matrix. These groups are preferably formed by thermal cleavage, but may be present before thermal cleavage has taken place. For example, polymers containing free carboxylic acid groups before thermal cleavage has taken place may be used. However, such polymers (for example poly(3-carboxyljc acid thiophene)) are typically not soluble in organic solvents.
In a preferred embodiment, the hole conducting polymer is a polythiophene or PPV substituted with ester groups (C=o-o-R) which cleave to give free carboxylic acid groups, for example 2- methylhexylcarboxylate ester groups. Tertiary ester groups are preferred as they are easily thermally cleaved, allowing low temperatures to be used. A preferred hole conducting polymer is poly(3-(2- methyihexylcarboxylate) thiophene) -co-thiophene. The synthesis and thermal cleavage of this polymer has been published in J. Am. Chem. Soc. 2004, vol. 126, p.9486-9487 by Jinsong Liu et al. Other suitable substituents are thioesters which may cleave to give thioacids.
The polymers may be further substituted to alter their electronic properties with electron withdrawing or donating groups, or to alter their physical properties, such as solubility, for example with alkyl groups. However, alkyl groups are not preferred as they affect formation of the polymer matrix.
A mixture of substituents may be used.
Preferably, the hole conducting polymer is unbranched.
The hole conducting polymer may be blended with a dye or a mixture of dyes. The hole conducting polymer may be a co-polymer, for example a block co-polymer.
Preferably, the hole conducting polymer layer is provided on the first electrode by coating a solution of hole conducting polymer on the first electrode followed by removal of the solvent. Coating may be carried out by spin coating or screen printing a solution of the hole conducting polymer, or by the use of a doctor blade.
Suitable solvents include any organic Or inorganic solvent: examples include chlorobenzene, chloroform, dichloromethane, toluene, benzene, pyridine, ethanol, methanol, acetone, dioxane, tetrahydrofuran, alkanes (pentane, hexane, heptane, octane etc.), water (neutral, acidic or basic solution) or mixtures thereof. To the solution, small amounts of a suitable polymer (for example, polystyrene or polyethylene glycol) may be added to adjust the viscosity.
There are various considerations which determine the optimum thickness of the hole conducting polymer layer.
An exciton is generated at the spot where a photon is absorbed. This occurs throughout the polymer material, but mostly close to the transparent electrode. In order to generate electricity, the exciton has to reach a dissociation location (for example the electrode surface, or the polymer/fullerene interface) and the charge carrier has to reach an electrode (holes and electrons go to opposite electrodes) The thicker the polymer layer, the more likely photon absorption is to take place. A certain thickness is required in order to absorb sufficient light. A thickness giving an absorbance of around 1 (this corresponds to 90% absorbance of the light) is preferable.
However, if the thickness is too high the average distance that an exciton or a charge carrier (a hole or an electron), has to diffuse becomes too long, because of the possibility that the exciton will recombine and produce heat, or that a free hole will meet a free electron and recombine.
The optimum thickness also depends on manufacturing considerations. Some techniques give thick films and others give thin films.
As the film thickness increases, the chance of film defects (holes that allows the two electrodes to touch) leading to a short circuit decreases.
Taking all these factors into consideration, it is preferred for the hole conducting polymer layer to have a thickness of at least 10 nm. Preferred thicknesses are in the range of 30 nm to 300 nm, for example about 100 nm.
Preferably, heating of the hole conducting polymer layer is carried out at a temperature between 50 and 400 C, more preferably between 100 and 300 C, for example at a temperature of 210 C. The temperature must not be too high because at high temperatures the polymer and/or electrode material may start to degrade.
Preferably, heating is carried out in at atmosphere without oxygen or with reduced oxygen, for example under an inert atmosphere or in a vacuum oven. This helps to prevent degradation of the polymer and/or electrode.
Preferably, the electron conducting material comprises optionally substituted fullerene or optionally substituted carbon nanotube. In a preferred embodiment, the electron conducting material is fullerene. Suitable substituted fullerenes are C60- [C(cooH)2] and Nmethylfulleropyrrolidjn The preparation of C60- [C(COoH)2] is described by Hirsch and co-workers in Lamparth et al. J. Chem. Soc., Chem. Commun., 1994, p1727, Hirsch et al. Angew.
Chem. mt. Ed. Engi., 1994, 33, p437, Hirsch et al. J. Am. Chem. Soc., 1994, 116, p9385 and Lamparth et al. Angew.
Chem. mt.. Ed. Engi. , 1995, 34, p1607) However, the electron conducting material may be a conducting polymer.
Preferably, the electron conducting ma.erial is provided on the hole conducting polymer layer by evaporation.
The term "electrode" is used to refer to a component which is capable of acting as an electron conductor throughout its thickness.
Preferably, the work function of each electrode is matched to the work function of the material in contact with that electrode so that carrier transfer between each material and its respective electrode is obtained with substantially no barrier energy.
Preferably, the electrodes are chosen from the following materials: calcium, aluminium, scandium, neodymium, yttrium, samarium, europium, magnesium or magnesium-indium, gold, silver, nickel, palladium, platinium, tungsten, chromium, poly(3,4-ethylenedioxythiophene) (PEDOT), indium-tinoxide (ITO) , zinc oxide or tin (IV) oxide.
Preferably, there is a difference in the work functions of the two electrodes. Preferably, the difference is above 0.1 eV.
Preferably, the second electrode is reflective. This increases the efficiency of the device. More preferably, the second electrode comprises aluminium.
Suitably, the first electrode is ITO and the second electrode is aluminium.
Suitably, where the solar cell comprises a metal electrode, this is a very thin evaporated metal electrode layer. The thickness of the electrode layer must be sufficient to give adequate electrical conductivity. For this reason it is preferably at least 10 nm, more preferably at least 100 nm. A thickness of around 1 pm is suitable.
The first and second electrodes must not touch, as this Optionally, the device further comprises a protective layer provided on the second electrode.
In a second aspect, the present invention provides a conducting polymer based photovoltaic device formed by the method described above.
Preferably, the photovoltaic device contains no further layers in addition to those described above.
In a third aspect, the present invention provides an assembly comprising at least one photovoltaic device as described above electrically connected to another component.
Where the photovoltaic device is a solar cell, the other component is preferably a power consuming device. The power consuming device may for example be a light source or a motor. The assembly may also comprise power storing means, for example a capacitor, supercapacitor or rechargeable battery. This means that light energy harvested by the solar cell can be stored until electrical power is needed.
Where the photovoltaic device is an electroluminescent device, the other component is preferably a power source, for example a battery.
In a fourth aspect, the present invention provides a conducting polymer based photovoltaic device comprising the following layers: a first electrode; a layer of hole conducting polymer containing free carboxylic acid and/or thioacid groups; a layer of electron conducting material; and a second electrode.
In a fifth aspect, the present invention provides the use of a hole conducting polymer containing free carboxylic acid and/or thioacid groups to increase the lifetime of a photovoltaic device.
Features described in connection with any aspect of the invention can also be applied to any other aspect of the invention.
The present invention will be further described with reference to a preferred embodiment, as shown in the accompanying Figure, in which: Fig. 1 shows the method of the preferred embodiment.
Poly(3- (2-methylhexylcarboxylate)thiophene) -co-- thiophene was synthesised by the method of Jinsong Liu et al. (J. Am. Chem. Soc. 2004, vol. 126, p.9486-9487) . The synthesis is outlined below:
HO Br4r
(H3C)3Sn s Sn(CH3)3 -_/ 1 A film of poly(3- (2-methylhexylcarboxylate) thiophene) co-thiophene of thickness about 100 nm was spin-coated from a chloroform solution (20 mg/ml) onto an indium-tin oxide covered glass substrate. The absorption of the film was about 1 at the absorption maximum (about 460 nm) The film was then heated to 210 C for 30 minutes in a vacuum oven. During this procedure the side groups were cleaved as shown below:
A
A layer of fullerene of thickness about 100 nm was formed on top of the conducting polymer layer by heating a sample of fullerene in a vacuum oven with the substrate fixed in a rotating shadow mask using standard procedures.
An aluminium second electrode was formed. In a high vacuum chamber the aluminum was heated thermally or by using an electron beam. Aluminum was evaporated in the same way as fullerene until a suitable electrode thickness (typically around 1000 nm) was obtained.
The finished cell had an active area of 3 cm2. Under a sun simulator (1000 W/m2) the cell supplied 1 mA/cm2 at 0.55 mV and had an overall efficiency of 0.28 % and a fill-factor of 49 %. The half-life of the cell was determined over 2000 h at 72 C under 1000 W/m2 as at least 10 000 h under the 1000 W/m2 sun simulator (assuming a linear decay of efficiency) The thermally cleavable ester groups used in the preferred embodiment of the invention improve solubility of the hole conducting polymer in chloroform. The hole conducting polymer layer can thus be formed by coating a solution of the hole conducting polymer onto the first electrode, which is a simple process step. As the ester groups are thermally cleaved, they are not present in the final solar cell, where they would affect formation of the polymer matrix.
The solar cell of the preferred embodiment of the invention has a much longer lifetime than other solar cells.
This solar cell therefore offers a number of advantages
over the prior art.
Without wishing to be bound by this theory, the inventors believe that heating the layer of hole conducting polymer causes an increase in density and also causes annealing/cross-linking. Important factors in the improved lifetime of the solar cell of the preferred embodiment are the high density of the hole conducting polymer layer, and the free carboxylic acid groups of the hole conducting polymer layer. The use of a hole conducting polymer layer with strongly interacting groups such as free carboxylic acid groups and with few or no "soft" side groups (such as flexible alkyl groups) locks the polymer chains together to form a hard matrix. The use of a fullerene electron conducting layer is also significant. This prevents chemical reaction between the aluminium electrode and hole conducting polymer.
Whilst the invention has been described with reference to a preferred embodiment, it will be appreciated that various modifications are possible within the scope of the invention.

Claims (1)

  1. Claims: 1. A method of forming a conducting polymer based photovoltaic
    device comprising the steps of: providing a first electrode with a layer of hole conducting polymer containing thermally cleavable groups; providing the hole conducting polymer layer with a layer of electron conducting material; and providing the layer of electron conducting material with a second electrode, wherein the hole conducting polymer layer is heated to cause thermal cleavage of the thermally cleavable groups.
    2. A method as claimed in Claim 1, wherein the photovoltaic device is a solar cell.
    3. A method as claimed in either one of the preceding claims, wherein the hole conducting polymer comprises polythiophene and/or PPV substituted with thermally cleavable groups.
    4. A method as claimed in Claim 3, wherein the thermally cleavable groups are ester groups.
    5. A method as claimed in Claim 4, wherein the hole conducting polymer comprises poly(3-(2- mechyihexylcarboxylate) thiophene) -co-thiophene.
    5. A method as claimed in any one of the preceding claims, wherein the hole conducting polymer layer contacts the first electrode.
    7. A method as claimed in any one of the preceding claims, wherein the hole conducting polymer layer has a thickness of at least 10 nm.
    8. A method as claimed in any one of the preceding claims, wherein the hole conducting polymer layer is provided on the first electrode by coating a solution of hole conducting polymer on the first electrode followed by removal of the solvent.
    9. A method as claimed in any one of the preceding claims, wherein thermal cleavage of the thermally cleavable groups is carried out by heating the hole conducting polymer layer to a temperature between 50 C and 400 oc.
    10. A method as claimed in any one of the preceding claims, wherein the hole conducting polymer after thermal cleavage contains free carboxylic acid groups.
    11. A method as claimed in any one of the preceding claims, wherein the electron conducting material comprises fullerene.
    12. A conducting-polymer based photovoltaic device formed by the method of any one of the preceding claims.
    13. An assembly comprising at least one photovoltaic device as claimed in Claim 12 electrically connected to another component.
    14. A conducting-polymer based photovoltaic device comprising the following layers: a first electrode; a layer of hole conducting polymer containing free carboxylic acid and/or thioacid groups; a layer of electron conducting material; and a second electrode.
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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2009103706A2 (en) * 2008-02-18 2009-08-27 The Technical University Of Denmark Method of thermocleaving a polymer layer
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WO2009103706A2 (en) * 2008-02-18 2009-08-27 The Technical University Of Denmark Method of thermocleaving a polymer layer
WO2009103705A1 (en) * 2008-02-18 2009-08-27 The Technical University Of Denmark Air stable photovoltaic device
WO2009103706A3 (en) * 2008-02-18 2009-10-29 The Technical University Of Denmark Method of thermocleaving a polymer layer
EP2311894A1 (en) * 2008-08-07 2011-04-20 Mitsubishi Chemical Corporation Polymer, material for luminescent layer, material for organic electroluminescent element, composition for organic electroluminescent element, and organic electroluminescent element, solar cell element, organic el display device, and organic el lighting utilizing same
EP2311894A4 (en) * 2008-08-07 2011-06-22 Mitsubishi Chem Corp Polymer, material for luminescent layer, material for organic electroluminescent element, composition for organic electroluminescent element, and organic electroluminescent element, solar cell element, organic el display device, and organic el lighting utilizing same
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CN104769154B (en) * 2012-10-18 2018-06-22 荷兰应用自然科学研究组织Tno The semiconductor subassembly for manufacturing the method for multi-lager semiconductor component and being manufactured by this method
EP2919288A4 (en) * 2012-11-09 2016-07-06 Sekisui Chemical Co Ltd Solar cell

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