WO2024094804A1

WO2024094804A1 - Compound

Info

Publication number: WO2024094804A1
Application number: PCT/EP2023/080586
Authority: WO
Inventors: Nir YAACOBI-GROSS; Michal MACIEJCZYK
Original assignee: Cambridge Display Technology Ltd; Sumitomo Chemical Co Ltd
Current assignee: Cambridge Display Technology Ltd; Sumitomo Chemical Co Ltd
Priority date: 2022-11-02
Filing date: 2023-11-02
Publication date: 2024-05-10
Anticipated expiration: 2025-05-02
Also published as: JP2025537078A; GB2623989A; CN119949073A; TW202440588A; GB202216325D0

Abstract

A compound of formula (I) or (II). A2 is a divalent heteroaromatic electron-accepting group; D1, D2 and D3 independently in each occurrence is an electron-donating group; B1, B2, and B3 independently in each occurrence is a bridging group; x1 - x6 are each independently 0, 1, 2 or 3; y1, y2 and y3 are each independently at least 1; and A1 in each occurrence is independently a group of formula (III) wherein J is C=O, C=S, S=O, SO2, NR11 or CR12R13, each Z1 is N and each Z2 is CR4, or each Z1 is CR4 and each Z2 is N wherein each R4 is independently H or a substituent.

Description

COMPOUND

BACKGROUND

Embodiments of the present disclosure relate to electron-accepting compounds and more specifically compounds suitable for use as an electron-accepting material in a photoresponsive device.

An organic photodetector may contain a photoactive layer of a blend of an electrondonating material and an electron-accepting material between an anode and a cathode. Known electron-accepting materials include fullerenes and non-fullerene acceptors (NF As). Yang et al, “End-capped group manipulation of indacenodithienothiophene-based non- fullerene small molecule acceptors for efficient organic solar cells” Nanoscale, 2020, 12, 17795-17804 discloses the non-fullerene acceptor ITIC with a series of fused ring end groups for solar cells.

Wang et al, “Enhancement of intra- and inter-molecular ^-conjugated effects for a non- fullerene acceptor to achieve high-efficiency organic solar cells with an extended photoresponse range and optimized morphology”, Mater. Chem. Front., 2018, 2, 2006-2012 discloses an A-D-A type non-fullerene electron acceptor for solar cells which possesses an electron-donating (D) core constructed by linking a 2,5-difluorobenzene ring with two cyclopentadithiophene moieties and two electron-accepting (A) end-groups of 2-(3-oxo-2,3-dihydro-177-cyclopenta[6]naphthalen-l -ylidene)malononitrile.

Swick et al, “Fluorinating n-Extended Molecular Acceptors Yields Highly Connected Crystal Structures and Low Reorganization Energies for Efficient Solar Cells” discloses the compounds ITN-F4 and ITzN-F4 for solar cells:

Wu et al, “New Electron Acceptor with End-Extended Conjugation for High-Performance Polymer Solar Cells”, Energy Fuels 2021, 35, 23, 19061-19068 discloses the compound IDTT8-N for solar cells:

IDTT8-N

Li et al, “Systematic Merging of Nonfullerene Acceptor ^-Extension and Tetrafluorination Strategies Affords Polymer Solar Cells with >16% Efficiency” discloses the non-fullerene acceptors BT-B1C. L1C. L4F. and BO-L4F for solar cells:

SUMMARY The present disclosure provides a compound of formula (I) or (II):

A¹ - (B^x¹ - (DV - (B³)X² - A¹

(I)

A¹ - (B²)X⁵ - (D²)y² - (B³)x³- A² - (B³)x⁴ - (D³)y³ - (B²)x⁶ - A¹

(II) wherein:

A² is a divalent heteroaromatic electron-accepting group;

D¹, D² and D³ independently in each occurrence is an electron-donating group;

B¹, B², and B³ independently in each occurrence is a bridging group; x¹ - x⁶ are each independently 0, 1, 2 or 3; y¹ ■ y^{3 are eac}h independently at least 1;

A¹ in each occurrence is independently a group of formula (III):

wherein: each R¹ is independently a substituent; R² is H or a substituent; each R³ is independently H or a substituent;

J is C=O, S=O, SO2, C=S, NR¹¹ or CR¹²R¹³ wherein R¹¹ is CN or COOR⁴⁰ and R⁴⁰ is H or a substituent and R¹² and R¹³ are each independently CN, CF3 or COOR⁴⁰; and either each Z¹ is N and each Z² is CR⁴, or each Z¹ is CR⁴ and each Z² is N wherein each R⁴ is independently H or a substituent.

Optionally, each R¹ is independently selected from CN, CF3 and COOR⁴⁰ wherein R⁴⁰ in each occurrence is H or a substituent. R⁴⁰ is preferably H or a C1-20 hydrocarbyl group.

Optionally, each R³ is an electron-withdrawing group.

Optionally, the electron-withdrawing group is selected from Cl, F, CN, C1-12 fluoroalkyl and COOR¹⁵ wherein R¹⁵ is a C 1-20 hydrocarbyl group.

Optionally, each R⁴ is independently selected from H or an electron-withdrawing group. The present disclosure provides a composition comprising an electron-donating material and an electron-accepting material wherein the electron accepting material is a compound according to any one of the preceding claims.

The present disclosure provides an organic electronic device comprising an active layer comprising a compound or composition as described herein.

Optionally, the organic electronic device is an organic photoresponsive device comprising a bulk heterojunction layer disposed between an anode and a cathode and wherein the bulk heterojunction layer comprises a composition as described herein.

Optionally, the organic photoresponsive device is an organic photodetector. The present disclosure provides a photosensor comprising a light source and an organic photodetector as described herein wherein the photosensor is configured to detect light emitted from the light source.

Optionally, the light source emits light having a peak wavelength of greater than 900 nm.

The present disclosure provides a formulation comprising a compound or composition as described herein dissolved or dispersed in one or more solvents.

The present disclosure provides a method of forming an organic electronic device as described herein wherein formation of the active layer comprises deposition of a formulation as described herein onto a surface and evaporation of the one or more solvents. DESCRIPTION OF DRAWINGS

The disclosed technology and accompanying figures describe some implementations of the disclosed technology.

Figure 1 illustrates an organic photoresponsive device according to some embodiments;

Figure 2 is a graph of wavelength vs extinction coefficient for a toluene solution of Compound Example 1 and a toluene solution of Comparative Compound 1; Figure 3 is a graph of wavelength vs normalised absorption for a film of Compound

Example 1 and a film of Comparative Compound 1;

Figure 4 is a graph of external quantum efficiency (EQE) vs wavelength for OPD

Device Example 1 in which the only acceptor is Compound Example 1 and for OPD Device Example 2 in which the acceptors are Compound Example 1 and PCBM;

Figure 5 is a graph of external quantum efficiency (EQE) vs wavelength for OPD Comparative Device 2 containing Comparative Compound 1 and PCBM; and

Figure 6 shows dark current at a reverse bias of -3V for OPD devices containing Compound Example 1 and for OPD devices containing Comparative Compound 1. The drawings are not drawn to scale and have various viewpoints and perspectives. The drawings are some implementations and examples. Additionally, some components and/or operations may be separated into different blocks or combined into a single block for the purposes of discussion of some of the embodiments of the disclosed technology. Moreover, while the technology is amenable to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and are described in detail below. The intention, however, is not to limit the technology to the particular implementations described. On the contrary, the technology is intended to cover all modifications, equivalents, and alternatives falling within the scope of the technology as defined by the appended claims. DETAILED DESCRIPTION

Unless the context clearly requires otherwise, throughout the description and the claims, 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." Additionally, 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. Where the context permits, words in the Detailed Description using the singular or plural number may also include the plural or singular number respectively. The word "or," in reference to a list of two or more items, covers all of the following interpretations of the word: any of the items in the list, all of the items in the list, and any combination of the items in the list. References to a layer “over” another layer when used in this application means that the layers may be in direct contact or one or more intervening layers may be present. References to a layer “on” another layer when used in this application means that the layers are in direct contact. References to a specific atom include any isotope of that atom unless specifically stated otherwise.

The teachings of the technology provided herein can be applied to other systems, not necessarily the system described below. The elements and acts of the various examples described below can be combined to provide further implementations of the technology. Some alternative implementations of the technology may include not only additional elements to those implementations noted below, but also may include fewer elements.

These and other changes can be made to the technology in light of the following detailed description. While the description describes certain examples of the technology, and describes the best mode contemplated, no matter how detailed the description appears, the technology can be practiced in many ways. As noted above, particular terminology used when describing certain features or aspects of the technology should not be taken to imply that the terminology is being redefined herein to be restricted to any specific characteristics, features, or aspects of the technology with which that terminology is associated. In general, the terms used in the following claims should not be construed to limit the technology to the specific examples disclosed in the specification, unless the

Detailed Description section explicitly defines such terms. Accordingly, the actual scope of the technology encompasses not only the disclosed examples, but also all equivalent ways of practicing or implementing the technology under the claims.

To reduce the number of claims, certain aspects of the technology are presented below in certain claim forms, but the applicant contemplates the various aspects of the technology in any number of claim forms.

In the following description, for the purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of implementations of the disclosed technology. It will be apparent, however, to one skilled in the art that embodiments of the disclosed technology may be practiced without some of these specific details.

The formulae (I) and (II) are

A¹ - (B - (DV - (B*)x² - A¹ (I)

(II)

A¹ is a monovalent electron-accepting group.

A² is a divalent heteroaromatic electron-accepting group. D¹, D² and D³ independently in each occurrence is an electron-donating group.

B¹, B², and B³ independently in each occurrence is a bridging group. x¹ - x⁶ are each independently 0, 1, 2 or 3, preferably 0 or 1. x¹ and x² are preferably the same and are preferably both 0 or both 1. x³ and x⁴ are preferably the same and are preferably both 0 or both 1, more preferably both 0. x⁵ and x⁶ are preferably the same and are preferably both 0 or both 1. y¹, y² andy³ are each independently at least 1, preferably 1, 2 or 3. y² andy³ are preferably the same. Each of the electron-accepting groups A¹, A² and A³ has a lowest unoccupied molecular orbital (LUMO) level that is deeper (i.e., further from vacuum) than the LUMO of any of the electron-donating groups D¹, D² or D³ of the compound of formula (I), preferably at least 1 eV deeper. The LUMO levels of electron-accepting groups and electron-donating groups may be as determined by modelling the LUMO level of these groups, in which each bond to adjacent group is replaced with a bond to a hydrogen atom. Modelling may be performed using Gaussian09 software available from Gaussian using Gaussian09 with B3LYP (functional) and LACVP* (Basis set).

A¹ in each occurrence is independently a group of formula (III):

Each R¹ is independently a substituent. Preferably, each R¹ is independently selected from CN; Ci-6 fluoroalkyl, preferably CFv and COOR⁴⁰ wherein R⁴⁰ in each occurrence is H or a substituent, preferably H or a Ci-2ohydrocarbyl group. A Ci -20 hydrocarbyl group as described herein may be selected from phenyl which may be unsubstituted or substituted with one or more substituents selected from C1-12 alkyl and a linear, branched or cyclic C1-20 alkyl.

R² is H or a substituent. Preferably, R² is H, F, Cl, CN, NO2, Ci-16 alkyl or Ci-16 alkoxy wherein one or more H atoms of the Ci-16 alkyl or Ci-16 alkoxy may be replaced with F. Each R³ is independently H or a substituent, preferably an electron-withdrawing group. Preferred electron-withdrawing groups are F, Cl, CN, C1-12 fluoroalkyl and COOR¹⁵ wherein R¹⁵ is a Ci-2o hydrocarbyl group.

J is C=O, C=S, S=O, SO2, NR¹¹ or CR¹²R¹³ wherein R¹¹, R¹² and R¹³are as described above. J is preferably C=O.

Either: (i) each Z¹ is N and each Z² is CR⁴, or (b) each Z¹ is CR⁴ and each Z² is N wherein each R⁴ is independently H or a substituent, preferably H or an electronwithdrawing group. Electron-withdrawing groups R⁴ are preferably selected from electron-withdrawing groups described with respect to R³. Preferably, the group of formula (III) has formula (Illa):

Exemplary groups of formula (III) include, without limitation:

In some embodiments, the compound of formula (I) or (II) has an absorption peak greater than 900 nm, optionally greater than 1100 nm, optionally greater than 1250 nm. The absorption peak is suitably less than 1500 nm. The present inventors have surprisingly found that compounds of formula (I) or (II) having a group A¹ of formula (III) may have low dark current.

Acceptor Unit A²

A² is preferably a fused heteroaromatic group comprising at least 2 fused rings, preferably at least 3 fused rings.

In some embodiments, A² of formula (II) is a group of formula (VIII):

wherein:

Ar¹ is an aromatic or heteroaromatic group; and Y is O, S, NR⁶ or R⁷-C=C-R⁷ wherein R⁷ in each occurrence is independently H or a substituent wherein two substituents R⁷ may be linked to form a monocyclic or polycyclic ring; and R⁶ is H or a substituent.

In the case where A² is a group of formula (VIII), Ar¹ may be a monocyclic or polycyclic heteroaromatic group which is unsubstituted or substituted with one or more R⁹ groups wherein R⁹ in each occurrence is independently a substituent.

Preferred R⁹ groups are selected from

F;

CN;

NO2; Ci -20 alkyl wherein one or more non-adjacent C atoms may be replaced with O, S, NR¹⁷ wherein R¹⁷ is a Ci-nhydrocarbyl, COO or CO and one or more H atoms of the alkyl may be replaced with F; an aromatic or heteroaromatic group, preferably phenyl, which is unsubstituted or substituted with one or more substituents; and a group selected from

wherein Z⁴⁰, Z⁴¹, Z⁴² and Z⁴³ are each independently CR¹³ or N wherein R¹³ in each occurrence is H or a substituent, preferably a C1-20 hydrocarbyl group; Y⁴⁰ and Y⁴¹ are each independently O, S, NX⁷¹ wherein X⁷¹ is CN or COOR⁴⁰; or CX⁶⁰X⁶¹ wherein X⁶⁰ and X⁶¹ is independently CN, CFs or COOR⁴⁰; W⁴⁰ and W⁴¹ are each independently O, S, NX⁷¹ or CX⁶⁰X⁶¹ wherein X⁶⁰ and X⁶¹ is independently CN, CF3 or COOR⁴⁰; and R⁴⁰ in each occurrence is H or a substituent, preferably H or a C1-20 hydrocarbyl group. Exemplary substituents of an aromatic or heteroaromatic group R⁹ are F, CN, NO2, and C1-12 alkyl wherein one or more non-adjacent C atoms may be replaced with O, S, NR⁷, COO or CO and one or more H atoms of the alkyl may be replaced with F.

R¹⁷ as described anywhere herein may be, for example, C1-12 alkyl, unsubstituted phenyl; or phenyl substituted with one or more C1-6 alkyl groups.

If a C atom of an alkyl group as described anywhere herein is replaced with another atom or group, the replaced C atom may be a terminal C atom of the alkyl group or a non- terminal C-atom.

By “non-terminal C atom” of an alkyl group as used anywhere herein means a C atom other than the C atom of the methyl group at the end of an n-alkyl chain or the C atoms of the methyl groups at the ends of a branched alkyl chain.

If a terminal C atom of a group as described anywhere herein is replaced then the resulting group may be an anionic group comprising a countercation, e.g., an ammonium or metal countercation, preferably an ammonium or alkali metal cation.

A C atom of an alkyl substituent group which is replaced with another atom or group as described anywhere herein is preferably a non-terminal C atom, and the resultant substituent group is preferably non-ionic. Exemplary monocyclic heteroaromatic groups Ar¹ are oxadiazole, thiadiazole, triazole and 1,4-diazine which is unsubstituted or substituted with one or more substituents. Thiadiazole is particularly preferred.

Exemplary polycyclic heteroaromatic groups Ar¹ are groups of formula (V):

X¹ and X², are each independently selected from N and CR¹⁰ wherein R¹⁰ is H or a substituent, optionally H or a substituent R⁹ as described above.

X³, X⁴, X⁵ and X⁶ are each independently selected from N and CR¹⁰ with the proviso that at least one of X³, X⁴, X⁵ and X⁶ is CR¹⁰.

Z is selected from O, S, SO2, NR⁶, PR⁶, C(R¹⁰)₂, Si(R¹⁰)₂ C=O, C=S and C=C(R⁵)₂ wherein R¹⁰ is as described above; R⁶ is H or a substituent; and R⁵ in each occurrence is an electron-withdrawing group.

Optionally, each R⁶ of any NR⁶ or PR⁶ described anywhere herein is independently selected from H; C1-20 alkyl wherein one or more non-adjacent C atoms other than the C atom bound to N or P may be replaced with O, S, NR⁷, COO or CO and one or more H atoms of the alkyl may be replaced with F; and phenyl which is unsubstituted or substituted with one or more substituents, optionally one or more C1-12 alkyl groups wherein one or more non-adjacent C atoms of the alkyl may be replaced with O, S, NR⁷, COO or CO and one or more H atoms of the alkyl may be replaced with F. Preferably, each R⁵ is CN, COOR⁴⁰; or CX⁶⁰X⁶¹ wherein X⁶⁰ and X⁶¹ is independently CN, CFs or COOR⁴⁰ and R⁴⁰ in each occurrence is H or a substituent, preferably H or a Ci-2ohydrocarbyl group.

A² groups of formula (VIII) are preferably selected from groups of formulae (Villa) and (Vlllb):

For compounds of formula (Vlllb), the two R⁷ groups may or may not be linked.

Preferably, when the two R⁷ groups are not linked each R⁷ is independently selected from H; F; CN; NO2; Ci -20 alkyl wherein one or more non-adjacent C atoms may be replaced with O, S, NR⁷, CO, COO, NR⁶, PR⁶, or Si(R¹⁰)2 wherein R¹⁰ and R⁶ are as described above and one or more H atoms may be replaced with F; and aryl or heteroaryl, preferably phenyl, which may be unsubstituted or substituted with one or more substituents. Substituents of the aryl or heteroaryl group may be selected from one or more of F; CN; NO2; and C1-20 alkyl wherein one or more non-adjacent C atoms may be replaced with O,

S, NR⁷, CO, COO and one or more H atoms may be replaced with F.

Preferably, when the two R⁷ groups are linked, the group of formula (Vlllb) has formula (Vlllb- 1) or (VIIIb-2):

(VIIIb-1) (VIIIb-2)

Ar² is an aromatic or heteroaromatic group, preferably benzene, which is unsubstituted or substituted with one or more substituents. Ar² may be unsubstituted or substituted with one or more substituents R² as described above.

X is selected from O, S, SO2, NR⁶, PR⁶, C(R¹⁰)₂, Si(R¹⁰)₂ C=O, C=S and C=C(R⁵)₂ wherein R¹⁰, R⁶ and R⁵ are as described above.

Exemplary electron-accepting groups of formula (VIII) include, without limitation:

wherein Ak¹ is a C1-20 alkyl group

Divalent electron-accepting groups A² other than formula (VIII) are optionally selected from formulae (IVa)-(IVj)

Y^A1 is O or S, preferably S.

R²³ in each occurrence is a substituent, optionally C1-12 alkyl wherein one or more nonadj acent C atoms other than the C atom attached to Z³ may be replaced with O, S, NR⁶, COO or CO and one or more H atoms of the alkyl may be replaced with F. R²⁵ in each occurrence is independently H; F; CN; NO2; C1-12 alkyl wherein one or more non-adj acent C atoms may be replaced with O, S, NR⁶, COO or CO and one or more H atoms of the alkyl may be replaced with F; an aromatic group, optionally phenyl, which is unsubstituted or substituted with one or more substituents selected from F and C1-12 alkyl wherein one or more non-adj acent C atoms may be replaced with O, S, NR⁶, COO or CO; or

wherein Z⁴⁰, Z⁴¹, Z⁴² and Z⁴³ are each independently CR¹³ or N wherein R¹³ in each occurrence is H or a substituent, preferably a Ci-2o hydrocarbyl group;

Y⁴⁰ and Y⁴¹ are each independently O, S, NX⁷¹ wherein X⁷¹ is CN or COOR⁴⁰; or CX⁶⁰X⁶¹ wherein X⁶⁰ and X⁶¹ is independently CN, CFs or COOR⁴⁰;

W⁴⁰ and W⁴¹ are each independently O, S, NX⁷¹ wherein X⁷¹ is CN or COOR⁴⁰; or CX⁶⁰X⁶¹ wherein X⁶⁰ and X⁶¹ is independently CN, CF3 or COOR⁴⁰; and

R⁴⁰ in each occurrence is H or a substituent, preferably H or a Ci-2ohydrocarbyl group.

Z³ is N or P. T¹, T² and T³ each independently represent an aryl or a heteroaryl ring, optionally benzene, which may be fused to one or more further rings. Substituents of T¹, T² and T³, where present, are optionally selected from non-H groups of R²⁵. In a preferred embodiment, T³ is benzothiadiazole.

R¹² in each occurrence is a substituent, preferably a Ci-2o hydrocarbyl group. Ar⁵ 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 R²⁵.

Bridging units

Bridging units B¹, B² and B³ are preferably each selected from vinylene, arylene, heteroarylene, arylenevinylene and heteroarylenevinylene wherein the arylene and heteroarylene groups are monocyclic or bicyclic groups, each of which may be unsubstituted or substituted with one or more substituents.

Optionally, B¹, B² and B³ are selected from units of formulae (Via) - (VIn):

wherein R⁵⁵ is H or a substituent; R⁸ in each occurrence is independently H or a substituent, preferably H or a substituent selected from F; CN; NO2; C1-20 alkyl wherein one or more non-adjacent C atoms may be replaced with O, S, NR⁶, COO or CO and one or more H atoms of the alkyl may be replaced with F; phenyl which is unsubstituted or substituted with one or more substituents; and -B(R¹⁴)2 wherein R¹⁴ in each occurrence is a substituent, optionally a Ci-2o hydrocarbyl group. R⁸ groups of formulae (Via), (VIb) and (Vic) may be linked to form a bicyclic ring, for example thienopyrazine.

R⁸ is preferably H, C1-20 alkyl or C1-19 alkoxy.

Electron-Donating Groups D¹, D² and D³

Electron-donating groups preferably are fused aromatic or heteroaromatic groups, more preferably fused heteroaromatic groups containing three or more rings. Particularly preferred electron-donating groups comprise fused thiophene or furan rings, optionally fused rings containing thiophene or furan rings and one or more rings selected from benzene, cyclopentadiene, tetrahydropyran, tetrahydrothiopyran and piperidine rings, each of said rings being unsubstituted or substituted with one or more substituents.

Exemplary electron-donating groups D¹, D² and D³ include groups of formulae (Vlla)- (VIIp):

wherein Y^A in each occurrence is independently O, S or NR⁵⁵, Y^A1 in each occurrence is independently O or S; X^A is C or Si; Z^A in each occurrence is O, CO, S, NR⁵⁵ or C(R⁵⁴)2; R⁵¹, R⁵² R⁵⁴ and R⁵⁵ independently in each occurrence is H or a substituent; R⁵³ independently in each occurrence is a substituent; and Ar⁴ is an optionally substituted monocyclic or fused heteroaromatic group.

Optionally, R⁵¹ and R⁵² independently in each occurrence are selected from H; F; C1-20 alkyl wherein one or more non-adjacent C atoms may be replaced with O, S, NR⁷, COO or CO and one or more H atoms of the alkyl may be replaced with F; and an aromatic or heteroaromatic group Ar³ which is unsubstituted or substituted with one or more substituents.

In some embodiments, Ar³ may be an aromatic group, e.g., phenyl.

Ar⁴ is preferably selected from optionally substituted oxadiazole, thiadiazole, triazole, and 1,4-diazine. In the case where Ar⁴ is 1,4-diazine, the 1,4-diazine may be fused to a further heterocyclic group, optionally a group selected from optionally substituted oxadiazole, thiadiazole, triazole, 1,4-diazine and succinimide.

The one or more substituents of Ar³, if present, may be selected from C1-12 alkyl wherein one or more non-adjacent C atoms may be replaced with O, S, NR⁷, COO or CO and one or more H atoms of the alkyl may be replaced with F.

Preferably, each R⁵⁴ is selected from the group consisting of:

H; F; linear, branched or cyclic C1-20 alkyl wherein one or more non-adjacent C atoms may be replaced by O, S, NR⁷, CO or COO wherein R¹⁷ is a Ci -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-(Ar⁷)v wherein Ak is a C1-20 alkylene chain in which one or more non-adjacent C atoms may be replaced with O, S, NR⁷, CO or COO; u is 0 or 1; Ar⁷ 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. Substituents of Ar⁷, if present, are preferably selected from F; Cl; NO2; CN; and C1-20 alkyl wherein one or more non-adjacent C atoms may be replaced with O, S, NR⁷, CO or COO and one or more H atoms may be replaced with F. Preferably, Ar⁷ is phenyl.

Preferably, each R⁵¹ is H.

Optionally, R⁵³ independently in each occurrence is selected from C1-20 alkyl wherein one or more non-adjacent C atoms may be replaced with O, S, NR⁷, COO or CO and one or more H atoms of the alkyl may be replaced with F; and phenyl which is unsubstituted or substituted with one or more substituents, optionally one or more C1-12 alkyl groups wherein one or more non-adjacent C atoms may be replaced with O, S, NR⁷, COO or CO and one or more H atoms of the alkyl may be replaced with F. Preferably, R⁵⁵ as described anywhere herein is H or C1-30 hydrocarbyl group.

In a preferred embodiment, D¹, D² and D³ are each independently a group of formula (Vila). Exemplary groups of formula (Vila) include, without limitation:

wherein He in each occurrence is independently a C1-20 hydrocarbyl group, e.g., C1-20 alkyl, unsubstituted aryl, or aryl substituted with one or more C1-12 alkyl groups. The aryl group is preferably phenyl.

In some embodiments, y¹ of formula (I) is 1.

In some embodiments, y² and y³ of formula (II) are each 1.

In some embodiments, y¹ of formula (I) or at least one of y² and y³ of formula (II) is greater than 1. In these embodiments, the chain of D¹, D² or D³ groups, respectively, may be linked in any orientation. For example, in the case where D¹ is a group of formula (Vila) and y¹ is 2, -[D^yi- may be selected from any of:

Exemplary compounds of formula (I) include, without limitation:

Electron-donating material

A bulk heterojunction layer as described herein comprises an electron-donating material and a compound of formula (I) as described herein. Exemplary donor materials are disclosed in, for example, WO2013/051676, the contents of which are incorporated herein by reference.

The electron-donating material may be a non-polymeric or polymeric material.

In a preferred embodiment the electron-donating material is an organic conjugated polymer, which can be a homopolymer or copolymer including alternating, random or block copolymers. The conjugated polymer is preferably a donor-acceptor polymer comprising alternating electron-donating repeat units and electron-accepting repeat units.

Preferred are non-crystalline or semi- crystalline conjugated organic polymers.

Further preferably the electron-donating polymer is a conjugated organic polymer with a low bandgap, typically between 2.5 eV and 1.5 eV, preferably between 2.3 eV and 1.8 eV.

Optionally, the electron-donating polymer has a HOMO level no more than 5.5 eV from vacuum level. Optionally, the electron-donating polymer has a HOMO level at least 4.1 eV from vacuum level. As exemplary electron-donating polymers, 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, polybenzothiophene, polybenzo[l,2-b:4,5-b']dithiophene, poly isothianaphthene, poly (monosubstituted pyrrole), poly(3,4-bisubstituted pyrrole), poly-1, 3, 4-oxadiazoles, polyisothianaphthene, derivatives and co-polymers thereof may be mentioned.

Preferred examples of donor polymers 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.

A particularly preferred donor polymer comprises donor unit (Vila) provided as a repeat unit of the polymer, most preferably with an electron-accepting repeat unit, for example divalent electron-accepting units A¹ as described herein provided as polymeric repeat units. Another particularly preferred donor polymer comprises repeat units of formula (X):

wherein R¹⁸ and R¹⁹ are each independently selected from H; F; 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; or an aromatic or heteroaromatic group Ar⁶ which is unsubstituted or substituted with one or more substituents selected from F and C1-12 alkyl wherein one or more non-adjacent, nonterminal C atoms may be replaced with O, S, COO or CO.

The donor polymer is preferably a donor-acceptor (DA) copolymer comprising a donor repeat unit, for example a repeat unit of formula (Vila) or (X), and an acceptor repeat unit.

Organic Electronic Device

A compound of formula (I) or (II) may be provided as an active layer of an organic electronic device. In a preferred embodiment, a bulk heterojunction layer of an organic photoresponsive device, more preferably an organic photodetector, comprises a composition as described herein.

The bulk heterojunction layer comprises or consists of an electron-donating material and an electron-accepting compound of formula (I) or (II) as described herein.

In some embodiments, the bulk heterojunction layer contains two or more accepting materials and / or two or more electron-accepting materials.

In some embodiments, the weight of the electron-donating material(s) to the electronaccepting material(s) is from about 1:0.5 to about 1:2, preferably about 1:1.1 to about 1:2.

Preferably, the electron-donating material has a type II interface with the electronaccepting material, i.e. the electron-donating material has a shallower HOMO and LUMO that the corresponding HOMO and LUMO levels of the electron-accepting material. Preferably, the compound of formula (I) or (II) has a HOMO level that is at least 0.05 eV deeper, optionally at least 0.10 eV deeper, than the HOMO of the electron-donating material.

Optionally, the gap between the HOMO level of the electron-donating material and the LUMO level of the electron-accepting compound of formula (I) or (II) is less than 1.4 eV.

Unless stated otherwise, HOMO and LUMO levels of materials as described herein are as measured by square wave voltammetry (SWV). Figure 1 illustrates an organic photoresponsive device according to some embodiments of the present disclosure. The organic photoresponsive device comprises a cathode 103, an anode 107 and a bulk heterojunction layer 105 disposed between the anode and the cathode. The organic photoresponsive device may be supported on a substrate 101, optionally a glass or plastic substrate.

Each of the anode and cathode may independently be a single conductive layer or may comprise a plurality of layers.

At least one of the anode and cathode is transparent so that light incident on the device may reach the bulk heterojunction layer. In some embodiments, both of the anode and cathode are transparent. The transmittance of a transparent electrode may be selected according to an emission wavelength of a light source for use with the organic photodetector.

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 organic photoresponsive device may comprise layers other than the anode, cathode and bulk heterojunction layer shown in Figure 1. In some embodiments, a holetransporting layer is disposed between the anode and the bulk heterojunction layer. In some embodiments, an electron-transporting layer is disposed between the cathode and the bulk heterojunction layer. In some embodiments, 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.

The area of the OPD may be less than about 3 cm², less than about 2 cm², less than about 1 cm², less than about 0.75 cm², less than about 0.5 cm² or less than about 0.25 cm². Optionally, 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 mm², optionally in the range of 0.5 micron² - 900 micron².

The substrate may be, without limitation, a glass or plastic substrate. The substrate can be an inorganic semiconductor. In some embodiments, the substrate may be silicon. For example, 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 bulk heterojunction layer contains a compound of formula (I) or (II) as described herein and an electron-donating compound. The bulk heterojunction layer may consist of these materials or may comprise one or more further materials, for example one or more further electron-donating materials and / or one or more further electron-accepting compounds.

Fullerene In some embodiments, a compound of formula (I) or (II) is the only electron-accepting material of a bulk heterojunction layer as described herein.

In some embodiments, a bulk heterojuction layer contains a compound of formula (I) or (II) and one or more further electron-accepting materials. Preferred further electron- accepting materials are fullerenes. The present inventors have surprisingly found that a combination of a compound of formula (I) or (II) and a fullerene may enhance external quantum efficiency of an OPD with little or no increase in dark current.

The compound of formula (I) or (II) : fullerene acceptor 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. Fullerenes may be selected from, without limitation, Ceo, C70, C76, C78 and Csr fullerenes or a derivative thereof, including, without limitation, PCBM-type fullerene derivatives including phenyl- Cei-butyric acid methyl ester (CeoPCBM), TCBM-type fullerene derivatives (e.g. tolyl- Cei-butyric acid methyl ester (CeoTCBM)), and ThCBM-type fullerene derivatives (e.g. thienyl-Cei-butyric acid methyl ester (CeoThCBM).

Fullerene derivatives may have formula (V):

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 (Va), (Vb) and (Vc):

wherein R²⁰-R³² are each independently H or a substituent.

Substituents R²⁰-R³² 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 C atoms may be replaced with O, S, NR⁷, CO or COO and one or more H atoms may be replaced with F. Substituents of aryl or heteroaryl, where present, are optionally selected from C1-12 alkyl wherein one or more non-adjacent C atoms may be replaced with O, S, NR⁷, CO or COO and one or more H atoms may be replaced with F.

Formulations The bulk heterojunction layer may be formed by any process including, without limitation, thermal evaporation and solution deposition methods.

Preferably, the bulk heterojunction layer is formed by depositing a formulation comprising the electron-donating material(s), the electron-accepting material(s) and any other components of the bulk heterojunction layer 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, inkjet printing, screen printing, gravure printing and flexographic printing.

The one or more solvents of the formulation may optionally comprise or consist of benzene or naphthalene substituted with one or more substituents selected from fluorine, chlorine, C1-10 alkyl and C1-10 alkoxy wherein two or more substituents may be linked to form a ring which may be unsubstituted or substituted with one or more C1-6 alkyl groups, optionally toluene, xylenes, trimethylbenzenes, tetramethylbenzenes, anisole, indane and its alkyl-substituted 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-10 alkyl benzoate, benzyl benzoate or dimethoxybenzene. In preferred embodiments, a mixture of trimethylbenzene and benzyl benzoate is used as the solvent. In other preferred embodiments, a mixture of trimethylbenzene and dimethoxybenzene is used as the solvent.

The formulation may comprise further components in addition to the electron-accepting material, the electron-donating material and the one or more solvents. As examples of such components, 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. Applications

A circuit may comprise the OPD connected to a voltage source for applying a reverse bias to the device and / or a device configured to measure photocurrent. The voltage applied to the photodetector may be variable. In some embodiments, the photodetector may be continuously biased when in use. In some embodiments, a photodetector system comprises a plurality of photodetectors as described herein, such as an image sensor of a camera.

In some embodiments, 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. In some embodiments, the light source has a peak wavelength of at least 900 nm or at least 1000 nm, optionally in the range of 900-1500 nm.

In some embodiments, the light from the light source may or may not be changed before reaching the OPD. For example, the light may be reflected, filtered, down-converted or up-converted before it reaches the OPD.

The organic photoresponsive device as described herein may be an organic photovoltaic device or an organic photodetector. An 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, reflection by and/or emission of light from an object, e.g. 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.

Examples

Example 1

A group of formula (III- 1) may be formed according to the following reaction scheme:

Step 5 Step 6

1. AC₂O, NE r.t., 16h Malononitrile

Pyridine

2. 1.5 M HC r.t., 2h 48h

Step 1: 1 (250g, 1.06 mol) was dissolved in 2.5 L of dichloroethane. N-Bromosuccinimide (754g, 4.24 mol), was added to reaction mixture portion wise and it was heated at 75 °C for 16 hours. Solid impurities were filtered off and washed with heptane. Filtrate was concentrated under vacuum to get 255g of crude material. Product 2 was used in the next step without further purification.

Step 2:

2 (99.9 g, 434 mmol) and 3 (55g, 310 mmol) were dissolved in IL of ethanol, p-toluene sulfonic acid (4.69g, 24.7 mmol) was added to the reaction mixture and it was heated at 68 °C for 3 hours. Then, the reaction was concentrated under vacuum to give 105g of crude product which was purified by column chromatography with dichloromethane to give 80g of the desired product.

Step 3:

4 (50 g, 134 mmol) was dissolved in 500 mL of methanol. Lithium hydroxide monohydride (12.9 g, 308 mmol) was added to the reaction mixture, and it was stirred at room temperature for 16 hours. The reaction mixture was filtered and the obtained solid was stirred in diluted hydrochloric acid for 3 hours. The solid was filtered to obtain 30g of the desired product 5.

Step 4:

5 (30 g, 104 mmol) and acetic anhydride (600 mL) were combined in the flask. The reaction mixture was heated at 130 °C for 6 hours. After this time, it was cooled down and concentrated under reduced pressure to obtain 30g of crude product 6 which was used directly in the next step without further purification.

Step 5

To stirred solution of 6 (30 g, l l lmmol) in acetic anhydride (240 mL) was added triethylamine (11.2 g, 111 mmol). To this tert-butyl acetoacetate (18.3 g, 116 mmol) was added dropwise. The reaction mixture was stirred at room temperature for 16 hours and then poured slowly into another flask containing 1.5 N hydrochloric acid (400 mL) and 400 mL of ice water. This was then stirred for 48 hours at room temperature. The obtained solid was isolated by filtration to give 15 g of the desired product 7 as a black solid which was used in the next step without further purification.

Step 6

7 (5 g, 18.7 mmol) was dissolved in pyridine (90 ml). To this malononitrile (3.08 g, 46.7 mmol) was added and the mixture was stirred for 2 hours at room temperature. The reaction was concentrated under reduced pressure to give 9g of crude material which was purified by neutral alumina column chromatography using dichloromethane and 1% triethylamine in methanol. The obtained product was triturated with hexane / di chloromethane and filtered off to give 2.013 g of pure III-l product (98.81% by HPLC) as triethylamine salt.

Example 2

A group of formula (III-2) may be formed according to the following reaction scheme:

Step 3 Step 4

L

Step 5 Molecular Weight: 404.02

1. AC₂O, r.t.. 16h Malononitrile

2. 1.5 M Pyridine 48h r.t., 2h

7 HI-2 Example 3

A group of formula (III-3) may be formed according to the following reaction scheme: h

3

¹ 2

Step 3 Step 4

Step 5 Step 6

1. Ac₂O, NEt₃ Ethane-1 ,2-diol r.t., 16h p-TsOH

2. 1.5 M HCI Toluene 48h

135 °C, 16h

Step 7 Step 8

K

Step 9

Malononitrile

AcONa r.t., 3h

111-3 Step 1 As for III-l.

Step 2

3 (150 g, 564 mmol) and 2 (181 g, 789 mmol) were dissolved in ethanol (2.5 L). p- toluenesulfonic acid monohydrate (8.57 g, 45.1 mmol) was added to the reaction mixture, and it was heated at 65°C for 4 hours. Then, it was concentrated under vacuum to obtain 390 g of crude product 4 which was used in the next step without further purification.

Step 3

4 (330g, 717 mmol) was dissolved in 3 L of methanol. To this lithium hydroxide monohydride (68.8 g, 1.64 mol) dissolved in 250 mL of water was added dropwise. The obtained solid was filtered and stirred with 1.5 N HC1 solution (2 L) for 3 hours. The precipitate was isolated by filtration, washed with 2 L of water, and dried under vacuum to give 220g of pure material 5 as an off-white solid.

Step 4

5 (150 g, 398 mmol) was taken in acetic anhydride (1.5 L, 14.6 mmol). The reaction mixture was heated at 130 °C for 16 hours. After completion the reaction mixture was concentrated under vacuum to give 125g of 6 which was used in the next step with further purification.

Step 5

6 (50 g, 139 mmol) and acetic anhydride (50 g, 139 mmol) were combined and cooled to 0°C. Triethylamine (20 ml, 0.197 mmol) was added, then tert-butyl acetoacetate (16.8 g,

145 mmol) and the reaction mixture was stirred at room temperature for 16 hours. After this time, the mixture was concentrated under reduce pressure and stirred with 1.5 N hydrochloric acid (480 mL) and water (1920 mL) for 3 days. Upon completion the mixture was filtered to give 35 g of desired product 7. LCMS indicated 60% purity and this material was then taken to next step.

Step 6 7 (30 g, 84.2 mmol) was dissolved in toluene (1 L), and ethane- 1,2-diol (104 g, 1.68 mol) and p-toluenesulfonic acid (3.19 g, 16.8 mmol) were added. The reaction mixture was heated to 135 °C for 16 hours. During this time, water was frequently removed using Dean-Stark apparatus. Upon completion the mixture was cooled to room temperature and filtered through a celite bed, washed with ethyl acetate, then with water, dried over sodium sulfate and concentrated under vacuum to give 38 g of crude product 8.

Step 7

To 8 (5 g, 11.2 mmol) in o-xylene (150 mL), was added potassium hexacyanoferrate (III) (4.93 g, 13.4 mmol), 1-butyl imidazole (2.91 g, 23.5 mmol) and copper (I) iodide (1.27 g, 6.71 mmol). The reaction mixture was heated at 148 °C for 24 hours. After this time potassium hexacyanoferrate (0.74 g), copper iodide (0.2 g) and 1-butyl imidazole (0.46 mL) were added, and the mixture was further heated to 148°C for 24 hours. Upon completion the mixture was cooled to room temperature and filtered through a celite pad, and the filtrate was washed with water and extracted with ethyl acetate. The organic phase was dried over sodium sulphate and concentrated under vacuum to give 7g of crude intermediate. This was further purified by column chromatography using ethyl acetate and hexane mixture to give 3.5g of the desired product 9 as a yellow solid.

Step 8

9 (3 g, 8.92 mmol) was dissolved in trifluoroacetic acid (21 mL). The reaction mixture was heated at 40°C for 3 hours. Then, it was concentrated under vacuum at 30°C to give crude material 10, 50% of desired product by LCMS which was used as such in the next step.

Step 9

To malononitrile (0.304 g, 4.61 mmol) and sodium acetate (9.18 g, 112 mmol) in ethanol (120 mL), 10 (1.5 g, 5.13 mmol) dissolved in 250 ml of ethanol was added dropwise. The reaction mixture was stirred at room temperature for 3 hours and then concentrated under vacuum to give the crude product. The crude product was purified by column chromatography using a dichloromethane/methanol solvent system. The obtained product was suspended in ethyl acetate and stirred for 30 minutes, and filtered to give 0.5g of III- 3 product as a dark solid (88% purity).

Compound Example 1

Compound Example 1 may be formed according to the following reaction scheme:

Compounds 2-4, shown in Table 1, were formed. Comparative Compounds 2-4 are also shown. Table 1

Measurement methods

HOMO and LUMO levels were measured by square wave voltammetry (SWV).

In SWV, 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 comprises 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 is 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 is dissolved in toluene (3 mg / 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). A typical SWV experiment runs at 15 Hz frequency; 25 mV amplitude and 0.004 V increment steps. Results are calculated from 3 freshly spun film samples for both the HOMO and LUMO data.

Absorption spectra were measured using a Cary 5000 UV-VIS-NIR Spectrometer. Measurements were taken from 175 nm to 3300 nm using a PbSmart NIR detector for extended photometric range with variable slit widths (down to 0.01 nm) for optimum control over data resolution.

Unless stated otherwise, absorption values are of a solution. Absorption data are obtained by measuring the intensity of transmitted radiation through a solution sample. Absorption intensity is plotted vs. incident wavelength to generate an absorption spectrum. A method for measuring absorption may comprise measuring a 15 mg / ml solution in a quartz cuvette and comparing to a cuvette containing the solvent only.

Unless stated otherwise, solution absorption data as provided herein is as measured in toluene solution.

Materials data With reference to Table 2, Compound Examples have a longer peak absorption wavelength than the corresponding Comparative Compound.. Table 2

o-DCB: o-dichlorobenzene TMB: 1,3,4-trimethylbenzne

With reference to Figure 2, Compound Example 1 has higher absorption intensity than Comparative Compound 1 under the same absorption conditions.

With reference to Figure 3 and as shown in Table 1, a film of Compound Example 1, formed by spin-coating from o-dichlorobenzene, absorbs at about 1300 nm which is around 150 nm longer than a film of Comparative Compound 1 formed by spin-coating from toluene.

Device Example 1

A glass substrate coated with a 150 nm thick layer of indium-tin oxide (ITO) was coated with a 0.2 % polyethyleneimine (PEIE) solution in water to form a ~5 nm film modifying the work function of the ITO. A ca. 500 nm thick bulk heterojunction layer of a mixture of Donor Polymer 1 : Compound Example 1 (1 : 0.7 by weight) was deposited over the modified ITO layer by bar coating from a 10 mg/ml solution in an o-di chlorobenzene / butylbenzoate solvent mixture (90:10 v/v). An anode stack of MoOs (lOnm) and ITO (50nm) was formed over the bulk heterojunction by thermal evaporation (MoOs) and sputtering (ITO).

Donor Polymer 1

Device Example 1A

A device was prepared as described for Device Example 1 except that the solution used to form the bulk heterojunction layer contained fullerene PCBM in addition to Donor Polymer 1 and Compound Example 1 in a weight ratio of Donor Polymer 1 : Compound Example 1 : PCBM 1 : 0.7 : 0.3.

Comparative Device 1 A device was prepared as described for Device Example 1A except that Comparative Compound 1 was used in place of Compound Example 1.

With reference to Figure 4, external quantum efficiency peaks at around 1300 nm for Device Examples 1 and 1A. The inclusion of PCBM increases EQE. With reference to Figure 5, EQE of Comparative Device 1 peaks at about 900 nm.

With reference to Figure 6, dark currents at a reverse bias of -3V of Device Examples 1 and 2 are much lower than that of Comparative Device 1.

Device Examples 2-4

Device Examples 2-4 were prepared as described for Device Example 1A except as follows:

Compound Examples 2-4, respectively, were used in place of Compound Example

1

Solvents used to form the bulk heterojunction layer are as set out in Table 3

For Device Examples 2 and 4, the Donor Polymer 1 : Compound Example : PCBM weight ratio was 1 : 0.875 : 0.625

Comparative Devices 2-4 containing Comparative Compounds 2-4 were formed in the same way as the corresponding Device Example.

Table 3

o-DCB: o-dichlorobenzene

BB: butylbenzoate

TMB : 1 ,3 ,4-trimethylbenzene DMOB: 1 ,2-dimethoxybenzene

1-ClNp: 1 -chloronaphthalene Modelling

The HOMO and LUMO energy levels of NF As of formula (I) containing a group of formula (III) and comparative NF As which do not have a group of formula (III) were modelled. Results are set out in Table 4 in which in which Slf corresponds to oscillator strength of the transition from SI (predicting absorption intensity) and Eopt is the modelled optical gap.

The NF As containing electron-accepting end-groups of formula (III) have a smaller modelled band gap and longer wavelength modelled optical gap than NF As containing a comparative electron-accepting end-group. Table 4

Claims

CLAIMS A compound of formula (I) or (II):

A¹ - (B - (DV - (B*)x² - A¹

(I)

(II) wherein:

A² is a divalent heteroaromatic electron-accepting group;

D¹, D² and D³ independently in each occurrence is an electron-donating group; B¹, B², and B³ independently in each occurrence is a bridging group; x¹ - x⁶ are each independently 0, 1, 2 or 3; y¹, y² and y³ are each independently at least 1;

A¹ in each occurrence is independently a group of formula (III):

wherein: each R¹ is independently a substituent;

R² is H or a substituent; each R³ is independently H or a substituent; J is C=O, C=S, S=O, SO2, NR¹¹ or CR¹²R¹³ wherein R¹¹ is CN or COOR⁴⁰ and R⁴⁰ is H or a substituent and R¹² and R¹³ are each independently CN, CF3 or COOR⁴⁰; and either each Z¹ is N and each Z² is CR⁴, or each Z¹ is CR⁴ and each Z² is N wherein each R⁴ is independently H or a substituent.

2. The compound according to claim 1 wherein each Z¹ is N and each Z² is CR⁴.

3. The compound according to claim 1 wherein each Z² is N and each Z¹ is CR⁴.

4. The compound according to any one of the preceding claims wherein each R¹ is independently selected from CN, CF3 and COOR⁴⁰ wherein R⁴⁰ in each occurrence is H or a substituent.

5. The compound according to any one of the preceding claims wherein each R³ is an electron-withdrawing group.

6. The compound according to claim 5 wherein the electron-withdrawing group is selected from Cl, F, CN, Ci -12 fluoroalkyl and COOR¹⁵ wherein R¹⁵ is a C1-20 hydrocarbyl group.

7. The compound according to any one of the preceding claims wherein each R⁴ is independently selected from H or an electron-withdrawing group.

8. A composition comprising an electron-donating material and an electron-accepting material wherein the electron accepting material is a compound according to any one of the preceding claims.

9. An organic electronic device comprising an active layer comprising a compound or composition according to any one of the preceding claims.

10. An organic electronic device according to claim 9 wherein the organic electronic device is an organic photoresponsive device comprising a bulk heterojunction layer disposed between an anode and a cathode and wherein the bulk heterojunction layer comprises a composition according to claim 8.

11. An organic electronic device according to claim 10 wherein the organic photoresponsive device is an organic photodetector.

12. A photosensor comprising a light source and an organic photodetector according to claim 11 wherein the organic photodetector is configured to detect light emitted from the light source.

13. The photosensor according to claim 12, wherein the light source emits light having a peak wavelength of greater than 900 nm.

14. A formulation comprising a compound or composition according to any one of claims 1 to 8 dissolved or dispersed in one or more solvents.

15. A method of forming an organic electronic device according to any one of claims 9-11 wherein formation of the active layer comprises deposition of a formulation according to claim 14 onto a surface and evaporation of the one or more solvents.