GB2624717A - Formulation - Google Patents

Abstract

A formulation comprising a solvent comprising at least one nitrile group e.g. benzonitrile; and a non-fullerene acceptor substituted with a nitrile group dissolved in the formulation. The formulation may also have an electron-donating material dissolved in the formulation. The formulation may be used in formation of a photoactive layer of a photoresponsive device.

Description

FORMULATION

BACKGROUND

Embodiments of the present disclosure relate to formulations containing an electron-accepting compound, in particular formulations suitable for use in forming a photoactive layer of a photoresponsive device.

An organic photoresponsive device 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).

Examples of NFAs are disclosed in W02022/129137. US20210198421 and US11289653. 10 SUMMARY In some embodiments, the present disclosure provides a formulation comprising a solvent comprising at least one nitrile group; and a non-fullerene acceptor substituted with a nitrile group dissolved in the formulation.

In some embodiments, the present disclosure provides a method of forming an organic photoresponsive device comprising an anode, a cathode and a photoactive layer disposed between the anode and the cathode wherein formation of the photoactive comprises depositing a formulation as described herein over one of the anode and cathode, the method further comprising forming the other of the anode and cathode over the photoactive layer.

DESCRIPTION OF DRAWINGS

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

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

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 S 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 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 photoactive 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 or consists of an electron-donating material and an electron-accepting compound. The electron-accepting compound is a non-fullerene acceptor (NFA) substituted with one or more nitrile substituents Formation of the bulk heterojunction layer comprises depositing a formulation comprising the electron-donating material, the NFA, and any other components of the 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 one or more solvents include a solvent substituted with at least one nitrile substituent.

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 first solvent substituted with at least one nitrile substituent and one or more further solvents.

The one or more further solvents may be selected from benzene or naphthalene substituted with one or more substituents selected from fluorine, chlorine. C1,10 alkyl and Ciin alkoxy wherein two or more substituents may be linked to form a ring which may be unsubstituted or substituted with one or more C1_6 alkyl groups, optionally toluene, xylenes, trimethylbenzenes, tetramethylbenzenes, anisole, indane and its alkyl-substituted derivatives, and tetralin and its alkyl-substituted derivatives; and esters, optionally alkyl or aryl esters of alkyl or aryl carboxylic acids, optionally a Ci_io alkyl benzoate, henzyl benzoate.

In some embodiments, the formulation consists of the first solvent, the NFA substituted with one or more nitrile substituents, the electron donating material and, optionally, the one or more further solvents.

In some embodiments, the formulation, and the bulk heterojunction layer formed from the formulation, may further comprise one or more further electron-accepting materials, .e.g. one or more further NFAs or fullerenes, and / or at least two electron-donating materials.

The formulation may comprise further components selected from 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.

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, or each, electron-accepting material, i.e. the electron-donating material has a shallower HOMO and LUMO that the corresponding HOMO and LUMO levels of the electron-accepting material(s). Preferably, the or each electron-accepting material 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, or each, electron-accepting material is less than 1.4 eV.

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 hulk heterojunction layer. In some embodiments, both of the anode and cathode are transparent. The transmittance of a transparent electrode may be selected according to an emission wavelength of a light source for use with the organic photodetector.

Figure 1 illustrates an arrangement in which the cathode is disposed between the substrate and the anode. In other embodiments, the anode may be disposed between the cathode and the substrate.

Figure 1 illustrates an arrangement in which the photoresponsive device comprises a photoactive bulk heterojunction photoactive layer 105. In other embodiments, the photoactive layer comprises an electron-accepting sub-layer comprising or consisting of one or more electron-accepting compounds 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. According to these embodiments, the electron-accepting sub-layer may be formed by depositing a foimulation comprising the NFA dissolved or dispersed in a solvent or a mixture of two or more solvents including a solvent comprising at least one nitrite group followed by evaporation of the one or more solvents. hi some embodiments, the electron-accepting sub-layer is formed on the electron-donating sublayer. In some embodiments, the electron-donating sub-layer is formed on the electron-accepting sub-layer.

The organic photoresponsive device may comprise layers other than the anode, cathode and bulk heterojunction layer shown in Figure 1. In some embodiments, a hole-transporting layer and / or an electron-blocking layer is disposed between the anode and the bulk heterojunction layer. In some embodiments, an electron-transporting layer and / or a hole-blocking layer is disposed between the cathode and the bulk heterojunction layer. In some embodiments, a work function modification layer is disposed between the hulk heterojunction layer and the anode, and/or between the bulk heterojunction 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.

Nitiile-containing solvent The nitrile-containing solvent may be benzene or naphthalene substituted with one or more nitrite groups and, optionally, one or more further substituents selected from fluorine, chlorine, CI Ho alkyl and CI alkoxy; and Ci_m alkane nitriles.

Exemplary nitrile-containing solvents include benzonitrile, p-Tolunitrile, 4-Butylbenzonitrile, 4-M etho x ybenzonitrile, 4-Chlorobenzonitrile, 4-tert-B utylbenzoni tri le, 4-Fl uorobenzoni trite.

4-Ethyllbenzonitrile, and Naphthalene-2-carbonitrile.

Preferably, the nitrile-containing solvent has a boiling point in the range of 140-275°C at 1 atmosphere pressure.

When used in combination with one or more other solvents, the nitrile-containing solvent or solvents preferably make up at least 1 vol% of the solvent mixture, optionally in the range of 1-99 vol %.

In some embodiments, the ni trile-containing solvent is the highest boiling sol vent of the solvent mixture. According to these embodiments, the nitrile-containing solvent preferably forms no more than 20 vol% of the total solvent mixture volume.

In some embodiments, the solvent mixture comprises a solvent having a higher boiling point that the nitrile-containing solvent. According to these embodiments, the nitrile-containing solvent preferably forms at least 50 vol% of the total solvent mixture volume.

Non-fullerene acceptor The NFA containing a nit-tile group may be a compound formula (I) or (II): Al -(BI)x1 -(D1)y1 -(BI)x2 -(I) AI -(B2)x5 -(D2)y2 -(B3)x3-A2 -(B3)x4 -(D3)y3 -(B2)x6 -AI wherein: A1 in each occurrence is independently a monovalent electron-accepting group; A= is a divalent heteroarornatic electron-accepting group; DI, D2 and D3 independently in each occurrence is an electron-donating group; B I, B2, and B3 independently in each occurrence is a bridging group; xl -x° arc each independently 0, 1, 2 or 3; and yi, y:2 and y 3 are each independently at least 1.

and wherein the compound of formula (I) or (E) contains at least one nitrite substituent.

Each of the electron-accepting groups AI 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 DI. 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 LAC VP* (Basis set).

Preferably at least one Ai, and more preferably each Al, comprises at least one nitrite substituent.

Exemplary compounds of formula (I) are: c4 o Bridginn units S Bridging units B1, B2 and B3 arc preferably each selected from vinylene, arylene, heteroarylene, arylenevinylene and heteroarylenevinylene wherein the arylene and heteroarylene groups are monocyclic or bicyclic groups, each of which may be unsubstituted or substituted with one or more substituents.

Optionally, B1, B2 and B3 arc, independently in each occurrence, selected from units of formulae (VIa) -(VIo): (Via) (Vlb) (Vic) R8 R55 (V Id) OrTh (Vie) (VII) (VIg) (Viii) R8 R8 \ N (Vii) (VI.j) (Va) (VI1) R8 R8 R8 (VIm) (VIn) (VIo) wherein R5 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; CM; NOn; C1220 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 R14 in each occurrence is a substituent, optionally a Ci_20hydrocarbyl 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 substituems selected from F; CN; NO2; C1_10 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, C1-20 alkyl or C1-19 alkoxy.

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

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

In compounds of formula (H), x3 and x4 are each preferably 0 and x5 and x6 are each preferably 0 or 1.

Electron-Accepting Groups Al The monovalent acceptor groups Al may each independently be selected from any such units known to the skilled person. Al may be the same or different, preferably the same.

Exemplary monovalent acceptor groups include, without limitation, groups of formulae (IXa)-(IXq) R10 (IXa) (IXh) (IXg)

NN

(IXf) NC\ Rio R16 R13 (lXi) R15 R15 (IXj) R13 (IXc) (IX6) (IXd) (IXc)

N

U C

NN (IM) R 6 R16 (IX in) R15 (IXn) Ri3 (IXo) R15 (IXp) R16 R10 (IXq) NC/ Rio 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.

Ci is C=0, C=S SO, SO2, NR33 or C(R33)2 wherein R33 is CN or C00R40. CI is preferably C=0 or 501, more preferably C=0.

The N atom of formula (1Xe) may be unsubstituted or substituted.

R1° is H or a substituent, preferably a substituent selected from the group consisting of 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; and an aromatic group, optionally phenyl, which is unsubstituted or substituted with one or more substituents selected from F and Ci-in alkyl wherein one or more non-adjacent C atoms may be replaced with 0, S. NR6, COO or CO.

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

Ri3 in each occurrence is a substituent, optionally Chil alkyl wherein one or more non-adjacent 10 C atoms may be replaced with 0, 5, NR6, COO or CO and one or more H atoms of Me alkyl may be replaced with F. R15 in each occurrence is independently H; F; C 1-12 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; 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 he replaced with 0, S. NR6, COO or CO; or a group selected from: R16 is H or a substituent, preferably a substituent selected from: -(Ar3), wherein Ar3 in each occurrence is independently an unsubstituted or substituted aryl or heteroaryl group, preferably thiophene, and w is 1, 2 or 3; Y40 Y40

NC

NC

NC CN; CN; NC R4° R10, y41 z40 ^-^ z41 z42 z41. R40

NC NC io

NC CN * NC ) '1;1 NN; Rio. and

z40 vv4° ^=.1*z41 z43 C 1 -1 2 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. Arc' is a 5-membered heteroaromatic group, preferably thiophene or furan, which is unsubstituted or substituted with one or more substituents.

Substituents of Ar3 and Ar6, where present, are optionally selected from CIA, 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. 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 T I, T2 and T3, where present, are optionally selected from non-H groups of R25. In a preferred embodiment, T3 is benzothiadiazole.

Z1 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 R1°, and which is bound to an aromatic C atom of B' or B2 and to a boron substituent of B I or B2.

Preferred groups AI are groups having a non-aromatic carbon-carbon bond which is bound directly to D1 of formula (I) or D2 or D3 of formula (II) or, if present to B1 of formula (I) or B2 of formula (II).

Preferably at least one A1, preferably both groups A1, are a group of formula (IXa-1): (IXa-1) wherein: G is as described above and is preferably C=0 or SO2, more preferably C=0; RI° is as described above; 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 COORID wherein R4° in each occurrence is H or a substituent, preferably H or a C1_20 hydrocarbyl group. Preferably, each X6D is CM.

Ar9 may be unsubstituted or substituted with one or more substituents. Substituents of Ar9 are preferably selected from groups RI2 as described below.

Preferably, the group of formula (IXa-1) has formula (IXa-2): x6° x60 I-' tio Xu 9

X

(IX a-2) each X7-X1° is independently CR12 or N wherein R12 in each occurrence is H or a substituent selected from CL20 hydrocarbyl and an electron withdrawing group. Preferably, the electron 15 withdrawing group is F, Cl, Br or CM.

In a particularly preferred embodiment, at least one of X7-X1° is CR12 R12 is CM. Yet more preferably, each of X7-Xl° is CR12 and at least one R12 CM.

Preferably, each X6° is CM. In a preferred embodiment, the group of formula (I(a-2) includes CM groups X6° and at least one CM group R12.

The C1_20 hydrocarbyl group le2 may be selected from C1_20 alkyl; unsubstituted phenyl; and phenyl substituted with one or more C 1_ 1 2 alkyl groups.

Exemplary groups of formula (ad) include: R13 Exemplary groups of formula (D(e) include: inks\ An exemplary group of formula (IXq) is: An exemplary group of formula (IXg) is: An exemplary group of formula (IXj) is:

ON

wherein Ak is a C1_17 alkylene chain in which one or more C atoms may be replaced with 0, S, NR6, CO or COO; An is an anion, optionally -S03-; and each benzene ring is independently unsubstituted or substituted with one or more substituents selected from substituents described with reference to RI°.

Exemplary groups of formula (IXm) are: R13 An exemplary group of formula (IXn) is: FV6 Groups of formula (IXo) are bound directly to a bridging group B1 or B2 substituted with a group of formula -B(RI4)2 wherein R14 in each occurrence is a substituent, optionally a Cl_20 hydrocarbyl group; -> is a bond to the boron atom -B(R14)); and ---is a C-C bond between formula (IXo) and the bridging group.

Optionally, R14 is selected from CI42 alkyl; unsubstituted phenyl; and phenyl substituted with one or more CIA/ alkyl groups.

The group of formula (IXo), the B1 or B2 group and the B(R14)-, substituent of B1 or B2 may be linked together to form a 5-or 6-membered ring.

Optionally groups of formula (IXo) are selected from: R15 R15 R1 R 1 5 Rie ( R15 R15 R15 Acceptor Unit A2 A= is preferably a fused heteroaromatic group comprising at least 2 fused rings, preferably at least 3 fused rings.

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

NN

(VIII) wherein: Arl is an aromatic or heteroaromatic group; and Y is 0, S, NR6 or R7-C=C-R7 wherein R7 in each occurrence is independently H or a substituent wherein two substituents R7 may be linked to form a monocyclic or polycyclic ring; and R6 is 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; C120 alkyl wherein one or more non-adjacent C atoms may be replaced with 0, S. NR17 wherein 5 R17 is a C1-i, 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 Y40 R40 z40 z41 :.z42 Z43 y41 '1":1or R40 w40 Z4'. z42 and,-. L43 wherein Z4°, are each independently CR13 or N wherein R13 in each occurrence is H or a substituent, preferably a C1_,0 hydrocarbyl group; Y4° and Y41 are each independently 0, S, NX71 wherein X71 is CN or COOR40; or CX60X61 wherein X6° and X61 is independently CN. CF3 or C00R40: w40 and W41 are each independently 0, S. NX71 or CX60A''61 wherein X6° and X61 is independently CN, CF3 or C00R40; 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 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. Br as described anywhere herein may be, for example, C1-12 alkyl, unsubstituted phenyl; or phenyl substituted with one or more CLe, 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-teiminal Cato m.

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): (V) XI and X2, are each independently selected from N and CR1° wherein le° is H or a substituent, optionally H or a substituent R9 as described above.

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

Z is selected from 0, S. 502, NR6, PR6, C(R1°)2, Si(RI°)2 C=0, 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. C00R40; or CX60X61 wherein X6° and X61 is independently CN, CF3 or COOR4° and R4° in each occurrence is H or a sub stituent, preferably H or a C hydrocarbyl group.

A2 groups of formula (VIII) are preferably selected from groups of formulae (Villa) and (V111b): (VIIIb) For compounds of formula (VHIb), 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; NOn; Cl_no alkyl wherein one or more non-adjacent C atoms may be replaced with 0, S. NR6, CO, COO, NR.6, PR6, or Si(R1°)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; NOn; 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 (VIM-I) or (VIIIb-2): ( l) (V111b-2) Ar2 is an aromatic or heteroaromatic group, preferably benzene, which is unsubstituted or substituted with one or more substituents. Ar2 may he unsubstituted or substituted with one or more substituents selected from H. F, Cl, CN, NO2. Ci_16 alkyl or Ci_16 alkoxy wherein one or more H atoms of the C146 alkyl or CiA6 alkoxy may be replaced with F. X is selected from 0, S, SO2, Nle, PR°, C(R1D)2, Si(R10)2 C=0, C=S and C=C(R5)2 wherein Rio, R6 and K-5 are as descrthed above.

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

AO AO

N)/ 'N N. N

N N Aki N,

N N \ / N"N

wherein Aki is a Cirio alkyl group Divalent electron-accepting groups A2 other than formula (VIII) are optionally selected from formulae (IVa)-(IVk) R75 (IVb) R" (IVd) (IVf) (IVh) R12 (We) S, I N\ /N-s-13-RI2 (Ivg) R25 R25 N)/ (IVi) (I Vj) R23 0 (lVk) R23 YA1 is 001 S. preferably S. R23 in each occurrence is a substituent, optionally Chi/ alkyl wherein one or more non-adjacent 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. R25 in each occurrence is independently H; F; CN; NO2; Ci_in 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 C 1-1, alkyl wherein one or more non-adjacent C atoms may be replaced with 0, S. NR6, COO or CO; or Y40 z43" or w40 R40 z40 z41 z142 wherein Z40, z41, z42 and c743 are each independently CR or N wherein R13 in each occurrence is flora substituent, preferably a C1_20 hydrocarbyl group; Y4° and Y4I are each independently 0, S. NX7I wherein X7I is CN or C00R40; or CX6°)(61 wherein X6° and X61 is independently CN, CF3 or C00R40; w4o and w41 are each independently 0, 5, NX7 I wherein X71 is CN or C00R40; or CX60x61 10 wherein X6° and X61 is independently CN, CF3 or C00R40; and R4° in each occurrence is H or a substituent, preferably H or a C; -20 hydrocarbyl group. Z3 is N or P. TI, 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 T I, T2 and T3, where present, are optionally selected from non-H groups of R2s. In a preferred embodiment, T3 is benzothiadiazole.

R12 in each occurrence is a substituent, preferably a C; -20 hydrocarbyl group.

Ars is an arylene or heteroarylene group, optionally thiophene, fluore,ne 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 DI, D2 and D3 Electron-donating groups preferably are fused aromatic or heteroaromatic groups, more preferably fused heteroaromatic groups containing three or more rings. Particularly preferred electron-donating groups comprise fused thiophene or furan rings, optionally fused rings containing thiophene or furan rings and one or more rings selected from benzene, cyclopentadiene, tetrahydropyran, tetrahydrothiopyran and piperidine rings, each of said rings being unsubstituted or substituted with one or more substituents.

Exemplary electron-donating groups D', D2 and D3 include groups of formulae (VIIa)-(VIIm).

(VI la) (VIlb) R52 R51 R52 (VHc) (VIId) R53 R" 51 R53 R53 R53 (Vile) (Vhf) R54 R54 (VIIg) (VIIh) R54 R54 R54 R5' R54 R54 (Viii) (VI1j) (VIII) wherein YA in each occurrence is independently 0, S or NR55; XA is C or Si; YA1 in each occurrence is independently 0 or S; ZA in each occurrence is 0, CO, S. NR" or C(R54)1; R51, R52 R54 and R55 independently in each occurrence is H or a substituent; R53 independently in each occurrence is a substituent; and Ar4 is an optionally substituted monocyclic or fused heteroaromatic group.

Optionally, R51 and R52 independently in each occurrence are selected from H; F; C1,70 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 or heteroaromatic group Ar3 which is unsubstituted or substituted with one or more substituents.

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

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

The one or more substituents of Ar3, if present, may be selected from C1-12 alkyl wherein one or more non-adjacent C atoms may be replaced with 0, S. NR6, COO or CO and one or more H atoms of die alkyl may be replaced with F. Preferably, each R54 is selected from the group consisting of: F; linear, branched or cyclic alkyl wherein one or more non-adjacent C atoms may be replaced by 0, S. NR17, CO or COO wherein R17 is a CI-12 hydrocarbyl and one or more H atoms of the C1_20 alkyl may be replaced with F; and a group of formula (Ak)u-(Ar7)v wherein Ak is a Cwo 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; Ar7 in each occurrence is independently an aromatic or heteroaromatic group which is unsubstituted or substituted with one or more substituents; and v is at least 1, optionally 1, 2 or 3.

Substituents of Ar7, if present, are preferably selected from F; Cl; NO2; CN; and Cl _no 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, Ar7 is phenyl.

Preferably, each R is H. Optionally, R53 independently in each occurrence is selected from 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; and phenyl which is unsubstitutcd or substituted with one or more substituents, optionally one or more Cup alkyl groups 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. Preferably, R55 as described anywhere herein is H or CI -30 hydrocarbyl group.

In a preferred embodiment, DI of the compound of formula (I) is a group of formula (Vile).

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

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

In some embodiments, y1 of formula (I) or at least one of y2 and y3 of formula (II) is greater than 1. In these embodiments, the chain of DI, D2 or D3 groups, respectively, may be linked in any orientation.

Electron-donating material A bulk heterojunction layer as described herein comprises an electron-donating material and a compound of formula (I) or (II) as described herein.

Exemplary donor materials are disclosed in, for example, W02013/051676, the contents of 10 which are incorporated herein by reference.

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

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

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

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

Optionally, the electron-donating polymer has a HOMO level no more than 5.5 eV from vacuum level. Optionally, the electron-donating polymer has a HOMO level at least 4.1 eV from vacuum level. As exemplary electron-donating polymers, polymers selected from conjugated hydrocarbon or heterocyclic polymers including polyacene, polyaniline, polyazulene, polybenzofuran, polyfluorene, polyfuran, polyindenofluorene, polyindole, polyphenylene, polypyrazoline, polypyrene, polypyridazine, polypyridine, polytriarylamine, poly(phenylene vinylene), poly( 3-substituted thiophene), poly(3,4-bisubstituted thiophene), polyselenophene, poly(3-substituted selenophene), poly(3,4-bisubstituted selenophene), poly(bisthiophene), poly(terthiophene), poly(bisselenophene), poly(terselenophene), polythieno[2,3-b]thiophene, polythieno[3,2-b]thiophene, polybenzothiophene, polybenzo [1.2-b:4,5-bldithiophene. polyisothianaphthene, poly(monosubstituted pyrrole), poly(3,4-bisubstituted pyrrole), poly-1,3,4-oxadiazoles, polyisothianaphthene, derivatives and copolymers thereof may be mentioned.

Preferred examples of donor polymers are copolymers of polyfluorenes and polythiophenes, each of which may be substituted, and polymers comprising bentothiadiazole-based and thiophene-based repeating units, each of which may he substituted.

A particularly preferred donor polymer comprises donor unit (VIIa) provided as a repeat unit of the polymer, most preferably with an electron-accepting repeat unit, for example divalent electron-accepting units A2 as described herein provided as polymeric repeat units.

A particularly preferred donor polymer comprises a repeat unit of formula (X): (X) wherein YA, ZA, Rm and R54 are as described above.

Another particularly preferred donor polymer comprises repeat units of formula (XI): wherein R18 and R19 are each independently selected from H; F; C1_12 alkyl wherein one or more non-adjacent, non-terminal C atoms may be replaced with 0, S. COO or CO and one or more H atoms of the alkyl may be replaced with F; or an aromatic or heteroaromatic group AO which is unsubstituted or substituted with one or more substituents selected from F and C 1 _In 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, a compound of formula (I) or (II) is the only electron-accepting material of a bulk heterojunction layer as described herein.

In some embodiments, a bulk heteroj unction layer contains a compound of formula (1) or (11) and one or more further electron-accepting materials. Preferred further electron-accepting materials are fullerenes.

Fullerenes may be selected from, without limitation, C60, C70, C76, 078 and C84 fullerenes or a derivative thereof, including, without limitation, PCBM-type fullerene derivatives including phenyl-C61.-bulyric acid methyl ester t.C60PCBM), TCBM-type fullerene derivatives (e.g. tolylCol-butyric acid methyl ester (C60TCBM)), and ThCBM-type fullerene derivatives (e.g. thienyl-C6i-butyric acid methyl ester (C60ThCBM).

Fullerene derivatives may have formula (V): (V) wherein A, together with the C-C group of the fullerene, forms a monocyclic or fused ring group which may be unsubstituted or substituted with one or more substituents.

Exemplary fullerene derivatives include formulae (Va), (Vb) and (Vc): R'4 (Vb)

C -C ( \

FULLERENE (Vc)

C --C (

FULLERENE (Va)

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

Substituents R20-R32 are optionally and independently in each occurrence selected from the group consisting of aryl or heteroaryl, optionally phenyl, which may be unsubstituted or substituted with one or more substituents; and C1.20 alkyl wherein one or more 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 CIA/ 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. The nitrile-substituted NFA: 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.

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 photorespon sive device as described herein may be an organic photovoltaic device or an organic photodetector. An organic photodetector as described herein may be used in a wide range of applications including, without limitation, detecting the presence and / or brightness of ambient light and in a sensor comprising the organic photodetector and a light source. The photodetector may be configured such that light emitted from the light source is incident on the photodetector and changes in wavelength and/or brightness of the light may be detected, e.g., due to absorption by, reflection by and/or emission of light from an object, e.g. a target material in a sample disposed in a lien 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 hell emitted from a target analytc 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 micron.= 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 10 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/AgC1 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 toluene solution. 10.

Claims (9)

1. CLAIMS1. A formulation comprising a solvent comprising at least one nitrile group; and a non-fullerene acceptor substituted with a nitrile group dissolved in the formulation.
2. 2. The formulation according to claim I wherein the non-fullerene acceptor is a compound of formula (1) or (H): A1 -(B1)x' -(D1)y' -(B1)x2 -.A1 (I) A1 -(B2)x.' -(D2)y2 -(BI)x3-A2 -(W)x4 -(D3)y3 -(B2)x6 -A1 (H) wherein: A1 in each occurrence is independently a monovalent electron-accepting group; A2 is a divalent heteroaromatic 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; and xl -x6 are each independently 0, 1, 2 or 3.
3. 3. The formulation according to claim 2 wherein at least one AI of formula (I) or at least one AI of formula (I) is substituted with at least one nitrile group.
4. 4. The formulation according to claim 3 wherein AI is a group of formula (IXa-1): R1° x6° x6° (IXa-1) wherein: G is C=0, C=S SO, 502, NR33 or 0R33)2 wherein R33 is CM or COOR4° and R4° is H or a substituent; Ar9 is an unsubstituted or substituted monocyclic or fused aromatic or heteroaromatic group; and X6° are each independently CN, CF3 or C00R40
5. 5. The formulation according to claim 4 wherein A1 is a group of formula (IXa-2): x60 X60 X7 x10 X8 ---x9 (IXa-2) wherein each X7-X10 is independently CR12 or N wherein in each occurrence is H or a substituent selected from CI -20 hydrocarbyl and an electron withdrawing group with the proviso that at least one of X7-X1° is CR12 and at least one R12 is CM.
6. 6. The formulation according to any one of claims 2-5 wherein D1 of formula (1) or at least one of D2 and D3 of formula (II) is a group of formula (VIIf): R53 R53 R51 R53 R" (Vile) wherein \TA is S or 0, R51 is H or a substituent and 1233 is a substituent.
7. 7. The formulation according to any one of the preceding claims wherein the formulation further comprises an electron-donating material dissolved in the formulation,
8. 8. The formulation according to any one of the preceding claims wherein the solvent comprising a nitrile group is selected from benzene or naphthalene substituted with one or more nitrile groups and, optionally, one or more further substituents; and CI _ in alkane nitrites.
9. 9. A method of forming an organic photoresponsive device comprising an anode, a cathode and a bulk heterojunction layer disposed between the anode and the cathode wherein formation of the bulk heterojunction comprises depositing a formulation according to any one of the preceding claims over one of the anode and cathode, the method further comprising forming the other of the anode and cathode over the bulk heterojunction layer.