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  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K50/00—Organic light-emitting devices
• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • 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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  • C09K11/00—Luminescent, e.g. electroluminescent, chemiluminescent materials
  • C09K11/06—Luminescent, e.g. electroluminescent, chemiluminescent materials containing organic luminescent materials
• • H—ELECTRICITY
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  • 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
  • H10K30/353—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 comprising blocking layers, e.g. exciton blocking layers
• • 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
  • H10K71/15—Deposition of organic active material using liquid deposition, e.g. spin coating characterised by the solvent used
• • 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
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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
  • H10K85/60—Organic compounds having low molecular weight
  • H10K85/611—Charge transfer complexes
• • H—ELECTRICITY
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  • 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
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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
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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

Definitions

• the present invention relates to a photovoltaic cell that comprises a first electrode, a second electrode, a photoactive layer between the first electrode and the second electrode, and a hole carrier layer between the first electrode and the photoactive layer, with the hole carrier layer comprising an oxidizing agent and a hole carrier polymer.
• Photovoltaic cells are commonly used to transfer energy in form of light into electricity.
• a typical photovoltaic cell comprises a first electrode, a second electrode and a photoactive layer between the first and second electrode.
• one of the electrodes allows light passing through to the photoactive layer.
• This transparent electrode may for example be made of a film of semiconductive material (such as for example indium tin oxide).
• photovoltaic cells have a hole carrier layer that comprises acidic hole carrier materials, such as for example poly(3,4-ethylenedioxythiophene) doped with polystyrenesulfonate (“PEDOT:PSS”), so as to provide a photovoltaic cell with sufficiently high conversion efficiency.
• PDOT:PSS polystyrenesulfonate
• the present application discloses an article comprising a first electrode, a second electrode, a photoactive layer between the first electrode and the second electrode, and a hole carrier layer between the first electrode and the photoactive layer, the hole carrier layer comprising an oxidizing agent and a hole carrier polymer, wherein the oxidizing agent is selected from the group consisting of
• R 1 to R 8 are independently of each other selected from the group consisting of hydrogen, fluorine, chlorine, bromine, iodine, N0 2 , COOH, and CN, with the provision that at least two of R 1 to R 8 are different from hydrogen, and wherein X 1 and X 2 are independently of each other selected from the group consisting of 0, S, Se, NR 9 with R 9 being selected from the group consisting of alkyl having from 1 to 10 carbon atoms, phenyl and phenyl substituted with alkyl having from 1 to 10 carbon atoms, or one of R 5 to R 8 may be -Sp-Pol selected from the group consisting of the following (l-Pol-A), (l-Pol-B), (I- Pol-C)
• R being hydrogen or fluorine, preferably fluorine; each n and m being independently of the other a number between 0 and 10, preferably between 0 and 5, most preferably 1 or 2; and "*" indicating the bonds to other monomeric units of the polymer, wherein the article is a photovoltaic cell.
• at least two of R 5 to R 8 are selected from the group consisting of hydrogen, fluorine, chlorine, N0 2 , COOH, and CN.
• the electron donor material comprises a polymer having the repeat unit of formula IV, below.
• R, R , R , and R are independently of each other selected from the group consisting of hydrogen, and hydrocarbyl with 1 to 40 C atoms that is optionally substituted and optionally comprises one or more hetero atoms, and A is C or Si.
• R, R 11 , R 12 , R 13 , and R 14 are independently of each other selected from the group consisting of hydrogen, substituted or unsubstituted C1-C24 alkyl, C1-C24 alkyl interrupted by one or more oxygen, aryl, Ci- C24 alkyoxy, and aryloxy.
• the present application also provides for a method for manufacturing the present article, wherein the method comprises the steps of
• step (b) subsequently coating the resulting solution from step (a) over a layer underneath,
• first and second solvent may be the same or different, and wherein the article is a photovoltaic cell.
• the present application provides for a method for manufacturing the present article, wherein the method comprises the steps of
• first and second solvent may be the same or different, and wherein the article is a photovoltaic cell.
• FIG. 1 is a cross-sectional view of an exemplary embodiment of a photovoltaic cell.
• FIG. 2 is a schematic of a system containing multiple photovoltaic cells electrically connected in series.
• FIG. 3 is a schematic of a system containing multiple photovoltaic cells electrically connected in parallel.
• the present disclosure provides a photovoltaic cell comprising a first electrode, a second electrode, a photoactive layer between the first electrode and the second electrode, and a hole carrier layer between the first electrode and the photoactive layer, the hole carrier layer comprising an oxidizing agent and a hole carrier polymer.
• compositions are disclosed that are useful in forming a hole carrier layer in such photovoltaic cells.
• the disclosed compositions comprise polymers or polymers plus small molecules that form ionomers once they are blended together.
• components of the compositions form a redox pair.
• the compositions are not water sensitive.
• the compositions are not acidic, and therefore not corrosive to metal and semiconductor electrodes. In some embodiments, the compositions are colorless. In certain embodiments, the composition the components of the redox pair can be synthesized separately. In certain embodiments, the polymers are solvent soluble.
• FIG. 1 shows a cross-sectional view of an exemplary photovoltaic cell 100 that includes a substrate 110, an electrode 120, an optional hole blocking layer 130, a photoactive layer 140 (e.g., containing an electron acceptor material and an electron donor material), a hole carrier layer 150, an electrode 160, and a substrate 170.
• a photoactive layer 140 e.g., containing an electron acceptor material and an electron donor material
• Electrodes 120 and 160 are in electrical connection via an external load so that electrons pass from electrode 120 though the load to electrode 160.
• the present hole carrier layer comprises an oxidizing agent as defined below and a hole carrier polymer as defined below. OXIDIZING AGENTS
• Suitable oxidizing agents may be selected from the group consisting of
• R 1 to R 8 are independently of each other selected from the group consisting of hydrogen, fluorine, chlorine, bromine, iodine, N0 2 , COOH, and CN, with the provision that at least two of R 1 to R 8 are different from hydrogen, and wherein X 1 and X 2 are independently of each other selected from the group consisting of 0, S, Se, NR 9 with R 9 being selected from the group consisting of alkyl having from 1 to 10 carbon atoms, : phenyl and phenyl substituted with alkyl having from 1 to 10 carbon atoms.
• one of R 5 to R 8 may be -Sp-Pol as defined below.
• at least two of R 5 to R 8 are selected from the group consisting of hydrogen, fluorine, chlorine, N0 2 , COOH, and CN.
• alkyl having from 1 to 10 carbon atoms are methyl, ethyl, n- propyl, iso-propyl, n-butyl, iso-butyl, tert-butyl, pentyl, hexyl, heptyl, octyl, nonyl and decyl, of which methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl and tert- butyl are preferred.
• R 1 to R 4 are CN, and R 5 to R 8 are hydrogen
• the compound of formula (I) is tetracyano-quinodimethane (TCNQ).
• Preferred examples of the compounds of formula (I) are those, wherein at least two, three or four of R 1 to R 4 and at least two, three or four of R 5 to R 8 are different from hydrogen.
• Particularly suited substituents R 1 to R 8 are selected from the group consisting of fluorine, N0 2 and CN; especially fluorine and CN.
• compound (l-a) may also be referred to as F4TCNQ, and compound (l-b) as F2TCNQ.
• Compound (I) may also be provided in the form of a polymer comprising a monomeric unit wherein one of one of R 5 to R 8 of compound (I) may be -Sp-Pol, wherein -Sp-Pol is selected from the group consisting of the following (l-Pol-A), (I- Pol-B), (l-Pol-C)
• R being hydrogen or fluorine, preferably fluorine; each n and m being independently of the other a number between 0 and 10, preferably between 0 and 5, most preferably 1 or 2; and "*" indicating the bonds to other monomeric units of the polymer.
• n is preferably 2.
• n is preferably 2 and m is preferably 7.
• An exemplary compound of formula (l-Pol-B) may for example be produced according to WO 2009/138010 from compound (I), wherein one of R 5 to R 8 is substituted with (CH 2 )2-NH 2 , and
• An exemplary compound of formula (l-Pol-C) may for example be synthesized from
• the polymers comprising a monomeric unit selected from the group consisting of (l-Pol-A), (l-Pol-B) and (l-Pol-C) may comprise a further monomer of formula
• R 10 are independently of each other hydrogen or fluorine, preferably fluorine, and R 11 is as defined above.
• the desired content in oxidizing compound can be adjusted by changing the molar ratio between monomeric units (l-k-A) and (l-k-B).
• the hole carrier polymer is a polymer capable of donating electrons.
• Exemplary polymers that are suitable may be selected from the list consisting of polythiophenes, polyanilines, polycarbazoles, polyvinylcarbazoles, polyphenylenes, polyphenylvinylenes, polysilanes, polythienylenevinylenes, poly- isothianaphthanenes, and copolymers or blends thereof.
• the hole carrier polymer comprises one or more monomeric unit selected from the following
• the hole carrier polymer comprises a first monomeric unit selected from the group consisting of D30, D31, D32, D33, D34 and D35 and a second monomeric unit selected from the group consisting of D117, D118 and D119, wherein R 11 , R 12 , R 13 , R 14 , X 11 and X 12 are as defined above.
• the hole carrier polymer comprises a first monomeric unit being D30 and a second monomeric unit selected from the group consisting of D117, D118 and D119, or alternatively a first monomeric unit selected from the group consisting of D30, D31, D32, D33, D34 and D35 and a second monomeric unit being D117, wherein R 11 , R 12 , R 13 , R 14 , X 11 and X 12 are as defined above.
• the hole carrier polymer comprises a first monomeric unit being D30 and a second monomeric unit being D117, wherein R 11 , R 12 , R 13 , R 14 , X 11 and X 12 are as defined above.
• p is a number from 0 to 10, preferably from 2 to 8 and most preferably p is 5.
• a specific example of a hole carrier polymer is
• EH CH 2 -CH(CH2-CH3)-(CH 2 )3-CH3.
• the hole carrier polymers have a number average molecular weight of at least 1,000 Da, more preferably of at least 1,500 Da and most preferably of at least 2,000 Da.
• the hole carrier polymers have a number average molecular weight of at most 200,000 Da, more preferably of at most 150,000 Da, even more preferably of at most 100,000 Da, and most preferably of at most 50,000 Da.
• reaction of the oxidizing agent and the hole carrier polymer can be as shown in Schema 1, below.
• a suitable hole carrier polymer using a terathofulvalene backbone can be obtained as shown in Schema 2, below.
• reaction of the oxidizing agent and the hole carrier polymer can be as shown in Schema 3, below.
• BBT-TTC6 is shown in the Schema 3, but most of the experimental work in the Examples, below, used BBT- TTEH.
• the TT (thienothiophene) family of polymers are relatively insoluble in all solvents, and they exhibit very low MWs, e.g., 2k - 4kDa.
• the mixture of a strong electron acceptor and a donor can spontaneously form a charge carrier complex (CTC), resulting in a p-type conductive polymer, i.e., a hole carrier polymer, that is not acidic.
• CTC charge carrier complex
• the cation content on the donor chain can be adjusted.
• hydrophobicity of the polymer can be adjusted by fluorinated pendants.
• hydrophobicity of the polymer can be adjusted by pendant hydrocarbon chains and the flexible polymer backbone. Exemplary embodiments are illustrated in Schema 4 and Schema 5, below.
• the present hole carrier layers can be substituted for a conventional hole carrier layer, such as for example PEDOT doped with PSS, to provide a photovoltaic cell with sufficiently high energy conversion and/or with sufficiently high lifetime due to the lack of corrosive substances. It is also believed that the present hole carrier layer allows for the production of sufficiently thick layers, thus offering the possibility to avoid, or at least reduce, shunting, which may produce short circuits, essentially by creating holes, during the production of photovoltaic cells on a large scale.
• a conventional hole carrier layer such as for example PEDOT doped with PSS
• the hole carrier layer can optionally comprise a binder.
• binder is a polymer.
• suitable polymers include acrylic resins, ionic resins, and polymers comprising an electron accepting group.
• Exemplary acrylic resins include methyl methacrylate homopolymers and copolymers, ethyl methacrylate homopolymers and copolymers, butyl methacrylate (e.g., n-butyl methacrylate or iso-butyl methacrylate) homopolymers and copolymers.
• Commercial examples of such acrylic resins include an ELVACITE series of polymers available from Lucite International (Cordova, TN).
• ionic polymers suitable for use as a binder can include positive and/or negative groups.
• positive groups include ammonium groups (e.g., tetramethylammonium), phosphonium, and pyridinium.
• negative groups include carboxylate, sulfonate, phosphate, and boronate.
• polymers containing an electron accepting group can be fluoro-containing polymers and cyano-containing polymers.
• Fluoro-containing polymers can be completely or partially fluorinated polymers. Examples of completely fluorinated polymers include poly(hexafluoropropylene), poly(perfluoroalkyl vinyl ether)s, poly(perfluoro-(2,2-dimethyl-l,3-dioxole), and poly(tetrafluoroethylene).
• partially fluorinated polymers include polyvinyl fluoride), poly(vinylidene fluoride), partially fluorinated polysiloxanes, partially fluorinated polyacrylates, and partially fluorinated polymethacrylates, partially fluorinated polystyrenes, and partially fluorinated poly(tetrafluoroethylene) copolymers
• fluoro-containing polymers include TEFLON, TEFLON AF, NAFION, and TEDLAR series of polymers available from E.I.
• Fluorinated ionic polymers e.g., polymers containing carboxyl, sulfonic acid, phosphonic acid
• suitable electron accepting groups include ⁇ -electron accepting groups (e.g., pentafluoro phenyl and pentafluoro benzyol) and boronate groups (e.g., pentafluoro phenyl boronate).
• the binder can include a sol gel.
• a hole carrier layer containing a sol gel as a binder can exhibit excellent mechanical properties and can form a very hard film. Such a layer can serve as an effective solvent barrier for the underlying layer during manufacturing of a photovoltaic cell.
• the sol gel can be a p-type semiconductor (i.e. a p- type sol gel).
• the p-type sol gel can be formed from a p-type sol, such as those containing vanadic acid, vanadium(V) chloride, vanadium(V) alkoxide, nickel(ll) chloride, nickel(ll) alkoxide, copper(ll) acetate, copper(ll) alkoxide, molybdenum(V) chloride, molybdenum(V) alkoxide, or a combination thereof.
• the binder can be at least about 1 vol% (e.g., at least about 2 vol%, at least about 5 vol%, at least about 10 vol%, or at least about 20 vol%) and/or at most about 50 vol% (e.g., at most about 40 vol%, at most about 30 vol%, at most about 25 vol%, or at most about 15 vol%) of hole carrier layer 150.
• the thickness of the hole carrier layer may be varied as desired.
• the thickness may for example depend upon the work functions of the neighboring layers in a photovoltaic cell.
• the layer comprising the hole carrier polymer has a thickness of at least 5 nm and/or of at most 500 nm.
• the photovoltaic cell comprises a photoactive layer, which in turn comprises an electron donor material and an electron acceptor material.
• the electron donor material may include a polymer selected from the group consisting of polythiophenes, polyanilines, polycarbazoles, polyvinylcarbazoles, polyphenylenes, polyphenylvinylenes, polysilanes, polythienylenevinylenes, polyisothianaphthanenes, polycyclopentadithiophenes, polysilacyclopentadithiophenes, polycyclopentadithiazoles, polythiazolothiazoles, polythiazoles, polybenzothiadiazoles, poly(thiophene oxide)s, poly(cyclopentadithiophene oxide)s, polythiadiazoloquinoxalines, polybenzoisothiazoles, polybenzothiazoles, polythienothiophenes, poly(thienothiophenes, poly(
• the electron donor material can include a polythiophene or a polycyclopentadithiophene.
• the electron acceptor material can include a material selected from the group consisting of fullerenes, inorganic nanoparticles, oxadiazoles, discotic liquid crystals, carbon nanorods, inorganic nanorods, polymers containing CN groups, polymers containing CF 3 groups, and combinations thereof.
• the electron acceptor material can include a substituted fullerene.
• hole carrier layer 150 can be prepared via a gas phase-based coating process, such as chemical or physical vapor deposition processes.
• a gas phase-based coating process generally involves evaporating the materials to be coated (e.g., in vacuum) and apply the evaporated materials to a surface (e.g., by sputtering).
• hole carrier layer 150 can be prepared via a liquid- based coating process.
• liquid-based coating process refers to a process that uses a liquid-based coating composition.
• the liquid-based coating composition include solutions, dispersions, and suspensions.
• the liquid-based coating process can be carried out by using at least one of the following processes: solution coating, ink jet printing, spin coating, dip coating, knife coating, bar coating, spray coating, roller coating, slot coating, gravure coating, flexographic printing, or screen printing. Examples of liquid-based coating processes have been described in, for example, commonly-owned co-pending U.S. Application Publication No. 2008-0006324.
• hole carrier layer 150 by a liquid-based coating process can result in a film with a sufficiently large thickness. Such a hole carrier layer can minimize shunting during manufacturing of photovoltaic cells in a large scale.
• the hole carrier polymer and the oxidizing agent may either first be mixed and then dissolved in a solvent, or they may be dissolved separately in a common solvent or different solvents and then mixed. After mixing the resulting solution is coated over the layer underneath by a liquid coating process as defined herein.
• a liquid coating process as defined herein.
• Such an approach is particularly suited for the oxidizing agents selected from the group consisting of (l-a), (l-b), (l-e), (l-f), (II) and (III) but may also be used with any other of the presently used hole carrier polymers and oxidizing agents.
• the hole carrier polymer may be dissolved in a first solvent, coated over the layer underneath and dried. Subsequently the solution of oxidizing agent in a second solvent is coated over the layer of hole carrier polymer.
• the first and second solvent may be the same or different.
• the present method for manufacturing the article of the present invention comprises the steps of
• step (b) subsequently coating the resulting solution from step (a) over a layer underneath,
• first and second solvent may be the same or different.
• the present method for manufacturing the article of the present invention comprises the steps of
• first and second solvent may be the same or different.
• the "layer underneath” may for example be a photoactive layer, e.g., in a photovoltaic cell of "inverted cell architecture".
• said layer underneath may be the first electrode, such that the photoactive layer will eventually be on top of the hole carrier layer.
• oxidizing agents selected from the group consisting of (I) and (III) but also be used with any other of the presently used hole carrier polymers and oxidizing agents.
• the solvents used in the present invention are preferably organic solvents.
• organic solvents are selected from the group consisting of aliphatic hydrocarbons, chlorinated hydrocarbons, aromatic hydrocarbons, ketones, ethers and mixtures thereof. Additional solvents which can be used include 1,2,4- trimethylbenzene, 1,2,3,4-tetra-methyl benzene, pentylbenzene, mesitylene, cumene, cymene, cyclohexylbenzene, diethylbenzene, tetralin, decalin, 2,6- lutidine, 2-fluoro-m-xylene, 3-fluoro-o-xylene, 2-chlorobenzotrifluoride, N,N- dimethylformamide, 2-chloro-6-fluorotoluene, 2-fluoroanisole, anisole, 2,3- dimethylpyrazine, 4-fluoroanisole, 3-fluoroanisole, 3-trifluoro-methylanisole, 1,
• the solution of hole carrier polymer may additionally comprise the binder.
• substrate 110 is generally formed of a transparent material.
• a transparent material is a material which, at the thickness used in a photovoltaic cell 100, transmits at least about 60% (e.g., at least about 70%, at least about 75%, at least about 80%, at least about 85%) of incident light at a wavelength or a range of wavelengths used during operation of the photovoltaic cell.
• Exemplary materials from which substrate 110 can be formed include polyethylene terephthalates, polyimides, polyethylene naphthalates, polymeric hydrocarbons, cellulosic polymers, polycarbonates, polyamides, polyethers, and polyether ketones.
• the polymer can be a fluorinated polymer.
• combinations of polymeric materials are used.
• different regions of substrate 110 can be formed of different materials.
• substrate 110 can be flexible, semi-rigid or rigid (e.g., glass). In some embodiments, substrate 110 has a flexural modulus of less than about 5,000 mPa (e.g., less than about 1,000 mPa or less than about 500 mPa). In certain embodiments, different regions of substrate 110 can be flexible, semi-rigid, or inflexible (e.g., one or more regions flexible and one or more different regions semi-rigid, one or more regions flexible and one or more different regions inflexible).
• substrate 110 has a thickness at least about one micron (e.g., at least about five microns or at least about 10 microns) and/or at most about 1,000 microns (e.g., at most about 500 microns, at most about 300 microns, at most about 200 microns, at most about 100 microns, or at most about 50 microns).
• a thickness at least about one micron (e.g., at least about five microns or at least about 10 microns) and/or at most about 1,000 microns (e.g., at most about 500 microns, at most about 300 microns, at most about 200 microns, at most about 100 microns, or at most about 50 microns).
• substrate 110 can be colored or non-colored. In some embodiments, one or more portions of substrate 110 is/are colored while one or more different portions of substrate 110 is/are non-colored.
• Substrate 110 can have one planar surface (e.g., the surface on which light impinges), two planar surfaces (e.g., the surface on which light impinges and the opposite surface), or no planar surface.
• a non-planar surface of substrate 110 can, for example, be curved or stepped.
• a non-planar surface of substrate 110 is patterned (e.g., having patterned steps to form a Fresnel lens, a lenticular lens or a lenticular prism).
• Electrode 120 is generally formed of an electrically conductive material.
• Exemplary electrically conductive materials include electrically conductive metals, electrically conductive alloys, electrically conductive polymers, and electrically conductive metal oxides.
• Exemplary electrically conductive metals include gold, silver, copper, aluminum, nickel, palladium, platinum, and titanium.
• Exemplary electrically conductive alloys include stainless steel (e.g., 332 stainless steel, 316 stainless steel), alloys of gold, alloys of silver, alloys of copper, alloys of aluminum, alloys of nickel, alloys of palladium, alloys of platinum, and alloys of titanium.
• Exemplary electrically conducting polymers include polythiophenes (e.g., doped poly(3,4-ethylenedioxythiophene) (doped PEDOT)), polyanilines (e.g., doped polyanilines), polypyrroles (e.g., doped polypyrroles).
• Exemplary electrically conducting metal oxides include indium tin oxide, fluorinated tin oxide, tin oxide and zinc oxide. In some embodiments, combinations of electrically conductive materials are used.
• electrode 120 can include a mesh electrode. Examples of mesh electrodes are described in U.S. Patent Application Publications Nos. 2004-0187911 and 2006-0090791.
• Electrode 120 In some embodiments, a combination of the materials described above can be used to form electrode 120.
• photovoltaic cell 100 can include a hole blocking layer 130.
• the hole blocking layer is generally formed of a material that, at the thickness used in photovoltaic cell 100, transports electrons to electrode 120 and substantially blocks the transport of holes to electrode 120.
• materials from which the hole blocking layer can be formed include LiF, metal oxides (e.g., zinc oxide or titanium oxide), and amines (e.g., primary, secondary, or tertiary amines). Examples of amines suitable for use in a hole blocking layer have been described, for example, in U.S. Application Publication No. 2008-0264488, now U.S. Patent No. 8,242,356.
• photovoltaic cell 100 when photovoltaic cell 100 includes a hole blocking layer made of amines, the hole blocking layer can facilitate the formation of ohmic contact between photoactive layer 140 and electrode 120 without being exposed to UV light, thereby reducing damage to photovoltaic cell 100 resulting from UV exposure.
• hole blocking layer 130 can have a thickness of at least about 1 nm (e.g., at least about 2 nm, at least about 5 nm, or at least about 10 nm) and/or at most about 50 nm (e.g., at most about 40 nm, at most about 30 nm, at most about 20 nm, or at most about 10 nm).
• Photoactive layer 140 generally contains an electron acceptor material (e.g., an organic electron acceptor material) and an electron donor material (e.g., an organic electron donor material).
• an electron acceptor material e.g., an organic electron acceptor material
• an electron donor material e.g., an organic electron donor material
• Examples of electron acceptor materials include fullerenes, inorganic nanoparticles, oxadiazoles, discotic liquid crystals, carbon nanorods, inorganic nanorods, polymers containing moieties capable of accepting electrons or forming stable anions (e.g., polymers containing CN groups or polymers containing CF3 groups), and combinations thereof.
• the electron acceptor material is a substituted fullerene (e.g., a phenyl-C61-butyric acid methyl ester (PCBM-C60) or a phenyl-C71-butyric acid methyl ester (PCBM-C70)).
• a combination of electron acceptor materials can be used in photoactive layer 140.
• electron donor materials include conjugated polymers, such as polythiophenes, polyanilines, polycarbazoles, polyvinylcarbazoles, polyphenylenes, polyphenylvinylenes, polysilanes, polythienylenevinylenes, polyisothianaphthanenes, polycyclopentadithiophenes, polysilacyclopentadithiophenes, polycyclopentadithiazoles, polythiazolothiazoles, polythiazoles, polybenzothiadiazoles, poly(thiophene oxide)s, poly(cyclopentadithiophene oxide)s, polythiadiazoloquinoxalines, polybenzoisothiazoles, polybenzothiazoles, polythienothiophenes, poly(thienothiophene oxide)s, polydithienothiophenes, poly(dithienothiophene oxide)s, polyfluoren
• the electron donor material can be polythiophenes (e.g., poly(3- hexylthiophene)), polycyclopentadithiophenes, and copolymers thereof.
• a combination of electron donor materials can be used in photoactive layer 140.
• Examples of other polymers suitable for use in photoactive layer 140 have been described in, e.g., U.S. Patent Nos. 7,781,673 and 7,772,485, PCT Application No. PCT/US2011/020227, and U.S. Application Publication Nos. 2010-0224252, 2010-0032018, 2008-0121281, 2008-0087324, 2007-0020526, and 2007-0017571.
• Electrode 160 is generally formed of an electrically conductive material, such as one or more of the electrically conductive materials described above with respect to electrode 120. In some embodiments, electrode 160 is formed of a combination of electrically conductive materials. In certain embodiments, electrode 160 can be formed of a mesh electrode.
• Substrate 170 can be identical to or different from substrate 110.
• substrate 170 can be formed of one or more suitable polymers, such as the polymers used in substrate 110 described above.
• each of layers 120, 130, 140, and 160 in photovoltaic cell 100 can vary as desired.
• layer 120, 130, 140, or 160 can be prepared by a gas phase based coating process or a liquid- based coating process, such as those described above.
• the liquid-based coating process can be carried out by (1) mixing the inorganic semiconductor material with a solvent (e.g., an aqueous solvent or an anhydrous alcohol) to form a dispersion, (2) coating the dispersion onto a substrate, and (3) drying the coated dispersion.
• a solvent e.g., an aqueous solvent or an anhydrous alcohol
• the liquid-based coating process used to prepare a layer (e.g., layer 120, 130, 140, or 160) containing an organic semiconductor material can be the same as or different from that used to prepare a layer containing an inorganic semiconductor material.
• the liquid-based coating process can be carried out by mixing the organic semiconductor material with a solvent (e.g., an organic solvent) to form a solution or a dispersion, coating the solution or dispersion on a substrate, and drying the coated solution or dispersion.
• a solvent e.g., an organic solvent
• photovoltaic cell 100 can be prepared in a continuous manufacturing process, such as a roll-to-roll process, thereby significantly reducing the manufacturing cost. Examples of roll-to-roll processes have been described in, for example, commonly-owned U.S. Patents Nos. 7,476,278 and 8,129,616.
• photovoltaic cell 100 includes a cathode as a bottom electrode (i.e. electrode 120) and an anode as a top electrode (i.e. electrode 160).
• photovoltaic cell 100 can include an anode as a bottom electrode and a cathode as a top electrode.
• photovoltaic cell 100 can include the layers shown in FIG. 1 in a reverse order. In other words, photovoltaic cell 100 can include these layers from the bottom to the top in the following sequence: a substrate 170, an electrode 160, a hole carrier layer 150, a photoactive layer 140, an optional hole blocking layer 130, an electrode 120, and a substrate 110.
• one of substrates 110 and 170 can be transparent. In other embodiments, both of substrates 110 and 170 can be transparent.
• the above disclosed hole carrier layer can also be used in a system in which two photovoltaic cells share a common electrode.
• a system is also known as tandem photovoltaic cell.
• Exemplary tandem photovoltaic cells have been described in, e.g., U.S. Application Publication Nos. 2009-0211633, 2007-0181179, 2007-0246094, and 2007-0272296.
• FIG. 2 is a schematic of a photovoltaic system 200 having a module 210 containing a plurality of photovoltaic cells 220. Cells 220 are electrically connected in series, and system 200 is electrically connected to a load 230.
• FIG. 3 is a schematic of a photovoltaic system 300 having a module 310 that contains a plurality of photovoltaic cells 320. Cells 320 are electrically connected in parallel, and system 300 is electrically connected to a load 330.
• some (e.g., all) of the photovoltaic cells in a photovoltaic system can be disposed on one or more common substrates.
• some photovoltaic cells in a photovoltaic system are electrically connected in series, and some of the photovoltaic cells in the photovoltaic system are electrically connected in parallel.
• photovoltaic cells While organic photovoltaic cells have been described, other photovoltaic cells can also be prepared based on the hole carrier layer described herein. Examples of such photovoltaic cells include dye sensitized photovoltaic cells and inorganic photoactive cells with a photoactive material formed of amorphous silicon, cadmium selenide, cadmium telluride, copper indium selenide, and copper indium gallium selenide.
• the present hole carrier layer can be used in other devices and systems.
• the present hole carrier layer can be used in suitable organic semiconductive devices, such as field effect transistors, photodetectors (e.g., I detectors), photovoltaic detectors, imaging devices (e.g., RGB imaging devices for cameras or medical imaging systems), light emitting diodes (LEDs) (e.g., organic LEDs (OLEDs) or IR or near IR LEDs), lasing devices, conversion layers (e.g., layers that convert visible emission into IR emission), amplifiers and emitters for telecommunication (e.g., dopants for fibers), storage elements (e.g., holographic storage elements), and electrochromic devices (e.g., electrochromic displays).
• suitable organic semiconductive devices such as field effect transistors, photodetectors (e.g., I detectors), photovoltaic detectors, imaging devices (e.g., RGB imaging devices for cameras or medical imaging systems), light emitting diodes (LEDs) (e.g.
• a TT polymer with ethyl-hexyl substituents was reacted with F4-TCNQ and the progress of the reaction was followed with uv/vis spectroscopy. The reaction appeared to be completed after 15 - 20 mole % of F4-TCNQ on the BBT- TTEH.
• the F4TCNQ is a strong Lewis acid capable of oxidizing TT polymers.
• F4-TCNQ tetrafluoro-tetracyano-quinodimethane, compound (l-a)
• ortho-dichlorobenzene tetrafluoro-tetracyano-quinodimethane, compound (l-a)
• a solution of BBT-TTEH in ortho-dichlorobenzene was prepared at 2.04 millimolar concentration, based on the MW of the repeating unit.
• the solution of BBT-TTEH was diluted to l/10 th of the initial concentration and added to a cuvette. Aliquots of 10 ml of the F4-TCNQ solution were added to the solution of BBT-TTEH with UV/VIS spectra taken after each addition.
• the spectrum of the F4TCNQ was taken of a l/10 th diluted sample, 0.433 millimolar.
• Table 1 Summary of FA -TCNQ ad dition to polymer.
• TCNQ was dissolved in an 80:20-blend of dimethoxyethane and acetonitrile to result in a TCNQ-concentration of 0.4 millimolar. This solution was diluted to l/5 th for taking an initial spectrum.
• the BBT-TTEH was prepared at approximately 0.2 millimolar and in the same solvent blended with overnight stirring. The resulting blue fluid scattered light somewhat, indicating that there was some dissolution and some fine particles present.
• Example 4 Resistivity of coatings made with the reaction production of BBT-TTEH and F4-TCNQ
• the measured resistivity for the test fluids #3 and #4 are similar to the control K-HIL fluid coating but with higher optical density (Table 6). Note that the optical for Exp #4, 3 passes, 20 mm/s is the same as the K-HIL control proprietary hole carrier layer, namely, 0.10, but the sheet resistance is 4 Kohms vs. the control at 4 Mohms/sq. Looking at the coatings, there are many more particles visible with the naked eye in the present experimental HILs.
• a stock solution of BBT-TTEH was made by dissolving 29.4 mg of BBT- TTEH (0.045 mmoles) in 4.4 grams of methylene chloride.
• BBT- TTEH 0.045 mmoles
• methylene chloride a polyethylene disposable pipet
• 4.02 grams (containing 26.7 mg, 0.041 mmoles) of this stock solution was then transferred into a clean 3 dram clear glass vial equipped with a magnetic stirrer.
• the F4TCNQ (4.0 mg, 0.0145 mmoles, in 4.0 grams of methylene chloride) solution was added drop- wise.
• the solution color rapidly changed from blue to black.
• the resulting solution had a final concentration of 0.38 w/w% with no observable insoluble material and was stable for several weeks.
• a two stage approach to making coatings of the CTC was made by coating and drying a solution of BBT-TTEH (17.0 mg in 1.5 g of toluene) onto ST- 504 (heat-stabilized PET) with a #3 coating rod to result in a blue layer.
• a solution of F4-TCNQ (2.0 mg in 2.0 g of ethyl acetate) was then coated with a #3 coating rod on the surface of the blue BBT-TTEH layer. The blue color was bleached immediately and the wet coating was rinsed with excess ethyl acetate leaving a light gray coating.
• Properties and spectra of this two stage coating were similar to coatings that were made by direct coating of o-DCB solutions of the CTC.
• oxidizing agents that have been used with BBT-TTC6 are nitrosonium hexafluorophosphate (NOPF 6 ) and thianthrenium hexafluorophosphate. The latter is made from the reaction of thianthrene and nitrosonium hexafluorophosphate.
• Schema 6, below illustrates the use of IMOPF 6 as an oxidizing agent with BBT-TTC6. In this titration the polymer is dissolved in dichloromethane; NOPF 6 is dissolved in acetonitrile. The reaction products are the radical cation of the polymer coupled with PF 6 anion and nitric oxide (NO).
• Nitric oxide and methylene chloride can be removed from the reaction mixture by bubbling nitrogen through the solution.
• the BBT-TTC6 itself is not soluble in acetonitrile, the reaction products are completely soluble. This is particularly advantageous because none of the active layer components of the PV cell are soluble in this solvent which means that the reaction products of redox couple can be coated on the active layer.
• the devices 100 included substrates 110 and 170, and silver grid electrodes 120 and 160.
• the photoactive layer 140 comprised poly(3-hexylthiophene) (P3HT) and a fullerene.
• a hole blocking layer 130 was interposed between a first side of the photoactive layer 140 and one electrode 120.
• a hole carrier layer 150 was between the opposite side of the photoactive layer 140 and electrode 160. Electrodes 120 and 160 were connected to an external load.
• the hole carrier layer 150 comprised a BBT- TTC6 F4TCNQ redox couple. In other embodiments, the hole carrier layer 150 comprised a BBT-TTC6 F2TCNQ redox couple.

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