CN112243538A

CN112243538A - Near-infrared organic photodetector

Info

Publication number: CN112243538A
Application number: CN201980030407.XA
Authority: CN
Inventors: J·布鲁格斯; G·博沃; N·雅可比-格罗斯
Original assignee: Sumitomo Chemical Co Ltd
Current assignee: Sumitomo Chemical Co Ltd
Priority date: 2018-04-03
Filing date: 2019-04-03
Publication date: 2021-01-19
Also published as: GB2572573A; GB201805469D0; WO2019193331A3; JP7473477B2; JP2021520069A; GB2572659A; WO2019193331A2; GB201815231D0

Abstract

The organic photodetector includes a photosensitive organic layer located between two electrodes. The photosensitive organic layer is formed from a donor compound and an acceptor compound, and the acceptor compound is a non-fullerene compound that does not contain a fullerene group. The acceptor compound has a LUMO level equal to or deeper than that of a fullerene derivative, such as C70 IPH. The photosensitive organic layer produces low dark current and good EQE, and can operate in the near infrared region.

Description

Near-infrared organic photodetector

Technical Field

The present disclosure relates to photoactive compounds and their use in organic electronic devices, in particular organic photodetectors (photodetectors), more particularly but not exclusively organic photodetectors to detect wavelengths greater than 900nm or 1000 nm.

Background

A range 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).

CN106025073 discloses an organic solar cell using a ternary composition as active layer.

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

CN108084409 discloses a wide band gap organic semiconductor material.

US 2018/0047862 relates to light conversion devices, such as photovoltaic cells or photodetectors.

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 that does not contain a fullerene moiety, and the electron donor is a p-type semiconductor, which is a conjugated copolymer comprising a donor unit and an acceptor unit.

WO 2018/078080 relates to organic semiconductor compounds comprising polycyclic units as organic semiconductors.

US 6,972,431 discloses organic photodetectors with reduced dark current.

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

US 2017/0057962 discloses non-fullerene electron acceptors for high efficiency OPVs.

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

CN106025073 discloses an organic solar cell.

WO 2013/182847 discloses novel organic compounds useful as electron acceptors.

US 2015/0270497 discloses highly efficient organic photosensitive devices.

US 7,893,428 discloses photosensitive organic semiconductor compositions.

Baran et al, Energy environ, sci, 2016, 3783-.

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.

Yao et al, Organic Electronics,2015, 305-313 discloses low band gap polymers based on 2,1, 3-benzothiadiazole-5, 6-dicarboxylic acid imide for solution processed photodiode applications.

Hu et al, polymer. chem., 2017, 528-one 536 discloses a strategy for reducing dark current using laterally aligned donor polymers to achieve high detectability and responsiveness of organic photodetectors.

US 8,853,679 relates generally to organic semiconductors and in particular to organic semiconductors used to form part of thin film transistors.

Zhao et al, j.am.chem.soc., 2017, 7148-.

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 (indacenobithieno [3,2-b ] thiophene, IT), with a 2- (3-oxo-2, 3-indan-1-ylidene) maleonitrile (INCN) group, and substituted with four 4-hexylphenyl groups thereon.

WO 2017/125719 discloses organic photodiodes for use as photodetectors. It shows the use of fullerene derivatives to reduce dark current in organic photodiodes.

Miao et al, adv.opt.mater, 2016, 1711-.

Wang et al, Nanoscale, 2016, 5578-.

Summary of The Invention

According to a first aspect of some embodiments of the present invention, there is provided an organic photodetector. The organic photodetector includes: a first electrode and a second electrode and a photosensitive organic layer between the electrodes. The photosensitive organic layer comprises a donor compound and an acceptor compound, wherein the acceptor compound does not comprise a fullerene group, and wherein the acceptor compound has a LUMO level equal to or deeper than the LUMO level of a fullerene derivative C70 IPH. Thus, the photoactive organic layer comprises a non-fullerene photoactive organic layer. Applicants have discovered that such non-fullerene photoactive organic layers can provide organic photosensors with low dark current, high EQE, and/or operation at wavelengths in excess of 900nm, 1000nm, and/or 1100 nm.

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

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

wherein:

R¹¹、R¹²、R¹³、R¹⁴、R¹⁵each of which is independently selected from one of: h, electron-withdrawing groups, e.g. halogen, CN, NO₂、CF₃A carbonyl group or a heteroaryl group, said heteroaryl group being unsubstituted or substituted with one or more substituents, or one of the following formulae (VIII) and (IX):

and is

Wherein: r¹⁶And R¹⁷Each independently selected from: h; branched, linear or cyclic C_1-20Alkyl radicals, one or more of which is notAdjacent 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, which is unsubstituted or substituted with one or more substituents.

In some embodiments, R¹⁵、R²⁰、R²¹、R²²And R²³Is H or an electron withdrawing group, such as a halogen selected from Cl, Br, I or F; or CN, NO₂、CF₃A carbonyl group or a heteroaryl group, the heteroaryl group being unsubstituted or substituted with one or more substituents, and R¹⁶And R¹⁷Each of which is- (CH)₂)_nCH₃Wherein n is an integer selected from 1 to 20.

In some embodiments, R²⁰-R²³Is F at least one occurrence of at least one of. Optionally, R²⁰-R²³Each H or F.

In some embodiments, R¹¹、R¹²、R¹³And R¹⁴Is of formula (VIII), wherein n is 5.

In some embodiments, R¹¹、R¹²、R¹³And R¹⁴Is of formula (IX), wherein n is 5.

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

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

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

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

wherein:

each R¹Independently selected from: h; branched, linear or cyclic C_1-20Alkyl, 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 or heteroaryl group, which is unsubstituted or substituted with one or more substituents;

R²and R³Each of which is independently selected from: h; branched, linear or cyclic C_1-20Alkyl, 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; an aryl or heteroaryl group, which is unsubstituted or substituted with one or more substituents; and a group having the following formula (II):

and is

R⁴And R⁵Each of which is independently selected from: h; branched, linear or cyclic C_1-20Alkyl, 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 or heteroaryl group, which is unsubstituted or substituted with one or more substituents.

In some embodiments, R¹And R⁴Each independently selected from the group having the following formula (IV):

wherein R is⁹And R¹⁰Each of which is independentIs selected from: -CH₃And- (CH)₂)_nCH₃Wherein n is an integer selected from 1 to 20.

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

wherein R is¹⁸Having the following formula (IV):

and wherein R⁹And R¹⁰Each of which is independently selected from: -CH₃And- (CH)₂)_nCH₃Wherein n is an integer selected from 1 to 20. In some embodiments, n is 4 or 5.

In some embodiments, the donor compound is a semiconducting polymer.

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

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

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.

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

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

According to a fourth aspect of some embodiments of the present invention there is provided use of a compound which does not comprise a fullerene group having a LUMO level and which is deeper than the LUMO level of the fullerene derivative C70IPH in a photoactive layer of an organic photodetector to reduce dark current.

Drawings

FIG. 1 illustrates an organic photodetector according to an embodiment of the present invention;

FIGS. 2,3 and 6 are graphs of current density versus applied voltage for a device under dark conditions according to an embodiment and a comparative device; and

fig. 4,5 and 7 are graphs of EQE versus wavelength for devices according to embodiments and comparative devices.

Detailed Description

A disadvantage of OPDs is the presence of dark current, i.e. current flowing through the device when no photons are incident on the device, which may affect the detection limit of the device. It is therefore an object of some embodiments of the present invention to provide an OPD with low dark current. It is a further object of some embodiments of the present invention to provide an OPD having low dark current and good External Quantum Efficiency (EQE).

Organic electronic devices comprising organic semiconducting materials include organic light emitting devices, organic field effect transistors, organic photovoltaic devices and OPDs. For OPD. The following properties may need to be balanced: the organic semiconductor material provides the functionality of low dark current (the current generated by the OPD when no light is present, which is caused by a reverse bias applied to the OPD) and the EQE of the organic semiconductor material. For example, organic semiconductor materials that typically have good EQE also produce high dark current.

Furthermore, it may be desirable to operate the OPD at wavelengths other than visible light in the sensing environment and/or at wavelengths when there is a gap in the wavelength of sunlight. For example, sunlight having a wavelength of about 940nm may be absorbed in the atmosphere, creating a gap at that wavelength, and the light emitting device may operate in the visible spectrum without producing any output beyond 900nm wavelength. Operating the OPD sensor at such wavelengths may reduce interference from sunlight/visible light. For example, organic semiconductor materials with an EQE that can be considered low may be useful for OPDs that operate at such wavelengths without interference (thus, for purposes of this disclosure, the term "high EQE" refers to a high EQE relative to OPDs operating in the near infrared spectrum).

In contrast, for OPVs it may not be desirable to operate at such wavelengths (>900nm) because OPVs use electromagnetic radiation present in the environment.

Fig. 1 shows an OPD according to an embodiment of the present invention. The OPD comprises a cathode 103 supported by a substrate 101, an anode 107 and a bulk heterojunction layer 105 between the anode and the cathode, the bulk heterojunction layer 105 comprising a mixture of electron acceptors and electron donors. Optionally, the bulk heterojunction layer consists of an electron acceptor and an electron donor. In the embodiment shown in fig. 1, the OPD comprises a layer 106 of material that adjusts the work function of the cathode 103. In other embodiments, this layer may or may not be present.

The OPD may comprise further layers not shown in fig. 1. For example, the device may include a Hole Transport Layer (HTL) between the anode 107 and the heterojunction layer 105.

In use, a photodetector as described in the present disclosure may be connected to a voltage source for applying a reverse bias to the device and a device configured to measure photocurrent. In some embodiments, the light detector is part of a system comprising a plurality of light detectors. For example, the light detector may be part of an array in an image sensor of a camera. The voltage applied to the light detector may vary. In some embodiments, the light detector may be continuously biased when in use.

The OPD may be incorporated into a sensor comprising a light source, and the OPD may be configured to receive light emitted from the light source.

In some embodiments, the light from the light source may or may not change before reaching the light source. For example, the light may be filtered, down-converted, or up-converted before it reaches the light source.

The high dark current in the photodetector limits the detectable optical input signal due to the low signal-to-noise ratio.

The inventors have surprisingly found that the inclusion of an acceptor compound (which has a deep LUMO level relative to the fullerene derivative C70IPH) into an OPD can reduce dark current compared to OPDs comprising C70IPH as acceptor. For example, according to some embodiments of the present disclosure, acceptor compounds described herein provide OPDs having at least 5-fold or at least 10-fold lower dark current than fullerene compounds (e.g., C70 IPH).

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

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

As noted above, the inventors have also found that acceptor compounds disclosed herein may be suitable for detecting light in the near infrared region, particularly wavelengths of about >900nm, or >1000nm, or >1100 nm. At about 940nm, sunlight is absorbed by atmospheric moisture, so the use of such acceptor compounds in light source-OPD detector sensor devices to detect light with wavelengths in this range may be effective without being shielded/disturbed by sunlight. Acceptor compounds according to the present disclosure are not suitable for OPV due to absorption of sunlight by the atmosphere at these wavelengths.

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

The organic photodetector includes:

a first electrode, which may be an anode or a cathode;

a second electrode, which may be the other of the anode or the cathode; and

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 comprise a fullerene group, and wherein the acceptor compound has a LUMO level equal to or deeper than the LUMO level of the fullerene derivative C70 IPH.

As used herein, "deeper" LUMO energy levels refer to levels further away from vacuum energy levels, and "shallower" LUMO energy levels refer to levels closer to vacuum energy levels. It will therefore be appreciated that the LUMO energy level of the acceptor compound described herein, which does not comprise a fullerene group, is further away from the vacuum level than the LUMO energy level of the fullerene derivative C70 IPH.

Preferably, the LUMO 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 3.75eV deeper than the vacuum level, as measured by square wave voltammetry.

The non-fullerene acceptor compounds described herein may be small molecule non-fullerene acceptors (SM-NFAs).

The non-fullerene acceptor compound may be a compound of general formula (I):

wherein:

R²and R³Each of which is independently selected from: h; branched, linear or cyclic C_1-20Alkyl, 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; an aryl or heteroaryl group, which is unsubstituted or substituted with one or more substituents; and a group having one of the following formulae (II) or (II I):

and wherein R⁴、R⁵、R⁶、R⁷And R⁸Each independently selected from: h; branched, linear or cyclic C_1-20Alkyl, 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 or heteroaryl group, which is unsubstituted or substituted with one or more substituents.

Preferably, each R¹、R⁴And R⁶Independently selected from branched, straight or cyclic C_1-20An alkyl group.

Preferably, each R¹、R⁴And R⁶Independently selected from the group having the following formula (IV):

wherein R is⁹And R¹⁰Each of which is independently selected from: h; branched, linear or cyclic C_1-20Alkyl, 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 or heteroaryl group, which is unsubstituted or substituted with one or more substituents.

Preferably, R⁹And R¹⁰Each of which is independently selected from: -CH₃And- (CH)₂)_nCH₃Wherein n is an integer selected from 1 to 20.

Preferably, R⁹And R¹⁰Each of which is independently selected from: -CH₃，-(CH₂)₄CH₃And- (CH)₂)₅CH₃. Preferably, R⁹And R¹⁰Is- (CH)₂)₄CH₃Or- (CH)₂)₅CH₃。

Preferably, each R²Independently selected from: h; branched, linear or cyclic C_1-20An alkyl group.

In a preferred embodiment, each R is²Is H.

Preferably, R³Selected from aryl or heteroaryl, said aryl or heteroaryl being unsubstituted or substituted with one or more substituents.

In a preferred embodiment, R³Selected from the group of formula (II) or (III). Preferably, R³Is formula (II).

Preferably, each R⁴Independently selected from branched, straight or cyclic C_1-20An alkyl group.

Preferably, each R⁴Independently selected from groups having the following formula (IV):

In a preferred embodiment, R⁹And R¹⁰Each of which is independently selected from: -CH₃，-(CH₂)₄CH₃And- (CH)₂)₅CH₃. Preferably, R⁹And R¹⁰Is- (CH)₂)₄CH₃Or- (CH)₂)₅CH₃。

Preferably, each R⁵Independently selected from: h; branched, linear or cyclic C_1-20An alkyl group.

In a preferred embodiment, each R is⁵Is H.

Preferably, each R⁶Independently selected from branched, straight or cyclic C_1-20An alkyl group.

Preferably, each R⁶Independently selected from groups having the following formula (IV):

Preferably, R⁹And R¹⁰Each of which is independently selected from: -CH₃、-(CH₂)₄CH₃And- (CH)₂)₅CH₃. Preferably, R⁹And R¹⁰Is- (CH)₂)₄CH₃Or- (CH)₂)₅CH₃。

Preferably, R⁷And R⁸Each of which is independently selected from: h; branched, linear or cyclic C_1-20An alkyl group.

In a preferred embodiment, R⁷And R⁸Each of which is H.

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

wherein R is¹¹、R¹²、R¹³、R¹⁴、R¹⁵、R²⁰、R²¹、R²²And R²³Each of which is independently selected from: h; electron withdrawing groups such as halogens (including Cl, Br, I, or F); CN, NO₂、CF₃A carbonyl group or a heteroaryl group, the heteroaryl group being unsubstituted or substituted with one or more substituents; branched, linear or cyclic C_1-20Alkyl, 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 or heteroaryl group, which is unsubstituted or substituted with one or more substituents.

In some embodiments, R¹¹、R¹²、R¹³、R¹⁴、R¹⁵、R²⁰、R²¹、R²²And R²³Each of which is independently selected from one of the following formulae (VI) and (VII):

in some embodiments, R¹¹、R¹²、R¹³、R¹⁴、R¹⁵、R²⁰、R²¹、R²²And R²³Each of formula (VI) and (VII) is independently selected from one of formula (VI) and (VII), wherein one or more H atoms of each of formula (VI) and (VII) are independently replaced by a substituent selected from: branched, linear or cyclic C_1-20Alkyl, 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 or heteroaryl group, which is unsubstituted or substituted with one or more substituents.

In some embodiments, R¹¹、R¹²、R¹³、R¹⁴Each of which is independently selected from the following: h; electric power absorptionSub-groups, such as halogen (including Cl, Br, I or F); CN, NO₂、CF₃A carbonyl group or a heteroaryl group, the heteroaryl group being unsubstituted or substituted with one or more substituents; (ii) a Formulas (VI) and (VII); wherein one or more H atoms of each of formulas (VI) and (VII) are independently replaced by a substituent selected from the group consisting of: branched, linear or cyclic C_1-20Alkyl, 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 or heteroaryl group, which is unsubstituted or substituted with one or more substituents; and R is¹⁵、R²⁰、R²¹、R²²And R²³Selected from: h; electron withdrawing groups such as halogens (including Cl, Br, I, or F); or CN, NO₂、CF₃A carbonyl group or a heteroaryl group, the heteroaryl group being unsubstituted or substituted with one or more substituents; branched, linear or cyclic C_1-20Alkyl, 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 or heteroaryl group, which is unsubstituted or substituted with one or more substituents.

In a preferred embodiment, R¹¹、R¹²、R¹³、R¹⁴Is independently selected from formulae (VI) and (VII), wherein one or more H atoms of each of formulae (VI) and (VII) are independently replaced by a substituent selected from: branched, linear or cyclic C_1-20Alkyl, 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, R¹⁵Is H, and R²⁰、R²¹、R²²And R²³Each of which is H.

In a preferred embodiment, R¹¹、R¹²、R¹³、R¹⁴Selected from the group consisting of formula (VI) or (VII), wherein one or more proH of each of formula (VI) and (VII)Each substituent is independently substituted with a substituent selected from the group consisting of: branched, linear or cyclic C_1-20Alkyl, 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, R¹⁵Is H, and R²⁰、R²¹、R²²And R²³Each of which is an electron withdrawing group, preferably a halogen selected from the group consisting of F, Cl, I, Br.

In some embodiments, the electron withdrawing group may comprise CN, NO₂、CF₃A carbonyl group or a heteroaryl group, which heteroaryl group is unsubstituted or substituted with one or more substituents.

Preferably, R¹¹、R¹²、R¹³、R¹⁴Selected from the following formulae (VIII) and (IX), R¹⁵Is H, and R²⁰、R²¹、R²²And R²³Each of which is H or an electron withdrawing group, preferably a halogen selected from F, Cl, I, Br:

wherein R is¹⁶And R¹⁷Each independently selected from: -CH₃And- (CH)₂)_nCH₃Wherein n is an integer selected from 1 to 20.

Preferably, R¹¹、R¹²、R¹³、R¹⁴Selected from the following formulae (X) and (XI), R¹⁵Is H, and R²⁰、R²¹、R²²And R²³Each of which is independently selected from: h or halogen selected from F, Cl, I, Br; or CN, NO₂、CF₃A carbonyl group or a heteroaryl group, the heteroaryl group being unsubstituted or substituted with one or more substituents:

preferably, R¹¹、R¹²、R¹³、R¹⁴Selected from any one of the following formulae (X) and (XI), R¹⁵Is H, R²⁰、R²¹、R²²And R²³Each of which is H:

preferably, R¹¹、R¹²、R¹³、R¹⁴Selected from the following formulae (X) and (XI), R¹⁵Is H, and R²⁰、R²¹、R²²And R²³Each of which is independently selected from halogens selected from F, Cl, I, Br:

preferably, R¹¹、R¹²、R¹³、R¹⁴Selected from the following formulae (X) and (XI), R¹⁵Is H, R²⁰、R²¹、R²²And R²³Three of (a) are H, and R is²⁰、R²¹、R²²And R²³Is independently selected from halogens selected from: F. cl, I, Br:

preferably, R¹¹、R¹²、R¹³、R¹⁴Selected from the following formulae (X) and (XI), R¹⁵Is H, R²⁰、R²¹、R²²And R²³Are H, and R²⁰、R²¹、R²²And R²³Are independently selected from halogens selected from: F. cl, I, Br:

preferably, R¹¹、R¹²、R¹³、R¹⁴Selected from the following formulae (X) and (XI), R¹⁵Is H, R²⁰And R²³Is H, and R²¹And R²²Independently selected from halogens selected from: F. cl, I, Br:

preferably, R¹⁵Is H, and R²⁰、R²¹、R²²And R²³Each of which is independently selected from H or a halogen selected from F, Cl, I, Br.

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

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

TABLE 1

From 1-Material Inc.

As can be seen from Table 1, the LUMO level of ITIC-2F is deeper than the unfluorinated acceptor ITIC.

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.

The donor compound may be a semiconducting polymer.

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 amorphous or semi-crystalline conjugated organic polymers. Further preferably, the p-type organic semiconductor is a conjugated organic polymer having a low band gap, typically between 2.5eV and 1.5eV, preferably between 2.3eV and 1.8 eV. As exemplary p-type donor polymers, there may be mentioned polymers selected from conjugated hydrocarbon or heterocyclic polymers including polyacenes, polyanilines, polyazulenes, polybenzofuranes, polyfluorenes, polyfuranes, polyindenofluorenes, polyindoles, polyphenylenes, polypyrazoles, polypyrenes, polypyridazines, polypyridines, polytriarylamines, poly (phenylenevinylenes), poly (3-substituted thiophenes), poly (3, 4-disubstituted thiophenes), polyselenophenes, poly (3-substituted selenophenes), poly (3, 4-disubstituted selenophenes), poly (dithiophenes), poly (trithiophenes), poly (diselenophenes), poly (triselenophenes), polythieno [2,3-b ] thiophenes, polythieno [3,2-b ] thiophenes, polybenzothiophenes, polybenzo [1,2-b:4,5-b' ] dithiophenes, polysulene, polys, Polyisothianaphthene, poly (monosubstituted pyrroles), poly (3, 4-disubstituted pyrroles), poly-1, 3, 4-oxadiazoles, polyisothianaphthene, derivatives and copolymers thereof. preferred examples of p-type donors are: copolymers of polyfluorenes and polythiophenes (each of which may be substituted), and polymers comprising benzothiadiazole-based repeating units and thiophene-based repeating units (each of which may be substituted). It should be understood that the p-type donor may also be comprised of a mixture of electron donating materials.

The electron donor preferably comprises a repeat unit of formula (XIII):

wherein R is²⁴Independently at each occurrence is H or a substituent.

Optionally, each R²⁴Independently selected from:

C_1-20alkyl group, wherein the alkyl groupMay be replaced by O, S or C ═ O, and wherein the C is_1-20One or more H atoms of the alkyl group may be replaced by F; aryl or heteroaryl, preferably phenyl, which may be unsubstituted or substituted with one or more substituents; and fluorine.

The substituents for aryl or heteroaryl being optionally selected from F, CN, NO₂And C_1-20Alkyl, wherein one or more non-adjacent non-terminal carbon atoms of the alkyl may be replaced with O, S or C ═ O.

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

The polymer comprising a repeat unit of formula (XIII) is preferably a copolymer comprising one or more co-repeat units.

The one or more co-repeat units may comprise or consist of: one or more C_6-20A monocyclic or polycyclic arylene repeat unit, which arylene repeat unit may be unsubstituted or substituted with one or more substituents; 5-20 membered monocyclic or polycyclic heteroarylene repeat unit, which may be unsubstituted or substituted with one or more substituents.

The one or more co-repeat units may have formula (XIV):

wherein Ar is¹At each occurrence is arylene or heteroarylene; m is at least 1; r²⁵Is a substituent; r²⁵Independently at each occurrence is a substituent; n is 0 or a positive integer; and two radicals R²⁵May be joined to form a ring.

Optionally, each R²⁵Independently selected from linear, branched or cyclic C_1-20Alkyl radical, wherein the C_1-20One or more non-adjacent non-terminal C atoms of the alkyl group may be replaced by O, S, COO or CO.

Two radicals R²⁵Can be connected to form C_1-10Alkylene, wherein one or more non-adjacent C atoms of the alkylene group may be replaced by O, S, COO or CO.

Optionally, m is 2.

Optionally, each Ar¹Independently a 5 or 6 membered heteroarylene group, optionally a heteroarylene group selected from thiophene, furan, selenophene, pyrrole, oxadiazole, triazole, pyridine, diazine and triazine, preferably thiophene.

Optionally, the repeat unit of formula (XIV) has formula (XIVa):

optionally, a group R²⁵Are linked to form a 2-5 membered bridging group. Optionally, the bridging group has the formula-O-C (R)²⁶)₂-, wherein R²⁶Independently at each occurrence is H or a substituent. Substituent R²⁶Is optionally selected from C_1-20An alkyl group. Preferably, each R²⁶Is H.

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

In some embodiments, the weight ratio of donor compound to 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.

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

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

at least one of the first and second electrodes is transparent so that light incident on the device can reach the bulk heterojunction layer. In some embodiments, the first electrode and the second electrode are both transparent.

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

In some embodiments, one electrode is transparent and the other electrode is reflective.

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.

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 double layer 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.

The device may be formed by: a bulk heterojunction layer is formed over one of the anode and cathode supported by the substrate, and the other of the anode or cathode is deposited over the bulk heterojunction layer.

The area of the OPD may be less than about 3cm²Less than about 2cm²Less than about 1cm²Less than about 0.75cm²Less than about 0.5cm²Or less than about 0.25cm². The substrate may be, without limitation, a glass or plastic substrate. The substrate may be described as an inorganic semiconductor. In some embodiments, the substrate may be silicon. For example, the substrate may be a silicon wafer. The substrate is transparent if, in use, incident light is to be transmitted through the substrate and electrodes supported by the substrate.

The substrate supporting one of the anode and cathode may or may not be transparent if, in use, incident light is to be transmitted through the other of the anode and cathode.

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

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 may 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, ink jet printing, screen printing, gravure printing, and flexographic printing.

One or more solvents in the formulation may optionally comprise or consist of benzene substituted with a substituent selected from chlorine, C_1-10Alkyl and C_1-10One or more substituents of an alkoxy group, wherein two or more substituents may be linked to form a ring, which may be unsubstituted or substituted with one or more C_1-6Alkyl, optionally toluene, xylene, trimethylbenzene, tetramethylbenzene, anisole, indane and alkyl-substituted derivatives thereof, and tetralin and alkyl-substituted derivatives thereof.

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 or aryl esters of alkyl or aryl carboxylic acids, optionally C_1-10Alkyl benzoates, benzyl benzoates or dimethoxybenzenes. In a preferred embodiment, a mixture of trimethylbenzene and benzyl benzoate is used as solvent. In other preferred embodiments, a mixture of trimethylbenzene and dimethoxybenzene is used as solvent.

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

The organic photodetectors described herein may 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 that include organic photodetectors and light sources. The organic light detector may be configured such that light emitted from the light source is incident on the organic light detector, and a change in wavelength and/or brightness of the light may be detected. The sensor may 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 photodetectors may form part of a 1D or 2D array in an image sensor. For example, the organic light detector may be part of an organic light detector array in a camera image sensor.

Examples

Comparison device 1

Preparing a device having the following structure:

cathode/Donor acceptor layer/Anode

The glass substrate coated with the patterned layer of ITO was treated with Polyethyleneimine (PEIE) to change the work function of the ITO.

A bulk heterojunction layer of a mixture of donor polymer 1 and acceptor compound C70IPH was deposited over the modified ITO layer by rod coating from 1,2, 4-trimethylbenzene to benzyl benzoate at a donor to acceptor mass ratio of 1: 1.7.

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

The donor polymer 1 has the following structure:

example 1

A device was formed as described for comparative device 1, except that a bulk heterojunction layer of a mixture of donor polymer 1 and di-PDI, ITIC or ITIC-Th as acceptor compounds was deposited by spin coating over the modified ITO layer from 1,2, 4-trimethylbenzene to benzyl benzoate with a donor to acceptor mass ratio of 1:1.

Referring to fig. 2 and 3, it can be seen that the dark current of comparative device 1 is significantly higher compared to the device of example 1 including di-PDI, ITIC, or ITIC-Th as an acceptor compound.

The External Quantum Efficiency (EQE) of the device fabricated according to example 1 was measured at reverse bias (2V). Referring to fig. 4 and 5, the EQE of the device containing the ITIC is higher than 40% in almost the entire region, and very close to the EQE achieved by the comparative device containing the C70IPH in the green region of the spectrum (i.e. between 495nm and 570 nm). This makes the device particularly suitable for X-ray imaging applications.

When the dark current and EQE measurements of example 1 are considered together, it will be appreciated that, overall, the device of example 1 exhibits an improved signal-to-noise ratio compared to the comparative device 1.

Comparison device 2

Preparing a device having the following structure:

cathode/Donor acceptor layer/Anode

A glass substrate coated with a patterned layer of ITO was treated with PEIE to change the work function of the ITO.

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

Example 2

Devices were formed as described for comparative device 2, except that ITIC-2F was used instead of C60PCBM as the acceptor compound, at a donor to acceptor mass ratio of 1: 1.5.

Referring to fig. 6, it can be seen that the dark current of comparative device 2 is significantly higher compared to the device of example 2 containing ITIC-2F as an acceptor compound.

The EQE of the device fabricated according to example 2 was measured under reverse bias (3V). Referring to FIG. 7, a slight decrease in EQE was observed for the device containing the ITIC-2F. However, when the dark current and EQE measurements of example 2 are considered together, it will be appreciated that, overall, the device of example 2 exhibits an improved signal-to-noise ratio compared to the comparative device 2.

Method for determining the LUMO energy level

The LUMO energy levels reported herein were determined using Square Wave Voltammetry (SWV) in solution at room temperature. In square wave voltammetry, the current at the working electrode is measured while the potential between the working and reference electrodes is linearly swept over time. The differential current between the forward and reverse pulses is plotted as a function of potential to produce a voltammogram. An apparatus for measuring HOMO or LUMO energy levels by SWV may comprise a cell (cell) containing tert-butyl ammonium perchlorate or tert-butyl ammonium hexafluorophosphate in acetonitrile; a glassy carbon working electrode; a platinum counter electrode and a no-leak Ag/AgCl reference electrode.

For calculation purposes, ferrocene was added directly to the existing cell at the end of the experiment, where the potential for oxidation and reduction of ferrocene relative to Ag/AgCl was determined using Cyclic Voltammetry (CV).

Equipment:

CHI 660D potentiostat

Glassy carbon working electrode with 3mm diameter

Leakage-free Ag/AgCl reference electrode

Pt wire auxiliary electrode or counter electrode

0.1M solution of tetrabutylammonium hexafluorophosphate in acetonitrile

The method comprises the following steps:

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

LUMO ═ 4.8-E ferrocene (peak to peak average) -E sample reduction (peak maximum)

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

A typical SWV experiment was performed as follows: a frequency of 15 Hz; 25mV amplitude and increment step size of 0.004V. For the HOMO and LUMO data, the results were calculated from 3 new spin-coated film samples.

All experiments were run under an argon purge.

While the present invention has been described with respect to specific exemplary embodiments, it will be appreciated that various modifications, alterations, and/or combinations of 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 comprises a donor compound and an acceptor compound, wherein the acceptor compound does not comprise a fullerene group, and wherein the acceptor compound has a LUMO level equal to or deeper than the LUMO level of a fullerene derivative C70 IPH.

2. The organic photodetector of claim 1, wherein said acceptor compound is represented by general formula (V):

wherein:

R¹¹、R¹²、R¹³、R¹⁴、R¹⁵each of which is independently selected from one of: h, an electron withdrawing group, or one of the following formulae (VIII) and (IX):

and wherein:

R¹⁶and R¹⁷Each independently selected from: h; branched, linear or cyclic C_1-20Alkyl, 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 or heteroaryl group, which is unsubstituted or substituted with one or more substituents.

3. The organic photodetector as claimed in claim 2, wherein: the electron-withdrawing group comprises halogen, CN, NO₂、CF₃A carbonyl group or a heteroaryl group, the heteroaryl group being unsubstituted or substituted with one or more substituents; and R is¹⁶And R¹⁷Each of which is- (CH)₂)_nCH₃Wherein n is an integer selected from 1 to 20.

4. The organic photodetector of claim 3, wherein R¹¹、R¹²、R¹³And R¹⁴Is of formula (VIII), wherein n is 5.

5. The organic photodetector of claim 3, wherein R¹¹、R¹²、R¹³And R¹⁴Is of formula (IX), wherein n is 5.

6. The organic photodetector of any one of claims 2 to 5, wherein R²⁰To R²³Is F at least one occurrence of at least one of.

7. The organic photodetector of any preceding claim, wherein the acceptor compound is ITIC, ITIC-2F, or ITIC-Th.

8. The organic photodetector of claim 1, wherein said acceptor compound is represented by general formula (I):

wherein each R¹Independently selected from: h; branched, linear or cyclic C_1-20Alkyl, 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 beingUnsubstituted or substituted with one or more substituents; wherein R is²And R³Each of which is independently selected from: h; branched, linear or cyclic C_1-20Alkyl, 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; an aryl or heteroaryl group, which is unsubstituted or substituted with one or more substituents; and a group having the following formula (II):

and wherein R⁴And R⁵Each of which is independently selected from: h; branched, linear or cyclic C_1-20Alkyl, 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 or heteroaryl group, which is unsubstituted or substituted with one or more substituents.

9. The organic photodetector of claim 8, wherein R¹And R⁴Each independently selected from the group having the following formula (IV):

wherein R is⁹And R¹⁰Each of which is independently selected from: -CH₃And- (CH)₂)_nCH₃Wherein n is an integer selected from 1 to 20.

10. The organic photodetector of one of claims 8 or 9, wherein the acceptor compound has the following formula (XII):

wherein R is¹⁸Having the following formula (IV):

and wherein R⁹And R¹⁰Each of which is independently selected from: -CH₃And- (CH)₂)_nCH₃Wherein n is an integer selected from 1 to 20.

11. The organic photodetector of any one of claims 9 or 10, wherein n is 4 or 5.

12. The organic photodetector of any preceding claim, wherein the donor compound is a semiconducting polymer.

13. An organic photodetector according to any one of the preceding claims, wherein the first electrode is an anode and the second electrode is a cathode.

14. The organic photodetector of any preceding claim, wherein the weight ratio of donor compound to acceptor compound is from about 1:0.5 to about 1: 1.2.

15. The organic photodetector of any preceding claim, wherein the organic photodetector is configured to receive light having a wavelength >900nm, a wavelength >1000nm, or a wavelength >1100 nm.

16. The organic photodetector of any one of the preceding claims, wherein the organic photodetector has an EQE of at least 30%, 20%, or 5%.

17. The organic photodetector of any preceding claim, wherein the organic photodetector produces a dark current at least 10 times less than a fullerene derivative C70 IPH.

18. A sensor comprising a light source and the organic photodetector of any one of claims 1 to 17, wherein the organic photodetector is configured to receive light emitted from the light source.

19. The sensor of claim 18, wherein the light source is configured to generate light at a wavelength >900nm or a wavelength >1000 nm.

20. A method of detecting light comprising measuring photocurrent generated by light incident on the organic photodetector of any of claims 1 to 19.

21. The method of detecting light according to claim 20, wherein the method comprises measuring photocurrent generated by light incident on the organic light detector and emitted from a light source of the sensor according to claim 18 or 19.

22. Use of an acceptor compound, which does not comprise a fullerene group having a LUMO level and being deeper than the LUMO level of a fullerene derivative C70IPH, in a photoactive layer of an organic photodetector to reduce dark current.

23. Use of an acceptor compound according to claim 22 wherein said acceptor compound is represented by general formula (V):

wherein R is¹¹、R¹²、R¹³、R¹⁴、R¹⁵Each of which is independently selected from one of: h, electron-withdrawing groups, e.g. halogen, CN, NO₂、CF₃A carbonyl group or a heteroaryl group, said heteroaryl group being unsubstituted or substituted with one or more substituentsA substituent group; or one of the following formulae (VIII) and (IX):

and wherein R¹⁶And R¹⁷Each independently selected from: h; branched, linear or cyclic C_1-20Alkyl, 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 or heteroaryl group, which is unsubstituted or substituted with one or more substituents.