GB2624715A

GB2624715A - Composition

Info

Publication number: GB2624715A
Application number: GB2217855.2A
Authority: GB
Inventors: Maciejczyk Michal
Original assignee: Sumitomo Chemical Co Ltd
Current assignee: Sumitomo Chemical Co Ltd
Priority date: 2022-11-28
Filing date: 2022-11-28
Publication date: 2024-05-29
Also published as: GB202217855D0

Abstract

A composition comprises a first electron-accepting compound of formula (I) and a second electron-accepting compound of formula (II): A 1 – (B1 )x1 – (D1 )y1 – (B1 )x2 – A1 (I) A 1 – (B2 )x5 – (D2 )y2 – (B3 )x3 – A2 – (B3 )x4 – (D3 )y3 – (B2 )x6 – A1 (II) wherein: A 1 in each occurrence is independently a monovalent electron-accepting group; A2 is a divalent heteroaromatic electron-accepting group; D1 , D2 and D3 in each occurrence is a heteroaromatic electron-donating group which is unsubstituted or substituted with one or more substituents; B 1 , 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 heteroaromatic group of at least one occurrence of D1 is the same as the heteroaromatic group of at least one occurrence of D2 or at least one occurrence of D3 . The composition may be used in the photoactive layer of an organic photoresponsive device.

Description

COMPOSITION

BACKGROUND

Embodiments of the present disclosure relate to electron-accepting compositions and more specifically compositions for use in 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.

Rui Wang et al, "Achieving high-performance ternary organic solar cells by adding a high hole-mobility non-fullerene acceptor" Dyes and Pigments, vol. 199, 2022, 110083 discloses a non-fullerene acceptor "BTP-cC9", incorporated into a -13M6:Y6" blend of an organic solar cell.

Wenyan Su et al, "Two compatible nonfullerene acceptors with similar structures as alloy for efficient ternary polymer solar cells", Nano Energy, Volume 38, August 2017, Pages 510-517 discloses ternary polymer solar cells based on two non-fullerene acceptors (IDIC and ITIC) with D-A-type polymer (PSTZ) donor.

Feilong Pan et al, "As-cast ternary polymer solar cells based on a nonfullerene acceptor and its fluorinated counterpart showing improved efficiency and good thickness tolerance", J. Mater. Chem. A, 2019,7, 9798-9806 discloses a polymer solar cell containing nonfullerene acceptors IDIC and ID4F and a PBDB-T-SF donor.

SUMMARY

In some embodiments, the present disclosure provides a composition comprising an electron-donating material, a first electron-accepting compound of formula (I) and a second electron-accepting compound of formula (II): Ai -(BI)x -(DI)yl -(BI)x -(I) -(B2)f -(D2)y2-(B3)x3-A2-(B3)x4-(D3)y3-(B2)x6-wherein: A1 in each occurrence is independently a monovalent electron-accepting group; A2 is a divalent heteroaromatic electron-accepting group; DI, D2 and D3 in each occurrence is a heteroaromatic electron-donating group which is unsubstituted or substituted with one or more substituents; B1, B2, and B3 independently in each occurrence is a bridging group; xl -x6 are each independently 0, 1,2 or 3; yl, y2 and y3 are each independently at least 1; and the heteroaromatic group of at least one occurrence of D1 is the same as the heteroaromatic group of at least one occurrence of D2 or at least one occurrence of D3.

In some embodiments, the present disclosure provides a formulation comprising a composition as described herein dissolved or dispersed in one or more solvents.

In some embodiments, 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 composition as described herein.

In some embodiments, the present disclosure provides a photosensor comprising a light source and an organic photocletector as described herein wherein the organic photodetector is configured to detect light emitted from the light source.

In some embodiments, the present disclosure provides a method of forming an organic photoresponsive device as described herein, the method comprising forming the photoactive layer comprising depositing a composition as described herein over one of the anode and cathode; and 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 is a schematic illustration of an organic photoresponsive device according to some 15 embodiments; and Figure 2 is a schematic illustration of the energy levels of a composition comprising an electron-donating material, a first NFA and a second NFA 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. Sonic 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 he 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 bulk heterojunction layer 105 disposed between the anode and the cathode. The organic photoresponsive device may be supported on a substrate 101, optionally a glass or plastic substrate.

The bulk heterojunction layer comprises a composition comprising a first non-fullerene acceptor (NFA) of formula (I), a second NFA of formula (II) and an electron-donating material: -(BI)x1 -(D1)y1 -(BI)x2-(I) Al -(B2)x5 -(D2)y= -(133)x3-A2 -(B3)x4 -(D3)y3 -(132)x6 -Al (1) wherein: Al in each occurrence is independently a monovalent electron-accepting group; A= 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; -x6 are each independently 0, 1, 2 or 3; and yl, y2 and y3 are each independently at least 1.

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 Ds, 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).

Each of DI, D2 and D3 is an optionally substituted conjugated heteroaromatic group. The compound of formula (1) contains at least one conjugated heteroaromatic group DI group which is the same as at least one of preferably both of, the conjugated heteroaromatic groups D2 and Ds of formula (II).

Any substituents of the conjugated heteroaromatic group Di may be the same as or different from any substituents of D2 and D3.

Preferably, DI, D2 and Ds have the same substitution pattern, i.e. if a substituent is present at a specific atom of DI then the same atom of D2 and D3 is preferably substituted. Likewise, if a specific atom of D1 is unsubstituted then the same atom of D2 and Ds is preferably unsubstituted.

Preferably, the, or each, substituent of DI may be the same as or different from the corresponding substituent or substituents of D2 and D3 with the proviso that the substituents are of the same class.

A "substituent class" is a class of substituents that are the same except for their carbon atom count, e.g. their alkyl chain length. Exemplary substituent classes are: CI-20 alkyl; C1-20 alkoxy; phenylene substituted with one or more C1-12 alkyl; and phenylene substituted with one or more Ci_12 alkoxy.

For example, if an atom of DI is substituted with a Cm/ alkoxy then the same atom of D2 and / or D3 is preferably substituted with the same or a different CM, alkoxy.

Most preferably the, or each, substituent of DI is the same as the corresponding substituent or substituents of D2 and D3.

Al of the first NFA of formula (I) may be the same as or different from Al of the second NFA, preferably the same.

Preferably, xl and x2 are the same as x5 and x6.

If xl and x= are each 0 then x5 and x6 are preferably each 0, and more preferably each of x3-x6 is 0.

If x and x= are each at least 1 then x5 and x6 are each preferably at least I. In a particularly preferred embodiment, xl and x= are each 1; x5 and x6 are each 1; and x3 and X4 are each 0.

Where present, 131-. B2 and B3 are preferably the same aromatic, heteroaromatic, vinylene or vinylene(hetero)arylene group and substituents of B1, B2 and B3 may be the same or different. Preferably, a substituent at a position of B1 is preferably of the same substituent class, and more preferably the same substituent, as a substituent at the corresponding position of B= and B3.

The bulk heterojunction layer may consist of the first and second NFA and the electron-donating compound or it may comprise one or more further materials, for example one or more further electron-donating materials and / or one or more further electron-accepting materials.

In some embodiments, the weight of the electron-donating material(s) to the electron-accepting materials 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 each of the first and second NFAs, i.e. the electron-donating material has a shallower HOMO and LUMO that the corresponding HOMO and LUMO levels of each of the NFAs. Preferably, the compounds of formula (I) and (II) each have 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 each one of the compounds of formula (I) and (II) is less than 1.4 eV.

The first and second NFAs preferably form a type II interface.

In some preferred embodiments, the HOMO and LUMO of the second NFA are shallower than those of the first NFA. This embodiment is illustrated schematically in Figure 2.

In some preferred embodiments, the HOMO and LUMO of the second NFA are deeper than those of the first NFA.

By selecting first and second NFAs that have a type II interface, stepwise charge transfer may be achieved, specifically stepwise electron-transport from the electron-donating material to the NFA having the deepest LUMO via the NFA having a LUMO intermediate between the electron-donating material LUMO and the deepest LUMO NFA, and stepwise hole transport from the electron-accepting material having the deepest HOMO to the electron-donating material via the NFA having a HOMO intermediate between the electron-donating material HOMO and the deepest HOMO NFA.

The presence of both a first NFA of formula (I) and a second NFA of formula (H) with the same donor groups may allow for selection of materials that provide stepwise charge transport whilst maintaining good morphology of the bulk heteroj unction layer arising from the presence 15 of the same donor group in both the first and second NFA.

Preferably, each one of the compounds of formula (I) and (II) has a peak absorption wavelength greater than 900 nm, or greater than 1000 nm, optionally less than 1500 nm or 1400 nm.

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

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

Figure 1 illustrates an arrangement in which the photoresponsive device comprises a bulk heteroj unction photoactive layer 105. In other embodiments, the pholoactive layer comprises an electron-accepting sub-layer comprising or consisting of the composition described herein disposed between the anode and cathode; and an electron-donating sub-layer comprising or consisting of one or more electron-donating materials disposed between the anode and the electron-accepting layer and in direct contact with the electron-accepting layer.

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

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

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

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

Optionally, B1 B2 and B3 are selected from units of formulae (VIa) -(VIo): R8 (VIa) (VIb) (VIc) (VId) R8 R8 R55 (Vie) (V1f) (V Ig) (Viii) R8 R8

N

(Vii) (VIj) (VW) (Vii) R8 R8 R8 (VIm) (VIo) wherein Rs is H or a substituent, optionally H or a C1_90 hydrocarbyl group; and R8 in each occurrence is independently H or a substituent, preferably H or a substituent selected from F; CN; NO2; C1_20 alkyl wherein one or more non-adjacent C atoms may be replaced with 0, S. NW, 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 C1_20 hydrocarbyl group.

128 groups of formulae (VIa), (VIb) and (Vic) may be linked to form a bicyclic ring which may be substituted with one or more substituents, optionally one or more substituents selected from F; CN; NO2; CI_20 alkyl wherein one or more non-adjacent C atoms may be replaced with 0, 10 S, NR6, COO or CO and one or more H atoms of the alkyl may be replaced with F. 128 is preferably H, Ci -20 alkyl or C 1_19 alkoxy.

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

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

In compounds of formula (11), 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.

The Al groups of the compound of formula (I) may be the same or different, preferably the same.

The Al groups of the compound of formula (11) may be the same or different, preferably the same.

The Al groups of the compound of formula (I) and the Ai groups of the compound of formula (10 are preferably the same.

Exemplary monovalent acceptor groups include, without limitation, groups of formulae (IXa)-(1Xq) (IXa) R13 (IXb) (IXc) (IXd) (IXe) (IX1) (IXg)

NN

(IX° NC\ Rio R1° NC>S\CN

NC

NC Rl° (IX1) R15 R15 (I)D R13 R16 R16

NN R13

(am) R15 (IXn) R13 (IXo) Ris (IXp) R16 Rio (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.

G is C=0, C=S SO, 502, NR33 or C(R33)2 wherein R33 is CN or C00R40. G is preferably C=0 or 502, more preferably C=0.

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

RI° 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, 5, 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 Ci42 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.

R13 in each occurrence is a substituent, optionally 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. R'5 in each occurrence is independently H; F; 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; aromatic group Ar2, optionally phenyl. which is unsubstituted or substituted with one or more substituents selected from F and C1-11 alkyl wherein one or more non-adjacent C atoms may be replaced with 0, S. NR6, COO or CO; or a group selected from: Y40 z4° **^** z41 z42 Z43 R1.5 < NC) * NC NC oN; ON NC Rio Ri6 is H or a substituent, preferably a substituent selected from: -(A13), wherein Arl in each occurrence is independently an unsubstituted or substituted aryl or heteroaryl group, preferably thiophene, and w is 1, 2 or 3; Y40 z42 z40 *^***:. z41 n> < NC) * CN NC)

NC

NC; Rio 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. Ar6 is a 5-membered heteroaromatic uoup, preferably thiophene or furan, which is unsubstituted or substituted with one or more substituents.

Substituents of Ar3 and Aix". where present, are optionally selected from 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. T', 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 R2' In a preferred embodiment, T3 is benzothiadiazole.

Z1 is N or P. Arg is a fused heteroaromatic group which is unsubstituted or substituted with one or more substituents, optionally one or more non-H substituents R'°. and which is bound to an aromatic C atom of B1 or B2 and to a boron substituent of B1 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 Ai, preferably both groups AI, are a group of formula (IXa-D: (IXa-1) wherein: G is as desciibed above and is preferably C=0 or SO2, more preferably C=0; RI° is as desciibed 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, CFI or COOR4° wherein R4° in each occurrence is H or a substituent, preferably H or a Ci_20hydrocarbyl 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): (IXa-2) each X7-X10 is independently CR12 or N wherein RI-2 in each occurrence is H or a substituent selected from C1.20 hydrocarbyl and an electron withdrawing group. Preferably, the electron withdrawing group is F, Cl. Br or CN, more preferably F. Cl or CN; and for example F or CN.

The C1.20 hydrocarbyl group R12 may be selected from C1.20 alkyl; unsubstituted phenyl; and phenyl substituted with one or more C 1_12 alkyl groups.

In a particularly preferred embodiment, each of X7-XID is CRI2 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. R10 x60 x60

Exemplary groups of formula (ad) include: Fe3 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:

ON

wherein Ak is a CiA2alkylene 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 RI3 R-13 An exemplary group of formula (IXn) is: R16 Groups of formula (IXo) are bound directly to a bridging group B1 or B2 substituted with a group of formula -B(1214)2 wherein 1214 in each occurrence is a substituent, optionally a Cino 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, IVA is selected from C142 alkyl; unsubstituted phenyl; and phenyl substituted with one or more C1-12 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 fol. ula (IXo) are selected from: R15 R15 R15 R15 N> < R15 Acceptor Unit A= A= is preferably a fused heteroaromatic group comprising at least 2 fused rings, preferably at least 3 fused rings.

In some embodiments. A= of formula (II) is a group of formula (VIII): Ris ( R15 * R15 R15 (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 14 or a substituent.

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

Preferred R9 groups are selected from F; CN; NO2; C1-20 alkyl wherein one or more non-adjacent C atoms may be replaced with 0, S. NR17 wherein R17 is a CI-1, 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 a group selected from or 42 4 z1, z and c743 wherein Z4°, z. are each independently CR or N wherein R13 in each occurrence is flora substituent, preferably a C1-20 hydrocarbyl group; Y4° and Y41 are each independently 0, S. NX71 wherein X71 is CN or C00R40; or CX60X61 wherein X6° and X61 is independently CN, CF3 or COOR40; W4° and W41 are each independently 0, S. NX71 or CX60x61 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. R17 as described anywhere herein may be, for example, C142 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 hetcroaromatic groups Arl are oxadiazolc, thiadiazole. triazolc 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 CR I° wherein RI° 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 CRI° with the proviso that at least one of X3, X4, X' and X6 is CR1°.

Z is selected from 0, S, SO2, NR6, PR6, C(R1°)2, Si(R1°)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 CM, COORTh; or CX60x61 wherein)(wand X6 is independently CN, CF3 or COOR4° and R4° in each occurrence is H or a substituent. preferably H or a Ci_20hydrocarbyl group.

A2 groups of formula (VIII) are preferably selected from groups of formulae (Villa) and (VIIIb): N%s7N (Villa) (VII 1b) For compounds of formula (V II lb), the two R7 groups may or may not be linked.

Preferably, when the two R7 groups are not linked each 12.7 is independently selected from H; F; CN; NOn; Ci_no alkyl wherein one or more non-adjacent C atoms may be replaced with 0, S. NR6, CO, COO, NR6, PR6, or Si(121°)2 wherein RI° 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 Cirm 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 IV groups are linked, the group of formula (VII1b) has formula (VIIIb-1) 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)-(Iyj) 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 Di, D2 and D3 include groups of formulae (VIIa)-(VIIp): (VI la) (VIlb) R52 R51 R52 (VHC) (VIId) R53 R53 91 R53 R53 R53 (Vile) (Vhf) R54 R54 (VIIg) R54 R54 R54 R5' R54 R54 (Viii) (V 11j) wherein YA in each occurrence is independently 0, S or NR55; YA1 in each occurrence is independently 0 or S; ZA in each occurrence is 0, CO, S. NR55 or C(R54)1; R51, R52 R54 and R55 independently in each occurrence is H or a substituent; R'3 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_,0 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 A13 which is unsubstituted or substituted with one or more substituents.

In some embodiments, A13 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, D2 and D3 are each a group of formula (Vile).

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

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

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

In the case where y1 of formula (I) is greater than 1, e.g. 2 or 3, or at least one of y2 and yn of formula (II) is greater than 1, e.g. 2 or 3, the chain of DI, D2 or D3 groups, respectively, may be linked in any orientation.

Exemplary first and second NFA combinations include: Electron-donatin2 material Exemplary electron-donating materials of a photoactive layer as described herein are disclosed in, for example, W02013/051676, the contents of which are incorporated herein by reference.

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

In a preferred embodiment the electron-donating material is an organic conjugated polymer, which can be a homopolymer or copolymer including alternating, random or block copolymers.

The conjugated polymer is preferably a donor-acceptor polymer comprising alternating electron-donating repeat units and electron-accepting repeat units.

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

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

Optionally, the electron-donating polymer has a HOMO level no more than 5.5 eV from vacuum level. Optionally, the electron-donating polymer has a HOMO level at least 4.1 eV from vacuum level. As exemplary electron-donating polymers, polymers selected from conjugated hydrocarbon or heterocyclic polymers including polyacene, polyaniline, polyazulene, polybenzofuran, polyfluorene, polyfuran, polyindenofluorene, polyindole, polyphenylene, polypyrazoline, polypyrene, polypyridazine, polypyridine, polytriarylamine, poly(phenylene vinylene), poly( 3-substituted thiophene), poly(3,4-bisubstituted thiophene), polyselenophene, poly -substituted selenophene), poly(3,4-bisubstituted selenophene), poly(bisthiophene), poly(terthiophene), poly(bisselenophenc), poly(tersclenophene), 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 benzothiadiazole-based and thiophene-based repeating units, each of which may be substituted.

A particularly preferred donor polymer comprises a repeat unit of formula (X): (X) wherein YA, ZA, WI and Rm 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 allcyl 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 Ar6 which is unsubstituted or substituted with one or more substituents selected from F and C1_11 alkyl wherein one or more non-adjacent, non-temtinal C atoms may be replaced with 0, S, COO or CO.

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

Fullerene In some embodiments, the compounds of formulae (I) and (II) are the only electron-accepting materials of an electron-accepting sub-layer or a bulk heterojunction layer as described herein.

In some embodiments, an electron-accepting layer or a bulk heterojunction layer contains compounds of formula (I) and (II) and one or more further electron-accepting materials. Preferred further electron-accepting materials are fullerenes. The combined weight of the compounds of formula (I) and (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, C60, C70, C76, C78 and C84 fullerenes or a derivative thereof, including, without limitation. PCBM-type fullerene derivatives including phenyl-Cm-butyric acid methyl ester (C60PCBM), TCBM-type fullerene derivatives (e.g. tolyl-Cm-butyric acid methyl ester (C60TCBM)), and ThCBM-type fullerene derivatives (e.g. thienyl-Cm-butyric acid methyl ester (C60ThCBM).

Fullerene derivatives may have formula (V): (CC

FULLERENE (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 Chi/ 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. Formulations The photoactive layer may be formed by any process including, without limitation, thermal evaporation and solution deposition methods.

Preferably, an electron-accepting sub-layer or a hulk heterojunction layer is formed by depositing a formulation comprising the first and second NFAs and any other components of the layer, including one or more electron-donating materials in the case of a bulk heterojunction layer, dissolved or dispersed in a solvent or a mixture of two or more solvents followed by evaporation of the one or more solvents. The formulation may be deposited by any coating or printing method including, without limitation, spin-coating, dip-coating, roll-coating, spray coating, doctor blade coating, wire bar coating, slit coating, ink jet printing, screen printing, gravure printing and flexographic printing.

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

The formulation may comprise further components in addition to the electron-accepting material, the electron-donating material and the one or more solvents. As examples of such components, adhesive agents, defoaming agents, deaerators, viscosity enhancers, diluents, auxiliaries, flow improvers colourants, dyes or pigments, sensitizers, stabilizers, nanoparticles, surface-active compounds, lubricating agents, wetting agents, dispersing agents and inhibitors may be mentioned.

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

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

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

In some embodiments, a sensor may comprise an OPD as descrthed 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 lid" 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 he 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 he, without limitation, a gas sensor, a biosensor, an X-ray imaging device, an image sensor such as a camera image sensor, a motion sensor (for example for use in security applications) a proximity sensor or a fingerprint sensor. A 1D or 2D photosensor array may comprise a plurality of photodetectors as described herein in an image sensor. The photodetector may be configured to detect light emitted from a tat-get 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 he selected according to the desired application. Optionally, an OPD as described herein has a detection surface area of less than about 3 em2, less than about 2 em2, less than about 1 cm2, less than about 0.75 em2, less than about 0.5 cm2 or less than about 0.25 cm2. Optionally, each OPD may he part of an OPD ifray 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 micron= -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 voltammogram. Measurement may he 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 20 data.

Unless stated otherwise, absorption spectra were measured using a Cary 5000 UV-VIS-NIR Spectrometer. Measurements were taken from 175 nm to 3300 mu using a PbSmart MR 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.

Claims

CLAIMS1. A composition compiising a first electron-accepting compound of formula (I) and a second electron-accepting compound of formula (II): A1 -(B1)x1 -(D1)y1 -(B1)x2 -A (I) A1 -(B2)x5 -(D2)y2 -(B3)x3-A2 -(B3)x4 -(D3)y3 -(B2)x6 -Al (II) wherein: Al in each occurrence is independently a monovalent electron-accepting group; A= is a divalent heteroaromatic electron-accepting group; DI, D2 and D3 in each occurrence is a heteroaromatic electron-donating group which is unsubstituted or substituted with one or more substituents; B2, and B3 independently in each occurrence is a bridging group; xl -x6 are each independently 0, 1,2 or 3; y2 and y3 are each independently at least 1; and the heteroaromatic group of at least one occurrence of DI is the same as the heteroaromatic group of at least one occurrence of D2 or at least one occurrence of D3.
2. The composition according to claim I wherein the compound of formula (1) and the compound of formula (11) form a type II interface.
3. The composition according to claim 1 or 2 wherein y I is 1.
4. The composition according to any one of the preceding claims wherein y2 and y3 are each 1.
5. The composition according to claim 3 or 4 wherein the heteroaromatic group of D1 is the same as the heteroaromatic group of each occurrence of D2 and each occurrence of D3.
6. The composition according to any one of the preceding claims the heteroaromatic group of DI is substituted with one or more substituents and wherein at least one of D2 and D3 is substituted with the same substituent or substituents as DI at the same substitution position or positions as D1.
7. The composition according to any one of the preceding claims wherein DI is a group of formula (VIIf): R53 R53 R51 R53 R53 (VIIf) wherein YA is S or 0, Rit is H or a substituent and R'3 is a substituent.
8. The composition according to any one of the preceding claims wherein x1 and x2 are each at least 1.
9. The composition according to claim 8 wherein at least one of x3-x6 is at least 1.
10. The composition according to claims 8 and 9 wherein B1 is selected from an unsubstituted or substituted vinylene, arylene, heteroarylene, arylenevinylene and heteroarylenevinylene and wherein B2 and / or B3 is the same unsubstituted or substituted vinylene, arylene, heteroarylene, arylenevinylene or heteroarylenevinylene.
11. The composition according to claim 10 wherein B1 is substituted with at least one substituent and wherein at least one of B2 andB3 is substituted with the same substituent or substituents as B1 at the same substitution position or positions as B1.
12. The composition according to any one of the preceding claims wherein each A1 is independently a group of formula (IXa-1): (1Xa-1) wherein: G is C=0, C=S SO, SO2, NR33 or C(R33)2 wherein R33 is CN 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
13. The composition according to any one of the preceding claims wherein Al groups of formula (I) are the same as Al groups of formula (II).
14. The composition according to any one of the preceding claims wherein the composition further comprises an electron-donating material.
15. A formulation comprising a composition according to any one of the preceding claims 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 composition according to any one of claims 1-14.
17. A photosensor comprising a light source and an organic photodetector according to claim 15 wherein the organic photodetector is configured to detect light emitted from the light source.
18. The photosensor according to claim 16, 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 15, the method comprising forming the photoaetive layer comprising depositing a composition according to any one of claims 1-13 over one of the anode and cathode; and formin the other of the anode and cathode over the photoactive layer.