GB2639045A - Compound - Google Patents

Abstract

A compound of formula (I) or (II): A2-(B1)x1-(D1)y1-(B1)x2-A3 (I) A2-(B2)z1-(D2)y2-(B3)x3-A1-(B3)x4-(D3)y3-(B2)z2-A3 (II) wherein: A1 is a divalent heteroaromatic electron-accepting group; A2 and A3 are each independently a monovalent electron-accepting group; D1, D2 and D3 are each independently an electron-donating group; B1, B2, and B3 are each independently a bridging group; x1 and x2 are each independently 0, 1, 2 or 3; x3 and x4 are each independently 0, 1, 2 or 3; y1, y2 and y3 are each independently at least 1; z1 and z2 are each independently 0, 1, 2 or 3; and wherein at least one occurrence of D1 of formula (I) or at least one occurrence of at least one of D2 and D3 of formula (II) is a group of formula (III): (III) wherein: X1 and X2 are each independently selected from is O, S and NR1 wherein R1 is H or a substituent, with the proviso that at least one of X1 and X2 is NR1; Y is O or S; Ar1 and Ar2 are each independently is a monocyclic or fused aromatic or heteroaromatic group or is absent; R1 is H or a substituent; and R2 in each occurrence is independently 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 photactive layer of a blend of an electron-donating material and an electron-accepting material between an anode and a cathode. Known electron-accepting materials include fullerenes and non-fullerene acceptors (NFAs).

Chuyi Huang et al, "Highly Efficient Organic Solar Cells Based on S,N-Heteroacene Non-Fullerene Acceptors" Chem. Mater. 2018, 30, 15, 5429-5434 discloses NFAs based on an S,N-heteroacene backbone for use in solar cells in which the cyclopentadiene fragments of commonly used acceptors were replaced with pyrrole rings to improve the electron-donating ability to increase the energy levels of the molecules.

Ji Wan et al, "High-performance ternary solar cells by introducing a medium bandgap acceptor with complementary absorption, reducing energy disorder and enhancing glass transition temperature", J. Mater. Chem. A, 2022,10, 17122 cited in the IP disclosure discloses solar cells in which the NFA "TPIIC" is introduced into a "PM6:Y6" host device.

Zhenghui Luo et al, "Fieteroheptacene-based acceptors with thieno13,2-b]pyrrole yield high-performance polymer solar cells", National Science Review, 2022, Vol. 9, Issue 12, nwac076 discloses acceptors ThPyl, ThPy2, ThPy3 and ThPy4: CN109776566 discloses a polysubstituted benzocyclopentadione derivative-based A-D-A conjugated molecule.

WO 2023/012366 discloses ADA'DA type non-fullerene acceptors. SUMMARY S The present disclosure provides compounds of formula (I) or (II): A2 -(31)x' (D1)y1 -(B1)x2 -A3 (I) A2 _ (B2)z' _ (D2)y2 _ (B3)x3_ Al _ (B3)x4 _ (D3)y3 (B2)z2 _ A3 wherein: Al is a divalent heteroaromatic electron-accepting group; A2 and A3 independently in each occurrence is a monovalent electron-accepting group; D', D2 and D3 independently in each occurrence is an electron-donating group; 131, 52, and 133 independently in each occurrence is a bridging group; IS and x2 are each independently 0, 1, 2 or 3; x3 and x4 are each independently 0, 1, 2 or 3; y', y2 and y3 are each independently at least 1; z1 and z2 are each independently 0, 1, 2 or 3; and wherein at least one occurrence of D' of formula (I) or at least one occurrence of at least one of D2 and D3 of formula (II) is a group of formula (III) wherein: XI and X2 are each independently selected from is 0, S and NR1 wherein 121 is H or a substituent, with the proviso that at least one of X' and X2 is NR'; Y is 0 or S; Ar' is a monocyclic, bicyclic or tricyclic aromatic or heteroaromatic group or is absent; S Ar2 is a monocyclic or bicyclic or tricyclic aromatic or heteroaromatic group or is absent; R2 in each occurrence is independently a substituent.

The compound according to claim 1 wherein one of X' and X2 is selected from 0 and S and the other of X' and X2 is NR'.

Optionally, X' is selected from 0 and S and X2 is NR'.

Optionally, X2 is selected from 0 and S and X1 is NR' Optionally, Ar' is not present and the group of formula (III) has formula (III-A): IS wherein R3 is H or a substituent.

Optionally, Ar2 is not present and the group of formula (III) has formula (III-B): Optionally, neither Art nor Ar2 is present and the group of formula (III) has formula (III-C): Optionally, Arl and / or Are is a group of formula (IV): Optionally, at least one of A2 and A3 comprises a non-aromatic carbon-carbon double bond and a carbon atom of the carbon-carbon double bond is bound directly to DI-, D2 or D3, or if present, to BI-or B2.

Optionally, A2 and A3 are each independently selected from groups of formulae (IXa)-(IXr): (IXa) R13 (IXb) (IXc) R10 (IXd) (IXe) C \.v" r N\c/ Rio \\CN (IXf) NC\ NN (IXg) NC> R10 Rio NC (IXh)

NC

R13 (IXi) (IXj)

R

(IXk) R15 R15 (IX!) N> R16 N% \N R16 (IXm) R15 (IXn) Ria (IXo) R15 (IXp) Rl° (IXq) (IXr) 2?

NC

wherein: U is a 5-or 6-membered ring which is unsubstituted or substituted with one or more substituents and which may be fused to one or more further rings; G is C=O, C=S SO, 502, NR33 or C(R33)2 wherein R33 is CN or COOR4° and R4° is H or a J is C=O, C=S, N R11 or CR12R13 wherein R11 is CN or COOR4° and R4° is H or a substituent and R12 and R13 are each independently CN, CF3 or COOR412; R13 in each occurrence is a substituent; R12 in each occurrence is independently H or a substituent Ar6 is a 5-membered heteroaromatic group which is unsubstituted or substituted with one or more substituents; T1, T2 and T3 each independently represent an aryl or a heteroaryl ring which may be fused to one or more further rings and each of T', T2 and T3 is independently unsubstituted or substituted with one or more substituents; Ar8 is a fused heteroaromatic group which is unsubstituted or substituted with one or more substituents and which is bound to an aromatic C atom of B1 or B2 and to a boron substituent of B1 or B2; and R24 is H or a halogen.

Optionally, at least one of A2 and A3 is a group of formula (IXa-2) and (IXa-3): R18 R18 wherein each X7-X1° is independently CR12 or N wherein R12 in each occurrence is H or a substituent selected from C1_20 hydrocarbyl and an electron withdrawing group; and R15 is H or a substituent. Optionally, the electron withdrawing group is F, CI or CN.

Ih A C1_20 hydrocarbyl group as described anywhere herein is preferably selected from C1-20 alkyl; unsubstituted phenyl; and phenyl substituted with one or more Ci-12 alkyl groups.

The present disclosure provides a composition comprising an electron-donating material and an electron-accepting material wherein the electron accepting material is a compound of formula (I) or (II).

The present disclosure provides an organic electronic device comprising an active layer comprising a compound of formula (I) or (II). The active layer may comprise a composition as described herein.

X60- x60 X60 x60 x? X8 xs R15 (IXa-2) (IXa-3) Optionally, the organic electronic device is an organic photoresponsive device comprising a photoactive layer comprising the compound of formula (I) or (II) or the composition as described herein disposed between the anode and cathode.

Optionally, the photoactive layer is a bulk heterojunction layer comprising 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 of formula (I) or (ii) or a 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 is a schematic illustration of an organic photoresponsive device according to some embodiments; and Figure 2 is a solution absorption spectrum of Compound Example 1; Figure 3 is a film absorption spectrum of Compound Example 1; Figure 4 is a plot of current density vs. voltage for an organic photodetector containing Compound Example 1; and Figure 5 is a plot of external quantum efficiency vs wavelength for the organic photodetector of Figure 3.

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.

Organic Electronic Device IS Figure 1 illustrates an organic photoresponsive device, preferably an organic photodetector, 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.

The bulk heterojunction layer comprises a non-fullerene acceptor (NFA) of formula (I) or a NFA of formula (II) and an electron-donating material: A2 -(B1)x1 -(D1)y1 -(B1)x2 -A3 (I) A2 _ (B2)z1 _ (D2)y2 _ (B3)x3_ Al _ (B3)x4 _ (D3)y3 (B2)z2 _ A3 (II) wherein: Al is a divalent heteroaromatic electron-accepting group; A2 and A3 independently in each occurrence is a monovalent electron-accepting group; DI, 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 and x2 are each independently 0, 1, 2 or 3; x3 and x4 are each independently 0, 1, 2 or 3; yl y2 and y3 are each independently at least 1; z1 and z2 are each independently 0, 1, 2 or 3.

Each of the electron-accepting groups Al and A2 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 Dl, D2 or D3, 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).

For compounds of formula (I), at least one Di-is a group of formula (III).

For compounds of formula (II), at least one occurrence of at least one of D2 and 133 is a group of Formula (III).

The bulk heterojunction layer may consist of the NFA of formula (I) or (II) and the electron-donating compound or it may comprise one or more further materials, for example one or more further electron-donating materials and / or one or more further electron-accepting materials.

In some embodiments, the weight of the electron-donating material(s) to the electron-accepting 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 compound of formula (I) or (II), i.e., the electron-donating material has a shallower HOMO and LUMO than the corresponding HOMO and LUMO levels the compound of formula (I) or (II).

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 compound of formula (I) or (II) is less than 1.4 eV.

Preferably, compounds of formula (I) and (II) have a peak absorption wavelength as measured in solution of greater than 900 nm, or greater than 1000 nm, optionally less than 1500 nm or 1400 nm.

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 photoresponsive device comprises a bulk heterojunction photoactive layer 105. In other embodiments, the photoactive layer comprises an electron-accepting sub-layer comprising or consisting of a compound of formula (I) or (II) described herein disposed between the anode and cathode; and an electron-donating sub-layer comprising or consisting of one or more electron-donating materials disposed between the anode and the electron-accepting layer and in direct contact with the electron-accepting layer.

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 the photoactive layer. In some embodiments, a hole-transporting layer and / or an electron-blocking layer is disposed between the anode and the photoactive layer. In some embodiments, an electron-transporting layer and / or a hole-blocking layer is disposed between the cathode and the photoactive layer. In some embodiments, a work function modification layer is disposed between the photoactive layer and the anode, and/or between the photoactive layer and the cathode.

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.

Formula (III) At least one occurrence of D3 of formula (I) or at least one occurrence of at least one of D2 and D3 of formula (II) is a group of formula (III):

R (III)

XI and X2 are each independently selected from is 0, S and NR1 wherein 123 is H or a substituent, with the proviso that at least one of X3 and X2 is NR'.

Preferably, one of Xl and X2 is selected from 0 and S and the other of Xl and X2 is NR1 wherein 123 is H or a substituent, i.e., X1 is selected from 0 and S and X2 is NR1 or X2 is is selected from 0 and S and Xl is NR1.

Y is 0 or 5, preferably S. RI is preferably selected from H or a C1-20 hydrocarbyl group. A C1-20 hydrocarbyl group as described anywhere herein may be selected from C1-20 alkyl; unsubstituted phenyl; and phenyl substituted with one or more C1-12 alkyl groups.

R2 in each occurrence is independently a substituent, preferably a substituent selected from: - C1-20 alkyl wherein one or more non-adjacent C atoms may be replaced with 0, 5, NR6, COO, CON R6 or CO and one or more H atoms of the alkyl may be replaced with F; and -aryl or heteroaryl, preferably phenyl, which is unsubstituted or substituted with one or more substituents, optionally one or more substituents R9 selected from F, CI, NO2 and C1-12 alkyl wherein one or more non-adjacent C atoms may be replaced with 0, 5, NR6, COO CONR6 or CO and one or more H atoms of the alkyl may be replaced with F. wherein R.6 in each occurrence is independently H or a substituent, preferably H or a C1-20 hydrocarbyl group.

Each R2 may be selected according to a required solubility of the compound of formula (I) or (II). Further, the choice of R.2 groups may be selected to influence packing of the compound of formula (I) or (II); for example, alkyl groups R2 may allow for closer packing than aromatic groups R2.

Arl and Are are each independently a monocyclic or fused bicyclic or tricyclic aromatic or heteroaromatic group or is absent.

In some preferred embodiments, Arl is not present and the group of formula (III) has formula (III-A): (III-A) In some preferred embodiments, Are is not present and the group of formula (III) has formula (III-B): Preferably, R3 and R4 are each independently selected from H and a substituent selected from F; CN; NO2; C1-20 alkyl wherein one or more non-adjacent C atoms may be replaced with 0, S, NR6, COO, CONR6 or CO wherein R6 is as described above 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 substituents R9 as described above.

More preferably, R3 and R4 are each H. In some preferred embodiments, neither Arl nor Are is present and the group of formula (III) has formula (III-C): Where present, Ari and Are are preferably each independently selected from monocyclic aromatic or heteroaromatic groups, optionally thiophene; furan; pyrrole; or benzene, and bicyclic or tricyclic fused aromatic or heteroaromatic groups, wherein each ring is selected from thiophene; furan; pyrrole; and benzene; or wherein the fused aromatic or heteroaromatic group is cyclopentadiene fused to at least one of thiophene; furan; pyrrole; and benzene.

M Optionally, where present Arl and Are are each independently a group of formula (IV): Bridging units Bridging units B', 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, B', B2 and B3 are selected from units of formulae (VIa) -(VIo): (VIa) (VIb) (VIc) (VId) (VIf) R8 R8 R" (VIe) (VIg) (VIh) R8 R8 R8 N/N (VIi) (VIj) (VIk) (VII) R8 R8 R8 (VIm) (VIn) (VIo) wherein R55 is H or a substituent, optionally H or a C1-20 hydrocarbyl group; and 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 0, 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 1214 in each occurrence is a substituent, optionally a C1-20 hydrocarbyl group.

R8 groups of formulae (VIa), (VIb) and (VIc) may be linked to form a bicyclic ring which may be substituted with one or more substituents, optionally one or more substituents selected from F; CN; NO2; Ci.-20 alkyl wherein one or more non-adjacent C atoms may be replaced with 0, S, NR6, COO or CO and one or more H atoms of the alkyl may be replaced with F. R8 is preferably H, C1-2o alkyl or C1-19 alkoxy.

R8 groups of formulae (VIa), (VIb) and (VIc) may be linked to form an optionally substituted bicyclic ring.

In compounds of formula (I), each x1 is preferably 0 or 1.

In compounds of formula (II), x3 and x4 are each preferably 0 and z1 and z2 are each preferably 0 or 1.

Electron-Accepting Groups A2 and A3 The monovalent acceptor groups A2 and A3 may each independently be selected from any such units known to the skilled person.

The A2 and A3 groups of the compound of formula (I) or (II) may be the same or different, preferably the same.

Exemplary monovalent acceptor groups include, without limitation, groups of formulae (IXa)-(IXr) (IXa) (IXb) (IXc) (IXd) (IXe)

C

U R13 Rio ric\/ (IXg)

NC

NC R10 (IXh) (IXk) (IX!)

R15 R15 \N

R R15 (IXn) (IXm) (IXj)

R R16 R13

(IXo) R15 (IXp) Rl° (IXq) (IXr) -2? NC Rl° U is a 5-or 6-membered ring which is unsubstituted or substituted with one or more substituents and which may be fused to one or more further rings.

G is C=O, C=S SO, 502, NR33 or C(R33)2 wherein R33 is CN or COOR43 and R40 is H or a substituent, optionally H or a C1-20 hydrocarbyl. G is preferably C=0 or 502, more preferably C=O.

RI° is H or a substituent, preferably a substituent selected from the group consisting of Cl12 alkyl wherein one or more non-adjacent C atoms may be replaced with 0, S, NR6, COO or CO and one or more H atoms of the alkyl may be replaced with F; and an aromatic group, optionally phenyl, which is unsubstituted or substituted with one or more ID substituents selected from F and C1-12 alkyl wherein one or more non-adjacent C atoms may be replaced with 0, S, NR6, COO or CO.

Preferably, 121° is H. J is 0 or S, preferably 0.

R13 in each occurrence is a substituent, optionally C1-12 alkyl wherein one or more non-IS adjacent C atoms may be replaced with 0, 5, NR6, COO or CO and one or more H atoms of the alkyl may be replaced with F. RI-3 in each occurrence is independently H or a substituent. Preferably, R16 in each occurrence is independently H; F; C1-12 alkyl wherein one or more non-adjacent C atoms may be replaced with 0, 5, NR6, COO or CO and one or more H atoms of the alkyl may be replaced with F; aromatic group Are, 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 C atoms may be replaced with 0, S, NR6, COO or CO; or a group selected from: Zoo z41 C. Z42 Z43 Woo R1-5 is H or a substituent, preferably a substituent selected from: -(Ar3),,, wherein Ara in each occurrence is independently an unsubstituted or substituted aryl or heteroaryl group, preferably thiophene, and w is 1, 2 or 3; Y40 R4° Zoo z41 Z42 Z43 w40 and Q-12 alkyl wherein one or more non-adjacent C atoms may be replaced with 0, S, NR6, COO or CO and one or more H atoms of the alkyl may be replaced with F. Ar6 is a 5-membered heteroaromatic group, preferably thiophene or furan, which is unsubstituted or substituted with one or more substituents.

Substituents of Ara and Ar6, where present, are optionally selected from C1-12 alkyl wherein one or more non-adjacent C atoms may be replaced with 0, S, NR6, COO or CO and one or more H atoms of the alkyl may be replaced with F. 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.

r is N or P. Ar8 is a fused heteroaromatic group which is unsubstituted or substituted with one or more substituents, optionally one or more non-H substituents R10, and which is bound to an aromatic C atom of Bi-or B2 and to a boron substituent of 132 or B2.

R24 is H or a halogen, preferably H, F or Cl.

Preferred groups A2 and A3 are groups having a non-aromatic carbon-carbon bond which is bound directly to DI-of formula (I) or D2 or D3 of formula (II) or, if present to BI-of formula (I) or B2 of formula (II).

Preferably at least one of A2 and A3, preferably both of A2 and A3, are a group of formula (IXa-1): (IXa-1) wherein: G is as described above and is preferably C=0 or 502, more preferably C=O; R10 is as described above and is preferably H; Ar9 is an unsubstituted or substituted monocyclic or fused aromatic or heteroaromatic group, preferably benzene or a monocyclic or bicyclic heteroaromatic group having C or N ring atoms only; and X60 are each independently CN, CF3 or COOR4° wherein R4° in each occurrence is H or a substituent, preferably H or a C1-20 hydrocarbyl group. Preferably, each X6° is CN.

Ar9 may be unsubstituted or substituted with one or more substituents. Substituents of Ar9 are preferably selected from groups R12 as described below.

Optionally, the group of formula (IXa-1) has formula (IXa-2) or (IXa-3): (IXa-2) (IXa-3) each X7-X10 is independently CR12 or N wherein R12 in each occurrence is H or a substituent ID selected from C1-20 hydrocarbyl and an electron withdrawing group. Preferably, the electron withdrawing group is F, CI, Br or CN, more preferably F, CI or CN; and, for example, F or CN.

The C1-20 hydrocarbyl group R12 may be selected from C1-20 alkyl; unsubstituted phenyl; and phenyl substituted with one or more C1-12 alkyl groups.

In a particularly preferred embodiment, each of X7-X1° of formula (IXa-3) is CR12 and each R12 is independently selected from H or an electron-withdrawing group, preferably H, F or CN. According to his embodiment, R12 of A,t8 and X9 is an electron-withdrawing group, preferably F or CN.

Exemplary groups of formula (IXd) include: Exemplary groups of formula (IXe) include: c(R1% Nt Pn An exemplary group of formula (IXq) is:

I

An exemplary group of formula (IXg) is: An exemplary group of formula (IXj) is:

CN

wherein Ak is a C1-12 alkylene chain in which one or more C atoms may be replaced with 0, S, NR6, CO or COO; An is an anion, optionally -503-; and each benzene ring is independently unsubstituted or substituted with one or more substituents selected from substituents described with reference to R1D.

Exemplary groups of formula (IXm) are: R13 R13 R13 An exemplary group of formula (IXn) is: Rle Groups of formula (IXo) are bound directly to a bridging group B1 or B2 substituted with a group of formula -B(R14)2 wherein R114 in each occurrence is a substituent, optionally a Cl-hydrocarbyl group; -> is a bond to the boron atom -B(R14)2; and ---is a C-C bond between formula (IXo) and the bridging group.

Optionally, 1214 is selected from C1-12 alkyl; unsubstituted phenyl; and phenyl substituted with one or more C1-12 alkyl groups.

The group of formula (IXo), the 131-or B2 group and the B(R14)2 substituent of 131-or B2 may be linked together to form a 5-or 6-membered ring.

Optionally groups of formula (IXo) are selected from: R15 R15 R15 R16 R15 R15 R15 Acceptor Unit Al Al is preferably a fused heteroaromatic group comprising at least 2 fused rings, preferably at least 3 fused rings.

In some embodiments, Al of formula (II) is a group of formula (VIII): (VIII) wherein: Ar' is an aromatic or heteroaromatic group; and Y is 0, S, NR6 or 122-C=C-R7 wherein R2 in each occurrence is independently H or a substituent wherein two substituents R2 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), Arl 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; C1-20 alkyl wherein one or more non-adjacent C atoms may be replaced with 0, 5, NR17 wherein 1219 is a C1-12 hydrocarbyl, 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: Z4° Z41 R40 R40 "42 Z43 or Lti w41 wherein Z40, Z41, r2 and Z43 are each independently CR13 or N wherein RE in each occurrence is H or a substituent, preferably a C1-22 hydrocarbyl group; Y4° and Y44 are each ID independently 0, S, NX71 wherein XII is CN or COOR 4a; or CX60x61 wherein X69 and X64 is independently CN, CF3 or COOR49; W49 and W41 are each independently 0, S, NX91 or 009)(61 wherein X69 and X61 is independently CN, CF3 or COOR49; and R4° 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 IS more non-adjacent C atoms may be replaced with 0, 5, NR6, COO or CO and one or more H atoms of the alkyl may be replaced with F. R1-7 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 Arl 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 Arl are groups of formula (V): IO XI and X2, are each independently selected from N and CR19 wherein Rim 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 CR19 with the proviso that at least one of X3, X4, X5 and X6 is CR19.

Z is selected from 0, 5, SO2, NR6, PR6, c(R10)2, si(R10)2 c=n, C=S and C=C(R5)2 wherein RI° is as described above; R6 is H or a substituent; and R5 in each occurrence is an electron-withdrawing group.

Preferably, each R5 is CN, COOR49; or CX60A''61 wherein X60 and X61 is independently CN, CF3 or COOR49 and R4° in each occurrence is H or a substituent, preferably H or a C1-20 hydrocarbyl group.

Al groups of formula (VIII) are preferably selected from groups of formulae (Villa) and (VIIIb): R7 R7 /\

N N

(VIIIb) For compounds of formula (VIIIb), 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; C1-20 alkyl wherein one or more non-adjacent C atoms may be replaced with 0, S, NR6, CO, COO, NR6, PR6, or Si(R10)2 wherein R1° 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 0, S, NR6, 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 (VIIIb) has formula (VIIIb-1) or (VIIIb-2): (VIIIb-1) (VIIIb-2) Are is an aromatic or heteroaromatic group, preferably benzene, which is unsubstituted or substituted with one or more substituents. Are may be unsubstituted or substituted with one or more substituents selected from H, F, CI, CN, NO2, C1-16 alkyl or C1-16 alkoxy wherein one or more H atoms of the C1-16 alkyl or C1-16 alkoxy may be replaced with F. X is selected from 0, S, 502, NR6, PR6, C(R10)2, Si(R10)2 C=0, 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: N.;soN CF3 CF3

N N

Ak1 Ak1 0 N N I/ N.; Ak1 wherein Aki is a C1_20 alkyl group Divalent electron-accepting groups A2 other than formula (VIII) are optionally selected from formulae (IVa)-(IVj) (IVa) (IVb) (IVc) R31 (IVd) Ri2 (Die) R25 R25 (IVf) N N S, N\ /NAB-R12 (IVi) 0r z3 ft23 (IVg) (IVh) 0 Z3 0 (Bin 0 Z3 R23 (IVk) YA1 is 0 or S, preferably S. R23 in each occurrence is a substituent, optionally C1-12 alkyl wherein one or more nonadjacent C atoms other than the C atom attached to Z3 may be replaced with 0, S, NR6, COO or CO and one or more H atoms of the alkyl may be replaced with F. R23 in each occurrence is independently H; F; CN; NO2; C1-12 alkyl wherein one or more non-adjacent C atoms may be replaced with 0, 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-adjacent C atoms may be replaced with 0, S, NR6, COO or CO; or Z4° Woo 1.Z42 Z43 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 C1_20 hydrocarbyl group; Y4° and Y41 are each independently 0, S, NX71 wherein X°1 is CN or COOR40; or CX60)01 wherein X60 and X61 is independently CN, CFs or COOR46; W4° and W41 are each independently 0, S, NX°1 wherein X71 is CN or COOR40; or CX60x61 wherein X6° and X61 is independently CN, CF3 or COOR46; and R4° in each occurrence is H or a substituent, preferably H or a C1_20 hydrocarbyl group. Z3 is N or P. T1, 12 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, 12 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 C1-20 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.

Electron-Donating Groups D1. D2 and D3 In some embodiments the, or each, D1 of formula (I) is a group of formula (III).

In some embodiments the, or each, D2 and D3 of formula (II) is a group of formula (III).

In the case of formula (I) wherein y1 is at least 2 then at least one DI-is a group of formula (III) and the one or more other groups D1-may be a donor group other than Formula (III).

In the case of formula (II) then at least one of D2 and D3 is optionally a donor group other than formula (III).

Exemplary electron-donating groups D1, D2 and D3 other than formula (III) include groups of formulae (VIIa)-(VIIp): R52 R51 (VIIa) R52 R52 (VIIc) (VIIb) R51 (VIId) R51 R52 yA R51 (VIIe) (VIIf) R54 R54 (VIIg) (VIIh) R51 (VIIi) (VIIk) R52 R52 R52 R52 R52 R55 R52 (VIIm) (VIIj) (VIII) wherein YA in each occurrence is independently 0 or S; YA1 in each occurrence is independently 0 or 5; ZA in each occurrence is 0, 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; CI-20 alkyl wherein one or more non-adjacent C atoms may be replaced with 0, 5, NR6, 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 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 0, S, NR6, 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 CI-20 alkyl wherein one or more non-adjacent C atoms may be replaced by 0, 5, NEW, CO or COO wherein R1-5 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-(Ar5)v wherein Ak is a C1-22 alkylene chain in which one or more non-adjacent C atoms may be replaced with 0, S, NR6, CO or COO; u is 0 or 1; AP 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; CI; NO2; CN; and CI-20 alkyl wherein one or more non-adjacent C atoms may be replaced with 0, S, NR6, CO or COO and one or more H atoms may be replaced with F. Preferably, AP 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 0, S, NR6, 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 0, S, NR6, 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 a group of formula (VIIe).

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

In some preferred embodiments, y1 of formula (I) is 2 or 3 and D1 in each occurrence is the same.

Preferably, y2 and y3 of formula (II) are each 1.

In the case where yl of formula (I) is greater than 1, e.g., 2 or 3, or at least one of y2 and y3 of formula (II) is greater than 1, e.g., 2 or 3, the chain of D1, D2 or D3 groups, respectively, may be linked in any orientation.

Electron-donating material Exemplary electron-donating materials of a photoactive layer as described herein are disclosed in, for example, W02013/051676, 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(3,4bisubstituted 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[1,2-b:4,5-b']dithiophene, polyisothianaphthene, 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 a repeat unit of formula (X): (X) wherein VA, ZA, R51 and R54 are as described above.

Another particularly preferred donor polymer comprises repeat units of formula (XI): wherein R28 and R'9 are each independently selected from H; C1-12 alkyl wherein one or more non-adjacent, non-terminal C atoms may be replaced with 0, 5, COO or CO and one or more H atoms of the alkyl may be replaced with F; or an aromatic or heteroaromatic group Are 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 0, 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 (X) or (XI), and an acceptor repeat unit, for example divalent electron-accepting units A2 as described herein provided as polymeric repeat units.

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

In some embodiments, an electron-accepting layer or a bulk heterojunction 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 combined weight of 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, C 0, C70, C76, C78 and Cm fullerenes or a derivative thereof, including, without limitation, PCBM-type fullerene derivatives including phenyl-Csi-butyric acid methyl ester (Cs3PCBts1), TCBM-type fullerene derivatives (e.g., tolyl-C61-butyric acid methyl ester (C60TCBM)), and ThCBM-type fullerene derivatives (e.g., thienyl-Csi-butyric acid methyl ester (CsaThCBM).

Fullerene derivatives may have formula (VI): (VI) 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 (VIa), (VIb) and (VIc):

C-C

FIJI I FRFNF (VIb) C -c

N

FUT I FRFNF (VIa) (VIc)

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 In substituted with one or more substituents; and C1-20 alkyl wherein one or more non-adjacent C atoms may be replaced with 0, S, NR6, 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 IS wherein one or more non-adjacent C atoms may be replaced with 0, S, NR6, CO or COO and one or more H atoms may be replaced with F. Formulations The photoactive layer may be formed by any process including, without limitation, thermal evaporation and solution deposition methods.

Preferably, an electron-accepting sub-layer or a bulk heterojunction layer is formed by depositing a formulation comprising the compound of formula (I) or (II) and any other components of the layer, including one or more electron-donating materials in the case of a bulk heterojunction layer, dissolved or dispersed in a solvent or a mixture of two or more solvents followed by evaporation of the one 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 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 C1-1D alkyl benzoate, benzyl benzoate or dimethoxybenzene. In preferred embodiments, a In 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.

The photoactive layer is formed over one of the anode and cathode of the organic photoresponsive device and the other of the anode and cathode is formed over the photoactive layer.

Applications A circuit may comprise the OPD connected to one or more of a voltage source for applying a reverse bias to the device; a device configured to measure photocurrent; and an amplifier configured to amplify an output signal of the OPD. 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 In 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 1D 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.

The detection surface area of an OPD as described herein may be selected according to the desired application. Optionally, an OPD as described herein has a detection surface area of 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.

Examples Measurements Unless stated otherwise, HOMO and LUMO levels of materials as described herein are as 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 may comprise 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/AgCI 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/AgCI 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.

Unless stated otherwise, 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 a methylated benzene solution, optionally a 1,2,4-trimethylbenzene solution.

Exemplary compounds of formula (I) are: C6H * NCWir 0 N t "4 CN * 4. ° S

H

C6Hia C6ia C4H9 CN

NC

Examples Donor Group 1

CN

Step 2 S Step 1 Step 3 + n-BuLi Bu3SnCI Step 4 Stille Coupling Step 5 C 61-11 3 H2 S 04 Step 8 Donor Group 1 C6 H 1 3 BuLi Li C6H 13 8A 1 Step 6 ".. Step 7 Et0H HOjC--N Cu,Quinoline LiOH H " I " H ArylBr -iN

Compound Example 1

C21-1, 0 N

CN

S \ \ S / * \ S S 0

CN

CN

NC

CN

NC

CN

Step 4 -...

NC C61-113

CN

C6Hi3C6H13

Compound Example 1 04H9 )---\

C2H5 0 C4H9 Deprotection _._ Step 3 Donor Group 1 Bromination Step 1 C21-1, C4H9-Suzuki 0 coupling + S 1 30 Step 2

O

Compound Example 1 has a HOMO of -5.19 eV, a LUMO of -4.06 eV, a band gap of 1204 nm and an absorption maximum in 1,2,4-trimethylbenzene solution of 1034 nm.

The solution absorption spectrum of Compound Example 1 in 1,2,4-trimethylbenzene is shown in Figure 2.

With reference to Figure 3, the absorption maximum of a film cast from 1,2,4-trimethylbenzene solution is 1204 nm.

Donor Group 2 H2SO4 Step 9 C6H1 Step 3 LiOH EtOH _...-Step 1 Cu,Quinoline _".

Step 2 Stille Coupling _._ Step 6 C6H13 C6H13

R 1 R

R3SnCI Sn N _,..

R I +

Step 5 /

TIPS -I

MIPS

n-BuLi n-BuLi TIPS-C1 Step 4 BuLi C6H13 co-113 4 9A 1 Step 7 C6H13 Donor Group 2 Donor Group 3 0 0 0 Cu powder Quinn aline ---N / KOH, EtOH / Step 3 THE 01C---N HO N I Step 2

S-- S--

Mel Step 1 Donor Group 3 Donor Groups 2 and 3 may be reacted in the same way as Donor Group 1 to form compounds of Formula (I).

Device Example 1

A glass substrate coated with a 45 nm thick layer of indium-tin oxide (ITO) was coated with a 0.2 (Ye 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 Bu g^3n Bu Bu Stille Coupling Step 5 Bu n-BuLi 1,13u / Bu3SnCI Bu Step 4 C6H13 8A BuLi Step 6 C6H13 C6H13 C61113 C6H13 C6H13 H2SO4. Step 8 Li 0\ Step 7 C6H13 C6H13 modified ITO layer by bar coating from a 10 mg/ml solution in an o-dichlorobenzene / butylbenzoate solvent mixture (90:10 v/v). An anode stack of Mo03 (10nm) and ITO (50nm) was formed over the bulk heterojunction by thermal evaporation (Mo03) and sputtering (ITO). 0.5

Ra = C12H25 Rb Donor Polymer 1 Figure 4 is a plot of current density vs. applied voltage for Device Example 1.

Figure 5 is a plot of external quantum efficiency (EQE) vs. wavelength for Device Example 1.

More than one Device Example 1 was made; Figures 4 and 5 show overlaid plots for these 10 devices.

Modelling The HOMO and LUMO energy levels of compounds of formula (I) and (II) containing a group of formula (III) and comparative NFAs which do not have a group of formula (III) were modelled using Gaussian09 software available from Gaussian using Gaussian09 with IS B3LYP (functional) and LACVP* (Basis set).

Results are set out in Tables 1-3 in which in which Slf corresponds to oscillator strength of the transition from S1 (predicting absorption intensity) and Eopt is the modelled optical gap.

Table 1 -effect of donor group -3.79 848 2.69 -3.89 845 3.00 -3.79 923 2.94 -3.79 888 2.63 -5.25 Modelled Structure/ID Comparative * 41 ik Comparative Comparative Amax / nm HOMO /eV -5.28 -5.35 -5.35 -5.14 -5.19 * * *

S S

/ S * * \ \ t° N S * St

N

-5.27 -3.92 919 3.35 961 -5.19 -3.98 1025 3.01 1030 -4.98 -4.10 1419 2.36 1474 -5.13 -3.76 903 2.94 962 -5.40 -4.02 899 2.14 987 -5.31 -3.85 850 2.13 936

NC

N 0 0,-

NC

CN

CN

""---'0 0

NC

C

C

N * o * * * *4'$

C

UN

NC

CN

S

*: * **

S S *s 11 * * *

S

CN

S

S

CN

S

S

N

S

0 0.. NC -3.97 851 3.22 -3.93 841 3.26 -3.79 852 3.15 -3.81 857 3.19 -3.97 836 3.26 -3.70 977 3.37 -5.43

ON

S * S 0

* .S * * * * S # 0 tiP * Os * * #

CN

CN

N S

C

CN

S N -5.40 -5.24 -5.26 -5.45 -4.97 s'i

CN

NC

NC

N

CN

CN

NC

N

ON

CN

NC

-5.29 -3.89 888 2.99 940 -5.35 -4.07 976 2.99 1004 Table 2 -effect of N substituents on pyrrole HOMO /eV LUMO Eg Slf Amax /eV /nm / nm -5.28 -3.84 864 2.95 923 -5.14 -3.79 923 2.94 963 -5.11 -3.77 925 2.92 964 Structure/ID Comparative

ON ON

-5.15 -3.79 916 2.93 958 Table 3 -compounds without Arl or AP groups

NC -5.28

HOMO /eV LUMO Eg /eV /nm Anmx mm Sit Comparative -3.84 864 2.95 Comparative 0 o/ 2.62 -5.63 -4.08 799 Comparative

NC

CN

NC

* Alt 0 N S

I : : * :

lir NC

CN *

ON

ON CN

-4.02 802 -3.94 870 Structure 2.61 2.66 Table 4 shows a comparison of modelled and experimental values for Compound Example 1 and a corresponding model compound in which alkyl and phenyl substituents have been replaced with methyl to simplify calculation.

Table 4 1.75 2.65 2.75

LUMO /eV Amax Slf / nm Eg /nm 1.75 Structure/ID HOMO /eV Compound Example 1 -Model

NC

NO

ON

CN 0 s 8

Modelled properties-vacuum -5.45 -3.96 Film Solution/Film

Compound Example 1

C4H9 NC C2H)5MCD Experimental properties n/a

ON

-5.19 -4.06 1034/1204

Claims (23)

1. CLAIMS1. A compound of formula (I) or (II): A2 -(B1)x1 -(D1)y1 -(131)x2 -A3 (I) A2 -(B2)z1 -(D2)y2 -(B3)x3-Al -(B3)x4 -(D3)y3 -(B2)z2 -A3 (II) wherein: Al is a divalent heteroaromatic electron-accepting group; A2 and A3 independently in each occurrence is a monovalent electron-accepting group; DI-, D2 and D3 independently in each occurrence is an electron-donating group; 131-, B2, and B3 independently in each occurrence is a bridging group; xl and x2 are each independently 0, 1, 2 or 3; x3 and x4 are each independently 0, 1, 2 or 3; yi y2 and y3 are each independently at least 1; and z2 are each independently 0, 1, 2 or 3; and wherein at least one occurrence of D1 of formula (I) or at least one occurrence of at least one of D2 and D3 of formula (II) is a group of formula (III) wherein: Xl-and X2 are each independently selected from is 0, S and NR' wherein 122 is H or a substituent, with the proviso that at least one of X1 and X2 is NR1; Y is 0 or 5; Arl is a monocyclic, bicyclic or tricyclic aromatic or heteroaromatic group or is absent; Ar2 is a monocyclic or bicyclic or tricyclic aromatic or heteroaromatic group or is absent; R2 in each occurrence is independently a substituent.
2. 2. The compound according to claim 1 wherein one of X' and X2 is selected from 0 and S and the other of X' and X2 is NEV.
3. 3. The compound according to claim 2 wherein X' is selected from 0 and S and X2 is 4. The compound according to claim 2 wherein X2 is selected from 0 and S and is
4. NW-
5. 5. The compound according to any one of the preceding claims wherein Ar' is not present and the group of formula (III) has formula (III-A): (III-A)
6. 6. The compound according to any one of claims 1-4 wherein Ar2 is not present and the group of formula (III) has formula (III-B):
7. 7. The compound according to any one of claims 1-4 wherein neither Arl nor Are is present and the group of formula (III) has formula (III-C): xl R4 R2 R2 (III-C)
8. 8. The compound according to any one of claims 1-5 wherein Are is a group of formula (IV):
9. 9. The compound according to any one of claims 1-4 and 6 wherein Arl is a group of formula (V):
10. 10. The compound according to any one of the preceding claims wherein the compound of formula (I) or (II) is a compound of formula (I).
11. 11. The compound according to any one of the preceding claims wherein at least one of A2 and A3 comprises a non-aromatic carbon-carbon double bond and a carbon atom of the carbon-carbon double bond is bound directly to D1, D2 or D3, or if present, to B1 or B2.
12. 12. The compound according to any one of the preceding claims wherein A2 and A3 are each independently selected from groups of formulae (IXa)-(IXr): R'° (IXa) Rl°NC CNNNCNC(IXf) NC\ (IXg) Rio CN (IXh) R13 (IXi) (IXj) R16 (IXb)J.\\ R13 (IXc) N/ ) /N "J R(IXd) (IXe) R13 NIJNi%N (IXk) R15 R115 (IM) (N R16 R 6 (IXm) R15 (IXn) (IXo) R15 (IXp) Rio (IXq) (IXr) NC Ro wherein: U is a 5-or 6-membered ring which is unsubstituted or substituted with one or more substituents and which may be fused to one or more further rings; G is C=O, C=S SO, 502, NR33 or C(R33)2 wherein R33 is CN or COOR4° and R4° is H or a substituent; is C=0, C=S, NR" or CR12R13 wherein R" is CN or COOR46 and R4° is H or a substituent and 1:212 and R13 are each independently CN, CF3 or COOR40; 12.13 in each occurrence is a substituent; F216 in each occurrence is independently H or a substituent R16 is a substituent; Ar6 is a 5-membered heteroaromatic group which is unsubstituted or substituted with one or more substituents; 611, T2 and T3 each independently represent an aryl or a heteroaryl ring which may be fused to one or more further rings and each of 611, T2 and T3 is independently unsubstituted or substituted with one or more substituents; Are is a fused heteroaromatic group which is unsubstituted or substituted with one or more substituents and which is bound to an aromatic C atom of BI-or B2 and to a boron substituent of BI-or B2; and R24 is H or a halogen.
13. 13. The compound according to claim 12 wherein at least one of A2 and A3 is a group of formula (IXa-2) and (IXa-3): (IXa-2) (IXa-3) wherein each X7-X1° is independently CR12 or N wherein R12 in each occurrence is H or a substituent selected from C1-20 hydrocarbyl and an electron withdrawing group; and 17215 is H or a substituent.
14. 14. The compound according to claim 13 wherein the electron withdrawing group is F, CI or CN.
15. 15. 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.
16. 16. An organic electronic device comprising an active layer comprising a compound according to any one of claims 1-14 or a composition according to claim 15.
17. 17. An organic electronic device according to claim 15 wherein the organic electronic device is an organic photoresponsive device comprising a photoactive layer comprising the compound according to any one of claims 1-14 or the composition according to claim 15 disposed between the anode and cathode.
18. 18. The organic electronic device according to claim 17 wherein the photoactive layer is a bulk heterojunction layer comprising a composition according to claim 15.
19. 19. An organic electronic device according to claim 18 wherein the organic photoresponsive device is an organic photodetector.
20. 20. A photosensor comprising a light source and an organic photodetector according to claim 17 wherein the photosensor is configured to detect light emitted from the light source.
21. 21. The photosensor according to claim 20, wherein the light source emits light having a peak wavelength of greater than 900 nm.
22. 22. A formulation comprising a compound according to any one of claims 1-14 or a composition according to claim 15 dissolved or dispersed in one or more solvents.
23. 23. A method of forming an organic electronic device according to claim 16 wherein formation of the active layer comprises deposition of a formulation according to claim 21 onto a surface and evaporation of the one or more solvents.