Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07D—HETEROCYCLIC COMPOUNDS
  • C07D495/00—Heterocyclic compounds containing in the condensed system at least one hetero ring having sulfur atoms as the only ring hetero atoms
  • C07D495/22—Heterocyclic compounds containing in the condensed system at least one hetero ring having sulfur atoms as the only ring hetero atoms in which the condensed system contains four or more hetero rings
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07D—HETEROCYCLIC COMPOUNDS
  • C07D495/00—Heterocyclic compounds containing in the condensed system at least one hetero ring having sulfur atoms as the only ring hetero atoms
  • C07D495/02—Heterocyclic compounds containing in the condensed system at least one hetero ring having sulfur atoms as the only ring hetero atoms in which the condensed system contains two hetero rings
  • C07D495/04—Ortho-condensed systems
• • 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
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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
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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
  • H10K85/649—Aromatic compounds comprising a hetero atom
  • H10K85/653—Aromatic compounds comprising a hetero atom comprising only oxygen as heteroatom
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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
  • H10K85/649—Aromatic compounds comprising a hetero atom
  • H10K85/654—Aromatic compounds comprising a hetero atom comprising only nitrogen as heteroatom
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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
  • H10K85/649—Aromatic compounds comprising a hetero atom
  • H10K85/655—Aromatic compounds comprising a hetero atom comprising only sulfur as heteroatom
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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
  • H10K85/649—Aromatic compounds comprising a hetero atom
  • H10K85/657—Polycyclic condensed heteroaromatic hydrocarbons
  • H10K85/6576—Polycyclic condensed heteroaromatic hydrocarbons comprising only sulfur in the heteroaromatic polycondensed ring system, e.g. benzothiophene
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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
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  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K39/00—Integrated devices, or assemblies of multiple devices, comprising at least one organic radiation-sensitive element covered by group H10K30/00
  • H10K39/30—Devices controlled by radiation
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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
  • 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

• Embodiments of the present disclosure relate to organic compounds for use in organic photoresponsive devices, in particular electron-accepting compounds for use in organic photodetectors.
• organic electronic devices comprising organic semiconductor materials are known, including organic light-emitting devices, organic field effect transistors, organic photovoltaic devices and organic photodetectors (OPDs).
• organic light-emitting devices including organic light-emitting devices, organic field effect transistors, organic photovoltaic devices and organic photodetectors (OPDs).
• OPDs organic photodetectors
• WO 2018/065352 discloses an OPD having a photoactive layer that contains a small molecule acceptor which does not contain a fullerene moiety and a conjugated copolymer electron donor having donor and acceptor units.
• WO 2018/065356 discloses an OPD having a photoactive layer that contains a small molecule acceptor which does not contain a fullerene moiety and a conjugated copolymer electron donor having randomly distributed donor and acceptor units.
• Yao et al, “Design, Synthesis, and Photovoltaic Characterization of a Small Molecular Acceptor with an Ultra-Narrow Band Gap”, Angew Chem Int Ed Engl. 2017 Mar 6;56(11):3045-3049 discloses a non-fullerene acceptor with a band gap of 1.24 eV.
• Gao et al “A New Non-fullerene Acceptor with Near Infrared Absorption for High Performance Ternary-Blend Organic Solar Cells with Efficiency over 13%” Advanced Science, Vol. 5(6), June 2018 discloses a solar cell containing an acceptor-donor-acceptor (A-D-A) type non-fullerene acceptor 3TT-FIC which has three fused thieno[3,2- b]thiophene as the central core and difluoro substituted indanone as the end groups.
• A-D-A acceptor-donor-acceptor
• the present disclosure provides a compound of formula (I):
• each EAG is independently an electron accepting group of formula (III): each X is independently O or S; each Y is independently O, S, Se, NR 8 or C(R 9 )2 wherein R 8 and R 9 independently in each occurrence are selected from H or a substituent;
• Ar 3 and Ar 4 independently in each occurrence is a monocyclic or polycyclic aromatic or heteroaromatic group; R 1 and R 2 independently in each occurrence is a substituent;
• R 3 - R 6 are each independently H or a substituent
• Z 1 is a direct bond or Z 1 together with the substituent R 4 forms Ar 1 wherein Ar 1 is a monocyclic or polycyclic aromatic or heteroaromatic group;
• Z 2 is a direct bond or Z 2 together with the substituent R 5 forms Ar 2 wherein Ar 2 is a monocyclic or polycyclic aromatic or heteroaromatic group; p is 0, 1, 2 or 3; q is 0, 1, 2 or 3;
• R 10 in each occurrence is H or a substituent
• — represents a linking position to EDG; and R 7 in each occurrence is H or a substituent with the proviso that at least one R 7 is CN.
• Ar 3 and Ar 4 are each independently selected from thiophene, furan, thi enothiophene, furofuran, thi enofuran benzothiophene and benzofuran.
• p and q are each 1.
• Z 1 and Z 2 are each a direct bond.
• the group of formula (III) has formula (Illa):
• R 1 and R 2 in each occurrence is selected from the group consisting of: linear, branched or cyclic C1.20 alkyl wherein one or more non-adjacent, non-terminal C atoms may be replaced by O, S, NR 12 , CO or COO wherein R 12 is a C1.12 hydrocarbyl and one or more H atoms of the C1.20 alkyl may be replaced with F; and a group of formula -(Ak)u-(Ar 6 )v wherein Ak is a C1.14 alkylene chain in which one or more C atoms may be replaced with O, S, CO or COO; u is 0 or 1; Ar 6 in each occurrence is independently an aromatic or heteroaromatic group which is unsubstituted or substituted with one or more substituents; and v is at least 1.
• R 1 and R 2 are phenyl which is unsubstituted or substituted with one or more substituents selected from C1.20 alkyl wherein one or more non-adjacent, nonterminal C atoms may be replaced by O, S, NR 12 , CO or COO and one or more H atoms of the Ci -20 alkyl may be replaced with F.
• each R 3 -R 6 is independently selected from:
• the present disclosure provides a composition comprising an electron donor and an electron acceptor wherein the electron acceptor is a compound according to any one of the preceding claims.
• the composition comprises at least one further electron acceptor.
• the composition comprises a fullerene further electron acceptor.
• the present disclosure provides a formulation comprising a compound or composition as described herein dissolved or dispersed in a solvent.
• the present disclosure provides an organic photoresponsive device comprising an anode, a cathode and a photoresponsive layer disposed between the anode and cathode wherein the photoresponsive layer comprises an electron acceptor and an electron donor wherein the electron-accepting material is a compound as described herein.
• the organic photoresponsive is an organic photodetector.
• the present disclosure provides a method of forming an organic photoresponsive device as described herein comprising formation of the photoresponsive organic layer over one of the anode and cathode and formation of the other of the anode and cathode over the photoresponsive organic layer.
• formation of the photoresponsive organic layer comprises deposition of the formulation as described herein.
• the present disclosure provides a photosensor comprising a light source and an organic photodetector according as described herein configured to detect light emitted from the light source.
• the light source emits light having a peak wavelength greater than 750 nm.
• the photosensor is configured to receive a sample in a light path between the organic photodetector and the light source.
• the present disclosure provides a method of determining the presence and / or concentration of a target material in a sample, the method comprising illuminating the sample and measuring a response of a photodetector as described herein configured to receive light emitted from the sample upon illumination.
• the organic photodetector is the organic photodetector of a photosensor as described herein. DESCRIPTION OF DRAWINGS
• Figure 1 illustrates an organic photodetector according to an embodiment of the invention
• Figure 2 shows solution and film absorption spectra for Compound Example 1 according to some embodiments of the present disclosure
• Figure 3 shows a film absorption spectrum for Compound Example 2 according to some embodiments of the present disclosure
• Figure 4A shows the external quantum efficiencies of an organic photodetector according to some embodiments of the present disclosure and a comparative photodetector containing a comparative electron acceptor;
• Figure 4B shows the dark current of the devices of Figure 3 A
• Figure 5 shows external quantum efficiencies of photodetectors according to some embodiments of the present disclosure having differing electron donor : electron acceptor ratios;
• Figure 6A is a graph of current densities vs wavelength for organic photodetectors containing Compound Example 2;
• Figure 6B is a graph of external quantum efficiencies vs wavelength for organic photodetectors containing Compound Example 2; and Figure 7 is a graph of external quantum efficiencies vs wavelength for organic photodetectors containing Compound Example 1 and a fullerene.
• the words “comprise,” “comprising,” and the like are to be construed in an inclusive sense, as opposed to an exclusive or exhaustive sense; that is to say, in the sense of "including, but not limited to.”
• the terms “connected,” “coupled,” or any variant thereof means any connection or coupling, either direct or indirect, between two or more elements; the coupling or connection between the elements can be physical, logical, electromagnetic, or a combination thereof.
• the words “herein,” “above,” “below,” and words of similar import when used in this application, refer to this application as a whole and not to any particular portions of this application.
• EDG is an electron-donating group of formula (II) and each EAG is an electron accepting group of formula (III).
• Formula (II) is: wherein: each X is independently O or S; each Y is independently O, S, Se, NR 8 or C(R 9 )2 wherein R 8 and R 9 independently in each occurrence are selected from H or a substituent;
• Ar 3 and Ar 4 independently in each occurrence is a monocyclic or polycyclic aromatic or heteroaromatic group
• R 1 and R 2 independently in each occurrence is a substituent;
• R 3 - R 6 are each independently H or a substituent;
• Z 1 is a direct bond or Z 1 together with the substituent R 4 forms Ar 1 wherein Ar 1 is a monocyclic or polycyclic aromatic or heteroaromatic group;
• Z 2 is a direct bond or Z 2 together with the substituent R 5 forms Ar 2 wherein Ar 2 is a monocyclic or polycyclic aromatic or heteroaromatic group; p is 0, 1, 2 or 3; and q is 0, 1, 2 or 3.
• R 1 and R 2 independently in each occurrence are selected from the group consisting of: linear, branched or cyclic C1.20 alkyl wherein one or more non-adjacent, non-terminal C atoms may be replaced by O, S, NR 12 , CO or COO wherein R 12 is a C1.12 hydrocarbyl and one or more H atoms of the C1.20 alkyl may be replaced with F; and a group of formula -(Ak)u-(Ar 6 )v wherein Ak is a Ci-14 alkylene chain in which one or more C atoms may be replaced with O, S, CO or COO; u is 0 or 1; Ar 6 in each occurrence is independently an aromatic or heteroaromatic group which is unsubstituted or substituted with one or more substituents; and v is at least 1, optionally 1, 2 or 3.
• Ci-i4 hydrocarbyl may be Ci-14 alkyl; unsubstituted phenyl; and phenyl substituted with one or more Ci-6 alkyl groups.
• Ar 6 is preferably phenyl.
• substituents of Ar 6 may be a substituent R 16 wherein R 16 in each occurrence is independently selected from F, C1.20 alkyl wherein one or more non- adjacent, non-terminal C atoms may be replaced by O, S, NR 12 , CO or COO and one or more H atoms of the C1.20 alkyl may be replaced with F.
• -(Ar 6 )v may be a linear or branched chain of Ar 6 groups.
• a linear chain of Ar 6 groups as described herein has only on monovalent terminal Ar 6 group whereas a branched chain of Ar 6 groups has at least two monovalent terminal Ar 6 groups.
• R 1 and R 2 in each occurrence is phenyl which is unsubstituted or substituted with one or more substituents selected from R 16 as described above.
• each R 3 -R 6 is independently selected from: H; F:
• Ar 6 is preferably an aromatic group, more preferably phenyl.
• the one or more substituents of Ar 6 may be selected from Ci-i4 alkyl wherein one or more non-adjacent, non-terminal C atoms may be replaced with O, S, COO or CO.
• non-terminal C atom of an alkyl group as used herein is meant a C atom of the alkyl other than the methyl C atom of a linear (n-alkyl) chain or the methyl C atoms of a branched alkyl chain.
• R 8 is selected from H and a Cl-30 hydrocarbyl group.
• the C1.30 hydrocarbyl group is optionally selected from be C1.30 alkyl; unsubstituted phenyl; and phenyl substituted with one or more C1.12 alkyl groups.
• R 9 in each occurrence is independently selected from a substituent as described with respect to R 1 .
• Ar 3 and Ar 4 are each independently selected from thiophene, furan, thi enothiophene, furofuran, thienofuran, benzothiophene and benzofuran.
• Ar 3 and Ar 4 are each independently unsubstituted or substituted with one or more substituents.
• Preferred substituents of Ar 3 and Ar 4 are selected from groups R 3 -R 6 described above other than H, preferably C1.20 alkyl wherein one or more non- adjacent, non-terminal C atoms are replaced with O, S, CO or COO.
• each R 3 -R 6 is H; C1.20 alkyl; or C1.20 alkoxy. In some embodiments at least one of, optionally both of, R 4 and R 5 is not H, and each R 3 and R 6 is H.
• p is 0 or 1, more preferably 1.
• q is 0 or 1, more preferably 1.
• Y in each occurrence is preferably O or S.
• Z 1 and Z 2 are each a direct bond.
• Z 1 is linked to R 4 to form a monocyclic aromatic or heteroaromatic group and / or Z 2 is linked to R 5 to form a monocyclic aromatic or heteroaromatic group.
• Z 1 is linked to R 4 to form a thiophene ring or furan ring and / or Z 2 is linked to R 5 to form a thiophene ring or furan ring.
• Each EAG is a group of formula (III): wherein:
• R 10 is H or a substituent
• — represents a linking position to EDG; and R 7 in each occurrence is H or a substituent with the proviso that at least one R 7 is CN.
• each R 7 is independently selected from H; C1.12 alkyl; and CN with the proviso that at least one R 7 is CN.
• R 10 is preferably H.
• Substituents R 10 are preferably selected from the group consisting of C1.12 alkyl wherein one or more non-adjacent, non-terminal C atoms may be replaced with O, S, COO or CO and one or more H atoms of the alkyl may be replaced with F; and an aromatic group Ar 9 , optionally phenyl, which is unsubstituted or substituted with one or more substituents selected from F and C1.12 alkyl wherein one or more non-adjacent, non-terminal C atoms may be replaced with O, S, COO or CO.
• the groups of formula (III) may be the same or different. Preferably, they are the same.
• the compound of formula (I) has a LUMO level of more than 4.00 eV from vacuum level, optionally at least 4.10 eV from vacuum level.
• HOMO and LUMO levels of a material as given herein are values measured by square wave voltammetry of a film of the material.
• the compound of formula (I) is the only electron acceptor of a composition comprising the compound of formula (I) and an electron donor.
• the composition may comprise one or more further electron acceptors.
• the one or more further acceptors may be selected from fullerenes and non-fullerene acceptors (NF As).
• the compound of formula (I) : further acceptor(s) weight ratio may be in the range of about 1 : 0.1 - 1 : 1, preferably in the range of about 1 : 0.1 - 1 : 0.5.
• the fullerene may be a Ceo, C70, C76, C78 or Cs4 fullerene or a derivative thereof including, without limitation, PCBM-type fullerene derivatives (including phenyl-C61 -butyric acid methyl ester (CeoPCBM) and phenyl -C 71 -butyric acid methyl ester (C70PCBM)), TCBM- type fullerene derivatives (e.g. tolyl-C61 -butyric acid methyl ester (CeoTCBM)), and ThCBM-type fullerene derivatives (e.g. thienyl-C61 -butyric acid methyl ester (CeoThCBM)
• PCBM-type fullerene derivatives including phenyl-C61 -butyric acid methyl ester (CeoPCBM) and phenyl -C 71 -butyric acid methyl ester (C70PCBM)
• a fullerene acceptor may have formula (VIII): (VIII) wherein A, together with the C-C group of the fullerene, forms a monocyclic or fused ring group which may be unsubstituted or substituted with one or more substituents.
• Exemplary fullerene derivatives include formulae (Villa), (Vlllb) and (VIIIc):
• R 30 -R 42 are each independently H or a substituent.
• Substituents R 30 -R 42 are optionally and independently in each occurrence selected from the group consisting of aryl or heteroaryl, optionally phenyl, which may be unsubstituted or substituted with one or more substituents; and C1.20 alkyl wherein one or more nonadj acent, non-terminal C atoms may be replaced with O, S, CO or COO and one or more H atoms may be replaced with F.
• Substituents of aryl or heteroaryl groups R 30 -R 42 are optionally selected from C1.12 alkyl wherein one or more non-adj acent, non-terminal C atoms may be replaced with O, S, CO or COO and one or more H atoms may be replaced with F.
• the donor (p-type) compound is not particularly limited and may be appropriately selected from electron donating materials that are known to the person skilled in the art, including organic polymers and non-polymeric organic molecules.
• the p-type compound has a HOMO deeper (further from vacuum) than a LUMO of the compound of formula (I).
• the gap between the HOMO level of the p-type donor and the LUMO level of the n-type acceptor compound of formula (I) is less than 1.4 eV.
• the donor and acceptor materials form a type II interface.
• the p-type donor compound is an organic conjugated polymer, which can be a homopolymer or copolymer including alternating, random or block copolymers.
• the p-type organic semiconductor is a conjugated organic polymer with a low band gap, typically between 2.5 eV and 1.5 eV, preferably between 2.3 eV and 1.8 eV.
• polymers selected from conjugated hydrocarbon or heterocyclic polymers including polyacene, polyaniline, polyazulene, polybenzofuran, polyfluorene, polyfuran, polyindenofluorene, polyindole, polyphenylene, polypyrazoline, polypyrene, polypyridazine, polypyridine, polytriarylamine, poly(phenylene vinylene), poly(3 -substituted thiophene), poly(3,4- bisubstituted thiophene), polyselenophene, poly(3 -substituted selenophene), poly(3,4- bisubstituted selenophene), poly(bisthiophene), poly(terthiophene), poly(bisselenophene), poly(terselenophene), polythieno[2,3-b]thiophene, polythieno[3,2-b]thiophene, polybenz
• Preferred examples of p-type donors are copolymers of polyfluorenes and polythiophenes, each of which may be substituted, and polymers comprising benzothiadiazole-based and thiophene-based repeating units, each of which may be substituted. It is understood that the p-type donor may also consist of a mixture of a plurality of electron donating materials.
• the donor polymer comprises a repeat unit of formula (X): wherein R 50 and R 51 independently in each occurrence is H or a substituent.
• Substituents R 50 and R 51 may be selected from groups other than H described with respect to R 3 .
• each R 50 is a substituent.
• the R 50 groups are linked to form a group of formula -Y 1 -C(R 52 )2- wherein Y 1 is O,
• each R 51 is H.
• the donor polymer may comprise a repeat unit selected from one or more of formulae
• R 23 in each occurrence is a substituent, optionally Ci-2oalkyl wherein one or more nonadj acent, non-terminal C atoms may be replaced with O, S, COO or CO and one or more H atoms of the alkyl may be replaced with F.
• R 25 in each occurrence is independently H; F; CN; NO2; C1-20 alkyl wherein one or more non-adjacent, non-terminal C atoms may be replaced with O, S, COO or CO and one or more H atoms of the alkyl may be replaced with F; or an aromatic group Ar 7 , optionally phenyl, which is unsubstituted or substituted with one or more substituents selected from F and Ci -12 alkyl wherein one or more non-adjacent, non-terminal C atoms may be replaced with O, S, COO or CO: or wherein Z 40 , Z 41 , Z 42 and Z 43 are each independently CR 14 or N wherein R 14 in each occurrence is H or a substituent, preferably a C 1-20 hydrocarb yl group; Y 40 and Y 41 are each independently O, S, NX 71 wherein X 71 is CN or COOR 40 ; or CX 60 X 61 wherein X 60 and
• W 40 and W 41 are each independently O, S, NX 71 wherein X 71 is CN or COOR 40 ; or CX 60 X 61 wherein X 60 and X 61 is independently CN, CF3 or COOR 40 ; and
• R 40 in each occurrence is H or a substituent, preferably H or a C1-20 hydrocarbyl group. ZHs N or P.
• T 1 , T 2 and T 3 each independently represent an aryl or a heteroaryl ring, optionally benzene, which may be fused to one or more further rings.
• Substituents of T 1 , T 2 and T 3 , where present, are optionally selected from non-H groups of R 25 .
• R 11 in each occurrence is a substituent, preferably a C1-20 hydrocarbyl group.
• Ar 8 is an arylene or heteroarylene group, optionally thiophene, fluorene or phenylene, which may be unsubstituted or substituted with one or more substituents, optionally one or more non-H groups selected from R 25 .
• the donor polymer is a donor-acceptor polymer comprising an electrondonating repeat unit, preferably a repeat unit of formula (X), and an electron-accepting repeat unit, preferably a repeat unit selected from formulae (XX)-(XXXI).
• Exemplary donor materials are disclosed in, for example, WO2013/051676, the contents of which are incorporated herein by reference.
• the p-type donor has a HOMO level no more than 5.5 eV from vacuum level.
• the p-type donor has a HOMO level at least 4.1 eV from vacuum level.
• the donor material (or at least one of the donor materials if more than one donor is present) and compound of formula (I) form a type (II) heterojunction.
• the compound of formula (I) has a HOMO level that is at least 0.05 eV deeper, optionally at least 0.10 eV deeper, than the HOMO of the donor material.
• the donor material or at least one of the donor materials if more than one donor is present, has a H0M0-LUM0 band gap of less than 2.00 eV.
• the donor material or at least one of the donor materials if more than one donor is present, has an absorption peak of at least 900 nm.
• absorption spectra as described herein are as measured in solution using a Cary 5000 UV- vis-IR spectrometer.
• HOMO and LUMO levels of a material as described herein are as measured from a film of the compound using square wave voltammetry.
• the weight of the donor compound(s) to the acceptor compound(s) is from about 1 :0.5 to about 1 :2.
• the electron donor(s) : electron acceptor(s) weight ratio is in the range of about 1 : 0.5 - 1 : 2, preferably 1 : 0.7 - 1 : 1.7. In a preferred embodiment, the weight of the electron acceptor(s) is greater than the weight of the electron donor(s).
• a compound of formula (I) as described herein may be provided as an electron acceptor in a bulk heterojunction layer of a photoresponsive device, preferably an OPD.
• Figure 1 illustrates an OPD according to some embodiments of the present disclosure.
• the OPD comprises a cathode 103, an anode 107 and a bulk heterojunction layer 105 disposed between the anode and the cathode.
• the OPD may be supported on a substrate 101.
• Figure 1 illustrates an arrangement in which the cathode is disposed between the substrate and the anode. In other embodiments, the anode may be disposed between the cathode and the substrate.
• the bulk heterojunction layer comprises a mixture of an electron acceptor and an electron donor.
• the bulk heterojunction layer consists of the electron acceptor and the electron donor.
• the bulk heterojunction layer comprises a further electron acceptor other than the electron acceptor of formula (I).
• the further electron acceptor is a fullerene.
• the bulk heterojunction layer has a thickness in the range of 100-1000 nm.
• Each of the anode and cathode may independently be a single conductive layer or may comprise a plurality of layers.
• the OPD may comprise layers other than the anode, cathode and bulk shown in Figure 1.
• a hole-transporting layer is disposed between the anode and the bulk heterojunction layer.
• an electron-transporting layer is disposed between the cathode and the bulk heterojunction layer.
• a work function modification layer is disposed between the bulk heterojunction layer and the anode, and / or between the bulk heterojunction layer and the cathode.
• Apparatus comprising the photodetector may further comprise a voltage source for applying a reverse bias to the photodetector and / or a device configured to measure photocurrent.
• the voltage applied to the photodetector may be variable.
• the photodetector may be continuously biased when in use.
• a photodetector system comprises a plurality of photodetectors as described herein, such as an image sensor of a camera.
• a sensor may comprise an OPD as described herein and a light source wherein the OPD is configured to receive light emitted from the light source.
• the light from the light source may or may not be changed before reaching the OPD.
• the light may be filtered, down-converted or up- converted before it reaches the OPD.
• the light source has a peak wavelength of greater than 750 nm, optionally less than 1500 nm, optionally in the range of 1300-1400 nm.
• At least one of the first and second electrodes is transparent so that light incident on the device may reach the bulk heterojunction layer. In some embodiments, both of the first and second electrodes are transparent.
• Each transparent electrode preferably has a transmittance of at least 70 %, optionally at least 80 %, to wavelengths in the range of 850-1500 nm.
• one electrode is transparent and the other electrode is reflective.
• the transparent electrode comprises or consists of a layer of transparent conducting oxide, preferably indium tin oxide or indium zinc oxide.
• the electrode may comprise poly 3, 4-ethylenedi oxythiophene (PEDOT).
• the electrode may comprise a mixture of PEDOT and polystyrene sulfonate (PSS).
• PSS polystyrene sulfonate
• the electrode may consist of a layer of PEDOT:PSS.
• the reflective electrode may comprise a layer of a reflective metal.
• the layer of reflective material may be aluminium or silver or gold.
• a bilayer electrode may be used.
• the electrode may be an indium tin oxide (ITO)/silver bi-layer, an ITO/aluminium bi-layer or an ITO/gold bi-layer.
• the device may be formed by forming the bulk heterojunction layer over one of the anode and cathode supported by a substrate and depositing the other of the anode or cathode over the bulk heterojunction layer.
• the area of the OPD may be less than about 3 cm 2 , less than about 2 cm 2 , less than about 1 cm 2 , less than about 0.75 cm 2 , less than about 0.5 cm 2 or less than about 0.25 cm 2 .
• each OPD may be part of an OPD array wherein each OPD is a pixel of the array having an area as described herein, optionally an area of less than 1 mm 2 , optionally in the range of 0.5 micron 2 - 900 micron 2 .
• the substrate may be, without limitation, a glass or plastic substrate.
• the substrate can be described as an inorganic semiconductor.
• the substrate may be silicon.
• the substrate can be a wafer of silicon.
• the substrate is transparent if, in use, incident light is to be transmitted through the substrate and the electrode supported by the substrate.
• the substrate supporting one of the anode and cathode may or may not be transparent if, in use, incident light is to be transmitted through the other of the anode and cathode.
• the bulk heterojunction layer may be formed by any process including, without limitation, thermal evaporation and solution deposition methods.
• the bulk heterojunction layer is formed by depositing a formulation comprising the acceptor material and the electron donor material dissolved or dispersed in a solvent or a mixture of two or more solvents.
• the formulation may be deposited by any coating or printing method including, without limitation, spin-coating, dip-coating, roll-coating, spray coating, doctor blade coating, wire bar coating, slit coating, ink jet printing, screen printing, gravure printing and flexographic printing.
• the one or more solvents of the formulation may optionally comprise or consist of benzene substituted with one or more substituents selected from chlorine, Ci-io alkyl and
• Ci-io alkoxy wherein two or more substituents may be linked to form a ring which may be unsubstituted or substituted with one or more Ci-6 alkyl groups, optionally toluene, xylenes, trimethylbenzenes, tetramethylbenzenes, anisole, indane and its alkylsubstituted derivatives, and tetralin and its alkyl-substituted derivatives.
• the formulation may comprise a mixture of two or more solvents, preferably a mixture comprising at least one benzene substituted with one or more substituents as described above and one or more further solvents.
• the one or more further solvents may be selected from esters, optionally alkyl or aryl esters of alkyl or aryl carboxylic acids, optionally a Ci-io alkyl benzoate, benzyl benzoate or dimethoxybenzene.
• esters optionally alkyl or aryl esters of alkyl or aryl carboxylic acids, optionally a Ci-io alkyl benzoate, benzyl benzoate or dimethoxybenzene.
• a mixture of trimethylbenzene and benzyl benzoate is used as the solvent.
• a mixture of trimethylbenzene and dimethoxybenzene is used as the solvent.
• the formulation may comprise further components in addition to the electron acceptor, the electron donor and the one or more solvents.
• adhesive agents, defoaming agents, deaerators, viscosity enhancers, diluents, auxiliaries, flow improvers colourants, dyes or pigments, sensitizers, stabilizers, nanoparticles, surface-active compounds, lubricating agents, wetting agents, dispersing agents and inhibitors may be mentioned.
• the organic photodetector as described herein may be used in a wide range of applications including, without limitation, detecting the presence and / or brightness of ambient light and in a sensor comprising the organic photodetector and a light source.
• the photodetector may be configured such that light emitted from the light source is incident on the photodetector and changes in wavelength and / or brightness of the light may be detected, e.g. due to absorption by and / or emission of light from a target material in a sample disposed in a light path between the light source and the organic photodetector.
• the sample may be a non-biological sample, e.g. a water sample, or a biological sample taken from a human or animal subject.
• the sensor may be, without limitation, a gas sensor, a biosensor, an X-ray imaging device, an image sensor such as a camera image sensor, a motion sensor (for example for use in security applications) a proximity sensor or a fingerprint sensor.
• a ID or 2D photosensor array may comprise a plurality of photodetectors as described herein in an image sensor.
• the photodetector may be configured to detect light emitted from a target analyte which emits light upon irradiation by the light source or which is bound to a luminescent tag which emits light upon irradiation by the light source.
• the photodetector may be configured to detect a wavelength of light emitted by the target analyte or a luminescent tag bound thereto.
• HOMO and LUMO values of Compound Example 1 were measured by square wave voltammetry.
• the current at a working electrode is measured while the potential between the working electrode and a reference electrode is swept linearly in time.
• the difference current between a forward and reverse pulse is plotted as a function of potential to yield a voltammogram. Measurement may be with a CHI 660D Potentiostat.
• the apparatus to measure HOMO or LUMO energy levels by SWV comprised a cell containing 0.1 M tertiary butyl ammonium hexafluorophosphate in acetonitrile; a 3 mm diameter glassy carbon working electrode; a platinum counter electrode and a leak free Ag/AgCl reference electrode.
• Ferrocene was added directly to the existing cell at the end of the experiment for calculation purposes where the potentials are determined for the oxidation and reduction of ferrocene versus Ag/AgCl using cyclic voltammetry (CV).
• the sample was dissolved in Toluene (3mg/ml) and spun at 3000 rpm directly on to the glassy carbon working electrode.
• LUMO 4.8-E ferrocene (peak to peak average) - E reduction of sample (peak maximum).
• HOMO 4.8-E ferrocene (peak to peak average) + E oxidation of sample (peak maximum).
• Comparative Compound 1 As shown in Table 1, Compound Example 1 has a significantly smaller band gap and significantly deeper LUMO than Comparative Compound 1.
• Figure 2 shows absorption spectra of Compound Example 1 in film, cast from a 15 mg/ml solution, and in a 15 mg / ml solution.
• Figure 3 shows an absorption spectrum of Compound Example 2 in film, cast from a 15 mg/ml solution
• a device having the following structure was prepared: Cathode / Donor : Acceptor layer / Anode
• a glass substrate coated with a layer of indium-tin oxide (ITO) was treated with polyethyleneimine (PEIE) to modify the work function of the ITO.
• PEIE polyethyleneimine
• a formulation containing a mixture of a donor polymer and Compound Example 1 (acceptor) in a donor : acceptor mas ratio of 1 : 1.5 was deposited over the modified ITO layer by bar coating from a 15 mg / ml solution in 1,2,4 Trimethylbenzene; 1,2- Dimethoxybenzene 95:5 v/v solvent mixture. The film was dried at 80°C to form a ca. 500 nm thick bulk heterojunction layer.
• An anode stack of MoO3 (lOnm) and ITO (50nm) was formed over the bulk heterojunction by thermal evaporation (MoOs) and sputtering (ITO).
• the donor polymer is a donor-acceptor polymer having a band gap of 1.86 eV and a donor repeat unit of formula (X) wherein R 50 groups are linked to form a group of formula -O- C(R 52 ) 2 -.
• the donor polymer forms a type II interface with Compound Example 1.
• Example 1 was replaced with Comparative Compound 1.
• Device Examples 2-4 were prepared as described for Device Example 1 except that the Donor Polymer 1 : Compound Example 1 weight ratio was changed as shown in Table 2.
• a number of devices were prepared as described for Device Example 1 except that the formulation deposited onto the modified ITO layer contained fullerene CeoPCBM in addition to the donor polymer and Compound Example 1 in a ratio of donor polymer 1.0 : Compound Example 1 0.8 : CeoPCBM 0.2.
• Model Compound Examples 1 and 2 and Model Comparative Compound 1 were modelled using Gaussian09 software available from Gaussian using Gaussian09 with B3LYP (functional). As set out in Table 4, Model Compound Examples 1 and 2 each have a deeper LUMO and smaller band gap than Model Comparative Compound 1.

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