WO2024115333A1

WO2024115333A1 - Method and compound

Info

Publication number: WO2024115333A1
Application number: PCT/EP2023/083067
Authority: WO
Inventors: Nir YAACOBI-GROSS; Michal MACIEJCZYK; Florence BOURCET
Original assignee: Cambridge Display Technology Limited; Sumitomo Chemical Co., Ltd
Priority date: 2022-11-28
Filing date: 2023-11-24
Publication date: 2024-06-06
Also published as: GB2624707A; GB202217829D0

Abstract

A method of forming an organic photoresponsive device comprising an anode (107), a cathode (103) and a photoactive layer (105) disposed between the anode and the cathode, the method comprising: forming a precursor layer over one of the anode and cathode, the precursor layer comprising a reactive non-fullerene acceptor substituted with at least two reactive groups; and forming the photoactive layer comprising reacting the reactive groups to form a chain or network comprising a plurality of molecules of the reacted non-fullerene acceptor; and forming the other of the anode and cathode before or after reaction of the reactive groups.

Description

METHOD AND COMPOUND

BACKGROUND

Embodiments of the present disclosure relate to methods of forming a photoresponsive device and electron- accepting compounds suitable for use in such methods. 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 WO2022/129137.

Kahle, F.-J., Sailer, C., Kohler, A., Strohriegl, P., “Crosslinked Semiconductor Polymers for Photovoltaic Applications” Adv. Energy Mater. 2017, 7, 1700306 discloses crosslinking of low bandgap polymers used as donors in bulk heterojunction cells, as well as the crosslinking of fullerene acceptors.

US 10,526,205 discloses a photoabsorbing composition having a structure from the group consisting of:

wherein DASM is a small molecule comprising one or more electron donor portions and one or more electron acceptor portions and NG is a nanographene structure, and m, n, and o are integers greater than or equal to 1. Fan Yang et al, “Boosting the Performance of Non-Fullerene Organic Solar Cells via Cross- Linked Donor Polymers Design”, Macromolecules 2019, 52, 5, 2214-2221 discloses cross- linked conjugated polymers as electron donor for application in organic solar cells.

Chih-Ping Chen et al, “Highly Thermal Stable and Efficient Organic Photovoltaic Cells with Crosslinked Networks Appending Open-Cage Fullerenes as Additives” vol. 25, Issue 2, p.207-215, 2015 discloses organic bulk heterojunction photovoltaic cells are demonstrated with crosslinkable open-cage fullerenes as additives in the active layer.

SUMMARY

The present disclsoure 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, the method comprising: forming a precursor layer over one of the anode and cathode, the precursor layer comprising a reactive non-fullerene acceptor substituted with at least two reactive groups; and forming the photoactive layer comprising reacting the reactive groups to form a chain or network comprising a plurality of molecules of the reacted non-fullerene acceptor; and forming the other of the anode and cathode before or after reaction of the reactive groups.

Optionally, the photoactive layer comprises a chain comprising a plurality of the non-fullerene acceptor molecules linked by a linking group formed upon reaction of the reactive groups with one another or with reactive groups of a linking agent.

Optionally, the photoactive layer is a bulk heterojunction layer further comprising an electron- donating material.

Optionally, the electron-donating material is a polymer comprising reactive groups capable of reacting with the non-fullerene acceptor reactive groups and wherein the photoactive layer comprises a crosslinked network comprising the electron-donating polymer crosslinked by the non-fullerene acceptor. Optionally, the photoactive layer comprises an electron-donating sublayer directly adjacent to and in contact with an electron- accepting sublayer and wherein the precursor layer is a precursor electron-accepting sublayer comprising the reactive non-fullerene acceptor.

Optionally, the photoactive layer comprises a bulk heterojunction sub-layer and at least one of an electron-donating sub-layer on an anode side of the bulk heterojunction sublayer and an electron-accepting sub-layer on a cathode side of the bulk heterojunction layer and wherein the precursor and wherein the precursor layer comprising the reactive non-fullerene acceptor is a precursor of the electron- accepting sublayer or a precursor of the bulk heterojunction sub-layer.

Optionally, the reactive groups in each occurence are independently selected from the group consisting of benzocyclobutene and an acyclic or cyclic group comprising a non-conjugated carbon-carbon double bond.

Optionally, the non-fullerene acceptor is a compound of formula (I) or (II):

A¹ - (B²)x⁵ - (D²)y² - (B³)x³- A² - (B³)x⁴ - (D³)y³ - (B²)x⁶ - A¹

(II) wherein:

A¹ in each occurrence is independently a monovalent electron- accepting group;

A² is a divalent heteroaromatic electron- accepting group;

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

B¹, B², and B³ independently in each occurrence is a bridging group; x¹ - x⁶ are each independently 0, 1, 2 or 3; y¹, y² and y³ are each independently at least 1; and the compound of formula (I) or (II) is substituted with at least two reactive groups. Optionally, the at least two reactive groups are substituents of one of D¹, D², D³, B¹, B² and B³.

Optionally, D¹ is a group of formula (Vile):

wherein Y^A is S or O, R⁵¹ is H or a substituent and R⁵³ is a substituent.

Optionally, A¹ is a group of formula (IXa-1):

s CN or COOR⁴⁰ and R⁴⁰ is H or a substituent;

R¹⁰ is H or a substituent;

Ar⁹ is an unsubstituted or substituted monocyclic or fused aromatic or heteroaromatic group; and X⁶⁰ are each independently CN, CF3 or COOR⁴⁰.

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

A¹ - (B')x¹ - (D')y¹ - (B ’)x² - A¹ (I)

(II) wherein:

A¹ in each occurrence is independently a monovalent electron- accepting group;

A² is a divalent heteroaromatic electron- accepting group;

B¹, B², and B³ independently in each occurrence is a bridging group; x¹ - x⁶ are each independently 0, 1, 2 or 3; y¹, y² and y³ are each independently at least 1; and the compound of formula (I) or (II) is substituted with at least two first reactive groups.

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

Optionally, the electron-donating material of the composition comprises second reactive groups capable of reacting with the first reactive groups.

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

The present disclosure provides an organic photoresponsive device comprising an anode, a cathode and a photoactive layer disposed between the anode and the cathode wherein the photoactive layer comprises a chain or network comprising a plurality of reacted molecules of formula (I) or (II).

The present disclosure provides a photosensor comprising a light source and an organic photodetector as described herein wherein the organic photodetector is configured to detect light emitted from the light source. Optionally, the light source emits light having a peak wavelength of greater than 900 nm. The present disclosure provides a method of forming an organic photoresponsive device according to claim 16, the method comprising forming a precursor layer comprising a compound of formula (I) or (II) over one of the anode and cathode; forming the photoactive layer comprising reacting the reactive groups to form a chain or network comprising a plurality of molecules of the reacted compound of formula (I) or (II); and forming the other of the anode or cathode before or after reaction of the reactive groups.

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 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 according to some embodiments of the present disclosure. The organic photoresponsive device comprises a cathode 103, an anode 107 and a bulk heterojunction layer 105 disposed between the anode and the cathode. The organic photoresponsive device may be supported on a substrate 101, optionally a glass or plastic substrate.

The photoactive layer as described herein comprises an electron-accepting material and an electron-donating material. Figure 1 illustrates an organic photoresponsive device in which the photoactive layer is a single bulk heterojunction layer containing both an electron-accepting material and an electron-donating material. In other embodiments, the photoactive layer comprises two or more sublayers.

In some embodiments, the photoactive layer comprises a crosslinked electron-accepting sub- layer comprising an electron-accepting material and an electron-donating sub-layer comprising an electron donating material wherein the sub-layers are directly adjacent to and in contact with one another.

In yet further embodiments, the photoactive layer comprises a bulk heterojunction layer containing both an electron- accepting material and an electron-donating material, and one or both of an electron-accepting layer comprising an electron-accepting material on a cathode side of the device and an electron-donating material comprising an electron-donating material on an anode side of the device.

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

Figure 1 illustrates an arrangement in which the cathode is disposed between the substrate and the anode. In other embodiments, the anode may be disposed between the cathode and the substrate. The organic photoresponsive device may comprise layers other than the anode, cathode and photoactive layer. In some embodiments, a hole-transporting layer and / or an electron- blocking layer is disposed between the anode and the photoactive layer. In some embodiments, an electron-transporting layer and / or a hole-blocking layer is disposed between the cathode and the photoactive layer. In some embodiments, a work function modification layer is disposed between the photoactive layer and the anode, and/or between the photoactive layer and the cathode.

The substrate may be, without limitation, a glass or plastic substrate. The substrate can be an inorganic semiconductor. In some embodiments, the substrate may be silicon. For example, the substrate can be a wafer of silicon. The substrate is transparent if, in use, incident light is to be transmitted through the substrate and the electrode supported by the substrate.

The bulk heterojunction layer comprises or consists of at least one electron-donating material and at least one electron- accepting material including a chain or network comprising a plurality of non-fullerene acceptor (NFA) molecules.

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.

Formation of the bulk heterojunction layer includes formation of a precursor layer containing NFA molecules substituted with reactive groups. The chain or network is formed by reacting the reactive groups of the NFA molecules. The NFA reactive groups may react with themselves to form linking groups between NFA molecules and / or the NFA reactive groups may react with reactive groups of another material of the precursor layer substituted with reactive groups, for example the electron-donating material or another linking agent substituted with reactive groups, for example a crosslinking agent.

The NFA reactive groups may react to form a chain or a network.

A chain may be formed by reacting a NFA with only two reactive groups, either with itself or with a linking agent having only two reactive groups.

A crosslinked network may be formed by reacting: a NFA with more than two reactive groups, e.g. three or four reactive groups, with itself; or a NFA with at least two reactive groups with a linking agent having more than two reactive groups.

The linking agent may be a non-poly meric linking agent having more than two reactive groups, e.g. three or four reactive groups. The linking agent may be a polymer comprising a repeat unit substituted with a reactive group capable of reacting with the reactive groups of the NFA to form a crosslinked network. In a preferred embodiment, the linking agent is an electron-donating polymer of the bulk heterojunction layer.

Exemplary compounds of formula (I) are:

wherein Sp is a spacer group or is absent; and Aik is Cl-12 alkyl.

The bulk heterojunction layer may consist of the NFA, the electron donating compound and (if present) a linking agent or it may comprise one or more further materials, for example one or more further electron-donating materials and / or one or more further electron-accepting compounds. Figure 1 schematically illustrates an OPD having a photoactive bulk heterojunction layer containing an electron-donating material a chain or network comprising a plurality of non- fullerene acceptor molecules. In other embodiments the photoactive layer may comprise an electron-accepting sublayer comprising or consisting of the NFA chain or network and an electron-donating sublayer directly adjacent to and in contact with the electron- accepting sublayer and comprising or consisting of the electron-donating material. In these embodiments, the sublayers may be formed in any order. Preferably, the electron- accepting sublayer comprising or consisting of the NFA chain or network is formed first and the electron- donating sublayer is formed on the electron-donating layer. The electron-accepting sublayer comprising the NFA chain or network may be less susceptible to dissolution upon deposition of a solution or suspension onto this layer as compared to the layer comprising the unreacted NFA.

Preferably, the electron-donating material has a type II interface with the 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. Preferably, the compound of formula (I) or (II) has a HOMO level that is at least 0.05 eV deeper, optionally at least 0.10 eV deeper, than the HOMO of the electron-donating material.

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

The NFA substituted with at least two reactive groups may be a compound formula (I) or (II):

A¹ - (BV - (D')y¹ - (B^x)x² - A¹

(I)

(II) wherein:

A¹ in each occurrence is independently a monovalent electron- accepting group;

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

B¹, B², and B³ independently in each occurrence is a bridging group; x¹ - x⁶ are each independently 0, 1, 2 or 3; and y¹, y² and y³ are each independently at least 1, wherein the compound of formula (I) or (II) is substituted with at least two reactive groups, optionally two, three or four reactive groups, capable of reacting with one another or with reactive groups of a linking material to form an NFA chain or network.

Each of the electron-accepting groups A¹ 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 D¹, D² or D³, preferably at least 1 eV deeper. The LUMO levels of electron- accepting groups and electron-donating groups may be as determined by modelling the LUMO level of these groups, in which each bond to adjacent group is replaced with a bond to a hydrogen atom. Modelling may be performed using Gaussian09 software available from Gaussian using Gaussian09 with B3LYP (functional) and LACVP* (Basis set).

In the case of compounds of formula (I), at least one of A¹, B¹ and D¹ is substituted with a reactive group. Preferably, at least one of x¹ and x² is at least 1 and at least one B ¹ is substituted with at least one reactive group.

In the case of compounds of formula (II), at least one of A¹, A², B², B³, D² and D³ is substituted with a reactive group. Preferably, at least one of x³-x⁶ is at least 1 and at least one of B² and B³ is substituted with at least one reactive group. More preferably, at least one of x⁵ and x⁶ is at least one and at least one B² is substituted with at least one reactive group.

Reactive groups

The NFA may be substituted with one or more reactive groups of formula (III):

wherein Sp represents a spacer group; x is 0 or 1; RG represents a reactive group; and * represents a point of attachment of the reactive group to the NFA. Preferably, x is 1.

RG may be selected from any reactive group known to the skilled person capable of reacting with itself to form a covalent bond, or any reactive group capable of reacting with reactive groups of a linking agent.

Optionally, the reactive group is selected from:

(i) a group comprising an acyclic unit of formula -CR¹=CH2 wherein R¹ is H or a substituent, preferably a C1-6 alkyl group, for example vinyl, acrylate or methacrylate;

(ii) a group comprising a cyclic alkene, preferably an optionally substituted norbornene, cyclopropene or cyclobutene;

(iii) optionally substituted benzocyclobutene;

(iv) halogen, preferably Cl, Br or I;

(v) boronic acid or ester thereof;

(vi) cyclic ether, preferably an optionally substituted, e.g. C1-6 alkyl substituted, epoxide or oxetane; and

(vii) azide.

Reactive groups of a non-fullerene acceptor as described herein may be selected for reaction with reactive groups of a linker or an electron-donating material. Exemplary combinations of groups capable of reacting with one another include: boronic acid or ester and halogen; groups of formula -CR¹=CH2 and an optionally substituted benzocyclobutene; fullerene and an optionally substituted benzocyclobutene; and azide and an optionally substituted benzocyclobutene .

The optionally substituted benzocyclobutene may have formula (IV):

wherein R² in each occurrence is H or a substituent; q is 0, 1, 2 or 3, preferably 0; and R³ in each occurrence is H or a substituent.

Preferably, of two R² groups bound to the same carbon atom at least one R² is H. Optionally, each R² of formula (IV) is H or only one R² of formula (IV) is not H. Exemplary non-H groups R² are C1-6 alkyl and C1-6 alkoxy.

R³, if present, is preferably selected from F, Cl, NO2, CN, C1-6 alkyl and C1-6 alkoxy.

Sp is preferably selected from optionally substituted phenylene; and Ci-20 alkylene wherein one or more H atoms of the Ci-20 alkylene may be replaced with F and one or more non- adjacent C atoms may be replaced with O, S, NR⁶, Si(R⁴)2, CO, COO or CONR⁶ wherein R⁶ is H or a substituent and each R⁴ is independently a substituent.

Optional substituents of a phenylene group Sp are F; CN; NO2; and Ci-20 alkylene wherein one or more H atoms may be replaced with F and one or more non-adjacent C atoms may be replaced with O, S, NR⁶, Si(R⁴)₂, CO, COO or CONR⁶.

Bridging units

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

Optionally, B¹, B² and B³ are, independently in each occurrence, selected from units of formulae (Via) - (VIo):

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

R⁸ is preferably H, Ci-20 alkyl or Ci-19 alkoxy. R⁸ groups of formulae (Via), (Vlb) and (Vic) may be linked to form an optionally substituted bicyclic ring.

In compounds of formula (I), each x¹ is preferably 0 or 1. In compounds of formula (II), x³ and x⁴ are each preferably 0 and x⁵ and x⁶ are each preferably 0 or 1.

Electron-Accepting Groups A¹

The monovalent acceptor groups A¹ may each independently be selected from any such units known to the skilled person. A¹ may be the same or different, preferably the same.

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

U is a 5- or 6-membered ring which is unsubstituted or substituted with one or more substituents and which may be fused to one or more further rings.

G is C=O, C=S SO, SO₂, NR³³ or C(R³³)₂ wherein R³³ is CN or COOR⁴⁰. G is preferably C=O or SO2, more preferably C=O.

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

R¹⁰ is 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.

Preferably, R¹⁰ is H.

J is O or S, preferably O.

R¹³ in each occurrence is a substituent, optionally 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.

R¹⁵ in each occurrence is independently H; F; 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; aromatic group Ar², optionally phenyl, which is unsubstituted or substituted with one or more substituents selected from F and Ci-12 alkyl wherein one or more non-adjacent C atoms may be replaced with O, S, NR⁶, COO or CO; or a group selected from:

R¹⁶ is H or a substituent, preferably a substituent selected from:

-(Ar³)_w wherein Ar³ in each occurrence is independently an unsubstituted or substituted aryl or heteroaryl group, preferably thiophene, and w is 1, 2 or 3;

and

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.

Ar⁶ 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 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.

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

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 R¹⁰, and which is bound to an aromatic C atom of B ¹ or B² and to a boron substituent of B ¹ or B². Preferred groups A¹ 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=O or SO2, more preferably C=O;

R¹⁰ 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 COOR⁴⁰ wherein R⁴⁰ in each occurrence is H or a substituent, preferably H or a Ci-2ohydrocarbyl group. Preferably, each X⁶⁰ is CN. Ar⁹ may be unsubstituted or substituted with one or more substituents. Substituents of Ar⁹ are preferably selected from groups R¹² as described below.

Optionally, the group of formula (IXa-1) has formula (IXa-2):

each X⁷-X¹⁰ is independently CR¹² or N wherein R¹² in each occurrence is H or a substituent selected from Ci-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 R¹² may be selected from Ci-20 alkyl; unsubstituted phenyl; and phenyl substituted with one or more Ci-12 alkyl groups.

In a particularly preferred embodiment, each of X⁷-X¹⁰ is CR¹² and each R¹² is independently selected from H or an electron-withdrawing group, preferably H, F or CN. According to his embodiment, R¹² of X⁸ and X⁹ is an electron-withdrawing group, preferably F or CN.

Exemplary groups of formula (IXd) include:

Exemplary groups of formula (IXe) include:

An exemplary group of formula (IXq) is:

An exemplary group of formula (IXg) is:

An exemplary group of formula (IXj) is:

wherein Ak is a Ci-12 alkylene chain in which one or more C atoms may be replaced with O, S, NR⁶, CO or COO; An is an anion, optionally -SO3’; and each benzene ring is independently unsubstituted or substituted with one or more substituents selected from substituents described with reference to R¹⁰. Exemplary groups of formula (IXm) are:

An exemplary group of formula (IXn) is:

Groups of formula (IXo) are bound directly to a bridging group B¹ or B² substituted with a group of formula -B(R¹⁴)2 wherein R¹⁴ in 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.

Optionally, R¹⁴ is selected from Ci-12 alkyl; unsubstituted phenyl; and phenyl substituted with one or more Ci-12 alkyl groups.

The group of formula (IXo), the B¹ or B² group and the B(R¹⁴)2 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:

Acceptor Unit A²

A² is preferably a fused heteroaromatic group comprising at least 2 fused rings, preferably at least 3 fused rings. In some embodiments, A² of formula (II) is a group of formula (VIII):

wherein:

Ar¹ is an aromatic or heteroaromatic group; and

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

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

Preferred R⁹ groups are selected from

F;

CN;

NO₂;

C1-20 alkyl wherein one or more non-adjacent C atoms may be replaced with O, S, NR¹⁷ wherein R¹⁷ is a Ci-nhydrocarbyl, COO or CO and one or more H atoms of the alkyl may be replaced with F; an aromatic or heteroaromatic group, preferably phenyl, which is unsubstituted or substituted with one or more substituents; and a group selected from

wherein Z⁴⁰, Z⁴¹, Z⁴² and Z⁴³ are each independently CR¹³ or N wherein R¹³ in each occurrence is H or a substituent, preferably a Ci-2ohydrocarbyl group; Y⁴⁰ and Y⁴¹ are each independently O, S, NX⁷¹ wherein X⁷¹ is CN or COOR⁴⁰; or CX⁶⁰X⁶¹ wherein X⁶⁰ and X⁶¹ is independently CN, CF3 or COOR⁴⁰; W⁴⁰ and W⁴¹ are each independently O, S, NX⁷¹ or CX⁶⁰X⁶¹ wherein X⁶⁰ and X⁶¹ is independently CN, CF3 or COOR⁴⁰; and R⁴⁰ in each occurrence is H or a substituent, preferably H or a Ci-20 hydrocarbyl group. Exemplary substituents of an aromatic or heteroaromatic group R⁹ are F, CN, NO2, and 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.

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

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

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

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

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

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

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

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

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

Preferably, each R⁵ is CN, COOR⁴⁰; or CX⁶⁰X⁶¹ wherein X⁶⁰ and X⁶¹ is independently CN, CF3 or COOR⁴⁰ and R⁴⁰ in each occurrence is H or a substituent, preferably H or a Ci-₂ohydrocarbyl group.

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

(Villa) (Vlllb)

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

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

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

(Vlllb- 1) (VIIIb-2) Ar² is an aromatic or heteroaromatic group, preferably benzene, which is unsubstituted or substituted with one or more substituents. Ar² may be unsubstituted or substituted with one or more substituents selected from H, F, Cl, CN, NO2, Ci-16 alkyl or Ci-16 alkoxy wherein one or more H atoms of the Ci-16 alkyl or Ci-16 alkoxy may be replaced with F. X is selected from O, S, SO₂, NR⁶, PR⁶, C(R¹⁰)₂, Si(R¹⁰)₂ C=O, C=S and C=C(R⁵)₂ wherein R¹⁰, R⁶ and R⁵ are as described above.

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

wherein Ak¹ is a Ci-20 alkyl group

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

Y^A1 is O or S, preferably S.

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

wherein Z⁴⁰, Z⁴¹, Z⁴² and Z⁴³ are each independently CR¹³ or N wherein R¹³ in each occurrence is H or a substituent, preferably a Ci-2ohydrocarbyl group; Y⁴⁰ and Y⁴¹ are each independently O, S, NX⁷¹ wherein X⁷¹ is CN or COOR⁴⁰; or CX⁶⁰X⁶¹ wherein X⁶⁰ and X⁶¹ is independently CN, CF3 or COOR⁴⁰;

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

R⁴⁰ in each occurrence is H or a substituent, preferably H or a Ci-20 hydrocarbyl group.

Z³ is N or P.

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

Ar⁵ is an arylene or heteroarylene group, optionally thiophene, fluorene or phenylene, which may be unsubstituted or substituted with one or more substituents, optionally one or more non- H groups selected from R²⁵.

Electron-Donating Groups D¹, D² and D³

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.

An electron-donating group as described herein may be substituted with one or more reactive groups.

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

wherein Y^A in each occurrence is independently 0, S or NR⁵⁵; X^A is C or Si; Y^A1 in each occurrence is independently O or S; Z^A in each occurrence is O, CO, S, NR⁵⁵ or C(R⁵⁴h; R⁵¹, R52 R54 _anc| j^55 | _nc|_ep_enc|_en ( j y j_{n eac}|-] occurrence is H or a substituent; R⁵³ independently in each occurrence is a substituent; and Ar⁴ is an optionally substituted monocyclic or fused heteroaromatic group.

Optionally, R⁵¹ and R⁵² independently in each occurrence are selected from H; F; Ci-20 alkyl wherein one or more non-adjacent C atoms may be replaced with 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 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 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.

Preferably, each R⁵⁴ is selected from the group consisting of: H; a reactive group as described herein;

F; linear, branched or cyclic Ci-20 alkyl wherein one or more non- adjacent C atoms may be replaced by O, S, NR¹⁷, CO or COO wherein R¹⁷ is a C1-12 hydrocarbyl and one or more H atoms of the Ci-20 alkyl may be replaced with F; and a group of formula (Ak)u-(Ar⁷)v wherein Ak is a Ci-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; 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 Ci-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, Ar⁷ is phenyl.

Preferably, each R⁵¹ is H.

Optionally, R⁵³ independently in each occurrence is selected from a reactive group as described herein; Ci-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 Ci-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.

Preferably, R⁵⁵ as described anywhere herein is H or C 1-30 hydrocarbyl group.

In a preferred embodiment, D¹ 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 (II) are each 1.

In some embodiments, y¹ of formula (I) or at least one of y² and y³ of formula (II) is greater than 1. In these embodiments, the chain of D¹, D² or D³ groups, respectively, may be linked in any orientation. Exemplary compounds of formula (I) or (II) having reactive groups include, without limitation:

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, WO2013/051676, the contents of which are incorporated herein by reference.

The electron-donating material may be a non-poly meric 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, poly thieno [3, 2-b] thiophene, polybenzothiophene, polybenzo [1,2- b:4,5-b']dithiophene, polyisothianaphthene, poly(monosubstituted pyrrole), poly(3,4- bisubstituted pyrrole), poly-1, 3, 4-oxadiazoles, polyisothianaphthene, derivatives and co- polymers thereof may be mentioned.

Preferred examples of donor polymers are copolymers of polyfluorenes and poly thiophenes, each of which may be substituted, and polymers comprising benzothiadiazole-based and thiophene-based repeating units, each of which may be substituted. A particularly preferred donor polymer comprises a repeat unit of formula (X):

wherein Y^A, Z^A, R⁵¹ 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; Ci-12 alkyl wherein one or more non-adjacent, non-terminal C atoms may be replaced with O, S, COO or CO and one or more H atoms of the alkyl may be replaced with F; or an aromatic or heteroaromatic group Ar⁶ which is unsubstituted or substituted with one or more substituents selected from F and Ci-12 alkyl wherein one or more non-adjacent, non-terminal C atoms may be replaced with O, S, COO or CO.

The donor polymer is preferably a donor-acceptor (DA) copolymer comprising a donor repeat unit, for example a repeat unit of formula (X) or (XI), and an acceptor repeat unit, for example divalent electron- accepting units A² as described herein provided as polymeric repeat units.

The donor polymer may be substituted with one or more reactive groups as described herein.

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 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 compound of formula (I) or (II) : fullerene acceptor weight ratio may be in the range of about 1 : 0.1 - 1 : 1, preferably in the range of about 1 : 0.1 - 1 : 0.5. Fullerenes may be selected from, without limitation, Ceo, C70, C76, C78 and 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).

Fullerene derivatives may have formula (V):

wherein A, together with the C-C group of the fullerene, forms a monocyclic or fused ring group which may be unsubstituted or substituted with one or more substituents.

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

(Va) (Vb) (Vc) wherein R²⁰-R³² are each independently H or a substituent.

Substituents R²⁰-R³² are optionally and independently in each occurrence selected from the group consisting of aryl or heteroaryl, optionally phenyl, which may be unsubstituted or substituted with one or more substituents; and Ci-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.

Substituents of aryl or heteroaryl, where present, are optionally selected from Ci-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.

NFA chain or network formation

A layer comprising a NFA chain or network may be formed by depositing the reactive NFA and any other components of the layer by any process including, without limitation, thermal evaporation and solution deposition methods followed by reaction of the reactive groups.

Preferably, the precursor layer is formed by depositing a formulation comprising the electron- accepting material(s) including the reactive NFA and any other components of the precursor layer, for example one or more electron-donating material(s) in the case of a bulk heterojunction layer, dissolved or dispersed in a solvent or a mixture of two or more solvents followed by evaporation of the one or more solvents. The formulation may be deposited by any coating or printing method including, without limitation, spin-coating, dip-coating, roll- coating, spray coating, doctor blade coating, wire bar coating, slit coating, ink jet printing, screen printing, gravure printing and flexographic printing.

The formulation may comprise a mixture of two or more solvents, preferably a mixture comprising at least one benzene substituted with one or more substituents as described above and one or more further solvents. The one or more further solvents may be selected from esters, optionally alkyl or aryl esters of alkyl or aryl carboxylic acids, optionally a Ci-10 alkyl benzoate, benzyl benzoate or dimethoxybenzene. In preferred embodiments, a mixture of trimethylbenzene and benzyl benzoate is used as the solvent. In other preferred embodiments, a mixture of trimethylbenzene and dimethoxybenzene is used as the solvent.

The formulation may comprise further components. As examples of such components, crosslinking agents, 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.

Following deposition of the materials of the precursor layer, reaction may be effected by any method known to the skilled person including thermal treatment and / or UV irradiation.

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 bulk heterojunction layer before or after reaction of the reactive NFA.

In some embodiments, the reactive NFA is deposited and crosslinked and a further active organic layer is formed on the crosslinked bulk heterojunction layer. The further active organic layer may be an electron-donating layer, a charge-transporting organic layer or charge-blocking organic layer. The material or materials of the further active organic layer may be deposited from a solution or suspension thereof.

Applications

A circuit may comprise the OPD connected to one or more of a voltage source for applying a reverse bias to the device; a device configured to measure photocurrent; and an amplifier configured to amplify an output signal of the OPD. The voltage applied to the photodetector may be variable. In some embodiments, the photodetector may be continuously biased when in use.

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

In some embodiments, a sensor may comprise an OPD as described herein and a light source wherein the OPD is configured to receive light emitted from the light source. In some embodiments, the light source has a peak wavelength of at least 900 nm or at least 1000 nm, optionally in the range of 900-1500 nm. In some embodiments, the light from the light source may or may not be changed before reaching the OPD. For example, the light may be reflected, filtered, down-converted or up- converted before it reaches the OPD.

The organic photoresponsive device as described herein may be an organic photovoltaic device or an organic photodetector. An organic photodetector as described herein may be used in a wide range of applications including, without limitation, detecting the presence and / or brightness of ambient light and in a sensor comprising the organic photodetector and a light source. The photodetector may be configured such that light emitted from the light source is incident on the photodetector and changes in wavelength and/or brightness 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.

The detection surface area of an OPD as described herein may be selected according to the desired application. Optionally, an OPD as described herein has a detection surface area of less than about 3 cm², less than about 2 cm², less than about 1 cm², less than about 0.75 cm², less than about 0.5 cm² or less than about 0.25 cm². Optionally, each OPD may be part of an OPD array wherein each OPD is a pixel of the array having an area as described herein, optionally an area of less than 1 mm², optionally in the range of 0.5 micron² - 900 micron².

Examples

Measurements

Unless stated otherwise, HOMO and LUMO levels of materials as described herein are as measured by square wave voltammetry (SWV). In SWV, the current at a working electrode is measured while the potential between the working electrode and a reference electrode is swept linearly in time. The difference current between a forward and reverse pulse is plotted as a function of potential to yield a voltammogram. Measurement may be with a CHI 660D Potentiostat.

The apparatus to measure HOMO or LUMO energy levels by SWV may comprise a cell containing 0.1 M tertiary butyl ammonium hexafluorophosphate in acetonitrile; a 3 mm diameter glassy carbon working electrode; a platinum counter electrode and a leak free Ag/AgCl reference electrode.

Ferrocene is added directly to the existing cell at the end of the experiment for calculation purposes where the potentials are determined for the oxidation and reduction of ferrocene versus Ag/AgCl using cyclic voltammetry (CV).

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

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

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

A typical SWV experiment runs at 15 Hz frequency; 25 mV amplitude and 0.004 V increment steps. Results are calculated from 3 freshly spun film samples for both the HOMO and LUMO data.

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.

Compound Example 1

Compound Example 1 may be prepared according to the following scheme:

Compound Example 1 Modelling

Modelling of Model Compounds 1 and 2 was performed using Gaussian09 software available from Gaussian using Gaussian09 with B3LYP (functional) and LACVP* (Basis set). Results are set out in Table 1. Table 1

As shown in Table 1, functionalising acceptor group A¹ with a group suitable for attachment of a reactive group, for example an alkoxy group as for Model Compound 2, may result in a shallowing of HOMO and resultant increase in band gap. Therefore, functionalisation of another group of the NFA with a reactive group, preferably the bridging unit or a donor unit, is preferred.

Claims

CLAIMS 1. A method of forming an organic photoresponsive device comprising an anode, a cathode and a photoactive layer disposed between the anode and the cathode, the method comprising: forming a precursor layer over one of the anode and cathode, the precursor layer comprising a reactive non-fullerene acceptor substituted with at least two reactive groups; and forming the photoactive layer comprising reacting the reactive groups to form a chain or network comprising a plurality of molecules of the reacted non-fullerene acceptor; and forming the other of the anode and cathode before or after reaction of the reactive groups.

2. The method according to claim 1 wherein the photoactive layer comprises a chain comprising a plurality of the non-fullerene acceptor molecules linked by a linking group formed upon reaction of the reactive groups with one another or with reactive groups of a linking agent.

3. The method according to claim 1 or 2 wherein the photoactive layer is a bulk heterojunction layer further comprising an electron-donating material.

4. The method according to claim 3 wherein the electron-donating material is a polymer comprising reactive groups capable of reacting with the non-fullerene acceptor reactive groups and wherein the photoactive layer comprises a crosslinked network comprising the electron-donating polymer crosslinked by the non-fullerene acceptor.

5. The method according to claim 1 or 2 wherein the photoactive layer comprises an electron-donating sublayer directly adjacent to and in contact with an electron- accepting sublayer and wherein the precursor layer is a precursor electron-accepting sublayer comprising the reactive non-fullerene acceptor.

6. The method according to claim 1 or 2 wherein the photoactive layer comprises a bulk heterojunction sub-layer and at least one of an electron-donating sub-layer on an anode side of the bulk heterojunction sublayer and an electron-accepting sub-layer on a cathode side of the bulk heterojunction layer and wherein the precursor and wherein the precursor layer comprising the reactive non-fullerene acceptor is a precursor of the electron-accepting sublayer or a precursor of the bulk heterojunction sub-layer.

7. The method according to any one of the preceding claims wherein the reactive groups in each occurence are independently selected from the group consisting of benzocyclobutene and an acyclic or cyclic group comprising a non-conjugated carbon- carbon double bond.

8. The method according to any one of the preceding claims wherein the non-fullerene acceptor is a compound of formula (I) or (II):

A¹ – (B²)x⁵ – (D²)y² – (B³)x³– A² – (B³)x⁴ – (D³)y³ – (B²)x⁶ – A¹ (II) wherein: A¹ in each occurrence is independently a monovalent electron-accepting group; A² is a divalent heteroaromatic electron-accepting group; D¹, D² and D³ independently in each occurrence is an electron-donating group; B¹, B², and B³ independently in each occurrence is a bridging group; x¹ – x⁶ are each independently 0, 1, 2 or 3; y¹, y² and y³ are each independently at least 1; and the compound of formula (I) or (II) is substituted with at least two reactive groups.

9. The method according to claim 8 wherein the at least two reactive groups are substituents of one of D¹, D², D³, B¹, B² and B³.

10. The method according to claim 8 or 9 wherein D¹ is a group of formula (VIIe):

11. The method according to any one of claims 8-10 wherein A¹ is a group of formula (IXa- 1):

(IXa-1) wherein: G is C=O, C=S SO, SO₂, NR³³ or C(R³³)₂ wherein R³³ is CN or COOR⁴⁰ and R⁴⁰ is H or a substituent; R¹⁰ is H or a substituent; Ar⁹ is an unsubstituted or substituted monocyclic or fused aromatic or heteroaromatic group; and X⁶⁰ are each independently CN, CF3 or COOR⁴⁰.

12. A reactive compound formula (I) or (II): A¹ – (B¹)x¹ – (D¹)y¹ – (B¹)x² – A¹ (I) A¹ – (B²)x⁵ – (D²)y² – (B³)x³– A² – (B³)x⁴ – (D³)y³ – (B²)x⁶ – A¹ (II) wherein: A¹ in each occurrence is independently a monovalent electron-accepting group; A² is a divalent heteroaromatic electron-accepting group; D¹, D² and D³ independently in each occurrence is an electron-donating group; B¹, B², and B³ independently in each occurrence is a bridging group; x¹ – x⁶ are each independently 0, 1, 2 or 3; y¹, y² and y³ are each independently at least 1; and the compound of formula (I) or (II) is substituted with at least two first reactive groups.

13. A composition comprising a compound according to claim 12 and an electron-donating material.

14. The composition according to claim 13 wherein the electron-donating material comprises second reactive groups capable of reacting with the first reactive groups.

15. A formulation comprising a compound or composition according to any one of claims 12-14 dissolved or dispersed in one or more solvents.

16. An organic photoresponsive device comprising an anode, a cathode and a photoactive layer disposed between the anode and the cathode wherein the photoactive layer comprises a chain or network comprising a plurality of reacted molecules of formula (I) or (II) according to claim 12.

17. A photosensor comprising a light source and an organic photodetector according to claim 16 wherein the organic photodetector is configured to detect light emitted from the light source.

18. The photosensor according to claim 17, wherein the light source emits light having a peak wavelength of greater than 900 nm.

19. A method of forming an organic photoresponsive device according to claim 16, the method comprising forming a precursor layer comprising a compound of formula (I) or (II) over one of the anode and cathode; forming the photoactive layer comprising reacting the reactive groups to form a chain or network comprising a plurality of molecules of the reacted compound of formula (I) or (II); and forming the other of the anode or cathode before or after reaction of the reactive groups.