GB2589570A

GB2589570A - Photoactive composition

Info

Publication number: GB2589570A
Application number: GB1917455.6A
Authority: GB
Inventors: Yaacobi-Gross Nir
Original assignee: Sumitomo Chemical Co Ltd
Current assignee: Sumitomo Chemical Co Ltd
Priority date: 2019-11-29
Filing date: 2019-11-29
Publication date: 2021-06-09
Also published as: WO2021105706A1; JP2023503338A; GB201917455D0; GB202011798D0; CN114746427A

Abstract

A composition comprising an electron donor material and a first electron accepting material wherein the electron donor material is a polymer; the electron accepting material is a nonpolymeric compound; and the electron donor material and electron accepting material both comprise an electron donor group of formula (I): X and Y are each independently selected from S, O or Se; Z is O, S, NR2 or CR32; Ar1-Ar6 are each independently an unsubstituted or a substituted benzene, an unsubstituted or a substituted 5- or 6- membered heteroaromatic group or are absent; A1 and A2 are each independently an unsubstituted or a substituted benzene, an unsubstituted or a substituted 5- or 6- membered heteroaromatic group, a non-aromatic 6-membered ring having ring atoms selected from C, N and O or are absent; n is 1, 2 or 3; R1 independently in each occurrence is H or a substituent; R2 is a substituent; each R3 is independently H or a substituent. Also shown is a method of forming an organic photoresponsive device and a method of determining the presence/concentration of a target material in a sample using the photoresponsive device.

Description

PHOTOACTIVE COMPOSITION

BACKGROUND

Embodiments of the present disclosure ure relate to photoactive compounds and more specifically, but not by way of limitation,to photoactive materials containing electron-donating units suitable for us as an electron-donating material or an electron-accepting material in a photoresponsive device.

Organic photoresponsive devices are knoiArr EP 3121211 discloses a polymer of formula: W02012008556A1 discloses a photoelectric conversion element con nina olymer having a repeat unit represented by Formula (I): (R)2 -Ar-W02011052712 discloses a photoelectric conversion element containing a polymeric compound having a structural unit represented by formula (1): Liu et al, "Ternary Blend Strategy for Achieving High-Efficiency Organic Solar Cells with Nonfullerene Acceptors Involved" Adv. Func. Mat, 2018, 28 (29), 1-20, discloses nonfullerene acceptor C0i8DFIC.

He et al, "A-D-A small molecule acceptors with ladder-type arenes for solar cell" .1. of lat. Chem. A, 2018, 6, 8839-8854" discloses C0i8DIFIC with an uhranarrow ba.ndgap of 1 26V.

Xu et al "The progress and prospects of non-fullerene acceptors in ternary blend organic solar cells" Mat. Horizons, 2018; 5,206-221, discloses C0i8DIFIC.

Xiao et al, "26 mA crn2 Jsc from organic solar cells with a low-bandgap nonfullerene to acceptor" Sol. Bull., 20 17 62, 1494, discloses the A-D-A non-full erene acceptor, COiSDFIC which has a narrow optical bandgap of 1.26eV.

SUMMARY

According to some embodiments of the present disclosure, there is provided a composition comprising an electron donor material and a first electron accepting; material. The electron donor material is a. polymer. The electron accepting material is a non-polymeric compound. The electron donor material and electron accepting material both comprise an electron donor woup of formula (1).

wherein: X and Y are each independently selected from S. 0 or Se; Z is 0, 5, NR2 orCR32.

are each independently an unsubstituted or a substituted benzene, an u ubstituted or a substituted 5-or 6-membered heteroaromatic group or are absent; AI and A' are each independently an unsubstituted or a substituted benzene, an unsubstiluted or a substituted 5-or 6-membered heteroaromatic group, a non-aromatic 6-membered ring having ring atoms selected from C, N and 0 or are absent; n is 1,2 or 3; R independently in each occurrence is H or a substituent; each R3 is independently H or a substituent.

Optionally, the electron acceptor mate s a compound of formula (II): EAG1 EAGI, (L2/0

RI (11)

10wnere in and o are each independentLy 0 or an integer of 1 or more, 1,1 is a bridging group when in is I or more or a direct bond when in is 0, L2 is a bridging group when o is 1 or more or a direct bond when o is 0, and each EAG1 independently represents an electron accepting group.

Optionally, the compound of formula (H) has formula Mal: Optionally" each ItAG1 is independently a g Ia ( "21).

wherein: RH' in each occurrence is H or a substituent selected from the group consisting of C1.12 alkyl wherein one or more non-adjacent, non-terminal C atoms may be replaced with 0, S, COO or CO and one or more H atoms of the alkyl may be replaced with F; and an aromatic group Ar7 which is unsubstituted or substituted with one or more substituents selected from F and C1-alkyl wherein one or more non-adjacent, non-terminal C atoms may be replaced with 0 S COO or CO, ----represents a linking position in the compound of formula (II); and each X'-X4 is independently CR' 7 or N wherein R'7 in each occurrence is H or a substituent selected from C1.20 hydrocarbyt and an electron withdrawing group.

Optionally, the electron-accepting material is C0i8DFIC: Optionally, the electron donor polymer comprises a repeating structure of ormul.

wherein EAG is an electron-accepting gro Optionally, the repeating structure of formula (Ill) has formula a): *

S

wherein each le is independently or a substituent.

Optionally, the electron donating polymer comprises a repeating structure of formula: Optionally, the composition further comprises a second electron accepting material.

Optionally, the second el ectron-acce a tullerene or a derivative thereof.

According to some embodiments of the present disclosure, there is provided a formulatior comprising one or more solvents and a composition as described herein dissolved Or dispersed in the one or more solvents According to some embodiments of the preset disclosure there is provided a. photoresponsive device comprising an anode, a cathode and a photosensitive layer disposed between the anode and the cathode:, wherein the photosensitive layer comprises a composition as described herein.

Optionally, the photoresponsive device is an organic photodetector.

According to some embodiments of the present disclosure, there is provided a photosensor comprising a light source and a photoresponsive device as described herein, wherein the photosensor is configured to detect light emitted from the light source.

Optionally., the light source emits lying a peak wavelength greater than 750 nm.

Optionally, the photosensor is configured to receive a sample in a light path between the organic photodetector and the light source.

According to some embodiments of the present disclosure, there is provided a method of forming an organic photoresponsive device as described herein comprising formation of the photosensitive organic layer over one of the anode and cathode a.nd formation of the other of the anode and cathode over the photosensitive organic layer.

Optionally, formation of the photosensitive organic layer comprises deposition of a formulation as described herein.

According to some embodiments of the present disclosure, there is provided a method of determining the presence and or concentration of a target material in a sample, the method comprising illuminating the sample and measuring a response of an organic photodetector as described herein.

DESCRIFTION 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 embodim Figure 2 shows external qitantum efficiencies vs. wavelength For an organic photodetector according to some embodiments and a comparative organic photodetector containing a comparative non-fullerene electron acceptor I FIC0-4F; Figure 3A shows external quantum efficiencies vs. wavelength for an organic photodetector according to some embodiments and a comparative organic photodetector containing a comparative non-fullerene electron acceptor lEIC0-4C11/44; Figure 3B shows current densities vs. voltage for organic ohotorletectors of Figure 3.A which are not exposed to light; Figure 4A shows external quantum efficiencies vswavelength for an organic photodetector according to some embodiments and a comparative organic phoiodetector containing a comparative electron donor; and Figure 4B shows current densities vs. voltage for the organic photodetectors of Figure 4A which are not exnosed to light 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 sonic 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 constnted 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 ir: 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 are may be present. References to a layer "on" another layer when used in this application means that the layers are ill direct contact.

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, certam 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, Figure i 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 heterojuncti on 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 heteroiunction layer comprises an electron donor material and a firstn acceptor material.

The electron donor (p--type) material has a HOMO deeper (further from vacuum) than a LUMO of the first election acceptor (n-type) material. Optionally, the gap between the HOMO level of the p-type donor material and the 'LIAM level of the n-type acceptor material is less than 1.4 eV. Unless stated otherwise. HOMO and LUMO levels of materials as described herein are as measured by square wave voltammetry The electron donor material and the first electron acceptor material both comprise an electron donor group of Formula (I): (I) wherein: X and Y are each independently selected from S, 0 or Se; Z is 0, 5, NR2 orCR32 Ari-Ar6 are each independently an unsubstituted or a substituted benzene, an unsubstituted or a substituted 5-or 6-membered heteroaromatic group or are absent; A' and A2 are each independently an unsubstituted or a substituted benzene, an ubstituted or a substituted 5-or 6-membered heteroaromatic group, a non-aromatic 6-membered ring having ring atoms selected from C, N and 0 or are absent; n is R independently in each occurrence is H or a substituent; R2 is a substituent; and each R is independently H or a substituent.

The prese nventors have found that a bulk hetero]unction layer of an organic photodetector containing a donor material and an first acceptor material which both comprise a donor group of formula (1) may result in lower dark current, i.e. current when no electromagnetic radiation n the device, as compared to a donor-acceptor system in which one of the donor and acceptor does not contain a donor group of formula (T).

The present inventors have found that an organic photodetector containing a. donor material and an acceptor material which both comprise a donor group of formula (j) may be particularly suitable for detecting long wavelengths of light, e.g. greater than about 850 mit optionally in the range of 850-1500 nm, optionally in the range of about 850-1000 nm.

The electron donor material and the first electron acceptor material may each contain an electron-donor group of formula (I) and an electron-accepting group (EACi).

For each electron donor material and electron acceptor material containing an electron donor group of formula (0 and an electron-accepting group the, or each, FAG has a LUMO level that is deeper (i.e. ftrther from vacuum) than the group of formula (1), preferably at least eV deeper. The LUMO levels of [AG and formula (I) may be as determined by modelling the LUMO level of EAG-H or H-EAG-H with that of II-Formula (01-H, i.e. by replacing the bonds between FAG and Formula (1) with bonds to a hydrogen atom. Modelling may be performed using Gaussian09 software available from Gaussian using Gaussian09 with B3LYP (functional) and LACVP* (Basis set).

Preferably, the first electron acceptor has a molecular weight of less than 5,000 Daltons, optionally less than 3,000 Dattons. Preferably, the first electron acceptor contains no more than 3 groups of formula Preferably, the polystyrene-equivalent number-average molecular weight (Mn) measured by gel permeation chromatography of the electron donor polymer described herein is in the -6 range of about 5x103 to lx10s, and preferably lx104 to 5x10-. The polystyrene-equivalent weight-average molecular weight (Mw) of the polymers described herein may be lx103 to IA108, and preferably lx104 to 1x107 Preferably, the first election acceptor is a non-polymeric compound. Preferably, the first electron acceptor contains only one group of formula. (I).

The first electron acceptor material is more preferably a compound of formula (fI): Ci m and o are each independently 0 or an integer of 1 or more, L is a bridging group when rn is 1 or more or a direct bond when m is 0; L2 is a bridging group o is l OF more or a direct bond when o * and each EAG Independently represents an electron accepting cup. Preferably, in and o are 0, or 2.. Preferably, m and o are he same. Preferably, the compound of formula (JO has formuLa Ma), EAG1 G1 Preferably, n of:Comilla (ha) is I An exemplary compound of formula olio is li0i81

II

Where the bridging groups LI and L2 are present, LI and L2 may each independently be a group of formula (XV) or formula (XVI): (XV) (XVI) v'Therein-X1, X1 and X are each independently 5, 0 or Se; represents a point of attachment to Formula (I); represents a point of attachment to EAG; and R6, R7, R8 and R9 are each independently H or a substituent, optionally a substituent selected from F.; C1,20 alkyl wherein one or more non-adjacent, non-terminal C atoms may be replaced with 0, S. COO or CC) 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 substiments, optionally one or more C1.42 alkyl groups 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 By "non-terminal" C atom of an alkyl group as used herein is meant a C atom of the alkyl other than the methyl C atom of a linear (n-alkyl) chain or the methyl C atoms of a branched alkyl chain.

Preferably. I_ and C are each independently selected from the following formulae: wherein R is a Ci 2 hydrocarbyl group, optionally C1-12 Preferably; the electron donor material comprising a group of formula (I) is a polymer comprising a repeat unit of formula (I), more preferably a polymer comprising a repeating group of formula (III): EAG2 wherein EAG2 is an electron-ace pting group.

Preferably, the repeating structure of formula WI as formula (pia): (111a) where, r Z. R1 and EAG2 are as described above, and Rri independently in each occurrence is H or a substiment. Preferably, each R4 is independentty selected from 11 or a substituent as described with respect to R6, R7, if and R9. More preferably, each R4 is H. Preferably. formula CO of the electron-donating polymer has formula: Optionally, R of the group of formula (I) cif the electron donor material or the electron acceptor material is, independently in each occurrence, selected from: -11; F; C1 -2 0 alkyl wherein one or more non-adjacent, non-terminal C atoms may be replaced with 0, S, COO or CO and one or more H atoms of the alkyl may be replaced with F, and phenyl which is unsubstituted or substituted with one or more substituents, optionally one or more C1..12 alkyl groups wherein one or more non-adjacent, 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. Optionally, R2 of the group of formula (1) of the electron donor material or the electron acceptor material is, independently in each occurrence, selected from C1.30 alkyl wherein one or more non-adjacent, non-terminal C atoms may be replaced with 0, S. (100 or CO and one or more H atoms of the alkyl may be replaced with F; and an aromatic group Ars, optionally phenyl, which is unsubstituted or substituted with one or more substituents selected from F and CI.12al kyt wherein one or more nonadjacent, non-terminal C atoms may be replaced with 0, 5, COO or CO.

Preferably, R2 is selected from a C1.41) alkyl; unsubstituted phenyl; or phenyl substituted with one or more substituents selected from C 1_12 alkyl and C1.12 at koxy.

Optionally, R3 of the group of formula (t) of the electron donor material or the electron acceptor material is, independently in each occurrence, selected from H; F; C1.20 alkyl wherein one or more non-adjacent, non-terminal C atoms may be replaced with 0, 5, COO or CO and one or more H atoms of the alkyl may be replaced with 114, Si(R2)3; and an aromatic group Ar, optionally phenyl, which is unsubstituted or substituted with one or more substituents. Two R2 groups attached to the same carbon atom may be linked to form a ring, e.g. a cycloalkyl ring or an aromatic or heteroaromatic ring, e.g. fluorene.

Substituents of Ars may be selected from selected from F; Ci.30 alkyl wherein one or more non-adjacent, non-terminal C atoms may be replaced with 0, 5, COO or CO; and COOII or a salt thereof -6 of the group of formula of electron donor material or the electron acceptor material are., independently in each occurrence, preferably benzene or thiophene, each of which is optionally and independently unsubstituted or substituted with one or more sub sti tuents.

Preferably, A and A-of the group of formula (I) of the electron donor material or the electron acceptor material are, independently in each occurrence, cyclohexane, wherein optionally one or more carbon atoms are replaced with S. MR or a Preferably, Al and A2 each independently have formula: wherein Z and R' are as described above.

s present then preferably at least Aril and Ar" of Arl-Ar-are present. If A2 is present the preferably at least Ar4 and AP of Ar4-Ar6 are present.

Ar2, Ar3, Ar4. Ar5, Ar6 A' and A2 are each independently and optionally unsubstituted or substituted with one or more substituents, optionally one or more substituents selected from F; C1,20 alkyl wherein one or more non-adjacent, non-terminal C atoms may be replaced with 0, 5, COO or CO and one or more Fl atoms of the alkyl may be replaced with F; and -B(RI4)2 wherein R14 in each occurrence is a substituent, optionally a C1.20hydrocarbyl group, 5is preferably 0 or NR2i X and Y are each preferably S. The monovalent EAG I groups of formula (II) may be the same or different, preferably the same. Optionally, each EAG of formula 0.0 is selected from forimilae (IV)-(XIV): (Iv) ( CVO (V ta) (Alb) NC (V11b) R1° CN NC C,N (Ville)

NC

N ' RI° (VW) (IX) 1 a

N

N Ri3

Rib (X) (XI) (XII) (XIV) ---represents a bond to L', L2 aposition de o cl by -of Formula (I) A 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.

Ril) is H or a substituent, preferably a substituclit selected from the group consisting of C1-12 alkyl wherein one or more non-adjacent, non-terminal C atoms may be replaced with 0, S, COO or CO and one or more H atoms of the alkyl may be replaced with F; and an aromatic group Ar7, 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, non-terminal C atoms may be replaced with 0, S, COO or CO.

Preferably, R" is FL J is 0 or S. in each occurrence is a substituerd optionally C1-12 alkyl wherein one or more nonadjacent, non-terminal C atoms may be replaced with 0, S, COO or CO and one or more El atoms of the alkyl may be replaced with F R15 in each occurrence is independently H; F; C14 2 alkyl wherein one or more non-adjacent, non-terminal C atoms may be replaced with 0, S, COO or CO and one or more IT atoms of the alkyl may be replaced with F; or an aromatic group Ar, optionally phenyl, which is unsubstituted or substituted with one or more substituents selected from F and C alkyl wherein one or more non-adjacent, non-terminal C atoms may be replaced with 0, S. COO or CO.

substituent, preferably a substituent selected from: -Oil. wherein Ar-in each occurrence is independently an unsubstituted or substituted aryl or heteroaryl group, preferably thiophene, and w is 1, 2 or 3; C1-12 alkyl wherein one or more non-adjacent, non-terminal C atoms may be replaced with 0, S, COO or CO and one or more H atoms of the alkyl may be replaced with F. Arm is a5--membered heteroarylene group, preferably throphene or furan, which is unsubstituted or substituted with one or more substituents.

Substituents of and Ar"), where present, optionally select 111 CI-12 alkyl wherein one or more non--adjacent, non-terminal C atoms may be replaced with 0, S, COO or CO and one or more H atoms of the alkyl may be replaced with F. Z1 is N or P T', T2 and T3 each independently represent an aryl or a heteroaryl ring which may be fused to one or more further rings. Substituents of ii.T2 and Tel, where present, are optionally selected from non-IT groups of R15 Ar8 is a fused heteroaromatic group which is unsubstituted or substituted with one or more A preferred group of formula (IV) s form ula IV a.).

Preferably at least one, more preferably each, EACi is a group of foi [Hula ' Pla) wherein: RI" is as described above; ----represents a linking position to Lt, L2 or * of forniuls each XI-X4 is independently CRI ' or N wherein R'' in each occurrence is H or a substituent selected from C1_70 hydrocarbyt and an electron withdrawing group. Optionally; the electron withdrawing group is F, Cl, Br or CN.

The C1.20 hydrocashyl group R-may be selected from Ci20 alk ubstituted phenyl; and phenyl substituted with one or more C i.12 alkyl groups.

Exemplary EM1 groups of -formula (IVO or (sib) include:

CN CN

CN

wherein Ak is a C112 alkyl ene chain in which one or more C atoms may be replaced with 0, S. CO or COO; An is an anion, optionally -S03-. and each benzene ring is independently unsubstitued or substituted with one OF more substituents selected from substituents described with reference to R 'n.

Exemplary FAG' groups of formula (X) are.

An exemplary EM' group of formula (XII) is: In the case where at least one FAG' is a group of formula (XIV), the group of formula (I) is substituted with a group of formula -B(414)2 wherein R14 in each occuiTence is a substituent, optionally a C120 hydrocarb-y1 group; is bound to a position denoted by * in Formula (I); and is a bond to the boron atom of --B(R14),.

Optionally, R" is selected from C1.12alkyl; unsubstituted phen and phenyl substituted with one or more C1.12 alkyl groups The group of formula (1.), the group of fommila (XIV) and the B(11.11) substituent of foimula (I) may be linked together to form a 5-or 6-membered ring.

in some embodiments, EAG or formula (XIV) is selected from formulae (Xlsizt) Vb) at (NriVc)- -Va) X) (XIV c) lent E '2 groups of formula (III) are preferably selected from -divalent analogues of formulae (IX)-(X0) wherein R16 is a bond to * of formula (I); and divalent analogues (Xala) and (Vila) of formulae (Xle and (respectively: R13 Preferred divalent E.AG2 groups are: wherein Xis S, Y is flora sub, IT a C1 alkyl or F and R is R.13.

In some embodiments, the bulk heterojunction layer consists of the electron donor material and the first electron acceptor material. In some embodiments, the bulk heterojunction layer comprises or consists of the electron donor material, the first electron acceptor material and one or more further electron acceptor materials. in some embodiments, the bulk heteroiunction layer comprises or consists of the electron donor material, the first (nonfullerene) electron acceptor material and a second fullerene electron acceptor material.

[0001] Exemplary fullerene electron acceptor materials are C60, C70, C76, C78 and C84 fullerenes or a derivative thereof including, without limitation, PC:BM-type fullerene derivatives (including phenyl-Col -buivric acid methyl ester. ( C113.N4)" TOM-type fullerene derivatives (e.g mlvi -C6 I -butyric acid opTCHIVW, and ThCBM-type fullerene derivatives (e.g i en 1-CbI-buLyric acid methyl esteriThCBI11).

[0002] Fulierene derivatives may have formula (111): 010 [0003] 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.

[0004] Exemplary fullerene derivatives include formulae (II la), (Nib) and (Ilk): R24 R29 R39 ()Ha) where R2c)-R.32 are each independently I-1 or a subs e [0005] Substi merits R21--13,232 are optionally and independently in each occurrence selected from the group consisting of aryl or neteroaryi, optionally phenyl, which may be unsubstituted or substituted with one or more substituents and C:.20 alkyl wherein one or more non-adjacent, non-fermi mil C atoms may be replaced with 0, S2 CO or COO and one or more H atoms may be replaced with E. [0006] Substituents of aryl or heteroaryl, where present., are optionally selected from C1.12 alkvl wherein one or more non-adjacent, non-terminal C atoms may be replaced with 0, S. CO or COO and one or more H atoms may be replaced with F. In some embodiments, the weight of the donor to the one or more acceptors is from about 1:0,5 to about 1:2.

Preferably, the weight ratio of the donor to the one or more acceptors is from about 1:1 about 1:2.

Optionally, the weight of the first acceptor is greater than the g.)t of the donor.

At least one of the anode and cathode is transparent so that light incident on the device may reach the bulk heterojunctiort layer. In some embodiments, both of the anode and cathode are transparent.

Each transparent electrode preferably has a transmittance of at least 70%, optionally at least 80%, to wavelengths in the range of 400-750 am or 750-1000 mu. The transmittance may be selected according to an emission wavelength of a. light source for use with the organic 20 photodetector.

Figure I 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 area of the OPD may be less than about 3 cm2, less than about 2 cm2, less than about 1 cm2, less than about 0.75 cm2, less than about (15 cm2 or less than about 0.25 cm2.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.

BO The bulk heterojunction layer may be formed by any process including, without limitation, thermal evaporation and solution deposition methods.

Preferably,the bulk heterojunction layer is formed by depositing a formulation comprising the electron donor match al, the first electron acceptor material and any other components of the bulk heterojunction layer dissolved or dispersed in a solvent or a mixmre of two 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 exograp hi c printing.

The one or more solvents of the formulation may optionally comprise or consist of benzene substituted with one or more substituents selected from chlorine, Ci-lo alkyl and Ciera alkoxy wherein two or more substituents may be linked to form a ring which may be unsubstituted or substituted with one or more CI _6 alkyl groups, optionally toluene, xylenes, trimethylbenzenes, tetramethylbenzenes, anisole, indane and its alkyl-substituted derivatives, and tetralin and its alkyl-substituted derivatives.

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 121;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 dimetboxybenzene is used as the solvent.

The formulation may comprise further components in addition to the electron acceptor, the electron donor and the one or more solvents. As examples of such components, adhesive agents, &foaming 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, Each of the anode and cathode ma) dependently be a single conductive layer or may comprise a plurality of layers.

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

A circuit may comprise the OPD connected to a voltage source for applying a reverse bias to the device and it or a device configured to measure photocurrent 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 fight sourc wherein the GPI) is configured to receive light emitted from the light source.

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 unconverted 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 tight 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 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 ot'photodetectors as described herein in an image sensor.

EXA MPLES

Formulation Exam Me 1 Semiconducting Polymer I (electron donor), C0i8DFIC (nomfullerene electron acceptor) and PCBM (fullerene electron acceptor) were dissolved in 1,2,4-trimethylbenzene 1,2-dimethoxybenzerte (95: 5 vt v) in a Polymer: C0i8DFIC PCBM weight ratio of 1: 1.05 to 045.

Semiconducting Polymer Example I C0i8DFIC Phenyl-Col-butyric acid methyl ester (PCBI'v) Comparative Formulation IA For the purpose of comparison, a formulation was prepared as described for Formulation Example 1 except that C0i8DF IC was replaced with the non-fullerene acceptor 1E1C0-4F: 1.0 ON IFICO-4CF Comparative F ation_AB For the purpose of comparison, a formulation was prepared as described for Formulation Example I except that C0i8OF IC was replaced with the non-fullerene acceptor IELCO-LICN:

NC C

WIC0-4C7N Comparative Formulation 2 For the purpose of comparison, a formulation was prepared as described for Formulation Example 1 except that Semiconducting Polymer Example 1 was replaced with Comparative Polymer Example 1, PTIVT-Th: 7.0 PTIP-Th The HOMO, 1,,TIVIO and band gap values of IFIC0-4F, -4( N and COi8IDFIC arc

provided in Table

HOMO and LUNIO measurement was carried out by square wave voltammetry using a CEI16601) Electrochemical workstation with software (II Cambria Scientific Ltd), CHI 104 3mm Glassy Carbon Disk Working Electrode (II Cambria Scientific Ltd), a platinum wire auxiliary electrode and a reference Electrode (AulAgC1) (Havard Apparatus Lid). Acetonitrile (available as Hi-dry anhydrous grade-ROM1L) was used as the cell solution solvent. Ferrocene (available from FLITKA) may be used as the reference standard. Tetrabutylammoniumhexalluorophosphate (available from ELLIKA) may be used as the cell solution salt. The HOMO and LIMO values are measured from a dilute solution (0.3w%) in toluene. The measurement cell contains the electrolyte, a glassy carbon working electrode, a platinum counter electrode, and a AglAgC1 reference glass electrode. Ferrocene is added into the cell at the end of the experiment as reference material (1,111410 (ferrocene)-= -4.8eV). 2.5

Table 1

HON 1 UN40 (eV) Band gap (e IEIC0-4CN;9 A.12 1.27 LEIC0-4F -3.91 1.36 C0i8DFIC -5.35 2 1.43

Device Example 1

A device having the following structure was prepa Cathode / Donor: Acceptor layer / Anode A glass substrate coated with indium-tin oxide ( 'O) was treated with polye yleneim ne (PE1E) to modify the work function of the ITO.

A ca. 600 nm thick bulk heterojunction layer of Formulation Example t was deposite«wer the modified VIO layer by bar coating. The resultant laver was dried under vacuum at 80"C.

An anode (CleviosHIL-E100) available from lieraeris was formed over the donor! acceptor mixture layer by spin-coating.

Comparative Devices IA, IB and 2 Comparative Devices 1A, 1B and 2 were prepared as described for Device Example 1 except that Comparative Formulations LA, IB and 2, respectively, were used in place of Formulation Example I. 1EIC0-4F used in Comparative Device IA has a smaller band gap than C0i8DFIC used in Device Example 1, which would suggest that Comparative Device I would be more effective at absorbing light of long wavelengths. However, with reference to Figure 2, external quantum efficiency of Device Example I is surprisingly geater than that of Comparative Device 1 at wavelengths in the range of about 900-1000 nm.

In Comparative Device 1B, the acceptor lEICO-4CN has an even smaller band gap than IEIC0-4F. With reference to Figures 3A and 3B, this device has higher external quantum efficiency at wavelengths above about 1000 nm as compared to Device Example 1, however Comparative Device 1B has significantly higher dark current.

With reference to Figure 4A, external quantum efficiency of Device Example 1 is greater than that of Comparative Device 2 at wavelengths greater than about 900 nm.

With eference to -1, sgure 413, Device Example I has lower dark current than Comparative Device 2.

Claims

CLAIMSA composition comprising an electron donor material and a first electron accepting material wherein the electron donor material is a polymer; the electron accepting material is a non-polymeric compound; and the electron donor material and electron accepting material both comprise an electron donor group of formula (I): wherein: X and V are each independently selected from S. 0 or Se; 15Z is 0, S. INR2 or CR32 Ar1-Ar6 are each independently an unsubstituted or a substituted benzene, an unsubstituted or a substituted 5-or 6-membered heteroaromatic group or are absent; and A2 are each independently an unsubstituted or a substituted benzene, an unsubstituted or a substituted 5-or 6-membered heteroaromatic group, a non-aromatic 5-membered ring having ring atoms selected from C, N and 0 or are absent; n is1, 2 or R1 independently in each occur' n * uent; each R3 is independently H or a substituent. LiThe composition according to claim 1 wherein the electron acceptor material is a compound of fommla (II): EAG1 (1--2)o wherein: m and o are eac ride iendently 0 or an integer of I or more; 0 is a bridging group when III is 1 or more or a direct bond when in is 0; ging group when o is I or more or a direct bond when o is 0; and each independently represents an electron accepting group The composition acc ling to claim 2 wherein the coinpowid of formula HI) has formula (Ha):EAGI EAGI (11a)The composition according claim 2 or 3 wherein each EA independently ncependently a group of formula (Wu):NCLJ (IVOwherein: RH' in each occurrence is H or a substituent selected from the group consisting o 12 alkyl wherein one or more non--adjacent, non-terminal C atoms may be replaced with 0, S, C.00 or CO and one or more H atoms of the alkyl may be replaced with F; and an aromatic group At which is unsubstituted or substituted with one or more substituents selected from F and C,,2 alkyl wherein one or more non--adjacent, non--terminal C atoms may be replaced with 0, S, COO or CO; --represents a. linking position in the compound of formula (II); and each X'-X4 is independently CR17 or N wherein RP in each occurrence is H or a substituent selected from C1-2 hydrocarbyl and an electron withdrawing group.The composition according to any one of the preceding claims wherein the electron-accepting material is C0i8DFICI The composition according to any one of the preceding claims wherein the electron donor polymer comprises a repeating structure of formula (OH 7. The composition according to claim 6 wherein the repeating structure of formula (III) has formula (Ma): The composition according to any one of the preceding claims \vherein the electron donating polymer comprises a repeating structure of formula: / R: wherein EAG2 is an eIectronaccepting group. EAG2 R4 R1 (lna)wherein each R4 is indenendently H or a substituent The composition according to any one of the preceding claims wherein composition further comprises a second electron accepting material.10. The composition according to claim 9 wherein the second electron-accepting material is a fullerene or a derivative thereof A formulation comprising one or more solvents and a composition according to any one of the preceding claims dissolved or dispersed in the one or more solvents.12. A photoresponsive device comprising an anode, a cathode and a photosensitive layer disposed between the anode and the cathode, wherein the photosensitive layer comprises a composition according to any one of claims 1-10.13. .A photoresponsive device as claimed in claim 12 wherein die photorespon.is an organic photodetector.A photosensor comprising a light source and a photoresponsive device as claimed in claim 13, wherein the photosensor configured to detect light emitted from the light source.A photosensor according to claim 14, wherein the light source emits light having a peak wavelength greater than 750 nm.16. A photosensor according to either claim 14 or claim 15 configured to receive a sample in a light path between the organic photodetector and the Light source.17. A method of forming an organic photoresponsive device according to claim 12 or 13 comprising fonnation of the photosensitive organic layer over one of the anode and cathode and formation of the other of the anode and cathode over the photosensitive organic layer.IS. A method according, to claim 17 wherein formation of the photosensitive organic layer comprises deposition of a formulation according to claim 9.19. A method of determining the presence and / or concentration of a target material in a sample, the method comprising illuminating the sample and measuring a response of an organic photodetector according to claim 1.3.