compound

Abstract

A compound of formula (I) or (II), wherein: A1 is a divalent heteroaromatic electron-accepting group; A2 and A3 independently in each occurrence is a monovalent 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 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), 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

[0001] COMPOUND

[0002] BACKGROUND

[0003] 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.

[0004] 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).

[0005] 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 electrondonating ability to increase the energy levels of the molecules.

[0006] 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.

[0007] Zhenghui Luo et al, "Heteroheptacene-based acceptors with thieno[3,2-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.

[0008] WO 2023 / 012366 discloses ADA'DA type non-fullerene acceptors.

[0009] SUMMARY

[0010] The present disclosure provides compounds of formula (I) or (II):

[0011] A2- (B1)x1- (D1)y1- (Bx)x2- A3

[0012] (I)

[0013] A2- (B2)zx- (D2)y2- (B3)x3- A1- (B3)x4- (D3)y3- (B2)z2- A3

[0014] (II) wherein:

[0015] A1is a divalent heteroaromatic electron-accepting group;

[0016] A2and A3independently in each occurrence is the same or different and is a monovalent electron-accepting group;

[0017] D1, D2and D3independently in each occurrence is the same or different and is an electrondonating group;

[0018] B1, B2, and B3independently in each occurrence is the same or different and is a bridging group; x1and x2are each independently the same or different and are each 0, 1, 2 or 3; x3and x4are each independently the same or different and are each 0, 1, 2 or 3; y1, y2and y3are each independently the same or different and are each at least 1; z1and z2are each independently the same or different and are each 0, 1, 2 or 3; and wherein at least one occurrence of D1of formula (I) or at least one occurrence of at least one of D2and D3of formula (II) is a group of formula (III) (HI) wherein:

[0019] X1and X2are each independently selected from is O, S and NR1wherein R1is H or a substituent, with the proviso that at least one of X1and X2is NR1;

[0020] Y is O or S;

[0021] Ar1is a monocyclic, bicyclic or tricyclic aromatic or heteroaromatic group or is absent;

[0022] Ar2is a monocyclic or bicyclic or tricyclic aromatic or heteroaromatic group or is absent;

[0023] R1is H or a substituent; and

[0024] R2in each occurrence is independently a substituent.

[0025] The compound according to claim 1 wherein one of X1and X2is selected from O and S and the other of X1and X2is NR1.

[0026] Optionally, X1is selected from O and S and X2is NR1.

[0027] Optionally, X2is selected from O and S and X1is NR1

[0028] Optionally, Ar1is not present and the group of formula (III) has formula (III-A):

[0029] (III-A) wherein R3is H or a substituent.

[0030] Optionally, Ar2is not present and the group of formula (III) has formula (III-B): wherein R4is H or a substituent. Optionally, neither Ar1nor Ar2is present and the group of formula (III) has formula (III- C):

[0031] (III-C)

[0032] Optionally, Ar1and / or Ar2is a group of formula (IV):

[0033] (IV). Optionally, at least one of A2and A3comprises a non-aromatic carbon-carbon double bond and a carbon atom of the carbon-carbon double bond is bound directly to D1, D2or D3, or if present, to B1or B2.

[0034] Optionally, A2and A3are each independently selected from groups of formulae (IXa)-(IXr):

[0035] wherein :

[0036] 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;

[0037] R10is H or a substituent; G is C=O, C=S SO, SO2, NR33or C(R33)2 wherein R33is CN or COOR40and R40is H or a substituent;

[0038] J is C=O, C=S, NR11or CR12R13wherein R11is CN or COOR40and R40is H or a substituent and R12and R13are each independently CN, CF3 or COOR40;

[0039] R13in each occurrence is a substituent; R15in each occurrence is independently H or a substituent; R16is a substituent;

[0040] Ar6is a 5-membered heteroaromatic group which is unsubstituted or substituted with one or more substituents;

[0041] T1, T2and T3each independently represent an aryl or a heteroaryl ring which may be fused to one or more further rings and each of T1, T2and T3is independently unsubstituted or substituted with one or more substituents;

[0042] Ar8is a fused heteroaromatic group which is unsubstituted or substituted with one or more substituents and which is bound to an aromatic C atom of B1or B2and to a boron substituent of B1or B2; and R24is H or a halogen.

[0043] Optionally, at least one of A2and A3is a group of formula (IXa-2) and (IXa-3):

[0044] (IXa-2) (IXa-3) wherein each X7-X10is independently CR12or N wherein R12in each occurrence is H or a substituent selected from C1-20 hydrocarbyl and an electron withdrawing group; and R15is H or a substituent. Optionally, the electron withdrawing group is F, Cl or CN.

[0045] 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 C1-12 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).

[0046] 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.

[0047] 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.

[0048] Optionally, the photoactive layer is a bulk heterojunction layer comprising a composition as described herein.

[0049] Optionally, the organic photoresponsive device is an organic photodetector.

[0050] 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.

[0051] Optionally, the light source emits light having a peak wavelength of greater than 900 nm.

[0052] 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.

[0053] 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.

[0054] DESCRIPTION OF DRAWINGS

[0055] The disclosed technology and accompanying figures describe some implementations of the disclosed technology.

[0056] Figure 1 is a schematic illustration of an organic photoresponsive device according to some embodiments;

[0057] Figure 2 is solution absorption spectra of Compound Examples 1 and 2 in 1,2,4- trimethylbenzene solution; Figure 3A is film absorption spectra of Compound Examples 1 and 2 formed by casting 1,2,4-trimethylbenzene solutions of the compounds;

[0058] Figure 3B is film absorption spectra of Compound Examples 1 and 2 formed by casting 1,2-dichlorobenzene solutions of the compounds;

[0059] Figure 4A is a solution absorption spectrum of Compound Example 3 in 1,2,4- trimethylbenzene solution;

[0060] Figure 4B is a film absorption spectrum of Compound Example 3 formed by casting a 1,2,4- trimethylbenzene solution of the compound;

[0061] Figure 5 is a plot of current density vs. voltage for an organic photodetector containing Compound Example 1;

[0062] Figure 6 is a plot of external quantum efficiency vs. wavelength for the organic photodetector of Figure 5;

[0063] Figure 7 shows plots of external quantum efficiency vs. wavelength for an organic photodetector containing Compound Example 1 and for an organic photodetector containing Compound Example 2;

[0064] Figure 8 shows plots of current density vs. voltage for the organic photodetectors of Figure 7;

[0065] Figure 9 is a plot of external quantum efficiency vs. wavelength for an organic photodetector containing Compound Example 3; and

[0066] Figure 10 is a plot of current density vs. voltage for the organic photodetector of Figure 9.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] Organic Electronic Device

[0073] 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.

[0074] The bulk heterojunction layer comprises a non-fullerene acceptor (NFA) of formula (I) or a NFA of formula (II) and an electron-donating material:

[0075] A2- (B1)x1- (D1)y1- (Bx)x2- A3

[0076] (I)

[0077] A2- (B2)zx- (D2)y2- (B3)x3- A1- (B3)x4- (D3)y3- (B2)z2- A3

[0078] (II) wherein:

[0079] A1is a divalent heteroaromatic electron-accepting group;

[0080] A2and A3independently in each occurrence is a monovalent electron-accepting group;

[0081] D1, D2and D3independently in each occurrence is an electron-donating group;

[0082] B1, B2, and B3independently in each occurrence is a bridging group; x1and x2are each independently 0, 1, 2 or 3; x3and x4are each independently 0, 1, 2 or 3; y1, y2and y3are each independently at least 1; z1and z2are each independently 0, 1, 2 or 3.

[0083] Each of the electron-accepting groups A1and A2has 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, D2or 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).

[0084] For compounds of formula (I), at least one D1is a group of formula (III).

[0085] For compounds of formula (II), at least one occurrence of at least one of D2and D3is a group of Formula (III).

[0086] The bulk heterojunction layer may consist of the NFA of formula (I) or (II) and the electrondonating compound or it may comprise one or more further materials, for example one or more further electron-donating materials and I or one or more further electron-accepting materials.

[0087] 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.

[0088] 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.

[0089] 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.

[0090] 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.

[0091] Each of the anode and cathode may independently be a single conductive layer or may comprise a plurality of layers.

[0092] 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.

[0093] 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.

[0094] 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.

[0095] The organic photoresponsive device may comprise layers other than the anode, cathode and the photoactive layer. In some embodiments, a hole-transporting layer and I 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.

[0096] 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.

[0097] Formula (III)

[0098] At least one occurrence of D1of formula (I) or at least one occurrence of at least one of D2and D3of formula (II) is a group of formula (III): X1and X2are each independently selected from is O, S and NR1wherein R1is H or a substituent, with the proviso that at least one of X1and X2is NR1.

[0099] Preferably, one of X1and X2is selected from O and S and the other of X1and X2is NR1wherein R1is H or a substituent, i.e., X1is selected from O and S and X2is NR1or X2is is selected from O and S and X1is NR1.

[0100] Y is O or S, preferably S.

[0101] R1is 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.

[0102] R2in each occurrence is independently a substituent, preferably a substituent selected from :

[0103] C1-20 alkyl wherein one or more non-adjacent C atoms may be replaced with O, S, NR6, COO, CONR6or 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 R9selected from F, Cl, NO2 and C1-12 alkyl wherein one or more non-adjacent C atoms may be replaced with O, S, NR6, COO CONR6or CO and one or more H atoms of the alkyl may be replaced with F. wherein R6in each occurrence is independently H or a substituent, preferably H or a C1-20 hydrocarbyl group.

[0104] Each R2may be selected according to a required solubility of the compound of formula (I) or (II). Further, the choice of R2groups may be selected to influence packing of the compound of formula (I) or (II); for example, alkyl groups R2may allow for closer packing than aromatic groups R2.

[0105] Ar1and Ar2are each independently a monocyclic or fused bicyclic or tricyclic aromatic or heteroaromatic group or is absent.

[0106] In some preferred embodiments, Ar1is not present and the group of formula (III) has formula (III-A) :

[0107] (in-A) wherein R3is H or a substituent.

[0108] In some preferred embodiments, Ar2is not present and the group of formula (III) has formula (III-B):

[0109] (III-B) wherein R4is H or a substituent.

[0110] Preferably, R3and R4are 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 O, S, NR6, COO, CONR6or CO wherein R6is 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 R9as described above.

[0111] More preferably, R3and R4are each H.

[0112] In some preferred embodiments, neither Ar1nor Ar2is present and the group of formula

[0113] (Ill) has formula (III-C):

[0114] (III-C)

[0115] Where present, Ar1and Ar2are 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.

[0116] Optionally, where present Ar1and Ar2are each independently a group of formula (IV):

[0117] Bridging units

[0118] Bridging units B1, B2and B3are 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.

[0119] Optionally, B1, B2and B3are selected from units of formulae (Via) - (VIo): (VII) wherein R55is H or a substituent, optionally H or a C1-20 hydrocarbyl group; and R8in 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 R14in each occurrence is a substituent, optionally a C1-20 hydrocarbyl group.

[0120] R8groups 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; 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.

[0121] R8is preferably H, C1-20 alkyl or C1-19 alkoxy.

[0122] R8groups of formulae (Via), (VIb) and (Vic) may be linked to form an optionally substituted bicyclic ring.

[0123] In compounds of formula (I), each x1is preferably 0 or 1.

[0124] In compounds of formula (II), x3and x4are each preferably 0 and z1and z2are each preferably 0 or 1.

[0125] Electron-Accepting Groups A2and A3

[0126] The monovalent acceptor groups A2and A3may each independently be selected from any such units known to the skilled person.

[0127] The A2and A3groups of the compound of formula (I) or (II) may be the same or different, preferably the same.

[0128] Exemplary monovalent acceptor groups include, without limitation, groups of formulae (IXa)-(IXs)

[0129]

[0130] 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.

[0131] G is C=O, C=S SO, SO2, NR33or C(33)2 wherein R33is CN or COOR40and R40 is H or a substituent, optionally H or a C1-20 hydrocarbyl. G is preferably C=O or SO2, more preferably C=O.

[0132] R10is H or a substituent, preferably a substituent selected from the group consisting of Ci- 12 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; and 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 O, S, NR6, COO or CO.

[0133] Preferably, R10is H.

[0134] J is O or S, preferably O.

[0135] R13in each occurrence is a substituent, optionally C1-12 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.

[0136] R15in each occurrence is independently H or a substituent. Preferably, R15in each occurrence is independently H; F; Cl; Br; CN; Ci i2 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; aromatic group Ar2, 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 O, S, NR6, COO or CO; or a group selected from :

[0137] Preferably, each R15is the same or different and is selected from H, F, Cl, Br and CN.

[0138] R16is H or a substituent, preferably a substituent selected from :

[0139] -(Ar3)wwherein Ar3in each occurrence is independently an unsubstituted or substituted aryl or heteroaryl group, preferably thiophene, and w is 1, 2 or 3; and

[0140] Ci-12 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.

[0141] Ar6is a 5-membered heteroaromatic group, preferably thiophene or furan, which is unsubstituted or substituted with one or more substituents.

[0142] Substituents of Ar3and Ar6, where present, are optionally selected from C1-12 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.

[0143] T1, T2and T3each independently represent an aryl or a heteroaryl ring, optionally benzene, which may be fused to one or more further rings. Substituents of T1, T2and T3, where present, are optionally selected from non-H groups of R25. In a preferred embodiment, T3is benzothiadiazole.

[0144] Z1is N or P.

[0145] Ar8is 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 B1or B2and to a boron substituent of B1or B2. R24is H or a halogen, preferably H, F or Cl.

[0146] Preferred groups A2and A3are groups having a non-aromatic carbon-carbon bond which is bound directly to D1of formula (I) or D2or D3of formula (II) or, if present to B1of formula (I) or B2of formula (II). Preferably at least one of A2and A3, preferably both of A2and A3, are a group of formula (IXa-1) : wherein: G is as described above and is preferably C=O or SO2, more preferably C=O;

[0147] R10is as described above and is preferably H;

[0148] Ar9is 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 X60are each independently CN, CF3 or COOR40wherein R40in each occurrence is H or a substituent, preferably H or a C1-20 hydrocarbyl group. Preferably, each X60is CN.

[0149] Ar9may be unsubstituted or substituted with one or more substituents. Substituents of Ar9are preferably selected from groups R12as described below.

[0150] Optionally, the group of formula (IXa-1) has formula (IXa-2) or (IXa-3):

[0151]

[0152] (IXa-2) (IXa-3) each X7-X10is independently CR12or N wherein R12in each occurrence is H or a substituent selected from C1-20 hydrocarbyl and an electron withdrawing group. Preferably, the electron withdrawing group is F, Cl, Br or CN, more preferably F, Cl or CN; and, for example, F or CN. The Ci -20 hydrocarbyl group R12may be selected from C1-20 alkyl; unsubstituted phenyl; and phenyl substituted with one or more C1-12 alkyl groups.

[0153] In a particularly preferred embodiment, each of X7-X10of formula (IXa-3) is CR12and each R12is independently selected from H or an electron-withdrawing group, preferably H, F or CN. According to his embodiment, R12of X8and X9is an electron-withdrawing group, preferably F or CN.

[0154] Exemplary groups of formula (IXd) include:

[0155] Exemplary groups of formula (IXe) include:

[0156] An exemplary group of formula (IXq) is:

[0157] An exemplary group of formula (IXg) is:

[0158] An exemplary group of formula (IXj) is: wherein Ak is a C1-12 alkylene chain in which one or more C atoms may be replaced with

[0159] O, S, NR6, CO or COO; An is an anion, optionally -SOs"; and each benzene ring is independently unsubstituted or substituted with one or more substituents selected from substituents described with reference to R10.

[0160] Exemplary groups of formula (IXm) are:

[0161]

[0162] An exemplary group of formula (IXn) is:

[0163] Groups of formula (IXo) are bound directly to a bridging group B1or B2substituted with a group of formula -B(R14)2 wherein R14in each occurrence is a substituent, optionally a Ci- 20 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.

[0164] Optionally, R14is selected from C1-12 alkyl; unsubstituted phenyl; and phenyl substituted with one or more C1-12 alkyl groups. The group of formula (IXo), the B1or B2group and the B(R14)2 substituent of B1or B2may be linked together to form a 5- or 6-membered ring.

[0165] Optionally groups of formula (IXo) are selected from :

[0166] Acceptor Unit A1

[0167] A1is preferably a fused heteroaromatic group comprising at least 2 fused rings, preferably at least 3 fused rings. In some embodiments, A1of formula (II) is a group of formula (VIII): wherein:

[0168] Ar1is an aromatic or heteroaromatic group; and Y is O, S, NR6or R7-C=C-R7wherein R7in each occurrence is independently H or a substituent wherein two substituents R7may be linked to form a monocyclic or polycyclic ring; and R6is H or a substituent.

[0169] In the case where A2is a group of formula (VIII), Ar1may be a monocyclic or polycyclic heteroaromatic group which is unsubstituted or substituted with one or more R9groups wherein R9in each occurrence is independently a substituent.

[0170] Preferred R9groups are selected from

[0171] F;

[0172] CN;

[0173] NO2; Ci-20 alkyl wherein one or more non-adjacent C atoms may be replaced with O, S, NR17wherein R17is 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 : wherein Z40, Z41, Z42and Z43are each independently CR13or N wherein R13in each occurrence is H or a substituent, preferably a C1-20 hydrocarbyl group; Y40and Y41are each independently O, S, NX71wherein X71is CN or COOR40; or CX60X61wherein X60and X61is independently CN, CF3 or COOR40; W40and W41are each independently O, S, NX71or CX60X61wherein X60and X61is independently CN, CF3 or COOR40; and R40in each occurrence is H or a substituent, preferably H or a C1-20 hydrocarbyl group. Exemplary substituents of an aromatic or heteroaromatic group R9are F, CN, NO2, and C1-12 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.

[0174] R17as described anywhere herein may be, for example, C1-12 alkyl, unsubstituted phenyl; or phenyl substituted with one or more C1-6 alkyl groups.

[0175] 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 nonterminal C-atom.

[0176] 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.

[0177] 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.

[0178] Exemplary monocyclic heteroaromatic groups Ar1are oxadiazole, thiadiazole, triazole and 1,4-diazine which is unsubstituted or substituted with one or more substituents. Thiadiazole is particularly preferred.

[0179] Exemplary polycyclic heteroaromatic groups Ar1are groups of formula (V) :

[0180] X1and X2, are each independently selected from N and CR10wherein R10is H or a substituent, optionally H or a substituent R9as described above.

[0181] X3, X4, X5and X6are each independently selected from N and CR10with the proviso that at least one of X3, X4, X5and X6is CR10.

[0182] 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 R10is as described above; R6is H or a substituent; and R5in each occurrence is an electronwithdrawing group.

[0183] Preferably, each R5is CN, COOR40; or CX60X61wherein X60and X61is independently CN, CF3 or COOR40and R40in each occurrence is H or a substituent, preferably H or a C1-20 hydrocarbyl group.

[0184] A1groups of formula (VIII) are preferably selected from groups of formulae (Villa) and (VUIb):

[0185]

[0186] (Villa) (VUIb)

[0187] For compounds of formula (VUIb), the two R7groups may or may not be linked.

[0188] Preferably, when the two R7groups are not linked each R7is independently selected from H; F; CN; NO2; C1-20 alkyl wherein one or more non-adjacent C atoms may be replaced with O, S, NR6, CO, COO, NR6, PR6, or Si(R10)2 wherein R10and R6are 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, NR6, CO, COO and one or more H atoms may be replaced with F.

[0189] Preferably, when the two R7groups are linked, the group of formula (VUIb) has formula (VIIIb-1) or (VIIIb-2): (VIIIb-1) (VIIIb-2)

[0190] Ar2is an aromatic or heteroaromatic group, preferably benzene, which is unsubstituted or substituted with one or more substituents. Ar2may be unsubstituted or substituted with one or more substituents selected from H, F, Cl, 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.

[0191] 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, R6and R5are as described above. Exemplary electron-accepting groups of formula (VIII) include, without limitation : wherein Ak1is a C1-20 alkyl group

[0192] Divalent electron-accepting groups A2other than formula (VIII) are optionally selected from formulae (IVa)-(IVj) <IVk)

[0193] YA1is O or S, preferably S.

[0194] R23in each occurrence is a substituent, optionally C1-12 alkyl wherein one or more non- adjacent C atoms other than the C atom attached to Z3may be replaced with O, S, NR6, COO or CO and one or more H atoms of the alkyl may be replaced with F.

[0195] R25in each occurrence is independently H; F; CN; NO2; C1-12 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; 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 O, S, NR6, COO or CO; or wherein Z40, Z41, Z42and Z43are each independently CR13or N wherein R13in each occurrence is H or a substituent, preferably a C1-20 hydrocarbyl group;

[0196] Y40and Y41are each independently O, S, NX71wherein X71is CN or COOR40; or CX60X61wherein X60and X61is independently CN, CF3 or COOR40;

[0197] W40and W41are each independently O, S, NX71wherein X71is CN or COOR40; or CX60X61wherein X60and X61is independently CN, CF3 or COOR40; and

[0198] R40in each occurrence is H or a substituent, preferably H or a C1-20 hydrocarbyl group.

[0199] Z3is N or P.

[0200] T1, T2and T3each independently represent an aryl or a heteroaryl ring, optionally benzene, which may be fused to one or more further rings. Substituents of T1, T2and T3, where present, are optionally selected from non-H groups of R25. In a preferred embodiment, T3is benzothiadiazole.

[0201] R12in each occurrence is a substituent, preferably a C1-20 hydrocarbyl group.

[0202] Ar5is 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.

[0203] Electron-Donating Groups D1, D2and D3

[0204] In some embodiments the, or each, D1of formula (I) is a group of formula (III).

[0205] In some embodiments the, or each, D2and D3of formula (II) is a group of formula (III). In the case of formula (I) wherein y1is at least 2 then at least one D1is a group of formula (III) and the one or more other groups D1may be a donor group other than Formula (III).

[0206] In the case of formula (II) then at least one of D2and D3is optionally a donor group other than formula (III).

[0207] Exemplary electron-donating groups D1, D2and D3other than formula (III) include groups of formulae (Vlla)-(VIIp):

[0208] wherein YAin each occurrence is independently O or S; YA1in each occurrence is independently O or S; ZAin each occurrence is O, CO, S, NR55or C(R54)?; R51, R52R54and R55independently in each occurrence is H or a substituent; R53independently in each occurrence is a substituent; and Ar4is an optionally substituted monocyclic or fused heteroaromatic group.

[0209] Optionally, R51and R52independently 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, NR6, COO or CO and one or more H atoms of the alkyl may be replaced with F; and an aromatic or heteroaromatic group Ar3which is unsubstituted or substituted with one or more substituents.

[0210] In some embodiments, Ar3may be an aromatic group, e.g., phenyl.

[0211] Ar4is preferably selected from optionally substituted oxadiazole, thiadiazole, triazole, and 1,4-diazine. In the case where Ar4is 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.

[0212] 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, NR6, COO or CO and one or more H atoms of the alkyl may be replaced with F.

[0213] Preferably, each R54is selected from the group consisting of:

[0214] H;

[0215] F; linear, branched or cyclic C1-20 alkyl wherein one or more non-adjacent C atoms may be replaced by O, S, NR17, CO or COO wherein R17is 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-(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, NR6, CO or COO; u is 0 or 1; Ar7in 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.

[0216] 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, NR6, CO or COO and one or more H atoms may be replaced with F. Preferably, Ar7is phenyl. Preferably, each R51is H.

[0217] Optionally, R53independently in each occurrence is selected from C 1-20 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; 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, NR6, COO or CO and one or more H atoms of the alkyl may be replaced with F.

[0218] Preferably, R55as described anywhere herein is H or C1-30 hydrocarbyl group.

[0219] In a preferred embodiment, D1, D2and D3are each a group of formula (Vile).

[0220] In some preferred embodiments, y1of formula (I) is 1.

[0221] In some preferred embodiments, y1of formula (I) is 2 or 3 and D1in each occurrence is the same.

[0222] Preferably, y2and y3of formula (II) are each 1.

[0223] In the case where y1of formula (I) is greater than 1, e.g., 2 or 3, or at least one of y2and y3of formula (II) is greater than 1, e.g., 2 or 3, the chain of D1, D2or D3groups, respectively, may be linked in any orientation.

[0224] Electron-donating material

[0225] Exemplary electron-donating materials of a photoactive layer as described herein are disclosed in, for example, WO2013 / 051676, the contents of which are incorporated herein by reference.

[0226] The electron-donating material may be a non-polymeric or polymeric material.

[0227] 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.

[0228] Preferred are non-crystalline or semi- crystalline conjugated organic polymers.

[0229] 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] th iophene, poly benzothiophene, poly benzo[ 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.

[0230] 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.

[0231] A particularly preferred donor polymer comprises a repeat unit of formula (X): wherein YA, ZA, R51and R54are as described above.

[0232] Another particularly preferred donor polymer comprises repeat units of formula (XI): wherein R18and R19are 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 Ar6which is unsubstituted or substituted with one or more substituents selected from F and C1-12 alkyl wherein one or more non-adjacent, non-terminal C atoms may be replaced with O, S, COO or CO.

[0233] 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 A2as described herein provided as polymeric repeat units.

[0234] Fullerene

[0235] 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.

[0236] 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.

[0237] Fullerenes may be selected from, without limitation, Ceo, C70, C76, C78 and Cs4 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).

[0238] Fullerene derivatives may have formu 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.

[0239] Exemplary fullerene derivatives include formulae (Via), (VIb) and (Vic): wherein R20-R32are each independently H or a substituent.

[0240] Substituents R20-R32are 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 non- adjacent C atoms may be replaced with O, S, NR6, CO or COO and one or more H atoms may be replaced with F.

[0241] 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, NR6, CO or COO and one or more H atoms may be replaced with F.

[0242] Formulations

[0243] The photoactive layer may be formed by any process including, without limitation, thermal evaporation and solution deposition methods.

[0244] 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.

[0245] 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.

[0246] 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.

[0247] 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.

[0248] Applications

[0249] 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.

[0250] In some embodiments, a photodetector system comprises a plurality of photodetectors as described herein, such as an image sensor of a camera.

[0251] 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.

[0252] 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 I 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.

[0253] 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 cm2or 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.

[0254] Examples

[0255] Measurements

[0256] 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.

[0257] 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.

[0258] 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).

[0259] The sample is dissolved in toluene (3 mg I ml) and spun at 3000 rpm directly on to the glassy carbon working electrode.

[0260] LUMO = 4.8-E ferrocene (peak to peak average) - E reduction of sample (peak maximum).

[0261] HOMO = 4.8-E ferrocene (peak to peak average) + E oxidation of sample (peak maximum).

[0262] 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.

[0263] 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.

[0264] 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 I ml solution in a quartz cuvette and comparing to a cuvette containing the solvent only.

[0265] Unless stated otherwise, solution absorption data as provided herein is as measured in a methylated benzene solution, optionally a 1,2,4-trimethylbenzene solution.

[0266] Exemplary compounds of formula (I) are:

[0267] Examples

[0268] Donor Group 1 os. dba)3 -78 C to r.t.

[0269] Donor Group 1 Compound Example 1

[0270] Compound Example 1 Acceptor Group 1 was prepared as described in WO2022 / 129137, the contents of which are incorporated herein by reference.

[0271] 1H-NMR (400 MHz, CHLOROFORM-D) 5 8.97 (s, 1H); 8.91 (s, 1H); 8.70 (s, 1H); 8.1 (s, 1H); 7.96 (s, 1H); 7.93 (bs, 1H); 7.46 (s, 1H); 6.95-7.00 (m, 6H); 6.76-6.80 (m, 6H);

[0272] 4.16 (d, 4H); 2.77 (m, 2H), 2.61 (m,4H); 0.89-2.59 (m, 34H)

[0273] Donor Group 2 Donor Group 3 oupling

[0274] Donor Group 3

[0275] Donor Groups 2 and 3 may be reacted in the same way as Donor Group 1 to form compounds of Formula (I). Acceptor Group 2

[0276] Acceptor Group 2 was prepared by the method described in W02024 / 094804, the contents of which are incorporated herein by reference.

[0277] Acceptor Group 2

[0278] Compound Example 2

[0279] Compound Example 2, illustrated below, was prepared in the same way as Compound Example 1 except that Donor Group 2 was used in place of Donor Group 1.

[0280] Compound Example 2

[0281] 1H-NMR (400 MHz, DICHLOROMETHANE-D) 5 8.99 (s, 1H); 8.98 (s, 1H); 8.75 (bs, 1H);

[0282] 8.73 (bs, 1H); 8.15 (s, 1H); 8.14(s, 1H); 7.97 (s, 1H); 7.89 (s, 1H); 7.66 (d, 2H); 7.54 (d, 2H); 6.98-6.99 (m, 6H); 4.23 (m, 4H); 2.84 (t, 2H), 2.57 (t, 8H); 0.83-1.94 (m,

[0283] 114H)

[0284] Compound Example 3

[0285] Compound Example 3 was prepared as described for Compound Examples 1 and 2, using Acceptor Group 2.

[0286]

[0287] Compound Example 3

[0288] Cyclic voltammetry and absorption data for Compound Examples 1, 2 and 3are set out in Table 1. Table 1 Device Example 1

[0289] A glass substrate coated with a 45 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-dichlorobenzene I 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).

[0290] Donor Polymer 1

[0291] Figure 5 is a plot of current density vs. applied voltage for Device Example 1.

[0292] Figure 6 is a plot of external quantum efficiency (EQE) vs. wavelength for Device Example 1.

[0293] More than one Device Example 1 was made; Figures 4 and 5 show overlaid plots for these devices.

[0294] Device Example 2

[0295] A glass substrate 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 a 1,2,4’trimethylbenzene : o- dichlorobenzene : 1,2-dimethoxybenzene mixture (3: 1 : 1 v / v). An anode stack of MoOs (lOnm) and ITO (70nm) was formed over the bulk heterojunction by thermal evaporation (MoOs) and sputtering (ITO).

[0296] Device Example 3

[0297] A device was prepared as described in Device Example 2 except that Compound Example

[0298] 2 was used in place of Compound Example 1 and the bulk heterojunction layer was formed by bar-coating a 1,2,4-trimethylbenzene : 1,2-dimethoxybenzene (95: 5 v / v) solution of Donor Polymer 1 : Compound Example 2 in a 1 :07 weight ratio.

[0299] Device Example 4

[0300] A device was prepared as described in Device Example 2 except that Compound Example

[0301] 3 was used in place of Compound Example 1 and the bulk heterojunction layer was formed by bar-coating a 1,2,4-trimethylbenzene : 1,2-dimethoxybenzene (95: 5 v / v) solution of Donor Polymer 1 : Compound Example 2 in a 1 :07 weight ratio.

[0302] Device performance of Device Examples 2 and 3 is set out in Table 2 and in Figures 7 and 8.

[0303] Device performance of Device Example 4 is set out in Table 2 and in Figures 9 and 10.

[0304] Table 2

[0305] With reference to Figure 6, Device Examples 2 and 3 show high efficiencies at wavelengths above about 1000 nm, indicating that both Compound Examples 1 and 2 are suitable for use in organic photodetectors for detection of wavelengths in the range of about 1000- 1500 nm. The difference in external quantum efficiencies between Device Examples 2 and 3 becomes more pronounced at wavelengths above 1000 nm and with reference to Figure 7, surprisingly, Device Example 3 has a lower dark current than Device Example 2 indicating that Compound Example 2 is particularly suited to use on an organic photodetector for detection of wavelengths in the 1000-1500 nm range.

[0306] Modelling

[0307] 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 B3LYP (functional) and LACVP* (Basis set).

[0308] Results are set out in Tables 3-5in which in which Slf corresponds to oscillator strength of the transition from SI (predicting absorption intensity) and Eopt is the modelled optical gap.

[0309] Table 3 - effect of donor group

[0310]

[0311]

[0312]

[0313] Table 4 - effect of N substituents on pyrrole

[0314]

[0315] Table 5 - compounds without Ar1or Ar2groups

[0316]

[0317] Model Compounds 27 and 28, which are based on Compound Example 1, show different conformers of the same compound, described herein as the "S-conformer" and the "C- conformer" respectively. As set out in Table 6, the modelled energy of Model Compound 27 is higher than that of Model Compound 28, indicating that the C-conformation of Model

[0318] Compound 27 is more favoured.

[0319] Model Compounds 32 and 33 also show the S-conformation and C-conformation of the same compound based on Compound Example 1. As with Model Compounds 27 and 28, the C-conformer of Model Compound 32 has the lower energy. In contrast, data for Model Compound 29, corresponding to Compound Example 2, indicates that the S-conformer is preferred. Without wishing to be bound by any theory, the S-conformer may pack differently in a film to the C-conformer in a way that results in lower conformational disorder and reduced defect (trap) density, resulting in lower dark current than a film of Compound Example 1. Table 6

[0320] Table 7 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 7

Claims

CLAIMS1. A compound of formula (I) or (II) :A2- (B1)x1- (D1)y1- (Bx)x2- A3(I)A2- (B2)z1- (D2)y2- (B3)x3- A1- (B3)x4- (D3)y3- (B2)z2- A3(II) wherein :A1is a divalent heteroaromatic electron-accepting group;A2and A3independently is the same or different and in each occurrence is a monovalent electron-accepting group;D1, D2and D3independently in each occurrence is the same or different and is an electron-donating group;B1, B2, and B3independently in each occurrence is the same or different and is a bridging group; x1and x2are each independently the same or different and are each 0, 1, 2 or 3; x3and x4are each independently the same or different and are each 0, 1, 2 or 3; y1, y2and y3are each independently the same or different and are each at least 1; z1and z2are each independently the same or different and are each 0, 1, 2 or 3; and wherein at least one occurrence of D1of formula (I) or at least one occurrence of at least one of D2and D3of formula (II) is a group of formula (III)wherein :X1and X2are each independently selected from is O, S and NR1wherein R1is H or a substituent, with the proviso that at least one of X1and X2is NR1;Y is O or S;Ar1is a monocyclic, bicyclic or tricyclic aromatic or heteroaromatic group or is absent;Ar2is a monocyclic or bicyclic or tricyclic aromatic or heteroaromatic group or is absent;R1is H or a substituent; andR2in each occurrence is independently a substituent.

2. The compound according to claim 1 wherein one of X1and X2is selected from O and S and the other of X1and X2is NR1.

3. The compound according to claim 2 wherein X1is selected from O and S and X2is NR1.

4. The compound according to claim 2 wherein X2is selected from O and S and X1is NR15. The compound according to any one of the preceding claims wherein Ar1is not present and the group of formula (III) has formula (III-A):(III-A) wherein R3is H or a substituent.

6. The compound according to any one of claims 1-4 wherein Ar2is not present and the group of formula (III) has formula (III-B):(III-B) wherein R4is H or a substituent.

7. The compound according to any one of claims 1-4 wherein neither Ar1nor Ar2is present and the group of formula (III) has formula (III-C):(III-C)8. The compound according to any one of claims 1-5 wherein Ar2is a group of formula(IV):(IV).

9. The compound according to any one of claims 1-4 and 6 wherein Ar1is a group of formula (V):(V).

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. The compound according to any one of the preceding claims wherein at least one of A2and A3comprises a non-aromatic carbon-carbon double bond and a carbon atom of the carbon-carbon double bond is bound directly to D1, D2or D3, or if present, to B1or B2.

12. The compound according to any one of the preceding claims wherein A2and A3are the same or different and are each independently selected from groups of formulae (IXa)-(IXr):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;R10is H or a substituent;G is C=0, C=S SO, SO2, NR33or C(R33)2 wherein R33is CN or COOR40and R40is H or a substituent;J is C=O, C=S, NR11or CR12R13wherein R11is CN or COOR40and R40is H or a substituent and R12and R13are each independently CN, CF3 or COOR40;R13in each occurrence is a substituent;R15in each occurrence is independently H or a substituentR16is a substituent;Ar6is a 5-membered heteroaromatic group which is unsubstituted or substituted with one or more substituents;T1, T2and T3each independently represent an aryl or a heteroaryl ring which may be fused to one or more further rings and each of T1, T2and T3is independently unsubstituted or substituted with one or more substituents;Ar8is a fused heteroaromatic group which is unsubstituted or substituted with one or more substituents and which is bound to an aromatic C atom of B1or B2and to a boron substituent of B1or B2; andR24is H or a halogen.

13. The compound according to claim 12 wherein at least one of A2and A3is a group of formula (IXa-2) and (IXa-3) :(IXa-2) (IXa-3) wherein each X7-X10is independently CR12or N wherein R12in each occurrence is H or a substituent selected from C1-20 hydrocarbyl and an electron withdrawing group; and R15is H or a substituent.

14. The compound according to claim 13 wherein the electron withdrawing group is F, Cl or CN.

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. 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. An organic electronic device according to claim 16 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. 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. An organic electronic device according to claim 18 wherein the organic photoresponsive device is an organic photodetector.

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. The photosensor according to claim 20, wherein the light source emits light having a peak wavelength of greater than 900 nm.

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. 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 22 onto a surface and evaporation of the one or more solvents.

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