Classifications

• • 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
• • 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
  • C08G61/00—Macromolecular compounds obtained by reactions forming a carbon-to-carbon link in the main chain of the macromolecule
  • C08G61/02—Macromolecular compounds containing only carbon atoms in the main chain of the macromolecule, e.g. polyxylylenes
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
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  • C08G61/00—Macromolecular compounds obtained by reactions forming a carbon-to-carbon link in the main chain of the macromolecule
  • C08G61/12—Macromolecular compounds containing atoms other than carbon in the main chain of the macromolecule
  • C08G61/122—Macromolecular compounds containing atoms other than carbon in the main chain of the macromolecule derived from five- or six-membered heterocyclic compounds, other than imides
  • C08G61/123—Macromolecular compounds containing atoms other than carbon in the main chain of the macromolecule derived from five- or six-membered heterocyclic compounds, other than imides derived from five-membered heterocyclic compounds
• • 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
  • C08G61/00—Macromolecular compounds obtained by reactions forming a carbon-to-carbon link in the main chain of the macromolecule
  • C08G61/12—Macromolecular compounds containing atoms other than carbon in the main chain of the macromolecule
  • C08G61/122—Macromolecular compounds containing atoms other than carbon in the main chain of the macromolecule derived from five- or six-membered heterocyclic compounds, other than imides
  • C08G61/123—Macromolecular compounds containing atoms other than carbon in the main chain of the macromolecule derived from five- or six-membered heterocyclic compounds, other than imides derived from five-membered heterocyclic compounds
  • C08G61/124—Macromolecular compounds containing atoms other than carbon in the main chain of the macromolecule derived from five- or six-membered heterocyclic compounds, other than imides derived from five-membered heterocyclic compounds with a five-membered ring containing one nitrogen atom in the ring
• • 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
  • C08G61/00—Macromolecular compounds obtained by reactions forming a carbon-to-carbon link in the main chain of the macromolecule
  • C08G61/12—Macromolecular compounds containing atoms other than carbon in the main chain of the macromolecule
  • C08G61/122—Macromolecular compounds containing atoms other than carbon in the main chain of the macromolecule derived from five- or six-membered heterocyclic compounds, other than imides
  • C08G61/123—Macromolecular compounds containing atoms other than carbon in the main chain of the macromolecule derived from five- or six-membered heterocyclic compounds, other than imides derived from five-membered heterocyclic compounds
  • C08G61/126—Macromolecular compounds containing atoms other than carbon in the main chain of the macromolecule derived from five- or six-membered heterocyclic compounds, other than imides derived from five-membered heterocyclic compounds with a five-membered ring containing one sulfur atom in the ring
• • 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
• • 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
  • H10K85/151—Copolymers
• • 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
  • 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

Definitions

• TECHNICAL FIELD This disclosure generally relates to the field of electron donor materials, as well as related photovoltaic cells.
• Photovoltaic cells are commonly used to transfer energy in the form of light into energy in the form of electricity.
• a typical photovoltaic cell includes a photoactive material disposed between two electrodes. Generally, light passes through one or both of the electrodes to interact with the photoactive material.
• the ability of one or both of the electrodes to transmit light can limit the overall efficiency of a photovoltaic cell, hi many photovoltaic cells, a film of semiconductive material (e.g., indium tin oxide) is used to form the electrode(s) through which light passes because, although the semiconductive material can have a lower electrical conductivity than electrically conductive materials, the semiconductive material can transmit more light than many electrically conductive materials.
• a film of semiconductive material e.g., indium tin oxide
• An aspect of the invention relates to a new combination of monomers that produce polymers, wherein the polymers have properties suitable for use as charge carriers in the active layer of a photovoltaic cell.
• the invention features a class of co-polymers including at least two co-monomers, at least one of which is a cyclopentadithiophene.
• this invention features a photovoltaic cell including a first electrode, a second electrode, and a photoactive material disposed between the first and second electrodes.
• the photoactive material includes a polymer having a first comonomer repeat unit and a second comonomer repeat unit.
• the first comonomer repeat unit includes a cyclopentadithiophene moiety.
• the second comonomer repeat unit includes a silole moiety, a thienothiophene moiety, a thienothiophene oxide moiety, a dithienothiophene moiety, a dithienothiophene oxide moiety, or a tetrahydroisoindole moiety.
• this invention features a photovoltaic cell including a first electrode, a second electrode, and a photoactive material disposed between the first and second electrodes.
• the photoactive material includes a polymer having a first comonomer repeat unit and a second comonomer repeat unit different from the first comonomer repeat unit.
• the first comonomer repeat unit includes a cyclopentadithiophene moiety.
• this invention features a polymer that includes a first comonomer repeat unit containing a cyclopentadithiophene moiety, and a second comonomer repeat unit containing a benzothiadiazole moiety, a thiadiazoloquinoxaline moiety, a cyclopentadithiophene oxide moiety, a benzoisothiazole moiety, a benzothiazole moiety, a thiophene oxide moiety, a fluorene moiety, a thiophene moiety, a silole moiety, a thienothiophene moiety, a thienothiophene oxide moiety, a dithienothiophene moiety, a dithienothiophene oxide moiety, a tetrahydroisoindole moiety, or a moiety containing at least three thiophene moieties.
• this invention features a polymer that includes a first comonomer repeat unit and a second comonomer repeat unit different from the first comonomer repeat unit.
• the first comonomer repeat unit contains a cyclopentadithiophene moiety substituted with at least one substituent selected from the group consisting of hexyl, ethylhexyl, dimethyloctyl, C 1 -C 20 alkoxy, aryl, heteroaryl, C 3 - C 20 cycloalkyl, and C 3 -C 20 heterocycloalkyl.
• this invention features a device (e.g., a photovoltaic cell) that includes a first electrode, a second electrode, and a photoactive material disposed between the first and second electrodes.
• the photoactive material includes a polymer having a first monomer repeat unit, which includes a benzothiadiazole moiety, a thiophene oxide moiety, a cyclopentadithiophene oxide moiety, a thiadiazoloquinoxaline moiety, a benzoisothiazole moiety, a benzothiazole moiety, a thienothiophene moiety, a thienothiophene oxide moiety, a dithienothiophene moiety, a dithienothiophene oxide moiety, a tetrahydroisoindole moiety, a fluorene moiety, a thiophene moiety, a silole moiety, or a fluorene moiety
• this invention features a device (e.g., a photovoltaic cell) that includes a first electrode, a second electrode, and a photoactive material disposed between the first and second electrodes.
• the photoactive material includes a polymer having a first monomer repeat unit, which includes a cyclopentadithiophene moiety substituted with at least one substituent selected from the group consisting of hexyl, ethylhexyl, dimethyloctyl, C 1 -C 20 alkoxy, aryl, heteroaryl, C 3 -C 20 cycloalkyl, C 3 -C 20 heterocycloalkyl halo, CN, NO 2 , or SO 2 R, in which R is Ci-C 2 O alkyl, C 1 -C 20 alkoxy, aryl, heteroaryl, C 3 -C 20 cycloalkyl, or C 3 -C 20 heterocycloalkyl.
• Embodiments can include one or more of the following features.
• the cyclopentadithiophene moiety is substituted with at least one substituent selected from the group consisting of Ci-C 20 alkyl, C 1 -C 20 alkoxy, aryl, heteroaryl, C 3 -C 20 cycloalkyl, C 3 -C 20 heterocycloalkyl, halo, CN, NO 2 , and SO 2 R, in which R is H, C 1 -C 20 alkyl, C 1 -C 20 alkoxy, aryl, heteroaryl, C 3 -C 20 cycloalkyl, or C 3 -C 20 heterocycloalkyl.
• Examples OfC 1 -C 20 alkyl can be hexyl, 2-ethylhexyl, or 3,7- dimethyloctyl.
• the cyclopentadithiophene moiety can be substituted at 4- position.
• the first monomer or comonomer repeat unit can include a cyclopentadithiophene moiety of formula (I):
• each of R 1 , R 2 , R 3 , and R 4 is H, C 1 -C 2O alkyl, C 1 -C 20 alkoxy, aryl, heteroaryl, C 3 -C 20 cycloalkyl, C 3 -C 20 heterocycloalkyl, halo, CN, NO 2 , or SO 2 R, in which R is H, C 1 -C 20 alkyl, C 1 -C 20 alkoxy, aryl, heteroaryl, C 3 -C 20 cycloalkyl, or C 3 -C 2O heterocycloalkyl.
• At least one of Ri and R 2 is hexyl, 2-ethylhexyl, or 3,7-dimethyloctyl. In certain embodiments, each of Ri and R 2 , independently, is hexyl, 2-ethylhexyl, or 3,7-dimethyloctyl.
• one of Ri and R 2 is hexyl, ethylhexyl, dimethyloctyl, Ci-C 20 alkoxy, aryl, heteroaryl, C 3 -C 20 cycloalkyl, or C 3 -C 20 heterocycloalkyl
• the other of Ri and R 2 is H, Ci-C 20 alkyl, Ci-C 20 alkoxy, aryl, heteroaryl, C 3 -C 20 cycloalkyl, or C 3 -C 20 heterocycloalkyl.
• At least one of Ri and R 2 is Ci-C 20 alkoxy optionally further substituted with Ci-C 20 alkoxy or halo (e.g., (OCH 2 CH 2 ) 2 OCH 3 or OCH 2 CF 2 OCF 2 CF 2 OCF 3 ).
• each of Ri and R 2 independently, is Ci-C 20 alkoxy optionally further substituted with C 1 -C 20 alkoxy or halo.
• the second comonomer repeat unit can include a benzothiadiazole moiety, a thiadiazoloquinoxaline moiety, a cyclopentadithiophene oxide moiety, a benzoisothiazole moiety, a benzothiazole moiety, a thiophene oxide moiety, a thienothiophene moiety, a thienothiophene oxide moiety, a dithienothiophene moiety, a dithienothiophene oxide moiety, a tetrahydroisoindole moiety, a fluorene moiety, a thiophene moiety, or a silole moiety, each of which is optionally substituted with at least one substituent selected from the group consisting of C 1 -C 20 alkyl, C 1 -C 20 alkoxy, aryl, heteroaryl, C 3 -C 20 cycloalkyl, C 3
• the second comonomer repeat unit can include a 3,4-benzo-l,2,5-thiadiazole moiety.
• the second comonomer repeat unit can include a benzothiadiazole moiety of formula (II), a thiadiazoloquinoxaline moiety of formula (III), a cyclopentadithiophene dioxide moiety of formula (IV), a cyclopentadithiophene monoxide moiety of formula (V), a benzoisothiazole moiety of formula (VI), a benzothiazole moiety of formula (VII), a thiophene dioxide moiety of formula (VIII), a cyclopentadithiophene dioxide moiety of formula (DC), or a cyclopentadithiophene tetraoxide moiety of formula (X): in which each of R 5 , R 6 , and R 7 , independently, is H, C 1 -C 20 al
• the second comonomer repeat unit can include a benzothiadiazole moiety of formula (II).
• R 5 and R 6 is H.
• the second comonomer repeat unit can include at least three thiophene moieties, hi some embodiments, at least one of the thiophene moieties is substituted with at least one substituent selected from the group consisting of Ci-C 20 alkyl, C 1 -C 20 alkoxy, aryl, heteroaryl, C 3 -C 20 cycloalkyl, C 3 -C 20 heterocycloalkyl, halo, CN, NO 2 , and SO 2 R, in which R is H, C 1 -C 20 alkyl, C 1 -C 20 alkoxy, aryl, heteroaryl, C 3 - C 20 cycloalkyl, or C 3 -C 20 heterocycloalkyl.
• the second comonomer repeat unit includes five thiophene moieties.
• the second comonomer repeat unit can include a thienothiophene moiety of formula (XI), a thienothiophene tetraoxide moiety of formula (XII), a dithienothiophene moiety of formula (XIII), a dithienothiophene dioxide moiety of formula (XIV), a dithienothiophene tetraoxide moiety of formula (XV), a tetrahydroisoindole moiety of formula (XVI), a thienothiophene dioxide moiety of formula (XVII), or a dithienothiophene dioxide moiety of formula (XVIII):
• the polymer can further include a third comonomer repeat unit that contains a thiophene moiety or a fluorene moiety.
• the thiophene or fluorene moiety is substituted with at least one s ⁇ bstituent selected from the group consisting OfC 1 -C 20 alkyl, Ci-C 20 alkoxy, aryl, heteroaryl, C 3 -C 20 cycloalkyl, and C 3 -C 20 heterocycloalkyl, halo, CN, NO 2 , and SO 2 R, in which R is H, Ci-C 20 alkyl, Ci-C 20 alkoxy, aryl, heteroaryl, C 3 -C 20 cycloalkyl, or C 3 -C 20 heterocycloalkyl.
• the first monomer or comonomer repeat unit can include a benzothiadiazole moiety of formula (II), a thiophene dioxide moiety of formula (VIII), a cyclopentadithiophene tetraoxide moiety of formula (X), or a fluorene moiety of formula (XIX): in which each of R 5 and R 6 , independently, is H, Ci-C 20 alkyl, C 1 -C 20 alkoxy, aryl, heteroaryl, C 3 -C 20 cycloalkyl, C 3 -C 20 heterocycloalkyl, halo, CN, NO 2 , or SO 2 R.
• R can be Ci-C 20 alkyl, Ci-C 20 alkoxy, aryl, heteroaryl, C 3 -C 20 cycloalkyl, or C 3 -C 20 heterocycloalkyl.
• at least one of R 5 and R 6 can be Ci-C 20 alkoxy optionally further substituted with Ci-C 20 alkoxy or halo (e.g., (OCH 2 CEb) 2 OCH 3 or OCH 2 CF 2 OCF 2 CF 2 OCF 3 ).
• the polymer can include a second monomer repeat unit different from the first monomer repeat unit.
• the second monomer repeat unit can include a cyclopentadithiophene moiety, a benzothiadiazole moiety, a thiophene oxide moiety, a cyclopentadithiophene oxide moiety, a fluorene moiety, or a thiophene moiety.
• the first or second monomer repeat unit can include at least one substituent on a ring selected from the group consisting of C 1 -C 20 alkyl, C 1 -C 20 alkoxy, aryl, heteroaryl, C 3 -C 20 cycloalkyl, C 3 -C 20 heterocycloalkyl, halo, CN, NO 2 , and SO 2 R, in which R is H, C 1 -C 2O aIlCyI, C 1 -C 20 alkoxy, aryl, heteroaryl, C 3 -C 20 cycloalkyl, or C 3 -C 20 heterocycloalkyl.
• the substituent can be hexyl, ethylhexyl, or C 1 -C 20 alkoxy optionally further substituted with Ci-C 20 alkoxy or halo (e.g., (OCH 2 CH 2 ) 2 OCH 3 or OCH 2 CF 2 OCF 2 CF 2 OCF 3 ).
• Ci-C 20 alkoxy or halo e.g., (OCH 2 CH 2 ) 2 OCH 3 or OCH 2 CF 2 OCF 2 CF 2 OCF 3 ).
• the second monomer repeat unit can include a cyclopentadithiophene moiety of formula (I), a benzothiadiazole moiety of formula (II), a thiophene dioxide moiety of formula (VIII), a cyclopentadithiophene tetraoxide moiety of formula (X), a fluorene moiety of formula (XIX), a thiophene moiety of formula (XX), or a silole moiety of formula (XXI): in which each OfR 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , and R 8 , independently, is H, C 1 -C 20 alkyl, C 1 - C 20 alkoxy, aryl, heteroaryl, C 3 -C 20 cycloalkyl, C 3 -C 20 heterocycloalkyl, halo, CN, NO 2 , or SO 2 R.
• R can be C 1 -C 20 alkyl, C 1 -C 20 alkoxy, aryl, heteroaryl, C 3 -C 20 cycloalkyl, or C 3 - C 20 heterocycloalkyl.
• at least one of Ri, R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , and R 8 can be Ci-C 20 alkoxy optionally further substituted with Ci-C 20 alkoxy or halo (e.g., (OCH 2 CH 2 ) 2 OCH 3 or OCH 2 CF 2 OCF 2 CF 2 OCF 3 ).
• At least one OfR 5 , R 6 , R 7 and R 8 can be Ci-C 20 alkyl optionally substituted with halo, or aryl optionally substituted with Ci-C 20 alkyl.
• each of R 5 and R 6 independently can be aryl optionally substituted with C1-C20 alkyl
• each of R 7 and R 8 independently, can be Ci-C 20 alkyl optionally
• silole moiety is
• the polymer can be an electron donor material or an electron acceptor material. In some embodiments, the polymer can be
• n can be an integer greater than 1.
• the photovoltaic cell can be a tandem photovoltaic cell.
• the photoactive material can include an electron acceptor material
• the electron acceptor material can be a Mlerene (e.g., C61-phenyl-butyric acid methyl ester, PCBM).
• the polymer and the electron acceptor material each can have a LUMO energy level.
• the LUMO energy level of the polymer can be at least about 0.2 eV (e.g., at least about 0.3 eV) less negative than the LUMO energy level of the electron acceptor material.
• the device can be an organic semiconductive device, hi certain embodiments, the device can be a member selected from the group consisting of field effect transistors, photodetectors, photovoltaic detectors, imaging devices, light emitting diodes, lasing devices, conversion layers, amplifiers and emitters, storage elements, and electrochromic devices.
• Embodiments can provide one or more of the following advantages.
• using a polymer containing a cyclopentadithiophene moiety can be advantageous because the cyclopentadithiophene moiety can contribute to a shift in the maximum absorption wavelength toward the red or near IR region of the electromagnetic spectrum.
• the current and efficiency of the cell can increase.
• substituted fullerenes or polymers containing substituted monomer repeat units can have improved solubility in organic solvents and can form an photoactive layer with improved morphology.
• a polymer containing a silole moiety can absorb light at a relatively long wavelength and have improved solubility in organic solvents.
• a polymer containing a silole moiety can be used to prepare an electron donor material with improved semiconductive properties.
• a polymer fullerene cell containing a polymer described above can have a band gap that is relatively ideal for its intended purposes.
• a photovoltaic cell having high cell voltage can be created, whereby the HOMO level of the polymer is at least about 0.2 electron volts more negative relative to the LUMO or conduction band of an electron acceptor material.
• a photovoltaic cell containing a polymer described above can have relatively fast and efficient transfer of an electron to an electron acceptor material, whereby the LUMO of the donor is at least about 0.2 electron volt (e.g., at least about 0.3 electron volt) less negative than the conduction band of the electron acceptor material.
• a photovoltaic cell containing a polymer described above can have relatively fast charge separation, whereby the charge mobility of the positive charge, or hole, is relatively high and falls within the range of 10 "4 to 10 "1 cm 2 /Vs.
• the polymer is soluble in an organic solvent and/or film forming. In some embodiments, the polymer is optically non-scattering.
• the polymer can be used in organic field effect transistors and OLEDs.
• FIG. 1 is a cross-sectional view of an embodiment of a photovoltaic cell.
• FIG. 2 is a schematic of a system containing one electrode between two photoactive layers.
• FIG. 1 shows a cross-sectional view of a photovoltaic cell 100 that includes a substrate 110, a cathode 120, a hole carrier layer 130, an active layer 140 (containing an electron acceptor material and an electron donor material), a hole blocking layer 150, an anode 160, and a substrate 170.
• a photovoltaic cell 100 that includes a substrate 110, a cathode 120, a hole carrier layer 130, an active layer 140 (containing an electron acceptor material and an electron donor material), a hole blocking layer 150, an anode 160, and a substrate 170.
• the electron donor material e.g., a polymer described above
• the electron acceptor material e.g., PCBM
• the electron acceptor material transmits the electrons through hole blocking layer 150 to anode 160, and the electron donor material transfers holes through hole carrier layer 130 to cathode 120.
• Anode 160 and cathode 120 are in electrical connection via an external load so that electrons pass from anode 160, through the load, and to cathode 120.
• Electron acceptor materials of active layer 140 can include fullerenes.
• active layer 140 can include one or more unsubstituted fullerenes and/or one or more substituted fullerenes.
• unsubstituted fullerenes include C 60 , C 70 , C 76 , C 78 , C 82 , C 84 , and Cc >2 .
• substituted fullerenes include PCBM or fullerenes substituted with C 1 -C 20 alkoxy optionally further substituted with C 1 -C 20 alkoxy or halo (e.g., (OCH 2 CH 2 ) 2 OCH 3 or OCH 2 CF 2 OCF 2 CF 2 OCF 3 ).
• fullerenes substituted with long-chain alkoxy groups e.g., oligomeric ethylene oxides
• fluorinated alkoxy groups have improved solubility in organic solvents and can form an photoactive layer with improved morphology.
• the electron acceptor materials can include polymers (e.g., homopolymers or copolymers).
• a polymers mentioned herein include at least two identical or different monomer repeat units (e.g., at least 5 monomer repeat units, at least 10 monomer repeat units, at least 50 monomer repeat units, at least 100 monomer repeat units, or at least 500 monomer repeat units).
• a copolymer mentioned herein refers to a polymer that includes at least two co-monomers of differing structures, hi some embodiments, the polymers used as an electron acceptor material can include one or more monomer repeat units listed in Tables 1 and 2 below. Specifically, Table 1 lists examples of the monomers that can be used as an electron donating monomer and can serve as a conjugative link.
• Table 2 lists examples of the monomers that can be used as an electron withdrawing monomer. Note that depending on the substituents, monomers listed in Table 1 can also be used as electron withdrawing monomers and monomers listed in Table 2 can also be used as electron donating monomers.
• the polymers used as an electron acceptor material include a high molar percentage (e.g., at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 90%) of an electron withdrawing monomer.
• Electron donor materials of active layer 140 can include polymers (e.g., homopolymers or copolymers).
• the polymers used as an electron donor material can include one or more monomer repeat units listed Tables 1 and 2.
• the polymers used as an electron donor material include a high molar percentage (e.g., at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 90%) of an electron donating monomer.
• the polymers include a monomer containing C 1 -C 20 alkoxy on a ring, which is optionally further substituted with C 1 -C 20 alkoxy or halo (e.g., (OCH 2 CH 2 ) 2 OCH 3 or OCH 2 CF 2 OCF 2 CF 2 OCF 3 ).
• C 1 -C 20 alkoxy or halo e.g., (OCH 2 CH 2 ) 2 OCH 3 or OCH 2 CF 2 OCF 2 CF 2 OCF 3 .
• each of X and Y can be CH 2 , O, or S; each OfR 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , and R 8 , independently, can be H, C 1 -C 20 alkyl, C 1 -C 20 alkoxy, aryl (e.g., phenyl or substituted phenyl), heteroaryl, C 3 -C 20 cycloalkyl, C 3 -C 20 heterocycloalkyl, halo, CN, NO 2 , or SO 2 R; and R 7 can be H, C]-C 20 alkyl, C 1 -C 20 alkoxy, aryl (e.g., phenyl or substituted phenyl), heteroaryl, C 3 -C 20 cycloalkyl, or C 3 -C 20 heterocycloalkyl; in which R is Ci-C 20 alky
• alkyl can be saturated or unsaturated and branch or straight chained.
• a C 1 -C 20 alkyl contains 1 to 20 carbon atoms (e.g., one, two , three, four, five, six, seven, eight, nine, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, and 20 carbon atoms).
• An alkoxy can be branch or straight chained and saturated or unsaturated.
• An C 1 -C 20 alkoxy contains an oxygen radical and 1 to 20 carbon atoms (e.g., one, two , three, four, five, six, seven, eight, nine, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, and 20 carbon atoms).
• Acycloalkyl can be either saturated or unsaturated.
• a C 3 -C 20 cycloalkyl contains 3 to 20 carbon atoms (e.g., three, four, five, six, seven, eight, nine, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, and 20 carbon atoms).
• cycloalkyl moieities include cyclohexyl and cyclohexen-3-yl.
• a heterocycloalkyl can also be either saturated or unsaturated.
• a C 3 -C 20 heterocycloalkyl contains at least one ring heteroatom (e.g., O, N, and S) and 3 to 20 carbon atoms (e.g., three, four, five, six, seven, eight, nine, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, and 20 carbon atoms).
• heterocycloalkyl moieties include 4-tetrahydropyranyl and 4-pyranyl.
• An aryl can contain one or more aromatic rings.
• aryl moieties include phenyl, phenylene, naphthyl, naphthylene, pyrenyl, anthryl, and phenanthryl.
• a heteroaryl can contain one or more aromatic rings, at least one of which contains at least one ring heteroatom (e.g., O, N, and S).
• heteroaryl moieties include furyl, furylene, fluorenyl, pyrrolyl, thienyl, oxazolyl, imidazolyl, thiazolyl, pyridyl, pyrimidinyl, quinazolinyl, quinolyl, isoquinolyl, and indolyl.
• Alkyl, alkoxy, cycloalkyl, heterocycloalkyl, aryl, and heteroaryl mentioned herein include both substituted and unsubstituted moieties, unless specified otherwise.
• substituents on cycloalkyl, heterocycloalkyl, aryl, and heteroaryl include C 1 - C 20 alkyl, C 3 -C 20 cycloalkyl, Ci-C 20 alkoxy, aryl, aryloxy, heteroaryl, heteroaryloxy, amino, Ci-Ci 0 alkylamino, Ci-C 20 dialkylamino, arylamino, diarylamino, hydroxyl, halogen, thio, Ci-Ci 0 alkylthio, arylthio, C 1 -Ci 0 alkylsulfonyl, arylsulfonyl, cyano, nitro, acyl, acyloxy, carboxyl, and carboxylic ester.
• substituents on alkyl include all of the above-recited substituents except C 1 -C 20 alkyl.
• Cycloalkyl, heterocycloalkyl, aryl, and heteroaryl also include fused groups.
• the copolymers described above can be prepared by methods known in the art. For example, a copolymer can be prepared by a cross-coupling reaction between one or more comonomers containing two alkylstannyl groups and one or more comonomers containing two halo groups in the presence of a transition metal catalyst.
• a copolymer can be prepared by a cross-coupling reaction between one or more comonomers containing two borate groups and one or more comonomers containing two halo groups in the presence of a transition metal catalyst.
• the comonomers can be prepared by the methods described herein or by the methods know in the art, such as those described in Coppo et al., Macromolecules 2003, 36, 2705-2711 and Kurt et al., J. Heterocycl. Chem. 1970, 6, 629, the contents of which are hereby incorporated by reference.
• polymers 1-3 Table 3 below lists three exemplary polymers (i.e., polymers 1-3) described in the Summary section above. These polymers can have unique properties, which make them particularly suitable as charge carriers in the active layer of a photovoltaic cell. Polymers 1 and 2 can be obtained by the methods described in Examples 4 and 7 below. TABLE 3
• one co-monomer in the polymers described in the Summary section above is a cyclopentadithiophene.
• An advantage of a co-polymer containing a cyclopentadithiophene moiety is that its absorption wavelength can shift toward the red and near IR portion (e.g., 650 - 800 nm) of the electromagnetic spectrum, which is not accessible by most other polymers.
• IR portion e.g., 650 - 800 nm
• the polymers described above can be useful in solar power technology because the band gap is close to ideal for a photovoltaic cell (e.g., a polymer-fullerene cell).
• the HOMO level of the polymers can be positioned correctly relative to the LUMO of an electron acceptor (e.g., PCBM) in a photovoltaic cell (e.g., a polymer-fullerene cell), allowing for high cell voltage.
• the LUMO of the polymers can be positioned correctly relative to the conduction band of the electron acceptor in a photovoltaic cell, thereby creating efficient transfer of an electron to the electron acceptor. For example, using a polymer having a band gap of about 1.4 - 1.6 eV can significantly enhance cell voltage.
• the positive charge mobility of the polymers can be relatively high and approximately in the range of lO ⁇ to 10 "1 cm 2 /Vs. In general, the relatively high positive charge mobility allows for relatively fast charge separation.
• the polymers can also be soluble in an organic solvent and/or film forming. Further, the polymers can be optically non-scattering.
• photovoltaic cell other than the electro acceptor materials and he electron donor materials are known in the art, such as those described in U.S. Patent Application Serial No. 10/723,554, the contents of which are incorporated herein by references.
• the polymer described above can be used as an electron donor material or an electro acceptor material in a system in which two photovoltaic cells share a common electrode.
• Such a system is also known as tandem photovoltaic cell. Examples of tandem photovoltaic cells are discussed in U.S. Patent Application Serial No. 10/558,878, filed November 29, 2005, the contents of which are hereby incorporated by reference.
• Fig. 2 is a schematic of a tandem photovoltaic cell 200 having a substrate 210, three electrodes 220, 240, and 260, and two photoactive layers 230 and 250. Electrode 240 is shared between photoactive layers 230 and 250, and is electrically connected with electrodes 220 and 260. hi general, electrodes 220, 240, and 260 can be formed of an electrically conductive material, such as those described in U.S. Patent
• one or more (i.e., one, two, or three) electrodes 220, 240, and 260 is a mesh electrode.
• one or more electrodes 220, 240, and 260 is formed of a semiconductive material. Examples of semiconductive materials include titanium oxides, indium tin oxides, fiuorinated tin oxides, tin oxides, and zinc oxides.
• one or more (i.e., one, two, or three) electrodes 220, 240, and 260 are formed of titanium dioxide. Titanium dioxide used to prepare an electrode can be in any suitable forms. For example, titanium dioxide can be in the form of interconnected nanoparticles.
• At least one (e.g., one, two, or three) of electrodes 220, 240, and 260 is a transparent electrode.
• a transparent electrode is formed of a material which, at the thickness used in a photovoltaic cell, transmits at least about 60% (e.g., at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%) of incident light at a wavelength or a range of wavelengths used during operation of the photovoltaic cell.
• both electrodes 220 and 260 are transparent electrodes.
• Each of photoactive layers 230 and 250 can contain at least one semiconductive material.
• the semiconductive material in photoactive layer 230 has the same band gap as the semiconductive material in photoactive layer 250.
• the semiconductive material in photoactive layer 230 has a band gap different from that of the semiconductive material in photoactive layer 250. Without wishing to be bound by theory, it is believed that incident light not absorbed by one photoactive layer can be absorbed by the other photoactive layer, thereby maximizing the absorption of the incident light.
• at least one of photoactive layers 230 and 250 can contain an electron acceptor material (e.g., PCBM or a polymer described above) and an electron donor material (e.g., a polymer described above).
• each of photoactive layers 230 and 250 contains an electron acceptor material and an electron donor material.
• Substrate 210 can be formed of one or more suitable polymers, such as those described in U.S. Patent Application Serial No. 10/723,554.
• an additional substrate (not shown in Fig. 2) can be disposed on electrode 260.
• Photovoltaic cell 200 can further contain a hole carrier layer (not shown in Fig. 2) and a hole blocking layer (not shown in Fig. 2), such as those described in U.S. Patent Application Serial No. 10/723,554.
• the polymers described herein can be used in other devices and systems.
• the polymers can be used in suitable organic semiconductive devices, such as field effect transistors, photodetectors (e.g., IR detectors), photovoltaic detectors, imaging devices (e.g., RGB imaging devices for cameras or medical imaging systems), light emitting diodes (LEDs) (e.g., organic LEDs 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., IR detectors), photovoltaic detectors, imaging devices (e.g., RGB imaging devices for cameras or medical imaging systems), light emitting diodes (LEDs) (e.g., organic LEDs
• Example 4 Polymerization of bis-(tributylstannyl)-4,4-dihexyl-cyclopenta[2,l- b:3,4-b']dithiophene and 4,7-dibromo-2,l,3-benzothiadiazole
• reaction mixture was allowed to warm to room temperature and stirred overnight (c.a. 16 hours). Water was added and the reaction was extracted with toluene. The organic layer was washed with water, dried over sodium sulfate, and concentrated. The residue was dissolved in toluene, and quickly passed through a small plug of silica gel pretreated with triethylamine. The solvent was removed and the residue was dried under vacuum. 1.25 g of the product was obtained.
• Example 7 Polymerization of Bis-(trimethyIstannyl)-4,4-Di(2-ethylhexyl)- cyclopenta[2,l-b:3,4-b']dithiophen and 4,7-dibromo-2,l,3-benzothiadiazole
• Example 8 Copolymerization of 4,4-DihexyI-2,6-bis-trimethylstannanyI-4H- cyclopenta[2,l-b;3,4-b*]dithiophene, 4,4-Bis-(2-ethyl-hexyl)-2,6-bis- trimethylstannanyl-4H-cyclopenta[2,l-b;3,4-b']dithiophene, and 4,7-Dibromo- benzo[l,2,5]thiadiazole
• the reaction mixture was diluted with toluene (50 mL) and the organic layer was separated and washed with warm water (3 x 50 mL).
• the solution was then treated with an aqueous solution of diethyldithiocarbamic acid sodium salt trihydrate (7.5 %, DDC, 5 mL) and heated at 8O 0 C overnight.
• the aqueous layer was separated and discarded and the organic layer was washed with warm water (3 x 50 mL) and the polymer precipitated into methanol (500 mL).
• the polymer was collected by filtration, washed with methanol (50 mL) and redissolved in hot toluene (200 mL).
• the hot polymer solution was passed through a tightly packed column of celite (1 x 8 cm), silica get (3 x 8 cm), and basic alumina (3 x 8 cm) (previously rinsed with 200 mL of hot toluene).
• the polymer solution was collected and the volume concentrated to approximately 50 mL.
• the polymer was precipitated into methanol (500 mL), washed with methanol (100 mL), acetone (100 mL) and again with methanol (100 mL). The polymer was then dried in vacuo overnight to yield a brick red material. Yield: 0.327 g.
• the polymer solar cells were fabricated by doctor-blading a blend of the polymer prepared in Example 7 (PCPDTBT) and PC 61 BM or PC 7 iBM (purchased fromNano-C, Wesrwood, MA) in a 1:3 w/w ratio sandwiched between a transparent anode and an evaporated metal cathode.
• the transparent anode was an indium tin oxide (ITO)-covered glass substrate (Merck, Whitehouse Station, NJ) which was coated with a ⁇ 60 nm thick PEDOT:PSS layer (Baytron PH from H.C. Starck) applied by doctorblading.
• ITO indium tin oxide
• the ITO- glass-substrate was cleaned by ultrasonification subsequently in acetone, isopropyl alcohol and deionized water.
• the cathode a bilayer of a thin (1 nm) LiF layer covered with 80 nm Al, was prepared by thermal evaporation.
• PCPDTBT and PC 61 BM or PC 71 BM were dissolved together in ⁇ -dichlorobenzene (ODCB) to give an overall 40 mg/ml solution and was stirred overnight at 60-70°C inside a glovebox.
• ODCB ⁇ -dichlorobenzene
• Device characterization was done under AM 1.5G irradiation (100 mW/cm 2 ) on an Oriel Xenon solar simulator with a well calibrated spectral mismatch of 0.98 jV-characteristics were recorded with a Keithley 2400. Active areas were in the range of 15 to 20 mm 2 . EQE was detected with a lock-in amplifier under monochromatic illumination. Calibration of the incident light was done with a monocrystalline silicon diode. Mobility measurements were done using an Agilent 4155C parameter analyzer. Absorption measurements were done inside the glovebox with an Avantes fiberoptic spectrometer or outside with a HP spectrometer. The interaction with PCBM and the photoinduced charge transfer was investigated by PL quenching. The PL of pristine PCPDTBT versus PCPDTBT / PCBM composites was measured at liquid N 2 temperatures in a cryostat, excitation was provided by an Ar laser at 488 nm.
• Electrochemical experiments were carried out on dropcast polymer films at room temperature in a glovebox.
• the supporting electrolyte was tetrabutylammonium- hexafluorophosphate (TBAPF 6 , electrochemical grade, Aldrich) ⁇ 0.1 M in acetonitrile anhydrous (Aldrich).
• the working electrode (WE), as well as the counter electrode (CE), was a platinum foil.

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