JP2021163810A - Organic semiconductor device - Google Patents

Abstract

To provide an organic semiconductor device with high external quantum efficiency (EQE).SOLUTION: An organic semiconductor device includes a p-type conjugated polymer, an n-type fullerene, and an n-type compound represented by the following formula (I) in an active layer (in the formula (I), X represents a carbon or silicon atom; Y1, Y2, Z1, and Z2 each independently represent a linear or branched hydrocarbon group having 6 or more and 20 or less carbon atoms; A and B each independently represent a fluorine atom or a chlorine atom; m and n independently represent an integer of 1 or more and 4 or less; p and q independently represent an integer of 0 or 1).SELECTED DRAWING: None

Description

The present invention relates to an organic semiconductor device, and more particularly to an organic semiconductor device suitable for an infrared photodetector.

The roles required of image sensors are diversifying, and there are increasing opportunities for them to be used in motion recognition, spatial measurement, spatial mapping, shape recognition, etc. by mechanical processing. As recognition by the sensor, not only visible light but also reflected light of infrared light that cannot be perceived by humans is processed, but the photoelectric conversion efficiency in the near infrared region is insufficient (for example, non-transmissive light). See Patent Documents 1 and 2).
In order to improve the photoelectric conversion efficiency (external quantum efficiency) in the near-infrared region, so far, the photoelectric conversion layer absorbs light to generate an exciter and separates the charge based on the principle of photoelectric conversion of CMOS. Therefore, it has been studied to use a photoelectric conversion layer having high absorbance with improved internal quantum efficiency, or to thicken the photoelectric conversion layer to improve the absorbance.
Non-Patent Documents 1 and 2 describe a general remarks on a photoelectric conversion device that detects near infrared rays, and in particular, describe an example using a squalene-based donor material. Then, an example of a device that absorbs near-infrared light, performs photoelectric conversion, and senses the light is described. Non-Patent Document 3 describes a non-fullerene compound having a narrow bandgap and a method for synthesizing the non-fullerene compound.
Further, Patent Documents 1 and 2 describe a photoelectric conversion element which is an image pickup element using an organic semiconductor.

JP-A-2018-129505 JP-A-2019-36641

DOI: 10.1021 / acs. chemmator. 9b90066, Chem. Mater. (2019) ACS Appl. Mater. Interfaces 2018, 10, 11063-11569 Adv. Energy Matter. , Volume 8, 1801212 (2018)

Research on new organic semiconductors has been conducted in order to obtain semiconductor devices with higher efficiency, particularly photoelectric conversion elements having high external quantum efficiency (EQE). As an organic semiconductor for improving the external quantum efficiency of an organic semiconductor device, an n-type compound has been developed. However, since the n-type compound has a donor part and an acceptor part in a small molecule, electron localization occurs and the electron mobility is not sufficient.
An object of the present invention is to solve the above problems and provide an organic semiconductor device having high external quantum efficiency.

As a result of diligent studies, the present inventors have obtained an organic semiconductor device having high external quantum efficiency (EQE) by constructing an active layer in which n-type fullerenes are added to a p-type conjugated polymer and an n-type compound. We have arrived at the present invention. That is, the gist of the present invention is as follows.

（式（Ｉ）中、Ｘは、炭素又はケイ素原子を表し；Ｙ１、Ｙ２、Ｚ１及びＺ２は、それぞれ独立に炭素数６以上２０以下の直鎖又は分岐の炭化水素基を表し；Ａ及びＢは、それぞれ独立にフッ素原子又は塩素原子を表し；ｍ及びｎは、それぞれ独立に１以上４以下の整数を表し；ｐ及びｑは、それぞれ独立に０又は１の整数を表す。）
［２］
前記ｎ型フラーレン類が、［６０］フラーレン、［７０］フラーレン、［６０］ＰＣＢＭ、［７０］ＰＣＢＭ、ｂｉｓ［６０］ＰＣＢＭ、ｂｉｓ［７０］ＰＣＢＭ、［６０］ＳＩＭＥＦ、［７０］ＳＩＭＥＦ、［６０］ＩＣＢＡ、［７０］ＩＣＢＡ、［６０］ＩＣＭＡ、および［７０］ＩＣＭＡからなる群より選択される少なくとも１種類の化合物である、［１］に記載の有機半導体デバイス。
［３］
前記活性層が、多環芳香族化合物又は１，８−ジヨードオクタンからなる添加物を含有する、［１］又は［２］に記載の有機半導体デバイス。
［４］
前記有機半導体デバイスが光電変換素子である、［１］〜［３］のいずれかに記載の有機半導体デバイス。
［５］
波長９４０ｎｍの光を照射した際の外部量子効率（ＥＱＥ）が５０％以上である、［１］〜［４］のいずれかに記載の有機半導体デバイス。
［６］
p型共役高分子、ｎ型フラーレン類、および、下記式（Ｉ）で表されるｎ型化合物を含
有し、
前記ｎ型フラーレン類が、［６０］フラーレン、［７０］フラーレン、［６０］ＰＣＢＭ、［７０］ＰＣＢＭ、ｂｉｓ［６０］ＰＣＢＭ、ｂｉｓ［７０］ＰＣＢＭ、［６０］ＳＩＭＥＦ、［７０］ＳＩＭＥＦ、［６０］ＩＣＢＡ、［７０］ＩＣＢＡ、［６０］ＩＣＭＡ、および［７０］ＩＣＭＡからなる群より選択される少なくとも１種類の化合物であり、
前記ｎ型化合物に対する前記ｎ型フラーレン類の重量比が、１．０以下である、有機半導体インク。

（式（Ｉ）中、Ｘは、炭素又はケイ素原子を表し；Ｙ１、Ｙ２、Ｚ１及びＺ２は、それぞれ独立に炭素数６以上２０以下の直鎖又は分岐の炭化水素基を表し；Ａ及びＢは、それぞれ独立にフッ素原子又は塩素原子を表し；ｍ及びｎは、それぞれ独立に１以上４以下の整数を表し；ｐ及びｑは、それぞれ独立に０又は１の整数を表す。）
［７］
多環芳香族化合物又は１，８−ジヨードオクタンからなる添加物をさらに含有する、［６］に記載の有機半導体インク。
［８］
［１］〜［５］のいずれかに記載の有機半導体デバイスを用いたフォトディテクタ。
［９］
波長７００〜１０００ｎｍの光を検知するために用いる、［８］に記載のフォトディテクタ。 [1]
An organic semiconductor device containing a p-type conjugated polymer, n-type fullerenes, and an n-type compound represented by the following formula (I) in an active layer.

(In formula (I), X represents a carbon or silicon atom; Y1, Y2, Z1 and Z2 each independently represent a linear or branched hydrocarbon group having 6 or more and 20 or less carbon atoms; A and B. Represents a fluorine atom or a chlorine atom independently; m and n independently represent an integer of 1 or more and 4 or less; p and q each independently represent an integer of 0 or 1).
[2]
The n-type fullerenes are [60] fullerenes, [70] fullerenes, [60] PCBM, [70] PCBM, bis [60] PCBM, bis [70] PCBM, [60] SIMEF, [70] SIMEF, [ The organic semiconductor device according to [1], which is at least one compound selected from the group consisting of 60] ICBA, [70] ICBA, [60] ICMA, and [70] ICMA.
[3]
The organic semiconductor device according to [1] or [2], wherein the active layer contains an additive consisting of a polycyclic aromatic compound or 1,8-diiodooctane.
[4]
The organic semiconductor device according to any one of [1] to [3], wherein the organic semiconductor device is a photoelectric conversion element.
[5]
The organic semiconductor device according to any one of [1] to [4], wherein the external quantum efficiency (EQE) when irradiated with light having a wavelength of 940 nm is 50% or more.
[6]
It contains a p-type conjugated polymer, n-type fullerenes, and an n-type compound represented by the following formula (I).
The n-type fullerenes are [60] fullerenes, [70] fullerenes, [60] PCBM, [70] PCBM, bis [60] PCBM, bis [70] PCBM, [60] SIMEF, [70] SIMEF, [ At least one compound selected from the group consisting of 60] ICBA, [70] ICBA, [60] ICMA, and [70] ICMA.
An organic semiconductor ink in which the weight ratio of the n-type fullerenes to the n-type compound is 1.0 or less.

(In formula (I), X represents a carbon or silicon atom; Y1, Y2, Z1 and Z2 each independently represent a linear or branched hydrocarbon group having 6 or more and 20 or less carbon atoms; A and B. Represents a fluorine atom or a chlorine atom independently; m and n independently represent an integer of 1 or more and 4 or less; p and q each independently represent an integer of 0 or 1).
[7]
The organic semiconductor ink according to [6], further containing an additive consisting of a polycyclic aromatic compound or 1,8-diiodooctane.
[8]
A photodetector using the organic semiconductor device according to any one of [1] to [5].
[9]
The photodetector according to [8], which is used to detect light having a wavelength of 700 to 1000 nm.

According to the present invention, it is possible to provide an organic semiconductor device having high external quantum efficiency (EQE).

Hereinafter, the present invention will be described in detail, but the description of the constituent elements described below is an example (representative example) of the embodiment of the present invention, and the present invention is not limited to these contents. It can be implemented with various modifications within the scope of the abstract.

The organic semiconductor device according to the embodiment of the present invention may take various forms, but as a typical form, a photoelectric conversion element used in a photodetector will be described below. Therefore, the organic semiconductor device is not limited to the photoelectric conversion element.

The photoelectric conversion element according to the embodiment of the present invention has an active layer (photoelectric conversion layer) containing a p-type conjugated polymer, fullerenes and n-type compounds as an organic semiconductor.
Further, the photoelectric conversion element according to the present embodiment may be a photoelectric conversion element including a photoelectric conversion layer that receives light in the near infrared region and performs photoelectric conversion, in which case the photoelectric conversion layer is a near infrared absorbing material. May include. The near infrared is a wavelength range of light located between the visible region and the infrared region, and generally refers to a region of 700 nm or more and 2500 nm or less, and in the present invention, a range of 700 nm or more and 1200 nm or less. As expected.

(N-type compound)
The active layer of the organic semiconductor device according to the present embodiment contains an n-type compound represented by the following general formula (I) as an n-type organic semiconductor. The n-type compound has an absorption maximum in the solution in the range of 850 nm or more and 1050 nm or less, and has a band gap suitable as a photoelectric conversion element for an infrared photodetector.

In formula (I), X represents a carbon or silicon atom; Y1, Y2, Z1 and Z2 each independently represent a linear or branched hydrocarbon group having 6 or more and 20 or less carbon atoms; A and B are. , Representing a fluorine atom or a chlorine atom independently; m and n independently represent an integer of 1 or more and 4 or less; p and q each independently represent an integer of 0 or 1.

X is preferably a silicon atom from the viewpoint of stable solubility.
The carbon number of the linear or branched hydrocarbon group represented by Y1, Y2, Z1 and Z2 having 6 or more and 20 or less carbon atoms is preferably 7 or more, more preferably 8 or more, and preferably 15 or less. It is more preferably 12 or less.
Examples of the linear or branched hydrocarbon group having 6 to 20 carbon atoms include a linear alkyl group such as an n-octyl group, an n-decyl group, a lauryl group, a myristyl group and a palmityl group; 2-ethylhexyl group and 2-ethylhexyl group. Examples thereof include a primary alkyl group having a branch such as a butyl octyl group; a secondary alkyl group such as a 2-octyl group, a 2-nonyl group, and a 2-decyl group; and the like.
Of these, Y1, Y2, Z1 and Z2 are preferably primary branched chain hydrocarbon groups.
A and B are preferably fluorine atoms from the viewpoint of improving solubility, and are preferably chlorine atoms from the viewpoint of the molecular arrangement when the active layer is formed.
m and n are preferably 2.
p and q are preferably 1.

The n-type compound represented by the general formula (I) can be synthesized by the method described in Non-Patent Document 3 (Adv. Energy Meter., Vol. 8, 1801212 (2018)).

(N-type fullerenes)
The active layer of the organic semiconductor device according to the present embodiment contains n-type fullerenes as an n-type organic semiconductor. The n-type fullerenes can be used alone or in combination of two or more. In the present embodiment, by adding n-type fullerenes to the active layer containing the p-type conjugated polymer and the n-type compound, both the improvement of electron mobility and the absorption of the n-type compound in the near infrared region are achieved at the same time. Can be made to. Further, by including n-type fullerenes in the active layer, the effect of efficiently constructing a bulk heterojunction with the p-type conjugated polymer to improve the charge separation efficiency and the effect of obtaining the balance between the mobility of holes and electrons. Etc. can also be expected.

The n-type fullerenes are not particularly limited, and fullerenes known as n-type semiconductors can be used. Known fullerenes include unmodified fullerenes such as fullerenes-C60, fullerenes-C70, fullerenes-C76, fullerenes-C78, fullerenes-C84, fullerenes-C240, fullerenes-C540, mixed fullerenes, fullerenes nanotubes; and these. Examples thereof include fullerene derivatives in which a part is substituted with a hydrogen atom, a halogen atom, an alkyl group, an alkenyl group, an aryl group, a heteroaryl group, a cycloalkyl group, a silyl group, an ether group, an amino group, a silyl group and the like. Of these, fullerenes that dissolve 10 mg or more, more preferably fullerenes that dissolve 15 mg or more, and fullerenes that dissolve 25 mg or more are particularly preferable with respect to 1 mL of an organic solvent (for example, chlorobenzene) described later.
Specific fullerene derivatives include [60] PCBM, [70] PCBM, bis [60] PCBM, bis [70] PCBM, [60] SIMEF, [70] SIMEF, [60] ICBA, [70] ICBA, Examples thereof include [60] ICMA, [70] ICMA, MP-C60, [60] PCBiB, and [60] PCBH.
Of these, the unmodified fullerene is preferably [60] fullerene or [70] fullerene.
The fullerene derivatives are [60] PCBM, [70] PCBM, bis [60] PCBM, bis [70] PCBM, [60] SIMEF, [70] SIMEF, [60] ICBA, [70] ICBA, [60]. ] ICMA, or [70] ICMA, more preferably [60] PCBM, [70] PCBM, or [60] SIMEF.

The weight ratio of n-type fullerenes to n-type compounds in the active layer is not particularly limited, and is usually 0.2 or more, preferably 0.3 or more, more preferably 0.5 or more, still more preferably 0.6 or more. In addition, it is usually 1.0 or less, preferably 0.9 or less, more preferably 0.85 or less, still more preferably 0.8 or less. By setting the weight ratio within the above range, the solubility of the active layer in the mixed solution can be ensured.

(P-type conjugated polymer)
The active layer of the organic semiconductor device according to the present embodiment contains a p-type conjugated polymer as a p-type organic semiconductor. Examples of the p-type conjugated polymer include a hole-transporting polymer, and a hole-transporting polymer having a structural unit having a property of easily donating electrons is preferable. Further, the p-type conjugated polymer is preferably one that can be mixed with an n-type organic semiconductor to form a film by coating.
Specific examples of the partial structure having excellent hole transportability in the hole transport polymer include a benzodithiophene structure, a thiophene structure, a carbazole structure, a dibenzofuran structure, a triarylamine structure, a naphthalene structure, a phenanthrene structure or pyrene. The structure can be mentioned.
Specific examples of the p-type conjugated polymer include a p-type conjugated polymer represented by the general formula (II). In formula (II), n is a positive number.

The weight ratio of the n-type compound to the p-type conjugated polymer in the active layer is usually 0.5 or more, preferably 0.6 or more, more preferably 0.65 or more, and usually 1.5 or less, preferably 1. It is 0.3 or less, more preferably 1.0 or less.
The weight ratio of n-type fullerenes to the p-type conjugated polymer in the active layer is usually 0.4 or more, preferably 0.5 or more, more preferably 0.6 or more, and usually 2.0 or less. It is preferably 1.5 or less, more preferably 1.0 or less.

The method for forming the active layer is not particularly limited, and a film can be formed by a known method, but it is typically a coating method.
When the active layer is formed by the coating method, the organic semiconductor is dissolved in an organic solvent by dissolving p-type conjugated polymers, n-type fullerenes, and n-type compounds, which are organic semiconductors, and other necessary substances as additives. An ink is prepared, the organic semiconductor ink is applied onto a substrate by a spin coating method or the like, and the mixture is dried to form the ink. The spin coating conditions may be appropriately determined according to a conventional method in consideration of the viscosity of the organic semiconductor ink and the like. The drying conditions are not particularly limited as long as the organic solvent in the organic semiconductor ink can be removed. For example, the organic semiconductor ink is heated and annealed at 70 ° C. to 130 ° C. for 5 to 20 minutes under atmospheric pressure to obtain the organic semiconductor ink. Can be dried.

The contents of the p-type conjugated polymer, n-type fullerenes and n-type compounds in the organic semiconductor ink are not particularly limited as long as the active layer can be formed by coating.
The content of the p-type conjugated polymer in the organic semiconductor ink is usually 0.5% by mass or more, may be 0.7% by mass or more, and is usually 1.5% by mass or less. It may be 3% by mass or less.
The content of n-type fullerenes in the organic semiconductor ink is usually 0.3% by mass or more, may be 0.4% by mass or more, and is usually 1.5% by mass or less. It may be 0% by mass or less.
The content of the n-type compound in the organic semiconductor ink is usually 0.7% by mass or more, may be 1.0% by mass or more, and is usually 2.0% by mass or less. It may be 0.8% by mass or less.
In the present embodiment, the weight ratio of n-type fullerene to the n-type compound in the organic semiconductor ink is usually 0.2 or more, preferably 0.3 or more, more preferably 0.5 or more, still more preferably 0.6. Above, usually 1.0 or less, preferably 0.9 or less, more preferably 0
.. It is 85 or less, more preferably 0.8 or less. By setting the weight ratio within the above range, there is an effect of improving EQE due to the high electron mobility of the n-type fullerene.

The organic solvent used for the organic semiconductor ink is not particularly limited, and an organic solvent generally used for a coating liquid for forming an active layer of an organic semiconductor device can be used. Specific examples thereof include halogen solvents such as chloroform and dichloroethane, aromatic hydrocarbon solvents such as toluene, xylene, chlorobenzene and dichlorobenzene, and organic solvents such as ether solvents such as THF and dibutyl ether. This is because organic semiconductors are generally highly soluble in these organic solvents. Further, by using these organic solvents, improvement in photoelectric conversion efficiency can be expected.
Among the above organic solvents, the organic solvent is preferably xylene, chlorobenzene or chloroform, although it depends on the type of the organic semiconductor. When adjusting the solubility, the organic solvent may be a mixed organic solvent of two or more kinds. The content ratio is not particularly limited and may be in the range of 1: 9 to 9: 1. The difference in boiling points of these organic solvents is preferably 50 ° C. or lower, more preferably 40 ° C. or lower, and even more preferably 30 ° C. or lower.

The organic semiconductor ink preferably contains an additive in addition to the p-type conjugated polymer, n-type fullerenes, and n-type compound for the purpose of stabilizing the bulk heterostructure.
As an additive, a compound capable of promoting the stacking of the aromatic portion of the p-type organic semiconductor and the aromatic moiety of the n-type organic semiconductor, and promoting the formation of a bulk heterostructure between the p-type organic semiconductor and the n-type organic semiconductor. For example, a polycyclic aromatic compound, 1,8-diiodooctane and the like can be mentioned.
Examples of the polycyclic aromatic compound include naphthalene, anthracene, and pyrene. Of these, the additive is preferably a bicyclic fused ring such as 1-chloronaphthalene.
The content of the additive in the organic semiconductor ink is usually 1.5% by mass or more, preferably 2.0% by mass or more, and usually 4.0% by mass or less, preferably 3.5% by mass or less. Is.

Further, the organic semiconductor ink may contain other components as long as the effects of the present invention are not impaired. The content of other components is usually 2.0% by mass or less with respect to the organic solvent.

When the organic semiconductor device is a photoelectric conversion element, the structure of the photoelectric conversion element can be referred to, for example, the description of JP-A-2007-324587, and is not particularly limited. The structure may be such that an electron transport layer, an active layer (photoelectric conversion layer), a hole transport layer, and a metal electrode are laminated in this order, and a transparent electrode, a hole transport layer, and an active layer (photoelectric conversion layer) are placed on a transparent substrate. ), The electron transport layer, and the metal electrode may be laminated in this order.

The transparent electrode is an electrode made of a material having an average transmittance of 80% or more in visible light of 450 nm or more. The material for forming the transparent electrode is not particularly limited as long as the transparent electrode can be formed, but tin-doped indium oxide (ITO), zinc-doped indium oxide (IZO), and tungsten-doped indium oxide are used. (IWO), oxide of zinc and aluminum (AZO), indium oxide (In ₂ O ₃ ), zinc oxide (ZnO), titanium oxide (TiO ₂ ) and the like.

The metal electrode is an electrode paired with the transparent electrode. The material constituting the metal electrode is not particularly limited, and examples thereof include metals such as gold, platinum, silver, aluminum, nickel, titanium, magnesium, calcium, barium, sodium, chromium, copper, and cobalt, or alloys thereof.
It is preferable that the metal electrode is a transparent electrode, that is, the pair of electrodes is a transparent electrode. In this case, the metal electrode is formed of the material forming the transparent electrode, and the pair of electrodes may be formed of the same material or may be different.
The film thickness of the metal electrode is not particularly limited, and if it is desired to obtain transparency, it may be usually about 10 nm. On the other hand, if transparency is not required, it may be 40 nm or more, more preferably 100 nm or more in consideration of durability and the like.

There are no particular restrictions on the constituent members of the electron transport layer and the hole transport layer and the manufacturing method thereof, and well-known techniques can be used. For example, the members described in publicly known documents such as International Publication No. 2013/171517, International Publication No. 2013/180230, and Japanese Patent Application Laid-Open No. 2012-191194, and methods for producing the same can be used.

When the organic semiconductor device is a photoelectric conversion element, the photoelectric conversion element is provided and used as a photodetector in an optical sensor or an image pickup element. In that case, known configurations of the optical sensor and the image sensor may be applied.
The organic semiconductor device according to the present embodiment forms an active layer in combination with an n-type organic semiconductor suitable for a p-type organic semiconductor, thereby achieving external quantum efficiency (EQE) at at least a part of wavelengths at 700 to 1000 nm. The EQE can be 50% or more, more preferably 50% or more at a wavelength of 940 nm, and even more preferably 50% or more at all wavelengths of 700 to 1000 nm.
By using an organic semiconductor device (photoelectric conversion element) having such an active layer, a photodetector used for detecting light having a wavelength of 700 to 1000 nm can be obtained.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

[Synthesis of n-type compounds]
(Synthesis Example 1)

Under a nitrogen stream, 11.4 g (100 mmol) of 3-methoxythiophene, 19.5 g (150 mmol) of 2-ethylhexanol, 1.72 g (10 mmol) of p-toluenesulfonic acid and 200 mL of toluene were placed in a 500 mL four-necked flask, and Dean was placed. The mixture was heated in an oil bath at 130 ° C. for 8 hours while removing water with a Stark apparatus. The reaction was mixed with 100 mL of water and the reaction product was extracted with 100 mL of ethyl acetate. The extract was washed with saturated brine, and the solvent was distilled off from the extract. The obtained residue was purified by column chromatography using a solvent of hexane: ethyl acetate = 95: 5 as a developing solvent to obtain 17.1 g (yield 81%) of 3- (2-ethylhexyl oki) thiophene. Obtained.

(Synthesis Example 2)

In a 200 mL four-necked flask, 4.3 g (20 mmol) of 3- (2-ethylhexyl oki) thiophene and 60 mL of N, N-dimethylformamide are placed, and a solution of 3.6 g (20 mmol) of N-bromosuccinimide in 40 mL of DMF under an ice bath. Was slowly added dropwise. After stirring for 1 hour, the mixture was poured into 100 mL of ice water and extracted with 100 mL of ethyl acetate. Wash with saturated aqueous ammonia chloride, saturated aqueous sodium hydrogen carbonate, and saturated brine, and after concentration, perform column purification with hexane: ethyl acetate = 98: 2 to quantify 6.0 g of 2-bromo-3- (2-ethylhexyloxy) thiophene. I got it.

(Synthesis Example 3)

3.8 g (13 mmol) of 2-bromo-3- (2-ethylhexyloxy) thiophene and 40 mL of tetrahydrofuran were placed in a 200 mL four-necked flask under a nitrogen stream and cooled to −78 ° C. To the obtained solution, 14.8 mL (1.1 M, 16.3 mmol) of a hexane-tetrahydrofuran solution of lithium diisopropylamide was added dropwise, and after stirring for 1 hour, 2.5 mL (33 mmol) of N, N-dimethylformamide was added. Then, the mixture was further stirred for 1 hour. After returning the reaction solution to room temperature, it was mixed with ice water, and the reaction product was extracted with 100 mL of ethyl acetate. The extract was washed successively with saturated aqueous ammonia chloride and saturated brine, and the solvent was distilled off from the extract. The obtained residue was purified by column chromatography using a mixed solvent of hexane: ethyl acetate = 90:10 as a developing solvent, and thus 5-bromo-4- (2-ethylhexyloxy) -2-thiophenecarboxyaldehyde. 2.3 g (yield 55%) was obtained.

(Synthesis Example 4)

Under a nitrogen stream, 5.5 g (30 mmol) of 4,5-difluorophthalic anhydride, 30 mL of acetic anhydride and 15 mL of triethylamine were placed in a 100 mL four-necked flask. To the obtained solution, 5.9 mL (36 mmol) of butyl acetate was added under an ice bath, the mixture was allowed to stand overnight, and then slowly added dropwise to 120 mL of cooled 6N hydrochloric acid. The obtained solution was heated at 80 ° C. for 1 hour, allowed to cool to room temperature, and then mixed with 400 mL of ice water. The precipitated light brown solid was filtered off to give 4.8 g (yield 87%) of 5,6-difluoroindene-1,3-dione.

(Synthesis Example 5)

3.6 g (20 mmol) of 5,6-difluoroindene-1,3-dione and 60 mL of ethanol were placed in a 200 mL four-necked flask, and 2.5 mL (40 mmol) of malononitrile was added under stirring. Further, 2.5 g (30 mmol) of sodium acetate was added, and the mixture was heated and stirred at 60 ° C. for 6 hours. After allowing to cool to room temperature, the mixture was poured into 60 mL of water and 14 mL of concentrated hydrochloric acid was added. The precipitated solid was filtered off, dissolved in 50 mL of chloroform, the insoluble matter was filtered off, and then concentrated to concentrate 2- (5,6-difluoro-2,3-dihydro-3-oxo-1H-indene-1-iriden). -3.6 g (78% yield) of malononitrile was obtained as a light brown solid.

(Synthesis Example 6)

In a 300 mL four-necked flask under a nitrogen stream, 3.0 g (7.2 mmol) of 4,4-bis (2-ethylhexyl) -dithieno [3,2-b: 2', 3'-d] silol, 42 mL of tetrahydrofuran was placed. And cooled to −78 ° C. To the obtained solution, 7.7 mL (1.1 M, 8.6 mmol) of a hexane-tetrahydrofuran solution of lithium diisopropylamide was added dropwise, and after stirring for 30 minutes, 8.6 mL (8. 6 mmol) was added. The four-necked flask was removed from the cooling bath and the reaction solution was returned to room temperature. Subsequently, the reaction solution was mixed with 200 mL of ice water, and the reaction product was extracted with hexane. By washing the extract with saturated brine and distilling off the solvent from the extract, 4,4-bis (2-ethylhexyl) -2,6-bis (trimethylstanyl) dithieno [3,2-b: 4.2 g (yield 79%) of 2', 3'-d] silol was obtained as a light green oil.

(Synthesis Example 7)

4,4-Bis (2-ethylhexyl) -2,6-bis (trimethylstanyl) dithieno [3,2-b: 2', 3'-d] silol in a 100 mL four-necked flask under a nitrogen stream. 22 g (2.98 mmol), 5-bromo-4- (2-ethylhexyloxy) -2-thiophenecarboxyaldehyde 2.0 g (6.26 mmol), tetrakistriphenylphosphine palladium (0) 3 mol% and toluene 30 mL were added. It was heated at 80 ° C. for 5 hours. Then, the reaction solution was allowed to cool to room temperature, and the solvent was distilled off from the reaction solution. The obtained residue was purified by column chromatography using a mixed solvent of hexane: ethyl acetate = 90:10 as a developing solvent, thereby purifying 5,5'-(4,4-bis (2-ethylhexyl) 4H-). Shiroro (3,2-b: 4,5-b') dithiophene-2,6-diyl) bis (4-((2-ethylhexyl) oxy) thiophen-2-carbaldehyde 2.1 g (yield 78%)) Was obtained as a vermilion oil.

(Synthesis Example 8)

5,5'-(4,4-bis (2-ethylhexyl) 4H-sirolo (3,2-b: 4,5-b') dithiophene-2,6 in a 200 mL four-necked flask under a nitrogen stream -Diyl) bis (4-((2-ethylhexyl) oxy) thiophene-2-carbaldehyde 1.0 g (1.1 mmol) and 2- (5,6-difluoro-2,3-dihydro-3-oxo-1H) -Inden-1-iriden) -0.77 g (3.3 mmol) of malononitrile,
It was completely dissolved in 40 mL of chloroform. To the obtained solution, 1.1 mL of pyridine was added, and the mixture was heated at 60 ° C. for 5 hours. Then, the reaction solution was allowed to cool to room temperature, and then the reaction solution and 80 mL of methanol were mixed. Subsequently, by filtering the precipitated precipitate, 2,2'-[(2Z, 2'Z)-{(5,5'-(4,54-bis (2-ethylhexyl)) 4H-sirolo ( 3,2-b: 4,5-b') dithiophene-2,6-diyl) bis (4-((2-ethylhexyl) oxy) thiophene-5,2-diyl)) bis (methanylylidene)} bis (5) , 6-Difluoro-3-oxo-2,3-dihydro-1H-inden-2,1-diylidene)] Dimarononitrile 1.2 g (yield 82%) was obtained. In the following Examples and Comparative Examples, this compound was used as an n-type compound.

The measurement results ^{of 1} H NMR of the obtained compound are shown below.
¹ H NMR (500MHz, CDCl ₃ , ppm): δ 8.70 (s, 2H), 8.51 (q, 2H), 7.74 (s, 2H), 7.65 (t, 2H), 7.52 (s, 2H), 4.16 ( t, 4H), 1.89 (t, 2H), 1.54 --1.70 (m, 8H), 1.35 --1.45 (br.s, 8H), 1.14 --1.28 (m, 20H), 0.95 --1.04 (m, 14H), 0.79 --0.82 (m, 12H)

[Manufacturing of photoelectric conversion element]
(Example 1)
(Preparation of organic semiconductor ink)
The n-type compound (12 mg) obtained in Synthesis Example 8 and the p-type conjugated polymer represented by the above general formula (II) so that the weight ratio is 3: 2: 1 (poly ([2,6')). -4,8-di (5-ethylhexyltienyl) benzo [1,2-b; 3,3-b] dithiophene] {3-fluoro-2 [(2-ethylhexyl l) carbonyl] thieno [3,4-b ] Thiophene diyl}, abbreviated as PCE10, 8 mg) and fullerene derivative [70] PCBM (4 mg) were weighed into the vial, then 1 mL of chlorobenzene was added to the vial to further adjust the structure (ie, p. 1-Chloronaphthalene as an additive (to promote stacking of aromatic moieties of type organic semiconductors and aromatic moieties of n-type organic semiconductors, and to promote bulk heterostructure formation between p-type organic semiconductors and n-type organic semiconductors) 2% by weight was added to the amount of the solvent, and the obtained mixed solution was stirred at 75 ° C. for 24 hours. The stirred solution was filtered through a PTFE motorcycle al (pore size 0.45 μm) to prepare an organic semiconductor ink. ..

(Creation of photoelectric conversion element)
Ultrapure cleaning of a glass substrate (manufactured by Geomatec) provided with a patterned indium oxide (ITO) transparent conductive film using a cleaning agent (manufactured by Yokohama Yushi Kogyo Co., Ltd., semi-clean M-LO). After that, washing with ultrapure water, drying with a nitrogen blow, and UV-ozone treatment immediately before application were performed.

Next, a _{nanodispersed solution of ZnO 2} (manufactured by Avantama) was mixed with isopropanol at a volume ratio of 1: 1 and ultrasonically treated for 10 minutes, and then filtered through a motorcycle al (pore diameter 0.2 μm). A ZnO ₂ nanodisperse solution was spin-coated on the substrate at room temperature at 500 rpm for 3 seconds, 2000 rpm for 20 seconds, and 4000 rpm for 20 seconds to form an electron extraction layer. The obtained substrate was heated at 90 ° C. for 20 minutes.

Subsequently, the substrate was cooled to room temperature in the air, and then spin-coated with an organic semiconductor ink at 1500 rpm for 20 seconds and 4000 rpm for 20 seconds to form an active layer. The obtained substrate was heated at 110 ° C. in the air for 20 minutes.

Next, MoO ₃ was vapor-deposited on the active layer using a patterning mask by a resistance heating type vacuum vapor deposition method to form a hole extraction layer having a thickness of 7 nm.

Finally, as an electrode, silver was vapor-deposited on the hole extraction layer by a resistance heating type vacuum vapor deposition method using a patterning mask to form a silver electrode having a thickness of 100 nm. In this way, a 25 × 30 mm square photoelectric conversion element was produced.

(Example 2)
A photoelectric conversion element was produced in the same manner as in Example 1 except that [60] PCBM was used instead of the fullerene derivative [70] PCBM when preparing the organic semiconductor ink.

(Example 3)
A photoelectric conversion element was produced in the same manner as in Example 1 except that [60] fullerene was used instead of the fullerene derivative [70] PCBM when preparing the organic semiconductor ink.

(Example 4)
A photoelectric conversion element was produced in the same manner as in Example 1 except that [70] fullerene was used instead of the fullerene derivative [70] PCBM when preparing the organic semiconductor ink.

(Example 5)
A photoelectric conversion element was produced in the same manner as in Example 1 except that [60] SIMEF was used instead of the fullerene derivative [70] PCBM when preparing the organic semiconductor ink.

(Example 6)
When preparing an organic semiconductor ink, the n-type compound (12 mg) obtained in Synthesis Example 8, the p-type conjugated polymer (PCE10, 8 mg) represented by the above general formula (II), and the fullerene derivative [70] PCBM. A photoelectric conversion element was produced in the same manner as in Example 1 except that a mixture having a weight ratio of (4 mg) of 3: 2: 2 was used as the organic semiconductor.

(Example 7)
When preparing an organic semiconductor ink, the n-type compound (12 mg) obtained in Synthesis Example 8, the p-type conjugated polymer (PCE10, 8 mg) represented by the above general formula (II), and the fullerene derivative [70] PCBM. A photoelectric conversion element was produced in the same manner as in Example 1 except that a mixture having a weight ratio of (4 mg) of 2: 2: 2 was used as the organic semiconductor.

(Comparative Example 1)
When preparing the organic semiconductor ink, the weight ratio of the n-type compound (12 mg) obtained in Synthesis Example 8 and the p-type conjugated polymer (PCE10, 8 mg) represented by the above general formula (2) is 3: 2. A photoelectric conversion element was produced in the same manner as in Example 1 except that the mixture was used as an organic semiconductor.

[Evaluation of photoelectric conversion element]
A 1 mm square metal mask was attached to the photoelectric conversion elements obtained in Examples and Comparative Examples, and the current-voltage characteristics between the ITO electrode and the silver electrode were measured. Table 1 shows the external quantum efficiency (EQE) at a wavelength of 940 nm when a bias of -1 V is applied.

In Comparative Example 1, the EQE of the photoelectric conversion element obtained without using fullerenes at a wavelength of 940 nm was 49%.
On the other hand, the photoelectric conversion elements of Examples 1 to 7 containing n-type fullerenes in the active layer showed a high EQE of 55% or more. Since the n-type fullerenes give the same high EQE in the case of [60] PCBM and the case of [70] PCBM (Examples 1 and 2), such a high EQE of the fullerenes themselves. It is considered that this is not due to light absorption but due to the fact that fullerenes promoted electron mobility. Further, since the unmodified fullerenes [60] fullerene and [70] fullerene were successfully dissolved in the chlorobenzene solvent to prepare an organic semiconductor ink (Examples 3 and 4), [60] PCBM. And [70] It is considered that the same electron movement promoting effect as that of PCBM was exhibited. Further, in Example 5, since the solubility of [60] SIMEF is higher than that of PCBM, it is considered that EQE is improved. Example 6 is an experimental example in which the amount of [70] PCBM used is double that of Example 1. In Example 6, it is probable that the EQE was slightly lower than that in Example 1 because [70] PCBM was not completely dissolved in the ink. Example 7 is an experimental example in which the amount of the n-type compound used is 8 mg, which is 2/3 of that of Example 1. Since the EQE of Example 7 was almost the same as that of Example 1, it is considered that [70] PCBM has a great effect of increasing the mobility of electrons.
From the above, by including n-type fullerenes in the active layer, bulk heterojunction can be efficiently constructed, charge separation efficiency is improved, and the mobility balance between holes and electrons can be better maintained. it is conceivable that.

Claims (9)

An organic semiconductor device containing a p-type conjugated polymer, n-type fullerenes, and an n-type compound represented by the following formula (I) in an active layer.

(In formula (I), X represents a carbon or silicon atom; Y1, Y2, Z1 and Z2 each independently represent a linear or branched hydrocarbon group having 6 or more and 20 or less carbon atoms; A and B. Represents a fluorine atom or a chlorine atom independently; m and n independently represent an integer of 1 or more and 4 or less; p and q each independently represent an integer of 0 or 1). The n-type fullerenes are [60] fullerenes, [70] fullerenes, [60] PCBM, [70] PCBM, bis [60] PCBM, bis [70] PCBM, [60] SIMEF, [70] SIMEF, [ The organic semiconductor device according to claim 1, which is at least one compound selected from the group consisting of 60] ICBA, [70] ICBA, [60] ICMA, and [70] ICMA. The organic semiconductor device according to claim 1 or 2, wherein the active layer contains an additive consisting of a polycyclic aromatic compound or 1,8-diiodooctane. The organic semiconductor device according to any one of claims 1 to 3, wherein the organic semiconductor device is a photoelectric conversion element. The organic semiconductor device according to any one of claims 1 to 4, wherein the external quantum efficiency (EQE) when irradiated with light having a wavelength of 940 nm is 50% or more. It contains a p-type conjugated polymer, n-type fullerenes, and an n-type compound represented by the following formula (I).
The n-type fullerenes are [60] fullerenes, [70] fullerenes, [60] PCBM, [70] PCBM, bis [60] PCBM, bis [70] PCBM, [60] SIMEF, [70] SIMEF, [ At least one compound selected from the group consisting of 60] ICBA, [70] ICBA, [60] ICMA, and [70] ICMA.
An organic semiconductor ink in which the weight ratio of the n-type fullerenes to the n-type compound is 1.0 or less.

(In formula (I), X represents a carbon or silicon atom; Y1, Y2, Z1 and Z2 each independently represent a linear or branched hydrocarbon group having 6 or more and 20 or less carbon atoms; A and B. Represents a fluorine atom or a chlorine atom independently; m and n independently represent an integer of 1 or more and 4 or less; p and q each independently represent an integer of 0 or 1). The organic semiconductor ink according to claim 6, further containing an additive consisting of a polycyclic aromatic compound or 1,8-diiodooctane. A photodetector using the organic semiconductor device according to any one of claims 1 to 5. The photodetector according to claim 8, which is used for detecting light having a wavelength of 700 to 1000 nm.