Near-infrared organic photodetector

Abstract

The organic photodetector includes a photosensitive organic layer located between two electrodes. The photosensitive organic layer is formed of a donor compound and an acceptor compound, and the acceptor compound is a non-fullerene compound that does not contain a fullerene group. The LUMO energy level of the acceptor compound is equal to or deeper than the LUMO energy level of a fullerene derivative such as C70IPH. The photosensitive organic layer generates a low dark current and good EQE, and can operate in the near-infrared region.

Description

Technical Field

[0001] The present disclosure relates to photoactive compounds and their use in organic electronic devices, particularly organic photodetectors, and more particularly but not limited to organic photodetectors for detecting wavelengths greater than 900 nm or 1000 nm. Background Art

[0002] A series of organic electronic devices comprising organic semiconductor materials are known, including organic light-emitting devices, organic field-effect transistors, organic photovoltaic devices, and organic photodetectors (OPDs).

[0003] CN106025073 discloses an organic solar cell using a ternary component as the active layer.

[0004] CN106058056 discloses the active layer of an organic solar cell and a method for preparing the active layer.

[0005] CN108084409 discloses a wide-bandgap organic semiconductor material.

[0006] US2018 / 0047862 relates to light-converting devices, such as photovoltaic cells or photodetectors.

[0007] WO 2018 / 065352 relates to an organic photodetector (OPD) comprising a photoactive layer containing an electron acceptor and an electron donor; the acceptor is an n-type semiconductor which is a small molecule not containing a fullerene structural moiety, and the electron donor is a p-type semiconductor which is a conjugated copolymer containing a donor unit and an acceptor unit.

[0008] WO 2018 / 078080 relates to organic semiconductor compounds containing polycyclic units as organic semiconductors.

[0009] US 6,972,431 discloses an organic photodetector with reduced dark current.

[0010] WO 2017 / 117477 discloses α-substituted PDI derivatives as small molecules and polymeric electron acceptors in organic photovoltaic cells.

[0011] US2017 / 0057962 discloses non-fullerene electron acceptors for highly efficient OPVs.

[0012] WO 2017 / 191468 discloses non-fullerene electron acceptors that can be used in organic optical or electronic devices.

[0013] CN106025073 discloses an organic solar cell.

[0014] WO 2013 / 182847 discloses novel organic compounds used as electron acceptors.

[0015] US2015 / 0270497 discloses efficient organic photosensitive devices.

[0016] US 7,893,428 discloses photosensitive organic semiconductor compositions.

[0017] Baran et al., Energy Environ. Sci., 2016, 3783–3793 disclose the use of non-fullerene acceptors in organic solar cells.

[0018] Susarova et al., Sol. Energy Mater Sol. Cells, 2010, 803-811 disclose novel perylene diimides Py-PDI and naphthalene diimides Py-NDI with chelating pyridine groups.

[0019] Yao et al., Organic Electronics, 2015, 305-313 disclose low-bandgap polymers based on 2,1,3-benzothiadiazole-5,6-dicarboximide for solution-processed photodiode applications.

[0020] Hu et al., Polym. Chem., 2017, 528–536 disclose a strategy for reducing dark current using laterally aligned donor polymers to achieve highly detective and responsive organic photodetectors.

[0021] US 8,853,679 generally relates to organic semiconductors and particularly to organic semiconductors for forming part of a thin film transistor.

[0022] Zhao et al., J. Am. Chem. Soc., 2017, 7148–7151 disclose the design and synthesis of a novel polymer donor (PBDB-T-SF) and a novel small molecule acceptor (IT-4F) for fullerene-free organic solar cells (OSCs).

[0023] Lin et al., Adv. Mater., 2015, 1170-1174 disclose the design and synthesis of a novel electron acceptor (ITIC) based on a large seven-ring fused core (indacenodithiophene[3,2-b]thiophene, IT), with 2-(3-oxo-2,3-dihydroinden-1-ylidene)malononitrile (INCN) groups and substituted with four 4-hexylphenyl groups thereon.

[0024] WO 2017 / 125719 discloses an organic photodiode used as a photodetector. It shows the use of fullerene derivatives to reduce the dark current in organic photodiodes.

[0025] Miao et al., Adv. Opt. Mater., 2016, 1711–1717 relate to an organic photodetector with tunable spectral response under biasing voltage.

[0026] Wang et al., Nanoscale, 2016, 5578 - 5586 relate to a photomultiplication photodetector with P3HT: non-fullerene materials as the active layer. SUMMARY OF THE INVENTION

[0027] According to a first aspect of some embodiments of the present invention, an organic photodetector is provided. The organic photodetector includes: a first electrode and a second electrode, and a photosensitive organic layer located between the electrodes. The photosensitive organic layer contains a donor compound and an acceptor compound, wherein the acceptor compound does not contain a fullerene group, and wherein the LUMO energy level of the acceptor compound is equal to or deeper than the LUMO energy level of the fullerene derivative C70IPH. Thus, the photosensitive organic layer includes a non-fullerene photosensitive organic layer. The applicant has found that such a non-fullerene photosensitive organic layer can provide an organic photosensor with low dark current, high EQE, and / or operating at wavelengths exceeding 900 nm, 1000 nm, and / or 1100 nm.

[0028] In some embodiments, the OPD is connected to a voltage source such that a reverse bias can be applied thereto during operation.

[0029] In some embodiments, the acceptor compound is represented by the general formula (V):

[0030]

[0031] Wherein:

[0032] R 11 、R 12 、R 13 、R 14 、R 15 Each of them is independently selected from one of the following: H, an electron-withdrawing group such as halogen, CN, NO2, CF3, carbonyl, or heteroaryl, the heteroaryl being unsubstituted or substituted with one or more substituents, or one of the following formulas (VIII) and (IX):

[0033]

[0034] And

[0035] Wherein: R 16and R 17 are each independently selected from: H; branched, straight-chain or cyclic C 1-20 alkyl, in which one or more non-adjacent non-terminal C atoms may be replaced by O, S, CO or COO, and one or more H atoms may be replaced by F; and aryl or heteroaryl, which aryl or heteroaryl is unsubstituted or substituted with one or more substituents.

[0036] In some embodiments, R 15 , R 20 , R 21 , R 22 and R 23 are H or an electron-withdrawing group, such as a halogen, selected from Cl, Br, I or F; or CN, NO2, CF3, carbonyl or heteroaryl, which heteroaryl is unsubstituted or substituted with one or more substituents, and each of R 16 and R 17 is -(CH2) n CH3, where n is an integer selected from 1 to 20.

[0037] In some embodiments, at least one occurrence of at least one of R 20 -R 23 is F. Optionally, each of R 20 -R 23 is H or F.

[0038] In some embodiments, R 11 , R 12 , R 13 and R 14 are of formula (VIII), where n is 5.

[0039] In some embodiments, R 11 , R 12 , R 13 and R 14 are of formula (IX), where n is 5.

[0040] In some embodiments, the compound of formula (V) has formula (Va):

[0041]

[0042] In some embodiments, each fluorine may independently be in the 3-, 4-, 5- or 6-position on the benzene ring. In some embodiments, each fluorine is in the 3-, 4-, 5- or 6-position on the benzene ring. Alternatively, one fluorine is in the 3-, 4-, 5- or 6-position on the benzene ring, and the other fluorine is in the 3-, 4-, 5- or 6-position on the benzene ring.

[0043] In some embodiments, the acceptor compound is ITIC, ITIC-2F or ITIC-Th.

[0044] In some embodiments, the acceptor compound is represented by the general formula (I):

[0045]

[0046] Wherein:

[0047] Each R 1 is independently selected from: H; branched, straight-chain or cyclic C 1-20 alkyl, wherein one or more non-adjacent non-terminal C atoms may be replaced by O, S, CO or COO, and one or more H atoms may be replaced by F; and aryl or heteroaryl, which aryl or heteroaryl is unsubstituted or substituted with one or more substituents;

[0048] R 2 and R 3 each independently selected from: H; branched, straight-chain or cyclic C 1-20 alkyl, wherein one or more non-adjacent non-terminal C atoms may be replaced by O, S, CO or COO, and one or more H atoms may be replaced by F; aryl or heteroaryl, which aryl or heteroaryl is unsubstituted or substituted with one or more substituents; and a group having the following formula (II):

[0049]

[0050] And

[0051] R 4 and R 5 each independently selected from: H; branched, straight-chain or cyclic C 1-20 alkyl, wherein one or more non-adjacent non-terminal C atoms may be replaced by O, S, CO or COO, and one or more H atoms may be replaced by F; and aryl or heteroaryl, which aryl or heteroaryl is unsubstituted or substituted with one or more substituents.

[0052] In some embodiments, R 1 and R 4 each independently selected from groups having the following formula (IV):

[0053]

[0054] Wherein, R 9 and R 10 each independently selected from: -CH3 and -(CH2) n CH3, where n is an integer selected from 1–20.

[0055] In some embodiments, the acceptor compound has the following formula (XII):

[0056]

[0057] wherein R 18 has the following formula (IV):

[0058]

[0059] and wherein R 9 and R 10 each independently selected from: -CH3 and -(CH2) n CH3, where n is an integer selected from 1 - 20. In some embodiments, n is 4 or 5.

[0060] In some embodiments, the donor compound is a semiconductor polymer.

[0061] In some embodiments, the first electrode is an anode and the second electrode is a cathode.

[0062] In some embodiments, the weight ratio of the donor compound to the acceptor compound is from about 1:0.5 to about 1:1.2.

[0063] According to a second aspect of some embodiments of the present invention, there is provided a sensor comprising a light source and an organic photodetector as described herein, wherein the organic photodetector is configured to receive light from the light source.

[0064] According to a third aspect of some embodiments of the present invention, there is provided a method of detecting light, the method comprising measuring a photocurrent generated by light incident on the organic photodetector of the first aspect.

[0065] In some embodiments, the method of detecting light comprises measuring a photocurrent generated by light incident on the organic photodetector and emitted from the light source of the sensor according to the second aspect.

[0066] According to a fourth aspect of some embodiments of the present invention, there is provided the use of the following compound in the photosensitive layer of an organic photodetector to reduce dark current, the compound not containing a fullerene group having a LUMO energy level and having a deeper LUMO energy level than the fullerene derivative C70IPH. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Figure 1 shows an organic photodetector according to an embodiment of the present invention;

[0068] Figure 2 and Figure 3is a plot of the current density of the device and the comparative device against the applied voltage under dark conditions according to an embodiment; and

[0069] Figure 4 and Figure 5 is a plot of the EQE of the device and the comparative device against the wavelength according to an embodiment.

[0070] Detailed Description

[0071] A disadvantage of an OPD is the presence of dark current, i.e., the current that flows through the device when no photons are incident on the device, which may affect the detection limit of the device. Accordingly, an object of some embodiments of the present invention is to provide an OPD having a low dark current. Another object of some embodiments of the present invention is to provide an OPD having a low dark current and a good external quantum efficiency (EQE).

[0072] Organic electronic devices containing organic semiconductor materials include organic light-emitting devices, organic field-effect transistors, organic photovoltaic devices, and OPDs. For an OPD, it may be necessary to balance the following properties: the functionality of the organic semiconductor material to provide a low dark current (the current generated by the OPD when there is no light, which is caused by the reverse bias applied to the OPD) and the EQE of the organic semiconductor material. For example, organic semiconductor materials that typically have a good EQE also generate a high dark current.

[0073] In addition, it may be desirable to operate the OPD at wavelengths other than visible light in the sensing environment and / or at wavelengths where there are gaps in the wavelengths of sunlight. For example, sunlight at a wavelength of about 940 nm may be absorbed in the atmosphere, creating a gap at that wavelength, and a light-emitting device may operate in the visible spectrum without producing any output at wavelengths longer than 900 nm. Operating an OPD sensor at such wavelengths can reduce interference from sunlight / visible light. For example, an organic semiconductor material having what can be considered a low EQE may be useful for an OPD that operates at such wavelengths without interference (thus, for the purposes of the present disclosure, the term "high EQE" refers to a high EQE relative to an OPD that operates in the near-infrared spectrum).

[0074] In contrast, for an OPV, it may not be desirable to operate at such wavelengths (>900 nm) because an OPV uses electromagnetic radiation present in the environment.

[0075] Figure 1 An OPD according to an embodiment of the present invention is shown. The OPD includes a cathode 103 supported by a substrate 101, an anode 107, and a bulk heterojunction layer 105 located between the anode and the cathode, the bulk heterojunction layer 105 including a mixture of an electron acceptor and an electron donor. Optionally, the bulk heterojunction layer consists of an electron acceptor and an electron donor. InFigure 1 In the illustrated embodiment, the OPD includes a material layer 106 that modulates the work function of the cathode 103. In other embodiments, this layer may or may not be present.

[0076] The OPD may include Figure 1 other layers not shown in. For example, the device may include a hole transport layer (HTL) located between the anode 107 and the heterojunction layer 105.

[0077] In use, a photodetector as described in the present disclosure may be connected to a voltage source to apply a reverse bias to the device and a device configured to measure photocurrent. In some embodiments, the photodetector is part of a system that includes multiple photodetectors. For example, the photodetector may be part of an array in an image sensor of a camera. The voltage applied to the photodetector may vary. In some embodiments, the photodetector may be continuously biased during use.

[0078] The OPD may be incorporated into a sensor that includes a light source, and the OPD may be configured to receive light emitted from the light source.

[0079] In some embodiments, the light from the light source may or may not be altered before reaching the light source. For example, the light may be filtered, downconverted, or upconverted before reaching the light source.

[0080] High dark current in the photodetector limits the detectable optical input signal due to a low signal-to-noise ratio.

[0081] The inventors surprisingly found that incorporating an acceptor compound (which has a deep LUMO energy level relative to the fullerene derivative C70IPH) into the OPD can reduce the dark current, compared to an OPD that includes C70IPH as an acceptor. For example, according to some embodiments of the present disclosure, the acceptor compounds described herein provide an OPD that has a dark current at least 5 times or at least 10 times lower than that of a fullerene compound (such as C70IPH).

[0082] The inventors also found that, according to some embodiments of the present disclosure, the acceptor compounds described herein provide an EQE greater than 30% within a broad wavelength spectrum. Surprisingly, an EQE of around 30% is even obtained at wavelengths between 900 and 1000 nanometers, and an EQE of around 5% to 20% is also shown at wavelengths up to 1100 nm.

[0083] The inventors also surprisingly found that the acceptor compounds described herein provide detection for longer wavelength applications of specific wavelengths greater than 900 nm and greater than 1000 nm.

[0084] As described above, the inventors have also found that the acceptor compounds disclosed herein can be suitable for detecting light in the near-infrared region, particularly at wavelengths of about >900 nm, or >1000 nm or >1100 nm. At about 940 nm, sunlight is absorbed by atmospheric moisture, and thus the use of such acceptor compounds in a light source-OPD detector sensor device for detecting light at wavelengths in this range can be effective without being shielded / interfered by sunlight. Due to the absorption of sunlight by the atmosphere at these wavelengths, the acceptor compounds according to the present disclosure are not suitable for OPV.

[0085] Preferably, the electron acceptor compounds described herein do not contain a fullerene group and are hereinafter described as "non-fullerene acceptors".

[0086] The organic photodetector comprises:

[0087] A first electrode, which can be an anode or a cathode;

[0088] A second electrode, which can be the other of the anode or the cathode; and

[0089] A photosensitive organic layer located between the electrodes, wherein the photosensitive organic layer comprises a donor compound and an acceptor compound, wherein the acceptor compound does not contain a fullerene group, and wherein the LUMO energy level of the acceptor compound is equal to or deeper than the LUMO energy level of the fullerene derivative C70IPH.

[0090] As used herein, a "deeper" LUMO energy level means further away from the vacuum energy level, and a "shallower" LUMO energy level as used herein means closer to the vacuum energy level. Thus, it should be understood that the LUMO energy level of the acceptor compound described herein that does not contain a fullerene group is further away from the vacuum energy level than the LUMO energy level of the fullerene derivative C70IPH.

[0091] Preferably, the LUMO energy level of the acceptor compound is at least 3.65, 3.66, 3.67, 3.68, 3.69, 3.70, 3.71, 3.72, 3.73, 3.74 or 3.75 eV deeper than the vacuum energy level, as measured by square wave voltammetry.

[0092] The non-fullerene acceptor compounds described herein can be small molecule non-fullerene acceptors (SM-NFAs).

[0093] The non-fullerene acceptor compound can be a compound of general formula (I):

[0094]

[0095] Wherein:

[0096] Each R 1Independently selected from: H; branched, straight-chain or cyclic C 1-20 alkyl, wherein one or more non-adjacent non-terminal C atoms may be replaced by O, S, CO or COO, and one or more H atoms may be replaced by F; and aryl or heteroaryl, which aryl or heteroaryl is unsubstituted or substituted with one or more substituents;

[0097] R 2 and R 3 each independently selected from: H; branched, straight-chain or cyclic C 1-20 alkyl, wherein one or more non-adjacent non-terminal C atoms may be replaced by O, S, CO or COO, and one or more H atoms may be replaced by F; aryl or heteroaryl, which aryl or heteroaryl is unsubstituted or substituted with one or more substituents; and a group having one of the following formulas (II) or (III):

[0098]

[0099] and wherein R 4 、R 5 、R 6 、R 7 and R 8 each independently selected from: H; branched, straight-chain or cyclic C 1-20 alkyl, wherein one or more non-adjacent non-terminal C atoms may be replaced by O, S, CO or COO, and one or more H atoms may be replaced by F; and aryl or heteroaryl, which aryl or heteroaryl is unsubstituted or substituted with one or more substituents.

[0100] Preferably, each R 1 、R 4 and R 6 is independently selected from branched, straight-chain or cyclic C 1-20 alkyl.

[0101] Preferably, each R 1 、R 4 and R 6 is independently selected from a group having the following formula (IV):

[0102]

[0103] wherein each of R 9 and R 10 is independently selected from: H; branched, straight-chain or cyclic C 1-20An alkyl group in which one or more non-adjacent non-terminal C atoms may be replaced by O, S, CO or COO, and one or more H atoms may be replaced by F; and an aryl or heteroaryl group, said aryl or heteroaryl group being unsubstituted or substituted with one or more substituents.

[0104] Preferably, each of R 9 and R 10 is independently selected from: -CH3 and -(CH2) n CH3, where n is an integer selected from 1 to 20.

[0105] Preferably, each of R 9 and R 10 is independently selected from: -CH3, -(CH2)4CH3 and -(CH2)5CH3. Preferably, each of R 9 and R 10 is -(CH2)4CH3 or -(CH2)5CH3.

[0106] Preferably, each R 2 is independently selected from: H; branched, straight-chain or cyclic C 1-20 alkyl.

[0107] In a preferred embodiment, each R 2 is H.

[0108] Preferably, R 3 is selected from an aryl or heteroaryl group, said aryl or heteroaryl group being unsubstituted or substituted with one or more substituents.

[0109] In a preferred embodiment, R 3 is selected from groups of formula (II) or (III). Preferably, R 3 is of formula (II).

[0110] Preferably, each R 4 is independently selected from branched, straight-chain or cyclic C 1-20 alkyl.

[0111] Preferably, each R 4 is independently selected from groups having the following formula (IV):

[0112]

[0113] where each of R 9 and R 10 is independently selected from: H; branched, straight-chain or cyclic C 1-20An alkyl group in which one or more non-adjacent non-terminal C atoms may be replaced by O, S, CO or COO, and one or more H atoms may be replaced by F; and an aryl or heteroaryl group, said aryl or heteroaryl group being unsubstituted or substituted with one or more substituents.

[0114] Preferably, each of R 9 and R 10 is independently selected from: -CH3 and -(CH2) n CH3, where n is an integer selected from 1 - 20.

[0115] In a preferred embodiment, each of R 9 and R 10 is independently selected from: -CH3, -(CH2)4CH3 and -(CH2)5CH3. Preferably, each of R 9 and R 10 is -(CH2)4CH3 or -(CH2)5CH3.

[0116] Preferably, each R 5 is independently selected from: H; branched, straight-chain or cyclic C 1-20 alkyl.

[0117] In a preferred embodiment, each R 5 is H.

[0118] Preferably, each R 6 is independently selected from branched, straight-chain or cyclic C 1-20 alkyl.

[0119] Preferably, each R 6 is independently selected from groups having the following formula (IV):

[0120]

[0121] where each of R 9 and R 10 is independently selected from: H; branched, straight-chain or cyclic C 1-20 alkyl, in which one or more non-adjacent non-terminal C atoms may be replaced by O, S, CO or COO, and one or more H atoms may be replaced by F; and aryl or heteroaryl, said aryl or heteroaryl being unsubstituted or substituted with one or more substituents.

[0122] Preferably, each of R 9 and R 10 is independently selected from: -CH3 and -(CH2) n CH3, where n is an integer selected from 1 - 20.

[0123] Preferably, R 9 and R 10 each independently selected from: -CH3, -(CH2)4CH3 and -(CH2)5CH3. Preferably, R 9 and R 10 each is -(CH2)4CH3 or -(CH2)5CH3.

[0124] Preferably, R 7 and R 8 each independently selected from: H; branched, straight-chain or cyclic C 1-20 alkyl.

[0125] In a preferred embodiment, R 7 and R 8 each is H.

[0126] In some embodiments, the non-fullerene acceptor compound may be a compound of formula (V):

[0127]

[0128] wherein R 11 、R 12 、R 13 、R 14 、R 15 、R 20 、R 21 、R 22 and R 23 each independently selected from: H; an electron-withdrawing group such as a halogen (including Cl, Br, I or F); CN, NO2, CF3, a carbonyl group or a heteroaryl group, which heteroaryl group is unsubstituted or substituted with one or more substituents; branched, straight-chain or cyclic C 1-20 alkyl, wherein one or more non-adjacent non-terminal C atoms may be replaced by O, S, CO or COO, and one or more H atoms may be replaced by F; and an aryl group or a heteroaryl group, which aryl group or heteroaryl group is unsubstituted or substituted with one or more substituents.

[0129] In some embodiments, R 11 、R 12 、R 13 、R 14 、R 15 、R 20 、R 21 、R 22 and R 23 each independently selected from one of the following formulas (VI) and (VII):

[0130]

[0131] In some embodiments, each of R 11 , R 12 , R 13 , R 14 , R 15 , R 20 , R 21 , R 22 , and R 23 is independently selected from one of formulas (VI) and (VII), wherein one or more H atoms of each of formulas (VI) and (VII) are independently replaced by substituents selected from: branched, straight-chain or cyclic C 1-20 alkyl, wherein one or more non-adjacent non-terminal C atoms may be replaced by O, S, CO or COO, and one or more H atoms may be replaced by F; and aryl or heteroaryl, which aryl or heteroaryl is unsubstituted or substituted with one or more substituents.

[0132] In some embodiments, each of R 11 , R 12 , R 13 , R 14 is independently selected from the following: H; an electron-withdrawing group such as a halogen (including Cl, Br, I or F); CN, NO2, CF3, a carbonyl group or heteroaryl, which heteroaryl is unsubstituted or substituted with one or more substituents;; formulas (VI) and (VII); wherein one or more H atoms of each of formulas (VI) and (VII) are independently replaced by substituents selected from: branched, straight-chain or cyclic C 1-20 alkyl, wherein one or more non-adjacent non-terminal C atoms may be replaced by O, S, CO or COO, and one or more H atoms may be replaced by F; and aryl or heteroaryl, said aryl or heteroaryl being unsubstituted or substituted with one or more substituents; and R 15 , R 20 , R 21 , R 22 , and R 23 are selected from: H; an electron-withdrawing group such as a halogen (including Cl, Br, I or F); or CN, NO2, CF3, a carbonyl group or heteroaryl, which heteroaryl is unsubstituted or substituted with one or more substituents; branched, straight-chain or cyclic C 1-20 alkyl, wherein one or more non-adjacent non-terminal C atoms may be replaced by O, S, CO or COO, and one or more H atoms may be replaced by F; and aryl or heteroaryl, which aryl or heteroaryl is unsubstituted or substituted with one or more substituents.

[0133] In preferred embodiments, R 11 , R 12 , R13 and each of R 14 is independently selected from Formula (VI) and (VII), wherein one or more H atoms in each of Formula (VI) and (VII) are independently replaced by substituents selected from: branched, straight-chain or cyclic C 1-20 alkyl, wherein one or more non-adjacent non-terminal C atoms may be replaced by O, S, CO or COO, and one or more H atoms may be replaced by F; and aryl or heteroaryl, which is unsubstituted or substituted with one or more substituents, R 15 is H, and R 20 and each of R 21 and each of R 22 and each of R 23 is H.

[0134] In a preferred embodiment, R 11 and each of R 12 and each of R 13 and each of R 14 is selected from Formula (VI) or (VII), wherein one or more H atoms in each of Formula (VI) and (VII) are independently replaced by substituents selected from: branched, straight-chain or cyclic C 1-20 alkyl, wherein one or more non-adjacent non-terminal C atoms may be replaced by O, S, CO or COO, and one or more H atoms may be replaced by F; and aryl or heteroaryl, which is unsubstituted or substituted with one or more substituents, R 15 is H, and R 20 and each of R 21 and each of R 22 and each of R 23 is an electron-withdrawing group, preferably a halogen selected from F, Cl, I, Br.

[0135] In some embodiments, the electron-withdrawing group may include CN, NO2, CF3, carbonyl or heteroaryl, which is unsubstituted or substituted with one or more substituents.

[0136] Preferably, R 11 and each of R 12 and each of R 13 and each of R 14 is selected from the following Formulas (VIII) and (IX), R 15 is H, and R 20 and each of R 21 and each of R 22 and each of R 23 is H or an electron-withdrawing group, preferably a halogen selected from F, Cl, I, Br:

[0137]

[0138] wherein R 16 and R 17 are each independently selected from: -CH3 and -(CH2) n CH3, where n is an integer selected from 1–20.

[0139] Preferably, R 11 , R 12 , R 13 , R 14 are selected from the following formulas (X) and (XI), R 15 is H, and each of R 20 , R 21 , R 22 and R 23 is independently selected from: H or a halogen, said halogen being selected from F, Cl, I, Br; or CN, NO2, CF3, a carbonyl group or a heteroaryl group, which heteroaryl group is unsubstituted or substituted with one or more substituents:

[0140]

[0141] Preferably, R 11 , R 12 , R 13 , R 14 is selected from any one of the following formulas (X) and (XI), R 15 is H, R 20 , R 21 , R 22 and R 23 are each H:

[0142]

[0143] Preferably, R 11 , R 12 , R 13 , R 14 is selected from the following formulas (X) and (XI), R 15 is H, and each of R 20 , R 21 , R 22 and R 23 is independently selected from halogens, said halogens being selected from F, Cl, I, Br:

[0144]

[0145] Preferably, R 11 , R 12 , R 13 , R 14 is selected from the following formulas (X) and (XI), R 15 is H, R20 , R 21 , R 22 and R 23 Among them, three are H, and R 20 , R 21 , R 22 and R 23 One of them is independently selected from halogens, and the halogens are selected from: F, Cl, I, Br:

[0146]

[0147] Preferably, R 11 , R 12 , R 13 , R 14 are selected from the following formulas (X) and (XI), R 15 is H, R 20 , R 21 , R 22 and R 23 Among them, two are H, and R 20 , R 21 , R 22 and R 23 Two of them are independently selected from halogens, and the halogens are selected from: F, Cl, I, Br:

[0148]

[0149] Preferably, R 11 , R 12 , R 13 , R 14 are selected from the following formulas (X) and (XI), R 15 is H, R 20 and R 23 are H, and R 21 and R 22 are independently selected from halogens, and the halogens are selected from: F, Cl, I, Br:

[0150]

[0151] Preferably, R 15 is H, and R 20 , R 21 , R 22 and R 23 Each of them is independently selected from H or halogens, and the halogens are selected from F, Cl, I, Br.

[0152] Preferably, as measured in the device as described in Device Example 1, the non-fullerene acceptor compound has an external quantum efficiency of at least 10%, optionally at least 15% or at least 20%.

[0153] A non-exhaustive list of compounds suitable for use as acceptor compounds in devices according to the present disclosure, and a comparison of the LUMO energy levels of these acceptor compounds with the LUMO energy level of the reference compound C70IPH, is shown in Table 1 below.

[0154] Table 1

[0155]

[0156]

[0157] *Purchased from 1-Material Inc.

[0158] From Table 1, it can be seen that the LUMO level of ITIC-2F is deeper than that of the unfluorinated acceptor ITIC.

[0159] The donor compound (p-type) is not particularly limited and may be appropriately selected from electron donor materials known to those skilled in the art, including organic polymers, oligomers, and small molecules.

[0160] The donor compound may be a semiconducting polymer.

[0161] In a preferred embodiment, the p-type donor compound comprises an organic conjugated polymer, which may be a homopolymer or a copolymer, including alternating, random or block copolymers. Preferred are non-crystalline or semi-crystalline conjugated organic polymers. Further preferably, the p-type organic semiconductor is a conjugated organic polymer with a low band gap, which is typically between 2.5 eV and 1.5 eV, preferably between 2.3 eV and 1.8 eV. As exemplary p-type donor polymers, mention may be made of polymers selected from conjugated hydrocarbon or heterocyclic polymers, including polyphenylenes, polyanilines, polyazulenes, polybenzofurans, polyfluorenes, polyfurans, polyindenylfluorenes, polyindoles, polyphenylenes, polypyrazolines, polypyrenes, polypyridazines, polypyridines, polytriarylamines, poly(phenylene vinylenes), poly(3-substituted thiophenes), poly(3,4-disubstituted thiophenes), polyselenophenes, poly(3-substituted selenophenes), poly(3 ,4-disubstituted selenophene), poly(dithiophene), poly(terthiophene), poly(diselenophene), poly(triselenophene), polythieno[2,3-b]thiophene, polythieno[3,2-b]thiophene, polybenzothiophene, polybenzo[1,2-b:4,5-b']dithiophene, polyisothionaphthene, poly(monosubstituted pyrrole), poly(3,4-disubstituted pyrrole), poly-1,3,4-oxadiazole, polyisothionaphthene, derivatives and copolymers thereof. Preferred examples of p-type donors are copolymers of polyfluorene and polythiophene (each of which may be substituted), and polymers comprising repeating units based on benzothiadiazole and repeating units based on thiophene (each of which may be substituted). It should be understood that the p-type donor may also be composed of a mixture of multiple electron-donating materials.

[0162] The electron donor preferably contains a repeating unit of formula (XIII):

[0163]

[0164] wherein R 24 is independently H or a substituent each time it appears.

[0165] Optionally, each R 24 is independently selected from:

[0166] C 1-20 alkyl, wherein one or more non-adjacent non-terminal carbon atoms of the alkyl may be replaced by O, S or C═O, and wherein one or more H atoms of the C 1-20 alkyl may be replaced by F; aryl or heteroaryl, preferably phenyl, which may be unsubstituted or substituted with one or more substituents; and fluorine.

[0167] The substituents of the aryl or heteroaryl are optionally selected from F, CN, NO2 and C 1-20 alkyl, wherein one or more non-adjacent non-terminal carbon atoms of the alkyl may be replaced by O, S or C═O.

[0168] As used herein, "non-terminal" refers to carbon atoms other than the methyl groups of a straight-chain alkyl (n-alkyl) chain and the methyl groups of a branched alkyl chain.

[0169] The polymer containing the repeating unit of formula (XIII) is preferably a copolymer containing one or more comonomer repeating units.

[0170] The one or more comonomer repeating units may comprise or consist of: one or more C 6-20 monocyclic or polycyclic arylene repeating units, which may be unsubstituted or substituted with one or more substituents; 5- to 20-membered monocyclic or polycyclic heteroarylene repeating units, which may be unsubstituted or substituted with one or more substituents.

[0171] The one or more comonomer repeating units may have the formula (XIV):

[0172]

[0173] wherein Ar 1 is arylene or heteroarylene each time it appears; m is at least 1; R 25 is a substituent; R 25 is independently a substituent each time it appears; n is 0 or a positive integer; and two groups R 25 may be linked to form a ring.

[0174] Optionally, each R 25 is independently selected from linear, branched or cyclic C 1-20 alkyl, wherein one or more non-adjacent non-terminal C atoms of the C 1-20 alkyl may be replaced by O, S, COO or CO.

[0175] Two groups R 25 may be linked to form a C 1-10 alkylene group, wherein one or more non-adjacent C atoms of the alkylene group may be replaced by O, S, COO or CO.

[0176] Optionally, m is 2.

[0177] Optionally, each Ar 1 is independently a 5- or 6-membered heteroarylene group, optionally a heteroarylene group selected from thiophene, furan, selenophene, pyrrole, diazole, triazole, pyridine, diazine and triazine, preferably thiophene.

[0178] Optionally, the repeating unit of formula (XIV) has the formula (XIVa):

[0179]

[0180] Optionally, the group R 25 is linked to form a 2- to 5-membered bridging group. Optionally, the bridging group has the formula -O-C(R 26 )2-, wherein R 26 is independently H or a substituent at each occurrence. The substituent R 26 is optionally selected from C 1-20 alkyl. Preferably, each R 26 is H.

[0181] Exemplary donor polymers are disclosed in WO2013 / 051676 and WO2011052709, the contents of which are incorporated herein by reference.

[0182] In some embodiments, the weight ratio of the donor compound to the acceptor compound is about 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9 or 1:2.

[0183] In some embodiments, the weight of the donor compound to the acceptor compound is from about 1:0.5 to about 1:2.

[0184] Preferably, the weight ratio of the donor compound to the acceptor compound is about 1:1 or about 1:1.5.

[0185] At least one of the first electrode and the second electrode is transparent such that light incident on the device can reach the bulk heterojunction layer. In some embodiments, both the first electrode and the second electrode are transparent.

[0186] Each transparent electrode preferably has a transmittance of at least 70%, optionally at least 80%, for wavelengths in the range of 300 - 900 nm.

[0187] In some embodiments, one electrode is transparent while the other electrode is reflective.

[0188] Optionally, the transparent electrode comprises or consists of a transparent conductive oxide layer, preferably indium tin oxide or indium zinc oxide. In a preferred embodiment, the electrode may comprise poly(3,4 - ethylenedioxythiophene) (PEDOT). In other preferred embodiments, the electrode may comprise a mixture of PEDOT and polystyrene sulfonate (PSS). The electrode may consist of a layer of PEDOT:PSS.

[0189] Optionally, the reflective electrode may comprise a reflective metal layer. The reflective metal layer may be aluminum or silver or gold. In some embodiments, a bilayer electrode may be used. For example, the electrode may be an indium tin oxide (ITO) / silver bilayer, an ITO / aluminum bilayer, or an ITO / gold bilayer.

[0190] The device can be formed by forming the bulk heterojunction layer above one of the anode and cathode supported by a substrate, and depositing the other of the anode or cathode above the bulk heterojunction layer.

[0191] The area of the OPD can be less than about 3 cm 2 , less than about 2 cm 2 , less than about 1 cm 2 , less than about 0.75 cm 2 , less than about 0.5 cm 2 or less than about 0.25 cm 2 . The substrate can be (but is not limited to) a glass or plastic substrate. The substrate can be described as an inorganic semiconductor. In some embodiments, the substrate can be silicon. For example, the substrate can be a silicon wafer. The substrate is transparent if, in use, the incident light is to transmit through the substrate and the electrode supported by the substrate.

[0192] If, in use, the incident light is to transmit through the other of the anode and cathode, the substrate supporting one of the anode and cathode can be transparent or can be non - transparent.

[0193] The bulk heterojunction layer can be formed by any process, including but not limited to thermal evaporation and solution deposition methods.

[0194] Preferably, the bulk heterojunction layer is formed by depositing a formulation comprising an acceptor material and an electron donor material dissolved or dispersed in a solvent or a mixture of two or more solvents. The formulation can be deposited by any coating or printing method, including but not limited to: spin coating, dip coating, roll coating, spray coating, knife coating, wire bar coating, slot coating, inkjet printing, screen printing, gravure printing, and flexographic printing.

[0195] One or more solvents in the formulation may optionally comprise benzene or consist of benzene, which is substituted with one or more substituents selected from chlorine, C 1-10 alkyl and C 1-10 alkoxy, where two or more substituents may be linked to form a ring, which may be unsubstituted or substituted with one or more C 1-6 alkyl, optionally toluene, xylene, trimethylbenzene, tetramethylbenzene, anisole, indane and their alkyl-substituted derivatives, and tetrahydronaphthalene and its alkyl-substituted derivatives.

[0196] 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 other solvents. The one or more other solvents may be selected from esters, optionally alkyl esters or aryl esters of alkyl or aryl carboxylic acids, optionally C 1-10 alkyl benzoates, benzyl benzoate or dimethoxybenzene. In a preferred embodiment, a mixture of trimethylbenzene and benzyl benzoate is used as the solvent. In other preferred embodiments, a mixture of trimethylbenzene and dimethoxybenzene is used as the solvent.

[0197] In addition to the electron acceptor, electron donor and one or more solvents, the formulation may further comprise other components. As examples of such components, mention may be made of: binders, defoamers, degassing agents, viscosity enhancers, diluents, auxiliaries, flow improvers, colorants, dyes or pigments, sensitizers, stabilizers, nanoparticles, surface-active compounds, lubricants, wetting agents, dispersants and inhibitors.

[0198] The organic photodetectors described herein can be used in a wide range of applications, including but not limited to detecting the presence and / or brightness of ambient light, and in sensors comprising an organic photodetector and a light source. The organic photodetector can be configured such that light emitted from the light source is incident on the organic photodetector, and changes in the wavelength and / or brightness of the light can be detected. The sensor can be, but is not limited to, a gas sensor, a biosensor, an X-ray imaging device, a motion sensor (e.g., for security applications), a proximity sensor or a fingerprint sensor. The organic photodetector can form part of a 1D or 2D array in an image sensor. For example, the organic photodetector can be part of an array of organic photodetectors in a camera image sensor. Example

[0199] Comparative device 1

[0200] Fabricate a device with the following structure:

[0201] Cathode / Donor:Acceptor layer / Anode

[0202] Treat a glass substrate coated with an ITO patterned layer with polyethylenimine (PEIE) to change the work function of ITO.

[0203] Deposit a bulk heterojunction layer of a mixture of donor polymer 1 and acceptor compound C70IPH from 1,2,4-trimethylbenzene:benzyl benzoate at a donor:acceptor mass ratio of 1:1.7 by bar coating over the modified ITO layer.

[0204] Form an anode (Clevios HIL-E100 available from Heraeus) over the donor / acceptor mixture layer by spin coating.

[0205] Donor polymer 1 has the following structure:

[0206]

[0207] Example 1

[0208] Form a device as described in Comparative Device 1, except that a bulk heterojunction layer of a mixture of donor polymer 1 and di-PDI, ITIC, or ITIC-Th as the acceptor compound is deposited from 1,2,4-trimethylbenzene:benzyl benzoate by spin coating at a donor:acceptor mass ratio of 1:1 over the modified ITO layer.

[0209] Reference Figure 2 and Figure 3 , it can be seen that the dark current of Comparative Device 1 is significantly higher than that of the devices of Example 1 containing di-PDI, ITIC, or ITIC-Th as the acceptor compound.

[0210] Measure the external quantum efficiency (EQE) of the device fabricated according to Example 1 at reverse bias (2V). Reference Figure 4 and Figure 5 , in almost the entire region, the EQE of the device containing ITIC is higher than 40%, and is very close to the EQE achieved by the comparative device containing C70IPH in the green region of the spectrum (i.e., between 495 nm and 570 nm). This makes the device particularly suitable for X-ray imaging applications.

[0211] When considering the dark current and EQE measurement results of Example 1 together, it will be understood that, generally, compared to Comparative Device 1, the device of Example 1 exhibits an improved signal-to-noise ratio.

[0212] Comparative device 2

[0213] A device having the following structure was fabricated:

[0214] Cathode / Donor:Acceptor layer / Anode

[0215] A glass substrate coated with an ITO patterned layer was treated with PEIE to change the work function of ITO.

[0216] A bulk heterojunction layer of a mixture of a donor polymer and an acceptor compound C60PCBM was deposited by bar coating 1,3-dimethoxybenzene:benzyl benzoate in a donor:acceptor mass ratio of 1:1.75 over the modified ITO layer.

[0217] An anode (Clevios HIL-E100) available from Heraeus was formed by spin coating over the donor / acceptor mixture layer.

[0218] Example 2

[0219] A device was formed as described for Comparative Device 2, except that ITIC-2F was used instead of C60PCBM as the acceptor compound, at a donor:acceptor mass ratio of 1:1.5.

[0220] The EQE of the device fabricated according to Example 2 was measured at a reverse bias (3V). When considering the dark current and EQE measurement results of Example 2 together, it will be realized that, generally, compared to Comparative Device 2, the device of Example 2 exhibits an improved signal-to-noise ratio.

[0221] Method for determining the LUMO energy level

[0222] The LUMO energy levels reported herein were determined at room temperature in solution using square wave voltammetry (SWV). In square wave voltammetry, the current at the working electrode is measured while the potential between the working electrode and the reference electrode is linearly scanned over time. The difference current between the forward and reverse pulses is plotted as a function of the potential to generate a voltammogram. A device for measuring HOMO or LUMO energy levels by SWV may comprise a cell containing ammonium tert-butyl perchlorate or ammonium tert-butyl hexafluorophosphate in acetonitrile; a glassy carbon working electrode; a platinum counter electrode and a leak-free Ag / AgCl reference electrode.

[0223] For computational purposes, ferrocene was added directly to the existing cell at the end of the experiment, and cyclic voltammetry (CV) was used to determine the oxidation and reduction potentials of ferrocene relative to Ag / AgCl.

[0224] Equipment:

[0225] CHI 660D potentiostat

[0226] 3 mm diameter glassy carbon working electrode

[0227] Leak - free Ag / AgCl reference electrode

[0228] Pt wire auxiliary electrode or counter electrode

[0229] 0.1 M tetrabutylammonium hexafluorophosphate in acetonitrile solution

[0230] Method:

[0231] The sample was dissolved in toluene (3 mg / ml) and spin - coated directly onto the glassy carbon working electrode at 3000 rpm.

[0232] LUMO = 4.8 - Eferrocene (average peak - to - peak) - Esample reduction (peak maximum)

[0233] HOMO = 4.8 - Eferrocene (average peak - to - peak)+Esample oxidation (peak maximum)

[0234] A typical SWV experiment was conducted as follows: 15 Hz frequency; 25 mV amplitude and 0.004 V incremental step size. For HOMO and LUMO data, results were calculated from 3 newly spin - coated film samples.

[0235] All experiments were run under argon purge.

[0236] Although the invention has been described with respect to specific exemplary embodiments, it will be understood that various modifications, changes, and / or combinations of the features disclosed herein will be apparent to those skilled in the art without departing from the scope of the invention as set forth in the following claims.

Claims

1. An organic photodetector, comprising: A first electrode; A second electrode; And A photosensitive organic layer located between the electrodes, wherein: The photosensitive organic layer contains a donor compound and an acceptor compound, The acceptor compound is a small molecule non-fullerene acceptor, The LUMO energy level of the acceptor compound is equal to or deeper than the LUMO energy level of the fullerene derivative C70IPH, and The donor compound is a polymer containing a repeating unit of formula (XIVa): where each R 25 is independently a substituent and the groups R 25 are linked to form a 2- to 5-membered bridging group.

2. The organic photodetector according to claim 1, wherein the acceptor compound is represented by general formula (V): Wherein: R 11 、R 12 、R 13 、R 14 、R 15 、R 20 、R 21 、R 22 and R 23 each independently selected from one of the following: H, an electron-withdrawing group, or one of the following formulas (VIII) and (IX): And wherein: R 16 and R 17 each independently selected from: H; branched, linear or cyclic C 1-20 alkyl in which one or more non-adjacent non-terminal C atoms may be replaced by O, S, CO or COO, and one or more H atoms may be replaced by F; and aryl or heteroaryl, said aryl or heteroaryl being unsubstituted or substituted with one or more substituents.

3. The organic optical detector according to claim 2, wherein: The electron-withdrawing group includes halogen, CN, NO2, CF3, carbonyl or heteroaryl, and the heteroaryl is unsubstituted or substituted with one or more substituents; and R 16 and R 17 each of which is -(CH2) n CH3, where n is an integer selected from 1 to 20.

4. The organic optical detector according to claim 3, wherein R 11 , R 12 , R 13 and R 14 are of formula (VIII), where n is 5.

5. The organic optical detector according to claim 3, wherein R 11 , R 12 , R 13 and R 14 are of formula (IX), where n is 5.

6. The organic photodetector according to any one of claims 2-5, wherein at least one occurrence of R 20 to R 23 is F.

7. The organic photodetector according to any one of claims 1-5, wherein the acceptor compound is ITIC, ITIC-2F or ITIC-Th.

8. The organic photodetector according to claim 1, wherein the acceptor compound is represented by general formula (I): where each R 1 is independently selected from: H; a branched, straight-chain or cyclic C 1-20 alkyl group in which one or more non-adjacent non-terminal C atoms may be replaced by O, S, CO or COO, and one or more H atoms may be replaced by F; and an aryl or heteroaryl group, said aryl or heteroaryl group being unsubstituted or substituted with one or more substituents; where R 2 and R 3 each independently is selected from: H; a branched, straight-chain or cyclic C 1-20 alkyl group in which one or more non-adjacent non-terminal C atoms may be replaced by O, S, CO or COO, and one or more H atoms may be replaced by F; an aryl or heteroaryl group, said aryl or heteroaryl group being unsubstituted or substituted with one or more substituents; and a group having the following formula (II): and wherein R 4 and R 5 each independently selected from: H; branched, straight-chain or cyclic C 1-20 alkyl, wherein one or more non-adjacent non-terminal C atoms may be replaced by O, S, CO or COO, and one or more H atoms may be replaced by F; and aryl or heteroaryl, said aryl or heteroaryl being unsubstituted or substituted with one or more substituents.

9. The organic photodetector according to claim 8, wherein R 1 and R 4 are each independently selected from groups having the following formula (IV): Among them, R 9 and R 10 each independently selected from: -CH3 and -(CH2) n CH3, where n is an integer selected from 1 - 20.

10. The organic photodetector according to claim 9, wherein n is 4 or 5.

11. The organic photodetector according to claim 8 or 9, wherein the acceptor compound has the following formula (XII): wherein R 18 has the following formula (IV): And wherein R 9 and R 10 each independently selected from: -CH3 and -(CH2) n CH3, where n is an integer selected from 1 - 20.

12. The organic photodetector according to claim 11, wherein n is 4 or 5.

13. The organic photodetector according to any one of claims 1-5, wherein the donor compound is a semiconductor polymer.

14. The organic photodetector according to any one of claims 1-5, wherein the first electrode is an anode and the second electrode is a cathode.

15. The organic photodetector according to any one of claims 1-5, wherein the weight ratio of the donor compound to the acceptor compound is 1:0.5 to 1:1.

2.

16. The organic photodetector according to any one of claims 1-5, wherein the organic photodetector is configured to receive light with a wavelength > 900 nm, a wavelength > 1000 nm or a wavelength > 1100 nm.

17. The organic photodetector according to any one of claims 1-5, wherein the EQE of the organic photodetector is at least 30%, 20% or 5%.

18. The organic photodetector according to any one of claims 1-5, wherein the dark current generated by the organic photodetector is at least 10 times smaller than that of the fullerene derivative C70IPH.

19. A sensor, comprising a light source and an organic photodetector according to any one of claims 1 to 5, wherein the organic photodetector is configured to receive light emitted from the light source.

20. The sensor according to claim 19, wherein the light source is configured to generate light with a wavelength > 900 nm or a wavelength > 1000 nm.

21. A method for detecting light with a wavelength greater than 900 nm, the method comprising measuring the photocurrent generated by light incident on an organic photodetector according to any one of claims 1 to 5.

22. The method for detecting light according to claim 21, wherein the method comprises measuring the photocurrent generated by light incident on the organic photodetector and emitted from the light source of the sensor according to claim 19 or 20.

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